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针对淬火过程中试件与淬火介质间的表面换热系数难于测量的问题,采用反传热求解方法,根据实验测定的试件表面的冷却曲线,通过非线性估计法和有限差分法计算表面换热系数随试件温度的变化规律。计算结果表明:氮气-雾化水混合物的冷却能力与水淬或油淬差不多。在氮气-雾化水混合物喷射淬火过程中,开始时的表面换热系数趋于平稳,在Ms点(170℃)附近,表面换热系数明显增加。马氏体相变过程中,相变潜热用于增加相变驱动力,从而克服相变阻力,完成马氏体相变。
In view of the difficulty of measuring the surface heat transfer coefficient between the test piece and the quenching medium during the quenching process, the method of inverse heat transfer is used to calculate the surface change of the test piece according to the cooling curve measured on the surface of the test piece through the nonlinear estimation method and the finite difference method The thermal coefficient changes with the temperature of the specimen. The calculation results show that the cooling capacity of nitrogen-atomized water mixture is similar to that of water quenching or oil quenching. During the jet quenching of the nitrogen-atomized water mixture, the surface heat transfer coefficient at the beginning tends to be steady, and the surface heat transfer coefficient increases significantly near the Ms point (170 ° C). During the martensitic transformation, the latent heat of phase transformation is used to increase the driving force of phase transformation so as to overcome the phase transformation resistance and complete the martensitic transformation.