JP2003142306A - Rare-earth magnet and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rare-earth magnet that is superior in magnetization factor and will not deteriorate in sinterability, and to provide a method of manufacturing the magnet. SOLUTION: The rare-earth magnet contains a compound crystalline phase containing at least one kind of element selected from among Cr, Mn, Fe, and Ni and B and/or P as main components in the crystal grain boundary of a sintered material, containing an R2 T14 B1 phase (where R, T, and B respectively denote rare-earth elements of Nd, Pr, Dy and Tb, transition elements of Fe and Co, and boron) as the main phase. Consequently, this rare-earth magnet is improved in magnetization factor and will not deteriorate in sinterablity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a permanent magnet excellent in magnetizability used for a motor in electric / electronic devices and a method for manufacturing the same.

[0002]

2. Description of the Related Art Rare earth magnets containing Nd, Fe and B as main components and having a tetragonal main phase have a large energy product, and therefore, their use is rapidly increasing for high performance and miniaturization of motors. However, a high magnetizing magnetic field is required due to the improvement of coercive force, but it is difficult to magnetize due to the demagnetizing field due to the eddy current, and it is a problem to solve this. There is.

That is, for the purpose of suppressing the generation of eddy current by increasing the resistance, for example, Japanese Patent Laid-Open No. 2000-82.
Japanese Patent No. 610 discloses a magnet alloy containing a rare earth oxide in a crystal grain boundary of a magnet alloy structure and having a high specific resistance. Further, a technique is disclosed in which the content has a gradient in the magnetization direction (the surface has a high specific resistance). In the manufacturing method, the oxide is 0.5% by weight or more, 0.05 to 4
Mixing with a particle size of μm is disclosed. Further, Japanese Patent Laid-Open No. 09-186010 proposes that a compound crystal grain intervenes in a grain boundary of a sintered material having an Nd ₂ Fe _{1 4} B ₁ phase as a main phase to obtain high specific resistance.

[0004]

Presently, Nd, Fe, B
In applying rare earth magnets containing as a main component to motors and the like, coercive force has been actively improved to improve weather resistance and the like. On the other hand, a magnet having a high coercive force generally requires a high magnetizing magnetic field, and if a high magnetic field is generated in a narrow area after being placed in a motor or the like, there is a problem that a leakage magnetic field unnecessarily magnetizes nearby magnets. Yes, there is a problem of making a magnet having good magnetism even in a magnetic field as low as possible.

Specifically, it is necessary to increase the specific resistance of the magnet material itself in order to suppress the generation of eddy currents with respect to the pulsed magnetic field that inhibits the magnetization. As this method, a structure in which a crystal grain boundary contains a rare earth oxide or a fluoride has been proposed, but in general, when a large amount of these is contained in the grain boundary, there is a problem that sinterability decreases. Therefore, it is also necessary that the means for increasing the resistance does not reduce the sinterability.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a rare earth magnet which has good magnetizability and is not inferior in sinterability, and a method for producing the same. To do.

[0007]

The present invention is directed to the rare earth element R
(R = Nd, Pr, Dy, Tb), transition element T (T = F
e, Co) and boron (B) as main components R ₂ T ₁₄ B ₁
Cr, Mn, Fe at the crystal grain boundaries of the sintered material whose main phase is
And a rare-earth magnet containing a compound crystal phase containing B and / or P as main components, and at least one element selected from the group consisting of Ni and Ni.

The compound crystal phase is Ni₃Cr₂B₆Phase, Ni₁
Cr₃B₆Phase, Cr_{twenty two}Mn_{twenty five}B₅₀Phase, FeCrB phase, B₂
Cr_FiveP phase, Cr_{twenty five}Mn_{twenty five}B₅₀Phase, Cr_{twenty one}Mn_{twenty one}B
₅₈Phase, Fe ₃Ni₂₀B₆Phase, FeMnP phase, Fe_TenMn₄₀
P₅₀Phase, Fe₂₀Mn₄₇P₃₃Phase, Fe ₃₃Ni₃₃P₃₄Phase, F
e₃₈Ni₃₈P_{twenty four}Phase, CrFeP phase, CrNiP phase, Cr
₁₂Ni₇P₁Phase, Cr_FourNi₃P_FourPhase, Cr_TenMn₄₀P
₅₀Phase, Cr₃₂Mn₃₂P₃₆It is preferably in phase.

The present invention also provides (i) a rare earth element (R =
Nd, Pr, Dy, Tb), transition elements (T = Fe, C
o) and RTB alloy powder containing boron (B) as a main component,
(A) Cr, M in an amount of 1% by weight or more and less than 6% by weight
at least 2 selected from the group consisting of n, Fe and Ni
Alloy powder mainly composed of seed elements, or (b) Cr, M
at least 2 selected from the group consisting of n, Fe and Ni
Alloy powder mainly composed of seed element and B and / or P,
And (ii) the obtained mixed alloy powder is crushed, shaped, sintered, and annealed.

(Sintered Material) In the present invention, the rare earth element R constituting the sintered material is at least one element selected from the group consisting of Nd, Pr, Dy and Tb. R is
Usually, one kind is sufficient, but two or more kinds may be used.
R preferably accounts for 10 to 30 atom% of the sintered material. The transition element T is Fe and / or Co. T is
It is preferable to occupy 65 to 80 atomic% of the sintered material. Boron (B) preferably accounts for 2 to 28 atomic%.
In addition to the above three elements, inevitable impurities in industrial production can be allowed in the sintered material. The sintered material is a melt-pulverization method in which a predetermined RTB-based alloy is melted and crushed after casting, a direct reduction diffusion method in which a powder is directly obtained by Ca reduction, and a predetermined RTB.
The system alloy can be manufactured by a quenching alloy method or the like in which a ribbon foil is obtained by a melt jet caster, and this is crushed and annealed.

(Compound Crystal Phase) In the present invention, the compound crystal phase contains at least one element selected from the group consisting of Cr, Mn, Fe and Ni and B and / or P as main components. The content of the compound crystal phase is preferably 1 to 10% by weight of the sintered material, and more preferably 1.5 to 8% by weight. The content of Cr in the compound crystal phase is preferably 10 to 80 atom%, more preferably 15 to 70 atom%. The content of Mn in the compound crystal phase is preferably 10 to 50 atom%, more preferably 15 to 40 atom%. The content of Fe in the compound crystal phase is preferably 5 to 50 atom%, more preferably 10 to 45 atom%.
Is. The Ni content in the compound crystal phase is preferably 5 to 70 atom%, more preferably 10 to 60 atom%. The content of B in the compound crystal phase is preferably 3 to
It is 70 atom%, and more preferably 5 to 65 atom%.
The content of P in the compound crystal phase is preferably 20 to 70.
Atomic%, more preferably 25 to 60 atomic%.

The rare earth magnet according to the present invention comprises a rare earth element R (R = Nd, Pr, Dy, Tb) and a transition element T (T = T).
R ₂ T ₁₄ B ₁ containing Fe (Co) and boron (B) as main components
Since the crystal grain boundary of the sintered material whose main phase is the phase contains a compound phase having a higher specific resistance than the R ₂ T ₁₄ B ₁ phase, the sintered material does not contain the compound phase. In comparison, a high specific resistance can be obtained. The compound phase is a metal and does not affect the sinterability of the sintered material.

The method for producing a rare earth magnet of the present invention comprises (i)
R containing a rare earth element (R = Nd, Pr, Dy, Tb), a transition element (T = Fe, Co), and boron (B) as main components
In the TB alloy powder, an amount of 1% by weight or more and less than 6% by weight,
(A) Alloy powder containing at least two elements selected from the group consisting of Cr, Mn, Fe, and Ni as a main component, or
(B) a step of mixing at least two kinds of elements selected from the group consisting of Cr, Mn, Fe and Ni, and an alloy powder containing B and / or P as a main component, and (ii) the obtained mixing The alloy powder is crushed, shaped, sintered, and annealed.

That is, the rare earth magnet of the present invention is (a) RT
The B alloy powder and the (Cr, Mn, Fe, Ni)-(B, P) alloy powder are mixed and sintered to form (Cr, Mn, Fe, Ni in the R ₂ T ₁₄ B ₁ grain boundary. )-(B, P) It is possible to obtain a tissue structure containing a compound phase.
Further, by adjusting the content of B in the RTB alloy powder, (b) R
It can be manufactured by mixing TB alloy powder and (Cr, Mn, Fe, Ni) alloy powder and sintering.

(Mixed) RTB alloy powder and (a) Cr, M
at least 2 selected from the group consisting of n, Fe and Ni
Alloy powder mainly composed of seed elements, or (b) Cr, M
at least 2 selected from the group consisting of n, Fe and Ni
The mixing of the alloy powder containing B and / or P as the main component with the RTB alloy powder (hereinafter, mixed raw material alloy powder) is carried out by a usual method, for example, using a likai machine while spraying nitrogen gas. Can be done. (Pulverization) The pulverization can be performed by a jet mill using nitrogen gas. The average particle size after pulverization is preferably 10 μm or less, more preferably 0.1 to 5 μm. (Molding) Molding is preferably performed in a magnetic field. The applied magnetic field is preferably in the range of 0.5 to 1.5 Tesla. The molding pressure is preferably in the range of 0.5 to 1.5 ton / cm ² .

(Sintering) Sintering is preferably performed in a non-oxidizing atmosphere such as hydrogen. Sintering temperature is 900-110
The range of 0 ° C is preferred. The sintering time is 1 to 10 hours. Before sintering, it is preferable to preheat at about 300 ° C. for about 1 hour to remove water and the like.

(Annealing) The annealing temperature is preferably in the range of 500 to 600 ° C. The sintering time is 1 to 10 hours. After sintering, it is preferable to anneal after slowly cooling at 80 to 120 ° C./hour.

[0018]

[Embodiment] Embodiment 1. The flow chart of sample preparation is shown below.

[Chemical 1]

(Preparation of RTB alloy powder) RTB alloy is N
Nd: F using each metal alloy of d, Fe, and Fe-B
e: B = 32.9: 65.8: 1.23 (wt%), weighed, and high-frequency melted in a reduced pressure Ar atmosphere of 0.2 atm, followed by casting into a water-cooled copper mold. did. R
The TB alloy powder was coarsely crushed using a jaw crusher to have a diameter of 1 mm or less.

(Preparation of mixed raw material alloy powder) For the mixed raw material alloy, Cr, Mn, Fe, Ni and B, P were weighed so as to have the mixing ratio shown in Table 1, and the same method as that for the RTB alloy was used. It was prepared in. In addition, the alloy powder was roughly crushed using a jaw crusher to have a diameter of 1 mm or less as in the case of preparing the RTB alloy powder.

[0021]

[Table 1]

(Mixing) The RTB alloy powder and the mixed raw material alloy powder were mixed with each other by using a Reiki machine while blowing nitrogen gas. (Pulverization) The mixed powder was finely pulverized using a jet mill using N ₂ gas. The particle size of the obtained pulverized powder was measured by a laser granulometer, and the average particle size was 10 μm or less. (Molding) A molded body was prepared in a transverse magnetic field of 1 Tesla at a molding pressure of 1.0 ton / cm ² . Incidentally, the molded body dimensions are 15 mm × ^l 10 mm. (Sintering) The compact is sintered in a hydrogen atmosphere at 1080 ° C.
(Holding time 1 to 10 hours). In addition, before sintering, it was heated at 300 ° C. for about 1 hour in order to release water and the like. Annealing is slow cooling (100 ° C / hour) after sintering and 1 hour at 580 ° C.
Hold for ~ 20 hours. A sample using the RTB alloy and the mixed raw material alloy was prepared by the above procedure. Details of each sample (S0 to S0103-8) (mixed raw material alloy (R0 to R0103) contained in each sample) are shown in Table 2.

(Measurement of resistivity of bulk material) The resistivity of the RTB alloy and the mixed raw material alloys (R1 to R0103) was measured using a 4-terminal probe, and the RTB alloy was 12 × 10 ^-8.
The values of Ωm and the alloys R1 to R0103 are shown in Table 1.
As can be seen from the table, R1 to R01 compared to RTB alloy
The resistivity of each of the 03 samples was high. Similarly, by the above, R
Table 2 shows the resistivity of each of the samples S1-1 to S0103-8 prepared by using the TB alloy powder and the mixed raw material alloy powder as raw materials.
Shown in. S1 compared to RTB alloy shown by sample name S0
The resistivity of each of the samples of -1 to S0103-8 was high, and in particular, the resistivity increased as the mixing amount increased.

[0024]

[Table 2]

The magnetic characteristics of the samples (S0 to S0103-8) were measured using a BH tracer. The dimensions of the characteristic measurement sample are φ10 mm, ^l 7 mm (permeance coefficient =
1). As a result, Br, iHc, (BH)
The max is shown in Table 2. Sample S containing no mixed raw material powder
Compared to 0, Br and iHc of the mixed sample tend to decrease. Especially, if the mixture is 6% or more (BH)
max decreases by 10% or more. However, as a practical material, it is a magnetic property that can be sufficiently utilized if it has a property that a mixed powder can be obtained within several percent.

The magnetism was evaluated by magnetizing it with a pulsed magnetic field (50 Hz half wave, 2 tesla) and then measuring the surface magnetic flux. The results are shown in Table 2. In the sample S0, a residual magnetic flux amount of 95% or more was obtained when the residual magnetic flux amount magnetized by the DC magnetic field was set to 100% by the pulse magnetic field of 3 Tesla or more. However, with a pulse magnetic field of 2 Tesla, as shown in Table 2, only 88% of the residual magnetic flux could be obtained. On the other hand, as shown in Table 2, the residual magnetic flux amount of the sample containing the mixed raw material at the time of 2 Tesla pulse magnetization was 8
A value higher than 8% was shown. This improvement in magnetizability is considered to be an effect of increasing the resistivity of the sample.

(Evaluation of Microstructure of Sample) As an evaluation of the material microstructure, the surface was polished and observed by SEM. As a result, the average particle size is 9
Along with the Nd2Fe14B crystal grains of μm, a different phase (S
The difference in brightness and darkness was observed by EM. Therefore, the composition of the grain boundary 1 μm diameter region was quantified by EDX, and X-ray diffraction measurement evaluation was performed by XD. The results are shown in Table 3.
As can be seen from the table, it can be inferred that the structure observed at the grain boundaries is the compound phase.

[0028]

[Table 3]

Embodiment 2. Nd as R of RTB alloy
An RTB alloy containing Pr, Dy, and Tb was prepared by the same manufacturing method as in the first embodiment. still,
R: Fe: B = 32.9: 65.8: 1.23 (wt%) (R: Nd: Pr = 10: 1, Nd: Dy = 10:
1, Nd: Tb = 10: 1). The resistivity, magnetic characteristics and magnetizability of the sample containing Pr are as follows:
No significant difference was obtained, and a good improvement in magnetizability was observed as compared with S0.

Embodiment 3. (Preparation of RTB alloy) RTB alloy is Nd, Fe, Fe-
Using each metal alloy of B, Nd: Fe: B = 33: 6
It was weighed so as to be 5: 1.5 (wt%), high-frequency melted in a reduced pressure Ar atmosphere of 0.2 atm, and subsequently cast in a water-cooled copper mold. The RTB alloy powder was coarsely crushed using a jaw crusher to have a diameter of 1 mm or less. (Preparation of mixed raw material alloy) The mixed raw material alloy is Cr: Ni =
3: 1 NiCr alloy powder (particle size 5 μm or less), RT
2% by weight of the B alloy was weighed. (Mixing) Mixing RTB alloy powder and mixed raw material alloy powder
It was performed by using a Raiki machine while blowing nitrogen gas. (Pulverization) The mixed powder was finely pulverized using a jet mill using N ₂ gas. The particle size of the obtained pulverized powder was measured by a laser granulometer, and the average particle size was 10 μm or less. (Molding) A molded body was prepared in a transverse magnetic field of 1 Tesla at a molding pressure of 1.0 ton / cm ² . Incidentally, the molded body dimensions are 15 mm × ^l 10 mm. (Sintering) The compact is sintered in a hydrogen atmosphere at 1080 ° C.
(Holding time 1 to 10 hours). In addition, before sintering, it was heated at 300 ° C. for about 1 hour in order to release water and the like. (Annealing) Annealing is gradually cooled (100 ° C./hour) after sintering,
It hold | maintained at 0 degreeC for 1 to 20 hours, and performed. Through the above procedure, samples using RTB alloy and NiCr alloy were prepared.

The resistivity of the NiCr alloy is the same as that of the green compact sintered material.
Measured by 4-terminal method, 152 × 10 at room temperature^-8In Ωm
It was. Also, books using RTB alloys and NiCr alloys
Magnetization by resistivity and 2 tesla pulse of the sample of the example
Sex is 12.7 × 10 each ^-8Ωm was 90%.
Furthermore, by XD diffraction measurement, Nd₂Fe₁₄B other than B phase₆
Cr₂Ni₃A peak that is thought to be a diffraction line from the phase was obtained
It was From this result, the mixed raw material for the RTB alloy contains B.
Mixed with RTB alloy
It can be inferred that it will react with the alloy to produce a high resistance phase at the grain boundaries.
It was This means that other alloys such as Fe, Ni, Mn are used.
It was conjectured that it would be possible if

[0032]

In the rare earth magnet of the present invention, the structure in which the high resistance compound phase is arranged at the grain boundary increases the resistivity as a bulk material and improves the magnetizability. In particular, the resistivity becomes higher as the amount of the alloy containing the compound phase base component mixed with the alloy containing the main phase base component increases. Further, according to the present invention, there is provided a method for producing a permanent magnet having excellent magnetizability.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hiroyuki Teramoto             2-3 2-3 Marunouchi, Chiyoda-ku, Tokyo             Inside Ryo Electric Co., Ltd. F-term (reference) 4K018 AA27 AD12 BA11 BA18 BC08                       KA46                 5E040 AA04 AA19 CA01 HB17 NN01

Claims (13)

[Claims] 1. A rare earth element R (R = Nd, Pr, Dy,
Tb), a transition element T (T = Fe, Co), and boron (B) as main components, and Cr, Mn, Fe, and Cr in the grain boundaries of the sintered material containing the R ₂ T ₁₄ B ₁ phase as the main phase. A rare earth magnet containing a compound crystal phase containing B and / or P as main components, and at least one element selected from the group consisting of Ni. 2. The rare earth magnet according to claim 1, wherein the compound crystal phase is a Ni ₃ Cr ₂ B ₆ phase and / or a Ni ₁ Cr ₃ B ₆ phase. 3. The rare earth magnet according to claim 1, wherein the compound crystal phase is a Cr ₂₂ Mn ₂₅ B ₅₀ phase. 4. The rare earth magnet according to claim 1, wherein the compound crystal phase is an FeCrB phase. 5. The rare earth magnet according to claim 1, wherein the compound crystal phase is a B ₂ Cr ₅ P phase. 6. The compound crystal phase is Cr_{twenty five}Mn_{twenty five}B₅₀Influence
And / or Cr_{twenty one}Mn _{twenty one}B₅₈Contracts characterized by being in phase
The rare earth magnet according to claim 1. 7. The rare earth magnet according to claim 1, wherein the compound crystal phase is a Fe ₃ Ni ₂₀ B ₆ phase. 8. The rare earth magnet according to claim 1, wherein the compound crystal phase is an FeMnP phase and / or an Fe ₁₀ Mn ₄₀ P ₅₀ phase and / or an Fe ₂₀ Mn ₄₇ P ₃₃ phase. 9. The compound crystal phase is Fe₃₃Ni₃₃P₃₄Influence
And / or Fe₃₈Ni ₃₈P_{twenty four}Contracts characterized by being in phase
The rare earth magnet according to claim 1. 10. The rare earth magnet according to claim 1, wherein the compound crystal phase is a CrFeP phase. 11. The compound crystal phase is a CrNiP phase and / or
Alternatively, the rare earth magnet according to claim 1, wherein the rare earth magnet has a Cr ₁₂ Ni ₇ P ₁ phase and / or a Cr ₄ Ni ₃ P ₄ phase. 12. The rare earth magnet according to claim 1, wherein the compound crystal phase is a Cr ₁₀ Mn ₄₀ P ₅₀ phase and / or a Cr ₃₂ Mn ₃₂ P ₃₆ phase. 13. (i) Rare earth element (R = Nd, Pr,
Dy, Tb), transition elements (T = Fe, Co) and boron (B) as the main components in RTB alloy powder, 1% by weight or more,
(A) Cr, Mn, Fe and Ni in an amount less than 6% by weight
Alloy powder containing as a main component at least two elements selected from the group consisting of, or (b) Cr, Mn, Fe and Ni
A step of mixing at least two elements selected from the group consisting of, and an alloy powder containing B and / or P as a main component,
And (ii) crushing, molding, sintering, and annealing the obtained mixed alloy powder.
The method for producing the rare earth magnet according to any one of 1.