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1. (WO2018043473) HIGH-STRENGTH STEEL PLATE AND PRODUCTION METHOD THEREOF

Pub. No.:    WO/2018/043473    International Application No.:    PCT/JP2017/030893
Publication Date: Fri Mar 09 00:59:59 CET 2018 International Filing Date: Wed Aug 30 01:59:59 CEST 2017
IPC: C22C 38/00
C21D 9/46
C22C 38/04
C22C 38/60
Applicants: JFE STEEL CORPORATION
JFEスチール株式会社
Inventors: MINAMI Hidekazu
南 秀和
KANEKO Shinjiro
金子 真次郎
Title: HIGH-STRENGTH STEEL PLATE AND PRODUCTION METHOD THEREOF
Abstract:
A high-strength steel plate is provided which has a 780 MPa or higher TS, which has excellent stretch flangeability as well as ductility, and which further has excellent in-plane anisotropy of TS. The component composition contains, in mass%, C: 0.08-0.35%, Si: 0.50-2.50%, Mn: 1.50-3.00%, P: 0.001-0.100%, S: 0.0001-0.0200%, and N: 0.0005-0.0100%, the remainder being Fe and unavoidable impurities; the steel composition comprises, by area percent, 20-50% ferrite, 5-45% upper bainite and 1-20% martensite, and, by volume percent, 5% or more retained austenite; the average crystal grain diameter of the retained austenite is less than or equal to 2 μm; and further, the aggregate composition of the steel plate is a microstructure in which the inverse strength ratio of γ-fibers to α-fibers is less than or equal to 3.0.