Effects of Batch Annealing Temperature on Microstructure and Mechanical Properties of 1500 MPa Grade Hot Stamping Steel

A batch annealing experiment at different temperatures was carried out on 1500 MPa grade hot stamping steel produced by Jiugang. The results show that the microstructure of the cold rolled steel plate is composed of fibrous ferrite and deformed pearlite. The tensile strength of the test steel reaches 931 MPa, the yield strength reaches 852 MPa, and the elongation is only 1.8%. With the increase of annealing temperature, the tensile strength and yield strength of the test steel decrease, and the plasticity improves significantly. Thermal forming simulation of annealed steel plate is carried out, the microstructure of annealed steel plate is composed of quenched martensite, tempered martensite and fine carbide particles. The mechanical properties of 1500 MPa grade hot forming steel cold rolled steel sheet annealed at 690 ℃ cover for 4 h are that the tensile strength is 474 MPa, the yield strength is 339 MPa and the elongation is 30.3%. The mechanical properties of the final thermal forming parts: the tensile strength is 1515 MPa, the yield strength is 1026 MPa and the elongation is 9.7%.