CN117790100A

CN117790100A - Method for regenerating rare earth element-containing powder and method for producing rare earth sintered magnet

Info

Publication number: CN117790100A
Application number: CN202311233256.2A
Authority: CN
Inventors: 蓬田贵裕; 国吉太
Original assignee: Bomeilicheng Co ltd
Current assignee: Bomeilicheng Co ltd
Priority date: 2022-09-29
Filing date: 2023-09-22
Publication date: 2024-03-29

Abstract

The technical problems to be solved by the invention are as follows: provided is a method for regenerating a rare earth element-containing powder, which can reduce the time required for disintegration. The solution of the invention is a regeneration method of rare earth element-containing powder, which comprises the following steps: a step of crushing a molded body for a rare earth sintered magnet containing a rare earth element-containing powder in an oil to contain a powder that can pass through a 149-mesh sieve and can be left on a 500-mesh sieve; and a step of separating and recovering the powder passing through a 149 mesh sieve from the crushed powder to obtain a reclaimed powder.

Description

Method for regenerating rare earth element-containing powder and method for producing rare earth sintered magnet

Technical Field

The present invention relates to a method for regenerating rare earth element-containing powder and a method for producing a rare earth sintered magnet.

Background

The rare earth sintered magnet such as an R-T-B sintered magnet (R is a rare earth element, T is Fe, or Fe and Co, and B is boron) and a samarium-cobalt sintered magnet can be produced as follows: raw materials such as metals are melted (fused) to prepare a raw material alloy cast having a desired composition by a thin-strip continuous casting method or the like, the raw material alloy cast is crushed to obtain an alloy powder having a predetermined particle size (particle size distribution), the alloy powder is subjected to a wet molding method or the like to obtain a molded body (green compact), and the molded body is further subjected to sintering and heat treatment.

In the molded article, for example, a part of the molded article is defective due to contact with other articles during handling, and thus, the molded article may be different from a desired shape, or a problem in molding may occur such as cracking.

In addition, for example, in order not to increase the types of dies used for press molding, a molded article of a desired size may be obtained by temporarily obtaining a molded article of a general size by press molding and then subjecting the molded article to cutting processing. At this time, a part of the molded body of the general size remains as a molded body of the flat bar size (hereinafter, sometimes referred to as "molded body end material").

As a supply of rare earth elements used for the rare earth sintered magnet, there is a strong demand for effectively recycling such defective molded products and molded body end materials, as compared with the conventional ones, because of an increase in both price and throughput.

Patent document 1 discloses a method of regenerating (slurry containing) rare earth element-containing powder by crushing a molded body for a rare earth sintered magnet containing the rare earth element-containing powder in oil with a small appropriate strength for a long period of time so as not to change the particle diameter of the powder. It is disclosed that, when the method of patent document 1 is adopted, even if the slurry after regeneration is used, the magnetic properties are not changed as compared with the rare earth sintered magnet which is usually manufactured.

Prior art literature

Patent literature

Patent document 1: international publication No. 2011/125578

Disclosure of Invention

Technical problem to be solved by the invention

In the prior art as disclosed in patent document 1, the molded article is crushed for a long period of time so that aggregates of powder are not present in the slurry (so that the powder can pass through a sieve of, for example, 500 mesh/inch (hereinafter, also referred to as "mesh 25 μm" or "500 mesh") (hereinafter, also referred to as "pass through a 500 mesh sieve"). However, in the production of rare earth sintered magnets, if a long time is spent in the crushing step, there are problems such as deterioration of the end material of the molded article and molding failure during storage in addition to a decrease in productivity.

The present invention has been made in view of such circumstances, and one of its objects is to: provided are a method for regenerating rare earth element-containing powder and a method for producing a rare earth sintered magnet, wherein the time required for the disintegration can be reduced.

Technical scheme for solving technical problems

Mode 1 of the present invention is a method for regenerating rare earth element-containing powder, comprising:

a step of crushing a molded body for a rare earth sintered magnet containing a rare earth element-containing powder in an oil to contain a powder that can pass through a 149-mesh sieve and can be left on a 500-mesh sieve; and

and a step of separating and recovering the powder passing through a 149 mesh sieve from the crushed powder to obtain a reclaimed powder.

The invention according to aspect 2 is a method for producing a rare earth sintered magnet, comprising:

a step of obtaining a slurry containing the reclaimed powder reclaimed by the method described in claim 1 and oil;

wet molding the slurry in a magnetic field to obtain a molded article; and

and sintering the molded body obtained by wet molding.

Detailed Description

The present inventors have studied from various points of view on a method for regenerating a rare earth element-containing powder, which can reduce the time required for the pulverization.

In order to ensure the magnetic properties of the sintered magnet as disclosed in patent document 1, the inventors of the present invention found that, in order to ensure the magnetic properties of the sintered magnet, the sintered magnet using the sintered magnet has sufficient magnetic properties (for example, a similar residual magnetic flux density can be obtained as compared with a sintered magnet using a normally produced unrenewable powder (for example, a powder capable of passing through a 500 mesh sieve) even if there is some degree of aggregates in the powder after the decomposition (that is, even if there is powder that cannot pass through a 500 mesh sieve and remains on a 500 mesh sieve (hereinafter, also referred to as "can remain on a 500 mesh sieve"), if the size is not more than a predetermined range (that is, a powder capable of passing through a 149 mesh (100 μm)) so as to ensure the magnetic properties of the sintered magnet. Namely, it was found that: by performing the crushing so as to contain the powder that can pass through the 149 mesh sieve and can remain on the 500 mesh sieve, the time taken for the crushing can be shortened as compared with the prior art, and the powder after the crushing will be separated and recovered from the powder that can pass through the 149 mesh sieve, whereby sufficient magnetic characteristics can be ensured in the sintered magnet using the same.

The following exemplifies the details of each condition defined in the embodiment of the present invention.

In the present specification, "crushing the molded article" means that an external force is applied to the molded article to obtain a powder, and the external force applied to the molded article is sufficient to crush the molded article to obtain the powder, and is not so strong as to crush the obtained powder or to abrade it. Among them, the obtained powder is agglomerated by weak forces such as intermolecular forces, but "crushing" is not required to break the agglomeration. The molded article of the present invention includes, in addition to a molded article obtained by molding a rare earth element-containing powder, a molded article end material produced when the molded article is subjected to cutting processing, and a molded article obtained by cutting the molded article to a desired size after the cutting processing.

< 1. Regeneration method of rare earth element-containing powder >)

The method for regenerating a rare earth element-containing powder according to an embodiment of the present invention includes: (1a) A step of crushing a molded body for a rare earth sintered magnet containing a rare earth element-containing powder in an oil to contain a powder that can pass through a 149-mesh sieve and can be left on a 500-mesh sieve; and (1 b) a step of separating and recovering the powder passing through a 149 mesh sieve from the crushed powder to obtain a reclaimed powder. This can shorten the time required for the disintegration and ensure sufficient magnetic characteristics in the sintered magnet using the reclaimed powder.

Hereinafter, each step will be described in detail.

(1 a) a step of pulverizing a molded article for a rare earth sintered magnet

In an embodiment of the present invention, the molded body for a rare earth sintered magnet to be subjected to the pulverization contains a rare earth element-containing powder. The rare earth element-containing powder may be any powder containing a rare earth element, and is preferably an alloy powder used for an R-T-B sintered magnet.

R of the R-T-B sintered magnet alloy powder is at least 1 selected from neodymium (Nd), praseodymium (Pr), dysprosium (Dy) and terbium (Tb), and preferably contains at least one of Nd and Pr. More preferably, R is 1 combination of rare earth elements selected from Nd-Dy, nd-Tb, nd-Pr-Dy and Nd-Pr-Tb. In addition, when Dy and/or Tb is contained as R in the alloy powder for R-T-B sintered magnets, the effect of improving coercive force is exhibited.

The R-T-B alloy powder for sintered magnets may contain a small amount of other rare earth elements such as Ce and La as well as the above elements, and a dense cerium alloy (Misch metal) and/or a didymium compound (an alloy containing Nd and Pr as main components) may be used. In addition, R may not be a pure element, and may contain unavoidable impurities within an industrially available range.

The R content in the R-T-B sintered magnet alloy powder may be 27 mass% or more and 33 mass% or less. The R content is preferably 28 mass% or more and 31 mass% or less, and higher magnetic properties can be obtained.

T of the alloy powder for R-T-B sintered magnet is Fe or Fe and Co. T contains Fe, and for example, 50 mass% or less of Fe may be replaced with cobalt (Co). Co is effective for improving temperature characteristics and corrosion resistance. The Co content in the alloy powder for R-T-B sintered magnets may be 10 mass% or less.

Regarding the T content in the R-T-B based alloy powder for sintered magnets, it is preferable that the remaining part of the R-T-B based alloy powder for sintered magnets is T and unavoidable impurities (for example, oxygen, nitrogen, carbon, and the like).

The B content in the alloy powder for R-T-B sintered magnets is not particularly limited, and may be, for example, within a range of the B content of a known R-T-B sintered magnet. For example, the content of B is preferably 0.9 to 1.2 mass%. When the residual magnetic flux density is set to 0.9 mass% or more, a higher residual magnetic flux density can be obtained, and when the residual magnetic flux density is set to 1.2 mass% or less, a higher coercive force can be obtained. In addition, a part of B may be substituted with C (carbon). The substitution with C has the effect of improving the corrosion resistance of the magnet. Regarding the content when B and C are added, the number of substitution atoms of C is converted to the number of atoms of B, and is preferably within the above-mentioned preferable range of the concentration of B.

In addition to the above elements, an M element for improving coercive force can be added. M is at least 1 selected from Al, si, ti, V, cr, ni, cu, zn, ga, zr, nb, mo, in, sn, hf, ta and W. The total amount of the M element is preferably 5.0 mass% or less. By setting the residual magnetic flux density to 5.0 mass% or less, a higher residual magnetic flux density can be obtained.

The rare earth element-containing powder can be obtained by pulverizing a raw material alloy cast product obtained by a strip casting method or the like using, for example, a jet mill or the like. In order to obtain a sintered magnet having a higher residual magnetic flux density and coercive force, the above-mentioned rare earth element-containing powder has a particle diameter D ₅₀ Preferably 1.0 μm or more and 10.0 μm or less, more preferably 2.0 μm or more and 5.0 μm or less. Here, particle diameter D ₅₀ The integrated particle size distribution (volume basis) from the small diameter among the particle size distribution obtained by the laser diffraction method using the gas flow dispersion method is 50% of the particle size. In addition, particle diameter D ₅₀ For example, a particle size distribution measuring apparatus "HELOS" manufactured by Sympatec corporation can be used&RODOS ", to disperse pressure: 4bar, measurement range: r2, measurement mode: measurement of conditions of HRLDAnd (5) setting.

In an embodiment of the present invention, the molded body for a rare earth sintered magnet is obtained by molding (for example, press molding) the rare earth element-containing powder by a known method. The molded article for the rare earth sintered magnet may be, for example, the above-described molded defective product or molded article end material, but is not limited to these, and may be, for example, various molded articles such as the remaining good molded article.

The molded article for a rare earth sintered magnet is preferably obtained by compacting the rare earth element-containing powder in a magnetic field (for example, 1 tesla (T) or more). This can improve the three-directional orientation degree (hereinafter, also simply referred to as "orientation degree") and the residual magnetic flux density of the sintered magnet to be described later.

Further, as a molding method, there are dry molding in which powder is directly molded and wet molding in which powder is mixed with a dispersion medium to form a slurry and then molded, and wet molding is preferable. In wet molding, the surface of the powder constituting the molded body is covered with the dispersion medium, and contact with oxygen and water vapor in the atmosphere can be suppressed. Therefore, the powder can be suppressed from being oxidized by the atmosphere before and after molding or during molding. Furthermore, in the present specification, the term "slurry" is a mixture of solid particles and a liquid, and refers to a fluid in which the solid particles are suspended in the liquid.

Hereinafter, a method for obtaining a molded body for a rare earth sintered magnet by wet press molding in a magnetic field will be described in detail.

In wet press molding in a magnetic field, a slurry obtained by mixing the rare earth element-containing powder with a dispersion medium is first prepared. Preferable dispersion media include one or more oils selected from mineral oils, synthetic oils, and vegetable oils. The oil preferably has a dynamic viscosity of 10cSt or less at normal temperature. This suppresses local bonding of the powders to each other, and improves the degree of orientation of the molded article obtained. The fractionation temperature of the oil is preferably 400 ℃ or lower. This facilitates deoiling after molding, and as a result, the amount of residual carbon in the sintered magnet can be reduced, and the magnetic properties can be improved.

The concentration of the rare earth element-containing powder in the slurry is not particularly limited, but is preferably 70 mass% or more. Thus, for example, the length of the film can be 20 to 600cm ³ The flow rate per second can efficiently supply the powder in the chamber and can improve the magnetic characteristics of the obtained sintered magnet. The upper limit of the concentration of the rare earth element-containing powder in the slurry is preferably 95 mass% or less from the viewpoint of fluidity of the slurry. The method of mixing the rare earth element-containing powder and the dispersion medium is not particularly limited. For example, a rare earth element-containing powder and a dispersion medium may be prepared separately, and the two may be weighed by a predetermined amount and mixed. In addition, when the rare earth element-containing powder is obtained by dry pulverization by a jet mill or the like, a container in which a dispersion medium is added may be disposed at a powder discharge port of a pulverizing apparatus such as a jet mill, and the rare earth element-containing powder obtained by pulverization may be directly collected in the dispersion medium in the container to obtain a slurry. In this case, it is preferable that the atmosphere of nitrogen and/or argon is also formed in the container, and the obtained rare earth element-containing powder is directly recovered in the dispersion medium without bringing the powder into contact with the atmosphere to form a slurry. In addition, a slurry can be obtained by wet-pulverizing a raw material in a dispersion medium using a vibration mill, ball mill, or attritor.

The slurry prepared as described above is supplied to the cavity of the die of the wet press molding apparatus, and press molding is performed in a magnetic field. The shaped bodies thus formed may have, for example, 4g/cm ³ Above 5g/cm ³ The following densities. As a method of cutting the molded article after molding, for example, known methods such as japanese patent application laid-open No. 8-181028, japanese patent application laid-open No. 2003-303728, japanese patent application laid-open No. 2021-155809 and the like can be used. These cut molded articles and molded article end materials are also included in the molded article of the present invention.

The molded article obtained as described above was crushed in oil. The term "oil" means a state in which the molded article is completely immersed in oil or a state in which the surface of the molded article is covered with a film of oil sufficient to prevent contact with oxygen in the atmosphere. As the oil, for example, one or more selected from mineral oil, synthetic oil, and vegetable oil can be used, and for example, the same oil as the oil of the dispersion medium of the slurry described above may be used, or a different oil may be used. The method of the crushing is not particularly limited as long as the molded article can be crushed to contain a powder that can pass through a 149 mesh sieve and can be retained on a 500 mesh sieve. For example, the molded article may be crushed by simply pressing it with a stainless steel member or the like, or may be crushed by using a device described in international publication No. 2011/125578 or international publication No. 2013/047429. Among the crushed powders, the more the proportion of the powder passing through a 149-mesh sieve is, the more preferable, for example, 10 mass% or more, 25 mass% or more, 50 mass% or more, 75 mass% or more, 90 mass% or more, and 100 mass% in this order. This can further improve the yield of the reclaimed powder. In addition, the more the proportion of the powder which can be left on the 500 mesh sieve, the more preferable the powder after the pulverization, for example, 10 mass% or more, 25 mass% or more, 50 mass% or more, 75 mass% or more, 90 mass% or more, and 100 mass% in this order. This can further shorten the time taken for the crushing, as compared with the conventional technique in which the entire crushing step is passed through a 500-mesh sieve. More preferably, the crushed powder is composed of a powder that can pass through a 149 mesh sieve and can remain on a 500 mesh sieve.

(1 b) a step of separating and collecting the powder passing through a 149 mesh sieve from among the crushed powders to obtain a reclaimed powder

The crushed powder obtained in the above-described manner was separated and recovered by passing through a 149-mesh sieve to obtain a reclaimed powder. For example, the crushed powder may be passed through a 149-mesh sieve, and the passed powder may be separated and recovered as a regenerated powder.

The reclaimed powder separated and recovered in the step (1 b) can be stored in oil until it is used for molding.

The method for regenerating a rare earth element-containing powder according to the embodiment of the present invention may include other steps within a range for achieving the object.

< 2 > method for producing rare earth sintered magnet

The method for manufacturing a rare earth sintered magnet according to an embodiment of the present invention includes: (2a) A step of obtaining a slurry containing the reclaimed powder and oil reclaimed by the method; (2b) Wet molding the slurry in a magnetic field to obtain a molded article; and (2 c) sintering the molded article obtained by wet molding.

Hereinafter, each step will be described in detail.

Step of obtaining a slurry

First, a slurry containing the reclaimed powder and oil reclaimed by the above method is prepared. Here, the rare earth element-containing powder contained in the slurry may contain only the reclaimed powder obtained by the method for reclaiming the rare earth element-containing powder according to the embodiment of the present invention, or may be mixed with the reclaimed powder having the same composition as the reclaimed powder and being unrenewed. The oil contained in the slurry may be the same as that contained in the slurry described in the above "1. Regeneration method of rare earth element-containing powder".

(2 b) a step of wet-molding the slurry to obtain a molded article

The slurry is wet-molded in a magnetic field. The wet molding method in a magnetic field can be performed in the same manner as the method described in "1. Regeneration method of rare earth element-containing powder".

(2 c) sintering the wet-molded article

The obtained molded article was sintered. The sintering temperature is not particularly limited, and may be a temperature at which densification sufficiently occurs by sintering, and may be, for example, 900 ℃ to 1100 ℃.

In the rare earth sintered magnet (for example, R-T-B sintered magnet) obtained after the step (2 c), the oxygen content as an unavoidable impurity is preferably 500ppm to 8000ppm, more preferably 500ppm to 3200ppm, and still more preferably 500ppm to 2500 ppm. The nitrogen content as an unavoidable impurity is preferably 50ppm to 1000 ppm. The content of carbon as an unavoidable impurity is preferably 50ppm to 2000 ppm.

The method for producing a rare earth sintered magnet according to the embodiment of the present invention may include other steps within a range for achieving the object. For example, it is preferable to perform heat treatment at 400 to 950 ℃ inclusive and at a temperature lower than the sintering temperature in a vacuum or an inert gas atmosphere after sintering. Thus, a high coercivity can be obtained.

Examples

Hereinafter, embodiments of the present invention will be described more specifically with reference to examples. The embodiments of the present invention are not limited to the following examples, and may be implemented with appropriate modifications within the scope of the foregoing and the following gist, and these are included in the technical scope of the embodiments of the present invention.

Experimental example 1

The raw materials of each element were weighed so as to be Nd:23.4%, pr:7.4%, B:0.89%, co:0.8%, al:0.1%, cu:0.15%, ga:0.4%, zr:0.1% (mass% in each case), the remainder: fe and unavoidable impurities, and obtaining a raw material alloy casting by a thin strip continuous casting method. The raw material alloy casting is subjected to hydrogen pulverization to obtain coarse pulverization powder. The coarse powder was mixed with 0.04 parts by mass of zinc stearate as a lubricant to 100 parts by mass of the coarse powder, and then dry-pulverized in a nitrogen stream using a jet mill to obtain a particle size D ₅₀ A rare earth element-containing powder of 4.8 μm. In addition, D ₅₀ Using particle size distribution measuring apparatus "HELOS" manufactured by Sympatec corporation&RODOS ", to disperse pressure: 4bar, measurement range: r2, measurement mode: the conditions of HRLD were measured.

A part of the rare earth element-containing powder was stored as unrenewed powder 1. The non-reclaimed powder 1 was all powder capable of passing through a 500-mesh sieve.

A slurry was prepared by immersing the other part of the rare earth element-containing powder in a mineral oil having a dynamic viscosity of 2cSt at room temperature at a fractionation temperature of 250 ℃ in a nitrogen atmosphere. The rare earth element-containing powder concentration in the slurry was 75 mass%. The obtained slurry was molded (wet molded) in a magnetic field of 1.6T to prepare a molded article.

A stainless steel vessel with oil added thereto was prepared in a tank under nitrogen atmosphere. The molded body was immersed in the oil, and the molded body was further crushed by pressing the molded body from above with another stainless steel container, and the powder passing through a 280 mesh (mesh 53 μm) sieve was recovered to obtain reclaimed powder 1. The reclaimed powder 1 is considered to be a powder which passes through a 280 mesh (mesh: 53 μm) sieve barely, and most of the reclaimed powder can be retained on a 500 mesh (mesh: 25 μm) sieve (for example, 50 mass% or more of the reclaimed powder can be retained on a 500 mesh sieve). Since the reclaimed powder 1 is a powder that can pass through a 280-mesh (53 μm) sieve, it can be said that the reclaimed powder is also a powder that can pass through a 149-mesh (100 μm) sieve having a mesh size larger than the reclaimed powder (i.e., a powder that can pass through a 149-mesh sieve).

The same procedure as for reclaimed powder 1 was repeated except that the powder which passed through the 149-mesh (mesh: 100 μm) sieve and which could be retained on the 280-mesh (mesh: 53 μm) sieve was separated and collected, to obtain reclaimed powder 2. Further, the reclaimed powder 2 is a powder which can be left on a 280-mesh (mesh 53 μm) sieve, and therefore, it can also be said that it is a powder which can be left on a 500-mesh (mesh 25 μm) sieve smaller than it (i.e., a powder which can be left on a 500-mesh sieve).

The same procedure as for reclaimed powder 1 was repeated except that the powder which passed through the 50-mesh (mesh: 300 μm) sieve and which could be retained on the 149-mesh (mesh: 100 μm) sieve was separated and collected, to obtain reclaimed powder 3.

The unrenewed powder 1 and the reclaimed powder 1 to 3 were immersed in a mineral oil having a dynamic viscosity of 2cSt at a fractionation temperature of 250℃and a room temperature in a nitrogen atmosphere to prepare a slurry. The rare earth element-containing powder concentration in the slurry was 75 mass%. The obtained slurry was molded (wet molded) in a magnetic field of 1.6T to prepare a molded article using each powder.

The obtained molded body was sintered in vacuum for 4 hours (the sintering temperature was selected to be a temperature at which densification by sintering occurred sufficiently), and then quenched to obtain a sintered body using each powder. The density of each sintered body was 7.5Mg/m ³ The above. Subsequently, the sintered body using each powder was subjected to heat treatment to 800 ℃. After the heat treatment, the entire surface of the sintered body using each powder was polished using a surface grinding diskCutting to obtain 7.0mm.times.7.0mm.times.7.0 mm cubic rare earth sintered magnets No.1 to 4.

The residual magnetic flux density B in the magnetic field application direction (referred to as X direction) at the time of molding was measured for the obtained rare earth sintered magnets No.1 to 4 by a B-H plotter _rx (unit: tesla (T)). Further, the residual magnetic flux density B in the direction perpendicular to the X direction (hereinafter also referred to as "Y direction") was measured by a B-H plotter _ry (unit: tesla (T)), and residual magnetic flux density B in a direction perpendicular to the X-direction and the Y-direction (hereinafter also referred to as "Z-direction") _rz (unit: tesla (T)) and the three-directional orientation degree OR was obtained by the following formula (1).

OR＝B _rx /((B _rx ) ² +(B _ry ) ² +(B _rz ) ² ) ^1/2 ···(1)

The oxygen and carbon contents in the obtained rare earth sintered magnets nos. 1 to 4 were measured using a gas analyzer using a gas fusion-infrared absorption method.

The results are summarized in table 1. In table 1, since the rare earth sintered magnet No.1 produced using the unrenewed powder 1 was the subject of comparison, the judgment column of the magnetic properties was denoted by "-". In Table 1, B in the columns for determining the magnetic characteristics of rare earth sintered magnets No.2 to 4 produced using the reclaimed powder 1 to 3 _rx B with rare earth sintered magnet No.1 _rx The case where the ratio was equal (lower than 0.1T even though the ratio was lower) was noted as sufficient (∈o), and the case where the ratio was lower than 0.1T or higher was noted as insufficient (×).

[ Table 1]

The following can be seen from table 1.

The reclaimed powder 1 and 2 are powders reclaimed by a method satisfying all the conditions specified in the method for reclaiming a rare earth element-containing powder according to the embodiment of the present invention, and are crushed to contain a powder that can be left on a 500-mesh sieve, and therefore, the time taken for crushing can be reduced as compared with the conventional art in which a molded body is crushed over a long period of time in such a manner that all the powder can pass through a 500-mesh sieve. The inventors confirmed that the same amount of reclaimed powder 2 was obtained in about half the time taken for obtaining the disintegration of the certain amount of reclaimed powder 1. Considering that the time taken for the disintegration when the mesh size of the sieving is about 149 mesh and about half the mesh size (i.e., the mesh size is about 2 times the size) becomes about half, the same amount of reclaimed powder 1 and the same amount of reclaimed powder 2 can be obtained in about half the time taken for the disintegration as compared with the case where a certain amount of powder passing through a 500 mesh sieve as that of unrenewed material is obtained.

The rare earth sintered magnets No.2 and 3 using the reclaimed powder 1 and 2 are sintered magnets produced by a method satisfying all the conditions specified in the method for producing a rare earth sintered magnet according to the embodiment of the present invention, and the oxygen content is increased to about 300ppm as compared with the rare earth sintered magnet No.1 using the unrenewed powder 1, but the carbon content is hardly changed in the allowable range, and the sintered magnets exhibit sufficient magnetic characteristics (namely, B _rx Equivalent to the rare earth sintered magnet No.1 using the unrenewed powder 1). In addition, the oxygen content of the rare earth sintered magnet No.2 of the reclaimed powder 1, which takes a long time for the pulverization, was as high as 1790ppm as compared with the oxygen content 1680ppm of the rare earth sintered magnet No.3 of the reclaimed powder 2, and it is considered that the length of time taken for the pulverization is correlated with the increase in the oxygen content. Therefore, it is presumed that the oxygen content of the rare earth sintered magnet No.2 using the reclaimed powder 1 increases as compared with the reclaimed powder that passes through the 500-mesh sieve, which is considered to take longer time than the disintegration of the reclaimed powder 1.

The reclaimed powder 3 was obtained by separating and collecting the crushed powder which passed through a 50 mesh (300 μm mesh) sieve and which could be retained on a 149 mesh (100 μm mesh) sieve, and the reclaimed powder 3 was shorter than the reclaimed powder 2 in terms of the time taken for the crushing to obtain a certain amount, and the rare earth sintered magnet No.4 using the reclaimed powder 3 had an oxygen content equivalent to that of the rare earth sintered magnet No.1 using the unrenewed powder 1, but the magnetic characteristics of the rare earth sintered magnet No.4 were insufficient. This is considered to be because the three-directional orientation degree OR of the rare earth sintered magnet No.4 is lower than that of the rare earth sintered magnet No. 1. The reason why the degree of orientation of the rare earth sintered magnet No.4 is lowered can be considered as follows. That is, it is considered that the reclaimed powder 3 is a relatively large powder which can be retained on a 149-mesh sieve, and the large powder is likely to be in contact with other powder and receive friction force, and therefore, it is difficult for the magnetization easy direction of the large powder to be sufficiently oriented in the magnetic field application direction at the time of molding.

Experimental example 2

The raw materials of each element were weighed so as to be Nd:23.8%, pr:6.7%, dy:0.0%, B:0.96%, co:0.9%, al:0.1%, cu:0.1%, ga:0.1%, zr:0.05% (mass% in each case), the remainder: fe and unavoidable impurities, and obtaining a raw material alloy casting by a thin strip continuous casting method. The raw material alloy casting is subjected to hydrogen pulverization to obtain coarse pulverization powder. The coarse powder was mixed with 0.04 parts by mass of paraffin wax as a lubricant to 100 parts by mass of the coarse powder, and then dry-pulverized in a nitrogen stream using a jet mill to obtain a particle diameter D ₅₀ A rare earth element-containing powder of 4.0 μm. In addition, D ₅₀ Using particle size distribution measuring apparatus "HELOS" manufactured by Sympatec corporation&RODOS ", to disperse pressure: 4bar, measurement range: r2, measurement mode: the conditions of HRLD were measured.

A part of the rare earth element-containing powder is stored as unrenewed powder 11. The non-reclaimed powder 1 was all powder capable of passing through a 500-mesh sieve.

A reclaimed powder 11 was obtained in the same manner as in example 1, except that the powder which passed through the 149-mesh (mesh: 100 μm) sieve and which could be retained on the 280-mesh (mesh: 53 μm) sieve was separated and recovered. Further, the reclaimed powder 11 is a powder that can be left on a 280 mesh (mesh 53 μm) sieve, and therefore, it can also be said that it is a powder that can be left on a 500 mesh (mesh 25 μm) sieve smaller than it (i.e., a powder that can be left on a 500 mesh sieve).

A reclaimed powder 12 was obtained in the same manner as in example 1, except that the powder which passed through the 50-mesh (mesh: 300 μm) sieve and which could be retained on the 149-mesh (mesh: 100 μm) sieve was separated and recovered.

The unrenewed powder 11 and the reclaimed powder 11 to 12 were immersed in a mineral oil having a dynamic viscosity of 2cSt at a fractionation temperature of 250℃and a room temperature in a nitrogen atmosphere to prepare a slurry. The rare earth element-containing powder concentration in the slurry was 75 mass%. The obtained slurry was molded (wet molded) in a magnetic field of 1.6T to prepare a molded article using each powder.

The obtained molded body was sintered in vacuum for 4 hours (the sintering temperature was selected to be a temperature at which sufficient densification by sintering was possible), and then quenched to obtain a sintered body using each powder. The density of each sintered body was 7.5Mg/m ³ . Next, the entire surface of the sintered body using each powder was cut using a surface grinding disk, thereby obtaining 7.0 mm. Times.7.0 mm-cube-shaped rare earth sintered magnets No.11 to 13.

The residual magnetic flux density B in the magnetic field application direction (referred to as X direction) at the time of molding was measured for the obtained rare earth sintered magnets 11 to 13 by a B-H plotter _rx (unit: tesla (T)).

The degree of orientation OR in three directions and the oxygen and carbon contents in the rare earth sintered magnets 11 to 13 were determined in the same manner as in example 1.

The results are summarized in table 2. In table 2, since the rare earth sintered magnet No.11 produced using the unrenewed powder 11 is a comparison target, the judgment column of the magnetic characteristics is indicated by "-". In Table 2, B in the column for determining the magnetic characteristics of the rare earth sintered magnets No.12 to 13 produced using the reclaimed powder 11 to 12 _rx B with rare earth sintered magnet No.11 _rx The case where the ratio is equivalent (lower than 0.1T even if the ratio is lowered) is described as sufficient (good), and the reduction is recognized as lowCases above 0.1T were noted as insufficient (x).

[ Table 2]

The following can be seen from table 2.

The reclaimed powder 11 is a powder reclaimed by a method satisfying all the conditions specified in the method for reclaiming a rare earth element-containing powder according to the embodiment of the present invention, and is crushed to contain a powder that can be retained on a 500-mesh sieve, and therefore, the time taken for crushing can be reduced as compared with the conventional technique in which a molded body is crushed over a long period of time so that all the powder can pass through a 500-mesh sieve.

The rare earth sintered magnet No.12 using the reclaimed powder 11 is a sintered magnet produced by a method satisfying all the conditions specified in the method for producing a rare earth sintered magnet according to the embodiment of the present invention, and the oxygen content is increased to about 700ppm as compared with the rare earth sintered magnet No.11 using the unrenewed powder 11, but the carbon content is hardly changed in the allowable range, and the sintered magnet exhibits sufficient magnetic characteristics (that is, B _rx Equivalent to the rare earth sintered magnet No.11 using the unrenewed powder 11).

On the other hand, the reclaimed powder 12 is obtained by separating and recovering the powder which passes through a 50 mesh (300 μm mesh) sieve and can be retained on a 149 mesh (100 μm mesh) sieve from among the crushed powders, and the reclaimed powder 12 is shorter than the reclaimed powder 11 in terms of time taken for crushing to obtain a certain amount, but the magnetic characteristics of the rare earth sintered magnet No.13 are insufficient. This is considered to be because the three-directional orientation degree OR of the rare earth sintered magnet No.13 is lower than that of the rare earth sintered magnet No. 11.

Experimental example 3

The raw materials of each element were weighed so as to be Nd:23.8%, pr:6.7%, dy:0.0%, B:0.96%, co:0.9%, al:0.1%, cu:0.1%, ga:0.1%, zr:0.05% (mass% in each case), the remainder: fe and unavoidable impurities, and obtaining a raw material alloy by a strip casting methodAnd (3) casting. The raw material alloy casting is subjected to hydrogen pulverization to obtain coarse pulverization powder. The coarse powder was mixed with 0.04 parts by mass of paraffin wax as a lubricant to 100 parts by mass of the coarse powder, and then dry-pulverized in a nitrogen stream using a jet mill to obtain a particle diameter D ₅₀ Is a rare earth element-containing powder of 3.2 μm. In addition, D ₅₀ Using particle size distribution measuring apparatus "HELOS" manufactured by Sympatec corporation&RODOS ", to disperse pressure: 4bar, measurement range: r2, measurement mode: the conditions of HRLD were measured.

A part of the rare earth element-containing powder is stored as unrenewed powder 21. The unrenewed powder 21 was all powder capable of passing through a 500-mesh sieve.

A reclaimed powder 21 was obtained in the same manner as in example 1, except that the powder which passed through the 149-mesh (mesh: 100 μm) sieve and which could be retained on the 280-mesh (mesh: 53 μm) sieve was separated and recovered. Further, the reclaimed powder 21 is a powder that can be left on a 280-mesh (mesh 53 μm) sieve, and therefore, it can also be said that it is a powder that can be left on a 500-mesh (mesh 25 μm) sieve smaller than it (i.e., a powder that can be left on a 500-mesh sieve).

A reclaimed powder 22 was obtained in the same manner as in example 1, except that the powder which had passed through a 50-mesh (mesh: 300 μm) sieve and which had been allowed to remain on a 149-mesh (mesh: 100 μm) sieve was separated and recovered.

The unrenewed powder 21 and the reclaimed powder 21 to 22 were immersed in a mineral oil having a dynamic viscosity of 2cSt at a fractionation temperature of 250℃and a room temperature in a nitrogen atmosphere to prepare a slurry. The rare earth element-containing powder concentration in the slurry was 75 mass%. The obtained slurry was molded (wet molded) in a magnetic field of 1.6T to prepare a molded article using each powder.

The resulting molded article was subjected to vacuum for 4 hoursAt the time of sintering (the sintering temperature is selected to be a temperature at which densification by sintering sufficiently occurs), and then quenching is performed to obtain a sintered body using each powder. The density of each sintered body was 7.5Mg/m ³ The above. Next, the entire surface of the sintered body using each powder was cut using a surface grinding disk, thereby obtaining 7.0 mm. Times.7.0 mm-cube-shaped rare earth sintered magnets Nos. 21 to 23.

The residual magnetic flux density B in the magnetic field application direction (referred to as X direction) at the time of molding was measured for the obtained rare earth sintered magnets 21 to 23 by a B-H plotter _rx (unit: tesla (T)).

The degree of orientation OR in three directions and the oxygen and carbon contents in the rare earth sintered magnets 21 to 23 were determined in the same manner as in example 1.

The results are summarized in table 3. In table 3, since the rare earth sintered magnet No.21 produced using the unrenewed powder 21 was the subject of comparison, the judgment column of the magnetic characteristics was denoted by "-". In Table 1, B in the column for determining the magnetic characteristics of the rare earth sintered magnets No.22 to 23 produced using the reclaimed powder 21 to 22 _rx B with rare earth sintered magnet No.1 _rx The case where the ratio was equal (lower than 0.1T even if the ratio was lower) was regarded as sufficient (good), and the case where the ratio was lower than 0.1T or more was regarded as insufficient (x).

[ Table 3]

The following can be seen from table 3.

The reclaimed powder 21 is a powder reclaimed by a method satisfying all the conditions specified in the method for reclaiming a rare earth element-containing powder according to the embodiment of the present invention, and is crushed to contain a powder that can be left on a 500-mesh sieve, and therefore, the time taken for crushing can be reduced as compared with the conventional technique in which a molded body is crushed over a long period of time so that all the powder can pass through a 500-mesh sieve.

Rare earth sintered magnet No.22 using the reclaimed powder 21 is obtained by using a solid sintered magnet satisfying the present inventionThe sintered magnet produced by the method of all conditions prescribed in the method for producing a rare earth sintered magnet according to the embodiment has an oxygen content increased to about 700ppm as compared with the rare earth sintered magnet No.21 using the unrenewed powder 21, but has little variation in carbon content within the allowable range, and exhibits sufficient magnetic characteristics (i.e., B _rx Equivalent to the rare earth sintered magnet No.21 using the unrenewed powder 21).

On the other hand, the reclaimed powder 22 is obtained by separating and recovering the crushed powder which can pass through a 50 mesh (300 μm mesh) sieve and can be retained on a 149 mesh (100 μm mesh) sieve, and the reclaimed powder 22 is shorter than the reclaimed powder 21 in terms of the time taken for crushing to obtain a certain amount, but the magnetic characteristics of the rare earth sintered magnet No.23 are insufficient. This is considered to be because the three-directional orientation degree OR of the rare earth sintered magnet No.23 is lower than that of the rare earth sintered magnet No. 21.

Experimental example 4

The raw materials of each element were weighed so as to be Nd:17.6%, pr:4.9%, dy:8.0%, B:0.96%, co:0.9%, al:0.1%, cu:0.1%, ga:0.1%, zr:0.05% (mass% in each case), the remainder: fe and unavoidable impurities, and obtaining a raw material alloy casting by a thin strip continuous casting method. The raw material alloy casting is subjected to hydrogen pulverization to obtain coarse pulverization powder. The coarse powder was mixed with 0.04 parts by mass of paraffin wax as a lubricant to 100 parts by mass of the coarse powder, and then dry-pulverized in a nitrogen stream using a jet mill to obtain a particle diameter D ₅₀ Is a rare earth element-containing powder of 3.2 μm. In addition, D ₅₀ Using particle size distribution measuring apparatus "HELOS" manufactured by Sympatec corporation&RODOS ", to disperse pressure: 4bar, measurement range: r2, measurement mode: the conditions of HRLD were measured.

A part of the rare earth element-containing powder is stored as unrenewed powder 31. The non-reclaimed powder 1 was all powder capable of passing through a 500-mesh sieve.

A reclaimed powder 31 was obtained in the same manner as in example 1, except that the powder which passed through the 149-mesh (mesh: 100 μm) sieve and which could be retained on the 280-mesh (mesh: 53 μm) sieve was separated and recovered. Further, the reclaimed powder 31 is a powder that can be left on a 280 mesh (mesh 53 μm) sieve, and therefore, it can also be said that it is a powder that can be left on a 500 mesh (mesh 25 μm) sieve smaller than it (i.e., a powder that can be left on a 500 mesh sieve).

A reclaimed powder 32 was obtained in the same manner as in example 1, except that the powder which passed through the 50-mesh (mesh: 300 μm) sieve and which could be retained on the 149-mesh (mesh: 100 μm) sieve was separated and recovered.

The unrenewed powder 31 and the reclaimed powder 31 to 32 were immersed in a mineral oil having a dynamic viscosity of 2cSt at a fractionation temperature of 250℃and a room temperature in a nitrogen atmosphere to prepare a slurry. The rare earth element-containing powder concentration in the slurry was 75 mass%. The obtained slurry was molded (wet molded) in a magnetic field of 1.6T to prepare a molded article using each powder.

The obtained molded body was sintered in vacuum for 4 hours (the sintering temperature was selected to be a temperature at which densification by sintering occurred sufficiently), and then quenched to obtain a sintered body using each powder. The density of each sintered body was 7.5Mg/m ³ The above. Next, the entire surface of the sintered body using each powder was cut using a surface grinding disk, thereby obtaining 7.0 mm. Times.7.0 mm-cube-shaped rare earth sintered magnets No.31 to 33.

The residual magnetic flux density B in the magnetic field application direction (referred to as X direction) at the time of molding was measured for the obtained rare earth sintered magnets 31 to 33 by a B-H plotter _rx (unit: tesla (T)).

The degree of orientation OR in three directions and the oxygen and carbon contents in the rare earth sintered magnets 31 to 33 were determined in the same manner as in example 1.

The results are summarized in table 4. In table 4, rare earth produced using unrenewed powder 31Since sintered magnet No.31 was the subject of comparison, it was denoted as "-" in the judgment column of magnetic characteristics. In Table 1, B in the column for determining the magnetic characteristics of rare earth sintered magnets No.32 to 33 produced using the reclaimed powder 31 to 32 _rx B with rare earth sintered magnet No.1 _rx The case where the ratio was equal (lower than 0.1T even if the ratio was lower) was regarded as sufficient (good), and the case where the ratio was lower than 0.1T or more was regarded as insufficient (x).

[ Table 4]

The following can be seen from table 4.

The reclaimed powder 31 is a powder reclaimed by a method satisfying all the conditions specified in the method for reclaiming a rare earth element-containing powder according to the embodiment of the present invention, and is crushed to contain a powder that can be left on a 500-mesh sieve, and therefore, the time taken for crushing can be reduced as compared with the conventional technique in which a molded body is crushed over a long period of time so that all the powder can pass through a 500-mesh sieve.

The rare earth sintered magnet No.32 using the reclaimed powder 31 is a sintered magnet produced by a method satisfying all the conditions specified in the method for producing a rare earth sintered magnet according to the embodiment of the present invention, and the oxygen content is increased to about 800ppm as compared with the rare earth sintered magnet No.31 using the unrenewed powder 31, but the carbon content is hardly changed in the allowable range, and the sintered magnet exhibits sufficient magnetic characteristics (namely, B _rx Equivalent to the rare earth sintered magnet No.31 using the unrenewed powder 31).

On the other hand, the reclaimed powder 32 is obtained by separating and recovering the powder which passes through a 50 mesh (300 μm mesh) sieve and can be retained on a 149 mesh (100 μm mesh) sieve from among the crushed powders, and the reclaimed powder 32 is shorter than the reclaimed powder 31 in terms of time taken for crushing to obtain a certain amount, but the magnetic characteristics of the rare earth sintered magnet No.33 are insufficient. This is considered to be because the three-directional orientation degree OR of the rare earth sintered magnet No.33 is lower than that of the rare earth sintered magnet No. 31.

Claims

1. A method for regenerating a rare earth element-containing powder, comprising:

2. A method for producing a rare earth sintered magnet, comprising:

a step of obtaining a slurry containing the reclaimed powder reclaimed by the method of claim 1 and an oil;

wet molding the slurry in a magnetic field to obtain a molded article; and

and sintering the molded body obtained by wet molding.