WO2022230979A1

WO2022230979A1 - Rolling bearing

Info

Publication number: WO2022230979A1
Application number: PCT/JP2022/019295
Authority: WO
Inventors: 悠介山田; 正典上野; 昌弘山田; 美有佐藤; 則暁三輪; 力大木; 直樹中杤; 直太山本
Original assignee: Ntn株式会社
Priority date: 2021-04-30
Filing date: 2022-04-28
Publication date: 2022-11-03

Abstract

Provided is a rolling bearing that exhibits an improved resistance to hydrogen embrittlement. The rolling bearing is provided with a bearing component. The bearing component is made of steel and has a surface layer region, which is the region to a distance of 20 µm from the surface. The steel contains 0.70-1.10 mass% carbon, 0.15-0.35 mass% silicon, 0.30-0.60 mass% manganese, 1.30-1.60 mass% chromium, not more than 0.50 mass% vanadium, and not more than 0.50 mass% molybdenum, with the balance being iron and unavoidable impurities.

Description

rolling bearing

The present invention relates to rolling bearings.

Patent Document 1 (Patent No. 5489111) describes a bearing component. The bearing component described in Patent Document 1 is formed by performing nitriding, quenching, and tempering on a steel member to be processed. The bearing component described in Patent Document 1 has high wear resistance because cementite is dispersed in the steel of the surface layer.

Patent Document 2 (Patent No. 6023422) describes a bearing component. The bearing component described in Patent Document 2 is formed by performing nitriding, quenching, and tempering on a steel member to be processed. In the bearing component described in Patent Document 2, since the amount of retained austenite in the steel of the surface layer is large, the durability against indentation-induced flaking under lubrication mixed with foreign matter is high.

Patent Document 3 (Japanese Patent Application Laid-Open No. 2007-263357) describes a gearbox for a wind power generator. A speed increaser for a wind power generator described in Patent Document 3 includes a planetary gear device. In a planetary gear device, planetary gears are rotatably supported by planetary shafts via bearings.

Japanese Patent No. 5489111 Japanese Patent No. 6023422 JP 2007-263357 A

As a result of extensive studies by the present inventors, the bearing components described in Patent Document 1 and Patent Document 2 have room for further improvement in durability. In particular, when the rolling bearing using the bearing component described in Patent Document 1 and the bearing component described in Patent Document 2 is applied to the gearbox for a wind power generator described in Patent Document 3, the oil film is likely to run out. There is room for improvement in durability when used under conditions. Specifically, a rolling bearing used in a gearbox for a wind power generator is required to have a design life of 20 years or more. Therefore, as the rolling bearing, a bearing having a large rolling element size is used in order to increase the load capacity. On the other hand, in wind power generators, the power generation torque fluctuates depending on weather conditions, and the load applied to the rolling bearings also fluctuates. At this time, the load applied to the rolling bearing may be less than the minimum required load for the rolling elements to roll. At this time, slippage may occur between the rolling elements and the raceway surface in the rolling bearing. Due to the slippage, oil film breakage may occur between the rolling elements and the raceway surface, resulting in metal-to-metal contact. As a result, new surfaces are generated on the rolling elements or raceway surfaces. When hydrogen penetrates into the inside of the steel material that constitutes the rolling element or the like from such a new surface, premature flaking due to hydrogen embrittlement is likely to occur.

In addition, in this application, cylindrical roller bearings that support the planetary gears and cylindrical roller bearings that support the output shaft are mainly used in the gearbox. Cylindrical roller bearings that support planetary gears may be relatively prone to slippage due to skew and uneven contact of rolling elements due to deformation. In addition, since cylindrical roller bearings that support output shafts that rotate at high speeds are used at high speeds, they are unable to follow rotational speed and torque fluctuations (bearing load). In some cases, slip occurs and wear is accelerated, creating conditions that facilitate hydrogen embrittlement flaking.

In the case of wind power generation, depending on the wind conditions, it may stop without rotating for a long time. In this case, the supply of oil to the bearing is stopped, leaving almost no lubricating oil in the bearing. Such a bearing, which has been at rest for a long time and is almost depleted of lubrication, will suddenly rotate due to a change in wind conditions. As a result, poor lubrication may lead to metal contact, making hydrogen embrittlement more likely to occur.

Hydrogen embrittlement flaking caused by slippage and lubrication of the raceway surface and rolling elements described above is extremely difficult to predict at the design stage of wind turbine equipment, equipment, and bearings used in them. measures are also difficult. On the other hand, there is also a need to improve the resistance to hydrogen embrittlement and improve the reliability of wind power generation equipment, and this is sometimes addressed by applying surface treatment to bearings.

The present invention improves durability against hydrogen embrittlement.

The rolling bearing of the present invention includes bearing components. The bearing component is made of steel and has a surface layer which is an area up to 20 μm away from the surface. The steel contains 0.70 to 1.10 mass percent carbon, 0.15 to 0.35 mass percent silicon, and 0.30 to 0.60 mass percent manganese. , 1.30 mass percent or more and 1.60 mass percent or less of chromium, 0.50 mass percent or less of vanadium, and 0.50 mass percent or less of molybdenum, and the balance being iron and unavoidable impurities. The surface layer steel has martensite block grains and precipitates. The precipitates are nitrides based on chromium or vanadium or carbonitrides based on chromium or vanadium. In the steel of the surface layer portion, the average grain size of martensite block grains with a comparative area ratio of 30% is 2.0 μm or less.

In the above rolling bearing, the bearing component may include an inner ring, an outer ring, and rolling elements. The rolling bearing may support a component of a wind turbine gearbox. That is, a rolling bearing according to a first aspect of the present invention includes an inner ring, an outer ring, and rolling elements. The rolling bearing supports the components of the gearbox for the wind power generator. At least one of the inner ring, the outer ring and the rolling elements is made of steel and has a surface layer portion which is a region with a distance of up to 20 μm from the surface. The steel contains 0.70 to 1.10 mass percent carbon, 0.15 to 0.35 mass percent silicon, and 0.30 to 0.60 mass percent manganese. , 1.30 mass percent or more and 1.60 mass percent or less of chromium, 0.50 mass percent or less of vanadium, and 0.50 mass percent or less of molybdenum, and the balance being iron and unavoidable impurities. The surface layer steel has martensite block grains and precipitates. The precipitates are nitrides based on chromium or vanadium or carbonitrides based on chromium or vanadium. In the steel of the surface layer portion, the average grain size of martensite block grains with a comparative area ratio of 30% is 2.0 μm or less.

The above rolling bearing may be used under conditions where the ratio of equivalent load to static load rating is 0.04% or less. The rolling bearing may be used under the condition that the oil film parameter is 0.5 or more and 10 or less.

The rolling bearings may be various rolling bearings such as ball bearings including tapered roller bearings, self-aligning roller bearings, deep groove ball bearings, four-point contact ball bearings, and the like. The surface of the rolling bearing may be subjected to nitriding treatment.

In the above rolling bearing, the bearing component may include at least one of an inner member, an outer member, and rolling elements. Rolling bearings may be used in transmissions. That is, a rolling bearing according to a second aspect of the present invention includes at least one of an inner member, an outer member, and rolling elements, and is used in a transmission. At least one of the inner member, the outer member, and the rolling elements is made of steel and has a surface layer portion that is a region with a distance of up to 20 μm from the surface. The steel contains 0.70 to 1.10 mass percent carbon, 0.15 to 0.35 mass percent silicon, and 0.30 to 0.60 mass percent manganese. , 1.30 mass percent or more and 1.60 mass percent or less of chromium, 0.50 mass percent or less of vanadium, and 0.50 mass percent or less of molybdenum, and the balance is iron and unavoidable impurities. The surface layer steel has martensite block grains and precipitates. The precipitates are nitrides based on chromium or vanadium or carbonitrides based on chromium or vanadium. In the steel of the surface layer portion, the average grain size of martensite block grains with a comparative area ratio of 30% is 2.0 μm or less.

In the above rolling bearing, the bearing component may include rolling elements and at least one of the inner member and the outer member. That is, the rolling bearing may include rolling elements and at least one of the inner member and the outer member. A combined roughness of the rolling surface of the rolling element and the raceway surface of the inner member or the raceway surface of the outer member may be 0.06 μm or more.

In the above rolling bearing, the bearing component may include an inner ring, an outer ring, and rolling elements. Rolling bearings may be used in transmissions. That is, a rolling bearing according to a third aspect of the present invention includes an inner ring, an outer ring, and rolling elements, and is used in a transmission. At least one of the inner ring, the outer ring and the rolling elements is made of steel and has a surface layer portion which is a region with a distance of up to 20 μm from the surface. The steel contains 0.70 to 1.10 mass percent carbon, 0.15 to 0.35 mass percent silicon, and 0.30 to 0.60 mass percent manganese. , 1.30 mass percent or more and 1.60 mass percent or less of chromium, 0.50 mass percent or less of vanadium, and 0.50 mass percent or less of molybdenum, and the balance is iron and unavoidable impurities. The surface layer steel has martensite block grains and precipitates. The precipitates are nitrides based on chromium or vanadium or carbonitrides based on chromium or vanadium. In the steel of the surface layer portion, the average grain size of martensite block grains with a comparative area ratio of 30% is 2.0 μm or less.

In the above rolling bearing, the combined roughness of the rolling surface of the rolling element and the raceway surface of the inner ring or the raceway surface of the outer ring may be 0.06 μm or more.

In the above rolling bearing, the bearing component may include an inner ring, an outer ring, and rolling elements. A rolling bearing may be mounted in a mechanical structure in which the inner ring is rotated in opposite directions relative to the outer ring, or in which the inner ring is rotated relative to the outer ring from rest. That is, the rolling bearing according to the fourth aspect of the present invention includes an inner ring, an outer ring, and rolling elements. Rolling bearings are mounted in mechanical structures in which the inner ring is rotated in opposite directions relative to the outer ring, or in which the inner ring is rotated relative to the outer ring from rest. At least one of the inner ring, the outer ring and the rolling elements is made of steel and has a surface layer portion which is a region with a distance of up to 20 μm from the surface. The steel contains 0.70 to 1.10 mass percent carbon, 0.15 to 0.35 mass percent silicon, and 0.30 to 0.60 mass percent manganese. , 1.30 mass percent or more and 1.60 mass percent or less of chromium, 0.50 mass percent or less of vanadium, and 0.50 mass percent or less of molybdenum, and the balance being iron and unavoidable impurities. The surface layer steel has martensite block grains and precipitates. The precipitates are nitrides based on chromium or vanadium or carbonitrides based on chromium or vanadium. In the steel of the surface layer portion, the average grain size of martensite block grains with a comparative area ratio of 30% is 2.0 μm or less.

The above rolling bearing may be used under conditions where the oil film parameter is less than 1.2. The rolling bearing may be used under the condition that the dn value is 200,000 or less.

The rolling bearing may be a tapered roller bearing. The rolling bearing may be a self-aligning roller bearing. A diamond-like carbon coating or an iron oxide coating may be formed on the surface of the rolling bearing.

In the rolling bearing, the steel contains 0.90 mass percent or more and 1.10 mass percent or less of carbon, 0.20 mass percent or more and 0.30 mass percent or less of silicon, and 0.40 mass percent or more and 0.50 mass percent. 1.40 to 1.60 mass percent chromium, 0.20 to 0.30 mass percent vanadium, and 0.10 to 0.30 mass percent of molybdenum, and the balance may be iron and unavoidable impurities.

In the above rolling bearing, the area ratio of precipitates in the steel of the surface layer portion may be 2.0% or more.

In the rolling bearing, the maximum grain size of precipitates in the steel of the surface layer may be 0.5 μm or less.

In the rolling bearing, the surface steel may further contain cementite. The maximum grain size of cementite in the steel of the surface layer portion may be 1.5 μm or less.

In the rolling bearing, the nitrogen concentration in the steel of the surface layer may be 0.15% by mass or more.

In the above rolling bearing, the volume ratio of retained austenite in the steel may be 15% or more at a position where the distance from the surface is 50 μm.

　In the above rolling bearing, the steel may have a hardness of 58 HRC or more at a position where the distance from the surface is 50 µm.

In the above rolling bearing, the volume ratio of retained austenite in the steel may be 25% or more and 35% or less at a position where the distance from the surface is 50 μm. The hardness of the steel may be 58 HRC or more and 64 HRC or less at the position where the distance from the surface is 50 μm.

According to the rolling bearing of the present invention, durability against hydrogen embrittlement can be improved.

3 is a cross-sectional view of an inner ring 10; FIG. It is an enlarged view in II in FIG. 4A to 4C are process diagrams showing a method of manufacturing the inner ring 10. FIG. 1 is a cross-sectional view of a rolling bearing 100; FIG. It is a sectional view of rolling bearing 100A. FIG. 3 is a cross-sectional view of the gearbox 300 for the wind power generator; 12 is a partial cross-sectional view of planetary gear transmission 1200. FIG. 13 is a cross-sectional view of transmission 1300. FIG. It is a sectional view of rolling bearing 2100A. FIG. 4 is a cross-sectional view of the axle device 2200; 4 is a graph showing measurement results of nitrogen concentration and carbon concentration in the vicinity of the raceway surface of the bearing washer of Sample 1. FIG. 7 is a graph showing measurement results of nitrogen concentration and carbon concentration in the vicinity of the raceway surface of the raceway washer of sample 2; 4 is an SEM image of the surface layer portion of the bearing washer of Sample 1. FIG. 4 is an SEM image of the surface layer portion of the bearing washer of Sample 2. FIG. 4 is a phase map of EBSD in the surface layer portion of the bearing washer of Sample 1. FIG. 4 is a phase map of EBSD in the surface layer portion of the bearing washer of Sample 2. FIG. 3 is a phase map of EBSD in the surface layer portion of the bearing washer of sample 3. FIG. 3 is a bar graph showing the average grain size of martensite block grains in surface layer portions of bearing washers of Samples 1 to 3. FIG. It is a graph which shows the result of a rolling contact fatigue life test.

Details of embodiments of the present invention will be described with reference to the drawings. Here, the same reference numerals are given to the same or corresponding parts, and redundant description will not be repeated.

A bearing component according to the embodiment is, for example, an inner ring 10 of a rolling bearing. In the following, the inner ring 10 will be described as an example of the bearing component according to the embodiment. However, the bearing component according to the embodiment is not limited to this. A bearing component according to an embodiment may be an outer ring of a rolling bearing or a rolling element of a rolling bearing.

(Configuration of inner ring 10)
FIG. 1 is a cross-sectional view of the inner ring 10. FIG. As shown in FIG. 1, the inner ring 10 is ring-shaped. Let the central axis of the inner ring 10 be central axis A. As shown in FIG. The inner ring 10 has a width surface 10a, a width surface 10b, an inner peripheral surface 10c, and an outer peripheral surface 10d. The width surface 10a, the width surface 10b, the inner peripheral surface 10c, and the outer peripheral surface 10d form the surface of the inner ring 10. As shown in FIG.

In the following, the direction of the central axis A is defined as the axial direction. Also, hereinafter, the direction along the circumference centered on the central axis A when viewed in the axial direction is defined as the circumferential direction. Furthermore, in the following description, the direction orthogonal to the axial direction is defined as the radial direction.

The width surface 10a and the width surface 10b are end surfaces of the inner ring 10 in the axial direction. The width surface 10b is the opposite surface of the width surface 10a in the axial direction.

The inner peripheral surface 10c extends in the circumferential direction. The inner peripheral surface 10c faces the central axis A side. One end in the axial direction of the inner peripheral surface 10c is continuous with the width surface 10a, and the other end in the axial direction is continuous with the width surface 10b. The inner ring 10 is fitted to a shaft (not shown) at the inner peripheral surface 10c.

The outer peripheral surface 10d extends in the circumferential direction. 10 d of outer peripheral surfaces face the side opposite to the central axis A. As shown in FIG. That is, the outer peripheral surface 10d is the opposite surface of the inner peripheral surface 10c in the radial direction. One end in the axial direction of the outer peripheral surface 10d is continuous with the width surface 10a, and the other end in the axial direction is continuous with the width surface 10b.

The outer peripheral surface 10d has a raceway surface 10da. The raceway surface 10da extends in the circumferential direction. The outer peripheral surface 10d is recessed toward the inner peripheral surface 10c on the raceway surface 10da. In a cross-sectional view, the raceway surface 10da has a partially circular shape. The raceway surface 10da is located in the center of the outer peripheral surface 10d in the axial direction. The raceway surface 10da is a portion of the outer peripheral surface 10d that contacts the rolling elements (not shown in FIG. 1).

The inner ring 10 is made of steel. More specifically, the inner ring 10 is made of steel that has been hardened and tempered. The steel forming the inner ring 10 contains 0.70 mass percent or more and 1.10 mass percent or less of carbon, 0.15 mass percent or more and 0.35 mass percent or less of silicon, and 0.30 mass percent or more and 0.60 mass percent. 1.30 to 1.60 weight percent chromium, 0.50 weight percent or less vanadium, and 0.50 weight percent or less molybdenum. In this steel, the content of molybdenum is 0.01% by mass or more, and the content of vanadium is 0.01% by mass or more.

The reason why the carbon content in the steel forming the inner ring 10 is 0.70% by mass or more is to improve the hardness. The reason why the carbon content in the steel forming the inner ring 10 is 1.10% by mass or less is to suppress quench cracking.

The reason why the silicon content in the steel forming the inner ring 10 is 0.15% by mass or more is to increase temper softening resistance and to improve workability. The reason why the silicon content in the steel forming the inner ring 10 is 0.35% by mass or less is that an excessive amount of silicon lowers workability.

The content of manganese in the steel forming the inner ring 10 is 0.30% by mass or more to ensure hardenability. The reason why the content of manganese in the steel forming the inner ring 10 is 0.60% by mass or less is that an excessive amount of manganese increases manganese-based non-metallic inclusions in the steel.

The reason why the content of chromium in the steel forming the inner ring 10 is 1.30% by mass or more is to ensure hardenability and to form nitrides and carbonitrides. The reason why the content of chromium in the steel forming the inner ring 10 is 1.60% by mass or less is to suppress the formation of coarse precipitates.

The reason why the steel forming the inner ring 10 contains vanadium is to refine nitrides and carbonitrides. The reason why the vanadium content in the steel forming the inner ring 10 is 0.50% by mass or less is to suppress an increase in cost due to the addition of vanadium.

The reason why molybdenum is contained in the steel forming the inner ring 10 is to refine nitrides and carbonitrides and to improve hardenability. The reason why the molybdenum content in the steel forming the inner ring 10 is 0.50% by mass or less is to suppress an increase in cost due to the addition of molybdenum.

The steel forming the inner ring 10 contains 0.90 mass percent or more and 1.10 mass percent or less of carbon, 0.20 mass percent or more and 0.30 mass percent or less of silicon, and 0.40 mass percent or more and 0.50 mass percent. 1.40 to 1.60 mass percent chromium, 0.20 to 0.30 mass percent vanadium, and 0.10 to 0.30 mass percent molybdenum may contain. The rest of the steel forming the inner ring 10 is iron and unavoidable impurities.

FIG. 2 is an enlarged view of II in FIG. As shown in FIG. 2 , in the inner ring 10 , a region up to 20 μm from the surface is the surface layer portion 11 . For example, the surface of the inner ring 10 is subjected to nitriding treatment. As a result, the nitrogen concentration in the steel of the surface layer portion 11 is, for example, 0.15% by mass or more. The nitrogen concentration in the steel of the surface layer portion 11 is preferably 0.20% by mass or more and 0.30% by mass or less. The nitrogen concentration in the steel of the surface layer portion 11 is measured using an EPMA (Electron Probe Micro Analyzer).

Precipitates are dispersed in the steel of the surface layer portion 11 . The precipitates are nitrides based on chromium or vanadium or carbonitrides based on chromium or vanadium.

Chromium (vanadium) nitrides are nitrides of chromium (vanadium) or those in which some of the chromium (vanadium) sites in the nitrides are replaced by alloying elements other than chromium (vanadium). is.

Carbonitrides whose main component is chromium (vanadium) are those in which some of the carbon sites in the chromium (vanadium) carbides are replaced with nitrogen. The chromium (vanadium) sites of the carbonitride containing chromium (vanadium) as a main component may be substituted with an alloying element other than chromium (vanadium).

The area ratio of precipitates in the steel of the surface layer portion 11 is preferably 2.0% or less. The maximum grain size of precipitates in the steel of the surface layer portion 11 is preferably 0.5 μm or less.

The area ratio and maximum grain size of precipitates in the steel of the surface layer 11 are measured by the following methods. First, a cross-sectional image (hereinafter referred to as “SEM image”) is acquired using a SEM (Scanning Electron Microscope) in a cross section of the inner ring 10 including the surface layer portion 11 . The magnification for acquiring this SEM image is 15000 times.

Second, image processing is performed on the acquired SEM image. More specifically, since the precipitate appears white in the SEM image, the area of each of the white portions in the SEM image and the total area are calculated by image processing.

The total area of the white portion in the SEM image is regarded as the area ratio of the precipitates in the steel of the surface layer portion 11. The square root of the value obtained by dividing the maximum area of each white portion in the SEM image by π/4 is regarded as the maximum grain size of precipitates in the steel of the surface layer portion 11 .

Cementite (Fe ₃ C) may be further dispersed in the steel of the surface layer portion 11 . Some of the iron sites in the cementite may be replaced by alloying elements, and some of the carbon sites in the cementite may be replaced by nitrogen. The maximum grain size of cementite in the steel of the surface layer portion 11 is preferably 1.5 μm or less.

The maximum grain size of cementite in the steel of the surface layer 11 is measured by the following method. First, a SEM image is acquired in a cross section of the inner ring 10 including the surface layer portion 11 . The magnification for acquiring this SEM image is 15000 times. Second, image processing is performed on the acquired SEM image. More specifically, since cementite appears oval gray in the SEM image, the area of each oval gray portion in the SEM image is calculated by image processing. Then, the square root of the value obtained by dividing the maximum value of the area of each elliptical gray portion in the SEM image by π/4 is regarded as the maximum grain size of cementite in the steel of the surface layer portion 11. be.

At a position where the distance from the surface of the inner ring 10 is 50 μm, the volume ratio of retained austenite in the steel is preferably 15% or more. More preferably, the volume ratio of retained austenite in the steel is 25% or more and 35% or less at the position where the distance from the surface of the inner ring 10 is 50 μm.

The volume ratio of retained austenite in steel is measured by the X-ray diffraction method. That is, the volume ratio of retained austenite in the steel is calculated by comparing the integrated intensity of the diffraction peak in X-ray diffraction of austenite and the integrated intensity of the diffraction peak in X-ray diffraction of phases other than austenite.

At a position where the distance from the surface of the inner ring 10 is 50 μm, the hardness of the steel is preferably 58 HRC or more. More preferably, the hardness of the steel is 58 HRC or more and 64 HRC or less at the position where the distance from the surface of the inner ring 10 is 50 μm. The hardness of steel is measured according to the Rockwell hardness test method defined in JIS (JIS Z 2245:2016).

The steel of the surface layer 11 has martensite block grains. Two adjacent martensite block grains have a crystal orientation difference of 15° or more at the grain boundary. From another point of view, even if there is a location with a deviation in crystal orientation, if the difference in crystal orientation is less than 15°, the location is different from the grain boundary of the martensite block grain. not considered. Grain boundaries of martensite block grains are determined by an EBSD (Electron Back Scattered Diffraction) method.

In the steel of the surface layer portion 11, the average grain size of martensite block grains with a comparative area ratio of 30% is 2.0 μm or less. In the steel of the surface layer portion 11, the average grain size of martensite block grains with a comparative area ratio of 50% is preferably 1.5 μm or less.

The average grain size of martensite block grains with a comparative area ratio of 30 percent (50 percent) is measured by the following method. First, cross-sectional observation is performed on a cross section of the inner ring 10 including the surface layer portion 11 . At this time, martensite block grains included in the observation field are specified by the EBSD method. This observation field of view is an area of 50 μm×45 μm. Second, the area of each martensite block grain included in the observation field is analyzed from the crystal orientation data obtained by the EBSD method.

Third, the area of each martensite block grain included in the observation field is added in descending order of area. This addition is performed until thirty percent (50 percent) of the total area of martensite block grains contained in the field of view is reached. The equivalent circle diameter is calculated for each of the martensite block grains subjected to the above addition. This equivalent circle diameter is the square root of the value obtained by dividing the area of martensite block grains by π/4. The average value of the circle-equivalent diameters of the martensite block grains subjected to the above addition is regarded as the average grain size of the martensite block grains with a comparative area ratio of 30% (50%).

(Manufacturing method of inner ring 10)
FIG. 3 is a process diagram showing a method of manufacturing the inner ring 10. As shown in FIG. As shown in FIG. 3, the method for manufacturing the inner ring 10 includes a preparation step S1, a nitriding step S2, a quenching step S3, a tempering step S4, and a post-treatment step S5. The nitriding step S2 is performed after the preparatory step S1. The hardening step S3 is performed after the nitriding step S2. The tempering step S4 is performed after the hardening step S3. The post-treatment step S5 is performed after the tempering step S4.

In the preparation step S1, members to be processed are prepared. The member to be processed is a ring-shaped member made of the same steel as the inner ring 10 .

In the nitriding step S2, a nitriding treatment is performed on the surface of the member to be processed. The nitriding treatment is performed by holding the member to be processed in an atmosphere containing a nitrogen source (for example, ammonia) at a temperature equal to or higher than the A1 transformation _point of the steel forming the member to be processed.

In the quenching step S3, the member to be processed is quenched. In quenching, the member to be processed is held at a temperature equal to or higher than the _A1 transformation _point of the steel constituting the member to be processed, and then rapidly cooled to a temperature equal to or lower than the MS transformation point of the steel constituting the member to be processed. It is done by It is preferable that the heating and holding temperature in the quenching step S3 is equal to or lower than the heating and holding temperature in the nitriding step S2. The hardening step S3 may be performed twice. The heating and holding temperature in the second hardening step S3 is preferably lower than the heating and holding temperature in the first hardening step S3. As a result, precipitates are finely and abundantly dispersed in the surface layer of the member to be processed.

In the tempering step S4, the member to be processed is tempered. Tempering is carried out by holding the workpiece at _a temperature below the A1 transformation point of the steel from which the workpiece is constructed. In the post-processing step S5, machining (grinding, polishing), cleaning, and the like are performed on the surface of the member to be processed. As described above, the inner ring 10 having the structure shown in FIGS. 1 and 2 is formed.

In addition, since the precipitates are finely and abundantly dispersed in the steel of the surface layer portion 11, the martensite block grains are less likely to become large. The average grain size of block grains is 2.0 μm or less.

(Effect of inner ring 10)
In the inner ring 10 , the martensite block grains in the steel of the surface layer portion 11 are refined so that the average grain size at a comparative area ratio of 30% is 2.0 μm or less. As a result, in the inner ring 10, the surface layer portion 11 is toughened, and the shear resistance of the surface of the inner ring 10 (specifically, the raceway surface 10da) in contact with the rolling elements is improved. Thus, the inner ring 10 has improved durability.

When the area ratio of the precipitates in the steel of the surface layer portion 11 is 2.0% or more, that is, when the precipitates are dispersed in the steel of the surface layer portion 11 at a high density, contact with the rolling elements Durability is further improved by improving the shear resistance of the surface of the inner ring 10 (specifically, the raceway surface 10da).

When the maximum grain size of the precipitates in the steel of the surface layer portion 11 is 0.5 μm, the precipitates are dispersed finely and at high density in the steel of the surface layer portion 11, so wear resistance and toughness are improved. As a result, the durability of the inner ring 10 is further improved. When the maximum grain size of cementite in the steel of the surface layer portion 11 is 1.5 μm or less, fine dispersion of cementite further improves the wear resistance and toughness of the inner ring 10 .

When the volume ratio of retained austenite in the steel at the position where the distance from the surface of the inner ring 10 is 50 μm is 15% or more (25% or more and 35% or less), durability against indentation-induced flaking in an environment containing foreign matter is improved. When the hardness of the steel at the position where the distance from the surface of the inner ring 10 is 50 μm is 58 HRC or more (58 HRC or more and 64 HRC or less), the wear resistance of the inner ring 10 is further improved.

(Rolling bearing according to the embodiment)
A rolling bearing (referred to as "rolling bearing 100") according to the embodiment will be described below.

4 is a cross-sectional view of the rolling bearing 100. FIG. As shown in FIG. 4, rolling bearing 100 is a deep groove ball bearing. However, the rolling bearing 100 is not limited to this. Rolling bearing 100 may be, for example, a thrust ball bearing. The rolling bearing 100 has an inner ring 10 , an outer ring 20 , rolling elements 30 and a retainer 40 .

The outer ring 20 has a width surface 20a, a width surface 20b, an inner peripheral surface 20c, and an outer peripheral surface 20d. The surface of the outer ring 20 is composed of a width surface 20a, a width surface 20b, an inner peripheral surface 20c and an outer peripheral surface 20d.

The width surface 20a and the width surface 20b are end surfaces of the outer ring 20 in the axial direction. The width surface 20b is the opposite surface of the width surface 20a in the axial direction.

The inner peripheral surface 20c extends in the circumferential direction. The inner peripheral surface 20c faces the central axis A side. One end in the axial direction of the inner peripheral surface 20c is continuous with the width surface 20a, and the other end in the axial direction is continuous with the width surface 20b. The outer ring 20 is arranged such that the inner peripheral surface 20c faces the outer peripheral surface 10d.

The inner peripheral surface 20c has a raceway surface 20ca. The raceway surface 20ca extends in the circumferential direction. The inner peripheral surface 20c is recessed toward the outer peripheral surface 20d on the raceway surface 20ca. In a cross-sectional view, the raceway surface 20ca has a partially circular shape. The raceway surface 20ca is located in the center of the inner peripheral surface 20c in the axial direction. The raceway surface 20ca is a portion of the inner peripheral surface 20c that contacts the rolling elements 30 .

The outer peripheral surface 20d extends in the circumferential direction. 20 d of outer peripheral surfaces face the side opposite to the central axis A. As shown in FIG. That is, the outer peripheral surface 20d is the opposite surface of the inner peripheral surface 20c in the radial direction. The outer peripheral surface 20d is continuous with the width surface 20a at one end in the axial direction, and is continuous with the width surface 20b at the other end in the axial direction. The outer ring 20 is fitted to a housing (not shown) on the outer peripheral surface 20d.

The rolling elements 30 are spherical. The rolling elements 30 are arranged between the outer peripheral surface 10d (raceway surface 10da) and the inner peripheral surface 20c (raceway surface 20ca). The retainer 40 is ring-shaped and arranged between the outer peripheral surface 10d and the inner peripheral surface 20c. The retainer 40 holds the rolling elements 30 such that the distance between the two rolling elements 30 adjacent in the circumferential direction is within a certain range.

The outer ring 20 and the rolling elements 30 may be made of the same steel as the inner ring 10. In addition, the surface layer portion of the outer ring 20 (region up to 20 μm from the surface of the outer ring 20) and the surface layer portion of the rolling element 30 (region up to 20 μm from the surface of the rolling element 30) are the same as the surface layer portion 11. may be configured.

(Modification 1)
A rolling bearing 100 (hereinafter referred to as “rolling bearing 100A”) according to Modification 1 will be described below.

FIG. 5 is a cross-sectional view of the rolling bearing 100A. As shown in FIG. 5, rolling bearing 100A is a cylindrical roller bearing. Rolling bearing 100</b>A has inner ring 110 , outer ring 120 and rolling elements 130 .

The inner ring 110 has a width surface 110a, a width surface 110b, an inner peripheral surface 110c, and an outer peripheral surface 110d. The width surface 110a, the width surface 110b, the inner peripheral surface 110c, and the outer peripheral surface 110d form the surface of the inner ring 110. As shown in FIG.

The width surface 110a and the width surface 110b are end surfaces of the inner ring 110 in the axial direction. The width surface 110b is the opposite surface of the width surface 110a in the axial direction.

The inner peripheral surface 110c extends in the circumferential direction. The inner peripheral surface 110c faces the central axis A side. One end in the axial direction of the inner peripheral surface 110c is continuous with the width surface 110a, and the other end in the axial direction is continuous with the width surface 110b.

The outer peripheral surface 110d extends in the circumferential direction. 110 d of outer peripheral surfaces face the side opposite to the central axis A. As shown in FIG. That is, the outer peripheral surface 110d is the opposite surface of the inner peripheral surface 110c in the radial direction. The outer peripheral surface 110d is continuous with the width surface 110a at one end in the axial direction, and is continuous with the width surface 110b at the other end in the axial direction. The outer peripheral surface 110d has a raceway surface 110da. The raceway surface 110da extends in the circumferential direction. The raceway surface 110da is a portion of the outer peripheral surface 110d that contacts the rolling elements 130. As shown in FIG.

The outer ring 120 has a width surface 120a, a width surface 120b, an inner peripheral surface 120c, and an outer peripheral surface 120d. The surface of the outer ring 120 is composed of a width surface 120a, a width surface 120b, an inner peripheral surface 120c and an outer peripheral surface 120d.

The width surface 120a and the width surface 120b are end surfaces of the outer ring 120 in the axial direction. The width surface 120b is the opposite surface of the width surface 120a in the axial direction.

The inner peripheral surface 120c extends in the circumferential direction. The inner peripheral surface 120c faces the central axis A side. One end in the axial direction of the inner peripheral surface 120c is continuous with the width surface 120a, and the other end in the axial direction is continuous with the width surface 120b. The outer ring 120 is arranged such that the inner peripheral surface 120c faces the outer peripheral surface 10d. The inner peripheral surface 120c has a raceway surface 120ca. The raceway surface 120ca extends in the circumferential direction. The raceway surface 120ca is a portion of the inner peripheral surface 120c that contacts the rolling elements 130 .

The outer peripheral surface 120d extends in the circumferential direction. 120 d of outer peripheral surfaces face the side opposite to the central axis A. As shown in FIG. That is, the outer peripheral surface 120d is the opposite surface of the inner peripheral surface 120c in the radial direction. The outer peripheral surface 120d is continuous with the width surface 120a at one end in the axial direction, and is continuous with the width surface 120b at the other end in the axial direction.

The rolling elements 130 are cylindrical rollers. The rolling elements 130 are arranged between the outer peripheral surface 110d (raceway surface 110da) and the inner peripheral surface 120c (raceway surface 120ca). The outer peripheral surface of the rolling element 130 is a rolling surface 130a that contacts the raceway surface 110da and the raceway surface 120ca.

The inner ring 110, the outer ring 120 and the rolling elements 130 may be made of the same steel as the inner ring 10. The surface layer portion of the inner ring 110 (region up to 20 μm from the surface of the inner ring 110), the surface layer portion of the outer ring 120 (region up to 20 μm away from the surface of the outer ring 120), and the surface layer portion of the rolling element 130 (rolling element 130 ) may have the same configuration as the surface layer portion 11 .

The oil film parameter is calculated, for example, by the formula h ₀ /{1.1×(R _a1 ² +R _a2 ² ) ^1/2 }. The oil film thickness between the rolling surface 130a and the raceway surface 110da (raceway surface 120ca) is h ₀ , the arithmetic mean roughness of the rolling surface 130a is R _a1 , and the arithmetic mean of the raceway surface 110da (raceway surface 120ca) is R _a2 is the roughness. Even when the oil film parameter is 0.5 or more and 10 or less, oil film breakage may easily occur.

The rolling bearing 100A is used, for example, in the gearbox 300 for a wind power generator. FIG. 6 is a cross-sectional view of the gearbox 300 for a wind power generator. As shown in FIG. 6 , the wind power generator gearbox 300 mainly includes a planetary gear device 303 , a secondary gearbox 305 and a casing 306 . The planetary gear device 303 accelerates the rotation of the input shaft 301 and transmits it to the low speed shaft 302 . The secondary speed increasing device 305 further speeds up the rotation of the low speed shaft 302 and transmits it to the output shaft 304 . The planetary gear device 303 and the secondary speed increasing device 305 are provided within a common casing 306 . The input shaft 301 is connected to a main shaft (not shown) of a windmill (not shown) or the like. The output shaft 304 is connected to a generator (not shown).

In the planetary gear device 303, planetary shafts 310 are provided at a plurality of places in the circumferential direction of a rotatable carrier 307. A planetary gear 308 as a constituent member is rotatably supported on each planetary shaft 310 via a rolling bearing 309 . The rolling bearing 309 is the rolling bearing 100A according to this embodiment shown in FIG. Although the rolling bearings 309 of each planetary gear 308 are arranged in two rows in the illustrated example, they may be arranged in one row. Also, the rolling bearings 309 may be used in three, four and more rows. The carrier 307 is a member that serves as an input portion in the planetary gear device 303 . A carrier 307 is provided as a member integrated with the input shaft 301 . Carrier 307 may be configured by integrally coupling a separate member to input shaft 301 . A carrier 307 as a component is rotatably supported by the casing 306 via a bearing 311 at the boundary with the input shaft 301 .

Each planetary gear 308 supported by the carrier 307 meshes with an internal toothed ring gear 312 provided on the casing 306 . Each planetary gear 308 also meshes with a sun gear 313 rotatably provided concentrically with the ring gear 312 . Ring gear 312 may be formed directly on casing 306 or may be fixed to casing 306 . The sun gear 313 is a component that serves as an output section in the planetary gear device 303 . A sun gear 313 is provided on the low speed shaft 302 . A low-speed shaft 302 as a component is rotatably supported by a casing 306 via

bearings

314 and 315 .

The secondary speed increasing device 305 is composed of a gear train. In the illustrated example, in the secondary speed increasing device 305 , a gear 317 fixed to the low speed shaft 302 meshes with a small diameter side gear 318 of the intermediate shaft 321 . A large-diameter side gear 319 provided on the intermediate shaft 321 meshes with the gear 320 on the output shaft 304 . A gear train is composed of the gear 317, the small-diameter side gear 318, the large-diameter side gear 319, and the gear 320. As shown in FIG. An intermediate shaft 321 and an output shaft 304 as constituent members are rotatably supported by a casing 306 by

bearings

322 and 323, respectively.

As the rolling bearing 309 and the

bearings

311, 314, 315, 322, 323, the rolling bearing 100A shown in FIG. 5 may be applied, but rolling bearings with other arbitrary configurations may also be used. For example, as the rolling bearing 309 or the like, a type in which a retainer retains cylindrical rollers, or a full complement type bearing that does not use a retainer may be used. The outer ring of the rolling bearing 309 or the like has both flanges, and the inner ring has no flanges. In addition, in the rolling bearing 309 or the like, the outer ring may have no flanges and the inner ring may have both flanges. Further, although the cylindrical rollers, which are rolling elements such as the rolling bearing 309, are solid bodies, hollow rollers may be used as the rolling elements.

The operation of the wind power generator gearbox 300 described above will be described. When the input shaft 301 rotates, the carrier 307 integrated with the input shaft 301 rotates. As a result, the planetary gears 308 supported at a plurality of positions of the carrier 307 revolve. At this time, each planetary gear 308 revolves while meshing with a fixed ring gear 312, thereby causing rotation. The sun gear 313 meshes with the planetary gear 308 that rotates while revolving in this way. Therefore, the sun gear 313 rotates at an accelerated speed with respect to the input shaft 301 . A sun gear 313 serving as an output portion of the planetary gear device 303 is provided on the low speed shaft 302 of the secondary speed increasing device 305 . Therefore, the rotation of the sun gear 313 is accelerated by the secondary speed increasing device 305 and transmitted to the output shaft 304 . Thus, the rotation of the wind turbine main shaft (not shown) input to the input shaft 301 is greatly amplified by the planetary gear device 303 and the secondary speed increasing device 305 and transmitted to the output shaft 304 . As a result, the output shaft 304 can rotate at a high speed to generate power.

　The rolling bearings 309 that support each planetary gear 308 are lubricated as follows. The planetary gear 308 and its rolling bearing 309 are supplied with lubricating oil by being immersed in the oil bath 316 when the carrier 307 revolves and is positioned at the bottom of the casing 6 . Lubricating oil may be supplied to planetary gear 308 and rolling bearing 309 by circulating oil supply.

Here, wind power generators may continue to be stopped for a long time due to maintenance of the wind turbine or the occurrence of no wind. At this time, the supply of lubricating oil to the rolling bearing 309 may be insufficient. In particular, in the wind power generator gearbox 300, the generated torque changes depending on weather conditions as described above, and a state occurs in which no load is applied to the rolling bearing 309 and other bearings. As a result, slippage occurs between the rolling elements of the rolling bearing 309 and the raceway surface, and metal contact may occur between the rolling elements and the raceway surface.

In particular, when the equivalent load to be used is 0.04 times or less of the static load rating, slip occurs between the rolling elements and the raceway surface, and metal contact occurs between the rolling elements and the raceway surface as described above. Sometimes. The static load rating mentioned above means a basic static load rating. Furthermore, even when the lubricating state is such that the oil film parameter Λ is 0.5 or more and 10 or less, which is a general use condition for a gearbox bearing, metal contact occurs between the rolling elements and the raceway surface. There is

In addition, in the rolling bearing 309 used in the gearbox 300 for the wind power generator as described above, there are cases where slip due to skew or uneven contact of the rolling elements due to deformation is likely to occur. Furthermore, the bearing 323 that supports the output shaft 304 that rotates at high speed cannot follow torque fluctuations caused by the high speed rotation of the output shaft 304, and slippage may occur between the rolling elements and the raceway surface. Also in this case, wear of the rolling elements and raceway surfaces is accelerated, and hydrogen embrittlement may occur.

The rolling bearing 100A according to this embodiment is applied to the rolling bearing 309 and the

bearings

311, 314, 315, 322, and 323 for the wind power generator gearbox 300 used under these conditions of use. In the rolling bearing 100A according to the present embodiment, a large number of hard and fine precipitates are dispersed in the surface layer structure due to the combination of the steel material having the composition described above and the nitriding treatment. In other words, in the rolling bearing 100A, precipitates are dispersed at a high density in the steel of the surface layer of the inner ring 110, the surface layer of the outer ring 120, and the surface layer of the rolling element 130. Wear does not progress easily. In addition, since the precipitates dispersed in the steel on the surface layer of the inner ring 110, the surface layer of the outer ring 120, and the surface layer of the rolling element 130 become trap sites for hydrogen atoms, the surface layer of the inner ring 110 and the surface layer of the outer ring 120 The amount of hydrogen penetration in the surface layer portion of the rolling element 130 and the rolling element 130 becomes smaller. Therefore, according to the rolling bearing 100A, it is possible to suppress the occurrence of premature flaking caused by hydrogen embrittlement.

In the rolling bearing 100A, the volume ratio of retained austenite in the steel is 15% or more (25% or more and 35% or less) at the position where the distance between the surfaces of the inner ring 110, the outer ring 120 and the rolling elements 130 is 50 μm. Therefore, durability against indentation-induced flaking in an environment containing foreign matter is improved.

In addition, since the rolling bearing 100A is subjected to advanced nitriding treatment, the resistance to foreign matter is enhanced, and a long life can be maintained even under lubrication conditions in which foreign matter is present. Furthermore, the generation of hydrogen atoms originating from the lubricating environment is suppressed, and the arrival of the hydrogen atoms to the stress load region is also delayed. From this point of view as well, the occurrence of premature flaking caused by hydrogen embrittlement can be suppressed, and the durability against premature damage caused by indentation is improved.

Although the speed increaser shown in FIG. 6 has been described in this embodiment, the speed increaser according to this embodiment may have any other configuration. For example, the planetary gear device may have multiple stages such as two stages, or the parallel shaft may have one stage instead of multiple stages. These number of steps can be changed as appropriate. Moreover, instead of a combination of a planetary gear device and parallel shafts, a speed increasing device configured by only a planetary gear device or only parallel shafts may be used.

(Modification 2)
A rolling bearing 1100 (hereinafter referred to as “rolling bearing 1100A”) according to Modification 2 will be described below.

7 is a partial cross-sectional view of the planetary gear transmission 1200. FIG. As shown in FIG. 7 , planetary gear transmission 1200 has shaft 1210 , planetary gear 1220 , rolling elements 1230 , retainer 1240 , carrier 1250 , and retaining member 1260 . The shaft 1210, the planetary gear 1220, the rolling elements 1230, and the retainer 1240 correspond to bearing parts forming the rolling bearing 1100A. Shaft 1210 is an inner member as a bearing component of rolling bearing 1100A, and planetary gear 1220 is an outer member as a bearing component of rolling bearing 1100A.

The shaft 1210 has an outer peripheral surface 1210a. Planetary gear 1220 has an inner peripheral surface 1220a. The outer peripheral surface 1210a faces the inner peripheral surface 1220a with a space therebetween. A rolling element 1230 is arranged between the outer peripheral surface 1210a and the inner peripheral surface 1220a. Rolling elements 1230 are, for example, needle rollers. The rolling element 1230 is arranged between the outer peripheral surface 1210a and the outer peripheral surface 1220a. Thereby, the planetary gear 1220 is rotatably attached to the shaft 1210 .

A rolling element 1230 as a bearing component has an outer peripheral surface 1230a. The outer peripheral surface 1230a contacts the outer peripheral surface 1210a and the inner peripheral surface 1220a. That is, the outer peripheral surface 1210 a is the raceway surface of the shaft 1210 , and the inner peripheral surface 1220 a is the raceway surface of the planetary gear 1220 . Further, the outer peripheral surface 1230a serves as the rolling surface of the rolling element 1230. As shown in FIG.

The retainer 1240 holds the rolling elements 1230 so that the intervals between the rolling elements 1230 adjacent in the circumferential direction are within a certain range. Carrier 1250 and retaining member 1260 are attached to one end of shaft 1210 and the other end of shaft 1210, respectively.

The shaft 1210, the planetary gear 1220 and the rolling elements 1230 may be made of the same steel as the inner ring 10. In addition, the surface layer of the shaft 1210 (the area up to 20 μm from the surface of the shaft 1210), the surface layer of the planetary gear 1220 (the area up to 20 μm from the surface of the planetary gear 1220), and the surface of the rolling element 1230 (A region up to 20 μm from the surface of the rolling element 1230 ) may have the same configuration as the surface layer portion 11 .

At least one of the combined roughness between the outer peripheral surface 1230a and the outer peripheral surface 1210a and the combined roughness between the outer peripheral surface 1230a and the inner peripheral surface 1220a is, for example, 0.06 μm or more. Note that the combined roughness between the outer peripheral surface 1230a and the outer peripheral surface 1210a (inner peripheral surface 1220a) is the arithmetic average roughness of the outer peripheral surface 1230a, R _a1 , and the arithmetic average roughness of the outer peripheral surface 1210a (inner peripheral surface 1220a). is R _a2 , it is calculated by the formula (R _a1 ² +R _a2 ² ) ^1/2 .

The oil film parameter is calculated by the ^formula h ₀ _/{1.1×(R _a1 ² ⁺ R _a2 ² ) ^1/2 _} _. When ^1/2 is 0.06 μm or more, the oil film parameter is less than 1.2, and oil film breakage is likely to occur.

Under conditions where the oil film is likely to run out, the surface of the shaft 1210 (outer peripheral surface 1210a), the surface of the planetary gear 1220 (inner peripheral surface 1220a), and the surface of the rolling element 1230 (outer peripheral surface 1230a) come into metallic contact with each other, causing wear. New surfaces are easily formed on the surface of the shaft 1210 , the surface of the planetary gear 1220 and the surface of the rolling element 1230 . Hydrogen is likely to be generated from the lubricating oil on the new surface, and when this hydrogen penetrates from the new surface, hydrogen embrittlement occurs on the surface of the shaft 1210, the surface of the planetary gear 1220, and the surface of the rolling element 1230.

However, since the precipitates are dispersed at high density in the steel of the surface layer of the shaft 1210, the surface layer of the planetary gear 1220, and the surface layer of the rolling element 1230, wear progresses even under conditions where oil film breakage is likely to occur. Hateful. In addition, precipitates dispersed in the steel of the surface layer of the shaft 1210, the surface layer of the planetary gear 1220, and the surface layer of the rolling element 1230 become trap sites for hydrogen atoms. and the surface layer of the rolling element 1230 becomes smaller. Therefore, according to the rolling bearing 1100A, it is possible to suppress the occurrence of premature flaking caused by hydrogen embrittlement.

In the rolling bearing 1100A, the volume ratio of retained austenite in the steel is 15% or more (25% or more and 35% or less) at the position where the distance between the surfaces of the shaft 1210, the planetary gear 1220 and the rolling elements 1230 is 50 μm. Therefore, durability against indentation-induced flaking in an environment containing foreign matter is improved.

(Modification 3)
A rolling bearing 1100 (hereinafter referred to as “rolling bearing 1100B”) according to Modification 3 will be described below. The rolling bearing 1100B basically has the same configuration as the rolling bearing 100A shown in FIG. The structure of the rolling bearing 1100B will be described below with appropriate reference to FIG. In the rolling bearing 1100B, in the configuration shown in FIG. 5, at least one of the combined roughness between the rolling surface 130a and the raceway surface 110da and the combined roughness between the rolling surface 130a and the raceway surface 120ca is, for example, , 0.06 μm or more. The combined roughness between the rolling contact surface 130a and the raceway surface 110da (raceway surface 120ca) is defined by R _a1 being the arithmetic mean roughness of the rolling contact surface 130a and the arithmetic mean roughness of the raceway surface 110da (raceway surface 120ca) is R _a2 , it is calculated by the formula (R _a1 ² +R _a2 ² ) ^1/2 .

FIG. 8 is a cross-sectional view of the transmission 1300. FIG. As shown in FIG. 8 , transmission 1300 has carrier 1310 , input shaft 1320 , multiple planetary gears 1330 , ring gear 1340 , sun gear 1350 and output shaft 1360 . Transmission 1300 is a gearbox used in industrial equipment such as wind turbines. However, transmission 1300 is not limited to this.

An input shaft 1320 is attached to the carrier 1310 . Carrier 1310 has an axis 1311 . A planetary gear 1330 is rotatably attached to the shaft 1311 via a rolling bearing 1100B. More specifically, the inner peripheral surface 110c (see FIG. 5) of the inner ring 110 (see FIG. 5) as a bearing component is fitted to the outer peripheral surface of the shaft 1311, and the inner peripheral surface 110c (see FIG. 5) of the planetary gear 1330 is fitted as a bearing component. 120d (see FIG. 5) of the outer ring 120 (see FIG. 5) is fitted. The teeth formed on the outer peripheral surface of planetary gear 1330 mesh with the teeth formed on the inner peripheral surface of ring gear 1340 . An output shaft 1360 is attached to the sun gear 1350 . The teeth formed on the outer peripheral surface of each of the plurality of planetary gears 1330 mesh with the teeth formed on the outer peripheral surface of the sun gear 1350 .

By rotating the input shaft 1320, the carrier 1310 rotates. As the carrier 1310 rotates, the planetary gear 1330 revolves along the inner peripheral surface of the ring gear 1340 while rotating. Since the sun gear 1350 is meshing with the planetary gear 1330, the rotation of the planetary gear 1330 is transmitted to the sun gear 1350, and the output shaft 1360 is rotated. In this way, the rotation input to the input shaft 1320 is output from the output shaft 1360 after being accelerated.

In the rolling bearing 1100B, under conditions where the oil film is likely to run out, the surface of the inner ring 110 (raceway surface 110da) and the surface of the outer ring 120 (raceway surface 120ca) shown in FIG. , new surfaces are likely to be formed on the surfaces of the inner ring 110, the outer ring 120, and the rolling elements 130 due to wear. Hydrogen is likely to be generated from the lubricating oil on the new surface, and this hydrogen penetrates from the new surface, causing hydrogen embrittlement on the surface of the inner ring 110, the surface of the outer ring 120, and the surface of the rolling element 130.

However, since precipitates are dispersed at a high density in the steel of the surface layer of the inner ring 110, the surface layer of the outer ring 120, and the surface layer of the rolling element 130, wear does not progress easily even under conditions where the oil film tends to break. . In addition, since the precipitates dispersed in the steel on the surface layer of the inner ring 110, the surface layer of the outer ring 120, and the surface layer of the rolling element 130 become trap sites for hydrogen atoms, the surface layer of the inner ring 110 and the surface layer of the outer ring 120 The diffusion amount of hydrogen in the surface layer portion of the rolling element 130 and the surface layer portion of the rolling element 130 becomes small. Therefore, according to the rolling bearing 100A, it is possible to suppress the occurrence of premature flaking caused by hydrogen embrittlement.

In the rolling bearing 1100B, the volume ratio of retained austenite in the steel is 15% or more (25% or more and 35% or less) at the position where the distance between the surfaces of the inner ring 110, the outer ring 120 and the rolling elements 130 is 50 μm. Therefore, durability against indentation-induced flaking in an environment containing foreign matter is improved.

(Modification 4)
A rolling bearing 2100 (hereinafter referred to as “rolling bearing 2100A”) according to Modification 4 will be described.

FIG. 9 is a cross-sectional view of the rolling bearing 2100A. As shown in FIG. 9, rolling bearing 2100A is a tapered roller bearing. Note that the rolling bearing 2100A may be a self-aligning roller bearing. The rolling bearing 2100A has an inner ring 2110, an outer ring 2120, rolling elements 2130, and a retainer 2140 as bearing components.

The inner ring 2110 has a width surface 2110a, a width surface 2110b, an inner peripheral surface 2110c, and an outer peripheral surface 2110d. The width surface 2110a, the width surface 2110b, the inner peripheral surface 2110c, and the outer peripheral surface 2110d form the surface of the inner ring 2110. As shown in FIG. The inner diameter of inner ring 2110 is preferably 60 mm or more.

A width surface 2110a and a width surface 2110b are end surfaces of the inner ring 2110 in the axial direction. The width surface 2110b is the opposite surface of the width surface 2110a in the axial direction.

The inner peripheral surface 2110c extends in the circumferential direction. The inner peripheral surface 2110c faces the central axis A side. The inner peripheral surface 2110c is continuous with the width surface 2110a at one end in the axial direction, and is continuous with the width surface 2110b at the other end in the axial direction.

The outer peripheral surface 2110d extends in the circumferential direction. 2110 d of outer peripheral surfaces face the side opposite to the central axis A. As shown in FIG. That is, the outer peripheral surface 2110d is the opposite surface of the inner peripheral surface 2110c in the radial direction. The outer peripheral surface 2110d continues to the width surface 2110a at one end in the axial direction, and continues to the width surface 2110b at the other end in the axial direction. The outer peripheral surface 2110d has a raceway surface 2110da. The raceway surface 2110da extends in the circumferential direction. The raceway surface 2110da is a portion of the outer peripheral surface 2110d that contacts the rolling elements 2130 .

The outer ring 2120 has a width surface 2120a, a width surface 2120b, an inner peripheral surface 2120c, and an outer peripheral surface 2120d. The surface of the outer ring 2120 is composed of a width surface 2120a, a width surface 2120b, an inner peripheral surface 2120c and an outer peripheral surface 2120d.

A width surface 2120a and a width surface 2120b are end surfaces of the outer ring 2120 in the axial direction. The width surface 2120b is the opposite surface of the width surface 2120a in the axial direction.

The inner peripheral surface 2120c extends in the circumferential direction. The inner peripheral surface 2120c faces the central axis A side. The inner peripheral surface 2120c continues to the width surface 2120a at one end in the axial direction, and continues to the width surface 2120b at the other end in the axial direction. Outer ring 2120 is arranged such that inner peripheral surface 2120c faces outer peripheral surface 2110d. The inner peripheral surface 2120c has a raceway surface 2120ca. The raceway surface 2120ca extends in the circumferential direction. The raceway surface 2120ca is a portion of the inner peripheral surface 2120c that contacts the rolling elements 2130 .

The outer peripheral surface 2120d extends in the circumferential direction. 2120 d of outer peripheral surfaces face the side opposite to the central axis A. As shown in FIG. That is, the outer peripheral surface 2120d is the opposite surface of the inner peripheral surface 2120c in the radial direction. The outer peripheral surface 2120d continues to the width surface 2120a at one end in the axial direction, and continues to the width surface 2120b at the other end in the axial direction.

The rolling elements 2130 are tapered rollers. The rolling elements 2130 are arranged between the outer peripheral surface 2110d (raceway surface 2110da) and the inner peripheral surface 2120c (raceway surface 2120ca). The retainer 2140 is ring-shaped and arranged between the outer peripheral surface 2110d and the inner peripheral surface 2120c. The retainer 2140 holds the rolling elements 2130 such that the interval between the two rolling elements 2130 adjacent in the circumferential direction is within a certain range.

Inner ring 2110 , outer ring 2120 and rolling elements 2130 may be made of the same steel as inner ring 10 . The surface layer of the inner ring 2110 (the region up to 20 μm from the surface of the inner ring 2110), the surface layer of the outer ring 2120 (the region up to 20 μm from the surface of the outer ring 2120), and the surface layer of the rolling element 2130 (the rolling element 2130 ) may have the same configuration as the surface layer portion 11 . The surfaces of the inner ring 2110, the outer ring 2120, and the rolling elements 2130 are subjected to surface modification such as forming a diamond-like carbon coating, forming an iron oxide ₍ _Fe3O4 ) coating (performing a blackening treatment), and the like. may

A rolling bearing 2100A is used in an axle device 2200, for example. The axle device 2200 is, for example, an axle device of a wheel loader. The axle device 2200 may be the axle device of a dump truck.

10 is a cross-sectional view of the axle device 2200. FIG. As shown in FIG. 10 , the axle device 2200 has a differential mechanism 2210 , a body case 2220 and a rotating shaft 2230 .

The differential mechanism 2210 is arranged inside the body case 2220 . The differential mechanism 2210 has a gear case 2211a and a gear case 2211b, a spider 2212, a pinion gear 2213, a side gear 2214a and a side gear 2214b, a rotating shaft 2215a and a rotating shaft 2215b, and a ring gear 2216.

The gear case 2211a and the gear case 2211b are attached to the rotating shaft 2215a and the rotating shaft 2215b, respectively. The body case 2220 has a partition wall 2221a and a partition wall 2221b. Gear case 2211a and gear case 2211b are rotatably supported by main body case 2220 by rolling bearing 2100A. More specifically, inner ring 2110 is attached to gear case 2211a (gear case 2211b), and outer ring 2120 is attached to partition wall 2221a (partition wall 2221b).

The spider 2212 is arranged within a space defined by the gear case 2211a and the gear case 2211b. Pinion gear 2213 is rotatably attached to spider 2212 . The side gear 2214 a and the side gear 2214 b mesh with the pinion gear 2213 . The side gear 2214a and the side gear 2214b are attached to the rotating shaft 2215a and the rotating shaft 2215b, respectively. The ring gear 2216 is attached to the gear case 2211a. Ring gear 2216 is a bevel gear.

The rotating shaft 2230 has a pinion gear 2231 at its tip. Pinion gear 2231 meshes with ring gear 2216 . Rotating shaft 2230 is rotatably supported within body case 2220 by a rolling bearing. By rotating the rotating shaft 2230, the rotation of the rotating shaft 2230 is transmitted to the rotating shaft 2215a via the pinion gear 2231, the ring gear 2216 and the gear case 2211a, thereby rotating the rotating shaft 2215a. Also, the rotation of the rotating shaft 2215a is transmitted to the rotating shaft 2215b via the side gear 2214a, the pinion gear 2213 and the side gear 2214b, and rotates the rotating shaft 2215b together with the gear case 2211b.

By changing the rotation direction of the rotation shaft 2230, the rotation directions of the rotation shaft 2215a and the rotation shaft 2215b (gear case 2211a and gear case 2211b) are changed. Therefore, in the rolling bearing 2100A, the inner ring 2110 rotates forward and backward with respect to the outer ring 2120 . Further, in the axle device 2200, the rotating shaft 2230 is repeatedly rotated and stopped, so in the rolling bearing 2100A, the inner ring 2110 is rotated with respect to the outer ring 2120 from a stationary state.

As described above, the rolling bearing 2100A is used under conditions where the oil film is likely to run out because the forward and reverse rotation of the inner ring 2110 with respect to the outer ring 2120 and the rotation of the inner ring 2110 from a stationary state with respect to the outer ring 2120 are repeated. More specifically, the rolling bearing 2100A is set under the condition that the oil film parameter (Λ) is less than 1.2 or the dn value (the inner diameter of the inner ring 2110 indicated in mm units multiplied by the number of revolutions of the inner ring 2110 indicated in rpm units). value) is 200,000 or less.

Under conditions where the oil film is likely to run out, the surface of the inner ring 2110 (raceway surface 2110da) and the surface of the outer ring 2120 (raceway surface 2120ca) and the surface of the rolling element 2130 come into metal contact with each other, and wear causes the surface of the inner ring 2110 and the surface of the outer ring 2120 to come into contact with each other. and the surfaces of the rolling elements 2130 are likely to form new surfaces. Hydrogen is likely to be generated from the lubricating oil on the new surface, and this hydrogen penetrates from the new surface, causing hydrogen embrittlement on the surface of the inner ring 2110, the surface of the outer ring 2120, and the surface of the rolling element 2130.

However, since precipitates are dispersed at a high density in the steel of the surface layer of the inner ring 2110, the surface layer of the outer ring 2120, and the surface layer of the rolling element 2130, wear does not progress easily even under conditions where oil film breakage is likely to occur. . In addition, the precipitates dispersed in the steel on the surface layer of the inner ring 2110, the surface layer of the outer ring 2120, and the surface layer of the rolling element 2130 become trap sites for hydrogen atoms. The amount of hydrogen penetration in the surface layer portion of the rolling element 2130 and the rolling element 2130 becomes small. Therefore, according to the rolling bearing 2100A, it is possible to suppress the occurrence of premature flaking caused by hydrogen embrittlement.

In the rolling bearing 2100A, the volume ratio of retained austenite in the steel is 15% or more (25% or more and 35% or less) at the position where the distance between the surfaces of the inner ring 2110, the outer ring 2120 and the rolling elements 2130 is 50 μm. Therefore, durability against indentation-induced flaking in an environment containing foreign matter is improved.

(Rolling contact fatigue life test)
A rolling contact fatigue life test was conducted in order to confirm the effect of the bearing component according to the embodiment (the effect of suppressing the occurrence of hydrogen embrittlement). Samples 1, 2 and 3 were used for the rolling contact fatigue life test. Samples 1 to 3 are thrust ball bearings of type 51106 specified in JIS.

In sample 1, the bearing washer (inner ring and outer ring) was formed from the first steel material. In samples 2 and 3, bearing washer was formed of the second steel material. The compositions of the first steel material and the second steel material are shown in Table 1. As shown in Table 1, the ingredients of the first steel material and the second steel material are almost the same except for the contents of molybdenum and vanadium. The second steel material corresponds to SUJ2, which is a high-carbon chromium bearing steel specified in JIS standards.

FIG. 11 is a graph showing the measurement results of the nitrogen concentration and carbon concentration in the vicinity of the raceway surface of the raceway washer of Sample 1. FIG. 12 is a graph showing the measurement results of the nitrogen concentration and the carbon concentration in the vicinity of the raceway surface of the raceway washer of Sample 2; The horizontal axis in FIGS. 11 and 12 is the distance from the orbital plane (unit: mm), and the vertical axis in FIGS. 11 and 12 is the carbon or nitrogen concentration (unit: mass percent). As shown in FIGS. 11 and 12, in samples 1 and 2, the surface of the washer was subjected to nitriding treatment. The heating and holding temperature during this nitriding treatment was set to 850°C. On the other hand, in sample 3, the bearing washer surface was not subjected to nitriding treatment.

Table 2 shows the nitrogen concentration in the surface layer of the raceway washer of Samples 1 to 3 (the area up to 20 μm from the raceway surface). As shown in Table 2, the nitrogen concentration in the surface layer steel of the bearing washers of samples 1 and 2 was 0.3% or more and 0.5% or less. The nitrogen concentration in the surface layer steel of the washer of Sample 3 was 0.0%.

Quenching and tempering were performed on the bearing washers of samples 1 to 3. The heating and holding temperature during quenching was set to 850°C. The heating and holding temperature during tempering was set to 180°C. The heating and holding time during tempering was set to 2 hours.

FIG. 13 is an SEM image of the surface layer of the bearing washer of Sample 1. 14 is an SEM image of the surface layer of the bearing washer of sample 2. FIG. In the SEM images of FIGS. 13 and 14, white portions are precipitates, and oval gray portions are cementite.

As shown in Table 3, the area ratio of precipitates in the surface layer steel of sample 1 was 2.7%. As shown in Table 3, the area ratio of precipitates in the surface layer steel of sample 2 was 1.6 percent. That is, in the surface layer portion of the bearing washer of Sample 1, the precipitates were dispersed at a higher density than in the surface layer portion of the bearing washer of Sample 2. From this comparison, it became clear that the addition of vanadium and molybdenum in an amount of 0.5% by mass or less resulted in a dense dispersion of precipitates in the surface layer steel of the bearing washer.

In the surface layer of the bearing washer of sample 1, the maximum grain size of precipitates was 0.5 μm. In the surface layer portion of the bearing washer of sample 2, the maximum grain size of precipitates was 1.1 μm. That is, in the surface layer portion of the bearing washer of sample 1, compared with the surface layer portion of the bearing washer of sample 2, the precipitates were finely dispersed. From this comparison, it became clear that the addition of vanadium and molybdenum in an amount of 0.5% by mass or less resulted in a high density and fine dispersion of precipitates in the surface layer steel of the bearing washer.

As shown in Table 4, the maximum grain size of cementite was 1.5 μm or less in the surface layers of the bearing washer of sample 1 and sample 2. In the surface layer portion of the bearing washer of sample 3, the maximum grain size of cementite exceeded 1.5 μm.

As shown in Table 5, in samples 1 and 2, the volume ratio of retained austenite in the steel was 15% or more at the position where the distance from the raceway surface was 50 μm. In sample 3, the volume ratio of retained austenite in the steel was less than 15% at the position where the distance from the raceway surface was 50 μm. In samples 1 to 3, the hardness of the steel was 58 HRC or more at the position where the distance from the raceway surface was 50 μm.

FIG. 15 is an EBSD phase map of the surface layer of the bearing washer of sample 1. FIG. 16 is a phase map of EBSD in the surface layer of the bearing washer of sample 2. FIG. FIG. 17 is an EBSD phase map of the surface layer of the bearing washer of Sample 3. FIG. In FIGS. 15 to 17, martensite block grains are white. FIG. 18 is a bar graph showing the average grain size of martensite block grains in the surface layer portion of bearing washer of Samples 1 to 3. FIG. The vertical axis of the graph in FIG. 18 is the average grain size (unit: μm) of martensite block grains.

As shown in FIGS. 15 to 18, in the surface layer portion of the bearing washer of Sample 1, the average grain size of martensite block grains at a comparative area ratio of 30% was 2.0 μm or less. On the other hand, in the surface layers of the bearing washer of Sample 2 and Sample 2, the average grain size of martensite block grains at a comparative area ratio of 30% exceeded 2.0 μm.

In the surface layer portion of the bearing washer of sample 1, the average grain size of martensite block grains at a comparative area ratio of 50% was 1.5 µm or less. On the other hand, in the surface layers of the bearing washer of Sample 2 and Sample 2, the average grain size of martensite block grains at a comparative area ratio of 50% exceeded 1.5 μm.

Fig. 19 is a graph showing the results of the rolling contact fatigue life test. The horizontal axis of the graph in FIG. 19 indicates life (unit: hours), and the vertical axis of the graph in FIG. 19 indicates cumulative damage probability (unit: percent). The rolling contact fatigue life test was conducted under the conditions shown in Table 6. That is, the maximum contact surface pressure between the rolling elements and the washer is 2.3 GPa, the washer is rapidly accelerated and decelerated between 0 rpm and 2500 rpm, and the lubricating fluid is polyglycol oil. was added with pure water.

As shown in FIG. 19 and Table 7, Sample 1 exhibited better rolling contact fatigue life than Sample 2. More specifically, the L10 life of sample 1 (the life at which the cumulative failure probability reaches ₁₀ percent) is 2.7 times the L10 life of sample ₃ , and the L10 life of sample 2 is the _L10 life of sample 3. It was 2.1 times the ₁₀ life.

As described above, in the surface layer portion of the bearing washer of Sample 1, the average grain size of martensite grains at a comparative area ratio of 30% was 2.0 μm or less. On the other hand, in the surface layer portion of the bearing washer of Samples 2 and 3, the average grain size of martensite grains at a comparative area ratio of 30% exceeded 2.0 μm. From this comparison, it became clear that the bearing component according to the embodiment has improved durability.

In addition, as described above, in the surface layer portion of the bearing washer of sample 1, the precipitates were dispersed finer and more densely than in the surface layer portion of the bearing washer of sample 2. From this comparison, it is clear that the durability of the bearing component according to the embodiment is further improved by setting the area ratio and maximum grain size of precipitates in the surface layer to 2.0% or more and 0.5 μm or less, respectively. Became.

Also, the L _{10 life of sample 2 was longer than the L 10} _life of sample 3. As described above, the maximum grain size of cementite in the surface layer of the washer of sample 2 was 1.5 µm or less, while the maximum grain size of cementite in the surface layer of the washer of sample 3 exceeded 1.5 µm. rice field. In addition, in the bearing washer of sample 2, the volume ratio of retained austenite at the position where the distance from the raceway surface is 50 μm is 15% or more, while in the bearing washer of sample 3, the distance from the raceway surface is 50 μm. The volume fraction of retained austenite at the location was less than 15 percent.

From this comparison, by setting the maximum grain size of cementite to 1.5 µm or less in the surface layer of the bearing component and setting the volume ratio of retained austenite to 15% or more at a position where the distance from the surface of the bearing component is 50 µm, , the durability of the bearing components is improved.

(Test on Hydrogen Penetration Characteristics)
The characteristics of hydrogen permeation into the surface layer portion of raceway washer (inner ring and outer ring) as raceway members of samples 1 and 3 were evaluated by the following method. In this evaluation, first, the raceway members of Sample 1 and Sample 3 before being subjected to the rolling contact fatigue life test were heated from room temperature to 400° C., so that the rolling contact fatigue life test was performed. was measured. Second, by heating the raceway members of Sample 1 and Sample 3 after being subjected to the rolling contact fatigue life test for 50 hours from room temperature to 400°, the samples after being subjected to the rolling contact fatigue life test for 50 hours The amount of hydrogen released from the track members of Sample 1 and Sample 3 was measured.

In sample 3, the ratio of the hydrogen release amount before and after the rolling contact fatigue life test (that is, the hydrogen release amount after being subjected to the rolling contact fatigue life test is ) was 3.2. On the other hand, in sample 1, the ratio of hydrogen release amounts before and after the rolling contact fatigue life test was 0.9. From this comparison, it was experimentally clarified that the formation of the surface layer portion 11 on the contact surface suppresses penetration of hydrogen into the surface layer portion 11 and suppresses premature flaking caused by hydrogen embrittlement.

Although the embodiment of the present invention has been described as above, it is also possible to modify the above embodiment in various ways. Moreover, the scope of the present invention is not limited to the above embodiments. The scope of the present invention is indicated by the scope of claims, and is intended to include all changes within the meaning and scope of equivalence to the scope of the claims.

This embodiment is particularly advantageously applied to bearing components and rolling bearings having the same.

6, 306 casing, 10, 110, 2110 inner ring, 10a, 10b, 20a, 20b, 110a, 110b, 120a, 120b, 2110a, 2110b, 2120a, 2120b width surface, 10c, 20c, 110c, 120c, 1220a, 2110c, 2120c Inner peripheral surface 10d, 20d, 110d, 120d, 1210a, 1220a, 1230a, 2110d, 2120d Outer peripheral surface 10da, 20ca, 110da, 120ca, 2110da, 2120ca Raceway surface 11 Surface layer 20, 120, 2120 Outer ring 30 , 130, 1230, 2130 Rolling elements, 40, 1240, 2140 Cage, 100, 100A, 309, 311, 314, 315, 322, 323, 1100, 1100A, 1100B, 2100, 2100A Bearing, 130a Rolling surface, 300 Gearbox for wind power generator, 301, 1320 input shaft, 302 low speed shaft, 303 planetary gear device, 304, 1360 output shaft, 305 secondary gearbox, 307, 1250, 1310 carrier, 308, 1220, 1330 planetary gear , 310 planetary shaft, 312 ring gear, 313 sun gear, 316 oil bath, 317, 320 gear, 318 small diameter side gear, 319 large diameter side gear, 321 intermediate shaft, 1200 planetary gear transmission, 1210, 1311 shaft, 1260 retainer Member, 1300 transmission, 1340, 2216 ring gear, 1350 sun gear, 2200 axle device, 2210 differential mechanism, 2211a, 2211b gear case, 2212 spider, 2213, 2231 pinion gear, 2214a, 2214b side gear, 2215a, 2215b, 2230 main body, 2220 Case, 2221a, 2221b: partition wall, A: center shaft, S1: preparation process, S2: nitriding process, S3: hardening process, S4: tempering process, S5: post-treatment process.

Claims

A rolling bearing comprising bearing parts,
The bearing component is made of steel and has a surface layer portion that is a region with a distance of up to 20 μm from the surface,
The steel contains 0.70 mass percent to 1.10 mass percent carbon, 0.15 mass percent to 0.35 mass percent silicon, and 0.30 mass percent to 0.60 mass percent manganese. and 1.30% by mass or more and 1.60% by mass or less of chromium, 0.50% by mass or less of vanadium, and 0.50% by mass or less of molybdenum, and the balance being iron and inevitable impurities,
The steel of the surface layer portion has martensite block grains and precipitates,
The precipitate is a nitride containing chromium or vanadium as a main component or a carbonitride containing chromium or vanadium as a main component,
The rolling bearing, wherein in the steel of the surface layer portion, the average grain size of the martensite block grains at a comparative area ratio of 30% is 2.0 µm or less.
The bearing component includes an inner ring, an outer ring, and rolling elements,
2. The rolling bearing according to claim 1, wherein said rolling bearing supports a component of a gearbox for a wind power generator.
The rolling bearing according to claim 2, wherein the rolling bearing is used under conditions where the ratio of equivalent load to static load rating is 0.04 or less.
The rolling bearing according to claim 2 or 3, wherein the rolling bearing is used under the condition that the oil film parameter is 0.5 or more and 10 or less.
The bearing component includes at least one of an inner member, an outer member and rolling elements,
The rolling bearing according to claim 1, wherein said rolling bearing is used in a transmission.
the bearing component includes the rolling element and at least one of the inner member and the outer member;
6. The rolling bearing according to claim 5, wherein the combined roughness of the rolling surface of the rolling element and the raceway surface of the inner member or the raceway surface of the outer member is 0.06 [mu]m or more.
The bearing component includes an inner ring, an outer ring, and rolling elements,
The rolling bearing according to claim 1, wherein said rolling bearing is used in a transmission.
The rolling bearing according to claim 7, wherein the combined roughness of the rolling surface of the rolling element and the raceway surface of the inner ring or the raceway surface of the outer ring is 0.06 µm or more.
The bearing component includes an inner ring, an outer ring, and rolling elements,
2. A rolling bearing according to claim 1, wherein said rolling bearing is mounted in a mechanical structure in which said inner ring is rotated in opposite directions relative to said outer ring or in which said inner ring is rotated relative to said outer ring from a stationary state.
The rolling bearing according to claim 9, wherein the rolling bearing is used under conditions where the oil film parameter is less than 1.2.
The rolling bearing according to claim 9 or 10, wherein the rolling bearing is used under conditions where the dn value is 200000 or less.
The rolling bearing according to any one of claims 9 to 11, wherein said rolling bearing is a tapered roller bearing.
The rolling bearing according to any one of claims 9 to 11, wherein said rolling bearing is a self-aligning roller bearing.
The rolling bearing according to any one of claims 9 to 13, wherein a diamond-like carbon coating or an iron oxide coating is formed on the surface.
The steel contains 0.90 to 1.10 mass percent carbon, 0.20 to 0.30 mass percent silicon, and 0.40 to 0.50 mass percent manganese. and 1.40% by mass or more and 1.60% by mass or less of chromium, 0.20% by mass or more and 0.30% by mass or less of vanadium, and 0.10% by mass or more and 0.30% by mass or less of molybdenum A rolling bearing according to any one of claims 1 to 14, comprising iron and the balance being iron and unavoidable impurities.
The rolling bearing according to any one of claims 1 to 15, wherein the area ratio of the precipitates in the steel of the surface layer portion is 2.0 percent or more.
The rolling bearing according to any one of claims 1 to 16, wherein the maximum grain size of said precipitates in said steel of said surface layer portion is 0.5 µm or less.
The steel of the surface layer further has cementite,
The rolling bearing according to any one of claims 1 to 17, wherein the cementite has a maximum grain size of 1.5 µm or less in the steel of the surface layer portion.
The rolling bearing according to any one of claims 1 to 18, wherein the nitrogen concentration in the steel of the surface layer portion is 0.15% by mass or more.
The rolling bearing according to any one of claims 1 to 19, wherein the volume ratio of retained austenite in the steel is 15% or more at a position where the distance from the surface is 50 µm.
The rolling bearing according to any one of claims 1 to 20, wherein the steel has a hardness of 58 HRC or more at a position where the distance from the surface is 50 μm.
At a position where the distance from the surface is 50 μm, the volume ratio of retained austenite in the steel is 25% or more and 35% or less,
The rolling bearing according to any one of claims 1 to 21, wherein the steel has a hardness of 58 HRC or more and 64 HRC or less at a position where the distance from the surface is 50 µm.