EFFECT OF COOLING RATE ON DURING SOLIDIFICATION OF STEELS

Effect of cooling rate on composition of oxides precipitated during so lidification have been investigated using Ti deoxidized steel. The com position and size of oxides in continuously cast steels have been meas ured and theoretically analyzed. The oxide mainly consists of Ti2O3, A l2O3 and MnO. The composition of oxide whose diameter is less than abo ut 10 mu m changes with the cooling Fate during solidification. The Ti 2O3 content increases and Al2O3 content increases and Al2O3 content de creases with the decrease in the cooling rate. On the other hand, the composition of oxide whose diameter is larger than about 10 mu m does not change with the cooling rate. When the size of oxide is smaller, t he effect of the cooling rate on oxide compositions is remarkable. As a result of the theoretical analysis of the oxide growth during solidi fication on the basis of a diffusion growth model, it has been found t hat the increase in the diameter of oxide which grows during solidific ation is larger when the size of oxide before solidification and the c ooling rate during solidification are smaller. The Ti2O3 content incre ases with the decrease in the diameter of oxide before solidification and in the cooling rate. The theoretically estimated results on the ch anges in compositions and diameter of oxides during solidification of steel qualitatively agree with the observed results.