Fluidity of eutectic grey iron in thin sections

A fluidity test has been devised which is particularly applicable to large thin-walled castings. SEM metallography and quantitative image analysis studies were performed on fluidity strips cast in a eutectic grey iron to discover the flow arresting mechanisms. These studies revealed that in thin sections, the high cooling rate resulted in chilled cast iron that had a channel closing mechanism at some distance behind the flow front. In thicker sections giving cooling rates to yield grey iron, it appears that the occurrence of eutectic cells (with fine dendrites and interdendritic type D graphite) at the flow tip acts to limit flow. The mechanisms are consistent with skin-freezing and pasty-freezing modes of solidification.