JP2009275283A - Surface-coated magnetic powder, permanent magnet, and method for producing them - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a permanent magnet and a method for producing the same in which production time can be shortened; coercive force characteristics can be made uniform even when the magnet is large; the amount of a rare earth element to be added can be reduced and simultaneously coercive force can be increased; and reduction of magnetization can be prevented. <P>SOLUTION: In step S1, magnetic powder and a substance containing a rare earth element are prepared. The magnetic powder is a flat powder having a higher hardness than the substance containing a rare earth element. In step S2, the surface of the flat magnetic powder is coated with the substance containing a rare earth element. In step S3, the magnetic powder coated with the substance containing a rare earth element on the surface thereof is subjected to hot compression molding to produce a molded product. In step S4, the molded product is subjected to hot plastic working to impart anisotropy thereto. In step S5, the molded product to which anisotropy is imparted is subjected to machining, and then, if necessary, the molded product machined into a desired shape is heat-treated. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a magnetic powder to which a rare earth element-containing material is added, a permanent magnet using the magnetic powder, and a method for producing the same, and more particularly to an improvement in addition technology of the rare earth element-containing material.

  In the manufacture of the permanent magnet, as shown in FIG. 9, a magnetic powder is prepared as a raw material powder in step S101. At this time, each powder of the magnetic powder is a single crystal having a size of about 5 to 10 μm, and the easy magnetization axis of the lump of powder that is an aggregate of the single crystals is oriented in a random direction. Next, in step S102, a compact is produced by press-molding the magnetic powder in a magnetic field. At this time, since the anisotropy is imparted to the compact, the easy axis of magnetization of the magnetic powder constituting the compact is in the same direction. Next, in step S103, the molded body is sintered at a temperature of about 1100 ° C. to produce a sintered body, and in step S104, the sintered body is machined into a desired shape. Thereby, a sintered magnet is manufactured as a permanent magnet.

  In such a sintered magnet, high heat resistance is achieved by adding a rare earth element such as Pr, Dy, Tb or the like to the magnetic material to improve the coercive force. However, when a rare earth element is used, in addition to an increase in cost due to its expensiveness, a decrease in magnetization due to the addition of the rare earth element is caused. For this reason, since the usage-amount of a magnetic material increases, the further cost increase is caused. In addition, the rare earth element production region is highly unevenly distributed, so rare earth elements are known as the element with the highest supply risk (see Materia, Vol. 46, No. 8, 2007). Among them, the production of heavy rare earth elements such as Dy is currently oligopolistic in one country, so the supply risk is even higher.

  From the above, in order to reduce the amount of rare earth element added, a technique for appropriately adding a rare earth element-containing material in a predetermined step of the manufacturing method shown in FIG. 9 has been developed. For example, there are the following methods 1 and 2.

  In method 1, in step S101 of FIG. 9, as shown in FIG. 10 (A), each powder of magnetic powder is a single crystal having a size of about 5 to 10 μm and its easy axis (each in the figure). The rare earth element-containing material Q1 is mixed with the magnetic powder Q2 in which the arrow in the powder Q1 is oriented in a random direction. And the mixed powder is used as a raw material powder, and step S2-step S4 of FIG. 9 are performed. In this technique, as shown in FIG. 10B, the rare earth element Q1 is concentrated only in the vicinity of the grain boundary (about several μm) of the magnetic material Q2 that requires high coercive force, so that the entire magnet of the rare earth element Q1 is obtained. The amount of added is reduced. On the other hand, in the method 2, after the machining in step S104 of FIG. 9, as shown in FIG. 11 (A), the rare earth element-containing material Q1 is applied to the surface of the magnet composed of the magnetic powder Q2, and about 700 to Heat treatment is performed at a temperature of 1000 ° C. In addition, the arrow in each powder Q2 in the figure is the axis of easy magnetization. In this technique, the rare earth element Q1 selectively diffuses in the magnetic powder Q2 grain boundary inside the magnet, and as shown in FIG. 11B, the rare earth element Q1 is concentrated near the grain boundary pole on the magnet surface. The amount of rare earth element Q1 added to the entire magnet is reduced.

  However, in Method 1, since the rare earth element diffuses to the inside of each particle inside the permanent magnet by sintering performed after the rare earth element-containing material Q1 is added to the magnetic powder Q2, the amount of the rare earth element Q1 added is increased. Reduction effect is small. On the other hand, in the method 2, the coercive force characteristic is uniform when manufacturing a micro magnet having a size of about several mm at the maximum, but when manufacturing a larger magnet, the rare earth element Q1 near the grain boundary pole on the magnet surface. Therefore, the concentration distribution of the rare earth element Q1 decreases as it goes toward the inside of the magnet, and the coercive force characteristic becomes non-uniform. Further, separate steps of coating and heat treatment are required, and the heat treatment takes time. As described above, there is a limit to reducing the amount of rare earth element Q1 added using a sintered magnet because various problems occur.

  Incidentally, there is a hot plastic working method as a method of manufacturing a permanent magnet. For example, in the hot plastic working method disclosed in Patent Document 1, as shown in FIG. 12, a magnetic powder and a rare earth element-containing material are prepared in step S201, and in step S202, the powders are mixed to obtain a raw material. A mixed powder is prepared as a powder. Next, in step S202, the mixed powder is hot-molded to produce a molded body. Subsequently, after giving anisotropy to the formed body by performing hot plastic working in step S204, the formed body is processed into a desired shape by machining in step S205. Thereby, a hot plastic working magnet is manufactured as a permanent magnet.

  However, although the rare earth element-containing material is added to the hot plastic working magnet of Patent Document 1, the coercive force is lowered unlike the sintered magnet. In general, in a hot plastic working magnet, if a large amount of heavy rare earth element such as Dy having an effect on high coercive force is added to a magnet alloy, plastic working becomes difficult and it becomes difficult to provide anisotropy.

JP 9-139305 A

  Therefore, the present invention can shorten the manufacturing time, and even if the magnet is large, the coercive force characteristic can be made uniform, as well as the amount of rare earth elements added and the coercive force increased. An object of the present invention is to provide a magnetic powder, a permanent magnet, and a method for producing them that can achieve both compatibility and prevent a decrease in magnetization.

  In the surface-coated magnetic powder of the present invention, a rare earth element-containing material consisting of at least one of a rare earth elemental metal, an alloy, and a compound is uniformly formed on the surface of a magnetic powder having a crystal or a mixed phase of a crystal and an amorphous phase. It is characterized by being attached.

  The 1st permanent magnet of this invention is a molded object produced by performing hot compression molding to the said surface covering magnetic powder. That is, the first permanent magnet of the present invention is a rare earth element-containing material comprising at least one of a rare earth element simple metal, an alloy, and a compound on the surface of a magnetic powder having a crystal or a mixed phase of a crystal and an amorphous phase. Is characterized in that it is a molded body produced by hot compression molding a surface-coated magnetic powder to which is uniformly attached.

  The second permanent magnet of the present invention produces a molded body with anisotropy by compressing the surface-coated magnetic powder in a magnetic field, and subjecting the molded body to hot compression molding or sintering. It is obtained by doing. In this case, in the magnetic powder used in the production of the surface-coated magnetic powder, the easy magnetization axes of the crystals are oriented in the same direction in advance. That is, the second permanent magnet of the present invention has a rare earth element elemental metal or alloy on the surface of a magnetic powder having a crystal or a mixed phase of a crystal and an amorphous phase and having an easy axis of magnetization oriented in the same direction. And forming a molded body provided with anisotropy by compression molding in a magnetic field on a surface-coated magnetic powder in which a rare earth element-containing material consisting of at least one compound is uniformly attached, It is obtained by performing hot compression molding or sintering on a molded body. The magnetic powder has a large number of crystal grains inside one powder, and each crystal grain is arranged in one direction. Further, the adhesion of the rare earth element-containing material to the surface-coated magnetic powder is optimally uniform, but even if it is not uniform, the following effects can be obtained.

  In the first and second permanent magnets of the present invention, the rare earth element is concentrated in the vicinity of the grain boundary as described below, so that it is possible to achieve both reduction in the addition amount of the rare earth element and high coercivity. . In addition, this makes it possible to obtain a coercive force increasing effect in the same manner as in the above-described conventional method 2, since the crystal grain size is slightly larger than the single domain particle diameter in the permanent magnet after hot plastic working or HDDR powder permanent magnet. be able to. Furthermore, even when the magnet is large, the coercive force characteristic can be made uniform.

  Various configurations can be used for the permanent magnet of the present invention. For example, in the first permanent magnet of the present invention, it is preferable that anisotropy is given to the molded body by hot plastic working. Moreover, in the 1st, 2nd permanent magnet of this invention, it is suitable to be obtained by the heat processing to a molded object.

  The manufacturing method of the 1st surface covering magnetic powder of this invention is a manufacturing method of the said surface covering magnetic powder. That is, the method for producing a surface-coated magnetic powder according to the present invention comprises a solid rare earth comprising at least one of a magnetic powder having crystals or a mixed phase of crystals and an amorphous phase, a rare earth element simple metal, an alloy, and a compound. A slurry is prepared by mixing the element-containing material with a liquid, and the slurry is irradiated with ultrasonic waves to pulverize the rare-earth element-containing material, and the slurry is dried to magnetize the pulverized rare-earth element-containing material. It is characterized by adhering to the surface of the powder.

  In the first method for producing a surface-coated magnetic powder of the present invention, the magnetic powder having a hardness higher than that of the rare earth element-containing material in the slurry functions as a fine particle medium for the rare earth element-containing material. In the initial state, the rare earth element-containing material that is an aggregate of primary particles (that is, composed of secondary particles) not only breaks the aggregation by colliding with the magnetic powder by vibration caused by ultrasonic irradiation, but also Until the primary particles are crushed. In this case, the collision is also caused by the burst energy of cavitation (small bubbles) formed in the liquid by irradiation with ultrasonic waves. On the other hand, in the slurry, the rare earth element-containing material is dispersed in the liquid by the action of diffusion. When the rare earth element-containing material itself is in a liquid state, the rare earth element-containing material is dispersed in the slurry by the action of diffusion. Such dispersion / pulverization of the rare earth element-containing material is locally repeated in all regions on the surface of the magnetic powder, whereby the rare earth element-containing material can be uniformly dispersed in the slurry. In addition, the primary particle here is a particle recognized as a single crystal by observation with an electron microscope such as TEM. The pulverization is crushing of primary particles.

  As described above, in the ultrasonic irradiation of the slurry, only the rare earth element-containing material can be selectively finely divided without pulverizing the magnetic powder, and the rare earth element-containing material can be uniformly dispersed in the slurry. it can. The slurry is then dried to obtain a surface-coated magnetic powder in which the finely divided rare earth element-containing material is attached to the surface of the magnetic powder. In this case, since the finely divided rare earth element-containing material can adhere to the magnetic powder due to the surface tension of the liquid when the slurry is dried, it is possible to uniformly coat the surface of the magnetic powder with the rare earth element-containing material. it can. Moreover, since the addition amount of rare earth elements can be reduced, when the surface-coated magnetic powder is applied to the following method for producing a permanent magnet, the produced permanent magnet can prevent a decrease in magnetization.

  The manufacturing method of the 2nd surface covering magnetic powder of this invention is a manufacturing method in case a rare earth element containing material is a liquid form. In this case, the liquid used in the production of the slurry is not necessary, and ultrasonic irradiation to the slurry is not necessary. That is, the second method for producing a surface-coated magnetic powder according to the present invention is a liquid comprising at least one of a magnetic powder having a crystal or a mixed phase of a crystal and an amorphous phase, a rare earth element simple metal, an alloy, and a compound. A slurry is prepared by mixing a rare earth element-containing material in the form of a slurry, and the finely divided rare earth element-containing material is adhered to the surface of the magnetic powder by drying the slurry. In the second method for producing a surface-coated magnetic powder of the present invention, since a liquid rare earth element-containing material is used, the surface of the rare earth element-containing material on the magnetic powder surface can be obtained without performing ultrasonic irradiation on the slurry. The coating can be performed uniformly. Moreover, since the addition amount of rare earth elements can be reduced, when the surface-coated magnetic powder is applied to the following method for producing a permanent magnet, the produced permanent magnet can prevent a decrease in magnetization.

  The first method for producing a permanent magnet according to the present invention is characterized in that a compact is produced by performing hot compression molding on the surface-coated magnetic powder produced by the method for producing a surface-coated magnetic powder. The second permanent magnet manufacturing method of the present invention is the surface-coated magnetic powder manufactured by using the magnetic powder in which the easy axis of crystal is oriented in the same direction as the magnetic powder in the method of manufacturing the surface-coated magnetic powder. In addition, a compact having anisotropy is produced by compression molding in a magnetic field, and hot compacting or sintering is performed on the compact.

  In the first and second methods for producing a permanent magnet of the present invention, a permanent magnet can be produced from a surface-coated magnetic powder obtained by adhering a finely divided rare earth element-containing material to the surface of the magnetic powder. In this case, the rare earth element selectively diffuses from the interface of the magnetic powder into the crystal grain boundary, and the rare earth element can be concentrated in the vicinity of the grain boundary, thereby reducing the amount of rare earth element added. In addition, it is possible to achieve both high coercivity. In addition, this makes it possible to obtain a coercive force increasing effect in the same manner as in the above-described conventional method 2, since the crystal grain size is slightly larger than the single domain particle diameter in the permanent magnet after hot plastic working or HDDR powder permanent magnet. be able to. Furthermore, even when the magnet is large, the coercive force characteristic can be made uniform.

  Even when hot plastic working, hot compression molding, or sintering is performed, the diffusion distance of rare earth elements to the magnetic powder is about half the thickness of the magnetic powder (distance between the interfaces of the magnetic powder). Therefore, the diffusion distance is shorter than that of the conventional method 2 described above. Thereby, the treatment necessary for the diffusion of rare earth elements is sufficient only by the usual hot plastic working method, hot compression molding, or sintering treatment, and even when heat treatment is applied if necessary, Since the heat treatment needs only a few, the manufacturing time can be shortened. Further, even when a large amount of a heavy rare earth element-containing material such as Dy having an effect on high coercive force is added to the magnetic powder, plastic working can be easily performed and anisotropy is easily imparted.

  Various configurations can be used for the manufacturing method of the first and second permanent magnets of the present invention. For example, in the first method for producing a permanent magnet of the present invention, anisotropy can be imparted to the compact by subjecting the compact to hot plastic working. In addition, in the first and second permanent magnets of the present invention, it is possible to remove distortion by performing heat treatment on the molded body as necessary, and to diffuse rare earth elements into the magnetic powder. Since it can be performed sufficiently, the coercive force characteristic can be made more uniform.

  Further, for example, in the production of slurry, the magnetic powder can be set to have a larger mixing weight ratio than the rare earth element-containing material. In this aspect, since the dispersion space of the magnetic powder at the time of ultrasonic irradiation becomes relatively large, the magnetic powder can be efficiently atomized. For example, the slurry can be dried while irradiating the slurry with ultrasonic waves. In this aspect, when the slurry is dried, the rare earth element-containing material can be adhered to the magnetic powder in a state where the finely divided rare earth element-containing material is uniformly dispersed in the liquid. It is possible to more uniformly coat the surface.

  The slurry can be dried at a pressure lower than atmospheric pressure. In this embodiment, since the liquid is easily vaporized, drying can be performed effectively. Furthermore, the slurry can be dried by heating. In this aspect, drying can be performed more effectively. An organic solvent can be used as the liquid. In this aspect, since the organic solvent is highly volatile, drying can be performed more effectively. In addition, when at least one of the magnetic powder and the rare earth element-containing material is a metal powder, oxidation of the metal powder can be prevented.

  According to the surface-coated magnetic powder of the present invention or the method for producing the same, by applying the permanent magnet of the present invention or the method for producing the same, it is possible to reduce both the amount of rare earth element added and increase the coercive force. Moreover, since the addition amount of rare earth elements can be reduced, when the surface-coated magnetic powder is applied to the following method for producing a permanent magnet, the produced permanent magnet can prevent a decrease in magnetization.

  According to the first and second permanent magnets of the present invention or the manufacturing method thereof, the surface-coated magnetic material in which the rare earth element-containing material is attached to the magnetic powder surface by attaching the finely divided rare earth element-containing material to the magnetic powder. Since the powder is used, the rare earth element can selectively diffuse the grain boundary from the interface to the inside of the magnetic powder. Therefore, since the concentration of the rare earth element can be performed in the vicinity of the grain boundary, it is possible to obtain effects such as a reduction in the addition amount of the rare earth element and a high coercive force.

(1) First Embodiment Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a process diagram showing a method for manufacturing a permanent magnet according to a first embodiment of the present invention. As shown in FIG. 1, first, in step S1, a magnetic powder and a rare earth element-containing material are prepared.

  The magnetic powder is a powder having a crystal or a mixed phase of a crystal and an amorphous phase and having a higher hardness than a rare earth element-containing material. The magnetic powder has a flat shape such as a plate shape. Specifically, the magnetic powder has a cross-sectional size of, for example, a length of 200 μm and a thickness of 30 μm. Each of the powders includes a large number of fine crystal grains of, for example, several tens of nm. ing. The easy axis of crystal grains is oriented in a random direction. The magnetic powder is, for example, a rare earth magnetic powder (Nd—Fe—B magnetic powder) containing a rare earth element, an iron group element, and boron.

  Examples of the rare earth element-containing material include rare earth element powders containing at least one of rare earth elemental metals, alloys and compounds, and rare earth element sols and rare earth element liquids such as sol and liquid rare earth element compounds. It is done. Specifically, the rare earth element powder is made of an oxide containing Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sc, or Y, or a fluoride. Examples thereof include powders and powders composed of a mixture thereof. Moreover, as rare earth element sol and rare earth element liquid, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sc, or sol-like fluoride containing Y, sol-like colloidal form, etc. Examples thereof include fluorides and fluorides composed of a mixture thereof.

  Next, in step S2, a coating process for coating the surface of the flat magnetic powder with the rare earth element-containing material is performed using the apparatus 100 shown in FIG. First, in the container 104, the slurry S is prepared by mixing the rare earth element-containing material, the magnetic powder, and the liquid. For example, an organic solvent is used as the liquid. As the organic solvent, for example, ethanol, acetone, or IPA (isopropyl alcohol) is used. In the production of the slurry, it is preferable that the mixing ratio of the magnetic powder is larger than that of the rare earth element-containing material.

  Next, the container 104 is placed in the vibration liquid 103 of the vibration liquid tank 102. Subsequently, ultrasonic waves are oscillated by the ultrasonic oscillator 101, and the ultrasonic waves are applied to the slurry S in the container 104 through the vibrating liquid 103 in the vibrating liquid tank 102. The frequency of the ultrasonic wave is, for example, 100 kHz or less.

  Here, in the first embodiment, in the slurry S, the flat magnetic powder functions as a fine particle medium for the rare earth element-containing material. As shown in FIG. 3A, the rare earth element-containing material P1, which is an aggregate of primary particles (that is, composed of secondary particles) in an initial state, is converted into a flat magnetic powder P2 by vibration caused by ultrasonic irradiation. The collision not only breaks the agglomeration, but also leads to the primary particles being crushed. In this case, the collision is also caused by the burst energy of cavitation (small bubbles) formed in the liquid by irradiation with ultrasonic waves. On the other hand, in the slurry S, as shown in FIG. 3B, the rare earth element-containing material P1 is dispersed in the liquid by the action of diffusion. Such pulverization / dispersion of the rare earth element-containing material P1 is locally repeated in all regions on the surface of the magnetic powder P2, so that the rare earth element-containing material P1 can be uniformly dispersed in the slurry S. In FIGS. 3A and 3B, the liquid is not shown.

  In the apparatus 100, only the rare earth element-containing material P1 can be selectively finely divided without pulverizing the magnetic powder P2 as described above, and the rare earth element-containing material P1 is uniformly dispersed in the slurry S. be able to. Next, the liquid is dried under reduced pressure while irradiating with ultrasonic waves. As a result, the finely divided rare earth element-containing material P1 is maintained in a uniformly dispersed state in the liquid, and therefore does not aggregate and adheres to the surface of the magnetic powder P2 by the surface tension of the liquid during drying. As a result, the finely divided rare earth element-containing material P1 is uniformly coated on the surface of the magnetic powder P2, as shown in FIG. In addition, in the coating process of step S2, when a liquid rare earth element-containing material is used, the liquid used in the preparation of the slurry is unnecessary, and the slurry is not irradiated with ultrasonic waves. In this case, the surface of the magnetic powder containing the rare earth element-containing material is uniformly applied without performing ultrasonic irradiation on the slurry.

  Subsequently, in step S3, the surface-coated magnetic powder obtained by attaching the rare earth element-containing material P1 to the surface of the magnetic powder P2 is subjected to hot compression molding, thereby crystallization and true densification of the surface-coated magnetic powder. Do. Thereby, a molded object is produced. At this time, the distance between the interfaces of the magnetic powder P2 constituting the compact is, for example, 30 μm. The easy magnetization axes of the crystal grains in the magnetic powder are oriented in random directions. As conditions for hot compression molding, for example, the temperature is 700 ° C. and the applied load is 100 MPa.

  Next, in step S4, anisotropy is imparted to the compact by performing hot plastic working on the compact. Thereby, the magnetization easy axis (the arrow direction in each particle in the figure) of the crystal grains in the magnetic powder P2 constituting the compact is oriented in the same direction. Further, as shown in FIG. 4B, the rare earth element is selectively diffused along the crystal grain boundary (arrow direction I) from the interface of the flat magnetic powder P2 to the inside thereof, and the concentration of the rare earth element is increased. Conversion takes place near the grain boundaries. At this time, the diffusion of the rare earth element into the flat magnetic powder P2 is performed from all the interfaces to the inside of the flat magnetic powder P2, and therefore the diffusion distance is determined by the thickness of the magnetic powder P2 (of the magnetic powder). It is about half of the distance between the interfaces. In this case, the distance between the interfaces of the magnetic powder constituting the compact is, for example, 10 μm. As conditions for hot plastic working, for example, the temperature is 750 ° C. and the applied load is 20 MPa. In FIG. 4B, the portion where the rare earth element-containing material P1 is illustrated is the powder interface of the magnetic powder P2. Subsequently, in step S5, the molded body provided with anisotropy is machined to be processed into a desired shape. Next, if necessary, the molded body processed into a desired shape is subjected to heat treatment.

  As described above, in the first embodiment, a hot plastic working magnet can be manufactured as a permanent magnet from the surface-coated magnetic powder obtained by attaching the finely divided rare earth element-containing material P1 to the surface of the flat magnetic powder P2. . In this case, the rare earth element can selectively diffuse the grain boundary from the interface of the magnetic powder P2 to the inside thereof, and the rare earth element can be concentrated in the vicinity of the grain boundary. Compatibility and high coercive force can be achieved. In addition, this makes it possible to obtain a coercive force increasing effect in the same manner as in the above-described conventional method 2, since the crystal grain size is slightly larger than the single domain particle diameter in the permanent magnet after hot plastic working or HDDR powder permanent magnet. be able to. Furthermore, even when the magnet is large, the coercive force characteristic can be made uniform. Furthermore, since the amount of rare earth element P1 added can be reduced, the permanent magnet can prevent a decrease in magnetization.

  Even when hot plastic working is performed, the diffusion distance of the rare earth element to the flat magnetic powder P2 is about half the thickness of the magnetic powder P2 (distance between the interfaces of the magnetic powder). The distance is shorter than that in the conventional method 2. Thereby, the treatment necessary for the diffusion of the rare earth element is sufficient only by the usual hot plastic working method, and even if a heat treatment is applied if necessary, the heat treatment may be slight. Manufacturing time can be shortened. Furthermore, even when a large amount of a heavy rare earth element-containing material such as Dy having an effect on high coercive force is added to the magnetic powder, plastic working can be easily performed and anisotropy is easily imparted.

  In particular, in the preparation of the slurry S, the dispersion space of the rare earth element-containing material P1 at the time of ultrasonic irradiation becomes relatively large by setting the mixing weight ratio of the rare earth element-containing material P1 larger than that of the magnetic powder P2. The fine particles of the rare earth element-containing material P1 can be efficiently formed. By drying the slurry S while irradiating the slurry S with ultrasonic waves, when the slurry S is dried, the rare earth element-containing material P1 is dispersed in a state where the finely divided rare earth element-containing material P1 is uniformly dispersed in the liquid. Since it can adhere to the flat magnetic powder P2, the surface of the magnetic powder P2 with the rare earth element-containing material P1 can be more uniformly coated. Further, when the slurry S is dried at a pressure lower than the atmospheric pressure, the liquid is easily vaporized, so that the drying can be effectively performed. Furthermore, the slurry S can be dried more effectively by heating. Further, when an organic solvent is used as the liquid, the organic solvent is highly volatile, so that drying can be performed more effectively. In this case, when at least one of the rare earth element-containing material P1 and the magnetic powder P2 is a metal powder, oxidation of the metal powder can be prevented.

  Further, in the fine particle formation of the rare earth element-containing material P1, the selective fine particle formation and uniform dispersion of the rare earth element-containing material P1 can be performed in the same process, so that the number of manufacturing steps can be reduced and the rare earth element-containing material can be reduced. The possibility of mixing impurities into P1 and magnetic powder P2 can be eliminated. Moreover, since it is not necessary to handle the atomized rare earth element-containing material P1 alone, difficult handling of the powder is eliminated. Furthermore, since it is not necessary to apply a strong mechanical impact force, even when the rare earth element-containing material P1 and the magnetic powder P2 both have high hardness, it is possible to prevent the magnetic powder P2 from being pulverized. In addition, it is possible to sufficiently remove the rare earth element into the magnetic powder P2 as well as to remove the strain by performing a heat treatment on the molded body as necessary. Can be made more uniform.

(2) Second Embodiment The second embodiment is different from the first embodiment in steps between step S2 and step S5. In the second embodiment, components similar to those in the first embodiment are denoted by the same reference numerals, and descriptions of components having the same functions as those in the first embodiment are omitted.

  In the second embodiment, similarly to the first embodiment, in step S1, magnetic powder and a rare earth element-containing material are prepared, and in step S2, the surface of the magnetic powder P2 is coated with the rare earth element-containing material P1. Do. In this case, in the magnetic powder P2, the easy magnetization axes of the crystals are oriented in the same direction in advance. Subsequently, in step S13, the surface-coated magnetic powder obtained by attaching the rare earth element-containing material P1 to the surface of the magnetic powder P2 is compression-molded in a magnetic field. Thereby, a molded body having anisotropy is produced. Next, in step S14, the compact is hot compression molded or sintered. Thereby, a molded body or a sintered body is obtained. In step S14, the rare earth element is selectively diffused along the crystal grain boundary (arrow direction I) from the interface of the magnetic powder P2 to the inside of the magnetic powder P2, as in the first embodiment, and the enrichment of the rare earth element is performed in the grain. Done near the field.

  Next, in the same manner as in the first embodiment, in step S5, the molded body or sintered body is machined to be processed into a desired shape. Next, if necessary, heat treatment is performed on the molded body or sintered body processed into a desired shape.

  As described above, in the second embodiment, the diffusion of the rare earth element occurs during the hot compression molding and sintering processes, or during the heat treatment performed as necessary, and the same actions and effects as in the first embodiment. Can be obtained.

(3) Modification Although the present invention has been described using the above embodiment, the present invention is not limited to the above embodiment, and various modifications can be made. For example, in the above-described embodiment, the apparatus 100 is used for the covering process, but for example, apparatuses illustrated in FIGS. 6A to 6D may be used. In addition to the configuration of the apparatus 100, the apparatus 110 in FIG. 6A includes a stirring means 111 that rotates in the slurry S in the arrow direction _RA in the figure. In the apparatus 110, the slurry S is agitated by the rotation of the agitation unit 111 in addition to the ultrasonic irradiation of the slurry S. The apparatus 120 in FIG. 6B includes a rotating unit (not shown) that rotates the container 104 in addition to the configuration of the apparatus 100. In the device 120, in addition to ultrasonic irradiation to the slurry S, the rotation of the slurry S by the rotation means is performed in the direction of the arrow R _B in FIG. 2 and 6A to 6C, the position of the ultrasonic oscillator 101 is not limited to the illustrated position, and the container is formed through the vibrating liquid 103 in the vibrating liquid tank 102. Any position can be used as long as the slurry S in 104 can be irradiated with ultrasonic waves. Further, in the apparatus shown in FIG. 6D, any position where ultrasonic irradiation can be directly performed on the container 104 may be used.

In the above embodiment, the content of all the rare earth elements in the magnetic powder (hereinafter, the total content of rare earth elements) of _the stoichiometric composition of _{Nd 2 Fe 14 B (26.7wt.} %) 1.01~1 It is preferable to be within a range of 20 times. If the content of the rare earth element in the magnetic powder is less than 1.01 of the stoichiometric composition of _Nd 2 _{Fe 14 B,} closer to the stoichiometric composition of Nd 2 _{Fe 14} B, there is no Nd-rich phase . For this reason, at the time of manufacturing the permanent magnet, the rare earth element of the rare earth element-containing material adhering to the surface of the magnetic powder becomes difficult to diffuse from the interface of the magnetic powder to the inside through the grain boundary. When the rare earth element content in the magnetic powder is 1.01 times or more the stoichiometric composition of Nd ₂ Fe ₁₄ B, the coercive force increases, but the magnetic powder If the content of the rare earth element in the composition exceeds 1.20 times the stoichiometric composition of Nd ₂ Fe ₁₄ B, the increase in coercive force is slowed and the residual magnetic flux density is lowered, which is not practical.

  Further, it is preferable that the magnetic powder contains at least Pr as a rare earth element. In this aspect, when the permanent magnet is manufactured, even if the rare earth element contained in the rare earth element-containing material adhering to the surface of the magnetic powder diffuses through the crystal grain boundary, the increase in the melting point of the crystal grain boundary is suppressed. Becomes easy.

  Hereinafter, embodiments of the present invention will be described in more detail with reference to specific examples.

(1) Example 1 (Distribution of additive element Dy in permanent magnet and influence of added amount of Dy)
In Example 1, the dependency of the additive element Dy on the permanent magnet and the Dy addition amount dependency on the coercive force of the permanent magnet were examined. In sample preparation, DyF ₃ powder was prepared as a rare earth element-containing material, and Nd—Fe—B magnetic powder was prepared as a flat magnetic powder having a hardness higher than that of the rare earth element-containing material. Next, the surface of the magnetic powder was coated with a rare earth element-containing material. In the coating treatment, a slurry was prepared by mixing the magnetic powder and the rare earth element-containing material with an organic solvent using the same method as in the embodiment. By irradiating the slurry with ultrasonic waves, the rare earth element-containing material was finely divided and uniformly dispersed in the slurry. And the surface of the magnetic powder was coated with the finely divided rare earth element-containing material by drying the slurry. In this case, surface-coated magnetic powders having 0%, 0.5%, and 1.5% addition of Dy converted from the coated rare earth element-containing material were prepared.

  Subsequently, after such a coating treatment, a compact was produced by performing hot compression molding on a magnetic powder having a surface coated with a rare earth element-containing material. The conditions for hot compression molding were a temperature of 700 ° C. and a pressure of 100 MPa. Next, anisotropy was imparted to the molded body by subjecting the molded body to hot plastic working. In this manner, a permanent magnet having Dy addition amounts of 0%, 0.5%, and 1.5% was manufactured as Sample 11. In addition, the analysis of the addition amount of Dy used ICP (high frequency inductively coupled plasma) analysis.

  In the preparation of the comparative sample, by performing hot plastic working on the Nd—Fe—B based magnetic alloy to which Dy is added in advance (Dy addition amount: 0%, 0.5%, 1.5%), Anisotropy was imparted to the Nd—Fe—B magnetic alloy. In this way, a permanent magnet having Dy addition amounts of 0%, 0.5%, and 1.5% was manufactured as the comparative sample 11.

  Among the permanent magnets of the sample 11 manufactured as described above, with addition of Dy, the crystal grains and grain boundaries inside the magnetic powder of Nd—Fe—B were observed with a transmission electron microscope (TEM). The distribution of Nd and Dy in the region was examined. The results are shown in FIGS. 7A to 7C are a TEM photograph, an Nd distribution photograph, and a Dy distribution photograph (Mα line). As can be seen from FIGS. 7A to 7C, it was confirmed that Dy added as the rare earth element was concentrated in the Nd-rich phase that is the grain boundary phase of the magnetic powder.

  Next, the coercive force of the permanent magnets of the sample 11 and the comparative sample 11 was measured using a VSM (vibrating sample magnetometer). The results are shown in FIG. FIG. 7 is a graph showing the relationship between the change in coercive force and the amount of Dy added. In FIG. 7 and Table 1, the coercive force when the added amount of Dy is 0.5% and 1.5% is a relative value based on the coercive force when the added amount of Dy is 0%.

As shown in FIG. 7, in the sample 11, the increase in coercive force can be increased up to about 2.9 times that in the prior art at a predetermined Dy addition amount. That is, in order to obtain a predetermined coercive force, the amount of Dy added can be reduced by up to about 2/3. As described above, the effect of the present invention was demonstrated.

(2) Example 2 (Influence of particle size of additive element Dy)
In Example 2, the influence of the particle size of the additive element Dy on the coercivity of the permanent magnet was examined. In sample preparation, DyF ₃ powder was used as the rare earth element-containing material, and Nd—Fe—B magnetic powder was used as the flat magnetic powder having a hardness higher than that of the rare earth element-containing material. A permanent magnet was manufactured. In this case, the permanent magnet of the sample 21 was manufactured by using DyF ₃ powder having a powder particle size of 0.5 μm by mixing with Nd—Fe—B magnetic powder with an ultrasonic wave. A permanent magnet of Comparative Sample 21 was manufactured using DyF ₃ powder having a thickness of 10 μm. In addition, regarding the content of each rare earth element in the sample 21 and the comparative sample 21, the composition ratios of Nd and Pr are 0.417 and 0.583, and the total rare earth element content is the chemical amount of Nd ₂ Fe ₁₄ B. 1.10 times the theoretical composition.

  And the coercive force of the sample 21 and the comparative sample 21 was measured, and Dy addition amount dependence was acquired. The results are shown in Tables 2 and 3. Table 2 shows the measurement results of the sample 21, and Table 3 shows the measurement results of the comparative sample 21. In Tables 2 and 3, the measurement results of the coercivity of the conventional example manufactured by the same method as the comparative sample of Example 1 are shown.

  As can be seen from Table 3, in the comparative sample 21 in which the particle diameter of the powder when mixed with the magnetic powder of Nd—Fe—B was 10 μm, the increase in coercive force was smaller than that of the conventional example. As can be seen from FIG. 2, in the comparative sample 21 in which the particle diameter of the powder when mixed with the magnetic powder of Nd—Fe—B was 0.5 μm, the increase in coercive force was larger than that of the conventional example. This confirmed that the particle size of the powder when mixed with the magnetic powder of Nd—Fe—B is preferably less than 10 μm.

(3) Example 3 (Influence of total rare earth element content in magnetic powder)
(A) Lower limit value of the content of all rare earth elements in the magnetic powder In Example 3, the influence of the content of all rare earth elements in the magnetic powder on the permanent magnet characteristics was examined. The effect of the content of all rare earth elements in the magnetic powder on the properties of the permanent magnet was investigated. In sample preparation, DyF ₃ powder was used as the rare earth element-containing material, and Nd—Fe—B magnetic powder was used as the flat magnetic powder having a hardness higher than that of the rare earth element-containing material. A permanent magnet was manufactured by changing the amount of Dy added.

In this case, the permanent magnets of Samples 31 to 34 corresponding to the respective magnetic powders were obtained using the magnetic powder having the composition ratio shown in Table 4 by changing the content of all rare earth elements. In Table 4, the content of each rare earth element in Samples 31 to 34 is shown as a composition ratio, and the content of all rare earth elements in Samples 31 to 34 is based on the stoichiometric composition of Nd ₂ Fe ₁₄ B. As shown. And the coercive force of the samples 31-34 was measured, and Dy addition amount dependence was acquired. The results are shown in Tables 4-8. Table 5 shows the measurement result of the sample 31, Table 6 shows the measurement result of the sample 32, Table 7 shows the measurement result of the sample 33, and Table 8 shows the measurement result of the sample 34.

As it can be seen from Tables 5 and 6, sample 22 was 1.07 times the stoichiometric composition of _Nd 2 _{Fe 14} B for the total content of rare earth _element, 1 stoichiometry of Nd 2 _{Fe 14} B. The increase rate of the coercive force was larger than that of the sample 21 set to 01 times. As a result, it was found that the coercivity increase rate increases as the content of all rare earth elements is increased from 1.07 times the stoichiometric composition of Nd ₂ Fe ₁₄ B.

Further, as can be seen from Tables 6 to 8, in Sample 24 in which the content of all rare earth elements was 1.10 times the stoichiometric composition of Nd ₂ Fe ₁₄ B, the coercive force increased on the high addition amount side of Dy. rate includes a sample 22 the content was 1.07 times the stoichiometric composition of _Nd 2 _{Fe 14} B of the total rare earth _elements, the sample was 1.14 times the stoichiometric composition of Nd 2 _{Fe 14} B 23 However, the increase rate of the coercive force on the high addition amount side of Dy is substantially the same as that of the sample 23. Since sample 24 contains a larger amount of Pr as a rare earth element than sample 23, it is presumed that sample 24 has an effect of suppressing the melting point rise of the crystal grain boundary by Pr.

  Specifically, in the combination of Nd-Dy, when Dy diffuses through the crystal grain boundary, the melting point of the crystal grain boundary increases, and the diffusion rate becomes slow. In contrast, the Pr-Dy combination has a lower melting point than the Nd-Dy combination, so that Dy can be easily diffused and many rare earth elements can be diffused through the grain boundaries. Is done.

  On the high addition amount side of Dy, the increase rate of the coercive force of the sample 24 tends to decrease, whereas in the sample 23, the increase rate of the coercive force is almost the same as the low addition amount side of Dy. . For this reason, it is considered that the amount of the grain boundary phase (Nd amount or Nd-Pr amount) affects the rate of increase of the coercive force. As the amount of the grain boundary phase increases, Dy diffuses inside the magnetic powder. Even so, it is assumed that the hardening of the grain boundary is suppressed until the ratio of Nd or Nd—Pr and Dy at which the melting point of the grain boundary phase rises is reached.

(B) Upper limit of total rare earth element content in magnetic powder Sample preparation uses DyF ₃ powder as the rare earth element-containing material and Nd-Fe-B magnetic powder as the powder. As with the sample, a permanent magnet was manufactured. In this case, the permanent magnets of samples 41 to 44 corresponding to the respective magnetic powders were obtained by using the magnetic powder in which the addition amount of the DyF ₃ powder was set to a predetermined amount and the content of all rare earth elements was changed. Table 9 shows the results of measuring the coercive force and residual magnetic flux density of the permanent magnets of Samples 41 to 44. In Table 9, the contents of all rare earth elements in samples 41 to 44 are shown based on the stoichiometric composition of Nd ₂ Fe ₁₄ B, and the measured values of the coercive force and residual magnetic flux density of samples 42 to 44 are as follows: The sample 41 is shown as a reference.

As can be seen from Table 9, when the content of the rare earth element in the magnetic powder is 1.01 times or more of the stoichiometric composition of Nd ₂ Fe ₁₄ B, the coercive force is increased, but the rare earth element in the magnetic powder is increased. It has been confirmed that when the content of C exceeds 1.20 times the stoichiometric composition of Nd ₂ Fe ₁₄ B, the increase in coercive force slows down and the residual magnetic flux density decreases.

From the above results, when producing, for example, an Nd—Fe—B magnet as a permanent magnet, the content of all rare earth elements in the magnetic powder (hereinafter referred to as the content of all rare earth elements) is Nd ₂ Fe ₁₄ B. It has been found that it is preferably in the range of 1.01 to 1.20 times the stoichiometric composition. It was also found that the magnetic powder preferably contains at least Pr as a rare earth element.

It is process drawing showing the manufacturing method of the permanent magnet of 1st Embodiment which concerns on this invention. It is a sectional side view showing the schematic structure of the apparatus used by the coating process of the manufacturing method of the permanent magnet of 1st Embodiment which concerns on this invention. 2 represents the state of the rare earth element-containing material and the magnetic powder during operation of the apparatus shown in FIG. 2, (A) is a conceptual diagram illustrating a state in which the rare earth element-containing material collides with the magnetic powder, and (B) is between the magnetic powders It is a conceptual diagram showing the state to which a rare earth element containing material disperse | distributes. The product in each process of the manufacturing method of the permanent magnet of 1st Embodiment which concerns on this invention is represented, (A) is a schematic block diagram of the state after a coating process, (B) is the state at the time of hot plastic working. It is a schematic block diagram. It is process drawing showing the manufacturing method of the permanent magnet of 2nd Embodiment which concerns on this invention. (A)-(D) are the modifications of the apparatus shown in FIG. (A)-(C) are the TEM photograph, Nd distribution photograph, and Dy distribution photograph (M (alpha) ray) of the permanent magnet which added Dy of Example 1 of this invention. It is a graph showing the relationship between the change of the coercive force of Example 1 of this invention, and Dy addition amount of a permanent magnet. It is process drawing showing the manufacturing method of the permanent magnet by the conventional method 1. The product in each process of the manufacturing method of the permanent magnet by the conventional method 1 is represented, (A) is a schematic block diagram of the state after mixing with a magnetic powder and a rare earth element containing material, (B) is the rare earth in a permanent magnet. It is a schematic block diagram of the addition state of an element. The product in each process of the manufacturing method of the permanent magnet by the conventional method 2 is represented, (A) is a schematic block diagram of the state after mixing with a magnetic powder and a rare earth element containing material, (B) is the rare earth in a permanent magnet. It is a schematic block diagram of the addition state of an element. It is process drawing showing the conventional hot plastic working method.

Explanation of symbols

  P1: Rare earth element-containing material, P2: Magnetic powder, S: Slurry

Claims (16)

  A rare earth element-containing material comprising at least one of a rare earth elemental metal, an alloy, and a compound is uniformly attached to the surface of a magnetic powder having a crystal or a mixed phase of a crystal and an amorphous phase. Surface coated magnetic powder.   A surface-coated magnetic powder in which a rare earth element-containing material composed of at least one of a rare earth element simple metal, an alloy, and a compound is uniformly attached to the surface of a magnetic powder having a crystal or a mixed phase of a crystal and an amorphous phase. A permanent magnet, which is a molded body produced by hot compression molding.   A rare earth comprising at least one of a rare earth elemental metal, an alloy, and a compound on the surface of a magnetic powder having a crystal or a mixed phase of a crystal and an amorphous phase and having an easy axis of magnetization oriented in the same direction. An anisotropy is imparted to the surface-coated magnetic powder in which the element-containing material is uniformly applied by compression molding in a magnetic field, and the compact is subjected to hot compression molding or sintering. A permanent magnet obtained by performing.   The permanent magnet according to claim 2, wherein anisotropy is imparted to the molded body by hot plastic working.   The permanent magnet according to any one of claims 2 to 4, wherein the permanent magnet is obtained by heat treatment of the molded body. A slurry is prepared by mixing a magnetic powder having a crystal or a mixed phase of a crystal and an amorphous phase, and a solid rare earth element-containing material composed of at least one of a rare earth element simple metal, an alloy, and a compound. And
The rare earth element-containing material is made fine by irradiating the slurry with ultrasonic waves,
A method for producing a surface-coated magnetic powder, characterized in that the finely divided rare earth element-containing material is adhered to the surface of the magnetic powder by drying the slurry. A slurry is prepared by mixing a magnetic powder having a crystal or a mixed phase of a crystal and an amorphous phase and a liquid rare earth element-containing material composed of at least one of a rare earth element simple metal, an alloy, and a compound,
A method for producing a surface-coated magnetic powder, characterized in that the finely divided rare earth element-containing material is adhered to the surface of the magnetic powder by drying the slurry.   A method for producing a permanent magnet, characterized in that a compact is produced by hot compression molding the surface-coated magnetic powder produced by the method for producing a surface-coated magnetic powder according to claim 6. A method for producing a surface-coated magnetic powder according to claim 6 or 7, wherein a surface-coated magnetic powder produced using a powder in which the easy axis of magnetization of the crystal is oriented in the same direction is used as the magnetic powder in a magnetic field. Make a molded body with anisotropy by compression molding,
A method for producing a permanent magnet, comprising performing hot compression molding or sintering on the molded body.   The method for producing a permanent magnet according to claim 8, wherein anisotropy is imparted to the compact by performing hot plastic working on the compact.   The method for producing a permanent magnet according to claim 8, wherein the molded body is heat-treated.   The method for producing a permanent magnet according to any one of claims 8 to 11, wherein in the production of the slurry, the magnetic powder has a mixing weight ratio larger than that of the rare earth element-containing material.   The method for producing a permanent magnet according to claim 8, wherein the slurry is dried while irradiating the slurry with ultrasonic waves.   The method for producing a permanent magnet according to claim 8, wherein the slurry is dried under reduced pressure.   The method for producing a permanent magnet according to claim 8, wherein the slurry is dried by heating.   An organic solvent is used as said liquid, The manufacturing method of the permanent magnet in any one of Claims 8-15 characterized by the above-mentioned.

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