(1) Quenched and tempered steel:
1. Pre-heat treatment: normalizing->annealing (pearlite steel)->high temperature tempering (martensitic steel)
(1) The purpose of normalizing is to refine the grains, reduce the degree of banding in the structure, and adjust the hardness to facilitate mechanical processing. After normalizing, the steel has equiaxed fine grains.
2. Quenching: The steel body is heated to about 850 °C for quenching. The quenching medium can be selected according to the size of the steel and the hardenability of the steel. Generally, water or oil or even air quenching can be selected. The steel in the quenched state has low plasticity and large internal stress.