Method for evaluating hydrogen embrittlement peeling of rolling bearing

Abstract

A hydrogen embrittlement peeling evaluation test method includes: preparing a rolling bearing (10) having a first bearing ring (11), a second bearing ring (12), and a rolling element (13), the first bearing ring (11) being a rotating ring including a first raceway surface (11da), the second bearing ring (12) being a stationary ring including a second raceway surface (12ca) opposite the first raceway surface, and the rolling element (13) being disposed between the first raceway surface and the second raceway surface; and rotating the first bearing ring around a central axis (A1) in a state where a load is applied between the first raceway surface and the second raceway surface via the rolling element. The first bearing ring, the second bearing ring, and the rolling element are each formed of steel. The first raceway surface and the second raceway surface are always completely immersed in lubricating oil during rotation. The lubricating oil is substantially free of water.

Description

Technical Field

[0001] This invention relates to a test method for evaluating hydrogen embrittlement peeling of rolling bearings. Background Technology

[0002] Non-Patent Literature 1 (Hamada Hiroshi et al., "The Influence of Hydrogen on Tensile, Compressive Fatigue and Rolling Fatigue of Bearing Steel", NTN Technical Review No. 74, p. 50, 2006) describes a test method for evaluating hydrogen embrittlement peeling of bearing steel. In the test method described in Non-Patent Literature 1, two cylindrical test pieces made of bearing steel are used for a rolling-sliding test. Each cylindrical test piece is hydrogen-filled before the rolling-sliding test. Therefore, the hydrogen embrittlement peeling of bearing steel can be evaluated according to the test method described in Non-Patent Literature 1.

[0003] Non-patent literature 2 (MIKA KOHARA et al., *Study on Mechanism of Hydrogen Generation from Lubricants*, Tribology Transactions No. 49, p. 53, 2006) describes a ball-disc sliding test method. In the test method described in Non-patent Literature 1, a steel ball is pressed onto a rotating disk in a vacuum, separated by an oil film, thereby forming a new surface on the steel ball. As a result, hydrogen is generated through a tribochemical reaction, and the hydrogen embrittlement of the steel ball is evaluated by detecting the hydrogen.

[0004] However, the test methods described in Non-Patent Literature 1 and Non-Patent Literature 2 require the special conditions of pre-filling the test piece with hydrogen and then conducting the test in a vacuum environment, which cannot reproduce the hydrogen embrittlement peeling under the actual use environment of rolling bearings.

[0005] Patent Document 1 (Japanese Patent Application Publication No. 2012-181167) discloses a method for testing the rolling sliding fatigue life of a rolling bearing. First, in the test method described in Patent Document 1, a simulated thrust ball bearing is prepared. The simulated bearing has an inner ring, an outer ring, and balls that serve as rolling elements disposed between the raceway surfaces of the inner and outer rings. Second, in the test method described in Patent Document 1, the inner ring rotates around a central axis under a load applied between the raceway surfaces of the inner and outer rings. At this time, the raceway surfaces of the inner and outer rings are immersed in lubricating oil. In the test method described in Patent Document 1, the hydrogen embrittlement peeling of the rolling bearing is evaluated through the above steps.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 2012-181167

[0009] Non-patent literature

[0010] Non-patent literature 1: Hiroshi Hamada et al., "The Influence of Hydrogen on Tensile, Compressive and Rolling Fatigue of Bearing Steel", NTN Technical Review No. 74, p. 50, 2006.

[0011] Non-patent literature 2: MIKA KOHARA et al., "Study on Mechanism of Hydrogen Generation from Lubricants", Tribology Transactions No. 49, p. 53, 2006. Summary of the Invention

[0012] Technical issues

[0013] The test method described in Patent Document 1 does not require pre-filling the test piece with hydrogen or conducting the test in a vacuum environment. However, in the test method described in Patent Document 1, water is injected into the lubricating oil, and it is necessary to suppress the evaporation of water in the lubricating oil, making it difficult to raise the temperature of the lubricating oil. As a result, in the test method described in Patent Document 1, it is difficult to thin the oil film between the raceway surface and the rolling elements by increasing the temperature of the lubricating oil, resulting in difficulty in achieving metal-to-metal contact between the raceway surface and the rolling elements.

[0014] This invention is a technology obtained in view of the problems of the prior art described above. More specifically, this invention provides a method for evaluating hydrogen embrittlement peeling, which facilitates the reproduction of hydrogen embrittlement peeling by making it easy to generate metal-to-metal contact between the raceway surface and the rolling element.

[0015] Technical solutions adopted to solve technical problems

[0016] One embodiment of the present invention relates to a hydrogen embrittlement peeling evaluation test method comprising: preparing a rolling bearing having a first bearing ring, a second bearing ring, and rolling elements, wherein the first bearing ring is a rotating ring including a first raceway surface, the second bearing ring is a stationary ring including a second raceway surface opposite to the first raceway surface, and the rolling elements are disposed between the first and second raceway surfaces; and rotating the first bearing ring about a central axis while a load is applied between the first and second raceway surfaces via the rolling elements. The first bearing ring, the second bearing ring, and the rolling elements are all made of steel. The first and second raceway surfaces are always completely immersed in lubricating oil during rotation. The lubricating oil is substantially water-free.

[0017] In the hydrogen embrittlement peel test method, the rolling bearing can be a radial ball bearing. The central axis can be horizontal. The load can be applied in a direction orthogonal to the central axis. In the hydrogen embrittlement peel test method, the load can be applied from the lower vertical direction to the upper vertical direction.

[0018] In the hydrogen embrittlement peeling test method, the rolling bearing can be a thrust ball bearing. The central shaft can be vertical. The load can be applied vertically.

[0019] In the hydrogen embrittlement peel test method, the water content in the lubricating oil can be below 200 ppm by mass. In the hydrogen embrittlement peel test method, the lubricating oil can be CVT transmission fluid. In the hydrogen embrittlement peel test method, the hydrogen concentration in the steel can be below 0.02 ppm by mass.

[0020] Invention Effects

[0021] In one embodiment of the present invention, the hydrogen embrittlement peeling test method can be made easier to reproduce by making the raceway surface and the rolling element easily come into metal contact. Attached Figure Description

[0022] Figure 1 This is a flowchart of the hydrogen embrittlement peel test method involved in Implementation Method 1.

[0023] Figure 2 This is a cross-sectional view along the central axis A1 of the rolling bearing 10.

[0024] Figure 3 This is a schematic cross-sectional view of the test apparatus 20.

[0025] Figure 4 This is a sectional view along the central axis A3 of the rolling bearing 30.

[0026] Figure 5 This is a schematic cross-sectional view of the test apparatus 40. Detailed Implementation

[0027] The detailed description of the embodiments will be given with reference to the accompanying drawings. In the following drawings, the same or equivalent parts are labeled with the same reference numerals and will not be described repeatedly.

[0028] (Implementation Method 1)

[0029] The hydrogen embrittlement peel test method involved in Embodiment 1 is described below.

[0030] Figure 1 This is a flowchart of the hydrogen embrittlement peel test method involved in Embodiment 1. For example... Figure 1As shown, the hydrogen embrittlement peel test method involved in Embodiment 1 includes a preparation step S1 and a rolling sliding test step S2.

[0031] In preparation step S1, a rolling bearing 10 is prepared for use in the hydrogen embrittlement peeling test method involved in Embodiment 1. Figure 2 This is a cross-sectional view along the central axis A1 of the rolling bearing 10. (Example) Figure 2 As shown, the rolling bearing 10 is a radial ball bearing. More specifically, the rolling bearing 10 is a deep groove ball bearing. The rolling bearing 10 has an inner ring 11, an outer ring 12, rolling elements 13, and a cage 14.

[0032] The inner ring 11 has an annular (circular) shape. The inner ring 11 is the rotating ring of the rolling bearing 10. The inner ring 11 has a central shaft A1. The inner ring 11 has an upper surface 11a, a bottom surface 11b, an inner circumferential surface 11c, and an outer circumferential surface 11d.

[0033] The upper surface 11a and the bottom surface 11b form the end face of the inner ring 11 along the central axis A1. The bottom surface 11b is the surface opposite to the upper surface 11a along the central axis A1. The inner circumferential surface 11c extends circumferentially along the inner ring 11. The outer circumferential surface 11d extends circumferentially along the inner ring 11. The outer circumferential surface 11d is the surface opposite to the inner circumferential surface 11c in the radial direction of the inner ring 11.

[0034] The outer peripheral surface 11d has a raceway surface 11da. The raceway surface 11da is the portion of the outer peripheral surface 11d that contacts the rolling element 13. In the raceway surface 11da, the outer peripheral surface 11d is recessed towards the inner peripheral surface 11c. When viewed in section along the central axis A1, the raceway surface 11da is partially arc-shaped.

[0035] The outer ring 12 has an annular (circular) shape. The outer ring 12 is the stationary ring of the rolling bearing 10. The outer ring 12 has an upper surface 12a, a bottom surface 12b, an inner circumferential surface 12c, and an outer circumferential surface 12d.

[0036] The upper surface 12a and the bottom surface 12b form the end face of the outer ring 12 along the central axis A1. The bottom surface 12b is the surface opposite to the upper surface 12a along the central axis A1. The inner circumferential surface 12c extends circumferentially along the outer ring 12. The outer circumferential surface 12d extends circumferentially along the outer ring 12. The outer circumferential surface 12d is the surface opposite to the inner circumferential surface 12c in the radial direction of the outer ring 12.

[0037] The inner circumferential surface 12c has a raceway surface 12ca. The raceway surface 12ca is the portion of the inner circumferential surface 12c that contacts the rolling element 13. In the raceway surface 12ca, the inner circumferential surface 12c is recessed towards the outer circumferential surface 12d. When viewed in section along the central axis A1, the raceway surface 12ca is partially arc-shaped.

[0038] The inner ring 11 and the outer ring 12 are configured such that the outer circumferential surface 11d and the inner circumferential surface 12c (raceway surface 11da and raceway surface 12ca) are opposite each other.

[0039] The rolling element 13 has a spherical shape. The rolling element 13 is disposed between raceway surface 11da and raceway surface 12ca. The number of rolling elements 13 is, for example, multiple. The retainer 14 is disposed between the outer circumferential surface 11d and the inner circumferential surface 12c. The retainer 14 retains the rolling element 13 such that the circumferential spacing of the rolling elements 13 in the rolling bearing 10 is maintained within a certain range.

[0040] The inner ring 11, outer ring 12, and rolling element 13 are all made of steel. For example, the inner ring 11, outer ring 12, and rolling element 13 are made of bearing steel. The steel grades used for the inner ring 11, outer ring 12, and rolling element 13 are, for example, high-carbon chromium bearing steels such as SUJ2 and SUJ3 specified in JIS standard (JIS G 4805:2008). It should be noted that the steel constituting the inner ring 11, the outer ring 12, and the rolling element 13 may not be the same steel grade. It should be noted that the hydrogen concentration in the aforementioned steel is, for example, below 0.02 ppm by mass, meaning that the aforementioned steel has not been hydrogen-charged. It should be noted that there is no lower limit to the hydrogen concentration in the aforementioned steel.

[0041] The rolling sliding test step S2 is performed by the test apparatus 20. Figure 3 This is a schematic cross-sectional view of the experimental setup 20. (For example...) Figure 3 As shown, the test apparatus 20 includes a housing 21, a rotating shaft 22, a drive unit 23 (not shown), support bearings 24 and 25, a load-bearing component 26, and a pressure rod 27. It should be noted that... Figure 3 The up and down directions in the text correspond to the vertical direction. Figure 3 The left and right directions in the diagram correspond to the horizontal direction.

[0042] The housing 21 is configured to store lubricating oil inside. The rotating shaft 22 has a central shaft A2. The rotating shaft 22 has a first end 22a and a second end 22b (not shown) in the direction along the central shaft A2. The second end 22b is the end opposite to the first end 22a in the direction along the central shaft A2. The rotating shaft 22 is configured such that the central shaft A2 is in a horizontal direction.

[0043] The rotating shaft 22 is positioned with its first end 22a side inside the housing 21. The rolling bearing 10 is disposed inside the housing 21, thereby rotatably supporting the first end 22a side of the rotating shaft 22 about the central axis A2. More specifically, the inner ring 11 is mounted on the rotating shaft 22, and the outer ring 12 is mounted on the housing 21. It should be noted that the central axis A1 of the inner ring 11 coincides with the central axis A2 of the rotating shaft 22.

[0044] The rotating shaft 22 is connected to the drive unit 23 at its second end 22b. The drive unit 23 is, for example, a motor. The drive unit 23 is configured to rotate the rotating shaft 22 about the central axis A2.

[0045] The support bearing 24 is, for example, a deep groove ball bearing. It should be noted that the support bearing 24 is not the bearing intended for use in the hydrogen embrittlement peeling test method described in Embodiment 1. The support bearing 24 is disposed inside the housing 21. The inner ring of the support bearing 24 is mounted on the rotating shaft 22, and the outer ring of the support bearing 24 is mounted on the housing 21. The support bearing 24 supports the rotating shaft 22 at a position away from the first end 22a in a manner rotatable about the central axis A2.

[0046] The support bearing 25 is, for example, a deep groove ball bearing. It should be noted that the support bearing 25 is not the bearing intended for use in the hydrogen embrittlement peeling test method described in Embodiment 1. The support bearing 25 is disposed inside the housing 21. The inner ring of the support bearing 25 is mounted on the rotating shaft 22, and the outer ring of the support bearing 25 is mounted on the load-bearing member 26. The support bearing 25 supports the rotating shaft 22 between the rolling bearing 10 and the support bearing 24, allowing it to rotate about the central axis A2.

[0047] One end of the pressure rod 27 is disposed inside the housing 21. The pressure rod 27 is inserted into the housing 21 from the bottom wall side. One end of the pressure rod 27 is mounted on the load-bearing member 26. The pressure rod 27 extends in the vertical direction. The pressure rod 27 moves from the lower vertical direction to the upper vertical direction, for example, via a load sensor. As a result, a load is applied between the raceway surface 11da and the raceway surface 12ca via the rolling element 13 in a direction orthogonal to the central axis A2 (central axis A1) (more specifically, in a direction from the lower vertical direction to the upper vertical direction).

[0048] The rolling sliding test step S2 is performed by rotating the rotating shaft 22 around the central axis A2 (by rotating the inner ring 11 around the central axis A1) under the aforementioned load. Figure 3 In the diagram, the level LL of the lubricating oil supplied to the housing 21 is indicated by a dashed line. It should be noted that the level of the lubricating oil supplied to the housing 21 is along the central axis A2.

[0049] When the rotating shaft 22 rotates, the raceway surfaces 11da and 12ca are completely immersed in lubricating oil. In other words, when the rotating shaft 22 rotates, the lubricating oil level LL is always above the vertical direction of the raceway surface 12ca.

[0050] The lubricating oil is substantially free of water (H2O). More specifically, the water content in the lubricating oil is, for example, below 200 ppm by mass. The water content in the lubricating oil can also be below 100 ppm by mass. It should be noted that there is no lower limit to the water content in the lubricating oil. When the rotating shaft 22 rotates, the temperature of the lubricating oil is preferably above 100°C and below its flash point. When the temperature of the lubricating oil is above 100°C and below its flash point, the water in the lubricating oil evaporates during the rotation of the rotating shaft 22, thus eliminating the water content in the lubricating oil. For example, CVT transmission fluid is used as the lubricating oil. However, the lubricating oil used in the hydrogen embrittlement peeling test according to Embodiment 1 is not limited to this.

[0051] The effects of the hydrogen embrittlement peel test method described in Embodiment 1 will be explained below.

[0052] Hydrogen embrittlement spalling in raceway surfaces is believed to be caused by the following mechanisms: First, the metal-to-metal contact between the raceway surface and the rolling element causes the oxide film formed on the raceway surface to peel off, thus forming a new surface. Second, the new surface is chemically unstable, and hydrogen generated through tribochemical reactions is absorbed by the new surface to stabilize it. Third, when hydrogen is absorbed by the steel, the bonding force between the steel's crystal lattices decreases, leading to premature spalling of the raceway surface.

[0053] Even if the oxide film formed on the raceway surface peels off due to metal-to-metal contact with the rolling element, thus forming a new surface, the oxygen in the surrounding area will be absorbed by the new surface, and an oxide film will be formed again. Therefore, the new surface will not absorb oxygen again, and thus hydrogen embrittlement peeling is not likely to occur.

[0054] In the hydrogen embrittlement peeling test method according to Embodiment 1, when the rotating shaft 22 rotates (the inner ring 11 rotates), since the raceway surfaces 11da and 12ca are completely immersed in lubricating oil (the liquid level LL is above the raceway surface 12ca in the vertical direction), the oxygen around the newly formed surface is thin, making it difficult for an oxide film to form again in the newly formed surface, and the hydrogen generated by the tribochemical reaction is easily absorbed by the newly formed surface. Therefore, according to the hydrogen embrittlement peeling test method according to Embodiment 1, hydrogen embrittlement peeling can be reproduced.

[0055] When lubricating oil contains water, it is difficult to increase its temperature to suppress water evaporation. In other words, when lubricating oil contains water, it is difficult to increase its temperature to improve oil film parameters (thinning the oil film formed between the raceway surface and the rolling elements). As a result, due to the metal-to-metal contact between the raceway surface and the rolling elements, the oxide film formed on the raceway surface is difficult to peel off, making it difficult to form a new surface on the raceway surface.

[0056] On the other hand, in the hydrogen embrittlement peeling test method according to Embodiment 1, since the lubricating oil is substantially water-free, the temperature of the lubricating oil can be increased without hindrance to improve the oil film parameters (thinning the oil film formed between the raceway surface and the rolling element). Therefore, according to the hydrogen embrittlement peeling test method according to Embodiment 1, hydrogen embrittlement peeling can be easily reproduced by making it easy for the raceway surface 11da (raceway surface 12ca) to make metal-to-metal contact with the rolling element 13.

[0057] It should be noted that in the hydrogen embrittlement peel test method according to Embodiment 1, when the load between the raceway surface 11da and the raceway surface 12ca is applied from the lower vertical direction to the upper vertical direction, the test device 20 can be easily and compactly configured in terms of its structure.

[0058] <Experimental Example>

[0059] To confirm that the hydrogen embrittlement peeling test method according to Embodiment 1 can reproduce hydrogen embrittlement peeling, the following test was conducted. In this test, a first experimental example and a second experimental example were performed. In the first experimental example, the lubricating oil level LL reached the rotating shaft 22 (shaft oil bath). In the second experimental example, the lubricating oil level LL was located above the raceway surface 12ca in the vertical direction (i.e., the raceway surfaces 11da and 12ca were completely immersed in the lubricating oil).

[0060] Other conditions were the same in Experiment 1 and Experiment 2. More specifically, in Experiment 1 and Experiment 2, the load applied to the rotating shaft 22 caused the surface pressure of the raceway surface 12ca to become 2844 MPa (causing the deformation of the outer ring 12 to be 100 μm), and the oil film thickness to become 0.09 μm.

[0061] In the first experimental example, no hydrogen embrittlement peeling occurred on the raceway surface 12ca, and the rotating shaft 22 (inner ring 11) continued to rotate until the lubricating oil burned. On the other hand, in the second experimental example, hydrogen embrittlement peeling occurred on the raceway surface 12ca, and the rotating shaft 22 (inner ring 11) stopped rotating when the rotational speed reached 27% of that in the first experimental example. Thus, the experiments show that according to the hydrogen embrittlement peeling test method according to Embodiment 1, when the lubricating oil level LL is above the raceway surface 12ca in the vertical direction and the lubricating oil is substantially free of water, hydrogen embrittlement peeling can be reproduced.

[0062] (A variation of the hydrogen embrittlement peel test involved in Embodiment 1)

[0063] In the example above, it is assumed that during the rotation of the rotating shaft 22 (inner ring 11), the level of the lubricating oil LL is always above the vertical direction of the raceway surface 12ca (i.e., the raceway surface 11da and the raceway 12ca are completely immersed in the lubricating oil). However, even if the level of the lubricating oil LL is not always above the vertical direction of the raceway surface 12ca during the rotation of the rotating shaft 22 (inner ring 11), hydrogen embrittlement can still be reproduced as long as the time during which the raceway surface 11da and the raceway surface 12ca are not immersed in the lubricating oil is short enough.

[0064] (Implementation Method 2)

[0065] The hydrogen embrittlement peel test method according to Embodiment 2 will be described below. Here, the differences from the hydrogen embrittlement peel test method according to Embodiment 1 will be mainly explained, and will not be repeated.

[0066] The hydrogen embrittlement peel test method according to Embodiment 2 includes a preparation step S1 and a rolling sliding test step S2. In this respect, the hydrogen embrittlement peel test method according to Embodiment 2 is the same as that according to Embodiment 1. However, the structure of the rolling bearing prepared in the preparation step S1 and the structure of the test apparatus used in the rolling sliding test step S2 in the hydrogen embrittlement peel test method according to Embodiment 2 differ from those in the hydrogen embrittlement peel test method according to Embodiment 1.

[0067] In the preparation step S1 of the hydrogen embrittlement peeling test method according to Embodiment 2, a rolling bearing 30 is prepared. Figure 4 This is a sectional view along the central axis A3 of the rolling bearing 30. (Example) Figure 4 As shown, rolling bearing 30 is a thrust ball bearing. More specifically, rolling bearing 30 is a one-way thrust ball bearing. Rolling bearing 30 has an inner ring 31 (shaft ring), an outer ring 32 (seat ring), rolling elements 33, and a cage 34.

[0068] The inner ring 31 has an annular (circular) shape. The inner ring 31 has a central axis A3. The inner ring 31 has a first surface 31a and a second surface 31b. The first surface 31a and the second surface 31b form an end face along the direction of the central axis A3. The second surface 31b is the surface opposite to the first surface 31a. The first surface 31a has a raceway surface 31aa. The raceway surface 31aa is the portion of the first surface 31a that contacts the rolling element 33. The first surface 31a is recessed towards the second surface 31b at the raceway surface 31aa. When viewed in section along the central axis A3, the raceway surface 31aa is partially arc-shaped.

[0069] The outer ring 32 has an annular (circular) shape. The outer ring 32 has a central axis A3. The outer ring 32 has a first surface 32a and a second surface 32b. The first surface 32a and the second surface 32b form an end face along the direction of the central axis A3. The second surface 32b is the surface opposite to the first surface 32a. The first surface 32a has a raceway surface 32aa. The raceway surface 32aa is the portion of the first surface 32a that contacts the rolling element 33. The first surface 32a is recessed towards the second surface 32b at the raceway surface 32aa. When viewed in section along the central axis A3, the raceway surface 32aa is partially arc-shaped.

[0070] The inner ring 31 and the outer ring 32 are configured such that the first surface 31a and the first surface 32a (raceway surface 31aa and raceway surface 32aa) are opposite each other.

[0071] The rolling element 33 has a spherical shape. The rolling element 33 is disposed between raceway surface 31aa and raceway surface 32aa. The number of rolling elements 33 is, for example, multiple. A retainer 34 is disposed between the first surface 31a and the first surface 32a. The retainer 34 retains the rolling element 33 such that the circumferential spacing of the rolling elements 33 in the rolling bearing 30 is maintained within a certain range.

[0072] The inner ring 31, outer ring 32, and rolling elements 33 are all made of bearing steel such as SUJ2. The hydrogen concentration in the steel is below 0.02 ppm by mass. That is, the steel is not hydrogen-charged.

[0073] In the rolling and sliding test step S2 of the hydrogen embrittlement peel test method according to Embodiment 2, the test apparatus 40 is used. Figure 5 This is a schematic cross-sectional view of the experimental setup 40. (For example...) Figure 5 As shown, the test apparatus 40 includes a housing 41, a rotating shaft 42, a drive unit 43 (not shown), and a support bearing 44. It should be noted that... Figure 5 The up and down directions in the text correspond to the vertical direction. Figure 5 The left and right directions in the diagram correspond to the horizontal direction.

[0074] The housing 41 is configured to store lubricating oil inside. The rotating shaft 42 has a central shaft A4. The rotating shaft 42 has a first end 42a and a second end 42b (not shown) in the direction along the central shaft A4. The second end 42b is the end opposite to the first end 42a in the direction along the central shaft A2. The rotating shaft 42 is configured such that the central shaft A4 is in the vertical direction.

[0075] The first end 42a of the rotating shaft 42 is disposed inside the housing 41. A rolling bearing 30 is disposed inside the housing 41 and rotatably supports the first end 42a of the rotating shaft 42 about a central axis A4. More specifically, an inner ring 31 is mounted on the rotating shaft 42, and an outer ring 32 is mounted on the housing 41, with the inner ring 31 positioned above the outer ring 32 in a vertical direction. It should be noted that the central axis A3 of the inner ring 31 coincides with the central axis A4 of the rotating shaft 42.

[0076] The rotating shaft 42 is connected to the drive unit 43 at its second end 42b. The drive unit 43 is configured, for example, by a motor and a load sensor. The drive unit 43 is configured to rotate the rotating shaft 42 about the central axis A4 and apply a load between the raceway surface 31aa and the raceway surface 32aa via the rolling elements 33. The direction of the load is along the central axis A4 (central axis A3) (more specifically, along the direction from the top of the vertical direction to the bottom of the vertical direction).

[0077] The support bearing 44 is, for example, a deep groove ball bearing. It should be noted that the support bearing 44 is not the bearing intended for use in the hydrogen embrittlement peeling test method described in Embodiment 2. The support bearing 44 is disposed outside the housing 41. The support bearing 44 supports the rotating shaft 42 at a position remote from the first end 42a in a manner rotatable about the central axis A4.

[0078] The rolling sliding test step S2 is performed by rotating the rotating shaft 42 around the central axis A4 (by rotating the inner ring 31 around the central axis A3) under the aforementioned load. Figure 5 In the diagram, the level LL of the lubricating oil supplied to the housing 41 is represented by a dashed line. It should be noted that the level of the lubricating oil supplied to the housing 41 is orthogonal to the central axis A4.

[0079] When the rotating shaft 42 rotates, the raceway surfaces 31aa and 32aa are completely immersed in lubricating oil. From another perspective, when the rotating shaft 42 rotates, the lubricating oil level LL is always above the raceway surface 31aa in the vertical direction. Therefore, even the hydrogen embrittlement peeling test method according to Embodiment 2 is the same as the hydrogen embrittlement peeling test method according to Embodiment 1, easily reproducing hydrogen embrittlement peeling by facilitating metal-to-metal contact between the raceway surface 31aa (raceway surface 32aa) and the rolling element 33.

[0080] As described above, embodiments of the present invention have been illustrated, but various modifications can be made to these embodiments. Furthermore, the scope of the present invention is not limited to the described embodiments. The scope of the present invention is indicated by the claims rather than the description of the described embodiments, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0081] Industrial applicability

[0082] The above-described embodiments are particularly advantageous for hydrogen embrittlement peeling test methods for rolling bearings.

[0083] Figure Labels

[0084] S1: Preparation steps; S2: Rolling sliding test steps; 10: Rolling bearing; 11: Inner ring; 11a: Upper surface; 11b: Bottom surface; 11c: Inner circumferential surface; 11d: Outer circumferential surface; 11da: Raceway surface; 12: Outer ring; 12a: Upper surface; 12b: Bottom surface; 12c: Inner circumferential surface; 12ca: Raceway surface; 12d: Outer circumferential surface; 13: Rolling element; 14: Retainer; 20: Test apparatus; 21: Housing; 22: Rotating shaft; 22a: First end; 22b: Second end; 23: Drive unit; 24: Support bearing; 25: Support bearing; 26: Load-bearing component; 27: Pressure bar; 30: Bearing; 31: Inner ring; 31a: First surface; 31aa: Raceway surface; 31b: Second surface; 32: Outer ring; 32a: First surface; 32aa: Raceway surface; 32b: Second surface; 33: Rolling element; 34: Retainer; 40: Test device; 41: Housing; 42: Rotating shaft; 42a: First end; 42b: Second end; 43: Drive unit; 44: Support bearing; A1, A2, A3, A4: Central shaft; LL: Liquid level.

Claims

1. A hydrogen embrittlement peeling evaluation test method characterized by, comprises: preparing a rolling bearing having a first bearing ring, a second bearing ring, and rolling elements, the first bearing ring being a rotating ring including a first raceway surface, the second bearing ring being a stationary ring including a second raceway surface opposite to the first raceway surface, the rolling elements being arranged between the first raceway surface and the second raceway surface; and rotating the first bearing ring around a central axis in a state where a load is applied via the rolling elements between the first raceway surface and the second raceway surface, wherein the first bearing ring, the second bearing ring, and the rolling elements are each formed of steel; the first raceway surface and the second raceway surface are always completely immersed in lubricating oil during rotation, the lubricating oil is substantially free of water, a temperature of the lubricating oil is above 100°C and less than an ignition point of the lubricating oil during the rotation, a metal neosurface is formed on at least either one of the first raceway surface and the second raceway surface along with the rotation, the lubricating oil blocks oxygen from the surroundings to thereby inhibit formation of an oxide film on the metal neosurface, so that hydrogen generated by a tribochemical reaction enters the steel to cause hydrogen embrittlement.

2. The hydrogen embrittlement flaking evaluation test method according to claim 1, characterized by the rolling bearing is a radial ball bearing, the central axis is in a horizontal direction, the load is applied in a direction orthogonal to the central axis.

3. The hydrogen embrittlement flaking evaluation test method according to claim 2, characterized by the load is applied from a lower direction in a vertical direction to an upper direction in the vertical direction.

4. The hydrogen embrittlement flaking evaluation test method according to claim 1, characterized by the rolling bearing is a thrust ball bearing, the central axis is in a vertical direction, the load is applied in the vertical direction.

5. The hydrogen embrittlement flaking evaluation test method according to claim 1, characterized by a content of water in the lubricating oil is above 100 mass ppm and below 200 mass ppm.

6. The hydrogen embrittlement flaking evaluation test method according to claim 1, characterized by the lubricating oil is CVT transmission oil.

7. The hydrogen embrittlement peeling evaluation test method according to any one of claims 1 to 6, wherein a hydrogen concentration in the steel is below 0.02 mass ppm.

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