Comparing Mechanical and Oxidation Properties of Cr- and Si-Alloyed Press-Hardened Steel with 22MnB5 Steel at Various Heating Temperatures

Abstract

High-performance press-hardened steels (PHS) are highly desired in automotive body-in-white due to their excellent strength and crashworthiness. PHS alloyed with high Cr and Si show promise in enhancing oxidation resistance as compared with traditional 22MnB5 steel, which may replace the use of expensive Al-Si coatings. Heating temperature, as a critical hot stamping process parameter, manipulates the mechanical properties and oxidation behaviors of PHS. In this study, the mechanical properties and oxidation behaviors of a 2000 MPa grade PHS alloyed with high contents of Cr and Si at heating temperatures ranging from 750 °C to 950 °C are systematically studied, as compared with those of the classical 22MnB5 steel. It shows that fully martensite structures for both steels can be achieved at the lowest heating temperature of 850 °C, and the products of strength and elongation of 32Cr2Si are greater than those of 22MnB5 at all heat-treatment conditions. The 32Cr2Si PHS exhibits much smaller weight gain than 22MnB5 when oxidized at all examining temperatures, due to the presence of thicker Cr- and Si-rich layer between the matrix and oxide scale. This work can provide guidance for material and process optimization for high-performance coating-free press-hardened steels.