JPWO2014087932A1 - Manufacturing method of Sr ferrite sintered magnet - Google Patents

Abstract

An object of the present invention is to provide a method for producing a sintered Sr ferrite magnet having excellent properties of both Br and HcJ and high reliability. The present invention provides a calcining step of firing a mixed powder containing at least an iron compound powder and a strontium compound powder at 850 to 1450 ° C. to obtain a calcined body containing Sr ferrite, and the calcined body. Pulverizing the calcination powder to obtain a calcined powder, adding the silicate glass powder to the calcined powder and mixing, and molding the mixed powder of the calcined powder and the silicate glass powder in a magnetic field. And firing the molded body obtained at 1000 to 1300 ° C. to obtain a sintered body containing Sr ferrite, and the silicate glass has a softening point of 450 to 800 ° C. Manufacturing method of ferrite sintered magnet. [Selection figure] None

Description

  The present invention relates to a method for producing a sintered Sr ferrite magnet.

As a magnetic material used for a ferrite sintered magnet, Ba ferrite, Sr ferrite, and Ca ferrite having a hexagonal crystal structure are known. In recent years, among them, magnetoplumbite type (M type) Sr ferrite is mainly used as a magnet material for motors and the like. The M-type ferrite is represented by a general formula of AFe ₁₂ O ₁₉ , for example. Sr ferrite has Sr at the A site of the crystal structure.

  In order to improve the magnetic properties of sintered ferrite magnets, attempts have been made to improve the magnetic properties by substituting some elements of the A site and B site with rare earth elements such as La and Co, respectively. ing. For example, Patent Document 1 discloses a technique for improving the residual magnetic flux density (Br) and the coercive force (HcJ) by replacing a part of the A site and the B site with a specific amount of rare earth element and Co. .

  A typical application of the sintered ferrite magnet is a motor. Although a ferrite sintered magnet used for a motor is required to be excellent in both properties of Br and HcJ, it is generally known that Br and HcJ are in a trade-off relationship. For this reason, it is required to establish a technique capable of further improving both characteristics of Br and HcJ.

  A calculation formula of Br (kG) + 1 / 3HcJ (kOe) is known as an index indicating magnetic characteristics considering both the characteristics of Br and HcJ (see, for example, Patent Document 1). It can be said that the higher this value, the more suitable the sintered ferrite magnet for applications that require high magnetic properties such as motors.

JP-A-11-154604

  As shown in Patent Document 1, it is effective to improve the magnetic characteristics by controlling the composition of the main crystal grains constituting the ferrite sintered magnet. However, even if only the composition of crystal grains is controlled, it is difficult to greatly improve the magnetic properties of conventional ferrite sintered magnets. On the other hand, some of the subcomponents contained in the sintered ferrite magnet have an effect of improving magnetic properties and sinterability. However, depending on the types and amounts of the subcomponents, reliability such as excellent strength and appearance of the sintered ferrite magnet may be impaired. For example, if a ferrite sintered magnet with low strength or a ferrite sintered magnet that easily deposits foreign matter on the surface is used for the motor, the ferrite sintered magnet may be damaged or peeled off during use of the motor. The For this reason, there is a demand for a sintered ferrite magnet having high reliability as well as magnetic characteristics.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a sintered Sr ferrite magnet having excellent properties of both residual magnetic flux density (Br) and coercive force (HcJ) and high reliability. And It is another object of the present invention to provide a motor with high efficiency and excellent reliability.

  The present inventors improve not only the composition of crystal grains but also the presence of glass components at the grain boundaries of Sr ferrite sintered magnets, and in particular, improving the magnetic properties by covering the crystal grains with a glass coating. It was investigated. As a result, it has been found that the magnetic properties and reliability can be improved by forming a glass coating on the surface of the sintered Sr ferrite magnet, and the present invention has been completed.

  That is, in one aspect, the present invention provides a calcining step of firing a mixed powder containing at least an iron compound powder and a strontium compound powder at 850 to 1450 ° C. to obtain a calcined body containing Sr ferrite, A pulverization step of pulverizing the calcined body to obtain a calcined powder, a step of adding and mixing the silicate glass powder to the calcined powder, and a magnetic field of the mixed powder of the calcined powder and the silicate glass powder. And a firing step of obtaining a sintered body containing Sr ferrite by firing the molded body obtained by intermediate molding at 1000 to 1300 ° C., and the silicate glass has a softening point of 450 to 800 ° C. A method for producing a certain Sr ferrite sintered magnet is provided.

  According to the above manufacturing method, a highly reliable Sr ferrite sintered magnet can be manufactured in a simple process while maintaining both the residual magnetic flux density (Br) and coercive force (HcJ) characteristics high.

The reason why such an effect is obtained is not necessarily clear, but is presumed as follows.
That is, by using a silicate glass having a low softening point, the silicate glass contained in the molded body flows even when firing at a relatively low temperature, and a uniform glass film is formed on the surface (interface) of the ferrite particles. Can be considered.

  Furthermore, the silicate glass that flows and exudes from the gaps between the ferrite particles becomes a glass film that covers the surface of the sintered Sr ferrite magnet, and can effectively prevent foreign matter from depositing on the surface of the sintered ferrite magnet. it can. As a result, it is considered that a ferrite sintered magnet with high reliability can be obtained.

  In the manufacturing method of this invention, it is preferable that the average particle diameter of the said silicate glass powder is 0.3-1.0 micrometer. As a result, the silicate glass in the molded body tends to flow by firing, and the obtained Sr ferrite sintered magnet tends to have a dense structure.

  In the production method of the present invention, the silicate glass preferably contains one or more of boron, an alkali metal, and an alkaline earth metal. Thereby, since the softening point of the silicate glass can be adjusted to a range of 450 to 800 ° C. without substantially including Pb or the like, there is no environmental problem.

  In the production method of the present invention, it is preferable that the mixed powder to be calcined further contains the silicate glass. As a result, the glass component helps to sinter the Sr ferrite in the calcination step, and a more uniform glass film can be formed to improve the magnetic properties.

  The Sr ferrite sintered magnet obtained by the production method of the present invention has high reliability while maintaining high characteristics of both residual magnetic flux density (Br) and coercive force (HcJ).

  In another aspect, the present invention provides a motor including the Sr ferrite sintered magnet described above. This Sr ferrite sintered magnet may be obtained by the manufacturing method described above. Since the motor of the present invention includes a sintered ferrite magnet having high reliability while maintaining high characteristics of both residual magnetic flux density (Br) and coercive force (HcJ), it combines high efficiency and high reliability. .

  In still another aspect, the present invention provides a generator including the above-described sintered Sr ferrite magnet. This Sr ferrite sintered magnet may be obtained by the manufacturing method described above. Since the generator of the present invention includes a sintered ferrite magnet having high reliability while maintaining both the characteristics of residual magnetic flux density (Br) and coercive force (HcJ) high, high efficiency and high reliability are achieved. Have both.

  According to the present invention, it is possible to provide a method for producing a sintered Sr ferrite magnet capable of producing an Sr ferrite sintered magnet having excellent magnetic properties and high reliability at a low production cost by a simple process. it can. In addition, a sintered Sr ferrite magnet having excellent magnetic properties and high reliability can be provided. Furthermore, it is possible to provide a motor and a power generation site having high efficiency and high reliability.

It is a perspective view showing typically a suitable embodiment of a ferrite sintered magnet of the present invention.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings as necessary.

  A method for manufacturing the Sr ferrite sintered magnet of this embodiment will be described below. The manufacturing method of the Sr ferrite sintered magnet of this embodiment has a mixing process, a calcination process, a crushing process, a forming process in a magnetic field, and a firing process. Hereinafter, details of each process will be described.

The mixing step is a step of preparing a mixed powder for calcination. In the mixing step, first, starting materials are weighed and blended at a predetermined ratio, and mixed with a wet attritor or a ball mill for about 1 to 20 hours and pulverized. As a starting material, a powder of a compound having a constituent element of Sr ferrite as a main component is prepared. Examples of such powders include iron compound powders and strontium compound powders. In the mixing step, powders such as SiO ₂ and CaCO ₃ which are subcomponents may be added.

As a compound having a constituent element of Sr ferrite, an oxide or a compound such as carbonate, hydroxide or nitrate that becomes an oxide by firing can be used. Examples of such compounds include SrCO ₃ , La (OH) ₃ , Fe ₂ O ₃ and Co ₃ O ₄ . The average particle diameter of the starting material is not particularly limited and is, for example, 0.1 to 2.0 μm. It is not necessary to mix all starting materials in the mixing step before calcination, and a part or all of each compound may be added after the calcination step.

  The calcining step is a step of calcining the raw material composition obtained in the mixing step. Calcination can be performed in an oxidizing atmosphere such as air. The calcination temperature is 850 to 1450 ° C, preferably 900 to 1350 ° C, and more preferably 1000 to 1300 ° C. The calcination time at the calcination temperature is preferably 1 second to 10 hours, more preferably 1 minute to 3 hours. The content of Sr ferrite having a hexagonal crystal structure in the calcined body obtained by calcining is preferably 70% by mass or more, and more preferably 90% by mass or more. The primary particle diameter of the calcined body is preferably 10 μm or less, and more preferably 2.0 μm or less.

  The pulverization step is a step of pulverizing the calcined body to obtain a calcined powder containing Sr ferrite. The pulverization process may be performed in one stage, or may be performed in two stages, a coarse pulverization process and a fine pulverization process. Since the calcined body is usually granular or massive, it is preferable to first perform a coarse pulverization step. In the coarse pulverization step, dry pulverization is performed using a vibrating rod mill or the like to prepare pulverized powder having an average particle size of 0.5 to 5.0 μm. The pulverized powder thus prepared is pulverized wet using a wet attritor, ball mill, jet mill, or the like to obtain an average particle size of 0.08 to 2.0 μm, preferably 0.1 to 1.0 μm. Preferably, a calcined powder (fine powder) of 0.2 to 0.8 μm is obtained.

The specific surface area of the calcined powder by the BET method is preferably 5 to 14 m ² / g, more preferably 7 to 12 m ² / g. The grinding time is, for example, 30 minutes to 10 hours when using a wet attritor, and 5 to 50 hours when using a ball mill. These times are preferably adjusted appropriately depending on the pulverization method.

In the pulverization step, silicate glass is added to the calcined powder. In this invention, the softening point of silicate glass is 450-800 degreeC, More preferably, it is 500-700 degreeC.
Such silicate glass is not particularly limited, but, for example, Si-B-Na-Ca-O glass, Si-Na-Ca-O glass, Si-B-Bi glass, and the like. Is mentioned. _{Other, B 2 O 3, SiO 2} , Bi 2 O 3, MgO, CaO, SrO, BaO, Li 2 O, Na 2 O, K 2 O, TiO 2, ZrO 2, V 2 O 5, CuO, Ag, Those containing at least one of GeO ₂ , Al ₂ O ₃ , and P ₂ O ₅ can be preferably used.
In particular, the silicate glass preferably contains one or more of boron, alkali metal, and alkaline earth metal, and particularly preferably contains an alkali metal. However, it is preferable to avoid the use of lead-based glass containing lead such as PbO in consideration of environmental aspects. The average particle size of the glass powder is more preferably in the range of 0.3 to 1.0 μm, particularly 0.4 to 0.8 μm. The average particle size of the glass powder is preferably smaller than the average particle size of the calcined powder.

  By adding such a silicate glass powder to the calcined powder, the fluidity of the glass component in the molded body can be ensured even at a relatively low firing temperature, and the surface of the ferrite particles is uniform in the firing process. A simple glass coating can be formed. Such a glass coating is considered to have an effect of stabilizing the ferrite composition of the sintered Sr ferrite magnet by being uniformly present as a glass component at the interface of the ferrite particles. In addition, since such a glass coating is a non-magnetic material, an electromagnetic shielding effect can be obtained by covering the Sr ferrite sintered magnet, and the Sr ferrite sintered magnet can maintain excellent magnetic properties. it can.

  When the softening point of the silicate glass is too low, the molten glass component may react with the ferrite particles and affect the ferrite composition, and a part of the reacted glass component may crystallize. As a result, it is difficult to obtain the expected ferrite characteristics, and it is easy to deposit as foreign matter on the surface of the sintered ferrite magnet, and it is difficult to obtain a uniform glass film. On the other hand, if the softening point of the silicate glass is too high, sufficient fluidity cannot be obtained at a relatively low firing temperature, a uniform glass film cannot be formed, and the effect of improving magnetic properties can be obtained. It tends to be difficult.

Temporary The baked powder, together with silicate glass _{powder, SiO 2, CaCO 3, SrCO} 3, BaCO 3, a powder such as _Na 2 CO ₃ and _K 2 CO ₃ may be added. As an alkali metal compound having a constituent element of Na or K, a silicate or an organic compound (dispersant) containing Na or K can be used in addition to the above-mentioned carbonate. By adding such a subcomponent, sinterability can be improved and magnetic properties can be improved. In addition, since these subcomponents may flow out together with the solvent of the slurry when forming in a wet manner, it is preferable to add more than the target content in the sintered Sr ferrite magnet.

  In order to increase the degree of magnetic orientation of the sintered Sr ferrite magnet, it is preferable to add a polyhydric alcohol in the pulverization step in addition to the above-mentioned subcomponents. The addition amount of the polyhydric alcohol is 0.05 to 5.0% by mass, preferably 0.1 to 3.0% by mass, more preferably 0.3 to 2.0% by mass with respect to the addition target. . The added polyhydric alcohol is thermally decomposed and removed in the baking step after the molding step in the magnetic field.

  In the magnetic field forming step, the calcined powder obtained in the pulverizing step is formed in a magnetic field to produce a molded body. The molding step in a magnetic field can be performed by either dry molding or wet molding. From the viewpoint of increasing the degree of magnetic orientation, wet molding is preferred. When wet molding is performed, the finely pulverizing step may be performed in a wet manner, and the resulting slurry may be adjusted to a predetermined concentration to form a wet molding slurry. Concentration of the slurry can be performed by centrifugation, filter press, or the like.

The content of the calcined powder in the wet molding slurry is preferably 30 to 85% by mass. As the dispersion medium of the slurry, water or a non-aqueous solvent can be used. In addition to water, a surfactant such as gluconic acid, gluconate, or sorbitol may be added to the wet molding slurry. Molding in a magnetic field is performed using such a slurry for wet molding. The molding pressure is, for example, 0.1 to 0.5 ton / cm ² , and the applied magnetic field is, for example, 5 to 15 kOe.

  A baking process is a process of baking a molded object and obtaining a sintered compact. The firing step is usually performed in an oxidizing atmosphere such as air. A calcination temperature is 1000-1300 degreeC, More preferably, it is 1100-1250 degreeC, More preferably, it is 1150-1250 degreeC. The firing time at the firing temperature is preferably 0.5 to 3 hours.

  If the firing temperature is too low, the silicate glass contained in the molded body does not flow sufficiently, a uniform glass film cannot be formed, and the effect of improving magnetic properties tends to be difficult to obtain. is there. If the firing temperature is too high, the molten glass component may react with the ferrite particles, affecting the ferrite composition, and a part of the reacted glass component may crystallize. As a result, it is difficult to obtain the expected ferrite characteristics, and it is easy to deposit as foreign matter on the surface of the sintered ferrite magnet, and it is difficult to obtain a uniform glass film. The firing temperature is preferably adjusted as appropriate in relation to the softening point of the silicate glass.

  A sintered body can be obtained by the above steps. The sintered body thus obtained can be processed into a predetermined shape as necessary, and a Sr ferrite sintered magnet made of the sintered body can be obtained.

  FIG. 1 is a perspective view schematically showing an example of an Sr ferrite sintered magnet obtained by the manufacturing method of the present embodiment. The Sr ferrite sintered magnet 10 has a shape that is curved so that the end surface is arcuate, and generally has a shape called an arc segment shape, a C shape, a roof shape, or an arc shape. The Sr ferrite sintered magnet 10 is suitably used as a motor magnet, for example.

The Sr ferrite sintered magnet 10 contains M-type Sr ferrite having a hexagonal crystal structure as a main component. The main component, Sr ferrite, is represented by the following formula (1), for example.
SrFe ₁₂ O ₁₉ (1)

In the Sr ferrite of the above formula (1), Sr at the A site and Fe at the B site may be partially substituted by impurities or intentionally added elements. Further, the ratio between the A site and the B site may be slightly shifted. In this case, the Sr ferrite can be expressed by, for example, the following general formula (2).
_{R x Sr 1-x (Fe} 12-y M y) zO 19 (2)
In the above formula (4), x and y are, for example, 0.1 to 0.5, and z is 0.7 to 1.2.

  M in the general formula (2) is, for example, one or more selected from the group consisting of Co (cobalt), Zn (zinc), Ni (nickel), Mn (manganese), Al (aluminum), and Cr (chromium). It is an element. R in the general formula (5) is, for example, one or more elements selected from the group consisting of La (lanthanum), Ce (cerium), Pr (praseodymium), Nd (neodymium), and Sm (samarium). . In this case, SrF, which will be described later, can be calculated assuming that M and R constitute Sr ferrite.

  The mass ratio of Sr ferrite in the sintered Sr ferrite magnet 10 is preferably 90% by mass or more, more preferably 95% by mass or more, and further preferably 97% by mass or more. Thus, by reducing the mass ratio of the crystal phase different from Sr ferrite, the magnetic properties can be further enhanced.

The Sr ferrite sintered magnet 10 contains a component different from Sr ferrite as a subcomponent. Subcomponents include silicate glass, oxides, and composite oxides. The silicate glass, oxide and composite oxide are at least selected from the constituent elements selected from Si (silicon), K (potassium), Na (sodium), Ca (calcium), Sr (strontium) and Ba (barium). Examples thereof include silicate glass, oxide, and composite oxide having one kind. Examples of the silicate glass include Si—B—Na—Ca—O glass, Si—Na—Ca—O glass, and Si—B—Bi glass. Examples of the oxide include SiO ₂ , K ₂ O, Na ₂ O, CaO, SrO, and BaO.

  The content of silicate glass in the Sr ferrite sintered magnet 10 is preferably 10% by mass or less, more preferably 0.1 to 5% by mass, and still more preferably 0.5 to 2.0% by mass. If the silicate glass content is too low, the silicate glass cannot uniformly cover the crystal grains, the ferrite composition cannot be stabilized, and the glass oozes out on the surface of the ferrite sintered magnet. In addition, there is a tendency that the effect of improving the magnetic properties cannot be obtained. On the other hand, if the content of silicate glass becomes too high, sufficiently excellent magnetic properties tend to be impaired.

  The content of each constituent element contained in the sintered Sr ferrite magnet 10 is generally as follows.

The Si content in the Sr ferrite sintered magnet 10 is preferably from 0.3 to 0.94 wt% in terms of SiO _2. The lower limit of the Si content is more preferably 0.4% by mass in terms of SiO ₂ , and still more preferably 0.45% by mass. If the Si content is too low, the sintered body is not sufficiently densified, and excellent magnetic properties tend to be impaired. The upper limit of the Si content is more preferably 0.9% by mass, and still more preferably 0.8% by mass in terms of SiO ₂ . If the Si content becomes too high, sufficiently excellent magnetic properties tend to be impaired.

The total content of Na and K in the sintered Sr ferrite magnet 10 is preferably 0.004 to 0.31% by mass in terms of Na ₂ O and K ₂ O, respectively. The lower limit of the total content of Na and K is preferably 0.01% by mass, more preferably 0.02% by mass, and particularly preferably 0, in terms of Na ₂ O and K ₂ O, respectively. 0.03 mass%. If the total content of Na and K is too low, the sintering temperature cannot be reduced, and crystal grains tend to grow and it becomes difficult to obtain sufficiently high magnetic properties.

The upper limit of the total content of Na and K is more preferably 0.2% by mass, further preferably 0.15% by mass, and particularly preferably 0, in terms of Na ₂ O and K ₂ O, respectively. .1% by mass. When the total content of Na and K becomes too high, white powder tends to be easily generated on the surface of the sintered Sr ferrite magnet 10. When powder is generated on the surface of the Sr ferrite sintered magnet 10, for example, the adhesive force between the motor member and the Sr ferrite sintered magnet 10 may be reduced, and the Sr ferrite sintered magnet 10 may be separated from the motor member. . That is, the reliability of the Sr ferrite sintered magnet 10 is impaired.

  The Sr content in the sintered Sr ferrite magnet 10 is preferably 10 to 13% by mass, more preferably 10.3 to 11.9% in terms of SrO, from the viewpoint of further improving the magnetic properties and reliability. %. Further, the Ba content in the Sr ferrite sintered magnet 10 is preferably 0.01 to 2.0% by mass, more preferably 0.01 to 0.2% by mass in terms of BaO from the same viewpoint. .

  The Ca content in the sintered Sr ferrite magnet 10 is preferably 0.05 to 2% by mass in terms of CaO, more preferably 0.1 to 1.% from the viewpoint of further improving the magnetic properties and reliability. 5% by mass.

  In addition to these components, the Sr ferrite sintered magnet 10 may include impurities contained in the raw materials and 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) oxides.

  The subcomponents are mainly contained in the grain boundaries of the Sr ferrite crystal grains in the Sr ferrite sintered magnet 10. If the ratio of each element contained in the subcomponent changes, the composition of the grain boundary changes, and as a result, the magnetic properties and reliability of the Sr ferrite sintered magnet 10 may be affected. The Sr ferrite sintered magnet 10 obtained by the manufacturing method of the present embodiment has excellent magnetic properties and high reliability by adjusting the ratio of the specific element contained in the subcomponent to a predetermined range. The content of each component of the Sr ferrite sintered magnet 10 can be measured by fluorescent X-ray analysis and inductively coupled plasma emission spectroscopic analysis (ICP analysis).

The Sr ferrite sintered magnet 10 preferably satisfies the following formula (3).
1.3 ≦ (SrF + Ba + Ca + 2Na + 2K) /Si≦5.7 (3)

In the above formula (3), SrF represents the Sr molar content of Sr ferrite sintered magnet 10 excluding Sr constituting Sr ferrite, and Ba, Ca, Na and K are the respective elements. The content on a molar basis is shown. SrF occurs when the ratio of the Sr source to the Fe source is made larger than the stoichiometric ratio of Sr ferrite (SrFe ₁₂ O ₁₉ ) in the manufacturing process of the Sr ferrite sintered magnet 10. When the Sr content is less than the stoichiometric ratio of Sr ferrite (SrFe ₁₂ O ₁₉ ), SrF is a numerical value less than 0, that is, a negative numerical value. Also in this case, if the above formula (3) is satisfied, the magnetic characteristics and reliability can be improved.

  Due to the presence of silicate glass at the grain boundaries of the Sr ferrite sintered magnet 10, the Sr ferrite sintered magnet 10 satisfies the above formula (3), and the composition of the grain boundary is stabilized. It is thought to contribute to the improvement of reliability.

  The average grain size of Sr ferrite crystal grains in the sintered Sr ferrite magnet 10 is preferably 2.0 μm or less, more preferably 1.0 μm or less, and further preferably 0.3 to 1.0 μm. When the average grain size of Sr ferrite crystal grains exceeds 2.0 μm, it tends to be difficult to obtain sufficiently excellent magnetic properties. On the other hand, the Sr ferrite sintered magnet 10 having an average grain size of Sr ferrite crystal grains of less than 0.3 μm tends to be difficult to manufacture.

  The average grain size of the Sr ferrite crystal grains of the sintered Sr ferrite magnet 10 can be measured by the following procedure. The cross section of the sintered Sr ferrite magnet 10 is mirror-polished and etched with an acid such as hydrofluoric acid. Then, the etched surface is observed with an SEM or the like. In an observation image including several hundred crystal grains, the outline of the crystal grains is clarified, and then image processing is performed to measure the grain size distribution on the c-plane. The “particle diameter” in the present specification refers to the long diameter (a-axis direction diameter) on the a-plane. The major axis is obtained as the long side of the “rectangle with the smallest area” circumscribing each crystal grain. Further, the ratio of the long side to the short side of the “rectangle having the smallest area” is the “aspect ratio”. Instead of etching with acid, so-called thermal etching in which the sample is heated and etched may be performed.

  From the measured number-based particle size distribution, the number-based average value of the crystal grain sizes is calculated. In addition, the standard deviation is calculated from the measured particle size distribution and the average value. In this specification, these are the average grain size and standard deviation of the Sr ferrite crystal grains. In the sintered Sr ferrite magnet 10, the ratio of the number basis of crystal grains having a grain size of 2.0 μm or more to the whole Sr ferrite crystal grains is preferably 1% or less, and 0.9% or less. It is more preferable that Thereby, a sintered ferrite magnet having sufficiently high magnetic properties can be obtained. From the same viewpoint, the number average value (average aspect ratio) of the aspect ratio of each crystal grain is preferably about 1.0.

The Sr ferrite sintered magnet 10 preferably satisfies the following formula (4). The Sr ferrite sintered magnet 10 has high magnetic properties that satisfy the formula (4) because the Sr ferrite crystal grains are sufficiently fine and have a specific composition. The Sr ferrite sintered magnet 10 that satisfies this formula (4) has sufficiently excellent magnetic properties. Such a Sr ferrite sintered magnet 10 can provide a motor having higher efficiency.
Br + 1 / 3HcJ ≧ 5.3 (4)
In formula (4), Br and HcJ represent a residual magnetic flux density (kG) and a coercive force (kOe), respectively.

Sr ferrite sintered magnet 10 is, for example, for fuel pump, power window, ABS (anti-lock brake system), fan, wiper, power steering, active suspension, starter, door lock, It can be used as a magnet for an automobile motor such as an electric mirror. 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.

  The Sr ferrite sintered magnet 10 is attached to the above-mentioned motor member and installed in the motor. Since the Sr ferrite sintered magnet 10 having excellent magnetic properties is sufficiently suppressed from generating cracks and foreign matter (white powder) on the surface, it is sufficiently firmly bonded to the motor member. Thus, it is possible to sufficiently suppress the Sr ferrite sintered magnet 10 from being separated from the motor member. For this reason, various motors including the Sr ferrite sintered magnet 10 have both high efficiency and high reliability.

  Applications of the sintered Sr ferrite magnet 10 are not limited to motors. For example, generators for motorcycles, magnets for speakers and headphones, magnetron tubes, magnetic field generators for MRI, clampers for CD-ROM, and sensors for distributors. It can also be used as a member such as an ABS sensor, a fuel / oil level sensor, a magnet latch, or an isolator. It can also be used as a target (pellet) when forming the magnetic layer of the magnetic recording medium by vapor deposition or sputtering.

  The preferred embodiment of the present invention has been described above, but the method for manufacturing a sintered Sr ferrite magnet and the motor of the present invention are not limited to those described above.

  For example, the silicate glass powder is not limited to addition in the above-described pulverization step, but may be added in a mixing step before calcination, or may be added separately before and after calcination. The shape of the Sr ferrite sintered magnet is not limited to the shape shown in FIG. 1, and can be appropriately changed to a shape suitable for each application described above.

  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.

Example 1
[Production of Sr ferrite sintered magnet]
Using a wet attritor, 1000 g of Fe ₂ O ₃ powder (primary particle size: 0.3 μm), 161.2 g of SrCO ₃ powder (primary particle size: 2 μm) and 3.6 g of SiO ₂ powder (primary particle size: 2 μm) were used. The mixture was mixed while being pulverized, dried and sized. The powder thus obtained was fired in the air at 1200 ° C. for 3 hours to obtain a granular calcined body. This calcined body was coarsely pulverized using a dry vibrating rod mill to prepare a powder having a specific surface area of 1 m ² / g by the BET method.

Sorbitol was added to 130 g of the coarsely pulverized powder, and wet pulverization was performed for 21 hours using a ball mill to obtain a slurry containing the calcined powder. The amount of sorbitol added was 1% by mass based on the mass of the calcined powder. The specific surface area of the calcined powder after wet pulverization was 8.8 m ² / g. To the slurry after the wet pulverization, 1.9 g of silicate glass powder having a softening point of 550 ° C. (Si—Na—Ca—O glass, average particle diameter of 0.4 μm) was added and stirred.

Thereafter, the solid content concentration of the slurry was adjusted, and molding was performed using a wet magnetic field molding machine in an applied magnetic field of 12 kOe to obtain a molded body. This molded body was fired at 1150 ° C. in the atmosphere to obtain a cylindrical Sr ferrite sintered magnet.
In this way, the Sr ferrite sintered magnet of Sample 1 was produced.

<Evaluation of magnetic properties>
After processing the upper and lower surfaces of the produced sintered Sr ferrite magnet, the magnetic properties were measured using a BH tracer with a maximum applied magnetic field of 25 kOe. In the measurement, Br and HcJ were obtained, and the value of Br + 1 / 3HcJ was calculated. The results are shown in Table 1.

<Appearance evaluation>
The produced Sr ferrite sintered magnet was left in the atmosphere for 7 days, and then its surface was visually observed and evaluated according to the following criteria. The results are shown in Table 1.
A: Neither crack nor white powder was generated on the surface of the magnet.
B: Cracks were generated on the surface of the magnet, but no white powder was generated.
C: Cracks were generated on the surface of the magnet, and white powder was adhered.

  Next, Sr ferrite sintered magnets of Samples 2 to 11 were produced. In Sample 2, a sample was prepared in the same manner as Sample 1 except that the silicate glass powder was not used, and the same evaluation was performed. In Samples 3 to 11, samples were prepared in the same manner as Sample 1 except that the softening point of the silicate glass powder added to the slurry and the firing temperature of the compact were changed as shown in Table 1, respectively. The same evaluation was performed. The results are shown in Table 1.

  As the silicate glass powder, Si-B-Na-Ca-O-based glass was used in Samples 3, 4, 8 and 9, and Si-Na-Ca-O-based glass was used in the other samples.

  As shown in Table 1, Sr ferrite sintered magnets (samples 1, 4 to 6, 9 and 10) obtained by firing a compact including a silicate glass powder having a predetermined softening point at a predetermined firing temperature. ), No cracks or white powder was generated, and the magnetic properties were excellent. In particular, the value of Br + 1 / 3HcJ was 5.3 or more.

  On the other hand, in the Sr ferrite sintered magnet (sample 2) not containing the silicate glass powder, the value of Br + 1 / 3HcJ was less than 5.3. Further, in the samples where the softening point of the silicate glass is not within the range of the present invention (samples 3 and 7) and the samples whose firing temperature is not within the range of the present invention (samples 8 and 11), both values of Br + 1 / 3HcJ Was less than 5.3. In particular, when the firing temperature was too high and the softening point of the silicate glass was too low, the appearance evaluation results were inferior.

(Example 2)
Next, Sr ferrite sintered magnets of Samples 21 to 24 were produced. In Samples 21 to 24, samples were prepared by the same method as Sample 1 except that the particle size of the silicate glass powder was changed as shown in Table 1, and the same evaluation was performed. The results are shown in Table 2.

  As shown in Table 2, even when the average particle size of the silicate glass powder is changed, there is no generation of cracks or white powder, and the magnetic properties are excellent. In particular, the value of Br + 1 / 3HcJ is 5.3 or more. It was confirmed that.

Example 3
Next, Sr ferrite sintered magnets of Samples 31 to 34 were produced. In samples 31 to 34, the addition timing of silicate glass and the addition amount thereof are shown in Table 1 so that the content of silicate glass in the finally obtained Sr ferrite sintered magnet is the same as that of sample 1. It was changed as follows.

  Here, 100% post-addition in Sample 1 means 1.9 g of silicate glass powder added to 130 g of the coarsely pulverized calcined powder. Therefore, for example, the pre-addition 25% in the sample 31 means that 1.9 g of the silicate glass added in the sample 1 is 100%, and that 25% is preliminarily included in the calcined powder. And the manufacturing method is as follows.

In sample 31, Fe ₂ O ₃ powder 1000 g, SrCO ₃ powder 161.2 g, SiO ₂ powder 3.6 g, and silicate glass powder having a softening point of 550 ° C. (Si—Na—Ca—O glass, average particle size is 0.3 g) was mixed while being pulverized using a wet attritor, and dried and sized. The powder thus obtained was fired at 1000 ° C. for 1 hour in the air to obtain a granular calcined body. Using a dry vibrating rod mill, a powder having a specific surface area of 1 m ² / g by BET method was prepared.

Sorbitol was added to 130 g of the coarsely pulverized powder, and wet pulverization was performed for 21 hours using a ball mill to obtain a slurry containing the calcined powder. The amount of sorbitol added was 1% by mass based on the mass of the calcined powder. The specific surface area of the calcined powder after wet pulverization was 10.4 m ² / g. To the slurry after the wet pulverization, 1.4 g of silicate glass powder having a softening point of 550 ° C. (Si—Na—Ca—O glass, average particle size is 0.3 μm) was added and stirred.

Thereafter, the solid content concentration of the slurry was adjusted, and molding was performed using a wet magnetic field molding machine in an applied magnetic field of 12 kOe to obtain a molded body. This molded body was fired at 1150 ° C. in the atmosphere to obtain a cylindrical Sr ferrite sintered magnet.
In this way, the Sr ferrite sintered magnet of Sample 31 was produced.

  Samples 32 to 34 were similarly manufactured by adjusting the amount of pre-added silicate glass powder to produce Sr ferrite sintered magnets. And about the samples 31-34, evaluation similar to the sample 1 was performed. The results are shown in Table 3.

  As shown in Table 3, even when the silicate glass is added before calcination, there is no generation of cracks or white powder, and the magnetic properties are excellent. In particular, the value of Br + 1 / 3HcJ is 5.3 or more. It was confirmed that there was.

Example 4
Instead of the calcined body used in Sample 1, a calcined body having a calcining temperature changed in the range of 850 to 1450 ° C. was used to obtain a sintered Sr ferrite magnet. In these Sr ferrite sintered magnets, excellent magnetic properties were confirmed as in Sample 1. Note that the calcined body calcined at 800 ° C. could not be molded, and the molded body and Sr ferrite sintered magnet could not be obtained.

(Example 5)
In place of the silicate glass used in Sample 1, Si-B-Na-Ca-O-based glass and Si-B-Bi-Na-O-based glass having a softening point of 550 ° C are used to form a Sr ferrite sintered magnet. Obtained. In these Sr ferrite sintered magnets, excellent magnetic properties were confirmed as in Sample 1.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the Sr ferrite sintered magnet which can manufacture the Sr ferrite sintered magnet which has a high magnetic characteristic and high reliability by a simple process can be provided. In addition, a sintered Sr ferrite magnet having high magnetic properties and high reliability can be provided. Furthermore, it is possible to provide a motor and a generator having high efficiency and high reliability.

  10. Ferrite sintered magnet

Claims (7)

A calcining step of firing a mixed powder containing at least an iron compound powder and a strontium compound powder at 850 to 1450 ° C. to obtain a calcined body containing Sr ferrite;
Crushing the calcined body to obtain a calcined powder; and
Adding and mixing silicate glass powder to the calcined powder; and
Firing a molded body obtained by molding the mixed powder of the calcined powder and the silicate glass powder in a magnetic field at 1000 to 1300 ° C. to obtain a sintered body containing Sr ferrite, ,
The said silicate glass is a manufacturing method of the Sr ferrite sintered magnet whose softening point is 450-800 degreeC.   The manufacturing method of the Sr ferrite sintered magnet of Claim 1 whose average particle diameter of the said silicate glass powder is 0.3-1.0 micrometer.   3. The method for producing a sintered Sr ferrite magnet according to claim 1, wherein the silicate glass includes one or more of boron, an alkali metal, and an alkaline earth metal.   The method for producing a sintered Sr ferrite magnet according to claim 1, wherein the mixed powder to be calcined further includes the silicate glass.   A sintered Sr ferrite magnet obtained by the production method according to claim 1.   A motor comprising the Sr ferrite sintered magnet according to claim 5.   A generator comprising the Sr ferrite sintered magnet according to claim 5.

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