JPH07245208A - Rare-earth magnet and rare-earth magnet alloy powder and its manufacturing method - Google Patents

Abstract

PURPOSE:To obtain a Fe3B type R-Fe-B system magnet enhancing iHc and (BH) max and having optimum residual magnetic flux density Br by a method wherein an alloy hot melt of a specific composition is made an amorphous organization by a quenching method and further heat-treated to obtain an ultra- fine crystal aggregate. CONSTITUTION:In an alloy hot melt that a composition range of Fe100-x-y-zCoxBy(R1-aDya)Pbw (R is Pr or Nd) satisfies 0.05<=x<=15at%, 16<=y<=22at%, 3<=z<=5.5at%, 0.02<=a<=0.9 and 0.1<=w<=3at%, it is made an amorphous organization by a quenching method, and further heat-treated. Thus, a mean crystal particle size becomes an ultra-fine cyrstal aggreate of 0.01 to 0.1mum, and a quantity ratio of Nd2Fe14B type crystal configuration increases in addition to a Fe3B type compound phase of a main phase to form a permanent magnet thin band. This can be pulverized to obtain magnetic characteristic of iHc>=4kOe, Br>=7kG and (BH)max>=8MGOe, and also obtain the optimum magnetic alloy powder for a bond magnet having residual magnetic flux density of 5kG or more.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rare earth sintered magnet or a bonded magnet most suitable for a motor, an actuator, etc., and Fe-Co of a specific composition containing a small amount of rare earth elements.
-B- (R, Dy) -Pb alloy molten metal (where R is Pr,
5d which could not be obtained with a hard ferrite magnet by forming an amorphous structure of Nd (1 or 2 types of Nd) by a super-quenching method and obtaining a fine crystal aggregate by a specific heat treatment.
The present invention relates to a manufacturing method for obtaining a rare earth magnet alloy powder most suitable for a bonded magnet having a residual magnetic flux density Br of G or more.

[0002]

2. Description of the Prior Art Permanent magnets used in motors and actuators for electrical equipment have been mainly limited to hard ferrite magnets, but they have low mechanical strength due to low temperature demagnetization associated with iHc reduction at low temperatures and ceramic materials. However, there were problems such as low hardness, easy cracking and chipping, and difficulty in obtaining a complicated shape.

Nowadays, automobiles are strongly required to reduce fuel consumption in order to save resources and to improve fuel efficiency, and electric components for automobiles are required to be further reduced in size and weight. Also,
Designs for maximizing the performance-to-weight ratio are also being considered for applications such as home electric motors other than automobile electrical components. In the current motor structure, magnet materials with Br of about 5 to 7 kG are optimal. It is said that. That is,
When the magnet material used has a Br of 8 kG or more, the current motor structure requires an increase in the cross-sectional area of the iron plate of the rotor or stator that becomes the magnetic path, which causes an increase in weight. If so, the performance-to-weight ratio can be maximized.

Therefore, a magnetic material for a small motor is required to have a residual magnetic flux density Br of 5 kG or more in terms of magnetic characteristics, but it cannot be obtained with a conventional hard ferrite magnet. For example, Nd-Fe-B based bonded magnets satisfy such magnetic characteristics, but Nd, etc., which require a large number of steps and a large-scale facility for separation and purification of metals and reduction reaction.
Since it is contained at ˜15 at%, it is remarkably expensive as compared with a hard ferrite magnet, and at present, a magnet material with a Br of about 5 to 7 kG that can be mass-produced and can be provided at low cost has not been found.

[0005]

On the other hand, Nd-Fe-B
Recently, a magnet material having a Fe ₃ B type compound as a main phase in the vicinity of Nd ₄ Fe ₇₇ B ₁₉ (at%) has been proposed (R. Coehorn et al., J. de Phys., C).
8, 1988, pp. 669-670). This magnet material is made of Fe by heat treatment of the amorphous ribbon.
_Although it is a metastable structure having a crystal texture of ₃ B and Nd ₂ Fe ₁₄ B, iHc is not as high as about 2 to 3 kOe, and the heat treatment conditions for obtaining this iHc are narrowly limited, which is practical for industrial production. Not.

[0006] A study has been published in which an additive element is added to the magnetic material having the Fe ₃ B type compound as a main phase to make it a multi-component to improve performance. One is to improve iHc by using Dy and Tb in addition to Nd as a rare earth element. However, in addition to the problem of adding an expensive element, the magnetic moment of the added rare earth element is Nd or Fe. There is a problem that the magnetization decreases due to coupling in antiparallel with the moment (R. Coehoorn, J. Magn. Magn. M.
at. 83 (1990) 228-230).

Other studies (Shen Bao-gen et al.,
J. Magn. Magn. Mat. 89 (1991) 3
35 to 340), a part of Fe is replaced with Co to raise the Curie temperature and improve the temperature coefficient of iHc, but there is a problem that Br is lowered with the addition of Co.

In any case, Fe ₃ B type Nd-Fe-B
The system magnet can be made into a hard magnet material by heat treatment after being made amorphous by the ultra-quenching method, but iHc is low, and the heat treatment condition is narrow, and if the iHc is increased by the additive element, the magnetic energy product decreases. As such, stable industrial production cannot be performed, and it cannot be provided at a low cost as an alternative to the hard ferrite magnet.

Further, in order to amorphize the Nd-Fe-B system alloy, it is necessary to remarkably increase the roll peripheral speed during the ultra-quenching, which causes a problem that the product recovery rate and the yield decrease. Since it is a base alloy, there is a problem that corrosion during storage tends to proceed, and the initial magnetic characteristics cannot be maintained and deteriorates after long-term storage.

The present invention focuses on an Fe ₃ B type Fe-BR magnet (R is a rare earth element), iHc and (BH) m
Fe ₃ B that can improve the ax and establish a manufacturing method that enables stable industrial production and has a residual magnetic flux density Br of 5 kG or more and can be provided at a low cost as an alternative to a hard ferrite magnet.
Intended for type R-Fe-B magnets.

[0011]

The present invention has been variously studied for the purpose of improving the iHc and (BH) max of Fe ₃ B type Fe-B-R magnets and enabling a stable industrial production. As a result, the rare earth element R improves the anisotropic magnetic field of the Nd ₂ Fe ₁₄ B phase by substituting Dy for a part of a mixture of Pr and Nd or a mixture of Pr and Nd in an arbitrary ratio. , Co to increase the amorphous forming ability using the ultra-quenching method and to improve the temperature coefficient of iHc, and to add a small amount of Pb to refine the crystal grains, and to perform heat treatment at a specific heating rate. By obtaining a fine crystal aggregate in, a rare earth magnet alloy powder suitable for a bond magnet, which is improved in coercive force and magnetization together with a residual magnetic flux density Br of 5 kG or more, which cannot be obtained in a hard ferrite magnet, can be obtained. The inventors have found that it can be obtained and completed the present invention.

This invention uses the composition formula Fe _100-xyz Co _{x
B y (R 1-a Dy} a) z Pb w ( where, R represents Pr, any mixtures of one or both of Nd) represents the symbol x to limit the composition range, y, z, a, w is Fe satisfies the following values and Fe
₃ B type compound as a main phase having a ferromagnetic phase having a Nd ₂ Fe ₁₄ B crystal structure, an average grain size of 0.01 to 0.1
It is a rare earth magnet characterized by comprising a fine crystal aggregate of μm. 0.05 ≦ x ≦ 15 at% 16 ≦ y ≦ 22 at% 3 ≦ z ≦ 5.5 at% 0.02 ≦ a ≦ 0.9 0.1 ≦ w ≦ 3 at%

Further, the present invention uses the composition formula Fe
_{100-xyz Co x B y (} R 1-a Dy a) z Pb w ( Here, R
Represents one of Pr and Nd or an arbitrary mixture of both, and the symbols x, y, z, a, and w that limit the composition range satisfy the above values, and Fe ₃ B type compound as the main phase, Nd ₂ Fe ₁₄
It has a ferromagnetic phase having a B-type crystal structure and is composed of a fine crystal aggregate having an average crystal grain size of 0.01 to 0.1 μm, an average grain size of 3 to 500 μm, and a magnetic property of iHc ≧ 4 kOe,
It is a rare earth magnet alloy powder characterized in that Br ≧ 7 kG and (BH) max ≧ 8 MGOe.

Further, according to the present invention, the composition formula (1) is represented by Fe
_{100-xyz Co x B y (} R 1-a Dy a) z Pb w ( Here, R
Represents one of Pr and Nd or an arbitrary mixture of both, and the alloy melt in which the symbols x, y, z, a and w for limiting the composition range satisfy the above-mentioned values is substantially prepared by the ultra-quenching method. 90%
The above is an amorphous structure, and (2) the heat treatment is performed by further increasing the heating rate from 500 ° C. at 1 to 15 ° C./min and holding at 550 to 700 ° C. for 30 seconds to 6 hours. ) Fe ₃ B type compound as a main phase and Nd ₂ Fe ₁₄
After obtaining a fine crystal aggregate having a ferromagnetic phase having a B-type crystal structure and an average crystal grain size of 0.01 to 0.1 μm,
(4) In the method for producing a rare earth magnet alloy powder, the magnet alloy powder is pulverized to obtain a magnet alloy powder.

Reasons for limiting composition The rare earth element has high magnetic properties only when it contains Dy in addition to a specific amount of R (R is one or both of Pr and Nd) and other rare earth elements, For example Ce, La
In iHc, the characteristics of 4 kOe or more cannot be obtained, and Sm
Subsequent medium rare earth elements and heavy rare earth elements are not preferable because they lead to deterioration of magnetic properties and make the magnet expensive. If R (one or two of Nd and Dy) is less than 3 at%, iHc of 4 kOe or more cannot be obtained, and 5.5 a
When it exceeds t%, the Fe ₃ B phase is not generated, and the metastable phase Nd ₂ Fe ₂₃ B ₃ phase which does not exhibit hard magnetism is extruded and iHc is significantly lowered. Range. Dy in R acts particularly to improve iHc. The reason why the amount of Dy in R is limited to 0.02 to 0.9 is that Dy acts particularly effectively to improve iHc, but if it is less than 0.02, iHc of 4 kOe or more cannot be obtained, and it is less than 0. This is because if it exceeds 9, the decrease of Br is extremely unfavorable.

When B is less than 16 at% or more than 22 at%, iHc of 2 kOe or more cannot be obtained.
The range is -22 at%.

Co is effective in improving the squareness of iHc and the demagnetization curve, but if it is less than 0.05 at%, such an effect cannot be obtained, and if it exceeds 15 at%, iHc is remarkably reduced and 2 kOe or more. IHc cannot be obtained, so 0.
The range is from 05 to 15 at%.

Pb has the effect of expanding the heat treatment temperature range to improve the squareness of the demagnetization curve and increasing the magnetic properties Br and (BH) max. To obtain such an effect, at least 0.1 atm is required. %, It is necessary to add 0.1% or more, but if it exceeds 3 at%, the squareness is rather deteriorated and (BH) max is also lowered, so the range is 0.1 to 3 at%.

Fe occupies the remaining content of the above-mentioned elements.

Reasons for limiting manufacturing conditions In the present invention, the molten alloy having the above-mentioned specific composition is made amorphous by the ultra-quenching method, and it is 1 to 15 from 500 ° C. or higher.
After raising the temperature at a temperature rising rate of ℃ / min, 3 at 550 ~ 700 ℃
By performing a heat treatment for holding for 0 seconds to 6 hours, the Fe ₃ B type compound and Nd ₂ Fe ₁₄ B which are thermodynamically metastable phases are obtained.
It is most important to obtain a fine crystal aggregate having a ferromagnetic phase having a type crystal structure and an average crystal grain diameter of 0.01 to 0.1 μm. Although it is possible to adopt the ultra-quenching method using
It is necessary to make substantially 90% or more amorphous.
For example, when a Cu roll is used, a roll surface peripheral velocity in the range of 10 to 50 m / sec is preferable because a suitable structure can be obtained. That is, when the peripheral speed is less than 10 m / sec, it does not become amorphous and the amount of α-Fe phase deposited increases, which is not preferable, and when the roll surface peripheral velocity exceeds 50 m / sec,
The rapidly cooled alloy does not form as a continuous ribbon, the alloy pieces scatter, and the recovery rate and recovery efficiency when recovering the alloy from the apparatus are reduced, which is not preferable. However, a small amount of α-Fe
The presence of phases in the quenched ribbon is acceptable as it does not significantly degrade the properties.

In the present invention, the heat treatment for maximizing the magnetic properties after the alloy melt of the above-mentioned specific composition is made amorphous by the ultra-quenching method depends on the composition, but when the heat treatment temperature is less than 550 ° C., the amorphous phase is formed. Until iHc of 4 kOe or more cannot be obtained, and when the temperature exceeds 700 ° C, the α-Fe phase and the Fe ₂ B or Nd _1.1 Fe ₄ B ₄ phase that are thermal equilibrium phases are generated and iHc does not originate, so the heat treatment temperature Is 550
Limited to ~ 700 ° C. The heat treatment atmosphere is preferably an inert gas atmosphere such as Ar gas.

The heat treatment time may be short, but if it is less than 30 seconds, a sufficient microstructure is not formed, iHc and the squareness of the demagnetization curve are deteriorated, and if it exceeds 6 hours, it is 4 kO.
Since iHc above e cannot be obtained, the heat treatment holding time is set to 3
Limited to 0 seconds to 6 hours.

An important feature of the present invention is the rate of temperature increase from 500 ° C. or higher during heat treatment, and
If the heating rate is less than a minute, the Nd ₂ Fe ₁₄ B phase and the F
The crystal grain size of the e ₃ B phase grows too large and iHc deteriorates, and iHc of 4 kOe or more cannot be obtained. Also, 15 ℃
If the heating rate exceeds / min, the Nd ₂ Fe ₁₄ B phase generated after passing 500 ° C. is not sufficiently precipitated, and α-
The amount of precipitation of the Fe phase increases and Br falls to the second quadrant of the magnetization curve.
It becomes a demagnetization curve with a decrease in magnetization near the point, (BH) m
It is not preferable because ax is deteriorated. However, a small amount of α-
The presence of the Fe phase is acceptable. In addition, at the time of heat treatment, 50
The rate of temperature increase such as rapid heating up to 0 ° C. is arbitrary.

Crystal Structure The crystal phase of the rare earth magnet and the rare earth magnet alloy powder according to the present invention is Fe ₃ B type compound as a main phase and Nd ₂ Fe ₁₄ B.
It is characterized by having a ferromagnetic phase having a type crystal structure and comprising a fine crystal aggregate having an average crystal grain size of 0.01 to 0.1 μm.

In the present invention, when the average grain size of the magnet alloy exceeds 0.1 μm, the squareness of the demagnetization curve is significantly deteriorated, and the magnetic properties of Br ≧ 7 kG and (BH) max ≧ 8 MGOe are obtained. I can't. Further, the smaller the average crystal grain size is, the more preferable, but it is difficult to obtain the average crystal grain size of less than 0.01 μm in industrial production.
It is set to 01 μm.

Magnetization method A molten alloy having a specific composition is made amorphous by a super-quenching method, and the temperature rising rate from 500 ° C. or higher is raised at 1 to 15 ° C./minute, and then at 550 to 700 ° C. for 30 seconds to. By performing a heat treatment of holding for 6 hours, the average crystal grain size is 0.01 to
To magnetize using the rare earth magnet alloy powder according to the present invention obtained as a 0.1 μm fine crystal aggregate, 700 ° C.
Any of known sintering magnetizing methods and bond magnetizing methods that can be solidified and consolidated below can be adopted, and in particular,
After crushing the alloy into alloy powder having an average particle size of 3 to 500 μm and mixing it with a known binder to form a required bond magnet, a bond magnet having a residual magnetic flux density Br of 5 kG or more can be obtained. .

[0027]

According to the present invention, substantially 90% or more of the Fe-Co-B- (Nd, Dy) -Pb alloy melt having a specific composition containing a small amount of rare earth elements is made into an amorphous structure by the superquenching method. And since the amorphous ribbon is contained in a specific amount, the recovery rate of the amorphous ribbon is remarkably improved. Further, the temperature of the obtained flakes and ribbons is increased from 500 ° C. or higher to 1 to 15 ° C./min, and then 550 The average crystal grain size is 0.0 by applying a heat treatment of holding at ~ 700 ° C for 30 seconds to 6 hours.
It becomes a fine crystal aggregate of 1 to 0.1 μm, and Fe _{3 of} the main phase
In addition to the B-type compound phase, the amount ratio of the ferromagnetic phase having the Nd ₂ Fe ₁₄ B-type crystal structure phase increases, the α-Fe phase decreases, and P
Since it contains b, iHc does not decrease even if Co is contained, and the squareness of the demagnetization curve is further improved.
iHc ≧ 4 kOe, Br ≧ 7 kG, (BH) max ≧ 8
The magnetic properties of MGOe are obtained, and by further pulverizing this to make a magnet alloy powder, Fe-Co-B- which is most suitable for a bonded magnet having a residual magnetic flux density Br of 5 kG or more.
It is possible to obtain an R-Pb based magnet alloy powder, and it is possible to obtain magnetic characteristics equal to or higher than those of a conventional alnico based magnet by forming a sintered magnet.

[0028]

【Example】

Example 1 No. 1 in Table 1 Purity 99.5 so that the composition is 1-3.
% Or more of Fe, Co, B, Nd, Pr, Dy, and Pb metals are weighed so that the total amount becomes 30 gr, and charged into a quartz crucible having an orifice with a diameter of 0.8 mm at the bottom, and pressure is applied. After melting by high-frequency heating in an Ar atmosphere of 56 cmHg and setting the melting temperature to 1400 ° C., the molten metal surface is pressurized with Ar gas and the roll peripheral speed is 20 m /
0.7mm on the outer surface of the Cu roll that rotates at high speed in seconds
The molten metal is ejected from the height of 2 to 3 mm in width and 30 in thickness.
An ultra-quenched ribbon of -40 μm was prepared. The obtained ultra-quenched ribbon was confirmed to be amorphous by the characteristic X-ray of CuKα.

After rapidly heating the ultra-quenched ribbon in Ar gas to 500 ° C., the temperature was raised to 500 ° C. or higher at the heating rate shown in Table 1 and kept at the heat treatment temperature shown in Table 1 for 10 minutes. Cool to room temperature, take out the ribbon, width 2-3 mm,
A sample having a thickness of 30 to 40 μm and a length of 3 to 5 mm is prepared,
The magnetic properties were measured using VSH. The measurement results are shown in Table 2. The measurement result of the sample is a multiphase structure in which the main phase is the Fe ₃ B phase in which the tetragonal crystal and the orthorhombic crystal are mixed and the Nd ₂ Fe ₁₄ B phase and the α-Fe phase are mixed, and the average crystal grain size is Was 0.1 μm or less. Although Co partially replaces Fe in each of these phases, Pb could not be analyzed because the addition amount was small and it was an ultrafine crystal. Also,
Dy substitutes a part of Nd of the main phase Nd ₂ Fe ₁₄ B phase.

Comparative Example No. 1 in Table 1 An ultra-quenched ribbon was prepared under the same conditions as in Example 1 using Fe, Co, B, and Nd having a purity of 99.5% or more so that the composition of Example 4 was obtained. The obtained ribbon was heat-treated under the same conditions as in Example 1, cooled, and then sampled under the same conditions as in Example 1 (Comparative Example No. 4), and the magnetic characteristics were measured using VSM. The measurement results are shown in Table 2.

Example 2 Composition No. of Table 1 obtained in Example 1 After the heat treatment shown in Table 1, the ultra-quenched ribbon No. 3 was crushed to an average particle size of 150 μm or less, and a binder of an epoxy resin was mixed at a ratio of 2 wt%, and then a bonded magnet having a size of 15 mm × 15 mm × 7 mm was prepared. The magnetic properties of the obtained bonded magnet are i
Hc = 5 kOe, Br = 6.4 kG, (BH) max =
It was 5 MGOe.

[0032]

[Table 1]

[0033]

[Table 2]

[0034]

INDUSTRIAL APPLICABILITY The present invention has a specific composition of Fe-Co-B.
A fine crystal aggregate having an average crystal grain size of 0.01 to 0.1 μm is obtained by forming an amorphous structure of a — (Nd, Dy) —Pb-based alloy melt by a super-quenching method and subjecting this to a heat treatment under specific conditions. In addition to the main phase Fe ₃ B type compound phase,
The amount ratio of the Nd ₂ Fe ₁₄ B type crystal structure phase is increased, and α-Fe
By reducing the phase, it becomes a permanent magnet ribbon, and by further pulverizing this into a magnet alloy powder, iH
c ≧ 4 kOe, Br ≧ 7 kG, (BH) max ≧ 8 MG
Oe magnetic characteristics are obtained, and residual magnetic flux density B of 5 kG or more
Fe-Co-B- (N optimal for bonded magnets with r
d, Dy) -Pb based magnet alloy powder can be obtained, and by forming a sintered magnet, magnetic characteristics equivalent to or higher than those of conventional alnico based magnets can be obtained. In addition, the present invention has a small content of rare earth elements, a simple manufacturing method, and is suitable for mass production, and therefore has a residual magnetic flux density B of 5 kG or more.
With r, it has magnetic performance exceeding that of hard ferrite magnets, and the process can be shortened by adopting integral molding of magnetic parts and magnet body, and the performance-to-cost ratio surpassing that of sintered hard ferrite. A bond magnet that can be realized can be provided.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location C22C 38/00 303 D 38/10 H01F 1/053

Claims (3)

[Claims] The method according to claim 1] composition formula _{Fe 100-xyz Co x B y} (R 1-a
Dy _a ) _z Pb _w (where R is one of Pr and Nd or a mixture of both at any ratio), and the symbols x, y, z, a and w that limit the composition range satisfy the following values: , Fe ₃ B
-Type compound as a main phase, a ferromagnetic phase having an Nd ₂ Fe ₁₄ B type crystal structure, and an average crystal grain size of 0.01 to 0.1 μm
A rare earth magnet comprising a fine crystal aggregate of m. 0.05 ≦ x ≦ 15 at% 16 ≦ y ≦ 22 at% 3 ≦ z ≦ 5.5 at% 0.02 ≦ a ≦ 0.9 0.1 ≦ w ≦ 3 at% 2. A method composition formula _{Fe 100-xyz Co x B y} (R 1-a
Dy _a ) _z Pb _w (where R is one of Pr and Nd or a mixture of both at any ratio), and the symbols x, y, z, a and w that limit the composition range satisfy the following values: , Fe ₃ B
-Type compound as a main phase, a ferromagnetic phase having an Nd ₂ Fe ₁₄ B type crystal structure, and an average crystal grain size of 0.01 to 0.1 μm
It is composed of m fine crystal aggregates and has an average particle size of 3 to 500 μ.
m, magnetic characteristics are iHc ≧ 4 kOe, Br ≧ 7 kG, (B
H) A rare earth magnet alloy powder characterized in that max ≧ 8 MGOe. 0.05 ≦ x ≦ 15 at% 16 ≦ y ≦ 22 at% 3 ≦ z ≦ 5.5 at% 0.02 ≦ a ≦ 0.9 0.1 ≦ w ≦ 3 at% The 3. A composition formula _{Fe 100-xyz Co x B y} (R 1-a
Dy _a ) _z Pb _w (where R is one of Pr and Nd or a mixture of both at any ratio), and the symbols x, y, z, a, and w that limit the composition range satisfy the following values: Substantially 90% or more of the molten alloy is formed into an amorphous structure by the ultra-quenching method, and further the heat treatment is performed at a temperature rising rate from 500 ° C of 1 to 15 ° C / min for 30 seconds to 550 to 700 ° C.
A fine crystal having a ferromagnetic phase having an Fe ₃ B type compound as a main phase and an Nd ₂ Fe ₁₄ B type crystal structure, which is subjected to heat treatment for 6 hours, and has an average crystal grain size of 0.01 to 0.1 μm. A method for producing a rare earth magnet alloy powder, which comprises obtaining an aggregate and then pulverizing the aggregate to obtain a magnet alloy powder. 0.05 ≦ x ≦ 15 at% 16 ≦ y ≦ 22 at% 3 ≦ z ≦ 5.5 at% 0.02 ≦ a ≦ 0.9 0.1 ≦ w ≦ 3 at%