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Technical MIG welding, What gas do I need?

Discussion in 'The Hokey Ass Message Board' started by dirttoo, Jan 6, 2017.

  1. dirttoo
    Joined: Feb 17, 2009
    Posts: 136

    dirttoo
    Member

    Ok, I was welding on my floorboards last nigh and ran out of gas on the mig welder. I have had this welder since 1994 and I think I have filled the bottle like 3 times. The label on the bottle says STARGON COMPRESSED GASSES N.O.S. (Argon, Carbon dioxide and Oxygen). The guy helping me asked me why I buy that crap. He didn't say what to buy so I thought I would ask the guys who do what I try to do. It's a Hobart 170 BetaMig sleeved down to .030 wire. I weld tubing and sheet metal that is sometimes rusty or not so clean. Can someone tell me which gas I should be using? Thanks
     
  2. gpohl6
    Joined: Sep 22, 2013
    Posts: 60

    gpohl6
    Member

    For mild steel shielded MIG welding, MaineOxy recommends a mix of 75% CO2 and 25% argon.
     
  3. Blue One
    Joined: Feb 6, 2010
    Posts: 11,143

    Blue One
    ALLIANCE MEMBER
    from Alberta

    That Argon CO2 and O2 mix is for MIG welding stainless steel. more than you need for mild steel. (More expensive too)
    For the mild steel you need a C25 mix. Argon 75% and 25% CO2.
     
  4. woodiewagon46
    Joined: Mar 14, 2013
    Posts: 1,916

    woodiewagon46
    Member
    from New York

    Yup, 75% Argon and 25% CO2 mix for steel, commonly called 75/25 and C25, and 100% Argon for Aluminum. Flow rate of about 15 to 20.
     
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  5. Relic Stew
    Joined: Apr 17, 2005
    Posts: 1,142

    Relic Stew
    Member
    from Wisconsin

    O2 in the mix increases the heat and penetration. It also makes the puddle more fluid for a wider, flatter weld bead. A place I used to work used the Argon/CO2/O2 mix for cosmetic reasons. Back when $99 Walmart bicycles were US made, they cranked the wire speed way up, used the O2 mix and got a big, fat, 1/2" radius weld between the tubes. Looked strong and purty, with great visual appeal to the average Walmart bicycle customer. Not necessary or proper for strength, but that's how it was done.
     
  6. gene-koning
    Joined: Oct 28, 2016
    Posts: 2,452

    gene-koning
    Member

    Clean steel is a must for Mig welding. If the steel was not clean, you have a poor weld! You may have been getting by with the extra O2, but with the 75/25 mix, you better be cleaning the steel you intend to weld, if you want good welds.

    I've been a welding supply sub-dealer (I exchange tanks here) for over 20 years, I have never sold a single tank of Argon/CO2/O2 gas mix. Gene
     
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  7. dirttoo
    Joined: Feb 17, 2009
    Posts: 136

    dirttoo
    Member

    Thanks guys, if the Argon/CO2/O2 mix is for cosmetic reasons my welds are really in trouble.
     
  8. theHIGHLANDER
    Joined: Jun 3, 2005
    Posts: 8,236

    theHIGHLANDER
    Member

    :eek:
     
  9. Blue One
    Joined: Feb 6, 2010
    Posts: 11,143

    Blue One
    ALLIANCE MEMBER
    from Alberta

    Not totally true. Read the section on Wire Selection here.
    https://www.millerwelds.com/resources/article-library/mig-welding-the-basics-for-mild-steel
     
    Texas Webb likes this.
  10. okiewelder
    Joined: May 10, 2008
    Posts: 218

    okiewelder
    Member
    from central Ok

    Hell if you are a totally cheap bastard like me you can run straight CO2!! I have always been told the Aragon is there for a better looking bead and the CO2 is for penetration. You may have issues with your regulator or flow meter which ever you are using but, you can get an adapter for it
     
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  11. Finnrodder
    Joined: Oct 18, 2009
    Posts: 2,965

    Finnrodder
    Member
    from Finland

    I use straight CO2 with the migwelder.It works fine and its really cheap.Argon is really pricey in here,specially for the private customers,so i use that only with the tig.
     
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  12. Blue One
    Joined: Feb 6, 2010
    Posts: 11,143

    Blue One
    ALLIANCE MEMBER
    from Alberta

    Straight CO2 will work, but will give a different weld puddle and penetration profile. Along with more spatter.
    As well it will not work as well for sheet metal work as an Argon CO2 mix will.
    On top of that, you are not MIG welding when you weld with 100% CO2. You are MAG welding.
    MIG welding = Metal Inert Gas welding
    MAG welding = Metal Active Gas welding
    CO2 is an active gas meaning that when you weld it reacts and changes in the heat of the weld puddle and one of the by products of that reaction is carbon monoxide.
    Argon is an inert gas which does not change in the arc heat.
    A 75% Argon 25% CO2 mixture gives better arc properties for thin sheet metal and overall better less spatter performance for MIG welding.
    Look it up...:)
    Class over :D
     
  13. okiewelder
    Joined: May 10, 2008
    Posts: 218

    okiewelder
    Member
    from central Ok

    Yes Blue one you are absolutely correct in your reply!! I actually switched a few years ago to 75/25 when my welding business allowed me to upgrade.
     
  14. volvobrynk
    Joined: Jan 30, 2011
    Posts: 3,587

    volvobrynk
    Member
    from Denmark

    You are very right!
    And I just wants to ad, MAG welding is the preferred welding for mechanics over here, because if dirt or oil gets to close to your weld, straight CO2 burns it up, especially when on the other side of a plate. When welding sub structures to a main structure, that is old (for instance sub rails on a monoqoue body) , Mixed gas will make it suck contamination back in the puddle and ruin the weld.
    With straight CO2 is pushed the oil back out and leaves a cleaner weld, this is true in small amounts.
    And if you weld new plate to previously welded newer plate to new plate, of a better quality, co2 weld will bond better.

    Being a welder/fabricator for a living, we run mixed gas, but we only use new material.
    And we still call it MAG when mixed gas I used.
    It's only MIG over here when you use straight Argon. Basically MIG is for welding welding Stainless and ALU.

    But I've seen before that stateside stuff gets named differently for some unknown reason.
     
  15. Blue One
    Joined: Feb 6, 2010
    Posts: 11,143

    Blue One
    ALLIANCE MEMBER
    from Alberta

    Over here we group all of the different wire feed processes under the GMAW designation, Gas Metal Arc Welding.
    Then of course we have FCAW Flux Cored Arc Welding.
    We also have MCAW Metal Cored Arc Welding which is similar to Mig but runs a tubular wire with a metal powder for deposition.
     

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