Brearing steel excellent in corrosion resistance

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EP 1 420 078 A3

(12)	EUROPEAN PATENT APPLICATION

(88)	Date of publication A3:
	03.05.2006 Bulletin 2006/18

(43)	Date of publication A2:
	19.05.2004 Bulletin 2004/21

(21)	Application number: 03026063.2

(22)	Date of filing: 12.11.2003

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International Patent Classification (IPC):

C23C 8/22^(2006.01)
C22C 38/44^(2006.01)

C23C 8/32^(2006.01)

(84)	Designated Contracting States:
	AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HU IE IT LI LU MC NL PT RO SE SI SK TR
	Designated Extension States:
	AL LT LV MK

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Priority:

12.11.2002 JP 2002328854

(71)	Applicant: Koyo Seiko Co., Ltd.
	Osaka-shi, Osaka 542-0081 (JP)

(72)	Inventors:
	Toshiva, Kinami, Koyo Seiko Co., Ldt. Osaka 542-0081 (JP) Toshimitsu, Kimura, Daido Tokushuko K.K. Aichi (JP) Hisato, Nishisaka, Koyo Seiko Co., Ldt. Osaka 542-0081 (JP) Masao, Goto, Koyo Seiko Co., Ldt. Osaka 542-0081 (JP)

(74)	Representative: Grünecker, Kinkeldey, Stockmair & Schwanhäusser Anwaltssozietät
	Maximilianstrasse 58 80538 München 80538 München (DE)

(54)	Brearing steel excellent in corrosion resistance

(57) Bearing steel containing 0.10 wt% to 0.35 wt% of C, less than 0.5 wt% of Si, 0.3 wt% to 1.5 wt% of Mn, 0.03 wt% or less of P, 0.03 wt% or less of S, 1.0 wt% to 3.5 wt% of Ni, 1.0 wt% to 5.0 wt% of Cr, 0.03 wt% to 2.5 wt% of Mo, 0.005 wt% to 0.050 wt% of Al, 0.003 wt% or less of Ti, 0.0015 wt% or less of O, 0.025 wt% or less of N, and a substantially residual part of Fe, wherein the bearing steel after carburizing or carbonitriding treatment exhibits a surface C concentration of not lower than 0.9 %, contains 15 % by area or less of carbide and contains 0.1 % by area or less of rod-like carbide 10 having an aspect ratio of not lower than 3 in terms of the ratio of major diameter to minor diameter and having a minor diameter of not smaller than 2 µm.

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