JP2007045878A - Magnetic abrasive grain - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide magnetic abrasive grains enabling surface finishing of greater precision in magnetic grinding technique. <P>SOLUTION: The magnetic abrasive grain 10 is such that grinding particles 13 are dispersed over the surface of a flexible particle formed of a flexible material 11 containing magnetic particles 12. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to magnetic abrasive grains, and more particularly to magnetic abrasive grains used in a magnetic polishing method or the like.

  “Magnetic polishing method (magnetic assisted processing method)”, which is a precision processing technology that incorporates the action of a magnetic field, is attracting attention as a new technology that is not bound by existing concepts. This magnetic polishing method realizes precise surface processing by applying a processing force and a kinetic force to magnetic abrasive grains or magnetic particles through the lines of magnetic force. The magnetic polishing method using magnetic lines of force is a technology that focuses on the phenomenon that magnetic lines of force pass through a non-magnetic material, similar to the X-ray object transmission phenomenon, and enables processing such as polishing of parts that are difficult with conventional machining. For example, it is possible to polish the surface of a part having a complicated shape, the inner surface of a hole where a tool does not enter, the inner surface of a tube where the tool does not reach, and the like (see, for example, Patent Document 1) .

Until now, the magnetic abrasive grains used in the magnetic polishing method were particulate solid magnetic abrasive grains composed mainly of iron powder, in which fine abrasives were integrated by a sintering technique or the like. . For this reason, the conventional processing with magnetic abrasive grains that presses the surface of the workpiece by receiving magnetic force is based on the fine cutting action of the abrasive, and the processing surface with such hard magnetic abrasive grains is completely It consists of scratched traces. Furthermore, the particle size of magnetic abrasive grains is originally a statistic and includes a large particle size. Excessive processing force acts on this large particle size, resulting in large scratches on the processed surface. to make. This large scratch hinders the ultra-precision machined surface and is a big problem.
JP 2002-192453 A

  As described above, the conventional hard magnetic abrasive grains obtained by integrating the abrasive in the iron powder by sintering have a large polishing effect, but are relatively contained in a part, for example. A problem arises in that the surface of the workpiece is unnecessarily polished with abrasive grains having a large particle diameter, and scratches remain on the surface to be polished. It could not be said to be abrasive grains.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide a magnetic abrasive grain that enables more precise surface processing.

  In order to achieve the above object, the magnetic abrasive grains of the present invention are characterized in that abrasive particles are dispersed on the surface of flexible particles formed of a flexible material containing magnetic particles.

  According to the present invention, since the matrix of magnetic abrasive grains is made of a flexible material, the magnetic abrasive grains pressed against the workpiece surface are composed of particles themselves and particles as shown in the schematic diagram of FIG. The abrasive particles are easily viscoelastically deformed by the processing force, and the abrasive particles themselves retreat into the viscoelastic body by the processing force acting on the abrasive particles dispersed on the surface of the viscoelastic body. As a result, excessive cutting by magnetic abrasive grains can be completely prevented for all abrasive particles, and a damage-free ultra-precise surface finish that does not cause polishing scratches on the workpiece surface can be realized. In addition, the use of a flexible material as a matrix reduces the weight of the magnetic abrasive grains, facilitating the movement of the magnetic abrasive grains during surface processing, and even more accurate for workpieces with complex shapes. Surface processing can be performed.

  The magnetic abrasive grains of the present invention are characterized in that abrasive particles are blended in a flexible material forming the flexible particles.

  According to the present invention, since the abrasive particles can be easily and stably dispersed and arranged on the surface of the magnetic abrasive grains, problems such as the falling off of the abrasive particles from the magnetic abrasive grains hardly occur.

  In the magnetic abrasive grains of the present invention, (1) the abrasive particles are blended with a flexible material that is the same as or different from the flexible material forming the flexible particles, and the blended material is The surface of the flexible particle may be coated directly or via a contact layer so as to be applied in a layered form. (2) The abrasive particle is applied to the surface of the flexible particle. Alternatively, the abrasive particles are applied to the surface of the layer made of a flexible material formed on the flexible particles by applying a mechanical impact force and fixed to form a layer. May be.

  According to these inventions, even if the blending amount of the abrasive particles is small, the abrasive particles can be effectively localized on the surface of the flexible particles, so that higher polishing action can be expected.

  Furthermore, in the magnetic abrasive grains of the present invention, the flexible particles are characterized by having magnetic particles as core particles and having a coating layer made of a flexible material on the surface thereof. In this case, the abrasive particles are blended in the flexible material as described above, or applied to the surface of the flexible particles made of the flexible material in a layered manner, so that the surface of the magnetic abrasive grains Placed in.

  According to the present invention, the magnetic particles as the core particles can secure more stable and large magnetic characteristics, and even when trying to obtain relatively large desired magnetic characteristics, Magnetic abrasive grains can be easily prepared without causing problems such as a decrease in mechanical strength due to an increase in the blending amount of the conductive material.

  As described above, according to the magnetic abrasive grains of the present invention, when applied to the magnetic polishing method, the magnetic abrasive grains pressing the workpiece surface are easily viscoelastic when the particles themselves and the particles are subjected to processing force. While being deformed, the abrasive particles having an excessive particle size are retracted into the flexible material of the magnetic abrasive grains by a processing force acting on the abrasive dispersed on the surface of the viscoelastic body. As a result, excessive cutting of the abrasive grains can be completely prevented for all the abrasive particles, and a damage-free polishing process can be realized without causing any polishing scratches on the workpiece surface.

  Hereinafter, the magnetic abrasive grains of the present invention will be described in detail with reference to the drawings.

  The magnetic abrasive grains of the present invention are characterized in that abrasive particles are dispersed on the surfaces of flexible particles formed of a flexible material containing magnetic particles.

  The magnetic abrasive grains of the present invention exhibit magnetism as the magnetic abrasive grains themselves, and exhibit viscoelasticity by a flexible material constituting the magnetic abrasive grains when an external force is applied, and the abrasive particles are at least in the surface region. As long as it exists, the form may include various forms.

  With respect to the magnetic particles, fine magnetic particles may be dispersed and mixed in a flexible material constituting the flexible particles, or magnetic particles having a relatively large particle diameter may be used as a core. As the particles, a layer made of a flexible material may be formed around the core particles. Also, the abrasive particles may be uniformly dispersed together with the magnetic particles throughout the flexible particles made of a flexible material, or may be localized only in a relatively surface area of the magnetic abrasive grains. It may be arranged (for example, in layers).

  1 to 4 are schematic sectional views showing examples of the magnetic abrasive grains of the present invention. A magnetic abrasive grain 10 shown in FIG. 1 has a configuration in which magnetic particles 12 and abrasive particles 13 are uniformly dispersed in flexible particles made of a flexible material 11. A magnetic abrasive grain 20 shown in FIG. 2 has an inner layer portion in which magnetic particles 22 are uniformly dispersed in flexible particles made of a flexible material 21a, and on the outer side (surface region) of the inner layer, The structure has an outer layer portion in which abrasive particles 23 are uniformly dispersed in a flexible material 21b that is the same as or different from the flexible material 21a. A magnetic abrasive grain 30 shown in FIG. 3 has core particles 32 made of magnetic particles, and abrasive particles 33 are uniformly dispersed in the flexible material 31 on the outer side (surface) of the core particles 32. It has a configuration having an outer layer portion. Furthermore, the magnetic abrasive grains 40 shown in FIG. 4 have core particles 42 made of magnetic particles, and an intermediate layer portion made of a flexible material 41a is provided on the outside (surface) of the core particles 42. The outer layer (surface) has a configuration in which an outer layer portion in which abrasive particles 43 are uniformly dispersed in a flexible material 41b that is the same as or different from the flexible material 41a is provided.

  As shown in FIGS. 2 and 4, as an example of a method for locally disposing the abrasive particles 23, 43 on the surfaces of the magnetic abrasive grains 20, 40, the inner side of the abrasive particles 23, 43 may be used. A compounded material in which abrasive particles 23 and 43 are dispersed and blended in the same or different flexible materials 21b and 41b as the flexible materials 21a and 41a on the surface of the flexible particles 21a and 41a. A method of coating directly or via a contact layer can be exemplified. By such a method, the abrasive particles 23 and 43 can be applied in layers to the surfaces of the magnetic abrasive grains 20 and 40. In addition, when coating the said compounding material directly on the surface of the matrix which consists of flexible material 21a, 41a, flexible material 21b, 41b has the favorable adherence with respect to flexible material 21a, 41a. As such flexible materials 21b and 41b, for example, the same or similar materials as the inner flexible materials 21a and 41a, and other inner flexible materials 21a and 41a are used. Examples thereof include a flexible material having good wettability on the surface.

  As another example, the abrasive particles 23 and 43 are placed in the air stream on the surface of the internal flexible particles or on the surface of the layer made of the flexible material formed on the flexible particles. And a method of hitting and fixing by the mechanical impact force. As yet another example, mixed particles containing abrasive particles 23 and 43 and fine particles made of a flexible material are caused to collide with the surface of the internal flexible particles in an air current, and the mechanical impact force An example is a method in which the fine particles of the flexible material are melted or partially melted by the heat generated during the impact, and the abrasive particles 23 and 43 are adhered to the layer formed of the melted flexible material.

  In addition, as shown in FIG.3 and FIG.4, when making magnetic body particle | grains 32 and 42 and coat | covering the surface of the nucleus particles 32 and 42 with the flexible material 31 and 41a, it is other than a normal coating method. In addition, a mechanochemical coating method using the mechanical impact force as described above can be used.

  As the flexible material, various flexible materials can be used as long as they have the desired viscoelasticity and satisfy various conditions in the magnetic polishing method (for example, conditions such as impact strength and heat resistance). Is possible. For example, organic polymers (including silicone resin and silicone rubber) such as various resins and rubbers can be used. In particular, hard plastic particles having heat resistance are preferably used because they have heat resistance against heat generated during surface processing of a workpiece. Specific examples include polyamides such as nylon 6 and nylon 66, polyimide, polyaramid, polyester, and the like.

  In selecting a flexible material, it is more preferable to consider the specific gravity of the entire magnetic abrasive grains. For example, when the magnetic abrasive grains of the present invention constitute a magnetic abrasive liquid together with a liquid medium, the specific gravity of the flexible material is considered in relation to the specific gravity of the liquid medium. Specifically, by using a flexible material made of a material having a specific gravity smaller than that of the liquid medium, the finally obtained magnetic abrasive grains can be used in a state of floating in the magnetic abrasive liquid. Further, by using a flexible material made of a material having a specific gravity similar to that of the liquid medium, the finally obtained magnetic abrasive grains can be used in a state of floating in the magnetic abrasive liquid. Further, by using a flexible material made of a material having a specific gravity greater than that of the liquid medium, the finally obtained magnetic abrasive grains can be used in a state where they are submerged in the magnetic abrasive liquid. In this way, the state of the finally obtained magnetic abrasive grains in the magnetic abrasive liquid is selected by considering the specific gravity of the material of the flexible material while considering the weight of the whole magnetic abrasive grains. Can be controlled as described above. Control of the state of the magnetic abrasive grains in the magnetic abrasive liquid is effective for precision processing such as a magnetic polishing method, particularly for precision processing at the nanometer level and for adjusting the accuracy.

  The magnetic particles only need to have at least magnetic properties that can be moved by a magnetic field. For example, a ferromagnetic material made of an iron-based metal or alloy is preferable. As shown in FIGS. 3 and 4, when the core particles 32 and 42 are formed of magnetic particles, the particle size is not particularly limited, but is, for example, about 50 to 1000 μm.

  On the other hand, as shown in FIGS. 1 and 2, when magnetic particles are blended in the flexible material as fine particles, the particle size is not particularly limited, but is, for example, about 5 to 300 μm. In this case, the shape of the fine particles can be various shapes such as a spherical shape (including a true spherical shape), a square shape, a needle shape, a scale shape, and the like. In addition, the blending amount with respect to the flexible material depends on the required magnetic characteristics, the kind of magnetic particles to be used, the film forming method, etc. From the viewpoint of sufficient mechanical strength of the layer used as the matrix, the amount is preferably about 30 to 60 parts by mass with respect to 100 parts by mass of the flexible material. In addition, when mix | blending abrasive | polishing particle | grains in the same layer, it is desirable for the sum total of both the compounding quantities not to exceed 70 mass parts.

As the abrasive particles, various inorganic particles and compound (oxide, carbide, nitride, etc.) particles that can be used as abrasive particles can be used. For example, A, WA, GC, SA, MA, C, Examples include Al ₂ O ₃ , SiC, ZrO ₂ , B ₄ C, diamond, cubic boron nitride, MgO, CeO _{2, and} fumed silica, including those such as MD and CBN.

  The particle size of the abrasive particles is appropriately selected according to the material and shape of the workpiece to be processed and the purpose of processing the workpiece. For example, when nanometer level precision machining is performed using the magnetic abrasive grains of the present invention, the average particle size of the abrasive particles is preferably 300 nm or less. The lower limit of the average particle size at this time is not particularly limited, and may be, for example, within a range that can be obtained from commercially available abrasive particles. For example, particles having an average particle size of 10 nm or more can be used.

  The shape of the abrasive particles 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, and a needle. Various shapes such as a shape can be mentioned. Of these, a spherical shape having an extremely fine cutting edge on the surface is particularly preferably used.

  The content of the abrasive particles is also appropriately selected according to the material and shape of the workpiece to be processed, the purpose of processing the workpiece, the characteristics of the flexible resin serving as the matrix, and the like. By increasing the content of the abrasive particles, the polishing performance can be improved and the polishing efficiency can be improved. On the other hand, by not increasing the content of the abrasive particles too much, it is possible to suppress the polishing efficiency and gradually advance the polishing to perform precise processing. Although it cannot be generally defined, for example, it is preferably contained within a range of about 10 to 25% by mass of the total mass of the magnetic abrasive grains.

  The shape of the magnetic abrasive according to the present invention is appropriately selected according to the material and shape of the workpiece to be processed, the purpose of processing the workpiece, and the like, for example, a spherical shape (including a true spherical shape). , Various shapes such as a square shape, a needle shape, and a scale shape. In particular, from the viewpoint of ease of movement as magnetic abrasive grains, it is desirable to have a spherical shape.

  The particle size of the magnetic abrasive grains according to the present invention is also appropriately selected according to the material and shape of the workpiece to be processed and the purpose of processing the workpiece. For example, when performing precision processing at the nanometer level using the magnetic abrasive grains of the present invention, the average grain size of the magnetic abrasive grains is preferably 10 to 500 μm.

  The magnetic abrasive grains of the present invention can be used as they are in the form as they are, for example, as abrasive grains for precision processing such as magnetic polishing, or as a magnetic abrasive liquid together with a liquid medium. The liquid medium when used as the magnetic abrasive liquid is appropriately selected in consideration of the type of workpiece and the specific gravity of the magnetic abrasive grains. For example, water, aqueous lubricant, oil, oil-based lubricant, and the like can be used. . Further, the content of the magnetic abrasive grains in the magnetic abrasive liquid is also appropriately adjusted according to the processing application and the workpiece.

  Further, as a magnetic polishing method using the magnetic abrasive grains of the present invention, in addition to the magnetic polishing method described above, magnetic abrasive grains are arranged in a variable magnetic field, and the magnetic abrasive grains are caused to move by the change of the magnetic field. It is also possible to perform processing by causing abrasive grains to collide with a workpiece. In this case, magnetic abrasive grains having magnetic anisotropy are used, and any grains other than a spherical shape may be used. The variable magnetic field may be a magnetic field in which the N and S poles alternately change, such as an N / S alternating magnetic field and a rotating magnetic field. These magnetic fields are composed of, for example, permanent magnets, electromagnetic coils, or combinations thereof. When N / S alternating magnetic field by electromagnetic coil is adopted, the magnetic field is controlled by current control (for example, energization of alternating current) of the electromagnetic coil extended to the vicinity of the sealed non-magnetic container as the processing site. The magnetic force can be controlled by changing the energization frequency to the electromagnetic coil. In addition, when a rotating magnetic field using a permanent magnet is employed, a variable magnetic field can be generated, for example, by rotating a rotary table equipped with a permanent magnet, and the magnetic force is controlled by changing the rotational speed. can do.

  In such a variable magnetic field generator, a sealed non-magnetic container serving as a processing field is arranged, and inside this container, an appropriate number of magnets necessary for active three-dimensional behavior with the workpiece are placed. After storing the abrasive grains, a variable magnetic field is applied to the container. Magnetic abrasive grains in a container to which a varying magnetic field is applied are pulled by the fluctuation of the magnetic field and cause three-dimensional irregular motion in the container. Such irregular movement of the magnetic abrasive grains results in relative movement between the workpiece and the magnetic abrasive grains. As a result, the magnetic abrasive grains collide with the surface of the workpiece, and surface polishing or surface finishing of the workpiece or edge Finishing or surface hardening can be performed.

  In addition, when employ | adopting the rotating magnetic field by a permanent magnet, it can also arrange | position so that the rotating shaft of a rotary table and the axis | shaft of a container may cross | intersect as needed. That is, by tilting the rotary table or the container, the distance between the rotating permanent magnet and the magnetic abrasive grains in the container can be sequentially changed. Furthermore, if the tilt angle is controlled so that it changes during rotation, the relative position between the magnetic abrasive grains and the workpiece will fluctuate, giving the magnetic tool a three-dimensional irregular motion. preferable.

  Although the magnetic polishing method has been briefly described above, the detailed configuration of the apparatus used can be changed as appropriate. For example, (a) the shape and material of the rotary table in the rotary magnetic field device, and its rotational drive mode, (b) the number of magnets installed on the rotary table and the magnetic pole array, and (c) the magnetic field fluctuation control mode. (D) The shape and material of the container serving as a processing field, (e) the shape and number of magnetic abrasive grains, (f) the material of the workpiece, the fixing form in the container, and the like can be appropriately changed. Of the above, for the rotational drive mode of the rotating magnetic field device of (a), the drive source may be not only electric but also hydraulic or pneumatic, and in order to make the behavior of magnetic abrasive grains more active, it is not driven by a pulse motor. Constant speed rotation and rotation direction control may be performed. In addition, as an arrangement form of the magnetic poles installed on the rotary table (b), in addition to the arrangement of the S poles and the N poles, the arrangement of the permanent magnets and the energization control of the electromagnets may be used in combination. As for the magnetic field fluctuation control mode of the magnet of (c), the magnetic field fluctuation control is performed by the frequency fluctuation by the rotation speed control of the rotary table on which the permanent magnet and the electromagnet are installed, or the rotation is performed when the electromagnet is installed. The magnetic field may be randomly controlled by changing the exciting force by random current control of the electromagnet in preference to the number control.

  The magnetic polishing method using the magnetic abrasive grains of the present invention can be expected to be applied to precision machining of various workpieces as an example of application. For example, products such as super clean pipes used in next-generation semiconductors and manufacturing processes in the medical field, etc. that require processing such as precision polishing, and high-precision processing (polishing etc.) of minute spaces such as in pipes ) Is effective for processing products that require it. In addition, for example, application to texture processing of a hard disk substrate surface of a hard disk device can be mentioned. Further, for example, 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. The damascene process is a process of removing unnecessary copper on the surface after forming a barrier layer and a copper plating layer in a wiring groove on an insulating film. The magnetic polishing method using the magnetic abrasive grain of the present invention is not limited to such an application, and details of a non-magnetic material or a magnetic material workpiece, inner surface, surface finishing and deburring finishing of an edge portion, or hardening of a surface layer, In order to improve bending fatigue strength due to residual compressive stress, etc., it can be widely applied to various applications.

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

Example 1
10 parts by weight of WA (white alumina) abrasive particles having an average particle diameter of 200 nm were dispersed and blended in 30 parts by weight of nylon 6 using a twin screw extruder. The obtained composition was coated with an iron particle having an average particle size of 330 μm as a core particle, and the surface of the core particle was coated with a commercially available adhesive so as to have a thickness of about 30 μm. Was made.

(Example 2)
Using the magnetic abrasive grains obtained in Example 1, magnetic polishing was performed on the surface of a stainless steel (SUS304) flat plate as a workpiece by a planar magnetic polishing method.

  In the experiment, a cylindrical magnetic pole having a diameter of 20 mm was first attached to the main spindle of a milling machine. The cylindrical magnetic pole is formed by cutting a SS400 steel bar with a diameter of 20 mm and sandwiching a neodymium permanent magnet with a diameter of 20 mm in the middle. The tip on the N pole side is used as a magnetic pole on the workpiece side, and the other Was chucked on the spindle of the milling machine. As a workpiece, a SUS304 stainless steel flat plate was used, and the stainless steel flat plate was placed on a milling machine table. The gap between the magnetic pole tip and the stainless steel flat plate is 2 mm, the abrasive grains of Example 1 are arranged in the gap, the magnetic pole is rotated at 1200 revolutions per minute, and the stainless steel flat plate is moved in the horizontal direction. While applying a feed movement of 200 mm per minute, a belt-like portion having a width of 20 mm and a length of 50 mm was magnetically polished. At this time, it was confirmed that the magnetic abrasive grains of Example 1 were polishing the surface of the stainless steel flat plate in a form in which the magnetic abrasive grains were continuously wound around a rotating magnetic pole.

  As a result of such planar magnetic polishing, after 5 minutes of polishing treatment, an initial roughness of 2 μm Rz (maximum height / JIS B 0601-2001; the same applies hereinafter) of the stainless steel flat plate surface is 0 over the entire surface of the magnetic polishing processed surface. .05 μmRz and could be processed into a very good mirror surface state, and as a result of SEM observation, no scratches that were observed specifically on the surface were observed.

(Comparative Example 1)
As the magnetic abrasive grains, conventionally used sintered type magnetic abrasive grains having an average particle diameter of 80 μm (Toyo Abrasive Co., Ltd .: KMX-80, composed of WA abrasive particles having an average particle diameter of 5 μm or less and iron powder are used. In the same manner as in Example 2, polishing using a planar magnetic polishing method and polishing conditions was performed except that the above was used. As a result, after the polishing process for 5 minutes, the initial roughness 2 μm Rz of the stainless steel flat plate surface was processed to be almost a mirror surface state of 0.2 μm Rz. However, as a result of SEM observation, the processed surface was extremely fine scratches. It was found that it was created by accumulation. On the processed surface, about 5 to 10 large scratches having a depth of about 0.5 μm were observed on average per unit area (cm ² ).

It is a schematic cross section which shows an example of the magnetic abrasive grain of this invention. It is a schematic cross section which shows another example of the magnetic abrasive grain of this invention. It is a schematic cross section which shows another example of the magnetic abrasive grain of this invention. It is a schematic cross section which shows another example of the magnetic abrasive grain of this invention. It is a schematic cross section which shows the use condition of the magnetic abrasive grain of this invention

Explanation of symbols

10, 20, 30, 40 Magnetic abrasive grains 11, 21a, 21b, 31, 41a, 41b Flexible material 12, 22 Magnetic fine particles 32, 42 Magnetic core particles 13, 23, 33, 43 Abrasive particles

Claims (5)

  A magnetic abrasive characterized in that abrasive particles are dispersed on the surface of flexible particles formed of a flexible material containing magnetic particles.   The magnetic abrasive according to claim 1, wherein the abrasive particles are blended in a flexible material forming the flexible particles.   The abrasive particles are blended in a flexible material that is the same as or different from the flexible material forming the flexible particles, and the blended material is directly or directly on the surface of the flexible particles. The magnetic abrasive grains according to claim 1, wherein the magnetic abrasive grains are provided in a layer form by coating via a magnetic field.   The abrasive particles are fixed to the surface of the flexible particles by applying a mechanical impact force to the surface of the flexible particles formed on the flexible particles. The magnetic abrasive grains according to claim 1, wherein the magnetic abrasive grains are provided in layers. The said flexible particle is comprised by having the said magnetic body particle as a core particle, and having the coating layer which consists of a flexible material on the surface, The any one of Claims 1-4 characterized by the above-mentioned. Magnetic abrasive grains.

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