Electrolytic plating equipment

Abstract

To provide an apparatus capable of uniformly plating the inner surface of a metal pipe having concentric bulges. [Solution] An electroplating apparatus for plating the inner surface of a metal pipe having concentric bulges, comprising a rod-shaped anode electrode inserted into the inside of the metal pipe, the rod-shaped anode electrode being rotatable around a core, and a flexible metal tape attached to the portion of the metal pipe corresponding to the bulge, such that the middle portion floats in the axial direction of the rod, the metal tape as both sides on either side of the middle portion move closer together, causing the middle portion to float, curve and protrude to form a protrusion, the protrusion to conform to the inner surface of the bulging portion of the metal pipe, and the electroplating apparatus for plating the inner surface of the bulging metal pipe by rotating the rod-shaped anode electrode around the core while the protrusion is formed. According to the present invention, the inner surface of a metal pipe having concentric bulges can be plated with a uniform film thickness, including the bulging portion.

Description

Technical Field

[0001] The present invention relates to an electrolytic plating apparatus for plating the inner surface of a metal pipe. More specifically, it relates to an electrolytic plating apparatus for plating the inner surface of a metal pipe having a concentric swelling.

Background Art

[0002] Plating is a technique for processing a thin metal film on the surface of a product. Among them, electrolytic plating is a technique for plating a product by reducing metal ions in a solution on the surface of the product by electricity to deposit metal. Since electroplating is a technique for plating by electricity, generally, the more electricity flows, the easier it is to plate, and the more difficult it is for electricity to flow, the more difficult it is to plate. If there are places on a product where it is easy to plate and places where it is difficult to plate, it is impossible to make the film thickness of the plating uniform. In the case of a metal pipe, compared with the outer surface of the pipe, the inner surface of the pipe is difficult for electricity to reach, difficult to plate, and the film thickness of the plating is also thinner than that of the outer surface. As a method for plating the inner surface of this difficult-to-plate pipe, generally, there is a method of inserting a rod-shaped auxiliary electrode into the inner surface of the pipe to facilitate the passage of electricity. Also, as a method for plating the inner surface of a pipe that is not simply linear, there is a method of plating a metal pipe having a bent portion using a flexible auxiliary electrode that can be bent flexibly (Patent Document 1). Furthermore, as a method for plating the inner surface of a pipe, in order to prevent unevenness in the inner surface plating treatment and plating unevenness due to bubbles, methods using micro-movement, rotation of the electrode, a bubble elimination plate attached to the electrode, and a brush are known (Patent Document 2 [Detailed Description of the Invention] (C)).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

[0004] Superconducting acceleration technology is used to accelerate particle beams in elementary particle experiments and medical applications. The superconducting accelerating cavities used in this technology are shaped like metal pipes with multiple concentric bulges. To achieve a superconducting state, the inner surface of these accelerating cavities is plated with a specific metal, and the uniformity of the plating thickness is crucial. If the plating thickness is uneven, it can lead to a decrease in the performance of the cavities, so it is necessary to plate the inner surface of these specially shaped metal pipes with a uniform thickness. Therefore, the object of the present invention is to provide an apparatus for uniformly plating the inner surface of a metal pipe having concentric bulges, and a method for manufacturing a metal pipe having concentric bulges with a uniformly plated inner surface using the apparatus. [Means for solving the problem]

[0005] As a result of various studies to achieve the above objective, the inventors of the present invention have found that by attaching a metal tape that curves and protrudes along the bulge of a metal pipe to a rod-shaped anode electrode, and rotating it around the rod axis in the protruding state, the inner surface of the bulge can be plated with a uniform film thickness, and have arrived at the present invention. In other words, the present invention is as follows. 1. An electrolytic plating apparatus for plating the inner surface of a metal pipe having concentric bulges, The metal pipe is equipped with a rod-shaped anode electrode that is inserted into the inside of the pipe. The rod-shaped anode electrode is rotatable about its core, and A flexible metal tape is attached to the portion of the metal pipe corresponding to the bulge, so that the middle portion floats in the axial direction of the rod. As the sides of the metal tape on either side of the middle portion move closer together, the middle portion floats, curves, and protrudes, forming a protruding portion that conforms to the inner surface of the bulge of the metal pipe. An electroplating apparatus that, with the protruding portion formed, rotates a rod-shaped anode electrode around its core to plate the inner surface of a metal pipe having a bulge. 2. Using the electroplating apparatus described in 1 above, a rod-shaped anode electrode is rotated around its core to plate a metal pipe having concentric bulges. A method for manufacturing a metal pipe having concentric bulges, with its inner surface plated to a uniform thickness. [Effects of the Invention]

[0006] According to the electroplating apparatus of the present invention, the inner surface of a metal pipe having concentric bulges can be plated with a uniform film thickness, including the bulging portions. Furthermore, it becomes possible to provide a product in which the inner surface of a metal pipe having concentric bulges, including the bulging portions, is plated with a uniform film thickness. [Brief explanation of the drawing]

[0007] [Figure 1] A schematic cross-sectional view of the main part of the apparatus of the present invention is shown, with the anode electrode inserted into a metal pipe having concentric bulges. The filled-in area is not a cross-section but a view from the side inside the metal pipe. [Figure 2] This schematic cross-sectional view shows a metal tape curving and protruding within a metal pipe having concentric bulges, forming a protruding portion. The filled-in area is the same as in Figure 1. [Figure 3] This diagram illustrates the mechanism by which a metal tape curves and protrudes to form a protrusion. (A) shows the tape before protrusion, and (B) shows it after protrusion. The filled-in area is the same as in Figure 1. [Figure 4] This diagram schematically illustrates the masking process for the anode electrode of the present invention. The dashed lines indicate where the cutouts for measuring the plating thickness correspond to the raised and non-raised portions of the plate. The numbers on the dashed lines correspond to the numbers in the photographs and graphs in Figures 6-8. [Figure 5] An example of the overall configuration of the apparatus of the present invention is shown. [Figure 6]The position where a sample for measuring the plating film thickness was drilled out and the state of the drilled-out sample are shown. The broken lines and numbers are the same as in Fig. 4. [Figure 7] The film thickness distribution when plating was performed without forming protrusions and without masking was shown. [Figure 8] The film thickness distribution when plating was performed by the apparatus of the present invention was shown.

Embodiments for Carrying Out the Invention

[0008] Hereinafter, the present invention will be described in detail with reference to the drawings, but the present invention is not limited to the electrolytic plating apparatus described in these drawings.

[0009] 1. Regarding the electrolytic plating apparatus of the present invention The electrolytic plating apparatus of the present invention is an electrolytic plating apparatus for plating the inner surface of a metal pipe (1 in Fig. 1) having a concentric swelling.

[0010] (1) Regarding the concentric swelling of the metal pipe to be plated The concentric swelling (2 in Fig. 1) is a swelling in which concentric circles having a circumference larger than that of the metal pipe are continuously formed in the axial direction with the central axis of the metal pipe as the center. Typically, the circumference of the concentric circles gradually increases from the circumference of the pipe, becomes maximum in the middle, and then gradually decreases to return to the circumference of the pipe. Of course, the inside of the swelling is a cavity. The number of concentric swellings (2) is not limited to one, and in the case of a plurality, it is also an object of plating by the apparatus of the present invention. The metal pipe having a plurality of such swellings is, for example, a superconducting acceleration cavity used in superconducting acceleration technology when performing elementary particle experiments, and an acceleration cavity of a linear collider. Note that 5 in Fig. 1 is a flange for connecting metal pipes having concentric swellings.

[0011] (2) Regarding the metal tape attached to the rod-shaped anode electrode The electroplating apparatus of the present invention includes a rod-shaped anode electrode (3 in FIG. 1) that is inserted into a pipe, similar to an apparatus for plating the inner surface of a normal pipe. A flexible metal tape (4) is attached to this rod-shaped anode electrode in the axial direction of the rod. This tape equalizes the current distribution on the inner surface of the bulging part of the metal pipe and electroplates with a uniform film thickness. This metal tape is attached to the portion corresponding to the bulge of the metal pipe with the anode electrode inserted (4 in FIG. 1). For example, when the bulge of the metal pipe is in the middle of the metal pipe, it is attached in the middle; when it is on the upper side, it is attached on the upper side; when it is on the lower side, it is attached on the lower side, in accordance with the position of the bulge. Although it is conceivable that there may be a plurality of metal tapes attached around the rod axis of the anode electrode, it is more preferable that there is one around the rod axis. If there are a plurality, the current distribution may become unbalanced when the anode electrode is rotated. Also, when there are a plurality of bulges on the metal pipe to be plated, a plurality of metal tapes are attached in order in the rod axis direction in accordance with the number and position.

[0012] This metal tape is attached to the rod-shaped anode electrode so that the middle part floats (4 in FIG. 1, 4 in FIG. 3(A)), and by bringing the two sides sandwiching the middle part closer, it has a bending mechanism that forms a protruding part while the middle part floats and curves (4 in FIG. 2, 4 in FIG. 3(B)), and becomes a shape along the inner surface of the bulge of the metal pipe. The shape along the inner surface of the bulging part of the metal pipe means that the metal tape has a shape along the cross-section of the bulge, and the distance between the curved and protruding metal tape and the bulging part facing it, that is, the interelectrode distance, is substantially constant (FIG. 2). It is more preferable to individually adjust the length of the metal tape so that it fits the size of the bulge when it is curved and protruding. Note that the inserted anode electrode is used as the main electrode, but when there is a separate main electrode for plating the outer surface of the pipe, it is not excluded from being used as an auxiliary electrode.

[0013] The anode electrode of the present invention may be a rod-shaped anode electrode that is extendable and retractable, for example, composed of two rods, rod 1 and rod 2, with different diameters, and rod 2 being housed in rod 1. For example, in Figure 3, rod 1 (11) is cylindrical, and its tip portion 18 is trough-shaped with a circular arc cross-section with a portion of the top cut off, and rod 2 (12) moves inside, causing the rod-shaped anode electrode to extend and retract. The middle portion of a metal tape is fixed to both rods 1 and 2 of this extendable anode electrode with rivets or screws (13, 14), respectively. When the anode electrode is retracted, both sides of the metal tape move closer together, and the middle portion curves and protrudes, forming a protrusion (Figure 3(A)→(B)). When extended, the protrusion is eliminated (Figure 3(B)→(A)).

[0014] Furthermore, for example, when fixing one end of a metal tape with the middle section in between (13 in Figure 3) and allowing the other end (14) to move, and forming a protrusion by bringing the other end closer to the other, a stopper (15) can be provided to press down from above to prevent the other metal tape from protruding at a fixed distance from the fixed end, so that the length of the base of the curved protrusion remains constant while adjusting the height. In this way, when the other end is brought closer to the other, the length of the base remains constant at the fixed distance, while the height of the protrusion can be adjusted.

[0015] There are no particular restrictions on the width of the metal tape, but it is more preferable if it is about 1 / 3 to 1 / 2 the diameter of the rod-shaped electrode in the portion corresponding to the bulge. The material is not particularly restricted as long as it is insoluble in the plating solution and can be used as an anode electrode. Examples include stainless steel and platinum.

[0016] (3) Regarding the rotatability of the anode electrode The anode electrode of the present invention is designed to rotate around a rod shaft as its central axis. As the anode electrode rotates, the curved and protruding portion rotates along the inner surface of the concentric bulge of the metal pipe, allowing the inner surface of the bulge to be plated with a uniform film thickness.

[0017] (4) Reasons why plating can be done with a uniform film thickness. A current distribution occurs on the surface of an object being electroplated. More current flows near the anode electrode, and less current flows further away. The higher the current distribution, the thicker the plating. Therefore, to achieve a uniform plating thickness, it is best to keep the inter-electrode distance between each point on the object being plated (the cathode electrode) and the anode electrode as constant as possible.

[0018] A typical electroplating apparatus for plating the inner surface of a pipe inserts the anode electrode into the pipe and passes an electric current through the pipe's inner surface, which is difficult to conduct current through. This causes metal to be deposited on the inner surface of the metal pipe acting as the cathode electrode, thereby plating the inner surface of the metal pipe.

[0019] In this invention, the rod-shaped anode electrode of the electroplating apparatus is inserted to the appropriate position, causing the metal tape to bend and protrude. At this time, the distance between the protruding portion of the bent metal tape and the opposing bulge remains approximately constant regardless of the point where the opposing bulge is located (Figure 2). Furthermore, the rod-shaped anode electrode is designed to rotate around its core, and this rotation causes the metal tape to approach every point on the inner surface of the bulging portion of the metal pipe at the same frequency and distance, thus achieving a state where the inter-electrode distances are equal. This ensures a constant current distribution on the inner surface of the bulge, allowing for uniform plating thickness on the inner surface of the bulge.

[0020] (5) Masking of the anode electrode The anode electrode should not be left exposed; an appropriate area should be masked with an insulator. The electrode portion corresponding to the bulge of the anode electrode is masked with an insulator so as not to interfere with the formation of the current distribution by the metal tape (Figures 4-3 to 4-5). The electrode portion corresponding to the non-bulging portion is also masked, but the position and extent of holes to be made in the masking are determined by experimental testing using conventional methods to ensure that the plating thickness is similar to that of the bulging portion, and holes (for example, the light gray rectangles in Figures 4-16 and 4-17) are made accordingly. According to the study, by partially creating holes in the masking, the inner surface of the non-bulging areas can be plated to the same thickness as the inner surface of the bulging areas. Because the anode electrode rotates and the plating solution is agitated by the metal tape, a uniform film thickness can be achieved by only partially creating holes.

[0021] (6) Regarding the application of the plating method using the electrolytic plating apparatus of the present invention The plating apparatus of the present invention can be used, for example, for tin plating and copper plating. Furthermore, it can also be used for plating niobium-tin, which exhibits superconductivity, using the bronzing process, that is, a series of plating processes in which a niobium substrate is copper-plated, then tin-plated on top of that, and finally copper-plated, followed by heat treatment.

[0022] (7) Overall configuration of the electroplating apparatus of the present invention The apparatus of the present invention is more preferably equipped with a system for circulating the plating solution inside the metal pipe, in addition to the cathode electrode. For example, a plating solution recovery tank (24 in Figure 5) is provided to recover the plating solution overflowing from the metal pipe, and a flow path is constructed to return it to the inside of the metal pipe via a pipe (23) and a pump (21), thereby circulating the plating solution. It is also more preferable to provide a device for measuring the flow rate of the circulating plating solution, and a water temperature sensor and heater for maintaining a constant water temperature. Note that a plating tank is not necessarily required when plating only the inner surface of a metal pipe, but a plating tank is required when plating the outer surface of the metal pipe as well. In that case, a plating solution recovery tank can be used as the plating tank.

[0023] (8) Electroplating using the apparatus of the present invention For pretreatment of metal pipes, common methods can be used to ensure the plating anchors to the surface. For example, cleaning with an alkaline solution, electrolytic degreasing, or acid treatment may be performed. Furthermore, to further improve the adhesion of the plating, blast treatment may be performed, followed by removal of the blast material with ammonium fluoride + nitric acid solution, and then alkaline cleaning with sodium hydroxide. When plating Nb cavities, such pretreatment is more preferable. The main plating process involves inserting a rod-shaped anode electrode into a metal pipe with a bulge, with the metal tape not touching on either side of the middle section, i.e., the metal tape not protruding. Inside the metal pipe, the sides of the metal tape are brought closer together to form a curved protrusion along the bulge (see Figures 1 and 2). It is more preferable to use an acidic plating solution. When performing an acidic tin plating bath, a sulfuric acid bath or a sulfonic acid bath is more preferable, a sulfonic acid bath is even more preferable, and an alkane sulfonic acid bath is particularly preferable. A rod-shaped anode electrode is rotated together with a curved projection made of metal tape, and an electric current is passed through it to plate the inner surface of a metal pipe having concentric bulges. A uniform current distribution ensures that the inner surface is plated with a uniform film thickness. The rotation speed at this time is 40-50 rpm, and the current density is 0.5-1.5 / dm². 2 The electrode distance is more preferably 5 to 20 mm. The time is more preferably 8 to 15 minutes. When plating niobium-tin using the bronzing method, it is more preferable to plate copper, tin, and copper in that order for 10 to 15 minutes, 8 to 13 minutes, and 10 to 15 minutes. Furthermore, the rate at which the plating solution is circulated is more preferably 4 to 6 L / min, and the plating temperature is more preferably 50 to 60°C for copper plating and 35 to 45°C for tin plating. Furthermore, post-treatment is preferable and should be carried out according to conventional methods. For example, multiple rinses with water may be performed.

[0024] (9) Products manufactured using the apparatus of the present invention The plating apparatus of the present invention can produce metal pipes with concentric bulges plated to a uniform film thickness; however, when we say "uniform film thickness," we do not require perfect uniformity. It is more preferable if the difference between the thickest and thinnest parts is 5 μm or less, and even more preferable if it is 2 μm or less. [Examples]

[0025] Example 1: Electrolytic plating apparatus of the present invention Figure 5 shows an example of the overall configuration of the electroplating apparatus of the present invention. It comprises a rod-shaped anode electrode (3) that can be inserted into a metal pipe (1) having concentric bulges. The rod-shaped anode electrode is installed so as to be rotatable around its axis. Rotation is performed by a motor (22). The metal tape (4) attached to the anode electrode curves and protrudes to form a protruding portion, which conforms to the shape of the bulge. The anode electrode is covered with masking tape that provides insulation, but the upper non-bulging portion has four square-shaped holes, the middle bulging portion has no holes, and the lower bulging portion has four rectangular-shaped holes (Figure 4). Furthermore, a flow path for circulating the plating solution is constructed. The plating solution is supplied from the bottom of the metal pipe (1) by a pump (21 in Figure 5), overflows from the top of the pipe, and spills into the plating solution recovery tank. This is then collected through a pipe (23) and returned to the pump 21. Furthermore, it is equipped with a heating heater 25 to maintain a constant temperature of the plating solution, a temperature control heater 26, a cock 27 to adjust the flow rate, a flow sensor 28 to measure the flow rate, and a plating solution discharge unit 29 for discharging the plating solution.

[0026] Example 2 Plating of Sn onto an iron accelerating cavity using the electrolytic plating apparatus of the present invention (1) This apparatus was tested to determine whether it could plate the inner surface of an accelerating cavity (corresponding to a metal pipe with concentric bulges, the same applies hereinafter) with a uniform film thickness by performing tin plating on an iron accelerating cavity (hereinafter referred to as Fe cavity or cavity). (2) Experimental materials and experimental methods Sn plating on Fe cavities was performed using the apparatus of Example 1. Pretreatment consisted of immersion cleaning with an alkaline solution, followed by electrolytic degreasing, and then activation with diluted hydrochloric acid. Sn plating was performed using an alkane sulfonic acid bath, with a target film thickness of 5 μm. First, for comparison, we used an anode electrode without a bending mechanism and without masking the electrode, at 3.40A (current density of 1.0A / dm²). 2The Fe cavity was plated by applying an electric current for 10.5 minutes. Afterwards, the device was rotated at 46 rpm with a protruding section formed using a bending mechanism, and under the same conditions as above, the current was applied and the masking of the electrodes was adjusted while creating several prototypes, until the final masking shape was determined as shown in Figure 4. Of the several cavities plated as prototypes, the film thickness distribution of the cavities was compared between the first one plated without the bending mechanism and without masking (comparative experiment example) and the last one plated with the bending mechanism and with masking (experiment example). The plating solution was circulated at a flow rate of 6.0 L / min and at a temperature of 40°C. As a post-treatment after plating, the surface was rinsed three times with room temperature water, hot water at approximately 60°C, and filtered water at room temperature. (3) Results The film thickness on the inner surface of the cavity was measured by X-ray fluorescence analysis after drilling holes in the cavity wall at positions 1-7 in Figure 6 using a screwdriver fitted with a hole saw. Figure 7 shows the film thickness distribution in a comparative experiment, and Figure 8 shows the film thickness distribution in the experimental example. In the experimental example, it was found that the film thickness range was within 1 μm, and by comparing these graphs, it was confirmed that the film thickness distribution was improved by the bending mechanism and masking of the electrodes. (4) Summary and Discussion To improve the film thickness distribution, Sn plating was performed on Fe cavities. During plating, the use of a bending mechanism and electrode masking were confirmed to improve the film thickness distribution. Since the superconducting accelerating cavities are made of niobium (Nb), the conditions obtained here can be similarly applied to plating Nb cavities. [Industrial applicability]

[0027] According to the present invention, a metal pipe-shaped accelerating cavity with concentric bulges can be plated with a uniform film thickness on its inner surface, providing a high-performance accelerating cavity. This can contribute to elementary particle experiments and the medical field, and is useful for the plating industry and the medical device industry that supply these products. [Explanation of Symbols]

[0028] 1. A metal pipe with concentric bulges (accelerating cavity) 2. Concentric bulges 3 Anode electrodes 4 Metal tape 5. Connecting flange 11 1 rod 12 2 rods 13 Fixing part 1 14 Fixing part 2 15 Stopper 16, 17 Masking holes 18 The tip of the rod 21 pumps 22 motors 23 tube 24 Plating solution recovery tank, or plating tank 25 Heating heater 26 Temperature-controlled heater 27 Temperature sensor 28 Cook 29 Plating solution discharge section

Claims

1. An electrolytic plating apparatus for plating the inner surface of a metal pipe having concentric bulges, The metal pipe is equipped with a rod-shaped anode electrode that is inserted into the inside of the pipe. The rod-shaped anode electrode is rotatable about its core, and A flexible metal tape is attached to the portion of the metal pipe corresponding to the bulge, so that the middle portion floats in the axial direction of the rod. As the sides of the metal tape on either side of the middle portion move closer together, the middle portion floats, curves, and protrudes, forming a protruding portion that conforms to the inner surface of the bulge of the metal pipe. An electroplating apparatus that, with the protruding portion formed, rotates a rod-shaped anode electrode around its core to plate the inner surface of a metal pipe having a bulge.

2. According to the electroplating apparatus of claim 1, a rod-shaped anode electrode is rotated around its core while a protrusion is formed, and a metal pipe having concentric bulges is plated. A method for manufacturing a metal pipe having concentric bulges, with its inner surface plated to a uniform thickness.

Images