| US 7,413,704 B2 | ||
| Case hardening bearing steel having excellent toughness and rolling contact fatigue life in intermediate temperature | ||
| Akihiro Matsuzaki, Chiyoda-ku (Japan); Takashi Iwamoto, Chiyoda-ku (Japan); Masao Goto, Osaka (Japan); and Katsuhiko Kizawa, Osaka (Japan) | ||
| Assigned to JFE Steel Corporation, (Japan); and Koyo Seiko Co., Ltd., (Japan) | ||
| Appl. No. 10/502,691 PCT Filed Apr. 09, 2003, PCT No. PCT/JP03/04527 § 371(c)(1), (2), (4) Date Jul. 27, 2004, PCT Pub. No. WO03/087421, PCT Pub. Date Oct. 23, 2003. |
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| Claims priority of application No. 2002-116065 (JP), filed on Apr. 18, 2002. | ||
| Prior Publication US 2005/0081962 A1, Apr. 21, 2005 | ||
| Int. Cl. C22C 38/18 (2006.01); C22C 38/22 (2006.01); C22C 38/38 (2006.01); C23C 8/22 (2006.01) | ||
| U.S. Cl. 420—105 [148/319; 148/906] | 4 Claims |
| 1. A case hardening bearing steel having excellent toughness and an excellent rolling contact fatigue life in intermediate
temperature comprising:
C of 0.15 to 0.30 mass percent,
Si of 0.5 to 2.0 mass percent,
Mn of 0.3 to 2.0 mass percent,
Cr of 1.75 to 2.5 mass percent,
Mo of 0.3 to 1.0 mass percent,
and O of not more than 0.0012 mass percent,
in a range where (Si+Mo)≧1.0 mass percent is satisfied, and containing iron and inevitable impurities as remnants; the maximum
size of oxide nonmetallic inclusions is not more than 12.5 μm when an examined area is 320 mm2; the number of the oxide nonmetallic inclusions having a diameter of equivalent circle of 3 μm or more is not more than 250
when the examined area is 320 mm2; and a C density of an outer layer is adjusted in a range from 0.7 to 1.2 mass percent by carburization.
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