How is Brazing Done?

Brazing, as people dealing with metals would know, is a process of joining metals (and non metals too.) There are different techniques for joining metals through brazing which are known as brazing processes but there is a common basic working principle for all these processes.

Basic Brazing Process

For brazing, a Braze Filler Metal (BFM) is used. Most brazing filler metals are alloys, or combinations of pure elements or materials. The filler metal must have a melting temperature above 840°F (450°C) but below the melting point of the base metals or the metals that need to be joined.

In brazing process, the base metals are heated, generally to a point that is slightly above the liquidus (liquidus is the temperature above which an alloy is completely molten. When an alloy exceeds the liquidus temperature, there are no solid phases present.) of the filler metal, causing it to melt. As a result, the filler metal flows into the parallel joint clearance between the two base materials by capillary attraction and bonds to their surfaces through atomic attraction and diffusion.

Thus, the basic principle through which brazing works is by joining the base metals by creating a metallurgical bond between the filler metal and the surfaces of the two metals being joined. However, there are certain differences in this basic technique of joining metals when we refer to different types of brazing processes.

Brazing Procedure

For an effective brazing, some conditions have to necessarily fulfilled. If not then problems associated with brazing occurs. Thus, the following conditions should be there:

• Good fit and proper clearance
• Clean base metals
• Proper fixturing
• Proper fluxing and atmosphere
• Heating the assembly
• Cleaning the brazed assembly

All these can be attained by following proper brazing procedure. To get step by step instructions about how to do brazing, read Basic Brazing Procedures