The heat treatment process of heating a metal or alloy to an appropriate temperature, holding it for a certain period of time, and then slowly cooling it (usually with furnace cooling) is called annealing.
The essence of annealing is to heat steel to austenitize and undergo pearlite transformation, and the microstructure after annealing is close to equilibrium.
The purpose of annealing:
(1) Reduce the hardness of steel, improve plasticity, and facilitate machining and cold deformation processing;
(2) Uniform chemical composition and microstructure of steel, refinement of grain size, improvement of steel properties or preparation of microstructure for quenching Be prepared;
(3) Eliminate internal stress and work hardening to prevent deformation and cracking.
Annealing and normalizing are mainly used for preliminary heat treatment. For parts with low stress and low performance requirements, annealing and normalizing can also be used as final heat treatment