Silver-plated material and its manufacturing method

Abstract

To provide: a silver-plated material which has higher hardness than ever before, while having excellent wear resistance; and a method for producing the same.SOLUTION: This invention relates to a method for producing a silver-plated material by forming a surface layer, which is formed of silver, on a base material by performing electroplating in a silver plating solution that is composed of an aqueous solution which contains silver potassium cyanide or silver cyanide, potassium cyanide or sodium cyanide, and a benzimidazole compound (such as 2-mercaptobenzimidazole, sodium 2-mercaptobenzimidazolesulfonate dihydrate). In the method for producing the silver-plated material, the respective ratios of the concentration of silver potassium cyanide or silver cyanide, the concentration of potassium cyanide or sodium cyanide, and the concentration of the imidazole compound in the silver plating solution to current density during the silver plating (or the respective ratios of the concentration of silver potassium cyanide or silver cyanide and the concentration of the imidazole compound in the silver plating solution to current density during the silver plating and the concentration of potassium cyanide or sodium cyanide) are set to values within predetermined ranges.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a silver-plated product and a method for manufacturing the same, and more particularly to a silver-plated product used as a material for contacts and terminal parts such as connectors, switches, and relays used in electrical wiring for automobiles and consumer use, and a method for manufacturing the same. [Background technology]

[0002] Conventionally, materials used for contacts and terminal parts of connectors and switches are relatively inexpensive materials such as copper, copper alloys, and stainless steel, which have excellent corrosion resistance and mechanical properties, and are plated with tin, silver, gold, etc. depending on the required properties such as electrical properties and solderability.

[0003] Tin-plated materials, which are made by plating copper or copper alloys or stainless steel with tin, are inexpensive but have poor corrosion resistance in high-temperature environments. Gold-plated materials, which are made by plating these materials with gold, have excellent corrosion resistance and high reliability, but are expensive. On the other hand, silver-plated materials, which are made by plating these materials with silver, are cheaper than gold-plated materials and have better corrosion resistance than tin-plated materials.

[0004] Furthermore, materials for contacts and terminal parts of connectors and switches must also be resistant to wear caused by the insertion and removal of connectors and the sliding of switches.

[0005] However, because silver-plated materials are soft and prone to wear, when used as materials for connection terminals and the like, they are prone to adhesion and wear due to insertion, removal, and sliding.Furthermore, when the connection terminal is inserted, the surface is scraped off, increasing the coefficient of friction and resulting in a high insertion force.

[0006] To solve this problem, there is a method for producing a silver-plated material by electroplating a material in a silver plating solution containing 80 to 130 g / L of silver, 60 to 130 g / L of potassium cyanide, 30 to 80 mg / L of selenium, and 50 to 190 g / L of potassium carbonate (see, for example, Patent Document 1). Another method is to produce a silver-plated material by electroplating a material in a silver plating solution containing 80 to 110 g / L of silver, 70 to 160 g / L of potassium cyanide, and 55 to 70 mg / L of selenium, where the product of the concentration of potassium cyanide in the silver plating solution and the current density is y (g·A / L·dm 2 ), and the solution temperature is x (°C), electroplating is performed so that (32.6x-300)≦y≦(32.6x+200) to form a surface layer made of silver on the material, thereby producing a silver-plated product (see, for example, Patent Document 2).

[0007] However, the Vickers hardness HV of the silver-plated products produced by the methods of Patent Documents 1 and 2 is 155 or less, and there is a demand for silver-plated products that are even harder and have better wear resistance.

[0008] On the other hand, in silver-plated materials, the crystal grain size of the silver plating is likely to increase due to recrystallization, and this increase in crystal grain size reduces hardness and wear resistance (see, for example, Patent Document 3).

[0009] In order to improve the wear resistance of such silver-plated products, a method is known in which elements such as antimony are added to the silver plating to increase the hardness of the silver-plated product (see, for example, Patent Document 4). [Prior art documents] [Patent documents]

[0010] [Patent Document 1] JP 2016-204719 A (paragraph number 0010) [Patent Document 2] JP 2016-145413 A (paragraph number 0010) [Patent Document 3] JP 2008-169408 A (paragraph number 0006) [Patent Document 4] JP 2009-79250 A (paragraphs 0003-0004) Summary of the Invention [Problem to be solved by the invention]

[0011] However, when elements such as antimony are added to the silver plating, as in the method of Patent Document 4, the silver is alloyed and the hardness is improved, but the improvement in wear resistance is not sufficient, and there is a demand for silver-plated materials with even better wear resistance.

[0012] In view of the above-mentioned problems of the prior art, it is therefore an object of the present invention to provide a silver-plated product that is harder and more wear-resistant than conventional products, and a method for producing the same. [Means for solving the problem]

[0013] As a result of intensive research by the present inventors to solve the above problems, they have found that in a method for producing a silver-plated product by forming a surface layer of silver on a base material by electroplating in a silver plating solution consisting of an aqueous solution containing potassium silver cyanide or silver cyanide, potassium cyanide or sodium cyanide, and benzimidazoles, by setting the concentration ratio of potassium silver cyanide or silver cyanide, potassium cyanide or sodium cyanide, and benzimidazoles in the silver plating solution relative to the current density during silver plating (or the concentration ratio of potassium silver cyanide or silver cyanide and benzimidazoles in the silver plating solution relative to the current density during silver plating, and the concentration of potassium cyanide or sodium cyanide), it is possible to produce a silver-plated product that is harder and more wear-resistant than conventional products, and have completed the present invention.

[0014] That is, the method for producing a silver-plated product according to the present invention is a method for producing a silver-plated product by electroplating a material in a silver plating solution comprising an aqueous solution containing potassium silver cyanide or silver cyanide, potassium cyanide or sodium cyanide, and benzimidazoles to form a surface layer made of silver, wherein the concentration of potassium silver cyanide or silver cyanide in the silver plating solution is A (g / L), the concentration of potassium cyanide or sodium cyanide is B (g / L), and the concentration of benzimidazoles is C (g / L), and the current density of the electroplating is D (A / dm 2 ), the concentration of potassium cyanide or sodium cyanide is 30 to 80 g / L, and A / D is 30 (g dm 2 / L·A) or more, or (if the silver plating solution contains silver cyanide) 15 (g·dm 2 / L·A) or more, C / D is 1.2 (g·dm 2 / L·A) or more.

[0015] The method for producing a silver-plated product according to the present invention comprises electroplating a material in a silver plating solution containing potassium silver cyanide or silver cyanide, potassium cyanide or sodium cyanide, and a benzimidazole to form a silver surface layer on the material, the method comprising the steps of: (a) defining the concentration of potassium silver cyanide or silver cyanide in the silver plating solution as A (g / L), the concentration of potassium cyanide or sodium cyanide as B (g / L), the concentration of the benzimidazole as C (g / L), and (b) defining the current density of the electroplating as D (A / dm 2 ), then A / D is 30 (g dm 2 / L·A) or more, or (if the silver plating solution contains silver cyanide) 15 (g·dm 2 / L·A) or more, and B / D (if the silver plating solution contains potassium cyanide) is 100 (g·dm 2 / L·A) or less, or (if the silver plating solution contains sodium cyanide) 150 (g·dm 2 / L·A) or less, C / D is 1.2 (g·dm2 In this method for producing a silver-plated product, the concentration of potassium cyanide or sodium cyanide in the silver plating solution is preferably 30 to 80 g / L.

[0016] In the above method for producing a silver-plated product, the benzimidazole is preferably 2-mercaptobenzimidazole or sodium 2-mercaptobenzimidazole sulfonate dihydrate, and the concentration of the benzimidazole in the silver plating solution is preferably 0.5 to 50 g / L. The silver plating solution may also contain 30 g / L or less of potassium carbonate. The electroplating for forming the silver surface layer is preferably carried out at a solution temperature of 10 to 50°C, and at a current density of 0.2 to 2.0 A / dm 2 It is also preferable that the material is made of copper or a copper alloy, and that an underlayer made of nickel is formed between the material and the surface layer.

[0017] The silver-plated product according to the present invention is characterized in that, in the silver-plated product, a surface layer made of silver is formed on a base material, the surface layer made of silver has an average crystallite diameter of 25 nm or less, a Vickers hardness HV of 150 or more, and an antimony content in the surface layer of 0.1 mass % or less.

[0018] In this silver-plated product, the surface layer preferably comprises 90 to 99 mass % silver, and the carbon content in the surface layer is preferably 1 to 10 mass %. The surface layer preferably has a Vickers hardness HV of 160 or more. Furthermore, the base material is preferably made of copper or a copper alloy, and a base layer made of nickel is preferably formed between the base material and the surface layer. [Effects of the Invention]

[0019] According to the present invention, it is possible to provide a silver-plated product that is harder and more wear-resistant than conventional products, and a method for producing the same. DETAILED DESCRIPTION OF THE INVENTION

[0020] In an embodiment of the method for producing a silver-plated product according to the present invention, a silver-plated product is produced by electroplating a material in a silver plating solution comprising an aqueous solution containing potassium silver cyanide or silver cyanide, potassium cyanide or sodium cyanide, and a benzimidazole (such as 2-mercaptobenzimidazole or sodium 2-mercaptobenzimidazole sulfonate dihydrate) to form a silver surface layer on the material. In this method, the concentration of potassium silver cyanide or silver cyanide in the silver plating solution is A (g / L), the concentration of potassium cyanide or sodium cyanide is B (g / L), and the concentration of the benzimidazole (such as 2-mercaptobenzimidazole or sodium 2-mercaptobenzimidazole sulfonate dihydrate) is C (g / L), and the current density of the electroplating is D (A / dm 2 ), the concentration of potassium cyanide or sodium cyanide is 30 to 80 g / L (preferably 35 to 75 g / L, more preferably 35 to 60 g / L), and A / D is 30 (g dm 2 / L·A) or more (preferably 35 (g·dm 2 / L·A) or more) or (if the silver plating solution contains silver cyanide) 15 (g·dm 2 / L·A) or more (preferably 17 (g·dm 2 / L·A) or more), C / D is 1.2 (g·dm 2 / L·A) or more (preferably 1.3 (g·dm 2 Electroplating should be performed so that A / D is 30 (g dm3 / L A) or more (if the silver plating solution contains potassium silver cyanide). 2 / L·A) or more (preferably 35 (g·dm 2 / L·A) or more) or (if the silver plating solution contains silver cyanide) 15 (g·dm 2 / L·A) or more (preferably 17 (g·dm 2 / L·A) or more), and B / D (if the silver plating solution contains potassium cyanide) is 100 (g·dm 2 / L·A) or less (preferably 90 (g·dm 2 / L·A) or less) or (if the silver plating solution contains sodium cyanide) 150 (g·dm2 / L·A) or less (preferably 120 (g·dm 2 / L·A) or less), C / D is 1.2 (g·dm 2 / L·A) or more (preferably 1.3 (g·dm 2 Electroplating is performed so that the silver plating solution has a concentration B of 30 to 80 g / L. In the latter case, the potassium cyanide or sodium cyanide concentration B in the silver plating solution is preferably 30 to 80 g / L. When electroplating (silver plating) is performed using a cyanide-based silver plating solution containing benzimidazoles (e.g., 2-mercaptobenzimidazole or sodium 2-mercaptobenzimidazole sulfonate dihydrate) as organic additives, the organic additives (at least a portion of them) are incorporated into the silver surface layer, suppressing grain growth (refining the grains) of the silver in the surface layer, thereby increasing the surface layer's hardness and improving wear resistance. The lubricating effect of the organic additives is also believed to reduce the surface layer's friction coefficient. Furthermore, when the silver-plated material is used as a material for connection terminals, for example, the incorporation of organic additives into the silver surface layer can suppress adhesion due to insertion / removal or sliding, improving wear resistance. In particular, electroplating under the above conditions can produce silver-plated products with higher hardness and superior wear resistance than conventional products.

[0021] In the above-mentioned method for producing a silver-plated product, the concentration of imidazoles in the silver plating solution is preferably 0.5 to 50 g / L (preferably 0.5 to 5 g / L in the case of 2-mercaptobenzimidazole, and preferably 10 to 50 g / L (more preferably 15 to 40 g / L) in the case of sodium 2-mercaptobenzimidazole sulfonate dihydrate). The silver plating solution may also contain 30 g / L or less (preferably 20 g / L or less, more preferably 15 g / L or less) of potassium carbonate. The electroplating for forming the silver surface layer is preferably carried out at a solution temperature of 10 to 50°C, more preferably 15 to 40°C. The electroplating is carried out at a current density of 0.2 to 2.0 A / dm 2 It is preferable to carry out the treatment at a current density of 0.3 to 1.7 A / dm 2The material is preferably made of copper or a copper alloy, and a base layer (made of copper, nickel or an alloy thereof) is preferably formed between the material and the surface layer.

[0022] In an embodiment of the silver-plated product according to the present invention, in the silver-plated product having a surface layer made of silver formed on a base material, the average crystallite size of the surface layer made of silver is 25 nm or less (preferably 24 nm or less) and the Vickers hardness HV is 150 or more (preferably 160 or more, more preferably 165 to 250), and the antimony content in the surface layer is 0.1 mass % or less.

[0023] In this silver-plated product, the surface layer preferably comprises 90 to 99% by mass of silver, and more preferably 92 to 99% by mass of silver. The carbon content in the surface layer is preferably 1 to 10% by mass, more preferably 2 to 8% by mass, and most preferably 3 to 6% by mass. The oxygen content in the surface layer is preferably 5% by mass or less, and more preferably 3% by mass or less. The potassium content in the surface layer is preferably 1% by mass or less, and more preferably 0.8% by mass or less. The base material is preferably made of copper or a copper alloy, and a base layer (made of copper, nickel, or an alloy thereof) is preferably formed between the base material and the surface layer. [Example]

[0024] Examples of the silver-plated product and the method for producing the same according to the present invention will be described in detail below.

[0025] [Example 1] First, a rolled plate made of oxygen-free copper (C1020 1 / 2H) measuring 67 mm x 50 mm x 0.3 mm was prepared as the substrate (material to be plated). As a pretreatment for this material to be plated, the material to be plated and the SUS plate were placed in an alkaline degreasing solution, and electrolytic degreasing was performed for 30 seconds at a voltage of 5 V, with the material to be plated as the cathode and the SUS plate as the anode. After rinsing with water, the material was pickled in 3% sulfuric acid for 15 seconds.

[0026] Next, in a matte nickel plating solution consisting of an aqueous solution containing 540 g / L of nickel sulfamate tetrahydrate, 25 g / L of nickel chloride, and 35 g / L of boric acid, the pretreated workpiece was used as the cathode and the nickel electrode plate was used as the anode, and the solution was stirred at 500 rpm with a stirrer at a liquid temperature of 55°C and a current density of 5 A / dm 2 The thickness of the matte nickel plating film at the approximate center was measured using a fluorescent X-ray film thickness meter (SFT-110A, manufactured by Hitachi High-Tech Science Corporation) and found to be 1 μm.

[0027] Next, in a silver strike plating solution consisting of an aqueous solution containing 3 g / L of potassium silver cyanide (KAg(CN)2) and 90 g / L of potassium cyanide (KCN), the workpiece on which the undercoat plating film was formed was used as the cathode, and a platinum-coated titanium electrode plate was used as the anode, and the plating was conducted at a current density of 2.0 A / dm at room temperature (25°C) while stirring at 500 rpm with a stirrer. 2 for 10 seconds to form a silver strike plating film, and then the silver strike plating solution was thoroughly washed away by rinsing with water.

[0028] Next, in a silver plating solution consisting of an aqueous solution containing 40 g / L of potassium silver cyanide (KAg(CN)2), 39 g / L of potassium cyanide (KCN), and 1 g / L of 2-mercaptobenzimidazole (2-MBI), the workpiece on which the silver strike plating film had been formed was used as the cathode, and the silver electrode plate was used as the anode. The solution was stirred at 500 rpm with a stirrer, and a current density of 0.5 A / dm was applied at a solution temperature of 25°C. 2The silver-plated material was electroplated (silver plating) for 18 minutes at 1000 K for 18 minutes to form a silver plating film, which was then rinsed with water and dried with air pressure from an air gun to obtain a silver-plated product. The thickness of the silver plating film at approximately the center of this silver-plated material was measured using the fluorescent X-ray film thickness meter described above and was found to be 5 μm. The concentrations of potassium silver cyanide (KAg(CN)2), potassium cyanide (KCN), and 2-mercaptobenzimidazole (2-MBI) in the silver plating solution used to form the silver plating film on this silver-plated material were designated A (g / L), B (g / L), and C (g / L), respectively, and the current density of the electroplating was D (A / dm 2 ), then A / D=80(g dm 2 / L·A), B / D=78(g·dm 2 / L·A), C / D=2.0(g·dm 2 / L·A).

[0029] The Vickers hardness HV of the surface of the silver-plated material thus obtained was measured in accordance with JIS Z2244 using a microhardness tester (HM-221 manufactured by Mitutoyo Corporation) by applying a measurement load of 10 gf for 10 seconds, and was found to be 171.1.

[0030] Two pieces of the above silver-plated material were prepared, one of which was indented (with an inner radius of 1.5 mm) and used as an indenter, while the other was used as a flat evaluation specimen. Using a precision sliding tester (CRS-G2050-DWA manufactured by Yamazaki Seiki Kenkyusho Co., Ltd.), the indenter was pressed against the evaluation specimen with a constant load (5 N) while undergoing a reciprocating sliding motion (sliding distance 5 mm, sliding speed 1.67 mm / s) until the material was exposed. The center of the sliding marks on the composite plated material was observed at 100x magnification using a microscope (VHX-1000 manufactured by Keyence Corporation) to evaluate the wear state of the silver-plated material. The results confirmed that the material was not exposed even after 1,000 reciprocating sliding motions, demonstrating its excellent wear resistance. In addition, before and after this sliding wear test, the contact resistance was measured at a measurement current of 10 mA while pressing an indenter against the evaluation sample with a constant load (5 N).The initial contact resistance before the sliding test was 0.32 mΩ, and the contact resistance after the sliding test was 0.13 mΩ.

[0031] The crystallite diameters perpendicular to the (111), (200), (220), and (311) crystal planes of the silver-plated film of this silver-plated material were calculated using the Scherrer equation from the half-widths of the peaks of the crystal planes (the (111) peak at approximately 38°, the (200) peak at approximately 44°, the (220) peak at approximately 64°, and the (311) peak at approximately 77°) in the X-ray diffraction pattern obtained with an XRD analyzer (Rigaku Corporation, fully automated multipurpose horizontal X-ray diffractometer, Smart Lab). The average crystallite diameter was calculated as a weighted average of the crystallite diameters of each crystal plane, weighted by the orientation ratio of each crystal plane. The average crystallite diameter of the silver-plated film was found to be 127.78 Å (12.778 nm). The orientation ratio was determined by using an X-ray diffraction (XRD) analyzer (Rigaku Corporation's fully automated multipurpose horizontal X-ray diffractometer, Smart Lab) with a Cu tube and a Kβ filter method to scan the scanning range 2θ / θ. The X-ray diffraction pattern was then corrected by dividing the X-ray diffraction peak intensities (X-ray diffraction peak intensities) of the (111), (200), (220), and (311) planes of the silver plating film by the relative intensity ratios (relative intensity ratios in powder measurement) listed in JCPDS Card No. 40783 ((111):(200):(220):(311)=100:40:25:26).

[0032] The silver plating film of this silver-plated material was measured using an electron probe microanalyzer (EPMA) (JXA8200 manufactured by JEOL Ltd.) at a voltage of 15 kV and a probe current of 3.0 × 10 -8 A surface analysis was performed using the ZAF method on a 50 μm square analysis area. The silver plating film contained 4.1 mass% carbon, 2.7 mass% oxygen, 0.6 mass% potassium, and the remainder silver. No other elements (such as antimony or tin) were detected in the silver plating film, and their contents were less than 0.1 mass%.

[0033] [Example 2] When forming the silver plating film, the current density is 0.7A / dm 2 A silver-plated product was produced in the same manner as in Example 1, except that electroplating (silver plating) was carried out for 13 minutes at 1000 kJ / cm². The thickness of the silver plating film at approximately the center of this silver-plated product was measured in the same manner as in Example 1, and was found to be 5 μm. In forming the silver plating film on this silver-plated product, A / D = 57 (g dm 2 / L·A), B / D=56(g·dm 2 / L·A), C / D=1.4(g·dm 2 / L·A).

[0034] The Vickers hardness HV of the silver plating film of the obtained silver-plated material was measured using the same method as in Example 1, the wear resistance was evaluated, and the crystallite diameter was calculated. The Vickers hardness HV was found to be 187.7. Furthermore, it was confirmed that the material was not exposed even after 1,000 reciprocating sliding operations, demonstrating excellent wear resistance. Furthermore, the average crystallite diameter of the silver plating film was found to be 147.34 angstroms (14.734 nm).

[0035] Furthermore, a surface analysis of the silver plating film of this silver-plated product was performed using the same method as in Example 1. The silver plating film contained 3.6 mass% carbon and the remainder silver. No other elements (such as antimony or tin) were detected in the silver plating film, and the content was less than 0.1 mass%.

[0036] [Example 3] A silver-plated product was prepared in the same manner as in Example 1, except that the amount of 2-mercaptobenzimidazole (2-MBI) in the silver plating solution was changed to 2 g / L. The thickness of the silver plating film on this silver-plated product at approximately the center was measured in the same manner as in Example 1 and was found to be 5 μm. In forming the silver plating film on this silver-plated product, A / D = 80 (g dm 2 / L·A), B / D=78(g·dm 2 / L·A), C / D=4.0(g·dm 2 / L·A).

[0037] For the silver-plated material thus obtained, the Vickers hardness HV of the silver-plated film was measured, the wear resistance was evaluated, and the crystallite diameter was calculated using the same method as in Example 1. The Vickers hardness HV was found to be 165.6. Furthermore, it was confirmed that the material was not exposed even after 1,000 reciprocating sliding operations, demonstrating excellent wear resistance. Furthermore, the average crystallite diameter of the silver-plated film was found to be 143.70 angstroms (14.370 nm).

[0038] Furthermore, a surface analysis of the silver plating film of this silver-plated product was performed using the same method as in Example 1. The silver plating film contained 5.3 mass% carbon, 0.6 mass% sulfur, and the remainder silver. No other elements (such as antimony or tin) were detected in the silver plating film, and the amounts were less than 0.1 mass%.

[0039] [Example 4] A silver-plated product was prepared in the same manner as in Example 1, except that the amount of potassium silver cyanide (KAg(CN)2) in the silver plating solution was 100 g / L. The thickness of the silver plating film on this silver-plated product at approximately the center was measured in the same manner as in Example 1 and was found to be 5 μm. In forming the silver plating film on this silver-plated product, A / D = 200 (g dm 2 / L·A), B / D=78(g·dm 2 / L·A), C / D=2.0(g·dm 2 / L·A).

[0040] The Vickers hardness HV of the silver plating film of the obtained silver-plated material was measured using the same method as in Example 1, the wear resistance was evaluated, and the crystallite diameter was calculated. The Vickers hardness HV was found to be 181.2. Furthermore, it was confirmed that the material was not exposed even after 1,000 reciprocating sliding operations, demonstrating excellent wear resistance. Furthermore, the average crystallite diameter of the silver plating film was found to be 231.46 angstroms (23.146 nm).

[0041] [Example 5] The amount of potassium silver cyanide (KAg(CN)2) in the silver plating solution was 100 g / L, the amount of 2-mercaptobenzimidazole (2-MBI) was 2 g / L, and the current density was 1.5 A / dm 2 A silver-plated product was produced in the same manner as in Example 1, except that electroplating (silver plating) was carried out for 6 minutes at 1000 kJ / cm². The thickness of the silver plating film at approximately the center of this silver-plated product was measured in the same manner as in Example 1, and was found to be 5 μm. In forming the silver plating film on this silver-plated product, A / D = 67 (g dm 2 / L·A), B / D=26(g·dm 2 / L·A), C / D=1.3(g·dm 2 / L·A).

[0042] The Vickers hardness HV of the silver plating film was measured for the silver-plated material obtained in this manner, and the wear resistance was evaluated and the crystallite diameter was calculated using the same method as in Example 1. The Vickers hardness HV was found to be 165.5. Furthermore, it was confirmed that the material was not exposed even after 1,000 reciprocating sliding operations, demonstrating excellent wear resistance. Furthermore, the average crystallite diameter of the silver plating film was found to be 100.15 angstroms (10.015 nm).

[0043] [Example 6] A silver-plated product was produced in the same manner as in Example 1, except that a silver plating solution consisting of an aqueous solution containing 40 g / L of potassium silver cyanide (KAg(CN)2), 39 g / L of potassium cyanide (KCN), 1 g / L of 2-mercaptobenzimidazole (2-MBI), and 20 g / L of potassium carbonate (K2CO3) was used. The thickness of the silver plating film at approximately the center of this silver-plated product was measured in the same manner as in Example 1, and was found to be 5 μm. In forming the silver plating film on this silver-plated product, A / D = 80 (g dm 2 / L·A), B / D=78(g·dm 2 / L·A), C / D=2.0(g·dm 2 / L·A).

[0044] The Vickers hardness HV of the silver-plated film was measured for the silver-plated material obtained in this manner, and the wear resistance was evaluated and the crystallite diameter was calculated using the same method as in Example 1. The Vickers hardness HV was found to be 188.6. Furthermore, it was confirmed that the material was not exposed even after 1,000 reciprocating sliding operations, demonstrating excellent wear resistance. Furthermore, the average crystallite diameter of the silver-plated film was found to be 166.07 angstroms (16.607 nm).

[0045] [Example 7] A silver-plated product was produced in the same manner as in Example 1, except that a matte nickel plating film was not formed. The thickness of the silver plating film at approximately the center of this silver-plated product was measured in the same manner as in Example 1, and was found to be 5 μm. In forming the silver plating film on this silver-plated product, A / D = 80 (g dm 2 / L·A), B / D=78(g·dm 2 / L·A), C / D=2.0(g·dm 2 / L·A).

[0046] The Vickers hardness HV of the silver plating film of the obtained silver-plated material was measured using the same method as in Example 1, the wear resistance was evaluated, and the crystallite diameter was calculated. The Vickers hardness HV was found to be 175.7. Furthermore, it was confirmed that the material was not exposed even after 1,000 reciprocating sliding operations, demonstrating excellent wear resistance. Furthermore, the average crystallite diameter of the silver plating film was found to be 156.82 angstroms (15.682 nm).

[0047] [Example 8] When forming the silver plating film, the current density is 1A / dm 2 A silver-plated product was produced in the same manner as in Example 7, except that electroplating (silver plating) was carried out for 9 minutes at 1000 kJ / cm². The thickness of the silver plating film at the approximate center of this silver-plated product was measured in the same manner as in Example 1, and was found to be 5 μm. In forming the silver plating film on this silver-plated product, A / D = 40 (g dm 2 / L·A), B / D=39(g·dm 2 / L·A), C / D=2.0(g·dm 2 / L·A).

[0048] The Vickers hardness HV of the silver-plated film was measured for the silver-plated material obtained in this manner, and the wear resistance was evaluated and the crystallite diameter was calculated using the same method as in Example 1. The Vickers hardness HV was found to be 170.4. Furthermore, it was confirmed that the material was not exposed even after 1,000 reciprocating sliding operations, demonstrating excellent wear resistance. Furthermore, the average crystallite diameter of the silver-plated film was found to be 156.82 angstroms (15.682 nm).

[0049] [Example 9] A silver-plated product was prepared in the same manner as in Example 1, except that the solution temperature was set to 18°C ​​when forming the silver plating film. The thickness of the silver plating film at the approximate center of this silver-plated product was measured in the same manner as in Example 1, and was found to be 5 μm. In forming the silver plating film on this silver-plated product, A / D = 80 (g dm 2 / L·A), B / D=78(g·dm 2 / L·A), C / D=2.0(g·dm 2 / L·A).

[0050] The Vickers hardness HV of the silver-plated film was measured for the silver-plated material obtained in this manner, and the wear resistance was evaluated and the crystallite diameter was calculated using the same method as in Example 1. The Vickers hardness HV was found to be 194.1. Furthermore, it was confirmed that the material was not exposed even after 1,000 reciprocating sliding operations, demonstrating excellent wear resistance. Furthermore, the average crystallite diameter of the silver-plated film was found to be 105.03 angstroms (10.503 nm).

[0051] [Example 10] A silver-plated product was produced in the same manner as in Example 1, except that the solution temperature was set to 35°C when the silver plating film was formed. The thickness of the silver plating film at the approximate center of this silver-plated product was measured in the same manner as in Example 1, and was found to be 5 μm. In forming the silver plating film on this silver-plated product, A / D = 80 (g dm 2 / L·A), B / D=78(g·dm 2 / L·A), C / D=2.0(g·dm 2 / L·A).

[0052] The Vickers hardness HV of the silver plating film of the obtained silver-plated material was measured using the same method as in Example 1, the wear resistance was evaluated, and the crystallite diameter was calculated. The Vickers hardness HV was found to be 185.8. Furthermore, it was confirmed that the material was not exposed even after 1,000 reciprocating sliding operations, demonstrating excellent wear resistance. Furthermore, the average crystallite diameter of the silver plating film was found to be 168.56 angstroms (16.856 nm).

[0053] [Example 11] A silver-plated product was produced in the same manner as in Example 3, except that the electroplating time for forming the silver plating film was 7.2 minutes. The thickness of the silver plating film at the approximate center of this silver-plated product was measured in the same manner as in Example 1, and was found to be 2 μm. In forming the silver plating film on this silver-plated product, A / D = 80 (g dm 2 / L·A), B / D=78(g·dm 2 / L·A), C / D=4.0(g·dm 2 / L·A).

[0054] For the silver-plated material thus obtained, the Vickers hardness HV of the silver-plated film was measured, the wear resistance was evaluated, and the crystallite diameter was calculated using the same method as in Example 1. The Vickers hardness HV was found to be 154.3. Furthermore, it was confirmed that the material was not exposed after 800 reciprocating sliding operations, demonstrating excellent wear resistance. Furthermore, the average crystallite diameter of the silver-plated film was found to be 209.40 angstroms (20.940 nm).

[0055] [Comparative Example 1] A silver-plated product was produced in the same manner as in Example 1, except that a silver plating solution consisting of an aqueous solution containing 40 g / L of potassium silver cyanide (KAg(CN)2) and 39 g / L of potassium cyanide (KCN) was used. The thickness of the silver plating film at approximately the center of this silver-plated product was measured in the same manner as in Example 1 and was found to be 5 μm. In forming the silver plating film on this silver-plated product, A / D = 80 (g dm 2 / L·A), B / D=78(g·dm 2 / L·A), C / D=0(g·dm 2 / L·A).

[0056] For the silver-plated material thus obtained, the Vickers hardness HV of the silver-plated film was measured, the wear resistance was evaluated, and the crystallite diameter was calculated using the same method as in Example 1. The Vickers hardness HV was found to be 105.8. Furthermore, it was confirmed that the material was exposed after 60 reciprocating sliding operations, indicating that the wear resistance was poor. Furthermore, the average crystallite diameter of the silver-plated film was 434.98 angstroms (43.498 nm).

[0057] Comparative Example 2 When forming the silver plating film, the current density is 1.5A / dm 2 A silver-plated product was produced in the same manner as in Comparative Example 1, except that electroplating (silver plating) was carried out for 6 minutes at 1000 kJ / cm². The thickness of the silver plating film at the approximate center of this silver-plated product was measured in the same manner as in Example 1, and was found to be 5 μm. In forming the silver plating film on this silver-plated product, A / D = 27 (g dm 2 / L·A), B / D=26(g·dm 2 / L·A), C / D=0(g·dm 2 / L·A).

[0058] For the silver-plated material thus obtained, the Vickers hardness HV of the silver plating film was measured and the crystallite size was calculated using the same method as in Example 1. The Vickers hardness HV was found to be 112.7. The average crystallite size of the silver plating film was 625.39 angstroms (43.498 nm). Since appearance unevenness was observed on the surface of the silver plating film of this silver-plated material, a sliding wear test was not performed.

[0059] Comparative Example 3 When forming the silver plating film, the current density is 1A / dm 2 A silver-plated product was produced in the same manner as in Example 1, except that electroplating (silver plating) was carried out for 9 minutes at 1000 kJ / cm². The thickness of the silver plating film at approximately the center of this silver-plated product was measured in the same manner as in Example 1, and was found to be 5 μm. In forming the silver plating film on this silver-plated product, A / D = 40 (g dm 2 / L·A), B / D=39(g·dm 2 / L·A), C / D=1.0(g·dm 2 / L·A).

[0060] For the silver-plated material thus obtained, the Vickers hardness HV of the silver plating film was measured and the crystallite size was calculated using the same method as in Example 1. The Vickers hardness HV was found to be 131.2. The average crystallite size of the silver plating film was 160.06 angstroms (16.006 nm). Since appearance unevenness was observed on the surface of the silver plating film of this silver-plated material, a sliding wear test was not performed.

[0061] Comparative Example 4 When forming the silver plating film, the current density is 1.5A / dm 2 A silver-plated product was produced in the same manner as in Example 3, except that electroplating (silver plating) was carried out for 6 minutes at 1000 kJ / cm². The thickness of the silver plating film at approximately the center of this silver-plated product was measured in the same manner as in Example 1, and was found to be 5 μm. In forming the silver plating film on this silver-plated product, A / D = 27 (g dm 2 / L·A), B / D=26(g·dm 2 / L·A), C / D=1.3(g·dm 2 / L·A).

[0062] For the silver-plated material thus obtained, the Vickers hardness HV of the silver-plated film was measured, the wear resistance was evaluated, and the crystallite diameter was calculated using the same method as in Example 1. The Vickers hardness HV was found to be 131.1. Furthermore, it was confirmed that the material was exposed after 100 reciprocating sliding operations, indicating that the wear resistance was poor. Furthermore, the average crystallite diameter of the silver-plated film was 105.20 angstroms (10.520 nm).

[0063] Comparative Example 5 The amount of potassium cyanide (KCN) in the silver plating solution is 99g / L, and the current density is 1.5A / dm 2 A silver-plated product was produced in the same manner as in Example 1, except that electroplating (silver plating) was carried out for 6 minutes at 1000 kJ / cm². The thickness of the silver plating film at the approximate center of this silver-plated product was measured in the same manner as in Example 1, and was found to be 5 μm. In forming the silver plating film on this silver-plated product, A / D = 27 (g dm 2 / L·A), B / D=66(g·dm 2 / L·A), C / D=0.7(g·dm 2 / L·A).

[0064] For the silver-plated material thus obtained, the Vickers hardness HV of the silver plating film was measured and the crystallite size was calculated using the same method as in Example 1. The Vickers hardness HV was found to be 118.6. The average crystallite size of the silver plating film was 318.16 angstroms (31.816 nm). Since appearance unevenness was observed on the surface of the silver plating film of this silver-plated material, a sliding wear test was not performed.

[0065] Comparative Example 6 A silver-plated product was prepared in the same manner as in Example 3, except that the amount of potassium cyanide (KCN) in the silver plating solution was changed to 99 g / L. The thickness of the silver plating film on this silver-plated product at approximately the center was measured in the same manner as in Example 1, and was found to be 5 μm. In forming the silver plating film on this silver-plated product, A / D = 80 (g dm 2 / L·A), B / D=198(g·dm 2 / L·A), C / D=4.0(g·dm 2 / L·A).

[0066] For the silver-plated material thus obtained, the Vickers hardness HV of the silver-plated film was measured, the wear resistance was evaluated, and the crystallite diameter was calculated using the same method as in Example 1. The Vickers hardness HV was found to be 121.3. Furthermore, it was confirmed that the material was exposed after 80 reciprocating sliding operations, indicating that the wear resistance was poor. Furthermore, the average crystallite diameter of the silver-plated film was found to be 736.65 angstroms (73.665 nm).

[0067] Comparative Example 7 When forming the silver plating film, the current density is 1A / dm 2 A silver-plated product was produced in the same manner as in Example 4, except that electroplating (silver plating) was carried out for 9 minutes at 100°C. The thickness of the silver plating film at approximately the center of this silver-plated product was measured in the same manner as in Example 1, and was found to be 5 μm. In forming the silver plating film on this silver-plated product, A / D = 100 (g dm 2 / L·A), B / D=39(g·dm 2 / L·A), C / D=1.0(g·dm 2 / L·A).

[0068] For the silver-plated material thus obtained, the Vickers hardness HV of the silver-plated film was measured, the wear resistance was evaluated, and the crystallite diameter was calculated using the same method as in Example 1. The Vickers hardness HV was found to be 138.4. Furthermore, it was confirmed that the material was exposed after 200 reciprocating sliding operations, indicating that the wear resistance was poor. Furthermore, the average crystallite diameter of the silver-plated film was found to be 205.78 angstroms (20.578 nm).

[0069] [Comparative Example 8] When forming the silver plating film, the current density is 1.5A / dm 2 A silver-plated product was produced in the same manner as in Example 4, except that electroplating (silver plating) was carried out for 6 minutes at 1000 kJ / cm². The thickness of the silver plating film at approximately the center of this silver-plated product was measured in the same manner as in Example 1, and was found to be 5 μm. In forming the silver plating film on this silver-plated product, A / D = 67 (g dm 2 / L·A), B / D=26(g·dm 2 / L·A), C / D=0.7(g·dm 2 / L·A).

[0070] For the silver-plated material thus obtained, the Vickers hardness HV of the silver plating film was measured and the crystallite size was calculated using the same method as in Example 1. The Vickers hardness HV was found to be 130.8. The average crystallite size of the silver plating film was 318.46 angstroms (31.846 nm). Since appearance unevenness was observed on the surface of the silver plating film of this silver-plated material, a sliding wear test was not performed.

[0071] Comparative Example 9 A silver plating solution consisting of an aqueous solution containing 100 g / L of potassium silver cyanide (KAg(CN)2), 99 g / L of potassium cyanide (KCN), and 1 g / L of 2-mercaptobenzimidazole (2-MBI) was used, with a current density of 1.5 A / dm 2A silver-plated product was produced in the same manner as in Example 1, except that electroplating (silver plating) was carried out for 6 minutes at 1000 kJ / cm². The thickness of the silver plating film at approximately the center of this silver-plated product was measured in the same manner as in Example 1, and was found to be 5 μm. In forming the silver plating film on this silver-plated product, A / D = 67 (g dm 2 / L·A), B / D=66(g·dm 2 / L·A), C / D=0.7(g·dm 2 / L·A).

[0072] For the silver-plated material thus obtained, the Vickers hardness HV of the silver plating film was measured and the crystallite size was calculated using the same method as in Example 1. The Vickers hardness HV was found to be 120.1. The average crystallite size of the silver plating film was 381.93 angstroms (38.193 nm). Since appearance unevenness was observed on the surface of the silver plating film of this silver-plated material, a sliding wear test was not performed.

[0073] [Comparative Example 10] A silver-plated product was prepared in the same manner as in Example 3, except that the amount of potassium silver cyanide (KAg(CN)2) in the silver plating solution was 100 g / L and the amount of potassium cyanide (KCN) was 99 g / L. The thickness of the silver plating film on this silver-plated product at approximately the center was measured in the same manner as in Example 1, and was found to be 5 μm. In forming the silver plating film on this silver-plated product, A / D = 200 (g dm 2 / L·A), B / D=198(g·dm 2 / L·A), C / D=4.0(g·dm 2 / L·A).

[0074] For the silver-plated material thus obtained, the Vickers hardness HV of the silver-plated film was measured, the wear resistance was evaluated, and the crystallite diameter was calculated using the same method as in Example 1. The Vickers hardness HV was found to be 121.4. Furthermore, it was confirmed that the material was exposed after 70 reciprocating sliding operations, indicating that the wear resistance was poor. Furthermore, the average crystallite diameter of the silver-plated film was 391.48 angstroms (39.148 nm).

[0075] [Comparative Example 11] A silver plating solution consisting of an aqueous solution containing 115 g / L of potassium silver cyanide (KAg(CN)2), 60 g / L of potassium cyanide (KCN), and 40 mg / L of selenium was used at a current density of 2 A / dm 2 A silver-plated product was produced in the same manner as in Example 1, except that electroplating (silver plating) was carried out for 5 minutes at 1000 kJ / cm². The thickness of the silver plating film at approximately the center of this silver-plated product was measured in the same manner as in Example 1, and was found to be 5 μm. In forming the silver plating film on this silver-plated product, A / D = 58 (g dm 2 / L·A), B / D=30(g·dm 2 / L·A), C / D=0(g·dm 2 / L·A).

[0076] For the silver-plated material thus obtained, the Vickers hardness HV of the silver-plated film was measured, the wear resistance was evaluated, and the crystallite diameter was calculated using the same method as in Example 1. The Vickers hardness HV was found to be 118.9. Furthermore, it was confirmed that the material was exposed after 100 reciprocating sliding operations, indicating that the wear resistance was poor. Furthermore, the average crystallite diameter of the silver-plated film was 635.73 angstroms (63.573 nm).

[0077] [Comparative Example 12] A silver plating solution consisting of an aqueous solution containing 148 g / L of potassium silver cyanide (KAg(CN)2), 140 g / L of potassium cyanide (KCN), and 8 mg / L of selenium was used at a current density of 8 A / dm at a solution temperature of 16°C. 2A silver-plated product was produced in the same manner as in Example 1, except that electroplating (silver plating) was carried out at 1000 kJ / cm² for 80 seconds (1.3 minutes). The thickness of the silver plating film on this silver-plated product at approximately the center was measured in the same manner as in Example 1 and was found to be 5 μm. In forming the silver plating film on this silver-plated product, A / D = 19 (g dm 2 / L·A), B / D=18(g·dm 2 / L·A), C / D=0(g·dm 2 / L·A).

[0078] For the silver-plated material thus obtained, the Vickers hardness HV of the silver-plated film was measured, the wear resistance was evaluated, and the crystallite diameter was calculated using the same method as in Example 1. The Vickers hardness HV was found to be 82.4. Furthermore, it was confirmed that the material was exposed after 50 reciprocating sliding operations, indicating that the wear resistance was poor. Furthermore, the average crystallite diameter of the silver-plated film was 749.72 angstroms (74.972 nm).

[0079] [Comparative Example 13] A silver plating solution consisting of an aqueous solution containing 175 g / L of potassium silver cyanide (KAg(CN)2), 95 g / L of potassium cyanide (KCN), and 70 mg / L of selenium was used at a solution temperature of 18°C ​​and a current density of 5 A / dm 2 A silver-plated product was produced in the same manner as in Example 1, except that electroplating (silver plating) was carried out for 2 minutes at 1000 kJ / cm². The thickness of the silver plating film at the approximate center of this silver-plated product was measured in the same manner as in Example 1, and was found to be 5 μm. In forming the silver plating film on this silver-plated product, A / D = 35 (g dm 2 / L·A), B / D=19(g·dm 2 / L·A), C / D=0(g·dm 2 / L·A).

[0080] For the silver-plated material thus obtained, the Vickers hardness HV of the silver-plated film was measured, the wear resistance was evaluated, and the crystallite diameter was calculated using the same method as in Example 1. The Vickers hardness HV was found to be 133.8. Furthermore, it was confirmed that the material was exposed after 80 reciprocating sliding operations, indicating that the wear resistance was poor. Furthermore, the average crystallite diameter of the silver-plated film was 278.25 angstroms (27.825 nm).

[0081] [Comparative Example 14] A silver plating solution consisting of an aqueous solution containing 40 g / L potassium silver cyanide (KAg(CN)2), 39 g / L potassium cyanide (KCN), 1 g / L 2-mercaptobenzimidazole (2-MBI), and 20 g / L potassium carbonate (K2CO3) was used at a current density of 1 A / dm 2 A silver-plated product was produced in the same manner as in Example 1, except that electroplating (silver plating) was carried out for 9 minutes at 1000 kJ / cm². The thickness of the silver plating film at approximately the center of this silver-plated product was measured in the same manner as in Example 1, and was found to be 5 μm. In forming the silver plating film on this silver-plated product, A / D = 40 (g dm 2 / L·A), B / D=39(g·dm 2 / L·A), C / D=1.0(g·dm 2 / L·A).

[0082] For the silver-plated material thus obtained, the Vickers hardness HV of the silver-plated film was measured, the wear resistance was evaluated, and the crystallite diameter was calculated using the same method as in Example 1. The Vickers hardness HV was found to be 134.4. Furthermore, it was confirmed that the material was exposed after less than 10 reciprocating sliding operations, indicating that the wear resistance was poor. Furthermore, the average crystallite diameter of the silver-plated film was 192.83 angstroms (19.283 nm).

[0083] [Comparative Example 15] When forming the matte nickel plating film, the solution temperature is 50°C and the current density is 4A / dm 2Electroplating was performed for 140 seconds at a current density of 2.0 A / dm when forming the silver strike plating film. 2 For forming the silver plating film, an Ag-Sb plating solution (a plating solution in which Nissin Bright N manufactured by Nissin Shinko Co., Ltd. was added to a silver plating solution (Na bath manufactured by Nissin Shinko Co., Ltd.) was used at a solution temperature of 18°C ​​and a current density of 3 A / dm 2 A silver-plated product was produced in the same manner as in Example 1, except that electroplating (silver plating) was carried out at 1000 kJ / min for 500 seconds (8.3 minutes). The thickness of the matte nickel plating film on this silver-plated product at approximately the center was measured by the same method as in Example 1 and was found to be 1 μm. The thickness of the silver plating film on this silver-plated product at approximately the center was also measured by the same method as in Example 1 and was found to be 5 μm. In forming the silver plating film on this silver-plated product, the B / D value was 0 (g dm 2 / L·A), C / D=0(g·dm 2 / L·A).

[0084] For the silver-plated material thus obtained, the Vickers hardness HV of the silver-plated film was measured, the wear resistance was evaluated, and the crystallite diameter was calculated using the same method as in Example 1. The Vickers hardness HV was found to be 170.4. Furthermore, it was confirmed that the material was exposed after 150 reciprocating sliding operations, indicating that the wear resistance was poor. Furthermore, the average crystallite diameter of the silver-plated film was 126.11 angstroms (12.611 nm).

[0085] Furthermore, a surface analysis of the silver plating film of this silver-plated product was performed using the same method as in Example 1. The silver plating film was found to contain 1.6 mass% carbon, 2.9 mass% antimony, and the remainder silver.

[0086] [Example 12] The silver plating solution was an aqueous solution containing 100 g / L of potassium silver cyanide (KAg(CN)2), 39 g / L of potassium cyanide (KCN), and 20 g / L of sodium 2-mercaptobenzimidazole sulfonate dihydrate (2-MBIS), and the current density was 0.7 A / dm2 A silver-plated product was produced in the same manner as in Example 1, except that electroplating (silver plating) was carried out for 13 minutes at 1000 kJ / min. The thickness of the silver plating film on this silver-plated product at approximately the center was measured in the same manner as in Example 1 and was found to be 5 μm. The concentrations of potassium silver cyanide (KAg(CN)2), potassium cyanide (KCN), and sodium 2-mercaptobenzimidazole sulfonate dihydrate (2-MBIS) in the silver plating solution used to form the silver plating film on this silver-plated product were A (g / L), B (g / L), and C (g / L), respectively, and the current density of electroplating was D (A / dm 2 ), then A / D=143(g dm 2 / L·A), B / D=56(g·dm 2 / L·A), C / D=28.6(g·dm 2 / L·A).

[0087] For the silver-plated material thus obtained, the Vickers hardness HV of the silver-plated film was measured, the wear resistance was evaluated, and the crystallite diameter was calculated using the same method as in Example 1. The Vickers hardness HV was found to be 226. Furthermore, it was confirmed that the material was not exposed even after 1,000 reciprocating sliding operations, demonstrating excellent wear resistance. Furthermore, the average crystallite diameter of the silver-plated film was 97 angstroms (9.7 nm).

[0088] [Example 13] When forming the silver plating film, the current density is 1.0A / dm 2 A silver-plated product was produced in the same manner as in Example 12, except that electroplating (silver plating) was carried out for 9 minutes at 100°C. The thickness of the silver plating film at approximately the center of this silver-plated product was measured in the same manner as in Example 1, and was found to be 5 μm. In forming the silver plating film on this silver-plated product, A / D = 100 (g dm 2 / L·A), B / D=39(g·dm 2 / L·A), C / D=20.0(g·dm 2 / L·A).

[0089] The Vickers hardness HV of the silver plating film of the obtained silver-plated material was measured using the same method as in Example 1, the wear resistance was evaluated, and the crystallite size was calculated. The Vickers hardness HV was found to be 175. It was also confirmed that the material was not exposed even after 1,000 reciprocating sliding operations, demonstrating excellent wear resistance. Furthermore, the average crystallite size of the silver plating film was 112 angstroms (11.2 nm).

[0090] [Example 14] When forming the silver plating film, the current density is 1.5A / dm 2 A silver-plated product was produced in the same manner as in Example 12, except that electroplating (silver plating) was carried out for 6 minutes at 1000 kJ / cm². The thickness of the silver plating film at approximately the center of this silver-plated product was measured in the same manner as in Example 1, and was found to be 5 μm. In forming the silver plating film on this silver-plated product, A / D = 67 (g dm 2 / L·A), B / D=26(g·dm 2 / L·A), C / D=13.3(g·dm 2 / L·A).

[0091] For the silver-plated material thus obtained, the Vickers hardness HV of the silver-plated film was measured, the wear resistance was evaluated, and the crystallite diameter was calculated using the same method as in Example 1. The Vickers hardness HV was found to be 155. Furthermore, it was confirmed that the material was not exposed after 500 reciprocating sliding operations, demonstrating excellent wear resistance. Furthermore, the average crystallite diameter of the silver-plated film was 138 angstroms (13.8 nm).

[0092] [Example 15] The silver plating solution was an aqueous solution containing 27 g / L of silver cyanide (AgCN), 39 g / L of sodium cyanide (NaCN), and 1 g / L of 2-mercaptobenzimidazole (2-MBI), and the current density was 0.5 A / dm 2A silver-plated product was produced in the same manner as in Example 1, except that electroplating (silver plating) was carried out for 18 minutes at 1000 kJ / min. The thickness of the silver plating film on this silver-plated product at approximately the center was measured in the same manner as in Example 1 and was found to be 5 μm. The concentrations of silver cyanide (AgCN), sodium cyanide (NaCN) and 2-mercaptobenzimidazole (2-MBI) in the silver plating solution used to form the silver plating film on this silver-plated product were A (g / L), B (g / L) and C (g / L), respectively, and the current density of electroplating was D (A / dm 2 ), then A / D=54(g dm 2 / L·A), B / D=78(g·dm 2 / L·A), C / D=2.0(g·dm 2 / L·A).

[0093] For the silver-plated material thus obtained, the Vickers hardness HV of the silver-plated film was measured, the wear resistance was evaluated, and the crystallite size was calculated using the same method as in Example 1. The Vickers hardness HV was found to be 166. Furthermore, it was confirmed that the material was not exposed even after 1,000 reciprocating sliding operations, demonstrating excellent wear resistance. Furthermore, the average crystallite size of the silver-plated film was 90 angstroms (9.0 nm).

[0094] Furthermore, the silver plating film of this silver-plated product was subjected to surface analysis in the same manner as in Example 1. The silver plating film contained 6.1 mass% carbon, 1.1 mass% sulfur, and the remainder silver. No other elements (such as antimony or tin) were detected in the silver plating film.

[0095] [Example 16] When forming the silver plating film, the current density is 0.7A / dm 2 A silver-plated product was produced in the same manner as in Example 15, except that electroplating (silver plating) was carried out for 13 minutes at 1000 kJ / cm². The thickness of the silver plating film at approximately the center of this silver-plated product was measured in the same manner as in Example 1, and was found to be 5 μm. In forming the silver plating film on this silver-plated product, A / D = 39 (g dm 2 / L·A), B / D=56(g·dm 2 / L·A), C / D=1.4(g·dm 2 / L·A).

[0096] The Vickers hardness HV of the silver plating film of the obtained silver-plated material was measured using the same method as in Example 1, the wear resistance was evaluated, and the crystallite size was calculated. The Vickers hardness HV was found to be 176. Furthermore, it was confirmed that the material was not exposed even after 1,000 reciprocating sliding operations, demonstrating excellent wear resistance. Furthermore, the average crystallite size of the silver plating film was found to be 81 angstroms (8.1 nm).

[0097] [Example 17] When forming the silver plating film, the solution temperature is 35°C and the current density is 0.5A / dm 2 A silver-plated product was produced in the same manner as in Example 15, except that electroplating (silver plating) was carried out for 18 minutes at 1000 kJ / cm². The thickness of the silver plating film at approximately the center of this silver-plated product was measured in the same manner as in Example 1, and was found to be 5 μm. In forming the silver plating film on this silver-plated product, A / D = 54 (g dm 2 / L·A), B / D=78(g·dm 2 / L·A), C / D=2.0(g·dm 2 / L·A).

[0098] For the silver-plated material thus obtained, the Vickers hardness HV of the silver-plated film was measured, the wear resistance was evaluated, and the crystallite diameter was calculated using the same method as in Example 1. The Vickers hardness HV was found to be 175. It was also confirmed that the material was not exposed even after 1,000 reciprocating sliding operations, demonstrating excellent wear resistance. Furthermore, the average crystallite diameter of the silver-plated film was 109 angstroms (10.9 nm).

[0099] [Example 18] The amount of 2-mercaptobenzimidazole (2-MBI) in the silver plating solution was 2 g / L, and the current density when forming the silver plating film was 1.5 A / dm2 A silver-plated product was produced in the same manner as in Example 15, except that electroplating (silver plating) was carried out for 6 minutes at 1000 kJ / cm². The thickness of the silver plating film at approximately the center of this silver-plated product was measured in the same manner as in Example 1, and was found to be 5 μm. In forming the silver plating film on this silver-plated product, A / D = 18 (g dm 2 / L·A), B / D=26(g·dm 2 / L·A), C / D=1.3(g·dm 2 / L·A).

[0100] The Vickers hardness HV of the silver plating film of the obtained silver-plated material was measured using the same method as in Example 1, the wear resistance was evaluated, and the crystallite size was calculated. The Vickers hardness HV was found to be 152. Furthermore, it was confirmed that the material was not exposed even after 1,000 reciprocating sliding operations, demonstrating excellent wear resistance. Furthermore, the average crystallite size of the silver plating film was found to be 72 angstroms (7.2 nm).

[0101] [Example 19] The silver plating solution was an aqueous solution containing 68 g / L of silver cyanide (AgCN), 64 g / L of sodium cyanide (NaCN), and 2 g / L of 2-mercaptobenzimidazole (2-MBI). The current density was 1.0 A / dm 2 A silver-plated product was produced in the same manner as in Example 1, except that electroplating (silver plating) was carried out for 9 minutes at 1000 kJ / min. The thickness of the silver plating film on this silver-plated product at approximately the center was measured in the same manner as in Example 1 and was found to be 5 μm. The concentrations of silver cyanide (AgCN), sodium cyanide (NaCN) and 2-mercaptobenzimidazole (2-MBI) in the silver plating solution used to form the silver plating film on this silver-plated product were A (g / L), B (g / L) and C (g / L), respectively, and the current density of electroplating was D (A / dm 2 ), then A / D=68(g dm 2 / L·A), B / D=64(g·dm 2 / L·A), C / D=2.0(g·dm 2 / L·A).

[0102] For the silver-plated material thus obtained, the Vickers hardness HV of the silver-plated film was measured, the wear resistance was evaluated, and the crystallite diameter was calculated using the same method as in Example 1. The Vickers hardness HV was found to be 161. It was also confirmed that the material was not exposed even after 1,000 reciprocating sliding operations, demonstrating excellent wear resistance. Furthermore, the average crystallite diameter of the silver-plated film was 122 angstroms (12.2 nm).

[0103] [Example 20] When forming the silver plating film, the current density is 1.5A / dm 2 A silver-plated product was produced in the same manner as in Example 19, except that electroplating (silver plating) was carried out for 6 minutes at 1000 kJ / cm². The thickness of the silver plating film at the approximate center of this silver-plated product was measured in the same manner as in Example 1, and was found to be 5 μm. In forming the silver plating film on this silver-plated product, A / D = 45 (g dm 2 / L·A), B / D=43(g·dm 2 / L·A), C / D=1.3(g·dm 2 / L·A).

[0104] The Vickers hardness HV of the silver-plated film was measured for the silver-plated material obtained in this manner, and the wear resistance was evaluated and the crystallite diameter was calculated using the same method as in Example 1. The Vickers hardness HV was found to be 161. Furthermore, it was confirmed that the material was not exposed even after 1,000 reciprocating sliding operations, demonstrating excellent wear resistance. Furthermore, the average crystallite diameter of the silver-plated film was 87 angstroms (8.7 nm).

[0105] [Example 21] The amount of sodium cyanide (NaCN) in the silver plating solution was set to 74 g / L, and the current density when forming the silver plating film was 0.7 A / dm 2A silver-plated product was produced in the same manner as in Example 19, except that electroplating (silver plating) was carried out for 13 minutes at 1000 kJ / cm². The thickness of the silver plating film at approximately the center of this silver-plated product was measured in the same manner as in Example 1, and was found to be 5 μm. In forming the silver plating film on this silver-plated product, A / D = 97 (g dm 2 / L·A), B / D=106(g·dm 2 / L·A), C / D=2.9(g·dm 2 / L·A).

[0106] The Vickers hardness HV of the silver plating film of the obtained silver-plated material was measured using the same method as in Example 1, the wear resistance was evaluated, and the crystallite diameter was calculated. The Vickers hardness HV was found to be 166. Furthermore, it was confirmed that the material was not exposed even after 1,000 reciprocating sliding operations, demonstrating excellent wear resistance. Furthermore, the average crystallite diameter of the silver plating film was 78 angstroms (7.8 nm).

[0107] [Example 22] The amount of sodium cyanide (NaCN) in the silver plating solution was set to 74 g / L, and the current density when forming the silver plating film was 1.0 A / dm 2 A silver-plated product was produced in the same manner as in Example 19, except that electroplating (silver plating) was carried out for 9 minutes at 1000 kJ / cm². The thickness of the silver plating film at approximately the center of this silver-plated product was measured in the same manner as in Example 1, and was found to be 5 μm. In forming the silver plating film on this silver-plated product, A / D = 68 (g dm 2 / L·A), B / D=74(g·dm 2 / L·A), C / D=2.0(g·dm 2 / L·A).

[0108] For the silver-plated material thus obtained, the Vickers hardness HV of the silver-plated film was measured, the wear resistance was evaluated, and the crystallite size was calculated using the same method as in Example 1. The Vickers hardness HV was found to be 162. It was also confirmed that the material was not exposed even after 1,000 reciprocating sliding operations, demonstrating excellent wear resistance. Furthermore, the average crystallite size of the silver-plated film was 106 angstroms (10.6 nm).

[0109] Tables 1 to 9 show the manufacturing conditions and properties of the silver-plated products obtained in these Examples and Comparative Examples.

[0110] [Table 1]

[0111] [Table 2]

[0112] [Table 3]

[0113] [Table 4]

[0114] [Table 5]

[0115] [Table 6]

[0116] [Table 7]

[0117] [Table 8]

[0118] Table 9

Claims

1. In a method for producing a silver-plated material by electroplating a material in a silver plating solution comprising an aqueous solution containing potassium silver cyanide, potassium cyanide, and benzimidazoles, the concentration of potassium silver cyanide in the silver plating solution is defined as A (g / L), the concentration of potassium cyanide is defined as B (g / L), and the concentration of benzimidazoles is defined as C (g / L), and the current density of the electroplating is defined as D (A / dm ２ ), the concentration of potassium cyanide is 30 to 80 g / L, and A / D is 30 (g dm ２ / L・A) or more, B / D is 100 (g・dm ２ / L・A) or less, C / D is 1.2 (g・dm ２ 1. A method for producing a silver-plated product, comprising: electroplating to obtain a silver-plated product having a silver content of 1.0 ppm or more;

2. In a method for producing a silver-plated material by electroplating a material in a silver plating solution containing an aqueous solution of silver cyanide, sodium cyanide, and benzimidazoles, the concentration of silver cyanide in the silver plating solution is defined as A (g / L), the concentration of sodium cyanide as B (g / L), and the concentration of benzimidazoles as C (g / L), and the current density of the electroplating is defined as D (A / dm ２ ), the concentration of sodium cyanide is 30 to 80 g / L, and A / D is 15 (g dm ２ / L・A) or more, B / D is 150 (g・dm ２ / L・A) or less, C / D is 1.2 (g・dm ２ 1. A method for producing a silver-plated product, comprising: electroplating to obtain a silver-plated product having a silver content of 1.0 ppm or more;

3. 3. The method for producing a silver-plated product according to claim 1, wherein the benzimidazole is 2-mercaptobenzimidazole or sodium 2-mercaptobenzimidazole sulfonate dihydrate.

4. 4. The method for producing a silver-plated product according to claim 1, wherein the concentration of the benzimidazole in the silver plating solution is 0.5 to 50 g / L.

5. 5. The method for producing a silver-plated product according to claim 1, wherein the silver plating solution contains 30 g / L or less of potassium carbonate.

6. 6. The method for producing a silver-plated product according to claim 1, wherein the electroplating is carried out at a solution temperature of 10 to 50°C.

7. The electroplating is performed at a current density of 0.2 to 2.0 A / dm ２ 7. The method for producing a silver-plated product according to claim 1, wherein the method is carried out by the steps of:

8. 8. The method for manufacturing a silver-plated product according to claim 1, wherein the material is made of copper or a copper alloy.

9. 9. The method for manufacturing a silver-plated product according to claim 1, wherein an underlayer made of nickel is formed between said base material and said surface layer.

10. A silver-plated product having a surface layer formed on a base material, the surface layer containing 1 to 10% by mass of carbon, 5% by mass or less of oxygen, 1% by mass or less of potassium, and the remainder being silver, characterized in that the surface layer made of silver has an average crystallite size of 25 nm or less, a Vickers hardness HV of 150 or more, and an antimony content of 0.1% by mass or less.

11. The silver-plated product according to claim 10, wherein the surface layer contains sulfur.

12. 12. The silver-plated product according to claim 10, wherein the Vickers hardness HV is 160 or more.

13. 13. The silver-plated product according to claim 10, wherein the base material is made of copper or a copper alloy.

14. 14. The silver-plated product according to claim 10, further comprising an underlayer made of nickel formed between the base material and the surface layer.

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