Brazing is joining two metals together with a molten filler metal. As a result, the filler metal will have a lower melting point than the two joined metals.
What is the difference between welding and brazing?
Brazing includes an additional element of the braze alloy (the joining metal), while welding comprises only the two ‘parent metals’.
What is the process of brazing?
Brazing can be done in many different ways. Two main styles are localized heating, where just the common area is heated, and diffuse heating, where the entire object is heated.
During the brazing process, the joining metal is melted and filled into the joint of the two parent metals by capillary action – that is, the ability for liquids to flow in narrow spaces without the help of gravity. In addition, the lux protects the liquid. The liquid metal is then cooled to join the pieces together.
What is flux?
Unless the brazing process is done in a contained environment, such as a furnace, the braze alloy must be protected by a flux. Flux is a material that keeps the metal from oxidizing during its liquid stage. Instead, the flux flows into the joint during the joining stage and is usually made of a material that prevents oxides from forming, such as borax.
What is the filler material made of?
The alloy used for filler can be a variety of metals.
- Aluminum-silicon
- Copper
- Copper-silver
- Copper-zinc
- Copper-tin
- Gold-silver
- Nickel alloy
- silver
Localized Heating Techniques
Torch Brazing
The brazing is done by a torch fueled with acetylene, hydrogen, or propane, combined with oxygen to melt the filler metal and join the two pieces.
Induction Brazing
This brazing technique uses a coil that sends heat into the metal using a rapidly alternating electrical current.
Diffuse Heating Techniques
Furnace Brazing
The brazing is done inside a furnace, allowing the ability to control the heat at every stage.
Dip Brazing
The entire assembly is dipped into a melted braze alloy. The temperature should be hot enough to melt the braze alloy but not hot enough to melt the parent metal.
