Copper-based sliding member

Abstract

The sliding member of the present application includes a bearing alloy composed of a Cu-Sn alloy containing 1.5 to 10 mass% of Sn, the remainder being Cu and impurities, and having a Sn concentration of 1.1 times or more the average Sn concentration of the Cu-Sn alloy from a cross section perpendicular to the sliding surface, an area of 500 μm 2 The above high tin concentration regions are dispersed, and the number of high tin concentration regions is 5 to 93 per 1 mm 2 2.

Description

Technical Field

[0001] This invention generally relates to copper sliding components, and more particularly to sliding components comprising bearing alloys containing Cu-Sn alloys. Background Technology

[0002] Cu-Sn alloys are widely used as bearing alloys due to their high strength and excellent wear resistance. In recent years, the increased load on bearings caused by higher engine output and smaller engine sizes, leading to reduced bearing area, has necessitated further improvements in the wear resistance of sliding materials. Countermeasures to improve existing wear resistance include those described in Patent Documents 1 and 2.

[0003] Patent Document 1 discloses a copper alloy in which Ag, Sn, Sb, In, Mn, Fe, Bi, Zn, Ni, and / or Cr are dissolved in a Cu matrix and do not substantially form secondary phases of these elements. These added elements dissolved in the Cu matrix migrate to the liner surface in parallel with the generation of frictional heat or changes in the liner surface microstructure, forming a concentrated layer of some of the added elements. This layer further reacts with sulfur-based additives in the lubricating oil to form sulfur compounds, and oxygen in the lubricating oil reacts with the added elements to form oxygen compounds. These concentrated layers and sulfur compounds provide excellent solid lubrication, exhibiting excellent sliding characteristics even under high surface pressure, thus reducing wear.

[0004] The bearing alloy of the sliding bearing in Patent Document 2 is characterized in that the concentration of dispersed fine components (e.g., Sn) continuously decreases from the top range of the bearing alloy towards the segmented surface. A large tin ratio over a wide range ensures greater load-bearing capacity in the sliding elements.

[0005] However, in Patent Document 1, due to severe wear before the formation of the concentrated layer of solid solution strengthening elements, the wear resistance is insufficient in applications with high wear. Patent Document 2 only considers the top area that mainly bears the load, and thus the top area that mainly bears the load only has the same wear resistance as other prior art. Moreover, the portion with low Sn concentration cannot be used as the main load-bearing part, and therefore is not suitable for use in applications where the load direction changes or where the bearing is in a flat plate shape.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 9-249924

[0009] Patent Document 2: Japanese Patent Application Publication No. 2000-27866 Summary of the Invention

[0010] The technical problem that the invention aims to solve

[0011] The purpose of this invention is to provide a sliding member having a novel microstructure that improves wear resistance, including a bearing alloy containing a Cu-Sn alloy.

[0012] Technical solutions adopted to solve technical problems

[0013] According to one aspect of the invention, a sliding member having a sliding surface is provided, comprising a bearing alloy containing a Cu-Sn alloy, wherein the Sn content of the Cu-Sn alloy is 1.5 to 10.0% by mass, the remainder being Cu and impurities, and having a tin concentration of more than 1.1 times the average Sn concentration (hereinafter also referred to as Sn composition) of the Cu-Sn alloy when viewed from a cross section perpendicular to the sliding surface, and having an area of ​​500 μm. 2 The high tin concentration regions mentioned above are scattered, with the number of high tin concentration regions per 1 mm. 2 5 to 93.

[0014] The Sn content in the Cu-Sn alloy is preferably 8.0% by mass or less. Furthermore, the Sn content in the Cu-Sn alloy is preferably 2% by mass or less.

[0015] In addition, Cu-Sn alloys may contain 0 to 5.0% by mass of Ni and 0 to 1.0% by mass of P, or both.

[0016] According to a specific embodiment of the present invention, when viewed from a cross section perpendicular to the sliding surface, the area occupied by the high tin concentration region is 5 to 47%.

[0017] According to one specific embodiment of the invention, the bearing alloy may also contain any one or both of solid lubricant particles and hard particles. The solid lubricant particles preferably contain graphite particles or graphite. The hard particles preferably comprise SiC particles or are SiC particles.

[0018] According to another aspect of the present invention, a sliding member is provided, which includes a liner layer and a bearing alloy layer on the liner layer, the bearing alloy layer comprising the aforementioned bearing alloy.

[0019] According to a specific embodiment of the present invention, the sliding member is a sliding bearing.

[0020] According to another aspect of the present invention, a bearing device comprising the above-described sliding member is provided.

[0021] The present invention and its numerous advantages are described in detail below with reference to the accompanying schematic diagrams. The drawings illustrate several non-limiting embodiments for illustrative purposes. Attached Figure Description

[0022] Figure 1This is a diagram illustrating a structural example of a sliding member according to a specific embodiment of the present invention.

[0023] Figure 2 This is a cross-sectional view of a sliding member of a specific embodiment of the present invention, perpendicular to the sliding surface of the Cu-Sn alloy. Detailed Implementation

[0024] The sliding member of the present invention relates to a sliding member having a Cu-Sn alloy as the bearing alloy. This sliding member is used, for example, in journal bearings or thrust bearings in the bearing portion of an internal combustion engine or automatic transmission for passenger vehicles. For example, in journal bearings, the sliding member can be a cylindrical sliding bearing, or a cylindrical sliding bearing formed by combining two semi-cylindrical members. In thrust bearings, a ring-shaped sliding bearing, or a ring-shaped sliding bearing formed by combining two semi-ring-shaped members, can be used. However, the sliding member can also be of other shapes and can be used as a sliding member other than a sliding bearing. For example, in an oil-lubricated environment, it can also be used as a flat plate sliding plate in the reciprocating sliding portion of industrial machinery.

[0025] The present invention also applies to bearing devices that include such sliding members.

[0026] A structural example of the sliding member 1 of the present invention will be described. (Refer to...) Figure 1 A bearing alloy layer 2 is provided on the backing layer 4. However, the backing layer 4 is an arbitrary element, and it is also possible to have only the bearing alloy layer 2 without the backing layer 4. The surface of the bearing alloy layer 2 is called the sliding surface 3. Although a cover layer may optionally be provided on the bearing alloy layer 2, in this case, the surface of the bearing alloy layer 2 is referred to as the sliding surface 3 in this specification.

[0027] The backing layer 4 can be provided to improve the strength of the sliding member 1. The backing layer is not particularly limited and can be made of metal plates such as steel, Fe alloy, Cu, Cu alloy, etc. As an ferrous material, it is preferred to use plates of specified dimensions of hypoeutectic steel or Fe alloys such as austenitic stainless steel or ferritic stainless steel.

[0028] Optionally, a cover layer may be provided on the bearing alloy layer 2. The cover layer may be a known cover layer, such as a metal such as Bi, Sn, Pb, Ag, or an alloy based on these metals, or a cover layer based on synthetic resin, used to improve the adaptability of the sliding layer surface. The method of forming the cover layer may also be a known method.

[0029] Alternatively, an intermediate layer may be provided between the backing layer 4 and the bearing alloy layer 2. The bonding strength between the sliding layer and the backing layer can also be improved by providing a porous metal layer or an intermediate layer on the surface of the backing layer, i.e., on the side serving as the interface with the bearing alloy layer.

[0030] The bearing alloy layer comprises a bearing alloy composed of Cu-Sn alloy. Figure 2 This is a cross-sectional view showing a specific embodiment of the sliding member 1 of the present invention. The cross-sectional view is a cut-off view with a plane perpendicular to the sliding surface. Figure 2 In the Cu-Sn alloy matrix 8, a high-tin concentration region 6 with a relatively high Sn concentration is dispersed. This high-tin concentration region 6 is a region with a Sn concentration more than 1.1 times the average Sn concentration of the Cu-Sn alloy, and its area is 500 μm. 2 That's all. Even in regions with a Sn concentration of 1.1 times or higher, if their area is less than 500 μm... 2 Therefore, it is not included in the high tin concentration region 6. In the Cu-Sn alloy of the present invention, the number of high tin concentration regions 6 is per 1 mm. 2 5 to 93.

[0031] Furthermore, due to the presence of high tin concentration regions such as region 6, the Sn concentration in the Cu-Sn alloy varies. Therefore, the "average Sn concentration of the Cu-Sn alloy" represents the average Sn concentration in the Cu-Sn alloy. In this invention, this value is considered equal to the Sn composition of the Cu-Sn alloy.

[0032] The high-tin-concentration region 6, with a higher Sn concentration, is harder and exhibits higher wear resistance. When Sn is uniformly dissolved in a Cu-Sn alloy, the entire Cu-Sn alloy bears the load. However, even in Cu-Sn alloys with the same composition, the presence of the harder high-tin-concentration region 6 within the relatively soft matrix 8 allows the high-tin-concentration region 6 to primarily support the surface, making the entire surface less prone to wear. As a result, even with the same average Sn concentration, wear resistance is improved compared to the case of uniform Sn dissolution. Moreover, regardless of depth, the cross-section perpendicular to the sliding surface exhibits the aforementioned microstructure; that is, by also having the high-tin-concentration region 6 in the depth direction, high wear resistance can be maintained even with increased wear.

[0033] In the sliding component of the present invention, the Cu-Sn alloy preferably has Sn dissolved in Cu and substantially does not form a secondary phase (intermetallic compound). The secondary phase (intermetallic compound) of Cu-Sn has high hardness but also high brittleness, making it prone to breakage and detachment. Fragments of the detached secondary phase enter the space between the sliding surface and the opposing surface, damaging the sliding surface and accelerating wear. Therefore, it may hinder the improvement of wear resistance. Furthermore, the substantial absence of a secondary phase in the Cu-Sn alloy means that if it does not have a 3μm... 2 The secondary phase with the area of ​​the above dimensions "practically does not exist." Using an electron microscope at magnification of 100x or higher, the presence of this 3μm-sized secondary phase was confirmed. 2 The above-mentioned area of ​​the second phase.

[0034] In Cu-Sn alloys, Sn comprises 1.5 to 10.0% by mass, with the remainder being Cu and impurities. When the Sn content is below 1.5% by mass, the hardness does not increase to a level sufficient for wear resistance. To achieve wear-resistant hardness, the minimum Sn content is more preferably 2.0% by mass. Furthermore, the minimum Sn content is more preferably 3.0% by mass. When the Sn content exceeds 10.0% by mass, the likelihood of forming a Cu-Sn secondary phase is high. To reliably reduce the likelihood of secondary phase formation, the maximum Sn content is more preferably 8.0% by mass. Furthermore, the maximum Sn content is more preferably 6.5% by mass.

[0035] In addition, Cu-Sn alloys may also contain 0–5.0% by mass of Ni and 0–1.0% by mass of P, or both. The presence of these elements within these ranges readily improves corrosion resistance and sinterability. Adding 0–5.0% by mass of Ni increases strength and improves wear resistance. However, adding more than 5.0% by mass of Ni increases the sintering temperature, leading to increased costs. Adding 0–1.0% by mass of P improves sinterability, thus increasing strength and improving wear resistance. However, adding more than 1.0% by mass of P results in over-sintering, which is difficult to control.

[0036] Viewed from a cross-section perpendicular to the sliding surface 3, the area fraction of the high tin concentration region 6 of the Cu-Sn alloy is preferably 5% to 47%. If the area fraction of the high tin concentration region 6 is 5% or more, the above-mentioned effect can be effectively achieved. If it is 47% or less, the stability of the sintering process can be reliably ensured without compromising the strength of the bearing alloy layer, and a bearing alloy layer with the desired wear resistance can be easily obtained.

[0037] The area of ​​high tin concentration region 6 is 500 μm. 2 That's all. Even in regions with a Sn content more than 1.1 times that of the Cu-Sn alloy, the area is less than 500 μm. 2 At the same time, it is not included in the high tin concentration region 6. If the area is so small, the effect of supporting the load is weak and it does not contribute to the improvement of wear resistance.

[0038] In the Cu-Sn alloy of the present invention, the number of high tin concentration regions 6 is 1 mm. 2 5–93. The number of high tin concentration regions 6 per 1 mm 2 When the number of elements is less than 5, the above effect cannot be achieved; when the number of elements exceeds 93, the tin concentration tends to become uniform, with an area of ​​500 μm. 2With a tin concentration of 1.1 times or more, there is a high probability that high tin concentration regions on the main support side cannot be obtained. Furthermore, in order to manufacture a bearing alloy layer containing more than 93 high tin concentration regions, it is necessary to further reduce the particle size of the copper-tin alloy powder during manufacturing. However, if the particle size of the copper-tin alloy powder is too small, Sn will easily diffuse during the sintering process. Therefore, the degree of Sn diffusion cannot be stably controlled during the sintering process, and high tin concentration regions cannot be stably produced.

[0039] As a preferred specific example, the area fraction of the region with a Sn concentration 1.2 times that of the Sn content in the Cu-Sn alloy (hereinafter referred to as the "threshold 1.2 times region", etc.) is 5 to 42%. More preferably, the area fraction of the region with a threshold of 1.3 times is 5 to 35%. More preferably, the area fraction of the region with a threshold of 1.4 times is 5 to 26%. In such a structure, the above-mentioned effects are more easily obtained.

[0040] As a preferred specific example, the number of regions with a threshold of 1.2 times is 5 to 84 per mm. 2 As a further preferred example, the number of regions with a threshold of 1.3 times is 5 to 61 per mm. 2 As a further preferred example, the number of regions with a threshold of 1.4 times is 5 to 54 per mm. 2 In such a structure, it is easier to achieve the aforementioned effects.

[0041] Optionally, the bearing alloy layer 2 may further contain 0.1 to 12.0% by mass of one or more solid lubricant particles selected from, for example, MoS2, WS2, graphite, and h-BN. The solid lubricant preferably contains graphite. More preferably, the solid lubricant is graphite. The 0.1 to 12.0% by mass of solid lubricant dispersed in the Cu-Sn alloy matrix improves lubricity and further enhances wear resistance. However, if the solid lubricant exceeds 12.0% by mass, it may sometimes hinder sintering.

[0042] Optionally, the bearing alloy layer 2 may further contain 0.1 to 5% by mass of one or more hard particles selected from, for example, Al2O3, SiO2, AlN, Mo2C, WC, Fe2P, and Fe3P. The hard particles preferably contain SiC. More preferably, the hard particles are SiC. The dispersion of 0.1 to 5.0% by mass of hard particles in the matrix further improves wear resistance. However, if the hard particles exceed 5.0% by mass, it may sometimes hinder sintering.

[0043] Next, a method for manufacturing the bearing alloy layer (Cu-Sn alloy) of the sliding member of the present invention will be described. This manufacturing method includes the following steps.

[0044] 1. Prepare copper-tin alloy powder and pure copper powder containing a specified amount of Sn. When either or both of Ni and P are optionally present, use copper powder containing that element instead of copper-tin alloy powder (in this case, also referred to as "copper-tin alloy powder" below).

[0045] 2. Weigh copper-tin alloy powder and pure copper powder to ensure that the Sn content reaches the specified value (Sn is 1.5 to 10.0% by mass) (or below the specified limit if Ni or P is present).

[0046] 3. Mix the weighed copper-tin alloy powder and pure copper powder. If optionally, these particles are further contained in the mixture, add them as well.

[0047] 4. Distribute the mixed powder onto the substrate. The substrate is, for example, a backing when a bearing alloy layer is formed on a backing.

[0048] 5. Sinter the dispersed powder at 800℃~900℃ for 10~31 minutes.

[0049] 6. Roll the sintered body to achieve the specified thickness.

[0050] 7. Sinter the sintered body of the specified thickness at 800℃~900℃ for 10~31 minutes.

[0051] Under the aforementioned sintering conditions, the Sn in the copper-tin alloy powder diffuses into the pure copper powder, but not uniformly, during sintering, forming a region with a relatively high Sn concentration centered on the copper-tin alloy powder. By adjusting the particle size of the copper-tin alloy powder, the Sn concentration, and the sintering conditions within the aforementioned range, the area ratio and the number of high-tin-concentration regions per unit area can be adjusted.

[0052] The Sn content of the copper-tin alloy powder used as a raw material is preferably 3 to 15% by mass, and the average particle size is preferably 10 to 75 μm. For example, even if pure tin powder is used instead of copper-tin alloy powder, a portion with a high Sn concentration can be produced, but due to the formation of a brittle secondary phase, the wear resistance is sometimes not improved.

[0053] Next, the measurement method for the high tin concentration region will be explained.

[0054] The high tin concentration region 6 was determined by surface analysis of the bearing alloy layer 2 perpendicular to the sliding surface 3 using SEM-EPMA, identifying a high tin concentration region with a tin concentration more than 1.1 times the average Sn concentration of the Cu-Sn alloy. Examples of the measurement conditions are shown in Table 1. The mapping obtained through surface analysis was expressed as concentration using a standard curve (standard conditions), and a median filter was applied for binarization. Then, a 500 μm area was... 2The Sn concentration region described above is identified as a high tin concentration region. The threshold and analysis for this high tin concentration region require a depth of 0.5 mm. 2 The above areas will be covered.

[0055] [Table 1]

[0056] Analytical device FE-EPMA (JXA-8530F from Nippon Electronics Corporation) Analytical methods Surface analysis using WDS Size of the analysis region 800μm × 800μm (= 400pix × 400pix) Analyze pixel size 2μm×2μm Analyze elements Sn Crystals used PETH Accelerating voltage 15kV Irradiation current <![CDATA[1×10 -8 A]]> Irradiation time 30ms / pix Scan direction Unidirectional scanning

[0057] Example

[0058] The samples shown in Tables 4 to 6 were prepared using the manufacturing method described above. Copper-tin alloy powder with a Sn content of 3 to 15% by mass and pure copper powder were mixed in the manner shown in the tables and dispersed on a substrate. However, for samples 24 and 25, Cu-12Sn-15Ni-3P alloy powder was used instead of copper-tin alloy powder. Furthermore, for samples 27 to 29, 31, and 32, a specified amount of graphite powder and SiC powder were also mixed in. A 2.2 mm thick steel plate was used as the substrate.

[0059] The dispersed powder was subjected to a first sintering, rolling, and a second sintering to obtain a bearing alloy layer with a thickness of 0.9 mm. The sintering conditions for each sample are shown in Table 2.

[0060] Furthermore, using the measurement method described above, the number and area ratio of high tin concentration regions (threshold 1.1 times, i.e., regions with Sn concentration more than 1.1 times the average Sn concentration) within the bearing alloy layer are determined.

[0061] Abrasion tests were conducted on each sample under the conditions shown in Table 3, and the abrasion amount of the samples after the tests was measured. The results are shown in Tables 4 to 6.

[0062] [Table 2]

[0063]

[0064] [Table 3]

[0065] testing machine Ring disk friction and wear testing machine surface pressure 10MPa Sliding speed 2.0 m / min temperature 200℃ lubricating lubricating oil Opposite axis S55C Test time 5 hours

[0066] Based on the results shown in Table 4, it was found that the Cu-Sn alloy contained 1.5–10.0% Sn by mass, and the number of high tin concentration regions per 1 mm with a threshold of 1.1 was [not specified]. 2 Compared to the comparative examples 41-47, which do not have a high tin concentration region, the wear amount based on the wear test is reduced if the Sn concentration is the same for the 5 to 93 samples 1 to 23 of the embodiments of the present invention.

[0067] [Table 4]

[0068]

[0069] As embodiments of the present invention, samples 24 and 25 are Cu-Sn alloys containing 5.0% by mass Ni and 1.0% by mass P in addition to 4.0% by mass Sn. Table 5 shows the wear amount of these samples in the wear test. Table 5 also shows the test results of samples 13 and 20, which have the same Sn concentration and number and area ratio of high-concentration regions as samples 24 and 25, but do not contain Ni and P. As can be seen from the results shown in Table 5, if the Sn concentration and the number and area ratio of high-concentration regions are the same, the wear amount is reduced due to the addition of Ni and P.

[0070] [Table 5]

[0071]

[0072] Table 6 shows a comparison between samples 26-29, 31, and 32 (in addition to a Cu-Sn alloy with a bearing alloy of 3.0% by mass Sn) and samples 26 and 30 (without graphite and SiC), which are embodiments of the present invention. The results in Table 6 show that the wear amount in the wear test is reduced by including graphite and SiC.

[0073] [Table 6]

[0074]

[0075] Table 7 shows a comparison of the wear amount of the sample of the present invention and a comparative example (without high-concentration regions) with the same average Sn concentration as the Cu-Sn alloy. As can be seen from Table 7, the number of high-concentration regions is 40 / mm. 2 The ratio is 5 / mm 2 The example shows superior performance in terms of improved wear resistance. Regardless of the number of high-concentration regions, the improvement in wear resistance is more significant within the range of an average Sn concentration of 2.0% to 8.0% by mass.

[0076] [Table 7]

[0077]

[0078] Symbol Explanation

[0079] 1. Sliding component

[0080] 2 Bearing alloy layer

[0081] 3 Sliding surface

[0082] 4. Backing layer

[0083] 6. High tin concentration areas

[0084] 8. Matrix

Claims

1. A sliding member having a sliding surface, comprising a bearing alloy containing a Cu-Sn alloy, characterized in that, The Cu-Sn alloy contains 1.5 to 10.0% Sn by mass, with the remainder being Cu and impurities. Viewed from a cross-section perpendicular to the sliding surface, it has a Sn concentration at least 1.1 times the average Sn concentration of the Cu-Sn alloy and an area of ​​500 μm. 2 The high tin concentration regions mentioned above are dispersed, and the number of high tin concentration regions is per 1 mm. 2 5 to 93.

2. The sliding member as described in claim 1, characterized in that, Viewed from a cross-section perpendicular to the sliding surface, the area fraction of the high tin concentration region is 5-47%.

3. The sliding member as described in claim 1 or 2, wherein, The Sn content of the Cu-Sn alloy is less than 8.0% by mass.

4. The sliding member as described in claim 1 or 2, wherein, The Sn content of the Cu-Sn alloy is 2% by mass or more.

5. The sliding member as described in claim 1 or 2, wherein, The Cu-Sn alloy also contains 0 to 5.0% by mass of Ni and 0 to 1.0% by mass of P, or both.

6. The sliding member as claimed in claim 1 or claim 2, wherein, The bearing alloy also contains either or both of solid lubricant particles and hard particles.

7. The sliding member as described in claim 6, characterized in that, The solid lubricant particles are graphite particles.

8. The sliding member as described in claim 6, characterized in that, The hard particles are SiC particles.

9. The sliding member as described in claim 1 or 2, characterized in that, It has a backing layer and a bearing alloy layer on the backing layer, the bearing alloy layer comprising the bearing alloy.

10. The sliding member as claimed in claim 9, characterized in that, The sliding component is a sliding bearing.

11. A bearing device, characterized in that, Includes the sliding member as described in claim 10.

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