Rolling member and rolling component

Abstract

To provide a rolling member capable of suppressing generation of hydrogen embrittlement.SOLUTION: A rolling member (10) is a steel rolling member having a surface and subjected to quenching and tempering, and includes an oxide layer (11) disposed on a surface (10a, 10b, 10c, 10d). Oxide particles are dispersed in the oxide layer. An average particle diameter of the oxide particles in the oxide layer is 0.2 μm or less. The steel contains 0.80 mass% or more and 1.10 mass% or less of carbon, 0.15 mass% or more and 0.50 mass% or less of silicon, 0.30 mass% or more and 0.70 mass% or less of manganese, and 1.30 mass% or more and 1.60 mass% or less of chromium, with the balance being iron and unavoidable impurities.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a rolling member and a rolling component. [Background technology]

[0002] In recent years, the operating conditions for rolling parts such as rolling bearings have become increasingly severe. More specifically, a reduction in the amount of lubricating oil or a decrease in the viscosity of the lubricating oil can prevent the formation of a sufficient oil film on the raceway surface, which can lead to hydrogen embrittlement caused by the lubricating oil. Furthermore, with the recent trend toward energy conservation, the development of fuel cell vehicles and hydrogen gas engines has been promoted, and the use of hydrogen as a power source is being promoted. Even in these devices, exposure of rolling parts to hydrogen gas can cause hydrogen embrittlement.

[0003] Examples of conventional rolling parts include those described in Patent Document 1 (JP 2009-7614 A), Patent Document 2 (JP Patent No. 6735589 A), and Patent Document 3 (JP Patent No. 6356881 A). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-7614 [Patent Document 2] Patent No. 6735589 [Patent Document 3] Patent No. 6356881 Summary of the Invention [Problem to be solved by the invention]

[0005] The rolling components described in Patent Documents 1 to 3 have room for improvement in terms of suppressing hydrogen embrittlement. The present invention provides a rolling member in which the occurrence of hydrogen embrittlement is suppressed. [Means for solving the problem]

[0006] The rolling contact member of the present invention is a rolling contact member made of quenched and tempered steel having a surface, with an oxide layer disposed on the surface. Oxide particles are dispersed in the oxide layer. The average particle size of the oxide particles in the oxide layer is 0.2 μm or less. The steel contains 0.80 to 1.10 percent by mass carbon, 0.15 to 0.50 percent by mass silicon, 0.30 to 0.70 percent by mass manganese, and 1.30 to 1.60 percent by mass chromium, with the remainder consisting of iron and unavoidable impurities. [Effects of the Invention]

[0007] The rolling contact member of the present invention can suppress the occurrence of hydrogen embrittlement. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 2 is a cross-sectional view of the inner ring 10. [Figure 2] FIG. 2 is an enlarged cross-sectional view of the inner ring 10. [Figure 3] 3 is a manufacturing process diagram of the inner ring 10. FIG. [Figure 4] 1 is a cross-sectional view of a rolling bearing 100. FIG. [Figure 5] 1 is a surface SEM image of Sample 1. DETAILED DESCRIPTION OF THE INVENTION

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the embodiments of the present invention will be described with reference to the drawings. In the following drawings, the same or corresponding parts are designated by the same reference numerals, and redundant description will not be repeated.

[0010] A rolling member according to an embodiment will be described. Here, a rolling part is a part that transmits power while rotating. Specific examples of rolling parts include rolling bearings, ball screws, drive shafts, cam followers, and gears. The rolling member is a component used in rolling parts. Note that rolling bearings also include hub bearings. The rolling part according to an embodiment is preferably a rolling part used in hydrogen-utilizing equipment. In the following, a raceway ring (inner ring 10) of a rolling bearing will be described as a specific example of a rolling member according to an embodiment.

[0011] (Configuration of inner ring 10) The configuration of the inner ring 10 will be described below.

[0012] Fig. 1 is a cross-sectional view of inner ring 10. As shown in Fig. 1, the central axis of inner ring 10 is defined as central axis A. The direction of central axis A is defined as the axial direction, the direction of the circumference centered on central axis A is defined as the circumferential direction, and the direction passing through central axis A and perpendicular to central axis A is defined as the radial direction. Inner ring 10 is ring-shaped and extends along the circumferential direction.

[0013] The inner ring 10 has a width surface 10a and a width surface 10b. The width surface 10a and the width surface 10b each form an end surface of the inner ring 10 in the axial direction. The width surface 10b is the surface opposite the width surface 10a in the axial direction. The width surface 10a faces one side in the axial direction (the left side in FIG. 1), and the width surface 10b faces the other side in the axial direction (the right side in FIG. 1).

[0014] The inner ring 10 further has an inner peripheral surface 10c and an outer peripheral surface 10d. The inner peripheral surface 10c and the outer peripheral surface 10d each extend circumferentially. The outer peripheral surface 10d is the opposite surface to the inner peripheral surface 10c in the radial direction. One axial end of the inner peripheral surface 10c and one axial end of the outer peripheral surface 10d are continuous with the width surface 10a. The other axial end of the inner peripheral surface 10c and the other axial end of the outer peripheral surface 10d are continuous with the width surface 10b. The width surface 10a, the width surface 10b, the inner peripheral surface 10c, and the outer peripheral surface 10d are sometimes collectively referred to as the surface of the inner ring 10.

[0015] The inner ring 10 is attached to a shaft (not shown) at its inner peripheral surface 10c. The outer peripheral surface 10d has a raceway surface 10da. The raceway surface 10da is located at the center of the outer peripheral surface 10d in the axial direction. The outer peripheral surface 10d is recessed toward the inner peripheral surface 10c at the raceway surface 10da. In a cross-sectional view perpendicular to the circumferential direction, the raceway surface 10da has, for example, a partial arc shape. The inner ring 10 contacts rolling elements (not shown) at the raceway surface 10da.

[0016] The inner ring 10 is made of hardened and tempered steel. This steel contains 0.80 to 1.10 percent by mass of carbon, 0.15 to 0.50 percent by mass of silicon, 0.30 to 0.70 percent by mass of manganese, 1.30 to 1.60 percent by mass of chromium, 0.50 percent by mass or less of molybdenum, and 0.50 percent by mass or less of vanadium, with the balance being iron and unavoidable impurities. Examples of unavoidable impurities include 0.005 to 0.05 percent by mass of aluminum, 0.02 percent by mass or less of phosphorus, 0.01 percent by mass or less of sulfur, 0.015 percent by mass or less of nitrogen, and 0.0015 percent by mass or less of oxygen. The composition of the steel used for the inner ring 10 is shown in Table 1.

[0017] [Table 1]

[0018] The carbon content of the steel used in the inner ring 10 may be 0.90 mass percent or more and 1.10 mass percent or less. The silicon content of the steel used in the inner ring 10 may be 0.20 mass percent or more and 0.30 mass percent or less. The manganese content of the steel used in the inner ring 10 may be 0.40 mass percent or more and 0.50 mass percent or less. The chromium content of the steel used in the inner ring 10 may be 1.40 mass percent or more and 1.60 mass percent or less.

[0019] The molybdenum content of the steel used for the inner ring 10 may be 0.20 mass percent or more and 0.30 mass percent or less. The molybdenum content of the steel used for the inner ring 10 may be 0 mass percent. That is, the steel used for the inner ring 10 may not contain molybdenum. The vanadium content of the steel used for the inner ring 10 may be 0.20 mass percent or more and 0.30 mass percent or less. The vanadium content of the steel used for the inner ring 10 may be 0 mass percent. That is, the steel used for the inner ring 10 may not contain vanadium.

[0020] If the carbon content of the steel used for the inner ring 10 is less than 0.80 percent, the hardness of the steel may be insufficient. On the other hand, if the carbon content of the steel used for the inner ring 10 is more than 1.10 percent, quench cracking may occur in the steel. From this perspective, the carbon content of the steel used for the inner ring 10 is set to 0.80 to 1.10 percent by mass.

[0021] If the silicon content in the steel used for the inner ring 10 is less than 0.15 percent by mass, temper softening resistance and workability may be insufficient. On the other hand, if the silicon content in the steel used for the inner ring 10 exceeds 0.50 percent by mass, workability will actually decrease. From this perspective, the silicon content in the steel used for the inner ring 10 is set to 0.15 percent by mass or more and 0.50 percent by mass or less.

[0022] If the manganese content in the steel used for the inner ring 10 is less than 0.30 percent by mass, the hardenability of the steel may be insufficient. On the other hand, if the manganese content in the steel used for the inner ring 10 exceeds 0.70 percent by mass, the amount of manganese-based non-metallic inclusions, which are impurities, increases. From this perspective, the manganese content in the steel used for the inner ring 10 is set to 0.30 percent by mass or more and 0.70 percent by mass or less.

[0023] If the chromium content of the steel used for the inner ring 10 is less than 1.30 percent by mass, the hardenability may be insufficient, and nitrides and carbonitrides may not easily form. On the other hand, if the chromium content of the steel used for the inner ring 10 exceeds 1.60 percent by mass, coarse precipitates may form, potentially shortening the life of the steel. From this perspective, the chromium content of the steel used for the inner ring 10 is set to be 1.30 percent by mass or more and 1.60 percent by mass or less.

[0024] The inclusion of molybdenum in the steel used for the inner ring 10 causes fine precipitation of nitrides and carbonitrides. On the other hand, if the molybdenum content in the steel used for the inner ring 10 exceeds 0.50 mass percent, the cost of the steel increases. From this perspective, the molybdenum content in the steel used for the inner ring 10 is set to 0.50 mass percent or less.

[0025] The inclusion of vanadium in the steel used for the inner ring 10 causes fine precipitation of nitrides and carbonitrides. On the other hand, if the vanadium content in the steel used for the inner ring 10 exceeds 0.50 mass percent, the cost of the steel increases. From this perspective, the vanadium content in the steel used for the inner ring 10 is set to 0.50 mass percent or less.

[0026] Fig. 2 is an enlarged cross-sectional view of inner ring 10. As shown in Fig. 2, an oxide layer 11 is disposed on the surface of inner ring 10. A plurality of oxide particles are dispersed in oxide layer 11. The oxide particles are formed of an oxide of iron (e.g., Fe3O4). However, the oxide particles may be formed of an oxide of iron other than Fe3O4.

[0027] In the oxide layer 11, the average particle size of the oxide particles is 0.2 μm or less. The average particle size of the oxide particles is measured by image analysis of an SEM (Scanning Electron Microscope) image. More specifically, first, an SEM image is obtained so that 20 or more oxide particles are included in the observation field. Second, the average length in length and width is calculated for the 20 or more oxide particles included in the SEM image. This average length is taken as the average particle size of the oxide particles. In the oxide layer 11, the oxide particles may be connected to each other or may form aggregates. The area ratio of the oxide particles in the oxide layer 11 is, for example, 30% or more. The area ratio of the oxide particles in the oxide layer 11 is, for example, 99% or less. The area ratio of the oxide particles in the oxide layer 11 is measured by image analysis of the SEM image. More specifically, the area ratio of the oxide particles is calculated by dividing the number of pixels occupied by oxide particles in the SEM image by the number of pixels in the observation field and multiplying the result by 100.

[0028] A region 5 μm or less deep from the oxide layer 11 is designated as region R1. The carbon concentration in the steel in region R1 is, for example, equal to or less than the average carbon concentration of the base steel material used for the inner ring 10 (i.e., the average carbon concentration of the steel in a region more than 5 μm deep from the oxide layer 11). The carbon concentration in the steel in region R1 is, for example, 0.90 mass percent or less. The carbon concentration in the steel is measured using an electron probe micro analyzer (EPMA). Region R1 may have been subjected to nitriding treatment. That is, the average nitrogen concentration in the steel in region R1 may be 0.1 mass percent or more. The nitrogen concentration in the steel is measured using EPMA.

[0029] The average grain size of cementite in the steel in region R1 is, for example, 2.0 μm or less, preferably 1.0 μm or less. Cementite may not be present (may have disappeared) in the steel in region R1. The average grain size of cementite in the steel is measured by image analysis of an SEM observation image. More specifically, first, an SEM observation image is acquired so that 20 or more cementite particles are included in the observation field. Second, the average length and width of the 20 or more cementite particles included in the SEM observation image are calculated. This average length is determined as the average grain size of cementite. The maximum grain size of martensite block grains in the steel in region R1 is, for example, 5 μm or less. The maximum grain size of martensite block grains in the steel is measured by electron backscattered diffraction (EBSD). More specifically, the martensite block grains included in the observation field are identified by EBSD. The observation field is set so that at least 20 martensite blocks are included in the observation field. The difference in crystal orientation between adjacent martensite block grains at the grain boundary is 15° or more. From another perspective, even if there is a location where the crystal orientation is misaligned, if the difference in crystal orientation is less than 15°, that location is not considered to be a grain boundary of martensite block grains. Second, the circle-equivalent diameter of each of the multiple martensite block grains included in the observation field is calculated. This circle-equivalent diameter is the square root of the value obtained by dividing the area of ​​the martensite block grain by π / 4. The maximum value of these circle-equivalent diameters is considered to be the maximum grain size of the martensite block grains.

[0030] In region R1, multiple precipitates may be present in the steel. The main component of the precipitate is chromium, vanadium, manganese, or silicon. The main component of the precipitate refers to the component with the highest content, evaluated in mass percent, among the components of the precipitate. The maximum grain size of the precipitates in region R1 is 2.0 μm or less. The maximum grain size of the precipitates in the steel is measured by image analysis of the SEM image. More specifically, first, an SEM image is obtained so that 20 or more precipitates are included in the observation field. Second, the average length in both the vertical and horizontal directions of the 20 or more precipitates included in the SEM image is calculated. This average length is taken as the average grain size of the precipitates. The area fraction of the precipitates in the steel in region R1 is, for example, 2.0% or more. The area fraction of the precipitates in the steel is measured by image analysis of the SEM image. More specifically, the area ratio of precipitates is calculated by dividing the number of pixels occupied by precipitates in the SEM observation image by the number of pixels in the observation field and multiplying the result by 100.

[0031] The region at a depth of 100 μm or less from the oxide layer 11 is designated as region R2. The amount of retained austenite in the steel in region R2 is, for example, less than 20 volume percent. The amount of retained austenite in the steel is measured by X-ray diffraction. More specifically, first, the integrated intensity of the diffraction peak of austenite in X-ray diffraction and the integrated intensity of the diffraction peak of phases other than austenite in X-ray diffraction are measured. Second, the volume ratio of retained austenite in the steel is calculated by comparing the integrated intensity of the diffraction peak of austenite in X-ray diffraction with the integrated intensity of the diffraction peak of phases other than austenite in X-ray diffraction.

[0032] Nitriding treatment may not be performed on region R1 (i.e., the nitrogen concentration in the steel in region R1 may be less than 0.1 mass percent). In this case, in region R1, the maximum grain size of martensite block grains in the steel may be 10 μm or less, precipitates in the steel may be mainly composed of chromium or vanadium, the maximum grain size of cementite in the steel may be 5 μm or less, and the area fraction of cementite may be 2.0% or more. The area fraction of cementite in the steel is measured by image analysis of the SEM observation image. More specifically, the area fraction of cementite is calculated by dividing the number of pixels occupied by cementite in the SEM observation image by the number of pixels in the observation field, and multiplying the result by 100. In this case, the amount of retained austenite in the steel in region R2 may be less than 10 volume percent.

[0033] (Manufacturing method of inner ring 10) A method for manufacturing the inner ring 10 will be described below.

[0034] Fig. 3 is a manufacturing process diagram of the inner ring 10. As shown in Fig. 3, the manufacturing method of the inner ring 10 includes a preparation step S1, a nitriding treatment step S2, a decarburization treatment step S3, a first quenching step S4, a second quenching step S5, a first tempering step S6, a grinding step S7, and a second tempering step S8.

[0035] In the preparation step S1, a ring-shaped workpiece is prepared. The workpiece is made of steel having the composition shown in Table 1. After the preparation step S1, a nitriding treatment step S2 is carried out.

[0036] In the nitriding process S2, the workpiece is heated in an atmospheric gas containing a nitrogen source to perform nitriding. As a result, nitrogen is introduced from the surface of the workpiece and diffuses into the workpiece. In the decarburization process S3, the workpiece is placed in a decarburization atmosphere to perform decarburization. This reduces the carbon concentration in the steel at the surface of the workpiece. The nitriding process S2 and the decarburization process S3 are usually performed simultaneously. Note that the decarburization process S3 promotes the precipitation of fine precipitates. After the nitriding process S2 and the decarburization process S3, a first quenching process S4 is performed.

[0037] In the first quenching step S4, the workpiece is heated to a temperature equal to or higher than the A1 transformation point, and then subjected to M S The steel is cooled to a temperature below the transformation point. As a result, martensite and retained austenite are formed in the steel used for the processed member. After the first quenching step S4, the second quenching step S5 is performed. In the second quenching step S5, the steel is heated to a temperature above the A1 transformation point and then cooled to a temperature below the A1 transformation point. S The workpiece is quenched again by cooling to a temperature below the transformation point, and the crystal grains in the steel are refined. After the second quenching step S5, a first tempering step S6 is performed.

[0038] In the first tempering step S6, the workpiece is heated to a temperature below the A1 transformation point, thereby tempering the steel used in the workpiece. After the first tempering step S6, a grinding step S7 is performed. In the grinding step S7, the workpiece is ground to form the shape of the inner ring 10. After the grinding step S7, a second tempering step S8 is performed.

[0039] In the second tempering step S8, the workpiece is heated to a temperature below the A1 transformation point, thereby further tempering the steel used in the workpiece. During this process, an oxide layer 11 is formed on the surface of the workpiece (the surface of the inner ring 10). The heating temperature in the second tempering step S8 is higher than the heating temperature in the first tempering step S6.

[0040] In the above, an example has been described in which the manufacturing method of the inner ring 10 includes a preparation step S1, a nitriding treatment step S2, a decarburization treatment step S3, a first quenching step S4, a second quenching step S5, a first tempering step S6, a grinding step S7, and a second tempering step S8, but the manufacturing method of the inner ring 10 does not necessarily require any of the nitriding treatment step S2, the decarburization treatment step S3, and the second quenching step S5.

[0041] (The effect of inner circle 10) The effects of the inner ring 10 will be described below.

[0042] Reaction between the new metal surface and the lubricating oil causes hydrogen embrittlement. An oxide layer 11 is formed on the surface of the inner ring 10. Fine oxide particles with an average particle size of 0.2 μm or less are dispersed in the oxide layer 11. As a result, the surface of the inner ring 10, including the raceway surface 10da, has high wear resistance, and new metal surfaces due to wear are less likely to form on the surface of the inner ring 10, making it possible for the inner ring 10 to suppress the occurrence of hydrogen embrittlement.

[0043] During the manufacturing process of the inner ring 10, a second tempering step S8, i.e., high-temperature tempering, is performed to form the oxide layer 11. This reduces atomic vacancies in the steel used for the inner ring 10. The high-temperature tempering described above also reduces the dislocation density in the steel, making it less likely for atomic vacancies to increase during use of the inner ring 10 and reducing diffusible hydrogen in the steel. When the high-temperature tempering described above is performed, some of the hydrogen previously present in the steel is released to the outside. The high-temperature tempering described above increases the amount of fine precipitates. These precipitates trap hydrogen and render it harmless. The high-temperature tempering described above reduces the amount of retained austenite in the steel, reducing dimensional change in the inner ring 10 during use and suppressing slippage, which causes wear. This suppresses the formation of new surfaces and reduces diffusible hydrogen in the steel. From these perspectives, the inner ring 10 is also less susceptible to hydrogen embrittlement.

[0044] If nitriding is performed during the manufacturing process of inner ring 10, dislocation motion is further suppressed by solid-solution strengthening associated with the dissolution of nitrogen, further reducing the likelihood of an increase in atomic vacancies that cause hydrogen embrittlement and further suppressing hydrogen embrittlement. Also, oxide particles are dispersed in oxide layer 11, i.e., gaps exist between the oxide particles, and these gaps relieve stress caused by differences in the amount of deformation between oxide layer 11 and the surrounding area due to temperature changes or load changes, thereby suppressing peeling of oxide layer 11 during use of inner ring 10.

[0045] (Rolling bearing using inner ring 10) FIG. 4 is a cross-sectional view of a rolling bearing 100. As shown in FIG. 4, the rolling bearing 100 has, as rolling components, an inner ring 10, an outer ring 20, and multiple rolling elements 30. The outer ring 20 has an inner circumferential surface 20a and an outer circumferential surface 20b. The inner circumferential surface 20a has a raceway surface 20aa. The outer ring 20 is disposed radially outward of the inner ring 10 so that the inner circumferential surface 20aa (raceway surface 20aa) faces the outer circumferential surface 10d (raceway surface 10da). The outer ring 20 is attached to a housing (not shown) at its outer circumferential surface 20b. The rolling elements 30 are disposed between the raceway surface 10da and the raceway surface 20aa. The rolling bearing 100 further includes a cage 40 disposed between the outer circumferential surface 10d and the inner circumferential surface 20a and holding the multiple rolling elements 30 so as to maintain the spacing between two adjacent rolling elements 30 within a certain range.

[0046] The outer ring 20 and the rolling element 30 may or may not be the rolling element according to this embodiment. That is, the rolling member according to this embodiment only needs to have the rolling element according to this embodiment as at least one rolling element.

[0047] (Example) In order to confirm the effects of the rolling contact member according to the embodiment, Samples 1 to 6 were prepared. Samples 1 to 6 were made of steel having a first composition or a second composition shown in Table 2. The first composition and the second composition were both within the range of the composition shown in Table 1. The heat treatment for Samples 1 to 6 was changed as shown in Table 3.

[0048] [Table 2]

[0049] [Table 3]

[0050] The second tempering step S8 was performed on Sample 1, but the second tempering step S8 was not performed on Sample 2. FIG. 5 is an SEM image of the surface of Sample 1. As shown in FIG. 5, an oxide layer 11 was formed on the surface of Sample 1, but no oxide layer 11 was formed on the surface of Sample 2. In order to evaluate hydrogen embrittlement in Sample 1 and Sample 2, a rolling fatigue life test was performed under the conditions shown in Table 4.

[0051] [Table 4]

[0052] As shown in Table 5, L in Sample 1 50 The life (time when the cumulative probability of failure reaches 50%) is L 50 This comparison reveals that the formation of the oxide layer 11 on the surface of the rolling member suppresses the occurrence of hydrogen embrittlement.

[0053] [Table 5]

[0054] In Samples 3 and 4, in addition to the second tempering step S8, the nitriding step S2 and the decarburization step S3 were also performed. Steel having the first composition was used in Sample 3, while steel having the second composition was used in Sample 4. Abrasion resistance tests were performed on Samples 2 to 4 under the conditions shown in Table 6.

[0055] [Table 6]

[0056] As shown in Table 7, Samples 3 and 4, on whose surfaces the oxide layer 11 was formed, exhibited better wear resistance than Sample 2, on whose surface the oxide layer 11 was not formed. Sample 3 had particularly excellent wear resistance because fine precipitates were formed in large quantities due to the vanadium and molybdenum contained in the steel.

[0057] [Table 7]

[0058] As shown in Table 8, the amounts of hydrogen trapped in Samples 5 and 6 during the manufacturing process up to grinding step S7 were measured. The amounts of hydrogen were measured by the temperature-programmed desorption method, varying the temperature from room temperature to 400°C. In Table 8, the amount of hydrogen trapped in Sample 5 is shown relative to the amount of hydrogen trapped in Sample 6, with the amount of hydrogen being set at 1. The amount of retained austenite in Sample 5 was 30 volume percent or more, while the amount of retained austenite in Sample 6 was less than 15 volume percent. The amount of hydrogen trapped in Sample 5 was 1.8 to 2.4 times the amount of hydrogen trapped in Sample 6. This comparison reveals that the amount of trapped hydrogen decreases when the amount of retained austenite is reduced.

[0059] [Table 8]

[0060] (Addendum) The above embodiment includes the following configurations.

[0061] <Appendix 1> A rolling element made of hardened and tempered steel having a surface, an oxide layer disposed on the surface; oxide particles are dispersed in the oxide layer, the average particle size of the oxide particles in the oxide layer is 0.2 μm or less; The rolling member, wherein the steel contains 0.80 to 1.10 percent by mass of carbon, 0.15 to 0.50 percent by mass of silicon, 0.30 to 0.70 percent by mass of manganese, and 1.30 to 1.60 percent by mass of chromium, with the remainder being iron and unavoidable impurities.

[0062] <Appendix 2> A rolling element made of hardened and tempered steel having a surface, an oxide layer disposed on the surface; oxide particles are dispersed in the oxide layer, the average particle size of the oxide particles in the oxide layer is 0.2 μm or less; the steel comprises from 0.80 to 1.10 percent by weight of carbon, from 0.15 to 0.50 percent by weight of silicon, from 0.30 to 0.70 percent by weight of manganese, from 1.30 to 1.60 percent by weight of chromium, from 0.50 to 0.50 percent by weight of molybdenum, and from 0.50 to 0.50 percent by weight of vanadium, with the balance being iron and unavoidable impurities; The rolling member has an average nitrogen concentration of 0.1 mass percent or more in a region at a depth of 5 μm or less from the oxide layer.

[0063] <Appendix 3> 2. The rolling contact member according to claim 1, wherein the area ratio of the oxide particles in the oxide layer is 30 percent or more.

[0064] <Appendix 4> 3. The rolling contact member according to claim 2, wherein the area ratio of the oxide particles in the oxide layer is 30 percent or more.

[0065] <Appendix 5> 4. The rolling contact member according to claim 1, wherein the amount of retained austenite in a region at a depth of 100 μm or less from the oxide layer is less than 10 volume percent.

[0066] <Appendix 6> 5. The rolling contact member according to claim 2, wherein the amount of retained austenite in a region at a depth of 100 μm or less from the oxide layer is less than 10 volume percent.

[0067] <Appendix 7> In a region having a depth of 100 μm or less from the oxide layer, precipitates are dispersed at an area ratio of 2.0% or more, The rolling member according to claim 2, 4 or 6, wherein the precipitates are mainly composed of chromium, vanadium, manganese or silicon.

[0068] <Appendix 8> A rolling component comprising the rolling member according to any one of Supplementary Note 1 to Supplementary Note 7.

[0069] <Appendix 9> 9. The rolling component according to claim 8, wherein the rolling component is a rolling bearing.

[0070] Although the embodiments of the present invention have been described above, the above-described embodiments can be modified in various ways. Furthermore, the scope of the present invention is not limited to the above-described embodiments. The scope of the present invention is defined by the claims, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0071] 10 Inner wheel, 10a Width, 10b Width, 10c Inner peripheral surface, 10d Outer peripheral surface, 10da Track surface, 11 Oxide layer, 20 Outer wheel, 20a Inner peripheral surface, 20aa Track surface, 20b Outer peripheral surface, 30 Rotating body, 40 Holder, 100 Rotating shaft, A Central shaft, R1, R2 Area, S1 Preparation process, S2 Impregnation process, S3 Decarburization process, S4 First blasting process, S5 Second blasting process, S6 First blasting process, S7 Grinding process, S8 Second blasting process.

Claims

1. A rolling element made of hardened and tempered steel having a surface, an oxide layer disposed on the surface; oxide particles are dispersed in the oxide layer, the average particle size of the oxide particles in the oxide layer is 0.2 μm or less; The rolling member, wherein the steel contains 0.80 mass percent to 1.10 mass percent carbon, 0.15 mass percent to 0.50 mass percent silicon, 0.30 mass percent to 0.70 mass percent manganese, and 1.30 mass percent to 1.60 mass percent chromium, with the remainder being iron and unavoidable impurities.

2. A rolling element made of hardened and tempered steel having a surface, an oxide layer disposed on the surface; oxide particles are dispersed in the oxide layer, the average particle size of the oxide particles in the oxide layer is 0.2 μm or less; the steel comprises 0.80 to 1.10 percent by weight of carbon, 0.15 to 0.50 percent by weight of silicon, 0.30 to 0.70 percent by weight of manganese, 1.30 to 1.60 percent by weight of chromium, 0.50 percent by weight or less of molybdenum and 0.50 percent by weight or less of vanadium, with the balance being iron and unavoidable impurities; The rolling member has an average nitrogen concentration of 0.1 mass percent or more in a region at a depth of 5 μm or less from the oxide layer.

3. 2. The rolling contact member according to claim 1, wherein an area ratio of said oxide particles in said oxide layer is 30 percent or more.

4. 3. The rolling contact member according to claim 2, wherein an area ratio of said oxide particles in said oxide layer is 30 percent or more.

5. 2. The rolling contact member according to claim 1, wherein the amount of retained austenite in the region at a depth of 100 μm or less from the oxide layer is less than 10 volume percent.

6. 3. The rolling contact member according to claim 2, wherein the amount of retained austenite in the region at a depth of 100 μm or less from the oxide layer is less than 10 volume percent.

7. In a region having a depth of 100 μm or less from the oxide layer, precipitates are dispersed at an area ratio of 2.0% or more, 3. The rolling contact member according to claim 2, wherein the precipitates are mainly composed of chromium, vanadium, manganese or silicon.

8. A rolling component, A rolling component comprising the rolling member according to any one of claims 1 to 7.

9. The rolling element according to claim 8 , wherein the rolling element is a rolling bearing.

Images