超高强度钢板热冲压成形同步淬火相变不均匀性影响因素分析

Analysis on influencing factors of phase transformation inhomogeneity of synchronous quenching in hot stamping for ultra-high-strength steel plates

以超高强度钢BR1500HS为研究对象,利用材料的应力-应变数据、热物理性参数、相变模型构建了U形件热冲压成形过程的热-力-相3场动态耦合有限元数值模型。有限元模拟结果表明,法兰区域和底部区域中的马氏体体积含量显著多于侧壁区域中的马氏体体积含量,揭示了钢板相变的不均匀性;同时对成形过程中板料和模具的温度场进行研究,揭示了钢板冷却速度的不均匀性。通过在整个热冲压过程中法兰区域、圆角区域、侧壁区域和底部区域选取观测点,分析了冷却速率不均匀性的影响因素,即温差、接触间隙、换热系数。最后通过实验验证了模拟结果具有较高的可靠性。

Taking ultra-high-strength steel BR1500 HS as the research object,a three-field dynamic coupling finite element numerical model of thermal-force-phase in hot stamping process of U-shaped parts was established by using the stress-strain data,thermal physical parameters and phase transformation model of the material.The finite element simulation results show that the martensite volume content in the flange region and the bottom region is significantly higher than that in the side wall region,which reveals the inhomogeneity of the steel plate phase transition.The temperature field of sheet metal and mold in the forming process was studied,and the inhomogeneity of cooling rate of steel plate was revealed.Through selecting observation points in flange region,rounded corner region,side wall region and bottom region in the whole hot stamping process,the influencing factors of non-uniformity of cooling rate were analyzed,namely the temperature difference,contact clearance and heat transfer coefficient.Finally,the simulation results were proved to be high reliable by experiments.