JPH09312211A - Oxide permanent magnet and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oxide permanent magnet and a manufacturing method thereof, such as anisotropic magnet having a superior magnetic characteristic and no break or crack, esp. a cylindrical, bow-like or flat annular magnet or another special-shaped anisotropic and isotropic magnets. SOLUTION: The permanent magnet has a density equal to 86-94% of the theoretical density and proportion of pores of 0.1μm or more equal to 5-60% of the total pores. It is obtained by mixing an oxide magnetic rough powder of 5-100μm in mean grain size with an oxide magnetic fine powder of 0.5-1.5μm in mean grain size so that the fine powder content is 10-60wt.% and forming and baking the mixture.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention has excellent magnetic properties,
The present invention relates to oxide permanent magnets such as anisotropic magnets and isotropic magnets without cracks and cracks, and a method for manufacturing the same.

[0002]

2. Description of the Related Art Generally, a ferrite magnet having a magnetoplumbite type crystal structure is prepared by mixing Fe ₂ O ₃ and an MO compound (M is one or two of Sr and Ba) in a predetermined molar ratio, and It is obtained by firing to obtain ferrite, crushing, molding and firing. At this time, the average particle diameter of the pulverized ferrite powder is generally in the range of 0.5 to 1.5 μm. If the average particle size is less than 0.5 μm, the formability and orientation deteriorate, and if the average particle size exceeds 1.5 μm, coarse particles exceeding the single domain critical particle size are generated in the sintered body after firing. This is because it is easy and the coercive force is significantly deteriorated.

An anisotropic magnet is one in which the easy magnetization axis (C axis) is aligned in the same direction during molding, and an isotropic magnet is one in a disordered state without alignment. Anisotropic magnets
It is known that the residual magnetic flux density Br is about twice and the maximum magnetic energy product (BH) max is about 3 to 4 times that of an isotropic magnet. Orientation is one factor. As a method for forming the anisotropic magnet, ferrite powder is filled in a mold and pressure-molded, so-called dry molding, and ferrite powder is mixed with a liquid such as water, and pressure-molded as a high-concentration slurry. Wet molding is known. Wet molding is superior to dry molding in orientation and can obtain high magnetic characteristics, but has drawbacks such as inability to mold a complicated shape. Further, during the firing, the anisotropic magnet is 20 to 20% in the C-axis direction.
25%, 13-16% in the direction perpendicular to the C-axis (A-axis), and isotropic magnets with 17-18%, so the dimensions after firing do not fall within the allowable range of design values, and many In some cases, processing is required.

Generally, a cylindrical magnet is used as a magnet for a rotor of a stepping motor. Since the cylindrical magnet uses a magnetic force in the radial direction, it can have anisotropy in the radial direction. , Is essential for improving the performance of magnets. For this reason, various molding methods in which the C-axis is aligned in the radial direction and multipolar anisotropic molding methods have been tried, but there is a drawback in that cracks occur in the process of firing to cooling. In order to solve such a problem, for example, Japanese Patent Laid-Open No. 60-182.
In Japanese Patent Laid-Open Publication No. 0-0,096, a multi-pole anisotropic magnet having either an outer peripheral portion or an inner peripheral portion having multipole anisotropy and an opposite side being isotropic, and having an integrated concentric circle structure, is disclosed. Kaihei 5-26
No. 7046 gazette discloses a radial variation obtained by firing a molded body in which a part of the cylindrical body in the circumferential direction, which is determined in consideration of the shrinkage amount at the time of firing, is axially removed by cutting at the time of molding or after cutting. Directional cylindrical magnets have been proposed.

[0005]

However, even the above proposal cannot fundamentally solve the cracks or the cause of the cracks. That is, in the method described in Japanese Patent Laid-Open No. 60-1820, cracks or cracks are generated when the magnetizing magnetic field at the time of molding is increased in order to improve the magnetic characteristics or when a product with a thin wall is produced. In addition, the method described in Japanese Patent Laid-Open No. 5-267046 requires steps such as cutting the molded body, which complicates the work and has a problem of yield. Furthermore, the anisotropic magnet
Not only the cylindrical magnet having anisotropy in the radial direction, but also the arc-shaped magnet, the flat annular magnet, and other magnets having a special shape have a problem of cracking or cracking.

As described above, the anisotropic magnet has different shrinkage rates depending on the axial direction, which is one of the causes of cracking and cracking. This can be solved by bringing the shrinkage ratios in the respective axial directions close to 0%, but in the method using the ferrite powder of the conventional particle size having the average particle size of 0.5 to 1.5 μm as described above, Generally, the density of the molded body was about 55 to 60% of the theoretical density, and the shrinkage during firing was unavoidable. In addition, even in the case of an isotropic magnet, making the shrinkage rate close to 0% suppresses the occurrence of cracks and cracks, and in some cases, the processing step becomes unnecessary. Furthermore, in order to improve the magnetic properties, strength, and other properties of anisotropic magnets and isotropic magnets, it is desirable that the theoretical density after firing be close to 100%. A fired body was obtained by the operation, but this was also inevitable for cracking.

Therefore, the present invention provides an anisotropic magnet which is excellent in magnetic properties and has no cracks or cracks, particularly a cylindrical magnet having anisotropy in the radial direction, a bow-shaped magnet, a flat annular magnet and other special shapes. An oxide permanent magnet such as an anisotropic magnet and an isotropic magnet, and a method for manufacturing the same are provided.

[0008]

As a result of extensive studies on oxide permanent magnets, the present inventor has found that the oxide permanent magnets after firing have cracks or cracks due to the presence of pores of 0.1 μm or more to some extent. Therefore, the present invention has been completed based on this finding.

Specifically, it is achieved by the following constitutions (1) to (5).

(1) The density is 86 to 94% of the theoretical density, and the pores of 0.1 μm or more are 5 to the total pores.
An oxide permanent magnet characterized by being 60%.

The above oxide permanent magnet has excellent magnetic properties,
It has high strength and does not easily crack or crack regardless of the shape of the molded product.

(2) The oxide permanent magnet described in (1) is
An oxide permanent magnet that is an anisotropic magnet.

(3) Oxide Permanent magnet coarse particles obtained by crushing a sintered body of an oxide permanent magnet and having an average particle diameter of 5 to 100 μm, and oxide having an average particle diameter of 0.5 to 1.5 μm A method for producing an oxide permanent magnet, characterized in that fine particles of magnetic powder are mixed so as to be 10 to 60 wt%, and the mixed powder is molded and fired.

With the above raw material, it is possible to obtain a molded body having a density which cannot be achieved by the raw material having the particle size used conventionally. Further, by the above-mentioned method for producing an oxide permanent magnet, it is possible to produce an oxide permanent magnet having a high density and free from cracks or cracks.

(4) A solution in which a binder is dissolved is added to and mixed with either coarse particles or fine particles of the above oxide magnetic powder, and the mixture is then mixed with the remaining particles for granulation. The method for producing an oxide permanent magnet according to (3), characterized in that the powder is molded and fired.

The above-mentioned raw materials have remarkably good fluidity as compared with the conventionally used raw materials having a particle size, filling in the mold in a short time, small variation in density and excellent in productivity. Further, since it has a structure in which fine particles surround the surface of coarse particles, it has better orientation and higher characteristics than conventional granulated powder for isotropic magnets.

(5) The oxide magnetic powder is molded so that the density of the molded body is 78% or more of the theoretical density, and then fired, and the firing is performed (3) or (4). Manufacturing method of oxide permanent magnet.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Oxide Permanent Magnet The oxide permanent magnet according to the present invention has a theoretical density of 86.
˜94%, and 5% to 60% of all pores having pores of 0.1 μm or more.

If the density after firing is less than 86% of the theoretical density, the magnetic properties and strength will deteriorate. On the other hand, when it exceeds 94% of the theoretical density, both magnetic properties and strength are improved, but cracks frequently occur depending on the shape of the molded body, which is not desirable. Furthermore, the oxide permanent magnet according to the present invention has pores of a certain size in order to prevent cracks or cracks from occurring regardless of the shape. This has a role of relieving mechanical stress, and the number of pores of 0.1 μm or more is 5 to 60% of all the pores. If it is less than 5%,
Mechanical stress cannot be relaxed, leading to cracks and cracks. On the other hand, if it exceeds 60%, the strength becomes insufficient.

The oxide magnet is a ferrite magnet, preferably a magnetoplumbite type M phase, W.
It is a hexagonal ferrite such as phases. As such a ferrite, it is particularly preferable that MO.nFe ₂ O ₃ (M is preferably one or more of Sr and Ba, n = 4.5 to 6.5). Such ferrites further include C
a, Pb, Al, Ga, Sn, Zn, In, Co, N
i, Ti, Cr, Mn, Cu, Ge, Nb, Zr, Cr
Etc. may be contained. The oxide magnet may be either an anisotropic magnet or an isotropic magnet, but preferably,
It is an anisotropic magnet.

Manufacturing Method of Oxide Permanent Magnet Such an oxide permanent magnet can be manufactured as follows.

The oxide magnetic powder, which is a raw material for the oxide permanent magnet according to the present invention, is adjusted to have a particle size distribution so that a high compact density can be obtained in order to minimize shrinkage during firing. Specifically, this oxide magnetic powder has an average particle size of 0.5 to
It is a mixture of fine particles of 1.5 μm and coarse particles having an average particle diameter of 5 to 100 μm, and the mixing ratio thereof is 10 to 60 wt% in terms of weight ratio of the fine particles.

The reasons for limiting each numerical value will be described below.

The fine particles are ferrite powders having a conventionally used particle size, and if the average particle size is less than 0.5 μm, the formability and orientation are deteriorated, while the average particle size is
If it exceeds 1.5 μm, coarse particles exceeding the single domain critical particle diameter are likely to occur in the sintered body after firing, and the coercive force is significantly deteriorated.

If the average particle size of the coarse particles is less than 5 μm, the density after molding does not increase and the shrinkage during firing becomes large, and the dimensional accuracy of the product does not differ much from the conventional one.
On the other hand, if the average particle size exceeds 100 μm, the binding property between particles at the time of molding deteriorates, so that the strength of the molded product decreases and handling becomes difficult.

Further, it is preferable that the oxide magnetic powder as a raw material of the oxide permanent magnet according to the present invention, that is, the mixed powder of fine particles and coarse particles does not contain particles exceeding 300 μm. This is because if the oxide magnetic powder contains particles having a particle size of more than 300 μm, the mold may be damaged and the surface of the product may not be smooth.

The mixing ratio of the fine particles is 10
If it is less than wt%, the binding property between particles during molding deteriorates, so that the strength of the molded product decreases and handling becomes difficult. Moreover, the density is low and the strength and magnetic properties are deteriorated after molding and after firing. On the other hand, if it exceeds 60 wt%, the shrinkage during firing becomes large, and the dimensional accuracy of the product does not differ much from the conventional one.

As the fine particles, commercially available ferrite magnetic powder can be used.

The coarse particles are obtained by crushing a sintered body of an oxide permanent magnet. Specifically, first, oxide magnetic powder is molded. The molding method may be a method usually used for producing an anisotropic magnet or an isotropic magnet, and for example, wet molding or dry molding (both performed in a magnetic field or without a magnetic field) is used. When obtaining an anisotropic magnet, wet magnetic field molding is preferably used. This is because the orientation is improved. Next, this molded body is heated to 1100 to 1300 ° C
Bake in about 30 minutes to 4 hours. This sintered body is densely sintered and the average grain size is about 0.7 to 2 μm. The obtained sintered body may be either an isotropic magnet or an anisotropic magnet. Further, the sintered body is pulverized, and the pulverization may be either wet type or dry type. After roughly crushing with a stamp mill, jaw crusher, etc., a vibration mill, a roller mill,
The target coarse particles are obtained by pulverizing to a desired particle size with an atomizer, a ball mill or the like.

The oxide magnetic powder composed of the mixed powder of the fine particles and the coarse particles is then molded. Molding may be either dry type or wet type. When dry molding is performed, the molding may be performed as it is, or may be performed by adding a surface modifier. This makes it possible to improve the sliding of the particles and to obtain a molded article having a higher density.

Here, the surface modifier may be any one commonly used, for example, a surfactant or wax. The surfactant may be any of cationic type, anionic type, nonionic type and amphoteric type, and in particular, carboxylic acid or a salt thereof such as stearic acid, oleic acid, zinc stearate, calcium stearate, stearic acid. Strontium, barium stearate, magnesium stearate, aluminum stearate, potassium stearate, sodium stearate, zinc oleate, calcium oleate, strontium oleate, barium oleate, magnesium oleate, aluminum oleate, potassium oleate, Those containing at least one saturated or unsaturated fatty acid having about 4 to 30 carbon atoms such as sodium oleate and ammonium oleate or salts thereof are suitably used.

The surface modification may be carried out by adding a surface modifier and water or an organic solvent to the oxide magnetic powder to form a slurry, mixing the slurry with a wet stirrer or a kneader, and drying. Further, a commercially available emulsion may be mixed, or the surface of the oxide magnetic powder may be treated with a surface modifier by spraying or the like. The content of the surface modifier in the slurry is preferably 0.1 to 1 wt% with respect to the oxide magnetic powder.
This is because if the amount is too small, the effect of surface modification does not appear, and if it is too large, the density of the sintered body decreases.

Further, in order to uniformly fill the mold in a shorter time, the mold may be granulated and molded to an appropriate size.

The granulation may be carried out by adding a solution of a binder such as polyvinyl alcohol (hereinafter referred to as PVA) to oxide magnetic powder, mixing the mixture with a Henschel mixer, etc. and drying. When the coarse particles are anisotropic, P is added to either the coarse particles or the fine particles.
It is preferable that a solution in which a binder such as VA is dissolved is added and mixed, and then the remaining particles are mixed with a Henschel mixer or the like. Further, depending on the addition amount of the solution in which the binder is dissolved, the solution may be dried after mixing with a Henschel mixer or the like. Here, in the case of adding and mixing a solution in which a binder is dissolved in any one of coarse particles or fine particles, the mixing method may be any method as long as the solution is dispersed substantially uniformly, For example, there is a method of spraying a solution in which a binder is dissolved while dispersing coarse particles or fine particles in a fluidized bed.

Generally, the granulation step is used when producing an isotropic magnet, and no granulation is performed when producing an anisotropic magnet. This is because the granulation lowers the orientation. However, the oxide magnetic powder used in the present invention is a granulated powder having a structure in which fine particles surround the surface of the coarse particles of the oxide magnetic powder by the above method, and the coarse particles have anisotropy. If so, deterioration of orientation can be suppressed as much as possible. Therefore, it may be granulated by the above method depending on the situation. A method in which a binder solution is added to both the coarse particles and the fine particles of the oxide magnetic powder and mixed and then the respective particles are mixed, or after the coarse particles and the fine particles of the oxide magnetic powder are mixed The method of adding and mixing the solution in which the binder is dissolved promotes granulation of coarse particles or fine particles and reduces the degree of orientation, which is not preferable when an anisotropic magnet is prepared.

The particle size of the granulated powder is usually 500 μm or less when the coarse particles are isotropic, but the particle size of the granulated powder when anisotropic is preferably 200 μm or less. . This is because if a granulated powder larger than this is produced, the degree of orientation will decrease.

When the oxide magnetic powder thus produced is used to obtain an anisotropic magnet without a magnetic field or in a magnetic field, it is preferably molded in a magnetic field to obtain a molded body. The molding pressure is 0.
When molding in a magnetic field at about 5 to 10 ton / cm ² , the applied magnetic field may be about 2 to 10 kG. The density of this molded product is preferably as high as possible because it affects the shrinkage factor during firing, and is preferably 78% or more of the theoretical density. If the density of the molded body is less than 78%, the shrinkage rate becomes large and cracks or cracks are likely to occur, and it is necessary to examine the firing conditions and the like, which is not preferable.

The molded body is fired at 1100 to 1300 ° C. for about 30 minutes to 4 hours to sinter the molded body. This firing temperature affects the shrinkage ratio and strength of the sintered body, and is therefore appropriately selected from the above firing temperature range, if necessary.

As described above, the oxide permanent magnet according to the present invention is manufactured. Further, the oxide permanent magnet according to the present invention,
Anisotropic magnet with excellent magnetic properties and no cracks or cracks,
In particular, a cylindrical magnet having a radial anisotropy, a bow-shaped magnet,
It can be used as a flat annular magnet or other permanent magnet such as an anisotropic magnet having a special shape or an isotropic magnet, but most preferably it can be used as a rotor of a stepping motor or the like.

[0040]

EXAMPLES Specific examples of the present invention will be described below.

(Example 1) First, coarse particles as a raw material for an oxide permanent magnet were prepared by the following procedure.

A sintered body of Sr ferrite magnet (Sr ferrite magnetic powder was subjected to wet magnetic field molding and fired at 1240 ° C. and sintered) was prepared, and this sintered body was roughly crushed to 3 to 10 mm. After that, coarse particles were obtained by pulverizing with a vibration mill until the average particle diameter became 45 μm. No particles of 300 μm or more were detected in this pulverized powder.

Next, the coarse particles and the average particle size of 0.9 μm.
The fine particles of Sr ferrite magnetic powder (particles of 300 μm or more are not included) of 0, 10,
Materials 1 to 7 were prepared by mixing so as to be 30, 50, 60, 70 and 100 wt%.

Each of these materials has a slurry concentration of 4
It was dispersed in water so as to be 0 wt%, potassium stearate was added as a surface modifier so as to be 2 mg per unit specific surface area of the oxide magnetic powder, and mixed for 30 minutes to prepare a slurry. These were dried at 130 ° C., and after drying, they were crushed by an atomizer to obtain oxide magnetic powder as a raw material for oxide magnets.

These oxide magnetic powders were dry-molded in a magnetic field to obtain a cylindrical molded body having a diameter of 25 mm and a height of 14 mm. This molded body was placed in a batch furnace, heated to 1240 ° C. at 5 ° C./min, and held at 1240 ° C. for 1 hour. 1-7 were created. Further, the above oxide magnetic powder, dry molding in a magnetic field,
A molded body of a radial anisotropic ring magnet having an outer diameter of 30.8 mm, an inner diameter of 26.8 mm and a height of 5 mm was prepared and fired under the same conditions as in the case of the cylindrical shape.

[0046]

[Table 1]

Sample No. 1 is shown in Table 1. Shrinkage rate for 1 to 7, magnetic flux density as magnetic characteristics Br, density, strength, 0.1
The ratio of pores of μm or more and the crack generation rate when a radial anisotropic magnet is used are shown. Here, the numerical value (%) in the parentheses of the density in the table is the ratio to the theoretical density for each of the molded body and the sintered body.

The above items were measured and determined by the following methods.

The shrinkage ratio was determined from the dimensions of the molded body and the sintered body. Specifically, a molded body is prepared from a mold having a diameter (φ) of 25 mm and a height (h) of 14 mm as described above, and the molded body is fired under the above conditions. The shrinkage ratios in the height (h) direction and the diameter (φ) direction were calculated by the equation.

Shrinkage rate (%) in height (h) direction = (hp-
hf) / hp × 100 Shrinkage rate (%) in diameter (φ) direction = (φp−φf) / φp ×
100 hp; height of molded body hf; height of sintered body φp; diameter of molded body φf; diameter of sintered body Magnetic characteristics, that is, magnetic flux density Br was determined by a BH tracer.

For the density, the diameter and height of the molded body and the sintered body were measured to determine the volume, and the weight of each was measured to determine the density. The ratio of the density of each of the molded body and the sintered body to the theoretical density is 5.11 g of the theoretical density.
/ Cm ³ (Magnetic handbook, Asakura Shoten, 1975
(Quoted from (year)).

The ratio of pores of 0.1 μm or more was measured by a mercury porosimeter.

For the strength, a cylindrical sintered body processed to have a diameter of 20 mm and a height of 10 mm was used, and the compressive strength in the diametrical direction was measured by a compressive strength tester.

The particle size was measured by the laser diffraction / scattering method.

As is clear from Table 1, the samples having the density of the sintered body of less than 86% of the theoretical density and the pores of 0.1 μm or more exceeding 60% of the total pores have magnetic properties, that is, magnetic flux. The density Br and the strength do not satisfy the generally required values. Here, the generally required value depends on the application etc., but the magnetic flux density is required to be 3500 G or more and the strength is required to be 800 kgf or more. on the other hand,
The density of the sintered body exceeds 94% of the theoretical density, and
Samples with pores of 0.1 μm or more less than 5% of all pores have good magnetic properties and strength, but cracks are generated when a radial anisotropic magnet is produced. .

(Example 2) The sintered body of the Sr ferrite magnet used in Example 1 was crushed at different crushing times to obtain coarse particles having an average particle size of 3, 4, 5, 9, 45, 100 µm. It was The coarse particles were mixed with the oxide magnetic powder used in Example 1, that is, fine particles of Sr ferrite magnetic powder having an average particle diameter of 0.9 μm so that the proportion of the fine particles was 30 wt%, Materials 8-13 were made. These materials were subjected to the same procedure as in Example 1 to have a diameter of 25 mm and a height of 1.
A 4 mm columnar shaped body was obtained. Further, firing was performed under the same conditions as in Example 1 to obtain Sample Nos. 8-13 were created. Further, as in Example 1, the oxide magnetic powder was dry-molded in a magnetic field to give an outer diameter of 3
A radial anisotropic ring magnet compact having a diameter of 0.8 mm, an inner diameter of 26.8 mm and a height of 5 mm was prepared and fired under the same conditions as in Example 1.

[0057]

[Table 2]

Table 2 shows sample No. The contraction rate for 8 to 13 and the magnetic characteristics are magnetic flux density Br, density, strength, 0.1
The ratio of pores of μm or more and the crack generation rate when a radial anisotropic magnet is used are shown. In addition, each measurement method and calculation method are the same as in Example 1.

As is clear from Table 2, when the average particle size of the coarse particles is less than 5 μm, the density of the molded product is lowered and the shrinkage ratio is increased, and cracks frequently occur when a radial anisotropic magnet is produced. are doing. Further, the average particle size of the coarse particles is in the preferred range of the present invention, that is, the average particle size is 5
When the thickness is up to 100 μm, the shrinkage ratio is 6% or less, and the effect of the present invention appears. Furthermore, the average particle size of coarse particles is 5 to 1
According to the method for producing an oxide permanent magnet of the present invention having a diameter of 00 μm, the density of the sintered body is 86 to 94% of the theoretical density, and the pores of 0.1 μm or more are 5 to the total pores.
It is possible to make an oxide permanent magnet of 60%.

Example 3 The coarse particles of the oxide magnetic powder prepared in Example 1 were sprayed and mixed with a 10 wt% PVA aqueous solution so that PVA was 1 wt% of the magnetic powder, and then mixed.
The oxide magnetic powder used in Example 1, that is, an average particle size of 0.9
Fine particles of Sr ferrite magnetic powder of μm were added so that the ratio was 30 wt%, and mixed by a Henschel mixer for 3 minutes to obtain a granulated powder of oxide magnetic powder. afterwards,
This granulated powder was dried at 80 ° C. for 24 hours to prepare material 14. This material was treated with the same procedure as in Example 1 so that
A cylindrical molded body having a size of 5 mm and a height of 14 mm was obtained. Furthermore,
The material 14 was fired under the same conditions as in Example 1 to obtain Sample No. 14 was created. Also, as in Example 1, the oxide powder was dried and formed in a magnetic field to give an outer diameter of 30.
A molded body of a radial anisotropic ring magnet having a diameter of 8 mm, an inner diameter of 26.8 mm and a height of 5 mm was prepared and fired under the same conditions as in Example 1.

[0061]

[Table 3]

Table 3 shows sample No. Shrinkage rate for 14, 3, and 7, magnetic flux density Br, density, strength as magnetic characteristics,
The ratio of pores of 0.1 μm or more and the crack generation rate when a radial anisotropic magnet is used are shown. In addition, each measurement method and calculation method are the same as in Example 1. Sample N
o. The angle of repose measured with a powder tester is also shown for 14, 3, and 7. Here, the angle of repose is a value measured by an injection method through a sample funnel, and a powder having a relatively good fluidity has a small angle of repose and a fine powder having a strong adhesion and cohesiveness, that is, a fluidity. The repose angle shows a large value in the case of powders with poor quality.

As is clear from Table 3, the sample 14 manufactured by the manufacturing method of the present invention has a density of 86 to the theoretical density.
It is 94% and the pores of 0.1 μm or more are 5 to 60% of all the pores, and the effect of the present invention is obtained. Further, the sample No. prepared by the preferred granulation method of the present invention. Sample No. 14 has a repose angle made by a conventional manufacturing method. 7 as well as sample No. 7 It can be seen that it is superior to Sample No. 3 and has good fluidity.

[0064]

EFFECT OF THE INVENTION The oxide permanent magnet according to the present invention has excellent magnetic properties, high strength, and is unlikely to cause cracks or cracks regardless of the shape of the molded body.

Further, by the method for producing an oxide permanent magnet according to the present invention, it is possible to obtain a compact having a density which cannot be reached by the conventionally used raw material having a particle size, and it is possible to suppress the shrinkage ratio before and after firing. it can. Furthermore, a high-density sintered body can be obtained. As a result, no cracks or cracks are generated, and in some cases, no processing step is required, and an oxide permanent magnet having high strength and excellent magnetic properties can be produced.

Claims (5)

[Claims] 1. The density is 86 to 94% of the theoretical density, and the pores of 0.1 μm or more are 5 to 60% of the total pores.
An oxide permanent magnet characterized by: 2. The oxide permanent magnet according to claim 1, which is an anisotropic magnet. 3. Coarse particles of oxide magnetic powder having an average particle size of 5 to 100 μm and oxides having an average particle size of 0.5 to 1.5 μm, which are obtained by crushing a sintered body of an oxide permanent magnet. A method for producing an oxide permanent magnet, characterized in that fine particles of magnetic powder are mixed so as to be 10 to 60 wt%, and the mixed powder is molded and fired. 4. A granulated powder obtained by adding and mixing a solution in which a binder is dissolved in either coarse particles or fine particles of the above oxide magnetic powder and then mixing with the remaining particles to granulate. The method for producing an oxide permanent magnet according to claim 3, wherein the oxide permanent magnet is molded and fired. 5. The permanent oxide according to claim 3, wherein the oxide magnetic powder is molded so that the density of the molded body is 78% or more of the theoretical density, and then fired. Magnet manufacturing method.