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1. (WO2017154401) HIGH-STRENGTH STEEL PLATE AND METHOD FOR MANUFACTURING SAME

Pub. No.:    WO/2017/154401    International Application No.:    PCT/JP2017/003154
Publication Date: Fri Sep 15 01:59:59 CEST 2017 International Filing Date: Tue Jan 31 00:59:59 CET 2017
IPC: C22C 38/00
C21D 8/02
C21D 9/46
C22C 38/06
C22C 38/58
Applicants: JFE STEEL CORPORATION
JFEスチール株式会社
Inventors: SHIIMORI Fusae
椎森 芳恵
KANEKO Shinjiro
金子 真次郎
NAGATAKI Yasunobu
長滝 康伸
Title: HIGH-STRENGTH STEEL PLATE AND METHOD FOR MANUFACTURING SAME
Abstract:
Provided are a high-strength steel plate having superior ductility and stretch flangeability and a method for manufacturing the same. This high-strength steel plate is formed from a prescribed component composition and has C/Mn of 0.08 - 0.20 with the balance being iron and inevitable impurities. The structure has, in surface area to total structure, a total of 40 - 70% ferrite and bainitic ferrite, 5 - 35% martensite, with the remainder austenite being 5 - 30%, and furthermore, the proportion of martensite (including the remainder austenite) adjacent to bainitic ferrite being 60% or greater of the total martensite (including the remainder austenite). The proportion of hardness differential for microhardness measured at a measurement interval of 0.5 µm being 4.0 GPa or less is 70% or greater, and the proportion of structure out of the total structure having a microhardness of 8.0 GPa or less is 85% or greater.