Showing posts with label Tungsten. Show all posts
Showing posts with label Tungsten. Show all posts

Monday, August 16, 2010

Welding Aluminum Using GTAW Aka the Gas Tungsten Arc Process - Compared to Welding Steel

Welding aluminum is harder than welding steel. Why? Because everything that can go wrong on steel is magnified times 10  when you are Tig welding aluminum.

Cleanliness, machine settings, arc length, welding with a dirty  tungsten electrode, torch angle, filler rod angle, type of electrode, and size of electrode . You name it, When you weld aluminum, its just more important to get all these things right,


If the aluminum you are welding has been left outside, like a boat dock ladder, or aluminum boat propeller, it is most likely heavily oxidized. It needs to be cleaned or it will weld like Fido's butt.
The machine settings have to be right too. Alternating current is the name of the game for tig welding aluminum and the  high frequency switch  needs to be on continuous...otherwise the arc will stutter.
Amperage is usually controlled with the foot pedal and with steel, you dont have to continually adjust amperage. At least not much. But since aluminum is such a good heat conductor, your foot pedal amperage control will get a workout. (Some tig welders even use the foot pedal to pulse the amperage to overcome heat buildup and to get the stack of dimes look.)

Arc length is important on steel, but on aluminum it is even more critical, too long an arc length and the heat will not be pinpointed enough casing your rod to ball up and contaminate, too short an arc length and metal will seem to jump on your electrode causing you to cuss like a sailor.
With steel, sometimes you can get away with a slightly dirty electrode... no big deal. But on aluminum, a dirty tungsten takes all the fun out of welding.  The weld will be sooty and will prompt your buddies to make fun of you.
Too much torch angle will cause the heat to melt the tip of your filler rod and the  filler wire will blob into the puddle,. This happens on steel too, just not as bad.
Type of tungsten electrode matters a lot too, especially if you are welding with a newer inverter type tig welder.  Old timers used to insist on using pure tungsten for tig welding aluminum. With the new tig inverters, using pure tungsten to weld aluminum will make you ask for a refund on your welding machine.
And what about the size of your tungsten electrode? With steel, it is possible to use a 3/32" tungsten for almost everything except razor blades. With aluminum, you need to use the right size electrode for different thickness metal. You really need to keep some 1/16", 3/32", and 1/8" tungsten handy and be willing to change electrodes when the  job calls for it...and sometimes even in the middle of doing the same job.

Do you get the picture yet? Welding aluminum is just plain harder because everything matters more.

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Sunday, April 25, 2010

Tungsten Electrodes For TIG Welding - What's the Big Deal With Sharpening?

Tungsten electrodes are available in Thoriated, lanthanated, ceriated, and a few other varieties. When you are welding steel, they all have one thing in common.

They need to be sharp. But is it really that important to sharpen them the way the welding textbooks describe?

I have been TIG welding for over 30 years and have sharpened tungsten electrodes all kinds of ways. Even with a cutting torch. That's right I said cutting torch. I don't recommend it, but it does work. I have also used Chem-Sharp, belt sanders, small 90 die grinders, bench grinders, big electric grinders, and even the new high dollar tungsten electrode grinders.

The bottom line is this. Unless you are welding razor blades, a lot of the anal retentive textbook methods for sharpening tungsten electrodes just don't make much difference. I know I am going to get a lot of hate mail over this but it's just plain true. Like most welders, I was taught in welding school that a bench grinder with a stone devoted exclusively for tungsten was the only way to sharpen tungsten. And that all the scratches from grinding had to run parallel with the electrode.

Then I got a job.

The real world has a way of separating the BS from the down and dirty stuff that really works and Its kind of hard to sharpen a tungsten to textbook standards when you are up 60 feet in the air on a scaffold and need to tie in a weld before the next wave of steam leaks past the safety valve. And If you have a small grinder in your tool bucket you do the math pretty quick and give it a try. I learned quickly that as long as I used a smooth enough grinding disc, spiraling grinding marks be damned, everything turned out fine. A couple of hundred good x rays without a tungsten grinder also tend to make you think you are not doing everything wrong.

So is this whole tungsten electrode sharpening thing getting Big-Dealed?

Yes and No. It definitely sells tungsten sharpeners.

Seriously, I can think of a few applications where textbook tungsten sharpening is important . Razor blade type thicknesses would be one, Another example is for automated processes like orbital TIG welding. In orbital TIG welding it is pretty common to join stainless or titanium tubing that is only ¼ " in diameter with wall thickness of less than .030". Amperage for these type welds is very low and even small changes in tungsten electrode preparation can really make a difference. Since the geometry of an electrode tip definitely does have an effect on the arc, you will want to use a special tungsten grinder to get every taper and tip consistent so that when something goes wrong, you can eliminate tungsten preparation as a variable.

But If you are TIG welding something like a 1/8" thick bracket for a set of headers, Don't sweat it. Just use a clean sharp electrode sharpened however you choose and weld the dog crap out of it.

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