DC TIG Aluminum

[aametalmaster]

Yes, No, Maybe. I have 2 Miller machines by my desk just calling my name. Multimatic 200 and a Multimatic 215. But no AC Tig. I see youtube vids on thicker alum with Helium which i have lots of. Just a thought...Bob

[Olivero]

The AC function acts as the oxide layer remover and "cleans it". The whole problem and idea behind A/C is that the oxide layer melts at a much higher temp than the base metal itself, so when you finally get through the oxide layer, you have waaaaaay overheated the base. That's why A/C is used for aluminum as it has a cleaning and penetration cycle in the wave length and it removes the oxide layer and keeps the aluminum bare and clean for welding.

If you clean it and weld it fast enough with a Stainless toothbrush, you might be able to do it but the layer rebuilds pretty fast, never tried it but you never know.

[aametalmaster]

Sort of like using a spoolgun and all of the black comes to the top. Thats how it looked to me on the vids...Bob

[Olivero]

Yeah, I don't do MIG so I would have no comparison to MIG but I do a lot of TIG on aluminum.

I guess if the oxide layer is not removed, it would become part of the weld which I am not sure what the oxide layer contains or if it traps oxygen or contaminants while forming, that might be why its sooting up.

[duaneb55]

B_C over on WeldingWeb TIGs aluminum with DC and helium on a semi-regular basis.

[ryanjones2150]

I've never done it and I've only heard of people doing it. Maybe one day when I run out of projects I'll see what happens when I try.

[Stefen7]

It is possible,but there are some issues. Check the resources already mentioned, to hear how people with actual experience solved these problems. I have not tried it since I don't have TIG equipment yet.

A good book is "Welding Kaiser Aluminum", published 1967. It has entire sections on DCSP and DCRP-TIG and all of the issues involved. Also a good explanation of AC-TIG, High-Frequency and all the challenges to welding aluminum. Most of those problems were solved with the invention of Square-Wave AC-TIG (and improvements to MIG), so DC and Sine-Wave AC fell out of use. It also has sections on Oxygas and SMAW welding of aluminum, which were being replaced by TIG or MIG.

DCRP has excellent cleaning action and a shallow arc. 70% of the heat is in the electrode, only 30% in the work, requiring much larger diameter electrodes than AC or DCSP for same amps. Arc is stable in Argon, and can be a little longer than AC, about 3/16" to 1/4". It works well on thin sheet, 0.050" recommended maximum thickness.

DCSP does not have any cleaning action, and requires a very short arc length, about 1/16", making manual welding difficult. Helium or Helium-Argon mix is preferred, but there are trade-offs with either, concerning initiating the arc or arc stability, and cleanliness of the HAZ. DCSP is hotter than AC, 70% heat in the work vs 50%, so a slightly different technique and joint design are used.

That's the basics. It looks like thin sheet would be fairly simple on DCRP. You could try playing around with DCSP on non-critical welds, but if you are doing anything critical, either lots of research and practice, or use AC and known parameters.

Good Luck.

[H80N]

Here is a pretty good overview of aluminum welding that includes DC TIG

"Welding Aluminum & It's Alloys" Mathers, 2002... 242 pages

https://ia800202.us.archive.org/11/i...Its_Alloys.pdf

https://archive.org/details/Welding_Aluminum_Its_Alloys

Well worth downloading and keeping for reference (Free Download.......)

[Olivero]

wooo. free downloads. Looks like a good history introduction to aluminum in the beginning. Always interested in learning how metals were discovered and evolved.

[Oldgrandad]

Had a job in the 90's welding 3/8" or 1/2" thick tube 2' to 4' dia. to 1 1/2" thick plate did it all DC tig with pure helium. Used a sycnrowave 350 set somewhere around 325 amps or so with 1/8 tungsten 2% sharp point and 1/8 4043 rod. Just hammer down and go. Got a big mushy weld pool just stuffed the rod and went. Welds were all black but with a quick hand wire brush it looked real good. Surprised me how good the bead looked. No preheat used.

[Oldgrandad]

A little more detail. Used DCSP after striking arc hang out a little to get the weld pool started. It looks dirty with a layer of slag on top. When its the size you want stuff the rod into the weld pool, you will feel the penetration. Now just start moving, dab move, dab move. The bead looks horrible as your welding but its really not as bad as it looks. When I first stared doing this I kept stopping because I thought the welds were terrible but after wire brushing off all the black soot the welds actually looked good. The parts we were making were rotating pedestals for satellite dishes for the government. Hope this helps.