Monday, April 28, 2014

Preheating Welds

I’m assembling a 6’ tall coconut palm sculpture and the assembly is done with MIG welding but I’m trying to make those joints nearly invisible.

When I first started welding, I bought a MIG welding setup and started welding.  I didn’t own a torch and never had any lessons.  I turned out some pretty ugly welds but I got a shop going.  It was some time before I caught on to the advantages of preheating welds.

Today I seem to divide my MIG welding into two general categories - welding which is part of a product and welding which part of a jig or other shop fixture.  In the products I do preheat because the weld metal flows so smoothly and blends with the base metal to hide the weld.  In the jigs I usually don’t preheat.  The welds don’t have to look good and they are easier to cut apart when disassembling the jig.

I keep a small cutting tip on my torch setup most of the time.  When I’m assembling sculptural elements (usually no thicker than 1/4”) I use the torch with a neutral flame to preheat to just about a welding heat then put in the MIG bead.  If the weld needs a little more dressing I turn the torch to a reducing flame and melt the bead and let it flow more.  It takes practice to not overdo it.

There is a lot more to good welding technique which I don’t know and don’t need in the type of work I do.



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