Yes. Maybe. According to google you should use what's called "tri-mix". I've never used any welders with gas, so I don't know.
I do know however, from experience, that you can weld stainless-to-stainless and stainless-to-mild exhausts together with regular flux core wire with no gas and it will hold until the welds rust out 3 years later.
Also I am considering buying some V-Clamp flanges and just welding those to my cuts instead.