JP2002141211A - Magnet powder, method of manufacturing bonded magnet, and bonded magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnet powder which is capable of forming a magnet, having high mechanical strength and superior magnetic properties and a bonded magnet. SOLUTION: This magnet powder is composed of at least rare earth elements and transition metal and shaped like plates or scales, and a plurality of protuberant stripes or grooves are provided to a part of the surface of plate-like or scaly powder. If the average grain diameter of the magnet powder is represented by a μm, it is preferable that the length of the protuberant stripe or groove be a/40 μm or larger. The protuberant stripes or grooves are provided in parallel and arranged at an average pitch of 0.5 to 100 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a magnet powder, a method for producing a bonded magnet, and a bonded magnet.

[0002]

2. Description of the Related Art In order to reduce the size of a motor or the like, it is desired that the magnetic flux density (in substantial permeance) of a magnet used in the motor be high. Factors that determine the magnetic flux density of the bonded magnet include the magnetization value of the magnet powder and the content (content) of the magnet powder in the bonded magnet. Therefore, when the magnetization of the magnet powder itself is not so high, a sufficient magnetic flux density cannot be obtained unless the content of the magnet powder in the bonded magnet is extremely increased.

[0003] Currently, high performance rare earth bonded magnets include R-TM-B based magnet powders (where R is at least one rare earth element, and TM is at least one of rare earth magnet powders). Most of the isotropic bonded magnets using one type of transition metal). Isotropic bonded magnets have the following advantages over anisotropic bonded magnets. That is, since the magnetic field orientation is not required in manufacturing the bonded magnet, the manufacturing process is simple, and as a result, the manufacturing cost is reduced. But this R-
Conventional isotropic bonded magnets typified by isotropic bonded magnets using TM-B-based magnet powder have the following problems.

1) A conventional isotropic bonded magnet has an insufficient magnetic flux density. That is, since the magnetization of the magnet powder used is low, the content (content) of the magnet powder in the bonded magnet must be increased. However, if the content of the magnet powder is increased, the moldability of the bonded magnet is deteriorated. ,There is a limit. Further, even if the content of the magnet powder is increased by devising molding conditions or the like, there is still a limit to the magnetic flux density that can be obtained, and therefore it is not possible to reduce the size of the motor.

[0005] 2) A nanocomposite magnet having a high residual magnetic flux density has been reported. However, in such a case, the coercive force is too small, and the magnetic flux density obtained as a motor in practical use (the magnetic flux density in actual use) has been reported. Permance) was very low. Further, since the coercive force is small, thermal stability is also poor.

3) The mechanical strength of the bonded magnet decreases. That is, in order to compensate for the low magnetic properties of the magnet powder, the content of the magnet powder in the bonded magnet must be increased (that is, the density of the bonded magnet is extremely increased). On the other hand, the bond magnet has low mechanical strength.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnet powder, a bonded magnet, and a method for manufacturing a bonded magnet capable of providing a magnet having high mechanical strength and excellent magnetic properties. .

[0008]

This and other objects are achieved by the present invention which is defined below as (1) to (17).

(1) A magnetic powder containing a rare earth element and a transition metal, wherein the magnetic powder has a plate-like or scale-like shape and has a plurality of ridges or grooves on at least a part of its surface. Magnet powder.

(2) The magnet powder according to the above (1), wherein the ridge or the groove is formed with a certain direction.

(3) The magnetic powder as described in (2) above, wherein the plurality of ridges or grooves are arranged substantially in parallel.

(4) When the average particle diameter is 5 to 300 μm and the average particle diameter of the magnet powder is a μm, the average length of the ridges or grooves is a / 40 μm or more. The magnet powder according to any one of (1) to (3).

(5) The average particle diameter is 5 to 300 μm, and the average height of the ridges or the average depth of the grooves is:
The magnet powder according to any one of the above (1) to (4), which has a diameter of 0.1 to 10 μm.

(6) The magnet powder according to any one of (1) to (5), wherein the ridges or the grooves are arranged in parallel, and the average pitch thereof is 0.5 to 100 μm.

(7) In any one of the above (1) to (6), the ratio of the area of the area where the ridges or grooves are formed to the total surface area of the magnet powder is 15% or more. Of magnet powder.

(8) The magnet powder according to any one of the above (1) to (7), wherein the magnet powder has a composite structure having a soft magnetic phase and a hard magnetic phase.

(9) The magnet powder according to the above (8), wherein the hard magnetic phase and the soft magnetic phase each have an average crystal grain size of 1 to 100 nm.

(10) A method for producing a bonded magnet by molding a kneaded product obtained by kneading the magnet powder according to any one of the above (1) to (9) and a binder resin into a desired shape. A method for manufacturing a bonded magnet, wherein the molding is performed under conditions such that the binder resin is in a softened or molten state.

(11) A bonded magnet manufactured by the method according to the above (10).

(12) A bonded magnet, wherein the magnet powder according to any one of (1) to (9) is bonded with a bonding resin.

(13) The bonded magnet according to the above (11) or (12), wherein the binder resin is embedded between the ridges provided side by side of the magnet powder or in the grooves provided side by side.

(14) The intrinsic coercive force H _cJ at room temperature is 32
(11) to (1) in the range of 0 to 1200 kA / m.
The bonded magnet according to any one of 3).

(15) Maximum magnetic energy product (BH)
(11) to (1) wherein _max is 40 kJ / m ³ or more.
The bonded magnet according to any one of 4).

(16) The content of the magnet powder is 75 to
The bonded magnet according to any one of the above (11) to (15), wherein the content is 99.5 wt%.

(17) The above (11) wherein the mechanical strength measured by a punching shear test is 50 MPa or more.
Or the bonded magnet according to any one of (16) to (16).

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of a magnet powder, a method for manufacturing a bonded magnet and a bonded magnet according to the present invention will be described in detail.

The magnet powder of the present invention has an alloy composition containing a rare earth element and a transition metal. Among them, the following [1]
Those having the composition of [5] to [5] are preferable.

[1] A rare earth element mainly composed of Sm and C
a transition metal mainly composed of o (hereinafter, referred to as a basic component)
Sm-Co alloy).

[2] R (where R is at least one of rare earth elements including Y), a transition metal (TM) mainly composed of Fe, and B as basic components (hereinafter, referred to as “B”)
R-TM-B alloy).

[3] A rare earth element mainly composed of Sm and F
A material mainly composed of a transition metal mainly composed of e and an interstitial element mainly composed of N (hereinafter, referred to as an Sm-Fe-N-based alloy).

[4] R (where R is at least one of rare earth elements including Y) and a transition metal such as Fe are basic components, and a soft magnetic phase and a hard magnetic phase are adjacent to each other ( Those having a composite structure (particularly, there is a structure called a nanocomposite structure) that exists (including a case where they are adjacent via a grain boundary phase).

[5] A mixture of at least two of the above-mentioned compositions [1] to [4]. In this case, the advantages of the respective magnet powders to be mixed can be obtained, and more excellent magnetic properties can be easily obtained.

Representative examples of Sm-Co alloys include SmCo ₅ and Sm ₂ TM ₁₇ (where TM is a transition metal).

Representative R-Fe-B alloys include Nd-Fe-B alloys, Pr-Fe-B alloys, and N-Fe-B alloys.
d-Pr-Fe-B-based alloy, Nd-Dy-Fe-B-based alloy, Ce-Nd-Fe-B-based alloy, Ce-Pr-Nd-
Fe-B alloys, in which some of Fe is Co, N
and those substituted with another transition metal such as i.

[0035] Typical examples of the Sm-Fe-N based alloy, Sm ₂ Fe ₁₇ was prepared by nitriding the Sm ₂ Fe ₁₇ alloy
Sm-Zr-Fe-C having N ₃ and TbCu ₇ type phase as main phase
o-N based alloys. However, these Sm-Fe
In the case of an -N-based alloy, N is generally introduced as an interstitial atom by preparing a quenched ribbon, subjecting the obtained quenched ribbon to an appropriate heat treatment, and nitriding.

The rare earth elements include Y, La, C
e, Pr, Nd, Pm, Sm, Eu, Gd, Tb, D
Examples thereof include y, Ho, Er, Tm, Yb, Lu, and misch metal, and one or more of these can be included. Examples of the transition metal include Fe, Co, and Ni, and one or more of these may be included.

In order to improve magnetic properties such as coercive force and maximum magnetic energy product, or to improve heat resistance and corrosion resistance, the magnetic material may contain A, if necessary.
1, Cu, Ga, Si, Ti, V, Ta, Zr, Nb,
Mo, Hf, Ag, Zn, P, Ge, Cr, W and the like can also be contained.

The above composite structure (nanocomposite structure)
The soft magnetic phase 10 and the hard magnetic phase 11 exist, for example, in a pattern (model) as shown in FIG. 1, FIG. 2 or FIG. 3, and the thickness and the particle size of each phase are at the nanometer level. Existing. Then, the soft magnetic phase 10 and the hard magnetic phase 11 are adjacent to each other (including the case where they are adjacent via the grain boundary phase), and a magnetic exchange interaction occurs.

Since the direction of the magnetization of the soft magnetic phase is easily changed by the action of the external magnetic field, if the magnetization is mixed with the hard magnetic phase, the magnetization curve of the entire system will become the second symbol in the BH diagram (JH diagram). It is now a stepped “snake-shaped curve”. However, when the size of the soft magnetic phase is as small as several tens of nanometers or less, the magnetization of the soft magnetic material is sufficiently strongly constrained by the coupling with the magnetization of the surrounding hard magnetic material so that the entire system behaves as a hard magnetic material. Become.

The magnet having such a composite structure (nanocomposite structure) mainly has the following features 1) to 5).
have.

1) In the second quadrant of the BH diagram (JH diagram),
The magnetization reversibly springs back (also referred to as a "spring magnet" in this sense). 2) Good magnetization and can be magnetized with a relatively low magnetic field. 3) The temperature dependence of the magnetic properties is smaller than in the case of the hard magnetic phase alone. 4) Changes in magnetic properties with time are small. 5) The magnetic properties do not deteriorate even when finely pulverized.

Thus, the magnet composed of the composite structure has excellent magnetic properties. Therefore, it is particularly preferable that the magnet powder has such a composite structure.

The patterns shown in FIGS. 1 to 3 are only examples, and the present invention is not limited to these patterns.

As shown in the photograph of FIG. 6, the magnetic powder of the present invention is in the form of a plate or scale, and has a plurality of ridges or grooves on at least a part of its surface. . As a result, the following effects can be obtained.

When such a magnet powder is used for the production of a bonded magnet, the binder resin is embedded in the groove (or between the ridges). For this reason, the binding force between the magnet powder and the binding resin is improved, and high mechanical strength can be obtained even when the amount of the binding resin is relatively small. Therefore, the content (content rate) of the magnet powder can be increased, and as a result, a bonded magnet having high magnetic properties can be obtained.

In addition, since the ridges or grooves are provided on the surface of the magnet powder, the contact property (wetting property) between the magnet powder and the binder resin during kneading and the like is improved. For this reason, the kneaded material tends to be in a state where the binding resin covers the periphery of the magnet powder, and even if the amount of the binding resin is relatively small,
Good moldability is obtained.

By these effects, it is possible to manufacture a bonded magnet having high mechanical strength and high magnetic properties with good moldability.

When the average particle diameter of the magnet powder is a μm (preferable value of a will be described later), the length of the ridge or groove is preferably at least a / 40 μm, and a / 3
More preferably, it is 0 μm or more.

If the length of the ridges or grooves is less than a / 40 μm, the above-described effects of the present invention may not be sufficiently exhibited depending on the value of the average particle diameter a of the magnet powder and the like.

The average height of the ridge or the average depth of the groove is
0.1 to 10 μm, preferably 0.3 to 5 μm
Is more preferable.

When the average height of the ridges or the average depth of the grooves is in such a range, when the magnet powder is used for manufacturing a bonded magnet, a binder resin is required between the ridges or in the grooves. By sufficiently embedding, the binding force between the magnet powder and the binder resin is further improved, and the mechanical strength of the resulting bonded magnet,
Magnetic properties are further improved.

The ridges or grooves may be formed in random directions, but are preferably arranged side by side with a certain directionality. The ridges or grooves may be, for example, a plurality of ridges 2 or grooves arranged substantially in parallel as shown in FIG. 4, or may extend in two directions as shown in FIG. However, they may cross each other. Further, the ridge or the groove may be formed in a wrinkle shape. Further, for example, when the ridges (or grooves) are present with a certain degree of directionality, the length, height (or depth of the grooves), shape, etc. of the ridges (or grooves) are individually There may be variations in the ridges (or grooves).

The average pitch of the juxtaposed ridges 2 or the juxtaposed grooves is preferably 0.5 to 100 μm,
More preferably, it is 3 to 50 μm.

When the average pitch of the juxtaposed ridges 2 or the juxtaposed grooves is in such a range, the effect of the present invention described above becomes particularly remarkable.

The area where the ridges 2 or grooves are formed is preferably at least 15% of the total surface area of the magnet powder 1.
More preferably, it is at least 5%.

If the area in which the ridges 2 or grooves are formed is less than 15% of the total surface area of the magnetic powder 1, the above-described effects of the present invention may not be sufficiently exerted.

The average particle diameter a of the magnet powder 1 is 5 to 300 μm.
m, more preferably 10 to 200 μm. If the average particle diameter a of the magnet powder 1 is less than the lower limit, the deterioration of magnetic properties due to oxidation becomes remarkable. In addition, there is a problem in handling such as a possibility of ignition. On the other hand, when the average particle diameter a of the magnet powder 1 exceeds the upper limit, in the case of manufacturing a bonded magnet described below,
There is a possibility that the fluidity of the composition during kneading and molding may not be sufficiently obtained.

In order to obtain better moldability during molding of the bonded magnet, it is preferable that the particle size distribution of the magnet powder is dispersed to some extent (varies). Thereby, the porosity of the obtained bonded magnet can be reduced, and as a result, when the content of the magnet powder in the bonded magnet is the same, the density and mechanical strength of the bonded magnet can be further increased. And the magnetic properties can be further improved.

The average particle diameter a is, for example, FSSS
(Fischer Sub-Sieve Sizer) method.

The magnet powder is subjected to at least one heat treatment during or after the manufacturing process for the purpose of promoting recrystallization of the amorphous structure (amorphous structure) and homogenizing the structure, for example. Is also good. The conditions of this heat treatment may be, for example, at 400 to 900 ° C. for about 0.2 to 300 minutes.

The heat treatment is performed under vacuum or reduced pressure (for example, 1 × 10 ⁻¹ to 1 × 1) in order to prevent oxidation.
0 ^-6 Torr) or in a non-oxidizing atmosphere such as an inert gas such as a nitrogen gas, an argon gas, or a helium gas.

The above-mentioned magnet powder preferably has an average crystal grain size of 500 nm or less, more preferably 200 nm or less, even more preferably about 10 to 120 nm. If the average crystal grain size exceeds 500 nm, the magnetic properties, particularly the coercive force and squareness, may not be sufficiently improved.

In particular, when the magnet material has a composite structure as described in the above [4], the average crystal grain size is 1 to 1
It is preferably 00 nm, more preferably 5 to 50 nm. When the average crystal grain size is in such a range, a magnetic exchange interaction occurs more effectively between the soft magnetic phase 10 and the hard magnetic phase 11, and a remarkable magnetic characteristic is obtained. Improvement is observed.

Such a magnetic powder may be manufactured by any method as long as a ridge or a groove is formed on at least a part of its surface.
Can be relatively easily miniaturized, and is effective in improving magnetic properties, particularly coercive force, etc., and therefore, a ribbon-shaped magnet material manufactured by a quenching method using a cooling roll ( It is preferably obtained by pulverizing a quenched ribbon.

In this case, the method of pulverizing the quenched ribbon is not particularly limited, and the pulverization can be performed using various pulverizers and crushers such as a ball mill, a vibration mill, a jet mill, and a pin mill. This pulverization is performed under vacuum or reduced pressure (for example, 1 × 10 ⁻¹ to 1 × 10 ⁻⁶ To prevent oxidation).
rr), or in a non-oxidizing atmosphere, such as in an inert gas such as nitrogen gas, argon gas, helium gas.

The magnet powder having such ridges or grooves can be formed by appropriately setting the alloy composition, the surface material of the cooling roll, the surface properties, cooling conditions, and the like. It is preferable to form a groove or a ridge on the peripheral surface of the cooling roll and transfer this to a quenched ribbon in order to control the shape and the like reliably.

When a cooling roll having grooves or ridges formed on the peripheral surface is used, in the single roll method,
The ridges or grooves as described above can be formed on at least one surface of the resulting quenched ribbon. In the twin roll method, by using two cooling rolls each having a groove or a ridge formed on the peripheral surface, each of a pair of opposing surfaces (both surfaces) of the obtained quenched ribbon is as described above. It is possible to form a convex ridge or a groove.

Next, the bonded magnet and the method for manufacturing the bonded magnet of the present invention will be described. The bonded magnet of the present invention is preferably one obtained by bonding the above-mentioned magnet powder with a bonding resin.

As the binding resin (binder), either a thermoplastic resin or a thermosetting resin may be used.

Examples of the thermoplastic resin include polyamide (eg, nylon 6, nylon 46, nylon 66, nylon 610, nylon 612, nylon 11, nylon 12, nylon 6-12, nylon 6-66), and thermoplastic polyimide. , Liquid crystal polymers such as aromatic polyesters, polyphenylene oxide, polyphenylene sulfide, polyethylene, polypropylene, polyolefins such as ethylene-vinyl acetate copolymer, modified polyolefins, polyesters such as polycarbonate, polymethyl methacrylate, polyethylene terephthalate, polybutylene terephthalate, and the like. Ether, polyetheretherketone, polyetherimide, polyacetal, etc.
Alternatively, copolymers, blends, polymer alloys, and the like mainly containing these may be used, and one or more of these may be used as a mixture.

Of these, polyamides and liquid crystal polymers and polyphenylene sulfides are preferred because they are particularly excellent in moldability and have high mechanical strength. These thermoplastic resins are also excellent in kneadability with magnet powder.

Depending on the type, copolymerization and the like of such a thermoplastic resin, a wide range of selections can be made, for example, one in which emphasis is placed on moldability, heat resistance, and mechanical strength. There is an advantage.

On the other hand, examples of the thermosetting resin include various epoxy resins such as bisphenol type, novolak type and naphthalene type, phenol resin, urea resin, melamine resin, polyester (unsaturated polyester) resin, polyimide resin and silicone resin. , Polyurethane resins, and the like, and one or more of these can be used as a mixture.

Among these, the moldability is particularly excellent, the mechanical strength is high, and the heat resistance is excellent.
Epoxy resins, phenol resins, polyimide resins and silicone resins are preferred, and epoxy resins are particularly preferred.
In addition, these thermosetting resins are kneadable with magnet powder,
Excellent in kneading uniformity.

The thermosetting resin used (uncured)
May be liquid at room temperature or solid (powder).

Such a bonded magnet of the present invention is manufactured, for example, as follows. Magnet powder, binding resin,
Mix with additives (antioxidants, lubricants, etc.) as necessary,
A composition for a bonded magnet (compound) is manufactured by kneading, and the desired magnet is produced in a magnetic field-free by a molding method such as compression molding (press molding), extrusion molding, or injection molding using the composition for a bonded magnet. Form into shape. When the binder resin is a thermosetting resin, it is cured by heating or the like after molding.

At this time, the kneading may be performed at room temperature, but is preferably performed at a temperature at which the binder resin used starts softening or higher. In particular, when the binder resin is a thermosetting resin, it is preferable that the binder resin is kneaded at a temperature equal to or higher than the temperature at which the binder resin starts to soften and at a temperature lower than the temperature at which the binder resin starts to harden.

By kneading at such a temperature,
The efficiency of kneading is improved, and it becomes possible to knead uniformly in a shorter time than in the case of kneading at room temperature,
Since the binder resin is kneaded in a lowered state, the adhesiveness between the magnet powder and the binder resin is improved, and the softened or melted binder resin is also provided between the ridges or grooves provided on the surface of the magnet powder. Is inserted efficiently. As a result, the porosity in the compound can be reduced. It also contributes to a reduction in the content (content) of the binder resin in the compound.

The molding by the above various methods is preferably performed at a temperature at which the binder resin is in a softened or molten state (warm molding).

By performing molding at such a temperature,
The flowability of the binding resin is improved, and high moldability can be ensured even when the amount of the binding resin is small. Further, by improving the fluidity of the binder resin, the adhesion between the magnet powder and the binder resin is improved, and the softened or melted binder resin is also provided between the ridges or grooves provided on the surface of the magnet powder. Insert efficiently. For this reason, the binding force between the magnet powder and the binding resin is improved, and the porosity in the obtained bonded magnet is reduced. As a result, a high-density bonded magnet having high magnetic properties and high mechanical strength can be obtained.

An example of an index representing the mechanical strength is a mechanical strength obtained by a punching shear test according to the standard of the Electronic Materials Industries Association of Japan, “Punching shear test method using small test specimen of bonded magnet” (EMAS-7006). However, in the bonded magnet of the present invention, the mechanical strength is preferably at least 50 MPa, more preferably at least 60 MPa.

The content (content) of the magnet powder in the bonded magnet is not particularly limited, and is usually determined in consideration of a molding method and compatibility between moldability and high magnetic properties. Specifically, it is preferably about 75 to 99.5 wt%,
More preferably, it is about 5 to 97.5 wt%.

In particular, when the bonded magnet is manufactured by compression molding, the content of the magnet powder is 90 to 9%.
It is preferably about 9.5 wt%, and 93 to 98.5.
More preferably, it is about wt%.

In the case where the bonded magnet is manufactured by extrusion molding or injection molding, the content of the magnet powder is preferably about 75 to 98 wt%, and 85 to 98 wt%.
More preferably, it is about 97% by weight.

According to the present invention, since at least a portion of the surface of the magnet powder is provided with a ridge or a groove, the binding force between the magnet powder and the binder resin is large. Therefore, high mechanical strength can be obtained even when the amount of the binding resin used is reduced. Therefore, the content (content rate) of the magnet powder can be increased, and as a result, a bonded magnet having high magnetic properties can be obtained.

The density ρ of the bonded magnet is determined by factors such as the specific gravity of the magnet powder contained therein, the content of the magnet powder, and the porosity. In the bonded magnets according to this invention, but are not limited to its density ρ is particularly preferably in the range of about 5.3~6.6Mg / m ^3, more preferably about 5.5~6.4Mg / m ³ .

The shape, dimensions, etc. of the bonded magnet of the present invention are not particularly limited. For example, regarding the shape, for example, a columnar shape, a prismatic shape, a cylindrical shape (ring shape), an arc shape, a flat plate shape, a curved plate shape, etc. And any size, from large to ultra-small, is possible. In particular, as described in this specification, it is advantageous for a magnet that is miniaturized and ultra-miniaturized.

The bond magnet of the present invention preferably has a coercive force (intrinsic coercive force at room temperature) H _{cJ of 320} to 1200 kA / m, more preferably 400 to 800 kA / m.
When the coercive force is less than the lower limit, demagnetization when a reverse magnetic field is applied becomes remarkable, and heat resistance at high temperatures is inferior.
When the coercive force exceeds the upper limit, the magnetization decreases. Therefore, by _setting the coercive force H _cJ within the above range,
In the case where a bonded magnet (especially, a cylindrical magnet) is subjected to multipolar magnetization or the like, even when a sufficient magnetization magnetic field cannot be obtained, good magnetization can be achieved, and a sufficient magnetic flux density can be obtained. A high-performance bonded magnet can be provided.

The bonded magnet of the present invention preferably has a maximum magnetic energy product (BH) _max of 40 kJ / m ³ or more, more preferably 50 kJ / m ³ or more, and more preferably 70 kJ / m ³ or more.
More preferably, it is 120 kJ / m ³ . If the maximum magnetic energy product (BH) _max is less than 40 kJ / m ³ , when used for a motor, sufficient torque cannot be obtained depending on its type and structure.

[0090]

Next, specific examples of the present invention will be described.

Example 1 Using a quenched ribbon manufacturing apparatus equipped with a cooling roll, the alloy composition was (Nd _0.75 Pr _0.2 Dy _0.05 ) _{8.9 Febal} Co _8.0 B by the method described below.
A magnet powder represented by _5.7 was obtained.

A cooling roll having a groove formed on its peripheral surface was prepared. The average depth, average length,
In addition, five types of cooling rolls having different average pitch conditions of the arranged grooves were prepared.

Using a quenched ribbon manufacturing apparatus provided with each of the cooling rolls, a quenched ribbon was produced by a single roll method.

First, Nd, Pr, Dy, Fe, Co, B
Were weighed to cast a mother alloy ingot.

After the inside of the chamber containing the quenched ribbon manufacturing apparatus was evacuated, an inert gas (helium gas) was introduced to obtain an atmosphere at a desired temperature and pressure.

Thereafter, the mother alloy ingot was melted to form a molten metal, and the peripheral speed of the cooling roll was set to 28 m / sec. Atmospheric gas pressure is 60 kPa and molten metal injection pressure is 4
After the pressure was adjusted to 0 kPa, the molten metal was sprayed toward the peripheral surface of the cooling roll to continuously produce a quenched ribbon. The thickness of the resulting quenched ribbon was about 17 μm (corresponding to the thickness of the magnet powder).

After each quenched ribbon thus obtained is pulverized, it is subjected to a heat treatment at 675 ° C. for 300 seconds in an argon gas atmosphere to obtain a plate-like magnet powder (sample N).
o. 1 to No. 5) was obtained (see FIG. 6).

As a comparative example, a cooling roll having a flat peripheral surface (having no grooves or ridges) was used.
The magnet powder was obtained (sample No. 6, No. 7). Table 1 shows the value of the average particle diameter a of each magnet powder.

The surface shape of the obtained magnet powder was observed using a scanning electron microscope (SEM). Sample No. 1 to No. 5 (invention), it was confirmed that ridges corresponding to the grooves formed on the peripheral surface of each cooling roll were formed on the surface of the magnet powder. On the other hand, the sample No. 6, no. No such ridges or grooves were found on the surface of the magnet powder No. 7 (all comparative examples).

Representatively, for sample no. FIG. 6 shows an electron micrograph of the magnet powder of No. 2 (the present invention).

The height and length of the ridges formed on the surface of each magnet powder and the pitch of the ridges arranged side by side were measured.
From the results of observation with a scanning electron microscope (SEM), for each magnet powder, the ratio of the area of the area where the ridges or grooves were formed to the total surface area was determined. These values are shown in Table 1.

In order to analyze the phase structure of each magnet powder, the diffraction angle (2θ) was set to 20 using Cu-Kα.
X-ray diffraction was performed in the range of ° to 60 °. From the diffraction pattern, the diffraction peaks of the R ₂ (Fe.Co) ₁₄ B type phase, which is a hard magnetic phase, and the α- (Fe, Co) type phase, which is a soft magnetic phase, can be confirmed. A transmission electron microscope (TEM) As a result, it was confirmed that all formed a composite structure (nanocomposite structure). The average crystal grain size of each phase was measured for each magnet powder. These values are shown in Table 1.

[0103]

[Table 1]

An epoxy resin and a small amount of a hydrazine-based antioxidant were mixed with each magnet powder, and these were mixed at 100 ° C. ×
The composition (compound) for a bonded magnet was prepared by kneading (warm kneading) for 10 minutes.

At this time, the mixing ratio (weight ratio) of the magnet powder, the epoxy resin, and the hydrazine-based antioxidant was as follows: 1 to No. As for 6, each 97.5w
t%, 1.3 wt% and 1.2 wt%, sample N
o. 7 is 97.0 wt%, 2.0 wt%,
1.0 wt%.

Next, the compound is pulverized into granules, and the granules are weighed and filled into a mold of a press machine, and compression-molded (warm forming) at a temperature of 120 ° C. and a pressure of 600 MPa in a non-magnetic field. ), Then cool and release, then 1
The epoxy resin is cured by heating at 75 ° C.
A 7 mm high columnar bonded magnet (for magnetic property and heat resistance test) and a 10 mm square × 3 mm thick flat bonded magnet (for measuring mechanical strength) were obtained. Note that five flat bonded magnets were produced for each magnet powder.

The sample No. 1 to No. 5 (invention) and sample no. The bonded magnet of No. 7 (Comparative Example) could be manufactured with good moldability.

Each of the columnar bonded magnets was subjected to pulse magnetization with a magnetic field strength of 3.2 MA / m, and then subjected to a maximum magnetic field of 2 with a DC self-recording magnetic fluxmeter (TRF-5BH, manufactured by Toei Kogyo Co., Ltd.). Magnetic properties (coercive force H _cJ , residual magnetic flux density Br and maximum magnetic energy product (BH) _max ) were measured at 0.0 MA / m. The temperature at the time of the measurement was 23 ° C. (room temperature).

Next, a test of heat resistance (thermal stability) was performed. The heat resistance was evaluated by measuring the irreversible demagnetization rate (initial demagnetization rate) when each bonded magnet was kept in an environment of 100 ° C. × 1 hour and then returned to room temperature. The smaller the absolute value of the irreversible demagnetization rate (initial demagnetization rate), the better the heat resistance (thermal stability).

Further, for each of the flat bonded magnets,
The mechanical strength was measured by a punching shear test. As a test machine, an autograph manufactured by Shimadzu Corporation was used, and a shearing speed of 1.0 mm /
Went in minutes.

After measuring the mechanical strength, the state of the fracture surface of each bonded magnet was observed using a scanning electron microscope (SEM). As a result, the sample No. 1 to No. In the bonded magnet of No. 5 (the present invention), it was confirmed that the binder resin was efficiently embedded between the juxtaposed ridges. Table 2 shows the results of the measurement of the magnetic properties, the heat resistance test, and the measurement of the mechanical strength.

[0112]

[Table 2]

As is clear from Table 2, the sample No.
1 to No. 5 (the present invention) has the following magnetic properties:
Both heat resistance and mechanical strength are excellent.

On the other hand, the sample No. 6 (Comparative example)
In the bonded magnet of Sample No. 2, the mechanical strength was low.
The bond magnet of Comparative Example 7 (Comparative Example) has low magnetic properties. This is presumed to be due to the following reasons.

Sample No. 1 to No. In the bonded magnet of No. 5 (the present invention), the ridges are juxtaposed on the surface of the magnet powder, so that the binding resin is efficiently embedded between the ridges. For this reason, the binding force between the magnet powder and the binding resin increases,
High mechanical strength can be obtained even with a small amount of binding resin. Further, since the amount of the bonding resin used is small, the density of the bonded magnet increases, and as a result, the magnetic properties also increase.

On the other hand, the sample No. 6 (Comparative example)
In the bonded magnet, the amount of the bonding resin used is the same as the bonded magnet of the present invention, but the binding force between the magnet powder and the bonding resin is lower than that of the bonded magnet of the present invention, and the mechanical strength is low. Has become.

The sample No. In the bonded magnet of Comparative Example 7 (Comparative Example), the content (content) of the binder resin was increased in order to improve moldability and mechanical strength, so that the content (content) of the magnet powder was relatively reduced, As a result, the magnetic properties have been reduced.

[0118]

As described above, according to the present invention, the following effects can be obtained.

Since at least part of the surface of the magnet powder is provided with ridges or grooves, the binding force between the magnet powder and the binder resin is increased, and a bonded magnet with high mechanical strength can be obtained.

-Even with a small amount of binder resin, good moldability is obtained.
Since a bonded magnet with high mechanical strength can be obtained, the content (content) of the magnet powder can be increased, and the porosity is also reduced. As a result, a bonded magnet with high magnetic properties can be obtained. .

Since the magnetic powder is composed of a composite structure having a soft magnetic phase and a hard magnetic phase, more excellent magnetic properties are exhibited, and in particular, the intrinsic coercive force and squareness are improved.

Since the density can be increased, compared to the conventional isotropic bonded magnet, the bonded magnet having a smaller volume can exhibit the same or better magnetic characteristics.

Since the adhesion between the magnet powder and the binder resin is high, even a high-density bonded magnet has high corrosion resistance.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing an example of a composite structure (nanocomposite structure) in a magnet powder of the present invention.

FIG. 2 is a diagram schematically illustrating an example of a composite structure (nanocomposite structure) in the magnet powder of the present invention.

FIG. 3 is a diagram schematically showing an example of a composite structure (nanocomposite structure) in the magnet powder of the present invention.

FIG. 4 is a diagram schematically showing an example of the shape of a ridge or groove formed on the magnet powder of the present invention.

FIG. 5 is a view schematically showing an example of the shape of a ridge or a groove formed on the magnet powder of the present invention.

FIG. 6 is an electron micrograph of the magnet powder of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Magnet powder 2 Ridge 10 Soft magnetic phase 11 Hard magnetic phase

Claims (17)

[Claims] Claims: 1. A magnet powder comprising a rare earth element and a transition metal, wherein the magnet has a plate-like or scale-like shape, and has a plurality of ridges or grooves on at least a part of its surface. Powder. 2. The magnet powder according to claim 1, wherein the ridge or the groove is formed with a certain direction. 3. The magnetic powder according to claim 2, wherein a plurality of the ridges or the grooves are arranged substantially in parallel. 4. An average particle diameter is 5 to 300 μm, and when an average particle diameter of a magnet powder is a μm, an average length of the ridges or grooves is a / 40 μm or more. The magnetic powder according to any one of the above. 5. An average particle diameter is 5 to 300 μm, and an average height of the ridge or an average depth of the groove is 0.1.
The magnetic powder according to any one of claims 1 to 4, which has a diameter of from 10 to 10 µm. 6. The magnet powder according to claim 1, wherein the ridges or the grooves are arranged side by side, and the average pitch is 0.5 to 100 μm. 7. The ratio of the area of the area where the ridges or grooves are formed to the total surface area of the magnet powder is 1%.
The magnetic powder according to any one of claims 1 to 6, which is at least 5%. 8. The magnetic powder according to claim 1, wherein the magnetic powder has a composite structure having a soft magnetic phase and a hard magnetic phase.
8. The magnet powder according to any one of items 1 to 7. 9. The magnet powder according to claim 8, wherein each of the hard magnetic phase and the soft magnetic phase has an average crystal grain size of 1 to 100 nm. 10. A kneaded product obtained by kneading the magnet powder according to claim 1 and a binder resin,
A method for producing a bonded magnet by molding into a desired shape, wherein the molding is performed under conditions such that the binding resin is in a softened or molten state. 11. A bonded magnet manufactured by the method according to claim 10. 12. A bonded magnet, wherein the magnet powder according to claim 1 is bonded by a bonding resin. 13. The bonded magnet according to claim 11, wherein the bonding resin is embedded in the juxtaposed ridges of the magnet powder or in the juxtaposed grooves. 14. An intrinsic coercive force H _cJ at room temperature of ₃₂₀ to 1
The bonded magnet according to any one of claims 11 to 13, wherein the bonded magnet is 200 kA / m. 15. The bonded magnet according to claim 11, wherein the maximum magnetic energy product (BH) _max is 40 kJ / m ³ or more. 16. The magnetic powder having a content of 75-99.
The bonded magnet according to any one of claims 11 to 15, wherein the content is 5 wt%. 17. The mechanical strength measured by a punching shear test is 50 MPa or more.
7. The bonded magnet according to any one of 6.