JPS61236426A - Electrochemically polishing method and its device for inside metal pipe - Google Patents

Abstract

PURPOSE:To electrochemically polish inside a long scaled metal pipe to predetermined surface roughness, by supporting an electrode to be moved holding a space with an internal wall by supporters in the metal pipe and circulating an electrolyte to flow in the metal pipe. CONSTITUTION:A device, providing blocking members, 2, 3 in both ends of a metal pipe 1 being a work to be polished, inserts an electrode 4 penetrating through the both blocking members 2, 3. Said electrode 4, being supported by supporters 5, 6 in the metal pipe 1, holds a distance between the electrode and a pipe wall. The blocking member 2, providing in its central part a hole 10 for the electrode 4 to pass through, is sealed by providing an O ring 11 in said hole 10. The device, providing a packing 12 in the surface of a recessed part inside the blocking member 2, seals an end surface of the metal pipe 1. An elctrolyte L, being fed from a supply path 14 via a ring groove 13, is supplied in a dispersed condition from a jetting port 15 into the metal pipe 1. The different blocking member 3, being also constituted similarly to the blocking member 2, provides many discharge ports 22.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention provides a method for efficiently electrolytically polishing the inner wall surface of a metal tube, particularly a long metal tube, and an apparatus used therefor.

[Prior art]

The present inventor has developed a method of electrolytic polishing by placing a metal plate and an electrode facing each other in an electrolytic solution and applying electricity. According to this method, it is possible to obtain a mirror surface by polishing a flat plate. .

Therefore, the present inventor attempted electrolytic polishing on a metal tube with an inner diameter of about 1 inch, and was able to obtain the expected polishing effect when the tube was short. However, although electrolytic polishing is possible for metal tubes with the above-mentioned inner diameter up to about 2 m, it is difficult to process metal tubes longer than that, and the processed and unprocessed parts are separated. They were often mixed.

According to the findings of the present inventors, when the inner surface of the metal tubes constituting the heat exchanger is polished to a mirror-like surface compared to the surface roughness of ordinary metal tubes, dirt and water scale are less likely to adhere to the metal tubes. We have confirmed that there is a significant decrease. It has also been confirmed that electrolytic polishing is efficient as a mirror finishing method and can provide the desired surface precision.

For example, when considering heat exchangers and various piping, 374
small diameter tube, such as 578 inches or 578 inches, with a length of at least 6
It is necessary to process metal tubes of about 2 m in length, but if electrolytic treatment is performed with the electrode simply inserted into the tube, the limit is on metal tubes of about 2 m in length, as mentioned above. The electrolytic polishing treatment of materials is substantially difficult, and the electrolytic polishing has the disadvantage of being uneven. Therefore, it has been difficult to electrolytically polish the inside of the long metal tube constituting the heat exchanger to a predetermined rough surface (mirror surface).

Furthermore, there has been no technical concept of electrolytically polishing metal tubes of heat exchangers, and no examples of attempts to do so have been found.

[Purpose of the invention]

A first object of the present invention is to eliminate the drawbacks of the conventional electrolytic polishing method and to provide a method and apparatus for electrolytically polishing the inside of a long metal tube.

Still another object is to provide a method and an apparatus for use in the method that can improve the reduced capacity of heat exchangers and boilers in operation all at once.

[Summary of the invention]

The configuration of the present invention to achieve the above object is characterized in that: (i) the electrode is supported and moved within the metal tube with a support body keeping a distance from the inner wall, and the electrolyte is made to flow within the metal tube; The electrolytic polishing method in a metal tube consists of a closing body that closes both ends of the metal tube that undergoes the electrolytic polishing process, an electrode that moves through these closing bodies, and an electrolytic solution that keeps this electrode spaced from the tube wall. This is an electrolytic polishing device in a metal tube, which includes a support body to be passed through, a pump to flow an electrolytic solution from the one closure body to the other closure body, and an electrolyte circulation path consisting of an electrolyte reservoir.

〔Example〕

Next, the present invention will be described in detail with reference to the drawings.

FIG. 1 shows an outline of the apparatus according to the present invention, in which a closure body 2.3 is provided at both ends of a metal tube 1 to be treated, and an electrode 4 is inserted through the re-closure body 2.3. ing. This electrode 4 is supported in a metal tube l by a support 5.6,
A gap is maintained between the pipe wall and the pipe wall.

As shown in FIGS. 2 and 3, the closure body 2 has a disk shape as a whole, and has a hole 10 in the center for passing the electrode 4, and an O-ring 11 is provided in the hole 10 for sealing. are doing. A banking 12 is provided on the surface of the inner recess of the closure body 2 to seal with the end face of the metal tube l. A ring groove 13 is provided on the bottom surface of the recess, and this ring groove 13 is connected to an external circuit through a supply path 14.

The ring groove 13 has a ring lid 16 provided with a large number of spouts 15.
The electrolyte supplied from the supply path 14 passes through the ring groove 13 and is supplied from the spout 15 into the metal tube l in a dispersed state.

As shown in FIG. 2, a bracket 19 is installed on the ring body 18 in order to fix the closure body 2 to the metal tube l, and a bolt 2 is inserted between the hole of the bracket 19 and the hole of the stopper 21.
The closing body 2 is drawn to the end face of the metal tube 1 through 0 and fixed in a sealed state with a backing 12.

Another closure body 3 is also formed into a concave shape at the portion that contacts the metal tube 1, and is provided with a backing 12. A large number of discharge ports 22 are provided.

As shown in FIGS. 4 and 5, the supports 5 and 6 are attached to a fixing portion 32 inside a ring portion 30 via a plurality of arm portions 31.
A large number of windows 33 are provided between the ring portion 30 and the fixing portion 32 for passing the electrolyte, and the fixing portion 3
2 is provided with a set screw 34.

In FIG. 1, most of the electrode 4 is covered, and the coating of the part between the supports 5 and 6 is removed to form a current-carrying part 4a. A current ■ is supplied. Further, the electrode 4 is gradually taken up by rollers 23 and moved within the metal tube 1 according to the electrolytic treatment.

FIG. 6 is a perspective view showing a part of the electrode 4, and is a metal part 4b.
A current-carrying part 4a is formed by removing a part of the electrically insulating coating 4C provided above, and the current-carrying part 4a is provided with a large number of protrusions 4d to form a shape that facilitates the supply of current. has been done.

FIG. 7 is a perspective view showing a part of another electrode 4, in which a large number of protrusions 4e are formed radially on the current-carrying portion 4a.

In FIG. 1, a positive voltage from a DC power supply is supplied to the metal tube 1 through a wiring 45, a negative voltage is supplied to the electrode 4 through a wiring 56, and the electrolyte in the tank 40 is supplied via piping 41, pump 42, and piping 43. The water is supplied to the supply path 14 of the closure body 2, flows through the metal tube 1, undergoes an electrolytic action at the current-carrying part 4a of the electrode 4, is discharged from the outlet 22 on the closure body 3 side, and is stored again in the tank 40. be done.

In the present invention, a metal tube suitable for electrolytic polishing is, for example, a stainless steel tube with a diameter of 1 inch and a length of about 6 m.

As the electrolytic solution, for example, a chromium-phosphate solution is suitable.

The distance between the current-carrying portion 4a of the electrode 4 and the inner wall surface of the metal tube 1 is suitably in the range of 2 to 8 mm. Further, the structure of the current-carrying part 4a can be the one shown in FIGS. 6 and 7, but it is also possible to use the structure shown in FIGS.
Furthermore, in the sense that even when the electrodes are eccentric, the distance between the inner wall surface and the electrodes is equalized, a windmill is installed on the electrodes, and this electrode is supported inside the metal tube via a bearing, thereby reducing the electrolyte. Electrodes that can be automatically rotated by force can also be used.

The current required for electrolytic polishing varies depending on various conditions, but
For example, when electrolytically polishing a stainless steel tube with an inner diameter of 20 fins, a range of 20 to 30 A/dm'' is appropriate.

〔Effect of the invention〕

(11) Supporting the electrode 4 in the metal tube 1 with a support 5.6 while maintaining a distance from the inner wall of the tube, moving the current-carrying part 4a, and flowing an electrolyte in the metal tube 1. (2) Closing bodies 2 and 3 that close both ends of a metal tube 1 that undergoes electropolishing treatment, and an electrode 4 that moves through these closing bodies 2.3. , a support 5.6 that keeps the electrode 4 spaced from the tube wall and allows the electrolyte to pass therethrough, a pump 42 that allows the electrolyte to flow from the one closure body 2 side to the other closure body 3 side, and the electrolyte solution. Since this is an electrolytic polishing apparatus in a metal tube, which consists of a tank 40 and a circulation path for an electrolytic solution, the following effects can be achieved.

B. Fluids with viscosity and many impurities, such as heat exchanger pipes used in synthetic resin manufacturing plants, have a lot of deposits and require a large amount of maintenance cost. By electrolytically treating the metal tube, the inner wall surface of the metal tube becomes a mirror surface. In this manner, the amount of deposits attached to the inside of the metal tube, which has a mirror surface, is extremely reduced, and it is possible to maintain heat exchange efficiency in a good state even during continuous operation for a long period of time.

Furthermore, since a passivation film is formed on the surface of the metal tube 1 by the electrolytic solution, corrosion resistance is improved.

C.Furthermore, the surface residual stress remaining on the inner surface of the metal tube 1 during manufacturing is alleviated by electrolytic treatment, so the metal tube 1
This makes it possible to prevent cracks from occurring.

20 According to the present invention, since the treatment is performed by moving the electrode while flowing the electrolyte inside the metal tube 1, the long metal tube 1
can be electrolytically polished. Therefore, there is no need for equipment such as a large tank for immersing it.

E. Since it is only necessary to fill the metal tube 1 and the small capacity tank 40 with electrolyte, the amount of electrolyte required is small, and activated electrolyte can be constantly supplied.

F. Since the distance between the current-carrying portion 4a of the electrode 4 and the inner wall surface of the metal tube 1 is maintained constant by the support 5 (6), the distance between the current-carrying portion 4a of the electrode 4 and the tube wall surface is uniform. Then,
The finish of electrolytic polishing becomes better.

By supplying the electrolytic solution into the metal tube 1 from one direction and discharging it from the other direction, a constant flow is created in the electrolytic solution, so that the hydrogen gas generated by the electrolytic action is moved downstream. It is possible to efficiently remove hydrogen gas and prevent the hydrogen gas from adhering to the inner surface of the tube, thereby forming a good electrolytically polished surface.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, in which Fig. 1 is an explanatory view showing the main parts of an electrolytic polishing device inside a metal tube, Fig. 2 is a front view of the closure, and Fig. 3 is a sectional view of the same side. . FIG. 4 is a front view of the support, and FIG. 5 is a sectional view of the center thereof. FIG. 6 and FIG. 7 are perspective views showing an example of the current-carrying part of the electrode. 1... Metal tube, 2.3... Closed body, 4... Electrode,
4a... Current carrying part, 5, 6... Support body, 40... Electrolyte tank, 42... Pump.

Claims (2)

[Claims] (1) A metal characterized by supporting an electrode within a metal tube with a support body while maintaining a distance from the inner wall of the tube, moving the electrode in the longitudinal direction of the metal tube, and causing an electrolyte to flow within the metal tube. In-tube electropolishing method. (2) A closure body that closes both ends of a metal tube that undergoes electrolytic polishing, an electrode that moves through these closure bodies, and a support that maintains a distance between this electrode and the inner wall of the tube and allows the electrolyte to pass through it. An electrolytic polishing device in a metal tube, comprising a body, a pump for circulating an electrolyte from the one closed body to the other closed body, and an electrolyte circulation path consisting of an electrolyte tank.