I now have about 10 hours of actual torch time and I can weld butt joints, lap joints and corner joints well enough that they will probably hold fluid. They certainly aren’t pretty though.
There are a few keys to welding aluminum that I don’t want to forget:
- Clean, clean, clean. Use a stainless steel wire brush and brush in and out towards the edge this clears the oxide layer from the side and the end. Leaving the oxide layer on the end destroys any chance of getting decent penetration.
- Fit. You can get away with some pretty lousy fit-up when gas welding steel. Aluminum is not forgiving at all. The best I have been able to do is to weld through a 1/16″ gap without blowing gaping holes. I have welded through twice that on 1/16″ mild steel.
- Tack hot, weld cool. Tacks need to be made fast and hot. Use a very hard flame and get them set. The finish weld needs to be made with a very soft flame and it takes a long time. The alternative is to blow big holes that cannot be easily repaired.
- Tack from the middle. Aluminum moves a lot when welding. Set the first tacks in the middle of the span and work your way out. Otherwise the span will probably buckle.
- Stay away from corner joints. They are ugly, at least I can’t seem to get then to stay uniform. Butt welds are much simpler. To weld a corner, use a brake to put a bend in the sheet (or both sheets) and turn the corner into a butt joint. This has the added advantage of adding stiffness to the panel while welding.
Oh, yeah… don’t practice a lot on Friday without checking your gas first, it ruins the weekend…