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  1. #1
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    Default mild steel to stainless steel

    Hi All,

    I have done a very brief search, but can't find a suitable answer.

    The question is, can I weld mild steel to stainless steel using a Unimig 190 with gasless mild steel wire?

    I am considering making a small furnace out of a stainless steel LPG tank and wanted to weld various brackets for the lid and stability legs etc.

    Is this achieveable with gasless mild steel wire, or not?

  2. #2
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    Default

    Welding an LPG tank - braver man that I....

    Normally you would use a 309L filler when welding SS to MS, the excess chromium in the filler compensates for the dilution at the SS to MS joint. There is a flux core 309L wire available but you'd have a heart attack at the price. My BOC price list shows around $550 for a 15 kg roll - for that price you'd want them to weld the joints as well.

    My experience welding SS to MS using normal MIG wire is that the joint is prone to cracking because of the pickup of chromium and nickel from the SS into the weld pool. Others may have had better luck but after a couple of early joints cracked I switched to 309L rods using the TIG and haven't had issues since.

    If it's just a few joints you might be able to find someone local who could TIG it in exchange for a slab.

  3. #3
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    Default

    Thanks Gavin. So, effectively it is a non-event.

    Back to the drawing board.

  4. #4
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    Default

    id say give it a go mate.if its only joins that are accesable easily enough then have a crack.ive welded many many items together with gas shielded mig and steel wire when it hasn't been important and they have all survuived

  5. #5
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    Default

    Is there any reason why you can't engineer the fittings so they can be bolted to the tank rather than welded?

  6. #6
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    Default

    Quote Originally Posted by Gavin Newman View Post
    Is there any reason why you can't engineer the fittings so they can be bolted to the tank rather than welded?
    To be honest, I hadn't given it much thought. I just assumed that welding would have been easier.

  7. #7
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    Default

    If you have access to a stick welder then that would be a good option with stainless sticks, otherwise use the mild steel fluxcore, but be aware that corrosion and heat resistance will be compromised. 400 series stainless is normally the grade of choice for applications involving heat, but the 300 series aren't too bad.
    Be aware that stainless distorts and moves far more than mild steel when heated and this can prove a problem if tolerances are made too tight.
    Make sure all your ducks are in a row before you commence work on any gas cylinder. Death tends to be very final.

  8. #8
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    Dec 2010
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    Default

    I appreciate your concerns KR. The LPG cylinder was cut open a few years ago, so I think that it should be OK by now.

    The Unimig has the option of using stick (if I can just figure out how ) so maybe I will look into sourcing a few 400 series rods and have a play.

  9. #9
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    Default

    The electrodes you will want are 309 or 316. Several manufacturers sell them in handy packs.

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