After the vacuum heat treatment of the parts, the distortion is small, the quality is high, and the process itself is flexible and pollution-free. Therefore, vacuum heat treatment is not only a necessary means of heat treatment for some special alloys, but also applied in the heat treatment of general engineering steels, especially tools, molds and precision couplings. The service life after vacuum heat treatment is longer than that of general heat treatment. improvement. For example, after vacuum heat treatment of some molds, the service life is 40-400% higher than that of the original salt bath treatment, and the service life of many tools can be increased by about 3-4 times. In addition, the vacuum heating furnace can work at a higher temperature, and the workpiece can maintain a clean surface, which can accelerate the adsorption and reaction process of chemical heat treatment. Therefore, some chemical heat treatments, such as carburizing, nitriding, chromizing, boronizing, and multi-component co-penetrating can get faster and better results.