Effect of Different Filling Systems on Casting Densities and Porosities of Sand Step-Casted Aluminum Al–7Si–0.3Mg (LM 25) Alloy

Abstract

In spite of abundant information of conventional gating system design, casting defects such as shrinkage and gas porosities were found in castings that make the final castings extremely vulnerable to deformation. Improper fluid flow and irregular solidification of metals is due to faulty gating system design that in turn produces major casting defects. In this paper, quantitative analysis of the densities of an Al–7Si–0.3Mg (LM 25) alloy sand casting was performed using mass/volume or Archimedean porosimetry technique along with optical microscopy. Stepped geometry was casted in this study using circular, square and rectangular cross sectional runners and ingates. Single and double runners were used within each variation of runners and ingates. Electronic weighing balance and water displacement methods were used for measuring densities and porosities of the casted samples. The results showed that the average values of densities for castings using single and double circular cross sectional runners and ingates are higher i.e., 2.64 gm/cm3 and 2.64 gm/cm3 as compared to square and rectangular runner and ingate system i.e., 2.52 gm/cm3, 2.57 gm/cm3 and 2.46 gm/cm3, 2.49 gm/cm3 with lower percentage porosity defects i.e., 1.41% and 1.64% as compared to square and rectangular cross sections i.e., 5.86%, 3.82% and 8.34%, 7.18%, respectively. The densities for the casted samples for rectangular cross section are lesser of all with high porosity defects.