Effect of hot-dip galvanizing process on microstructure and properties of 1 180 MPa grade dual-phase steel
YU Cansheng1, ZHENG Zhiwang1, CHANG Zhiyuan1, GONG Hui2, LIU Qingchun1, ZHANG Longchao2
1. State Key Laboratory of Vanadium and Titanium Resources Comprehensive Utilization, Pangang Group Research Institute Co., Ltd., Panzhihua 617000, Sichuan, China; 2. Science and Technology Quality Department, Xichang Steel and Vanadium Co., Ltd., Xichang 615000, Sichuan, China
Abstract：In order to explore the production feasibility of 1 180 MPa grade hot dip galvanized dual phase steel, the influence of key process on its microstructure and properties was studied. The continuous annealing simulator was used to investigate the influence of soaking temperature, slow cooling temperature and galvanizing(equilibrium)temperature on microstructure and properties of 1 180 MPa grade hot-galvanized dual-phase(DP) steel. The results show that when the slow cooling temperature and galvanizing (equilibrium) temperature are 720 ℃ and 460 ℃ respectively, with the increase of soaking temperature, the content and size of ferrite in test steel decrease, the total amount of martensite and the content of self-tempered martensite increase, the yield strength of test steel increases, and the tensile strength increases first and then tends to be stable. When the soaking temperature and galvanizing (equilibrium) temperature are 820 ℃ and 460 ℃ respectively, with the increase of slow cooling temperature, the content of ferrite in test steel decreases, the total amount of martensite and self-tempered martensite increases, resulting in a slight increase in tensile strength, but the elongation after fracture keeps stable. When soaking temperature and slow cooling temperature are 820 ℃ and 720 ℃ respectively, with the increase of galvanizing (equilibrium) temperature, the self-tempering degree of martensite increases, the yield strength of test steel increases, the tensile strength decreases slightly, but the elongation after fracture does not change much. When the soaking temperature, slow cooling temperature and galvanizing (equilibrium) temperature are 820 ℃, 720 ℃ and 460 ℃, respectively, the 1 180 MPa grade hot-dip galvanized dual-phase steel can obtain the best mechanical properties, that is, the yield strength is 887 MPa, the tensile strength is 1 212 MPa, the elongation after fracture is 7.0 %, and the yield ratio is 0.732. Its microstructure is 30% ferrite (average grain size is 1.5 μm) + 35% martensite + 35% self-tempered martensite(volume fraction). This study can provide a reference for the industrial production of 1 180 MPa grade hot-dip galvanized dual-phase steel.
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2023, Vol. 33 
