Oxygen in MIG gas mix???

[Fabfan]

OK... I've been welding for over 30 years, and I've never heard of using any O2 in MIG welding gas mixes, save for one or two percent some guys use when spraying SS.
Now I've encountered this cat who only uses 92/8 (argon/ oxygen) and can't really explain to me what he's after but says it runs smoother (less spatter) and better penetration. (mild steel)
So I said "better than what?" I told him penetration is a skill not a gas, and that if he knew how to set a CV source penetration would not be an elusive issue. He insists its the way to go.
But at what cost? Excessive oxidation? Welds rusting from the inside out?
Would like some feedback from ya'll on this matter.
I was always taught that oxygen is the enemy. Your thoughts

[H80N]

Yup....there are O2 MIG Mixes

The Oxy helps to "Wet" the bead

The Praxair Gas Selection Manual explains some of the physics of it

http://www.awssection.org/uploads/lo...Gas_Manual.pdf

[Fabfan]

Thanks for the reply and link, H80N.
Interesting read, but no O2 concentrations above 5% are mentioned. I've seen 2% used, but eight????
Is the oxidation rate of 8% O2 higher than that of 8% CO2? Using 5 -8% CO2 for spaying mild steel I've never lacked "wetness" or penetration.
The guy I mentioned in the OP is using 8% O2 for short circuit welding on ¼" - ½" steel.
When I suggested spraying, he looked at me like I was speaking Greek.

[H80N]

Thanks for the reply and link, H80N.
Interesting read, but no O2 concentrations above 5% are mentioned. I've seen 2% used, but eight????
Is the oxidation rate of 8% O2 higher than that of 8% CO2? Using 5 -8% CO2 for spaying mild steel I've never lacked "wetness" or penetration.
The guy I mentioned in the OP is using 8% O2 for short circuit welding on ¼" - ½" steel.
When I suggested spraying, he looked at me like I was speaking Greek.

I have used 98/2 Argon/Oxy for cast iron with Cronatron™ 211 Cast Iron MIG Welding Wire


https://www.lawsonproducts.com/Crona...5.lp#documents

[gnforge]

My guess is his gas supplier feed him a line and now sells him expensive bottle of mix with a smile. <br />
Deer in the headlight look when you mentioned spray kinda gives you a hint. <br />
I use spray transfer 99% and don't use Oxy with any of my wire. I never liked the idea of using it in my welding. <br />
With that said I do keep one bottle of 98/2% on hand for my drop carbide hard surface wire application. I use it for extra the heat needed as carbide drops in. But that's for hard surfacing application only. <br />
I agree with you!! Never liked putting Oxy in a weld when we've done everything under the sun to keep it out for past 100 years. Especially when we have the ability with new style welders to get penetration and wetting with proper setting and technique.

[Oldgrandad]

Had a job years ago the boss wanted tig looking welds with the mig on 1" .083 wall steel tube. After talking to the welding sales rep settled on 98/2 mix with .023 wire. Had to move fast and not blink but the welds came out really nice.