JPH05190311A - Production of magnet and magnetic powder - Google Patents

Abstract

PURPOSE:To provide a magnet which allows high coercive force and stability by holding particles in nonaqueous solvent or non-oxidizing atmosphere during a finely powdering process, a coating process and the process between such processes. CONSTITUTION:Magnet constituted of the following is manufactured; 5-15atom% of R (R is an element of one or more kinds selected from rare earth elements and that contains Sm as an essential element.), 0.5-25atom% of N and T (T is Fe or Fe and Co.). The method has roughly powdering process which roughly powders mother alloy which contains the R and T so as to provide alloy particles, nitriding process which finely powders nitride particles so as to provide magnetic grains and coating process with forms non-magnetic coat on the surface of the magnet grains. The finely powdering process and the coating process are continually performed in nonaqueous solvent. Thus, magnetic particles which allow high coercive force and low coercive force deterioration in the lapse of time are provided.

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 an Sm-Fe-N system magnet.

[0002]

2. Description of the Related Art Sm-Co is a high-performance rare earth magnet.
System magnets and Nd-Fe-B system magnets are known, but in recent years, new rare earth magnets have been actively developed.

For example, with a composition near Sm ₂ Fe ₁₇ N _2.3 which is a compound of Sm ₂ Fe ₁₇ and N, 4πIs = 15.
4kG, Tc = 470 ° C., H _A = 14T basic physical properties are obtained, (BH) max of 10.5 MGOe is obtained as a metal bonded magnet with Zn as a binder, and
It has been reported that the introduction of N into the Sm ₂ Fe ₁₇ intermetallic compound significantly improved the Curie temperature and improved the thermal stability (PaperNo.S1.3 at the Sixth Internatio).
nal Symposium on Magnetic Anisotropy and Coercivity
in Rare Earth-Transition Metal Alloys, Pittsburgh,
PA, October 25, 1990. (Proceedings Book: Carnegie Mell
on University, Mellon Institute, Pittsburgh, PA 1521
3, USA)).

In this report, when Sm ₂ Fe ₁₇ N _2.3 powder was mixed with Zn powder and cold pressed, μ ₀ H
c = 0.2T (iHc = 2kG), but when further magnetically pressed and heat-treated at a temperature near the melting point of Zn to form a metal-bonded magnet, μ ₀ Hc = 0.6T (iHc =
6kG) has been obtained.

The magnet particles used in the metal-bonded magnets reported above have a particle size of about single crystal particles, and the coercive force generating mechanism is of the creation type. Therefore, the magnetic properties are easily affected by the surface state of the particles. That is, defects such as minute protrusions are generated on the surface of the magnet particles due to mechanical impact during crushing, oxidation of particles, etc., and when a magnetic field is applied on the side opposite to the magnetization direction, the defects become nuclei for generation of reverse magnetic domains. A domain wall is generated in the grain, but in a nucleation type magnet, there is no pinning site of the domain wall in the crystal grain, so domain wall movement easily occurs,
Coercive force is low. In the above report, when a metal bonded magnet is used, the magnet particles are brought into contact with a molten high-temperature binder, thereby reducing the surface roughness of the magnet particles and suppressing the generation of domain walls, and obtaining a high coercive force. it is conceivable that.

However, the metal bonded magnet is inferior in moldability to the resin bonded magnet using the resin binder and has a large specific gravity, so that the application field is limited.

On the other hand, the resin-bonded magnet is hard to obtain a high coercive force as compared with the metal-bonded magnet. Also,
The inventors of the present invention have found that resin-bonded magnets using Sm-Fe-N-based magnet particles have a relatively high coercive force immediately after production, but the coercive force is deteriorated with time, and the resin-bonded magnets are particularly stored in a high temperature environment. In this case, it was found that the coercive force was significantly deteriorated.
The cause of this deterioration of coercive force is considered as follows.

A small amount of oxygen is contained in magnet particles used for manufacturing various Sm-Fe-N magnets. The magnet particles are usually produced by roughly crushing a mother alloy ingot, subjecting it to a nitriding treatment, and then finely crushing it.
Oxygen in the magnet particles may be contained in the master alloy from the beginning, and may be mixed in each step. EP 0 41773
3 A2 discloses Sm-Fe-N-H-O-based magnet particles.
It is described that 6 atomic% of oxygen is mixed. Then, it is described that at least 80% of oxygen in the magnet particles exists in a region within several hundred angstroms from the surface of the particles.

The present inventors have found that Sm-Fe-N after fine pulverization
When the surface of the system magnet particles was analyzed by EPMA and electron diffraction, it was found that Sm and Fe existed in an amorphous state on the surface. Therefore, it is considered that an oxide layer of Sm and Fe having a thickness of several tens of nm exists in an amorphous state on the surface of the magnet particles. 200 magnet particles
If heated above about 0 ° C., the oxide layer will be crystallized even in an inert gas atmosphere. Specifically, it is considered that it is decomposed into Sm ₂ O ₃ and α-Fe. Further, even if the temperature is lower than 200 ° C., similar crystallization occurs when heated for a long time.

From these considerations, the present inventors have found that the amorphous oxide layer on the surface of the magnet particles suppresses the generation of reverse magnetic domains, and when the magnet particles are heated, the oxide layer crystallizes. It has been found that the action of preventing reverse magnetic domains is reduced and the coercive force is deteriorated.

[0011]

SUMMARY OF THE INVENTION The present invention has been made under the circumstances as described above, and when a magnet containing Sm, Fe and N is manufactured, the coercive force is prevented by preventing the surface of the magnet particle from being oxidized. It is an object of the present invention to provide a magnet having high stability and high stability.

[0012]

[Means for Solving the Problems]

Such an object is achieved by the present invention described in (1) to (7) below. (1) R (where R is selected from rare earth elements 1
It is an element of at least one kind and contains Sm as an essential element. ) In an amount of 5 to 15 atomic%, N in an amount of 0.5 to 25 atomic%, and the balance being T (wherein T is Fe, or Fe and Co). And T
Coarse crushing step of crushing a mother alloy containing to obtain alloy particles, nitriding step of nitriding the alloy particles to obtain nitride particles, and pulverizing step of crushing the nitride particles to obtain magnet particles And a coating step of forming a non-magnetic coating on the surface of the magnet particles, the finely pulverizing step and the coating step,
A method for producing a magnet, which is continuously performed in a non-aqueous solvent.

(2) R (wherein R is one or more elements selected from rare earth elements and contains Sm as an essential element) is 5 to 15 atomic% and N is 0.5 to 25 atomic%.
A method for producing a magnet containing, the balance being T (where T is Fe, or Fe and Co), comprising:
Coarse crushing step of coarsely crushing the master alloy containing R and T to obtain alloy particles, nitriding step of subjecting the alloy particles to nitriding treatment to obtain nitrided particles, and finely pulverizing the nitrided particles to obtain magnet particles A fine pulverizing step and a coating step of forming a non-magnetic coating on the surface of the magnet particles, wherein the fine pulverizing step and the coating step are performed in a non-oxidizing atmosphere or in a non-aqueous solvent, A method for manufacturing a magnet, wherein the magnet particles are held in a non-oxidizing atmosphere when the step shifts from the step to the coating step.

(3) R (where R is one or more elements selected from rare earth elements and contains Sm as an essential element) is 5 to 15 atomic% and N is 0.5 to 25 atomic%.
A method for producing a magnet containing, the balance being T (where T is Fe, or Fe and Co), comprising:
Coarse crushing step of coarsely crushing a master alloy containing R and T to obtain alloy particles, fine crushing step of finely crushing alloy particles to obtain fine alloy particles, and nitriding treatment of the fine alloy particles to obtain magnet particles. A nitriding step to obtain and a coating step of forming a non-magnetic coating on the surface of the magnet particles, wherein the fine pulverizing step and the coating step are performed in a non-oxidizing atmosphere or in a non-aqueous solvent, The alloy fine particles are held in a non-oxidizing atmosphere when shifting from the step to the nitriding step, and the magnet particles are held in a non-oxidizing atmosphere when shifting from the nitriding step to the coating step. A method for manufacturing a magnet, which is characterized by the above.

(4) The method for producing a magnet according to any one of (1) to (3) above, wherein the non-magnetic coating is made of a metal, an inorganic compound or an organic compound.

(5) The method for producing a magnet according to any one of the above (1) to (4), which comprises a step of dispersing the magnet particles having a non-magnetic coating in a resin binder to produce a resin-bonded magnet. ..

(6) 5 to 15 atomic% of R (wherein R is one or more elements selected from rare earth elements and contains Sm as an essential element) and 0.5 to 25 atomic% of N
And the balance is T (where T is Fe, or Fe and Co), a non-magnetic coating composed of a metal is formed on the surface, and the oxygen content is 6000 pp
A magnet powder comprising magnet particles having a size of m or less.

(7) R (wherein R is one or more elements selected from rare earth elements and contains Sm as an essential element) is 5 to 15 atomic% and N is 0.5 to 25 atomic%.
And the balance is T (where T is Fe, or Fe and Co), and includes magnetic particles having a non-magnetic coating composed of an inorganic compound or an organic compound formed on the surface thereof. Characterized magnet powder.

[0020]

In the present invention, the particles are kept in the non-aqueous solvent or in the non-oxidizing atmosphere during the fine pulverizing step, the coating step and between these steps, so that the surface of the magnet particles is prevented from being oxidized and the amorphous state is not oxidized. Generation of a physical layer is suppressed. Therefore, deterioration of coercive force when exposed to high temperature can be suppressed. Further, since the defects on the surface of the magnet particles, which are the core of the generation of the reverse magnetic domain, are repaired by the non-magnetic coating, high coercive force can be obtained.

Therefore, when the magnet particles having the non-magnetic coating are applied to the resin-bonded magnet, a coercive force equivalent to that of the metal-bonded magnet is obtained, the weight is lighter than that of the metal-bonded magnet, and the flexibility of molding is high. improves.

The magnet particles produced according to the present invention are Sm
₂ (Fe, Co) ₁₇ series alloy particles containing nitrogen (N). Since this magnet particle contains N, it has a high Curie temperature and is excellent in thermal stability. Further, by containing N, high saturation magnetization is obtained, anisotropic energy is also improved, and high coercive force is obtained. The improvement of magnetic characteristics is
It is considered that N forms an interstitial solid solution at a specific position of the crystal lattice, thereby optimizing the distance between Fe atoms and the distance between Fe atoms and rare earth metal atoms.

[0023]

Specific Structure The specific structure of the present invention will be described in detail below.

<Magnet Composition> The magnet particles contained in the magnet produced according to the present invention contain R, N and T.

R is Sm alone or one or more of Sm and other rare earth elements. Examples of rare earth elements other than Sm include Y, La, Ce, Pr, Nd, and E.
u, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu
Etc. If the amount of rare earth elements other than Sm is too large, the crystal magnetic anisotropy decreases, so the content of rare earth elements other than Sm is preferably 70% or less of R. The content rate of R is
It is 5 to 15 atom%, preferably 7 to 14 atom%. R
If the content is less than the above range, the coercive force iHc will decrease, and if it exceeds the above range, the residual magnetic flux density Br will decrease.

The N content is 0.5 to 25 atom%, preferably 5 to 20 atom%. In the present invention, a part of N may be replaced with C and / or Si. In this case, the N content is 0.5 atomic% or more,
The total content of N, C and Si is 25 atomic% or less. If the N content is less than the above range, the Curie temperature is not raised and the saturation magnetization is insufficiently improved. If the total content of N, C and Si exceeds the above range, Br is lowered. C and / or Si contained in place of part of N
Shows an effect of improving saturation magnetization, coercive force and Curie temperature. The lower limit of the total content of C and Si is not particularly limited, but if the total content is 0.25 atom% or more, the above-mentioned effects are sufficiently exhibited.

The Curie temperature of the magnet particles varies depending on the composition, but is about 430 to 650 ° C.

T is Fe, or Fe and Co,
The content of Fe in T is 20 atomic% or more, especially 30 atomic%.
The above is preferable. If the content of Fe in T is less than the above range, Br will decrease. There is no particular upper limit to the Fe content in T, but if it exceeds 80 atomic%, Br tends to decrease.

The magnet may contain elements other than the above, such as Mn, Ni and Zn. The content of these elements is preferably 3% by weight or less. Also, B,
Elements such as O, P, and S may be contained, but the content of these elements is preferably 2% by weight or less.

The magnet mainly has a Th ₂ Zn ₁₇ type rhombohedral crystal structure.

In the present invention, since the surface of the magnet particles is prevented from being oxidized as will be described later, the oxygen content of the magnet particles themselves is extremely low, 6000 ppm or less, and further 4000 ppm.
It can be: Oxygen is most likely to be mixed during fine pulverization and is rarely mixed during the formation of the non-magnetic coating, so if the non-magnetic coating is composed of a metal or if it is composed of an inorganic compound or organic compound containing no oxygen, Even if the measurement is performed without removing the magnetic coating, the oxygen content falls within the above range. The oxygen content can be measured by a gas analysis method or the like. On the other hand, when the non-magnetic coating is composed of an inorganic compound or an organic compound having oxygen as a constituent element, the non-magnetic coating may be removed to measure the oxygen content of the magnet particles themselves.

The magnet particles inevitably contain at least 50 ppm, usually about 250 ppm or more of oxygen.

<Non-magnetic coating>

In the magnet powder of the present invention, a nonmagnetic coating is formed on the surface of such magnet particles. The non-magnetic coating is
It suppresses the generation of reverse domains on the surface of magnet particles and realizes high coercive force. When the coating has magnetism, the effect of preventing reverse magnetic domain generation is significantly reduced.

The constituent material of the non-magnetic coating is not particularly limited as long as it can coat the surface of the magnet particles and can repair defects on the surface of the magnet particles, and it is appropriately selected from various metals, inorganic compounds, organic compounds and the like. Just select it. Examples of the metal include Zn, Sn, Cu, In, Pb, Ga and S.
b and the like, alloys or intermetallic compounds and inorganic compounds containing them, nitrides and carbides of the above metals are preferable, fatty acid salts and the like are preferable as organic compounds, and among these, particularly low melting point, and An element that forms a non-magnetic compound with Fe at low temperature is preferable.

The non-magnetic coating is preferably a continuous film that coats the entire surface of the magnet particles, but since the magnet particles having the above composition have a large crystal magnetic anisotropy energy,
If the non-magnetic coating covers at least a part of the surface of the magnet particles, preferably 70% or more of the surface, a sufficient coercive force improving effect is realized.

The thickness of the non-magnetic coating is preferably 5 nm or more, more preferably 10 nm or more in order to improve the coercive force. There is no particular upper limit on the thickness of the non-magnetic coating, but in order to increase the filling rate of the magnet particles in the resin-bonded magnet and to obtain good moldability during the production of the resin-bonded magnet, it is usually 5 μm. Below, preferably less than 100 nm,
More preferably, it is 90 nm or less.

The ratio of the non-magnetic coating to the total of the magnetic particles and the non-magnetic coating depends on the thickness of the non-magnetic coating, but is usually preferably 15% by volume or less. When the ratio of the non-magnetic coating exceeds the above range, it becomes difficult to increase the filling rate of the magnet particles when applied to the resin bonded magnet, and the moldability also deteriorates.

Although two or more magnet particles may be present in the non-magnetic coating, when magnetic field orientation is performed to form an anisotropic resin bonded magnet, each magnet particle is independently formed. It preferably has a non-magnetic coating.

<Production Method> The production method of the present invention comprises a coarse crushing step of coarsely crushing a master alloy containing R and T to obtain alloy particles, and a nitriding step of nitriding the alloy particles to obtain nitrided particles. And a step of finely pulverizing the nitride particles to obtain magnet particles.

Method for Producing Alloy Particles Each raw material metal or alloy is mixed, and then the mixture is melted and cast to produce a master alloy ingot, and the master alloy ingot is coarsely crushed to produce alloy particles. The composition of the mother alloy ingot may be appropriately selected so that the magnet having the above composition can be obtained.

The crystal grain size of the mother alloy ingot is not particularly limited, and it is preferable that the size is such that single crystal grains can be obtained by fine pulverization described later.

Next, the mother alloy ingot is subjected to solution treatment, if necessary. Solution treatment is performed to eliminate the heterogeneous phase and improve the homogeneity of the ingot. The conditions of the solution treatment are not particularly limited, but usually the treatment temperature is 900 to
It is preferable that the temperature is 1250 ° C., particularly 1000 to 1200 ° C., and the treatment time is 0.5 to 60 hours. Although the solution treatment can be performed in various atmospheres, it is preferably performed in a non-oxidizing atmosphere such as an inert gas atmosphere, a reducing atmosphere, or a vacuum.

Next, the mother alloy ingot is coarsely crushed into alloy particles. The average particle diameter of the alloy particles is not particularly limited, but in order to obtain sufficient oxidation resistance, the average particle diameter of the alloy particles is preferably 2 μm or more, more preferably 10 μm.
The thickness is preferably m or more, more preferably 15 μm or more, and is preferably about 1000 μm or less, and particularly preferably 200 μm or less.

The crushing means is not particularly limited, and various ordinary crushers may be used, but coarse crushing is performed in a non-oxidizing atmosphere.

In the present invention, the average particle diameter means the weight average particle diameter D ₅₀ obtained by sieving. The weight average particle diameter D ₅₀ is a particle diameter when the weight is added from the particles having a smaller diameter and the total weight becomes 50% of the total weight of all the particles.

Method for producing nitrided particles Next, the alloy particles are subjected to a nitriding treatment to form a solid solution of N to obtain nitrided particles. In this nitriding treatment, the alloy particles are heat-treated in a nitrogen atmosphere, whereby the alloy particles absorb nitrogen. In order to form a solid solution of N as described above, it is preferable to perform the nitriding treatment under the following conditions.
The holding temperature is preferably 400 to 700 ° C, particularly preferably 450 to 650 ° C. Temperature holding time is 0.5-2
It is preferably set to 00 hours, particularly 2 to 100 hours.

If the mother alloy ingot is occluded with hydrogen to cause crushing or cracking and the alloy particles are subjected to the nitriding process without being exposed to the atmosphere, generation of an oxide film on the particle surface can be suppressed. Therefore, high reactivity can be obtained during the nitriding treatment.

Further, by occluding hydrogen in the alloy, a fine gas passage is formed in the alloy, and during the subsequent nitriding treatment, nitrogen penetrates to the deep portion of the alloy, so that N is absorbed. It becomes possible to easily form a solid solution.
Therefore, alloy particles having a large size can be nitrided, and the oxidation resistance of the alloy particles and the nitride particles can be improved. For example, the distance to the surface is 0.25
Even alloy particles having a region of mm or more, further 5 mm or more can be nitrided. However, for uniform nitriding, the distance from the surface is 15 mm.
It is preferable to use an alloy particle having a size and shape such that there is no portion exceeding the above.

The hydrogen storage treatment is a process of storing hydrogen in the alloy by heat treatment in a hydrogen gas atmosphere.
The heat treatment temperature at this time is 350 ° C. or lower, particularly 100 to 3
It is preferable to set the temperature to 00 ° C, and the temperature holding time is 0.5 to
It is preferably 24 hours, particularly 1 to 10 hours. The pressure of the hydrogen gas is 0.1 to 10 atm, especially 0.5.
It is preferable to set the pressure to 2 atm.

The atmosphere during hydrogen storage is not limited to hydrogen gas, but may be a mixed atmosphere of hydrogen gas and inert gas. In this case, the inert gas is preferably He or Ar, or a mixed gas thereof.

When the hydrogen storage treatment is carried out before the nitriding treatment, the holding temperature during the nitriding treatment can be lowered, and 3
Nitriding is possible at 50 to 650 ° C, especially at 400 to 550 ° C. However, the temperature at this time is preferably higher than the temperature of the hydrogen storage treatment.

In order to increase the productivity, it is preferable to carry out a nitriding treatment without releasing hydrogen from the alloy after the hydrogen storage treatment. In this case, since hydrogen in the alloy is released from the alloy by heating during the nitriding treatment, hydrogen is not substantially contained in the nitride particles.

However, it is also possible to release hydrogen from the alloy after the hydrogen occlusion treatment and then perform the nitriding treatment. in this case,
By subjecting the alloy storing hydrogen to a heat treatment in a reduced pressure atmosphere, hydrogen can be released from the alloy.
In this case, the heat treatment temperature is preferably 200 to 400 ° C., and the temperature holding time is preferably 0.5 to 2 hours. The pressure is 1 × 10 ^-2 Torr or less, especially 1 ×
It is preferably 10 ⁻³ Torr or less, and heat treatment is preferably performed in an Ar gas atmosphere.

In order to make the distribution of nitrogen atoms in the nitride particles uniform, it is preferable to subject the nitride particles to heat treatment in a non-oxidizing atmosphere such as an Ar atmosphere. The temperature during this heat treatment is
The temperature is preferably higher than the temperature at which the alloy particles are nitrided. Specifically, the temperature is 20% higher than the temperature during the nitriding treatment.
Higher than ℃, 700 ℃ to prevent decomposition reaction
It is preferably not more than about this level. Further, in order to make the distribution of nitrogen atoms more uniform, it is preferable to use nitride particles in which there is no region where the distance from the surface exceeds 30 μm. By performing the heat treatment under such conditions, it is possible to obtain the nitride particles in which the ratio of the surface nitrogen atom concentration to the central nitrogen atom concentration is about 0.80 or more. The distribution of nitrogen atoms in the nitride particles can be confirmed by EPMA or the like.

Since the magnet particles are manufactured by pulverizing the nitride particles, by homogenizing the nitrogen atom distribution of the nitride particles, magnet particles having a uniform nitrogen content, that is, magnet particles having a uniform coercive force can be obtained. As a result, a magnet having a high squareness ratio is realized.

Method for producing magnet particles and shape of non-magnetic coating
Method of Composition Next, the nitride particles are crushed into almost monocrystalline magnet particles, and a non-magnetic coating is further formed on the magnet particles.

The average particle size of the magnet particles obtained by fine pulverization is not particularly limited and may be appropriately determined depending on the application so as to obtain a desired coercive force, and usually 0.5 to 50 μm.
It should be about m. If a non-magnetic coating is formed, the necessary coercive force can be obtained without crushing to a particle size so as to obtain a single magnetic domain.

In the present invention, the fine pulverization step and the coating step are carried out continuously in a non-aqueous solvent, or these steps are carried out continuously in a non-oxidizing atmosphere. Of these, the method of using a non-aqueous solvent is preferable because it is simple and sufficient effects can be obtained.

First, a method for continuously pulverizing and forming a non-magnetic coating in a non-aqueous solvent will be described.

In this method, the nonmagnetic coating made of metal can be formed by the plating method. It is also possible to form a non-magnetic coating made of an organic compound such as resin.

When the plating method is used, first, the nitride particles are wet finely pulverized in a non-aqueous solvent to obtain magnet particles. The means for wet pulverization is not particularly limited, and ordinary means such as a ball mill or a vibration mill may be used. Then, the slurry containing the magnet particles is taken out from the pulverizer and mixed with a plating bath to form a non-magnetic coating by a plating method. In this plating bath,
A non-aqueous solvent is used. Further, as the non-aqueous solvent used in the wet fine pulverization, those which can be dissolved in the plating bath are selected. The composition of the plating bath may be used as a solvent for the wet pulverization. In this case, however, the plating bath solution is usually corrected so that the amount and the liquid properties required for plating are obtained.

When the magnet particles may come into contact with gas during the wet fine pulverization, it is preferable to perform the wet pulverization in a non-oxidizing atmosphere. In this case, the non-oxidizing atmosphere is preferably a non-oxidizing gas atmosphere such as nitrogen or Ar and has an oxygen partial pressure of 10 ⁻³ Torr or less, and the same applies to the following description.

As the plating method, various methods such as electroplating, electroless plating and displacement plating can be used, but the electroplating method is used because a non-magnetic coating having a uniform and uniform thickness can be easily formed. Preferably.

The plating bath used in the electroplating method is one in which the compound of the nonmagnetic coating constituent element is dissolved in a nonaqueous solvent. The compound is not particularly limited, and various compounds that can be dissolved in a non-aqueous solvent, for example, various compounds such as chlorides, nitrates, and carbonates may be used.

The non-aqueous solvent used in the plating bath may be appropriately selected from organic solvents and the like in which those compounds can be dissolved, depending on the material used for the non-magnetic coating. Specifically, for example, it may be selected from dimethylformamide, dimethylsulfoxide, propylene carbonate, acetonitrile and the like.

Further, the above non-aqueous solvent may be used for fine pulverization, and further, those which can be dissolved in these, for example,
Xylene, acetone, etc. can also be used.

The conditions of electroplating are not particularly limited, and various conditions such as current density and plating bath temperature may be appropriately set according to the nonmagnetic coating to be formed. Further, the apparatus used for the electroplating method is not particularly limited, and for example, according to the text of “9th latest powder metallurgy technology course” (October 22 to 23, 1991, Tokyo University of Science) A vertical type electroplating apparatus or a gradient type electroplating apparatus suitable for electroplating may be used. These particles have a configuration in which a stirring blade is provided in a plating bath to form a suspension layer of powder on a mesh-shaped cathode, or the mesh-shaped cathode rotates to stir the powder, and particles constituting the powder are formed. This is an electroplating apparatus capable of uniformly forming an electroplating film on the surface of.

When forming a non-magnetic coating composed of an organic compound in a non-aqueous solvent, it is preferable to use a chelate resin. In this case, magnet particles are put into a solution in which a chelate resin is dissolved in a non-aqueous solvent, and the magnet particles are pulverized by a wet pulverizer such as a ball mill. After the pulverization, the resin particles are formed on the surface of the magnet particles by heating and drying. Since the chelate resin in the solution binds to R, T, etc. on the surface of the magnet particles, the magnet particles are hardly bound to each other through the chelate resin, and a magnetic powder with easy magnetic field orientation can be obtained. The dispersion obtained by finely pulverizing in a non-aqueous solvent containing no resin may be mixed with a non-aqueous solvent in which the resin is dissolved and dried by heating.

Besides, the non-magnetic coating can be formed by various thermosetting resins such as epoxy resin. In this case, it is preferable to perform heat drying and curing using a fluidized bed or the like in order to avoid binding of the magnet particles during drying or curing.

Next, a method of continuously performing the finely pulverizing step and the covering step in a non-oxidizing atmosphere will be described. In this case, the non-oxidizing atmosphere is preferably composed of the above-mentioned non-oxidizing gas having an oxygen partial pressure. In this method, after performing the pulverization step in a non-oxidizing atmosphere, the non-magnetic coating is formed without exposing the magnet particles to the oxidizing atmosphere.

The finely pulverizing means in this case is not particularly limited,
Dry crushing may be performed with an attritor, ball mill, jet mill, or the like.

In this case, the vapor phase growth method can be preferably used as the method for forming the non-magnetic coating. Vapor growth method
It is suitable for forming a non-magnetic coating of a metal or an inorganic compound. The vapor phase growth method includes CV such as thermal CVD and plasma CVD.
It may be appropriately selected from the D method, PVD methods such as vapor deposition, sputtering, and ion plating.

When the sputtering method is used, the above-mentioned "9th latest powder metallurgy technology course" (October 2, 1991)
It is preferable to use a powder sputtering apparatus as described in the text of Tokyo University of Science, 2-23 days. This apparatus puts powder in a vacuum chamber having a target inside and performs sputtering while rotating the vacuum chamber, and can form a non-magnetic coating on the surface of magnet particles with a uniform thickness. ..

The CVD method is preferable because it has a high step coverage and can form a non-magnetic coating having a substantially uniform thickness on the entire surface of the magnet particles. When the thermal CVD method is used, for example, the magnetic particles may be placed on a heated dish and the thermal CVD may be performed while vibrating or rotating the dish.

When the non-magnetic coating is formed by thermal CVD, various volatile compounds containing non-magnetic coating constituent elements may be used as raw materials.

In addition to the vapor phase growth method described above, the nonmagnetic coating can be formed by mechanical energy. For example,
Non-magnetic coating raw material particles containing a non-magnetic coating constituent element and magnet particles are mixed, and mechanical energy is given to these particles to fuse them. At this time, mechanical energy is applied so that at least the magnetic characteristics of the magnet particles are not destroyed.

As a method of applying mechanical energy as described above, it is easy to control the coating conditions and work, form a continuous film having a uniform and uniform thickness, and control the film thickness easily. Fusion is preferred.

In the present specification, the mechanofusion is a technique in which mechanical energy, particularly mechanical strain force is applied between a plurality of different material particles to cause a mechanochemical reaction. As a device for applying such mechanical strain force, there is, for example, a powder or granular material processing device as described in JP-A-63-42728.
Specifically, a mechanofusion system manufactured by Hosokawa Micron Co., Ltd. or a hybridization system manufactured by Nara Machinery Co., Ltd. is suitable.

FIG. 1 shows an example of a mechanofusion coating device.
Shown in. In FIG. 1, the mechanofusion coating device 7
Rotates the casing 8 containing the powder at a high speed to form the powder layer 6 on the inner peripheral surface 81 thereof, and at the same time, causes the friction piece 91 and the scraping piece 95 to rotate relative to the casing 8 to form the inner periphery of the casing 8. On the surface 81, the friction layer 91 compresses and rubs the powder layer 6, and at the same time, the scraping piece 95 scrapes, disperses, and agitates.

Various conditions at the time of mechanofusion may be appropriately set according to the composition of the non-magnetic coating raw material particles and the intended composition of the non-magnetic coating. For example, in the above apparatus, the mixing time is 20 to About 40 minutes, the number of rotations of the casing 8 is about 800 to 2000 rpm, the temperature is about 15 to 70 ° C., and other conditions may be normal. The average particle size of the non-magnetic coating raw material particles is 0.5 to 10
It is preferably about μm.

By properly selecting various conditions in such a mechanofusion, it is possible to form the mixed portion together with the formation of the non-magnetic coating.

When the non-magnetic coating is formed by each of the above-mentioned methods, the magnet particles may aggregate, but when applied to a resin bonded magnet, it may be crushed if necessary. Multiple magnet particles may be present therein.

In addition to the method of directly forming the non-magnetic coating on the magnet particles as described above, the method of crushing the metal bonded magnet in which the magnet particles are dispersed in the binder of the non-magnetic metal may be used. , Magnetic particles having a non-magnetic coating can be produced. In this case, the binder is a non-magnetic coating.

There is no particular limitation on the method for producing the crushed metal bonded magnet. For example, when a magnet powder composed of magnet particles and a binder powder composed of binder particles are mixed and molded and then heat treated, the magnet particles can be bonded by the binder, and a metal bonded magnet is obtained.

When this method is used, a binder capable of binding magnet particles at 550 ° C. or lower, preferably 500 ° C. or lower is used. Further, the average particle diameter of the binder powder is not particularly limited, but in order to mix it uniformly with the magnet powder,
It is preferably about 0.5 to 30 μm. The mixing means is also not particularly limited, and, for example, a Raikai machine or the like may be used.

The content of the binder powder in the mixture of the magnet powder and the binder powder is not particularly limited,
If the content of the binder powder is too low, it becomes difficult to obtain a uniform non-magnetic coating when crushed due to poor formability, and if the content is too high, the non-magnetic coating becomes too thick, so Usually, it is preferable to be 2 to 25% by volume. The molding means is not particularly limited, but usually compression molding is performed. The pressure during molding is not particularly limited, but is usually about 0.2 to 16 t / cm ² .

In such a case, since the metal bonded magnet is crushed and used, it is not necessary to impart anisotropy to the metal bonded magnet, but a crushed powder containing a plurality of magnet particles in the non-magnetic coating is obtained. In such a case, it is preferable that the directions of the easy axis of magnetization of the plurality of magnet particles are oriented. For such orientation, the above-mentioned molding may be performed in a magnetic field.

The heat treatment temperature for binding the magnet particles with the binder is 550 ° C. or lower, preferably 500 ° C. or lower. When the heat treatment temperature exceeds 550 ° C., the magnet powder is decomposed to release N at a higher speed, and the magnetic characteristics are deteriorated. The heat treatment temperature is not particularly limited as long as it is 550 ° C. or lower, and may be appropriately selected depending on the melting point of the binder so that the required viscosity can be obtained. Sufficient thermal stability cannot be obtained. Further, the temperature holding time during the heat treatment is preferably about 10 minutes to 5 hours. The heat treatment means is not particularly limited, but means for heating while applying pressure is preferable, and for example, hot pressing, plasma activated sintering (PAS), etc. are preferable.

When a pressurizing and heating means such as a hot press is used when binding the magnet particles with the binder, even if the heat treatment temperature is lower than the melting point of the binder, that is, the binder is not in a molten state, It is possible to form metal bonded magnets.

After the heat treatment, it is cooled. By cooling in a magnetic field, it is possible to favorably maintain the anisotropy due to the above-mentioned magnetic field molding.

When manufacturing a metal bonded magnet,
Molding may be performed by a casting method. When the casting method is used, a fluid in which magnet powder is dispersed in a molten binder is formed by casting. The method for producing the fluid is not particularly limited. For example, a method may be used in which the binder is melted to form a molten metal, and the magnet powder is put into this and stirred and mixed, or alternatively, the binder powder and the magnet powder are mixed and then heated to melt the binder. The method of doing may be used.

When the method of charging the magnet powder into the molten metal binder is used, the means for stirring and mixing the magnet powder and the binder is not particularly limited. For example, stirring is performed with an impeller made of a material (stainless steel etc.) that does not react with the binder. A method etc. can be used.

The content of the binder in the fluid is not particularly limited, but if the content of the binder is too low, the moldability deteriorates and it becomes difficult to obtain a uniform non-magnetic coating when pulverized. If too much, the non-magnetic coating becomes too thick when crushed, so the binder content is usually 10 to 10.
It is preferably 40% by volume.

Further, after producing the above-mentioned fluid, a part of the binder may be removed if necessary. A certain amount or more of binder is required to uniformly disperse the magnet powder in the binder, but when manufacturing a metal-bonded magnet with a relatively simple shape such as a plate, high fluidity is required during molding. Therefore, the binder amount may be small. When used in the manufacture of resin-bonded magnets, the shape of metal-bonded magnets may be simple lumps or plates,
After dispersing with a sufficient amount of binder, molding can be performed even if a part of the binder is removed, whereby the thickness of the nonmagnetic coating can be reduced. If the thickness of the non-magnetic coating can be reduced, the filling rate of the magnet particles can be increased when forming the resin-bonded magnet, and the moldability does not deteriorate. As a method of removing a part of the binder, for example, filtration or centrifugation is preferable, and a method of heating under reduced pressure to evaporate the binder may be used.

The fluid composed of the molten binder and the magnet powder is cooled and solidified in the mold, but if the solidification temperature of the binder is not higher than the Curie temperature of the magnet powder, the magnetic particles are solidified in the magnetic field. Since the easy axis of magnetization can be oriented and an anisotropic metal-bonded magnet can be obtained, it is possible to improve the magnetic properties when a plurality of magnet particles are contained in the non-magnetic coating as described above. is there.

The temperature of the fluid during dispersion and casting is
The temperature is 550 ° C. or lower, preferably 500 ° C. or lower. The reason for this limitation is to suppress the release of N as described above. The temperature of the fluid is not particularly limited as long as it is 550 ° C. or lower, and may be appropriately selected according to the melting point of the binder so that the viscosity required for casting can be obtained, but a binder that melts below 150 ° C. is used. If so, practically sufficient thermal stability cannot be obtained.

There is no particular limitation on the method of crushing the metal bonded magnet produced by these methods.
It may be crushed with a disc mill or an attritor.
By pulverization, magnet particles having a non-magnetic metal binder as a non-magnetic coating are obtained. The non-magnetic coating is preferably pulverized so that one magnet particle is contained therein, but a plurality of magnet particles may be contained as described above.

In the present invention, after forming the non-magnetic coating, a part of the non-magnetic coating may be removed if necessary. The non-magnetic coating may prevent oxidation of the magnet particles and may have a function of repairing surface defects of the magnet particles. Therefore, if the non-magnetic coating in the region exceeding the thickness required for these is removed, It is possible to further improve the magnetic characteristics while maintaining the coercive force improving effect. In particular, when the method of crushing a metal bonded magnet is used among the above-mentioned non-magnetic coating forming methods, this method is effective because the non-magnetic coating tends to be thick.

The method of removing a part of the non-magnetic coating is not particularly limited, but a method of washing the magnetic particles having the non-magnetic coating with an alkaline solution or an acidic solution is preferable.

Incidentally, either one of the fine pulverization step and the coating step may be carried out in a non-oxidizing atmosphere and the other in a non-aqueous solvent. In this case, the magnet particles are kept in a non-oxidizing atmosphere during the transition from the finely pulverizing step to the coating step to prevent the surface of the magnet particles from being oxidized. Alternatively, the finely pulverizing step may be performed in a non-aqueous solvent, the magnet particles may be kept in a non-oxidizing atmosphere until the coating step, and then the coating step may be performed in a non-aqueous solvent.

In the above description, the case of performing the coarse pulverizing step → nitriding step → fine pulverizing step → covering step is described. However, except when the fine pulverizing step and the coating step are continuously performed in a non-aqueous solvent, You may perform in order of a coarse pulverization process-> a fine pulverization process-> a nitriding process-> a coating process. In this case, the alloy particles obtained by the coarse crushing step are made into alloy fine particles by the fine crushing step,
The alloy particles are nitrided in a nitriding process to produce magnet particles. Then, the pulverizing step and the coating step are performed in a non-oxidizing atmosphere or in a non-aqueous solvent. When the steps are performed in this order, the alloy fine particles are kept in a non-oxidizing atmosphere during the transition from the fine pulverization step to the nitriding step, and the magnetic particles are removed during the transition from the nitriding step to the coating step. Keep in an oxidizing atmosphere.

Method for producing resin-bonded magnet The magnet particles having a non-magnetic coating produced as described above are usually dispersed in a resin binder to obtain a resin-bonded magnet.

The resin-bonded magnet may be manufactured by an ordinary method. That is, the magnet particles having a non-magnetic coating and the resin binder are mixed, molded, and heat-treated as necessary.

The molding method is not particularly limited, and either a compression bonded magnet using compression molding or an injection bonded magnet using injection molding may be used.

The binder to be used is not particularly limited, and various resins used for known resin-bonded magnets may be used. For example, in the case of compression bonded magnets, various thermosetting resins such as epoxy resins using various curing agents may be used, and in the case of injection bonded magnets, various thermoplastic resins such as polyamide resins may be used. The state of the binder at the time of mixing is not particularly limited.

There is no particular limitation on the mixing method of the magnet particles and the binder, and a horizontal rotary cylindrical mixer, a cubic cube mixer,
Any of a vertical double cone type mixer, a V type mixer, a plow plate mixer, a spiral mixer, a ribbon mixer, an impact rotary mixer and the like may be used. The conditions for compression molding or injection molding are not particularly limited, and may be appropriately selected from known conditions.

The resin-bonded magnet may contain a lubricant, a coupling agent, a plasticizer, an antioxidant, etc., if necessary, in addition to the above-mentioned magnet particles and binder.

[0109]

EXAMPLES Specific examples of the present invention will be given below.

[Example 1] <Production of alloy particles> First, a master alloy ingot having an atomic ratio composition of 10.9Sm-89.1Fe was produced by high frequency induction heating. This mother alloy ingot is Th ₂ Zn
_{It had 17} type rhombohedral crystal grains and had an average grain size of about 300 μm. The crystal structure was confirmed by the X-ray diffraction method.

Next, the mother alloy ingot was subjected to solution treatment. The solution heat treatment is performed at 1150 ° C. in an Ar gas atmosphere.
For 16 hours.

After the solution treatment, the mother alloy ingot was crushed to an average particle size of 20 μm to obtain alloy particles.

<Production of Nitrided Particles> Next, the alloy particles were subjected to a nitriding treatment to produce nitrided particles. The nitrogen content of the nitride particles was 14 atom%. The nitriding treatment was performed by heat treatment at 450 ° C. for 10 hours in an N ₂ gas atmosphere.

<Production of Magnet Particles> Next, the nitride particles were finely pulverized into magnet particles by the following methods, and a non-magnetic coating was formed on the surfaces of the magnet particles.

Fine grinding and non-magnetic property in non-aqueous solvent
Formation of coating First, the nitrided particles were mixed with xylene and dimethylformamide to prepare a dispersion, which was placed in a ball mill and ground to an average particle size of 4 μm. The container of the ball mill was filled with nitrogen gas and the container was sealed. The oxygen partial pressure in the container was 10 ^-4 Torr or less. Then, the dispersion was taken out of the ball mill, mixed with a plating bath, and a non-magnetic coating was formed by an electroplating method using the above-mentioned inclined electroplating apparatus. A CuCl ₂ dimethylformamide solution was used for the plating bath. CuC after mixing the dispersion
concentration of l ₂ was 0.15mol / l. The plating bath temperature was 30 ° C. and the current density was 0.5 A / dm ² .

The Cu coating thus formed had an average thickness of 20 nm and covered the entire surface of the magnet particles. The powder composed of these magnet particles was designated as Sample No. 1.

An acetonitrile solution of CrCl ₃ (concentration after mixing was 0.1 mol / l) was used in the plating bath, and other conditions were the same as above, and the average thickness of the magnet particles was 20 nm.
Of Cr coating was formed. The magnet powder composed of these magnet particles was designated as Sample No. 2.

Fine milling and non-milling in a non-oxidizing atmosphere
Formation of Magnetic Coating The above-mentioned nitride particles were finely pulverized in a nitrogen gas atmosphere having an oxygen partial pressure of 10 ⁻⁵ Torr or less to a mean particle diameter of 3 μm by a jet mill to obtain magnet particles. Then, while maintaining the atmosphere, magnet particles were placed in a vacuum chamber having a sputter target inside, and the interior of the vacuum chamber was evacuated to 10 ^-9 Torr or less. Then, Ar gas was introduced to bring the inside of the vacuum chamber to 10 ^-2 Torr.
Then, sputtering was performed while rotating the vacuum chamber. In was used as the target. The In coating thus formed had an average thickness of 10 nm and covered the entire surface of the magnet particles. Sample No. is the powder consisting of these magnet particles.
It was set to 3.

For comparison, the above-mentioned nitride particles were pulverized in a nitrogen gas atmosphere having an oxygen partial pressure of 10 ^-2 Torr to an average particle diameter of 3 μm to produce magnet particles. A magnet powder composed of these magnet particles was designated as sample No. 4. This sample No. 4
Was analyzed by Auger spectroscopy.
The oxygen intensity up to a depth of 0 to 20 nm was 10 times higher than the oxygen intensity near the center of the magnet particles.

The coercive force iHc and the saturation magnetization 4πIs of these samples were measured by VSM. Also, the oxygen content of these samples was measured by gas analysis. These were measured immediately after sample preparation and after standing in air at 200 ° C. for 1 hour. The results are shown in Table 1 below.

[0121]

[Table 1]

From the results shown in Table 1, the effect of the present invention is clear.

Example 2 <Manufacture of Resin Bonded Magnet> Using each magnet powder sample manufactured in Example 1, a resin bonded magnet was manufactured.

First, an epoxy resin powder was dissolved in an organic solvent, and then magnet particles were put into the organic solvent and stirred to obtain a slurry. The slurry was dried with a spray dryer and the magnet particles were coated with an epoxy resin. Specifically, discharging the slurry into nitrogen gas which is injected at a pressure of 8 kgf / cm ^2, dried with nitrogen gas at a flow rate of 50 m ³ / 10min to the slurry 1 kg.

Next, the magnet particles were compression-molded and further heat-cured to obtain a resin-bonded magnet.

When the coercive force of these resin-bonded magnets was measured, the coercive force was shown according to the magnet particles used.

[0127]

INDUSTRIAL APPLICABILITY According to the present invention, the formation of an oxide layer on the surface of the magnet particles is prevented and the non-magnetic coating is formed on the surfaces of the magnet particles, so that the magnet particles having high coercive force and little deterioration over time are realized.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of a coating device by mechanofusion used when forming a non-magnetic coating on the surface of magnet particles.

[Explanation of symbols]

 6 Powder layer 7 Mechanofusion coating device 8 Casing 91 Friction piece 95 Scraping piece

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H01F 41/02 G 8019-5E // C23C 8/26 7516-4K

Claims (7)

[Claims] 1. Containing 5 to 15 atomic% of R (wherein R is one or more elements selected from rare earth elements and including Sm as an essential element) and 0.5 to 25 atomic% of N And the balance is T (where T is Fe, or Fe and C
It is o. ) Is a method for producing a magnet, wherein a coarse crushing step of roughly crushing a mother alloy containing R and T to obtain alloy particles, and a nitriding step of subjecting the alloy particles to a nitriding treatment to obtain nitride particles. It has a fine pulverizing step of finely pulverizing the nitride particles to obtain magnet particles, and a coating step of forming a non-magnetic coating on the surface of the magnet particles, wherein the fine pulverizing step and the coating step are performed in a non-aqueous solvent. A method for manufacturing a magnet, which is continuously performed in step 1. 2. Containing 5 to 15 atomic% of R (wherein R is one or more elements selected from rare earth elements and including Sm as an essential element) and 0.5 to 25 atomic% of N And the balance is T (where T is Fe, or Fe and C
It is o. ) Is a method for producing a magnet, wherein a coarse crushing step of roughly crushing a mother alloy containing R and T to obtain alloy particles, and a nitriding step of subjecting the alloy particles to a nitriding treatment to obtain nitride particles. It has a fine pulverizing step of finely pulverizing the nitride particles to obtain magnet particles, and a coating step of forming a non-magnetic coating on the surface of the magnet particles, wherein the fine pulverizing step and the coating step are performed in a non-oxidizing atmosphere. Alternatively, the method for producing a magnet is performed in a non-aqueous solvent, wherein the magnet particles are held in a non-oxidizing atmosphere when the fine pulverizing step is transferred to the coating step. 3. R (wherein R is one or more elements selected from rare earth elements and contains Sm as an essential element) in an amount of 5 to 15 atomic% and N in an amount of 0.5 to 25 atomic%. And the balance is T (where T is Fe, or Fe and C
It is o. ) Is a method for producing a magnet, wherein a coarse crushing step of coarsely crushing a master alloy containing R and T to obtain alloy particles, and a fine crushing step of finely crushing the alloy particles to obtain fine alloy particles, A nitriding step of subjecting the alloy fine particles to a nitriding treatment to obtain magnet particles, and a coating step of forming a non-magnetic coating on the surface of the magnet particles, wherein the pulverizing step and the coating step are performed in a non-oxidizing atmosphere. Or in a non-aqueous solvent, the alloy fine particles are held in a non-oxidizing atmosphere during the transition from the pulverizing step to the nitriding step, and during the transition from the nitriding step to the coating step A method for producing a magnet, characterized in that the magnet particles are held in a non-oxidizing atmosphere. 4. The method for producing a magnet according to claim 1, wherein the non-magnetic coating is made of a metal, an inorganic compound or an organic compound. 5. The method for producing a magnet according to claim 1, further comprising a step of dispersing the magnet particles having a non-magnetic coating in a resin binder to produce a resin-bonded magnet. 6. Containing 5 to 15 atomic% of R (wherein R is one or more kinds of elements selected from rare earth elements and including Sm as an essential element) and 0.5 to 25 atomic% of N And the balance is T (where T is Fe, or Fe and C
It is o. ), A non-magnetic coating made of metal is formed on the surface, and the magnet powder contains magnet particles having an oxygen content of 6000 ppm or less. 7. R (wherein R is one or more elements selected from rare earth elements and contains Sm as an essential element) in an amount of 5 to 15 atomic% and N in an amount of 0.5 to 25 atomic%. And the balance is T (where T is Fe, or Fe and C
It is o. 3.) A magnetic powder comprising a magnetic particle having a non-magnetic coating formed of an inorganic compound or an organic compound formed on the surface thereof.