采用数值模拟方法对水轮机下环铸件凝固过程中的应力场进行了模拟和分析。模拟中采用接触单元法处理铸件与砂芯之间力的作用,改进了传统的铸件/铸型边界条件处理方法。文中重点分析了下环凝固过程中准固相区的受力情况,根据准固相区受力特点建立了适当的热裂判据,对下环凝固过程热裂倾向性进行预测。实际生产结果与预测结果相符合。 The numerical simulation method was used to simulate and analyze the stress field during the solidification of the lower ring castings. In the simulation, the contact element method is used to deal with the force between the casting and the sand core, and the traditional casting / mold boundary conditions are improved. In this paper, the stress conditions of the quasi-solid-phase zone during the solidification of the lower ring are analyzed emphatically. Based on the characteristics of the quasi-solid-phase zone, the appropriate thermal cracking criterion is established to predict the thermal cracking tendency of the lower ring solidification. The actual production results are in line with the forecast results.