Rolling bearing

• US 20070151634A1
• Filed: 01/18/2005
• Published: 07/05/2007
• Est. Priority Date: 01/20/2004
• Status: Active Grant

• Current Assignee: NSK Limited
• Original Assignee: NSK Limited
• Inventors: Fujita, Shinji
• Granted Patent: US 8,083,868 B2
• Time in Patent Office: Days
• US Class Current: 148/318
• 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 9/36 for balls; for rollers
• CPC Class Codes: C21D 9/40 for rings; for bearing races
• CPC Class Codes: C22C 38/02 containing silicon
• CPC Class Codes: C22C 38/04 containing manganese
• CPC Class Codes: C22C 38/22 with molybdenum or tungsten
• CPC Class Codes: C22C 38/44 with molybdenum or tungsten
• CPC Class Codes: C22C 38/46 with vanadium
• CPC Class Codes: C23C 8/22 of ferrous surfaces
• CPC Class Codes: C23C 8/34 more than one element being applied in more than one step
• CPC Class Codes: C23C 8/80 After-treatment
• CPC Class Codes: F16C 2204/70 with chromium as the next major constituent
• CPC Class Codes: F16C 2240/18 Stress
• CPC Class Codes: F16C 33/62 Selection of substances
• CPC Class Codes: F16C 33/64 Special methods of manufacture
• CPC Class Codes: Y10S 148/906 Roller bearing element

Abstract

A rolling bearing comprises an outer ring, an inner ring and rolling elements rotatably disposed between the outer and inner rings. At least a member selected from the outer ring, inner ring and rolling elements has C content of 0.2 or more and 0.6 or less wt %, Cr content of 2.5 or more and 7.0 or less wt %, Mn content of 0.5 or more and 2.0 or less wt %, Si content of 0.1 wt % or more and 1.5 or less wt %, and Mo content of 0.5 or more and 3.0 or less wt %. Further, a carburizing or carbo-nitriding treatment, a quenching treatment and a tempering treatment are applied to the selected member. Furthermore, retained austenite on a surface thereof is 15 % or more and 45 % or less vol. %, and the surface hardness thereof is HRC60 or more.

Claims

1. A rolling bearing comprising an outer ring, an inner ring and a plurality of rolling elements disposed between the outer and inner rings in such a manner as to freely roll therebetween, wherein

at least a member selected from the outer ring, inner ring and rolling elements is such that:

the content of C is not less than 0.2 wt %, not more than 0.6 wt %;

the content of Cr is not less than 2.5 wt %, not more than 7.0 wt %;

the content of Mn is not less than 0.5 wt %, not more than 2.0 wt %;

the content of Si is not less than 0.1 wt %, not more than 1.5 wt %;

the content of Mo is not less than 0.5 wt %, not more than 3.0 wt %;

a carburizing or carbo-nitriding treatment, a quenching treatment and a tempering treatment are applied thereto;

the volume of retained austenite on a surface thereof is not less than 15%, not more than 45% by volume ratio; and

the surface hardness is not less than HRC60.

3. The rolling bearing as set forth in claim 1, wherein the selected member is further such that:

the sum of carbon concentration and nitrogen concentration on the surface thereof is not less than 1.0 wt %, not more than 2.5 wt %.

4. The rolling bearing as set forth in claim 3, wherein the selected member is further such that:

the content of V is not more than 2.0 wt %; and

the content of Ni is not more than 2.0 wt %.

5. The rolling bearing as set forth in claim 4, wherein the selected member is further such that:

the residual of a precipitate of at least one of carbide and carbonitride is not less than 15%, not more than 35% by area ration.

6. The rolling bearing as set forth in claim 5, wherein the selected member is further such that:

the precipitate is an Fe—

Cr, Mo system precipitate comprising at least one of double carbonitrides of M₇C₃ type, M₂₃C₆ type, M₇(C, N)₃ and M₂₃(C, N)₆ type.

7. The rolling bearing as set forth in claim 6, wherein the selected member is further such that:

the Fe—

Cr, Mo system precipitate contains 30 wt % or more of Cr and Mo in total.

8. The rolling bearing as set forth in claim 5, wherein the selected member is further such that:

the maximum value of compression residual stress at a surface layer portion thereof is not less than 150 MPa, not more than 2000 MPa.

9. The rolling bearing as set forth in claim 3, wherein the rolling bearing is a needle rolling bearing, and the selected member is at least one of the inner ring and the rolling elements.

10. The rolling bearing as set forth in claim 9, wherein the selected member is further such that:

the average retained austenite volume is not more than 8% by volume ratio.

11. The rolling bearing as set forth in claim 1, wherein the selected member is further such that:

the average retained austenite volume is not more than 2.5 times a sum of the contents of Cr and Mo.

2. A rolling bearing comprising an outer ring, an inner ring and a plurality of rolling elements disposed between the outer and inner rings in such a manner as to freely roll therebetween, wherein

at least a member selected from the outer ring, inner ring and rolling elements is such that:

the content of C is not less than 0.8 wt %, not more than 1.2 wt %;

the content of Cr is not less than 2.0 wt %, not more than 4.0 wt %;

the content of Mn is not less than 0.1 wt %, not more than 2.0 wt %;

the content of Si is not less than 0.5 wt %, not more than 1.5 wt %;

the content of Mo is not less than 0.1 wt %, not more than 2.0 wt %;

a carburizing or carbo-nitriding treatment, a quenching treatment and a tempering treatment are applied thereto;

the volume of retained austenite on a surface thereof is not less than 15%, not more than 45% by volume ratio; and

the surface hardness is not less than HRC60.

12. The rolling bearing as set forth in claim 2, wherein the selected member is further such that:

the average retained austenite volume is not more than 2.5 times a sum of the contents of Cr and Mo.

13. The rolling bearing as set forth in claim 2, wherein the selected member is further such that:

the sum of carbon concentration and nitrogen concentration on the surface thereof is not less than 1.0 wt %, not more than 2.5 wt %.

14. The rolling bearing as set forth in claim 13, wherein the selected member is further such that:

the content of V is not more than 2.0 wt %; and

the content of Ni is not more than 2.0 wt %.

15. The rolling bearing as set forth in claim 14, wherein the selected member is further such that:

the residual of a precipitate of at least one of carbide and carbonitride is not less than 15%, not more than 35% by area ration.

16. The rolling bearing as set forth in claim 15, wherein the selected member is further such that:

the precipitate is an Fe—

Cr, Mo system precipitate comprising at least one of double carbonitrides of M₇C₃ type, M₂₃C₆ type, M₇(C, N)₃ and M₂₃(C, N)₆ type.

17. The rolling bearing as set forth in claim 16, wherein the selected member is further such that:

the Fe—

Cr, Mo system precipitate contains 30 wt % or more of Cr and Mo in total.

18. The rolling bearing as set forth in claim 15, wherein the selected member is further such that:

the maximum value of compression residual stress at a surface layer portion thereof is not less than 150 MPa, not more than 2000 MPa.

19. The rolling bearing as set forth in claim 13, wherein the selected member is at least one of the inner ring and the rolling elements.

20. The rolling bearing as set forth in claim 19, wherein the selected member is further such that:

the average retained austenite volume is not more than 8% by volume ratio.