JP2003224009A - Method for manufacturing anisotropic rare earth magnetic powder and bonded magnet using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rare earth magnetic powder for bonded magnets, and a method for manufacturing anisotropic rare earth bonded magnets by using the same, wherein rare earth magnet wastes are efficiently converted into a rare earth powder for bonded magnets with but a little recycling energy and manpower, consequently, contributing for effective use of rare earth resources. <P>SOLUTION: Deficient products or wastes of rare earth magnets, wherein a hard magnetic phase is constituted by intermetallic compounds of rare earths and transition metals, are utilized as the alloy material or part thereof for manufacturing magnetic powder. The alloy material is melted and then rapidly cooled for development into an alloy piece by the strip cast method. The alloy piece is made to absorb hydrogen gas at high temperature and then to desorb the same. The result is a rare earth alloy powder having an average diameter of 1 μm or less in its hard magnetic phase, with crystal axes uniformly in a specified direction. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing anisotropic rare earth magnet powder and a method for producing a bonded magnet using the same.

[0002]

2. Description of the Related Art In recent years, high-performance rare earth sintered magnets have been used in information and communication equipment, control equipment, light electric appliances for consumer use that use small motors, medical diagnostic equipment, etc., and their production volume has been increasing year by year. There is. In addition, a rare earth bonded magnet used for a cylindrical magnet for a small motor and the like can be manufactured by a simple process as compared with a sintered magnet, so that the production amount is increasing. Especially in the manufacture of Nd-Fe-B system sintered magnet, starting from alloy melting, crushing, molding,
The final magnet product is completed after sintering, cutting / polishing, and surface treatment, but the magnet scrap such as defective sintering and polishing scraps generated in this manufacturing process reaches several tens% of the charged amount of magnet,
It is estimated to reach several thousand tons per year. In addition, it is expected that the amount of magnet scrap that is discarded after being incorporated into household electric appliances in the city will increase in the future. Since these scraps contain a considerable amount of rare earth elements which are rare resources, their recovery and reuse are required. Since the rare earth bonded magnet does not have a cutting or polishing step after molding and the quality such as magnetic characteristics and dimensional characteristics is stable, scrap generation in the step is relatively small as compared with the sintered magnet.

The following method has been proposed as a method for reusing a defective product of the above sintered magnet.
After being dissolved in an acid, only the rare earth element is solvent-extracted, separated and dried, and further oxidized to obtain a raw material for a sintered magnet again (JP-A-5-287405, JP-A-9-217).
132 publication). Defective sintering products are crushed, acid-washed and dried, and then calcium reduction is performed to reuse them as an auxiliary material for sintering alloy powder (Japanese Patent Laid-Open No. 11-319752,
JP-A-11-329811). Nd-Fe-B
A Ni plating film may be formed on the surface of the system sintered magnet as a rust preventive treatment. Ni is a factor that reduces the residual magnetization in Nd-Fe-B system sintered magnets, so N
When a sintered magnet scrap having an i-plated film is reused as a raw material for a sintered magnet, it is considered necessary to remove it. As a specific method, a method is used in which a sintered magnet is made to absorb and release hydrogen to be pulverized, only the Ni plating film is separated, and the residual powder is used as a raw material alloy (Japanese Patent Laid-Open No. HEI 5-
No. 33073), a method of separating the Ni film by mechanical means such as shot peening and using the residual powder as a raw material alloy (Japanese Patent Laid-Open No. 13-40425), and the like.

Generally, rare earth sintered magnets are Nd, Fe, B
Since high magnetic properties are secured by manufacturing by suppressing as much as possible O, C, Ni, Al, etc. other than the main constituent elements such as, the removal of these impurity elements during scrap reuse It has become a challenge. However, Nd-Fe-B, which is a raw material for anisotropic rare earth bonded magnets,
HDDR powder produced by hydrogen treatment of a system alloy ingot can secure magnetic properties by controlling the size and direction of the fine crystal structure inside the powder, and the influence of raw material impurities is better than that of a sintered magnet. Small. Furthermore, in recent years, a strip casting method, which can obtain a homogeneous alloy in which the segregation of the components is suppressed by rapidly solidifying the molten alloy, is being put to practical use in the production of alloys for sintered magnets.

[0005]

The rare earth sintered magnet has a large amount of scraps generated in the process, and in order to reuse the recovered products in the city in the future, a method with high production efficiency and low renewable energy is required. Is required. However, the above method requires a large amount of energy for oxidation, needs to repeat the step of extracting and separating rare earth elements several times, and has many problems such as the problem of acid solution treatment, which is economically problematic. The other method also requires high-temperature energy for calcium reduction, and also has a problem that the powder is easily oxidized when the calcium oxide, which is a by-product of the reduction treatment, is removed from the reduced powder by washing with water. On the other hand, the Ni film peeling method (1) has the problems that complete separation is difficult and that it takes time to regenerate the raw material alloy. The method of re-grinding a sintered magnet, press-molding it, and re-sintering it into a magnet is an industrial method because the magnetic properties such as coercive force are significantly deteriorated due to the oxidation of powder and deterioration of particle size distribution. Is not used.

The object of the present invention is to efficiently convert rare earth magnet scraps into anisotropic rare earth bonded magnet powders with a small amount of regeneration energy and man-hours, and thus to improve the effective utilization of rare earth resources. It is to provide a manufacturing method and a bonded magnet manufacturing method using the manufacturing method.

[0007]

In order to achieve the above object, the present invention provides a defective manufactured product or a discarded product of a rare earth magnet having a hard magnetic phase composed of an intermetallic compound of a rare earth element and a transition metal element. (Hereinafter, both are collectively referred to as rare earth magnet scrap) is used as a part or all of the alloy raw material, and the alloy raw material is melted by a strip casting method and then rapidly cooled to form an alloy piece, and subsequently the alloy piece is hydrogenated at high temperature By absorbing the gas and then desorbing the hydrogen gas, the hard magnetic phase is made into fine particles with an average particle size of 1 μm or less, and a powder having a crystal structure in which the crystal axes are aligned in a specific direction is formed. A method for producing anisotropic rare earth magnet powder is provided.

[0008] Further, defectively manufactured or discarded rare earth magnets whose hard magnetic phase is composed of an intermetallic compound of a rare earth element and a transition metal element (hereinafter, both are collectively referred to as rare earth magnet scraps) are used as an alloy raw material. The alloy raw material was melted by the strip casting method and then rapidly cooled to form alloy pieces, and the crystal structure in the alloy pieces was homogenized by high temperature heat treatment, and subsequently hydrogen gas was absorbed at high temperature. An anisotropic rare earth, which is made into a powder having a crystal structure in which the hard magnetic phase has an average particle size of 1 μm or less by desorption of hydrogen gas later and the crystal axes thereof are aligned in a specific direction. A method for manufacturing magnet powder is provided.

Further, in the rare earth magnet scrap, the intermetallic compound forming the hard magnetic phase is R ₂ Fe ₁₄ B (where R is N
(a rare earth element whose main component is d) having a stoichiometric composition of
R-Fe-B system rare earth sintered magnet scrap in which a hard magnetic phase is sinter-bonded by a grain boundary phase containing a rare earth element R as a main component, and the rare earth magnet powder is an R-Fe-B system anisotropic rare earth. A method for manufacturing a bonded magnet powder is provided. Also, R-
Fe-B rare earth sintered magnet scrap has Ni,
Provided is a method for producing anisotropic rare earth bonded magnet powder which has a coating film of either Al or Cr and is used as an alloy raw material without peeling off the coating film.

The R-Fe-B rare earth magnet powder is
Provided is a method for producing anisotropic rare earth bonded magnet powder, wherein the total content of Ni, Al and Cr is 0.2 to 6% by mass. Further, the R-Fe-B rare earth magnet powder provides a method for producing an anisotropic rare earth bonded magnet powder in which the total content of O and C is 0.3 to 2 mass%.

Furthermore, a method for producing an anisotropic rare earth bonded magnet, in which a binder resin is mixed with the rare earth magnet powder to form a compound, and the compound is molded into a predetermined magnet shape to form a bond magnet, and The bond magnet is provided.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The magnet scrap which is the object of the present invention is a defective crack of a sintered body which occurs in a manufacturing process of a rare earth sintered magnet, a chip at cutting, a scrap material, polishing scraps, Ni or Al plating. It also refers to defective resin coating, defective dimensions and magnetic characteristics in the inspection process, and magnets incorporated into commercial products such as electrical products that have been discarded. Also,
It refers to the residual material obtained by separating and removing the resin component with an organic solvent from the defective rare earth bonded magnet.

The rare earth magnet scrap may be used alone as a bonded magnet, but when the sintered magnet is converted into a bonded magnet, the compositions of the two may not always match. Thus, when the rare earth bond magnet powder to be finally obtained has a composition different from that of the rare earth magnet scrap, the rare earth magnet scrap is used as an alloy raw material, and the composition difference between the rare earth magnet scrap and the rare earth bond magnet powder is obtained. It is possible to use the one prepared by blending the composition adjusting raw material for solving the problem. As a result, the types of rare earth magnet scrap that can be used can be significantly increased, and more effective recycling can be achieved.

Regarding the Nd-Fe-B system magnet material of interest, other constituent elements such as rare earth elements such as Pr and Dy, transition elements such as Co, Zr, Nb and Ga, and trace impurities such as O, C and It does not matter if it contains Si or the like. Normally, about 0.5% in the manufacturing process for sintered magnets
Contains oxygen and about 0.1% carbon as impurities,
The magnetic powder of the bonded magnet contains almost no carbon, but contains about 0.1% oxygen. In the case of magnets recovered from commercial products, it is expected that the oxygen content in the magnets will increase slightly from the time of shipment due to oxidation, depending on the environment in which they are used. When reusing magnet scrap, the total amount of oxygen and carbon is different due to the use of various materials and types, but the lower limit of the total amount is 0.3% is reasonable, and scrap less than that is practically available. Difficult to do. Also, the upper limit must be 2%,
If this amount is exceeded, the magnetic properties, especially the coercive force, will decrease significantly, which is not preferable.

On the other hand, Ni or Al formed on the surface of the magnet,
The anticorrosive metal film such as Cr may be used without being separated and removed, and of course, the deterioration of the magnetic properties may be suppressed by going through a step of mechanically or chemically removing it. Further, in the case of an epoxy resin-based rustproof film, it is used by peeling and removing it in a solvent pressurized at high temperature or by mechanically removing it. When recycled, the total amount of Ni, Al, Cr contained is
A magnet having a plating film and a non-plated sintered body may be used alone or as a mixture of both, and an effect of improving corrosion resistance is recognized when the total amount is 0.2% or more. In particular, both remanent magnetization and coercive force are reduced.

As a method of strip-casting scrap, a method of directly ejecting a molten alloy onto a rotating copper roll to produce flakes, which is practiced in the production of Nd-Fe-B type alloys for sintering, is described. Can be adopted. As the alloy raw material to be melted at this time, it is advantageous to use scrap that has been separated according to the component composition in advance, and a new alloy raw material other than scrap may be added and mixed for composition adjustment. As a strip casting condition, a cooling rate of several hundreds to several thousands ° C./second is generally used, and a fine and uniform Nd ₂ Fe ₁₄ B crystal structure of several to several tens of microns is used, and an approximate thickness of 0.1. Alloy flakes of ~ 2 mm are obtained.

Hydrogen absorption / desorption treatment for alloy flakes, so-called HDDR (Hydrogenation Disproportionation Desorpt)
The basics of ion recombination) processing are described in, for example, Japanese Patent Laid-Open No. 2-4
The method disclosed in JP-A No. 901504 and the method for producing a raw material alloy by strip casting are disclosed in JP-A-7-109504. Also in the present application, by applying the above strip casting method, α-Fe and R ₂ Fe can be obtained.
Homogeneous alloy flakes without impurity layers such as ₁₇ phases can be produced, and hydrogen gas is absorbed in the alloy at 600 to 900 ° C. to temporarily decompose the Nd ₂ Fe ₁₄ B phase, and then at the same temperature. Dehydrogenate again to precipitate the previous phase,
As a result of a series of steps for obtaining a fine recrystallized structure of 1 micron or less, an alloy powder having a well-arranged crystal orientation is obtained due to the homogeneity of the alloy flakes used. The powder obtained from the flakes in this way has a more uniform internal structure of the starting alloy than the powder subjected to HDDR treatment using a conventional alloy lump, and therefore the recrystallized grains have less variation in size and the crystal orientation is not disturbed. Get smaller.

This powder is crushed to a proper particle size and sieved to be used as a bonded magnet. As the bonded magnet, a compression molded magnet manufactured by press molding by adding and mixing a thermosetting resin such as epoxy or phenol, nylon or PP.
There are injection-molded magnets manufactured by adding and mixing thermoplastic resins such as S, and extrusion-molded magnets manufactured by mixing urethane and vulcanized rubber. In either method, direct current or pulse current is used in the molding process. By applying a magnetic field, a high-performance anisotropic bonded magnet can be manufactured. An epoxy-based anticorrosive film is usually formed on the surface of the magnet after molding by spraying or electrodeposition to obtain a final magnet product.

[0019]

According to the present invention, a large amount of magnet scraps that will be produced in the manufacturing process and in the city in the future are alloyed by strip casting without stripping the coating such as Ni plating film, and then hydrogen treated. It can be regenerated as a raw material for anisotropic bonded magnets. Therefore, the anisotropic bonded magnet can be manufactured at low cost, and the resources can be effectively reused.

[0020]

EXAMPLES The present invention will be described in detail below with reference to examples. Example 1 Of the Nd-Dy-Fe-Co-B system sintered magnets, which are defective in cracking and defective in polishing dimension, 5 m for an optical pickup.
A square magnet having a shape of m × 6 mm × 2 mm was prepared. As a result of measuring the magnetic characteristics of this magnet with a BH tracer,
The maximum magnetic energy product BH _max was 336 kJ / m ³ . This square magnet was loaded into a quartz tube installed in a quenching device equipped with a vacuum gas replacement section, a high-frequency heating section, and a rotating roll section, melted by high-frequency heating under a pressure of 50 kPa, and then placed in a quartz tube. A pressurized gas was introduced and the molten alloy was ejected from the pores in the lower part of the quartz tube onto a rotating copper roll to produce an alloy flake with a thickness of 0.9 mm. At this time, the hole diameter at the bottom of the quartz tube is 0.6 mm, and the copper roll diameter is 200 m.
m, and the peripheral speed was 3 m / s.

Next, the alloy flakes and Nd-Fe-Co-Ga-Z produced by a die casting method using the new raw material.
r-B alloy in a hydrogen gas atmosphere of 100 kPa 78
The mixture was kept at 0 ° C. for 3 hours to occlude the hydrogen gas, and then the hydrogen gas was switched to Ar gas at the same temperature and further evacuated to expel hydrogen in the alloy. The alloy powder obtained from the scrap was used as the sample (1) of the present invention, and the alloy powder manufactured from the new raw material through die casting was used as the comparative sample (2).

Both samples were pulverized and adjusted to 150 μm or less, fixed with wax in a magnetic field, applied with a pulsed magnetic field of 4.8 MA / m, and then measured for magnetic characteristics using a vibrating sample magnetometer. Figure 1 shows the hysteresis curve of each sample.
Table 1 shows typical magnetic characteristic values. As is clear from the respective charts, the sample (1) of the present invention has almost the same maximum magnetic energy product BH _{max as} that of the sample (1) of the comparative example, although it contains a large amount of oxygen and nickel impurities. Was given. More specifically, the remanent magnetization B of the sample (1) of the present invention
r is larger than that of the comparative sample (1) due to the excellent crystal orientation after HDDR treatment, while the coercive force Hcj
Shows a rather low value due to the influence of impurities. The reason why each hysteresis curve in FIG. 1 is smaller below the H axis than above is that the magnitude of the reversal magnetic field in the third quadrant is insufficient due to the large coercive force of the powder. ing. From this result, it was found that the sample of the present invention can be sufficiently put to practical use as a raw material magnetic powder for anisotropic bonded magnets. Further, the adjustment of the values of Br and Hcj is performed by correcting the type of scrap to be used, the amount of Nd, etc.
It can be easily performed by adjusting the processing conditions.

[Table 1]

Example 2 Nd-Fe-Co-B having a BH _max of 355 kJ / m ^3.
A fan-shaped Ni-plated defective product for VCM was prepared using a sintered magnet. This defective product was roughly crushed, then charged into a high-pressure container, filled with 200 kPa of pressurized hydrogen for further hydrogen collapse, and powder containing a large amount of Ni plating film was magnetically separated from the taken out crushed product. The powder remaining after separation is
After vacuum evacuation and dehydrogenation, a pressure of 50 MPa was applied to make a solid, and strip casting was performed in the same manner as in Example 1 to obtain an alloy thin piece. Subsequently, hydrogenation was carried out at 800 ° C. for 2 hours in pressurized hydrogen of 200 kPa, and then dehydrogenation treatment was carried out at the same temperature to produce sample (2) of the present invention. As a result of ICP analysis of the component composition of this sample, the mass ratio was 3
The composition was 0.2Nd-3.1Co-1.1B-remaining Fe. On the other hand, as a comparative example, 30.0 having almost the same composition
An alloy of Nd-3.2Co-0.1Ga-1.1B-remaining Fe was die-cast, and HDDR treatment was performed to produce powder.
Comparative sample (2) was used. FIG. 2 shows the hysteresis curve of each sample measured by the vibrating sample magnetometer. Figure 2
As a result, the coercive force of each sample is slightly larger than that of Example 1. When the sample of the present invention (2) is compared with the sample of Comparative example (2), the samples have high Br and low Hcj, but have almost the same BH.
_max was obtained.

Next, 2.2 mass% of one-pack type epoxy resin was added to and mixed with each of the above powder samples, and compression molding was carried out by applying a pressure of 1 GPa in a magnetic field of 1.2 MA / m, and at 120 ° C. for 1 hour. The resin was heated to cure to form a cylindrical magnet, which was used as the sample of the present invention (3) and the sample of comparative example (3). Table 2 also shows the magnetic properties of the sample (3) of the present invention and the sample (3) of the comparative example, and the magnetic properties of the sample (2) of the present invention and the sample (2) of the comparative example, which were measured by a BH tracer. As is clear from Table 2, the sample (3) of the present invention has a BH _max comparable to that of the sample (3) of the comparative example, and it is clear that the sample (3) can be regenerated as a bonded magnet.

[Table 2]

Example 3 Among Nd-Fe-B system sintered magnets, scraps with poor polishing of sintered bodies, scraps of Ni, Al, and Cr plating, and VCM magnets disassembled and collected from a used personal computer were used. When the magnetic characteristics of the magnet were measured by selecting the appearance and shape, the BH _max was 270 to 366 kJ /
It was m ³ . These magnets were crushed to about several mm, melted and quenched in the same manner as in Example 1 at a peripheral speed of 2 m / s,
An alloy flake having a thickness of about 1.2 mm was manufactured. On the other hand, Nd,
Metals of Fe, Ga, Zr and 20% B-Fe were used as new raw materials, and melted and die-casted to produce an alloy lump. Subsequently, the alloy flakes and the alloy lumps are respectively subjected to 200 kPa.
Was kept at 780 ° C. for 1 hour to absorb the hydrogen gas and then dehydrogenated at the same temperature.

Epoxy resin was mixed with each of the obtained powders,
A bonded magnet was manufactured by compression molding in a magnetic field in the same manner as in Example 2. Magnets made from scrap were designated as Samples (4) to (9) of the present invention, and magnets made from new raw materials were designated as Comparative Samples (4). Table 3 shows the results of the metal element analysis by ICP and the oxygen and carbon analysis by the gas combustion method, and the measurement results of the magnetic properties by the BH tracer for each sample powder. From the results of Table 3, the present invention samples (4) to
Although (9) contains a small amount of impurity elements such as Ni, Al, and Cr, and a small amount of oxygen and carbon, a BH _max value almost equal to that of the comparative sample (4) was obtained. , It was clarified that the anisotropic bonded magnet regenerated from scrap has excellent magnetic properties at a practical level.

[Table 3]

[0027]

EFFECTS OF THE INVENTION According to the present invention, the magnet scraps discarded in the manufacturing process and in the commercial products are alloyed by the strip casting method without stripping the coating such as the Ni plating film, and then subjected to the hydrogen treatment. As a result, it can be regenerated as a raw material for anisotropic bonded magnets. Therefore, the anisotropic rare-earth bonded magnet can be manufactured at low cost, and resources can be effectively reused.

[0028]

[Brief description of drawings]

FIG. 1 is a hysteresis curve of a sample (1) of the present invention and a sample (1) of a comparative example.

FIG. 2 is a hysteresis curve of a sample of the present invention (2) and a sample of a comparative example (2).

Front page continuation (51) Int.Cl. ⁷ Identification code FI theme code (reference) C22C 38/56 C22C 38/56 H01F 41/02 H01F 41/02 G F term (reference) 4K017 AA04 BA06 BB12 CA07 DA04 EA12 EC02 FA07 FA08 4K018 AA27 BA18 BB04 CA04 CA11 CA29 CA31 FA25 KA46 5E040 AA04 BC01 BC08 BD01 CA01 HB17 NN05 NN06 5E062 CC05 CD05 CE04 CF02 CG07

Claims (8)

[Claims] 1. A defective raw material or a waste product (hereinafter, both are collectively referred to as a rare earth magnet scrap) of a rare earth magnet having a hard magnetic phase formed of an intermetallic compound of a rare earth element and a transition metal element, as an alloy raw material. Used as a part or all of the above, the alloy raw material is melted by a strip casting method and then rapidly cooled to form an alloy piece, and then the alloy piece is absorbed with hydrogen gas at a high temperature and then desorbed to remove the hard gas. A method for producing anisotropic rare earth magnet powder, characterized in that the magnetic phase is made into fine particles having an average particle size of 1 μm or less and a crystal structure in which the crystal axes are aligned in a specific direction. 2. A defective manufacturing product or a waste product (hereinafter, both are collectively referred to as a rare earth magnet scrap) of a rare earth magnet having a hard magnetic phase formed of an intermetallic compound of a rare earth element and a transition metal element as an alloy raw material. The alloy raw material was melted by the strip casting method and then rapidly cooled to form alloy pieces, and the crystal structure in the alloy pieces was homogenized by high temperature heat treatment, and subsequently hydrogen gas was absorbed at high temperature. By desorbing hydrogen gas later, the hard magnetic phase is made into fine particles with an average particle size of 1 μm or less, and the powder has a crystal structure in which the crystal axes are aligned in a specific direction. Method for producing anisotropic rare earth magnet powder. 3. In the rare earth magnet scrap, the intermetallic compound forming the hard magnetic phase is R ₂ Fe ₁₄ B (provided that R
Is a rare earth element containing Nd as a main component) and an R—Fe—B system in which the hard magnetic phase is sinter-bonded by a grain boundary phase containing the rare earth element R as a main component. It is a rare earth sintered magnet scrap, and the rare earth magnet powder is R
The method for producing anisotropic rare earth magnet powder according to claim 1 or 2, which is a powder for a -Fe-B-based rare earth bonded magnet. 4. The R-Fe-B rare earth sintered magnet scrap has a coating film of any one of Ni, Al and Cr on the surface, and the alloy is formed without peeling the coating film. The method for producing anisotropic rare earth magnet powder according to claim 3, which is used as a raw material. 5. The anisotropic rare earth magnet according to claim 4, wherein the R-Fe-B anisotropic rare earth magnet powder has a total content of Ni, Al and Cr of 0.2 to 6% by mass. Method of manufacturing magnet powder. 6. The anisotropic rare earth magnet powder for R—Fe—B system, wherein the total content of O and C is in the range of 0.3 to 2 mass%. Item 1. The method for producing anisotropic rare earth magnet powder according to item 1. 7. A compound obtained by mixing the rare earth magnet powder obtained by the method according to claim 1 with a binding resin to form a compound, and molding the compound into a predetermined magnet shape. A method for producing an anisotropic rare earth bonded magnet, comprising: 8. A compound is formed by compounding a binder resin with the rare earth bonded magnet powder obtained by the method according to claim 1, and the compound is molded into a predetermined magnet shape. An anisotropic rare-earth bonded magnet characterized by being obtained by the above.