JP2012033865A - Powder for magnetic member, powder compact, and magnetic member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic member capable of obtaining a rare earth magnet with high coercive force even in high temperature environment, a powder compact suitable for a raw material of the magnetic member, and a powder for the magnetic member with high moldability.SOLUTION: Each magnetic particle 1 constituting the powder for the magnetic member consists of a hydride (NdH) 3 of a rare earth element of less than 40 volume % and an iron-containing material 2 containing Fe and Fe-B alloy as the remainder. The hydride 3 is discretely in the phases of the iron-containing material 2. The surface of the magnetic particle 1 has a supply source particle 4a consisting of a rare earth supply source material (for example, hydride:DyH) containing a rare earth element and a heat-resistant precursive layer 4 including a resin layer 4b consisting of a resin with a small oxygen transmission coefficient. Uniform presence of the phases of the iron-containing material 2 in the magnetic particle 1 enhances moldability of the powder. Heat treatment of the powder compact formed by the powder with the heat-resistant precursive layer 4 can obtain the magnetic member with the heat-resistant coercive force layer 6 formed on the surface of an alloy particle 5. The magnetic member can obtain a rare earth magnet with high coercive force even in high temperature environment.

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 can obtain a rare earth magnet having a high coercive force even in a high temperature environment and is excellent in moldability.

  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 their high magnetic phase ratio, 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). Therefore, it is necessary to cut the sintered material so as to have a complicated shape and a desired size. On the other hand, although the bond magnet has a high degree of freedom in shape, the presence of the binder resin has a low magnetic phase ratio and is inferior to the magnet characteristics than the sintered magnet.

Further, it is known that a rare earth magnet made of an Nd—Fe—B alloy has a high coercive force but a large demagnetization at a high temperature. For example, parts placed in an engine room of an automobile are required to operate sufficiently in a high temperature range of about 100 ° C to 200 ° C. However, a rare earth magnet made of a conventional Nd—Fe—B alloy is greatly demagnetized at about 80 ° C. In order to improve the basic coercive force so that it can have a high coercive force even in a high temperature environment, a part of Nd of the Nd-Fe-B alloy (mother alloy) is a rare earth element having a higher coercive force than Nd, specifically Specifically, substitution of Dy or Tb to produce a Dy-Fe-B alloy or the like has been investigated (0003 of Patent Document 1). In addition, Patent Document 1 discloses that a heat treatment is performed by mixing rare earth oxides such as Dy ₂ O ₃ with HDDR powder in order to improve the coercive force.

JP 2004-134552 JP

  As described above, sintered magnets require processing such as cutting in order to obtain a desired shape, and the degree of freedom in shape is small, resulting in poor productivity. In bonded magnets, the magnetic phase ratio is about 80% by volume at most. However, it is difficult to improve the ratio of the magnetic phase.

  In order to obtain a rare earth magnet having a high magnetic phase ratio without sintering, for example, it is conceivable to produce a powder compact having a high relative density as the material. However, an alloy powder composed of an Nd—Fe—B alloy and an HDRD powder obtained by subjecting the alloy powder to HDRR 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, resulting in poor productivity.

  In order to maintain a high coercive force even in a high-temperature environment, basic magnetic properties such as saturation magnetization can be obtained by replacing Dy and Tb with Dy-Fe-B alloy by adding 10% to 30% by mass in the master alloy. It becomes a magnet inferior to. In addition, Dy and Tb are generally more expensive than Nd, leading to increased costs. On the other hand, as described in Patent Document 1, when a rare earth oxide is mixed with HDDR powder, the degree of freedom in shape is small as described above by using HDDR powder.

  As described above, it is desired to develop a raw material suitable for a magnetic material such as a rare earth magnet which can be easily manufactured even with a complicated shape, has a high magnetic phase ratio, and is excellent in heat resistance. In addition, it is desired to develop a raw material that can easily form a powder compact having a high relative density.

  Accordingly, one of the objects of the present invention is to provide a powder for a magnetic member that is excellent in moldability and that can provide a rare earth magnet having a high coercive force even in a high temperature environment.

  Another object of the present invention is a magnetic member made of a rare earth-iron-boron alloy and having a high coercive force even in a high temperature environment, and a powder molded body suitable for the material of the magnetic member. Is to provide.

  In order to obtain a magnetic member suitable for a magnetic material such as a rare earth magnet without increasing the ratio of the magnetic phase without sintering, 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 and HDDR powders made of Nd-Fe-B alloys are hard and have low deformability, inferior formability during compression molding, and the density of the powder compact is low. It is difficult to improve. 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, the magnetic member is the same as when the green compact is subjected to the HDDR treatment or when the compact is produced using the HDDR powder. I got the knowledge that In particular, the knowledge that a rare earth magnet having a high magnetic phase ratio, specifically, a rare earth-iron-boron alloy magnet can be obtained by using a magnetic member obtained from a powder compact having a high relative density. It was.

  Unlike the sintered body, the magnetic member obtained by subjecting the powder compact to heat treatment and the rare earth magnet obtained by magnetizing the magnetic member can confirm the grain boundaries of the powder used as the raw material. And, if there is a coating layer (heat-resistant coercive force layer) containing rare earth elements whose basic coercive force such as Dy or Tb is higher than that of Nd, etc. on the surface of this grain boundary, that is, the alloy particle constituting the magnetic member, It was found that a high coercive force can be maintained even when the temperature rises. The heat-resistant coercive force layer was found to be formed as follows, for example. Prepare a powder for a magnetic member having the above specific structure, and the surface of each magnetic particle constituting the powder contains a rare earth element having a relatively high coercive force (the above-mentioned Dy or Tb). It is present as a source of rare earth elements for forming the layer. Specifically, a compound with a nonmetallic element (however, other than an oxide), an intermetallic compound with a metal element other than a rare earth element, and an alloy with a metal element other than a rare earth element can be given. A powder compact is formed from the powder containing the rare earth element containing rare earth element, and the powder compact is subjected to a specific heat treatment. By this heat treatment, the rare earth element (the element to form a high coercive rare earth-iron-boron composite) is decomposed from the rare earth source material present on the surface of the magnetic particles, and the decomposed rare earth element, Another compound (rare earth-iron-boron composite) containing the main component of the magnetic member (rare earth element such as Nd, Fe, B) is generated. Thus, the above-mentioned composite constituting the heat-resistant coercive force layer can be formed by the rare earth element decomposed from the rare earth supply source present in the magnetic member powder and the components of the magnetic particles.

  Based on the above knowledge, in the present invention, each magnetic particle constituting the powder for a magnetic member has a form having a specific structure as described above, and the heat-resistant coercive force layer is formed on the surface of the magnetic particle having the specific form. It is proposed to provide a heat-resistant precursor layer for forming.

  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 rare earth element is at least one selected from Nd, Pr, Ce and Y. 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. And the surface of the said magnetic particle is provided with a heat-resistant precursor layer. This heat-resistant precursor layer is a rare earth element comprising at least one of a rare earth element different from the rare earth element in the magnetic particles, specifically, at least one element of Dy and Tb and not containing oxygen and an alloy. Contains source material.

  The powder compact of the present invention is used as a raw material for a magnetic member, and is produced by compression molding the powder for a magnetic member of the present invention. The magnetic member of the present invention is used as a material for rare earth magnets, and is manufactured by heat-treating the above-mentioned powder molded body of the present invention in an inert atmosphere or a reduced pressure atmosphere. And on the surface of the alloy particles constituting the magnetic member, the rare earth element contained in the heat-resistant precursor layer provided on the surface of the magnetic particles constituting the magnetic member powder of the present invention, and the constituent elements of the magnetic particles, And a heat-resistant coercive force layer made of a rare earth-iron-boron composite.

  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 iron-containing phase is softer and more formable than the R-Fe-B alloys, R-Fe-N alloys (including those subjected to HDDR treatment), and the rare earth element hydrogen compounds. Rich. 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, a magnetic material such as a rare earth magnet having a magnetic phase ratio of 80% by volume or more, preferably 90% by volume or more can be obtained 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. . In addition, by eliminating the need for cutting, the yield of raw materials can be dramatically improved, the productivity of magnetic materials such as rare earth magnets can be improved, and deterioration of magnetic properties associated with cutting can be suppressed. it can.

  Furthermore, the magnetic member obtained by subjecting the powder compact of the present invention obtained by compression-molding the powder for a magnetic member of the present invention having the above heat-resistant precursor layer to the specific heat treatment is the surface of the alloy particles constituting the magnetic member ( By providing a heat-resistant coercive force layer containing a rare earth element having a high coercive force at the grain boundary), it can have a high coercive force even in a high temperature environment. Therefore, the rare earth magnet made of the magnetic member of the present invention has excellent magnet characteristics even when used at high temperatures.

  The powder for a magnetic member of the present invention provides a magnetic body such as the powder compact of the present invention having a high moldability and a high relative density, and a rare earth magnet excellent in heat resistance. By using the powder molded body of the present invention or the magnetic member of the present invention, a rare earth magnet having a high magnetic phase ratio and excellent heat resistance, specifically, a rare earth magnet excellent in high temperature coercive force can be obtained without sintering.

FIG. 1 is a process explanatory diagram illustrating an example of a process for manufacturing a magnetic member using the magnetic member powder of the 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 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 5% by mass to 50% by mass when the content of iron is 100%. When the content of the iron-boron alloy is 5% 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 Y (yttrium), Nd, Ce (cerium) and Pr (praseodymium). In particular, Nd is preferable because an R—Fe—B alloy magnet having excellent magnet characteristics can be obtained at a relatively low cost. An example of the rare earth element hydrogen compound is NdH 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 ratio of about the same as 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-based alloy powder, when the ratio of iron or boron (atomic ratio) is increased or the temperature during the heat treatment (hydrogenation) is increased within the specific range, the interval increases. There is a tendency.

  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. The circularity satisfying the above range is preferable because it is easy to form a heat-resistant precursor layer and an insulating coating described later with a uniform thickness, and the damage of the heat-resistant precursor 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.

  The magnetic particles may be single crystalline or polycrystalline. The magnetic particles made of a single crystal can be obtained, for example, by preparing particles made of a polycrystal and appropriately performing a heat treatment.

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.

≪Heat-resistant precursor layer≫
Each of the magnetic particles has a heat-resistant precursor layer on the surface thereof. The heat-resistant precursor layer is a raw material for forming a heat-resistant coercive force layer provided in the magnetic member of the present invention formed from the powder for a magnetic member of the present invention.

  The heat resistant precursor layer is a rare earth source comprising at least one of a rare earth element having a basic coercive force relatively higher than that of the rare earth elements such as Nd, Pr, Y, and Ce in the magnetic particles: a compound and an alloy containing Dy and Tb. Contains material. In particular, Dy has a larger element abundance than Tb, and can secure a stable raw material. Further, the rare earth source material does not contain oxygen. That is, when the rare earth source material is a compound, it is not an oxide. Here, the rare earth element oxide is very stable, and it is very difficult to remove oxygen from the oxide. Therefore, the heat resistant precursor layer is formed so that the heat resistant coercive force layer can be easily formed by decomposing the rare earth element such as Dy from the compound or alloy containing the rare earth element such as Dy by the heat treatment applied to the powder compact as described above. The rare earth source material contained is not an oxide.

  As a rare earth element compound that can easily form a heat-resistant coercive force layer by heat treatment (dehydrogenation treatment) applied to the powder compact, for example, at least one selected from hydride, iodide, fluoride, chloride, and bromide Species are mentioned. These compounds can easily extract Dy and Tb by decomposing hydrogen, iodine, fluorine, chlorine, bromine and rare earth elements by the heat treatment. The heat-resistant precursor layer may be in the form containing only one kind of the above-mentioned compounds, intermetallic compounds and alloys described later, or may be in the form containing plural kinds of compounds, intermetallic compounds and alloys.

  When the compound in the heat-resistant precursor layer is the hydride, both the rare-earth element compound in the magnetic particles and the rare-earth element compound in the heat-resistant precursor layer present on the surface of the magnetic particles are hydrogen compounds. Therefore, it is preferable to easily adjust the heat treatment conditions. When the compound is the iodide, the melting point is relatively low. For example, the heat-resistant precursor layer can be easily formed by melting the iodide and applying it to the surface of the magnetic particles. When the above compounds are fluorides, chlorides, and bromides, these compounds are more inert than hydrides, so that they are difficult to oxidize and have excellent oxidation resistance.

As another rare earth source material capable of forming the heat-resistant coercive force layer, for example, an intermetallic compound or alloy of a rare earth element and a metal element other than the rare earth element can be given. Specifically, an intermetallic compound or alloy of Dy and at least one metal element selected from Mn, Fe, Co, Ni, Cu, Zn, and Ga can be given. For example, many types of intermetallic compounds exist in Dy-Ni alloys and their eutectic melting points are 950 ° C or lower. For example, a eutectic melting point exists in the vicinity of Dy-30 atomic% Ni, and Dy ₃ Ni has a melting point (primary crystal temperature) of 693 ° C. Because of this low eutectic melting point, the temperature during the heat treatment (dehydrogenation treatment) applied to the powder compact can be adjusted and a sufficient liquid phase can be generated. From this liquid phase, rare earth elements such as Dy are efficiently magnetized. Can be supplied to particles. Therefore, a heat resistant coercive force layer can also be formed by heat treatment (dehydrogenation treatment) for the heat resistant precursor layer containing the intermetallic compound or alloy. Specific examples of those having a low eutectic melting point include Dy ₃ Ni and Dy ₃ Ni ₂ .

  Specific examples of the heat-resistant precursor layer include, for example, (1) a form made of a film containing a rare earth element such as Dy (including an intermetallic compound) or an alloy, and (2) a compound of the rare earth element or Examples include an alloy and a fixed layer for covering at least a part of the surface of the rare earth element compound or alloy and fixing the compound or alloy on the surface of the magnetic particles. In the form (2), if the rare earth element compound or alloy is granular, it is easy to form a heat-resistant precursor layer, and a form containing a plurality of types of compounds and alloys can be easily formed.

  Here, when the powder compact is heat-treated as described above, rare earth elements such as Dy decomposed from the rare earth source material diffuse and penetrate from the surface of the magnetic particles constituting the powder compact to the inside. And the heat-resistant coercive force layer which consists of a composite containing the said rare earth element and the component of the said magnetic particle can be formed. That is, at least a part of the rare earth element such as Nd is replaced with a rare earth element such as Dy in the surface layer region of the magnetic particle to form the heat-resistant coercive force layer. Therefore, the thickness of the coating (1) and the compound (2) are adjusted so that the substitution amount is 30% to 100% of the rare earth element such as Nd and the thickness of the heat-resistant coercive force layer is about 100 nm to 2000 nm. It is preferable to adjust the average particle diameter and addition amount of particles (including intermetallic compounds) and alloys (hereinafter referred to as supply source particles), the heat treatment conditions applied to the powder compact, and the like. The thickness of the coating is preferably 50 nm or more and 1000 nm or less. If the average particle size of the source particles is 0.1 μm (100 nm) or more, compounds and alloys can exist stably, and if the average particle size is 5 μm (5000 nm) or less, a decrease in the packing density of the powder composed of magnetic particles is suppressed. it can. Moreover, it is preferable that the addition amount of the said source particle becomes an amount which covers 15%-50% with respect to the surface area of a magnetic particle.

  The source particles are not particularly limited in shape as long as they are small pieces. For example, a foil piece other than a spherical outer shape may be used. When the rare earth source material is a compound, the source particles can be produced by appropriately pulverizing a lump or foil of the compound. When the rare earth source material is an intermetallic compound or alloy, the source particles can be produced by pulverizing a melt-cast ingot or using a gas atomizing method. Alternatively, commercially available products (powder etc.) can be used as the source particles.

  The fixing layer is preferably made of a resin. That is, as an embodiment of the present invention, the rare earth source material is granular, and the source particles are fixed to the surface of the magnetic particles by the resin layer.

  When the fixed layer is made of a resin, (1) at the time of compression molding, can sufficiently follow the deformation of the magnetic particles, (2) when the powder compact is heat-treated, etc. It has the effect that the fall of the magnetic phase by the residue of resin can be suppressed.

The resin preferably has an oxygen permeability coefficient (30 ° C.) of less than 1.0 × 10 ⁻¹¹ m ³ · m / (s · m ² · Pa). Here, when the powder for a magnetic member of the present invention is compression molded, a new surface is formed on each magnetic particle 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. As a means for preventing this oxidation, for example, molding may be performed in a non-oxidizing atmosphere, but in this case, a large facility is required.

  On the other hand, as described above, at least a part of the surface of the magnetic particle is covered with a resin having a low oxygen permeability coefficient and a high antioxidant effect, preferably the entire circumference of the magnetic particle is covered. If the form is cut off from the outside air, the new surface of the magnetic particles can be effectively prevented from being oxidized at the time of compression molding, even if compression molding is performed in an atmosphere containing oxygen such as an atmospheric atmosphere. Accordingly, it is possible to suppress a decrease in the magnetic phase due to the presence of the rare earth oxide, and it is possible to produce a magnetic body such as a rare earth magnet having a high magnetic phase ratio with high productivity. Thus, by using what has an antioxidant function as said resin, the layer which consists of the said resin functions also as an antioxidant layer in addition to fixation of the said source particle.

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. In addition, the new surface is oxidized to produce an oxide, and the presence of this oxide causes a decrease in the magnetic phase in the magnetic member. Therefore, the oxygen permeability coefficient (30 ° C.) is preferably as small as possible, more preferably 0.01 × 10 ⁻¹¹ m ³ · m / (s · m ² · Pa) or less, and no lower limit is provided.

  The resin layer having the antioxidant function is preferably provided so as to cover the surface of the coating even when the heat-resistant precursor layer is formed of the coating described above. That is, as one form of the heat-resistant precursor layer, a resin that covers the rare earth source material (typically the coating film or the source particles) and at least a part, preferably all of the surface of the rare earth source material. And the resin has a form in which the permeability coefficient of oxygen satisfies the specific range.

Further, the resin preferably satisfies 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 resin 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 resin layer may be a single layer or a multilayer. For example, a single layer form comprising only a low oxygen permeability layer composed of a resin having an oxygen permeability coefficient (30 ° C.) of less than 1.0 × 10 ⁻¹¹ m ³ · m / (s · m ² · Pa), oxygen permeability coefficient was (30 ° C.) is ^{1.0 × 10 -11 m 3 · m} / less than ^{(s · m 2 · Pa)} , and moisture permeability (30 ° C.) is 1000 × 10 of ^-13 kg / (m · s・ Single layer form with oxygen / moisture low permeability layer composed of resin less than (MPa), the above oxygen low permeability layer, and moisture permeability (30 ° C.) of 1000 × 10 ⁻¹³ kg / (m ・ s -The multilayer form which laminates | stacks the moisture low-permeability layer comprised from resin which is less than (MPa) is mentioned.

Examples of the constituent resin for the low oxygen permeability layer include one selected from polyamide resins, polyesters, 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 resin of the low moisture permeable layer include 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).

  In the case where the oxygen low-permeability layer and the moisture low-permeability layer are laminated, any layer may be disposed on the inner side (the magnetic particle side) and the outer side (outermost surface side), It is expected that oxidation can be more effectively prevented by disposing the low oxygen permeable layer on the inside and the low moisture permeable layer on the outside. Moreover, it is excellent in the adhesiveness of both layers because both layers of a low oxygen permeable layer and a low moisture permeable layer are comprised with resin as mentioned above. Further, in the case where the oxygen low-permeability layer and the moisture low-permeability layer are laminated, the layer disposed on the magnetic particle side is a fixed layer, which contributes to maintenance of coercive force in a high temperature environment. Rare earth elements such as Dy are preferably present at the grain boundaries of the magnetic member.

  The thickness of the resin layer can be selected as appropriate, but if it is too thin, the supply source particles cannot be sufficiently fixed, or the antioxidant effect cannot be sufficiently obtained. On the other hand, if it is too thick, the density of the powder compact is reduced, and for example, it becomes difficult to form a powder compact with a relative density of 85% or more or to remove it by burning. When the resin layer has a multilayer structure such as a two-layer structure, or a single-layer structure including only the oxygen low-permeability layer or the moisture low-permeability layer, the thickness of each layer is preferably 10 nm or more and 500 nm or less. The total thickness is preferably 20 nm or more and 1000 nm or less. In particular, the thickness of the layer functioning as the fixed layer is, for example, about the same or less than the average particle diameter of the source particles, particularly 200 nm to 1000 nm. In addition to being suppressed, it has excellent moldability.

≪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 organic-inorganic hybrid compounds such as silsesquioxane compounds. In order to improve thermal conductivity, Si-N or Si-C ceramic coating may be applied. These insulating coatings and ceramic coatings may have an antioxidant function, and in this case, they can also function as an antioxidant layer. In the form including these insulating coatings and ceramic coatings, it is preferable to provide the heat-resistant precursor layer so as to be in contact with the surface of the magnetic particles, and to provide the insulating coating and ceramic coating thereon. Moreover, these insulating coatings can also be made into the form which is a fixed layer for fixing the supply source particle which comprises the said heat-resistant precursor layer.

[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 an atmosphere containing a hydrogen element at a temperature equal to or higher than the disproportionation temperature of the rare earth-iron-boron alloy, and a rare earth element hydrogen compound phase, iron, iron, and boron. Forming a phase of an iron-containing material containing an iron-boron alloy containing iron, and forming a base powder in which the phases of the rare earth element hydrogen compounds are discretely present in the phase of the iron-containing material.
Coating step: A heat-resistant precursor layer containing a rare earth source material comprising at least one of a compound and an alloy containing at least one of Dy and Tb and not containing oxygen on the surface of each magnetic particle constituting the base powder. Forming step.

≪Preparation process≫
The alloy powder may be 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 using 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, as the alloy powder made of the rare earth-iron-boron alloy, a powder obtained by a known powder production method or a powder obtained by further pulverizing a powder produced by an atomization method may be used. 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, it is easy to obtain a powder having a high sphericity and an excellent filling property at the time of molding. For example, a nearly spherical powder having a circularity of 0.5 to 1.0 can be obtained. In other words, the circularity satisfying the above range is one index indicating that the powder is manufactured by the atomizing method.

  The size of the alloy powder prepared in this preparation step is substantially the size of the magnetic member powder of the present invention when the heat treatment is performed so that the size is not substantially changed during the subsequent hydrogenation treatment. Become. 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, for example, a raw material powder (powder constituting a green body before sintering) used for manufacturing a sintered magnet has a fine particle size of 10 μm or less. The pulverization can be eliminated, and the manufacturing cost can be reduced by shortening the manufacturing process.

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

Examples of the atmosphere containing hydrogen element include a single atmosphere containing only hydrogen (H ₂ ) or a mixed atmosphere of hydrogen (H ₂ ) 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 hard rare earth element hydrogen compounds that precipitate at the same time are less likely to be a hindrance to deformation. However, if the temperature is too high, problems such as melting and fixing of the powder 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 a heat resistant precursor layer on the surface of each magnetic particle constituting the obtained base powder.

In the case where the heat-resistant precursor layer is the above-described film, for example, the following forming method may be mentioned.
(I) After forming a metal film of a rare earth element such as Dy on the surface of the magnetic particles by a film deposition method such as physical vapor deposition (PVD method) or plating, a desired compound such as the hydrogen compound described above is formed. Heat treatment is performed in an appropriate atmosphere (for example, a hydrogen-containing atmosphere) so that it can be generated.
(II) Prepare a deposition source on the surface of the magnetic particles by a deposition method such as physical vapor deposition (PVD method) so that a desired alloy such as the above-mentioned Dy-Ni alloy can be generated. . For example, a rare earth element such as Dy and a metal element such as Ni are prepared as a deposition source, and a film is formed by supplying both of these elements simultaneously, or an alloy containing a rare earth element such as a Dy-Ni alloy as a deposition source. And preparing a film.
(III) As described above, a desired compound such as iodide or an alloy is melted and applied to the surface of the magnetic particles.
(IV) A desired alloy such as the above-described Dy-Ni alloy is mixed with the magnetic particles by mechanical alloying to form the alloy coating on the surface of the magnetic particles.
After forming the heat-resistant precursor layer, a resin layer having the above-described antioxidant function may be further formed. For the formation of the resin layer, for example, in a wet method, a wet dry coating method or a sol-gel method can be used. More specifically, by mixing a solution prepared by dissolving and mixing a resin in an appropriate solvent and magnetic particles having the heat-resistant precursor layer, the resin is cured and the solvent is dried. A resin layer can be formed. In the dry method, powder coating can be used.

In the case where the heat-resistant precursor layer is provided with the above-described supply source particles and the fixed layer, for example, the following forming method may be mentioned.
(I) The source particles are mixed with the constituent material of the fixed layer, and the mixture is applied to the surfaces of the magnetic particles.
(II) After the constituent material of the fixed layer is applied to the surface of the magnetic particles, the source particles are adhered.
As the constituent material of the fixed layer, as described above, a resin, particularly a resin having an antioxidant function can be suitably used. In this case, a solution prepared by dissolving and mixing the resin in an appropriate solvent, the base powder and the separately supplied source particles are mixed, and the resin is cured and the solvent is dried. After the solution and the base powder are mixed and the source particles are adhered in a state where the resin is uncured, the heat-resistant precursor layer can be formed by completely curing the resin.

For the formation of the heat-resistant precursor layer, both the dry method and the wet method can be used as described above. In the dry method (for example, PVD method), in order to prevent the magnetic particles from contacting the 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 or the like is preferable. In the wet method, since the surface of the magnetic particles does not substantially contact oxygen in the atmosphere, it is not necessary to use the above-described inert atmosphere, and for example, the heat-resistant precursor layer can be formed in an air atmosphere. Therefore, the wet method is excellent in the workability of forming the heat-resistant precursor layer, and it is easy to form the coating film and the resin layer on the surface of the magnetic particles with a uniform thickness.

  In the case where the above-described insulating coating or ceramic coating is separately provided, the insulating coating or the like may be appropriately formed on the surface of the base powder after forming the heat-resistant precursor layer.

[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 ratio can be obtained. The higher the relative density, the higher the magnetic phase ratio. However, when the component (typically resin) of the fixed layer is burned off in the heat treatment step for forming the magnetic member described later, or the heat treatment for removing the component of the fixed layer is burned away, When the density is too high, it becomes difficult to sufficiently burn out the constituent components of the fixed layer. 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 fixed layer or to sufficiently perform a separate heat treatment (coating removal) as will be described later in order to easily remove the constituent components of the fixed layer.

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. 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.

  Furthermore, when the powder for a magnetic member of the present invention includes a layer made of a resin having a small oxygen permeability coefficient as described above, it is possible to sufficiently prevent oxidation of a new surface formed on the magnetic particles constituting the powder during compression molding. The molding can be performed in an oxygen-containing atmosphere such as an air atmosphere and is excellent in workability. The powder compact 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. Combine. By this combination, a main component of the magnetic member, typically a rare earth-iron-boron alloy can be generated. At the same time, the rare earth element is separated from the rare earth source material constituting the heat-resistant precursor layer, and the separated rare earth element is diffused into the surface layer portion of the magnetic particles constituting the powder compact, whereby the rare earth-iron-boron composite is formed. Generate. By this diffusion, a heat-resistant coercive force layer made of a rare earth-iron-boron composite can be formed. Through this step, the magnetic member of the present invention is obtained.

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. The higher this temperature, the more hydrogen can be 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.

  The heat treatment (dehydrogenation) also serves to form a heat-resistant coercive force layer as described above. Furthermore, when the heat-resistant precursor layer includes a phase such as a resin that can be burned out by high heat, the heat treatment (dehydrogenation) also serves to remove the resin component. A heat treatment (coating removal) for removing the resin component may be separately performed. Although this heat treatment (coating removal) depends on the resin component, 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 resin component is rapidly heated to the heating temperature for dehydrogenation, causing incomplete combustion and generating residue. This is preferable because it can be effectively prevented.

  The alloy particles (internal composition) constituting the magnetic member of the present invention are substantially in a single form composed of a rare earth-iron-boron alloy phase, substantially an iron phase, an iron-boron alloy phase, and A mixed form composed of a combination of at least one phase selected from a rare earth-iron alloy phase and a rare earth-iron-boron alloy phase, for example, an iron phase and a rare earth-iron-boron alloy phase. Examples thereof include a morphology, a morphology of an iron-boron alloy phase and a rare earth-iron-boron alloy phase, and a morphology of a rare earth-iron alloy phase and a rare earth-iron-boron alloy phase. 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.

On the other hand, the composition of the surface layer portion of the alloy particles constituting the magnetic member of the present invention is composed of the rare earth elements such as Dy and Tb contained in the heat-resistant precursor layer as described above and the constituent elements of the magnetic particles constituting the powder compact ( Examples include composites containing rare earth elements such as Y, Nd, Pr, and Ce, Fe, and B), for example, (Dy, Nd) ₂ Fe ₁₄ B. A region where the composite exists functions as a heat-resistant coercive force layer.

  The thickness of the heat-resistant coercive force layer is adjusted by adjusting the thickness of the coating of the rare earth source material constituting the heat-resistant precursor layer, the size of the source particles, the amount of the source particles added, and the heat treatment conditions as described above. Can be changed. A thickness of 100 nm to 2000 nm is preferable because a high coercive force can be sufficiently provided even in a high temperature environment.

  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 the sintered compact as mentioned above. 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 can be 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 ratio of 80% by volume or more and further 90% by volume or more can be obtained, and the rare earth magnet can be used in a high temperature environment. However, a high coercive force can be maintained.

  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, the hydrogen compound of rare earth elements and the heat-resistant precursor layer are exaggerated for easy understanding.

[Embodiments 1 and 2]
A powder containing a rare earth element, iron and boron was prepared, and the obtained powder was compression molded to examine the moldability 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 a heat-resistant precursor 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 atomization method is used to produce a material in which each particle constituting the alloy powder is made of a polycrystalline body, and this powder is subjected to heat treatment (powder annealing: 1050 ° C. × 120 minutes, in high concentration argon). An alloy powder made of a single crystal (FIG. 1 (II)) was prepared.

The alloy powder was heat-treated at 800 ° C. for 1 hour in a hydrogen (H ₂ ) atmosphere. To the base powder obtained after this heat treatment (hydrogenation), a Dy hydrogen compound (DyH ₂ ) or a binary alloy of Dy and Ni (Dy-30 atomic% Ni) and a polyamide resin (here, nylon 6 And a heat-resistant precursor layer including an oxygen permeability coefficient (30 ° C.): 0.0011 × 10 ⁻¹¹ m ³ · m / (s · m ² · Pa). A 1 μm commercial DyH ₂ powder or a commercial DyNi powder having an average particle diameter of 1 μm was prepared, and a mixture prepared by mixing DyH ₂ powder or DyNi powder in the polyamide-based resin dissolved in an organic solvent was prepared. The base powder is further mixed, and then the solvent is dried and the resin is cured to provide a powder comprising a heat-resistant precursor layer containing DyH ₂ (Embodiment 1), or a heat-resistant precursor layer containing DyNi (Embodiment 2) In each of Embodiments 1 and 2, the average thickness of the resin component of the heat-resistant precursor layer is 200 nm. The amount of the resin was adjusted so that the average thickness (the volume of the resin / the above each of the resin layers) was assumed to be uniformly formed on the surface of each magnetic particle constituting the base powder. In addition, the DyH ₂ powder and the DyNi powder are in a state where a part of the source particles constituting the powder are fixed by the resin component, and the thickness of the resin layer The surface area of the magnetic particles can be measured by, for example, the BET method, and the oxygen permeability coefficient (30 ° C.) is formed on the surface of the magnetic particles constituting the magnetic member powder. With the resin layer having a density of less than 1.0 × 10 ⁻¹¹ m ³ · m / (s · m ² · Pa), a powder for magnetic member in which granular DyH ₂ or DyNi is fixed is obtained.

In this test, the obtained powder and polyethylene (moisture permeability (30 ° C.): 50 × 10 ⁻¹³ kg / (m · s · MPa)) were above the melting point of polyethylene and below the melting point of nylon 6. The mixture was heated to 150 ° C. while mixing and then cooled as it was to prepare a further coated polyethylene. By this step, a powder for a magnetic member having a resin layer (oxygen low-permeability layer) for fixing the rare earth source material (supply source particles) and a moisture low-permeability layer 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 (III) and 1 (IV), each of the magnetic particles 1 is a phase of the iron-containing material 2, specifically iron (Fe) and 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 iron-containing substances are present between adjacent rare earth element hydrogen compound 3 particles. It was confirmed that two phases were present. Further, as shown in FIG. 1 (IV), the surface of the magnetic particle 1 is provided with a heat resistant precursor layer 4 in which a granular rare earth source material (here DyH ₂ or DyNi) 4a is fixed by a resin layer 4b. It was confirmed. Furthermore, it was confirmed that substantially the entire circumference of the surface of the magnetic particle 1 was covered with the resin layer 4b and was blocked from the outside air. In addition, 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 (or polished surface), the peak position of NdH ₂ was extracted, the interval between the peak positions of adjacent NdH ₂ was measured, and the average value of all the intervals was obtained. .

Using the sample prepared by kneading the epoxy resin, the content (volume%) of NdH ₂ and iron-containing material (Fe, Fe-B) of each magnetic particle was determined. NdH ₂ : 33 volume% 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 kneading the epoxy resin, the circularity of the magnetic particles was determined to be 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 heat-resistant precursor layer produced as described above was compression-molded by a hydraulic press device at a surface pressure of 10 ton / cm ² (FIG. 1 (V)). Here, the molding was performed in an air atmosphere (temperature: 25 ° C., humidity: 75%). 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 (VI)) 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 90%. 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. 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 can be seen that by using a resin as a constituent component of the heat-resistant precursor layer, it is possible to sufficiently follow the deformation of the magnetic particles constituting the magnetic member powder during compression molding, and the powder is excellent in moldability. Furthermore, by using a powder having the surface of the magnetic particles covered with a resin having an antioxidant effect, the formation of a rare earth element oxide can be suppressed, and a powder molded body substantially free of the oxide can be obtained. I understand.

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 (VII))) 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, the cylindrical member is composed of a alloy particles 5 made of the Nd ₂ Fe ₁₄ B, that the surface layer portion of the alloy particles 5 _{(Dy, Nd) 2 Fe 14} B ingredients are present confirmed. The component of (Dy, Nd) ₂ Fe ₁₄ B can be confirmed by confirming the crystal structure by XRD, performing surface analysis using an EDX apparatus, or performing line analysis. Since (Dy, Nd) ₂ Fe ₁₄ B component exists in the surface layer portion of alloy particle 5, DyH ₂ and DyNi constituting the heat-resistant precursor layer are decomposed by the heat treatment, and the Dy component is the powder compact. The heat-resistant coercive force layer 6 made of a composite containing the rare-earth element (Dy) of the heat-resistant precursor layer and the elements (Nd, Fe, B) of the magnetic particle 1 is diffused into the magnetic particles constituting You can see that it was formed.

Further, when the columnar member was analyzed by X-ray, a clear diffraction peak of a rare earth element oxide (here, Nd ₂ O ₃ ) or a resin component residue of the heat-resistant precursor layer was not detected.

  It can be seen that a magnetic member having a heat-resistant coercive force layer made of a rare earth-iron-boron composite can be obtained by using a powder for a magnetic member having a heat-resistant precursor layer containing a specific rare earth element as described above. A rare earth magnet made of a magnetic member that excels this heat-resistant coercive force layer is expected to have a high coercive force even in a high temperature environment.

In addition, this powder for magnetic members can suppress the generation of oxides of rare earth elements such as Nd ₂ O ₃ that causes a decrease in coercive force by including a resin having an anti-oxidation effect as a constituent component of the heat-resistant precursor layer. I understand. In this embodiment, by providing a moisture low permeability layer in addition to the oxygen low permeability layer, even when the atmosphere during compression molding is high humidity, each magnetic particle constituting the magnetic member powder is formed during compression molding. It is considered that the formed new surface could be prevented from being oxidized by contact with moisture in the atmosphere, and the generation of rare earth element oxides could be suppressed. From this point, it is expected that a rare earth magnet having a high coercive force will be obtained.

  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.

[Test example]
Samples obtained after magnetizing a magnetic member made of a rare earth-iron-boron alloy using the magnetic member powder of Embodiments 1 and 2 described above with a pulse magnetic field of 2.4 MA / m (= 30 kOe) ( The magnet characteristics of the rare earth-iron-boron alloy magnet) were examined using a BH tracer (DCBH tracer manufactured by Riken Denshi Co., Ltd.). The results are shown in Table 1. Here, as magnetic properties, saturation magnetic flux density at room temperature: RT (about 20 ° C): Bs (T), residual magnetic flux density: Br (T), intrinsic coercivity: iHc (kA / m), magnetic flux density B and decrease. Maximum value of product with magnetic field magnitude H: (BH) max (kJ / m ³ ), and Bs (T), Br (T), iHc (kA / m), (BH) max (kJ) at 100 ° C / m ³ ). In addition, as a comparison, magnetic particles having only a resin layer made of nylon 6 without using DyH ₂ powder and DyNi powder were formed in the same manner as in Embodiments 1 and 2, and using this powder, Embodiments 1 and 2 were used. A sample (rare earth-iron-boron alloy magnet) was prepared in the same manner as in 2, and the above-mentioned magnet characteristics were measured. The results are shown in Table 1.

  As shown in Table 1, a magnetism in which the rare earth element hydrogen compound is less than 40% by volume and the balance is substantially iron-containing, and the rare earth element hydrogen compound is discretely present in the iron-containing phase. It can be seen that a rare earth magnet produced using a powder comprising particles having a specific heat-resistant precursor layer on the surface of the particles has a high coercive force and excellent magnet characteristics even in a high temperature environment.

[Modification]
In the above embodiment, a resin layer having a low oxygen permeability is used as the resin layer constituting the heat-resistant precursor layer on the surface of the magnetic member, and the moisture composed of a resin having a lower moisture permeability on the oxygen low-permeability layer. Although the embodiment including the low-permeability layer has been described, the resin layer constituting the heat-resistant precursor layer can be the oxygen low-permeability layer only.

  Note that the present invention is not limited to the above-described embodiment, and can be modified as appropriate without departing from the gist of the present invention. For example, composition of magnetic particles (constituent elements, proportion of rare earth element hydrogen compounds and iron-containing materials), circularity, average particle size of powder for magnetic member, form of heat-resistant precursor layer (for example, coating), heat-resistant precursor layer Material (compound and alloy constituent elements, resin type, etc.), average particle size of the rare earth source material constituting the heat-resistant precursor layer, thickness of the resin layer constituting the heat-resistant precursor layer, oxygen permeability coefficient, moisture permeability The ratio, 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 particles 2 Iron-containing materials 3 Rare earth element hydrogen compounds 4 Heat-resistant precursor layer
4a Granular rare earth source 4b Resin layer 5 Alloy particles 6 Heat resistant coercive force layer

Claims (10)

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 rare earth element is at least one selected from Nd, Pr, Ce and Y,
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,
Provided with a heat-resistant precursor layer on the surface of the magnetic particles,
The magnetic member powder according to claim 1, wherein the heat-resistant precursor layer contains a rare earth source material containing at least one of a compound and an alloy containing at least one rare earth element of Dy and Tb and not containing oxygen.   2. The rare earth source material contained in the heat-resistant precursor layer is at least one selected from hydrides, iodides, fluorides, chlorides, bromides, intermetallic compounds, and alloys. The powder for magnetic members as described in 2. The heat-resistant precursor layer includes the rare earth source material and a layer made of a resin covering at least a part of the surface of the rare earth source material,
^3. The magnetic member according to claim 1, wherein the resin has an oxygen permeability coefficient (30 ° C.) of less than 1.0 × 10 ⁻¹¹ m ³ · m / (s · m ² · Pa). Powder.   4. The powder for a magnetic member according to claim 3, wherein the rare earth source material is granular, and the source particles are fixed to the surface of the magnetic particles by the layer made of the resin.   5. The magnetic member powder according to claim 3, wherein the resin is one selected from a polyamide-based resin, polyester, and polyvinyl chloride.   6. 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. 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 6.   8. The powder compact according to claim 7, wherein a relative density of the powder compact is 85% or more. A magnetic member used for a rare earth magnet material,
The powder molded body according to claim 7 or 8 is produced by heat treatment in an inert atmosphere or a reduced pressure atmosphere,
Characterized in that a heat-resistant coercive force layer made of a rare earth-iron-boron composite containing the rare earth element of the heat resistant precursor layer and the constituent elements of the magnetic particle is provided on the surface of the alloy particles constituting the magnetic member. Magnetic member to be used.   10. The magnetic member according to claim 9, 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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