JP4874853B2 - Cutting method of sintered rare earth magnet alloy - Google Patents

Description

  The present invention relates to a method and apparatus for cutting a sintered rare earth magnet alloy having a grain boundary phase around a hard ferromagnetic phase.

A sintered rare earth magnet alloy mainly composed of Nd-Fe-B has a metallic structure composed of a ferromagnetic phase mainly composed of Fe ₁₄ Nd ₂ B and an Nd-rich grain boundary phase (soft magnetic phase) around the ferromagnetic phase. It can be used as a high-performance magnet with an energy product (BHmax) of 35 (MGOe) or higher, and the magnet has a low corrosion resistance and oxidation resistance and has a low Curie point. Various improvements have been made to various properties such as high dependence, and in terms of composition, a part of Nd as a rare earth is replaced with another light rare earth or heavy rare earth, Co is an alloy element, Various proposals have been made to date, including those containing C (carbon) and those containing other alloy components.

  In addition, many improvements have been made to the manufacturing method, and technology for economically producing high-quality sintered rare earth magnet alloys is accumulating. Rare earth magnet alloys have been widely used.

The present invention is directed to such a sintered rare earth magnet alloy, but the term “sintered rare earth magnet alloy” as used herein refers to a sintered rare earth magnet alloy mainly composed of Nd—Fe—B. Of course, in terms of composition, Nd is partially substituted with other rare earth elements, Co is used as an alloy element, C (carbon) is included, and other alloy elements are included. It refers to the entire sintered body of rare earth magnets. These are collectively called Nd-based sintered rare earth magnet alloys in this specification, but they are abbreviated as sintered rare earth magnet alloys. Typically, it is a sintered magnet alloy of (Nd, R)-(Fe, Co)-(B, C) system. R is a rare earth element other than Nd. In any case, this sintered rare earth magnet alloy has magnetic crystal grains made of an intermetallic compound, (Nd, R) rich grain boundary phase around the magnetic crystal grains, and further B rich, It has a grain boundary phase including a Co-rich or C-rich phase, and these grain boundary phases are generally softer than magnetic crystal grains made of the intermetallic compound. Strictly speaking, the intermetallic compounds forming magnetic crystal grains differ depending on the alloy components contained, but it is generally assumed that the composition ratio of Fe (Co) ₁₄ Nd (R) ₂ (B, C) is present. ing.

  Such a sintered rare earth magnet is typically manufactured through a manufacturing process as shown in FIG. In the press forming process of alloy powder prior to sintering, it may be formed into the final magnet shape, but for productivity reasons, it is usually formed into a rod or cylinder and the sintered product is cut. Has been done.

  For example, in the case of manufacturing a disc-shaped sintered rare earth magnet having a thickness of about several millimeters and a diameter of about 10 mm, first, the alloy fine powder pulverized to a particle size of 10 μm or less is about 10 mm in diameter and long. Is formed into a round bar shape of about several tens of centimeters. This forming is performed in a magnetic field to orient the powder alloy particles. The orientation direction may be the axial direction of the round bar, the direction perpendicular to the axis, or the radial direction. This orientation treatment is performed when an anisotropic magnet is obtained. Since sintered rare earth magnets often exhibit high performance as an anisotropic magnet, this orientation treatment is performed in most cases. When obtaining an isotropic magnet, no orientation is performed and the crystal orientation is random. The obtained rod-shaped fired product is heat-treated or not heat-treated, and is cut into a circular shape having a thickness of about 2 mm, and the above-mentioned disk-like shape is formed. After boring, the magnet is magnetized to obtain a magnet with a desired shape.

The above-mentioned cutting process is a slicing process in which a thin piece is sliced from a rod. Conventionally, a slicing process of a sintered rare earth magnet alloy is performed by using an outer peripheral blade having abrasive grains fixed to the outer peripheral surface of a metal disk, or a metal circle. An inner peripheral blade having abrasive grains fixed to the inner peripheral edge of the central hole of the plate has been used, but the outer peripheral blade is most commonly used. Sintered rare earth magnet alloys have a hardness of 500 or more in Hv, and are usually very hard, 600 to 1000 Hv. For this reason, cutting with an outer peripheral blade (saw blade), the most advanced technology development in wafer slicing, etc. Has been commonly employed for cutting sintered rare earth magnet alloys.
Japanese Patent Laid-Open No. 9-248821 Japanese Patent Laid-Open No. 10-324889 JP-A-10-278040 JP-A-11-77663 JP-A-3-10760 JP 2000-108010 A

  As described above, the sintered rare earth magnet alloy has an extremely hard hardness of about Hv 500 to 1000, and has a structure in which hard magnetic crystal grains are dispersed in the grain boundary phase. Magnetic crystal grains are easy to cut and have so-called hard and brittle properties. Therefore, cutting so as to obtain a good cutting surface while increasing the cutting efficiency is a problem different from the case of cutting a single crystal such as a wafer, and the cutting conditions as well as the blade material are appropriate. Ingenuity is necessary.

  Various improvements have been made in the cutting method using a peripheral blade that has been adopted for sintered rare earth magnet alloys so far, and some results have been obtained, but there is a limit to reducing the thickness of the peripheral blade. For this reason, there is a basic problem that the amount of generated cutting waste increases and the production yield of expensive sintered rare earth magnets decreases.

  In addition, when slicing a rod-shaped or cylindrical sintered product into a ring shape with an outer peripheral blade as described above, a plurality of outer peripheral blades are usually arranged at a predetermined interval on one rotating shaft in order to increase cutting efficiency. Many blades are cut at once with the multi-blade method that is open and arranged. However, there is a problem that the number of defective cuts increases as the number of peripheral blades increases. There is a limit to the number that can be made, and there is also a limit to narrowing the distance between the outer peripheral blades (corresponding to the thickness of the ring cutting).

  Furthermore, if the outer peripheral edge wears out, it must be replaced and the work management cannot be neglected. In the case of the multi-outer peripheral edge, when the degree of wear differs, the cut surface becomes uneven or the structure where the magnetic crystal grains are missing on the cut surface. Since the occurrence of defective products becomes remarkable, the cutting work process requires skill.

  For this reason, in the production of sintered rare earth magnet alloys composed of a number of processes, the process of cutting a sintered product into small parts is the most burdensome process. Therefore, streamlining and improving the yield in this cutting process have been a major issue for the production of sintered rare earth magnet alloys. However, as described above, many improvements have been made in the method using an outer peripheral blade. However, the improvement is limited for the reasons described above, and in particular, it is difficult to cut a large number of thin objects at a high yield. An object of the present invention is to solve such problems and to provide a method and apparatus for cutting a sintered rare earth magnet alloy with reasonable and high yield.

  The inventors of the present invention have made various tests and researches to solve the above-mentioned problems. However, when an appropriate flexible wire and an abrasive liquid are used, the sintered rare earth magnet alloy can be cut well. Thus, it was found that the sintered rare earth magnet alloy side was cut without breaking the wire even if it was a soft flexible wire compared to a very hard sintered rare earth magnet alloy. It is considered that the metal structure peculiar to the sintered rare earth magnet alloy is involved as one of the factors that cause the hard sintered rare earth magnet alloy side to be cut because the soft wire side is difficult to cut. The present invention has been made on the basis of this finding and has a wire diameter of 1.2 mm with respect to a sintered rare earth magnet alloy having a hard-to-machine grain boundary phase around hard ferromagnetic crystal grains. Sintering characterized by pressing the following flexible wire and moving the wire in the axial direction while interposing an abrasive liquid in which abrasive grains are dispersed in a dispersion medium between the alloy and the wire A method of cutting a rare earth magnet alloy (Nd sintered rare earth magnet alloy) is provided.

  In addition, the present invention provides a magnetic anisotropy that has a hard-bounded grain boundary phase around hard ferromagnetic crystal grains and the orientation of the ferromagnetic crystals is oriented in a predetermined direction. A polishing liquid in which a flexible wire having a wire diameter of 1.2 mm or less is pressed against a rare earth magnet alloy in a direction substantially crossing or substantially along the crystal orientation method, and abrasive grains are dispersed in a dispersion medium. There is provided a method for cutting a sintered rare earth magnet alloy, characterized in that the wire is moved in the axial direction while being interposed between the alloy and the wire.

  Furthermore, according to the present invention, a plurality of rod-like sintered products made of sintered rare earth magnet alloy having hard-cutting grain boundary phases around hard ferromagnetic crystal grains are bundled with their axes parallel. Then, a flexible wire having a wire diameter of 1.2 mm or less is pressed against the bundle of sintered products in a direction orthogonal to the axial direction of each rod, and an abrasive liquid in which abrasive grains are dispersed in a dispersion medium is Provided is a method of cutting a sintered rare earth magnet alloy, wherein the wire is moved in the axial direction while being interposed between a sintered product and a wire.

  Here, a metal wire having a wire diameter of 0.06 to 1.2 mm can be used as the flexible wire, and the abrasive liquid is one or more kinds of abrasive grains of silicon carbide, alumina and diamond in the oil. Those in which is dispersed are preferred. Also, during cutting, sufficient abrasive grains are interposed between the metal wire and the cut surface to maintain the cut surface of the sintered rare earth magnet alloy and the metal wire in a substantially non-contact state. It is important to cut. In this case, the viscosity of the abrasive liquid is preferably 10 to 1000 mPa · s.

  According to this cutting method, a rod-like sintered rare earth magnet alloy can be simultaneously cut at a plurality of locations by moving one continuous wire in the axial direction. The axial movement of the wire is preferably a method in which the forward movement and the backward movement of a shorter distance are repeated, and the abrasive liquid is supplied to the surface of the wire before contacting the magnet for each of the forward movement and the backward movement.

  As an apparatus for carrying out such a cutting method, according to the present invention, a wire running means for running a flexible wire in the axial direction, a material to be cut made of a sintered rare earth magnet alloy, and a running wire are provided. There is provided a cutting device for sintered rare earth magnet alloy comprising cutting depth adjusting means for pressing each other and means for supplying abrasive grains between the cutting surface of the material being cut and the outer peripheral surface of the wire. Is.

  According to the present invention, a sintered rare earth magnet alloy having a very hard intermetallic compound crystal as a magnetic phase can be easily and precisely cut using the characteristics of the metal structure. This can greatly contribute to the improvement of magnet productivity.

Among the sintered rare earth magnet alloys, the structure of the sintered magnet alloy mainly composed of Nd—Fe—B is Fe ₁₄ Nd ₂ B having a diameter of about 10 μm as schematically shown in FIG. Around the ferromagnetic crystal grains (matrix), non-magnetic such as Nd rich phase (bcc Fe—Nd phase: soft magnetic phase) and boron rich phase (Nd _{1 + e} Fe ₄ B ₄ , Nd ₂ Fe ₇ B ₆₎ Phase) is said to have a metallographic structure present as a grain boundary phase. For example, when the Nd-rich phase is formed in a stable state with a uniform interface around the Fe ₁₄ Nd ₂ B phase by heat treatment after sintering, when a reverse magnetic field is applied, First, it is described that the reverse magnetic domain nuclei are generated, and the reverse magnetic domain nuclei are prevented from penetrating and growing into the Fe ₁₄ Nd ₂ B phase beyond the grain boundary, so that a high coercive force is maintained.

  Similarly, FIG. 2B shows a (Nd, Dy)-(Fe, Co)-(B, C) -based sintered magnet in which a part of Nd is replaced with Dy and Co and C are contained. The structure of the alloy is shown schematically, but this also has Nd, Dy, Fe around the magnetic crystal grains (compound phase) of Fe (Co) · Nd (Dy) · B · C having a diameter of about 10 μm. , Co, B, and C contain grain boundary phases (alloy phases), and the presence of the grain boundary phases plays an important role in giving high coercive force to the magnetic crystal grains as described above. , C (carbon) is considered to contribute to the improvement of corrosion resistance and oxidation resistance.

  Nd-based sintered magnets that can have a high energy product due to such a characteristic metal structure are such that large magnetic crystal grains made of extremely hard intermetallic compounds have a grain boundary phase (alloy phase) containing each component. ) It has a hard and brittle nature dispersed in it. From the viewpoint of processing, it can be said that it has a metal structure that is very difficult to cut with a smooth cut surface. In fact, even when cutting with an outer peripheral blade that has been conventionally employed, if the cutting speed is increased, a notch is generated, resulting in a defective cut surface, and it is difficult to cut into a thin object. That is, when cutting hard magnetic crystal grains, the wear of the cutting edge is not avoided, and the crystal grains are also peeled off, which induces the generation of cracks. For this reason, when cutting with an outer peripheral blade that applies high stress to the cutting surface through the cutting edge, defective products are apt to occur inevitably, and it has been difficult to obtain thin objects with a smooth fracture surface at a high yield. .

The above problem is not only due to the Nd—Fe—B based sintered magnet alloy that is supposed to have an intermetallic compound of Fe ₁₄ Nd ₂ B, but also part of Nd with other light rare earths and / or heavy rare earths. Substituted ones, those containing Co to increase their Curie point, those containing C to improve corrosion resistance and heat resistance, those containing other alloy components to improve various properties, etc. However, since the metallographic state has a softer grain boundary phase around hard ferromagnetic crystal grains, it has similar processing problems. Here, “softer than that” means that the hardness is actually difficult to achieve, but it means that the bond is loose and fragile compared to the ferromagnetic crystal grains, and therefore wear compared to the magnetic crystal grains. This means the property of being easily removed by impact, and such a property of the grain boundary phase is referred to as “easy machinability” in this specification.

  Therefore, the sintered rare earth magnet alloy to be cut by the present invention is not only Nd-Fe-B type, but also has substantially the same metal structure, that is, it is easier to cut around hard ferromagnetic crystal grains. All of the sintered rare earth magnet alloys having various component compositions as described above having a metallographic state having a grain boundary phase.

  The inventors of the present invention have a problem in cutting the sintered rare earth magnet alloy by pressing a flexible wire against the magnet alloy and supplying an abrasive liquid in which abrasive grains are dispersed in a dispersion medium. It was found that this problem can be solved by moving the wire in the axial direction without directly contacting the cut surface. Even if the wire is not harder than the sintered rare earth magnet alloy, the wire is not cut and the hard alloy side is cut.

  For example, as shown in FIG. 3, the flexible wire 2 is pressed against the sintered rare earth magnet alloy 1 having the metal structure as described above, and the abrasive grains are applied to the dispersion medium 3 as schematically shown in FIG. The wire 2 is moved in the axial direction while an abrasive liquid in which 4 is dispersed is interposed between the magnet alloy 1 and the wire 2. In the example of FIG. 3, the sintered rare earth magnet alloy 1 is pressed by pressing the sintered rare earth magnet alloy 1 from above the flexible wire 2 having the longitudinal direction of the wire substantially horizontal and moving in the axial direction. Is cut in the direction from the bottom to the top (the cutting direction is the direction from the bottom to the top).

  FIG. 4 is a schematic drawing of the cutting part in the middle of cutting in FIG. 3 with a plane orthogonal to the wire 2, but as shown in FIG. 4, the wire 2 and the cut surface 5 on the magnet alloy side are directly The wire 2 is moved in the axial direction (the front and back direction of the paper surface in FIG. 4) with the abrasive liquid interposed between them so that no direct contact occurs. Of course, the wire 2 is moved in the axial direction so that a pressure acts on the face portion 6 of the sintered rare earth magnet alloy 1 (upper surface portion of the cut surface 5 in FIG. 4). However, it is important that the state where the abrasive liquid exists between the face portion 6 and the wire 2 is maintained during the movement in the axial direction. This is because, when the abrasive liquid is not present, the wire 2 is worn and breaks. For this purpose, it is desirable that the abrasive liquid has an appropriate viscosity and the abrasive grains have an appropriate concentration and particle size distribution.

  In the cutting of the sintered rare earth magnet alloy 1, the wire 2 has a wire diameter of 1.2 mm or less, preferably 1.0 mm or less and 0.1 mm or more, more preferably 0.6 mm or less and 0.1 mm or more. Use metal wires. Here, the flexibility means a property that can be freely wound on the take-up reel and can be freely moved while changing the direction between pulleys or grooved guide rollers with an arbitrary angle change. In order to actually construct an apparatus for moving the wire 2 in the axial direction at a predetermined speed while applying a predetermined pressure to the sintered rare earth magnet alloy 1 under a predetermined tension, such a flexible property is required. This is because the wire 2 needs to have. For this reason, the wire 2 is necessarily a softer material than the sintered rare earth magnet alloy 1. The sintered rare earth magnet alloy 1 having the above-described metal structure usually has a hardness of 500 Hv or more, and in some cases 1000 Hv. However, a wire having a hardness equal to or higher than that has flexibility as described above. It is virtually impossible to do. As an example of the actual wire 2, a steel wire, a piano wire, a stainless steel wire or the like can be used, and those subjected to surface treatment such as brass plating or copper plating can also be used.

  As schematically shown in FIG. 4, when both of the soft wire 2 and the hard face 6 are moved relative to each other in the front and back direction of the paper, abrasive grains are formed on the surface of the wire 2 and the face 6. The acting force is almost equal according to the law of action and reaction, and when the same stress acts on both, the surface on the soft side should be ground. However, according to the method of the present invention, in practice, the surface of the soft-side wire 2 is rarely cut, and the face 6 of the hard-side sintered rare earth magnet alloy 1 is ground and cutting proceeds. The reason for this is not necessarily clear, but among the abrasive grains 4, those having a small grain size scrape off (peel the grain boundary phase (more easily machinable soft phase) in the metal structure of the sintered rare earth magnet alloy 1. If this grain boundary phase is ground, hard magnetic crystal grains will come out and will eventually be detached from the wall surface. In other words, the grain boundary is cut or removed preferentially, so that the magnetic crystal grains are separated from the grain boundary. On the other hand, the abrasive grains 4 having a large grain size serve as a spacer for maintaining the distance between the surface of the wire 2 and the face surface 6 and prevent the surfaces of both from coming into contact with each other. On the other hand, even if the abrasive grains 4 act on the surface of the wire 2, the wire 2 has a circular surface, and the wire 2 of FIG. 4 moving in the horizontal direction has an open space below the abrasive 2. Since the abrasive grains move in the moving direction of the wire when the viscosity of the abrasive liquid is appropriate, the stress acting between the abrasive grains and the wire becomes lower than that acting on the abrasive grains and the face surface 6. As a result, the stress acting on the abrasive grains per unit area of the wire is alleviated, so that it is considered that the cutting of the wire 2 hardly occurs.

  When cutting progresses by such a phenomenon, it is natural that powdered cutting scraps of the sintered rare earth magnet alloy 1 are accompanied in the abrasive liquid. When cutting proceeds as described above, the cutting scraps are composed of grain boundary phase cuttings (fine powder) and magnetic crystal grains separated from the grain boundaries. The grain boundary phase may be coated on the surface of the latter magnetic crystal grain. In any case, it is considered that when the sintered rare earth magnet alloy is cut, the cutting waste moves into the abrasive fluid, and the cutting waste in the abrasive fluid also acts as abrasive grains on the next cutting surface. However, in this case as well, it was confirmed that almost no phenomenon occurred in which the surface of the wire 2 was ground by the hard magnetic grains separated from the cutting chips, particularly from the grain boundaries. The reason may be that the magnetic crystal grains separated from the grain boundaries have a relatively large particle size and are immediately discharged by gravity into the open space below the wire 2.

  Since the abrasive liquid used in the present invention causes the abrasive grains to move on the cutting surface while moving the wire as the wire moves, the characteristics of the abrasive liquid are very important. It is necessary to select an appropriate one according to various factors such as the type and size of the rare earth magnet alloy, the material and diameter of the wire used, and the cutting speed. Oils such as mineral oils and hydrocarbon oils can be used as the dispersion medium, and silicon carbide, alumina, boron nitride (C · BN), diamond, etc. can be used as the abrasive grains.

  In this case, the viscosity of the abrasive liquid is preferably in the range of 30 to 1000 mPa · s as measured with an E-type viscometer. The average grain size of the abrasive grains should be in the range of 1 to 100 μm, and the concentration of the abrasive grains in the dispersion medium should be in the range of 10 to 90 wt%, preferably in the range of 30 to 80 wt% to ensure the above viscosity. It is good. In order to maintain this viscosity, it is desirable to add a thickener or to control the temperature of the abrasive liquid so that the temperature of the abrasive liquid during cutting is constant. It is also desirable to add a dispersant or a fluidizing agent to the abrasive liquid as necessary. It is desirable to control the temperature of the abrasive liquid in use, and it should be maintained at a temperature that does not solidify, for example, 20 ° C. or higher and as low as possible, for example 50 ° C.

  When using such an abrasive fluid and moving the abrasive grains in the abrasive fluid along with the movement of the wire and acting on the cutting surface to advance the cutting of the sintered rare earth magnet alloy, the moving speed of the wire is the highest. It is good to control so that speed may be in the range of 100-2000 m / min. At that time, in order to make the cut surface smooth, it is preferable to maintain the highest possible tension on the wire. However, there is a limit to the tension applied by the wire material. In our experiments, the tension applied to the wire near the winding roller side was 25 ± 10N.

  In the practice of the present invention, when cutting a magnetically anisotropic sintered rare earth magnet alloy in which the orientation of a ferromagnetic crystal is oriented in a predetermined direction, the direction substantially crossing the orientation direction of the crystal or the orientation It is preferable that the wire is pressed in a direction substantially along the direction, and the wire is moved in the axial direction and cut while the abrasive liquid is interposed between the alloy and the wire in the same manner as described above. As explained with reference to FIG. 1, when a magnetic rare-earth sintered rare earth magnet alloy is molded in a strong magnetic field during press molding of the alloy powder, the easy magnetization axis of the magnetic crystal grains is aligned with the direction of the magnetic flux. When a green compact is obtained and sintered, a magnetically anisotropic sintered rare earth magnet alloy having a fixed orientation of magnetic crystal grains is obtained. When sintering to a rod-like sintered rare earth magnet alloy, it is common for the axial direction of the rod to be the orientation direction, and this is thinly cut in a direction perpendicular to the axis (crossing the orientation direction) In this way, a plate magnet oriented in the front and back direction can be obtained. Moreover, if it cut | disconnects in the direction along an orientation direction, the magnet orientated in the direction along a cut surface can be obtained.

  Cutting a magnetically anisotropic sintered rare earth magnet alloy in a direction transverse to the orientation direction or in a direction along the orientation direction results in a cut surface having regularity in the direction of each crystal grain. Such a cutting mode is advantageous in that a magnetic anisotropic magnet product having a good surface quality can be obtained.

  FIG. 5 shows that a plurality of rod-like sintered products made of sintered rare earth magnet alloy 1 are bundled with their axes parallel to each other, and the same flexible wire 2 is attached to each bundle of the sintered products. By moving the wire in the axial direction while pressing the abrasive in a direction perpendicular to the axial direction and interposing an abrasive liquid in which the abrasive grains are dispersed in the dispersion medium between the sintered product and the wire, Fig. 3 shows an embodiment of the invention for cutting multiple rods.

  When bundling the rods, as shown in FIG. 6, the first stage rod group a is laid in parallel on the pedestal 7, the second stage rod group b is laid in parallel thereon, and further on It is preferable to pile up the rod group c in the third stage (however, it is in an inverted state in the drawing), the junction point between the base 7 and the rod group a of the first section, and the rod groups a to It is preferable that the bonding points between the rods c are fixed to each other with an adhesive interposed therebetween, or are bonded to each other by winding an adhesive tape between the rods. If the rods are bundled with adhesive tape while being bonded and fixed, the cut products will remain in their fixed state, so that the cut products will not be separated from each other even during or after cutting. The original shape of the rod bundle can be maintained as it is. In order to remove the adhesive and the adhesive tape after the cutting is completed, it is only necessary to immerse the original product in which the cut is included in the release agent solution together with the base. Stainless steel material or carbon material can be used as the pedestal 7, and if the cutting operation is performed until a part of the thickness of the pedestal 7 is incised, the first stage rod group a can be cut into a ring. it can.

  In implementing the present invention, in order to increase the productivity of cutting, it is preferable to simultaneously cut a plurality of locations on the rod of the sintered rare earth magnet alloy 1 as shown in FIG. FIG. 5 shows a state in which the wire 2 is cut while being pressed against the rod in parallel with each other at six locations. In practice, however, the wire 2 is pressed at many locations with respect to the entire length of the rod at regular intervals. It is better to cut at the same time. In that case, the wire 2 can be one continuous piece. That is, although not shown in FIG. 5, by winding a long wire between a pair of grooved guide rollers arranged in parallel and facing each other with a certain distance from each other, As shown in FIG. 5, a row of wire rods 2 parallel to each other may be formed, and the row of wire rods 2 may be simultaneously moved in the same direction.

  More specifically, as shown in FIG. 6, with respect to a pair of grooved guide rollers 8a and 8b arranged in parallel with a predetermined interval, a single wire 1 is placed, for example, from the front side to the back side of the paper surface. For example, in the guide roller 8a, the feed end 9 of the wire 2 is positioned on the front side of the paper surface, and in the guide roller 8b, the winding end 10 is positioned on the back side of the paper surface. You just have to do it. Thus, a number of parallel rows are formed by the single wire 2 between the guide rollers 8a and 8b. On this row, a rod bundle of the sintered rare earth magnet alloy 1 is placed in the direction of the arrow 11. When the wire 2 is moved in the axial direction while being pressed at a predetermined pressure, a plurality of locations can be cut simultaneously by moving the single continuous wire in the axial direction.

  At that time, it is desirable to repeat the movement of the wire 2 in the axial direction by repeating the forward movement and the backward movement over a short distance. The surface of the wire before contacting the sintered rare earth magnet alloy 2 in both the forward movement and the backward movement. It is desirable to supply the abrasive liquid from the abrasive liquid supply headers 12a and 12b each time. For example, in FIG. 6, if the wire 2 is moved from the left guide roller 8a toward the right guide roller 8b by a distance X, then in the opposite direction, only a distance Y (= X−α) shorter than X by X. The reciprocation of moving is repeated, and one reciprocation is wound on a take-up reel (not shown, but connected to the take-up end 10 of the wire 2) for a length α. By this step movement, the abrasive liquid is alternately supplied to the cut surface from the abrasive liquid supply headers 12a and 12b on both sides, so that the abrasive grains are between the wire 2 and the face 6 of the sintered rare earth magnet alloy 1. And cutting waste can exist in good condition.

  The method of the present invention as described above includes a wire rod traveling means for causing a flexible wire rod to travel in the axial direction, and a cutting depth adjusting means for pressing a workpiece to be cut made of a sintered rare earth magnet and a running wire rod against each other. And means for supplying abrasive grains between the cutting surface of the material being cut and the outer peripheral surface of the wire, and using a cutting device for sintered rare earth magnets. Here, for example, as shown in FIG. 6, the wire travel means moves the wire 2 suspended between a pair of guide rollers 8 a and 8 b arranged parallel to each other at a predetermined interval in the axial direction. Although not shown in the drawing, it can be constituted by a wire take-up reel, a rewind reel, and a wire drive roller. The cutting depth adjusting means may employ a press mechanism that presses the base 7 that fixes the sintered rare earth magnet alloy 1 in the direction of the wire 2 with a predetermined pressure. Also, as means for supplying the abrasive grains, an abrasive liquid supply device 12 is used which discharges a predetermined amount of abrasive liquid in which abrasive grains are dispersed in a dispersion medium, which is installed in the vicinity of the cutting section and fed into the cutting section. It is preferable to supply the abrasive liquid to the surface of the wire immediately before being applied.

[Example 1]
According to the manufacturing method described in Example 8 of Patent No. 2777654 to the same applicant, it has the same composition as that of Example 8, that is, 18Nd-61Fe-15Co-1B-5C, and is shown in FIG. A plate-like sintered body (plate thickness 30 mm × 25 mm × thickness 8 mm) made of a sintered rare earth magnet alloy having a metal structure equivalent to that of a magnetic crystal grain having an Nd-rich grain boundary around a magnetic crystal grain of about 10 μm. The test specimen is a steel wire (with a brass plating on the surface) and silicon carbide-based abrasive grains made of mineral oil. A cutting test was carried out using the abrasive liquid dispersed in. The test conditions are as follows.

〔Test conditions〕
Material to be cut: Sintered rare earth magnet alloy (hardness: 650 Hv).
Wire material: Brass-plated steel wire having a diameter of 0.2 mm (tensile strength = 3000 N / mm ² , cutting load = 80 N).
Abrasive liquid: A viscous liquid having a viscosity of 110 mPa · s obtained by dispersing silica carbide-based abrasive grains (# 700) having an average particle diameter of 17 μm in mineral oil (trade name Re-Coloring Oil FB-10) at a concentration of 65 wt%.
Cutting direction: The wire is pressed in parallel with a side of 25 mm against the plate back surface of the material to be cut, and the wire is moved in the axial direction.
Wire travel speed:
Forward speed of wire: An initial speed is given at an acceleration of 3.0 m / sec ² , the speed is maintained for 10 seconds when the speed reaches 700 m / min, and the speed is stopped for 4 seconds from that speed.
Return speed of the wire: When the forward path stops, the initial speed is continuously applied in the opposite direction at an acceleration of 3.0 m / sec ² , and when the speed reaches 700 m / min, the speed is maintained for 5 seconds, and from that speed for 4 seconds Stop at.
Abrasive fluid supply: Abrasive fluid is supplied to the surface of the wire rod at a position 100 mm away from the cutting portion in both the forward and return paths of the wire, and the wire rod surface is completely covered with the abrasive fluid so that it proceeds to the cutting portion. .
Slice thickness of material to be cut: 1.0 mm

  Under the above test conditions, a strip-shaped cut piece having a length of 25 mm × width of 8 mm and a thickness of 1.0 mm was cut out in about 35 minutes. Meanwhile, the temperature of the abrasive liquid supplied to the wire was controlled to be a constant 25 ° C. The cut surface of the obtained cut piece was very smooth, and saw marks and notches were not seen. When the cut surface was observed with an electron microscope, it was found that the cut surface was cut at the grain boundary.

[Example 2]
As a test material, a sintered rare earth magnet alloy having a metal structure composed of 18Nd-76Fe-6B and having an average grain size of 5.0 μm surrounded by an Nd-rich grain boundary phase was used. Example 1 was repeated. As a result, a strip-shaped cut piece of 25 mm × width 8 mm and thickness 1.0 mm was cut out in about 35 minutes, the cut surface was very smooth, and saw marks and notches were not seen.

Example 3
Example 1 was repeated except that SiC-based abrasive grains (average particle size = 17.0 μm, 700) having a viscosity of 280 mPa · s dispersed in mineral oil at a concentration of 65 wt% were used as the abrasive liquid. It was. As a result, a strip-shaped cut piece of 25 mm × width 8 mm and thickness 1.0 mm was cut out in about 40 minutes, the cut surface was very smooth, and neither saw marks nor notches were seen.

Example 4
Example 1 was repeated except that the orientation direction of the test material was the plate width direction. As a result, a strip-shaped cut piece of 25 mm × width 8 mm and thickness 1.0 mm was cut out in about 35 minutes, the cut surface was very smooth, and saw marks and notches were not seen.

[Comparative Example]
Example 1 was repeated except that the abrasive concentration was 10 wt% and the viscosity was 28 mPa · s. As a result, the wire broke during cutting.

It is process drawing which shows the example of the general manufacturing method of a sintered rare earth magnet alloy. (A) And (B) is the structure explanatory drawing which illustrated and showed the general metal structure state of the sintered rare earth magnet alloy. It is a perspective view which shows the example of the cutting method of the sintered rare earth magnet alloy according to this invention. It is the schematic sectional drawing which showed typically the state of the cutting part at the time of cut | disconnecting a sintered rare earth magnet alloy according to this invention. It is a perspective view which shows the example of the aspect of the cutting method of the sintered rare earth magnet alloy according to this invention. It is a schematic sectional drawing which shows the example of the aspect of the cutting method of the sintered rare earth magnet alloy according to this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sintered rare earth magnet alloy 2 Flexible wire 3 Abrasive fluid 4 Abrasive grain 5 Cutting surface 6 Face 7 Seat 8 Guide roller 9 Wire feed end 10 Wire take-up end 11 Pressing direction 12 Abrasive feed header

Claims (4)

Nd-Fe-B as a main component, containing Co and further containing 5% C by atomic percentage , having a grain boundary phase more easily machinable around the ferromagnetic crystal grains, and the ferromagnetic A direction in which a flexible wire having a wire diameter of 1.2 mm or less is substantially crossed with the crystal orientation direction on a magnetically anisotropic sintered rare earth magnet alloy plate having a crystal orientation in the plate width direction. The alloy plate is moved by moving the wire in the axial direction while interposing an abrasive liquid formed by dispersing abrasive grains in a dispersion medium between the alloy plate and the wire. A method of cutting at the grain boundary phase, wherein the flexible wire is made of a metal wire having a wire diameter of 0.06 to 1.2 mm, and the abrasive liquid is silicon carbide, alumina, boron nitride (C BN), one or more abrasive grains of diamond dispersed therein, and the magnet alloy during the cutting Abrasive grains sufficient to maintain the cut surface and the metal wire in a substantially non-contact state are interposed between the metal wire and the cut surface, and the viscosity of the abrasive liquid is 30 to 1000 mPa · s. A method for cutting a sintered rare earth magnet alloy, comprising:   The method for cutting a sintered rare earth magnet alloy according to claim 1, wherein a plurality of locations are simultaneously cut by moving one continuous wire in the axial direction.   The movement of the wire in the axial direction is composed of repetition of forward movement and backward movement of a shorter distance, and the abrasive liquid is supplied to the surface of the wire before contacting the magnet in each of the forward movement and the backward movement. 2. A method for cutting a sintered rare earth magnet alloy according to 2.   A sintered rare earth magnet alloy plate is pressed from above against a flexible wire arranged so that the longitudinal direction of the wire is substantially horizontal, and the cutting progress direction of the alloy plate from the top to the bottom The method for cutting a sintered rare earth magnet alloy according to any one of claims 1 to 3, wherein the cutting direction is a direction toward the surface.

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