Experimental and FEA investigation of shrinkage cavity, shrinkage porosity, and air entrainment defects in vertical centrifugal casting

The presence of large shrinkage cavity defects strongly influences casting accuracy. Therefore, this study aims to conduct experiments in addition to finite element simulations to determine the volume of this defect in castings produced by vertical centrifugal casting. It also aims to examine shrinkage porosity and air entrainment defects. These were planned using the Taguchi method with three variables: rotational speed, die aspect ratio, and casting temperature at five levels. Simulations were then performed using three-dimensional models based on the finite element method for both the filling and solidification processes. The experiments were then conducted, and the results were compared with the simulations. A good match was found, confirming the accuracy of the simulations in tracking the molten metal and air during casting. The results showed that shrinkage cavity volume increased with the rotational speed and die aspect ratio, with percentage increases ranging from 233.33% to 775% depending on the aspect ratio, while the reduced relative increase at the highest aspect ratio was attributed to higher initial defect levels. Shrinkage porosity is located in the center of the casting near the top surface, while air entrainment is located near the die walls, primarily at the bottom of the die at low rotational speeds, and then shifts toward the top of the casting as the rotational speed increases.