JP2002043111A - Magnet powder and isotropic bonded magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnet which is possessed of excellent magnetic characteristics, high reliability, and especially thermally stable. SOLUTION: This magnet powder contains B and has a TbCu7 phase as a main phase, binding resin is mixed into the magnet powder, and the mixture is molded into an isotropically bonded magnet. A demagnetization curve is drawn in Figure J-H, to represent the magnetic characteristics of the bonded magnet at room temperature. When the irreversible magnetic susceptibility (χirr) of the bonded magnet is measured, regarding as a starting point an intersection of a straight line which has a slope (J/H) of -3.8×10-6 henry/m, passing through the origin of the Figure J-H and the demagnetization curve, the magnetic susceptibility (χirr) is as large as 5.0×10-7 henry/m or smaller, and furthermore an intrinsic coercive force HcJ is 400 to 1,000 kA/m at room temperature. Especially, the magnet powder is preferably formed of an alloy composition represented by a formula, (R1-aR'a)x(Fe1-bCob)100-x-y-zNyBz (where R is, at least, a rare earth element of a kind; R' is an element selected from among Zr, Hf, and Sc; x is 4 to 20 at.%; y is 5 to 20 at.%; z is 0.05 to 10 at.%; a is 0.05 to 0.50; and b is 0 to 0.50.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnet powder and an isotropic 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] By the way, most of the rare earth magnet magnets which are currently used as the high performance rare earth magnet powder are isotropic bonded magnets using MQP-B powder manufactured by MQI Co., Ltd. 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. However, the conventional isotropic bonded magnet represented by the MQP-B powder has 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 formability 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 magnet having a relatively high residual magnetic flux density has also been reported. In such a case, however, the coercive force is too small, and the magnetic flux density practically obtained as a motor (permeance in actual use) has been reported. Was very low. Further, since the coercive force is small, thermal stability is also poor.

3) The corrosion resistance and heat resistance of the bonded magnet are reduced. 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, bond magnets have poor corrosion resistance and heat resistance and low reliability.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnet powder and an isotropic bonded magnet capable of providing a magnet having excellent magnetic properties and excellent reliability, especially temperature properties. .

[0008]

This and other objects are achieved by the present invention which is defined below as (1) to (16).

(1) A magnetic powder containing B and having a TbCu ₇ type phase as a main phase, and when mixed with a binder resin and formed into an isotropic bonded magnet, has magnetic properties at room temperature. In the demagnetization curve in the JH diagram representing the above, the inclination (J / H) passes through the origin in the JH diagram and the slope (J / H) is −3.8 × 10 ^−6.
The irreversible magnetic susceptibility (χ _irr ) is 5.0 × 10 ⁻⁷ Henry / m or less when measured starting from the intersection with the straight line that is Henry / m, and the intrinsic coercive force H _cJ at room temperature.
Is 400 to 1000 kA / m.

(2) The magnet powder is an R-TM-NB alloy (where R is at least one rare earth element, TM
(1) is a transition metal mainly composed of Fe).

(3) The magnet powder is (R _1-a R ′ _a )
_x (Fe _1-b Co _b ) _100-xyz N _y B _z (where R ′ is Z
at least one element among r, Hf and Sc, x: 4 to
20 atomic%, y: 5 to 20 atomic%, z: 0.05 to 10
Atomic%, a: 0.05 to 0.50, b: 0 to 0.50)
The magnet powder according to the above (1) or (2), comprising the alloy composition represented by the following formula:

(4) The magnet powder, after quenching the molten alloy,
The magnet powder according to any one of the above (1) to (3), which is obtained by nitriding.

(5) The magnet powder according to any one of the above (2) to (4), wherein R is a rare earth element mainly composed of Sm.

(6) The magnet powder according to any one of the above (1) to (5), wherein the magnet powder is obtained by nitriding and pulverizing a quenched ribbon produced using a cooling roll. .

(7) The magnet powder according to any one of the above (1) to (6), wherein the magnet powder has been subjected to a heat treatment at least once during the production process or after the production.

(8) The magnet powder according to any one of the above (1) to (7), wherein the average particle size is 0.5 to 150 μm.

(9) The magnet powder according to any one of the above (1) to (8), wherein the TbCu ₇ type phase has an average crystal grain size of 5 to 100 nm.

(10) The magnet powder is Cu, Si, G
a, Ti, V, Ta, Nb, Mo, Ag, Zn, P, G
The magnet powder according to any one of the above (1) to (9), containing at least one element selected from the group consisting of e, Cr and C.

(11) The magnet powder according to the above (10), wherein the content of the element is 3 atomic% or less.

(12) An isotropic bonded magnet, wherein the magnet powder according to any one of (1) to (11) is bonded with a bonding resin.

(13) The isotropic bonded magnet according to (12), wherein the absolute value of the irreversible demagnetization rate (initial demagnetization rate) is 6.2% or less.

(14) Magnetic energy product (BH) _max
(12) or (1) above is 40 kJ / m ³ or more.
The rare earth bonded magnet according to 3).

(15) The isotropic bonded magnet according to any one of the above (12) to (14), which is subjected to multipolar magnetization or multipolarly magnetized.

(16) The above (1) used for the motor
The isotropic bonded magnet according to any one of 2) to (15).

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the magnet powder and the isotropic bonded magnet of the present invention will be described in detail.

[Summary of the Invention] In order to reduce the size of a motor or the like, it is an object to obtain a magnet having a high magnetic flux density. Factors that determine the magnetic flux density in the bonded magnet include the value of the magnetization of the magnet powder and the content (content) of the magnet powder in the bonded magnet, but when the magnetization of the magnet powder itself is not so high, Unless the content of the magnet powder in the bonded magnet is extremely increased, a sufficient magnetic flux density cannot be obtained.

The above-mentioned MQI manufactured by MQI is now widely used.
As described above, the P-B powder has insufficient magnetic flux density depending on the application, and therefore, when producing a bonded magnet,
There is a disadvantage that the content of the magnet powder in the bonded magnet must be increased, that is, the density must be increased, and reliability is poor in terms of corrosion resistance, heat resistance, mechanical strength, and the like.

On the other hand, the magnet powder and the isotropic bonded magnet of the present invention can obtain a sufficient magnetic flux density and an appropriate coercive force, thereby reducing the content (content) of the magnet powder in the bonded magnet. As a result, there is no need to increase the strength so much, and as a result, a highly reliable bonded magnet having high strength, excellent moldability, corrosion resistance, excellent magnetization, and the like can be provided. In addition, the magnetic powder of the present invention having a TbCu ₇ type phase as a main phase has a higher Curie temperature than MQP-B and excellent thermal stability. It has contributed to the offer. Further, the miniaturization and high performance of the bonded magnet can greatly contribute to miniaturization of magnet-mounted devices such as motors.

[Alloy composition of magnet powder] First, the alloy composition of the magnet powder of the present invention will be described.

The magnetic powder of the present invention has an alloy composition containing at least B (boron). Among them, R-TM-N-B-based alloy (wherein, R represents at least one rare earth element, TM is a transition metal mainly containing Fe) is preferably one made of, (R _1-a R ' _a ) _x (F
e _1-b Co _b ) _100-xyz N _y B _z (where R ′ is Zr,
At least one element of Hf and Sc, x: 4 to 20
Atomic%, y: 5 to 20 atomic%, z: 0.05 to 10 atomic%, a: 0.05 to 0.50, b: 0 to 0.50). Is more preferred.

R (rare earth element) is an element that is advantageous for improving the coercive force. As R (rare earth element), Y, La,
Ce, 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.

R ′ is an element composed of at least one kind of ZrHfSc, and contributes to stabilization of the TbCu ₇ type phase, which is the main phase, by partially substituting the R site.

The sum (x) of the contents (contents) of R and R '
Is preferably 4 to 20 atomic%. If x is less than 4 atomic%, a sufficient coercive force may not be obtained. On the other hand, if x exceeds 20 at%, the magnetization potential is lowered, so that a sufficient magnetic flux density may not be obtained.

Here, R is preferably a rare earth element mainly composed of Sm. The reason is that the main phase, TbCu
_This is because the value of the essential magnetic characteristics (saturation magnetization, anisotropic magnetic field) of the _7- type phase is highest when R is Sm.

The substitution ratio of R 'to R (a)
Is preferably 0.05 to 0.50. If the substitution ratio of R ′ to R is less than 0.05, TbCu ₇
In some cases, the effect of stabilizing the mold phase may not be sufficiently obtained. On the other hand, when the substitution ratio of R ′ to R exceeds 0.5, magnetization and coercive force decrease, and sufficient magnetic characteristics may not be obtained.

Examples of the TM include Fe, Co, Ni and the like, and one or more of these can be contained.

Co is a transition metal having the same characteristics as Fe. By adding Co (substituting part of Fe), the Curie temperature is increased and the temperature characteristics are improved, but the substitution ratio of Co to Fe is 0.50.
When it exceeds, the magnetic flux density tends to decrease. When the substitution ratio of Co to Fe is in the range of 0.05 to 0.20,
In addition to improving temperature characteristics, while maintaining good coercive force,
It is more preferable because a high magnetic flux density can be obtained.

N forms a solid solution as an interstitial atom in the TbCu ₇ type phase as the main phase, thereby increasing the Curie temperature of the TbCu ₇ type phase, and contributing to the improvement of the coercive force and the saturation magnetization. . The preferred content is 5
To 20 at%. When N is less than 5%, such an effect is small. On the other hand, when N exceeds 20%, the decrease in magnetization becomes remarkable, the squareness decreases, and the maximum magnetic energy product also decreases.

B is an element that is advantageous for refining crystal grains, and as a result, a high magnetic flux density can be obtained. The preferred content is 0.05 to 10 atomic%. B is 0.0
If it is less than 5 atomic%, such an effect is small. On the other hand, when B exceeds 10 atomic%, the nonmagnetic phase increases,
The magnetic flux density decreases.

Another important effect of containing B in the above-mentioned range is that the irreversible susceptibility (χ _irr ) described later can be reduced and the irreversible demagnetization rate can be improved. And the heat resistance (thermal stability) of the magnet is improved.

Although B itself is not a novel substance, in the present invention, as a result of repeated experiments and studies, B is contained in a magnetic powder having a TbCu ₇ type phase as a main phase, thereby providing an excellent angle. It is possible to improve the coercive force while securing the moldability and the maximum magnetic energy product, to reduce the irreversible susceptibility (χ _irr ) described later, and to improve the irreversible demagnetization rate (reducing the absolute value). It has been found that two effects can be obtained, in particular, that these effects can be obtained at the same time, and this point has significance of the present invention.

The preferred range of the B content is 0.05 to 10 atomic%, as described above, more preferably 0.1 to 5 atomic%, and 0.2 to 3 atomic%. More preferably, there is.

For the purpose of further improving the magnetic properties, the alloy constituting the magnet powder may contain C if necessary.
u, Ga, Si, Ti, V, Ta, Nb, Mo, Ag,
At least one element selected from the group consisting of Zn, P, Ge, Cr, and C (hereinafter, this group is represented by "Q") can be contained. When an element belonging to Q is contained, its content is preferably at most 3 atomic%,
It is more preferably 0.05 to 3 atomic%, and 0.1 to
More preferably, it is 2 atomic%.

The inclusion of the element belonging to Q exerts a specific effect according to its type. For example, C, P, and Si have an effect of making crystal grains fine, and as a result, an effect of improving coercive force. Also, Ta, Cu, Ga, S
i and Al have an effect of improving corrosion resistance.

[Constitutional Structure] The magnet material is TbCu.
It is composed of an organization whose main phase is Type ₇ . Here, the main phase refers to a constituent phase having the largest volume ratio among all constituent phases (including an amorphous phase) in the alloy. The fact that the TbCu ₇ type phase having high magnetization is the main phase greatly contributes to the fact that the magnet powder of the present invention exhibits excellent magnetic properties.

The average crystal grain size of this TbCu ₇ type phase is 5
It is preferably from 100 to 100 nm, and more preferably from 10 to 50 nm. If the average crystal grain size is less than the lower limit, the influence of the exchange interaction between the crystal grains becomes too strong,
The magnetization reversal becomes easy, and the coercive force may deteriorate.
On the other hand, if the average crystal grain size exceeds the upper limit, the influence of the exchange interaction between the crystal grains and the crystal grain becomes weak, so that the magnetic flux density, coercive force, squareness, and maximum energy product are reduced. It may deteriorate.

The magnet powder is, for example, R ₂ TM ₁₄ B
Type phase, Th ₂ Zn ₁₇ type phase, Th ₂ Ni _{1 7} type phase, ThMn ₁₂
A phase having a crystal structure such as a type phase, an α-Fe type phase, an amorphous phase, or the like may be included as a constituent phase.

[Production of Magnet Powder] The magnet powder of the present invention comprises:
It is preferably manufactured by quenching a molten alloy, and particularly preferably manufactured by crushing a quenched ribbon (ribbon) obtained by quenching and solidifying a molten alloy. . Hereinafter, an example of the method will be described.

FIG. 1 is a perspective view showing an example of the configuration of an apparatus for manufacturing a magnet material by a quenching method using a single roll (a quenched thin strip manufacturing apparatus), and FIG. 2 is a roll for cooling the molten metal in the apparatus shown in FIG. FIG. 4 is a cross-sectional side view showing a state near a collision site with the vehicle.

As shown in FIG. 1, a quenched ribbon manufacturing apparatus 1
Includes a cylindrical body 2 capable of storing a magnet material, and a cooling roll 5 that rotates in the direction of arrow 9A in the figure with respect to the cylindrical body 2. A nozzle (orifice) 3 for injecting molten metal of a magnet material (alloy) is formed at a lower end of the cylindrical body 2.

On the outer periphery of the cylinder 2 near the nozzle 3,
A heating coil 4 is arranged, and the inside of the cylinder 2 is heated (induction heating) by applying, for example, a high frequency to the coil 4 to bring the magnet material in the cylinder 2 into a molten state.

The cooling roll 5 is composed of a base 51 and a surface layer 52 forming a peripheral surface 53 of the cooling roll 5.

The surface layer 52 may be integrally formed of the same material as that of the base 51, but is preferably formed of a material having a lower thermal conductivity than the material of the base 51.

The constituent material of the base 51 is not particularly limited, but is made of a metal material having a high thermal conductivity such as copper or a copper-based alloy so that the heat of the surface layer 52 can be dissipated more quickly. Is preferred.

The constituent material of the surface layer 52 is, for example, a thin metal layer or metal oxide layer of Cr, Ni, Pd, W, or an alloy containing these, or a ceramic. Among them, ceramics is particularly preferable in that the difference in cooling rate between the roll surface 81 and the free surface 82 of the quenched thin ribbon (thin strip magnet material) 8 can be further reduced.

As ceramics, for example, Al
₂ O ₃ , SiO ₂ , TiO ₂ , Ti ₂ O ₃ , ZrO ₂ , Y
Oxide ceramics such as ₂ O ₃ , barium titanate and strontium titanate, AlN, Si ₃ N ₄ , TiN, B
N-based ceramics such as N, graphite, SiC,
Examples thereof include carbide-based ceramics such as ZrC, Al ₄ C ₃ , CaC ₂ , and WC, and composite ceramics obtained by arbitrarily combining two or more of these.

The surface layer 52 is not limited to a single layer as shown in the figure, but may be, for example, a laminate of a plurality of layers having different compositions. In this case, it is preferable that the adjacent layers have high adhesiveness, and examples thereof include those in which the same element is contained in the adjacent layers.

Further, even when the surface layer 52 is composed of a single layer, the composition is not limited to a uniform composition in the thickness direction. ).

The quenched ribbon manufacturing apparatus 1 is installed in a chamber (not shown), and operates in a state where the chamber is preferably filled with an inert gas or other atmospheric gas. In particular, the atmosphere gas is preferably an inert gas such as an argon gas, a helium gas, or a nitrogen gas in order to prevent the quenched ribbon 8 from being oxidized.

In the quenched ribbon manufacturing apparatus 1, a magnet material (alloy) is put in a cylindrical body 2, heated by a coil 4 and melted.
When the molten metal 6 is discharged from the nozzle 3, as shown in FIG. 2, the molten metal 6 collides with the peripheral surface 53 of the cooling roll 5, forms a paddle (pool) 7, and then rotates around the rotating cooling roll 5. It is rapidly cooled and solidified while being dragged by the surface 53, and the quenched ribbon 8 is formed continuously or intermittently. The roll surface 81 of the quenched ribbon 8 thus formed is separated from the peripheral surface 53 and advances in the direction of arrow 9B in FIG. In FIG. 2, the solidification interface 71 of the molten metal is indicated by a dotted line.

The preferred range of the peripheral speed of the cooling roll 5 varies depending on the composition of the molten alloy, the wettability of the peripheral surface 53 to the molten metal 6, and the like.
It is preferably from 100 to 100 m / sec, more preferably from 30 to 85 m / sec. If the peripheral speed of the cooling roll 5 is too slow, the thickness t of the quenched ribbon 8 increases, depending on the volume flow rate of the quenched ribbon 8 (the volume of the molten metal discharged per unit time), and the crystal grain size increases. Therefore, even if a heat treatment and a nitriding treatment are performed thereafter, improvement in magnetic properties cannot be expected. Conversely, if the peripheral speed of the cooling roll 5 is too high, the thickness of the quenched ribbon 8 becomes too thin, so that the characteristic deterioration due to surface oxidation cannot be ignored, and it is difficult to obtain a high density when molded as a bonded magnet. There are problems such as becoming.

The obtained quenched ribbon 8 may be subjected to at least one heat treatment in order to promote crystallization of the amorphous structure and homogenize the structure, for example. The condition of this heat treatment is, for example, at 400 to 900 ° C.
It can be about 0.5 to 600 minutes.

This 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 argon gas, such as inert gas such as helium gas, preferably carried out in a non-oxidizing atmosphere.

The quenched ribbon (strip-shaped magnet material) 8 obtained by the above-described manufacturing method has a fine crystal structure or a structure in which fine crystals are contained in an amorphous structure. Characteristics are obtained. Then, by crushing the quenched ribbon 8, the magnet powder of the present invention is obtained.

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

The average particle size of the magnet powder is not particularly limited. However, in the case of manufacturing an isotropic bonded magnet described later, it is necessary to take into consideration prevention of oxidation of the magnet powder and prevention of deterioration of magnetic properties due to grinding. , Preferably about 0.5 to 300 μm, more preferably about 10 to 250 μm, and 30 to 20 μm.
About 0 μm is more preferable.

Further, in order to obtain better moldability when molding 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 obtained magnet powder may be subjected to a heat treatment for the purpose of, for example, removing the influence of the strain introduced by pulverization and controlling the crystal grain size. The condition of this heat treatment is, for example, 350 to 800 ° C.
Thus, it can be set to about 0.5 to 300 minutes.

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

In particular, when N is contained in the alloy composition,
Is introduced by, for example, a nitriding treatment. This nitriding treatment is performed, for example, in a nitrogen gas atmosphere at 350 to 650.
The heat treatment can be carried out at a temperature of about 0.1 to 200 hours. The heat treatment (nitriding treatment) may be performed for the purpose of controlling the crystal grain size as described above.

The nitriding treatment may be performed after the quenching of the quenched ribbon, or may be performed before the crushing.

The introduction of N is not limited to the heat treatment (nitriding treatment). For example, N may be introduced by a solid phase reaction using a nitrogen compound such as RN as a raw material.

When a bonded magnet is manufactured using the above-described magnet powder, such a magnet powder has a good bonding property with the binding resin (wetting property of the binding resin). High mechanical strength, heat stability (heat resistance),
Excellent corrosion resistance. Therefore, the magnet powder is
Suitable for manufacturing bonded magnets.

Although the single-roll method has been described as an example of the quenching method, the twin-roll method may be employed. In addition, for example, atomizing method such as gas atomizing, rotating disk method, melt extraction method,
It may be manufactured by a mechanical alloying (MA) method or the like. Such a quenching method is effective for improving the magnetic properties of the bonded magnet, particularly the coercive force, since the metal structure (crystal grains) can be refined.

[Bond Magnet and Production Thereof] Next, the isotropic bonded magnet of the present invention (hereinafter, also simply referred to as “bonded magnet”) will be described.

The bonded magnet of the present invention is preferably obtained by bonding the above-mentioned magnet powder with a bonding resin.

The binding resin (binder) may be either a thermoplastic resin or a thermosetting resin.

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 have particularly good moldability and high mechanical strength, and therefore, from the viewpoint of improving heat resistance. These thermoplastic resins are also excellent in kneadability with magnet powder.

Depending on the type and copolymerization of such a thermoplastic resin, it is possible to select a wide range of thermoplastic resins, for example, those giving importance to moldability and those giving importance to 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.

Of 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).

The bonded magnet of the present invention is manufactured, for example, as follows. Magnet powder, binding resin,
Mix with additives (antioxidants, lubricants, etc.) as necessary,
Kneading (for example, warm kneading) to produce a bonded magnet composition (compound), and using the bonded magnet composition, a molding method such as compression molding (press molding), extrusion molding, injection molding, or the like is used. It is formed into a desired magnet shape without a magnetic field. When the binder resin is a thermosetting resin, it is cured by heating or the like after molding.

Here, of the three molding methods, extrusion molding and injection molding (in particular, injection molding) have advantages such as wide freedom of shape selection and high productivity. In the method, in order to obtain good moldability, it is necessary to ensure sufficient fluidity of the compound in the molding machine. Cannot be densified. However, in the present invention, as described below, a high magnetic flux density is obtained, and therefore, excellent magnetic properties can be obtained without increasing the density of the bonded magnet. Can also enjoy its advantages.

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%.

When 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.

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 4.5~6.6Mg / m ^3, more preferably about 5.5~6.4Mg / m ³ .

In the present invention, since the magnetic flux density and the coercive force of the magnet powder are large, when molded into a bonded magnet, not only when the content of the magnet powder is large, but also when the content is relatively small, it is excellent. Magnetic properties (in particular, high maximum magnetic energy product (BH) _max ) are obtained.

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.

From the above, it is preferable that the bonded magnet of the present invention be subjected to multipolar magnetization or magnetized.

The above-described bonded magnet of the present invention is demagnetized in a JH diagram (magnetization (J) on the vertical axis and a magnetic field (H) on the horizontal axis) representing the magnetic properties at room temperature. In the curve, J-
It passes through the origin in the H diagram and the inclination (J / H) is -3.8 ×
The irreversible susceptibility (χ _irr ) measured at the intersection with a straight line of 10 ⁻⁶ Henry / m as a starting point is 5.0 × 10
⁻⁷ Henry / m or less, and has a magnetic property (magnetic performance) of an intrinsic coercive force (H _cJ ) at room temperature of 400 to 1000 _kA / m. Hereinafter, the irreversible susceptibility (χ _irr ) and the intrinsic coercive force (H _cJ ) will be sequentially described.

[Regarding Irreversible Magnetic Susceptibility] The irreversible magnetic susceptibility ( _{を irr} ) is defined as the slope of the tangent of the demagnetization curve at a certain point P in the demagnetization curve in the JH diagram as shown in FIG. The differential susceptibility (と_{き dif} ), and the slope of the recoil curve (the slope of the straight line connecting both ends of the recoil curve) when the magnitude of the demagnetizing field is once reduced from the point P to draw the recoil curve is the reversible susceptibility. When (χ _rev ) is used, it is expressed by the following equation (unit: Henry / m).

Irreversible susceptibility (χ _irr ) = differential susceptibility (χ
_dif ) -reversible magnetic susceptibility (χ _rev ) In the present invention, in the demagnetization curve in the JH diagram, J
-Passing the origin in the H diagram and having a slope (J / H) of -3.8 ×
The point of intersection with the straight line y of 10 ⁻⁶ Henry / m was defined as the point P.

In the present invention, the reason for setting the upper limit of the irreversible susceptibility (χ _irr ) at room temperature to 5.0 × 10 ⁻⁷ Henry / m is as follows.

As described above, the irreversible magnetic susceptibility (χ _irr )
Indicates the rate of change of the magnetization with respect to the magnetic field, which does not return even if the absolute value is reduced after the demagnetizing field is applied. Therefore, by suppressing this irreversible susceptibility (χ _irr ) to a small value, The thermal stability of the bonded magnet can be improved, and in particular, the absolute value of the irreversible demagnetization rate can be reduced. Actually, in the range of the irreversible susceptibility (χ _irr ) in the present invention, the absolute value of the irreversible demagnetization rate when the bonded magnet is left in an environment of, for example, 100 ° C. × 1 hour and returned to room temperature is about 5%. As a result, sufficient heat resistance, that is, thermal stability is obtained in practical use (especially in use of a motor or the like).

On the other hand, if the irreversible susceptibility (χ _irr ) exceeds 5.0 × 10 ^-7 Henry / m, the absolute value of the irreversible demagnetization increases, and sufficient thermal stability cannot be obtained. In addition, since the specific coercive force is reduced and the squareness is deteriorated, the actual use of the bonded magnet is limited to the use where the permeance coefficient (Pc) is large (for example, Pc ≧ 5). . Also, the decrease in coercive force
It also leads to a decrease in thermal stability.

The irreversible susceptibility (χ _irr ) at room temperature is 5.0
While × reason defined as 10 ^-7 H / m or less is as described above, the irreversible susceptibility (chi _irr) is as small as possible is preferred, therefore, in the present invention, the irreversible susceptibility (chi
_irr ) is preferably 4.5 × 10 ⁻⁷ Henry / m or less, and more preferably 4.0 × 10 ⁻⁷ Henry / m or less.

[Regarding intrinsic coercive force] The intrinsic coercive force (H _cJ ) of the bonded magnet at room temperature is 400 to 1000 _kA / m.
It is. Particularly, 480 to 750 kA / m is more preferable.

When the intrinsic coercive force (H _cJ ) exceeds the upper limit, the magnetization is inferior and a sufficient magnetic flux density cannot be obtained.

On the other hand, if the intrinsic coercive force (H _cJ ) is less than the lower limit, the demagnetization when a reverse magnetic field is applied becomes remarkable depending on the use of the motor, and the heat resistance at high temperatures is inferior. Therefore, by _{setting the} specific coercive force (H _cJ ) within the above range, even in the case where a bonded magnet (particularly a cylindrical magnet) is subjected to multipolar magnetization or the like, even when a sufficient magnetization magnetic field cannot be obtained. It is possible to provide a high-performance bond magnet, particularly a motor-use bond magnet, in which good magnetization can be achieved, a sufficient magnetic flux density can be obtained, and a high-performance bond magnet can be provided.

Further, the bonded magnet of the present invention preferably satisfies the following conditions with respect to the maximum magnetic energy product and the irreversible demagnetization rate.

[0104] [maximum magnetic for energy product (BH) _max] maximum magnetic energy product (BH) _max is, 40 kJ
/ M ³ or more is preferably in the range, more preferably at 60 kJ / m ³ or more, even more preferably 75～130KJ / m ^3. 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.

[Regarding Irreversible Demagnetization Rate] The absolute value of the irreversible demagnetization rate (initial demagnetization rate) is preferably 6.2% or less, more preferably 5% or less, and more preferably 4% or less. More preferred. Thereby, a bonded magnet having excellent thermal stability (heat resistance) can be obtained.

[0106]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described.

(Example 1)
Gold composition is (Sm_0.7Zr_0.3)_TenFe_balCo_8.5N ₁₂B_z
(B content z as shown in Table 1
Seven kinds of magnetic powders) were obtained.

First, the raw materials of Sm, Zr, Fe, Co, and B were weighed to cast a mother alloy ingot, and a sample was cut out from the ingot.

A quenched ribbon manufacturing apparatus 1 having the structure shown in FIGS. 1 and 2 was prepared, and the sample was placed in a quartz tube provided with a nozzle (circular orifice) 3 at the bottom. After evacuating the inside of the chamber in which the quenched ribbon manufacturing apparatus 1 was housed, an inert gas (argon gas, helium gas) was introduced to obtain an atmosphere of a desired temperature and pressure.

Thereafter, the ingot sample in the quartz tube is melted by high-frequency induction heating, and the injection pressure of the molten metal (the sum of the internal pressure of the quartz tube and the pressure applied in proportion to the height of the liquid surface in the cylinder 2) A quenched ribbon was prepared by adjusting the peripheral pressure of the cooling roll and the peripheral pressure of the cooling roll.

After the obtained quenched ribbon was roughly pulverized, a heat treatment was performed at 720 ° C. for 15 minutes in an argon gas atmosphere. Furthermore, in order to adjust the particle size, a crusher (raikai machine)
To obtain a powder having an average particle diameter of 50 μm.

The powder thus obtained is heat-treated (nitriding) at 450 ° C. × 20 hours in a nitrogen atmosphere.
To obtain magnet powder of each alloy composition.

In order to analyze the phase constitution of each of the obtained magnet powders, the diffraction angle (2θ) was 2 using Cu-Kα.
X-ray diffraction was performed in the range of 0 ° to 80 °. From the diffraction pattern, it was confirmed that the TbCu ₇ type phase was present as the main phase. The average crystal grain size of the TbCu ₇ type phase was measured for each magnet powder. These values are shown in Table 1.

Each of these magnet powders was mixed with an epoxy resin and kneaded at 225 ° C. for 15 minutes to prepare a composition (compound) for a bonded magnet. At this time, the compounding ratio (weight ratio) of the magnet powder and the epoxy resin was set to be substantially equal for each bonded magnet. That is, the content (content) of the magnet powder in each bonded magnet is about 97 wt.
%Met.

Next, the compound was pulverized into granules, and the granules were weighed, filled into a mold of a press machine, and compression-molded at a pressure of 800 MPa (without a magnetic field) to obtain a compact. After release, the epoxy resin was cured at 150 ° C. to obtain a cylindrical isotropic bonded magnet having a diameter of 10 mm and a height of 7 mm. The density ρ of each bonded magnet was about 6.3 Mg / m ³ .

<Evaluation of Magnetic Characteristics and Irreversible Magnetic Susceptibility> Each of the bonded magnets was pulse-magnetized at a magnetic field strength of 3.2 MA / m, and then subjected to a DC self-recording magnetometer (trade name, manufactured by Toei Industry Co., Ltd., TR
F-5BH), the magnetic properties (residual magnetic flux density Br, intrinsic coercive force H _cJ , and maximum magnetic energy product (BH) _max ) were measured at a maximum applied magnetic field of 2.0 MA / m. The temperature at the time of measurement is
23 ° C (room temperature).

As shown in FIG. 4, the obtained JH diagram was reduced.
In the magnetic curve, the slope (J / H) passing through the origin is -3.8
× 10^-6The intersection P with the straight line of Henry / m is set as a starting point,
From here, change the magnetic field to 0 once and then back again
Draw a recoil curve, and calculate the slope of this recoil curve
Of the reversible susceptibility (χ)
_rev). The demagnetization curve at the intersection P
The slope of the tangent to the line is calculated as the differential susceptibility (χ_dif).
Irreversible susceptibility at room temperature (χ_irr) Is χ_irr= Χ_dif−χ
_revAsked. The results are shown in Table 1 below.

<Evaluation of Heat Resistance> Next, the heat resistance (thermal stability) of each bonded magnet (column having a diameter of 10 mm and a height of 7 mm) was examined. This heat resistance is 100% for bonded magnets.
After being kept in an environment of ° C. × 1 hour, the irreversible demagnetization rate (initial demagnetization rate) when returning to room temperature was measured and evaluated. The results are shown in Table 1 below. The smaller the absolute value of the irreversible demagnetization rate (initial demagnetization rate), the better the heat resistance (thermal stability).

[0119]

[Table 1]

<Comprehensive Evaluation> As can be seen from Table 1, an isotropic bonded magnet containing B and manufactured using a magnetic powder having a TbCu ₇ type phase as a main phase, and having an irreversible susceptibility (χ All of the isotropic bonded magnets (Sample Nos. 2 to ⁷ ) having an _irr ) of 5.0 × 10 ⁻⁷ Henry / m or less have excellent magnetic properties (residual magnetic flux density, specific coercive force, maximum magnetic energy). Product) and a small absolute value of the irreversible demagnetization rate, so that the heat resistance (thermal stability) is high and the magnetization is also good. Among them, the sample No. in which the content of B was optimized. 2-No. The isotropic bonded magnet according to No. 6 has particularly excellent magnetic properties (particularly, residual magnetic flux density).

As described above, according to the present invention,
It is possible to provide a bonded magnet having high performance and high reliability (in particular, heat resistance). In particular, high performance is exhibited when a bonded magnet is used as a motor.

Example 2 As raw materials of a mother alloy ingot, Sm, Fe, Co, B, R ′ and Q (however,
R ′ is at least one element of Zr, Hf and Sc;
Q is Cu, Si, Ga, Ti, V, Ta, Nb, Mo,
Example 1 except that at least one element selected from the group consisting of Ag, Zn, P, Ge, Cr, and C) was used.
In the same manner as described above, magnet powders (sample Nos. 8 to 14) represented by the alloy compositions shown in Table 2 were produced.

[0123]

[Table 2]

Using each of the thus obtained magnet powders, a bonded magnet was manufactured in the same manner as in Example 1. For these, the average crystal grain size of the TbCu ₇ type phase was measured, and the magnetic properties, irreversible susceptibility, and heat resistance were evaluated in Example 1.
Was performed in the same manner as described above. Table 3 shows the results.

[0125]

[Table 3]

<Comprehensive Evaluation> As is clear from Table 3, the sample No. Each of the bonded magnets Nos. 8 to 14 has particularly excellent magnetic properties and thermal stability (heat resistance).

As described above, by adding a predetermined amount of Q, the bonded magnet of the present invention has more excellent magnetic properties and thermal stability (heat resistance). This is considered to be because the synergistic effect is obtained by containing Q together with B.

(Example 3) Sample no. 1 to No. 1
4 using the respective magnet powders in the same manner as in Examples 1 and 2.
A cylindrical (ring-shaped) isotropic bonded magnet having an outer diameter of 22 mm, an inner diameter of 20 mm, and a height of 4 mm was manufactured, and each of the obtained bonded magnets was multipole magnetized to 8 poles. The current flowing through the magnetizing coil during magnetization was 16 kA.

At this time, the magnitude of the magnetizing magnetic field required to achieve the magnetizing rate of 90% was relatively small, and the magnetizing was good.

A spindle motor for a CD-ROM was assembled using the thus-bonded bonded magnets as rotor magnets.

In each spindle motor for CD-ROM, the back electromotive force generated in the winding coil when the rotor was rotated at 1000 rpm was measured. As a result, the sample No. The motor using the bonded magnet according to Comparative Example 7 (Comparative Example) had a voltage of 0.80 V, while the sample N
o. 1 to No. 6, no. 8 to No. In all of the motors using the bonded magnets No. 14 (all of the present invention), values higher than 0.96 V and higher by 20% or more were obtained.

As a result, it was confirmed that a high-performance motor could be manufactured by using the bonded magnet of the present invention.

A bonded magnet and a motor of the present invention were manufactured in the same manner as in Examples 1 and 2 except that a bonded magnet was manufactured by extrusion (the content of magnet powder in the bonded magnet: 92 to 95 wt%). When the performance was evaluated, the same results as described above were obtained.

A bonded magnet and a motor of the present invention were manufactured in the same manner as in Examples 1 and 2, except that the bonded magnet was manufactured by injection molding (the content of the magnet powder in the bonded magnet: 90 to 93 wt%). When the performance was evaluated, the same results as described above were obtained.

[0135]

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

The magnet powder contains B, and TbCu ₇
By having a constitutional structure having a mold phase as a main phase, magnetization is high, excellent magnetic properties are exhibited, and in particular, intrinsic coercive force and squareness are improved.

The absolute value of the irreversible demagnetization rate is small, and excellent heat resistance (thermal stability) is obtained. A predetermined amount of Q (where Q is C, Cu, Si, Ga, Ti, V, Ta, N
By containing at least one element selected from the group consisting of b, Mo, Ag, Zn, P, Ge, and Cr) together with B, a synergistic effect is obtained, and further excellent magnetic properties are obtained. . Further, heat resistance and corrosion resistance are further improved.

Since a high magnetic flux density can be obtained, a bonded magnet having high magnetic properties can be obtained even if it is isotropic. In particular, compared to a conventional isotropic bonded magnet, a smaller-sized bonded magnet can exhibit the same or better magnetic performance, so that a smaller and higher-performance motor can be obtained.

Also, since a high magnetic flux density can be obtained, sufficiently high magnetic properties can be obtained without pursuing higher densities in the production of the bonded magnet. Further improvements in dimensional accuracy, mechanical strength, corrosion resistance, heat resistance (thermal stability), and the like can be achieved, and a highly reliable bonded magnet can be easily manufactured.

Since the magnetization is good, the magnetization can be performed with a lower magnetization magnetic field. In particular, multipolar magnetization can be easily and reliably performed, and a high magnetic flux density can be obtained.

[Brief description of the drawings]

FIG. 1 Apparatus for manufacturing magnet material (Quenched strip manufacturing apparatus)
It is a perspective view which shows the example of a structure of.

FIG. 2 is a cross-sectional side view showing a state near a collision site of a molten metal against a cooling roll in the apparatus shown in FIG.

FIG. 3 is a diagram (JH diagram) for explaining irreversible magnetic susceptibility;
It is.

FIG. 4 is a JH diagram showing a demagnetization curve and a recoil curve.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Quenched ribbon manufacturing apparatus 2 Cylindrical body 3 Nozzle 4 Coil 5 Cooling roll 51 Base 52 Surface layer 53 Peripheral surface 6 Molten 7 Paddle 71 Solidification interface 8 Quenched ribbon 81 Roll surface 9A Arrow 9B Arrow

Claims (16)

[Claims] 1. A magnetic powder containing B and having a TbCu ₇ type phase as a main phase, and when mixed with a binder resin to form an isotropic bonded magnet, exhibits magnetic properties at room temperature. In the demagnetization curve in the JH diagram shown, it passes through the origin in the JH diagram and has a slope (J /
H) an irreversible susceptibility (χ _irr ) of 5.0 × 10 ^-7 Henry / m or less when measured starting from an intersection with a straight line having -3.8 × 10 ^-6 Henry / m;
Further, the intrinsic coercive force H _cJ at room temperature is 400 to 1000 _k.
A / m is a magnetic powder characterized by the fact that it is A / m. 2. The magnet powder is an R-TM-NB alloy (where R is at least one rare earth element and TM is F
2. The magnetic powder according to claim 1, wherein the magnetic powder comprises a transition metal mainly composed of e. 3. The magnet powder of (R_1-aR '_a)_x(Fe_1-b
Co_b)_100-xyzN _yB_z(However, R 'is Zr, Hf,
At least one element of Sc, x: 4 to 20 atoms
%, Y: 5 to 20 atomic%, z: 0.05 to 10 atomic%,
a: 0.05 to 0.50, b: 0 to 0.50)
The alloy according to claim 1 or 2, wherein the alloy is composed of:
Of magnet powder. 4. The magnet powder according to claim 1, wherein the magnet powder is obtained by quenching the molten alloy and then nitriding. 5. The magnet powder according to claim 2, wherein R is a rare earth element mainly containing Sm. 6. The magnet powder according to claim 1, wherein the magnet powder is obtained by nitriding and pulverizing a quenched ribbon produced using a cooling roll. 7. The magnet powder according to claim 1, wherein the magnet powder has been subjected to a heat treatment at least once during the production process or after the production. 8. The magnetic powder according to claim 1, having an average particle size of 0.5 to 150 μm. 9. The TbCu ₇ type phase having an average crystal grain size of 5
The magnetic powder according to any one of claims 1 to 8, which has a thickness of from 100 to 100 nm. 10. The magnet powder is made of Cu, Si, Ga, T
i, V, Ta, Nb, Mo, Ag, Zn, P, Ge, C
The magnet powder according to any one of claims 1 to 9, further comprising at least one element selected from the group consisting of r and C. 11. The magnetic powder according to claim 10, wherein the content of the element is 3 atomic% or less. 12. An isotropic bonded magnet, wherein the magnet powder according to claim 1 is bonded with a bonding resin. 13. The isotropic bonded magnet according to claim 12, wherein the absolute value of the irreversible demagnetization rate (initial demagnetization rate) is 6.2% or less. 14. The magnetic energy product (BH) _max is 40.
14. The rare earth bonded magnet according to claim 12, wherein the magnet is kJ / m ³ or more. 15. The isotropic bonded magnet according to claim 12, which is subjected to multipolar magnetization or is multipolar magnetized. 16. The isotropic bonded magnet according to claim 12, which is used for a motor.