K439B高温合金变截面铸件缩孔缩松数值模拟与试验

Simulation and Experimental Investigation of Shrinkage and Porosity for K439B Superalloy Castings with Variable Cross-Sections

具有变截面结构特征的铸件极易产生缩孔缩松缺陷,而准确预测并抑制缩孔缩松是制定合理铸造工艺的关键技术之一。采用有限元方法对K439B高温合金变截面铸件精密铸造过程进行了数值模拟,对比分析了Porosity判据、Niyama无量纲判据和APM(Advanced Porosity Model)判据的缩孔缩松数值模拟结果,结合铸造试验结果,确定了APM判据具有更高的数值模拟精度。在此基础上,采用APM判据数值模拟了不同截面铸件的缩孔缩松演化特点。数值模拟结果表明:随着截面比值由2∶1增加到12∶1,特征区域的孔隙率由2.31%增大到4.56%,孔隙总体积由0.44 cm^(3)增加到3.65 cm^(3),并且大体积分数的宏观缩孔逐渐增多,而锥形孔隙的长宽比则不断减小。

Castings with variable cross-sections are prone to shrinkage and porosity defects, and it is one of key technologies to accurately predict and eliminate these defects in developing rational casting processes. The numerical simulation was established for the gravity investment casting process of K439B alloy casting with variable cross-sections by employing the finite element method. The numerical simulation results of shrinkage and porosity by using porosity criterion, Niyama dimensionless criterion, and APM(Advanced Porosity Model) criterion, respectively were compared and analyzed, and it demonstrated that the APM criterion had higher numerical simulation accuracy through casting experiments. On this basis, the APM criterion was used to simulate and analyze the evolution characteristics of shrinkage and porosity in castings with different cross-sectional ratios. The numerical simulation results indicate that the porosity in the characteristic region increases from 2.31% to 4.56%, the total porosity volume increase from 0.44 cm^(3) to 3.65 cm^(3), and the macro shrinkage with large volume fractions gradually increases, while the aspect ratio of the conical pore distribution region decreases continuously as the cross-sectional ratio increases from 2∶1 to 12∶1.