JP2002356724A - Method for reclaiming rare earth magnet alloy slag, and method for manufacturing rare earth magnet alloy - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an industrial method for reclaiming rare earth magnet alloy slag by which a rare earth magnet alloy can be extracted from various scraps (solid or powder scraps) and slag generated from a process for manufacturing rare earth magnet alloy such as a Nd-Fe-B magnet, or from recovered the magnet scraps, and also to provide a method for manufacturing a rare earth magnet alloy. SOLUTION: In this method for reclaiming the rare earth magnet alloy slag, the slag formed in melting the rare earth magnet alloy is reclaimed as a magnetic material. This reclaiming method comprises: (1) Previously pulverized slag is heated in an inert-gas atmosphere together with metal calcium or calcium hydride as a reducing agent to undergo reduction and then cleaned and the resultant reduced magnetic alloy is recovered: (2) The melting and solidification of the magnetic alloy are performed in an inert gas atmosphere to remove calcium.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for regenerating rare earth magnet alloy slag and a method for producing a rare earth magnet alloy.
More specifically, the present invention relates to a method for manufacturing a rare earth sintered magnet which is a high-performance permanent magnet, for example, in a manufacturing process of a Nd-Fe-B based rare earth sintered magnet or a melting process for regenerating a magnet scrap. The present invention relates to a method of regenerating rare earth magnet alloy slag and a method of manufacturing a rare earth magnet alloy for reusing slag generated in large amounts on the surface of a molten metal or the surface of a melting crucible as a raw material of a rare earth magnet alloy.

[0002]

2. Description of the Related Art Rare earth sintered magnets are extremely useful for miniaturization and high performance of equipment due to their excellent magnetic properties. For this reason, there is a great demand for VCMs (voice coil motors), home electric motors, motors for electric vehicles, and even MRIs (magnetic resonance tomography apparatuses), and their production has increased dramatically in recent years.

[0003] The rare earth sintered magnet is obtained by mixing the mixed raw materials.
The quenched material that has been quenched and solidified after melting under Ar gas atmosphere,
Particle size 3-5μm by hydrogen pulverization or jet mill pulverization
It is manufactured by forming a magnet powder of a fine degree, compacting by a press molding method, and then sintering in an atmosphere. Then, after finishing to a predetermined size by machining, plating with Ni or the like or surface treatment with a resin or the like is performed, and then used as a magnet.

[0004] In the manufacturing process of the rare earth sintered magnet, scraps such as defective shaping during pressing, cracking debris during sintering, powdery debris during machining, defective plating during plating, and cracking debris during transportation, etc. Occurs. Further, the rare earth magnet used in the device also becomes a used magnet after the use period of the device has elapsed, and is regarded as scrap. In addition, rare earth metals,
When a virgin rare earth magnet alloy is manufactured by melting the atmosphere using pure iron, Fe-B alloy, or the like, slag remains in the crucible after the molten metal is rapidly solidified or poured into a mold. In particular, the slag remaining in the crucible is 25 to 30% of the dissolved amount when the atmosphere is melted to regenerate magnet scrap such as solid waste (in this specification, unless otherwise specified, "%" is " Mass%)
Also reach. For this reason, it is an extremely important technical subject to recycle and effectively utilize the scrap and slag of these rare-earth magnets in order to save energy and resources and to reduce the manufacturing cost of the rare-earth magnet.

Heretofore, as a method for regenerating a rare earth sintered magnet alloy from a rare earth sintered magnet scrap,
For example, scrap is dissolved using an acid, and a rare earth metal (Nd, Pr, Dy) is separated and purified in the form of a fluoride or oxide by a chemical treatment, and reduced to a rare earth metal by a reducing agent such as Ca. A method and a method of recovering a rare earth metal by subjecting a scrap to molten salt electrolysis and then dissolving at a high temperature by high frequency melting, arc melting, plasma melting or the like are known.

However, according to the former method of the chemical treatment, although it is possible to recover a rare earth metal having high purity, there is a problem that the treatment cost is remarkably increased due to a complicated treatment step. Also, in the latter method using high-temperature melting, when the scrap surface is significantly oxidized, it is not easily melted even when heated in an argon gas or a vacuum atmosphere, so that the melting crucible or the like is damaged, Even if it could be dissolved, there was a problem that the yield of regenerated rare earth metal was very low because of the large amount of slag generated. Thus, these methods of regenerating rare earth sintered magnets could be implemented at the laboratory level, but were almost impossible to implement on an industrial scale.

On the other hand, JP-A-56-38438 discloses that a rare earth magnet scrap is mixed with a metal equivalent of calcium or calcium hydride by 1.8 to 2.5 times the chemical equivalent of calcium combined with the oxygen contained in the scrap. An invention in which calcium oxide is removed by molding and reducing in a stream of argon gas to convert the contained oxygen into a compound of calcium oxide, cooling and crushing the reduced compression-molded body, and then washing with water is disclosed in JP-A-73731 and JP-A-58-136728 disclose that a rare earth magnet scrap is mixed with metallic calcium or calcium hydride in an amount of 2 to 4 times the chemical equivalent of calcium combined with oxygen contained in the scrap. Heated to 900-1200 ° C in active gas,
Japanese Patent Application Laid-Open No. Sho 61-153201 discloses an invention in which after containing oxygen is converted into calcium oxide, the material is immediately disintegrated in water and then calcium oxide is removed. The invention that removes carbon and then performs direct reduction with calcium,
Further, JP-A-8-31624 discloses that when melting a rare earth magnet scrap in a melting furnace in order to reuse it as a rare earth magnet raw material, the constituent elements of the rare earth magnet are used as all or a part of the raw material when melting is started. Inventions each using a metal or an alloy containing as a main component have been proposed.

[0008]

However, according to the conventional inventions according to these proposals, various kinds of scrap (solid waste and powder waste) and slag generated in the process of manufacturing rare earth magnets, slag, and even rare earth magnets are recovered from scraps. Extracting and regenerating the alloy on an industrial scale could not be actually performed at all.

That is, various kinds of scrap (solid waste and powder waste) and slag generated in the process of manufacturing the rare earth magnet, and slag generated when the recovered magnet scrap is melted amount to 10 to 30% of the melted amount. Therefore, even with the inventions according to these proposals, the recovery efficiency of the rare earth magnet alloy is extremely low, and taking into account the processing cost and the like, implementation on an industrial scale was practically impossible. Therefore, at present, most of these scraps have to be disposed of as industrial waste.

An object of the present invention is to provide a method for regenerating rare earth magnet alloy slag and a method for producing a rare earth magnet alloy.
Specifically, for example, a rare-earth magnet alloy is extracted from various scraps (solid debris, powder debris) and slag generated in a manufacturing process of a rare-earth magnet alloy such as an Nd-Fe-B-based magnet and slag, and is recovered from the recovered magnet scrap. It is an object of the present invention to provide a method for regenerating rare earth magnet alloy slag and a method for producing a rare earth magnet alloy, which makes it possible to do so on an industrial scale.

[0011]

SUMMARY OF THE INVENTION The present invention relates to a method for regenerating rare earth magnet alloy slag, which regenerates slag generated when the rare earth magnet alloy is melted as a magnet material, wherein the slag pulverized in advance is used as a reducing agent. The first step of heating and reducing in an inert gas atmosphere together with calcium metal or calcium hydride, followed by washing to recover the reduced magnet alloy, and in the inert gas atmosphere, preferably for a predetermined time. A rare earth magnet alloy slag comprising both a second step of melting and solidifying the magnet alloy to remove calcium under a reduced pressure atmosphere, more desirably a part of the entire melting time under a vacuum atmosphere. It is a regeneration method.

[0012] From another viewpoint, the present invention provides a method of pulverizing a rare earth magnet alloy slag produced when a rare earth magnet alloy is melted, and using the pulverized rare earth magnet alloy slag as a reducing agent such as calcium metal or calcium hydride. A first step of heating and reducing after reduction in an inert gas atmosphere, and then recovering the reduced magnet alloy; and in an inert gas atmosphere, preferably in a reduced pressure atmosphere for a predetermined time, Preferably, the second step of manufacturing a rare earth magnet alloy as a magnet material by removing and melting calcium by performing melting and solidification of the recovered magnet alloy in a vacuum atmosphere for a part of the entire melting time. A method for producing a rare earth magnet alloy, comprising:

[0013] In either of the rare earth magnet alloy slag regeneration method and the rare earth magnet alloy production method according to the present invention, the pulverized rare earth magnet alloy slag is heated to the atmosphere to sufficiently remove carbon and then reduced. It is desirable to use the reducing agent calcium metal or calcium hydride.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a method for regenerating a rare earth magnet alloy slag and a method for manufacturing a rare earth magnet alloy according to the present invention will be described in detail.

The method of regenerating the rare earth magnet alloy slag and the method of manufacturing the rare earth magnet alloy according to the present embodiment are performed by a first step and a second step. Therefore, these two steps will be sequentially described in detail below.

[First Step] (1) Pulverization of Rare Earth Magnet Alloy Slag Generated When Rare Earth Magnet Alloy is Melted In the present embodiment, first, rare earth magnet alloy slag generated when the rare earth magnet alloy is melted Is crushed beforehand, preferably to 1 mm or less. When the carbon present as a rare earth carbide in the slag is caused to react with oxygen and disappear by the atmospheric heating described below, when the particle size of the slag exceeds 1 mm,
Although it is desirable that the amount of carbon remaining inside the slag is low, it can exceed 300 ppm. Then, even if the rare earth magnet alloy is regenerated through the steps described below, it is difficult to reduce the amount of carbon finally remaining to 300 ppm or less, and the magnetic properties (particularly the coercive force Hc) of the manufactured rare earth magnet alloy Is likely to be significantly deteriorated. This is because if the particle size of the slag is large, it becomes difficult for oxygen to be supplied to the rare earth carbide inside the slag during atmospheric heating,
This is considered to be because the bonding between carbon and oxygen becomes difficult and carbon is likely to remain. For this reason, the slag is preliminarily pulverized to a small particle size, preferably 1 mm or less, so that sufficient oxygen is supplied to the surface of all the slag, thereby reducing the carbon content after decarburization by air heating. Can be reliably reduced to 300 ppm or less.

For this reason, it is desirable that the slag be ground in advance to a particle size of 1 mm or less. In the present embodiment,
The particle size of the pulverized slag is determined by the size of the sieve mesh. That is, "slag having a particle size of 1 mm or less" means slag powder present below the sieve when a 1-mm sieve is used.

(2) Heat reduction between the reducing agent and the pulverized rare earth magnet alloy slag in an inert gas atmosphere The present inventors have conducted detailed studies on the properties of the slag, and as a result, Is a mixture of a rare-earth oxide and a rare-earth magnet component, and has been found to be slightly lower in density and higher in viscosity than a rare-earth magnet alloy melt. For this reason, it has been found that, for example, even when the molten metal is poured from the melting crucible into the mold, the molten metal remains inside the melting crucible. According to the results of the study by the present inventors,
The amount of slag produced increases as the amount of oxygen in the molten raw material increases, and the oxygen contained in the slag is 2% or more and 3% or less, and carbon is almost the same as the value of the magnet raw material to be charged. 0, when melting the magnet scrap.
It was also found that it was between 06% and 0.08%.

As described above, when a rare earth magnet alloy is manufactured by regenerating a slag having a high carbon content and a high oxygen content, carbon is
In order to greatly reduce the coercive force of rare earth magnets, especially Nd-Fe-B magnets, it is desirable to remove them as much as possible. The carbon is mixed in from the molten metal, but is mixed into the molten metal from a grinding aid, a lubricant, or the like when manufacturing the magnet. Furthermore, this carbon is not removed by reduction or dissolution with calcium.

Therefore, in the present embodiment, carbon is sufficiently reduced by using a decarburization step by heating in the atmosphere. That is,
In this embodiment, in order to remove carbon to the maximum by atmospheric oxidation, the slag pulverized as described above is preferably heated to a temperature range of 900 ° C to 1200 ° C for a heating time of 1 hour to 5 hours. By doing so, the carbon contained in the slag powder is sufficiently reacted with oxygen in the atmosphere. This ensures that the carbon content of the slag is reduced to 300 ppm or less.

In the present embodiment, atmospheric heating is used as the heating condition because the supply of oxygen that reacts with carbon is insufficient when heating in vacuum or in an inert gas, and sufficient decarburization is performed. Because there are times when you can't.

In the present embodiment, the heating temperature of the atmospheric heating is preferably set at 900 ° C. or more and 1200 ° C. or less for the following reason. That is, the heating temperature is 900 ℃
If the heating temperature is lower than the above, the reaction between carbon and oxygen may not be sufficient and decarburization may be insufficient.
If the temperature exceeds 1200 ° C, sintering of the pulverized slag powder progresses, and it takes time and effort to pulverize before the next step, and for example, severe fusion with a stainless steel container may cause peeling from the container. This may be difficult.

In the present embodiment, the heating time of the atmospheric heating is preferably set to 1 hour or more and 5 hours or less because if the heating time is less than 1 hour, decarburization cannot be performed sufficiently. On the other hand, if the heating time exceeds 5 hours, the heat treatment cycle becomes longer and the cost may increase.

In the present embodiment, as described above,
In the slag powder by using the decarburization process
The carbon possessed reacts with oxygen in the atmosphere,
Decarburized enough. At this point, the slag
Other elements, that is, rare earth elements such as Nd, Pr, and Dy
And Fe, B, etc. are oxides (eg, Fe_TwoO_Three, FeNdO_Three, NdBO
_Three). Therefore, decarburization by atmospheric heating
All can not be dissolved immediately after performing
It is effective to once reduce the oxides of But straight
When trying to reduce calcium, the existing Fe
_TwoO_ThreeExcessive heat generated by the reduction reaction between
The stainless steel container used for the reduction process is melted
There is a possibility that it will.

Therefore, in the present embodiment, the slag powder oxidized by heating in air is heated to 600 ° C. or more in a hydrogen atmosphere.
It is preferable to reduce the iron oxide (Fe ₂ O ₃ ) to Fe by heating to 1100 ° C. or lower, and then perform the calcium reduction treatment. In this way, since the iron oxide (Fe ₂ O ₃ ) is reduced to Fe with hydrogen, the calorific value of the rare earth oxide in the calcium reduction treatment is sufficiently suppressed. Even if a low-cost container is used, the calcium reduction treatment can be performed without any problem.

The range of the pressure of hydrogen in the hydrogen treatment is, for example, not less than 100 Pa and not more than 100 kPa. Further, the heating time is desirably from 1 hour to 5 hours. If the heating time is less than 1 hour, the iron oxide (Fe ₂ O ₃ ) may not be sufficiently reduced, and if the heating time exceeds 5 hours, the heat treatment cycle becomes longer. This is because the cost may increase. In addition, the heating temperature should be between
It is desirable that the temperature is not more than ° C. If the heating temperature is lower than 600 ° C, the reduction of Fe ₂ O ₃ with hydrogen may not proceed sufficiently.On the other hand, if the heating temperature is higher than 1100 ° C, the slag powder will fuse with the container, hindering the subsequent processing. This is because it may cause

In the present embodiment, the calcium reduction treatment is performed next. Prior to the calcium reduction treatment, the slag powder previously decarburized and hydrogen-reduced as described above is powdered, for example, from 10 μm to 300 μm. It is preferable to further pulverize to a particle size. This is for sufficiently performing the deoxidation reduction with Ca.

In this embodiment, at the time of the calcium reduction treatment, metallic Ca is mixed with slag powder, which is preferably further pulverized to a particle size of 10 μm or more and 300 μm or less, for example, at a ratio of 1.1 to 2.0 times the chemical equivalent. It is preferable to further mix calcium chloride corresponding to 3 to 20% of the amount of powder. The reason for mixing calcium chloride is to facilitate disintegration during washing with pure water performed after the calcium reduction treatment.

The calcium reduction treatment is performed at a treatment temperature of 800 ° C.
It is preferable to carry out the treatment under the conditions of not less than 1000 ° C. and treatment time: not less than 0.5 hours and not more than 6 hours. That is, if the treatment temperature of the calcium reduction is lower than 800 ° C., there is a possibility that the reduction cannot be practically performed, while the treatment temperature is reduced.
If the temperature exceeds 1000 ° C., the slag powder is melted and fused with the reaction vessel to make it difficult to take out, which may hinder the subsequent processing. Further, if the treatment time of calcium reduction is shorter than 0.5 hours, the reduction reaction may be insufficient, while if the treatment time exceeds 5 hours, the production cost may increase.

The calcium reduction treatment is performed under the above treatment conditions.
However, this calcium reduction treatment generates heat of reaction.
However, prior to this calcium reduction treatment,
(Fe _TwoO_Three) To Fe, the calorific value is sufficiently suppressed.
It is controlled and does not become too hot. Because of this, calcium
Use a stainless steel container for the reduction process
Can be.

When performing a calcium reduction treatment using this stainless steel container, a welding prevention member made of a heat-resistant metal such as Mo or Ta having a higher melting point than stainless steel is used.
It is desirable to lay at the bottom of the stainless steel container in order to completely prevent fusion with the stainless steel container.

(3) Washing after Reduction and Recovery of Reduced Magnet Alloy Next, the calcium-reduced powder is washed with pure water to separate and remove the Ca component.

That is, in order to separate the Ca reactant from the reduced slag powder and take out the deoxidized slag powder (rare earth magnet alloy powder not yet), it is washed with pure water. On this occasion,
It is desirable to repeat decantation (repeated water injection) about 10 times. By this cleaning with pure water, Ca
Cl ₂ , CaO, and any remaining unreacted Ca,
Separated and removed as hydroxide.

At this time, in order to sufficiently remove Ca, the pH value of the water after washing is desirably 10 or less. However, since Ca is completely removed by the subsequent dissolving step, it does not matter much if some Ca remains.

In the case where the dissolution step described below is not performed,
Ca compounds may remain, and if the magnet is manufactured in the powder metallurgy process as it is, the remaining Ca compounds may cause corrosion or deteriorate magnetic properties. For this reason, from this viewpoint, it is effective to perform the dissolving step described below.

As described above, in the first step, the slag, which has been pulverized in advance, is reduced by heating in an inert gas atmosphere together with the reducing agent metal calcium or calcium hydride, and then washed. And recover the reduced magnet alloy. That is, the rare-earth magnet alloy slag generated when the rare-earth magnet alloy is melted is pulverized, and the pulverized rare-earth magnet alloy slag is reduced in an inert gas atmosphere together with a reducing agent such as calcium metal or calcium hydride in an inert gas atmosphere. After the cleaning, the reduced magnet alloy is recovered.

In the present embodiment, the first step is performed as described above. [Second Step] In the present embodiment, as a second step, an inert gas atmosphere, desirably under a reduced pressure atmosphere for a predetermined time, and more desirably, a part during the entire dissolution time is subjected to a vacuum atmosphere. Then, the recovered magnet alloy is melted and solidified to remove calcium, thereby producing a rare earth magnet alloy as a magnet material.

That is, in the second step of this embodiment, the powder obtained in the first step is
Perform vacuum drying as it is by replacing with ethyl alcohol or the like, or perform water removal or alcohol removal by pressing to perform solidification and vacuum drying, and then, for example, by high-frequency melting in an inert gas atmosphere, etc. By throwing it into a seed water in which a rare-earth metal with a low melting point whose surface is not oxidized is dissolved,
A regenerated ingot having a rare earth magnet component can be obtained, and slag can be regenerated.

As the above-mentioned solidification method, it is preferable to perform green compacting while excluding water by hydraulic pressure, water pressure, mechanical press or the like. The solidification is performed to facilitate the dissolution treatment during dissolution.

In addition, when the powder is put into a melting crucible as it is, it is oxidized during the melting to form a slag, or it is difficult to dissolve on the slag to reduce the yield of the recycled ingot. It is preferable to feed directly into the molten metal.

If a lubricant is used at the time of compacting for solidification, carbon is mixed in, so that water is preferably used instead of the lubricant. Ethyl alcohol or the like may be used as the lubricant. If the pressure for the powder compact is about 50 to 200 MPa, it can be sufficiently solidified.

The heating temperature during vacuum drying is desirably 80 ° C. or less. The degree of vacuum may be a degree of vacuum that can be achieved with a commercially available rotary pump or the like.However, if the degree of vacuum is low, there is a risk of ignition during high-temperature drying. When taking out, it is effective to take out after cooling sufficiently to prevent ignition.

Next, in order to completely remove the remaining Ca components (CaO, CaCl ₂ ), a dissolution temperature of 1487 ° C. or more, which is the boiling point of calcium (for example, 1490 ° C.), preferably in a reduced pressure Ar gas atmosphere (about 40 KPa or less), is used. (Temperature range of 16001600 ° C.), for example, using a known melting method such as high frequency melting or plasma melting. In consideration of cost, it is most preferable to use high-frequency melting.

That is, a melting material of a magnet alloy having a low oxygen and a low melting point is previously melted as seed water, and decarburized and deoxidized slag powder or slag compact is charged and melted. be able to. It is also possible to first put the seed material and the green compact in a melting crucible, then apply high frequency to dissolve the seed metal, and then melt the green compact, and further externally apply a new compact. It is also possible to dissolve by adding a powder material. In addition, in the case of powder, it is good to directly inject into a molten metal using a chute. After melting, it is poured into, for example, a water-cooled mold to form an ingot of a regenerative magnet alloy.

Further, the atmosphere at the time of melting may be set to 2 Pa even for a short time.
It is more preferable to set the high vacuum to less than 10% because the Ca content in the molten metal is further removed. When the atmosphere is melted using a virgin material, the amount of carbon in the slag is, for example, 30.
Since it is as low as less than 0 ppm, the step after the calcium reduction step may be performed without performing the decarburization step by heating in the air in the first step.

As described above, in the second step, the magnet alloy is placed in an inert gas atmosphere, preferably in a reduced pressure atmosphere for a predetermined time, and more preferably in a vacuum atmosphere for a part of the entire melting time. Is dissolved and coagulated to completely remove calcium.

The ingot can be used as a low-carbon and low-oxygen high-quality raw material alloy. The components of this raw material alloy are measured, melted while adjusting the components again, and a rare-earth magnet alloy is prepared by rapid solidification.
Rare earth sintered magnets can be manufactured through the steps of magnetic field press-sintering-processing-surface treatment. This magnet has good magnetic properties because of its low carbon content.

Further, the components of the decarburized and deoxidized slag powder are analyzed in advance, and the raw material to which the insufficient components are added is directly poured into the molten metal as a raw material for melting, and rapidly solidified to form a magnet alloy. A rare-earth magnet can be manufactured by the above-described steps of the present embodiment.

As described above, in the present embodiment, for example, Nd
-When regenerating Fe-B based rare earth magnet scrap in an atmosphere, after slag generated is pulverized, it is heated at high temperature in the air to completely decarburize, and the Fe in the oxidized slag powder is removed.
₂ O ₃ is reduced in a hydrogen atmosphere, and then the rare earth oxide is
By reducing and deoxidizing Ca, desulfurized and decarburized slag powder is desirably compacted and then melted to completely separate and remove the Ca component, thereby making it possible to manufacture a regenerated ingot of a rare earth magnet. .

Therefore, according to the present embodiment, the magnetic properties (particularly the coercive force Hc) contained in the slag generated in large quantities when the atmosphere is melted to regenerate the magnet scrap.
It is possible to regenerate slag while separating and removing the carbon content that extremely deteriorates the carbon content to 300 ppm or less, which is the same level of carbon content as the ingot material made of a virgin magnet. Even if the slag powder is significantly oxidized during the decarburization treatment, the slag powder can be reduced in a subsequent step, and the adverse effect of the Ca reduction can be removed by a subsequent dissolution step. For this reason, it is possible to reliably manufacture a recycled ingot of the rare earth magnet alloy.

Therefore, according to the present embodiment, it is possible to extract and regenerate the rare earth magnet alloy from various scraps (solid waste, powder waste) and slag generated in the process of manufacturing the rare earth magnet alloy, and further from the recovered magnet scrap. Really possible on an industrial scale.

[0052]

The present invention will be described in more detail with reference to examples. (Example 1) 100 kg of solid waste scrap of Nd-Fe-B based rare earth magnet was subjected to high frequency melting in an atmosphere, and 25 kg of slag was mixed with 75 kg of slag.
kg of recycled ingot and got. Slag composition is 25.0Nd
−6.8OPr−3.0Dy −1.0B−0.8Co −0.08C −2.20O −Ba
l.Fe (%), and the component of the recycled ingot is 22.4Nd-6.
7Pr -2.9Dy -1.0B-0.7Co -0.08C -0.05O -Bal.Fe
(%) there were.

In order to regenerate the slag, the slag was crushed to 0.7 mm or less using a crusher.
Put 5kg each in a stainless steel container and use an atmospheric furnace.
After heating at 850 ° C., 950 ° C., 1050 ° C., 1150 ° C., and 1250 ° C. for 5 hours, the mixture was air-cooled. Table 1 summarizes the results of analyzing the carbon content and the oxygen content of these samples.

[0054]

[Table 1]

As shown in Table 1, at a heating temperature in the range of 900 to 1200 ° C., the carbon content is a sufficiently low value of 300 ppm or less, whereas when the heating temperature is less than 900 ° C., the carbon content is high. If the heating temperature was higher than 1200 ° C., the slag was welded to the container, making subsequent processing difficult.

From the above results, the decarburization treatment temperature was 900 ° C.
It was found that the temperature was preferably 1200 ° C. or lower.
In addition, the case where the decarburization treatment time was set to be longer than 2 hours was examined. The amount of carbon tended to decrease, but the amount of oxygen did not change much at about 20%.

Next, 5 kg of the powder heated at 1050 ° C. in the atmosphere was used.
And the following steps were performed. 1kg each in stainless steel container
At 500 ℃, 650 ℃, 850 ℃ using a hydrogen reduction furnace
After heating for 3 hours at five heating temperatures of 10 ° C., 1050 ° C. and 1200 ° C., the furnace was cooled. At this time, the pressure of hydrogen was set to 133 kPa. Table 2 summarizes the results of analyzing the carbon and oxygen contents of the sample thus obtained.

[0058]

[Table 2]

As shown in Table 2, after the hydrogen reduction treatment,
The carbon content was about 150 ppm without change from the value at the time of the decarburization treatment.
On the other hand, when the heating temperature was in the range of 600 ° C. to 1100 ° C., the oxygen content was about 8%, which was a sufficiently low value that the Fe oxide was reduced. On the other hand, if the heating temperature is lower than 600 ° C, the amount of oxygen does not decrease, and if the heating temperature exceeds 1100 ° C, the amount of oxygen decreases, but it does not adhere to the stainless steel container used for hydrogen reduction treatment. Alternatively, sintering progressed, and it was difficult to proceed to the next step.

From the above results, it was found that the hydrogen reduction temperature is preferably from 600 ° C. to 1100 ° C. The amount of carbon and the amount of oxygen did not change much even if the hydrogen reduction time was long.

Next, 1 kg of slag powder hydrogen-reduced at 1050 ° C., 300 g of metallic Ca (particle size of 5 mesh or less), and 70 g of anhydrous calcium chloride (particle size of 100 mesh or less) were mixed and placed in a stainless steel container. 900 in gas atmosphere
After heating to 2 ° C. for 2 hours, the mixture was cooled to room temperature, and then pulverized to 3 mm or less. After the decantation was repeated 13 times, the obtained slurry was put into a mold and solidified with a hydraulic press at a pressure of 98 MPa to obtain a green compact. After performing vacuum drying, the components were analyzed. As a result, the components of this compact were 24.5Nd-6.5Pr-
2.9Dy -1.0B -0.8Co -0.20Ca -0.02C -0.53O -bal.
Fe (%). As a result, carbon and oxygen in the slag were removed, and other components were not much different from the components of the slag. Note that Ca remained slightly.

Then, this green compact was mixed in a crucible in which a seed metal (a molten metal heating temperature of 1530 ° C.) was melted in an Ar gas atmosphere of 40 KPa with a mixing ratio of 70% (seed metal 3, compact 7). And then melted, and then cast into a water-cooled mold to obtain a recycled ingot.

This regenerated ingot had a carbon content of 210 ppm, an oxygen content of 500 ppm, and other elements were substantially the same as the powder of the compact, while the calcium content was 0.03% or less. Therefore, it was found that this regenerated ingot was a high-quality regenerated ingot having an extremely low carbon content and a low oxygen content and being equivalent to a virgin ingot in composition.

As a comparative example, 1 kg of slag powder heated to 1050 ° C. in the air was used, and without passing through a hydrogen reduction step,
Calcium reduction treatment (addition amount: Ca = 700 g, CaCl ₂ = 70 g
), It was found that the stainless steel container containing the slag powder was melted and damaged by the heat generated during the calcium reduction, and it was impossible to use a low-cost stainless steel container.

Then, after measuring the components of the regenerated ingot, various metals were added so as to have predetermined components, dissolved by high frequency dissolution in Ar gas, and rapidly solidified.
The rapidly solidified product is pulverized by a jet mill to obtain an average particle size of 3
μm powder and press molding under a magnetic field strength of 800 kA / m (pressure
118 MPa) to obtain a green compact having a diameter of 25 mm and a height of 10 mm. Then, it is sintered at a temperature of 1070 ° C. for 2 hours in an atmosphere furnace, and Nd-Fe-
B Magnet was created. Then, the obtained magnet component and B
-H tracer and magnetic properties were measured. Table 3 shows the results
Are shown together.

[0066]

[Table 3]

Table 3 shows, as a conventional example, Nd prepared using a material prepared from a virgin ingot having substantially the same components.
The magnetic properties of -Fe-B based rare earth magnets are also shown. Example Nd
The -Fe-B based rare earth magnet has magnetic properties comparable to those of the conventional example made from a virgin ingot, and was found to be sufficiently usable as a high performance magnet.

From the above, it has been found that slag can be recycled by the method of the present invention. (Example 2) The decarburized and deoxidized green compact prepared under the same conditions as in Example 1 was mixed in a crucible in which a seed metal was melted (a molten metal heating temperature of 1530 ° C) in an Ar gas atmosphere of 40 KPa. Is 70
% (Seed water 3, green compact 7)
During the melting, the atmosphere in the furnace was set to 1 Pa for about 10 minutes, and then cast into a water-cooled mold to obtain a recycled ingot. The components of the regenerated ingot were the same as in Example 1 except for Ca,
Was further removed to 0.01% or less.

As described above, by applying a vacuum during melting,
It was found that Ca was further removed and a higher quality regenerated ingot was obtained. (Example 3) The slag powder not crushed to 0.7 mm in Example 1 was subjected to atmospheric oxidation treatment under the conditions of a heating temperature of 1050 ° C and a heating time of 2 hours, and then a heating temperature of 1050 ° C and a heating time of: 3 hours and hydrogen atmosphere conditions: After hydrogen reduction treatment under 133 kPa treatment conditions, the following two types of rare earth magnets (A)
And (B) were prepared.

(A) Under the same conditions as in Example 1, (Ca reduction) −
(Pure water washing)-(Solidification)-(Resolution in Ar gas at 1500 ° C or higher (vacuum atmosphere for a short time)) After producing a regenerated ingot, this regenerated ingot was jet milled and averaged. 3μm particle size powder, magnetic field strength 800
By performing pressure molding (pressure of 118 MPa) at kA / m, 100 cylindrical compacts having a diameter of 25 mm and a height of 10 mm were produced. Thereafter, sintering was performed in an atmosphere furnace under the conditions of a heating temperature of 1070 ° C. and a heating time of 2 hours to produce an Nd—Fe—B magnet. The Ca analysis value of each of these magnets was less than 0.01%.

(B) 100 rare earth magnets having a diameter of 25 mm and a height of 10 mm were manufactured by the same manufacturing process as that of the magnet of (A) except that solidification and dissolution in Ar gas were not performed. The Ca analysis values of these magnets were 0.2
In the range of ~ 0.3%.

Then, these rare earth magnets (A) and
(B) The temperature: 60 ° C and the humidity: 50% in a 60% humidity chamber.
After holding for 0 hour, the occurrence of rust was observed. As a result, Ar
Rust was observed in all of the rare earth magnets (B) that were not melted in the gas, but rust was observed only in 5 out of 100 rare earth magnets (A). It was found that removing the compound was effective in preventing rust.

When the starting portion of the rust was analyzed by EPMA, it was confirmed that a Ca compound was present. (Example 4) A material constituting a Nd-Fe-B-based rare earth magnet was blended and subjected to atmospheric high frequency melting to produce a 100 kg virgin rare earth magnet ingot. At this time, the slag is 8
kg occurred. The component of this slag is 25.1Nd-6.9Pr-3.
0Dy-1.0B-0.8Co-0.01C-2.30O-Bal.Fe (%), which had a large amount of oxygen but a small amount of carbon.

Then, after the powder was reduced to 0.8 mm or less by using a pulverizer, each step of Ca reduction or less was performed under the same conditions as in Example 1 to produce a regenerated ingot. The components of this recycled ingot were 130 ppm of carbon and 400 ppm of oxygen, and the other elements were almost the same as the values of the slag, indicating that a high-quality recycled ingot was obtained.

As described above, when regenerating slag having a sufficiently low carbon content, a high-quality regenerated ingot can be obtained by performing each step after the Ca deoxidation step even if the decarburization step is omitted. I understood.

[0076]

As described above in detail, according to the present invention, a rare earth magnet alloy is extracted from various scraps (solid waste, powder waste), slag, or recovered magnet scrap generated during the manufacturing process of the rare earth magnet alloy. Regeneration on a truly industrial scale.

[0077] For this reason, slag that has been conventionally discarded as industrial waste because there has been no industrial-scale recycling method can be converted into a recycled ingot, and reused. did it. This is extremely effective for the effective use of rare earth metals not produced in Japan.

[Procedure amendment]

[Submission date] May 23, 2001 (2001.5.2)
3)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Name of invention

[Correction method] Change

[Correction contents]

Title: Method for regenerating rare earth magnet alloy slag and method for producing rare earth magnet alloy

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01F 41/02 B09B 3/00 304A // B22F 8/00 ZAB 303D (72) Inventor Kazutaka Asabe Hyogo 1-8 Fuso-cho, Amagasaki-shi Sumitomo Metal Industries, Ltd.Electronic Technology Research Laboratories (72) Inventor Katsutoshi Ono Yoshida Honcho, Sakyo-ku, Kyoto, Kyoto Prefecture 4F004 AA21 AA43 AB10 BA10 CA04 CA14 CA29 CA37 CA40 CA42 CB03 CB04 CB31 CC11 DA02 DA06 DA07 DA12 DA20 4K001 AA10 AA39 BA12 BA22 CA01 CA05 DA05EA05 EA03 GA19 HA07 4K018 AA27 BA18 BB08 BB10 BC40 KA45 5E062 CD04 CG00

Claims (8)

[Claims] 1. A method of regenerating a rare earth magnet alloy slag for regenerating slag generated when a rare earth magnet alloy is melted as a magnet material, wherein the slag that has been pulverized in advance is reduced together with a reducing agent such as calcium metal or calcium hydride. A first step of recovering by heating and reducing in an inert gas atmosphere to recover the reduced magnet alloy, and dissolving and solidifying the magnet alloy in an inert gas atmosphere to remove calcium A method for regenerating a rare earth magnet alloy slag, comprising a second step. 2. The method for reclaiming rare earth magnet alloy slag according to claim 1, wherein the melting is performed in a reduced pressure atmosphere for a predetermined time. 3. The method for reclaiming rare earth magnet alloy slag according to claim 1, wherein the melting is performed in a vacuum atmosphere for a part of the entire melting time. 4. The method for regenerating a rare earth magnet alloy slag according to claim 1, wherein the pulverized rare earth magnet alloy slag is reduced by heating the atmosphere to remove carbon. . 5. A rare earth magnet alloy slag generated when the rare earth magnet alloy is melted is pulverized, and the pulverized rare earth magnet alloy slag is heated together with a reducing agent such as calcium metal or calcium hydride in an inert gas atmosphere. Washing after reducing and recovering the reduced magnet alloy
By dissolving and solidifying the recovered magnet alloy in an inert gas atmosphere to remove calcium,
A method for producing a rare earth magnet alloy, comprising both a second step of producing a rare earth magnet alloy as a magnet material. 6. The method according to claim 5, wherein the melting is performed in a reduced-pressure atmosphere for a predetermined time. 7. The method for producing a rare earth magnet alloy according to claim 5, wherein the melting is performed in a vacuum atmosphere for a part of the entire melting time. 8. The method for producing a rare earth magnet alloy according to claim 5, wherein the pulverized rare earth magnet alloy slag is reduced by heating the air by air heating to remove carbon.