JP3131022B2 - Fe-BR bonded magnet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Fe-BR based bonded magnet which is most suitable for a motor or an actuator, and has a specific composition of Fe-Ni-B- (R, Dy) -M having a low rare earth element content. system molten alloy (where R is one or two Pr or Nd) forms a majority of an amorphous tissue in rapid quenching, containing iron as a main component having a body-centered tetragonal Akirayui <br/> crystal structure Boride phase and Nd ₂ Fe ₁₄ B
The present invention relates to a Fe-BR based bonded magnet having a residual magnetic flux density Br of 5 kG or more, which cannot be obtained with a hard ferrite magnet, by bonding an alloy powder comprising a fine crystal aggregate with a constituent phase having a type crystal structure with a resin.

[0002]

2. Description of the Related Art Permanent magnets used in motors and actuators for electrical components are mainly limited to hard ferrite magnets.
Due to the ceramic material, there were problems such as low mechanical strength, cracking and chipping easily occurring, and difficulty in obtaining 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.
Approximately 7 kG is considered optimal. In other words, when the Br of the magnet material 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 a magnetic path, and causes an increase in weight.
5-7kG can maximize the performance to weight ratio.

Accordingly, magnetic materials for small motors are required to have a residual magnetic flux density Br of at least 5 kG in terms of magnetic properties, but cannot be obtained with conventional hard ferrite magnets. For example, an Nd-Fe-B bonded magnet satisfies such magnetic properties, but contains 10 to 15 at% of Nd or the like, which requires a large number of steps and large-scale facilities for metal separation and purification and reduction reactions. Magnet materials with a Br of about 5 to 7 kG, which are significantly more expensive than ferrite magnets and can be mass-produced and can be provided at low cost, have not been found at present.

[0005]

On the other hand, among Nd-Fe-B based magnets, recently, 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 (R .Coehoorn et al., J.de Phy
s., C8, 1988, 669-670). This magnet material is made by heat-treating an amorphous ribbon to obtain Fe ₃ B and Nd ₂ Fe.
It is a metastable structure with a crystal texture of ₁₄ B, but iHc
It is not as high as about 2 to 3 kOe, and the heat treatment conditions for obtaining this iHc are narrow and limited, which is not practical for industrial production.

Researches have been published to improve the performance by adding an additional element to the magnet material having the Fe ₃ B type compound as a main phase to make it a multi-component. One of them is rare earth elements, Nd, and Dy.
And Tb to improve iHc, but in addition to the problem of adding expensive elements, the magnetization of the added rare earth element decreases because its magnetic moment couples antiparallel to the magnetic moment of Nd or Fe (R. Coehoorn, J. Magn,
Magn, Mat., 83 (1990) pp. 228-230).

Other studies (Shen Bao-gen et al., J. Magn, Magn, M.
at., 89 (1991) pp. 335-340), a part of Fe is replaced with Co to increase the Curie temperature and improve the temperature coefficient of iHc, but with the addition of Co, Br There is a problem of lowering.

In any case, the Fe ₃ B type Nd—Fe—B magnet is
After being made amorphous by the super-quenching method, heat treatment can be performed to form a hard magnet material.However, the iHc is low, and the heat treatment conditions are narrow. It cannot be manufactured industrially and cannot be provided at low cost as a substitute for hard ferrite magnets.

Further, in order to make the Nd-Fe-B alloy amorphous, it is necessary to remarkably increase the peripheral speed of the roll during super-quenching, which causes a problem of lowering the product recovery rate and the yield. 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), improves iHc and (BH) max, and has a stable industrial flux having a residual magnetic flux density Br of 5 kG or more. Fe ₃ B can be provided at low cost as an alternative to hard ferrite magnets that can be produced
It is intended for B-Fe-R type bonded magnets.

[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. Rare earth element R (R: Pr, Nd
By substituting Dy for one part of (1 or 2 types), Nd ₂ F
improve the anisotropic magnetic field of the e ₁₄ B phase, there is ensured a high coercive force, a small amount of additives Ni, part of Fe of the Fe ₃ B phase is replaced with Ni, as a result, a completely amorphous phase without obtain the same crystal structure as Fe ₃ B, i.e., out boride phase folding composed mainly of iron having a body-centered tetragonal Akirayui crystal structure, after further quenching, by appropriate heat treatment, and the borides Nd ₂ F
additive element M (M is Al, Si, Cu, Ga, Ag, 1 kind or two kinds of Au) of refining the crystal grain size when crystallizing the compound of e ₁₄ B type crystal structure by the addition of Can solve the problems of demagnetization curve squareness deterioration and remanence magnetization decrease due to Dy addition, and the boride phase and the compound phase of Nd ₂ Fe ₁₄ B type crystal structure coexist in the same powder particles. In addition, when the average crystal grain size is in the range of 5 nm to 100 nm, a specific coercive force of 2 kOe or more, which is practically necessary, is exhibited, and the alloy powder is molded and solidified into a required shape with a resin, thereby reducing the room temperature. The metastable crystal structure phase is not decomposed in the vicinity, and can be provided as a form usable as a permanent magnet.

According to the invention, the composition formula of the alloy powder is Fe
_{100-xyz Ni x B y (} R 1-a Dy a) z M w ( where R is 1 Pr or Nd
Species or two, M is one or two of Al, Si, Cu, Ga, Ag, Au
And x, y, z, a, w
There satisfies the following values, and the body-centered boride phase composed mainly of iron having a tetragonal Akirayui crystal structure and Nd ₂ Fe ₁₄ configuration phase B type crystal structure coexist in the same powder particles, the respective constituent phases Has an average grain size of
A Fe-BR-based bonded magnet characterized in that powder having an average particle diameter of 3 nm to 500 μm in a range of 5 nm to 100 nm is bonded with a resin. 0.01 ≦ x ≦ 2at% 16 ≦ y ≦ 22at% 3 ≦ z ≦ 5.5at% 0.02 ≦ a ≦ 0.9 0.1 ≦ w ≦ 3at%

To obtain the Fe-BR based bonded magnet according to the present invention, the following manufacturing method is used. (1) the composition formula _{Fe 100-xyz Ni x B y} (R 1-a Dy a) z M w ( where R is P
r or Nd one or two, M is Al, Si, Cu, Ga, Ag, Au
One or two or more), and a symbol that limits the composition range
x, y, z, a, w make the molten alloy satisfying the above values substantially 90% or more amorphous structure by ultra-quenching method. (2) Further increase the heating rate from 500 ° C during heat treatment. 1 ~ 15 ℃ /
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 5 nm to 100 nm, (4) molding and solidifying a powder having an average grain size of 3 to 500 μm obtained by grinding the resin into a required shape. .

Reasons for Limiting Constituent Phase of Powder The alloy powder constituting the bonded magnet according to the present invention is 1.6 T
It is characterized in that the main phase of boride phase composed mainly of iron having a body-centered tetragonal Akirayui crystal structure having a high saturation magnetization that. This boride is composed of Fe ₃ B or a part of Fe
In this boride phase, Fe ₃ B or a part of Fe therein is substituted by Ni. This boride phase is metastable in a specific range with Nd ₂ Fe in the space group P ₄ / nmn.
_It can coexist with Nd ₂ (Fe, Ni) ₁₄ B ferromagnetic phase having ₁₄ B type crystal structure. The coexistence of these boride phase and ferromagnetic phase is essential for obtaining high magnetic flux density and sufficient iHc,
Be the same composition, for example in such casting due to its production method, when the Fe ₂ B phase and the body-centered cubic alpha-Fe phase becomes the main phase having a C16 type crystal structure, high magnetization is obtained But i
Hc is not preferable because it deteriorates to 1 kOe or less and cannot be used as a magnet.

Reasons for Limiting Composition Rare earth elements R can obtain high magnetic properties only when they contain Dy in addition to one or two kinds of specific amounts of Pr or Nd, and other rare earth elements such as Ce and La Characteristics with iHc of 2 kOe or more cannot be obtained, and medium rare earth elements and heavy rare earth elements after Sm are not preferable because they cause deterioration of magnetic characteristics and increase the price of magnets. If R is less than 3 at%, iHc of 2 kOe or more cannot be obtained, and if it exceeds 5.5 at% , iron having a body-centered tetragonal crystal structure
A boride phase containing no main component is not generated, and the metastable phase R ₂ Fe ₂₃ B ₃ phase showing no hard magnetism is undesirably reduced because the iHc is remarkably reduced. I do. In R
The reason for limiting the Dy amount to 0.02 to 0.9 is that if it is less than 0.02, 4 kOe
This is because the above iHc cannot be obtained, and when it exceeds 0.9, the decrease in Br is extremely undesirable.

B is 2 kO if it is less than 16 at% and more than 22 at%.
Since iHc higher than e cannot be obtained, the range is 16 to 22 at%.

Ni is effective for improving and improving the squareness of the iHc and demagnetization curve. However, if the content is less than 0.01 at%, such an effect cannot be obtained. If the content exceeds 2 at%, the iHc is remarkably reduced, and i more than 2 kOe.
Since Hc cannot be obtained, the range is 0.01 to 2 at%.

Al, Si, Cu, Ga, Ag, and Au contribute to control of the microcrystalline structure, expand the heat treatment temperature range, improve the squareness of the demagnetization curve, and increase the magnetic properties of Br and (BH) max. It is necessary to add at least 0.1 at% or more to obtain such an effect.However, if it exceeds 3 at%, the squareness is rather deteriorated, and (BH) max also decreases. The range is 3 at%.

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

The crystal grain size, powder particle size limitation reasons boride phase and Nd ₂ Fe ₁₄ composed mainly of iron having a body-centered tetragonal Akirayui crystal structure coexist in the alloy powder constituting the bonded magnet of the present invention The B-type crystal phases are all ferromagnetic phases,
The former phase alone is magnetically soft, and the coexistence of the latter phase is essential for expressing iHc. However, simply coexisting both phases is not enough, and if the average crystal grain size of both is not in the range of 5 nm to 100 nm, the squareness of the second quadrant of the demagnetization curve deteriorates, and as a permanent magnet, Since sufficient magnetic flux cannot be extracted at the operating point, the average crystal grain size is limited to 5 nm to 100 nm. In order to perform high-precision molding by taking advantage of the characteristics of bonded magnets that can produce magnets with complex shapes and thin shapes, it is necessary that the particle size of the powder 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.
Limited to 3 μm to 500 μm.

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 ratio of the magnetic powder in the bonded magnet varies depending on the above-mentioned manufacturing method.
And the remaining 0.5 to 30% by weight is resin and the like. In the case of compression molding, the filling rate of magnetic powder is 95 to 99.5 wt%, in the case of injection molding, the filling rate of magnetic powder is 90 to 95 wt%, and in the case of resin impregnation method, the filling rate of magnetic powder is 96 to 99.5 wt% Is preferred

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.

[0024]

According to the present invention, by replacing a part of the rare earth element R (R is one or two of Pr and Nd) with Dy, a specific composition F
e-Ni-BRM alloy melt is heat treated after ultra-rapid cooling method
When forming a metastable mixed structure of boride phase and Nd ₂ Fe ₁₄ B crystal phase composed mainly of iron having a body-centered tetragonal Akirayui crystal structure of I _4, for containing a certain amount of Ni, quasi Space group that is stable phase
Boride phase is stabilized mainly composed of iron having a body-centered tetragonal Akirayui crystal structure of I _4, completely without the amorphous structure, the average crystal main phase the boride phase of space group I ₄ It becomes a fine crystal aggregate with a particle size of 5 nm to 100 nm, and the body-centered square of the main phase
Other boride phase composed mainly of iron having a Akirayui crystal structure, an alloy powder for a bonded magnet ferromagnetic phase having a Nd ₂ Fe ₁₄ B crystal structures coexist is obtained, by coupling with the resin, iH
It is possible to obtain a bonded magnet having magnetic characteristics of c ≧ 4 kOe, Br ≧ 5 kG, and (BH) max ≧ 3MGOe.

[0025]

Examples Example 1 was prepared so that the composition of No. 1 to 6 in Table 1 had a purity of 99.5% or more.
Using a metal of e, Ni, B, Nd, Pr, Dy, Cu, Ga, Ag, Au, Al, Si, weigh so that the total amount becomes 30 gr,
Put into a quartz crucible with an orifice of 0.8 mm, melt it by high frequency heating in an Ar atmosphere at a pressure of 56 cmHg, set the melting temperature to 1400 ° C, pressurize the molten metal surface with Ar gas, and roll Spraying molten metal from a height of 0.7 mm onto the outer peripheral surface of a Cu roll that rotates at a high speed of 20 m / sec.
An ultra-quenched ribbon having a thickness of 30 to 40 μm was prepared. It was confirmed that most of the obtained ultra-quenched ribbons were amorphous (about 90 vol% or more) by characteristic X-rays of CuKα and SEM photographs of cross sections of the ribbons.

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 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. Tissue samples, boride phase composed mainly of iron having a body-centered positive <br/>-cubic crystal structure in the main phase,
It had a multiphase structure in which Nd ₂ Fe ₁₄ B phase and α-Fe phase were mixed, and the average crystal grain size was 0.1 μm or less in each case. Note that Co replaces a part of Fe in each of these phases.

This ribbon was pulverized to obtain a powder having an average particle diameter of 60 μm distributed over a particle size of 5 to 120 μm. Then, 98% by weight of the powder was mixed with 2% by weight of an epoxy resin, and then 6 tons. It was compression molded at a pressure of / cm ² and cured at 150 ° C. to obtain a bonded magnet. The density of this bonded magnet is 5.6gr /
cm ³ and the magnet properties are shown in Table 2.

Comparative Example Fe and N having a purity of 99.5% or more so as to have the compositions of Nos. 7 to 9 in Table 1.
Using i, B, Nd, and Ga, a super-quenched ribbon was produced under the same conditions as in Example 1. The obtained super-quenched ribbon is placed in Ar gas for 500
After rapidly heating to 500 ° C, the temperature was raised to 500 ° C or higher at the temperature raising rate shown in Table 1, subjected to a heat treatment for 10 minutes at the heat treatment temperature shown in Table 1, cooled, and then sampled under the same conditions as in Example 1. The magnetic properties were measured. Table 2 shows the measurement results.

[0029]

[Table 1]

[0030]

[Table 2]

[0031]

According to the present invention, R (R is Nd, Pr)
One or two types) Fe-N of a specific composition in which a part of
iB- (R, Dy) after rapid quenching the -M species alloy, heat treatment, even without completely amorphous structure, the main phase of boride phase composed mainly of iron having a body-centered tetragonal Akirayui crystal structure An average crystal grain size of 5 nm to 100 nm becomes a fine crystal aggregate, in addition to the boride phase, an alloy powder for a bonded magnet in which a ferromagnetic phase having an Nd ₂ Fe ₁₄ B type crystal structure is obtained, and a resin is obtained. By bonding, a bonded magnet having magnetic characteristics of iHc ≧ 4 kOe, Br ≧ 5 kG, and (BH) max ≧ 3MGOe can be obtained.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H01F 1/08 B22F 1/00 B22F 3/00 C22C 38/00

Claims (1)

(57) [Claims] The method according to claim 1] of the alloy powder composition formula _{Fe 100-xyz Ni x B y} (R
_1-a Dy _a ) _z M _w (where R is one or two of Pr or Nd, M is A
l, Si, Cu, Ga, Ag, expressed as one or more Au), symbol x to limit the composition range, y, z, a, w satisfies the following values, body-centered tetragonal Akirayui crystal and the configuration phases of boride phase and Nd ₂ Fe ₁₄ B crystal structure composed mainly of iron coexist in the same powder particle having a structure, average grain size of each component phase is in the range of 5nm~100nm A Fe-BR-based bonded magnet, wherein powder having an average particle diameter of 3 μm to 500 μm is bonded with a resin. 0.01 ≦ x ≦ 2at% 16 ≦ y ≦ 22at% 3 ≦ z ≦ 5.5at% 0.02 ≦ a ≦ 0.9 0.1 ≦ w ≦ 3at%