JP2003277814A - Method for manufacturing alloy powder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To optimize the particle size of a transition metal used as a raw material and to provide a rare earth ferromagnetic powder having a particle size close to a single domain of the particle size and having high magnetic properties. <P>SOLUTION: The method for manufacturing an alloy powder comprising a rare earth element and at least one transition metal selected from Fe, Co and Ni comprises steps of reacting a cation of at least one kind among rare earth elements and a cation of at least one kind selected from the group consisting of Fe, Co and Ni with a substance forming insoluble salts together with these cations in a solution to form precipitates; firing the precipitates to obtain metal oxides; and heating the metal oxides in a reduced atmosphere. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel method for producing not only intermetallic compound powders but also alloy powders containing rare earth elements, and more particularly to alloy powders having high magnetic properties.

[0002]

2. Description of the Related Art Generally, rare earth elements and Fe, Co, Ni
An intermetallic compound or alloy with a transition metal such as is an industrially useful material. For example, a thin film of Tb-Fe-Co is a magneto-optical memory, Sm-Co is a permanent magnet, and La-Ni is a hydrogen storage alloy. Used with. In this case, these intermetallic compounds or alloys are often required in the powder state. In order to obtain a powder, it is a general method to melt a component metal into an ingot and then crush the ingot.

The magnetic substance has a unique single domain particle size, and the coercive force is maximized by bringing the particle size of the magnetic powder close to this single domain particle size. In the rare earth element-transition metal magnetic material, the single domain particle size is several μm. Therefore, for the alloy powder as a magnetic material, a technique for producing fine particles is indispensable for improving magnetic properties.

On the other hand, a reduction diffusion method is known in which a rare earth oxide powder and a transition metal powder are mixed and heated in calcium vapor to reduce the rare earth oxide and diffuse it into a transition metal. . (JP-A-61-295308, JP-A-5-148517, JP-A-5-27)
No. 9714, JP-A-6-81010) The reduction-diffusion method has an advantage that an inexpensive rare earth oxide is used and that an alloy can be reduced and reduced at the same time.
This method is widely used in the production of Co5 intermetallic compounds or Sm-Co alloys.

This method has not yet been sufficient for obtaining a fine magnetic powder having a particle size of a single domain. This is because the particle diameter of the raw iron group metal is considerably larger than that of the rare earth element oxide. In order to obtain a magnetic powder having a single domain particle size, it is necessary to optimize the particle size of the iron group transition metal used as a raw material, and the optimum particle size is approximately 1
It will be about μm.

[0006]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to optimize the particle size of the transition metal used as a raw material and obtain a magnetic powder having a high magnetic performance close to the particle size of a single magnetic domain. It is to provide a ferromagnetic powder (alloy powder).

Further, another object is to enhance the reactivity by sufficiently mixing the rare earth element, which is the main constituent element of the alloy powder, with a transition metal element such as Fe, Co, Ni, etc. It is intended to homogenize the composition, suppress the generation of unnecessary phases as a magnetic material, and supply a permanent magnet having a magnetic property having a high coercive force.

[0008]

Means for Solving the Problems As a result of intensive studies for solving the above-mentioned problems, the present inventors have found that rare earth elements and transition metals such as Fe, Co and Ni are ionized by dissolving them with an acid or the like. In the state of the above, by thoroughly mixing and precipitating these ions by a precipitation reaction, it was found that the obtained precipitate is a very highly mixed alloy powder raw material with a very good mixed state, and the invention was completed. Came to let.

That is, the method for producing the alloy powder of the present invention has the following characteristics (1) to (13).

(1) Rare earth element and Fe, Co and Ni
At least one transition metal selected from among the following, in the method for producing an alloy powder consisting of at least one cation of a rare earth element, and at least one cation selected from the group consisting of Fe, Co and Ni. , A step of reacting these cations and a substance that forms an insoluble salt in a solution to deposit a precipitate, a step of firing the precipitate to obtain a metal oxide, and heating the metal oxide in a reducing atmosphere. It is characterized by including a process.

(2) A precipitate composed of precipitate particles having a uniform distribution of constituent elements, a sharp particle size distribution, and a regular particle shape is obtained by firing a metal oxide, and the metal oxide is reduced in an atmosphere. A method for producing an alloy powder, which comprises the step of heating at.

(3) The average particle size of the precipitate particles is 0.05
The method for producing an alloy powder according to the item (2), wherein the alloy powder has a particle size and a particle size distribution of ˜20 μm and a total particle size in the range of 0.1 to 20 μm.

(4) The method for producing an alloy powder according to (1), characterized in that a precipitate existing in the precipitate particles in a state where the rare earth element and the transition metal element are sufficiently mixed is used.

(5) The method for producing an alloy powder according to (1), wherein the precipitate is easily burnt or decomposed by heating in the air at a high temperature to produce a metal oxide.

(6) In the step of firing the precipitate,
The method for producing an alloy powder according to (1), characterized in that the firing atmosphere is in the atmosphere or is oxygen-rich relative to the atmosphere.

(7) A substance which forms an insoluble salt with at least one ion of a rare earth element and at least one ion selected from the group consisting of Fe, Co and Ni,
The method for producing an alloy powder according to (1), characterized in that the composition contains oxygen.

(8) The alloy according to (7), wherein the substance that forms an insoluble salt is at least one of hydroxide ion, carbonate ion, bicarbonate ion, and oxalate ion. Powder manufacturing method.

(9) The method is characterized by including a step of reducing a metal oxide in which the rare earth element and the transition metal are sufficiently mixed in the particles and the particle shape and particle size distribution of the precipitate particles are inherited. A method for producing the alloy powder described.

(10) The reduction of the metal oxide is performed by heating the metal oxide in a reducing gas atmosphere, and then heating by mixing a reducing substance having a reduction potential negative than that of the rare earth element. The method for producing an alloy powder according to (1), which comprises a multi-step process including:

(11) In the reduction in the reducing gas atmosphere, the heating temperature is in the range of 300 to 900 ° C., and 40% or more of the stoichiometric amount of oxygen with respect to the transition metal is reduced and removed. The method for producing the alloy powder according to (10).

(12) The metal oxide and B are sufficiently mixed and reduced with a reducing gas, and then reduced and diffused with a reducing agent, or the metal oxide is reduced with a reducing gas. After that, stoichiometric amount of B is mixed, and reduction diffusion is performed, and the method for producing the alloy powder according to (1).

(13) After the reduction reaction by the reducing agent is completed, nitrogen gas is introduced in the same furnace at a temperature in the range of 300 to 600 ° C. or a compound gas capable of decomposing by heating to supply nitrogen. The method for producing the alloy powder according to (1), characterized in that

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION The object of the present invention is an alloy powder in which a cation is a rare earth element and a transition metal such as Fe, Co and Ni, and it is also applicable to an intermetallic compound. The rare earth element means at least one of rare earth elements including light rare earth and heavy rare earth, that is, Y, N.
d, Pr, La, Ce, Tb, Dy, Ho, Er, E
The rare earth oxide powder is at least one of u, Sm, Gd, Er, Tm, Yb, and Lu, and the rare earth oxide powder means an oxide, a complex oxide, or a mixture thereof. Therefore, the present invention provides alloy powders such as Pr-Ni, Sm-Co, and Nd.
Applicable to -Fe-Co, Ce-Fe, and
Nd-Fe-B, Sm-Fe-N, Nd-Fe, such as B (boron) or N (nitrogen) partially substituted in the composition
-N, Nd-Fe-NB, Ce-Fe-N, Pr-F
It is also applicable to alloys such as e-N or intermetallic compounds. It is also possible to apply to the production of alloys of rare earth elements-transition elements other than these.

In the production method of the present invention, the cations of the constituents are uniformly mixed in the solvent. Therefore, it is necessary to prepare a liquid in which the rare earth element and the transition metal, which are the constituents of these alloys and the like, are dissolved. An aqueous acid solution can be used as a solvent capable of commonly ionizing and dissolving these metal elements. Preferred acids include mineral acids such as hydrochloric acid, sulfuric acid and nitric acid, which can dissolve the above-mentioned metal ions in high concentration. Further, as another method of preparing a solution of a metal element, it is also possible to dissolve chlorides, sulfates and nitrates of these constituent metals in water. Further, the solution is not limited to an aqueous solution, and may be a solution in which an organic metal in the form of metal alkoxide or the like is dissolved in an organic solvent such as alcohol, acetone, cyclohexane, or tetrahydrofuran.

From the solution in which the above metal ions are dissolved,
As a substance which forms an insoluble salt with these ions, anions (non-metal ions) such as hydroxide ion, carbonate ion and oxalate ion can be preferably used. That is, any solution of a substance capable of supplying these ions can be used. For example, oxalic acid can be used as a substance that supplies hydroxide ions, such as ammonia and caustic soda, as a substance that supplies carbonate ions, ammonium bicarbonate, soda bicarbonate, and the like that can supply oxalate ions. In the case of a liquid in which a metal alkoxide is dissolved in an organic solvent, it is possible to deposit a precipitate in the form of a metal hydroxide by adding water. In addition to this, any substance that reacts with a metal ion to form an insoluble salt is applicable to the present invention. The sol-gel method can be preferably used as a method for producing an insoluble salt of hydroxide.

By controlling the reaction between the metal ion and the non-metal ion, an ideal alloy powder raw material having a uniform distribution of constituent elements in the precipitate particles, a sharp particle size distribution, and a regular particle shape can be obtained. Obtainable. The use of such a raw material improves the magnetic properties of the final alloy powder (magnetic material). The precipitation reaction can be controlled by appropriately setting the supply rate of metal ions and non-metal ions, the reaction temperature, the concentration of the reaction solution, the stirring state of the reaction solution, the pH during the reaction, and the like. To set these conditions,
First, each condition is determined while observing with a microscope such that the yield of the precipitate is optimized and the independence of the precipitate particles (particle shape) and the particle size distribution of the precipitate particles are sharp. Further, it goes without saying that the form of the precipitate largely changes depending on what kind of chemical species is selected as the raw material and what kind of precipitation reaction is applied. By this precipitation step, the particle diameter, particle shape, and particle size distribution of the alloy powder as the final magnetic material are roughly determined. As described above, the control of this precipitation reaction is very important in that the particle performance is closely reflected in the magnetic material. The particle size of the precipitate particles is 0.05 to 20 μm, preferably 0.1 to 1
The size and distribution are preferably such that almost all particles fall within the range of 0 μm. The average particle size is 0.1 to 10
It is preferably in the range of μm. In the precipitate particles thus obtained, the rare earth element and the transition metal element exist in a sufficiently mixed state.

In the present invention, the precipitate obtained from the precipitation reaction is calcined to produce a metal oxide. Usually, the precipitate is calcined after desolvation before calcining. This is because if the solvent is sufficiently removed in this step, calcination is easy. Further, when the precipitate has a high solubility in a solvent at a high temperature, it is necessary to sufficiently remove the solvent. This is because the precipitate particles dissolve and the particles aggregate, which adversely affects the particle size distribution and particle size.

During firing of the precipitate, the insoluble salt consisting of metal ions and non-metal ions is heated, and as a result, the non-metal ions are decomposed to form metal oxides. Therefore, this firing is preferably performed under oxygen-rich conditions. Further, it is preferable to select a material containing oxygen as a constituent element of the non-metal ion. Such things include hydroxide ions,
There are bicarbonate ion, oxalate ion, citrate ion and the like.
On the other hand, sulfide ions and the like are ions that commonly cause precipitation in these metals, but they are not suitable because they do not decompose into oxides because they do not contain oxygen. Also,
Phosphate ion, borate ion, silicate ion, etc. are also substances that produce insoluble salts with rare earth element ions and transition metal ions. Phosphate, borate, and silicate, respectively, easily form oxides in the subsequent firing. It is not generated and is difficult to apply to the present invention. Therefore, the non-metal ions that can be preferably applied to the precipitation reaction that constitutes the present invention are hydroxide ions, carbonate ions, inorganic salts that can easily form oxides when heated, and oxalate ions when heated. It is an insoluble organic salt that burns easily. When an insoluble organic salt is hydrolyzed with water like an alkoxide to form a hydroxide, it is preferable to heat the hydroxide once as a hydroxide.

Since the main point of this calcination is to decompose non-metal ions to obtain a metal oxide, the calcination temperature is also a temperature above the temperature at which such decomposition reaction occurs. Therefore, the firing temperature varies depending on the type of metal ion and the type of non-metal ion, but it is appropriate to perform firing at a temperature of 800 to 1300 ° C. for several hours, more preferably 900 to 1
Bake in the range of 100 ° C. In this case, the furnace atmosphere is preferably one in which air is sufficiently blown in using a blower or the like, or oxygen is introduced into the furnace for firing.

By this firing, it is possible to obtain a metal oxide in which the rare earth element and the transition metal element are microscopically mixed in the particles. These oxide particles are oxides having very good particle performance that inherits the shape distribution of the precipitate particles as they are.

To obtain an alloy powder from a metal oxide, a reduction reaction is basically applied. Here, even if it is referred to as a metal oxide in one word, the present metal oxide is a rare earth element and Fe, Co,
It is a transition metal of Ni. The reduction potentials of Fe, Co, and Ni are -0.447v and-, respectively, with respect to the standard hydrogen electrode.
0.28v and -0.257v, on the other hand, the rare earth element is a very base element of -2.3 to -2.5v, in other words, an element that is difficult to reduce.

Therefore, H is used for the reduction of transition elements to metals.
It is sufficiently possible to introduce an ordinary reducing gas into the furnace, such as reduction with a reducing gas such as 2, a hydrocarbon gas such as CO, CH4, etc., to form a reducing atmosphere for heating. During this reduction reaction, the oxygen contained in the transition metal oxide powder is H2O.
Alternatively, it is gradually removed in the form of CO. The heating temperature in this case is set in the range of 300 to 900 ° C. Reduction of the transition metal oxide is difficult to occur at a temperature lower than this range, and reduction occurs at a temperature higher than this range, but the oxide particles cause particle growth and segregation at a high temperature and deviate from the desired particle size. Is. Therefore, the heating temperature is 400 ~
The range of 800 ° C. is more preferable.

The oxide component of the rare earth element in the metal oxide cannot be reduced by heating in the above-mentioned reducing gas atmosphere. The method of reducing the rare earth element is not limited, but it can be achieved by mixing and heating a metal of an element having a reduction potential lower than that of the target rare earth element. For example, as an alkali metal, Li is -3.04, Na is -2.71, K
Is -2.93v, Rb is 2.98v, and Cs is -2.92.
v, among the alkaline earth metals, Mg is -2.372v,
Ca is -2.87v, Sr is -2.89v, and Ba is-.
The rare earth element in the particles can be reduced to a metal by having a reduction potential of 2.912 v and mixing with the metal oxide and heating in an inert gas. The use of metallic calcium is most preferable in terms of handling safety and cost.

Regarding the application of calcium as a reducing agent, a method for producing an alloy powder called a reduction diffusion method has been applied to a rare earth cobalt magnet and has been put into practical use. It is most preferable in the present invention to apply this reduction diffusion method. That is, calcium metal or calcium hydroxide is added to powder in a mixed state of a fine metal obtained by reducing a transition metal element obtained by reduction with a reducing gas to a metal state and a rare earth element oxide, and an inert gas is added. By heating in an atmosphere or vacuum, the rare earth oxide is brought into contact with the calcium melt or its vapor, and the rare earth oxide is reduced to a metal. By this reduction reaction, an alloy block of a rare earth element and a transition metal element can be obtained.

The alkali metal and alkaline earth metal reducing agents described above are used in the form of granules or powders. Particularly, in view of cost, granular metal calcium having a grain size of 4 mesh or less is preferable. These reducing agents are equivalent to the reaction (the stoichiometric amount required to reduce the rare earth oxide, and when the transition metal is used in the form of oxide, include the amount necessary to reduce it). The amount is 1.1 to 3.0 times, preferably 1.5 to 2.0 times.

The reduction with the reducing agent can naturally reduce the transition metal element. Therefore, the reduction of the transition metal oxide with a reducing agent such as Ca cannot be performed without reducing the reducing gas. However, in that case, the required amount of Ca becomes excessive, and not only the particles become coarse due to the heat generated during the reduction reaction by Ca, but in the worst case, there is a risk that the product will scatter into the furnace due to an explosive reaction. . Therefore, it is preferable that most of the transition metals are reduced and metallized before the reduction of the rare earth element by reduction diffusion. Therefore, it is desirable that the oxygen removal rate of the transition metal before the reduction diffusion step is 40% or more. This is because not only is it uneconomical to use a large amount of reducing agent to be used in the next step in order to remove more than 40% of oxygen, but it is also impossible to obtain a uniform alloy powder particle shape. is there. Here, the oxygen removal rate is the percentage of the amount of oxygen reduced and removed with respect to the total amount of oxygen existing in the oxide of the transition metal.

In the present invention, a disintegration accelerator can be used, if necessary, together with the reducing agent. This disintegration accelerator is used to disintegrate the product during the wet treatment described below,
It is appropriately used to promote granulation,
For example, there are alkaline earth metal salts such as calcium chloride and calcium oxide disclosed in JP-A-63-105909. These disintegration accelerators are used in a proportion of 1 to 30% by weight, particularly 5 to 30% by weight, based on the rare earth oxide used as the rare earth source.

In the present invention, the above-mentioned raw material powder is mixed with a reducing agent, and optionally a disintegration accelerator, and the mixture is heated in an inert atmosphere other than nitrogen, for example, argon gas. Make a reduction. The heat treatment temperature for reduction is 700 to 1200 ° C.,
It is particularly preferable to set it in the range of 800 to 1100 ° C., and the heat treatment time is not particularly limited, but in order to carry out the reduction reaction uniformly, it can be carried out for a time in the range of 10 minutes to 10 hours. More preferably, it is carried out in the range of minutes to 2 hours. The reason why the reduction diffusion reaction can be carried out in such a short time is that the mixing level of the raw materials is high according to the method of the present invention. By this reduction reaction, porous lumps of rare earth-
A transition metal based alloy is obtained.

At this time, the reaction product is Ca by-produced.
It is a mixture of O, unreacted excess calcium, and produced alloy powder, which are in the state of a complex sintered lump. Therefore, this product mixture is then poured into cooling water to produce CaO.
And metallic calcium as Ca (OH) 2 suspension separated from the alloy powder. The remaining Ca (OH) 2 is
The alloy powder is removed by washing with acetic acid or hydrochloric acid. When the porous lump-shaped rare earth-transition metal alloy of the product was put into water, oxidation of metallic calcium with water and by-product Ca
The hydration reaction of O promotes the disintegration, that is, the pulverization, of the complex sintered sinter-shaped product mixture.

After stirring the slurry produced by the disintegration,
By removing the hydroxide such as the alkali metal on the upper portion by decantation and repeating the operations of water injection-stirring-decantation, the hydroxide can be removed from the obtained alloy powder. In addition, a part of the remaining hydroxide is adjusted to pH 3 to 6, by using an acid such as acetic acid or hydrochloric acid.
It is preferably completely removed by acid washing in the range of pH 4 to 5. After the completion of the wet treatment, for example, after washing with water, washing with an organic solvent such as alcohol or acetone, dehydration, and vacuum drying, a rare earth-transition metal alloy powder is produced.

The above-mentioned method is the basic configuration of the present invention,
Although a rare earth-transition metal-based alloy powder can be obtained, a rare earth-transition metal-boron-based or rare earth-transition metal-nitrogen-based alloy powder can be obtained by applying this method. That is, the present invention is applicable to all alloys containing a rare earth element-transition metal, which is the basic structure.

In order to obtain the rare earth-transition metal-boron alloy of (1), a stoichiometrically necessary amount of B for obtaining the target composition is obtained after the firing step of obtaining the rare earth element-transition element metal oxide. It is possible to sufficiently mix (boron) with the metal oxide, perform the reduction with the above-described reducing gas, and subsequently perform the reduction diffusion with the reducing agent. Alternatively, after reducing with a reducing gas once to sufficiently reduce the transition metal oxide, stoichiometric amount of B (boron) is mixed and then reduction diffusion is carried out to obtain rare earth-transition metal-boron. A system alloy can be obtained. You can get either of these,
The former method is more preferable. It is 1 for B (boron)
% Oxygen, and by mixing this before the reducing step with a reducing gas, the oxygen contained in B is removed, and the reduction diffusion reaction in the next step is easily performed. Is.

In order to obtain the rare earth-transition metal-nitrogen-based alloy powder of (1), basically, after the reduction reaction by reduction diffusion is completed, nitrogen gas or heating is continued in the same furnace before proceeding to the disintegration step. Nitrogen can be nitrided by introducing a compound gas that is decomposed by and can supply nitrogen. Since the rare earth-transition metal alloy is obtained in a porous lump form in the reduction-diffusion step, it is possible to immediately perform heat treatment in a nitrogen atmosphere without crushing, whereby nitriding is uniformly performed, and rare earth-transition metal- Obtain a nitrogen alloy. This nitriding treatment is performed by lowering the temperature from the heating temperature range for the above reduction.
The temperature is set to 00 to 600 ° C., particularly 400 to 550 ° C., and the atmosphere is replaced with a nitrogen atmosphere in this temperature range. For example, if the nitriding temperature is lower than 300 ° C., the diffusion of nitrogen into the rare earth-transition metal alloy, which is the reaction product obtained in the above step, becomes insufficient, and nitriding is performed uniformly and effectively. Will be difficult. Further, when the nitriding temperature exceeds 600 ° C., the rare earth-transition metal alloy is decomposed into a rare earth-nitrogen compound and a transition metal such as α-iron, so that the magnetic properties of the obtained alloy powder are significantly deteriorated. Cause The heat treatment time is set to such an extent that nitriding is performed sufficiently uniformly, but this time is generally about 2 to 20 hours.

[0044]

EXAMPLES Examples of the present invention will be described below based on production examples of Sm-Fe-N alloy powder which is a permanent magnet material.

Example 1 <1. Precipitation reaction> 51 anhydrous samarium chloride SmCl3
2747.6 g of anhydrous iron chloride FeCl3 was weighed out, poured into 10 liters of ion-exchanged water at the same time, and completely dissolved while stirring in a reactor to obtain a metal liquid. While continuing to stir the reactor, 5.1 kg of a 15 wt% caustic soda solution is gently charged therein. PH of solution is 10
After confirming the above, stop stirring and let stand,
The product will settle to the bottom of the container.

<2. Filtration and washing> The precipitated product is placed on a filter paper and suctioned while supplying ion-exchanged water from above. This decantation is continued until the electrical conductivity of the filtrate falls below 50 μS / m. The precipitate cake, which is washed and suction filtered, is dried in a dryer at 80 ° C.

<3. Firing in air> The dried cake is placed in an alumina crucible and fired in the air at 1000 ° C. for 5 hours.

<4. Grain size adjustment> After loosening the fired product by hand, grind with a hammer mill. Regarding the particle size of this powder, the average particle size by a Fisher Subsieve Sizer (FSSS) was 1.2 μm.

<5. Hydrogen reduction> A crushed powder was filled in a steel tray, placed in a tubular furnace, and subjected to heat treatment at 700 ° C. for 10 hours while circulating hydrogen having a purity of 100% at 20 liters / minute. The oxygen concentration of the obtained black powder is 7.0 w
It was t%.

<6. Reduction / Diffusion Reaction> 1000 g of the black powder obtained in the previous step and 350.7 g of granular Ca are mixed, placed in a steel tray and set in an argon gas atmosphere furnace. After evacuating the inside of the furnace, it is heated at 1050 ° C. for 0.5 hours while passing an argon gas. Then turn off the heating and subsequently cool to 450 ° C. in argon gas,
After that, the temperature is kept constant. Then, the inside of the furnace is evacuated again, and then nitrogen gas is introduced. After heating at a pressure of atmospheric pressure or higher for 5 hours while passing nitrogen gas through, heating is stopped and the mixture is allowed to cool.

<7. Washing with water> The obtained reaction product is poured into 5 liters of ion-exchanged water, whereby the reaction product is immediately disintegrated and the separation of the alloy powder and the Ca component is started. The stirring in water, standing, and removal of the supernatant are repeated 5 times, and finally, washing is carried out in 5 liters of a 2 wt% acetic acid aqueous solution to complete the separation of the Ca component. By vacuum drying this, Sm2Fe17
Obtain N3 alloy powder.

<8. Characteristic evaluation> The obtained powder had good dispersibility and had a spherical shape when observed by an electron microscope. The average particle size of the powder is measured by FSSS.
It was 5 μm. The magnetic properties of the powder are Br13.5KG,
The iHc was 16.2 KOe. The concentration of oxygen contained in the powder was 0.2 wt%, and segregation of Sm and Fe could not be confirmed by observing the cross section with EPMA. Also Cu
According to X-ray diffraction using -Kα as a radiation source, nothing other than the main phase was observed, and in particular, no trace was found of pure iron component α-Fe.

Example 2 <1. Precipitation reaction> Add 30 liters of pure water to the reaction tank, add 520 g of 97% H2SO4, and add 48m of Sm2O3.
4.8 g was charged and dissolved, and 25% ammonia water was added to add p.
Adjust H to near neutral. FeSO4 ・ 7 in this aqueous solution
5200 g of H2O was added and completely dissolved to obtain a metal liquid. In a separate tank, 12 liters of pure water was mixed with 2524 g of ammonium bicarbonate and 1738 g of 25% aqueous ammonia to prepare a carbonate ion solution. While stirring the reaction tank, the carbonate ion solution was gradually added, and aqueous ammonia was added so that the final pH of the total amount added was 8.0 ± 0.5. When the stirring is stopped and the mixture is left to stand, the product will settle at the bottom of the container.

<2. Filtration and washing> The precipitated product is placed on a filter paper and suctioned while supplying ion-exchanged water from above. This decantation is continued until the electrical conductivity of the filtrate falls below 50 μS / m. The precipitate cake, which is washed and suction filtered, is dried in a dryer at 80 ° C.

<3. Air baking> The dried cake is put in an alumina crucible and baked in the air at 1100 ° C. for 3 hours.

<4. Grain size adjustment> After loosening the fired product by hand, grind with a hammer mill. Regarding the particle size of this powder, the average particle size by Fischer Subsieve Sizer (FSSS) was 1.3 μm.

<5. Hydrogen reduction> A crushed powder was filled in a steel tray, placed in a tubular furnace, and subjected to heat treatment at 700 ° C. for 10 hours while circulating hydrogen having a purity of 100% at 20 liters / minute. The oxygen concentration of the obtained black powder is 7.2w
It was t%.

<6. Reduction / Diffusion Reaction> 1000 g of the black powder obtained in the previous step and 350.7 g of granular Ca are mixed, placed in a steel tray and set in an argon gas atmosphere furnace. After evacuating the inside of the furnace, it is heated at 1000 ° C. for 1 hour while passing an argon gas. The heating is then stopped and subsequently cooled to 450 ° C. in argon gas and subsequently kept constant at this temperature. Then, the inside of the furnace is evacuated again, and then nitrogen gas is introduced. After heating at a pressure of atmospheric pressure or higher for 5 hours while passing nitrogen gas through, heating is stopped and the mixture is allowed to cool.

<7. Washing with water> The obtained reaction product is poured into 5 liters of ion-exchanged water, whereby the reaction product is immediately disintegrated and the separation of the alloy powder and the Ca component is started. The stirring in water, standing, and removal of the supernatant are repeated 5 times, and finally, washing is carried out in 5 liters of a 2 wt% acetic acid aqueous solution to complete the separation of the Ca component. By vacuum drying this, Sm2Fe17
Obtain N3 alloy powder.

<8. Characteristic evaluation> The obtained powder had good dispersibility and had a spherical shape when observed by an electron microscope. The average particle size of the powder is measured by FSSS.
It was 7 μm. The magnetic properties of the powder are Br13.7KG,
The iHc was 15.8 kOe. The concentration of oxygen contained in the powder was 0.25 wt%, and segregation of Sm and Fe could not be confirmed by observing the cross section with EPMA. Also C
According to X-ray diffraction using u-Kα as a radiation source, the main phase Sm
Nothing was observed other than the —Fe alloy, and in particular, no trace was found of α-Fe, which is a pure iron component.

[Embodiment 3] <1. Precipitation reaction> Samarium nitrate hexahydrate Sm (NO
3) 513.4 g of 3.6H2O, iron nitrate nonahydrate Fe
3432.3 g of (NO3) 3.9H2O is weighed and simultaneously added to 10 liters of ion-exchanged water while stirring. After confirming the complete dissolution, urea (NH
2) Add 2992.5 g of 2CO. The liquid temperature is raised to 80 ° C. while continuing stirring. At this time, urea is hydrolyzed into ammonia and carbon dioxide, and the metal content is precipitated by a uniform reaction.

<2. Filtration and washing> The precipitated product is placed on a filter paper and suctioned while supplying ion-exchanged water from above. This operation is continued until the specific resistance of the filtrate falls below 50 μS / m. The washed cake is dried in a dryer at 80 ° C.

<3. Air baking> The dried cake is put in an alumina crucible and baked in the air at 1100 ° C. for 3 hours.

<4. Grain size adjustment> After loosening the fired product by hand, grind with a hammer mill. The particle size of this powder was 1.3 microns on a Fisher subsieve sizer.

<5. Hydrogen reduction> The pulverized powder was placed in a steel tray, placed in a tubular furnace in which 100% pure hydrogen was flowing at 20 liters / minute, and heat-treated at 700 ° C. for 10 hours. The oxygen concentration of the obtained black powder was 7.2 wt%.

<6. Reduction-diffusion reaction> 1000 g of the black powder obtained in the previous step and granular Ca3 with a particle size of 6 mm or less
50.7 g are mixed, put in a steel tray and set in an inert gas atmosphere furnace. After evacuating the inside of the furnace, it is heated at 1000 ° C. for 1 hour while passing an argon gas. Then the heating is stopped and subsequently 450 ° C. in argon gas.
After that, the temperature is kept constant at this temperature. afterwards,
After the inside of the furnace is evacuated again, nitrogen gas is introduced. After heating at a pressure of atmospheric pressure or higher for 5 hours while passing nitrogen gas through, heating is stopped and the mixture is allowed to cool.

<7. Washing with water> The obtained reaction product is poured into 5 liters of ion-exchanged water, whereby the reaction product is immediately disintegrated and the separation of the alloy powder and the Ca component begins. The stirring in water, standing, and removal of the supernatant are repeated 5 times, and finally, washing is carried out in 5 liters of a 2 wt% acetic acid aqueous solution to complete the separation of the Ca component. By vacuum drying this, Sm2Fe17
Obtain N3 alloy powder.

<8. Characteristics> The obtained powder had good dispersibility and had a spherical shape when observed by an electron microscope. The particle size of the powder was 2.8 microns on a Fisher subsieve sizer. The magnetic properties of the powder are Br1
It was 3.8KG and iHc14.6KOe. The concentration of oxygen contained in the powder is 0.25 wt%,
Segregation of Sm and Fe could not be confirmed by observing the cross section with A. Further, according to X-ray diffraction using Cu-Kα as a radiation source, nothing was observed other than the Sm-Fe alloy as the main phase, and in particular, no trace of α-Fe as a pure iron component was found.

[Comparative Example 1] Metal Sm and metal Fe were melted at an atomic ratio of 2:17. The melt was cast into a water-cooled copper mold to obtain an Sm2Fe17 alloy. The obtained ingot was roughly crushed with a jaw crusher and then heat-treated in argon at 1100 ° C. for 40 hours for homogenization. The obtained alloy was pulverized by a ball mill of steel balls for 2 hours. Further, this powder was heat-treated at 100% nitrogen and 450 ° C. for 5 hours. The obtained powder was in an agglomerated state with poor dispersibility and had an angular shape when observed by an electron microscope. Average particle size by FSSS method is 2.5
was μm. The magnetic properties of the powder are Br13.3kG, i
The Hc was 8.2 kOe. The concentration of oxygen contained in the powder was 0.6 wt%, and segregation of Sm and Fe could be confirmed by observing the cross section with EPMA. Further, according to X-ray diffraction using Cu-Kα as a radiation source, a clear peak due to α-Fe was observed.

[0070]

As described above, according to the present invention, the following effects can be obtained.

Since the elements constituting the alloy powder are already homogeneously mixed at the raw material stage, it is easy to obtain a homogeneous alloy. Therefore, it becomes possible to bring out the physical properties peculiar to the material.

In the method of forming an ingot of a rare earth element and a fiber metal by a usual melting method and crushing the ingot, a heat treatment for several tens of hours is often required to obtain a homogeneous alloy, but according to the present invention. For example, the heat treatment time is about several hours. By shortening the heat treatment time, a powdery product can be easily obtained.

Furthermore, the particle shape of the precipitate particles obtained in the precipitation step is inherited by the alloy powder of the final product, and by controlling the shape of the precipitate particles, it is possible to obtain a dispersed alloy powder with a uniform particle shape. As a result, a magnetic material having high magnetic performance can be obtained.

Claims (13)

[Claims] 1. A method for producing an alloy powder comprising a rare earth element and at least one transition metal selected from Fe, Co and Ni, wherein at least one cation of the rare earth element, Fe, Co and A step of reacting at least one cation selected from the group consisting of Ni with a substance that forms an insoluble salt with these cations in a solution to deposit a precipitate; And a step of heating the metal oxide in a reducing atmosphere. 2. A precipitate composed of precipitate particles having a uniform distribution of constituent elements, a sharp particle size distribution, and a regular particle shape is obtained by firing a metal oxide, and the metal oxide is subjected to a reducing atmosphere. A method for producing an alloy powder, comprising the step of heating. 3. The average particle size of the precipitate particles is 0.1-10.
The particle size and the particle size distribution are such that the total particle size is in the range of 0.05 to 20 μm.
5. A method for producing an alloy powder according to claim 1. 4. The method for producing an alloy powder according to claim 1, wherein a precipitate which is present in the precipitate particles in a state in which the rare earth element and the transition metal element are sufficiently mixed is used. 5. The method for producing an alloy powder according to claim 1, wherein the precipitate is easily burnt or decomposed by heating in the atmosphere at a high temperature to produce a metal oxide. 6. The method for producing an alloy powder according to claim 1, wherein in the step of firing the precipitate, the firing atmosphere is in the atmosphere or oxygen-rich from the atmosphere. 7. A substance which forms an insoluble salt with at least one ion of a rare earth element and at least one ion selected from the group consisting of Fe, Co and Ni contains oxygen in its composition. The method for producing the alloy powder according to claim 1. 8. The alloy powder according to claim 7, wherein the substance that forms an insoluble salt is at least one of hydroxide ion, carbonate ion, bicarbonate ion, and oxalate ion. Manufacturing method. 9. The method according to claim 2, further comprising the step of reducing a metal oxide in which the rare earth element and the transition metal element are sufficiently mixed in the particles and the particle shape and particle size distribution of the precipitate particles are inherited. A method for producing the alloy powder described. 10. The reduction of a metal oxide comprises the step of heating the metal oxide in a reducing gas atmosphere, and then the step of mixing and heating a reducing substance having a reduction potential more negative than that of the rare earth element. The method for producing an alloy powder according to claim 1, comprising a multi-step process including the steps. 11. The reduction in the reducing gas atmosphere is characterized in that the heating temperature is in the range of 300 to 900 ° C., and 40% or more of the stoichiometric amount of oxygen with respect to the transition metal is reduced and removed. Item 10. A method for producing an alloy powder according to Item 10. 12. The metal oxide and B are sufficiently mixed and reduced with a reducing gas, and then reduced and diffused with a reducing agent, or after the metal oxide is reduced with a reducing gas. The method for producing an alloy powder according to claim 1, wherein stoichiometric amount of B is mixed and reduction diffusion is performed. 13. After completion of the reduction reaction by the reducing agent,
The method for producing an alloy powder according to claim 1, wherein nitrogen gas or a compound gas capable of being decomposed by heating to supply nitrogen is introduced in the same furnace at a temperature in the range of 300 to 600 ° C. .