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1. (WO2018127984) HIGH STRENGTH COLD ROLLED STEEL SHEET AND METHOD FOR MANUFACTURING SAME

Pub. No.:    WO/2018/127984    International Application No.:    PCT/JP2017/015713
Publication Date: Fri Jul 13 01:59:59 CEST 2018 International Filing Date: Thu Apr 20 01:59:59 CEST 2017
IPC: C22C 38/00
C21D 9/46
C22C 38/06
C22C 38/58
Applicants: JFE STEEL CORPORATION
JFEスチール株式会社
Inventors: HIRASHIMA Takuya
平島 拓弥
YOSHITOMI Hiromi
吉冨 裕美
Title: HIGH STRENGTH COLD ROLLED STEEL SHEET AND METHOD FOR MANUFACTURING SAME
Abstract:
Provided are: a high strength cold rolled steel sheet having a high yield ratio and excellent flexibility; and a method for manufacturing the same. The high strength cold rolled steel sheet has a composition containing, in mass%, 0.12-0.25% of C, less than 0.5% of Si, 2.0-3.0% of Mn, at most 0.05% of P, at most 0.005% of S, 0.01-0.10% of Al, and at most 0.010% of N with the remainder comprising Fe and inevitable impurities, and satisfies, by area fraction, 20-90% total of martensite and tempered martensite, at most 10% of ferrite, and 10-80% of bainite, wherein the area fraction of island-shaped martensite in the bainite is 1-10%, and the area fraction of cementite having an average particle size of 1 µm or less in the bainite is 0.1-5.0%.