JPH07201543A - Rare earth permanent magnet and its manufacture - Google Patents

Abstract

PURPOSE:To obtain a magnet of high energy product by a method wherein a magnet is lessened in B rich phase as much as possible, enhanced in sintered body density, and reduced in crystal grain diameter. CONSTITUTION:In an R-T-B rare earth permanent magnet whose main phase is an RRB phase represented by Nd-Fe-B, a B rich phase indicated by R1+epsilonT2B14 is limited to 3% or below in content, a sintered body density is set to 7.5gr/co or above, and RRB is 3 to 12mum in crystal grain diameter. This magnet is formed through such a method that R-T-B crystalline alloy powder whose main phase is a R2R14B phase where R amounts to 26.5 to 29wt.% and liquid quenched alloy amorphous or fine crystalline powder where R amounts to 50 to 100wt.% are mixed together, molded, and sintered or thermally treated, if necessary. By this setup, an excellent R-T-B magnet which has at least a coercive force of 640kA/m and a maximum energy product of 360kj/m<3> or above can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an RTB based permanent magnet having an R ₂ R ₁₄ B intermetallic compound as a main phase and a method for producing the same, and more particularly to a high performance rare earth permanent magnet and a method for producing the same. .

[0002]

_2. Description of the Related Art A representative document relating to a sintered magnet for producing an Nd-Fe-B magnet, which is a magnet typified by an R ₂ T ₁₄ B rare earth permanent magnet, by a powder metallurgy method is disclosed in Japanese Unexamined Patent Publication 59-46008, or the 35th research paper of the Japan Institute of Applied Magnetics (March 1984), many publications aiming at higher performance have been published so far.

Each of these documents discloses a method of crushing, molding, sintering and heat treating an ingot of a magnet composition. According to the conventional method, melting is carried out in a vacuum or an inert atmosphere using an arc, high frequency, etc. R ₂ T ₁₄ B
An ingot containing a magnetic phase is produced. The phase crushing of the ingot is performed by a disc mill, a hammer mill, etc., and the fine crushing is performed by a ball mill, a jet mill, an attritor, etc. Alignment and compression formation in a magnetic field are usually performed simultaneously in a magnetic field using a mold. Sintering is 10
It is carried out in an inert atmosphere or vacuum in the range of 0 to 1150 ° C. The heat treatment is performed at a temperature of about 300 to 900 ° C. if necessary.

[0004]

At present, the magnet characteristics obtained by this method are 280 to 320 kJ / m ³ (35 to 4).
0MGOe), which is 4π of the magnetic compound of this system magnet.
Energy product of magnet theoretically derived from Is (1.61T = 16.1kG), 512kJ / m ³ (64MGOe)
It is a significantly lower value than

The source of the coercive force of this system magnet is R ₂ T ₁₄ B
The phase is to take on the rare morphology that comes into the RT solid solution phase. In order to improve the (BH) max of the magnet, it is indispensable to increase the space factor of the R ₂ T ₁₄ B phase in the sintered body and increase Jr. In addition, the present magnet is liquid-phase sintered with the RT solid solution phase as the core of the liquid phase, and not only for generating the coercive force but also for obtaining the sintered body.
The T solid solution phase has become indispensable. From the above, in order to achieve a high energy product ratio of this system magnet, the volume of the R ₂ T ₁₄ B phase should be increased as much as possible, and the RT solid solution phase, which is essential for sintering and coercive force generation, should be the minimum required. It is essential to keep it to the limit.

However, using the conventional starting material powder, the RT solid solution phase produced is different from the other phase (Nd ₂ Fe ₁₄
Compared to B), its abundance is extremely low (34 wt% Nd
(The amount of the RT solid solution phase present in -1.0 wt% B-Febal is 6 vol% or less.) Moreover, the ductility is extremely high, and the pulverizability is extremely poor. For this reason, the particle size distribution becomes wide, and it is extremely difficult to uniformly mix the RT solid solution powder, which is the core of the liquid phase during sintering, and the R ₂ T ₁₄ B phase powder, which is the solid phase. Further, this RT solid solution phase is easily oxidized and has a drawback that the wetting of the liquid phase during sintering is deteriorated.

The above-mentioned various drawbacks cannot be solved, and a magnet has been manufactured by using a starting material containing an excessive R-rich phase. Therefore, only magnets having a low density and a non-uniform sintered structure, such as Jr, (BH) max and Hcj, could be manufactured.

[0008] Therefore, the technical problem of the present invention is to overcome these drawbacks and to obtain an extremely high performance N which has not been obtained in the past.
An object is to provide an RTB-based permanent magnet represented by d-Fe-B and a method for manufacturing the same.

[0009]

The inventors of the present invention have previously disclosed, as a method for improving the above-mentioned drawbacks, Japanese Patent Laid-Open No. 62-12.
No. 0826 is proposed. In this document, a composition powder that becomes a liquid phase component at the time of sintering is obtained by a liquid quenching method, and this powder and an ingot crushed powder having a magnetic pole phase Nd ₂ Te ₁₄ B phase as a main phase are mixed and crushed, The (BH) max of 280 kJ / m ³ (3
It is proposed that a high-performance R-T-B system permanent magnet exceeding 5 MGOe) can be obtained.

Using these manufacturing processes as basic techniques, the present inventors have conducted various studies for the purpose of various improvements and improvements, and as a result, have found that they are stable and 360 kJ / m ³ (45 MGOe).
It has an energy product of 640 kA / m ³ (8
A rare earth permanent magnet having a coercive force of kOe) or more and a manufacturing method thereof have been found.

The above-mentioned JP-A-6-1 proposed by the present inventors.
In No. 20826, R- represented by Nd-Fe-B magnet
Focusing on the fact that the TB magnet is manufactured by liquid phase sintering,
N, which is unnecessary because it is possible to disperse the liquid phase during sintering in the compact with a much higher degree of uniformity than in the conventional method.
Nd-rich phase, B-rich phase, and oxide phase are reduced as much as possible to increase the Nd ₂ Fe ₁₄ B phase amount ratio that contributes to magnetism, and high Jr and high energy product Nd -Fe
-B magnet could be manufactured.

However, even in this method, 36
It was difficult to stably supply a sintered body having an energy product of 0 kJ / m ³ (45 MGOe) or more.

Therefore, as a result of various investigations, the inventors of the present invention can stably supply a magnet having an extremely high energy product of 360 kJ / m ³ or more by satisfying the following. It has been found that it is indispensable to manufacture under the following conditions also in the manufacturing method.

In the structure of the sintered body of the present magnet, Nd ₂ Fe ₁₄ B phase which is responsible for magnetism and Nd rich phase which is called Nd-rich phase are usually used.
_In addition to the Nd-Fe solid solution phase of ₉₅ Fe ₅ , Nd _{1 + ε} Fe ₄
3 phases B-rich phase is present as indicated by B _4. Among these phases, the Nd ₂ Fe ₁₄ B phase and the Nd rich phase are indispensable phases in order to obtain the magnet characteristics. Since the other B-rich phase does not contribute to magnetism at all, its existence is suppressed as much as possible, and it is important to reduce it to obtain a high energy product. The present inventors set the amount ratio of the B-rich phase to be 9% or less and set the grain size of the B-rich phase to 5 μm.
It has been found out that setting it to m or more is one condition for obtaining a high energy product Nd-Fe-B magnet. In addition, in order to obtain a particularly high Jr among the magnet characteristics, it is essential that the density of the sintered body be as high as possible and close to the theoretical density. The theoretical density of this magnet is 7.55 to 7.60, though it varies slightly depending on the composition.
It is about gr / cc. This density is at least 7.5 gr
It has been found that a high Jr cannot be obtained unless it is / cc or more, and a high energy product cannot be obtained due to the deterioration of the squareness ratio. The density of Nd-Fe-B magnets currently on the market is at most 7.45 gr.
Since it is as low as / cc, a high Jr and squareness ratio cannot be obtained, and at most a maximum energy product of 320 kJ / m ³ (40 kGOe) is obtained.

Furthermore, in order to obtain a high energy product,
It cannot be achieved only by high Jr, and it is essential to have high coercive force. In the case of such a magnet, Nd ₂ Fe
_The smaller the crystal grain size of the ₁₄ B phase magnetic particles, the more advantageous it is to have a high coercive force. The details of the cause have not been clarified so well, but it is generally said that the coercive force generation of this system magnet is of the pinning type. Therefore, it is indispensable that the crystal grain size is as small as possible in order to obtain a high coercive force.

By minimizing the B-rich phase described above, the density of the sintered body is increased. Moreover, even if the conditions for reducing the crystal grain size are lacking, a magnet having a high energy product exceeding 360 kJ / m ³ cannot be stably obtained.

The above three conditions for obtaining this high energy product cannot be realized in the conventional processes of crushing, molding, sintering and heat treating an ingot melted with a magnet composition.

Originally, the B-rich phase itself does not contribute to the magnetic characteristics as described above. However, it is known that HG can be increased by increasing the B content of the magnet composition to some extent, and the composition of the commercially available magnet material is also the original B content.
It is manufactured with a certain level higher than the composition. Therefore, B
With the appearance of the rich phase, the volume cost is over 6%.

Further, it is impossible in the conventional manufacturing process to secure the sintered body density of 7.5 gr / cc or more and to set the crystal grain size to 3 to 12 μm.

In the conventional manufacturing method, this is as described above.
Since it is difficult to uniformly disperse the Nd-rich phase, which is the core of the liquid phase, in the compact, the sintering temperature must be raised in order to increase the density of the sintered body, and the amount of liquid phase during sintering should be increased. It has to be increased. Therefore, it is unavoidable that the crystal grain size becomes large. On the other hand, if the sintering temperature is lowered in order to reduce the crystal grain size, the density of the sintered body cannot be increased, and both cannot be satisfied.

The inventors of the present invention have made it possible to manufacture a high-energy product magnet because the previously proposed measures can realize the above drawbacks.

Further, as a result of various studies to make it possible to stably manufacture this high energy product magnet, R is 26.5 to 29 wt%, and R ₂ T ₁₄ B phase is mainly contained. Phase R-T-B crystalline alloy powder and R is 50 to 50
Stable (BH) max of 360 kJ / m ³ with high energy product by stable mixing (BH) max by mixing 100 wt% (not including 100) amorphous or microcrystalline liquid quenching alloy powder. It was discovered that a -T-B magnet is manufactured.

Here, the RT having the R ₂ R ₁₄ B phase as the main phase
The reason why the R value of the -B crystalline alloy powder is set to 26.5 to 29 wt% is that the precipitation of hetero-phase such as α-Fe is remarkable in the composition lower than 26.5, which not only deteriorates the pulverizability of the powder but also the magnetic field. 26.5w to significantly reduce the orientation during molding
It was set to t% or more. Further, the reason for setting the content to 29 wt% or less is that the R-rich phase, which uses the powder on the higher R-value side and has poor grindability, is present in a large amount in the powder, and the liquid phase cannot be uniformly dispersed in the compact, or The reason is that the amount of the liquid quenching alloy powder to be mixed is too small, so that it is not possible to densify it by uniform liquid sintering, resulting in structural irregularity and significantly deteriorating the magnet characteristics.

Further, the composition of R of the liquid quenched alloy powder is set to 50
If the R value is less than this, the amount of the liquid phase at the time of sintering is too large, and the amount of unoriented R ₂ T ₁₄ B particles precipitated in the cooling process of the sintering from the liquid phase. The ratio increases and only deteriorates the Jr of the magnet.

Further, in the structure of the magnet manufactured by the above manufacturing method, the crystal grain size is set to 3 to 12 μm, and the amount ratio of the B-rich phase is 9%.
The reason for setting the sintered body density to 7.5 gr / cc or more is that a high coercive force cannot be obtained if the crystal grain size is 12 μm or more. However, since it is a region where the coercive force does not improve significantly, it does not make much sense and it is 3μ.
In order to realize a crystal grain of m or less, it is necessary to make the pulverized powder particle size considerably fine, and therefore it becomes difficult to prevent oxidation, and the oxygen content of the sintered body becomes high, and it becomes difficult to obtain high characteristics. This is because. In the B-rich (-rich) phase, the coercive force is slightly improved in the region exceeding 9%, but Jr is deteriorated.
Similarly, when the density of the sintered body is 7.5 gr / cc or less, not only the Jr is low but also the coercive force is deteriorated, so that neither of them has a high energy product, particularly a magnet characteristic of 360 kJ / m ³ or more cannot be obtained.

Further, it is necessary that the Nd-rich phase having a crystal grain size of 1 μm or less is uniformly distributed in the structure of the sintered body.

It has been found that setting the grain size of the B-rich phase to 5 μm or less is a condition for obtaining a high energy product Nd-Fe-B magnet.

Originally, the B-rich phase itself does not contribute to the magnetic characteristics at all as described above.

However, it is known that Hcj is increased by increasing the B content of the magnet composition to some extent,
The composition of the commercially available magnet material is also made higher than the original B composition to some extent. Therefore, the appearance of the B-rich phase is unavoidable, and the particle size is 10 μm or more, which is large. In the process of crushing an ingot melted with a conventional magnet composition, molding, sintering, and heat treatment, keep the grain size of the B-rich phase below 5 μm, Hcj is 400 kA / m or more, and (BH) max is 360 kJ / m ³ A magnet that obtains the above cannot be obtained. This is a method of mixing a composition powder as a liquid phase component and a powder having a Nd ₂ Fe ₁₄ B composition close to a magnetic phase,
It can be manufactured.

[0030]

EXAMPLES Examples of the present invention will be described below.

(Example 1) 26.7 to 39.5 Nd-0.97 to 1.3B-F using high-purity Nd, Fe, and B
An ingot having a composition of e bal (wt%) was melted in a vacuum to prepare.

Next, this ingot was roughly crushed. This powder was used as the first raw material powder.

Similarly, by using high-purity Nd, Fe, and B, 50-99Nd-0.8-2.0B-Febal
An ingot having a composition of (wt%) was melted in a vacuum to prepare.

Next, using this ingot, a liquid quenching thin piece was prepared by the single roll method.

This powder obtained by roughly crushing this thin piece was used as the second raw material powder.

The first raw material powder and the second raw material powder are 29 to 31 Nd-1.0 to 1.5B-Fe bal (w
t%) was mixed and pulverized using a ball mill. The powder particle size at this time was 2 to 5 μm. Next, these powders were φ in a magnetic field of 20 kOe at a molding pressure of 1 ton / cm ² .
It was molded into a size of 18 × 12t. 10 these molded bodies
After firing in a vacuum of 00 to 1100 ℃, 400 to 700 ℃
The heat treatment of was added.

The magnetic properties of the thus-obtained sintered body, the density of the sintered body, and the Nd ₂ Fe content in the B-rich phase amount sintered body
The crystal grain size of the ₁₄ B phase is shown in Table 1 below. For the B-rich phase, the area ratio was obtained using an image analyzer and converted into a volume ratio. For the crystal grain size, the section length was determined using an image analyzer, and 3/2 times that was taken as the average crystal grain size.

[0038]

[Table 1]

From Table 1 above, the amount of B-rich phase is 3 vol%
Below, the sintered body density is 7.5 gr / cc or more, and the crystal grain size is 3 ~
It can be seen that all the 12 μm samples have an energy product of 360 kJ / m ³ or more.

(Example 2) High purity Nd, Fe and B were used to obtain 26-29.5 Nd-1.0B-Fe bal (w).
t%) of the Nd ₂ Fe ₁₄ B phase as the main phase of the ingot was melted in a vacuum to prepare.

Next, these ingots were roughly crushed to obtain a first raw material powder. Next, 60Nd-1.0B-Fe bal
An ingot having a composition of (wt%) was melted in a vacuum and prepared in the same manner as the first raw material powder.

Using this ingot, a liquid quenched thin piece was further obtained by the single roll method.

This thin piece was roughly crushed and this powder was used as the second raw material powder.

Next, the first raw material powder and the second raw material powder are weighed to obtain 31Nd-1.0B-Febal.
(Wt%), and then pulverized using a ball mill.

The particle size of this pulverized powder was measured and found to be 2
It was 5 μm.

Next, these powders were molded in a magnetic field of 20 kOe at a molding pressure of 1 ton / cm ² into a size of φ18 × 12 t. These compacts were sintered in vacuum at 1040 to 1100 ° C. Further, heat treatment at 400 to 700 ° C. was applied to the obtained sintered body.

FIG. 1 shows the relationship between the Nd composition value of the first raw material powder used and the obtained magnet characteristics. Hd of the first raw material powder
When the composition is in the range of 26.5 to 29 wt%, magnet characteristics with an energy product of 45 MGOe or more are obtained.
In addition, the density of each sintered body is 7.55 to 7.60 gr / c.
c, there is no B-rich phase, and the average crystal grain size is 8 to
It was 11 μm.

(Example 3) 45-97Nd-1.0B-Febal (wt) using high-purity Nd, Fe, and B
%) Was melted in vacuum. The obtained ingot was then liquid-cooled by the single roll method to obtain amorphous flakes. This thin piece was roughly pulverized and the obtained powder was used as the second raw material powder. Of the second raw material powder and the first raw material powder obtained in Example-1, 27 Nd-
1.0B-Fe bal (wt%) was used to mix to obtain a weighed composition of 30 Nd-1.0B-Fe bal (wt%), which was further pulverized using a ball mill. The particle size of this ground powder was measured and found to be 2 to 5 μm.

Next, these powders were molded into a size of φ18 × t12 in a magnetic field of 20 kOe at a molding pressure of 1 ton / cm ² . These compacts were sintered in vacuum at 1040 to 1100 ° C. Further, heat treatment at 400 to 700 ° C. was applied to the obtained sintered body.

FIG. 2 shows the relationship between the Nd composition value of the II material used and the obtained magnet characteristics. The Hd composition of the second raw material powder is 5
In the range of 0 wt% or more, all show excellent magnet characteristics exceeding 360 kJ / m ³ . In addition, no B-rich phase was found in any of the sintered bodies. The density of all the sintered bodies is 7.55 to 7.60 gr / cc, and
There was no rich phase, and the average crystal grain size was 8 to 11 μm.

As described above in Examples 1 to 3, N
Lower R mainly composed of R ₂ R ₁₄ B phase represented by d-Fe-B
In -T-B system rare earth permanent magnet of B-rich (-rich) Airyo represented by _{R 1 +} ε T ₄ B ₄ is 3% or less, the sintered density was 7.5gr / cc or more R ₂ R ₁₄ B crystal grain size is 3 to 1
By setting it to 2 μm, an energy product of 360 kJ / m ³ or more can be obtained from a high-performance RTB-based magnet. The above high-performance magnet has an R-T-B crystalline alloy powder having an R ₂ T ₁₄ B phase of R of 26.5 to 29 wt% as a main phase and R of 50 to 10%.
It can be realized by mixing, molding, sintering, and optionally heat treating liquid quenching alloy powder consisting of 0 wt% (not including 100) of amorphous or fine crystals. this is,
Since it was possible to uniformly disperse the liquid phase, which was difficult with the conventional method, the structure can be controlled easily, and as a result, the excess phase such as B-rich phase can be reduced to the utmost limit, and the high density and fine grain system It is possible to obtain a uniform sintered body,
It is considered that Jr and Hcj can be derived close to the limit value of the original magnet of this system magnet, and a magnet having a high energy product can be stably manufactured.

(Example 4) Using high-purity Nd, Fe, and B, 26-29.5 Nd-1.0B-Fe bal (w
An ingot having a composition of t%) was melted in a vacuum to prepare. Next, this ingot was roughly crushed. This powder first
The raw material powder was used.

Similarly, by using high-purity Nd, Fe and B, 45.0 to 100.0 Nd-0.2 to 2.0B-F
An ingot having a composition of e bal (wt%) was melted in a vacuum to prepare. Next, using this ingot, a liquid-quenched thin body was produced by the single roll method. This powder was used as the second raw material powder.

29.0 of these first and second raw material powders are added.
~ 32.0 Nd-1.0B-Febal (wt%) composition was mixed and ground using a ball mill. The powder particle size at this time was 2 to 5 μm.

Next, these powders were mixed at 600 kA / m (20 kO).
φ18 × 12 at a molding pressure of 1 ton / cm ² in the magnetic field of e)
It was molded into a size of t. These molded bodies are made to be 1040-11
After sintering in a vacuum of 00 ° C, a heat treatment of 400 to 700 ° C was applied.

The sintered body thus obtained, the magnetic properties, the amount of Nd-rich phase in the sintered body and the crystal grain size are shown in Table 2 below.
Shown in. The area of the Nd-rich phase was calculated using an image analyzer and converted into a space factor. For the crystal grain size, the cutting edge length was determined using an image analysis device, and 3/2 times that was taken as the average crystal grain size. Further, as Comparative Example 1, a 29.0 Nd-1.0B-Fe bal (wt%) sintered body was prepared by a conventional powder metallurgy method, and the characteristics thereof are also shown in Table 2 below.

[0057]

[Table 2]

As described above in the fourth embodiment, Nd
-Fe-B represented by R ₂ T ₁₄ B phase as the main phase R-
In the case of a TB rare earth permanent magnet, R _100-x −T _x (0 ≦ x
≦ 20) R-rich (-rich) phase content of 4% or less and the crystal grain system of 1.0 μm or less, the coercive force is 0.8T or more high performance R-T-B system A rare earth permanent magnet is obtained.

(Example 5) Using high-purity Nd, Fe, and B, 26.7 to 29.5 Nd-0.97 to 1.3B-F
An ingot having a composition of e bal (wt%) was prepared by vacuum melting. Next, this ingot was roughly crushed in Ar. This powder is used as the first raw material powder.

Similarly, by using high-purity Nd, Fe, and B, 50-99Nd-0.8-2.0B-Febal
An ingot having a composition of (wt%) was prepared by vacuum melting. Using this ingot, a liquid quenching thin piece was prepared by the single roll method. The flakes were coarsely crushed. This powder was used as the second raw material powder.

The first raw material powder and the second raw material powder are treated with 29-31 Nd-1.0-1.5 B-Fe bal (w).
t%) was mixed and finely pulverized using a ball mill. The powder particle size at this time was 2 to 5 μm.
Next, these powders were molded under a magnetic field of 1600 kA / m at a molding pressure of 1 ton /
It was molded into a size of φ18 mm × t12 mm with a pressure of cm ² . These compacts were sintered in a vacuum of 1040 to 1070 ° C. and then heat-treated at 400 to 700 ° C.

The magnetic properties and the grain size of the B-rich phase of the sintered body thus obtained are shown in Table 3 below.

[0063]

[Table 3]

It can be seen that the Hcj of 600 kA / m or more (BH) max of 360 kJ / m ³ or more is obtained for all the materials having a B-rich phase particle diameter of 5 μm or less.

As described in Example 5 above, Nd-Fe-
In the R-T-B system rare earth permanent magnet having the R ₂ T ₁₄ B phase represented by B as the main phase, B represented by R _{1 + ε} T ₄ B ₄
By making the particle size of the rich (-rich) phase 5 μm or less, H
A high-performance R-T-B magnet having a cj of 600 kA / m or more and a (BH) max of 360 kJ / m ³ or more can be obtained.

The above high-performance magnet has an R of 26.5 to 29.
wt% R-T-B crystalline alloy powder having R ₂ T ₁₄ B phase as a main phase and R of 50 to 100 wt% (100 is not included)
Liquid quenching alloy powder consisting of amorphous or microcrystalline
It can be realized by molding, sintering, or heat treatment if necessary. This is because it is possible to uniformly disperse the liquid phase, which was difficult with the conventional method, and it becomes easier to control the structure, and as a result, it is possible to reduce the excess phase such as B-rich phase to the limit. Hcj, (BH) max
It is thought that the high-performance magnet could be manufactured because it was possible to derive the above-mentioned magnets to the limit that is inherent to this system magnet.

[0067]

As described above, according to the present invention,
RTB represented by extremely high performance Nd-Fe-B
A permanent magnet and a method for manufacturing the same can be provided.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between an Nd composition value of a crystalline Nd—Fe—B alloy powder having an Nd ₂ Fe ₁₄ B phase as a main phase and a magnet characteristic in Example 2.

FIG. 2 is a diagram showing a relationship between an Nd composition value of an amorphous Nd—Fe—B alloy powder and a magnet characteristic in Example 3.

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[Procedure amendment]

[Submission date] March 15, 1995

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 1

[Correction method] Change

[Correction content]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Change

[Correction content]

In the sintered body structure of the magnet of the present system, Nd ₂ Fe ₁₄ B phase, which is responsible for magnetism, and Nd rich phase, which are generally called N, are called.
In addition to the Nd-Fe solid solution phase of d ₉₅ Fe ₅ , Nd _{1 + ε}
There are three B-rich phases represented by Fe ₄ B ₄ (where ε is a number of 0 or more) . Among these phases, in order to obtain the magnet characteristics, the Nd ₂ Fe ₁₄ B phase and the Nd rich phase are
This is an essential phase. Another B rich (-ric
Since the h) phase does not contribute to magnetism at all, its existence is suppressed as much as possible, and it is important to reduce it to obtain high energy product. The present inventors set the B-rich phase amount ratio to 9% or less and set the B-rich phase particle size to 5 μm or more under one condition for obtaining a high energy product Nd-Fe-B magnet. It was one that was found. In addition, in order to obtain a particularly high Jr among the magnet characteristics, it is essential that the density of the sintered body be as high as possible and close to the theoretical density. The theoretical density of this system magnet is about 7.55 to 7.60 gr / cc, although it varies slightly depending on the composition. This density is at least 7.5 gr / cc
It has been found that a high Jr cannot be obtained unless the above value and a high energy product cannot be obtained due to deterioration of the squareness ratio. The density of Nd-Fe-B magnets currently on the market is at most 7.45 gr /
Since it is as low as cc, a high Jr and squareness ratio cannot be obtained, and at most a maximum energy product of 320 kJ / m ³ (40 kGOe) is obtained.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number in the agency FI Technical indication location H01F 1/08 41/02 G (72) Inventor Kazuhiro Saito 6 Koriyama, Taichiro-ku, Sendai City, Miyagi Prefecture No. 7 Tokin Co., Ltd.

Claims (5)

[Claims] 1. An R ₂ T ₁₄ B intermetallic compound (wherein R is Y
At least one of rare earth elements including T, T is a transition metal, and R _100-x −T _x (where x = 0 to 0).
20) R rich phase and R _{1 + ε} T ₄ B ₄ (however,
R-T including a B-rich phase composed of ε is an integer of 0 or more)
-B A rare earth permanent magnet, characterized in that the rare earth magnet has a coercive force of at least 640 kA / m and a maximum energy product of at least 360 kJ / m ³ . 2. The rare earth permanent magnet according to claim 1, wherein the main phase has a crystal grain size of 3 to 12 μm. 3. The rare earth permanent magnet according to claim 2, wherein the R-rich phase has a space factor of at most 9 vol% and a crystal grain size of 1 μm or less. . 4. The rare earth permanent magnet according to claim 3, wherein the B-rich phase has a crystal grain size of 3 to 12 μm and a space factor of 3 vol% or less at most. magnet. 5. An R-T-B crystalline alloy powder having an R ₂ T ₁₄ B phase as a main phase and an amorphous or microcrystalline liquid containing R in an amount of 50 to 100 wt% (not including 100). A method for producing a rare earth magnet, which comprises mixing with a quenched alloy powder, molding, and sintering.