HIGH-STRENGTH COLD-ROLLED STEEL SHEET AND PROCESS FOR PRODUCTION THEREOFF

摘要

A high-strength cold-rolled steel sheet comprising (in mass%) 0.10 to 0.40% of C, 0.5 to 4.0% of Mn, 0.005 to 2.5% of Si, 0.005 to 2.5% of Al, 0 to 1.0% of Cr, and iron and unavoidable impurities which make up the remainder, wherein the contents of P, S and N are limited to 0.05% or less, 0.02% or less and 0.006% or less, respectively, 2 to 30% by area of retained austenite, 20% by area or less of martensite and cementite having an average particle diameter of 0.01 to 1 µm inclusive are contained as the steel structures, and cementite particles having an aspect ratio of 1 to 3 inclusive make up 30 to 100% of the cementite.