Copper-plated steel sheet

Abstract

A copper-plated steel sheet (10) is provided with a base steel sheet (20) and a dendritic copper-plated film (30) formed on at least one surface of the base steel sheet (20). The copper-plated steel sheet (10) is immersed in 0.5 mass% dilute sulfuric acid at 25 DEG C for 5 seconds, then washed with water and dried, and then the brightness (L) of the copper-plated film (30) measured within 1 hour is 50-71.

Description

Technical Field

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

[0002] Copper-plated steel sheets with a copper plating layer on the base steel plate are widely used in various products such as double-wound tubes (automotive brake pipes, fuel supply pipes, etc.), welded pipes (grounding rods, etc.), and oil coolers due to their excellent brazing and soldering properties. In addition, copper-plated steel sheets are also used as the base material for sliding components such as cylindrical rolled bushings (sliding bearings) used in transmissions.

[0003] For example, Patent Document 1 discloses a sliding member (copper-plated steel plate) comprising: a sliding substrate such as a steel plate, a pure copper plating layer formed on the surface of the sliding substrate, and a composite copper plating layer. The composite copper plating layer is formed on the pure copper plating layer and includes multiple blocky portions containing copper and graphite, and has a Vickers hardness of 120 or less. However, this sliding member incurs costs in forming the composite copper plating layer, and under heavy loads, its ability to maintain sliding properties (the duration of friction coefficient maintenance) is sometimes insufficient.

[0004] Furthermore, as a coating with excellent sliding properties, sliding resin coatings formed from lubricating resins are known. For example, Patent Document 2 discloses a sliding resin coating (coating) formed by applying a sliding-improving coating to the surface of a substrate such as a metal plate and baking it. The sliding-improving coating contains 95-50% by weight of a matrix resin with a film-forming temperature 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 as main components. However, such sliding resin coatings have poor adhesion to substrates such as metal plates and are easily peeled off from the substrate in sliding environments, thus sometimes resulting in insufficient maintenance of sliding properties.

[0005] On the other hand, steel sheets with improved durability, functionality, and design through coating are widely used in various applications, primarily building materials and home appliances. When coating base steel sheets, phosphate coating is typically used as a substrate treatment to improve coating adhesion and corrosion resistance. However, the heat resistance of the phosphate coating formed by this treatment is sometimes insufficient, making it unsuitable as a coating substrate depending on the application; sometimes the coating peels off from the base steel sheet under high temperatures. Copper plating offers excellent heat resistance, making it a viable alternative to phosphate coating as a substrate; however, typical copper plating exhibits poor adhesion to paint.

[0006] On the other hand, as a technique to reduce the unevenness of the copper plating film surface, Patent Document 3 describes a method in which, while forming a copper plating film on an insulating substrate on which a metal film for power supply is formed in stages, the stirring speed V of the plating solution is increased accordingly as the current density Dk increases. Additionally, Non-Patent Document 1 also discloses a technique for forming a dendritic copper plating film on a Zn-Al substrate.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: Japanese Patent Application Publication No. 2018-197387

[0010] Patent Document 2: Japanese Patent No. 4339960

[0011] Patent Document 3: Japanese Patent Application Publication No. 2013-95968

[0012] Non-patent literature

[0013] Non-patent literature 1: H Tanabe et al., “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 Summary of the Invention

[0014] The problem the invention aims to solve

[0015] The purpose of this invention is to provide a copper-plated steel sheet in which the coating is not easily peeled off when the coating is applied to a copper-plated film.

[0016] Solution for solving the problem

[0017] The inventors conducted in-depth research on copper-plated steel sheets and found that the brightness L measured after treatment under specific conditions... The dendritic copper plating film within the specified range exhibits excellent adhesion to the copper plating film when the coating is applied to it, thus completing the present invention.

[0018] That is, the present invention provides a copper-plated steel sheet comprising a base steel sheet and a dendritic copper plating film formed on at least one side of the base steel sheet.

[0019] The aforementioned copper-plated steel sheet was immersed in 0.5% by mass dilute sulfuric acid at 25°C for 5 seconds, then rinsed with water and dried. The brightness L of the aforementioned copper-plated coating was then measured within 1 hour. The range is 50 to 71.

[0020] The effects of the invention

[0021] According to the present invention, it is possible to provide a copper-plated steel sheet in which the coating is not easily peeled off when the coating is applied to a copper-plated film. Attached Figure Description

[0022] Figure 1 This is a schematic cross-sectional view of a copper-plated steel sheet according to an embodiment of the present invention.

[0023] Figure 2 This is a schematic cross-sectional view of a copper-plated steel sheet of an embodiment of the present invention further having a coating.

[0024] Figure 3 This is an example of a three-dimensional image of a protrusion in a copper-plated steel plate obtained using X-ray CT.

[0025] Figure 4 This is a schematic diagram illustrating the formation process of copper plating film.

[0026] Figure 5 This is a diagram used to illustrate the evaluation of sales inventory. Detailed Implementation

[0027] The embodiments of the present invention will be described in detail below. It should be understood that the present invention is not limited to the following embodiments. Without departing from the spirit of the present invention, appropriate changes or improvements to the following embodiments based on the common knowledge of those skilled in the art also fall within the scope of the present invention.

[0028] It should be noted that, unless otherwise specified, the "%" in this specification refers to "mass%" when referring to ingredients.

[0029] Figure 1 This is a schematic cross-sectional view of a copper-plated steel sheet according to an embodiment of the present invention.

[0030] like Figure 1 As shown, the copper-plated steel sheet 10 of the embodiment of the present invention includes a base steel sheet 20 and a copper-plated coating 30 formed on one side of the base steel sheet 20. It should be noted that... Figure 1 An example is shown where a copper plating film 30 is formed on one side of the base steel plate 20, but the copper plating film 30 can also be formed on both sides of the base steel plate 20.

[0031] The copper-plated steel sheet 10 of the embodiments of the present invention may further include a coating. Here, a schematic cross-sectional view of the copper-plated steel sheet of the embodiments of the present invention further including a coating is shown. Figure 2 .

[0032] like Figure 2 As shown, the coating 40 is disposed on the copper plating film 30.

[0033] In this specification, "steel plate" refers to steel in sheet form (including strip form).

[0034] There are no particular limitations on the base steel plate 20; various steel plates such as hot-rolled steel plates and cold-rolled steel plates can be used. Among them, cold-rolled steel plates are preferred as the base steel plate 20.

[0035] There are no particular restrictions on the composition of the base steel plate 20; it can be selected appropriately according to the intended use.

[0036] The copper plating film 30 is a film with good adhesion to the substrate steel plate 20 and the coating film 40. Therefore, by providing the copper plating film 30, the coating film 40 can be made less likely to peel off from the copper-plated steel plate 10.

[0037] The copper plating film 30 is dendritic. Here, in this specification, "dendritic copper plating film 30" refers to a cross-section viewed parallel to the thickness direction, such as... Figure 1 As shown, the copper plating film 30 has dendritic protrusions 31. If the copper plating film 30 is dendritic, when the coating film 40 is applied to the copper plating film 30, an anchoring effect is achieved between the copper plating film 30 and the coating film 40, so the coating film 40 is not easy to peel off.

[0038] It should be noted that whether the copper plating film 30 is dendritic can be determined by observation using a microscope (e.g., SEM) in a cross section parallel to the thickness direction of the copper-plated steel plate 10.

[0039] Regarding the copper-plated coating 30, the copper-plated steel plate 10 is immersed in 0.5% by mass dilute sulfuric acid at 25°C for 5 seconds, then rinsed with water and dried. The brightness L of the copper-plated coating 30 is then measured within 1 hour. The value is 50–71, preferably 52–65. This brightness L This relates to the formation state of the dendritic protrusions 31 in the copper-plated coating 30. If the brightness L is within the aforementioned range... This can be seen as the formation of dendritic protrusions 31 in the copper-plated film 30, thus improving the anchoring effect.

[0040] Here, the brightness L For L a b Luminance in the color space (CIE 1976) can be measured according to JIS K5600-4-4:1999. Additionally, after washing, the product is dried using a dryer with hot air at 40°C for 3 minutes.

[0041] It should be noted that when a coating 40 is provided on the copper-plated film 30, the brightness L The measurement was performed under the above conditions after the coating 40 was removed. There are no particular limitations on the method for removing the coating 40; it can be dissolved and removed using a solvent or similar agent capable of removing the coating 40. This also applies when the anti-discoloration treatment layer, as described below, is applied to the copper-plated film 30.

[0042] The copper plating film 30 preferably continuously covers the substrate steel plate 20 with a thickness T of 1.5 μm or more when viewed in a section parallel to the thickness direction. The thickness T of the copper plating film 30 refers to the minimum thickness of the copper plating film 30 covering the substrate steel plate 20.

[0043] In this specification, "the copper plating film 30 continuously covers the substrate steel plate 20" means that there is no part of the substrate steel plate 20 that is exposed without the copper plating film 30 being formed.

[0044] By continuously covering the substrate steel plate 20 with a copper-plated film 30 of thickness T as described above, a dendritic copper-plated film 30 can be easily obtained. Therefore, when the coating 40 is applied to the copper-plated film 30, the effect of suppressing the peeling of the coating 40 can be stably ensured. The thickness T of the copper-plated film 30 is preferably 1.7 μm or more. It should be noted that there is no particular upper limit to the thickness T of the copper-plated film 30, but considering manufacturing costs, it is usually 10.0 μm or less, and preferably 8.0 μm or less.

[0045] The thickness T of the copper-plated coating 30 can be determined by observation using a microscope (e.g., SEM) in a section parallel to the thickness direction of the copper-plated steel plate 10.

[0046] Dendritic protrusions 31 formed on the portion of the substrate steel plate 20 continuously covered with a thickness T of 1.5 μm or more (hereinafter referred to as the "substrate coating portion") provide an anchoring effect between the copper-plated coating 30 and the copper-plated coating 30, thus preventing the coating 40 from peeling off even under heavy sliding conditions. Therefore, from the viewpoint of ensuring this effect, it is preferable that the volume fraction of the protrusions 31 in the region from the substrate coating portion to a height of 10 μm is 0.10% or more. By controlling the volume fraction of the protrusions 31 within such a range, a state is achieved where there are protrusions 31 sufficient to achieve an anchoring effect. From the viewpoint of stably ensuring this effect, the volume fraction of the protrusions 31 is more preferably 0.20% or more, and even more preferably 0.30% or more. It should be noted that a higher volume fraction of the protrusions 31 generally leads to a greater ease of obtaining an anchoring effect, and therefore is not particularly limited, typically 50.0% or less.

[0047] The volume fraction of the protrusions 31 in the region extending from the substrate coating to a height of 10 μm can be determined using X-ray CT. X-ray CT obtains a transmission image by rotating the object being measured (copper-plated steel plate 10) while irradiating it with X-rays, and then reconstructs the obtained image, thereby enabling three-dimensional observation of the internal structure of the copper-plated steel plate 10.

[0048] Here, an example of a three-dimensional image of the protrusion 31 in the copper-plated steel plate 10, measured using X-ray CT, is shown. Figure 3 .

[0049] The substrate steel plate 20 and the copper-plated coating 30 have uniformly flat substrates (continuously covered portions). When the object to be measured (copper-plated steel plate 10) is rotated, the X-ray absorption contrast changes uniformly with the thickness. Therefore, the X-ray absorption contrast of the substrate steel plate 20 and the substrate coating of the copper-plated coating 30 becomes the same and indistinguishable. On the other hand, the area where the protrusion 31 is formed has uneven surfaces. When the object to be measured (copper-plated steel plate 10) is rotated, the X-ray absorption contrast changes according to the shape of the uneven surfaces. Therefore, by setting a threshold for the X-ray absorption contrast of the entire three-dimensional image of the copper-plated steel plate 10 obtained by X-ray CT, it is possible to extract only the three-dimensional image of the protrusion 31. That is, the brightness values ​​of the X-ray CT differ between the protrusion 31 and the substrate steel plate 20 and the substrate coating of the copper-plated coating 30 due to the difference in X-ray absorption contrast. Figure 3 As shown, it is possible to easily extract only the three-dimensional image of the protrusion 31.

[0050] The volume fraction of the protrusions 31 in the region extending from the base coating to a height of 10 μm can be obtained using a three-dimensional image obtained by X-ray CT measurement. Figure 3 And calculated. Figure 3 Since only the region where the protrusion 31 is formed was extracted, the starting point of the height of the region where the volume fraction of the protrusion 31 is measured (the surface of the substrate coating) becomes the lowest point.

[0051] It should be noted that even in the presence of the coating 40, by performing X-ray CT measurements in the same manner as described above, it is possible to extract only the three-dimensional image of the protrusion 31.

[0052] There is no particular limitation on the amount of copper adhering to the copper-plated coating 30, but it is preferably 10 to 150 g / m². 2 More preferably, it is 13–120 g / m 2 More preferably, it is 15–60 g / m 2 By controlling the amount of copper adhesion within such a range, it is possible to stably obtain a copper-plated film 30 with good adhesion to the substrate steel plate 20 and the coating film 40.

[0053] An anti-discoloration treatment layer can also be formed on the copper plating film 30 to inhibit discoloration of the copper plating film 30. The anti-discoloration treatment layer is effective in inhibiting discoloration of the copper plating film 30 over time, especially in inhibiting discoloration within a few days after the copper plating film 30 is formed.

[0054] As an anti-discoloration treatment layer, there are no particular limitations as long as it does not impair the adhesion of the subsequently formed coating film 40. For example, an anti-discoloration treatment layer can be formed by immersing the substrate steel plate 20 in an aqueous solution / dispersion of a commercially available anti-discoloration agent and then drying it. Examples of commercially available anti-discoloration agents include: VERZONESee-You Guard D manufactured by Yamato Kasei Corporation; silane coupling agents containing benzotriazole groups 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 Metal Chemical Technology Research Institute Co., Ltd.; CU-5600 manufactured by Meltex Inc.; and BTZ-M manufactured by Kyodo Pharmaceutical Co., Ltd.

[0055] It should be noted that the anti-discoloration treatment layer can be formed entirely on the copper-plated film 30, or it can be formed locally.

[0056] There are no particular limitations on the coating film 40; it can be made to impart the required properties according to various applications.

[0057] For example, when the copper-plated steel sheet 10 is used in building materials, home appliances, etc., a coating 40 that imparts durability and a specific design can be formed. Such a coating 40 can be formed using commercially available paints.

[0058] Furthermore, when the copper-plated steel sheet 10 is used for a sliding component, a coating 40 that imparts sliding properties can be formed. Examples of such a coating 40 include a sliding resin coating formed from a resin with sliding properties. Here, "sliding resin coating" in this specification refers to a resin coating with a dynamic friction coefficient of 0.2 or less when a flat portion of a plated steel sheet with a resin coating is collected as a test material and subjected to a friction and wear test using a surface roughness measuring instrument (HEIDON-TYPE14) manufactured by Shin-To Science Co., Ltd., under conditions of a load of 1N, a 10mm φ SUS ball as the test material, a sliding (moving) speed of 150mm / min, and a test material temperature of 20–30°C.

[0059] The sliding resin coating is not particularly limited, and any sliding resin coating known in the art can be used. For example, a resin coating with added lubricant or a self-lubricating resin coating can be used as the sliding resin coating. Among these, a coating in which polytetrafluoroethylene (PTFE) resin is dispersed in a matrix resin is preferred. The matrix resin is not particularly limited, and examples include polyester resin, linear polymer polyester resin, acrylic resin, epoxy resin, polyurethane resin, phenoxy resin, phenolic resin, polyvinylidene fluoride (PVdF) / acrylic resin, and vinyl chloride resin.

[0060] The thickness of the coating 40 is not particularly limited, and is 3 to 40 μm. By controlling the thickness of the coating 40 to within this range, peeling of the coating 40 can be stably suppressed.

[0061] The aforementioned anti-discoloration treatment layer can also be formed between the copper plating film 30 and the coating film 40.

[0062] The manufacturing method of the copper-plated steel sheet 10 according to the embodiments 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 characteristics, and can be carried out according to known methods. Hereinafter, an example of the manufacturing method of the copper-plated steel sheet 10 according to the embodiments of the present invention will be described.

[0063] The manufacturing method of the copper-plated steel plate 10 according to the embodiments of the present invention includes an electroplating process in which a copper-plated coating 30 is formed on at least one surface of the base steel plate 20 by electroplating.

[0064] The preferred electroplating process is to perform copper sulfate plating after copper pyrophosphate plating.

[0065] Copper pyrophosphate plating is performed by immersing the base steel plate 20 in a copper pyrophosphate plating solution.

[0066] There are no particular limitations on the conditions for copper pyrophosphate plating; they can be appropriately set according to known methods. Typical conditions are as follows.

[0067] Composition of copper pyrophosphate plating solution: 50 g / L copper pyrophosphate, 250 g / L potassium pyrophosphate, 10 g / L oxalic acid

[0068] The pH of the copper pyrophosphate plating solution is 9.2.

[0069] Temperature of copper pyrophosphate plating solution: 20~60℃

[0070] Current density: 1~10A / dm 2

[0071] Time: 5-100 seconds

[0072] It should be noted that copper pyrophosphate plating can be done once or multiple times under different conditions.

[0073] Preferably, the base steel plate 20 is immersed in a copper sulfate plating solution, and copper sulfate plating is performed while changing the flow rate of the copper sulfate plating solution. More specifically, more preferably, copper sulfate plating at low flow rates (e.g., flow rates below 0.30 m / s) and copper sulfate plating at high flow rates (e.g., flow rates above 0.50 m / s) are alternately repeated.

[0074] Here, a schematic diagram illustrating the formation process of the copper plating film 30 is shown. Figure 4 .

[0075] When copper sulfate plating is performed at a low flow rate, insufficient copper ion supply to the plating surface is easily caused, and the deposited copper is easily destroyed by bubbles generated by hydrogen during the plating process. 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 and sufficiently supplied to the plating surface. As a result, the plating layer grows along the surface, thereby forming a copper plating film 30 that covers the entire surface with attached particulate copper (state B). Next, if 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 into dendritic crystals (dendritic crystals) (state C). Next, if copper sulfate plating is performed again at a high flow rate, a copper plating film 30 is formed that covers the entire surface, thereby strengthening the dendritic copper and increasing the thickness of the copper plating film 30 (state D). By alternating between copper sulfate plating at low flow rates and copper sulfate plating at high flow rates, a copper plating film 30 with the protrusions 31 described above can be formed.

[0076] The number of repetitions of copper sulfate plating at low flow rates and high flow rates, as well as the energizing time for each repetition, can be adjusted appropriately based on the composition of the copper sulfate plating solution, the current density, and the desired plating adhesion. Typically, the current density is 20–60 A / dm³. 2 The energizing time for each cycle (the energizing time for plating at low flow rate and plating at high flow rate) is 1 to 30 seconds, and the cycle is repeated 5 to 50 times.

[0077] It should be noted that copper sulfate plating can be performed using electroplating equipment that allows the plating solution to flow (such as a flow bath).

[0078] There are no particular limitations on the conditions for copper sulfate plating; they can be appropriately set according to known methods. Typical conditions are as follows.

[0079] Composition of copper sulfate plating solution: 220 g / L copper sulfate, 45 g / L sulfuric acid

[0080] The pH of the copper sulfate plating solution is 1.0.

[0081] Temperature of copper sulfate plating solution: 20~50℃

[0082] The manufacturing method of the copper-plated steel sheet 10 according to the embodiments of the present invention may further include a coating forming step of forming a coating film 40 on the copper-plated film 30.

[0083] The coating formation process is not particularly limited as long as it can form a coating 40, and can be carried out according to known methods. In a typical coating formation process, the coating 40 can be formed by applying a coating material onto the copper-plated film 30 and allowing it to dry.

[0084] There are no particular limitations on the coating method; for example, known methods such as dip coating, rod coating, roller coating, spin coating, and spray coating can be used. The coating can be applied once or multiple times to achieve a film thickness of 40%. Furthermore, the drying temperature can be set appropriately according to the composition of the coating and is not particularly limited.

[0085] When an anti-discoloration treatment layer is provided on the copper plating film 30 or between the copper plating film 30 and the coating film 40, the anti-discoloration treatment process can be performed after the electroplating process or between the electroplating process and the coating film formation process.

[0086] The anti-discoloration treatment process simply involves applying a solution containing anti-discoloration agents such as benzotriazole onto the copper-plated film 30 and allowing it to dry.

[0087] There are no particular limitations on the coating method for the solution containing the anti-discoloration agent, and the known methods described above can be used. Furthermore, the drying temperature can be set appropriately according to the type of solution, and there are no particular limitations.

[0088] Example

[0089] The following examples illustrate the content of the present invention in detail, but the present invention is not limited to these examples.

[0090] (Examples 1-7)

[0091] A 0.5mm thick cold-rolled steel sheet was prepared as the base steel plate. This cold-rolled steel sheet was then subjected to electrolytic degreasing, water washing, and pickling in sequence. Electrolytic degreasing involved immersing the cold-rolled steel sheet as the anode in a 5% Na-based degreasing agent (at 60°C) with a current density set to 2A / dm³. 2 The pickling process is performed with a timer set to 10 seconds. Additionally, the steel sheet is immersed in a 2% hydrochloric acid aqueous solution (at 20°C) for 30 seconds. Next, the cold-rolled steel sheet is immersed in a 60°C copper pyrophosphate plating solution with a current density set to 5 A / dm³. 2 The copper pyrophosphate plating process was performed for 15 seconds. Next, the cold-rolled steel sheet coated with copper pyrophosphate was immersed in a copper sulfate plating solution at 35°C. Under the conditions of current density and copper sulfate plating solution flow rate shown in Table 1, copper sulfate plating was alternately performed at low flow rate and high flow rate, for a total of 21 cycles (11 cycles at high flow rate and 10 cycles at low flow rate). This resulted in a copper-plated steel sheet with a copper coating. It should be noted that the composition and pH of the pyrophosphate and copper sulfate plating solutions used are as described below.

[0092] Composition of copper pyrophosphate plating solution: 50 g / L copper pyrophosphate, 250 g / L potassium pyrophosphate, 10 g / L oxalic acid

[0093] The pH of the copper pyrophosphate plating solution is 9.2.

[0094] Composition of copper sulfate plating solution: 220 g / L copper sulfate, 45 g / L sulfuric acid

[0095] The pH of the copper sulfate plating solution is 1.0.

[0096] In addition, the flow rate in this embodiment refers to the speed of the plating solution flowing between the electrodes (cold-rolled steel sheet - anode) along the direction of the cold-rolled steel sheet.

[0097] Next, the copper-plated steel sheet with the copper coating was immersed in a 2 g / L benzotriazole aqueous solution (60°C) for 3 seconds and dried to form an anti-discoloration treatment layer. Then, a coating (resin composition) containing 25% PTFE particles with an average particle size of 10 μm was applied to the copper-plated steel sheet with the anti-discoloration treatment layer and dried at 200°C to form a 20 μm thick coating (sliding resin coating). In a portion of the copper-plated steel sheets (Example 7), a sliding resin coating was formed without the anti-discoloration treatment layer. Here, the average particle size refers to the particle size at which the cumulative value in the particle size distribution determined by laser diffraction / scattering method reaches 50%.

[0098] (Comparative Examples 1-6)

[0099] Instead of alternating between a total of 21 copper sulfate plating operations at low or high flow rates, only 21 copper sulfate plating operations at low or high flow rates were performed. Then, an anti-discoloration treatment layer and coating were formed in the same manner as in the above embodiment.

[0100] The copper-plated steel sheets obtained in the above embodiments were evaluated as follows.

[0101] <Copper adhesion amount of copper plating film>

[0102] A copper-plated steel sheet with only a copper coating was immersed in a mixed aqueous solution of ammonia (28% ammonia concentration) and hydrogen peroxide to dissolve the copper coating. The mass difference [g] before and after dissolution was measured, and the mass difference was divided by the area [m] of the region with the copper coating. 2 From this, the amount of copper adhering [g / m] can be calculated. 2 ].

[0103] <Copper plating coating thickness T (minimum thickness)>

[0104] A copper-plated steel sheet with only a copper coating was cut in a manner that allows observation of a section parallel to the thickness direction, and resin filling was performed with the cut surface serving as the observation surface. Next, the resin-filled test piece was mirror-finished by wet grinding. The mirror-finished surface was observed using a SEM (Hitachi High Technology Co., Ltd. SU6600 model). In the 2000x SEM image, the minimum thickness [μm] at a length of 1000 μm in a direction orthogonal to the thickness direction was taken as the thickness T of the copper coating.

[0105] It should be noted that the cross-sectional observation in this evaluation also confirmed whether the copper plating film was dendritic.

[0106] <Volume fraction of protrusions>

[0107] A copper-plated steel plate with only a copper coating was machined into a circular plate-shaped sample with a diameter of 10 mm. X-ray CT was performed using an Xradia 520 versa manufactured by Carl Zeiss. The pixel size of the X-ray transmission image was 1 μm / pixel, the magnification was 28x (4x objective lens), and the observation area was 1.0 mm × 1.0 mm × 0.5 mm. In addition, the tube voltage was set to 140 kV.

[0108] Next, the obtained X-ray CT images were reconstructed to obtain a three-dimensional image of the protrusion. Then, using Avizo (ver. 2022.2) manufactured by FEI as image analysis software, the protrusion within a region (1000μm × 1000μm × 10μm) from the basement membrane to a height of 10μm was identified, and its volume fraction was calculated.

[0109] Brightness L of copper plating >

[0110] A copper-plated steel sheet with only a copper coating was immersed in 0.5% by mass dilute sulfuric acid at 25°C for 5 seconds, then washed with water and dried. The brightness L of the copper coating was then measured within 1 hour. After washing, the product is dried using a dryer with hot air at 40°C for 3 minutes. Additionally, the brightness (L) The determination was carried out under the following conditions.

[0111] Measuring apparatus: Spectrophotometer (TC-1800 manufactured by Tokyo Denshoku Co., Ltd.)

[0112] Optical conditions: d / 8° method (two-beam optical system)

[0113] Field of view: 2 degrees

[0114] Measurement method: Reflected light measurement

[0115] Standard light: C

[0116] Color system: CIELAB

[0117] Measurement wavelength: 380–780 nm

[0118] Measurement wavelength interval: 5nm

[0119] Beam splitter: Diffraction grating 1200 / mm

[0120] Lighting: Halogen lamp (12V, 50W, rated life 2000 hours)

[0121] Measurement area: 7.25mmφ

[0122] Detection element: Photomultiplier tube (Hamamatsu Photonics KK R928)

[0123] Reflectivity: 0–150%

[0124] Measurement temperature: 23℃

[0125] Standard board: White

[0126] <Evaluation of Coating Adhesion>

[0127] A copper-plated steel sheet with a coating was punched into a disc shape with a diameter of 6 mm. 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 resin filling was performed with the cut surface as the observation surface. Then, the resin-filled test piece was mirror-finished by wet grinding. For the mirror-finished surface, the peel length of the coating from the punched end face was measured. The evaluation criteria are as follows.

[0128] Peel length less than 20 μm: Excellent coating adhesion

[0129] Peel length of 20–100 μm: good adhesion of the coating (qualified).

[0130] Peel length exceeding 100 μm: Poor coating adhesion (unacceptable)

[0131] <Sales Evaluation>

[0132] A 6mm diameter disc-shaped test piece was obtained by punching a copper-plated steel sheet with a coating (slip-resistant resin coating). The test piece was evaluated using a pin-disc friction and wear testing machine (Rhesca, model FPR-2100). Specifically, as... Figure 5 As shown, a test piece was attached to the front end (14mm in diameter) of a pin on the testing machine. The disc (material: SKD11) was rotated and slid along the disc, and the time required for the copper plating on the test piece to be exposed was measured. The load during sliding was 3 kgf, and the rotation speed was 32 rpm. The evaluation criteria are as follows.

[0133] The time required until the copper plating film is exposed is over 200 hours: excellent maintenance of slip properties.

[0134] If the time required for the copper plating to be exposed is more than 100 hours but less than 200 hours: the lubrication performance is well maintained (qualified).

[0135] If the time required for the copper plating to be exposed is less than 100 hours: the maintenance of slipability is poor (unacceptable).

[0136] The evaluation results described above are shown in Table 1. It should be noted that in Examples 1 to 7, it was confirmed that the volume fraction of the protrusions in the region from the substrate coating to a height of 10 μm was 0.10% or more.

[0137] [Table 1]

[0138]

[0139] Based on cross-sectional observation of the copper-plated steel sheet with only a copper coating, it was confirmed that the copper coatings of Examples 1-7 were dendritic. In contrast, the copper coatings of Comparative Examples 1-3 were smooth films growing along the surface, and the copper coatings of Comparative Examples 4-6 were films in which granular copper was attached to the surface.

[0140] In addition, as shown in Table 1, the brightness L of the copper-plated steel plates in Examples 1 to 7 Within the range of 50 to 71, the results of each characteristic evaluation were also good. In contrast, the brightness L of the copper-plated steel sheets in Comparative Examples 1 to 6 was... The values ​​are not within the range of 50 to 71, therefore the results of the evaluation of each characteristic are unsatisfactory.

[0141] As can be seen from the above results, according to the present invention, it is possible to provide a copper-plated steel sheet in which the coating is not easily peeled off when the coating is applied to a copper-plated film.

[0142] Explanation of reference numerals in the attached figures

[0143] 10 Copper-plated steel sheet

[0144] 20 Base steel plate

[0145] 30 Copper plating coating

[0146] 31. Protrusion

[0147] 40. Coating.

Claims

1. A copper-plated steel sheet comprising a base steel sheet and a dendritic copper-plated film formed on at least one surface of the base steel sheet. The brightness L of the copper-plated film of the copper-plated steel sheet was measured within 1 hour after the copper-plated steel sheet was immersed in 0.5 mass% dilute sulfuric acid at 25°C for 5 seconds, washed with water, and dried. was 50 to 71.

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

3. The copper plated steel sheet according to claim 2, wherein The coating film is a sliding resin film.

4. The copper-plated steel sheet according to claim 1, further comprising an anti-tarnish treatment layer provided on the copper-plated film.

5. The copper-plated steel sheet according to claim 2 or 3, further comprising an anti-tarnish treatment layer provided between the copper-plated film and the coating film.

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