JP2019149405A - Ferrite sintered magnet and rotary machine - Google Patents

Abstract

To provide a ferrite sintered magnet having both of a high coercive force and a high residual magnetic flux density.SOLUTION: A ferrite sintered magnet 10 comprises a ferrite phase having a crystal structure of a magnetoplumbite type of hexagonal crystal. In the ferrite sintered magnet 10, a Ga content is 0.027-0.217 mass% in terms of GaO. The ferrite sintered magnet 10 has a composition represented by RAFeCo, where R is at least one element selected from rare earth elements including Y, and A is at least one element selected from Ba and Ca or a combination of Ca and Sr and x, y and m satisfy the following formulas (1), (2) and (3): 0.2≤x≤0.8 (1); 0.1≤y≤0.65 (2); and 3≤m<14 (3).SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to a ferrite sintered magnet and a rotating machine including the same.

As a magnetic material used for a ferrite sintered magnet, Ba ferrite, Sr ferrite, and Ca ferrite having a hexagonal crystal structure are known. As the crystal structure of such ferrite, magnetoplumbite type (M type), W type, and the like are known. Among these, magnetoplumbite type (M type) ferrite is mainly used as a magnet material for motors and the like. M-type ferrite is usually represented by the general formula of AFe ₁₂ O ₁₉ .

  Generally, residual magnetic flux density (Br) and coercive force (HcJ) are used as indicators of magnetic properties of sintered ferrite magnets. Conventionally, from the viewpoint of improving Br and HcJ, attempts have been made to add various elements different from the constituent elements of ferrite. For example, Patent Document 1 proposes a magnetoplumbite type ferrite particle powder containing Al or Ga. Further, Patent Document 2 proposes a ferrite magnetic material in which a hexagonal W-type ferrite forms a main phase and contains a Ga component.

Japanese Patent Laid-Open No. 2-66902 JP 2009-280498 A

  Ferrite sintered magnets are used in rotating machines such as motors and generators, for example. Such a ferrite sintered magnet is required to have both sufficiently high coercive force (HcJ) and residual magnetic flux density (Br). Here, since HcJ and Br are normally in a trade-off relationship, it is expected to establish a technique for improving both characteristics of the ferrite sintered magnet.

  Accordingly, in one aspect, the present disclosure provides a sintered ferrite magnet having both a high coercive force and a high residual magnetic flux density. In another aspect, the present disclosure provides a rotating machine including such a sintered ferrite magnet.

In one aspect, the present disclosure is a ferrite sintered magnet including a ferrite phase having a hexagonal magnetoplumbite-type crystal structure, and the Ga content is 0.027 to 0 in terms of Ga ₂ O _3. Provided is a sintered ferrite magnet that is 217% by weight.

The ferrite sintered magnet has a high coercive force and a high residual magnetic flux density. The reason is guessed as follows. The following relational expression (a) is established between the coercive force (HcJ) and the saturation magnetic polarization (J _s ) of ferrite. From the relationship of equation (a), HcJ increases as the saturation magnetic polarization (J _s ) decreases. In the formula (a), mu ₀ denotes the permeability of vacuum, K _A represents the anisotropy constant.
HcJ = 0.48 × (2 × K _A /Js−0.5×J _s / μ ₀ ) (a)

Here, Br and J _s of ferrite is proportional to the following equation (b). From the relationship of the formula (b), Br increases as the saturation magnetic polarization (J _s ) increases. From this, it can be said that Br and HcJ are normally in a trade-off relationship.
_{Brα (1-a) × J} s × d f / d 0 × f 0 (b)

Wherein (b), a is the volume ratio of the non-magnetic material, a d _f is the density of the sintered ferrite magnet, d ₀ is the true density of the sintered ferrite magnet, f ₀ denotes the orientation ratio, respectively. In the ferrite sintered magnet of the present disclosure, it is presumed that saturation magnetic polarization (J _s ) is reduced by containing a predetermined amount of Ga, and as a result, HcJ is improved. Here, as shown in the above formula (b), when the saturation magnetic polarization (J _s ) decreases, Br usually tends to decrease. However, in the sintered ferrite magnet of the present disclosure, it is presumed that the effect of improving the orientation ratio f ₀ is larger than the effect of decreasing the saturation magnetic polarization (J _s ), and as a result, Br is also improved. . Therefore, the ferrite sintered magnet can have a high coercive force and a high residual magnetic flux density.

The ferrite magnet is composed of at least one element selected from rare earth elements including Y, and R, and Ca or at least one element selected from Ca and Sr and Ba, and the composition is R _1-x. when expressed in _{a x Fe m-y Co y} , x, y and m, the following formula (1), it is preferable to satisfy (2) and (3). Thereby, the coercive force and the residual magnetic flux density can be further improved.
0.2 ≦ x ≦ 0.8 (1)
0.1 ≦ y ≦ 0.65 (2)
3 ≦ m <14 (3)

The ferrite magnet preferably has a B content of 0.1 to 0.6% by mass in terms of B ₂ O ₃ . Thereby, the coercive force can be further increased.

  In another aspect, the present disclosure provides a rotating machine including the ferrite sintered magnet. The ferrite sintered magnet has a high coercive force and a high residual magnetic flux density. By providing such a ferrite sintered magnet, the output of the rotating machine can be improved. Moreover, since it has a high coercive force, the ferrite sintered magnet can be thinned and mounted on a rotating machine. Therefore, it can contribute to size reduction of rotating machines, such as a motor or a generator.

  In one aspect, the present disclosure can provide a sintered ferrite magnet having both a high coercive force and a high residual magnetic flux density. In another aspect, the present disclosure can provide a rotating machine including such a sintered ferrite magnet.

FIG. 1 is a perspective view schematically showing one embodiment of a sintered ferrite magnet. FIG. 2 is a schematic cross-sectional view of a motor that is an example of a rotating machine. 3 is a cross-sectional view of the motor of FIG. 2 taken along the line III-III. FIG. 4 is a graph showing the relationship between the Ga content in terms of Ga ₂ O ₃ and Br in Production Examples 1-1 to 1-5. FIG. 5 is a graph showing the relationship between Ga content in terms of Ga ₂ O ₃ and HcJ in Production Examples 1-1 to 1-5. FIG. 6 is a graph showing the relationship between the Ga content in Ga ₂ O ₃ conversion and the square shape in Production Examples 1-1 to 1-5. FIG. 7 is a graph showing the relationship between x and Br in a production example containing Ga and a production example not containing Ga. FIG. 8 is a graph showing the relationship between x and HcJ in a production example containing Ga and a production example not containing Ga. FIG. 9 is a graph showing the relationship between y and Br in a production example containing Ga and a production example not containing Ga. FIG. 10 is a graph showing the relationship between y and HcJ in a production example containing Ga and a production example not containing Ga. FIG. 11 is a graph showing the relationship between m and Br in a production example containing Ga and a production example not containing Ga. FIG. 12 is a graph showing the relationship between m and HcJ in a production example containing Ga and a production example not containing Ga.

  Hereinafter, some embodiments will be described with reference to the drawings in some cases. In the description, the same reference numerals are used for the same elements or elements having the same function, and redundant description is omitted in some cases. The dimensional ratio of each member is not limited to the illustrated ratio.

  FIG. 1 is a perspective view schematically showing a ferrite sintered magnet according to one embodiment. The anisotropic sintered ferrite magnet 10 has a shape that is curved so that the end surface has an arc shape, and generally has a shape called an arc segment shape, a C shape, a roof shape, or an arc shape. ing. The ferrite sintered magnet 10 is suitably used as a magnet for a rotating machine such as a motor and a generator. However, the application of the sintered ferrite magnet is not limited to the above. Further, the shape of the ferrite sintered magnet is not limited to the shape of FIG.

  The sintered ferrite magnet preferably contains a ferrite phase having a hexagonal magnetoplumbite type crystal structure as a main phase. In the present disclosure, the “main phase” refers to a crystal phase that is contained most in a sintered ferrite magnet. The ferrite sintered magnet may contain a grain boundary phase as a crystal phase (different phase) different from the ferrite phase.

The content of Ga (gallium) in the ferrite sintered magnet is 0.027 to 0.217% by mass in terms of Ga ₂ O ₃ . From the viewpoint of further improving HcJ and Br, the content of Ga may be 0.1 to 0.22% by mass or 0.15 to 0.2% by mass. The reason why the magnetic characteristics are improved by the inclusion of Ga, believed to improve the orientation ratio f _0. That is, in the ferrite magnet of this embodiment, it is considered that the saturation magnetic polarization is reduced and HcJ is increased. Then, usually, though Br the saturation magnetic polarization is small tends to decrease, the influence of the saturation magnetic polarization by improving the orientation ratio f ₀ decreases, it believed Br is high.

From the viewpoint of improving the coercive force, the B content in the sintered ferrite magnet may be 0.1 to 0.6% by mass in terms of B ₂ O ₃ . From the viewpoint of further increasing the magnetic properties, the B content may be 0.5% by mass or less, or 0.4% by mass or less. From the same viewpoint, the content of B may exceed 0.1% by mass or may exceed 0.2% by mass.

The overall composition of the ferrite sintered magnet may satisfy the following formulas (1), (2) and (3), for example, when expressed by the following general formula (I). In the general formula (I), x, y, and m represent a molar basis ratio. In the general formula (I), R represents at least one element selected from rare earth elements including Y, and A represents an element composed of Ca, or Ca and one or both of Sr and Ba.
_{R 1-x A x Fe m} -y Co y (I)
0.2 ≦ x ≦ 0.8 (1)
0.1 ≦ y ≦ 0.65 (2)
3 ≦ m <14 (3)

  X in the general formula (I) may be 0.7 or less or 0.6 or less from the viewpoint of further increasing the coercive force. From the viewpoint of further increasing the residual magnetic flux density, x may be 0.25 or more, or 0.3 or more.

  Y in the general formula (I) may be 0.15 or more, or 0.2 or more from the viewpoint of further increasing the coercive force and the residual magnetic flux density. From the same viewpoint, y may be 0.55 or less, and may be 0.5 or less. m in the general formula (I) is from the viewpoint of further increasing the coercive force and the residual magnetic flux density. It may be 4 or more, or 5 or more. From the same viewpoint, m in the general formula (I) may be 12 or less, or 11 or less.

The ferrite sintered magnet may satisfy formulas (4), (5), and (6).
0.25 ≦ x ≦ 0.7 (4)
0.15 ≦ y ≦ 0.55 (5)
4 ≦ m ≦ 12 (6)
By satisfying the above formulas (4), (5) and (6), both the coercive force and the residual magnetic flux density can be achieved at a higher level.

A in the general formula (I) preferably contains Ca or Ca and Sr as the main component from the viewpoint of increasing the magnetic properties. A may consist of only Ca or only Ca and Sr.
The content ratio of each element represented by the general formula (I) can be measured by fluorescent X-ray analysis. In addition, the content ratio of each element shown by the general formula (I) is usually the same as the blend ratio of each raw material in the blending step described later. The contents of Ga (gallium) and B (boron) can be measured by inductively coupled plasma emission spectroscopy (ICP emission spectroscopy).

  R in the general formula (I) is one or more selected from the group consisting of La (lanthanum) or La (lanthanum) and Ce (cerium), Pr (praseodymium), Nd (neodymium) and Sm (samarium). It is preferable to contain these elements. R may consist only of La.

  The sintered ferrite magnet may contain an element not shown in the general formula (I) as a subcomponent. The ferrite sintered magnet may contain at least one of Si and Na as a subcomponent. These subcomponents may be included in the sintered ferrite magnet as, for example, respective oxides or composite oxides.

The Si content in the ferrite sintered magnet may be, for example, 3% by mass or less in terms of Si converted to SiO ₂ . From the viewpoint of further increasing the magnetic properties, the content of Si in the sintered ferrite magnet may be less than 0.3% by mass when Si is converted to SiO ₂ . From the same viewpoint, the total content of Si and B in the sintered ferrite magnet may be 0.1 to 0.8% by mass when Si and B are converted into SiO ₂ and B ₂ O ₃ , respectively. 0.2-0.5 mass% may be sufficient.

The content of Na in the sintered ferrite magnet may be, for example, 0.2% by mass or less, or 0.01 to 0.15% by mass when Na is converted to Na ₂ O, and may be 0. It may be 0.02 to 0.1% by mass. The contents of Si and Na can be measured by inductively coupled plasma emission spectroscopy (ICP emission spectroscopy).

  In addition to the above-described components, the ferrite sintered magnet may contain impurities contained in the raw materials or inevitable components derived from the manufacturing equipment. Examples of such components include Ti (titanium), Cr (chromium), Mn (manganese), Mo (molybdenum), V (vanadium), and Al (aluminum). These components may be contained in the ferrite sintered magnet as respective oxides or composite oxides. Content of the above-mentioned impurities and inevitable components can be measured by fluorescent X-ray analysis or ICP emission spectroscopic analysis.

  The average particle size of the crystal grains (ferrite particles) including the main phase in the ferrite sintered magnet may be, for example, 5 μm or less, 4 μm or less, or 0.5 to 3 μm. By having such an average particle diameter, the coercive force can be further increased. The average grain size of the crystal grains of the sintered ferrite magnet can be obtained using an observation image of a cross section of the sintered ferrite magnet by TEM or SEM. Specifically, in an SEM or TEM observation image containing several hundred crystal grains, image processing is performed to measure the particle size distribution. From the measured number-based particle size distribution, the number-based average value of the crystal grain sizes is calculated. The average value thus measured is taken as the average grain size of the crystal grains.

  The coercive force at 20 ° C. of the sintered ferrite magnet is, for example, preferably 5000 Oe or more, more preferably 5800 Oe or more. The residual magnetic flux density at 20 ° C. of the ferrite sintered magnet is preferably 3500 G or more, more preferably 3900 G or more. The square shape of the sintered ferrite magnet is, for example, 86% or more. The orientation rate of the sintered ferrite magnet is, for example, 93% or more.

  Ferrite sintered magnets are suitably used as magnets for rotating machines such as motors and generators. Specifically, for fuel pump, power window, ABS (anti-lock brake system), fan, wiper, power steering, active suspension, starter, door lock, electric mirror, etc. It can be used as a magnet for automobile motors. Also for FDD spindle, VTR capstan, VTR rotary head, VTR reel, VTR loading, VTR camera capstan, VTR camera rotary head, VTR camera zoom, VTR camera focus, radio cassette etc. It can be used as a magnet for motors for OA / AV devices such as CD / DVD / MD spindle, CD / DVD / MD loading, and CD / DVD optical pickup. Furthermore, it can also be used as a magnet for a motor for home appliances such as an air conditioner compressor, a freezer compressor, an electric tool drive, a dryer fan, a shaver drive, an electric toothbrush and the like. Furthermore, it can also be used as a magnet for a motor for FA equipment such as a robot shaft, joint drive, robot main drive, machine tool table drive, machine tool belt drive and the like.

  FIG. 2 is a schematic cross-sectional view of a motor that is an example of a rotating machine. The motor 30 in FIG. 2 includes the ferrite sintered magnet 10. The motor 30 is a DC motor with a brush, and includes a bottomed cylindrical housing 31 (stator) and a rotatable rotor 32 disposed concentrically on the inner peripheral side of the housing 31. The rotor 32 includes a rotor shaft 36 and a rotor core 37 fixed on the rotor shaft 36. A bracket 33 is fitted into the opening of the housing 31, and the rotor core is accommodated in a space formed by the housing 31 and the bracket 33. The rotor shaft 36 is rotatably supported by bearings 34 and 35 provided at the center portion of the housing 31 and the center portion of the bracket 33 so as to face each other. Two C-type sintered ferrite magnets 10 are fixed to the inner peripheral surface of the cylindrical portion of the housing 31 so as to face each other.

  3 is a cross-sectional view taken along line III-III of the motor 30 of FIG. The sintered ferrite magnet 10 as a motor magnet is bonded to the inner peripheral surface of the housing 31 with an adhesive, with the outer peripheral surface serving as an adhesive surface. Since the sintered ferrite magnet 10 can be reduced in thickness, the gap between the housing 31 and the rotor 32 can be sufficiently reduced. Therefore, the motor 30 can be reduced in size while maintaining its performance.

  Next, an example of a method for manufacturing a ferrite sintered magnet will be described. The manufacturing method described below includes a blending step, a calcining step, a pulverizing step, a forming step, and a baking step. Details of each step will be described below.

In the blending step, a raw material composition is obtained by blending a plurality of raw materials. Examples of the raw material include a compound (raw material compound) containing, as a constituent element, an element represented by the general formula (I), gallium, boron, or silicon. The raw material compound is preferably, for example, a powder. Examples of the raw material compound include oxides and compounds that become oxides upon firing (carbonates, hydroxides, nitrates, etc.). For example, SrCO ₃ , La (OH) ₃ , Fe ₂ O ₃ , BaCO ₃ , CaCO ₃ , Co ₃ O ₄ , Ga ₂ O ₃ , B ₂ O ₃ and SiO ₂ can be exemplified. The average particle diameter of the raw material compound powder is, for example, about 0.1 to 2.0 μm from the viewpoint of facilitating blending.

  Boron compounds such as boron oxide tend to be more soluble in water than other raw materials and easily scattered under heating conditions. For this reason, when mix | blending a boron compound, it is necessary to increase the compounding ratio of the boron compound in the raw material composition of a compounding process compared with the content rate of the boron in a ferrite sintered magnet. The ratio of the blending ratio with respect to the content ratio is, for example, 120 to 300%.

  In the blending step, the auxiliary component raw material compounds (elemental elements, oxides, etc.) may be blended as necessary. The raw material composition is, for example, weighed and mixed each raw material so as to obtain a desired sintered ferrite magnet, and then mixed and pulverized for about 0.1 to 20 hours using a wet attritor, ball mill, etc. By doing so, a raw material composition can be obtained.

  In the calcining step, the raw material composition obtained in the blending step is calcined. For example, the calcination may be performed in an oxidizing atmosphere such as air. The calcination temperature may be, for example, 1100 to 1400 ° C, or 1200 to 1350 ° C. The calcination time may be, for example, 1 second to 10 hours, or 1 second to 3 hours. The ratio of the ferrite phase (M phase) in the calcined powder (ferrite particles) obtained by calcining may be, for example, 70% by volume or more, or 75% by volume or more. The ratio of the ferrite phase can be obtained in the same manner as the ratio of the main phase of ferrite in the sintered ferrite magnet.

  In the pulverization step, the calcined powder that has been granulated or agglomerated by the calcination step is pulverized. In this way, ferrite particles are obtained. For example, the pulverization step may be performed by dividing the calcined powder into a coarse powder (coarse pulverization step), and then pulverizing the calcined powder more finely (fine pulverization step).

Coarse pulverization can be performed, for example, using a vibration mill or the like until the average particle size of the calcined powder becomes 0.5 to 5.0 μm. In the fine pulverization, the coarse powder obtained by the coarse pulverization is further pulverized by a wet attritor, a ball mill, a jet mill or the like. In fine pulverization, pulverization is performed so that the average particle size of the fine powder (ferrite particles) obtained is, for example, about 0.08 to 2.0 μm. The specific surface area of the fine powder (for example, determined by the BET method) is, for example, about 7 to 12 m ² / g. The pulverization time varies depending on the pulverization method. For example, in the case of a wet attritor, the pulverization time is 30 minutes to 10 hours, and in the wet pulverization with a ball mill, it is 10 to 50 hours. The specific surface area of the ferrite particles can be measured using a commercially available BET specific surface area measuring device (manufactured by Mountaintech, trade name: HM Model-1210).

In the pulverization step, for example, a polyhydric alcohol represented by the general formula C _n (OH) _n H _{n + 2} may be added in order to increase the degree of magnetic orientation of the sintered body obtained after firing. N in the general formula may be, for example, 4 to 100 or 4 to 30. Examples of the polyhydric alcohol include sorbitol. Two or more polyhydric alcohols may be used in combination. Furthermore, other known dispersants may be used in combination with the polyhydric alcohol.

  When adding a polyhydric alcohol, the addition amount may be 0.05-5.0 mass% with respect to an addition target (for example, coarse powder), for example, 0.1-3.0 mass% It may be. The polyhydric alcohol added in the pulverization step is thermally decomposed and removed in the baking step described later.

  In the molding step, the ferrite particles obtained in the pulverization step are molded in a magnetic field to obtain a molded body. Molding can be performed by either dry molding or wet molding. From the viewpoint of increasing the degree of magnetic orientation, it is preferably performed by wet molding.

  In the case of molding by wet molding, for example, a slurry for wet molding is obtained by obtaining the slurry by performing the above-described fine grinding step in a wet manner, and then concentrating the slurry to a predetermined concentration. Molding can be performed using this wet molding slurry. Concentration of the slurry can be performed by centrifugation or a filter press. The content of the ferrite particles in the wet molding slurry is, for example, 30 to 80% by mass. An example of the dispersion medium in which the ferrite particles are dispersed in the slurry is water. A surfactant such as gluconic acid, gluconate, sorbitol may be added to the slurry. A non-aqueous solvent may be used as the dispersion medium. As the non-aqueous solvent, an organic solvent such as toluene or xylene can be used. In this case, a surfactant such as oleic acid may be added. The wet-forming slurry may be prepared by adding a dispersion medium or the like to the dried ferrite particles after pulverization.

In the wet molding, the wet molding slurry is then molded in a magnetic field. In this case, the molding pressure is, for example, 9.8 to 49 MPa (0.1 to 0.5 ton / cm ² ). The applied magnetic field is, for example, 398 to 1194 kA / m (5 to 15 kOe).

  In the firing step, the compact obtained in the molding step is fired to obtain a sintered ferrite magnet. Firing of the molded body can be performed in an oxidizing atmosphere such as the air. The firing temperature may be, for example, 1050 to 1270 ° C, or may be 1080 to 1240 ° C. Moreover, baking time (time to hold | maintain to baking temperature) is 0.5 to 3 hours, for example.

  In the firing step, before reaching the firing temperature, for example, heating from room temperature to about 100 ° C. may be performed at a temperature rising rate of about 0.5 ° C./min. Thereby, the molded body can be sufficiently dried before the sintering proceeds. Moreover, the surfactant added in the molding step can be sufficiently removed. In addition, these processes may be performed at the beginning of a baking process, and may be performed separately before a baking process.

  Thus, a ferrite sintered magnet can be manufactured. However, the manufacturing method of a ferrite sintered magnet is not limited to the above-mentioned example. For example, you may perform a formation process and a baking process in the following procedures. That is, the molding process may be performed by a CIM (Ceramic Injection Molding) molding method or PIM (Powder Injection Molding), which is a dried ferrite. The particles are heated and kneaded together with a binder resin to form pellets, which are injection molded in a mold to which a magnetic field is applied, to obtain a preform. A more detailed procedure is described below.

  The finely pulverized slurry containing ferrite particles obtained by wet pulverization is dried. The drying temperature may be, for example, 80 to 150 ° C or 100 to 120 ° C. The drying time may be 1 to 40 hours, or 5 to 25 hours. The average particle diameter of the primary particles of the magnetic powder after drying may be, for example, 0.08 to 2 μm, or 0.1 to 1 μm.

  The dried ferrite particles are kneaded together with organic components such as a binder resin, waxes, lubricants, plasticizers and sublimable compounds, and formed into pellets with a pelletizer or the like. The organic component may be contained in the molded body, for example, 35 to 60% by volume, or 40 to 55% by volume. The kneading may be performed with a kneader, for example. As the pelletizer, for example, a twin-screw single-screw extruder is used. The kneading and pellet forming may be performed while heating depending on the melting temperature of the organic component to be used.

  As the binder resin, a polymer compound such as a thermoplastic resin is used. Examples of the thermoplastic resin include polyethylene, polypropylene, ethylene vinyl acetate copolymer, atactic polypropylene, acrylic polymer, polystyrene, and polyacetal.

  As the waxes, in addition to natural waxes such as carnauba wax, montan wax, and beeswax, paraffin wax, urethanized wax, and synthetic waxes such as polyethylene glycol are used.

  Examples of the lubricant include fatty acid esters. Examples of the plasticizer include phthalic acid esters.

  The addition amount of the binder resin is, for example, 3 to 20% by mass with respect to 100% by mass of the ferrite particles. The amount of the wax added is, for example, 3 to 20% by mass with respect to 100% by mass of the ferrite particles. The addition amount of the lubricant is, for example, 0.1 to 5% by mass with respect to 100% by mass of the ferrite particles. The addition amount of a plasticizer is 0.1-5 mass% with respect to 100 mass% of binder resin, for example.

  Next, the pellets are introduced into a normal magnetic field injection molding apparatus and injection molded into a mold having a cavity with a predetermined shape. Prior to injection into the mold, a magnetic field is applied to the mold. The pellets are heated and melted, for example, at 160 to 230 ° C. inside the extruder and injected into the mold cavity by a screw. The mold temperature is, for example, 20 to 80 ° C. The magnetic field applied to the mold may be about 398 to 1592 kA / m (5 to 20 kOe). In this way, a preform is obtained by the magnetic field injection molding apparatus.

  The obtained preform is heat-treated at a temperature of 100 to 600 ° C. in the air or nitrogen, and a binder removal treatment is performed to obtain a molded body. When a plurality of organic components are used, the binder removal process may be performed in a plurality of times.

  Next, in the firing step, the molded body subjected to the binder removal treatment is fired, for example, in the atmosphere at a temperature of 1050 to 1270 ° C. or 1080 to 1240 ° C. for about 0.2 to 3 hours to obtain a sintered ferrite magnet.

  The sintered ferrite magnet of this embodiment has a high coercive force and a high residual magnetic flux density. Therefore, for example, it can be suitably used as a magnet for a rotating machine. Moreover, it is excellent also in a square shape.

  Although several embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments. For example, the rotating machine is not limited to the motor shown in FIGS. 2 and 3, and may be a motor of another form or a generator.

  The contents of the present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to the following examples.

(Production Examples 1-1 to 1-9)
[Manufacture of sintered ferrite magnets]
As raw materials, iron oxide (Fe ₂ O ₃ ), calcium carbonate (CaCO ₃ ), cobalt oxide (Co ₃ O ₄ ), and lanthanum hydroxide (La (OH) ₃ ) were prepared. These raw materials were blended so that the composition of the general formula (I) was as shown in Table 1. Obtained in this manner formulation, it was added 0.35 wt% of silicon oxide (SiO _2), to obtain a slurry followed by mixing and grinding for 10 minutes using a wet attritor (mixing step ).

After drying this slurry, calcination was performed in air at 1300 ° C. for 2 hours to obtain a calcination powder (calcination step). The obtained calcined powder was coarsely pulverized for 10 minutes with a small rod vibration mill to obtain coarse powder. The following additives were added to this coarse powder. Thereafter, it was pulverized for 35 hours using a wet ball mill to prepare a slurry containing ferrite particles (pulverization step). In addition, about manufacture example 1-1, the slurry was prepared, without adding an additive with respect to coarse powder.
<Additives>
Production Examples 1-2 to 1-5: Gallium oxide (Ga ₂ O ₃ )
Production Examples 1-6 and 1-7: Aluminum oxide (Al ₂ O ₃ )
Production Examples 1-8 and 1-9: Chromium oxide (Cr ₂ O ₃ )

  The slurry obtained after pulverization was adjusted to a solid content concentration of 73 to 75% by mass to obtain a slurry for wet molding. This wet molding slurry was molded in an applied magnetic field of 796 kA / m (10 kOe) using a wet magnetic field molding machine to obtain a molded body having a cylindrical shape with a diameter of 30 mm and a thickness of 15 mm (molding step). The obtained molded body was dried at room temperature in the air, and then fired in the air at 1140 ° C. for 1 hour (firing step). Thus, a cylindrical ferrite sintered magnet was obtained.

<Composition analysis>
The content of Ga in terms _{of Ga} 2 _{O 3} in the sintered ferrite magnets of each manufacturing example, the amount of Al in terms _{of Al} 2 _{O 3,} and the content of Cr in terms _{of Cr} 2 _{O 3} was measured by the following procedure. A ferrite sintered magnet sample (0.1 g) was mixed with 1 g of sodium peroxide and 1 g of sodium carbonate, heated and melted. The melt was dissolved in a solution of 40 ml of pure water and 10 ml of hydrochloric acid, and pure water was added to make a 100 ml solution. This solution was used by ICP emission spectroscopy (ICP-AES), the content of Ga in terms _{of Ga} 2 _{O 3,} the content of Al in terms _{of Al} 2 _{O 3,} and the content of Cr in terms _{of Cr} 2 _{O 3} Asked. For the ICP emission spectroscopic analysis, an analysis device (device name: ICPS 8100CL) manufactured by Shimadzu Corporation was used, and matrix matching was performed in the measurement. The composition in the general formula (I) was calculated based on the blending ratio of raw materials in the blending step. These results are shown in Table 1.

[Evaluation of sintered ferrite magnet]
<Evaluation of magnetic properties>
After processing the upper and lower surfaces of the sintered ferrite magnet, the magnetic properties at 20 ° C. were measured using a B—H tracer with a maximum applied magnetic field of 29 kOe. The residual magnetic flux density [Br (G)], saturation magnetic moment [Bs (G)], and coercive force [HcJ (Oe)] were determined by measurement. The orientation ratio (Br / Bs) was determined with Br being the value of B at H = 0 (Oe) measured with a B-H tracer and Bs being the maximum value of B measured with a B-H tracer. Further, for some of the production examples, the external magnetic field strength (Hk) at 90% of Br was measured, and based on this, the square shape (Hk / HcJ (%)) was obtained. These results are shown in Table 2. The distinction between the examples and comparative examples is shown in the remarks column of Table 2.

FIG. 4 is a graph showing the relationship between the Ga content in terms of Ga ₂ O ₃ and Br in Production Examples 1-1 to 1-5. FIG. 5 is a graph showing the relationship between Ga content in terms of Ga ₂ O ₃ and HcJ in Production Examples 1-1 to 1-5. FIG. 6 is a graph showing the relationship between the Ga content in Ga ₂ O ₃ conversion and the square shape in Production Examples 1-1 to 1-5.

As shown in Tables 1 and 2, and FIGS. 4, 5, and 6, among Production Examples 1-2 to 1-5 containing Ga, the Ga content in terms of Ga ₂ O ₃ is 0.027 to Production Example 1-2 to 1-4, which is 0.217% by mass, has improved squareness and both Br and HcJ compared to Production Example 1-1 that does not contain Ga, which has both high HcJ and high Br. did. On the other hand, in each of Production Examples 1-5 to 1-9, Br decreased as compared with Production Example 1-1. In Production Examples 1-2 to 1-4, the orientation ratio is high, which is considered to be a factor for improving Br.

(Production Examples 2-1 to 2-6)
As an additive for the coarse powder, the boron oxide in addition to gallium oxide _{(Ga 2 O 3) (B} 2 O 3) was added a predetermined amount, each raw material, the composition of the general formula (I) are as shown in Table 3 A sintered ferrite magnet was obtained in the same manner as in Production Examples 1-2 to 1-5, except that it was blended as described above. In Production Example 2-1, gallium oxide (Ga ₂ O ₃ ) was not added, and only a predetermined amount of boron oxide (B ₂ O ₃ ) was added. The obtained sintered ferrite magnet was subjected to composition analysis and evaluation of magnetic properties in the same manner as in Production Examples 1-2 to 1-5. The results were as shown in Table 3 and Table 4. The distinction between Examples and Comparative Examples is shown in the remarks column of Table 4.

As shown in Table 3 and Table 4, in Production Examples 2-2 to 2-5 in which the Ga content in terms of Ga ₂ O ₃ is 0.054 to 0.217 mass%, Production Example 2 containing no Ga Compared to 1, both Br and HcJ were improved. In Production Examples 2-2 to 2-5, the orientation ratio is higher than that in Production Example 2-1, and this is considered to be a cause of Br improvement. On the other hand, in Production Example 2-6 in which the Ga content was outside the predetermined range, HcJ was lower than in Production Example 2-1. As shown in Tables 1 to 4, it was confirmed that HcJ and Br can be achieved at a higher level by containing both Ga and B.

(Production Examples 3-1 to 3-6)
Ferrite sintered magnets were obtained in the same manner as in Production Examples 2-1 to 2-6 except that the composition of the general formula (I) was blended so as to be as shown in Table 5. In Production Example 3-1 to Production Example 3-3, only a predetermined amount of boron oxide (B ₂ O ₃ ) was added without adding gallium oxide (Ga ₂ O ₃ ). The obtained sintered ferrite magnet was subjected to composition analysis and evaluation of magnetic properties in the same manner as in Production Examples 2-1 to 2-6. The results were as shown in Table 5 and Table 6. The distinction between Examples and Comparative Examples is shown in the remarks column of Table 6.

  7 shows production examples containing Ga (Production Examples 3-4 to 3-6 and Production Example 2-4) and production examples not containing Ga (Production Examples 3-1 to 3-3 and Production Example 2- In 1), it is a graph which shows the relationship between x and Br in general formula (I). 8 shows production examples containing Ga (Production Examples 3-4 to 3-6 and Production Example 2-4) and production examples not containing Ga (Production Examples 3-1 to 3-3 and Production Example 2- In 1), it is a graph which shows the relationship between x and HcJ in general formula (I). 7 and 8, black square plots are data of production examples containing Ga, and white circle plots are data of production examples not containing Ga.

  As shown in Tables 5 and 6, and FIGS. 7 and 8, even if the atomic ratio of A, Fe and R in the general formula (I) is changed, both Br and HcJ are contained by containing a predetermined amount of Ga. It was confirmed to improve.

(Production Examples 4-1 to 4 to 4)
Ferrite sintered magnets were obtained in the same manner as in Production Examples 2-1 to 2-6 except that the composition of the general formula (I) was blended as shown in Table 7. In Production Example 4-1 and Production Example 4-2, gallium oxide (Ga ₂ O ₃ ) was not added, but only a predetermined amount of boron oxide (B ₂ O ₃ ) was added. The obtained sintered ferrite magnet was subjected to composition analysis and evaluation of magnetic properties in the same manner as in Production Examples 2-1 to 2-6. The results were as shown in Table 7 and Table 8. The distinction between Examples and Comparative Examples is shown in the remarks column of Table 8.

  FIG. 9 shows production examples containing Ga (Production Examples 4-3 to 4-4 and Production Example 2-4) and production examples not containing Ga (Production Examples 4-1 to 4-2 and Production Example 2- In 1), it is a graph which shows the relationship between y and Br in general formula (I). FIG. 10 shows production examples containing Ga (Production Examples 4-3 to 4-4 and Production Example 2-4) and production examples not containing Ga (Production Examples 4-1 to 4-2 and Production Example 2- In 1), it is a graph which shows the relationship between y and HJ in general formula (I). 9 and 10, black square plots are data of manufacturing examples containing Ga, and white circle plots are data of manufacturing examples not containing Ga.

  As shown in Tables 7 and 8, and FIGS. 9 and 10, even when the atomic ratio of Co in the general formula (I) changes, both Br and HcJ can be improved by containing a predetermined amount of Ga. confirmed.

(Production Examples 5-1 to 5-12)
Ferrite sintered magnets were obtained in the same manner as in Production Examples 2-1 to 2-6, except that the composition of general formula (I) was as shown in Table 9. In Production Example 5-1 to Production Example 5-6, a predetermined amount of boron oxide (B ₂ O ₃ ) was added without adding gallium oxide (Ga ₂ O ₃ ). The obtained sintered ferrite magnet was subjected to composition analysis and evaluation of magnetic properties in the same manner as in Production Examples 2-1 to 2-6. The results were as shown in Table 9 and Table 10. The distinction between Examples and Comparative Examples is shown in the remarks column of Table 10.

  FIG. 11 shows production examples containing Ga (Production Examples 5-7 to 5-12 and Production Example 2-4) and production examples not containing Ga (Production Examples 5-1 to 5-6 and Production Example 2- In 1), it is a graph which shows the relationship between m and Br in general formula (I). 12 shows production examples containing Ga (Production Examples 5-7 to 5-12 and Production Example 2-4) and production examples not containing Ga (Production Examples 5-1 to 5-6 and Production Example 2- In 1), it is a graph which shows the relationship between m and HcJ in general formula (I). In FIG. 11 and FIG. 12, the black square plot is data of a production example containing Ga, and the white circle plot is data of a production example not containing Ga.

  As shown in Tables 9 and 10, and FIGS. 11 and 12, even if the value of m in the general formula (I) changes, it is confirmed that both Br and HcJ are improved by containing a predetermined amount of Ga. It was done.

  According to the present disclosure, a sintered ferrite magnet having both a sufficiently high residual magnetic flux density and a coercive force is provided. Moreover, a rotating machine provided with the said ferrite sintered magnet is provided.

  DESCRIPTION OF SYMBOLS 10 ... Ferrite sintered magnet, 30 ... Motor, 31 ... Housing, 32 ... Rotor, 33 ... Bracket, 34, 35 ... Bearing, 36 ... Rotor shaft, 37 ... Rotor core.

Claims (4)

A ferrite sintered magnet containing a ferrite phase having a hexagonal magnetoplumbite-type crystal structure,
Ferrite sintered magnet Ga content is 0.027 to 0.217 wt% in terms _{of Ga} 2 _{O 3.} At least one element of R selected from rare earth elements including Y, and, Ca, or Ca and the element comprising at least one and as A is selected from Sr and Ba, the composition _{R 1-x} A x _{Fe m-} The ferrite sintered magnet according to claim 1, wherein x, y, and m satisfy the following formulas (1), (2), and (3) when expressed by _y Co _y .
0.2 ≦ x ≦ 0.8 (1)
0.1 ≦ y ≦ 0.65 (2)
3 ≦ m <14 (3) The content of B is 0.1 to 0.6 mass% in terms _{of B} 2 _{O 3,} ferrite sintered magnet according to claim 1 or 2.   A rotating machine comprising the ferrite sintered magnet according to any one of claims 1 to 3.

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