Research on chemical composition and annealing temperature of high strength dual phase steel for automobile

High strength dual phase steel for automobile with two kinds of chemical compositions was designed.The microstructure and mechanical properties of the steel were compared and analyzed to determine the composition design suitable for the hot-dip galvanized continuous annealing production line.The influence of the annealing temperature temperature on the microstructure and mechanical properties was studied by using the VAI thermal simulation tester.The test results show that the test steels designed by two kinds of chemical components meet the microstructure and mechanical performance requirements of high strength dual phase steel.The test steel with Cr added alone can replace the test steel with Cr and Mo added.With the increase of annealing temperature in the dual phase zone,the volume fraction of ferrite decreased gradually,the volume fraction of martensite increased gradually and then decreased gradually,and the yield strength gradually increased,the tensile strength and the elongation rate gradually increased and then gradually decreased.The test steel had good comprehensive mechanical properties at annealing temperature of 820℃,the product of strength and ductility was 20.04 GPa·%.