Calculation of the coupled thermal stress of a cylinder with non-linear surface heat-transfer coefficient and phase transformation during the quenching with various quenching media

摘要

The coupled temperature and stress fields with phase transformation were calculated using finite element technique during the quenching with various quenching medium, which are water and nitrogen gas at atmosphere pressure with various gas velocities. From the TTT diagram of the 45 steel, the CCT diagram was simulated and the volume fraction of phase constituent in continuous cooling was calculated. The thermal physical and mechanical properties were treated as the functions of temperature and the volume fraction of phase constituents. The obtained results show that: (1) The thermal stresses during water quenching are greatly larger than that during the gas quenching; (2). During gas quenching, the higher gas velocities are, the larger magnitudes of thermal stresses, meanwhile, the higher gas velocities are, the better hardness-ability is. Taking gas as quenching medium, such as nitrogen, the thermal stresses and hardness-ability can be controlled; (3). The inelastic-coupled effect should be considered during quenching.