I will be welding aluminum, stainless steel, and regular mild steel with my future 220v mig welder, with mild steel being ~85% of the welding. I am wondering if there is a certain combo that will work decently on all 3, or will I have to pick up 2 or 3 tanks? I've read a couple times that full argon works OK on mild steel, but the only withdrawl is it is alittle colder. Any truth to that? What is the recommended set up for welding stainless steel? I'm still very much a greenie at the whole MIG scene. I know 75/25 is the choice for mild steel and 100% argon for aluminum, but still unsure of stainless. Thank you PBB! :D

I have run stainless 309 type wire with straight C02. Might not loose as nice as trimix but works.

Argon or helium for stainless. Argon would be fine, and if I am not mistaken is cheaper than helium. You dont want to weld stainless with a CO2 based gas because the carbon from the gas gets absorbed by the weld and will cause your stainless to rust. Argon will be a bit colder for mild steel, bt the only other real drawback is that it costs nearly 2xs as much for a fill. If you are not going to do a lot of stainless/aluminum welding, lease a small bottle of argon and use it just for that purpose. I highly recoment tig over mig for aluminum and stainless. Mig welding aluminum is a pain in the ass.

BTW, absolutely no CO2 Based gas with aluminum. The carbon makes the welds porus as hell.

Later,
Jason

The best thing to use for stainless is a Helium/Argon/CO2 mix, but it's outrageously expensive - $65 to fill an 80 cu/ft cylinder.

I have a cylinder of Argon for stainless and aluminum and a cylinder of CO2/Argon (about $50 for a fill) mix for mild steel.

As mentioned, the Argon would work for an "all around" gas but you'd give up some with the steel. And it's way more $$ than straight CO2.

If I were you, I would either run like I do or just straight CO2 (for cost savings) for the steel and Argon for the stainless and aluminum.