I'm picking up from the this alum.repair idea posted, few years back. Got an idea, possibly helping with the heat range needed, near 1200 deg. to weld alum. cast properly. In the video their using a bbq grill to heat up part, near 500 deg along with a torch, yet reading the replies, the oven is near that temp but not the part, which would be something less. I'm thinking, what about building a hot wood fire, with a rack above it and setting a metal plate on the rack a little larger than the part to be welded to set part on which would direct the flames around the part indirectly. Then cover with a dome of some kind containing heat inside with a temp gauge on the part or on the metal plate and when the temp reaches the desired melting point for alum welding rod to take (you might not even need the torch) then hopefully it would run deep into the part body and not just sit outside/around the break making for a stronger hold? Maybe trial and error on scrap pcs first. I'll try it as soon as I can find some cast alum. and reply back or possibly one of you, have already tried and give your thoughts on heating part hot enough for a good weld. My only concern might be distortion to the part because of the extreme heat, yet using the torch gets that hot, too!
I know that there is an aluminum type welding rod that is claimed that you can weld and repair with a propane or mapp gas torch. I've never tried it so I can't truthfully comment on how well it works. But one property of aluminum that makes it, as some welders say "difficult", is that it gives little to no clue as to when it's at the proper temperature to be welded. One minute you may be heating up a crack and the next, you are looking at a silver dollar sized hole where the crack used to be and wondering what the £?@× just happened? And as with welding any metal, oxygen contamination is a real issue. For this reason, I prefer TIG welding aluminum because of the shielding gas. And although I have personal preference to the Miller & a few Lincoln welding machines, I cannot stress enough to stay far away from the Harbor Freight crap welding machines.
Fortunately i don't need a weld, yet in the past I could have used one, so for now I'll just practice doing a weld, then try beating it to death to see how well it holds. Still looking for scrap alum cast to try. I've got some old alum rods, yet I don't know what kind and if they have the flux coating.
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