JP2002105503A - Method for manufacturing magnetic material, and magnetic material powder with rust preventive layer thereon and bonded magnet using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing excellent corrosion resistance by uniformly depositing a trace metal as a rust preventive coating film on the surface of a magnetic material and also to provide a method for improving, as compared with those obtained by the conventional technology, the rust preventive function and magnetic properties of the magnetic material by using the interdiffusion and reaction between the component in the vicinity of the surface of the magnetic material and the supplied highly activated metal. SOLUTION: The magnetic material powder composed of a magnetic alloy or a magnetic intermetallic compound and having grain boundaries of magnetic material phase in powder particles and a supply source (hereinafter referred to as rust preventive metal supply source) of a metallic component (hereinafter referred to as rust preventive metallic component) having a rust preventive action upon the magnetic material powder are introduced in a mixed state into a hermetically sealed vessel. Temperature is raised while maintaining a nonoxidizing atmosphere inside the hermetically sealed vessel in the above state, and the rust preventive metallic component is supplied from the metal supply source to the particle surface of the magnetic material powder. By this procedure, the rust preventive layer composed essentially of the rust preventive metallic component can be deposited on the particle surface and also on the region along the grain boundaries in the powder particles, by which the magnetic material powder with the rust preventive layer can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a magnetic material, a magnetic material powder having a rust-proof layer, and a bonded magnet using the same.

[0002]

2. Description of the Related Art In recent years, Nd-Fe-B based magnet materials or
Is mainly composed of Fe, such as Sm-Fe-N based magnet material
High performance rare earth permanent magnet materials (hereinafter referred to as Fe-based rare earth magnet materials)
The permanent magnet member composed of
Based rare earth magnet) has been developed, especially Nd-F
Since e-B magnet materials have excellent magnetic properties,
Motors for various electric devices and automobiles, or computers
Widely used for voice coil motors for motors. N
The d-Fe-B based magnet material is made of sintered magnetic material by its manufacturing method.
Stones, hot-worked magnets, and bonded magnets (resin-bonded magnets)
Broadly classified into types. Of these, the bonded magnets
After mixing and dissolving the gold components, the molten metal is quenched by the single roll method, etc.
The quenched ribbon obtained by coagulation is crushed to produce raw material magnet powder.
Make the powder and use epoxy resin or nylon resin
Molded with a resin binder such as
Is what you do. The above magnet powder is the main hard magnetic phase
Nd ₂Fe₁₄B-type tetragonal intermetallic compound phase (hereinafter referred to as 2-
14-1 phase) is smaller than a single magnetic domain particle size.
It has a grain structure and shows a high coercive force in a powder state. this
Unlike bonded magnets and rolled magnets, such bonded magnets
Almost no post-forming processing, high dimensional accuracy, and high degree of freedom
Motor and high productivity, especially small motors
It is used in large quantities for ring magnets and other applications. On the other hand, S
m-Fe-N-based magnet material is Sm-F which plays a leading role in magnetism.
Because the e-N-based compound phase is easily decomposed at high temperatures,
The application as a bonded magnet is being sought.

[0003] For example, the above-mentioned Fe-based rare earth magnet material contains Fe as a main component and contains a relatively large amount of a chemically active rare earth element. Corrosion may be a problem in an environment where the temperature is easily increased. Generally, in order to secure stable magnetic properties, an Fe-based rare-earth magnet material has a rare-earth component in excess of a stoichiometric ratio of an intermetallic compound (for example, the 2-14-1 phase) forming a magnetic phase. In many cases, the composition is adjusted so as to contain, and the excess rare earth component becomes a rare earth rich phase to form a multiphase structure together with the magnetic phase. In such a case, it can be said that corrosion is more likely to progress due to the local battery reaction between different phases. The progress of such corrosion not only leads to deterioration of the performance of electronic devices such as motors using the Fe-based rare earth magnet as an exciting medium, but also adversely affects peripheral circuits and the like due to scattering of corrosion reactants. is there.

[0004] The above-mentioned situation in which corrosion is likely to occur does not change even at the raw material powder stage. For example, if the powder is exposed to the atmosphere (particularly high humidity) for a long time, the powder is oxidized and degraded. Due to such factors, it is difficult to avoid magnetic properties such as coercive force and maximum energy product.

[0005] Therefore, in the rust prevention treatment for the alloy and the intermetallic compound magnetic material as described above, an appropriate rust prevention treatment is required. Conventionally, a vapor deposition method and an electrolytic plating method have been used as specific methods. However, in the former method, the formation of the coating on the surface of the magnetic material proceeds only from the direction of the evaporation source. Therefore, it is not possible to uniformly coat the surface of a magnetic material having a three-dimensional shape, especially a magnetic material powder having a small particle size. Very difficult. In addition, it is considered that the laminated coated metal may cause agglomeration between the powders, and it is difficult to perform the coating process on a large amount of magnetic powder.
On the other hand, in the latter case, the magnetic material, particularly the raw material powder is seriously damaged by the electrolyte used for forming the film, and a uniform film is formed on the surface oxide layer of the magnetic powder having low electric conductivity. C with high conductivity as pretreatment
There is a problem that a multi-stage treatment for pre-coating with u or the like is required.

Further, alloy and intermetallic compound magnetic powders,
In particular, in the case of rare earth-Fe based magnetic materials, the reactivity between the oxygen source and the rare earth metal component present in the atmosphere is high, and the accompanying reduction in magnetic properties becomes an important problem. It is necessary that the surface can be completely covered. For this purpose, the former method requires a large amount of metal (usually nonmagnetic metal) to form a complete film.
Must be deposited, and this non-magnetic metal causes a dilution effect to cause a decrease in magnetization. On the other hand, in the latter, a uniform film can be formed, but the oxygen in the oxide film on the surface of the magnetic material generated at the time of plating diffuses and penetrates into the inside of the magnetic powder in the heat treatment step at the time of manufacturing the bonded magnet, whereby oxidation proceeds. Magnetic properties are degraded.

[0007] In addition, when the alloy and the intermetallic compound magnetic powder are of the Sm-Fe-N type, the metal formed as a film modifies the surface of the magnetic powder by heat treatment to improve the magnetic properties, especially the coercive force Hcj. It is known to cause. In this heat treatment, a high temperature (up to 600 ° C.) is used in order to efficiently promote the interdiffusion and reaction between the coating metal and the components of the magnetic material.
C.) (for example, disclosed in JP-A-05-234729) or at a low temperature (380 to 400 ° C.).
℃) for a long time (30 hours or more) (K. Mak
ita, S. Hirosawa, J. Alloys Compd., 260 (1997) 236
-241).

[0008]

In the case of the surface coating by the current vapor deposition method and electrolytic plating method applied to alloys and intermetallic compound magnetic materials, the magnetic material is finely pulverized and chemically unstable. In the former, the metal is deposited only along the direction from the evaporation source with respect to the material fine powder, and a film is formed to cause unevenness in the film. In addition, since the powder is a dry process, agglomeration is likely to occur between the powders, so that a surface having poor rust-preventing ability or a surface on which no film is formed partially remains, and as a result, oxidation proceeds from this region to improve the magnetic properties. It will still lead to degradation. Further, it has been difficult by vapor deposition to form a protective film on inner surfaces such as cracks and grain boundaries where oxygen is likely to be a path for diffusing into the magnetic material.

Further, in the electrolytic plating method, the electrolytic solution used damages the active magnetic material itself, such as oxidation, so that the magnetic properties are greatly reduced with the rust prevention treatment, and the conductive material formed on the surface of the magnetic powder is further reduced. An oxide layer having a low rate hinders electroplating, and requires a pretreatment to form a uniform coating.

Therefore, in order to produce a magnetic material having excellent corrosion resistance that can maintain high magnetic properties for a long period of time regardless of the atmosphere in which the alloy and the intermetallic compound magnetic material are stored and used, it is necessary to use the magnetic material itself. It is necessary to establish a new technique for forming a uniform anti-corrosion coating on the surface without damaging itself.

According to the conventional film forming technique by the vapor deposition method, since it is difficult to uniformly coat the individual surfaces of the alloy and the intermetallic compound magnetic material, the desired corrosion resistance is achieved by coating with an unnecessarily large amount of metal. I've been. Along with this, there is a disadvantage that a metal coated in a large amount (in many cases, a non-magnetic material is used) causes a dilution effect and causes deterioration in magnetic properties of the magnetic material. Therefore, in order to avoid such a decrease in magnetic properties, it is desirable to make the rust preventive coating formed on the surface of the magnetic material more uniform and to reduce the amount of metal used as the coating metal as much as possible.

On the other hand, after coating the metal on the surface of the alloy and the intermetallic compound-based magnetic material, the metal is heated in an inert gas atmosphere or in a vacuum to promote mutual diffusion of the metal with the constituents near the surface of the magnetic material. This may improve the adhesion between the metal coating and the surface of the magnetic material, improve the corrosion resistance, and further improve the environmental resistance and magnetic properties of the magnetic material. However, since this heat treatment has been performed at a high temperature (up to 600 ° C.) which is higher than the melting point of the metal used as the coating film, especially in the case of fine powder of a magnetic material, the deterioration of the original magnetic properties cannot be avoided due to the progress of oxidation. .
This is considered to be caused by the fact that the oxide layer generated in the step of forming the film by the heat treatment modifies the magnetic phase existing near the surface of the magnetic powder. Therefore, in order to maintain or improve the original high magnetic properties of the magnetic material after such heat treatment, it is necessary to prevent the magnetic material from being deteriorated by oxidation or the like at the time of metal coating.
It is necessary to establish a method for effectively improving the corrosion resistance and magnetic properties even at a low heat treatment temperature.

An object of the present invention is to provide a permanent magnet material used for a magnetic circuit of various motors and actuators, and to provide a permanent magnetic material having an alloy and an intermetallic compound represented by a rare earth material. It is effective to reduce magnetic properties due to oxidation caused by oxygen, water, etc. present in the storage atmosphere, which is the main cause of the decline, and to efficiently form a uniform rust preventive coating with strong adhesion on the magnetic powder surface. To provide a method for producing a magnetic material capable of ensuring the stability of the magnetic properties of the magnetic material, and a magnetic material powder with a rust-proof layer obtained thereby, and a bonded magnet using the same. is there. More specifically, by supplying a highly reactive metal as a coating metal to the surface of the alloy and the intermetallic compound-based magnetic material, the metal can be uniformly applied to the powder surface by utilizing the reaction affinity between the metal and the constituents of the magnetic material. Precipitates and imparts oxidation resistance by promoting the formation of a uniform rust-preventive coating, and further provides a strong adhesion rust-preventive coating by causing the supplied metal to interdiffuse and react with constituent components near the surface of the magnetic material. At the same time as improving the environmental resistance and magnetic properties of the magnetic material, and providing a technique that contributes to the stability and durability of the bonded magnet made from the obtained surface-coated magnetic powder. Things.

[0014]

Means for Solving the Problems and Action / Effect To solve the above-mentioned problems, a method for producing a magnetic material according to the present invention comprises:
A magnetic material powder comprising a magnetic alloy or a magnetic intermetallic compound and having crystal grain boundaries of a magnetic material phase in powder particles, and a metal component having a rust-preventive action on the magnetic material powder (hereinafter referred to as a rust-preventive metal component) And a supply source (hereinafter referred to as a rust-preventive metal supply source) in a mixed state in a sealed container, and in this state, the temperature is raised while maintaining the inside of the sealed container in a non-oxidizing atmosphere, and the rust-prevention from the metal supply source By supplying the metal component to the particle surface of the magnetic material powder, a rust-preventive layer mainly composed of the rust-preventive metal component is formed on the particle surface, and the rust-preventive metal is also formed in the region along the crystal grain boundary inside the powder particle. It is characterized in that a rust preventive layer mainly composed of components is formed to obtain a magnetic material powder having a rust preventive layer. In the present specification, “a metal component having a rust-preventing action on a magnetic material powder” refers to an action of protecting the magnetic material powder particles from oxidative corrosion when the magnetic material powder particles are coated in a metallic state. As long as it has, any thing may be used. For example, a metal having a passivation film formed on its surface to exhibit oxidation resistance, and a metal having an effect of protecting an alloy or an intermetallic compound constituting a magnetic material powder particle as a result of a sacrificial corrosion effect, Can be exemplified by a metal having a higher corrosion potential than the alloy or the intermetallic compound (in this case, it is desirable that the surface of the alloy or the intermetallic compound is covered as densely as possible). In the present invention, “main component” or “main component”
Means that the component of interest in the target substance is the component with the highest weight content.

The magnetic material powder having a rust-preventive layer according to the present invention is a magnetic material powder comprising a magnetic alloy or a magnetic intermetallic compound and having a crystal grain boundary in a particle. A rust-preventive layer mainly composed of the rust-preventive metal component is formed in a region along the border.

Further, the bonded magnet of the present invention is characterized in that the magnetic material powder having the rust-preventive layer is resin-bonded.

In the rust-proofing process for the alloy and the intermetallic compound-based magnetic material, in order to form a uniform film on the surface of the magnetic material without unevenness, it is necessary to uniformly three-dimensionally coat the surface of the magnetic material having a three-dimensional shape. It is necessary to supply a rust-preventive metal supply source and to form a rust-preventive coating with a small amount of metal as required. In order to uniformly coat the magnetic powder surface in this way, the coating metal is made into a gaseous state, penetrates into the gaps of the stacked magnetic powders, and is adsorbed and precipitated on the surface by the reaction affinity with the magnetic material, or the magnetic powder is This can be achieved by dispersing in a dispersion medium containing a rust-preventive metal supply source, generating an active metal from the supply source in this dispersed state, and precipitating the active metal on the powder surface by reaction affinity with the magnetic material. Therefore, in the present invention, a metal source used for coating and a magnetic material powder are mixed to uniformly supply a rust-preventive metal supply source to the surface of the magnetic material, and the mixture is heated in a sealed container, so that the generated activity is reduced. By precipitating on the surface by utilizing the reaction affinity between the high metal component (for example, metal vapor or organometallic compound) and the constituent components of the magnetic material, the magnetic material can be uniformly coated, The amount of metal coated on the surface can be reduced, whereby the dilution effect is suppressed and a magnetic material with high magnetization can be manufactured. Furthermore, since the coating is performed under conditions that do not include an oxygen source, deterioration due to oxidation of the magnetic material can be suppressed,
An alloy and an intermetallic compound magnetic powder having both excellent magnetic properties and environmental resistance can be produced.

Further, the magnetic material powder having a rust-preventive layer of the present invention, which can be realized by the above-mentioned production method, has a rust-preventive layer mainly composed of a rust-preventive metal component (hereinafter referred to as a rust-preventive layer) also in a region along a crystal grain boundary inside a powder particle. (Referred to as a grain boundary rust-preventing layer), the crystal grain boundary region serving as a component diffusion path for oxidative deterioration is firmly protected, which is further advantageous in reducing the properties of the magnetic material due to oxidation. In particular, an Nd-Fe-B-based or Sm-F
In the case of a nucleation type hard magnetic material using an eN-based intermetallic compound, the formation of the grain boundary rust preventive layer as described above effectively contributes to the improvement of the coercive force of the hard magnetic material.

In this case, the rust-preventive metal component is made to penetrate into the particle surface portion from the particle surface to a certain depth to form a rust-preventive layer along the crystal grain boundaries existing in the particle surface portion where oxidation progresses easily. This is desirable from the viewpoint of improving rust prevention while maintaining high magnetic properties. In the magnetic material powder with a rust-preventive layer obtained in this way, the amount of the rust-preventive layer formed along the crystal grain boundaries is larger at the particle surface layer than inside the particles. It is desirable that the penetration depth of the rust preventive layer formed along the crystal grain boundaries from the particle surface be adjusted, for example, to a range of 1 μm to 10 μm. When the penetration depth is 1 μm or less, the effect of imparting rust resistance may be insufficient, and when it exceeds 10 μm, it is difficult to avoid adverse effects on magnetic properties and the like. The rust-preventive metal component is infiltrated by, for example, diffusion of the component along the crystal grain boundary or supply / precipitation of the metal vapor into the space inside the crack formed along the crystal grain boundary.

It is desirable that a rust preventive layer is formed on the surface layer of the magnetic material powder particles so that the thickness is 5 nm to 50 μm. The rust prevention layer thickness of the surface layer of the particles is 5n
If it is less than m, the rust-preventing property becomes insufficient, and if it exceeds 50 μm, the ratio of the hard magnetic phase decreases, so that the residual magnetic flux density cannot be sufficiently secured. Further, the thickness of the rust preventive layer formed along the crystal grain boundaries is desirably 1 to 100 nm for the same reason.

When the surface of the alloy and the intermetallic compound magnetic material is uniformly coated, by controlling the temperature at which the magnetic material is heated, a film is formed on the surface of the magnetic material, and at the same time, supplied near the surface of the magnetic material. The interdiffusion and reaction between the metal and the constituent components occur smoothly. This interdiffusion and reaction are highly active because the supplied metal is in an atomic, molecular, or cluster state, thereby effectively improving environmental resistance and magnetic properties even at a lower temperature heat treatment than conventional methods. You.

The alloy and the intermetallic compound-based magnetic material are applied to a bonded magnet by being mixed with a resin, molded and magnetized. For bonded magnets, especially compression-molded bonded magnets, which are regarded as important as high-performance magnets, considering the molding process of bonded magnets, it is effective to apply oxidation-resistant treatment to the magnetic material powder as the raw material. Since the oxidation deterioration is suppressed, it is possible to suppress the oxidation deterioration caused from the magnet molding step and the atmosphere in which the magnet is used by forming a uniform anti-rust coating on the surface of the magnetic material powder in the present invention. The performance is improved and the durability of the magnet performance is improved.

Specifically, as a rust preventive treatment for the alloy and the intermetallic compound magnetic material, the magnetic material and a substance serving as a rust preventive metal supply source for the rust preventive film are mixed and sealed in a heat-resistant sealed container. Atomic or cluster-like metal is generated by uniformly heating under an atmosphere not containing tens of ppm or more of an oxygen source such as oxygen or water, and this is supplied to the target magnetic material powder surface, and the magnetic material or Utilizing the reaction affinity between the constituent components of the metal and the metal, the metal is uniformly deposited on the surface of the magnetic material, and subsequently penetrated through the grain boundary interface inside the powder, so that the metal, alloy Alternatively, a rust preventive coating composed of an intermetallic compound can be formed (hereinafter, also referred to as a sorption method). Thereby, an alloy and an intermetallic compound magnetic material having high magnetic properties and environmental resistance can be realized.

The rust-preventive metal component can be supplied to the particle surface of the magnetic material powder in the form of metal vapor. The rust-preventive layer described above can be formed uniformly by precipitation of the metal vapor on the surface of the powder particles and diffusion through the grain boundaries. In this case, specifically, the rust-preventive metal source is a metal ingot or powder containing a rust-preventive metal component, and the inside of the sealed container is depressurized and heated to reduce the rust-preventive metal component from the metal ingot or powder. It is preferable to promote the vaporization because a uniform rust prevention layer can be easily formed. In order to generate metal vapor efficiently, it is desirable to heat the inside of the sealed container to a temperature higher than the melting point of the ingot or powder of the rust-proof metal, preferably higher than the boiling point.

As the rust-preventive metal component, for example, Al, G
a, In, Si, Ge, Sn, Ti and Zn can be used. These rust-preventive metal components are particularly excellent in terms of rust-preventive effect on magnetic material powder mainly composed of metallic Fe, and Zn has a large rust-preventive effect and forms a rust-preventive layer. Since the temperature can be relatively low, there is a great cost advantage. When using Zn, it is desirable to raise the temperature in the sealed container to 300 to 500 ° C.
If the temperature is lower than 300 ° C., the generation of Zn vapor may be insufficient. If the temperature is higher than 500 ° C., the effect of accelerating the sorption of Zn to the magnetic material powder due to the temperature rise cannot be expected any more. Waste increases.
If the temperature is too high, as in the case of the Sm-Fe-N-based magnetic material, the diffusion of Zn metal into the bulk of the magnetic phase may cause a decrease in magnetic properties such as residual magnetization. In this case, the rust-preventive metal component forming the rust-preventive layer is naturally Al, I
One or two or more of n and Zn are mainly used.

For example, a rust-preventive metal supply source is a metal ingot or a metal powder, and this and a desired magnetic powder are sealed in a heat-resistant sealed container in a mixed state, and then the metal is sufficiently vaporized under reduced pressure. By heating uniformly at an appropriate temperature, it can be supplied to the magnetic powder surface as atomic or cluster-like metal vapor. Then, it is possible to form a uniform rust-preventive coating composed of a metal, an alloy or an intermetallic compound on the surface of the magnetic material powder and at the grain boundary interface by utilizing the reaction affinity between the magnetic material and the metal. . in this case,
After using Zn which is a low boiling point metal as a metal serving as a rust prevention coating source, vacuum-encapsulating a mixture of this and a target magnetic powder in a glass or metal container, and then at 300 ° C. to 500 ° C. for several minutes to several hours, By performing the heat treatment uniformly, atomic or cluster Zn metal vapor can be supplied to the magnetic powder surface and the grain boundary interface. As a result, Zn or Zn
It is possible to form a film having a thickness of 5 nm to 50 μm composed of an alloy or an intermetallic compound of iron and magnetic powder.

On the other hand, it is also possible to use an organometallic compound as a rustproof metal component as a rustproof metal supply source. According to this method, a uniform rust preventive layer can be formed on the magnetic powder by decomposing the organometallic compound from the gas phase or the liquid phase (or a critical phase in which both are uniformly mixed and coexistent). Specifically, in a sealed container, the magnetic material powder is dispersed in an organic solvent containing the organometallic compound, and the temperature is raised while the organometallic compound is decomposed / reduced. The rust preventive layer can be formed by supplying the material powder to the surface of the particles.

The rust-preventive metal components contained in the organometallic compound include Al, Ga, In, Si, Ge, Sn, and Ti.
And those mainly composed of one or more of Zn. Each of them can be decomposed at a relatively low temperature, and has an advantage that a rustproof layer having excellent rustproofness can be uniformly formed. In this case, the organometallic compound is Al, Ga, In, Si, G
e, Sn, Ti and Zn, in which an organic chain CmHn is bonded to a rust-preventive metal atom M composed of one or more kinds,
The use of the organic chain CmHn in which the number m of carbon atoms contained in the organic chain CmHn is 1 or more (preferably 3 or more) can effectively lower the decomposition temperature and reduce the production cost of the rust preventive layer. Contribute. In this case, the rust-preventive metal component forming the rust-preventive layer is naturally Al, Ga, In, Si, Ge, Sn,
One or more of Ti and Zn are mainly used.

For example, a low-boiling organometallic compound (MRx;
(M = metal element, R = CmHn), a magnetic powder can be dispersed in an organic solvent containing the organometallic compound in a sealed container such as a stainless steel autoclave and heat-treated. And decompose and reduce the organometallic compound,
By sorbing the generated metal on the surface of the magnetic powder and the grain boundary interface, a rust-preventive layer composed of a metal, an alloy or an intermetallic compound can be formed. As a result, an alloy and an intermetallic compound-based magnetic material having high magnetic properties and environmental resistance can be manufactured.

When the source of the metal for coating the surface of the magnetic powder is an organometallic compound, among them, M = Al, Ga, In, Si, Ge, Sn, Ti having a relatively low decomposition temperature.
And the use of an organometallic compound containing Zn,
By heating at a temperature of from 500 ° C. to 500 ° C. for several minutes to several hours, a rust-preventive coating composed of a metal, an alloy or an intermetallic compound can be formed on the surface of the magnetic powder and on the grain boundary interface. In particular, Al as a metal precursor for coating the magnetic powder surface,
Organometallic compounds containing Ga, In, Si, Ge, Sn, Ti and Zn and having an organic chain (m ≧ 1; desirably m ≧ 3) whose thermal decomposition is promoted at lower temperature It is effective to use In this case, 50 ° C
By heating at a temperature of from 500 to 500 ° C. for several minutes to several hours, it is possible to produce an alloy and an intermetallic compound magnetic material having high magnetic properties and imparting higher environmental resistance.

Regardless of whether a metal ingot or powder is used or an organometallic compound is used, a rust-proof layer is formed by raising the temperature to a first temperature in a sealed container, and then the temperature is raised to a temperature higher than the first temperature. It is advantageous to raise the temperature to the second temperature and then perform the heat treatment from the viewpoint of forming a uniform rust preventive layer with few defects. The first temperature and the second temperature may be set so as to change continuously or stepwise within a certain temperature range.

For example, after a metal is supplied to the alloy and intermetallic compound magnetic material powder surface and the grain boundary interface to form a film, the temperature in the heat-resistant sealed container is raised as it is, and heat treatment is performed at a temperature higher than the film forming temperature. The processing can be performed in two or more stages. This allows
Diffusion and reaction of the metal deposited on the surface near the surface of the magnetic material and at the grain boundary interface can be further promoted, and as a result, the magnetic properties and environmental resistance can be further improved.

As described above, as the magnetic material powder, Sm-
A compound mainly composed of an Fe-N-based intermetallic compound or Nd-Fe-TM (transition metal) -N-based intermetallic compound can be used.

Further, as the magnetic material powder, a powder mainly composed of an Nd-Fe-B-based intermetallic compound can be employed. A magnet powder (magnetic material powder) for a bonded magnet mainly composed of an Nd-Fe-B-based intermetallic compound is obtained by pulverizing a quenched ribbon as described below. The quenched ribbon is one obtained by quenching the melt containing alloy components in a predetermined amount, the average crystal grain size is 1μm or less, represents a general composition formula in _{R x Fe 100-x- y B} y be able to.
Here, R is Nd as a main component (at least the atomic content in all rare earth elements is 50% or more), and a part thereof is Dy or Pd.
R is a rare earth component that can be replaced by at least one of r, and 9 ≦ x ≦ 15 and 4 ≦ y ≦ 10. Incidentally, according to the _purpose, in the form of _{R x Fe 100-x-y} -v B y M v,
Another part of Fe is converted to another metal element (eg, Co:
It is also possible to replace with M).
The replacement amount v is appropriately set in a range where the magnetic characteristics are not significantly reduced, for example, in a range of about 0.1 ≦ v <50.

The quenched ribbon is quenched from the molten metal by
R ₂ having both large saturation magnetic flux density and crystal magnetic anisotropy
Fe ₁₄ B-type tetragonal intermetallic compound phase (hereinafter 2-14-1)
Phase) produces a microcrystalline structure having an average particle size of 1 μm or less, and exhibits a high coercive force and a high residual magnetic flux density immediately after quenching. Can be used as high performance bonded magnet powder.
If the average particle size exceeds 1 μm, the coercive force of the ribbon or the squareness of the demagnetization curve is impaired and sufficient magnet performance cannot be obtained, so the average particle size is in the above range, The thickness is desirably 0.5 μm or less, and more desirably 0.1 μm or less.

The above-mentioned Fe substitution element M can be substituted by Co in the range of v <30. By containing Co within the above composition range, 2
As the Curie temperature of the -14-1 phase increases, the temperature coefficient of the residual magnetic flux density is improved, and stable and excellent magnetic properties are secured even in a high-temperature use environment such as an automobile motor. You can get a belt.
Further, the chemical stability of the quenched ribbon is improved by the addition of Co, and even under a high-temperature and high-humidity environment, the bond magnet using the ribbon is prevented from being corroded or having deteriorated magnetic properties. However, if the content exceeds 30 atomic%, the saturation magnetic flux density of the 2-14-1 phase decreases, leading to a reduction in the maximum energy product, which is not preferable. Note that C
The content of o is desirably set in the range of 2.5 to 20 at%, and more desirably 5 to 10 at%.

Next, other than the above components, the rare-earth component R is a main component of the 2-14-1 phase which is responsible for the excellent magnetic properties of the quenched ribbon, and is mainly composed of Nd. The amount is set in the range of 9 to 15 atomic% (that is, 9 ≦
x ≦ 15). When the content of the rare earth component R is less than 9 atomic%, the ratio of the α-Fe phase, which is a soft magnetic phase, increases, and the coercive force decreases. On the other hand, when the content exceeds 15 atomic%, the ratio of the nonmagnetic phase mainly composed of the rare earth component increases, leading to a decrease in the saturation magnetic flux density. Since all of them lead to a reduction in the maximum energy product, the content of the rare earth component R is set in the above range, preferably set to 10 to 13 atomic%, and more preferably set to 11 to 12 atomic%. Is good.

Further, a part of the rare earth component R mainly composed of Nd can be replaced with Dy or Pr. By adding Dy, the anisotropic magnetic field of the 2-14-1 phase is increased, and the coercive force of the quenched ribbon can be significantly improved. Accordingly, when the magnet is used in an environment where the temperature is likely to increase, such as a hard disk drive of a computer or a motor for an automobile, a decrease in the coercive force at a high temperature is compensated, so that the magnet can be used in a severe temperature environment. You can get a magnet. The addition amount is, for example, 0.1 to 5
It can be appropriately selected within the range of atomic%. However, the addition amount is 5
If it exceeds atomic%, the saturation magnetic flux density of the 2-14-1 phase decreases, leading to a decrease in the maximum energy product. In addition, since Dy is expensive, the raw material cost of the magnet increases, which is not preferable. Although Tb is more expensive than Dy, Dy
Since it has a coercive force improving effect substantially equal to or more than that of the present invention, it can be used depending on the purpose.

On the other hand, when Pr replaces Nd in the 2-14-1 phase, the saturation magnetic flux density and the value of the anisotropic magnetic field do not change so much. Depending on the case, it is possible to replace the entire amount with Pr, but the separated rare earth of Pr is more expensive than that of Nd, and the compounding of the separated rare earth in the form of the separated rare earth leads to an increase in raw material cost, which is not preferable. . However, Pr is separated and extracted together with Nd in the step of separating and purifying the rare earth material,
Since dymium, which is a non-separable rare earth of Nd and Pr, is less expensive than the separated rare earth of Nd and Pr, if these are blended in the form of dymium (for example, dymium metal), the raw material cost can be reduced, which is advantageous. is there. In this case, the Pr content in the quenched ribbon finally obtained is determined by the Pr content ratio in the dymium used.

It is to be noted that any of the rare earth elements other than those described above do not contribute to or increase the energy product, and are desirably not contained as much as possible. However, rare earth elements such as Nd, Dy, Pr, etc. are preferable. Along with the components, for example, those inevitably mixed in a total amount of 1 atomic% or less may be contained.

Next, B is 2-1 as in the case of the rare earth component R.
4-1 is an essential component of the phase, and its content is 4 to 10
It is set within the range of atomic% (that is, 4 ≦ y ≦ 10). When the B content is less than 4 atomic%, soft magnetic Nd
Cause a decrease in ₂ Fe ₁₇ type phase is generated coercive force, saturation magnetic flux density generated by the NdFe ₄ B ₄ type phase nonmagnetic and the content exceeds 10 atomic% is reduced. In any case, the maximum energy product is reduced, so that the B content is in the above range. The content of B is desirably set in the range of 4 to 8 at%, more desirably 5 to 7 at%.

Fe is an essential component of the 2-14-1 phase and plays a major part in its large saturation magnetization.

Such a quenched ribbon can be pulverized so as to have an average particle diameter of 500 μm or less to obtain a powder for a bonded magnet. Then, a coating film is formed on the powder as described later, and further bonded with a resin such as an epoxy resin, a phenol resin, or a nylon resin, thereby forming a bonded magnet. Here, when the average particle diameter of the bonded magnet powder is 500 μm or more,
Since the distribution of the magnet powder and the resin in the bonded magnet becomes non-uniform and causes a variation in the surface magnetic flux distribution of the bonded magnet, the average particle diameter is set to the above-mentioned value. On the other hand, if the average particle size is too small, for example, when manufacturing a bonded magnet by compression molding, the flowability of the magnet powder is reduced, and it becomes difficult to smoothly fill the mold and the productivity is reduced. Is set to a predetermined average particle size or more. The average particle diameter of the magnet powder is preferably 50 to 400 μm, more preferably 100 to 30 μm.
It is good to set within the range of 0 μm.

Hereinafter, a quenched ribbon for a bonded magnet, a bonded magnet powder using the same, and a method for producing a bonded magnet will be described. First, a predetermined amount of an alloy component is blended, and then the alloy component is dissolved in a predetermined atmosphere such as an inert gas atmosphere or a vacuum atmosphere. The alloy components to be blended may be either alone or blended in the form of a master alloy such as an Nd-Fe alloy or ferroboron. For the melting, a known melting method such as high-frequency induction melting and arc melting can be used.

Next, the molten metal is quenched and solidified to produce a quenched ribbon in the form of a ribbon or flake.
As the quenching atmosphere, for example, an inert gas atmosphere such as argon is used. As the quenching method, various methods such as a single roll method, a twin roll method, a splat quench method, a centrifugal quenching method, and a gas atomizing method can be applied. Of these,
In particular, the single-roll method is suitable for mass-producing a uniform and high-performance quenched ribbon, in which the cooling efficiency of the molten metal is high and the cooling rate can be easily adjusted by the peripheral speed of the roll. In this case, a roll peripheral speed of 5 to 35 m / sec, desirably 10 to 30 m / sec is desirable for obtaining a quenched ribbon having fine and uniform crystal grains and excellent magnetic properties.

The quenched ribbon thus obtained is pulverized by a known pulverizing method using a stamp mill, a feather mill, a disc mill or the like so as to have the above-mentioned average particle diameter, and is used as a powder for a bonded magnet. The pulverization may be performed in two stages (or more stages) of coarse pulverization followed by fine pulverization. It is desirable that the powder after pulverization is appropriately sized with a mesh or the like to adjust the particle size.

Here, the quenched ribbon obtained by the above-mentioned quenched solidification can be subjected to a heat treatment in a temperature range of 400 to 1000 ° C. before or after the pulverization. The ribbon immediately after quenching may have an amorphous portion in a portion where the cooling rate becomes particularly high, for example, in the vicinity of a contact portion with a quenching roll.
This amorphous portion is soft magnetic, and may cause a decrease in coercive force, squareness of demagnetization curve, decrease in energy product, and the like. Therefore, by performing the above heat treatment on the quenched ribbon,
The amorphous portion generated immediately after quenching can be crystallized, and a decrease in energy product and the like can be prevented.
When the heat treatment temperature is lower than 400 ° C., the crystallization of the amorphous portion does not proceed sufficiently, and the above-mentioned effects cannot be sufficiently obtained. On the other hand, when the heat treatment temperature exceeds 1000 ° C., crystal grains grow and become coarse, and the coercive force or energy product is rather reduced. Therefore, the heat treatment temperature is set within the above range,
Preferably 500 to 800 ° C., more preferably 600
It is set within the range of -700 ° C.

Powder for bonded magnet obtained by the above method
Finally, the rust preventing layer is formed by the method of the present invention,
Mixing with post-resin components and press-molding or injection-molding
Thus, a bonded magnet is manufactured. In the case of pressure molding,
A powdery thermosetting resin such as epoxy resin is added to the above magnet powder.
Fat in a predetermined amount, for example, about 1 to 5% by weight.
Example by press molding using a mold with b and pan
For example, 5-10t / cm ²Compression molding is performed with a moderate pressure.
After molding, the obtained molded body is cooled to a predetermined temperature, for example, 80 to 18
The resin is cured by heating to about 0 ° C
Get a magnet. The heating for curing the resin is performed under the above pressure.
It may be performed during molding. According to this method, the obtained
For high-density magnet powder in compact magnets for small motors
Suitable for manufacturing high performance ring magnets.

On the other hand, in the case of injection molding, first, a thermoplastic resin such as a nylon resin is added to the magnet powder in an amount slightly larger than that in the case of compression molding, for example, about 10 to 30% by weight, and this is kneaded. A compound for molding is produced. Then, the compound is heated and softened, and injection-molded into a mold cavity using a predetermined molding machine to obtain a bond magnet having a desired shape. The bonded magnet obtained by this method has a slightly lower magnet powder density,
Although the performance is not as high as that obtained by compression molding, there is an advantage that magnets of various and complicated shapes can be easily manufactured, and accessory parts such as a motor spindle can be integrally molded (insert molding) together with the above-mentioned compound. For example, a ring-shaped bonded magnet is radially magnetized and used as a motor rotor or a stator.

[0050]

Embodiments of the present invention will be described below with reference to the drawings and experimental data. (Embodiment 1) An example in which a rust-preventing metal supply source is made of Zn powder for the Sm-Fe-N-based rare earth magnetic material using the sorption method of the present invention will be described below. What is used here is that the rust-preventive metal supply source is a metal ingot or metal powder, and after enclosing this and the intended magnetic powder in a heat-resistant sealed container in a mixed state, the metal is vaporized under reduced pressure. Uniformly heated at a temperature sufficient to supply it to the surface of the magnetic powder as an atomic or cluster-like metal vapor, and utilizing the reaction affinity between the magnetic material and the metal, the magnetic material powder surface and the grain boundary interface Next, a method for forming a rust-preventive coating composed of a uniform metal, alloy or intermetallic compound (hereinafter referred to as a first method).

The Sm-Fe-N-based magnetic material is wet ball-milled in a non-polar organic solvent to which a surfactant is added, so that it is hard to be oxidized due to oxygen or water in the atmosphere and can be uniformly milled. Thus, a fine powder having a small oxygen content and a small particle size distribution can be produced.

5% by weight or less of Zn metal is mixed with the produced Sm-Fe-N type fine powder and introduced into a glass container. In addition, by introducing steel balls into the glass container together with these mixed powders, it becomes possible to effectively suppress agglomeration between the powders generated in the sorption process, and to form a uniform and uniform coating. The inside of the glass container is evacuated to about 1 × 10 ⁻⁶ Torr and then sealed (see FIGS. 1 and 2).

The entire vacuum-sealed glass container is uniformly heated at various temperatures of 300 to 500 ° C. for 2 hours to vaporize Zn metal, and the magnetic fine powder is exposed to the Zn vapor to expose the surface thereof. Promotes Zn sorption to Zn.

FIG. 3 shows the dependence of the residual magnetic flux density Br and the coercive force Hcj of the sorbed magnetic powder on the sorption temperature. Conventionally, an increase in the coercive force Hcj has been observed by a heat treatment near the melting point of the Zn metal (419.6 ° C.). In order to obtain a sufficient coercive force Hcj, the amount of the Zn metal deposited or plated must be smaller than that of the magnetic powder. However, in the present invention, the improvement of the coercive force Hcj becomes remarkable even at a lower temperature of 350 ° C. than the conventional method, and the Zn metal content at that time is also smaller than that of the magnetic powder. A sufficient improvement in coercive force was observed with a small amount of about 4% by weight. In the magnetic powder subjected to the sorption treatment, the residual magnetic flux density Br also shows 0.8 T, which is equal to or higher than the magnetic powder obtained by the vapor deposition method and the electrolytic plating method and subjected to the heat treatment for increasing the coercive force. High residual magnetic flux density Br value was obtained.

Next, FIG. 5 shows the value of the coercive force Hcj when the sorption temperature is fixed at 350 ° C. and the sorption processing time is changed. Further, as a comparison, a change in coercive force of the coating powder produced by the vapor deposition method is also shown.

In the case of a coating powder produced by a vapor deposition method, 1M
In order to obtain a coercive force of about A / m, 3 3
The need for additional heat treatment at about 80 ° C. for about 30 hours required Zn / Zn fabricated using the sorption method developed this time.
The Sm-Fe-N-based powder can obtain a sufficiently large coercive force under the conditions of 350 ° C. and a low temperature of 2 hours and a short time,
It has been clarified that the magnetic properties can be efficiently improved even by one-stage processing. This is because the highly active metal sorption on the powder surface proceeds three-dimensionally and uniformly,
Further, it is considered that the reaction proceeds more easily because the permeation / diffusion of the sorbed metal proceeds from active cracks on the surface portion of the magnetic powder and crystal grain boundaries.

FIG. 4 shows the dependency of the coercive force of the Zn / Sm—Fe—N coating powder coated by the sorption method according to the first method on the amount of Zn metal. As a comparison, the dependence of the coercive force of the coating powder produced by the vapor deposition method on the amount of Zn metal is shown.

In the vapor deposition method, it is considered that a minimum of 5 to 6% by weight of Zn metal is required in order to improve the value of coercive force. In the sorption method according to the present invention, the amount of Zn metal is 3% by weight. It turns out that about% is sufficient. As a result, a decrease in magnetic flux density due to the presence of the non-magnetic metal is suppressed, and the amount of metal mixed with the magnetic powder as a coating supply source can be reduced.

FIG. 6 is a scanning electron microscope (SEM) photograph of a magnetic fine powder having Zn metal sorbed on the surface thereof using the method utilizing the sorption action according to the first method. In Table 1,
The abundance ratio of the coating metal Zn on the surface of the magnetic fine powder measured by an electron probe X-ray microanalyzer (EPMA) is shown in comparison with Sm. In addition, the measurement surface of the magnetic material in Table 1 is:
This corresponds to the surface of the magnetic material shown in FIG. From this, it can be seen that the surface of the magnetic fine powder is almost uniformly coated with Zn metal.

[0060]

[Table 1]

FIG. 7 shows a thin-film X-ray pattern of a Sm—Fe—N-based magnetic fine powder having a surface sorbed with Zn metal when the heating temperature was set to 350 ° C. or 500 ° C. in the first method. Is shown. For comparison, a thin-film X-ray pattern of an Sm—Fe—N-based magnetic fine powder that has not been subjected to rust prevention treatment is also shown. The magnetic fine powder that has not been subjected to rust prevention treatment has an oxidized surface in the atmosphere to form an amorphous phase.
The magnetic fine powder subjected to sorption treatment at 50 ° C. has a slight amount of α-Fe
It can be seen that, though precipitates were observed, the Th ₂ Zn ₁₇ type mother structure remained, and oxidation was effectively suppressed.

FIG. 8 shows the change over time of the coercive force Hcj in the air of the Sm—Fe—N-based magnetic fine powder subjected to the rust prevention treatment by the first method. For comparison, see JP-A-08-
Sm coated with Zn metal using a technique of decomposing diethylzinc (Zn (C ₂ H ₅ ) ₂ ), which is one of the organometallic compounds disclosed in JP-A-143913, by ultraviolet light to generate a coated metal. -Coercivity H of Fe-N based magnetic fine powder
The change with time of cj is also shown. JP-A-08-14391
Sm-Fe-N treated with rust prevention by the coating method of No. 3
The coercive force Hcj of the system magnetic fine powder could not be maintained at 50 ° C. in the atmosphere, but gradually decreased. On the other hand, Sm-Fe-N treated with the rust preventive treatment according to the present invention
The coercive force Hcj of the fine magnetic powder is 60 at 50 ° C. in the atmosphere.
Even when left for 0 hours, the value did not change and the value was maintained at a high value, and it became clear that the film formed by the sorption method was more excellent in rust prevention effect.

(Embodiment 2) An example in which a rust-preventing metal supply source is implemented using Zn powder for the Nd-Fe-B-based rare earth magnetic material according to a first method similar to that of Embodiment 1. It is shown below. First, hydrogenation-disproportionation-
5% by weight or less of Zn metal is mixed with the Nd-Fe-B-based magnetic powder subjected to the dehydrogenation-recombination method (known as HDDR method), and the mixture is introduced into a glass container. Is evacuated to about 1 × 10 ⁻⁶ Torr and then sealed. In addition, by introducing a mixed medium such as a steel ball into a glass container together with a mixed powder of the Nd—Fe—B-based magnetic powder and the Zn metal powder, it is possible to effectively suppress aggregation during the sorption treatment (FIGS. 1 and 2). reference).

The entire vacuum-sealed glass container was uniformly heated at various temperatures of 300 to 450 ° C. for 2 hours to vaporize Zn metal, and Nd—Fe—
Exposure to the B-based magnetic fine powder promotes sorption on the surface of the powder and on the grain boundary interface. Since a large number of cracks are formed between Nd ₂ Fe ₁₄ B crystal grains in the surface layer of the particles obtained by the HDDR method, it is considered to be advantageous in performing the sorption of Zn to the grain boundary interface. .

FIG. 9 shows a composition image of the FE-SEM composition at a photographing magnification of 1500 times for all the powder particles. FIG. 10 shows a composition image of the FE-SEM composition.
The surface portion of the powder particles is shown at a magnification of 5000 times. According to these figures, the powder surface has a thickness of 3 to
A surface layer of 4 μm is present, indicating that this layer uniformly surrounds the whole particle. A similar surface layer is Sm-F
It can also be performed with eN-based and Sm-Fe-TM-N-based powder particles.

On the other hand, the results of observation of these surface layers by FE-SEM and TEM are shown in FIGS. From the figure, it was clarified that the surface layer was composed of fine Nd ₂ Fe ₁₄ B crystal grains, and their crystal grain boundaries were covered with a grain boundary phase having a width of 5 to 40 nm. The compositional analysis by EDX confirmed that these grain boundary layers were composed of not only Zn metal but also an alloy or a compound phase of Zn and Nd or Fe. However, it was also found that the content of Zn was 50% by mass or more, and Zn was the main component.

Next, the anisotropic Nd-Fe
Table 2 shows the magnetic characteristics of the -B-based magnetic powder.

[0068]

[Table 2]

The magnetic properties of the Nd—Fe—B-based magnetic powder that has been subjected to the rust-preventive treatment using the sorption method according to the first method are different from those of the raw material magnetic powder by increasing the sorption treatment temperature. Compared to decline. In the sorption treatment at 300 ° C., the Zn metal powder mixed with the magnetic powder did not evaporate and remained.

When the sorption treatment was performed at 350 ° C., the sorption time was prolonged and the magnetic properties were lowered.
However, even after the sorption treatment, the dilution effect due to the coating of the non-magnetic Zn metal occurred and a slight decrease was observed, but the high residual magnetic flux density Br of about 1.3 T was still maintained.
It was found that the maximum energy product (BH) max also showed a very high characteristic of 300 kJ / m ³ (see FIG. 13).

FIGS. 14 and 15 show compression-molded resin-bonded magnets made of Nd—Fe—B-based magnetic powder that has been subjected to rust-preventive treatment by the sorption method according to the first method at 80 ° C. in air.
Also, the time-dependent change of the magnetic flux density when left at 120 ° C. is shown.

The demagnetization rate of the compression-molded resin-bonded magnet produced using the Nd—Fe—B-based magnetic powder that has been subjected to the rust-preventive treatment by the sorption method according to the first method can be obtained at both 80 ° C. and 120 ° C. Table 3 shows the results obtained by determining the permanent demagnetization rate after the magnet was re-magnetized after 1000 hours, and smaller than the bonded magnet using untreated Nd-Fe-B-based magnetic powder. The permanent magnet demagnetization rate of the bonded magnet produced using the Zn / Nd—Fe—B-based magnetic powder coated by the sorption method according to the present invention is 80.
-3.9% and -3.
6% of those of bonded magnets using untreated powder (-
(8.1% and -10.9%), indicating that the durability in the atmosphere is greatly improved.

[0073]

[Table 3]

Next, the residual magnetic flux density Br and the coercive force Hcj of the resin-bonded magnet prepared from the Zn / Nd—Fe—B-based magnetic powder coated with the surface by the sorption method of the present invention at 120 ° C. Table 4 shows the temperature coefficients α (Br) and β (Hcj) at

[0075]

[Table 4]

From Table 4, the temperature coefficient β (Hcj) of the coercive force Hcj of the resin-bonded magnet made from the Zn / Nd—Fe—B-based magnetic powder subjected to the sorption treatment in the present invention is equal to that of the untreated powder. Compared to those of the used bonded magnet and the commercially available anisotropic bonded magnet MQA-T, the values were equivalent, but the temperature coefficient α (Br) of the residual magnetic flux density Br showed a significant improvement. It was possible to improve the heat resistance of the Nd—Fe—B-based bonded magnet.

Nd- which has been subjected to sorption treatment under various conditions
Table 5 shows the coercive force Hcj and the temperature coefficient α (Br) at 150 ° C. of the residual magnetic flux density Br and (Hcj) of the resin-bonded magnet produced using the Fe—B-based magnetic powder as a raw material, respectively.

[0078]

[Table 5]

From the table, it can be seen that the sorbed Nd-Fe-B
It can be seen that, in the resin-bonded magnet made from the base magnetic powder, the residual magnetic flux density Br and the temperature coefficient α (Br) and (Hcj) of the coercive force Hcj are improved by increasing the sorption processing time. Even if the particle size of the Nd-Fe-B-based magnetic powder is reduced, it is possible to produce a resin-bonded magnet having the same temperature coefficient.

(Embodiment 3) Used in this embodiment.
Is a rust-proof metal source that forms a coating on the surface of the magnetic powder.
And a low-boiling organometallic compound (MRx; M = metal element,
R = CmHn), stainless steel autoclave, etc.
Organic solvent containing the organometallic compound in a sealed container of
By dispersing magnetic powder in it and subjecting it to heat treatment,
Compounds are decomposed and reduced, and the resulting metal is placed on the surface of magnetic powder.
Metal, alloy or gold by sorption at the grain boundary interface
Method for forming antirust coating composed of intergeneric compounds
(Hereinafter referred to as the second method). Below, organometallic compounds
Rust prevention treatment by thermal decomposition of rare earth magnetic material Sm-F
Diethyl zinc (Zn (C₂H₅)₂)
The following is an example of implementation using. In addition, the organometallic compound
Other than this, Al (C₂H₅)₃, Ga
(C₂H₅)₃, In (C₂H₅)₃, Si (CH ₃)
₄, Ge (CH₃)₄, Sn (CH₃)₄, Ti (CH
₃)₄Etc. can be used.

When the Sm-Fe-N-based magnetic material is wet ball milled in a non-polar organic solvent to which a surfactant has been added, it is hard to be oxidized from the atmosphere and can be uniformly milled. And a fine powder having a small particle size distribution can be produced. The prepared Sm-Fe-N-based magnetic fine powder and a nonpolar organic solvent containing diethylzinc as a dispersion medium are introduced into an autoclave in a glove box filled with an inert gas, and sealed. The sealed autoclave is heated uniformly above the thermal decomposition temperature of diethyl zinc while shaking for various times to thermally decompose diethyl zinc and coat the surface of the Sm-Fe-N magnetic powder (see FIG. 16). ). Here, the thermal decomposition temperature of diethyl zinc (Zn (C ₂ H ₅ ) ₂ ) is 170 ° C. to 2 ° C.
30 ° C (Applied Organome)
tallic Chemistry, 5, 337 (1991)).

Table 6 shows the residual magnetic flux density Br and coercive force of the Zn / Sm-Fe-N-based magnetic powder coated with 0.15 g of diethylzinc and coated at various heating temperatures higher than the thermal decomposition temperature. Hcj and oxygen content are shown together with those of the raw material powder. Here, the addition amount of diethyl zinc was 0.15.
g can generate 3% by weight of the coating metal based on the magnetic powder, assuming that all the thermal decomposition occurs by the heat treatment.

[0083]

[Table 6]

As shown in Table 6, the Zn / Sm—Fe—N magnetic fine powder coated with metal by utilizing the thermal decomposition of diethylzinc, one of the organometallic compounds according to the present invention, was subjected to the thermal decomposition coating treatment. Coercive force Hc at 350 ° C
j was improved. Such an increase in the coercive force Hcj can be seen by performing a heat treatment at a temperature close to or higher than the melting point (419.6 ° C.) of Zn metal as described above. The method or the electroplating method required an amount of Zn metal of about 10% by weight or more with respect to the Sm-Fe-N magnetic powder. However, similar to the sorption method in the present invention, the active metal is activated by thermal decomposition of the organometallic compound. By supplying metal to the surface of the magnetic powder, the coercive force Hcj is improved from 350 ° C., which is lower than the conventional heat treatment temperature,
Further, the effect of increasing the coercive force Hcj was observed even with a very small amount of Zn metal, about 2.5% by weight, with respect to the amount of metal to be coated.

On the other hand, the residual magnetic flux density Br of the Zn / Sm—Fe—N-based magnetic fine powder that has been subjected to rust-prevention treatment using a metal formed by thermal decomposition of diethyl zinc as the organometallic compound in the present invention is as described above. Zn / S with sorption treatment
0.8T, which is about the same as that of the m-Fe-N-based magnetic fine powder, and the residual magnetic flux density B of the magnetic powder which has been subjected to the coating treatment by the vapor deposition method and the electroplating method and then to the coercive force treatment.
A value equal to or higher than r was obtained.

From Table 6, it can be seen that Zn / Sm-Fe produced by the method of thermal decomposition of an organometallic compound according to the present invention was used.
-N-based magnetic powder does not cause a significant increase in the oxygen content in the film forming process, and the organic solvent used as the dispersion medium disperses the magnetic powder and simultaneously oxidizes the magnetic powder by shielding the magnetic powder from the oxygen source. Can be effectively suppressed.

FIG. 17 shows the change with time of the coercive force Hcj of Zn / Sm-Fe-N magnetic powder which has been subjected to rust prevention treatment by thermal decomposition of the organometallic compound according to the present invention at 50 ° C. in the air. As a comparison of the coated powder, see JP-A-08-143.
No. 913, the coercive force of Sm-Fe-N magnetic powder coated with Zn metal by a technique of forming a metal using photolysis and forming a film on the surface using the metal. The change with time of Hcj is also shown. Zn / S coated by a method according to JP-A-08-143913
The coercive force Hcj of the m-Fe-N-based magnetic powder is
At 0 ° C., the initial value could not be maintained and gradually decreased. On the other hand, the coercive force Hcj of the Zn / Sm-Fe-N magnetic powder subjected to the rust prevention treatment by the thermal decomposition of the organometallic compound according to the present invention has a high value even when left at 50 ° C. in the air. It was found to maintain and have excellent environmental resistance.

(Embodiment 4) Similar to Embodiment 3, an Nd-Fe-B system of a rare earth magnetic material subjected to a rust-proof treatment by thermal decomposition of an organometallic compound according to the second method was used. An example is shown below. Table 7 shows the magnetic properties of Nd-Fe-B-based magnetic powders whose surfaces were coated using a metal produced by the thermal decomposition of diethylzinc according to the present invention, and the method disclosed in JP-A-08-143913 as a comparative sample. The magnetic properties of the Nd-Fe-B-based magnetic powder coated on the surface are also shown.

[0089]

[Table 7]

From the table, it can be seen that the Nd—Fe—B magnetic powder that has been subjected to the rust-preventive treatment using the coating method according to the present invention has a residual magnetic flux density B
r, coercive force Hcj and maximum energy product (BH) ma
Although the x value was still high, it was slightly lower due to the heat treatment at the thermal decomposition temperature of the organometallic compound as compared with the values of the raw material powder and the coated powder according to the method of JP-A-08-143913. Indicated. However, Japanese Patent Application Laid-Open No. 08-1439
The amount of Zn metal covering the surface of the Nd-Fe-B magnetic powder by the method of No. 13 was 0.02% by weight. On the contrary,
The Zn / Nd-Fe-B magnetic powder surface-coated by pyrolysis of diethylzinc according to the present invention has a Zn metal content of 0.58.
By weight, the coating amount was greatly improved as compared with the method of JP-A-08-143913, and it was possible to coat the surface with a large amount of Zn metal while maintaining high magnetic properties.

FIG. 18 shows a scanning electron microscope (SEM) photograph of a cross section of the Zn / Nd—Fe—B magnetic powder whose surface is coated by thermal decomposition of the organometallic compound according to the present invention. FIG. 19 and Table 8 show the results obtained by measuring the abundance ratios of neodymium Nd and Zn from the surface of the magnetic powder in FIG. 18 to the inside using an electron probe X-ray microanalyzer (EPMA). Thus, Zn generated by the thermal decomposition of diethyl zinc and deposited on the surface of the magnetic powder diffuses from the surface to the inside at the thermal decomposition temperature, while Nd, which is a component of the magnetic material, diffuses to the surface. Therefore, the Zn metal deposited on the surface by the thermal decomposition of diethylzinc, which is an organometallic compound, interdiffuses with the constituents of the magnetic material at the thermal decomposition treatment temperature to form a more adhesive rust-proof coating. You can see that it is.

[0092]

[Table 8]

The Zn / Nd-F which has been subjected to a rust-preventive treatment using a sorption method utilizing the thermal decomposition of an organometallic compound according to the present invention.
A prototype of an anisotropic resin-bonded magnet using e-B magnetic powder as a raw material was produced, and the change over time of the magnetic flux density at 80 ° C. in the atmosphere was tracked to measure the demagnetization rate. The result is the unprocessed N
FIG. 20 also shows the demagnetization ratio of the resin-bonded magnet using d-Fe-B magnetic powder as a raw material under the same conditions. Thus, Nd-Fe-B surface-coated by the coating method according to the present invention
It was found that the bonded magnet using the magnetic powder maintained a high magnetic flux density for a long time and had high environmental resistance.

[0094]

According to the present invention, the deposition of the coating metal proceeds in a plane (two-dimensional) manner on the surface of the powder in the method conventionally used for the surface rust prevention treatment of the alloy and the intermetallic compound magnetic material. Therefore, a large amount of coating metal was required to completely cover the surface, but the surface treatment of the rare-earth magnetic material was performed by depositing the metal in a three-dimensional manner. It is possible to produce a rust-preventive coating having excellent corrosion resistance and to reduce the amount of coated metal, thereby avoiding a decrease in magnetization due to a dilution effect caused by a non-magnetic metal, thereby producing a magnetic material having high magnetization. further,
Interdiffusion between the coating metal and the constituent components near the surface also proceeds at a lower temperature compared to the conventional method, so that a coating with high adhesion is formed without performing a heat treatment at a high temperature, and a significant decrease in magnetic properties is avoided. In addition to that, the magnetic properties are improved in one step, so that a complicated process in multiple steps is not required.

That is, in the present invention, a highly active metal is supplied to the powder surface by heating in an airtight container with respect to the alloy and the intermetallic compound magnetic material whose magnetic properties are degraded by oxidation. In addition to being able to form a uniform rust-preventive coating on the surface of a complex three-dimensional part, metal diffusion and interdiffusion and reaction with the components of the underlying magnetic material proceed even at lower temperatures compared to conventional methods. Thus, the magnetic characteristics can be improved. Further, the metal rust preventive film thus formed is effective in effectively suppressing inevitable oxidation of the target magnetic material and maintaining its original high magnetic properties even in the atmosphere. This is expected to greatly contribute to higher performance and higher corrosion resistance of bonded magnets, which have been increasing in demand in recent years as application fields of magnetic materials.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an apparatus used for a sorption method in the present invention.

FIG. 2 is a sectional view of a sealed container of a sorption method according to the present invention.

FIG. 3 shows the dependence of the residual magnetic flux density Br and the coercive force Hcj on the processing temperature of a Sm—Fe—N-based magnetic fine powder that has been surface-treated with Zn metal vapor by using a sorption method.

FIG. 4 shows Zn / S coated using the sorption method according to the invention.
It is Zn metal amount dependence of the coercive force of m-Fe-N type coating powder.

FIG. 5 shows Zn / Sm—Fe— when the treatment temperature was fixed at 350 ° C. and the sorption treatment time was changed by the sorption method of the present invention.
This is a change in the coercive force Hcj of the N-based magnetic powder.

FIG. 6 is a scanning electron micrograph of a magnetic fine powder having a surface coated with Zn metal by using the sorption method according to the present invention.

FIG. 7 shows a Sm-Fe-N-based magnetic fine powder which has been subjected to rust-prevention treatment using the sorption method according to the present invention, and Sm which has not been subjected to rust-prevention treatment.
3 is a thin film X-ray pattern of a Fe—N-based magnetic fine powder.

FIG. 8 shows a Sm—Fe—N-based magnetic fine powder surface-treated by using the Zn metal vapor sorption method according to the present invention and a Sm coated by the method disclosed in JP-A-08-143913. -Coercive force Hcj of the Fe-N based magnetic fine powder in air at 50 ° C over time.

FIG. 9 is an FE-SEM composition image of a Nd—Fe—B-based magnetic fine powder surface-treated using a Zn metal vapor sorption method according to the present invention at a magnification of 1500 times.

FIG. 10 is an FE-SEM composition image of a Nd—Fe—B-based magnetic fine powder subjected to surface treatment using a Zn metal vapor sorption method according to the present invention at a magnification of 5000 times.

FIG. 11 is an FE-SEM composition image of a Nd—Fe—B-based magnetic fine powder surface-treated using a Zn metal vapor sorption method according to the present invention at a magnification of 35,000 times.

FIG. 12 is a TEM bright-field image of a Nd—Fe—B-based magnetic fine powder subjected to a surface treatment using a Zn metal vapor sorption method according to the present invention at a magnification of 25,000 times.

FIG. 13 shows Zn / Nd− coated by the sorption method of the present invention.
Fe-B based magnetic powder and Nd-Fe-
It is a demagnetization curve of B type magnetic powder.

FIG. 14: Nd-F subjected to rust prevention treatment by the sorption method of the present invention
It is a time-dependent change of a magnetic flux density (demagnetization rate) at 80 ° C. in the atmosphere of a compression-molded resin-bonded magnet using an EB-based magnetic powder as a raw material.

FIG. 15: Nd-F subjected to rust prevention treatment by the sorption method of the present invention
It is a time-dependent change of a magnetic flux density (demagnetization rate) at 120 ° C. in the air of a compression-molded resin-bonded magnet using an eB-based magnetic powder as a raw material.

FIG. 16 is a rust prevention scheme in an autoclave container used for thermal decomposition of an organometallic compound in the present invention.

FIG. 17 is a time-dependent change in the coercive force Hcj of a Zn / Sm—Fe—N magnetic powder that has been subjected to rust prevention treatment by thermal decomposition of an organometallic compound according to the present invention at 50 ° C. in air.

FIG. 18 is a scanning electron microscope (SEM) photograph of a cross section of a Zn / Nd—Fe—B magnetic powder coated by thermal decomposition of an organometallic compound according to the present invention.

FIG. 19 shows the results of measuring the abundance ratios of neodymium Nd and Zn from the surface of the Zn / Nd—Fe—B magnetic powder in FIG. 3 to the inside using an electron probe X-ray microanalyzer (EPMA).

FIG. 20 shows a magnetic flux density at 80 ° C. in the air of an anisotropic resin bonded magnet made of Zn / Nd—Fe—B magnetic powder that has been subjected to rust-proofing treatment by thermal decomposition of an organometallic compound according to the present invention. Over time.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Kenichi Machida, Inventor Kenichi Noguchi, Room 401, Green Hill Higashi-Mino, 1-4 1-4 Aowamatanishi, Minoh-shi, Osaka (72) Inventor Kenji 4-1-1 Ogishima, Yokosuka-cho, Tokai-shi, Aichi Prefecture Aichi Steel Corporation Yokosuka Dormitory Room 611 (72) Inventor Masafumi Nishimura 23-5 Kawaguchimayajiri, Yawata City, Kyoto Prefecture (72) Inventor Yu Yu Hamaguchi 17-1 1-1 Kutani Higashi, Takarazuka City, Hyogo Pref. 72) Inventor Noriyuki Kuwano 8-92, Momijioka, Kasuga-shi, Fukuoka Prefecture (72) Ken Itakura 1-19-24 Takasago, Chuo-ku, Fukuoka-shi, Fukuoka 1002 F-term, Aeons Plaza Watanabe Dori 4K018 BA18 BB06 BC25 BC35 BD01 GA04 KA46 5E040 AA03 AA04 CA01 HB15 HB17 NN03 NN06 NN18

Claims (26)

[Claims] 1. A magnetic material powder comprising a magnetic alloy or a magnetic intermetallic compound and having crystal grain boundaries of a magnetic material phase in powder particles, and a metal component having a rust-preventive action on the magnetic material powder (hereinafter referred to as a "anti-rust"). Rust metal component)
And a rust-proof metal source) in a sealed state in a sealed container. In this state, the temperature is increased while maintaining the inside of the sealed container in a non-oxidizing atmosphere, and the rust-preventive metal component is removed from the metal source. By supplying to the particle surface of the magnetic material powder, a rust-preventive layer mainly composed of the rust-preventive metal component is formed on the particle surface, and the rust-preventive layer is also formed in a region along the crystal grain boundary inside the powder particle. Form a rust-preventive layer mainly composed of metal components,
A method for producing a magnetic material, characterized by obtaining a magnetic material powder having a rustproof layer. 2. The rust-preventive layer is formed along crystal grain boundaries existing in the surface of the particle by infiltrating the rust-preventive metal component into the surface of the particle from the particle surface to a certain depth. A method for producing the magnetic material described above. 3. The method for producing a magnetic material according to claim 1, wherein the rust-preventive metal component is supplied to a particle surface of the magnetic material powder in the form of a metal vapor. 4. The rust-proof metal from the metal ingot or powder by reducing the pressure in the sealed container and raising the temperature in the sealed container, wherein the rust-proof metal supply source is a metal ingot or powder containing the rust-proof metal component. Claim 1 which promotes the vaporization of the components.
4. The method for producing a magnetic material according to any one of items 3 to 3. 5. The method for producing a magnetic material according to claim 4, wherein the inside of the sealed container is heated to a temperature equal to or higher than the melting point of the ingot or powder of the rustproof metal. 6. The method for producing a magnetic material according to claim 1, wherein Zn is used as the rust-preventive metal. 7. The temperature in the sealed container is 300 to 500.
The method for producing a magnetic material according to claim 6, wherein the temperature is raised to ° C. 8. The method for producing a magnetic material according to claim 1, wherein an organic metal compound of the rustproof metal component is used as the rustproof metal supply source. 9. A method in which the temperature of the magnetic material powder is dispersed in an organic solvent containing the organometallic compound in the hermetically sealed container and the temperature is raised, whereby the organometallic compound is decomposed and reduced, thereby preventing the organometallic compound from being generated. The method for producing a magnetic material according to claim 8, wherein rust metal is supplied to the particle surface of the magnetic material powder. 10. The magnetic material according to claim 8, wherein the rust-preventive metal component contained in the organometallic compound is mainly composed of one or more of Al, In, and Zn. Production method. 11. The organic metal compound may be Al, Ga,
An organic chain CmHn is bonded to a rust-preventive metal atom M composed of one or more of In, Si, Ge, Sn, Ti and Zn, and the number m of carbon atoms contained in the organic chain CmHn is 1 or more. The method for producing a magnetic material according to claim 10, wherein: 12. The method according to claim 1, wherein the rust prevention layer is formed in the sealed container by raising the temperature to a first temperature, and then the heat treatment is performed by raising the temperature to a second temperature higher than the first temperature. Item 12. The method for producing a magnetic material according to any one of Items 1 to 11. 13. The method of manufacturing a magnetic material according to claim 1, wherein the magnetic material powder is made of an alloy or an intermetallic compound containing a rare earth. 14. The magnetic material powder according to claim 1, wherein the magnetic material powder is Sm—Fe—N.
-Based intermetallic compound or Nd-Fe-TM (transition metal) -N
14. The method for producing a magnetic material according to claim 13, wherein the method mainly comprises a system intermetallic compound. 15. The magnetic material powder comprises Nd—Fe—B.
14. The method for producing a magnetic material according to claim 13, wherein the method mainly comprises a system intermetallic compound. 16. The method for producing a magnetic material according to claim 15, wherein the magnetic material powder mainly composed of the Nd—Fe—B-based intermetallic compound is produced by an HDDR method. 17. The method for producing a magnetic material according to claim 1, wherein the magnetic material powder having a rust-preventive layer is resin-bonded to form a bonded magnet. 18. The rust-preventive metal in a magnetic material powder made of a magnetic alloy or a magnetic intermetallic compound and having a grain boundary in a particle, in a surface layer portion of the particle and in a region along the grain boundary inside the particle. A magnetic material powder having a rust-preventive layer, wherein a rust-preventive layer mainly composed of components is formed. 19. The magnetic material powder with a rust-preventive layer according to claim 18, wherein the amount of the rust-preventive layer formed along the crystal grain boundaries is larger than the inside of the particle at the surface portion of the particle. 20. The magnetic material powder with a rust-preventive layer according to claim 18, wherein the rust-preventive layer is formed so as to have a thickness of 5 nm to 50 μm in a surface layer portion of the magnetic material powder particles. 21. The rust-preventive layer formed along the crystal grain boundaries has a penetration depth from the particle surface of 1 μm to 10 μm.
The magnetic material powder with a rust-proof layer according to any one of claims 18 to 20, which is in the range of: 22. The magnetic material powder with a rust preventive layer according to claim 18, wherein the thickness of the rust preventive layer formed along the crystal grain boundaries is 1 to 100 nm. 23. The rust-preventive metal component comprises Al, Ga, I
23. The magnetic material powder with a rust-preventive layer according to any one of claims 18 to 22, wherein one or more of n, Si, Ge, Sn, Ti, and Zn are mainly used. 24. The magnetic material powder, comprising Sm—Fe—N
-Based intermetallic compound or Nd-Fe-TM (transition metal) -N
24. The magnetic material powder with a rust-preventive layer according to any one of claims 18 to 23, which is mainly composed of a system intermetallic compound. 25. The magnetic material powder, comprising Nd—Fe—B
24. The magnetic material powder with a rust-preventive layer according to any one of claims 18 to 23, which is mainly composed of a system intermetallic compound. 26. A bonded magnet, wherein the magnetic material powder with a rust-proof layer according to claim 18 is resin-bonded.