JPH02156603A - Manufacture of magnetic powder - Google Patents

Abstract

PURPOSE:To recover the coercive force of magnetic powder reduced when the powder is produced by grinding a press-compacted body of a magnetically anisotropic substance so as to obtain high-performance magnetic powder by heat-treating the powder at a temperature higher than a specific value after powder of a rare earth oxide is mixed with the powder. CONSTITUTION:Powder obtained by grinding a press-compacted body of a magnetically anisotropic substance is heat-treated at a temperature of >=250 deg.C after powder of a rare earth oxide is mixed with the powder. When the powder is processed in such way, the surface of each particle of the powder is coated with the rare earth oxide powder and the distortion produced in the surface of the particles can be relieved. Therefore, the coercive force of the magnetic powder reduced by the grinding can be recovered and high-performance magnetic powder can be obtained.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for producing magnetic powder.

[Prior Art] Conventionally, rare earth-iron-boron (hereinafter abbreviated as R-Fe-B) based magnetic materials for permanent magnets have been developed or mass-produced using the following manufacturing method.

(1) A powder obtained by heat-treating and pulverizing a quenched thin flake with a thickness of about 10 to 30 μm produced using a quenched ribbon production apparatus used for manufacturing an amorphous alloy, and a resin-bonded magnet using the powder. (Reference Document (2) A magnetically anisotropic consolidated magnet obtained by mechanically orienting the quenched flake obtained in (1) using a two-step hot pressing method.
(Reference Document 1) (3) Anisotropic sintered magnet created by a powder metallurgy method or a sintering method. (Reference 2) (4
) A magnetically anisotropic cast alloy magnet obtained by hot working an alloy ingot at a temperature of 500° C. or higher to refine the crystal grains and orient the crystal axes in a specific direction. (Reference 3) (Reference 1: R, W
, Lee; Appl, Phys, Lett.

VOl, 46(8), 15 April 1985.
p790. ) (Reference 2: M, Sagawa,
S, Fujimura, 'N.

Togawa, H. Yamamoto and
Y, Matsuura; J, Appl.

Phys, Vol, 55(6), 15 March
1984. p2083) (Reference 3: Japanese Unexamined Patent Publication No. 1983
-276803) [Problems to be Solved by the Invention] Among the above-mentioned conventional techniques, the quenched flakes of (1) have a sufficiently high coercive force (8 to 16 kOe or more) for practical use.
However, as mentioned above, since it is magnetically isotropic, the problem is that the obtained magnetic properties (eg, energy product) are low.

In addition, (3) and (4) have the problem that when the particle size is used for magnetic powder for resin-bonded magnets, the coercive force is less than 1 kOe, making it completely impractical.

Furthermore, in (2), the coercive force decreases as the powder is crushed, although the degree is small, and in the powder state of several to several hundred micrometers, there is a large decrease in the squareness of the demagnetization curve as well as a decrease in the coercive force. The problem is that this not only causes a decrease in magnetic properties but also a large decrease in thermal stability.

The present invention solves these problems, and its purpose is to provide a method for producing high-performance magnetic powder.

[Means for Solving the Problems] The method for producing magnetic powder of the present invention involves creating a magnetically anisotropic compacted body, mixing rare earth oxide powder with the powder obtained by pulverizing it, and It is characterized by heat treatment at a temperature of 250°C or higher.

In the present invention, rare earth oxide powder is mixed with the powder obtained by pulverizing a magnetically anisotropic compacted body, and the mixture is heat-treated at a temperature of 250°C or higher to achieve the effect of coating the surface of the powder with rare earth metal. is obtained, and the surface distortion caused during pulverization can be alleviated, so that the coercive force reduced by pulverization can be recovered.

Note that Nd-Fe-B is well known as a rare earth magnet whose basic composition is a rare earth metal, iron, and boron, but Y is a rare earth magnet.

L al Cel' P r, N d+ P
m, S ml E u.

Gd+ T b+ D yI HO,E r,
Any one or more of the rare earth elements T m, Y b and Lu may be used, and didymium (Pr-Nd
) and cerium didymium (Ce-Pr-Nd) can also provide sufficient magnetic performance and are advantageous in terms of supply and price. Furthermore, by adding a small amount of heavy rare earth elements such as Dy and Tb, the coercive force iHc can be increased and a substantial improvement in temperature characteristics can be achieved.

This also applies to rare earth oxide powder.

Furthermore, by replacing a portion of Fe with Co, the Curie temperature can be improved. Since Zr replaces rare earth metals, practical magnetic properties can be obtained with a low rare earth composition, which not only reduces costs, but also greatly improves corrosion resistance, which has been a problem. Substitution with other transition metal groups also improves magnetic performance, corrosion resistance, etc.

[Examples] Hereinafter, the present invention will be described in detail based on Examples.

(Example-1) In Example-1, a compacted body manufactured by the manufacturing method according to claim 2 will be described.

The ingot was melted and cast in an argon gas atmosphere using a high frequency melting furnace so that it had the composition of N d I3F e @a, yB a, s, and the obtained ingot was melted in an argon gas atmosphere using a quenching ribbon production device. A quenched ribbon was prepared using a copper roll having a diameter of 20 mm. This quenched flake was lightly broken, placed in a mold, and heated to 700 to 800 ml in an argon atmosphere.
Hot compression molding was carried out at a temperature of 00° C. for a short time and at a pressure of 20 kg/mm 2 .

The compacted body obtained had a density of approximately 100%.

This compacted body was heated again at 700 to 800 in an argon atmosphere.
Hot compression molding was carried out at a temperature of "C" and a pressure of 10 kg/mm2 in a direction perpendicular to the initial compression direction.

(That is, die-up setting was performed.) The magnetic properties of the obtained bulk magnet are as follows: 1Hc = 14.2 [kOe] Br = 12.3 [kG] (B H)max = 37.9 [MGOe] Met.

The bulk magnet obtained here was pulverized and sieved into powder particle sizes as shown in Table 1, and the iHc of the powder of each particle size was measured. This is taken as a comparative example.

In addition, the obtained powder was mixed with terbium oxide powder and then heat-treated at 600°C for 10 minutes.
was measured. This is the present invention.

The results are shown in Table 1.

Table 1 As is clear from Table 1, in the comparative example, the coercive force decreases as the particle size of the powder becomes finer, whereas in the present invention, the decrease in coercive force is small even compared to the bulk. I understand that.

Further, the powder of the present invention was mixed and kneaded with an epoxy resin, pressure-molded in a magnetic field, and then cured to create a resin-bonded magnet. Magnetic measurements were performed on this in the anisotropic direction (easy magnetization direction) and the direction perpendicular thereto (difficult magnetization direction).

The results are shown in Table 2.

Table 2 As is clear from Table 2, the values of Br in the easy magnetization direction and the difficult magnetization direction are significantly different, indicating that a resin-bonded magnet with a large degree of anisotropy has been obtained, and the maximum energy A high value was also obtained for the product.

(Example 2) In Example 2, a consolidated body produced by the manufacturing method according to claim 3 will be described.

First, melting and casting was performed in an argon gas atmosphere using a high frequency melting furnace so that the composition was Nd+5FevvB@.
It was pulverized using a stamp mill/ball mill to obtain magnetic powder with an average particle size of 3 to 5 μm. This magnetic powder was filled into a mold and oriented in a magnetic field of 15 kOe.
Compression molding was performed at a molding pressure of kg/mm2, sintering was performed at an optimal temperature of 1000 to 1250°C in an argon gas atmosphere, and then heat treatment was performed as necessary at an optimal temperature of 400 to 1250°C. .

The magnetic properties of the obtained sintered magnet are as follows: 1Hc=16.7 [kOe Br=12.8 [kG] (BH)max=38.4 [MGOel.

Here, a resin-bonded magnet was prepared using the same method as in Example 1 except that neodymium oxide powder was used instead of terbium oxide powder of the present invention, and magnetic measurements were performed.

The magnetic properties of the obtained resin bonded magnet were 1Hc=15.
4 [kOe] Br=10.0 [kG] (BH)max=20.9 [MGOe], and a high maximum energy product value is obtained.

(Example 3) In Example 3, a consolidated body manufactured by the manufacturing method according to claim 4 will be described.

In addition, the ingot was melted and cast in an argon gas atmosphere using a high-frequency melting furnace so that it had a composition of Pr+vFeya, 5Bscu+, s, and the obtained ingot was hot pressed at 1000°C for 80% in an argon gas atmosphere. , heat treatment was performed at 1000° C. for 24 hours in an argon gas atmosphere.

The magnetic properties of the obtained bulk magnet are 1Hc=13.2 [kOe] Br = 12.6 [kG] (BH)max=36.2 [MGOe].

Similarly, a resin-bonded magnet was created using dysprosium oxide powder, and magnetic measurements were performed. The results are shown below.

1Hc = 12.1 [kOe] Br = 9.3 [k, Gco (BH) max = 19.7 [MGOe] As can be seen, a resin-bonded magnet with a high maximum energy product value was obtained. There is.

As can be seen from Examples 1, 2 and 3 above, the present invention is not limited to the type of magnetic powder, and any powder can be used effectively. Further, the type of rare earth oxide powder to be mixed is not limited.

(Example 4) Injection molding and extrusion molding were performed using the powders of Examples 1, 2, and 3 and nylon 12 as a binder, but there were no problems under any conditions. It is clear that it does not depend on the manufacturing method of the type magnet.

[Effects of the Invention] As described above, according to the present invention, a magnetically anisotropic compacted body is created, a rare earth oxide powder is mixed with the powder obtained by pulverizing the compacted body, and 250 By being heat-treated at a temperature of ℃ or higher, the coercive force lost due to the strain caused by crushing is recovered, so it is an anisotropic material with much higher performance than isotropic quenched flakes produced by the conventional quenching method. Since a magnetic powder can be obtained, it has great effects not only in improving magnetic properties but also in applications such as realizing higher performance in products using it.

that's all Applicant: Seiko Epson Corporation

Claims (4)

[Claims] (1) Magnetic powder is produced by creating a magnetically anisotropic compacted body, pulverizing it, mixing rare earth oxide powder with the powder, and heat-treating the mixture at a temperature of 250°C or higher. Production method. (2) The above-mentioned magnetically anisotropic consolidated body is produced by quenching an alloy consisting of rare earths, iron, boron, and impurities that are unavoidable in manufacturing, using a quenching ribbon manufacturing device, and then processing this thin flake in two stages. Claim 1, characterized in that it is a compacted body that has been subjected to mechanical orientation treatment using a hot pressing method and has been made magnetically anisotropic.
A method for producing the magnetic powder described above. (3) After the magnetically anisotropic compacted body melts and casts an alloy consisting of rare earths, iron, boron, and impurities unavoidable in manufacturing, the alloy ingot is pulverized using a so-called powder metallurgy method. 2. The method for producing magnetic powder according to claim 1, wherein the magnet is a sintered magnet that has been made magnetically anisotropic through steps such as forming in a magnetic field, sintering, and heat treatment. (4) After the magnetically anisotropic compacted body melts and casts an alloy consisting of rare earth elements, iron, boron, copper, and impurities unavoidable in manufacturing, this alloy ingot is hot-processed at a temperature of 500°C or higher. Production of the magnetic powder according to claim 1, characterized in that it is a cast alloy made magnetically anisotropic by refining the crystal grains and orienting the crystal axes in a specific direction. Method.