JP3096105B2 - Rare earth magnet manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a rare earth magnet for producing a rare earth magnet powder such as an R--Co magnet or an R--Fe--B magnet by wet pulverization without using a toxic organic solvent. In connection with the above, when wet pulverization using water as a solvent, a specific water temperature, without adding a specific amount of complexing agent and reducing agent to water, the amount of insoluble impurities in the powder after pulverization is 0.1 ppm or less The present invention also relates to a method of manufacturing a rare earth magnet which prevents deterioration and corrosion of the magnet properties of a permanent magnet and prevents a composition deviation of a pulverized powder.

[0002]

2. Description of the Related Art Conventionally, as a magnetic powder used for producing an R-Co magnet, a raw material powder has been obtained by a Ca reduction method or a pulverization method. In addition, magnet powder used for manufacturing rare earth magnets such as R-Fe-B magnets is melted and cast into a mold using a rare earth raw material reduced by electrolysis to form an alloy lump having a required magnet composition. And pulverization to obtain an alloy powder having a required particle size (JP-A-60-63304, JP-A-60-1190701). This melting and pulverization method can easily perform oxidation-preventive pulverization in the ingot coarse pulverization step, so that an alloy powder having a relatively low oxygen content can be obtained.

[0003] Such a rare earth magnet powder is roughly pulverized by mechanical pulverization in order to obtain a required particle size, and then further treated with an organic solvent such as toluene, methanol or hexane.
It is common to carry out wet pulverization in an attritor or the like.

[0004]

The above-mentioned organic solvent used for the wet pulverization is toxic and dangerous, and has a problem of pollution. Therefore, a wet pulverization method using water as a solvent has recently been proposed. Use of water as a solvent is superior to organic solvents in terms of safety and cost

However, water generally has an O ₂ content of 10 ppm or less.
To contain 20 ppm, using water as a solvent during milling, when applied rare earth magnet, especially production of Nd-Fe-B magnets, the O ₂ in water solvent, the generated finely pulverized powder corrosion And Nd (OH) ₃ ,
Insoluble impurities such as FeOOH are generated, and there is a problem that the magnet properties of the permanent magnet obtained from the finely pulverized powder are deteriorated and corroded, so that practical use has been difficult.

Accordingly, the inventor of the present invention has conducted a wet pulverization using water to which a complexing agent and a reducing agent have been added or water which has been further subjected to bubbling treatment with an inert gas as a solvent. The production method of reducing the amount of insoluble impurities was proposed, but the element temperature eluted during the pulverization due to the water temperature of the solvent, resulting in a compositional deviation of the obtained pulverized powder. Had to be kept.

The present invention relates to an R-Co magnet or an R-Co magnet.
The purpose of the present invention is to provide a method for producing a rare earth magnet in which a rare earth magnet powder such as an Fe-B based magnet is produced by wet pulverization without using a toxic organic solvent. It is an object of the present invention to provide a method of manufacturing a rare earth magnet in which the magnet properties of the magnet can be degraded and the amount of corroded impurities can be reduced, and the composition deviation of the pulverized powder is prevented.

[0008]

According to the present invention, when water is used as a solvent in a pulverization step in the production of a rare earth magnet, the amount of O ₂ contained in the water is reduced and the generation of insoluble impurities in the solution is reduced. After various investigations to prevent the composition of the pulverized powder and to prevent the composition deviation of the pulverized powder,
Fe eluting solution with ₂ weight reduction, R (in particular N
As a method for preventing the formation of the insoluble precipitate of d), a complexing agent and a reducing agent are added to water as a solvent, or an inert gas is blown into the water and bubbling is carried out so as to be contained in the water in the solvent. In addition to reducing the amount of O ₂ , the insoluble precipitate is dissolved in the solution, and when the finely pulverized powder is recovered by filtration after the fine pulverization, impurities can be removed from the system as a filtrate, and the water temperature of the solvent water can be reduced. By adjusting the temperature to 10 ° C. or less, it was found that the composition deviation of the pulverized powder could be prevented, and the invention was completed.

That is, the present invention relates to a method for producing R by wet pulverization.
In a method for producing a rare-earth magnet for obtaining a rare-earth magnet powder such as a -Co-based magnet or an R-Fe-B-based magnet, a complex-forming agent is used in an amount of 0.001 to 1 mol / l and a reducing agent of 10 g /
l or less of Na ₂ SO ₃ or wet pulverization using water having a water temperature of 10 ° C. or less in which the amount of O ₂ in the water has been reduced to 1 ppm or less by injecting an inert gas into the water, A method for producing a rare earth magnet, characterized in that the amount of insoluble impurities in the powder separated by filtration after the fine pulverization is reduced to 0.1 ppm or less and the composition deviation of the pulverized powder is prevented.

[0010]

More specifically, the present invention provides a method of manufacturing a rare-earth magnet, which comprises adding a complexing agent to water as a solvent before the wet pulverization step at the time of manufacturing the rare-earth magnet.
01 to 1 mol / l, N of 10 g / l or less as a reducing agent
a ₂ SO ₃ is added, or Ar gas or N ₂
Bubbling by blowing an inert gas such as a gas to reduce the amount of O _{2 in the} solvent water to 1 ppm or less and reduce the water temperature to 10 ppm.
℃ or less, wet fine grinding using the treated water as a solvent, the amount of insoluble impurities in the solution can be reduced to 0.1 ppm or less, and elution of constituent elements can be prevented, so that impurities are filtered during filtration after the fine grinding. Removed as a liquid outside the system, the amount of insoluble impurities in the powder separated by filtration can be reduced to 0.1 ppm or less, and the composition deviation of the pulverized powder can be prevented, thus preventing deterioration of the magnet properties and corrosion of the obtained rare earth magnet. It has a great effect.

In the present invention, water as a solvent includes:
Neutral or alkaline water is preferable. As the alkaline water, concentrated ammonia is 300 ml / l or less,
OH, KOH, Ca (OH) 2, KH 2 PO 4, NaHP
O ₄ , NaHCO ₃ , NaCH ₃ COO 100 ml / l
It is obtained by adding at least one of the following. Also, by using alkaline water as a solvent,
Elution of Nd, Fe, etc. can be reduced more than acidic and neutral solutions,
It is possible to prevent deterioration of the magnet properties due to corrosion of the raw material powder and to improve and improve the corrosion resistance.

The water temperature of the solvent which is a feature of the present invention is 10 ° C.
The reason for the following is that, when the water temperature exceeds 10 ° C., R, Fe, etc. in the raw material powder at the time of fine pulverization are easily eluted, and the magnet characteristics of the obtained magnet are deteriorated due to a composition deviation. A more preferred water temperature is 5 ° C. or lower.

Further, tap water or the like can be used. Conductivity of tap water is 200 μs / cm · 25 ° C. or less, impurities are 40 ppm or less of Cl, 15 ppm or less of Si,
40 ppm or less, Mg 10 ppm or less is preferable, and the conductivity is set to 1 μs / c by treatment such as ion exchange and distillation.
It is better to reduce the temperature to m · 25 ° C. or less.

In the present invention, the complexing agent to be added to water may be either a carboxylic acid ligand or an amine ligand which forms a complex with the constituent elements of the raw material powder. Are preferably succinic acid, maleic acid and the like, and the amine-based ligand is preferably EDTA and DTPA. The addition amount of the complexing agent is 0.0
The amount is preferably from 1 to 1 mol, and the amount of the complexing agent is 0.001 m.
When it is less than ol / l, complex formation is not sufficient, and when it exceeds 1 mol / l, there is no problem in effect, but it is economically unfavorable.

The present invention is characterized in that Na ₂ SO ₃ is added as a reducing agent in an amount of 10 g / l or less together with the addition of a complexing agent. Is not preferred.

Further, in the present invention, before the wet pulverization, A is added to water of a solvent containing a complexing agent and a reducing agent.
By injecting and bubbling an inert gas such as r or N ₂ gas, the amount of O ₂ contained in the solvent water can be reduced, and the corrosion of the obtained finely pulverized powder can be reduced.

In the present invention, the bubbling conditions using an inert gas such as an Ar gas or a N ₂ gas include a gas pressure of 1.0 to 3.0 kg / cm ² and a blowing time of 10 minutes to 6 hours.
The gas flow rate is preferably 3 to 20 l / min for 0 minute. When the gas pressure is less than 1.0 kg / cm ² , sufficient gas cannot be introduced. When the gas pressure exceeds 3.0 kg / cm ² , water is scattered, which is not preferable. If the blowing time is less than 10 minutes, the removal of O ₂ is not sufficient, and if it exceeds 60 minutes, it is not economical. Further, if the gas flow rate is less than 3 l / min, it is not possible to sufficiently remove O ₂ , and if it exceeds ₂₀ l / min, it is not economically preferable.

[0018]

【Example】

Example 1 30.7 wt% Nd-6 obtained by dissolution / pulverization method
A raw material powder for magnet having a composition of 8.2 wt% Fe-1.1 wt% B was put into a 100-liter attritor together with a steel ball having a diameter of 12 mm, and tartaric acid was used as a complex-forming agent at 0.03 ml / l and EDTA 0.1. Water containing 8 g / l of a reducing agent Na ₂ SO ₃ (conductivity 1 μs /
cm. 25 ° C., pH 11.5) was adjusted to the water temperature shown in Table 1 and used as a solvent.
Then, after the pulverization was completed, the mixture was filtered to obtain a finely pulverized powder having a composition and an average particle diameter shown in Table 1. The amount of insoluble impurities such as R and Fe in the obtained finely pulverized powder is as follows:
Table 1 shows the results measured by the ICP measurement method. The solvent water has an O ₂ content of 11.1 before the addition of the complexing agent and the reducing agent.
It was 0 ppm.

Further, this finely pulverized powder is charged into a mold, oriented in a magnetic field of about 10 kOe, and placed in a direction perpendicular to the magnetic field for about 1.
Molded at a pressure of 5 ton / cm ² , 15mm x 20m
A molded body of mx 8 mm was prepared. 1100
Sintering in an Ar atmosphere at 2 ° C. × 2 hours.
An aging treatment was performed at 00 ° C. for 2 hours. Table 2 shows the magnet properties of the obtained test piece magnets.

Comparative Example 1 The same raw material powder as in Example 1 was pulverized in the same production step except that the complexing agent and the reducing agent were not added to the solvent water in the pulverization step. Table 1 shows the composition of the powder, the average particle size, and the amount of insoluble impurities such as R and Fe in the powder. The water temperature was 7 ° C (No. 9) and 20 ° C (No. 1).
0). Further, Table 2 shows the magnet characteristics of the magnet obtained by molding, sintering, and magnetizing in the same manner as in Example 1.

[0021]

[Table 1]

[0022]

[Table 2]

Example 2 As a complexing agent, tartaric acid 0.03 ml / l, EDTA 0.1.
05 ml / l, 8 g / l of Na ₂ SO ₃ as a reducing agent, and Ar gas in water at a gas pressure of 2.0 kg / cm.
^2. Water with an O ₂ content reduced to 0.6 ppm by bubbling under the conditions of a gas flow rate of 10 l / min and a blowing time of 30 minutes (conductivity: 1 μs / cm at 25 ° C., pH: 11.0)
Is adjusted to the water temperature shown in Table 3 and used as a solvent, and is pulverized into powder by the same production process as in Example 1. The amount of insoluble impurities such as R and Fe in the obtained pulverized powder is as follows. ,
Table 3 shows the results measured by the ICP measurement method. Table 4 shows the magnet properties of the magnet obtained by molding, sintering, and magnetizing in the same manner as in Example 1.

[0024]

[Table 3]

[0025]

[Table 4]

[0026]

According to the present invention, wet pulverization is carried out using water having a water temperature of 10 ° C. or lower to which a specific amount of a complexing agent and a reducing agent are added or water having a water temperature of 10 ° C. or lower in which an inert gas is bubbled. Therefore, compared to the conventional pulverization method using an organic solvent, there is no deviation in the composition of the pulverized powder. Rare earth magnets with characteristics were obtained.

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Claims (2)

(57) [Claims] 1. A method for producing a rare earth magnet for obtaining a rare earth magnet powder such as an R—Co magnet or an R—Fe—B magnet by wet pulverization.
Wet pulverization using water having a water temperature of 10 ° C. or less to which 1 g / l and 10 g / l or less of Na ₂ SO ₃ as a reducing agent has been added, and reducing the amount of insoluble impurities in the powder separated by filtration after the fine pulverization to 0. 1. A method for producing a rare earth magnet, wherein the composition is adjusted to 1 ppm or less and the composition deviation of the pulverized powder is prevented. 2. A method for producing a rare earth magnet which obtains a rare earth magnet powder such as an R—Co magnet or an R—Fe—B magnet by wet pulverization.
l / l and 10 g / l or less of Na ₂ SO ₃ as a reducing agent are added, and an inert gas is injected into the water to reduce O 2 in the water.
₍₂ ) Wet pulverization using water having a water temperature of 10 ° C. or less with the amount reduced to 1 ppm or less as a solvent, reducing the insoluble impurity content in the powder separated by filtration after the pulverization to 0.1 ppm or less, and the composition deviation of the pulverized powder. A method for manufacturing a rare earth magnet, characterized in that the occurrence of the rare earth magnet is prevented.