| 摘要 |
PROBLEM TO BE SOLVED: To provide a high-tensile-strength cold-rolled steel sheet which shows superior shapeability, shows superior formability for an extension flange and has a tensile strength of 980 MPa or higher, and to provide a manufacturing method therefor. SOLUTION: The high-tensile-strength cold-rolled steel sheet is manufactured by the steps of: preparing a base steel material which has a component composition composed of, by mass%, 0.04% to 0.20% of C, 2.5% or less of Si, 1.0% to 3.0% of Mn, 0.1% or less of P, 0.03% or less of S, 0.01% to 0.10% of Sol.Al and the balance Fe with unavoidable impurities; hot-rolling the material; cold-rolling the steel plate; annealing the steel sheet at an Ac<SB>1</SB>transformation temperature or higher, rapidly cooling the steel sheet from a temperature range between 650°C and 750°C at an average cooling rate of 400°C/sec or higher, and subsequently subjecting the steel sheet to tempering treatment which holds the sheet in a temperature range between 100°C and 450°C for 100 to 1,200 sec, through a continuous annealing process; and temper-rolling the steel sheet so that the steel sheet has a surface roughness of 1.4μm or more by arithmetic mean roughness Ra. COPYRIGHT: (C)2009,JPO&INPIT
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