Explanation

heat treatment process in vacuum or under vacuum with special gas below atmospheric pressure. It is mainly divided into three categories: vacuum quenching, vacuum annealing and vacuum thermo-chemical treatment. Vacuum quenching is heated under vacuum and then cooled in different cooling medium. Air cooling and oil cooling are widely used in vacuum quenching. Inert gas argon or high-purity nitrogen is mostly used for gas cooling. Vacuum annealing is mainly used for annealing of high temperature alloy, refractory metal and alloy. Vacuum thermo-chemical treatment is commonly used for vacuum carburizing, vacuum carbonitriding, vacuum ion carburizing, vacuum chromizing, vacuum jet, etc. The advantages of vacuum heat treatment are: ① bright heat treatment without oxidation and decarburization can be achieved. Since vacuum heat treatment is heated under negative pressure, the purpose of oxide scale removal and vacuum degassing can be achieved, and the workpiece surface does not need to be cleaned after heat treatment; ② Vacuum heating mainly depends on radiation, the heating rate is slow, the temperature difference between the surface and the center of the workpiece is small, and heat treatment deformation is small; ③ When heated in vacuum, oxygen, hydrogen, nitrogen, etc. dissolved in the metal can escape, which can significantly reduce the content of gas elements in the surface layer, thus improving the performance of materials; ④ vacuum heat treatment of magnetic materials can improve the stability of magnetism; ⑤ Vacuum carburizing has high speed and good quality. The main disadvantage of vacuum heat treatment is that the equipment is complex and expensive, and the heat treatment cycle is not suitable for materials containing alloy elements that are easy to evaporate.

Classification