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Machinable MIG Welds

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Machinable MIG Welds

Postby KenK » Sun Oct 01, 2017 10:19 am

I have question for you guys. From time to time, I need to make repairs to some item where I would need to re-drill or machine the part after welding. I have notice that welds made using the MIG process are very hard. You can grind them but re-drilling or re-machining the part is pretty much impossible. Generally when I need to do this I TIG weld the part and the weld is much softer. There are time when I do not have the ability to TIG weld the item.

Question, is there a way to MIG weld a part and get a soft weld?? I am using C25 gas with the MIG machine. Would straight Argo work??
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Re: Machinable MIG Welds

Postby MinnesotaDave » Sun Oct 01, 2017 12:30 pm

I'm puzzled by your experience. I've re-drilled many items after mig, stick, or tig welding.

Mig and tig wire are generally both 70s-2 or 70s-6. So are both 70,000 psi filler.
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Re: Machinable MIG Welds

Postby noddybrian » Mon Oct 02, 2017 3:34 am

As mentioned it's not likely the filler material itself - more likely the part you are building up has sufficient carbon content that the weld is picking some up by dilution & the mig welds cool quickly enough in a small area by the mass of the part to at least partially harden it - if the size of the part allows normalizing will correct this or pre-heat the part so the weld does not chill off quickly enough to cause it in the first place.
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Re: Machinable MIG Welds

Postby KenK » Mon Oct 02, 2017 12:39 pm

Generally the part involved is relatively small but they could be part of a much larger item. I was thinking that the welded area was picking up the carbon from the gas(C25). I have not tried to anneal the part, nor a have I tried to preheating the part. Most of the material I have worked with was cooled roll steel which I would not think would be a hardenable steel.

Often the work involves repairing worn out holes where the idea is to fill the hole and re-drill it.

Thanks for you inputs

Ken
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Re: Machinable MIG Welds

Postby DonaldE » Wed Oct 04, 2017 2:31 am

Gas and TiG welding heat the panel slowly, then it takes a lot longer to cool it down, This is an annealing process. But MIG heats up the metal quickly and cools a lot faster, which I think is a hardening process.

Now there are few wires like ESAB Easy Grind that helps make a softer weld, by changing the alloy, but it's still not as soft of a weld which you get gas or TIG welding process.
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Re: Machinable MIG Welds

Postby KenK » Wed Oct 04, 2017 1:07 pm

Thanks for the input

Ken
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