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Shielding Gas Confusion???

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  • Shielding Gas Confusion???

    Let me start by saying that I am very new to welding. I've done some rough stick welding before on a borrowed machine, but that's about it.

    I just bought a MM 210. My primary intent is to weld aluminum with the spool gun and argon. I have a trawl boat with aluminum rigging that needs constant repairs and modifications.

    I would, however, like to use the machine for welding mild steel and stainless on ocaision. The topic of shielding gas has me spinning.

    I set up an account with my local dealer and have argon set up on my machine.

    If I want to switch to the mig gun and weld steel, the manual recommends an argon/co2 mixture and a tri-mix gas for stainless. I'm not interested in switching to flux core and having to reverse polarity every time I want to weld steel, but on the other hand I don't want 3 bottles hanging around my garage with a rental fee on each.

    What are my options for using argon with mild steel and stainless? I've heard that some flux core wires, when used with shielding gas do not require reversing the polarity to DCEN. If so, can these wires be used with pure argon as opposed to switching to argon/co2 or tri mix?

    Any information of clearing up my issues around shielding gas will be greatly appreciated. I'm just looking for the best options with the least amound of hassle and cost.

    Thanks in advance..

  • #2

    I just spent an hour at Airgas talking to my dealer, who convinced me to stay away from flux cored wire if at all possible if I did not want the hassle of switching the polarity ion my machine. SO, I wound up setting up another bottle of 75/25 Ar/CO2 on my account for welding mild steel. Luckily my MM 210 package came with a dual cylinder rack that is attached to the machine to accomodate the 2 bottles I now have.

    The dealer also told me that he uses stainless wire through his spool gun at home running on pure argon. He said that it "crackles" a bit more, and the weld is not nearly as pretty, but it sticks just fine and has good strength. This is basically what I'm looking for with stainless (strength over appearance), so I bought a roll of stainless wire and I'll give it a go and see what happens..

    Has anyone else tried mig welding stainless using pure argon? If so, are there any special considerations I need to know about?


    • #3

      Are you primarily welding 304 S/S? And what filler metal are you using 308?

      Try the 75/25 on the stainless steel when in spray arc mode and see how it works. Using pure Argon may work, but ideally you want some O2 or He in the gas to increase the arc temp to assist in burning out impurities that may be present in the stainless weld puddle, the lower arc temp using argon may cause what your local dealer described as increased "crackles". The impurites are not vaporizing thoroughly but being released as gas bubbles which can cause a crackle sound. This has the potential of leaving gas pockets or porosity in the completed weld, be careful!
      Kevin Disney


      • #4
        Shielding gas

        Moe...I just purchased my first mig a MM175. Right now I'm using flux core wire and am getting very good looking beads. I was going to try solid wire but I was going to use straight co2 for mild steel. My welding dealer said that I could find a co2 bottle just about anywhere as long as it had a stamp on it indicating at least 1800 psi and also had the code 3AL, 3A, or 3AA stamped on it. A 20 lb bottle would cost about $16.00 to fill and they can fill it. The main thing is, when welding with shielding gas, I've been told you can't have hardly any breeze or the gas cloud will be blown away. My manual shows straight argon for aluminum but there again if there's any wind the gas is gone. Let me know what you find out.....Ken
        KenCO " Uccahay "


        • #5
          Hi Moe,

          You may also want to check out the Hobart forums for some additional information. It's a great resource. Much experience to be shared.



          • #6
            Shielding Gases


            It sounds like you want to use the shielding gases, but don't want the monthly rental fees. You say you have an occasional use for welding mild steel and stainless steel. Perhaps you could rent the large bottle of argon for you major need of welding aluminum and outright purchase smaller bottles of 75Ar/25Co2 for steel and a trimix or 98Ar/2O2 for stainless. These smaller sizes for 40-160 are typically available for outright purchase and are good until the inspection test stamp expires(10 years for most tanks). The 98/2 will also work for mild steel, but probably only in the spray mode. It's a very hot gas mix. These tank purchases are relatively inexpensive compared to piling up rent on unused bottles throughout the year.


            • #7
              You guys are a wealth of knowledge.....

              Thanks for all of the tips and information on the stainless issue.

              Yesterday evening after I set up my spool gun with a roll of SS, I had my son (who is a welding student) weld up a large SS stirring paddle for my jambalaya pot which was cut out and fit over the weekend. I told him to try both gasses. On the T-handle, which is 2 pieces of 3/8" 304 round stock welded at a 90 deg. as a Tee, he used pure argon. The weld came out ok, was indeed strong enough, but it crackled and popped like **** as he made the weld. He grinded it down a bit, lowered the voltage a notch and mad another pass and it looked good.

              On the paddle, where 3/16" plate was welded to the other end of the 3/8" shaft he used the 75/25 mix. Both he and I agreed that this method was better. He tuned the machine and gun by slowing down the wire a bit and making very small adjustments to the output votlage. Less crackle and only a single pass was needed. No grinding.

              He (my son) had never mig welded before (they're still covering basic stick in school), but he seemed to really like the machine. After the spoon, he tacked and welded out a set of angle iron legs for our future welding table (mild CS 1/4" AI to 3/8" plate) with the mig gun and the 75/25 mix . I must sat that the finished welds looked like something that came off of a robotic welder.. Absolutely perfect! I think the boy will do ok with this welding stuff. Now me... That's another story.......

              Again, thanks for all of your tips and information. I'll stick around and share future experiences as they come up.