Steel sliding parts and methods for manufacturing steel sliding parts

Abstract

To provide a steel sliding component capable of reducing a friction coefficient.SOLUTION: A steel sliding component (10) in this embodiment has a circular or annular cross section vertical to a center axis, and has a sliding face. Vickers hardness at a testing force of 1kN on the sliding face is 500HV or more. An outermost surface rectangular area having the sliding face and located at depth of 10 μm from the sliding face and width of 50 μm among the cross sections of the steel sliding component (10) including the center axis includes a specific aggregate composition area whose area ratio of a {203} crystal orientation obtained by crystal orientation analysis in a direction parallel to the sliding face is 7.0% or more.SELECTED DRAWING: Figure 1

Description

【Technical Field】 【0001】 The present disclosure relates to a steel sliding part and a method for manufacturing the steel sliding part. 【Background Art】 【0002】 Sliding parts typified by the outer ring, inner ring, raceway plate, and rolling elements of bearings are used, for example, as parts of an automobile transmission. Many of these parts are made of steel. In the following description, a sliding part made of steel is referred to as a "steel sliding part." 【0003】 The steel sliding parts used for the above applications are required to have high fatigue strength. As a means of increasing the fatigue strength of these steel sliding parts, quenching and tempering treatment (quenching and tempering) is known. 【0004】 The steel sliding part subjected to quenching and tempering treatment has a martensite structure. The martensite structure increases the hardness of the surface layer of the steel part. Therefore, the fatigue strength of the steel sliding part increases. The steel sliding part with increased fatigue strength by quenching and tempering treatment has been proposed, for example, in Japanese Patent Application Laid-Open No. 2013-112861 (Patent Document 1). 【Prior Art Documents】 【Patent Documents】 【0005】 【Patent Document 1】 Japanese Patent Application Laid-Open No. 2013-!12861 【Summary of the Invention】 【Problems to be Solved by the Invention】 【0006】 By the way, recently, further improvement in fuel efficiency of automobiles has been demanded. If the energy loss in the transmission can be suppressed, further improvement in fuel efficiency can be achieved. One of the energy losses in the transmission is the frictional loss of power transmission. If this frictional loss can be reduced, the energy loss can be reduced. 【0007】 To reduce frictional losses in power transmission, it is effective to reduce the coefficient of friction (static friction coefficient and kinetic friction coefficient) of the steel sliding parts involved in power transmission. Here, the static friction coefficient is a coefficient proportional to the frictional force that acts to hinder the movement of a steel sliding part when it starts to rotate or perform other movements. The kinetic friction coefficient is a coefficient proportional to the frictional force that acts to hinder the movement of a steel sliding part while it is rotating. If the coefficient of friction (static friction coefficient and kinetic friction coefficient) can be reduced, the static friction force and kinetic friction force can be reduced. As a result, frictional losses in power transmission can be reduced. 【0008】 The object of this disclosure is to provide a steel sliding part capable of reducing the coefficient of friction and a method for manufacturing a steel sliding part. [Means for solving the problem] 【0009】 The steel sliding component according to this disclosure has the following configuration: 【0010】 A steel sliding component having a circular or annular cross-section perpendicular to its central axis, Having a sliding surface, The Vickers hardness at a test force of 1 kN is 500 HV or higher. In the cross-section of the steel sliding component including the central axis, the outermost rectangular region including the sliding surface and extending 10 μm to a depth and 50 μm to a width from the sliding surface includes a specific texture region in which the area ratio of the {203} crystal orientation obtained by crystal orientation analysis in a direction parallel to the sliding surface is 7.0% or more. Steel sliding parts. 【0011】 The method for manufacturing steel sliding parts according to this disclosure includes the following steps: 【0012】 The above-mentioned method for manufacturing steel sliding parts, An intermediate product preparation step is performed to prepare an intermediate product in which the cross-section perpendicular to the central axis is circular or annular, the Vickers hardness at a test force of 1 kN is 500 HV or more, the volume fraction of retained austenite in the outermost rectangular area is 10.0 to 40.0%, the arithmetic mean roughness Ra of the sliding surface in accordance with JIS B 0601:2013 is 0.05 to 2.00 μm, and the KAM value of the outermost rectangular area is 0.40° or more. The process includes a step of adjusting the crystal orientation of the outermost layer, in which the intermediate product is rotated around the central axis, and a reduction tool harder than the intermediate product is pressed against the sliding surface of the intermediate product with a pressure of 8.5 to 15.0 GPa, while the reduction tool is slid relative to the sliding surface in a direction perpendicular to the rotational direction of the intermediate product, thereby plastically deforming the surface layer including the sliding surface and forming the specific texture region. A method for manufacturing steel sliding parts. [Effects of the Invention] 【0013】 The steel sliding parts according to this disclosure enable a reduction in the coefficient of friction. The method for manufacturing steel sliding parts according to this disclosure can manufacture the aforementioned steel sliding parts. [Brief explanation of the drawing] 【0014】 [Figure 1] Figure 1 is a cross-sectional view including the central axis of the steel sliding component of this embodiment. [Figure 2] Figure 2 is an enlarged view of region 50 shown in Figure 1. [Figure 3] Figure 3 shows an example of orientation mapping in the outermost rectangular area shown in Figure 2. [Figure 4A] Figure 4A shows the relationship between the area ratio of the {203} crystal orientation in the outermost rectangular region of a steel sliding component and the coefficient of static friction. [Figure 4B] Figure 4B shows the relationship between the area ratio of the {203} crystal orientation in the outermost rectangular region of a steel sliding component and the coefficient of dynamic friction. [Figure 5] Figure 5 is a schematic diagram of a device (surface plastic deformation device) for performing surface plastic deformation. [Figure 6]FIG. 6 is a schematic diagram of a block-on-ring test. [Figure 7] FIG. 7 is a diagram showing an example of a graph of the coefficient of friction obtained in the rotation test after the second time in the block-on-ring test. 【Embodiments for Carrying Out the Invention】 【0015】 The inventors of the present invention studied means for reducing the coefficient of friction (static coefficient of friction and dynamic coefficient of friction) of steel sliding parts. First, the inventors of the present invention thought that if the hardness of the steel sliding parts was increased by performing a quenching and tempering treatment on the steel sliding parts, the coefficient of friction would be suppressed. 【0016】 However, simply increasing the hardness of the steel sliding parts could not sufficiently reduce the coefficient of friction. Therefore, the inventors of the present invention studied other means for reducing the coefficient of friction. 【0017】 Assume a case where the surface of a quenched and tempered steel sliding part contacts and operates with other parts. Here, a surface that contacts other parts and slides relative to the other parts is defined as a "sliding surface". 【0018】 The inventors of the present invention thought that the orientation of the crystal orientation in the surface layer of the sliding surface of the steel sliding parts might affect the coefficient of friction. Therefore, the inventors of the present invention investigated and studied the relationship between the orientation of the crystal orientation in the surface layer of the sliding surface and the coefficient of friction. 【0019】 The inventors of the present invention manufactured a plurality of types of steel sliding parts, and performed crystal orientation analysis in the direction parallel to the sliding surface in the surface layer of the cross section including the central axis of each steel sliding part to create an orientation mapping. Further, the coefficient of friction of these steel sliding parts was obtained, and the relationship between the orientation mapping and the coefficient of friction was investigated. As a result, the inventors of the present invention found that the higher the area ratio of the {203} crystal orientation in the surface layer, the more the coefficient of friction was suppressed. And as a result of further study, it was first found that if the area ratio of the {203} crystal orientation in the surface layer is 7.0% or more, the coefficient of friction (static coefficient of friction and dynamic coefficient of friction) can be sufficiently suppressed. 【0020】 The steel sliding component of this embodiment was completed based on the above-described technical concept and has the following configuration. 【0021】 [1] A steel sliding component having a circular or annular cross-section perpendicular to its central axis, Having a sliding surface, The Vickers hardness at a test force of 1 kN is 500 HV or higher. In the cross-section of the steel sliding component including the central axis, the outermost rectangular region including the sliding surface and extending 10 μm to a depth and 50 μm to a width from the sliding surface includes a specific texture region in which the area ratio of the {203} crystal orientation obtained by crystal orientation analysis in a direction parallel to the sliding surface is 7.0% or more. Steel sliding parts. 【0022】 [2] [1] Steel sliding parts, The aforementioned steel sliding component is one of the outer ring, inner ring, raceway, or rollers of the bearing. Steel sliding parts. 【0023】 [3] [1] Steel sliding parts, The area fraction of the {203} crystal orientation is 10.0% or more. Steel sliding parts. 【0024】 [4] [1] Steel sliding parts, The area fraction of the {203} crystal orientation is 12.5% ​​or more. Steel sliding parts. 【0025】 [5] A method for manufacturing a steel sliding component as described in any one of items [1] to [4], An intermediate product preparation step is performed to prepare an intermediate product in which the cross-section perpendicular to the central axis is circular or annular, the Vickers hardness at a test force of 1 kN is 500 HV or more, the volume fraction of retained austenite in the outermost rectangular area is 10.0 to 40.0%, the arithmetic mean roughness Ra of the sliding surface in accordance with JIS B 0601:2013 is 0.05 to 2.00 μm, and the KAM value of the outermost rectangular area is 0.40° or more. The process includes a step of adjusting the crystal orientation of the outermost layer, in which the intermediate product is rotated around the central axis, and a reduction tool harder than the intermediate product is pressed against the sliding surface of the intermediate product with a pressure of 8.5 to 15.0 GPa, while the reduction tool is slid relative to the sliding surface in a direction perpendicular to the rotational direction of the intermediate product, thereby plastically deforming the surface layer including the sliding surface and forming the specific texture region. A method for manufacturing steel sliding parts. 【0026】 [6] A method for manufacturing steel sliding parts as described in [5], The aforementioned intermediate product preparation process is: The processing steps for working with steel materials, The process includes a tempering step in which the processed steel material is hardened and tempered to achieve a Vickers hardness of 500 HV or more at a test force of 1 kN for the intermediate product, and the volume fraction of retained austenite in the outermost rectangular region is 10.0 to 40.0%. A method for manufacturing steel sliding parts. 【0027】 [7] A method for manufacturing steel sliding parts as described in [6], The aforementioned intermediate product preparation process further, The process includes a surface adjustment step in which the sliding surface of the intermediate product after the tempering step is machined to set the arithmetic mean roughness Ra of the sliding surface to 0.05 to 2.00 μm in accordance with JIS B 0601:2013, and the KAM value of the outermost rectangular area of ​​the sliding surface to 0.40° or more. A method for manufacturing steel sliding parts. 【0028】 The steel sliding components according to this embodiment will be described in detail below. 【0029】 [Structure of steel sliding parts] Figure 1 is a cross-sectional view including the central axis of the steel sliding component of this embodiment. Figure 1(A) is a cross-sectional view of a ball bearing. Figure 1(B) is a cross-sectional view of a thrust ball bearing. Figure 1(C) is a cross-sectional view of a roller bearing. Figure 1(D) is a cross-sectional view of a thrust roller bearing. 【0030】 The ball bearing in Figure 1(A) comprises an outer ring 10A, an inner ring 10B, and a plurality of balls BR. The outer ring 10A has an annular cross-section perpendicular to the central axis and has a raceway surface 10SA. The inner ring 10B has an annular cross-section perpendicular to the central axis and has a raceway surface 10SB. The raceway surfaces 10SA and 10SB are surfaces that contact the plurality of balls BR and slide relative to the balls BR. In a ball bearing, the outer ring 10A corresponds to the steel sliding component 10, and the raceway surface 10SA corresponds to the sliding surface 10S. Similarly, the inner ring 10B corresponds to the steel sliding component 10, and the raceway surface 10SB corresponds to the sliding surface 10S. 【0031】 The thrust ball bearing shown in Figure 1(B) comprises a raceway plate 10C, a raceway plate 10D, and a plurality of balls BR. The raceway plate 10C has an annular cross-section perpendicular to the central axis and has a raceway surface 10SC. The raceway plate 10D has an annular cross-section perpendicular to the central axis and has a raceway surface 10SD. The raceway surfaces 10SC and 10SD are surfaces that contact the plurality of balls BR and slide relative to the balls BR. In a thrust ball bearing, the raceway plate 10C corresponds to the steel sliding component 10, and the raceway surface 10SC corresponds to the sliding surface 10S. The raceway plate 10D corresponds to the steel sliding component 10, and the raceway surface 10SD corresponds to the sliding surface 10S. 【0032】 The roller bearing shown in Figure 1(C) comprises an outer ring 10A, an inner ring 10B, and a plurality of rollers 10BR. The outer ring 10A has an annular cross-section perpendicular to the central axis and has a raceway surface 10SA. The inner ring 10B has an annular cross-section perpendicular to the central axis and has a raceway surface 10SB. The raceway surfaces 10SA and 10SB are surfaces that contact the plurality of rollers 10BR and slide relative to the rollers 10BR. 【0033】 Roller 10BR may be a needle-shaped roller, a cylindrical roller, or a conical roller. Roller 10BR has a circular cross-section perpendicular to its central axis, and its outer surface 10SBR is the surface that slides relative to the raceway surfaces 10SA and 10SB. 【0034】 In a roller bearing, the outer ring 10A corresponds to the steel sliding component 10, and the raceway surface 10SA corresponds to the sliding surface 10S. Similarly, the inner ring 10B corresponds to the steel sliding component 10, and the raceway surface 10SB corresponds to the sliding surface 10S. Furthermore, the roller 10BR corresponds to the steel sliding component 10, and the outer surface 10SBR of the roller 10 around its axis corresponds to the sliding surface 10S. 【0035】 The thrust roller bearing shown in Figure 1(D) comprises a raceway plate 10C, a raceway plate 10D, and a plurality of rollers 10BR. The raceway plate 10C has an annular cross-section perpendicular to the central axis and has a raceway surface 10SC. The raceway plate 10D has an annular cross-section perpendicular to the central axis and has a raceway surface 10SD. The raceway surfaces 10SC and 10SD are surfaces that contact the plurality of rollers 10BR and slide relative to the rollers 10BR. Roller 10BR may be a needle-shaped roller, a cylindrical roller, or a conical roller. Roller 10BR has a circular cross-section perpendicular to its central axis, and its outer surface 10SBR is the surface that slides relative to the raceway surfaces 10SA and 10SB. 【0036】 In a thrust roller bearing, the raceway plate 10C corresponds to the steel sliding component 10, and the raceway surface 10SC corresponds to the sliding surface 10S. The raceway plate 10D corresponds to the steel sliding component 10, and the raceway surface 10SD corresponds to the sliding surface 10S. Furthermore, the roller 10BR corresponds to the steel sliding component 10, and the surface 10SBR, which is the outer circumferential surface of the roller 10 around its axis, corresponds to the sliding surface 10S. 【0037】 As described above, the outer ring 10A, inner ring 10B, raceway 10C and 10D, and roller 10BR of the bearing all correspond to the steel sliding component 10. The steel sliding component 10 has a circular or annular cross-section perpendicular to the central axis and has a sliding surface 10S. 【0038】 [Regarding the Vickers hardness of the steel sliding part 10] The steel sliding part 10 has been heat-treated. Therefore, the Vickers hardness of the steel sliding part 10 at a test force of 1 kN is 500 HV or higher. When the Vickers hardness of the steel sliding part 10 is 500 HV or higher, it means that the microstructure of the steel sliding part 10 is mainly composed of martensite. 【0039】 [Method for measuring Vickers hardness] The Vickers hardness of the steel sliding part 10 is determined by the following method. The steel sliding part 10 is cut along a cross-section that includes its central axis. In this cross-section, the steel sliding part 10 is divided into four radial sections. At the radial center of each divided region, the Vickers hardness is measured with a test force of 1 kN in accordance with JIS Z 2244:2020. In the steel sliding component 10, the Vickers hardness was 500 HV or higher at all four measured center positions. 【0040】 [Chemical composition of steel sliding part 10] The steel sliding part 10 is made of steel. The chemical composition of the steel constituting the steel sliding part 10 is not particularly limited. More specifically, the chemical composition of the steel constituting the steel sliding part 10 is such that when heat treatment is performed, martensite becomes the dominant structure, and such chemical compositions are well known. For example, the chemical composition of the steel constituting the steel sliding part 10 contains 90.0% or more Fe. For example, the chemical composition of the steel constituting the steel sliding part 10 contains 90.0% or more Fe, 0.70 to 1.20% C, 0.10 to 2.00% Si, and 0.10 to 2.00% Mn. 【0041】 More preferably, the chemical composition of the steel constituting the steel sliding part 10 of this embodiment contains C: 0.70-1.20%, Si: 0.10-2.00%, Mn: 0.10-2.00%, P: less than 0.030%, S: less than 0.030%, Ni: 0-2.00%, Cr: 0.40-2.00%, Mo: 0-0.50%, Cu: 0-0.50%, V: 0-0.200%, Nb: 0-0.100%, Ti: 0-0.200%, B: 0-0.0050%, Ca: 0-0.0050%, Al: 0.001-0.100%, N: 0.0250% or less, and O: 0.0050% or less, with the remainder being Fe and impurities. 【0042】 The chemical composition of the steel constituting the steel sliding part 10 of this embodiment may, for example, satisfy any of SUJ2, SUJ3, SUJ4, or SUJ5 as specified in JIS G4805:2019. As described above, the chemical composition of the steel constituting the steel sliding part 10 of this embodiment may be a known one. 【0043】 [Method for measuring the chemical composition of steel sliding parts 10] The chemical composition of the steel sliding part 10 in this embodiment can be measured by a well-known component analysis method. Specifically, chips are collected from the steel sliding part 10 using a cutting tool such as a drill. The collected chips are dissolved in acid to obtain a solution. Elemental analysis of the chemical composition is performed on the solution using ICP-AES (Inductively Coupled Plasma Atomic Emission Spectrometry). The C and S content is determined by a well-known high-frequency combustion method (combustion-infrared absorption method). The N content is determined by a well-known inert gas melting-thermal conductivity method. 【0044】 [Regarding specific organizational domains] The steel sliding component 10 of this embodiment includes a specific texture region in the surface layer including the sliding surface 10S. The specific texture region is defined as follows: 【0045】 Figure 2(A) is an enlarged view of region 50 of the steel sliding component 10 (10A) in Figure 1(A). Figure 2(B) is an enlarged view of region 50 of the steel sliding component 10 (10B) in Figure 1(A) and the steel sliding component 10 (10BR) in Figure 1(C). Figure 2(C) is an enlarged view of region 50 of the steel sliding component 10 (10C) in Figure 1(B) and the steel sliding component 10 (10BR) in Figure 1(D). Figure 2(D) is an enlarged view of region 50 of the steel sliding component 10 (10D) in Figure 1(B). Referring to Figures 1(A) to (D) and Figures 2(A) to (D), the "outermost rectangular region" 20 is defined as any rectangular area within the cross-section CS of the steel sliding component 10 that includes the sliding surface 10S, has a depth D of 10 μm from the sliding surface 10S, and a width W of 50 μm. 【0046】 In the outermost rectangular region 20, a crystal orientation analysis is performed in a direction parallel to the sliding surface 10S to obtain an orientation mapping in the outermost rectangular region 20. Figure 3 shows an example of the orientation mapping in the outermost rectangular region 20. Referring to Figure 3, the black areas in the outermost rectangular region 20 are regions with the {203} crystal orientation. 【0047】 In the obtained orientation mapping, the area fraction of the {203} crystal orientation is determined. If the area fraction of the {203} crystal orientation in the outermost rectangular region 20 is 7.0% or more, that outermost rectangular region 20 is defined as a "specific texture region". 【0048】 Figure 4A shows the relationship between the area ratio of {203} crystal orientation in the outermost rectangular area of ​​the steel sliding component 10 and the static friction coefficient. Figure 4B shows the relationship between the area ratio of {203} crystal orientation in the outermost rectangular area of ​​the steel sliding component 10 and the dynamic friction coefficient. Figures 4A and 4B were created using the friction coefficients (static friction coefficient and dynamic friction coefficient) obtained from the block-on-ring test described later. 【0049】 Referring to Figures 4A and 4B, the friction coefficient (static friction coefficient, dynamic friction coefficient) does not change significantly even as the area ratio of the {203} crystal orientation increases, as long as the area ratio of the {203} crystal orientation increases, obtained by crystal orientation analysis in the outermost rectangular region 20 of the cross section CS containing the central axis of the steel sliding part 10, in a direction parallel to the sliding surface 10S. On the other hand, when the area ratio of the {203} crystal orientation exceeds 7.0%, the friction coefficient (static friction coefficient, dynamic friction coefficient) decreases significantly as the area ratio of the {203} crystal orientation increases. In other words, the graphs in Figures 4A and 4B have an inflection point near 7.0% of the area ratio of the {203} crystal orientation. 【0050】 Therefore, in the cross-section CS containing the central axis of the steel sliding part 10, in the specific texture region where the area ratio of the {203} crystal orientation obtained by crystal orientation analysis in the direction parallel to the sliding surface 10S in the outermost rectangular region 20 is 7.0% or more, the coefficient of friction can be sufficiently suppressed. In other words, if the surface of the steel sliding part 10 includes the specific texture region, the coefficient of friction of the steel sliding part 10 is sufficiently suppressed. 【0051】 The preferred lower limit for the area fraction of the {203} crystal orientation in a specific texture region is 10.0%, more preferably 12.5%, more preferably 15.0%, more preferably 20.0%, and more preferably 25.0%. The upper limit for the area fraction of the {203} crystal orientation in a specific texture region is not particularly limited. For example, the upper limit for the area fraction of the {203} crystal orientation in a specific texture region is 80.0%, more preferably 70.0%, more preferably 65.0%, more preferably 60.0%, more preferably 50.0%, more preferably 40.0%, and more preferably 35.0%. 【0052】 [Method for measuring the area fraction of the {203} crystal orientation in the outermost rectangular region 20] The area ratio of the {203} crystal orientation in the outermost rectangular region 20 of the cross section CS containing the central axis of the steel sliding part 10 is determined using electron backscatter diffraction (EBSD) by the following method. 【0053】 As shown in Figures 1 and 2, a test specimen is taken that has a cross-section CS including the central axis of the steel sliding component 10 and includes the outermost rectangular region 20. The size of the test specimen is not particularly limited as long as it includes the outermost rectangular region 20. 【0054】 The cross section CS, which includes the outermost rectangular region 20, is defined as the observation surface. Mirror polishing is performed on the observation surface. From the mirror-polished observation surface, an arbitrary outermost rectangular region 20 (a rectangular region including the sliding surface 10S, with a depth of 10 μm from the sliding surface 10S and a width W of 50 μm) is selected. EBSD measurement is performed on the selected outermost rectangular region 20. In the EBSD measurement, the acceleration voltage is set to 15 kV, the irradiation current to 25 nA, and the irradiation interval to 0.04 μm. The incident direction of the electron beam is tilted 70 degrees from the normal direction of the observation surface. The EBSD measurement provides information on the position of each measurement point within the outermost rectangular region 20 (hereinafter referred to as position information) and information on the crystal orientation at the measurement point (hereinafter referred to as orientation information). An orientation mapping is created based on the obtained position information and orientation information. In the created orientation mapping, the region of the {203} crystal orientation is identified. In this case, the allowable azimuth difference is set to 10°. Furthermore, data with a Confidence Index (CI value) greater than 0.1 will be selected. 【0055】 As shown in Figure 3, orientation mapping makes it possible to distinguish specific crystal orientations. Therefore, using the obtained orientation mapping, the area percentage of the region where the {203} crystal orientation is oriented parallel to the sliding surface 10S is determined on the observation surface (cross-section CS). Specifically, in the outermost rectangular region 20, the ratio of the area of ​​the region with the {203} crystal orientation obtained by crystal orientation analysis parallel to the sliding surface 10S to the area of ​​the region with a CI value greater than 0.1 is defined as the area percentage (%) of the {203} crystal orientation. By this method, the area percentage of the region showing the {203} crystal orientation in the outermost rectangular region 20 can be measured. Orientation mapping can be performed on a computer using, for example, well-known analysis software (OIM DATA Collection / Analysis Ver.7.3.1: manufactured by TSL Solutions Co., Ltd.). 【0056】 The steel sliding component 10 having the above configuration has a low coefficient of friction (static friction coefficient and kinetic friction coefficient). Therefore, friction loss in power sources such as engines and powertrains in which the steel sliding component 10 is used can be reduced, contributing to improved fuel efficiency. 【0057】 In this embodiment, the steel sliding component 10 may include a specific texture region over the entire sliding surface 10S, or it may include a specific texture region in a part of the sliding surface 10S. In other words, the steel sliding component 10 includes a specific texture region in at least a part of the sliding surface 10S. 【0058】 [Manufacturing method for steel sliding parts 10] An example of a manufacturing method for the steel sliding component 10 according to this embodiment will be described. The manufacturing method for the steel sliding component 10 described below is an example for manufacturing the steel sliding component 10 according to this embodiment. Therefore, the steel sliding component 10 having the above-described configuration may be manufactured by a manufacturing method other than the manufacturing method described below. However, the manufacturing method described below is a preferred example of a manufacturing method for the steel sliding component 10 according to this embodiment. 【0059】 An example of a method for manufacturing the steel sliding component 10 of this embodiment includes the following steps. (1) Intermediate product preparation process (2) Outermost layer crystal orientation adjustment process The following describes each step. 【0060】 [(1) Intermediate product preparation process] In the intermediate product preparation process, an intermediate product, which is the material for the steel sliding part 10, is prepared. The intermediate product has a circular or annular cross-section perpendicular to the central axis. The intermediate product has a shape close to that of the final product. The intermediate product may be provided by a third party. Alternatively, the intermediate product may be manufactured and prepared. 【0061】 The intermediate product to be prepared further has the following components (A) to (D). (A) The Vickers hardness at a test force of 1 kN is 500 HV or higher. (B) The volume fraction of retained austenite in the outermost rectangular region is 10.0 to 40.0%. (C) The arithmetic mean roughness Ra of the sliding surface 10S conforming to JIS B 0601:2013 is 0.05 to 2.00 μm. (D) The KAM (Kernel Average Misorientation) value of the outermost rectangular area is 0.40° or higher. The following describes the configurations (A) through (D). 【0062】 [(A) Regarding the Vickers hardness of intermediate products] The intermediate material used for the steel sliding component 10 has a Vickers hardness of 500 HV or higher at a test force of 1 kN, just like the steel sliding component 10. When the Vickers hardness of the intermediate material is 500 HV or higher, it means that the microstructure of the steel sliding component 10 is mainly composed of martensite. 【0063】 [(B) Regarding the volume fraction of retained austenite in the outermost rectangular region] The volume fraction of retained austenite in the outermost rectangular region of the intermediate product affects the area fraction of the {203} crystal orientation in the outermost rectangular region 20 of the steel sliding part 10. If the volume fraction of retained austenite is less than 10.0% or more than 40.0%, even if the next process of adjusting the outermost crystal orientation is performed, the area fraction of the {203} crystal orientation in the outermost rectangular region 20 of the steel sliding part 10 will be less than 7.0%. Therefore, the volume fraction of retained austenite in the outermost rectangular region of the intermediate product is set to 10.0 to 40.0%. In this case, by performing the outermost crystal orientation adjustment process, the area fraction of the {203} crystal orientation in the outermost rectangular region 20 of the steel sliding part 10 can be set to 7.0% or more. 【0064】 [(C) Regarding the arithmetic mean roughness Ra of the sliding surface of the intermediate product] The surface roughness of the surface of the intermediate product corresponding to the sliding surface 10S of the steel sliding part 10 (hereinafter referred to as the sliding surface) affects the area ratio of the {203} crystal orientation in the outermost rectangular area 20 of the steel sliding part 10 in the outermost crystal orientation adjustment process described later. If the arithmetic mean roughness Ra of the sliding surface of the intermediate product is less than 0.05 μm, the area ratio of the {203} crystal orientation in the outermost rectangular area 20 of the steel sliding part 10 after the outermost crystal orientation adjustment process will be less than 7.0%. Therefore, the arithmetic mean roughness Ra of the sliding surface of the intermediate product should be 0.05 μm or more. 【0065】 On the other hand, if the surface roughness of the sliding surface of the intermediate product becomes excessively rough, cracks may occur on the surface of the steel sliding part 10 after the outermost crystal orientation adjustment process. Therefore, the arithmetic mean roughness Ra of the sliding surface of the intermediate product should be 2.00 μm or less. 【0066】 [(D) Regarding the KAM value of the outermost rectangular area of ​​the intermediate product] The KAM value of the outermost rectangular region of the intermediate product also affects the area ratio of the {203} crystal orientation in the outermost rectangular region 20 of the steel sliding part 10. Here, the KAM value is an index that indicates the deviation of the crystal orientation from the surroundings at the measurement point. At a measurement point with a large KAM value, the difference in crystal orientation between that measurement point and its surroundings is large. In this case, it means that the strain is large at that measurement point. On the other hand, at a measurement point with a small KAM value, the difference in crystal orientation between that measurement point and its surroundings is small. Therefore, it means that the strain is small at that measurement point. In this embodiment, the KAM value is the arithmetic mean obtained at each measurement point. Therefore, the KAM value represents the degree of strain in the steel material constituting the intermediate product. 【0067】 As described above, the KAM value also affects the area ratio of the {203} crystal orientation in the outermost rectangular region 20 of the steel sliding part 10. Specifically, if the KAM value is less than 0.40°, even if the outermost crystal orientation adjustment process is performed, the area ratio of the {203} crystal orientation in the outermost rectangular region 20 of the steel sliding part 10 will be less than 7.0%. Therefore, the KAM value of the outermost rectangular region of the intermediate product should be set to 0.40° or higher. In this case, by performing the outermost crystal orientation adjustment process, the area ratio of the {203} crystal orientation in the outermost rectangular region 20 of the steel sliding part 10 can be set to 7.0% or higher. 【0068】 An intermediate product having the above configuration can be manufactured, for example, in the following manufacturing process. (11) Processing process (12) Tempering process (13) Surface layer adjustment process The following describes each step. 【0069】 [(11) Processing process] In the manufacturing process, the steel material that will become the steel part is processed to shape it into a form close to the final product (steel part). 【0070】 The processing method for the steel material may be any well-known method. For example, the steel material may be hot-worked to form a predetermined shape. Examples of hot-working methods include hot forging and hot rolling. The steel material may also be cold-worked to form a predetermined shape. Examples of cold-working methods include cold forging and cold drawing. The steel material may also be machined to form a predetermined shape. After hot-working or cold-working the steel material, further machining may be performed to form a predetermined shape. 【0071】 [(12) Tempering process] In the tempering process, the processed steel material is hardened and tempered to achieve a Vickers hardness of 500 HV or higher for the intermediate product, and a volume fraction of retained austenite in the outermost rectangular region is set to 10.0-40.0%. The hardening and tempering processes are described below. 【0072】 [Hardening] In quenching, the steel material is A c3 The steel is heated to a quenching temperature above its transformation point and held there, then rapidly cooled. The cooling method during the quenching process is oil cooling or water cooling. Specifically, the steel, held at the quenching temperature, is immersed in a cooling bath containing oil or water as the cooling medium and rapidly cooled. The temperature of the oil or water used as the cooling medium is, for example, room temperature to 200°C. Sub-zero treatment may also be performed as needed. The quenching temperature and the holding time at the quenching temperature are appropriately controlled to adjust the volume fraction of retained austenite in the outermost rectangular region to 10.0 to 40.0%. 【0073】 [Tempering] Tempering is performed after quenching. In tempering, the steel material is subjected to a well-known tempering process after quenching. The tempering temperature is, for example, 100 to 200°C. The holding time at the tempering temperature is, for example, 90 to 150 minutes. 【0074】 By appropriately adjusting the conditions for the above-mentioned heat treatment (quenching and tempering), the Vickers hardness of the intermediate product can be set to 500 HV or higher, and the volume fraction of retained austenite in the outermost rectangular region can be adjusted to 10.0-40.0%. 【0075】 [(13) Surface layer adjustment process] In the surface preparation process, the sliding surface of the steel material after the tempering process is machined to adjust the surface roughness of the sliding surface of the intermediate product to a predetermined roughness, and a predetermined strain is introduced into the surface layer including the sliding surface. Here, machining refers to grinding and / or cutting. 【0076】 Specifically, the arithmetic mean roughness of the sliding surface of the intermediate product is adjusted to 0.05 to 2.00 μm by appropriately adjusting the depth of cut and feed rate during machining. The preferred lower limit of the arithmetic mean roughness Ra is 0.10 μm, more preferably 0.15 μm, even more preferably 0.20 μm, and even more preferably 0.25 μm. The preferred upper limit of the arithmetic mean roughness Ra is 1.50 μm. 【0077】 In the surface preparation process, the KAM value of the outermost rectangular area of ​​the intermediate product is further set to 0.40° or higher. By appropriately adjusting the peripheral speed and feed rate during machining, the KAM value of the outermost rectangular area of ​​the steel material is set to 0.40° or higher. The preferred lower limit of the KAM value is 0.45°, more preferably 0.50°, and even more preferably 0.60°. The upper limit is not particularly limited. The maximum value of the KAM value obtained in the surface preparation process is, for example, about 2.00°. 【0078】 Through the above process, an intermediate product is prepared in which the Vickers hardness at a test force of 1 kN is 500 HV or higher, the volume fraction of retained austenite in the outermost rectangular area is 10.0 to 40.0%, the arithmetic mean roughness Ra of the sliding surface is 0.05 to 2.00 μm, and the KAM value of the outermost rectangular area is 0.40° or higher. 【0079】 [Methods for measuring Vickers hardness, volume fraction of retained austenite, arithmetic mean roughness Ra, and KAM value] The Vickers hardness of the intermediate material, the volume fraction of retained austenite in the outermost rectangular region, the arithmetic mean roughness Ra of the sliding surface, and the KAM value of the outermost rectangular region can be measured by the following method. 【0080】 [Method for measuring the Vickers hardness of intermediate products] The method for measuring the Vickers hardness of the intermediate product is the same as the method for measuring the Vickers hardness of the steel sliding part 10. Specifically, the intermediate product is cut in a cross-section that includes the central axis of the intermediate product. In this cross-section, the intermediate product is divided into four radial sections. At the radial center position of each divided region, the Vickers hardness is measured with a test force of 1 kN in accordance with JIS Z 2244:2020. In the intermediate sample, the Vickers hardness was 500 HV or higher at all four measured center positions. In other words, the lowest of the four Vickers hardness values ​​obtained was 500 HV or higher. 【0081】 [Method for measuring the volume fraction of retained austenite in the outermost rectangular region] The volume fraction of retained austenite in the outermost rectangular region of the intermediate material is determined by X-ray diffraction. Specifically, a sample containing the outermost rectangular region is taken from the intermediate material. X-ray diffraction is performed on the sliding surface of the sample to obtain the integral intensity ratio of the diffraction peaks of the (211) plane of the bcc structure and the (220) plane of the fcc structure. Based on the obtained diffraction intensity ratio, the volume fraction (%) of retained austenite is determined. A Cr tube is used as the light source. The light source voltage is set to 40kV and the current to 40mA. 【0082】 [Method for measuring the arithmetic mean roughness Ra of a sliding surface] The arithmetic mean roughness Ra of the sliding surface of the intermediate product shall be measured in accordance with the measurement method specified in JIS B 0601:2013. Specifically, 10 arbitrary locations shall be selected as measurement points on the sliding surface of the intermediate product. At each measurement point, the arithmetic mean roughness Ra shall be measured over an evaluation length extending in the direction normal to the sliding direction. The reference length (cutoff wavelength) shall be 0.25 mm if the arithmetic mean roughness Ra is between 0.02 and 0.10 μm, and 0.80 mm if the arithmetic mean roughness Ra is greater than 0.10 to 2.00 μm. Furthermore, the evaluation length shall be 5 times the reference length (cutoff wavelength). The arithmetic mean roughness Ra shall be measured using a stylus-type roughness meter, with a measurement speed of 0.2 mm / sec. Of the 10 arithmetic mean roughness values ​​Ra obtained, the arithmetic mean roughness Ra (μm) is defined as the arithmetic mean mean roughness Ra (μm) of the six values ​​remaining after excluding the largest, second largest, smallest, and second smallest arithmetic mean roughness values ​​Ra. 【0083】 [Method for measuring KAM values ​​in the outermost rectangular area] The KAM value of the outermost rectangular area of ​​the intermediate product is measured by the following method. Specifically, as shown in Figures 1 and 2, a test specimen is taken from the intermediate product that includes the region corresponding to the outermost rectangular area 20 of the cross section CS containing the central axis of the steel sliding part 10 (hereinafter simply referred to as the outermost rectangular area). The size of the test specimen is not particularly limited as long as it includes the outermost rectangular area. 【0084】 The surface of the specimen, including the outermost rectangular region and corresponding to the cross-section CS, is defined as the observation surface. Mirror polishing is performed on the observation surface. From the mirror-polished observation surface, an arbitrary outermost rectangular region (including the sliding surface, a rectangular area with a depth D of 10 μm and a width W of 50 μm radially from the sliding surface) is selected. EBSD measurement is performed on the selected outermost rectangular region. In the EBSD measurement, the acceleration voltage is set to 15 kV, the irradiation current to 25 nA, and the irradiation interval to 0.04 μm. The direction of incidence of the electron beam is tilted 70 degrees from the normal direction of the observation surface. EBSD measurement provides information on the position of each measurement point within the outermost rectangular region (hereinafter referred to as position information) and information on the crystal orientation at the measurement point (hereinafter referred to as orientation information). Based on the obtained position information and orientation information, the KAM value is determined. Data with a Confidence Index (CI value) greater than 0.1 is adopted. 【0085】 The KAM value is defined as described above. Specifically, the outermost rectangular area is divided into regular hexagonal pixel units. Each pixel corresponds to the measurement point described above. One regular hexagonal pixel is selected as the center pixel. The azimuth difference between the selected center pixel and the six pixels adjacent to it outside the center pixel is calculated. The average value of the obtained azimuth differences is calculated, and this average value is defined as the KAM value of the center pixel (measurement point). At this time, the maximum azimuth difference of the KAM value is defined as 5.0°, and data of 5.0° or less is used in the calculation of the average value described later. The KAM value is calculated for all pixels in the outermost rectangular area using the same method. 【0086】 After calculating the KAM value for each pixel in the observation field, the arithmetic mean of the KAM values ​​for each pixel is determined. The obtained value is defined as the KAM value of the outermost rectangular area of ​​the steel material. 【0087】 For calculating KAM values, any well-known EBSD analysis program can be used. For example, OIM DATA Collection / Analysis Ver.7.3.1 from TSL Solutions can be used. 【0088】 [(2) Outermost layer crystal orientation adjustment process] In the outermost crystal orientation adjustment process, for intermediate products where the Vickers hardness at a test force of 1 kN is 500 HV or higher, the volume fraction of retained austenite in the outermost rectangular region is 10.0 to 40.0%, the arithmetic mean roughness Ra of the sliding surface in accordance with JIS B 0601:2013 is 0.05 to 2.00 μm, and the KAM value in the outermost rectangular region is 0.40° or higher, the area fraction of the {203} crystal orientation obtained by crystal orientation analysis in the direction parallel to the sliding surface on the observation surface is increased. 【0089】 Specifically, a reduction tool harder than the intermediate product is pressed against the sliding surface of the intermediate product at a pressure of 8.5 to 15.0 GPa. Furthermore, while pressing at 8.5 to 15.0 GPa, the reduction tool is slid relative to the sliding surface in a direction perpendicular to the rotational direction of the intermediate product, thereby plastically deforming the surface layer, including the sliding surface. Through these steps, a specific texture region is formed in the outermost layer. This point will be explained below. 【0090】 Figure 5 is a schematic diagram of an apparatus for performing surface plastic deformation (surface plastic deformation apparatus). Figure 5(A) is a schematic diagram of a surface plastic deformation apparatus as an example, when the steel sliding part 10 is a roller. Referring to Figure 5(A), the surface plastic deformation apparatus 30 comprises a support jig 31 and a reduction tool 32. The reduction tool 32 has a hemispherical shape. The reduction tool 32 is positioned so that the convex portion of the reduction tool 32 contacts the sliding surface 100S of the intermediate product 100. The support jig 31 supports the reduction tool 32 by fixing it to its lower end. The reduction tool 32 is made of a material harder than the intermediate product 100. The reduction tool 32 is, for example, a carbide tool, or for example, a diamond tip. 【0091】 Surface plastic deformation using the surface plastic deformation apparatus 30 is performed as follows. First, the intermediate product 100 is rotated around its central axis. Then, the reduction tool 32 of the surface plastic deformation apparatus 30 is pressed against the sliding surface 100S of the intermediate product 100 with a pressure P1. While pressing the reduction tool 32 with a pressure P1, the reduction tool 32 is slid on the sliding surface 100S in a direction perpendicular to the rotational direction of the intermediate product 100, thereby plastically deforming the surface of the sliding surface 100S. 【0092】 Specifically, in Figure 5(A), the intermediate product 100 is rotated around its central axis while the reduction tool 32 is pressed against it. At this time, while the intermediate product 100 is rotating around its central axis, the reduction tool 32 is moved relative to the sliding surface 100S in a direction M perpendicular to the rotational direction of the intermediate product 100 (here, along the central axis). As a result, the reduction tool 32 slides on the sliding surface 100S while being pressed against it with pressure P1. This causes the surface layer of the sliding surface 100S of the intermediate product 100 to undergo plastic deformation. At this time, crystal orientation rotation occurs in the surface layer due to the plastic deformation. 【0093】 In surface plastic deformation using the surface plastic deformation apparatus 30, the reduction tool 32 is pressed against the sliding surface 100S of the intermediate product 100 at a pressure P1 of 8.5 to 15.0 GPa. 【0094】 If the pressure P1 is less than 8.5 GPa, the area ratio of the {203} crystal orientation in the outermost rectangular region 20 of the final steel sliding part 10 will be less than 7.0%. On the other hand, if the pressure P1 exceeds 15.0 GPa, cracks will occur on the sliding surface 10S of the steel sliding part 10. Therefore, the pressure P1 should be set to 8.5 to 15.0 GPa. 【0095】 If surface plastic deformation is performed on the intermediate product 100 with the above-described pressure P1, the accumulation of {203} crystal orientations in the direction parallel to the sliding surface 10S of the steel sliding part 10 will increase. As a result, the area ratio of {203} crystal orientations in the outermost rectangular region 20 will be 7.0% or more. 【0096】 Although Figure 5(A) illustrates the case where the steel sliding component 10 is a roller, the surface crystal orientation adjustment process can be performed in the same manner as in Figure 5(A) even if the steel sliding component 10 is an outer ring, inner ring, or raceway. For example, if the steel sliding component 10 is an inner ring, as shown in Figure 5(B), an intermediate product 100 with a ring-shaped cross-section perpendicular to the central axis is rotated around the central axis. Then, a reduction tool 32, which is harder than the intermediate product 100, is pressed against the sliding surface 100S corresponding to the outer circumferential surface of the intermediate product 100 with a pressure of 8.5 to 15.0 GPa, and the reduction tool 32 is slid relative to the sliding surface 100S in a direction M perpendicular to the rotation direction of the intermediate product 100 (in this case, the direction along the central axis), thereby plastically deforming the surface including the sliding surface 100S and forming a specific texture region. 【0097】 For example, if the steel sliding part 10 is an outer ring, as shown in Figure 5(C), an intermediate part 100 with an annular cross-section perpendicular to the central axis is rotated around the central axis. Then, a reduction tool 32, which is harder than the intermediate part 100, is pressed against the sliding surface 100S corresponding to the inner circumferential surface of the intermediate part 100 with a pressure of 8.5 to 15.0 GPa, and the reduction tool 32 is slid relative to the sliding surface 100S in a direction M perpendicular to the rotational direction of the intermediate part 100 (in this case, along the central axis), thereby plastically deforming the surface layer including the sliding surface 100S and forming a specific texture region. 【0098】 For example, if the steel sliding part 10 is a raceway plate, as shown in Figure 5(D), an intermediate part 100 with an annular cross-section perpendicular to the central axis is rotated around the central axis. Then, a reduction tool 32, which is harder than the intermediate part 100, is pressed against the sliding surface 100S, which corresponds to the surface of the intermediate part 100 perpendicular to the central axis, with a pressure of 8.5 to 15.0 GPa. The reduction tool 32 is then slid relative to the sliding surface 100S in a direction M perpendicular to the rotational direction of the intermediate part 100 (here, the radial direction of the intermediate part), causing plastic deformation of the surface layer including the sliding surface 100S and forming a specific texture region. 【0099】 The steel sliding component 10 of this embodiment is manufactured by the manufacturing method described above. The above manufacturing method is just one example of a manufacturing method for the steel sliding component 10 of this embodiment. Therefore, as long as the steel sliding component 10 has the above-described configuration, the steel sliding component 10 of this embodiment may be manufactured by other manufacturing methods. [Examples] 【0100】 The effects of one embodiment of the steel sliding component 10 of this embodiment will be described in more detail below with reference to examples. The conditions in the following examples are just one example of conditions adopted to confirm the feasibility and effects of the steel sliding component 10 of this embodiment. Therefore, the steel sliding component 10 of this embodiment is not limited to this one example of conditions. 【0101】 Steel materials (round bars) having the chemical composition shown in Table 1 were prepared. 【0102】 [Table 1] 【0103】 [Table 2] 【0104】 For each test number of steel material, a heat treatment process (quenching and tempering) was performed to adjust the Vickers hardness and the volume fraction of retained austenite in the outermost rectangular area. After the heat treatment process, a surface adjustment process was performed on the steel material. Specifically, machining was performed on the sliding surface of the steel material to adjust the surface roughness and KAM value of the sliding surface. Through these processes, intermediate products (round bars) for each test number were manufactured. The outer surface of the intermediate product was used as the sliding surface. 【0105】 [Measurement test of Vickers hardness, volume fraction of retained austenite, arithmetic mean roughness Ra of the sliding surface, and KAM value of intermediate samples for each test number after the surface preparation process] The Vickers hardness, volume fraction of retained austenite, arithmetic mean roughness Ra of the sliding surface, and KAM value of the intermediate sample for each test number after the surface preparation process were determined by the following method. 【0106】 [Vickers hardness of intermediate grades] Based on the method described in the above-mentioned [Method for Measuring Vickers Hardness of Intermediate Samples], the Vickers hardness (HV) of the intermediate samples for each test number at a test force of 1 kN was determined. As a result, the minimum Vickers hardness for all test numbers was 500 HV or higher. 【0107】 [Volume fraction of retained austenite in the outermost rectangular region of the intermediate material] Based on the method described in [Method for Measuring the Volume Percentage of Retained Austenite in the Outermost Rectangular Region] above, the volume percentage (%) of retained austenite in the outermost rectangular region of the intermediate sample for each test number was determined. The volume percentage of retained austenite obtained is shown in the "Volume Percentage of Retained Austenite (Volume %)" column in Table 2. 【0108】 [Arithmetic mean roughness Ra of the sliding surface of the intermediate product] Based on the method described in [Method for Measuring Arithmetic Mean Roughness Ra of Sliding Surfaces] above, the arithmetic mean roughness Ra (μm) of the sliding surface of the intermediate sample for each test number was determined. A surface roughness measuring instrument manufactured by Mitutoyo Corporation (product name: Surftest SJ-301) was used as a contact-type roughness meter. The obtained arithmetic mean roughness Ra (μm) is shown in the "Ra (μm)" column of Table 2. 【0109】 [KAM value of the outermost rectangular area of ​​the intermediate product] Based on the method described in [Measurement Method for the Outermost Rectangular Region] above, the KAM value of the outermost rectangular region of the intermediate sample for each test number was determined. The EBSD analysis program used to determine the KAM value was OIM Data Collection / Analysis Ver.7.3.1 from TSL Solutions Co., Ltd. The obtained KAM values ​​are shown in the "KAM(°)" column in Table 2. 【0110】 A surface crystal orientation adjustment process was performed on the intermediate products after the surface preparation process. Specifically, surface plastic deformation was performed on the sliding surface (outer surface) of the intermediate products for each test number using the surface plastic deformation apparatus 30 shown in Figure 5. A diamond tip was used as the reduction tool 32. The pressure P1 during surface plastic deformation was as shown in the "P1 (GPa)" column of Table 2. The sliding parts (round bars) for each test number were manufactured using the above manufacturing process. 【0111】 [Evaluation Test] The following evaluation tests were performed on the steel parts for each test number. 【0112】 [Area fraction measurement test for {203} crystal orientation in the outermost rectangular area] Based on the method described in [Method for measuring the area ratio of the {203} crystal orientation in the outermost rectangular area 20] above, the area ratio (%) of the {203} crystal orientation in the outermost rectangular area of ​​the steel sliding parts (round bars) for each test number was determined. The orientation mapping was created by running OIM Data Collection / Analysis Ver.7.3.1 from TSL Solutions Co., Ltd. on a computer. The obtained area ratio (%) of the {203} crystal orientation is shown in the "{203} Area Ratio (%)" column in Table 2. 【0113】 [Maximum static friction coefficient measurement test] Block-on-ring tests were performed on the steel sliding parts for each test number to determine the maximum static friction coefficient. 【0114】 Figure 6 is a schematic diagram of the block-on-ring test. Referring to Figure 6, the block-on-ring test machine 200 is equipped with a bath 201 containing lubricating oil 202 and a ring test piece 203. The lubricating oil 202 has a kinematic viscosity of 5.4 mm at 100°C. 2 I used commercially available engine oil with a / s rating. 【0115】 Ring test specimens 203 were prepared from the steel sliding parts of each test number. The outer diameter D0 of ring test specimen 203 was 34.99 mm, the same as the outer diameter of the steel sliding part. The width W0 of ring test specimen 203 was 8.74 mm. The outer surface of ring test specimen 203 corresponded to the sliding surface of the steel sliding part of each test number. 【0116】 The material of block specimen 300 was SAEO1. Of the surfaces of block specimen 300, the surface facing the circumferential surface of ring specimen 203 (referred to as the opposing surface) had dimensions of 15.75 mm in length and 6.35 mm in width. 【0117】 As shown in Figure 6, the lower part of the ring test piece 203 was immersed in the lubricating oil 202 in the bathtub 201. Then, the block test piece 300 was placed above the ring test piece 203. At this time, the block test piece 300 was positioned so that the longitudinal direction of the opposing surface of the block test piece 300 was the circumferential direction of the ring test piece 203. 【0118】 After completing the above preparations, steps 1 through 4 were repeated 10 times. Step 1: A pressure of 100N P is applied to the block test specimen 300 from above downwards, 300 was pressed against the circumferential surface of the ring test piece 203. Step 2: The state in step 1 was held for 30 seconds in order to allow the lubricating oil 202 to be discharged from between the opposing surfaces of the block test piece 300 and the circumferential surface of the ring test piece 203. Step 3: The ring test piece 203 was started to rotate at a sliding speed of 0.1 m / s (55 rpm) and then rotated for 30 seconds. Step 4: After rotating for 30 seconds, the pressure P was removed. Then, the rotation of the ring test piece 203 was stopped. 【0119】 During steps 1 to 4, the force F applied to the block test specimen 300 was measured using a load cell. The coefficient of friction μ(-) was then calculated using the following formula. F=μP The relationship between the obtained coefficient of friction μ and the test time was determined. Figure 7 shows an example of a graph of the coefficient of friction for the second and subsequent rotation tests. In the graph in Figure 7, the horizontal axis is time and the vertical axis is the coefficient of friction. Referring to Figure 7, the peak of the coefficient of friction during ring rotation (within the circular area in the figure) was defined as the static friction coefficient. The arithmetic mean of the static friction coefficients obtained from the second to the tenth tests was defined as the static friction coefficient (-) for each test number. The obtained static friction coefficients are shown in the "Static friction coefficient (-)" column in Table 2. 【0120】 In the first test, the static friction coefficient obtained was significantly higher than that obtained in the second to tenth tests because the lubricating oil had not sufficiently permeated the ring test piece 203. Therefore, the static friction coefficient obtained in the first test was excluded from consideration. 【0121】 [Dynamic friction coefficient measurement test] For each steel component with a given test number, a block-on-ring test similar to the static friction coefficient measurement test was performed to determine the dynamic friction coefficient. 【0122】 In the block-on-ring test shown in Figure 6, the kinematic viscosity of the lubricating oil 202, the outer diameter D0 of the ring test piece 203, the width W0 of the ring test piece 203, the material of the block test piece 300, and the size of the opposing surface of the block test piece 300 that faces the circumferential surface of the ring test piece 203 were all the same as in the static friction coefficient measurement test. 【0123】 As shown in Figure 6, the lower part of the ring test piece 203 was immersed in the lubricating oil 202 in the bathtub 201. Then, the block test piece 300 was placed above the ring test piece 203. At this time, the block test piece 300 was positioned so that the longitudinal direction of the opposing surface of the block test piece 300 was the circumferential direction of the ring test piece 203. 【0124】 After completing the above preparations, steps 1 through 3 were carried out. Step 1: The rotation of the ring test piece 203 was started at a sliding speed of 1.0 m / sec (550 rpm). Step 2: A pressure P of 300N is applied to the block test specimen 300 from above downwards, 300 was pressed against the circumferential surface of the ring test piece 203. Step 3: After rotating for 2100 seconds, the pressure P was removed. Then, the rotation of the ring test piece 203 was stopped. 【0125】 During steps 1 to 3, the force F applied to the block test specimen 300 was measured using a load cell. The coefficient of friction μ(-) was then calculated using the following formula. F=μP Of the friction coefficients μ obtained during 2100 seconds of rotation, the arithmetic mean value between 1500 and 2000 seconds was defined as the kinetic friction coefficient (-) for each test number. The obtained kinetic friction coefficients are shown in the "Kinetic Friction Coefficient (-)" column in Table 2. 【0126】 [Test Results] For test numbers 1-20, the Vickers hardness of the intermediate product before the outermost crystal orientation adjustment process, the volume fraction of retained austenite in the outermost rectangular region, the arithmetic mean roughness Ra of the sliding surface, and the KAM value of the outermost rectangular region were all appropriate. Furthermore, the pressure P1 in the outermost crystal orientation adjustment process was appropriate. As a result, the area fraction of the {203} crystal orientation obtained by crystal orientation analysis in the outermost rectangular region, including the sliding surface and extending 10 μm to a depth of 50 μm from the sliding surface, within the cross-section including the central axis of the manufactured steel sliding part, was 7.0% or more. Consequently, the static friction coefficient was low (0.163 or less), and the dynamic friction coefficient was also low (0.076 or less). 【0127】 In tests 21 and 22, the volume fraction of retained austenite in the outermost rectangular region of the intermediate product before the outermost crystal orientation adjustment process was too low. As a result, the area fraction of the {203} crystal orientation in the outermost rectangular region of the steel sliding parts was less than 7.0%. Consequently, the static friction coefficient was higher than 0.163, and the kinetic friction coefficient was also higher than 0.076. 【0128】 In tests 23 and 24, the volume fraction of retained austenite in the outermost rectangular region of the intermediate product before the outermost crystal orientation adjustment process was too high. As a result, the area fraction of the {203} crystal orientation in the outermost rectangular region of the steel sliding parts was less than 7.0%. Consequently, the static friction coefficient was higher than 0.163, and the kinetic friction coefficient was also higher than 0.076. 【0129】 In tests 25 and 26, the arithmetic mean roughness Ra of the sliding surface of the intermediate product before the outermost crystal orientation adjustment process was too low. As a result, the area percentage of {203} crystal orientation in the outermost rectangular area of ​​the steel sliding part was less than 7.0%. Consequently, the static friction coefficient was higher than 0.163, and the kinetic friction coefficient was also higher than 0.076. 【0130】 In tests 27 and 28, the KAM value of the outermost rectangular area of ​​the intermediate product before the outermost crystal orientation adjustment process was too low. As a result, the area ratio of the {203} crystal orientation in the outermost rectangular area of ​​the steel sliding parts was less than 7.0%. Consequently, the static friction coefficient was higher than 0.163, and the dynamic friction coefficient was also higher than 0.076. 【0131】 In tests 29 and 30, the pressure P1 during the surface crystal orientation adjustment process was too low. As a result, the area ratio of {203} crystal orientation in the surface rectangular region of the steel parts was less than 7.0%. Consequently, the static friction coefficient was higher than 0.163, and the kinetic friction coefficient was also higher than 0.076. 【0132】 The embodiments of this disclosure have been described above. However, the embodiments described above are merely examples for implementing this disclosure. Therefore, this disclosure is not limited to the embodiments described above, and the embodiments described above can be modified as appropriate without departing from the spirit of this disclosure.

Claims

[Claim 1] A steel sliding component having a circular or annular cross-section perpendicular to its central axis, Having a sliding surface, The Vickers hardness at a test force of 1 kN is 500 HV or higher. In the cross-section of the steel sliding component including the central axis, the outermost rectangular region including the sliding surface and extending 10 μm to a depth and 50 μm to a width from the sliding surface includes a specific texture region in which the area ratio of the {203} crystal orientation obtained by crystal orientation analysis in a direction parallel to the sliding surface is 7.0% or more. Steel sliding parts. [Claim 2] A steel sliding component according to claim 1, The aforementioned steel sliding component is one of the outer ring, inner ring, raceway, or rollers of the bearing. Steel sliding parts. [Claim 3] A steel sliding component according to claim 1, The area fraction of the {203} crystal orientation is 10.0% or more. Steel sliding parts. [Claim 4] A steel sliding component according to claim 1, The area fraction of the {203} crystal orientation is 12.5% ​​or more. Steel sliding parts. [Claim 5] A method for manufacturing a steel sliding component according to any one of claims 1 to 4, An intermediate product preparation step is performed to prepare an intermediate product having a circular or annular cross-section perpendicular to the central axis, a Vickers hardness of 500 HV or more at a test force of 1 kN, a volume fraction of retained austenite in the outermost rectangular region of the sliding surface of 10.0 to 40.0%, an arithmetic mean roughness Ra of the sliding surface in accordance with JIS B 0601:2013 of 0.05 to 2.00 μm, and a KAM value of 0.40° or more in the outermost rectangular region of the sliding surface. The process includes a step of adjusting the crystal orientation of the outermost layer, in which the intermediate product is rotated around the central axis, and a reduction tool harder than the intermediate product is pressed against the sliding surface of the intermediate product with a pressure of 8.5 to 15.0 GPa, while the reduction tool is slid relative to the sliding surface in a direction perpendicular to the rotational direction of the intermediate product, thereby plastically deforming the surface layer including the sliding surface and forming the specific texture region. A method for manufacturing steel sliding parts. [Claim 6] A method for manufacturing a steel sliding component according to claim 5, The aforementioned intermediate product preparation process is: The processing steps for working with steel materials, The process includes a heat treatment step in which the processed steel material is quenched and tempered to achieve a Vickers hardness of 500 HV or more at a test force of 1 kN for the intermediate product, and the volume fraction of retained austenite in the outermost rectangular area is 10.0 to 40.0%. A method for manufacturing steel sliding parts. [Claim 7] A method for manufacturing a steel sliding component according to claim 6, The aforementioned intermediate product preparation process further, The process includes a surface adjustment step in which the sliding surface of the intermediate product after the tempering step is machined to set the arithmetic mean roughness Ra of the sliding surface to 0.05 to 2.00 μm in accordance with JIS B 0601:2013, and the KAM value of the outermost rectangular area of ​​the sliding surface to 0.40° or more. A method for manufacturing steel sliding parts.

Images