Investigation of erosive-corrosive wear in the low pressure die casting of aluminum A356

摘要

Die surfaces are exposed to a wide range of operating conditions during permanent mould casting. The combination of materials, temperature, pressure, and flow can result in erosive-corrosive wear. The resulting accelerated wear can be a recurring problem along the sprue exit surface during the low pressure die casting of aluminum A356 wheels. The primary factor determining the occurrence of wear in wheel model-sprue combinations was sprue geometry, which led to the study of the influence of flow behaviour on erosive-corrosive wear. Laboratory erosive-corrosive wear experiments were performed by immersing and rotating test pins in liquid aluminum A356 under different test conditions. In addition to round cross-section pins, profiled cross-section pins were used to study the influence of flow on wear behaviour. Flow simulations were developed to predict the flow of liquid aluminum both within the sprue during die filling and around the rotating profiled cross-section pins. It was found that less wear occurred along the trailing edge of the profiled cross-section pins where flow was directed away from the pin surface. Increasing the pin draft angle or test rotation rate increased this effect and decreased the amount of wear occurring along this edge. This partially explains why accelerated wear is a problem for low exit angle sprues, but does not explain why some sprue geometries were more prone to accelerated wear on the surface preceding the constriction point.