The Selection Of Wheel Steel And The Study Of Its Preparation Process

lightweighting can effectively save energy and reduce emission of automobiles.The lightweighting wheel as a rotating part can do better in energy saving and emission reduction.According to the working characteristics of the wheel,the hot-rolled DP600 was selected for wheel making in this paper.First,the chemical composition and hot rolling precdure parameters were designed in this paper.Then,the influence of isothermal temperature and time in the controlled cooling process after hot rolling on microstructure and properties of the steel was studied.On the basis of that,industrial production was carried out.And the key process parameters in production which specifically referred to finishing rolling temperature and coiling temperature were centrally experimented to know their influence on the microstructure and properties of hot-rolled DP600.Experiments show that the high content of martensite in the dual-phase steel leads to high strength but insufficient plasticity of the steel.When isothermal temperature decreases after hot rolling,the plasticity and n value of dual-phase steel increase,but the strength decreases.While with the increase of isothermal time,the strength decreases,but the plasticity and n value of dual-phase steel increase.When the isothermal temperature changes within 600-670℃ and the isothermal time ranges from 5s to 25 s,the mechanical properties of steel meet the national standard of DP600.Further more,when the isothermal temperature is about 670℃ and the isothermal time ranges from 8s to 11 s,the dual-phase steel possesses better comprehensive mechanical properties.In production the increase of finishing rolling temperature increases the martensite content,resulting in an increase in tensile strength and a decrease in elongation.Meanwhile,when the finishing rolling temperature is 821℃,the value of n is the highest of the steel.Coiling temperature has little influence on grain size and tensile strength.However,with the coil temperature increasing from 100℃ to 400℃,the yield strength and yield ratio of dual-phase steel increase,and the n value decreases,at the same time the elongation increases first and then decreases.The mechanical properties of dual phase steel in larger scale industrical production as a whole meet the requirements of national standard of DP600.It is the optimum process that the finishing rolling temperature is 820℃ and the coiling temperature is 100℃.The mechanical properties of the steel obtained by this process are as follows: the tensile strength is 625 MPa,the yield strength is 323 MPa,the elongation is 24.5%,n value is 0.21 and yield ratio is 0.517.