Patent ID: 8828153

Claim:
A cold-rolled steel sheet characterized by having a structure comprising a main phase which is a ferrite and a secondary phase which is a low temperature transformation product including a martensite, with the hardness distribution of the ferrite phase in an arbitrary cross section having a length of 10 mm in the widthwise direction of the sheet satisfying the following Equation (1): Hv (max) −Hv (ave) <0.4×Hv (ave) (1) wherein Hv (max) is the maximum Vickers hardness of ferrite grains in a region where the distance from the surface in the depth direction is at least (⅛)t and at most (¼)t when the thickness of the cold-rolled steel sheet is t, and Hv (ave) is the average Vickers hardness of ferrite grains in this region, wherein the high-strength cold-rolled steel sheet has a steel composition consisting of, in mass percent, C: at least 0.0025% and at most 0.029%, Si: at most 0.5%, Mn: at least 0.5% and at most 2.5%, P: at most 0.05%, S: at most 0.01%, sol. Al: at most 0.15%, N: less than 0.008%, Cr: at least 0.02% and at most 2.0%, and a remainder of Fe and impurities and a yield strength of the cold rolled sheet in a direction perpendicular to a rolling direction is 300 MPa or less.