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Thread: Tack welding stainless steel with a Mig welder

  1. #31
    Registered Member
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    Apr 2012

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    I did a little reading on mig welding stainless steel. Seems "tri-mix" gases of varying percentages are the most often recommended. The third gas is oxygen. The majority is argon, with more argon than the usual 75% for steel (often 85-90%). Didn't see any recommendations for 100% argon.

    Bottom line, it kind of sounds like you'd have to pioneer it for your own application as to which gas to use. And that would run some $ for a small job. I'm confident you could use 308 or 309 wire, and whatever gas you had on hand to tack the exhaust system.

    Bitchin57, were those welds black after doing some wire brushing?

    The above is just based on a google search, all my stainless welding experience is with tig and 100% argon. You use 100% argon to tig weld carbon steel too. And I will say this, my limited experience with tig welding stainless is that I've had great results and it welds really nice. For me, easier than carbon steel if you're welding on 16 gauge.

  2. #32
    Registered Member 56Mark's Avatar
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    I have a very few times welded small parts that were 316 SST to carbon steel with regular steel MIG wire and the 75/25 mix gas. I can't tell it welds much different and after grinding and polishing a little it is hard to tell which is which. The last thing I welded like this was 1/4" SST tubing that I put all thread in the ends which makes great little linkage rods. I still have the original gas pedal linkage in my 56 and needed a rod from the linkage to the carb with a small dogleg offset in it. 3 years ago,I made that rod out of SST tubing and steel all-thread and the weld still has not rusted significantly. I know an exhaust pipe will be hotter and more exposed to moisture but I bet it will last many years no matter how you weld it. If I had a lot of money in exhaust parts and building a nice car I would probably have it TIG'd with stainless.
    56-210, 283, 200-4R, Power steering, Power Brakes

  3. #33
    Registered Member chevynut's Avatar
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    Stainless steel also has a lot lower thermal conductivity than mild steel, so it takes a lot less current to weld it. You get a lot of penetration and a small HAZ with it as a result. I welded my 16 gauge (.065") exhaust with 30 amps and mild steel would take more like 60 amps. It's easy to over-heat it and the welds end up looking oxidized. IMO TIG is the only way to go with stainless if you want show-quality welds. But I think you could tack it with mild steel too.

    These are some welds from my exhaust system:

    09300004.JPG

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    20151217_011.JPG
    56 Nomad, Ramjet 502, Viper 6-speed T56, C4 Corvette front and rear suspension


    Other vehicles:

    56 Chevy 2-door BelAir sedan
    56 Chevy 210 4-door sedan
    57 Chevy 210 4-door sedan
    1962 327/340HP Corvette
    1961 Willys CJ3B Jeep
    2001 Porsche Boxster S
    2003 Chevy Silverado 2500 HD Duramax
    2019 GMC Sierra Denali Duramax

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