problems with MIG-welding stainless
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  1. #1
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    problems with MIG-welding stainless

    Helly guys,

    this is going to be my very first post in this board, happy welding everyone and please be patient with a more or less, yeah rather less experienced/skilled , welder.

    Today I tried MIG welding stainless steel for the first time. I modified my little Iskra MIG 210L welder the last 3 month and I am quite happy with the results on mild steel. The problem is the surface of welded stainless which does look absolutely strange, kind of porous and oxydized.
    Wire material is ER308 (1.4316), base material 1.4301 I guess. Gas was 10L/min of argon 4.6. I installed a teflon/carbon liner previous in the gun.

    Unfortunately I could not change the appearance by changing the gas to argon/CO2 82/18 mixed. I highly doubt this is a general problem of wire feed speed, voltage or tension since I have no problems with steel although I use a 1m longer mig gun.

    stainless on pure argon:




    (Had some problems with the wire feeder here but this does not affect the weld bead surface).

    mild steel in 82/18 (called C18?):


    Quite a difference in my opinion...

    Any help is greatly appreciated..

    Best regards from Germany,
    Phil

  2. #2
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    Re: problems with MIG-welding stainless

    Phil, maybe I can offer you some help with the gas. Unless I've been out to lunch for the past while, I've not heard of anyone recommending stainless MIG welding with either of the gas mixes you're using. Pure Argon would be fine for TIG stainless. I don't know what you'd use 82/18 for -- my guess would be mild steel, a slight variation of 75/25.

    I've successfully used tri-mix gas in the past, a 90 Helium/7.5 Argon /2.5 CO2 mix. I've never heard anyone whose opinion I respected recommend a CO2 content over 5 percent, and most would like to see 2-3 percent. This is to maintain the corrosion resistance of the weld and HAZ.

    There is another website around that recommends a duplex mix, but it's not the one you're using and I have no personal experience with it.
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  3. #3
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    Re: problems with MIG-welding stainless

    Quote Originally Posted by tbone550 View Post
    Phil, maybe I can offer you some help with the gas. Unless I've been out to lunch for the past while, I've not heard of anyone recommending stainless MIG welding with either of the gas mixes you're using. Pure Argon would be fine for TIG stainless. I don't know what you'd use 82/18 for -- my guess would be mild steel, a slight variation of 75/25.

    I've successfully used tri-mix gas in the past, a 90 Helium/7.5 Argon /2.5 CO2 mix. I've never heard anyone whose opinion I respected recommend a CO2 content over 5 percent, and most would like to see 2-3 percent. This is to maintain the corrosion resistance of the weld and HAZ.
    82/18 is the most common gas in Germany for welding mild steel. Next time i will try to get 75/25 i.e. C25 and see what happens. I imagine better burn in and a flatter weld bead while maintaining low spatter. ZTFab uses C25 on his impressive welds so it must be good.

    98/2 argon/CO2 was recommended to me for welding stainless steel. I thought of mixing it by myself with two flow meters but I doubt this, as well as using an expensive tri-mix gas which is out of budget, will change anything.
    The point is that both gases, pure argon (got the bottle cheap and aimed at using it for a future tig-welder) and 82/18, produced horrible results.

    Thanks for your help.

    Best regards,
    Phil

  4. #4
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    Re: problems with MIG-welding stainless

    c25 or pure argon will not work on stainless mig...

    tri mix or ~98Ar/2CO2 will work but don't expect pretty welds with short circuit mig on stainless

    price of welding gases that don't have helium in the mix is usually low
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  5. #5
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    Re: problems with MIG-welding stainless

    Quote Originally Posted by Donoharm View Post
    don't expect pretty welds with short circuit mig on stainless
    Guess you are right. Asked a guys in a fab shop today and was told this is the usual look of a stainless mig weld.

    Although turning down the WFS so every time a blob of wire falls down into the weld puddle you can hear it presumably is not the right way to produce a proper weld I managed to get a decent looking bead:


    What do you say (please ignore the ugly spotwelds)? Settings were about 17,5-18V, pure argon 10l/min / 20cfm, very very low wire feed speed. Has the HAZ become too hot? Any concerns regarding corrosion resistance?

    Best regards,
    Phil

  6. #6
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    Re: problems with MIG-welding stainless

    Yep, that's mig on stainless. Doesn't look nice, but works ok for some aplications. Welds don't have full corrosion resistance and they will rust in salty water.

  7. #7
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    Re: problems with MIG-welding stainless

    Conclusion: buying a tig welder is unevitable for professional stainless welds? Crap.

    Best regards,
    Phil

  8. #8
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    Re: problems with MIG-welding stainless

    There is a study somewhere on the internet that said that once you hit about 5% CO2, the carbon pickup of stainless goes way up. Its the chromium that likes the carbon and you effectively loose the protection of the chromium.

    So you'll see stainless gas mixes that are 2-4% CO2.

    Some people will add O2 instead, but as you can imagine, O2 reacts will the iron and I understand the limit is about 2%.

    The preferred solution (at least in the USA) is various tri-mix formulas which adds helium (which I understand gets more heat into the metal and maybe a more stable arc).

    There was some discussion about using 4% mixtures on thinner stainless and tri-mix on thicker stuff. Most comments (Sundown I believe) leaned toward tri-mix for everything.

    In US, tri-mix has gotten expensive (cost of helium) and the fact that you have to mix 3 different gases (cost of mixing). So, not sure if its worth the cost just to practice.

    Note: If you wire brush the stainless with a carbon steel brush, it will rust as well. Playing with stainless and you want to use dedicated stainless brushes etc. Even drilling hole with a carbon steel drill can cause rust. There are chemical ways to help - search for "passivate stainless." However, I don't think that will help if you weld with 20% CO2.
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  9. #9
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    Re: problems with MIG-welding stainless

    I bought a bottle of TRI-MIX awhile back just to see how it worked for stainless.....
    My mig machine is an old Hobart Beta Mig 200 and it says it can spray weld but
    never got that far........I tig everything.....




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  10. #10
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    Re: problems with MIG-welding stainless

    Quote Originally Posted by con_fuse9 View Post
    However, I don't think that will help if you weld with 20% CO2.
    I don't! I use pure argon and will add ~3% carbon dioxide in the future.

    I am quite familiar with the metallurgical processes happening during mig welding and of course the risks of using gas with too much co2 when welding stainless (chromium carbides are the big problem, as you already mentioned). But this is just theory and I was wondering if I could affect the bead surface with the gas - obviously I can't.

    Only one picture in the "MIG like TIG" thread shows a great stainless mig-weld:
    http://weldingweb.com/showpost.php?p...&postcount=331

    I have no idea how he did that and I don't see any possibility to duplicate this with my machine. Does a pulse function make such a big difference?

    I have dedicated stainless wire brushes for stainless projects.

    B_C, your picture shows a tig weld, right?

    Best regards,
    Phil
    Last edited by RST Driver; 03-07-2013 at 11:12 PM.

  11. #11
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    Re: problems with MIG-welding stainless

    The welds in the post you reference are using spray transfer, not sure if you are running at suitable parameters for spray x-fer on SS. you will want something ~3%CO2 and you will need some decently thick base metal (3/16-1/4) at least to pull the heat out. You should be able to duplicate the weld on the right side of his coupon without too much trouble, yours may be a bit darker
    Experience is something you get right after you need it

  12. #12
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    Re: problems with MIG-welding stainless

    Quote Originally Posted by RST Driver View Post
    I don't! I use pure argon and will add ~3% carbon dioxide in the future.

    I am quite familiar with the metallurgical processes happening during mig welding and of course the risks of using gas with too much co2 when welding stainless (chromium carbides are the big problem, as you already mentioned). But this is just theory and I was wondering if I could affect the bead surface with the gas - obviously I can't.

    Only one picture in the "MIG like TIG" thread shows a great stainless mig-weld:
    http://weldingweb.com/showpost.php?p...&postcount=331

    I have no idea how he did that and I don't see any possibility to duplicate this with my machine. Does a pulse function make such a big difference?

    I have dedicated stainless wire brushes for stainless projects.

    B_C, your picture shows a tig weld, right?

    Best regards,
    Phil
    YES that's TIG........Never could get a great weld with the mig and Wire I had, the Si works better for wetting out from what Im told....



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  13. #13
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    Re: problems with MIG-welding stainless

    Quote Originally Posted by Fred s View Post
    The welds in the post you reference are using spray transfer, not sure if you are running at suitable parameters for spray x-fer on SS. you will want something ~3%CO2 and you will need some decently thick base metal (3/16-1/4) at least to pull the heat out. You should be able to duplicate the weld on the right side of his coupon without too much trouble, yours may be a bit darker
    Spray transfer is impossible with my machine. It was a home use welder for just 450€ brandnew (about 600$). A nice guy gave me some parts of an old German industry welder which I installed in the case.

    before:


    after:


    Although the results are pretty awesome I feel the need of a tig welder for stainless steel and aluminum.

    Best regards,
    Phil

  14. #14
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    Re: problems with MIG-welding stainless

    Doh - pictures are way too big and I can't even click the edit button. Sorry guys.

    Best regards,
    Phil

  15. #15
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    Re: problems with MIG-welding stainless

    Tri mix (90helium7.5argon2.5co2) is the way to go on gas, with 0.035inch 316L solid wire try 21volts and 275inches per min. With solid stainless wire you have to move the wire side to side in the puddle fast to get it to go where you want.

  16. #16
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    Re: problems with MIG-welding stainless

    Quote Originally Posted by RST Driver View Post
    I don't! I use pure argon and will add ~3% carbon dioxide in the future.

    I am quite familiar with the metallurgical processes happening during mig welding and of course the risks of using gas with too much co2 when welding stainless (chromium carbides are the big problem, as you already mentioned). But this is just theory and I was wondering if I could affect the bead surface with the gas - obviously I can't.

    Only one picture in the "MIG like TIG" thread shows a great stainless mig-weld:
    http://weldingweb.com/showpost.php?p...&postcount=331

    I have no idea how he did that and I don't see any possibility to duplicate this with my machine. Does a pulse function make such a big difference?
    That picture you linked to said it was twin pulse. I think Lincoln calls it pulse over pulse. Miller has something that might be the same called allumination. Meaning a high frequence pulsed spray - which gives you spray transfer but more control over the heat (so you can do thinner stuff), the top pulse is a low frequency pulse that puts the cosmetic stacking of dimes on the bead.

    To achieve a similar look, short circuit, you can move the gun in small arcs. Watch Welding Tips and Tricks video. In one, Jody talks about tracing little cursive L's or E's. On the up stroke you watch the top of the puddle, on the down stroke you watch the bottom. With a constant rythm you can a rather uniform looking bead. You might trade a little penetration (you are spreading the heat out) and it makes the resulting bead typically a little wider than normal. But you can run a slightly hotter setting.
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  17. #17
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    Re: problems with MIG-welding stainless

    Quote Originally Posted by colindstark View Post
    Tri mix (90helium7.5argon2.5co2) is the way to go on gas, with 0.035inch 316L solid wire try 21volts and 275inches per min. With solid stainless wire you have to move the wire side to side in the puddle fast to get it to go where you want.
    Try these settings on thin sheet metal and exhaust tubes - one hole, two holes, three holes, even bigger fourth hole...

    Quote Originally Posted by con_fuse9 View Post
    That picture you linked to said it was twin pulse. I think Lincoln calls it pulse over pulse. Miller has something that might be the same called allumination. Meaning a high frequence pulsed spray - which gives you spray transfer but more control over the heat (so you can do thinner stuff), the top pulse is a low frequency pulse that puts the cosmetic stacking of dimes on the bead.

    To achieve a similar look, short circuit, you can move the gun in small arcs. Watch Welding Tips and Tricks video. In one, Jody talks about tracing little cursive L's or E's. On the up stroke you watch the top of the puddle, on the down stroke you watch the bottom. With a constant rythm you can a rather uniform looking bead. You might trade a little penetration (you are spreading the heat out) and it makes the resulting bead typically a little wider than normal. But you can run a slightly hotter setting.
    Ok, that's high-tech I don't have.

    I really like the cursive-e technique on thicker stuff in combination with a slower welding speed to burn in the edges. Haven't tried it on thin metal but I'll give it a shot. The problem is that 1mm (0.04 inches) thick pipes for example of an exhaust system cannot handle much heat, especially when there is a little gap - the results are holes and/or a molten bath that is about to fall through and solidifies inside the pipe so it interferes the gas flow.

    Best regards,
    Phil

  18. #18
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    Re: problems with MIG-welding stainless

    Quote Originally Posted by RST Driver View Post
    Try these settings on thin sheet metal and exhaust tubes - one hole, two holes, three holes, even bigger fourth hole...



    Ok, that's high-tech I don't have.

    I really like the cursive-e technique on thicker stuff in combination with a slower welding speed to burn in the edges. Haven't tried it on thin metal but I'll give it a shot. The problem is that 1mm (0.04 inches) thick pipes for example of an exhaust system cannot handle much heat, especially when there is a little gap - the results are holes and/or a molten bath that is about to fall through and solidifies inside the pipe so it interferes the gas flow.

    Best regards,
    Phil
    My settings are for 1/8th and thicker.

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