Brazing is the process of joining metallic materials using a molten filler metal, drawn into the joint by capillary action. The filler metal is usually a solder paste and it is placed on the parts prior to heating. Usually, filler metal becomes molten well below the melting point of the materials being joined.
Furnace soldering or brazing
The popularity of furnace soldering or brazing stems from the clean atmosphere used, which mostly eliminates use of fluxes and also eliminates post-braze cleaning. Various types of furnace are used for brazing, mostly employing a gaseous atmosphere. The overall furnace construction is based on either batch type or continuous operation.
The parts to be brazed are usually placed in machined carbon boards as shown above. Carbon boards are manufactured carbon plate, which are machined with the contour of the piece to be brazed. The allow consistency in the brazing process. Carbon will not breakdown in the heating and cooling process
Most materials can be furnace brazed. All materials need to be cleaned prior to insertion in the furnace to remove surface scale, grease and other contaminants (high quality in, high quality out). The most widely used fillers for furnace brazing are based on silver, copper, nickel and gold, the latter two being most applicable to stainless steels, and heat and corrosion resistant alloys.