Vacuum brazing process specification

    The brazing specifications of commonly used materials include brazing temperature, heating rate, brazing holding time and cooling rate.

    The brazing temperature should generally be 20~100℃ higher than the pour point temperature of the solder. If the soldering temperature is too low, it will affect the fluidity of the solder. If it is too high, it will cause the loss of the solder and change the structure and chemical properties of the base metal and solder.

    The heating rate of brazing mainly depends on the properties of the base metal and the size and shape of the parts. For large and complex parts with ceramic seals and low thermal conductivity, the heating rate should be slower, and the temperature should be consistent throughout the parts as much as possible.

    The holding time of brazing is very important. Appropriate holding time can ensure that the solder fills the gap, and dissolves and diffuses the solder and the base metal to form an alloy. Excessive holding time will cause the base metal grains to increase significantly and cause excessive erosion of the base metal by the solder. In addition, the holding time is also Related to the brazing temperature, the holding time can be reduced correspondingly when the brazing temperature is higher. The holding time is generally between a few seconds to a few minutes.

    The cooling speed can be faster, but it must also be properly controlled to avoid the formation of stress at the weld due to the difference in expansion coefficient, or even cracks at the joint.

(Huiputech)