JPH0657311A - Production of rare earth alloy magnet powder - Google Patents

Abstract

PURPOSE:To improve iHc and (BH)max and residual magnetic flux density by rapidly cooling a molten iron-base alloy having a specific compsn. contg. rare earths at a lower ratio by an atomization method and heat treating the rapidly cooled alloy under specific conditions, thereby forming a fine crystalline assemblage. CONSTITUTION:The molten alloy expressed by Fe100-x-y-zCoxByRz is rapidly cooled by the atomization method, by which substantially >=90% thereof is made into an amorphous structure. In the formula, R is one or two kinds of Pr and Nd; (x), (y), (z) are 0.05<=x<=15at.%, 16<=y<=22%, 3<=z<=5.5%. The average grain size of the resulted alloy powder is specified to 0.1-100mum. This alloy powder is heated up at 1-15 deg.C/min from 500 deg.C and is held for 30 seconds - 6 hours at 550-700 deg.C. The alloy powder for the rare earth magnet yielding the fine crystalline assemblage which has a ferromagnetic phase having an Nd2Fe14B type crystal structure contg. an Fe3B type compd. as a main phase and has 5 to 100nm average crystal grain sizes is obtd. by this heat treatment.

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.
-By forming the amorphous structure of the B-R alloy molten metal by the atomizing method and obtaining the fine crystal aggregate by the specific heat treatment, 5 kG which could not be obtained by the hard ferrite magnet
The present invention relates to a manufacturing method for obtaining a rare earth magnet alloy powder most suitable for a bonded magnet having the above residual magnetic flux density Br.

[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 a metastable structure having a crystal texture of Fe ₃ B and Nd ₂ Fe ₁₄ B obtained by converting the alloy having the above composition into an amorphous ribbon by a super-quenching method using a rotating roll and heat-treating this amorphous ribbon. Is obtained. However, 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 not practical in industrial production.

[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
A system magnet can be made into a hard magnet material by heat treatment after it is made amorphous by a super-quenching method using a rotating roll.
The iHc is low, the heat treatment conditions are severe, and the magnetic energy product is lowered when the iHc is increased by adding elements, so stable industrial production cannot be performed, and it should be provided at a low cost as a substitute for the hard ferrite magnet. I can't.

Further, when adopting the super-quenching method using a rotating roll for amorphizing the Nd-Fe-B type alloy, it is necessary to remarkably increase the roll peripheral speed during the super-quenching, and thus the product recovery rate. In addition, since the alloy powder is pulverized after the heat treatment to make an alloy powder, the process becomes complicated and mass production cannot be performed at low cost.

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 type Nd which has improved ax and is capable of providing stable industrial production without using a super-quenching method and which has a residual magnetic flux density Br of 5 kG or more and can be provided at a low cost as a substitute for a hard ferrite magnet. The purpose is a -Fe-B system magnet.

[0011]

Means for Solving the Problems The inventors of the present invention have variously studied for the purpose of a manufacturing method capable of improving iHc and (BH) max of a Fe ₃ B type Fe-BR magnet and enabling stable industrial production. did. Conventionally, in this alloy composition, an amorphous structure was obtained by using a super-quenching method using a rotating roll,
With the specific alloy composition, the amorphous structure is obtained even in the region where the peripheral speed of the rotating roll is relatively slow (5 to 20 m / sec), and the gas atomizing method with a slower cooling rate than the ultra-quenching method is adopted. , Low content of rare earth elements, Co and Al, Si, Cu, Ga, Ag, Au
Of the iron-based alloy having a specific composition containing a small amount of at least one of the above are rapidly cooled by an atomizing method to obtain an alloy powder having an amorphous structure for the most part, and a fine crystal aggregate is formed by heat treatment at a specific heating rate. It has been found that by obtaining the above, it is possible to stably mass-produce the rare earth magnet alloy powder which is most suitable for the bond magnet having the residual magnetic flux density Br of 5 kG or more, which could not be obtained by the hard ferrite magnet, and completed the present invention.

[0012] The present invention, 1) represents the composition formula _{Fe 100-xyz Co x B y} R z ( where R is Pr or one or two of Nd), symbol limiting the composition range x, y, z Of the alloy melt satisfying the following values by an atomizing method to have substantially 90% or more of an amorphous structure and an alloy powder having an average particle diameter of 0.1 to 100 μm. 2) The obtained alloy powder has a temperature of 500 ° C. Heating rate from 1
Temperature rises at -15 ° C / min and 550-700 ° C for 30 seconds-6
3) Fe ₃ B type compound as a main phase and a ferromagnetic phase having an Nd ₂ Fe ₁₄ B type crystal structure and an average crystal grain size of 5 to 1
A method for producing a rare earth magnet alloy powder, which comprises obtaining a magnet alloy powder having a fine crystal aggregate of 00 nm. 0.05 ≦ x ≦ 15 at% 16 ≦ y ≦ 22 at% 3 ≦ z ≦ 5.5 at%

Further, the present invention is 1) the 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 Al, Si,
(Cu, Ga, Ag, Au, one or more kinds), and a symbol x, y, z, w that limits the composition range is substantially 90% or more of the molten alloy by the atomizing method. The average grain size is 0.1-100
μm alloy powder was obtained, and 2) the temperature rise rate from 500 ° C. was 1 for the obtained alloy powder.
Temperature rises at -15 ° C / min and 550-700 ° C for 30 seconds-6
3) Fe ₃ B type compound as a main phase and a ferromagnetic phase having an Nd ₂ Fe ₁₄ B type crystal structure and an average crystal grain size of 5 to 1
A method for producing a rare earth magnet alloy powder, which comprises obtaining a magnet alloy powder having a fine crystal aggregate of 00 nm. 0.05 ≦ x ≦ 15 at% 16 ≦ y ≦ 22 at% 3 ≦ z ≦ 5.5 at% 0.1 ≦ w ≦ 3 at%

[0014]

According to the present invention, the Fe-Co-B-R-M type alloy melt having a specific composition containing a small amount of rare earth elements is rapidly cooled by the atomizing method to substantially 90% or more of the amorphous structure. Alloy powder having an average particle size of 0.1 to 100 μm was obtained, and the obtained alloy powder was heated from 500 ° C. at a heating rate of 1 to 15 ° C./min, and then 550 to 7
By performing a heat treatment of holding at 00 ° C for 30 seconds to 6 hours, an alloy powder for rare earth magnets having a fine crystal aggregate having an average particle size of 5 to 100 nm is obtained, which is different from the ultra-quench method using a rotating roll. The magnet alloy powder can be manufactured without the need for the step of crushing the ribbon after the heat treatment.

Further, according to the present invention, in addition to the Fe ₃ B type compound phase of the main phase, the amount ratio of the ferromagnetic phase having the Nd ₂ Fe ₁₄ B type crystal structure phase is increased and the α-Fe phase is decreased, Al, S
Since at least one of i, Cu, Ga, Ag, and Au is contained, Br does not decrease even if Co is contained, and the squareness of the demagnetization curve is improved, resulting in iHc ≧ 3.
Magnetic properties of kOe, Br ≧ 8 kG, (BH) max ≧ 8 MGOe are obtained, and by further pulverizing this to make a magnetic alloy powder, Fe-Co most suitable for a bond magnet having a residual magnetic flux density Br of 5 kG or more. -B-R-M system magnet alloy powder can be obtained.

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 projected and iHc is remarkably lowered, which is not preferable, so that 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%.

Al, Si, Cu, Ga, Ag and Au have the effects of expanding the heat treatment temperature range to improve the squareness of the demagnetization curve and increasing the magnetic properties Br and (BH) max. In order to obtain the effect, it is necessary to add at least 0.1 at% or more, but if it exceeds 3 at%, the squareness is rather deteriorated and (BH) max is also lowered.
The range is 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 rapidly cooled by an atomizing method to make most of it amorphous.
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 thermodynamically stable Fe ₃ B type compound and a ferromagnetic phase having an Nd ₂ Fe ₁₄ B type crystal structure are obtained, It is most important to obtain a fine crystal aggregate having an average crystal grain size of 5 to 100 nm, and a known atomizing method can be used for quenching the molten alloy, but the alloy powder obtained by the atomizing method is substantially It is necessary to make 90% or more amorphous. For example, in the case of gas atomizing using Ar gas as a quenching gas, the substantial injection pressure is 10
The range of -80 kgf / cm ² is preferable because a suitable structure and powder particle size can be obtained. That is, the injection pressure is 10 kg
If it is less than f / cm ² , it does not become amorphous and α-Fe
Not only the amount of precipitation of the phase increases, but also the powder is deposited in the recovery container in a state where it is not sufficiently cooled, so that the powder is fused to form a lump, and the recovery rate of the alloy powder is significantly reduced. When the injection pressure exceeds 80 kgf / cm ² , the powder particle size is 0.1 μm.
Since the following fine powder is used, not only the recovery rate and recovery efficiency from the apparatus are lowered, but also the density is lowered during pressing, which is not preferable.

In the present invention, after the molten alloy having the above-mentioned specific composition is rapidly cooled by the atomizing method to make most of it amorphous, the heat treatment at which the magnetic characteristics become maximum depends on the composition, but the heat treatment temperature is 550 ° C. If less than 2, iHc of 2 kOe or more cannot be obtained in the amorphous phase and 700
When the temperature exceeds ℃, α-Fe phase and Fe ₂ B or Nd _1.1 Fe ₄ B ₄ phase, which are thermal equilibrium phases, are generated and iHc is not generated. Therefore, the heat treatment temperature is limited to 550 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 alloy powder according to the present invention is Fe ₃
A B-type compound as a main phase, a ferromagnetic phase having an Nd ₂ Fe ₁₄ B-type crystal structure, and a fine crystal aggregate having an average crystal grain size of 5 to 100 nm are featured.

In the present invention, if the average crystal grain size in the magnet alloy powder exceeds 100 nm, the squareness of the demagnetization curve is significantly deteriorated and Br ≧ 7 kG, (BH) max ≧ 8 MG.
The magnetic properties of Oe cannot be obtained. 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 5 nm in industrial production.
m.

Magnetization Method A molten alloy having a specific composition is rapidly cooled by an atomizing method, and most of the molten alloy has an amorphous structure. Average particle size is 0.1 to 100 μm.
Alloy powder was obtained, and the temperature was raised from 500 ° C. or higher at a rate of 1 to 10 ° C./minute, and then 30 at 550 to 700 ° C.
By magnetizing using the rare earth magnet alloy powder according to the present invention obtained as a fine crystal aggregate having an average crystal grain size of 5 to 100 nm by performing heat treatment for holding for 2 seconds to 6 hours, solidification at 700 ° C. or lower, Any of the known sintered magnetizing method and bond magnetizing method that can be consolidated can be adopted, and a bond having a residual magnetic flux density Br of 5 kG or more can be obtained by mixing with a known binder to form a required bond magnet. You can get a magnet.

[0028]

【Example】

Example 1 No. 1 in Table 1 Purity 99.5% so that the composition is 1-7
Fe, Co, B, Nd, Pr, Al, Si, C
Metals of u, Ga, Ag, and Au were weighed so that the total amount was 1 kg, and the mixture was put into an alumina crucible having an orifice with a diameter of 2.0 mm at the bottom, and the pressure was 56 cm.
It was melted by high-frequency heating in an Ar atmosphere of Hg, and when the melting temperature reached 1300 ° C., the stopper that closed the orifice was pulled out, the molten metal was allowed to flow out, and the gas injection nozzle immediately below the crucible had a purity of 99.9% By injecting Ar gas at a substantial pressure of 40 kgf / cm ² and quenching the molten alloy, an alloy powder having a particle size of several μm to 50 μm was obtained. The obtained alloy powder was confirmed to be amorphous by characteristic X-ray of CuKα.

This alloy powder was rapidly heated to 500 ° C. in Ar gas, then heated to 500 ° C. or more at a temperature rising rate of 10 ° C./min, heat-treated at the temperature and time shown in Table 1, and then to room temperature. Cool down to take out alloy powder, powder 30mg
After being mixed with paraffin, the magnetic properties of the sample that was heated and cured were measured using VSM. 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 Is 10
It was 0 mm or less. Note that Co is Fe in each of these phases.
Of Al, Si, Cu, Ga, Ag,
With respect to Au, the addition amount was small, and since it was an ultrafine crystal, analysis was impossible.

Example 2 Composition No. of Table 1 obtained in Example 1 After mixing the magnetic powder of No. 3 with a binder of epoxy resin at a ratio of 2 wt%, a bonded magnet having dimensions of 15 mm × 15 mm × 7 mm was prepared. The magnetic properties of the obtained bond magnet are iHc =
3.5 kOe, Br = 7.0 kG, (BH) max =
It was 5.5 MGOe.

[0031]

[Table 1]

[0032]

[Table 2]

[0033]

INDUSTRIAL APPLICABILITY The present invention has a specific composition of Fe-Co-B.
-RM alloy melt is rapidly cooled by a gas atomization method, and most of it has an amorphous structure.
By obtaining a 0 μm alloy powder and subjecting it to heat treatment under specific conditions, the amorphous alloy powder has an average crystal grain size of 5
The magnet alloy powder is a fine crystal aggregate of ˜100 nm.
Conventionally, in this alloy composition, a super-quenching method using a rotating roll was adopted to obtain an amorphous structure, but in the present invention, by adopting a quenching method using a gas atomizing method, a super-cooling method using a rotating roll is adopted. The crushing process of the ultra-quenching ribbon, which was required in the quenching method, is eliminated, and iHc can be simplified.
≧ 3 kOe, Br ≧ 8 kG, (BH) max ≧ 8 MGO
It is possible to stably supply a large amount of Fe-Co-B-R-M-based magnet alloy powder, which is optimum for a bonded magnet having a magnetic characteristic of e and a residual magnetic flux density Br of 5 kG or more. In addition, the present invention has a low content of rare earth elements, a simple manufacturing method, and is suitable for mass production, and therefore has a residual magnetic flux density Br of 5 kG or more and magnetic performance exceeding that of a hard ferrite magnet. By adopting integral molding of the magnetic component and the magnet body, the process can be shortened, and it is possible to provide a bond magnet that can realize a performance-to-cost ratio exceeding that of sintered hard ferrite.

Claims (2)

[Claims] The method according to claim 1] composition formula _{Fe 100-xyz Co x B y} R z
(However, R is one or two of Pr or Nd)
An alloy melt having a composition range limiting symbols x, y, and z satisfying the following values was obtained by an atomizing method to have substantially 90% or more of an amorphous structure, and an alloy powder having an average particle diameter of 0.1 to 100 μm was obtained. , The obtained alloy powder is heated at a heating rate from 500 ° C. at a rate of 1 to 15 ° C./min to 3 at 550 to 700 ° C.
A fine crystal aggregate having an average crystal grain size of 5 to 100 nm, which has been subjected to heat treatment for 0 second to 6 hours and has a ferromagnetic phase having an Fe ₃ B type compound as a main phase and an Nd ₂ Fe ₁₄ B type crystal structure. A method for producing a rare earth magnet alloy powder, comprising obtaining a magnet alloy powder having a body. 0.05 ≦ x ≦ 15 at% 16 ≦ y ≦ 22 at% 3 ≦ z ≦ 5.5 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
1, 1 or 2 or more of Si, Cu, Ga, Ag, and Au) and the symbols x, y, z, and w that limit the composition range substantially satisfy the following values by an atomizing method. 90% or more of which has an amorphous structure and an average grain size of 0.1
˜100 μm alloy powder was obtained, and the obtained alloy powder had 50
The temperature rising rate from 0 ° C. is raised at 1 to 15 ° C./min to 550
Heat treatment at ~ 700 ° C for 30 seconds to 6 hours is performed, and F
e 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 5 to 100 nm
2. A method for producing a rare earth magnet alloy powder, comprising obtaining a magnet alloy powder having the fine crystal aggregate according to 1. 0.05 ≦ x ≦ 15 at% 16 ≦ y ≦ 22 at% 3 ≦ z ≦ 5.5 at% 0.1 ≦ w ≦ 3 at%