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CN-116249792-B - Bearing component and rolling bearing

CN116249792BCN 116249792 BCN116249792 BCN 116249792BCN-116249792-B

Abstract

The bearing member (10) is made of steel and has a quench-hardened layer (11) on the surface thereof. The quench-hardened layer includes a plurality of martensite grains. The martensite grains are divided into group 1 and group 2. The minimum value of the crystal grain size of the martensitic crystal grain belonging to group 1 is larger than the maximum value of the martensitic crystal grain belonging to group 2. The total area of the martensite grains belonging to group 1 divided by the total area of the martensite grains is 0.3 or more. The value obtained by dividing the total area of the martensitic grains belonging to group 1 after removing the martensitic grains having the smallest grain size belonging to group 1 by the total area of the martensitic grains is less than 0.3. The average grain size of the martensitic grains belonging to group 1 is 1.5 μm or less. The quench-hardened layer (11) further contains a plurality of cementite grains. The cementite grains having a grain diameter of 1 μm or more have a number density of 0.025 grains/μm 2 or more.

Inventors

  • FUJIMURA NAOHIRO
  • YAMADA MASAHIRO
  • DA MULI

Assignees

  • NTN株式会社

Dates

Publication Date
20260505
Application Date
20210916
Priority Date
20200924

Claims (6)

  1. 1.A bearing component, which comprises a bearing body, Which is a bearing member composed of steel and having a quench-hardened layer on the surface thereof, The quench-hardened layer comprises a plurality of martensite grains, The total area ratio of the martensite grains in the quench-hardening layer is more than 70%, The martensite grains are divided into group 1 and group 2, The minimum value of the crystal grain size of the martensitic grains belonging to the 1 st group is larger than the maximum value of the martensitic grains belonging to the 2 nd group, The total area of the martensite grains belonging to group 1 divided by the total area of the martensite grains is 0.3 or more, The value obtained by dividing the total area of the martensitic grains belonging to group 1 after removing the martensitic grains having the smallest grain size belonging to group 1 by the total area of the martensitic grains is less than 0.3, The average grain size of the martensitic grains belonging to group 1 is 1.4 μm or less, The quench-hardened layer further comprises a plurality of cementite grains, The cementite grains having a grain diameter of 1 μm or more have a number density of 0.040 grains/μm 2 or more, The average aspect ratio of the martensitic grains to which group 1 belongs is 3.1 or less.
  2. 2. The bearing component according to claim 1, wherein, The quench-hardened layer contains nitrogen, The average nitrogen concentration of the quench-hardened layer between the surface and a position spaced from the surface by a distance of 10 [ mu ] m is 0.15 mass% or more.
  3. 3. The bearing component according to claim 1 or claim 2, wherein the retained austenite amount of the surface is 20% by volume or more.
  4. 4. The bearing component according to claim 1 or claim 2, wherein the quench-hardened layer of the surface has a hardness of 730Hv or more.
  5. 5. The bearing component according to claim 1 or claim 2, wherein the steel is high carbon chromium bearing steel SUJ2 specified according to JIS standard.
  6. 6. A rolling bearing, which comprises a bearing body, Which comprises an outer ring, an inner ring and rolling bodies, At least 1 of the outer ring, the inner ring, and the rolling element is the bearing member according to any one of claims 1 to 5.

Description

Bearing component and rolling bearing Technical Field The present invention relates to a bearing member and a rolling bearing. Background In recent years, as the fuel consumption of vehicles and the like is reduced, the use environment of the bearing is becoming severe, and there is a need for a bearing excellent in abrasion resistance and pressure mark formation. For improvement of wear resistance, miniaturization of martensite grains is effective (see japanese patent application laid-open No. 2019-108576). This is because, as the martensite grains are finer, the plastic deformation resistance of the martensite phase increases, and the interface of the martensite grains is further improved to promote the gas adsorption on the wear surface, thereby suppressing the serious wear. On the other hand, the miniaturization of the martensite grains is also effective for the improvement of the pressure mark formation property (refer to japanese patent No. 6626918). This is because the indentation formation resistance increases with an increase in the plastic deformation resistance of the martensite phase as described above. As a technique for refining martensite grains, japanese patent No. 6626918 describes a technique of quenching at a lower temperature than nitriding quenching after nitriding quenching (low-temperature secondary quenching). Prior art literature Patent literature Patent document 1 Japanese patent laid-open publication No. 2019-108576 Patent document 2 Japanese patent application laid-open No. 6626918 Disclosure of Invention Technical problem to be solved by the invention However, the present inventors have found that even in the technique of performing the low-temperature secondary quenching after nitriding quenching, there is room for improvement from the viewpoint of the refinement of the martensite grains. The main object of the present invention is to provide a bearing member and a rolling bearing having high abrasion resistance and high resistance to formation of pressure marks. Technical proposal adopted for solving the technical problems The bearing member of the present invention is composed of steel, and has a quench-hardened layer on the surface. The quench-hardened layer includes a plurality of martensite grains. The total area ratio of martensite grains in the quench-hardening layer is 70% or more. The martensite grains are divided into group 1 and group 2. The minimum value of the crystal grain size of the martensitic crystal grain belonging to group 1 is larger than the maximum value of the martensitic crystal grain belonging to group 2. The total area of the martensite grains belonging to group 1 divided by the total area of the martensite grains is 0.3 or more. The value obtained by dividing the total area of the martensitic grains belonging to group 1 after removing the martensitic grains having the smallest grain size belonging to group 1 by the total area of the martensitic grains is less than 0.3. The average grain size of the martensitic grains belonging to group 1 is 1.5 μm or less. The quench-hardened layer further includes a plurality of cementite grains. The cementite grains having a grain diameter of 1 μm or more have a number density of 0.025 grains/μm 2 or more. In the bearing member of the present invention, the average aspect ratio of the martensitic grains to which group 1 belongs may be 3.1 or less. In the bearing member of the present invention, the retained austenite amount of the surface may be 20% by volume or more. In the bearing member of the present invention, the quench-hardened layer may contain nitrogen. The average nitrogen concentration of the quench-hardened layer between the surface and the position at a distance of 10 μm from the surface may be 0.15 mass% or more. In the bearing member of the present invention, the hardness of the quench-hardened layer on the surface may be 730Hv or more. In the bearing member of the present invention, the steel may be high carbon chromium bearing steel SUJ2 specified according to JIS standard. The method for producing a bearing member comprises a step of preparing a molded body of a high-carbon chromium bearing steel, a carburizing and nitriding step of heating the molded body in a carburizing and nitriding atmosphere to a1 st temperature which is equal to or higher than the A 1 transformation point of the steel and then cooling the molded body to a temperature which is equal to or lower than the Ms transformation point of the steel, a1 st tempering step of holding the molded body at a2 nd temperature which is equal to or higher than 180 degrees and smaller than the A 1 transformation point after the carburizing and nitriding step, a quenching step of reheating the molded body to A3 rd temperature which is equal to or higher than the A 1 transformation point and smaller than the 1 st temperature and then cooling the molded body to a temperature which is equal to or lower than the Ms transformation point of the steel,