Thread: Brazing aluminium to steel.

I have alloy brazing rods that work pretty well on aluminium. I need to join some 32mm alloy tube to a steel flange and saw a suggestion about using silver brazing rod on the steel, then using the alloy rod to join the two but it didn't work for me. Any suggestions for a way to do this?

In domestic refrigeration the evaporator is aluminium while the the remainder of piping is steel. I always thought it was bonded by aluminium coating to steel and then heat treatment to fuse both together. But I stand to be corrected.

Found this on Google for you. Can I Weld Aluminum to Steel?
Hopefully it's not a structural join?
Kryn

Some of the current crop of aluminium "welding rods" (which they are not), say that they work on some non-ferrous materials like copper or brass. So with a little experimenting, you could silver solder some brass or copper shim to the steel as an intermediate layer and the braze the aluminium to the shim. Try your brazing rod on brass and copper first to see if the advertising is even close to right.
I would have been surprised if it worked on silver solder.... Actually, it may depend on the silver solder! If you used 'plumbers' silver solder (1.5% silver - the rest zinc alloys), rather than tool makers' silver solder (45% silver or more), it might just work....
If you find a solution, PLEASE post it here!

Watching this one, may want to post it in the "welding" section

Originally Posted by SurfinNev

I need to join some 32mm alloy tube to a steel flange and saw a suggestion about using silver brazing rod on the steel, then using the alloy rod to join the two but it didn't work for me. Any suggestions for a way to do this?

The easiest way would be to make up a sleeve to go over (or inside) the Al tube from steel and weld that onto the steel flange, bolting the Al tube to the steel.

Originally Posted by eskimo

I always thought it was bonded by aluminium coating to steel and then heat treatment to fuse both together. But I stand to be corrected.

Yes - usually a mechanical bond of some sort that then allows a joint in 'similar' metals. Cabac friction weld Al and Cu together for example

Michael

Some info on steel/Al bonding here
https://metalworkforums.com/f65/t204...nded-al-ms-bar

Put it in the too hard basket for now and used some steel tube I had lying around. Still interested to find a way to bond alloy to steel though.

Originally Posted by SurfinNev

Put it in the too hard basket for now and used some steel tube I had lying around. Still interested to find a way to bond alloy to steel though.

its fairly simple mate. I think you lay the steel and aluminum together. in a vacuume chamber ok .. with careful placement of explosives on either piece. cause an implosion power-fill enough to bond both metals together. dead simple mate. dont worry about all that fancy stuff.
I think thats how thaey do it.

What diameters are you wanting to join...can get some largish mechanical stuff such as flare nuts etc?

Had to make two handles for a roller that will be used for stretch wrap. Two cup shaped flanges 50mm diameter brazed to two 25mm x100mm round tube.