JP3481739B2 - High heat resistant bonded magnet - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high heat resistant bonded magnet which is required to have high heat resistance in the use environment and the manufacturing environment such as the use of automobiles and home electric appliances, and has a hard magnetic property of a specific multiphase. The present invention relates to a highly heat-resistant bond magnet capable of injection molding, which is characterized by comprising a nano-composite magnetic material having a metal structure as a body and having excellent heat resistance and a thermoplastic resin having a melting point of 250 ° C. or more as a binder.

[0002]

2. Description of the Related Art As a static magnetic field source for electronic devices, permanent magnets incorporated in acoustic parts such as field magnets for small motors and buzzers have been polished to meet the demand for device manufacturing cost reduction by simplifying the assembly process. In recent years, there has been an increasing tendency to use resin-bonded magnets that do not require post-processing. Among them, magnets manufactured by injection molding using thermoplastic polyimide as resin are widely used because of their high productivity, high dimensional accuracy, and the ability to handle complex shapes. ing.

However, when the above-mentioned polyimide is used, there is a problem that the heat resistance temperature is low because the softening temperature of the resin is low, and soldering to the electronic circuit board of the device in automobile parts and manufacturing processes where the use environment temperature is high. There is a problem that it cannot be applied to general consumer electronic devices, etc., which are manufactured by a reflow furnace. Therefore, hard ferrite powder is used as the magnet powder, and P having a high softening temperature is used as the binder.
Ferrite-bonded magnets using PS resin or heat-resistant polyimide (66 nylon, etc.) have been put to practical use as a compound for highly heat-resistant injection-molded bond magnets.

On the other hand, in order to reduce the size and weight of electronic devices and to improve their performance, it is necessary to improve the magnetic properties of magnet materials, and injection-molded bond magnets using rare earth magnet powder as magnet powder have also been developed. That is, samarium cobalt magnet powder has been used as the rare earth magnet powder,
Recently, a compound for injection-molded magnets has been developed that uses neodymium iron-based ultra-quenched magnet powder that contains almost no samarium or cobalt, which has a high raw material cost, and is supplied at a lower price than samarium-cobalt magnet powder.

However, the rare earth iron-based magnet powder obtained by the above-mentioned ultra-quenching method is more easily oxidized than hard ferrite or samarium-cobalt magnetic powder. Since the temperature when kneading with the heat-resistant thermoplastic resin is higher than that of polyimide (nylon 6 etc.) which has a low softening temperature that is usually used for injection-molded bonded magnets, deterioration of properties due to oxidation of magnetic powder during kneading. Therefore, a compound for injection-molded bond magnet with high heat resistance using neodymium iron-based ultra-quenched magnet powder has not been put to practical use.

[0006]

Therefore, in order to develop a highly heat-resistant injection-molded bonded magnet, the development of a high-performance and highly-oxidation-resistant magnet material containing iron as a main component with a low raw material cost is awaited. Was there. The resin currently used for the injection-molded bond magnet is mainly a polyamide having a low softening temperature and a low heat-resistant temperature. From the viewpoint of kneading temperature, injection molding temperature, compatibility with magnet powder, etc., nylon 6 or nylon 12 is used.
Is used.

To express the heat resistance of these polyamide resins in terms of load deformation temperature, when the load is 0.45 MPa, nylon 6 which is not reinforced with glass fiber is 175 ° C. and nylon 12 is about 145 ° C. On the other hand, nylon 46 is used as a polyamide of a high melting point thermoplastic resin that is a high heat resistant resin that is practically used in some ferrite bonded magnets.
(Heat distortion temperature 285 ° C), nylon 66 (heat distortion temperature 2
40 ° C.), and a crystalline polymer such as polyphenylene sulfide (PPS) resin (heat distortion temperature of about 260 ° C.).

Generally, in manufacturing a compound, after resin powder and magnet powder of similar particle size are mixed in advance,
The resin is heated to melt and kneaded while applying sufficient shear stress. The temperature at this time is about 200 to 250 ° C for nylon 6 and 12 and nylon 46 to 66 and PPS.
In the case of a high melting point resin such as, the temperature is about 300 ° C or higher. Furthermore, since the compound must have high fluidity during injection molding, nylon 6 or nylon 12 should be used at 270 ° C to 30 ° C.
It is heated to 0 ° C, and to 300 ° C or higher for high melting point resin.

However, the conventional fine powder of neodymium iron-based ultra-quenched magnet deteriorates in magnetic properties rapidly at high temperature due to oxidation, and an injection molding bond using a high melting point resin which requires a kneading temperature of 300 ° C. or higher. The manufacture of magnets has not been industrially successful.

The present invention relates to a bonded magnet for automobiles and home electric appliances, which is required to have high heat resistance in use environment and manufacturing environment, and is a magnet alloy composed of a nanocomposite magnetic material having a multiphase metal structure and excellent heat resistance. It is an object of the present invention to provide a highly heat-resistant bonded magnet which is injection-molded by using a high melting point resin in fine powder.

[0011]

Means for Solving the Problems
3-323778, Japanese Patent Application No. 3-323779, Japanese Patent Application No. 4-93780, Japanese Patent Application No. 4-93781, Japanese Patent Application No. 4-93782, Japanese Patent Application No. 4-124180,
Japanese Patent Application No. 4-124181, Japanese Patent Application No. 4-130139, Japanese Patent Application No. 4-130140
Japanese Patent Application No. 4-130141, Japanese Patent Application No. 4-174767, Japanese Patent Application No. 4-17
4768, Japanese Patent Application 4-176197, Japanese Patent Application 4-176198, Japanese Patent Application
4-176199, Japanese Patent Application No. 4-176200, Japanese Patent Application No. 4-209771, Japanese Patent Application No. 4-209772, Japanese Patent Application No. 4-209773, Japanese Patent Application No. 4-209774
Japanese Patent Application No. 5-31326, Japanese Patent Application No. 5-59524, Japanese Patent Application No. 5-1137
No. 31, Japanese Patent Application No. 5-294769, Japanese Patent Application No. 5-294770, Japanese Patent Application No. 5-
341646, Japanese Patent Application No. 5-314647, Japanese Patent Application No. 5-341648, Japanese Patent Application No. 5-341649, Japanese Patent Application No. 5-341650, Japanese Patent Application No. 5-343903,
Japanese Patent Application No. 5-343575, Japanese Patent Application No. 5-343904, Japanese Patent Application No. 6-060324
No. 6-060325, No. 6-074465, No. 6-07
At No. 6543, it has proposed a ferrous permanent magnet material having a low rare earth containing a Nanoko down Pojitto magnetic constituted by a soft magnetic phase and a hard magnetic phase.

In this iron-based permanent magnet material, the magnetization of the soft magnetic phase is coupled with the magnetization of the hard magnetic phase by exchange interaction,
The composite as a whole behaves as if it were a conventional permanent magnet composed of a single magnetic phase, and is generally called an "exchange spring magnet" or "Exch."
It is also referred to as an "ang Spring Magnet". This all-new type of permanent magnet material has the following features which are very important for realizing the present invention.

FIG. 1 shows changes in weight of the nanocomposite magnetic material of the present invention (shown by a solid line) and a conventional neodymium iron-based ultra-quench magnet (MQP-B manufactured by Magnechwench, shown by a broken line) due to oxidation in the atmosphere. The comparison is made as a function of the sample temperature, and the magnetic material of the present invention exhibits extremely high stability even in the vicinity of 300 ° C.
It shows that it undergoes rapid oxidation above about 0 ° C.

[0014] We, the Nanoko down Pojitto magnets oxidation tendency is strong rare earth compound phase if present by itself
(Composite hard magnetic phase component) has a microstructure surrounded by an iron-based alloy phase containing Cr (soft magnetic phase component of the composite), which has a low oxidation tendency. It is much less sensitive than ultra-quench magnets, and therefore has a high ignition temperature, low ignitability even when pulverized into fine powder, and high safety. The heat resistance is increased by making it a specific composition and structure, and even in the process of mixing with a high heat resistant thermoplastic resin, the safety of the kneading process can be ensured on an industrial scale, and the magnetic properties due to oxidation during kneading It was found that the deterioration can be reduced to a negligible level. In addition, a certain amount of Cr
It has been found that the structure of the nanocomposite becomes finer, the coercive force is improved, and the irreversible thermal demagnetization rate is significantly lower than that of the conventional magnet even when it is heated to a high temperature of 200 ° C. or higher. , Completed this invention.

That is, in the present invention, the composition formula is R
_{x (Fe 1-u Co u} ) 100-x-y-z B y C
r _z , (R: one or more of Pr, Nd and Dy), x (at%), y (at%), z (at%) and u satisfy the following values, And the content ratio of Cr and Co
The atomic concentration ratio is 0.5 to 2.0, and Nd ₂ Fe ₁₄ B
It is composed of a hard magnetic phase having a type crystal structure and a soft magnetic phase of body-centered cubic iron and iron boride, and the average crystal grain size of each phase is 50.
having a nanocomposite structure that is less than or equal to nm and a diameter of 30
Including 50 vol% or more of hard magnetic powder of 0 μm or less,
It is a high heat resistant bonded magnet formed by using a thermoplastic resin having a melting point of 250 ° C. or more as a binder. 4.5 ≦ x ≦ 6.0, 15 ≦ y ≦ 20, 3 ≦ z ≦ 7,
0.04 ≦ u ≦ 0.10

Further, according to the present invention, in the high heat resistant bonded magnet having the above structure, the hard magnetic powder has a diameter of 75 μm.
Below, in a magnetic circuit having an average permeance coefficient of 1.0 or more, by heating to a temperature of 200 ° C. or less,
Suggest together high heat resistance bonded magnet and, respectively therewith, wherein the irreversible heat demagnetization rate when returned to room temperature is 10% or less.

[0017]

DETAILED DESCRIPTION OF THE INVENTION

Magnet Manufacturing Method and Structure The nanocomposite magnetic material of the present invention is an alloy of iron-boron alloy, which is easily amorphized, to which some rare earth and chromium are added. After being obtained, it can be obtained by crystallization by heat treatment, further pulverized into powder, and then mixed with a resin and molded to be used as a resin-bonded magnet. The inventors of the present invention have industrially manufacturable properties, high magnetic properties, and high oxidation resistance.
As an iron-based magnetic material with low ignition property, the soft magnetic phase constituting the nanocomposite magnetic material contains body-centered cubic iron and iron boride compound, and the hard magnetic phase has an Nd ₂ Fe ₁₄ B type crystal structure. , Having a microstructure surrounded by the soft magnetic phase, and increasing the coercive force by adding a specific amount of Cr, reducing the irreversible heat demagnetization rate, and further having a lower oxidation tendency than the conventional ultra-quenched magnet , Developed an iron-based low rare earth magnet alloy with excellent heat resistance, pulverized it and kneaded it with a high heat resistant thermoplastic resin and at a temperature above the melting point of that resin, and it has excellent heat resistance and is suitable for use at 200 ° C or higher. We have developed a bond magnet that can withstand.

As described above, the multi-phase structure composed of at least two phases of the soft magnetic phase and the hard magnetic phase exhibits the two-stage demagnetization behavior peculiar to a simple mixture of ferromagnetic materials having different coercive forces. Instead, in order to have a smooth demagnetization curve as if it were a magnetic material composed of a single hard magnetic phase, the exchange coupling distance (L _ex) which is an index of the size of the region where the directions of atomic magnetic moments are aligned. ), The crystal grain size of each phase is as small as possible, and in order to secure the exchange coupling between the soft magnetic phase and the hard magnetic phase, a metal having crystal grain boundaries that do not sandwich a non-magnetic grain boundary phase. We need to create an organization.

The nanocomposite magnetic material of the present invention is characterized in that the amorphous alloy having the above composition produced by the ultra-quenching method is heat-treated to crystallize, and the crystal phase is directly obtained by the ultra-quenching method. The manufacturing method is completely different from the conventional neodymium iron-based ultra-quench magnet. Further, in the conventional neodymium iron rapidly quenched magnet, but preparation is possible to perform the crystallization heat treatment thereto after once prepared amorphous alloy, in which case the microstructure best characteristics are obtained, the phase structure Including the above, it must be the same as when the crystallized structure is directly obtained from the molten metal.

On the other hand, in the present invention, it is an important feature that the metastable phase is precipitated from the amorphous state and the crystal grain size thereof is several tens of nanometers or less, and the quenching rate of the molten metal is slowed down. The microstructure is completely different from that obtained by directly obtaining the crystallized structure. In other words, if the latter step is taken, not a metastable phase but a stable phase precipitates, and the grain size does not become nanometer size due to coarsening of the body-centered cubic iron phase. I can't. In addition, even when an amorphous alloy is obtained, the heating rate of heating in the step of performing the crystallization heat treatment is an important manufacturing parameter, and is 10 per second in the temperature range of 500 ° C. or higher at which crystallization is started. The range from 0 ° C to 50 ° C is preferred.

Manufacturing Method of Bonded Magnet, Reason for Limitation Since the bonded magnet according to the present invention has very good oxidation resistance due to the inclusion of Cr, a high coercive force is obtained and the thermal stability of magnetic properties of the magnetic powder is excellent. Even when the ambient temperature in actual use is as high as 200 ° C., it can be used for a long time. When manufactured under appropriate conditions, the magnet powder of the present invention has no ignitability even with fine powder of 25 μm or less, and irreversible thermal demagnetization and permanent deterioration are negligible even when used up to 200 ° C. or higher. Has heat resistance superior to iron-based ultra-quench magnets.

The magnet alloy obtained according to the present invention has a thickness of 2
It has a flaky flake shape of about 0 to 50 μm and can be crushed to a size of several hundred μm by an ordinary crusher. When the maximum particle size is expressed by the length of fine powder, 300 μm is the upper limit suitable for injection molding, and even if it exceeds this limit, it can be used as a raw material for injection molding, but its application range is limited, In many cases, the particle size of the magnetic powder in the compound due to the magnetic powder cracking of 3
It is less than about 00 μm, and the magnetic characteristics are 150 μm.
If it is m or more, there is no grain size dependency, so the maximum is 300 μm.

The larger the ratio of the magnetic powder is, the larger Br is.
Regarding the ratio of the magnetic powder and the particle size of the magnetic powder, the smaller the particle size of the magnetic powder, the lower the ratio of the magnetic powder that can be filled, and even if the ratio of the magnetic powder is constant, the magnetic particle size dependence of the magnetic powder is recognized when the magnetic particle size is 100 μm or less.

On the other hand, regarding the moldability, in order to completely eliminate or significantly reduce the post-processing of the product after injection molding, it is necessary to perform injection molding through an extremely thin gate, and good fluidity is obtained. Therefore, the diameter of the magnetic powder is preferably 300 μm or less, more preferably 100 μm or less, and further preferably 75 μm or less.
In many cases, the maximum particle size of the magnetic powder that can be used is determined by the gate diameter of the injection molding machine, and the maximum particle size may be restricted within the range of 10 to 75 μm. Therefore, it is necessary to select the particle size range in time to meet the requirements. There is.

The conventional neodymium iron-based ultra-quenched magnet magnetic powder has a problem that when it is pulverized into fine powder, the magnetic properties are remarkably deteriorated due to the oxidation of the crystal grains in the surface layer of the magnetic powder, and the change over time becomes large. However, the magnet powder of the present invention is hard to be oxidized, and the crystal grain size is smaller than that of the conventional neodymium iron-based ultra-quenched magnet, so even if the crystal grains in the surface layer of the magnetic powder are oxidized, the effect is slight. The change over time is also small.

The hard magnetic material of the present invention has a melting point of 250 ° C.
Produced as a magnetic component directly by injection molding method by mixing and kneading the above PPS or high melting point polyimide resin, or these high melting point resin and other resins with alloyed engineering plastics or the like in order to enhance toughness. However, in that case, it can be designed as a structural part of the magnetic circuit as a magnetic and structural part that simultaneously causes the attraction force between the structural parts generated by the magnetostatic energy stored in the magnetic gap to function, or simply as a magnetomotive force source. It is also possible to design the support structure component to be provided in addition to the above-mentioned function.

The resin used in the present invention is limited to a high melting point thermoplastic resin, and nylon 46, 2 having a melting point of 290 ° C.
A thermoplastic resin such as nylon 66 at 60 ° C. or PPS resin at 280 ° C. is used. Therefore, the melting point of the high melting point resin of the present invention is limited to 250 ° C. or higher in order to distinguish it from the conventional resin, but the kind of the resin is not limited to the one exemplified in the specification and may be changed to other ones for strengthening. Mixed with resin,
That is, various designs such as alloying are possible.

The typical properties of the anisotropic injection-molded hard ferrite bonded magnets currently used are Br = 2.2.
3.0 Tesla, HcJ = 180 to 240 kA / m, (B
H) _max = about 9 to 18 kJ / m ³ . On the other hand, an object of the present invention is to provide a bond magnet having higher characteristics, and if the filling volume ratio of the magnetic powder is not higher than 50%, the anisotropic hard ferrite injection-molded bond magnet currently used is used. Higher magnetization cannot be obtained compared to. Therefore,
The lower limit of the magnetic powder filling amount is 50% by volume.

On the other hand, the upper limit is not particularly limited. However, if the magnetic powder filling amount is too large, the fluidity of the melt compound during injection molding will decrease and molding will not be possible.Therefore, consider the individual target shape and the characteristics of the injection molding machine, and The upper limit of the magnetic powder filling rate is naturally determined by the property. Generally, the volume ratio is preferably about 52% to 62%.

When it is not necessary to increase the filling rate of the magnetic powder, by mixing a powder such as a non-magnetic compound as a filler, the usage ratio of the expensive resin and the magnetic powder can be reduced, and the manufacturing cost can be reduced. it can. In the most preferred embodiment, (BH) max = 30-48.
It is possible to obtain an extremely high-performance injection-molded bonded magnet with kJ / m ³ .

When the magnet powder and the high melting point resin are kneaded as described above, the conventional neodymium iron-based ultra-quenched magnet powder is easily oxidized and cannot withstand the kneading at a high temperature, but as a magnet powder of the present invention, a small amount is required. Has a microstructure surrounded by a soft magnetic phase of body-centered cubic iron or an iron boride containing no rare earth element, and has a specific amount of C
Kneading with a high melting point resin by adding nanoparticle size by adding r to increase the coercive force, reduce the irreversible thermal demagnetization rate, and use the nanocomposite magnet powder with excellent oxidation resistance. Will be possible.

Reason for limiting the structure In the present invention, the particle size of the soft magnetic phase must be as small as the size of the exchange coupling distance Lex, which is the characteristic length of the constituent phases in the nanocomposite magnet, and the average particle size. Is 50
In the case of about nm, since the recoil magnetic permeability and coercive force suitable for the target magnetic circuit can be obtained, the average crystal grain size is 5
It is limited to 0 nm or less.

The magnet of the present invention is used in the process of industrially producing a fine metal structure of nanometer size,
The coexistence of the soft magnetic phase and the hard magnetic phase constituting it is an important technical issue. That is, both phases must be in a relationship capable of coexisting in a thermal equilibrium or quasi-equilibrium state, and further, it is necessary that crystal grain growth does not easily occur. As a hard magnetic phase that can coexist with the soft magnetic phase, Nd ₂ Fe ₁₄ B type compound or Sm ₂ Fe ₁₇ N can be considered, but the latter requires a step of nitriding treatment and the raw material is Sm with respect to Nd. In addition to being expensive, the vapor pressure becomes high at high temperature, and control of the composition during dissolution becomes more complicated, which is not preferable.

Since Sm ₂ Fe ₁₇ N vaporizes Sm at a high temperature, a method of superfinely mixing and alloying iron and samarium by a mechanical alloying method is proposed. However, it is necessary to store and handle a large amount of very active ultrafine metal powder, and it is necessary to impose strict atmosphere control to avoid the risks associated with this storage and handling. It is not established as an industrial manufacturing method. Therefore, the phase composition of the hard magnetic nanocomposite material used in the present invention includes body-centered cubic iron and iron boride as the soft magnetic phase and Nd ₂ as the hard magnetic phase.
The system is limited to a combination of Fe ₁₄ B type compounds.

Composition and Reason for Limitation From the viewpoint of the price of the raw material metal, the composition preferably contains a large amount of iron and a rare earth element having a large single-ion crystal magnetic anisotropy. However, iron-based low rare earth alloys are much more difficult to be amorphized than alloys containing a large amount of rare earths, and in order to promote the amorphization, it is necessary to use a non-containing material such as boron, carbon, or phosphorus. It is necessary to add a crystal formation promoting element.

In the present invention, when Nd or Pr is mainly used as the rare earth R, the rare earth R is contained in the range of 4.5 to 6 atomic percent (at%) and 15 to 20 at% of boron.
When added, the target magnet material can be stably obtained by passing through the ultra-quenching method and the subsequent crystal heat treatment, and further, when Dy is contained as a constituent component of R, the effective coercive force is effectively increased. Is possible.

Further, when a specific amount of Cr is contained in the starting alloy, the crystal grain growth of the soft magnetic phase is effectively suppressed during the crystallization heat treatment, and the target 50 nm or less, particularly the preferable composition range. In this case, the size is reduced to 20 nm or less, the coercive force is improved accordingly, and the recoil rate is remarkably enhanced, and at the same time, the temperature dependence of H _CJ is reduced.
Here, the recoil rate is the minor loop on the hysteresis curve, that is, the magnetic flux density when removed by applying a demagnetizing field equal to the coercive force H _CJ in the BH diagram of the recoil curve, and after saturation magnetization. Is expressed as the ratio of the residual magnetic flux density to the residual magnetic flux density.

With conventional magnet materials, the recoil ratio is about 0 to 0.2, except for materials with extremely small H _CJ , such as alnico magnets, and even nanocomposite magnets called spring magnets have a recoil ratio of 0.5 to 0.5. It is about 0.7. C
When r is added, the recoil rate reaches 0.7 or more, and reaches 0.9 when it is particularly excellent. This characteristic of the Cr-containing material is maintained almost as it is even when the temperature is raised, and the irreversible demagnetization is suppressed together with the decrease in the temperature dependence of the coercive force. As a result, in a magnetic circuit having an average permeance coefficient of 1.0 or more, the irreversible thermal demagnetization rate when heated to a temperature of 200 ° C. or less and returned to room temperature is Nd-
14% of Fe-B based ultra-quench magnets and nanocomposite magnets
Compared with the above, the magnetic material is remarkably reduced, and the irreversible thermal demagnetization rate is 10% or less even when heated to 200 ° C., and the magnetic material has excellent thermal stability. Further, when Cr is contained, Cr is contained in the constituent phase, and particularly, the moisture resistance and the oxidation resistance of the body-centered cubic iron phase are significantly improved, so that the oxidation resistance of the nanocomposite itself is also improved.

The content of Cr having the above-mentioned various effects is
It is better to increase the coercive force, but the magnetization decreases with an increase in the Cr content, and when it exceeds 7 at%, the decrease in the magnetization becomes remarkably accelerated and the magnetization in the case of a bonded magnet decreases. It is appropriate to set the upper limit to 7 at% because it loses the competitiveness with the material. If the Cr content is reduced, the effect of improving the coercive force and the recoil rate becomes small, and if it is less than 3 at%, the irreversible thermal demagnetization rate increases and the characteristics as a heat resistant bonded magnet are lost, so the lower limit of the Cr content is 3 at%. And

When Cr is contained in the constituent phase, the oxidation resistance is improved as described above, but the temperature dependence of the magnetization of the constituent phase tends to be large, and the reversible temperature coefficient of the magnetic flux density is rather an absolute value. Will increase. Inclusion of Co can reduce or offset this decrease. In particular, the contribution ratios of Cr and Co to the Curie temperature of the iron-based alloy are almost the same in absolute value when the effects are (+) and (-), so if both are contained in equal amounts, the irreversible heat demagnetization ratio and the reversible heat demagnetization ratio are A well-balanced permanent magnet material can be obtained. The particularly preferable range of the content ratio of Cr and Co can be expressed by the ratio of the atomic concentrations of both, and if this value is less than 0.5, the effect of recovering the reversible thermal demagnetization rate due to the addition of Co is not sufficient and 2 If it exceeds 0.0, Co is excessive and the coercive force is reduced to increase the irreversible thermal demagnetization rate, which is not preferable. Therefore, it is limited to 0.5 to 2.0.

La and Ce as R do not play a role in magnetism, which is not preferable, and heavy rare earths tend to remarkably reduce the magnetization due to the property that the magnetic moment is directed in the direction opposite to Nd, and therefore their use must be limited. . Of the heavy rare earth elements, Tb and Ho have the same effect of increasing the intrinsic coercive force as Dy, but they are not selected because they have a low natural abundance ratio, a small production amount, and are expensive. In addition, Sm, Er,
The second-order Stevens factors of Tm and Yb are Pr, Nd,
Since it has the opposite sign to Tb, Dy, Ho, etc., the single-ion magnetocrystalline anisotropy has the opposite sign, and Nd ₂ Fe ₁₄ B
The addition of these rare earths is not preferable, because the contribution of the type compounds to the magnetocrystalline anisotropy has the opposite effect of Nd and the like and cancels each other out. Therefore, R is limited to Pr, Nd, and Dy.

At least one of Pr, Nd and Dy is selected as the rare earth R, and the range is limited to 4.5 to 6 at%. When the R concentration is less than 4.5 at%, H _CJ higher than 4 kOe cannot be obtained, and when it exceeds 6 at%, the constituent phase changes and the above-mentioned body-centered cubic iron, iron boride, Nd ₂ Fe ₁₄
Since it becomes difficult to manufacture a nanocomposite magnet by combining B-type compounds, the upper limit of the R concentration is limited to 6 at%.

When boron is added in an amount of 15 to 20 at%, not only body-centered cubic iron but also boride of iron is formed during crystallization. The latter has magnetic properties that are acceptable as a good soft magnetic phase. There is. A Nd ₂ Fe ₁₄ B type compound is precipitated as a hard magnetic phase. Therefore, in the present invention, the constitutive phases are limited to body-centered cubic iron, iron boride and Nd ₂ Fe ₁₄ B type compounds.

[0044]

Example 1 After obtaining an amorphous alloy having a chemical formula of Nd _5.5 Fe ₆₆ B _18.5 Cr ₅ Co ₅ composition by ultraquenching, the temperature rise rate is 15 ° C./min in a furnace at 640 ° C. in an argon atmosphere. The resulting crystalline alloy was crushed by a pin mill in the air to obtain a nanocomposite magnetic powder with a maximum particle size of 63 μm . When the crystal grain size of the nanocomposite magnetic powder of the present invention was observed using a transmission electron microscope, it was about 20 nm. The magnetic properties of this nanocomposite magnetic powder are Br = 0.8
6T, H _CJ = 0.61 MA / m.

As a comparative example, the composition (wt%) is 2
6.9Nd-0.3Pr-67.3Fe-1.0B-
In order to avoid dust explosion of magnetic powder, 4.5Co (trade name MQP-B, manufactured by GM) was ground by a pin mill installed in an Ar atmosphere to obtain a magnetic powder having a maximum particle size of 63 μm. Magnetic properties of the obtained magnetic powder B = 0.87T, (BH) max = 1
It was 00 kJ / m ³ .

The nanocomposite magnetic powder of the present invention is extremely stable even in the air and generates little heat due to oxidation, and there was no problem in handling the powder in the air, but MQP
The -B powder generates heat that can be felt even when deposited in Ar, and it was essential to handle it in an inert atmosphere. In particular, it was necessary to pay close attention to the kneader when it was preheated to a high temperature, and fire accidents frequently occurred.

As shown in Table 1, these magnet powders were mixed with nylon 46, nylon 66 and PPS resin powders at various ratios, then kneaded at 330 ° C. for 15 minutes using a small biaxial mixer and then cooled. I got a compound. This compound was heated again to 310 ° C. in an injection molding tester to melt it, and was injected into a molding die heated to 120 ° C. and cooled to obtain a test piece of 10 mm × 10 mm × 3.5 mm. Table 1 shows the magnetic properties of these test pieces.

Example 2 The nanocomposite magnetic powder of the present invention (No. 11, 14, 15, 16) having the magnetic powder composition shown in Table 2 and the nanocomposite magnetic powder No. outside the composition range of the present invention. 12 and 13 were prepared in the same manner as in Example 1 to obtain powder having a maximum diameter of 150 μm or less. Moreover, No. Ultra-quenched powders (trade name: MQP-B, manufactured by GM) labeled 17 and 18 were passed through a comb to obtain powders having a maximum particle size of 150 μm or less. No. 1 whose composition is shown in Table 2 11-No. 18 powders were kneaded with PPS resin in a volume ratio of magnet powder: resin ratio of 53:47,
Injection-molded in the same manner as in Example 1 to 10 × 10 × 3.5 mm
After being magnetized, it was heated to 200 ° C. and cooled to room temperature, and the irreversible thermal demagnetization rate and magnetic characteristics were measured. The results are shown in Table 2.

[0049]

[Table 1]

[0050]

[Table 2]

[0051]

The present invention, as is apparent from the examples,
Conventional neodymium iron-based ultra-quench magnet magnet powder was difficult to manufacture due to its tendency to easily oxidize. It is possible to manufacture injection-molded resin-bonded magnets with a heat-resistant temperature of 200 ° C or higher, and the magnetic characteristics exceed the upper limit of ferrite injection-molded bonded magnets. It can be used for applications such as automobile parts that require stability of magnet characteristics and mechanical strength at high temperature in addition to dimensional accuracy of bonded magnets, compatibility with complex shapes, and ease of integral molding with other parts. Therefore, it is possible to supply a magnetic material having high industrial utility value.

[Brief description of drawings]

FIG. 1 compares the weight change due to oxidation in air as a function of sample temperature between the nanocomposite magnetic material of the present invention (solid line) and the conventional neodymium iron-based superquenched magnetic material (dashed line). It is a graph.

─────────────────────────────────────────────────── --- Continuation of front page (56) Reference JP-A-7-54106 (JP, A) JP-A-6-61025 (JP, A) JP-A-6-251919 (JP, A) JP-A-6- 283317 (JP, A) JP-A 1-125906 (JP, A) JP-A 6-36915 (JP, A) JP-A 1-251704 (JP, A) JP-A 1-219142 (JP, A) Tokuhyo Hira 6-505366 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01F 1/00-1/375 C22C 38/00 303

Claims (3)

(57) [Claims] 1. The composition formula is R _x (Fe _{1 -u} Co _u ).
_{100-x-y-z B} y Cr z, (R: Pr, Nd, D
one or more of y), x (at%), y
(At%), z (at%) and u satisfy the following values,
Moreover, the content ratio of Cr and Co is 0.5 to 2 in terms of atomic concentration ratio.
0, a nanocomposite structure composed of a hard magnetic phase having a Nd ₂ Fe ₁₄ B type crystal structure and a soft magnetic phase of body-centered cubic iron and iron boride and having an average crystal grain size of 50 nm or less in each phase A high heat-resistant bond magnet having a hard magnetic powder having a diameter of 300 μm or less and 50 vol% or more and having a melting point of 250 ° C. or more as a binder. 4.5 ≦ x ≦ 6.0, 15 ≦ y ≦ 20, 3 ≦ z ≦ 7,
0.04 ≦ u ≦ 0.10 2. A high heat-resistant bonded magnets Oite to claim 1, the diameter of the hard magnetic powder is 75μm or less. 3. The method of claim 1, Oite to claim 2, in the magnetic circuit permeance coefficient of 1.0 or more in average, are irreversible heat demagnetization rate when returned to room temperature and heated to a temperature of 200 ° C. or less A highly heat resistant bonded magnet having a content of 10% or less.