Lincoln Electric Named Official Welder of Jay Leno's Big Dog Garage

Car Enthusiast Chooses Lincoln for His Shop

Somewhere in Southern California – a world of movies, magic and make believe – is Jay Leno's Big Dog Garage, a place not without its fair share of magic itself. Spread across two low-slung buildings cooked by the sun, is one of the world’s great car collections and one of the world's best-equipped garages, custom-built from the ground up to keep everything running in tip-top shape.

The garage itself is about 100,000 square feet, sizeable, to say the least, for a private garage, which is enough space to work on about a dozen cars at any one given time. About a quarter of that space is taken up by the machine shop, which includes a massive amount of equipment, including welders from Lincoln Electric, which has just been named the garage’s official welder.

As a whole, Leno’s collection spans 100 years of automotive history. The oldest cars are a 1906 Stanley Steamer and a 1909 Baker electric car, while the newest is a 2006 Corvette.

To keep everything in proper running order, Leno employs a crack team of mechanical wizards led by head mechanic Bernard Juchli (pictured with Jay), who are adept at fixing, restoring and customizing just about every type of vehicle imaginable.

For all the projects around the shop, Leno’s team relies on Lincoln Electric for all of the welding needs including welding and cutting equipment, technical training, and welding application support.

"In my shop we work on a lot of old and foreign cars, but when it comes to welding, we want the latest technology from an American company. That's why we choose Lincoln Electric," says Jay Leno.

For more information on Jay Leno's Big Dog Garage and collection, visit www.jaylenosgarage.com. See Lincoln featured on Leno’s website under "Videos" (watch video) to learn about what you should look for when buying a MIG welder or TIG welder for your shop or garage.

www.lincolnelectric.com

Lincoln Electric named the Official Welder of Goodguys

Leonard Lopez	Troy Trepanier	Sal Perez

The Goodguys Rod & Custom Association has named Lincoln Electric as its Official Welder. Goodguys is the world’s largest rod and custom association and the leader in producing and promoting hot rod enthusiast events. Goodguys has more than 70,000 members worldwide and offers 22 annual events across the country which attract nearly 2 million people annually.

“As the Official Welder of Goodguys, Lincoln will offer welding and cutting exhibits, demonstrations and technical advice at Goodguys events from coast to coast.,” said Dick Smith, Marketing Manager for The Lincoln Electric Company. “We will have expert welding personnel on-hand to answer questions, discuss the latest technologies and recommend the best equipment for the job.”

“The Goodguys Rod & Custom Association is proud to call Lincoln Electric its Official Welder. It is a huge benefit to our association members and event participants to have representatives from Lincoln on hand at our events demonstrating their line of fine products and offering technical support,” said Gary Meadors, owner of Goodguys Rod & Custom Association. “Lincoln Electric’s products use advanced technology and are designed to offer the best weld’s in any arena whether it’s on a 1932 Ford or a 1960 Cadillac!”

In addition, Lincoln Electric offers the industry’s most extensive network of well-stocked local distribution centers to back-up its welders, plasma cutters and electrodes. Hot rod enthusiasts can count on Lincoln’s quality products as well as the company’s exemplary service and unmatched welding expertise.

For those who build and refurbish classic and custom-built automobiles, Lincoln offers welding instruction at its Motorsports Training courses. These classes provide classroom theory and hands-on guided practice.

www.lincolnelectric.com

Lincoln Electric Supports Aviation As An Official Sponsor Of The Experimental Aircraft Association (EAA)

As an Official Sponsor of the Experimental Aircraft Association (EAA), The Lincoln Electric Company is an active participant at EAA events across the country. This includes hosting TIG training courses, providing equipment for hand-on welding, and participating as exhibitors in both national and regional shows for the association’s 170,000 members.

AirVenture
By far the most visible event held by the association annually is the EAA AirVenture Oshkosh held in Wisconsin. AirVenture attracts more than 700,000 people, including those who build, repair and fly aircraft. At the last AirVenture 2,800 aircraft were on display, including homebuilts, antiques, classics, warbirds, ultralights and rotorcraft.

During this week-long event, more than 500 workshops are presented on a variety of topics by aviation leaders, NASA researchers, FAA personnel, and aircraft designers. For seven years, Lincoln Electric personnel have taught TIG welding workshops emphasizing gas selection and polarity, tungsten selection, and welding techniques on metal such as chrome moly, aluminum, titanium and inconels.

“Lincoln Electric is committed to educating our members about TIG welding,” said Charlie Becker, Director of Aviation Information Services for EAA. “The company wants to ensure that aircraft are built and maintained using proper techniques. In this sport, it is critical to have sound welds and a safe aircraft.”

The workshops offer the widest variety of aviation welding knowledge available in one place. For the hobbyist who may be more familiar with oxyacetylene, or oxy-fuel, techniques, this is a great opportunity to receive personalized instruction in TIG, which offers the cleanest, highest quality weld for this type of application. TIG welding has several other advantages for aircraft welding. It allows precise control of heat and has better penetration and fewer problems with cracking and stressing than MIG welding. Finally, TIG welding is especially well suited for welding on the light materials used on many aircraft frames.

Another highlight of AirVenture is the exhibits area where more than 700 exhibitors display everything from instruments to avionics to aircraft parts. Lincoln Electric also has a strong presence in this area as it provides live demonstrations of the latest welding equipment, such as the new Precision TIG 185. At a typical AirVenture, 10,000 people will visit Lincoln’s booth.

Regional Fly-Ins
Five times per year, Lincoln is involved in regional fly-in events at airports around the country which offer the same workshops, exhibits and other attractions as does the AirVenture event, just on a smaller scale for a regional audience.

SportAir
Held throughout the year, EAA offers SportAir weekend instructional courses where recreational aviation enthusiasts can attend hand-on instruction in technical aspects of building aircraft. One of the essential components of these workshops is the TIG welding course staffed by the experts at Lincoln Electric. Held six times per year, the SportAir workshops are almost always full to capacity.

“Not only is Lincoln Electric an Official Sponsor of EAA and intimately involved in the events we hold, the company also provides technical support throughout the year. When members have a technical welding question, we know who to call,” said Becker.

www.lincolnelectric.com

Racing Game Meets Racing Reality

Lincoln Electric Official Welder of innovative Speed Channel show

Lincoln Electric is proud to be the official welder of the new series Forza Motorsport Showdown on the SPEED Channel. SPEED, the automotive lifestyle and motorsports network, has joined forces with Microsoft Game Studios in presenting a live-action mini-series based on Xbox 360's new Forza Motorsport 2 video game.

Forza Motorsport Showdown, a four-episode series from executive producer Bud Brutsman, is set to debut February 21, 2007 at 11 p.m. EST. Each episode rigors a diverse group of competitors through a roster of competitive motorsports disciplines - drag racing, road racing, autocross and drifting - in a $100,000 winner-take-all format. Forza Motorsport Showdown is designed to be the ultimate test of high-performance driving and mechanical skills.

This new series is inspired by Forza Motorsport 2, Microsoft Game Studios' sequel presentation to its award-winning Forza Motorsport title, which debuted in 2003. This offering is expected to set new standards for high-definition gaming, customization, driving, physical and damage simulation. In addition, Forza Motorsport 2 allows gamers to collect more than 300 personalized racers and pursue worldwide competitions through its revolutionary Xbox Live gaming community.

The Lincoln Electric products featured in the show include:

Precision TIG® 225 & 275 Power MIG® 140C Power MIG 255C Pro-Cut 25 & 55 Ultrashade® Auto-Darkening Welding Helmets Forza Motorsport Showdown will be the first of its kind -- merging reality based television and cutting edge video game play. The dynamics of fast cars, hi-stakes races, and diverse competitors create the suspense and excitement only a true life video game can deliver. Check your local listings for dates and times. www.lincolnelectric.com

Old Welders Are the Best Welders

While most people look for the latest 'bells and whistles', when it comes to welding machines, Clay Layman of Layman's Welding in Peace Valley, Mo., sticks with the tried and true. In fact, Layman currently owns nine Lincoln Electric Pipeliner™ 200 (formerly Shield-Arc® 200) stick welding machines dating back to the 1940s. Many are used on a daily basis in his one-man fabrication shop and welding busines. According to Layman, the Pipeliner 200 is the best welding machine ever made. And he should know, since he has been welding for nearly 45 years.

The earliest model Pipeliner 200 Layman has in his shop was manufactured by Lincoln in 1946. His other units range from 1953 to 1966 models -- all of which are still running. Layman has not even purchased a welder since the early 1970s -- a testament to the quality and durability of Lincoln machines.

Just why does he prefer the Lincoln Pipeliner 200? "The windings are made of 100 percent copper, it has a soft arc and it starts easily," said Layman. "For 10 years, I was working in west Texas on high pressure petroleum pipelines. In that industry, which requires x-rays on all welds, Lincoln machines are the only ones you see."

Also a cattle rancher, much of Layman’s fabrication business is repair and building for farm and heavy equipment in the field. Recent jobs include welding fences, gates, truck frames, dozer grouser bars, fuel tanks and tool boxes.

Even though he’s never had any formal training, Layman enjoys the career path he has chosen. “Welding is my life. I was born to weld.”

In his spare time, Layman’s hobby is rebuilding old welding machines. He currently has four SA-200s that are waiting their turn for some ‘TLC’. “As I’m rebuilding these old units, the people at Lincoln are very helpful in walking me through the parts I need – most of which are still available – even on these units that are now 50 years old,” noted Layman.

Because its machines are built to last, Lincoln stocks parts even on discontinued models such as the SA-200.

Do you have a service related question?

• Service Related Questions
• Locate an Authorized Field Service Facility

www.lincolnelectric.com

"Pneumatic Dreamer" Sculpted of Bronze-and Air

By Carla Rautenberg Welding Innovation Contributing Writer James F. Lincoln
Arc Welding Foundation Cleveland, Ohio>
A welded bronze sculpture depicting a slumbering human body has been installed over the entrance to the W San Francisco Hotel. Sculptor Michael Stutz, who likes to say that the figure is "made of bronze and air," aptly named it Pneumatic Dreamer. The piece (Figure 1) was fabricated of annealed bronze strips intricately woven and then welded together at Matt Gil's Studio, which specializes in doing fabrication work for San Francisco area artists.

A Public/Private Partnership

The $400,000 project was funded by Starwood Hotels & Resorts Worldwide (manager of the W San Francisco) in accordance with the San Francisco Redevelopment Agency One Percent for Art Program. The program stipulates that for major private developments in the Yerba Buena Center Redevelopment project area, where W San Francisco was built, one percent of the construction costs be set aside for the creation of permanent, public art.

Figure 2. The artist, Michael Stutz, in front of the entrance to San Francisco’s W Hotel.

Stutz received the commission by unanimous vote of a panel that included representatives from the San Francisco Museum of Modern Art, which is located in the Yerba Buena neighborhood.

An Artist’s Growth

Stutz, who hails from Tennesee, moved to San Francisco in 1987, and supported himself early in his career by creating merchandise displays for Macy’s. His commitment to public art grew out of work he did in New Orleans, designing and building large-scale papier mache figures for the city’s Mardi Gras parades. Later, he began using recycled materials to create sculptures that have been shown in exhibitions throughout the Bay Area. Pneumatic Dreamer is Stutz’s first work in bronze, and initially, he considered having the piece cast. He consulted a foundry but learned the cost would be "astronomical."

The sculpture was specifically designed for installation on the fourth floor terrace of the neoclassical hotel building, overlooking the street below (Figure 2). Stutz points out that the figure, the gender of which is intentionally ambiguous, "could be going into a dream state, or arising from it" and that it illustrates "a very private moment in a very public space." In keeping with that idea, the piece is literally a woven shell, in which, Stutz says, "the inside is outside, and the outside is inside."

Pneumatic Dreamer is lit from both the inside and the front, emphasizing the woven lattice aspect of the design. Its bronze patina will weather to a greenish-blue shade in about a decade.

The Fabrication Process

The 30 ft (9,144 mm) long, 7 ft (2,134 mm) high sculpture was too large to be fabricated inside the shop at Matt Gil’s Studio. Thanks to the temperate climate of the Bay Area, it was possible to weld it in the yard outdoors. Gil notes that "We had hoped to plug weld it from the outside, but that was going to be too time-consuming and would have left the surface blemished. So we had to weld it from the inside." The work was accomplished by a team of three welders, three assistants, and the artist, working together for 3-1/2 months. Michael Stutz, while not a welder himself, put the 0.083 in. (21 mm) thick bronze strips in place and served as the "eyes" during fabrication.

Asked to describe the welding process itself, Matt Gil responds, "We used MIG and standard heliarc TIG welding with a serium electrode. I weld bronze using AC and continuous high frequency as I would do for aluminum, but the use of the serium electrode was unique." All of the smallest parts (the fingers, toes, and face) had to be TIG welded because that was the only tool that could be manipulated in such small spaces. The four mild steel structural columns that support the sculpture were shop-fabricated using Lincoln 7018 electrode.

Stutz and Gil agree that the most difficult aspect of fabricating the piece was the challenge posed by working in such tight quarters. Gil says "We were literally working on top of each other. The welding was like stitching on the inside of the piece, while simultaneously there were guys on the outside doing the weaving. The tediousness was a little unexpected."

Although the soft and tactile appearance of Pneumatic Dreamer fittingly echoes that of a sleeping human body, both Gil and Stutz were surprised at the strength and rigidity of the finished sculpture. When it was completed, Sheedy Crane & Rigging hoisted it out of the fabrication yard and it was trucked to the Third Street location of W San Francisco. Delighted pedestrians gawked as the sculpture was lifted into the air and set onto its supports on the fourth floor terrace above. Like a contented hotel guest, the slumbering figure never stirred, but nestled comfortably into place, dreaming all the while.

MIG welders TIG welders MIG wire TIG cut-length consumables

This project has been published to show how individuals used their ingenuity for their own needs, convenience and enjoyment. Only limited details are available and the projects have NOT been engineered by the Lincoln Electric Company. Therefore, when you use the ideas for projects of your own, you must develop your own details and plans and the safety and performance of your work is your responsibility.

www.lincolnelectric.com

Adding a Utility Box to Your Trailer

For those of us who enjoy outdoor activities, such as boating, riding dirt bikes, bicycling, or snowmobiling, and own one or more of these “toys”, it’s likely that you also own an open style trailer to haul them back and forth. The one thing these activities have in common is that you have to tote along all the accessories. Most open trailers don’t have adequate storage space, if any, to accommodate the life jackets, helmets, paddles and gear, not to mention any spare parts or tools you may need.

Staring at my boat trailer sparked an idea for an easy do-it-yourself solution for all my accessories and spare parts. What about attaching a utility box to the trailer? The first thing that came to mind was a truck storage box.

In order to achieve a lasting solution, the truck box needs to be securely attached to the trailer. As you can see from the list of materials, tools you’ll need, and the all important safety equipment below – the trouble of where and how to get started on this great do-it-yourself project has all been laid out for you. So what do you say, go grab your trusty Lincoln Electric AC-225 stick welder and let’s get started!

The first step is to drill bolt holes into the channel pieces that will serve as the brackets. After securing the channel piece in a vice, drill a hole at each end of the bracket. This will allow the bolts to slide easily through and into the casing of the storage box. Handy Tip: Depending on how thick the channel pieces are, you may want to keep both hands on the drill and apply steady pressure to drill the holes.

With that one simple step complete, let’s move on to the outside pieces, fabrication, and safety equipment needed to complete the project. Note: We are using a boat trailer in this example. You may have a different style trailer, so make adjustments accordingly. The storage box will be secured between the upright post (which serves as a mast support on the trailer) and the first cross bar. Four channel pieces will serve as brackets and will have to be welded to the main “tongue” – one at each end and two in the middle.

Before we make the first weld, there are a couple of things to know. Since the first bracket can only go as far as the first crossbar, this bracket needs to be welded first. Be sure that the holes drilled in Step 1 are on the topside of the bracket. All other measurements will be based on this single piece. The “C” shape formed by the channels will face inward and the bin will rest on top. Ready to weld, think safety first – put on your welding gloves, safety goggles and helmet. Make sure the channel piece is centered and even on the tongue. Place a stick of Lincoln 7018 AC into the electrode holder, attach the ground clamp to the trailer and make a small tack weld on each side. An amperage setting of 120 is appropriate for the 7018 electrode being used. A 1/8" diameter electrode is appropriate for this metal thickness.

Measure everything to be sure it is square. The spacing of the brackets depends on the length of the box. So measure the box first. Handy tip: The good thing about tack welds is that they can be easily removed with a quick knock of a hammer if you find that your measurements are off.

Now it’s time to tack weld the bracket on the opposite end, close to the upright. Use the length of the box to measure the distance between the bracket you just welded and the bracket you are now going to weld. Center the bracket on the tongue and measure the diagonal lines from bracket-to-bracket to ensure they are square.

Using the same amperage settings for the electrode, put on all your safety equipment (as mentioned in Step 3) and tack weld the second channel piece to the main tongue of the trailer. This is a simple step, placing a small weld on each side of the channel piece.

Time to weld the two center brackets to the main tongue. Handy Tip: If you have a problem striking an arc with the stick, check to see if there is paint or rust where you want to weld. If there is, use a metal file to clear the metal down to its original base. You can paint over the welds later..

Center the two middle brackets and make sure they are evenly spaced from the end channel pieces. The box we are using has a corrugated bottom. If you are using the same style box, measure the pieces to ensure they match up with the corrugation so the bolts are long enough to fall through both the box and the channel bracket. Now tack weld each of the channel pieces. When done with the tack welds and you are sure all is square, weld along all the joints in order to entirely fuse the channel pieces to the tongue.

Once the welding is complete, place the storage box on top of the channel brackets. Locate all the holes you drilled into the brackets earlier and using chalk, mark these holes on the box.

Remove the box from its mounting place and turn it upside down onto a flat surface. With the holes clearly marked, begin drilling holes into the box on each chalk spot.

Drum roll please! The final step. Place the box back on the brackets, line up the holes and drop a bolt with a flat washer through each hole. Secure all the bolts with another flat washer and a lock washer and nut from the inside.

Presto! Your trailer storage box is complete and ready to cart around all your stuff!

Fabrication Tools Lincoln Electric AC-225 welder 1/8" Lincoln 7018 AC Electrode Storage bin (You can use anything you can get your hands on and be a little creative on exactly how you attach it.) Standard drill Metal file 3/8” bolts and nuts Flat washers and lock washers 4 pieces of 3” channel cut to size (these would be the mounting brackets for the box – since they are pretty thick, you may want to get them cut somewhere, or you can give it a go yourself with a reciprocating saw.) C-clamps

Safety Equipment: Long sleeve cotton shirt – don’t wear polyester! Safety glasses Welding helmet or face shield Welding gloves

To learn more about the AC-225 welder click here!.
Or, read up on all you need to know about Lincoln 7018 AC and other stick electrodes by clicking here.

Related Articles

How to Strike and Establish an Arc
Creating High Quality Stick Welds: A User's Guide
Arc Welding Fundamentals
Stick Weldirectory

This project has been published to show how individuals used their ingenuity for their own needs, convenience and enjoyment. Only limited details are available and the projects have NOT been engineered by the Lincoln Electric Company. Therefore, when you use the ideas for projects of your own, you must develop your own details and plans and the safety and performance of your work is your responsibility.

www.lincolnelectric.com

An Improved Gas Cylinder Clamping System

by Ralph Waters

I recently decided to treat myself to a capable MIG welder, and purchased a Lincoln Power MIG™ (see compact wire feeder/welders). I decided to build my own shielding gas bottle platform at the rear of the machine that would allow me to accommodate small CO₂ gas bottles, and add a handle to aid in moving the unit around the shop.

My clamping system consists of two components:

(1)	a more positive cylinder clamp that would keep the cylinder from rattling around, and
(2)	an adapter to support my CO2 bottle, which is considerably smaller than a compressed gas bottle because its contents are liquefied.

PART 1 - The main clamp consists of an inverted "U" which rotates at the base and presses the cylinder firmly into the factory stabilizers with two small feet. A turnbuckle on each side adjusts the clamping force and will accommodate any size cylinder. One side benefit of the round tube handle is that the welder can now be maneuvered just like a shopping cart, and the power cable coils neatly around it for storage.

When the turnbuckles are unhooked from the eye bolts, the assembly pivots down to ground level so that loading a fresh cylinder is a simple matter. A variation on this design could be to mount the bracket legs on the outside of the welder chassis instead of the inside, using longer tabs to allow the legs to lie flat on the ground, making a large gas cylinder easier to load.

The dimensions shown are "as built" for my welder (from scrap, of course) and may have to be modified to fit yours. The one piece of round tubing makes a comfortable handle, and the square tubing everywhere else simplifies alignment during fabrication. The tabs at the base of the vertical legs were drilled to accommodate the bolts used to mount the OEM cylinder tray. Be sure to check the full range of motion on the handle before drilling & welding these tabs, so that the handle touches the ground before the arms contact the lip of the cylinder support tray. It's best to mount the cylinder support legs last so they will fit your cylinder perfectly, and maintain a little gap between the cylinder and tubular handle. Don't do any welding near that cylinder!

List of Material for Clamp
Qty	Material	Length	Usage
1	1-3/8" Round Steel Tube, .062" wall	14"	Horizontal Handle
2	1-1/4" Square Steel Tube, .080" wall	24"	Vertical Arm
2	2" x 1/8" Flat Hot-Rolled Steel Bar	2-1/2"	Mounting Tab
2	2" x 1/8" Flat Hot-Rolled Steel Bar	1-1/2"	Cylinder Foot
2	3/4" Square Steel Tube, 0.080" wall	3-1/2"	Cylinder Leg
2	5/16" Eye bolt w/ 2 flat washers + 2 nuts ea.	3"	Arm connector
2	5/16" U-bolt w/ 4 flat washers + 4 nuts ea.	2"	Bracket connector
2	1/4" Turnbuckle	4-7"	Clamp Adjuster
2	Nuts to fit OEM tray mounting screws		Main Mounts

PART 2 - I'll be the first to admit that the adapter to support my choice of CO₂ bottle appears "unrefined" (to say the least), but it is simple to make and has served me well for several years now. My only regret is that no welding is required.

A wooden 2x4 is placed on top of the welder's lower stabilizer bracket, elevating the bottle so that its shoulder now extends above the welder's upper cylinder stabilizer bracket, and the valve is at a convenient height for use. The sheet aluminum is formed to the curvature of the cylinder, then sheared on each side to create two tabs which are bent parallel to each other and screwed to the 2x4. In place, the aluminum skirt then cups the base of the cylinder, extending well beyond the edge of the lower stabilizer bracket, and the 2x4 is roughly centered under the bottle. The weight of the cylinder and the vertical tubes of the new clamp (above) keep the 2x4 and cylinder exactly in place, held securely against both the upper and lower stabilizer brackets

List of Material for Clamp
Qty	Material	Length	Usage
1	2x4 Douglas Fir	13"	Support beam
1	Aluminum Sheet 6061-T0, .062 Thick	12" x 12"	Extension skirt
2	#10 x 1" Self-Tapping Cap Screws

When both components are in use together, a 20 lb. CO₂ cylinder is held securely.

This project has been published to show how individuals used their ingenuity for their own needs, convenience and enjoyment. Only limited details are available and the projects have NOT been engineered by the Lincoln Electric Company. Therefore, when you use the ideas for projects of your own, you must develop your own details and plans and the safety and performance of your work is your responsibility.

www.lincolnelectric.com

Building The Perfect Snowblower

I never had any problems with my Country Home Products' DR Field and Brush Mower. The 12.5 hp, 26" rotary had the ability to do just about everything. However, after using the DR for a summer I started thinking about the approaching winter season and the work I had ahead of me. Because of this, I called the factory that manufactures the DR and asked what kinds of snowblower attachments they offer. Although they could not supply one, I knew the machine would work well if it had a blower on it, so I set out to build my own.

During my research, I came across a 36" Sears tractor snowblower attachment laying derelict in a yard while at a garage sale. I pleaded with the owner and obtained the attachment for the bargain price of $25.

I took the mower deck off the DR, propped the blower up at the right angle and put the wheeled power unit against the back of it. After pondering for a while I figured out what I needed to do in order to mount the blower on the DR. It was essential that I make the connection close-coupled-for handling and weight considerations, yet far enough away to permit a drive system. I made some calls and checked the Internet for drive options-all of which were either cost prohibitive or cumbersome. Since this project was an 'experiment', I figured I'd couple them together, then simply eyeball the drive solution.

Upon visiting a local steel yard and collecting 10' of 1" square steel tubing, 5' of 1 1/2" square steel tubing, a piece of 3/16" plate about 24" x 24" and 2' of 1 3/8" OD round aircraft tubing (to match the 'insert' tube-and-sleeve connection for the mower deck)., I was ready to build my snowblower. Using a portable band saw, oxy/acetylene torch set, 7" disc grinder, 4" disc grinder, a drill, and my Lincoln Electric AC 225 "buzz box" stick welder and Lincoln Electric Weld-Pak™ 100 wire-feeder/welder, I went to work. I'm a 'backyard' mechanic with no formal welding training but knew I could use the Weld-Pak for the light and delicate work and the buzz box for heavier material. I used the existing attachment points on the blower housing as anchors and cut and welded a 1" tubing frame to give my machine a base, then beefed it up with 1 1/2" tubing in the center, where the round tubing passed through. I cut and welded a piece of the plate steel to give myself a flat, solid base for the back of the mount. My AC-225 made the 'heavy' work easy.

Following this, I cut a hole, passed the round tubing through and, using the wire feed welder, attached the round tubing to the back of the blower and the mount plate. I was now ready to connect my DR to the blower.

My innovative snowblower was belt driven from the right-hand side - the DR drive pulley was under the engine deck on the machine centerline. I was once again back to the eyeball stage. I finally figured out that I could completely change the existing drive assembly, incorporating the 'clutch', etc. by moving it to a different plane. I cut the drive assembly off the back of the blower housing and started cutting and welding again. In the end, I mounted the entire former assembly with a new driveshaft (a slotted 3/4" 'PTO' shaft about 7" longer, to reach the centerline) about 4" lower on the back of the blower. I added a pillow block on the (new) outer end of the extended shaft for support. The plate steel surface made it easy to weld and bolt the necessary parts right where I needed them. I also had to weld a piece of angle iron to the back of my mounting plate to keep the blower, which was heavy on one end, from oscillating - the DR Field and Brush Mower is designed to oscillate with uneven ground and I used the same mounting system. The drive belt now comes from the horizontal drive pulley to the vertical driven sheave with a 1/4 twist.

I also needed a bracket to hold the upper end of the discharge chute rotation handle so I cut and welded a couple of pieces of the 1 1/2" tubing together at the correct angle, then used hose clamps to attach them to the handlebar assembly. A hole drilled through the tubing lets me remove-or-replace the chute handle very easily, just like a factory assembly.

One of the principal goals I wanted to achieve was adaptability without any change to the basic machine, and exchangeability without hassle. I can change from blower to mower or back in a matter of about 15-20 minutes and because I didn't change any of the original parts on the DR there is no loss of integrity.

I am happy to report that my 12.5 hp, 36" blower moves compacted snow without even breathing hard while in third gear. I've got about 4 trouble-free hours on the machine now and am convinced it will last a long time.

Now I've got a two-season machine that works great - and I've got my snowblower! I proved that if you want something bad enough, and have the right tools, materials and some time, you can do just about anything!

This project has been published to show how individuals used their ingenuity for their own needs, convenience and enjoyment. Only limited details are available and the projects have NOT been engineered by the Lincoln Electric Company. Therefore, when you use the ideas for projects of your own, you must develop your own details and plans and the safety and performance of your work is your responsibility.

www.lincolnelectric.com

Building The Perfect Snowblower

I never had any problems with my Country Home Products' DR Field and Brush Mower. The 12.5 hp, 26" rotary had the ability to do just about everything. However, after using the DR for a summer I started thinking about the approaching winter season and the work I had ahead of me. Because of this, I called the factory that manufactures the DR and asked what kinds of snowblower attachments they offer. Although they could not supply one, I knew the machine would work well if it had a blower on it, so I set out to build my own.

During my research, I came across a 36" Sears tractor snowblower attachment laying derelict in a yard while at a garage sale. I pleaded with the owner and obtained the attachment for the bargain price of $25.

I took the mower deck off the DR, propped the blower up at the right angle and put the wheeled power unit against the back of it. After pondering for a while I figured out what I needed to do in order to mount the blower on the DR. It was essential that I make the connection close-coupled-for handling and weight considerations, yet far enough away to permit a drive system. I made some calls and checked the Internet for drive options-all of which were either cost prohibitive or cumbersome. Since this project was an 'experiment', I figured I'd couple them together, then simply eyeball the drive solution.

Upon visiting a local steel yard and collecting 10' of 1" square steel tubing, 5' of 1 1/2" square steel tubing, a piece of 3/16" plate about 24" x 24" and 2' of 1 3/8" OD round aircraft tubing (to match the 'insert' tube-and-sleeve connection for the mower deck)., I was ready to build my snowblower. Using a portable band saw, oxy/acetylene torch set, 7" disc grinder, 4" disc grinder, a drill, and my Lincoln Electric AC 225 "buzz box" stick welder and Lincoln Electric Weld-Pak™ 100 wire-feeder/welder, I went to work. I'm a 'backyard' mechanic with no formal welding training but knew I could use the Weld-Pak for the light and delicate work and the buzz box for heavier material. I used the existing attachment points on the blower housing as anchors and cut and welded a 1" tubing frame to give my machine a base, then beefed it up with 1 1/2" tubing in the center, where the round tubing passed through. I cut and welded a piece of the plate steel to give myself a flat, solid base for the back of the mount. My AC-225 made the 'heavy' work easy.

Following this, I cut a hole, passed the round tubing through and, using the wire feed welder, attached the round tubing to the back of the blower and the mount plate. I was now ready to connect my DR to the blower.

My innovative snowblower was belt driven from the right-hand side - the DR drive pulley was under the engine deck on the machine centerline. I was once again back to the eyeball stage. I finally figured out that I could completely change the existing drive assembly, incorporating the 'clutch', etc. by moving it to a different plane. I cut the drive assembly off the back of the blower housing and started cutting and welding again. In the end, I mounted the entire former assembly with a new driveshaft (a slotted 3/4" 'PTO' shaft about 7" longer, to reach the centerline) about 4" lower on the back of the blower. I added a pillow block on the (new) outer end of the extended shaft for support. The plate steel surface made it easy to weld and bolt the necessary parts right where I needed them. I also had to weld a piece of angle iron to the back of my mounting plate to keep the blower, which was heavy on one end, from oscillating - the DR Field and Brush Mower is designed to oscillate with uneven ground and I used the same mounting system. The drive belt now comes from the horizontal drive pulley to the vertical driven sheave with a 1/4 twist.

I also needed a bracket to hold the upper end of the discharge chute rotation handle so I cut and welded a couple of pieces of the 1 1/2" tubing together at the correct angle, then used hose clamps to attach them to the handlebar assembly. A hole drilled through the tubing lets me remove-or-replace the chute handle very easily, just like a factory assembly.

One of the principal goals I wanted to achieve was adaptability without any change to the basic machine, and exchangeability without hassle. I can change from blower to mower or back in a matter of about 15-20 minutes and because I didn't change any of the original parts on the DR there is no loss of integrity.

I am happy to report that my 12.5 hp, 36" blower moves compacted snow without even breathing hard while in third gear. I've got about 4 trouble-free hours on the machine now and am convinced it will last a long time.

Now I've got a two-season machine that works great - and I've got my snowblower! I proved that if you want something bad enough, and have the right tools, materials and some time, you can do just about anything!

This project has been published to show how individuals used their ingenuity for their own needs, convenience and enjoyment. Only limited details are available and the projects have NOT been engineered by the Lincoln Electric Company. Therefore, when you use the ideas for projects of your own, you must develop your own details and plans and the safety and performance of your work is your responsibility.

www.lincolnelectric.com

Fifty-Five Gallon Drum Dolly

From Arc Welded Projects, Volume III
The James F. Lincoln Arc Welding Foundation

If you have ever considered building a fifty-five gallon drum dolly, here is a simple set of plans developed by a competitor in one of the past James F. Lincoln Arc Welding Foundation School/Shop Award programs. So, gather up your materials, practice your welding skills and jump in!

Bill of Materials

Part No.	Part Name	Material	Qty.
1	Rolled Circle	Flat steel 2" x 1/4" x 76"	1
2	Vertical diameter	Flat steel 2" x 1/4" x 24"	1
3	Horizontal diameter	Flat steel 2" x 1/4" x 11"	2
4	Caster Supports	Steel pipe 1" dia. x 3" long	4
5	Caster Support Covers	Steel rod 1" dia. x 1/8" thick	4
6	Colson casters	Self-locking wheels 3-1/2" dia.	4

This design project when completed will support a fifty-five gallon metal drum, in a vertical position on four equally spaced casters, which will make the drum mobile, thus, making it easy to move when it is full of waste engine oil.

The first step in the assembly of the drum dolly is to take a length of 2" wide by 1/4" thick, by 76" long flat steel and mechanically roll it into a 24" diameter circle. Then, where the ends meet, tack them together leaving a 1/8 gap, then make a full penetration butt weld, thus, making the circle complete.

Position circle on flat table with the 1/4" side down.

Next, lift up circle slightly and slide 2" by 1/4 by 24" flat steel under circle, so that the circle supported at top and bottom of its diameter. This flat steel should have the 2" side flat down on the table, thus raising the circle 1/4".

Next, slide 2" wide by 1/4 by 11" length of flat steel from left to right to form half of the circle's horizontal diameter, (allow 1/8" gap at center for weld).

Then, slide 2" by 1/4 by 11" length of flat steel from right to left to form the other half of the horizontal diameter (allow 1/8 gap at center for weld).

Use a small square and rule to equally space the vertical and horizontal diameter now created by the flat steel supports.

Weld the vertical 2" by 1/4 by 24" length of flat steel at both ends of the circle. Then, weld the horizontal pieces of flat steel into position.

Position the caster supports at the ends where the horizontal and vertical supports meet the outside of the circle. These pieces of pipe must be in a vertical position. Weld both sides of pipe at all four stations around circle.

Cut four slices off a solid 1" diameter steel rod 1/8" wide and weld each on top of the four 3" pieces of pipe. These act as cosmetic covers for the wheel assembly, and are called caster support covers.

Remove slag, grind and paint, insert Colson casters into 1" diameter pipe from the bottom. Casters are self-locking and will tighten into the 1" diameter. The design project is now completed.

This project has been published to show how individuals used their ingenuity for their own needs, convenience and enjoyment. Only limited details are available and the projects have NOT been engineered by the Lincoln Electric Company. Therefore, when you use the ideas for projects of your own, you must develop your own details and plans and the safety and performance of your work is your responsibility.

www.lincolnelectric.com

Fireplace Door

FIREPLACE DOOR MATERIAL LIST (For 34” x 22-1/2” opening)

Curved flat spring 1/2” x 4”	1
Angle iron 3/4” x 3/4” x 1/8”	26 ft.
Copper strip 1/2” x 4” x 1/16”	2 ea.
Piano hinge 1/2” x 22” (brass, stainless)	2 ea.
Tempered glass 1/4” x 7” x 21-1/4”	4 ea.
Sheet metal strip 1-1/2” x 26 GA.	19 ft.
Right angle clamps 1/2” x 16 GA. or 1/16”	24 ea.
Flat head machine screws 1/8” x 1/4”	24 ea.
Phillips head machine screws 1/8” x 5/8” w/nuts	24 ea.
Mild steel round stock 1/4” and 1/2”	2” ea.

ASSEMBLY INSTRUCTIONS

1. Measure and cut the angle iron at 45 degrees for all doors.

2. Assembly each door frame, make sure all corners are absolutely square and in the same plane.

3. Clamp and tack weld each corner. Check for square again and finish the welds.

4. Grind smooth any area that will hinder the sheet metal holding the glass from fitting flush against the angle iron or any part of the weld that will not allow the frames to fit snugly together at assembly.

5. Center punch and bore holes in the face of the frames that will hold the glass frame clamps. Make sure there is clearance for the glass and frame.

6. Can be primed now. Align piano hinge to edges of door frame and center punch. Bore and tap, or use self-tapping flat head screws. The heads must be countersunk for the doors to close flush.

7. Assemble hinges to frames and check to be sure all frames fit together snugly and squarely.

8. Place completed frame work in opening. C clamp center together and determine best location. Mark hearth on both sides of hinge ends. Locate center of 1/2” circle on hearth that is equidistant from sides and ends.

9. Using masonry bit, bore 1/2” holes in hearth approx. 3/8” deep.

10. Measure depth of holes & cut a section from 1/2” round rod that will be approx. 1/8” above hearth when installed or what will allow smooth folding of doors.

11. Locate center of flat ends of cut rod and bore holes thru them for 1/4” pins.

12. Center these bearings on bottom of hinge ends in line with side edge of door & mark center of hole.

13. Center punch & bore 1/4” hole thru 3/4” frame. (both ends)

14. Repeat steps 12 & 13 for tops of hinge doors.

15. Cut 2 pieces 1” long from 16d nail. Bend one end of each approx. 1/4” from end @ 45 deg.

16. Weld other ends to bottom inside vertical edge of center doors so that it doesn’t drag on 3/4 angle behind doors and doesn’t interfere with flush closing of doors.

17. This step can be eliminated if one wishes to attach the glass directly to the door frames. This will result in greater glass breakage however. Otherwise, measure and cut the 26 GA. 1-1/2” metal strips to length. Form a “U” that will snugly slip over the edge of the glass-trim with aviation snips to form matching 45 deg. angles each piece.

18. Cut 24 1-1/4” pieces from 1/2” wide by 16 GA. or 1/16” stock & bend at right angles-one side being the same length or slightly less than the thickness of the sheet metal trim around glass.

19. Center punch and bore 1/8” hole thru other side so that the bolts thru face of frames will line up with edge of sheet metal holding glass.

20. Cut 4 pieces approx. 3/8” long from 1/4” mild round stock (or could use soft bolt)

21. Place all four frames in opening. C clamp together at center & put a 1/4” pin in each hole on bottom fitting it into the hole in bearing (you may have to place a spacer under pin to it will extend up in to the door frame).

22. Plumb face of doors and hold in place. Use lipstick or other marking paint on end of other pins and push thru top holes to mark holes in angle holding masonry. Center punch and drill holes for 1/4” pins.

23. Place pins thru upper holes into pivot holes. Tack weld or otherwise support while releasing C clamp at center and checking operation of doors. Adjustment may be necessary.

24. If doors fold OK, tack weld each pin inside door frame.

25. Cut length of 3/4 angle to match width of opening. Both top and bottom.

26. Close doors-align 3/4 angle with top inside of doors. Drill and attach as necessary.

27. Attach spring strip to bottom 3/4 angle at center either with a machine screw thru hole punched thru spring or if unable to do that use wire to pull a depression in the spring so that it will remain in place when doors are closed. If a wire is used, two small holes will have to be drilled thru the 3/4 angle and the wire anchored in front.

28. Bend copper strips to form handles-turn under approx. 1/2” on each end for attaching. Attach with blind rivets. Be sure that the rivet will not interfere with glass.

29. Install glass using clamps made (item 19).

30. Install decorative strips (should be a right angle to hide both edge of folding door and to allow area to force rock wool behind to make it more air tight).

31. If desired, tightly clamp doors at upper center and bore hole between for damper control shaft and finish painting. (Both should be done BEFORE installing glass however.)

Blueprint Drawings

Fireplace Door Blueprints

SAFETY FIRST

Ventilation
It is important to use enough ventilation to keep the fumes and gases from your breathing zone. For occasional welding in a large room with good cross-ventilation, natural ventilation may be adequate if you keep your head out of the welding fumes. However, be aware that strong drafts directed at the welding arc may blow away the shielding gas and affect the quality of your weld. In planning your workshop ventilation, it is preferable to use ventilation that pulls fume from the work area rather than blows necessary shielding gas away.

Electric Shock
Remember, electric shock can kill. Wear dry, hole-free leather gloves when you weld. Never touch the electrode or work with bare hands when the welder is on. Be sure you are properly insulated from live electrical parts, such as the electrode and the welding table when the work clamp is attached. Be sure you and your work area stay dry; never weld when you or your clothing is wet. Be sure your welding equipment is turned off when not in use. Note that Lincoln wire feed / welders have a relatively low open circuit voltage and include an internal contactor that keeps the welding electrode electrically 'cold' until the gun trigger is pressed. These important safety features reduce your risk of electric shock during any welding project.

Arc Rays
It is essential that your eyes are protected from the welding arc. Infrared radiation has been known to cause retinal burning. Even brief unprotected exposure can cause eye burn known as 'welder's flash'. Normally, welder's flash is temporary, but it can cause extreme discomfort. Prolonged exposure can lead to permanent injury.

Workspace - Protection from Sparks
Before you get started on any welding project, it is important that you make sure your work area is free of trash, sawdust, paint, aerosol cans and any other flammable materials. A minimum five-foot radius around the arc, free of flammable liquids or other materials, is recommended. Extra care should be taken in workshops that are primarily used for woodworking as sawdust can collect inside machines and in other hard to clean spaces. If a spark finds its way into one of these sawdust crannies, the results could be disastrous. If your shop area is too small to allow for a safe radius, please use an alternate area like a garage or driveway.

Gas Cylinders
Cylinders can explode if damaged. Always keep your shielding gas cylinder upright and secured. Never allow the welding electrode to touch the cylinder.

Safety Equipment

It is also imperative to make sure you have all the necessary safety equipment and that you're wearing welding friendly clothes. You should wear:

• Welding gloves - dry and in good condition
• Safety glasses with side shields
• Protective welding shield with a dark lens shade appropriate for the type of welding you do
• Head protection - like a fire retardant cotton or leather cap
• Long-sleeve cotton shirt
• Long cotton pants
• Leather work boots

A fire extinguisher should also be on hand during any welding.

Also, make certain no children are in the area when you are welding. They may watch the arc and can experience retinal damage from its intense light. There is also a risk of a child getting burned by welding spatter.

Finally, see the instruction manual for your welder for added safety information. You can also visit the following web pages for added information on safety.

Welding Safety
http://www.lincolnelectric.com/community/safety/
Material Safety Data Sheets
http://www.lincolnelectric.com/products/msds/

This project has been published to show how individuals used their ingenuity for their own needs, convenience and enjoyment. Only limited details are available and the projects have NOT been engineered by the Lincoln Electric Company. Therefore, when you use the ideas for projects of your own, you must develop your own details and plans and the safety and performanc

Hay Feeder

By Don Dewerff and John Frazier
Instructed by Paul Stevenson, Kansas State University, Manhattan, KS
From Arc Welded Projects, Volume II
The James F. Lincoln Arc Welding Foundation

If you have ever considered building a hay feeder, here is a simple set of plans developed by a competitor in one of the past James F. Lincoln Arc Welding Foundation School/Shop Award programs. So, gather up your materials, practice your welding skills and jump in!

The feeder is built on skids so it can be easily pulled from plate to place in a cow lot. The actual length is 19' 7". All the pipes were welded in the Tee position for added strength. This required much cutting to form each joint. Identical sides were made.

After forming and welding the side portions together, the braces or center pieces were welded to the sides. Metal clamps were used to help hold the pipes together while tacking. The pipes were positioned so the water does not remain in the pipes when it rains. The best way to keep water out is to cover the ends of the pipes or lay one pipe on top of the next at a 90º angle and weld.

The end section was made to swing open and closed as it was moved in the field. The strap iron was heated and bent around the two-inch pipe. This iron serves as a mounting bracket for the 2 x 10's which fit on each end of the feeder.

Strap iron 2-1/2" was welded to the center and end braces for a mount to bolt boards to. Rods were diagonally spaced at 14" intervals to reduce hay loss. A slightly wider space is recommended for dairy cows - perhaps 16".

Holes were cut in the pipes for inserting the rod instead of just welding the butt end of the rod to the pipe. The feeder was painted with a rust preservative. The 2 x 10's were bolted in place with 3/16" carriage bolts and the feeder was ready for use.

This project has been published to show how individuals used their ingenuity for their own needs, convenience and enjoyment. Only limited details are available and the projects have NOT been engineered by the Lincoln Electric Company. Therefore, when you use the ideas for projects of your own, you must develop your own details and plans and the safety and performance of your work is your responsibility.

www.lincolnelectric.com

Joining aluminum with GTAW: Advice for the novice

By Mike Sammons, Contributing Writer

Aluminum is a real challenge to weld, especially for beginners. A knowledge of the gas tungsten arc welding equipment that is available to do the job as well as required accessories, preparation tips, and proper techniques is a good thing to have before jumping in.

Aluminum: beautiful, lightweight, strong, versatile—and a real challenge to weld, especially for beginners. This article describes some of the new gas tungsten arc welding (GTAW) equipment available and its benefits, accessories required, points to consider before welding, and the techniques required to make a good weld bead.

In general, GTAW power sources with an AC/DC output come in four categories, which are listed here in order of lowest to highest price:

GTAW Power Sources

1. Light fabrication. Machines designed for light fabrication usually have an AC output from 20 to 165 amps. While they don't incorporate a square wave output or balance control technology, they do produce an arc suitable for a variety of work, including applications for the home hobbyist.

2. Light industrial, maintenance/ repair, metal fabrication. This newer class of light-industrial machine provides about 15- to 180-AC output and a professional-quality arc. Key features include a square wave output, a fixed balance control set for more penetration than cleaning (a 60/40 electrode negative [EN] to electrode positive [EP] ratio works best for most applications), built-in high-frequency starting for positive starts without arc wandering, and a built-in stabilizer for a more consistent arc while welding.

3. Industrial production, fabrication, aerospace, repair. Industrial-production GTAW power sources can have a square wave output with an adjustable balance control. Greater amounts of EN create a deeper, narrower weld bead and better joint penetration. Greater EP values remove more oxide and create a shallower, wider bead. Transformer-rectifier GTAW machines can adjust EN values from 45 to 68 percent.

Machines are available with a variety of outputs, typically rated at 250, 350, and 500 amps with a 40 or 60 percent duty cycle. The low-end amperage range listed for these machines usually is 5, 3, or 25 amps, respectively.

4. Inverter-based AC. Also considered an industrial power source, an inverter gives the professional welder more capability to tailor the width, depth, and appearance of the weld bead for an application.

Inverters can adjust EN duration from 50 to 90 percent. Adding more EN to the cycle may increase travel speed by as much as 20 percent, narrow the weld bead, achieve greater penetration, allow use of a smaller-diameter tungsten to direct the heat more precisely or to make a narrower weld bead, and reduce the size of the etched zone for improved cosmetics.

Operators can adjust the welding output frequency in the range of 20 to 250 hertz. Increasing frequency produces a tight, focused arc cone. This narrows the weld bead, which helps when welding in corners, on root passes, and fillet welds. It also permits faster travel speed on some joints. Decreasing output frequency produces a broader arc cone, which widens the weld bead profile and provides greater cleaning action.

GTAW inverters accept single- or three-phase, 50- or 60-hertz, 230- or 460-volt input power. This provides flexibility when moving the machine between job sites or around a large facility. Using three-phase power and welding at 300 amps (460 volts primary), an AC/DC GTAW inverter requires only 18 amps of primary current. A 5- to 300-amp AC/DC GTAW machine weighs about 90 pounds.

Accessories

If most welding is done at 200 amps or less, an air-cooled torch works well. For welding above 200 amps, a water-cooled torch should be considered. For portability, water coolers can be mounted on wheeled carts that also carry the power source and gas bottles.

Remote control capabilities usually include current (amperage) and contactor control (the contactor keeps the torch electrically cold until energized and starts and stops the gas flow to the torch). The most popular remote control is a foot pedal that operates much like an auto's gas pedal—the more it is depressed, the more amperage flows. Another type of control—one that affords greater mobility but is more difficult to learn—is a fingertip control, which is mounted on the torch.

If most work is done on a bench or around structures that permit mobility, the foot pedal remote control probably is a better option because it's easier to use. Conversely, if most work is done in awkward positions, a fingertip control may be the better choice.

Before Welding Starts: Steps 1-4

The following steps and suggestions address the basic areas of GTAW setup. However, they are no substitute for carefully reading the operator's manual, watching instructional videos, and following safety precautions such as wearing protective gloves and glasses.

1. Determine amperage requirements. Each 0.001 inch of metal to be melted requires about 1 amp of welding power. For example, welding 1/8-inch aluminum requires about 125 amps.

2. Select the correct current. AC should be used for aluminum, magnesium, and zinc die cast. When exposed to air, these metals form an oxide layer that melts at a much higher temperature than the base metal. If not removed, this oxide causes incomplete weld fusion.

Fortunately, AC inherently provides a cleaning action. While the EN portion of the AC cycle directs heat into the work and melts the base metal, the EP portion—where current flows from the work to the electrode—blasts off the surface oxides.

3. Use the right gas. Usually, pure argon is employed, although thicker weldments may require an argon/helium or other specialty mix. If the wrong gas is used, the tungsten immediately will be consumed or deposited in the weld puddle.

4. Set the proper gas flow rate. More is not better, so 15 to 20 cubic feet per hour (CFH) should suffice. Argon is about 1-1/3 heavier than air. When used to weld in a flat position, the gas naturally flows out of the torch and covers the weld pool. For overhead welding, the gas flow rate should begin at 20 CFH, and small increments of 5 CFH can be made, if necessary.

In any position, if the gas flows out at too high a velocity, it can start a swirling motion parallel to the torch cup, called a venturi. A venturi can pull air into the gas flow, bring in contaminating oxygen and nitrogen, and create pinholes in the weld. Unfortunately, some operators automatically increase the gas flow when they see a pinhole, worsening the problem.

Before Welding Starts: Steps 5-12

5. Select the right type of tungsten. For AC welding, traditional practice calls for selecting a pure tungsten electrode and forming a ball at the end of it. This still holds true for most applications and welding with a conventional power source.

However, for making critical welds on materials thinner than 0.09 inch, or when using a GTAW power source with an adjustable frequency output, new recommendations call for treating the tungsten almost as if the weld were being made in the DC mode. A 2 percent-type tungsten (thorium, cerium, etc.) should be selected and ground to a point in the long direction, making the point roughly two times as long as the diameter. A 0.010- to 0.030-inch flat should be made on the end to prevent balling and the tungsten from being transferred across the arc.

With a pointed electrode, a skilled operator can place a 1/8-inch bead on a fillet weld made from 1/8-inch aluminum plates. Without this technology, the ball on the end of the electrode would have forced the operator to make a larger weld bead and then grind the bead down to final size.

6. Select the right diameter of tungsten. The current-carrying capacity of a tungsten is directly proportional to the area of its cross section. It also is a function of the amount of AC unbalance and the composition of the electrode. For example, a 2 percent thoriated, 3/32-inch (0.093-inch) tungsten has a current-carrying capacity of 150 to 250 amps, whereas a 2 percent thoriated, 0.040-inch tungsten has a 15- to 80-amp capacity.

There is no such thing as an all-purpose electrode, despite the reputation of the 3/32-inch electrode. Attempting to weld at 18 amps with a 3/32-inch electrode will create arc starting and stability problems; the current is insufficient to drive through the electrode. Conversely, attempting to use a 3/32-inch tungsten to weld at 300 amps creates tungsten "spitting"—the excess current causes the tungsten to migrate to the workpiece.

7. Avoid tungsten contamination. If the tungsten electrode becomes contaminated by accidentally touching the weld pool, welding must be stopped, because a contaminated electrode can produce an unstable arc. To break off the contaminated portion, the tungsten should be removed from the torch, placed on a table with the contaminated end hanging over the edge, and the contaminated portion struck firmly. The tungsten then should be resharpened.

8. Set the proper tungsten extension. Electrode extension may vary from flush with the gas cup to a distance equal to the cup diameter. A general rule is to start with one electrode diameter, or about 1/8 inch. Joints that make the root of the weld hard to reach require additional extension, although extensions farther than 1/2 inch may result in poor gas coverage and require a special gas cup.

9. Select the correct filler metal. The filler rod needs to be appropriate for the base metal in terms of type and hardness. It should be the same diameter as the tungsten electrode. The welder should refer to charts published by filler metal manufacturers detailing what filler to use for what base metal.

10. Select a high-frequency (HF) mode. For AC welding with transformer-rectifier-type machines, continuous HF typically is required to start and maintain the arc, which has a tendency to go out when the AC square wave travels through the zero amperage point. HF bridges the gap between the electrode and the work, forming a path for the current to follow.

Inverters require HF for arc starting only because they drive the arc through the zero point so quickly that the arc does not have a chance to go out. For this same reason, inverters produce much less arc flutter. They also offer a lift arc starting method that avoids the use of HF altogether.

11. Control HF emissions. High frequency interferes with computers, printed circuit boards, televisions, and other electronic equipment but is a necessary evil. It can be minimized by hooking the work clamp as close to the weldment as possible, keeping the welding torch and clamp cables close together (spreading them apart is like creating a big broadcast dish), and keeping the cables in good condition to prevent current leaks.

12. Set the balance control. There are no hard rules about setting balance control, but the typical error involves overbalancing the cycle.

Too much cleaning action (EP duration) causes excess heat buildup on the tungsten, which creates a large ball on the end. Subsequently, the arc loses stability, and the operator loses the ability to control the arc's direction and the weld puddle. Arc starts begin to degrade as well.

Too much penetration (or, more precisely, insufficient EP current) results in a scummy weld puddle. If the puddle looks like it has black pepper flakes floating on it, adding more cleaning action will remove these impurities.

Storage and Delivery

The often-overlooked storage tank area and the lines between the storage tank and the mixer are also important areas to consider.

In most applications, the gas supplier's equipment and piping responsibilities end at the final pressure regulator. For this reason, large portions of piping between the vaporizers and the mixer are a no-man's land regarding inspections. Quite often, malfunctioning relief mechanisms exist around storage tanks, such as tank fill valves that may not be completely closed off and/or may have packing and bonnet leaks. Even though maintaining these areas is not the customer's responsibility, the customer will pay for any gas losses occurring there.

Argon suppliers usually develop a good feel for their customers' consumption rates and develop a trend regarding the amount of liquid argon required to fill a tank to capacity based on the number of loads delivered over time. Any time a customer anticipates a significant drop in consumption, the supplier should be notified so that deliveries can be adjusted accordingly. The supplier also should be notified of any plant shutdowns that will last more that a few days because liquid argon must be stored at supercold temperatures to remain in its liquid state.

If a tank remains at or close to full for a long time, the liquid will absorb some heat, causing it to flash into a vapor. This causes pressure to build in the internal tank, resulting in the release of safety devices such as rupture disks or pressure relief valves. Should this occur, large amounts of gas can be released in a very short period of time. By matching storage tank levels to efficient consumption levels, the chances of pressure-related, inadvertent releases are greatly diminished.

Gas Suppliers and Services

Most suppliers of argon and other gases are concerned about the efficient and safe use of their product. Some provide applications programs, ongoing technical support, and training. While these suppliers perhaps understand the effects of various system inefficiencies more than most, their primary responsibility is to keep the customer supplied with a high-quality product. Because leaks and other system losses are the primary sources for contamination after delivery, suppliers often inform their customers of various types of system deficiencies that may exist, especially if the customer has lodged complaints about quality.

However, it usually is up to the user to correct system inefficiencies. Although some suppliers will provide limited or abbreviated services using their own personnel and resources, for a more thorough and cost-effective analysis, expert, professional, and nonbiased individuals in the field of piping and distribution system analysis should be consulted.

www.thefabricator.com

Advantages of plasma welding: Often-overlooked PAW offers speed and affordability

February 19, 2001

Plasma arc welding sometimes offers greater welding speed than gas tungsten arc welding at lower cost than laser beam welding.

Plasma arc welding (PAW) often is overlooked when a fusion welding process must be selected for high-integrity applications such as those found in the medical, electronics, aerospace, and automotive industries.

This process has been overlooked because it is more complex and requires more expensive equipment than other arc processes and because welders want increased welding speeds such as those found with laser beam welding (LBW). However, automotive manufacturers have turned to PAW for a number of applications, including body panels and exhaust system components.

Gas tungsten arc welding (GTAW), also known as tungsten inert gas (TIG) welding, is commonly used for high-quality welds at slower speeds, while LBW is often selected for higher-speed welding.

PAW sometimes offers greater welding speed than GTAW at lower cost than LBW, and it may be the most effective process for many applications. These include welding stainless steel expandable bellows, where PAW is more tolerant to joint misalignment than LBW and gives better penetration than GTAW; welding coated steels like those used in automotive exhaust systems; and welding in keyhole mode to make full-penetration welds in relatively thick material in a single pass.

Basics of PAW

PAW is an arc welding process that uses a nonconsumable tungsten or tungsten alloy electrode, much like GTAW.

The primary difference between these two welding processes is that in PAW, the electrode is recessed in a nozzle that serves to constrict the arc. Plasma gas is ionized in the constricting nozzle and exits the nozzle at high speed.

The plasma gas alone is not adequate to shield the molten weld pool from the atmosphere, so shielding gas is supplied around the plasma column, as with GTAW. The flow rate for the plasma gas is much lower than that of the shielding gas to minimize turbulenc

The conical shape of a gas tungsten arc requires that arc length control (ALC) or arc voltage control (AVC) equipment be used for automated welding to ensure consistent spot size and energy density.

The constricted arc in PAW results in a much more columnar-shaped arc. This minimizes the effect of arc length variation on energy density and minimizes the need for ALC or AVC.

Another advantage of recessing the electrode in a nozzle is that electrode contamination is minimized. An electrode can usually last for an entire production shift without needing to be reground.

Another unique feature of PAW is how the arc is initiated. High-frequency (HF) current typically is used to establish a pilot arc between the electrode and the copper nozzle. HF is turned off after the pilot arc is started. The pilot arc current usually is fixed at one level or can be set at one of two levels, typically somewhere between 2 and 15 amps.

For welding, the arc is transferred to the work, which becomes part of the electrical circuit. Because the arc is established prior to making a weld, welding arc starts tend to be very reliable.

The pilot arc remains on after welding is completed, and the torch is ready to make the next weld without needing additional HF. This can be beneficial when welding in automated applications in which electromagnetic noise from HF can interfere with computerized process controllers. One side effect of the pilot arc is that plasma torches must be water-cooled, even for low-current applications.

Operating Modes

There are three different operating modes for PAW that are determined by the welding current level. Microplasma welding current ranges from less than 0.1 amp to about 20 amps.

Medium-current plasma welding or melt-in-mode current typically ranges from 20 to 100 amps. High plasma welding current is greater than 100 amps and typically is done in keyhole mode, similar to LBW or electron beam welding (EBW).

The combination of high current and plasma gas flow creates a hole in the material, and molten metal flows behind the moving hole to create the weld bead. When welding in keyhole mode, the plasma gas flow rate must be controlled carefully to make a weld. A slightly higher flow rate will blow the molten metal away and result in cutting.

Advantages and Disadvantages

While PAW is not as fast as LBW (depending on the application and laser source, LBW may be five times faster than PAW) or EBW, the capital equipment costs for PAW are typically a small fraction of the cost of the high-energy density equipment.

One disadvantage of PAW is its greater heat input, which produces wider welds and heat-affected zones than LBW and EBW. This may result in more distortion and loss of mechanical properties.

However, PAW offers an advantage over these processes in tolerance to joint gaps and misalignment. Although the arc is constricted, the plasma column has a significantly larger diameter than the beams. Adding filler metal also is accomplished more easily with PAW than with LBW or EBW.

The main disadvantages of PAW compared to GTAW are that the equipment is more complex and costly, and the need for water cooling of the torch limits how small the torch can be made (GTAW torches may be gas-cooled and can be made to fit into smaller areas). Also, the narrow PAW arc is less tolerant to joint misalignment than the conical gas tungsten arc.

Microplasma offers an advantage over GTAW because a stable arc can be maintained at lower current levels. This was a driving force in the development of this process.

In the early 1960s, it was difficult to get a stable gas tungsten arc at much less than 15 amps. Microplasma proved capable of overcoming this limitation. GTAW has evolved considerably since then with claims of stable arcs at less than 1 amp.

But PAW has a lower current limit of roughly one-tenth that of GTAW. The low current capability, along with reliable arc starting, makes PAW suitable for many small precision welding applications, especially in the medical and electronics industries.

GTAW and LBW also are used in medical and electronics industries. GTAW is used for lower-volume applications because of the low cost of equipment and relative simplicity. LBW is used when higher-volume production can justify the expense, when heat input must be minimized, and when joint fit-up can be tightly controlled.

Using PAW in the medium current range in melt-in mode is similar to using GTAW, but the arc tends to be stiffer and less affected by changes in arc length with PAW.

This allows for longer arc lengths to be used, and that combined with the recessed electrode can make it easier to add filler metal when welding manually. Electrode contamination by the filler metal rarely occurs with PAW.

Melt-in mode PAW can be beneficial compared to GTAW in automated applications because of more reliable arc starts, longer electrode life, no need for AVC or ALC, and no electromagnetic noise from HF at the start of each weld.

PAW offers a significant advantage over GTAW in many applications that require high current. Making welds with PAW in keyhole mode can result in full-penetration welds in relatively thick materials in a single pass.

Compared to welding thicker sections with GTAW, keyhole PAW minimizes the need for costly joint preparation and reduces or eliminates the need for filler metal.

The high depth-to-width ratio of a keyhole plasma weld compared to a GTA weld also can greatly reduce angular distortion. This technique is best applied using automated equipment. The keyhole can be difficult to maintain during manual welding.

Most materials can be welded with PAW using direct current electrode negative (DCEN). DC welding current also can be pulsed to control penetration with both melt-in mode and keyhole mode.

Variable polarity plasma arc (VPPA) welding power sources enhance the joining of materials such as aluminum and magnesium. The VPPA square waveform can be tailored so that the electrode-positive portion of each cycle that cleans tenacious surface oxides can be balanced with the electrode-negative portion that provides more penetration.

Using PAW and GTAW Together

PAW also may be combined with GTAW in various ways for automated welding to optimize welding speed and weld quality.

One example of this is a research project for tube welding that was performed at the Edison Welding Institute (EWI) using three torches to make a single-pass weld.

The lead GTAW torch was used for preheating and edge preparation. A second PAW torch was operated in keyhole mode to provide full penetration. A GTAW torch was used as the trailing torch to smooth and shape the weld bead.

The material welded was 0.315-inch (8-millimeter) 304 stainless steel plate with sheared edges. Material of this thickness could not be welded with conventional GTAW in a single pass without edge preparation no matter how many torches were used.

Acceptable results were obtained using GTAW/PAW/GTAW without adding filler metal, but more consistent results were obtained when filler metal was added to the weld pool of the trailing torch. Wire feed speed was adjusted to control fill to get flush or slightly convex weld profiles.

To get the full benefit of PAW, robust welding procedures must be established, such as defining operating windows for welding parameters.

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Advantages of plasma welding: Often-overlooked PAW offers speed and affordability

February 19, 2001

Plasma arc welding sometimes offers greater welding speed than gas tungsten arc welding at lower cost than laser beam welding.

Plasma arc welding (PAW) often is overlooked when a fusion welding process must be selected for high-integrity applications such as those found in the medical, electronics, aerospace, and automotive industries.

This process has been overlooked because it is more complex and requires more expensive equipment than other arc processes and because welders want increased welding speeds such as those found with laser beam welding (LBW). However, automotive manufacturers have turned to PAW for a number of applications, including body panels and exhaust system components.

Gas tungsten arc welding (GTAW), also known as tungsten inert gas (TIG) welding, is commonly used for high-quality welds at slower speeds, while LBW is often selected for higher-speed welding.

PAW sometimes offers greater welding speed than GTAW at lower cost than LBW, and it may be the most effective process for many applications. These include welding stainless steel expandable bellows, where PAW is more tolerant to joint misalignment than LBW and gives better penetration than GTAW; welding coated steels like those used in automotive exhaust systems; and welding in keyhole mode to make full-penetration welds in relatively thick material in a single pass.

Basics of PAW

PAW is an arc welding process that uses a nonconsumable tungsten or tungsten alloy electrode, much like GTAW.

The primary difference between these two welding processes is that in PAW, the electrode is recessed in a nozzle that serves to constrict the arc. Plasma gas is ionized in the constricting nozzle and exits the nozzle at high speed.

The plasma gas alone is not adequate to shield the molten weld pool from the atmosphere, so shielding gas is supplied around the plasma column, as with GTAW. The flow rate for the plasma gas is much lower than that of the shielding gas to minimize turbulenc

The conical shape of a gas tungsten arc requires that arc length control (ALC) or arc voltage control (AVC) equipment be used for automated welding to ensure consistent spot size and energy density.

The constricted arc in PAW results in a much more columnar-shaped arc. This minimizes the effect of arc length variation on energy density and minimizes the need for ALC or AVC.

Another advantage of recessing the electrode in a nozzle is that electrode contamination is minimized. An electrode can usually last for an entire production shift without needing to be reground.

Another unique feature of PAW is how the arc is initiated. High-frequency (HF) current typically is used to establish a pilot arc between the electrode and the copper nozzle. HF is turned off after the pilot arc is started. The pilot arc current usually is fixed at one level or can be set at one of two levels, typically somewhere between 2 and 15 amps.

For welding, the arc is transferred to the work, which becomes part of the electrical circuit. Because the arc is established prior to making a weld, welding arc starts tend to be very reliable.

The pilot arc remains on after welding is completed, and the torch is ready to make the next weld without needing additional HF. This can be beneficial when welding in automated applications in which electromagnetic noise from HF can interfere with computerized process controllers. One side effect of the pilot arc is that plasma torches must be water-cooled, even for low-current applications.

Operating Modes

There are three different operating modes for PAW that are determined by the welding current level. Microplasma welding current ranges from less than 0.1 amp to about 20 amps.

Medium-current plasma welding or melt-in-mode current typically ranges from 20 to 100 amps. High plasma welding current is greater than 100 amps and typically is done in keyhole mode, similar to LBW or electron beam welding (EBW).

The combination of high current and plasma gas flow creates a hole in the material, and molten metal flows behind the moving hole to create the weld bead. When welding in keyhole mode, the plasma gas flow rate must be controlled carefully to make a weld. A slightly higher flow rate will blow the molten metal away and result in cutting.

Advantages and Disadvantages

While PAW is not as fast as LBW (depending on the application and laser source, LBW may be five times faster than PAW) or EBW, the capital equipment costs for PAW are typically a small fraction of the cost of the high-energy density equipment.

One disadvantage of PAW is its greater heat input, which produces wider welds and heat-affected zones than LBW and EBW. This may result in more distortion and loss of mechanical properties.

However, PAW offers an advantage over these processes in tolerance to joint gaps and misalignment. Although the arc is constricted, the plasma column has a significantly larger diameter than the beams. Adding filler metal also is accomplished more easily with PAW than with LBW or EBW.

The main disadvantages of PAW compared to GTAW are that the equipment is more complex and costly, and the need for water cooling of the torch limits how small the torch can be made (GTAW torches may be gas-cooled and can be made to fit into smaller areas). Also, the narrow PAW arc is less tolerant to joint misalignment than the conical gas tungsten arc.

Microplasma offers an advantage over GTAW because a stable arc can be maintained at lower current levels. This was a driving force in the development of this process.

In the early 1960s, it was difficult to get a stable gas tungsten arc at much less than 15 amps. Microplasma proved capable of overcoming this limitation. GTAW has evolved considerably since then with claims of stable arcs at less than 1 amp.

But PAW has a lower current limit of roughly one-tenth that of GTAW. The low current capability, along with reliable arc starting, makes PAW suitable for many small precision welding applications, especially in the medical and electronics industries.

GTAW and LBW also are used in medical and electronics industries. GTAW is used for lower-volume applications because of the low cost of equipment and relative simplicity. LBW is used when higher-volume production can justify the expense, when heat input must be minimized, and when joint fit-up can be tightly controlled.

Using PAW in the medium current range in melt-in mode is similar to using GTAW, but the arc tends to be stiffer and less affected by changes in arc length with PAW.

This allows for longer arc lengths to be used, and that combined with the recessed electrode can make it easier to add filler metal when welding manually. Electrode contamination by the filler metal rarely occurs with PAW.

Melt-in mode PAW can be beneficial compared to GTAW in automated applications because of more reliable arc starts, longer electrode life, no need for AVC or ALC, and no electromagnetic noise from HF at the start of each weld.

PAW offers a significant advantage over GTAW in many applications that require high current. Making welds with PAW in keyhole mode can result in full-penetration welds in relatively thick materials in a single pass.

Compared to welding thicker sections with GTAW, keyhole PAW minimizes the need for costly joint preparation and reduces or eliminates the need for filler metal.

The high depth-to-width ratio of a keyhole plasma weld compared to a GTA weld also can greatly reduce angular distortion. This technique is best applied using automated equipment. The keyhole can be difficult to maintain during manual welding.

Most materials can be welded with PAW using direct current electrode negative (DCEN). DC welding current also can be pulsed to control penetration with both melt-in mode and keyhole mode.

Variable polarity plasma arc (VPPA) welding power sources enhance the joining of materials such as aluminum and magnesium. The VPPA square waveform can be tailored so that the electrode-positive portion of each cycle that cleans tenacious surface oxides can be balanced with the electrode-negative portion that provides more penetration.

Using PAW and GTAW Together

PAW also may be combined with GTAW in various ways for automated welding to optimize welding speed and weld quality.

One example of this is a research project for tube welding that was performed at the Edison Welding Institute (EWI) using three torches to make a single-pass weld.

The lead GTAW torch was used for preheating and edge preparation. A second PAW torch was operated in keyhole mode to provide full penetration. A GTAW torch was used as the trailing torch to smooth and shape the weld bead.

The material welded was 0.315-inch (8-millimeter) 304 stainless steel plate with sheared edges. Material of this thickness could not be welded with conventional GTAW in a single pass without edge preparation no matter how many torches were used.

Acceptable results were obtained using GTAW/PAW/GTAW without adding filler metal, but more consistent results were obtained when filler metal was added to the weld pool of the trailing torch. Wire feed speed was adjusted to control fill to get flush or slightly convex weld profiles.

To get the full benefit of PAW, robust welding procedures must be established, such as defining operating windows for welding parameters.

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The fundamentals of gas tungsten arc welding: Preparation, consumables, and equipment necessary for the process

By Larry D. Smith, Contributing Writer

February 19, 2001

Learning the fundamentals of the GTAW process will increase the welder's ability to produce quality weldments. Knowing the correct consumables, equipment, and preweld preparation necessary will help the welder troubleshoot welding problems.

Gas tungsten arc welding (GTAW) is an electric arc welding process that produces an arc between a nonconsumable electrode and the work to be welded. The weld is shielded from the atmosphere by a shielding gas that forms an envelope around the weld area (see Figure 1).

Figure 1: The GTAW process is versatile and can be used on ferrous and nonferrous metals. An arc is produced between a nonconsumable electrode and the work to be welded. The weld is shielded from the atmosphere by a shielding gas that forms an envelope around the weld area.

GTAW is versatile and can be used on ferrous and nonferrous metals and, depending on the base metal, in all welding positions. The process can be used to weld thin or thick materials with or without a filler metal.

When welding thinner materials, edge joints, and flange, filler metals are not used. For thicker materials, an externally fed filler wire is generally used. The type of filler metal wire to be used is based on the chemical analysis of the base metal. The size of the filler metal wire depends on the thickness of the base metal, which usually dictates the welding current.

The methods of operation for GTAW can be manual or automatic.

Welding Procedure Variables and Joint Configurations

Welding procedure variables control the welding process and the quality of the welds produced. Joint configuration is determined by the design of the weldment, the metallurgical analysis, and by the process and procedure required by the weldment.

Welding variables are selected after the base metal, filler metal, and joint configuration have been selected. The fixed welding variables include the type of filler metal, electrode type and size, the type of current, and the type of shielding gas.

The adjustable variables control the shape of the weld by affecting things such as bead height, bead width, penetration, and weld integrity. The primary adjustable variables for GTAW are welding current, arc length, and travel speed.

Secondary variables also aid in controlling the welding process, but it is more difficult to calculate the extent of effect. The secondary variables include work and travel angle and the distance the electrode extends beyond the end of the cup.

Tungsten Electrodes

The electrode material for GTAW is made from a tungsten alloy. Tungsten has one of the highest melting temperatures of any metal, about 6,170 degrees Fahrenheit (3,410 degrees Celsius).

The size of an electrode to be used is determined by the welding current required. Larger electrodes permit higher currents to be used. Smaller diameter electrodes may be used for welding thinner materials or while welding out of position.

Following is a list of various types of tungsten alloys used:

1. Pure tungsten is used on nonferrous metals, such as aluminum and magnesium, and is typically used with a balled-end preparation on alternating current (AC) (see Figure 2).

Figure 2: Pure tungsten is typically used with a balled-end preparation.

2. Thoriated tungsten is the most common type of tungsten electrode for use on carbon and stainless steel. It can be purchased with 1 or 2 percent thorium. The thoriated tungsten starts readily and maintains a stable arc. It has a greater resistance to contamination and will maintain a sharp point and will not break down as readily as pure tungsten.

3. Zirconiated tungsten is typically used for welding with higher AC currents on nonferrous metals.

Preparing a point or using an electrode taper angle applies to thoriated tungsten. Thoriated tungsten electrodes are ground to a point to give better arc starting, with high frequency added. This provides the arc ignition and keeps the electrode from contacting the work. It also aids in stabilizing the arc.

The degree of taper affects the shape and amount of penetration of a weld. To reduce the number of times the electrode must be sharpened, the welder needs to develop the skill of not touching the tungsten to the work during the welding process. The recommended taper length is 21/2 to 3 times the diameter of the electrode (see Figure 3).

Figure 3: Proper electrode tip preparation is essential for achieving proper weld penetration.

Shielding Gases

Argon and helium are the two most commonly used shielding gases used for GTAW. The characteristics most desirable for shielding purposes are the chemical inertness of the gases and their ability to produce smooth arc action at high currents. Both gases are inert, causing an ionization effect in the welding arc. They protect the tungsten electrode and the molten weld pool from the atmosphere.

Gas purity affects a weld. Metals will withstand small amounts of impurities, but, for the best results, the percent of inert gas used should be at least 99.9 percent pure.

Argon is heavier than helium and may be supplied in liquid or gaseous form. Argon provides for good cleaning action. The flow rates are determined by the size of the tungsten and the gas cup diameter. Argon is suitable for welding similar and dissimilar metals and works well while welding in the vertical and overhead welding positions.

Helium is a lighter inert gas. It can be distributed as a liquid, but is used more often as a compressed gas. It leaves the weld area faster than argon, and higher flow rates are necessary when using it.

Helium produces a narrow but deep heat-affected zone (HAZ), which is good for welding on heavier metals. It is suitable for welding at high speeds and gives good coverage in vertical and overhead welding positions. It helps to increase the penetration, and when used as a back purge, it tends to flatten the pass of the weld bead. Helium is suitable for use on thicker nonferrous metals.

Argon and helium mixtures are used when welders need the control of the argon and the penetration of the helium. This mixture is not necessary when welding plain carbon steels.

Typical mixtures vary, depending on the application. It is often used for automatic welding applications.

Argon and hydrogen mixtures are often used for welding of stainless steel, INCONEL®, and MONEL®. This mixture should not be used when welding plain carbon steels. The typical mixture is a 95 percent argon and 5 percent hydrogen.

Nitrogen can also be used as a shielding gas, but is rarely used because of its higher current requirements. It is suitable for welding copper.

Welding Current, Joint Design

The current depends primarily on the type of metal to be welded, the current levels required, and the availability of the machine that produces that type of welding current.

Direct current electrode positive (DCEP) (reverse polarity) is sometimes used to weld very thin nonferrous metals, and is also used for balling the tungsten electrode. Direct current electrode negative (DCEN) (straight polarity) is used most commonly to weld stainless steel and ferrous metals.

AC current, with the addition of high frequency, is most commonly used for welding some nonferrous metals such as aluminum and magnesium. It provides good cleaning action and gives moderate penetration.

Weld Joint Design

The five basic types of joints are the butt joint, the corner joint, the edge joint, the lap joint, and the tee joint (see Figure 4). Of the five types of joint designs, the butt and the tee joint are the most commonly used.

Figure 4

The strength of a weld joint is another factor contributing to weld joint design. Weld joints can be either partial or full penetration, depending on the strength required of the joint. Weld joint design or weldment configuration for GTAW is determined by the type of metal, configuration of the weldment, designated codes and specifications, and the metallurgical analysis. Several factors influence the joint design to be used, including the strength required, the welding position, the metal thickness, and how accessible the joint is to the welder.

The purpose of any joint design is to produce a sound weld deposit with the desired properties as economically as possible. The edge and joint preparation are important because they will affect both the quality and the cost of welding.

Preweld Preparations

Before using GTAW, several steps must be taken to prepare the electrode and the weld joint, fixture the weldment, set the variables, and preheat the base metal, if necessary. The amount of preparation depends on the size of the weldment, type of base material, fit-up, and the quality requirements.

Electrode Preparation. Electrode preparation depends on the type of electrode and the welding application. The tip may have a ground point or a ball end for welding with AC.

To prepare an electrode with a point, the grind marks should run parallel to the electrode.

To prepare a ball on the end of a tungsten, the power supply must be switched to DCEP (reverse polarity). Then, after starting the arc between the electrode and a piece of scrap metal or copper, it must be maintained at a moderate current level. The tip of the ball should be perfectly clean, shiny, and have a mirror-like finish.

Preparing the Weld Joint. When preparing the weld joint, several different methods can be used, including oxyfuel cutting, plasma cutting, shearing, machining, air carbon arc gouging, grinding, or chipping. Remember, preparing the weld joint properly will help produce a sound weldment and meet the requirements of quality standards for welding.

Cleaning. Cleaning the material to be welded is important. GTAW welds are often susceptible to contamination during welding. The surface to be welded must be free from oil, grease, paint, dirt, oxides, and other foreign material.

Aluminum has an oxide coating that, if not removed, will contaminate the weld area. Cleaning solutions, wire brushes, grinders, and abrasive blasting are some of the methods used to remove these contaminants.

Fixturing and Positioning. Fixturing and positioning will also affect the shape, size, and uniformity of a weld. Fixtures hold the weldment in place while controlling distortion, helping to locate and maintain parts in their position relative to the weldment.

When fixturing is employed, it can reduce the time for welding. Positioning will help move the weldment into a flat position to improve productivity for the welder.

Chill blocks, heat sinks, or backing bars may be used when welding some metals to prevent burn-through, reduce base material temperatures, or to minimize distortion.

Preheating. Depending on the alloying elements in the base material, the thickness of the steel, and the configuration of the joint, preheat is sometimes needed. The amount of preheat needed for a given application is usually obtained from the welding procedure. Several methods of controlling preheat temperature are available, including furnace heating, electric induction coils, oxyfuel torches, and resistance heating blankets.

The preheat temperature can be measured using temperature sticks, crayon pellets, temperature indicators, thermocouples, thermistors, or infrared thermometers.

Conclusion

Learning the fundamentals of the GTAW process will increase the welder's ability to produce quality weldments. Knowing the correct consumables, equipment, and preweld preparation necessary will help the welder troubleshoot welding problems.

Having a good understanding of the GTAW process will help the welder make wiser choices when choosing filler metals, tungsten electrodes, and shielding gases. The welder will also be able to choose the correct type of equipment based on the welding application when welding carbon steel, stainless steel, or nonferrous metals. Preweld preparation is also essential to producing sound weldments.

Another essential skill for a welder in producing quality work is getting the correct training for various applications, and practicing those learned skills necessary for quality workmanship.

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Advanced variable-polarity plasma arc welding

Using the process for welding aluminum tailor-welded blanks

By John Micheli and Chris Pilcher, Contributing Writers
November 29, 2000

This article examines variable-plasma arc welding and its uses in the welding of tailor-welded blanks.

Figure 1
The PAW process is a hybrid method of GTAW. Both methods use a tungsten electrode, but their torches are different. The electrode in a PAW torch is surrounded by a copper nozzle with a constricting orifice.

Automotive companies are struggling to produce more fuel-efficient vehicles capable of meeting new stringent corporate average fuel economy (CAFE) requirements. These environmentally friendly modes of transportation range from battery-powered to fuel cell and cleaner petroleum-burning vehicles.

Shedding weight is a major contributor to achieving these goals; therefore, aluminum is being used more in the manufacture of automotive inner and outer body components in addition to its more traditional role in castings and forgings. Many companies are struggling with manufacturing aluminum-alloy (AA) tailored-welded blanks (TWB), and no joining process has evolved as a leading technology in this process.

A method that has received very little attention is variable-polarity plasma arc welding (VP-PAW). This method of welding is a proven form of welding AA under difficult and demanding applications, such as the manufacture of many aluminum components including cryogenic fuel tanks for the space shuttle and other commercially available launch vehicles.

Variable-polarity PAW is also used in the manufacture of automotive air-conditioning components, with thousands of parts produced daily. Using this method with a proper weld schedule and part preparation can produce X-ray-quality welds consistently. In addition, the weld bead profile produced with VP-PAW enhances the material flow characteristics of the aluminum, producing the optimal weld bead profile for forming AA TWBs.

This article discusses the metallurgical considerations that must be addressed before welding AA. This is followed with a description of VP-PAW and its range of applications for other forms of transportation. The article concludes with some results of work performed in the manufacture of productionworthy AA TWBs.

Metallurgical Considerations

The metallurgical characteristics of the aluminum (see Table 1) alloy to be used in a tailor-welded blank must be considered. In short, weldable and nonweldable grades of aluminum can be categorized as heat treatable or strain hardenable. The heat-treatable grades can be welded but require an alloy filler to prevent cracking on solidification.

Table 1
Aluminum alloys traditionally come in weldable and nonweldable grades.

Another characteristic of aluminum is its susceptibility to oxidation. Aluminum readily forms oxides, which makes it difficult to weld. The oxides are trapped in the weld pool, forming inclusions and producing weak joints prone to failure. Oxides typically are removed by one of the following three methods used in variable-polarity welding: chemical etch, mechanical grindings or cathodic etch.

Aluminum alloys also are susceptible to porosity during welding. Porosity generally is produced when the weld pool absorbs hydrogen. The solubility of hydrogen in aluminum is very high in the molten state and requires good gas coverage to provide a protective environment. Common sources of hydrogen are water in the form of moisture on the metal surface, shield gas leaks, and water stains. Oil and other lubricants also act as hydrogen sources.

Defining Variable-polarity Plasma Arc Welding

Plasma arc welding is a hybrid method of GTAW. Both methods use a tungsten electrode, but their torches are different. The GTAW arc is bell-shaped, unlike the highly focused, strong arc produced with a PAW torch.

The electrode in a PAW torch is surrounded by a copper nozzle with a constricting orifice (see Figure 1, top of page ). Initiating an arc requires two power supplies — a pilot supply connected between the electrode and the nozzle and one to provide the current between the electrode and the workpiece.

When the pilot current is activated, an arc is established between the electrode and the orifice. The stream of gas is ionized and forms a plasma plume called the pilot arc. The welding arc, or transferred arc, occurs when the main power supply is activated, and it establishes a current path through the ionized gas from the electrode to the workpiece.

Figure 2
Typical waveforms needed for welding 6-mm aluminum alloys are illustrated here

The arc produced by the plasma torch is stiff and provides directional stability of the plasma jet. The highly focused arc is less susceptible to magnetic fields and arc wandering. High current densities and energy concentration produce a constricted arc that allows welds with deeper penetration and a small heat-affected zone (HAZ). More important, the arc also is less susceptible to arc gap variations or standoff distance, making it more desirable for the manufacturing production environment.

A PAW power source with variable polarity allows the current waveform to be fine-tuned. The polarity of the arc can be switched and controlled by varying the amounts of direct current electrode negative (DCEN), or straight polarity, and direct current electrode positive (DCEP), or reverse polarity.

These variable-polarity parameters are programmed in the power supply to produce the most effective VP-PAW weld. The example shown in Figure 2 demonstrates a typical waveform and variable-polarity welding parameters required when welding a 6-millimeter-thick aluminum alloy.

Figure 3
The two types of electrode polarity that produce variable polarity are known as straight and reverse polarity.

As mentioned previously, aluminum has a tendency to form oxides, and this barrier must be removed to produce a quality weld. One of these methods is cathodically etching the metal during variable-polarity welding. To understand this effect, it is important to distinguish between and explain the two types of electrode polarity that produce the variable polarity. These differing forms of electrode polarity (see Figure 3) are known as straight polarity (DCEN) and reverse polarity (DCEP).

Straight polarity produces higher arc efficiencies when compared to reverse polarity. In reverse polarity, much of the heat does not transfer to the part. The main advantage of reverse polarity is the ability to clean/ etch the weld surface. The etching effect is necessary to remove the oxide and produce a high-quality aluminum weld. In addition, the cathodic etching produced by DCEP enhances the weld pool flow characteristics significantly, making keyhole welding possible. Visually, a VP-welded aluminum joint is clean in appearance with a clear indication of the etched zone.

Welding Tailor-welded Blanks

A lack of variable control of the AC waveform limits the use of AC DCEP. The welder cannot optimize the arc for heat transfer and cleaning. The process that combines both of these two forms of electrode polarities takes advantage of the high input of DCEN welding and the cleaning effects of DCEP welding.

Table 2
LDH results of a biaxial stretching test on ASTM 5182 0.8-mm to 1.6mm aluminum TWBs are shown here.

Test Number (200 mm x 200 mm)	Dome Height (mm)	Peak Force (kN)	Comments
1 Biaxal	19.9	-21.8	The test completed its cycle before speciman failure
2 Biaxal	20.6	-24.1	Failure in thinner parent material 2.5 mm from weld
3 Biaxal	19.2	-21.4	Failure in thinner parent material 3.0 mm from the weld
4 Biaxal	20.2	-24.3	Failure in thinner parent material 2.5 mm from the weld
5 Biaxal	19.8	-22.6	The test completed its cycle before speciman failure
6 Biaxal	18.6	-24.8	Failure in thinner parent material 2.0 mm from the weld
7 Biaxal	17.7	-22.6	The test completed its cycle before speciman failure

Table 3
LDH results of a plane strain test on ASTM 5182 0.8-mm to 1.6-mm aluminum TWBs are shown here.

Test Number (125 mm x 200 mm)	Dome Height (mm)	Peak Force (kN)	Comments
1 Plane Strain	18.8	-22.0	Neck in the parent material 4 mm from the weld
2 Plane Strain	18.8	-18.8	Failure in thinner parent material 2.0 mm from the weld
3 Plane Strain	19.6	-23.2	Failure in thinner parent material 8.0 mm from the weld
4 Plane Strain	19.1	-22.9	Neck in the parent material 4 mm from the weld

Tables 2 and 3 show the results of the 101.6-millimeter limiting dome height (LDH) tests performed on ASTM 5182 material. The geometry of the welded coupons was 200 millimeters ¥ 200 millimeters for the biaxial stretching test and 125 millimeters ¥ 200 millimeters for the plane strain test. The material thickness was 0.8 millimeter to 1.6 millimeters.

Figure 5
The weld bead in this weld profile of a blank produced using VP-PAW has a smooth transition between the two different material thicknesses, thus promoting improved material flow during forming.

The weld was performed in the transverse direction to the rolling direction. No lubricants were used to reduce friction. The weld speed for these tests was 2.5 meters/minute. All the welds were produced using a 400-amp VP-PAW power supply integrated with a simple seamer.

Figure 4 shows the weld profile of a blank produced using VP-PAW. The weld bead has a smooth transition between the two different material thicknesses. This profile promotes improved material flow and produces a panel with improved stamping characteristics when compared to profiles produced with a smaller weld bead. It is important to note the equiaxed grains, which are produced by pulsing the current during welding. This grain structure promotes improved formability.

The sample shown in Figure 5 is a macro view of a VP-PAW-produced weld. The white area surrounding the weld is the cathodic-etched zone. Again, in VP-PAW, the polarity of the arc can be switched and controlled by varying the amounts of DCEN (straight polarity) and DCEP (reverse polarity).

Figure 5
Th white area surrounding the weld in this macro view of a weld produced using VP-PAW is the zone in which cathodic etching has occured.

Conclusions

VP-PAW is a proven, stable method for welding many types of aluminum alloys for stringent applications. The two forms of electrode polarity produced with VP-PAW cathodically etch the metal, removing the layer of aluminum oxide. Removing this layer is essential for producing quality welds. These characteristics of VP-PAW can help to overcome the metallurgical obstacles of welding AA.

VP-PAW is an operation that is being used in high-production applications. The flexibility in its standoff distance and arc size makes fit-up more forgiving than some other conventional methods of producing TWBs. The constricted arc also produces a weld bead profile conducive to good metal flow.

The reflection characteristic of aluminum does not affect VP-PAW and so operating speed is maximized. Typical seam welding speeds approach 5.5 meters/minute, making it production-capable for the number of AA-TWBs that are forecasted to be produced over the next several years.

For future high-production operations, VP-PAW can be combined with a laser to produce metallurgically sound welds. The cathodic etching produced by VP-PAW drastically reduces the reflection of the aluminum, enabling the laser to weld it.

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Fabricator finds new opportunities in energy sector

Green applications for advanced pulsed GMAW

July 10, 2007

Welding chrome-moly steel has strict requirements concerning the welding process, preheat temperatures, and postheat temperatures. The specifications provided by the engineers for the New Hope Power Partnership project required GTAW on the first three passes of the pipe.

Founded in 1988 in Miami, CMN Steel Fabricators Inc. has carved out a niche for itself in fabricating tubular sections, mainly structural steel and pipe for the waste energy, waste management, and quarry industries. It also performs maintenance during scheduled plant shutdowns. Roughly half of its 60 employees are welders.

The bulk of the work is in mild steel, but recently the company had an opportunity to branch out and bid on a project involving a more challenging material, P11 chrome-moly pipe.

The P11 project was the New Hope Power Partnership, an expansion of the Okeelanta Cogeneration Plant in Okeelanta, Fla. With a capacity of 75 megawatts, the cogeneration plant is one of the largest of its kind in the country. It uses sugar cane stalks to produce bagasse, a biomass fuel that in turn is used to create steam to produce electricity at the power plant. In return for the bagasse produced by the sugar mill, the power plant sends along the steam it creates for use in the sugar mill's operation. The result is a symbiotic and environmentally friendly relationship in which each partner benefits from the other's waste material—the power plant from the sugar cane stalks and the sugar mill from the excess steam from the power plant.

Chrome-Moly
Chemistry and
Welding Precautions

Chrome-moly pipe is specified by the amount of chromium, molybdenum, and vanadium. These three elements increase the creep resistance for high-temperature strength, allowing the material to be lighter and thinner than carbon steel pipe and still achieve the same pressure capability. However, the higher levels of those three elements in the steel make it more susceptible to cracking if it is not properly preheated and postweld heat-treated.

Pro-Pulse technology uses two control loops: constant current (CC) and constant voltage (CV). After the current reaches the desired level (indicated by the starbursts), the CC control shuts off and the CV controller takes over. The system can monitor and adjust parameters up to 10,000 times per second to maintain optimum arc conditions.

Preventing chrome-moly steel from becoming brittle and cracking requires preheating, typically between 250 degrees F and 500 degrees F, to drive off moisture, thereby reducing hydrogen and slowing the cooling rate. Hydrogen embrittlement leads to cold cracking of the finished weld. Slowing the cooling rate reduces thermal stresses and further allows hydrogen to diffuse from the weld. Maintaining a minimum interpass temperature is also necessary to continue to keep hydrogen level low and reduce thermal gradients. A maximum interpass temperature prevents overheating the material. Overheating can adversely affect the pipe's mechanical properties and, most important, makes the weld puddle too fluid, which is difficult to control and can lead to hot cracking.

Chrome-moly steel, while stronger and lighter than carbon steel, is more sensitive to cracking caused by hydrogen embrittlement and residual stress. Welder Chico Nuñez knew that relying on the same technologies CMN Steel used for carbon steel would not position the company for success in welding chrome-moly steel.

Postweld heat treatment, from 1,100 degrees F to 1,250 degrees F, is required to reduce the hydrogen in the weld and to relieve residual stress within the material—stress caused by the high thermal gradients in the weld joint area and weld solidification.

The Players. Coming from a long line of sugar mill workers, CMN President Carlos Manuel Nuñez took special pride in the chance to bid on the Okeelanta sugar mill job, but was concerned about making sure it was a success.

Chico Nuñez, Carlos' brother and a welder for nearly 30 years, began by researching the various technologies available to help ensure the company's success.

Chico sought the advice of the company's welding distributor, Julio Montecino of Matheson Tri-Gas, concerning Pro-Pulse™, a modified pulsed spray transfer gas metal arc welding (GMAW-P) process, and induction heating technology.

Insulating blankets are applied to the pipe beneath the induction coils. The blankets help to keep the heat in the pipe.

"I heard about these new welding and heating processes when they were first introduced, but we didn't really have a need for such an advanced system at that time," Chico said."When the power plant project came up, I had a feeling that Pro-Pulse and induction heating would be the right technologies for the application."

"We have complete faith in Julio," recalled Marisa Nuñez, Carlos' daughter and the vice president of CMN Steel Fabricators."He has never recommended a product that didn't work out, so we knew he would give us a straight answer when it came to whether these new welding and heating systems would meet our needs."

The Parameters. The power plant expansion project called for 280 feet of Schedule 160, 12-in.-diameter, 1.25-in.-thick P-11 pipe with 66 joints beveled at 35 degrees. Welding Procedure Specifications called for the root, hot, and first fill passes to be performed with gas tungsten arc welding (GTAW), using 1/8-in.-diameter ER80S-B2 filler metal with a 3/32-in. or 1/8-in. thoriated tungsten electrode and pure argon shielding gas.

The shielded metal arc welding (SMAW), or stick, specifications called for an additional 15 passes using 1/8-in. E8018-B2 electrodes. Alternatively, GMAW-P process specifications would allow the company to nearly halve the number of required passes. It was still required to make the first three welds using GTAW, but the increased deposition rates of the Pro-Pulse process compared to SMAW (less than 3 pounds per hour for a 1/8-in. E7018 electrode for SMAW versus 4.5 to 14.4 lbs. per hour for an 0.045-in. ER70S-6 electrode for GMAW-P) allowed the welders to fill the rest of the joint with just seven more passes.

Each joint also required a 300-degree-F preheat, a 450-degree-F interpass temperature, and a 1,150-degree-F postweld temperature maintained for 11/2 hours.

Insulating blankets are applied to the pipe beneath the induction coils. The blankets help to keep the heat in the pipe.

The Project. The contract called for welding 66 joints on pipe made from a chromium-molybdenum alloy, 11/4 Cr/1/2 Mo-V, commonly called P11 or 11/4 chrome pipe. The P11 pipe would transport high-pressure steam between the power plant and a neighboring sugar mill.

Three key criteria figured into CMN's decision to switch from SMAW to GMAW-P. First, the new technologies needed to produce high-quality welds. Second, operators needed to learn them quickly so that the company wouldn't spend more time on training than it would take to complete the job using conventional technologies. Third, the technologies needed to provide a return on investment.

Weld Parameter Control

The PipePro™'s Pro-Pulse feature is a modified spray transfer process that monitors, controls, and adjusts both current and voltage to stay within the optimum range for a specific wire type and diameter, wire feed speed, and gas combination. The Pro-Pulse control scheme starts by ramping up the current. Once the target current is reached at the beginning of each phase, the constant-current (CC) control turns off and the constant-voltage (CV) control loop turns on. The CV loop modulates the current within a range that maintains the target voltage. This occurs independently of the contact-tip-to-work distance.

The new GMAW-P process simplifies training because it adapts to individual operator preferences and does not force the operator to adapt to the machine. Typically, operators prefer to hold a short stickout, about 3/8 in. for short-circuit GMAW and 5/8 in. for FCAW, because it gives them better control over the molten weld puddle.

With older pulsing technology, the sound, feel, and appearance of the arc change as the arc length varies. Conversely, this GMAW-P technology maintains optimum arc length and weld parameters, even if operators vary travel speed or electrode stickout within a broad range (stickouts up to 1 in. are possible). This is a benefit when welding in deep grooves or when operators shift welding positions, such as when moving from the bottom to the top of the pipe. It can alleviate arc stumbling, subsequent porosity, and the need to waste an hour grinding out and repairing a bad weld.

In the past the limits of available technology forced operators to weld with a longer arc length to help prevent short circuits, resulting in spatter (encountering a tack weld was a common culprit). Holding long arc lengths also had a tendency to produce undercut if travel speeds were not reduced. Pro-Pulse's shorter arc lengths and more focused arc column help eliminate undercuts, providing good side wall fusion and fill at the toes of the weld.

Last, the GMAW-P technology lowers overall heat input, which can reduce interpass cooling time and weld cycle time. On thick-wall pipe that requires multiple passes (such as the seven passes CMN needed to weld the 1.25-in.-thick P11 pipe), reducing interpass cooling time may save an hour or more per joint.

Safer, Faster Heating

Induction heating technology allowed CMN Steel Fabricators to save considerable time in pre- and postweld heat treatment, and it also provided consistency and safety not possible with other heating methods, the company said.

"Induction heating is the way to go," Chico said."Induction is faster than using rosebuds or ceramic blankets and gives us greater control over the ramping rates than other methods. Plus, the heat is concentrated at the place of the weld, so you don't have to worry about touching the pipe in other places."

Induction heating differs from other heating methods in that it uses an electromagnetic field to heat the metal from below the surface without actually contacting the material. The electromagnetic field excites the molecules within the material, which can reduce cycle time up to two hours on thick pipe sections.

The system can be air-cooled or liquid-cooled, but for high-temperature postweld treatments, as was necessary for the sugar mill job, a liquid-cooled system was required.

Designed for preheating, hydrogen bakeout, and postheat stress-relieving applications up to 1,450 degrees F, the liquid-cooled system differs from the air-cooled system in that it houses the heating coils in flexible, liquid-cooled hoses instead of heating blankets encased in a protective Kevlar® sleeve.

The system also has a built-in temperature controller with multiple thermocouple inputs for precise and uniform heating.

The unit also provides a safer work environment compared to methods using flammable gases or high-temperature electrical components. Because the heat is generated by the electromagnetic field and affects only nearby metal, the induction coils themselves do not get hot.

A Look Back,
a Look Ahead

The decision to invest in the equipment paid off. For the joints that needed to be heated and welded in the field, the company used a propane rosebud heating method and SMAW. With those processes, it took Chico 11 hours to complete a single joint. Using the Pro-Pulse and induction heating technology in CMN's shop, it took him five hours per joint, a 55 percent improvement.

This productivity increase also pleased the welders, who were given the choice of getting paid per hour or per piece. They naturally chose piecework.

"Our welders were used to 12-hour days," Marisa said."On this project, they were able to earn the same income in six hours that they would normally make in 12 hours. They were very happy with the results."

CMN completed the P11 project two weeks early, in six weeks instead of eight, and reduced welding time by 55 percent. Further, every weld passed ultrasonic testing (UT) on the first try; none of the 66 joints required rework. Last, the productivity increases paid for both new systems with this job. CMN Steel Fabricators' success on the New Hope Power Partnership project has positioned the company to take on future projects using P11 and other types of high-pressure chrome-moly steel.

This is nothing new to CMN. Founded on the principle of a solid work ethic, CMN never shies away from a challenge.

"I don't remember my dad once saying we couldn't do something," said Marisa."He'd always find a way to get the job done. That determination and belief in himself made the company what it is today, and it carries over to all of our employees.

"This experience has shown us and potential employers that we are capable of welding high-pressure chrome-moly steel where all joints pass UT inspection without rework," Marisa continued."Our performance on the New Hope Power Partnership project gives us the credentials and confidence to bid on jobs involving other types of chrome-moly steel as well."

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Orbital Welding of Stainless Steel Pipe for Water Systems

Productivity and quality improved over manual welding

October 9, 2007

Needing to provide a product line with standard, repeatable, and interchangeable components, American Water Technology, a manufacturer of water treatment systems, integrated stainless steel tubing and orbital welding.

This typical AWT skid shows orbitally welded stainless steel tubing mounted on a stainless frame.

After being the industrial wing of a regional water treatment company for more than 15 years, American Water Technology Inc. (AWT), Redding, Calif., spun off as an independent company and settled into a market niche targeting small, mostly rural water districts with production of less than half a million gallons per day. These customers had been overlooked by big companies that provide larger water treatment packages and had been affected recently by tightened treatment specifications mandated by regulatory agencies.

Typically, many water specifiers look strictly at material cost for a new installation. However, ATW believed that it might be more interested in units that would require less maintenance and would have a long service life. As a result, the company decided to integrate stainless steel into its systems and use orbital welding equipment wherever possible.

"Stainless steel is the best material considering life cycle cost, sanitation, and physical properties, such as strength, for the water system operator. Other, cheaper materials simply cannot match stainless in the long run," said Chris Beebe, AWT's president.

Deciding to Go Stainless

AWT uses an Arc Machines model 207A orbital welding power supply with a water-cooling unit and a model 8-4000 weld head for its stainless steel welds. Steve Bates holds a large tube that encloses the weldment for purging.

The decision to use stainless steel tubing for its systems was based on AWT's examination of different methods and materials in an effort to reduce manufacturing costs and shorten production schedules while improving overall quality. At the time of the spinoff, AWT was primarily using PVC and CPVC on reverse osmosis (RO) systems and galvanized pipe on water softeners and filters. Both PVC and pipe require pipe-fitting techniques for manufacture, and glued assemblies require custom fit-up.

"We wanted to move toward a product line that had standard, repeatable, and interchangeable components. To that end, we looked at stainless steel tube," said Beebe.

Stainless steel also had the added benefit of sanitary compliance. The strength of stainless steel allows the use of higher water velocities that can help to minimize the growth of biofilm. Biofilm can be reduced by the higher velocities used for flushing systems, but higher flow rates also increase the risk of triggering a water hammer. Such force can fracture plastic piping but is more readily tolerated by stainless steel.

Orbitally Welded Stainless Steel Tubing

These ID fillet welds are actually made by orbital welding from the OD. No filler is added to the weld.

AWT's first experience with a welded stainless steel assembly was the face piping for a water softener. That project had comparable material cost to the other options; however, using manual welding took longer than the previous fabrication methods. In an effort to improve productivity, AWT decided to investigate using orbital welding equipment. Dave Buttress at Digital Welding in Sunnyvale, Calif., a representative of Arc Machines Inc. (AMI), Pacoima, Calif., demonstrated the orbital fusion welding equipment at AWT's facility.

"We could see the benefits of this technology right away" said Steve Bates, production manager for AWT.

Bates visited Arc Machines headquarters for training on the equipment. AWT rented an Arc Machines model 207 orbital welding system in late 2004. By March 2006, ATW was able to justify the purchase of its own system, which comprised a model 207A power supply with a model 8-4000 weld head.

Bates determined that Arc Machines' expertise saved the company both time and money. AWT's innovative approach to orbital welding was evident in the welding of the conductivity probes that require a female pipe thread (FPT) fitting-to-tubing joint. Based on Arc Machines' training, AWT developed its own weld schedules for this joint using step rotation, in which the electrode halts during the primary, or high-current, pulse to maximize penetration and moves on the background, or low-current, pulse. Making an orbital weld on the OD of FPT-to-tube weld results in what appears to be a fillet weld inside the tube even though no filler wire is added. AWT said that it could not have made this joint using manual welding techniques.

An Arc Machines model 8-4000 weld head is set to make the final weld on an RO permeate line.

For another application, AWT needed a stainless globe valve with sanitary fittings. It purchased an off-the-shelf valve, machined the valve body, and orbitally welded sanitary ferrules onto the body.

Almost all of AWT's welds are done orbitally now. The repeatability of the process allows AWT to make interchangeable components so it can now make parts ahead of time. The portable model 207 power supply also allows the company to do on-site modifications or repairs. To date all of AWT's products have orbitally welded stainless tube assemblies, and 90 percent of its systems are built using stainless steel tube.

Using SolidWorks® CAD software, AWT prebuilds its assemblies. Drawings are made from the CAD models and components are fabricated from them. Tube is cut with a precision band saw, then end-prepped with a GF tube trimmer to make a square butt joint. Close tolerances are held to ensure interchangeability.

By converting to orbitally welded stainless steel, AWT now is able to produce uniform, interchangeable components. Upgrading both materials and fabrication technology has reduced the company's cost to a level comparable with PVC construction while producing a superior product.

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Up to speed

Welders at Penske Racing strive for strength and safety

November 6, 2007

The success of a racecar depends heavily on the quality of its welds. The welding team for Penske Racing’s NASCAR® automobiles must stay on top of their game to ensure that their vehicle is not only fast but safe. This article provides a brief look at Penske Racing and describes how its welders push toward the fast track to success and safety.

NASCAR® roots run deep in the American Southeast. More than 50 years ago, atop sandlot racetracks with haystack walls, local thrill-seekers sought mere bragging rights behind the wheels of their modified family sedans.

Today's racecars cost upward of $200,000, and the stakes are among racing's highest. The cars scarcely resemble any street-legal machine, incorporating technology that has more in common with jet aircraft than anything driven to a peewee soccer game.

The bodies alone are products of highly engineered aerodynamic research in multimillion-dollar wind tunnels. Their frames slice a thin line between safety in strength and performance in weight. Every gram matters. At 200 miles per hour, there is no margin for error. And like their drivers, racecar fabricators are forever seeking to advance their place in the sport.

"If you don't keep up with the latest technology, you fall behind," said Jeff Baker, director of fabrication for Penske Racing. "It's just that simple."

That was the mantra passed down from Baker's boss, Roger Penske, a legendary racer and entrepreneur. Since Penske's racing inception at the Marlboro Motor Raceway in 1958, he has been known to demand the best in people, technology, and equipment. It was his penchant to win—to be the best—that has set his teams apart for nearly half a century.

Having ingrained an indelible mark on Indy racing, Penske has helped elevate NASCAR from its humble beginnings in rural North Carolina to the sophisticated racecar laboratories of today.

GTAW is used to piece together this racecar. Welders must comply with quality standards similar to those in the aerospace industry.

Penske's newest 400,000-square-foot, state-of-the-art NASCAR facility on eight acres in Mooresville, N.C., near Charlotte, employs about 200 expert welders. They fabricate some of the most advanced automobiles in the world year-round for drivers Sam Hornish Jr., Kurt Busch, and Ryan Newman.

Fab teams build and maintain about a dozen cars for each driver, customizing separate designs that suit each track. From the observation deck high above the wide-open work floor, visitors typically see 10 or more of what appear to be identical cars lined up in separate bays. But under the body, each car differs in camber, weight distribution, suspension, aerodynamics, and turn ratios to match varying track conditions.

On first impression, Penske's facility speaks directly to racing enthusiasts with an unparalleled aesthetic. Encircling the facility's walls are 1,000 linear feet of historicphotographs depicting the sport's five decades. Fans are encouraged to walk the 330-foot catwalk to view an army of fabricators meticulously creating individual parts by hand.

Penske uses gas tungsten arc welding (GTAW) units from The Lincoln Electric Co. to piece together its NASCAR cars. Welding takes place using Lincoln's Precision TIG machines, rated at 275 and 375 amps. When it comes to welding, Baker said, each bead has its own character.

"I can look at a specific weld and tell you exactly who laid the bead," Baker said.

"These guys take great pride in their work. When a wrecked car comes through the door, they're all lined up to see how their weld held."

Weld failure isn't an option for cars that travel more than 200 miles per hour. For safety and performance reasons, NASCAR quality standards mirror those of the aerospace industry, which has become the sport's technological model. Fit tolerances often dip as low as 1⁄1,000 inch for some parts. Every weld is visually inspected, and many key welds are X-rayed.

Penske selects its welding personnel by experience and reference. Hundreds of highly qualified welders apply for work every year, but in the end, those who make the cut are chosen by an on-site welding test, Baker said.

"These are the best welders in the world," he said. "They have a touch and sense that you just can't teach. These guys truly are artists, and that's how they approach their work."

Drivers work closely with fabricators to convey their performance preferences. A variety of experts are routinely involved in car production, from fabricators and engineers to research analysts and drivers.

Lincoln Electric also has a full-time representative who provides support, new welding technologies, and techniques to the shop, Baker said.

"Lincoln has helped us get the most out of this equipment, and it's really paid off," he said. "In this shop, welding is everything. Our drivers' lives depend on it, and everyone who works on these cars knows it."

Training Day

Jeff Baker, director of fabrication for Penske Racing, stands by his welders, calling them the best in the world.

To assist ongoing training, Lincoln hosts a two-day seminar for racing's elite welders each year. Representatives from Penske attend the class each December at Lincoln's world headquarters in Cleveland.

"It's amazing the things these guys teach you," Baker said.

"You have to stay on top of the technology, especially in this industry. These seminars are an important part of that. Welding isn't a static skill, it's an evolving technology that grows much faster than most people realize," he said.

The annual seminars focus on Lincoln's technical research conducted all year by its team of race welding experts. Annual studies focus on metallurgy, cracking, and weld failures and how emerging technologies can be applied to racing and newly incorporated materials.

Weld teams review the latest best practices and study ways to minimize weight without sacrificing strength—especially when NASCAR material rules change to allow more exotic metals previously forbidden, such as chromium-molybdenum and titanium for parts.

"Welding racecars has become far more technologically centered than ever before," said Dennis Klingman, who lead's Lincoln's racecar research and seminars.

"We're doing much more with software applications, where we can control the arc with more and more precision, especially with materials such as aluminum and titanium."

The seminars have become an annual gathering for race welders of many teams in NASCAR, Indy, Champ, and other series. Klingman said it's a unique event because fabricators from competing teams share techniques and compare notes. Their common bond, Klingman explained, is a mutual drive toward safety.

"These guys all recognize that a driver's safety takes precedence over winning a race," he said. "They're not revealing speed secrets, but it's great to see all these different teams working together for a common cause. And while the cars continue to get faster, there have also been fewer injuries."

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The whats, whys, and whens of GTAW

By Jack Fulcer, Contributing Writer

November 6, 2007

More difficult to learn than some welding processes, gas tungsten arc welding (GTAW) can be used to weld a greater range of materials than most other processes. This article explains GTAW, examines its advantages and disadvantages, describes appropriate and inappropriate applications, and discusses how important cleanliness is in GTAW

If you are among those who want to learn about welding just for fun, or if you are considering a new career, knowledge is always the key to success. Well, that and a little practice!

Gas tungsten arc welding (GTAW) is among the more difficult welding processes to learn, and just like shielded metal arc welding (SMAW) or gas metal arc welding (GMAW), it has distinct advantages and disadvantages (see Figure 1). GTAW is suitable for certain applications and totally inappropriate for others. To master GTAW, it is important to know these details before you begin.

GTAW Advantages	GTAW Disadvantages
Clean, high-quality welds	Lower deposition rates
Welds a wide range of metals	Requires high level of operator skill
No spatter or slag, sparks, or smoke	Higher level of UV rays
Allows for welding in all positions	Requires good eye and hand coordination to achieve quality weld

Figure 1

What Is GTAW?

The GTAW process uses a nonconsumable electrode—tungsten—to create an arc and transfer heat (or, the current) to the base metal that is being welded. At the same time, an inert gas, usually argon or an argon/helium mixture, shields the weld puddle from the atmosphere and protects the weld from contamination.

Unlike SMAW or GMAW, GTAW does not require a consumable filler metal for every application; however, when one is used, it is slowly fed into the weld pool by the hand opposite that holding the torch. GTAW filler metals, often called rods or cut-lengths, are available in diameters ranging from 1/16 in. to ¼ in. They also are available in multiple compositions or specifications to meet the chemical and mechanical properties of the base material being welded (see Figure 2).

Base Material	Common GTAW Filler Metals
Carbon Steel	ER70S-6 or ER70S-3
Aluminum	ER4043 or ER5356
Stainless Steel	ER308, ER309, or ER316
Chrome-Molybdenum	ER80S-D2 or ER70S-2
Titanium	ERti-5ELI

Figure 2

Why Use GTAW?

Considering what GTAW is, the next logical question seems to be: Why use it?

First, it can be used to weld more materials than any other welding process, even exotic and heavier-alloyed metals. Among those materials you can successfully use GTAW for (with practice!) are stainless steel, aluminum, chrome-moly, nickel, and titanium. Of course, you also can weld plain old carbon steel with GTAW.

Next, GTAW produces very clean and high-quality welds, making it a good choice for applications in which aesthetics count or X-ray-quality welds are required. It also works well on thin materials, even those measured by gauge as opposed to inches.

For example, you can weld material down to 30 gauge with GTAW, which makes it a good process for computer housings, electronic components, and tubing. This is because the process allows for a more direct, or concentrated, arc and produces a narrow heat-affected zone (HAZ) on the base material. HAZ comprises the area surrounding the weld, which has not melted but has been altered by the heat. By minimizing the HAZ, GTAW helps prevent distortion, particularly on thin materials. Overall, the lower heat generated by the GTAW process also minimizes the chances of burn-through on thin materials.

As a rule, GTAW does not produce sparks, spatter, or fumes, making it a relatively clean process. It can be, and often is, completed in the comfort of an air-conditioned room, although proper ventilation is always critical.

An important note: If the material being welded is dirty, then the previous rule may not apply. For that reason, one of the oldest and most important adages about GTAW is clean and clean some more!

The base material you are welding should be cleaned either with a brush, cloth, or an appropriate chemical compound to achieve the full GTAW advantage. If you are not certain of the best cleaning method for the material you are welding, check with your local welding distributor.

Finally, another reason GTAW is often used is that it does not require a lot of postweld cleaning. For example, you will not have to chip slag or grind spatter after welding. Note, however, that you may have to, or simply want to, grind a gas tungsten arc weld for aesthetic reasons.

Appropriate Applications

All of this said, GTAW sounds great, right? Well, it is—but only under the right circumstances. Good applications (especially for material less than ½ in. thick) include:

• Automotive work, including roll cages, frames, and exhausts
• HVAC applications, including ductwork
• Petrochemical and pipe applications
• Metal artwork and ornamental applications
• Maintenance and repair, including machine components and tools

Not the Fastest

If you have thicker materials (about ½ in. or thicker) that can be welded using GMAW or SMAW, you may want to consider these processes instead of GTAW, because they generally are faster. That is a drawback of GTAW: It is a slow process.

For example, whereas the travel speed (the rate at which you weld) during GMAW is determined by the rate at which the welding wire is being fed through the gun and the amperage at which you are welding (among other factors), generally GTAW is only as fast as you are, or, more accurately, as fast as you can feed the filler rod into the weld puddle. The GTAW process requires much practice and skill to master, and even more of both to do it quickly and precisely.

Also, GTAW deposition rates are lower than SMAW's or GMAW's. Deposition rate is the amount of filler metal that is deposited in a given amount of time. As an example, the average deposition rate for a GMAW application using a solid welding wire is 8 to 9 lbs. per hour, but GTAW deposits only 2 to 3 lbs. per hour.

In short, GTAW probably won't be your first choice to weld thick materials quickly. It also should not be your first choice for material that is rusty or has mill scale on it, as GTAW filler rods do not have the added deoxidizers that allow many SMAW electrodes and GMAW welding wires to produce successful welds under these conditions.

GTAW has its place, just like the other welding processes. It is neither superior to SMAW or GMAW, nor is it inferior. Rather, it is more suitable for certain metals, material thicknesses, and environments.

If you are at all confused about when or how to use the GTAW process, or if you are ready to take your skill to the next level, contact your local welding distributor or welding equipment manufacturer for pointers. Often these groups have technical support teams whose advice can be invaluable. And don't forget the importance of just a bit of practice too!

www.thefabricator.com

Holding up under 'pier' pressure

Metal pier manufacturer banks on durability, service to stay afloat

November 6, 2007

A manufacturer and installer of steel docks in Ontario, Canada, purchased new welding equipment that gave the company increased reliability in adverse weather conditions.

Nordcap began using steel to build its docks because the steel lasts longer than wood and it creates a minimal footprint on the bottom of the lake.

The Lake of Bays and Muskoka Lake in Ontario, Canada, offer the perfect escape for those who wish to trade in the chaos of city life for the beauty and serenity of Canada's great outdoors. However, while the residents sleep in, the crew of Nordcap Steel Docks are already hard at work to meet the ongoing demand for steel docks. In fact, the demand is so great that the Nordcap crew works year-round, taking off only a week or two in the dead of winter and a few other days when the weather forces them inside.

When the lakes freeze over, Nordcap employees bring their supplies in on sleds. At other times they work from one of their barges—portable shops that carry everything they need to complete a job. A few things can stop them: waves that crest over the dock, howling winds, ice, temperatures below -25 degrees F, and equipment that breaks down or won't start.

The Nordcap crew can't do much about the weather, of course, but if their equipment breaks down, it can cost up to $200 an hour in lost labor—more than that if they've rented additional equipment. Plus, even a single lost day can throw off weeks of scheduling.

Taking the Plunge

When Philipp Spoerndli, Nordcap president, started in the business, he built and repaired wooden docks, which were on cribs, wooden structures that take up a large footprint on the lake bottom. Over time the wooden structures would settle in or deteriorate.

"Fixing them was a tough job," Spoerndli recalled. "You'd have to lift the boat houses and remove the rocks from the crib. After a while I said to myself, 'There has to be a better way,' and I turned to steel docks in 1991."

At that time steel docks were a fad; now they've become the preferred choice of many. In contrast to wooden docks, steel docks have less of an environmental impact because they create a minimal footprint on the lake bottom and use steel instead of wood. Plus, they last longer than wooden docks—two to three times longer—according to Spoerndli, who uses the heaviest-wall steel pile he can while still remaining competitively priced.

Spoerndli and the Nordcap crew distinguish themselves from their competitors in other ways too. They sandblast and epoxy-coat all steel used on the docks. They also use sacrificial anodes to inhibit corrosion and increase longevity and drive the piles all the way down to the bedrock to prevent settling. A Nordcap dock can be expected to last 75 or 85 years before needing maintenance, compared to about 25 years for a wooden dock.

Carpenters out, Welders In

Dock construction takes place year-round and in weather conditions that are less than ideal.

As wooden docks gave way to steel ones, welders took up the work previously performed by carpenters. When Spoerndli began working with steel docks, he hired knowledgeable welders and took classes to become a Canadian Welding Bureau-certified (CWB-) supervisor. He now has two all-position, CWB-certified welders on his crew, one welder certified in flat and horizontal positions, and a second CWB-certified supervisor.

Initially Spoerndli and his crew worked from a raft and rented a barge to do the pile driving. He later bought the barge, which they now use as a floating workstation and to transport tools and equipment on the lake. They've also made a switch to Miller welding equipment: two Miller PRO 300 diesel welder/generators and two Maxstar 200 SMAW/GTAW welders. The switch to Miller equipment came two years ago while Nordcap was working on the Muskoka wharf with a different equipment brand. The oil cap suddenly blew off of a welder/generator and filled the air with white smoke.

"We got it working again, but I was really dissatisfied with the service we received from our distributor at the time," Spoerndli said. "If we hadn't been able to get it going, we would have really been stuck. I had rented equipment that was costing $500 an hour, labor costs of $200 an hour, and I couldn't afford to have any downtime. I never wanted to be in that situation again."

After that experience, Spoerndli turned to Praxair.

To solve Spoerndli's equipment issues, Dave Middlebrook of Miller and Roger Barton of Praxair recommended the low-speed, multiprocess diesel welder/ generator. Capable of SMAW, GTAW, GMAW, FCAW, and air carbon arc gouging, the unit has low noise output (73 dBA at 23 feet at maximum output), which is an important consideration for a company that works year-round in a location where people come to enjoy the scenery and relax.

"You have to appreciate where we work," said Edward McNaughton, a Nordcap CWB-certified welder, indicating the beautiful scenery. "Customers here are very particular about noise levels, but we can run a PRO 300 at 7 a.m. without any noise complaints."

But Spoerndli's appreciation goes beyond the welding unit's low noise. Because of its light weight and compact size (1,100 pounds with a 26-inch by 56-in. footprint), the company can easily fit two on its barge. Plus, the unit has all the welding power the crew needs for the 3⁄8-in. steel they work with.

"The penetration is great," said McNaughton. "We can strike an arc right through the paint without prepping the metal, if necessary. The machine is easy to dial in. About 60 percent of a good weld is having the right equipment. The rest is skill."

But there were some unexpected benefits to the welding system that make Nordcap's life easier. Spoerndli also bought a gas-powered unit for those cold days when it would be difficult to start a diesel engine. But through the winter they never had to use the gas engine drive, which would have been less economical than the diesel model.

"We were out here year-round, in all conditions, and the PRO 300 started every time," McNaughton said. "If there's fuel and oil in it, it's a done deal—we're going to work. That's a really big thing. A breakdown would cause major headaches. First of all, it would put us behind on the next project. Since we're committed to so many projects a year, a machine that doesn't run means we have to work overtime on Saturdays and nobody wants to do that. Second, you don't want to have a crew standing around at $200 an hour while someone tries to start the machine."

Being able to use the diesel power unit year-round saves on fuel prices too. Since Nordcap needs to add only about 5 gallons a shift and uses off-road diesel (priced lower than automotive), which costs about $0.78 Canadian a liter, the company can run the welding machine for less than $14 Canadian per day.

Two Arcs, One Welder/Generator

Nordcap welders must be comfortable welding in many different positions.

There was another unexpected benefit. With 10,000-W (12,000-W peak) generator power, the unit has enough power to run grinders, chop saws, microwaves, and a Miller Maxstar 200 SMAW/GTAW unit that allows the company to get two arcs from one machine, cutting fuel use in half and saving room on the barge.

The Maxstar 200 is a 37-lb., inverter-based power source that provides 150 amps at 26 volts (60 percent duty cycle); draws 5 kilowatts maximum and, by incorporating Auto-Line™ technology, can run off any 115-V to 460-VAC power supply, single- or three-phase, and keep the output constant regardless of fluctuations in power of ± 10 percent.

Finding a Level of Comfort

While the welding machine has answered many of Norcap's needs, it is not perfect. For instance, it doesn't float.

"The PRO 300s are great machines as long as we don't submerge them," said Spoerndli, referring to the time the boat was swamped and the welding unit sank.

No one was sure if the machine was salvageable—submerging it isn't a factory-recommended procedure. However, the welding unit is protected by The Vault, which houses the control board in a hardened, watertight case, and a marine-grade ignition switch, which is sealed and protected for water and dust.

Spoerndli was advised that the machine would need to be scrapped, but Jack Lowe at Northern Machine in Barrie, Ont., dried it out and got it back in working order.

With the switch to Miller equipment came the level of comfort Spoerndli had hoped for, both in the equipment and the service. Now he just has to worry about the weather.

www.thefabricator.com

Weld Small Part Accurately

BERNARD MANNION Chairman JACK HEINZMAN President Pro-Fusion, Inc. Newbury Park, CA	Today's welding requirements have become more stringent with regard to the quality and appearance of a typical weld. Manufacturers are addressing quality and consistency issues by looking more closely at all parts of their welding operations. Here, we look at welding system components, and focus on those that may have been ignored in the past, but are vital to producing small parts. Weld Quality--Today's Expectations Quality in all manufacturing areas is now demanded, rather than hoped for or applauded when received. Welding, the last process in the manufacturing cycle, is also subject to this demand and has been making its own changes to keep up with changing times. It also seems to be a general trend that most modern products are becoming more physically compact. Thus, it is incumbent upon the welding process to be more precise and to apply the right amount of heat in exactly the right place. In short the modern world requires precision welding, welding that can be repeatedly executed within a close set of tolerances. What Kinds of Miniature Parts Require Precision Welding? A surprisingly large number of products, including batteries, capacitors, sensors, pressure devices, light bulb filaments, metal bellows and seals, and surgical tools, require precision welding to seal, shape, or join to complete the manufacturing process. Not only must these welds be extremely reliable because of the product's critical nature, they must also be created without compromising the device's function. Welding is considered by many to be more of an art rather than a true mathematical science. It seems to change gradually rather than quickly, and often lags behind the other manufacturing processes in investigating the full details of its own technologies. Progressive manufacturers are now changing this thought paradigm and are willing to investigate any technology that can improve output consistency. The science of welding is extremely complicated with an immense number of variables to consider, not only in the welding processes and equipment available, but also in the detail of consumable elements and how they affect the welded output. Joining & Welding Processes: A Quick Review In the manufacturing industry, the two most popular methods used for precision joining are the TIG and plasma weld processes. TIG and plasma welding processes were originally developed to provide a means to produce acceptable weld quality on a variety of metal materials and alloys. Advances in power supplies, welding techniques, and process controls have allowed for greater weld accuracy. The process is now used in even more precision and miniature applications. In the Gas Tungsten Arc Welding process (GTAW), also referred to as the Tungsten Inert Gas process (TIG), an electric arc is established between a tungsten electrode and the part to be welded. To start the arc, high voltage breaks down the insulating gas between the electrode and the workpiece. Current is then transferred through the electrode to create an electrode arc. The metal to be welded is melted by the arc's intense heat and fuses together. The plasma weld process is a TIG welding variant with an additional copper housing around the electrode that directs and further constricts the arc. Both processes use a Tungsten electrode ground to a point both as the source of the arc ignition and as an transfer medium. Welding System Elements A typical welding system consists of the following elements: Welding power supply Arc starter Welding torch Tungsten welding electrode Welding parameters Welding Power Supply: Historically, welding power supplies were often large crude devices to deliver electrical power to a welding arc. Power supplies have been improved, and now offer faster response, with accuracy and reliability in a more compact design. Arc Starters: High frequency arc starters were the primary means of starting a TIG arc. Now, the welding industry also offers DC arc starters. These devices offer better arc starting, longer electrode life, and less electrical noise that may cause interference with other electrical or control systems near the welding system.
Figure 1. Two commercially available grinding finishes are compared to a manually ground electrode (lower) that many welders use. Crosswise grinding restricts welding current, and causes ignition problems and arc wander. Longitudinal grinding improves current flow.	Welding Torches: Arc welding torches also have seen significant improvements. Modern GTAW and plasma torches are available in many styles and shapes, and provide current delivery improvements. Their designs have been improved, offering torches that allow for electrical power, shield gas(es), and any required water cooling, all in a device as small as the diameter of your little finger. Tungsten Welding Electrodes: Tungsten welding electrodes, the source of the welding arc, is the welding system's most important element, and the most commonly ignored. While no one would refute the importance of the ignition device on an automobile airbag, gasoline for a turbo-charged Ferrari, the violin strings for a Stradivarius, or the rip cord for a parachute, the importance of tungsten electrodes is often overlooked. Whether in manual or automatic welding, this is where many companies can improve their welding output's consistency with minor effort. Pre-Ground Electrodes and Tungsten Electrode Grinders: Consistency and repeatability are key to welding applications. The tungsten electrode's shape is an important process variable. Once a weld procedure has been established, it is important that consistent electrode geometry be maintained (See Figure1). Using electrodes pre-ground to requirements or a dedicated commercial electrode grinder (see lead photo) offer the following benefits to the user in their welding process: Improved arc starting, increased arc stability and more consistent weld penetration. Longer electrode life before electrode wear or contamination. Reduced tungsten shedding, minimizing the possibility of tungsten inclusions in the weld. A dedicated electrode grinder ensures that the welding electrodes will not become contaminated by residue or material left on a standard shop grinder wheel. Tungsten electrode grinding equipment requires less skill grind a tungsten electrode correctly and with more consistency. Tungsten electrode grinders are now available that provide all the necessary features for precision electrode grinding at a starting cost of about $750.
Figure 2. These small parts were joined using an arc-welding technique. Note the pulsed arc finish on the weld surface.	Arc Welding Parameters: Welding small parts, or welding near polymer or glass-to-metal seals, requires low heat input to the welded part. The pulsed arc welding technique, used both in GTAW and plasma welding, rapidly increases and decreases the arc welding current. This creates a seam weld in the part material consisting of a series of overlapping spots welds (Figure 2). It focuses the weld energy, allows for weld speed increases, and reduces the overall heat input to the part. Some welding component suppliers offer spreadsheets to calculate the required arc pulsation parameters for many precision/miniature applications. This eliminates the requirement that an engineer needs ten years of experience to analyze a welding application. Using these techniques, the welding department can improve it's output quality and repeatability. Watch the Little Things The trials and investigations of the past in advancing the welding process have brought new triumphs in welding, improving quality and precision, and leaving less waste. These are lessons that when applied, can offer modern manufacturing organizations an exceptional advantage over their competition. Available technology has revolutionized many manufacturing operations. In the current global marketplace, manufacturers are looking for ways to increase output, consistency, and quality. Organizations must open their eyes to the continually evolving world of manufacturing. The welding industry, although historically slow in responding, is now offering more and more to those who are willing to listen. For a company to increase market share, or even to remain competitive, it must find more efficient and better production methods. A willingness to test where the limits of existing technology really lie can result in more and better precision/miniature products at substantial cost savings. www.pro-fusiononline.com

Igniting Advances in Weld Quality and Consistency

By Bernard Mannion
Pro-Fusion Technologies, Inc.
Newbury Park, CA
Liam O'Mainnin/Consultant

Quality that measures up to customer demands is the norm in all manufacturing processes today, and the welding industry is no exception. Practitioners cannot ignore advances if they wish to remain competitive. This article reviews and analyzes some of the recent developments in the welding industry, with an eye toward their impact on the manufacturing engineer.

Historically, the art of welding has changed more slowly than other manufacturing processes in its application of the latest technologies. But today, welders have many variables to consider. The sheer variety of materials is expanding daily and increasing the burden on welding personnel to stay abreast with technological innovations.

Technological Advances

The trend toward smaller and neater products has forced welders to be more accurate in their application of heat, both in the amount and location. Customer expectations continue to demand greater precision in the entire welding process.

Precision welding is required for the manufacture of parts such as enclosures, batteries, capacitors, metal seals, pressure devices, sensors, surgical tools, and many other metal components. Because of the need to maintain part integrity, the sealing, shaping, or joining technique must be extremely reliable. The welding process must also be accomplished without detriment to the function or cosmetics of the part.

Joined by an arc welding technique, this solenoid component has a pulsed arc finish on the weld surface.

Many manufacturers are misled by the generally held belief that laser welding is "the most modern technology available," and therefore the only method for making precision welds or producing miniature parts. If secure in this belief, they may not consider alternative methods that can be much less expensive, and which make use of equipment that is much easier to operate.

A new use of technology has recently emerged for short-duration spot welding of delicate parts. The plasma arc welding process, with its pilot arc always ignited between the welding electrode and copper nozzle, has always allowed for brief welds. But recent developments in fast-response power supplies, solid-state weld transfer contactors, and crystal timer controls (CTC programmers) have permitted total weld times of less than 0.005 seconds, with 0.001-second increments.

This has opened an entirely new field of investigation that involves controlling the arc to give exceptional control. As a result, micro-components such as light bulb filaments, small wires, and thermocouple elements can be welded with near-perfect accuracy. When applied to larger components, the same technology can produce perfect welds on larger, thicker sections.

Background

In the manufacturing industry, the two most popular methods used for precision joining are the gas tungsten arc welding (GTAW) process--also referred to as the tungsten inert gas (TIG) process--and the plasma weld process. Both were originally developed to provide a means to produce acceptable weld quality on a variety of metal materials and alloys. Since then, advances in power supplies, welding techniques, and process controls have permitted greater weld accuracy. Today, the process is used in even more applications requiring precision and miniature parts.

In the TIG process, an electric arc is established between a tungsten electrode and the part to be welded. To start the arc, a high voltage is used to break down the insulating gas between the electrode and the workpiece. Current is then transferred through the electrode to create and electrode arc. The metal to be welded is melted by the intense heat of the arc and fuses together.

The plasma weld process is a variant of TIG welding: An additional copper housing around the electrode directs and further constricts the arc. Both processes use a tungsten electrode, ground to a point, as the source of the arc ignition and the means of energy transfer.

Advanced Arc Welding Techniques

The pulsed arc welding technique offers low heat input. It is used for welding thin components or metals next to a fragile material such as glass or polymer.

In this technique, the arc welding current is rapidly increased and decreased. This makes a seam weld of overlapping spot welds, which reduces the overall heat input to the area and permits increases in weld speed. Welders can use the technique to great advantage with a combination of rapid response power supplies and weld process controllers. The result is improved weld quality and increased output.

Trends in Equipment

By examining more closely all the elements of the welding system, welders can reduce or eliminate many of the reasons why arc welding systems occasionally seem to develop a "personality of their own."

Power supplies. The welding power supply itself has been refined. The method of delivering "brute force" power to a welding arc has become outdated as customers have demanded superior products. As a result, higher-performance machines with greater efficiency, accuracy, and response time have replaced the earlier version, sometimes known as "beasts."

Welding control systems. In order to meet the more rigorous demands for quality, the welding industry has moved to a much stricter control of standards. It has also witnessed the development of weld programmers--devices that store and execute welding programs.

In addition to automating the welding process portion of the work, these programmers/controllers help reduce scrap parts by executing repeatable, pre-arranged weld programs within precise welding parameters. The welding capability is thus built into the system through the controller, as opposed to being taught to the manual welder. A positive result is that less opportunity exists for error or fatigue. Besides improving weld quality and consistency, weld controllers offer lower operating costs.

Manufacturers and job shops use the controllers for medium-to-large contract runs. Lower costs are derived mainly by limiting the skill requirements of an operator to the level needed for loading and unloading parts. Although repetitive welding is accepted as an operation to be automated, the need for a skilled welder will always exist. Here, too, manufacturing firms and job shops have found ways to improve output.

The Tungsten Welding Electrode Tip

The tungsten welding electrode, the source of the welding arc, may be the most important element of the welding system to be commonly ignored by manufacturing organizations and job shops. While no one would refute the importance of the ignition device and an automobile airbag, the rip cord for a parachute, or quality tires for out automobiles, the importance of tungsten electrode for quality welding is often overlooked. This is an area where manufacturing firms and job shops can increase the consistency of their welding output with minor effort.

To achieve highly consistent welds, it is essential that electrode dimensions be held to close tolerances.

In addition to restricting welding current, crosswise grinding (left) causes arc ignition problems and arc wander. The proper technique is longitudinal grinding (right), which improves welding current flow.

Safety issues associated with the tungsten electrode material are also being examined more closely. Many users of the Tig and plasma welding processes fail to realize that the welding electrode that they are using contains Thorium, a radioactive element added to the tungsten material to improve arc starting and welding characteristics. Although the level of radioactivity is low, it raises the issue of danger, especially with regard to radioactive dust generated when grinding the electrodes to a point for welding.

Today, new tungsten materials are commercially available, such as Lanthanated electrodes. They offer superior arc welding characteristics and are safer because they lack radioactivity. Despite their availability, however they have been largely ignored.

Pre-ground Electrodes and Tungsten Electrode Grinders

Given the radioactivity issues associated with Thorium electrodes, and the ever-increasing quality requirements of the final weld, many companies are searching for ways to ensure that their weld quality is up to par.

Consistency and repeatability are the keys to welding applications. Finally, the shape and quality of the tungsten electrode tip is being recognized as an important process variable. Once a weld procedure has been established, it is important that a consistent electrode geometry and surface condition be used.

By using electrodes pre-ground to requirements, or a dedicated commercial electrode grinder for quality and consistency of the electrode tip, welders can obtain numerous benefits. These include improved arc starting, increased arc stability, and more consistent weld penetration; longer electrode life before wear or contamination; and reduction of tungsten shedding, which minimizes the possibility of tungsten inclusions in the weld. A dedicated electrode grinder helps ensure that welding electrodes do not become contaminated by residue or material left on a standard shop grinder wheel. Also, tungsten electrode grinding equipment requires less skill to ensure that the tungsten electrode is ground correctly and with more consistency.

Using the Technology

Spot welding. J&J Precision, of Thomaston, Connecticut, took on a contract that involved sealing the end of small tube diameters. The firm is a contract manufacturer of eyelets and performs stamping, forming, machining, grinding, and assembly of precision metal components.

The firm's owner, John Maxwell, investigated the latest arc welding technology not as a joining, but as a heating and sealing procedure. By using a specialty arc welding system with very short weld times, Mr. Maxwell was able to seal the tube by momentarily imposing a welding arc on its ending. This melted the tube and produced a smooth hemispherical surface. He currently uses the same technology for rod and wire end rounding, welding of custom endings to tubes, and creation of ball endings on wire.

By imposing a welding arc for a controlled period of time, welders can close small diameter tubes to a perfect hemisphere.

Seam welding. In a similar manner, many job ships have used semi-automatic welding equipment to fulfill contracts that involve much repetitious welding for sensors, or welding of floats, circular enclosures and canisters, and fittings to tube endings. Instead of employing manual welding with its high labor costs and issues of quality, consistency, and availability of skilled practitioners, job shops have invested in a precision power supply, welding lathe, and welding controller.

With these systems, an operator manually loads the parts into the welding fixture. A weld controller then controls the part rotation motion and welding parameters to ensure a quality, repeatable weld. After the weld is completed, the operator removes the completed part and the process begins again. In addition to providing favorable weld quality, the systems increase output, decrease scrap and rework, and reduce operating costs with easily available labor.

Suitable applications for these welding systems include repetitive welds on identical parts, quality or critical-function welds, and parts with significant accumulated value prior to welding. If a firm has sufficient contracts and a flexible welding system, the total cost of the welding system equipment usually can be paid within six months.

Modern technology has revolutionized production operations. Progressive companies that aim at a local, national, or global market are searching for methods and approaches that increase output, consistency, and quality. For a company to increase its share of the market, or even to remain competitive, it must improve its efficiency and methods of production.

Though it has sometimes been lethargic in response to change, the welding industry currently offers exciting opportunities for improving weld quality and increasing production. To test where new technology is progressing can result in improved products with increased profits.

Pro-Fusion Technologies, Inc., of Newbury Park, California, is a firm that specializes in assisting companies in the welding industry. The company manufactures and supplies welding products such as pre-ground welding electrodes, tungsten electrode grinders, and plasma welding torches. Recently, the firm introduced a welding website, some 75% of the site is devoted to providing information on welding technology and educating users on how to apply it to various applications.

Information is available on tungsten electrode materials, welding processes and their uses, weld application data, software for developing pulsed arc welding parameters, and troubleshooting welding systems.

The website address is www.Pro-FusionOnline.com.

Welding Technology Information

A review of the Pro-Fusion web site by the AWS Welding Journal

By Mary Ruth Johnsen

Pro-Fusion, Inc. Although this Web site provides plenty of information about the company's line of tungsten electrodes, electrode grinders and plasma arc welding torches, welding technology information and how to apply it to a variety of welding applications makes up more than 75% of the site. The site contains three major sections: products, tungsten electrode data and welding application data. Other parts of the site offer information about the company, provide a way to contact it via e-mail, link to other welding related sites and detail some free offers such as how to obtain literature, copies of welding-related magazine articles and free samples of pre-ground tungsten electrodes.

The Tungsten Data section includes tips sheets that provide some general rules on how to identify amperage ratings for a variety of grind angles and tip diameters and outline proper grinding and cutting techniques for tungsten electrode preparation. Besides the guidelines from the AWS A5.12 standard, the company recommends the following: " 1) Always use a dedicated tungsten grinder (to avoid contamination of the electrode). 2) Grind longitudinally and concentrically so that the lines on the ground surface move in the same direction as the electrode and the electrode has no flat spots. 3) Since tungsten is a very hard material, grinding wheels should be made of diamond or borazon. 4) electrodes should be cut using a cutting wheel where possible. Notching and breaking or using pliers to snap electrodes can cause splintering in the electrode that is difficult to see and can create a weld defect."

The Welding Application Data section offers information on the fundamentals of welding parameter development including welding physics, weld current, arc length, weld speed and the benefits of arc pulsation. It also includes a troubleshooting guide for arc welding systems and information on how to analyze a welding application for automation. This includes details on the benefits of automatic welding, how to plan for system automation, strategies for implementing an automated welding project and a table giving a sample calculation for return on investment based on equipment and labor costs.

http://www.pro-fusiononline.com

Trends in the welding industry

An overview of recent developments in the welding industry
and how they impact weld quality and consistency.

By Bernard Mannion and Liam O'Mannin

The manufacture of metal seals, pressure devices, sensors, and many other metal components require precision welding. The sealing, shaping, or joining technique must be extremely reliable because it is necessary to maintain the integrity of the product. The weld process must also be accomplished without interfering with the cosmetics or function of the product.

There are many variables to consider in the welding process. The variety of materials is growing daily and thus the burden on welding personnel to stay current with technology becomes more essential. Moreover, it seems that the predominant expertise in welding is acquired at the workplace by trial and error rather than by training in educational institutions.

A Brief Summary of Joining and Welding Processes

Soldering and Brazing: An economical means of applying filler metal to join components both in low and high volume.

Resistance Welding: This process applies large current flow to heat the components at the point of highest resistance-- at the weld joint.

Electron Beam Welding: This is a fusion process performed in a vacuum chamber where a high velocity beam of electrons is focused on the surface to be welded.

Laser Welding: This process uses focused coherent light (a laser) to melt the base material and is used for precision welding or production of quality parts.

Gas Tungsten Arc Welding: Gas Tungsten Arc Welding (GTAW), also known as Tig (Tungsten Inert Gas) Welding, is the most commonly used precision arc welding process. A welding arc is established between a Tungsten electrode and the part to be welded. The metal of the part is melted by the intense heat of the arc and fuses together.

Plasma Arc Welding: Plasma arc welding, basically an advancement of the GTAW process, uses a copper nozzle to surround the Tungsten electrode. A pilot arc is first established between the electrode and copper nozzle and then transferred to the part to be welded.

Tig and Plasma weld processes are the most commonly used methods for precision joining. Weld quality and repeatability has improved in sync with advances in power supply, process controls, and welding techniques. These advances allow the use of the process in even more precision applications.

The electrode tip dimensions shown must be held to close tolerances and the surface finish (ground or polished) of the electrode grind must be consistent.

Arc Welding and Joining Processes

In the manufacturing industry, the two most popular methods used for precision joining are the Tig and Plasma weld processes.

The Tig and Plasma welding processes were originally developed to provide a means to produce acceptable weld quality on a variety of metal materials and alloys. Advances in power supplies, welding techniques, and process controls have allowed for greater weld accuracy and the process is now used in an even broader range of precision applications.

In the Tig process an electric arc is established between a Tungsten electrode and the part to be welded. To start the arc, a high voltage is used to break down the insulating gas between the electrode and the workpiece. Current is then transferred through the electrode to create an electrode arc. The metal to be welded is melted by the intense heat of the arc and fuses together.

The plasma weld process is a variant of Tig welding that has an additional copper housing around the electrode that directs and further constricts the arc. Both processes use a Tungsten electrode ground to a point both as the source of the arc ignition and the means of energy transfer.

A variety of parts of all sizes can be joined with precision arc welding techniques. Note the pulsed arc finish on the weld surface.

Advanced Arc Welding Techniques

The pulsed arc wleding technique offers low heat input as it is used in welding thin components or metals next to fragile material such as glass or polymer. This is done by rapidly increasing and decreasing the arc welding current. This makes a seam weld of overlapping spot welds, which reduces the overall heat input to the area and also allows for increases in weld speed. This technique is used to great advantage by combination of rapid response power supplies and weld process controllers. The result is improved weld quality and increased output.

Equipment Trends

Looking more closely at all the elements of the welding system will reduce or eliminate many of the reasons arc welding systems occasionally seem to develop a personality of their own.

Power Supplies: The welding power supply itself has been refined. The method of delivering brute force power to a welding arc has become outdated as cutomers demand superior products. Higher performance machines with greater efficiency, accuracy, and response time have replaced these earlier "beasts."

Welding Control Systems: In order to meet more rigorous quality demands, the welding industry has moved to a much stricter control of standards and has developed weld programmers-devices that store and execute weld programs.

The welding process section of the work is automated by these programmers/ controllers and helps to reduce scrap parts by executing repeatable, pre-arranged weld programs within precise welding parameters. The welding capability is thus built into the welding system through the weld controller rather than taught to the manual welder. As a result, there is less opportunity for error or fatigue.

These controllers are used by manufacturing organizations for medium to large contract runs. Lower costs are attained mainly by confining the necessary skill level of an operator to loading and unloading parts. While repetitive welding is now accepted as an operation to be automated, there will always be a need for the skilled welder and manufacturing organizations have found ways to improve output here, too.

Orbital Welding Systems: Orbital welding systems were designed to be used in applications where a tube or pipe to be welded cannot easily be rotated or where the space restrictions for access limits the size of the welding device. In the orbital welding process, tubes/pipes are clamped in place and an orbital weldhead rotates an electrode around the part to make the required weld. Orbital welding systems are used for welding tubing in industries such as aerospace, boiler tubing, food and dairy, nuclear, pharmaceutical, and semiconductor.

Sidebar - Fundamentals of Precision Arc Welding

Tungsten Welding Electrode Tips: The Tungsten electrode, the source of the welding arc, is the element most commonly ignored by manufacturing organizations. Whether in manual or automatic welding, this is the area where manufacturing organizations can improve the consistency of their welding output with minor effort.

The safety issues of Tungsten electrode material are also being looked at more closely now. Many users of the Tig or plasma welding process do not realize that the welding electrodes they use contain Thorium, a radioactive element added to the Tungsten material to improve arc starting and welding characteristics. While the radioactivity is of a low level it brings an issue of danger--especially with the radioactive dust generated when grinding the electrodes to a point for welding. New Tungsten materials are now available, such as Lanthanated electrodes which offer superior arc welding characteristics and are safer due to their lack of radioactivity. While these materials are now commercially available, they have been largely ignored until recently.

A typical tungsten electrode grinder.

Pre-Ground Electrodes and Tungsten Electrode Grinders: Given the Thoriated electrode radioactivity issues and the ever-increasing weld quality requirements of the final weld, more and more companies are looking for ways to ensure that their weld quality is up to par.

Consistency and repeatability are key to welding applications. The shape and quality of the tungsten electrode tip is finally being recognized as a vital process variable. Once a weld procedure has been established, it is important that consistent electrode material, tip geometry, and surface condition be used.

Using electrodes pre-ground to requirements or a dedicated commercial electrode grinder to provide electrode tip quality and consistency offers the following benefits:

• Improved arc starting, increased arc stabblity, and more consistent weld penetration.
• A longer electrode life.
• A reduction of tungsten shedding minimizing the possibility of Tungsten inclusions in the weld.
• A dedicated electrode grinder helps ensure that the welding electrodes will not become contaminated by residue or material left on a standard shop grinder wheel.
• Tungsten electrode grinding equipment requires less skill to ensure that the tungsten electrode is ground correctly and with more consistency.

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Precision Welding Of Parts As Small As Needle Tips

Preground electrodes and specialty electrode materials are being used to enhance the performance of gas tungsten arc welding (Tig) and plasma welding of wires, needles, pacemakers, medical tools and components, bellows, batteries, and a variety of precision instruments.

High-quality electrode materials with exact tip geometry tolerances offer a noticeable difference in precision at the arc to produce higher-quality welds with much longer electrode life. One supplier of these products and services is Pro-Fusion, a new company founded by Bernard Mannion and Jack Heinzman III in Newbury Park, CA.

Pro-Fusion, a new company in Newbury Park, CA, is offering the technology and services to use specialty electrode materials with pre-ground electrode tips to enhance precision arc welding.

Their new company will begin by offering preground welding electrodes, tungsten electrode grinders, several tungsten alternatives, and a new line of plasma welding torches. Pro-Fusion also offers job shop welding services and precision machine shop services.

Pro-Fusion's customer, J&J Precision of Thomaston, CT, offers contract welding that can involve sealing the ends of small tube diameters. J&J makes eyelets and performs stamping, forming, machining, grinding, and assembly of precision metal components.

J&J's owner, John Maxwell, investigated the latest arc welding technology not as a joining, but as a heating and sealing, procedure. By using precision preground electrodes with a micro-arc welding system, Maxwell was able to seal the tube by momentarily imposing a welding arc on its ending. This melted the tube and produced a smooth hemispherical surface. The preground electrodes ensure accuracy and repeatability, according to Pro-Fusion. J&J uses the same technology for rod and wire end rounding, welding of custom endings to tubes, and creation of ball endings on wire.

Other applications for pre-ground electrodes include repetitive welds on identical parts, quality or critical-function welds, and parts with significant accumulated value prior to welding.

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Setting up and determining Parameters for Orbital Tube Welding

How to proceed when specs are not available

By Bernard Mannion and Jack Heinzman III

Orbital welding was first used in the 1960s in the aerospace industry. By the early 1980s, it became practical for many industries, when combination power supply/control systems were developed that operated from 110 volts alternating current (VAC) and were physically small enough to be carried around construction sites for multiple in-place welds.

Currently, typical industries using orbital welding include aerospace; food, dairy, and beverage; nuclear; offshore; pharmaceutical; and semiconductor. Other applications include boiler tubing and tube and pipe fittings, valves, and regulators.

Today's orbital welding systems offer computer controls that store a variety of welding parameters that can be called up as needed. In effect, the skills of a certified welder are built into the system, allowing it to produce consistent welds and leaving less room for error or defects.

Figure 1 Standard enclosed orbital weld heads can be used to weld tube sizes up to 6 inches and wall thicknesses up to 0.154 inch.

In the orbital welding process, tubes and pipes are clamped in place, and an orbital weld head rotates an electrode and electric arc around the weld joint to make the weld (see Figure 1). An orbital welding system consists of this weld head and a power supply.

Orbital weld heads come in enclosed and open styles and provide an inert atmosphere chamber that surrounds the weld joint. Standard enclosed orbital weld heads are practical for welding tube sizes from 1/16 to 6 inches (1.6 to 162 millimeters) with wall thicknesses of up to 0.154 inch (3.9 millimeters). Large diameters and wall thicknesses can be accommodated with open-style weld heads.

The power supply/control system supplies and controls the welding parameters according to the specific weld program created or recalled from memory. The power supply provides the control parameters, the arc welding current, and the power to drive the motor in the weld head, and it switches the shield gases on and off as necessary.

For orbital welding in many precision or high-purity applications, the base material, tube diameter, weld joint and part fit-up requirement, shield gas type and purity, arc length, tungsten electrode material, electrode tip geometry, and electrode grind surface condition may already be written into a specification covering the application.

Each orbital welding equipment supplier differs slightly in recommended welding practices and procedures. Where possible, the recommendations of the supplier should be followed, especially in areas that pertain to warranties.

This article presents guidelines for applications that have no specifications and for which the welding engineer must create the welding setup and derive the welding parameters.

Physics of the GTAW Process

Orbital welding uses the gas tungsten arc welding (GTAW) process as the source of the electric arc that melts the base material and forms the weld. In the GTAW process, an electric arc in established between a tungsten electrode and the part to be welded.

To start the arc, a high-voltage signal (usually 3.5 to 7 kilovolts) is used to break down (ionize) the insulating properties of the shield gas and make it electrically conductive to pass through a tiny amount of current. A capacitor dumps current into this electrical path, which reduces the arc voltage to a level at which the power supply can then supply current for the arc.

The power supply responds to the demand and provides weld current to keep the arc established. The metal to be welded is melted by the intense heat of the arc and fuses together.

Material Weldability

The material selected varies according to the application and environment the tubing must survive. The mechanical, thermal, stability, and corrosion resistance requirements of the application dictate the material chosen. For complex applications, a significant amount of testing is necessary to ensure the long-term suitability of the chosen material from a functionality and cost standpoint.

In general, the most commonly used 300 series stainless steels have a high degree of weldability, with the exception of 303/303SE, which contain additives for ease of machining. The 400 series stainless steels are often weldable but may require post weld treatment.

Potential differences of material heats must be accommodated. Each heat batch number will have minor differences in the concentration of alloying and trace elements. These trace elements can vary the conductivity and melting characteristics of the overall material. When a change in heat number is made, a weld test coupon should be made for the new heat. Changes in amperage may be required to return the weld to its original profile.

Certain elements of the material must be held to close tolerances. Minor deviations in elements such as sulfur can vary the fluid flow in the weld pool, completely changing the weld profile and potentially causing arc wander (see Figure 2).

Figure 2 Minor changes in sulfur content can change weld pool flow characteristics.

Weld Joint Fit-up

Weld joint fit-up depends on the weld specification requirements for tube straightness, weld concavity, reinforcement, and drop-through. If no specification exists, the molten material must flow and compensate for tube mismatch and any gap in the weld joint.

Wall thickness should be repeatable at the weld joint from part to part. Differences in tube diameter or out-of-roundness cause weld joint mismatch and arc gap variations from one welding setup to another. In addition, tube ends must be square and flat, and both the inside diameter (ID) and outside diameter (OD) should be burr-free with no chamfer. In general, the following rules apply regarding mismatch and gaps:

1. Any gap should be less than 5 percent of the wall thickness. It is possible to perform orbital welding with gaps of 10 percent of wall thickness or greater, but the quality of the weld suffers, and repeatability becomes challenging.

2. Wall thickness variations at the weld zone should be ±5 percent of nominal wall thickness. Again the laws of physics can sometimes allow welding with a mismatch of up to 25 percent of wall thickness, but weld quality and repeatability are compromised.

3. Alignment mismatch (high-low) can be avoided by using engineering stands and clamps to align the two tubes to be welded. This system also removes the mechanical requirement of aligning the tubes from the orbital weld head.

Shield gases

An inert gas is required on the tube OD and ID during welding to prevent the molten material from combining with the oxygen in the ambient atmosphere. The objective of the welder should be to create a weld that has zero heat tint at the weld zone.

Argon is the most commonly used shield gas (for the OD) and purge gas (for the ID). Helium is often used for welding on copper material. Mixed gases such as 98 percent argon/2 percent hydrogen, 95 percent argon/5 percent hydrogen, 90 percent argon/10 percent hydrogen, 75 percent helium/25 percent argon are often used to create the optimal balance of arc starting, arc stability, final weld cleanliness, molten puddle fluidity, and weld penetration.

Mixtures of 95 percent argon/5 percent hydrogen are incompatible with carbon steels and some exotic alloys and can cause hydrogen embrittlement in the weld. To simplify matters and reduce shield gas cost, 100 percent argon gas is often used.

Gas purity is dictated by the application. For high-purity situations in which the concern for microcontamination is paramount, such as semiconductor and pharmaceutical applications, the shield and purge gases must minimize the heat tint that could otherwise be undesirable. In these applications, ultrahigh-purity gas or gas with at local purifier is used. For noncritical applications, commercial-grade argon gas may be acceptable.

Tungsten Electrodes

The tungsten welding electrode--the source of the welding arc--is one of the most important elements of the welding system that is commonly ignored by welding system users. While no one would refute the importance of the ignition device on an automobile air bag, the rip cord for a parachute, or quality tires for automobiles, the importance of tungsten electrodes for quality welding is often overlooked.

The objective for the choice of tungsten parameters is to balance the benefits of a clean arc start with reduced arc wander with good weld penetration and a satisfactory electrode life.

Electrode Materials. For quire some time, tungsten manufacturers have added an oxide to pure tungsten to improve the arc starting characteristics and longevity of pure tungsten electrodes. In the orbital welding industry, the most commonly used electrode materials are 2 percent thoriated tungsten and 2 percent ceriated tungsten. While both types have their own advantages and drawbacks, it is always best to follow the advice of the orbital welding manufacturer.

Electrode Tip Geometry. Given the ever-increasing weld quality requirements of the final weld, more companies are looking for ways to ensure that their weld quality is up to par. The shape and quality of the tungsten electrode tip are finally being recognized as vital process variables.

Welders should follow the equipment suppliers' suggested procedures and dimensions first because they have usually performed a significant amount of qualifying and troubleshooting work to optimize electrode preparation for their equipment. However, when these specifications do not exist or the welder or engineer would like to change those settings to possible improve and optimize welding the following guidelines apply:

1. Electrode taper. This is usually called out in degrees of included angle (usually anywhere between 14 and 60 degrees). Figure 3 illustrates that characteristics of both sharp and blunt tapers. Figure 4 demonstrates how taper selection affects the size of the weld bead and the amount of penetration by showing a typical representation of the arc shape and resultant weld profile for different tapers.

Sharper Electrode	Blunter Electrode
Easy arc starting	Usually harder to start
Handles less amperage	Handles more amperage
Wider arc shape	Narrower arc shape
Good arc stability	More chance of arc wander
Less weld penetration	More weld penetration
Shorter electrode life	Longer electrode life

Figure 3 This table compares the characteristics of both sharper and blunter electrode tapers.

Figure 4 This drawing shows typical representations of the arc shape and resultant weld profile for various electrode tapers.

2. Electrode tip diameter. Grinding an electrode to a point is sometimes desirable for certain applications, especially if arc starting is difficult or short-duration welds on small parts are performed. However, in most cases, the welder should leave a flat spot or tip diameter at the end of the electrode. This reduces erosion at the thin part of a point and reduces the possibility of the tip falling into the weld. Large and small tip diameters offer the trade-offs shown in Figure 5.

Smaler Tip	Larger Tip
Easy arc starting	Usually harder to start
Good arc stability	More chance of arc wander
Less weld penetration	More weld penetration
Shorter electrode life	Longer electrode life

Figure 5 Depending on the welding application, different-sized tips may be required.

Electrode Grinders. A dedicated commercial electrode grinder can be used to provide electrode tip quality and consistency.

In addition, a dedicated electrode grinder helps to ensure that the welding electrodes will not become contaminated by residue or material left on a standard shop grinder wheel.

Figure 6 Using preground electrodes ensures that the electrode material quality, tip geometry, and ground electrode surface input to the welding process is constant.

Preground Electrodes. Because each operator grinding the electrodes has a slightly different touch, resulting in variable results, some manufacturers purchase electrodes pre-ground (see Figure 6). This option helps to ensure that the electrode material quality, tip geometry, and ground electrode surface input to the welding system is constant. Electrode charts or elctrode suppliers can provide the electrode diameter and tip geometry that are most suitable for particular welding application. Using an electrode grinder or preground electrodes (preferred):

1. Improves arc starting, increase arc stability, and make weld penetration more consistent.

2. Increases electrode life before electrode wear or contamination.

3. Reduces tungsten shedding, which minimizes the possibility or tungsten inclusions in the weld.

Weld Parameter Development

Many welding equipment suppliers offer a series of precalculated weld programs for a variety of tube diameters, wall thicknesses, and materials. Welders should always follow an equipment supplier's suggested procedures first. However, it is impossible for the equipment suppliers to have welding procedures for every welding application, and there will always be a trade-off in maximum possible weld speed versus weld quality and repeatability.

Given the ever-increasing weld quality requirements of the final weld, more companies are looking for ways to ensure that their weld quality is up to par.

When weld parameter specifications do not exist or welders or engineers would like to change those settings possibly to improve their welding, the following guidelines should be followed for modifying the welding parameters for a desired result. Note that these rules are general guidelines and do not apply to every possible welding application and mix of parameters. Some industry standards have been developed as starting points, but experimentation and experience determine the final weld parameters.

Arc Length. The arc gap setting depends on weld current, arc stability, and tube concentricity/ovality. The objective of the welding engineer is to keep the electrode at a constant distance from the tube surface with sufficient gap to avoid stubbing out.

The welder should try a base arc gap of 0.010 inch and add to this half the penetration required (usually the tube wall thickness), expressed in thousandths of an inch. Thus, if the tube wall is 0.030 inch, a good starting arc gap would be 0.010 inch + 0.015 inch = 0.025 inch. For a wall thickness/penetration requirement of 0.154 inch, the arc gap would be 0.010 inch + 0.070 inch = 0.080 inch.

Weld Speed. The weld speed depends on the flow rate of the material and the wall thickness. The objective is to weld as fast as possible while still yielding a quality output.

As a starting point for orbital welding, the tungsten surface speed should be 4 to 10 inches per minute (IPM), with faster welding speeds used for thinner-wall materials and the slower welding speeds used for heavy wall thickness. A good beginning speed is 5 IPM.

Welding Current. The welding current depends on the material, wall thickness, weld speed, and shield gas. The objective is to achieve full-penetration, defect-free welds.

As a starting point, the welder should use 1 ampere average current for every 0.001 inch of wall thickness if the material is stainless steel. Thus, for a 0.030-inch-wall tube, the average weld current is 30 amps in the first level.

Orbital welding typically uses multiple levels of weld current to compensate for heat buildup in the tube during the welding process. If the weld current used to penetrate the tubing initially were held at the same level for the complete weld, the weld penetration would increase as the weld progressed around the tube, producing too much penetration.

Usually, orbital welding uses a minimum of four levels of weld time, with each level decreasing in weld amperage. To start, weld level 4 should be set at 80 percent of weld level 1 amperage. Weld levels 2 and 3 should be set to decrease the current from level 1 to level 4 gradually.

Figure 7 This weld surface has a pulsed arc finish.

Arc Pulsing. Arc pulsing involves using the weld power supply to alternate the weld current rapidly from a high (peak current) to a low (background current) value. This creates a seam of overlapping spot welds. This technique reduces the overall heat input to the welding procedure, often improving weld quality and repeatability.

In some cases, materials and weld joints with poor fit-up that are difficult to weld successfully with a nonpulsed arc can be welded with a pulsed arc technique (see Figure 7). The result is improved weld quality and increased output.

In orbital welding, arc pulsing offers another advantage because gravity pulls the weld puddle in different directions as the weld is created around the tube. When the arc is at peak current, the base materials melt and flow together; at the lower background current, the puddle can solidify before becoming liquid at the next peak current pulse.

This diminishes the effect of gravity on the molten weld, minimizes the weld sagging at the 12 and 6 o'clock positions, and reduces the molten weld puddle running/slumping downhill at the 3 and 9 o'clock positions; without pulsing, the molten puddle running/slumping could alter the electrode-to-weld puddle distance. The arc pulsing technique thus becomes more advantageous as the wall thickness increases, resulting in a larger weld puddle.

Arc pulsing involves four welding parameters: peak current, background current, pulse width (duty cycle), and pulse frequency. Parameter combinations vary from company to company and welder to welder. Many welders arrive at the same visual welding result even after having used somewhat different welding parameters.

Peak-to-background current ratios provide a means for the welding current to pulse from one level to another. The industry usually uses ratios varying from 2:1 to 5:1. A good starting point is to use a 3:1 ratio, make the required weld, and test other ratios to see if any benefits can be gained.

The pulse frequency depends on the spot overlap required. A good starting parameter is a 75 percent spot overlap. For orbital welding, the pulses-per-second (PPS) rate for thin-wall tube is often equal to the weld speed in inches per minute (5 IPM = 5 PPS).

The pulse width (the percentage of time spent on the peak current) depends on the heat sensitivity of the material and the available current from the power supply. Higher heat sensitivity may require a lower pulse width percentage on the peak current. Standard pulse widths are often 20 to 50 percent. A good starting parameter is a pulse width of 35 percent.

Free arc pulsation software is available from the Internet that precalculates a variety of arc pulsation parameter for any given amperage or an application. In this fashion, welders can arrive at an acceptable weld program and quickly obtain a variety of alternative arc pulsation options to examine without requiring lengthy calculations or tedious empirical trial and error test welding.

Conclusion

Optimizing the welding process improves weld quality, increases weld speed, and reduces scrap and rework costs. Companies that can achieve this goal can realize lower costs per unit of product, quicker delivery of product, and fewer defects in workmanship. Using orbital welding systems, in conjunction with weld programs, control of input material and shield gas quality, and properly prepared preground electrodes, can be one step toward welding process optimization.

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Determining parameters for GTAW

By Bernard Mannion and Jack Heinzman III

The gas tungsten arc welding (GTAW) process originally was created in the 1940s to weld magnesium and aluminum alloys for aircraft applications.

It was developed because a welding method was needed that performed better on these materials than did shielded metal arc welding (SMAW). Today, many precision parts are gas tungsten arc welded, including batteries, metal bellows, pacemakers, medical components, and surgical tools (see Figure 1).

Originally, helium was used as the shielding gas, and the process became known as heliarc welding. Argon gas soon became the most widely used shield gas because of its lower cost and smoother arc.

In the GTAW process, an electrical arc is established between a tungsten electrode and the part to be welded. To start the arc, a high voltage is used to break down the insulating gas between the electrode and the part.

Current is then transferred through the electrode to create an electrode arc. The metal to be welded is melted by the intense heat of the arc and fuses together either with or without a filler material.

The arc zone is filled with an inert gas to protect the tungsten electrode and molten material from oxidation and to provide a conducting path for the arc current. Shield gases used are argon, helium, mixtures, of argon and helium, or small percentages of hydrogen mixed with argon. The shield gas usually is chosen according to the material to be welded.

A typical welding system usually consists of the following elements:

1. Welding power supply.
2. Weld controller.
3. Welding torch.
4. Tungsten electrode.

Besides the equipment, on of the most important aspects of the GTAW process is the welding parameters used. A weld program consists of a list of welding parameters developed to achieve a specific weld quality and production output.

A change in any parameter will have an effect on the final weld quality, so the welding variables normally are written down or stored in the welding equipment memory.

Figure 1 Many precision parts are made using GTAW, including batteries, metal bellows, medical components, and surgical tools.

For welding in many precision or high-purity applications, a specification may already be written that outlines the recommended welding parameters, including the base material; part diameter(s); weld joint and part fit-up requirements; shield gas type and purity; arc length; and tungsten electrode material, tip geometry, and surface condition.

Some welding equipment suppliers offer a series of precalculated weld programs for a variety of part diameters, materials, and thicknesses. Welders should always follow an equipment supplier's suggested procedures first because the suppliers usually have performed a significant amount of qualifying and troubleshooting work.

Of course, equipment suppliers can not possible have welding procedures for every welding application, This article is intended as a guideline for those GTAW applications in which no specification exists and the engineer responsible for the welding must create the welding setup and derive the welding parameters.

The rules of thumb noted here are general guidelines only and will not apply to every welding application and mix of parameters chosen. Although the welding parameters often are chosen and changed according to the specific needs of the application, some industry standards have been developed as starting points. Experimentation and experience will determine the final weld parameters.

The addition of wire to the process creates many additional parameters. This article focuses on fusion welding only.

Arc Length

The arc length (sometimes called the arc gap) is the distance from the electrode tip to the part to be welded. This setting is dependent on weld current, arc stability, and part concentricity/ovality. The welding engineer's objective is to keep the electrode at a constant distance from the part surface with a sufficient gap to avoid stubbing out.

As a rule of thumb, an arc length of 0.10 inch acts as a base. Half the weld penetration required, expressed in thousandths of an inch, is added to the base measurement to give the arc length for a given amperage.

Thus, if the part material thickness is 0.030 inch, the a good starting arc length would be 0.010 inch + 0.015 inch = 0.025 inch. For a material thickness/ penetration of 0.154 inch, a good starting arc length would be 0.010 inch + 0.072 inch = 0.082 inch.

Weld Speed

The weld speed, which is the speed of travel of the torch over the part or the part under the torch, is dependent on the flow rate of the material to be welded and the material thickness. The objective is to weld as quickly as possible while still yielding a quality output. Weld speed is a predominant factor in defining the production output of a welding system.

Orbital welding equipment weld speeds usually are 4 to 10 inches per minute (IPM), lathe welding speeds may be 5 to 60 IPM, and tube mill welding speeds can vary from 3 IPM to 60 feet per minute (FPM).

As a starting point for parts rotated under a welding torch, the tungsten surface speed should be 10 to 20 IPM, with the faster welding speeds used for thinner-wall materials and the slower speeds used for heavy-wall thicknesses.

Welding Current

The welding current corresponds to the amount of heat applied to the part to effect the weld, and it depends on the material to be welded, material thickness, welding speed, and shield gas. The objective is the achieve defect-free welds with the required penetration.

Free arc pulsation software, available on the Internet, precalculates a variety of arc pulsation parameters.

The welder should start by using 1 amp of welding current for every 0.001 inch of material thickness and for each 10-IPM weld speed increment if the material is stainless steel. Thus, for a 0.030 inch material thickness, the average weld current would be 30 amps in the first level with average weld speeds.

To compensate for heat buildup in circular parts during welding, a downslope at the end of the weld or multiple levels of weld current can be used. If the weld current used to initially penetrate the parts were held at the same level for the complete weld, the weld penetration would increase as the weld progressed around the part potentially producing too much penetration.

The number of levels of welding current needed depend greatly on the welding application and the associated welding speed.

Arc Pulsing

Arc pulsing involves using the welding power supply to alternate the weld current rapidly from a high (peak current) to a low (background current) value. This creates a seam of overlapping spot welds. This technique reduces the overall heat input to the base material and also can allow for increases in weld speed.

Arc pulsing brings many benefits to the welding procedure, often improving weld quality and repeatability. In some cases, materials and weld joints with poor fit-up that are difficult to weld successfully with a nonpulsed arc can be welded easily with a pulsed arc technique. The results are improved weld quality and increased output.

Arc pulsing involves four welding parameters: peak current, background current, pulse width (duty cycle), and pulse frequency. Many welders arrive at the same welding result using somewhat different welding parameters. The primary objective is to use the benefits of weld pulsation to improve weld quality and output.

Peak-to-background current ratios. The peak-to-background current ratios basically provide a means for the welding current to pulse form one level to another. Industry usage generally varies from 2:1 to 5:1 ratios. A good starting point is to use a 3:1 ratio, make the required weld, and test other parameters to see if any benefit can be gained.

Optimizing the welding process in manufacturing will improve weld quality, increase weld speed, and reduce scrap and rework costs.

Pulse frequency. The pulse frequency depends on the required spot overlap. A good starting parameter is to try to achieve 75 percent spot overlap. The pulse rate for thin-material parts welded at slow speed soften is equal to the weld speed in IPM (for example, 5 IPM = 5 pulses per second).

Pulse width. The pulse width--the percentage of time spent on the peak current--is dependent on the heat sensitivity of the material and the maximum available current from the power supply.

Material with higher heat sensitivity may require a lower pulse width percentage on the peak current. Standard pulse width are often 20 to 50 percent. A good starting point is to set a pulse width of 35 percent.

Free arc pulsation software, available on the Internet, precalculates a variety of arc pulsation parameters for any given amperage of an application. In this fashion, welders can arrive at an acceptable weld program and quickly obtain a variety of alternative arc pulsation options to examine without requiring lengthy calculations or tedious trial-and-error test welding.

Tungsten Welding Electrode

While no one would refute the importance of the ignition device on an automobile air bag or the ripcord of a parachute, the importance of the tungsten electrode for quality welding is of ten overlooked. Whether in manual or automatic welding, this is the area where manufacturing organizations can improve the consistency of their welding output with minor effort.

Safety. The safety issues related to tungsten electrode material are being looked at more closely. Many users of GTAW or plasma welding do not realize that the electrode they use contain thorium, a radioactive element added to the tungsten material to improve arc starting and welding characteristics. The radioactivity is of a low level, but it can be a hazard, especially if radioactive dust is generated when grinding the electrodes to a point.

New tungsten materials now are available, such as lanthanated electrodes, which offer superior arc welding characteristics and are safer because they lack radioactivity.

Electrode Diameter. Larger-diameter electrodes have a longer life but may be more difficult to arc-start at low amperages.

Here is a rule of thumb for electrodes at medium amperages: The electrode diameter multiplied by 1,500 equals the average amperage for acceptable electrode life (with a 20- to 30-degree angle).

Sharper Versus Blunt Electrodes. Sharper electrodes have less arc wander at lower amperages, more consistent arc starting, and a wider arc. More blunt electrodes have a longer life, provide deeper weld penetration for the same amperage levels, and can handle higher amperage levels.

Generally, use 20- to 30-degree angles for up to an average of 90 amps. Higher currents can use larger included angles.

Parameter Development Example

Following is an example of how to determine welding parameters for a 1-inch-diameter part with a 0.030-inch penetration requirement:

1. Arc length = 0.010 inch + (1/2 x Penetration required) 0.010 inch + (1/2 x 0.030 inch) = 0.025 inch
2. Weld speed = 15-IPM surface speed RPM = IPM/(3.1415 x Diameter) 15/(3.1415 x 1 inch) = 4.77 RPM
3. Average welding current levels
   • Use 1 amp of welding current per 0.001 inch of material thickness.
   • Downslope the weld at weld termination to form a gradual taper with a length approximately two to three times the weld width.
   • If heat builds in the part, causing excessive weld pool size or excessive weld penetration at the final stages of the weld, use multiple levels to decrease the weld current gradually as the part is welded.
4. Arc pulsation
   • Peak current = 0.030-inch material thickness x 1.7 = 51 amps
   • Background current = 1/2 of peak current = 17 amps
   • Pulse width/duty cycle = 35 percent
5. Tungsten electrode diameter and tip geometry
   For a 30-amp average welding current, a 0.040-inch or 0.060-inch-diameter electrode ground with a 20-degree included angle and a 0.005-inch tip flat diameter is a good starting point.

Conclusion

Optimizing the welding process is manufacturing will improve weld quality, increase weld speed, and reduce scrap and rework costs.

From this, a company can realize lower costs per unit of product, quicker delivery of product, and fewer defects in workmanship. These can be accomplished through the use of fine-tuned weld programs that offer consistency and repeatability.

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Arc welding on a stainless steel tube mill

Tips for gaining maximum output

By Bernard Mannion

Tube mills produce pipe and tube by roll forming a continuous strip of material until the edges of the strip meet together at a weld station. At this point, the welding process melts and fuses the edges of the tube together, and the material exits the weld station as welded tube.

Many times the main limitation to product output is the welding speed. The welding speeds at which tube mills operate thus are usually more than 10 times the welding speeds for other applications. It is with these significantly higher-than-normal welding speeds that many tubing manufacturers must struggle to gain a competitive edge.

Arc Welding Stainless Steel Tube

GTAW. Manufacturing stainless steel tubing with arc welding usually employs the gas tungsten arc welding (GTAW/Tig) process as the source of the electric arc that melts the base material and forms the weld. In the GTAW process, an electric arc is established between a tungsten electrode and the part to be welded. To start the arc, a high-voltage signal (usually 3.5 to 7 kilovolts) is used to break down (ionize) the insulating properties of the shield gas and make it electrically conductive for a tiny amount of current.

A capacitor dumps current into this electrical path, which reduces the arc voltage to a level at which the power supply then can supply current for the arc. The power supply responds to the demand and provides weld current to keep the arc established. The metal to be welded is melted by the intense heat of the arc and fuses together.

Plasma Arc. In the plasma welding torch, the tungsten electrode is located within a copper nozzle that has a small opening at the tip. A pilot arc is initiated between the torch electrode and nozzle tip. This arc then is transferred to the metal to be welded.

By forcing the plasma gas and arc through the constricted orifice of the nozzle, the torch delivers a high concentration of heat to a small area. This can produce a stiff arc that offers good arc stability and consistent welds. Given that the tungsten electrode is protected within the copper nozzle, the plasma process usually allows for many more hours of welding before maintenance on the electrode is required.

Whether using the GTAW or plasma arc process, the output of the tube mill depends on the arc welding speed and total time spent welding. Therefore, for maximum tube mill output, these important welding issues should be considered:

1. Material weldability
2. Shielding gas
3. Tube mill consideration-the ability of the tube mill to provide consistent, high-quality material edge presentation under the welding arc
4. Welding system considerations-the ability of the welding system to provide a consistent welding arc for optimum weld quality and maximum number of hours of welding

Material Weldability

Weldability is a word used only in the welding industry, and a search for it in Webster's dictionary will be fruitless. The word "weldability" usually means the ease with which a metal material melts and flows together to form a weld joint that exhibits almost as much mechanical, thermal, and corrosion resistance properties as the base metal.

Weldability also implies an ability to produce an acceptable weld speed under the welding arc, and this can vary greatly according to the material. In general, the 300 stainless steels used in tubing possess a high degree of weldability. The 400 series stainless steels also are weldable, but postweld treatment is an issue to consider. Copper, aluminum, nickel-based alloys (INCONEL®, MONEL®, and HASTELLOY®), titanium, and other precious metals possess some degree of weldability but may present challenges with surface oxides and molten metal flow.

Shielding Gas

Mixing small percentages of hydrogen with the argon shield gas (90 to 98 percent argon, 10 to 2 percent hydrogen) can have a beneficial effect on the resultant weld for these reasons:

1. The hydrogen acts like a lubricant within the molten weld material, thus increasing the wettability of the weld joint. The result of this effect is that the two edge materials flow together faster, and thus welding speed can be increased.
2. The hydrogen becomes a part of the energy transfer process to the weld, producing a deeper weld profile with less energy from the arc. This means that less weld current and a smaller weld puddle can be used for the same weld penetration. The physical size of the weld pool is a speed limitation, so a smaller weld puddle offers higher weld speeds.
3. The hydrogen has a scrubbing effect on the weld, producing a cleaner weld.

Naturally, with every benefit comes a drawback. A hydrogen addition is not suitable for welding all tube materials, especially some exotic alloys, because it can cause hydrogen embrittlement in the resultant weld. However, for the more commonly used stainless steels, there is no issue with embrittlement.

Adding hydrogen to the shield gas reduces the life of a standard 2 percent thoriated tungsten welding electrode. Under these conditions, some manufacturers use 1.5 percent lanthanated tungsten, which can more easily accommodate the hydrogen addition.

Tube Mill Considerations

It is important for the tube mill to provide consistent, high-quality material edge presentation under the welding arc. The mill should provide clean edge material mated together without any sway of the weld seam under the welding arc, even at high speeds. Failure to accomplish this will result in decreased weld quality and most likely a reduction in tube mill speed to achieve the required quality.

Weld joint fit-up depends on the weld specification requirements. Tubing is produced according to loose or rigid tolerances, depending on the application for which the tube is to be purchased. When the two edges of the tubes are butted together for welding, two of the main considerations are mismatch and gaps.

Usually, the tube mill weld box will be set up to ensure that the weld box rollers or shoes guide the tube endings together and hold them in position under the welding arc.

The weld produced by any tube mill is a function of the heat input for a given length of tubing. For a given welding amperage, the tube mill must maintain mill welding speed within close tolerances. Products are available that tie the welding current amperage exactly to the tube mill actual speed rather than the programmed speed. These systems also have assisted in minimizing the scrap tubing produced at tube mill shutdown and start-up.

Welding System Considerations

With any welding system, the equipment used must provide a stable welding arc within close tolerances to produce consistent-output weld quality. The parameters under which a tube mill performs are even more critical because of the welding speeds involved.

By examining more closely all the elements of the welding system, tube suppliers can reduce or eliminate some of the reasons that welding systems seem to develop a personality of their own. A typical welding system comprises many of the following elements.

Power Supply/Arc Starter. The engine behind the arc, the power supply, and arc starter provide the means to initiate the welding arc and provide stable power by which the tube material is fused together. At first, these power supplies were simple, large transformers delivering brute force to the arc. Many of these systems now have been replaced by power supplies of greater efficiency and accuracy. Recently, high-power linear amplifiers have offered tube producers a constant-current power supply capable of correcting arc instabilities in milliseconds.

Arc Distance Control. The quality and repeatability of welding depend to a great extent on the arc shape and voltage, which are proportional to the distance between the torch electrode and the workpiece. The arc gap distance should be kept constant during welding. Arc distance controllers offer the ability to preset and maintain the arc gap within closely defined tolerances.

Arc distance control in conventional welding provides the ability to hold constant the distance the electrode remains from the part to be welded. This normally is a means to accommodate part runout or to move back the electrode as the part is built up through the addition of filler material to the weld zone. Arc distance control for tube mill welding provides a means to position and modify the electrode arc gap quickly on changing electrodes and to modify the position of the electrode to accommodate some amount of electrode wear.

Magnetic Arc Control. Tube mill weld speeds are so high, and the material moves so rapidly under the arc, that magnetic arc control systems sometimes are used to hold the welding arc in a precise and repeatable position over the material to be welded. This prevents the arc from moving around or from being attracted to the high-speed weld pool moving away below. With a simple setup, a magnetic arc control unit easily can add at least 5 percent to the output speed of a tube mill.

Tungsten Electrode. The tungsten welding electrode, the source of the welding arc, is one of the most important elements of the welding system, but it also is one of the most commonly ignored by tube mill users. Each time the mill shuts down and starts up again, a certain amount of scrap is produced, and the issue of getting the whole system stable again for continuous output becomes paramount.

Some tubing producers continue to grind their tungsten electrodes manually and then wonder why they get inconsistent results. For tube mill welding, keeping close tabs on the tungsten welding electrode is one step that can improve the consistency of welding output with minor effort. Many tube mill users now purchase their electrodes preground by a supplier. This helps to eliminate the variability of operators grinding the electrodes with slightly different geometries.

Modifying tungsten electrode material, keeping electrode tip geometry consistent, and using polished electrode surface finishes can improve electrode arc starting ability, improve arc stability, and increase electrode life.

Recommendations for Improving Weld Performance

Given the ever-increasing weld quality requirements of the tubing industry, more and more companies are looking for ways to ensure that their weld quality is up to snuff. The easiest way to improve weld quality and consistency is to improve quality right at the arc. Suggestions include the following:

1. Use an arc distance control system to maintain the correct distance from the electrode to the tube when performing GTAW. This is likely to improve arc and weld output consistency.
2. Consider using the plasma weld process to improve arc stability, weld penetration, weld speed, and electrode arc life.
3. Use specialty electrode materials such as lanthanated tungsten with optimized tungsten tip geometry and polished electrode tip surface.
4. Install a magnetic arc control system to hold the arc as stable as possible. This allows for higher welding speeds and increased tube mill output.
5. Consider using shield gas mixtures such as argon/hydrogen or others to improve the wetting of the metals when they are in the molten form. This can allow for increases in welding speed and improve overall tube mill output.

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Fundamentals of Orbital Welding

Modern orbital-welding systems offer computer controls that store welding schedules in memory. The skills of a certified welder are thus built into the system, enabling the production of enormous numbers of identical welds and leaving little room for error or defects. This article serves as a guide to the technical and financial considerations of orbital welding.

Bernard Mannion

Orbital welding first found use in the 1960s when the aerospace industry recognized the need for a superior joining technique for aircraft hydraulic lines. The solution: a mechanism to rotate a welding arc from a tungsten electrode around a tube-weld joint. Regulating weld current with a control system automated the entire process. The result was a more precise, reliable method than manual welding.

Orbital welding became practical for many industries in the early 1980s with the development of portable combination power supply/control systems that operated from 110-V AC. Modern orbital-welding systems offer computer controls that store welding schedules in memory. The skills of a certified welder are thus built into the system, enabling the production of enormous numbers of identical welds and leaving little room for error or defects.

Orbital welding uses the gas-tungsten-arc-welding (GTAW) process as the source of the electric arc that melts the base material and forms the weld. During GTAW an electric arc forms between a tungsten electrode and the workpiece. To initiate the arc, an RF or high-voltage signal will ionize the shielding gas to generate a path for the weld current. A capacitor dumps current into the arc to reduce arc voltage to a point where the power supply can regulate. The power supply responds to the demand and provides current to maintain the arc.

A typical orbital tube weld. Note the overlapping, pulsed arc finish to the weld surface.

Material weldability

In general, the commonly used 300-series stainless steels offer a high degree of weldability using orbital equipment, except for types 303/303SE, which contain additives for ease of machining. The 400-series stainless steels, while generally weldable, may require post-weld heat treatment.

Fabricators should be prepared to adjust the orbital-welding setup to accommodate for potential differences among material heats.

Weld joint fitup

Fitup is dependent on the weld specification requirements on tube straightness, weld concavity, reinforcement, and drop through. If no specification exists, the laws of physics require that the molten material flow and compensate for tube mismatch and any gap in the weld joint.

The use of tube and pipe end-prep facing equipment helps to ensure end squareness and flatness. The i.d. and o.d. should be burr-free with no chamfer.

Sidebar - Industries and Applications for Orbital Welding

Shielding gas basics

During welding, an inert gas directed to the tube o.d. and i.d. prevents the molten material from combining with oxygen in the ambient atmosphere. With sufficient shielding gas coverage, welds can have practically zero tint at the weld zone i.d.

Argon is the most commonly used shielding gas for the o.d. and as the i.d. purge gas. Argon/hydrogen gas mixtures or helium gas may be used as the shielding gas for benefits to specific applications.

Tungsten electrode choice: The right tool for the job

The tungsten electrode, the source of the welding arc, is singularly the most important element of the welding system most often ignored by orbital welders. While no one would refute the importance of the ignition device on an automobile airbag, the rip cord for a parachute, or quality tires for our automobiles, the importance of the tungsten electrode is often overlooked. Whether in manual or automatic welding, this is one area where users can improve the consistency of their welding output with minor effort.

Sharper Electrode Angle	Blunter Electrode Angle
Last less than blunt	Last longer
Less penetration	Better penetration
Wider arc shape	Narrower arc shape
Handle less Amps	Handle more Amps
Less arc wander	More arc wander
More consistent arc	Less consistent arc
Smaller Tip	Larger Tip
Easier to start	Usually harder to start
Less arc wander	More arc wander
Less electrode life	More electrode life
Less penetration	More penetration

The welding procedure

Many welding equipment suppliers offer a series of pre-engineered weld schedules for a variety of tube diameters, wall thicknesses, and base materials. Welders should always follow these suggested procedures first. However, there will always exist a trade-off in maximum possible weld speed and weld quality and repeatability. Where weld parameter specifications do not exist or the engineer would like to change those settings, follow these guidelines:

Arc Length: Arc-gap setting depends on the weld current, arc stability, and tube concentricity or ovality. The welding engineer must keep the electrode at a constant distance from the tube surface with sufficient gap to avoid stubbing-out.

As a rule of thumb, set a base arc gap of 0.010 in. and add to this half the tube-wall thickness (or required penetration) expressed in thousandths of an inch. Thus, if the tube wall is 0.030 in. thick, then a good starting arc gap would be 0.010 + 0.015 = .025 in.

Weld Speed: Weld speed depends on flow rate of material to be welded and wall thickness. The objective: to weld as fast as possible while still producing a high-quality weld.

As a starting point, set welding speed at 4 to 10 in./min, running faster on thinner-wall materials and lower on heavy-wall tube.

To produce consistent, high-quality welds, the tungsten electrode must be of high-quality material and tip dimensions must be held to close tolerances.

Welding Current: Welding current depends on the base material, wall thickness, weld speed, and shielding gas. The objective: to achieve full penetration defect-free welds.

As a starting point, for welding of stainless steel use 1 A of weld current for every 0.001 in. of wall thickness. Thus, for 0.030 in.-wall tubing, set average weld current to 30A.

Weld Current Levels: Orbital welding typically calls for multiple levels of weld current to compensate for heat buildup in the tube during welding. If the current used to initially penetrate the tubing was held at the same level for the complete weld, penetration would increase as the weld progressed around the tube, resulting in excessive penetration.

Typically, orbital-welding procedures employ a minimum of four levels of weld time, with amperage decreasing from level 1 to level 4.

Sidebar - Oribtal Welding Equipment Cost Justification

Industries and Applications for Orbital Welding Aerospace: The aerospace industry was the first to recognize the advantages of automated orbital welding. The high-pressure systems of a single aircraft can contain more than 1,500 welded joints, all automatically created with orbital equipment. Boiler tube: Boiler-tube installation and repair offer perfect applications for orbital welding. Compact orbital weld heads can be clamped in place between rows of heat-exchanger tubing. Food, dairy and beverage industries: These industries require consistent full-penetration welds on all weld joints. For maximum piping-system efficiency, the tubing and tube welds must be as smooth as possible. Any pit, crevice, crack, or incomplete weld joint can trap the fluid flowing inside the tubing, becoming a harbor for bacteria. Nuclear piping: The nuclear industry, with its severe operating environment and associated specifications for high-quality welds, has long been an advocate of orbital welding. Offshore applications: Sub-sea hydraulic lines use materials whose properties can be altered during the thermal changes that accompany a typical weld cycle. Hydraulic joints welded with orbital equipment offer superior corrosion resistance and mechanical properties. Pharmaceutical industry: Pharmaceutical process lines and piping systems deliver high-quality water to their processes. This requires high-quality welds to ensure a source of water from the tubes uncontaminated by bacteria, rust, or other contaminant. Orbital welding ensures full-penetration welds with no overheating that could undermine the corrosion resistance of the final weld zone. Semiconductor industry: The semiconductor industry requires piping systems with extremely smooth internal surface finish to prevent contaminant buildup on the tubing wall or weld joints. Once large enough, a build-up of particulate, moisture, or contaminant could release and ruin the batch process. Tube/pipe fittings, valves, and regulators: Hydraulic lines, liquid- and gas-delivery systems, and medical systems all require tubing with termination fittings. Orbital systems provide a means to ensure high productivity of welding and optimum weld quality. Return to article

Orbital Welding Equipment Cost Justification

Modern automatic orbital welding equipment now makes it affordable for any company doing a small amount of orbital welding to justify its cost. With the availability of leasing programs, not owning one of these systems can actually be costing a company money. An automatic orbital welding system can do the work of at least two skilled manual welders. Below is a breakdown of the cost of two skilled manual welders versus one operator and orbital welding equipment.

Costs For Two Skilled Manual TIG Welders

A welder's basic wages vary somewhat according to geographic location. Welders wages usually range from $15.00/hr - $25.00/hr. An average basic wage of $20.00/hour was taken for the purposes of the calculations below. The full cost of employees can be shocking when all payroll contributions and benefits are taken into consideration.

Welder's Wages		Annual Cost
1.0	Average pay for one welder: ($20.00/hour) Work hours per year: 2080 (40hours/week x 52 weeks/year)	$41,600.00
2.0	Employer Payroll Contributions Social Security, Medicare, Fed. Unemployment, State Unemployment	$3,987.00
3.0	Other Direct Employee Costs National holidays, vacation time, sick days, medical insurance	$5,760.00
4.0	Employee Direct Overhead Costs Pension plans, workman's comp, liability insurance, etc.	$1,000.00
COST PER WELDER EMPLOYEE:		$ 52,347.00
TOTAL COST OF TWO WELDER EMPLOYEES:		$104,694.00

Costs For Operator and Orbital Equipment

Orbital Welding Equipment Cost	Annual Cost
Fully Loaded Orbital Welding System CobraTig 150 Orbital Welder, Cobra Cooler Accessory Kit, Copperhead 2-inch weldhead, Weldhead Collets, Bench Mount. Purchase Price = $18,030. Lease at $450/mo or $5,400.00 per year.	$ 5,400.00
Operator's Wages
1.0 Average pay for one operator: ($10.00/hour) Work hours per year: 2080 (40hours/week x 52 weeks/year)	$20,800.00
2.0 Employer Payroll Contributions Social Security, Medicare, Fed. Unemployment, State Unemployment	$2,375.00
3.0 Other Direct Employee Costs National holidays, vacation time, sick days, medical insurance	$3,942.00
4.0 Employee Direct Overhead Costs Pension plans, workman's comp, liability insurance, etc.	$1,000.00
COST OF ONE OPERATOR:	$ 28,117.00
TOTAL COST OF ONE OPERATOR AND SYSTEM:	$33,517.00

CONCLUSIONS

Using just one orbital welding system will save $71,177.00 per year. If a company has enough work to operate orbital welding equipment, they are losing $34.20 every hour that they do not choose to do so.

Owning orbital welding equipment also offers the user the following benefits not included in the above financial considerations:

Weld Quality -- The quality and consistency of welds that are produced by an automated welding system will far exceed that of a manual welder.

Lower Scrap Rates -- Lowered scrap and rework costs due to improved weld consistency.

Welding Department Output -- An orbital welding system improves a company's ability to meet tighter project schedules and to bid on larger and more precision welding jobs due to increased output capability and higher weld quality.

Reduced Skill Level Risks -- Using orbital welding equipment decreases reliance on welding department skills, welder training, and availability of skilled welders in the local labor pool. Modern day orbital welding equipment is easy for an operator to learn how to use.

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Orbital Tube Welding

Understanding the basic principles behind orbital tube welding may help you arrive more rapidly at the optimum weld procedure for your specific application.

By Bernard Mannion and Jack Heinzman III

Orbital welding was first used in the 1960s, when the aerospace industry recognized the need for a superior joining technique for aerospace hydraulic lines. A mechanism was developed in which the arc from a Tungsten electrode was rotated around the tubing weld joint. The arc welding current was regulated with a control system thus automating the entire process. The result was a more precision and reliable method than the manual welding method it replaced.

In the early 1980s, Orbital welding became practical for many industries when combination power supply/control systems were developed that operated from 110 VAC. These systems were physically small enough to be carried from place-to-place on a construction site for multiple in-place welds. Modern day orbital welding systems offer computer control, where welding parameters for a variety of applications can be stored in memory and later called up for a specific application. Hence, the skills of a certified welder are thus built into the welding system, producing enormous numbers of identical welds and leaving significantly less room for defects.

Orbital Welding Equipment

In the orbital welding process, tubes/pipes are clamped in place, and an orbital weldhead rotates an electrode and electric arc around the weld joint to make the required weld. An orbital welding system consists of a power supply and an orbital weldhead.

The power supply/control system supplies and controls the welding parameters according to the specific weld program created or recalled from memory This supply provides the control parameters, the arc welding current, the power to drive the motor in the weldhead, and switches the shield gas(es) on/off as necessary.

Orbital weld heads are normally of the enclosed type, and provide an inert atmosphere chamber that surrounds the weld joint. Standard enclosed orbital weld heads are practical in welding tube sizes from 1/16 inch (1.6 mm) to 6 inches (152 mm) with wall thicknesses of up to .154 inches (3.9 mm). Larger diameters and wall thicknesses can be accommodated with open style weld heads.

Reasons for Using Orbital Welding Equipment

Sidebar - Can it save you money?

There are many reasons for using orbital welding equipment. The ability to make high quality, consistent welds repeatedly, at a speed close to the maximum weld speed, offer many benefits to the user:

1. Productivity. An orbital welding system will drastically outperform manual welders, many times paying for the cost of the orbital equipment in a single job.
2. Quality. The quality of a weld created by an orbital welding system (with the correct weld program) will be superior to that of manual welding. In applications such as semiconductor or pharmaceutical tube welding, orbital welding is the only means to reach the weld quality requirements.
3. Consistency. Once a weld program has been established, an orbital welding system can repeatedly perform the same weld hundreds of times, eliminating the normal variability, inconsistencies, errors, and defects of manual welding.
4. Skill level. Certified welders are increasingly hard to find. With orbital welding equipment, you don't need a certified welding operator. All it takes is a skilled mechanic with some weld training.
5. Versatility. Orbital welding may be used in applications where a tube or pipe to be welded cannot be rotated or where rotation of the part is not practical. In addition, orbital welding may be used in applications where access space restrictions limit the physical size of the welding device. Weld heads may be used in rows of boiler tubing, where it would be difficult for a manual welder to use a welding torch or view the weld joint.

Many other reasons exist for the use of orbital equipment over manual welding. For example, applications where inspection of the internal weld is not practical for each weld created. By making a sample weld coupon that passes certification, the logic holds that if the sample weld is acceptable, that successive welds created by an automatic machine with the same input parameters should also be sound.

Standard enclosed orbital weld heads are practical in welding tube sizes from 1/16 inch (1.6 mm) to 6 inches (152 mm) with wall thicknesses of up to .154 inches (3.9 mm) Larger diameters and wall thicknesses can be accommodated with open style weld heads.

General Guidelines for Orbital Tube Welding

For orbital welding in many precision or high purity applications, the base material to be welded; the tube diameter(s); weld joint and part fit-up requirements; shield gas type and purity; arc length; and Tungsten electrode material, tip geometry, and surface condition may already be written into a specification covering the application.

Each orbital welding equipment supplier differs slightly in recommended welding practices and procedures. Where possible, follow the recommendations of your orbital equipment supplier for equipment set-up and use, especially in areas that pertain to warranty issues. Note that, this section is only intended as a guideline for those applications where no specification exists. The engineer responsible for the welding must create the welding set-up, and derive the welding parameters, in order to arrive at the optimum welding solution.

Welding Basics and Set-Up

The Physics of the GTAW Process

The orbital welding process uses the Gas Tungsten Arc Welding process (GTAW), as the source of the electric arc that melts the base material and forms the weld. In the GTAW process (also referred to as the Tungsten Inert Gas process -- TIG) an electric arc is established between a Tungsten electrode and the part to be welded. To start the arc, an RF or high voltage signal (usually 3.5 to 7 KV) is used to break down (ionize) the insulating properties of the shield gas and make it electrically conductive in order to pass through a tiny amount of current. A capacitor dumps current into this electrical path, which reduces the arc voltage to a level where the power supply can then supply current for the arc. The power supply responds to the demand and provides weld current to keep the arc established. The metal to be welded is melted by the intense heat of the arc and fuses together.

Material Weldability

The material selected varies according to the application and environment the tubing must survive. The mechanical, thermal, stability, and corrosion resistance requirements of the application will dictate the material chosen. For complex applications, a significant amount of testing will be necessary to ensure the long term suitability of the chosen material from a functionality and cost viewpoint.

In general, the most commonly used 300 series stainless steels have a high degree of weldability with the exception of 303/303SE which contain additives for ease of machining. For hundred series stainless steels are often weldable, but may require post weld heat treatment.

Accommodation must be made for the potential differences of different material heats. The chemical composition of each heat batch number will have minor differences in the concentration of alloying and trace elements. These trace elements can vary the conductivity and melting characteristics slightly for each heat. when a change in heat number is make, a test coupon should be make for the new heat. Minor changes in amperage may be required to return the weld to its original profile.

It is important that certain elements of the material be held to close tolerances. Minor deviations in elements, such as sulfur, can vary the fluid flow in the weld pool, completely changing the weld profile and causing arc wander.

For orbital welding, the goal is to have the minimum sufficient weld penetration to consistently weld through the tube wall.

How electrode tip geometry affects the weld profile.

Weld Joint Fit-Up

Weld joint fit-up is dependent on the weld specification requirements on tube straightness, weld concavity, reinforcement, and drop through. If no specification exists, the laws of physics will require that the molten material flow and compensate for tube mismatch and any gap in the weld joint.

Tubing is produced according to tolerances that are rigid or loose according to the application for which the tube was purchased. It is important that the wall thickness is repeatable at the weld joint from pat to part. Differences in tube diameter or out-of-roundness will cause weld joint mismatch and arc gap variations from one welding set up to another.

Tube and pipe end prep facing equipment is recommended in order to help ensure end squareness and end flatness. Both the O.D. and O.D. should be burr free with no chamfer.

When two tubes are butted together for welding, two of the main considerations are mismatch and gaps. In general, the following rules apply:

• Any gap should be less than five percent of the wall thickness. It is possible to weld with gaps of up to 1- percent ( or greater) of wall thickness, but the resultant quality of weld will suffer greatly, and repeatability will also become a significant challenge.
• Wall thickness variations at the weld zone should be +/- five percent of nominal wall thickness. Again, the laws of physics will allow welding with mismatch of up to 25 percent of wall thickness if this is the only challenge. Again, the resultant quality of weld will suffer greatly, and repeatability will become an issue.
• Alignment mismatch (high-low) should be avoided by using engineering stands and clamps to align the two tubes to be welded. This system also removes the mechanical requirements of aligning the tubes from the orbital weldhead.

Minor changes in sulfur content can change weld pool flow characteristics with a dramatic effect on penetration (The Maragoni Effect).

Shield Gas(es)

An inert gas is required on the tube O.D. and I.D. during welding to prevent the molten material from combining with the oxygen in the ambient atmosphere. The objective of the welder should be to create a weld that has zero tint at the weld zone I.D.

Argon is the most commonly used shield gas (for the O.D. of the tube and the purge gas (for the I.D. of the tube). Helium is often used for welding on copper material. Mixed gases, such as 98 percent Argon/two percent Hydrogen; 95 percent Argon/five percent Hydrogen; 90 percent Argon/10 percent Hydrogen; or 75 percent Helium/25 percent Argon may be used when the wall thickness to be welded is heavy (.1" or above). Using mixtures of 95 percent Argon/five percent Hydrogen is incompatible with carbon steels and some exotic alloys, often causing hydrogen embrittlement in the resultant weld. As a general rule, for simplicity and reduction of shield gas cost, use 100 percent Argon gas.

Gas purity is dictated by the application. For high purity situations, where the concern for micro-contamination is paramount, such as semiconduction and pharmaceutical applications, the shield and purge gases must minimize the heat tint that could otherwise be undesirable. In these applications, ultra high purity gas or gas with a local purifier are employed. For non-critical applications, commercial grade argon gas may be used.

The combination of the electrode tip geometry and shield gas can have a major effect on the weld penetration, weld quality, welding speed, and electrode life.

Using pre-ground electrodes ensures that the electrode material quality, tip geometry, and ground electrode surface input to the welding process is constant.

Tungsten Electrode

The Tungsten welding electrode, the source of the welding arc, is one of the most important elements of the welding system that is commonly ignored by welding system users. Users continue to manually grind and wonder why they produce inconsistent results. Whether in manual or automatic welding, this is the area where manufacturing organizations can improve the consistency of their welding output with minor effort.

Basically, the objective for the choice of Tungsten parameters is to balance the benefits of a clean arc start and reduced arc wander with good weld penetration and satisfactory electrode life.

Electrode Materials

For quite some time, Tungsten manufacturers have added an oxide to pure Tungsten to improve the arc starting characteristics and longevity of pure Tungsten electrodes. In the orbital welding industry, the most commonly used electrode materials are two percent thoriated Tungsten and two percent ceriated Tungsten.

Many users of the TIG welding process do not realize that the welding electrode they use contains Thorium, a radioactive element added to the Tungsten.

Safety

The safety issues of Tungsten electrode material are now being looked at more closely. Many users of the TIG welding process do not realize that the welding electrode the use contains Thorium, a radioactive element added to the Tungsten. While the radioactivity is of a low level, it brings an issue of danger, especially with the radioactive dust that is generated when grinding the electrodes to a point for welding.

Alternative, non-radioactive Tungsten materials are now available, such as two percent ceriated electrodes, which often offer superior arc welding. While these materials are commercially available they have been largely ignored until recently.

A typical orbital tube weld. Note the pulsed arc finish on the weld surface.

Recommended Electrode Materials

Cerium, as a base material, has a lower work function than Thorium, offering superior emission characteristics. So, not only do ceriated electrodes offer an advance in electrode safety, they also improve the arc starting ability of the orbital equipment. However, as mentioned earlier, it is always best to follow the advice of your orbital equipment manufacturer.

Electrode Tip Geometry

Given the ever-increasing weld quality requirements of the final weld, more and more companies are looking for ways to ensure that their weld quality is up to par. Consistency and repeatability are key to welding applications. The shape and quality of the Tungsten electrode tip is also being recognized as a vital process variable. Once a weld procedure has been established, it is important that consistent electrode material, tip geometry, and surface condition be used.

Welders should follow an equipment supplier's suggested procedures and dimensions first, because they have usually performed a significant amount of qualifying and troubleshooting work to optimize electrode preparation for their equipment. However, where these specifications do not exist, or the welder or engineer would like to change those settings to possibly improve and optimize their welding, the following guidelines apply:

Electrode Taper

This is usually called out in degrees of included angle usually anywhere between 14deg and 60deg). Below is a summary chart that illustrates how different tapers offer different arc shapes and features:

Sharper Electrodes	Blunter Electrodes
Last less than blunt	Last longer
Less weld penetration	Better weld penetration
Wider arc shape	Narrower arc shape
Handle less amperage	Handle more amperage
Less arc wander	Potential for more arc wander
More consistent arc	Less consistent arc

To demonstrate graphically how the taper selection will effect the size of the weld bead and the amount of penetration, the drawing on page 20 show typical representations of the arc shape and resultant weld profile for different tapers.

Electrode Tip Diameter

Grinding an electrode to a point is sometimes desirable for certain applications, especially where arc starting is difficult or short duration welds on small parts are performed. In most cases, however, it is best for a welder to leave a flat spot or tip diameter at the end of the electrode. This reduces erosion at the thin part of a point, and reduces the concern that the tip may fall into the weld. Larger and smaller tip diameters offer the following trade-offs:

Smaller Tip	Larger Tip
Easier to start	Usually harder to start
Less arc wander	More chance of arc wander
Less electrode life	More electrode life
Less weld penetration	More weld penetration

Tungsten Electrode Grinder and Pre-Ground Electrode

Using electrodes pre-ground to requirements or a dedicated commercial electrode grinder to provide electrode tip quality and consistency, offers the following benefits to the user in their welding process:

• Improved arc starting, increased arc stability, and more consistent weld penetration.
• Longer electrode life before electrode wear or contamination.
• Reduction of Tungsten shedding. This minimizes the possibility of Tungsten inclusions in the weld.
• A dedicated electrode grinder helps ensure that the welding electrodes will not become contaminated by residue or material left on a standard shop grinder wheel.
• Tungsten electrode grinding equipment requires less skill to ensure that the Tungsten electrode is ground correctly and with more consistency.

Pre-Ground Electrodes

Rather than risk electrode radioactivity issues, and constantly endure the variability of each operator grinding the electrodes with a slightly different touch, many manufacturing organizations have chosen to purchase electrodes pre-ground. Since a small difference in the dimensions of an orbital electrode can produce a big difference in the weld results, pre-ground electrodes are the preferred electrode choice to maintain the consistency of your welding. This low-cost option ensures that the electrode material quality, tip geometry, and ground electrode surface input to the welding process is constant. Consult electrode charts or a pre-ground electrode supplier to obtain the electrode diameter and tip geometry that is most suitable for your welding application.

This weld profile shows a single level of weld time. Orbital welding normally uses a minimum of four levels of weld time, with each level decreasing in weld amperage as the tube heats up during the welding process.

image - weld profile

Conclusion

In conclusion, the important points to remember are:

• Orbital welding has been used by many industries to improve the quality and quantity of tube welding when compared to what can be accomplished by manual welders.
• The effective cost of an employee computes to be significantly more that just his base salary. The output of a $20 per hour skilled welder actually costs over $72,000 per year (almost twice his yearly base wage).
• If a complete orbital welding system costs between $15,000 and $20,000 and can output over twice the amount of welding that a manual welder can produce when the equipment will pay for itself in a matter of months.
• Finally, the volume of welds that are produced by an automated welding system will far exceed that of a manual welder. In addition to weld quality improvements, this will bring two additional financial benefits: One, increased output per day at lower cost. Two, lowered scrap and rework costs due to improved weld consistency.

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Plasma arc welding brings better control

By Bernard Mannion Marketing Manager and Jack Heinzman III, President Pro-Fusion Technologies, Inc, Newbury Park, CA

The plasma welding process was introduced to the welding industry in 1964 as a method of bringing better control to the arc welding process in lower current ranges. Today, plasma retains the original advantages it brought to the industry by providing an advanced level of control and accuracy to produce high quality welds in both miniature and precision applications and to provide long electrode life for high production requirements at all levels of amperage. Plasma welding is equally suited to manual and automatic applications. It is used in a variety of joining operations ranging from welding of miniature components to seam welding, to high volume production welding, and many others.

Pictured above is a plasma arc on the left and a TIG arc on the right. Below, the diagram shows the schematic difference between the plasma arc on the left and the TIG arc on the right. Note the cylindrical shape of the plasma arc when compared to the conical shape of the TIG arc.

How it works

A plasma is a gas which is heated to an extremely high temperature and ionized so that it becomes electrically conductive. Similar to GTAW (TIG), the plasma arc welding process uses this plasma to transfer an electric arc to a workpiece. The metal to be welded is melted by the intense heat of the arc and fuses together.

In the plasma welding torch a Tungsten electrode is located within a copper nozzle having a small opening at the tip. A pilot arc is initiated between the torch electrode and nozzle tip. This arc is then transferred to the metal to be welded. By forcing the plasma gas and arc through a constricted orifice, the torch delivers a high concentration of heat to a small area. With high performance welding equipment, the plasma process produces exceptionally high quality welds.

Plasma gases are normally argon. The torch also uses a secondary gas which can be argon, argon/hydrogen, or helium, which assists in shielding the molten weld puddle thus minimizing oxidation of the weld.

In order to perform plasma arc welding, the following is required: a power supply; a plasma console (sometimes external, sometimes built in); a water recirculator (sometimes external, sometimes built in); a plasma welding torch; and a torch accessory kit (tips, ceramics, collets, electrodes, and setup gages).

Features and benefits

There are a range of features and benefits to plasma arc welding.

Plasma arc welding features a protected electrode which allows for less electrode contamination. This is especially advantageous in welding materials that out gas when welded and contaminate the unprotected GTAW electrode. Plasma arc welding has forgiveness in arc length changes due to arc shape and even heat distribution. This results in the arc stand off distances not being as critical as in GTAW. Plasma arc welding gives a good weld consistency and no AVC is needed in 99% of applications, sometimes even with wirefeed.

The arc transfer is gentle and consistent so it provides for welding of thin sheet, fine wire, and miniature components where the harsh GTAW arc start would damage the part to be welded. Offering a stable arc in welding reduces arc wander so the arc welds where it is aimed allowing weld tooling in close proximity to the weld joint for optimum heat sinking.

A plasma welding torch has an intricate internal design to carry plasma pilot gas, shield gas, water cooling hoses, and power cables for plasma pilot arc current and weld current.

There is only minimal high frequency noise used in plasma arc welding to start the pilot arc, thus plasma can be more easily used with NC controls with less fear of the arc starting noise causing glitches in any electrical equipment. Another benefit lies in welding applications involving hermetic sealing of electronic components where the GTAW arc start would cause electrical disturbances possible damaging the electronic internals of the component to be welded.

Arc energy in plasma welding can reach three times that of TIG welding causing less weld distortion and smaller welds with higher welding speeds. Welding time can be as short as 0.005 sec, ideal for spot welding of fine wires, while the accurate weld times, combined with precision motion devices, provide for repeatable weld start/stop positions in seam welding. Low amperage arc welding (as low as 0.05A) allows welding of miniature components and good control in downsloping to a weld edge. The arc diameter chosen via the nozzle orifice used assists in predicting the weld bead size.

Applications

The plasma process can gently yet consistently start an arc to the tip of wires or other small components and make repeatable welds with very short weld time periods. This is advantageous when welding components such as needles, wires, light bulb filaments, thermocouples, probes, and some surgical instruments.

When dealing with hermetically sealed medical and electronic components, sealed via welding, the plasma process provides the ability to--1) reduce the heat input to the part; 2) weld near delicate insulating seals; and, 3) start the arc without high frequency electrical noise which could be damaging to the electrical internals.

A whole repair industry has sprung up to assist companies wishing to reuse components with slight nicks and dents from misuse or wear. The ability of modern microarc power supplies to gently start a low amperage arc and make repairs has provided users with a unique alternative to conventional repair and heat treatment. Both the micro-TIG and microplasma welding processes are used for tool, die, and mold repair. For outside edges the plasma process offers great arc stability and requires less skill to control the weld puddle. To reach inside corners and crevices the TIG process allows the tungsten welding electrode to be extended in order to improve access.

In strip metal welding, the plasma process provides the ability to consistently transfer the arc to the workpiece and weld up to the edges of the weld joint. In automatic applications no arc distance control is necessary for long welds and the process requires less maintenance to the torch components.

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Plasma Welding: More Accurate, Better Control At Lower Currents

Equally suited to manual and automated applications, plasma offers many advantages in producing miniature and precision welds, high-volume strip metal joining, and equipment assembly.

Since its introduction to the welding industry in 1964, plasma welding has expanded on its original advantages of control and accuracy by producing high-quality welds with long electrode life in high-production applications. Now, plasma is being used to weld everything from precision surgical instruments and weld kitchen equipment for the food industry, to repairing jet engine blades.

The plasma is actually a gas that is heated to an extremely high temperature and ionized so that it becomes electrically conductive. Similar to GTAW (gas tungsten arc welding), the plasma arc welding process uses this plasma to transfer an electric arc to the workpiece. The metal to be welded is melted by the intense heat of the arc and fuses together. Metals hat can be welded using plasma include: stainless, heat-resistant, and other steels; titanium; Inconel; Kovar; zircalloy; tantalum; copper; brass; gold; and silver.

A comparison of the TIG/GTAW (left) and Plasma (right) welding arcs.

In the plasma welding torch a tungsten electrode is located within a copper nozzle that has a small opening at the tip. A pilot arc is initiated between the torch electrode and the nozzle tip; and the arc is then transferred to the metal to be welded. By forcing the plasma gas and arc through a constricted orifice, the torch delivers a high concentration of heat to a small area. With this process, high-performance plasma welding equipment is able to produce exceptionally high-quality welds. The protected electrode is less exposed to contamination, especially when welding materials that tend to outgas when heated. This results in longer electrode life and increased time between electrode maintenance (usually one eight-hour shift).

Plasma gases are normally argon; and the torch also uses a secondary gas (argon, argon/hydrogen or helium) to assist in shielding the molten weld puddle, which minimizes oxidation of the weld. The nozzle orifice is selected to control arc diameter, with assists in predicting the weld bead size. Additional equipment required for plasma welding includes: a power supply; a plasma console (external or built-in); a water recirculator (external or built-in); and plasma welding torch and accessory kit (tips, ceramics, collets, and electrode set-up gages).

The plasma arc starting and transfer is gentle and consistent, which is an advantage in welding thin sheet materials, fine wires, and miniature parts. The arc length, shape, and heat distribution make the welding standoff distance less critical than with GTAW; no AVC (automatic voltage control) is needed in nearly all applications. High stability during welding reduces arc wandering and enables the operator to use an arc-starting tool in close proximity to the weld joint for optimum heat sinking. The arc energy density is about three times that of GTAW, which reduces weld distortion and the heat-affected zone, makes smaller welds possible, and enables higher weld speeds (with welds completed in as little as 0.005 seconds).

Starting currents of less than 1.0 Amp enable precision welding of miniature components and good control in down sloping to a weld edge. Once the pilot arc is started, plasma power supplies generate minimal high-frequency noise, enabling plasma to be used with NC (numerical control) equipment without electrical interference. This also allows the use of plasma welding in such applications as hermetic sealing of electronic components, unlike GTAW arc welding where electrical disturbances would possibly damage sensitive internal electronic components. Plasma supplies also offer a wide range of frequency options for pulsing applications, sometimes as high as 10 kHz.

Arc energy density is about three times that of GTAW

Other plasma welding applications are many and varied. An entire repair industry has grown from using plasma in die and mold repair. The ability of micro-arc supplies to start a low-current arc and repair slight nicks and dents from misuse or wear has provided an effective alternative to conventional repair and heat treatment. For outside edges the plasma process offers greater arc stability and requires less skill in controlling the weld puddle. To reach inside corners and crevices, the tungsten electrode of the GTAW/TIG process can be extended to provide improved access.

In strip metal welding the plasma process is consistent in transferring the arc to the workpiece and working up to the edges of the weld joint. In automated applications no arc distance control is needed for long welds, and the process requires less maintenance to the torch components. Tube mills produce tube and pipe by roll forming strip material and welding the mating edges at a weld station. The output of the tube mill depends on the arc welding speed and total time spent at the welding station. The characteristics of the plasma welding process give it a significant advantage in this application, namely: maximum tube mill weld speed; arc stability for optimum weld quality and consistency; and maximum electrode tip life.

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MIG vs. Flux-Cored: Which Welding Process Is Right for You?

MIG vs. Flux-Cored: Which Welding Process Is Right for You?

You are about to make the plunge and buy your first wire feeder welder. Being a toolguy (or gal), you don't want to waste your money on a toy that goes out with the trash in a few weeks. You most likely are very comfortable building things from wood, but you always wanted to step up to steel. You probably want to run it off of 115 volt input, so that it is very portable, but maybe stepping up to the 230 volt input machines with the option of welding thicker material (more than ¼") is a valid point. You think the decision-making process is over when you are hit with yet another question - which welding process will you use? . . . GMAW (MIG) or FCAW (flux-cored)? If you are like most novice welding operators, you may be confused as to the differences of these two choices. The best answer depends on 3 things. First, what you are welding. Second, where are you welding it. And third, the surface finish of what you are welding. We will help you to decipher between the two processes, then describe advantages and disadvantages of each and wrap up by giving you usage tips. Ultimately, we hope to help you decide on a solution that will give you the best results for your application. The suggestions here are conservative and should be attainable by a beginner. Welding is a skill and an art about 95% can learn to do. Very few baseball players are able to hit over .350 in the majors. Very few welders have the skills to make picture perfect welds. It is critical to have good eye/hand coordination and a steady hand. Arc practice time is the only instructor that will teach you to truly set the machine properly. With basic motor skills, practice and patience, you should attain success at making sound welds.

The Definitions

Gas Metal-Arc Welding:

GMAW as identified by the American Welding Society, is also popularly known as MIG (Metal Inert Gas) and uses a continuous solid wire electrode for filler metal and an externally supplied gas(typically from a high-pressure cylinder) for shielding. The wire is usually mild steel, typically copper colored because it is electroplated with a thin layer of copper to protect it from rusting, improve electrical conductivity, increase contact tip life and generally improve arc performance. The welder must be setup for DC positive polarity. The shielding gas, which is usually carbon dioxide or mixtures of carbon dioxide and argon, protects the molten metal from reacting with the atmosphere. Shielding gas flows through the gun and cable assembly and out the gun nozzle with the welding wire to shield and protect the molten weld pool. Molten metal is very reactive to oxygen, nitrogen and hydrogen from the atmosphere, if exposed to it. The inert gas usually continues to flow for some time after welding to keep protecting the metal as it cools. A slight breeze can blow the shielding away and cause porosity, therefore welding outdoors is usually avoided unless special windscreens are erected.

However, if done properly, operator appeal and weld appearance are excellent with MIG and it is most welders' favorite process to use. Good technique will yield excellent results. The properly made finished weld has no slag and virtually no spatter. A "push" gun angle is normally used to enhance gas coverage and get the best results. If the material you are welding is dirty, rusty, or painted it must be cleaned by grinding until you see shiny bare metal. MIG welding may be used with all of the major commercial metals, including low carbon steel, low alloy steel, and stainless steel and aluminum with potential for excellent success by a novice.

Aluminum MIG Welding

Welding aluminum requires much more than just changing to aluminum wire. Get comfortable welding steel first. Since aluminum is very soft, it requires aluminum drive rolls that have a U-groove and no teeth to bite or cause wire flaking. Cleanliness of the wire and base metal are critical. Wipe the material with acetone on a clean shop rag. Use stainless steel wire brushes that have only been used on aluminum. Drive roll tension and gun length must be minimized. A Teflon, nylon or similar gun liner is needed to minimize friction in feeding the wire and 100% pure Argon gas is required for shielding. Special contact tips are often recommended. Special gun movement techniques are often highly desirable. It is a challenge, but it can be done.

Self-shielded Flux-Cored Arc-Welding process

FCAW per the American Welding Society, or flux-cored for short, is different in that it uses a wire which contains materials in its core that, when burned by the heat of the arc, produce shielding gases and fluxing agents to help produce a sound weld, without need for the external shielding gas. We achieve a sound weld, but in a very different way. We have internal shielding instead of external shielding. The shielding is very positive and can endure a strong breeze. The arc is forceful, but has spatter. When finished, the weld is covered with a slag that usually needs to be removed. A "drag" angle for the gun is specified which improves operator visibility. The settings on the wire feeder welder are slightly more critical for this process. Improper technique will have results that are magnified. This type of welding is primarily performed on mild steel applications outdoors. The Innershield® .035" NR-211-MP is often used for the 115 volt machines and the .045" Innershield NR-211-MP is typically used in the 230 volt machines. Farmers have found that these products can save a planting or harvest by repairing a broken machine out in the middle of the field in record time.

General Usage Rules

MIG

As a rule of thumb, it is recommended to use a compact 115 volt input (or 230 volt) MIG wire feeder welder indoors on clean new steel that is 24 to 12 gauge thick. 12 gauge is a little less than 1/8" thick. 24 gauge is less than 1/16" thick. The smallest wire (.025") will make it the easiest to weld the thinnest (24 gauge) material. The .030" diameter wire will weld a little faster deposition rate. If you need to weld 1/8" to ¼" thick material with MIG, you will need the higher capacity compact machine which will require 230 volt input. The higher amperage range of this machine can better handle your welding needs in a single pass and you may not have to waste time with second or third passes. The 230 volt machine could also run .035" diameter wire. To MIG weld material more than ¼" thick, you need a higher capacity truly industrial machine. If most of your welding will be performed indoors on clean material that is less than 1/8" thick, a MIG machine that operates on 115 volts is probably your best bet for economic reasons in that a 230 volt input machine will be more expensive.

Flux-Cored

The flux-cored process is only recommended on materials as thin as 20 gauge, a bit thicker than the 24 gauge we said for MIG. In general, this process is best for welding thicker materials with a single pass, especially if you need to weld outdoors such as to repair a tractor out in the field. A 115 volt flux-cored machine using an electrode such as .035" Innershield NR-211-MP will generally allow you to weld steel up to ¼"thick. Note that this is more than double the thickness maximum of 12 gauge with MIG on 115 volts. With the proper electrode on a proper machine, such as .045" Innershield NR-211MP, and a 230 volt input machine, you can weld steel up to 1/2" thick. Note that Innershield® NR-211-MP requires that the machine be setup for DC negative polarity.

Advantages/Disadvantages

While there are advantages and disadvantages to both processes, we will try to outline for you some of the most common.

MIG

Advantages

• The best choice when cosmetic appearance is an issue since it provides lower spatter levels than flux-cored. The arc is soft and less likely to burn through thin material.
  
• The lower spatter associated with MIG welding also means no slag to chip off and faster cleaning time.
  
• MIG welding is the easiest type of welding to learn and is more forgiving if the operator is somewhat erratic in holding arc length or providing a steady travel speed. Procedure settings are more forgiving.
  
• If you are skilled and get specific proper guns, shielding gas, liners, drive rolls, and electrode, MIG can weld a wider range of material including thinner materials and different materials such as stainless, nickel alloys or aluminum.
  

Disadvantages

• Since a bottle of external shielding gas is required, MIG welding may not be the process of choice if you are looking for something that offers portability and convenience. MIG also requires additional equipment such as a hose, regulator, solenoid (electric valve) in the wire feeder and flowmeter.
  
• The welder's first job is to prepare the surface by removing paint, rust and any surface contamination.
  
• MIG has a soft arc which will not properly weld thicker materials (10 gauge would be the maximum thickness that MIG could soundly weld with the 115 volt compact wire feeder welder we are referring to or ¼" with the 230 volt input compact wire feeder welder.) As the thickness of the material (steel) increases, the risk of cold lapping also increases because the heat input needed for good fusion is just not possible with these small machines.

Flux-Cored

Advantages

• The Self-Shielded electrodes are optimal for outdoor procedures since the flux is built into the wire for positive shielding even in windy conditions. An external shielding gas and additional equipment are not needed, so setting up is simpler, faster and easier.
  
• The flux-cored process is most suited for applications with thicker materials as it is less prone to cold lapping.

Disadvantages

• It is not recommended for very thin materials (less than 20 gauge).
  
• When flux-cored welding, machine settings need to be precise. A slight change in a knob position can make a big difference in the arc. In addition, the gun position is more critical in that it must be held consistently, and at the proper angle, to create a good weld.
  
• This process creates spatter and slag that may need to be cleaned for painting or finishing.

It should be noted that the same machine can be used to weld with both MIG and flux-cored processes though a special package is usually needed to change from one application to the other. Drive rolls, shielding gas, gun liners, contact tips and procedure settings need to be addressed when changing processes.

Choosing Wire

Another area that may cause the novice welder some concern is how to choose the best wire. Proper electrode diameter is related to plate thickness and the welder you have. A smaller wire makes it easier to weld thinner plate.

For a 110 volt input MIG machine, an electrode such as Lincoln's .025" SuperArc® L-56 is the smallest available size and the easiest to use on very thin material. A .030" SuperArc would weld slightly thicker material a little faster. For flux-cored, a 110v machine would run a .035" wire (such as Lincoln's Innershield NR-211-MP) because this is the smallest size made and this is all the machine can run.

For a 230v MIG machine, most people are welding heavier plate and step up to the .030" or even .035" diameter solid electrode such as .030" or .035" SuperArc® L-56 because they deposit weld metal faster and they can weld heavier plate. For flux-cored with the 230 volt input machine, most people move up to Lincoln's .045" diameter Innershield NR-211-MP for plate up to ½" thick.

Realize that these small machines are excellent at what they do, but they cannot do everything. Electrodes for production welding, hardfacing to resist wear, and most specialty electrodes will exceed the capacity of these machines. You must be careful to match the output voltage of your machine with the voltage of the electrode and the appropriate wire diameter and wire feed speeds to make sure you have a compatible system.

Tips for All

1) It is very important to get a good, solid work connection. This means you should thoroughly clean or grind the surface of the metal where attaching the work clamp and use a tightly attached work clamp so electricity can easily flow through the workpiece and back to the welder. Paint and rust are insulators. Remove them. This is a very common mistake to overlook.

2) Put the welder on a separate circuit breaker that is properly fused as stated in your Operators Manual. This is not another strand of Christmas lights. You are melting steel at around 5,000 degrees F. You cannot weld with inadequate input power. Don't even try.

3) Good fit-up is a big plus. Weld joints are laps, fillets and butts. Avoid gaps whenever possible to minimize burnthrough problems. This is especially critical on thin sheet metal.

4) Keep the gun cable as straight as possible for smooth wire feeding. Don't sharply bend it.

5) Make sure the contact tip looks good (not elongated or melted) and it is tightened to the diffuser.

6) Cut the wire at an angle to a point before starting to weld for better starts.

7) Use correct electrode stickout and maintain it as well as proper welding procedures.

8) Make sure the drive rolls feed smoothly with proper tension.

9) Relax and try to hold the gun as steady and smooth as possible.

10) Observe and follow all welding safety precautions as specified in your Operators Manual. Pay special attention to the potential for electric shock, arc rays that can burn skin and eyes, fire and explosion, and proper ventilation. For more details, consult ANSI Z 49.1.

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MIG Welding Stainless Steel

MIG Welding Stainless Steel
Source: Adapted from The Procedure Handbook of Arc Welding. The Lincoln Electric Company, 1994.

Although welding stainless steel may not be as difficult as welding aluminum, the metal does have its specific properties that vary from your more common steels.

When MIG welding on stainless, you usually have three choices of transfer depending on your equipment: spray-arc, short-circuiting, or pulsed-arc transfer.

Spray-Arc Transfer

Filler metals for gas metal arc welding stainless steel are specified in AWS - A5.9-93. Click here to view full-size Acrobat .pdf file.

Electrode diameters as great as 1/16-in., but usually 0.045", 0.035", and 0.030", are used with relatively high currents to create the spray-arc transfer. A current of approximately 300-350 amperes is required for a 1/16-in. electrode, depending on the shielding gas and type of stainless wire being used. The degree of spatter is dependent upon the composition and flow rate of the shielding gas, wire-feed speed, and the characteristics of the welding power supply. DCEP (Direct Current Electrode Positive) is used for most stainless-steel welding. A 1or 2% argon-oxygen mixture is recommended for most stainless steel spray arc welding.

On square butt welds, a backup strip should be used to prevent weld-metal drop through. When fitup is poor or copper backing cannot be used, drop-through may be minimized by short-circuit welding the first pass.

Forehand techniques are beneficial when welding with a semiautomatic gun. Although the operator's hand is exposed to more heat, better visibility is obtained. For welding plate ¼-in. and thicker, the gun should be moved back and forth in the direction of the joint and at the same time moved slightly from side to side. On thinner metal, however, only back and forth motion along the joint is used.

The more economical short-circuiting transfer process for thinner material should be used in the overhead and horizontal position for, at least, the root and first passes. Although some operators use a short digging spray arc to control the puddle, the weld is apt to be unduly porous.

Short-Circuiting Transfer

Power supply units with slope, voltage, and inductance controls are recommended for the welding of stainless steel with short-circuiting transfer. Inductance, in particular, plays an important part in obtaining proper puddle fluidity.

The shielding gas recommended for short-circuiting welding of stainless-steel contains 90% helium, 7.5% argon, and 2.5% carbon dioxide. The gas gives the most desirable bead contour while keeping the CO2 level low enough so that it does not influence the corrosion resistance of the metal. High inductance in the output is beneficial when using this gas mixture.

Single-pass welds may also be made by using argon-CO2 gas. The CO2 in the shielding gas will affect the corrosion resistance of multipass welds made with short-circuiting transfer.

Wire extension or stickout should be kept as short as possible. Backhand welding is usually easier on fillet welds and will result in a neater weld. Forehand welding should be used for butt welds. Outside corner welds may be made with a straight motion. A slight backward and forward motion along the axis of the joint should be used. Short-circuiting transfer welds on stainless steel made with a shielding gas of 90% He, 7-1/2% A, 2-1/2% CO2 show good corrosion resistance and coalescence. Butt, lap, and single fillet welds in material ranging from 0.60-in. to .125-in. in 321, 310, 316, 347, 304, 410, and similar stainless steels can be successfully made.

Pulsed-Arc Transfer

The pulsed arc process is normally a process wherein one small drop of molten metal is transferred across the arc for each high current pulse of weld current. The high current pulse must be of sufficient magnitude and duration to cause at least one small drop of molten metal to form and be propelled by the pinch effect from the end of the wire to the weld puddle. During the low current portion of the weld cycle the arc is maintained and the wire is heated, but the heat developed is not adequate to transfer metal. For this reason, the time duration at the low current value must be limited otherwise metal would be transferred in the globular mode.

Wire diameters of 0.030", 0.035", and 0.045" are most commonly used with this process. Gases for pulsed arc welding are argon plus 1% oxygen, the same as used for spray arc welding. These and other wire sizes can be welded in the spray transfer mode at lower average current with pulsed current than with continuous weld current. The advantage of this is that thin material can be welded in the spray transfer mode which produces a smooth weld with less spatter than the short circuiting mode. Another advantage is that for a given average current, spray transfer can be obtained with a larger wire. Larger diameter wires are less costly than smaller sizes, and the lower ratio of surface to volume reduces the possibility of weld contamination from surface oxides.

Pulsed MIG welding characteristics are excellent with lower currents. There are many advantages with the process including low spatter, penetration without melt-through and excellent operator appeal.

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Plasma Cutting: Determining if it's Right for You and What to Look for in a Machine

Plasma Cutting: Determining if it's Right for You and What to Look for in a Machine

Introduction
Do you need a cutting tool for occasional repair and maintenance work? Have you recently embarked on a new project that requires higher cutting volumes? Or, are you looking for a new alternative to your current mechanical saw? All of these scenarios provide great reasons to investigate plasma cutting. With the cost of machines on the decline, smaller-sized, portable machines flooding the market and technology offering increased benefits and easier usage -- it may be time to take a serious look at plasma for your cutting applications. The benefits of plasma cutting include ease of use, higher quality cuts and faster travel speeds.

What is Plasma Cutting Technology?
In simplest terms, plasma cutting is a process that uses a high velocity jet of ionized gas that is delivered from a constricting orifice. The high velocity ionized gas, that is, the plasma, conducts electricity from the torch of the plasma cutter to the work piece. The plasma heats the workpiece, melting the material. The high velocity stream of ionized gas mechanically blows the molten metal away, severing the material.

How Does Plasma Cutting Compare to Oxyfuel cutting?
Plasma cutting can be performed on any type of conductive metal - mild steel, aluminum and stainless are some examples. With mild steel, operators will experience faster, thicker cuts than with alloys.

Oxyfuel cuts by burning, or oxidizing, the metal it is severing. It is therefore limited to steel and other ferrous metals which support the oxidizing process. Metals like aluminum and stainless steel form an oxide that inhibits further oxidization, making conventional oxyfuel cutting impossible. Plasma cutting, however, does not rely on oxidation to work, and thus it can cut aluminum, stainless and any other conductive material.

While different gasses can be used for plasma cutting, most people today use compressed air for the plasma gas. In most shops, compressed air is readily available, and thus plasma does not require fuel gas and compressed oxygen for operation.

Plasma cutting is typically easier for the novice to master, and on thinner materials, plasma cutting is much faster than oxyfuel cutting. However, for heavy sections of steel (1 inch and greater), oxyfuel is still preferred since oxyfuel is typically faster and, for heavier plate applications, very high capacity power supplies are required for plasma cutting applications.

What Can I Use a Plasma Cutter for?
Plasma cutting is ideal for cutting steel, and non-ferrous material less than 1 inch thick. Oxyfuel cutting requires that the operator carefully control the cutting speed so as to maintain the oxidizing process. Plasma is more forgiving in this regard. Plasma cutting really shines in some niche applications, such as cutting expanded metal, something that is nearly impossible with oxyfuel. And, compared to mechanical mean of cutting, plasma cutting is typically much faster, and can easily make non-linear cuts.

What are the limitations to Plasma Cutting? Where is Oxyfuel preferred?
The plasma cutting machines are typically more expensive than oxyacetylene, and also, oxyacetylene does not require access to electrical power or compressed air which may make it a more convenient method for some users. Oxyfuel can cut thicker sections (>1 inch) of steel more quickly than plasma.

What to Look for When Purchasing a Plasma Cutting Machine
Once you have determined plasma cutting is the right process for you, look at the following factors when making a buying decision.

1. Determine The Thickness of the Metal that You will Most Frequently Cut
One of the first factors you need to determine is the thickness of metal most frequently cut. Most plasma cutting power sources are rated on their cutting ability and amperage. Therefore, if you most often cut ¼" thick material, you should consider a lower amperage plasma cutter. If you most frequently cut metal that is ½" in thickness look for a higher amperage machine. Even though a smaller machine may be able to cut through a given thickness of metal, it may not produce a quality cut. Instead, you may get a sever cut which barely makes it through the plate and leaves behind dross or slag. Every unit has an optimal range of thickness -- make sure it matches up with what you need. In general, a ¼" machine has approximately 25 amps of output, a 1/2” machine has a 50-60 amp output while a ¾" - 1" machine has 80 amps output.

2. Select Your Optimal Cutting Speed
Do you perform most of your cutting in a production environment or in an atmosphere where cutting speed isn't as critical? When buying a plasma cutter, the manufacturer should provide cutting speeds for all thickness of metal measured in IPM (inches per minute). If the metal you cut most frequently is ¼", a machine that offers higher amperages will be able to cut through the metal much faster than one rated at a lower amperage, although both will do the job. For production cutting, a good rule of thumb is to choose a machine, which can handle approximately twice your normal cutting thickness. For example, to perform long, fast, quality production cuts on ¼" steel, choose a 1/2” class (60 amp) machine.

If you are performing long, time-consuming cuts or are cutting in an automated set-up, be sure to check into the machine's duty cycle. Duty cycle is simply the time you can continuously cut before the machine or torch will overheat and require cooling. Duty cycle is rated as a percentage of a ten-minute period. For example, a 60 percent duty cycle at 50 amps means you can cut with 50 amps output power continuously for six minutes out of a 10-minute period. The higher the duty cycle, the longer you can cut without taking a break.

3. Can the Machine Offer an Alternative to High Frequency Starting?
Most plasma cutters have a pilot arc that utilizes high frequency to conduct electricity through the air. However, high frequency can interfere with computers or office equipment that may be in use in the area. Thus, starting methods that eliminate the potential problems associated with high frequency starting circuits may be advantageous.

The lift arc method features a DC+ nozzle with a DC- electrode inside. Initially, the nozzle and the electrode physically touch. When the trigger is pulled, current flows between the electrode and the nozzle. Next, the electrode pulls away from the nozzle and a pilot arc is established. The transfer from pilot to cutting arc occurs when the pilot arc is brought close to the work piece. This transfer is caused by the electric potential from nozzle to work.

Lincoln Electric's Pro-Cut® line offers patented Dual Winding Technology with separate windings for the pilot and cutting arc. With Dual Windings, the pilot arc is optimized during current transfer for a fast, positive transfer without the use of a resistor. Dual Windings work by creating the electric potential for a transfer - they create a voltage difference to snap the arc to the work piece. Because Lincoln has eliminated the large resistor usually found in plasma cutting machines, it can offer units that are smaller in size with increased portability.

4. Compare Consumable Cost Versus Consumable Life
Plasma cutting torches have a variety of wear items that require replacement, commonly called consumables. Look for a manufacturer that offers a machine with the fewest number of consumable parts. A smaller number of consumables mean less to replace and more cost savings. For example, Lincoln Electric's Pro-Cut line has only three front-end parts in the torch and only two of those are consumables: the electrode and the nozzle. Lincoln also offers tool-less changeovers when replacing these consumables.

Look in the manufacturer's specifications for how long a consumable will last - but be sure when comparing one machine against another that you are comparing the same data. Some manufacturers will rate consumables by number of cuts, while others will use the number of starts as the measurement standard.

5. Test the Machine and Examine Cut Quality
Make test cuts on a number of machines, traveling at the same rate of speed on the same thickness of material to see which machine offers the best quality. As you compare cuts, examine the plate for dross on the bottom side and see if the kerf (the gap left by cut) angle is perpendicular or angular.

Look for a plasma cutter that offers a tight, focused arc. Lincoln Electric offers its Pro-Cut line with VORTECH™ Technology consumables which are specially designed to concentrate the plasma swirl, offering a tighter arc and concentrating more cutting power on the work piece.

Another test to perform is to lift the plasma torch up from the plate while cutting. See how far you can move the torch away from the work piece and still maintain an arc. A longer arc means more volts and the ability to cut through thicker plate.

6. Pilot to Cut and Cut to Pilot Transfers
The transfer from pilot arc to cutting arc occurs when the pilot arc is brought close to the work piece. A voltage potential from nozzle to work is mechanism for this transfer. Traditionally, a large resistor in the pilot arc current path created this voltage potential. This voltage potential directly affects the height at which the arc can transfer. After the pilot arc transfers to work a switch (relay or transistor) is used to open the current path.

Look for a machine that provides a quick, positive transfer from pilot to cutting at a large transfer height. These machines will be more forgiving to the operator and will better support gouging. A good way to test transfer characteristics is by cutting expanded metal or gratings. In these instances, the machine will be required to quickly transfer from pilot to cut and back to pilot very quickly. To get around this, they may recommend you cut expanded metal using only the pilot current.

Lincoln's Pro-Cut products excel at this process because they employ Dual Winding Technology™. This technology utilizes two separate power systems (windings): one tailored for pilot arcs, the other for cutting. This patented configuration creates the nozzle to work voltage potential without a large resistor. Additionally, the control system can rapidly select which winding is required for the task. The result is instantaneous positive transfers from up to ¼" away from the work. At the end of the cut, the control system maintains the arc by instantly retracting back into a pilot arc.

*Pro-Cut 55 and 80 only.

7. Check the Machine's Working Visibility
As you are working on an application, you want to be able to see what you are cutting, especially when tracing a pattern. Visibility is facilitated by the geometry of the torch - a smaller, less bulky torch will enable you to better see where you are cutting, as will an extended nozzle.

8. Look for the Portability Factor
Many consumers use their plasma cutter for a variety of cutting applications and need to move the machine around a plant, job site or even from site to site. Having a lightweight, portable unit and a means of transportation for that unit - such as a valet style undercarriage or shoulder strap - make all the difference. Additionally, if floor space in a work area is limited, having a machine with a small footprint is valuable.

Also, you want a machine that offers storage for the work cable, torch and consumables. Built-in storage drastically improves portability since these items will not drag on the ground or get lost during machine transport.

9. Determine the Ruggedness of the Machine
For today's hard job site environments, look for a machine that offers durability and has protected controls. For example, fittings and torch connections that are protected will wear better than those that aren't. Some machines offer a protective cage around the air filter and other integral parts of the machine. These filters are an important feature since they ensure oil is removed from the compressed air. Oil can cause arcing and reducing cutting performance. Protection of these filters is important as they ensure oil and water, which reduces cutting performance, is removed from the compressed air.

10. Find Out if the Machine is Easy to Operate and Feels Comfortable
Look for a plasma cutter that has a big, easy-to-read control panel that is user-friendly. Such a panel allows someone who does not normally use a plasma cutter to be able to pick it up and use it. In addition, a machine with procedural information clearly printed on the unit will help with set-up and troubleshooting.

How does the torch feel in your hand? You want something that has good ergonomics and feels comfortable.

11. Look for Safety Features
Look for a machine that offers a true Nozzle-in-Place safety sensor. With such a feature, the plasma cutter will not start an arc unless the nozzle is in place. Some safety systems can be fooled into thinking the nozzle is in place (i.e. shield cup sensing), even when it is not. If the output is turned on, the operator will be exposed to 300 VDC, a very unsafe condition. This cannot happen with the Lincoln Nozzle-in-Place safety sensor.

Look for a machine that provides a pre-flow sequence. This feature provides an advanced warning to the use before the arc initiates. In addition, look for a machine which provides a three-second pre-flow safety which gives users advanced warning to make sure all body parts are clear of the nozzle before the arc initiates.

How Can I Make the Most of This Cutting Tool?
After you have selected the plasma cutting machine that is right for you, here are some tricks-of-the-trade that will help beginners make the best possible cut.

1. Set-Up Procedures
Before you start, check for the following items:

• A clean compressed air supply, without water or oil. Consumables that wear quickly, or black burn marks on the plate, may indicate that the air is contaminated

• Correct air pressure - this can be checked by looking at the gauges on the unit

• A nozzle and electrode are correctly in place

• A good connection of the work lead to a clean portion of the work

2. Safety Gear
Some basic safety practices should be observed. You should read your instruction manual thoroughly to understand the machine. Wear long sleeves and gloves while cutting since molten metal is generated during the cutting process. Eye protection such as dark goggles or a welding shield is required to protect your eyes from the cutting arc. Typically a darkness shade of #7 to #9 is acceptable. Finally, follow all safety tips and guidelines that are detailed in your instruction manual.

3. Piercing the Work
Many inexperienced users try to pierce the metal by coming straight down, perpendicular (90 degrees) to the work. This results in molten metal being blown back into the torch. A better method is to approach the metal at an angle (60 degrees from horizontal, 30 degrees from vertical) and then rotate the torch to the vertical position. This way, the molten metal is blown away from the torch.

4. Don't Touch the Nozzle to the Work Piece
Do not touch the nozzle to the work when using current levels of 45 amps or more. Doing so will drastically reduce the nozzle life as the cutting will double arc through the nozzle. Double arcing can also occur if the torch is guided by dragging it against a metal template. The result is the same as dragging the nozzle on the work -- prematurely worn nozzles.

5. Beginners Should Use a Drag Cup to Facilitate the Cut
Many systems offer an insulated drag cup, which snaps over the nozzle. This allows the torch to rest on the work piece and dragged along to facilitate a consistent cut.

6. Travel at the Right Speed
When moving at the right cutting speed, the molten metal spray will blow out the bottom of the plate at a 15 to 20 degree angle. If you are moving too slowly, you will create slow speed dross, which is an accumulation of molten metal on the bottom edge of the cut. When moving too fast, high-speed dross on the top surface is created since you are not allowing time for the arc to completely go through the metal. Traveling too fast or too slow will create a low-quality cut. Typically, low speed dross can be distinguished from high-speed dross by ease of removal. For example, low speed dross can be removed by hand whereas high-speed dross typically requires grinding.

7. Set the Current to Maximum As You Begin
When setting the current, put it on the maximum output of the machine, then turn it down as needed. More power is usually better, except when doing precision cutting or when you need to keep a small kerf.

8. Minimize Pilot Arc Time
Because of the wear it creates on the consumables, try to minimize the amount of time spent in pilot arc mode. To do this, position the plasma torch by the edge of the work before starting the arc so you can get right to cutting.

9. Maintain A Constant Work Distance
Optimally, you should maintain a 3/16" to 1/8" distance from the nozzle to the work. Moving the torch in an up and down fashion will only hinder your efforts.

10. Travel in the Direction that will Give You the Best Finished Work
If you are making a circular cut and plan to keep the round piece as your finished work, move in a clockwise direction. If you plan to keep the piece from which the circle was cut, move in a counterclockwise direction.

As you push the torch away from you, the better cut will appear on the metal that is on the right hand side, since it will tend to have a better, squarer edge.

11. End with a Push Angle on Thick Material
One trick to use on thicker material is to rotate the torch slightly, increasing the torch orientation to a push, rather than drag angle as you cut through the last section of material. This increase in the push angle at the finish will cut through the bottom first and get rid of the bottom corner that is usually left at the end of thick plate. Never finish a cut by using the torch to hammer away the last corner of the work.

After finding the right machine for your application and learning some of the tricks of the trade, you should be ready to cut. Remember that plasma cutting offers a number of benefits and should provide you with faster, higher quality cuts.

www.lincolnelectric.com

Power Shopping: Choosing the Ideal Welding Power Source by Selecting the Proper Welding Process

Power Shopping: Choosing the Ideal Welding Power Source by Selecting the Proper Welding Process

The process of choosing a welding power source is much like that of buying a car. It involves searching for a product that is efficient, powerful, easy to handle and, most importantly, suited to the customer's particular needs. But with such a wide selection of power sources on the market, how do welders select the right one for them?

The first step is to understand their shop's internal needs. To determine this, examine some commonly used welding processes and for which materials they are best suited.

Gas Metal Arc Welding (GMAW)/Flux-Cored Arc Welding (FCAW)
GMAW/FCAW (most commonly referred to as MIG or Flux-Cored Welding) uses a spool of wire that is either housed inside the power source or fed from an external wire feeder. This wire or filler material is fed through a welding gun. The power source is used to start and maintain the arc between the wire and the base metal.

GMAW or MIG welding utilizes solid metal wire, which requires the use of a shielding gas to protect the weld puddle from the atmosphere. FCAW uses a hollow wire filled with a flux powder that may or may not need an external shielding gas, because the gas may be produced from the flux within the wire as it burns in the arc. The flux in the wire serves many of the same purposes as the electrode coating in SMAW.

GMAW requires the least operator skill, because the machine feeds the wire. The welding operator holds the gun in one hand, squeezes the trigger, and welds. It's that easy! The shielding gas makes for a very smooth arc that remains stable. Since other processes typically require very specific electrode positioning and manipulation, GMAW is the fastest growing process. With compact units now retailing for less than $500 and the ability to easily weld on much thinner material than stick electrode, this type of unit has become very popular.

Welding speeds are also higher because of the continuously fed electrode, absence of slag (with GMAW) and higher filler metal deposition rates. Its operating factor is typically 30-50 percent so 3-5 minutes out of every 10 can be spent creating an arc. In addition, GMAW/FCAW does not require the degree of operator skill that TIG or stick welding does.

GMAW can be used on all of the major commercial metals. FCAW is currently used primarily on steels and stainless steels. These two processes also can be used over a wide range of material thickness and operate in all positions. For these reasons, they are usually the welding processes of choice for most fabrication and production shops.

On the downside, equipment for GMAW and FCAW is more complex, more costly and traditionally less portable than stick welding processes (although some new portable models do exist). Welding is typically done within a 10 to 12 foot radius of the wire feeder and the work is usually brought to the weld station.

Shielded Metal Arc Welding (SMAW)
SMAW, or stick welding, is the most common form of arc welding. In the process, a stick or electrode is placed at the end of a holder. Using electricity from the power source, an arc is struck between the tip of the electrode and the metal welding surface. The heat of the arc melts the tip of the electrode creating the filler material that is deposited as the electrode is consumed. A coated material on the electrode burns and protects the arc from the atmosphere. The burning of the coating produces CO2, which becomes the shielding gas. A slag is also formed which helps refine the weld metal and protect it as it freezes.

SMAW is one of the easiest and most versatile ways to weld, since filler material can be easily changed to match different metals just by switching stick electrodes. Whether it is steel, stainless steel, cast iron or high alloy metals, users can clamp in a new rod to be ready for the next project. In addition, stick is versatile because it takes the least equipment, which makes it easy to setup or move to a new location.

When compared to other types of power sources, SMAW welders are generally the least expensive. As a result, they are utilized most often by novice welders, farmers, smaller fabricating shops, maintenance shops and large field construction contractors that weld on a variety of jobs over a large physical area.

The main disadvantage to SMAW is the amount of downtime associated with the process. An electrode is only so many inches in length and must be changed once it is consumed. This requires the operator to stop welding to change the electrode. Frequently, the amount of skill required by the operator is greater than that required for wire fed processes.

In addition, it takes time to chip or grind the slag or impurities from the weld. The operating factor or time that the welder is actually "creating sparks" is typically two to three minutes per 10-minute interval. In general, stick welders sacrifice productivity for versatility.

Gas Tungsten Arc Welding (GTAW)
In GTAW, an electric arc is established between a non-consumable tungsten electrode and the base metal. The arc zone is filled with an inert gas, typically argon, which protects the tungsten and molten metal from oxidation and provides an easily ionized path for the arc current. GTAW produces high quality welds on almost all metals and alloys. Because it can be controlled at very low amperages, it is ideally suited for welding on thin metal sheets and foils.

The biggest advantage of GTAW is that high quality welds can be made on almost any weldable metal or alloy. Another major advantage is that filler metal can be added to the weld pool independently of the arc current. With other arc welding processes, the rate of filler metal addition controls the arc current. Other advantages include low spatter, no slag and relatively easy clean up.

The main disadvantage of GTAW is that it produces the slowest metal