Numerical Simulation Of Heat Treatment And Determination Of Heat Transfer Coefficient For42CrMo Steel

The quenching process is a highly nonlinear problem, which has many influences. The boundary condition is complicated. The heat transfer coefficient is a very important boundary condition in the numerical simulation of quenching process. The precision of heat transfer coefficient can have a direct effect on numerical simulations. However, it is very difficult to measure. There are formidable difficulties in numerical simulations. The numerical simulation of quenching process and determination of heat transfer coefficient has very important theoretical and practical significance.Completely considering the transient heat conduction, latent heat of phase change, temperature-dependent thermal conduction, and temperature-structure-stress coupling, numerical simulation of spray oil end quenching process and quenching process of multidimeter for42CrMo steel were performed. By using COSMAP of the finite element simulation software, a three-dimensional finite element model was established, the instantaneous variations in temperature, stress, microstructure and hardness of the specimen during the quenching process were achieved by numerical simulation. The part of the simulation results was verified by experiments.Inverse methodology has been applied to calculate heat transfer coefficient of42CrMo steel and KR128oil. The results showed that the coefficient of heat transfer can reach a maximum(5360w/m2.K) at about600℃. Numerical simulation of spray oil end quenching process for42CrMo steel were performed by using the heat transfer coefficient that has been obtained, the instantaneous variations in temperature, stress, microstructure and hardness of the specimen during the quenching were achieved. The results showed that the volume fraction of martensite in the cold junction can reach a maximum(99%); the hardness of the cold junction can reach701HV(60.6HRC); the maximum of compressive stress is408MPa, which is located away from the cold end12mm; the maximum of tensile stress is600MPa, which is located in the constraining surface; the maximum amount of deformation(0.06mm) occurs in the spray oil end. The simulated results of temperature field, stress field, microstructure field and hardness were verified by experiments.Numerical simulation of quenching process of multidimeter for42CrMo steel were performed by using heat transfer coefficient of inverse methodology. The results got the temperature field at different time, stress field, microstructure field and hardness field. The results showed that the volume fraction of martensite in the end surface and the edges and corners can reach a maximum of98%, and it gradually decreases from the surface to the core. The thickness of semi-martensitic layer is about15mm; the hardness of multidimeter can reach679HV(60HRC); the edges and corners of upper end-face suffered the maximum stress that is the pulling stress, about600Mpa.