Influence of Quenching and Partitioning Process on Microstructure and Mechanical Properties of a Novel 1 800 MPa Hot Stamping Steel

Abstract

At present, hot stamping forming steel has some potential problems, such as poor plasticity, low impact toughness, limited bending energy absorption, which need to be sloved by some new technologies to make it serve the automobile lightweigh better. So microstructure and mechanical properties of a novel 1 800 MPa hot stamping steel carried out one step method quenching and partitioning process are investigated. Quenching temperature, partitioning temperature and partitioning time are controlled by salt bath. What's more, the content and distribution of retained austenite are observed via XRD and EBSD and carbon content in retained austenite is calculated. It is found that when the partitioning temperature is constant, the tensile strength and yield strength of the specimens decrease with the increase of the partitioning time, while the elongation increases, and when the partitioning temperature and the partitioning time are 230 ℃and 30 s respectively, the comprehensive mechanical properties of the experimental steel are best, the tensile strength is up to 2 034 MPa, while the elongation is up to 10.2%, and the production of tensile strength and plasticity is 20 747 MPa•%. Compared to the direct quenching, the tensile strength, elongation and production of them are increased by 9.5%, 73.5%, and 90%, respectively. This is that the plasticity and toughness have been significantly improved to meet the requirements of automotive steel, while maintaining ultrahigh strength, and this steel can better serve in automotive lightweight manufacturing.