Stainless Mig Welding Setup?

  1. James1979 Member

    Messages:
    646
    Location:
    Orkney
    Hi All.

    Just looking for some pointers about Mig-ing Stainless, 316 in particular. Ive a transformer Mig and I'm assuming that as long as I put new liner tips rollers etc in and the appropriate wire and 100%argon, I'm good to go?

    I'll be pickling the welds as normal. I just need something a bit quicker than arc which is how I'm doing this particular job at the moment. I am experienced with arc and stainless - I've a lot of hours doing it so its an easy thing to me and I'm fairly efficient at it, but I need something a bit quicker for lots of smaller bits. TIG would be nice but at the moment I cant run to a set. I have one I borrow when I need but the guy it belongs to is using it at the moment, hence looking at Mig.

    Cant think I've overlooked anything kit-wise?
     
  2. gt6s Member

    Messages:
    790
    Location:
    Newtownards Co Down Northern Ireland
    argon co2 mix will be fine
     
  3. James1979 Member

    Messages:
    646
    Location:
    Orkney
    ok thanks. I thought it needed to be pure? Thats handy, one less expense! I've currently got 5% in the welder so that should be ok then?
     
    gt6s likes this.
  4. gt6s Member

    Messages:
    790
    Location:
    Newtownards Co Down Northern Ireland
    Yup
     
  5. Hood

    Hood If it walks like a duck....

    Messages:
    11,651
    Location:
    Carnoustie, Scotland
    Pure Argon and Mig is for Aluminium.
    I think 2% CO2 is more normal for stainless but likely your 5% will be ok if it is not a critical thing. Then again if you are using 316 I suspect you are wanting the corrosion resistance so 5% may not be ideal.
    @backpurge may be able to advise better.
     
    slim_boy_fat and James1979 like this.
  6. James1979 Member

    Messages:
    646
    Location:
    Orkney
    I am wanting the corrosion resistance, as its for a place that makes vinegar. Its not in direct contact but that stuff gets in the air and it eats everything it lands on! Not certain I can get 2% on the Hobbyweld scheme, I'll have to ask.
     
  7. Hood

    Hood If it walks like a duck....

    Messages:
    11,651
    Location:
    Carnoustie, Scotland
    In that case I think 5% will be too much. Then again the only thing I ever weld with Mig is Aluminium so I am certainly not an authority on it :D
     
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  8. Paul.

    Paul. Moderator Staff Member

    Messages:
    6,504
    Location:
    Northampton. UK
    5% Co2 will do the job but the welds will be a bit sooty, an acid pickle or stainless wire brush will clean them up but for proper corrosion resistance you should look at using a Tri mix gas which is argon, Co,2 and helium, BOC Stainshield is one option sit on something sturdy when you look at the price though, but if you are doing the job properly then it costs............

    The mesh in these cages was tacked in with a 5% mix, https://www.mig-welding.co.uk/forum/threads/stainless-cages.101017/#post-1563965
     
    tom2207 likes this.
  9. James1979 Member

    Messages:
    646
    Location:
    Orkney
    Thanks gents. @Paul. That's the sort of thing in doing. How did they fare long term?
     
  10. Paul.

    Paul. Moderator Staff Member

    Messages:
    6,504
    Location:
    Northampton. UK
    It was only the mesh that was migged, everything else was tigged, they were only made in May of this year so its not a long term job yet but I've done it before and am not expecting any problems, you can stainless wire brush them to take out the discolouration then use a proper hydrofluoric / nitric pickling paste such as Antox or Metinox ,or an electrolytic system to re passivate the welds.
     
  11. James1979 Member

    Messages:
    646
    Location:
    Orkney
    Thanks. I use pickling paste when I arc / tig so that's no bother. I'll try it and see how it goes. Cheers
     
  12. steviec_lj

    steviec_lj Rust Welding Professional

    Messages:
    2,699
    Location:
    Barnetby, N.Lincs
    What luck.

    I was about to ask the same question regarding gas. I could go down the TIG route but to be fair I still need a bit of practice it’s been that long.

    Ive got BOC’s Argoshield Light which is 93% Ar, 5% Co2, 2% O2. Material is 2mm 304 or 316.
     
    James1979 likes this.
  13. James1979 Member

    Messages:
    646
    Location:
    Orkney
    Wonder if that’s better than the hobby weld 5% I have. BOC have a better range of gas but I won’t ever go back to them on principle after my last experience with them.
     
    gt6s likes this.
  14. Agreed, would always recommend a CO2 content no higher than 2.5%, and that would be with either pure argon or a argon/helium mix. Any higher and you start to run the risk of carbon pick up, this not only affects the surface of the weld, causing the formation of corrosion but will cause embrittlement within the weld, so pickling or wire brushing the surface of the weld is not really going to solve the problem
    Also, if you use an Argoshield Light flavour gas not only have you got twice as much CO2 as you really want but you have 2% O2 in there which is going to cause excessive surface oxidation.
    Theses may not be issues, depending upon what you are welding and what you are using it for
     
    James1979 and Hood like this.
  15. James1979 Member

    Messages:
    646
    Location:
    Orkney
    Thank you. Its a series of stands and tank for a brewing system. Whats in contact with it will be beer / cider, but its in an environment where vingear is the end product. while this wont contact what Im doing it is in the air.

    TIGing is not an option at the moment so if you dont think it'll work with MIG i may carry on as I am?
     
  16. MIG welding it will be fine just so long as you get set up right, I take it that the welds will have to be clinically clean because they will be coming into contact with food stuffs. A thing you may need to look for is, if the material is fairly thin and you can’t weld it in spray transfer there is a possibility you may end up with a weld with pronounced convex profile that doesn’t blend in very well at the toes, these areas can sometimes be considered as potential traps for bacteria
     
  17. James1979 Member

    Messages:
    646
    Location:
    Orkney
    It’s the gas that I’m thinking about. The job hasn’t enough money in it for a bottle of tri mix and it’s not readily available up here anyhow! If I did mig it, which is th preferred option, I’d be using the 5%

    I’m blending the welds back to get smooth edges so there’s no traps for bacteria. The convex profile is a nuisance but I can get in to most of it with die grinder, or a pad
     
  18. The gas I would recommend is argon + 2.5% CO2. A lot of people use an Argoshield Light type mixture and don’t have a problem but it is not something I would recommend
     
  19. James1979 Member

    Messages:
    646
    Location:
    Orkney
    Cheers. I’ll see what I can get hold of. Up here it’s often a case of what’s about and make do rather than the 100% correct thing.

    I would like to do it properly if I can though. Thanks for the help
     
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