JPS61214958A - Inner-surface polishing for metal pipe - Google Patents

Abstract

PURPOSE:To permit the mirror-surface polishing with high precision by shifting the outer peripheral surface of a rope, etc. which passes through a metal pipe, along the inner surface of the metal pipe, and allowing the etching agent containing abrasive grains mixed to pass in slidable contatc with the inner surface of the metal pipe. CONSTITUTION:The cable article 3 such as rope is inserted inside a long metal pipe 1 having a small diameter. Onto said cable article 3, slidable contact bodies 4 impregnated with etching agent containing abrasive grains mixed are installed at a cetrain intervals in the longitudinal direction. When the cable article 3 is pulled and shifted in the longitudinal direction into the metal pipe by allowing the slidable contact body 4 to be impregnated with etching agent, the inner peripheral surface is polished by allowing the outer peripheral surface of the slidable contact body 4 to pass from one edge to the other edge of the metal pipe 1, in slidable contact with the inner peripheral surface of the metal pipe 1. It is necessary for the slidable contact body 4 in stable state to revolve the metal pipe 1 so as to contact with the polished surface, and the polishing to the max. roughness of 0.5 or less is performed over the whole length of the inner peripheral surface of the metal pipe 1 by carrying-out the polishing work for a proper time.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for polishing the inner surface of a metal tube through which high-purity gas or liquid is passed.

(Background of the Invention) In recent years, with the development of the electronic industry, particularly the semiconductor industry, the removal of fine dust or microorganisms from gases and liquids used in the manufacturing process has become an important technical issue.

For example, in a 1 megabit DRAM (dynamic random access memory), the minimum design line width is 1 to 1
．． 2μ, and 1μ for 4 megabits.
The following is easily understood.

In addition, to give another example, it can be easily estimated that in MO3 structure transistors, a silicon oxide film thickness of about 200 layers is required for 1 megabit, and a thickness of 100 layers is required for 4 megabits. can.

However, if the design has a minimum line width of 1μ and there is 1μ of dust in the gas used for this, it is natural that if even one piece of dust falls onto an important part of the chip, the chip will be defective. Accordingly, what is currently generally considered to be approximately 1/10 of the minimum line width. For example, it is said that if the minimum line width is 1 μm, foreign matter up to 0.1 μm can be tolerated.

On the other hand, high-performance filters have been developed, and 0.1 #
Although there are filters on the market that can collect even 500 m of foreign matter with a collection efficiency close to 100%, the problem lies in the foreign matter that is occluded or attached to the inner surface of the piping after the filter. These foreign substances are released little by little out of the pipe as the pipe vibrates, expands, and contracts over an extremely long period of time (in some cases, for over a year) along with the gas flow, causing undesirable phenomena in semiconductor manufacturing. It's clear.

In addition, in the production of the silicon oxide film mentioned above, the thickness is 100 mm.
The time is approaching when human materials will be needed, and with a film thickness of 100 people, that is, 0.01 μm, most of the foreign particles contained in it will be the size of 4 to 5 atoms. Conceivable.

Although there is still no established theory regarding the behavior of particles (dust) in pipes under such extreme conditions, it is safe to imagine that particles are absorbed and desorbed at least at the interface between the inner surface of the pipe and the gas. You can discover phenomena.

According to the research conducted by the inventors, for example, a commercially available pipe with a maximum height of 1.6μ (hereinafter referred to as inner surface roughness) and a pipe whose inner surface is completely polished to reduce the inner surface roughness to 0. .2μm
Both pipes were completely degreased with alkali, washed with pure water, then passivated, thoroughly washed with pure water, and dried. From the air inlet side of 4 mm), a pressure of 4 kg /
ci G, INn at room temperature? /Hr of dry air is introduced, and a particle counter (PM
When we conducted a particle detection experiment while applying vibration to a pipe using a pipe (manufactured by S company, AS-X), we found that one particle of 0.1 μm or larger was detected in one measurement in a commercially available pipe.
It takes at least 500 hours to reduce particles to 0.0018m particles per measurement angle in less than 2 hours with an internally polished tube with an inner surface roughness of 0.2μ. This is what I found through experimentation. or,
After removing the filters on the inlet side of the air flowing through these pipes and introducing particles into these pipes again, we reinstalled the filters and counted the particles at the pipe outlet side. While it takes about 500 hours to
An internally polished tube with an inner surface roughness of μ-0.0 in less than 1 hour.
It was confirmed that the number of particles of 1 μm was reduced to 10 or less. Such effective dust collection becomes noticeable when the inner surface roughness is at least 0.5 μm or less.

It is not hard to imagine that when the inner surface roughness of a pipe becomes 0.5 μm or less, granular particles are more likely to be ejected from the pipe due to the reduction in rolling friction resistance, but the 0.18 m Among the particles of this type, many are observed as linear when viewed from the surface.

The phenomenon in which even linear particles can be easily ejected outside the tube cannot be adequately explained simply by a reduction in rolling resistance, but because the adsorption force at the interface between the tube's passive film and the particles becomes extremely small. It is easier to explain if you think that there is.

Of course, in the case of a normal pipe, the inner surface area would be several times the theoretical surface area, but for a pipe polished to 0.5 μm or less, the inner surface area would be 1.1 times the theoretical surface area.
Since it is thought that it is about 1.5 times larger, the effect that the particle adhesion area is reduced by that amount is also appearing.

On the other hand, pipes made of metals or alloys generally have scales and scratches on their inner surfaces during heat treatment and molding processes during pipe manufacturing, resulting in an extremely rough inner surface with a surface roughness of 5 to 30 microns.

In addition, for plate-shaped metals, if extremely smooth rolls are used during the rolling process, the roll surface will be transferred to the metal surface, making it possible to manufacture a plate with a smooth surface. If requested, surface roughness of 0.1 μm can be achieved by surface polishing.
It is also possible to easily manufacture a plate.

Furthermore, during pipe making, a smooth roll is inserted into the inner surface of the pipe from a large diameter pipe to a small diameter pipe with a smooth roll surface similar to that of a plate, and the pipe is contracted from the outer surface using three rolls. Therefore, technical attempts have been made to reduce the surface roughness of the inner surface of the tube, but the surface roughness of the pipe obtained using this method is limited to 1 μm to avoid scratches that occur when the rolls are removed in the final process. It is difficult to do so.

There is also a technique for polishing the inner surface of a pipe called honing, but this method uses a grindstone to polish the inner surface of the pipe, and it is possible to polish the inner surface of the pipe to a surface roughness of 0°2 μm or less. There is a limit to the length and inner diameter that can be polished, and honing is possible even for pipes with large inner diameters that exceed 4 m in total length, but
It is impossible to polish long tubes arranged in a row at level III, and at best, the polishing is 0.
．． The maximum length that can be processed is about 5 to 1 m. Further, for an inner diameter of about 10 lll11, the maximum length that can be polished is about 2 m.

Electrolytic polishing is another well-known technique for polishing the inner surface of pipes, but due to the resistance of the electrolytic electrodes installed on the inner surface of the pipe, electrolytic polishing is required for both ends and the center of small diameter pipes with a total length of 4 m or more. If the amount is different and the center is polished to the best finished surface, both ends will be over-polished.In alloys such as stainless steel, especially alloy tubes containing molybdenum such as 5US316, electrolytic polishing is caused by the different ionization tendencies of each component of the alloy. There is a problem in that a difference occurs in the amount and the surface roughness increases due to over-electrolytic polishing.

Of course, tube inner surface polishing methods using these combined techniques have also been widely studied, but it is difficult to overcome the inherent drawbacks of each, and conventional techniques are difficult to improve the inner surface roughness of pipes with an inner diameter of 20n+m or less and a length of 3m or more. It was impossible to reduce the thickness to 0.5 μm or less.

(Objective of the Invention) The present invention has been made in view of the above problems, and provides a method for polishing the inner surface of a metal tube, which enables mirror polishing of the inner surface of a long metal tube with high precision. This is what we provide.

(Structure of the Invention) In order to achieve the above object, the internal surface polishing method of the present invention includes polishing abrasive particles supplied into the metal tube by moving the outer peripheral surface of a rope or the like inserted through the metal tube along the inner surface of the metal tube. This method is characterized in that the mixed etching agent is passed through the inner surface of the metal while being in sliding contact with the inner surface to polish the inner surface to a surface roughness of 0.5 μm or less.

(Description of Embodiments) To explain the embodiments of the present invention with reference to the drawings, (1) is a long thin metal tube with an inner diameter of 20 m+w or less and a length of 3 m or more. Appropriate fixing jig (2)
Fix according to (2).

Next, a cable such as a rope (
3) Insert. This cable (3) has a sliding body (4) such as a piece of cloth or a sponge-like material that can be impregnated with an etching agent mixed with abrasive grains at regular intervals in the length direction.
・(4) is attached.

As the etching agent to be impregnated into the sliding contact body (4), when the metal tube (1) to be polished is made of copper or copper alloy, the following composition is used.

Nitric acid 15% by weight Sulfuric acid 5 Phosphoric acid
10 Sulfamic acid 1
〃 Nonionic surfactant 1 ~ Alumina 30 〃 Water 38 〃 In addition, when the metal pipe is a stainless steel pipe or a pipe containing metal such as titanium or zirconium, the following composition is used as an etching agent. .

Nitric acid 200% by weight acidic fluorammonium 5 Fluoric acid 2
Acid 10 Inhibitor having a carboxyl group 5 Surfactant 1 - Alumina 25 Water Residual In the above composition, nitric acid is added to make the inner surface of the metal tube immobile and brittle, and this nitric acid is combined with sulfuric acid, phosphoric acid or Hydrofluoric acid is used as a mixed acid to prevent selective dissolution of metal surfaces.

In addition, sulfamic acid is an oxidation inhibitor that acts as an inhibitor and prevents over-etching of the metal surface.It reduces the surface tension of the acid solution, improves the wetting characteristics with the metal inner surface, and improves the leveling of the solution at the interface. An activator is added.

Furthermore, the particle size of alumina as abrasive grains is 0°5°μ~
A particle size of 40μ is used. The viscosity of this etching liquid may be determined as appropriate, but it is adjusted to 250 to 400 cps when the inner surface of the metal tube (1) is polished by absorbing and impregnating the above-mentioned sliding contact member. Also, many tfM
If an appropriate amount of i-type thickener is added to the etching agent, the dispersibility of alumina can be further improved.

In order to impregnate the sliding contact body (4) with the etching agent by adjusting the etching agent in this manner, before inserting it into the metal tube (11), use an abrasive-containing gill, infiltrate and pass through the etching agent, or insert it into the metal tube (11). This is done by supplying an etching agent mixed with abrasive grains.

The sliding body (4) is impregnated with an etching agent to form a cable (3).
When the sliding body (4
) passes from one end of the metal tube (1) to the other end while sliding on the inner surface of the metal tube (1), during which time the etching agent mixed with abrasive grains is actively applied by the sliding member (4). It slides on the inner circumferential surface of the metal tube (1) and polishes the inner circumferential surface. The cable (3) to which the sliding body (4) is attached may be moved only in one direction within the metal tube, or may be moved back and forth, and the cable (3) attached to the sliding body (4) may be It is also necessary to rotate the metal tube (1) so that it is in contact with the polished surface, and this polishing operation is performed for an appropriate amount of time until the metal tube (1) is in contact with the polished surface.
) is polished to a maximum height roughness of 0.5 or less over the entire length.

Note that similar polishing can be performed by directly sliding the outer peripheral surface of a fiber lobe impregnated with an etching agent containing abrasive grains onto the inner surface of the metal tube without using the sliding member (4).

Next, Fig. 2 shows another polishing means, in which a fitting hole (5) into which the end of the tube is inserted and fixed, and a small diameter shaft inserted in communication with the center line of the fitting hole (5). A pair of support jigs (8) each having a liquid guide hole (7) extending through the hole (6) between the front and rear end surfaces and communicating with the shaft insertion hole (6) from an appropriate position on the outer peripheral surface.
), install the support jig (8) (8) oppositely to each other with the same length as the tube, and insert the metal tube (1) into the fitting hole (5) (51).
) and secure it. Furthermore, the support jig (8)
The rotating shaft (9) is inserted between the insertion holes (61 (61) of (8), and one end thereof is connected to the motor αω. Also, the shaft portion inserted into the metal tube (11) is inserted into the metal tube (11). A brush body made of a polymer compound such as polypropylene or a liquid agent transfer member 11 such as a felt tape is wound spirally around the inner peripheral surface of the brush body.

Note that the end of the shaft insertion hole (6) is closed with a packing or the like.

Now, when the abrasive grain-containing etching agent having the composition described above is supplied from the guide hole (6) of one of the support jig (8) and the shaft (9) is rotated by driving the motor α, the etching agent is The metal tube (1) by the helical transfer member 11 of the shaft (9)
The inner circumferential surface of the metal tube (1) is polished while being transferred to the other supporting jig (8) while being in sliding contact with the inner circumferential surface of the metal tube (1). The abrasive grain-containing etching agent flowing out from the other end of the metal tube is discharged from the downward guide hole (6) of the other supporting jig (8).

In the case of this polishing method, it is desirable that the viscosity of the etching agent be set to about 4,000 to 6,000 cps, which is higher than the above-mentioned viscosity.

In such polishing work, the polishing effect will be even greater if the metal tube (1) is horizontally reciprocated in the axial direction, and
A similar method can be achieved by rotating a spiral metal or polymer compound shaft material in a metal tube and stirring an etching agent containing abrasive grains with a high viscosity (20,000 cps) in the metal tube without using a sliding body. This provides a polishing effect.

The inner surface of the thus polished metal tube (1) is thoroughly washed with ion-exchanged water and dried using dry air.

(Effects of the Invention) As described above, according to the method for polishing the inner surface of a metal tube of the present invention, since the etching agent containing abrasive grains is brought into sliding contact with the inner surface of the metal tube, the inner diameter of the metal tube is 20 or less. and the length is 3
It is possible to uniformly polish the inner surface of a metal tube over its entire length even if it is a metal tube with a diameter of 0.5 μm or more, and it can be efficiently polished to a polishing degree with a maximum height roughness of 0.5 μm or less. This invention is extremely useful as a high-precision polishing method.

In addition, the polished tube thus obtained does not allow even extremely fine dust to adhere to its inner surface, making it ideal for piping from the filter to the semiconductor manufacturing department, and used in the manufacturing process. Gas can always be kept at a high purity, and therefore highly accurate products can be manufactured efficiently.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is a simplified diagram of a polishing means using a sliding contact, and FIG. 2 is a +! 1 is a simplified diagram of a polishing means using a monovolute; FIG. (1)... Metal pipe, (3)... Cable, (4...
Sliding contact body, (9)... Rotating shaft, 11... Liquid agent transfer member.

Claims (1)

[Claims] By moving the outer peripheral surface of a rope, etc. inserted into the metal tube along the inner surface of the metal tube, the etching agent and abrasive grains supplied into the metal tube are brought into sliding contact with the inner surface of the metal tube, and the inner surface is made to have the maximum surface roughness. A method for polishing the inner surface of a metal tube, characterized by polishing the inner surface of a metal tube to a height (Rmax) of 0.5 μm or less.