I have finally had the time to try welding two pieces of aluminum using my OA setup. The pieces were 100x70x6 mm and I tried to butt weld these pieces.
I had ordered the oerlikon F14 (F LH-1) powdered flux, which I mixed with rain water so that I had a white cream. I used a stainless steel wire brush to clean the edges of the aluminum pieces. I then applied the flux to the weld area. Then I started the flame using a number 3 tip and adjusted a carburizing flame. But when I started to heat the weld area, the area quickly got covered with a black coating (carbon?) When I applied the aluminum rod (covered with flux as well), it melted, but it ended up being a ball of melted aluminum and didn't adhere to the base metal. It just kept rolling around the base metal. The base metal also melted at the joint, but not so much.
Now, one thing I am confused about is whether I was doing aluminum welding or aluminum brazing. Either one would work for me, but I think brazing would be easier. Do the plain aluminum rods and the above flux work for brazing? Should I have adjusted a neutral flame instead? Maybe my heat was too much and I just burned the flux.
Any help about what could be wrong appreciated...