WO2019188303A1 - Method for manufacturing industrial article comprising sintered compact - Google Patents

Method for manufacturing industrial article comprising sintered compact Download PDF

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Publication number
WO2019188303A1
WO2019188303A1 PCT/JP2019/010341 JP2019010341W WO2019188303A1 WO 2019188303 A1 WO2019188303 A1 WO 2019188303A1 JP 2019010341 W JP2019010341 W JP 2019010341W WO 2019188303 A1 WO2019188303 A1 WO 2019188303A1
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WIPO (PCT)
Prior art keywords
punch
molded body
mold
inorganic powder
powder
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PCT/JP2019/010341
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French (fr)
Japanese (ja)
Inventor
俊英 遠藤
明弘 大澤
真史 後藤
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Tdk株式会社
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Publication of WO2019188303A1 publication Critical patent/WO2019188303A1/en

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/02—Compacting only
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
    • H01F41/02—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets

Definitions

  • the present invention relates to a manufacturing method of an industrial product having a sintered body.
  • Sintered bodies such as rare earth magnets, ferrite magnets, dielectrics, and piezoelectrics are used in various industrial products such as motors, actuators, inductors, capacitors, insulating materials, isolators, sensors, and resonators.
  • a molded body is formed by molding inorganic powder using a mold, and the sintered body is obtained by sintering the molded body.
  • a molding step in which a rare earth element-containing alloy powder is pressed with a mold to produce a molded body, a magnetic field is applied to the molded body in the mold, An orientation process for orienting the alloy powder in the compact and a sintering process for sintering the compact that has undergone the orientation process are provided.
  • Molding defects include, for example, burrs, irregularities on the surface of the molded body, distortion of the molded body, or cracks in the molded body.
  • a molding defect of the molded body causes defects in the sintered body. For example, when the sintered body has burrs, since the burrs of the sintered body are harder and stronger than the burrs of the molded body, it is difficult to remove the burrs from the sintered body. It may be damaged. Therefore, it is desirable to eliminate molding defects in the molded body before sintering. For example, the burr is removed from the molded body by a process such as cutting or polishing.
  • the molded body itself may be damaged along with the processing for eliminating the molding defect.
  • a part of the molded body is also removed together with the burr.
  • the molded body does not have sufficient mechanical strength, so that the molded body itself is easily damaged along with the processing to eliminate molding defects.
  • An object of the present invention is to provide a manufacturing method of an industrial product that can suppress molding defects of a molded body formed from an inorganic powder in the manufacture of an industrial product having a sintered body.
  • the manufacturing method of an industrial product according to one aspect of the present invention is a manufacturing method of an industrial product having a sintered body, and is a molding process in which inorganic powder supplied into a die is pressed with a punch to form a molded body. And sintering the molded body to obtain a sintered body.
  • the punch is pulled back, and the inorganic powder is again fed with the punch or another Press with a punch.
  • the true density of the inorganic powder may be expressed as D [g / cm 3 ]
  • the bulk density of the molded body may be expressed as d [g / cm 3 ]
  • the relative density of the molded body is 100 ⁇ d. / D [%] may be defined, and the relative density may be adjusted to 40% or more and 60% or less in the molding step.
  • the pressure exerted on the inorganic powder by the punch may be adjusted to 0.049 MPa or more and 20 MPa or less.
  • the inorganic powder may be a granule.
  • the manufacturing method of the industrial product according to one aspect of the present invention may further include an alignment step of applying a magnetic field to the formed body held by the punch and the die and aligning the inorganic powder contained in the formed body.
  • a sintering step may be performed later, the inorganic powder may be a magnetic powder, at least a part of the punch may be insulative, at least a part of the die may be insulative, and the sintered body
  • the industrial product having a may be a sintered magnet.
  • the magnetic powder may be a metal powder containing a rare earth element, and the sintered magnet may be a rare earth magnet.
  • an industrial product manufacturing method capable of suppressing molding defects of a molded body formed from an inorganic powder in manufacturing an industrial product having a sintered body.
  • FIG. 2 and FIG. 2 are schematic cross-sectional views of a mold and an inorganic powder (molded body), and show an example of a molding process.
  • FIG. 3 and (c) in FIG. 3 are schematic cross-sectional views of the mold and the inorganic powder (molded body), and show an example of the molding process.
  • X, Y, and Z shown in each figure mean three coordinate axes orthogonal to each other.
  • the direction indicated by each coordinate axis is common to all drawings.
  • the Z axis corresponds to the vertical direction.
  • the XY plane corresponds to the horizontal direction.
  • the manufacturing method of the industrial product which concerns on this embodiment is a manufacturing method of the industrial product which has a sintered compact.
  • the industrial product manufacturing method according to the present embodiment includes a punching process in which inorganic powder supplied in a die is pressed with a punch to form a molded body, and a sintered body is obtained by sintering the molded body. And a knotting process.
  • the inorganic powder is pressurized with a punch, the punch is pulled back, and the inorganic powder is again pressurized with the punch or another punch. That is, in the molding step, the inorganic powder is pressurized at least twice with a punch. Details of the molding process will be described later.
  • the inorganic powder that is the raw material of the sintered body is not particularly limited.
  • the inorganic powder is, for example, a kind selected from the group consisting of metal powder containing rare earth elements (alloy powder), ferrite powder, alnico alloy powder (alloy powder containing Al, Ni and Co), and dielectric powder. It's okay.
  • the dielectric powder may be, for example, one type selected from the group consisting of silicon carbide powder, aluminum oxide powder, zirconium oxide powder, and mullite powder.
  • the dielectric material implies a piezoelectric material, a pyroelectric material, and a ferroelectric material. Details of the metal powder containing the rare earth element will be described later.
  • the inorganic powder may be a granule.
  • the fluidity of the inorganic powder is increased, and thus there may be a case where density variation and chipping of the sintered body can be further suppressed.
  • Granules may be produced by a known granulation method using an inorganic powder and a granule forming agent.
  • the granulation method may be, for example, rolling granulation, spray granulation, or vibration granulation. Specifically, the granulation method described in Japanese Patent No. 4662046 can be used.
  • the granule forming agent may be, for example, at least one compound selected from the group consisting of alkylbenzene compounds, alcohol compounds, ether compounds, ester compounds, ketone compounds, fatty acid compounds, and terpene compounds.
  • the ether compound may include a glycol ether compound.
  • the ester compound may include a glycol ester compound.
  • the alkylbenzene compound may be at least one compound selected from the group consisting of toluene and xylene.
  • the alcohol compound may be at least one compound selected from the group consisting of terpineol and ethanol.
  • the ether compound may be at least one compound selected from the group consisting of butyl cellosolve, cellosolve, carbitol and butyl carbitol.
  • the ester compound may be ethyl acetate.
  • the ketone compound may be at least one compound selected from the group consisting of acetone (dimethyl ketone), methyl isobutyl ketone, and methyl ethyl ketone.
  • other organic liquids such as ethylene glycol, diethylene glycol and glycerin may be used as the granule forming agent.
  • a binder such as a polymer may be used as the granule forming agent.
  • the particle size D50 of the granules in the volume-based particle size distribution by laser diffraction method may be 20 ⁇ m or more and 1000 ⁇ m or less.
  • the sintered body produced in the present embodiment is not particularly limited.
  • the sintered body may be, for example, a sintered magnet.
  • the sintered magnet may be a kind selected from the group consisting of rare earth magnets, ferrite magnets, and alnico magnets, for example. Details of the rare earth magnet will be described later.
  • the sintered body may be a dielectric.
  • Dielectric sintered bodies are, for example, barium titanate, calcium titanate, lead titanate, lead zirconate titanate, potassium niobate, lithium niobate, barium niobate, sodium potassium niobate, bismuth ferrite, It may be a ceramic such as bismuth titanate, barium neotitanate, bismuth sodium titanate, sodium tungstate, zinc oxide, aluminum oxide, cordierite, stearite, yttrium oxide, iron oxide, garnet, mullite or forsterite. .
  • Industrial products having the above sintered body include, for example, rare earth magnets, ferrite magnets, alnico magnets, motors, generators, actuators, inductors, transformers, capacitors, insulators, isolators, microwave integrated circuits (MICROWAVE INTEGRATED CIRCUIT; MIC). , Electromagnetic wave filter, pressure sensor, resonator, abrasive, cutter, mirror, or various ceramic substrates. Details of the rare earth magnet will be described later.
  • the size and shape of the sintered body vary depending on the use of the sintered body and are not particularly limited.
  • the shape of the sintered body may be, for example, a rectangular parallelepiped shape, a cubic shape, a polygonal column shape, a segment shape, a fan shape, a rectangular shape, a plate shape, a spherical shape, a disc shape, a columnar shape, a ring shape, or a capsule shape.
  • the cross-sectional shape of the sintered body may be, for example, a polygonal shape, a chordal shape, an arc shape, or a circular shape.
  • FIG. 1 An example of a mold used in the molding process is shown in FIG.
  • the procedure of the molding process using the mold shown in FIG. 1 is as follows: (a) in FIG. 2, (b) in FIG. 2, (a) in FIG. 3, (b) in FIG. (C).
  • the mold 2 includes a punch 4 (upper mold) and a die 3.
  • the die 3 includes a lower mold 8 and a cylindrical side mold 6 disposed on the lower mold 8.
  • the side mold 6 can be separated from the lower mold 8. However, the side mold 6 and the lower mold 8 may be continuous without being separated from each other.
  • a space corresponding to the shape and size of the molded body penetrates the side mold 6 in the vertical direction.
  • the side mold 6 may be rephrased as a mold side wall (die side wall).
  • the lower mold 8 may be plate-shaped.
  • the punch 4 has a shape that fits into the die 3 (a space penetrating the side mold 6).
  • the size and shape of another punch 4a (second punch) shown in (a) in FIG. 3, (b) in FIG. 3, and (c) in FIG. 3 are shown in FIGS.
  • the size and shape of the punch 4 (first punch) shown in a) and (b) in FIG. 2 may be substantially the same.
  • the size and shape of the mold 2
  • the punches 4 and 4a, the side mold 6 and the lower mold 8 are each made of, for example, iron, silicon steel, stainless steel, permalloy, aluminum, aluminum alloy, molybdenum, tungsten, ceramics (for example, alumina), carbon, glass, and resin. It may be formed from at least one selected from the group consisting of
  • the lower die 8, the side die 6 and the punch 4 shown in FIG. 1 are inclined with respect to the vertical direction in the molding process. It may be.
  • the entire mold 2 may be inclined with respect to the vertical direction in the molding process. .
  • the angle formed by the entire mold 2 with respect to the vertical direction Z-axis direction
  • the relative positional relationship of the lower die 8, the side die 6, and the punch 4a shown in (a) in FIG. 3, (b) in FIG. 3, and (c) in FIG. 3 is maintained.
  • the side mold 6, and the punch 4a are inclined with respect to the vertical direction.
  • the side mold 6 is placed on the lower mold 8 and the opening (hole) on the lower surface side of the side mold 6 is formed in the lower mold. Close with 8. With such an arrangement, the side mold 6 and the lower mold 8 constitute the die 3. Subsequently, the inorganic powder 10 is supplied from the opening on the upper surface side of the side mold 6 into the die 3 (a space penetrating the side mold 6). The inorganic powder 10 may be filled into the die 3. That is, the inside of the die 3 may be filled with the inorganic powder 10.
  • the punch 4 is inserted into the die 3 and the inorganic powder 10 in the die 3 is pressurized with the punch 4.
  • the inorganic powder 10 is molded so as to correspond to the inner shape and dimensions of the die 3, and a molded body 10b is obtained.
  • a molding defect of the molded body 10b may occur.
  • the inorganic powder 10 may enter the clearance between the side surface of the punch 4 and the inner wall of the die 3 to form a burr 10a. The larger the clearance, the easier the burr 10a is formed. This burr 10a is eliminated by the following method.
  • the inorganic powder 10 is pressurized with the punch 4, and then the punch 4 is pulled back.
  • the pressure inside the die 3 becomes negative, and the burr 10a tends to fall toward the surface of the molded body 10b.
  • the burrs 10a are pressed against the surface of the molded body 10b by pressurizing the inorganic powder 10 (formed body 10b) with the punch 4a again. It is integrated with the surface of the molded body 10b.
  • FIG. 3C the burr 10a is eliminated, and a molded body 10b having a flat surface is obtained.
  • Molding defects other than the burr 10a are also suppressed or eliminated by the above molding process.
  • unevenness on the surface of the molded body 10b is formed by pressurizing the inorganic powder 10 with the punch 4
  • the punch 4 is pulled back, and the inorganic powder 10 (formed body 10b) is pressed again with the punch 4a. Is eliminated and the surface of the molded body 10b becomes flat.
  • the distorted molded body 10b is formed by pressurizing the inorganic powder 10 with the punch 4
  • the punch 4 is pulled back, and the inorganic powder 10 (molded body 10b) is pressed again with the punch 4a. Is resolved.
  • the molded body 10b having a crack is formed by pressurizing the inorganic powder 10 with the punch 4
  • the crack is resolved by pulling back the punch 4 and pressurizing the inorganic powder 10 (formed body 10b) with the punch 4a again.
  • molding defects such as the burr 10a can be suppressed and eliminated without cutting and polishing a part of the molded body 10b. Therefore, a change (decrease) in the mass of the molded body 10b due to processing for eliminating the molding defect is unlikely to occur. That is, almost no waste (inorganic powder 10 removed from the molded body 10b) is generated due to processing for eliminating molding defects.
  • a sintered body for example, a sintered magnet
  • desired characteristics for example, magnetic characteristics
  • the end face of the punch 4 may be separated from a part or the whole of the inorganic powder 10.
  • the end face of the punch 4 may be pulled back upward from the tip of the burr 10a.
  • the burr 10a is easily pressed against the surface of the molded body 10b by re-pressing with the punch 4a.
  • the entire punch 4 may not be completely pulled out from the die 3. That is, the tip of the punch 4 may be located inside the die 3 in a state where the punch 4 is pulled back.
  • the punch 4a used for the second pressurization may be the same as the punch 4 used for the first pressurization. That is, the inorganic powder 10 may be pressed at least twice using one punch 4. After pressing the inorganic powder with the first punch (punch 4), the inorganic powder may be pressed again with a second punch (punch 4a) different from the first punch (punch 4). As a result, compared with the case where only the first punch (4) is used, wear of the first punch (punch 4) and the second punch (punch 4a) is suppressed.
  • the relative position and stroke of the first punch (punch 4) relative to the die 3 may be the same as the relative position and stroke of the second punch (punch 4a) relative to the die 3.
  • the second punch (punch 4a) may be thicker than the first punch (punch 4). The thicker the second punch (punch 4a), the more easily the second punch (punch 4a) comes into contact with the burr 10a attached to the inside of the die 3 and the burr 10a is easily eliminated.
  • the true density of the inorganic powder 10 is expressed as D [g / cm 3 ].
  • the bulk density of the molded body 10b is expressed as d [g / cm 3 ].
  • the relative density of the molded body 10b is defined as 100 ⁇ d / D [%].
  • the relative density may be adjusted to 40% or more and 60% or less.
  • the relative density is low, neither the compact 10b nor the burr 10a is excessively compressed, and the burr 10a is soft and brittle, so that the burr 10a is easily integrated with the compact 10b. Therefore, when the relative density is 60% or less, the burr 10a is easily eliminated by the second and subsequent pressurization by the punch 4a.
  • the relative density is 60% or less, molding defects other than the burr 10a are easily eliminated.
  • the relative density is 40% or more, the molded body 10b tends to have sufficient mechanical strength, and the molded body is not easily damaged in the subsequent process following the molding process.
  • the pressure exerted by the punch (4 or 4a) on the inorganic powder 10 (molded body 10b) may be adjusted to 0.049 MPa or more and 20 MPa or less.
  • the molding pressure is 0.049 MPa or more and 20 MPa or less, neither the compact 10b nor the burr 10a is compressed excessively, so the burr 10a is brittle and the burr 10a is easily integrated with the compact 10b. That is, when the molding pressure is 0.049 MPa or more and 20 MPa or less, the burr 10a is easily eliminated by the second and subsequent pressurization by the punch 4a.
  • the molding pressure is 0.049 MPa or more and 20 MPa or less, molding defects other than the burr 10a are easily eliminated.
  • the pressure which a punch (4 or 4a) exerts on the inorganic powder 10 (molded body 10b) is not limited.
  • the pressure that the punch (4 or 4a) exerts on the inorganic powder 10 (molded body 10b) may be a high pressure in the range of 50 MPa to 200 MPa. Even in the case where the molded body 10b is formed by molding the inorganic powder 10 at such a high pressure, according to the present embodiment, molding defects can be suppressed and eliminated.
  • the inorganic powder 10 is a magnetic powder and a sintered magnet is produced from the magnetic powder
  • the following alignment process is performed after the molding process, and the sintering process is performed after the alignment process.
  • a magnetic field may be applied to the compact 10b held by the punch (4 or 4a) and the die 3 to orient the magnetic powder contained in the compact 10b.
  • a magnetic field may be applied to the molded body 10b held by the punch 4a and the die 3.
  • Part or all of the punch (4 or 4a) and the die 3 used in the alignment step are preferably insulative.
  • the punch (4 or 4a) and the die 3 are insulative, the eddy current in the punch (4 or 4a) and the die 3 is suppressed in the alignment step, and the degree of orientation of the magnetic powder in the compact 10b Will improve.
  • the punch 4 When one punch 4 (first punch) is used from the forming step to the orientation step, it is preferable that at least a part of the punch 4 (first punch) is insulative, and the punch 4 (first punch) More preferably, the entire punch) is insulative.
  • the orientation step when the compact 10b is held by the second punch (punch 4a) and the die 3, it is preferable that at least a part of the second punch (punch 4a) is insulative. More preferably, the entire punch 4a) is insulative.
  • the first punch (punch 4) may be a metal, for example. At least a part of the die 3 used in the alignment step may be insulative, and the entire die 3 is preferably insulative.
  • the side mold 6 may be seamless. That is, the side mold 6 may be seamless. If the side mold 6 has a seam (for example, when the side mold 6 can be disassembled into a plurality of members), the inorganic powder 10 is transferred from the seam (gap) of the side mold 6 to the mold 2 in the molding step or the orientation step. May leak out. As a result, the shape retention of the molded body 10b is impaired, and for example, burrs may be formed on the molded body 10b. When the side mold 6 is separated from the molded body 10b by disassembling the side mold 6 into a plurality of members, a force may be applied to the molded body 10b by mistake and the molded body 10b may be damaged.
  • a seam for example, when the side mold 6 can be disassembled into a plurality of members
  • the temperature of the molded body in the sintering step may be appropriately adjusted according to the composition of the inorganic powder constituting the molded body.
  • Rare earth magnets are components such as motors or actuators, such as hard disk drives, hybrid cars, electric cars, magnetic resonance imaging devices (MRI), smartphones, digital cameras, thin TVs, scanners, air conditioners, heat pumps, refrigerators, and vacuum cleaners. It is used in various fields such as washing and drying machines, elevators and wind power generators. Depending on these various applications, the dimensions and shape required for rare earth magnets vary. Therefore, in order to efficiently manufacture a wide variety of rare earth magnets, a molding method that can easily change the size and shape of the rare earth magnet is desired.
  • motors or actuators such as hard disk drives, hybrid cars, electric cars, magnetic resonance imaging devices (MRI), smartphones, digital cameras, thin TVs, scanners, air conditioners, heat pumps, refrigerators, and vacuum cleaners. It is used in various fields such as washing and drying machines, elevators and wind power generators.
  • a molding method that can easily change the size and shape of the rare earth magnet is desired.
  • a magnetic field is applied to a metal powder while pressing a metal powder (for example, an alloy powder) containing a rare earth element with a high pressure (for example, 50 MPa or more and 200 MPa or less).
  • a high pressure for example, 50 MPa or more and 200 MPa or less.
  • a high-pressure magnetic field pressing method According to the high-pressure magnetic field pressing method, it is possible to obtain a molded body having a high residual magnetic flux density Br and excellent shape retention, since the metal powder is easily oriented.
  • a sintered product is obtained by sintering the compact, and the sintered product is processed into a desired shape to complete a magnet product.
  • the shape of a general molded body obtained by a high-pressure magnetic field pressing method is limited to a coarse block. Therefore, when manufacturing various types of magnet products by the conventional method, after obtaining the sintered body by sintering the block-shaped molded body, the sintered body is prepared according to the size and shape required for the magnet product. Need to be processed. In the processing of the sintered body, since the sintered body is cut or polished, scraps containing expensive rare earth elements are generated. As a result, the yield rate of magnet products decreases. In the high-pressure magnetic field pressing method, the mold or the molded body is easily damaged due to galling between the molds or between the mold and the molded body. For example, cracks may occur in a molded body obtained by a high-pressure magnetic field pressing method.
  • the conventional manufacturing method using the high-pressure magnetic field pressing method is not suitable for manufacturing a variety of products or a small amount of magnet products.
  • the pressure exerted on the metal powder (inorganic powder) by the mold 2 is 0.049 MPa or more and 20 MPa or less (0.5 kgf / cm 2 or more). 200 kgf / cm 2 or less).
  • metal powder is molded at such a low pressure, durability against high pressure is not required for the mold, and a large-scale and complicated molding apparatus is not required. Therefore, when molding metal powder at a low pressure, the material, size and shape of the mold are not limited, and various types of rare earth magnets can be manufactured relatively easily using molds having various sizes and shapes. it can.
  • the high-pressure magnetic field press method takes a long time to form and orient the metal powder, but by forming the metal powder at a low pressure, the time required for the forming and orientation is greatly shortened and the productivity of the rare earth magnet is improved. To do.
  • a raw material alloy is cast.
  • the casting method may be, for example, a strip casting method.
  • the raw material alloy may be in the form of flakes or ingots.
  • the raw material alloy contains a rare earth element R.
  • the rare earth element R may be at least one selected from the group consisting of Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. .
  • the raw material alloy is selected from the group consisting of B, N, Fe, Co, Cu, Ni, Mn, Al, Nb, Zr, Ti, W, Mo, V, Ga, Zn, Si, and Bi. It may contain at least one element selected.
  • the chemical composition of the raw material alloy may be adjusted according to the chemical composition of the main phase and grain boundary phase of the rare earth magnet to be finally obtained. That is, the raw materials for the raw material alloy may be prepared by weighing and blending the starting materials containing the above elements according to the composition of the target rare earth magnet.
  • the rare earth magnet may be, for example, a neodymium magnet, a samarium cobalt magnet, a samarium-iron-nitrogen magnet, or a praseodymium magnet.
  • the main phase of the rare earth magnet may be, for example, Nd 2 Fe 14 B, SmCo 5 , Sm 2 Co 17 , Sm 2 Fe 17 N 3 , Sm 1 Fe 7 N x , or PrCo 5 .
  • the grain boundary phase may be, for example, a phase (R rich phase) in which the content of the rare earth element R is larger than that of the main phase.
  • the grain boundary phase may include a transition metal rich phase, a B rich phase, an oxide phase, or a carbide phase.
  • a coarse powder is obtained by coarse pulverization of the above raw material alloy.
  • the raw material alloy may be pulverized by occluding hydrogen in the alloy grain boundaries (R-rich phase).
  • a mechanical pulverization method such as a disk mill, a jaw crusher, a brown mill, or a stamp mill may be used.
  • the particle size of the coarse powder obtained by coarse pulverization may be, for example, 10 ⁇ m or more and 100 ⁇ m or less.
  • Fine powder is obtained by fine pulverization of the above coarse powder.
  • the coarse powder may be pulverized by a jet mill, a ball mill, a vibration mill, a wet attritor or the like.
  • the particle size of the fine powder obtained by pulverization may be, for example, 0.5 ⁇ m or more and 5 ⁇ m or less.
  • Organic substances may be added to the coarse powder obtained by coarse pulverization.
  • An organic substance may be added to the fine powder obtained by fine pulverization. That is, the organic substance may be mixed with the raw material alloy powder either before or after pulverization.
  • the organic substance functions as a lubricant, for example.
  • By adding the lubricant to the raw material alloy powder aggregation of the raw material alloy powder is suppressed.
  • the friction between the mold and the raw material alloy powder is easily suppressed in the subsequent process. As a result, the raw material alloy powder is easily oriented in the orientation step, and it is easy to suppress scratches on the surface of the molded body or the mold surface obtained from the raw material alloy powder.
  • the organic substance may be, for example, a fatty acid or a fatty acid derivative.
  • Organic substances include, for example, oleic acid amide, zinc stearate, calcium stearate, stearic acid amide, palmitic acid amide, pentadecylic acid amide, myristic acid amide, lauric acid amide, capric acid amide, pelargonic acid amide, caprylic acid amide, enanthic acid It may be at least one selected from the group consisting of amide, caproic acid amide, valeric acid amide and butyric acid amide.
  • the lubricant may be a powdery organic material.
  • the lubricant may be a liquid organic material.
  • An organic solvent in which a powdery lubricant is dissolved may be added to the raw alloy powder.
  • the raw material alloy powder obtained by the above procedure is referred to as “metal powder” below.
  • the metal powder corresponds to “inorganic powder” and “magnetic powder” described in “Summary of Embodiment”.
  • a molded body is formed from metal powder by the molding process described in “Summary of the present embodiment”.
  • the pressure of the mold 2 on the metal powder 10 may be adjusted to more than 0.049 MPa 20 MPa or less (0.5 kgf / cm 2 or more 200 kgf / cm 2 or less).
  • the pressure may be, for example, a pressure exerted on the metal powder 10 by the end face of the punch (4 or 4a).
  • a magnetic field is applied to the compact 10b held in the mold 2, and the metal powder 10 constituting the compact 10b is oriented in the mold 2 along the magnetic field.
  • the magnetic field may be a pulsed magnetic field or a static magnetic field.
  • the molded body 10b held in the mold 2 is placed inside the air core coil (solenoid coil) together with the mold 2, and an electric current (alternating current) is passed through the air core coil, so that the molding in the mold 2 is performed.
  • a magnetic field may be applied to the body 10b. You may apply a magnetic field to the molded object 10b in the type
  • a double coil is a magnetic field generator arranged such that two coils have the same central axis.
  • a double coil or a Helmholtz coil By using a double coil or a Helmholtz coil, a more homogeneous magnetic field can be applied to the molded body 10b than when an air-core coil is used.
  • the orientation of the metal powder 10 in the molded body 10b is likely to be improved, and the magnetic properties of the rare earth magnet (sintered body) finally obtained are likely to be improved.
  • a magnetic field may be applied to the molded body 10b in the mold 2 using a magnetized yoke.
  • the strength of the magnetic field applied to the molded body 10b in the mold 2 may be, for example, 796 kA / m or more and 5173 kA / m or less (10 kOe or more and 65 kOe or less). You may demagnetize the molded object 10b after an orientation process.
  • the intensity of the magnetic field applied to the molded body 10b in the mold 2 is not necessarily limited to the above range.
  • the magnetic field applied to the compact 10b is preferably a pulsed magnetic field.
  • the pulse magnetic field has a higher magnetic field strength than the static magnetic field frequently used in the conventional high-pressure magnetic field pressing method, and is applied to the compact 10b in a short time. Therefore, compared with the case where a static magnetic field is used, the compact 10b having a high degree of orientation can be obtained in a short time by the orientation process using a pulsed magnetic field, and as a result, a rare earth magnet having a high residual magnetic flux density is manufactured.
  • an electrical conductor for example, metal
  • part or all of the mold 2 is formed of an insulating material (for example, an insulating resin)
  • the orientation of the metal powder 10 is improved, and as a result, the magnetic properties of the rare earth magnet are also improved.
  • the mold 2 is formed of an insulating material (for example, an insulating resin)
  • the temperature increase of the mold 2 due to eddy current loss is suppressed in the alignment process, and the mold 2 itself It is difficult to apply an impact (magnetic force) instantaneously. As a result, the mold 2 is not easily consumed.
  • the insulating material constituting part or all of the mold 2 may be a resin.
  • Resins constituting part or all of the mold 2 are, for example, acrylic resin, polyethylene (such as high-density polyethylene), polyethylene terephthalate, polybutylene terephthalate, polychlorotrifluoroethylene, polytetrafluoroethylene, ethyl cellulose, polypropylene, polybutene, Polystyrene, acrylonitrile-butadiene-styrene copolymer, acrylonitrile-styrene copolymer, styrene-butadiene copolymer, ethylene-vinyl acetate copolymer, ethylene / ethyl acrylate copolymer, atactic-polypropylene, polymethyl methacrylate, Methacrylic acid copolymer, polycarbonate, polyetheretherketone, polyetherimide, polyacetal, modified polyphenylene oxide, poly
  • only the side mold 6 may be formed from the above resin.
  • the side mold 6, and the punch 4a only the lower mold 8 may be formed of the above resin.
  • the side mold 6, and the punch 4a only the punch 4a may be made of resin.
  • the saturation magnetic flux density of the metal (for example, iron) constituting the mold is limited. Therefore, the intensity of the magnetic field that effectively acts on the molded body 10b in the mold is lower than the intensity of the pulse magnetic field outside the mold.
  • the mold 2 is formed of a resin, a strong pulse magnetic field can be applied to the molded body 10b in the mold 2 and the orientation of the metal powder 10 is improved.
  • the contact area between the side mold 6 and the molded body 10b is wider than the contact area between the lower mold 8 and the punch 4a and the molded body 10b. Therefore, at least the side mold 6 among the lower mold 8, the side mold 6, and the punch 4a may be formed of a resin.
  • the side mold 6 By forming the side mold 6 having a large area in contact with the molded body 10b from resin, generation of eddy current and reverse magnetic field in the side mold 6 is effectively suppressed, and cracks in the rare earth magnet due to the eddy current and reverse magnetic field are suppressed. In addition, it is easy to suppress deterioration of the magnetic characteristics.
  • the position of the part formed from the resin in the mold 2 is not limited.
  • the part of the mold 2 that needs to suppress eddy currents may be formed from resin.
  • an eddy current and a reverse magnetic field are easily generated in a portion of the mold 2 where a circuit that circulates in the direction of the pulse magnetic field that orients the metal powder 10 is formed. That is, when the penetrating portion of the side mold 6 (inner wall of the side mold 6) is parallel to the direction of the pulse magnetic field, eddy currents and reverse magnetic fields are likely to occur. Therefore, when the side mold 6, which is a part that forms a circuit that circulates in the direction of the pulse magnetic field that orients the metal powder 10 in the mold 2, is formed of resin, eddy currents and reverse magnetic fields are easily suppressed. .
  • the side die 6, and the punch 4a are made of metal, metal scraps from the surface of the side die 6 or the punch 4a due to friction between the side die 6 and the punch 4a in the molding process. It may be detached and mixed into the molded body 10b. Metal scraps (for example, aluminum or aluminum alloy) mixed in the molded body 10b may impair the magnetic characteristics of the finally obtained rare earth magnet.
  • the wear debris (resin) of the mold 2 affects the magnetic properties of the rare earth magnet as compared with the case where the mold 2 is made of only metal. Influence is suppressed.
  • one side for example, side mold 6
  • the other for example, punch 4a
  • resin scraps having a hardness lower than that of metal tend to form. Resin scrap is less likely to impair the magnetic properties of rare earth magnets than metal scrap.
  • the side mold 6 may be formed from a resin
  • the lower mold 8 and the punch 4a may be formed from a metal (for example, aluminum or an aluminum alloy).
  • the shrinkage rate of rare earth magnets eg neodymium magnets
  • the interior of the mold 2 may be cleaned each time molding and orientation are performed.
  • the inside of the mold 2 may be cleaned by attracting excess metal powder 10 remaining in the mold 2 with a magnetic field.
  • the mold 2 is made of a ferromagnetic metal (for example, iron), the mold 2 itself is attracted by a magnetic field when the mold 2 is cleaned, so that the mold 2 is difficult to clean. However, when the mold 2 is formed of a resin that does not have ferromagnetism, the mold 2 itself is not attracted by the magnetic field, so that the interior of the mold 2 can be easily cleaned. If the mold 2 is formed of a ferromagnetic metal (for example, iron), the mold 2 itself is magnetized in the orientation process, and the metal powder 10 adheres to the mold 2. The orientation may be disturbed, or the shape retention of the molded body 10b may be impaired. However, by using the mold 2 made of resin, the magnetization of the mold 2 itself is suppressed.
  • a ferromagnetic metal for example, iron
  • the mass of the metal powder 10 molded in the mold 2 may be measured together with the mass of the mold 2 while supplying the metal powder 10 into the mold 2.
  • the mass of the metal powder 10 molded in the mold 2 and the mass of the mold 2 the heavier the mass of the mold 2, the lower the accuracy of the scale, and the measurement of the mass of the metal powder 10 itself. The accuracy of this also decreases.
  • the mass of the metal powder 10 can be measured with high accuracy together with the mass of the mold 2 itself.
  • a magnetic field may be applied to the metal powder 10 while pressing the metal powder 10 of the die 3 with the punch 4a (second punch). That is, in the orientation process, the molded body 10b in the mold 2 may be compressed.
  • the pressure exerted on the molded body 10b by the mold 2 may be adjusted to 0.049 MPa or more and 20 MPa or less for the above reason.
  • the density of the molded body 10b (molded body 10b before the sintering process) that has undergone the molding process and the orientation process is, for example, 3.0 g / cm 3 or more and 4.4 g / cm 3 or less, preferably 3.2 g / cm 3 or more. It may be adjusted to 4.2 g / cm 3 or less, more preferably 3.4 g / cm 3 or more and 4.0 g / cm 3 or less.
  • the separation step at least a part of the mold 2 is separated from the molded body 10b.
  • the molded body 10b may be placed on the lower mold 8 by separating and removing the punch 4a and the side mold 6 from the molded body 10b.
  • the side mold 6 may be moved upward with the position of the punch 4a in the vertical direction (Z-axis direction) fixed.
  • the punch 4 a inserted into the side mold 6 penetrates the side mold 6, and the end surface of the punch 4 a pushes the molded body 10 b downward from the side mold 6. That is, the molded body 10 b held in the side mold 6 is extracted from the lower surface of the side mold 6.
  • the separation step the side mold 6 and the punch 4a holding the molded body 10b are separated from the lower mold 8, and the side mold 6 and the punch 4a holding the molded body 10b are placed on the heating process tray. Good. Then, the side mold 6 and the punch 4a may be separated from the molded body 10b, and the molded body 10b may be placed on the heating process tray.
  • the side mold 6 may be capable of being disassembled and assembled. In the separation step, the side mold 6 may be disassembled to remove the punch 4a and the side mold 6 from the molded body 10b.
  • the following heating step may be performed following the separation step. However, the heating step is not essential.
  • the molded body 10b may be heated to adjust the temperature of the molded body 10b to 200 ° C. or higher and 450 ° C. or lower.
  • the temperature of the molded body 10b may be adjusted to 200 ° C. or higher and 400 ° C. or lower, or 200 ° C. or higher and 350 ° C. or lower.
  • the pressure applied to the metal powder 10 is lower than that of the conventional high-pressure magnetic field pressing method, the metal powder 10 is hard to be pressed and hardened, and the resulting molded body 10b is likely to collapse.
  • the mechanical strength and shape retention of the molded body 10b are easily improved by the heating process.
  • the molded body 10b starts to harden and the shape retention of the molded body 10b is improved.
  • the mechanical strength of the molded body 10b is improved. Since the shape-retaining property of the molded body 10b is improved, the molded body 10b is unlikely to be damaged when the molded body 10b is transported or handled in the subsequent process. For example, when the molded body 10b is gripped by a transport chuck or the like and arranged on the sintering tray, the molded body 10b is unlikely to collapse. As a result, defects in the finally obtained rare earth magnet are suppressed.
  • the temperature of the molded body 10b exceeds 450 ° C. in the heating process, cracks are easily formed in the molded body 10b in the sintering process performed after the heating process.
  • the reason for the formation of cracks is not clear. For example, there is a possibility that cracks are formed in the molded body 10b due to the hydrogen remaining in the molded body 10b blowing out as a gas to the outside of the molded body 10b due to a rapid temperature rise of the molded body in the heating process. However, by adjusting the temperature of the molded body to 450 ° C. or lower in the heating process, cracks in the molded body 10b in the sintering process are suppressed.
  • the temperature of the molded body 10b is adjusted to 450 ° C. or lower in the heating step, the time required for raising or cooling the molded body 10b is suppressed, and the productivity of the rare earth magnet is improved.
  • the temperature of the molded body 10b in the heating process is 450 ° C. or lower and lower than a general sintering temperature, even if the molded body 10b is heated together with a part of the mold 2 (for example, the lower mold), the mold 2 Or chemical reaction between the molded body and the mold hardly occurs. Therefore, even a mold composed of a composition (resin) that does not necessarily have high heat resistance can be used.
  • the mechanism by which the shape retention of the molded body 10b is improved by adjusting the temperature of the molded body 10b to 200 ° C. or higher and 450 ° C. or lower is not clear.
  • the lubricant added to the metal powder 10 becomes carbon in the heating process, and the metal particles constituting the metal powder 10 are bound together via carbon.
  • the shape retention of the molded body 10b may be improved.
  • the temperature of the molded body 10b exceeds 450 ° C. in the heating step, there is a possibility that a metal carbide composing the metal powder 10 is generated or the metal particles are directly sintered.
  • the temperature of the molded body 10b is adjusted to 200 ° C. or higher and 450 ° C. or lower, metal carbide is not necessarily generated, and metal particles are not necessarily directly sintered.
  • the time for maintaining the temperature of the molded body 10b at 200 ° C. or higher and 450 ° C. or lower in the heating step is not particularly limited, and may be appropriately adjusted according to the size and shape of the molded body 10b.
  • the molded body 10b may be heated by irradiating the molded body 10b with infrared rays.
  • infrared rays that is, radiant heat
  • the time required for raising the temperature of the molded body 10b is shortened compared to heating by conduction or convection, and production efficiency and energy efficiency are increased.
  • the molded body 10b may be heated by heat conduction or convection in the heating furnace.
  • the infrared wavelength may be, for example, 0.75 ⁇ m to 1000 ⁇ m, preferably 0.75 ⁇ m to 30 ⁇ m.
  • the infrared rays may be at least one selected from the group consisting of near infrared rays, short wavelength infrared rays, medium wavelength infrared rays, long wavelength infrared rays (thermal infrared rays), and far infrared rays.
  • near infrared rays are relatively easily absorbed by metals. Therefore, when near-infrared rays are irradiated to the molded body 10b, the temperature of the metal (metal powder 10) is easily raised in a short time.
  • far infrared rays among the above infrared rays are relatively easily absorbed by organic substances and easily reflected by metal (metal powder 10). Therefore, when irradiating a far-infrared ray to a molded object, the lubricant mentioned above is easy to be selectively heated, and the molded object 10b is easy to be cured by the mechanism resulting from the lubricant.
  • an infrared heater ceramic heater or the like
  • an infrared lamp may be used.
  • the molded body 10b separated from part or all of the mold 2 is heated in the heating step, deterioration of the mold 2 (for example, deformation, hardening, or wear) of the mold 2 due to heating is easily suppressed. It is easy to suppress seizure.
  • mold 2 is hard to insulate heat and the molded object 10b is easy to be heated. As a result, the shape retention of the molded body 10b is improved.
  • the possibility that the mold 2 chemically reacts with the molded body 10b is low.
  • the mold 2 is not necessarily required to have heat resistance, and the material of the mold 2 is not easily limited. Therefore, as a raw material for the mold 2, it is easy to process into a desired size and shape, and it is easy to select an inexpensive material. If the molded body 10b and all of the mold 2 are heated together in the heating step, stress acts on the molded body 10b due to the difference in coefficient of thermal expansion between the molded body 10b and the mold 2. The molded body 10b is easily deformed or damaged. Moreover, when the molded object 10b and all the type
  • the molded body 10b placed on the lower mold may be heated.
  • the molded body 10b placed on the heating process tray may be heated.
  • the molded body 10b may be heated in an inert gas or vacuum to suppress oxidation of the molded body 10b.
  • the inert gas may be a noble gas such as argon.
  • the molded body 10b may be cooled to 100 ° C. or lower.
  • the surface of the chuck used for transporting the molded body 10b after the heating process is made of resin, the chemical reaction between the surface of the chuck and the molded body 10b is suppressed by the cooling of 10b, the deterioration of the chuck, and the molded body. Contamination of the 10b surface is suppressed.
  • the cooling method may be natural cooling, for example.
  • the sintering process is performed after the orientation process. After the alignment step, the sintering step may be performed without passing through the heating step. After the orientation step, the sintering step may be performed through the heating step.
  • the sintering step the compact 10b separated from the entire mold 2 is sintered.
  • the metal powders 10 in the compact 10b are sintered to obtain a sintered body (rare earth magnet).
  • the density of the compact 10b to be sintered in the sintering process is, for example, 3.0 g / cm 3 or more and 4.4 g / cm 3 or less, 3.2 g / cm 3 or more. It may be adjusted to 4.2 g / cm 3 or less, 3.4 g / cm 3 or more and 4.0 g / cm 3 or less, or 3.7 g / cm 3 or more and 4.1 g / cm 3 or less.
  • the pressure exerted by the mold 2 on the molded body 10b (metal powder 10) is too low in the molding process and the orientation process, the shape retention (mechanical strength) of the molded body 10b is insufficient and the molding accompanying the separation process.
  • the orientation of the metal powder 10 located on the surface of the molded body 10b is disturbed. As a result, the residual magnetic flux density of the rare earth magnet finally obtained decreases. Therefore, when the density of the compact 10b immediately before the sintering process is too low, the residual magnetic flux density of the rare earth magnet is low.
  • the higher the pressure applied to the molded body 10b (metal powder 10) from the molding process to the sintering process the higher the density of the molded body 10b immediately before the sintering process, and the shape retention ( High mechanical strength). As a result, cracks in the finally obtained rare earth magnet are easily suppressed.
  • the higher the density of the molded body 10b immediately before the sintering step the easier the cracks in the rare earth magnet are suppressed.
  • the pressure exerted by the mold 2 on the molded body 10b (metal powder 10) is too high in the molding process and the orientation process, cracks are easily formed in the molded body 10b due to the springback, and the rare earth magnet obtained from the molded body 10b. Cracks will remain.
  • the spring back is a phenomenon in which the molded body 10b expands when the pressure is released after the metal powder 10 is pressed and molded.
  • the density of the compact 10b immediately before the sintering process correlates with the residual magnetic flux density and cracks of the rare earth magnet.
  • the molded body 10b placed on the lower mold may be transferred onto a sintering tray.
  • the molded body 10b placed for the heating step may be transferred onto the sintering tray. Since the shape-retaining property of the molded body 10b is improved in the heating step, the molded body 10b is prevented from being damaged when the molded body 10b is gripped by the conveying chuck and arranged on the sintering tray.
  • the plurality of molded bodies 10b may be placed on the sintering tray, and the plurality of molded bodies 10b placed on the sintering tray may be heated together.
  • the composition of the sintering tray may be any composition that does not easily react with the molded body 10b during sintering and does not easily generate substances that contaminate the molded body 10b.
  • the sintering tray may be made of molybdenum or a molybdenum alloy.
  • the sintering temperature may be 900 ° C. or more and 1200 ° C. or less, for example.
  • the sintering time may be, for example, from 0.1 hours to 100 hours.
  • the sintering process may be repeated.
  • the molded body 10b may be heated in an inert gas or vacuum.
  • the inert gas may be a noble gas such as argon.
  • Aging treatment may be applied to the sintered body.
  • the sintered body may be heat-treated at, for example, 450 ° C. or more and 950 ° C. or less.
  • the sintered body may be heat-treated for 0.1 hours to 100 hours, for example.
  • the aging treatment may be performed in an inert gas or vacuum.
  • the aging treatment may be composed of a multi-stage heat treatment at different temperatures.
  • the sintered body may be cut or polished.
  • a protective layer may be formed on the surface of the sintered body.
  • the protective layer may be, for example, a resin layer or an inorganic layer (for example, a metal layer or an oxide layer).
  • the method for forming the protective layer may be, for example, a plating method, a coating method, a vapor deposition polymerization method, a gas phase method, or a chemical conversion treatment method.
  • the present invention in the process of manufacturing industrial products such as rare earth magnets, it is possible to suppress molding defects of a molded body formed from inorganic powder.

Abstract

This method for manufacturing an industrial article is a method for manufacturing an industrial article comprising a sintered compact, the method comprising: a molding step for using a punch to compress an inorganic powder supplied to the interior of a die, thereby forming a compact; and a sintering step for sintering the compact to obtain a sintered compact, wherein, in the molding step, after the inorganic powder has been compressed by the punch, the punch is withdrawn, and the inorganic powder is again compressed using the punch or another punch.

Description

焼結体を有する工業製品の製造方法Manufacturing method of industrial product having sintered body
　本発明は、焼結体を有する工業製品の製造方法の製造方法に関する。 The present invention relates to a manufacturing method of an industrial product having a sintered body.
　希土類磁石、フェライト磁石、誘電体、及び圧電体等の焼結体は、モータ、アクチュエータ、インダクタ、コンデンサ、絶縁材、アイソレータ、センサ及び共振器等の様々な工業製品に用いられる。これらの焼結体の製造では、型を用いた無機粉末の成形によって成形体を形成し、成形体の焼結によって焼結体を得る。例えば、下記特許文献１に記載の焼結磁石の製造方法は、希土類元素を含む合金粉末を型で加圧して成形体を作製する成形工程と、型中の成形体に磁場を印加して、成形体中の合金粉末を配向させる配向工程と、配向工程を経た成形体を焼結させる焼結工程と、を備えている。 Sintered bodies such as rare earth magnets, ferrite magnets, dielectrics, and piezoelectrics are used in various industrial products such as motors, actuators, inductors, capacitors, insulating materials, isolators, sensors, and resonators. In the production of these sintered bodies, a molded body is formed by molding inorganic powder using a mold, and the sintered body is obtained by sintering the molded body. For example, in the method for producing a sintered magnet described in Patent Document 1 below, a molding step in which a rare earth element-containing alloy powder is pressed with a mold to produce a molded body, a magnetic field is applied to the molded body in the mold, An orientation process for orienting the alloy powder in the compact and a sintering process for sintering the compact that has undergone the orientation process are provided.
国際公開第２０１６／０４７５９３号パンフレットInternational Publication No. 2016/047593 Pamphlet
　型を用いて無機粉末から成形体を形成する場合、成形不良（ｓｈａｐｅ　ｄｅｆｅｃｔｓ）が生じることがある。成形不良とは、例えば、バリ（ｂｕｒｒ）、成形体の表面の凹凸、成形体の歪み、又は成形体の亀裂等である。成形体の成形不良は焼結体の欠陥の原因となる。例えば、焼結体がバリを有する場合、焼結体のバリは成形体のバリよりも硬く丈夫であるため、バリを焼結体から除去し難く、バリの除去に伴って焼結体自体が破損することもある。したがって、焼結前に成形体の成形不良を解消することが望ましい。例えば、バリは、切削又は研磨等の加工によって成形体から除去される。しかし、成形不良を解消する加工に伴って、成形体自体が破損することがある。例えば、バリと共に、成形体の一部も除去されてしまう。特に、成形工程において型が無機粉末に及ぼす圧力が低い場合、成形体は十分な機械的強度を有していないため、成形不良を解消する加工に伴って、成形体自体が容易に破損する。 When forming a molded body from an inorganic powder using a mold, shape defects may occur. Molding defects include, for example, burrs, irregularities on the surface of the molded body, distortion of the molded body, or cracks in the molded body. A molding defect of the molded body causes defects in the sintered body. For example, when the sintered body has burrs, since the burrs of the sintered body are harder and stronger than the burrs of the molded body, it is difficult to remove the burrs from the sintered body. It may be damaged. Therefore, it is desirable to eliminate molding defects in the molded body before sintering. For example, the burr is removed from the molded body by a process such as cutting or polishing. However, the molded body itself may be damaged along with the processing for eliminating the molding defect. For example, a part of the molded body is also removed together with the burr. In particular, when the pressure exerted on the inorganic powder by the mold in the molding process is low, the molded body does not have sufficient mechanical strength, so that the molded body itself is easily damaged along with the processing to eliminate molding defects.
　本発明は、焼結体を有する工業製品の製造において、無機粉末から形成される成形体の成形不良を抑制することができる工業製品の製造方法を提供することを目的とする。 An object of the present invention is to provide a manufacturing method of an industrial product that can suppress molding defects of a molded body formed from an inorganic powder in the manufacture of an industrial product having a sintered body.
　本発明の一側面に係る工業製品の製造方法は、焼結体を有する工業製品の製造方法であって、ダイ内に供給された無機粉末をパンチで加圧して、成形体を形成する成形工程と、成形体を焼結させて、焼結体を得る焼結工程と、を備え、成形工程では、無機粉末をパンチで加圧した後、パンチを引き戻し、再び無機粉末を上記パンチ又は別のパンチで加圧する。 The manufacturing method of an industrial product according to one aspect of the present invention is a manufacturing method of an industrial product having a sintered body, and is a molding process in which inorganic powder supplied into a die is pressed with a punch to form a molded body. And sintering the molded body to obtain a sintered body. In the molding process, after pressing the inorganic powder with a punch, the punch is pulled back, and the inorganic powder is again fed with the punch or another Press with a punch.
　無機粉末の真密度が、Ｄ［ｇ／ｃｍ３］と表されてよく、成形体の嵩密度が、ｄ［ｇ／ｃｍ３］と表されてよく、成形体の相対密度が、１００・ｄ／Ｄ［％］と定義されてよく、成形工程において、相対密度が４０％以上６０％以下に調整されてよい。 The true density of the inorganic powder may be expressed as D [g / cm 3 ], the bulk density of the molded body may be expressed as d [g / cm 3 ], and the relative density of the molded body is 100 · d. / D [%] may be defined, and the relative density may be adjusted to 40% or more and 60% or less in the molding step.
　パンチが無機粉末に及ぼす圧力を、０．０４９ＭＰａ以上２０ＭＰａ以下に調整してよい。 The pressure exerted on the inorganic powder by the punch may be adjusted to 0.049 MPa or more and 20 MPa or less.
　無機粉末が顆粒であってよい。 The inorganic powder may be a granule.
　本発明の一側面に係る工業製品の製造方法は、パンチとダイによって保持された成形体に磁場を印加して、成形体に含まれる無機粉末を配向させる配向工程を更に備えてよく、配向工程後に焼結工程が実施されてよく、無機粉末が、磁性粉末であってよく、パンチの少なくとも一部が絶縁性であってよく、ダイの少なくとも一部が絶縁性であってよく、焼結体を有する工業製品が、焼結磁石であってよい。 The manufacturing method of the industrial product according to one aspect of the present invention may further include an alignment step of applying a magnetic field to the formed body held by the punch and the die and aligning the inorganic powder contained in the formed body. A sintering step may be performed later, the inorganic powder may be a magnetic powder, at least a part of the punch may be insulative, at least a part of the die may be insulative, and the sintered body The industrial product having a may be a sintered magnet.
　磁性粉末が、希土類元素を含む金属粉末であってよく、焼結磁石が、希土類磁石であってよい。 The magnetic powder may be a metal powder containing a rare earth element, and the sintered magnet may be a rare earth magnet.
　本発明によれば、焼結体を有する工業製品の製造において、無機粉末から形成される成形体の成形不良を抑制することができる工業製品の製造方法が提供される。 According to the present invention, there is provided an industrial product manufacturing method capable of suppressing molding defects of a molded body formed from an inorganic powder in manufacturing an industrial product having a sintered body.
成形工程に用いる型（パンチ及びダイ）の模式的な斜視図である。It is a typical perspective view of the type | mold (punch and die | dye) used for a formation process. 図２中の（ａ）及び図２中の（ｂ）は、型及び無機粉末（成形体）の模式的な断面図であり、成形工程の一例を示す。(A) in FIG. 2 and (b) in FIG. 2 are schematic cross-sectional views of a mold and an inorganic powder (molded body), and show an example of a molding process. 図３中の（ａ）、図３中の（ｂ）及び図３中の（ｃ）は、型及び無機粉末（成形体）の模式的な断面図であり、成形工程の一例を示す。(A) in FIG. 3, (b) in FIG. 3, and (c) in FIG. 3 are schematic cross-sectional views of the mold and the inorganic powder (molded body), and show an example of the molding process.
　以下、図面を参照しながら、本発明の好適な実施形態が説明される。図面において、同等の構成要素には同等の符号が付される。本発明は下記実施形態に限定されるものではない。各図に示すＸ，Ｙ及びＺは、互いに直交する３つの座標軸を意味する。各座標軸が示す方向は、全図に共通する。Ｚ軸は鉛直方向に対応する。ＸＹ面は水平方向に対応する。 Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In the drawings, equivalent components are denoted by the same reference numerals. The present invention is not limited to the following embodiment. X, Y, and Z shown in each figure mean three coordinate axes orthogonal to each other. The direction indicated by each coordinate axis is common to all drawings. The Z axis corresponds to the vertical direction. The XY plane corresponds to the horizontal direction.
（本実施形態の概要）
　本実施形態に係る工業製品の製造方法は、焼結体を有する工業製品の製造方法である。本実施形態に係る工業製品の製造方法は、ダイ内に供給された無機粉末をパンチで加圧して、成形体を形成する成形工程と、成形体を焼結させて、焼結体を得る焼結工程と、を備る。成形工程では、無機粉末をパンチで加圧した後、パンチを引き戻し、再び無機粉末を上記パンチ又は別のパンチで加圧する。つまり、成形工程では、無機粉末をパンチで少なくとも二回加圧する。成形工程の詳細は後述される。 (Outline of this embodiment)
The manufacturing method of the industrial product which concerns on this embodiment is a manufacturing method of the industrial product which has a sintered compact. The industrial product manufacturing method according to the present embodiment includes a punching process in which inorganic powder supplied in a die is pressed with a punch to form a molded body, and a sintered body is obtained by sintering the molded body. And a knotting process. In the molding step, the inorganic powder is pressurized with a punch, the punch is pulled back, and the inorganic powder is again pressurized with the punch or another punch. That is, in the molding step, the inorganic powder is pressurized at least twice with a punch. Details of the molding process will be described later.
　焼結体の原料である無機粉末は、特に限定されない。無機粉末は、例えば、希土類元素を含む金属粉末（合金粉末）、フェライト粉末、アルニコ合金の粉末（Ａｌ，Ｎｉ及びＣｏを含む合金粉末）、及び誘電体の粉末からなる群より選ばれる一種であってよい。誘電体の粉末は、例えば、炭化ケイ素粉末、酸化アルミニウム粉末、酸化ジルコニウム粉末、及びムライト粉末からなる群より選ばれる一種であってよい。誘電体とは、圧電体、焦電体、及び強誘電体を含意する。希土類元素を含む金属粉末の詳細は後述される。 The inorganic powder that is the raw material of the sintered body is not particularly limited. The inorganic powder is, for example, a kind selected from the group consisting of metal powder containing rare earth elements (alloy powder), ferrite powder, alnico alloy powder (alloy powder containing Al, Ni and Co), and dielectric powder. It's okay. The dielectric powder may be, for example, one type selected from the group consisting of silicon carbide powder, aluminum oxide powder, zirconium oxide powder, and mullite powder. The dielectric material implies a piezoelectric material, a pyroelectric material, and a ferroelectric material. Details of the metal powder containing the rare earth element will be described later.
　無機粉末は、顆粒であってもよい。無機粉末が顆粒である場合、無機粉末の流動性が高くなるため、焼結前の成形体における密度のバラツキ及び焼結体の欠けをより抑制できる場合がある。 The inorganic powder may be a granule. In the case where the inorganic powder is a granule, the fluidity of the inorganic powder is increased, and thus there may be a case where density variation and chipping of the sintered body can be further suppressed.
　顆粒は、無機粉末と顆粒形成剤とを用いて、公知の造粒法により作製されてよい。造粒法は、例えば、転動造粒、スプレー造粒、又は振動造粒等であってよい。具体的には、特許４６６２０４６号公報に記載された造粒方法を使用することができる。 Granules may be produced by a known granulation method using an inorganic powder and a granule forming agent. The granulation method may be, for example, rolling granulation, spray granulation, or vibration granulation. Specifically, the granulation method described in Japanese Patent No. 4662046 can be used.
　顆粒形成剤は、例えば、アルキルベンゼン系化合物、アルコール系化合物、エーテル系化合物、エステル系化合物、ケトン系化合物、脂肪酸系化合物、及びテルペン系化合物からなる群より選ばれる少なくとも一種の化合物であってよい。エーテル系化合物は、グリコールエーテル系化合物を含んでよい。エステル系化合物は、グリコールエステル系化合物を含んでよい。アルキルベンゼン系化合物は、トルエン及びキシレンからなる群より選ばれる少なくとも一種の化合物であってよい。アルコール系化合物は、ターピネオール及びエタノールからなる群より選ばれる少なくとも一種の化合物であってよい。エーテル系化合物は、ブチルセロソルブ、セロソルブ、カルビトール及びブチルカルビトールからなる群より選ばれる少なくとも一種の化合物であってよい。エステル系化合物は、酢酸エチルであってよい。ケトン系化合物は、アセトン（ジメチルケトン）、メチルイソブチルケトン及びメチルエチルケトンからなる群より選ばれる少なくとも一種の化合物であってよい。これら以外にも、例えばエチレングリコール、ジエチレングリコール及びグリセリン等の他の有機液体が顆粒形成剤として用いられてよい。顆粒形成剤として、ポリマー等のバインダーが用いられてもよい。 The granule forming agent may be, for example, at least one compound selected from the group consisting of alkylbenzene compounds, alcohol compounds, ether compounds, ester compounds, ketone compounds, fatty acid compounds, and terpene compounds. The ether compound may include a glycol ether compound. The ester compound may include a glycol ester compound. The alkylbenzene compound may be at least one compound selected from the group consisting of toluene and xylene. The alcohol compound may be at least one compound selected from the group consisting of terpineol and ethanol. The ether compound may be at least one compound selected from the group consisting of butyl cellosolve, cellosolve, carbitol and butyl carbitol. The ester compound may be ethyl acetate. The ketone compound may be at least one compound selected from the group consisting of acetone (dimethyl ketone), methyl isobutyl ketone, and methyl ethyl ketone. Besides these, other organic liquids such as ethylene glycol, diethylene glycol and glycerin may be used as the granule forming agent. A binder such as a polymer may be used as the granule forming agent.
　レーザー回折法による体積基準の粒度分布における顆粒の粒径Ｄ５０は、２０μｍ以上１０００μｍ以下であってよい。 The particle size D50 of the granules in the volume-based particle size distribution by laser diffraction method may be 20 μm or more and 1000 μm or less.
　本実施形態において製造される焼結体は、特に限定されない。焼結体は、例えば、焼結磁石であってよい。焼結磁石は、例えば、希土類磁石、フェライト磁石、及びアルニコ磁石らなる群より選ばれる一種であってよい。希土類磁石の詳細は後述される。焼結体は、誘電体であってよい。誘電体の焼結体は、例えば、チタン酸バリウム、チタン酸カルシウム、チタン酸鉛、チタン酸ジルコン酸鉛、ニオブ酸カリウム、ニオブ酸リチウム、ニオブ酸マグネシウム酸バリウム、ニオブ酸ナトリウムカリウム、ビスマスフェライト、チタン酸ビスマス、チタン酸ネオジウム酸バリウム、チタン酸ビスマスナトリウム、タングステン酸ナトリウム、酸化亜鉛、酸化アルミニウム、コージェライト、ステアライト、酸化イットリウム、酸化鉄、ガーネット、ムライト又はフォルステライト等のセラミックスであってよい。 The sintered body produced in the present embodiment is not particularly limited. The sintered body may be, for example, a sintered magnet. The sintered magnet may be a kind selected from the group consisting of rare earth magnets, ferrite magnets, and alnico magnets, for example. Details of the rare earth magnet will be described later. The sintered body may be a dielectric. Dielectric sintered bodies are, for example, barium titanate, calcium titanate, lead titanate, lead zirconate titanate, potassium niobate, lithium niobate, barium niobate, sodium potassium niobate, bismuth ferrite, It may be a ceramic such as bismuth titanate, barium neotitanate, bismuth sodium titanate, sodium tungstate, zinc oxide, aluminum oxide, cordierite, stearite, yttrium oxide, iron oxide, garnet, mullite or forsterite. .
　上記の焼結体を有する工業製品は、例えば、希土類磁石、フェライト磁石、アルニコ磁石、モータ、発電機、アクチュエータ、インダクタ、トランス、コンデンサ、インスレータ、アイソレータ、マイクロ波集積回路（Ｍｉｃｒｏｗａｖｅ　Ｉｎｔｅｇｒａｔｅｄ　Ｃｉｒｃｕｉｔ；　ＭＩＣ）、電磁波フィルタ、圧力センサ、共振器、研磨材、カッター、ミラー、又は各種のセラミック基板であってよい。希土類磁石の詳細は後述される。 Industrial products having the above sintered body include, for example, rare earth magnets, ferrite magnets, alnico magnets, motors, generators, actuators, inductors, transformers, capacitors, insulators, isolators, microwave integrated circuits (MICROWAVE INTEGRATED CIRCUIT; MIC). , Electromagnetic wave filter, pressure sensor, resonator, abrasive, cutter, mirror, or various ceramic substrates. Details of the rare earth magnet will be described later.
　焼結体の寸法及び形状は、焼結体の用途に応じて様々であり、特に限定されない。焼結体の形状は、例えば、直方体状、立方体状、多角柱状、セグメント状、扇状、矩形状、板状、球状、円板状、円柱状、リング状、又はカプセル状であってよい。焼結体の断面の形状は、例えば、多角形状、円弦状、弓状、又は円状であってよい。 The size and shape of the sintered body vary depending on the use of the sintered body and are not particularly limited. The shape of the sintered body may be, for example, a rectangular parallelepiped shape, a cubic shape, a polygonal column shape, a segment shape, a fan shape, a rectangular shape, a plate shape, a spherical shape, a disc shape, a columnar shape, a ring shape, or a capsule shape. The cross-sectional shape of the sintered body may be, for example, a polygonal shape, a chordal shape, an arc shape, or a circular shape.
　成形工程に用いる型の一例は、図１に示される。図１に示される型を用いた成形工程の手順は、図２中の（ａ）、図２中の（ｂ）、図３中の（ａ）、図３中の（ｂ）及び図３中の（ｃ）に示される。 An example of a mold used in the molding process is shown in FIG. The procedure of the molding process using the mold shown in FIG. 1 is as follows: (a) in FIG. 2, (b) in FIG. 2, (a) in FIG. 3, (b) in FIG. (C).
　型２は、パンチ４（上型）とダイ３とを備える。ダイ３は、下型８と、下型８の上に配置される筒状の側型６と、を備える。側型６は下型８から分離可能である。ただし、側型６と下型８は、互いに分離されずに連続してよい。成形体の形状及び寸法に対応する空間が、側型６を鉛直方向に貫通している。側型６は、型の側壁（ダイの側壁）と言い換えてよい。下型８は板状であってよい。パンチ４は、ダイ３（側型６を貫通する空間）に嵌合する形状を有する。図３中の（ａ）、図３中の（ｂ）及び図３中の（ｃ）に示される別のパンチ４a（第二のパンチ）の寸法及び形状は、図１、図２中の（ａ）及び図２中の（ｂ）に示されるパンチ４（第一のパンチ）の寸法及び形状とほぼ同じであってよい。型２の寸法及び形状は、焼結体の寸法及び形状に対応するものであり、限定されない。 The mold 2 includes a punch 4 (upper mold) and a die 3. The die 3 includes a lower mold 8 and a cylindrical side mold 6 disposed on the lower mold 8. The side mold 6 can be separated from the lower mold 8. However, the side mold 6 and the lower mold 8 may be continuous without being separated from each other. A space corresponding to the shape and size of the molded body penetrates the side mold 6 in the vertical direction. The side mold 6 may be rephrased as a mold side wall (die side wall). The lower mold 8 may be plate-shaped. The punch 4 has a shape that fits into the die 3 (a space penetrating the side mold 6). The size and shape of another punch 4a (second punch) shown in (a) in FIG. 3, (b) in FIG. 3, and (c) in FIG. 3 are shown in FIGS. The size and shape of the punch 4 (first punch) shown in a) and (b) in FIG. 2 may be substantially the same. The size and shape of the mold 2 correspond to the size and shape of the sintered body and are not limited.
　パンチ４，４ａ、側型６及び下型８其々は、例えば、鉄、ケイ素鋼、ステンレス鋼、パーマロイ、アルミニウム、アルミニウム合金、モリブデン、タングステン、セラミックス（例えばアルミナ）、カーボン、ガラス、及び樹脂からなる群より選ばれる少なくとも一種から形成されていてよい。 The punches 4 and 4a, the side mold 6 and the lower mold 8 are each made of, for example, iron, silicon steel, stainless steel, permalloy, aluminum, aluminum alloy, molybdenum, tungsten, ceramics (for example, alumina), carbon, glass, and resin. It may be formed from at least one selected from the group consisting of
　図１に示される下型８、側型６及びパンチ４の相対的な位置関係が維持されている限り、成形工程では、下型８、側型６、及びパンチ４が鉛直方向に対して傾いていてよい。換言すると、パンチ４が側型６の上に位置し、且つ側型６が下型８の上に位置している限り、成形工程では、型２の全体が鉛直方向に対して傾いていてよい。例えば、成形工程では、型２の全体が鉛直方向（Ｚ軸方向）に対してなす角度は、０度以上４５度以下であってよい。同様に、図３中の（ａ）、図３中の（ｂ）及び図３中の（ｃ）に示される下型８、側型６及びパンチ４ａの相対的な位置関係が維持されている限り、下型８、側型６、及びパンチ４ａが鉛直方向に対して傾いていてよい。 As long as the relative positional relationship of the lower die 8, the side die 6 and the punch 4 shown in FIG. 1 is maintained, the lower die 8, the side die 6 and the punch 4 are inclined with respect to the vertical direction in the molding process. It may be. In other words, as long as the punch 4 is positioned on the side mold 6 and the side mold 6 is positioned on the lower mold 8, the entire mold 2 may be inclined with respect to the vertical direction in the molding process. . For example, in the molding step, the angle formed by the entire mold 2 with respect to the vertical direction (Z-axis direction) may be 0 degree or greater and 45 degrees or less. Similarly, the relative positional relationship of the lower die 8, the side die 6, and the punch 4a shown in (a) in FIG. 3, (b) in FIG. 3, and (c) in FIG. 3 is maintained. As long as the lower mold 8, the side mold 6, and the punch 4a are inclined with respect to the vertical direction.
　図２中の（ｂ）、図３中の（ｂ）及び図３中の（Ｃ）に示されるように、パンチ（４又は４ａ）がダイ３に嵌合された状態において、パンチ（４又は４ａ）の側面とダイ３（側型６）の内壁との間にクリアランス（ｃｌｅａｒａｎｃｅ）が設けられている。クリアランスにより、パンチ（４又は４ａ）及びダイ３の摩耗、変形及び損傷が抑制される。特にパンチ（４又は４ａ）及びダイ３の一部又は全体が、金属等の硬い素材に比べて機械的強度に劣る素材から形成されている場合、クリアランスによってパンチ（４又は４ａ）及びダイ３の摩耗、変形及び損傷を抑制することが望ましい。例えば、パンチ（４又は４ａ）及びダイ３の一部又は全体が樹脂から形成されている場合、パンチ（４又は４ａ）及びダイ３間の摩擦、摩擦による発熱、発熱に因る樹脂の劣化、型２の変形及び破損を抑制することが望まれる。成形工程において、パンチ（４又は４ａ）の位置が固定され、ダイ３をパンチ（４又は４ａ）の直下に移動させる必要がある場合、ダイ３の位置決めの精度には限界がある。したがって、ダイ３の位置のずれのｔｏｌｅｒａｎｃｅとして、パンチ４の側面とダイ３の内壁との間にクリアランスを設けることにより、パンチ（４又は４ａ）及びダイ３間の過度の摩擦が抑制される。 As shown in (b) in FIG. 2, (b) in FIG. 3, and (C) in FIG. 3, in the state where the punch (4 or 4a) is fitted to the die 3, the punch (4 or A clearance is provided between the side surface of 4a) and the inner wall of the die 3 (side mold 6). By the clearance, wear, deformation and damage of the punch (4 or 4a) and the die 3 are suppressed. In particular, when the punch (4 or 4a) and the die 3 are partially or entirely formed of a material that is inferior in mechanical strength as compared to a hard material such as metal, the clearance between the punch (4 or 4a) and the die 3 It is desirable to suppress wear, deformation and damage. For example, when a part or the whole of the punch (4 or 4a) and the die 3 is formed of resin, friction between the punch (4 or 4a) and the die 3, heat generation due to friction, deterioration of the resin due to heat generation, It is desired to suppress the deformation and breakage of the mold 2. In the molding process, when the position of the punch (4 or 4a) is fixed and the die 3 needs to be moved directly below the punch (4 or 4a), the positioning accuracy of the die 3 is limited. Therefore, by providing a clearance between the side surface of the punch 4 and the inner wall of the die 3 as a tolerance of the displacement of the die 3, excessive friction between the punch (4 or 4a) and the die 3 is suppressed.
　図１及び図２中の（ａ）に示されるように、成形工程では、側型６を下型８の上に載置して、側型６の下面側の開口部（穴）を下型８で塞ぐ。このような配置により、側型６及び下型８がダイ３を構成する。続いて、無機粉末１０を、側型６の上面側の開口部からダイ３（側型６を貫通する空間）内へ供給する。無機粉末１０を、ダイ３へ充填してよい。つまり、ダイ３の内側を無機粉末１０で満たしてよい。 As shown in FIG. 1 and FIG. 2A, in the molding step, the side mold 6 is placed on the lower mold 8 and the opening (hole) on the lower surface side of the side mold 6 is formed in the lower mold. Close with 8. With such an arrangement, the side mold 6 and the lower mold 8 constitute the die 3. Subsequently, the inorganic powder 10 is supplied from the opening on the upper surface side of the side mold 6 into the die 3 (a space penetrating the side mold 6). The inorganic powder 10 may be filled into the die 3. That is, the inside of the die 3 may be filled with the inorganic powder 10.
　図２中の（ｂ）に示されるように、成形工程では、パンチ４をダイ３内へ挿入して、ダイ３内の無機粉末１０をパンチ４で加圧する。その結果、無機粉末１０がダイ３の内側の形状及び寸法に対応するように成形され、成形体１０ｂが得られる。ただし、パンチ４による無機粉末１０の加圧に伴い、成形体１０ｂの成形不良が生じることがある。例えば、パンチ４の側面とダイ３の内壁との間のクリアランスに無機粉末１０が入り込み、バリ１０ａが形成されることがある。クリアランスが大きいほど、バリ１０ａは形成され易い。このバリ１０ａは以下の方法によって解消される。 As shown in FIG. 2B, in the molding step, the punch 4 is inserted into the die 3 and the inorganic powder 10 in the die 3 is pressurized with the punch 4. As a result, the inorganic powder 10 is molded so as to correspond to the inner shape and dimensions of the die 3, and a molded body 10b is obtained. However, with the pressurization of the inorganic powder 10 by the punch 4, a molding defect of the molded body 10b may occur. For example, the inorganic powder 10 may enter the clearance between the side surface of the punch 4 and the inner wall of the die 3 to form a burr 10a. The larger the clearance, the easier the burr 10a is formed. This burr 10a is eliminated by the following method.
　図２中の（ｂ）及び図３中の（ａ）に示されるように、無機粉末１０をパンチ４で加圧した後、パンチ４を引き戻す。パンチ４を引き戻すことにより、ダイ３の内側（キャビティ）の気圧が負圧になり、バリ１０ａが成形体１０ｂの表面に向かって倒れ易い。続いて、図３中の（ｂ）に示されるように、再び無機粉末１０（成形体１０ｂ）をパンチ４ａで加圧することにより、バリ１０ａが成形体１０ｂの表面に押し当てられ、バリ１０ａが成形体１０ｂの表面と一体化する。その結果、図３中の（ｃ）に示されるように、バリ１０ａが解消され、平坦な表面を有する成形体１０ｂが得られる。 As shown in (b) in FIG. 2 and (a) in FIG. 3, the inorganic powder 10 is pressurized with the punch 4, and then the punch 4 is pulled back. By pulling back the punch 4, the pressure inside the die 3 (cavity) becomes negative, and the burr 10a tends to fall toward the surface of the molded body 10b. Subsequently, as shown in FIG. 3B, the burrs 10a are pressed against the surface of the molded body 10b by pressurizing the inorganic powder 10 (formed body 10b) with the punch 4a again. It is integrated with the surface of the molded body 10b. As a result, as shown in FIG. 3C, the burr 10a is eliminated, and a molded body 10b having a flat surface is obtained.
　バリ１０ａ以外の成形不良も上記の成形工程によって抑制又は解消される。例えば、パンチ４による無機粉末１０の加圧により、成形体１０ｂの表面の凹凸が形成された場合、パンチ４を引き戻し、再び無機粉末１０（成形体１０ｂ）をパンチ４aで加圧することにより、凹凸が解消して成形体１０ｂの表面が平坦になる。パンチ４による無機粉末１０の加圧により、歪んだ成形体１０ｂが形成された場合、パンチ４を引き戻し、再び無機粉末１０（成形体１０ｂ）をパンチ４aで加圧することにより、成形体１０ｂの歪みが解消される。パンチ４による無機粉末１０の加圧により、亀裂がある成形体１０ｂが形成された場合、パンチ４を引き戻し、再び無機粉末１０（成形体１０ｂ）をパンチ４aで加圧することにより、亀裂が解消される。 Molding defects other than the burr 10a are also suppressed or eliminated by the above molding process. For example, when unevenness on the surface of the molded body 10b is formed by pressurizing the inorganic powder 10 with the punch 4, the punch 4 is pulled back, and the inorganic powder 10 (formed body 10b) is pressed again with the punch 4a. Is eliminated and the surface of the molded body 10b becomes flat. When the distorted molded body 10b is formed by pressurizing the inorganic powder 10 with the punch 4, the punch 4 is pulled back, and the inorganic powder 10 (molded body 10b) is pressed again with the punch 4a. Is resolved. When the molded body 10b having a crack is formed by pressurizing the inorganic powder 10 with the punch 4, the crack is resolved by pulling back the punch 4 and pressurizing the inorganic powder 10 (formed body 10b) with the punch 4a again. The
　以上のように、本実施形態では、成形体１０ｂの一部を切削及び研磨することなく、バリ１０ａ等の成形不良を抑制及び解消することができる。したがって、成形不良を解消するための加工に伴う成形体１０ｂの質量の変化（減少）が起き難い。つまり、成形不良を解消するための加工に伴う屑（成形体１０ｂから除去される無機粉末１０）が殆ど生じない。その結果、所望の特性（例えば磁気特性）を有する焼結体（例えば焼結磁石）を高い歩留まり率（Ｙｉｅｌｄ　ｒａｔｅ）で製造することができる。 As described above, in this embodiment, molding defects such as the burr 10a can be suppressed and eliminated without cutting and polishing a part of the molded body 10b. Therefore, a change (decrease) in the mass of the molded body 10b due to processing for eliminating the molding defect is unlikely to occur. That is, almost no waste (inorganic powder 10 removed from the molded body 10b) is generated due to processing for eliminating molding defects. As a result, a sintered body (for example, a sintered magnet) having desired characteristics (for example, magnetic characteristics) can be manufactured with a high yield rate (Yield rate).
　無機粉末１０をパンチ４で加圧してパンチ４を引き戻した後、無機粉末１０をダイ３内へ追加することなく、無機粉末１０をパンチ４ａで再び加圧したほうがよい。無機粉末１０をパンチ４ａで再び加圧する前に無機粉末１０をダイ３内へ追加する場合、成形不良が再度の加圧によって抑制及び解消され難く、再度の加圧によって成形不良が更に生じることもある。 It is better to press the inorganic powder 10 again with the punch 4a without adding the inorganic powder 10 into the die 3 after the inorganic powder 10 is pressed with the punch 4 and pulled back. When the inorganic powder 10 is added into the die 3 before the inorganic powder 10 is pressed again with the punch 4a, the molding failure is hardly suppressed and eliminated by the re-pressing, and the molding failure may be further caused by the re-pressing. is there.
　無機粉末１０をパンチ４で加圧した後、パンチ４を引き戻す場合、パンチ４の端面を無機粉末１０の一部又は全体から離してよい。パンチ４の端面をバリ１０ａの先端よりも上方へ引き戻してもよい。パンチ４の端面をバリ１０ａの先端よりも上方へ引き戻す場合、パンチ４aでの再度の加圧により、バリ１０ａが成形体１０ｂの表面に押し当てられ易い。無機粉末１０をパンチ４で加圧した後、パンチ４の全体をダイ３から完全に引き抜かなくてもよい。つまり、パンチ４が引き戻された状態において、パンチ４の先端はダイ３の内側に位置してよい。 When the inorganic powder 10 is pressed with the punch 4 and then pulled back, the end face of the punch 4 may be separated from a part or the whole of the inorganic powder 10. The end face of the punch 4 may be pulled back upward from the tip of the burr 10a. When the end surface of the punch 4 is pulled back higher than the tip of the burr 10a, the burr 10a is easily pressed against the surface of the molded body 10b by re-pressing with the punch 4a. After pressing the inorganic powder 10 with the punch 4, the entire punch 4 may not be completely pulled out from the die 3. That is, the tip of the punch 4 may be located inside the die 3 in a state where the punch 4 is pulled back.
　二度目の加圧に用いるパンチ４ａは、一回目の加圧に用いるパンチ４と同じであってよい。つまり、一つのパンチ４を用いて無機粉末１０を少なくとも二回加圧してよい。無機粉末を第一のパンチ（パンチ４）で加圧した後、第一のパンチ（パンチ４）とは異なる第二のパンチ（パンチ４ａ）で無機粉末を再び加圧してよい。その結果、第一のパンチ（４）のみを用いる場合に比べて、第一のパンチ（パンチ４）及び第二のパンチ（パンチ４ａ）其々の摩耗が抑制される。ダイ３に対する第一のパンチ（パンチ４）の相対的な位置及びストロークは、ダイ３に対する第二のパンチ（パンチ４ａ）の相対的な位置及びストロークと同じであってよい。第二のパンチ（パンチ４ａ）は、第一のパンチ（パンチ４）よりも太くてよい。第二のパンチ（パンチ４ａ）が太いほど、第二のパンチ（パンチ４ａ）が、ダイ３の内側に貼り付いたバリ１０ａと確実に接触し易く、バリ１０ａが解消され易い。 The punch 4a used for the second pressurization may be the same as the punch 4 used for the first pressurization. That is, the inorganic powder 10 may be pressed at least twice using one punch 4. After pressing the inorganic powder with the first punch (punch 4), the inorganic powder may be pressed again with a second punch (punch 4a) different from the first punch (punch 4). As a result, compared with the case where only the first punch (4) is used, wear of the first punch (punch 4) and the second punch (punch 4a) is suppressed. The relative position and stroke of the first punch (punch 4) relative to the die 3 may be the same as the relative position and stroke of the second punch (punch 4a) relative to the die 3. The second punch (punch 4a) may be thicker than the first punch (punch 4). The thicker the second punch (punch 4a), the more easily the second punch (punch 4a) comes into contact with the burr 10a attached to the inside of the die 3 and the burr 10a is easily eliminated.
　無機粉末１０の真密度は、Ｄ［ｇ／ｃｍ３］と表される。成形体１０ｂの嵩密度は、ｄ［ｇ／ｃｍ３］と表される。成形体１０ｂの相対密度は、１００・ｄ／Ｄ［％］と定義される。成形工程において、相対密度が４０％以上６０％以下に調整されてよい。相対密度が低い場合、成形体１０ｂ及びバリ１０ａのいずれも過度に圧縮されておらず、バリ１０ａが軟らかく脆いので、バリ１０ａが成形体１０ｂと一体化され易い。したがって、相対密度が６０％以下である場合、パンチ４ａによる二回目以降の加圧により、バリ１０ａが解消され易い。相対密度が６０％以下である場合、バリ１０ａ以外の成形不良も解消され易い。相対密度が４０％以上である場合、成形体１０ｂが十分な機械的強度を有し易く、成形工程に続く後工程において成形体が破損し難い。 The true density of the inorganic powder 10 is expressed as D [g / cm 3 ]. The bulk density of the molded body 10b is expressed as d [g / cm 3 ]. The relative density of the molded body 10b is defined as 100 · d / D [%]. In the molding step, the relative density may be adjusted to 40% or more and 60% or less. When the relative density is low, neither the compact 10b nor the burr 10a is excessively compressed, and the burr 10a is soft and brittle, so that the burr 10a is easily integrated with the compact 10b. Therefore, when the relative density is 60% or less, the burr 10a is easily eliminated by the second and subsequent pressurization by the punch 4a. When the relative density is 60% or less, molding defects other than the burr 10a are easily eliminated. When the relative density is 40% or more, the molded body 10b tends to have sufficient mechanical strength, and the molded body is not easily damaged in the subsequent process following the molding process.
　成形工程では、パンチ（４又は４ａ）が無機粉末１０（成形体１０ｂ）に及ぼす圧力が、０．０４９ＭＰａ以上２０ＭＰａ以下に調整されてよい。成形圧力が０．０４９ＭＰａ以上２０ＭＰａ以下である場合、成形体１０ｂ及びバリ１０ａのいずれも過度に圧縮されていないため、バリ１０ａが脆く、バリ１０ａが成形体１０ｂと一体化され易い。つまり、成形圧力が０．０４９ＭＰａ以上２０ＭＰａ以下である場合、パンチ４ａによる二回目以降の加圧により、バリ１０ａが解消され易い。成形圧力が０．０４９ＭＰａ以上２０ＭＰａ以下である場合、バリ１０ａ以外の成形不良も解消され易い。ただし、パンチ（４又は４ａ）が無機粉末１０（成形体１０ｂ）に及ぼす圧力は限定されない。例えば、パンチ（４又は４ａ）が無機粉末１０（成形体１０ｂ）に及ぼす圧力は、５０ＭＰａ以上２００ＭＰａ以下の範囲の高圧であってもよい。このような高圧での無機粉末１０の成形によって成形体１０ｂを形成する場合であっても、本実施形態によれば成形不良を抑制及び解消することができる。 In the molding step, the pressure exerted by the punch (4 or 4a) on the inorganic powder 10 (molded body 10b) may be adjusted to 0.049 MPa or more and 20 MPa or less. When the molding pressure is 0.049 MPa or more and 20 MPa or less, neither the compact 10b nor the burr 10a is compressed excessively, so the burr 10a is brittle and the burr 10a is easily integrated with the compact 10b. That is, when the molding pressure is 0.049 MPa or more and 20 MPa or less, the burr 10a is easily eliminated by the second and subsequent pressurization by the punch 4a. When the molding pressure is 0.049 MPa or more and 20 MPa or less, molding defects other than the burr 10a are easily eliminated. However, the pressure which a punch (4 or 4a) exerts on the inorganic powder 10 (molded body 10b) is not limited. For example, the pressure that the punch (4 or 4a) exerts on the inorganic powder 10 (molded body 10b) may be a high pressure in the range of 50 MPa to 200 MPa. Even in the case where the molded body 10b is formed by molding the inorganic powder 10 at such a high pressure, according to the present embodiment, molding defects can be suppressed and eliminated.
　無機粉末１０が磁性粉末であり、磁性粉末から焼結磁石を作製する場合、成形工程後に以下の配向工程が実施され、配向工程後に焼結工程が実施される。配向工程では、パンチ（４又は４ａ）とダイ３によって保持された成形体１０ｂに磁場を印加して、成形体１０ｂに含まれる磁性粉末を配向させてよい。例えば、図３中の（ｃ）に示されるように、配向工程では、パンチ４ａとダイ３によって保持された成形体１０ｂに磁場が印加されてよい。配向工程に用いるパンチ（４又は４ａ）及びダイ３の一部又は全部は絶縁性であることが好ましい。パンチ（４又は４ａ）及びダイ３の一部又は全部が絶縁性である場合、配向工程においてパンチ（４又は４ａ）及びダイ３における渦電流が抑制され、成形体１０ｂ中の磁性粉末の配向度が向上する。 When the inorganic powder 10 is a magnetic powder and a sintered magnet is produced from the magnetic powder, the following alignment process is performed after the molding process, and the sintering process is performed after the alignment process. In the orientation step, a magnetic field may be applied to the compact 10b held by the punch (4 or 4a) and the die 3 to orient the magnetic powder contained in the compact 10b. For example, as shown in FIG. 3C, in the alignment step, a magnetic field may be applied to the molded body 10b held by the punch 4a and the die 3. Part or all of the punch (4 or 4a) and the die 3 used in the alignment step are preferably insulative. When some or all of the punch (4 or 4a) and the die 3 are insulative, the eddy current in the punch (4 or 4a) and the die 3 is suppressed in the alignment step, and the degree of orientation of the magnetic powder in the compact 10b Will improve.
　成形工程から配向工程に至るまで、一つのパンチ４（第一のパンチ）を用いる場合、パンチ４（第一のパンチ）の少なくとも一部が絶縁性であることが好ましく、パンチ４（第一のパンチ）の全体が絶縁性であることがより好ましい。配向工程において、第二のパンチ（パンチ４ａ）とダイ３によって成形体１０ｂを保持する場合、第二のパンチ（パンチ４ａ）の少なくとも一部が絶縁性であることが好ましく、第二のパンチ（パンチ４ａ）のの全体が絶縁性であることがより好ましい。配向工程において、第二のパンチ（パンチ４ａ）とダイ３によって成形体１０ｂを保持する場合、第一のパンチ（パンチ４）は、例えば、金属であってよい。配向工程に用いられるダイ３の少なくとも一部が絶縁性であってよく、ダイ３の全体が絶縁性であることが好ましい。 When one punch 4 (first punch) is used from the forming step to the orientation step, it is preferable that at least a part of the punch 4 (first punch) is insulative, and the punch 4 (first punch) More preferably, the entire punch) is insulative. In the orientation step, when the compact 10b is held by the second punch (punch 4a) and the die 3, it is preferable that at least a part of the second punch (punch 4a) is insulative. More preferably, the entire punch 4a) is insulative. In the alignment step, when the molded body 10b is held by the second punch (punch 4a) and the die 3, the first punch (punch 4) may be a metal, for example. At least a part of the die 3 used in the alignment step may be insulative, and the entire die 3 is preferably insulative.
　図１に示されるように、側型６には継ぎ目がなくてよい。つまり、側型６はシームレス（ｓｅａｍｌｅｓｓ）であってよい。仮に側型６に継ぎ目がある場合（例えば、側型６が複数の部材へ分解可能である場合）、成形工程又は配向工程において、無機粉末１０が、側型６の継ぎ目（隙間）から型２の外へ漏れ出ることがある。その結果、成形体１０ｂの保形性が損なわれ、例えばバリが成形体１０ｂに形成されることがある。側型６を複数の部材へ分解することによって側型６を成形体１０ｂから分離する場合、誤って力が成形体１０ｂへ作用して、成形体１０ｂが破損することがある。無機粉末１０が側型６の継ぎ目から型２の外へ漏れ出た場合、成形体１０ｂの寸法、密度及び形状がばらつき、最終的に得られる焼結体の寸法、形状、及び特性もばらつくこともある。これらの問題は、継ぎ目がない側型６を用いることにより、抑制され易い。 As shown in FIG. 1, the side mold 6 may be seamless. That is, the side mold 6 may be seamless. If the side mold 6 has a seam (for example, when the side mold 6 can be disassembled into a plurality of members), the inorganic powder 10 is transferred from the seam (gap) of the side mold 6 to the mold 2 in the molding step or the orientation step. May leak out. As a result, the shape retention of the molded body 10b is impaired, and for example, burrs may be formed on the molded body 10b. When the side mold 6 is separated from the molded body 10b by disassembling the side mold 6 into a plurality of members, a force may be applied to the molded body 10b by mistake and the molded body 10b may be damaged. When the inorganic powder 10 leaks from the joint of the side mold 6 to the outside of the mold 2, the size, density and shape of the molded body 10b vary, and the size, shape and characteristics of the finally obtained sintered body also vary. There is also. These problems are easily suppressed by using the side mold 6 without a seam.
　焼結工程における成形体の温度は、成形体を構成する無機粉末の組成に応じて、適宜調整されてよい。 The temperature of the molded body in the sintering step may be appropriately adjusted according to the composition of the inorganic powder constituting the molded body.
（従来の希土類磁石の製造方法）
　希土類磁石は、モータ又はアクチュエータ等の部品であり、例えば、ハードディスクドライブ、ハイブリッド自動車、電気自動車、磁気共鳴画像装置（ＭＲＩ）、スマートフォン、デジタルカメラ、薄型ＴＶ、スキャナー、エアコン、ヒートポンプ、冷蔵庫、掃除機、洗濯乾燥機、エレベーター及び風力発電機等の様々な分野で利用されている。これらの多様な用途に応じて、希土類磁石に要求される寸法及び形状は異なる。したがって、多品種の希土類磁石を効率的に製造するためには、希土類磁石の寸法及び形状を容易に変更することが可能な成形方法が望まれる。 (Conventional rare earth magnet manufacturing method)
Rare earth magnets are components such as motors or actuators, such as hard disk drives, hybrid cars, electric cars, magnetic resonance imaging devices (MRI), smartphones, digital cameras, thin TVs, scanners, air conditioners, heat pumps, refrigerators, and vacuum cleaners. It is used in various fields such as washing and drying machines, elevators and wind power generators. Depending on these various applications, the dimensions and shape required for rare earth magnets vary. Therefore, in order to efficiently manufacture a wide variety of rare earth magnets, a molding method that can easily change the size and shape of the rare earth magnet is desired.
　従来の希土類磁石の製造では、希土類元素を含む金属粉末（例えば合金粉末）を高圧(例えば、５０ＭＰａ以上２００ＭＰａ以下)で加圧しながら、磁場を金属粉末へ印加する。その結果、磁場に沿って配向した金属粉末から成形体が形成される。このような成形方法を、以下では「高圧磁場プレス法」と記す。高圧磁場プレス法によれば、金属粉末が配向し易く、高い残留磁束密度Ｂｒと優れた保形性とを有する成形体を得ることが可能である。この成形体の焼結によって焼結体を得て、焼結体を所望の形状に加工することにより、磁石製品が完成する。 In the production of a conventional rare earth magnet, a magnetic field is applied to a metal powder while pressing a metal powder (for example, an alloy powder) containing a rare earth element with a high pressure (for example, 50 MPa or more and 200 MPa or less). As a result, a compact is formed from the metal powder oriented along the magnetic field. Hereinafter, such a forming method is referred to as a “high-pressure magnetic field pressing method”. According to the high-pressure magnetic field pressing method, it is possible to obtain a molded body having a high residual magnetic flux density Br and excellent shape retention, since the metal powder is easily oriented. A sintered product is obtained by sintering the compact, and the sintered product is processed into a desired shape to complete a magnet product.
　しかし、高圧磁場プレス法では、磁場中で高い圧力を金属粉末へ及ぼす必要があるため、大規模で複雑な成形装置が必要であり、成形用の金型の寸法及び形状が制限される。この制限のために、高圧磁場プレス法によって得られる一般的な成形体の形状は、粗大なブロックに限られる。したがって、従来の方法によって多品種の磁石製品を製造する場合、ブロック状の成形体を焼結させて焼結体を得た後、磁石製品に要求される寸法及び形状に応じて焼結体を加工する必要がある。焼結体の加工では、焼結体を切削したり、研磨したりするため、高価な希土類元素を含む屑が生じてしまう。その結果、磁石製品の歩留まり率が低下する。また、高圧磁場プレス法では、金型同士のカジリ（ｇａｌｌｉｎｇ）、又は金型と成形体との間におけるカジリによって、金型又は成形体が破損し易い。例えば、高圧磁場プレス法で得られた成形体には亀裂（ｃｒａｃｋ）が発生することがある。 However, in the high-pressure magnetic field pressing method, since it is necessary to apply a high pressure to the metal powder in a magnetic field, a large-scale and complicated molding apparatus is required, and the size and shape of the molding die are limited. Due to this limitation, the shape of a general molded body obtained by a high-pressure magnetic field pressing method is limited to a coarse block. Therefore, when manufacturing various types of magnet products by the conventional method, after obtaining the sintered body by sintering the block-shaped molded body, the sintered body is prepared according to the size and shape required for the magnet product. Need to be processed. In the processing of the sintered body, since the sintered body is cut or polished, scraps containing expensive rare earth elements are generated. As a result, the yield rate of magnet products decreases. In the high-pressure magnetic field pressing method, the mold or the molded body is easily damaged due to galling between the molds or between the mold and the molded body. For example, cracks may occur in a molded body obtained by a high-pressure magnetic field pressing method.
　上記のような理由のため、従来の高圧磁場プレス法を用いた製造方法は、多品種又は少量の磁石製品の製造に適していない。 For the reasons described above, the conventional manufacturing method using the high-pressure magnetic field pressing method is not suitable for manufacturing a variety of products or a small amount of magnet products.
（本実施形態に係る希土類磁石の製造方法）
　上記の高圧磁場プレス法に関する問題を解決するために、本実施形態の成形工程では、型２が金属粉末（無機粉末）に及ぼす圧力が、０．０４９ＭＰａ以上２０ＭＰａ以下（０．５ｋｇｆ／ｃｍ２以上２００ｋｇｆ／ｃｍ２以下）に調整されてよい。このような低圧で金属粉末を成形する場合、高圧に対する耐久性が金型に要求されず、大規模で複雑な成形装置も不要である。したがって、低圧で金属粉末を成形する場合、金型の材質、寸法及び形状が制限されず、多様な寸法及び形状を有する型を用いて、多品種の希土類磁石を比較的容易に製造することができる。また、高圧磁場プレス法では、金属粉末の成形及び配向に長時間を要するが、低圧で金属粉末を成形することにより、成形及び配向に要する時間が大幅に短縮され、希土類磁石の生産性が向上する。 (Rare earth magnet manufacturing method according to this embodiment)
In order to solve the above-described problems relating to the high-pressure magnetic field pressing method, in the molding step of this embodiment, the pressure exerted on the metal powder (inorganic powder) by the mold 2 is 0.049 MPa or more and 20 MPa or less (0.5 kgf / cm 2 or more). 200 kgf / cm 2 or less). When metal powder is molded at such a low pressure, durability against high pressure is not required for the mold, and a large-scale and complicated molding apparatus is not required. Therefore, when molding metal powder at a low pressure, the material, size and shape of the mold are not limited, and various types of rare earth magnets can be manufactured relatively easily using molds having various sizes and shapes. it can. The high-pressure magnetic field press method takes a long time to form and orient the metal powder, but by forming the metal powder at a low pressure, the time required for the forming and orientation is greatly shortened and the productivity of the rare earth magnet is improved. To do.
　本実施形態に係る希土類磁石の製造方法の詳細は以下の通りである。 Details of the method of manufacturing the rare earth magnet according to the present embodiment are as follows.
　希土類磁石（焼結磁石）の製造方法では、まず原料合金を鋳造する。鋳造方法は、例えば、ストリップキャスト法であってよい。原料合金はフレーク状であってよく、インゴット状であってもよい。原料合金は、希土類元素Ｒを含む。希土類元素Ｒは、Ｓｃ，Ｙ，Ｌａ，Ｃｅ，Ｐｒ，Ｎｄ，Ｐｍ，Ｓｍ，Ｅｕ，Ｇｄ，Ｔｂ，Ｄｙ，Ｈｏ，Ｅｒ，Ｔｍ，Ｙｂ及びＬｕからなる群より選ばれる少なくとも一種であればよい。原料合金は、希土類元素Ｒに加えて、Ｂ，Ｎ，Ｆｅ，Ｃｏ，Ｃｕ，Ｎｉ，Ｍｎ，Ａｌ，Ｎｂ，Ｚｒ，Ｔｉ，Ｗ，Ｍｏ，Ｖ，Ｇａ，Ｚｎ，Ｓｉ及びＢｉからなる群より選ばれる少なくとも一種の元素を含んでよい。原料合金の化学組成は、最終的に得たい希土類磁石の主相及び粒界相の化学組成に応じて調整すればよい。つまり、目的とする希土類磁石の組成に応じて上記元素を含む各出発原料を秤量及び配合して、原料合金の原料を調製すればよい。希土類磁石は、例えば、ネオジム磁石、サマリウムコバルト磁石、サマリウム‐鉄‐窒素磁石、又はプラセオジム磁石であってよい。希土類磁石の主相は、例えば、Ｎｄ２Ｆｅ１４Ｂ，ＳｍＣｏ５，Ｓｍ２Ｃｏ１７，Ｓｍ２Ｆｅ１７Ｎ３，Ｓｍ１Ｆｅ７Ｎｘ，又はＰｒＣｏ５であってよい。粒界相は、例えば、主相に比べて希土類元素Ｒの含有量が大きい相（Ｒリッチ相）であってよい。粒界相は、遷移金属リッチ相、Ｂリッチ相、酸化物相又は炭化物相を含んでもよい。 In the method of manufacturing a rare earth magnet (sintered magnet), first, a raw material alloy is cast. The casting method may be, for example, a strip casting method. The raw material alloy may be in the form of flakes or ingots. The raw material alloy contains a rare earth element R. The rare earth element R may be at least one selected from the group consisting of Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. . In addition to the rare earth element R, the raw material alloy is selected from the group consisting of B, N, Fe, Co, Cu, Ni, Mn, Al, Nb, Zr, Ti, W, Mo, V, Ga, Zn, Si, and Bi. It may contain at least one element selected. The chemical composition of the raw material alloy may be adjusted according to the chemical composition of the main phase and grain boundary phase of the rare earth magnet to be finally obtained. That is, the raw materials for the raw material alloy may be prepared by weighing and blending the starting materials containing the above elements according to the composition of the target rare earth magnet. The rare earth magnet may be, for example, a neodymium magnet, a samarium cobalt magnet, a samarium-iron-nitrogen magnet, or a praseodymium magnet. The main phase of the rare earth magnet may be, for example, Nd 2 Fe 14 B, SmCo 5 , Sm 2 Co 17 , Sm 2 Fe 17 N 3 , Sm 1 Fe 7 N x , or PrCo 5 . The grain boundary phase may be, for example, a phase (R rich phase) in which the content of the rare earth element R is larger than that of the main phase. The grain boundary phase may include a transition metal rich phase, a B rich phase, an oxide phase, or a carbide phase.
　上記の原料合金の粗粉砕により、粗大粉末を得る。粗粉砕では、例えば、水素を合金の粒界（Ｒリッチ相）に吸蔵させることより、原料合金を粉砕してよい。原料合金の粗粉砕では、ディスクミル、ジョークラッシャー、ブラウンミル又はスタンプミル等の機械的な粉砕方法を用いてもよい。粗粉砕によって得られた粗大粉末の粒径は、例えば、１０μｍ以上１００μｍ以下であってよい。 粗 A coarse powder is obtained by coarse pulverization of the above raw material alloy. In the coarse pulverization, for example, the raw material alloy may be pulverized by occluding hydrogen in the alloy grain boundaries (R-rich phase). In the coarse pulverization of the raw material alloy, a mechanical pulverization method such as a disk mill, a jaw crusher, a brown mill, or a stamp mill may be used. The particle size of the coarse powder obtained by coarse pulverization may be, for example, 10 μm or more and 100 μm or less.
　上記の粗大粉末の微粉砕により、微粉末を得る。微粉砕では、ジェットミル、ボールミル、振動ミル、又は湿式アトライター等により、粗大粉末を粉砕してよい。微粉砕によって得られた微粉末の粒径は、例えば、０．５μｍ以上５μｍ以下であってよい。 微 Fine powder is obtained by fine pulverization of the above coarse powder. In the fine pulverization, the coarse powder may be pulverized by a jet mill, a ball mill, a vibration mill, a wet attritor or the like. The particle size of the fine powder obtained by pulverization may be, for example, 0.5 μm or more and 5 μm or less.
　粗粉砕で得た粗大粉末へ有機物を添加してよい。微粉砕で得た微粉末へ有機物を添加してもよい。つまり、微粉砕の前後いずれかにおいて、有機物を原料合金の粉末と混ぜてよい。有機物は、例えば、潤滑剤として機能する。潤滑剤を原料合金の粉末へ添加することにより、原料合金の粉末の凝集が抑制される。また、潤滑剤を原料合金の粉末へ添加するにより、後工程において型と原料合金の粉末との摩擦が抑制され易い。その結果、配向工程において原料合金の粉末が配向し易く、原料合金の粉末から得られる成形体の表面又は型の表面における傷を抑制し易い。有機物は、例えば、脂肪酸又は脂肪酸の誘導体であってよい。有機物は、例えば、オレイン酸アミド、ステアリン酸亜鉛、ステアリン酸カルシウム、ステアリン酸アミド、パルミチン酸アミド、ペンタデシル酸アミド、ミリスチン酸アミド、ラウリン酸アミド、カプリン酸アミド、ペラルゴン酸アミド、カプリル酸アミド、エナント酸アミド、カプロン酸アミド、バレリアン酸アミド及びブチル酸アミドからなる群より選ばれる少なくとも一種であってよい。潤滑剤は、粉末状の有機物であってよい。潤滑剤は、液状の有機物であってもよい。粉末状の潤滑剤が溶解した有機溶媒を原料合金の粉末へ添加してもよい。 Organic substances may be added to the coarse powder obtained by coarse pulverization. An organic substance may be added to the fine powder obtained by fine pulverization. That is, the organic substance may be mixed with the raw material alloy powder either before or after pulverization. The organic substance functions as a lubricant, for example. By adding the lubricant to the raw material alloy powder, aggregation of the raw material alloy powder is suppressed. Further, by adding the lubricant to the raw material alloy powder, the friction between the mold and the raw material alloy powder is easily suppressed in the subsequent process. As a result, the raw material alloy powder is easily oriented in the orientation step, and it is easy to suppress scratches on the surface of the molded body or the mold surface obtained from the raw material alloy powder. The organic substance may be, for example, a fatty acid or a fatty acid derivative. Organic substances include, for example, oleic acid amide, zinc stearate, calcium stearate, stearic acid amide, palmitic acid amide, pentadecylic acid amide, myristic acid amide, lauric acid amide, capric acid amide, pelargonic acid amide, caprylic acid amide, enanthic acid It may be at least one selected from the group consisting of amide, caproic acid amide, valeric acid amide and butyric acid amide. The lubricant may be a powdery organic material. The lubricant may be a liquid organic material. An organic solvent in which a powdery lubricant is dissolved may be added to the raw alloy powder.
　上記の手順で得られた原料合金の粉末は、以下では「金属粉末」と表記される。金属粉末とは、「本実施形態の概要」に記載の「無機粉末」及び「磁性粉末」に相当する。 The raw material alloy powder obtained by the above procedure is referred to as “metal powder” below. The metal powder corresponds to “inorganic powder” and “magnetic powder” described in “Summary of Embodiment”.
　「本実施形態の概要」に記載の成形工程により、金属粉末から成形体を形成する。 A molded body is formed from metal powder by the molding process described in “Summary of the present embodiment”.
　成形工程では、型２が金属粉末１０に及ぼす圧力が、０．０４９ＭＰａ以上２０ＭＰａ以下（０．５ｋｇｆ／ｃｍ２以上２００ｋｇｆ／ｃｍ２以下）に調整されてよい。圧力とは、例えば、パンチ（４又は４a）の端面が金属粉末１０に及ぼす圧力であってよい。このように、従来の高圧磁場プレス法よりも低圧で、金属粉末１０から成形体１０ｂを形成することにより、型２と成形体１０ｂとの摩擦が抑制され易く、型２又は成形体１０ｂの破損（例えば成形体１０ｂの亀裂）が抑制され易い。圧力が高過ぎる場合、型２が撓んでしまい、目的のキャビティの容量を確保し難く、目的の成形体１０ｂの密度が得られ難い。従来の高圧磁場プレス法では、高圧下で金属粉末の成形及び配向を同時に行う必要があった。一方、本実施形態では、成形及び配向を同時に行う必要がないので、成形工程後に、配向工程を行うことができる。成形工程と配向工程とを分けることにより、従来よりも小型で安価な装置（例えば、プレス成形装置、及び磁場印加装置）を各工程に用いることができる。成形工程及び配向工程を略同時に行ってもよい。 In the molding step, the pressure of the mold 2 on the metal powder 10, may be adjusted to more than 0.049 MPa 20 MPa or less (0.5 kgf / cm 2 or more 200 kgf / cm 2 or less). The pressure may be, for example, a pressure exerted on the metal powder 10 by the end face of the punch (4 or 4a). Thus, by forming the molded body 10b from the metal powder 10 at a lower pressure than the conventional high-pressure magnetic field pressing method, friction between the mold 2 and the molded body 10b is easily suppressed, and the mold 2 or the molded body 10b is damaged. (For example, cracks in the molded body 10b) are easily suppressed. When the pressure is too high, the mold 2 is bent, it is difficult to secure the capacity of the target cavity, and it is difficult to obtain the density of the target molded body 10b. In the conventional high-pressure magnetic field pressing method, it has been necessary to simultaneously form and align the metal powder under high pressure. On the other hand, in this embodiment, since it is not necessary to perform shaping | molding and orientation simultaneously, an orientation process can be performed after a shaping | molding process. By separating the molding process and the orientation process, apparatuses that are smaller and less expensive than conventional ones (for example, a press molding apparatus and a magnetic field application apparatus) can be used for each process. You may perform a shaping | molding process and an orientation process substantially simultaneously.
　配向工程では、型２内に保持された成形体１０ｂに磁場を印加して、成形体１０ｂを構成する金属粉末１０を型２内で磁場に沿って配向させる。磁場は、パルス磁場又は静磁場であってよい。例えば、型２内に保持された成形体１０ｂを、型２と共に、空芯コイル（ソレノイドコイル）の内側に配置して、空芯コイルに電流（交流）を流すことにより、型２内の成形体１０ｂに磁場を印加してよい。ダブルコイル又はヘルムホルツコイルに電流を流すことにより、型２内の成形体１０ｂに磁場を印加してよい。ダブルコイルとは、二つのコイルが同一の中心軸を持つように配置された磁場発生装置である。ダブルコイル又はヘルムホルツコイルを用いることにより、空芯コイルを用いる場合に比べて、より均質な磁場を成形体１０ｂに印加することができる。その結果、成形体１０ｂにおける金属粉末１０の配向性が向上し易く、最終的に得られる希土類磁石（焼結体）の磁気特性が向上し易い。着磁ヨークを用いて、型２内の成形体１０ｂに磁場を印加してもよい。型２内の成形体１０ｂに印加する磁場の強度は、例えば、７９６ｋＡ／ｍ以上５１７３ｋＡ／ｍ以下（１０ｋＯｅ以上６５ｋＯｅ以下）であってよい。配向工程後、成形体１０ｂを脱磁してもよい。型２内の成形体１０ｂに印加する磁場の強度は、必ずしも上記の範囲に限定されない。 In the orientation step, a magnetic field is applied to the compact 10b held in the mold 2, and the metal powder 10 constituting the compact 10b is oriented in the mold 2 along the magnetic field. The magnetic field may be a pulsed magnetic field or a static magnetic field. For example, the molded body 10b held in the mold 2 is placed inside the air core coil (solenoid coil) together with the mold 2, and an electric current (alternating current) is passed through the air core coil, so that the molding in the mold 2 is performed. A magnetic field may be applied to the body 10b. You may apply a magnetic field to the molded object 10b in the type | mold 2 by sending an electric current through a double coil or a Helmholtz coil. A double coil is a magnetic field generator arranged such that two coils have the same central axis. By using a double coil or a Helmholtz coil, a more homogeneous magnetic field can be applied to the molded body 10b than when an air-core coil is used. As a result, the orientation of the metal powder 10 in the molded body 10b is likely to be improved, and the magnetic properties of the rare earth magnet (sintered body) finally obtained are likely to be improved. A magnetic field may be applied to the molded body 10b in the mold 2 using a magnetized yoke. The strength of the magnetic field applied to the molded body 10b in the mold 2 may be, for example, 796 kA / m or more and 5173 kA / m or less (10 kOe or more and 65 kOe or less). You may demagnetize the molded object 10b after an orientation process. The intensity of the magnetic field applied to the molded body 10b in the mold 2 is not necessarily limited to the above range.
　成形体１０ｂに印加される磁場はパルス磁場であることが好ましい。パルス磁場は、従来の高圧磁場プレス法で多用された静磁場に比べ、高い磁場強度を有しており、短時間で成形体１０ｂへ印加される。したがって、パルス磁場を用いた配向工程により、静磁場を用いる場合に比べて、短時間で配向度の高い成形体１０ｂが得られ、結果的に残留磁束密度の高い希土類磁石を製造される。しかし、仮に電気伝導体（例えば金属）から構成される型２内に保持された成形体１０ｂにパルス磁場が印加されると、静磁場が印加される場合に比べて、型２に作用する磁場の強度が短時間で急激に変化する。その結果、電磁誘導に因る渦電流が型２に流れ易く、逆磁場が生じ易い。しかし型２の一部又は全部が絶縁性の物質（例えば絶縁性の樹脂）から形成されている場合、型２において渦電流が流れ難く、逆磁場も発生し難い。したがって、成形体１０ｂを構成する金属粉末１０が逆磁場によって型２の表面に引き寄せられる現象が抑制される。その結果、成形体１０ｂの密度が均一になり易く、焼結工程において焼結体（希土類磁石）に亀裂が発生し難くなる。また配向工程において渦電流及び逆磁場を抑制することにより、金属粉末１０の配向性が向上し、結果的に希土類磁石の磁気特性も向上する。さらに型２の一部又は全部が絶縁性の物質（例えば絶縁性の樹脂）から形成されている場合、配向工程おいて、渦電流損に起因する型２の温度上昇が抑制され、型２自体に瞬間的に衝撃（磁力）が作用し難い。その結果、型２が消耗し難くなる。 The magnetic field applied to the compact 10b is preferably a pulsed magnetic field. The pulse magnetic field has a higher magnetic field strength than the static magnetic field frequently used in the conventional high-pressure magnetic field pressing method, and is applied to the compact 10b in a short time. Therefore, compared with the case where a static magnetic field is used, the compact 10b having a high degree of orientation can be obtained in a short time by the orientation process using a pulsed magnetic field, and as a result, a rare earth magnet having a high residual magnetic flux density is manufactured. However, if a pulsed magnetic field is applied to the molded body 10b held in the mold 2 composed of an electrical conductor (for example, metal), the magnetic field acting on the mold 2 is compared to when a static magnetic field is applied. The strength of the abruptly changes in a short time. As a result, eddy currents due to electromagnetic induction are likely to flow through the mold 2 and a reverse magnetic field is likely to occur. However, when part or all of the mold 2 is formed of an insulating material (for example, an insulating resin), it is difficult for the eddy current to flow in the mold 2 and a reverse magnetic field is not easily generated. Therefore, the phenomenon in which the metal powder 10 constituting the molded body 10b is attracted to the surface of the mold 2 by a reverse magnetic field is suppressed. As a result, the density of the molded body 10b tends to be uniform, and cracks are less likely to occur in the sintered body (rare earth magnet) in the sintering process. Further, by suppressing the eddy current and the reverse magnetic field in the alignment step, the orientation of the metal powder 10 is improved, and as a result, the magnetic properties of the rare earth magnet are also improved. Further, when part or all of the mold 2 is formed of an insulating material (for example, an insulating resin), the temperature increase of the mold 2 due to eddy current loss is suppressed in the alignment process, and the mold 2 itself It is difficult to apply an impact (magnetic force) instantaneously. As a result, the mold 2 is not easily consumed.
　型２の一部又は全部を構成する絶縁性の物質は、樹脂であってよい。型２の一部又は全部を構成する樹脂は、例えば、アクリル樹脂、ポリエチレン（高密度ポリエチレンなど）、ポリエチレンテレフタレート、ポリブチレンテレフタレート、ポリクロロトリフルオロエチレン、ポリテトラフルオロエチレン、エチルセルロース、ポリプロピレン、ポリブテン、ポリスチレン、アクリロニトリル‐ブタジエン‐スチレン共重合体、アクリロニトリル‐スチレン共重合体、スチレン‐ブタジエン共重合体、エチレン‐酢酸ビニル共重合体、エチレン・エチルアクリレート共重合体、アタクチック‐ポリプロピレン、ポリメタクリル酸メチル、メタクリル酸共重合体、ポリカーボネート、ポリエーテルエーテルケトン、ポリエーテルイミド、ポリアセタール、変性ポリフェニレンオキサイド、ポリフェニレンサルファイド、ポリアミド（ポリアミド６、ポリアミド４６、ポリアミド６６、ポリアミド６．６６）、ポリイミド、ポリアリレート、ポリビニルアルコール、エポキシ樹脂、フェノール樹脂、ポリエステル樹脂、不飽和ポリエステル樹脂、液晶ポリマー、パラフィンワックス及びシリコン樹脂ならなる群より選ばれる一種又は複数種であってよい。下型８、側型６、及びパンチ４ａの全てが上記の樹脂から形成されていてよい。下型８、側型６、及びパンチ４ａのうち、側型６のみが上記の樹脂から形成されていてよい。下型８、側型６、及びパンチ４ａのうち、下型８のみが上記の樹脂から形成されていてもよい。下型８、側型６、及びパンチ４ａのうち、パンチ４ａのみが樹脂から形成されていてもよい。 The insulating material constituting part or all of the mold 2 may be a resin. Resins constituting part or all of the mold 2 are, for example, acrylic resin, polyethylene (such as high-density polyethylene), polyethylene terephthalate, polybutylene terephthalate, polychlorotrifluoroethylene, polytetrafluoroethylene, ethyl cellulose, polypropylene, polybutene, Polystyrene, acrylonitrile-butadiene-styrene copolymer, acrylonitrile-styrene copolymer, styrene-butadiene copolymer, ethylene-vinyl acetate copolymer, ethylene / ethyl acrylate copolymer, atactic-polypropylene, polymethyl methacrylate, Methacrylic acid copolymer, polycarbonate, polyetheretherketone, polyetherimide, polyacetal, modified polyphenylene oxide, polyphenylenesulfur And polyamide (polyamide 6, polyamide 46, polyamide 66, polyamide 6.66), polyimide, polyarylate, polyvinyl alcohol, epoxy resin, phenol resin, polyester resin, unsaturated polyester resin, liquid crystal polymer, paraffin wax and silicone resin It may be one or more selected from the group consisting of: The lower mold 8, the side mold 6, and the punch 4a may all be formed from the above resin. Of the lower mold 8, the side mold 6, and the punch 4a, only the side mold 6 may be formed from the above resin. Of the lower mold 8, the side mold 6, and the punch 4a, only the lower mold 8 may be formed of the above resin. Of the lower mold 8, the side mold 6, and the punch 4a, only the punch 4a may be made of resin.
　仮に金型内に保持された成形体１０ｂにパルス磁場を印加する場合、金型を構成する金属（例えば鉄）の飽和磁束密度が限られている。したがって、金型内の成形体１０ｂに実効的に作用する磁場の強度は、金型外のパルス磁場の強度よりも低い。一方、型２が樹脂から形成されている場合、強いパルス磁場を型２内の成形体１０ｂへ印加することが可能であり、金属粉末１０の配向性が向上する。 If a pulse magnetic field is applied to the molded body 10b held in the mold, the saturation magnetic flux density of the metal (for example, iron) constituting the mold is limited. Therefore, the intensity of the magnetic field that effectively acts on the molded body 10b in the mold is lower than the intensity of the pulse magnetic field outside the mold. On the other hand, when the mold 2 is formed of a resin, a strong pulse magnetic field can be applied to the molded body 10b in the mold 2 and the orientation of the metal powder 10 is improved.
　型２において渦電流が流れる部分と成形体１０ｂとの接触面積が広い程、渦電流に起因する焼結体の亀裂、及び磁気特性の劣化が起き易い。下型８、側型６、及びパンチ４ａのうち、側型６と成形体１０ｂとの接触面積が、下型８及びパンチ４ａ其々と成形体１０ｂとの接触面積よりも広い。したがって、下型８、側型６、及びパンチ４ａのうち、少なくとも側型６が樹脂から形成されていてよい。成形体１０ｂと接触する面積が広い側型６を樹脂から形成することにより、側型６における渦電流及び逆磁場の発生が効果的に抑制され、渦電流及び逆磁場に起因する希土類磁石の亀裂及び磁気特性の劣化が抑制され易くなる。 In the mold 2, the larger the contact area between the portion where the eddy current flows and the compact 10b, the easier the cracking of the sintered body and the deterioration of the magnetic properties due to the eddy current occur. Of the lower mold 8, the side mold 6, and the punch 4a, the contact area between the side mold 6 and the molded body 10b is wider than the contact area between the lower mold 8 and the punch 4a and the molded body 10b. Therefore, at least the side mold 6 among the lower mold 8, the side mold 6, and the punch 4a may be formed of a resin. By forming the side mold 6 having a large area in contact with the molded body 10b from resin, generation of eddy current and reverse magnetic field in the side mold 6 is effectively suppressed, and cracks in the rare earth magnet due to the eddy current and reverse magnetic field are suppressed. In addition, it is easy to suppress deterioration of the magnetic characteristics.
　型２のうち、樹脂から形成される部分の位置は限定されない。型２の寸法及び形状、又はパルス磁場の方向に応じて、型２のうち渦電流を抑制する必要がある部分を樹脂から形成すればよい。例えば、型２のうち、金属粉末１０を配向させるパルス磁場の方向に対して周回する回路を形成する部分において、渦電流及び逆磁場が生じ易い。すなわち、側型６の貫通部（側型６の内壁）がパルス磁場の方向と平行となる場合において、渦電流及び逆磁場が生じ易い。したがって、型２のうち、金属粉末１０を配向させるパルス磁場の方向に対して、周回する回路を形成する部分である側型６が樹脂から形成される場合、渦電流及び逆磁場が抑制され易い。 The position of the part formed from the resin in the mold 2 is not limited. Depending on the size and shape of the mold 2 or the direction of the pulse magnetic field, the part of the mold 2 that needs to suppress eddy currents may be formed from resin. For example, an eddy current and a reverse magnetic field are easily generated in a portion of the mold 2 where a circuit that circulates in the direction of the pulse magnetic field that orients the metal powder 10 is formed. That is, when the penetrating portion of the side mold 6 (inner wall of the side mold 6) is parallel to the direction of the pulse magnetic field, eddy currents and reverse magnetic fields are likely to occur. Therefore, when the side mold 6, which is a part that forms a circuit that circulates in the direction of the pulse magnetic field that orients the metal powder 10 in the mold 2, is formed of resin, eddy currents and reverse magnetic fields are easily suppressed. .
　仮に、下型８、側型６、及びパンチ４ａの全てが金属から形成されている場合、成形工程において側型６とパンチ４ａとの摩擦により、金属屑が側型６又はパンチ４ａの表面から脱離して、成形体１０ｂに混入する場合がある。成形体１０ｂに混入した金属屑（例えば、アルミニウム又はアルミニウム合金）は、最終的に得られる希土類磁石の磁気特性を損なう場合がある。対照的に、型２の一部又は全部が樹脂から形成されて場合、型２が金属のみから構成されている場合に比べて、型２の摩耗屑（樹脂）が希土類磁石の磁気特性に及ぼす影響が抑制される。例えば、成形工程において摩擦し合う側型６及びパンチ４ａのうち、一方（例えば、側型６）が樹脂であり、他方（例えば、パンチ４ａ）が金属である場合、側型６とパンチ４ａとの摩擦により、金属屑の代わりに、金属よりも硬度が低い樹脂屑が型の生じ易い。樹脂屑は、金属屑に比べて、希土類磁石の磁気特性を損ない難い。例えば、側型６のみが樹脂から形成され、下型８及びパンチ４ａが、金属（例えば、アルミニウム又はアルミニウム合金）から形成されていてよい。 If all of the lower die 8, the side die 6, and the punch 4a are made of metal, metal scraps from the surface of the side die 6 or the punch 4a due to friction between the side die 6 and the punch 4a in the molding process. It may be detached and mixed into the molded body 10b. Metal scraps (for example, aluminum or aluminum alloy) mixed in the molded body 10b may impair the magnetic characteristics of the finally obtained rare earth magnet. In contrast, when part or all of the mold 2 is made of a resin, the wear debris (resin) of the mold 2 affects the magnetic properties of the rare earth magnet as compared with the case where the mold 2 is made of only metal. Influence is suppressed. For example, when one side (for example, side mold 6) is resin and the other (for example, punch 4a) is metal among the side mold 6 and the punch 4a that rub in the molding process, the side mold 6 and the punch 4a Due to this friction, instead of metal scraps, resin scraps having a hardness lower than that of metal tend to form. Resin scrap is less likely to impair the magnetic properties of rare earth magnets than metal scrap. For example, only the side mold 6 may be formed from a resin, and the lower mold 8 and the punch 4a may be formed from a metal (for example, aluminum or an aluminum alloy).
　焼結過程における希土類磁石（例えばネオジム磁石）の収縮率には異方性があるため、収縮後の希土類磁石（焼結体）の形状（特に複雑な形状）を精密に予測することは困難である。したがって、ネットシェイプのためには、型２の寸法及び形状を調整するための試行錯誤が必要であり、型２の材料としては、切削し易い樹脂が適している。つまり、多様な用途に応じた多品種の希土類磁石を効率的に製造するためには、樹脂から形成された型２が適している。従来の金型は、加工し難く、高価であるため、多様な用途に応じた多品種の希土類磁石の製造に適していない。 Because the shrinkage rate of rare earth magnets (eg neodymium magnets) during the sintering process is anisotropic, it is difficult to accurately predict the shape of the rare earth magnet (sintered body) after shrinkage (especially complex shape). is there. Therefore, trial and error for adjusting the size and shape of the mold 2 is necessary for the net shape, and as the material of the mold 2, a resin that is easy to cut is suitable. That is, in order to efficiently produce a wide variety of rare earth magnets according to various uses, the mold 2 made of resin is suitable. Conventional molds are difficult to process and expensive, and are not suitable for manufacturing a wide variety of rare earth magnets for various applications.
　同一の型２を用いた成形工程及び配向工程を繰り返す場合、成形及び配向の度に型２内を清掃してよい。例えば、型２内に残った余分な金属粉末１０を磁場で吸引することによって、型２内を清掃してよい。成形及び配向の度に型２内を清掃することにより、型２内で成形される金属粉末１０の秤量の精度が向上し、得られる成形体１０ｂの密度及び寸法のばらつきが抑制される。その結果、最終的に得られる希土類磁石の密度、寸法及び磁気特性のばらつきが抑制される。仮に、型２が強磁性を有する金属（例えば鉄）から形成されている場合、型２内を清掃する際に、型２自体が磁場によって吸引されるので、型２を清掃し難い。しかし、型２が、強磁性を有しない樹脂から形成されている場合、型２自体が磁場によって吸引されないので、型２内を清掃し易い。仮に、型２が強磁性を有する金属（例えば鉄）から形成されている場合、配向工程において型２自体が着磁して、金属粉末１０が型２に付着してしまうため、金属粉末１０の配向性が乱れたり、成形体１０ｂの保形性が損なわれたりする。しかし、樹脂から構成される型２を用いることにより、型２自体の着磁が抑制される。 When repeating the molding process and orientation process using the same mold 2, the interior of the mold 2 may be cleaned each time molding and orientation are performed. For example, the inside of the mold 2 may be cleaned by attracting excess metal powder 10 remaining in the mold 2 with a magnetic field. By cleaning the inside of the mold 2 each time it is molded and oriented, the accuracy of the weighing of the metal powder 10 molded in the mold 2 is improved, and variations in the density and dimensions of the resulting molded body 10b are suppressed. As a result, variations in the density, size, and magnetic properties of the finally obtained rare earth magnet are suppressed. If the mold 2 is made of a ferromagnetic metal (for example, iron), the mold 2 itself is attracted by a magnetic field when the mold 2 is cleaned, so that the mold 2 is difficult to clean. However, when the mold 2 is formed of a resin that does not have ferromagnetism, the mold 2 itself is not attracted by the magnetic field, so that the interior of the mold 2 can be easily cleaned. If the mold 2 is formed of a ferromagnetic metal (for example, iron), the mold 2 itself is magnetized in the orientation process, and the metal powder 10 adheres to the mold 2. The orientation may be disturbed, or the shape retention of the molded body 10b may be impaired. However, by using the mold 2 made of resin, the magnetization of the mold 2 itself is suppressed.
　上述の成形工程では、金属粉末１０を型２内へ供給しながら、型２内で成形される金属粉末１０の質量を、型２の質量と合わせて、測定してもよい。型２内で成形される金属粉末１０の質量と、型２の質量と、を同時に測定する場合、型２の質量が重い程、秤の精度が低下して、金属粉末１０自体の質量の測定の精度も低下する。しかし、従来の金属粉末１０よりも比重が軽い樹脂から構成される型２を用いることにより、金属粉末１０の質量を型２自体の質量と共に高い精度で測定することができる。 In the molding step described above, the mass of the metal powder 10 molded in the mold 2 may be measured together with the mass of the mold 2 while supplying the metal powder 10 into the mold 2. When simultaneously measuring the mass of the metal powder 10 molded in the mold 2 and the mass of the mold 2, the heavier the mass of the mold 2, the lower the accuracy of the scale, and the measurement of the mass of the metal powder 10 itself. The accuracy of this also decreases. However, by using the mold 2 made of a resin having a specific gravity lower than that of the conventional metal powder 10, the mass of the metal powder 10 can be measured with high accuracy together with the mass of the mold 2 itself.
　配向工程では、ダイ３の金属粉末１０をパンチ４ａ（第二のパンチ）で加圧しながら、金属粉末１０へ磁場を印加してもよい。つまり、配向工程においても、型２内の成形体１０ｂを圧縮してよい。型２が成形体１０ｂに及ぼす圧力は、上記の理由により、０．０４９ＭＰａ以上２０ＭＰａ以下に調整してよい。 In the orientation step, a magnetic field may be applied to the metal powder 10 while pressing the metal powder 10 of the die 3 with the punch 4a (second punch). That is, in the orientation process, the molded body 10b in the mold 2 may be compressed. The pressure exerted on the molded body 10b by the mold 2 may be adjusted to 0.049 MPa or more and 20 MPa or less for the above reason.
　成形工程及び配向工程を経た成形体１０ｂ（焼結工程前の成形体１０ｂ）の密度は、例えば、３．０ｇ／ｃｍ３以上４．４ｇ／ｃｍ３以下、好ましくは３．２ｇ／ｃｍ３以上４．２ｇ／ｃｍ３以下、より好ましくは３．４ｇ／ｃｍ３以上４．０ｇ／ｃｍ３以下に調整されていてよい。 The density of the molded body 10b (molded body 10b before the sintering process) that has undergone the molding process and the orientation process is, for example, 3.0 g / cm 3 or more and 4.4 g / cm 3 or less, preferably 3.2 g / cm 3 or more. It may be adjusted to 4.2 g / cm 3 or less, more preferably 3.4 g / cm 3 or more and 4.0 g / cm 3 or less.
　分離工程では、型２の少なくとも一部を、成形体１０ｂから分離する。例えば、分離工程では、パンチ４ａ及び側型６を成形体１０ｂから分離及び除去することにより、成形体１０ｂを下型８の上に載置してよい。例えば、鉛直方向（Ｚ軸方向）におけるパンチ４ａの位置を固定した状態で、側型６を上へ移動させてよい。その結果、側型６内へ挿入されていたパンチ４ａが側型６を貫通して、パンチ４ａの端面が成形体１０ｂを側型６の下方へ押し出す。つまり、側型６内に保持されていた成形体１０ｂが、側型６の下面から抜き出される。分離工程では、成形体１０ｂを保持した側型６及びパンチ４ａを下型８から分離して、成形体１０ｂを保持した側型６及びパンチ４ａを加熱工程用トレイの上に載置してもよい。そして、側型６及びパンチ４ａを成形体１０ｂから分離して、成形体１０ｂを加熱工程用トレイに載置してもよい。側型６は、分解及び組立てが可能であってよい。分離工程において、側型６を分解することにより、パンチ４ａ及び側型６を成形体１０ｂから外してよい。 In the separation step, at least a part of the mold 2 is separated from the molded body 10b. For example, in the separation step, the molded body 10b may be placed on the lower mold 8 by separating and removing the punch 4a and the side mold 6 from the molded body 10b. For example, the side mold 6 may be moved upward with the position of the punch 4a in the vertical direction (Z-axis direction) fixed. As a result, the punch 4 a inserted into the side mold 6 penetrates the side mold 6, and the end surface of the punch 4 a pushes the molded body 10 b downward from the side mold 6. That is, the molded body 10 b held in the side mold 6 is extracted from the lower surface of the side mold 6. In the separation step, the side mold 6 and the punch 4a holding the molded body 10b are separated from the lower mold 8, and the side mold 6 and the punch 4a holding the molded body 10b are placed on the heating process tray. Good. Then, the side mold 6 and the punch 4a may be separated from the molded body 10b, and the molded body 10b may be placed on the heating process tray. The side mold 6 may be capable of being disassembled and assembled. In the separation step, the side mold 6 may be disassembled to remove the punch 4a and the side mold 6 from the molded body 10b.
　分離工程に続いて、以下の加熱工程を行ってよい。ただし、加熱工程は必須ではない。 The following heating step may be performed following the separation step. However, the heating step is not essential.
　加熱工程では、成形体１０ｂを加熱して、成形体１０ｂの温度を２００℃以上４５０℃以下に調整してよい。加熱工程では、成形体１０ｂの温度を２００℃以上４００℃以下、又は２００℃以上３５０℃以下に調整してもよい。成形工程では、金属粉末１０にかかる圧力が、従来の高圧磁場プレス法よりも低いため、金属粉末１０が押し固まり難く、得られる成形体１０ｂが崩れ易い。しかし、加熱工程によって、成形体１０ｂの機械的強度及び保形性が向上し易い。 In the heating step, the molded body 10b may be heated to adjust the temperature of the molded body 10b to 200 ° C. or higher and 450 ° C. or lower. In the heating step, the temperature of the molded body 10b may be adjusted to 200 ° C. or higher and 400 ° C. or lower, or 200 ° C. or higher and 350 ° C. or lower. In the molding process, since the pressure applied to the metal powder 10 is lower than that of the conventional high-pressure magnetic field pressing method, the metal powder 10 is hard to be pressed and hardened, and the resulting molded body 10b is likely to collapse. However, the mechanical strength and shape retention of the molded body 10b are easily improved by the heating process.
　加熱工程では、成形体１０ｂの温度が２００℃以上になると、成形体１０ｂが固まり始めて、成形体１０ｂの保形性が向上する。換言すると、成形体１０ｂの温度が２００℃以上になると、成形体１０ｂの機械的強度が向上する。成形体１０ｂの保形性が向上するため、成形体１０ｂの搬送、又は後工程における成形体１０ｂのハンドリングの際に、成形体１０ｂが破損し難い。例えば、成形体１０ｂを搬送用チャック（ｃｈｕｃｋ）等により掴んで焼結用トレイ上に並べる際に、成形体１０ｂが崩れ難い。その結果、最終的に得られる希土類磁石の欠陥が抑制される。 In the heating step, when the temperature of the molded body 10b is 200 ° C. or higher, the molded body 10b starts to harden and the shape retention of the molded body 10b is improved. In other words, when the temperature of the molded body 10b is 200 ° C. or higher, the mechanical strength of the molded body 10b is improved. Since the shape-retaining property of the molded body 10b is improved, the molded body 10b is unlikely to be damaged when the molded body 10b is transported or handled in the subsequent process. For example, when the molded body 10b is gripped by a transport chuck or the like and arranged on the sintering tray, the molded body 10b is unlikely to collapse. As a result, defects in the finally obtained rare earth magnet are suppressed.
　仮に加熱工程において成形体１０ｂの温度が４５０℃を超えた場合、加熱工程後に実施される焼結工程において、成形体１０ｂに亀裂が形成され易い。亀裂が形成される原因は定かでない。例えば、加熱工程における成形体の急激な温度上昇により、成形体１０ｂ中に残存する水素が、ガスとして成形体１０ｂ外へ吹き出すことで、成形体１０ｂに亀裂が形成される可能性がある。しかし、加熱工程において成形体の温度を４５０℃以下に調整することにより、焼結工程における成形体１０ｂの亀裂が抑制される。その結果、最終的に得られる希土類磁石における亀裂も抑制され易い。また、加熱工程において成形体１０ｂの温度を４５０℃以下に調整するため、成形体１０ｂの昇温又は冷却に要する時間が抑制され、希土類磁石の生産性が向上する。また、加熱工程における成形体１０ｂの温度が４５０℃以下であり、一般的な焼結温度よりも低いため、型２の一部（例えば下型）とともに成形体１０ｂを加熱したとしても、型２の劣化又は成形体と型との化学反応が起き難い。したがって、必ずしも耐熱性が高くない組成物（樹脂）から構成される型であっても利用することができる。 If the temperature of the molded body 10b exceeds 450 ° C. in the heating process, cracks are easily formed in the molded body 10b in the sintering process performed after the heating process. The reason for the formation of cracks is not clear. For example, there is a possibility that cracks are formed in the molded body 10b due to the hydrogen remaining in the molded body 10b blowing out as a gas to the outside of the molded body 10b due to a rapid temperature rise of the molded body in the heating process. However, by adjusting the temperature of the molded body to 450 ° C. or lower in the heating process, cracks in the molded body 10b in the sintering process are suppressed. As a result, cracks in the finally obtained rare earth magnet are easily suppressed. In addition, since the temperature of the molded body 10b is adjusted to 450 ° C. or lower in the heating step, the time required for raising or cooling the molded body 10b is suppressed, and the productivity of the rare earth magnet is improved. Further, since the temperature of the molded body 10b in the heating process is 450 ° C. or lower and lower than a general sintering temperature, even if the molded body 10b is heated together with a part of the mold 2 (for example, the lower mold), the mold 2 Or chemical reaction between the molded body and the mold hardly occurs. Therefore, even a mold composed of a composition (resin) that does not necessarily have high heat resistance can be used.
　成形体１０ｂの温度を２００℃以上４５０℃以下に調整することにより、成形体１０ｂの保形性が向上するメカニズムは明らかではない。例えば、金属粉末１０に添加されている潤滑剤が、加熱工程において炭素になり、金属粉末１０を構成する金属粒子同士が炭素を介して結着される可能性がある。その結果、成形体１０ｂの保形性が向上するのかもしれない。仮に加熱工程において成形体１０ｂの温度が４５０℃を超えた場合、金属粉末１０を構成する金属の炭化物が生成したり、金属粒子同士が直接焼結したりする可能性がある。一方、成形体１０ｂの温度が２００℃以上４５０℃以下に調整される場合、金属の炭化物は必ずしも生成せず、金属粒子同士は必ずしも直接焼結しない。 The mechanism by which the shape retention of the molded body 10b is improved by adjusting the temperature of the molded body 10b to 200 ° C. or higher and 450 ° C. or lower is not clear. For example, there is a possibility that the lubricant added to the metal powder 10 becomes carbon in the heating process, and the metal particles constituting the metal powder 10 are bound together via carbon. As a result, the shape retention of the molded body 10b may be improved. If the temperature of the molded body 10b exceeds 450 ° C. in the heating step, there is a possibility that a metal carbide composing the metal powder 10 is generated or the metal particles are directly sintered. On the other hand, when the temperature of the molded body 10b is adjusted to 200 ° C. or higher and 450 ° C. or lower, metal carbide is not necessarily generated, and metal particles are not necessarily directly sintered.
　加熱工程において成形体１０ｂの温度を２００℃以上４５０℃以下に維持する時間は、特に限定されず、成形体１０ｂの寸法及び形状に応じて適宜調整すればよい。 The time for maintaining the temperature of the molded body 10b at 200 ° C. or higher and 450 ° C. or lower in the heating step is not particularly limited, and may be appropriately adjusted according to the size and shape of the molded body 10b.
　加熱工程では、赤外線を成形体１０ｂへ照射することにより、成形体１０ｂを加熱してよい。赤外線の照射（つまり輻射熱）によって成形体１０ｂを直接加熱することにより、伝導又は対流による加熱の場合に比べて、成形体１０ｂの昇温に要する時間が短縮され、生産効率及びエネルギー効率が高まる。ただし、加熱工程では、加熱炉内の熱伝導又は対流により、成形体１０ｂを加熱してもよい。赤外線の波長は、例えば、０．７５μｍ以上１０００μｍ以下、好ましくは０．７５μｍ以上３０μｍ以下であってよい。赤外線は、近赤外線、短波長赤外線、中波長赤外線、長波長赤外線（熱赤外線）、及び遠赤外線からなる群より選ばれる少なくとも一つであってよい。上記の赤外線のうち近赤外線は比較的金属に吸収され易い。したがって、近赤外線を成形体１０ｂへ照射する場合、短時間で金属（金属粉末１０）を昇温し易い。一方、上記の赤外線のうち遠赤外線は比較的有機物に吸収され易く、金属（金属粉末１０）によって反射され易い。したがって、遠赤外線を成形体へ照射する場合、上述した潤滑剤が選択的に加熱され易く、潤滑剤に起因する上記のメカニズムによって成形体１０ｂが硬化し易い。赤外線を成形体１０ｂへ照射する場合、例えば、赤外線ヒーター（セラミックヒーター等）又は赤外線ランプを用いてよい。 In the heating step, the molded body 10b may be heated by irradiating the molded body 10b with infrared rays. By directly heating the molded body 10b by irradiation with infrared rays (that is, radiant heat), the time required for raising the temperature of the molded body 10b is shortened compared to heating by conduction or convection, and production efficiency and energy efficiency are increased. However, in the heating step, the molded body 10b may be heated by heat conduction or convection in the heating furnace. The infrared wavelength may be, for example, 0.75 μm to 1000 μm, preferably 0.75 μm to 30 μm. The infrared rays may be at least one selected from the group consisting of near infrared rays, short wavelength infrared rays, medium wavelength infrared rays, long wavelength infrared rays (thermal infrared rays), and far infrared rays. Of the above infrared rays, near infrared rays are relatively easily absorbed by metals. Therefore, when near-infrared rays are irradiated to the molded body 10b, the temperature of the metal (metal powder 10) is easily raised in a short time. On the other hand, far infrared rays among the above infrared rays are relatively easily absorbed by organic substances and easily reflected by metal (metal powder 10). Therefore, when irradiating a far-infrared ray to a molded object, the lubricant mentioned above is easy to be selectively heated, and the molded object 10b is easy to be cured by the mechanism resulting from the lubricant. When irradiating the molded object 10b with infrared rays, for example, an infrared heater (ceramic heater or the like) or an infrared lamp may be used.
　型２の一部又は全部と分離された成形体１０ｂを加熱工程において加熱する場合、加熱による型２の劣化（例えば、型の変形、硬化又は摩耗）が抑制され易く、成形体１０ｂと型２との焼き付きも抑制され易い。また型２の一部又は全部と分離された成形体１０ｂを加熱する場合、型２が熱を断熱し難く、成形体１０ｂが加熱され易い。その結果、成形体１０ｂの保形性が向上する。型２の一部又は全部と分離された成形体１０ｂを加熱する場合、型２が成形体１０ｂと化学的に反応する可能性が低い。そのため、必ずしも型２に耐熱性が要求されるわけではなく、型２の材質が制限され難い。したがって、型２の原料として、所望の寸法及び形状に加工し易く、且つ安価な材料を選定し易い。仮に、加熱工程において成形体１０ｂと型２の全部とを一括して加熱した場合、成形体１０ｂと型２との間の熱膨張率の差に起因して、成形体１０ｂに応力が作用し易く、成形体１０ｂが変形したり、破損したりする。また、加熱工程において成形体１０ｂと型２の全部とを一括して加熱した場合、加熱対象全体の体積及び熱容量が大きい。その結果、一括して加熱される成形体の数量が制限され、加熱工程に要する時間が長くなり、エネルギーが浪費され、希土類磁石の生産性が低下する。 When the molded body 10b separated from part or all of the mold 2 is heated in the heating step, deterioration of the mold 2 (for example, deformation, hardening, or wear) of the mold 2 due to heating is easily suppressed. It is easy to suppress seizure. Moreover, when heating the molded object 10b isolate | separated from a part or all of the type | mold 2, the type | mold 2 is hard to insulate heat and the molded object 10b is easy to be heated. As a result, the shape retention of the molded body 10b is improved. When the molded body 10b separated from part or all of the mold 2 is heated, the possibility that the mold 2 chemically reacts with the molded body 10b is low. Therefore, the mold 2 is not necessarily required to have heat resistance, and the material of the mold 2 is not easily limited. Therefore, as a raw material for the mold 2, it is easy to process into a desired size and shape, and it is easy to select an inexpensive material. If the molded body 10b and all of the mold 2 are heated together in the heating step, stress acts on the molded body 10b due to the difference in coefficient of thermal expansion between the molded body 10b and the mold 2. The molded body 10b is easily deformed or damaged. Moreover, when the molded object 10b and all the type | molds 2 are heated collectively in a heating process, the volume and heat capacity of the whole heating object are large. As a result, the number of compacts that are heated together is limited, the time required for the heating process is lengthened, energy is wasted, and the productivity of the rare earth magnet is reduced.
　加熱工程では、例えば、下型の上に載置された成形体１０ｂを加熱してよい。加熱工程では、加熱工程用トレイに載置された成形体１０ｂを加熱してもよい。加熱工程では、成形体１０ｂの酸化を抑制するために、不活性ガス又は真空中で成形体１０ｂを加熱してよい。不活性ガスは、アルゴン等の希ガスであってよい。 In the heating step, for example, the molded body 10b placed on the lower mold may be heated. In the heating process, the molded body 10b placed on the heating process tray may be heated. In the heating step, the molded body 10b may be heated in an inert gas or vacuum to suppress oxidation of the molded body 10b. The inert gas may be a noble gas such as argon.
　加熱工程において、成形体１０ｂの温度を２００℃以上４５０℃以下に調整した後、成形体１０ｂを１００℃以下に冷却してよい。加熱工程後の成形体１０ｂの搬送に用いるチャックの表面が樹脂から構成されている場合、１０ｂの冷却により、チャックの表面と成形体１０ｂとの化学反応が抑制され、チャックの劣化、及び成形体１０ｂ表面の汚染が抑制される。冷却方法は、例えば、自然冷却であってよい。 In the heating step, after the temperature of the molded body 10b is adjusted to 200 ° C. or higher and 450 ° C. or lower, the molded body 10b may be cooled to 100 ° C. or lower. When the surface of the chuck used for transporting the molded body 10b after the heating process is made of resin, the chemical reaction between the surface of the chuck and the molded body 10b is suppressed by the cooling of 10b, the deterioration of the chuck, and the molded body. Contamination of the 10b surface is suppressed. The cooling method may be natural cooling, for example.
　配向工程後、焼結工程を行う。配向工程後、上記の加熱工程を経ることなく、焼結工程を行ってよい。配向工程後、上記の加熱工程を経て、焼結工程を行ってよい。焼結工程では、型２の全部から分離された成形体１０ｂを焼結させる。焼結工程では、成形体１０ｂ中の金属粉末１０同士が焼結して、焼結体（希土類磁石）が得られる。 The sintering process is performed after the orientation process. After the alignment step, the sintering step may be performed without passing through the heating step. After the orientation step, the sintering step may be performed through the heating step. In the sintering step, the compact 10b separated from the entire mold 2 is sintered. In the sintering step, the metal powders 10 in the compact 10b are sintered to obtain a sintered body (rare earth magnet).
　焼結工程において焼結させる成形体１０ｂの密度（焼結工程直前の成形体１０ｂの密度）は、例えば、３．０ｇ／ｃｍ３以上４．４ｇ／ｃｍ３以下、３．２ｇ／ｃｍ３以上４．２ｇ／ｃｍ３以下、３．４ｇ／ｃｍ３以上４．０ｇ／ｃｍ３以下、又は３．７ｇ／ｃｍ３以上４．１ｇ／ｃｍ３以下に調整されていてよい。成形工程及び配向工程において型が成形体１０ｂ（金属粉末１０）に及ぼす圧力が低いほど、焼結工程直前の成形体１０ｂの密度が低い傾向がある。また、成形工程及び配向工程において型が成形体１０ｂ（金属粉末１０）に及ぼす圧力が低いほど、成形体１０ｂを構成する金属粉末１０が自由に回転し易く、磁場に沿って配向し易い。その結果、最終的に得られる希土類磁石の残留磁束密度が高まり易い。したがって、焼結工程直前の成形体１０ｂの密度が低いほど、希土類磁石の残留磁束密度が高まり易い、といえる。ただし、成形工程及び配向工程において型２が成形体１０ｂ（金属粉末１０）に及ぼす圧力が低過ぎる場合、成形体１０ｂの保形性（機械的強度）が不十分であり、分離工程に伴う成形体１０ｂと型２との摩擦により、成形体１０ｂの表面に位置する金属粉末１０の配向性が乱れる。その結果、最終的に得られる希土類磁石の残留磁束密度が低下する。したがって、焼結工程直前の成形体１０ｂの密度が低過ぎる場合、希土類磁石の残留磁束密度が低い。一方、成形工程から焼結工程に至るまでの間に成形体１０ｂ（金属粉末１０）に及ぶ圧力が高いほど、焼結工程直前の成形体１０ｂの密度が高く、成形体１０ｂの保形性（機械的強度）が高い。その結果、最終的に得られる希土類磁石における亀裂が抑制され易い。したがって、焼結工程直前の成形体１０ｂの密度が高いほど、希土類磁石における亀裂が抑制され易い。ただし、成形工程及び配向工程において型２が成形体１０ｂ（金属粉末１０）に及ぼす圧力が高過ぎる場合、スプリングバックに因り、成形体１０ｂに亀裂が形成され易く、成形体１０ｂから得られる希土類磁石に亀裂が残ってしまう。なお、スプリングバックとは、金属粉末１０を加圧して成形した後、圧力を解除した時に、成形体１０ｂが膨張する現象である。以上の通り、焼結工程直前の成形体１０ｂの密度は、希土類磁石の残留磁束密度及び亀裂に相関している。焼結工程直前の成形体１０ｂの密度が上記の範囲内に調整されることにより、希土類磁石の残留磁束密度が高まり易く、且つ希土類磁石における亀裂が抑制され易い。 The density of the compact 10b to be sintered in the sintering process (the density of the compact 10b immediately before the sintering process) is, for example, 3.0 g / cm 3 or more and 4.4 g / cm 3 or less, 3.2 g / cm 3 or more. It may be adjusted to 4.2 g / cm 3 or less, 3.4 g / cm 3 or more and 4.0 g / cm 3 or less, or 3.7 g / cm 3 or more and 4.1 g / cm 3 or less. The lower the pressure exerted by the mold on the molded body 10b (metal powder 10) in the molding process and the orientation process, the lower the density of the molded body 10b immediately before the sintering process. Further, the lower the pressure exerted by the mold on the molded body 10b (metal powder 10) in the molding process and the orientation process, the easier the metal powder 10 constituting the molded body 10b rotates and the easier it is to align along the magnetic field. As a result, the residual magnetic flux density of the finally obtained rare earth magnet tends to increase. Therefore, it can be said that the lower the density of the molded body 10b immediately before the sintering step, the higher the residual magnetic flux density of the rare earth magnet. However, when the pressure exerted by the mold 2 on the molded body 10b (metal powder 10) is too low in the molding process and the orientation process, the shape retention (mechanical strength) of the molded body 10b is insufficient and the molding accompanying the separation process. Due to the friction between the body 10b and the mold 2, the orientation of the metal powder 10 located on the surface of the molded body 10b is disturbed. As a result, the residual magnetic flux density of the rare earth magnet finally obtained decreases. Therefore, when the density of the compact 10b immediately before the sintering process is too low, the residual magnetic flux density of the rare earth magnet is low. On the other hand, the higher the pressure applied to the molded body 10b (metal powder 10) from the molding process to the sintering process, the higher the density of the molded body 10b immediately before the sintering process, and the shape retention ( High mechanical strength). As a result, cracks in the finally obtained rare earth magnet are easily suppressed. Therefore, the higher the density of the molded body 10b immediately before the sintering step, the easier the cracks in the rare earth magnet are suppressed. However, if the pressure exerted by the mold 2 on the molded body 10b (metal powder 10) is too high in the molding process and the orientation process, cracks are easily formed in the molded body 10b due to the springback, and the rare earth magnet obtained from the molded body 10b. Cracks will remain. The spring back is a phenomenon in which the molded body 10b expands when the pressure is released after the metal powder 10 is pressed and molded. As described above, the density of the compact 10b immediately before the sintering process correlates with the residual magnetic flux density and cracks of the rare earth magnet. By adjusting the density of the compact 10b immediately before the sintering step within the above range, the residual magnetic flux density of the rare earth magnet is likely to be increased, and cracks in the rare earth magnet are likely to be suppressed.
　焼結工程では、下型に載置された成形体１０ｂを、焼結用トレイの上に移してよい。焼結工程では、加熱工程用に載置された成形体１０ｂを、焼結用トレイの上に移してもよい。加熱工程において成形体１０ｂの保形性が向上しているため、成形体１０ｂを搬送用チャックで掴んで焼結用トレイ上に並べる際に、成形体１０ｂの破損が抑制される。 In the sintering step, the molded body 10b placed on the lower mold may be transferred onto a sintering tray. In the sintering step, the molded body 10b placed for the heating step may be transferred onto the sintering tray. Since the shape-retaining property of the molded body 10b is improved in the heating step, the molded body 10b is prevented from being damaged when the molded body 10b is gripped by the conveying chuck and arranged on the sintering tray.
　焼結工程では、複数の成形体１０ｂを焼結用トレイ上に載置してよく、焼結用トレイ上に載置された複数の成形体１０ｂを一括して加熱してよい。多数の成形体１０ｂを狭い間隔で焼結用トレイ上に並べて、多数の成形体１０ｂを一括して加熱することにより、希土類磁石の生産性が向上する。 In the sintering step, the plurality of molded bodies 10b may be placed on the sintering tray, and the plurality of molded bodies 10b placed on the sintering tray may be heated together. By arranging a large number of compacts 10b on a sintering tray at a narrow interval and heating the numerous compacts 10b at once, the productivity of the rare earth magnet is improved.
　焼結用トレイの組成は、焼結時に成形体１０ｂと反応し難く、且つ成形体１０ｂを汚染する物質を生成し難い組成物であればよい。例えば、焼結用トレイは、モリブデン又はモリブデン合金から構成されていてよい。 The composition of the sintering tray may be any composition that does not easily react with the molded body 10b during sintering and does not easily generate substances that contaminate the molded body 10b. For example, the sintering tray may be made of molybdenum or a molybdenum alloy.
　焼結温度は、例えば９００℃以上１２００℃以下であればよい。焼結時間は、例えば０．１時間以上１００時間以下であればよい。焼結工程を繰り返してもよい。焼結工程では、不活性ガス又は真空中で成形体１０ｂを加熱してよい。不活性ガスは、アルゴン等の希ガスであってよい。 The sintering temperature may be 900 ° C. or more and 1200 ° C. or less, for example. The sintering time may be, for example, from 0.1 hours to 100 hours. The sintering process may be repeated. In the sintering step, the molded body 10b may be heated in an inert gas or vacuum. The inert gas may be a noble gas such as argon.
　焼結体に対して時効処理を施してよい。時効処理では、焼結体を例えば４５０℃以上９５０℃以下で熱処理してよい。時効処理では、焼結体を例えば０．１時間以上１００時間以下の間、熱処理してよい。時効処理は不活性ガス又は真空中で行えばよい。時効処理は、温度の異なる多段階の熱処理から構成されてもよい。 Aging treatment may be applied to the sintered body. In the aging treatment, the sintered body may be heat-treated at, for example, 450 ° C. or more and 950 ° C. or less. In the aging treatment, the sintered body may be heat-treated for 0.1 hours to 100 hours, for example. The aging treatment may be performed in an inert gas or vacuum. The aging treatment may be composed of a multi-stage heat treatment at different temperatures.
　焼結体を切削又は研磨してもよい。焼結体の表面に保護層を形成してもよい。保護層は、例えば、樹脂層、又は無機物層（例えば、金属層若しくは酸化物層）であってよい。保護層の形成方法は、例えば、めっき法、塗布法、蒸着重合法、気相法、又は化成処理法であってよい。 The sintered body may be cut or polished. A protective layer may be formed on the surface of the sintered body. The protective layer may be, for example, a resin layer or an inorganic layer (for example, a metal layer or an oxide layer). The method for forming the protective layer may be, for example, a plating method, a coating method, a vapor deposition polymerization method, a gas phase method, or a chemical conversion treatment method.
　本発明によれば、希土類磁石等の工業製品の製造過程において、無機粉末から形成される成形体の成形不良を抑制することができる。 According to the present invention, in the process of manufacturing industrial products such as rare earth magnets, it is possible to suppress molding defects of a molded body formed from inorganic powder.
　２…型、３…ダイ、４，４ａ…パンチ、６…筒状の側型、８…下型、１０…無機粉末、１０ａ…バリ、１０ｂ…成形体。

  2 ... Mold, 3 ... Die, 4, 4a ... Punch, 6 ... Cylindrical side mold, 8 ... Lower mold, 10 ... Inorganic powder, 10a ... Burr, 10b ... Molded body.

Claims (6)

  1. 　焼結体を有する工業製品の製造方法であって、
    　ダイ内に供給された無機粉末をパンチで加圧して、成形体を形成する成形工程と、
    　前記成形体を焼結させて、前記焼結体を得る焼結工程と、
    を備え、
    　前記成形工程では、前記無機粉末を前記パンチで加圧した後、前記パンチを引き戻し、再び前記無機粉末を前記パンチ又は別のパンチで加圧する、
    　焼結体を有する工業製品の製造方法。     A method for producing an industrial product having a sintered body,
    A molding process for forming a compact by pressing the inorganic powder supplied into the die with a punch,
    Sintering the molded body to obtain the sintered body; and
    With
    In the molding step, after pressing the inorganic powder with the punch, the punch is pulled back, and the inorganic powder is pressed again with the punch or another punch.
    A method for producing an industrial product having a sintered body.
  2. 　前記無機粉末の真密度が、Ｄ［ｇ／ｃｍ３］と表され、
    　前記成形体の嵩密度が、ｄ［ｇ／ｃｍ３］と表され、
    　前記成形体の相対密度が、１００・ｄ／Ｄ［％］と定義され、
    　前記成形工程において、前記相対密度が４０％以上６０％以下に調整される、
    　請求項１に記載の工業製品の製造方法。     The true density of the inorganic powder is expressed as D [g / cm 3 ],
    The bulk density of the molded body is expressed as d [g / cm 3 ],
    The relative density of the molded body is defined as 100 · d / D [%],
    In the molding step, the relative density is adjusted to 40% or more and 60% or less.
    The manufacturing method of the industrial product of Claim 1.
  3. 　前記パンチが前記無機粉末に及ぼす圧力を、０．０４９ＭＰａ以上２０ＭＰａ以下に調整する、
    請求項１又は２に記載の工業製品の製造方法。     Adjusting the pressure exerted on the inorganic powder by the punch to 0.049 MPa or more and 20 MPa or less,
    The manufacturing method of the industrial product of Claim 1 or 2.
  4. 　前記無機粉末が顆粒である、
    請求項１～３のいずれか一項に記載の工業製品の製造方法。     The inorganic powder is a granule,
    The method for producing an industrial product according to any one of claims 1 to 3.
  5. 　前記パンチと前記ダイによって保持された前記成形体に磁場を印加して、前記成形体に含まれる前記無機粉末を配向させる配向工程を更に備え、
    　前記配向工程後に前記焼結工程が実施され、
    　前記無機粉末が、磁性粉末であり、
    　前記パンチの少なくとも一部が絶縁性であり、
    　前記ダイの少なくとも一部が絶縁性であり、
    　前記焼結体を有する前記工業製品が、焼結磁石である、
    請求項１～４のいずれか一項に記載の工業製品の製造方法。     An orientation step of orienting the inorganic powder contained in the shaped body by applying a magnetic field to the shaped body held by the punch and the die;
    The sintering step is performed after the orientation step,
    The inorganic powder is a magnetic powder;
    At least a portion of the punch is insulative;
    At least a portion of the die is insulative;
    The industrial product having the sintered body is a sintered magnet.
    The method for producing an industrial product according to any one of claims 1 to 4.
  6. 　前記磁性粉末が、希土類元素を含む金属粉末であり、
    　前記焼結磁石が、希土類磁石である、
    請求項５に記載の工業製品の製造方法。

          The magnetic powder is a metal powder containing a rare earth element,
    The sintered magnet is a rare earth magnet,
    The manufacturing method of the industrial product of Claim 5.

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Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS4825978A (en) * 1971-08-10 1973-04-04

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS4825978A (en) * 1971-08-10 1973-04-04

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