JPS63116405A - Manufacture of resin-coupled rare earth element magnet - Google Patents

Abstract

PURPOSE:To improve the orientation of a rare earth element magnet thereby to maintain its coercive force high by compression molding 2-17 rare earth element magnet powder having 100-70wt.% and 0.9 or more of sphericality in a magnetic field so that its coercive force is 6kOe or less, age-hardening it and impregnating it with resin. CONSTITUTION:A sintered material is first pulverized, and the particles are sphered to become 0.9 or more of sphericity. Then, it grain size is regulated to become 70wt.% of powder from larger particle diameter toward smaller particle diameter. Then, the magnet powder is compression molded in a magnetic field in the state that coercive force is small before age-hardening, and age-hardened while the molded shape is held. It is eventually impregnated with thermoset synthetic resin, and aftercured.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a method for manufacturing a resin-bonded magnet in which magnet powder is bonded using a resin, and more specifically, the present invention relates to a method for manufacturing a resin-bonded magnet in which magnet powder is bonded using a resin. The present invention relates to a method for manufacturing a resin bonded rare earth magnet, in which 2-17 rare earth magnet powder is compression molded in a magnetic field, then subjected to aging treatment, impregnated with resin, and bonded.

[Prior Art] Magnets in which rare earth magnet powder is bonded with a binder are conventionally known. Thermoplastic or thermosetting resin is used as the binder, and it is manufactured by molding methods such as compression, injection, and extrusion. These magnets have advantages such as good magnetic properties, excellent mass productivity, easy dimensional accuracy, and a large degree of freedom in shape, and are rapidly being used in a variety of applications in recent years.

Regarding the compression molding method, many manufacturing methods have already been developed, and a typical example is the method shown in FIG. 2 or 3. In the case of Fig. 2, an alloy of a predetermined composition is first crushed, formed, and sintered, and then subjected to aging treatment as it is.
It is kneaded with molding aids such as MC, PEG, and paraffin, and compression molded in a magnetic field. Then, heat to evaporate the forming aid,
Impregnate with resin and perform after-cure treatment. Also the third
In the case shown in the figure, the particle size-adjusted material is kneaded with resin, compression molded in a magnetic field, and then subjected to an after-cure treatment.

[Problems to be Solved by the Invention] In order to improve the magnetic properties of a resin-bonded rare earth magnet, it is important to highly fill the magnet powder and increase the degree of orientation. It is said that in order to completely orient the magnetic powder during molding in a magnetic field, the strength of the applied magnetic field needs to be at least 4 to 5 times the coercive force of the raw material, the magnetic powder. Therefore, in the prior art, for example, in the case of an S m z Co Hq resin-bonded magnet, a strong magnetic field of 40 to 50 kOe or more is required.

However, the strength of the magnetic field obtained by the currently widely used magnetic field forming machines does not reach the above value (generally, the magnetic field that can be applied on the production line is about 15 kOe), so the magnetic field strength that is actually used In medium molding, raw material powder cannot be oriented sufficiently.

For this reason, there is a drawback that the magnetic properties are not sufficiently high.

In addition, in conventional technology, particle size is adjusted to achieve high filling, and molding additives or resin are kneaded before molding, but since pulverized magnet powder with an irregular shape is used, an orienting magnetic field is applied. However, it is difficult for the magnet powder to rotate, and the magnetic properties cannot be improved to a degree commensurate with the higher filling.

The purpose of the present invention is to eliminate the drawbacks of the prior art as described above,
The object of the present invention is to provide a method for producing a resin-bonded 2-17 rare earth magnet having excellent magnetic properties, particularly an improved degree of orientation, and a high coercive force.

[Means for Solving the Problems] The present invention, which can achieve the above objects, has a particle diameter of at least 70
Compression molding of 2-17 rare earth magnet powder in which the shape of coarse particles distributed by weight percent has a sphericity of 0.9 or more in a magnetic field when the coercive force before aging treatment is 6 kOe or less,
This is a method for producing a resin-bonded rare earth magnet in which the magnet is then subjected to an aging treatment and then impregnated with a resin and bonded.

The raw material 2-17 rare earth magnet powder is RtTM
+y (However, R is Sm or Ce containing Y.

One or more rare earth elements such as Pr and Nd, TM
The main component is a transition metal element mainly consisting of Co, Fe, and Ni. Such raw materials are usually obtained by pulverizing an alloy having a predetermined composition, forming it into a predetermined shape and sintering it, and, if necessary, solution-treating it under predetermined conditions.

In 2-17 rare earth magnets, precipitation hardening occurs due to aging treatment and a high coercive force appears. In addition, if the powder used is approximately spherical, there will be less unevenness on the particle surface, and it will move more easily when an orienting magnetic field is applied, and the disorder of orientation that may occur due to the shape of the particles during molding will be less likely to occur. It was created by focusing on the phenomenon.

As shown in FIG. 1, in the present invention, the raw material sintered body as described above is first crushed and sphericalized to have a sphericity of 0.9 or more. Next, the particle size is adjusted from the larger particle size to the smaller particle size so that at least 70% by weight of the powder is as described above. Here, sphericity refers to a value expressed by the following formula.

(Actual particle surface area) In order to obtain spherical particles, an etching method, a method using mechanical abrasion, etc. are used. For example, the magnet powder is placed in an acid (hydrochloric acid, nitric acid, etc.) in which the magnet powder easily dissolves, and stirred for an appropriate period of time. Since melting generally occurs from the edges (sharp corners) of the magnet powder, it is thereby possible to obtain the magnet powder with the desired sphericity. After acid treatment, thoroughly wash with water and dry. Alternatively, put the magnetic powder in a container lined with abrasive material and apply a suitable gas (air, nitrogen gas, argon gas, etc.)
It is also possible to make the powder into a spherical shape by blowing and stirring the powder, causing the powder to collide with the vessel wall and abrading the edges.

Also, unlike the above, spheroidization can also be made from molten alloy. There are several ways to do this, such as the following:

■ Spray method (atomization method) Molten alloy is made to flow out of a nozzle, and a high-pressure spray medium (liquid or gas) is sprayed onto the molten alloy flow to pulverize it and make it spherical.

■ Cavitation method When molten metal is squirted into the small gap between two rolls,
Cavitation occurs in the molten metal in the two rolls and the powder is ejected, which can be spheroidized by being rapidly cooled with a cooling plate or an aqueous solution.

(2) Ejection method in rotating liquid By forming a liquid layer on the inner wall of a rotating drum by centrifugal force and ejecting a molten alloy beam into this rotating liquid layer, spheroidized powder can be produced depending on the ejection conditions.

(2) Conical roll method A spheroidized powder can be produced by ejecting molten alloy from a nozzle, making it contact and scatter onto a rotating conical body to form a powder, and cooling the powder.

Incidentally, the above-mentioned methods (1) to (2) are methods for producing metal or alloy powders, which are generally called quenching methods, and anisotropy can be achieved by heat treatment in a magnetic field, electric field, heat treatment under stress, or the like. Further, the particle size and sphericity of the powder can be controlled by manufacturing conditions, and unlike the above-mentioned etching method and method using mechanical abrasion, there is no loss during sphericalization, making this method suitable for mass production.

Compression molding is performed in a magnetic field using magnet powder with a small coercive force (6 k Oe or less) whose particle size has been adjusted as described above before aging treatment, and then aging treatment is performed while maintaining the molded shape. to produce high coercive force. Finally, it is impregnated with a thermosetting synthetic resin such as epoxy resin, phenol resin, or acrylic resin, and subjected to an after-cure treatment to be bonded and integrated.

Furthermore, in order to improve magnetic properties, especially residual magnetic flux density, and improve moldability, PVA is used during molding.

Molding aids such as PVB, CMC, PEG, paraffin, etc. may be used and these shaping aids may be blown off by heating before or during the aging treatment.

In the present invention, the sphericity of at least 70% by weight of coarse particles is set to be 0.9 or more from the larger particle size to the smaller particle size because the sphericity of the magnet powder is determined by the filling rate and orientation. As a result of research on the effect on magnetic powder particle size, it was found that at least 70
This is because it has been found that it is appropriate for the sphericity of the coarse particles to have a sphericity of 0.9 or more by weight. This value is the lower limit value,
Of course, when the filling rate is increased to 70% by weight or more and the sphericity is 0.9 or more, the degree of orientation is improved.

The reason why the magnet powder before aging treatment which is molded in a magnetic field in the present invention is set to be 6 kOe or less is as follows. As mentioned above, in order to sufficiently orient the magnetic powder when molding is performed in a magnetic field, the strength of the applied magnetic field needs to be at least 4 to 5 times as strong as the magnetic powder that is the raw material. Therefore, when forming in a magnetic field, it is desirable that the coercive force of the magnet powder before aging treatment be as low as possible, and generally the magnetic field that can be applied on the production line is about 15 kOe.

The present inventors conducted various experiments on the relationship between the coercive force of magnet powder before molding in a magnetic field and the magnetic properties of resin-bonded rare earth magnets after aging treatment, and found that using magnet powder with a coercive force of 6 kOe or less, It has been found that by producing a resin-bonded rare earth magnet based on the method of the present invention, magnetic properties are much better than resin-bonded rare earth magnets obtained by conventional methods. This value is the upper limit, and as described above, when magnetic powder of 6 kOe or less is used, the magnetic properties are significantly improved.

Regarding the direction of the orientation magnetic field during molding in a magnetic field, a magnetic field in any orientation direction such as vertical, horizontal, radial, multipolar, etc. can be applied depending on the product to be manufactured.

[Function] The magnetic powder used when forming in a magnetic field is a powder that has not been subjected to aging treatment, so its coercive force is small. The grains are almost spherical.

Therefore, in the present invention, since the magnet powder moves easily, there is little disturbance in orientation during molding, and sufficient orientation is achieved. Since the aging treatment is performed in that state, the orientation state is maintained as it is even if the coercive force of the magnet powder increases after the aging treatment.

As a result, according to the present invention, it is possible to manufacture a resin-bonded magnet with far superior magnetic properties than conventional magnets.

[Example 1] Samarium-cobalt (Sml) with an average particle size of 1000 μm
Co+y) based alloy was milled with an average particle size of 4 μm by jet milling.
The resulting powder was molded in a magnetic field and sintered to serve as the raw material in this example.

In this example, this raw material sintered body was crushed using a show crusher to obtain irregularly shaped magnet powder with a particle size of approximately 300 μm.
A part of the amorphous powder with a particle size of about 300 μm was ground in toluene using a ball mill to obtain an amorphous fine powder with a particle size of about 40 μm.

In addition, amorphous powder with a particle size of about 300 μm is etched by immersing it in concentrated hydrochloric acid for 5 minutes, washed with hexane for 60 minutes, and dried to obtain a coarse powder with a particle size of about 200 μm and a sphericity of 0.9 or more. I got it.

The magnetic powder thus obtained has a sphericity of 0.9 or more and a particle size of approximately 2.
It is a mixture of 75% by weight of coarse powder of 0.00 μm and 25% by weight of irregularly shaped fine powder with particle size of about 40 μm.

Without using a molding aid, this magnetic powder was compression molded using a magnetic field molding machine in a magnetic field of 12 kOe at 3 ton/cm".The resulting molded product was then heated at 800°C in a vacuum.
Aging treatment was performed for 1 hour. Finally, it was degassed in vacuum, impregnated with epoxy resin, and subjected to an after-cure treatment at 120° C. for 1 hour to produce a resin-bonded rare earth magnet.

Further, for comparison, comparative samples were manufactured based on the conventional method shown in FIGS. 2 and 3. In the method based on FIG. 2, the raw material sintered body is first aged under the same conditions as in the above example, and then pulverized to obtain amorphous magnetic powder with an average particle size of 200 μm. After kneading with carboxymethylcellulose), molding was carried out in a magnetic field under the same conditions, and after heating to drive off the molding aid, they were similarly impregnated with epoxy resin and integrated. The method based on FIG.
Using the same powder as in the method shown in the figure, it was kneaded with epoxy resin, molded in the same magnetic field, and after-cured.

An example of the measurement results is shown in Table 1.

In the case of the conventional method shown in Table 1, the molding aid or resin is kneaded with the magnet powder in order to improve the packing density of the magnet powder.
As shown in Table 1, the magnetic properties are low due to poor orientation.

On the other hand, in the present invention, the degree of orientation is high even without using a forming aid, so the magnetic properties are extremely good.

[Example 2] Particle size of about 200/Jm with sphericity of 0.9 or more, same as Example 1
Magnet powder is a mixture of 75% by weight of coarse powder and 25% by weight of irregularly shaped fine powder with a particle size of about 40 μm, CMC is used as a molding aid, and this molding aid is heated during the aging treatment. After scattering, a resin-bonded rare earth magnet was manufactured in the same manner as in Example 1.

The magnetic properties of the obtained magnet are as follows.

Br-8400G bHc=56000e (BH)--X=15.8MG.Oe If a molding aid is used in this way, the present invention can produce a resin-bonded rare earth magnet with unprecedented magnetic properties.

[Example 3] Using the same 3 m z CO + q alloy as in Example 1 as a material, it was spheroidized by the atomization method using argon gas as a spray medium and a non-oxidizing solution as a cooling solution, and the spheroidized alloy was subjected to a magnetic field. Anisotropy was achieved by medium heat treatment. Specifically, a spheroidized alloy is sealed in an electric furnace installed between the poles of an electromagnet (approximately 5 koe), and heated in a vacuum (~10-' Torr).
The temperature was maintained at 770° C. for 5 hours, followed by cooling in a furnace and cooling to room temperature.

The magnet powder used to manufacture the resin-bonded rare earth magnet was a spherical alloy powder with a sphericity of 0.9 or more and a particle size of about 200 μm and a weight of 75% by weight, and a fine powder with a particle size of about 40 μm and a weight of 25% by weight. It is a mixture of

Using the magnet powder whose particle size was adjusted in this manner, resin-bonded rare earth magnets were produced with and without the use of a forming aid. The former is the same method as in Example 1, and the latter is the same method as in Example 2.

The magnetic properties of the obtained magnet are shown in Table 2.

(Leaving space below) Table 2 [Effects of the Invention] As described above, the present invention uses 2-17 rare earth magnet powder in a state of small coercive force, which is almost spherical and has not been aged, and is compressed in a magnetic field. The shape is then aged and precipitation hardened to develop a high coercive force, which is then impregnated with resin and bonded, resulting in a highly oriented resin-bonded type with significantly improved magnetic properties compared to conventional technology. This has an excellent effect in producing rare earth magnets.

In addition, according to the present invention, it is possible to achieve magnetic properties equivalent to or better than conventional ones without using a molding aid, so the process of kneading the molding aid or heating the molding aid after molding to evaporate the molding aid is no longer necessary.
This also has the effect of simplifying the manufacturing process. Furthermore, if a molding aid is used as in the prior art, good magnetic properties that could not be achieved in the past can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a process explanatory diagram showing the main part of the manufacturing process of a resin-bonded rare earth magnet according to the method of the present invention, and FIGS. 2 and 3 are process explanatory diagrams showing the main part of the conventional process, respectively. Patent applicant: Fuji Electric Chemical Co., Ltd. Representative: Minoru Shigeru Figure 1 Figure 2 Figure 3 Raw material sintered product

Claims (1)

[Claims] 1. The shape of the coarse particles, which are distributed at least 70% by weight from the larger particle size to the smaller particle size, has a sphericity of 0.
．． 9 or higher is compression molded in a magnetic field when the coercive force is 6 kOe or less before aging treatment, and then after aging treatment, it is impregnated with resin and bonded. A method for manufacturing a resin-bonded rare earth magnet.