JP2012253247A - Composite magnetic material and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a composite magnetic material which excels in magnetic properties and is suitable as a material for magnets, and to provide a method for manufacturing the same.SOLUTION: Granulated powders made by mixing nano iron powders, multiphase powders containing a hydrogen compound of a rare earth element and an iron-containing material, and a binder are pressure-molded. The pressure molding is carried out while performing exhaust at 0.9 atmospheres or less and a temperature of ±20°C of a decomposition temperature of the binder. Heat treatment (dehydrogenation) of the obtained first molded body is performed under a reduced-pressure atmosphere at a temperature equal to or higher than a recombination temperature to form a recombination alloy containing a rare earth element and Fe from the multiphase powders, and heat treatment (nitriding) of the obtained second molded body is performed under a nitrogen atmosphere at a temperature of 200°C to 450°C to form α''FeNfrom the nano iron powders and a rare earth-iron-nitrogen alloy from the recombination alloy. Both heat treatments are performed by applying a strong magnetic field. A magnetic field is applied in the nitriding treatment to form α''FeN, and orientation directions of easy axes of magnetization in the rare earth-iron-nitrogen alloy and α''FeNare uniformed.

Description

  The present invention relates to a composite magnetic material suitable for a material of a magnetic member such as a permanent magnet, and a manufacturing method thereof. In particular, the present invention relates to a composite magnetic material having excellent magnetic properties.

  Rare earth magnets are widely used as permanent magnets used in motors and generators. Typical rare earth magnets include sintered magnets and bonded magnets made of an R—Fe—B alloy (R: rare earth element) such as Nd (neodymium) —Fe (iron) —B (boron). As a bonded magnet, a magnet made of an Sm (samarium) -Fe—N (nitrogen) alloy has been studied as one having superior magnetic properties as compared with a magnet made of an Nd—Fe—B alloy.

  Sintered magnets have a low degree of freedom in shape. Bond magnets are typically manufactured by compression-molding or injection-molding a mixture of an alloy powder composed of an R-Fe-B alloy or Sm-Fe-N alloy and a binder resin. Therefore, the degree of freedom of shape is high, and it is possible to cope with a desired shape.

On the other hand, for materials such as magnetic recording media, a mixture of nano-powder made of spherical iron nitride with a particle size of nano-order or columnar iron nitride with a short axis of nano-order and a binder such as resin or organic resin A tape-shaped iron nitride material applied to a support film made of the above is used (see Patent Document 1). As this iron nitride, α ”type Fe ₁₆ N ₂ with very high saturation magnetization and excellent magnetic properties (saturation magnetization: about 2.8 T in tetragonal calculations, thin film experiments, tetragonal, a = 5.72Å, c = 6.29mm, crystal symbol: I4 / mmm).

JP 2007-335592 A

  However, the conventional rare earth magnet has a small magnetic force. Therefore, it is desired to develop a material having better magnetic properties.

  The alloy powders used in the above-mentioned bonded magnets can be treated with HDRR (Hydrogenation-Disproportionation-Desorption-Recombination, HD: hydrogenation and disproportionation, DR: dehydrogenation and recombination) to increase the coercive force. Has been done. However, the bonded magnet has a low magnetic phase ratio due to the presence of inclusions such as a binding resin, and has poor magnetic properties due to a low magnetic phase ratio.

On the other hand, if the iron nitride material containing α ″ Fe ₁₆ N ₂ described above is used as a magnet material, it is expected that a permanent magnet having excellent magnetic properties will be obtained. However, conventional iron nitride materials are bonded as described above. Due to the presence of the agent, the support film, etc., the magnetic properties are inferior, and it is difficult to apply to a material of a magnetic member such as a magnet.

  Moreover, when using the nanopowder described above as a raw material powder, the magnetic properties can be further improved by forming the nanoparticle with the crystal orientation in a specific direction. However, nanopowder generally tends to aggregate and has high surface energy. For this reason, it is difficult to shape the crystal orientation of the nanoparticles in a specific direction. When coarsening is caused by aggregation, the magnetic properties are lowered.

  Accordingly, one of the objects of the present invention is to provide a composite magnetic material having excellent magnetic properties. Another object of the present invention is to provide a method for producing the composite magnetic material.

Use of composite magnetic materials containing both rare earth elements and Fe, such as R-Fe-B alloys and Sm-Fe-N alloys mentioned above, and α "Fe ₁₆ N ₂ as magnet materials It is expected that permanent magnets with excellent magnetic properties will be obtained, and in order to improve the magnetic properties, (1) increase the proportion of the magnetic phase, and (2) the orientation structure will depend on magnetic anisotropy. In view of this, the present inventors have studied a raw material for obtaining such a composite magnetic material and a method for producing the same.

  In order to increase the degree of magnetic phase without sintering and having a high degree of freedom in shape, it is desirable to use a powder excellent in moldability without using a binder resin such as a bonded magnet. However, alloy powders such as Sm-Fe-N alloys and Nd-Fe-B alloys used for the above-mentioned rare earth magnet raw powders, and processed powders obtained by applying HDDR treatment to the above alloy powders are hard and deformed. Low performance and inferior moldability during compression molding. As a result of various investigations on powders having excellent formability, the present inventors have found that rare earth elements and Fe are not bonded, such as Sm-Fe-N alloys and Nd-Fe-B alloys, but rare earth elements. It was found that if a powder having a multiphase structure in which the element and Fe do not bond, that is, the rare earth element component and the Fe component exist independently, the deformability is high and the moldability is excellent. In addition, the powder compact having a specific multiphase structure is subjected to heat treatment under specific conditions (heat treatment for recombination and, optionally, nitriding treatment), so that Sm-Fe-N alloys and Nd-Fe It was found that an alloy material containing rare earth elements and Fe, such as an -B alloy, and having excellent magnetic properties can be obtained. Furthermore, the knowledge that a crystal orientation was orientated by applying a specific magnetic field at the time of the heat treatment to obtain an oriented structure was obtained. In particular, when a rare earth-iron-nitrogen alloy such as an Sm-Fe-N alloy is produced by nitriding, an arbitrary lattice axis (a-axis, b-axis, c-axis) is applied by applying a specific magnetic field. ) Can be distorted by magnetostriction between Fe atoms and Fe atoms aligned along a uniaxial direction (for example, c-axis direction), and selectively between the distorted (stretched) Fe atoms and Fe atoms. It was found that a rare earth-iron-nitrogen alloy having an ideal atomic ratio can be obtained by arranging N atoms. And the knowledge that the powder which has the said specific multiphase structure | tissue can be manufactured by giving specific heat processing to the alloy containing rare earth elements and Fe was acquired.

On the other hand, nano-powder containing α ″ Fe ₁₆ N ₂ as a main component can be obtained by subjecting raw material to nitriding treatment on nano-order pure iron powder (powder mainly composed of α-iron). By applying a heat treatment including nitriding treatment to a molded body in which a powder having a phase structure and this nano-order pure iron powder are mixed, a rare-earth element and Fe are finally obtained from the powder having a multi-phase structure. It is considered that an alloy (a recombination alloy or an alloy containing nitrogen) is obtained, and α "Fe ₁₆ N ₂ can be generated from pure iron powder. In particular, the present inventors applied a specific magnetic field in the production of α ”Fe ₁₆ N ₂ , so that any lattice axis (a axis, b axis) of the basic lattice of iron (body-centered cubic lattice: bcc) , c axis) can be distorted by magnetostriction between Fe atoms and Fe atoms arranged along one axis direction (for example, c axis direction), and between these distorted (stretched) Fe atoms and Fe atoms. We obtained knowledge that α "Fe ₁₆ N ₂ can be efficiently generated by selectively arranging N atoms.

And by applying a specific magnetic field during nitriding treatment, we obtained knowledge that the orientation direction of the crystal of the alloy containing rare earth elements and Fe can be aligned with the orientation direction of the crystal of α "Fe ₁₆ N ₂ .

  However, the nano-order pure iron powder is easy to aggregate and easily coarsen when mixed with the powder having the specific multiphase structure described above. When the coarsened pure iron powder is nitrided, iron nitride having excellent magnetic properties cannot be obtained.

  In mixing the powder having the specific multiphase structure and the nano-order pure iron powder, the present inventors further mixed a specific binder, and the granulated powder produced by the mixture containing the binder. It was found that by filling the mold and degassing while heating to a specific temperature and molding while removing the binder, aggregation can be prevented and the moldability is excellent. The present invention is based on these findings.

The method for producing a composite magnetic material of the present invention relates to a method for producing a composite magnetic material containing a plurality of magnetic bodies, and includes the following preparation step, granulation step, molding step, dehydrogenation step, A nitriding step.
Preparation process: The process of preparing the following nano iron powder and multiphase powder as raw material powder.
Nano iron powder is a powder composed of columnar particles containing Fe as a main component and having an average minor axis length of 100 nm or less. The multiphase powder is a powder composed of multiphase particles containing a phase of a rare earth element hydrogen compound and a phase of an iron-containing material containing Fe.
Granulation step: A step of mixing a binder having a decomposition temperature of 240 ° C. or lower and the raw material powder to form a granulated powder.
Molding step: a step of forming a first molded body by filling the granulated powder into a molding die and then press-molding the molding die in a state heated to the following temperature while evacuating the molding die to 0.9 atm or less.
The temperature in the molding step is set to {(decomposition temperature of the binder) −20} ° C. or more and {(decomposition temperature of the binder) +20} ° C. or less.
Dehydrogenation step: In the reduced pressure atmosphere of 100 Pa or less, the first molded body is subjected to a heat treatment at a temperature equal to or higher than the recombination temperature of the multiphase particles to separate hydrogen from the multiphase particles, and the rare earth element and the above The process of producing | generating the recombination alloy couple | bonded with the iron containing material and forming the 2nd molded object containing the said recombination alloy.
Nitriding step: The second molded body is subjected to heat treatment at a temperature of 200 ° C. or higher and 450 ° C. or lower in an atmosphere containing nitrogen element and an oxygen concentration of 200 mass ppm or less, and α′Fe ₁₆ N from the nano iron powder. ₂ is a process for forming a composite magnetic material containing α "Fe ₁₆ N ₂ .
The heat treatment in the dehydrogenation step is performed by applying a magnetic field of 2 T or more to the first molded body, and the heat treatment in the nitriding step is performed on the second molded body in the direction in which the magnetic field is applied in the dehydrogenation process. Apply a magnetic field of 3T or more in the same direction.

The decomposition temperature in the binder is the temperature at which the binder begins to lose weight (TG / DTA) after the differential thermal / thermogravimetric curve (TG / DTA) of the binder is obtained at atmospheric pressure (1 atm ≒ 0.1 MPa). Temperature), and here, offset temperature is used. Offset temperature: T _o is determined as follows. First, in the TG curve obtained as described above, as the temperature at which the reduction of the weight of the binder starts, as shown in FIG. 2, it takes the straight line L ₁ parallel to the X axis. The weight ratio of the amount of the binder to the weight of the iron nitride particles used in the raw material powder X (wt%), when the initial weight of the binder M1, which is parallel to the straight line L _1, the initial weight from the straight line L ₁ : Take a straight line L ₂ which takes (5 × X) wt% smaller weight of M1. Further, a tangent line L ₃ at the intersection of the TG curve and the straight line L ₂ is taken. Then, taking the intersection of the straight line L ₁ and the tangent line L _3, the temperature of the intersection point and the offset temperature T _O.

According to the method for producing a composite magnetic material of the present invention, the composite magnetic material of the present invention having the following specific orientation structure can be obtained. Specifically, the composite magnetic material of the present invention is obtained by the above-described production method of the present invention, and includes a plurality of alloy particles mainly composed of an alloy containing a rare earth element and Fe, α ″ Fe ₁₆ The composite magnetic material is formed of a plurality of iron nitride particles mainly composed of N _2. The composite magnetic material includes an orientation direction of an easy axis in a pole figure analysis of X-ray diffraction performed on the alloy particles. The solid angle formed by the orientation direction of the easy magnetization axis in the pole figure analysis of the X-ray diffraction performed on the iron nitride particles is within 10 °.

Alternatively, the composite magnetic material of the present invention is composed of a plurality of alloy particles whose main component is an alloy containing rare earth elements and Fe and a plurality of iron nitride particles whose main component is α ”Fe ₁₆ N _2. And the iron nitride particles having a columnar shape, the short axis having an average length of 100 nm or less, and at least one iron nitride particle interposed between the alloy particles. This composite magnetic material has an orientation direction of the easy axis in the pole figure analysis of X-ray diffraction performed on the alloy particles, and an orientation direction of the easy axis in the pole figure analysis of X-ray diffraction performed on the iron nitride particles. The solid angle formed by is within 10 °.

The composite magnetic material of the present invention is composed of a molded body in which the iron nitride particles having high saturation magnetization are interposed between the alloy particles having high coercive force. In the composite magnetic material of the present invention, the easy magnetic axis of the crystal inside the alloy particle and the easy magnetic axis of the crystal inside the iron nitride particle are aligned in a certain direction. As described above, the composite magnetic material of the present invention has a high coercive force of an alloy containing rare earth elements and Fe, such as an Sm-Fe-N alloy, and a high saturation magnetization of α "Fe ₁₆ N ₂ . By using a common orientation direction, both are compatible and excellent in magnetic properties.

The production method of the present invention can produce a composite magnetic material containing both an alloy component containing a rare earth element such as an Sm—Fe—N-based alloy and Fe and an α ″ Fe ₁₆ N ₂ component. Uses a multi-phase powder with excellent moldability as a raw material powder, so that a molded body having a desired shape can be obtained without using a binder resin or the like, and an alloy component containing a rare earth element and Fe or α ″ A molded body having a high magnetic phase ratio such as Fe ₁₆ N ₂ component can be obtained. The nano iron powder used for the raw material powder is an ultrafine particle and does not hinder the deformation of the multiphase powder. Further, the production method of the present invention can effectively suppress aggregation by using the granulated powder mixed with the binder while using the nano iron powder as the raw material powder. Therefore, α "Fe ₁₆ N ₂ produced by nano iron powder can also be in the nano order. Also, since this binder can be easily removed by heating to a specific temperature and exhausting during molding, Since the binder hardly remains, the production method of the present invention provides a composite magnetic material having a high magnetic phase ratio, and further, by preventing aggregation, the nano iron powder can be uniformly present around the multiphase particles. In this state, nano iron powder can be interposed between multiphase particles by press molding. By producing α "Fe ₁₆ N ₂ from the intervened nano iron powder, the production method of the present invention is It is possible to produce a composite magnetic material in which iron nitride particles containing α ″ Fe ₁₆ N ₂ as a main component, which does not substantially contain a binder and have excellent magnetic properties, are supported by alloy particles having excellent magnetic properties.

In addition, when producing a recombination alloy from a multiphase powder in the dehydrogenation step, the production method of the present invention applies a specific strong magnetic field so that the easy axis of magnetization of the crystal of the alloy is in a certain direction (for example, a magnetic field (The application direction is referred to as an orientation axis hereinafter). In addition, by applying this strong magnetic field, the easy axis of magnetization of the nano iron powder is aligned in a certain direction (for example, the application direction of the magnetic field). That is, the orientation direction of the recombination alloy and the orientation direction of the nano iron powder can be made the same direction. The production method of the present invention applies a specific strong magnetic field in the same direction as in the dehydrogenation process to produce α "Fe ₁₆ N ₂ from the nano iron powder in the nitriding process, thereby aligning the dehydrogenation process. The orientation axis thus formed can be maintained as it is, or the solid angle due to the orientation axis can be made smaller. In this way, the production method of the present invention uses the orientation direction of the crystal of the alloy after nitriding treatment and α ″ A composite magnetic material having a specific orientation can be manufactured in which the orientation direction of the crystal of iron nitride mainly composed of Fe ₁₆ N ₂ is aligned in the same direction.

In addition, the production method of the present invention distorts the basic lattice of iron in one direction by applying a specific strong magnetic field when generating α "Fe ₁₆ N ₂ from nano iron powder in the nitriding step. The position between the Fe atom and the Fe atom can be set as the arrangement position of the N atom.In other words, the production method of the present invention can regulate the penetration direction of the N atom, so that α "Fe ₁₆ N ₂ can be produced. Can be manufactured well. Furthermore, when a rare earth-iron-nitrogen alloy is produced by applying a specific strong magnetic field in the nitriding process, the crystal lattice can be distorted in one direction and the penetration direction of N atoms can be regulated. The method can produce a rare earth-iron-nitrogen based alloy with an ideal atomic ratio.

Furthermore, the production method of the present invention prevents the oxidation of nano iron powder or recombination alloy by making the atmosphere during the nitriding treatment a low oxygen atmosphere, thereby efficiently generating α "Fe ₁₆ N ₂ , -An iron-nitrogen alloy can be produced efficiently.

From the above, the production method of the present invention has a high magnetic phase ratio, contains α ″ Fe ₁₆ N ₂ , and has a specific orientation structure (the orientation direction of the crystal of the alloy particles and the orientation direction of the crystals of the iron nitride particles). A composite magnetic material having excellent magnetic properties (typically, the composite magnetic material of the present invention) can be produced by the composition of the recombination alloy. Can simultaneously produce a rare earth-iron-nitrogen alloy and α ″ Fe ₁₆ N ₂ , so that the composite magnetic material can be produced with high productivity.

  As one form of the production method of the present invention, a form in which the average particle diameter of the multiphase powder is 10 μm or more can be mentioned.

  The above form is easy to handle the multiphase powder and is excellent in moldability. Moreover, the said form has multi-phase particle | grains large enough with respect to nano iron powder, and it is easy to make the particle | grains of nano iron powder exist on the surface of multi-phase particle.

  As one form of this invention manufacturing method, the form whose content of Fe in the said nano iron powder is 80 volume% or more is mentioned.

By using nano iron powder with high Fe content (high purity) as a raw material, the content of α "Fe ₁₆ N ₂ in iron nitride particles can also be increased (purity increased). Thus, the saturation magnetization of the composite magnetic material can be increased, and the orientation can be improved, so that the above-described embodiment can produce a composite magnetic material having more excellent magnetic properties.

In the production method of the present invention, the multiphase powder is obtained by subjecting an alloy containing a rare earth element and Fe to a heat treatment at a temperature equal to or higher than the disproportionation temperature of the alloy in an atmosphere containing a hydrogen element. . The alloy is one or more elements selected from RE = Y, La, Pr, Nd, Sm, Dy and Ce, and one or more elements selected from Me = Fe or Fe and Co, Ni, Mn and Ti. When the element is x = 2.0 to 2.2, one or more selected from RE _x Me ₁₄ B, RE _x Me ₁₄ C, RE _x Me ₁₇ and RE _{x / 2} Me ₁₂ may be mentioned. Further, as one form of the composite magnetic material of the present invention, the above alloy is one or more elements selected from RE = Y, La, Pr, Nd, Sm, Dy and Ce, Me = Fe or Fe and Co, Ni , one or more elements selected from Mn and Ti, when the _{x = 1.5~3.5, RE 2 Me 14} B, RE 2 Me 14 C, RE 2 Me 17 N x, RE 1 Me 12 N x and RE 1 or more in a form selected from ₁ Me ₁₂ thereof.

The production method of the present invention of the above-mentioned form uses RE ₂ Me ₁₄ B, RE ₂ Me ₁₄ C, RE ₂ Me ₁₇ N _x , RE ₁ Me ₁₂ N _x , RE ₁ by using a multiphase powder having a specific composition. A composite magnetic material containing an alloy component having excellent magnetic properties such as Me ₁₂ (x = 1.5 to 3.5) can be obtained. The composite magnetic material of the present invention having the above configuration is excellent in magnetic properties by containing an alloy component having excellent magnetic properties as described above.

  As one form of the manufacturing method of the present invention, in the nitriding step, a form in which the recombination alloy is nitrided to generate a rare earth-iron-nitrogen based alloy containing a rare earth element and Fe can be mentioned.

Examples of the rare earth-iron-nitrogen alloy include Sm—Fe—N alloys such as RE ₂ Me ₁₇ N _x . The said form contains the rare earth-iron-nitrogen alloy which is excellent in a magnetic characteristic, The composite magnetic material which is further excellent in a magnetic characteristic can be manufactured.

  As one form of the manufacturing method of the present invention, the binder has a melting point of 90 ° C. or less.

  The said form is easy to make a binder a molten and softened state at comparatively low temperature, and is excellent in the workability | operativity at the time of granulation.

As one form of the production method of the present invention, in the granulation step, a low oxygen atmosphere with an oxygen concentration of 3000 ppm by mass or less is used, and the product is cooled from {(melting point of the binder) +5} ° C. to room temperature. The form which performs a grain is mentioned. In addition, melting | fusing point in a binder is calculated | required as follows. The differential scanning calorimetry curve (DSC) of the binder is obtained in the state of atmospheric pressure (1 atm.apprxeq.0.1 MPa), and a tangent L _p1 at the peak of heat amount change is taken as shown in FIG. When the heat quantity change peak value is Y, a straight line L _p2 parallel to the tangent L _p1 and separated by Y is taken. The straight line L _p2 in parallel, taking the direction of the peak point from the straight line L _p2 the (Y / 2) apart by a straight line L _p3. The intersection of the DSC and the straight line L _p3 is taken, and the tangent L _p4 at the intersection on the low temperature side (the intersection on the left side in FIG. 3) is taken. Then, an intersection point between the straight line L _p2 and the tangent line L _p4 is taken, and the temperature of this intersection point is set as an offset temperature T _Op .

  The multiphase powder easily oxidizes by containing a rare earth element, and the nano iron powder easily oxidizes. The said form can manufacture the composite magnetic material which can prevent the oxidation of raw material powder effectively and is excellent in a magnetic characteristic by setting it as a low-oxygen atmosphere. In addition, since the raw material powder and the binder can be easily mixed by setting the temperature to be higher than the melting point of the binder, and by cooling from the above temperature to room temperature, it is easy to form granulated powder. Excellent productivity of granulated powder.

  As one mode of the production method of the present invention, there is a mode in which the magnetic field is applied using a high-temperature superconducting magnet in at least one of the dehydrogenation step and the nitridation step.

  In the above embodiment, a strong magnetic field such as 2T or more or 3T or more can be stably applied to a large space. In addition, since the magnetic field can be changed at high speed in the above form, the heat treatment time can be shortened, and it is easy to set an appropriate magnetic field strength in accordance with the change in the crystal structure during the heat treatment. Increases sex.

  As an embodiment of the composite magnetic material of the present invention, there is an embodiment in which the molded body satisfies at least one of saturation magnetization of 1.5 T or more and coercivity of the molded body of 10 kOe (800 kA / m) or more.

  Since the said form has high saturation magnetization and a coercive force, it can be utilized suitably for the raw materials of magnets, such as a permanent magnet.

  One form of the composite magnetic material of the present invention is a form in which the relative density of the molded body is 90% or more.

  In the above-mentioned form, since the relative density of the molded body is sufficiently high, the ratio of the magnetic phase is also high, and the magnetic properties are excellent.

  As one form of the composite magnetic material of the present invention, a form in which the content of the alloy component in the alloy particles is 90% by volume or more can be mentioned.

  The said form is excellent in a magnetic characteristic because there is much content (the purity is high) of the alloy component in the alloy particle which comprises a composite magnetic material.

  The composite magnetic material of the present invention is excellent in magnetic properties. The method for producing the composite magnetic material of the present invention can produce the composite magnetic material of the present invention with high productivity.

FIG. 1 is a process explanatory view showing an example of a method for producing a composite magnetic material of the present invention. FIG. 2 is an explanatory diagram for explaining the decomposition temperature of the binder. FIG. 3 is an explanatory diagram for explaining the melting point of the binder.

Hereinafter, the present invention will be described in more detail.
[Method of manufacturing composite magnetic material]
(Preparation process)
One feature of the production method of the present invention is that two types of powder: nano-iron powder and multiphase powder are used as raw materials.

{Nano iron powder}
The nano iron powder is composed of columnar iron particles containing Fe as a main component, and the average length of the minor axis of the iron particles is 100 nm or less. “Fe as a main component” means that the Fe content (purity) is 75% by volume or more. The content of Fe in the iron particles, an elevated the more (as high purity) alpha "easily generate Fe ₁₆ N _2, alpha iron nitride particles" content of Fe ₁₆ N ₂ (Purity) From the viewpoint of enhancing the orientation and saturation magnetization of the composite magnetic material, it is preferably 80% by volume or more, more preferably 85% by volume or more, and particularly preferably 90% by volume or more. The surface of the iron particles is appropriately subjected to oxidation treatment and coating treatment to form nano iron powder with an oxide layer, which prevents excessive oxidation during the nitriding process and has a high Fe content. It is preferable to maintain. The thickness of the oxide layer may be about several atoms, and such an extremely thin oxide layer can sufficiently perform nitriding in the nitriding step.

A well-known manufacturing method can be utilized for manufacture of the columnar nano iron powder whose length of a short axis is nano order. For example, a coprecipitation method, a reverse micelle method, a sol-gel method, or the like can be used. When the coprecipitation method is used, nano iron powder can be obtained by reducing nano-order iron oxide (hematite: Fe ₂ O ₃ ), and when reverse micelle method is used, iron carbonyl: Fe (CO) ₅ By synthesizing, nano iron powder can be obtained. Nano iron powder is substantially composed of alpha iron. It can be made columnar by adjusting the manufacturing conditions, or the length of the short axis of the nano iron powder and the length of the long axis of the nano iron powder can be changed. In producing the nano iron powder, the crystal growth direction can be controlled by applying an external magnetic field or electric field when generating an initial crystal or increasing the particle size. The crystal grain size tends to decrease when the temperature during the reaction is lowered or when the reaction time is shortened. Therefore, by adjusting the reaction temperature and reaction time with the growth direction controlled by a magnetic field or electric field, the crystal can be made columnar, the length of the short axis can be shortened, or the length of the long axis can be increased. can do. When a crystal grows to a desired size, a coupling agent having a hydrophilic group is added to modify the end of the oxygen-iron bond existing in the iron oxide or iron surface layer to be grown. You can stop. The external magnetic field and electric field may be applied with direct current or applied with alternating current. Examples of the coupling agent having a hydrophilic group include silane coupling agents and unsaturated fatty acids (oleic acid, linoleic acid, etc.).

When the average length of the short axis of nano iron powder exceeds 100 nm, the generated α ”Fe ₁₆ N ₂ also becomes large, and it is difficult to obtain the effect of improving magnetic properties due to shape magnetic anisotropy, leading to a decrease in coercive force. In addition, the smaller the nano iron powder, the smaller the difference in the nitriding progress between the surface layer part and the inside of the particle, and the excessive nitriding can be prevented, so the content of α "Fe ₁₆ N ₂ is increased (purity) Can be enhanced). Furthermore, the smaller the nano iron powder, the easier it is for each iron particle constituting the nano iron powder to become a single crystal and substantially all the crystals inside the iron particle can be oriented, so the orientation of the iron nitride particles can be improved. As a result, a composite magnetic material having a high coercive force and excellent magnetic properties can be obtained. On the other hand, when the nano iron powder is large, the iron particles are easily subjected to a magnetic field, so that the iron particles themselves can be easily oriented. However, when nano iron powder becomes large, each iron particle tends to be polycrystalline, and the orientation of crystals inside each iron particle tends to be random. Therefore, when the average length of the minor axis of the nano iron powder is increased within a range of 100 nm or less, the magnitude of the magnetic field applied is adjusted (increased) so that each crystal in each iron particle is oriented. It is preferable. The average length of the minor axis of the nano iron powder can be, for example, 80 nm or less, 50 nm or less, particularly 20 nm or less.

  When iron particles having a short minor axis and a long major axis, that is, iron particles having a large aspect ratio (long axis / short axis) are used, iron nitride particles having a large aspect ratio are easily obtained. Therefore, the aspect ratio of the iron particles is preferably 2 or more. As described above, the aspect ratio can be controlled by applying an external magnetic field or an electric field at the time of generating an initial crystal or increasing the particle size, and adjusting the magnitude of the external magnetic field or the electric field. Increasing the external magnetic field or electric field makes it easier to increase the aspect ratio. When the magnitude of the external magnetic field or electric field is constant, the particle size varies depending on the reaction temperature and reaction time, but the aspect ratio is generally constant.

{Multiphase powder}
The multiphase powder is in a hydrogen disproportionation decomposition state, and is a powder composed of multiphase particles containing a rare earth element hydrogen compound phase and an iron-containing material phase containing Fe. This multiphase powder includes an element containing one or more rare earth elements selected from Sc (scandium), Y (yttrium), lanthanoid and actinoid and Fe (hereinafter referred to as a starting alloy) containing a hydrogen element. It is obtained by performing heat treatment (hydrogenation) at a temperature equal to or higher than the disproportionation temperature of the alloy in the atmosphere.

The starting alloy is a rare earth-iron-boron alloy such as an alloy containing a rare earth element, Fe, and one element selected from B, C, and N, and an alloy containing a metal element other than Fe in the alloy. , Rare earth-iron-carbon alloys, and rare earth-iron-nitrogen alloys. Alternatively, the starting alloy is an alloy containing a rare earth element and Fe, or an alloy containing a metal element other than Fe in the alloy, and a rare earth-iron-nitrogen alloy that becomes a rare earth-iron-nitrogen alloy by nitriding treatment. Can be mentioned. More specific starting alloy is one or more elements selected from RE = Y, La (lanthanum), Pr (praseodymium), Nd, Sm, Dy (dysprosium) and Ce (cerium), only Me = Fe, Or one or more elements selected from Co (cobalt), Ni (nickel), Mn (manganese) and Ti (titanium) and Fe, where x = 2.0 to 2.2, RE _x Me ₁₄ B, RE _x Me One or more selected from ₁₄ C, RE _x Me ₁₇ and RE _{x / 2} Me ₁₂ may be mentioned. More specifically, RE _x Me ₁₄ B is Nd ₂ Fe ₁₄ B, Nd ₂ (Co ₁ Fe ₁₃ ) B, RE _x Me ₁₄ C is Nd ₂ Fe ₁₄ C, RE _x Me ₁₇ is Sm ₂ Fe ₁₇ , Y ₂ Fe ₁₇ , RE _{x / 2} Me ₁₂ are Sm ₁ (Ti ₁ Fe ₁₁ ), Sm ₁ (Mn ₁ Fe ₁₁ ), Y ₁ (Ti ₁ Fe ₁₁ ), Y ₁ (Mn ₁ Fe ₁₁ ). The content ratio of Fe and other elements: Co, Ni, Mn, Ti in Me can be changed continuously. In addition, the starting alloy is allowed to contain an element (for example, Cu, Al, Cr, Ga, Nb, etc.) that controls crystal growth when changing from a multiphase structure to a recombined alloy structure.

When an alloy containing Sm and Fe is used as the starting alloy, a composite magnetic material containing an Sm—Fe—N alloy having excellent magnetic properties can be obtained. In particular, when an Sm-Ti-Fe alloy such as Sm ₁ (Ti ₁ Fe ₁₁ ) is used as the starting alloy, (1) compared to the case where Sm ₂ Fe ₁₇ is used, the iron is relatively less than the rare earth element. A multi-phase powder that is excellent in moldability by increasing the content ratio can be obtained, (2) it is easy to stably perform nitriding after heat treatment (dehydrogenation), and (3) a molded body having a high magnetic phase ratio. There are excellent effects such as (4) the amount of Sm used can be reduced.

  As the starting alloy, powdered powder (hereinafter referred to as starting alloy powder) is easy to use. The starting alloy powder can be obtained by crushing a foil-like body obtained by a melt casting ingot or a rapid solidification method with a crushing device such as a jaw crusher, jet mill, or ball mill, or by an atomizing method such as a gas atomizing method, or by an atomizing method. It can be obtained by further pulverizing the produced powder. In the gas atomization method, when a non-oxidizing atmosphere is used, a powder containing substantially no oxygen (oxygen concentration: 500 mass ppm or less) can be produced. A known powder production method can be used for the production of the starting alloy powder. In addition, the particle size distribution of the starting alloy powder and the shape of the particles constituting the powder (hereinafter referred to as starting alloy particles) can be adjusted by appropriately changing the pulverization conditions and the manufacturing conditions. The starting alloy particles are typically spherical, but irregularly shaped particles or flakes may be used. When the atomizing method is used, it is easy to produce a powder having a high sphericity and excellent filling properties at the time of molding. The starting alloy particles may be polycrystalline or single crystal. The particles made of a polycrystal can be appropriately heat treated to form particles made of a single crystal.

  When the starting alloy powder is subjected to the heat treatment (hydrogenation) so that the size is not substantially changed during the heat treatment (hydrogenation), the size of the starting alloy powder and the size of the multiphase powder obtained after the heat treatment (hydrogenation) And become substantially the same. In particular, when the average particle size is 10 μm or more, the multiphase powder is sufficiently large with respect to the nano iron powder, so that the nano iron powder does not impair the moldability, and it is easy to increase the density during molding. It is easy to obtain a powder compact with high density (first compact). In addition, since multiphase powder is excellent in a moldability by containing an iron-containing material, for example, the average particle diameter of multiphase powder can be about 100 μm. In this case, since the coarse starting alloy powder of about 100 μm can be used, the pulverization process can be shortened (for example, only coarse pulverization), or an atomizing method such as a melt spraying method can be used. Productivity can be improved and manufacturing costs can be reduced. However, if the multiphase powder is too large, the filling rate of the mold is reduced, so that the average particle size is preferably 500 μm or less, and more preferably 30 μm or more and 200 μm or less. The size of the starting alloy powder may be adjusted so that a multiphase powder having such a size can be obtained.

Examples of the atmosphere containing hydrogen element in the heat treatment (hydrogenation) 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 (hydrogenation) is set to a temperature at which the disproportionation reaction of the starting alloy proceeds, that is, the disproportionation temperature or higher. The disproportionation reaction is a reaction that separates a rare earth element hydrogen compound and Fe (or Fe and iron compound) by preferential hydrogenation of the rare earth element, and the lower limit temperature at which this reaction occurs is defined as the disproportionation temperature. Call. The disproportionation temperature varies depending on the composition of the starting alloy and the type of rare earth element. For example, if the starting alloy is Sm ₂ Fe ₁₇ , Sm ₁ (Ti ₁ Fe ₁₁ ), Sm ₁ (Mn ₁ Fe ₁₁ ), etc., 600 ° C. or higher, Nd ₂ Fe ₁₄ B, Nd ₂ (Co ₁ Fe ₁₃ ) B In the case of Nd ₂ Fe ₁₄ C, etc., 650 ° C. or higher is mentioned. If the temperature during the heat treatment (hydrogenation) is close to the disproportionation temperature, the rare earth element hydrogen compound tends to be layered, and if the temperature is increased to a disproportionation temperature + 100 ° C or higher, the rare earth element hydrogen compound becomes granular Easy to be. The higher the temperature during the heat treatment (hydrogenation), the more the phase of the iron compound is matrixed, and a multiphase powder with excellent formability is obtained, but if it is too high, problems such as melting and fixing of the starting alloy powder occur. Therefore, 1100 ° C. or lower is preferable. When the starting alloy is Sm ₂ Fe ₁₇ , Sm ₁ (Ti ₁ Fe ₁₁ ), Sm ₁ (Mn ₁ Fe ₁₁ ), etc., the temperature during the heat treatment (hydrogenation) is 700 ° C. or more and 900 ° C. or less, Nd ₂ Fe ₁₄ In the case of B, Nd ₂ (Co ₁ Fe ₁₃ ) B, Nd ₂ Fe ₁₄ C, etc., if the temperature is made relatively low at 750 ° C. or more and 900 ° C. or less, a fine structure with a small interval between phases will be easily obtained. Examples of the holding time during the heat treatment (hydrogenation) include 0.5 hours or more and 5 hours or less. This heat treatment (hydrogenation) corresponds to the above-described processing up to the disproportionation step of the HDDR processing, and known disproportionation conditions can be applied.

  For heat treatment (hydrogenation), a swing furnace such as a rotary kiln furnace can be used in addition to a general heating furnace. When a rocking furnace is used, even if a relatively large material such as a cast ingot is used, it is pulverized by embrittlement as the hydrogenation proceeds, and becomes powder.

  Multiphase particles obtained by heat treatment (hydrogenation), when the content of iron-containing material is 60% by volume or more, there are relatively few hard rare earth element hydrogen compounds (less than 40% by volume), It is preferable because of excellent moldability. If the amount of iron-containing material is too large, the magnetic properties are ultimately lowered. Therefore, the content of iron-containing material in the multiphase particles is preferably 90% by volume or less. The content of the rare earth element hydrogen compound is more than 0% by volume, preferably 10% by volume or more and less than 40% by volume.

The iron-containing material is (1) a form that is Fe (pure iron), (2) a compound containing Fe and an element other than Fe (e.g., B, C, Co, Mn, Ti, etc.) (e.g., Fe ₃ B (CoFe ₂ ) B, Fe ₃ C, FeMn compound, FeTi compound, etc.), (3) a form including both (1) and (2), (4) at least one of (1) and (2) Examples include a form containing one element other than Fe (for example, Co, Ni, Mn, Ti, etc.). In the form in which the iron-containing material contains an element other than Fe, the magnetic properties and corrosion resistance can be improved. Examples of the rare earth element hydrogen compound include SmH ₂ and NdH ₂ . The multiphase particles allow the inclusion of inevitable impurities.

  The multiphase particles have a structure in which a phase of a rare earth element hydride and a phase of an iron-containing material are uniformly dispersed. In the discrete state, in the multiphase particles, both the phase of the rare earth element hydrogen compound and the phase of the iron-containing material are adjacent to each other, and the hydrogen of the rare earth element adjacent to each other through the phase of the iron-containing material is present. The interval between the compound phases is 3 μm or less. Typically, a layered form in which both phases have a multilayer structure, the phase of the rare earth element hydrogen compound is granular, and the phase of the iron-containing material is the parent phase. Examples include a granular form in which the compound is present in a dispersed state. The correlation interval is preferably 0.5 μm or more, particularly preferably 1 μm or more.

  Since the iron-containing material is uniformly present around the rare earth element hydride particles in the granular form, it is easier to deform the iron-containing material than the layered form, and the powder molded body having a complicated shape or multiphase It is easy to obtain a powder compact having a high density such that the relative density of the powder is 85% or more, further 90% or more, particularly 95% or more. In 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 particles when the cross section of the multiphase particle is taken. In which iron-containing materials exist, and iron-containing materials exist between adjacent rare earth element hydrogen compound particles. 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 two adjacent rare earth element hydrogen compound particles in the cross section.

  The composition of the multiphase particles (constituent elements, content, etc.), the content of iron-containing materials, the content of rare earth element hydrogen compounds, and the spacing between the above phases are the same as the composition of the starting alloy and the production of the multiphase powder. It can be adjusted by appropriately changing the heat treatment conditions (mainly temperature). For example, if the iron ratio (atomic ratio) in the starting alloy is increased or the temperature during the heat treatment (hydrogenation) is increased, the spacing between the phases tends to increase. The composition of the starting alloy and the heat treatment conditions may be adjusted so that the desired multiphase powder can be obtained.

  The multiphase powder can have a form including an antioxidant layer and an insulating coating so as to cover the entire circumference of each multiphase particle. The form including the antioxidant layer can prevent the oxidation of the new surface generated during the pressure molding. In the form having an insulating coating, a composite magnetic material having a high electric resistance and a small eddy current loss can be obtained due to the presence of the insulating coating (or an insulating material transformed from the constituent material of the insulating coating by heat treatment).

The antioxidant layer has an oxygen permeability coefficient (30 ° C) of less than 1.0 × 10 ^-11 m ³・ m / (s ・ m ²・ Pa), especially 0.01 × 10 ^-11 m ³・ m / (s ・ m ² Pa) A form including at least an oxygen low-permeability layer made of the following oxygen low-permeability material may be mentioned. Oxygen low permeability materials include, for example, polyamide 6 such as nylon 6 (oxygen permeability coefficient (30 ° C): 0.0011 × 10 ^-11 m ³ · m / (s · m ² · Pa)), polyester, polychlorinated Vinyl etc. are mentioned. In addition to the low oxygen permeability layer, the antioxidant layer has a moisture permeability (30 ° C) of less than 1000 × 10 ^-13 kg / (m ・ s ・ MPa), especially 10 × 10 ^-13 kg / (m ・s · MPa) A moisture low permeability layer composed of the following moisture low permeability materials effectively prevents oxidation even when stored in high humidity conditions (for example, temperature 30 ° C / humidity 80%, etc.) This is preferable. Moisture low permeability material is moisture permeability (30 ℃): 7 × 10 ^-13 kg / (m ・ s ・ MPa) to 60 × 10 ^-13 kg / (m ・ s ・ MPa) polyethylene, other fluorine Resin, polypropylene, etc. are mentioned. It is preferable to provide the oxygen low-permeability layer on the multiphase particle side and the moisture low-permeability layer on the oxygen low-permeability layer. The thickness of each layer constituting the antioxidant layer is preferably 10 nm or more and 500 nm or less.

  For forming the antioxidant layer, for example, a wet method such as a wet dry coating method or a sol-gel method, or a dry method such as powder coating can be used.

Insulating coatings include, for example, crystalline films of oxides such as Si, Al, and Ti, amorphous glass films, ferrites such as X-Fe-O (X = Ba, Sr, Ni, Mn, etc.) Examples thereof include a film made of a metal oxide such as magnetite (Fe ₃ O ₄ ) and Dy ₂ O ₃ , a resin such as a silicone resin, and an organic-inorganic hybrid compound such as a silsesquioxane compound. These crystalline coatings, glass coatings, oxide coatings and the like may have an antioxidant function, and in this case, oxidation of multiphase particles can also be prevented. In order to improve thermal conductivity, Si-N or Si-C based ceramic coating may be applied to the multiphase particles.

  In the form including both the insulating coating or ceramic coating and the antioxidant layer, the insulating coating is formed so as to contact the surface of the multiphase particles, and then the ceramic coating or the antioxidant layer is formed on the insulating coating. It is preferable to do. In a form with an insulation coating or an anti-oxidation layer, when the multiphase particles are close to a true sphere, (1) it is easy to form an anti-oxidation layer or an insulation coating with a uniform thickness. (2) Pressure molding It is preferable because the effect that the breakage of the antioxidant layer or the insulating coating can be sometimes suppressed is obtained.

(Granulation process)
One feature of the production method of the present invention is that the raw material powder and the binder are mixed to form a granulated powder.

  The binder is temporarily present from granulation to the middle of molding and is removed by heating and exhaust during molding. This binder functions as an auxiliary agent for ensuring the fluidity of the granulated powder until it is put into the mold and for uniformly mixing the nano iron powder on the surface of the multiphase powder. The binder can also function as a lubricant during molding. When the decomposition temperature of the binder is high, it is necessary to increase the heating temperature during molding. Here, since the oxidation progress temperature of the iron particles (mainly α iron) constituting the nano iron powder is substantially 250 ° C., in order to prevent deterioration of magnetic properties due to oxidation, the heating temperature at the time of molding is 250 ° C or less is desired. Therefore, in the production method of the present invention, a binder having a low decomposition temperature, specifically, 240 ° C. or lower, preferably 220 ° C. or lower is used. In addition, a binder that can be vaporized and removed by decomposition into volatilization or gas at a decomposition temperature + 20 ° C. or lower is used. Since the binder can be removed at such a relatively low temperature, the temperature during molding can be lowered, the nano-iron powder can be coarsened, the raw material powder can be prevented from being oxidized, and the thermal decomposition of the binder itself can be prevented. . Moreover, a binder does not react with nano iron powder and multiphase powder, and shall be granulated. Examples of such a binder include organic substances such as oleic acid amide, erucic acid amide, and ricinoleic acid amide. Commercially available wax that satisfies the above specifications (decomposition temperature etc.) may be used.

  In granulation, when the binder is in a molten or softened state, it is easy to uniformly mix the three of the nano iron powder, the multiphase powder, and the binder, and the iron particles are universally spread on the surface of the multiphase particles by the binder. A granulated powder in which the dispersed state is maintained can be formed. Therefore, it is preferable to mix the raw material powder and the binder at a temperature equal to or higher than the melting point of the binder, preferably higher than the melting point + 5 ° C. If the temperature at the time of mixing is too low, it is difficult to mix the raw material powder and the binder uniformly, and granulation is difficult. As a result, the binder does not uniformly adhere to the raw material powder, and the raw material powder does not slide, and there is a risk that the filling rate into the mold and the moldability will deteriorate. On the other hand, if the temperature at the time of mixing is too high, the binder is reduced due to adhesion or deposition in the mixing equipment during granulation. Therefore, the melting point is preferably about (melting point + 5) ° C. to (melting point + 15) ° C.

  The melting point of the binder is preferably 90 ° C. or less. Since the melting point is low, the binder can be easily melted or softened. Therefore, the binder and the raw material powder can be mixed uniformly at a relatively low temperature, and the workability of the granulation process is excellent, and a granulated powder in which the binder exists uniformly can be formed. The granulated powder in which the binder is uniformly present can prevent the raw material powder from being oxidized, and also can improve the sliding of the raw material powder, and is excellent in the filling ability and moldability to the mold.

  The binder content can be selected as appropriate, but if it is too much, the removal time becomes longer or it remains and causes a decrease in the proportion of the magnetic phase. Therefore, the content of the binder is preferably 0.5% by mass to 5% by mass with respect to the mass of the raw material powder (the total mass of the multiphase powder and the nano iron powder).

The compounding ratio of the nano iron powder and the multiphase powder can be appropriately selected. When there are many multiphase powders, it is excellent in moldability, and it is easy to form a large bulk material. When there are many nano iron powders, it is easy to obtain the effect of improving magnetic properties by containing α "Fe ₁₆ N ₂ component. Considering the characteristics, the blending ratio of the nano iron powder is preferably 5% by mass or more and 10% by mass to 25% by mass when the total mass of the multiphase powder and the nano iron powder is 100% by mass. .

  When sufficiently mixed, the mixture of the raw material powder and the binder is cooled to room temperature, and the binder is solidified to form granulated powder. When the average particle diameter is 10 μm or more, particularly 50 μm or more, the granulated powder is preferable because it has excellent advantages such as excellent fluidity and filling property in a mold, easy to produce granulated powder, and excellent moldability. . However, if the granulated powder is too large, the average particle size is preferably 500 μm or less because the binder becomes excessive or the filling rate of the raw material powder is lowered due to the remaining binder component. As described above, it is easy to produce granulated powder of a desired size by cooling after melting the binder. The average particle size of the granulated powder can be changed by adjusting the cooling rate in the above-described cooling step to room temperature, and tends to decrease as the cooling rate is increased.

Nano iron powder and multiphase powder are easily oxidized as described above. When nano iron powder is oxidized, nitriding is inhibited and the amount of α "Fe ₁₆ N ₂ produced decreases, the proportion of the magnetic phase decreases, and the orientation decreases due to the small amount of α" Fe ₁₆ N ₂ component. Or When the multiphase powder is oxidized, re-alloying is inhibited by the generated oxide, and the proportion of the magnetic phase is lowered. Therefore, the oxidation of the raw material powder causes a decrease in magnetic properties such as a decrease in saturation magnetization. For this reason, the granulation step is preferably a low oxygen atmosphere. Specifically, the oxygen concentration is preferably 3000 mass ppm or less, more preferably 2500 mass ppm or less, and particularly preferably 2000 mass ppm or less. Specific examples of the granulation step include a rare gas atmosphere such as Ar (argon) and He (helium) and an inert atmosphere such as N ₂ (nitrogen). When the multiphase powder including the above-described antioxidant layer is used, the oxidation of the multiphase powder before being covered with the binder can be effectively prevented.

  The granulated powder may basically be in a state in which nano iron powder is adhered to the surface layer of the multi-phase particle by a binder, for example, a plurality of multi-phase particles having nano powder adhered to the surface layer of the multi-phase particle. May be combined with a binder. When the binder is melted as described above and the granulated powder covers the entire circumference of the iron particles and multiphase particles with the binder, the binder can also function as an antioxidant layer for the iron particles and multiphase particles. .

(Molding process)
One feature of the production method of the present invention is that heating and exhausting are performed when forming the compact (first compact) by pressure-molding the granulated powder.

{heating}
Heating at the time of molding is performed mainly for melting and vaporizing (volatilizing) the binder in the granulated powder. Therefore, the heating temperature (final temperature reached) in this step is preferably in the vicinity of the binder decomposition temperature, and is set to the decomposition temperature ± 20 ° C. If the heating temperature is less than (decomposition temperature -20) ° C, the binder cannot be sufficiently melted, the raw material powder cannot be prevented from sliding or vaporized sufficiently, and the binder remains and the filling rate of the raw material powder is reduced. Or invite you. The higher the heating temperature, the easier it is to melt and vaporize the binder, which can be reliably removed, but when it exceeds (decomposition temperature +20) ° C, for example, unintended decomposition proceeds in the binder to be volatilized, and the constituent components of the binder ( For example, C (carbon) or the like) remains in the molded body as a residue, or the raw material powder is easily oxidized, resulting in a decrease in magnetic properties. The granulated powder can be heated not only by applying external heat but also by heating the mold to a predetermined temperature. Moreover, when the granulated powder is preheated at a temperature lower than the melting point of the binder, the temperature raising time of the granulated powder itself can be shortened. Due to this preheating, the deformation of the multiphase powder can be promoted, and a high-density molded body and a molded body having a complicated shape can be easily obtained.

{exhaust}
Exhaust during molding is performed mainly to remove the binder vaporized by the heating to the outside. Specifically, exhaust is performed so that the pressure becomes 0.9 atm (91.2 kPa) or less. That is, the molding is performed in a reduced pressure atmosphere. If the atmospheric pressure exceeds 0.9 atm, sufficient degassing cannot be performed, and the binder remains to cause a reduction in the filling rate of the raw material powder. The higher the pressure of the atmosphere, the more the exhaust can be performed, the binder can be easily discharged, and the oxygen concentration in the atmosphere can be reduced, so 0.8 atm (81.1 kPa) or less is more preferable. At the time of molding, since the oxygen concentration in the atmosphere is low, even when the binder is removed and the iron particles and the multiphase particles are exposed, the oxidation of the particles can be suppressed.

{Pressurization}
The pressurization at the time of molding is mainly performed to increase the density of the raw material powder. Molding pressure is preferably from 1 ton / cm ² or ^{more, 5ton / cm 2 ~10ton / cm} 2 about the easily available. By pressurization, the binder present between the particles constituting the raw material powder is also easily discharged.

  The first molded body obtained through the molding process is typically a powder molded body having a compacted structure in which nano-iron powder is interposed between multiphase particles that are flattened by compression deformation. Since the multiphase particles are excellent in moldability and can be deformed so as to cover the iron particles, the gaps between the multiphase particles are small, or the gaps do not substantially exist. The iron particles in the first molded body substantially maintain the size of the nano iron powder prepared as a raw material. The consolidated structure means that when a cross-sectional structure parallel to the pressing direction (pressing direction) of the first compact is taken, the multiphase particles are mainly short in the pressing direction and long in the direction perpendicular to the pressing direction. The tissue is deformed so as to extend.

(Dehydrogenation process)
In the production method of the present invention, a two-stage heat treatment is performed. In the first-stage heat treatment, hydrogen is separated from the multiphase powder constituting the first molded body, and the rare earth element and the iron-containing material are recombined. The composition of the recombined alloy is substantially equal to the composition of the starting alloy. One feature of the manufacturing method of the present invention is that a specific strong magnetic field is applied when the heat treatment of the first stage is performed.

{atmosphere}
In the dehydrogenation step, heat treatment is performed in a non-hydrogen atmosphere so as not to react with the multiphase particles and to efficiently remove hydrogen. Examples of the non-hydrogen atmosphere include an inert atmosphere and a reduced pressure atmosphere. 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. When hydrogen is removed from a rare earth element hydrogen compound in a reduced-pressure atmosphere, the rare earth element hydrogen compound hardly remains and recombination can be caused completely. As a result, the composition of the recombined alloy can be increased, and finally a composite magnetic material having excellent magnetic properties can be obtained. Therefore, in the manufacturing method of the present invention, a reduced pressure atmosphere is used. In particular, a reduced pressure atmosphere of 100 Pa or less is used. More preferably, in the dehydrogenation treatment, the temperature raising step up to a predetermined temperature (reaction start temperature) is set to a hydrogen atmosphere at atmospheric pressure (1 atm), and then hydrogen is discharged to make a non-hydrogen atmosphere and 100 Pa or less. The reduced pressure atmosphere is preferable. 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. Moreover, when the pressure during the dehydrogenation reaction treatment is 100 Pa or less, the dehydrogenation reaction is likely to proceed, and the recombination alloy crystal is prevented from coarsening, and a composite magnetic material having a high coercive force can be obtained. The lower the pressure of the atmosphere during the dehydrogenation reaction treatment, the easier the dehydrogenation reaction proceeds. Therefore, the pressure is preferably 50 Pa or less, and the final ultimate pressure (final ultimate vacuum) is preferably 10 Pa or less, particularly preferably 1 Pa or less.

{heating}
The temperature of the heat treatment (dehydrogenation) in the dehydrogenation step is equal to or higher than the recombination temperature. The recombination temperature means that a multiphase particle has a phase of a rare earth element hydrogen compound and a phase of an iron-containing material, and the rare earth element and the iron-containing material are combined to form a rare earth element and Fe. The temperature at which it transforms into a single phase consisting of the alloy it contains. The recombination temperature varies depending on the composition of the multiphase particles, but typically includes 600 ° C. or higher when Sm is included, and 700 ° C. or higher when Nd is included. The higher the temperature during heat treatment (dehydrogenation), the more hydrogen can be removed and recombination can proceed, but if it is too high, rare earth elements with high vapor pressure will volatilize and decrease, or the crystal of the recombination alloy May be coarsened, and the coercive force of the finally obtained composite magnetic material may be reduced. The holding time at the time of heat treatment (dehydrogenation) is 10 minutes or more and 600 minutes or less. As the temperature condition, a known DR process condition in the HDR process can be applied.

{Magnetic field applied}
In the dehydrogenation step, heat treatment (dehydrogenation) is performed with a magnetic field applied to the first compact. The magnetic field is a strong magnetic field of 2T or more. Such a strong magnetic field can be stably formed by using a high-temperature superconducting magnet. The high-temperature superconducting magnet can change the magnetic field at high speed, for example, the arrival time from the preliminary application state to the maximum magnetic field is short. When a low-temperature superconducting magnet is used, the magnetic field fluctuation speed is generally about 5 to 10 minutes per 1T, whereas with a high-temperature superconducting magnet, it can be performed in a very short time, for example, within 10 seconds per 1T. When the high-temperature superconducting magnet is used in this way, a desired strong magnetic field can be easily obtained, so that the heat treatment time can be shortened. By shortening the heat treatment time, the growth of crystal grains in the particles constituting the compact can be suppressed to reduce the coarsening, so that a composite magnetic material having a large coercive force can be easily obtained. Furthermore, since the magnetic field fluctuation speed is fast, the application of the magnetic field is stopped (OFF) when the granulated powder is filled in the mold or the molded product is taken out, or the application of the magnetic field is started (ON) during the heat treatment. The application of the magnetic field can be quickly controlled. When the high-temperature superconducting magnet is used in this way, heat treatment can be performed continuously, and the productivity of the composite magnetic material is excellent. A high-temperature superconducting magnet is typically used by cooling a superconducting coil composed of an oxide superconductor, for example, by conducting cooling with a refrigerator (operating temperature is about −260 ° C. or more).

  When filling the granulated powder into the mold, it is preferable that the above-described specific strong magnetic field is not applied to easily prevent the granulated powder from being charged unevenly in the mold. On the other hand, after filling the granulated powder into a mold (preferably in a state heated to the above heating temperature), until the temperature of the granulated powder rises and the binder is in a molten state, for example, It is desired to make the above-mentioned specific strong magnetic field within a very short time of about 10 seconds to 15 seconds. A high-temperature superconducting magnet is an electromagnet having a high-temperature superconducting coil that can rapidly excite a strong magnetic field, and can sufficiently meet this requirement. Therefore, after filling granulated powder into a mold, the above-mentioned high-temperature superconducting magnet is used. It is preferable to apply a specific magnetic field.

  In the dehydrogenation step, a liquid phase (rare earth rich phase) having a high content of rare earth elements is present around crystal nuclei containing rare earth elements and Fe formed by removing hydrogen. At this time, when the above-described specific strong magnetic field is applied, the crystal orientation of the crystal nucleus is easily oriented in a fixed direction, and each crystal grain is oriented when the recombination reaction is completed. In addition, when the above-described specific strong magnetic field is applied, the nanoiron powder existing around the crystal grains is easily oriented in one direction and is in an oriented state. That is, the easy axis (typically c-axis) of the crystal of the recombined alloy and the easy axis of magnetization (typically <100> direction) of the nano-iron powder crystal are aligned. The larger the magnetic field, the easier it is to align the crystal orientation of the recombination alloy and the crystal orientation of the nano iron powder in one direction. As a result, it is easy to prevent the recombination alloy from becoming an isotropic crystal, and finally a composite magnetic material having excellent magnetic properties (particularly coercive force) is obtained. In addition, 4T or more is preferable.

  When the multiphase powder is provided with the above-described antioxidant layer and the antioxidant layer is made of a material that can be removed by heating, such as a resin, heat treatment (dehydrogenation) is performed to remove the antioxidant layer. It can also serve as. A heat treatment (coating removal) for removing the antioxidant layer may be separately performed. Although this heat treatment (coating removal) depends on the material of the antioxidant layer, for example, the heating temperature is 200 ° C. or more and 400 ° C. or less, and the holding time is 30 minutes or more and 300 minutes or less. By performing this heat treatment (coating removal), the residue of the antioxidant layer can be effectively prevented.

  When a product with a high relative density is produced as the first molded body, the degree of volume change (shrinkage amount after heat treatment (dehydrogenation)) can be reduced before and after the dehydrogenation process, for example, the volume change rate is set to 5% or less. be able to. Accordingly, post-processing such as cutting for shape adjustment can be omitted, and the manufacturing method of the present invention can increase the productivity of the composite magnetic material.

  The second molded body obtained through the dehydrogenation process typically has a compacted structure in which nano iron powder is interposed between particles made of a flat recombination alloy (hereinafter referred to as recombination particles). It is a molded body.

(Nitriding process)
In the second stage heat treatment, the nano iron powder constituting the second molded body is mainly nitrided to produce α "Fe ₁₆ N _{2. In the} manufacturing method of the present invention, the second stage heat treatment is performed. One characteristic is that a specific strong magnetic field is applied.

{atmosphere}
The atmosphere in the nitriding step includes at least a nitrogen element. For example, a single atmosphere of only nitrogen (N ₂ ), or an ammonia (NH ₃ ) atmosphere, or a mixed gas atmosphere of a gas containing a nitrogen element such as nitrogen (N ₂ ) or ammonia and an inert gas such as Ar, or the above nitrogen A mixed gas atmosphere of a gas containing an element and hydrogen (H ₂ ) can be given. In particular, since the atmosphere containing hydrogen element is a reducing atmosphere, oxidation of the produced nitride, oxidation of recombination particles, and excessive nitridation can be prevented, which is preferable. In particular, in the production method of the present invention, the oxidation in the nitriding step can be effectively prevented by setting the oxygen concentration to 200 mass ppm or less. Therefore, it is possible to satisfactorily nitride the nano iron powder, and it is possible to prevent the ratio of the magnetic phase (alloy containing rare earth element and Fe, α "Fe ₁₆ N ₂ ) from being lowered by the generated oxide, and to be saturated. A composite magnetic material excellent in both magnetization and coercive force can be obtained.The lower the oxygen concentration, the more preferable, and 100 mass ppm or less is more preferable.

{heating}
The temperature of the heat treatment (nitriding) is 200 ° C. or higher and 450 ° C. or lower. By setting the temperature to 200 ° C. or higher, the reactivity between Fe and N can be increased, and N atoms can sufficiently penetrate between Fe atoms and Fe atoms constituting the basic lattice of iron. The higher the temperature is, the higher the reactivity is, the more the nitriding can proceed, the α ”Fe ₁₆ N ₂ can be sufficiently produced, and a composite magnetic material having excellent magnetic properties such as high coercive force can be obtained. temperature of nitriding) is magnetostrictive effect by the application of a magnetic field which will be described later too high is reduced, excess alpha by nitriding "generation efficiency of Fe ₁₆ N ₂ is decreased, alpha" Fe ₁₆ N ₂ that the ratio of components is reduced In order to reduce the saturation magnetization, the temperature is set to 450 ° C. or less, more preferably about 200 ° C. to 350 ° C. The holding time during heat treatment (nitridation) is, for example, 10 minutes to 1800 minutes. When the atmosphere in which nitriding proceeds is fast, the heat treatment (nitriding) holding time can be shortened.

When a rare earth-iron alloy such as RE _x Me ₁₇ or RE _{x / 2} Me ₁₂ is used as a starting alloy, in the nitriding step, a recombination alloy composed of the rare earth-iron alloy is nitrided, and the rare earth element and Fe To produce rare earth-iron-nitrogen based alloys. That is, in this embodiment, both the nano iron powder and the recombination alloy are simultaneously nitrided. The temperature at which the rare earth-iron-nitrogen alloy is produced is equal to or higher than the temperature at which the recombination alloy reacts with the nitrogen element (nitriding temperature) and the nitrogen disproportionation temperature (the rare earth element and the iron-containing material are separated and independent of each other). The temperature at which the element reacts with the nitrogen element) is preferred. Although the nitriding temperature and the nitrogen disproportionation temperature vary depending on the composition of the recombination alloy, examples include 200 ° C. or more and 550 ° C. or less. As described above, if the temperature of the heat treatment (nitriding) is 200 ° C. to 450 ° C., more preferably about 200 ° C. to 300 ° C., the recombination alloy can be sufficiently nitrided, and a rare earth-iron-nitrogen alloy is formed. it can. In addition, a composite magnetic material having a sufficiently high ratio of α "Fe ₁₆ N ₂ and a rare earth-iron-nitrogen alloy and a high coercive force is obtained. RE _x Me ₁₄ B, RE _x Me ₁₄ C When rare earth-iron-boron alloys and rare earth-iron-carbon alloys are used, only nitriding of nano iron powder is performed in the nitriding process. The nitriding temperature of _{x / 2} Me ₁₂ ) tends to be higher than the nitriding temperature of Fe, so when using a RE-Me alloy as a raw material, the RE-Me alloy is not substantially nitrided depending on the temperature of the nitriding process. only Fe is nitrided, the composite magnetic material RE ₁ Me ₁₂ there can be produced even in this case, the composite magnetic material excellent in magnetic properties already rare earth such as RE ₁ Me ₁₂ N ₃ in the starting alloy -.. iron - An alloy that is a nitrogen-based alloy can also be used.

{Magnetic field applied}
In the nitriding step, heat treatment (nitriding) is performed in a state where a magnetic field is applied to the second compact. The magnetic field is a strong magnetic field of 3T or more. The high-temperature superconducting magnet described above can be suitably used for applying such a strong magnetic field. By applying such a strong magnetic field, it can be sufficiently stretched in the direction of the magnetic field in which the basic lattice of Fe is applied, and the intrusion direction of N atoms can be easily controlled in one direction. Therefore, it is possible to efficiently generate α "Fe ₁₆ N ₂ by suppressing the intrusion of N atoms at random and the generation of Fe ₄ N and Fe ₃ N which are inferior in magnetic properties. As a result, the saturation magnetization is reduced. A composite magnetic material with excellent magnetic properties, such as high, can be obtained.The larger the magnetic field, the easier it is to stretch the iron basic lattice in one direction, and it is easier for N atoms to penetrate between the stretched Fe atoms-Fe atoms. That is, α ″ Fe ₁₆ N ₂ is easily generated. In addition, the larger the magnetic field, the easier the recombination alloy crystal lattice stretches in one direction, and N atoms penetrate between the stretched Fe atoms-Fe atoms, so that nitrides with an ideal atomic ratio (for example, Sm ₂ Fe ₁₇ N ₃ ) is easily obtained. That is, the larger the magnitude of the applied magnetic field, the more restrictive the direction in which N atoms enter is, so 3.5T or more, and further 4T or more are preferable.

In addition, by applying this magnetic field, the magnetic easy axis of the generated α ”Fe ₁₆ N ₂ , the magnetic easy axis of the generated rare earth-iron-nitrogen alloy, and the recombined rare earth-iron-boron alloy And the magnetic easy axis of rare earth-iron-carbon alloys, rare earth-iron-nitrogen alloys, etc. As described above, in the production method of the present invention, alloy particles and iron nitride particles are aligned. Thus, the composite magnetic material of the present invention having an oriented structure is obtained.

  If the second molded body obtained after the dehydrogenation step has a high relative density, the degree of volume change can be reduced before and after the nitriding step, for example, the volume change rate can be 5% or less. Therefore, post-processing such as cutting for the final shape can be omitted, and the manufacturing method of the present invention can increase the productivity of the composite magnetic material.

[Composite magnetic material]
In the composite magnetic material of the present invention, at least one iron nitride particle mainly composed of α ″ Fe ₁₆ N ₂ is interposed between a plurality of alloy particles mainly composed of an alloy containing a rare earth element and Fe. That is, the composite magnetic material of the present invention can confirm the grain boundaries of alloy particles and iron nitride particles.

The alloy constituting the alloy particles may be, for example, RE ₂ Me ₁₄ B, RE ₂ Me ₁₄ C, RE ₂ Me ₁₇ N _x , RE using the above-described RE and Me (where x = 1.5 to 3.5). _One or more selected from ₁ Me ₁₂ N _x and RE ₁ Me ₁₂ can be mentioned. More specifically, RE ₂ Me ₁₄ B is Nd ₂ Fe ₁₄ B, Nd ₂ (Co ₁ Fe ₁₃ ) B, RE ₂ Me ₁₄ C is Nd ₂ Fe ₁₄ C, RE ₂ Me ₁₇ N _x is Sm ₂ Fe ₁₇ N ₃ , Y ₂ Fe ₁₇ N ₃ , RE ₁ Me ₁₂ N _x are Sm ₁ (Ti ₁ Fe ₁₁ ) N ₂ , Sm ₁ (Mn ₁ Fe ₁₁ ) N ₂ , Y ₁ (Ti ₁ Fe ₁₁ ) N ₂ , Y ₁ (Mn ₁ Fe ₁₁ ) N ₂ , RE ₁ Me ₁₂ are Sm ₁ (Ti ₁ Fe ₁₁ ), Sm ₁ (Mn ₁ Fe ₁₁ ), Y ₁ (Ti ₁ Fe ₁₁ ), Y ₁ (Mn ₁ Fe ₁₁ ) and the like. In particular, the Sm—Fe—N alloy is preferable because of its excellent magnetic properties. The content ratio of Fe and other elements: Co, Ni, Mn, Ti in Me can be changed continuously. In addition, alloy particles that contain elements (for example, Cu, Al, Cr, Ga, Nb, etc.) that control crystal growth when changing from a multiphase structure to a recombined alloy structure are allowed.

  The alloy component content in the alloy particles is 80% by volume or more. The greater the content (the higher the purity), the greater the magnetic phase with excellent magnetic properties and the better magnetic properties. Therefore, the content of the alloy component in the alloy particles is more preferably 90% by volume or more. The content of the alloy component is increased by preventing oxidation in the manufacturing process. For example, as described above, a multiphase powder having an antioxidant layer may be used, or the oxygen concentration in the granulation process or nitriding process may be reduced to prevent oxidation. The alloy particles allow inclusion of inevitable impurities. Examples of inevitable impurities include oxides and binder residues.

The content of α ”Fe ₁₆ N ₂ component in iron nitride particles should be 80% by volume or more. The higher this content (the higher the purity), the more the magnetic phase with excellent magnetic properties and the orientation The coercive force and saturation magnetization are high, and the magnetic properties are excellent. Therefore, the content of the α ″ Fe ₁₆ N ₂ component is preferably 85% by volume or more, and more preferably 90% by volume or more. The iron nitride particles allow inclusion of inevitable impurities. Examples of inevitable impurities include α-iron and oxides. The content of the α ”Fe ₁₆ N ₂ component can be increased, for example, by preventing oxidation in the production process. For example, reducing the oxygen concentration in the granulation process or nitriding process to prevent oxidation. It is done.

  The iron nitride particles are columnar like the nano iron powder used as a raw material, and the average length of the minor axis is 100 nm or less. The average length of the short axis is preferably 80 nm or less, more preferably 50 nm or less, and particularly preferably 20 nm or less. Here, when the crystal grain size is 10 nm or more, the coercive force increases as the crystal grain boundary increases, that is, as the crystal grain size decreases. The shorter the length of the minor axis relative to the major axis of the iron nitride particles, that is, the larger the aspect ratio, the easier the inside of the iron nitride particles to be single crystallized, resulting in a smaller crystal grain size. The coercive force can be increased. The aspect ratio of the iron nitride particles is preferably 2 or more, and more preferably 2.2 or more. Further, when the average length of the minor axis of the iron nitride particles is 10 nm or more, the aspect ratio does not become too small, and the iron nitride particles are unlikely to be in a so-called superparamagnetic state, and loss of magnet characteristics can be suppressed.

  In the composite magnetic material of the present invention, the solid angle formed by the orientation direction (parallel direction) of the easy axis of alloy particles and the orientation direction (parallel direction) of the easy axis of iron nitride particles is 10 ° or less. This is one of the characteristics. Since the composite magnetic material of the present invention is manufactured by applying a specific strong magnetic field as described above, the crystal orientations of both the alloy particles and the iron nitride particles are oriented in the same direction, and the solid angle is small. Become. The smaller the solid angle, the more the above particles are oriented in the same direction and the better the magnetic properties. Therefore, the solid angle is preferably 9 ° or less, and more preferably 7 ° or less. The solid angle can be adjusted by the shape of the starting alloy powder and the production conditions. The magnetic easy axis of alloy particles and iron nitride particles typically has a (00n) direction (an integer where n ≠ 0, typically n = 2 to 6). The orientation direction of the easy axis of the alloy particles (or iron nitride particles) is obtained as follows. The pole figure of the composite magnetic material is measured, and the distribution information of the easy magnetization axis with respect to the observation surface is obtained. From this distribution information, assuming that the easy axis of 70% or more of all alloy particles (or iron nitride particles) has a solid angle within 30 ° from the orientation direction, The average direction of all the alloy particles (or iron nitride particles) present is defined as the orientation direction of the easy magnetization axis. The above-mentioned precondition is established for the composite magnetic material manufactured by the manufacturing method of the present invention.

  The composite magnetic material of the present invention includes both (1) alloy particles having excellent magnetic properties (particularly coercive force) and iron nitride particles having excellent magnetic properties (particularly saturation magnetization). Since the iron nitride particles are aligned together, the magnetic properties such as coercive force and saturation magnetization are excellent. For example, a form in which the saturation magnetization satisfies 1.5 T or more, a form in which the coercive force satisfies 10 kOe (800 kA / m) or more, a form that satisfies both the saturation magnetization: 1.5 T or more and the coercivity: 10 kOe (800 kA / m) or more. It is done. Thus, since it is excellent in a magnetic characteristic, this invention composite magnetic material can be utilized suitably for the raw material of a permanent magnet.

  In the multi-production method of the present invention, it is easy to obtain a high-density powder molded body by using the multiphase powder having excellent moldability as a raw material as described above, and a high-density composite can be obtained by using such a powder molded body. A magnetic material is obtained. For example, by sufficiently removing the above-mentioned binder at the time of manufacture, the composite magnetic material of the present invention can have a relative density of 90% or more, further 95% or more. Such a high-density composite magnetic material has a high magnetic phase ratio and thus has excellent magnetic properties.

Hereinafter, more specific embodiments of the present invention will be described with reference to test examples.
[Test Example 1]
Prepare two different types of powder as raw material powder, mix this raw material powder and binder to produce granulated powder, press the granulated powder, and then perform two-stage heat treatment (dehydrogenation and nitriding) ) To produce a magnetic material and investigate the magnetic properties. In this test, in particular, the effects of the raw material powder size, binder decomposition temperature, molding conditions (temperature, atmospheric pressure), and heat treatment conditions (temperature, applied magnetic field, atmosphere) were examined.

As shown in FIG. 1, the composite magnetic material has a preparation process: preparation of raw material powder → granulation process: production of granulated powder → molding process: formation of a first molded body → dehydrogenation process: formation of a second molded body → Nitriding process: Fabricated by the procedure of α ”Fe ₁₆ N ₂ and rare earth-iron-nitrogen alloy.

(Preparation process)
The following nano iron powder and multiphase powder were prepared as raw material powder.
{Nano iron powder}
According to the coprecipitation method, iron (II) chloride and sodium hydroxide were charged and controlled to be in a state of pH ≈ 8-9, to prepare an Fe ₂ O ₃ powder, and after hydrogen reduction, Oxidation treatment was performed to produce nano iron powder having an oxide layer on the surface. The nano Fe ₂ O ₃ powder used for each sample was prepared by placing an electromagnet outside the reaction vessel and applying a constant external magnetic field (0.1 T). In this synthesis, the particle size of the nano Fe ₂ O ₃ powder was appropriately changed by adjusting the reaction time (30 minutes to 180 minutes) and the reaction temperature (60 ° C. to 90 ° C.). Sample Nos. 1-1 to 1-4, 1-101 to 1-103 produced Fe ₂ O ₃ powder with an average particle size of 20 nm to 300 nm, and samples other than the above were Fe ₂ O with an average particle size of 50 nm. _Three powders were made. The oxide layer was formed under known conditions. Sample Nos. 1-1 to 1-4, 1-11, 1-12, 1-101 to 1-103, 1-111 are different from other samples in the formation time of the oxide layer. The formation time of No. 1 was the shortest, and the formation time of Sample No. 1-103 was the longest. In addition, when the size of the powder before and after hydrogen reduction was examined, an increase in particle size was not substantially observed. In other words, both the nano Fe ₂ O ₃ powder and the nano iron powder had substantially the same particle size.

  The Fe content in each obtained nano iron powder was examined. The results are shown in Tables 1 and 2. In this test, it was confirmed that the nano iron powder of any sample had an Fe content of 80% by volume and Fe (α iron) as a main component (80% by volume or more). The Fe content (% by volume) can be measured, for example, as follows. Each iron particle that composes the nano iron powder is focused by a transmission electron microscope: TEM, and electron beam diffraction is performed, and the ratio of the electron beam diffraction intensity in the Fe crystal to the electron beam diffraction intensity in other components (impurities) is determined. measure. From the ratio of the electron diffraction intensity, the volume ratio of Fe in the iron particles can be measured. In addition, the component of the iron particles can be measured by Mossbauer spectrum analysis or, when the size is large, by X-ray diffraction.

When each of the obtained nano iron powders was observed with a transmission electron microscope: TEM, all were columnar. The average length of the short axis was measured using this observation image. Here, the observation image is subjected to image processing, and the length of the minor axis perpendicular to the major axis is measured at the center position in the major axis direction for the iron particles constituting each nano iron powder present in the visual field. The length of the axis is defined as the length of the minor axis of the iron particles, and the average of the lengths of the minor axes of 50 or more iron particles is defined as the average length of the minor axes. The results are shown in Tables 1 and 2. Depending on the size of the Fe ₂ O ₃ powder, the average length of the minor axis was different. For example, sample Nos. 1-101 to 1-103 have a large average length of the short axis by using a large Fe ₂ O ₃ powder, and sample No. 1-1 has Fe ₂ O ₃ By using a small powder, the average length of the short axis was small.

{Multiphase powder}
Prepare an alloy ingot of Sm ₂ Fe ₁₇ in which the atomic ratio (at%) of Sm to Fe is Sm: Fe≈10: 90, and pulverize this alloy ingot with a cemented carbide mortar in an Ar atmosphere. A starting alloy powder with an average particle size of 30 μm was prepared. The average particle size was measured with a laser diffraction particle size distribution device so that the cumulative weight was 50% (50% particle size).

The starting alloy powder was heat-treated (hydrogenated) at 850 ° C. for 3 hours in a hydrogen (H ₂ ) atmosphere. The powder obtained by this heat treatment (hydrogenation) was hardened with an epoxy resin to prepare a sample for tissue observation. The sample is cut or polished at an arbitrary position so that the powder inside the sample is not oxidized, and the composition of each particle constituting the powder existing on the cut surface or the polished surface is determined by EDX (energy dispersive X-ray spectroscopy). Method) Investigated with equipment. Further, the cut surface or the polished surface was observed with an optical microscope or a scanning electron microscope: SEM (100 to 10,000 times), and the form of each particle constituting the powder was examined. As a result, each particle constituting the obtained powder has a phase of an iron-containing material (here, Fe) as a parent phase, and a plurality of granular rare earth element hydrogen compounds (here, SmH ₂ ) are contained in the parent phase. It was confirmed that the phase consisted of a multiphase structure in which phases existed (hereinafter, the powder is referred to as multiphase powder, and the particles are referred to as multiphase particles). It was also confirmed that iron-containing materials were present between adjacent rare earth element hydrogen compound particles.

Using the sample containing the epoxy resin, the content (volume%) of the rare earth element hydrogen compound: SmH ₂ and the iron-containing material: Fe in the multiphase particles was less than 40 volume%. (About 30% by volume), and iron-containing material was the main component (about 70% by volume). The content was obtained by calculating the volume ratio using the composition of the starting alloy powder and the atomic weight of SmH ₂ and Fe. Further, using the surface analysis (mapping data) of the composition of the multiphase powder by the above EDX apparatus, the distance between adjacent rare earth element hydrogen compound particles (the distance between the above-mentioned centers) was measured to be 3 μm or less. (About 2 μm). Here, the interval, performing a surface analysis on the cut surface or polished surface, extracts the peak position of SmH _2, to measure the distance between the peak positions of adjacent SmH _2, the average of all intervals did.

  In this test, nano iron powder was prepared so that all the samples were 20% by mass with respect to the total mass of the produced multiphase powder and nano iron powder.

(Granulation process)
As binders, oleic acid amide (melting point: 75 ° C, decomposition temperature: 220 ° C), erucic acid amide (melting point: 85 ° C, decomposition temperature: 240 ° C), ethylenebisstearic acid amide (melting point: 115 ° C, decomposition temperature: 250 (All are commercially available waxes). The binder content was adjusted to 1.0 mass% with respect to the mass of the raw material powder (total mass of the multiphase powder and nano iron powder). Then, in a nitrogen atmosphere with an oxygen concentration of 2000 mass ppm, the raw material powder and the binder are mixed in a state heated to the temperatures shown in Tables 1 and 2, and after sufficiently mixed, cooled to room temperature and kneaded. Thus, a granulated powder having an average particle size of 75 μm was formed. The average particle size of the granulated powder was measured as follows. A sufficient amount of granulated powder is dispersed on the glass plate, and a projected image of the granulated powder on the glass plate is taken with an optical microscope. About 50 or more granulated powders present in the obtained image, The ferret diameter of the granulated powder (here, the average value of the vertical ferret diameter and the parallel ferret diameter) was determined, and the average of the ferret diameters of 50 or more granulated powders was defined as the average particle diameter. The granulated powder can be classified using sieve classification, air classification, or the like.

(Molding process)
Each of the obtained granulated powders was subjected to pressure molding under the conditions shown in Tables 1 and 2 at a molding pressure of 9 ton / cm ² . Specifically, after filling the mold with the granulated powder, the pressure in the mold becomes a reduced pressure atmosphere of the size shown in Table 1 and Table 2 (the atmospheric atmosphere of the pressure shown in Table 1 and Table 2). While being evacuated by a degassing pump, the pressure molding was performed in a state heated to the temperature shown in Table 1. Sample No. 1-132 was at atmospheric pressure (1 atm≈101.3 kPa) and was not evacuated. After sufficiently pressurizing, the powder compact (a cylinder having a diameter of 10 mm and a height of 10 mm) was taken out from the mold.

(Dehydrogenation process)
Each powder molded body (first molded body) obtained through the molding process was subjected to heat treatment (dehydrogenation) in a reduced pressure atmosphere. Specifically, the molded body was heated to a predetermined temperature (here, 750 ° C.) in a hydrogen atmosphere (1 atm), and then the hydrogen was exhausted by a deaeration pump and switched to vacuum (VAC). The pressure was reduced to the pressure shown in Table 2, and heat treatment (dehydrogenation) was performed in this reduced pressure atmosphere. This heat treatment (dehydrogenation) was performed at a temperature of 750 (° C.) × 60 minutes. All samples except Sample Nos. 1-141 and 1-142 are heat treated (dehydrogenated by setting the conditions so that the dehydrogenation reaction start temperature is reached when the atmospheric pressure becomes 100 Pa or less. ) Was done enough. Note that each sample except Sample Nos. 1-141 and 1-142 was finally depressurized to 0.5 Pa.

  Further, this heat treatment (dehydrogenation) was performed in a state where a magnetic field (T) shown in Tables 1 and 2 was applied. The magnetic field was applied using a high temperature superconducting magnet. Here, the application direction of the magnetic field was the same as the pressing direction in the molding step. Sample No. 1-151 was heat-treated (dehydrogenated) without applying a magnetic field.

When the composition of the molded body (second molded body) obtained after the heat treatment (dehydrogenation) was examined by an EDX apparatus, each sample was substantially composed of a plurality of particles composed of a rare earth-iron alloy of Sm ₂ Fe ₁₇ ( Recombined particles) were present. Therefore, it can be seen that hydrogen was removed from the multiphase particles by the heat treatment (dehydrogenation). Further, it was confirmed by scanning electron microscope: SEM or transmission electron microscope: TEM that nano iron powder (iron particles) was present between the recombined particles.

(Nitriding process)
In the nitrogen (N ₂ ) atmosphere of the oxygen concentration (mass ppm) shown in Table 1 and Table 2 in the molded body (second molded body) obtained through the dehydrogenation step, the temperature (° C. ) × 30 hours were subjected to heat treatment (nitriding). This heat treatment (nitriding) was performed in a state where a magnetic field (T) shown in Tables 1 and 2 was applied. The magnetic field was applied using a high temperature superconducting magnet. The application direction of the magnetic field was the same as the application direction of the magnetic field in the dehydrogenation step. Sample No. 1-171 was heat-treated (nitrided) without applying a magnetic field.

  When the composition of the molded body obtained after the heat treatment (nitriding) was examined with an EDX apparatus, a rare earth-iron-nitrogen alloy was confirmed in all the samples. Therefore, it can be seen that the recombination particles are nitrided by this heat treatment (nitriding). The compositions of the alloys are shown in Tables 3 and 4 (x = 1.5 to 3.5). Further, the content (volume%) of the alloy component in the alloy particles made of a rare earth-iron-nitrogen alloy was examined. The results are shown in Tables 3 and 4. The content (volume%) of the alloy component is obtained using SEM-EDX and performing X-ray diffraction locally on the compact (targeting the alloy particles) and using the obtained X-ray diffraction intensity. It was.

The molded body obtained after the heat treatment (nitriding) was subjected to composition analysis using an EDX apparatus and scanning electron microscope: SEM or transmission electron microscope: TEM, and sample Nos. 1-161 and 1-171 to 1- It was confirmed that each compact except 173 and 1-183 was composed of a plurality of alloy particles containing a rare earth-iron-nitrogen based alloy and a plurality of iron nitride particles containing α "Fe ₁₆ N ₂ . From this, it can be seen that nitrides such as α "Fe ₁₆ N ₂ were formed by nano iron powder in each molded body excluding Sample Nos. 1-161, 1-171 to 1-173, 1-183. Further, in each molded body except for sample Nos. 1-161, 1-171 to 1-173, 1-183, iron nitride particles are interposed between alloy particles, and the iron nitride particles are columnar. It was confirmed. For the columnar iron nitride particles, the average length of the short axis of the iron nitride particles was measured using the transmission electron microscope: TEM observation image in the same manner as the nanoiron powder described above. The average minor axis length of the flour was substantially maintained.

Further, for each molded body except for sample Nos. 1-161, 1-171 to 1-173, 1-183, the content of α "Fe ₁₆ N ₂ component in the iron nitride particles was examined. The content of ααFe ₁₆ N ₂ component (% by volume) can be measured, for example, as follows. Each iron nitride particle dispersed in each molded body is individually subjected to transmission electron microscope: TEM focusing and electron diffraction, and electron beam diffraction intensity and other components in α "Fe ₁₆ N ₂ crystal (α- (Fe, Fe ₃ N, Fe ₄ N, etc.) The ratio of the electron diffraction intensity is measured.From this ratio of the electron diffraction intensity, the volume ratio of α ”Fe ₁₆ N ₂ in the iron nitride particles is measured. Can do. The component of the iron nitride particles can be measured by Mossbauer spectrum analysis or, when the size is large, by X-ray diffraction.

The relative density (the ratio of the actual density to the true density) was determined for the molded body obtained after the heat treatment (nitriding). The results are shown in Tables 3 and 4. The actual density was measured using a commercially available density measuring device. The true density is determined as follows, for example. The constituent components of the compact are identified by X-ray diffraction, electron beam diffraction, and the like, and the true density and volume ratio of the particles constituting each constituent component phase (mainly alloy phase, iron nitride phase) are determined from the identification results. By using the true density and volume ratio of the particles constituting each phase, the true density of each component can be calculated. From the blending ratio of the raw material powder and the true density of each component, the volume ratio of each component can be calculated. From the volume ratio of each constituent component and the calculated true density of each constituent component, the true density of the molded body can be obtained. In addition, the relative density is obtained as follows. For the composite magnetic material, take a cross-section in which any orthogonal axis direction (x, y, z) is a normal line, observe the cross-sectional image by an optical microscope or scanning electron microscope: SEM, the plane filling rate (Sx _i , Sy _i , Sz _i ) is derived. The plane filling rate is obtained by dividing the existing area of the constituent components of the composite magnetic material by the area of the visual field within the cross-sectional visual field. The field of view does not include the boundary (outline) of the composite magnetic material. A plane filling rate is obtained for 50 or more fields of view (i = 1 to 50), and an average value (Sx, Sy, Sz) of N = 50 or more is obtained. The relative density V is V = (Sx * Sy * Sz) ^1/2 .

  The magnetic properties of the compacts obtained after heat treatment (nitriding): saturation magnetization (T) and coercivity (kOe) were investigated. The results are shown in Tables 3 and 4. Here, after each molded body is magnetized with a pulse magnetic field of 3 T or more, saturation magnetization (T) and coercive force (T) in the axial direction of the cylinder (= magnetic field application direction = pressing direction during molding) for each molded body ( kOe) was examined using a BH tracer (DCBH tracer manufactured by Riken Denshi Co., Ltd.).

  Pole figure of X-ray diffraction for a plane perpendicular to the magnetic field direction applied in the nitriding process (= the magnetic field direction applied in the dehydrogenation process = the pressurizing direction during molding) in the molded body obtained after the heat treatment (nitriding) The analysis was conducted to examine the solid angle formed by the orientation direction of the magnetic easy axis of the alloy particles and the orientation direction of the magnetic easy axis of the iron nitride particles. The results are shown in Tables 3 and 4. In any sample whose solid angle can be measured, 70% or more of the easy axis of the crystal constituting each alloy particle in the compact of each sample has a solid angle of 30 ° from the orientation direction. Met within. Similarly, in any sample in which the solid angle can be measured, 70% or more of the easy magnetization axes of the crystals constituting the iron nitride particles in the molded body of each sample are from the orientation direction. The solid angle was within 30 °. “Unevaluable” in Table 4 indicates that the dispersion of the easy magnetic axis of the crystal constituting each particle is large and the crystal is not oriented in a specific direction.

As shown in Tables 3 and 4, using specific nano iron powder and multiphase powder as raw material powder, mixing raw material powder and binder into granulated powder, this granulated powder under specific conditions (heating temperature: Binder decomposition temperature ± 20 ° C, atmospheric pressure: exhausted to 0.9 atm or less), and specific conditions (atmospheric pressure: 100 Pa or less, heating temperature: above recombination temperature, applied magnetic field: applied magnetic field: 2T or more) is subjected to a first heat treatment (dehydrogenation), and the molded body obtained after this first heat treatment is further specified conditions (atmosphere: nitrogen element-containing atmosphere with an oxygen concentration of 200 mass ppm or less, heating temperature: By performing the second heat treatment (nitriding) at 200 ° C. to 450 ° C. (applied magnetic field: 3 T or more), a composite magnetic material containing an alloy containing rare earth elements and Fe and α ”Fe ₁₆ N ₂ can be obtained. In addition, in the obtained composite magnetic material, the solid angle formed by the crystal orientation axis of the above alloy and the crystal orientation axis of α "Fe ₁₆ N ₂ is within 10 °. It can be seen that the crystal of the above alloy and the crystal of α "Fe ₁₆ N ₂ are aligned together. And the composite magnetic material having a specific orientation structure obtained as described above is saturated. It can be seen that the magnetization is 1.5T or more and the coercive force is 10kOe or more, and the magnetic characteristics are very good.From this test, the saturation magnetization: 1.5T or more and the coercive force: 10kOe by adjusting the manufacturing conditions etc. It turns out that the iron nitride material which satisfy | fills the above is obtained.

In addition, the following can be understood from this test.
(1) When nano-iron powder having an average minor axis length of more than 100 nm is used, the coercive force is lowered due to an increase in solid angle.
(2) If a binder with a high decomposition temperature and melting point is used, it is necessary to increase the temperature during molding and the temperature during granulation, and the raw material powder may be oxidized or the granulated powder may not be satisfactory. In particular, the saturation magnetization is lowered.
(3) When the heating temperature at the time of molding is too low or the pressure of the atmosphere is too high, the binder remains, and the relative density is lowered, and finally the saturation magnetization is lowered.
(4) If the heating temperature at the time of molding is too high, the raw material powder will be oxidized and the coercive force will eventually be lowered.

(5) If the atmospheric pressure at the time of heat treatment (dehydrogenation) is too large, the coercive force is lowered due to the coarsening of crystals and the like.
(6) If the applied magnetic field at the time of heat treatment (dehydrogenation) is too small, the recombination alloy will not be sufficiently oriented, resulting in isotropic crystals, and the coercive force will be low.
(7) If the heating temperature during heat treatment (nitriding) is too high or too low, saturation magnetization will decrease due to excessive nitriding, and α "Fe ₁₆ N ₂ and rare earth-iron-nitrogen alloys cannot be generated sufficiently. The coercive force is lowered.
(8) If the applied magnetic field at the time of heat treatment (nitridation) is too small, α ”Fe ₁₆ N ₂ cannot be generated sufficiently and the saturation magnetization becomes low, or the alloy component and α” Fe ₁₆ N ₂ component are sufficiently oriented. The coercive force cannot be reduced.
(9) If the oxygen concentration during heat treatment (nitridation) is too high, the recombination alloy or nano iron powder will be oxidized, resulting in poor magnetic properties.

[Test Example 2]
A composite magnetic material was produced in the same process as in Test Example 1, and the magnetic properties were examined. In this test, in particular, the influence of the content of Fe component in the nano iron powder and the granulation conditions (temperature, oxygen concentration, blending ratio of nano iron powder) were investigated.

(Preparation process)
In the same manner as in Test Example 1, an Fe ₂ O ₃ powder having an average particle size of 20 nm was prepared by coprecipitation method, subjected to hydrogen reduction, and then subjected to oxidation treatment to obtain nano iron powder having an oxide layer on the surface. Produced. Sample Nos. 2-1 to 2-4 and 2-201 to 2-203 differ from other samples in the formation time of the oxide layer, and the formation time of sample No. 2-201 is the shortest. The formation time of 2-4 was the longest. The Fe content of each nano iron powder obtained was examined in the same manner as in Test Example 1. The results are shown in Table 5. Further, in the same manner as in Test Example 1, the average length of the short axis of each nano iron powder was measured. The results are shown in Table 5. Furthermore, Table 5 shows the blending ratio of the prepared nano iron powder (ratio to the total mass of the multiphase powder and nano iron powder).

The same multiphase powder as that prepared in Test Example 1 was prepared (a rare earth element hydrogen compound: SmH ₂ and an iron-containing material: containing Fe. Average particle size: 30 μm).

(Granulation process)
As a binder, the same oleic amide (melting point: 75 ° C., decomposition temperature: 220 ° C.) as in Test Example 1 was prepared. The content of the binder was 1.0% by mass with respect to the mass of the raw material powder as in Test Example 1. Then, in a nitrogen atmosphere having the oxygen concentration shown in Table 5, the raw material powder and the binder were mixed in a state heated to the temperature shown in Table 5, mixed thoroughly, then cooled to room temperature, kneaded, and tested. A granulated powder having an average particle size of 75 μm was formed in the same manner as in Example 1. The average particle size was measured in the same manner as in Test Example 1.

(Molding process)
Each obtained granulated powder was subjected to pressure molding in the same manner as in Test Example 1 to produce a molded body having the same shape and size as in Test Example 1. In this test, the molding conditions were heating temperature: 230 ° C., atmospheric pressure: 0.8 atm, and molding pressure: 10 ton / cm ² .

(Dehydrogenation process)
Each powder molded body (first molded body) obtained through the molding process was subjected to heat treatment (dehydrogenation) in a reduced-pressure atmosphere in the same manner as in Test Example 1. Specifically, the molded body was heated to 750 ° C. in a hydrogen atmosphere (1 atm), then discharged with a deaeration pump, switched to vacuum (VAC), and decompressed to 1.0 Pa or less. Then, heat treatment (dehydrogenation) was performed in a reduced pressure atmosphere (final vacuum degree: 0.5 Pa) at 750 ° C. for 60 minutes. The heat treatment (dehydrogenation) was performed in a state where a 3 T magnetic field was applied. The magnetic field was applied using a high temperature superconducting magnet. Here, the application direction of the magnetic field was the same as the pressing direction in the molding step.

(Nitriding process)
The molded body (second molded body) obtained through the dehydrogenation step was heat-treated (nitrided) at 300 ° C. for 30 hours in a nitrogen (N ₂ ) atmosphere with an oxygen concentration of 100 mass ppm. This heat treatment (nitriding) was performed in a state where a 4 T magnetic field was applied. The application of the magnetic field was performed using a high-temperature superconducting magnet, and the application direction of the magnetic field was the same as the application direction of the magnetic field in the dehydrogenation step.

When the composition of the molded body obtained after the heat treatment (nitriding) was examined by an EDX apparatus, a rare earth-iron-nitrogen alloy (Sm ₂ Fe ₁₇ N _x (x = 1.5 to 3.5)) was confirmed in all the samples. . Therefore, it can be seen that the recombination particles are nitrided by this heat treatment (nitriding). Further, when the content (volume%) of the alloy component in the alloy particles composed of the rare earth-iron-nitrogen based alloy was examined in the same manner as in Test Example 1, all the samples were 91 volume%.

When the molded body obtained after the heat treatment (nitriding) was examined in the same manner as in Test Example 1, each molded body except Sample Nos. 2-231 and 2-232 was mainly composed of a rare earth-iron-nitrogen alloy. And a plurality of iron nitride particles containing α "Fe ₁₆ N _{2. From} this, each molded body except for sample Nos. 2-231 and 2-232, It can be seen that a nitride such as α "Fe ₁₆ N ₂ was formed by the nano iron powder. In addition, it was confirmed that each molded body except for sample Nos. 2-231 and 2-232 had iron nitride particles interposed between alloy particles and that the iron nitride particles were columnar. For the columnar iron nitride particles, the average minor axis length of the iron nitride particles was measured in the same manner as in Test Example 1, and the average minor axis length of the nanoiron powder was substantially maintained. It was.

For each molded body except Sample Nos. 2-231 and 2-232, the content of α "Fe ₁₆ N ₂ component in the iron nitride particles was examined in the same manner as in Test Example 1. All samples except ˜2-203 were 80% by volume or more.

  The molded body obtained after the heat treatment (nitriding) was examined in the same manner as in Test Example 1 for the relative density (%), saturation magnetization (T), coercive force (kOe), and solid angle (°). The results are shown in Table 5.

As shown in Table 5, when nano-iron powder with high Fe content (high purity) is used as raw material powder, it is easy to increase the orientation of α "Fe ₁₆ N ₂ and reduce the solid angle, and saturation magnetization. It can be seen that a composite magnetic material having a high relative density can be obtained by increasing the filling rate of the granulated powder when the temperature during granulation is sufficiently higher than the melting point. Furthermore, it can be seen that when the oxygen concentration is set to 3000 mass ppm or less in the granulation step, oxidation of the raw material powder is prevented, and a composite magnetic material having both high coercive force and saturation magnetization can be obtained. Thus, it can be seen that by increasing the compounding ratio of the nano iron powder, α ″ Fe ₁₆ N ₂ can be sufficiently generated, and a composite magnetic material having both high coercive force and saturation magnetization can be obtained.

[Test Example 3]
A composite magnetic material was produced in the same process as in Test Example 1, and the magnetic properties were examined. In this test, in particular, a multiphase powder having a composition different from that of Test Examples 1 and 2 was prepared.

(Preparation process)
As the nano iron powder, a columnar product prepared in the same manner as Sample No. 1-2 in Test Example 1 was prepared (average length of minor axis: 50 nm, Fe content: 89% by volume). Moreover, nano iron powder was prepared so that it might become 20 mass% with respect to the total mass of each multiphase powder mentioned later and nano iron powder.

Multi-phase powder as the starting alloy powder, samples No.3-1 the Nd ₂ Fe ₁₄ B, samples No.3-2 the _{Nd 2 (Co 1 Fe 13)} B, samples No.3-3 is Sm ₁ ( Mn ₁ Fe ₁₁ ) and Sample No. 3-4 were prepared with Sm ₁ (Ti ₁ Fe ₁₁ ) (both average particle size: 30 μm. Measurement of the average particle size is the same as in Test Example 1). The alloy powder was also prepared by heat treatment (hydrogenation) in a hydrogen (H ₂ ) atmosphere under conditions of 850 ° C. × 3 hours.

  When the morphology and composition of each powder obtained by heat treatment (hydrogenation) were examined in the same manner as in Test Example 1, the phase of the iron-containing material was the parent phase, and a plurality of granular rare earth element hydrogens were contained in the parent phase. It was confirmed that the compound phase consisted of a multiphase structure in which the phases were dispersed. The constituent phases are shown in Table 6.

  For each multiphase powder, the content of the iron-containing material and the content of the rare earth element hydrogen compound were examined in the same manner as in Test Example 1. In each sample, the rare earth element hydrogen compound was less than 40% by volume. (About 30% by volume), iron-containing material was the main component (about 70% by volume). Further, for each multiphase powder, the spacing between adjacent rare earth element hydrogen compound particles (interphase spacing) was measured in the same manner as in Test Example 1, and all the samples were 3 μm or less (2 μm). degree).

(Granulation process)
As a binder, the same oleic amide (melting point: 75 ° C., decomposition temperature: 220 ° C.) as in Test Example 1 was prepared. The content of the binder was 1.0% by mass with respect to the mass of the raw material powder as in Test Example 1. And, in an atmosphere of oxygen concentration: 2000 mass ppm, the raw material powder and the binder were mixed in a state heated to 80 ° C., mixed well, then cooled to room temperature and kneaded, as in Test Example 1. A granulated powder having an average particle size of 75 μm was formed. The average particle size was measured in the same manner as in Test Example 1.

(Molding process)
Each obtained granulated powder was subjected to pressure molding in the same manner as in Test Example 1 to produce a molded body having the same shape and size as in Test Example 1. In this test, the molding conditions were heating temperature: 230 ° C., atmospheric pressure: 0.8 atm, and molding pressure: 10 ton / cm ² .

(Dehydrogenation process)
In the same manner as in Test Example 2, each powder compact (first compact) obtained through the molding process was heated in a hydrogen atmosphere to sample Nos.3-1 and 3-2. .3-3 and 3-3 were heated to 775 ° C., and then the hydrogen was discharged by a deaeration pump and switched to vacuum (VAC), and the pressure was reduced to 1.0 Pa or less. Then, under a reduced pressure atmosphere (final vacuum: 0.5 Pa), Sample Nos. 3-1 and 3-2 were heat treated at 800 ° C. for 60 minutes, and Samples No. 3-3 and 3-4 were heat treated at 775 ° C. for 60 minutes (Dehydrogenation) was performed. The heat treatment (dehydrogenation) was performed in a state where a 3T magnetic field was applied to all the samples. The magnetic field was applied using a high temperature superconducting magnet. Here, the application direction of the magnetic field was the same as the pressing direction in the molding step.

(Nitriding process)
The molded body (second molded body) obtained through the dehydrogenation step was heat-treated (nitrided) at 300 ° C. for 30 hours in a nitrogen (N ₂ ) atmosphere with an oxygen concentration of 100 mass ppm. This heat treatment (nitriding) was performed in a state where a 4 T magnetic field was applied. The application of the magnetic field was performed using a high-temperature superconducting magnet, and the application direction of the magnetic field was the same as the application direction of the magnetic field in the dehydrogenation step.

  The composition of the molded body obtained after the heat treatment (nitriding) was examined by an EDX apparatus. As a result, in each sample, an alloy containing rare earth elements and Fe (alloy shown in Table 6) was confirmed. Therefore, a recombination alloy is produced by heat treatment (dehydrogenation) or heat treatment (nitridation) (Sample No.3-1, 3-2), or a recombination alloy is nitrided (Sample No.3-3, 3- 4) I understand what I did.

When the molded body obtained after the heat treatment (nitriding) was examined in the same manner as in Test Example 1, each molded body had a plurality of alloy particles mainly composed of an alloy containing a rare earth element and Fe, and α "Fe It was confirmed that it consists of a plurality of iron nitride particles mainly composed of ₁₆ N _{2. From} this, it can be seen that each molded body was formed with a nitride such as α "Fe ₁₆ N ₂ by nano iron powder. . In addition, it was confirmed that each molded body had iron nitride particles interposed between alloy particles and that the iron nitride particles were columnar. For the columnar iron nitride particles, the average minor axis length of the iron nitride particles was measured in the same manner as in Test Example 1, and the average minor axis length of the nanoiron powder was substantially maintained. It was.

For each compact, the alloy component content (volume%) in the alloy particles was examined in the same manner as in Test Example 1. The results are shown in Table 6. For each molded body, the content of the α ”Fe ₁₆ N ₂ component in the iron nitride particles was examined in the same manner as in Test Example 1. As a result, all the samples were 80% by volume or more.

  The molded body obtained after the heat treatment (nitriding) was examined in the same manner as in Test Example 1 for the relative density (%), saturation magnetization (T), coercive force (kOe), and solid angle (°). The results are shown in Table 6.

  As shown in Table 6, it can be seen that by using the production method of the present invention, a composite magnetic material having excellent magnetic properties can be obtained using multiphase powders having various compositions. Even when multiphase powders of various compositions are used, the solid angle is as small as 10 ° or less, and the crystal orientation axis of the alloy particles constituting the composite magnetic material is aligned with the crystal orientation axis of the iron nitride particles. It can be seen that they are oriented. In addition, from sample Nos. 3-1 and 3-2, by using a raw material containing Nd, a composite magnetic material having a very high saturation magnetization can be obtained, from sample Nos. 3-3 and 3-4, It can be seen that a composite magnetic material having excellent magnetic properties can be obtained even when the amount of Sm used is reduced. Note that Sample No. 3-4 contained Ti having hydrogen occlusion, so that the inclusion of hydrogen was recognized in the iron-containing material (here, Fe-Ti phase).

  The present invention is not limited to the above-described embodiments, and can be appropriately changed without departing from the gist of the present invention. For example, the mixing amount of the binder can be appropriately changed.

  The composite magnetic material of the present invention can be suitably used as a permanent magnet, for example, a material of a permanent magnet used in various motors, in particular, a high-speed motor provided in a hybrid vehicle (HEV) or a hard disk drive (HDD). it can. The manufacturing method of the composite magnetic material of the present invention can be suitably used for manufacturing the composite magnetic material of the present invention.

Claims (14)

As a raw material powder, it contains nano iron powder consisting of columnar particles with Fe as the main component and an average minor axis length of 100 nm or less, a rare earth element hydrogen compound phase, and an iron-containing material phase containing Fe Preparing a multi-phase powder comprising multi-phase particles to be
A granulation step of mixing a binder having a decomposition temperature of 240 ° C. or less and the raw material powder to form a granulated powder;
After filling the granulated powder into a mold, the inside of the mold is evacuated to 0.9 atm or less, {(decomposition temperature of the binder) −20} ° C. or more {(decomposition temperature of the binder) +20} ° C. or less A molding step in which the first molded body is formed by pressure molding in a state heated to a temperature of
The first molded body is subjected to a heat treatment at a temperature equal to or higher than the recombination temperature of the multiphase particles in a reduced-pressure atmosphere of 100 Pa or less to separate hydrogen from the multiphase particles, and the rare earth element and the iron-containing material Producing a recombined alloy bonded with each other, and forming a second compact including the recombined alloy;
The second molded body is heat treated at a temperature of 200 ° C. or higher and 450 ° C. or lower in an atmosphere containing nitrogen element and an oxygen concentration of 200 mass ppm or lower to produce α ”Fe ₁₆ N ₂ from the nano iron powder. And a nitriding step for forming a composite magnetic material containing α "Fe ₁₆ N ₂ ,
The heat treatment in the dehydrogenation step is performed by applying a magnetic field of 2T or more to the first molded body,
The heat treatment in the nitriding step is performed by applying a magnetic field of 3 T or more to the second compact in the same direction as the direction of applying the magnetic field in the dehydrogenation step.   2. The method for producing a composite magnetic material according to claim 1, wherein an average particle size of the multiphase powder is 10 μm or more.   3. The method for producing a composite magnetic material according to claim 1, wherein the content of Fe in the nano iron powder is 80% by volume or more. The multiphase powder is obtained by subjecting an alloy containing a rare earth element and Fe to a heat treatment at a temperature equal to or higher than the disproportionation temperature of the alloy in an atmosphere containing a hydrogen element,
The alloy is one or more elements selected from RE = Y, La, Pr, Nd, Sm, Dy and Ce, and one or more elements selected from Me = Fe or Fe and Co, Ni, Mn and Ti. The element, when x = 2.0 to 2.2, is at least one selected from RE _x Me ₁₄ B, RE _x Me ₁₄ C, RE _x Me ₁₇ and RE _{x / 2} Me ₁₂ The method for producing a composite magnetic material according to any one of 1 to 3.   5. The composite according to claim 1, wherein in the nitriding step, the recombination alloy is nitrided to generate a rare earth-iron-nitrogen based alloy containing a rare earth element and Fe. Manufacturing method of magnetic material.   6. The method for producing a composite magnetic material according to claim 1, wherein the binder has a melting point of 90 ° C. or less.   The granulation step is performed in a low oxygen atmosphere with an oxygen concentration of 3000 ppm by mass or less, and granulated by cooling from a temperature of {(melting point of the binder) +5} ° C. to room temperature. Item 7. The method for producing a composite magnetic material according to any one of Items 1 to 6.   8. The production of a composite magnetic material according to claim 1, wherein the application of the magnetic field in at least one of the dehydrogenation step and the nitriding step is performed using a high-temperature superconducting magnet. Method. A composite magnetic material obtained by the method for producing a composite magnetic material according to any one of claims 1 to 8,
A plurality of alloy particles mainly composed of an alloy containing a rare earth element and Fe;
It consists of a compact composed of a plurality of iron nitride particles mainly composed of α "Fe ₁₆ N ₂ ,
The solid angle formed by the orientation direction of the easy axis in the pole figure analysis of X-ray diffraction performed on the alloy particles and the orientation direction of the easy axis in the pole figure analysis of X-ray diffraction performed on the iron nitride particles is A composite magnetic material characterized by being within 10 °. A plurality of alloy particles mainly composed of an alloy containing a rare earth element and Fe;
It consists of a compact composed of a plurality of iron nitride particles mainly composed of α "Fe ₁₆ N ₂ ,
The iron nitride particles are columnar, the average length of the minor axis is 100 nm or less,
At least one iron nitride particle is interposed between the alloy particles;
The solid angle formed by the orientation direction of the easy axis in the pole figure analysis of X-ray diffraction performed on the alloy particles and the orientation direction of the easy axis in the pole figure analysis of X-ray diffraction performed on the iron nitride particles is A composite magnetic material characterized by being within 10 °. The alloy is one or more elements selected from RE = Y, La, Pr, Nd, Sm, Dy and Ce, and one or more elements selected from Me = Fe or Fe and Co, Ni, Mn and Ti. Element, when x = 1.5 to 3.5, one or more selected from RE ₂ Me ₁₄ B, RE ₂ Me ₁₄ C, RE ₂ Me ₁₇ N _x , RE ₁ Me ₁₂ N _x and RE ₁ Me ₁₂ 11. The composite magnetic material according to claim 9 or 10, wherein:   12. The composite magnetic material according to claim 9, wherein the molded body satisfies at least one of a saturation magnetization of 1.5 T or more and a coercive force of the molded body of 10 kOe or more.   13. The composite magnetic material according to claim 9, wherein a relative density of the molded body is 90% or more.   14. The composite magnetic material according to claim 9, wherein a content of an alloy component in the alloy particles is 90% by volume or more.

Images