| 摘要 |
PROBLEM TO BE SOLVED: To provide a high strength cold rolled steel sheet which has a tensile strength of≥980 MPa, satisfies both of an elongation of≥12% and a stretch-flanging property of≥100%, and has excellent formability. SOLUTION: The high strength cold rolled steel sheet has a componential composition comprising, by mass, 0.03 to 0.30% C,≤3.0% (including 0%) Si, 0.5 to 5.0% Mn,≤0.1% P,≤0.005% S,≤0.01% N and 0.01 to 1.00% Al, and the balance iron with inevitable impurities, and has a structure composed of, by area ratio, 10 to 80% ferrite, and in which the total of martensite and retained austenite is <5% (including 0%), and the balance tempered martensite having a hardness of 320 to 450 Hv, and in which the ratio of the total area of the ferrite whose crystal orientation difference with the adjacent tempered martensite to the total area of the whole ferrite observed in the visual field of 50μm×50μm is≤5°is≥30%. COPYRIGHT: (C)2011,JPO&INPIT |
