MICRODISTRIBUTION OF NODULIZER IN VARIOUS PHASES OF CAST IRON

By means of the low temperature electrolysis with organic electrolyte and the radioassay method, either alloyed Ce in commercial cast iron and in high purity Fe-C-Si alloy or Ce in graphite was measured. The Ce in graphite is slightly higher than in neighboured matrix in most cases. With the same Ce content, more is alloyed in cast iron in comparison with steel. The eoating-autography shows that the Ce distributes uniformly in the flaky graphite, yet variously in the nodular graphite. The exploded graphite gets the most Ce among flaky and nodular ones. Ce is depleted from ferrite and pearlite surrounded by nodular graphite, and enriched in pearlite and ledeburite far apart from nodular graphite. Minor Ce is found in pearlite and honeycomb ledeburite which transformed by the dendrite of primary austenite, while major Ce in ledeburite of lathy cementite type. The Ce is remarkably concentrated in the last solidification zone on the eutectic transformation. It could be believed that the formation of nodular graphite mainly depends upon the anti-nodulizer, e. g. S, which is more effective than residual nodulizer or alloying contribution in the raw melted iron.