By definition, brazing is a metal-joining technique using a molten filler metal alloy with a melting temperature grater of about 425°C (800°F). In brazing, a filler metal is melted and drawn into a capillary formed by assembling two or more workpieces, and the filler metal has a lower melting point than the adjoining metal. Brazing differs from welding because it does not involve melting the work pieces and soldering in higher temperatures for a similar process. It also requires much more closely fitted parts than soldering, and the filler metal flows between the closely fitting joint surfaces using capillary action.
Advantages and Disadvantages of Brazing
Advantages:
- Strong, uniform, leakproof joints can be made rapidly, inexpensively, and even simultaneously.
- Joints that are inaccessible and parts that may not be joinable by other methods often can be joined by brazing.
- A major advantage of brazing is joining the same or different metals with considerable strength.
Disadvantages:
- One of the main disadvantages is the lack of joint strength compared to a welded joint due to the softer filler metals used.
- The strength of the brazed joint is likely to be less than that of the base metal(s) but greater than the filler metal.
- Another disadvantage is that brazed joints can be damaged under high service temperatures.
Brazing Filler Material
Various alloys are used as filler metals for brazing, depending on the intended use or application method. Wire and rod forms are generally used for manual brazing as they are the easiest to apply while heating. Some of the more common types of filler metals used are:
- Aluminum-silicon
- Copper
- Copper-silver
- Copper-zinc (brass)
- Copper-tin (bronze)
- Gold-silver
- Nickel alloy
