Brazing Alloys

Brazing alloys are also known as brazing filler metals. They are used to be added in making a brazed joint. They have a lower melting point than the metal members being joined. There are many types of brazing alloys, which are used in different industries. For joining different pairs of metals, the brazing alloys can be different. The selection of brazing alloys depend on the metals being joined and their physical and chemical characteristics.

The brazing alloys when heated liquefy and melt to flow onto the space between the closed metal surfaces thus creating a brazed joint. The brazing alloys should have adequate melting and flow properties to allow proper distribution by capillary attraction in the prepared joints.

Temperature Range
The melting temperature range for a particular brazing alloy is determined by the minimum temperature at which that alloy will start melting (solidus) and the temperature at which the alloy is totally liquid (liquidus). All of the brazing alloys have the actual brazing temperature above the liquidus, almost 50°F to 200°F (30°C to 110°C).

The melting range of an alloy is primarily determined by its chemical composition. But the individual batch characteristics also have a slight effect. Some brazing alloys have wide melting range while others have a comparatively very narrow range. Alloys having wide melting ranges are used for filling larger gaps while narrow range alloys are better for filling narrow gaps. Wide range alloys, if heated too slowly, tend to decompose into their basic components. So it is always better to heat rapidly through the melting range to attain the brazing temperature.

Properties

Forms of Brazing Alloys
Brazing alloys are mainly found in solid forms.

Selection of Brazing Alloys
Different types of metals have different physical and chemical characteristics, so they require different brazing alloys for brazing. The selection of brazing alloys depends on a number of criteria. Some of the important points are: