JP2985546B2 - Manufacturing method of alloy powder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel method for producing not only an intermetallic compound powder but also an alloy powder containing a rare earth metal.

[0002]

2. Description of the Related Art Generally, rare earth metals and Fe, Co, Ni
Intermetallic compounds or alloys with transition metals such as Tb—Fe—Co thin films for magneto-optical memory, Sm—Co for permanent magnets, and La—Ni for hydrogen storage alloys are industrially useful materials. Used with In this case, these intermetallic compounds or alloys are often required in a powder state. In order to obtain the powder, it is common to melt the metal as a component into an ingot and then pulverize the ingot.However, as a method of directly obtaining the powder, a rare earth oxide powder and a transition metal powder A reduction diffusion method is known in which a rare earth oxide is reduced by mixing and heating in a calcium vapor to diffuse the rare earth oxide into a transition metal.

[0003] The reduction diffusion method has the advantage of using an inexpensive rare earth oxide and the fact that an alloy can be formed at the same time as the reduction. Therefore, the SmCo5 intermetallic compound or Sm-C
This method is widely used in the production of o-alloys. But,
When the reduction diffusion method is performed in a large production unit, that is, in a large capacity, or when the alloy components become complicated, there is a problem that it is difficult to perform a uniform reaction. In addition, a water washing step is required to remove CaO and unreacted Ca, which are reaction by-products, and water-unstable substances cannot be used. For example, when applied to an Nd-Fe alloy, the reaction itself is completed, but there is a disadvantage that the amount of oxygen is significantly increased in a subsequent washing step. Even if the amount of oxygen in water can be reduced as much as possible, or even if the washing step can be simplified with an organic solvent, etc., the alloy powder obtained by the reduction diffusion method does not fundamentally improve the corrosion resistance. In many cases, exposure to the atmosphere alone increases the amount of oxygen, and significantly impairs the development of required physical properties or characteristics.

[0004]

Therefore, an object of the present invention is to improve the conventional reduction-diffusion method to obtain a uniform reaction, whereby the amount of oxygen does not increase even after a water washing step. Further, it is an object of the present invention to provide a method for producing an alloy powder capable of obtaining an alloy powder which is stable against moisture in ordinary atmosphere.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies on the improvement of the reduction diffusion method. It finds usefulness in application to the diffusion method, for example, to make the reaction more uniform and more efficient by positively utilizing the exothermic effect when iron oxide is reduced by Ca, and furthermore, water and weak acid. Even after the aqueous solution washing step, the amount of oxygen does not increase, and a method for producing an alloy powder capable of obtaining an alloy powder stable to moisture in ordinary air has been completed.

That is, the present invention provides a method for producing an alloy powder comprising a rare earth metal and at least one metal selected from the group consisting of Fe, Co and Ni. Powder, the transition metal powder, the transition metal oxide powder in an amount corresponding to a range of up to 30 atomic% of the transition metal in the alloy powder, and granular Ca are mixed, and the mixture is mixed with argon. After heating in an atmosphere to induce self-heating due to the reduction of the oxide of the transition metal, the mixture is subsequently heated in the range of 600 ° C. to 1200 ° C., and then the reaction product is diluted with water and a weak acid aqueous solution. It is characterized by processing.

Further, according to the manufacturing method of the present invention, after a heating step in a range of 600 ° C. to 1200 ° C. in an argon atmosphere, the system is cooled and evacuated once, and then continuously in a nitrogen gas atmosphere or a nitrogen element. And heating the mixture at a pressure of at least atmospheric pressure in a gas atmosphere containing at least 250 ° C. to 800 ° C.

[0008]

The self-heating caused by the reduction of the transition metal oxides of Fe, Co and Ni facilitates the reduction-diffusion reaction of reducing the rare earth oxide and diffusing it into the transition metal,
Reaction efficiency can be increased.

In the production method of the present invention, after the reduction-diffusion reaction, nitrogen treatment may be performed in an atmosphere containing nitrogen or nitrogen. Rare earths not increasing in amount-Fe, Co, Ni
Based alloy powder can be manufactured.

That is, according to the conventional reduction diffusion method, CaO, which is a by-product, quickly reacts with water to produce Ca (OH) 2
However, since unreacted Ca reacts relatively slowly, it takes time to remove it, which also causes a decrease in purity.On the other hand, according to the present invention, since nitrogen treatment is performed, Most of the unreacted Ca becomes nitride such as CaN, and the nitride such as CaN reacts with water as quickly as CaO, which is very convenient for the removal.

[0011]

EXAMPLES Examples of the present invention will now be described with reference to Nd-Fe.
An example of the production of an alloy powder will be described.

First, Nd is added at a ratio corresponding to the desired composition.
2O3 powder, Fe powder and Ca powder are mixed. In this case, substitution is made with Fe2 O3 or Fe3 O4 in a range up to 30 atomic% based on the atomic weight of Fe. These iron oxides are C
Due to the reaction heat at the time of reduction by a, a uniform reaction can be performed as a whole, which leads to saving of external energy and improvement of the yield. In addition, the mixing amount of the granular Ca powder needs to be sufficient to reduce the oxide of the rare earth oxide and the metal oxide to be selectively mixed. The quantities are Nd2O3 and F
1.5 relative to the equivalent of oxygen atoms in e2O3 or Fe3O4
About double is desirable.

[0013] The mixed powder thus obtained is placed in a heating vessel capable of evacuating. After evacuating the inside of the heating vessel, the temperature was reduced from 600 ° C. to 120 ° C. while passing argon gas.
The heating is performed within a range of 0 ° C., preferably within a range of 800 ° C. to 1000 ° C. for several hours, preferably for about 2 hours. When the heating temperature is lower than 600 ° C., the reduction reaction of the oxide does not proceed, which is not preferable. On the other hand, when the heating temperature is higher than 1200 ° C., Ca is scattered, which is not preferable. Here, since an appropriate amount of Fe2 O3 or Fe3 O4 is contained in the mixed powder and the starting system, self-heating occurs during the temperature rise, and a uniform reaction can be efficiently performed. If Fe2O3 or Fe3O4 equivalent to 30 atomic% or more of Fe is mixed, explosion or scattering occurs due to extremely large heat generation, which is not preferable.

Then, the heating is stopped and subsequently cooled to a certain temperature in the range of 250 ° C. to 800 ° C., preferably in the range of 300 ° C. to 600 ° C. in argon gas, and thereafter kept at this temperature. I do. Thereafter, the heating vessel is evacuated again, and then nitrogen gas is introduced. The gas to be introduced is not limited to nitrogen, and may be a gas containing nitrogen atoms, for example, ammonia, or a mixed gas of nitrogen and hydrogen. Within 1 hour, preferably 30 minutes, while passing nitrogen gas at a pressure higher than atmospheric pressure.
After heating for about a minute, stop heating and allow to cool. The pressure of nitrogen gas is not particularly specified, and if it becomes high pressure,
Processing time can be shortened.

The obtained reaction product is put into ion-exchanged water, whereby the reaction product immediately collapses and separation of the alloy powder and the Ca component starts. Stirring in water, standing, and removal of the supernatant liquid are repeated several times, and finally treatment with a weak acid such as acetic acid completes the separation of the Ca component. The obtained alloy powder has a sharp particle size and fluidity.

The fact that the nitrogen treatment in the atmosphere containing nitrogen or nitrogen is carried out prior to the water washing step contributes to obtaining an alloy powder containing no oxygen component even in the water washing step. That is, conventionally, a Ca component such as CaO, which is a reaction by-product, quickly reacts with water to produce Ca (OH) 2, but unreacted Ca reacts relatively slowly, so that it takes time to remove it, and thus purity. In contrast, when nitrogen treatment was performed as in the present invention, most of unreacted Ca became nitrides such as CaN,
Since the nitride such as CaN reacts with water as quickly as CaO, it is very convenient for the removal.

Hereinafter, a specific example of the present invention will be described in comparison with a conventional example.

Example 1 23.15 g of Nd2O3 powder having an average particle size of 1 μm and 37.17 g of Fe powder having an average particle size of 30 μm
And 3.42 g of Fe 2 O 3 powder having an average particle size of 1 μm,
Further, 16.28 g of granular Ca is added and mixed well. Of the mixed powder, Fe atom was equivalent to 6.5 atom% as Fe 2 O 3 powder, and Ca equivalent was Nd 2 O 3
It is 1.5 times the equivalent of the oxygen atom in the medium. The mixture is placed in a mild steel crucible and set in a heating vessel. After evacuating the inside of the heating vessel to 1 × 10 ^-2 Torr or less,
Argon gas is introduced and circulated at atmospheric pressure.

The heating vessel is heated and 620 ° C. during the initial heating.
, Rapid self-heating was observed, and the system temperature instantaneously rose to 87
Reach 0 ° C. Thereafter, the temperature is kept at 850 ° C. for 2 hours, and thereafter, cooling is performed while the argon gas is kept flowing. 500
When the temperature reaches ° C, the temperature is maintained, the flow of argon gas is stopped, and the inside of the heating vessel is immediately evacuated. After the inside of the heating vessel is evacuated to 1 × 10 ^-2 Torr or less, the evacuation is stopped, nitrogen gas is introduced, nitrogen gas flows at atmospheric pressure, and then heat treatment is performed for 30 minutes. Then stop heating and allow to cool.

The obtained reaction product is a porous block and can be easily taken out of the crucible. When the reaction product is put into 3000 cc of deionized water, it immediately disintegrates. At this time, CaO in the reaction product and unreacted Ca mostly composed of nitride such as CaN are fine C
a (OH) 2. After stirring this slurry for 10 minutes, it is left still for 10 minutes, and the supernatant liquid in which fine Ca (OH) 2 is floating is discarded. Here, 3000 cc of ion-exchanged water is added again, and the same operation as above is performed. After repeating this operation several times, the mixture is stirred for 15 minutes in an aqueous acetic acid solution initially adjusted to pH 4.5, allowed to stand, and the supernatant is discarded.
Thereafter, washing with water is performed several times again to complete the removal of the Ca content. Finally, the alloy powder from which the Ca component has been removed is separated from water while substituting alcohol with Nutsche, and the separated cake is vacuum dried at 80 ° C., thereby obtaining an Nd—Fe alloy powder.

The obtained alloy powder weighs 50.15 g.
It was a black powder with good fluidity and a particle size of about 50 μm. According to chemical analysis, Nd 28.2%, Fe70.
1%, Ca 0.07% and O (oxygen atom) 0.56%. The yield based on the starting materials Nd and Fe is 8
3.0%.

Example 2 23.01 g of Nd 2 O 3 powder having an average particle size of 1 μm and 37.17 g of Fe powder having an average particle size of 30 μm
And 6.43 g of Fe2O3 powder having an average particle size of 1 .mu.m. Of the Fe atoms of these raw materials, those originating from Fe2 O3 account for 13 atomic%. Furthermore, granular Ca19.
Add 60 g and mix well. The equivalent of Ca is Nd2O3
And 1.5 times the equivalent of oxygen atoms in Fe2 O3. Thereafter, heat treatment with argon gas, nitrogen treatment, and post-treatment were performed in exactly the same manner as in Example 1, but rapid self-heating was observed from 570 ° C during the initial temperature increase, and the system temperature was instantaneously increased. Reaches 1070 ° C.

The obtained Nd—Fe alloy powder was 54.76.
g of a powder having a particle size of about 50 μm and having good fluidity. According to chemical analysis, Nd 28.1%, Fe6
9.9%, Ca 0.12% and O (oxygen atom) 0.88
%Met. The yield based on the starting materials Nd and Fe was 87.1%.

Example 3 22.88 g of Sm 2 O 3 powder having an average particle size of 1 μm and 38.64 g of Fe powder having an average particle size of 30 μm
And 1.43 g of Fe2O3 powder having an average particle size of 1 .mu.m. Of the Fe atoms in these raw materials, those derived from Fe2O3 are 2.6 atomic%. In addition, granular Ca1
Add 3.44 g and mix well. Ca equivalent is Sm
It is 1.5 times the equivalent of oxygen atoms in 2O3 and Fe2O3. Thereafter, the same operation as in Example 1 was performed,
Rapid self-heating is observed from 690 ° C. during the initial temperature rise, and the temperature of the system instantaneously reaches 830 ° C.

The obtained Sm-Fe alloy powder was 54.26.
g of a powder having a particle size of about 50 μm and having good fluidity. According to chemical analysis, Sm 28.5%, Fe7
0.0%, Ca 0.11% and O (oxygen atom) 0.36
%Met. The yield based on the starting materials Sm and Fe was 97.9%.

Example 3 A reaction was performed under the same conditions as in Example 1 except that the heating temperature in argon gas was 750 ° C. The obtained alloy powder was 49.21 g, and was a black powder having good fluidity and a particle size of about 50 μm. According to chemical analysis, Nd 27.2%, Fe 71.1%, Ca
0.11% and O (oxygen atom) 0.71%. The yield based on the starting materials Nd and Fe was 81.4%.

(Comparative Example 1) The same atomic weight ratio of Nd and Fe as in Example 1 was used, and Nd-Fe was used without mixing Fe2O3 powder.
An alloy powder was produced. That is, Nd2O3 having an average particle size of 1 .mu.m
23.15 g of powder and 39.44 of Fe powder having an average particle size of 30 μm
g of the mixture, and 12.41 g of granular Ca were added and mixed well. The equivalent of Ca is 1.5 times the oxygen atom in Nd2O3. Subsequent operations were performed in the same manner as in Example 1.

The obtained Nd—Fe alloy powder was 46.22.
g of red-black powder having a particle size of about 50 μm. According to chemical analysis, Nd 27.7%, Fe 70.2%, C
a 0.08% and O (oxygen atom) 0.85%.
The yield based on the starting materials Nd and Fe was 70.3%.

Comparative Example 2 In Comparative Example 1, a comparative example in which nitrogen treatment was performed but nitrogen treatment was not performed will be described.

23.15 g of Nd 2 O 3 powder having an average particle size of 1 μm
And 39.44 g of Fe powder having an average particle size of 30 μm,
Further, 12.41 g of granular Ca is added and mixed well. In this case, as in Comparative Example 1, the same Nd as in Example 1 was used.
And the atomic weight ratio of Fe, and the equivalent of Ca is Sm2
It is 1.5 times the equivalent of the oxygen atom in O3. Since then
Except for the nitrogen treatment after the reduction diffusion reaction, the same treatment as in Example 1 is performed.

The obtained Nd—Fe alloy powder was 40.45
g of red-black powder having a particle size of about 50 μm. According to chemical analysis, Nd 15.12%, Fe 82.1%,
Ca was 1.6% and O (oxygen atom) was 0.86%. The yield based on the starting materials Nd and Fe was 66.4%.

(Comparative Example 3) Next, the same atomic weight ratio of Sm and Fe as that of Example 3
-A comparative example in which an Fe alloy powder was produced will be described.

22.88 g of Sm 2 O 3 powder having an average particle size of 1 μm
And 39.73 g of Fe powder having an average particle size of 30 μm, and 11.83 g of granular Ca are further added and sufficiently mixed.
The equivalent of Ca is 1.5 times the equivalent of the oxygen atom in Sm2O3.
It is twice. Thereafter, the same processing as in Example 3 was performed.

The obtained Sm-Fe alloy powder was 51.22.
g of red-black powder having a particle size of about 50 μm. According to chemical analysis, Sm 28.7%, Fe 69.8%, C
a 0.09% and O (oxygen atom) 0.33%. The yield based on the starting materials Sm and Fe was 84.8%.

It is apparent from the comparison between the above-described example and the comparative example that the yield of the example of the present invention is higher than that of the case where the starting material powder does not contain iron oxide, and Since the uniform reduction-diffusion reaction is performed, the obtained alloy powder has a uniform fluidity.

In the examples of the present invention, the obtained alloy powder was stable even when left in the air, with little change in the oxygen content.

In the above description, rare earth and F
Although the alloy powder composed of e, Ni, and Co has been described, according to the present invention, part of the metal powder selected from Fe, Ni, and Co is Ti, Zr, Hf, V, Nb, Ta,
It is needless to say that it is possible to substitute in the form of oxides or metals of Cr, Mo, W, Mn, B, Al, Ca, In, Si and Cu. An alloy of the composition may be produced.

[0038]

As described above, according to the present invention, the conventional reduction-diffusion method is improved to obtain a uniform reaction, whereby the amount of oxygen does not increase even after the water washing step, and the ordinary It is possible to provide a method for producing an alloy powder capable of obtaining an alloy powder stable in water.

Continuation of the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) B22F 9/20 B22F 1/00 C21B 15/02 C22C 1/00 C22C 28/00

Claims (2)

(57) [Claims] 1. A method for producing an alloy powder comprising a rare earth metal, at least one metal selected from the group consisting of Fe, Co and Ni, and Ca, wherein the rare earth oxide powder and the transition A metal powder of a metal, an oxide powder of a transition metal corresponding to a range of up to 30 atomic% of the transition metal in the alloy powder, and granular Ca are mixed, and the mixture is heated in an argon atmosphere. After the self-heating by the reduction of the oxide of the transition metal is induced,
By heating in the range of 0 ° C. to 1200 ° C. and then in a nitrogen gas atmosphere or a gas atmosphere containing a nitrogen element, the mixture is heated in a range of 250 ° C. to 800 ° C. at a pressure higher than the atmospheric pressure and a temperature of 250 ° C. A method for producing an alloy powder, characterized in that a part of calcium is converted into calcium nitride together with an oxidation resistance treatment, and the reaction product is treated with water and a weak acid aqueous solution to elute and remove calcium nitride. 2. A method for producing an alloy powder comprising a rare earth metal, at least one metal selected from the group consisting of Fe, Co and Ni, and Ca uniformly, wherein the rare earth oxide powder and the transition metal , A transition metal oxide powder in an amount corresponding to a range of up to 30 atomic% of the transition metal in the alloy powder, and granular Ca, and heating the mixture in an argon atmosphere. After inducing self-heating by the reduction of the oxide of the transition metal, 600
C. to 1200.degree. C., followed by cooling and evacuation, and subsequently at 250.degree. C. to 800.degree. C. in a nitrogen gas atmosphere or a gas atmosphere containing nitrogen element at a pressure higher than atmospheric pressure. Heating the mixture within the range,
A method for producing an alloy powder, comprising treating the reaction product with water and a weak acid aqueous solution.