5CrNiMo钢挤压模具淬火过程的数值模拟

Numerical Simulation of Quenching Process for 5CrNiMo Extrusion Die Steel

借助ABAQUS有限元分析软件对几何形状复杂的5CrNiMo钢挤压模具淬火过程的温度场及热应力场进行数值模拟。计算综合考虑了非线性的材料热物性参数、力学性能参数、表面换热系数及相变潜热的影响。研究表明,淬火初期,工件表面与心部仅存在较小的温差,随淬火时间的延长,该温差不断增大,淬火约5 s时,该温差达到最大值,此时表面温度虽已降低到192℃,但心部温度仍高达780℃,此后该温差不断减小,淬火约460 s时,工件表面和心部温度趋于与介质相同的温度(20℃);淬火过程的热应力变化在工件内外表现为不同的特点,对于表面和心部节点,其主要表现为:表面先呈拉应力后呈压应力,心部先呈压应力后呈拉应力。

The temperature and thermal stresses fields in quenching process for 5CrNiMo extrusion die steel were simulated by ABAQUS finite element software.The influence of nonlinear physical properties parameters,mechanical properties parameters,surface heat transfer coefficient and latent heat induced by phase transformation are taken into account comprehensively in this simulation.The research results show that only a small temperature difference exists bettwen the surface and the center of the quenched part at the initial stage of quenching.With the increase of quenching time,the temperature difference between the surface and center of the work-piece continues to grow.When quenching for about 5 s,the temperature difference reaches maximum.Although the temperature on the surface of the quenched part decrease to 192 ℃,the temperature in the center is still as high as 780 ℃.When quenching for about 460 s,the temperature on the surface and in the center tends to be the same as the quenching medium（20 ℃）.The thermal stress change in quenching process exhibits different characteristics inside and outside of the work-piece.Firstly,the thermal tensile stress forms on the surface and the thermal compressive stress forms in the centre.Then,because the cooling rate changes its character,the stresses change their directions.Finally,compressive stresses forms on the surface and tensile stresses formed in the centre.