1. Definition: A heat treatment process in which the metal or alloy whose structure deviates from the equilibrium state is heated to an appropriate temperature, kept for a certain period of time, and then slowly cooled to achieve a structure close to the equilibrium state.
2. Purpose: Reduce hardness, uniform chemical composition, improve machinability and cold plastic deformation performance, eliminate or reduce internal stress, and prepare suitable internal structure for final heat treatment of parts.
Spheroidizing Annealing: Annealing performed to spheroidize the carbides in the workpiece.
Stress relief annealing: Annealing is performed to remove the internal stress caused by plastic deformation processing, cutting processing or welding of the workpiece and the residual stress existing in the casting.