| 摘要 |
PROBLEM TO BE SOLVED: To provide a steel sheet which has been difficult to be manufactured in the prior art and has a tensile strength of 590 MPa or higher and superior bendability. SOLUTION: The high-strength steel sheet has a chemical composition including 0.03-0.20% C, 0.005-2.0% Si, 1.2-3.0% Mn, 0.1% or less P, 0.01% or less S, 0.003-1.0% sol. Al, 0.01% or less N, 0.0001-0.05% Bi, and the balance Fe with impurities, and has a steel structure containing 2.0-20 area% of retained austenite. In (1/20) deep position of the sheet thickness from the surface of the steel sheet, the average space between Mn-concentrated parts which have been extended in the rolling direction is 300μm or less in the direction orthogonal to the rolling direction. COPYRIGHT: (C)2010,JPO&INPIT
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