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Thread: Mig Welding Stainless with mild steel wire

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    Mig Welding Stainless with mild steel wire

    To start, I am mostly familiar with stick welding, but I have an old airco mig I picked up for doing real thin stuff. I am not familiar with all the different types of Mig wire available. I belive I have ER70S-6 In the machine now, I bought it from a farmer that was retiring and it came with a roll of wire.

    I have the opportunity to get get some stainless scraps from work if I need to do something small, normally I would use some 309L if I am using stainless for something. I assume there is an equivalent for MIG.

    I'm not using the stainless for any other reason than It's available for no cost. So the million dollar question, Does using a wire that is designed for mild steed have any downside when used on stainless besides the ability for the weld to rust or is there going to be an issue with metal fusion?

    On a side note, is there a special shielding gas that should be used for stainless or is the normal Mig Mix OK for this? Should I be using straight argon?

    Thanks,
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    Re: Mig Welding Stainless with mild steel wire

    First, know that MIG welding stainless exposes you to high levels of toxic fumes: https://weldingweb.com/vbb/threads/7...ght=hexavalent
    Second, using ER70S6 on stainless will sort of work, but stainless is prone to "sugaring" (oxidation on the back of the weld) and stainless reacts more to heat (warping) than mild steel, and in my mind you are making learning harder than it needs to be.

    If you were welding stainless with stainless wire, and looking to make the welds rust resistant, then in that case there is a special gas (its an argon/co2/helium blend).

    My advice is to ditch the stainless unless you specifically plan on welding stainless and need to learn how to do it correctly. In that case get stainless filler wire (308 or 309 wire should work for lots of stainless alloys), the tri-mix gas, and some solar flux for the back sides of the weld.
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    Re: Mig Welding Stainless with mild steel wire

    Typically tri mix is used for short circuit mig( argon ,CO2 and helium. 98-2 can be used for spray transfer ( argon , CO2). If you understand the rusting and realize the metal is somewhat compromised, I see no problem using the 70s6 wire. 308l stick electrodes may be a cost effective solution if you want to avoid rust.

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    Re: Mig Welding Stainless with mild steel wire

    QUOTE=Louie1961;8831312]First, know that MIG welding stainless exposes you to high levels of toxic fumes: https://weldingweb.com/vbb/threads/7...ght=hexavalent
    Second, using ER70S6 on stainless will sort of work, but stainless is prone to "sugaring" (oxidation on the back of the weld) and stainless reacts more to heat (warping) than mild steel, and in my mind you are making learning harder than it needs to be.

    If you were welding stainless with stainless wire, and looking to make the welds rust resistant, then in that case there is a special gas (its an argon/co2/helium blend).

    My advice is to ditch the stainless unless you specifically plan on welding stainless and need to learn how to do it correctly. In that case get stainless filler wire (308 or 309 wire should work for lots of stainless alloys), the tri-mix gas, and some solar flux for the back sides of the weld.


    Yes, definitely wouldn't recommend stainless welding especially with mig, fcaw, or stick. You can get some nasty stuff like Cr+6 (Hexavalent Chromium) and some other nasty stuff. As well as that it may need preheating and shielding gas flow from the back as well. Definitely not beginner friendly or healthy to do with MIG. I'd pick up some cheap flat bar (mild steel/ low carbon steel) to avoid nasty fumes and complicated welds.

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    Re: Mig Welding Stainless with mild steel wire

    Quote Originally Posted by M J D View Post
    308l stick electrodes may be a cost effective solution if you want to avoid rust.
    Unless I grossly misunderstood, he is using the stainless as coupons to learn how to MIG weld. That's why I answered the way I did. I wouldn't try to learn on stainless.
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    Re: Mig Welding Stainless with mild steel wire

    I still think these are the best deal if you are looking for coupons to learn on: https://www.jflf.org/ProductDetails....ductCode=METAL

    A box of 10 "kits" gets you 60 1/8th inch coupons and 20 1/4 inch coupons, already cut and cleaned (cold rolled steel so no mill scale to deal with) for $45.
    Miller Multimatic 255

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    Re: Mig Welding Stainless with mild steel wire

    I am not using the stainless to try and learn Mig. I don't really have much issues welding mild steel with the MIG.

    I just have a convenient access to scrap stainless, so I am wondering if there welding stainless with Mild steel wire is going to cause fusion issues, vs using a wire designed for mild steel. I am not really concerned about rusting.


    Thanks for the replies.
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    Re: Mig Welding Stainless with mild steel wire

    I would agree, this reduces hazardous fumes, rids the need for shielding gas on the back and also allows c25 (a more versatile gas) to weld with. I can see where they're coming from not wanting to spend money on steel practice metal, but I would do it to save your lungs at the very least.

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    Re: Mig Welding Stainless with mild steel wire

    Quote Originally Posted by Roert42 View Post
    I am not using the stainless to try and learn Mig. I don't really have much issues welding mild steel with the MIG.

    I just have a convenient access to scrap stainless, so I am wondering if there welding stainless with Mild steel wire is going to cause fusion issues, vs using a wire designed for mild steel. I am not really concerned about rusting.


    Thanks for the replies.
    I completely understand and relate to having access to free material especially stainless. Why not just get the right filler metal so you can actually utilize this material to some benefit to you or your shop. My understanding is that you are not looking to learn how to mig weld, you're looking to utilize the Free material for projects. In this particular case trying to save money on the proper filler material is really wasteful on all accounts.

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    Re: Mig Welding Stainless with mild steel wire

    Thanks for the input guys. I mainly am using the machine to weld body panels at the moment, and swapping wire regularly seem a bit of a pain. It is what it is, I will probably pick up a small spool of 309L and use that when I am doing something with stainless as it is not expensive for a small roll.


    All that said, what's the downside of using C25 vs Trimix? Are we simply reducing the rust resistant properties of the stainless or reducing the weld quality?
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    Re: Mig Welding Stainless with mild steel wire

    I keep on hand a spool of 308 ss for few times I need to do stainless steel.
    If have gas just try using what see works.
    I had argon for aluminum welding and used that gas.
    If is code or spec work I use the correct gas.

    Dave

    Quote Originally Posted by Roert42 View Post
    To start, I am mostly familiar with stick welding, but I have an old airco mig I picked up for doing real thin stuff. I am not familiar with all the different types of Mig wire available. I belive I have ER70S-6 In the machine now, I bought it from a farmer that was retiring and it came with a roll of wire.

    I have the opportunity to get get some stainless scraps from work if I need to do something small, normally I would use some 309L if I am using stainless for something. I assume there is an equivalent for MIG.

    I'm not using the stainless for any other reason than It's available for no cost. So the million dollar question, Does using a wire that is designed for mild steed have any downside when used on stainless besides the ability for the weld to rust or is there going to be an issue with metal fusion?

    On a side note, is there a special shielding gas that should be used for stainless or is the normal Mig Mix OK for this? Should I be using straight argon?

    Thanks,

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    Re: Mig Welding Stainless with mild steel wire

    Quote Originally Posted by Roert42 View Post
    I am not using the stainless to try and learn Mig. I don't really have much issues welding mild steel with the MIG.

    I just have a convenient access to scrap stainless, so I am wondering if there welding stainless with Mild steel wire is going to cause fusion issues, vs using a wire designed for mild steel. I am not really concerned about rusting.


    Thanks for the replies.
    I welded stainless with steel wire, and it keeps perfectly ok for 18 years now, and it didn't even rust.
    BUT it is permanently indoors without humidity or water, galvanic corrosion is important when you have stainless metal and a steel bead.
    The weldment doesn't take any form of stress, it just sits there.
    The drawback? it looks bad.

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    Re: Mig Welding Stainless with mild steel wire

    Quote Originally Posted by Roert42 View Post
    Thanks for the input guys. I mainly am using the machine to weld body panels at the moment, and swapping wire regularly seem a bit of a pain. It is what it is, I will probably pick up a small spool of 309L and use that when I am doing something with stainless as it is not expensive for a small roll.


    All that said, what's the downside of using C25 vs Trimix? Are we simply reducing the rust resistant properties of the stainless or reducing the weld quality?
    C25 vs Trimix:
    1. Corrosion is the main thing.
    2. Next, if the wire's carbon combines with chromium it forms carbides that can make the bead brittle, but for simple stuff it's no problem. See my previous post.
    3. Good appearance is another one.


    Pure argon will make things worse than C25 IMO, the gas is for the wire, not the metal, and all steel wires need some oxygen.

    As for fumes, most fumes come from the wire, not the metal.
    If you weld with stainless wire on mild steel, you breathe lots of Cr6.
    If you weld with mild steel wire on stainless steel, you don't breathe lots of Cr6.

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    Re: Mig Welding Stainless with mild steel wire

    Tri-Mix has helium which seems to help with wetting out when short circuit welding. Best for sheet metal, and thin forms. It will look flatter, and shinier , and run amps a little lower than C25.

    Argon seemed the worst to me, someone forgot to change the bottle once, it was the worst of the three. My SnapOn MIG manual mentions 98/2 ArO2 but I have never used it.

    I haven't had too many problems with cracking when substituting some stainless for plain steel in a pinch, but none were structural , mostly covers, guards, and braces.


    FYI : The last bottle of tri-mix the company bought was about $85 for a 125cf from Praxair (not the cheapest).

    With steel prices up right now , I've been digging deeper into the scrap pile lately. Even making things out of stainless that really didn't need to be, but I just had the material on hand in stainless. Plus, if its been in the pile over a year, its time for it to move.

    Whichever wire or gas you choose, don't go cheap on your respirator, and make sure you have good ventilation also ( even to the detriment of the shielding gas ). Allowable exposure to Cr (IV) is supposed to be limited to micrograms per cubic Meter of air (very low even occasionally)

    I guess you can decide on the pro's , and con's and if its really worth using stainless with what you have, and want to achieve.

    Best Regards
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    Re: Mig Welding Stainless with mild steel wire

    Point of pointless order: Hexa denotes 6. 6 in Roman numerals is VI not IV which is 4.
    ---Meltedmetal

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    Re: Mig Welding Stainless with mild steel wire

    OOps ,

    even worse there is such a thing, although that's not what I meant.

    Chromium(IV) oxide
    Chemical compound
    Chromium dioxide or chromium(IV) oxide is an inorganic compound with the formula CrO₂. It is a black synthetic magnetic solid. It once was widely used in magnetic tape emulsion.
    With the increasing popularity of CDs and DVDs, the use of chromium(IV) oxide has declined. -- Wikipedia
    Formula: CrO2

    I stand corrected.

    Thanks, couldn't edit
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