This study was carried out to investigate the oxides formed from molten iron with addition of small amount of aluminium during cooling and solidifing. Electrolytic iron with addition of small amount of aluminium (0.05 and 0.1 wt%) was melted in a levitation furnace of purified Ar-gas atmosphere, and molten iron was kept at 2200°-2300°C for about 40 sec or at 1580°-1610°C for 1-2 sec. Then, the molten iron was quenched by moulding it into a copper mould or putting it between two copper plates. The oxides formed during cooling and solidifing were extracted from the quenched iron by the Iodine-Alcohol method and identified by the X-ray diffraction.
The oxides identified were hercynite, γ-, κ-, θ-and α-Al2O3 in the case of quenched iron with addition of 0.05 wt%Al and γ-, κ-, θ-and α-Al2O3 in the case of quenched iron with addition of 0.1 wt%Al. It was considered from these results that γ-, κ- and θ-Al2O3's were the oxides of intermediate state of change from hercynite to α-Al2O3 by the reaction of hercynite with aluminium in molten iron.
