JPH11124605A - Manufacture of alloy powder containing rare earth and transition metal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacture of an SmFe alloy powder, capable of obviating the necessity of a stage for crushing of a reducing reaction product, improving product yield, and giving high quality SmFeN alloy powder, by solving the problem of difficulty in the crushing of a reducing reaction product and improving the disintegrability of the reducing reaction product in water at the time of manufacture of an alloy powder by a reduction-diffusion process. SOLUTION: In this method, a rare earth oxide powder, a transition metal powder, powder of other raw materials, and a reducing agent in a sufficient quantity to reduce the above rare earth oxide are mixed. Heating treatment is applied to the resultant mixture under a practically oxygen-free atmosphere to initiate reducing reaction, and the resultant rare earth metal is diffused into the above transition metal powder to form the desired alloy. After cooling down to room temp., the resultant reduction product is put into water, washed by means of decantation, picked, and subjected to solid-liquid separation, by which the desired alloy powder is manufactured. In this case, hydrogen treatment is carried out after the heating treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an SmFe alloy powder used as a permanent magnet material.

[0002]

2. Description of the Related Art SmFe alloy powder is a permanent magnet material S
It is a raw material for mFeN alloy powder. It is known that this alloy powder exhibits the maximum characteristics when its composition becomes Sm2Fe17N3. For this reason, when diffusing nitrogen into the SmFe alloy, it is necessary to perform uniform nitriding so as to have the above composition. Therefore, it is necessary that the particles of the SmFe alloy powder before nitriding have an average particle size in the range of 30 to 100 microns and have a sharp particle size distribution. Therefore, pulverization and sieving are performed before the nitriding treatment.

[0003] As a method for producing such an SmFe alloy powder, there is a method using a reduction diffusion method.

[0004] The method of producing an alloy by this reduction diffusion method is as follows.
A mixture is obtained by mixing a rare earth oxide powder, a transition metal powder, and other raw material powders with a reducing agent such as metal calcium. Then, the mixture is heat-treated in an atmosphere substantially free of oxygen to reduce the rare earth metal oxide to a rare earth metal, diffuse the rare earth metal into a transition metal powder to form a desired alloy, and cool to room temperature. The obtained product is poured into water to dissolve the residual reducing agent and generated oxides, etc., and at the same time, the processed material is disintegrated into powder, and the decantation is repeated after passing through the target opening sieve. Rinsing with water and then pickling to collect the alloy powder.

[0005]

In the above-mentioned reduction diffusion method, the above-mentioned raw material mixture is heated in a stainless steel container to cause a reduction diffusion reaction, but the product shrinks and solidifies firmly. Therefore, the product is pulverized by a physical or mechanical means before the product is poured into water and granulated, but there is a problem that the pulverization is difficult because the product is solidified. Further, the pulverized material thus obtained has poor reactivity with water, so that about 10% of the sieve is generated on the sieve even after passing through the sieve, resulting in a loss and a low product yield.

The present invention solves the above-mentioned problem in the production of alloy powder by the reduction diffusion method, and eliminates the pulverizing step of the reduction reaction product by improving the collapse property of the reduction reaction product in water. SmFe capable of improving product yield and obtaining high quality SmFeN alloy powder
It is an object to provide a method capable of producing an alloy powder.

[0007]

According to the present invention, a rare earth oxide powder, a transition metal powder, and other raw material powders are mixed with a reducing agent in an amount sufficient to reduce the rare earth oxide. After mixing, the mixture is subjected to a heat treatment under an atmosphere substantially free of oxygen to cause a reduction reaction, and the resulting rare earth metal is diffused into the transition metal powder to form a desired alloy, and after cooling to room temperature, The reduction product is poured into water, washed by decantation, and then pickled,
In a method of producing a desired alloy powder by solid-liquid separation, hydrogen treatment is performed after the heat treatment.

According to the present invention, the reduced product after the heat treatment is significantly improved in disintegration in water, so that the pulverizing step in the conventional method can be omitted, and the reduced product can be used for sieving before washing by decantation. The sieve can be reduced. Further, the number of decantations can be reduced. As a result, not only can the productivity be improved, but also the amount of waste liquid treated can be reduced.

In the present invention, the above-mentioned hydrogen treatment is desirably performed with the reaction vessel attached to the heating furnace during the step of cooling the reaction product after reduction and diffusion by firing. This is because the process can be simplified and the energy consumption can be reduced. The hydrogen treatment is performed at 100 to 600 ° C.
It is preferable to carry out in the temperature range described above. Below 100 ° C., the effect is small, and above 600 ° C., the energy consumption increases. In addition, the target alloy may be decomposed or a by-product may be generated.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The hydrogen treatment carried out in the present invention has been carried out by flowing an inert gas such as argon gas during a cooling period after a calcination step in a conventional reduction diffusion method at a predetermined temperature. , The inert gas may be partly or entirely replaced with hydrogen gas for a desired time and then flow. As a result of the study by the present inventors, it seems that the rate of occlusion of hydrogen into the reduction product basically depends on the temperature and is not greatly affected by the hydrogen gas partial pressure.

The hydrogenated reduction product is cooled to room temperature, then spontaneously decomposes only by being exposed to the atmosphere, and the conventionally required reduction product is reduced by 1 cm.
Not only does it need not be crushed to the size of a square, but also it naturally disintegrates more finely than the particle size after the conventional crushing and crushing step, so that the time required for the subsequent washing and separation step can be reduced. That is, the number of sieving and decanting operations can be greatly reduced. As a result, it is possible to reduce the amount of waste liquid treatment and to improve the recovery rate of the alloy powder product.

Furthermore, the particle size of the alloy powder obtained by this method has a sharp distribution, with most of the particles falling within the range of (average particle size + several tens of microns). For this reason, when manufacturing the SmFeN-based magnet using this alloy powder, further pulverization as a pretreatment is not required.

[0013]

Next, the present invention will be further described with reference to examples.

(Example 1) 20 kg of Sm2O3 powder, F
45 kg of e-powder and 9 kg of metallic calcium were mixed, and the resulting mixture was placed in a stainless steel reaction vessel, filled with argon gas, and charged into a heating furnace.
The temperature was raised to 0 ° C., and maintained at this temperature for about 10 hours to cause a reduction diffusion reaction. Thereafter, the reaction vessel was cooled to room temperature while the reaction vessel was loaded in the heating furnace, and the reaction product was taken out of the reaction vessel. The reaction product weighed 70 kg and was in a hard sintered state. The reaction product was crushed using a hammer and divided into two parts.

One calcined product (35 kg) was returned to the stainless steel reactor, filled with argon gas, charged into a heating furnace, and heated to 300 ° C. Thereafter, the argon gas was replaced with hydrogen gas, and the mixture was maintained at 300 ° C. for 2 hours while flowing hydrogen gas. Thereafter, the mixture was cooled to room temperature while flowing hydrogen gas.

The reaction product thus obtained was allowed to stand in the air for about one hour, and the whole was put into 100 liters of water. Then, the mixture was stirred for 1 hour to disintegrate the reaction product. The obtained slurry was passed through a JIS # 48 sieve and transferred to a washing tank having an effective capacity of 1 m3. At this time, the pH of the slurry was 12, and the loss remaining on the sieve was 0.03 kg.

The decantation was repeated until the pH of the slurry became 10 or less. Decantation condition is 1
m3 of water was injected, and the mixture was stirred for 1 minute, allowed to stand and separated for 1 minute, and drained. The time from the start to the end of the decantation was defined as one washing time. As a result, the total washing time was about 80 minutes until the slurry pH reached 10.

Thereafter, acetic acid is added so that the pH of the slurry becomes 5, acid-washed, solid-liquid separated, dried and dried with SmF
33 kg of e-alloy powder was obtained. The SmFe alloy powder was mixed well, spread so as to have a uniform thickness, and sampled at 10 g each from four arbitrary positions to obtain a sample for particle size measurement. This sample was subjected to a vibration screen type particle size distribution meter to determine the particle size distribution. As a result, this SmFe alloy powder had an average particle diameter of 43 μm, and 99% of particles having a particle diameter of 106 μm or less.

(Conventional example) The remaining 35 kg of the reaction product obtained in the example was crushed to a size of about 3 cm square by a jaw crusher, and then left for 1 hour. Thereafter, this was poured into 100 liters of water, and thereafter decantation was performed until the pH of the slurry became 10 as in the example. After pickling, 32 kg of an SmFe alloy powder was obtained. The pH of the slurry at the time of water granulation was 12, and the value on the JIS # 48 sieve was as large as 1.2 kg. The total washing time is about 1 hour.
It was 50 minutes.

The particle size distribution of the obtained alloy powder was determined in the same manner as in the example. As a result, the average particle size was 65 μm,
Only 70% of the particles were 106 μm or less.

The SmFe alloy powder thus obtained is nitrided into a magnet powder. In this case, particles having a size of 106 μm or less are used in order to improve the nitriding ratio. Therefore, 30% of the SmFe alloy powder obtained in the conventional example cannot be used for magnets unless further pulverized.

(Example 2) Hydrotreating temperature 3 in Example 1
S in the same manner as in Example 1 except that the temperature was changed from 100 ° C. to 100 ° C.
An mFe alloy powder was obtained. The weight on the sieve of JIS # 48 at this time was 0.1 kg. The total amount of washing time was about 100 minutes. Further, of the obtained SmFe alloy powder,
The average particle size is 50 μm, and 9
5%.

Example 3 Hydrotreating temperature 3 of Example 1
Except that 00 ° C was changed to 600 ° C, S
An mFe alloy powder was obtained. At this time, the size on the sieve according to JIS # 48 was 0.03 kg. Further, the total amount of washing time was about 80 minutes. Further, of the obtained SmFe alloy powder,
The average particle size is 50 μm, and 9
9%.

(Example 4) An SmFe alloy powder was obtained in the same manner as in Example 1 except that a mixed gas of hydrogen gas and argon gas was used instead of the hydrogen gas of Example 1. The total washing time and the particle size distribution were not significantly different from those in Example 1.

(Comparative Example) Hydrotreating temperature of Example 1 30
SmF was obtained in the same manner as in Example 1 except that 0 ° C. was changed to 80 ° C.
An attempt was made to obtain an e-alloy powder. However, it was clear that the result was worse than that of Comparative Example 1 when the amount of spontaneous decay was small and the material was not pulverized. Therefore, the subsequent operation was stopped.

[0026]

As described above, in the present invention, by subjecting the reduction reaction product to hydrogen treatment, the degradability of the reduction product can be improved. As a result, not only the recovery rate of the alloy powder can be improved, but also the crushing step can be omitted and the cleaning time can be shortened. Therefore, the industrial value of the present invention is extremely high,

Claims (4)

[Claims] 1. A rare earth oxide powder, a transition metal powder, and other raw material powders are mixed with a reducing agent in an amount sufficient to reduce the rare earth oxide, and the mixture is mixed under an atmosphere substantially free of oxygen. To cause a reduction reaction,
The resulting rare earth metal is diffused into the transition metal powder to form a desired alloy, and after cooling to room temperature, the reduced product is poured into water, washed by decantation, then pickled, and solid-liquid separated to obtain a desired alloy. A method for producing an alloy powder containing a rare earth element and a transition metal, wherein the heat treatment is followed by a hydrogen treatment. 2. The production method according to claim 1, wherein the hydrogen treatment is performed while the reaction vessel is attached to the heating furnace during the step of cooling the reaction product after reduction diffusion by calcination. 3. The method according to claim 1, wherein the hydrogen treatment is performed in a temperature range of 100 to 600 ° C. 4. An alloy powder containing rare earth and transition metal is S
The method according to any one of claims 1 to 3, wherein the method is an mFe-based alloy.