JPH06208911A - Rare earth magnetic body, produciton thereof and rare earth bonded magnet - Google Patents

Abstract

PURPOSE:To obtain a rare earth magnetic body having high remanent magnetic flux density and coercive force irrespective of its isotropy easily by employing a basic composition of rare earth metal and transition metal wherein the composition is lower than the stoichiometric composition of intermetallic compound or rare earth metal and containing N with the crystal particle size being set at a specific value or below. CONSTITUTION:An alloy having basic composition of one or more than one kind of rare earth element and a transition metal of Fe containing Co and having stoichionmetric composition of intermetallic compound or a composition where the rare earth metal is lower than that and the crystal particle size is 50nm or less is heat treated in a gas containing N so that N intrudes into the alloy. Consequently, high remanent flux density and coercive force can be obtained easily irrespective of its isotropy and the cost is reduced because expensive rare earth metal is reduced. Furthermore, a thermally stable and reliable rare earth magnetic body and rare earth bonded magnet can be obtained because of its high rectangularity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rare earth magnetic material composed of a rare earth metal and a transition metal group and a rare earth bonded magnet.

[0002]

2. Description of the Related Art Conventionally, R-TM-N-based rare earth bonded magnets have been disclosed in, for example, JP-A-2-57663, JP-A-2-257603 and J. Pat. Ma
gn. Magn. Mater. , 87 (1990) L2
51 (Cited document 1) and Appl. Phys. Lett.
56 (1990), 587 (cited document 2) and the like, and the like are reported as Sm ₂ Fe ₁₇ N _x system.

[0003]

However, the conventional R-TM-N system has the following problems.

(1) Monocrystalline Sm described in the cited document 1
₂ Fe ₁₇ N _x has a strong magnetic property, particularly the coercive force strongly depends on the powder particle size, and it is extremely difficult to obtain a practical iHc of 7 kOe or more even with a fine powder of 1 to 3 μm.

(2) Sm of nanocrystal system described in cited document 2
₂ Fe ₁₇ N _x is suitable for use as a bonded magnet because it can obtain a high coercive force of 20 kOe or more with relative ease and has a weak powder particle size dependency. The density is low, and the energy product of the bonded magnet is also small.

(3) The magnetic powder is expensive because it contains 25% by weight or more of expensive Sm among rare earth elements.

Therefore, the present invention solves such a problem, and its object is to obtain a high residual magnetic flux density and easily obtain a coercive force even though it is substantially isotropic. Another object of the present invention is to provide a rare earth magnetic material having high reliability such as thermal stability because it has low cost due to a small amount of expensive rare earth metal and has good squareness, a method for producing the rare earth magnetic material, and a rare earth bonded magnet.

[0008]

The rare earth magnetic material of the present invention has a basic composition of R and TM, has a stoichiometric composition of an intermetallic compound or less rare earth metal, and contains N. Composition, crystal particle size is 50n
It is characterized by being m or less. The intermetallic compound consisting of R and TM is R ₂ TM ₁₇ system or RTM ₁₂ system, and each R is 11 atomic% or less or 8 atomic% or less. It is magnetically substantially isotropic, and has a residual magnetic flux density of 8 kG or more and a coercive force of 7 kOe or more. It is characterized by having a fine structure in which a main phase and a grain boundary phase having a composition containing more Fe than the main phase exist.

In the method for producing a rare earth magnetic material of the present invention, the basic composition comprises R and TM, the stoichiometric composition of the intermetallic compound or the composition in which the rare earth metal is less than that, and the crystal grain size is 50 nm or less. It is characterized in that the alloy is heat-treated in a gas containing N to allow nitrogen to penetrate into the alloy. It is characterized by using the melt span method, mechanical alloying method, hydrogen treatment method, and gas atomizing method.

The rare earth bonded magnet of the present invention is characterized in that the above rare earth magnetic material is bonded with a binder.

[0011]

According to the above construction of the present invention, the following effects are obtained in the R-TM-N system.

(1) Only a high coercive force can be obtained due to the fine structure by setting the crystal grain size to 50 nm or less in the stoichiometric composition of the intermetallic compound or the composition containing less rare earth metal and containing N. Instead, a high residual magnetic flux density can be obtained by the inter-particle exchange interaction of single domain particles. In addition, the fine structure is composed of only the main phase,
A grain boundary phase having a composition containing more Fe than the main phase exists at the grain boundaries of the main phase.

(2) Even if a composition range in which the rare earth is less than the stoichiometric composition of the intermetallic compound is adopted, high magnetic characteristics can be obtained.

(3) Since it is magnetically substantially isotropic, the application of an orientation magnetic field is unnecessary at the time of molding, the molding cost is low, and the direction of magnetization is not considered. Since the squareness is greatly improved while maintaining the merit, reliability such as thermal stability is improved.

Regarding a magnetic material having a high remanent magnetization which does not follow the SW model, Japanese Patent Laid-Open No. 62-260039 and IEEE.
Trans. Mag. , MAG-25 (1989) 4
123 and the like have reports on the R ₂ Fe ₁₄ B system. In the former, the description of SmCo ₅ and Sm ₂ Co ₁₇ is also seen, and Si, Al and the like are mentioned as the modifying elements as the crystal grain refining agent, but in any case, the R-TM-N-based compound of the present invention is used. There is no description, and in particular, no mention is made of an interstitial element (nitrogen in the present invention).

Regarding the fine structure in the R-TM-N system, as described in the cited document 2 etc., Sm ₂
Isotropic powders of the Fe ₁₇ N _x- based mechania alloying method are known, but all of them are Sm _12.5 Fe _87.5 N _x (≈Sm ₂ Fe ₁₄ N _x ) for the purpose of suppressing αFe.
As described above, the composition has a large amount of rare earth metal (Sm), and the stoichiometric composition of the intermetallic compound and the composition having a smaller amount of rare earth metal than that are not mentioned at all. In particular, regarding the microstructure, αFe and the 1-3 phase (SmFe ₃ ) are often present, and there is no description about the grain boundary phase having a composition in which Fe is larger than the main phase.

Of the intermetallic compounds consisting of R and TM, 2-
Sm ₂ Fe ₁₇ is used as the 17 system and N is used as the 1-12 system.
d (Fe, M) ₁₂ , M = Ti, V, Mo, etc., but Sm and Nd are replaced with other rare earth metals, and Fe
Can be replaced with other transition metals such as Co and Ni, but is not limited thereto.

[0018]

EXAMPLES The present invention will be described in detail below based on examples.

(Example 1) Sm = 24.1, Fe = 75.
9% by weight composition (R = 10.5 atomic%)
A ribbon-shaped alloy was prepared at about 30 m / sec using a copper single roll having a diameter of 200 mm. After homogenizing this alloy at 900 ° C. for 1 hour in an argon gas atmosphere,
It was pulverized to <150 μm and subjected to nitriding treatment at 550 ° C. for 6 hours in nitrogen gas. This is referred to as Invention 1.

Nitrified powder was prepared by the same method as in the first embodiment of the present invention so that the composition was Sm = 25.5, Fe = 74.5% by weight (R = 12.5 atomic%). However, the homogenization treatment required 6 hours at 1000 ° C. This is Comparative Example 1.

The microstructure of Comparative Example 1 was αFe and 1-3.
While the phases were mixed, in the present invention 1, only the main phase 2-17 was observed. The average crystal grain size of the present invention 1 is 24n
m of Comparative Example 1 was 62 nm.

The magnetic characteristics of the obtained magnetic material were measured using VSM. The obtained demagnetization curve was subjected to demagnetizing field correction with reference to a pure Ni ribbon, and each magnetic characteristic value was calculated. Also, the same magnetic substance (thin band) was measured in three different directions, and it was confirmed that it was magnetically isotropic.

In Comparative Example 1, the saturation magnetization was low, and the demagnetization curve was markedly scooped out. Br = 6.3 kG, iHc = 14.5 kO
e, (BH) max = 7.4 MGOe, which was a low value, whereas in the present invention 1, the saturation magnetization of the compound (15.6 to 16) was obtained.
Br of more than half of kG) is obtained, and the squareness is also good.
= 9.2 kG, iHc = 9.7 kOe, (BH) max = 1
A high magnetic characteristic value of 8.7 MGOe was obtained.

(Example 2) Sm = 21.5, Ce = 1.
5, Fe = 72.0, Co = 5.0 wt% and Sm = 2
2.1, Fe = 71.1, Co = 4.8, Zr = 1.5, A
An alloy was prepared in the same manner as in Example 1 so that the composition was 1 = 0.5% by weight. These are designated as Invention 2 and Invention 3. The rare earth components of each alloy are 10.5 atom% and 9.5 atom%.

The microstructures of Inventions 2 and 3 had an average crystal grain size of 21 and 17 nm, respectively.
The grain boundary phase was observed though it was very thin by the detailed observation using. As a result of triple point EDX analysis, it was found that the composition had more Fe than the main phase.

The magnetic characteristics of Invention 2 are shown below.

Br = 9.5 kG, iHc = 7.9 kO
e, (BH) max = 17.9MGOe Rare earth is lower than stoichiometric composition, Sm is Ce, Fe
Even if is replaced by Co, high magnetic characteristics are obtained.

Further, in the present invention 3, by adding Zr, a sufficiently high coercive force is obtained even with a composition containing a considerably small amount of rare earth, and the magnetic characteristics are also extremely high values as shown below.

Br = 9.8 kG, iHc = 10.5 kO
e, (BH) max = 19.4MGOe (Example 3) The magnetic particles of the inventions 1 and 3 had an average particle size of 2
Grind to a powder having an appropriate particle size distribution of 0 to 30 μm, mix and knead with 2% by weight of epoxy resin,
Pressure molding at 50 kg / mm ² in a magnetic field of 17 kOe,
Curing treatment was performed at 150 ° C. for 1 hour to obtain a bonded magnet. These are designated as Invention 4 and Invention 5.

The magnetic characteristics of the bonded magnets of the present inventions 4 and 5 are shown below, respectively, and as isotropic bonded magnets, a high value has been obtained as never before.

Br = 8.1 kG, iHc = 9.3 kO
e, (BH) max = 13.0 MGOe Br = 8.4 kG, iHc = 10.1 kOe, (BH) max
= 14.2 MGOe (Example 4) Nd = 16.1, Fe = 62.5, Mo = 2
Metal alloy powders (<200-300 μm) of each element were mechanically alloyed in an argon gas atmosphere so as to have a composition of 1.4% by weight. The obtained powder is 750 ° C. in an argon gas atmosphere.
Heat treatment was performed at 450 ° C. for 6 hours in a nitrogen gas atmosphere for 0.5 hours. This powder is designated as present invention 6.

Further, Nd = 15.8, Fe = 55.9, C
Similarly, mechanical alloying treatment and nitriding treatment were performed so that the composition was o = 22.0, Mo = 5.9, Si = 0.4% by weight. This is referred to as Invention 7.

The magnetic properties of the magnetic powders of the present inventions 6 and 7 are shown below, respectively, and show high magnetic properties as in the case of the present inventions 1 to 5.

Br = 8.7 kG, iHc = 9.2 kO
e, (BH) max = 15.3MGOe Br = 8.4kG, iHc = 8.4kOe, (BH) max
= 14.0 MGOe Further, the magnetic characteristics of the bonded magnets using the magnetic powders of the present inventions 6 and 7 are also shown below, but high magnetic characteristics are obtained.

Br = 7.7 kG, iHc = 9.0 kO
e, (BH) max = 11.9GOe Br = 7.3kG, iHc = 8.3kOe, (BH) max
= 10.7 MGOe The effects of the present invention have been described above. For example, although the melt span method and the mechanical alloying method have been described as an example of the manufacturing method, the same applies to the powders by the atomizing method, the hydrogen treatment method, and the like. The effects of the above have been confirmed, and the present invention is not limited to the above-described embodiments, and the scope of the present invention is limited only by the claims.

[0036]

As described above, according to the present invention, the basic composition is composed of R and TM, the composition is a stoichiometric composition of an intermetallic compound or a composition containing less N than rare earth metal and containing N. Since the crystal grain size is 50 nm or less, the remanent magnetization is high even though it is substantially isotropic, the coercive force is easily obtained, and the amount of expensive rare earth metal is small, so that the cost is low. In addition, due to its good squareness, it is possible to obtain rare earth magnetic materials and rare earth bonded magnets with high reliability such as thermal stability, and to achieve higher performance, smaller size, and higher reliability of applied motors and devices. Also has a great effect.

Claims (8)

[Claims] 1. A basic composition of rare earth metal (one or more kinds of rare earth elements including Y: hereinafter abbreviated as R) and transition metal (mainly composed of Fe, Co, Ni, Zr, T).
i, V, Mo, Al, Si, etc .: hereinafter abbreviated as TM), and the composition is a stoichiometric composition of an intermetallic compound or a composition in which the rare earth metal is less than that and N is contained. A rare earth magnetic material having a particle diameter of 50 nm or less. 2. The intermetallic compound consisting of R and TM is R
₂ TM ₁₇ system (hereinafter abbreviated as 2-17 system), and R is 11
The rare earth magnetic material according to claim 1, which is at most atomic%. 3. The intermetallic compound consisting of R and TM is R
The rare earth magnetic material according to claim 1, which is a TM ₁₂ system (hereinafter abbreviated as 1-12 system) and R is 8 atomic% or less. 4. The rare earth magnetic material is magnetically substantially isotropic, has a residual magnetic flux density of 8 kG or more and a coercive force of 7 kOe.
The rare earth magnetic material according to claim 1, which is the above. 5. The rare earth magnetic material according to claim 1, wherein the rare earth magnetic material has a fine structure in which a main phase and a grain boundary phase having a composition containing more Fe than the main phase are present. 6. A gas containing N in an alloy having a basic composition of R and TM, a stoichiometric composition of an intermetallic compound or a composition of less rare earth metal, and a crystal grain size of 50 nm or less. A method for producing a rare earth magnetic material, which comprises subjecting an alloy to heat treatment to allow nitrogen to penetrate into the alloy. 7. A melt-span method, a mechanical alloying method, to obtain the alloy having a crystal grain size of 50 nm or less,
The method for producing a rare earth magnetic material according to claim 6, wherein a hydrogen treatment method or a gas atomization method is used. 8. A rare earth bonded magnet, wherein the rare earth magnetic material is bound with a binder.