可淬火硼钢板热成形过程中的传热行为

Heat transfer behavior in hot stamping of quenchable boron steel sheet

可淬火硼钢板热成形技术在汽车车身制造中的应用是实现汽车轻量化的重要途径,该成形过程中板料和模具之间的传热行为是实现板料精确成形所迫切需要解决的重要问题。本文考虑模内水道的冷却作用和随接触压力变化的板料-模具接触界面换热系数,基于ABAQUS建立了可淬火硼钢U形梁热弯曲过程有限元模型,研究了该过程中板料和模具之间的传热行为。研究结果表明:在高温成形过程中,板料底部区域和模具之间的传热迅速,并发生了马氏体相变。在保压淬火过程中,位于板料侧壁中部高温区的平均降温速率高于马氏体的临界转变速率,但淬火结束时其温度高于马氏体开始相变温度,因此未充分发生马氏体相变。

The application of hot stamping of quenchable boron steel sheet （QBSS） to the automobile body manufacturing is an important way to realize lightweight of automobile. It is an urgent subject to study the heat transfer behavior between the sheet and dies in hot form- ing of QBSS. Taking the U-shaped part as the object, a finite element （FE） model of hot bending of QBSS was established based on ABAQUS, considering of the cooling waterway of dies and the sheet-die contact interface heat transfer coefficient being changed with con- tact pressure. The heat transfer behavior between the sheets and dies in the hot stamping process was revealed. The results show that the bottom of the sheet has a rapid heat transfer to dies and thus martensite phase transition （MPT） has happened in the forming process, while in the quenching process, the middle of side wall of the sheet with higher temperature has an average temperature drop rate which is higher than the martensitic critical transition rate, but its temperature after quenching is higher than the temperature for MPT, so MPT is not adequate.