常压高速气雾喷射淬火表面换热系数

Surface heat transfer coefficient of nitrogen-spray water eject quenching under normal pressure and high velocity

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。

The surface heat transfer coefficient is difficult to measure during quenching process. According to the cooling curve of surface and centre of specimen measured experimentally, the variations of surface heat transfer coefficient and specimen temperature were calculated by nonlinear estimate methods and finite difference method based on inverse heat transfer method. The results show that the cooling performance of mixture of Nitrogen and spray water is the same as that of water or oil. During quenching, the surface heat transfer coefficient is calm at early stage. Around Ms point （170℃）, the surface heat transfer coefficient increases distinctly. During Martensite phase transformation, the latent heat is used to increase the drive force of phase transformation and to overcome resistance of phase transformation, thus the Martensite phase transformation can be fulfilled.