Research On B1500HS Continuous Hot Stamping Phase Transformation Simulation And Key Process Parameters

Hot stamping technology of Ultra-high strength steel is an advanced forming technology arised in the background of lightweight automobile body.The results of Microstructure transformation is the essence of this technology and affected by many factors in hot stamping process,which directly affects the mechanical properties of hot stamping parts.In this paper,B1500 HS steel was taken to be reseached,and the phrase transformation model for ultra-high strength steel was determined.The key parameters of hot stamping technology(initial forming temperature,holding pressure,holding time)were systematically studied by means of finite element simulation and experiment.1)Based on the theory of solid-state transition of metals,the transformation process of ultra-high strength steel during hot stamping was analyzed,and the equilibrium temperature of phase transition was deduced.By comparing the applicationg scope and shortcomings of JMAK model,K-V model and its modified forms(Li model,A-O model and Lee model).The Lee model was determined as the theoretical carrier for simulating the phase transformation of B1500 HS,and its kinetics parameters were deduced by Scheil superposition rule.2)With the secondary development interface of ABAQUS software,an algorithm script for calculating the phase transformation result of hot stamping was developed using Python language.The effects of different initial forming temperature,holding pressure and holding time on the temperature field distribution and phase transformation of U-shaped parts during hot stamping were simulated by the control variable method.The results show that for B1500 HS with 1.2mm,in order to obtain martensite transformation rate of more than 97%,the initial forming temperature should not be less than 800?,the holding pressure should be more than 20 MPa,and the best holding time is at least 10 s.3)According to the simulation scheme,the hot stamping test of B1500 HS Ushaped parts was designed.The effects of initial forming temperature,holding pressure and holding time on the temperature field and phase transformation of U-shaped parts were investigated based on the continuous stamping condition.The microstructure transformation and hardness value of simulation and experiment are compared to evaluate the accuracy of simulation.The experimental results show that the changing trend of phase transformation and hardness with hot stamping parameters is in good agreement with the simulation results.When the initial forming temperature is 800?,the holding pressure is 20 MPa and the holding time is 6s,the hardness difference of simulation and experiment is the biggest,which is 50 HV,and the corresponding error value is 9.9%.This verifies the correctness of the parameters of phase transformation model and the validity of simulation results.