Rage13

Any one here know how to TIG aluminum? I've been welding 16 gage 316L stainless for a little over 2 years now. Picked it up on my own with no school and little help from others. At this point about 85% of my welds are a nice gold color and the rest is kinda a metalic blue, and they hold up well to the destructive tests I've tryed. But it seems aluminum is just a whole different kinda animal.. I'm using a Miller Dialarc HF and when trying aluminum I swich to helium, ball the end of the tungsten and set the machine to DC. But no matter what I do I just can't weld it... What am I doing wrong here?

Aqua FBody

Sounds like you know what you are doing but I personally know aluminum is a bitch try AC with the high frequency on constant and if that still doesnt work lower your amps oh yeah find out how much copper is in the aluminum that is what determens if it is weldable

Aqua FBody

and your gas I use Argon

Rage13

i use argon with AC and high freq. start for the stainless, i've tryed using argon and helium for the aluminum, didn't notice any difference but have heard you'd want to use helium cause it makes a hoter weld. i've also tryed AC high freq. on start and all it dose is make a krackling sound and arcs like crazy but doesn't do anything useful.. i'll see if i can dig up some other aluminum to try out on tomarrow (some that has been welded) that way i'll know if the metal had anything to do with it..

ede

argon, ac high freq

Mathius

Set the machine for AC, and use Argon as already said. Make sure you set your amperage nice and hot (for penetration). I use 250 amps on 3/16's plate at school.

Aluminum requires a lot of heat to weld, and it spreads the heat out well. Make sure the material you're working with is good and clean, no oils. Make sure you're using a green tungsten and ball the end of it, not pencil sharp like stainless.

It's possible to simply fusion weld with alumium, but it's very difficult. Because the heat spreads out so well, it will pull a lot of the base metal out, and you end up with a hole nine times out of ten. I just use fusion welding for tacking, then I use a filler rod.

Preheating really helps. If you don't want to go to the trouble of using an oxy/ac torch, you don't have to, but make a pass or two with the tungsten over the metal real quick to heat it up before you actually start your bead. This wil help some. Also, for good penetration, I run it the same way I do 6010 rod on an arc welder. I get my nice hot puddle, move the torch in the direction of my bead, then push the puddle back to form my bead, adding the filler rod at this point, ahead of the puddle. This cuts a path ahead into your base material, allowing for good penetration.

I haven't spent a lot of time with stainless, but I imagine the same theory holds for weld contamination. The tungsten melts at a higher point than what aluminum does, so if you should accidently brush your tungsten into your puddle, or base material, OR bump the tungsten with your filler rod, you're going to contaminate your weld. Just stop what you're doing, cut the tip off your filler rod, clean your base material off (wire brush, or grind it out), and re-ball your tungsten.

What happens is the tungsten will "flake off" from the heat, but it won't melt, and it creates little fragments in your weld, similar to when you get flux deposits in your welds. If it's not bad, you can continue to weld, but your weld will look awful and won't be as strong. If it's bad enough, your weld will wrinkle up like a prune and fall off, also creating a huge gouge in your work. It's usually better to just stop and clean up the contaminated area.

Hope this helps some. Feel free to ask more questions. I'm taking my certification test on aluminum, in fact I'm waiting to turn it in. Next I start stainless. I'm by no means an expert, but I pay attention and ask questions, so I can explain it well. Doing it just takes time and practice.

Mathius

ede

ac and high freq doesn't work for stainless, use dcen, high freq on start only, if at all, and argon. very seldon will you use anything but argon for GTAW

Rage13

when i was typing last night i mixed up AC and DC.. i use DC for the stainless. whats the diffence with the reverse and straight polarity?

Mathius, how do you ball the tungsten? I've just been making an arc and sticking the tip to the metal to get a ball on the end (I'm sure your instructor would freak after hearing that lol). Also you said "green tungsten", I'm assuming the colored end (the ones I'm using are red) are how you identify them. So whats the difference between the red and green?

ede

the differance between DCEP and DCEN is the direction the current flows and the amount of "heat" and penetration. you can't use DCEP for GTAW because the electrode would be consumed. most tungstun will ball naturally on AC high freq. if you want to preball it use DCEP and strike an arc for a second or two. only tungstun i use is 2% thorided, but there are a lot of differant kinds.

Mathius

Ok, first I don't wanna throw you off, I was thinking about my statement on heat settings.... I'm running 250 on the high side, 45 on the low side. I think high side is panel, 45 is remote, maybe ede can clarify, so you'll want to run at 45 (remote= foot pedal I think)

As far as the difference in tungstens, it has to do with the content, as some of them have thoria added or zirconium added as ede stated. My book recommends pure tungsten, so I'd imagine that's the equivalent of green, since that's what my instructor insisted on. He said you could run it with yellow, but it wouldn't be as good.

Ede is also correct on balling the tungsten, it can be done by running a small puddle first as it will naturally ball up on its own if you're welding properly. I usually keep a scrap piece of aluminum on the welding table. It serves two purposes. #1, if I contaminate, instead of going back to the grinding wheel, I can run a bead and work out the contamination by burning it off the tungsten. #2, it'll ball the tip naturally by doing this. To preball it, I usually just use a grinding wheel to just knock the tip off the end, and then lightly notch the sides to give it a little curve. It doesn't have to be perfect. My book recommends flipping over to DC reverse polarity and striking an arc on copper, but that seems like a lot of effort to me. Their exact measurements:

"The ball must not be over 1 1/2 times the diameter of the electrode. (A larger ball indicates that the current is too high)"

So take that for the technical aspects. I can't seem to find a color breakdown on tungstens in my book. Keep in mind that the tungsen is not really considered consumable, so if you find that you constantly have to trim it down, then you need more practice

I can't stress too much how important it is when welding aluminum to keep it clean. My book goes so far as to recommend keeping a separate grinding/cutting wheel just for your aluminum.

And like I said, the other big deal is heat. If you have access to fire bricks, you might want to set your project on them. Steel is what's usually used for welding tables, and it tends to just absorb the heat, which makes your job even harder. If you have a steel table, try setting your work on another piece of aluminum, that might help initially as you're just starting out.

Hope that helps a bit more.

Mathius

jocww

is ur tungston pure or thoriated

Rage13

ok, so what is DCEP and DCEN ? i don't know any of the abbreviations people use for welding...

Mathius

DCEP is straight polarity, DCEN is reverse, I believe. where P is positive, and N is negative. I don't know why ede always uses technical abbreviations either, ask him

I think it just confuses the issue. They're good to know, but none of my teacher's uses them in everday speech, DC reverse, or DC straight polarity is sufficient.

Mathius

ede

i use them becasue it's the correct way to say what you want to say or to identify welding parameters. i try to use the AWS approved terms and definations. funny thing is when i talk about it i don't say it that way. guess it's just from filling out WPS and other paper work.

Mathius

Somehow I knew you'd say that

Mathius

1983Fbody

DCEP- Direct Current Electrode Positive
DCEN- " " " Negative

I think that's correct, either way it doesn't matter as long as you know the way current should be flowing. A good book to read is called "Performance Welding" it covers alumminum, stainless, unobtanium (titanium), etc.

Rage13

didn't have any time to get some green tungsten yet, will get some on monday to try out. need to get some alumminum too, only alumminum we have in the shop the owner is hogging for some other projects..
think i'm going to run by the library this weekend to see if i can find that Performance Welding book, stainless and titanium is pretty easy, but theres always room for improvement

Aqua FBody

Oh and be sure the base metal is clean clean clean if there is any other substance on it you will blow it out.

Aqua FBody

DCEP is electrode positive or reverse polarity
DCEN is electrode negative or straight polairty