JP2999648B2 - Rare earth magnet, rare earth magnet alloy powder and method for producing the same - Google Patents

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 which is most suitable for a motor or an actuator, and more particularly to a Fe--Co having a specific composition containing a small amount of a rare earth element.
A bonded magnet having a residual magnetic flux density Br of 5 kG or more, which cannot be obtained with a hard ferrite magnet, by forming an amorphous structure of a molten BR alloy by a super-quenching method and obtaining a fine crystal aggregate by a specific heat treatment. The present invention relates to a production method for obtaining a rare earth magnet alloy powder most suitable for the invention.

[0002]

2. Description of the Related Art Permanent magnets used in motors and actuators for electrical components are mainly limited to hard ferrite magnets. However, low-temperature demagnetization due to a decrease in iHc at low temperatures and mechanical strength due to ceramic materials. However, there are problems that cracks and chips are apt to occur due to the low shape, and that it is difficult to obtain a complicated shape.

[0003] Today, there is a strong demand for automobiles to improve fuel efficiency by reducing the weight of the vehicles in order to save resources, and it is required to further reduce the size and weight of electrical components for automobiles. Also,
Designs to maximize the performance-to-weight ratio are also being considered for applications such as motors for home appliances other than automotive electrical components, and the current motor structure is optimal for magnet materials with a Br material of about 5 to 7 kG. It has been. That is,
When Br of the magnet material to be used is 8 kG or more, the current motor structure needs to increase the cross-sectional area of the iron plate of the rotor or the stator which becomes the magnetic path, which leads to an increase in weight. If so, the performance to weight ratio can be maximized.

Accordingly, a magnetic material for a small motor is required to have a residual magnetic flux density Br of at least 5 kG in terms of magnetic properties, but cannot be obtained with a conventional hard ferrite magnet. For example, an Nd—Fe—B-based bonded magnet satisfies such magnetic properties, but Nd or the like, which requires a large number of steps and large-scale facilities for metal separation and purification or reduction reaction, is required.
Since it contains １５15 at%, it is significantly more expensive than a hard ferrite magnet, and at present, a magnet material having 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
In recent years, a magnet material having a main phase of Fe ₃ B type compound in the vicinity of Nd ₄ Fe ₇₇ B ₁₉ (at%) has been proposed as a system magnet (R. Cohoenor et al., J. de Phys., C.
8, 1988, 669-670). This magnet material is obtained by heat-treating an amorphous ribbon to obtain Fe.
₃ is a metastable structure with a crystal texture of B and Nd ₂ Fe ₁₄ B but, iHc is not high as about 2～3KOe, also the heat treatment conditions for obtaining the iHc is narrowly restricted, industrial production practical Not.

Researches have been published to improve the performance by adding an additional element to the magnetic material having the Fe ₃ B-type compound as a main phase to make it multi-component. One of them is to improve iHc by using Dy and Tb in addition to Nd as a rare earth element. In addition to the problem of adding an expensive element, the added rare earth element has a magnetic moment of Nd or Fe. There is a problem that magnetization decreases due to coupling in anti-parallel to the moment (R. Coehorn, J. Magn, Magn, M
at, 83 (1990) 228-230).

[0007] Other studies (Shen Bao-gen et al.,
J. Magn, Magn, Mat, 89 (1991) 3
(Pages 35 to 340) is to improve the temperature coefficient of iHc by replacing a part of Fe with Co to improve the temperature coefficient of iHc, but there is a problem that Br is reduced 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 a rapid quenching method. However, the iHc is low and the heat treatment conditions are severe. As a result, stable industrial production cannot be performed, and it cannot be provided at a low cost as a substitute for a hard ferrite magnet.

Further, in order to make the Nd-Fe-B-based alloy amorphous, it is necessary to remarkably increase the roll peripheral speed at the time of ultra-quenching, and there is a problem that the product recovery rate and the yield are reduced. Since it is a base alloy, there is a problem that corrosion at the time of storage is apt to progress, and the magnetic properties at the initial stage cannot be maintained due to long-term storage, resulting in deterioration.

The present invention focuses on Fe ₃ B type Fe—BR based magnets (R is a rare earth element) and focuses on iHc and (BH) m
a. Manufacturing method that enables stable industrial production by improving ax and Fe ₃ B that has a residual magnetic flux density Br of 5 kG or more and can be provided at low cost as a substitute for hard ferrite magnets
It is intended for a type Nd-Fe-B based magnet.

[0011]

DISCLOSURE OF THE INVENTION The present invention has been studied variously for the purpose of improving the iHc and (BH) max of a Fe ₃ B type Fe—BR magnet and enabling a stable industrial production. As a result, the content of the rare earth element was small, and Co and A
g, Al, a molten alloy having a specific composition of an iron base to which a small amount of at least one of Si is added is formed into an amorphous structure by a rapid quenching method, and a fine crystal aggregate is obtained by heat treatment at a specific heating rate. The present inventors have found that a rare earth magnet alloy powder optimal for a bonded magnet having a residual magnetic flux density Br of 5 kG or more, which cannot be obtained with a hard ferrite magnet, can be obtained, and completed the present invention.

According to the present invention, the composition formula is represented by Fe _100-xyz Co _x
B _y R _z M _w (where R is one of Pr or Nd or 2
Species, M is one or more of Ag, Al or Si)
And the symbols x, y, z, and w that limit the composition range satisfy the following values, the main phase is Fe ₃ B type compound, and Nd ₂ Fe ₁₄
A rare earth magnet having a ferromagnetic phase having a B-type crystal structure and comprising a fine crystal aggregate having an average crystal grain size of 0.01 to 0.1 μm. 0.05 ≦ x ≦ 15 at% 16 ≦ y ≦ 22 at% 3 ≦ z ≦ 5.5 at% 0.1 ≦ w ≦ 3 at%

Further, according to the present invention, the composition formula is Fe
_{100-xyz Co x B y R} z M w ( where R is Pr or Nd
And M is one or more of Ag, Al or Si), and symbols x,
y, z, and w satisfy the above-mentioned values, have a ferromagnetic phase having a Fe ₃ B-type compound as a main phase and an Nd ₂ Fe ₁₄ B-type crystal structure, and have an average crystal grain size of 0.01 to 0. .1 μm, having an average particle size of 3 to 500 μm, magnetic properties iHc ≧ 3 kOe, Br ≧ 8 kG, (BH) max ≧
It is a rare earth magnet alloy powder characterized by being 8MGOe.

The present invention also provides (1) a composition formula of Fe
_{100-xyz Co x B y R} z M w ( where R is Pr or Nd
And M is one or more of Ag, Al or Si), and symbols x,
An alloy structure in which y, z, and w satisfy the above-mentioned values substantially has an amorphous structure of at least 90% by an ultra-quenching method,
(2) Further, the rate of temperature rise from 500 ° C.
The temperature is raised at -15 ° C / minute and at 550-700 ° C for 30 seconds-6.
(3) a ferromagnetic phase having an Nd ₂ Fe ₁₄ B type crystal structure with an Fe ₃ B type compound as a main phase and an average crystal grain size of 0.01 to 0.1 μm; (4) A method for producing a rare earth magnet alloy powder, which comprises obtaining a fine crystal aggregate and then pulverizing the aggregate to obtain a magnet alloy powder.

[0015]

According to the present invention, when a molten alloy of Fe-Co-B-RM alloy having a specific composition having a small content of rare earth elements has an amorphous structure of substantially 90% or more by an ultra-quenching method, , The recovery rate of the amorphous ribbon is remarkably improved.
After the temperature is raised from 0 ° C. or higher at a rate of 1 to 15 ° C./min,
By performing a heat treatment at 550 to 700 ° C. for 30 seconds to 6 hours, a fine crystal aggregate having an average crystal grain size of 0.01 to 0.1 μm is formed, and in addition to the main phase Fe ₃ B-type compound phase, Nd the amount ratio of the ferromagnetic phase is increased with ₂ Fe ₁₄ B type crystalline structure phase, alpha-Fe phase decreases, Ag, Al, no decrease in Br also contain Co for containing Si, further By improving the squareness of the demagnetization curve, iHc ≧
3 kOe, Br ≧ 8 kG, (BH) max ≧ 8 MGOe
Is obtained, and is further pulverized into a magnet alloy powder to obtain a residual magnetic flux density Br of 5 kG or more.
It is possible to obtain an Fe-Co-B-R-M based magnet alloy powder that is optimal for a bonded magnet having the following characteristics, and it is possible to obtain magnetic properties equivalent to or higher than those of a conventional alnico-based magnet by forming a sintered magnet. .

Reasons for Restriction of Composition High magnetic properties can be obtained only when the rare earth element R contains one or two kinds of Pr or Nd in a specific amount.
For example, in Ce and La, iHc characteristics of 2 kOe or more cannot be obtained, and middle rare earth elements and heavy rare earth elements after Sm cause deterioration of magnetic characteristics and make the magnet expensive, which is not preferable. If R is less than 3 at%, iHc of 2 kOe or more cannot be obtained, and if it exceeds 6 at%, Fe ₃
R ₂ Fe, a metastable phase that does not produce a B phase and does not exhibit hard magnetism
Since ₂₃ B ₃ phase is not preferable because folding out iHc decreases significantly, and the range of 3~5.5at%.

When B is less than 16 at% or more than 22 at%, iHc of 2 kOe or more cannot be obtained.
２２22 at%.

Co is effective for improving and improving the squareness of the iHc and demagnetization curve. However, if the content is less than 0.05 at%, such an effect cannot be obtained. If the content exceeds 15 at%, iHc is remarkably reduced, and 2 kOe or more. Is not obtained, so that
The range is from 0.5 to 15 at%.

Ag, Al, and Si increase the heat treatment temperature range, improve the squareness of the demagnetization curve, and improve the magnetic properties of Br, (B
H) has an effect of increasing max, and at least 0.1 at% or more is required to obtain such an effect, but if it exceeds 3 at%, the squareness is rather deteriorated,
Since (BH) max also decreases, the range is 0.1 to 3 at%.

Fe accounts for the residual 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 a rapid quenching method,
After the temperature was raised at a rate of 500 ° C./min,
By performing the heat treatment for holding for 0 seconds to 6 hours, the Fe ₃ B-type compound which is thermodynamically a metastable phase and the Nd ₂ Fe ₁₄ B
It is most important to obtain a fine crystal aggregate having a ferromagnetic phase having a type crystal structure and an average crystal grain size of 0.01 to 0.1 μm. The rapid quenching method using
It is necessary to make substantially 90% or more amorphous.
For example, when a Cu roll is used, the roll surface peripheral speed is preferably in the range of 10 to 50 m / sec because a suitable structure can be obtained. In other words, if the peripheral speed is less than 10 m / sec, it does not become amorphous and the amount of precipitation of the α-Fe phase increases, which is not preferable. If the roll surface peripheral speed exceeds 50 m / sec,
The quenched alloy is not generated as a continuous ribbon, the alloy pieces are scattered, and the recovery rate and recovery efficiency when recovering the alloy from the apparatus are undesirably reduced. However, a small amount of α-Fe
The presence of phases in the quenched ribbon is acceptable without significant degradation of properties.

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

Although the heat treatment time may be short, if it is less than 30 seconds, a sufficient microstructure is not formed, iHc and the squareness of the demagnetization curve deteriorate, and if it exceeds 6 hours, 2 kO 2
e, iHc longer than e cannot be obtained.
Limited to 0 seconds to 6 hours.

An important feature of the present invention is that the rate of temperature rise from 500 ° C. or higher during heat treatment is 1 ° C. /
At a heating rate of less than 10 minutes, the Nd ₂ Fe ₁₄ B phase and F
The crystal grain size of the e ₃ B phase grows too large to deteriorate iHc, and iHc of 2 kOe or more cannot be obtained. 15 ° C
If the temperature rise rate exceeds 500 ° C./min, the precipitation of the Nd ₂ Fe ₁₄ B phase formed after passing through 500 ° C. is not sufficiently performed, and α-
The precipitation amount of the Fe phase increases, and Br in the second quadrant of the magnetization curve.
A demagnetization curve with a decrease in magnetization near the point is obtained, and (BH) m
This is not preferable because ax deteriorates. However, a small amount of α-
The presence of the Fe phase is acceptable. In addition, 50
Up to a temperature of less than 0 ° C., the heating rate such as rapid heating 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 mainly composed of Fe ₃ B type compound, and Nd ₂ Fe ₁₄ B.
It is characterized by having a ferromagnetic phase having a type crystal structure and being composed of a fine crystal aggregate having an average crystal grain size of 0.01 to 0.1 μm.

In the present invention, if the average crystal grain size of the magnet alloy exceeds 0.1 μm, the squareness of the demagnetization curve is remarkably deteriorated, and the magnetic properties of Br ≧ 7 kG and (BH) max ≧ 8MGOe are obtained. Can not. Although the average crystal grain size is preferably as small as possible, it is difficult to obtain an average crystal grain size of less than 0.01 μm in industrial production.
01 μm.

Magnetization Method A molten alloy having a specific composition is made amorphous by a super-quenching method, and the temperature is raised from 500 ° C. or higher at a rate of 1 to 15 ° C./min. By performing the heat treatment for 6 hours, the average crystal grain size becomes 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 the following methods of solidifying and consolidating known sintered magnets and bond magnets that can be consolidated can be used.
After the alloy is pulverized into an alloy powder having an average particle diameter of 3 to 500 μm and mixed with a known binder to form a required bonded magnet, a bonded magnet having a residual magnetic flux density Br of 5 kG or more can be obtained. .

[0028]

Example 1 Example 1 of Table 1 99.5 purity so as to have a composition of 1 to 8.
% Or more of Fe, Co, B, Nd, Pr, Ag, Al, S
Using the metal of i, weigh so that the total amount becomes 30 gr, put it into a quartz crucible having an orifice with a diameter of 0.8 mm at the bottom, and melt it by high frequency heating in an Ar atmosphere at a pressure of 56 cmHg, and adjust the melting temperature. After the temperature was raised to 1400 ° C., the molten metal surface was pressurized with Ar gas, and molten metal was jetted from a height of 0.7 mm onto the outer peripheral surface of a Cu roll rotating at room temperature at a high speed of 20 m / sec. 2-3m
m, a super-quenched ribbon having a thickness of 30 to 40 μm was produced. The obtained ultra-quenched ribbon was confirmed to be amorphous by characteristic X-rays of CuKα.

After the ultra-quenched ribbon was rapidly heated to 500 ° C. in Ar gas, the temperature was raised to 500 ° C. or more at the temperature raising rate shown in Table 1, and kept at the heat treatment temperature shown in Table 1 for 10 minutes. After cooling to room temperature, take out the ribbon, width 2-3mm,
A sample having a thickness of 30 to 40 μm and a length of 3 to 5 mm is prepared,
Magnetic properties were measured using VSH. Table 2 shows the measurement results. The measurement results of the sample show that the main phase is a Fe ₃ B phase in which tetragonal and orthorhombic are mixed, and a multiphase structure in which Nd ₂ Fe ₁₄ B and α-Fe are mixed. Was 0.1 μm or less. Note that Co replaces part of Fe in each of these phases, but Ag, Al, and Si could not be analyzed due to the small amount of addition and ultrafine crystals.

Comparative Example The composition No. of Example 1 obtained under the same conditions as Example 1 2 was rapidly heated to 500 ° C. in Ar gas, and then the temperature was raised from 500 ° C. or higher at 11 ° C./min.
A heat treatment of holding for 0 minutes was performed, and after cooling, a sample was prepared under the same conditions as in Example 1 (Comparative Example No. 9), and magnetic characteristics were measured using a VSM. Table 2 shows the measurement results.

The composition No. of Example 1 obtained under the same conditions as Example 1 After rapidly heating the ultra-quenched ribbon of Example 2 to 500 ° C. in Ar gas, Comparative Example No. 2 was heated. Comparative Example No. 10 was subjected to a heat treatment at 500 ° C. for 10 minutes. No. 11 heat-treated at a temperature of 500 ° C. or higher at 4 ° C./min, and maintained at 750 ° C. for 10 minutes.
Magnetic properties were measured using SM. Table 2 shows the measurement results. Comparative Example No. No. 10 is an amorphous structure; 1
No. 1 was a multiphase structure in which the Fe ₂ B phase and the α-Fe phase were mixed.

The composition No. of Example 1 2 with the same composition as S
Comparative Example No. No. 9 as composition no. The magnetic properties were measured using VSH, manufactured and sampled under the same conditions as in Example 2. Table 2 shows the measurement results.

Example 2 The composition No. of Table 1 obtained in Example 1 was used. The ultra-quenched ribbon No. 4 was pulverized to a mean particle size of 150 μm or less after the heat treatment shown in Table 1, and a binder of an epoxy resin was mixed at a ratio of 2 wt% to prepare a bond magnet having a size of 15 mm × 15 mm × 7 mm. The magnetic properties of the resulting bonded magnet are i
Hc = 3.5 kOe, Br = 7.0 kG, (BH) ma
x = 5.5 MGOe.

[0034]

[Table 1]

[0035]

[Table 2]

[0036]

According to the present invention, Fe-Co-B having a specific composition
The RM-based alloy melt is formed into an amorphous structure by a super-quenching method, and is subjected to a heat treatment under specific conditions to form a fine crystal aggregate having an average crystal grain size of 0.01 to 0.1 μm. In addition to the Fe ₃ B type compound phase described above, the amount ratio of the Nd ₂ Fe ₁₄ B type crystal structure phase increases, and the α-Fe phase decreases, resulting in a permanent magnet ribbon. By powdering, iHc ≧ 3 kOe, B
Magnetic properties of r ≧ 8 kG and (BH) max ≧ 8 MGOe can be obtained, and it is possible to obtain an Fe—Co—B—R—M based magnet alloy powder most suitable for a bonded magnet having a residual magnetic flux density Br of 5 kG or more. In addition, by using a sintered magnet, it is possible to obtain magnetic properties equal to or higher than those of a conventional alnico magnet. Further, the present invention has a low rare earth element content,
Since the manufacturing method is simple and suitable for mass production, it has a residual magnetic flux density Br of 8 kG or more, has magnetic performance exceeding that of hard ferrite magnets, and adopts integral molding of magnetic parts and a magnet body. Process can be shortened,
It is possible to provide a bonded magnet capable of realizing a performance-to-cost ratio exceeding that of sintered hard ferrite.

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields investigated (Int. Cl. ⁷ , DB name) H01F 1/053 B22F 1/00 C22C 33/02 C22C 38/00 303 H01F 1/06

Claims (3)

(57) [Claims] The method according to claim 1] composition formula _{Fe 100-xyz Co x B y} R z M w
(Where R is one or two of Pr or Nd, M is A
g, one or more of Al or Si), and the symbols x, y, z, and w for limiting the composition range satisfy the following values, the main phase is Fe ₃ B type compound, and Nd ₂ Fe ₁₄ It has a ferromagnetic phase having a B-type crystal structure and an average crystal grain size of 0.01
A rare-earth magnet comprising a fine crystal aggregate having a diameter of about 0.1 μm. 0.05 ≦ x ≦ 15 at% 16 ≦ y ≦ 22 at% 3 ≦ z ≦ 5.5 at% 0.1 ≦ w ≦ 3 at% 2. A method composition formula _{Fe 100-xyz Co x B y} R z M w
(Where R is one or two of Pr or Nd, M is A
g, one or more of Al or Si), and the symbols x, y, z, and w for limiting the composition range satisfy the following values, the main phase is Fe ₃ B type compound, and Nd ₂ Fe ₁₄ It has a ferromagnetic phase having a B-type crystal structure and an average crystal grain size of 0.01
Consisting of fine crystal aggregates having a mean particle size of 3 to 0.1 μm.
５００500 μm, magnetic properties iHc ≧ 3 kOe, Br ≧ 8
A rare earth magnet alloy powder characterized in that kG and (BH) max ≧ 8MGOe. 0.05 ≦ x ≦ 15 at% 16 ≦ y ≦ 22 at% 3 ≦ z ≦ 5.5 at% 0.1 ≦ w ≦ 3 at% The 3. A composition formula _{Fe 100-xyz Co x B y} R z M w
(Where R is one or two of Pr or Nd, M is A
g, Al or Si), and the symbols x, y, z, and w defining the composition range satisfy the following values. An amorphous structure was formed, and the temperature was raised from 500 ° C. at a rate of 1 to 15 ° C./min to 550 to 700 ° C. during the heat treatment.
At a temperature of 30 seconds to 6 hours, a ferromagnetic phase having an Fe ₃ B-type compound as a main phase and an Nd ₂ Fe ₁₄ B-type crystal structure, and having an average crystal grain size of 0.01 to 0. A method for producing a rare earth magnet alloy powder, comprising: obtaining a fine crystal aggregate of 1 μm, and pulverizing the aggregate to obtain a magnet alloy powder. 0.05 ≦ x ≦ 15 at% 16 ≦ y ≦ 22 at% 3 ≦ z ≦ 5.5 at% 0.1 ≦ w ≦ 3 at%