JP3208739B2 - Manufacturing method of ferrite particle powder material for bonded magnet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a ferrite for a bonded magnet.
The present invention relates to a method for producing a particle material.

[0002]

2. Description of the Related Art Bonded magnets have advantages over sintered magnets in that they are lighter, have better dimensional accuracy, and can be easily mass-produced in complex shapes. Therefore, bonded magnets are used for toys, office tools, audio equipment, etc. Widely used for various applications.

[0003] In recent years, along with the reduction in size and weight of tools and equipment in various fields, there is a strong demand for downsizing of the magnet itself by improving the performance of bonded magnets used therein.

[0004] Bonded magnets are generally produced by kneading a rubber or plastics material and a magnetic powder material and then molding in a magnetic field or by mechanical means.

A magnetic-field-oriented molded product molded in a magnetic field is used especially for a part having a complicated shape, and is used in a field where a high residual magnetic flux density Br and a maximum energy product BHmax are required.

On the other hand, mechanically oriented molded articles formed by mechanical means are not suitable for parts having complicated shapes, but are widely used especially in the field of micromotors because they are easy to process. .

The residual magnetic flux density Br of the bonded magnet is
Since it contains a non-magnetic rubber or plastics material, its volume is lower than that of a sintered magnet, so its improvement is required.

The residual magnetic flux density Br of the bonded magnet
Depends on the magnitude of the saturation magnetization value, the degree of orientation, and the filling factor of the magnetic powder used.In particular, the influence of the saturation magnetization value and the degree of orientation is large, and the improvement of the saturation magnetization value and the degree of orientation of the magnetic powder is not improved by the bond magnet. Can be said to be a condition for increasing the residual magnetic flux density Br value.

[0009]

SUMMARY OF THE INVENTION High residual magnetic flux density B
The bond magnet having the r and the energy product BHmax is currently the most demanded, and for this purpose, it is necessary to increase the saturation magnetization value and the degree of orientation of the magnetic powder used as described above as much as possible.

When the magnetic powder material is mixed with a rubber or plastic material at a higher filling rate of the magnetic powder to improve the magnetic properties, the melt viscosity of the kneaded product with the rubber or plastic material becomes higher. The tendency of the orientation of the magnetic powder tends to decrease.On the other hand, if the orientation is to be increased, the filling rate of the magnetic powder may be set low. In this case, the orientation of the magnetic powder is improved, Since the absolute amount of the magnetic powder content is small, there is a limit to increase the magnetic properties, particularly the residual magnetic flux density Br value, and the degree of orientation of the bonded magnet obtained using the magnetic powder that is commercially available today (Equation 2) -
The same-) was about 0.91 at most.

[0011]

(Equation 2)

Therefore, it is the greatest technical problem in the art to obtain a ferrite particle powder material for a bonded magnet having a high saturation magnetization and a high degree of orientation.

[0013]

Means for Solving the Problems In producing a ferrite particle powder material for a bonded magnet, the present inventors obtained a ferrite particle powder for a bonded magnet having a large saturation magnetization value and a high degree of orientation by obtaining the ferrite particle powder. As a result of various studies to solve the technical problems, the present invention has been completed.

That is, the present invention relates to a method in which a magnetoplumbite-type ferrite particle powder obtained by firing a magnetoplumbite-type ferrite raw material mixture at 1100 ° C. or higher is used.
e in an amount of 0.30 to 3.00% by weight in terms of Fe ₂ O ₃ ,
0.20 to 0.60% by weight of Bi compound in terms of Bi ₂ O ₃
After blending, after fine pulverization, 700-950
Heat treatment in the temperature range of ° C. , the saturation magnetization (σ
s) is Ri der 70 emu / g or more, the ferrite particles for bonded magnet orientation degree (number 2) is characterized in that to obtain a magnetoplumbite-type ferrite particles can be manufactured bonded magnets is 0.92 or more It is a manufacturing method of the material.

## EQU2 ## (Br //) / (Br //) + (BrＢ)

Next, various conditions for implementing the present invention will be described.

As the Fe compound in the present invention, α-
Fe ₂ O ₃ , γ-Fe ₂ O ₃ , Fe ₃ O _{4 and the} like can be used. Bi compounds include Bi ₂ O ₃ , NaBiO _2
3 etc. can be used.

The compounding amount of the Fe compound and the Bi compound is 0.30 to 3.0 in terms of Fe ₂ O _{3 with} respect to the product, the magnetoplumbite type ferrite particles.
0 wt%, _Bi 2 _{O 3} in terms of at 0.20-0.60 wt%
Is valid. 3.00% by weight in terms of Fe ₂ O ₃
As described above, when the content is 0.60% by weight or more in terms of Bi ₂ O ₃ , the heat treatment conditions must be largely changed, and it is not economical. On the other hand, when the content is less than 0.30% by weight in terms of Fe ₂ O _{3 and} less than 0.20% by weight in terms of Bi ₂ O ₃ , the effect of the present invention cannot be exhibited.

It is appropriate to mix the Fe compound and the Bi compound at the time of pulverization. That is, in each of the steps of mixing the raw materials, firing, finely pulverizing, and heat treating, the raw materials are mixed at the time after firing.

When the Fe compound and the Bi compound are blended before firing, for example, if the Fe compound is blended at the time of blending the raw materials, the raw material becomes a magnet plumbite-type ferrite raw material mixture in excess of Fe ₂ O _3. If growth is not performed and ferrite particles having a desired particle size are to be obtained, high-temperature firing is required. High-temperature sintering has the disadvantage of promoting coarsening of particles and sintering between particles. On the other hand, when the Bi compound is blended before firing, depending on the blending amount, the ferrite particles may have roundness or may have an effect of facilitating pulverization, but have a large saturation magnetization value in the present invention and a high degree of orientation. Ferrite particles for bonded magnets cannot be obtained.

In the present invention, the magnetoplumbite-type ferrite particles before the compounding of the Fe compound and the Bi compound are obtained by mixing a raw material such as iron oxide or hydrated iron oxide and an auxiliary raw material such as strontium carbonate or barium carbonate into a predetermined composition. 1
It can be obtained by firing at a temperature of 100 ° C. or higher. If a flux, such as barium chloride, is used in combination,
Generation of magnetoplumbite-type ferrite particles at low temperatures is facilitated.

When the sintering temperature is 1100 ° C. or lower, a ferrite-forming reaction cannot be sufficiently caused.

The temperature of the heat treatment after the pulverization in the present invention is preferably in the range of 700 to 950 ° C. When the temperature is 700 ° C. or lower, the object of the present invention cannot be sufficiently achieved. A temperature of 950 ° C. or more is not preferable because light sintering occurs between particles.

[0023]

[Action] The most important point in the present invention is to provide magnetoplumbite ferrite particles with magnetoplumbite type ferrite raw material mixture was fired at 1100 ° C. or more, the Fe compound in terms of Fe ₂ O ₃ 0.30 3.0
0 wt%, 0.20 to Bi compound calculated as _Bi 2 _{O 3}
After blending 0.60% by weight, after performing a fine pulverization process,
When the heat treatment is performed in the temperature range of 700 to 950 ° C., the saturation magnetization (σs) is 70 emu / g or more, and the degree of orientation (Equation 2)
Is 0.92 or more, which is the fact that ferrite particles having excellent orientation can be obtained.

Regarding the reason why the orientation of the ferrite particle powder in the present invention is excellent, the present inventor has proposed that the plate-like particles produced by the conventional method are subjected to a pulverizing treatment in order to increase the filling ratio of rubber or plastics material. , And the individual particles are broken up into single particles. At this time, the corners of the particles are removed, fine powder is generated, and the particles themselves are rounded. Even if the particles in this state are subjected to a heat treatment to remove the strain generated during pulverization, only those having a low saturation magnetization value and a low degree of orientation can be obtained, and the ferrite particle powder obtained according to the present invention has a Fe compound and It contains a Bi compound, and promotes the absorption of some of the fine powder generated during the fine pulverization due to the presence of the Fe compound and the Bi compound during the heat treatment after the fine pulverization into large particles, It is considered that by replenishing the defects generated in the above, ferrite particles having a large saturation magnetization value and a high degree of magnetic field orientation can be obtained.

[0025]

Next, the present invention will be described with reference to Examples and Comparative Examples.

The degree of orientation (Equation 2) in the following Examples and Comparative Examples is a residual magnetic flux density (a magnetic flux density obtained by measuring a magnetic-field-oriented compact formed in a magnetic field from a direction parallel to the orientation magnetic field). It is shown by the value obtained from Equation 3) and the residual magnetic flux density (Equation 4) measured from the direction perpendicular to the orientation magnetic field.

[0027]

(Equation 3)

[0028]

(Equation 4)

The saturation magnetization (σ s) value is determined by measuring the orientation of a magnetic-field-oriented compact formed in a magnetic field by a cylinder (φ5.5 mm × 3 m
m), and using VSM (manufactured by Toei Kogyo Co., Ltd.)
The measurement was performed with a measurement magnetic field of 15 KOe.

Example 1 861.4 g of α-Fe ₂ O ₃ ,
138.6 g of SrCO ₃ and 30 g of BaCl ₂ are mixed well and granulated with water. After the granulated product was fired at 1150 ° C. for 1 hour, iron oxide (α-
Fe ₂ O ₃ ) of 16 g (corresponding to 1.60% by weight based on the magnetoplumbite type ferrite particle powder);
2.7 g of bismuth oxide (Bi ₂ O ₃ ) (0.27% by weight based on the magnetoplumbite type ferrite particle powder)
Is equivalent to ) And pulverized using an attritor. Next, heat treatment was performed at 850 ° C. for 1.5 hours to obtain a ferrite particle powder material for a bonded magnet.

As a result of composition analysis, the obtained ferrite particle powder was found to have Fe ₂ O ₃ /SrO+BaO=6.07.

121 g of the ferrite particle powder material for a bonded magnet thus obtained, EVA (ethylene-vinyl acetate copolymer resin: manufactured by Mitsui Dupont Polychemical Co., Ltd.) 12
g and 0.5 g of zinc stearate, and then mixed at 80 ° C.
The mixture was heated and kneaded, and then cooled and solidified, and then pulverized. The pulverized material was heated and melted, a magnetic field of 10,000 Oe was applied, and then cooled and solidified to obtain a bonded magnet.

The resulting bonded magnet has a degree of orientation (Equation 2).
0.93, residual magnetic flux density Br is 2860 Gauss, coercive force _I Hc2600 Oe, energy product (BH) ma
x2.02MGOe. The saturation magnetization σS is 7
It was 0.5 emu / g.

Examples 2 to 7, Comparative Examples 1 to 5 Amount of Fe raw material, amount of Sr raw material, firing temperature, blending amount of Fe compound, B
A ferrite particle powder material for a bonded magnet was produced in the same manner as in Example 1 except that the amount of the i-compound and the heat treatment temperature were variously changed, and a bonded magnet was produced using the particle powder material.

Table 1 shows the main manufacturing conditions and various characteristics at this time. The time when the Fe compound and the Bi compound were blended in Comparative Example 5 was when the raw materials were blended before firing.

[0036]

[Table 1]

[0037]

According to the method for producing a ferrite particle powder material for a bonded magnet according to the present invention as described above, an Fe compound and a Bi compound are blended after firing, By performing heat treatment after the pulverization treatment, ferrite particle powder capable of producing a bonded magnet having a large saturation magnetization value and having improved orientation by the magnetic field orientation means can be obtained. It is most suitable as a magnetic particle powder for a bonded magnet.

 ──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-63-162532 (JP, A)

Claims (1)

(57) [Claims] 1. An Fe compound is added to Fe ₂ powder in a magnetoplumbite-type ferrite particle powder obtained by firing a magnetoplumbite-type ferrite raw material mixture at 1100 ° C. or more.
0.30 to 3.00% by weight in terms of O ₃ ,
After mixing 0.20 to 0.60% by weight in terms of i ₂ O ₃ , fine pulverization is performed, and then heat treatment is performed in a temperature range of 700 to 950 ° C., so that the saturation magnetization (σs) is 70 emu.
/ G or more der is, the degree of orientation (number 1) is 0.92 or more
A method for producing a ferrite particle powder material for a bonded magnet, comprising obtaining a magnetoplumbite type ferrite particle powder capable of producing a bonded magnet. [Equation 1] (Br //) / (Br //) + (Br⊥)