brazing aluminum

[henkie]

got some aluminum brazing rods.use acetylene torches around the 5 lb setting but I"m unable to fuse two pieces of aluminum together.The aluminum just melts away and the brazing rod material just lay"s on top of it. What am I doing wrong?

 

[Anonymous-0]

brazing aluminum is very hard to do but it can be done. Its like tig welding aluminum. Are you cleaning the metal before braze? Second Its been a while but i thought you needed a diifernt gas to weld aluminum some types. You can use silver bright on aluminum silver bearing metal solder. and a regular torch. I dont know what your trying to do as far as welding. But i Know is hit the aluminum with a scotty really good get all the crap off and get a good flux like stay clean. If the aluminum is really old your out of luck aluminum is like wood if left on concrete it becomes really hard warps and just cracks not matter what. Metallurgy aluminum is a paint in the but. You may want to try and anneal it just take the rose buz lay a sooty flame over it and burn it off normally more soot you lay down the more it will be easy to work with you have about 12 hours to work with it and then it will go bac to being harder then it was. I doo it all the time before putting project in the english wheel or power hammer makes it easier to work with. any questions (860)805-2200 Jon

 

[MarkB_MI]

I've never used the brazing rods, but they should melt well before the aluminum does. Are you sure your base metal is aluminum?

I've played around a bit with gas welding aluminum. There are a lot of things that make it tricky: There's very little color change, so it's hard to know the temperature. Aluminum has a low specific heat and is very conductive, so once it starts to fuse you have to move very fast or it will let go. The last thing is that aluminum forms an oxide layer than doesn't conduct heat, so it's important to get it clean before you start and to use an appropriate flux.

 

[Earl - IL]

Heat the metal & not the rod & let the rod melt to it.

 

[GeneMO]

I bought some aluminum brazing rods that came with a special flux. I had a crack in an aluminum Jon boat. I cleaned it good, scuffed it with steel wool, and even "V'd" it just a tad bit. I had to be real careful not to melt through, but like someone said, heat the metal, not the rod, then basically melt the piece of rod into the crack.

It worked for me, and it was my first attempt at welding aluminum. I used a regular torch, but mine is set up with propane for gas, instead of acytelene.

Good luck, Gene

 

[Gearhead210]

First off, avoid annealing the aluminum how Jon Mc explains- that will only add impurities to the aluminum, and it will also "over age" the aluminum. Aging aluminum is somewhat of an equivelant to hardening steel by quenching a red hot piece- but the difference is that alum. has to be brought back up to a raised temperature (nowhere near melting point), and be held there for a time for it to actually gain its strength- and the earlier post would do just this, and make the aluminum quite brittle.


As far as the welding goes, the cleaner the better: If its clean enough for surgery its almost clean enough to weld. With gas welding, since you have no shielding gas like in TIG, it is easy to "drive" impurities into the material or start the corrosion layer.
Your rod likely has a lower melting temp than the base metal, so heat the base metal until you barely see a small molten pool to form- things will happen fast now.
Add your filler metal (rod) to the molten pool in "drops" to make the weld bead, and move along the part.

I recommend practicing a time or two on some scrap metal to be certain not to destroy the parts you are trying to save