JP5051270B2 - Powder for magnetic member, powder molded body, and magnetic member - Google Patents

Description

  The present invention relates to a magnetic member suitable for a rare earth magnet material such as a rare earth-iron-boron magnet, a powder for a magnetic member used as a raw material for the magnetic member, and a powder compact. In particular, the present invention relates to a powder for a magnetic member that is excellent in moldability and hardly oxidizes.

  Rare earth magnets are widely used as permanent magnets used in motors and generators. The rare earth magnet is typically a sintered magnet or a bond magnet made of an R—Fe—B alloy (R: rare earth element, Fe: iron, B: boron) such as Nd (neodymium) -Fe—B.

  Sintered magnets are manufactured by compressing and then sintering R-Fe-B alloy powder, and bonded magnets are a mixture of R-Fe-B alloy powder and binder resin. The mixture is produced by compression molding or injection molding. In particular, powders used for bonded magnets may be subjected to HDRR treatment (Hydrogenation-Disproportionation-Desorption-Recombination, HD: hydrogenation and disproportionation, DR: dehydrogenation and recombination) to increase the coercive force. Has been done.

  Sintered magnets have excellent magnetic properties due to the high density of the magnetic phase, but have a low degree of freedom in shape, for example, to form complex shapes such as cylindrical shapes, columnar shapes, and pot shapes (bottomed tubular shapes). In the case of a complicated shape, it is necessary to cut the sintered material. On the other hand, although a bonded magnet has a high degree of freedom in shape, it is inferior in magnet characteristics to a sintered magnet. On the other hand, in Patent Document 1, the alloy powder made of the Nd-Fe-B alloy is made fine, and the green compact (powder compact) obtained by compression molding the alloy powder is subjected to the HDDR treatment. It is disclosed that a magnet having excellent magnet characteristics can be obtained in addition to increasing the degree of freedom of shape.

JP 2009-123968

  As described above, the sintered magnet has excellent magnet characteristics, but the degree of freedom in shape is small, and the bond magnet has high degree of freedom in shape, but the presence of the binder resin makes the magnetic phase density at most 80% by volume. It is difficult to improve the density of the magnetic phase. Therefore, it is desired to develop a magnetic material such as a rare earth magnet that has a high magnetic phase density and can be easily manufactured even in a complicated shape.

  In order to obtain a rare earth magnet having a high magnetic phase density without sintering, for example, it is conceivable to produce a powder compact having a high relative density as a raw material. However, the alloy powder made of an Nd-Fe-B alloy as disclosed in Patent Document 1 and the powder obtained by subjecting this alloy powder to HDDR treatment have high rigidity of the particles constituting the powder and are difficult to deform. . Therefore, in producing a powder compact having a high relative density, a relatively large pressure is required during compression molding. In particular, if the particles constituting the alloy powder are coarse, a larger pressure is required. Therefore, it is desired to develop a raw material that can easily form a powder compact having a high relative density.

  Further, as described in Patent Document 1, when the green compact is subjected to the HDDR treatment, the green compact may be collapsed due to expansion and contraction of the green compact during the treatment. Accordingly, it is desired to develop a raw material and a material that are difficult to disintegrate during production, have sufficient strength, and can obtain a magnetic material such as a rare earth magnet having excellent magnet characteristics.

  Furthermore, rare earth elements are easily oxidized and it is very difficult to remove oxygen from the oxide. If a rare earth element oxide produced during production is present in a magnetic material such as a rare earth magnet, the magnetic phase is lowered. Therefore, it is desired to develop a raw material that is difficult to oxidize when the magnetic material is manufactured.

  Accordingly, one of the objects of the present invention is to provide a powder for a magnetic member that is excellent in moldability and has a high relative density, and that is difficult to oxidize.

  Another object of the present invention is to provide a magnetic member suitable for a rare earth magnet material made of a rare earth-iron-boron alloy having excellent magnet characteristics, and a powder compact suitable for the material of this magnetic member. is there.

  In order to increase the density of the magnetic phase without sintering and to obtain a magnetic member suitable for a magnetic material such as a rare-earth magnet, the present inventors do not use a bonding resin as in a bonded magnet. The use of powder compacts was studied. As described above, conventional raw material powders, that is, alloy powders made of Nd-Fe-B alloys, and processed powders obtained by applying HDDR treatment to these alloy powders are hard, have low deformability, and are molded during compression molding. It is difficult to improve the density of the powder compact. Therefore, as a result of various investigations to improve the formability, the present inventors have found that a rare earth element is not a state in which the compound is formed like a rare earth-iron-boron alloy, that is, a state in which the rare earth element and iron are combined. If the powder has a structure in which the iron component and iron-boron alloy component are present independently of the rare earth element component, the powder molded body has high deformability, excellent formability, and high relative density. I got the knowledge that Further, the knowledge that the powder having the above specific structure can be produced by subjecting the alloy powder made of a rare earth-iron-boron alloy to a specific heat treatment, specifically, a heat treatment in an atmosphere containing hydrogen. Obtained. Then, by applying a specific heat treatment to the powder compact obtained by compression molding the obtained powder, a compact was produced using the processed powder subjected to the HDDR treatment or when the green compact was subjected to the HDRD treatment. The knowledge that a magnetic member similar to the case can be obtained was obtained. In particular, by using a magnetic member obtained from a powder molded body having a high relative density, a rare earth magnet having a high magnetic phase density and excellent magnet characteristics, specifically, a rare earth-iron-boron alloy magnet can be obtained. And gained knowledge.

  Here, when a powder containing the above-described iron component or iron-boron alloy component is compression-molded, a new surface is formed on each magnetic particle constituting the powder by the pressure during the molding. There is a rare earth element hydrogen compound in each of the magnetic particles, and the rare earth element hydrogen compound exposed on the new surface is oxidized, so that the new surface may be oxidized. In order to prevent the oxidation, for example, it is conceivable to perform molding in a non-oxidizing atmosphere. However, since it is necessary to arrange a molding apparatus in the atmosphere, the equipment becomes large. Therefore, it is difficult to oxidize even in an atmosphere containing oxygen such as an air atmosphere, and a moldable powder is desired.

  Therefore, according to the above knowledge, the present invention makes each magnetic particle constituting the powder for a magnetic member into a form having a specific structure as described above, and an antioxidant layer is formed on the surface of the magnetic particle of the specific form. Propose to provide.

The magnetic member powder of the present invention is a powder used as a raw material for a magnetic member such as a rare earth magnet material, and each magnetic particle constituting the magnetic member powder includes less than 40% by volume of a rare earth element hydrogen compound, The balance is composed of iron-containing material. The iron-containing material includes iron and an iron-boron alloy containing iron and boron. The rare earth element hydrogen compounds are discretely present in the phase of the iron-containing material. The surface of the magnetic particle is provided with an antioxidant layer having an oxygen permeability coefficient (30 ° C.) of less than 1.0 × 10 ⁻¹¹ m ³ · m / (s · m ² · Pa).

  Each magnetic particle constituting the powder for a magnetic member of the present invention is not composed of a single-phase rare earth alloy like an R-Fe-B alloy or an R-Fe-N alloy, but an iron-containing material. It is composed of a plurality of phases of a phase and a phase composed of a rare earth element hydrogen compound. The phase of the iron-containing material is softer and more formable than the R-Fe-B alloy, the R-Fe-N alloy, and the rare earth element hydrogen compound. Further, each of the magnetic particles has an iron-containing material as a main component (60% by volume or more), so that when the powder of the present invention is compression-molded, the phase of the iron-containing material in the magnetic particle can be sufficiently deformed. Furthermore, since the rare earth element hydrogen compound is dispersed in the phase of the iron-containing material, the magnetic particles are uniformly deformed during compression molding. From these facts, a powder compact having a high relative density can be easily molded by using the powder of the present invention. Moreover, by using such a powder compact having a high relative density, a magnetic material such as a rare earth magnet having a high magnetic phase can be obtained without sintering. Furthermore, since the iron-containing material is sufficiently deformed, the magnetic particles are meshed with each other and bonded to each other. Therefore, by using the powder of the present invention, it is possible to obtain a magnetic material such as a rare earth magnet having a magnetic phase density of 80% by volume or more, preferably 90% by volume or more, without using a binder resin like a bonded magnet. Can do.

  In addition, since the powder compact of the present invention obtained by compression molding the magnetic member powder of the present invention does not sinter like a sintered magnet, it has a shape due to the shrinkage anisotropy that occurs during sintering. There are no restrictions, and the degree of freedom of shape is large. Therefore, by using the powder of the present invention, for example, even a complicated shape such as a cylindrical shape, a columnar shape, or a pot shape can be easily formed without substantially performing post-processing such as cutting. . Also, by eliminating the need for cutting, the yield of raw materials can be dramatically improved, and the productivity of magnetic materials such as rare earth magnets can be improved.

  In addition, the magnetic member powder of the present invention is provided with an anti-oxidation layer on the outer periphery of the magnetic particles as described above, so that even when compression molding is performed in an atmosphere containing oxygen such as an air atmosphere, the powder is compressed. It is possible to effectively prevent the new surface formed on the magnetic particles from being oxidized during molding. Therefore, by using the powder of the present invention, it is possible to suppress a decrease in the magnetic phase due to the presence of the rare earth element oxide, and it is possible to produce a magnetic body such as a rare earth magnet having a high magnetic phase density. In addition, by using the powder of the present invention, a large-scale facility as in the case of molding in a non-oxidizing atmosphere is unnecessary, and the magnetic body can be manufactured with high productivity.

  The powder for magnetic member of the present invention is excellent in moldability and can provide the powder molded body of the present invention having a high relative density, and can prevent oxidation of the powder. By using the powder molded body of the present invention or the magnetic member of the present invention, a magnetic body such as a rare earth magnet having a high magnetic phase density can be obtained without sintering.

FIG. 1 is a process explanatory view for explaining an example of a process for producing a magnetic member using the magnetic member powder of Embodiment 1. FIG. 2 is a process explanatory diagram for explaining an example of a process for producing a magnetic member using the magnetic member powder according to the second embodiment.

Hereinafter, the present invention will be described in more detail.
[Powder for magnetic members]
≪Magnetic particles≫
Each magnetic particle constituting the powder of the present invention contains an iron-containing material as a main component, and the content thereof (total content of iron and iron-boron alloy) is 60% by volume or more. When the content of iron-containing material is less than 60% by volume, the amount of hard rare earth element hydrogen compound is relatively large, and it is difficult to sufficiently deform the iron-containing component during compression molding. 90 volume% or less is preferable because it causes a decrease in magnet characteristics. On the other hand, if a rare earth element hydrogen compound is not contained, a rare earth magnetic material such as a rare earth magnet cannot be obtained. Therefore, its content is more than 0% by volume, preferably 10% by volume or more, and less than 40% by volume. The content of the iron-containing material or the rare earth element hydrogen compound appropriately changes the composition of the rare earth-iron-boron alloy used as the raw material of the powder of the present invention and the heat treatment conditions (mainly the temperature) when producing the powder of the present invention. Can be adjusted. In addition, each said magnetic particle accept | permits inclusion of an unavoidable impurity.

The iron-containing material includes both iron and an iron-boron alloy. Examples of the iron-boron alloy include Fe ₃ B. Other examples include Fe ₂ B and FeB. The magnetic particles are excellent in formability by containing pure iron (Fe) in addition to the iron-boron alloy. The content of the iron-boron alloy is preferably 10% by mass to 50% by mass when the content of iron is 100%. When the content of the iron-boron alloy is 10% by mass or more, boron can be sufficiently contained, and the rare earth-iron-boron alloy (typically Nd ₂ Fe ₁₄ in the magnetic member finally obtained) The proportion of B) can be 50% by volume or more. Formability is excellent when the content of the iron-boron alloy is 50% by mass or less. The ratio of iron to the iron-boron alloy in the iron-containing material is obtained, for example, by measuring the peak intensity (peak area) of X-ray diffraction and comparing the measured peak intensity. In addition, the iron-containing material can be in a form in which a part of iron is substituted with at least one element selected from Co, Ga, Cu, Al, Si, and Nb. In the form in which the iron-containing material contains the above element, magnetic properties and corrosion resistance can be improved. The abundance ratio of iron and iron-boron alloy can be adjusted by appropriately changing the composition of the rare earth-iron-boron alloy used as the raw material for producing the magnetic member powder of the present invention.

The rare earth element contained in each of the magnetic particles is one or more elements selected from Sc (scandium), Y (yttrium), lanthanoid and actinoid. In particular, it is preferable to contain at least one element selected from Nd, Pr, Ce, Dy, and Y, and in particular, Nd (neodymium) should obtain an R—Fe—B alloy magnet having excellent magnet characteristics. Is preferable. Examples of the rare earth element hydrogen compound include NdH ₂ and DyH ₂ .

  Each of the magnetic particles has a structure in which the phase of the iron-containing material and the phase of the hydrogen compound of the rare earth element are uniformly dispersed. This discrete state means that in each of the magnetic particles, the rare earth element hydrogen compound phase and the iron-containing material phase are adjacent to each other, and the rare earth element is adjacent to each other via the iron-containing material phase. The distance between the phases of the elemental hydrogen compound is 3 μm or less. Typically, a layered form in which both phases have a multilayer structure, a phase of the hydrogen compound of the rare earth element is granular, and the phase of the iron-containing material is a parent phase. A granular form in which a rare earth element hydrogen compound is present may be mentioned.

  The existence form of both phases depends on the heat treatment conditions (mainly temperature) when producing the magnetic member powder of the present invention, and when the temperature is raised, it becomes a granular form, and the temperature is near the disproportionation temperature described later. Then, it tends to be a layered form.

  By using the layered powder, for example, a rare earth magnet having a magnetic phase density similar to that of a bonded magnet (about 80% by volume) can be obtained without using a binder resin. In the case of the layered form, the phase of the rare earth element hydrogen compound and the phase of the iron-containing material are adjacent to each other when the cross-section of the magnetic particle is taken. To tell. In the case of the layered form, the interval between the phases of the adjacent rare earth element hydrogen compounds is the distance between the centers of the two rare earth element hydrogen compound phases adjacent to each other through the iron-containing material phase in the cross section. Say.

  In the granular form, the iron-containing component is uniformly present around the rare-earth element hydrogen compound particles, so that the iron-containing component is more easily deformed than the layered form. It is easy to obtain a powder molded body having a complicated shape such as a pot shape and a high density powder molded body having a relative density of 85% or more, particularly 90% or more. In the case of the granular form, the phase of the rare earth element hydride and the phase of the iron-containing material are typically adjacent to the rare earth element hydride particle when the cross section of the magnetic particle is taken. The iron-containing material is present so as to cover the surface, and the iron-containing material is present between the adjacent hydrogen compound particles of each rare earth element. In the case of the granular form, the interval between phases of adjacent rare earth element hydrogen compounds refers to the distance between the centers of the two adjacent rare earth element hydrogen compound particles in the cross section.

  The interval may be measured by, for example, etching the cross section to remove the iron-containing phase and extracting the rare earth element hydrogen compound, or removing the rare earth element hydrogen compound depending on the type of the solution. It can be measured by extracting an iron-containing material or by analyzing the composition of the cross section with an EDX (energy dispersive X-ray spectroscopy) apparatus. When the interval is 3 μm or less, when the magnetic material is formed by appropriately heat-treating the powder compact, it is not necessary to input excessive energy, and the rare earth-iron-boron alloy crystal The deterioration of characteristics due to coarsening can be suppressed. In order for the iron-containing material to be sufficiently present between the phases of the rare earth element hydrogen compound, the interval is preferably 0.5 μm or more, and more preferably 1 μm or more. The interval can be adjusted by adjusting the composition of the rare earth-iron-boron alloy powder used as a raw material, or by adjusting the heat treatment conditions, particularly the temperature, in producing the magnetic member powder of the present invention. For example, in the rare earth-iron-boron alloy powder, when the ratio of iron or boron (atomic ratio) is increased or the temperature during the heat treatment is increased within the specific range, the interval tends to increase.

  When the average particle size of the magnetic particles is 10 μm or more and 500 μm or less, the proportion of rare earth element hydrogen compounds on the surface of each magnetic particle can be relatively small, and there is some effect in suppressing oxidation of the magnetic particles. Be expected. In addition, the magnetic particles have an iron-containing material phase as described above and have excellent moldability.For example, even a coarse powder having an average particle size of 100 μm or more has few pores and a relative density. A high powder compact can be formed. If the average particle size is too large, the relative density of the powder compact is reduced, and therefore it is preferably 500 μm or less. The average particle size is more preferably 50 μm or more and 200 μm or less.

  The magnetic particles may have a form in which the circularity in the cross section is 0.5 or more and 1.0 or less. When the circularity satisfies the above range, it is preferable to obtain an effect that it is easy to form an antioxidant layer or an insulating coating to be described later with a uniform thickness, and damage to the antioxidant layer can be suppressed during compression molding. . As the magnetic particle is closer to a true sphere, that is, the circularity is closer to 1, the above effect can be obtained.

In addition, at least a part of boron can be substituted with carbon. For example, as a powder for a magnetic member that is a material for a rare earth-iron-carbon alloy magnet, the above-described iron-containing material may include iron and an iron-carbon alloy containing iron and carbon. The powder containing this iron-carbon alloy also has excellent formability by containing the phase of the iron-containing material in the same manner as the powder containing the iron-boron alloy described above. In addition, the description of the iron-boron alloy or the rare earth-iron-boron alloy in each item described above and below can be replaced with an iron-carbon alloy or a rare earth-iron-carbon alloy. A typical rare earth-iron-carbon alloy is Nd ₂ Fe ₁₄ C.

≪Antioxidation layer≫
And each said magnetic particle is equipped with the antioxidant layer in the outer periphery, It is set as one of the characteristics. The antioxidant layer particularly functions to prevent the new surface of the magnetic particles formed during compression molding from being oxidized, and in order to obtain this effect, the antioxidant layer covers the entire circumference of the magnetic particles. And the oxygen permeability coefficient (30 ° C) is less than 1.0 × 10 ^-11 m ³・ m / (s ・ m ²・ Pa) so that the magnetic particles are sufficiently shielded from oxygen in the atmosphere. And When the oxygen permeability coefficient (30 ° C) is 1.0 × 10 ^-11 m ³・ m / (s ・ m ²・ Pa) or higher, the atmosphere during compression molding is, for example, an atmosphere containing oxygen such as an air atmosphere. The new surface is oxidized to produce an oxide, and the presence of the oxide causes a decrease in the magnetic phase in the magnetic member. Therefore, it is preferable that the antioxidant layer has a smaller oxygen permeability coefficient (30 ° C.), more preferably 0.01 × 10 ⁻¹¹ m ³ · m / (s · m ² · Pa) or less, and no lower limit is provided.

Furthermore, the antioxidant layer preferably has a moisture permeability (30 ° C.) of less than 1000 × 10 ⁻¹³ kg / (m · s · MPa). In a humid state (for example, temperature of about 30 ° C./humidity of about 80%, etc.) in which a relatively large amount of moisture (typically water vapor) is present in the atmosphere, there is a risk that the new surface of the magnetic particles may be oxidized by contact with moisture There is. Therefore, if the antioxidant layer has a low moisture permeability, oxidation due to moisture can be effectively prevented. The moisture permeability is preferably as small as possible, more preferably 10 × 10 ⁻¹³ kg / (m · s · MPa) or less, and no lower limit is set.

  The antioxidant layer can be composed of various materials having an oxygen permeability coefficient and moisture permeability satisfying the above ranges, such as resins, ceramics (non-oxygen permeable materials), metals, and glassy materials. In particular, in the case of a resin, (1) during compression molding, sufficiently following the deformation of each of the above magnetic particles, it is possible to effectively prevent the new surface of the magnetic particles from being exposed during the deformation, (2) powder molding When the body is heat-treated, it is burned down, and the magnetic phase can be prevented from decreasing due to the residue of the antioxidant layer. In particular, in the case of ceramics and metal, the antioxidant effect is high, and the vitreous material can function as an insulating film as described later.

The antioxidant layer may be a single layer or a multilayer. For example, the antioxidant layer includes only an oxygen low-permeability layer composed of a material having an oxygen permeability coefficient (30 ° C.) of less than 1.0 × 10 ⁻¹¹ m ³ · m / (s · m ² · Pa). monolayer form to obtain the transmission coefficient of oxygen (30 ° C.) is the ^{1.0 × 10 -11 m 3 · m} / less than ^{(s · m 2 · Pa)} , and moisture permeability (30 ° C.) is 1000 × 10 ^-13 Single layer form comprising a low oxygen / moisture permeable layer composed of a material less than kg / (m · s · MPa), the low oxygen permeable layer, and a moisture permeability (30 ° C.) of 1000 × 10 ⁻¹³ A multilayer form comprising a low moisture permeation layer composed of a material of less than kg / (m · s · MPa) is mentioned.

As for the constituent material of the low oxygen permeable layer, the resin may be one selected from polyamide resin, polyester, and polyvinyl chloride. A typical example of the polyamide-based resin is nylon 6. Nylon 6 has an oxygen permeability coefficient (30 ° C.) of 0.0011 × 10 ⁻¹¹ m ³ · m / (s · m ² · Pa) and is very small. Examples of the constituent material of the moisture low-permeability layer include resins such as polyethylene, fluororesin, and polypropylene. Polyethylene is preferable because it has a very low moisture permeability (30 ° C.) of 7 × 10 ⁻¹³ kg / (m · s · MPa) to 60 × 10 ⁻¹³ kg / (m · s · MPa).

  When the anti-oxidation layer has a two-layer structure of the above-described oxygen low-permeability layer and moisture low-permeability layer, any layer may be disposed on the inner side (the magnetic particle side) and the outer side (the outermost surface side). However, it is expected that oxidation can be more effectively prevented by disposing the oxygen low-permeability layer on the inner side and the moisture low-permeability layer on the outer side. In addition, when both the oxygen low-permeability layer and the moisture low-permeability layer are formed of a resin as described above, it is preferable because the adhesion between the two layers is excellent.

  The thickness of the antioxidant layer can be appropriately selected, but if it is too thin, the antioxidant effect cannot be sufficiently obtained, and if it is too thick, the density of the powder molded body is lowered, for example, the relative density is 85%. It becomes difficult to form the above powder compact or to remove it by burning. Therefore, the thickness of the antioxidant layer is preferably 10 nm or more and 1000 nm or less, and particularly when it is 2 or less times the diameter of the magnetic particle, and further 100 nm or more and 300 nm or less, oxidation and density reduction can be suppressed and moldability can be reduced. Excellent and preferred. When the antioxidant layer has a multilayer structure such as a two-layer structure as described above, the thickness of each layer is preferably 10 nm or more and 500 nm or less.

≪Insulation coating≫
Further, the magnetic member powder of the present invention can be provided with an insulating coating made of an insulating material on its outer periphery. By using a powder having an insulating coating, a magnetic member having high electrical resistance can be obtained. When this magnetic member is used as a material for a magnet of a motor, for example, eddy current loss can be reduced. Insulating coatings include, for example, crystalline films of oxides such as Si, Al, Ti, amorphous glass films, ferrites such as Me-Fe-O (Me = Ba, Sr, Ni, Mn, etc.) Examples thereof include films made of metal oxides such as magnetite (Fe ₃ O ₄ ) and Dy ₂ O ₃ , resins such as silicone resins, and oxides such as silsesquioxane compounds. In order to improve thermal conductivity, Si-N or Si-C ceramic coating may be applied. The crystalline film, glass film, oxide film, ceramic film, etc. may have an anti-oxidation function. In this case, by providing these films in addition to the anti-oxidation layer, oxidation can be further prevented. Can do. In the form of providing these insulating coatings and ceramic coatings, it is preferable to provide an insulating coating so as to be in contact with the surface of the magnetic particles, and further to provide the ceramic coating and the antioxidant layer thereon.

[Method for producing powder for magnetic member]
The said powder for magnetic members can be manufactured with the manufacturing method which comprises the following preparatory processes, a hydrogenation process, and a coating | coated process, for example.
Preparation step: a step of preparing an alloy powder made of a rare earth-iron-boron alloy (for example, Nd ₂ Fe ₁₄ B).
Hydrogenation step: The alloy powder is heat-treated in a hydrogen-containing atmosphere at a temperature equal to or higher than the disproportionation temperature of the rare earth-iron-boron alloy, and the rare earth element hydrogen compound phase, iron, iron, and boron are removed. Forming a phase of an iron-containing material including an iron-boron alloy and forming a base powder in which the phases of the hydrogen compound of the rare earth element are discretely present in the phase of the iron-containing material.
Coating step: An antioxidant layer having an oxygen permeability coefficient (30 ° C.) of less than 1.0 × 10 ⁻¹¹ m ³ · m / (s · m ² · Pa) on the surface of each magnetic particle constituting the base powder. Forming step.

≪Preparation process≫
The alloy powder is obtained by, for example, melting a cast ingot made of a rare earth-iron-boron alloy or a foil obtained by a rapid solidification method with a crushing device such as a jaw crusher, a jet mill or a ball mill, or an atomizing method such as a gas atomizing method. It can be manufactured using the law. In particular, when the gas atomization method is used, a powder containing substantially no oxygen (oxygen concentration: 500 mass ppm or less) can be obtained by forming the powder in a non-oxidizing atmosphere. That is, the oxygen concentration in the particles constituting the alloy powder being 500 mass ppm or less is one index indicating that the powder is produced by the gas atomization method in a non-oxidizing atmosphere. In addition, a known powder production method can be used, or a powder produced by the atomization method can be further pulverized. By appropriately changing the pulverization conditions and the production conditions, the particle size distribution of the powder and the shape of the magnetic particles can be adjusted. For example, when the atomizing method is used, a nearly spherical powder having a circularity of 0.5 to 1.0 is easily obtained. In other words, the circularity satisfying the above range is one index indicating that the powder is manufactured by the atomizing method. Each particle constituting the alloy powder may be a polycrystal or a single crystal. The particles made of a polycrystal can be appropriately heat treated to form particles made of a single crystal.

  The size of the alloy powder prepared in this preparation step is substantially the size of the magnetic member powder of the present invention. Since the powder of the present invention has the above-mentioned specific form and is excellent in moldability, it can be made relatively coarse with an average particle diameter of about 100 μm. Therefore, the alloy powder can also have an average particle size of about 100 μm. Such a coarse alloy powder can be produced by, for example, performing only coarse pulverization on a molten cast ingot or an atomizing method such as a molten metal spraying method. Since such a coarse alloy powder can be used, fine pulverization to make particles as small as 10 μm or less like raw material powder (powder constituting the compact before sintering) used in the production of sintered magnets is possible. The manufacturing cost can be reduced by shortening the manufacturing process.

≪Hydrogenation process≫
In this process, the prepared alloy powder is heat-treated in an atmosphere containing hydrogen to separate the rare earth element, iron, and iron-boron alloy in the alloy, and combine the rare earth element and hydrogen. This is a step of producing a base powder.

Examples of the atmosphere containing hydrogen include a single atmosphere of only hydrogen (H ₂ ), or a mixed atmosphere of hydrogen and an inert gas such as Ar or N ₂ . The temperature during the heat treatment in the hydrogenation step is set to a temperature at which the disproportionation reaction of the rare earth-iron-boron alloy proceeds, that is, the disproportionation temperature or higher. The disproportionation reaction is a reaction that separates rare earth element hydrogen compounds, iron, and iron-boron alloys by preferential hydrogenation of rare earth elements, and the lower limit temperature at which this reaction occurs is called the disproportionation temperature. . The disproportionation temperature varies depending on the composition of the alloy and the type of rare earth element. For example, when the rare earth-iron-boron alloy is Nd ₂ Fe ₁₄ B, the temperature may be 650 ° C. or higher. When the temperature at the time of heat treatment is in the vicinity of the disproportionation temperature, the above-described layered form is obtained, and when the temperature is increased to the disproportionation temperature + 100 ° C. or higher, the above-described granular form is obtained. The higher the temperature during the heat treatment in the hydrogenation step, the easier it is for the iron phase and iron-boron alloy phase to appear and the powder formability to be improved, but if it is too high, problems such as melting and fixing of the powder will occur. Therefore, the temperature during the heat treatment is preferably 1100 ° C. or lower. In particular, when the rare earth-iron-boron alloy is Nd ₂ Fe ₁₄ B, if the temperature during the heat treatment in the hydrogenation process is relatively low, such as 750 ° C. or more and 900 ° C. or less, the microstructure becomes small with a small interval. By using such a powder, for example, a rare earth magnet having a high coercive force can be easily obtained. Examples of the holding time include 0.5 hours or more and 5 hours or less. This heat treatment corresponds to the processing up to the disproportionation step of the above-described HDDR processing, and known disproportionation conditions can be applied.

≪Coating process≫
This step is a step of forming an antioxidant layer on the surface of each of the magnetic particles constituting the obtained base powder.

Either the dry method or the wet method can be used to form the antioxidant layer. In the dry method, in order to prevent the magnetic particles from coming into contact with oxygen in the atmosphere and oxidizing the surface, a non-oxidizing atmosphere, for example, an inert atmosphere such as Ar or N ₂ , a reduced pressure atmosphere, etc. Is preferred. In the wet method, since the surface of the magnetic particles is not substantially in contact with oxygen in the atmosphere, it is not necessary to use the above-described inert atmosphere or the like, and for example, an antioxidant layer can be formed in an air atmosphere. Therefore, the wet method is preferable because it is excellent in workability for forming the antioxidant layer and is easy to form the antioxidant layer in a uniform thickness on the surface of the magnetic particles.

For example, when the antioxidant layer is formed of a resin or glassy material by a wet method, a wet dry coating method or a sol-gel method can be used. More specifically, by mixing was prepared by such dissolving and mixing the raw materials in an appropriate solvent solution and the said base powder to form an oxidation layer by performing a dry curing, the solvent of the starting material be able to. When the antioxidant layer is formed of a resin by a dry method, for example, powder coating can be used. When the antioxidant layer is formed of ceramics or metal by a dry method, a vapor deposition method such as PVD method such as sputtering or a CVD method or a mechanical alloying method can be used. When the antioxidant layer is formed of a metal by a wet method, various plating methods can be used.

  In addition, when it is set as the form which provides the insulating coating and ceramics coating mentioned above, it is preferable to form the said antioxidant layer and a ceramics film after forming an insulating coating on the surface of the said base powder.

[Powder compact]
The powder molded body of the present invention can be obtained by compression molding the above magnetic member powder of the present invention. As described above, since the powder of the present invention is excellent in moldability, it is possible to form a powder compact having a high relative density (actual density relative to the true density of the powder compact). For example, one form of the powder compact of the present invention is one having a relative density of 85% or more. By using such a high-density powder compact, a magnetic material such as a rare earth magnet having a high magnetic phase density can be obtained. The higher the relative density, the higher the magnetic phase. However, when the components of the antioxidant layer are burned off in a heat treatment step for forming a magnetic member described later, or in a heat treatment for removal separately, if the relative density is too high, the structure of the antioxidant layer It becomes difficult to burn down the ingredients sufficiently. Therefore, it is considered that the relative density of the powder compact is preferably about 90% to 95%. In order to increase the relative density of the powder molded body, it is preferable to reduce the thickness of the antioxidant layer or to perform a separate heat treatment (coating removal) as will be described later so that the antioxidant layer can be easily removed.

Since the magnetic member powder of the present invention is excellent in moldability, the pressure at the time of compression molding can be made relatively small, for example, from 8 ton / cm ^{2 to} 15 ton / cm ² . Furthermore, since the powder of the present invention is excellent in moldability, it can be easily formed even if it is a powder molded body having a complicated shape such as a cylindrical shape. In addition, the present invention powder is excellent in bondability between magnetic particles because the above-mentioned magnetic particles constituting the powder can be sufficiently deformed (expression of strength (so-called necking strength) generated by engagement of irregularities on the surface of the magnetic particles) ), It is possible to obtain a powder molded body which has high strength and hardly disintegrates during production.

  In addition, since the powder for a magnetic member of the present invention includes the above-described antioxidant layer, it can sufficiently prevent oxidation of the new surface formed on the magnetic particles constituting the powder during compression molding. It can be performed in an oxygen-containing atmosphere such as an atmosphere and has excellent workability. It can also be molded in a non-oxidizing atmosphere.

  In addition, by appropriately heating the molding die during compression molding, deformation can be promoted, and a high-density powder molded body can be easily obtained.

[Magnetic member and manufacturing method thereof]
The powder compact is heat-treated in an inert atmosphere or a reduced-pressure atmosphere to remove hydrogen from the rare earth element hydrogen compound, iron, an iron-boron alloy, and a rare earth element from which hydrogen has been removed. The magnetic member of the present invention is obtained by combining. The magnetic member of the present invention is substantially selected from a single form composed of a rare earth-iron-boron alloy phase, substantially an iron phase, an iron-boron alloy phase, and a rare earth-iron alloy phase. Mixed form composed of a combination of at least one phase and a rare earth-iron-boron alloy phase, for example, an iron phase and a rare earth-iron-boron alloy phase, an iron-boron alloy phase and a rare earth -The form with the phase of the iron-boron alloy, the form with the rare earth-iron alloy phase and the phase of the rare earth-iron-boron alloy. Examples of the single form include those having substantially the same composition as the rare earth-iron-boron alloy used as the raw material for the magnetic member powder of the present invention. The mixed form typically varies depending on the composition of the rare earth-iron-boron alloy used as the raw material. For example, when a material having a high iron ratio (atomic ratio) is used, a form of an iron phase and a phase of a rare earth-iron-boron alloy can be formed.

The heat treatment (dehydrogenation) is performed in a non-hydrogen atmosphere in order to remove hydrogen from the rare earth element hydrogen compound. Examples of the non-hydrogen atmosphere include an inert atmosphere and a reduced-pressure atmosphere as described above. Examples of the inert atmosphere include Ar and N ₂ . The reduced pressure atmosphere refers to a vacuum state in which the pressure is lower than that of a standard air atmosphere, and the final vacuum is preferably 10 Pa or less. By using a reduced-pressure atmosphere, the remaining rare earth element hydrogen compound is suppressed, and the rare earth-iron-boron alloying is completely caused to obtain a magnetic material (typically, a rare earth magnet) having excellent magnetic properties. Material (magnetic member) can be manufactured.

  The temperature during the dehydrogenation treatment is equal to or higher than the recombination temperature of the powder compact (the temperature at which the separated iron-containing material and rare earth element combine). Although the recombination temperature varies depending on the composition of the powder compact (magnetic particles), a typical example is 700 ° C. or higher. When this temperature is high, hydrogen can be sufficiently removed. However, if the temperature during the dehydrogenation process is too high, the rare earth element having a high vapor pressure may volatilize and decrease, or the coercivity of the rare earth magnet may decrease due to the coarsening of the rare earth-iron-boron alloy crystal. Therefore, 1000 ° C. or less is preferable. The holding time is 10 minutes or more and 600 minutes (10 hours) or less. This dehydrogenation process corresponds to the above-described DR process of the HDR process, and can be applied with known DR process conditions.

  When the antioxidant layer is made of a material that can be burned down by high heat, such as a resin, the dehydrogenation treatment can also serve to remove the antioxidant layer. A heat treatment (coating removal) for removing the antioxidant layer may be separately performed. Although this heat treatment (coating removal) depends on the constituent material of the antioxidant layer, a heating temperature of 200 ° C. to 400 ° C. and a holding time of 30 minutes to 300 minutes are easy to use. This heat treatment (coating removal) is performed particularly when the density of the powder compact is high, and the antioxidant layer is rapidly heated to the heating temperature for the dehydrogenation treatment, causing incomplete combustion, and residue is generated. It can be effectively prevented from occurring.

  By utilizing the above-described powder molded body of the present invention, the volume change degree (shrinkage amount after heat treatment) before and after the heat treatment (dehydrogenation) is small, and a large volume compared with the case of manufacturing a conventional sintered magnet. There is no change. For example, the volume change rate between the powder compact before the heat treatment (dehydrogenation) and the magnetic member after the heat treatment (dehydrogenation) is 5% or less. Thus, the magnetic member of the present invention has a small volume change before and after heat treatment (dehydrogenation), i.e., it is a net shape, and processing (for example, cutting, cutting) for obtaining a final shape is unnecessary. Excellent magnetic member productivity. In addition, the magnetic member obtained after heat processing can confirm the grain boundary of a powder unlike a sintered compact. Therefore, the presence of the grain boundaries of the powder is one that indicates that the powder compact has been heat-treated and is not a sintered body. It becomes one of the indexes indicating that the volume change rate at is small.

[Rare earth magnet]
A rare earth magnet can be produced by appropriately magnetizing the magnetic member of the present invention. In particular, by using the above-described powder compact having a high relative density, a rare earth magnet having a magnetic phase density of 80% by volume or more, and further 90% by volume or more can be obtained. Moreover, since the fall of the magnetic phase by an oxide can be suppressed by utilizing the powder for magnetic members of this invention, the rare earth magnet with a high density of a magnetic phase is obtained also from this point.

  Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. The same reference numerals in the figure indicate the same names. In FIG. 1 and FIG. 2, the rare earth element hydrogen compound and the antioxidant layer are exaggerated for easy understanding.

[Embodiment 1]
A powder containing a rare earth element, iron and boron was prepared, and the obtained powder was compression molded to examine the moldability and oxidation state of the powder.

  The powder was prepared in the order of preparation step: preparation of alloy powder → hydrogenation step: heat treatment in a hydrogen atmosphere → coating step: formation of an antioxidant layer.

First, a powder made of a rare earth-iron-boron alloy (Nd ₂ Fe ₁₄ B) and having an average particle size of 100 μm (FIG. 1 (I)) was produced by a gas atomization method (Ar atmosphere). The average particle size was measured with a laser diffraction particle size distribution device so that the cumulative weight was 50% (50% particle size). In addition, here, a gas atomizing method was used to produce a material in which each particle constituting the alloy powder was made of a polycrystal.

The alloy powder was heat-treated at 800 ° C. for 1 hour in a hydrogen (H ₂ ) atmosphere. Polyamide resin (here nylon 6, oxygen permeability coefficient (30 ° C): 0.0011 × 10 ^-11 m ³・ m / (s ・ m ²・ Pa)) to the base powder obtained after this heat treatment (hydrogenation) An antioxidant layer made of was formed. Specifically, after the base powder was mixed with the polyamide-based resin dissolved in an alcohol solvent, the solvent was dried and the resin was cured to form an antioxidant layer. The amount of the resin was adjusted so that the thickness of the antioxidant layer was 200 nm. This thickness is an average thickness (the volume of the resin / the total surface area of the magnetic particles) assuming that an antioxidant layer is uniformly formed on the surface of each magnetic particle constituting the base powder. The surface area of the magnetic particles can be measured by, for example, the BET method. Through this process, an antioxidant layer having an oxygen permeability coefficient (30 ° C.) of less than 1.0 × 10 ⁻¹¹ m ³ · m / (s · m ² · Pa) is provided on the outer periphery of the magnetic particles constituting the magnetic member powder. A magnetic member powder is obtained.

The obtained powder for a magnetic member was hardened with an epoxy resin to prepare a sample for observing the structure. The composition of each magnetic particle constituting the powder for a magnetic member present on the cut surface (or polished surface) is cut or polished at an arbitrary position so that the powder inside the sample is not oxidized. Investigated with EDX equipment. Further, the cut surface (or polished surface) was observed with an optical microscope or a scanning electron microscope: SEM (100 to 10,000 times), and the form of each magnetic particle was examined. Then, as shown in FIGS. 1 (II) and (III), each of the magnetic particles 1 has a phase of iron-containing material 2, specifically, a phase of iron (Fe) and an iron-boron alloy (Fe ₃ B). And a plurality of granular rare earth element hydrogen compounds (NdH ₂ ) 3 are dispersed in the mother phase, and between the adjacent rare earth element hydrogen compound 3 particles, It was confirmed that a phase was present. Further, as shown in FIG. 1 (III), it was confirmed that substantially the entire surface of the magnetic particle 1 was covered with the antioxidant layer 4 and was blocked from the outside air. Furthermore, rare earth oxides (here, Nd ₂ O ₃ ) were not detected from the magnetic particles 1.

The distance between adjacent rare earth element hydrogen compound particles was measured by the above EDX apparatus using the surface analysis (mapping data) of the composition of the obtained magnetic member powder, and found to be 0.6 μm. Here, surface analysis was performed on the cut surface, NdH ₂ peak positions were extracted, intervals between adjacent NdH ₂ peak positions were measured, and an average value of all intervals was obtained.

Using a sample prepared by the above epoxy resin was mixed kneaded, NdH ₂ of each of the magnetic particles, iron-containing material was determined (Fe, Fe-B) content (volume%), NdH _2: 33 vol% Iron content: 67% by volume. Here, the content was obtained by calculating the volume ratio using the composition of the alloy powder used as a raw material and the atomic weight of NdH ₂ , Fe, and Fe ₃ B. In addition, for example, the content is obtained by determining the area ratio of NdH ₂ , Fe, Fe ₃ B in the area of the cut surface (or polished surface) of the molded body produced using the base powder, respectively, and the obtained area ratio Is converted into a volume ratio, or X-ray analysis is performed to use the peak intensity ratio.

Using a sample prepared by the above epoxy resin was mixed kneaded, it was determined the circularity of the magnetic particles was 0.86. Here, the circularity is obtained as follows. Obtain a projected image of the powder cross-section with an optical microscope or SEM, and determine the actual cross-sectional area Sr and the actual perimeter for each particle. The actual cross-sectional area Sr and the same perimeter as the actual perimeter are obtained. Ratio with the area Sc of a perfect circle having a length: Sr / Sc is the circularity of the particle. Sampling with n = 50 is performed, and the average value of the circularity of the particles with n = 50 is defined as the circularity of the magnetic particles.

The magnetic member powder including the antioxidant layer produced as described above was compression-molded by a hydraulic press device at a surface pressure of 10 ton / cm ² (FIG. 1 (IV)). Here, the molding was performed in an air atmosphere (temperature: 25 ° C., humidity: 40%). As a result, it was possible to sufficiently compress at a surface pressure of 10 ton / cm ² and to form a cylindrical powder compact (FIG. 1 (V)) having an outer diameter of 10 mmφ × height of 10 mm.

The relative density (actual density with respect to the true density) of the obtained powder compact was determined to be 93%. The actual density was measured using a commercially available density measuring device. The true density is NdH ₂ density: 5.96 g / cm ³ , Fe density: 7.874 g / cm ³ , Fe ₃ B density: 7.474 g / cm ^3, and the volume ratio of NdH ₂ and iron-containing materials described above is used. It was calculated by calculation. Further, when the obtained powder compact was subjected to X-ray analysis, a clear diffraction peak of a rare earth element oxide (here, Nd ₂ O ₃ ) was not detected.

As described above, the rare earth element hydrogen compound is less than 40% by volume, the balance is substantially iron-containing material such as Fe or Fe ₃ B, and the rare earth element hydrogen compound is discretely present in the iron-containing material phase. It can be seen that a powder molded body having a complicated shape such as a columnar shape or a high-density powder molded body having a relative density of 85% or more can be obtained by using the powder. Moreover, it turns out that the production | generation of the oxide of a rare earth element is suppressed by using the powder which provides an antioxidant layer, and the powder compact | molding | casting which the said oxide does not exist substantially is obtained.

After holding the obtained powder compact in a nitrogen atmosphere at 300 ° C. for 120 minutes, the temperature was raised to 750 ° C. in a hydrogen atmosphere, then switched to vacuum (VAC) and in vacuum (VAC) (final vacuum degree: 1.0 Pa) and heat treatment was performed at 750 ° C. × 60 min. By making the temperature rise into a hydrogen atmosphere, the dehydrogenation reaction can be started after the temperature is sufficiently high, and reaction spots can be suppressed. When the composition of the cylindrical member (magnetic member (FIG. 1 (VI))) obtained after this heat treatment was examined with an EDX apparatus, Nd ₂ Fe ₁₄ B was the main phase (87% by volume or more). It can be seen that the hydrogen has been removed.

Further, when X-ray analysis was performed on the cylindrical member, a clear diffraction peak of a rare earth element oxide (here, Nd ₂ O ₃ ) or a residue of the antioxidant layer was not detected. Thus, it can be seen that the use of the powder for a magnetic member having the antioxidant layer can suppress the generation of an oxide of a rare earth element such as Nd ₂ O ₃ that causes a decrease in coercive force. Furthermore, in Embodiment 1, since the antioxidant layer is formed of a resin, the antioxidant layer can sufficiently follow the deformation of the magnetic particles constituting the powder during compression molding, and is excellent in moldability.

  Furthermore, when the volume of the powder compact before the heat treatment was compared with the volume of the cylindrical member (magnetic member) obtained after the heat treatment, the volume change rate before and after the heat treatment was 5% or less. Therefore, when such a magnetic member is used as a material for a rare earth magnet, machining such as cutting for obtaining a desired external shape is unnecessary, and it is expected that it can contribute to the improvement of the productivity of the rare earth magnet. Is done.

[Embodiment 2]
As a raw material powder for the magnetic member, a powder having an antioxidant layer in a form different from that of Embodiment 1 was prepared, and the moldability and oxidation state of the powder were examined.

In this second embodiment, the magnetic member powder prepared in the first embodiment described above, in which the outer periphery of the magnetic particles is coated with a polyamide-based resin (nylon 6), is prepared. Moisture rate (30 ° C.): 50 × 10 ⁻¹³ kg / (m · s · MPa)). Specifically, the solvent: polyethylene dissolved in xylene was mixed with the powder having the coating with the polyamide resin, and then the solvent was dried and the polyethylene was cured. Here, the amount of polyethylene was adjusted so that the average thickness of the coating made of polyethylene was 250 nm. This thickness is an average thickness (polyethylene volume / total surface area of each particle) assuming that a layer made of polyethylene is uniformly formed on the surface of each particle constituting the prepared powder. The surface area of each particle can be measured by, for example, the BET method. Through this process, the outer circumference of the magnetic particles 1 constituting the magnetic member powder has a polyamide system with an oxygen permeability coefficient (30 ° C.) of less than 1.0 × 10 ⁻¹¹ m ³ · m / (s · m ² · Pa) Low oxygen moisture permeation layer 4a made of resin, and on the outer periphery of this low oxygen permeation layer 4a, moisture permeation rate (30 ° C.) made of polyethylene having a moisture permeability (30 ° C.) of less than 1000 × 10 ⁻¹³ kg / (m · s · MPa) A magnetic member powder comprising the multilayered antioxidant layer 4 (total average thickness: 450 nm) laminated with the transmission layer 4b is obtained.

The obtained powder for a magnetic member was prepared in the same manner as in Embodiment 1 to prepare a sample for tissue observation, and the composition of the magnetic particles constituting the powder was examined. As in Embodiment 1, Fe, Fe _Three phases of ₃ B and NdH ₂ were detected, and it was confirmed that Fe and Fe ₃ B were used as a parent phase, and a plurality of granular NdH ₂ existed in the parent phase. Further, as shown in FIG. 2 (III), the surfaces of the magnetic particles 1 are sequentially covered with a multilayer antioxidant layer 4 including an oxygen low-permeability layer 4a made of polyamide resin and a moisture low-permeability layer 4b made of polyethylene. Confirmed that. Furthermore, rare earth oxides (here, Nd ₂ O ₃ ) were not detected from the magnetic particles 1. Further, when the distance between adjacent NdH ₂ particles was measured in the same manner as in Embodiment 1, it was 0.6 μm, and the content of NdH ₂ and iron-containing materials (Fe, Fe-B) in the magnetic particles (volume%) ) Was determined to be NdH ₂ : 32 % by volume and iron-containing material: 68 % by volume.

The magnetic member powder including the antioxidant layer having the multilayer structure produced as described above was compression-molded with a hydraulic press device at a surface pressure of 10 ton / cm ² (FIG. 2 (IV)). Here, the molding was performed in an air atmosphere (temperature: 25 ° C., humidity: 75% (humidity)). As a result, it was possible to sufficiently compress at a surface pressure of 10 ton / cm ² as in Embodiment 1, and to form a cylindrical powder compact (FIG. 2 (V)) having an outer diameter of 10 mmφ × height of 10 mm. When the relative density of the obtained powder compact was determined in the same manner as in Example 1, it was 91%.

Further, the obtained powder compact was subjected to heat treatment (dehydrogenation) under the same conditions as in Embodiment 1, and the composition of the obtained cylindrical member (magnetic member (FIG. 2 (VI))) was examined using an EDX apparatus. However, it was confirmed that mainly Nd ₂ Fe ₁₄ B was the main phase (89% by volume or more), and hydrogen was removed by the heat treatment. Further, when X-ray analysis was performed on the cylindrical member, a clear diffraction peak of a rare earth element oxide (here, Nd ₂ O ₃ ) or a residue of the antioxidant layer was not detected. Further, the volume change rate before and after the heat treatment (dehydrogenation) of the magnetic member of Embodiment 2 was 5% or less.

Thus, it can be seen that by using the powder for a magnetic member having the antioxidant layer, it is possible to suppress the formation of an oxide of a rare earth element such as Nd ₂ O ₃ which causes a decrease in coercive force. In particular, it can be seen that the generation of oxides of rare earth elements can be effectively suppressed even when compression molding is performed in a humid state where a relatively large amount of moisture exists. In Embodiment 2, since both the oxygen low-permeability layer and the moisture low-permeability layer are formed of resin, both layers can sufficiently follow the deformation of the magnetic particles constituting the powder during compression molding. Excellent formability and excellent adhesion between both layers.

[Test example]
After magnetizing the magnetic member made of the rare earth-iron-boron alloy prepared in Embodiments 1 and 2 with a pulsed magnetic field of 2.4 MA / m (= 30 kOe), each obtained sample (rare earth-iron-boron alloy magnet) The magnet characteristics of the were examined using a BH tracer (DCBH tracer manufactured by Riken Denshi Co., Ltd.). The results are shown in Table 1. Here, as the magnetic characteristics, saturation magnetic flux density: Bs (T), residual magnetic flux density: Br (T), intrinsic coercive force: iHc, maximum value of product of magnetic flux density B and demagnetizing field size H: (BH ) max was determined.

  As shown in Table 1, less than 40% by volume of a rare earth element hydrogen compound and the balance substantially consisting of an iron-containing material, and the rare earth element hydrogen compound is discretely present in the iron-containing material phase. It can be seen that the rare earth magnets produced using the above have excellent magnet characteristics. In particular, it can be seen that by using a powder compact having a relative density of 85% or more, the magnetic phase becomes high without sintering and a rare earth magnet having excellent magnetic properties can be obtained.

  The above-described embodiment can be appropriately changed without departing from the gist of the present invention, and is not limited to the above-described configuration. For example, type of rare earth elements, composition of magnetic particles (ratio of rare earth element hydrogen compounds and iron-containing materials), circularity, average particle size of powder for magnetic members, material / thickness of antioxidant layer, oxygen transmission The coefficient / moisture permeability, the relative density of the powder compact, various heat treatment conditions (heating temperature, holding time), the composition of the rare earth-iron-boron alloy used as a raw material, and the like can be appropriately changed.

  The magnetic member powder of the present invention, the powder compact obtained from the powder, and the magnetic member are permanent magnets used in various motors, in particular, high-speed motors included in hybrid vehicles (HEV) and hard disk drives (HDD). It can be suitably used for raw materials and materials.

1 Magnetic particle 2 Iron-containing material 3 Rare earth element hydrogen compound 4 Antioxidation layer
4a Oxygen low permeability layer 4b Moisture low permeability layer

Claims (12)

A magnetic member powder used as a raw material for a magnetic member,
Each magnetic particle constituting the powder for a magnetic member,
A rare earth element hydrogen compound of less than 40% by volume, and the balance consists of iron-containing materials,
The iron-containing material includes iron and an iron-boron alloy containing iron and boron,
The rare earth element hydride is present discretely in the phase of the iron-containing material,
A magnetic member comprising an antioxidant layer having an oxygen permeability coefficient (30 ° C.) of less than 1.0 × 10 ⁻¹¹ m ³ · m / (s · m ² · Pa) on the outer periphery of the magnetic particles Powder.   2. The magnetic member powder according to claim 1, wherein the antioxidant layer is made of a resin. 3. The powder for a magnetic member according to claim 1, wherein the antioxidant layer has a moisture permeability (30 ° C.) of less than 1000 × 10 ⁻¹³ kg / (m · s · MPa). The oxidation preventing layer comprises an oxygen low permeability layer composed of a material having an oxygen permeability coefficient (30 ° C.) of less than 1.0 × 10 ⁻¹¹ m ³ · m / (s · m ² · Pa), and a moisture permeability A moisture low permeability layer composed of a material having a (30 ° C) of less than 1000 × 10 ^-13 kg / (m · s · MPa). The powder for magnetic members as described in 2.   5. The magnetic member powder according to claim 1, wherein the magnetic particles have a circularity of 0.5 or more and 1.0 or less.   6. The magnetic member powder according to claim 1, wherein the antioxidant layer has a thickness of 10 nm to 1000 nm. The antioxidant layer is selected from polyamide resin, polyester, and polyvinyl chloride having an oxygen permeability coefficient (30 ° C.) of less than 1.0 × 10 ⁻¹¹ m ³ · m / (s · m ² · Pa). 7. The powder for a magnetic member according to claim 1, further comprising an oxygen low-permeability layer composed of one kind.   8. The magnetic member powder according to claim 1, wherein the rare earth element contains at least one element selected from Nd, Pr, Ce, Dy, and Y. A powder molded body used as a raw material for a magnetic member,
A powder molded body produced by compression molding the powder for a magnetic member according to any one of claims 1 to 8.   10. The powder compact according to claim 9, wherein a relative density of the powder compact is 85% or more.   11. A magnetic member produced by heat-treating the powder compact according to claim 9 or 10 in an inert atmosphere or a reduced-pressure atmosphere.   12. The magnetic member according to claim 11, wherein a volume change rate between the powder compact before the heat treatment and the magnetic member after the heat treatment is 5% or less.

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