Abstract
To investigate the formation of oxide layer on the surface of cast iron, seven kinds of pellets, containing 10 to 50 wt % Si and having the various ratios of electrolytic iron, metallic silicon, ferro-silicon (41.7 wt %) and Fe3Si, were prepared by mixing and pressing, and heated in air for 10 to 300min. The oxide layer and sintered metallic grains were observed and analyzed with EPMA and XRD. The exothermic reaction was observed on all specimens except for the specimen of ferro-silicon alone. On four specimens, containing silicon less than 20 wt % of which temperature rose above 1250°C, the oxide layer were thick, and on the other specimens, containing 20.9 and 50 wt % Si with the temperature going up about 1200°C, the oxide layer were thin. The difference in the composition of initial melts formed in specimens at high temperature could account for these results.
