Co2 vs. mix gas, your experiences?

[DennisCA]

I bought a bottle of Co2 on monday for my mig welder, have wasted a lot of mix gas on autobody repair and the weld gets ground down anyway. And I then saw that Fitzee (youtube) uses co2 for his impressive work so why should I pay twice as much for mix gas refills. I decided to try it out.



After welding with it for an evening on my car I have so far found I needed to set the voltage two steps higher on my machine and also up the wire feed. But at the same time it seems less prone to blowing holes than when I was using mix gas. Which I found really strange. It does spatter more and feels a little "rougher". But for half the price of mix gas I think it's entirely viable as long as short circuit or globular is enough.

To me this goes to show you can't just trust what you read on message boards. Gotta try things out yourself. Based on what I've read there I would've thought Co2 was barely workable alternative to mix gas.

[no704]

CO2 is all I ever use. And the spare bottle can be used in the kegerator too!

[Mike279]

My little Lincoln has chart to show setting on the inside of the wire door. One line for CO2 and one line for argon/co2 mix and another for inner shield flux core wire. I like the mix as it seems to be the least spatter and runs just a bit hotter. If I welded a lot I think differently.

[strokersix]

Not directly in answer but I'll share a recent observation. I had a short production run of weldments recently. All 3/8 inch laser cut steel plate. Not sure the material, A36? I have always run a tri-mix which I think was 75/25 plus a little O2. Plate was not pickled so the mill scale was present plus a little very light rusting. I had to exchange gas bottle in the middle of the job. Tri mix not available so I got 75/25. I immediately noticed more spatter compared to tri mix gas. That was the only change. I didn't touch welder settings at first but then I did try to tune out the spatter without much success.

I don't know why but I suspect that the tri mix was better able to handle the mill scale. Again, just an observation. I don't know. I ended up using a little more spatter shield to prevent the spatter from sticking and kept going.

[BigMike782]

Argon/CO2/oxygen tri mix has two basic advantages over 75/25. The small amount of oxygen helps the puddle wet out and gives the ability for spray transfer(with a machine that has enough output).
I would not bother using straight co2, but then I am biased, cylinder gases don’t cost me anything.

[jmm03]

if ever there was a time to post comparison pictures now would be it. (for those occasional fabricators)

[BigMike782]

if ever there was a time to post comparison pictures now would be it. (for those occasional fabricators)

Comparison of what?
if I showed you a picture of short arc and spray transfer there is NO chance you could tell the difference.

[DrMike]

I don't think the requested comparison was between short arc and spray, but between different gasses and mixes.

Can we get a comparison of MIG welds with
- 75/25 Argon/CO2 mix (commonly recommended as an all-round good choice for steel)
- Pure argon (commonly recommended for MIG welding aluminum and MIG brazing)
- Pure CO2 (which seems to be recommended here, but almost nowhere else)
- Argon/CO2/oxygen or Argon/CO2/helium tri mix recommended here (not sure of percentages)

[BigMike782]

I don't think the requested comparison was between short arc and spray, but between different gasses and mixes.

Can we get a comparison of MIG welds with
- 75/25 Argon/CO2 mix (commonly recommended as an all-round good choice for steel) Most common steel MIG gas, easiest to hit the "sweet spot"
- Pure argon (commonly recommended for MIG welding aluminum and MIG brazing) Aluminum and silicon bronze
- Pure CO2 (which seems to be recommended here, but almost nowhere else) Cheaper than 75/25, harder to hit the "sweet spot", more spatter
- Argon/CO2/oxygen Steel mix, 2.5% oxygen helps wet, gives slightly better penetration out and argon content with enable easier spray transfer with enough machine power
- Helium/Argon/CO2 helium tri mix or argon/CO2/nitrogen, stainless steel, former unavailable during helium allocation, latter available because of the lack of helium

Steel tri mix is 89% argon/8.5% CO2/2.5% oxygen
Stainless tri mix is 90% helium/7.5% argon/2.5% CO2