BRAZING. 

Brazing is a group of welding processes in which materials are joined by heating to a suitable temperature and by using a filler metal with a melting point above 840°F (449°C), but below that of the base metal. The filler metal is distributed to the closely fitted surfaces of the joint by capillary action. The various brazing processes are described below.

a. Torch Brazing (TB). Torch brazing is performed by heating the parts to be brazed with an oxyfuel gas torch or torches. Depending upon the temperature and the amount of heat required, the fuel gas may be burned with air, compressed air, or oxygen. Brazing filler metal may be preplaced at the joint or fed from handheld filler metal. Cleaning and fluxing are necessary. Automated TB machines use preplaced fluxes and preplaced filler metal in paste, wire, or shim form. For manual torch brazing, the torch may be equipped with a single tip, either single or multiple flame.

b. Twin Carbon-Arc Brazing. In this process, an arc is maintained between two carbon electrodes to produce the heat necessary for welding.

 c. Furnace Brazing. In this process, a furnace produces the heat necessary for welding. In furnace brazing, the flame does not contact the workpiece. Furnace brazing is used extensively where the parts to be brazed can be assembled with the filler metal preplaced near or in the joint. brazing operation. Figure 6-8 illustrates a furnace