JPH0688159A - Rare earth magnet and rare earth magnet alloy powder as well as production therefor - Google Patents

Abstract

PURPOSE:To stably produce rare earth magnet alloy powder having excellent magnetic properties at low cost by subjecting the molten metal of an alloy having a specified compsn. constituted of Fe, Co, B and Pr or Nd, Ag or the like to ultrarapid solidification and executing specified heat treatment. CONSTITUTION:The molten metal of an alloy expressed by Fe100-x-y-zCoxByRzMw (R denotes Pr or Nd and M denotes Ag, Al Si as well as 0.05<=x<=15at%, 1.6<=y<=22%, 3<=z<=5.5% and 0.1<=w<=3% are satisfied) is subjected to ultrarapid solidification to form its structure into a one in which >=90% is substantially constituted of amorphous one. The temp. of this alloy is raised at 1 to 15 deg.C/min temp. rising rate from 500 deg.C, and it is held at 550 to 700 deg.C for 30sec to 6hr. By this heat treatment, the aggregate of fine crystals consisting of Fe3B type compounds as the main phase, having a ferromagnetic phase with an Nd2Fe14B type crystalline structure and having 0.01 to 0.1mum average crystalline grains is obtd., which is thereafter pulverized to regulate its average grain size into 3 to 500mum. In this way, the rare earth magnet alloy powder having magnetic properties of iHc<=3kOe, Br>=8kG and (BH)max>=8MGOe can be obtd.

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.
-A bond magnet having a residual magnetic flux density Br of 5 kG or more, which cannot be obtained by 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 manufacturing method for obtaining an optimal rare earth magnet alloy powder.

[0002]

2. Description of the Related 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 accompanying 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 so 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 the performance. One of them 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 added rare earth element has a magnetic moment of Nd or Fe. There is a problem that the magnetization decreases due to coupling in antiparallel to 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 it is made amorphous by the ultra-quenching method, but iHc is low and the heat treatment conditions are severe, and when the iHc is increased by the additive element, the magnetic energy product is increased. It is not possible to provide stable industrial production such as deterioration, 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.
Aims to be a type Nd-Fe-B system magnet.

[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 content of rare earth elements is low, and Co and A
g, Al, by forming a small amount of at least one of Si, an alloy melt of a specific iron-based composition into an amorphous structure by the ultra-quenching method, and obtaining a fine crystal aggregate by heat treatment at a specific heating rate, The inventors have found that an optimum rare earth magnet alloy powder can be obtained for a bond magnet having a residual magnetic flux density Br of 5 kG or more, which could not be obtained with a hard ferrite magnet, and completed the present invention.

This invention uses the composition formula Fe _100-xyz Co _x
B _y R _z M _w (where R is Pr or Nd, one or two)
Seed, M is Ag, Al or Si, one or more kinds)
And the symbols x, y, z, and w that limit the composition range satisfy the following values, the Fe ₃ B type compound is the main phase, 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, the present invention uses the composition formula Fe
_{100-xyz Co x B y R} z M w ( where R is Pr or Nd
1 or 2 of M, 1 or 2 or more of Ag, Al or Si), and a symbol x for limiting the composition range,
y, z and w satisfy the above 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. It is composed of a fine crystal aggregate of 1 μm, has an average grain size of 3 to 500 μm, and has magnetic properties of iHc ≧ 3 kOe, Br ≧ 8 kG, (BH) max ≧.
It is a rare earth magnet alloy powder characterized by being 8 MGOe.

Further, according to the present invention, the composition formula (1) is represented by Fe
_{100-xyz Co x B y R} z M w ( where R is Pr or Nd
1 or 2 of M, 1 or 2 or more of Ag, Al or Si), and a symbol x for limiting the composition range,
The alloy melt in which y, z, and w satisfy the above-mentioned values is made into an amorphous structure by substantially 90% or more by the superquenching method,
(2) In the heat treatment, the temperature rising rate from 500 ° C is set to 1
Temperature rises at -15 ° C / min and 550-700 ° C for 30 seconds-6
A heat treatment for holding for a period of time (3) having 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 an average crystal grain size of 0.01 to 0.1 μm A method for producing a rare earth magnet alloy powder, comprising: (4) pulverizing the fine crystal aggregate to obtain a magnet alloy powder.

[0015]

According to the present invention, when a Fe-Co-B-R-M type alloy melt having a specific composition containing a small amount of rare earth elements is made to have an amorphous structure in an amount of substantially 90% or more by an ultra-quenching method, the specific amount is Since it contains Co, the recovery rate of amorphous ribbon is significantly improved, and the obtained flakes and ribbons are
After raising the temperature from 0 ° C. or higher at a heating rate of 1 to 15 ° C./min,
By performing a heat treatment of holding 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 Fe ₃ B type compound phase of the main phase, Nd The amount ratio of the ferromagnetic phase having the ₂ Fe ₁₄ B-type crystal structure phase is increased, the α-Fe phase is decreased, and since Ag, Al, and Si are contained, even if Co is contained, Br does not decrease. Since the squareness of the demagnetization curve is improved, iHc ≧
3 kOe, Br ≧ 8 kG, (BH) max ≧ 8 MGOe
Magnetic properties are obtained, and by further pulverizing this to make a magnetic alloy powder, the residual magnetic flux density Br of 5 kG or more is obtained.
The optimum Fe-Co-B-R-M based magnet alloy powder can be obtained for the bonded magnet having the above-mentioned properties, and it is possible to obtain the magnetic characteristics equal to or higher than those of the conventional alnico based magnet by making the sintered magnet. .

Reasons for limiting the composition The rare earth element R has high magnetic properties only when it contains one or two Pr or Nd in a specific amount.
For example, in the case of Ce and La, the characteristic that iHc is 2 kOe or more cannot be obtained, and medium 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
A metastable phase R ₂ Fe that does not form B phase and does not exhibit hard magnetism
₂₃ B ₃ phase is unfavorable because the iHc is significantly lowered, and the range is 3 to 5.5 at%.

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 for 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%.

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

Fe occupies the remaining content of the above 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 the temperature is from 500 ° C. or higher to 1-15.
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 if the heat treatment temperature is less than 550 ° C. Until iHc of 2 kOe or more cannot be obtained, and if 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 2 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, which is 1 ° C. /
If the heating rate is less than a minute, the Nd ₂ Fe ₁₄ B phase and the F
Since the crystal grain size of the e ₃ B phase grows too large and iHc deteriorates, iHc of 2 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, the temperature is raised from 500 ° C. or more at a rate of 1 to 10 ° 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. .

[0028]

【Example】

Example 1 No. 1 in Table 1 Purity 99.5 so that the composition is 1 to 5
% Or more of Fe, Co, B, Nd, Pr, Ag, Al, S
The metal i was weighed so that the total amount was 30 gr, put into a quartz crucible having an orifice with a diameter of 0.8 mm at the bottom, and melted by high-frequency heating in an Ar atmosphere with a pressure of 56 cmHg to set the melting temperature. After the temperature was set to 1400 ° C., the molten metal surface was pressurized with Ar gas, and the molten metal was ejected from a height of 0.7 mm onto the outer peripheral surface of a Cu roll which was rotated at a high speed at a roll peripheral speed of 20 m / sec at room temperature. 2-3m
An ultra-quenched ribbon having a thickness of m and a thickness of 30 to 40 μm was produced. 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. Co replaces part of Fe in each of these phases, but Ag, Al, and Si could not be analyzed because the addition amount was small and the crystals were ultrafine.

Comparative Example Composition No. 1 of Example 1 obtained under the same conditions as in Example 1. After rapidly heating the ultra-quenched ribbon of No. 2 in Ar gas to 500 ° C., the temperature is raised to 500 ° C. or more at 11 ° C./min, and the temperature is increased to 1 at 680 ° C.
A heat treatment of holding for 0 minutes was performed, and after cooling, a sample was made under the same conditions as in Example 1 (Comparative Example No. 9) and the magnetic characteristics were measured using VSM. The measurement results are shown in Table 2.

Composition No. 1 of Example 1 obtained under the same conditions as in Example 1 After rapidly heating the ultra-quenched ribbon of No. 2 to 500 ° C. in Ar gas, Comparative Example No. No. 10 was subjected to heat treatment of holding at 500 ° C. for 10 minutes, and Comparative Example No. No. 11 was heated to 500 ° C. or higher at 4 ° C./min, heat-treated at 750 ° C. for 10 minutes, cooled, sampled under the same conditions as in Example 1, and V
The magnetic characteristics were measured using SM. The measurement results are shown in Table 2. Comparative Example No. No. 10 is an amorphous structure, and No. 10 is the same. 1
No. 1 had a multi-phase structure in which Fe ₂ B phase and α-Fe phase were mixed.

Composition No. of Example 1 Same composition as 2
Comparative Example No. containing no i. 9 is the composition No. The magnetic properties were measured by using VSH after manufacturing under the same conditions as in Example 2 and sampling. The measurement results are shown in Table 2.

Example 2 Composition No. of Table 1 obtained in Example 1 The ultra-quenched ribbon of No. 4 was crushed to have an average particle size of 150 μm or less after the heat treatment shown in Table 1 and mixed with a binder of epoxy resin 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 = 3.5 kOe, Br = 7.0 kG, (BH) ma
x was 5.5 MGOe.

[0034]

[Table 1]

[0035]

[Table 2]

[0036]

INDUSTRIAL APPLICABILITY The present invention has a specific composition of Fe-Co-B.
-The RM alloy melt is formed into an amorphous structure by the ultra-quenching method, and by subjecting this to a heat treatment under specific conditions, a fine crystal aggregate having an average crystal grain size of 0.01 to 0.1 μm is formed, and the main phase is formed. Fe ₃ other B compound phase, the amount ratio of Nd ₂ Fe ₁₄ B crystal structure phase is increased by alpha-Fe phase decreases, becomes permanent magnet ribbon, magnet alloy was further pulverized into a By powdering, iHc ≧ 3 kOe, B
Magnetic properties of r ≧ 8 kG and (BH) max ≧ 8 MGOe are obtained, and an optimal Fe—Co—B—R—M magnet alloy powder for a bond magnet having a residual magnetic flux density Br of 8 kG or more can be obtained, Further, by using a sintered magnet, it is possible to obtain magnetic characteristics equal to or higher than those of conventional alnico magnets. Further, the present invention has a low content of rare earth elements,
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 a hard ferrite magnet, and adopts integral molding of a magnetic component and a magnet body. The process can be shortened,
It is possible to provide a bonded magnet that can achieve a performance-to-cost ratio that exceeds that of sintered hard ferrite.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H01F 1/08 B

Claims (3)

[Claims] The method according to claim 1] composition formula _{Fe 100-xyz Co x B y} R z M w
(However, R is one or two of Pr or Nd, M is A
g, Al or Si), and symbols x, y, z and w that limit the composition range satisfy the following values, Fe ₃ B type compound as the main phase, and Nd ₂ Fe ₁₄ It has a ferromagnetic phase with a B-type crystal structure and an average crystal grain size of 0.01
A rare earth magnet comprising a fine crystal aggregate of 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
(However, R is one or two of Pr or Nd, M is A
g, Al or Si), and symbols x, y, z and w that limit the composition range satisfy the following values, Fe ₃ B type compound as the main phase, and Nd ₂ Fe ₁₄ It has a ferromagnetic phase with a B-type crystal structure and an average crystal grain size of 0.01
Consisting of fine crystal aggregates of ~ 0.1 μm and having an average particle size of 3
~ 500 μm, magnetic characteristics iHc ≧ 3 kOe, Br ≧ 8
A rare earth magnet alloy powder characterized in that kG and (BH) max ≧ 8 MGOe. 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
(However, R is one or two of Pr or Nd, M is A
g, Al or Si, or two or more of them), and the alloy melts in which the symbols x, y, z, and w which limit the composition range satisfy the following values, are substantially 90% or more by the superquenching method. Amorphous structure, further heat treatment at a heating rate from 500 ℃ at 1 to 15 ℃ / min to 550 ~ 700 ℃
At a temperature of 30 seconds to 6 hours, a 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. A method for producing a rare earth magnet alloy powder, which comprises obtaining a 1 μm fine crystal aggregate and then pulverizing this 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%