As a part of the study on the effect of oxides on heterogenuous nucleation during iron solidification, the effects of Al2O3, SiO2, and rare earth oxides were examined, by measuring the critical supercooling of 300g electrolytic iron under special slag in a Tammann furnace. The following results have been obtained.
1) The critical supercooling for heterogenuous nucleation is remarkably lowered than that of homogenuous nucleation. This value is 3°C by the addition of R. E. M, and this is extremely small when compared with 14°C by Al2O3, 30°C by SiO2, and 53°C by MnO.
2) The heterogenuous nucleating potency of oxide catalyzers is dependent upon the difference of interfacial energy between the oxide substrate and δ-Fe. This interfacial energy can be theoretically explained by the disregistry between both crystals.
