JP2005206904A - METHOD OF PRODUCING Ni-W ALLOY FILM - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an Ni-W alloy film which is utilizable for wide applications owing to its excellent bending properties while maintaining the characteristics of an Ni-W alloy of high hardness as well as heat resistance, corrosion resistance and wear resistance. <P>SOLUTION: The Ni-W alloy film is obtained by dipping a metal whose surface is polished so as to be finished into a specular shape as a cathode into an electrolytic bath prepared by adding 0.05 to 0.15 mol/L of nickel sulfate and 0.2 to 0.4 mol/L of sodium tungstate, and performing electrolysis treatment under the condition satisfying a cathode current density of 5 to 15 A/dm<SP>2</SP>while keeping the electrolytic bath temperature at 50 to 70°C, thus forming an Ni-W alloy plating film on the surface of the cathode metal, and thereafter peeling the obtained plating film from the cathode metal. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for producing a Ni-W alloy coating by electroplating, and more specifically, so-called compressive stress, tensile stress, etc., while maintaining the characteristics of a Ni-W alloy having high hardness and excellent wear resistance. The present invention relates to a method for producing a high-strength Ni—W alloy film having a small plating stress and excellent bending characteristics.

Ni-W alloy plating film has high hardness and excellent corrosion resistance, heat resistance and wear resistance, so in glass molds, continuous casting molds and various equipment, plating is mainly applied to the parts that receive mechanical wear. Is used by. As a conventional Ni-W alloy plating method, a Holt method using citric acid as an organic complexing agent and a Brenner method using tartaric acid as an organic complexing agent are known. Since the pH was around 9, there was a problem that intense ammonia odor was generated and the working environment was remarkably deteriorated. In order to avoid this, a cathode current density of 10 A / liter was used using an electrolytic bath containing sodium tungstate, nickel sulfate and citric acid, which was adjusted with ammonia so that the ammonia odor was not generated, that is, pH was 7 or less. A method of applying Ni—W plating while maintaining dm ² and the bath temperature at 70 ° C. has also been proposed. However, when plating on an industrial scale, maintaining the bath temperature at 70 ° C. is extremely difficult in terms of heating capacity, especially when there are factories in winter and cold regions, and tungsten of Ni—W alloy plating. Along with the sodium tungstate used as a source, it was inevitable that the cost would be a heavy burden. Moreover, in the said prior art, since the pit was produced in the plating film and the electrodeposition tensile stress was high, there existed a problem that a crack would arise if a film thickness was formed in 30 micrometers or more.

Therefore, 25.0 to 38.5 g / L of a first ion generating material that generates tungstate ions and alkali metal ions at the time of dissolution, 10.0 to 20.0 g / L of nickel sulfate, and a second material that generates citrate ions at the time of dissolution. An electrolytic bath containing 30.0 to 50.2 g / L of an ion generating material and having a pH adjusted to 6.0 to 7.0 was used. The electrolytic bath temperature was 60 to 65 ° C., and the cathode current density was 3 to 3. A method of forming a Ni—W alloy plating film having a W content of 44 wt% or more under the condition of 7 A / dm ² is disclosed (for example, see Patent Document 1), and the bath temperature of the electrolytic cell is suppressed to 65 ° C., By using low-concentration sodium tungstate as a source of tungsten ions, the cost can be reduced, and the electrodeposition stress can be reduced to obtain a thick Ni-W alloy plating with uniform electrodeposition. Report It has been tell.

Further, it contains nickel sulfamate, a tungsten compound and citric acid, the total value of nickel molar concentration and tungsten molar concentration (Ni + W) is 0.1 to 0.4 mol / L, tungsten molar fraction {W / (W + Ni)} is 0.35 to 0.8, the molar concentration of the citric acid is equal to or higher than the total value of the molar concentrations of nickel and tungsten, and the pH is adjusted to 6 to 7, A method of applying Ni—W alloy plating to a material to be plated under the condition of heating to 80 ° C. and a cathode current density of 3 to 30 A / dm ² is disclosed (for example, refer to Patent Document 2). Nickel sulfamate is used as the source, and the total molar concentration of nickel and tungsten, the molar fraction of tungsten, the molar concentration of citric acid and the pH are defined within a predetermined range. Thus, it is reported that a so-called plating stress such as a tensile stress can be lowered to form a Ni—W alloy plating film that can avoid the generation of cracks even when the thermal load is repeated.

  Further, in a continuous casting mold comprising a pair of long-side mold copper plates arranged in parallel and a pair of short-side mold copper plates arranged therebetween, the inside of the long-side mold copper plate and / or the short-side mold copper plate Disclosed is a continuous casting mold (see, for example, Patent Document 3) in which a Ni—W alloy plating containing 20 to 50% by weight of tungsten is formed on the entire surface of the lower part or the inner side. Even in a corrosive environment, the mold copper plate wear and corrosion and corrosion wear are reduced, and no seizure with the slab occurs. Therefore, it is possible to provide a continuous casting mold that can be suitably used in molten steel continuous casting equipment. It has been reported.

  According to each of the above conventional techniques, excellent results have been reported as methods for forming a Ni—W alloy plating film on a base material, and many of them have been put to practical use. However, the coating film obtained is excellent in heat resistance and corrosion resistance and has high hardness, but on the other hand, it has poor spreadability and bending characteristics, so its use is mainly for molds and members that are susceptible to mechanical wear as described above. However, it is currently limited to the surface coating of the base metal.

However, recently, it is an alloy containing 15 to 30 mol% of tungsten or molybdenum and the balance being nickel or cobalt, and has a Vickers hardness of 500 DPN or more by limiting the hydrogen content to 5 mol% or less. And a nickel-based or cobalt-based electrodeposited alloy having a high elastic deformability having a strain amount of 0.01 or more in the anti-bending test and having a high plastic deformability that does not break even at a strain amount of 1.0 The cathode plate was developed by immersing a platinum anode plate and a copper cathode plate in an electrolytic aqueous solution consisting of nickel sulfate, sodium tungstate, sodium citrate, ammonium chloride and sodium bromide. It is disclosed that Ni-W alloy is electrolytically deposited on the top. In addition, the alloy is used as an electrode for microarray connectors to ensure the mechanical and chemical stability of the contact sliding surface, and high elastic and high plastic deformability with low contact electrical resistance due to sufficient contact pressure and long without breakage. The lifetime is guaranteed (see, for example, Patent Document 4).
JP-A-4-365890 (pages 1-6, FIGS. 1-2) Japanese Patent Laid-Open No. 7-310196 (pages 1-6, FIGS. 1-4) Japanese Patent Laid-Open No. 2001-212651 (pages 1 to 12, FIGS. 1 to 12) Japanese Patent Laid-Open No. 11-269587 (pages 1-8, FIGS. 1-7)

  Thus, a Ni-W alloy film having excellent bending characteristics is obtained by forming a deposited layer on a base metal used as a cathode to a predetermined thickness and then physically peeling the base metal from the alloy film. Can do. In addition, a method in which an easily soluble metal is used for the base metal and the base metal is dissolved and removed after formation of the Ni-W alloy film is preferably employed. As a result, a new problem arises in that the bending characteristics of the substrate are greatly affected by the morphology of the underlying metal surface. That is, when scratches such as rolling streaks remain in the base metal, the obtained Ni-W alloy plating film has excellent bending characteristics when the film is bent perpendicularly to the scratch direction. Can be bent 180 degrees, but there remains an unsolved problem that cracking easily occurs when bent parallel to the scratch direction. The present invention is not limited to continuous casting molds and glass molds by solving such problems, and Ni-W alloy coatings used in a wide range of applications as microstructures and long-life surface coating materials, that is, high hardness and corrosion resistance. High-strength Ni-W alloy film with excellent bending characteristics that has high elastic deformation ability and high plastic deformation ability in addition to the unique function of Ni-W alloy, which is excellent in heat resistance and wear resistance, at a relatively low cost It is intended to provide.

The present invention that solves the above-mentioned problems is a method for producing a high-strength Ni—W alloy film having excellent bending characteristics by electroplating, and includes nickel sulfate 0.05 to 0.15 mol / L and sodium tungstate 0.2 In the electrolytic bath prepared by adding ~ 0.4 mol / L, a metal whose surface was polished and mirror finished was immersed as a cathode, and while maintaining the electrolytic bath temperature at 50 to 70 ° C, the cathode current by electrolysis treatment under the conditions of a density 5~15A / dm ^2, after forming the Ni-W alloy plating film on the cathode metal surface, characteristic configuration to peel the plating film obtained from the cathode metal The gist of the manufacturing method of the required Ni-W alloy coating.

  The present invention also provides a preferred embodiment of a method for producing a Ni-W alloy coating, wherein the cathode metal is copper or a copper alloy plate.

The present invention further provides a preferred embodiment of a method for producing a Ni-W alloy coating, wherein the electrolytic bath temperature is 55 to 65 ° C. and the cathode current density is 5 to 10 A / dm ² .

  The method for producing a Ni—W alloy coating by the electroplating method according to the present invention is to finish a mirror surface by polishing the surface of a base metal serving as a cathode, and deposit a Ni—W alloy by electrolysis on the surface of the mirror metal. Then, after forming a plating film with a predetermined thickness, the plating film is peeled off from the base metal serving as the cathode, whereby a desired Ni—W alloy film can be obtained. The obtained alloy film has high hardness, heat resistance, abrasion resistance, corrosion resistance, etc., and has a characteristic unique to Ni-W alloys, regardless of the position and direction of bending of the film. In the bending test from all directions, it was confirmed to have excellent bending characteristics. Further, the peeling means from the base metal is not limited. However, when the method of dissolving and removing the base metal is used, there is no possibility of leaving a processing scratch on the formed film at the time of peeling, and higher quality is guaranteed. Thereby, it is possible to provide a Ni—W alloy coating that can be used for a wide range of applications as a microstructure or a long-life surface coating material, without being limited to wear-resistant members such as glass molds and continuous casting molds.

Hereinafter, the embodiment of the present invention will be described more specifically based on examples and the like. However, the present invention is not limited thereto, and can be freely modified within the scope of the gist of the present invention. .
FIG. 1 is a side view schematically showing a test jig used for confirming the bending characteristics of a Ni—W alloy coating obtained by the present invention and the state of a sample Ni—W alloy.

  The high-strength Ni—W alloy coating according to the present invention can be obtained by employing a conventionally known electroplating method, but the electrolytic bath solution used (hereinafter sometimes simply referred to as “electrolytic bath”). Prepared by adding 0.05 to 0.15 mol / L of nickel sulfate and 0.2 to 0.4 mol / L of sodium tungstate in a solution containing sodium citrate, ammonium sulfate and sodium laurate in advance. . At this time, sodium citrate is arbitrarily selected from the total of Ni ions and tungsten ions, and the concentration of ammonium sulfate in the solution is arbitrary within the range of 40% in the upper and lower limits centering on 0.5 mol / L, and sodium laurate is 0 It is optional in the range of 1 to 1.0 g / L. Here, sodium citrate acts as a metal ion complexing agent, and ammonium sulfate acts as a conductivity enhancing component of the bath. Sodium laurate is a pit inhibitor.

In the electrolytic bath, nickel sulfate as a source of nickel ions (Ni ²⁺ ) is added in a range of 0.05 to 0.15 mol / L, preferably 0.06 to 0.12 mol / L. If the lower limit is less than the lower limit, proper electroplating does not proceed and component adjustment is required during electrolysis, and the efficiency drops significantly.If the upper limit is exceeded, the electrodeposition stress of the coating increases and bending Characteristics are degraded. In addition, sodium tungstate serving as a supply source of tungstate ion (WO ₄ ²⁻ ) is added in a range of 0.2 to 0.4 mol / L, preferably 0.25 to 0.35 mol / L. When sodium acid salt is less than the lower limit, the bending properties of the coating are lowered, and when the upper limit is exceeded, the electrodeposition stress of the coating increases and expensive raw materials are consumed unnecessarily, leading to an increase in cost.

  In the present invention, the Ni—W alloy film is formed by depositing and forming on the cathode serving as the base metal by electroplating, but the base metal serving as the cathode is polished in advance to a mirror surface state. It is a requirement to leave. As the polishing means, in addition to mechanical means such as buffing, a chemical polishing method for obtaining a smooth glossy surface by immersing the metal surface in a predetermined solution for a short time is preferably employed. The base metal is not particularly limited as long as it is a metal that can be finished in a mirror state by the above means, but in the present invention, a copper or copper alloy plate is preferably employed. Since the surface of the copper or copper alloy plate can be mirror-finished easily by the above-described chemical polishing method as well as buffing, even a fine flaw can be completely smoothed.

  One anode material employs a Pt / Ti clad material in the present invention as a metal that can withstand a corrosive solution in an electrolytic bath. If it is a corrosion-resistant metal, it will not prevent it from being used.

The electrolysis conditions in the present invention are such that the bath temperature of the electrolytic bath is 50 to 70 ° C., preferably 55 to 65 ° C., and the cathode current density is 5 to 15 A / dm ² , preferably 5 to 10 A / dm ² . It prescribes. When the bath temperature of the electrolytic bath is 50 ° C. or lower, efficient electrolysis does not proceed, and maintaining a bath temperature exceeding 70 ° C. requires an excessive heating device for the bathtub, and the cost burden is large. Become. In addition, when the cathode current density is 5 A / dm ² or less, appropriate electrolytic deposition does not proceed. When the cathode current density is 15 A / dm ² or more, the current efficiency is reduced and power consumption is wasted, and deposition occurs on the cathode surface. There is a concern that it may adversely affect the crystal particle composition of the Ni—W alloy coating and inhibit the formation of a plating coating having high hardness and excellent bending properties. Therefore, in order to efficiently produce a Ni-W alloy film in a healthy state, it is desirable that the bath temperature and the cathode current density of the electrolytic bath are correctly controlled within a predetermined range.

  The Ni—W alloy plating film formed by depositing on the base metal to be the cathode as described above, specifically, the mirror-finished copper plate, is peeled off from the base metal and the Ni—W alloy according to the present invention. Form a film. The method of peeling from the base metal is arbitrary, but in the present invention, a method of dissolving and removing the base metal using a copper solution is preferably employed. Although it does not restrict | limit especially as a melt | dissolution solution, For example, the mixed solution of ammonium persulfate 100g / L and sulfuric acid 20ml / L etc. are used. Since the peeling means from the base metal is dissolution and removal by a chemical method, unlike the method of physically peeling off, the possibility of leaving a processing scratch on the alloy coating is avoided.

[Example 1]
Plating by adding nickel sulfate 0.08 mol / L and sodium tungstate 0.32 mol / L into a solution consisting of sodium citrate 0.5 mol / L, ammonium sulfate 0.5 mol / L and sodium lauryl sulfate 0.5 g / L A 0.3 mm thick rolled copper plate whose surface was processed into a mirror surface by buffing as a base metal to be a cathode and a Pt / Ti clad material as an anode metal were immersed in an electrolytic bath prepared with a liquid composition. Electroplating was performed under the condition of a cathode current density of 10 A / dm ² while maintaining the bath temperature at 60 ° C., and a 20 μm thick Ni—W alloy plating film was formed on the surface of the base metal. Next, in order to peel off the generated Ni—W alloy plating film from the base metal taken out from the bath, a copper solution prepared with a composition of ammonium persulfate 100 g / L and sulfuric acid 20 ml / L is used as the base metal. The copper plate was dissolved and removed to obtain a 20 μm thick Ni—W alloy coating. It was confirmed that the obtained Ni—W alloy film had excellent gloss without appearance and no pits or processing flaws. In addition, in order to confirm the influence of the rolling reinforcement of the copper plate which is a base metal, the adhesion bending test to each direction was done by the method shown in FIG. The spacing between the test jigs 1 was gradually reduced, and the bending deformation rate was determined using Equation 1 from the spacing when the coating broke. The close contact bending is shown when 2R = 2T.
[Formula 1]
Bending deformation rate = T / (2R-T)
Table 2 shows the test results obtained for T: sample film thickness and R: radius of curvature of the outer periphery of the sample.

[Examples 2 to 4]
Except for changing the plating solution composition and plating conditions of the electrolytic bath as shown in Table 1 below, an NI-W alloy film was produced in the same manner as in Example 1, and the conditions for peeling from the base metal were as in Example 1. Similarly, a Ni—W alloy film was obtained. It was confirmed that the obtained Ni—W alloy film had excellent gloss without appearance and no pits or processing flaws. In addition, the adhesion bending test was implemented similarly to Example 1 about this obtained alloy film. The test results obtained are as shown in Table 2.

[Comparative Example 1]
A Ni—W alloy film having a thickness of 20 μm was obtained in the same manner as in Example 1 except that buffing was not performed, and a copper plate with the rolling streaks remaining on the surface was used as the base copper foil. Fine streaks in which rolling streaks were transferred on the appearance were confirmed on the obtained alloy coating. An adhesion bending test was performed on the obtained alloy coating in the same manner as in Example 1. The test results obtained are as shown in Table 2.

[Comparative Example 2]
After roughening the surface of the rolled copper foil by chemical polishing, a Ni—W alloy plating film having a thickness of 20 μm was obtained in the same manner as in the example. It was confirmed that the obtained alloy film had irregularities affected by the base metal in appearance and was inferior in gloss. An adhesion bending test was performed on the obtained alloy coating in the same manner as in Example 1. The results obtained are as shown in Table 2.

    As is clear from the examples and comparative examples, the Ni-W alloy coating obtained by the present invention has high hardness and performance unique to the Ni-W alloy in heat resistance, wear resistance, corrosion resistance, and the like. Of course, it was confirmed that the film has excellent folding characteristics in bending tests from any direction regardless of the folding position and the folding direction of the coating. Further, the peeling means from the base metal according to the present invention employs a method of dissolving and removing the base metal by chemical means, and therefore, unlike the physical peeling method, there is a possibility that processing scratches may remain on the formed film. And high quality is guaranteed. By using the present invention, it becomes possible to produce high-quality coatings at low cost, so it is not limited to wear-resistant members such as glass molds and continuous casting molds, but it can be used for a wide range of applications as microstructures and long-life surface coating materials. It is expected as a highly reliable Ni-W alloy coating that can be used for

It is a side view for demonstrating the state of the test jig | tool used in order to confirm the bending characteristic of the Ni-W alloy film obtained by this invention, and the sample Ni-W alloy.

Explanation of symbols

1 Test jig 2 Test piece (Ni-W alloy coating)

Claims (3)

In a method for producing a high-strength Ni—W alloy film having excellent bending properties by electroplating, nickel sulfate 0.05 to 0.15 mol / L and sodium tungstate 0.2 to 0.4 mol / L are added. A metal whose surface was polished to a mirror finish was dipped in the electrolytic bath prepared as a cathode, and the electrolytic bath temperature was maintained at 50 to 70 ° C., while the cathode current density was 5 to 15 A / dm ² . A method for producing a Ni-W alloy film, comprising forming a Ni-W alloy plating film on the surface of the cathode metal by electrolytic treatment in step 1 and then peeling the obtained plating film from the cathode metal. The method for producing a Ni-W alloy coating according to claim 1, wherein the cathode metal is copper or a copper alloy plate. ^{2. The} method for producing a Ni—W alloy coating according to claim 1, wherein the electrolytic bath temperature is 55 to 65 ° C. and the cathode current density is 5 to 10 A / dm ² .

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