Tempering can be divided into the following types according to the different performance requirements of the workpiece and the different tempering temperatures:
1. Low temperature tempering (150-250 degrees)
The structure obtained by low temperature tempering is tempered martensite. The purpose is to reduce the quenching internal stress and brittleness under the premise of maintaining the high hardness and high wear resistance of the quenched steel, so as to avoid cracking or premature damage during use. It is mainly used for various high-carbon cutting tools, measuring tools, cold stamping dies, rolling bearings and carburized parts. The hardness after tempering is generally HRC58-64.
2. Medium temperature tempering (350-500 degrees)
The structure obtained by tempering at moderate temperature is tempered bainite. The purpose is to obtain high yield strength, elastic limit and higher toughness. Therefore, it is mainly used for the processing of various springs and hot work dies. The hardness after tempering is generally HRC35-50.
3. High temperature tempering (500-650 degrees)
The structure obtained by high-temperature tempering is tempered sorbite. The heat treatment combined with quenching and high temperature tempering is conventionally called quenching and tempering, and its purpose is to obtain comprehensive mechanical properties with good strength, hardness, plasticity and toughness. Therefore, it is widely used in important structural parts of automobiles, tractors, machine tools, such as connecting rods, bolts, gears and shafts. The hardness after tempering is generally HB200-330.