JP2017157663A - PRODUCTION METHOD OF BASE POWDER OF RFeB-BASED SINTERED MAGNET, AND MANUFACTURING METHOD OF RFeB-BASED SINTERED MAGNET - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of producing a base powder of RFeB-based sintered magnet not containing particles of large grain size, when recycling the RFeB-based sintered magnet.SOLUTION: A RFeB-based sintered magnet 11 of recycle object is heated at 60-200°C in hydrogen gas having pressure of 200 kPa or more. When heating in high pressure hydrogen gas at a low temperature, hydrogen gas can infiltrate the RFeB-based sintered magnet easily through grain boundaries rather than grains, and thereby the RFeB-based sintered magnet can be mainly separated only by the grain boundaries, into particles consisting only of old grains. Consequently, production of particles having large diameter of several tens μm-100 μm can be prevented at the time of re-sintering.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for producing a raw material powder of an RFeB-based sintered magnet by recycling an RFeB-based sintered magnet mainly composed of rare earth elements (R), iron (Fe) and boron (B), and The present invention relates to a method for manufacturing an RFeB-based sintered magnet using raw material powder.

  The RFeB-based sintered magnet was discovered by Hayato Sagawa in 1982 and has a feature that it has high magnetic properties far surpassing the permanent magnets used so far. The demand for RFeB sintered magnets for permanent magnets for automobile motors used in hybrid vehicles, electric vehicles, fuel cell vehicles and the like is expected to further increase in the future.

Of the elements that make up RFeB-based sintered magnets, rare earth element R is particularly expensive, so RFeB-based sintered magnets that are no longer used or defective products that have cracks or defects during the manufacture of RFeB-based sintered magnets Is required to be reused. In Patent Document 1, an RFeB-based sintered magnet to be reused is heated to 250 to 400 ° C. in hydrogen gas of about 1.3 kgf / cm ² (about 127 kPa, 0.3 kgf / cm ² higher than atmospheric pressure). In other words, it is disclosed that a powder is obtained as a raw material for an RFeB-based sintered magnet. This is considered to be because the crystal grains constituting the RFeB-based sintered magnet expand due to occlusion of hydrogen, and the strain generated thereby concentrates at the grain boundaries, causing cracks at the grain boundaries.

JP 2012-062533 A JP 2006-019521 A

  In the method described in Patent Document 1, particles having different particle diameters in the range of 1 to 100 μm are mixed in the obtained raw material powder. In an RFeB-based sintered magnet, the average grain size of crystal grains is usually about several μm to 10 μm. Therefore, a plurality of crystal grains are included in powder particles having a maximum grain size of several tens μm to 100 μm. It will remain unseparated from each other. In particular, when an RFeB-based sintered magnet is produced using raw material powder containing particles whose maximum particle size greatly exceeds 50 μm (generally 70 μm or more), it is said that 70 μm or more from these multiple crystal grains during sintering. One crystal grain having a large diameter may be formed (abnormal grain growth). When such crystal grains are formed, the coercive force of the RFeB-based sintered magnet is lowered. The coercive force is a force that resists the reversal of magnetization when a magnetic field opposite to the direction of magnetization is applied to the magnet, and if the value is low, it cannot be used for an automobile motor.

  The problem to be solved by the present invention is a method for producing a raw material powder of an RFeB-based sintered magnet that does not contain particles having a large particle size when recycling an RFeB-based sintered magnet, and an RFeB using the raw material powder It is providing the manufacturing method of a system sintered magnet.

  The RFeB-based sintered magnet raw material powder manufacturing method according to the present invention, which has been made to solve the above-mentioned problems, is a range of 20 to 200 ° C. in a hydrogen gas at a pressure of 200 kPa or higher in an RFeB-based sintered magnet to be recycled. It is characterized in that the temperature is maintained for a predetermined time.

  According to the RFeB-based sintered magnet raw material powder manufacturing method according to the present invention, the RFeB-based sintered magnet to be recycled is 20 to 200 in hydrogen gas at a high pressure of 200 kPa or more (about 100 kPa or more than atmospheric pressure). By maintaining the temperature within a low range of ℃ for a predetermined time, that is, by setting the pressure to 200 kPa or higher at the temperature within the range, hydrogen gas penetrates into the RFeB sintered magnet through the grain boundary rather than inside the grain. It becomes easy. Thereby, the RFeB-based sintered magnet can be separated mainly only at the grain boundaries, and can be separated only into particles made of old crystal grains. Thereby, it is possible to prevent the generation of particles having a large diameter of 70 μm or more during re-sintering.

  In addition, according to the RFeB-based sintered magnet raw material powder manufacturing method according to the present invention, it is possible to obtain a raw material powder having a small particle size with a median particle size distribution of 10 μm or less. Therefore, if the raw material powder is used, an RFeB-based sintered magnet having a high coercive force can be produced. Furthermore, the number of aggregates of a plurality of crystal grains can be minimized.

  In addition, you may stir the raw material powder obtained by said process. As a result, in the aggregate of the plurality of remaining crystal grains, the bonds between the crystal grains that have become brittle by the treatment with the hydrogen gas are cut, and the particle diameter of the RFeB-based sintered magnet raw material powder is made smaller. Can do. Further, after the treatment with hydrogen gas or the treatment with stirring, the particle size of the RFeB-based sintered magnet raw material powder may be further reduced by performing a pulverization treatment using a jet mill or the like.

  The temperature at the time of processing in the present invention may be maintained at a constant temperature during the predetermined time or may vary within the above range. The temperature may be adjusted by heating the RFeB-based sintered magnet to be recycled, or by naturally raising the temperature with heat generated when the RFeB-based sintered magnet occludes hydrogen. Good. Further, when the temperature may exceed the above range due to heat generation during hydrogen storage, the RFeB sintered magnet to be recycled is maintained within the range by cooling.

  The predetermined time can be determined in a preliminary experiment, but in order to sufficiently separate old crystal grains from each other regardless of the average grain size of the RFeB sintered magnet to be recycled, it may be 0.3 hours or more. desirable.

  In the present invention, in order to achieve the above effect, there is no upper limit to the pressure of hydrogen gas, but the pressure of hydrogen gas is preferably 1100 kPa or less at a temperature of 35 ° C. According to the Japanese High Pressure Gas Safety Law, a gas having a pressure of approximately 1101 kPa (gauge pressure of 1000 kPa) or higher at a temperature of 35 ° C. is defined as a “high pressure gas” and is subject to regulations such as storage and trading. By setting the pressure of the gas to a value lower than that, it can be carried out without being subject to these regulations.

  The hydrogen gas used in the present invention may be pure hydrogen gas or a mixed gas containing other gases. When using a mixed gas containing other gases, the partial pressure of hydrogen gas in the mixed gas is set to 200 kPa or more. Examples of the mixed gas include argon mixed gas, methane reformed gas (mixed gas of hydrogen and carbon monoxide), ammonia decomposition gas (mixed gas of hydrogen and nitrogen), and the like.

  In the present invention, if the temperature to be held is too low, the speed of the hydrogen storage reaction is slow, and it takes time to secure the amount of stored hydrogen necessary to separate all grain boundaries. Therefore, the temperature is desirably 60 ° C. or higher.

The upper limit of the temperature was determined for the following reason.
In the conventional method described above, heating is performed so that the temperature is 250 to 400 ° C. However, heating at such a high temperature in a hydrogen gas having a pressure of 200 kPa or more only separates the crystal grains at the grain boundary. In addition, one crystal grain in the RFeB sintered magnet to be recycled absorbs a large amount of hydrogen and collapses to a particle size of 1 μm or less, and the obtained raw material powder contains such small particles. It becomes. Since particles having a small particle size are easily oxidized, if an RFeB-based sintered magnet is produced using a raw material powder containing such particles, the magnetic properties may be lowered. On the other hand, if the temperature is set to 200 ° C. or lower, more preferably 160 ° C. or lower, the crystal grains do not occlude excessive hydrogen, so that the crystal grains are separated from each other at the grain boundaries without causing the crystal grains to collapse. can do.

In the RFeB-based sintered magnet raw material powder manufacturing method according to the present invention, when a coating is provided on the surface of the RFeB-based sintered magnet to be recycled, a defective portion reaching the surface is formed in the coating. It is desirable to keep it. As a result, hydrogen gas enters the RFeB-based sintered magnet through the defect, and the above grain boundary separation becomes possible. In general, a gap or a crack through which hydrogen molecules can pass is naturally formed in a resin coating such as an epoxy resin or a silica (SiO ₂ ) coating, so that a defect portion is formed. There is no need to perform any operation.

  When the above processing is performed on the RFeB-based sintered magnet to be recycled whose coating is provided on the surface, the residue after the processing includes the remnants of the coating together with the raw material powder. Therefore, by performing a classification process (for example, by sieving or air classification) based on a difference in the size or weight of the raw material powder particles and the coating debris, it is possible to easily remove the coating debris from the processed residue. The raw material powder can be obtained by removing.

An apparatus for producing raw material powder of an RFeB-based sintered magnet according to the present invention,
A sealable container containing the RFeB sintered magnet to be recycled;
A hydrogen gas supply unit for supplying hydrogen gas having a pressure of 200 kPa or more into the container;
And a temperature adjusting unit for adjusting the temperature in the container so as to be maintained within a range of 20 to 200 ° C.

  According to this RFeB-based sintered magnet raw material powder production apparatus, after storing the RFeB-based sintered magnet to be recycled in the container, the hydrogen gas supply unit supplies hydrogen gas having a pressure of 200 kPa or more to the container, The said manufacturing method can be implemented by adjusting the temperature of the said container in the range of 20-200 degreeC with a temperature adjustment part.

  The RFeB-based sintered magnet manufacturing method according to the present invention is characterized in that the raw material powder produced by the RFeB-based sintered magnet raw material powder manufacturing method is oriented in a magnetic field and then sintered.

  According to this RFeB-based sintered magnet manufacturing method, since the raw material powder having a small particle diameter of 10 μm or less, which does not contain particles having a large particle diameter and is produced by recycling, is inexpensive. In addition, an RFeB-based sintered magnet having a high coercive force can be manufactured.

  In the method for producing an RFeB-based sintered magnet according to the present invention, a normal method (press method) with compression molding may be used, and orientation and sintering are performed without performing compression molding as described in Patent Document 2. A PLP (press-less process) method may be used. The PLP method can increase the coercive force while suppressing the decrease in the residual magnetic flux density (see Patent Document 2). The raw material powder is accommodated in a container having a shape corresponding to the final product for orientation and sintering. This is superior to the press method in that a complex shaped RFeB sintered magnet can be easily manufactured.

  In the method for producing an RFeB-based sintered magnet according to the present invention, the orientation and the powder obtained by mixing the raw material powder produced by the above method and the non-recycled raw material powder produced by pulverizing the RFeB-based alloy ingot Sintering may be performed. Thereby, the coercive force of the RFeB-based sintered magnet can be further increased.

  According to the RFeB-based sintered magnet raw material powder manufacturing method according to the present invention, when recycling an RFeB-based sintered magnet, it is possible to manufacture an RFeB-based sintered magnet raw material powder that does not contain particles having a large particle size. .

  With the RFeB sintered magnet manufacturing method according to the present invention, an RFeB sintered magnet having a high coercive force can be manufactured at low cost.

Schematic which shows one Embodiment of the manufacturing method of the raw material powder of the RFeB type sintered magnet which concerns on this invention. FIG. 6 is a schematic view showing another embodiment of a method for producing a raw material powder for an RFeB-based sintered magnet according to the present invention, in which an RFeB-based sintered magnet to be recycled with a coating provided on the surface is used. Schematic which shows one Embodiment of the manufacturing method of the RFeB type sintered magnet which concerns on this invention.

  1 to 3, an embodiment of a method for producing a raw material powder for an RFeB-based sintered magnet according to the present invention and a method for producing an RFeB-based sintered magnet using the raw material powder produced by the method will be described. To do.

  FIG. 1 shows an embodiment of a method for producing a raw material powder of an RFeB-based sintered magnet using an RFeB-based sintered magnet (raw material sintered magnet 11) to be recycled whose surface is not provided with a coating (coating). Show. In this method, the raw material sintered magnet 11 is housed as it is in a sealed container 12 that can withstand the pressure of hydrogen gas, which will be described later, and the air in the sealed container 12 is removed (FIG. 1 (a)). The air in the airtight container 12 is removed by, for example, evacuating the airtight container 12 with a vacuum pump or by replacing the air with hydrogen gas by supplying atmospheric hydrogen gas into the airtight container 12. be able to. Next, hydrogen gas having a pressure of 200 kPa or more is supplied into the sealed container 12 ((b)). At that time, a mixed gas of hydrogen gas and other gas (nitrogen gas, carbon monoxide gas, rare gas, etc.) may be used. In that case, the partial pressure of hydrogen gas should be 200 kPa or more. To do. In this state, the inside of the sealed container 12 is kept at 20 to 200 ° C., preferably 60 to 160 ° C. ((c)). Thereby, the raw material sintered magnet 11 is mainly separated only at the grain boundary, and the raw material powder P separated only into particles made of old crystal grains is obtained. Since the raw material powder P separated into particles made of old crystal grains is easily oxidized in this way, it can be oxidized in an inert gas such as nitrogen gas (or from the first stage (a) using a glove box or the like. After the above operation is performed, the container is taken out from the sealed container 12 ((d)).

  FIG. 2 shows a method of manufacturing a raw material powder of an RFeB-based sintered magnet using an RFeB-based sintered magnet (raw material sintered magnet 11A) to be recycled having a coating 111 such as metal plating that does not allow hydrogen to pass through. 1 shows an embodiment. In this method, scratches (defects 113) reaching the sintered body 112 are formed on the coating 111 of the raw material sintered magnet 11A using a cutting tool 13, a file, a polishing machine, or the like (FIG. 2 (a)). Thereafter, as in the case of the raw material sintered magnet 11 without a coating, the raw material sintered magnet 11A is accommodated in the sealed container 12 to remove air in the sealed container 12 ((b)), and then the sealed container. Hydrogen gas having a pressure of 200 kPa or more is supplied into the chamber 12 (same (c)), and the inside of the sealed container 12 is heated to 60 to 200 ° C., preferably 100 ° C. or less (same (d)). Thereafter, the residue 15 in the sealed container 12 is taken out in an inert gas ((e)). This residue 15 is composed of the raw material powder P in which the sintered body of the raw material sintered magnet 11A is separated only at the grain boundaries and separated only into particles made of old crystal grains, and the remnant 111A of the coating 111. By applying the residue 15 to the sieve 16 or performing air classification, the film residue 111A is removed from the residue 15 to obtain only the raw material powder P ((f)).

FIG. 3 shows an embodiment of a method for producing an RFeB-based sintered magnet using the raw material powder P obtained by the above method. First, the raw material powder P is filled in the mold 21, and the lid 22 is attached to the mold 21 (FIG. 3 (a)). At that time, the filling density of the raw material powder P is preferably set to 3.2 to 3.8 g / cm ³ higher than the natural filling density by pushing the raw material powder P into the mold 21 with a punch or the like. The value of the filling density is lower than the density when compression molding is performed. Next, the raw material powder P is oriented by applying a magnetic field to the raw material powder P in the mold 21 ((b)). The intensity of the magnetic field is, for example, 1T to several T. Then, the raw material powder P is sintered by heating the raw material powder P while being accommodated in the mold 21 ((c)). The temperature of heating shall be between 800-1100 degreeC, for example. Thereby, the RFeB system sintered magnet M is obtained ((d)).

  In the above RFeB sintered magnet manufacturing method, instead of using the raw material powder P as it is, the mold 21 is filled with a powder obtained by mixing the raw material powder P and the non-recycled raw material powder, and the subsequent orientation and sintering operations are performed. Also good.

  In order to obtain an RFeB-based sintered magnet with higher coercive force, the surface of the RFeB-based sintered magnet produced by the above method contains one or more elements selected from Dy, Ho and Tb. After adhering powder, paste, etc., it is good to perform the grain boundary diffusion process which heats to the temperature of 700-950 degreeC. By this treatment, the element diffuses to the vicinity of the surface of the crystal grains through the grain boundary of the RFeB-based sintered magnet, and the coercive force can be increased while suppressing the decrease in the residual magnetic flux density.

  Hereinafter, examples of the method for producing the raw material powder of the RFeB-based sintered magnet and the method for producing the RFeB-based sintered magnet according to the present invention and comparative examples will be described.

  In each of the following examples, defective products generated when an RFeB-based sintered magnet is manufactured by the following method using non-recycled raw material powder are targeted for recycling. Non-recycled raw material powder was blended to have a composition of Nd: 26.0, Pr: 4.7, Dy: 0.3, B: 0.99, Co: 0.9, Cu: 0.1, Al: 0.2, Fe: balance (unit: wt%) The alloy is melted to produce a flake-shaped alloy piece with a thickness of 0.3 mm or less by the strip casting method. After hydrogenating and pulverizing to a size of about 0.1 to 1 mm, the average particle size is about 3 μm with a jet mill. It was prepared by grinding. This non-recycled raw material powder was filled into a mold, and oriented in a magnetic field without being subjected to compression molding, then heated to 1000 ° C. in a vacuum, and held for 4 hours to produce an RFeB-based magnet sintered body . Thereafter, this sintered body was shaped into the final product shape by cutting to produce an RFeB-based sintered magnet. Part of the RFeB-based sintered magnet thus obtained was further subjected to a treatment to form a coating film on the surface by epoxy resin, silica, or nickel plating. The defective product used in each example was discovered at each stage after sintering, after cutting, and after film formation. In one example, a defective product obtained at the same stage was used. In the case of using a defective product after the formation of the film, one having the same kind of film was used in one example.

[Example 1]
A defective product (without coating) discovered after sintering was placed in a sealed container of about 0.5 kg and a capacity of 3 L, and the inside of the sealed container was evacuated. Next, hydrogen gas at a pressure of 400 kPa was introduced into the sealed container, and the heat generation temperature by hydrogen occlusion was adjusted to 160 ° C. and held for 1 hour. Then, when it cooled to room temperature and the residue in a sealed container was taken out in the glove box of nitrogen atmosphere, all was a powder state. After mixing the raw material powder thus obtained 3 and the non-recycled raw material powder in a ratio of 7 (regeneration rate 30%), filling the mixed powder into a mold and orienting it in a magnetic field without performing compression molding An RFeB sintered magnet was manufactured by heating to 1000 ° C. in a vacuum and holding for 4 hours.

[Example 2]
Defective product (without coating) discovered after cutting was placed in a sealed container of about 0.5 kg and 3 L capacity, and the inside of the sealed container was evacuated. Next, hydrogen gas having a pressure of 300 kPa was introduced into the sealed container, and the exothermic temperature by hydrogen storage was adjusted to 120 ° C. and held for 1 hour. Then, it cooled to room temperature and when the residue of the airtight container was taken out by the same method as the above, all the residues were a powder state. The raw material powder thus obtained was mixed at a ratio of 6 and the above non-recycled raw material powder at a rate of 4 (regeneration rate 60%), and the mixed powder was filled into a mold, and RFeB-based sintering was performed in the same manner as in Example 1. A magnet was manufactured.

[Example 3]
A defective product (without coating) discovered after cutting was placed in a sealed container of about 1 kg and 3 L capacity, and the inside of the sealed container was evacuated. Next, hydrogen gas with a pressure of 200 kPa was introduced into the sealed container, and the exothermic temperature by hydrogen occlusion was adjusted to 60 ° C. and held for 1 hour. When the residue in the closed container was taken out by the same method as described above, the residue was a part of the unsintered sintered body together with the powder. Therefore, the residue was returned to the sealed container, hydrogen gas at a pressure of 200 kPa was again introduced into the sealed container, heated to 60 ° C., and held for another hour. As a result, the residue was free of unsintered sintered body. All were in a powder state. The raw material powder thus obtained was filled into a mold without mixing the non-recycled raw material powder (regeneration rate 100%), and an RFeB-based sintered magnet was produced by the same method as in Example 1.

[Example 4]
Defective products discovered after forming a coating made of epoxy resin on the surface were placed in a sealed container of about 2 kg and a capacity of 3 L. No defects were formed in the coating. After the inside of the sealed container was evacuated, hydrogen gas having a pressure of 300 kPa was introduced into the sealed container, and the exothermic temperature due to hydrogen storage was adjusted to 120 ° C. and held for 1 hour. When the residue in the sealed container was taken out in the same manner as described above, all the residue was in a powder state except for the remains of the coating. The residue was passed through a sieve having an opening of 250 μm to remove the coating debris and obtain a raw material powder. The raw material powder thus obtained was filled into a mold without mixing the non-recycled raw material powder (regeneration rate 100%), and an RFeB-based sintered magnet was produced by the same method as in Example 1.

[Example 5]
Defective products discovered after forming a silica coating on the surface were placed in a sealed container of about 2 kg and 3 L capacity. No defects were formed in the coating. After the inside of the sealed container was evacuated, hydrogen gas having a pressure of 300 kPa was introduced into the sealed container, and the exothermic temperature due to hydrogen storage was adjusted to 120 ° C. and held for 1 hour. When the residue in the sealed container was taken out in the same manner as described above, all the residue was in a powder state except for the remains of the coating. The residue was passed through a sieve having an opening of 250 μm to remove the coating debris and obtain a raw material powder. The obtained raw material powder was filled in a mold without mixing the non-recycled raw material powder (regeneration rate 100%), and an RFeB-based sintered magnet was produced by the same method as in Example 1.

[Example 6]
About 2 kg of defective products discovered after forming a nickel plating coating on the surface. First, it is housed in a 3 L sealed container without forming a defect in the coating, and the sealed container is evacuated and then sealed. Hydrogen gas at a pressure of 300 kPa was introduced therein, and the exothermic temperature due to hydrogen occlusion was adjusted to 120 ° C. and held for 1 hour. When the residue in the sealed container was taken out in the same manner as described above, the defective product remained almost in its original form. Therefore, after forming scratches (defects) that reach the sintered body with a file on the defective coating, it is housed in the above-mentioned sealed container, the inside of the sealed container is evacuated, and then the pressure in the sealed container is reached. Hydrogen gas of 300 kPa was introduced, the exothermic temperature due to hydrogen occlusion was adjusted to 120 ° C. and held for 1 hour. The residue was all in powder form except for the remnants of the coating. The residue was passed through a sieve having an opening of 250 μm to remove the coating debris and obtain a raw material powder. The obtained raw material powder was filled in a mold without mixing the non-recycled raw material powder (regeneration rate 100%), and an RFeB-based sintered magnet was produced by the same method as in Example 1.

[Example 7]
After sintering, paste containing a mixture of Tb-based alloy powder and silicone grease is applied to the surface of the sintered body and heat-treated in a vacuum at about 900 ° C for 15 hours (grain boundary diffusion treatment). After aging treatment at about 500 ° C. for 5 hours, cutting was performed, and then 2 kg of defective RFeB sintered magnet having a nickel plating film formed on the surface was prepared. A flaw that reaches the sintered body using a file is formed on the defective coating, and then stored in a sealed container. After the inside of the sealed container is evacuated, hydrogen gas at a pressure of 300 kPa is introduced into the sealed container, The exothermic temperature by occlusion was adjusted to 120 ° C and held for 1 hour. When the residue in the sealed container was taken out in the same manner as described above, all the residue was in a powder state except for the remains of the coating. The residue was passed through a sieve having an opening of 250 μm to remove the coating debris and obtain a raw material powder. The obtained raw material powder was filled in a mold without mixing the non-recycled raw material powder (regeneration rate 100%), and an RFeB-based sintered magnet was produced by the same method as in Example 1.

  In addition, the grain boundary diffusion treatment performed on the RFeB-based sintered magnet (defective product) to be recycled in Example 7 supplies Tb only to the vicinity of the surface of the RFeB-based crystal grain through the grain boundary of the RFeB-based sintered magnet. By doing this, the coercive force is further increased while suppressing the decrease in the residual magnetic flux density. The raw material powder obtained in this example contains Tb in addition to the elements contained in the original non-recycled raw material powder.

  Defective product (without coating) discovered after sintering is stored in a sealed container of about 3 kg and capacity of 3 L, and after the inside of the sealed container is evacuated, hydrogen gas at a pressure of 400 kPa is introduced into the sealed container to store hydrogen. The exothermic temperature was adjusted to 160 ° C and held for 1 hour. Then, it cooled to room temperature and took out the residue in a sealed container in the glove box of nitrogen atmosphere. When the particle size distribution of the residue was measured at this stage, a peak was observed at a particle size of about 8 μm, and a peak was also observed at a particle size of about 40 μm. Therefore, the residue was passed through a sieve having an opening of 500 μm and stirred with a stirrer (“SUPERMIXER PICCOLO”, model SMP-2, manufactured by Kawata Corporation). When the particle size distribution of the residue thus obtained was measured, no peak was observed at a particle size of about 40 μm, and a peak was observed only at a particle size of about 8 μm.

[Comparative example]
A defective product (without coating) discovered after cutting was placed in a sealed container of about 1 kg and 3 L capacity, and the inside of the sealed container was evacuated. Next, hydrogen gas having a pressure of 150 kPa was introduced into the sealed container, and heat generation due to occlusion of hydrogen was suppressed to cool to 10 ° C. and maintained for 2 hours. When the residue in the sealed container was taken out in the same manner as described above, a large amount of agglomerated portion was visually confirmed, so the experiment under this condition was stopped.

Per raw material powder prepared in Example 1-8, and the maximum value D _max median D ₅₀ and particle size of the particle size distribution was measured by a dry particle size distribution measuring apparatus. Here, in Examples 1 and 2, the measurement was performed on a powder composed only of a recycled product before mixing the non-recycled raw material powder. Also, every RFeB based sintered magnet produced in Examples 1 to 7, cut into cuboid 7 mm × 7 mm × 3 mm, and measuring the residual magnetic flux density B _r and coercivity H _cj at room temperature. At the same time, the same method is applied to non-recyclable non-recycled non-recycled powders in the median value D ₅₀ and maximum value D _max of the non-recycled raw material powder, and the residual magnetic flux density _Br and coercive force of the RFeB-based sintered magnet. H _cj was measured (non-recycled products 1 to 3). Non-recycled product 1 corresponds to an RFeB-based sintered magnet without a coating (good product corresponding to Examples 2 and 3), and non-recycled product 2 corresponds to an RFeB-based sintered magnet formed with a nickel plating coating (corresponding to Example 6). The non-recycled product 3 and the non-recycled product 3 are RFeB-based sintered magnets (good products corresponding to Example 7) in which a film is formed by nickel plating after the grain boundary diffusion treatment. Table 1 summarizes the measurement results and the manufacturing conditions described above.

Both in the embodiment, the median D ₅₀ of the particle size distribution was obtained raw material powder of small particle size of less than 10 [mu] m. Moreover, in each Example, the maximum value D _max of the particle diameter of the raw material powder is suppressed within the range of 36.5 to 51.5 μm, and the occurrence of abnormal grain growth can be prevented.

When the magnetic characteristic values of the samples of Examples 1 to 6 that are not subjected to the grain boundary diffusion treatment are compared with the magnetic characteristic values of the non-recycled products 1 and 2, the residual magnetic flux density _Br is 3 to 4%, and the coercive force H _cj is Although these are 9-15% lower, these values are acceptable. Further, when the magnetic property value of the sample of Example 7 produced from the non-recycled product 3 subjected to the grain boundary diffusion treatment is compared with the magnetic property value of the non-recycled product 3, the residual magnetic flux density _Br is substantially the same, The coercive force H _cj is reduced by about 10%, but this value is also acceptable.

  In each of the above examples, the temperature during the hydrogen treatment is in the range of 60 to 160 ° C, but this temperature may be in the range of 20 to 200 ° C. Furthermore, in each of the above examples, during the hydrogen treatment, a constant temperature was maintained after reaching the target temperature, but the temperature fluctuated within the range of 20 to 200 ° C., preferably 60 to 160 ° C. during the treatment. Is also acceptable. In each of the above examples, the hydrogen treatment time is 1 hour or 2 hours, but the time may be 0.3 hours or more, and may exceed 2 hours.

11, 11A ... Raw material sintered magnet 111 ... Raw material sintered magnet film 111A ... Film debris 112 ... Sintered body 113 ... Film defect 12 ... Sealed container 13 ... Cutting tool 15 ... Residue 16 ... Sieve 21 ... Mold 22 ... Lid

Claims (8)

  A method for producing a raw material powder of an RFeB-based sintered magnet, characterized in that an RFeB-based sintered magnet to be recycled is maintained in a hydrogen gas at a pressure of 200 kPa or higher at a temperature within a range of 20 to 200 ° C. for a predetermined time.   The said range is 60-160 degreeC, The manufacturing method of the raw material powder of the RFeB type sintered magnet of Claim 1 characterized by the above-mentioned.   In the case where a coating is provided on the surface of the RFeB-based sintered magnet to be recycled, the heating is performed in hydrogen gas at the pressure after forming a defect portion reaching the surface in the coating. The method for producing a raw material powder for an RFeB-based sintered magnet according to claim 1 or 2, wherein   4. The RFeB-based sintered magnet according to claim 3, wherein after the heating in the hydrogen gas at the pressure, the residue of the coating is removed from the residue by subjecting the residue to a classification process. Of manufacturing raw material powder. A sealable container containing the RFeB sintered magnet to be recycled;
A hydrogen gas supply unit for supplying hydrogen gas having a pressure of 200 kPa or more into the container;
An apparatus for producing a raw material powder for an RFeB-based sintered magnet, comprising: a temperature adjusting unit that adjusts the temperature in the container so as to be maintained within a range of 20 to 200 ° C.   A method for producing an RFeB-based sintered magnet, wherein the raw material powder produced by the method according to claim 1 is sintered after being oriented in a magnetic field.   The method for producing an RFeB-based sintered magnet according to claim 6, wherein the orientation and the sintering are performed without performing compression molding.   The RFeB system according to claim 6 or 7, wherein the orientation and sintering are performed on a powder obtained by mixing the raw material powder with a non-recycled raw material powder produced by pulverizing an RFeB-based alloy lump. Manufacturing method of sintered magnet.

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