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  1. #1
    Join Date
    Mar 2009

    Default just bought a MIG welder....question on gas

    I finally bit the bullet and bought a welder for my home, for doing projects on my boats. I bought a Miller 250 with a 30A spool gun. i also got a 50 ft extension cord...the cart has a place for 2 bottles of gas. the guy said one is for pure argon and the other is for argon -co2 mix( for welding steel). OK ill have to rent the bottles. DO i really need the mixed gas bottle? the reason i ask, is that i have a TIG machine at work and we use ultra pure Argon on that machine.. and i weld aluminum, stainless steel and regular steel with the same gas....seems to be fine.

    gan i use the pure argon at home with my MIG machine to weld steel ( knowing I have to revert the regular wire feed in the machine)


    PS the mig welded way way easier than i had heard...we did test welds before i bought it, and we used just aluminum sitting on the shelf..didnt wire brush it or nothing...welded fine9 to my eyes.... I was welding in 5 minutes...of course my welds are a little high......but the finess is like learning to use a clutch in a standard car.....


  2. #2


    you can use pure argon for mig welding steel and stainless. The only difference is the mix is cheaper. If you are mig welding aluminum, you are going to need pure argon anyways. Keep an eye out on Craigslist for owners tanks. They should be about $80-$100 bucks. Renting them gets expensive if you aren't doing production work and they are just sitting in your garage.

  3. #3
    Join Date
    Aug 2010
    Los Angeles


    Lift the cover on the spool side of the machine. The chart will tell you which gas to use.
    Nothing welded, Nothing gained

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  4. #4
    Join Date
    Feb 2012


    You can't mig steel with pure argon. You can run co2 or some blend of argon co2. The most commonly used is a 75/25 mix, or also referred to as c25. When migging aluminum with the spool gun you must run pure argon. Using straight co2 will result in a little more spatter than with c25. Stainless requires a tri mix it stainless mix. Obviously you can run flux core with no gas as well, but will have different characteristics. Then there is dual shield and many other blends for different configurations...

  5. #5
    Join Date
    Sep 2005
    northern NJ


    Do not use pure argon for steel & stainless mig.

    Aluminum mig = pure argon

    steel mig = argon/co2 mix or straight co2

    Stainless mig = trimix
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  6. #6
    Join Date
    Dec 2011


    There is a good explaination of the why's and the wherefore's in Praxair's Shielding Gas Selection Manual. Should be available at the Praxair website.-Meltedmetal

  7. #7
    Join Date
    Feb 2010


    I will have to second both MMW and Meltedmetal.
    You DO NOT want to use 100% argon to MIG anything steel.

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  8. #8
    Join Date
    Oct 2005
    North Central Indiana


    pure argon doesn't offer the penetration 75/25 blend does on steel, bead shape and depth along with arc characteristics are effected with different gas mixtures.

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