Abstract
Melts of spheroidal graphite cast iron were poured into a phenol sand mold at various carbon content in order to investigate the cooling curves, graphite structure and internal shrinkage volume. The surface of each casting was analyzed by EDS. The results show that the nodule count increases as the carbon content is raised until the hypereutectic range is entered, after which no further increase occurs. With hypereutectic compositions, the total graphite amount increases but owing to carbon flotation, the increase is concentrated in the upper section of the casting; the middle and lower sections of the casting contain the same graphite amount as with a eutectic composition. The internal shrinkage cavity decreases to zero as carbon content is increased to a eutectic composition and then increases when the hypereutectic composition range is entered. The internal shrinkage cavity is dendritic in the hypoeutectic range but has a smooth shape in the hypereutectic range. Mushy degree of eutectic solidification increases consistently as the carbon content is raised.
