Copper-plated steel sheet

Abstract

A copper-plated steel sheet 10 comprises a base steel sheet 20 and a copper plating film 30 formed on at least one surface of the base steel sheet 20. The copper-plated film 30, when a cross section parallel to a thickness direction is viewed, comprises a base film portion 31 continuously covering the base steel sheet 20 and projection portions 32 dendritically grown from the base film portion 31. The volume proportion of the projection portions 32 in a range extending from the base film portion 31 to the height of 10 μm is 0.10% or higher.

Description

[Technical Field]

[0001] This invention relates to copper-plated steel sheets. [Background technology]

[0002] Copper-plated steel sheets, which have a copper plating layer applied to a base steel sheet, have good brazing and solderability and are therefore widely used in various products such as double-wound pipes (automobile brake pipes, fuel supply pipes, etc.), welded pipes (grounding rods, etc.), and oil coolers. Copper-plated steel sheets are also used as a base material for sliding components such as cylindrical coiled bushings (sliding bearings) used in transmissions and the like. For example, Patent Document 1 proposes a sliding member (copper-plated steel sheet) comprising a sliding base material such as a steel sheet, a pure copper plating layer formed on the surface of the sliding base material, and a composite copper plating layer formed on the pure copper plating layer, which includes a plurality of lumpy portions containing copper and graphite and has a Vickers hardness of 120 or less. However, this sliding member is costly to form due to the composite copper plating layer, and may not have sufficient ability to maintain sliding properties (maintenance time of the coefficient of friction) when the load is large.

[0003] Furthermore, Patent Document 2 proposes a multilayer bearing comprising a metal substrate, a porous layer formed on its surface, and a resin composition impregnated and coated into the porous layer (for example, claim 1). Patent Document 2 describes a configuration in which a copper-plated steel sheet is used as the metal substrate and a sintered copper layer is used as the porous layer (paragraphs 0045, 0046, 0051). It is said that the anti-seizure effect is improved by providing such a substrate and porous layer. Although this bearing has excellent product performance, the manufacturing cost can be somewhat disadvantageous because copper plating and sintering are separate processes.

[0004] Furthermore, sliding resin coatings formed from lubricating resins and the like are known to have excellent sliding properties. For example, Patent Document 3 proposes a sliding resin coating (coated product) obtained by applying a paint for improving sliding properties, mainly composed of 95-50% by weight of a matrix resin whose film formation temperature is lower than the melting point of polytetrafluoroethylene resin, and 5-50% by weight of polytetrafluoroethylene resin with an average particle size of 2-40 μm, to the surface of a substrate such as a metal plate and baking it. However, such sliding resin coatings have low adhesion to substrates such as metal plates and tend to peel off from the substrate in sliding environments, so their ability to maintain sliding properties may not be sufficient.

[0005] On the other hand, as a technique for reducing surface irregularities of copper plating films, Patent Document 4 describes a method of forming a copper plating film on an insulating substrate on which a metal film for power supply is formed on the surface, while gradually increasing the current density Dk, and increasing the stirring speed V of the plating solution in accordance with the increase in current density Dk. Non-Patent Document 1 also describes a technique for forming a dendritic copper plating film on a Zn-Al substrate. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2018-197387 [Patent Document 2] International Publication No. 2010 / 079719 [Patent Document 3] Patent No. 4339960 [Patent Document 4] Japanese Patent Publication No. 2013-95968 [Non-patent literature]

[0007] [Non-Patent Document 1] H Tanabe and 7 others, “Cu Dendrite Crystal Ball Formation on a Zn-Al Substrate by Electroplating Method”, e-Journal of Surface Science and Nanotechnology, Vol. 20, No. 4, pp. 232-236, 2022 [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] The present invention aims to provide a copper-plated steel sheet in which the sliding resin coating is less likely to peel off when the sliding resin coating is applied on top of the copper-plated film. [Means for solving the problem]

[0009] As a result of diligent research on copper-plated steel sheets, the inventors discovered that copper plating films having a specific surface shape exhibit excellent adhesion to sliding resin films when a sliding resin film is applied on top of the copper plating film, and thus completed the present invention.

[0010] In other words, the present invention is Copper-plated steel sheet used in sliding members, It comprises a base steel sheet and a copper plating film formed on at least one surface of the base steel sheet. picture, The copper plating film, when viewed in cross-section parallel to the thickness direction, has a base film portion that continuously covers the base steel plate and projections that grow in a dendritic manner from the base film portion. This is a copper-plated steel sheet in which the volume fraction of the protrusions in the region from the base coating portion up to a height of 10 μm is 0.10% or more. [Effects of the Invention]

[0011] According to the present invention, when a sliding resin coating is applied on a copper-plated film, it is possible to provide a copper-plated steel sheet in which the sliding resin coating is less likely to peel off. [Brief explanation of the drawing]

[0012] [Figure 1] This is a schematic cross-sectional view of a copper-plated steel sheet according to an embodiment of the present invention. [Figure 2] This is a schematic cross-sectional view of a copper-plated steel sheet according to an embodiment of the present invention, which further includes a slidable resin film. [Figure 3] This is an example of a three-dimensional image of a protrusion in a copper-plated steel sheet measured by X-ray CT. [Figure 4] This is a schematic diagram for explaining the formation process of the copper plating film.

Mode for Carrying Out the Invention

[0013] Hereinafter, embodiments of the present invention will be specifically described. The present invention is not limited to the following embodiments, and it should be understood that modifications and improvements can be appropriately made to the following embodiments based on the ordinary knowledge of those skilled in the art without departing from the spirit of the present invention, and such modified and improved embodiments also fall within the scope of the present invention. In addition, in this specification, the “%” display regarding components means “mass%” unless otherwise specified.

[0014] FIG. 1 is a schematic cross-sectional view of a copper-plated steel sheet according to an embodiment of the present invention. As shown in FIG. 1, the copper-plated steel sheet 10 according to an embodiment of the present invention includes a base steel sheet 20 and a copper plating film 30 formed on one surface of the base steel sheet 20. In FIG. 1, an example in which the copper plating film 30 is formed on one surface of the base steel sheet 20 is shown, but the copper plating film 30 may be formed on both surfaces of the base steel sheet 20.

[0015] The copper-plated steel sheet 10 according to an embodiment of the present invention can further include a slidable resin film. Here, FIG. 2 shows a schematic cross-sectional view of a copper-plated steel sheet according to an embodiment of the present invention that further includes a slidable resin film. As shown in FIG. 2, the slidable resin film 40 is provided on the copper plating film 30.

[0016] Herein, in this specification, "steel plate" means a steel material in the form of a plate (including strips). The base steel sheet 20 is not particularly limited, and various types of steel sheets such as hot-rolled steel sheets and cold-rolled steel sheets can be used. Among these, cold-rolled steel sheets are preferably used as the base steel sheet 20. The composition of the base steel sheet 20 is not particularly limited and can be selected appropriately depending on the application.

[0017] The copper plating film 30 is a film that exhibits good adhesion to the base steel sheet 20 and the sliding resin film 40. Therefore, by providing the copper plating film 30, when the sliding resin film 40 is applied on the copper plating film 30, the sliding resin film 40 is less likely to peel off from the copper-plated steel sheet 10. As a result, it becomes possible to maintain sliding properties over a long period of time even in sliding environments with high loads. When viewed in cross-section parallel to the thickness direction, the copper plating film 30 has a base film portion 31 that continuously covers the base steel sheet 20 and projections 32 that grow in a dendritic manner from the base film portion 31. Here, in this specification, "base coating portion 31 that continuously covers the base steel sheet 20" means the portion that uniformly covers the base steel sheet 20 without exposing it. Therefore, the base coating portion 31 is the region in a cross-section parallel to the thickness direction from the surface of the base steel sheet 20 to the point where a portion without copper plating film 30 appears when a line parallel to the surface of the base steel sheet 20 is drawn. For example, in Figure 1, the dotted line portion is the boundary between the base coating portion 31 and the projection portion 32, and the thickness T of the base coating portion 31 is the height from the base steel sheet 20 to the dotted line portion.

[0018] The thickness T of the base film portion 31 is not particularly limited, but is preferably 1.0 μm or more, more preferably 1.3 μm or more, and even more preferably 1.5 μm or more. By continuously covering the base steel plate 20 with a base coating portion 31 of the thickness T described above, when the sliding resin coating 40 is provided on the copper plating film 30, the sliding resin coating 40 becomes less likely to peel off even under heavy sliding loads. The upper limit of the thickness T of the base coating portion 31 is not particularly limited, but considering manufacturing costs, it is generally 10.0 μm or less, preferably 8.0 μm or less. The thickness T of the base coating portion 31 can be measured by observing a cross-section parallel to the thickness direction of the copper-plated steel sheet 10 using a microscope (e.g., SEM).

[0019] The protrusions 32 that grow in a dendritic (tree-like) manner from the base coating portion 31 create an anchoring effect between the copper plating portion 30 and the sliding resin coating 40 when the sliding resin coating 40 is applied on the copper plating portion 30. This effect makes the sliding resin coating 40 less likely to peel off even in sliding environments with heavy loads. To obtain this effect, the volume fraction of the protrusions 32 in the region from the base film portion 31 to a height of 10 μm is set to 0.10% or more. By controlling the volume fraction of the protrusions 32 within this range, a sufficient number of protrusions 32 are present to obtain the anchoring effect. From the viewpoint of stably ensuring this effect, the volume fraction of the protrusions 32 is preferably 0.20% or more, more preferably 0.30% or more. The volume fraction of the protrusions 32 is not particularly limited, as a higher volume fraction makes it easier to obtain the anchoring effect, but it is generally 50.0% or less.

[0020] The volume fraction of the protrusions 32 in the region from the base coating portion 31 to a height of 10 μm can be measured by X-ray CT. X-ray CT allows for three-dimensional observation of the internal structure of the copper-plated steel sheet 10 by irradiating the object to be measured (copper-plated steel sheet 10) with X-rays while rotating it, acquiring a transmission image, and then reconstructing the acquired image. Here, Figure 3 shows an example of a three-dimensional image of a protrusion 32 on a copper-plated steel sheet 10 measured by X-ray CT. The base coating portion 31 (continuously coated portion) of the raw steel sheet 20 and the copper plating film 30 is uniformly flat, and when the object to be measured (copper-plated steel sheet 10) is rotated, the X-ray absorption contrast changes uniformly according to the change in thickness. For this reason, the base coating portion 31 of the raw steel sheet 20 and the copper plating film 30 have the same X-ray absorption contrast and are indistinguishable. On the other hand, the region where the protrusions 32 are formed has irregularities on its surface, and when the object to be measured (copper-plated steel sheet 10) is rotated, the X-ray absorption contrast changes in the region with irregularities on its surface according to its shape. For this reason, by setting a threshold for the X-ray absorption contrast of the three-dimensional image of the entire copper-plated steel sheet 10 obtained by X-ray CT, it is possible to extract only the three-dimensional image of the protrusions 32. In other words, because the brightness values ​​of the X-ray CT differ between the protrusion 32 and the base coating portion 31 of the raw steel sheet 20 and the copper plating film 30 due to the difference in X-ray absorption contrast, it is possible to easily extract only the three-dimensional image of the protrusion 32, as shown in Figure 3. The volume fraction of the protrusions 32 in the region from the base coating portion 31 to a height of 10 μm can be calculated from the three-dimensional image (Figure 3) obtained by X-ray CT measurement. In Figure 3, only the region in which the protrusions 32 are formed is extracted, so the starting point of the height of the region in which the volume fraction of the protrusions 32 is measured (the surface of the base coating portion 31) is at the bottom. Furthermore, even when the sliding resin coating 40 is present, the same X-ray CT measurement can be performed to extract only the three-dimensional image of the protrusion 32.

[0021] The amount of copper deposited on the copper plating film 30 is not particularly limited, but is preferably 10 to 150 g / m². 2 Comfortably 13-120 g / m 2 More preferably 15-60 g / m² 2 By controlling the amount of copper deposition within this range, a copper plating film 30 with good adhesion to the base steel sheet 20 and the sliding resin coating 40 can be stably obtained.

[0022] A discoloration-preventing treatment layer may be formed on the copper plating film 30 to suppress discoloration of the copper plating film 30. Providing a discoloration-preventing treatment layer is effective in suppressing discoloration of the copper plating film 30 over time, and is particularly effective in suppressing discoloration for several days after the formation of the copper plating film 30. The anti-discoloration treatment layer is not particularly limited as long as it does not impair the adhesion of the sliding resin film 40 that is formed thereafter. For example, the anti-discoloration treatment layer can be formed by immersing the base steel sheet 20 in an aqueous solution / dispersion of a commercially available anti-discoloration agent and drying it. Examples of commercially available anti-discoloration agents include VERZONE SeeU Guard D manufactured by Yamato Kasei Co., Ltd., a benzotriazole group-containing silane coupling agent manufactured by Shin-Etsu Chemical Co., Ltd., Gospel (C-30, C-70, or C-220) manufactured by Gospel Chemical Co., Ltd., Top Rinse CU-5 manufactured by Okuno Pharmaceutical Co., Ltd., KPC-2003 manufactured by Kinzoku Kako Gijutsu Kenkyusho Co., Ltd., CU-5600 manufactured by Meltex Co., Ltd., and BTZ-M manufactured by Kyodo Yakuhin Co., Ltd. The anti-discoloration treatment layer may be formed entirely on the copper plating film 30, or it may be formed only partially.

[0023] The sliding resin coating 40 is a coating formed from a resin that has sliding properties. Hereinafter, "sliding resin coating 40" as used herein refers to a resin coating in which a dynamic friction coefficient of 0.2 or less is obtained when a flat portion is taken from a plated steel sheet on which the target resin coating is formed and used as a test material, and a friction and wear test is performed using a surface properties measuring instrument (HEIDON-TYPE14) manufactured by Shinto Kagaku Co., Ltd. under the conditions of a load of 1N, a mating material of a 10mmφ SUS ball, a sliding (movement) speed of 150mm / min, and a test material temperature of 20~30℃. The sliding resin coating 40 is not particularly limited and can be any known in the art. For example, a resin coating with added lubricant or a self-lubricating resin coating can be used as the sliding resin coating 40. Among these, the sliding resin coating 40 is preferably a coating in which polytetrafluoroethylene (PTFE) resin is dispersed in a matrix resin. The matrix resin is not particularly limited, but examples include polyester resin, linear polymer polyester resin, acrylic resin, epoxy resin, polyurethane resin, phenoxy resin, phenolic resin, polyvinylidene fluoride resin (PVdF) / acrylic resin, and vinyl chloride resin.

[0024] The thickness of the sliding resin coating 40 is not particularly limited, but is typically 3 to 40 μm. By controlling the thickness of the sliding resin coating 40 within this range, stable sliding properties can be ensured.

[0025] A discoloration prevention treatment layer, as described above, may be formed between the copper plating film 30 and the sliding resin film 40.

[0026] The method for manufacturing the copper-plated steel sheet 10 according to the embodiment of the present invention is not particularly limited as long as it is a method capable of manufacturing the copper-plated steel sheet 10 having the above-described features, and can be carried out in accordance with known methods. An example of a method for manufacturing the copper-plated steel sheet 10 according to the embodiment of the present invention will be described below.

[0027] A method for manufacturing a copper-plated steel sheet 10 according to an embodiment of the present invention includes an electroplating step of forming a copper plating film 30 on at least one surface of a base steel sheet 20 by electroplating. In the electroplating process, it is preferable to perform copper sulfate plating after copper pyrophosphate plating.

[0028] Copper pyrophosphate plating is performed by immersing the base steel sheet 20 in a copper pyrophosphate plating solution. The conditions for copper pyrophosphate plating are not particularly limited and can be set appropriately in accordance with known methods. Typical conditions are as follows: Composition of copper pyrophosphate plating solution: 50 g / L copper pyrophosphate, 250 g / L potassium pyrophosphate, 10 g / L oxalic acid pH of copper pyrophosphate plating solution: 9.2 Temperature of copper pyrophosphate plating solution: 20-60°C Current density: 1~10A / dm 2 Time: 5-100 seconds The copper pyrophosphate plating can be performed once or multiple times under different conditions.

[0029] Copper sulfate plating is preferably performed by immersing the base steel sheet 20 in a copper sulfate plating solution while changing the flow rate of the copper sulfate plating solution. More specifically, it is more preferable to alternately repeat copper sulfate plating at a low flow rate (e.g., a flow rate of 0.30 m / sec or less) and copper sulfate plating at a high flow rate (e.g., a flow rate of 0.50 m / sec or more). Here, Figure 4 shows a schematic diagram illustrating the formation process of the copper plating film 30. When copper sulfate plating is performed at a low flow rate, copper ions tend to be insufficiently supplied to the plated surface, and the deposited copper is easily destroyed by bubbles caused by hydrogen generated during plating. As a result, particulate copper adheres to the surface (State A). On the other hand, when copper sulfate plating is performed at a high flow rate, copper ions are easily supplied to the plated surface. As a result, the plating grows along the surface, and a copper plating film 30 is formed to cover the entire surface to which particulate copper has adhered (State B). Next, when copper sulfate plating is performed again at a low flow rate, particulate copper adheres in the same way as in State A, and the copper grows as dendritic crystals (dendrites) (State C). Next, when copper sulfate plating is performed again at a high flow rate, a copper plating film 30 is formed to cover the entire surface, reinforcing the dendritic copper and increasing the thickness of the copper plating film 30 (State D). In this way, by repeatedly alternating between copper sulfate plating at a low flow rate and copper sulfate plating at a high flow rate, a copper plating film 30 having the protrusions 32 described above can be formed.

[0030] The number of repetitions of copper sulfate plating at low flow rate and copper sulfate plating at high flow rate, as well as the energizing time per cycle, should be appropriately adjusted according to the composition of the copper sulfate plating solution used, the current density, and the amount of plating to be achieved. Typically, the current density is 20-60 A / dm². 2 The energizing time per cycle (the energizing time for both low-flow and high-flow plating) is 1 to 30 seconds, and the number of repetitions is 5 to 50. Copper sulfate plating can be performed using an electroplating apparatus capable of flowing the plating solution (for example, a flow cell).

[0031] Other conditions for copper sulfate plating are not particularly limited and can be set as appropriate in accordance with known methods. Typical conditions are as follows: Composition of copper sulfate plating solution: 220 g / L copper sulfate, 45 g / L sulfuric acid pH of copper sulfate plating solution: 1.0 Temperature of copper sulfate plating solution: 20-50°C

[0032] A method for manufacturing a copper-plated steel sheet 10 according to an embodiment of the present invention may further include a resin film forming step of forming a sliding resin film 40 on a copper plating film 30. The resin film formation process is not particularly limited as long as a sliding resin film 40 can be formed, and can be carried out in accordance with known methods. In a typical resin film formation process, a sliding resin film 40 can be formed by applying a resin composition containing a matrix resin and a polytetrafluoroethylene (PTFE) resin onto the copper plating film 30 and drying it. The method for applying the resin composition is not particularly limited, and known methods such as dipping, bar coating, roll coating, spin coating, and spraying can be used. The resin composition can be applied in one or more steps so that the formed sliding resin film 40 reaches a predetermined thickness. The drying temperature is not particularly limited and can be set appropriately according to the composition of the resin composition.

[0033] When a discoloration prevention treatment layer is provided on the copper plating film 30, or between the copper plating film 30 and the sliding resin film 40, the discoloration prevention treatment process can be performed after the electroplating process, or between the electroplating process and the resin film formation process. The discoloration prevention treatment process involves applying a solution containing a discoloration inhibitor such as benzotriazole onto the copper plating film 30 and allowing it to dry. The method for applying the solution containing the discoloration inhibitor is not particularly limited, and the known methods described above can be used. Furthermore, the drying temperature is not particularly limited and can be set appropriately depending on the type of solution. [Examples]

[0034] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

[0035] (Examples 1-3) A cold-rolled steel sheet with a thickness of 0.5 mm was prepared as the base material. Electrolytic degreasing, water washing, and pickling were performed sequentially on this cold-rolled steel sheet. For electrolytic degreasing, the cold-rolled steel sheet was immersed in a sodium-based degreasing agent with a sodium concentration of 5% (at 60°C) with the anode, and a current density of 2 A / dm² was applied. 2 The process was performed for 10 seconds. For pickling, the sheet was immersed in a 2% hydrochloric acid solution (at 20°C) for 30 seconds. Next, the cold-rolled steel sheet was immersed in a copper pyrophosphate plating solution at 60°C, with a current density of 5 A / dm². 2 Copper pyrophosphate plating was performed for a time of 13 seconds. Next, the cold-rolled steel sheet plated with copper pyrophosphate was immersed in a copper sulfate plating solution at 35°C, and copper sulfate plating at low flow rate and copper sulfate plating at high flow rate were alternately performed under the current density and flow rate conditions of the copper sulfate plating solution shown in Table 1, for a total of 21 times (11 times at high flow rate and 10 times at low flow rate). In this way, a copper-plated steel sheet with a copper plating film was obtained. The composition and pH of the pyrophosphate plating solution and copper sulfate plating solution used are as follows. Composition of copper pyrophosphate plating solution: 50 g / L copper pyrophosphate, 250 g / L potassium pyrophosphate, 10 g / L oxalic acid pH of copper pyrophosphate plating solution: 9.2 Composition of copper sulfate plating solution: 220 g / L of copper sulfate, 45 g / L of sulfuric acid pH of copper sulfate plating solution: 1.0 In addition, the flow rate in this example refers to the velocity of the plating solution flowing in the direction along the cold-rolled steel sheet between the electrodes (cold-rolled steel sheet - anode).

[0036] Next, the copper-plated steel sheet formed with a copper plating film was immersed in an aqueous solution of benzotriazole (60 °C) with a concentration of 2 g / L for 3 seconds and dried to form an anti-discoloration treatment layer. Next, a resin composition containing 25% of PTFE particles with an average particle size of 10 μm in a polyester resin (matrix resin) was applied to the copper-plated steel sheet formed with the anti-discoloration treatment layer and dried at 200 °C to form a sliding resin film with a thickness of 20 μm. In some copper-plated steel sheets (Example 3), a sliding resin film was formed without forming an anti-discoloration treatment layer. Here, the average particle size means the particle size at 50% of the integrated value in the particle size distribution determined by the laser diffraction / scattering method.

[0037] (Comparative Example 1) Instead of performing copper sulfate plating at a low flow rate and copper sulfate plating at a high flow rate alternately for a total of 21 times, only copper sulfate plating at a high flow rate was performed 21 times. Next, an anti-discoloration treatment layer and a sliding resin film were formed in the same manner as in the above example.

[0038] The following evaluations were performed on the copper-plated steel sheets obtained in the above examples.

[0039] <Copper deposition amount of copper plating film> The copper-plated steel sheet formed with only the copper plating film was immersed in a mixed aqueous solution of ammonia aqueous solution (ammonia concentration 28%) and hydrogen peroxide to dissolve the copper plating film, and the mass difference [g] before and after the dissolution of the copper plating film was measured. The mass difference was divided by the area [m 2 to calculate the copper deposition amount [g / m 2 .

[0040] <Thickness T of base film part> A copper-plated steel sheet, with only a copper plating film formed on it, was cut so that a cross-section parallel to the thickness direction could be observed, and resin was applied to the cut surface so that it would be the observation surface. Next, the resin-filled test piece was polished to a mirror finish by wet polishing. The mirror-finished surface was observed using a SEM (Hitachi High-Tech Corporation SU6600). In the 2,000x SEM image, the thickness T [μm] of the base film portion at a length of approximately 1,000 μm in the direction perpendicular to the thickness direction was measured.

[0041] <Volume ratio of protrusions> A copper-plated steel sheet, with only a copper plating film formed on it, was processed into a φ10 mm disc-shaped sample, and X-ray CT was performed using a Carl Zeiss Xradia 520 versa. The pixel size of the X-ray transmission image was set to 1 μm / pixel, the observation magnification to 28x (4x objective lens), and the observation area to 1.0 mm × 1.0 mm × 0.5 mm. The tube voltage was set to 140 kV. Next, the obtained X-ray CT images were reconstructed to obtain a three-dimensional image of the protrusions. Then, using Avizo (ver. 2022.2) from FEI as image analysis software, the protrusions in the region from the base coating up to a height of 10 μm (1000 μm × 1000 μm × 10 μm) were identified, and their volume fraction was calculated.

[0042] <Evaluation of adhesion of sliding resin coatings> A copper-plated steel sheet with a sliding resin coating was punched out into a 6 mm diameter disc shape. The clearance was set to 0.1 mm. Next, the punched copper-plated steel sheet was cut so that a cross-section parallel to the thickness direction could be observed, and the cut surface was filled with resin to serve as the observation surface. Then, the resin-filled test piece was polished to a mirror finish by wet polishing. The length of the peeling of the sliding resin coating from the punched end face was measured on the mirror-polished surface. The evaluation criteria are as follows. Peel length less than 20 μm: Excellent adhesion of the sliding resin coating (◎) Peel length of 20 μm or more and less than 100 μm: Good adhesion of the sliding resin coating (○) Peel length of 100 μm or more: Poor adhesion of the sliding resin coating (×)

[0043] The evaluation results are shown in Table 1.

[0044] [Table 1]

[0045] As shown in Table 1, the copper-plated steel sheets of Examples 1 to 3 exhibited good adhesion of the sliding resin coating because the volume ratio of the protrusions in the region from the base coating up to a height of 10 μm was within an appropriate range. In contrast, in Comparative Example 1, the copper-plated steel sheet did not exhibit sufficient adhesion of the sliding resin coating because the volume ratio of the protrusions in the region from the base coating up to a height of 10 μm was not within an appropriate range.

[0046] As can be seen from the above results, the present invention provides a copper-plated steel sheet in which the sliding resin coating is less likely to peel off when the sliding resin coating is provided on the copper-plated film. For this reason, the copper-plated steel sheet with the sliding resin coating provided on the copper-plated film can maintain its sliding properties over a long period of time. [Explanation of Symbols]

[0047] 10 Copper-plated steel sheet 20 Untreated steel sheet 30 Copper plating film 31 Base coating section 32 Protrusion 40. Sliding resin coating

Claims

1. A copper-plated steel sheet used in a sliding member, The device comprises a base steel sheet and a copper plating film formed on at least one surface of the base steel sheet. The copper plating film, when viewed in cross-section parallel to the thickness direction, has a base film portion that continuously covers the base steel plate and projections that grow in a dendritic manner from the base film portion. A copper-plated steel sheet in which the volume fraction of the protrusions in the region from the base coating portion to a height of 10 μm is 0.10% or more.

2. The copper-plated steel sheet according to claim 1, wherein the thickness of the base coating portion is 1.0 μm or more.

3. The copper-plated steel sheet according to claim 1 or 2, further comprising a sliding resin coating provided on the copper-plated film.

4. The copper-plated steel sheet according to claim 1 or 2, further comprising a discoloration prevention treatment layer provided on the copper plating film.

5. The copper-plated steel sheet according to claim 3, further comprising a discoloration prevention treatment layer provided between the copper plating film and the sliding resin film.

Images