Advanced Aluminum Welding ??

[ammoyer]

I've been a fabricator at Pinkee's Rod Shop going on 4 years now. And I can tig a very nice looking aluminum bead on sheet and heavier stuff, but I always get this "frosty" looking coating next to the bead on the parent metal. Even when the weld looks perfect. Would a gas lens help in this?? What I'm going for is a a weld that looks like the Wilson Manifolds welds. Any thoughts????

www.wilsonmanifolds.com

[z28orshoot]

your not talking about the cleaning part of the weld are you? if you have a lot of frosty area you need to turn the ac balance to get more electrode negative. the neg action is the weld and the positive action on ac current is the cleaning action. you need more EN time to have more penitration and less cleaning(frosty area).

i do not believe a gas lense will help with this, i may be wrong. post up some pics and i can tell you for sure.

hope this helps

[ammoyer]

I usually turn "up" (more penetration, less cleaning) as high as the material I'm welding at the time will allow. Usually dialling back a little when I see little black impurities in the bead. I looked at a Stef's oil pan today and the weld had the same thing I was talking about, the whitish frosty coating next to the bead on the parent metal. I'll see if I can get a pic or two and post.

[Matt@RFR]

The DC- portion of the AC cycle has electrons (current) flowing from the tungsten to the work, putting most of the energy (don't call it heat) in the work (good for a deeper puddle as you note). The DC+ portion has the electrons flowing from the work to the tungsten which creates a ton of resistance (big surface area flowing into small surface area), which super-heats the surface of the work, causing minor impurities to vaporize off the work and flow onto the tungsten or just into the atmosphere. The DC+ side is the reason you have to grind tungsten a lot when welding aluminum; The intense heat as well as the impurities from the work corrode it.

The white "frosty" stuff is what you call the etched zone, and is critical for AC aluminum welding. It's not a coating, it is perfectly clean aluminum...for about 10 seconds. This is partly why you never want to just stand on the pedal when starting your arc. If you gently ramp on the amerage, not only will you avoid thermal shock, but you'll get a more stable arc and also give the DC+ side of the cycle time to do the dirty work for you before establishing a puddle. Yes, you can tune the size of this zone via AC balance, as well as arc length to a limited extent. Gas mixes other than pure argon and flow rates will effect how you tune your balance, but will not effect the size of the etched zone. Also, don't confuse this with the HAZ. They are two seperate things with two seperate influencers.

In other words; Deal with it.

When you see an AC TIG weld with no etched zone, but is otherwise a sound looking weld, it's either been chemically or mechanically polished.

[toxicz28]

Good to see you around Matt. Your input has been missed.

[ammoyer]

Exactly what I was looking for. Thanks.