| 摘要 |
PROBLEM TO BE SOLVED: To provide a high strength cold rolled steel sheet having excellent elongation properties and chemical convertibility while having high strength satisfying a tensile strength of≥440 MPa, and to provide its production method. SOLUTION: The high strength cold rolled steel sheet is obtained by subjecting a steel slab comprising, by mass, 0.15 to 0.20% C,≤0.10% Si, 0.60 to 0.80% Mn,≤0.040% P,≤0.030% S, 0.01 to 0.07% Al and≤0.0150% N to hot rolling in which finish rolling is completed at 880 to 960°C, is coiled at 540 to 660°C, is cold-rolled, so as to be a cold-rolled sheet with a sheet thickness of≥0.8 mm, and is subsequently subjected to continuous annealing at 720 to 820°C, preferably, in an atmosphere of 3 to 8 vol%H<SB>2</SB>+remainder N<SB>2</SB>gas at a temperature of a dew point-40°C, so as to obtain the high strength cold rolled steel sheet. COPYRIGHT: (C)2008,JPO&INPIT
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