K418合金车用增压涡轮热裂倾向性分析及预测Hot tearing susceptibility analysis and prediction of K418 superalloy for auto turbocharger turbine wheel

为解决K418合金用于浇注车用增压涡轮时出现的热裂问题，采用有限元模拟软件ProCAST的热弹塑性模型，对不同浇注工艺下K418合金车用增压涡轮的充型和凝固过程进行模拟，通过对温度场、固相分数和应力场模拟结果的分析，预测热裂缺陷的形成倾向，模拟结果与实际情况基本吻合。分析结果表明，涡轮叶稍处产生热裂的根本原因是凝固过程中产生了拉应力，应力值越大，铸件处于热裂敏感区的时间越长，热裂倾向性越大；采用较高的模壳温度和较低的浇注温度有利于降低铸件的热裂倾向。

The filling and solidification processes under different pouring processes were simulated by the thermal elasto-plastic stress model in finite element simulation software ProCAST in order to solve the hot tearing problem in the K418 superalloy auto turbocharger turbine wheel. The susceptibility of hot tearing defects was predicted by analyzing the simulation results of temperature field, solid fraction and stress field. The simulation results agree well with the real circumstances. The analysis results show that the main reason for the hot tearing in the blade margin of turbine is the tensile stress induced during the solidification. Both the higher stress and the longer time in the hot tearing sensitive range will result in the higher hot tearing susceptibility of the casting. The higher shell temperature and the lower pouring temperature are advantageous to reducing the hot tearing susceptibility of the casting.

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