Selection Of Cooling Method For High Frequency Quenching Machine

The choice of the cooling method of the high frequency quenching machine The choice of the cooling method is generally considered from the process requirements. The oil cooling equipment is simple and easy to use, but the working conditions are poor, and the quenching deformation and cracking tendency of the tool cannot be avoided. The speed of chloride salt classification cooling is enough to prevent the precipitation of carbides for a tool with a thickness of about 80mm, but the residence time should not be too long. When the large tool is cooled to the surface temperature equivalent to that of the salt bath, it should be taken out for air cooling. Small and medium-sized knives can be calculated according to the quenching heating time to meet the operation rhythm. After the chloride salt is graded and cooled, it stays in the lower bainite transformation zone, which helps to reduce the quenching stress. If the residence time is more than 1h, a large amount of bainite will be formed (see Table 4-22), which can improve the strength and plasticity of the high-speed steel in the quenched state. When the residence time is increased to more than 3h, the martensitic transformation will be suppressed during the subsequent cooling to room temperature. Therefore, long-term isothermal quenching can effectively reduce quenching deformation and prevent quenching cracking. After sufficient tempering, the hardness of long-term isothermal quenching is less different from that of general quenching, but the toughness is higher, so the usability of the tool with larger impact load can be improved. When isothermal quenching is not available, oil quenched or graded quenched tools are used, and they are tempered immediately after cooling to about 100 °C, which can also effectively avoid quenching cracks. ④Cold treatment: The cold treatment of high-speed steel is mainly used to improve the dimensional stability and wear resistance of the tool.