JP2010052123A - Ultraprecise magnetic polishing method and polishing slurry for ultraprecise magnetic polishing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultraprecise magnetic polishing method capable of attaining highly precise polishing of a pipe inner surface and easy cleaning and to provide a polishing slurry for ultraprecise magnetic polishing. <P>SOLUTION: Using a pipe 1 to be polished, polishing slurry 2 introduced into the pipe 1 to be polished and a pipe inner surface magnetic polishing apparatus 3 for agitating the polishing slurry 2 by relatively moving the pipe 1 to be polished and the polishing slurry 2, the inner surface of the pipe 1 to be polished is polished with the polishing slurry 2 by moving the pipe inner surface magnetic polishing apparatus 3. At this time, the polishing slurry 2 comprises spherical magnetic particles, polishing particles having average particle diameter in the range of 1/4 to 1/1000 of the average particle diameter of the magnetic particle, and a slurry medium which is a medium for making the magnetic particles and the polishing particles into a slurry state and does not contain additive for dispersing the polishing particles in the polishing slurry. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an ultraprecision magnetic polishing method and a polishing slurry used therefor, and more specifically, an ultraprecision magnetic polishing method capable of extremely precisely polishing an inner surface of a tube and easy to clean, and a polishing slurry used in the method. About.

  High precision precision parts are required in various technical fields such as the semiconductor field, the medical device field, and the biotechnology field. In these fields, clean pipes are used in devices for transporting high purity gas and high purity fluid. This clean pipe is required to have a mirror-finished inner surface, and in order to meet these requirements, the pipe inner surface magnetic polishing method using magnetic abrasive grains, magnetic sensitive particles, magnetic fluid, magnetorheological fluid, etc. Has been proposed (see, for example, Patent Documents 1 to 3 and Non-Patent Document 1).

  In Patent Document 1, a steel ball having a particle diameter of 4 mm is put in a pipe as magnetic abrasive grains, and the pipe and the two magnets arranged on the outer peripheral side of the pipe are moved relative to each other so that the inner surface of the pipe is covered with the magnetic abrasive grains. A magnetic polishing method for polishing is described. Patent Document 2 discloses magnetic polishing in which magnetically sensitive magnetic abrasive grains are arranged inside and outside a tube, and the inner surface and the outer surface of the tube are polished with the magnetic abrasive particles by moving the tube and a magnetic field relative to each other. A method is described. Further, in Patent Document 3, a magnetic fluid mixed with alumina abrasive grains having an average particle diameter of 4 to 30 μm is put into a pipe, and the inner surface of the pipe is polished with the magnetic abrasive grains by relatively moving the pipe and the magnetic field. A magnetic polishing method is described. Further, in Non-Patent Document 1, a polishing slurry in which alumina abrasive grains having an average particle diameter of 4 μm and iron powder particles having an average particle diameter of 5 μm are mixed in a magnetorheological fluid whose viscosity is changed by a magnetic field is put in the pipe, A magnetic polishing method is described in which the inner surface of a tube is polished with the magnetic abrasive grains by moving the magnetic field relative to each other.

JP 2002-210648 A WO2006 / 090741 JP 2003-062747 A Hitomi Yamaguchi, Takeo Shinmura, Takashi Sato and Akira Taniguchi, “Development and Research of Precision Machining Technology Using Magnetorheological Fluid (Development of Magnetorheological Fluid-Based Slurries and Its Machining Properties)”, Journal of Precision Engineering, Vol. 72, No. 1 100 (2006).

  In recent years, the diameter of a pipe to be polished has become smaller and it has become more difficult to polish the inner surface of the pipe, and a higher level of smoothness of the inner surface of the pipe has been demanded. Further, it has been required that the slurry remaining inside the tube after polishing can be easily washed.

  However, in the magnetic polishing method described in Patent Document 1, the magnetic abrasive grains are steel balls having a particle diameter of 4 mm, and it is difficult to polish the inner surface of the small diameter tube so as to have high smoothness. Further, in the magnetic polishing method described in Patent Document 2, magnetic particles having a diameter of 5 to 2000 μm are used. However, there is a problem that such magnetic particles are easily aggregated. In order to prevent such agglomeration, it is effective to contain a surfactant in the slurry. However, such a surfactant is difficult to wash and cannot be easily washed away. Further, in the magnetic polishing method described in Patent Document 3, polishing is performed with a magnetic fluid mixed with magnetic abrasive grains, but the processing force for the object to be polished is not sufficient, and it is difficult to efficiently perform precision finishing. Further, in the magnetic polishing method described in Non-Patent Document 1, since a magnetorheological fluid containing a special additive is used, there is a problem in that cleaning after polishing must be performed sufficiently, which tends to increase costs. .

The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an ultra-precise magnetic polishing method capable of extremely precisely polishing the inner surface of a tube and easy to clean, and to use the method. It is to provide an abrasive slurry.
Is to provide.

  The present inventor prepared a polishing slurry obtained by simply mixing fine spherical iron powder, ultrafine abrasive grains, and general polishing oil in the course of conducting earnest research for the purpose of solving the above problems, When the inner surface of the tube is magnetically polished using the polishing slurry, the inner surface of the tube can be polished very smoothly and can be cleaned very easily only when predetermined conditions are satisfied. The headline and the present invention were completed.

  That is, the ultra-precision magnetic polishing method of the present invention includes a tube to be polished, a polishing slurry introduced into the tube to be polished, and a tube in which the polishing slurry is stirred by relatively moving the tube to be polished and the polishing slurry. A surface magnetic polishing apparatus, and operating the tube inner surface magnetic polishing apparatus to polish the inner surface of the pipe to be polished with the polishing slurry, wherein the polishing slurry comprises spherical magnetic particles and Abrasive particles having an average particle size in the range of 1/4 to 1/1000 of the average particle size of the magnetic particles, and a slurry medium in which the magnetic particles and the abrasive particles are in a slurry state, and polishing the abrasive particles And a slurry medium not containing an additive for dispersing in the slurry.

  According to the present invention, the stirring of the polishing slurry caused by the relative movement of the tube to be polished and the polishing slurry by the tube inner surface magnetic polishing apparatus is caused by the movement of the spherical magnetic particles so as to swirl large (this The agitation phenomenon is referred to by the present inventor as the “autogenous agitation phenomenon”.) As a result, the small-diameter abrasive particles are prevented from agglomerating and can be uniformly dispersed in the abrasive slurry. Fine polishing of the inner surface of the tube can be realized by non-aggregated abrasive particles. Since the magnetic particles 4 to 1000 times larger than the abrasive particles are spherical, it is possible to prevent the inner surface of the polished tube from being scratched as much as possible and do not act to impair the smoothness. Furthermore, since the magnetic particles can cause a self-stirring phenomenon that does not agglomerate abrasive particles, it is necessary to add an additive (such as a surfactant) for dispersing abrasive particles to the slurry medium as in the past. Disappear. Therefore, it is possible to eliminate the difficulty of cleaning and removing such additives after polishing, and cleaning can be performed extremely efficiently and easily. Furthermore, the abrasive particles having a small diameter of 1/4 to 1/1000 of the magnetic particles are polished between the magnetic particles and the tube to be polished so that the fine particles uniformly dispersed without agglomeration are polished. The inner surface of the tube to be polished can be precisely polished with the abrasive particles.

  In the ultraprecision magnetic polishing method of the present invention, the magnetic particles stirred in the tube to be polished are configured to disperse the abrasive particles while suppressing aggregation of the abrasive particles.

  According to the present invention, the tube inner surface magnetic polishing apparatus is controlled to give the magnetic particles a kinetic force that rotates in a spiral manner, thereby generating a spontaneous stirring phenomenon. As a result, the magnetic particles stirred in the polished tube are polished. Since the agglomeration of the particles is suppressed and the abrasive particles are dispersed, it is not necessary to add an additive (such as a surfactant) for dispersing the abrasive particles to the slurry medium as in the prior art. Therefore, it is possible to eliminate the difficulty of cleaning and removing such additives after polishing, and it is possible to clean very efficiently and easily, and the inner surface of the tube to be polished with fine abrasive particles uniformly dispersed without agglomeration. Can be precision polished.

  In the ultraprecision magnetic polishing method of the present invention, a plurality of polishing slurries in which the average particle size of the magnetic particles and the average particle size of the polishing particles are changed are prepared, and the polishing slurry containing particles having a large average particle size is used. Therefore, it is configured to polish by replacing the inside of the pipe to be polished.

  According to the present invention, a plurality of polishing slurries having magnetic particles and abrasive particles having a suitable average particle diameter are prepared depending on whether the polishing is performed by, for example, rough polishing, intermediate polishing, or finish polishing. If polishing is performed by gradually replacing the polishing slurry containing large particles into the tube to be polished, rough polishing, intermediate polishing, and finish polishing can be sequentially performed. As a result, the polishing efficiency can be improved by using the most suitable polishing slurry for each polishing stage.

  The polishing slurry of the present invention that solves the above problems is a polishing slurry that is introduced into a tube to be polished and moves relative to the tube to be polished to polish the inner surface of the tube to be polished. Abrasive particles having an average particle size in the range of 1/4 to 1/1000 of the average particle size of the magnetic particles, and a slurry medium in which the magnetic particles and the abrasive particles are in a slurry state, the abrasive particles And a slurry medium not containing an additive for dispersing the powder in the polishing slurry.

  According to the present invention, the polishing slurry that moves relative to the pipe to be polished has spherical magnetic particles and abrasive particles having a smaller diameter (1/4 to 1/1000) than the magnetic particles. The movement of the magnetic particles can prevent agglomeration of small-diameter abrasive particles. As a result, the abrasive particles in the polishing slurry can be uniformly dispersed, and fine polishing of the inner surface of the tube can be realized by the uniformly dispersed abrasive particles. Since the magnetic particles 4 to 1000 times larger than the abrasive particles are spherical, it is possible to prevent the inner surface of the polished tube from being scratched as much as possible and do not act to impair the smoothness. Further, since the abrasive particles do not aggregate, it is not necessary to add an additive (such as a surfactant) for dispersing the abrasive particles to the slurry medium as in the conventional case. Therefore, it is possible to eliminate the difficulty of cleaning and removing such additives after polishing, and cleaning can be performed extremely efficiently and easily. Furthermore, the abrasive particles having a small diameter of 1/4 to 1/1000 of the magnetic particles are polished between the magnetic particles and the tube to be polished so that the fine particles uniformly dispersed without agglomeration are polished. The inner surface of the tube to be polished can be precisely polished with the abrasive particles.

  In the polishing slurry of the present invention, the magnetic particles are spherical carbonyl iron powder, and the polishing particles are diamond particles.

  According to the ultra-precise magnetic polishing method of the present invention and the polishing slurry used in the method, a small diameter is obtained by agitation of the polishing slurry (spontaneous stirring phenomenon) caused by relative movement of the pipe to be polished and the polishing slurry by the pipe inner surface magnetic polishing apparatus. Since the abrasive particles are prevented from agglomerating and can be uniformly dispersed in the polishing slurry, fine polishing of the inner surface of the tube can be realized by the abrasive particles having a smaller diameter than the magnetic particles and not agglomerated. Since the magnetic particles 4 to 1000 times larger than the abrasive particles are spherical, it is possible to prevent the inner surface of the polished tube from being scratched as much as possible and do not act to impair the smoothness. Further, since the magnetic particles can cause a self-stirring phenomenon that does not aggregate abrasive particles, it is not necessary to add additives (surfactants, etc.) for dispersing abrasive particles to the slurry medium as in the past. . Therefore, it is possible to eliminate the difficulty of cleaning and removing such additives after polishing, and cleaning can be performed extremely efficiently and easily. Furthermore, the abrasive particles having a small diameter of 1/4 to 1/1000 of the magnetic particles are polished between the magnetic particles and the tube to be polished so that the fine particles uniformly dispersed without agglomeration are polished. The inner surface of the tube to be polished can be precisely polished with the abrasive particles.

  Hereinafter, the ultraprecision magnetic polishing method of the present invention and the polishing slurry used in the method will be described with reference to the drawings. In addition, this invention includes the range which has the technical feature, and is not limited to description, drawing, etc. which are shown below.

  FIG. 1 is a schematic diagram showing the processing principle of the ultraprecision magnetic polishing method of the present invention. FIG. 2 is an explanatory diagram of a polishing slurry used in the ultraprecision magnetic polishing method of the present invention. As shown in FIG. 1, the ultraprecision magnetic polishing method of the present invention moves a pipe 1 to be polished, a polishing slurry 2 introduced into the pipe 1 to be polished, and the polishing pipe 1 and the polishing slurry 2 relative to each other. And a polishing method for polishing the inner surface of the pipe 1 to be polished with the polishing slurry 2 by operating the tube inner surface magnetic polishing device 3 using the tube inner surface magnetic polishing device 3 for stirring the polishing slurry 2. As shown in FIG. 2, the feature of the present invention is that the polishing slurry 2 has spherical magnetic particles 11 and an average particle diameter d in the range of 1/4 to 1/1000 of the average particle diameter D of the magnetic particles 11. And a slurry medium 13 which is a slurry medium in which the magnetic particles 11 and the abrasive particles 12 are made into a slurry and does not contain an additive for dispersing the abrasive particles 12 in the polishing slurry 2. It is in.

(Pipe inner surface magnetic polishing equipment)
In FIG. 1, the tube inner surface magnetic polishing apparatus 3 applies a varying magnetic field to the polishing slurry 2 from a magnet 31 (31 a to 31 d) arranged outside the polished tube 1, and these varying magnetic fields are generated in the polishing slurry 2. The magnetic particles 11 are magnetically attracted to act on the inner surface of the tube 1 to be polished. Such a tube inner surface magnetic polishing apparatus 3 can be of various forms. In the example of FIG. 1, four magnets 31a to 31d arranged at intervals of 90 ° on the outside of the polished tube 1, and 2 A yoke 32 (32a, 32b) connecting the two magnets (31a and 31b, 31c and 31d), and a rotating device (not shown) for rotating the polished tube 1 to move the polished tube 1 and the magnet 31 relative to each other. (See also FIG. 5 described later). In the example of FIG. 1, the magnets 31a to 31d are disposed around the polished tube 1 so as to have an angle of 90 °, but the angle is arbitrary.

  Specifically, a composite magnet 36a formed by connecting a pair of S pole 31a and N pole 31b arranged at 90 ° with a yoke 32a, and a pair of S pole 31c and N pole 31d arranged at 90 ° are yoked. Magnetic fields are formed by the composite magnets 36b connected by 32b. The composite magnet 36a and the composite magnet 36b are arranged so as to face each other around the polished tube 1 in a 180 ° positional relationship, and the polished tube 1 is arranged so as to be sandwiched between the two composite magnets 36a and 36b. The A polishing slurry 2 is contained in the polished tube 1. 1 and 5, the composite magnets 36a and 36b are fixed and the polished tube 1 is rotated to move the polished tube 1 and the polishing slurry 2 relative to each other. However, the polished tube 1 is fixed. Then, the composite magnets 36a and 36b may be rotated to cause the polished tube 1 and the polishing slurry 2 to move relative to each other. Further, the composite magnet and the tube 1 to be polished may be simultaneously rotated in opposite directions. The relative motion occurs between the polished tube 1 and the polishing slurry 2. However, since the polishing slurry 2 is magnetically attracted to the composite magnets 36a and 36b, the relative motion occurs between the polished tube 1 and the magnet (magnetic field). It can also be said.

  The speed of the relative motion may be a speed that allows the magnetic particles 11 in the polishing slurry 2 to cause the self-stirring phenomenon 35 to uniformly disperse the abrasive particles 12 in the polishing slurry 2. Although it will be set, for example, the relative moving speed between the pipe 1 to be polished and the polishing slurry 2 (magnet) can be set in the range of 50 to 200 m / min.

  The polishing slurry 2 containing the magnetic particles 11 and the abrasive particles 12 is magnetically attracted by the two composite magnets 36a and 36b and does not move from a predetermined region even when the polished tube 1 rotates 33, and the rotating slurry 1 is rotated. Move relative to the inner surface. By the relative movement of the polishing slurry 2, the inner surface of the polished tube 1 can be polished.

  Since the strength (magnetic force) of the magnet is determined in consideration of other conditions, it cannot be generally stated. However, it is preferable that the polishing slurry 2 has a magnetic force that causes the spontaneous stirring phenomenon 35 in the polished pipe 1. . There is no restriction | limiting in particular in the kind of magnet 31 which comprises the composite magnet 36, A permanent magnet or an electromagnet may be sufficient. Examples of permanent magnets include rare earth magnets, ferrite magnets, alnico magnets, and MA magnets. Rare earth magnets are preferred in that a strong magnetic field can be obtained. Specifically, a neodymium magnet (Nd—Fe—B) or a samarium cobalt magnet (Sm—Co) is preferably used as the rare earth magnet.

  There are no particular restrictions on the number and arrangement of magnets, and the number and arrangement may be such that the polished tube 1 can be arranged in a magnetic field formed by magnets. For example, a pair of N poles and S poles may be disposed so as to face each other with the polished tube 1 interposed therebetween, or a pair of N poles and S poles are adjacent to each other as shown in FIG. You may arrange. In the former case, it is easy to form a uniform magnetic field at the place where the polished tube 1 is disposed, and in the latter case, it is easy to form a non-uniform magnetic field. Usually, it is preferable to arrange the polished tube 1 in a non-uniform magnetic field. The number of magnets may be one, but when the polished pipe 1 is large, it is preferable to increase the number of magnets to 2 or more. In this case, the pair of N poles and S poles are arranged adjacent to each other. It is preferable to arrange a plurality of magnets arranged around the pipe 1 to be polished.

  There are no particular restrictions on the shape of the N and S poles. Normally, columnar magnets such as cylinders and polygonal columns are used as the N pole and S pole. Further, from the viewpoint of increasing the magnetic flux density, the tip of the N pole and / or the S pole may be a frustum shape, for example, a truncated cone shape or a truncated pyramid shape. In addition, since the magnetic field strength at the corners of the magnet is increased, the tip of the N pole or S pole can be formed with a notch. The yokes 32a and 32b are not particularly limited, and those generally used as yokes can be used. For example, the general structural rolled steel (SS400) shown in the Example mentioned later is used.

  The tube inner surface magnetic polishing apparatus 3 may include a vibration device for vibrating the magnet 31.

  The to-be-polished tube 1 is a tube to be polished, and the material thereof may be a non-magnetic tube or a magnetic tube. Examples of the material of the nonmagnetic tube include plastics, glass, ceramics, and nonmagnetic metals (copper, aluminum, nonmagnetic steel, nonmagnetic stainless steel, titanium, and the like). Examples of the material of the magnetic tube include a steel tube, a magnetic stainless steel tube, a nickel tube, and a magnetic alloy tube. However, when the pipe 1 to be polished is a magnetic pipe, it is necessary to cause a spontaneous stirring phenomenon in the polishing slurry 2 by the magnetic force of the magnet 31 against the magnetism of the pipe.

  The inner diameter of the pipe 1 to be polished is not particularly limited, and may be a thin pipe having a diameter of about 0.2 mm to a pipe having a diameter of about 80 mm. Further, the inner diameter of the tube 1 to be polished may be constant in the longitudinal direction or may change in the middle. The polished tube 1 may be straight or bent. If the pipe 1 to be polished is straight, either the pipe 1 to be polished or the magnet 31 may move while rotating in the longitudinal direction of the pipe 1 to be polished, but when the pipe 1 to be polished is bent. Since the bent pipe 1 to be polished is difficult to rotate, the magnet 31 is preferably rotated.

(Polishing slurry)
As illustrated in FIG. 2, the polishing slurry 2 includes magnetic particles 11, polishing particles 12, and a slurry medium 13. The polishing slurry 2 is introduced into the polished tube 1 and is moved relative to the polished tube 1 to polish the inner surface of the polished tube 1.

  The magnetic particle 11 is a spherical particle and may be a true spherical shape or an elliptical shape. In short, it may be any shape as long as it has a smooth curved surface without a sharp edge on its outer periphery. Even when the magnetic particle 11 having such a shape hits the inner surface of the tube 1 to be polished, there is an advantage that the inner surface is hardly damaged. In addition, the magnetic particles 11 are held in a position opposite to the magnet in the polished tube, and are an essential element for causing the self-stirring phenomenon 35 by the relative movement of the polished tube 1 and the polishing slurry 2. Therefore, the magnetic particle 11 needs to have a magnetic characteristic and a particle size that cause the spontaneous stirring phenomenon 35 due to the relative movement of the polished tube 1 and the polishing slurry 2. Therefore, the material of the magnetic particles 11 needs to be particles that are magnetically attracted to the magnet and pressed against the inner wall of the tube 1 to be polished and cause the self-stirring phenomenon 35.

  As the magnetic particles 11, particles containing all or part of an element generally called a magnetic substance such as iron, cobalt, nickel, chromium, oxides, alloys, and compounds thereof are used. As specific examples, nickel alloy powder such as carbonyl iron powder, electrolytic iron powder, nickel powder, Ni-P alloy powder or Ni-B alloy powder can be used. It is also possible to use spherical aluminum oxide powder sintered with iron in an inert gas under high temperature and pressure, or a product powder of a thermite reaction between aluminum and iron oxide in an inert gas atmosphere. is there. In addition, even if it is a commercially available magnetic abrasive grain (Toyo Abrasives Co., Ltd .; KMX-80) or other non-commercially available magnetic abrasive grains, the surface thereof is processed into a spherical shape and is itself abrasive grains. As long as the effect is reduced, it can be used. Moreover, the particle | grains which coat | cover another material on the surface of the spherical powder with magnetism may be sufficient.

  The size of the magnetic particle 11 is 4 times or more and 1000 times or less, preferably 4 times or more and 50 times or less, more preferably 5 times or more and 20 times or less that of the abrasive particles 12 in the relative relationship with the abrasive particles 12. It is a range. The relationship between the size of the magnetic particles 11 and the size of the abrasive particles 12 is that the surface state of the inner surface of the tube to be polished (including the degree of surface roughness) before polishing, the required surface state of the inner surface of the tube to be polished, and the requirements. The polishing time is arbitrarily selected from the above range depending on the polishing time, the degree of prevention of aggregation of the abrasive particles 12, and the like.

  If the size of the magnetic particles 11 is less than 4 times the size of the abrasive particles 12, the sizes of both particles may approach each other and the abrasive particles 12 may not be uniformly dispersed by the magnetic particles 11, and will be described later with reference to FIG. As in the embodiment, it becomes difficult for the abrasive particles 12 to be sandwiched between the magnetic particles 11 and the inner surface of the tube to be polished, and as a result, it becomes difficult to polish the inner surface of the tube to be polished. On the other hand, if the size of the magnetic particles 11 exceeds 1000 times that of the abrasive particles 12, the difference between the two is too large, and the abrasive particles 12 are too small relative to the size of the magnetic particles 11, and efficient polishing is performed. Cannot be realized. In the range of 5 times or more and 20 times or less, the polishing particles 12 are sandwiched between the magnetic particles 11 and the inner surface of the tube to be polished as in the embodiment shown in FIG. Therefore, it is particularly preferable.

  The absolute value of the magnetic particles 11 is preferably 0.5 μm or more and 500 μm or less in average particle diameter D, more preferably 0.5 μm or more and 50 μm or less, and within the range of 0.5 μm or more and 10 μm or less. It is particularly preferred. These average particle diameters D are arbitrarily selected according to the inner diameter of the polished tube 1 to be polished. When using a large abrasive particle 12 when the inner diameter is large or during rough polishing, the magnetic particle 11 having a large particle diameter is selected within the relative size range between the abrasive particles 12 and the inner diameter is small. In the case where small abrasive particles 12 are used at the time of finish polishing or the like, the magnetic particles 11 having a small particle diameter are selected within a relative size range with respect to the abrasive particles 12 described above. That is, it is arbitrarily selected depending on the inner diameter of the tube 1 to be polished or by the polishing step (rough polishing, normal polishing, finish polishing, etc.). In particular, in the range of 0.5 μm or more and 10 μm or less, there is an effect that it is possible to precisely polish a small-diameter tube that has been difficult to polish with high accuracy. The average particle diameter D is an average value measured from an electron micrograph of the magnetic particles 11, and the surface roughness (Ra) is an arithmetic average roughness measured based on JIS B 0601 (2001).

The abrasive particles 12 are abrasive particles having an average particle diameter d in the range of 1/4 to 1/1000 of the average particle diameter D of the magnetic particles 11 described above. The form of the abrasive particles 12 is not particularly limited, and various forms can be used. Examples of the abrasive particles 12 include diamond particles, aluminum oxide particles, cerium oxide particles, silicon carbide particles, silicon dioxide particles, chromium oxide particles, and composites thereof. Also, A in JIS display, WA, GC, SA, MA , C, MD, include those represented as _{CBN, Al 2 O 3, SiC} , ZrO 2, B 4 C, diamond, cubic boron nitride, Abrasive particles such as MgO, CeO ₂ or fumed silica may also be used.

  The particle size of the abrasive particles 12 is in the range of 1/4 to 1/1000 of the magnetic particles 11 with an average particle size d as described above with the reason for the magnetic particles 11, and preferably 1/4 to 1 / 50, more preferably 1/5 to 1/20. The abrasive particles 12 in such a range are uniformly dispersed without being agglomerated because the polished tube 1 is polished so as to be sandwiched between the magnetic particles 11 and the polished tube 1 as shown in FIG. The inner surface of the tube to be polished 1 can be precisely polished with fine abrasive particles 12 (see FIGS. 3 and 4 described later). The average particle diameter d is an average value measured from an electron micrograph of the abrasive particles 12, and the surface roughness (Ra) is an arithmetic average roughness measured based on JIS B 0601 (2001).

  The slurry medium 13 is a medium in which the magnetic particles 11 and the abrasive particles 12 are made into a slurry, and does not contain an additive for dispersing the abrasive particles 12 in the abrasive slurry 2. As a preferable medium in the slurry state, water-soluble and oil-soluble liquids generally used as polishing liquids can be used in addition to light oil and water.

  Particularly in the present invention, there has been a problem that additives such as surfactants, which have been added so as not to condense the small abrasive particles in the slurry, hinder the cleaning efficiency in the cleaning step after polishing. The problem is also solved, and the polishing slurry 2 used in the present invention is characterized by not containing such an additive. Even if such an additive is not included, the present invention does not require such an additive because the magnetic particles 11 can be uniformly dispersed by the self-stirring phenomenon 35 as described above. It becomes. As a result, in the cleaning process after polishing, it is not necessary to perform cleaning with a special cleaning liquid, and effective cleaning can be performed only by simple water cleaning or ethanol cleaning.

  In the thus configured polishing slurry 2, the content of the magnetic particles 11 contained in the polishing slurry 2 is usually in the range of 30 wt% to 70 wt%, and the content of the abrasive particles 12 is 10 wt% to 60 wt%. The total content of the magnetic particles 11 and the abrasive particles 12 is in the range of 70% by weight to 90% by weight. The content of the magnetic particles 11 is related to conditions such as the particle diameter of the pipe inner surface magnetic polishing apparatus 3 and the magnetic particles 11 and is set so as to easily cause the self-stirring phenomenon 35. The content of the abrasive particles 12 Is set in consideration of the degree of polishing of the inner surface of the tube to be polished (rough polishing, normal polishing, finish polishing, etc.) and polishing efficiency. Further, the content of the slurry medium 12 has a certain degree of viscosity so that the prepared polishing slurry 2 remains as a fluid in the position opposite to the magnet even by the relative movement between the tube to be polished 1 and the magnet. It is set as follows.

  As described above, the spherical magnetic particles 11 contained in the polishing slurry 2 are 4 to 1000 times (preferably 4 to 50 times, particularly preferably 5 to 20 times) larger than the abrasive particles 12, The inner surface of the polishing tube 1 can be prevented from being scratched as much as possible, and there is an effect that it does not act so as to impair the smoothness. Furthermore, since the self-stirring phenomenon 35 that does not aggregate the abrasive particles 12 can be caused, it is not necessary to add an additive (such as a surfactant) for dispersing the abrasive particles 12 to the slurry medium as in the conventional case. . Therefore, it is possible to eliminate the difficulty of washing and removing such additives after polishing, and there is an effect that the washing can be performed very efficiently and easily. The self-stirring phenomenon 35 is a stirring phenomenon that occurs when the spherical magnetic particles 11 move in a large spiral shape when the tube 1 and the polishing slurry 2 are relatively moved by the tube inner surface magnetic polishing device 3. As a result, it is possible to prevent the abrasive particles 12 having a small diameter from agglomerating and to uniformly disperse the abrasive particles 12 in the polishing slurry 2. Fine polishing of the inner surface of the can be realized.

(Polishing behavior)
FIG. 3 is a dynamic model diagram acting on the polishing slurry in the tube to be polished. As shown in FIG. 3, the polishing slurry 2 inserted into the polished tube 1 receives magnetic forces Fx and Fy from the magnets 31a and 31b in the direction of the magnetic lines and the direction of the equipotential lines, respectively, and is attracted from the magnets 31a and 31b. It is held near the magnet. The magnetic forces Fx and Fy are related to the diameter of the magnetic particles 11, the magnetic susceptibility of the magnetic particles 11, the strength of the magnetic field, and the rate of change thereof. When the polished tube 1 is rotated, the polishing slurry 2 receives a polishing resistance ft between the polished slurry 2 and the inner surface of the polished tube 1. At this time, the behavior of the polishing slurry 2 during processing is related to the magnetic forces Fx and Fy, gravity mg, and polishing resistance ft. When the particle size and content ratio of the magnetic particles 11 constituting the polishing slurry 2 are constant, the self-stirring phenomenon 35 is caused to occur in the polishing slurry 2 by selecting the rotation speed of the polished tube 1 and the strength of the magnetic field, and the small diameter Uniform dispersion of the abrasive particles 12 can be realized. As described above, the generation factors of the spontaneous stirring phenomenon 3 include the strength of the magnetic field, the amount and particle size of the magnetic particles, the number of rotations of the pipe to be polished (degree of relative movement), the polishing resistance received from the inner surface of the pipe to be polished, Etc.

  FIG. 4 is a schematic view showing an aspect when the polishing slurry of the present invention polishes the inside of the pipe to be polished. In the embodiment shown in FIGS. 1 and 3, when the polished tube 1 and the polishing slurry 2 (magnet 31) are moved relative to each other, the polishing slurry 2 receives an attractive magnetic force from the magnet 31 and is held between the N and S poles. In this state, relative movement occurs between the polishing slurry 2 and the inner surface of the pipe to be polished. This relative motion causes resistance between the magnetic particles 11 constituting the polishing slurry 2 and the inner surface of the polished pipe, and thus the self-stirring phenomenon occurs in the magnetic particles 11, and the self-stirring phenomenon 35 of the magnetic particles 11 is caused. The abrasive particles 12 are uniformly dispersed without causing aggregation, and ultraprecision polishing of the inner surface of the polished pipe can be realized.

  The mode at this time is as shown in FIG. 4. The non-aggregated abrasive particles 12 are sandwiched between the large-diameter magnetic particles 11 and the inner surface of the tube 1 to be polished, thereby efficiently covering the inner surface of the tube to be polished. Precision polishing.

  After the polishing process is completed, the polishing slurry 2 is separated from the polished tube 1. At this time, the polishing slurry 2 can be separated from the polished tube 1 relatively easily by using magnetism. Even when the diameter of the opening is smaller than the inner diameter of the pipe 1 to be polished or when the inner diameter differs depending on the location, the polishing slurry 2 can be separated from the pipe 1 to be polished relatively easily by using magnetism. be able to. Specifically, when the tube 1 to be polished is polished in the manner shown in FIG. 1, the polishing slurry 2 is moved by moving the tube 1 to be polished relative to the magnet 31 in the axial direction. The polishing slurry 2 can be discharged from the opening of the tube 1 to be polished by moving the polishing tube 1 relative to the polishing tube 1 in the axial direction.

  Further, in the ultraprecision magnetic polishing method of the present invention, polishing is performed at each stage by preparing a plurality of types of polishing slurry 2 suitable for each stage of polishing accuracy, such as rough polishing, normal polishing, and finish polishing. be able to. Specifically, a plurality of polishing slurries in which the average particle diameter D of the magnetic particles 11 and the average particle diameter d of the abrasive particles 12 are changed are prepared, and particles having large average particle diameters D and d (magnetic particles 11 and / or Alternatively, polishing is performed by gradually replacing the polishing slurry containing the abrasive particles 12) into the polishing pipe 1. Thus, a plurality of polishing slurries having suitable average particle diameters D and d for the magnetic particles 11 and the abrasive particles 12 are prepared depending on, for example, rough polishing, intermediate polishing, or finish polishing. If polishing is performed by gradually replacing the polishing slurry containing particles having large D and d into the tube 1 to be polished, rough polishing, intermediate polishing, and finish polishing can be sequentially performed. As a result, the polishing efficiency can be improved by using the most suitable polishing slurry for each polishing stage.

  In addition, a tube inner surface polishing method other than the ultraprecision magnetic polishing of the present invention may be applied before the application of the ultraprecision magnetic polishing method of the present invention. For example, polishing may be performed by a method described in the above-described patent documents and non-patent documents as conventionally performed, or a polishing slurry containing an additive that is difficult to clean such as surface activity may be used. . In short, if the ultra-precision magnetic polishing method of the present invention is used as the final polishing, the effects of the present invention can be achieved.

  The present invention will be described more specifically with reference to experimental examples. The scope of the present invention is not limited to the following experimental examples.

[Experiment 1]
FIG. 5 shows a magnetic polishing apparatus used in the experiment, which has the same configuration as the magnetic polishing apparatus shown in FIG. The used magnetic polishing apparatus is an apparatus having a function of rotating the polished tube 1 and vibrating the magnet 31. As the magnet 31, four neodymium of N pole, S pole, S pole and N pole are used. Permanent magnets (18 × 12 × 10 mm) were arranged in order at intervals of 90 °, and two magnets were connected by yokes 32a and 32b to form composite magnets 36a and 36b. The polished tube 1 is fixed to a lathe chuck and rotated at a rotational speed of 2800 per minute, and the composite magnets 36a and 36b are vibrated, thereby causing a relative motion between the inner surface of the polished tube and the polishing slurry 2. As a result, the spontaneous stirring phenomenon 35 occurred, and the inner surface of the polished tube was polished. The experimental conditions are as follows.

(Polishing conditions)
Polished pipe: SUS316 stainless steel circular tube (inner diameter 12.4 mm, outer diameter 12.7 mm) subjected to bright annealing treatment
Magnet: Fe-Nd-B rare earth magnet Clearance between polished tube and magnet: 3 mm
Magnet vibration: amplitude 5mm, vibration frequency 0.8Hz
Magnet rotation speed: 2800 rpm
Treatment time: 15 minutes Polishing slurry: Magnetic particles (carbonyl iron powder with an average particle size of 6 μm, manufactured by BASF Japan Ltd.), abrasive particles (diamond with a particle size range of 0.25 μm to 0.75 μm and an average particle size of 0.5 μm) Particles, manufactured by Microdiamant), slurry medium (manufactured by Castrol, trade name: Honairo 998, chlorine free)
Composition of polishing slurry: 62% by weight of magnetic particles, 21% by weight of polishing particles, 17% by weight of polishing slurry

(Measurement and results)
FIG. 6 is a graph showing the surface roughness Ra and the polishing amount M measured for each polishing time. Polishing was performed for 15 minutes, and the surface roughness before polishing, the surface roughness after polishing in increments of 5 minutes, and the final surface roughness after 15 minutes were measured. As for the surface roughness when polishing in increments of 5 minutes, the rotation was stopped when a predetermined time passed, and the polished tube was ultrasonically cleaned with ethanol for 5 minutes, and the polishing amount M and the surface roughness Ra were measured. For the surface roughness Ra, a stylus type roughness measuring machine was used, and the inner surface of the polished pipe was measured at 120 locations in the circumferential direction at 120 ° intervals, and the average value thereof was adopted. As shown in FIG. 6, the surface roughness of the inner surface of the polished tube before polishing was 43 nmRa, but the surface roughness after polishing for 15 minutes was 5 nmRa, and extremely smooth mirror polishing could be realized. In addition, the measurement of surface roughness measured by the method based on JISB0601 (2001) using the surface roughness measuring machine (Mitutoyo Corporation, model number: SV-624-3D), and obtained arithmetic average roughness The value of the roughness was expressed as the surface roughness Ra. The polishing amount M was evaluated by measuring the weight of the tube to be polished before and after polishing.

  FIG. 7 is a diagram showing a surface roughness result measured using a non-contact surface shape roughness measuring apparatus and three-dimensional shape images before and after polishing. It can be seen that the rough surface before processing becomes a smooth nano-level smooth surface after processing. The non-contact surface shape roughness measuring device is an optical interference type surface roughness measuring device, but the surface roughness measured using this device is slightly different from that shown in FIG. The surface roughness of the inner surface of the tube was 184.48 nmRa, but the surface roughness after polishing for 15 minutes was 9.47 nmRa. Note that the non-contact surface shape roughness measuring device is manufactured by Veeco Instruments, model number: WYKO NT1100M), and the three-dimensional shape image is an image obtained by measuring with this device.

  As described above, by using the new polishing slurry 2 prepared by simply mixing the spherical magnetic particles 11, the small-diameter polishing particles 12 and the slurry medium 13, polishing is performed using the self-stirring phenomenon 35 during the polishing process. The inner surface of the tube to be polished 1 was subjected to ultra-precision polishing while uniformly dispersing the particles 12. As a result of the polishing process experiment, it was clarified that the surface roughness measured with a stylus type roughness measuring machine could be changed from 43 nmRa to 5 nmRa, and finished to an ultra-precision surface. In addition, it was also confirmed that ordinary cleaning was sufficient for the ultra-precision magnetic polishing method of the present invention for cleaning that was a problem in conventional processing methods.

It is a schematic diagram which shows the processing principle of the ultraprecision magnetic polishing method of this invention. It is explanatory drawing of the polishing slurry used with the ultraprecision magnetic polishing method of this invention. It is a dynamic model figure which acts on the polishing slurry in a to-be-polished pipe | tube. It is a schematic diagram which shows an aspect when the polishing slurry of this invention grind | polishes the inside of a to-be-polished pipe | tube. The magnetic polishing apparatus used in the experiment is an apparatus having the same configuration as the magnetic polishing apparatus shown in FIG. It is a graph which shows the surface roughness measured for every grinding | polishing time, and grinding | polishing amount. It is a figure which shows the surface roughness result measured using the non-contact surface shape roughness measuring apparatus, and the three-dimensional shape image before and behind grinding | polishing process.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tube to be polished 2 Polishing slurry 3 Tube inner surface magnetic polishing device 11 Magnetic particle 12 Polishing particle 13 Slurry medium 31, 31a, 31b, 31c, 31d Magnet 32, 32a, 32b Yoke 33 Rotation 35 Self-stirring phenomenon 36, 36a, 36b Composite Magnet D Average particle size of magnetic particles d Average particle size of abrasive particles

Claims (5)

Using a pipe to be polished, a polishing slurry introduced into the pipe to be polished, and a pipe inner surface magnetic polishing device that stirs the polishing slurry by moving the pipe to be polished and the polishing slurry relative to each other. An ultra-precise magnetic polishing method of operating a polishing apparatus to polish the inner surface of the pipe to be polished with the polishing slurry,
The abrasive slurry comprises spherical magnetic particles, abrasive particles having an average particle size in the range of 1/4 to 1/1000 of the average particle size of the magnetic particles, and the magnetic particles and the abrasive particles are made into a slurry. An ultra-precise magnetic polishing method comprising: a slurry medium that does not contain an additive for dispersing the abrasive particles in the polishing slurry.   The ultra-precise magnetic polishing method according to claim 1, wherein the magnetic particles stirred in the polishing pipe are dispersed by suppressing aggregation of the polishing particles.   Prepare a plurality of polishing slurries with the average particle size of the magnetic particles and the average particle size of the abrasive particles changed, and gradually replace the polishing slurry containing particles having a large average particle size into the polished pipe for polishing. The ultraprecision magnetic polishing method according to claim 1 or 2. A polishing slurry that is introduced into a pipe to be polished and moves relative to the pipe to be polished to polish the inner surface of the pipe to be polished,
A spherical magnetic particle, an abrasive particle having an average particle size in the range of 1/4 to 1/1000 of the average particle size of the magnetic particle, and a slurry medium in which the magnetic particle and the abrasive particle are made into a slurry. A polishing slurry for ultra-precise magnetic polishing, comprising a slurry medium containing no additive for dispersing the abrasive particles in the polishing slurry.   The polishing slurry according to claim 4, wherein the magnetic particles are spherical carbonyl iron powder, and the polishing particles are diamond particles.