My first attempt at OA welding aluminum

I have gone over the information in this link:

========================================================= A good example of how aluminum reacts when heated can be seen if you place a small piece of sheet aluminum on a welding table and heat it with a neutral flame. Hold the flame perpendicular to the surface of the sheet and bring the tip of the inner cone almost in contact with the metal. Observe that almost without warning the metal suddenly melts and runs away, leav- ing a hole in the sheet. Now repeat the operation with the torch held at an angle of about 30 degrees to the plane of the surface. With a little practice, you will be able to melt the surface metal without forming a hole. Now try moving the flame slowly along the surface of the sheet, melting a small puddle. Observe how quickly the puddle solidifies when the flame is removed. Continue this practice until you are able to control the melting. When you have mastered this, proceed by practicing actual welding. =========================================================

Should this exercise be done without applying flux?

Adjust the flame to Neutral, you don't want a carburizing flame on aluminum. The reason for the troubles you had are the excess carbon from the flame.

maybe this will be some help.

I went to the osh kosh air show thing once and they had some guy doing flame aluminum welding trying to sell some equipment. It was fast and I recall he said you clean up after not before like in tig. He had an aerosol can of magnesium cleaner for mag wheels to clean up with.

I went home and attempted to do the same. Initially I bought some flux It is probably somewhere. Later I came across a bunch of coated electrodes for stick welding and now if I do any aluminum welding that is what I use. It takes a while to get going and then it goes real fast I suppose if you aren't holding the flame in the right direction it won't go fast in the right direction. The fumes are awful. If you have ever seen these salesmen for low temp rods that poke holes in beer cans and fix them with a propane torch that stuff you kind of have to scrape the rod into the metal to get it going that might help. I have a box of some eutectic product I think is very similar but it is hard to have real confidence in it. Maybe if I used flux I would have more confidence. Since I have tig capability I rarely use flame however one repair I did makes me think the weld is more flexible for repeated flexing than tig and 4043.

Fran

I've not done gas welding of aluminium in awhile but I always recall the flux was so deliquescent that you could just leave it for a short while, 30 minutes or so in the UK, and it would absorb enough water from the atmosphere to dissolve itself and a rinse afterwards to be safe.

Must try it again over the weekend as I have all the stuff still. One thing I never seemed to have an issue with was seeing the weld, I recall the flux went water clear when upto temperature and I never had problems with glare from the flux when using normal goggles.

Regarding aluminium brazing, I think 4047 alloy is suitable for this when a higher melting point parent metal is used. The 4047 alloy being a eutectic composition, or near, and melting significantly below many common aluminium alloys that you might want to join.