Influence of Austenitizing Parameters on the Microstructures and Mechanical Properties of 22MnB5 Hot Stamping Steel Produced by TSCR Process

Abstract

Thin gauge hot strip steel can be produced by thin slab continuous casting and rolling (TSCR) process without the aid of cold rolling. However, few attempts have been made to produce hot stamping steel by using TSCR technology. As given steel, the hot stamping steel produced by the TSCR process was used to study the influence of austenitizing parameters on the final microstructures and mechanical properties. A Gleeble3500 thermal simulator was employed to heat the samples to obtain different austenite microstructures. After quenching, the Vickers hardness examination along the thickness of the sample and tensile testing were conducted. The microstructure was observed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results showed that on the condition of relatively lower temperature and shorter holding time, the sample exhibited better mechanical properties at the cost of microstructure uniformity along the thickness, although higher austenitizing temperature enhanced the carbide dissolution which would increase the effective carbon content in the martensite matrix. Lower heating temperature led to small prior austenite grain size and small blocks which contributed greatly to the mechanical properties.