It’s been years since I was hands on but MIG welds are different from TIG or a gas weld in that the weld is harder than the metal being welded. This means the weld is difficult to work often cracking, TIG or gas welding is what works.
I've seen people (with a name) who'll MIG weld things like part of a chop and then come back with a torch, get it red hot and proceed to hammer it out. I guess it worked but I'd argue why do 2 processes & introduce more heat into the panel than necessary. Fit up is priority #1 and then just TIG or Gas Weld the joint followed by the required hammer & dolly work to finish out the seam. Hope that kinda answers your question.
I have tried it yet but plan to the next time I have a project that requires this type of work. It’s Esabs EZ grind mig wire. It’s softer and as the mane implys it grinds easier. I’m assuming it would also hammer and dolly better but haven’t tried it. Will be following
Post results when you do please. Thanks for replies. It was just something I was thinking over as I recover.... Did a search and found a similar thread I posted years ago. I think I’ll start practising my gas welding again...!
Disclaimer: I’m no where near a professional, nor did I sleep in a HolidayInn express recently. But, I have done many patch panels with my MIG. Crap ton of spot welds , jumping around. Waiting for the spots to cool to the touch before putting another next to it. Takes a long time. Once I’m done, angle grinder with the rubber pad thing and sanding disc. Slow and even and flush the spots to the metal. Verify no holes, or spot again. Should have little “weld bumps” on the back side of the seams. Once all airtight and sanded, I’ve never had an issue with some hammer and dolly work. I hit “off dolley” and not direct. But never even thought of annealing it, I thought that was for non-ferrous metals. Been fortunate to not have to use much filler this way.
When my old friend Stan chopped my 3W he had a welder come to the shop, actually the backyard garage, to mig the top back on. The welder used the ESAB easy weld .023" and as he welded Stan would cool the weld with an air hose. When it was cool he hammered the weld on and off dolly. The finished top required very little filler, no more than a thin skim coat.. Both Stan and his welder friend were experts and the results showed. RIP Stan Beringhele
@Fortunateson, are you thinking about softening the weld then planishing, ie without removing the excess material of the weld? I think you'll find if you do that once the weld is hammered flat there will be a ton of distortion as the excess material has to go somewhere. If you're thinking that annealing a ground flat weld might make planishing possible / easier / better I'd guess you could be right, or maybe not? Chris
If you can get to both sides and have a willing friend with a mid level of skill, you can finish and "stretch" the weld as you go. 2 spots, gentle hammer n dolly while still red. You don't blast it into the next door neighbor's garage, just tap hard enough so the ball of weld resembles the head of a nail. You only have to tap it 3-5 times if that. And if you can do that with EZ-Grind all the better, yes it's softer. Done right and well you can do a zero mud metal finished seam. It sucks a little, it ain't easy, but it ain't hard once you get your mojo on. I hope you can "see it" just how I spelled it out. Why do it? While it's red and cooling you're stretching the weld vs how it will contract and warp the panel. Lemme know if this all makes sense.
Have you...say looked through the ...INTERNET..? HOURS of reading...already in print. Without having to rewrite it all ! Mike
Trying to anneal a mig weld is like trying to anneal a piece of gravel. Hard and unflinching. Seriously suggest you either tig weld or gas weld if you want to anneal your welds.
I am not an expert but I recall reading the carbon in C25 welding gas is added to the MIG weld and that additional carbon is one factor in making it harder. As was mentioned, the additional heat will likely cause additional distortion. If you just weld it gradually as is mentioned, you will have minimal distortion, most of which can be planished out. If you truly want to metal finish it, and it's a lot of work, learn to TIG.
All interesting replies so thanks! When I mig I do the tacks about 3” or so apart, take a cutoff wheel and grind down what’s proud, and then do the whole process over again. I may buy some easy grind wire if I can find some... When I Metal finish it I use a hammer and ONLY tap (they should be called body tapperss not hammers!). Like I said as I recover I’ve been doing some thinking and this popped into my head. And I guess it’s time to try to improve my gas welding...I’ll be using a Dillon/Henrob/Cobra to have with its tiny focused flame. Maybe that will help me from creating “ventilation holes”! LOL EXIT: I forgot to say that while the tacos are still hot/warm I try to tap them flat...
I only do mig right now, argon is way too expensive for how much I would use a tig at home. But I try to leave a cutoff wheel size gap for mig instead of butting the filler piece tight. Then I do 2 or 3 tacks then hammer and dolly right away while they’re still warm. It does take a while, but then it’s also minimal grinding and there is still some room for the weld to stretch within the gap.
I believe that without planishing, the shrinkage from the weld cooling will distort the parent metal even more than with planishing.
I have been unable to find the easy grind wire for some time. Saw reference to it a few times, and asked at a couple of local weld supply places. They all had never heard of the product.
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