Learning TIG

WWW.THEFABRICATOR.COM MARCH 2008

March 11, 2008

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Think you want to learn TIG welding, also known as GTAW? To master the craft and avoid injury, it's imperative that you receive proper instruction. TIG is not a process that lends itself to self-teaching. This overview compares TIG with other welding processes and outlines some important steps of the process.

GTAW Arc Welding

Photo courtesy of The Lincoln Electric Company

Gas tungsten arc welding (GTAW), which used to be called heliarc, is referred to by most welders in the shop and field as TIG. In the field, TIG applications include welding stainless in the food industry; stainless, aluminum, titanium, and magnesium in the aircraft and aerospace industry; Chromaloy® in race car frames; and mild steel on pressure vessels. For the home hobby welder and artist, TIG is great for sculptures and other projects, such as chopper frames. Hobbyists and artists generally use mild steel, stainless, aluminum, and, to a lesser extent, copper.

For those of you wanting to learn TIG on your own, I have good news and bad news. The bad news is that you should not attempt to learn TIG on your own. More bad news is that many welding programs have been radically slimmed down or cut completely. The good news is a few community colleges still have intro classes that allow you to learn the basics in a relatively short period of time.

Go to School

If there is no course available in your area, a trip to Cleveland might be in order. Lincoln Welding School has a five-day TIG course with reasonably priced hotels on-site. I recommend the school all of the time and, as a matter of fact, listed it in the resource box of my last article,"Why in the heck would you want to weld?"

This school is one of the few places I recommend that I haven't actually visited. I recommend it because all of my students who've gone there really liked it and have been very successful using the skills they learned. Lincoln is also one of the only places I know that offers such a course.

Take this course and you'll be more than capable for hobby welding and artwork.

Build Your Foundation

I recommend you take a class because that is where you'll build your foundation. There's a good story from the Bible about a couple of guys building a house. I think both their names were Del. Del Smartguy built his foundation on a rock, while Del Dumbutt built his on sand. A big biblical-time thunderstorm came along, and of course, Del Dumbutt's house came crashing down because of the shifting and sinking sand. Del Smartguy's house was just fine, because of its sturdy, solid rock foundation.

I may get struck by lightning one day as I explain that to my students, but my loose interpretation gets the point across. The reason Chicago and New York City have all the high-rises is that they have plenty of bedrock. You have to start with bedrock for the foundation of a tall structure. Heck, to be successful, just about every endeavor in life depends on how you build your foundation.

If you teach yourself to weld, no one is there to correct bad habits or stop you from doing something wrong. Teaching yourself, you also will never learn the many tricks of the trade.

One exception to self-teaching that I grudgingly make is gas metal arc welding (GMAW), usually called MIG in the shop and field.

With MIG, you can learn a lot on your own with written instructions and media. (You can see more of what I have to say about MIG by going to the Article Archivepage and typing Rice in the author space.

But even with MIG, I prefer that at the very least you check with a qualified welder to make sure you are not only welding correctly, but doing it safely! With TIG, you dang sure better know the safety procedures, because this process can be really dangerous.

TIG Versus MIG

TIG is way more complex than MIG. I'd say it is hard as heck in some ways, and in other ways, easy. To explain that contradiction of terms, while TIG basics are fairly easy to grasp, it takes a lot of control, skill, and coordination to master.

In MIG the wire is fed through the gun to the base metal. In stick welding (again, to be technical, you can call it shielded metal arc welding, and again, nobody calls it that in the shop or field) you feed the filler rod coated with flux into the weld pool with your stinger (electrode holder).

In MIG and stick welding, the filler metal melts into the base metal, which means it is consumable—we use it up as we go. TIG uses a nonconsumable electrode to make heat (amps), and we feed a wire rod into the weld pool. In my shop we use a machine with a foot pedal to control the heat.

You have to hold the rod in one hand at the right angle, torch in the other, feed the rod into the weld pool, while pushing the pedal down to give more heat. So you're pushing the pedal to make molten metal while feeding the puddle. The way they keep coming up with all these crazy technical terms, maybe they'll refer to TIG as PMP for pedal metal puddle, or PPM for puddle pedal metal. (Many Ph.D.s and engineers are grimacing as they read this.)

What You'll Learn

It takes skill, timing, and coordination to TIG weld correctly. Off the top of my head, just some of the things you have to do are:

1. Clean it!—I cannot stress this enough! It is important to have a clean surface in all welding processes, but in TIG cleanness is essential. Using 6010 or 6011 rods, I can get by with some dirt and rust and even paint on the surface because these are deep-penetrating rods. I can even burn through dirt, rust, and paint with 7018 to a lesser extent. Try that with MIG and it will sputter and spatter and the weld pool will not cooperate at all. But even with MIG you can fight through it and get a decent weld. Of course, I'm talking about hobby work and art projects here. Anything structural, I want it absolutely clean for the best weld possible, because if these welds fail, injury or death could occur.

With TIG any little bit of anything that contaminates the tungsten will mess up your weld. And believe me, any bit of anything will contaminate the tungsten. You cannot be too careful when preparing the tungsten, or putting the tungsten in the torch. If you even touch the end of it with your finger, the oil from your skin can contaminate it. If you touch the rod with your glove, the residue from whatever you touched previously or even a minute particle of the leather can contaminate the tungsten.

In highly specialized TIG welding, such as welding exotic metal for aerospace parts, an atmosphere of pure argon is used to ensure cleanness. The welder sticks his or her hands through portholes and looks through a window to do the welding. Another method is to have argon flowing under and/or over the plate or through the pipe and tubing along with the argon from the torch.

You can choose from several methods to clean base metal. The most widely available, easiest, and cheapest is brushing. Use a stainless steel brush for stainless and aluminum. Use a mild steel brush for mild steel. Use a separate brush for each so you don't contaminate the base metal from using the brush on a dissimilar metal.

2. Select the proper rod diameter.

3. Set the machine to the right polarity,which means current and current flow; for example, AC or direct current electrode positive or direct current electrode negative.

4. Set the machine heat (amps) correctly—Different machines have different dial settings; some have fine-tuning controls, and others have just the basic amps.

5. Use the right shielding gas (usually argon) at the right flow—Shielding gas is measured in cubic feet per hour (CFH). Too little gas allows air to enter the weld pool; too much causes turbulence that also introduces air in the weld pool. Also make sure there are no drafts that will displace the shielding gas while you are welding. Air contains hydrogen, nitrogen, oxygen, and carbon dioxide, which will contaminate your weld pool.

6. Hold the rod at the correct angle and feed it correctly—Make sure to keep the rod preheated in the heat envelope while welding, especially when welding aluminum. You also must hold the torch at the correct angle for correct burn-in of the puddle and to make sure the shielding gas is flowing properly over the puddle.

7. Use the appropriate tungsten electrode diameter with the right tip.

8. Learn how to stop correctly at the end of the bead.

This is a lot to learn on your own, and there is no way you're gonna get it right without someone helping you. So get out there and find a course, or maybe even find a good welder who will freelance and give you some private lessons. Good luck and good welding.



High School Career Center in Texas

Marty Rice

Contributing Writer
High School Career Center in Texas
Marty Rice is a welding instructor at a high school career center in Texas. He is an honorary member of the Ironworkers Local 263.

 

Questions for the author can be e-mailed to vickib@thefabricator.com

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