JP2005297117A - Polishing media, metallic work polishing method and magnetic material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide polishing media for largely restraining generation of media powder being industrial waste, by providing a stable polishing quantity and superior surface processing when barrel polishing a metallic work. <P>SOLUTION: A diamond abrasive grain 12 having the average particle size falling within a range of 10 μm to 200 μm is fixed by a plating film 13 to a surface of a core 11 having the average particle size of 1 mm to 20 mm. The core 11 is composed of at least one kind of construction material of WC, TiC, aluminum, titanium or rare earth metal (including yttrium), and a specific gravity of the polishing media 10 is set to 4 or less. When barrel polishing by inputting a polishing liquid suspending these polishing media 10 in a liquid medium and the metallic work in the barrel, due to being extremely low in an abrasion level of the polishing media 10, the stable polishing quantity and the superior surface processing are provided, and generation of media powder being the industrial waste can be largely restrained. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a polishing medium and a method for polishing a metal workpiece and a magnetic material polished by the method. More specifically, the present invention provides a stable polishing amount and good surface finishing when barreling a metal workpiece. The present invention relates to a chamfering medium for a metal workpiece, a method for polishing the metal workpiece, and a magnetic material polished by the method.

  A barrel polishing method is known as one method for chamfering a workpiece made of a metal material such as a magnetic alloy. The barrel polishing method is a chamfering method excellent in mass productivity, and a rotary barrel polishing method, a vibration barrel polishing method, a centrifugal barrel polishing method, and the like are known.

  Chamfering a metal workpiece by barrel polishing is performed by adding a metal workpiece that is an object to be polished, polishing powder (media) for polishing the metal workpiece, and a liquid medium (for example, a rust inhibitor or a surfactant to water) Is carried out by sliding the metal workpiece and the medium against each other by applying rotation or vibration.

  This barrel polishing method is widely used for polishing brittle materials such as ceramics and rare earth alloys, and various contrivances have been made to prevent generation of chips and cracks during polishing. For example, Patent Document 1 discloses that when a brittle material such as ceramics that is prone to cracking or chipping is subjected to vibration barrel polishing, one of the unbalance weights is made heavier than the other to spiral the movement of the media in the liquid medium. A vibrating barrel polishing method is disclosed that achieves polishing with very few cracks and chips.

  Also, in Patent Document 2, when a rare earth magnet or the like that is likely to be chipped is subjected to fluid barrel polishing in a rotating tank, bubbles are uniformly ejected from a minute gap between the rotating tank and the fixed tank to the tank wall. A polishing method is disclosed that prevents the workpiece from staying and suppresses chipping caused by impact. Further, Patent Document 3 discloses a rare earth alloy chamfering method for solving the problem that uniform chamfering may not be possible although the occurrence of chipping can be suppressed to some extent by the vibration barrel polishing method described in Patent Document 1. Is disclosed.

  When chamfering a metal workpiece by barrel polishing, the polishing power of the media depends on its shape and size. Therefore, in order to uniformly polish a metal workpiece and obtain a good surface processing, it is necessary to confirm the shape and size of the media for each barrel polishing batch and maintain a predetermined polishing level.

  In general, such media can be obtained by bonding abrasive grains such as alumina and silicon dioxide to each other with a bonding material and molding the particles into a predetermined shape. For example, there are vitrified media using a special ceramic powder as a binder and rubber bond media using rubber as a binder. However, such conventional media may wear to such an extent that the shape and size of the media itself change greatly during single batch barrel polishing depending on the polishing conditions. For this reason, there is a problem that it is difficult to ensure a stable polishing amount for each batch and a surface processing state with high reproducibility.

  By the way, in patent document 4 and patent document 5, in order to reduce the degree of media wear and improve the polishing efficiency and durability, an abrasive layer containing fine abrasive grains such as diamond and CBN is provided on the surface of the core. The media provided in is disclosed. The abrasive layer provided on the surface of these media is obtained by mixing ultra-hard fine abrasive grains in a bond layer made of resin, metal, or vitrified, and reduces the degree of media consumption by the abrasive layer. At the same time, after the abrasive layer falls off, the core, which is a base material, acts as free abrasive grains.

  The degree of wear of the media provided with such an abrasive layer is mainly determined by the adhesion force of the abrasive layer to the core surface, but the adhesion force of the resin, metal, or vitrified to the core surface is not necessarily limited. This is not sufficient, and as a result, it falls off during the barrel polishing process and the core begins to wear out rapidly. Therefore, even in such media, there is a problem that it is difficult to ensure a stable polishing amount for each batch and a highly reproducible surface processed state.

In addition, as a result of media wear during the polishing process, the worn portions become fine particles (media powder) and adhere to the metal workpiece, which also hinders uniform polishing of the metal workpiece surface. Furthermore, there has been a problem that media powder must be collected and processed as industrial waste after polishing.
Japanese Patent Laid-Open No. 5-208360 JP-A-5-329765 JP 2002-79452 A JP-A-63-267157 No. 7-18522

  The present invention has been made to solve such problems, and one of its purposes is to obtain a stable polishing amount and a highly reproducible surface processing state when polishing a metal workpiece, It is another object of the present invention to provide a chamfering medium for metal workpieces that significantly suppresses the generation of media powder that becomes industrial waste. Another object of the present invention is to provide a method of polishing a metal workpiece with such a medium and a magnetic material having a good surface processed state polished by the method.

  In order to solve this problem, the polishing media of the present invention is characterized in that abrasive grains are fixed by plating on the surface of a ball-shaped metal core. Preferably, the abrasive grains are diamond or cubic boron nitride, and more preferably, the average grain diameter of the abrasive grains is in the range of 10 μm to 200 μm.

  Preferably, the polishing media has a specific gravity of 4 or less, more preferably, the metal core is made of at least one material of WC, TiC, aluminum, titanium, or rare earth metal (including yttrium), and Preferably, the ball core has an average particle diameter of the metal core in the range of 1 mm to 20 mm.

  The method for polishing a metal workpiece of the present invention includes a first step in which a polishing liquid in which the polishing medium of the present invention is suspended in a liquid medium and a metal workpiece are put into a barrel, and the barrel is driven to A second step of polishing the metal workpiece. Preferably, the metal workpiece is a rare earth metal workpiece.

  According to the present invention, ultra high-grade abrasive grains such as diamond having an average particle diameter of 10 μm or more and 200 μm or less are plated and fixed on the surface of a ball-shaped metal core such as Al having an average particle diameter of 1 mm or more and 20 mm or less. As a result, the wear level of the polishing media can be kept extremely low, and the shape and size of the media being polished can be maintained approximately constant, resulting in stable polishing amount and reproducibility when polishing metal workpieces. It is possible to provide a medium for chamfering a metal workpiece that has a high surface processing state and that significantly suppresses the generation of media powder as industrial waste.

  In addition, a specific surface condition can be obtained by polishing the brittle material such as a magnetic alloy with a polishing liquid in which the specific gravity of the polishing medium is 4 or less and the polishing medium is suspended in a liquid medium.

  The best mode for carrying out the present invention will be described below with reference to the drawings. In the following description, chamfering of a metal workpiece such as a rare earth alloy by a barrel polishing method using a ball medium will be described as an example. However, the present invention is not limited to this, and the medium of the present invention can be a surface-shaped medium having a curved surface other than the ball medium, and can be used for polishing metal workpieces other than the barrel polishing method. Can also be widely used.

  FIG. 1 is a schematic cross-sectional view for explaining a structural example of a metal workpiece chamfering medium according to the present invention, and FIG. 2 is a diagram for explaining an example of a production process of the medium. In the metal workpiece chamfering medium 10 of the present invention, diamond abrasive grains 12 are firmly fixed to the surface of the core 11 of the medium 10 by a plating film 13. Instead of the diamond abrasive grains 12, silicon carbide (SiC) having a modified Mohs hardness (15-step Mohs hardness) or 14 cubic boron nitride (CBN) may be used. Also, depending on the material of the metal workpiece or the core, softer materials such as fused alumina, tungsten carbide (both modified Mohs hardness 12), silicon oxide (modified Mohs hardness 7-8), etc. can be used.

  The material of the core 11 is selected by comprehensively considering the compatibility with the material of the metal workpiece to be barrel-polished and the target surface processing state. Examples of such core materials include cemented carbides such as WC and TiC, simple metals such as rare earth elements including aluminum, titanium and yttrium (Y) or alloys thereof, and examples of materials included in these groups. It can also be set as the composite material designed by selecting 2 or more types from the inside.

  The shape of the core 11 is generally spherical as shown in FIG. 1 (including a substantially spherical pseudo-spherical shape) in order to perform barrel polishing using the surface evenly with the shape of the medium isotropic. The ball media. The spherical shape of the media has a smaller impact force on the workpiece compared to media with a triangular shape, etc., and is effective in suppressing workpiece chipping during barrel polishing, as well as chamfering uniformity. It is because it is excellent. Note that the shape of the media of the present invention is not limited to a spherical shape, and may be an anisotropic shape depending on barrel polishing conditions.

  Further, the size of the core 11 (core diameter in the case of a ball medium) is determined by the size and shape of the metal workpiece to be polished, the state of the surface processing finish, and the like. In the case of standard chamfering, a spherical (or pseudo-spherical) ball medium having a particle size of about 0.5 to 30 mm, preferably about 1 to 20 mm is preferable.

  In addition, when barrel-polishing a work made of a magnetic material alloy such as ferrite or alnico or a work made of a rare earth alloy, the specific gravity of the material used for the core 11 is preferably selected so that the specific gravity of the entire medium is 4 or less. Rare earth alloys such as Nd-based and Sm-based materials are materials used for voice coil motor materials used for positioning of magnetic heads of magnetic recording devices, but these rare earth alloys are susceptible to brittle fracture. Since it consists of a grain boundary phase that causes ductile fracture, chipping is likely to occur during barrel polishing. If such a brittle material workpiece is barrel-polished with a media having a specific gravity of more than 4, the workpiece will be subjected to excessive impact, resulting in chipping and cracking. It is preferable to suppress the occurrence of cracks. For this reason, the specific gravity of the core 11 suitable for barrel polishing a work made of a brittle material such as a rare earth alloy is selected so that the specific gravity of the entire medium is 4 or less.

  Here, since the specific gravity of the entire medium only needs to be 4 or less, when the core 11 is hollow or includes pores, the degree of freedom in selecting the specific gravity of the material of the core 11 is high. Needless to say.

  The average particle size of the diamond abrasive grains 12 is selected according to the uneven state of the surface of the metal workpiece to be polished and the surface state to be finished, but is generally in the range of 10 to 200 μm in diameter. In the case of diamond abrasive grains 12 having a diameter of less than 10 μm, sufficient chamfering power may not be obtained and chamfering may be insufficient. Moreover, in the case of diamond abrasive grains having a diameter exceeding 200 μm, a sufficient polishing amount can be secured, but due to the large polishing power, the impact when colliding with a metal workpiece is large, and the cause of chipping and cracking is caused. Because it can be. Particularly when a brittle material workpiece such as a rare earth alloy is barrel-polished, the diameter of the diamond abrasive grains 12 is preferably in the range of 10 μm to 200 μm.

  After preparing the core 11 and the diamond abrasive grains 12 (FIG. 2 (a), FIG. 2 (b)), the metal salt aqueous solution, the core 11 and the diamond abrasive grains 12 are put into a barrel, and the metal is placed in the barrel. Metal ions (such as nickel ions) in the aqueous salt solution are reduced and deposited on the surface of the core 11 as a reducing agent (FIG. 2 (c)). In this plating process, approximately one layer of diamond abrasive grains 12 is firmly fixed to the surface of the core 11 by the plating film 13 (FIG. 2 (d)), and the presence thereof significantly reduces the degree of wear of the core 11 during barrel polishing. It becomes possible to make it. Moreover, you may make it provide the layer of the diamond abrasive grain 12 in a multilayer as needed.

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

  In this embodiment, a process of polishing a metal workpiece using the metal workpiece chamfering medium of the present invention will be described. In the following description, rotating barrel polishing will be described, but almost the same result can be obtained when vibration barrel polishing is performed.

  FIG. 3 is a schematic diagram for explaining an outline of a barrel used for polishing a metal workpiece in the present embodiment. The barrel 100 has a cylindrical or polygonal column shape as a whole, and a metal work, a medium and a liquid medium placed in the barrel are swung using a centrifugal force generated by the rotation of the barrel 100. The mechanism that polishes the surface of the metal workpiece.

  Here, there is no restriction | limiting in particular in the shape of the metal workpiece | work which is to be polished, It can be set as desired polygonal shapes, such as spherical shape, square shape, cylindrical shape, ring shape, and fan shape. Further, fine particles such as resin beads may be introduced into the tank for the purpose of preventing metal workpieces from adhering during polishing. Examples of such fine particles include abrasive particles such as SiC and polymer particles such as polystyrene beads. The specific gravity of such fine particles is preferably 4 or less from the viewpoint of dispersion uniformity and from the viewpoint of suppressing the occurrence of chips and cracks as already described.

  In general, when the amount of liquid medium input is small and the metal workpiece is not sufficiently immersed, the metal workpieces are sufficiently immersed during polishing and uniform chamfering is difficult, so that the metal workpiece is sufficiently immersed. As described above, it is preferable that a liquid medium (for example, water or an organic solvent) is introduced in an amount of 50% or more of the inner volume of the barrel, and the amount of the medium input is 10 to 150 times the amount of the metal workpiece input. . Preferably, the polishing time is 1 to 24 hours, and the rotational speed of the barrel 100 is 5 to 100 rpm.

  It should be noted that when the metal workpiece is a rare earth alloy material, it is very easy to oxidize. Therefore, a rust inhibitor or a surfactant is added to the liquid medium, or the polishing time (rotation time of the rotary tank 30) is set short. It is preferable to apply processing.

  Specific barrel chamfering conditions will be described below. An Al sphere having a diameter of 14 mm was used as the media core 11, and synthetic diamond 12 having an average particle size of 125 μm was fixed to the core 11 by plating to obtain a ball media.

  The metal workpiece to be polished is a flat Nd-Fe-B alloy (neodymium alloy) metal workpiece (specific gravity of about 7.5) having a generally fan shape shown in FIG. 8g. These metal workpieces were obtained by cutting Nd—Fe—B alloy blocks obtained by sintering.

  The internal volume of the barrel 100 is 100 liters, and the above-mentioned 500 metal workpieces and 60 kg of media are put into the barrel 100, and a liquid medium is immersed so as to immerse up to 3/4 or more of the bulk volume of these metal workpieces and media. I put it in.

  The liquid medium used is TKX Compound # 803 (trade name), and the specific gravity is 1.05 to 1.10. In addition, it can replace with TKX compound # 803 (brand name), and can also use the liquid medium which added the antirust agent (5-35 mass%) to water (20-50 mass% of the whole). Moreover, you may use what added surfactant (5 mass% or less) and an antifoamer (5 mass% or less) to this liquid medium as needed.

  At the time of barrel polishing, the number of rotations of the barrel 100 was 30 rpm, the rotation time was 4 hours, and the metal workpieces were exchanged for each batch of barrel chamfering, so that a total of 10 batches of polishing were executed. However, no media is exchanged during these 10 batches.

  In order to confirm the sustainability of the polishing power of the media of the present invention, the polishing amount of the metal workpiece is determined for each batch, and the diameter of the media before the input and after the end of 10 batches to check the degree of media wear. Was measured.

  For comparison, barrel polishing was performed under the same conditions using a conventional medium. The media used is a ceramic ball media (specific gravity: about 2.6, diameter: about 14 mm) containing aluminum abrasive grains (abrasive rate: 46 wt%).

  Tables 1 and 2 summarize the evaluation results for each media.

表１に示した結果から明らかなように、本発明のメディアを使用した場合には、１０バッチ連続してバレル面取りを行ってもその研磨量の減少は認められていない。これに対して、従来メディアであるセラミックメディアでは１０バッチの連続使用により研磨量が１０％以上も減少している。すなわち、本発明のメディアにおいては、その研磨力の低下が著しく抑制されており、安定したバレル面取りが可能であることが分かる。

As is apparent from the results shown in Table 1, when the media of the present invention is used, no reduction in the polishing amount is recognized even when barrel chamfering is performed for 10 batches. On the other hand, the polishing amount of ceramic media, which is a conventional media, is reduced by 10% or more by continuous use of 10 batches. That is, in the media of the present invention, it can be seen that the decrease in the polishing power is remarkably suppressed, and stable barrel chamfering is possible.

  Further, according to the results shown in Table 2, the ceramic media has been reduced in diameter by 2 mm (corresponding to about 14%) by continuous use of 10 batches. A decrease in diameter of about 14% corresponds to a decrease of about 36% in terms of volume, and 21 kg or more of 60 kg of the medium that has been charged is powdered. In fact, about 16 kg of media powder was recovered from the liquid medium after 10 batches using ceramic media, and this was treated as industrial waste. Note that the estimated amount of pulverization of media (21 kg) and the amount of recovered powder (16 kg) do not match, but this is because the size of the pulverization is too fine to recover from the liquid medium, Further, it is presumed to be due to the media powder taken out of the barrel 100 in the form of being attached to the metal arc exchanged for each batch.

  On the other hand, the media of the present invention maintained the diameter before charging even after continuous use of 10 batches, and as a result, no generation of media powder was confirmed. This is in contrast to the case where the abrasive layer of the media described in Patent Documents 4 and 5 in which ultra-hard abrasive grains are fixed with resin, metal, or vitrified drops off during barrel polishing, and the core starts to wear rapidly. Further, the low wear level of the media of the present invention in which diamond abrasive grains are fixed by plating on the core surface is remarkably exhibited.

  As described above, the metal workpiece chamfering media of the present invention has no change in shape and size during barrel polishing, and by using this media, a stable polishing amount and highly reproducible surface processing when barreling metal workpieces are used. It is possible to significantly suppress the generation of media powder that becomes an industrial waste.

  According to the present invention, it is possible to obtain a stable amount of polishing when barrel-polishing a metal workpiece and a highly reproducible and good surface processing state, and the chamfering of the metal workpiece which greatly suppresses the generation of media powder as industrial waste. Media can be provided.

  In addition, it is possible to provide a magnetic material such as a magnetic alloy in a favorable surface processed state by polishing using the medium of the present invention.

It is a cross-sectional schematic diagram for demonstrating the structural example of the medium for metal workpiece chamfering of this invention. It is a figure for demonstrating an example of the production process of the medium of this invention. It is a schematic diagram for demonstrating the outline | summary of the barrel used for grinding | polishing of the metal workpiece in the Example. It is a figure which represents typically the example of a shape of the neodymium-type alloy workpiece | work used in a barrel grinding | polishing process.

Explanation of symbols

10 Media 11 Core 12 Diamond abrasive grain 13 Plating film 100 Barrel

Claims (10)

A polishing media characterized in that abrasive grains are fixed by plating on the surface of a ball-shaped metal core. The polishing media according to claim 1, wherein the abrasive grains are diamond or cubic boron nitride. The polishing media according to claim 1 or 2, wherein the average grain size of the abrasive grains is in the range of 10 µm to 200 µm. 4. The polishing media according to claim 1, wherein the polishing media has a specific gravity of 4 or less. 5. The polishing media according to claim 1, wherein the metal core is made of at least one material of WC, TiC, aluminum, titanium, or a rare earth metal (including yttrium). The polishing media according to any one of claims 1 to 5, wherein the polishing media is a ball media having an average particle diameter of the metal core in a range of 1 mm to 20 mm. A polishing liquid comprising the polishing medium according to claim 1 suspended in a liquid medium. A first step of charging the polishing liquid according to claim 7 and a metal workpiece into a barrel;
And a second step of polishing the metal workpiece by driving the barrel. The metal workpiece polishing method according to claim 8, wherein the metal workpiece is a rare earth metal workpiece. A magnetic material polished using the polishing media according to claim 1.

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