Study On Hot Deformation Behavior And Ferritic Rolling Of P-added High Strength IF Steel

P-added high strength IF steels are developed by adding P, Si, Mn or other solution strengthening elements into traditional IF steels, which have excellent deep drawing properties and high strength. They are popular in autobolible industry and widely used on automobile in that they can dramatically rudece the weight of vehicles, decrease the produce cost, save energy and protect environment. Studies showed that ferritic rolled IF steels possessed{111}//RD texture type which is comparable with cold rolled IF steels. Compared with tranditional process of cold rolled, ferritic rolled can simplify the process and reduce the production cost, which is full of theoretical significance and application value. But, so far the study on hot deformation and ferritic rolled of P-added IF steels has been relatively less.In this paper, hot deformation behavior of B210P steel has been studied on the MMS-300thermo-mechanical simulatior and its micro structural evolution has been observed by different kinds of microscope, such as EBSD, TEM and EPMA. Additionally, the process of ferritic rolled and annealed for B210P steel has been studied as well. The main work were shown as follows:(1) The phase transformation points from austenite to ferrite were measured by thermal expansion experiments. The true stress-true strain curves of B210P steel were drawn by single-pass compression tests, and the effects of hot deformation paramenters on flow stress of B210P steel were analyzed.(2) The hyperbolic sine constitutive equations have been established for both austenite and ferrite area by using the parameter of Zener-Holloman, and a6th order polynomial were applied to represent the compersation of strains to evaluate the values of the material constants and the hot deformation activation energy. The flow stress has been predictived by the above constitutive equations, which have a good accuracy.(3) The volume fraction of static recrystallization (SRX) for B210P steel has been calculated through0.2%off-set method by double-pass compression tests. The law of effect of hot working processing parameters on the rate of SRX has been analyzed. The SRX kinetics equation of ferrite area has been established based on Avrami equation.(4) The influence of hot deformation parameters on the microstructure of B210P steel at ferrite area was studied based on single-pass compression tests. The characteristic of morphology and distribution for precipitations has been discussed. Besides, the mechanism of the dynamic recrystallization of B210P steel at ferrite area has been discussed.(5) The influence of annealed temperature and time on the microstructure and hardness of B210P steel sheets has been studied by ferritic rolling and annealing test. Compared with the properties of cold rolled B210P steel sheets, the sheets produced by ferritic rolled and annealed process can be achieved and have application prospect.