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铸造工作者普遍认为铸件的凝固速度是同铸件的内部质量紧密相关的.而铸件/铸型界面热交换行为又是决定铸件凝固速度的控制因素.目前尚未出现一种实用性强、便于灵活掌握的处理铸件/铸型界面热交换问题的方法,它已被公认为实现铸造CAD(电子计算机辅助设计)的一大障碍. 本文首次在国内开发和应用了一种能正确求解铸件/铸型界面热交换问题的新方法——热传导反算法.编制了两部程序HIP及HIC,分别用于计算平面及圆柱形的一维热传导反算问题.它们不仅能求出界面热交换系数随时间变化曲线(H-τ曲线),而且能同时计算出使用该H-τ曲线作为铸件/铸型界面热交换条件后所计算出的铸件、铸型温度场.通过采用试验数据及有关文献的试验数据进行计算,结果表明热传导反算法的应用是成功的. 试验和计算发现,圆柱形球铁件在凝固期间,由于石墨化膨胀的影响,在铸件-铸型之间不会形成气隙,其H值是随时间增长而逐步上升的.这同有色及钢铸件的情况刚好相反. 从试验和计算分析中,可看出铸件/铸型界面间的接触情况决定着界面热交换情况. 本文最后比较和分析了几种主要因素对界面热交换行为的影响,对铸件/铸型界面热交换机理进行了初步的探讨.
Casting workers generally believe that the solidification rate of castings is closely related to the internal quality of the castings.The heat exchange behavior of the castings / molds is also the control factor that determines the solidification rate of castings.At present, there is not a practical, flexible and easy to grasp Has been recognized as a major obstacle to the CAD (Electronic Computer Aided Design) of casting.This paper, for the first time, develops and applies a method which can solve the problem of casting / mold interface A New Method of Heat Exchange Problem - Heat Conduction Inverse Algorithm Two programs, HIP and HIC, were developed for the one-dimensional heat conduction backcalculation of planar and cylindrical shapes, respectively. They not only yield the curves of the interface heat exchange coefficient over time (H-τ curve), and the calculated temperature field of the castings and molds calculated by using the H-τ curve as the heat exchange condition of the casting / mold interface can be calculated simultaneously by using the experimental data and the experimental data of the related literatures The results show that the application of inverse heat conduction algorithm is successful.Experiments and calculations show that during the solidification of cylindrical ductile iron pieces, due to the influence of graphitization expansion , There is no air gap between the casting and the mold and the value of H increases gradually with time, which is the opposite of that for the colored and steel castings. From the experimental and computational analysis, it can be seen that the castings / castings The contact between the interfacial interface determines the heat exchange at the interface.Finally, the influence of several main factors on the interfacial heat exchange behavior is compared and analyzed, and the heat exchange mechanism of the interfacial interface is preliminarily discussed.