Bearing component and rolling bearing

• US 10,107,335 B2
• Filed: 05/28/2014
• Issued: 10/23/2018
• Est. Priority Date: 06/06/2013
• Status: Active Grant

• Current Assignee: NTN Corporation
• Original Assignee: NTN Corporation
• Inventors: Sato, Daisuke, Ohki, Chikara
• Primary Examiner(s): Turner, Archene
• Application Number:
  US14/895,470
• Publication Number:
  US 20160131188A1
• Time in Patent Office: 1,609 Days
• Field of Search: 384492, 428325, 428469, 428698
• CPC Class Codes: C21D 1/06 Surface hardening
• CPC Class Codes: C21D 1/25 Hardening, combined with annealing between 300 degrees Celsius and 600 degrees Celsius, i.e. heat refining ("Vergüten")
• CPC Class Codes: C21D 2211/001 Austenite
• CPC Class Codes: C21D 2211/004 Dispersions; Precipitations
• CPC Class Codes: C21D 9/40 for rings; for bearing races
• CPC Class Codes: C22C 38/00 Ferrous alloys, e.g. steel alloys cast-iron alloys C22C37/00
• CPC Class Codes: C22C 38/001 containing N
• CPC Class Codes: C22C 38/002 containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
• CPC Class Codes: C22C 38/02 containing silicon
• CPC Class Codes: C22C 38/04 containing manganese
• CPC Class Codes: C22C 38/18 containing chromium
• CPC Class Codes: C22C 38/42 with copper
• CPC Class Codes: C22C 38/44 with molybdenum or tungsten
• CPC Class Codes: C23C 8/32 of ferrous surfaces
• CPC Class Codes: C23C 8/80 After-treatment
• CPC Class Codes: F16C 19/06 with a single row or balls
• CPC Class Codes: F16C 19/364 with tapered rollers, i.e. rollers having essentially the shape of a truncated cone
• CPC Class Codes: F16C 33/32 Balls
• CPC Class Codes: F16C 33/366 Tapered rollers, i.e. rollers generally shaped as truncated cones
• CPC Class Codes: F16C 33/62 Selection of substances
• CPC Class Codes: F16C 33/64 : Special methods of manufacture

Abstract

A bearing component composed of steel which contains carbon not less than 0.95 mass % and not more than 1.1 mass %, silicon less than 0.3 mass %, manganese less than 0.5 mass %, sulfur less than 0.008 mass %, and chromium not less than 1.4 mass % and less than 1.6 mass % and is composed of remainder iron and an impurity and having a carbonitrided layer formed at a surface portion including a contact surface is provided. An average concentration of nitrogen in the surface portion is not lower than 0.3 mass % and not higher than 0.6 mass % and variation in nitrogen concentration in the surface portion is not higher than 0.1 mass %. An area ratio of a precipitate in a region where no carbonitrided layer is formed is not higher than 7%.

Claims

1. A bearing component, composed of steel which contains carbon not less than 0.95 mass % and not more than 1.1 mass %, silicon less than 0.3 mass %, manganese less than 0.5 mass %, sulfur less than 0.008 mass %, and chromium not less than 1.4 mass % and less than 1.6 mass % and is composed of remainder iron and an impurity and having a carbonitrided layer formed at a surface portion including a contact surface which is a surface in contact with other components,

an average concentration of nitrogen in said surface portion being not lower than 0.3 mass % and not higher than 0.6 mass % and variation in nitrogen concentration in said surface portion being not higher than 0.1 mass %,

an area ratio of a precipitate in a region where no said carbonitrided layer is formed being not higher than 7%, and

the surface portion being a region extending from the contact surface to a depth of not more than 20 μ

m in a direction of thickness of the bearing component.

2. The bearing component according to claim 1, wherein a hardness in said contact surface is not lower than 700 HV.

3. The bearing component according to claim 1, wherein crystal grains of prior austenite have a grain size number not smaller than No. 9 and not greater than No. 11 defined under JIS.

4. The bearing component according to claim 1, wherein an inclination of nitrogen concentration in a direction of thickness of said bearing component is not less than −

15 (1/m).

5. The bearing component according to claim 1, wherein an average amount of retained austenite at a position at a depth of 0.05 mm from said contact surface is not lower than 25 volume % and not higher than 35 volume %, and variation in amount of retained austenite at the position at the depth of 0.05 mm from said contact surface is not higher than 3 volume %.

6. The bearing component according to claim 1, wherein an average amount of retained austenite as a whole is not higher than 18 volume %.

7. The bearing component according to claim 1, wherein said surface portion includes five or more carbonitrides per 100 μ

m², the carbonitrides each having a diameter not greater than 0.5 μ

m.

8. The bearing component according to claim 1, wherein the nitrogen concentration in a non-ground portion including a non-ground surface which is a surface other than said contact surface is lower than 0.7 mass %.

9. The bearing component according to claim 8, wherein a hardness at a position at a depth of 0.1 mm from said non-ground surface is not lower than 700 HV.

10. The bearing component according to claim 1, wherein after heat treatment in which a heating temperature is set to 500°

C. and a retention time period is set to 1 hour, a Vickers hardness at a position at a depth of 0.4 (mm) from said contact surface is higher by at least 80 HV than a Vickers hardness in the region where no said carbonitrided layer is formed in the direction of thickness of said bearing component.

11. A rolling bearing, comprising the bearing component according to claim 1.