JP2986611B2 - Fe-BR bonded magnet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION This invention, have to relate to a motor and the optimum Fe-BR based bonded magnet such as actuators, is Fe-Co-BR type having a specific composition containing a small amount of rare earth elements
Is made of an Fe-Co-RM alloy molten alloy by an ultra-quenching method to form an amorphous structure for the most part, and a main phase of a boride phase mainly composed of iron having a body-centered tetragonal Fe ₃ P type crystal structure and Nd _2. Fe-BR with a residual magnetic flux density Br of 5 kG or more, which was not obtained with hard ferrite magnets, by combining an alloy powder consisting of fine crystal aggregates with constituent phases of Fe ₁₄ B type crystal structure with resin
Related to bonded magnets.

[0002]

2. Description of the Related Art Permanent magnets used for motors and actuators for electrical components are mainly limited to hard ferrite magnets. 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. See Magn, Magn, Mat. , 89 (1991)
335-340), a part of Fe is replaced with Co to raise the Curie temperature 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 super-quenching method. For example, 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
It is an object of the present invention to provide an Fe ₃ B-type B-Fe-R bonded magnet that can improve the value of ax and has a residual magnetic flux density Br of 5 kG or more and can be provided at low cost as a substitute for a hard ferrite magnet that can be stably manufactured industrially.

[0011]

SUMMARY OF THE INVENTION The present invention provides an Fe ₃ B type Fe
As a result of various studies for the purpose of improving the iHc and (BH) max of the -BR magnet and enabling stable industrial production, the magnet was completed with the following knowledge.

When the content of the rare earth element is small,
When the Fe ₃ B phase is deposited by heat treatment after ultra-quenching the molten gold
In addition, a part of Fe in the Fe ₃ B phase is replaced by Co
In other words, as a result, it is not possible to obtain a completely amorphous phase
Also has the same crystal structure as Fe ₃ B, ie, body-centered tetragonal Fe ₃ P type
The main phase of the boride phase mainly composed of iron having a crystal structure is
After quenching and quenching, an appropriate heat treatment is applied.
The boride phase and the compound phase having the Nd ₂ Fe ₁₄ B type crystal structure
Coexist in the same powder particles and have an average crystal grain size of 10
When it is within the range of ~ 100 nm, the solid
Demonstrate coercive force and make this alloy powder into required shape with resin
Metastable crystal structure around room temperature by molding and solidifying
Form that can be used as a permanent magnet without phase decomposition
Can be provided as

According to the present invention, the composition formula of the alloy powder is Fe
_100-xyz Co _x B _y R _z (where R is one or two of Pr or Nd
The symbol x, y, z that limits the composition range satisfies the following values, and is composed mainly of iron having a body-centered tetragonal Fe ₃ P-type crystal structure.
And the constituent phases of the Nd ₂ Fe ₁₄ B type crystal structure are the same.
Coexist in one powder particle, the average crystal grain size of each constituent phase is 10nm
~ 100nm range, average particle size is 3μm ~ 500μm
This is a Fe-BR based bonded magnet characterized by combining powders with a resin . 0.05 ≦ x ≦ 15at% 16 ≦ y ≦ 22at% 3 ≦ z ≦ 5.5at%

Further, according to the present invention , the composition formula of the alloy powder is Fe
_{100-xyz -w} Co _x B _y R _z M _w (where R is one or two of Pr or Nd, M is one or more of Al, Si, Cu, Ga, Ag, Au) , Symbols x, y, z, w that limit the composition range satisfy the following values
Iron with a body-centered tetragonal Fe ₃ P-type crystal structure
Boride phase and constituent phase of Nd ₂ Fe ₁₄ B type crystal structure
Powder, and the average crystal grain size of each constituent phase is 10 nm to 10
Powder in the range of 0 nm with an average particle size of 3 μm to 500 μm
Are bonded by a resin . 0.05 ≦ x ≦ 15at% 16 ≦ y ≦ 22at% 3 ≦ z ≦ 5.5at% w ≦ 3at%

To obtain the Fe-BR based bonded magnet according to the present invention, the following production method is used. (1) The composition formula is Fe _100-xyz Co _x B _y R _z (where R is Pr or Nd
1 or 2), or the composition formula is Fe _{100-xyz -w} Co _x B
_y R _z M _w (where R is one or two of Pr or Nd, M is Al, S
i, Cu, Ga, Ag, one or two or more of Au), and the symbols x, y, z, and w that limit the composition range are substantially the same as those of the alloy melt that satisfies the above-described values by the ultra-quenching method. (2) In addition, the rate of temperature increase from 500 ° C to 1-15 ° C /
Heat treatment at 550 to 700 ° C for 5 minutes to 6 hours, and (3) a ferromagnetic phase having a Fe ₃ B type compound as a main phase and an Nd ₂ Fe ₁₄ B type crystal structure. Then, after obtaining a fine crystal aggregate having an average crystal grain size of 10 to 100 nm, (4) a powder having an average grain size of 3 to 500 μm obtained by pulverizing this is solidified into a required shape with a resin. .

Reasons for Limiting Constituent Phase of Powder The alloy powder constituting the bonded magnet according to the present invention comprises:
It is characterized in that the main phase is a boride phase mainly composed of iron having a body-centered tetragonal Fe ₃ P type crystal structure having a high saturation magnetization of 6T. In this boride phase, Fe ₃ B or a part of Fe therein is substituted with Co. This boride phase is metastable in a specific range in the space group P ₄ / nm.
Nd _{2 (} Fe, C having n-type Nd ₂ Fe ₁₄ B-type crystal structure
o) Can coexist with _14B ferromagnetic phase. The coexistence of these boride phase and ferromagnetic phase requires high magnetic flux density and sufficient iHc
For example, in the casting method or the like, the Fe ₂ B phase having the C16 type crystal structure and the body-centered cubic α-Fe phase are indispensable for obtaining In the main phase, high magnetization is obtained, but iHc is 1 kOe.
It is not preferable because it deteriorates below and cannot be used as a magnet.

Reasons for Limiting Composition Rare earth element R can provide high magnetic properties only when it contains one or two 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 5.5 at%, F
R ₂ F, a metastable phase that does not produce e ₃ B phase and shows no hard magnetism
Since e ₂₃ B ₃ phase folding out iHc is not preferable because it decreases significantly, and the range of 3~5.5at%.

When B is less than 16 at% and 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 the demagnetization curve. However, if the content is less than 0.05 at%, such an effect cannot be obtained. If it exceeds 15 at%, iHc is remarkably reduced, and 2 kOe or more. Since iHc cannot be obtained, 0.
The range is from 0.5 to 15 at%.

Al, Si, Cu, Ga, Ag and Au have the effect of expanding the heat treatment temperature range, improving the squareness of the demagnetization curve, and increasing the Br and (BH) max of the magnetic characteristics. %, It degrades the squareness,
Since (BH) max also decreases, the range is set to 3 at% or less.

Fe accounts for the residual content of the above-mentioned elements.

Reasons for Limiting Crystal Particle Size and Powder Particle Size Coexist in the alloy powder constituting the bonded magnet of the present invention.
Both the boride phase mainly composed of iron having the body-centered tetragonal Fe ₃ P type crystal structure of the main phase and the Nd ₂ Fe ₁₄ B type crystal phase are ferromagnetic phases, but the former phase alone is magnetic. It is indispensable to express iHc that it is soft in nature and the latter phase coexists. However, simply coexisting both phases is not enough, and if the average grain size of both is not in the range of 10 to 100 nm,
Since the squareness of the second quadrant of the demagnetization curve deteriorates and the operating point cannot extract a sufficient magnetic flux as a permanent magnet, the average crystal grain size is limited to 10 nm to 100 nm. Making use of the characteristics of bonded magnets that can produce magnets with complex shapes and thin shapes, high-precision molding requires that the powder particle size be sufficiently small. It is necessary to use a large amount of resin as a binder as the surface area increases, and the packing density decreases, which is not preferable.

The bonded magnet according to the present invention is an isotropic magnet, and has the following compression molding, injection molding, extrusion molding,
Any known production method such as rolling molding and resin impregnation may be used. In the case of compression molding, it is obtained by adding and kneading a thermosetting resin, a coupling agent, a lubricant and the like to the magnetic powder, and then compressing and heating to cure the resin. In the case of injection molding, extrusion molding, and rolling molding, a thermoplastic resin, a coupling agent, a lubricant, etc. are added and kneaded to the magnetic powder, and then molded by any of injection molding, extrusion molding, and rolling molding. Can be In the resin impregnation method, after magnetic powder is compression-molded, heat-treated if necessary, then impregnated with a thermosetting resin, and heated to cure the resin. Further, the magnetic powder is obtained by compression molding, heat-treating as necessary, and then impregnating with a thermoplastic resin.

In the present invention, the filling rate of the magnetic powder in the bonded magnet varies depending on the above-mentioned manufacturing method.
5 wt%, and the remaining 0.5 to 30 wt% is resin and others. In the case of compression molding, the filling ratio of the magnetic powder is 95 to 9
9.5 wt%, in the case of injection molding, the filling rate of the magnetic powder is 9
In the case of the resin impregnation method, the filling rate of the magnetic powder is preferably 96 to 99.5 wt%.

As the synthetic resin used as the binder, those having both thermosetting properties and thermoplastic properties can be used, but thermally stable resins are preferable. For example, polyamides, polyimides, phenol resins, fluorine resins, and silicon resins are used. A basic resin, an epoxy resin, or the like can be appropriately selected.

[0026]

SUMMARY OF THE INVENTION This invention after rapid quenching method Fe-Co-BRM species alloy having a specific composition containing a small amount of rare earth elements, a body-centered tetragonal Fe ₃ P type crystalline structure of the space group I ₄ was heat-treated When forming a metastable mixed structure of a main phase of a boride phase having iron as a main component and a Nd ₂ Fe ₁₄ B type crystal phase, since a specific amount of Co is contained, a space group I ₄ which is a metastable phase An iron-based boride phase having a body-centered tetragonal Fe ₃ P-type crystal structure is stabilized, and even if it does not have a completely amorphous structure, an average having the boride phase of the space group I ₄ as a main phase It becomes a fine crystal aggregate with a crystal grain size of 10 to 100 nm, and in addition to a boride phase mainly composed of iron having a body-centered tetragonal Fe ₃ P type crystal structure of the main phase, a Nd ₂ Fe ₁₄ B type crystal structure An alloy powder for a bonded magnet in which a ferromagnetic phase having coexistence is obtained, and by bonding with a resin, iHc ≧ 2 kOe, Br ≧ 5 kG, (BH)
A bonded magnet having magnetic properties of max ≧ 3MGOe can be obtained.

[0027]

【Example】

Example No. 1 in Table 1 Purity 99.
5% or more of Fe, Co, B, Nd, Pr, Cu, Ga,
Using metals of Ag, Au, Al and Si, the total amount is 30 g
r, and put into a quartz crucible having an orifice with a diameter of 0.8 mm at the bottom, and a pressure of 56 cmHg.
Melted by high-frequency heating in an Ar atmosphere, and the melting temperature was set to 1400 ° C., and the molten metal surface was pressurized with Ar gas to rotate at room temperature at a peripheral speed of 20 m / sec. The molten metal was blown out from a height of 0.7 mm to produce a super-quenched ribbon having a width of 2 to 3 mm and a thickness of 30 to 40 μm. Most of the obtained ultra-quenched ribbon was characterized by CuKα characteristic X-ray and SEM photograph of the cross section of the ribbon (about 90 vol.).
% Or more) was amorphous.

After the ultra-quenched ribbon was rapidly heated to 500 ° C. in Ar gas, the temperature was raised to 500 ° C. or higher at the temperature rising rate shown in Table 1, and kept at the heat treatment temperature shown in Table 1 for 10 minutes. After cooling to room temperature, the ribbon was removed. The structure of the sample was such that the tetragonal Fe ₃ B phase was the main phase, and the Nd ₂ Fe ₁₄ B phase and α
-Fe phase was mixed, and the average crystal grain size was 0.1 µm or less in each case. Note that Co replaces part of Fe in each of these phases.

This ribbon is pulverized to a particle size of 5 to 120 μm.
After obtaining a powder having an average particle size of 60 μm distributed over m, an epoxy resin was mixed at a ratio of 2 wt% with respect to 98 wt% of the powder, compression molded at a pressure of 6 ton / cm ² , and cured at 150 ° C. To obtain a bonded magnet. The density of this bonded magnet was 5.6 gr / cm ³ , and the magnet properties are shown in Table 2.

Comparative Example The composition No. of Example 1 obtained under the same conditions as Example 1 5 was rapidly heated to 500 ° C. in Ar gas, and the temperature was raised from 500 ° C. or higher at 11 ° C./min.
A heat treatment was performed for 5 minutes, and after cooling, a sample was prepared under the same conditions as in Example 1 (Comparative Example No. 12), and the magnetic properties were measured. 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. No. 13 was heat-treated at 500 ° C. for 10 minutes. In No. 14, a heat treatment was performed at 500 ° C. or more at a rate of 4 ° C./min and held at 750 ° C. for 10 minutes. After cooling, a sample was formed under the same conditions as in Example 1 and the magnetic properties were measured. Table 2 shows the measurement results. Comparative Example N
o. No. 13 is an amorphous structure; 14 is Fe ₂ B
It had a multiphase structure in which a phase and an α-Fe phase were mixed.

[0032]

[Table 1]

[0033]

[Table 2]

[0034]

According to the present invention, a Fe-Co-BR-based or Fe-Co-BRM-based alloy melt having a specific composition with a small content of rare earth elements can be ultra-quenched and then heat-treated to obtain a completely amorphous structure. The average crystal grain diameter of the main phase is a boride phase having iron as a main component having a body-centered tetragonal Fe ₃ P-type crystal structure and 10 to 100 n
m, and in addition to the boride phase, Nd ₂ Fe
₁₄ An alloy powder for a bonded magnet in which a ferromagnetic phase having a B-type crystal structure coexists is obtained, and by bonding with a resin, iHc ≧ 2 kO
e, a bond magnet having magnetic properties of Br ≧ 5 kG and (BH) max ≧ 3MGOe can be obtained.

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01F 1/08 C22C 38/00 303 H01F 1/053

Claims (2)

(57) [Claims] The method according to claim 1] of the alloy powder composition formula _{Fe 100-xyz Co x B y} R z
(Where R is one or two of Pr or Nd), and the symbols x, y, and z that limit the composition range satisfy the following values, and the body-centered square
Fe-based boride phase with crystalline Fe ₃ P-type crystal structure
And the constituent phases of the Nd ₂ Fe ₁₄ B type crystal structure in the same powder particle
And the average crystal grain size of each constituent phase is in the range of 10 nm to 100 nm.
Yes, powder with an average particle size of 3 μm to 500 μm
Fe-BR based bonded magnet characterized by being combined . 0.05 ≦ x ≦ 15at% 16 ≦ y ≦ 22at% 3 ≦ z ≦ 5.5at% 2. A method of the alloy powder composition formula _{Fe 100-xyz -w Co x B} y
R _z M _w (where R is one or two of Pr or Nd, M is Al, Si, C
u, Ga, Ag, one or more of Au), and the symbols x, y, z, and w that limit the composition range satisfy the following values, and the body-centered tetragonal Fe
₃ Boride phase mainly composed of iron with P-type crystal structure and Nd
₂ Constituent phases of Fe ₁₄ B type crystal structure coexist in the same powder particle
The average crystal grain size of each constituent phase is in the range of 10 nm to 100 nm.
Powder with an average particle size of 3 μm to 500 μm
Fe-BR based bonded magnet is characterized in that the. 0.05 ≦ x ≦ 15at% 16 ≦ y ≦ 22at% 3 ≦ z ≦ 5.5at% w ≦ 3at%