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michaelng1674 04-04-2007 11:29 PM

Which sheet metal is the most difficult to weld?
Which sheet metal is the most difficult to weld? Copper, aluminum, galvanized, and stainless steel?

Please help. This was one of the question on my C-6 exam which failed.

Bozak 04-06-2007 06:56 PM

What a cruddy question. Because I have seen guys who can zip up stainless like nothing but can't weld aluminum to save their lives, and I have seen guys that can weld aluminum like a machine but booger up anything stainless. i bet the answer is copper, because it sucks up so much heat before it melts. That is to say, it transfers a lot of heat away from the weld zone before it melts. That's my money.

SteveB 06-13-2007 11:57 PM

Copper is the worst to weld- but if you have a square wave machine you can weld anything-- including brass/copper/etc....
I just went out on google and found a few for sale.
I've done aluminum with mig, and had no trouble-- as long as I used copper block heat sinks. I.e., I would take copper blocks, and vice-grip them on the opposite side of my weld location.
We did however have to use a special gas.

Bozak 07-14-2007 10:42 AM

What kind of aluminum? Why did you have to use a special gas? My shop amounts of aluminum with GMAW and GTAW, and we use 100% argon. Anything else is a waste of money and may compromise the weld quality. There are a few instances where helium will serve better than argon, but not many. As far as using bulk copper for heat sinks, yes that works very well as long as your joint is set up properly; i.e. proper root gap, etc.

I have welded a lot of copper funnels in my day, and yeah it is a pain in the butt. However, I always went DCEN, 100% argon, and cranked up the heat to a 2% thoriated electrode with a razor-sharp point on the end...seemed to work ok for me. Never tried it with AC, but I guess it would do ok as long as the current was balanced slightly to the positive.

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