JPH04342104A - Magnetic powder for anisotropic bonded magnet; its manufacture - Google Patents

Abstract

PURPOSE:To provide a magnetic powder, for anisotropic bonded magnet use, whose coercive force is high and which is provided with an excellent energy product and to provide the manufacturing method, of said magnetic powder for anisotropic bonded magnet use, whose productivity is excellent and whose cost is low. CONSTITUTION:A manufacturing method and a magnetic powder, for anisotropic bonded magnet use, which is obtained by said manufacturing method are featured in the following manner: an alloy which is composed of 10 to 30 atomic % of R (where R represents at least one kind of rare-earth elements including yttrium), 2 to 28 atomic % of boron and 65 to 82 atomic % of M (where M represents at least one kind out of Fe, Co and Ni) is crushed to an average particle size of 0.5 to 50mum; after that, the crushed alloy particles are pressed and molded in a magnetic field; a molded body whose easy axis of magnetization has been arranged to a direction in which the magnetic field has been exerted is obtained; after that, a heat treatment is executed at a temperature of 400 to 900 deg.C in an inert gas or in a reducing atmosphere; and the heat-treated molded body is crushed so as to obtain an average particle size of 0.5 to 500mum.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention has excellent magnetic The present invention relates to magnetic powder for anisotropic bonded magnets having characteristics and a method for manufacturing the same.

0002

BACKGROUND OF THE INVENTION As materials for rare earth bonded magnets, Sm--Co based and Nd--Fe--B based magnetic powders have been proposed. The former has resource problems because it uses Sm, which contains only a few atomic percent of all rare earth elements, and also contains a large amount of Co, whose raw material supply is unstable. The latter is a permanent magnet material that has been actively researched in recent years, and is attracting attention because it does not contain expensive Co and is mainly composed of Nd, which is more abundant than Sm in terms of resources. Nd-Fe-B that has been put into practical use so far
As typified by Japanese Unexamined Patent Publication No. 59-64739, the bonded magnet uses magnetic powder obtained by turning a molten alloy into an amorphous ribbon using a quenching ribbon production device, followed by heat treatment and pulverization. moreover,
A method for producing anisotropic magnet powder using this method is disclosed in Japanese Patent Application Laid-Open No.
As disclosed in Japanese Patent No. 100402, the above-mentioned isotropic magnetic powder is formed into a compact by hot pressing, then plastically deformed at high temperature to obtain an anisotropic bulk magnet, and then this bulk magnet is crushed. By doing this, anisotropic magnetic powder for bonded magnets is obtained, and by using such anisotropic magnetic powder, anisotropic bonded magnets are obtained. Furthermore, as another method for producing anisotropic magnetic powder, there is a method of obtaining anisotropic magnetic powder by pulverizing a sintered magnet, but this method is impractical because the coercive force is greatly reduced by pulverization. Not in a good way. Furthermore, as another method of obtaining anisotropic magnetic powder, a method of obtaining anisotropic magnetic powder by pulverizing a magnet alloy has been proposed. This method simplifies the process because anisotropic magnetic powder can be obtained by simply crushing the melted and cast alloy, and the magnetic properties are not only stable, but also advantageous in terms of production costs. it is conceivable that.

0003

[Problems to be Solved by the Invention] However, in order to increase the coercive force of the anisotropic magnetic powder obtained by the above-mentioned method of pulverizing the cast alloy, part of the neodymium (Nd) must be replaced with a heavy rare earth element. It is necessary to replace dysprosium (Dy) and terbium (Tb), which reduces the saturation magnetization of the magnetic powder and makes it impossible to obtain high-performance magnetic powder.
), there is a problem in that the cost of raw materials for magnetic powder increases significantly.

0004

[Means for Solving the Problems] In order to solve the problems of these conventional techniques, the present inventors have developed a method that reduces the amount of expensive heavy rare earth elements dysprosium (Dy) and terbium (Tb). In order to develop a method that can inexpensively provide magnetic powder for anisotropic bonded magnets with high magnetic properties, we conducted intensive studies on heat treatment methods for magnetic powder after crushing a magnet alloy, and as a result we arrived at the present invention. .

That is, the first aspect of the present invention is R (where R is at least one rare earth element including yttrium) 10 to 3
0 atom%, boron: 2 to 28 atom%, M (however, M is F
After grinding an alloy consisting of 65 to 82 atomic % of at least one of e, Co, and Ni) to an average particle size of 0.5 to 50 μm, press molding is performed in a magnetic field to form an axis of easy magnetization in the direction of application of the magnetic field. A molded body with a uniform temperature of 400 to 90
The average particle diameter obtained by performing heat treatment at a temperature of 0 ° C. and pulverizing the heat-treated molded product is 0.5 to 50.
This is magnetic powder for anisotropic bonded magnets with a diameter of 0 μm, and the second aspect of the present invention is
is R (wherein R is at least one rare earth element including yttrium) 10 to 30 at%, boron: 2 to 28 at%, and at least one of M (where M is Fe, Co, Ni).
species): After pulverizing an alloy consisting of 65 to 82 at% to an average particle size of 0.5 to 50 μm, press molding is performed in a magnetic field to obtain a molded body with the axis of easy magnetization aligned in the direction of application of the magnetic field, After that, heat treatment is performed at a temperature of 400 to 900 degrees in a vacuum, an inert gas, or a reducing atmosphere,
The heat-treated molded body has an average particle size of 0.5 to 500 μm.
The content is a method for manufacturing magnetic powder for anisotropic bonded magnets.

The rare earth element (R) in the present invention is one or more rare earth elements including yttrium (Y), neodymium (Nd), praseodymium (Pr), lanthanum (La), cerium (Ce), samarium ( Sm), gadolinium (Gd), promethium (Pm), europium (Eu), lutetium (Lu), dysprosium (
Examples include Dy), terbium (Tb), and holmium (Ho). Although yttrium (Y) is not a rare earth element, it can be treated in the same manner as other rare earth elements in the present invention. If the rare earth element (R) content is less than 10 atomic%, the coercive force (iHc) will be low, and if it is 30 atomic% or more, the residual magnetic flux density (Br) will be low and it cannot be a high-performance magnet. . In the present invention, the preferable rare earth element is neodymium (
In order to obtain higher coercive force, it is preferable to replace a portion of neodymium (Nd) with dysprosium (Dy) or terbium (Tb). If the substitution amount of dysprosium (Dy) or terbium (Tb) is less than 1 atomic %, a sufficiently high coercive force cannot be obtained, and if it exceeds 5 atomic %, although a high coercive force can be obtained, the saturation magnetic flux density decreases significantly. However, magnetic particles with high energy product cannot be obtained. Further, if the boron content is less than 2 atomic %, the coercive force will be low, and if it is 28 atomic % or more, the residual magnetic flux density will be low.

[0007] The method for producing anisotropic magnetic powder in the present invention is as follows:
50 to 500 pieces of alloy prepared to a predetermined composition, melted and cast
The process of coarsely pulverizing the powder to about μm and then pulverizing it to 0.5 to 50 μm in an organic solvent or inert gas, and press-molding the finely pulverized magnetic powder in a magnetic field to achieve the axis of easy magnetization of the magnetic powder. After aligning the molded body in the direction of applying a magnetic field, heat treatment is performed at a temperature lower than the general sintering temperature in a vacuum, an inert gas, or a reducing atmosphere, and the heat-treated molded body is crushed again to 0.5 to 500 μm. This is a manufacturing method consisting of: The average particle diameter of the heat-treated molded product is 0.5 μm
If it is less than 500 μm, the oxidation of the magnetic powder will be severe and the coercive force will be significantly reduced, and if it exceeds 500 μm, there will be a lot of air shock when producing a bonded magnet, which is not preferable. It is more preferable that the magnetic powder has an average particle diameter of 0.5 to 100 μm, which can be used for both injection molding and press molding as a method for molding a bonded magnet. The key point of the present invention is to heat-treat the crushed magnetic powder after aligning it in the axis of easy magnetization.The heat treatment increases the coercive force while suppressing the grain growth of the magnetic particles, and improves the orientation of the magnetic particles. The purpose is to improve squareness. That is, unlike the production of normal sintered magnets, it is important to suppress grain growth of magnetic powder as much as possible through heat treatment. Normal NdFeB-based sintered magnets have a dense structure consisting of the main phase of 2-14-1 phase, Nd-rich phase, and B-rich phase, and when crushed, the crystal grains themselves are destroyed. Therefore, the coercive force decreases significantly, and the decrease is particularly large when the powder is pulverized to 500 μm or less. On the other hand, in a molded body in which grain growth is suppressed by low-temperature heat treatment as in the present invention, the grain boundaries of the magnetic powder are preferentially destroyed, so that the molded body after heat treatment can be easily ground into powder. Moreover, even if the particle size is 500 μm or less, the coercive force of the magnetic powder can be prevented from significantly decreasing. Therefore, if the temperature of the heat treatment in the present invention exceeds 900°C, the grain growth of the magnetic powder will become intense, and the coercive force after pulverization will decrease significantly, which is not preferable. Further, if the heat treatment temperature is 400° C. or lower, although the above-mentioned grain growth can be suppressed, the coercive force cannot be sufficiently improved, which is not preferable. A more preferable heat treatment temperature is 650°C to 750°C. Further, after the heat treatment, the molded body may be directly cooled to room temperature, but it is more preferable to cool it to a predetermined temperature at a cooling rate of 0.5 to 6° C./min, and then rapidly cool it to room temperature. Further, the compacting pressure of the press in the magnetic field may be a pressure capable of holding the compact, but a pressure of 0.5 to 3 t/cm2 is preferable in order to suppress grain growth of the magnetic powder during the heat treatment described above. This is because when molding is performed at a pressure exceeding 3 t/cm2, the distance between particles of the magnetic powder becomes short, so that even if heat treatment is performed at a temperature within the range of the present invention, grain growth will occur to some extent. In addition, in the present invention, a normal mechanical crushing method can be used to crush the molded body after heat treatment, but in order to cause more destruction at the grain boundaries, a hydrogen storage method is used in which the molded body absorbs hydrogen and disintegrates. Grinding is preferred. In the mechanical pulverization method, it is more preferable to pulverize in an inert gas or an organic solvent in order to prevent rapid oxidation of the magnetic powder during pulverization.

[0008]

[Examples] The present invention will be explained below with reference to Examples, but the present invention is not limited to these in any way.

Examples 1 to 3 As a starting material, an alloy having a composition of Nd12Dy3 Fe77B8 was produced in an arc melting furnace. The obtained alloy was coarsely ground to 50 to 500 μm using a stamp mill,
Grinding was performed for 90 minutes in a ball mill together with "Florinert (FC-72)", a perfluorocarbon inert liquid manufactured by Sumitomo 3M Limited. Thereafter, a compact was obtained by pressing in a magnetic field under conditions of an applied magnetic field strength of 20 kOe and a compacting pressure of 1 t/cm2. As shown in Table 1, such molded bodies are heated at temperatures of 600, 700, and 800°C.
Heat treatment was performed in vacuum for 1 hour and in Ar gas for 1 hour, and after the heat treatment, it was cooled to 400°C at a cooling rate of 4°C/min, and then rapidly cooled to room temperature. The obtained heat-treated molded body was pulverized in nitrogen using a hammer mill so that the average particle size became 0.5 to 100 μm, thereby obtaining anisotropic magnetic powder according to the present invention. Furthermore, such magnetic powder and epoxy resin were mixed so that the magnetic powder content was 97% by weight to obtain a composition for a bonded magnet. Subsequently, the mixture was press-molded in a magnetic field of 20 kOe to obtain an anisotropic bonded magnet. Table 1 shows the magnetic properties of the obtained bonded magnet.

Comparative Examples 1 and 2 The heat treatment temperatures were 1080°C and 380°C as shown in Table 1.
Anisotropic magnetic powder was obtained in exactly the same manner as in Example 1 except that a bonded magnet was produced. Table 1 shows the magnetic properties of the obtained bonded magnet.

Comparative Example 3 An alloy having a composition of Nd12Dy3 Fe77B8 was prepared as a starting material in an arc melting furnace. The obtained alloy was coarsely ground to 50 to 500 μm using a stamp mill, and then ground for 90 minutes using a ball mill with Fluorinert (FC-72), a perfluorocarbon inert liquid manufactured by Sumitomo 3M Limited, to determine the average particle size. is 3
．． Anisotropic magnetic powder of 43 μm was obtained. The magnetic powder and epoxy resin were mixed so that the magnetic powder content was 97% by weight to obtain a composition for a bonded magnet. Subsequently, the mixture was press-molded in a magnetic field of 20 kOe to obtain an anisotropic bonded magnet. Table 1 shows the magnetic properties of the obtained bonded magnet.

0012

[Table 1]

[0013] All of Examples 1 to 3 shown in Table 1 have higher coercive force (iHc) and better energy product ((BH) max) than Comparative Examples 1 to 3, and the present invention It can be seen that magnetic powder for anisotropic bonded magnets with good magnetic properties can be obtained by orienting the axis of easy magnetization of crushed magnetic powder in a certain direction and then heat-treating it at a low temperature.

Example 4 A heat-treated molded body was obtained in exactly the same manner as in Example 2 up to the heat treatment of the magnetic powder, and the average particle diameter of the crushed magnetic powder after the heat treatment was 0.5.
After pulverizing in nitrogen using a hammer mill to a particle size of ~100 μm, the magnetic powder and nylon 12 were mixed to have a magnetic particle content of 93% by weight, and the mixture was kneaded with a kneader to form pellets. Such pellets are subjected to an applied magnetic field of 15 kOe.
An anisotropic bonded magnet according to the present invention was obtained by molding using a magnetic field orientation injection molding machine. Table 2 shows the magnetic properties of the obtained bonded magnet.

Comparative Example 4 An anisotropic injection-molded bonded magnet was obtained in exactly the same manner as in Example 4, except that the magnetic powder used in Example 4 was the same as in Comparative Example 3. Table 2 shows the magnetic properties of the obtained bonded magnet.

[0016]

[Table 2]

From the results of Example 4 and Comparative Example 4, it can be seen that the anisotropic magnetic powder of the present invention has good magnetic properties even when producing injection molded bonded magnets.

[0018]

[Effects of the Invention] As detailed above, according to the present invention,
It is possible to produce anisotropic magnetic powder with high coercive force and good energy product with good productivity, and it can be said that the industrial value is extremely high.

Claims (6)

[Claims] Claim 1: R (wherein R is at least one rare earth element including yttrium) 10 to 30 at%, boron: 2 to 28 at%, M (however, M is at least one of Fe, Co, and Ni) (above): After pulverizing an alloy consisting of 65 to 82 at% to an average particle size of 0.5 to 50 μm, press molding is performed in a magnetic field to obtain a compact with the axis of easy magnetization aligned in the direction of magnetic field application, and then Anisotropic particles with an average particle size of 0.5 to 500 μm obtained by heat treatment at a temperature of 400 to 900 °C in vacuum, in an inert gas, or a reducing atmosphere, and pulverizing the heat-treated molded body. Magnetic powder for bonded magnets. 2. Magnetic powder for an anisotropic bonded magnet according to claim 1, having an average particle diameter of 0.5 to 100 μm. 3. R (wherein R is at least one kind of rare earth element including yttrium) 10 to 30 atomic %, boron: 2 to 28 atomic %, M (however, M is at least one of Fe, Co, and Ni) (above): After pulverizing an alloy consisting of 65 to 82 at% to an average particle size of 0.5 to 50 μm, press molding is performed in a magnetic field to obtain a compact with the axis of easy magnetization aligned in the direction of magnetic field application, and then , heat treatment is performed at a temperature of 400 to 900 degrees in a vacuum, an inert gas, or a reducing atmosphere, and the heat-treated molded product has an average particle size of 0.5.
A method for producing magnetic powder for an anisotropic bonded magnet, which comprises pulverizing the powder to a particle size of 500 μm. 4. The method for producing magnetic powder for an anisotropic bonded magnet according to claim 3, wherein the magnetic powder is pulverized to have an average particle diameter of 0.5 to 100 μm. [Claim 5] The applied pressure for press forming in a magnetic field is 0.5.
4. The method for producing magnetic powder for an anisotropic bonded magnet according to claim 3, wherein the magnetic powder is 3 t/cm2. [Claim 6] The cooling rate after heat treatment is 0.5 to 6°C/
4. The method for producing magnetic powder for an anisotropic bonded magnet according to claim 3, wherein