JPH05129119A - Manufacture of granulated powder of rare earth magnet and resin bond magnet - Google Patents

Abstract

PURPOSE:To fill a die cavity with a compound uniformly and easily and to promote the densification of a compact at the time of the compression molding by using granulated powder, in the granulated powder compound which has been developed for the purpose of manufacturing efficiently a rare earth bond magnet having an excellent magnetic characteristic. CONSTITUTION:In granulated powder which is constituted of two rare earth magnet powders of the same kind with average grain diameter DA and DB (DA>=DB) respectively and resin, a solid resin coating is formed as the first layer and a solid resin coating is formed as the second layer around the surface of a core powder A and the plurality of powders B are attached to the surface of the liquid resin coating. Since this granulated powder has an excellent fluidity, a narrow die cavity can be easily filled with this powder. At the time of compression molding, a space formed between large magnet powder grains can be filled with small grains, and therefore a high-density compact can be obtained.

Description

Detailed Description of the Invention

[0001]

The present invention relates to R-Co type, R-Fe type
The present invention relates to a rare earth magnet represented by a —B system and an R—Fe—N system (R is Y and a rare earth metal).

[0002]

BACKGROUND OF THE INVENTION Resin-bonded magnets are made by binding magnet powders with an organic material such as epoxy resin. Resin-bonded magnets can form compacts with high dimensional accuracy without post-processing, and can be integrally molded with other parts. Many are installed in the center. In particular, anisotropic bonded magnets have excellent magnetic properties as compared with isotropic bonded magnets, and therefore are expected to be further developed.

The rare earth magnet powder described above is based on the following R--Co system,
It can be obtained by an alloy system such as R-Fe-B system and R-Fe-N system (R is Y and a rare earth metal).

The R-Co magnet powder can be produced by using an alloy containing SmCo ₅ and Sm ₂ Co ₁₇ intermetallic compounds as main phases. The SmCo ₅ based magnet powder is obtained by melting and solidifying the SmCo ₅ based magnet powder in a suitable composition system using high frequency melting or the like, and then finely pulverizing the alloy. The Sm ₂ Co ₁₇ magnet powder is obtained by subjecting an alloy having an appropriate composition system to solution treatment and aging treatment, and then finely pulverizing it.

The magnetically isotropic R-Fe-B magnet powder can be produced by an alloy system containing an Nd ₂ Fe ₁₄ B intermetallic compound. A typical manufacturing method is to rapidly quench the molten alloy by a single roll liquid quenching method (JP-A-59-64).
739, JP-A-60-9852).

The magnetically anisotropic R-Fe-B magnet powder is obtained by subjecting the above-mentioned isotropic quenched powder to plastic working to impart anisotropy. A specific method is to increase the density of the quenched powder to a density close to the true density of the alloy by hot pressing, and then hot set up the compact again (RW Lee, Appl. Phys. L
ett. 46 (8), 15 April 1985, p.
p790-791). An anisotropic powder is obtained by grinding this upset magnet. The applicant has previously proposed that the RF
As a production method for more easily obtaining an e-B anisotropic powder,
A method has been proposed in which the above-mentioned quenched powder is packed in a metal container and hot-rolled together with the container (Japanese Patent Application No. 1-220675).
issue).

R-Fe-N magnet powder is, for example, Sm ₂ F
It can be produced using an alloy system containing an e ₁₇ N _x (x = 1 to 3) intermetallic compound. Coey et al. Have an appropriate composition of Sm.
It has been reported that magnet powder can be obtained by pulverizing an —Fe-based alloy, followed by heat treatment in a nitrogen atmosphere and nitriding (JMD Coey et al, P.
ROCEEDINGS OF THE ELEVENT
H INTERNATIONAL WORKSHOP
ON RARE-EARTH MAGNETSAND
THEIR APPLICATIONS, Vol. Two
edited by S. G. Banker (CARNE
GIE MELLONUNIVERSITY, Pitt
sburgh, 1990), pp36-59).

As a method for molding the above-mentioned rare earth magnet powder, a method is generally used in which a resin such as epoxy is added to the magnet powder, kneaded, and compression molded. Above all, the anisotropic resin bonded magnet is obtained by compression molding anisotropic powder in a magnetic field. For example, when a compound obtained by kneading SmCo ₅ based powder or Sm ₂ Co ₁₇ based powder and a liquid organic resin as a compound is used for molding, a molded product having a high density can be obtained (for example, JP-A-54-15415). ..

Further, as a concept for realizing a high density of the molded body, T. Shimoda et al. Have proposed that the density can be increased by filling the voids generated between magnet powder particles with a plurality of small particles (Th.
e Fourth International Wor
kshop on Rare Earth-Cobal
t Permanent Magnets and T
hair Applications, Hakone,
Japan, May 22-24 1979, 335-.
345).

[0010]

DISCLOSURE OF THE INVENTION The present invention makes it easy to reduce the thickness and density of a resin-bonded permanent magnet, and contributes to miniaturization, weight reduction, and high performance of electronic-related components. is there.

In order to manufacture an actual magnet part (for example, a thin ring magnet) by a compression molding method with high productivity and high dimensional accuracy, it is essential to be able to uniformly and quickly fill the compound into the mold cavity. On the other hand, since the magnet characteristics depend on the density of the molded body, a molded body having a high density is desired.

The compound obtained by kneading the liquid resin and the magnet powder can obtain a compact having a high density, but since the fluidity is very low, the compound cannot be uniformly filled in the cavity. On the other hand, in the case of a compound mixed with a powdery resin, the fluidity is remarkably improved, but since voids are likely to remain inside the molded product, a high-density molded product cannot be obtained.

The present invention provides a compound in which a rare earth magnet powder is granulated using a solid resin and a liquid resin, thereby improving the filling property of the compound into the cavity and at the same time increasing the density of the molded product. It will be realized.

[0014]

The gist of the present invention is as follows. That is, in the present invention, the average particle diameter is D _A and D _B , respectively, and in the granulated powder formed of the same kind of rare earth magnet powder and D _A ≧ D _B and the resin, the surface of the powder A particle serving as the core is A solid resin coating is on the first layer, a liquid resin coating is on the second layer, and a plurality of powder B particles are attached to the surface of the coating. It is a powder. In the above granulated powder, the liquid resin amount is 20 to 8% by weight of the total resin amount.
Setting to 0% is a more effective means for filling the cavity with the magnet powder and increasing the density of the molded body.

Further, the present invention provides a method for producing a resin-bonded magnet, which comprises mixing a rare earth magnet powder of the same kind having a mean particle diameter of D _A and D _B and D _A ≧ D _B with a resin and molding the mixture. A solid resin coating film is formed on the first layer, a liquid resin coating film is formed on the second layer, and a plurality of powder B particles are attached to the surface of the powder A particles. A method for producing a resin-bonded magnet, which comprises compression-molding granular powder.

[0016]

The inventors of the present invention use the liquid resin and the solid resin in combination with the resin to be kneaded with the rare earth magnet powder,
It was found that a press-molded product can be densified and a granulated powder having excellent filling properties can be obtained.

That is, the present invention is a granulated powder in which a coating film is formed in the order of a solid resin and a liquid resin on the surface of a magnet powder serving as a core, and powder particles having a smaller size than the core particles are attached to the surface. is there.

This granulated powder has excellent fluidity because the granulated powders do not adhere to each other. In addition, since voids formed between large magnet powder particles during molding can be filled with small particles, a compact having a high density can be obtained.

The magnets produced by the present invention have the possibility of high performance and low cost, and are therefore expected to be used widely and in large quantities as magnet parts for various actuators such as small motors.

The details of the present invention will be described below. The following is used as the resin to be kneaded with the rare earth magnet powder.
A thermosetting resin is used as the liquid resin, and an epoxy resin having excellent dimensional stability, moisture resistance, chemical resistance and mechanical properties is most effective. The viscosity of the resin is not particularly limited, but it is desired that the magnet powder B easily adheres to the surface.
As the solid resin, a thermoplastic or thermosetting resin is used.

First, a coating of solid resin is formed on the surface of powder A particles having a large particle size among magnet powders A and B having different particle size distributions. This coating is formed by mixing the magnet powder A and an organic solvent in which an appropriate amount of solid resin is dissolved, and then volatilizing only the organic solvent. Next, an appropriate amount of liquid resin is mixed and applied to the surface. Thereafter, magnet powder B having a predetermined weight ratio is mixed and granulated. This granulation is efficient when using a ball mill or the like. 1 (a), 1 (b) and 1 (c) schematically show the difference in the state of the resin surrounding the magnet powder according to the prior art and the present invention. (A) shows the case where only the liquid resin is used, but since the liquid resin adheres the magnet powders to each other, the fluidity of this compound is poor. The state where only the powdered resin is kneaded is shown in (b). In this compound, magnet powders are separated from each other, so that the fluidity is high. However, in a molded product using this compound, voids are easily generated, and it is difficult to increase the density of the molded product.

On the other hand, (c) is the structure of the granulated powder according to the present invention. Since each of the granulated powder particles surrounds the magnet powder A with the magnet powder B, it is difficult to adhere to each other. That is, the fluidity of the granulated powder is superior to that of (a), and it is easy to fill the mold cavity. On the other hand, since the magnet powder B surrounds the magnet powder A by the adhesive force of the liquid resin, the voids generated between the magnet powder A can be filled with the powder B, so that the densification can be efficiently promoted during molding. It The average particle size of the magnet powder used is preferably 500 μm or less, which allows molding of ordinary magnet parts. Further, if the magnet powder is pulverized excessively finely, it becomes difficult to increase the density by molding, and it becomes difficult to handle industrially. Therefore, the average particle diameter is preferably 1 μm or more.

Two types of magnet powders A and B forming granulated powder
It is necessary that the particle diameters D _A and D _B of D _A ≧ D _B. When D _A <D _B , it is difficult to surround the powder A particles with a plurality of B particles, and a granulated powder having high fluidity cannot be obtained.

The total amount of resin added to the magnet powder is generally 1 to 5% in weight percentage with respect to the amount of magnet powder. This is because if it is less than 1%, the amount of resin is small and the binding of the magnet powder is insufficient, and if it exceeds 5%, the density of the molded magnet becomes extremely low.

The weight percentage of the liquid resin with respect to the total amount of resin is preferably 20% or more and 80% or less. If it exceeds 80%, the fluidity of the granulated powder is significantly reduced.
When it is less than 20%, the adhesive force between the powders A and B by the liquid resin is insufficient and it is difficult to form the structure of the granulated powder. As a result, it is difficult to increase the density of the molded body.

[0026]

Example 1 An experiment was conducted using Nd-Fe-B type anisotropic magnet powder. The composition of the magnet powder is Fe-14% Nd- in atomic percentage.
5% B-1% Cu (Nd ₁₄ Fe ₈₀ B ₅ Cu ₁ ).
First, a quenching powder was produced by the single roll quenching method. Anisotropy was achieved by inserting the above-mentioned quenched powder into an iron container and
^The pressure was reduced to ^-3 to 10 ^-4 torr, sealed, and then hot-rolled at 700 ° C. The rolled material thus obtained was mechanically pulverized to obtain magnet powder having a particle size of 300 μm or less. After that, classification with a sieve is performed and powder A (30
0 ≧ D (μm) ≧ 150) and powder B (D (μm) <15
0) was prepared.

A predetermined amount of solid epoxy resin was used as a solvent to uniformly form a film on the powder A particles. A predetermined amount of liquid epoxy resin was added and kneaded. Powder B was added thereto and mixed to obtain granulated powder. Here, the weight percentage of the powder A with respect to the total magnet powder was 50%. The percentage of the total epoxy resin to the weight of the magnet powder was fixed at 3.0 wt%.

The filling property of the powder is represented by the bulk density of the filled magnetic powder. The cavity of the mold used in the experiment was a slit with a width of 2 mm, and the filling depth was fixed at 5 mm. The feeder supplying the powder moved at 20 cm / sec and reciprocated 5 times in the width direction on the slit.

FIG. 2 shows the filling property of the granulated powder with respect to the weight ratio of the solid epoxy resin and the liquid epoxy resin. The filling was performed 5 times, and the variation in bulk density was indicated by an error bar. The excellent filling property is represented by the large bulk density and the small variation. Further, these compounds were molded in a magnetic field at a molding pressure of 4 ton / cm ² , and the density of the molded body was measured.

FIG. 2 shows the weight ratio of the solid epoxy resin and the liquid epoxy resin, the density of the molded body and the residual magnetic flux density (B
The relationship of r) is shown. When only liquid epoxy is used, the bulk density is low and the dispersion is large, so the filling property is poor.

On the other hand, the density of the molded product is low when only the solid epoxy resin is used. The granulated powder using both the liquid epoxy resin and the solid epoxy resin as in the present invention has a high bulk density of about 3 g / cm ³ at the time of filling, and has a very small variation, and therefore has excellent filling properties.

The density obtained when the granulated powder is molded is also high. The density was 5.6 g / cm ³ when only the solid epoxy resin was used, whereas the density of the granulated powder was about 5.9 to 6.1 g / cm ³ . The Br of the molded product was 7.9 kg when the solid resin was used, but was 8.2 to 8.5 kg for the granulated powder.

Example 2 A granulated powder was molded using an isotropic Nd-Fe-B system powder. Here, the molding pressure dependence of the molding density and the residual magnetic flux density (Br) was investigated. The isotropic powder is a super-quenched powder produced using the single roll method. Powder particle size is 150 μm
As follows, powder A (150 ≧ D (μm) ≧
105) and powder B (D (μm) <105).
The granulation was performed in the same manner as in Example 1 using a solid epoxy resin and a liquid epoxy resin, with the total amount of resin fixed at 3.0 wt% with respect to the weight of the magnet powder.

Here, the weight ratio of the powder B is 50% with respect to the total amount of the magnet powder. The ratio of liquid epoxy resin and solid epoxy resin was 1: 1.

FIG. 3 shows the density and Br of the obtained molded product with respect to the molding pressure. When compared at the same molding pressure, the density of the granulated powder of the present invention is 0.
It is ^{3 to} 0.5 g / cm ³ higher and Br is 0.3 to 0.5 kg higher.

[0036]

The method of the present invention relates to an improvement in the production of resin-bonded magnets, which has been difficult until now. The method of the present invention makes it possible to achieve both excellent magnetic properties and high mass productivity. In particular, the improvement of the filling property facilitates the manufacture of thin-walled ring magnets and the like, and thus the application range of the magnets to small motors and the like is widened, and the industrial value is high.

[Brief description of drawings]

1A, 1B, and 1C are schematic views of a state in which a magnet powder and a resin are kneaded.

FIG. 2 is a table showing the bulk density of the filled granulated powder, the density of the molded product, and the residual magnetic flux density (Br) with respect to the weight ratio of the solid epoxy resin and the liquid epoxy resin.

FIG. 3 is a table showing the molding pressure dependence of the density and residual magnetic flux density (Br) obtained when molding the granulated powder of the present invention and the powder coated with only solid resin.

Claims (4)

[Claims] 1. An average particle size of D _A and D _B , respectively,
In a granulated powder formed from the same kind of rare earth magnet powder and resin having D _A ≧ D _B , a solid resin coating film is on the first layer on the surface of the powder A particle serving as a core, There is a coating on the second layer, and more than one powder B on the surface.
Granulated powder of a rare earth magnet, which has a structure in which particles are attached. 2. The granulated powder of a rare earth magnet according to claim 1, wherein the liquid resin amount is 20 to 80% in weight percentage with respect to the total resin amount. 3. An average particle size of D _A and D _B , respectively,
In a method for producing a resin-bonded magnet formed from a resin and a rare earth magnet powder of the same kind, wherein D _A ≧ D _B , a solid resin film is formed as a first layer on the surface of the powder A particles that are cores. A method for producing a resin-bonded magnet, comprising forming a coating film of liquid resin on the second layer, and compression-molding a granulated powder having a plurality of powder B particles attached to the surface thereof. 4. The method for producing a resin-bonded magnet according to claim 3, wherein the liquid resin amount is 20 to 80% in weight percentage with respect to the total resin amount.