I was wondering how hard it would be on the tungsten.  I've seen students do it on accident before and it made the tungsten all black and the stainless all black, but it still welded for them.  I know welding copper nickel to carbon steel is very tricky with pure argon so I thought maybe this might be some kind of fat freddy fab shop trick or something.

I agree, C02 is a no no for tungsten.  But, I have never seen any data on just how much can be tolerated. Maybe a tiny amount could work.  You know, like 2% oxygen with 98% Argon for GMAW?

Any % of CO2 shielding gas with GTAW will result in Tungsten Contamination/Oxidation! If you have any doubts, just try it! You will soon see the outcome!

I get it, but it would be interesting to see what they tried to use as a filler metal and what the guided bend samples looked like.

I have had contractors weld copper silicon, as well as copper nickel, to carbon steel. When they did their bend samples using a 4T bend diameter the welds became shrapnel.

We had success with Monel to HSLA80, but it wasn’t easy to get it to pass the guided bend tests. It is all about using the right filler metal and the right gas.

We were told to use SG-ArHeC, but when we tried it the welds actually turned green/olive drab. We got rid of the CO2 and things went a lot better. Key point; the process was GMAW, not GTAW.

There’s nothing like testing a coupon to see what works and what doesn’t work.  What other business provides entertainment and pays you to participate?

Al