Recently we had a project that wanted us to build frames out of 1x1
1/8th inch wall aluminum box tube. The catch was that there are panels that fit into these frames, like glass into a mullioned window, so we were trying not to weld the inside fillet welds in the corners, instead, the only welds were to be on the surface and back. For paint and finish, the welds on the front were to be ground/sanded flush. Using a Miller 210 Pulse Mig welder, I could not find settings that gave decent penetration at the first part of the weld without blowing away the metal at the end. Even starting near the middle of the tube and backing up then running the whole inch left me with a big underpenetrated lump where the weld started. If I slowed down enough to get some penetration, I had a huge divot on the far end. In most cases when we ground the test welds flat, they were not tough enough to stand up to the handling and abuse between now and installation.We finally switched to steel.
I really don't like grinding welds because I feel it seriously reduces the strength of the weld. I thought about trying TIG, since filler metal can be added without adding heat and vice versa, but I haven't yet taught myself well enough.
Should I have been able to do this with MIG? What should I try next time?
Thanks guys!
Stuart