Abstract:
A system developed at Nagoya University combining a cooling slope, gravity pouring and pressurisation was utilised to cast components from hypoeutectic cast iron in the semi-solid state. Investigation of resulting microstructure and attendant defects was carried out, which revealed significant improvements in primary particle size refinement and globularity in components produced through semi-solid casting (SSC) when compared with normal gravity die casting (GDC) of super-heated melt. Sub-surface anomalies such as chilling tendency and skin-deep shrinkage cavities were unavoidable in components cast under pressure in a metallic mould at room temperature but, increasing the mould preheat temperature reduced the anomalies whereas increased pressurisation improved melt feeding and drastically reduced porosity attributed to gas entrapment and solidification shrinkage