Invention Publication
- Patent Title: BEARING PART AND ROLLING BEARING
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Application No.: US18025379Application Date: 2021-09-16
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Publication No.: US20240035515A1Publication Date: 2024-02-01
- Inventor: Naoki FUJIMURA , Masahiro YAMADA , Chikara OHKI
- Applicant: NTN Corporation
- Applicant Address: JP Osaka
- Assignee: NTN Corporation
- Current Assignee: NTN Corporation
- Current Assignee Address: JP Osaka
- Priority: JP 20159671 2020.09.24 JP 20207596 2020.12.15 JP 21052153 2021.03.25
- International Application: PCT/JP2021/034141 2021.09.16
- Date entered country: 2023-03-08
- Main IPC: F16C33/62
- IPC: F16C33/62 ; F16C19/06 ; C21D9/40 ; C21D1/18 ; C21D1/74 ; C23C8/32

Abstract:
A bearing part (10) is composed of a steel, and has a quench-hardened layer (11) in a surface of the bearing part. The quench-hardened layer includes a plurality of martensite crystal grains. The plurality of martensite crystal grains are classified into a first group and a second group. A minimum value of crystal grain sizes of the martensite crystal grains belonging to the first group is larger than a maximum value of crystal grain sizes of the martensite crystal grains belonging to the second group. A value obtained by dividing a total area of the martensite crystal grains belonging to the first group by the total area of the plurality of martensite crystal grains is more than or equal to 0.3. A value obtained by dividing, by the total area of the plurality of martensite crystal grains, a total area of the martensite crystal grains belonging to the first group except for a martensite crystal grain that has a minimum crystal grain size and that belongs to the first group is less than 0.3. An average grain size of the martensite crystal grains belonging to the first group is less than or equal to 1.5 μm. The quench-hardened layer (11) further includes a plurality of cementite grains. A number density of cementite grains each having a grain size of more than or equal to 1 μm is more than or equal to 0.025/μm2.
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