Quality Aspects of A356 Castings with Multiple Gates

This work examines the quality aspects of multiple gated castings in aluminum A356 alloys. During the casting of parts in which multiple ingates are used to distribute the liquid melt throughout the mold, oxidation of the surface may prevent the adherence of the opposing fronts upon rejoining, thus producing sites prone to defect formation referred to as confluence welds. This phenomenon is investigated by the production of thin vertically sand-cast plates via the Electromagnetic Pump Green Sand (EPGS) process developed by the Foundation for the Research and Development in Transport and Energy (CIDAUT), Valladolid, Spain. For this research, three multiple-gated designs and one single-gated design were used to research an optimal configuration for melt delivery throughout the mold cavity. A series of numerical simulations were developed for each of the gating designs in order to compare modeling results with plates cast in the overseas counterpart’s foundry. Four-point bend testing was used to obtain information about the mechanical properties of the castings, and from this data, a Weibull statistical analysis was performed in order to quantify specimen failure rate for each of the configurations. Metallographic analysis was carried out using optical microscopy and fractography using a field emission gun scanning electron microscope (FEG-SEM). The numerical and experimental studies provided interesting insights on the formation of defects associated with the confluence of flow fronts.