Numerical Simulation And Determination Of The Heat Transfer Coefficient Of GCr15Steel In Spray Quenching Process

Spray Cooling is a new type of heat transfer mode. Compared to traditional cooling methods, it has some advantage like higher heat transfer ability and uniform cooling, as well as no boiling lag, and so on. Spray cooling has a broad application prospect in the field of metals and their alloys quenched. However, spray cooling of heat transfer mechanism is more complex, and the research related in the home and abroad is not mature. In this thesis, inverse heat transfer method has been applied to calculate the heat transfer coefficient in the spray quenching process. The effect of the nozzle inlet pressure parameters on heat transfer is researched based on the experiment, and the heat transfer mechanism is also analyzed compared with the traditional quenchant in the water and oil spray quenching process. Taken surface heat transfer coefficient as the boundary condition, FE software is used to simulate the spray quenching process. The calculated heat transfer coefficient is proved to have reasonable accuracy by experimental verification.Surface heat transfer coefficient is calculated by inverse heat transfer method in the spray quenching with the cooling curve during spray quenching process of GCrl5specimen. The results show:when the nozzle inlet pressure is7MPa,8Mpa and9MPa, heat transfer coefficient reaches its maximum at500℃,420℃and350℃, and the maximum value is6600w.m2.℃-1、7200w.m2.℃-1、8000w.m2.℃-1respectively. Therefore, as the nozzle inlet pressure increases, the maximum surface heat transfer coefficient of the spray quenching process under different pressures and the spray heat transfer process in the nucleate boiling region both increases.The comparison of heat transfer coefficient among fog, water and oil spray quenching shows that the maximum of surface heat transfer coefficient of water quenching is9800w.m2.℃-1and the minimum is4390w.m2.℃-1. The maximum of three pressure spray quenching heat transfer coefficient is between water spray and oil spray.In this paper, the finite element software COSMAP is used as a platform. Considering the temperature field, structure field and stress field coupling effect, three-dimensional nonlinear finite element model in the quenching process is established. Taken surface heat transfer coefficient as the boundary condition, the end quenching spray quenching process of GCrl5sample is simulated and temperature field, structure field, stress field and hardness field of quenching process is obtained. In order to verify accuracy of heat transfer coefficient, determination of the cooling curve and hardness value curve of the of7MPa spray after quenching the specimen is conducted. Structure observation is also processed. The simulated value is verified by the measured value. The results show:temperature field, hardness field and structure field agree well with the simulated, thus proving the accuracy of the calculated surface heat transfer coefficient.