Originally Posted by lwill
I failed to pay attention to your earlier posts, are you using AC or DC? AL needs AC if you are using argon or argon/helium mix to help "scrub" the oxide away. If you are using DC you can use pure helium I am told. (never tried it myself) Steel needs to be welded using DC with ground on the work peice. 2% thoriated(sp?) "red" tungsten will give you a better weld and last alot longer on steel but will contaminate aluminum.
I hope this info helps, good luck! Keep on posting!