JPH04341600A - Method for polishing inside of steel pipe - Google Patents

Abstract

PURPOSE:To efficiently electropolish the inside of a steel pipe with a tool while almost preventing the deterioration of the tool. CONSTITUTION:When the inside of a steel pipe is electropolished, elastic platelike bodies 1 of polyurethane, polyethylene or other resin having electric nonconductivity are radially fixed around a metal core wire 2 and this wire 2 is inserted as a counter electrode into the steel pipe. The inside of the steel pipe is polished by supplying electric current between the steel pipe and the counter electrode while rotating one or both of them.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for polishing the inner surface of a steel pipe, and more particularly to a method for electrolytically polishing the inner surface of a stainless steel pipe for high-purity gas used in semiconductor manufacturing processes.

0002

[Background Art] In the field of semiconductor manufacturing, the degree of integration has increased in recent years, and devices called VLSIs have become smaller than 1 μm.
There is a need for processing micropatterns of less than m. In this type of VLSI manufacturing process, minute amounts of dust and impurity gases adhere to or adsorb onto wiring patterns, causing circuit defects. A low gas content and high purity are required. Therefore, in such high-purity gas piping and members, it is required that gas emissions from the inner surface of the material and attached dust be extremely small.

[0003] Conventionally, seamless pipes made of austenitic stainless steel such as SUS316 have been used for high-purity gas piping and components used in the manufacture of semiconductors, and those with an outer diameter of 10 mm or less are usually used. has been done. These steel pipes have an inner surface roughness smoothed to Rmax of 1 μm or less in order to reduce adhesion and adsorption of dust and moisture. Examples of methods for smoothing the inner surface include cold drawing, mechanical polishing, electrolytic polishing, etc.
Electrolytic polishing is essential in order to obtain a high degree of smoothness of 0.8 μm or less.

[0004] Electrolytic polishing methods for stainless steel include a method in which stainless steel is electrolyzed in an electrolytic solution mainly containing phosphoric acid or sulfuric acid, and a method in which stainless steel is electrolyzed as an anode in an electrolytic solution containing mainly phosphoric acid or sulfuric acid, and a method in which a neutral salt aqueous solution such as sodium nitrate is used as the electrolytic solution and polishing using abrasive grains. Electrolytic composite polishing, which polishes by superimposing polishing actions, is known.

[0005] Regarding electrolytic composite polishing, see Japanese Patent Application Laid-Open No. 1982-82.
No. 626 and Japanese Unexamined Patent Publication No. 61-30328 disclose a method of polishing using a roll-shaped or disc-shaped polishing tool by regulating the current density and the pressing force of the tool against the stainless steel material to be polished. . However, it is difficult to polish the inner surface of small diameter steel pipes using this method.

Furthermore, Japanese Unexamined Patent Publication No. 137200/1983 describes a method of electrolytic polishing of the inner surface of a hollow body as shown in FIGS. As shown in the cross-sectional view), a non-conductive linear body 8 is spirally wound and fixed around a conductive core wire 9 as a counter electrode, and the counter electrode is inserted into a hollow body for electrolytic polishing. is disclosed. However, when attempting to electrolytically composite polish the inner surface of a steel pipe using this counter electrode, the polishing tool (the non-conductive linear body 8 wound and fixed in a spiral around the conductive core wire 9) deteriorates over time. is large and the contact area of the polishing tool with the tube to be polished is small, making it difficult to polish a large amount of tubes to be polished with high efficiency. That is, the non-conductive linear body 8 is connected to the core wire 9.
The outer diameter of the counter electrode, which is wound and fixed in a spiral around the tube, is slightly larger than the inner diameter of the tube to be polished in consideration of ease of insertion into the tube, so that the polishing tool does not come into contact with the inner surface of the tube to be polished. The area is small from the beginning of polishing, and it wears out early. When worn, the contact area becomes even smaller and the polishing effect decreases, so it cannot be used for a long time.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide an electrolytic composite polishing method that is capable of polishing the inner surfaces of a large number of steel pipes with high efficiency and that causes less deterioration of the polishing tool.

[0008]

[Means for Solving the Problems] The gist of the present invention is that a non-conductive elastic plate-like body radially fixed to a metal core wire is inserted into a steel pipe as a counter electrode, and the steel pipe and the counter electrode are rotated relative to each other. A method for polishing the inner surface of a steel pipe, which polishes the inner surface of a steel pipe by applying current between the steel pipe and a counter electrode while

[0009] The above-mentioned steel pipe contains 13 to 30% Cr and N.
Fe-based alloy tubes containing 40% or less of i, SU
Although austenitic stainless steel pipes such as S316L steel are exemplified, other pipes such as ferritic, two-phase or martensitic stainless steel pipes, low alloy steel, carbon steel, etc. may also be used.

[0010] Relatively rotating the steel pipe and the counter electrode means rotating either one of the steel pipe and the counter electrode, or rotating both of them in opposite directions.

FIG. 1 is a diagram showing the configuration of an example of a counter electrode used when carrying out the method of the present invention, in which (a) is a side view and (b) is a side view.
) The figure is a sectional view taken along the line A-A in figure (a). As shown in this figure, a non-conductive elastic plate-like body 1 is radially fixed to a metal core wire 2. As shown in FIG.

FIG. 2 is a diagram showing the structure of an example of an electrolytic polishing apparatus for carrying out the method of the present invention, in which the counter electrode 3 is rotatably inserted into the tube 4 to be polished. The counter electrode 3 and the tube to be polished 4 are each connected to a DC power source 7, and the structure is such that an electrolytic solution can be circulated in the tube to be polished 4 from an electrolyte tank 6 by a pump 5 in the direction of the arrow.

[0013]

[Operation] The method of the present invention is a method of electrolytically polishing the inner surface of a steel pipe using a counter electrode in which a non-conductive elastic plate-like body is radially fixed to a metal core wire as described above.

FIG. 3 is a sectional view showing the counter electrode 3 inserted into the tube 4 to be polished. The elastic plate-shaped body 1 radially fixed to the metal core wire 2 is deformed so that its side surface is uniformly pressed over a wide range of the inner surface of the tube to be polished 4. In this state, electric current is applied between the metal core wire 2 and the tube to be polished 4 while rotating the metal core wire 2 in the direction of the arrow to perform electrolytic polishing. Since the contact area of the polishing tool (elastic plate-like body 1) with the tube to be polished 4 is large, the polishing effect is large, and a large amount of tubes to be polished can be polished with high efficiency. Furthermore, even if the contact surface, that is, the side surface of the elastic plate 1 is worn out, since the elastic plate 1 has flexibility as described later, the side surface of the plate 1 is always kept close to the surface of the tube to be polished. The polishing effect will not deteriorate early due to the force acting to press the inner surface.

In other words, the usable life of the polishing tool is long.

[0016] As the non-conductive elastic plate, a resin that is flexible and chemically stable in the electrolyte is suitable; for example, foamed resin such as polyurethane, polyethylene, or polyester is suitable. be.

The metal core wire serving as the counter electrode may be any material as long as it is stable in the electrolyte, such as steel, stainless steel, corrosion-resistant Ni alloy,
Suitable materials include copper and gold.

It is preferable that 3 to 12 non-conductive elastic plates are arranged radially at equal intervals in the circumferential direction of the core wire.

Furthermore, the maximum inner diameter of the tube that allows suitable treatment while maintaining a stable pressing force on the inner surface of the tube to be polished over a long period of time using the counter electrode of the present invention is determined by the elastic plate fixed to the metal core wire. An imaginary circle formed by connecting the outer ends of the shaped body (
The outer diameter of the circle indicated by the broken line in FIG. 1(b) is assumed to be approximately 0.8 times the virtual outer diameter. on the other hand,
The minimum inner diameter of the tube that allows suitable treatment is such that the outer end of the elastic plate comes into contact with the adjacent elastic plate when the counter electrode shown in FIG. 3 is inserted into the tube. is the inner diameter of the tube.

[0020] The non-conductive elastic plate can be radially fixed to the metal core wire by using adhesive or by sandwiching the elastic plate between several metal core wires. There may be. In addition, the elastic plate-like body does not need to be fixed continuously over the entire length of the metal core wire, and a gap 10 (see Fig. 1(a)) is provided in a part to promote the flow of the electrolyte in the inner circumferential direction of the steel pipe. It may be provided.

[0021] As the electrolytic solution, an acidic aqueous solution such as phosphoric acid or sulfuric acid, or a neutral salt aqueous solution such as sodium nitrate can be used. In the case of electrolytic composite polishing in which the polishing action of abrasive grains is superimposed, a neutral salt aqueous solution is preferable.

The abrasive grains used in electrolytic composite polishing may be those commonly used as abrasives for steel pipes, such as aluminum oxide or chromium oxide. The grain size of the abrasive grains can be adjusted in various ways depending on the roughness of the target polished surface. The abrasive grains may be mixed and suspended in the electrolytic solution, or may be used in a state in which they are fixed to the elastic plate-like body. When mixing and suspending the abrasive particles in an electrolytic solution, it is preferable to use a porous elastic plate because the abrasive grain retention force is greater.

Since the electrolytic conditions and the rotation speed of the polishing tool vary depending on the material of the non-polishing tube, they may be adjusted as appropriate.

Further, when the unpolished pipe is long, it is possible to polish the entire length by, for example, moving a polishing tool in the longitudinal direction of the steel pipe while rotating it.

[0025]

[Example] Outer diameter 9.5mm, wall thickness 1mm, length 10
SUS31 with 0mm and inner surface roughness Rmax 0.8μm
A counter electrode configured as shown in FIG. 1 was inserted into a 6L stainless steel tube, and the tube was assembled into an electrolytic polishing apparatus having the configuration shown in FIG. 2, and electrolytic composite polishing was performed under the conditions shown in Table 1. For comparison, electrolytic composite polishing was performed under the same conditions using the counter electrode shown in FIG. In FIG. 1, the material of the non-conductive elastic plate 1 is polyurethane foam, and the height (FIG. 1(b)
h) is 4.2 mm, the material of the metal core wire 2 is copper, and the diameter is 3 mm. In addition, in FIG. 4, the material of the non-conductive linear body 8 is polyurethane foam, the wire diameter is 2 mm, and the pitch when winding in a spiral is 3 mm winding/cm.
The conductive core wire 9 is made of copper and has an outer diameter of 5 mm.

[0026]

[Table 1]

The results are shown in Table 2. The polishing effect of the present invention example is superior to that of the comparative example, and polishing can be performed with high efficiency. In addition, in the comparative example, as the number of times of polishing increases, the wear of the linear body progresses and the smoothness of the inner surface deteriorates, whereas in the example of the present invention, no deterioration of the polishing effect was observed even if the number of times of polishing increased. , a stable and good polishing process was possible.

[0028]

[Table 2]

[0029]

[Effects of the Invention] If the method of the present invention is applied to polishing the inner surface of a steel pipe, the polishing can be performed with high efficiency and the deterioration of the tool can be reduced. It is particularly effective for polishing the inner surface of stainless steel pipes for high-purity gases.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of an example of a counter electrode used when carrying out the method of the present invention. FIG. 2 is a diagram showing the configuration of an example of an electrolytic polishing apparatus for carrying out the method of the present invention. FIG. 3 is a sectional view showing a state in which the counter electrode used in the method of the present invention is inserted into the tube to be polished. FIG. 4 is a diagram showing the configuration of a counter electrode used for comparison.

Claims (1)

[Claims] [Claim 1] A non-conductive elastic plate-like body radially fixed to a metal core wire is inserted into a steel pipe as a counter electrode, and current is applied between the steel pipe and the counter electrode while rotating the steel pipe and the counter electrode relative to each other. A method for polishing the inner surface of a steel pipe, which is characterized by polishing.