【摘要】 采用基于连续介质的耦合求解模型研究了镍基合金线材K418和GH4169在真空水平连铸过程中的流动、传热和凝固过程。模型考虑了流体流动过程对凝固过程的影响,以及间隙性的水平连铸周期性拉坯曲线(拉-停-拉)对水平连铸过程中的流动和温度场分布的影响。利用校正后的模型分析了水平连铸过程中拉-停-拉过程中的瞬态流动和凝固过程,研究了不同合金种类、拉速、冷却强度对线材水平连铸过程中的凝固行为的影响。结果表明:在水平连铸周期性拉坯过程中,结晶器内的熔体流动模式和温度模式是周期性变化的,其影响着线材初始坯壳的生长。与K418相比,在相同的计算条件下,GH4169有较低的表面温度而显示了更快的坯壳增长。高拉速和低冷却强度将增加线材表面温度,并增加液芯长度。目前模型再现了水平连铸过程中特定拉坯曲线引起的凝固的本质特征,可为水平连铸过程中改进生产工艺、优化拉坯曲线、减少合金线材缺陷提供指导和参考。更多还原

【Abstract】 Based on the continuum model, a coupled mathematical model is developed to study the fluid flow, heat transfer and solidification behaviors in the vacuum horizontal continuous casting(VHCC) for the Ni- based superalloy(K418 and GH4169). The developed model includes the effect of the fluid flow on the solidification and the influence of the intermittent casting cycle(i.e. pulling-pause-pulling) in VHCC on the melt flow and temperature distribution. Using the verified model,the transient melt flow and solidification in the pulling-pause-pulling casting cycle is analyzed and the effects of the varying superalloy, casting speed and the cooling intensity on the solidification process are discussed. The results show that the flow and solidification behavior are periodical due to the intermittent casting cycle in VHCC,which affects the growth of the initial solidifying shell. Under the given computation conditions, the GH4169 has a lower surface temperature and quicker solidified shell growth compared with the K418. The higher casting speed and lower cooling intensity will increase the surface temperature and extend the liquid core length of the cast bar. The present model numerically re- presents the solidification process at the intermittent casting cycle in VHCC and can be useful for improving the production process, optimizing the casting cycle and reducing the quality defects in VHCC process for the superalloy bar.更多还原