Studies On The Numerical Simulation For Metals And Alloys During Different Medium Quenching And Its Application

This dissertation aims at having a profound study of the theory of metals and alloys during quenching and its applications, at improving the qualities of quenching processing, at predicting the properties of materials after quenching, and at investigating the quenching process quantitatively. Some fundamental researches are carried out to have a further research on the theories of metals and alloys during high pressure gas quenching. Based on the experiments of quenching process, in which four typical metals and alloys, namely 45 steel, T10 steel, 9SiCr steel and W18Cr4V steel, are quenched in water, oil and high-pressure nitrogen gas, the processes of metals and alloys quenched in different quenching medium were simulated with numerical methods and the concerning theories are compared and studied.From the industrial applications of ordinary quenching processing and high pressure gas quenching processing, the following contents are analyzed ?the development of numerical simulation on quenching process, phase transformation, temperature field and thermal stress field for metals and alloys during quenching. And the actuality of calculation on the synthetic surface heat-transfer coefficient for metals and alloys during quenching was also analyzed. The nonlinear heat conduction process of metals and alloys during quenching and its mathematics model were studied. The phase transformation process of metals and alloys during quenching were simulated. The phase constituents, the latent heat and the synthetic surface heat-transfer coefficient of metals and alloys during quenching were calculated. The transient temperature field and the thermal stress field of metals and alloys during quenching were studied. The cooling curves of metals and alloys workpieces during quenching were tested. The hardness and the residual stress of these workpieces after quenching were measured. The microstructures of metals and alloys after quenching were also measured. Finally, the qualities of metals and alloys quenched by different medium were compared and the main results of this researchwere discussed.The results of experiments have shown: 1. By means of the computerautomatic sampling system produced by the author of the dissertation, the cooling curves of metals and alloys quenched in water, oil and high-pressure nitrogen gas can be measured. High-pressure nitrogen gas quenching technology can readily be applied in industry of materials with high quenching capacity, such as alloy steels. With the increasing of the pressure of the gas, the carbon steel can be dealt with highpressure quenching technology. 2. Similar to water and oil quenching process, the microstructures and the properties of metals and alloys after high-pressure nitrogen gas quenching process can also be changed. 3. The thermal strain and thermal stress of the workpieces quenched in high-pressure nitrogen gas are less than that of the workpieces quenched in water or oil. The distributing of stress in the workpieces after high-pressure nitrogen gas quenching process is satisfactory. The surface qualities of the workpieces quenched in high-pressure nitrogen gas are much better than that of the workpieces quenched in water or oil, the surface of workpieces after high-pressure nitrogen gas quenching process is clean.The results of theory research and numerical simulation have shown: l.With the nonlinear estimate method, the finite difference method and the results of cooling curves measured by the experiments, the nonlinear synthetic surface heat-transfer coefficient which coupled with phase transformation process of metals and alloys during quenching can be calculated. During the quenching processing of metals and alloys in water or oil, the heat transfer between solid materials and liquid medium appears boiling heat transference, which includes bubble and film heat transference. The synthetic surface heat-transfer coefficients appear galactic nonlinear characteristic. However, during the high-p...