Eutectic Solidification of Oxidized Cast Iron

KAYAMA Nobutaro, MURAI Koichi

doi:10.11279/imono.38.7_449

Processes of the eutectic solidifications of grey cast irons melted with various melting conditions have been quantitatively observed by slowly cooling the irons in a thermostat held at a fixed temperature below the equilibrium eutectic point. Synthetic irons made in a high frequency vacuum melting furnace were melted together with various ratios of metalic silicon, Fe₂O₃ or SiO₂ in a Tammann-furnace, inoculated with SiC powder in some cases, and poured into a silica tube mould in the thermostat. The irons were held in the thermostat for a ceratin time and then quenched into water together with the silica tube mould. Thus obtained specimens were used for the microscopic examinations. Many such specimens were taken every five or ten seconds of the holding time in the thermostat and the process of the eutectic sclidification with each melting condition was examined and compared each other. The specimen is very small and slender, 6 gram in weight and 6mm in diameter, and the bath in the thermostat is composed of copper alloy, so that the cooling effect of the irons poured in the silica tube mould in the thermostat will be very good, and therefore, there is no difference in the microscopic structure all over the section of a specimen and a high reproducibility is obtained. Experimental results are summarized in the followings : (1) Starting time of eutectic solidification of iron oxidized by Fe₂O₃ lags behind. (2) Iron together melted with SiO₂ shows the same time lag in the start of eutectic solidification as in the iron oxidized by Fe₂O₃. (3) Solidification rates after starting are almost the same both in the standard iron and oxidized iron.

Eutectic Solidification of Oxidized Cast Iron

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