Aluminum brazing?

[Bonnewagon]

I have several rare aluminum pieces that I would like to save. I saw a video on brazing that looks interesting. But when researching the brazing rods, I see very few dedicated to aluminum repair using a torch. Some vendors claim that their aluminum TIG rods are usable for brazing. Is that a fact? I will probably stick to dedicated rods like the HTS-2000 brand. Anyone have experience with this?

 

[axisg]

It's a delicate touch. I watched a good friends dad at his welding shop for years. If it's cast metal it's a pia as it's so pourus. Alum cast and alum rod are near the same melting point. He tried to teach me welding fittings to a scrap forklift tank. His side was nice. I kept blowing thru with the torch. Tig was easier to control the flow and the heat.

 

[Bonnewagon]

I thought the aluminum brazing rods melted at several hundred degrees less than most aluminum alloys? The videos I watched they used a MAPP torch or propane, not oxi-acetylene. MAPP burns hotter than propane, but not as hot as acetylene. They showed how you heat the base metal enough so the rod melts when touched to it.

 

[axisg]

yes, if you are skilled it should flow just like joining copper plumbing fittings. Although not great I was shown many years ago how to braze using brass / copper rod and flux ( really they were clothes hangers ) to repair steel joints ( repairing bike frames, exhaust work, ect... ). Len would always use either using oxy / acet or oxy / propane. He could tell by looking at the metal and poking it with the rod if it was hot enough to braze. When working with aluminum he said I kept blowing thru by making the base metal too hot. Then to show off he would heat it up, and add filler bit by bit to close up the hole I would blow thru. Whereas when I got the base metal to where I thought it was hot enough I would add the rod it watch it all fall into itself. Brazing is really becoming a lost art. Although retired now I bring him all the brass, stainless and copper store fixtures we get to repair as nobody else can seem to do it. If they cant mig it then they don't want seem to want to do it !

Either way, grab some scrap aluminum and give it a shot. I have a little 2lb bottle of MAP / Oxy here for heating up stubborn bolts maybe I should try again myself.

 

[Bonnewagon]

Great- thank's for that info. I'm no stranger to brazing. I've done stainless steel to chromed steel on a motorcycle fork with nickel/silver rods. I even fixed a big cast iron skillet with bronze rods. It's aluminum, that confounds me. I once tried to fix a bicycle brake caliper and it got too hot and just collapsed! It's very unforgiving stuff.