Brazing liquifies the alloy at temperatures higher than 450 degrees C and below the melting point of the substrate material. The typical processing temperature is 540-1620 degrees C. The typical brazing process includes preheating (optional), holding, ramp to temperature, brazing, cool down and, finally, exit.
Preheating and Holding- Preheating is done to the temperature below the melting point of the filler metal. It helps stabilize the temperature before heating. The time required for this stage is determined by the parts' thickness and volume.
Ramp to Temperature- The parts should heat quickly and uniformly. The heating time is limited due to the risk of creating distortion from thermal stress build up.
Brazing- Brazing time is the minimum time in which the braze alloy is allowed to flow through the joint. It should be controlled within suitable range depending upon the brazing situation. Theoretically, the joint between the filler and the base form quickly. Extending the processing time can lead to excessive interactions between the filler metal and the base metal, grain growth, and recrystallization.
Cooling and Exit- A controlled cool down within a protective atmosphere allows the joint to solidify. Usually, a temperature of about 150 degrees C will avoid discoloration of parts exiting the furnace.
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