水轮机下环铸件凝固过程热应力模拟分析

Thermal Stress Analysis of the Solidification Process of Francis Turbine Band Casting

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。

Thermal stress field during the solidification process of the Francis turbine band casting has been simulated by numerical simulation method. The interaction between the casting and core was treated with contact element method in numerical simulation, thus improve traditional method for studying casting/model boundary conditions. The stress status of semi-solid phase area was emphasized. The hot tearing criterion was established to predict the tendency of occurrence of hot tearing of the casting. The simulated results are in accordance with the practical cases approximately.