Method for manufacturing high strength steel plate with improved ductility and formability and steel plate obtained by the method

摘要

The invention relates to a method for manufacturing steel plate, which successively comprises: cold rolled steel plate, and the chemical composition of the steel plate contains weight% 0.15% = C = 0.23%2.0%=MN=2.8%1.0% = if = 2.1%Page: 11.7%=SI+AL=2.1%0=NB=0.035%0=MO=0.3%0=CR=0.4%The rest consists of unavoidable Fe and impurities. The steel plate is annealed at annealing temperature to form a structure consisting of at least 65% austenite and up to 35% intergranular ferrite, and the steel plate is annealed at a temperature of at least 20 ℃/ The sheet was heated to the PT zone temperature of 350 ° C to 450 ° C at the impregnation temperature of ms-170 ° C to ms-80 ° C, and the sheet was kept at that temperature, and the sheet was immediately cooled at room temperature during the PT partitioning time between 80 ° and 440 ° C,The surface portion of the steel plate with final microstructure consists of 40% to 70% martensite regeneration, 7% to 15% retained austenite, 15% to 35% ferrite, 5% to the latest martensite, and 15% to 15% of the latest martensite.