JP2020169389A - Manufacturing method of anisotropic magnetic powder - Google Patents

Abstract

To provide a manufacturing method of an anisotropic magnetic powder excellent in magnetic property.SOLUTION: There is related to a manufacturing method of an anisotropic magnetic powder including a pretreatment process for obtaining partial oxide by a heat treatment of oxide containing Sm and Fe under reductive gas atmosphere, a process for obtaining an alloy particle by a heat treatment of the partial oxide under a reductant at a first temperature of 1000°C to 1090°C, then a heat treatment at a second temperature of 980°C to 1070°C, which is lower than the first temperature, and a process for obtaining the anisotropic magnetic powder by nitriding the alloy particle.SELECTED DRAWING: None

Description

The present invention relates to a method for producing an anisotropic magnetic powder.

Patent Document 1 discloses a method for producing a rare earth-iron-nitrogen anisotropic magnetic powder in which a raw material powder and a reducing agent are mixed and then the rare earth oxide powder is reduced and diffused into iron. However, the magnetic properties were not sufficient and there was room for improvement.

Patent Document 2 discloses a method for producing an alloy powder containing a rare earth metal, which performs a second reduction diffusion after the initial reduction diffusion of the rare earth metal oxide. However, for neodymium-based magnetic materials, the temperature of reduction and diffusion is also very low, and when producing neodymium-based magnetic materials, some of the low melting point alloy components hang down to the bottom of the reaction vessel. The purpose was to suppress.

Japanese Unexamined Patent Publication No. 2008-171868 Japanese Patent Application Laid-Open No. 05-78715

An object of the present invention is to provide a method for producing an anisotropic magnetic powder having excellent magnetic properties.

The present inventor examined various heat treatment temperature profiles for the purpose of improving the magnetic properties. As a result, the partial oxide was heat-treated at the first temperature in the presence of a reducing agent, and then the second temperature was lower than the first temperature. We have found that the magnetic properties of the anisotropic magnetic powder can be improved by heat treatment at temperature, and completed the present invention.

That is, the present invention is a pretreatment step of obtaining a partial oxide by heat-treating an oxide containing Sm and Fe in a reducing gas atmosphere.
The partial oxide is heat-treated at a first temperature of 1000 ° C. or higher and 1090 ° C. or lower in the presence of a reducing agent, and then heat-treated at a second temperature of 980 ° C. or higher and 1070 ° C. or lower, which is lower than the first temperature. The process of obtaining particles, and
The present invention relates to a method for producing an anisotropic magnetic powder, which comprises a step of obtaining an anisotropic magnetic powder by nitriding the alloy particles.

In the method for producing an anisotropic magnetic powder of the present invention, the partial oxide is heat-treated at the first temperature in the presence of a reducing agent and then at a second temperature lower than the first temperature. A magnetic powder having an excellent coercive force can be produced.

Hereinafter, embodiments of the present invention will be described in detail. However, the embodiments shown below are examples for embodying the technical idea of the present invention, and the present invention is not limited to the following. In this specification, the term "process" is used not only as an independent process but also as a term as long as the intended purpose of the process is achieved even if it cannot be clearly distinguished from other processes. included. Further, the numerical range indicated by using "~" indicates a range including the numerical values before and after "~" as the minimum value and the maximum value, respectively.

The method for producing an anisotropic magnetic powder of the present embodiment is a pretreatment step of obtaining a partial oxide by heat-treating an oxide containing Sm and Fe in a reducing gas atmosphere.
The partial oxide is heat-treated at a first temperature of 1000 ° C. or higher and 1090 ° C. or lower in the presence of a reducing agent, and then heat-treated at a second temperature of 980 ° C. or higher and 1070 ° C. or lower, which is lower than the first temperature. The process of obtaining particles, and
It is characterized by including a step of obtaining an anisotropic magnetic powder by nitriding the alloy particles.

It is generally known that the coercive force is highest when the average particle size of the SmFeN powder is around 3 μm. If only the heat treatment at the first temperature is performed in the presence of the reducing agent, the heat treatment becomes insufficient, and there are many particles in which the particles are strongly bonded (necking). When a magnetic field is applied to the necked particles, the individual particles do not rotate due to their strong bond, so that the magnetic field orientation deteriorates and the coercive force decreases. For example, if the heat treatment time at the first temperature is extended as a countermeasure against these neckings, the necking is eliminated by fusing the particles, but the coercive force is lowered because coarse particles exceeding 3 μm are generated. On the other hand, when the heat treatment is performed at the first temperature and then at the second temperature lower than the first temperature as in the present embodiment, the necked particles are separated without being fused, so that coarse particles are generated. It is considered that the necking can be eliminated while suppressing the occurrence of the particles, and the coercive force of the anisotropic magnetic powder is improved.

The oxide containing Sm and Fe used in the pretreatment step can be obtained by mixing Sm oxide and Fe oxide. For example, a solution containing Sm and Fe and a precipitant are mixed to mix Sm and Fe. It can be produced by a step of obtaining a precipitate containing Sm (precipitation step) and a step of obtaining an oxide containing Sm and Fe by firing the precipitate (oxidation step).

[Precipitation process]
In the precipitation step, the Sm raw material and the Fe raw material are dissolved in a strongly acidic solution to prepare a solution containing Sm and Fe. When Sm ₂ Fe ₁₇ N ₃ is obtained as the main phase, the molar ratio of Sm and Fe (Sm: Fe) is preferably 1.5:17 to 3.0:17, and 2.0:17 to 2.5:17. Is more preferable. Raw materials such as La, W, Co, Ti, Sc, Y, Pr, Nd, Pm, Gd, Tb, Dy, Ho, Er, Tm and Lu may be added. La is preferably contained in terms of residual magnetic flux density, W is preferably contained in terms of coercive force and square ratio, and Co is preferably contained in terms of temperature characteristics.

The Sm raw material and Fe raw material are not limited as long as they can be dissolved in a strongly acidic solution. For example, in terms of availability, Sm oxide is used as the Sm raw material, and FeSO ₄ is used as the Fe raw material. The concentration of the solution containing Sm and Fe can be appropriately adjusted within a range in which the Sm raw material and the Fe raw material are substantially dissolved in the acidic solution. Examples of the acidic solution include sulfuric acid in terms of solubility.

By reacting the solution containing Sm and Fe with the precipitant, an insoluble precipitate containing Sm and Fe is obtained. Here, the solution containing Sm and Fe may be a solution containing Sm and Fe at the time of reaction with the precipitant. For example, raw materials containing Sm and Fe are prepared as separate solutions, and each solution is added dropwise. And react with the precipitant. Even when they are prepared as separate solutions, they are appropriately adjusted within a range in which each raw material is substantially dissolved in an acidic solution. The precipitant is not limited as long as it is an alkaline solution that reacts with a solution containing Sm and Fe to obtain a precipitate, and examples thereof include aqueous ammonia and caustic soda, and caustic soda is preferable.

In the precipitation reaction, a method of dropping a solution containing Sm and Fe and a precipitant into a solvent such as water is preferable because the properties of the particles of the precipitate can be easily adjusted. By appropriately controlling the supply rate of the solution containing Sm and Fe and the precipitant, the reaction temperature, the concentration of the reaction solution, the pH at the time of reaction, etc., the distribution of the constituent elements is homogeneous, the particle size distribution is sharp, and the powder shape is formed. A well-organized precipitate is obtained. By using such a precipitate, the magnetic properties of the final product, the magnetic powder, are improved. The reaction temperature can be 0 to 50 ° C., preferably 35 to 45 ° C. The reaction solution concentration is preferably 0.65 mol / L to 0.85 mol / L, more preferably 0.7 mol / L to 0.85 mol / L, as the total concentration of metal ions. The reaction pH is preferably 5-9, more preferably 6.5-8.

The solution containing Sm and Fe preferably further contains La, W and / or Co in terms of magnetic properties. The La raw material is not limited as long as it can be dissolved in a strongly acidic solution, and examples thereof include LaCl ₃ in terms of availability. Along with the Sm raw material and the Fe raw material, the La raw material, the W raw material, and the Co raw material are appropriately adjusted within a range in which they are substantially dissolved in an acidic solution, and examples of the acidic solution include sulfuric acid in terms of solubility. Examples of the W raw material include ammonium tungstate, and examples of the Co raw material include cobalt sulfate. It is preferable to prepare the solution separately from the solution containing Sm and Fe in a range that is substantially soluble in water.

If the solution containing Sm and Fe further contains La, W and / or Co, an insoluble precipitate containing Sm, Fe and La, W and / or Co is obtained. Here, the solution may be Sm, Fe, La, W and / or Co at the time of reaction with the precipitant. For example, each raw material is prepared as a separate solution, and each solution is added dropwise. It may be reacted with a precipitant or prepared with a solution containing Sm and Fe.

The anisotropic magnetic powder particles obtained in the precipitation step roughly determine the powder particle size, powder shape, and particle size distribution of the finally obtained magnetic powder. When the particle size of the obtained particles is measured by a laser diffraction type wet particle size distribution meter, the size and distribution of the total powder should be within the range of 0.05 to 20 μm, preferably 0.1 to 10 μm. Is preferable. The average particle size is measured as a particle size corresponding to a cumulative volume of 50% from the small particle size side in the particle size distribution, and is preferably in the range of 0.1 to 10 μm.

After separating the precipitate, the precipitate is redissolved in the remaining solvent in the heat treatment of the subsequent oxidation step, and when the solvent evaporates, the precipitate aggregates and the particle size distribution, powder diameter, etc. change. In order to suppress this, it is preferable to remove the solvent. Specific examples of the method for removing the solvent include, for example, when water is used as the solvent, a method of drying in an oven at 70 to 200 ° C. for 5 to 12 hours can be mentioned.

After the precipitation step, a step of separating and washing the obtained precipitate may be included. The washing step is appropriately performed until the conductivity of the supernatant solution becomes 5 mS / m ² or less. As a step of separating the precipitate, for example, a filtration method, a decantation method, or the like can be used after adding a solvent (preferably water) to the obtained precipitate and mixing them.

[Oxidation process]
The oxidation step is a step of obtaining an oxide containing Sm and Fe by calcining the precipitate formed in the precipitation step. For example, the precipitate can be converted to an oxide by heat treatment. When the precipitate is heat-treated, it must be carried out in the presence of oxygen, for example, in the air atmosphere. Moreover, since it is necessary to carry out in the presence of oxygen, it is preferable that the non-metal portion in the precipitate contains an oxygen atom.

The heat treatment temperature (hereinafter, oxidation temperature) in the oxidation step is not particularly limited, but is preferably 700 to 1300 ° C, more preferably 900 to 1200 ° C. If the temperature is lower than 700 ° C., the oxidation becomes insufficient, and if the temperature exceeds 1300 ° C., the desired shape, average particle size and particle size distribution of the magnetic powder tend not to be obtained. The heat treatment time is also not particularly limited, but 1 to 3 hours is preferable.

The obtained oxide is an oxide particle in which Sm and Fe are sufficiently microscopically mixed in the oxide particle, and the shape, particle size distribution, etc. of the precipitate are reflected.

[Pretreatment process]
The pretreatment step is a step of obtaining a partial oxide in which a part of the oxide is reduced by heat-treating the oxide containing Sm and Fe in a reducing gas atmosphere. Here, the partial oxide means that a part of oxygen bonded to Fe is reduced. The oxygen concentration of the partial oxide is preferably 10% by mass or less, preferably 8% by mass or less. The oxygen concentration can be measured by the non-dispersed infrared absorption method (ND-IR).

The reducing gas is appropriately selected from hydrocarbon gases such as hydrogen (H ₂ ), carbon monoxide (CO), and methane (CH ₄ ), and combinations thereof, but hydrogen gas is preferable in terms of cost, and the gas is preferable. The flow rate of the above is appropriately adjusted as long as the oxide does not scatter. The heat treatment temperature (hereinafter, pretreatment temperature) in the pretreatment step is in the range of 300 ° C. or higher and 950 ° C. or lower, preferably 400 ° C. or higher, more preferably 750 ° C. or higher, and preferably less than 900 ° C. When the pretreatment temperature is 300 ° C. or higher, the reduction of oxides containing Sm and Fe proceeds efficiently. Further, when the temperature is 950 ° C. or lower, the oxide particles are suppressed from growing and segregating, and the desired particle size can be maintained. When hydrogen is used as the reducing gas, it is preferable to adjust the thickness of the oxide layer to be used to 20 mm or less, and further adjust the dew point in the reaction furnace to −10 ° C. or less.

[Reduction process]
In the reduction step, the partial oxide is heat-treated at a first temperature of 1000 ° C. or higher and 1090 ° C. or lower in the presence of a reducing agent, and then heat-treated at a second temperature of 980 ° C. or higher and 1070 ° C. or lower, which is lower than the first temperature. This is a step of obtaining alloy particles.

Reduction occurs when the oxide comes into contact with a calcium melt or calcium vapor. The first temperature is 1000 ° C. or higher and 1090 ° C. or lower, but preferably 1010 ° C. or higher and 1080 ° C. or lower. If it is less than 1000 ° C., the reduction becomes insufficient, and if it exceeds 1090 ° C., coarse particles are generated and the coercive force is lowered. The heat treatment time is preferably less than 120 minutes, more preferably less than 90 minutes, from the viewpoint of more uniform reduction reaction. The lower limit of the heat treatment time is not particularly limited, but 10 minutes or more is preferable, and 30 minutes or more is more preferable.

The second temperature is 980 ° C. or higher and 1070 ° C. or lower, but is preferably 990 ° C. or higher and 1060 ° C. or lower. If the temperature is lower than 980 ° C., the necking is not eliminated and a sufficient coercive force cannot be obtained. If the temperature exceeds 1070 ° C., coarse particles are generated and the coercive force is lowered. The heat treatment time is preferably 10 minutes or longer, more preferably 30 minutes or longer, from the viewpoint of suppressing the formation of coarse particles and eliminating necking. The upper limit of the heat treatment time is not particularly limited, but is preferably less than 120 minutes, more preferably less than 90 minutes.

The temperature difference between the first temperature and the second temperature is not particularly limited, but the second temperature is preferably lower in the range of 15 ° C. or higher and 60 ° C. or lower than the first temperature, and lower in the range of 15 ° C. or higher and 30 ° C. or lower. Is more preferable. If the temperature is lower than 15 ° C., coarse particles are generated and the coercive force is lowered. If the temperature exceeds 60 ° C., necking is not eliminated and a sufficient coercive force cannot be obtained.

The heat treatment at the first temperature and the heat treatment at the second temperature may be performed continuously, and between these heat treatments, a heat treatment at a heat treatment temperature lower than the temperature range of the second temperature may be included, but in terms of productivity. , It is preferable to carry out continuously.

In the reduction step, a disintegration accelerator can be used, if necessary, together with the metallic calcium which is the reducing agent. This disintegration accelerator is appropriately used to promote the disintegration and granulation of the product in the washing step described later. For example, alkaline earth metal salts such as calcium chloride and alkaline soil such as calcium oxide. Examples include oxides. These disintegration accelerators are used in a proportion of 1 to 30% by mass, preferably 5 to 30% by mass, per rare earth oxide used as a rare earth source.

Metallic calcium is used in the form of granules or powder, and the average particle size thereof is preferably 10 mm or less. As a result, aggregation during the reduction reaction can be suppressed more effectively. Here, the average particle size is calculated by measuring the particle size of 10 particles with an optical microscope and using the arithmetic mean thereof. In addition, metallic calcium is the reaction equivalent (a stoichiometric amount required to reduce rare earth oxides, and when Fe is in the form of an oxide, it includes the amount required to reduce it). It can be added in an amount of 1.1 to 3.0 times, preferably 1.5 to 2.0 times.

[Nitriding process]
The nitriding step is a step of obtaining anisotropic magnetic particles by nitriding the alloy particles obtained in the reduction step. Since the particulate precipitate obtained in the precipitation step is used instead of melting the metals together, porous massive alloy particles can be obtained in the reduction step. As a result, nitriding can be performed uniformly by heat treatment in a nitrogen atmosphere immediately without performing pulverization treatment.

The heat treatment temperature (hereinafter referred to as the nitriding temperature) in the nitriding treatment of the alloy particles is preferably a temperature of 300 to 600 ° C., particularly preferably 400 to 550 ° C., and is carried out by substituting the atmosphere with a nitrogen atmosphere in this temperature range. The heat treatment time may be set so that the nitriding of the alloy particles is sufficiently uniform.

The product obtained after the nitriding step contains CaO produced as a by-product, unreacted metallic calcium, and the like in addition to the magnetic particles, and may be in a sintered mass state in which these are combined. Therefore, in that case, this product can be put into cooling water to separate CaO and metallic calcium from the magnetic particles as calcium hydroxide (Ca (OH) ₂ ) suspension. Further, the residual calcium hydroxide may be sufficiently removed by washing the magnetic particles with acetic acid or the like. Next, for surface treatment, a phosphoric acid solution is added as a surface treatment agent in the range of 0.10 to 10 wt% as PO _{4 with} respect to the magnetic particle solid content obtained in the nitriding step. Anisotropic magnetic powder can be obtained by appropriately separating from the solution and drying.

The anisotropic magnetic powder obtained as described above typically has the following general formula Sm _v Fe _{(100-v-w-x-y-z)} N _w La _x W _y Co _z.
(In the formula, 3 ≦ v ≦ 30, 5 ≦ w ≦ 15, 0 ≦ x ≦ 0.3, 0 ≦ y ≦ 2.5, 0 ≦ z ≦ 2.5).
It is represented by.

In the general formula, v is defined as 3 or more and 30 or less because if it is less than 3, the unreacted portion (α-Fe phase) of the iron component is separated and the coercive force of the nitride is lowered, so that it is no longer a practical magnet. If it exceeds 30, the element of Sm is precipitated, the magnetic powder becomes unstable in the atmosphere, and the residual magnetic flux density decreases. Further, the reason why w is defined as 5 or more and 15 or less is that when it is less than 5, coercive force can hardly be exhibited, and when it exceeds 15, elements of Sm and nitrides of iron itself are generated.

From the viewpoint of magnetic characteristics, x is 0 ≦ x ≦ 0.3, but 0.11 ≦ x ≦ 0.22 is preferable, y is 0 ≦ y ≦ 2.5, and z is 0 ≦ z ≦ 2. It is .5.

<Composite material>
Hereinafter, the composite material and the bonded magnet will be described.

The composite material is made of the anisotropic magnetic powder described above and a resin. By including this anisotropic magnetic powder, a composite material having high magnetic properties can be constructed.

The resin contained in the composite material may be a thermosetting resin or a thermoplastic resin, but is preferably a thermoplastic resin. Specific examples of the thermoplastic resin include polyphenylene sulfide resin (PPS), polyetheretherketone (PEEK), liquid crystal polymer (LCP), polyamide (PA), polypropylene (PP), polyethylene (PE) and the like. it can.

The weight ratio (resin / magnetic powder) of the anisotropic magnetic powder to the resin when obtaining the composite material is preferably 0.10 to 0.15, more preferably 0.11 to 0.14. ..

The composite material can be obtained, for example, by mixing the anisotropic magnetic powder and the resin at 280 to 330 ° C. using a kneader.

<Bond magnet>
By using a composite material, a bonded magnet can be manufactured. Specifically, for example, a bonded magnet can be obtained by aligning magnetic domains that are easily magnetized with an alignment magnetic field (alignment step) while heat-treating the composite material, and then pulse magnetizing with a magnetizing magnetic field (magnetization step).

The heat treatment temperature in the alignment step is preferably, for example, 90 to 200 ° C, more preferably 100 to 150 ° C. The magnitude of the alignment magnetic field in the alignment step can be, for example, 720 kA / m. The magnitude of the magnetizing magnetic field in the magnetizing step can be, for example, 1500 to 2500 kA / m.

Hereinafter, examples will be described. Unless otherwise specified, "%" is based on mass.

Production Example 1 (Fe-Sm sulfuric acid solution)
It was mixed and dissolved FeSO ₄ · _7H 2 O 5.0kg of pure water 20.0 kg. Further, 0.49 kg of Sm ₂ O _{3 and} 0.74 kg of 70% sulfuric acid were added and stirred well to completely dissolve the mixture. Next, pure water was added to the obtained solution to adjust the Fe concentration to 0.726 mol / l and the Sm concentration to 0.112 mol / l to prepare a Fe-Sm sulfuric acid solution.

Production Example 2 (Fe-Sm-La sulfuric acid solution)
It was mixed and dissolved FeSO ₄ · _7H 2 O 5.0kg of pure water 20.0 kg. Further, 0.48 kg of Sm ₂ O _3, 0.071 kg of LaCl _{3 of} 31.8% and 0.72 kg of 70% sulfuric acid are added and stirred well to completely dissolve. Next, pure water was added to the obtained solution to adjust the Fe concentration to 0.726 mol / l, the Sm concentration to 0.109 mol / l, and the La concentration to 0.0063 mol / l. It was prepared as a −Sm—La sulfuric acid solution.

Production Example 3 (Fe-Sm-La-Co sulfuric acid solution)
It was mixed and dissolved FeSO ₄ · _7H 2 O 5.0kg of pure water 20.0 kg. Further, 0.48 kg of Sm ₂ O _3, 0.071 kg of LaCl _{3 of} 31.8%, 0.015 kg of cobalt sulfate of 20.8%, and 0.72 kg of 70% sulfuric acid were added and stirred well to completely dissolve. To do. Next, pure water was added to the obtained solution, and finally the Fe concentration was 0.726 mol / l, the Sm concentration was 0.109 mol / l, the La concentration was 0.0063 mol / l, and the Co concentration was 0.002 mol / l. The concentration was adjusted to 1 l, and a Fe-Sm-La-Co sulfuric acid solution was prepared.

Example 1 (Fe-Sm)
[Precipitation process]
The entire amount of the Fe-Sm sulfuric acid solution prepared in Production Example 1 was added dropwise to 20 kg of pure water maintained at a temperature of 40 ° C. with stirring for 70 minutes from the start of the reaction, and at the same time, a 15% ammonia solution was added dropwise to adjust the pH. Adjusted to 7-8. As a result, a slurry containing Fe-Sm hydroxide was obtained. The obtained slurry was washed with pure water by decantation, and then the hydroxide was solid-liquid separated. The separated hydroxide was dried in an oven at 100 ° C. for 10 hours.

[Oxidation process]
The hydroxide obtained in the precipitation step was calcined in the air at 900 ° C. for 1 hour. After cooling, a red Fe-Sm oxide was obtained as a raw material powder.

[Pretreatment process]
100 g of the Fe-Sm oxide obtained above was placed in a steel container so as to have a bulk thickness of 10 mm. The container was placed in a furnace, the pressure was reduced to 100 Pa, and then the temperature was raised to the pretreatment temperature of 850 ° C. while introducing hydrogen gas, and the temperature was maintained for 15 hours. The oxygen concentration was measured by the non-dispersed infrared absorption method (ND-IR) (EMGA-820 manufactured by HORIBA, Ltd.) and found to be 5% by mass. As a result, it was found that the oxygen bound to Sm was not reduced, and 95% of the oxygen bound to Fe was reduced to obtain a black partial oxide.

[Reduction process]
60 g of the partial oxide obtained in the pretreatment step and 19.2 g of metallic calcium having an average particle size of about 6 mm were mixed and placed in a furnace. After evacuating the inside of the furnace, argon gas (Ar gas) was introduced. Fe—Sm alloy particles were obtained by raising to a first temperature of 1045 ° C. and holding for 45 minutes, then cooling to a second temperature of 1000 ° C. and holding for 30 minutes.

[Nitriding process]
Subsequently, after cooling the temperature inside the furnace to 100 ° C., vacuum exhaust was performed, the temperature was raised to 450 ° C. while introducing nitrogen gas, and the temperature was maintained as it was for 23 hours to obtain a massive product containing magnetic particles. It was.

[Washing-Surface treatment process]
The massive product obtained in the nitriding step was put into 3 kg of pure water and stirred for 30 minutes. After allowing to stand, the supernatant was drained by decantation. Addition to pure water, stirring and decantation were repeated 10 times. Then 2.5 g of 99.9% acetic acid is added and stirred for 15 minutes. After allowing to stand, the supernatant was drained by decantation. Addition to pure water, stirring and decantation were repeated twice.

A phosphoric acid solution was added to the obtained slurry. The phosphoric acid solution was added in an amount of 1 wt% as PO _{4 with} respect to the solid content of the magnetic particles. After stirring for 5 minutes, solid-liquid separation was performed, and then vacuum drying was performed at 80 ° C. for 3 hours to obtain a magnetic powder. The obtained magnetic powder was represented by Sm9.50Fe76.92N13.58.

Examples 2-10 and Comparative Examples 1-3
A magnetic powder was obtained in the same manner as in Example 1 except that the first temperature and holding time and the second temperature and holding time were changed to the temperatures and times shown in Table 1.

[Evaluation]
<Magnetic characteristics>
The magnetic particles obtained by the production methods of each example were packed in a sample container together with paraffin wax, the paraffin wax was melted with a dryer, and then the magnetic domains that were easily magnetized were aligned with an orientation magnetic field of 16 kA / m. This magnetic field oriented sample was pulse-magnetized with a magnetizing magnetic field of 32 kA / m, and the coercive force (iHc) was measured using a VSM (vibrating sample magnetometer) with a maximum magnetic field of 16 kA / m. The evaluation results are shown in Table 1.

From the results in Table 1, when the reduction is performed at only one temperature, the coercive force iHc becomes small as shown in Comparative Examples 1 to 3. On the other hand, as shown in Examples 1 to 10, when the heat treatment is performed even at the second temperature lower than the first temperature, the coercive force iHc is greatly improved.

Example 11 and Comparative Examples 4-5
Examples except that the Fe-Sm-La sulfuric acid solution prepared in Production Example 2 was used and the first temperature and holding time and the second temperature and holding time were changed to the temperatures and times shown in Table 2. The same operation as in 1 was carried out to obtain a magnetic powder. The obtained magnetic powder was represented by Sm9.08Fe77.2N13.63La0.09. Table 2 shows the results of measuring the coercive force (iHc) of the obtained magnetic powder.

From the results in Table 2, even if the anisotropic magnetic powder containing La is reduced at only one temperature, the coercive force iHc becomes small as shown in Comparative Examples 4 and 5. On the other hand, as shown in Example 11, when the heat treatment is performed even at the second temperature lower than the first temperature, the coercive force iHc is greatly improved.

Examples 12-19 and Comparative Examples 6-7
[Precipitation process]
The entire amount of the Fe-Sm-La sulfuric acid solution prepared in Production Example 2 was added dropwise to 20 kg of pure water maintained at a temperature of 40 ° C. with stirring for 70 minutes from the start of the reaction, and at the same time, a 15% ammonia solution and 12. 50 g of a 5% ammonium tungstate solution was added dropwise to adjust the pH to 7-8. As a result, a slurry containing Fe-Sm-La-W hydroxide was obtained. The obtained slurry was washed with pure water by decantation, and then the hydroxide was solid-liquid separated. The separated hydroxide was dried in an oven at 100 ° C. for 10 hours. The steps after the precipitation step were carried out in the same manner as in Example 1 except that the first temperature and holding time and the second temperature and holding time were changed to the temperatures and times shown in Table 3 to obtain a magnetic powder. It was. The obtained magnetic powder was represented by Sm9.49Fe76.8N13.55La0.09W0.07. Table 3 shows the results of measuring the coercive force (iHc) of the obtained magnetic powder.

From the results in Table 3, even if the anisotropic magnetic powder containing La and W is reduced at only one temperature, the coercive force iHc becomes small as shown in Comparative Examples 6 and 7. On the other hand, as shown in Examples 12 to 19, when the heat treatment is performed even at the second temperature lower than the first temperature, the coercive force iHc is greatly improved.

Examples 20-21 and Comparative Examples 8-9
The Fe-Sm-La-Co sulfuric acid solution prepared in Production Example 3 was used, except that the first temperature and holding time and the second temperature and holding time were changed to the temperatures and times shown in Table 4. The same operation as in Examples 12 to 19 was carried out to obtain a magnetic powder. The obtained magnetic powder was represented by Sm9.06Fe76.98N13.58La0.09W0.06Co0.23. Table 4 shows the results of measuring the coercive force (iHc) of the obtained magnetic powder.

From the results in Table 4, even if the anisotropic magnetic powder containing La, W and Co is reduced at only one temperature, the coercive force iHc becomes small as shown in Comparative Examples 8 and 9. On the other hand, as shown in Examples 20 to 21, when the heat treatment is performed even at the second temperature lower than the first temperature, the coercive force iHc is greatly improved.

Since the anisotropic magnetic powder obtained by the production method of the present invention has high magnetic properties, it can be suitably applied to applications such as motors as a composite material and a bond magnet.

Claims (8)

A pretreatment step of obtaining a partial oxide by heat-treating an oxide containing Sm and Fe in a reducing gas atmosphere.
The partial oxide is heat-treated at a first temperature of 1000 ° C. or higher and 1090 ° C. or lower in the presence of a reducing agent, and then heat-treated at a second temperature of 980 ° C. or higher and 1070 ° C. or lower, which is lower than the first temperature. The process of obtaining particles, and
A method for producing an anisotropic magnetic powder, which comprises a step of obtaining an anisotropic magnetic powder by nitriding the alloy particles. The method for producing an anisotropic magnetic powder according to claim 1, wherein the second temperature is lower than the first temperature in the range of 15 ° C. or higher and 60 ° C. or lower. The method for producing an anisotropic magnetic powder according to claim 1 or 2, wherein the heat treatment at the first temperature and the heat treatment at the second temperature are continuously performed. The method for producing an anisotropic magnetic powder according to any one of claims 1 to 3, wherein the heat treatment at the first temperature takes less than 120 minutes. The method for producing an anisotropic magnetic powder according to any one of claims 1 to 4, wherein the heat treatment at the second temperature takes 10 minutes or more. The method for producing an anisotropic magnetic powder according to any one of claims 1 to 5, wherein the oxide containing Sm and Fe further contains La. The method for producing an anisotropic magnetic powder according to any one of claims 1 to 6, wherein the oxide containing Sm and Fe further contains W. The method for producing an anisotropic magnetic powder according to any one of claims 1 to 7, wherein the oxide containing Sm and Fe further contains Co.