Effect of Austenitization Process on Oxidative Decarbonization Behavior and Mechanical Properties of 22MnB5 Steel

The effects of austenitizing temperature and holding time on oxidative decarbonization behavior of bare 22MnB5 steel sheet were investigated by OM, SEM, XRD, XPS, and room temperature tensile measurement. The oxidation kinetic model of 22MnB5 steel was calculated and revealed that early oxidation was controlled by chemical reaction, and later oxidation was controlled by elemental diffusion, for oxide layer structure from inside to outside of SiO2 + Cr2O3, wustite (FeO + Fe3O4), Fe3O4, and Fe2O3. With the increase in heating temperature (890-950 degrees C) and holding time (5-15 min), both oxidation and decarburization layers of 22MnB5 steel increased continuously, leading to a decrease in tensile strength and increase in elongation, making an increase in product of strength and ductility of about 1-4 GPa%. Based on the oxidative decarbonization and mechanical properties, the optimal heat treatment of 22MnB5 steel is 920 degrees C for 5 min.