JP2002217052A - Method of regenerating rare earth magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To regenerate low-carbon rare earth magnet materials by removing resins from scrapped Nd-Fe-B rare earth bond magnets. SOLUTION: The method comprises a step of pulverizing rare earth bond magnets into grains of 2 mm or less, heating the grains at 900-1200 deg.C in the air to remove resins, heating and reducing the oxidated grains with a reducing agent of metal calcium in an inert gas atmosphere to deoxidate them, washing them with pure water to remove the resins, recovering resulting magnet alloys and dissolving, and solidifying them in an inert gas atmosphere to more remove calcium, thus obtaining a regenerated low-carbon, low-oxygen rare earth magnet material containing little Ca causing magnets to corrode.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rare earth magnet as a high performance permanent magnet, and
Magnet scrap (hereinafter simply referred to as scrap) generated from the manufacturing process of used Fe-B based magnets (R is one or more rare earth metals such as Nd, Pr, Dy, etc.) and used equipment And a method of regenerating so that it can be used as a magnet raw material.

[0002]

2. Description of the Related Art Rare-earth bonded magnets have a particle size of 100 to 150 μm.
After mixing about 1-3% by mass of a thermosetting resin (epoxy resin, urethane resin, phenol resin, etc.) as a binder with rare earth magnet powder of about m as a binder, heat compression by hot pressing etc. to mold and cure the resin And is generally manufactured. In order to improve the rust prevention of the magnet, plating with Ni or the like or surface treatment with a resin or the like may be performed after molding.

[0003] Unlike sintered magnets, bonded magnets have good dimensional accuracy even when they are molded and do not require processing, so that they have good yield and excellent productivity. Nd-Fe-B rare earth bonded magnets have come to be used for a wide range of applications because they exhibit the most excellent magnetic properties among currently mass-produced bonded magnets. In particular, the demand for precision motors for HD and the like is rapidly increasing, and accordingly, the production is also increasing dramatically.

In the manufacturing process of rare earth bonded magnets, defective products (scraps) which cannot be used as products are generated to some extent due to molding defects, plating defects, cracks, scratches, and the like. Also, when a device using a rare bond magnet is discarded, the magnet becomes scrap. Since rare earth bonded magnets use rare earth metals, which are expensive and whose production is limited, the recycling of rare earth bonded magnets has become an important issue.

The rare-earth bonded magnet is a mixture of a magnet powder and a thermosetting resin. For recycling, it is necessary to separate and extract only the magnet powder from the rare-earth bonded magnet. However, a thermosetting resin such as an epoxy resin is extremely strongly adhered to the magnet powder, and it is difficult to separate the magnet powder from the resin by ordinary means.

[0006] Japanese Patent Application Laid-Open No. Hei 6-260314 proposes recycling scrap by pulverizing the scrap, mixing and shaping the scrap with a thermoplastic resin such as polyamide.

[0007] In Japanese Patent Application Laid-Open No. Hei 7-111208, a scrap is baked in a vacuum or in an inert gas atmosphere.
A method has been proposed in which the magnet powder is heated at a temperature of 0 ° C. to eliminate magnetism while preventing oxidation of the magnet particles, and then pulverized to 300 μm or less to obtain a magnet powder as a raw material for a bonded magnet.

[0008] Japanese Patent Application Laid-Open No. 2000-1602011 discloses that Sm-Fe-N
The bonded magnet scrap is heated at 600 to 1500 ° C in the presence of oxygen to calcine the resin, reduced by Ca, then nitrided, then collapsed in water to form a powder, washed with an acid, As a way to play.

[0009]

SUMMARY OF THE INVENTION Incidentally, Nd-Fe-B
Magnets (R-Fe-B systems in a broader sense) are Sm-
Unlike other rare magnets such as Co-based, Sm-Fe-N-based, and other nitrogen-infiltrated magnets, the coercive force decreases when the carbon content is high, and when the carbon content exceeds 1000 ppm, the coercive force decreases. Is extremely reduced.

[0010] Since a new magnet material contains almost no carbon, no problem occurs when an Nd-Fe-B rare earth magnet is manufactured using a new material. However, when recycling scrap, it is not easy to reduce the carbon in the recycled magnet alloy. In particular, in the case of a bonded magnet, since the thermosetting resin containing a large amount of carbon is firmly adhered to the magnet powder, there is a problem in how much carbon can be removed by the regeneration treatment.

However, in the above-mentioned conventional techniques, it is not possible to obtain a recycled magnet material in which the carbon content is reduced to about the same level as that of a new article. Therefore, these techniques are used for the regeneration of Nd-Fe-B based rare earth bonded magnets. Not applicable. JP 20
As used in Japanese Patent Publication No. 00-161021, the removal (carbon removal) of carbon from a rare earth magnet is generally performed by heating the magnet in the presence of oxygen to oxidize (combust) the carbon. Even if this method is applied to an Nd—Fe—B-based bonded magnet as it is, carbon cannot be removed.

When a rare-earth magnet is heated in the presence of oxygen for decarburization, the magnet alloy is oxidized to an oxide and loses magnetism. (Deacidification). The oxidized rare earth magnet alloy can be deoxidized by reduction by a direct reduction (Ca reduction) method using metal Ca or Ca hydride as a reducing agent. Thereafter, the Ca content is removed by washing with pure water, and the regenerated magnet material is recovered.

However, in pure water cleaning, the recycled magnet material
Ca components such as CaO ₂ and CaCl ₂ cannot be completely removed. When a rare earth magnet is manufactured using a regenerated magnet material with Ca remaining obtained by pure water washing, the Ca remaining inside the magnet is reduced even if the magnet is subjected to rust prevention treatment such as plating or resin coating. May cause corrosion of rare earth alloys.

This corrosion phenomenon due to Ca is not unique to Rd-Fe-B based rare earth magnets such as Nd-Fe-B, but is also observed in other rare earth magnets such as Sm-Co based. Therefore, when the oxidized rare earth magnet is regenerated by a method including deoxidation by Ca reduction, the problem of corrosion of the magnet alloy due to the residual Ca content remains, and for the regeneration of the rare earth magnet, an effective removal of the Ca component is effective. It is desired to establish a Ca removal method.

An object of the present invention is to remove even a trace amount of carbon which extremely deteriorates magnetic properties (in particular, coercive force, Hc) when removing resin from a rare earth bonded magnet and reproducing it as a rare earth magnet material. It is another object of the present invention to provide a reproducing method capable of reproducing a rare bond magnet.

[0016] Another object of the present invention is to provide a magnet alloy made of a rare-earth magnet alloy oxidized by decarburization or other treatment, which is reduced by Ca or the like and deoxidized by Ca or the like remaining after washing with pure water. It is to provide a method for preventing corrosion of the steel.

[0017]

Means for Solving the Problems When the scrap of the R-Fe-B rare earth magnet was heated in the air and the resin was removed by combustion decomposition, the processing conditions and the heating temperature were examined in detail. When crushed into particles of the following size and heated in a temperature range of 900 to 1200 ° C, the resin is completely decomposed and the remaining carbon content is also oxidized and removed, and the carbon content in the oxidized magnet alloy Was found to be less than 1000 ppm. Since carbon in the magnet alloy is not removed at all in the subsequent Ca reduction step or melting / solidification step, it must be sufficiently removed in the decarburization step by oxidation until it reaches the target value.

The rare earth magnet oxidized in the decarburization step loses magnetic properties by oxidizing the rare earth element (R), iron and boron in the magnet alloy to form an oxide. In addition, these oxides all have a high melting point and cannot be dissolved as they are. Therefore, it is necessary to reduce the oxidized magnet alloy to remove oxygen (deoxidize). This deoxidation can be performed by a conventional Ca reduction method.

The magnet alloy that has been deoxidized by Ca reduction is repeatedly washed with pure water to remove the Ca component, as is conventionally done. However, pure water washing cannot completely remove Ca. As in the prior art,
If used as it is in the manufacture of the magnet, there is a risk that the residual Ca may cause corrosion of the product magnet or the magnetic properties may be reduced.

As a result of studying a means for completely removing a trace amount of Ca remaining even after pure water washing, a magnet alloy in which Ca remains is melted in an inert gas atmosphere such as Ar and solidified. Thus, it was found that a magnet alloy from which the residual Ca content (CaO, CaCl ₂ , Ca) was substantially completely removed, which could not be completely removed by pure water washing, was obtained. As a result, a regenerated ingot having the same level of quality as an ingot made from a new raw material can be obtained, and no corrosion occurs in a magnet manufactured from the ingot. Therefore, a recycled magnet material that can be used in the same manner as a new raw material is obtained.

It is a common operation to dissolve and solidify a new rare earth magnet material in an inert gas atmosphere to form an ingot. This operation is used for the purpose of removing Ca in the regeneration of the rare earth magnet. That is not known until now.

The present invention relates to an R—Fe—B based rare earth bonded magnet (R is Nd or one or more rare earth metals)
A method of regenerating a rare-earth magnet by removing resin from the magnet and regenerating the magnet as a magnet material, wherein the magnet is pulverized into particles of 2 mm or less, and the particles are heated at a temperature of 900 ° C. or more and 1200 ° C. or less in the atmosphere. To remove the resin
And a method for regenerating a rare earth magnet.

The above-mentioned method for regenerating a rare earth magnet preferably further includes the following steps: heating the particles from which the resin has been removed together with a reducing agent such as calcium metal or calcium hydride in an inert gas atmosphere. A step of collecting the reduced magnet alloy by washing after reduction; and a step of dissolving and solidifying the magnet alloy in an inert gas atmosphere to remove calcium.

In another aspect, the present invention is a method of regenerating a rare earth magnet containing carbon, comprising the steps of: removing carbon from the rare earth magnet containing carbon by oxidation, Step of obtaining a magnet alloy that has been oxidized, reducing the oxidized magnet alloy by heating in an inert gas atmosphere together with a reducing agent such as calcium metal or calcium hydride, and then washing to recover the reduced magnet alloy And a step of melting and solidifying the magnet alloy in an inert gas atmosphere to remove calcium.

In still another aspect, the present invention is a method for regenerating an oxidized rare earth magnet alloy, comprising the steps of: A step of heating and reducing in an inert gas atmosphere together with calcium, followed by washing and recovering the reduced magnetic alloy, and dissolving and solidifying the magnetic alloy in an inert gas atmosphere to remove calcium Process.

In still another aspect, the present invention is a method for regenerating a rare earth magnet material containing calcium, comprising:
A method for regenerating a rare earth magnet material, characterized in that the rare earth magnet material is dissolved and solidified in an inert gas atmosphere to remove calcium.

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION A method for regenerating an R-Fe-B based rare earth bonded magnet according to the present invention is a method for reclaiming scrap of an arbitrary R-Fe-B based rare earth magnet in a state where a rare earth magnet powder is bonded with a resin. Can be used for As the binder resin, a thermosetting resin such as an epoxy resin is often used, but a thermoplastic resin may be used.

As such a scrap, R-Fe-
There are defective products generated in the compression molding step in the manufacturing process of the B-based rare earth bonded magnet, or in the rust prevention step by plating or resin coating. Bond magnets taken out of discarded products are also subject to regeneration processing. Scraps that have been coated with resin as rust prevention treatment can be treated as they are, but scraps that have been plated are removed by appropriate means such as shot blasting before the treatment of the present invention. deep.

Since the above-mentioned scraps all contain a resin as a binder, the carbon content is usually as high as 1% by mass (10,000 ppm) or more. The carbon content in rare-earth bonded magnets is mostly due to the binder, but other sources such as grinding aids (eg, zinc stearate) added when mechanically grinding the magnet alloy into powder. It also contains carbon from sources. As described above, particularly in the case of R-Fe-B rare earth magnets, when a magnet is produced using a raw material alloy having a carbon content of 1000 ppm or more, the magnetic properties, especially the coercive force, are extremely reduced. Otherwise, it cannot be used as a magnet material.

According to the present invention, first, a scrap of an R-Fe-B-based rare earth bonded magnet in which magnet powder is bound by a resin and solidified is pulverized to a size of 2 mm or less to form particles. . If the particle size is larger than 2 mm, even if the resin and residual carbon are removed by air heating next time, a carbon content of 1000 ppm or more will remain inside the alloy. Since the amount does not decrease, the magnetic properties (especially the coercive force iHc) of the rare magnet made from this regenerated ingot deteriorate.

This is because magnet particles approach each other and sinter in the process of decomposition and disappearance of the resin while the resin is burned by heating in the air. However, the size of the scrap particles is 2 mm or more. During the sintering process, the resin is trapped inside,
It is considered that oxygen is hardly supplied to the resin in the inside, and as a result, the residual carbon content increases.

By pulverizing the scrap to a size of 2 mm or less, even if it is sintered, oxygen is supplied to all the resins and the residual carbon content can be reduced to 1000 ppm or less. It is desirable that the residual carbon content is as low as possible, more preferably 300 ppm or less. For this purpose, it is preferable that the size of the scrap is 1 mm or less.

In the present invention, the size (particle size) of the pulverized scrap particles is defined by the size of the sieves used for sizing (classifying). For example, particles of 2 mm or less are particles that pass through a 2 mm eye sieve.

The lower limit of the size of the crushed scrap particles is not particularly defined. However, if the size is too small, crushing takes time, the surface area increases, and the amount of oxidation of the alloy in the next oxidation step increases. It is not preferable to reduce the size to 0.05 mm or less.

The grinding of the scrap of the bonded magnet can be performed by a crusher such as a crusher, a stamp mill, a ball mill, and a vibration mill. The particles of the bonded magnet pulverized as described above are heated in the air at a temperature in the range of 900 to 1200 ° C. to decompose or oxidize the resin and other carbon components (that is, decarbonize). Since the particles are heated in the strongly oxidizing atmosphere, the rare earth magnet alloy (that is, the rare earth metal, iron, and boron) is oxidized.

When heating is performed in a vacuum or in an inert gas atmosphere, as is usually done, to prevent oxidation of the magnet alloy, since there is almost no oxygen in the atmosphere, the resin is sufficiently burned to reduce the carbon. It cannot be removed. In the present invention, since the object is to make the residual carbon amount extremely low, the heating is performed in an atmosphere having sufficient oxygen. However, other oxidizing atmospheres can be used as long as they have the same oxidizing power as the atmosphere.

When the heating temperature is lower than 900 ° C., the reaction between carbon and oxygen does not proceed sufficiently, and decarburization becomes insufficient. On the other hand, when the heating temperature exceeds 1200 ° C, sintering of the particles during heating progresses, and it takes time and effort to pulverize necessary for Ca reduction,
Oxidation of the alloy component remarkably progresses, the amount of Ca required for Ca reduction increases, and the cost increases. Further, the calorific value of the reaction between Ca and oxygen in the Ca reduction step is increased, and the container containing the magnet powder is easily damaged.

The heating time is set so that the carbon content in the particles becomes 1000 ppm or less, preferably 300 ppm or less by oxidation. This time varies depending on the heating temperature, but is usually about 1 to 5 hours. A long heating time exceeding 10 hours is not preferable from the viewpoint of cost.

The decarburization treatment produced by this atmospheric heating produces
The oxidized magnet alloy is generally in the form of a mass of sintered particles. However, if the heating temperature and time are appropriate, the degree of sintering is small. Also, since the binder resin has been removed, the magnet powder as the raw material of the bonded magnet is not bonded with the resin but is simply lightly sintered.

Next, the magnet alloy oxidized by the decarburization is reduced by a Ca reduction method to remove oxygen (deoxidize). Since Ca reduction is a solid-liquid reaction in which a reaction occurs between molten metal Ca and a solid oxidized magnet alloy, the larger the reaction area, the more smoothly the reaction proceeds. Therefore, it is preferable to increase the reaction area of the oxidized magnet alloy that has been sintered and formed into a lump before the reduction by Ca, to obtain a powder. As described above, since the magnet powder is only lightly sintered, it can be easily pulverized by ordinary mechanical pulverization. The pulverization is preferably performed so that the average particle size is about 10 to 300 μm.

To the powder of the oxidized magnet alloy obtained by the pulverization, metal Ca (a part or all of which may be converted to a Ca hydride) is added for Ca reduction. The amount of Ca added is preferably in the range of 1.1 to 2.0 times the chemical equivalent required to reduce the oxidized magnet alloy. If it is too large, the required amount of Ca increases and
Since the load when removing Ca later increases, the cost increases. In addition to metal Ca, it is preferable to add a flux so that collapse of the alloy during pure water washing performed after the Ca reduction treatment proceeds easily. As the flux, chlorides of alkali metals and alkaline earth metals are generally used. Among them, calcium chloride is not particularly used because it does not volatilize during heating. The addition amount of the flux is preferably in the range of 3 to 20% by mass of the oxide magnet alloy.

The Ca reduction is preferably performed at a temperature of 800 to 1000 ° C. If the reaction temperature is lower than 800 ° C., the reduction is not carried out. If the reaction temperature is higher than 1000 ° C., the reduced magnetic alloy is melted and fused with the container, making it difficult to take out. The reduction reaction is preferably performed so that the oxygen content is 1% by mass (10,000 ppm) or less. The reaction time for that usually ranges from 0.5 to 6 hours. If the reaction time is too short,
If the amount of residual oxygen increases and is too long, the amount of residual oxygen decreases, but the processing cost increases.

In this Ca reduction reaction, a large amount of reaction heat is generated. Therefore, the material of the reaction vessel is preferably a metal having a melting point as high as possible. It is preferable that a high melting point metal such as Mo or Ta is lined inside the stainless steel container, or that the entire container is made of a high melting point metal such as Mo or Ta.

In order to reduce the calorific value of the Ca reduction reaction, the oxidized magnet alloy powder is pre-
After heating to 00 ° C. to reduce the iron oxide, a Ca reduction treatment may be performed. Thereby, the calorific value at the time of Ca reduction becomes small, and inexpensive stainless steel or the like can be used for the reaction vessel, so that the cost can be reduced.

The unreacted and reacted Ca component and the Ca component of the flux (Ca, CaO, CaCl ₂ ) are removed from the reduced magnet alloy, and the reduced (ie, carbon and oxygen removed) magnet alloy is removed. To remove the powder, the reaction mixture of the reduction reaction removed from the reaction vessel is preferably crushed and then washed with pure water. As pure water, non-resistance is 50 × 10 ³ Ω · cm /
It is preferable to use one having a temperature of 25 ° C. or higher.

The washing with pure water is usually performed by repeating water injection and decantation about 10 times.
By this treatment, CaO and most of the remaining unreacted Ca are removed as hydroxides. As an indication that Ca was removed, the pH value of the solution during decantation was 10
It is desirable to repeat the pure water washing until
Since Ca is almost completely removed in the next dissolution step,
It does not matter if there is any. Therefore, the number of times of cleaning with pure water can be reduced as compared with the related art.

By this washing, a powder of a regenerated rare earth magnet alloy from which carbon and oxygen have been removed is obtained. In the prior art,
This powder is used as it is as a raw material powder for the magnet, and is again used for the production of a bonded magnet or a finely pulverized sintered magnet. However, as described above, the Ca content is not sufficiently removed from this powder, and particularly when a sintered magnet is manufactured, the remaining Ca content causes corrosion inside the magnet, and the magnet is defective. It is possible that

Therefore, it is necessary to almost completely remove the Ca content in the rare earth magnet powder, but this cannot be achieved only by the above-described cleaning with pure water. In the present invention, the rare-earth magnet powder is once dissolved in an inert gas atmosphere and then solidified, whereby the remaining Ca content can be almost completely removed and the corrosion of the product can be prevented.

In order to dissolve magnet powder containing water that is not completely dried, it is necessary to dry the powder as it is, or to solidify and then vacuum dry to remove the water. However, when the powder is put into a melting crucible as it is, it is oxidized during melting to form slag, and the yield in the regeneration step may be reduced. Therefore, it is preferable to solidify and then vacuum dry. It is also preferable to adopt a method of directly feeding the powder into the molten metal so as not to be oxidized during melting.

As a method of solidification, it is preferable to use a compression method such as hydraulic pressure, hydraulic pressure, mechanical press or the like, and to compress while removing water. If a lubricant is used at the time of solidification, carbon is mixed. Therefore, the lubricant is not used, and water coming out at the time of compression is used instead of the lubricant. The compression pressure is preferably about 49 to 196 MPa.

Thereafter, the solidified or powdered magnetic alloy is dried under reduced pressure. The heating temperature at this time is preferably 80 ° C. or less. The degree of vacuum is preferably 100 Pa or less. After complete drying, the solidified or powdered magnetic alloy is sufficiently cooled before it is removed from the dryer.

The solidified or powdered magnetic alloy is 40
Dissolve at a temperature of 1487 ° C or higher (preferably a temperature range of 1490 to 1600 ° C), which is the boiling point of Ca, in an inert gas atmosphere such as Ar gas under a reduced pressure of about kPa or less, and then cool and solidify. The remaining Ca content after pure water washing (CaO, CaC
1 ₂ , Ca) can be completely removed. In order to effectively remove the Ca content by this dissolution, the Ca content is set to 0.1 before dissolution.
It is preferably at most 5% by mass.

As the dissolving method, a method such as plasma dissolving may be used as long as the dissolving can be performed in an inert gas atmosphere, but high-frequency dissolving is preferable in terms of cost. Another magnet alloy material may be melted in advance as seed water, and the solidified or powdered magnet alloy may be put into the melt and melted. Also, from the beginning, another magnet alloy material and the solidified or powdered magnet alloy are put in a melting crucible, high frequency is applied thereto, and first another magnet alloy material is melted. Solidified or powdered magnetic alloy may be melted. Further, the solidified or powdered magnet alloy may be additionally introduced from the outside to the melted magnet alloy to be melted. When melting the powdered magnetic alloy, it is preferable to use a chute to directly charge the powdered magnetic alloy. By this melting, the remaining Ca content can be almost completely removed, and a magnet alloy having a Ca content of 0.05% by mass or less, preferably less than 0.01% by mass can be obtained.

The molten magnet alloy was poured into a water-cooled mold,
Ingot of recycled magnet material. The ingot thus obtained has less than 1000 ppm of carbon and
, Which can be used directly as a raw material for rare earth magnet alloys. For example, the components of the ingot are measured, and if necessary, the components are redissolved to adjust the components and the missing elements are added.

Thereafter, the melt of the magnet alloy whose components have been adjusted is quenched and solidified to prepare a magnet raw material powder, and the steps of pulverization → magnetic field pressing → sintering → processing → surface treatment are performed to produce a rare earth sintered magnet. can do. Rapid solidification is generally performed by roll quenching. When manufacturing a sintered magnet, the raw material powder is finely pulverized so that the average particle size is about 2 to 5 μm. The resulting sintered magnet has a low carbon content and exhibits good magnetic properties comparable to a new magnet.In addition, the Ca content is extremely low. There is no danger of corrosion. Of course, the magnet raw material powder obtained from the recycled magnet material can be used for the production of the bonded magnet.

As described above, the scrap of the R—Fe—B based rare earth bonded magnet is first deaired by heating in the air, then reduced by the Ca reduction method, deoxidized, and further dissolved and solidified to obtain the Ca.
The case of removing minutes has been described. However, the decarburization, deacidification, and Ca removal steps of the present invention are not limited to the above-described embodiments.

For example, various rare earth magnets containing carbon other than bonded magnets (eg, sintered magnets coated with resin,
Sintered magnets with organic substances such as adhesives, scraps in the manufacturing process such as grinding chips, etc.) are decarburized by appropriate oxidizing means, and then deoxidized by Ca reduction and dissolved / dissolved as described above.
By performing Ca removal by solidification, a regenerative magnet material can be obtained. The Ca reduction (deoxidation) step + the melting / solidification (Ca removal) step can be used to regenerate various rare earth magnet alloys oxidized for some reason. The melting and solidification (Ca removal) process is used to create a magnet material that is free from corrosion by removing Ca almost completely from rare earth magnet materials containing trace amounts of Ca of less than 0.5% by mass. can do.

[0058]

EXAMPLES In the following examples,% is% by mass unless otherwise specified. All test materials used in the examples were 25.3% Nd-0.9% B-2.8% Co-1.48% C-0.71% O
-A Nd-Fe-B based rare earth bonded magnet having a composition of balance Fe. The carbon and oxygen in the above components are derived from the binder epoxy resin.

[0059]

[Embodiment 1] This embodiment shows the effect of the heating temperature in air heating for removing the resin on the resin removing effect.

[Removal of Resin by Atmospheric Heating] The above bonded magnet was pulverized using a crusher until it passed through a sieve of 0.7 mm, and five 1 kg samples were prepared. Next, each sample was heated and burned using an air heating furnace to remove the epoxy resin. At this time, the heating temperature of each sample was 850 ° C, 950 ° C, 1050 ° C, 1150 ° C, 1250 ° C,
Each was heated for 2 hours. After air cooling each heated sample, the carbon content and oxygen content of each heated
(Infrared absorption method). Table 1 below shows the analysis results.
Are shown in the column after air heating.

[0061]

[Table 1]

As shown in Table 1, the heating temperature was 950 ° C.
In the examples at 50 ° C. and 1150 ° C., the carbon content was sufficiently decarburized to 1000 ppm or less, and the oxygen content was 20% or less. It can be safely and well reduced to a regenerated magnet material.

On the other hand, in the comparative example in which the heating temperature was 850 ° C., the amount of carbon after heating greatly exceeded 1000 ppm. I can not use it. On the other hand, when the heating temperature is as high as 1250 ° C., the amount of carbon is lower than that of the example, but the amount of oxygen is lower.
Since it is higher than 25%, the Ca required for reduction increases and the possibility of damaging the container that holds the powder during reduction increases, so reducing this oxidized magnet alloy by the Ca reduction method In practice, it is difficult.

[Deoxidation by Ca Reduction] Each sample (oxidized magnet alloy) from which the resin was removed by heating in the above atmosphere was reduced. 1 kg of each sample was mixed with 450 g of metal Ca (particle size of 5 mesh or less) and 70 g of anhydrous calcium chloride (particle size of 100 mesh or less), and placed in a stainless steel container.
After heating at 900 ° C. for 2 hours in a 6 kPa Ar atmosphere to reduce Ca, the mixture was cooled to room temperature.

The reaction mixture was taken out of the stainless steel container, poured into pure water having a mass ratio of about 10 times, and disintegrated in water. Next, after the decantation and water injection were repeated 13 times, the obtained slurry was put into a mold, solidified by applying a pressure of 98 MPa using a hydraulic press, vacuum-dried at 20 ° C for 24 hours, and then deaerated. A charcoal and a deoxidized regenerative magnet alloy were obtained. Table 1 also shows the values of the carbon content and the oxygen content of the Ca-reduced magnet alloy (analyzed as described above).

As shown in Table 1, when the sample from which the resin has been removed by heating in the atmosphere is reduced with Ca, a magnet alloy in which the amount of carbon hardly changes and the amount of oxygen is greatly reduced is obtained.
As a result, the atmospheric heating temperature is 950 ℃, 1050 ℃ or 1150 ℃
From the sample according to the present invention, after the Ca reduction, the carbon content is 1000 ppm or less, the oxygen content is 10000 ppm or less, low carbon and low oxygen, carbon content and oxygen that can be used as a regenerative magnet material An amount of magnet alloy was obtained. In all samples, the amount of metal elements of the magnet alloy was almost the same as the amount contained in the original bonded magnet, and it was found that there was almost no change in the composition of the magnet alloy due to atmospheric oxidation and Ca reduction.

The sample having an atmospheric heating temperature of 850 ° C. has a carbon content after reduction of Ca of more than 1000 ppm and cannot be used as a regenerative magnet material. In the sample heated at 1250 ° C. in the atmosphere, the phenomenon in which the stainless steel container was melted by the heat generated during the Ca reduction was observed, and the Ca reduction treatment could not be performed.

[Formation of Ingot by Melting and Coagulation]
30.3% Nd-1.0% B-1.1% Co-Rare-earth magnet alloy cast material with the balance being Fe is put into a melting crucible as seed water and 40 kPa Ar
Melted at 1530 ° C. in an atmosphere. The reclaimed alloy was charged and melted in this melting crucible until the mass ratio of the seed metal: regenerated magnet alloy became 3: 7. The obtained solution was cast in a water-cooled mold to prepare an ingot serving as a recycled magnet material.
Table 1 also shows the results of measuring the amounts of carbon and oxygen in the reproduced magnet material in the same manner as described above.

As can be seen from Table 1, oxygen was trapped in the slag during the melting and solidification, and the oxygen content in the ingot was further reduced. With oxygen, a regenerative magnet material of the same level as that of a new rare earth magnet raw material was obtained. If the air heating temperature was too low, 850 ° C., the carbon content after melt-solidification exceeded 1000 ppm, which was unsuitable for use as a regenerative magnet material.

[0070]

[Embodiment 2] This embodiment shows the influence of the particle size of the particles in the air heating step. Using a crusher, the bonded magnet was pulverized to a size passing through sieves of 0.5 mm, 1.5 mm, 3 mm, and 5 mm. Thereafter, the obtained crushed particles were removed in the same manner as in Example 1 by removing the resin by heating at 1050 ° C. for 2 hours in the air, deoxidizing and washing with pure water by Ca reduction, solidifying / vacuum drying, and Melting and solidification were performed to produce a regenerative magnet material.

The obtained regenerative magnet material was melted by high frequency melting under an Ar atmosphere, and 31.0% Nd-1.30% Dy-1.
Insufficient elements were added and dissolved so as to be an Nd-Fe-B-based rare earth magnet component of 05% B-2.70% Co-balance Fe, and the resulting molten metal was rapidly solidified by roll quenching.
The powder produced by the rapid solidification was further pulverized using a jet mill to obtain a rare-earth magnet alloy powder having an average particle size of 3 μm.

A fine powder of this magnet alloy was treated with a magnetic field strength of 800 kA.
/ m in a magnetic field under pressure (pressure 118 MPa) to obtain a green compact having a diameter of 25 cm and a thickness of 10 cm. This green compact is placed in an Ar atmosphere furnace for 10 minutes.
Sintering was performed at 70 ° C. for 2 hours to prepare a Nd—Fe—B rare earth sintered magnet. The residual magnetization (Br), coercive force (iHc), and maximum energy product [(BH) max] of the obtained magnet were measured with a BH tracer, and the carbon content and oxygen of the magnet measured as described above were measured. The results are shown in Table 2 together with the amounts. for reference,
Table 2 also shows the magnetic properties and the amounts of carbon and oxygen of the rare earth sintered magnet using the new magnet raw material having the same composition as described above.

[0073]

[Table 2]

The particle size of the crushed bonded magnet is 0.5
mm or 1.5 mm, the carbon content in the regenerative magnet is
At 1000 ppm or less, the performance was equivalent to that of a sintered magnet made from new raw materials. In particular, when the particle size was 1 mm or less, the carbon content was 300 ppm or less, and the carbon content could be further reduced.

In the comparative example in which the size of the crushed bond magnet was 3 mm or more, carbon was not sufficiently removed at the time of resin removal, and 1000 ppm or more of carbon remained in the sintered magnet produced from the recycled material. . As a result, in this sintered magnet, the coercive force (iHc) is significantly reduced, and (BH) max is also significantly reduced, so that the original performance of the Nd-Fe-B-based magnet cannot be brought out.

[0076]

[Embodiment 3] This embodiment shows the effect of the removal of Ca by the dissolution / coagulation process. The crushed particles of the bonded magnet having a particle size of 1.5 mm used in Example 2 were treated as described in Example 1 with a particle size of 10 mm.
Removal of the resin by air heating at 50 ° C. × 2 hours, deoxidation by Ca reduction, washing with pure water, solidification and vacuum drying, dissolution in Ar and rapid solidification were performed. The obtained powder was finely pulverized with a jet mill to an average particle size of 3 μm to prepare a regenerated magnet material (A) having undergone a melting step.

Separately, a regenerated magnet material (B) which had not been subjected to a melting step was prepared in the same manner as described above, except that the solidification and dissolution / solidification were omitted. In this case, the magnet alloy washed with pure water after Ca reduction was vacuum-dried without solidification, and then finely pulverized by a jet mill.

Regenerated magnet material in the obtained two types of fine powder
(A) and (B) are pressed in a magnetic field with a magnetic field strength of 800 kA / m (pressure
118 MPa) to produce 100 compacts each having a diameter of 25 cm and a thickness of 10 cm. These compacts were placed in an Ar atmosphere furnace for 10 minutes.
Sintering was performed at 70 ° C. for 2 hours to prepare rare earth sintered magnets (A) and (B).

The amount of Ca in the sintered magnets (A) and (B) was measured by ICP emission spectroscopy. As a result, the sintered magnet (A) after the melting step was less than 0.01%. The sintered magnet (B) which did not go through the process was as high as 0.1-0.2%.

The two types of sintered magnets (A) and (B) were
Leave it in a thermostat at 60 ° C and a relative humidity of 60% for 500 hours,
The occurrence of rust on the surface of the sintered magnet was observed. Only 5 out of 100 sintered magnets (A) that had undergone the melting step in Ar showed rust, whereas the sintered magnets that had not been melted
In (B), rust was observed in all 100 pieces.

When the starting point of the rust was analyzed by EPMA, the presence of a Ca compound was confirmed in all the parts. As described above, by dissolving in Ar, Ca
Has been found to be almost completely removed, which makes it possible to prevent rust and corrosion of the regenerated magnet.

[0082]

According to the present invention, the resin is removed from the rare-earth bonded magnet, which has conventionally been difficult to regenerate, so that the amount of carbon that adversely affects the performance of the magnet is sufficiently reduced, and the Ca that causes corrosion is sufficiently reduced. Thus, a magnet having substantially the same performance as a magnet made from a new raw material can be produced using the regenerated magnet material produced by this method. As described above, the present invention is a technology that enables reuse of precious rare earth resources, and is useful for resource protection and stable supply of rare earth magnets.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazutaka Asabe 1-8 Fuso-cho, Amagasaki-shi, Hyogo Sumitomo Metal Industries, Ltd. Electronics Research Laboratory (72) Inventor Katsutoshi Ono Yoshida-honmachi, Sakyo-ku, Kyoto-shi, Kyoto Kyoto University, Faculty of Engineering, Graduate School of Energy Science (72) Inventor Ryosuke Suzuki, Kyoto Prefecture, Kyoto, Japan

Claims (5)

[Claims] An R—Fe—B based rare earth bonded magnet (R is Nd
A method of regenerating a rare-earth magnet by removing resin from one or more rare-earth metals) to regenerate as a magnet material, wherein the step of pulverizing the magnet into particles of 2 mm or less; A method of removing the resin by heating at a temperature of 900 ° C. or more and 1200 ° C. or less. 2. The particles from which the resin has been removed are reduced by heating in an inert gas atmosphere together with a reducing agent such as calcium metal or calcium hydride, and then washed to recover the reduced magnetic alloy. 2. The method for regenerating a rare magnet according to claim 1, further comprising: a step of melting and solidifying the magnet alloy in an inert gas atmosphere to remove calcium. 3. A method for regenerating a rare earth magnet containing carbon, comprising the steps of: removing carbon by oxidation from the rare earth magnet containing carbon to obtain an oxidized magnet alloy; Heating the reduced magnet alloy together with the reducing agent calcium metal or calcium hydride in an inert gas atmosphere, and then washing and recovering the reduced magnet alloy, and inactivating the magnet alloy A step of dissolving and coagulating in a gas atmosphere to remove calcium. 4. A method for regenerating an oxidized rare earth magnet alloy, comprising the steps of: oxidizing the rare earth magnet alloy together with a reducing agent such as calcium metal or calcium hydride in an inert gas atmosphere. After heating and reducing,
Washing and recovering the reduced magnet alloy; and dissolving and solidifying the magnet in an inert gas atmosphere to remove calcium. 5. A method of regenerating a rare earth magnet material containing calcium, characterized in that the rare earth magnet material is dissolved and solidified in an inert gas atmosphere to remove calcium, wherein the calcium is removed. Playback method.