| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a high-strength thin steel plate which is so high so as to be not lower than 1,180 MPa in tensile strength even if its plate thickness is not larger than 1.6 mm, satisfies a Young's modulus of 230 GPa or larger in a rolling perpendicular direction, and is excellent in rigidity. <P>SOLUTION: The high-strength steel plate contains, by mass, C: 0.12 to 0.20%, Si: 0.5 to 1.5%, Mn: 1.0 to 3.0%, P: 0.05% or lower, S: 0.01% or lower, Al: 0.5% or lower, N: 0.01% or lower and T: 0.02 to 0.20%, and satisfies a relationship indicated in the following formulae (1), (2). A remaining part of the steel has a composition composed of Fe and inevitable impurities, a ferrite phase is not lower than 50% and a martensite phase is 35 to 45% at area ratio, the total of the ferrite phase and the martensite phase is not smaller than 95%, an average particle diameter of ferrite is not larger than 4.0 μm and an average particle diameter of martensite is not larger than 3.0 μm in organization, the tensile strength (TS) in the rolling perpendicular direction is not lower than 1,180 MPa, the Young's modulus is not smaller than 230 GPa, and rigidity-elongation balance (TS×EL) expressed by a product of the tensile strength (TS) and the whole elongation (EL) is set to be not smaller than 15,000 MPa.%. Formula (1) is 0.11≤[%C]-(12/47.9)×[%Ti<SP POS="POST">*</SP>]≤0.15. Here, formula (2) is Ti<SP POS="POST">*</SP>=[%Ti]-47.9/14×[%N]-(47.9/32.1)×[%S]. [%M] is a content of an M element (mass%). <P>COPYRIGHT: (C)2013,JPO&INPIT |
