SLAB FOR THIN STEEL SHEET WITH FEW DEFECT CAUSED BY INCLUSION, AND MANUFACTURING METHOD THEREFOR

摘要

PROBLEM TO BE SOLVED: To provide a slab for a thin steel sheet which stably reduces number of inclusions, and refines the size of inclusions, and a manufacturing method therefor. SOLUTION: The method for manufacturing the slab for the thin steel sheet, which has few defects caused by the inclusions independently of contents of Mn, Si, and Al which are constrained in the slab for the thin steel sheet, comprises decarburizing a carbon steel containing an appropriate quantity of C, Mn, Si, P, S, Al, Ti, Mg, N, and oxygen, while smelting it, then deoxidizing it with C under atmosphere of reduced pressure to make the concentration of oxygen in the molten steel to be 300 ppm or less, then sequentially adding Ti and Zr or Ti and Ce, of a metallic or alloy state, deoxidizing it, and adding Al as needed.