Numerical Simulation And Applied Research Of T10 Steel During High Pressure Gas Quenching

This dissertation aims at having a profound study of the theory of metals and alloys during high pressure gas quenching and its applications, at predicting the properties of materials after high pressure gas quenching. Mechanics, heat transfer, material science and computer science are integrated in this dissertation. Based on the experiments of T10 steel during high pressure nitrogen quenching, the processes of metals and alloys quenched in high pressure gas were simulated with numerical methods and the concerning theories were studied.From the industrial applications of high pressure gas quenching, the following contents are analyzed - the development of high pressure gas quenching technique, the development of numerical simulation on high pressure gas quenching. The nonlinear heat conduction process of metals and alloys during high pressure gas quenching and its mathematics model were studied. The phase transformation processes of T10 steel during high pressure nitrogen quenching were simulated. The phase constituents, the latent heat and the synthetic surface heat-transfer coefficient of T10 steel during high pressure nitrogen quenching were calculated. The transient temperature field and the thermal stress field of T10 steel during high pressure nitrogen quenching were studied. The cooling curves of T10 steel workpieces during high pressure nitrogen quenching were tested. The hardness and the microstructures of these workpieces after quenching were measured. Finally, the qualities of T10 steel quenched by different nitrogen pressure were compared and the main results of this research were discussed.The results of experiments have shown: 1. The temperature difference between inner and outer of T10 steel during high pressure nitrogen quenching is small, and the concerning thermal deformation and thermal stress are also small. The surface of these workpieces are superior in quality after high pressure nitrogen quenching and the surface of these workpieces is clean. 2. With increasing of nitrogen pressure, the cooling capacity of nitrogen, the cooling velocity and hardness of the workpieces after quenching are improved.The results of theoretical research and numerical simulation have shown: 1. With the help of the finite difference method, the nonlinear estimate method and the results of cooling curves measured by the experiments, the synthetic surface heat transfer coefficient which coupled with phase transformation process of metals and alloys during high pressure nitrogen quenching can be calculated. During high pressure nitrogen quenching, besides the phase transformation process, the synthetic surface heat transfer coefficient is smooth. With increasing of nitrogen pressure, the synthetic surface heat transfer coefficient is improved. 2. Using the TTT diagram, Johnson-Mehlhe's dynamic computation formula and the Avrami's dynamic computation formula, the continuous cooling model of metals and alloys during high pressure gas quenching can be established and the phase constituents of metals and alloys during high pressure gas quenching can be calculated. 3. The ANSYS software was used to calculate the transient temperature field, the thermal stress and the residual stress coupled with phase transformation process of T10 steel during high pressure nitrogen quenching.The results of calculation and experiment have shown: the numerical simulation results of T10 steel during high pressure nitrogen quenching respond to the practical situation. The results of transient temperature field calculated by finite difference method and ANSYS software agree with the experimental results. The calculated results of phase constituents accord with the practical process.