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1. (WO2013161231) HIGH-STRENGTH STEEL SHEET AND PROCESS FOR PRODUCING SAME

Pub. No.:    WO/2013/161231    International Application No.:    PCT/JP2013/002638
Publication Date: Fri Nov 01 00:59:59 CET 2013 International Filing Date: Fri Apr 19 01:59:59 CEST 2013
IPC: C22C 38/00
B21B 3/00
C21D 9/46
C22C 38/12
C22C 38/60
Applicants: JFE STEEL CORPORATION
JFEスチール株式会社
Inventors: KIZU, Taro
木津 太郎
FUNAKAWA, Yoshimasa
船川 義正
OOKUBO, Hidekazu
大久保 英和
KANEMURA, Tokunori
金村 篤謙
SHIGEMI, Masato
重見 將人
KASAI, Shoji
笠井 勝司
YAMAZAKI, Shinji
山崎 伸次
YASUFUKU, Yusuke
安福 悠祐
Title: HIGH-STRENGTH STEEL SHEET AND PROCESS FOR PRODUCING SAME
Abstract:
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.