The details are as follows:
1. Improve or eliminate all kinds of structural defects and residual stresses caused by casting, forging, rolling and welding of iron and steel, and prevent deformation and cracking of workpiece.
2. Soften the workpiece for cutting.
3. Refine the grain and improve the structure to improve the mechanical properties of the workpiece.
4. Prepare for the final heat treatment (quenching and tempering).
