CO2/Argon 5%, 10%, 15% ?? When? Why?

[graham-xrf]

After a little tangle not getting through the Brexit border, the new welder has finally arrived. I have found a place not too far away that will always return the entire deposit on a gas bottle, no matter how long you keep it (years), so it's never on hire. They supply the three different mixes of CO2/Argon, and also Argon Pure, and Oxygen, and Acetylene.

My welder does MIG, and Lift-TIG (and some other options for stick, polarity, AC or DC). To choose a particular gas mix, one needs reasons.
So - what are the conditions that would motivate one to choose (say) 5% CO2, or 10% maybe. What drives the choice?

 

[DavidR8]

I'm far from an expert but TIG requires 100% Argon, MIG is 75% Argon + 25% Co2

 

[benmychree]

For MIG, I use straight CO2, that is the cheapest and the best penetration, but an argon mix will give smoother welds.

 

[DavidR8]

Yes, I totally forgot about straight Co2!

 

[Buffalo21]

I use 90/10 on my Miller 350P pulse mig and 75/25 on my Miller Millermatic 252

 

[General Zod]

For MIG, I use straight CO2, that is the cheapest and the best penetration, but an argon mix will give smoother welds.

Straight CO2 does make for a hot, fluid puddle, but you should check out the video Jody did on welding a Jeep bumper where he also tested some welded samples by putting them in a 20Ton press, one was welded with straight CO2 and the other with 75/25 Argon/CO2. The winner, as determined by Jody, would surprise you, as it did me.

 

[Janderso]

Benmychree is correct in my experience.
This may help

 

[Janderso]

Straight CO2 does make for a hot, fluid puddle, but you should check out the video Jody did on welding a Jeep bumper where he also tested some welded samples by putting them in a 20Ton press, one was welded with straight CO2 and the other with 75/25 Argon/CO2. The winner, as determined by Jody, would surprise you, as it did me.

I need to check this one out.

 

[Janderso]

I'm far from an expert but TIG requires 100% Argon, MIG is 75% Argon + 25% Co2

Whoa,
I didn't recognize you. Hi David. I like it = chips.

 

[General Zod]

After a little tangle not getting through the Brexit border, the new welder has finally arrived. I have found a place not too far away that will always return the entire deposit on a gas bottle, no matter how long you keep it (years), so it's never on hire. They supply the three different mixes of CO2/Argon, and also Argon Pure, and Oxygen, and Acetylene.

My welder does MIG, and Lift-TIG (and some other options for stick, polarity, AC or DC). To choose a particular gas mix, one needs reasons.
So - what are the conditions that would motivate one to choose (say) 5% CO2, or 10% maybe. What drives the choice?

For welding Mild steel using the short-circuit transfer process, the addition of argon to CO2 provides "smoother" welds, and may also provide higher tensile strength and enhanced ductility via better Charpy V-notch ratings. 25% CO2 concentration is good all-around blend since the Argon component costs more than the CO2 component, but you'll rarely see less than 75% in the mix because you start to lose the advantages of argon but still have to pay for the premium of having argon in there anyways.

Using C10 can provide higher Yield and Tensile strengths and better Charpy V-notch performance, as seen from this snippet from Lincoln:

Less than 10% CO2 is usually reserved for spray-transfer or pulsed-spray transfer modes.