关键词: 数值模拟, 大模块, 气淬, 组织演变, 压铸模具钢

Abstract: A numerical model of vacuum gas quenching cooling process of a 500 mm×500 mm×500 mm SDDVA die steel module was investigated by using DEFORM to investigate the cooling behaviour, microstructure evolution and stress evolution of the large module under different quenching pressure conditions in a vacuum air quenching furnace, and to predict the maximum size of the module that can be produced from a theoretical point of view. The results show that the proeutectoid carbide precipitation along the crystal is unavoidable in large module cores when quenched under 0.4, 0.6 and 0.9 MPa. And in order to avoid carbide precipitation, the cooling rate from 800 ℃ to 500 ℃ should be at least greater than 0.25 ℃/s. When gas quenched under pressure of 0.4 MPa, the maximum temperature difference between the core and the surface of the module is the smallest, about 120 ℃. The martensite content obtained in the core of large modules quenched under 0.9 MPa is higher than that obtained by quenching under 0.4 and 0.6 MPa, and the bainite content is also lower. The surface and core of the module mainly exhibit thermal and phase transformation stresses. The theoretical maximum thickness of SDDVA modules quenched by vacuum and high pressure gas under 0.4, 0.6 and 0.9 MPa is 280, 320 and 380 mm, respectively.

Key words: numerical simulation, large module, gas quenching, microstructure evolution, die-casting die steel