# aluminum to copper brazing



## r2d2 (Sep 30, 2006)

I found a leak in the condensors aluminum tubing which was right next to the copper lines, so I cut out the piece and got a 3/8 coupling thinking that I can fix the problem, I was able to soft solder the coupling to the copper liquid line but now my problem is brazing the coupling to the condensors aluminum line. I just graduated from hvac school and I learned brazing but would brazing be to hot to melt the aluminum? and what kind of brazing rods would I use if I did braze? what would be the correct way to fix this problem? thanks


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## KillerToiletSpider (May 27, 2007)

You can't braze aluminum.


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## MechAcc (Feb 27, 2005)

Sounds like you are working on a Trane unit. They have a special coupler for repairing aluminum to copper leaks. Call your Trane distributor.


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## mdshunk (Mar 13, 2005)

Got enough room to get a flaring tool on the aluminum line? That's one method I've used when put in a position to fix a copper-to-aluminum leak with stuff that was on the truck already. Do it with flare fittings.


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## mickeyco (May 13, 2006)

I'm sure you can braze aluminum but you'd really have to heat it up, and I don't know about brazing it to copper. I like MD's flaring idea, that seems like a good way to go, if you can or the special coupler mentioned.


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## Railman (Jan 19, 2008)

Braze is brass, & doesn't do aluminum, unless maybe you can get the aluminum copper coated. Thats how they chrome aluminum. The first copper coat, & then chrome. It's a very specialized process to get it done.
Joe


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## mickeyco (May 13, 2006)

Railman said:


> Braze is brass, & doesn't do aluminum, unless maybe you can get the aluminum copper coated. Thats how they chrome aluminum. The first copper coat, & then chrome. It's a very specialized process to get it done.
> Joe


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> Brazing is a joining process whereby a filler metal or alloy is heated to melting temperature above 450°C (842°F), or, by the traditional definition that has been used in the United States, above 800°F (425°C) and distributed between two or more close-fitting parts by capillary action. At its liquid temperature, the molten filler metal and flux interacts with a thin layer of the base metal, cooling to form a strong, sealed joint. By definition the melting temperature of the braze alloy is lower (sometimes substantially) than the melting temperature of the materials being joined. The brazed joint becomes a sandwich of different layers, each metallurgically linked to the adjacent layers. Common brazements are about 1/3 as strong as the parent materials due either to the inherent lower yield strength of the braze alloy or to the low fracture toughness of intermetallic components. To create high-strength brazes, a brazement can be annealed to homogenize the grain structure and composition (by diffusion) with that of the parent material .
> 
> A variety of alloys of metals, including silver, tin, zinc, copper and others are used as filler for brazing processes. There are specific brazing alloys and fluxes recommended, depending on which metals are to be joined.* Metals such as aluminum can be brazed*, although aluminum requires more skill and special fluxes. It conducts heat much better than steel and is more prone to oxidation. Some metals, such as titanium, cannot be brazed because they are insoluble with other metals, or have an oxide layer that forms too quickly at high temperatures











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## BigJon3475 (Oct 15, 2007)

Flare fitting or follow mechacc idea......All my aluminum coils are flare fitted to the coper line set.


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