Effect of annealing temperatures on microstructure and properties of rare earth microalloyed medium manganese automobile steel

An ultra-high strength cold-formed automobile steel containing 48 ppm rare earth Ce was designed based on 0.1C-5Mn medium manganese steel. The microstructure and properties of the material were analyzed using scanning electron microscopy (SEM), X-ray diffraction (XRD), and a universal tensile testing machine, focusing on the austenite reverse phase transformation annealing process. The effects of different annealing temperatures on the microstructure and properties of rare earth microalloyed medium manganese automobile steel were investigated. The experimental results show that the microstructure of the experimental steel is mainly ferrite, retained austenite and new martensite. The comprehensive mechanical properties are the best when annealed at 800 °C -5 min / 640 °C -15 min. The residual austenite content of the experimental steel reaches 25.77 %, and the yield strength is 896 MPa, and the tensile strength is 1198 MPa, and the elongation is 33.24 %, and the multiplication of strength and plastic is 39.82 GPa ·%.