In the mechanical parts processing process, annealing is a leading technology, with a connecting role.

Annealing is the steel is heated to the temperature Ac1 above the critical points or less, with the furnace slowly get equilibrium state organization cooling process after thermal insulation.

Its main purpose is the chemical composition and microstructure, grain refinement, homogeneous steel hardness adjustment, eliminate stress and work hardening, improve the performance of the steel and cutting, and the organization for quenching.

Annealing process of large types, according to the heating temperature can be divided into at the critical temperature (Ac1 and Ac3) above or below the annealing. The former is also called phase recrystallization annealing, including full annealing, diffusion annealing and incomplete annealing, spheroidization annealing. The latter includes recrystallization annealing and stress relief annealing. Annealing method for different heating temperature has certain requirements.

According to the method of cooling and annealing can be divided into isothermal annealing and continuous annealing