Patent ID: 8679265
Filing Date: 2014-03-25
Classification: C21D,C22C

Abstract:
1. A high-strength cold-rolled steel sheet having a componential composition comprising: Fe and unavoidable impurities; C: 0.12-0.30 mass %; Si: 0.1-3.0 mass %; Mn: 0.1-5.0 mass %; P: 0.1 mass % or below; S: 0.005 mass % or below; N: 0.01 mass % or below; and Al: 0.01-1.00 mass %; wherein: the sheet has a structure comprising from 70 to 100%, in terms of area fraction, of tempered martensite having a hardness of 300 to 380 Hv, with a balance being ferrite; and cementite particles in the tempered martensite are dispersed such that: 10 or more cementite particles having equivalent-circle diameters of 0.02 μm or more and less than 0.1 μm are present per one μm three or fewer cementite particles having equivalent-circle diameters of 0.1 μm or above are present per one μm