| 摘要 |
PROBLEM TO BE SOLVED: To obtain a cast slab having little defect caused by inclusions by making a specific number or lower of pieces of the inclusions having a specific size or larger among oxide base inclusions in a cast slab and a specific number or lower of pieces of alumina cluster inclusion among these inclusions with respect to a carbon steel having a specific composition. SOLUTION: Relating to the carbon steel composed, by wt.%, of 0.001-0.2 C, 0.01-0.5 Mn, 0.001-0.5 Si, 0.001-0.3 P, 0.0005-0.05 S, >0.006 to 0.1 Al, 0.005-0.06 Ti, 0.0005-0.01 Mg, 0.0005-0.01 N, 0.0005-0.0050 oxygen and the balance iron with inevitable impurities, the pieces of the inclusions having >=53μm among the oxide base inclusions in the cast slab are <=200 pieces/kg and therein, the pieces of the alumina cluster inclusions are regulated to <=20 pieces/kg. Desirably, the carbon steel contains, by wt.%, one or more elements among 0.001-0.10 Nb, 0.005-0.20 V, 0.01-0.50 Cr, 0.01-0.50 Mo, 0.01-0.50 Cu, 0.01-0.50 Ni and 0.0002-0.0020 B.
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