Gentlemen. I am not by anyones measure a body man or a weldor. I have removed some simple dents and I can fuse two pieces of metal together by electrical or Oxy/ Ac methods (not good at TIG). Recently there was a thread on shrinking surrounding metal adjacent to a weld seam to accommodate the shrinkage of the weld process ( as I understand the original thread). I assume this was due to the weld process (Mig I assume and the resultant brittle nature of the MIG seam and heat affected zone). When I was about 12 years old my dad introduced me to the concept of hammer welding, mostly I got to hold the torch while he hammer on dollied the weld seam. But Oxy/ Ac welds can be stretched (it is ductile enough) after the metal has cooled also. This is the metallurgical part. Can a MIG weld be annealed to allow hammer on dolly stretching, after the weld seam has cooled? If so what color?... straw... light straw... rose....or is it even possible? Thanks. Mike.
It doesn't need to move much, so you wont need to anneal it. the heat from the welding caused it to shrink. Just use a hammer and dolly to stretch the metal. If your going to be doing alot of metal work, they also make an easy grind MIG wire that does doesn't get as hard (brittle). If you want to watch a video of a pro doing some panel welding the correct way check out this video by Peter Tommasini
Tunafoot. Thank you for the reply. Mr. Tomasini can certainly Ox/AC weld and planish his welds. I think I referenced the ductility of a gas weld in my original post. My question remains: can you anneal a MIG weld. Trying to planish a MIG weld usually results (in my experience) to fractures occurring in the heat affected zone proximal to the bead. Maybe it's just me. Thanks. Mike.
Yes you can, however it's pointless in my opinion. O/A is a much better welding process for sheet metal. People seem to be afraid of the heat, or think it's hard to learn. Too bad......so many doing this the hard way.
After I weld sheet metal with my mig I then anneal the weld with my torch. I turn the torch rich, lots of black smoke, cover the area with the black then turn the torch to lean and heat the surface lightly till the black goes away. you results may vary
There is something I've never understood about the hardness of the MIG welds, Often when TIG welding a panel I'll use MIG wire for filler rod and the resulting weld is easy to planish. So it seems to be more about the type of welding than the wire used. J.
It is for the most part the process. MIG puts heat into a small area quickly and then cools off quickly which results in a harder weld. TIG and O/A both add heat more slowly and heat a slightly larger area so the weld tends to cool at a slower rate and doesn't develop the hardness a MIG weld does. The rapid cooling causing brittle metal is one of the big reasons quenching with water is falling out of favour as a method of heat shrinking because that rapid cooling process makes the metal brittle.
I'm thinking that this thread isn't getting the notice it should because of the title. I would have expected a good number of welding gurus would have chimed in by now with a definitive answer and recommended methods. So, maybe we can keep it bumped up for a bit, but it may need a new thread with a more descriptive title.
I've planished MIG welds before, just takes a bit more work. I usually grind the weld down slightly to reduce the amount of material and to get rid of any slag beads, top and bottom. Then hammer on dolly as normal, watching the panel and weld. Then dress down the weld/metal finish as necessary. It's not as forgiving as a TIG weld can be, but can be done to a degree.
The question has been answered. Good information has been added (K13's post) Hopefully good discussion will follow, with more good information. But more likely we'll get argument. Oh, and most of the guys that really know how are out doing it!..... Me, I get to come home for lunch and a little HAMB!
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