Weld shielding gas question
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Weld shielding gas question
Can anyone tell me what the results would be if I use only Argon gas as a shielding gas for mig welding? The reason I ask is because we have three big cylinders of argon at work used for TIG welding which we don't do anymore and I could use these cylinders rather that having to buy my own for CAD$200. The welding I would be doing is car sheet metal, small stuff with the Hobart 140 mig welder.
The hobart welding guide suggests blended gases for steel MIG welding but I have access to a free argon cylinder.
Guy
The hobart welding guide suggests blended gases for steel MIG welding but I have access to a free argon cylinder.
Guy
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My guess it will work, but you'll get a hotter arc on pure Argon. You may have to up the presssure to 30 - 35 psi though. Give it a test shot and then cut your work in half. Try to break one piece. Take the other piece and cut it in half through the weld to see if you got good penetration.
More Turbo
Joined: May 2004
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From: BC, Canada
Like Mike W does, I use straight Co2 for medium and thick stock welding. I use a mig mix for thin sheet stock welding. Co2 has a deeper penetration than mix and is cheaper/ easier to get in my town. I had a bottle and regulator handy from my beer making, so the bottle of Co2 made it's way out to the shop. I like naturally carbonated beer better anyway. ;-) ...Terry
Tuned
Joined: Sep 2003
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There is a reason it isnt recommendrd for steel. I dont remember all the details but there was an extensive thread on the Hobart board about it. Maybe Mike W remembers where it was. Something about metalurgical properties.
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Thanks for the input guys. I think I'll go do a search on the hobart post. I am picking up the welder next week. The tanks are not mine, they are work's, but I will ask about exchanging it.
We have CO2 in the plant as well but it's used for fire protection. haha. I won't be using those.
We have CO2 in the plant as well but it's used for fire protection. haha. I won't be using those.
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From: Central Kali
I have a tank of argon for my tig. I am experimenting with mixing CO2 and argon for the mig. I tried pure argon with the mig just for the heck of it. It goes pop...pop..pop and the bead is high and narrow, on steel. 
Post Fiend
Joined: Apr 2002
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From: Central Kali
I have looked for the answer why pure argon in not used for mig welding and haven't found it yet. All I know is that pure CO2 gives more penetration and that a argon/CO2 blend gives better "weld metal properties". I did some aluminum tonight using the tig with argon. Nice stable arc. I will do some more research. 
Senior User
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From: Fosen, Norway
Hi
Over here we ofen use a mix of 23% co2 and 77%Argon for steel, and pure Argon for Aluminium, this is for Mig welding.
Found a link with some information about it.
Snubber
http://www.johndavies.co.uk/howmig.htm
Over here we ofen use a mix of 23% co2 and 77%Argon for steel, and pure Argon for Aluminium, this is for Mig welding.
Found a link with some information about it.
Snubber
http://www.johndavies.co.uk/howmig.htm
Elder User
Joined: Feb 2003
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From: Tottenham Ontario Canada
Straight argon will work for mig welding steel, but the welds won't look very good and the strength may be suspect.
It all has to do with the surface tension of the molten steel droplets and how well the filler metal 'wets' to the base metal. When welding with CO2 or an argon/CO2 mix, some of the CO2 breaks down in the arc and the oxygen lowers the surface tension of the molten steel. If the surface tension is too high, the filler metal sits on top like water drops on a freshly waxed car. When there is some oxygen (or CO2) in the shielding gas, the filler metal spreads out better.
If you are welding body metal, the strength of the welds really isn't that important, and you will most likely grind the welds down anyway, so appearance isn't important anyway. But before you drag the tank home, try welding on some body-gauge sheet metal and see how it looks.
Cheers,
Eric
It all has to do with the surface tension of the molten steel droplets and how well the filler metal 'wets' to the base metal. When welding with CO2 or an argon/CO2 mix, some of the CO2 breaks down in the arc and the oxygen lowers the surface tension of the molten steel. If the surface tension is too high, the filler metal sits on top like water drops on a freshly waxed car. When there is some oxygen (or CO2) in the shielding gas, the filler metal spreads out better.
If you are welding body metal, the strength of the welds really isn't that important, and you will most likely grind the welds down anyway, so appearance isn't important anyway. But before you drag the tank home, try welding on some body-gauge sheet metal and see how it looks.
Cheers,
Eric
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From: Central Kali
I found this at the Miller forum.
"The CO2 is a reactive gas that gives a deeper root penetration but usually a narrower bead profile that may lead to undercut at the toes. The addition of Argon will wet the toes out better and give less root penetration which when welding thinner material is better as the chance of burn through is reduced when going with the mix gas. The higher the Argon %, the less penetration you will get. There is a happy medium as if you try to go with 100% Argon to weld steel, you will get a bead that is ropey and has low penetration. You need a small amount of CO2 to increase the heat to help the puddle penetrate properly. As you stated before, CO2 is a hotter gas. This is why you would use a higher voltage to weld the same thickness with CO2 and a lower voltage with AR/CO2.
Example:
1/8" steel
approx 20-21 Volts for CO2 and 17-18 Volts Ar/CO2"
"The CO2 is a reactive gas that gives a deeper root penetration but usually a narrower bead profile that may lead to undercut at the toes. The addition of Argon will wet the toes out better and give less root penetration which when welding thinner material is better as the chance of burn through is reduced when going with the mix gas. The higher the Argon %, the less penetration you will get. There is a happy medium as if you try to go with 100% Argon to weld steel, you will get a bead that is ropey and has low penetration. You need a small amount of CO2 to increase the heat to help the puddle penetrate properly. As you stated before, CO2 is a hotter gas. This is why you would use a higher voltage to weld the same thickness with CO2 and a lower voltage with AR/CO2.
Example:
1/8" steel
approx 20-21 Volts for CO2 and 17-18 Volts Ar/CO2"
