球墨铸铁件收缩缺陷判据的研究

Criterion of Shrinkage Defect for Ductile Iron Castings

根据球墨铸铁件收缩缺陷形成的本质 ,对铸件凝固过程中形成的孤立区进行了体积变化计算 ,并以孤立区的净体积变化量与此孤立区刚形成时的体积之比作为判别收缩缺陷严重程度的依据 .在呋喃树脂砂型条件下 ,针对不同模数、不同冒口颈尺寸的圆柱试样进行了模拟计算和浇注试验 .通过比较计算和试样解剖结果 ,确定了各模数试样恰好不产生收缩缺陷时孤立区净体积变化率的临界值 ,以此作为球铁件宏观缩孔、缩松收缩缺陷的判据 。

Formation of shrinkage defect in ductile iron casting is modeled numerically. The process includes the volume variation of an isolated zone formed in solidification of the casting. The ratio of the net volume variation to the original volume of the isolated zone is used to predict the degree of shrinkage defect in the casting. Several cylindrical castings with different modulus and size of riser necks cast in furan bonded silicon sand molds are examined and analyzed numerically. The critical ratios, at which the shrinkage defects just disappear, are determined by comparing the results of numerical calculation with the tests. It is used as a criterion for controlling macro shrinkage defect.