JP2005290233A - Magnetic abrasive grain, its manufacturing method, and magnetic grinding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic abrasive grain for a more precise surface treatment, and to provide a method for manufacturing the same. <P>SOLUTION: The magnetic abrasive grain 1 is flat, and has an aspect ratio of ≥1.5. Preferably, the magnetic abrasive grain 1 is formed of nickel or a nickel-based metal such as a nickel alloy or formed of cobalt or a cobalt-based metal such as a cobalt alloy. Also preferably, the magnetic abrasive grain 1 is formed by cutting, pulverizing, or forging a magnetic thin film. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a magnetic abrasive grain, a manufacturing method thereof, and a magnetic polishing method, and more particularly to a magnetic abrasive grain capable of performing more precise surface processing, a manufacturing method thereof, and a magnetic polishing method.

  The magnetic polishing method is a precision processing method for polishing the surface of a workpiece by moving magnetic abrasive grains having a polishing action by the action of a magnetic field. This magnetic polishing method is a method that enables polishing of parts that are difficult with conventional machining, such as the surface of a part having a complicated shape, the inner surface of a hole that does not receive a tool, the inner surface of a tube that does not reach the tool, etc. Part of the polishing has been put to practical use.

  Magnetic abrasive grains used in the magnetic polishing method move relative to the workpiece by the action of a magnetic field. In general, magnetic abrasive grains containing magnetic abrasive particles and magnetic abrasive grains made of a mixture of non-magnetic non-magnetic abrasive particles and magnetic magnetic particles are known. In the former case, the abrasive particles move by the magnetic field. In the latter case, the magnetic particles move by the magnetic field, and the abrasive particles move along with the movement of the magnetic particles to polish the surface of the workpiece. To do. Therefore, the latter magnetic abrasive grains have a problem that the abrasive particles may not perform a desired movement with the movement of the magnetic particles.

On the other hand, the former magnetic abrasive grains do not have such a problem. For example, magnetic abrasive grains in which an electroless plating film containing abrasive particles is formed on the surface of the magnetic particles (see, for example, Patent Document 1), sintering, and the like. In this method, magnetic abrasive grains in which magnetic particles and abrasive particles are integrated have been reported. As such magnetic abrasive grains, there are few kinds of magnetic abrasive grains in Japan to the extent that one kind of magnetic abrasive grains (Toyo Abrasive Co., Ltd .; KMX-80) is commercially available.
JP 2002-265933 A (Claim 3)

  By the way, although the above-mentioned commercially available magnetic abrasive grains have a processing effect, when performing a more precise polishing process, they enter the minute recesses on the surface of the workpiece more than necessary, and excessively add the recesses in addition to the protrusions. In some cases, it may be removed, and it is not necessarily a preferable magnetic abrasive grain.

  The present invention has been made to solve the above-mentioned problems, and its object is to provide a magnetic abrasive that enables more precise surface processing, a manufacturing method thereof, and a magnetic polishing method using the magnetic abrasive. It is to provide.

  The magnetic abrasive grains of the present invention for achieving the object are flat magnetic abrasive grains having magnetism, and the flatness of the magnetic abrasive grains is 1.5 or more.

  According to the present invention, since the magnetic abrasive grains are formed in a flat shape having a flatness of 1.5 or more, the peripheral portion acts as a polishing portion for polishing, so that the polishing can be performed more precisely. . Further, by being formed in a flat shape, it can easily enter into details such as a minute groove of a workpiece while maintaining a large volume as compared with a case where the cross section is formed in a substantially circular shape. There is an advantage that more precise surface processing can be performed.

  In the magnetic abrasive grains of the present invention, the magnetic abrasive grains are preferably formed of nickel, cobalt, or an alloy thereof. According to this invention, since the magnetic abrasive grains are formed of nickel, cobalt, or an alloy thereof, the magnetic abrasive grains are difficult to rust. Also, magnetic abrasive grains having different working forces can be obtained by changing the alloy composition.

  In order to achieve the above object, the magnetic abrasive grain manufacturing method of the present invention cuts, crushes or forges a magnetic thin film having magnetism to form a flat magnetic abrasive grain having a flatness of 1.5 or more. It is characterized by. According to the present invention, flat magnetic abrasive grains can be easily formed. Since the formed magnetic abrasive grains are formed in a flat shape, the peripheral portion acts as a polishing portion for polishing, and has a volume larger than that in the case where it is formed in a granular shape having a substantially circular cross section. Thus, for example, it is possible to easily enter details such as minute grooves of the workpiece, and surface processing can be performed more precisely.

  In order to achieve the above object, a magnetic polishing method of the present invention is characterized by polishing the surface of a workpiece using the magnetic abrasive grains of the present invention described above. According to the present invention, it is possible to perform a more precise surface processing as described above, and to easily process a workpiece having a complicated shape.

  As described above, the magnetic abrasive grains according to the present invention and the magnetic polishing method according to the present invention can be processed more precisely and have a complicated shape since the magnetic abrasive grains are formed in a flat shape. The workpiece to be processed can be easily processed.

  Further, according to the magnetic abrasive grain manufacturing method of the present invention, flat magnetic abrasive grains that can be processed more precisely and can easily process a workpiece having a complicated shape can be easily obtained. Can be formed.

  Hereinafter, the magnetic abrasive grains of the present invention, the method for producing the magnetic abrasive grains, and the magnetic polishing method of the present invention will be described in detail based on the drawings.

(Magnetic abrasive)
FIG. 1 is a view showing an example of magnetic abrasive grains of the present invention. FIG. 2 is a view showing another example of the magnetic abrasive grains of the present invention. The magnetic abrasive grain of the present invention is used in a magnetic polishing method. As shown in FIGS. 1 and 2, the magnetic abrasive grain 1 is a flat magnetic abrasive grain 1 having magnetism, and the magnetic abrasive grain 1 is flattened. It is characterized in that the degree is 1.5 or more.

  The magnetic abrasive grains 1 have magnetism in a magnetic field when used in a magnetic polishing method, and move with fluctuations in the magnetic field. The material of the magnetic abrasive grain 1 may be magnetized in the magnetic field, and may be always magnetized, or may be magnetized by being placed in the magnetic field, although not magnetized outside the magnetic field. Examples of the material of the magnetic abrasive grain 1 include nickel-based metals such as nickel and nickel alloys, cobalt-based metals such as cobalt and cobalt alloys, ferrite, and iron oxide. Preferred examples include nickel-based metals such as alloys and cobalt-based metals such as cobalt and cobalt alloys.

  The magnetic abrasive grain 1 is appropriately selected according to the material and shape of the workpiece to be processed and the purpose of processing the workpiece, and the shape in plan view is approximately circular, approximately elliptical, approximately triangular, approximately It has various shapes such as a rectangle and a substantially polygon, and is formed in a flat shape. The magnetic abrasive grain 1 of the present invention is characterized in that it is formed in a flat shape as shown in FIGS. In the present invention, the flat shape means that the thickness is thin, and if the thickness is small, it may be referred to as a plate shape or a flake shape, and may be a scale shape.

  The thickness T of the magnetic abrasive grain 1 is preferably in the range of 1 μm to 100 μm, particularly preferably 10 μm to 30 μm. In the present invention, the thickness T is based on the definition of Heywood, and as shown in FIG. 1, when one magnetic abrasive grain 1 is stationary on the horizontal plane in the most stable state, the horizontal plane It is the maximum distance between parallel surfaces that are parallel to and in contact with the surface of the magnetic abrasive grain 1. If the thickness T of the magnetic abrasive grain 1 is less than 1 μm, the workpiece may not be processed. On the other hand, when the thickness T of the magnetic abrasive grains 1 exceeds 100 μm, it may be impossible to perform more precise surface processing.

  The flatness m of the magnetic abrasive grain 1 is 1.5 or more, preferably 4 or more. The upper limit of the flatness m is not particularly limited, but is preferably 30. In the present invention, the flatness m is based on the definition of Heywood, and is represented by m = B / T, where B is the short axis length of the magnetic abrasive grain 1. Here, the minor axis length B of the magnetic abrasive grain 1 means that when one magnetic abrasive grain 1 is stationary on the horizontal plane in the most stable state, it extends on the same horizontal plane and the surface of the magnetic abrasive grain 1 This is the minimum distance between parallel surfaces in contact with. If the flatness m is less than 1.5, more precise surface processing may not be performed.

  The major axis length L of the magnetic abrasive grain 1 is not particularly limited, but is preferably in the range of 200 μm to 2000 μm, and preferably in the range of 450 μm to 1700 μm. In the present invention, the long axis length L is based on the definition of Heywood. When one magnetic abrasive grain 1 is stationary on the horizontal plane in the most stable state, the long axis length L is The maximum distance between parallel surfaces that are perpendicular to each other, extend on the same horizontal plane, and are in contact with the surface of the magnetic abrasive grain 1. If the major axis length L of the magnetic abrasive grains 1 is less than 200 μm, the magnetic abrasive grains are reduced in size and the magnetic force that is the basis of the processing force becomes weak, so that more precise surface processing may not be performed. On the other hand, when the major axis length L of the magnetic abrasive grains 1 exceeds 2000 μm, the magnetic abrasive grains become large and the processing pressure becomes too high, and a more precise surface processing may not be possible. The minor axis length B of the magnetic abrasive grain 1 is not particularly limited, but is preferably in the range of 100 μm to 1000 μm, more preferably in the range of 140 μm to 450 μm. If the minor axis length B of the magnetic abrasive grains 1 is less than 100 μm, the magnetic abrasive grains are reduced in size and the magnetic force that is the basis of the processing force becomes weak, so that more precise surface processing may not be performed. On the other hand, if the minor axis length B of the magnetic abrasive grains 1 exceeds 1000 μm, the magnetic abrasive grains 1 are increased in size and the processing pressure becomes too large, and it may be impossible to perform more precise surface processing.

  Thus, since the magnetic abrasive grain 1 of this invention is formed in the flat shape whose flatness m is 1.5 or more, the peripheral part (edge part) 2 acts as a grinding | polishing part which grind | polishes. Further, when the magnetic abrasive grain 1 of the present invention is formed flat by forging, pressing or the like, it has a characteristic that it is easily magnetized in a direction parallel to the surface of the magnetic abrasive grain 1, that is, magnetic anisotropy. For this reason, the magnetic abrasive grain 1 stands in the direction of the magnetic field in the magnetic field. For example, as shown in FIG. 3, magnetic abrasive grains 1 are placed inside a circular tube (also referred to as a circular tube 21) that is a workpiece, and two pieces of 1 are placed outside the circular tube 21. When a pair of magnetic poles 22 is arranged and a magnetic field is generated in the circular tube 21, the surface of the magnetic abrasive grain 1 becomes parallel to the direction of the magnetic field, and the peripheral edge of the magnetic abrasive grain 1 is on the inner wall of the circular tube 21. Since they adhere, the surface of the workpiece can be polished more precisely by the peripheral edge 2 of the magnetic abrasive grain 1.

  In addition, the magnetic abrasive grain 1 of the present invention is formed in a flat shape, so that the magnetic abrasive grain 1 has a large volume as compared with the case where the magnetic abrasive grain 1 is formed, for example, in a substantially circular cross section. It is possible to easily enter details such as minute grooves, and to perform more precise surface processing.

  Further, as shown in FIG. 2, the magnetic abrasive grains 1 may contain 70% by weight or less of abrasive particles 5 based on the total amount of magnetic abrasive grains. As the abrasive particles 5, various inorganic particles and compound (oxide, carbide, nitride, etc.) particles that can be used as abrasive particles can be used. For example, diamond particles, alumina (aluminum oxide) particles, silicon carbide particles, etc. Can be mentioned. The shape of the abrasive particles 5 is appropriately selected according to the material and shape of the workpiece to be processed and the purpose of processing the workpiece, such as a spherical shape (including a true spherical shape), a polygonal shape, Various shapes such as a needle shape can be mentioned. The particle size of the abrasive particles 5 is also appropriately selected according to the material and shape of the workpiece to be processed and the purpose of processing the workpiece.

  The content of the abrasive particles 5 is preferably 70% by weight or less based on the total amount of the magnetic abrasive grains. However, the content of the abrasive particles 5 is appropriately determined according to the material and shape of the workpiece to be processed and the purpose of processing the workpiece. It is desirable to select. For example, the polishing performance can be improved by increasing the content of the abrasive particles 5 within the above range. On the other hand, by reducing the content of the abrasive particles within the above range, it is possible to suppress the polishing efficiency and gradually advance the polishing to perform precise processing.

  Among the abrasive particles 5 contained in the magnetic abrasive grain 1, at least a part of the abrasive particles 5 taken in the vicinity of the peripheral edge 2 of the magnetic abrasive grain 1 protrudes from the peripheral edge 2 of the magnetic abrasive grain 1. Is desirable. With such an embodiment, it is possible to exhibit a sufficient polishing function even in the initial stage of processing. Even if a part of the abrasive particles 5 taken in the vicinity of the peripheral edge 2 of the magnetic abrasive grain 1 does not protrude from the peripheral edge surface of the magnetic abrasive grain 1, the peripheral edge of the magnetic abrasive grain 1 during processing Since the surface layer of the part is worn and the abrasive particles 5 are exposed, the same effect as in the case of the above aspect can be obtained.

(Method for producing magnetic abrasive grains)
Next, the manufacturing method of the magnetic abrasive grain of this invention is demonstrated.

  The method for producing magnetic abrasive grains of the present invention is suitable as a method for producing the magnetic abrasive grains used in the magnetic polishing method, particularly the magnetic abrasive grains of the present invention described above. The method for producing magnetic abrasive grains according to the present invention is characterized in that a magnetic thin film having magnetism is cut, ground or forged to form flat magnetic abrasive grains having a flatness of 1.5 or more.

  The magnetic thin film having magnetism is preferably formed of a material for forming the magnetic abrasive grains 1, for example, a nickel-based metal such as nickel or a nickel alloy, or a cobalt-based metal such as cobalt or a cobalt alloy. The magnetic thin film may be any material as long as it is formed of a magnetic material such as a nickel-based metal or a cobalt-based metal, may be a metal piece, may be formed by rolling, It may be formed by plating such as electroforming. The electroforming method is a method using a chemical plating method such as an electroplating method or an electroless plating method.

  Next, the case where a magnetic thin film is formed using an electroforming method will be described. The electroforming method is a method in which a magnetic thin film is first formed on a mother die by electroplating or electroless plating, and then the magnetic thin film is peeled off from the mother die to obtain a magnetic thin film. As a plating bath used in the electroforming method, for example, in the case of a nickel-based metal, it is preferable to use a watt bath mainly composed of nickel sulfate, nickel chloride and boric acid, or a sulfamic acid plating bath. In the case of a cobalt-based metal, it is preferable to use a cobalt plating bath mainly composed of cobalt sulfate and cobalt chloride.

  When the abrasive particles are contained in the magnetic abrasive grains, a predetermined amount of the abrasive particles are put in the plating bath and stirred to prepare the plating bath. In this case, stirring means such as mechanical stirring, gas stirring such as air, ultrasonic stirring using an ultrasonic homogenizer, etc. may be used so that the abrasive particles can be uniformly dispersed in the magnetic thin film serving as magnetic abrasive grains. preferable. By such means, the abrasive particles can be uniformly dispersed in the magnetic thin film that becomes the magnetic abrasive grains, so that the content of the abrasive particles can be adjusted. As a result, the mechanical properties and magnetic properties of the magnetic abrasive grains can be adjusted by adjusting the content of the abrasive particles.

  The mother die is preferably one in which the surface on which the magnetic thin film is formed is formed on a flat surface, for example, a plate. Non-metallic materials such as iron, stainless steel, copper and copper alloys, aluminum and aluminum alloys, metals such as zinc and lead, epoxy resins, oils and fats, various plastics, gypsum, glass, rubber, ceramics, leather, etc. Is mentioned. The mother die can form a magnetic thin film without limiting its material.

  Moreover, although the case where the plate-shaped thing was used as a mother mold was demonstrated, you may use a drum as a mother mold. In this case, the drum is rotated slowly, and a part of the drum is immersed in, for example, a nickel plating bath, and a part of the drum is plated to form a magnetic thin film, and the formed magnetic thin film is continuously drummed. It is also possible to form a belt-like magnetic thin film by peeling off the film.

  The thickness of the magnetic thin film is arbitrarily selected from the range in which the magnetic powder 1 can be formed by cutting, grinding or forging. For example, when the magnetic powder 1 is formed by cutting, the thickness of the magnetic thin film becomes the thickness of the magnetic powder 1, so that the thickness of the magnetic thin film is the same as the thickness of the desired magnetic powder 1. Further, when the magnetic powder 1 is formed by pulverization, the thickness of the magnetic thin film is the same as the thickness of the magnetic powder 1, and therefore the thickness of the magnetic thin film is the same as the thickness of the desired magnetic powder 1. When the magnetic powder 1 is formed by forging, the thickness of the magnetic thin film is selected from a range thicker than the desired thickness of the magnetic powder 1. The thickness of the magnetic thin film is not generally determined, but is preferably in the range of 100 μm to 200 μm, for example. If the thickness of the magnetic thin film is less than 100 μm, processes such as pulverization and forging are simplified, and it may not be possible to obtain sufficiently magnetically hard magnetic abrasive grains. On the other hand, if the thickness of the magnetic thin film exceeds 200 μm, for example, processes such as pulverization and forging to reduce the thickness of the magnetic thin film to 30 μm or less may be complicated and may not be manufactured.

  Such a magnetic thin film is cut, ground or forged to form flat magnetic abrasive grains having a flatness of 1.5 or more. The means for cutting is not particularly limited as long as the magnetic thin film can be made fine to form flat magnetic abrasive grains, and examples thereof include a cutting blade. The means for pulverizing is not particularly limited as long as the magnetic thin film can be made fine to form flat magnetic abrasive grains, and examples thereof include a mill such as a ball mill and a shredder. Forging is to form flat magnetic abrasive grains by hitting or pressing a magnetic thin film. Forging, for example, as shown in FIG. 4, a predetermined amount of magnetic thin film 11 is placed in a container 10, and these magnetic thin films 11 are pressed against the bottom wall of the container 10 with a rod-shaped crushing member 12 to form a flat shape. Magnetic abrasive grains may be formed. Of these cutting, grinding and forging, it is preferable to form the magnetic abrasive grain 1 of the present invention by forging. This is because when the flat magnetic abrasive grains 1 are formed by forging, the formed magnetic abrasive grains 1 are likely to have magnetic anisotropy. In addition, as long as magnetic anisotropy can be imparted to the flat magnetic abrasive grains 1, the flat magnetic abrasive grains 1 may be formed by pressing or the like without being limited to forging.

  In this way, flat magnetic abrasive grains having a flatness of 1.5 or more can be easily formed by cutting, pulverizing, or forging the magnetic thin film.

(Magnetic polishing method)
The magnetic polishing method of the present invention is characterized by polishing the surface of a workpiece using the magnetic abrasive grain 1 of the present invention. The magnetic abrasive grain 1 of the present invention can be expected to be applied to precision machining of various workpieces, and can be used, for example, for polishing the inner surface of a tube. An example of a magnetic polishing apparatus for carrying out the magnetic polishing method of the present invention is shown in FIG.

  As shown in FIG. 5, this magnetic polishing apparatus is disposed outside a circular tube 21 and a tube support portion (not shown) that rotatably supports a circular tube 21 that is a workpiece in the circumferential direction. Mainly composed of the magnetic pole 22. For example, four magnetic poles 22 are arranged at approximately 90 ° intervals in the circumferential direction via yokes 23. The yokes 23 on which the magnetic poles 22 are arranged are provided so as to be reciprocally movable (for example, amplitude) in the axial direction of the circular tube 21, so that the magnetic poles 22 are amplified in the axial direction of the circular tube 21. . The magnetic pole 22 may be anything as long as it can generate a magnetic field in the circular tube 21, and may be a permanent magnet or an electromagnet. Further, the number and arrangement of the magnetic poles 22 may be arbitrary. The magnetic abrasive grain 1 of the present invention is placed inside the circular pipe 21, and the magnetic abrasive grain 1 that has been put in contact with the inner wall of the circular pipe 21 by the magnetic field generated in the circular pipe 21. That is, the magnetic abrasive grain 1 presses the inner wall of the circular tube 21 to generate a pressing force.

  When the circular tube 21 is rotated in the circumferential direction in this state, the magnetic abrasive grains 1 move relative to the inner surface of the circular tube 21, and the magnetic abrasive particles 1 act as an electric brush, for example. Is polished. In addition, although the case where the circular pipe 21 is rotated to perform the polishing process has been described, the circular pipe 21 may be fixed and the magnetic pole 22 may be rotated to perform the polishing process, or the circular pipe 21 and the magnetic pole 22 may be processed. Both may be rotated to perform polishing.

  Thus, when the inner surface of the circular tube 21 is polished, the magnetic abrasive grain 1 of the present invention is formed in a flat shape, so that the frictional force and the destructive force against the inner surface of the circular tube 21 that is a workpiece are formed. Therefore, the inner surface is not cut deeper than necessary and more precise surface processing can be performed.

  The magnetic polishing method of the present invention is not limited to the case of polishing the inner surface of a circular tube, and can be widely applied to various applications that can exhibit the functions of the magnetic abrasive grains and the magnetic polishing method of the present invention. For example, as another example of use of the magnetic polishing method of the present invention, application to texture processing of the hard disk substrate surface of a hard disk device can be expected. Moreover, application as an alternative process of chemical mechanical polishing (CMP) used in a damascene process for forming a copper wiring on a semiconductor substrate can be expected.

  Hereinafter, the present invention will be described more specifically with reference to examples.

(Example 1)
A stainless steel matrix having a length of 100 mm, a width of 100 mm, and a thickness of 10 mm was prepared. Also, a Watt bath containing nickel sulfate 1 to 2 mol / L (liter, the same shall apply hereinafter), nickel chloride 0.1 to 0.2 mol / L, boric acid 0.4 to 0.5 mol / L, brightener and smoothing agent. Was adjusted to pH 3-5 with sulfuric acid. The mother die was immersed in this watt bath, the temperature of the plating solution was 55 ° C., and electroplating was performed for 120 minutes while stirring with air to form a nickel magnetic thin film having a thickness of 100 μm on the surface of the mother die. . The formed magnetic thin film was peeled from the matrix.

  Next, the peeled magnetic thin film was finely cut into a length of about 10 mm × width of 1 mm × thickness of about 100 μm using a cutting blade. As shown in FIG. 4, these fine magnetic thin films are placed in a container 10 and pressed against the bottom wall of the container 10 with a bar-shaped crushing member 12 to forge them, and the magnetic abrasive grains 1 of the present invention having a thickness of 10 μm to 30 μm. Formed. The flatness of the formed magnetic abrasive grain 1 of the present invention was 4-30. The magnetic abrasive grains 1 of the present invention were observed using a scanning electron microscope (SEM), and the observation results are shown in FIG. FIG. 6A is a diagram with a magnification of 100 times.

  Using the magnetic abrasive grain 1 thus formed, the inner surface of a stainless steel tube (outer diameter 20 mm, inner diameter 18 mm SUS304 stainless steel (BA tube)) was magnetically polished, and the polishing performance was evaluated. As the magnetic poles, four Nd—Fe—B rare earth permanent magnets were arranged on the outer circumference of the stainless steel circular tube at 90 ° intervals in the circumferential direction. The magnetic field applied to the stainless steel tube by the permanent magnet was 3600 gauss. 1.0 g of magnetic abrasive grains are put in a stainless steel circular tube, and the stainless steel circular tube is rotated at 1800 rpm, and the magnetic pole is vibrated at an amplitude of 5 cm and an amplitude of 0.8 Hz for 5 minutes and 10 minutes. Internal processing was performed.

  After processing, the polishing amount (M) and the surface roughness of the inner surface of the stainless steel circular tube were measured. The surface roughness was measured with a stylus type surface roughness measuring machine for the arithmetic average height (Ra) and maximum height (Rz) of the roughness curve based on JISB0601-2001 (based on ISO4287-1997). The results are shown in FIGS. The polishing amount may be referred to as a weight reduction amount. Further, the inner surface of the stainless steel circular tube after processing for 10 minutes was observed at a magnification of 700 times using a scanning electron microscope (SEM). The observation results are shown in FIG. FIG. 9A and FIG. 9B are diagrams showing two different places. FIG. 10 is a view showing the inner surface of the stainless steel circular tube before processing.

(Comparative Example 1)
For comparison, the inner surface of a stainless steel circular tube was processed in the same manner as in Example 1 described above using commercially available magnetic abrasive grains (Toyo Abrasive Co., Ltd .; KMX-80). After processing, the polishing amount (M) and the surface roughness of the inner surface of the stainless steel circular tube were measured. The surface roughness was measured with a stylus type surface roughness measuring machine for the arithmetic average height (Ra) and maximum height (Rz) of the roughness curve based on JISB0601-2001 (based on ISO4287-1997). The results are shown in FIGS. Moreover, the stainless steel circular tube inner surface after processing for 10 minutes as in Example 1 was observed with a scanning electron microscope (SEM) at a magnification of 700 times, and the result is shown in FIG.

  As is apparent from the results of FIGS. 7 to 11, in the case of Example 1 using the magnetic abrasive grain 1 of the present invention (sometimes referred to as E-02), the polishing amount (M) is extremely small. The surface was smooth. On the other hand, in the case of Comparative Example 1 using commercially available magnetic abrasive grains (KMX-80), the polishing amount (M) was large and the surface was rougher than before polishing. In addition, although FIG.11 (b) seems to be a smooth surface, the surface of the to-be-processed object was grind | polished in one direction more than necessary. That is, the unevenness | corrugation extended in the vertical direction used as a process direction in FIG.11 (b) was formed, and the surface was rougher than before grinding | polishing.

(Example 2)
Using the magnetic abrasive grains (E-02) formed in Example 1 and iron powder (electrolytic Fe) having an average particle size of 330 μm, the inner surface processing of the stainless steel circular tube was performed in the same manner as in Example 1. In a stainless steel circular tube, 0.2 g of magnetic abrasive grains (E-02) and 0.8 g of iron powder (electrolytic Fe) were put. Processing time (t) After 5 minutes, 10 minutes, 15 minutes and 20 minutes, the polishing amount (M) and the surface roughness of the inner surface of the stainless steel circular tube were measured. The surface roughness was measured with a stylus type surface roughness measuring machine for the arithmetic average height (Ra) and maximum height (Rz) of the roughness curve based on JISB0601-2001 (based on ISO4287-1997). The results are shown in FIGS.

(Comparative Example 2)
Using the magnetic abrasive grains (KMX-80) used in Comparative Example 1 and iron powder (electrolytic Fe) having an average particle size of 330 μm, the inner surface processing of the stainless steel circular tube was performed in the same manner as in Example 1. In a stainless steel circular tube, 0.2 g of magnetic abrasive grains (KMX-80) and 0.8 g of iron powder (electrolytic Fe) were put. Processing time (t) After 5 minutes, 10 minutes, 15 minutes, 20 minutes, 25 minutes, and 30 minutes, the polishing amount (weight reduction amount) and the surface roughness of the stainless steel circular tube inner surface were measured. The surface roughness was measured with a stylus type surface roughness measuring machine for the arithmetic average height (Ra) and maximum height (Rz) of the roughness curve based on JISB0601-2001 (based on ISO4287-1997). The results are shown in FIGS.

  As is apparent from the results of FIGS. 12 and 13, in the case of Example 2 using the magnetic abrasive grain (E-02) 1 of the present invention, the surface can be polished sufficiently in a short time of 5 minutes and extremely smooth. It became. On the other hand, in the case of Comparative Example 2 using magnetic abrasive grains (KMX-80), it takes time to process, for example, a surface substantially similar to the surface roughness obtained by processing in 5 minutes of Example 2. In order to obtain roughness, processing had to be performed for 20 minutes or more.

It is a figure which shows an example of the magnetic abrasive grain of this invention, (a) is a top view, (b) is an elevation view. It is a figure which shows the other example of the magnetic abrasive grain of this invention, (a) is a top view, (b) is an elevation view. It is a schematic sectional drawing which shows the state which put the magnetic abrasive grain of this invention in the magnetic field. It is a schematic sectional drawing for demonstrating an example of crushing and forging. It is a schematic perspective view which shows an example of a magnetic polishing apparatus. It is a scanning electron microscope (SEM) observation photograph of the magnetic abrasive grain of this invention. It is a figure which shows the relationship between processing time (t), arithmetic mean height (Ra), and polishing amount (M). It is a figure which shows the relationship between processing time (t), maximum height (Rz), and polishing amount (M). It is a scanning electron microscope (SEM) observation photograph of the inner surface of the stainless steel circular tube processed with the magnetic abrasive grain of the present invention. It is a scanning electron microscope (SEM) observation photograph of the inner surface of the stainless steel circular tube before processing. It is a scanning electron microscope (SEM) observation photograph of the inner surface of a stainless steel circular tube processed with a commercially available magnetic abrasive grain (KMX-80). It is a figure which shows the relationship between processing time (t), arithmetic mean height (Ra), and polishing amount (M). It is a figure which shows the relationship between processing time (t), maximum height (Rz), and polishing amount (M).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Magnetic abrasive grain 2 Peripheral part 5 Abrasive particle 10 Container 11 Magnetic thin film 12 Crushing member 21 Circular tube 22 Magnetic pole 23 York

Claims (4)

  A magnetic abrasive grain having magnetic properties, wherein the magnetic abrasive grain has a flatness of 1.5 or more.   2. The magnetic abrasive grain according to claim 1, wherein the magnetic abrasive grain is made of nickel, cobalt, or an alloy thereof.   A method for producing a magnetic abrasive grain comprising cutting a magnetic thin film having magnetism, crushing or forging to form a flat magnetic abrasive grain having a flatness of 1.5 or more.   A magnetic polishing method comprising polishing a surface of a workpiece using the magnetic abrasive grain according to claim 1.

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