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1. (WO2018179387) HOT-ROLLED STEEL SHEET

Pub. No.:    WO/2018/179387    International Application No.:    PCT/JP2017/013743
Publication Date: Fri Oct 05 01:59:59 CEST 2018 International Filing Date: Sat Apr 01 01:59:59 CEST 2017
IPC: C22C 38/00
C22C 38/58
C21D 9/46
Applicants: NIPPON STEEL & SUMITOMO METAL CORPORATION
新日鐵住金株式会社
Inventors: YOKOI, Tatsuo
横井 龍雄
YOSHIKAWA, Nobuo
吉川 伸麻
YONEMURA, Shigeru
米村 繁
OOTSUKA, Kazuya
大塚 和也
Title: HOT-ROLLED STEEL SHEET
Abstract:
A hot-rolled steel sheet, wherein: the chemical composition, in mass%, is C: 0.07-0.22%, Si: 1.00-3.20%, Mn:0.80-2.20%, Al: 0.010-1.000%, N≤0.0060%, P≤0.050%, S≤0.005%, Ti: 0-0.150%, Nb: 0-0.100%, V: 0-0.300%, Cu: 0-2.00%, Ni: 0-2.00%, Cr: 0-2.00%, Mo: 0-1.00%, B: 0-0.0100%, Mg: 0-0.0100%, Ca: 0-0.0100%, REM: 0-0.1000%, Zr: 0-1.000%, Co: 0-1.000%, Zn: 0-1.000%, W: 0-1.000%, Sn: 0-0.050%, balance: Fe and impurities; the metal structure located at 1/4W or 3/4W from the edge face of the steel sheet and 1/4t or 3/4t from the surface is, in area%, retained austenite: greater than 2% to 10%, martensite≤2%, bainite: 10-70%, pearlite≤2%, balance: ferrite; the mean equivalent circular diameter of the metal phases made of retained austenite/martensite is 1.0-5.0 µm; the mean value for the shortest distance between adjacent metal phases is at least 3 µm; and the standard deviation for nano-hardness is 2.5 GPa or less.