JP2002043110A - Magnetic anisotropic agglomerate of r2t17nx magnet material, its manufacturing method, and bonded magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the magnetic anisotropic agglomerate of Sm-Fe-N magnet material which is easy to handle, processed into a bonded magnet through a conventional device, and superior in oxidation resistance at a lower cost than conventionally. SOLUTION: A mixture is composed of (zinc: 2 mass% or higher) of zinc powder and magnet alloy powder whose main phase is an R2T17NX phase (R is, at least, rare earth elements of a kind, including Sm as an essential component; T is metal elements of a kind, including Fe as essential component; x is 2.6 to 3.2). The mixture is molded into a molding under compression in a magnetic field, and the molding is pulverized into granules of size 40 to 400 μm. The molding or the granules are subjected to thermal treatment at a temperature of 380 deg.C or higher in a non-oxidizing atmosphere. The molding or granules may be thermally treated at the Curie temperature for demagnetization. By this setup, magnetically anisotropic agglomerates which are prescribed in size and in which magnet alloy powder is magnetically oriented in the same direction can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetically anisotropic aggregate of R ₂ T ₁₇ N _X -based magnet powder useful for bonded magnets used in magnet-applied equipment such as motors and speakers, and a method for producing the same. Further, the present invention relates to a bonded magnet.

[0002]

2. Description of the Related Art High magnetic properties using high performance rare earth magnet powder such as Nd-Fe-B or Sm-Co anisotropic magnet powder or Nd-Fe-B isotropic magnet powder. Bonded magnets are used in magnet-applied devices such as small motors. The field of use and amount of this bonded magnet
The demand for smaller, thinner, and lighter equipment has been increasing year by year, and accordingly, magnets having various characteristics have been demanded. Against this background, new magnet powders are being actively developed. Among them, rare earth (R) -iron (Fe) -nitrogen (N) based magnet materials, particularly samarium (Sm) -iron Attention has been paid to (Fe) -nitrogen (N) -based magnet materials.

[0003] This Sm-Fe-N magnet material is Th ₂
A nitride of Sm ₂ Fe ₁₇ having a Zn ₁₇ type structure,
Those having a composition in the vicinity of Sm ₂ Fe ₁₇ N ₃ have the best magnetic properties, saturation magnetization 4πIs = 1.57 T, anisotropic magnetic field Ha = 20.7 MA / m, Curie point Tc = 47.
The basic physical property of 0 ° C. has been clarified. This Sm-
Since the coercive force mechanism of the Fe-N-based magnet material is a nucleus growth type, to increase the coercive force, about 3% of the magnet powder is required.
It is desirable to reduce the particle size to single domain particles of μm or less, mainly ball mill, vibration mill, attritor,
Pulverization by a jet mill or the like is performed. Recently, a raw material such as Fe powder or oxidized Sm powder has been used as a fine powder having a size smaller than the size of a single magnetic domain particle, and the Sm powder has been reduced by a diffusion method.
To produce a ₂ Fe ₁₇ N ₃ based single magnetic domain particles, does not perform milling methods have been developed. Sm-Fe-N magnet powder is
It is used as a raw material magnet powder for a bonded magnet, and is processed into a bonded magnet using an organic resin as a binder.

[0004] However, although a resin-bonded magnet using an organic resin as a binder has good initial magnetic properties,
There arises a problem that the magnetic properties deteriorate with the passage of time, and solving this change over time is a major issue. The cause of this change with time is that the Sm-Fe-N-based magnet powder is mainly composed of Sm or Fe, which is easily oxidized, and is present in the bonded magnet because the magnet powder is a fine powder and has a large surface area. It is believed that the oxygen and invading oxygen gradually oxidize the magnet powder. For this reason, in order to prevent the deterioration of the magnetic properties, it is important to impart oxidation resistance to the Sm-Fe-N-based magnet powder.

[0005] Attempts have been made to impart oxidation resistance to Sm-Fe-N magnet powders. For example, a non-magnetic coating composed of a metal, an inorganic compound or an organic compound is formed on the surface of magnet particles. A method for producing magnet particles has been proposed (Japanese Unexamined Patent Publication No. Hei 5-190311). The metal here means, for example, Zn, Sn, Cu, In, Pb, G
a, Sb, alloys containing these or compounds thereof, and the inorganic compound is a nitride or carbide of the metal,
The organic compound is a fatty acid salt. In particular, an element that forms a nonmagnetic compound with Fe at a low melting point and at a low temperature is considered to be suitable. As a coating method, a wet plating method,
In the dry method, a vapor phase growth method (CVD method), a vapor deposition method, and a sputtering method are mentioned.

Further, Sm ₂ Fe ₁₇ having an average particle size of 1 to 5 μm
On the surface of the N _X based magnetic powder, the surface 1 m ² per 50
After coating with 0 mg Zn, 300-450 ° C
(Japanese Patent Application Laid-Open No. 9-190909) has been proposed. Here, as a method of coating Zn,
A vapor phase film forming method such as sputtering or vacuum deposition, or a method of attaching ultrafine powder (0.3 μm or less) of Zn vaporized and solidified by plasma heating to the surface of a magnet powder are mentioned. According to the above method, the average particle size is 1
Sm ₂ Fe ₁₇ N _X -based magnetic powder of ５5 μm can be surface-modified without agglomerating each other and maintaining the original form.

Further, Zn, Sn, Pb, B
i. An oxide powder of at least one element selected from i and granular Ca are mixed at a predetermined ratio, and this mixture is heated and reacted in an inert atmosphere, and the resulting reaction product is mixed with water or a weak acid. A method has been proposed in which the particles are treated with an aqueous solution to form a magnetic powder whose particle surface is coated with the metal. (JP-A-5-326229).

Further, there has been proposed a method in which an organometallic compound such as diethylzinc is added after pulverization, and the powder is decomposed and generated by light irradiation to obtain a magnet powder coated with Zn (JP-A-8-143913).

As described above, many conventional techniques for imparting oxidation resistance form a low-melting metal, particularly Zn, as a coating on the surface of a magnet powder. This method makes use of the characteristics of low melting point Zn to make the Zn adhere to the particle surface of the Sm ₂ Fe ₁₇ N _X based magnet powder and reduce the surface roughness of the magnet particle surface to prevent oxidation of the magnet powder. It is.

[0010]

However, the Sm-Fe-N based magnet material imparted with oxidation resistance by the above method has not yet been put to practical use. One of the causes is the high cost of coating and film formation.

The Sm-Fe-N magnet material has a thickness of 3 μm.
It is a fine powder of single magnetic domain particles of m or less. Nd-Fe-B anisotropic by 2-17 type SmCo magnet, Nd-Fe-B type super-quenched flakes and HDDR method (hydrogenation phase decomposition dehydrogenation recombination method) used for conventional rare earth type bonded magnets The conductive powder has a particle size of 30 to 400 μm and is easy to handle, and the manufacturing apparatus is made to fit the size. On the other hand, 3 μm of Sm—Fe—N magnet material
The following fine powders are difficult to handle and are not compatible with conventional manufacturing equipment. This point is also one of the factors that hinder the practical use of Sm-Fe-N-based magnet materials.

In view of the above, the present invention provides a magnetically anisotropic aggregate of Sm-Fe-N based magnet material having a size that is easy to handle, and oxidation resistance provided by a cost-effective method different from the conventional method. An object of the present invention is to provide a method for producing the magnetic anisotropic aggregate, and a bonded magnet using the magnetic anisotropic aggregate.

[0013]

Means for Solving the Problems In order to achieve the above object, the magnetic anisotropic aggregate of the present invention is an aggregate of a magnetic alloy powder mainly composed of R ₂ T ₁₇ N _X phase, and 2% by mass. It is characterized in that it contains the above zinc, and the magnetic alloy powder is magnetically oriented in one direction, and has a size of 40 μm or more and 400 μm or less. Here, R is at least one kind of rare earth element that requires Sm, T is at least one kind of metal element that requires Fe, and x is a numerical value in the range of 2.6 to 3.2. .

The magnetic anisotropic aggregate of the present invention has oxidation resistance and a size that is easy to handle, and it is easy to manufacture a bonded magnet using a conventional bonded magnet manufacturing apparatus.

The magnetic anisotropic aggregate of the present invention preferably contains zinc adhering to the surface of the magnet alloy powder and zinc existing in a lump between the magnet alloy powders. Lumped zinc can act as a binder when forming a metal-bonded magnet. The content of zinc is not particularly limited, but is preferably 40% by mass or less. Further, the magnetic anisotropic aggregate of the present invention is preferably substantially demagnetized. Here, “substantially demagnetized” refers to a state in which the magnetization has been reduced to such an extent that it is attracted to each other and is not attracted. Note that the size of the aggregate is measured in a state where the magnet is substantially demagnetized.

[0016] To achieve the above object, a manufacturing method of the magnetic anisotropy aggregate of the present invention, zinc powder and R ₂ T ₁₇
A step of said zinc powder and magnet alloy powder to obtain a pressure-molded to the molded body in a magnetic field of the blended mixture to be 2 mass% or more of the N _X phase mainly, by grinding the molded body The method includes a step of forming a lump having a size of 40 μm or more and 400 μm or less, and a step of heat-treating the compact or the lump at a temperature of 380 ° C. or more in a non-oxidizing atmosphere. Here, R is at least one kind of rare earth element that requires Sm, T is at least one kind of metal element that requires Fe, and x is 2.6 to 3.2.
Is a number in the range

According to the production method of the present invention, a magnetically anisotropic aggregate having a size advantageous for handling can be obtained by a cost-effective method of mixing inexpensive zinc powder. In particular, the heat treatment in the above temperature range improves the effect of attaching zinc to the surface of the magnet alloy powder, and the R ₂ T
₁₇ N oxidation of _X-based magnetic powder is improved. Note that the non-oxidizing atmosphere specifically includes an inert gas atmosphere, a nitrogen gas atmosphere, a reducing atmosphere in which a trace amount of hydrogen gas is mixed into nitrogen gas, and the like, and further includes a reduced pressure atmosphere. Does not include the atmosphere.

In the production method of the present invention, it is preferable that the heat treatment is performed at a temperature equal to or higher than the Curie point of the magnetic alloy powder. This is because the aggregate can be substantially demagnetized. The heat treatment may be performed at a temperature lower than the Curie point of the magnet alloy powder. In this case, it is preferable to further carry out, in advance, a step of reducing the magnetization of the molded body or the lump, preferably a step of substantially demagnetizing.

In the manufacturing method of the present invention, the heat treatment can increase the intrinsic coercive force iHc of the compact or the lump as compared to before the heat treatment. This improvement in iHc is due to F
It is thought to be related to the formation of the e-Zn alloy.

Further, the present invention also provides a bonded magnet comprising the above magnetic anisotropic aggregate as a constituent. Since the magnetic anisotropic aggregate has a size that is easy to handle,
The bonded magnet of the present invention can be easily manufactured using a conventional manufacturing apparatus.

The bonded magnet of the present invention can be a metal bonded magnet in which zinc contained in the magnetically anisotropic aggregate serves as a binder.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below. In the present invention, an R ₂ T ₁₇ N _X -based magnet material mainly containing an R ₂ T ₁₇ N _X phase is used. Typical R ₂ T ₁₇ N _X
Examples of the phase include an Sm ₂ Fe ₁₇ N _X phase.
Among them, the Sm ₂ Fe ₁₇ N ₃ phase has a possibility of becoming a magnet material excellent in its physical properties.

The R ₂ T ₁₇ N _X phase is not limited to the Sm ₂ Fe ₁₇ N ₃ phase, but also includes a phase whose composition is changed by adding various additional elements. For example, R in which a part of samarium (Sm) is substituted with another rare earth element may be used. S
m, Y, La, Ce, Pr, N
d, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb
And at least one rare earth element selected from Lu. In this case, the substitution amount is preferably 50 atomic% or less. If the substitution amount exceeds 50 atomic%, the magnetic properties may be reduced and the practicality may be impaired.

The metal element T may be one obtained by substituting a part of iron (Fe) with another metal element. Elements that replace Fe include Co, Ti, V, Cr, Mn, Ni, and C.
At least one metal element selected from u, Zn, Zr, Hf, Nb, Ta, Mo, W, Ga and Al is preferred. In this case, the substitution amount is preferably 55 atomic% or less. If the substitution amount exceeds 55 atomic%, the magnetic properties may be reduced and the practicability may be impaired as in the above case.

Considering the preferred amount of substitution, R ₂ T ₁₇ N _X
The phase can be represented by the following equation (1).

[0026] _{(Sm a R 'b) 2} (Fe c T' d) 17 N X (1)

Here, R ′ is a rare earth element that substitutes for Sm, and specifically, the elements exemplified above are preferable.
T ′ is a metal element that replaces Fe, and specifically, the elements exemplified above are preferable, and a, b, c, and d are respectively 0.5 ≦ a ≦ 1, 0 ≦ b ≦ 0.5. , A + b = 1,
0.45 ≦ c ≦ 1, 0 ≦ d ≦ 0.55, c + d = 1, and x is a value in the range of 2.6 to 3.2. In addition, x is more preferably 2.6 to 3.0 in terms of magnetic characteristics, and the case where x = 3 shows the most excellent magnetic characteristics.

[0028] Note that the R ₂ T ₁₇ N _X-based magnet material, R ₂
Mainly of T ₁₇ N _X phase, i.e. as long as the R ₂ T ₁₇ N _X phase takes up more than 50 wt%, contains an oxide, alpha-Fe Other manufacturing unavoidable impurities typified by SmO ₂ You can go out.

Hereinafter, an example of a method for preparing a powder of an Sm ₂ Fe ₁₇ N _X -based magnet material will be described as a method for preparing a powder of an R ₂ T ₁₇ N _X -based magnetic material. An Sm-Fe binary alloy is melted at a high frequency to produce a cast ingot, which is heat-treated at about 1100 ° C. for 12 hours to form an alloy ingot having a Sm ₂ Fe ₁₇ phase (Th ₂ Zn ₁₇ type structure) as a main phase. I do. By this heat treatment, segregation is reduced and the composition is made uniform (uniform heat treatment). This alloy lump is roughly pulverized by mechanical pulverization or hydrogen storage pulverization to have a size of 1
A powder having a size of 50 μm or less is formed, and then heat-treated in a nitrogen atmosphere and nitrided. The optimum temperature is 470 ° C., which requires about 100 hours. If the temperature is further increased, nitriding is completed in a short time. However, when the temperature exceeds about 600 ° C., the nitrided Sm ₂ Fe ₁₇ N _X phase starts to decompose. Therefore, the nitriding temperature is preferably 600 ° C. or less.

The Sm ₂ Fe ₁₇ phase is converted into a Sm ₂ Fe ₁₇
Although it becomes an N _x phase, the crystal structure is the same Th ₂ Zn ₁₇ type structure. However, in the crystal lattice, the c-axis is greatly extended and the a-axis is also extended due to the penetration of N. Note that when heat treatment is performed in ammonia, nitridation is accelerated, but the surface of the powder may become amorphous due to excessive nitrogen. For this reason, when heat-treating in ammonia, to obtain a uniform nitrogen composition,
It is preferable to subsequently perform an annealing treatment.

Further, the powder having a particle size of 150 μm or less is finely pulverized by a jet mill or a ball mill into a powder having a particle size of 3 μm or less. In addition, it is preferable that each of the above steps is performed so as not to contact oxygen to suppress oxidation of the magnet powder.

Alternatively, powder of the Sm ₂ Fe ₁₇ phase may be prepared by the reduction diffusion method. The particle size of the powder obtained by this method is 30 to 100 μm, and no homogenizing heat treatment or coarse pulverization is required. it can. In addition, by improving the reduction diffusion method, the S
Since a method of producing the m ₂ Fe ₁₇ N _X phase and eliminating the need for pulverization has been developed, this method may be used.

Regardless of the production method applied, Sm ₂ Fe ₁₇
The particle size of the powder of the N _X -based magnetic material (R ₂ T ₁₇ N _X -based magnet material) is preferably 3 μm or less. This is because excellent magnetic properties can be obtained.

Further, zinc (Zn) powder is used to impart oxidation resistance to the powder of the R ₂ T ₁₇ N _X -based magnetic material.
The provision of oxidation resistance using Zn itself is known as described above, but the high cost of coating and coating hinders practical application. However, here, an inexpensive metal zinc powder, which is a general-purpose material, is used, and oxidation resistance is imparted to the magnet material by a process that does not involve high costs. Commercially available general-purpose zinc powder has a particle size of approximately 3 to 10 μm, but this zinc powder may be applied as it is. The price of commercially available zinc powder is about 400 yen per kg. The particle size of the zinc powder may be smaller.

The excellent oxidation resistance of Zn is evident from the fact that Zn-plated products are used in large quantities in steel products. Zn easily reacts with Fe and Fe-Z
An n alloy is easily formed. Zn has a low melting point of 420 ° C., a boiling point of 903 ° C., a high vapor pressure, and is easily evaporated. Utilizing this property, Zn can be attached to the surface of the powder of the magnetic material by a simple operation of mixing the powder of the magnetic material and the powder of Zn and performing a heat treatment. This heat treatment can be performed after the powder of the magnet material and the Zn powder are compacted, so that the Zn can be firmly attached and
This is advantageous because scattering of n can be reduced.

The pressure molding is basically performed for granulating the powder of the magnetic material. That is, the powder of the magnet material and Z
The n-powder is granulated to a size of 40 to 400 μm, which is appropriate as the size of the compound for a rare-earth bonded magnet.

The rare-earth bonded magnet currently used in large quantities is an isotropic ring-shaped magnet obtained by compression molding Nd-Fe-B-based magnetic material powder. This magnet, HDD, CD
-Used for spindle motors of storage devices for disks such as ROM, MD, and DVD. The Nd-Fe-B based isotropic magnet powder has a size of 40 to 300 µm, and is used as a compound having excellent fluidity by being mixed with an epoxy-based thermosetting organic resin. The manufacturing apparatus is a compression molding apparatus at room temperature, and the compound needs to be supplied accurately in a short time. That is, the compound is strongly required to have good fluidity. Therefore, the compound is in a form in which a thermosetting organic resin is thinly applied to the surface of the magnet powder and dried. In many cases, the compound is composed of one magnet powder, but in some cases, a small magnet powder is attached to a large magnet powder. , Resulting in a compound size of 40-400
It is about μm. The conditions of the manufacturing apparatus are adjusted according to the current compound size. Therefore, the particle size 3
Powder of Sm ₂ Fe ₁₇ N _X -based magnet material (R ₂ T ₁₇ N _X -based magnet material) having a size of μm or less (for example, about 2 μm) is too fine as it is and is not suitable for the above manufacturing apparatus. If the fine powder is used as it is, it enters into the gap between the inside of the mold and the punch, and the movement of the punch is deteriorated, and sometimes the punch does not move due to biting.

Since the powder of the R ₂ T ₁₇ N _X -based magnetic material is an anisotropic powder, if it is simply granulated, it becomes an isotropic aggregate,
It cannot exhibit its original characteristics. Therefore, at the time of pressure molding, a pressure is applied in a magnetic field in a state where the directions of the easy axes of magnetization of the respective magnet powders are aligned to obtain a molded body having magnetic anisotropy.

In the compact thus obtained, the axis of easy magnetization of the powder of the magnet material is oriented and has uniaxial magnetic anisotropy.
In the present specification, if the uniaxial magnetic anisotropy is provided as described above, it is considered that the magnetic material powder is magnetically oriented in one direction.

This compact has a size of 40 to 400 μm.
To form a lump. However, since the mass (granulated powder) thus granulated is magnetized by being fixed in a magnetic field, the granulated powder cannot be supplied to the mold properly by suction and condensation of the granules. For this reason, it is preferable that the granulated powder is substantially demagnetized.
The degaussing may be performed in the state of the granulated powder or in the state of the compact.

The intrinsic coercive force iHc of the magnet powder mainly composed of the Sm ₂ Fe ₁₇ N _X phase is as large as 0.8 MA / m or more. Therefore, in order to substantially demagnetize, it is necessary to perform an operation of fixing (by applying pressure in the case of granulated powder), applying an alternating magnetic field, and gradually lowering the magnetic field to demagnetize. Another method of degaussing is to heat the magnet powder above the Curie point. In particular, when heating for improving the adhesion of zinc is performed at a temperature equal to or higher than the Curie point, demagnetization can be performed at the same time. As described above, the Curie point of Sm ₂ Fe ₁₇ N ₃ is 470 ° C.

The heat treatment may be performed on the compact or the granulated powder as long as it is after the compaction of the magnet material powder and the zinc powder. By this heat treatment, zinc having a low melting point adheres to the surface of the magnet powder, and preferably spreads as a thin film on this surface, thereby imparting oxidation resistance to the magnet powder. The heating temperature may be 380 ° C. or higher, and more preferably, the melting point of zinc is 420 ° C. or higher. The upper limit of the heating temperature is generally 600 ° C., at which the R ₂ T ₁₇ N _X phase starts to decompose, similarly to the nitriding temperature. The heat treatment is performed in a non-oxidizing atmosphere. As the non-oxidizing atmosphere, an inert gas atmosphere is suitable.

By the heat treatment, a thin film of the Fe—Zn alloy can be formed on the surface layer of the surface of the magnet powder.
The thin film of the Fe—Zn alloy on the surface of the magnet powder has an intrinsic coercive force i
Hc has been reported to contribute to improvement (Heisei 11
Annual Meeting of the Institute of Electrical Engineers of Japan, p2-230). The improvement in the intrinsic coercive force iHc is presumed to be due to the fact that the Fe—Zn alloy prevents the generation of buds in the reverse magnetic domain. Specific coercive force iHc
The temperature of the heat treatment suitable for improving the temperature depends on the heat treatment time and the like, as described later, but is generally preferably 400 to 550 ° C.

Since the oxidation resistance is imparted by the heat treatment, the pulverization after the heat treatment may be performed in the air. On the other hand, the pulverization before the heat treatment is preferably performed in a non-oxidizing atmosphere.

Thus, Sm ₂ Fe ₁₇ , which is provided with the oxidation resistance by Zn and has a form of massive granulated powder having a size of 40 to 400 μm which is easy to handle, preferably having an improved intrinsic coercive force iHc, It is possible to obtain a magnetically anisotropic aggregate of an N _x -based magnet material (R ₂ T ₁₇ N _x -based magnet material).

Hereinafter, specific embodiments of the present invention will be further described. (Embodiment 1) Metal Sm, electrolytic Fe and a small amount of additive element Ti are melted by high-frequency induction heating, then cast, and the cast mass is homogenized and heat-treated at 1100 ° C. in argon gas to form an Sm ₂ Fe ₁₇ phase. Of the structure. As a result of the analysis, the composition of the alloy ingot after the homogenization heat treatment was found to have an Sm of 24.4% by mass (mass).
s%), Ti was 0.3 mass%, and the balance was Fe. The additional element Ti is added to improve the magnetic properties, and is presumed to be substituted for part of Fe. However, part of Ti may be present in the grain boundary part.

[0047] The the Sm ₂ Fe ₁₇ phase of the alloy ingot was heat-treated in a hydrogen gas to collapse to absorb hydrogen, and nitriding by heat treatment thereafter nitrogen gas replacement to nitrogen gas, Sm ₂ F
e ₁₇ N ₃ phase alloy powder was obtained. The powder having the Sm ₂ Fe ₁₇ N ₃ phase structure was pulverized with a ball mill to obtain a fine powder having an average particle size of 1.8 μm. The magnetic properties of the fine powder were measured by a vibration sample type magnetometer (VSM). As a result, the residual magnetic flux density was Br = 1.41 T, and the intrinsic coercive force was iHc = 0.98.
MA / m, coercive force: bHc = 0.77 MA / m, maximum energy product: (BH) max = 346 kJ / m ³ .

On the other hand, as zinc powder, pure zinc (manufactured by Kojundo Chemical Laboratory Co .; average particle size: 7 μm) was prepared. The zinc powder and the magnet powder were mixed in a nitrogen atmosphere at the following compounding ratio, and mixed by stirring with a cross rotary mixer. The composition is represented by the content of zinc, 5, 10, 15, 20, 40, 60, 70 mass.
% Of seven types. The mixed powder was placed in a mold and pressed under a magnetic field of 0.8 MA / m perpendicular to the pressing direction. The pressure was 590 MPa. After applying a magnetic field in the opposite direction in a pressurized state, the pressurization was released and the molded body was taken out of the mold. However, the demagnetization was incomplete, and the magnetization remained to the extent that it absorbed the iron plate. This compact was pulverized in a nitrogen atmosphere to obtain a granulated powder of 40 to 400 μm.

In order to firmly attach zinc to the magnet powder,
The granulated powder was heat-treated in an argon gas atmosphere furnace. The processing temperature and time are as follows. Processing temperature is 380,
430, 480 and 4 points of 500 ° C. were carried out for several points between 5 minutes and 8 hours. The magnetic properties of the heat-treated granulated powder were measured. The results are shown in FIG. 1 and FIG.

FIG. 1 shows the Zn content, the saturation magnetization and the intrinsic coercivity iHc after the heat treatment at 480 ° C. for 30 minutes.
The relationship is shown below. As the amount of non-magnetic Zn increases, Fe is consumed due to the formation of an Fe—Zn alloy, and S
The amount of m ₂ Fe ₁₇ N ₃ phase is reduced. For this reason, the saturation magnetization decreases as the content of Zn increases. Even if the saturation magnetization is small, it can be used as a magnet material, so the upper limit of the Zn composition is not limited, but the saturation magnetization of ferrite, which is currently used in large quantities as a magnet material, is 0.1%.
Considering that it is of the order of 4T, the upper limit of the Zn composition is preferably 40 mass%.

On the other hand, the intrinsic coercive force iHc is small when the Zn content is small, but is 1.6 MA when the Zn content is 15 mass% or more.
/ M. However, since the upper limit of the magnetic field that can be measured by the magnetic measurement device used is 1.75 MA / m, iHc exceeding 1.75 MA / m was not measured. In FIG. 1, the curve over 1.75 MA / m is an estimate from the data obtained. The specific coercivity iHc of ferrite is on the order of 0.24 MA / m. Therefore,
From the viewpoint of a practical magnet material, the lower limit of the blending amount of Zn is preferably 2 mass%. However, compared to the ferrite magnet, the temperature characteristics of iHc of Sm ₂ Fe _{1 7} N ₃ phase slightly inferior. Taking this into account, 0.4 times twice the iHc of ferrite.
In order to obtain 8 MA / m, the lower limit of the Zn composition is preferably 5 mass%.

FIG. 2 shows a change in the intrinsic coercive force iHc depending on the heat treatment temperature and the heat treatment time when the Zn content is 10 mass%. The iHc was 0.98 MA / m at the fine powder stage, but decreased to 0.86 MA / m after molding in a magnetic field, that is, before heat treatment (the point indicated by the square in FIG. 2).

The intrinsic coercive force iHc further decreased by the heat treatment at 380 ° C., and decreased to 0.18 MA / m after the treatment for 30 minutes, but recovered to 0.44 MA / m after the treatment for 8 hours. On the other hand, the decrease in the saturation magnetization was small, and after the treatment for 8 hours, about 1.04 T, which was higher than that of ferrite, was confirmed. As described above, by performing the heat treatment at 380 ° C. for 2 hours or more, practical magnetic properties were obtained although the iHc was low. However, from the above results, 3
At a heat treatment temperature of 80 ° C., the effect of attaching Zn is not sufficiently exhibited, and it can be said that the heat treatment temperature is almost the lower limit.

In the heat treatment at 430 ° C., the intrinsic coercive force iHc rapidly recovered when the heat treatment time was lengthened, returned to the value before the heat treatment after 30 minutes, and reached 1.11 MA / m after 2 hours. However, over 2 hours, iHc tended to decrease. In the heat treatment for more than 2 hours, a depression was observed in the demagnetization curve of the magnetic properties.
It is presumed to be due to the decomposition of the m ₂ Fe ₁₇ N ₃ phase.

Further, as the heat treatment temperature was increased to 480 ° C. and 500 ° C., the peak of the intrinsic coercive force iHc shifted to the shorter time side. Thus, when the heat treatment temperature is increased, Zn
Is promoted, and the intrinsic coercive force increases in a short time. The time at which the best magnetic properties are obtained depends on the heat treatment time.

When the heat treatment temperature is set to 480 ° C.,
The granulated powder is virtually demagnetized and smooth for hands,
The resulting granulated powder had excellent fluidity. At 430 ° C., the demagnetization was not complete, and the granulated powders were slightly attracted and aggregated.
Therefore, in order to improve the fluidity of the granulated component, if the heat treatment temperature is set to be lower than the Curie point, it is preferable to keep the demagnetized state after the pressure molding.

The decrease, increase, and decrease in the intrinsic coercive force iHc observed with the heat treatment time are as described above because the increase phenomenon is because the formation of the Zn—Fe phase makes it difficult for the reverse magnetic domain to sprout. And the last decrease phenomenon is Sm ₂
This is presumed to be due to the decomposition of the Fe ₁₇ N ₃ phase. But,
The initial decline has not yet been fully elucidated.

FIG. 2 shows data in which the Zn content is 10 mass%. However, when the Zn content is less than 10 mass%, the value of iHc becomes small, and the final decrease shifts to the long-time side. When the Zn content exceeds 10 mass%, the intrinsic coercive force iHc increases and becomes 1.6.
When MA / m is exceeded, the last decrease shifts to the short-time side. Thus, the optimal heat treatment conditions also depend on the Zn composition.

As described above, the compact after pressure molding may be heat-treated and then pulverized. After the oxidation resistance has been improved by heat treatment, it can be pulverized in the air.

Embodiment 2 In this embodiment, an example of a method for manufacturing a bonded magnet using the above-described magnetic anisotropic aggregate will be described. The magnetic anisotropic agglomerate is filled in a mold for forming a prism, the upper surface of the mold is covered with an upper punch, and a magnetic field of 0.8 MA / m is applied to the rectangular surface inside the mold from the lateral direction of the mold. By applying a pressure of 980 MPa with the upper and lower punches, molding was performed by a floating die method in which the mold was lowered while pressing with the upper punch while applying the pressure vertically. The molded body removed from the mold had mechanical strength that could be used as a magnet as it was. Heat treatment at a temperature of 420 ° C. or higher, which is the melting point of Zn, further increased the mechanical strength. However, when heat treatment is performed after molding, the internal stress is released, so that the dimensions of the molded body expand. Therefore, if you do not like the dimensional change of the molded body,
When the temperature of the mold at the time of molding is set to 420 ° C. or higher and warm molding is performed, the dimensional accuracy of the obtained molded body is maintained, and the pressure during molding can be reduced.

The bond magnet thus obtained is a Zn bond magnet, that is, a metal bond magnet. In the magnetic anisotropic aggregate used for the metal bond magnet, it is preferable that metal Zn contributing to bonding remains. When the magnetically anisotropic aggregate obtained by the method described above was observed by scanning electron microscope (SEM) and analyzed for composition by XMA,
High Zn is present on the surface of the fine Sm ₂ Fe ₁₇ N ₃ phase magnet powder.
A thin film having a concentration was observed, and Sm ₂ Fe ₁₇ N ₃
It was confirmed that massive Zn was present in the mixed phase magnetic powder. It is considered that the massive Zn plays a role of a binding binder that provides mechanical strength in forming a bonded magnet.

When the amount of Zn is around 2 mass%, the amount of this bulk Zn is small, and when it is processed into a metal-bonded magnet, the mechanical strength may be insufficient. In this case, it is advisable to add Zn powder to the mold during the production of the metal bond. When a metal-bonded magnet is used, the preferred amount of Zn is 5 to 40 mass%.

However, as in the prior art, a resin bonded magnet (epoxy bonded magnet) using an epoxy resin as a binder may be processed. In this case, an epoxy resin is applied together with a curing agent to the surface of the magnetic anisotropic aggregate, and after molding in a magnetic field, a curing heat treatment of the epoxy resin is performed. Since this heat treatment is performed at a low temperature of about 150 ° C., dimensional accuracy is maintained.

[0064]

The present invention will be described in more detail with reference to the following Examples, which by no means limit the present invention.

Example 1 Particles Produced by Reduction Diffusion Method
Sm with a diameter of 30 to 100 μm_TwoFe₁₇Nitriding to phase alloy powder
Sm after heat treatment_TwoFe₁₇N_ThreePhase powder and then
Sm with an average particle size of 2.0 μm
_TwoFe₁₇N_ThreePhase magnetic powder. This Sm _TwoFe₁₇N_Threephase
Zn powder having an average particle size of 7 μm was added to
s% mixed, put into hexane solvent and cross rotary
The mixture was mixed by stirring with a mixer. This mixed powder is mixed with hexane solvent
Is placed in a mold with the mold attached, and this mold is
Install and evacuate, apply a magnetic field from the side,
And pressed. Pressurization pressure is 590MPa
Was. After degaussing while applying pressure, the compact is removed from the mold
Extract and crush to 40-400μm in nitrogen atmosphere
Into granulated powder.

The obtained granulated powder was heat-treated at 430 ° C. for 10 minutes in an argon gas, and the granulated powder was subjected to magnetic measurement with a VSM. As a result, the granulated powder after the heat treatment had a true density of 7.56 kg / m ³ and Br = 0.85T, iHc =
0.65 MA / m, (BH) max = 116 kJ / m ³
Thus, the magnetic anisotropic aggregate had an easy magnetization direction in one direction.

The obtained magnetically anisotropic aggregate was subjected to 10
An oxidation resistance test was performed in a furnace at 0 ° C. for 1 hour.
Almost no change was observed in the magnetic properties before and after the standing, and it was found that there was practically necessary oxidation resistance.

Example 2 A compact obtained in the same manner as in Example 1 was heat-treated at 450 ° C. for 10 minutes in argon gas without pulverization. The obtained heat-treated compact was pulverized in the air to 40 to 400 μm to obtain granulated powder. This granulated powder was subjected to magnetic measurement with a VSM. As a result, the granulated powder after the heat treatment had a true density of 7.56 kg / m ³ and Br = 0.78.
T, iHc = 1.03 MA / m, (BH) max = 10
It was 2 kJ / m ^3, which was a magnetic anisotropic aggregate having an easy magnetization direction in one direction. An oxidation resistance test was performed, but no change was observed in the magnetic properties, and the product had oxidation resistance necessary for practical use.

(Example 3) A cast lump produced by a melting casting method was subjected to a homogenizing heat treatment at 1100 ° C for 12 hours to obtain Sm _2.
A binary alloy ingot of Fe ₁₇ phase was prepared. This binary alloy ingot is heat-treated in a high-pressure hydrogen gas of 3.9 MPa to cause hydrogen occlusion and collapse, and then heat-treated in a nitrogen gas at 430 ° C. to 540 ° C. to be nitrided to obtain a powder of Sm ₂ Fe ₁₇ N ₃ phase. The powder was further pulverized with a ball mill to obtain a Sm ₂ Fe ₁₇ N ₃ phase magnet powder having an average particle size of 1.9 μm. This Sm ₂ Fe ₁₇
15 m of Zn powder having an average particle diameter of 7 μm is added to N ₃ phase magnet powder.
ass%, and the mixture was put into a hexane solvent and stirred and mixed by a cross rotary mixer. This mixed powder is filled in a mold with the hexane solvent adhered thereto, and the mold is set in a vacuum device and evacuated, and is pressed with a punch while applying a magnetic field of 0.8 MA / m from the lateral direction. Molded. The pressure was 590 MPa. Thereafter, the molded body was extracted from the mold and pulverized to 40 to 400 μm in a nitrogen atmosphere to obtain granulated powder. Since they were not demagnetized, the granulated powder attracted each other and became in an agglomerated state.

The granulated powder obtained in this manner is mixed with argon gas in argon gas.
Heat treatment was performed at 80 ° C. for 10 minutes. The granulated powder after the heat treatment was substantially demagnetized and became a free flowing and extremely good powder. This granulated powder was subjected to magnetic measurement with a VSM.
As a result, the granulated powder after the heat treatment had a true density of 7.59 kg /
as ^{m 3 Br = 0.82T, iHc =} 1.43MA /
m, (BH) max = 120 kJ / m ³ , and the magnetic anisotropic aggregate had an easy magnetization direction in one direction.

The obtained magnetically anisotropic aggregate was subjected to 10
An oxidation resistance test was performed in a furnace at 0 ° C. for 1 hour.
Almost no change was observed in the magnetic properties before and after the standing, and it was found that there was practically necessary oxidation resistance.

Example 4 A component obtained in the same manner as in Example 3
15 min at 480 ° C. in argon gas without grinding
During the heat treatment. The resulting heat-treated compact is substantially
Demagnetized, then pulverized to 40-400 μm in air
The granulated powder obtained by crushing does not attract each other,
It became granulated powder with good flowability. This granulated powder is
The magnetism was measured by SM. As a result, the granulated powder after heat treatment
True density 7.59 kg / m^ThreeWhere Br = 0.80T, i
Hc = 1.51 MA / m, (BH) max = 115 kJ
/ M ^ThreeAnd has a magnetic easy direction in one direction.
It was an isotropic aggregate.

The obtained magnetic anisotropic agglomerate was left in an atmosphere of 100 ° C. for 1 hour in an atmosphere, which was an oxidation resistance test, but no change was observed in the magnetic properties, and it had the oxidation resistance required for practical use. Turned out to be.

(Example 5) The magnetic anisotropic aggregate obtained in Example 1 was filled in a mold for forming a prism, and a magnetic field of 0.8 MA / m was applied to the mold in a direction transverse to the pressing direction. Pressure molding was performed at a pressure of 980 MPa by applying a pressure from the direction. Thereafter, the pressure was reduced to demagnetize, the molded body was extracted from the mold, and further heat-treated at 450 ° C. for 10 minutes in an argon gas.
The magnetic properties of the obtained molded body (Zn-bonded magnet) are Br
= 0.65T, iHc = 1.63 MA / m, (BH) m
ax = 76 kJ / m ³ , and the magnet was usable even at a high temperature of 150 ° C. because of its large intrinsic coercive force.

Due to the effect of the Zn coating and the Zn binder, the Zn bonded magnet is the same as the epoxy resin or nylon resin bonded magnet mainly composed of Sm ₂ Fe ₁₇ N ₃ phase which is currently being developed. It is a magnet that cannot be realized and has excellent coercive force and excellent oxidation resistance.

[0076]

As described above, according to the present invention,
Sm-Fe with excellent oxidation resistance that is easy to handle and can be processed into a bonded magnet by a conventionally used device
The magnetically anisotropic aggregate of the -N-based magnet material can be provided by a method that is more cost effective than before.

[Brief description of the drawings]

FIG. 1 is a view showing the relationship between the Zn content of a magnetic anisotropic aggregate according to the present invention, saturation magnetization and intrinsic coercive force.

FIG. 2 shows a magnetic anisotropic aggregate of the present invention (Zn content: 1).
FIG. 4 is a diagram showing a relationship between a heat treatment temperature and a heat treatment time and a specific coercive force iHc in a manufacturing process (0 mass%).

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) C22C 33/02 C22C 38/00 303D 38/00 303 H01F 1/08 A H01F 1/053 B22F 1/02 E 1/08 H01F 1/06 A // B22F 1/02 1/04 A

Claims (11)

[Claims] 1. An agglomerate of magnetic alloy powder mainly comprising an R ₂ T ₁₇ N _X phase, containing 2% by mass or more of zinc, wherein the magnetic alloy powder is magnetically oriented in one direction. , Size 4
A magnetically anisotropic aggregate having a size of 0 μm or more and 400 μm or less. Here, R is at least one kind of rare earth element that requires Sm, T is at least one kind of metal element that requires Fe, and x is a numerical value in the range of 2.6 to 3.2. . 2. A method according to claim 1, wherein the zinc adhered to the surface of the magnet alloy powder comprises:
2. The magnetically anisotropic aggregate according to claim 1, further comprising zinc present in a lump between the magnet alloy powders. 3. The magnetically anisotropic aggregate according to claim 1, comprising 40% by mass or less of zinc. 4. The magnetically anisotropic aggregate according to claim 1, which is substantially demagnetized. 5. A compact formed by pressing a mixture of zinc powder and a magnetic alloy powder mainly composed of R ₂ T ₁₇ N _X phase so that the zinc powder is 2% by mass or more in a magnetic field. And a step of pulverizing the molded body so that the size is 40 μm or more and 40 μm or more.
A method for producing a magnetically anisotropic aggregate, comprising: a step of forming a lump having a size of 0 μm or less; and a step of heat-treating the compact or the lump at a temperature of 380 ° C. or more in a non-oxidizing atmosphere. Here, R is at least one kind of rare earth element that requires Sm, T is at least one kind of metal element that requires Fe, and x is 2.6 to
It is a numerical value in the range of 3.2. 6. The method according to claim 5, wherein the heat treatment is performed at a temperature equal to or higher than the Curie point of the magnetic alloy powder. 7. The method for producing a magnetic anisotropic aggregate according to claim 5, further comprising a step of reducing the magnetization of the compact or lump, wherein the heat treatment is performed at a temperature lower than the Curie point of the magnet alloy powder. 8. The method for producing a magnetically anisotropic aggregate according to claim 5, wherein the heat treatment increases the intrinsic coercive force iHc of the compact or lump as compared to before the heat treatment. 9. A bonded magnet comprising the magnetic anisotropic aggregate according to claim 1. 10. A bonded magnet comprising a magnetically anisotropic aggregate obtained by the method according to claim 5. 11. The bonded magnet according to claim 9, wherein zinc contained in the magnetic anisotropic aggregate serves as a binder.