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|1. (WO2013161231) HIGH-STRENGTH STEEL SHEET AND PROCESS FOR PRODUCING SAME|
|Applicants:||JFE STEEL CORPORATION
|Title:||HIGH-STRENGTH STEEL SHEET AND PROCESS FOR PRODUCING SAME|
Provided are a high-strength steel sheet having excellent shape fixability and a process for producing the steel sheet. The high-strength steel sheet has a composition containing, in terms of mass%, 0.08-0.20% C, up to 0.3% Si, 0.1-3.0% Mn, up to 0.10% P, up to 0.030% S, up to 0.10% Al, up to 0.010% N, and 0.20-0.80% V, with the remainder comprising Fe and unavoidable impurities, and has a structure which comprises 95% or more ferrite phase in terms of areal proportion and in which fine grains have been precipitated. The fine grains have been dispersedly precipitated so that precipitate grains having a grain diameter less than 10 nm are present at a population density of 1.0×105 grains/µm3 or higher and so as to result in a distribution in which the standard deviation of the natural logarithms of the grain diameters of the precipitate grains having a grain diameter less than 10 nm is 1.5 or less. Thus, a high-strength steel sheet combining high strength with shape fixability is stably obtained, the steel sheet having such a high strength that the yield strength YP is 1,000 MPa or higher and having a structure in which a large number of fine grains having a grain diameter less than 10 nm have been precipitated so as to form a narrow size distribution.