JP6724972B2 - Method for producing anisotropic magnetic powder - Google Patents

Description

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

Patent Document 1 discloses a method for producing a rare earth-iron-nitrogen based 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 comprises performing a second reduction diffusion after an initial reduction diffusion of a rare earth metal oxide. However, the temperature of reduction and diffusion is very low for neodymium-based magnetic materials, and when manufacturing neodymium-based magnetic materials, some of the low-melting-point alloy components hang down to the bottom of the reaction vessel. Was intended to be suppressed.

JP, 2008-171868, A Japanese Patent Laid-Open No. 05-78715

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

The present inventor conducted various studies on the profile of the heat treatment temperature for the purpose of improving the magnetic properties. As a result, after the partial oxide was heat-treated at the first temperature in the presence of a reducing agent, the second oxide having a second temperature lower than the first temperature was used. The present invention has been completed by finding that the magnetic properties of anisotropic magnetic powder can be improved by heat treatment at a temperature.

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 in the presence of a reducing agent at a first temperature of 1000° C. or higher and 1090° C. or lower, and then at a second temperature of 980° C. or higher and 1070° C. or lower, which is lower than the first temperature. Obtaining particles, and
The present invention relates to a method for producing anisotropic magnetic powder, which comprises the step of nitriding the alloy particles to obtain anisotropic magnetic powder.

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

Hereinafter, embodiments of the present invention will be described in detail. However, the following embodiments are examples for embodying the technical idea of the present invention, and the present invention is not limited to the following. In the present specification, the term “process” is used not only as an independent process but also in the case where the intended purpose of the process is achieved even when it cannot be clearly distinguished from other processes. included. Moreover, the numerical range shown using "-" shows the range including the numerical values described before and after "-" as the minimum value and the maximum value, respectively.

The method for producing an anisotropic magnetic powder according to the present embodiment includes 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 in the presence of a reducing agent at a first temperature of 1000° C. or higher and 1090° C. or lower, and then at a second temperature of 980° C. or higher and 1070° C. or lower, which is lower than the first temperature. Obtaining particles, and
The method is characterized by including a step of obtaining anisotropic magnetic powder by nitriding the alloy particles.

It is generally known that the coercive force is highest when the average particle size of 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 many particles in which the particles are strongly bonded (necking) are present. When the magnetic field is applied to the necked particles, the individual particles do not rotate due to the strong bond, so that the magnetic field orientation is deteriorated and the coercive force is lowered. For example, if the heat treatment time at the first temperature is extended as a measure against these necking, the necking is resolved by fusing the particles with each other, but coarse particles exceeding 3 μm are generated, so that the coercive force is lowered. On the other hand, when the heat treatment is performed at the first temperature as in the present embodiment and then at the second temperature lower than the first temperature, the necked particles are separated without fusing, so that coarse particles are generated. It can be considered that the necking can be eliminated while suppressing the occurrence of the phenomenon 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 precipitating agent are mixed to obtain Sm and Fe. It can be manufactured by a step of obtaining a precipitate containing (precipitation step) and a step of baking the precipitate to obtain an oxide containing Sm and Fe (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. From the standpoint of residual magnetic flux density, it is preferable to contain La, from the viewpoint of coercive force and squareness ratio, it is preferable to contain W, and from the viewpoint of temperature characteristics, it is preferable to contain Co.

The Sm raw material and the Fe raw material are not limited as long as they can be dissolved in a strongly acidic solution. For example, in view of easy availability, the Sm raw material may be an Sm oxide, and the Fe raw material may be FeSO ₄ . 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 precipitating agent, an insoluble precipitate containing Sm and Fe is obtained. Here, the solution containing Sm and Fe only needs to be a solution containing Sm and Fe at the time of reaction with the precipitating agent. For example, the raw materials containing Sm and Fe are prepared as separate solutions, and each solution is dropped. It may be reacted with the precipitating agent. Even when prepared as separate solutions, the respective raw materials are appropriately adjusted within the range in which they are substantially dissolved in the acidic solution. The precipitant is not limited as long as it can react with a solution containing Sm and Fe in an alkaline solution to obtain a precipitate, and examples thereof include aqueous ammonia and caustic soda, with caustic soda being preferred.

The precipitation reaction is preferably a method in which the solution containing Sm and Fe and the precipitating agent are added dropwise to a solvent such as water 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 during the reaction, etc., the distribution of the constituent elements is uniform and the particle size distribution is sharp, and the powder form A solid precipitate is obtained. The use of such a precipitate improves the magnetic properties of the final product, magnetic powder. The reaction temperature may be 0 to 50°C, preferably 35 to 45°C. The concentration of the reaction solution is preferably 0.65 mol/L to 0.85 mol/L as the total concentration of metal ions, and more preferably 0.7 mol/L to 0.85 mol/L. 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. The La raw material, the W raw material, and the Co raw material, as well as the Sm raw material and the Fe raw material, are appropriately adjusted within a range in which they are substantially dissolved in the acidic solution. As the acidic solution, sulfuric acid can be used in terms of solubility. Examples of the W raw material include ammonium tungstate, and examples of the Co raw material include cobalt sulfate. Separately from the solution containing Sm and Fe, it is preferable to prepare it in a range in which it is substantially soluble in water.

When 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 and La, W and/or Co at the time of reaction with the precipitating agent. 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 may be prepared together 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 with a laser diffraction type wet particle size distribution meter, the size and distribution of all the powders are substantially within the range of 0.05 to 20 μm, preferably 0.1 to 10 μm. Is preferred. Further, the average particle size is measured as a particle size corresponding to 50% in volume accumulation 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 the precipitate agglomerates when the solvent evaporates, or the particle size distribution, powder size, etc. change. In order to suppress this, it is preferable to remove the solvent. Specific examples of the method of removing the solvent include a method of drying in an oven at 70 to 200° C. for 5 to 12 hours when water is used as the solvent.

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. In the step of separating the precipitate, for example, a solvent (preferably water) is added to the obtained precipitate and mixed, and then a filtration method, a decantation method, or the like can be used.

[Oxidation process]
The oxidation step is a step of obtaining an oxide containing Sm and Fe by firing the precipitate formed in the precipitation step. For example, heat treatment can convert the precipitate to an oxide. The heat treatment of the precipitate needs to be performed in the presence of oxygen, and can be performed, for example, in the atmosphere. Further, since it is necessary to carry out in the presence of oxygen, it is preferable that the non-metal part in the precipitate contains an oxygen atom.

The heat treatment temperature (hereinafter, oxidation temperature) in the oxidation step is not particularly limited, but 700 to 1300°C is preferable, and 900 to 1200°C is more preferable. If the temperature is lower than 700° C., the oxidation is insufficient. Although the heat treatment time is not particularly limited, it is preferably 1 to 3 hours.

The obtained oxide is oxide particles in which Sm and Fe are sufficiently microscopically mixed in the oxide particles and the shape of the precipitate, the particle size distribution, and the like 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 an oxide in which a part of oxygen bonded to Fe is reduced. The oxygen concentration of the partial oxide is preferably 10% by mass or less, and more preferably 8% by mass or less. The oxygen concentration can be measured by a non-dispersive infrared absorption method (ND-IR).

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

[Reduction process]
The reducing step is performed by heat treating the partial oxide in the presence of a reducing agent at a first temperature of 1000° C. or more and 1090° C. or less and then at a second temperature of 980° C. or more and 1070° C. or less, which is lower than the first temperature. This is a step of obtaining alloy particles.

The reduction is carried out by contacting the oxide with the calcium melt or vapor of calcium. The first temperature is 1000° C. or higher and 1090° C. or lower, and preferably 1010° C. or higher and 1080° C. or lower. If it is less than 1000°C, reduction is 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 performing the reduction reaction more uniformly. The lower limit of the heat treatment time is not particularly limited, but is preferably 10 minutes or longer, more preferably 30 minutes or longer.

The second temperature is 980° C. or higher and 1070° C. or lower, preferably 990° C. or higher and 1060° C. or lower. If the temperature is lower than 980°C, necking is not eliminated, and 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 generation 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 than the first temperature in the range of 15°C or more and 60°C or less, and is lower in the range of 15°C or more and 30°C or less. Is more preferable. If it is lower than 15° C., coarse particles are generated and the coercive force is lowered, and if it exceeds 60° C., necking is not eliminated and sufficient coercive force cannot be obtained.

The heat treatment at the first temperature and the heat treatment at the second temperature may be continuously performed, and a heat treatment at a heat treatment temperature lower than the temperature range of the second temperature may be included between these heat treatments, 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 metallic calcium that is a reducing agent. This disintegration accelerator is used as appropriate in order to promote the disintegration and granulation of the product in the water washing step described later, and examples thereof include alkaline earth metal salts such as calcium chloride and alkaline earth such as calcium oxide. Examples thereof include oxides. These disintegration accelerators are used in a proportion of 1 to 30% by mass, preferably 5 to 30% by mass, based on the rare earth oxide used as the rare earth source.

The metallic calcium is used in the form of particles or powder, and its average particle size is preferably 10 mm or less. Thereby, aggregation during the reduction reaction can be suppressed more effectively. Here, the average particle diameter is calculated by measuring the particle diameters of 10 particles with an optical microscope and calculating the arithmetic mean thereof. Further, metallic calcium is equivalent to the reaction equivalent (the stoichiometric amount necessary for reducing the rare earth oxide, and when Fe is in the oxide form, the amount necessary for reducing this is included). It can be added in a ratio of 1.1 to 3.0 times, preferably 1.5 to 2.0 times.

[Nitriding process]
The nitriding step is a step of nitriding the alloy particles obtained in the reducing step to obtain anisotropic magnetic particles. Since the particulate precipitate obtained in the precipitation step is used instead of melting the metals, porous lump-like alloy particles are obtained in the reduction step. Accordingly, the nitriding can be performed uniformly because the nitriding can be immediately performed by performing the heat treatment in the nitrogen atmosphere without performing the crushing treatment.

The heat treatment temperature (hereinafter, nitriding temperature) in the nitriding treatment of the alloy particles is preferably 300 to 600° C., particularly preferably 400 to 550° C., and the atmosphere is replaced 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 and uniformly performed.

The product obtained after the nitriding step contains CaO, unreacted metallic calcium, and the like, which are by-products, in addition to the magnetic particles, and may be in a sintered lump state in which these are compounded. Therefore, in this case, this product can be put into cooling water to separate CaO and metallic calcium from the magnetic particles as a 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 solid content of the magnetic particles obtained in the nitriding step. An anisotropic magnetic powder can be obtained by appropriately separating from the solution and drying.

The anisotropic magnetic powder obtained as described above, the following general formula Typically _{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, and 0≦z≦2.5.)
It is represented by.

In the general formula, v is defined to be 3 or more and 30 or less. When it is less than 3, unreacted part of the iron component (α-Fe phase) is separated and the coercive force of the nitride is lowered, so that it is not a practical magnet. , 30, the element of Sm precipitates, the magnetic powder becomes unstable in the atmosphere, and the residual magnetic flux density decreases. Further, w is defined to be 5 or more and 15 or less because if it is less than 5, coercive force is hardly expressed, and if it exceeds 15, elements of Sm and a nitride of iron itself are generated.

From the viewpoint of magnetic properties, 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. .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 formed.

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), polyether ether ketone (PEEK), liquid crystal polymer (LCP), polyamide (PA), polypropylene (PP), polyethylene (PE), and the like. it can.

The weight ratio of the anisotropic magnetic powder and the resin (resin/magnetic powder) for obtaining the composite material is preferably 0.10 to 0.15, and 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>
A bonded magnet can be manufactured by using a composite material. Specifically, for example, a bond magnet can be obtained by aligning easy magnetic domains with an aligning magnetic field while heat-treating the composite material (aligning step) and then pulse-magnetizing with a magnetizing magnetic field (magnetizing step).

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

Examples will be described below. In addition, "%" is based on mass unless otherwise specified.

Production Example 1 (Fe-Sm sulfuric acid solution)
FeSO ₄ .7H ₂ O (5.0 kg) was mixed and dissolved in pure water (20.0 kg). Furthermore, 0.49 kg of Sm ₂ O _{3 and} 0.74 kg of 70% sulfuric acid were added and well stirred to completely dissolve them. Next, pure water was added to the obtained solution to adjust the final 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)
FeSO ₄ .7H ₂ O (5.0 kg) was mixed and dissolved in pure water (20.0 kg). Further, 0.48 kg of Sm ₂ O _3, 0.071 kg of 31.8% LaCl ₃ and 0.72 kg of 70% sulfuric acid are added and thoroughly stirred to completely dissolve. Next, pure water was added to the obtained solution so that the Fe concentration was 0.726 mol/l, the Sm concentration was 0.109 mol/l, and the La concentration was 0.0063 mol/l. -Sm-La sulfuric acid solution was used.

Production Example 3 (Fe-Sm-La-Co sulfuric acid solution)
FeSO ₄ .7H ₂ O (5.0 kg) was mixed and dissolved in 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 thoroughly stirred to completely dissolve them. 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 Fe-Sm-La-Co sulfuric acid solution was adjusted to be l.

Example 1 (Fe-Sm)
[Precipitation process]
The total amount of the Fe-Sm sulfuric acid solution prepared in Production Example 1 was added dropwise to 20 kg of pure water kept at 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. Thereby, 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 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 put into a steel container so that the bulk thickness was 10 mm. The container was put in a furnace, the pressure was reduced to 100 Pa, the temperature was raised to a pretreatment temperature of 850° C. while introducing hydrogen gas, and the temperature was maintained for 15 hours. When the oxygen concentration was measured by the non-dispersive infrared absorption method (ND-IR) (EMGA-820 manufactured by Horiba Ltd.), it was 5% by mass. As a result, it was found that oxygen bound to Sm was not reduced and 95% of 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 furnace, argon gas (Ar gas) was introduced. The temperature was raised to a first temperature of 1045° C. and kept for 45 minutes, then cooled to a second temperature of 1000° C. and kept for 30 minutes to obtain Fe—Sm alloy particles.

[Nitriding process]
Then, after cooling the temperature in the furnace to 100° C., evacuation 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 lump product containing magnetic particles. It was

[Washing-surface treatment step]
The lumpy product obtained in the nitriding step was added to 3 kg of pure water and stirred for 30 minutes. After standing still, the supernatant was drained by decantation. The addition of pure water, stirring and decantation were repeated 10 times. Next, 2.5 g of 99.9% acetic acid is added and stirred for 15 minutes. After standing still, the supernatant was drained by decantation. The addition of pure water, stirring and decantation were repeated twice.

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

Examples 2-10 and Comparative Examples 1-3
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 those shown in Table 1.

[Evaluation]
<Magnetic characteristics>
The magnetic particles obtained by the manufacturing method of each example were packed in a sample container together with paraffin wax, and the paraffin wax was melted by a dryer, and then the easily magnetized magnetic domains were aligned by an orienting 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 of 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 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 were obtained. The same operation as in 1 was performed to obtain magnetic powder. The magnetic powder obtained was represented by Sm9.08Fe77.2N13.63La0.09. The results of measuring the coercive force (iHc) of the obtained magnetic powder are shown in Table 2.

From the results shown 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, the coercive force iHc is greatly improved by heat treatment at a second temperature lower than the first temperature.

Examples 12-19 and Comparative Examples 6-7
[Precipitation process]
The total amount of the Fe-Sm-La sulfuric acid solution prepared in Production Example 2 was added dropwise to 20 kg of pure water kept at 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. This obtained the slurry containing Fe-Sm-La-W hydroxide. 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 performed 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 temperature and time shown in Table 3, to obtain a magnetic powder. It was The obtained magnetic powder was represented by Sm9.49Fe76.8N13.55La0.09W0.07. The results of measuring the coercive force (iHc) of the obtained magnetic powder are shown in Table 3.

From the results shown in Table 3, even when 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 at the second temperature lower than the first temperature, the coercive force iHc is greatly improved.

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

From the results of Table 4, even with anisotropic magnetic powders containing La, W and Co, the coercive force iHc becomes small as shown in Comparative Examples 8 and 9 when reducing only at one temperature. On the other hand, as shown in Examples 20 to 21, when the heat treatment is performed 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 bonded magnet.

Claims (6)

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