基于改进集中热容法的TC17钛合金淬火表面换热系数测算

Calculation of Quenching Surface Heat Transfer Coefficient of TC17 Titanium Alloy Based on Improved Concentrated Heat Capacity Method

表面换热系数是TC17钛合金淬火数值分析研究的重要边界条件,其准确性影响工件淬火温度与应力场的分布精度。基于深埋热电偶动态实测的温降曲线,采用改进后的集中热容法,计算求解TC17钛合金淬火表面换热系数,并通过数值模拟验证了结果的可靠性。结果表明,TC17钛合金水浴淬火过程中会经历3个主要阶段:蒸汽膜阶段、核沸腾阶段及对流冷却阶段。表面换热系数在蒸汽膜阶段、核沸腾阶段会快速增大,随后在对流冷却阶段会逐渐减小,在第50 s达到峰值1299 W/(m^(2)·℃),此时淬火面温度为355℃。将换热系数代入数值模型中进行温度场计算验证,计算结果与实测温降曲线吻合较好,平均相对误差仅为1.4%。

Surface heat transfer coefficient is an important boundary condition for numerical analysis of TC17 titanium alloy quenching.Its accuracy will affect the distribution accuracy of quenching temperature and stress field.Based on the dynamic measured temperature drop curve of deep buried thermocouple,the heat transfer coefficient of TC17 titanium alloy quenched surface is calculated by using the improved concentrated heat capacity method,and the reliability of the results is verified by numerical simulation.The results show that there are three main stages in the process of TC17 titanium alloy water bath quenching:Steam film stage,nucleate boiling stage and convective cooling stage.The surface heat transfer coefficient increases rapidly in the steam film stage and nucleate boiling stage,and then decreases gradually in the convective cooling stage.The surface heat transfer coefficient reaches a peak of 1299 W/(m^(2)·℃)at the 50th s,and the quenching surface temperature is 355℃.The calculated results are in good agreement with the measured temperature drop curve,and the average relative error is only 1.4%.