Effect of Cooling Rate on Composition of Oxides Precipitated during Solidification of Steels.

Abstract

Effect of cooling rate on composition of oxides precipitated during solidification have been investigated using Ti deoxidized steel. The composition and size of oxides in continuously cast steels have been measured and theoretically analyzed. The oxide mainly consists of Ti2O3, Al2O3 and MnO. The composition of oxide whose diameter is less than about 10 μm changes with the cooling rate during solidification. The Ti2O3 content increases and Al2O3 content increases and Al2O3 content decreases with the decrease in the cooling rate. On the other hand, the composition of oxide whose diameter is larger than about 10 μm does not change with the cooling rate. When the size of oxide is smaller, the effect of the cooling rate on oxide compositions is remarkable.As a result of the theoretical analysis of the oxide growth during solidification on the basis of a diffusion growth model, it has been found that the increase in the diameter of oxide which grows during solidification is larger when the size of oxide before solidification and the cooling rate during solidification are smaller. The Ti2O3 content increases with the decrease in the diameter of oxide before solidification and in the cooling rate. The theoretically estimated results on the changes in compositions and diameter of oxides during solidification of steel qualitatively agree with the observed results.