I did a search but didn't find much. What gas are you using for your MIG welder? 100% CO2, CO2/argon, or 100% Argon?

Just Curious,
John W.

You could either have Aaron come over and fart around the welds or use the most common C02/argon mix which should be available from Airco or one of your local welding supply houses.

When all else fails or when in dought, us straight argon brother. Any weld supply place will answer any of your technical questions though.

What I use....

Thick metals with more penetration (not as pretty) use straight CO2
Fabricating and thinner metals (better looking welds) use CO2/Argon mix
YMMV

50/50 fart / argon mix as skline mentioned

Mild steel, 75% Argon / 25% CO2. Aluminum, 100% Argon... Larry

FWIW, the gas mix Argon and CO2 reasoning is 75%/25% because Argon excels with purity of the weld and the CO2 excels with the penetration of the weld. Aluminum needs purity so Argon&Helium are the ideal gases. Steel isn't as picky and benefits from the CO2 mix for strength.

Cheers, Don.

if you're cheap, use straight CO2. it costs nothing. 75/25 mix is more workable and pretty. I much prefer the latter.

For steel, I prefer the 75/25 ARGON/CO2 mix. You can go CO2, but your welds may not be as clean looking. I feel that the Argon helps with less than ideal welding conditions.

For Aluminum TIG, I think our shop uses Helium.

just my $0.02

75/25 Argon/CO2 Mix

helistar I do believe its called.. but its 75/25..

75/25 aka "Steel Mix"
marty

I use 100% CO2 but then I only weld steel and my welder (Miller Passport)
was specifically designed for using CO2 in paint ball cylinders.
It is inverter based and is a self contained 50 lb suitcase.
One 12 oz paint ball cylinder is good for over 45 minutes
of trigger time, which is quite a bit of welding and costs
about $2.00 to fill.

--- bill

Good advice so far. A few other points of interest:

CO2 is stored as a liquid, and will last much much longer than an equivalent cylinder of 75/25 shop mix which is stored as a gas. The cylinders are not compatible.

As noted, CO2 will typically give more penetration. I agree that 75/25 is a little cleaner, but you can make very nice welds with either of them. It really depends on what you are doing. For most automotive fabrication which is typically thinner material with less deposition, I'd go with the 75/25. If money is tight, then there's no shame in using CO2, it's perfectly acceptable.

Some guys will actually refuse to run CO2 which I just don't get. A good welder can make great welds with either gas, and a bad welder is just as likely to make bad welds with either of them.

I actually have a bottle of each. I generally use the 75/25, but if I run low, the CO2 is always there and it seems to last forever. I can guarantee that even an expert would be hard pressed to tell the finished welds apart. The characteristics are a little different, but once you adjust for them, it's business as usual.

Good preparation, free of paint, oil, undercoating, and rust will make much more of a difference than the type of gas. The extra time it takes to get down to nice clean metal is worth the effort.