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WO1999007006A1 - Procede de production d'un aimant fritte annulaire anisotrope radial a base r-t-b - Google Patents

Procede de production d'un aimant fritte annulaire anisotrope radial a base r-t-b Download PDF

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Publication number
WO1999007006A1
WO1999007006A1 PCT/JP1998/003376 JP9803376W WO9907006A1 WO 1999007006 A1 WO1999007006 A1 WO 1999007006A1 JP 9803376 W JP9803376 W JP 9803376W WO 9907006 A1 WO9907006 A1 WO 9907006A1
Authority
WO
WIPO (PCT)
Prior art keywords
density
sintered magnet
magnet
mold
shaped sintered
Prior art date
Application number
PCT/JP1998/003376
Other languages
English (en)
Japanese (ja)
Inventor
Wataru Takahashi
Seiichi Kohara
Naoyuki Ishigaki
Original Assignee
Sumitomo Special Metals Co., Ltd.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Sumitomo Special Metals Co., Ltd. filed Critical Sumitomo Special Metals Co., Ltd.
Publication of WO1999007006A1 publication Critical patent/WO1999007006A1/fr

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
    • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
    • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
    • H01F1/032—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials
    • H01F1/04—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys
    • H01F1/047—Alloys characterised by their composition
    • H01F1/053—Alloys characterised by their composition containing rare earth metals
    • H01F1/055—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5
    • H01F1/057—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B
    • H01F1/0571—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes
    • H01F1/0575—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes pressed, sintered or bonded together
    • H01F1/0577—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes pressed, sintered or bonded together sintered
    • 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
    • H01F41/0253—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 for manufacturing permanent magnets
    • H01F41/0273—Imparting anisotropy
    • H01F41/028—Radial anisotropy

Definitions

  • the present invention relates to an improvement in a method for manufacturing an RTB-based radially anisotropic ring-shaped sintered magnet having high strength and high magnetic properties used for applications such as VCM, AC servomotors, and small DC motors.
  • the magnetic alloy powder that has been supplied and filled in the mold is molded in a magnetic field with the specific density in the mold before molding in a magnetic field before molding in a magnetic field, and molded in a magnetic field.
  • the present invention relates to a method for manufacturing a radially anisotropic ring-shaped sintered magnet based on RTB.
  • Radial anisotropic ring-shaped magnets as shown in Fig. 1 are widely used in VCMs, AC servomotors, actuators for small DC motors, and especially in step motors. It has been mass-produced as sintered ferrite magnets or Sm-Co bonded magnets.
  • rare earth magnets especially RTB systems with excellent magnetic properties (where R is at least one of the rare earth elements including Y, and T is Fe or Fe and Co force) Radial anisotropic ring-shaped sintered magnets manufactured using magnet alloy powder have been put to practical use.
  • the outline of the conventional manufacturing process that has been employed for manufacturing the radially anisotropic ring-shaped sintered magnet is as follows (1) to (6).
  • arrow 2 indicates the axial direction
  • arrows 3 and 4 indicate the radial direction.
  • the R-T-B magnet alloy has about 2-3 times higher mechanical strength such as tension and bending than ferrite magnet material and Sm-Co magnet alloy.
  • the radially anisotropic ring-shaped sintered magnet using the RTB-based magnet alloy has an internal crack in the axial direction of the inner peripheral surface of the radially anisotropic ring-shaped sintered magnet 1. It is observed that it occurs quite frequently after sinter cooling and machining.
  • the cracks shown in Fig. 2 are considered to be due to the circumferential stress (hoop stress) generated on the inner surface of the radial ring exceeding the strength of the magnet material.
  • this crack is formed in the radial direction inside the ring due to the anisotropy of the thermal shrinkage in the radial direction and the axial direction below the Curie point (about 320 ° C) of the magnet alloy. It was found that this was caused by large residual stresses that occurred near the material strength (powder and powder metallurgy, vol. 43.7, 1996, p940).
  • the present invention provides an RTB-based radial that can reduce axial cracks on the inner peripheral surface of the ring of a radially anisotropic ring-shaped sintered magnet that has occurred after firing and can greatly improve the production yield.
  • the purpose is to provide a method for manufacturing an anisotropic ring-shaped sintered magnet.
  • the inventors have found that in order to reduce the inner surface cracking of the radially anisotropic ring-shaped sintered magnet, it is only necessary to reduce the circumferential (inner surface) tensile stress generated at one point or less after the sintering and cooling. Attention was paid to the method for reducing the tensile residual stress, and as a result of the detailed examination, the following findings (a) to (d) were obtained, and the present invention was completed.
  • orientation in the present invention means that the direction of the easy axis of magnetization (C-axis direction) of the RTB-based magnet alloy powder, which is substantially single magnetic domain particles, is uniformed by a magnetic field. In this case, it means applying a magnetic field in the radial direction and aligning the C axis of the powder particles in the radial direction.
  • the inventors of the present invention believe that the reduction of the number of crystals in which the C axis of the alloy powder is oriented in the radial direction may be achieved by reducing the radial orientation magnetic field strength during press molding. An attempt was made to reduce the degree of orientation by reducing the size, but it was difficult to control the degree of orientation, and the strength of the sintered ring did not improve.
  • the magnetic field is generated by a pair of upper and lower coils, and the intensity of the magnetic field can be changed by the current flowing through the coil.
  • FIG. 1 is a perspective explanatory view showing the entire radially anisotropic ring-shaped sintered magnet.
  • FIG. 2 is a perspective explanatory view showing a crack state of the radially anisotropic ring-shaped sintered magnet.
  • 3A to 3D are cross-sectional explanatory views of a molding die showing a press molding step according to the present invention. BEST MODE FOR CARRYING OUT THE INVENTION
  • the rare earth sintered permanent magnet produced according to the present invention is substantially made of an RTB alloy having a composition represented by R 2 T 14 B.
  • the composition of the alloy is substantially R 2 T 14 B As long as an alloy composed of crystal grains is formed, there is no particular limitation, but generally, in terms of% by weight.
  • the R content In general, the smaller the R content, the higher the residual magnetic flux density. However, if the R content is less than 27%, an iron-rich phase equivalent to ⁇ -Fe precipitates, adversely affects the pulverization, and the residual magnetic flux density also decreases. No more drops. On the other hand, if the R content exceeds 38%, the residual magnetic flux is conspicuously reduced, and high magnet properties cannot be obtained. Therefore, 27 to 38 wt% is desirable.
  • B is desirably in the range of 0.2 to 4.5 wt%.
  • the T content is desirably 51 to 72% by weight.
  • Co is desirably 30% by weight or less of the entire T.
  • one or more elements such as Al, Cr, Mn, Mg, Si, Cu, C, Nb, Sn, Ga, W, V, Zr, Ti, and Mo are added. However, if these total exceed 6 wt%, the residual magnetic flux density will decrease.
  • an R-T-B-based magnetic alloy powder An example of a method for producing an R-T-B-based magnetic alloy powder will be described.
  • an R-T-B-based alloy having a predetermined composition is melted by dissolving a mixture of appropriate raw material powders. This dissolution is performed, for example, in a non-oxidizing atmosphere such as an argon atmosphere.
  • the obtained alloy melt is quenched and solidified into a thin plate or flake (scale) with a thickness of 0.05 to 3 mm by the single-hole method (one-way solidification) or the twin-roll method (two-way solidification).
  • a rapidly solidified alloy material (master alloy) having a homogeneous structure with a diameter of 3 to 30 ⁇ is obtained.
  • the single-roll method is more preferable because of its higher efficiency and quality stability. Of course, there is no problem in using ordinary type-I manufactured ingot alloys.
  • the thin plate etc. obtained by rapid solidification described above is pulverized so that powder suitable for powder metallurgy can be obtained.
  • ordinary hydrogenation and jet milling methods may be applied.
  • the RTB-based permanent magnet alloy sheet obtained by the rapid solidification method shows better pulverizability than the ⁇ type ingot alloy, and has an average FSS particle size of 3 to 4 pm (FSS particle size: powder average particle size obtained by air permeation method). Fine powder having a narrow particle size distribution width can be easily obtained.
  • a radially anisotropic ring-shaped green compact is press-molded.
  • the molding die is formed in the radial direction from the center of the inner surface of the ring as disclosed in Japanese Patent Application Laid-Open No. 8-083728.
  • a magnetic circuit design that allows magnetic flux to flow through is desirable.
  • 3A to 3D are cross-sectional explanatory views of a molding die showing a press molding step.
  • the feeder box moves onto a molding die 10 and is subjected to the action of a vibration shaker or gravity to form the molding metal.
  • the magnet alloy powder 13 is filled in the molding chamber 11 formed by the space of the mold 10 and the lower punch 12 (FIG. 3A).
  • the packing density using a feeder box is usually about 1.7 to 2.0 g / cm 3 .
  • the upper punch 14 is lowered, and the magnetic alloy powder 13 is pressed and pressed with the lower punch 12 until the specific density becomes 2.3 to 3.0 g / cm 3 , and then, in the radial direction.
  • the magnetic field strength is usually about 8 to 10 OkEe, but there is no problem in orientation even in a static magnetic field or a pulse magnetic field.
  • the upper punch 14 is further lowered to compress the green compact density in the molding chamber 11 to 3.9 to 4.5 g / cm 3 . Remove the green compact.
  • the reason why the magnet alloy powder is filled in the mold at a specific density of 2.3 to 3.0 g / cm 3 or the supplied magnet alloy powder is compressed in the mold to control the specific density within the above range. is in the 2.3 ⁇ 3.0g / cm3 increases the specific density of the molded material during the orientation, be to enable control of the predetermined orientation, more fully oriented in the radial oriented magnetic field is less than 2.3Gm 3 This is because the internal residual stress increases after sintering, and 3.0 g / cm 3 At specific densities exceeding, even when a radial orientation magnetic field is applied, the powder is entangled with each other, the C axis is unlikely to be oriented in the radial direction, and the residual stress on the inner surface after sintering is reduced. This is because it causes problems in use and is not preferable.
  • the specific density of the magnetic alloy powder after being supplied and filled in the mold is set to 2.3 to 3.0 g / cm 3 , radially oriented and then compressed to obtain a radial anisotropic ring-shaped pressure.
  • the magnetic field strength can be reduced by lowering the coil current.However, the coil current is usually 500 A to 700 A. At 1.7 to 2.0 g / cm 3 , the degree of C-axis orientation did not decrease, and the ring strength (measured by a crush test) was small. Therefore, it is preferable to make the filling density high during orientation because the orientation degree can be easily controlled.
  • the molding die was naturally filled by a gravity or a vibration shaker from a feeder, but the filling density at this time is only about 1.7 to 2.0 g / cm 3 .
  • the packing density of the powder in the mold is set in advance to the specific density of the present invention.
  • the packing density In order to increase the packing density to 2.3 to 3.0 g / cm3, it is preferable to increase the packing density by ultrasonically vibrating the lower mold or by attaching a device for pushing the powder into the mold in the feeder.
  • a device for pushing the powder into the mold in the feeder For example, if a general vacuum suction device is used in combination, the packing density can be easily controlled, which is convenient.
  • the radial direction orientation direction A green compact with a density of 0.9 to 4.5 g / cm 3 with controlled properties can be formed efficiently.
  • a method for measuring the degree of orientation of the radial ring a small piece is cut out from the ring-shaped sintered body and the magnetic properties are measured (Br, iHc, (BH) max), or the (004) plane is measured by the X-ray pole figure measurement method. There is a method of measuring the degree of integration.
  • the residual tensile stress on the inner surface can be measured by a strain gauge or estimated by a ring crush test.
  • the obtained ring-shaped green compact is sintered by a conventionally known firing method.
  • the sintering temperature is preferably in the range of 950 to 1150 ° C
  • the aging treatment is performed in a low-pressure argon gas at a temperature of 1030 ° C. C. to 1080.degree. C. for 1 hour to 4 hours.
  • the quenched alloy was pulverized by a conventional hydrogenation pulverization method and a jet mill pulverization method to obtain a magnet powder having an FSS average particle size of 3.5 ⁇ .
  • This pulverized powder was put into a feeder box and supplied to a radial anisotropic ring-shaped molding die. At this time, the packing density of the powder in the mold was 1.98 g / cm 3 .
  • molding was performed under the following four conditions (a) to (2).
  • the green compact is a ring product with an outer diameter of 56.5mm x inner diameter of 43.4mm x height of 30.5mm.
  • (I) remains packing density of the powder in the mold is 1.98 g / cm 3, in the magnetic field in the radial direction of LOkOe, perform press molding at a molding pressure of 1.2 t / cm 2, a green compact density 4.2 g / When molding a green compact of cm 3
  • the obtained green compact is heated and sintered at 1045 ° C for 4 hours in argon.After cooling, it is subjected to an aging treatment at 500 ° C for 1 hour in argon to obtain a radially anisotropic ring-shaped sintered magnet.
  • Table 1 summarizes the results of packing density (specific density), green compact density, sintered body ring strength, and magnetic properties.
  • the ring strength is the radial crushing strength represented by the following formula (JIS Z 2507).
  • P is the load
  • D 0 is the ring outside diameter
  • t is the ring thickness
  • W is Ru ring height Sadea.
  • the magnetic properties are slightly lowered, but the radial crushing strength is improved, and the balance between the two properties is improved, so that there is no problem in use. Further, in the comparative examples outside the range of the present invention, the radial crushing strength is improved, and the reduction in the magnetic properties is too large to be used. Therefore, the effectiveness of the present invention is clear.
  • the powder was put into a feeder box and supplied to a mold for molding a radially anisotropic ring-shaped sintered magnet. At this time
  • a windmill with a diameter of 40 mm having eight blades in the feeder will be installed in the part of the feeder that is directly above the hall, and will be fed at a rotation speed of 60 rpm.
  • press molding was performed at a molding pressure of 1.2 t / cm 2 while applying a magnetic field in the radial direction of lOkOe to form a green compact having a green density of 4.2 g / cm 3 .
  • the compact size is the same as in the first embodiment.
  • the method of the present invention enables the mold to be filled with the magnet alloy powder at a higher packing density than the conventional example shown in Table 1, so that there is little decrease in the magnetic properties and the crushing strength is increased. It has become clear that it can be improved.
  • the present invention relates to a method for manufacturing an RTB-based radially anisotropic ring-shaped sintered magnet, in which a specific density of a magnetic alloy powder filled in a mold before molding in a magnetic field is set to a predetermined range of density. , Which can reduce axial cracks on the inner peripheral surface of the ring, which often occur after cooling or machining, is extremely effective in reducing costs and improving quality by improving product yield, and has high industrial value .
  • a ring-shaped sintered magnet manufactured without causing cracks has the advantage that it can be applied to motors that could not be used conventionally because its ring strength is improved.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Manufacturing & Machinery (AREA)
  • Powder Metallurgy (AREA)
  • Manufacturing Cores, Coils, And Magnets (AREA)
  • Hard Magnetic Materials (AREA)

Abstract

L'invention porte sur un procédé de production d'un aimant fritté annulaire anisotrope radial à base R-T-B permettant de réduire les craquelures de l'aimant fritté qui se forment, après frittage, sur sa surface périphérique interne dans un axe axial, ce procédé permettant également d'améliorer considérablement le rendement. Le procédé de l'invention consiste à alimenter et tasser la poudre d'alliage de l'aimant dans un moule dans un champ magnétique de densité de tassement supérieure aux densités de tassement traditionnelles avant moulage dans un champ magnétique ou, en d'autres termes, à augmenter la densité du matériau de moulage au moment de l'orientation à une valeur prédéterminée et à réguler cette orientation. Le procédé consiste notamment à compresser la poudre d'alliage tassée dans le moule à une densité spécifique comprise entre 2,3 et 3,0 g/cm3, le moulage étant ensuite effectué dans le champ magnétique. Selon une autre variante, le procédé consiste à amener à l'avance la poudre d'alliage à une densité spécifique comprise entre 2,3 et 3,9 g/cm3 au moyen, par exemple, d'un appareil d'alimentation de poudre à pression élevée, d'un appareil à oscillation ultrasonique ou d'un appareil à vide, et à mouler la poudre dans le champ magnétique. Il est ainsi possible de réguler l'orientation, de réduire l'effort de traction dans le sens circonférentiel (surface interne) se produisant au-dessous d'un point de Curie après frittage et refroidissement, et de réduire éventuellement les craquelures de la surface interne de l'aimant fritté.
PCT/JP1998/003376 1997-07-30 1998-07-29 Procede de production d'un aimant fritte annulaire anisotrope radial a base r-t-b WO1999007006A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP9/219914 1997-07-30
JP9219914A JPH1154352A (ja) 1997-07-30 1997-07-30 Ｒ−ｔ−ｂ系ラジアル異方性リング状焼結磁石の製造方法

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WO1999007006A1 true WO1999007006A1 (fr) 1999-02-11

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6432158B1 (en) 1999-10-25 2002-08-13 Sumitomo Special Metals Co., Ltd. Method and apparatus for producing compact of rare earth alloy powder and rare earth magnet
US7618496B2 (en) * 2001-10-31 2009-11-17 Shin-Etsu Chemical Co., Ltd. Radial anisotropic sintered magnet and its production method, magnet rotor using sintered magnet, and motor using magnet rotor

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
TWI298892B (en) 2002-08-29 2008-07-11 Shinetsu Chemical Co Radial anisotropic ring magnet and method of manufacturing the ring magnet
JP2006108591A (ja) * 2004-10-08 2006-04-20 Tdk Corp 希土類焼結磁石及びその製造方法
FR3008224B1 (fr) 2013-07-08 2015-08-07 Commissariat Energie Atomique Aimant fritte annulaire a aimantation radiale, presentant une tenue mecanique renforcee
JP2024119308A (ja) * 2023-02-22 2024-09-03 千住金属工業株式会社 摺動部材および摺動部材を製造する方法

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0748604A (ja) * 1993-08-02 1995-02-21 Inter Metallics Kk 圧粉成型体成型装置
JPH0778710A (ja) * 1993-09-06 1995-03-20 Sumitomo Special Metals Co Ltd Ｒ−Ｆｅ−Ｂ系永久磁石材料の製造方法

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0748604A (ja) * 1993-08-02 1995-02-21 Inter Metallics Kk 圧粉成型体成型装置
JPH0778710A (ja) * 1993-09-06 1995-03-20 Sumitomo Special Metals Co Ltd Ｒ−Ｆｅ−Ｂ系永久磁石材料の製造方法

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6432158B1 (en) 1999-10-25 2002-08-13 Sumitomo Special Metals Co., Ltd. Method and apparatus for producing compact of rare earth alloy powder and rare earth magnet
US6756010B2 (en) 1999-10-25 2004-06-29 Sumitomo Special Metals Co., Ltd. Method and apparatus for producing compact of rare earth alloy powder and rare earth magnet
US7618496B2 (en) * 2001-10-31 2009-11-17 Shin-Etsu Chemical Co., Ltd. Radial anisotropic sintered magnet and its production method, magnet rotor using sintered magnet, and motor using magnet rotor
US7948135B2 (en) 2001-10-31 2011-05-24 Shin-Etsu Chemical Co., Ltd. Radial anisotropic sintered magnet and its production method, magnet rotor using sintered magnet, and motor using magnet rotor

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