JP3797582B2 - Cylinder inner surface plating method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method of plating an inner surface of a cylindrical body such as a barrel of a weapon gun or a reaction cylinder, and in particular, a cylindrical body that is required to form a plating layer whose film thickness varies in the axial direction thereof. The present invention relates to a surface plating method .
[0002]
[Prior art]
In the gun barrel, a protective layer is provided on the inner surface in order to improve its life. As a protective layer in that case, it is known that a chromium layer formed by electrolysis is most suitable. Japanese Patent Application Laid-Open No. 7-167590 discloses a loading chamber that receives a large thermal load and a bore portion connected to the loading chamber in order to protect it from a thermal load in a large-bore (for example, 155 mm) gun barrel. In this region, a method of forming a thick electrolytic chromium layer having a thickness of 100 to 200 μm by plating is disclosed. In this method, an electrode having a length corresponding to the region where the electrolytic chromium layer is to be provided is disposed in the axial center of the gun barrel, the electrode and the gun barrel are immersed in a plating solution, and an electric current is passed between them. The target area on the inner surface is plated. In this case, the plating thickness is uniform.
[0003]
By the way, in the case of a gun barrel, in addition to the thermal load as described above, sliding friction with the bullet band is added, and further corrosion due to the use environment occurs. It is required to provide a protective layer over the entire inner surface. However, when a thick chromium plating film having a thickness of 100 to 200 μm is provided over the entire inner surface of the gun barrel, the plating film is often peeled and broken by a mechanical impact force in the front region on the muzzle side of the gun barrel. After that, gas escape and turbulent flow occur from the location, and the corrosion of the gun barrel and the wear of the bullet band are accelerated.
On the other hand, as a result of experiments, it has been confirmed that the resistance to peeling of the plating film increases as the film thickness decreases.
Therefore, the portion of the gun barrel that receives a particularly large thermal load, that is, the chromium layer in the loading chamber and the aperture region adjacent to the loading chamber is thick, and the chromium layer in the front region on the muzzle side that receives mechanical impact force. It is done to make it thinner.
[0004]
When forming a plating layer with a different film thickness depending on the position in the axial direction on the inner surface of a cylindrical body such as a gun barrel, conventionally, first, the entire area of the inner surface of the gun barrel is first formed using an electrode having a length corresponding to the entire length of the gun barrel. Was then thinly plated, and then the inner surface of the part was thickly plated using an electrode having a length corresponding to the part requiring a thick plating layer.
[0005]
[Problems to be solved by the invention]
However, in such a method, since it is immersed twice in the plating solution, in order to prevent other parts from being corroded by the plating solution during the initial plating, the part to be plated is used. It is necessary to cover other than with lacquer. Further, current concentrates on the boundary between the part to be plated and the part not to be plated, and the plated metal is abnormally deposited in the boundary region. Therefore, it is necessary to flatten by plating after the plating. Furthermore, since the plating layer is formed on the plating layer formed first, there is a problem that the overlapping surface often peels off.
[0006]
The present invention has been made in view of such circumstances, and its purpose is to form a cylindrical body in which a plating layer whose thickness changes in the axial direction can be formed on the inner surface of the cylindrical body by a single plating process. It is to provide a surface plating method .
[0007]
[Means for Solving the Problems]
In order to achieve this object, in the present invention, the temperature of the plating solution positioned between the inner surface of the cylindrical body, which is the object to be plated, and the outer peripheral surface of the electrode for plating disposed at the axial center thereof , Alternatively, the temperature and flow rate are changed along the axial direction, and plating is performed in that state.
In order to change the temperature of the plating solution , or the temperature and the flow velocity along the axial direction as described above, as the electrode for plating treatment, an axial flow hole through which the plating solution flows, and the flow hole A plating solution may be supplied from the outside to the flow hole of the holed electrode using a holed electrode having a radial discharge hole communicating with the outer peripheral surface. In this case, if plating solutions having different temperatures are supplied from the outside, the temperature of the plating solution on the downstream side from the discharge hole can be made different from the temperature of the plating solution on the upstream side. Further , if the plating solution supplied from the outside is pumped by a pump or the like, a flow having a high flow velocity is formed downstream of the radial discharge holes.
[0008]
[Action]
At the same current density, when the temperature of the plating solution increases, the electrodeposition rate, that is, the plating deposition rate decreases. Therefore, when the temperature of the plating solution is changed along the axial direction as described above, a plating layer whose film thickness changes in the axial direction is formed.
Further, as the current density on the plated surface increases, the electrodeposition rate also increases. The current density is known to change depending on the flow rate of the plating solution. Therefore, when the temperature and flow rate of the plating solution located between the cylindrical body that is the object to be plated and the electrode that performs the plating process on the cylindrical body are changed along the axial direction as described above, the plating process at that time the thickness of the plated layer formed on the inner surface of the cylindrical body will vary in the axial direction by.
In this way, by changing the temperature of the plating solution , or the temperature and flow rate along the axial direction, a plating layer whose thickness changes in the axial direction is formed on the inner surface of the cylindrical body by a single plating process. It becomes possible.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
In the figure, FIG. 1 is a schematic sectional view showing an example of a method for plating an inner surface of a cylindrical body according to the present invention.
As is apparent from this figure, the inner surface 2 of the cylindrical body 1 to be plated has a small diameter portion 3 on the distal end side (left end side in the figure) and a large diameter on the base end side (right end side in the figure). Each of the diameter portions 4 is provided. The small-diameter portion 3 and the large-diameter portion 4 are smoothly connected so that current does not concentrate on the portion during the plating process. The small diameter portion 3 is a portion where a thin plating layer 5 is formed on the inner surface, and the large diameter portion 4 is a portion where a thick plating layer 6 is formed on the inner surface.
[0010]
When the plating layers 5 and 6 whose thickness varies in the axial direction are formed on the inner surface 2 of the cylindrical body 1, the electrode 7 with a hole as shown in the drawing is slightly longer than the entire length of the cylindrical body 1. Is used. The electrode 7 is provided with a flow hole 8 extending in the axial direction at the center on the tip side. The length of the flow hole 8 is set to be slightly longer than the length of the portion where the thin plating layer 5 is formed, that is, the length of the small diameter portion 3 of the cylindrical body 1. The flow hole 8 communicates with the outer peripheral surface of the electrode 7 by a plurality of discharge holes 9, 9,... Formed in the radial direction at the bottom on the base end side. The discharge hole 9 is slightly inclined toward the base end side of the electrode 7.
[0011]
The holed electrode 7 thus formed is arranged at the axial center of the cylindrical body 1 such that the discharge hole 9 faces the boundary between the small diameter portion 3 and the large diameter portion 4 of the cylindrical body 1. Then, they are immersed in the plating solution in the plating tank 10. In that case, the cylindrical body 1 is degreased in advance. In addition, a pump 11 and a tank 12 with a temperature control device that stores the same plating solution as the plating solution in the plating tank 10 are provided outside the plating tank 10, and the suction port of the pump 11 and the tank 12 are connected to each other. It is connected by a pipe 13. As usual, a DC power supply 14 which is a power supply device for plating is also provided outside the plating tank 10.
[0012]
And the front-end | tip of the flow hole 8 of the electrode 7 immersed in plating solution and the discharge port of the pump 11 are connected by the pipe 15, and the pump 11 is operated. Then, the plating solution in the tank 12 is pumped to the flow hole 8 of the electrode 7 and ejected from the discharge ports 9, 9. As described above, the discharge ports 9, 9,... Are inclined toward the base end side of the cylindrical body 1. Therefore, the plating solution ejected from the discharge ports 9, 9... Flows between the inner peripheral surface of the large diameter portion 4 of the cylindrical body 1 and the outer peripheral surface of the electrode 7 toward the base end side. Thus, a plating solution flow having a high flow velocity is formed on the downstream side of the discharge hole 9 of the electrode 7. At that time, along with the flow, a flow toward the base end also occurs in the plating solution located on the small diameter portion 3 side of the cylindrical body 1, but the flow velocity is small.
[0013]
In this state, the electrode 7 is connected to the positive electrode of the DC power supply 14 via the conductive wire 16, and the cylindrical body 1 is connected to the negative electrode of the power supply 14 via the conductive wire 17, and between the electrode 7 and the cylindrical body 1. Energize to. Then, metal ions in the plating solution are deposited on the inner surface 2 of the cylindrical body 1. Accordingly, when a Sargent solution that forms the basis of a chromium plating bath, for example, is used as the plating solution, chromium ions in the plating solution are deposited, and an electrolytic chromium layer is formed on the inner surface 2 of the cylindrical body 1.
[0014]
In that case, the flow of the plating solution having a larger flow velocity than the small diameter portion 3 side is formed in the portion of the large diameter portion 4 of the cylindrical body 1 as described above. It is known that the current density when the plating solution flows is proportional to the square root of the flow velocity v in the case of laminar flow and proportional to v ^2/3 to v in the case of turbulent flow (Motoo Kawasaki). "Practical electroplating", Nikkan Kogyo Shimbun, 1980, p. 177). Therefore, the current density generated between the inner surface 2 of the cylindrical body 1 and the electrode 7 is larger in the current density in the large diameter portion 4 than in the small diameter portion 3. That is, the small diameter portion 3 of the cylindrical body 1 is plated with a small current density, and the large diameter portion 4 is plated with a large current density. As is apparent from FIG. 2, the relationship between the current density and the electrodeposition rate (plating rate) in the normal bath of chrome plating is that the plating rate increases as the current density increases at the same plating bath temperature. It is in. Therefore, due to the difference in current density, a thin plating layer 5 is formed on the inner surface of the small diameter portion 3 of the cylindrical body 1, and a thick plating layer 6 is formed on the inner surface of the large diameter portion 4.
[0015]
In this way, the plating solution is ejected from the intermediate portion of the electrode 7 using the holed electrode 7, and the flow rate of the plating solution is changed along the axial direction of the cylindrical body 1, whereby the inner surface 2 of the cylindrical body 1 is changed. The plating layers 5 and 6 having different film thicknesses can be formed by a single plating process. In this case, if the diameters of the small diameter portion 3 and the large diameter portion 4 provided on the inner surface 2 of the cylindrical body 1 are appropriately set in advance, the inner surfaces of the plating layers 5 and 6 are made to have a uniform diameter. Can do.
[0016]
Further, the temperature of the plating solution in the tank 12 is made lower than the temperature of the plating solution in the plating tank 10 using a temperature control device provided in the tank 12, and the low-temperature plating solution is discharged from the electrode 7. If it is made to discharge from the hole 9, the temperature of the plating solution located in the large diameter part 4 side of the cylindrical body 1 will become lower than the temperature of the plating solution located in the small diameter part 3 side.
As shown in FIG. 2, at the same current density, the lower the plating solution temperature, the higher the plating rate. Therefore, if the temperature of the plating solution located on the small diameter portion 3 side of the cylindrical body 1 and the temperature of the plating solution located on the large diameter portion 4 side are made different from each other as described above, the cylinder that is the portion where the plating solution temperature is high. A thin plating layer 5 is formed on the inner surface of the small-diameter portion 3 of the body 1, and a thick plating layer 6 is formed on the inner surface of the large-diameter portion 4, which is a portion having a low plating solution temperature.
[0017]
Based on such a principle, the thin plating layer 5 and the thick plating layer 6 can be formed at the same time only by making a difference in either the temperature or the flow rate of the plating solution. If the temperature of the plating solution is mainly varied, the pump 11 only needs to be able to supply the plating solution from the discharge hole 9 of the electrode 7, so that a small-sized one can be used. It can be used. However, in particular, when it is required to increase the film thickness ratio of the plating layers 5 and 6, it is desirable to make both the temperature and the flow rate of the plating solution different from each other. If the electrode 7 with a hole is used and the low temperature plating solution is pumped to the flow hole 8 of the electrode 7 by the pump 11 and ejected from the discharge holes 9, 9,. It is also easy to change both the temperature and the flow rate along the axial direction of the cylindrical body 1, and the plating layers 5 and 6 having a large thickness ratio can be formed by a single plating process.
[0018]
In the above-described embodiment, the case where the plating layers 5 and 6 whose film thickness changes in two stages in the axial direction of the cylindrical body 1 has been described. However, the electrode 7 has a plurality of flow holes 8 having different lengths. , And discharge holes 9, 9,... That communicate with the outer peripheral surface of the electrode 7 at different positions in the axial direction, respectively, so that plating solutions having different temperatures are pumped to the flow holes 8, respectively. If so, the film thickness can be changed in multiple stages.
[0019]
【The invention's effect】
As apparent from the above description, according to the present invention, it becomes possible to be formed by a single plating process the plating layer having a thickness varying in the axial direction, at the first time of plating, such as in the prior art No anticorrosion work or machining after plating is required, and the treatment work can be greatly simplified. In addition, since plating layers having different film thicknesses can be formed without overlapping the plating layers, a plating layer that is extremely resistant to peeling can be obtained.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view showing an example of a method for plating an inner surface of a cylindrical body according to the present invention.
FIG. 2 is a characteristic diagram showing the relationship between the plating solution temperature and the plating rate in accordance with the current density for explaining the principle of the plating method.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Cylindrical body 2 Cylindrical inner surface 5 Thin plating layer 6 Thick plating layer 7 Electrode with a hole 8 Flow hole 9 Discharge hole 10 Plating tank 11 Pump 12 Tank 14 with a temperature control apparatus DC power supply (power supply apparatus for plating)

Claims (4)

An electrode that extends in the axial direction of the cylindrical body is disposed at the axial center of the cylindrical body, the electrode and the cylindrical body are immersed in a plating solution, and a current is passed between the electrodes and the cylindrical body, whereby the cylinder In the method of plating the inner surface of the body;
By changing the temperature of the plating solution located between the inner surface of the cylindrical body and the outer peripheral surface of the electrode along the axial direction and performing plating in that state, the inner surface of the cylindrical body can be obtained by a single plating process. It is characterized by forming a plating layer whose film thickness changes in the axial direction.
A plating method for the inner surface of a cylindrical body. As the electrode, a holed electrode having an axial flow hole through which a plating solution flows inside and a radial discharge hole communicating with the outer peripheral surface of the flow hole is used, and the flow hole of the holed electrode from the outside By supplying a plating solution having a different temperature to the temperature, the temperature of the plating solution on the downstream side of the radial discharge hole is changed,
The method for plating an inner surface of a cylindrical body according to claim 1 . An electrode that extends in the axial direction of the cylindrical body is disposed at the axial center of the cylindrical body, the electrode and the cylindrical body are immersed in a plating solution, and a current is passed between the electrodes and the cylindrical body, whereby the cylinder In the method of plating the inner surface of the body;
In the plating solution located between the inner surface of the cylindrical body and the outer peripheral surface of the electrode, a flow in which the temperature and the flow velocity change along the axial direction is formed, and in this state, the plating process is performed. Forming a plating layer whose thickness changes in the axial direction on the inner surface of the cylindrical body,
A plating method for the inner surface of a cylindrical body. As the electrode, a holed electrode having an axial flow hole through which a plating solution flows inside and a radial discharge hole communicating with the outer peripheral surface of the flow hole is used, and the flow hole of the holed electrode from the outside The flow of the plating solution having a low temperature and a high flow rate is formed downstream of the radial discharge holes by pumping a plating solution having a low temperature to
The method for plating an inner surface of a cylindrical body according to claim 3 .

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