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Welding stainless

Discussion in 'The Pub' at netrider.net.au started by Jeimbo, Jun 3, 2007.

  1. Hi

    What kind of welder do I need for stainless? Just doing 25mm angle and 4mm plate.

    Will an arc do it?


  2. Depends a lot on just exactly what alloy stainless it is. Can't remember it off hand but there's a formula for working out the "carbon equivalence" of a stainless steel - which then determines what welding methods will work. Though that said I have seen high-alloy stainless succesfully welded to cast iron with a cheapo arc welder :shock:.
  3. Stainless Steel - Grade 304

    stainless steel top, bottom plate and square tube used for a recent diy project.


    i think my my dad used the arc? the weld beading is not crash hot...


    man, i need to learn how to weld.
  4. You can buy arc welding rods for SS, also Mig wire for SS.
    You'll need to buy some pickling paste (or hydrochloric acid) and a wire brush on a drill to get the welds nice though.
    It basically welds like mild steel, but the finished weld is muuuuuch harder to grind.

    Regards, Andrew.
  5. Pickling paste is to remove the surface layer of the heat affected zone and return the "stainless" aspect of stainless steel. Otherwise it can corrode just like normal carbon steel.

    Any welding process is possible, most common is manual metal arc and TIG. The class of stainless is important so that you match the filler wire/rod - most welding supplies companies will be able to set you right on the filler metal -just let them know what stainless to what stainless.

    The amount of heat poured is important too if it's a critical weld.

    My old man had a manual welder, used satincraft rods for some of his DIY stainless jobs - the welds looked horrible, sometimes pourous and always had lots of splatter - but for non critical structural work (i.e., not load bearing) it worked. And the lucky bugger never had one corrode... buggered if I know how... he went against all the rules!

    Oh and be sure to use stainless wire brush and a fresh non contaminated grinding disk, otherwise the weld will corrode.

    Good luck.
  6. Couldn't Have said it better myself.
    Im a boilermaker by trade.
  7. Also, while we are at it, does anyone have any tips for welding of galvanised sheeting?

    I have a galvanised watertank with crush damage on one side, I intend to cut-and-shut the damage, and weld a sheet over the inlet, and flip the tank over (crushed side on the top), welding a new inlet and distribution tap.

    Rough guesstimate of maximum applied force is 16.58 kg (approx 0.16268kPa) on the inlet area.

    Any thoughts about if an exterior weld will be sufficient to retain the plate? (will be too messy to weld it from the inside). Also, is there the potential for the weld to be okay with an arc on thin sticks, or fork out the money to rent a mig.

    And the parent sheet is approximately 2-3mm thick, from memory.
  8. Remove the gal first around the weld area otherwise you will get gas inclusions in the weld.
    on 2mm you will be ok if your skills are up to it, use thin rods, low amps and make sure the rods are dry (put them in enclosed box with a 60w globe for a day or 2)

    Also zinc in its gaseous form is toxic make sure you do it in a well ventilated area and wear a mask, while not specific to just zinc fumes see below for some information.

  9. Thankyou, There doesn't seem to be much on the 'net about welding with gal steel, and most of my welding so far has been untreated bar and sheet steel.
  10. Thin gauge galvanised sheeting - you'd be game to try it with manual metal arc!

    Ok, I have a slightly different view.

    Galvanising results in metallographic change for some depth into the steel. On structural steel - there's plenty of thickness and removing the galvanising layer is not an issue. On thin gauge sheet - removing the galvanising has a very good chance of leaving the sheet too thin to support manual metal arc welding.

    If too thin you'll blow holes in the sheet with the arc.

    TIG has a much better chance of success... maybe even brazing???????
  11. Yeah but he did say parent metal was 2mm - 3mm, so thats heaps. Tig on a cleaned up gal? i'm not so sure, brazing should work AND if the gal is OK even soldering with an old fashioned blow torch and anvil soldering iron
  12. Not really, total affected depth is only going to be around 3 micron in most cases - that's 0.003mm. It'd have to be a pretty thin sheet of steel to notice that amount of material missing.
  13. OK "some" is a loose term.

    My experience is with structural steel. The layer of zinc is relatively thick and the process of grinding off the layer tends to contaminate the substrate. Grinding down to clean metal takes some effort and some metal removal. Well in excess of 3 microns.

    I was giving practical information. I challenge anyone to remove 3microns with a grinding wheel...

    On gal sheet where the mass produced galvanising is to a minimum standard, the layer of zinc is probably miniscule and as is the microstructural depth. If I could be arsed looking up the AS I'd share the number.

    Woodsy I missed the 2mm reference. We've done pad weld repairs using LH electrodes on 1 - 2mm remaining carbon steel wall... it's not easy, but we do it - however it takes a gun welder and good control of the variables.

    Mia culpa, I got my welding processes confused, MIG is the preferred process for light gauge sheet.
  14. From memory it's around 10-30 micron (ie bugger all). Not debating that grinding the layer of zinc may be difficult - just pointing out that aside from a thin layer where the zinc and iron intermingles the steel remains largely unchanged. Oh and incidentally I have "ground" (ie polished) a lot less than 3 micron from a sample before ;). Of course grinding isn't necessary anyway - far easier to strip the zinc using acid.
  15. Agree on the steel remaining largely unchanged... "some" depth would suggest that too, but as to the rest of what you wrote - sorry JD, but this is spoken like a true lab person.

  16. Eh :? Using Hydrochloric acid to strip the zinc from galvanised steel prior to welding is common practice, especially with thin zinc coatings. It's certainly not just a "lab" thing (polshing of metallographic specimens is but that's often only done to find the mistakes made by engineers :p).
  17. ...and you can control the application of HCl to remove 30odd microns of zinc? Out in the field? On a windy day? Up on a scaffold?? etc etc etc :roll:

    Are we done now?
  18. Fine, although I don't think the OP mentioned anything about hanging from a scaffold on a windy day :? . For backyard work I'm simply suggesting that a little bit of HCl is going to make life a whole lot easier, and leave you with a lot more metal to work with, than attacking it with an angle grinder.
  19. I just wanted to make a new BBQ hotplate/grill for when I go bush :grin:

    No scaffolds or microns or lab coats but the advice on how to do it is well appreciated - specially the arc rods and stuff to put on to retain stainless qualities.

    Was interested to hear about welding thin gauge as I burn holes in steel I weld - I know it's technique as I hover too much and put too much weld on but the other side of the coin is the weld isn't strong enough if I speed up.
  20. If you have a MIG welder & can get a hold of some silicon bronze wire then this is definately the way to go for welding thin gal sheet. Don't even bother with the TIG unless you like grinding tungstens. Even a tiny bit of gal left behind will make the filler jump straight back on the electrode. Thicker section (2mmm plus) just hit it with some ordinary garden variety GP welding rods (Satincraft etc) with the good old fashioned stick welder.

    SS welding -anything over 3mmm is fine with a stick welder. If you're not sure what grade SS just hit it with some 309 electrodes. Will weld just about anything (even non SS) Below that thickness & TIG is your friend.