JP6447804B2 - Method for manufacturing magnet compact - Google Patents

Description

  The present invention relates to a method for producing a molded body for a magnet, which is a material for a rare earth magnet used for a permanent magnet, etc., a molded body for a magnet, and a magnet obtained by subjecting the molded body for a magnet to a heat treatment. It relates to members. In particular, the present invention relates to a method for producing a molded article for a magnet having a high relative density at a low molding pressure.

For applications such as motors and generators, rare earth magnets using rare earth-iron alloys having a rare earth-iron compound containing rare earth elements and Fe as a main phase are widely used. As the rare earth magnet, a neodymium magnet using an Nd—Fe—B alloy having a Nd—Fe—B compound (eg, Nd ₂ Fe ₁₄ B) as a main phase is typical. Conventional rare earth magnets are mainly sintered magnets obtained by sintering rare earth-iron alloy powders and bonded magnets obtained by solidifying alloy powders with a binder resin. Further, it has been studied to use an Sm—Fe—N-based alloy having a Sm—Fe—N-based compound (eg, Sm ₂ Fe ₁₇ N ₃ ) as a main phase for the bond magnet.

  Recently, as a rare earth magnet other than a sintered magnet or a bonded magnet, a dust magnet in which powder is compression-molded has been developed (see Patent Documents 1 and 2). In Patent Documents 1 and 2, a magnetic member is manufactured through the following preparation process → pulverization process → hydrogenation process → molding process → dehydrogenation process, and this magnetic member is used as a material for a rare earth magnet. Preparation step: An ingot of a rare earth-iron alloy such as an Nd—Fe—B alloy or an Sm—Fe—N alloy is prepared. Crushing step: The alloy is crushed. Hydrogenation step: The pulverized alloy powder is subjected to a hydrogenation (HD) treatment at a disproportionation temperature or higher. Molding process: compression-molding the hydrogenated magnet powder. Dehydrogenation step: The molded powder compact is subjected to a dehydrogenation (DR) process at a recombination temperature or higher.

Thus, by performing the molding step after the hydrogenation step and before the dehydrogenation step, the moldability of the magnet powder can be improved, and a powder compact (magnet compact) having a high relative density can be obtained. This is because if the alloy powder is hydrotreated, a magnet powder having a structure in which rare earth element hydride phases (for example, NdH ₂ and SmH ₂ ) are dispersed in the Fe-containing phase can be obtained. That is, each magnetic particle constituting the magnet powder contains a lot of soft parts (α-Fe, etc.) excellent in moldability.

JP2011-236498A JP 2011-137218 A

There is a need for further improvement in formability. Even though it can be said that the moldability can be improved by going through the above-described steps, each magnetic particle of the magnet powder includes a hard portion (eg, NdH ₂ , Fe ₂ B, SmH _2, etc.) that is inferior in moldability. In order to obtain a molded article having a high relative density, it was necessary to increase the molding pressure. If the molding pressure is increased, the mold is easily worn. When compression molding is performed at a high pressure, the springback after molding becomes large, and when the molded body is extracted from the mold, the frictional force between the molded body and the mold increases.

  The present invention has been made in view of the above circumstances, and one of its purposes is to provide a method for producing a molded body for a magnet that can obtain a molded body for a magnet having a high relative density at a low molding pressure. .

  Another object of the present invention is to provide a magnet molded body having a high relative density and a magnetic member obtained by subjecting the magnet molded body to a heat treatment.

  The manufacturing method of the molded object for magnets concerning one mode of the present invention comprises a hydrogenation process, a crushing process, and a forming process. In the hydrogenation step, a hydrogenated alloy obtained by hydrogenating a rare earth-iron-based alloy at a temperature equal to or higher than the disproportionation temperature in an atmosphere containing hydrogen is produced. In the pulverization step, the hydrogenated alloy is mechanically pulverized to produce a hydrogenated powder. In the forming step, a magnet powder containing hydrogenated powder is compression-molded to produce a powder compact. And a shaping | molding process is performed by the shaping pressure of 588 Mpa or less in the state which heated the powder for magnets to 250 to 600 degreeC.

  According to the above method for producing a molded article for magnets, a molded article for magnets having a high relative density can be obtained at a low molding pressure.

It is process explanatory drawing explaining the manufacturing method of the molded object for magnets which concerns on Embodiment 1. FIG. It is process explanatory drawing explaining the manufacturing method of the molded object for magnets which concerns on Embodiment 2. FIG. It is process explanatory drawing explaining the manufacturing method of the conventional molded object for magnets.

<< Description of Embodiments of the Present Invention >>
The inventors diligently studied a production method for obtaining a molded article for a magnet having a high relative density at a low molding pressure. Specifically, paying attention to the hard part such as NdH ₂ which is inferior in formability, an attempt was made to improve the formability by softening the hard part. However, a sufficient effect was not achieved. When the cause was considered, in the conventional magnet powder manufacturing method in which the rare earth-iron alloy is pulverized and then hydrotreated, unintended fine particles are generated in the manufactured magnet powder, and the particle size is reduced. It was found that variations occurred. Then, it is considered that the generation of the fine particles did not sufficiently increase the relative density because the molding pressure could not be sufficiently transmitted to the fine particles at a low molding pressure even if the hard portion was softened as described above. . The mechanism that causes variation in the particle size is considered as follows.

  In the conventional manufacturing method, as shown in the lower part of FIG. 3, a raw material rare earth-iron alloy 100 is prepared (first figure from the left), and the alloy 100 is crushed into alloy powder 120 (from the left). The second figure), the alloy powder 120 is hydrogenated to produce a hydrogenated powder (magnet powder) 140 (third figure from the left). Thereafter, the magnet powder 140 is compression-molded to form a powder compact (magnet compact) 150 (fourth figure from the left), and then the magnet compact 150 is dehydrogenated to produce the magnetic member 160. (5th figure from the left).

  As shown in the upper part of FIG. 3, the rare earth-iron-based alloy (particles 121 of the alloy powder 120) has rare earth-iron-based compound crystal grains as the main phase 101, and crystal grain boundaries of the main phase 101 (the main phases 101 to each other) In the meantime, there is a grain boundary phase 102 containing a large amount of rare earth elements. In the conventional manufacturing method, when the alloy powder 120 is hydrogenated, the grain boundary phase 102 occludes hydrogen to cause embrittlement and volume expansion of the grain boundary phase 102, and the grain boundary phase 102 is cracked. C occurs (center view). Therefore, when the alloy powder 120 is hydrogenated to produce a hydrogenated powder (magnet powder) 140, the particles 141 of the hydrogenated powder (magnet powder) 140 are pulverized along the grain boundary phase 102 and are used for a magnet. Fine particles 141 are generated in the powder 140, and the particle sizes of the particles 141 are not uniform. Therefore, in the conventional manufacturing method, even if the particle size of the alloy powder 120 is controlled to the target particle size in the pulverization step, the particles are cracked by the hydrogenation treatment, so that fine particles are generated and the magnet The particle size variation of the powder 140 for use becomes large.

  Even if fine particles are generated, particles outside the range are removed by, for example, sieving the magnet powder before molding so that the particle size of the magnet powder is within the range suitable for compression molding. It is possible. However, in this case, productivity and yield are reduced. Moreover, since fine particles are easily oxidized, there is a possibility that the magnetic properties of the rare earth magnet will be lowered as a result.

  In view of this, various methods for obtaining magnet powders that can suppress the generation of fine particles and have a small variation in particle size, instead of removing the generated fine particles, were studied. As a result, it has been found that if the rare earth-iron-based alloy is hydrotreated and then mechanically pulverized, the generation of fine particles can be suppressed and the variation in the particle size of the magnet powder can be reduced. And the knowledge that the compact | molding | casting for magnets with a high relative density was obtained even if it was compression-molded by heating the powder for magnets with the small dispersion | variation in the particle size to a specific temperature was acquired. The present invention is based on these findings. First, embodiments of the present invention will be listed and described.

  (1) The manufacturing method of the molded object for magnets which concerns on 1 aspect of this invention is equipped with a hydrogenation process, a grinding | pulverization process, and a shaping | molding process. In the hydrogenation step, a hydrogenated alloy obtained by hydrogenating a rare earth-iron-based alloy at a temperature equal to or higher than the disproportionation temperature in an atmosphere containing hydrogen is produced. In the pulverization step, the hydrogenated alloy is mechanically pulverized to produce a hydrogenated powder. In the forming step, a magnet powder containing hydrogenated powder is compression-molded to produce a powder compact. And a shaping | molding process is performed by the shaping pressure of 588 Mpa or less in the state which heated the powder for magnets to 250 to 600 degreeC.

  According to the above configuration, the formability can be improved by compressing and molding the magnet powder containing the hydrogenated powder that has been subjected to the hydrogenation treatment and then pulverized the hydrogenated powder to the above temperature, A molded article for a magnet having a high relative density can be produced even at a low molding pressure.

By the hydrogenation process, a hydrogenated alloy containing pure iron (Fe) that is soft and easily deformed is obtained. A disproportionation reaction is caused by heat-treating the rare earth-iron-based alloy in a hydrogen-containing atmosphere at a temperature equal to or higher than the disproportionation temperature (hydrogenation treatment). Thereby, the rare earth-iron-based compound is composed of a phase of a rare earth element hydrogen compound (eg, NdH ₂ or SmH ₂ ) and an iron-containing material containing iron (eg, an iron compound such as Fe or Fe ₂ B). This is because it is decomposed into phases.

  By mechanically pulverizing the hydrogenated alloy in the pulverization step, generation of fine particles can be suppressed and variation in the particle size of the hydrogenated powder can be reduced. Since the bulk of rare earth-iron alloy before pulverization is hydrotreated, it is finer by hydrotreating compared to the conventional case of hydrotreating the alloy powder. This is because pulverization can be suppressed and generation of fine particles in the magnet powder can be suppressed. Moreover, by carrying out the hydrogenation treatment and then mechanically pulverizing, it is easy to uniformly control the particle size, and the desired particle size can be stably obtained.

By setting the heating temperature to 250 ° C. or higher in the molding step, hard portions such as rare earth element hydrogen compounds and iron compounds can be softened, and the moldability of the magnet powder can be improved. Since the magnet powder to be molded has a small variation in particle size as described above, the molding pressure can be sufficiently transmitted to the magnet powder having improved moldability. Therefore, a molded article for a magnet having a high relative density (for example, 80% or more) can be obtained even at a molding pressure lower than that of 588 MPa (6 ton / cm ² ). By setting the heating temperature to 600 ° C. or less, the temperature rise time and the cooling time of the magnet molded body do not become too long, and the productivity can be improved.

(2) As one form of the manufacturing method of the said molded object for magnets, the powder for magnets is a mixed powder containing the said hydrogenation powder and the anisotropic powder which satisfy | fills the following structures (a)-(c). Can be mentioned.
(A) containing 10% by volume or more and less than 40% by volume of a rare earth element, an iron group element, and at least one element selected from B, C, and N (b) an average crystal grain size of 700 nm or less (c ) The average particle size is 3μm or more and 500μm or less

  According to said structure, the magnet compact | molding | casting from which the rare earth magnet excellent in a magnetic characteristic is obtained can be manufactured because the powder for magnets contains hydrogenated powder and anisotropic powder. The magnet compact is formed by bonding anisotropic powder with hydrogenated powder. By utilizing the characteristic that hydrogenated powder has a high degree of freedom of shape, that is, excellent plastic workability, it is strong by the hydrogenated powder obtained by deforming particles of anisotropic powder inferior in plastic workability during molding. It is because it can couple | bond with. Then, when the magnet compact is dehydrogenated, the hydrogenated powder as a binder is finally changed to a magnetic component, and a magnetic member substantially composed of only the magnetic component is obtained. Therefore, a rare earth magnet having excellent magnetic properties can be obtained.

  As in the configuration (a), by forming the rare earth element in an amount of 10% by volume or more and less than 40% by volume, it is possible to produce a molded article for a magnet that can obtain a rare earth magnet having excellent magnetic properties.

  As in the configuration (b), the effect of improving the coercive force due to fine crystals can be expected by setting the average crystal grain size of these alloys constituting the anisotropic powder to 700 nm or less. Therefore, it is possible to produce a molded article for a magnet from which a rare earth magnet having excellent magnetic properties (particularly residual magnetic flux density and coercive force) can be obtained.

  As in the configuration (c), by setting the average particle size to 3 μm or more, each particle of the anisotropic powder can be sufficiently brought into contact with the hydrogenated powder particles serving as a binder, and a strong magnet molded body is obtained. can get. Therefore, a strong rare earth magnet can be obtained. By setting the average particle size to 500 μm or less, it is possible to suppress a decrease in the relative density of the magnet compact. Moreover, the crack of the anisotropic powder inferior to plastic workability at the time of compression molding can be suppressed.

  (3) As one form of the manufacturing method of the said molded object for magnets, when the powder for magnets is the said mixed powder, it is mentioned that the crystal orientation degree of anisotropic powder is 70% or more.

  According to said structure, since the degree of crystal orientation of anisotropic powder is high and it is excellent in magnetic anisotropy, the rare earth magnet excellent in a magnetic characteristic can be manufactured.

  (4) As one form of the manufacturing method of the said magnet molded object, when magnet powder is the said mixed powder, a shaping | molding process applies a magnetic field of 0.5T or more to magnet powder, and the said anisotropy It can be performed in a state where the orientation direction of the powder is aligned.

  According to said structure, by applying a magnetic field at a shaping | molding process, anisotropic powder rotates according to the application direction of a magnetic field, etc., and the orientation direction of anisotropic powder can be substantially aligned in one direction. Therefore, a magnet molded article having excellent orientation can be obtained, and as a result, a rare earth magnet having excellent orientation can be produced.

(5) As one form of the manufacturing method of the said molded object for magnets, it is mentioned that a hydrogenated alloy is equipped with the following structures (a)-(c).
(A) A rare earth element hydrogen compound phase of 10 volume% or more and less than 40 volume%, and the balance is a phase of an iron-containing material.
(B) The rare earth element hydrogen compound phase and the iron-containing material phase are adjacent to each other.
(C) The space between the phases of the rare earth element hydrogen compounds adjacent to each other through the phase of the iron-containing material is 3 μm or less.

  According to said structure, the rare earth magnet which is excellent in a magnetic characteristic is obtained by making the phase of the hydrogen compound of rare earth elements into 10 volume% or more and less than 40 volume% like the said structure (a). Moreover, the balance excluding the rare earth element hydrogen compound phase is substantially the phase of the iron-containing material, and the soft and highly deformable iron-containing material phase is the main component (60 vol% or more and 90 vol% or less). Thus, the moldability of the magnet powder can be improved.

  By providing the above configurations (b) and (c), the structure in which the phase of the iron-containing material exists between the phases of the rare earth element hydrogen compound and both phases exist at the specific intervals described above is uniform in both phases. Is an organization that exists. Therefore, when the hydrogenated powder (magnet powder) obtained by pulverizing the hydrogenated alloy is compression-molded, the particles are uniformly deformed, so that the moldability can be improved. The “interval between phases of rare earth element hydrogen compounds” is the distance between the centers of adjacent rare earth element hydrogen compound phases in the cross section.

  (6) As one form of the manufacturing method of the said compact | molding | casting for magnets, the phase of the rare earth element hydrogen compound is granular, and the phase of the granular rare earth element hydrogen compound is dispersed in the phase of the iron-containing material. To do.

  According to the above-described configuration, the phase of the rare earth element hydrogen compound and the phase of the iron containing substance can be obtained by forming a dispersed form in which the iron-containing substance phase uniformly exists around the rare earth element hydrogen compound phase. The moldability can be improved as compared with the layered form having a laminated structure.

  (7) As one form of the manufacturing method of the said molded object for magnets, it is mentioned that D50 particle size of hydrogenation powder is 100 micrometers or more and 500 micrometers or less.

  According to the above configuration, since the D50 particle size is in the above range, the proportion of fine particles is small, the particle size is suitable for compression molding (for example, 75 μm to 355 μm), and the particle size is uniform. Therefore, the moldability is particularly excellent. Moreover, since the ratio of the fine particles contained in the magnet powder is small, the magnetic properties are hardly deteriorated due to the oxidation of the fine particles.

  (8) As one form of the manufacturing method of the said magnet molded object, performing a shaping | molding process in the atmosphere whose oxygen concentration is 1 volume% or less is mentioned.

  According to said structure, since the oxidation of the powder for magnets and the molded object for magnets can be suppressed, the fall of the magnetic characteristic by oxidation is hard to produce.

  (9) The magnet molded body according to an aspect of the present invention is manufactured by the method for manufacturing a magnet molded body according to any one of (1) to (8), and the relative density is 80% or more.

  According to the above configuration, since the relative density of the magnet compact is 80% or more, by using this magnet compact, a magnetic member having a relative density of 80% or more can be obtained. A magnet is obtained. If the density of the rare earth magnet is increased, the magnetic properties are improved. The relative density of the rare earth magnet depends on the relative density of the magnet compact, which is an intermediate product in the manufacturing process, and although there is a slight increase due to thermal shrinkage caused by heat treatment after molding, the relative density of this magnet compact The density is substantially maintained. Therefore, the relative density of the rare earth magnet can be increased by using a molded article for a magnet having a high relative density. The relative density is an actual density (percentage of [apparent density of magnet compact / true density of magnet compact]) with respect to the true density.

  (10) A magnetic member according to an aspect of the present invention is obtained by dehydrogenating the above-described magnet molded body at a temperature equal to or higher than the recombination temperature in an inert atmosphere or a reduced pressure atmosphere.

  According to said structure, since it recombines with the original rare earth-iron type compound and the crystal grain of a rare earth-iron type compound can be refined | miniaturized by a dehydrogenation process, a rare earth magnet with high coercive force is obtained.

<< Details of Embodiment of the Present Invention >>
Details of the embodiment of the present invention will be described. In addition, this invention is not limited to these illustrations, is shown by the claim, and is intended that all the changes within the meaning and range equivalent to the claim are included.

Embodiment 1
[Method for producing magnet compact]
The manufacturing method of the molded object for magnets which concerns on Embodiment 1 is equipped with the powder preparation process for magnets which prepares the powder for magnets, and the shaping | molding process which compresses and forms the powder for magnets and produces a powder molded object. The main feature of the method for manufacturing a magnet molded body is that it includes the following (1) and (2). (1) In the magnet powder preparation step, a magnet powder including a hydrogenated powder obtained by pulverizing a rare earth-iron alloy after hydrogenation is prepared. (2) In the molding step, compression molding is performed at a low molding pressure while the magnet powder is heated to a specific temperature. As will be described in detail later by passing through this specific step, a magnet molded body having a high relative density can be produced with a low molding pressure. Hereinafter, each step will be described in detail with reference to FIG.

(Magnet powder preparation process)
In the magnet powder preparation step, a magnet powder 40a including the hydrogenated powder 20 is prepared (the lower middle diagram in FIG. 1). The preparation of the magnet powder includes a raw material alloy preparation step for preparing the rare earth-iron alloy 10 (lower left diagram in FIG. 1), and a hydrogenated alloy 10h (from the lower left in FIG. 2nd figure) and the pulverization process which mechanically pulverizes the hydrogenated alloy 10h to produce the hydrogenated powder 20 are performed. By performing the pulverization step after the hydrogenation step, variation in particle size can be suppressed, which contributes to improving moldability in the molding step.

<Raw alloy preparation process>
The rare earth-iron alloy 10 includes a rare earth-iron compound containing a rare earth element and an iron group element as a main phase.

  Examples of the rare earth element include one or more elements selected from scandium (Sc), yttrium (Y), lanthanoid, and actinoid. Among these, when the rare earth element contains at least one element selected from neodymium (Nd), samarium (Sm), praseodymium (Pr), cerium (Ce), dysprosium (Dy), and Y, the magnetic properties are excellent. A rare earth magnet is preferably obtained. In particular, when Nd or Sm is contained, a rare earth magnet having excellent magnetic properties can be obtained.

The rare earth element content is preferably 10% by mass or more and less than 40% by mass. For example, in the case of a composition containing Nd, the Nd content is preferably 25% by mass or more (further 28% by mass or more) and 35% by mass or less. In the case of a composition containing Sm, the Sm content is preferably 25% by mass or more and 26.5% by mass or less. When the content of Nd or Sm is within the above range, a rare earth-iron compound (rare earth-iron alloy 10) having a stoichiometric composition such as Nd ₂ Fe ₁₄ B or Sm ₂ Fe ₁₇ is obtained. 1 As shown in the upper left figure, a structure is obtained in which the grain boundary phase 12 is thin with a uniform thickness at the crystal grain boundary of the main phase 11 of the rare earth-iron-based compound. Such a structure works to break the magnetic coupling between the main phases 11 in which the grain boundary phase 12 is a ferromagnetic phase, thereby increasing the coercive force.

  Examples of the iron group element include one or more elements selected from iron (Fe), cobalt (Co), and nickel (Ni). A typical example is an embodiment in which Fe is a main component (greater than 50% by mass) of a rare earth-iron alloy. In addition, the form containing both Fe and Co is mentioned, for example. In particular, when Co is included as an additive element, an effect of suppressing precipitation of Fe due to disproportionation decomposition of the rare earth-iron compound (main phase 11) due to oxidation can be expected, and this effect further improves the coercive force. Can be expected.

  The element other than the rare earth element and the iron group element of the rare earth-iron-based alloy 10 is at least one selected from boron (B), carbon (C), and nitrogen (N) particularly in the case of a composition containing Nd. The element is included. Examples of the content of B, C, and N include 0.1% by mass or more and 5.0% by mass or less, and further 0.5% by mass or more and 1.5% by mass or less.

  Other additive elements in the rare earth-iron-based alloy 10 include one or more elements selected from transition metal elements, gallium (Ga), aluminum (Al), and silicon (Si). In particular, when Ga is contained, an effect of homogenizing the grain boundary phase 12 can be expected, and a further improvement in coercive force can be expected by this effect. Examples of the transition metal element include copper (Cu), titanium (Ti), manganese (Mn), and niobium (Nb). The rare earth-iron alloy 10 allows the inclusion of inevitable impurities. The content of these additive elements (the total content in the case of plural elements) is 0.1% by mass or more and 20% by mass or less, and further 0.1% by mass or more and 5% by mass or less. When these elements are contained, for example, an effect such as an improvement in coercive force can be expected. These additive elements are present, for example, by being replaced with part of Fe.

When the rare earth element contains Nd, the specific composition of the rare earth-iron alloy 10 is an Nd—Fe—B alloy having a main phase of an Nd—Fe—B compound (eg, Nd ₂ Fe ₁₄ B), Nd-Fe-C-based alloys and Nd-Fe-Co-B-based compounds (eg, Nd ₂ (Fe ₁₃ Co ₁ ) B having an Nd-Fe-C-based compound (eg, Nd ₂ Fe ₁₄ C) as a main phase Nd—Fe—Co—B alloy having a main phase of Nd—Fe—Co—C alloy, Nd—Fe—Co—C alloy having a main phase of Nd ₂ (Fe ₁₃ Co ₁ ) C, etc. Is mentioned. When the rare earth element contains Sm, an Sm—Fe based alloy containing a Sm—Fe based compound (eg, Sm ₂ Fe ₁₇ , Sm ₁ Ti ₁ Fe ₁₁ ) as a main phase may be mentioned.

  The maximum diameter of the rare earth-iron alloy 10 is preferably 100 μm or more and 50 mm or less. When the maximum diameter is 100 μm or more, it is easy to pulverize to a medium particle size in the subsequent pulverization step, and it is easy to produce a magnet powder having a particle size (75 μm to 355 μm) suitable for compression molding. When the maximum diameter is 50 mm or less, the time required for the subsequent pulverization step can be shortened. The shape of the rare earth-iron-based alloy 10 is not particularly limited, and may be various shapes such as a spherical shape, a rod shape, and a flake shape. The “maximum diameter” is the length of the longest portion of the rare earth-iron alloy 10 when the rare earth-iron alloy 10 is viewed in plan from all directions.

  The manufacturing method of the rare earth-iron-based alloy 10 is not particularly limited, and can be manufactured by, for example, a melt casting method, a rapid solidification method, a gas atomizing method, or the like. When the rare earth-iron-based alloy 10 is manufactured by a strip casting method which is a kind of rapid solidification method, a flaky alloy 10 is obtained, and the alloy 10 having the above-mentioned size is preferable because it is easy to manufacture.

<Hydrogenation process>
In the hydrogenation step, the rare earth-iron-based alloy 10 is heat-treated in a hydrogen-containing atmosphere at a temperature equal to or higher than the disproportionation temperature to produce a hydrogenated alloy 10h (second figure from the left in the lower part of FIG. 1). ).

The hydrogenated alloy 10h has a structure in which the main phase rare earth-iron-based compound is phase-decomposed into a rare earth element hydrogen compound phase and an iron-containing iron-containing phase. The structure of the hydrogenated alloy 10h, the presence form of both phases (described later), and the like are maintained in the hydrogenated powder 20 that has undergone the pulverization process. Here, the above-described structure and the like are not shown, and are shown in a diagram (a middle diagram in the lower part of FIG. 1) showing a hydrogenated powder 20 described later. Examples of the rare earth element hydrogen compound include NdH ₂ and SmH ₂ . Examples of the iron-containing material containing iron include both pure iron (Fe) and iron compounds such as Fe ₂ B and Fe ₂ C. The hydrogenated alloy 10h is deformed when it is compression-molded because pure iron (Fe), which is a soft soft part, is present in comparison with the rare earth-iron-based compound and the rare earth element hydrogen compound phase before phase decomposition. To improve moldability. However, even if the moldability can be improved, there are hard parts such as hydrogen compounds (NdH ₂ , SmH ₂ ) and iron compounds (Fe ₂ B, Fe ₂ C, etc.) of rare earth elements that are harder than pure iron. Therefore, conventionally, in order to increase the relative density, the molding pressure was increased in the molding process. On the other hand, although mentioned later in detail, the said hard part is softened by heating to a specific temperature at a formation process, and a moldability can be improved.

  The existence form of the phase of the rare earth element hydrogen compound and the phase of the iron-containing material is a layered form in which the phase of the rare earth element hydrogen compound and the phase of the iron-containing substance are laminated, or in the phase of the iron-containing substance. And a dispersed form in which a phase of a particulate rare earth element hydrogen compound is dispersed. These forms of existence depend on heat treatment conditions (mainly temperature) in the hydrogenation treatment described later. In the dispersed form, the formability of the iron-containing material is uniformly present around the rare earth element hydride phase, so that the moldability can be improved as compared with the layered form. Therefore, complex shaped powder compacts (magnet compacts) such as arcs, cylinders, columns, and pots, and a relative density of 80% or higher, 85% or higher, 90% or higher, especially 95% or higher. It is easy to obtain a compacted powder compact.

  The hydrogenated alloy 10h preferably has a structure composed of a rare earth element hydrogen compound phase of 10 volume% or more and less than 40 volume% and an iron-containing material phase containing iron. If the remainder of the rare earth element hydrogen compound phase is substantially an iron-containing material phase, and the iron-containing material phase is the main component (60 to 90 vol%), the moldability of the magnet powder Can be enhanced. The phase of the rare earth element hydrogen compound and the phase of the iron-containing material are adjacent to each other, and the interval between the phases of the rare earth element hydrogen compound adjacent to each other through the phase of the iron-containing material is preferably 3 μm or less. Since the phase of the iron-containing material exists between the phases of the rare earth element hydride and both phases exist at the specific intervals described above, both phases are uniformly present. Deforms.

  The above-mentioned distance measurement can be performed, for example, by etching the cross section to remove the phase of the iron-containing material and extracting the rare earth element hydride phase, or removing the rare earth element hydride phase depending on the type of solution. Then, the phase of the iron-containing material can be extracted, or the cross section can be measured by analyzing the composition with an EDX (energy dispersive X-ray analyzer). When the distance is 3 μm or less, excessive energy is input when the rare earth element hydride phase and the iron-containing material phase are recombined with the original rare earth-iron compound by dehydrogenation later. In addition, the deterioration of characteristics due to the coarsening of crystal grains of the rare earth-iron compound can be suppressed. In order for the iron-containing material phase to be sufficiently present between the phases of the rare earth element hydrogen compound, the distance is preferably 0.5 μm or more, and more preferably 1 μm or more. The interval can be controlled, for example, by adjusting the composition of the rare earth-iron alloy used as a raw material, or adjusting the conditions of the hydrogenation treatment, particularly the heat treatment temperature. For example, when the iron ratio (atomic ratio) is increased in the rare earth-iron-based alloy or the heat treatment temperature is increased within the above temperature range, the interval tends to increase.

  In the hydrogenated alloy 10h, as shown in the center diagram in the upper part of FIG. 1, the grain boundary phase 12 embrittles and the volume expansion occurs when the grain boundary phase 12 occludes hydrogen, and cracks (cracks) C occur in the grain boundary phase 12. Is generated and pulverized, but the rare earth-iron-based alloy 10 having a relatively large size is subjected to a hydrogenation treatment, and therefore, it is rarely pulverized finely. That is, as shown in the upper right diagram in FIG. 1, although the size of the hydrogenated alloy 10h is not uniform, fine particles are rarely generated. Even if the size of the hydrogenated alloy 10h is not uniform, the particle size of the magnet powder is controlled by mechanically grinding the hydrogenated alloy 10h in the subsequent grinding step.

The conditions of the hydrogenation treatment are, for example, atmosphere: H ₂ gas atmosphere, or mixed gas atmosphere of H ₂ gas and inert gas such as Ar or N ₂ , temperature: hydrogen disproportionation temperature of prepared alloy (material Although it depends, for example, 600 degreeC or more and 1100 degrees C or less), Holding time: 0.5 hour or more and 5 hours or less are mentioned. When the heat treatment temperature is set in the vicinity of the disproportionation temperature, the existence form of both phases becomes the layered form, and when the heat treatment temperature is set to a high disproportionation temperature + 100 ° C. or more, the existence form of both phases is It becomes a distributed form.

<Crushing process>
In the pulverizing step, the hydrogenated alloy 10h is mechanically pulverized to produce the magnet powder 40a including the hydrogenated powder 20 (lower center diagram in FIG. 1). Here, the magnet powder 40 a is composed of the hydrogenated powder 20.

  In the pulverization step, the hydrogenated alloy 10h is pulverized to a predetermined particle size, and the particle size of the hydrogenated powder 20 is controlled to the target particle size. In the pulverization step, the particles 21 of the hydrogenated powder 20 are easily controlled uniformly because they are mechanically pulverized. Specifically, the hydrogenated alloy 10h is pulverized to a medium particle size to produce a hydrogenated powder 20 having a particle size (75 μm or more and 355 μm or less) suitable for compression molding.

  Examples of the device for pulverizing the hydrogenated alloy 10h include a grinding pulverizer or a collision pulverizer. The grinding type pulverizer typically includes a brown mill, and the collision type pulverizer typically includes a pin mill. These apparatuses are suitable for pulverizing the hydrogenated alloy 10h to a medium particle size, and the particle size can be easily controlled.

  In order to suppress the oxidation of the hydrogenated alloy 10h (hydrogenated powder 20), the atmosphere at the time of pulverization is preferably set so that the oxygen concentration is 5% or less by volume. A more preferable oxygen concentration in the atmosphere is 1% or less by volume. Examples of such an atmosphere include an inert atmosphere (Ar atmosphere) or a reduced pressure atmosphere (a vacuum atmosphere of 10 Pa or less).

  The hydrogenated powder 20 obtained by mechanically pulverizing the hydrogenated alloy 10h has, for example, a ratio of medium-sized particles having a particle size of 75 μm or more and 355 μm or less of 90% by mass or more (preferably 95% by mass or more). is there. In the hydrogenated powder 20, the proportion of fine particles having a particle size of less than 75 μm is preferably 5% by mass or less, more preferably 3% by mass or less. The hydrogenated powder 20 preferably has a 50 volume% particle size (D50) of 100 μm or more and 500 μm or less and a 90 volume% particle diameter (D90) of 200 μm or more and 750 μm or less. Such a hydrogenated powder 20 is particularly excellent in moldability because the proportion of fine particles is small, the particle size is suitable for compression molding (75 μm to 355 μm), and the particle size of the particles 21 is uniform. Moreover, since the ratio of the fine particles contained in the hydrogenated powder 20 is small, the magnetic properties are hardly deteriorated due to oxidation of the fine particles. D50 is more preferably from 100 μm to 300 μm, and D90 is more preferably from 350 μm to 550 μm. The 50% by volume particle size (D50) is a particle size value at which accumulation is 50% from the small diameter side of the volume-based particle size distribution when measured by a laser diffraction particle size distribution measuring device, and is 90% by volume. The particle size (D90) is a particle size value at which accumulation is 90% from the small diameter side.

  Each particle 21 of the hydrogenated powder 20 substantially maintains the structure of the hydrogenated alloy 10h described above, the existence form of both phases, and the like. That is, each particle 21 of the hydrogenated powder 20 has a structure including a phase 22 of a rare earth element hydrogen compound of 10 volume% or more and less than 40 volume%, and a phase 23 of an iron-containing material containing iron as the balance. The phase 22 of the rare earth element hydride is granular and has a dispersed form in which it is dispersed in the phase 23 of the iron-containing material. The phase 22 of the rare earth element hydride and the phase 23 of the iron-containing substance are adjacent to each other, and the interval between the phases 22 of the rare earth element hydride adjacent to each other through the phase 23 of the iron-containing substance is 3 μm or less. It is.

(Molding process)
In the molding step, the hydrogenated powder 20 (magnet powder 40a) is compression-molded to produce a powder compact (magnet compact) 50a (fourth figure from the lower left in FIG. 1).

In the forming step, the magnet powder 40a is heated. The heating temperature is set to a temperature at which the hard portion (NdH ₂ , SmH ₂ , Fe ₂ B, Fe ₂ C, etc.) in the magnet powder 40a is softened to improve the moldability of the magnet powder 40a. For example, the heating temperature may be 250 ° C. or higher. The higher the heating temperature is, the easier it is to soften the hard part. However, if the heating temperature is too high, the productivity decreases because the time for heating the magnet powder 40a and the time for cooling the powder compact 50a after molding become longer. I will let you. Therefore, the heating temperature is set to 600 ° C. or lower. The heating temperature is preferably 300 ° C. or higher. The magnet powder 40a can be heated, for example, by heating a mold to be used.

The molding pressure on the magnet powder 40a can be lowered by heating the magnet powder 40a as described above. Specifically, the molding pressure can be 588 MPa (6 ton / cm ² ) or less. Even when the molding pressure is 588 MPa or less, the powder compact 50a having a high relative density can be obtained. Specifically, the relative density can be 80% or more, more preferably 85% or more, 90% or more, and particularly 95%. This molding pressure can be 540 MPa or less, and further 490 MPa or less. The molding pressure is preferably 392 MPa or more.

  In order to suppress the oxidation of the magnet powder 40a (powder compact 50a), the atmosphere at the time of compression molding is an inert atmosphere in which the oxygen concentration is 5% or less by volume, and further 1% or less, as in the pulverization step. Ar atmosphere) or reduced pressure atmosphere (vacuum atmosphere of 10 Pa or less) is preferable.

  For molding, a mold 90 having a desired shape may be used. The mold 90 typically includes a die 91 having a through hole and a pair of upper and lower punches that form a molding space together with the inner peripheral surface of the die 91 and insert into the through hole to compress the magnet powder 40a. 92, 93. When molding a cylindrical or annular powder compact having a through hole, a rod (not shown) inserted into the through hole of the die 91 is used. In the molding process, the magnet powder 40a is heated to increase the moldability, and the relative density can be increased even at a low molding pressure. Therefore, lubrication to reduce friction with the mold during molding and demolding. It is not necessary to use an agent or a release agent. In that case, even if heat treatment (dehydrogenation treatment) is performed after molding, carbides associated with the use of a lubricant, a mold release agent, and the like are not generated, so that it is possible to prevent a decrease in magnetic properties due to carbide generation.

[Effects of manufacturing method of magnet compact]
According to the method for producing a molded body for magnets of Embodiment 1, a hydrogenated powder obtained by pulverizing a rare earth-iron alloy after hydrogenation treatment is heated to 250 ° C. or more and 600 ° C. or less, so that the molding is as low as 588 MPa or less. A magnet molded body having a high relative density can be produced even by compression molding with pressure. This is because (1) a hydrogenated powder having a small variation in particle size can be produced by pulverizing a rare earth-iron-based alloy after the hydrogenation treatment. (2) This hydrogenated powder is used as a raw material for a compact for a magnet. Therefore, it is possible to sufficiently transfer the molding pressure to the hydrogenated powder at the time of compression molding because the variation in particle size is small. (3) Hydrogenation by heating the hydrogenated powder to 250 ° C. or more and 600 ° C. or less at the time of compression molding. This is because the hard part (NdH ₂ , Fe ₂ B, etc.) contained in the powder can be softened, so that the moldability of the hydrogenated powder can be improved. Thus, by reducing the molding pressure when producing a magnet compact having a high relative density, it is possible to suppress the wear of the mold as in the case of compression molding at a high pressure.

[Magnet compact (powder compact)]
The magnet compact (powder compact) 50a is obtained by compression molding the above-described magnet powder 40a (fourth diagram from the lower left in FIG. 1). Since the magnet powder 40a has a small variation in particle size and excellent moldability, and the moldability can be further improved by the above-described molding process, even if the molding pressure during compression molding is relatively small as described above, Thus, a magnet compact 50a having a high density can be obtained. For example, the magnet compact 50a having a relative density of 80% or more is obtained. The relative density of the magnet molded body 50a is more preferably 85% or more, further 90% or more, and particularly 95% or more. The higher the relative density of the magnet compact 50a (the magnetic member 60a described later), the higher the density of the rare earth magnet, and the more the magnetic properties can be improved. The relative density is an actual density (percentage of [apparent density of magnet compact / true density of magnet compact]) with respect to the true density.

[Magnetic member]
The magnetic member 60a is obtained by heat-treating the magnet compact 50a at a temperature equal to or higher than the recombination temperature in an inert atmosphere or a reduced-pressure atmosphere (lower right diagram in FIG. 1). That is, when manufacturing the magnetic member 60a, in addition to the above-described manufacturing process of the magnet molded body, a dehydrogenation process of dehydrogenating and recombining the magnet molded body 50a is provided. If the magnet compact 50a is used, a magnetic member 60a having a relative density of 80% or more can be obtained, thereby obtaining a high-density rare earth magnet. In addition, the relative density of the magnetic member 60a may be improved by the heat treatment in the dehydrogenation process as compared with the relative density of the magnet molded body 50a. The magnet powder 40a (magnet compact 50a) is in a state of being phase-decomposed into the phase 22 of the rare earth element hydrogen compound and the phase 23 of the iron-containing material by the hydrogenation treatment (center view in FIG. 1), and is dehydrogenated. Thus, it recombines with the original rare earth-iron compound. That is, the magnetic member 60a is formed of a rare earth-iron alloy having the same rare earth-iron compound as the raw material as a main phase.

(Dehydrogenation process)
The conditions for the dehydrogenation treatment are, for example, atmosphere: non-hydrogen atmosphere (inert gas atmosphere such as Ar or N ₂ or reduced-pressure atmosphere (for example, vacuum atmosphere whose pressure is lower than the standard atmospheric pressure)), temperature: hydrogenated alloy (For example, 600 ° C. to 1000 ° C.) and holding time: 10 minutes to 600 minutes. In particular, a reduced-pressure atmosphere (for example, the degree of vacuum is 100 Pa or less, the final degree of vacuum is 10 Pa or less, and further 1 Pa or less) is preferable because rare earth element hydrogen compounds hardly remain. By setting it as the said temperature, the growth of the crystal | crystallization of a recombination alloy is suppressed and a fine crystal structure is obtained. The dehydrogenation process can be performed in a state where a strong magnetic field (for example, 4T or more) is applied to the magnet compact 50a. If it does so, the orientation of a recombination alloy can be raised and by extension, the orientation of the molded object 50a for magnets can be raised.

(Nitriding process)
Depending on the alloy composition, the magnetic member 60a may be subjected to nitriding by heat treatment at a temperature equal to or higher than the nitriding temperature in a nitrogen-containing atmosphere. In this case, in addition to the manufacturing process of the magnetic member described above, a nitriding process of nitriding the magnetic member 60a is provided. The nitrogen-containing atmosphere is an atmosphere containing nitrogen element, for example, an atmosphere containing at least one of nitrogen (N ₂ ) and ammonia (NH ₃ ) as will be described later. For example, when the magnetic member 60a is formed of an Sm—Fe based alloy, the Sm—Fe based alloy can be changed to an Sm—Fe—N based alloy by nitriding.

Nitriding conditions include, for example, nitrogen-containing atmosphere: NH ₃ gas atmosphere, mixed gas atmosphere of NH ₃ gas and H ₂ gas, N ₂ gas atmosphere, or mixed gas atmosphere of N ₂ gas and H ₂ gas, temperature : 200 ° C. or more and 550 ° C. or less, preferably 300 ° C. or more and 450 ° C. or less, Holding time: 10 minutes or more and 1000 minutes or less, preferably 30 minutes or more and 800 minutes or less. Nitriding can be performed with a magnetic field applied. By applying a magnetic field, it is easy to stretch the crystal lattice in one direction, and nitrogen atoms are preferentially penetrated between the stretched iron atoms-iron atoms, so that an ideal stoichiometric composition (eg, Sm ₂ Fe ₁₇ N ₃ ) It is easy to obtain rare earth magnets. The magnitude | size of the magnetic field to apply is 3T or more.

[Rare earth magnet]
The rare earth magnet is obtained by magnetizing the magnetic member 60a. The rare earth magnet is made of a rare earth-iron alloy, and has a relative density of 80% or more, for example. The relative density of the rare earth magnet depends on the relative density of the magnet compact 50a (magnetic member 60a) used as a raw material, although a slight increase is observed due to heat shrinkage caused by heat treatment (dehydrogenation treatment) after molding. The relative density of the magnet molded body 50a is substantially maintained. The relative density of the rare earth magnet is preferably 85% or more, more preferably 90% or more, and particularly preferably 95% or more. When the rare earth element contains Nd, the specific composition of the rare earth-iron alloy forming the rare earth magnet is the same as the composition of the rare earth-iron alloy 10 of the raw material described above, and when the rare earth element contains Sm, Sm—Fe—N alloys (eg, Sm ₂ Fe ₁₇ N ₃ ), Sm—Ti—Fe—N (eg, Sm ₁ Ti ₁ Fe ₁₁ N ₂ ), Sm—Mn—Fe—N and the like can be mentioned.

[Embodiment 2]
[Method for producing magnet compact]
As Embodiment 2, with reference to FIG. 2, the manufacturing method which manufactures the compact 50b for magnets using the mixed powder containing the anisotropic powder 30 in addition to the hydrogenated powder 20 of Embodiment 1 as the powder 40b for magnets. Will be explained. When the anisotropic powder 30 is included as the magnet powder 40b, a magnet compact 50b can be produced from which a rare earth magnet having excellent magnetic properties can be obtained. However, since the anisotropic powder 30 is inferior in plastic deformability compared to the hydrogenated powder 20, in the method for manufacturing a molded article for magnets of this embodiment, the hydrogenated powder 20 having excellent plastic deformability is replaced with the anisotropic powder 30. Used as a binding material. Hereinafter, a description will be given focusing on differences from the first embodiment.

(Magnet powder preparation process)
In the magnet powder preparation step, a magnet powder 40 b including a mixed powder of the hydrogenated powder 20 and the anisotropic powder 30 is prepared. Specifically, a hydrogenated powder preparing step for preparing the hydrogenated powder 20, an anisotropic powder preparing step for preparing the anisotropic powder 30, and a mixed powder of the hydrogenated powder 20 and the anisotropic powder 30 are prepared. And a mixing step for producing the magnet powder 40b.

<Hydrogen powder preparation process>
The preparation of the hydrogenated powder 20 can be performed through the same raw material alloy preparation process, hydrogenation process and pulverization process as in the first embodiment.

<Anisotropic powder preparation process>
The anisotropic powder 30 prepared in this step is a powder having crystal magnetic anisotropy. Having crystal magnetic anisotropy means that the ratio Br / Js of the residual magnetization Br (T) of the anisotropic powder to the saturation magnetization Js (T) of the anisotropic powder is the crystal orientation degree of the anisotropic powder. In this case, it means that the degree of crystal orientation of this anisotropic powder is 70% or more. The higher the degree of crystal orientation, the better the magnetic anisotropy and the rare-earth magnet with excellent magnetic properties. The degree of crystal orientation of the anisotropic powder is preferably 75% or more, 80% or more, 85% or more, further 87% or more, and more preferably 90% or more. The degree of crystal orientation of the anisotropic powder can be measured using a vibrating sample magnetometer (VSM-5 type manufactured by Toei Kogyo Co., Ltd.). For example, the magnetization curve (BH curve) is measured with a vibrating sample magnetometer, and the degree of orientation can be calculated from the ratio of the magnetization of 2300 kA / m as the saturation magnetization Js and the residual magnetization Br.

Examples of the constituent material of the anisotropic powder 30 include a rare earth-iron alloy having a rare earth-iron compound containing a rare earth element and an iron group element as a main phase. The types of rare earth elements, the types and contents of iron group elements, the types and contents of elements other than rare earth elements and iron group elements, and the types and contents of other additive elements in the rare earth-iron-based alloy are the same as in Embodiment 1. This is the same as the rare earth-iron alloy 10. The rare earth element content may be 10% by volume or more and less than 40% by volume. The specific composition of the rare earth-iron alloy is the same as that of the rare earth-iron alloy 10 of the first embodiment, such as an Nd—Fe—B alloy (eg, Nd ₂ Fe ₁₄ B), Nd—Fe—C alloy ( Example, Nd ₂ Fe ₁₄ C), Nd—Fe—Co—B alloy (eg, Nd ₂ (Fe ₁₃ Co ₁ ) B), Nd—Fe—Co—C alloy (eg, Nd ₂ (Fe ₁₃ Co ₁ )) C).

  The anisotropic powder 30 may have a form in which all of the anisotropic powders are composed of substantially the same composition, that is, a form in which the anisotropic particles constituting the anisotropic powder are all composed of a single composition, or a plurality of different compositions. Or can be configured as

  The average crystal grain size of the rare earth-iron alloy particles 31 constituting the anisotropic powder 30 is 700 nm or less. When the average crystal grain size is as fine as 700 nm or less, an effect of improving magnetic properties (particularly coercive force) due to the fine crystal structure can be expected. The smaller the average crystal grain size, the closer to the single domain particle critical diameter and the better the magnetic properties. The average crystal grain size is preferably 500 nm or less, more preferably 300 nm or less. The average crystal grain size of the anisotropic powder 30 is measured as follows. The surface or cross section (observation surface) of the anisotropic powder 30 is observed with a scanning electron microscope (SEM), the area of each crystal grain is examined from the observed image, and the average equivalent circle diameter of each area is the average crystal grain diameter. And When calculating using an observation image, it can be easily calculated using commercially available image processing software.

  As for the average particle diameter of the anisotropic powder 30, 3 micrometers or more and 500 micrometers or less are mentioned. When the particle 31 of the anisotropic powder 30 has a large particle size, the deterioration of the magnetic properties due to surface layer oxidation can be suppressed. Therefore, when a particle having a relatively large particle size is provided, a rare earth magnet having excellent magnetic properties can be obtained. The average particle diameter is preferably 30 μm or more and 400 μm or less, more preferably 50 μm or more and 350 μm or less, and particularly preferably 100 μm or more and 300 μm or less. The average particle diameter of the anisotropic powder 30 refers to a 50 volume% particle diameter (D50).

  The average particle diameter of the anisotropic powder 30 and the average particle diameter of the hydrogenated powder 20 can be the same or different. If the average particle sizes of both powders 20 and 30 are about the same (difference in average particle size is about 50 μm or less), it is considered that they are easily mixed uniformly in the mixing step described later.

  When the rare earth element contains Nd, the anisotropic powder 30 is an HDDR (Hydrogen Deposition Decomposition Recombination) with specific conditions of hydrogen pressure and temperature for the rare earth-iron alloy powder having the above composition containing Nd. It can be manufactured by processing. As such specific HDDR processing conditions, known conditions can be used. The rare earth-iron-based alloy powder can be manufactured using, for example, a known powder manufacturing method such as a strip casting method or an atomizing method. Or the anisotropic powder 30 can be manufactured by performing the process which combined hot processing, such as hot press and hot foam, to the powder produced by the melt span method, for example.

<Mixing process>
In the mixing step, a magnet powder 40b including a mixed powder obtained by mixing the hydrogenated powder 20 and the anisotropic powder 30 is produced. As the blending ratio of the anisotropic powder 30 in the mixed powder is larger, the magnet compact 50b (magnetic member 60b) having a higher ratio of the anisotropic powder 30 is obtained. As a result, a rare earth magnet having a high proportion of the anisotropic powder 30 is obtained. Therefore, the blending ratio of the anisotropic powder 30 is preferably a majority, specifically, more than 50% by mass ratio. The blending ratio of the anisotropic powder 30 is 60% or more, more preferably 70% or more, and further preferably 75% or more by mass ratio. If the blending ratio of the anisotropic powder 30 is too large, the hydrogenated powder 20 serving as a binder becomes relatively small, and the particles 31 of the anisotropic powder 30 may not be sufficiently bonded. Therefore, the blending ratio of the anisotropic powder 30 is preferably 95% or less, and more preferably 90% or less. If the blending ratio of the hydrogenated powder 20 is 5% or more by mass ratio, the anisotropic powders 30 can be sufficiently bonded together. The blending ratio of the anisotropic powder 30 is maintained at the ratio of the anisotropic powder 30 contained in the obtained magnet compact 50b (magnetic member 60b).

(Molding process)
In the molding step, the magnet powder 40b is compression molded to produce a magnet compact 50b. In the molding step, the magnet powder 40b is heated to the same heating temperature (250 ° C. or higher and 600 ° C. or lower) as in the first embodiment, and compression molding is performed at the same molding pressure (588 MPa or lower) as in the first embodiment.

  Since the magnet powder 40b includes the anisotropic powder 30, the molding step is preferably performed in a state where a magnetic field is applied to the magnet powder 40b (anisotropic powder 30). Then, the particles 31 of the anisotropic powder 30 having magnetocrystalline anisotropy are arranged in the mold 90 by rotating according to the application direction of the magnetic field. Therefore, the magnet compact 50b having excellent orientation can be obtained, and as a result, a rare earth magnet (anisotropic magnet) having excellent orientation can be produced. When the orientation direction of the anisotropic powder 30 is substantially aligned in one direction at the time of molding, a rare earth magnet having excellent orientation can be produced without applying a strong magnetic field as described above during the dehydrogenation treatment. Therefore, it is easy to control the dehydrogenation process. Moreover, when shape | molding in the application of a magnetic field and improving orientation, since each particle | grain 31 of the anisotropic powder 30 is easy to arrange without unevenness, it is easy to improve orientation. That is, a rare earth magnet having excellent magnetic properties can be produced with high productivity. It is preferable to start the application of the magnetic field in a normal temperature state before heating the magnet powder 40b to the above-described temperature. This makes it easy to align the alignment direction in one direction.

  The magnitude of the applied magnetic field is preferably 0.5 T or more. The larger the applied magnetic field, the higher the orientation and the rare earth magnet having excellent magnetic properties. The magnitude of the applied magnetic field is preferably 1.5 T or more. The magnitude of the applied magnetic field is about 10T or less. For the application of the magnetic field, either a normal conducting magnet having a normal conducting coil or a superconducting magnet having a superconducting coil can be used. The application direction of the magnetic field can be selected as appropriate. In the fourth diagram from the left in the lower part of FIG. 2, the direction in which the magnetic field is applied is indicated by a one-dot chain line arrow. Here, the case where the application direction of the magnetic field is orthogonal to the compression direction (the vertical direction here) is illustrated.

  As in the first embodiment, a mold 90 including a die 91 and a pair of upper and lower punches 92 and 93 may be used for molding. A magnet (not shown) for applying a magnetic field is disposed around the mold 90.

[Effects of manufacturing method of magnet compact]
According to the method for manufacturing a molded article for magnets of Embodiment 2, a hydrogenated powder obtained by pulverizing a rare earth-iron alloy after hydrogenation treatment while the magnet powder contains an anisotropic powder inferior in plastic workability. Therefore, by heating the magnet powder to 250 ° C. or more and 600 ° C. or less, a compact for magnet having a high relative density can be produced even if compression molding is performed at a low molding pressure such as 588 MPa or less.

[Magnet compact (powder compact)]
A magnet compact (powder compact) 50b is obtained by compression-molding the above-described magnet powder 40b (fourth diagram from the lower left in FIG. 2), and the anisotropic powder 30 is bonded by the hydrogenated powder 20. Has been configured. The hydrogenated powder 20 of the magnet powder 40b has a small variation in particle size and excellent moldability, and can be bonded to the anisotropic powder 30. Moreover, the moldability and bondability of the hydrogenated powder 20 can be further enhanced by the above-described molding process. Therefore, even if the molding pressure during compression molding is relatively small as described above, a high-density magnet molded body 50b can be obtained. For example, the magnet compact 50b having a relative density of 80% or more is obtained.

[Magnetic member]
The magnetic member 60b is obtained by subjecting the produced magnet compact 50b to a dehydrogenation process to change the hydrogenated alloy 10h constituting the hydrogenated powder 20 to a recombination alloy such as the rare earth-iron alloy 10. . That is, when manufacturing the magnetic member 60b, in addition to the above-described manufacturing process of the magnet molded body, a dehydrogenation process of dehydrogenating and recombining the magnet molded body 50b is provided. The dehydrogenation conditions can be the same as the dehydrogenation conditions of the first embodiment. By passing through this process, the magnetic member 60b in which the particles 31 of the anisotropic powder 30 are bonded by a recombination alloy instead of a hydrogenated alloy is obtained. Through this bonding step, the hydrogenated powder 20 constituting the magnet compact 50b is changed to a magnetic component (for example, a recombination alloy such as an Nd—Fe—B alloy), which is substantially magnetic. The magnetic member 60b comprised only with a component is obtained.

[Test Example 1]
Sample No. of molded body for magnet 1-1 to 1-7 and 1-101 were prepared, and the relative density of each sample was measured. Thereafter, a magnetic member was prepared using each sample, and the magnetic characteristics of each sample were evaluated.

[Sample No. 1-1 to 1-7]
Sample No. of molded body for magnet 1-1 to 1-7 were prepared in the order of raw material alloy preparation step → hydrogenation step → pulverization step → molding step.

  First, as a raw material alloy, an ingot of an Nd—Fe—B alloy having a particle size of 0.5 mm to 30 mm and a composition of 32.0 mass% Nd-1.0 mass% B—the balance being Fe and inevitable impurities ( A small piece) was prepared.

  Next, the raw material alloy was subjected to hydrogenation treatment to produce a hydrogenated alloy. The hydrogenation treatment was performed using a vacuum heat treatment furnace under conditions of 850 ° C. × 3 hours in a hydrogen atmosphere.

  Next, the hydrogenated alloy was pulverized to produce a hydrogenated powder. This pulverization was performed using a mortar made of cemented carbide so that the average particle diameter (D50) of the hydrogenated alloy was approximately 150 μm. When the volume particle size distribution of the obtained hydrogenated powder was measured by a laser diffraction particle size distribution analyzer, D10 was 100 μm, D50 was 150 μm, and D90 was 260 μm. Note that “D10” is a particle size value (10 vol% particle size) at which accumulation is 10% from the small diameter side in the volume particle size distribution. Further, when the ratio of particles having a particle diameter of less than 75 μm was determined, the ratio was 2% by mass, and when the ratio of particles having a particle diameter of 75 μm or more and 355 μm or less was determined, the ratio was 98% by mass. .

  Next, hydrogenated powder (magnet powder) was filled into a mold, compression-molded, and sample No. of a cylindrical powder compact (magnet compact) having a diameter of about 10 mm and a height of about 10 mm. 1-1 to 1-7 were produced. The compression molding was performed at a temperature and a molding pressure shown in Table 1, with the atmosphere being a vacuum.

[Sample No. 1-101]
Except that the order of performing the hydrogenation step and the pulverization step was changed, the sample No. In the same manner as in 1-1, the sample No. 1-101 was produced. That is, sample no. The magnet molded body of 1-101 was produced through a raw material alloy preparation step → crushing step → hydrogenation step → forming step.

  The volume particle size distribution of the alloy powder obtained by the pulverization process is shown in Sample No. When measured in the same manner as 1-1, D10 was 180 μm, D50 was 335 μm, and D90 was 400 μm.

  When the volume particle size distribution of the hydrogenated powder obtained by hydrogenating the alloy powder in the hydrogenation step was measured in the same manner, D10 was 95 μm, D50 was 138 μm, and D90 was 275 μm. Further, when the ratio of particles having a particle diameter of less than 75 μm was determined, the ratio was 7.5% by mass, and when the ratio of particles having a particle diameter of 75 μm or more and 355 μm or less was determined, the ratio was 92.5 mass. %Met.

  Using this hydrogenated powder, Sample No. Sample No. 1 of a powder compact (magnet compact) of the same size as in 1-1. 1-101 was produced. The compression molding was performed at a temperature and a molding pressure shown in Table 1, with the atmosphere being a vacuum.

[Measurement of relative density]
The relative density of the magnet molded body of each of the samples 1-1 to 1-7 and 1-101 was determined from the percentage of “apparent density of the magnet molded body / true density of the magnet molded body”. The apparent density of the magnet compact was calculated from the size and mass. The true density of the magnet compact was the true density (7.5 g / cm ³ ) of the Nd—Fe—B alloy. Table 1 shows the density and relative density of each sample.

[Evaluation of magnetic properties]
Demagnetization treatment was performed on the magnet compacts of Samples 1-1 to 1-7 and 1-101 to produce magnetic members. The dehydrogenation treatment was performed by switching the atmosphere in the vacuum heat treatment furnace from a hydrogen atmosphere to a vacuum atmosphere, and in a vacuum atmosphere at 800 ° C. for 3 hours. The degree of vacuum in the vacuum atmosphere was set to less than 0.5 Pa.

After magnetizing the magnetic member of each sample with a pulse magnetic field of 3.5 T, the magnetic properties were examined. The magnetic characteristics are obtained by using a BH tracer (DCBH tracer manufactured by Riken Denshi Co., Ltd.), the residual magnetic flux density Br (T), the maximum value of the product of the magnetic flux density B and the magnitude H of the demagnetizing field, that is, the maximum energy product (BH ) Max (kJ / m ³ ) was examined. The results are shown in Table 1.

  As shown in Table 1, the magnet powder prepared by pulverization after the hydrogenation treatment was heated to 250 ° C. or more and 600 ° C. or less and subjected to compression molding. The magnet compacts 1-1, 1-4, and 1-5 had a relative density of 80% or more while the molding pressure was 588 MPa or less. This sample No. 1-1, 1-4, and 1-5 have high residual magnetic flux density Br and maximum energy product (BH) max, and were found to be excellent in magnetic characteristics.

  On the other hand, Sample No. No. 1 was compression-molded at room temperature without heating the magnet powder produced by pulverization after hydrogenation. 1-2 shows the molding pressure of sample No. 1-2. When the pressure was 588 MPa or less as in 1-1, the magnet powder was not hardened, and a magnet compact was not obtained. Sample No. Sample No. 1 compression-molded at room temperature as in 1-2. In 1-3, compression molding was carried out with the molding pressure as high as before (980 MPa), and a magnet compact having a relative density of about 80% was obtained. Sample 1-3 was found to have a high residual magnetic flux density Br and a maximum energy product (BH) max, and excellent magnetic properties. However, since the molding pressure is too high, the mold is considered to be easily worn. From this result, when the magnet powder produced by pulverization after the hydrogenation treatment is molded, if it is heated to 250 ° C. or more and 600 ° C. or less, the molding pressure is 600 MPa or less, and further 590 MPa or less, thereby suppressing the wear of the mold. In addition, it is considered that a molded article for a magnet having a high relative density can be produced.

  The magnet powder obtained by hydrating the alloy powder obtained by pulverization was heated to 250 ° C. or higher and 600 ° C. or lower to prepare a magnet compact. Sample No. 1-101, which has a high relative density, produced a magnet compact under the same molding conditions. Compared with 1-5, the relative density was low. Sample No. No. 1-101 was obtained by subjecting the pulverized alloy powder to a hydrogenation treatment, and the proportion of fine powder having a particle size of less than 75 μm as described above was changed to Sample No. It is thought that it increased compared with 1-5. Therefore, sample no. Compared to 1-5, it is considered that the relative density is low. For this reason, when the raw material powder is heated to 250 ° C. or higher and 600 ° C. or lower to form a molded body for a magnet, if this molding process is performed under the same conditions, the raw material powder includes a magnet pulverized after hydrogenation It is thought that the relative density can be increased by using the powder for use compared with the case of using the magnet powder that has been hydrogenated after pulverization.

  The method for producing a molded body for magnet according to the present invention can be suitably used for producing a material for a rare earth magnet used for a permanent magnet or the like. A magnet molded body manufactured by the method for manufacturing a magnet molded body of the present invention and a magnetic member obtained by using the magnet molded body are permanent magnets such as various motors, in particular, hybrid cars and hard disk drives. It can utilize suitably for the raw material of the permanent magnet used for the high-speed motor with which it is equipped.

DESCRIPTION OF SYMBOLS 10 Rare earth-iron type alloy 10h Hydrogenated alloy 11 Main phase 12 Grain boundary phase C Crack 20 Hydrogenated powder 21 Particle of hydrogenated powder 22 Phase of hydrogen compound of rare earth element 23 Phase of iron-containing material 30 Anisotropic powder 31 Different Isotropic powder particles 40a, 40b Magnet powder 50a, 50b Powder compact (magnet compact)
60a, 60b Magnetic member 90 Die 91 Die 92 Upper punch 93 Lower punch 100 Rare earth-iron alloy 101 Main phase 102 Grain boundary phase C crack 120 Alloy powder 121 Alloy powder particle 140 Hydrogenated powder (magnet powder)
141 Particles of hydrogenated powder (magnet powder) 150 Powder compact (magnet compact)
160 Magnetic members

Claims (8)

A hydrogenation step of producing a hydrogenated alloy obtained by hydrotreating a rare earth-iron-based alloy at a temperature equal to or higher than the disproportionation temperature in an atmosphere containing hydrogen;
Crushing step of mechanically crushing the hydrogenated alloy to produce a hydrogenated powder;
A molding step of compressing and molding a powder for a magnet that is a mixed powder including the hydrogenated powder and an anisotropic powder satisfying the following configurations (a) to (c),
The said shaping | molding process is a manufacturing method of the molded object for magnets performed with the shaping | molding pressure of 588 MPa or less in the state which heated the said powder for magnets to 250 degreeC or more and 600 degrees C or less.
(A) containing 10% by volume or more and less than 40% by volume of a rare earth element, an iron group element, and at least one element selected from B, C, and N (b) an average crystal grain size of 700 nm or less (c ) The average particle size is 3μm or more and 500μm or less   The method for producing a molded body for a magnet according to claim 1, wherein a degree of crystal orientation of the anisotropic powder is 70% or more.   The magnet forming body according to claim 1 or 2, wherein the forming step is performed in a state in which a magnetic field of 0.5 T or more is applied to the magnet powder and the orientation direction of the anisotropic powder is aligned. Production method. The hydrogenated alloy is
10% by volume or more and less than 40% by volume of a rare earth element hydrogen compound phase, and the balance consisting of an iron-containing material phase,
The rare earth element hydrogen compound phase and the iron-containing material phase are adjacent to each other;
The method for producing a molded body for a magnet according to any one of claims 1 to 3, wherein an interval between phases of the hydrogen compound of the rare earth element adjacent to each other through the phase of the iron-containing material is 3 µm or less. The phase of the rare earth element hydrogen compound is granular,
The method for producing a molded body for a magnet according to claim 4, wherein a phase of the particulate hydrogen compound of the rare earth element is dispersed in the phase of the iron-containing material.   The method for producing a molded body for a magnet according to any one of claims 1 to 5, wherein the D50 particle size of the hydrogenated powder is 100 µm or more and 500 µm or less.   The said shaping | molding process is a manufacturing method of the molded object for magnets of any one of Claims 1-6 performed in the atmosphere whose oxygen concentration is 1 volume% or less. The method for producing a molded body for a magnet according to any one of claims 1 to 7, wherein a blending ratio of the anisotropic powder in the mixed powder is more than 50% and not more than 95% by mass ratio.

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