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1. (WO2018078844) METHOD FOR PRODUCING STEEL MEMBER, AND STEEL MEMBER

Pub. No.:    WO/2018/078844    International Application No.:    PCT/JP2016/082222
Publication Date: Fri May 04 01:59:59 CEST 2018 International Filing Date: Tue Nov 01 00:59:59 CET 2016
IPC: C21D 9/00
B21D 22/20
C21D 1/18
C22C 38/00
C22C 38/38
C23C 8/22
C23C 8/32
Applicants: NIPPON STEEL & SUMITOMO METAL CORPORATION
新日鐵住金株式会社
Inventors: OKAMOTO, Riki
岡本 力
KOJIMA, Nobusato
小嶋 啓達
HIKIDA, Kazuo
匹田 和夫
MAEKAWA, Noriyuki
前川 紀之
Title: METHOD FOR PRODUCING STEEL MEMBER, AND STEEL MEMBER
Abstract:
This method for producing a steel member includes: a step for heating, in a carburizing atmosphere, a steel sheet so as to form a carburizing layer on the surface of the steel sheet, the steel sheet having a chemical composition containing, in terms of mass%, 0.0005-0.1% of C, 0.01-2.0% of Si, 0.05-3.0% of Mn, 0.9% or less of Al, 0.05% or less of P, 0.01% or less of S, 0.0-0.2% of Ti, 0.0-0.1% of Nb, 0-2% of Cr, 0.0-0.2% of Mo and 0.000-0.005% of B, with the remainder being Fe and impurities, and the steel sheet having a steel structure in which the areal proportion of ferrite is 70% or more; and a step for molding the steel sheet in a metal mold and subjecting the steel sheet to quenching while still housed in the metal mold so as to transform the carburizing layer into martensite and obtain a steel structure in which the areal proportion of ferrite is 50% or more in that part of the steel sheet that is further to the inside than the carburizing layer.