Sliding member, method for manufacturing sliding member, and method for evaluating sliding member

Abstract

The sliding member of one embodiment of the present application includes: an axle member having a first sliding surface; and a bearing member having a second sliding surface that slidably supports the first sliding surface, the first sliding surface and the second sliding surface having different hardnesses, and a roughness parameter R calculated from the following formula 1 is 0.276 or less. ac 0.276 or less.

Description

Technical Field

[0001] The present invention relates to a sliding member, a method for manufacturing a sliding member, and a method for evaluating a sliding member. Background Art

[0002] Shaft components such as marine crankshafts, intermediate shafts, and propeller shafts are slidably supported by bearing members, such as sliding bearings. Lubricating fluid is supplied to the gap between the shaft and bearing members. This lubricating fluid forms a lubricating film between the shaft and bearing members, thereby preventing seizure between the two components. However, even when a lubricating film is formed between the shaft and bearing members, the likelihood of seizure between the two components increases if the surface roughness of the shaft and bearing members is greater than the thickness of the lubricating film.

[0003] Therefore, in order to suppress seizure of shaft members, etc., it is effective to reduce the surface roughness of the sliding surface. For example, Patent Document 1 describes a composite sliding member that corresponds to friction reduction in an internal combustion engine.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2004-116707 Summary of the Invention

[0007] Problems to be solved by the invention

[0008] When manufacturing sliding components with large shafts, the sliding surface of the shaft is manually polished after machining to achieve sufficient dimensional accuracy. Manual polishing increases the radius of curvature of the roughness projections on the sliding surface, making it more likely to cause galling. On the other hand, the sliding component described in Patent Document 1 fails to adequately consider the radius of curvature of the roughness projections on the sliding surface, making it difficult to fully prevent galling on the sliding surface.

[0009] The present invention has been made based on the above circumstances, and an object of the present invention is to provide a sliding member capable of suppressing seizure on a sliding surface.

[0010] Means of solving the problem

[0011] A sliding member according to one embodiment of the present invention, proposed to solve the above-mentioned problems, comprises: a shaft member having a first sliding surface; and a bearing member having a second sliding surface that slidably supports the first sliding surface, wherein the first sliding surface and the second sliding surface have different hardnesses, and a roughness parameter R calculated by the following formula 1 is: ac Below 0.276.

[0012] [Formula 1]

[0013]

[0014] In the above formula 1, δ means that the average value of the top height of the roughness protrusions on the first sliding surface is δ A [μm], let the average value of the top height of the roughness protrusions on the second sliding surface be δ B [μm], the value [μm] calculated by the following formula 2, σ means that the root mean square of the height of the top of the roughness protrusions on the first sliding surface is σ A [μm], let the root mean square of the height of the top of the roughness protrusion of the second sliding surface be σ B [μm], the value [μm] calculated by the following formula 3, η means that the density of roughness protrusions per unit area of ​​the first sliding surface is η A [μm －2 ], let the roughness protrusion density per unit area of ​​the second sliding surface be η B [μm －2 ], the value calculated by the following formula 4 [μm －2 ], β means the median of the curvature radius of the roughness protrusions of the first sliding surface and the second sliding surface as a whole [μm], E * It means the equivalent longitudinal elastic modulus [GPa] of the first sliding surface and the second sliding surface.

[0015] [Formula 2]

[0016] δ=δ A +δ B ···2

[0017]

[0018] η=η A +η B ···4

[0019] Effects of the Invention

[0020] A sliding member according to one embodiment of the present invention can suppress seizure on a sliding surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic cross-sectional view showing a section perpendicular to the central axis of the shaft member in the sliding member according to one embodiment of the present invention.

[0022] Figure 2 This is a flowchart showing a method for manufacturing a sliding member according to one embodiment of the present invention.

[0023] Figure 3This is a flowchart showing a sliding member evaluation method according to one embodiment of the present invention.

[0024] Explanation of symbols

[0025] 1 shaft component

[0026] 11. First sliding surface

[0027] 2 Bearing components

[0028] 21 Second sliding surface

[0029] 3 Lubricant

[0030] d Shaft diameter of the first sliding surface DETAILED DESCRIPTION

[0031] [Description of Embodiments of the Invention]

[0032] First, embodiments of the present invention will be listed and described.

[0033] A sliding member according to one embodiment of the present invention comprises: a shaft member having a first sliding surface; and a bearing member having a second sliding surface that slidably supports the first sliding surface, wherein the first sliding surface and the second sliding surface have different hardnesses, and a roughness parameter R calculated by the following formula 1 is: ac Below 0.276.

[0034] [Formula 3]

[0035]

[0036] In the above formula 1, δ means that the average value of the top height of the roughness protrusions on the first sliding surface is δ A [μm], let the average value of the top height of the roughness protrusions on the second sliding surface be δ B [μm], the value [μm] calculated by the following formula 2, σ means that the root mean square of the height of the top of the roughness protrusions on the first sliding surface is σ A [μm], let the root mean square of the height of the top of the roughness protrusion of the second sliding surface be σ B [μm], the value [μm] calculated by the following formula 3, η means that the density of roughness protrusions per unit area of ​​the first sliding surface is η A [μm －2 ], let the roughness protrusion density per unit area of ​​the second sliding surface be η B [μm －2 ] is calculated by the following formula 4 [μm －2 ], β means the median of the curvature radius of the roughness protrusions of the first sliding surface and the second sliding surface as a whole [μm], E* It means the equivalent longitudinal elastic modulus [GPa] of the first sliding surface and the second sliding surface.

[0037] [Formula 4]

[0038] δ=δ A +δ B ···2

[0039]

[0040] η=η A +η B ···4

[0041] Generally speaking, the roughness contact stress P between two sliding surfaces is a [GPa], when the distance between the sliding surfaces is h [μm], it is calculated using the Greenwood-Tripp model by the following formula 5. In addition, h is expressed by the following formula 6 based on the following formula 5. Let the limit roughness contact stress at which galling occurs be P lim [GPa], in the following formula 6, P a =P lim Under the condition of h, h is the distance between the sliding surfaces at which the seizure occurs. lim It is represented by the following formula 7. lim It depends only on the roughness characteristics and material properties of the two sliding surfaces, so h can be lim Defined as the roughness parameter R ac Therefore, the sliding member is lim The roughness parameter R obtained by setting the above formula 1 to an appropriate value is ac By controlling the viscosity to be below the above value, seizure on the sliding surface can be suppressed.

[0042] [Formula 5]

[0043]

[0044]

[0045]

[0046] In addition, since the hardness of the first sliding surface and the second sliding surface of the sliding component is different, when the first sliding surface contacts the second sliding surface, the microscopic protrusions on the surface of the sliding surface with higher hardness are easily maintained. In contrast, the surface of the sliding surface with lower hardness is more likely to undergo plastic deformation. Therefore, the sliding component can grind the sliding surface with lower hardness through the contact between the first sliding surface and the second sliding surface, and it is easy to reduce the roughness parameter R acKeep below the above values.

[0047] The above roughness parameter R ac , the sliding surface with lower hardness between the first sliding surface and the second sliding surface can be regarded as a mirror surface without roughness protrusions. In this sliding component, R in the above formula 1 can be calculated more easily by regarding the sliding surface with lower hardness between the first sliding surface and the second sliding surface as a mirror surface without roughness protrusions. ac .

[0048] Preferably, lubricating liquid is supplied between the first sliding surface and the second sliding surface. In this way, by supplying lubricating liquid between the first sliding surface and the second sliding surface, seizure of the sliding surfaces can be further suppressed.

[0049] The shaft member may have a diameter of 180 mm or greater on the first sliding surface. For shaft members with a large diameter, such as a shaft member with a diameter greater than the lower limit, it may be desirable to manually polish the first sliding surface. Even in such a situation, this sliding member can easily prevent seizure on the sliding surface.

[0050] Preferably, δ is 0.232 or less, and σ is 0.209 or less. By setting δ and σ to be less than the above upper limits, seizure on the sliding surface can be easily suppressed.

[0051] Another aspect of the present invention is a method for manufacturing a sliding member comprising a shaft member having a first sliding surface and a bearing member having a second sliding surface slidably supporting the first sliding surface, wherein the first sliding surface and the second sliding surface have different hardnesses and have a roughness parameter R calculated according to the following formula 1: ac A smoothing step of smoothing the sliding surface having a higher hardness between the first sliding surface and the second sliding surface so that the hardness is 0.276 or less.

[0052] [Formula 6]

[0053]

[0054] In the above formula 1, δ means that the average value of the top height of the roughness protrusions on the first sliding surface is δ A [μm], let the average value of the top height of the roughness protrusions on the second sliding surface be δ B [μm], the value [μm] calculated by the following formula 2, σ means that the root mean square of the height of the top of the roughness protrusions on the first sliding surface is σ A [μm], let the root mean square of the height of the top of the roughness protrusion of the second sliding surface be σ B[μm], the value [μm] calculated by the following formula 3, η means that the density of roughness protrusions per unit area of ​​the first sliding surface is η A [μm －2 ], let the roughness protrusion density per unit area of ​​the second sliding surface be η B [μm －2 ], the value calculated by the following formula 4 [μm －2 ], β means the median of the curvature radius of the roughness protrusions of the first sliding surface and the second sliding surface as a whole [μm], E * It means the equivalent longitudinal elastic modulus [GPa] of the first sliding surface and the second sliding surface.

[0055] [Formula 7]

[0056] δ=δ A +δ B ···2

[0057]

[0058] η=η A +η B ···4

[0059] According to the manufacturing method of the sliding member, the roughness parameter R in the above formula 1 is ac When the hardness is less than the above value, the sliding surface with higher hardness between the first sliding surface and the second sliding surface is smoothed in the smoothing step, thereby manufacturing a sliding member capable of suppressing seizure on the sliding surface.

[0060] Another aspect of the present invention provides a method for evaluating a sliding member comprising a shaft member having a first sliding surface and a bearing member having a second sliding surface slidably supporting the first sliding surface, wherein the method comprises the following evaluation step: using the roughness parameter R calculated according to the following formula 1: ac Based on this, the possibility of seizure occurring between the first sliding surface and the second sliding surface was evaluated.

[0061] [Formula 8]

[0062]

[0063] In the above formula 1, δ means that the average value of the top height of the roughness protrusions on the first sliding surface is δ A [μm], let the average value of the top height of the roughness protrusions on the second sliding surface be δ B [μm], the value [μm] calculated by the following formula 2, σ means that the root mean square of the height of the top of the roughness protrusions on the first sliding surface is σA [μm], let the root mean square of the height of the top of the roughness protrusion of the second sliding surface be σ B [μm], the value [μm] calculated by the following formula 3, η means that the density of roughness protrusions per unit area of ​​the first sliding surface is η A [μm －2 ], let the roughness protrusion density per unit area of ​​the second sliding surface be η B [μm －2 ], the value calculated by the following formula 4 [μm －2 ], β means the median of the curvature radius of the roughness protrusions of the first sliding surface and the second sliding surface as a whole [μm], E * It means the equivalent longitudinal elastic modulus [GPa] of the first sliding surface and the second sliding surface.

[0064] [Formula 9]

[0065] δ=δ A +δ B ···2

[0066]

[0067] η=η A +η B ···4

[0068] According to the evaluation method of the sliding member, in the evaluation step, the roughness parameter R is expressed as ac The possibility of occurrence of seizure between the first sliding surface and the second sliding surface is evaluated based on this, so that the possibility of occurrence of seizure can be easily evaluated.

[0069] In the present invention, the "roughness protrusion vertex" is calculated using the following steps based on a roughness curve with a measurement length of 4.0 mm and a cutoff value of 0.25 mm, as measured in accordance with JIS-B0601 (2013). First, based on the mean line of the roughness curve set in accordance with JIS-B0601 (2013), the heights of measurement points located above the mean line are defined as positive values, while the heights of measurement points located below the mean line are defined as negative values. The average value of the heights of all measurement points with positive heights is Thr0. Next, among the measurement points on the roughness curve, the measurement points that are higher than the adjacent measurement points on both sides and have a height greater than -Thr0 are considered as hypothetical vertices. Among the measurement points located between adjacent hypothetical vertices, the measurement point with the smallest height is considered as a valley. Then, for each hypothetical vertex, the height difference between the hypothetical vertex and the valleys adjacent to it is calculated. If any of these height differences is less than 0.2 × Thr0, the hypothetical vertex is removed. As a result, the remaining tentative vertices are determined as the roughness protrusion vertices. Furthermore, when drawing a straight line from all measurement points on the roughness curve connecting the roughness protrusion vertex and the valley adjacent to the roughness protrusion vertex to the roughness protrusion vertex, the measurement points on the left and right of the roughness protrusion vertex where the straight line has the maximum gradient are determined and defined as the ends of the roughness protrusion vertex.

[0070] In the present invention, the term "roughness protrusion vertex height" refers to the height of the roughness protrusion vertex relative to the above-mentioned average line. The term "average roughness protrusion vertex height" refers to the value obtained by taking the arithmetic average of the heights of all roughness protrusion vertices present on the roughness curve. The term "root mean square of roughness protrusion vertex height" refers to the square root of the arithmetic average of the values ​​obtained by square the relative heights of the roughness protrusion vertices relative to the average of the heights of all roughness protrusion vertices present on the roughness curve.

[0071] In the present invention, the so-called "curvature radius of the roughness protrusion" is calculated by the following steps. First, the roughness curve between the two ends of each roughness protrusion vertex is approximated by the least squares method. Then, when the quadratic coefficient of the quadratic function obtained by the least squares approximation result is set to a, the curvature radius of each roughness protrusion vertex is calculated as -0.5 / a. In addition, the so-called "median of the curvature radius of the roughness protrusions of the first sliding surface and the second sliding surface as a whole" means the median of the curvature radius of all roughness protrusion vertices on the roughness curve of the first sliding surface and the roughness curve of the second sliding surface.

[0072] In the present invention, the “roughness protrusion density per unit area” refers to the value obtained by (m / L) when the measurement length of the roughness curve, i.e., the length of the horizontal axis of the roughness curve is L and the number of roughness protrusion vertices on the roughness curve is m. 2 Calculated density.

[0073] In the present invention, the "equivalent longitudinal elastic modulus" refers to the Poisson's ratio of the first sliding surface as ν A , let the longitudinal elastic modulus of the first sliding surface be E A [GPa], let the Poisson's ratio of the second sliding surface be ν B , let the longitudinal elastic modulus of the second sliding surface be E B [GPa], the E [GPa] value is calculated according to the following formula 8.

[0074] [Formula 10]

[0075]

[0076] In the present invention, the so-called "treating the sliding surface of the side with lower hardness as a mirror surface without roughness protrusions" means converting the average value of the roughness protrusion apex height, the root mean square of the roughness protrusion apex height and the roughness protrusion density per unit area of ​​the sliding surface of the side with lower hardness to 0, and converting the median of the curvature radius of the roughness protrusions of the first sliding surface and the second sliding surface as a whole to the median of the curvature radius of the roughness protrusions on the side with higher hardness.

[0077] [Details of Embodiments of the Invention]

[0078] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0079] [Sliding member]

[0080] Figure 1 A sliding member, for example, is a marine sliding member installed on a ship. The sliding member includes: a shaft member 1 having a first sliding surface 11; and a bearing member 2 having a second sliding surface 21 that slidably supports the first sliding surface 11. The first sliding surface 11 and the second sliding surface 21 face each other. The second sliding surface 21 surrounds the outer circumference of the first sliding surface 11. Lubricating fluid 3 is supplied between the first sliding surface 11 and the second sliding surface 21.

[0081] <Shaft member>

[0082] The shaft member 1 is a rotating body that rotates in the circumferential direction relative to the bearing member 2. Examples of the shaft member 1 include marine crankshafts, intermediate shafts, and propeller shafts. Examples of the material of the shaft member 1 include carbon steel and low alloy steel.

[0083] The shaft diameter d of the first sliding surface 11 is not particularly limited and may be 180 mm or greater. Alternatively, the shaft diameter d of the first sliding surface 11 may be 280 mm or greater, or 360 mm or greater. When the shaft diameter d of the first sliding surface 11 is greater than the above lower limit, it may be desirable to manually grind the first sliding surface 11. Even in such a case, this sliding member can easily suppress galling between the first sliding surface 11 and the second sliding surface 21.

[0084] The upper limit of the axial diameter d of the first sliding surface 11 is preferably 1500 mm, more preferably 1400 mm, and further preferably 1300 mm. If the axial diameter d of the first sliding surface 11 exceeds the upper limit, the sliding member becomes too large, which may violate the requirements of device miniaturization.

[0085] <Bearing components>

[0086] Examples of the bearing member 2 include a marine crank bearing, an intermediate bearing, and a propulsion bearing. Examples of the material of the bearing member 2 include white metal, trimetal, oil film bearing alloy, and aluminum alloy.

[0087] The roughness parameter R of the first sliding surface 11 and the second sliding surface 21 of the sliding member is calculated by the following formula 1: ac Below 0.276.

[0088] [Formula 11]

[0089]

[0090] In the above formula 1, δ means that the average value of the top height of the roughness protrusions on the first sliding surface 11 is δ A [μm], the average value of the top height of the roughness protrusions on the second sliding surface 21 is δ B [μm], the value [μm] calculated by the following formula 2, σ means that the root mean square of the height of the top of the roughness protrusions on the first sliding surface 11 is σ A [μm], the root mean square of the height of the top of the roughness protrusions on the second sliding surface 21 is σ B [μm], the value [μm] calculated by the following formula 3, η means that the density of roughness protrusions per unit area of ​​the first sliding surface 11 is η A [μm －2 ], let the roughness protrusion density per unit area of ​​the second sliding surface 21 be η B [μm －2 ], the value calculated by the following formula 4 [μm －2 ], β means the median of the curvature radius of the roughness protrusions of the first sliding surface 11 and the second sliding surface 21 as a whole [μm], E* means the equivalent longitudinal elastic modulus [GPa] of the first sliding surface 11 and the second sliding surface 21 .

[0091] [Formula 12]

[0092] δ=δ A +δ B ···2

[0093]

[0094] η=η A +η B ···4

[0095] As the roughness parameter R ac The upper limit of the roughness parameter R is preferably 0.185, more preferably 0.141. ac If the value exceeds the upper limit, it may be difficult to suppress seizure between the first sliding surface 11 and the second sliding surface 21 .

[0096] The lower limit of β is not particularly limited and may be, for example, higher than 51, higher than 55, or higher than 58. In this sliding member, the β value tends to increase when the first sliding surface 11 is manually polished. Even in such a case, this sliding member can easily suppress galling between the first sliding surface 11 and the second sliding surface 21.

[0097] On the other hand, the upper limit of β is preferably 338, more preferably 330, and further preferably 320. If β exceeds the upper limit, it may be difficult to suppress seizure between the first sliding surface 11 and the second sliding surface 21 .

[0098] It is preferred that δ is less than 0.232 and σ is less than 0.209. By setting δ and σ to be less than the above upper limits, it is easy to suppress the seizure between the first sliding surface 11 and the second sliding surface 21. To explain in more detail, if the first sliding surface 11 is manually polished, the β value increases, resulting in the roughness parameter R in the above formula 1. ac Even in this case, by controlling δ and σ below the upper limit, the roughness parameter R can be easily reduced. ac Therefore, it is easy to suppress the seizure between the first sliding surface 11 and the second sliding surface 21.

[0099] The upper limit of δ is more preferably 0.181, and even more preferably 0.166. On the other hand, the lower limit of δ is preferably 0.034, more preferably 0.040, and even more preferably 0.050. If δ exceeds the upper limit, it may be difficult to prevent galling between the first sliding surface 11 and the second sliding surface 21. Conversely, if δ is below the lower limit, manual polishing may be required, which may increase the manufacturing cost of the sliding component.

[0100] The upper limit of σ is preferably 0.166, and even more preferably 0.130. The lower limit of σ is preferably 0.052, more preferably 0.060, and even more preferably 0.070. If σ exceeds the upper limit, it may be difficult to prevent seizure between the first sliding surface 11 and the second sliding surface 21. Conversely, if σ is below the lower limit, manual polishing may be required, which may increase the manufacturing cost of the sliding component.

[0101] The hardness of the first sliding surface 11 and the second sliding surface 21 is different. For example, the hardness of the first sliding surface 11 can be made higher than the hardness of the second sliding surface 21. In this sliding component, since the hardness of the first sliding surface 11 and the second sliding surface 21 is different, when the first sliding surface 11 and the second sliding surface 21 are in contact, the microscopic protrusions on the surface of the side with higher hardness of the two sliding surfaces are easy to maintain. In contrast, the surface of the side with lower hardness of the first sliding surface 11 and the second sliding surface 21 is easy to undergo plastic deformation due to the rotational contact between the sliding surfaces. Therefore, the side with lower hardness of the first sliding surface 11 and the second sliding surface 21 can be regarded as a surface with substantially the same roughness protrusions as the side with higher hardness, or a mirror surface with substantially no roughness protrusions. In other words, the roughness parameter R is calculated by the above formula 1. ac When β is calculated, the average value of the height of the top of the roughness protrusions, the root mean square of the height of the top of the roughness protrusions, and the density of the roughness protrusions per unit area of ​​the sliding surface with lower hardness between the first sliding surface 11 and the second sliding surface 21 can be converted to the values ​​of the sliding surface with higher hardness, or these values ​​can be converted to 0. In addition, β can also be converted to the median of the curvature radius of the roughness protrusions in the sliding surface with higher hardness. In this way, the sliding surface with lower hardness between the first sliding surface 11 and the second sliding surface 21 is regarded as a surface with the same roughness protrusions as the one with higher hardness, or as a mirror surface without roughness protrusions. This makes it easier to calculate R in the above formula 1 by taking into account the future plastic deformation of the sliding surface with lower hardness. ac In addition, by calculating R in this way ac, it is easy to obtain the effect of suppressing seizure between the first sliding surface 11 and the second sliding surface 21 when manually polishing the sliding surface with higher hardness between the first sliding surface 11 and the second sliding surface 21. In addition, the "hardness" here means the Brinell hardness specified in JIS-Z2243 (2018).

[0102] It is preferable that the hardness difference between the first sliding surface 11 and the second sliding surface 21 is large. The lower limit of the hardness difference between the first sliding surface 11 and the second sliding surface 21 is preferably 100 HB, more preferably 130 HB, and even more preferably 150 HB.

[0103] <Lubricant>

[0104] The lubricating liquid 3 forms a lubricating film between the first sliding surface 11 and the second sliding surface 21, thereby improving the sliding properties between the first sliding surface 11 and the second sliding surface 21. Examples of the lubricating liquid 3 include lubricating oils such as paraffin-based oils and seawater.

[0105] The lubricating liquid 3 forms the aforementioned lubricating film, making it easier to maintain a fluid lubrication state between the first sliding surface 11 and the second sliding surface 21. By maintaining a fluid lubrication state between the first sliding surface 11 and the second sliding surface 21, galling between the first sliding surface 11 and the second sliding surface 21 can be suppressed. The term "fluid lubrication state" herein refers to a state of fluid lubrication as categorized using the Stribeck curve.

[0106] Advantages

[0107] The sliding member is formed by using the roughness parameter R ac By controlling the viscosity to be below the above value, seizure on the sliding surface can be suppressed.

[0108] In this sliding component, for example, when the shaft component 1 is a marine crankshaft, the crank pin is eccentric with respect to the journal, so the dimensional accuracy of the machined sliding surface is likely to be insufficient. In more detail, for example, when the first sliding surface 11 is provided on the peripheral surface of the crank pin, it is easy to need to grind the first sliding surface 11 manually. The curvature radius of the roughness protrusion of the manually ground first sliding surface 11 becomes larger, and there is a possibility that biting is likely to occur. In other words, when the shaft component 1 is a marine crankshaft, the β value is likely to increase. Even in such a case, this sliding component also makes the roughness parameter R of the above formula 1 ac Other roughness parameters such as δ and σ are controlled to be equal to or less than the above values. Therefore, in this sliding member, even when the shaft member 1 is a marine crankshaft, seizure on the sliding surface can be appropriately suppressed.

[0109] [Method for manufacturing a sliding member]

[0110] Reference Figure 2 ,for Figure 1 An example of a method for manufacturing a sliding member is described. The method for manufacturing a sliding member is a method for manufacturing a sliding member comprising a shaft member 1 having a first sliding surface 11 and a bearing member 2 having a second sliding surface 21 that slidably supports the first sliding surface 11, wherein the first sliding surface 11 and the second sliding surface 21 have different hardnesses, and the method comprises a smoothing step S1 of smoothing the sliding surface having the higher hardness between the first sliding surface 11 and the second sliding surface 21.

[0111] <Smoothing process>

[0112] The smoothing process S1 is performed after the shaft component 1 and the bearing component 2 are formed by mechanical processing. The shaft component 1 and the bearing component 2 after mechanical processing may have insufficient dimensional accuracy. In order to improve the dimensional accuracy, it is necessary to manually grind the sliding surface with higher hardness between the first sliding surface 11 and the second sliding surface 21 (for example, the first sliding surface 11 of the shaft component 1). If the first sliding surface 11 is manually ground, the curvature radius of the roughness protrusion of the first sliding surface 11 is likely to increase. To explain in more detail, for example, when the β value after mechanical processing is in the range of 23.78 or more and 51.00 or less, the β value after manual grinding of the first sliding surface 11 may rise to the range of 55.79 or more and 337.9 or less. If the β value increases like this, the roughness parameter R calculated by the above formula 1 ac Therefore, the roughness parameter R calculated by the above formula 1 is set to ac In the case where the roughness parameter R is less than 0.276, the sliding surface with higher hardness between the first sliding surface 11 and the second sliding surface 21 is smoothed. In other words, in the smoothing step S1, even when the β value is large, the roughness parameter R is made ac The value of δ and σ etc. is reduced by being 0.276 or less on the sliding surface having higher hardness between the first sliding surface 11 and the second sliding surface 21. In the smoothing step S1, the sliding surface is preferably polished manually.

[0113] In the manufacturing method of the sliding member, since the hardness of the first sliding surface 11 and the second sliding surface 21 is different, the sliding surface with the lower hardness between the first sliding surface 11 and the second sliding surface 21 can be regarded as a surface having substantially the same roughness protrusions as the surface with the higher hardness, or as a mirror surface having substantially no roughness protrusions. In other words, when calculating the roughness parameter R by the above formula 1, acWhen β is used as the value of β, the average value of the height of the top of the roughness protrusions, the root mean square of the height of the top of the roughness protrusions, and the density of roughness protrusions per unit area of ​​the sliding surface with lower hardness between the first sliding surface 11 and the second sliding surface 21 can be converted to the values ​​of the sliding surface with higher hardness, or these values ​​can be converted to 0. In addition, β can also be converted to the median of the curvature radius of the roughness protrusions on the sliding surface with higher hardness. In this way, the sliding surface with lower hardness between the first sliding surface 11 and the second sliding surface 21 can be regarded as a surface with the same roughness protrusions as the surface with higher hardness, or as a mirror surface without roughness protrusions, so that R in the above formula 1 can be calculated more easily. ac .

[0114] In the smoothing step S1, it is preferred to grind at least one of the first sliding surface 11 and the second sliding surface 21 while setting the δ value to be 0.232 or less and the σ value to be 0.209 or less. By grinding at least one of the first sliding surface 11 and the second sliding surface 21 while setting the δ and σ values ​​to be less than the above upper limits, the roughness parameter R can be easily reduced even when the β value is large. ac The value of .

[0115] The method for smoothing at least one of the first sliding surface 11 and the second sliding surface 21 of the shaft member 1 is not particularly limited, and examples thereof include polishing at least one of the first sliding surface 11 and the second sliding surface 21 with sandpaper.

[0116] When polishing at least one of the first sliding surface 11 and the second sliding surface 21 with sandpaper, for example, sandpaper with a roughness of 240 or higher is preferred. Using sandpaper with the appropriate roughness rating facilitates increasing the β value while keeping the δ and σ values ​​low. This effectively prevents galling between the first sliding surface 11 and the second sliding surface 21.

[0117] Advantages

[0118] According to the manufacturing method of the sliding member, the roughness parameter R in the above formula 1 is changed to ac By controlling the viscosity to be equal to or less than the above value, a sliding member capable of suppressing seizure on the sliding surface can be manufactured.

[0119] [Evaluation method of sliding member]

[0120] Reference Figure 3 An example of the evaluation method of the sliding member is described below. The evaluation method of the sliding member is a method for evaluating a sliding member comprising a shaft member having a first sliding surface and a bearing member having a second sliding surface slidably supporting the first sliding surface, wherein the evaluation step S1 is performed using a roughness parameter R calculated by the following formula 1. acBased on the above, the possibility of seizure between the first sliding surface and the second sliding surface is evaluated. This evaluation method is suitable for evaluating Figure 1 Whether seizure occurs between the first sliding surface 11 and the second sliding surface 21 of the sliding member. In the evaluation step S1, the roughness parameter R ac When the roughness parameter R is below the threshold, it is evaluated that the possibility of the occurrence of the above-mentioned seizure is low. On the contrary, the roughness parameter R ac When the value is higher than the threshold value, it is evaluated that the possibility of the occurrence of the above-mentioned seizure is high.

[0121] [Formula 13]

[0122]

[0123] In the above formula 1, δ means that the average value of the top height of the roughness protrusions on the first sliding surface is δ A [μm], let the average value of the top height of the roughness protrusions on the second sliding surface be δ B [μm], the value [μm] calculated by the following formula 2, σ means that the root mean square of the height of the top of the roughness protrusions on the first sliding surface is σ A [μm], let the root mean square of the height of the top of the roughness protrusion of the second sliding surface be σ B [μm], the value [μm] calculated by the following formula 3, η means that the density of roughness protrusions per unit area of ​​the first sliding surface is η A [μm －2 ], let the roughness protrusion density per unit area of ​​the second sliding surface be η B [μm －2 ], the value calculated by the following formula 4 [μm －2 ], β means the median of the curvature radius of the roughness protrusions of the first sliding surface and the second sliding surface as a whole [μm], E * It means the equivalent longitudinal elastic modulus [GPa] of the first sliding surface and the second sliding surface.

[0124] [Formula 14]

[0125] δ=δ A +δ B ···2

[0126]

[0127] η=η A +η B ···4

[0128] <Evaluation Process>

[0129] The evaluation step S1 is performed after the shaft member and the bearing member are formed by machining. Alternatively, the evaluation step S1 may be performed after the first sliding surface and the second sliding surface are brought into contact with each other in a certain degree of rotation.

[0130] The threshold value is preferably 0.276, more preferably 0.185, and even more preferably 0.141.

[0131] In the evaluation step S1, the roughness parameter R is calculated by the above formula 1. ac When β is the value of β, the average value of the height of the top of the roughness protrusions, the root mean square of the height of the top of the roughness protrusions, and the density of the roughness protrusions per unit area of ​​the sliding surface with lower hardness between the first sliding surface and the second sliding surface can be converted into the values ​​of the sliding surface with higher hardness, or these values ​​can be converted to 0. In addition, β can also be converted into the median of the radius of curvature of the roughness protrusions on the sliding surface with higher hardness. By treating the sliding surface with lower hardness between the first sliding surface and the second sliding surface as a surface with the same roughness protrusions as the surface with higher hardness, or as a mirror surface without roughness protrusions, it is easier to calculate R in the above formula 1. ac .

[0132] Advantages

[0133] The evaluation method of the sliding member is as follows: in the evaluation step S1, the roughness parameter R ac Based on this, the possibility of occurrence of seizure between the first sliding surface and the second sliding surface is evaluated, thereby making it possible to easily evaluate the possibility of occurrence of the seizure.

[0134] [Other embodiments]

[0135] The above embodiments do not limit the configuration of the present invention. Therefore, the above embodiments may omit, replace, or add components of each part of the above embodiments based on the description of this specification and common technical knowledge, and all of these should be interpreted as falling within the scope of the present invention.

[0136] For example, the sliding member may be configured such that lubricating fluid is not supplied between the first sliding surface and the second sliding surface.

[0137] In addition, even if the first sliding surface and the second sliding surface have different hardnesses, the roughness parameter R can be calculated based on the shape of the roughness protrusions on each sliding surface. ac .

[0138] [Example]

[0139] Hereinafter, the present invention will be described in detail based on Examples, but the present invention is not to be construed in a limitative manner based on the description of these Examples.

[0140] A shaft member and a bearing member were fixed in a bearing life tester manufactured by Kobelco Machinery Co., Ltd. to confirm whether seizure occurred between the shaft member and the bearing member. In the bearing life tester, the portion of the shaft member's outer circumference sliding against the bearing member was designated as the first sliding surface, and the portion of the bearing member's inner circumference sliding against the shaft member was designated as the second sliding surface. The shaft member was then rotated while being pressed against the bearing member's second sliding surface with a constant load. While the shaft member was rotating, lubricating oil at a temperature of 70°C was supplied to the shaft member's first sliding surface. Furthermore, a thermocouple installed at a depth of 2 mm from the bearing member's second sliding surface was used to measure the temperature [°C], and this temperature was used as the lubricating oil temperature.

[0141] [No.1]

[0142] In No. 1, the shaft member is rotated under the following conditions. The load applied by the shaft member to the bearing member is set to 10 kN. The rotation speed of the shaft member is set to 3000 rpm when the shaft member starts rotating and is reduced by 250 rpm every 5 minutes. The rotation of the shaft member ends when the rotation speed of the shaft member reaches 0 rpm or when seizure occurs between the shaft member and the bearing member. The results of confirming whether seizure occurs between the shaft member and the bearing member are shown in Table 1. However, the roughness parameter R in Table 1 is ac [μm] is calculated by the above formula 1, taking the average value of the height of the top of the roughness protrusions on the second sliding surface, the root mean square of the height of the top of the roughness protrusions, and the density of the roughness protrusions per unit area as 0, and converting the median of the curvature radius of the roughness protrusions on the first sliding surface and the second sliding surface as a whole into the median of the curvature radius of the roughness protrusions on the first sliding surface. In addition, the arithmetic mean roughness Ra [μm] and the protruding peak height Rpk [μm] in Table 1 are the arithmetic mean roughness Ra of the first sliding surface specified by JIS-B0601 (2013) and the protruding peak height Rpk of the first sliding surface specified by JIS-B0671-2 (2002), respectively. However, the roughness parameter R in Table 1 ac, the arithmetic mean roughness Ra and the height of the protruding peak Rpk are obtained by averaging the values ​​calculated through multiple measurements. In addition, the oil film thickness h [mm] when the bite occurs in Table 1 is calculated using the Ertel-Grubin formula represented by the following formula 9. Here, γ [Pa·second] is the viscosity of the lubricating oil calculated based on the lubricating oil temperature when the bite occurs, R [m] is the equivalent radius calculated by the following formula 10 based on the radius R1 of the shaft component and the radius R2 of the bearing component, α [1 / GPa] is the viscosity pressure coefficient of the lubricating oil, u [m / second] is the circumferential speed of the shaft component calculated based on the rotational speed of the shaft component, and w [N / m] is the load per unit contact length in the bearing width direction obtained by dividing the load applied by the shaft component to the bearing component by the bearing width. In this embodiment, the oil film thickness h when the bite occurs is calculated with α = 0.02. Roughness parameter R ac The calculation method of the oil film thickness h when seizure occurs is the same as that in No. 2 to No. 8 described later.

[0143] [Formula 15]

[0144]

[0145]

[0146] (Shaft component)

[0147] In No. 1, as the shaft component, carbon steel S45C specified in JIS-G4051 (2016) with a Young's modulus of 210,000 MPa, a Poisson's ratio of 0.3, a first sliding surface diameter of 39.96 mm, and a hardness of approximately 172 HB was used. In No. 1, after machining, the first sliding surface was manually polished to adjust the average value of the roughness protrusion vertex height on the first sliding surface to 0.074 μm, the root mean square of the roughness protrusion vertex height to 0.078 μm, the curvature radius of the roughness protrusion to 60.91 μm, and the roughness protrusion density per unit area to 0.0134 μm. －2 However, the average value of the top height of the roughness protrusions on the first sliding surface, the root mean square of the top height of the roughness protrusions, the curvature radius of the roughness protrusions, and the density of the roughness protrusions per unit area are calculated by averaging the values ​​calculated through multiple measurements. The calculation method of the average value of the top height of the roughness protrusions on the first sliding surface, the root mean square of the top height of the roughness protrusions, the curvature radius of the roughness protrusions, and the density of the roughness protrusions per unit area is the same as that for No. 2 to No. 8 described below.

[0148] (Bearing components)

[0149] In No. 1, as the bearing member, white alloy WJ2 specified in JIS-H5401 (1958) having a Young's modulus of 55,000 MPa, a Poisson's ratio of 0.33, a second sliding surface diameter of 40.2 mm, a bearing width of 35 mm, and a hardness of approximately 27 HB is used.

[0150] (lubricating oil)

[0151] In No. 1, a lubricating oil having a dynamic viscosity of 32.1 mm at 40°C was used. 2 / second, and the density at 15°C is 0.871 g / cm 3 "FBK OIL RO32" manufactured by ENEOS Co., Ltd.

[0152] [No.2]

[0153] In No. 2, the following shaft member, the same bearing member as in No. 1, and the same lubricating oil as in No. 1 were used, and the shaft member was rotated under the following conditions. The load applied by the shaft member to the bearing member was set to 10 kN. The rotation speed of the shaft member was set to 3000 rpm at the beginning of the shaft member rotation and was reduced by 100 rpm every 5 minutes. After the rotation speed of the shaft member reached 300 rpm or less, the rotation speed of the shaft member was reduced by 50 rpm every 5 minutes. The rotation of the shaft member was terminated when the rotation speed of the shaft member reached 0 rpm or when seizure occurred between the shaft member and the bearing member. The results of confirming whether seizure occurred between the shaft member and the bearing member are shown in Table 1.

[0154] (Shaft component)

[0155] In No. 2, the first sliding surface was manually polished after machining to adjust the average value of the top height of the roughness protrusions on the first sliding surface to 0.166 μm, the root mean square of the top height of the roughness protrusions to 0.130 μm, the curvature radius of the roughness protrusions to 17.88 μm, and the density of the roughness protrusions per unit area to 0.0158 μm. －2 The other structures are the same as those of the shaft member No. 1.

[0156] [No.3]

[0157] In No. 3, after machining, the first sliding surface was manually polished to adjust the average value of the top height of the roughness protrusions on the first sliding surface to 0.181 μm, the root mean square of the top height of the roughness protrusions to 0.166 μm, the curvature radius of the roughness protrusions to 29.53 μm, and the roughness protrusion density per unit area to 0.0096 μm. －2 The other structures were the same as those in No. 1, and the shaft member was rotated under the same conditions as in No. 1. The results of confirming whether or not seizure occurred are shown in Table 1.

[0158] [No.4]

[0159] In No. 4, after machining, the first sliding surface was manually polished to adjust the average value of the roughness protrusion vertex height of the first sliding surface to 0.232 μm, the root mean square of the roughness protrusion vertex height to 0.209 μm, the curvature radius of the roughness protrusion to 18.78 μm, and the roughness protrusion density per unit area to 0.0119 μm. －2 The other structures were the same as those in No. 2, and the shaft member was rotated under the same conditions as in No. 2. The results of confirming whether or not seizure occurred are shown in Table 1.

[0160] [No.5]

[0161] In No. 5, after machining, the first sliding surface was manually polished to adjust the average value of the top height of the roughness protrusions on the first sliding surface to 0.272 μm, the root mean square of the top height of the roughness protrusions to 0.203 μm, the curvature radius of the roughness protrusions to 16.20 μm, and the roughness protrusion density per unit area to 0.0121 μm. －2 , except that the structure was the same as No. 2, and the shaft member was rotated under the same conditions as No. 2. The results of confirming whether or not seizure occurred are shown in Table 1.

[0162] [No.6]

[0163] In No. 6, after machining, the first sliding surface was manually polished to adjust the average value of the roughness protrusion vertex height of the first sliding surface to 0.544 μm, the root mean square of the roughness protrusion vertex height to 0.320 μm, the curvature radius of the roughness protrusion to 9.40 μm, and the roughness protrusion density per unit area to 0.0075 μm. －2 , except for the above, the structure was the same as that of No. 2, and the shaft member was rotated under the same conditions as No. 2. The results of confirming whether or not seizure occurred are shown in Table 1.

[0164] [No.7]

[0165] In No. 7, after machining, the first sliding surface was manually polished to adjust the average value of the roughness protrusion vertex height of the first sliding surface to 0.634 μm, the root mean square of the roughness protrusion vertex height to 0.298 μm, the curvature radius of the roughness protrusion to 13.94 μm, and the roughness protrusion density per unit area to 0.0049 μm. －2 , except for the above, the structure was the same as that of No. 2, and the shaft member was rotated under the same conditions as No. 2. The results of confirming whether or not seizure occurred are shown in Table 1.

[0166] [No.8]

[0167] In No. 8, after machining, the first sliding surface was manually polished to adjust the average value of the roughness protrusion vertex height of the first sliding surface to 0.460 μm, the root mean square of the roughness protrusion vertex height to 0.534 μm, the curvature radius of the roughness protrusion to 18.94 μm, and the roughness protrusion density per unit area to 0.0055 μm. －2 , except for the above, the structure was the same as that of No. 1, and the shaft member was rotated under the same conditions as No. 1. The results of confirming whether or not seizure occurred are shown in Table 1.

[0168]

Table 1

[0169]

[0170] It can be seen from Table 1 that the roughness parameter R ac In No. 1 to No. 4, which have a roughness of 0.276 or less, seizure is suppressed. ac Positively correlated with the oil film thickness h when seizure occurs. Roughness parameter R ac The correlation between the roughness parameter R and the oil film thickness h at the time of seizure is higher than the correlation between the arithmetic mean roughness Ra and the oil film thickness h at the time of seizure and the correlation between the protruding peak height Rpk and the oil film thickness h at the time of seizure. ac This parameter is suitable for evaluating the likelihood of galling.

[0171] In this embodiment, carbon steel is used as the shaft member and white alloy WJ2 is used as the bearing member. For example, when carbon steel S45C is used as the shaft member and Al-Sn alloy is used as the bearing member, the roughness parameter R ac If the hardness is below 0.276, it is considered that seizure can also be suppressed. The reason for this is that the hardness of carbon steel S45C after annealing specified in JIS-G4051 (2016) is generally above 137HB and below 170HB. On the other hand, in ISO 3547-4 Table 2, the hardness of AlSn6Cu is specified to be above 35HB and below 45HB, and the hardness of AlSn20Cu is specified to be above 30HB and below 45HB. Therefore, the hardness difference between carbon steel S45C and Al-Sn alloy is about 100HB. That is, the hardness difference between carbon steel S45C and Al-Sn alloy is a value similar to the hardness difference between carbon steel S45C and white alloy WJ2 in this embodiment. Therefore, it is considered that the hardness depends only on the roughness characteristics of the sliding surface and the R of the material properties. ac The value of is also the same.

[0172] Industrial applicability

[0173] The sliding member according to one embodiment of the present invention can suppress seizure on the sliding surface and thus can be suitably used in, for example, a crankshaft, an intermediate shaft, a propeller shaft, and the like for a ship.

Claims

1. A sliding member comprising: a shaft member having a first sliding surface; a bearing member having a second sliding surface capable of slidably supporting the first sliding surface, The first sliding surface and the second sliding surface have different hardnesses. The roughness parameter R is calculated by the following formula 1: ac is below 0.276, [Formula 1] in, In the above formula 1, δ means that the average value of the top height of the roughness protrusions on the first sliding surface is δ A , let the average value of the top height of the roughness protrusions on the second sliding surface be δ B When the value calculated by the following formula 2 is σ, the root mean square of the height of the top of the roughness protrusion of the first sliding surface is σ A , let the root mean square of the height of the top of the roughness protrusion of the second sliding surface be σ B When the value calculated by the following formula 3 is: η means that the roughness protrusion density per unit area of ​​the first sliding surface is η A , let the roughness protrusion density per unit area of ​​the second sliding surface be η B When the value calculated by the following formula 4 is: β is the median of the curvature radius of the roughness protrusion of the first sliding surface and the second sliding surface as a whole, E * Refers to the equivalent longitudinal elastic modulus of the first sliding surface and the second sliding surface, wherein the above δ, δ A , δ B , σ, σ A , σ B The unit of β is μm. The above η and η A ,η B The unit is μm －2 , the above E * The unit is GPa, δ is less than 0.232, σ is less than 0.209, and β is less than 338. The roughness protrusion vertex refers to a condition in which the height of a measurement point located above the average line is defined as a positive value, the height of a measurement point located below the average line is defined as a negative value, and the average value of the heights of all measurement points with positive heights is Thr0. Among the measurement points on the roughness curve, the measurement point that is higher than the measurement points adjacent to it on both sides and has a height greater than -Thr0 is defined as an assumed vertex, and the measurement point with the smallest height among the measurement points located between the adjacent assumed vertices is defined as a valley. For all the assumed vertices, the height difference between each assumed vertex and the left and right valleys adjacent to the assumed vertex is calculated. If any of the height differences is less than 0.2×Thr0, the assumed vertex is removed, and the remaining assumed vertices are calculated as the roughness protrusion vertex. [Formula 2] 。 2. The sliding member according to claim 1, wherein The above roughness parameter R ac The calculation is performed by assuming that the sliding surface with lower hardness between the first sliding surface and the second sliding surface is a mirror surface without any roughness protrusions.

3. The sliding member according to claim 1 or claim 2, wherein: Lubricating fluid is supplied between the first sliding surface and the second sliding surface.

4. The sliding member according to claim 1 or claim 2, wherein: The first sliding surface of the shaft member has a shaft diameter of 180 mm or more.

5. A method for manufacturing a sliding member comprising a shaft member having a first sliding surface and a bearing member having a second sliding surface that slidably supports the first sliding surface, wherein: The first sliding surface and the second sliding surface have different hardnesses, and have a roughness parameter R calculated according to the following formula 1: ac a smoothing step of smoothing the sliding surface having a higher hardness between the first sliding surface and the second sliding surface so that the hardness is not more than 0.276; [Formula 3] In the above formula 1, δ means that the average value of the top height of the roughness protrusions on the first sliding surface is δ A , let the average value of the top height of the roughness protrusions on the second sliding surface be δ B When the value calculated by the following formula 2 is σ, the root mean square of the height of the top of the roughness protrusion of the first sliding surface is σ A , let the root mean square of the height of the top of the roughness protrusion of the second sliding surface be σ B When the value calculated by the following formula 3 is: η means that the roughness protrusion density per unit area of ​​the first sliding surface is η A , let the roughness protrusion density per unit area of ​​the second sliding surface be η B When the value calculated by the following formula 4 is: β is the median of the curvature radius of the roughness protrusion of the first sliding surface and the second sliding surface as a whole, E * Refers to the equivalent longitudinal elastic modulus of the first sliding surface and the second sliding surface, wherein the above δ, δ A , δ B , σ, σ A , σ B The unit of β is μm. The above η and η A ,η B The unit is μm －2 , the above E * The unit is GPa, δ is less than 0.232, σ is less than 0.209, and β is less than 338. The roughness protrusion vertex refers to a condition in which the height of a measurement point located above the average line is defined as a positive value, the height of a measurement point located below the average line is defined as a negative value, and the average value of the heights of all measurement points with positive heights is Thr0. Among the measurement points on the roughness curve, the measurement point that is higher than the measurement points adjacent to it on both sides and has a height greater than -Thr0 is defined as an assumed vertex, and the measurement point with the smallest height among the measurement points located between the adjacent assumed vertices is defined as a valley. For all the assumed vertices, the height difference between each assumed vertex and the left and right valleys adjacent to the assumed vertex is calculated. If any of the height differences is less than 0.2×Thr0, the assumed vertex is removed, and the remaining assumed vertices are calculated as the roughness protrusion vertex. [Formula 4] 。 6. A method for evaluating a sliding member comprising a shaft member having a first sliding surface and a bearing member having a second sliding surface that slidably supports the first sliding surface, wherein: The following evaluation process is provided: the roughness parameter R is calculated according to the following formula 1 ac Based on the evaluation of the possibility of seizure between the first sliding surface and the second sliding surface, the roughness parameter R ac The threshold value is 0.276, [Formula 5] In the above formula 1, δ means that the average value of the top height of the roughness protrusions on the first sliding surface is δ A , let the average value of the top height of the roughness protrusions on the second sliding surface be δ B When the value calculated by the following formula 2 is σ, the root mean square of the height of the top of the roughness protrusion of the first sliding surface is σ A , let the root mean square of the height of the top of the roughness protrusion of the second sliding surface be σ B When the value calculated by the following formula 3 is: η means that the roughness protrusion density per unit area of ​​the first sliding surface is η A , let the roughness protrusion density per unit area of ​​the second sliding surface be η B When the value calculated by the following formula 4 is: β is the median of the curvature radius of the roughness protrusion of the first sliding surface and the second sliding surface as a whole, E * Refers to the equivalent longitudinal elastic modulus of the first sliding surface and the second sliding surface, wherein the above δ, δ A , δ B , σ, σ A , σ B The unit of β is μm. The above η and η A ,η B The unit is μm －2 , the above E * The unit is GPa, δ is less than 0.232, σ is less than 0.209, and β is less than 338. The roughness protrusion vertex refers to a condition in which the height of a measurement point located above the average line is defined as a positive value, the height of a measurement point located below the average line is defined as a negative value, and the average value of the heights of all measurement points with positive heights is Thr0. Among the measurement points on the roughness curve, the measurement point that is higher than the measurement points adjacent to it on both sides and has a height greater than -Thr0 is defined as an assumed vertex, and the measurement point with the smallest height among the measurement points located between the adjacent assumed vertices is defined as a valley. For all the assumed vertices, the height difference between each assumed vertex and the left and right valleys adjacent to the assumed vertex is calculated. If any of the height differences is less than 0.2×Thr0, the assumed vertex is removed, and the remaining assumed vertices are calculated as the roughness protrusion vertex. [Formula 6] 。

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