Influence of oxides on crystal nucleation in supercooled iron

The effect was investigated of oxides of rare-earth metals (r.e.m., Al20L3 and SiO2 upon the nucleation in iron on supercooling. It was shown that the ability of the oxides to stimulate the heterogeneous formation of nuclei increases in the following sequence: r.e.m. oxides, Al2O3, SiO2. The critical supercooling on addition of r.e.m. oxides amounts to 3-12 deg C. Addition of r.e.m. to continuously-cast steels increases the zone of equiaxial crystals from 19 to 29 % across the thickness of the casting and results in the disappearance of segregation in its centre. Noted are the dependence of the modifying ability of various oxides on the interphase energy on the ''modifier-solid iron'' interface and the effect on said parameter of differences in crystalline lattices of both components. The experimentally found values of the critical supercooling agree well with the results of calculations based on the concept of crystalline correspondence of lattices