The purpose of the heat treatment after brazing of the parts is to remove the stress in the material and improve the overall performance of the brazed parts, which is specifically manifested in the following two aspects:
1. The change of thermal cycle during brazing will cause changes in the properties of the base metal, so the heat treatment after brazing is mainly carried out to restore the properties of the base metal.
2. When heat treatment is performed to strengthen the base material itself, a brazing material with a suitable brazing temperature is selected so that the two processes of brazing and heat treatment can be completed in the same thermal cycle, which can achieve the effect of improving productivity. If the heat treatment of the weldment is arranged separately after brazing, the maximum temperature of the heat treatment must be performed below the remelting temperature of the solder to avoid cracking of the brazing seam and deformation of the weldment.
There are two main types of heat treatment to improve and enhance the overall performance of brazed joints:
1. Diffusion treatment to improve the structure of brazed joints. When vacuum separate diffusion treatment is used, the heat treatment temperature should be controlled below the solidus temperature of the solder.
2. Annealing treatment to eliminate residual stress.