Patent ID: 8052807

Claim:
A high strength cold-rolled steel sheet excellent in deep drawability, comprising: steel including, by mass, 0.03 to 0.25% C, 0.001 to 3.0% Si, 1.11 to 2.55% Mn, 0.003 to 0.015% P, at most 0.05% S, 0.0005 to 0.03% N, 0.005 to 0.3% Al, and Fe balance and inevitable impurities having an average size of a plurality of ferrite grains of said cold-rolled steel sheet being at least 15 μm, and an average r-value of 1.61 or more and containing at least one of bainite, martensite and austenite by 3 to less than 100%, in volume percentage, in total in the metallographic microstructure of said cold-rolled steel sheet, a balance consisting of ferrite, and wherein the cold rolled sheet has been subjected to hot rolling before cold rolling to produce a hot rolled sheet as intermediate material having a metallographic microstructure wherein the volume percentage of at least one of a bainite phase and a martensite phase is 70% to 100% at least in the region from ¼ to ¾ of the thickness of the steel sheet.