Continuous Casting of Special Steel Slabs

Recent developments of continuous casting of special steel slabs are described. High carbon steel has been found susceptible to the formation of internal cracks and corner longitudinal cracks owing to low strength at elevated temperatures. The effect of cooling condition on the crack formation has been studied using finite element stress analysis. The formation of these cracks was prevented by increasing the stiffness of solid shell and decreasing the cooling intensity on narrow face just below the mold. The center-line segregation in continuously cast slab has been decreased without causing appreciable white bands by the improvement of electromagnetic stirring. The use of low SiO2 tundish powder was effective to reduce the oxygen content of SUS 430. The ridging of SUS 430 of continuously cast process was reduced to the same value as that of ingot process by the application of electromagnetic stirring. The crack sensitivity of 9% Ni steel was extremely high owing to the low ductility between 600°C and 900°C and large thermal expansion with transformation. The uniform cooling, prevention of reheating, and unbending over 950°C were cleared to be important to avoid the surface transverse cracks and subsurface cracks in the continuous casting of 9% Ni steel.