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1. (WO2018047955) CASE-HARDENED STEEL, METHOD FOR PRODUCING SAME, AND METHOD FOR MANUFACTURING GEAR PART

Pub. No.:    WO/2018/047955    International Application No.:    PCT/JP2017/032544
Publication Date: Fri Mar 16 00:59:59 CET 2018 International Filing Date: Sat Sep 09 01:59:59 CEST 2017
IPC: C22C 38/00
C21D 1/06
C21D 8/06
C21D 9/32
C22C 38/60
Applicants: JFE STEEL CORPORATION
JFEスチール株式会社
Inventors: ANDO Keisuke
安藤 佳祐
IWAMOTO Takashi
岩本 隆
NISHIMURA Kimihiro
西村 公宏
ICHIMIYA Katsuyuki
一宮 克行
Title: CASE-HARDENED STEEL, METHOD FOR PRODUCING SAME, AND METHOD FOR MANUFACTURING GEAR PART
Abstract:
Provided are: a case-hardened steel suitable as a material for manufacturing a mechanical structural part having high rotary bending fatigue strength and impact fatigue strength at relatively low cost; and a method for producing the case-hardened steel. The case-hardened steel contains C, Si, Mn, P, S, Cr, Mo, B, Ti, N, and O in mass% determined by predetermined relationships, contains at least a predetermined amount of Al in relation to the amounts of B, N, and Ti, and contains the remainder comprising Fe and inevitable impurities. Moreover, √I≤80 is satisfied (where I represents the area (μm2) of oxide-based inclusions located at the center of the fisheye in the fractured surface following a rotary bending fatigue test conducted after subjecting the case-hardened steel to carburizing quenching and tempering).