A carbide (VC: vanadium carbide) layer is formed on the surface of the material by immersing a material such as steel and cemented carbide in a salt bath maintained at a high temperature. Mainly widely used in the field of thick material stamping that needs to withstand high surface pressure.

Metal heat treatment is a process in which a metal workpiece is heated to a suitable temperature in a certain medium, maintained at this temperature for a certain period of time, and cooled at different speeds. It is one of the important processes in mechanical manufacturing. Compared with other processing processes, heat treatment generally does not change the shape and overall chemical composition of the workpiece, but by changing the microstructure inside the workpiece or changing the chemical composition of the workpiece surface, giving or Improve the performance of the workpiece. In order to make the metal workpiece have the required mechanical properties, physical properties and chemical properties, in addition to the reasonable selection of materials and various forming processes, heat treatment process is often essential. The metal heat treatment process generally includes three processes: heating, heat preservation, and cooling. 

This process is interconnected and uninterrupted. Heating is one of the important processes of heat treatment, and there are many methods. Heating temperature is one of the important process parameters of heat treatment process. Selection and control of heating temperature are the main issues to ensure the quality of heat treatment. The heating temperature varies with the metal material to be heat treated and the purpose of the heat treatment. Generally, it is heated above the phase transition temperature to obtain a high temperature structure. In addition, the transformation takes a certain amount of time. Therefore, when the surface of the metal workpiece reaches the required heating temperature, it needs to be maintained at this temperature for a certain period of time to make the internal and external temperatures consistent and the microstructure to be completely transformed. This period of time is called the holding time. Cooling is an indispensable step in the heat treatment process. The cooling method varies with the process, and the cooling rate is mainly controlled. Generally, the cooling rate of annealing is slow, the cooling rate of normalizing is faster, and the cooling rate of quenching is faster. But there are also different requirements due to different steel grades.