Tempering is a process in which the quenched steel is heated to a temperature below Ac1, the heat is inevitable, and then cooled to room temperature. Its main purpose is:
(1) Reasonably adjust the hardness and strength of the steel, improve the toughness of the steel, and make the workpiece meet the application requirements;
(2) Stable structure, so that the workpiece does not undergo structural transformation during the permanent application process, thereby stabilizing the style and size of the workpiece;
(3) The low internal pressure of the workpiece is reduced or eliminated to reduce the deformation of the workpiece and prevent cracking.