Brazing is a method of joining two pieces of metal (but also to ceramics) in which a non-ferrous alloy (the braze alloy) is introduced in a liquid state between the pieces of metal to joining allowed to solidify. It is an alternative to welding.
Brazing differs from welding in that it does not involve melting the work pieces. Brazing differs from soldering through the use of a higher temperature and much more closely fitted parts than when soldering. During the brazing process, the filler metal flows into the gap between close-fitting parts by capillary action. The filler metal is brought slightly above its melting (liquidus) temperature while protected by a suitable atmosphere, usually a flux. It then flows over the base metal (in a process known as wetting) and is then cooled to join the work pieces together.
Brazing creates the coalescence of metallic materials by initially heating them to the process temperature, as well as through the use of filler metals having a liquid state above 450 °C, and below the melting point of the base metals being joined; which distinguishes the process from welding where high temperatures are used to melt the base metals together.
Advantages of brazing
- Strong joints with good mechanical strength (stronger joint than soldering).
- Corrosion resistance of joints when correct filler materials are used.
- Lower temperatures and consequently lower cost than welding.
- Base metals’ properties are retained.
- Dissimilar materials can be joined.
Types of brazing
- Torch brazing
- Furnace brazing
- Silver brazing
- Braze welding
- Cast iron welding
- Vacuum brazing
- Dip brazing