i have always used CO2 in my mig welder and she runs great. i had a guy give me a tank of CO2/argon mix and a tank of straight argon also. well the mix was a 70%/30% mix and she welded pretty good but i ran out this afternoon while welding a new flat bed up and switched to the straight argon and i can't get a good weld to save my back side. they are all cold turn up the power and she gets to hot and gives me junk i can't get it dialed in at all. heading to get CO2 thursday but wondering why the argon would mess thins up so bad or if i am over looking something.

 

I always thought argon kept things cooler, that's why its used for really thin metal and stainless. Thats about all I know.

 

MIG stands for "Metal Inert Gas". The basic process uses argon as that inert gas. The intent is to keep atmospheric oxygen away from the weld, and prevent the buildup of slag and crud.

At welding temperatures, CO2 is not entirely inert, and breaks down somewhat. Some carbon is introduced into the weld material, and some oxygen increases the weld temperature and penetration. With enough flow, the atmosphere is still kept away and the net result is a good penetrating weld on steel, with more spatter than straight argon, but still acceptable. The extra carbon in the weld is a good thing for modern "high alloy" steel body panels, which is one reason body shops use MIG. On the other hand, the higher carbon in the weld material makes it harder and somwhat brittle, so you can't readily hammer form a mig weld, the way you can with a torch weld.

The most common mix is C25. (25 percent CO2, 75 percent argon). This gives good penetration on most thicknesses of steel while not burning through on sheet metal. Pure CO2 will work on thicker steels, but the arc is too hot for sheet metal.

Argon doesn't really "mess things up" (it is inert). But you are used to the extra penetration you get from CO2, and that's why you can't get the weld dialed in the way you want it.

 

fefarms thank you so much for that explanation and it makes total sense. the tubing i am welding now is 1/16 wall mild tubing and i am use to welding on heaver stuff. i will look into geting the C25 mix. after i finish this project maybe i'll hook the argon back up and try it on some sheet metal or just save it for when i get a TIG hopefully later this year.

 

Good explanation. Straight argon will never provide satisfactory results. It's meant for TIG welding. CO2 will give more penetration and a hotter weld, while cooling the gun better, but with more spatter. That's why there are different mixtures out there. 75/25 is the most common for most MIG welds, used by probably 98% of the shops out there.

 

stopped at the welding store and picked up a tank of 75/25 and wow what a difference. laying down some very very nice welds probab;y some of trhe nicest that i have layed on this tubing. gona just save the straight argon for a tig someday. thanks again.