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.