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基于有限元和Panda热动力学数据库建立了单晶叶片真空熔模铸造定向凝固过程的数理模型,对不同工艺下单晶叶片试样凝固过程中的温度场、糊状区演变及枝晶二次臂间距进行了仿真,研究了缺陷形成机理和规律。计算结果与实验吻合良好。计算结果显示,拉速大时二次臂细小,但杂晶产生的趋势加大;拉速小时杂晶不易形成,但二次臂增粗。对实际空心薄壁复杂单晶叶片定向凝固过程的模拟研究表明,二次臂间距在叶身部分分布比较均一,3.5mm/min抽拉时有可能在缘板处产生杂晶。采用变拉速工艺,不仅可避免杂晶缺陷,还能保证工件大部分枝晶细小,提高生产效率和成品率。
Based on the finite element method and the Panda thermodynamic database, the mathematical model of the directional solidification process of the vacuum investment casting of the single crystal blade was established. The temperature field, the evolution of the mushy zone and the secondary The simulation results show that the formation mechanism and rule of defects are studied. The calculated result is in good agreement with the experiment. The calculation results show that the secondary arm is small while the pulling speed is large, but the trend of miscellaneous grains is increased. When the drawing speed is small, the miscellaneous grains are not easy to form, but the secondary arm is thick. Simulation studies on the directional solidification process of the actual hollow thin-walled complex single-crystal blade show that the secondary arm spacing is relatively uniform in the blade body, and the occurrence of miscellaneous crystals at the edge plate may occur during the drawing at 3.5 mm / min. The use of variable speed process, not only to avoid miscellaneous crystal defects, but also to ensure that most of the workpiece dendritic small, improve production efficiency and yield.