Bearing shaft and bearing

• US 10,458,461 B2
• Filed: 12/06/2016
• Issued: 10/29/2019
• Est. Priority Date: 12/09/2015
• Status: Active Grant

• Current Assignee: NTN Corporation
• Original Assignee: NTN Corporation
• Inventors: Ohno, Yasunobu
• Primary Examiner(s): Roe, Jessee R
• Application Number:
  US16/060,388
• Publication Number:
  US 20180363694A1
• Time in Patent Office: 1,057 Days
• CPC Class Codes: C21D 1/06 Surface hardening
• CPC Class Codes: C21D 1/18 Hardening C21D1/02 takes precedence; Quenching with or without subsequent tempering quenching devices C21D1/62
• CPC Class Codes: C21D 2211/001 Austenite
• CPC Class Codes: C21D 9/40 for rings; for bearing races
• CPC Class Codes: C23C 8/32 of ferrous surfaces
• CPC Class Codes: F16C 2361/61 Toothed gear systems, e.g. support of pinion shafts
• CPC Class Codes: F16C 3/02 Shafts; Axles
• CPC Class Codes: F16C 33/36 with bearing-surfaces other than cylindrical, e.g. tapered; with grooves in the bearing surfaces
• CPC Class Codes: F16C 33/546 with a M- or W-shaped cross section
• CPC Class Codes: F16C 33/586 outside the space between the races, e.g. end faces or bore of inner ring
• CPC Class Codes: F16C 33/62 Selection of substances
• CPC Class Codes: F16C 33/64 Special methods of manufacture
• CPC Class Codes: F16C 33/6677 from radial inside, e.g. via a passage through the shaft and/or inner ring

Abstract

The present invention relates to a bearing shaft provided with an outer peripheral surface that includes a raceway surface (side surface) on which a rolling element rolls. The bearing shaft is made of steel containing carbon of 0.7% or more. The raceway surface is forming with a nitrogen-enriched layer. The absolute value of compressive residual stress in the surface of the nitrogen-enriched layer (i.e., the surface of a hardened layer which is formed on the side surface of the bearing shaft by shot peening) is 600 MPa or more and 1700 MPa or less. Thereby, it is possible for the present invention to prolong the operation life of a bearing.

Claims

1. A bearing shaft provided with an outer peripheral surface that includes a raceway surface on which a rolling element rolls,

the bearing shaft being made of steel containing carbon of 0.7% by mass or more,

the raceway surface being formed with a nitrogen-enriched layer, and

the absolute value of compressive residual stress in the surface of the nitrogen-enriched layer being 600 MPa or more and 1700 MPa or less.

2. The bearing shaft according to claim 1, wherein the surface hardness of the nitrogen-enriched layer is 850 Hv or more and 1000 Hv or less.

3. The bearing shaft according to claim 1, wherein the surface roughness of the nitrogen-enriched layer is 0.2 μ

m or less when calculated as arithmetic average roughness Ra.

4. The bearing shaft according to claim 1, wherein the amount of residual austenite in an outer portion of the nitrogen-enriched layer is 9% or less by volume.

5. The bearing shaft according to claim 1, wherein the steel is high-carbon chromium bearing steel.

6. A bearing comprising a bearing shaft provided with an outer peripheral surface that includes a raceway surface, and a rolling element that has a surface in contact with the raceway surface,

the bearing shaft being made of steel containing carbon of 0.7% by mass or more,

the raceway surface being formed with a nitrogen-enriched layer,

the absolute value of compressive residual stress in the surface of the nitrogen-enriched layer being 600 MPa or more and 1700 MPa or less, and

the amount of residual austenite in an outer portion of the surface of the rolling element being greater than the amount of residual austenite in an outer portion of the nitrogen-enriched layer formed on the raceway surface of the bearing shaft.

7. The bearing according to claim 6, wherein the surface of the rolling element is formed with a nitrogen-enriched layer.

8. The bearing according to claim 6, wherein the rolling element is a crowned roller.

9. The bearing according to claim 6, wherein the surface hardness of the nitrogen-enriched layer formed on the raceway surface of the bearing shaft is 850 Hv or more and 1000 Hv or less.

10. The bearing according to claim 6, wherein the surface roughness of the nitrogen-enriched layer formed on the raceway surface of the bearing shaft is 0.2 μ

m or less when calculated as arithmetic average roughness Ra.

11. The bearing according to claim 6, wherein the amount of residual austenite in an outer portion of the nitrogen-enriched layer formed on the raceway surface of the bearing shaft is 9% or less by volume.

12. The bearing according to claim 6, wherein the steel is high-carbon chromium bearing steel.