Joining Method Brazing

Image provided by Ferris State University

Brazing is a joining process that produces coalescence of metals by heating the components to a suitable temperature and then using a filler metal whose melting point is below that of the parent metal. The filler metal is thus distributed by capillary attraction between closely fitted joint surfaces.

In brazing, one tube end must be expanded using a swedging tool to form a socket, which allows another tube to be inserted. A torch is used which blends oxygen and a fuel gas together and burns them at the tip of the torch. The socket and the inserted tube to be joined are heated to the brazing temperature with the torch, and the filler metal is fed into the gap between the socket and the tube. A properly brazed joint is stronger than the pipe or tube being joined.

It is easier to join copper and copper alloys to one another by brazing than it is by welding. In addition, it is easier to join copper and its alloys to steel by brazing than it is by welding. A brazed joint is similar to a soldered joint. In brazing, a tube is inserted into a closely fitted socket and held together by filler metal which flows into the space between the tube and socket.

The significant differences between soldered and brazed joints are melting temperature and strength. Brazing materials melt at temperatures above 840°F, while soldering filler metals melt below 840°F. Braze metal is much stronger than solder. Because of its strength, the tube that is inserted into the socket does not have to be as deep when the joint is brazed as it does when it is soldered.

The parts to be brazed must be freshly cleaned. Flux is almost always used, except that copper-to-copper joints may be made without flux when the correct filler metal is used.

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