HIGH-STRENGTH STEEL SHEET AND PROCESS FOR PRODUCING MOLTEN STEEL FOR HIGH-STRENGTH STEEL SHEET

摘要

A high-strength steel sheet includes: 0.03 to 0.20% of C, 0.08 to 1.5% of Si, 0.5 to 3.0% of Mn, 0.05% or less of P, 0.0005% or more of S, 0.008 to 0.20% of acid-soluble Ti, 0.0005 to 0.01 % ofN, more than 0.01% of acid-soluble Al, and 0.001 to 0.04% of one or both of Ce and La in terms of mass%; and the balance including Fe and inevitable impurities. The ratio of (Ce+La)/acid-soluble Al is equal to or more than 0.1 and the ratio of (Ce+La)/S is in the range of 0.4 to 50 in a mass base, and the density of the number of inclusions, having a circle equivalent diameter of 2 µm or less, which are present in the steel sheet is equal to or more than 15/mm 2 .