Research And Application On Phase Transformation Model Of High Strength Steel In Hot Stamping

The hot stamping of high strength steel is one of the most effective methods to lightening vehicle’s weight, which produces high strength accessories to guarantee security requirements and, in the same time, achive the goal of energy saving and emmission reduction by reducing vehicle’s body weight. So it’s of great significance to be studied. Some accessories requiring different strength in different part need the process to be more complicated, then this work studies on phase transformation of BR1500HS’ T-type variable strength hot stamping process by theoretical analysis, numerical simulation and experimental verification.The types and characteristics of phase transformation of hot stamping of high strength steel were analized, based on the theory of solid metal phase transformation. The data of temperature and expansion of material BR1500 HS changed with the time in its thermal expansion test were acquired under ways of isothermal transformation and continuous cooling transformation. Based on typical ones, transformation kinetics models of Pearlite and Bainite in BR1500 HS variable strength hot stamping process were established by curve fitting. Parameters of martensite transformation kinetics were also acquired by tangent method.The established transformation kinetics models are applied to finite element analysis software-ABAQUS by programming with Python. The interaction of thermal, force, phase transformation in BR1500HS’ T-type variable strength hot stamping process is numerically analized, through which temperature and phase distributions in different mold heating temperature or compress time were analized, and it had been used to predict the optimal parameters.BR1500HS’ T-type variable strength hot stamping process in different mold heating temperature or compress time were implemented. Through microstructure comparing in metallographic test and tensile strength analyzing in stretching test of heating zone and cooling zone of the workpiece, the accuracy of the transformation kinetics models and the simulation results was conformed.