JP6563348B2 - Soft magnetic powder, soft magnetic body molded with soft magnetic powder, and soft magnetic powder and method for producing soft magnetic body - Google Patents

Description

  The present invention relates to a soft magnetic powder, a soft magnetic body formed from the soft magnetic powder, and a method for producing the soft magnetic powder and the soft magnetic body.

  Conventionally, development of a core (a dust core) having excellent magnetic properties (for example, a low coercive force, a high magnetic permeability, and a low loss) has been actively performed.

  For example, pure iron powder having a predetermined particle size is heated to a predetermined temperature range, Si (silicon) is concentrated on the surface of the pure iron powder to a predetermined concentration by a gas phase reaction, and then the oxidation process is performed. A method for producing a metal powder for a dust core, which is characterized by forming a silicon oxide film having a predetermined thickness on the surface of a powder (see, for example, Patent Document 1). An insulating film such as spinel ferrite magnetic oxide may be coated on the surface of the silicon oxide film. A core having a high electrical resistance and a high molding density can be obtained by performing pressure forming using such a metal powder for a powder magnetic core as a raw material, followed by annealing treatment (distortion heat treatment) in a predetermined temperature range. . Therefore, by using the dust core, a motor and a transformer having excellent magnetic characteristics can be obtained.

  Further, the Fe—Si based iron-based soft magnetic powder or a mixture of Fe (iron) powder and Si powder is heated in a non-oxidizing atmosphere to provide a Fe—Si based iron based soft magnetic material having a high concentration Si diffusion layer on the surface. By producing magnetic powder, oxidizing the powder to form an oxide film on the high-concentration Si diffusion layer, and heating the mixture of the powder and Mg (magnesium) powder under predetermined conditions An oxide film-covered Fe-Si iron-based soft magnetic powder characterized by forming an oxide film made of Mg, Si, Fe, and O (oxygen) on the surface of an Fe-Si iron-based soft magnetic powder Is known (see, for example, Patent Document 2).

  The oxide film contains part of Fe as a metal and also includes a fine crystal structure made of MgO (magnesium oxide) solid solution wustite phase. For this reason, the said oxide film has toughness and tends to follow the deformation | transformation of the powder at the time of compacting. In addition, the oxide film has excellent adhesion to the Fe-Si based iron-based soft magnetic powder and is chemically stable as compared with the Mg-containing ferrite oxide film conventionally used as an insulating film. As a result, the insulating properties of the oxide film are unlikely to deteriorate even when subjected to annealing at a high temperature after press molding of the powder, and the resulting core has low eddy current loss and low coercivity (ie, low hysteresis loss). ) Can be achieved simultaneously. That is, a composite soft magnetic material (core) having a low iron loss can be obtained.

In addition, a soft magnetic powder made of permalloy (Fe—Ni alloy) whose surface is coated with a mixture of metal oxides made of MgO fine particles, Fe ₂ O ₃ (iron oxide) fine particles, and MnO (manganese oxide) fine particles. A technique is known in which after forming under a hydrostatic pressure and forming the above mixture into a ferrite film by pulsed current pressure sintering (SPS), a hot isostatic pressing (HIP) treatment is performed under predetermined conditions ( For example, see Patent Document 3). According to this, a magnetic nanocomposite having high magnetic permeability and high electric resistance can be obtained even in a high frequency region.

JP 2009-235517 A Japanese Patent No. 4883755 JP 2011-2104026 A

  The conventional techniques including the above-described patent documents have the following problems, for example.

  When pure iron powder is used as the soft magnetic powder, the core formed by the soft magnetic powder is sufficiently annealed at a high temperature (for example, 1000 ° C.) to be comparable to an Fe—Si alloy. Low coercivity cannot be achieved. Therefore, the hysteresis loss of the core is large, and as a result, it is difficult to sufficiently reduce the iron loss in the core.

  In addition, when pure iron powder is molded at a high density, the magnetic permeability is increased, but the DC superposition characteristics are inferior. Therefore, it is necessary to adjust the magnetic permeability by providing an air gap in the magnetic path in the core. Such a configuration may lead to an increase in the number of core parts and assembly man-hours, for example, and as a result, the core manufacturing cost may increase.

  Furthermore, a metal oxide film containing MgO as a main component does not have magnetism. Therefore, when such a metal oxide film is formed on the surface of the soft magnetic powder with a film thickness that can achieve sufficient insulation, the overall magnetic properties of the core formed by the soft magnetic powder are reduced. There is a risk of inviting.

  In addition, when a hard soft magnetic powder such as Permalloy is used, it is necessary to go through a plurality of pressurizing steps in order to increase the density, which increases the core manufacturing cost. Further, when a film (for example, a silicon oxide film) that can suppress the reaction between the soft magnetic powder and the ferrite film is not interposed, these films react directly, so that the heat resistance is poor. As a result, when annealed at a sufficiently high temperature (eg, 900 ° C. or higher), the layer structure composed of metal and insulating film (soft magnetic powder and ferrite) cannot be maintained, and eddy current loss occurs. May increase.

  As described above, in this technical field, there is a continuous demand for a soft magnetic powder that can achieve a low iron loss while maintaining a low coercive force and a high magnetic permeability, and a soft magnetic body formed by the soft magnetic powder. Exists.

  The present invention has been made to solve the above problems. That is, the present invention relates to a soft magnetic powder that can achieve a low iron loss while maintaining a low coercive force and a high magnetic permeability, a soft magnetic body molded from the soft magnetic powder, the soft magnetic powder, and the soft magnetic body. One object is to provide a manufacturing method.

  In view of the above, the soft magnetic powder according to the present invention includes Fe-Si-based iron-based soft magnetic particles, a silicon oxide film formed on the surface of the Fe-Si-based iron-based soft magnetic particles, and the silicon oxide film. A magnesium-containing ferrite film formed on the surface. The silicon oxide film has a thickness of 0.5 μm or more and 1.0 μm or less.

  Furthermore, the soft magnetic body according to the present invention is a soft magnetic body that is a powder compact formed of the soft magnetic powder. The iron loss measured at room temperature when an AC magnetic field having an amplitude of 0.2 T and a frequency of 10 kHz is applied to the soft magnetic material is 75 W / kg or less.

The method for producing the soft magnetic powder according to the present invention described above,
A silicon oxide film is formed on the surface of the Fe—Si-based iron-based soft magnetic particles by subjecting the Fe—Si-based iron-based soft magnetic particles to a heat treatment in an inert atmosphere at a temperature of 900 ° C. or higher and 1100 ° C. or lower. An oxide film forming step;
An insulating film forming step of forming a magnesium-containing ferrite film on the surface of the silicon oxide film;
including.

Furthermore, the manufacturing method of the soft magnetic body according to the present invention described above is as follows.
A powder production process for producing a soft magnetic powder by the above-described method for producing a soft magnetic powder according to the present invention;
A compacting step of pressurizing the soft magnetic powder to produce a compacted compact;
A sintering step of sintering the green compact to obtain a sintered body;
including.

  According to the soft magnetic body (core) obtained by compacting and sintering the soft magnetic powder according to the present invention, the Fe—Si based iron-based soft magnetic particles achieve a low holding force and have soft magnetism. When the contained ferrite film is interposed between the soft magnetic particles, eddy current loss can be reduced while maintaining the magnetic characteristics of the entire core. Furthermore, when the core is subjected to annealing at a high temperature for the purpose of reducing hysteresis loss, the reactivity between magnesium-containing ferrite and Fe is low, and a silicon oxide film is interposed between the soft magnetic particles and the ferrite film. The reaction between ferrite and Fe can be suppressed and the above layer structure can be maintained. As a result, an increase in eddy current loss associated with the annealing process can be suppressed.

  That is, according to the present invention, a soft magnetic powder that can achieve a low iron loss while maintaining a low coercive force and a high magnetic permeability, a soft magnetic material molded with the soft magnetic powder, the soft magnetic powder, and the soft magnetic powder. A method for producing a magnetic material can be provided.

It is a graph which shows the analysis result by X-ray photoelectron spectroscopy (XPS) of the composition distribution in the depth direction of the powder sample P2 in which the silicon oxide film was formed on the surface. It is a graph which shows the analysis result by X-ray photoelectron spectroscopy (XPS) of the composition distribution in the depth direction of the powder sample P3 in which the silicon oxide film was formed on the surface. It is a scanning electron microscope (SEM) photograph of the external appearance (a) and the cross section (b) of the ferrite coating powder sample MP2 corresponding to the powder sample P2. It is a scanning electron microscope (SEM) photograph of the external appearance (a) and the cross section (b) of the ferrite coating powder sample MP3 corresponding to the powder sample P3. It is a graph (b) showing the analysis result by the energy dispersive X-ray spectroscopy (EDX) in the linear part shown in the SEM image (a) and SEM image of the cross-sectional structure | tissue of the ring-shaped sample of soft-magnetic material MP2. It is a graph (b) showing the analysis result by the energy dispersive X-ray spectroscopy (EDX) in the linear part shown in the SEM image (a) and SEM image of the cross-sectional structure | tissue of the ring-shaped sample of soft-magnetic material MP3. It is a graph which shows the change ((DELTA) micror) of the relative magnetic permeability (micro | micron | mu) r with the increase in the DC magnetic field in the sample of the soft magnetic body which concerns on Example WE3, WE5, and WE7 and comparative example CE3.

  Hereinafter, embodiments of the present invention will be described.

(1) Soft magnetic powder The soft magnetic powder according to the present invention includes Fe-Si-based iron-based soft magnetic particles, a silicon oxide film formed on the surface of the Fe-Si-based iron-based soft magnetic particles, and the silicon oxide. A magnesium-containing ferrite film formed on the surface of the film.

  As the Fe—Si-based iron-based soft magnetic particles, Fe—Si-based iron-based soft magnetic particles widely used as a constituent material of a dust core can be used. The Si content in the Fe—Si-based iron-based soft magnetic particles is preferably 1.0 wt% or more and 10 wt% or less. The average particle diameter of the Fe—Si-based iron-based soft magnetic particles is desirably 50 μm or more and 200 μm or less. If the average particle diameter of the Fe—Si-based iron-based soft magnetic particles is less than 50 μm, the coercive force is large and hysteresis loss may increase. On the other hand, when the average particle diameter of the Fe—Si-based iron-based soft magnetic particles exceeds 200 μm, eddy currents easily flow through the individual particles, and eddy current loss may increase.

  Specific examples of such Fe—Si-based iron-based soft magnetic particles include atomized powder. Therefore, the Fe—Si-based iron-based soft magnetic particles can achieve a low coercive force and a high magnetic permeability required for soft magnetic materials including a dust core. Among various atomized powders, water atomized powder is advantageous in terms of cost. In addition, the surface of the Fe—Si based iron-based soft magnetic particles produced by the water atomization method is covered with an oxide film. That is, iron oxide and silicon oxide exist on the outermost surface of the Fe—Si based iron-based soft magnetic particles.

  The silicon oxide film is formed by subjecting the Fe—Si based iron-based soft magnetic particles to a predetermined heat treatment, and oxygen constituting the iron oxide existing on the outermost surface of the Fe—Si based iron based soft magnetic particles as described above. It can be formed by reacting with silicon existing inside the particles (details will be described later).

  As will be described in detail later, the soft magnetic material obtained by compacting and sintering the soft magnetic powder according to the present invention is subjected to an annealing treatment at a high temperature for the purpose of reducing hysteresis loss. The At this time, the silicon oxide film suppresses an increase in eddy current loss of the soft magnetic material due to a decrease in the insulation of the ferrite film due to a reaction between the soft magnetic particles and the ferrite film.

  The silicon oxide film has a thickness of 0.5 μm or more and 1.0 μm or less. When the thickness of the silicon oxide film is less than 0.5 μm, the silicon oxide film is damaged and / or peeled off due to the formation of the magnesium-containing ferrite film, and the reaction between the soft magnetic particles and the ferrite film during the annealing treatment. May not be sufficiently suppressed, resulting in an increase in eddy current loss. On the other hand, when the thickness of the silicon oxide film exceeds 1.0 μm, the proportion of silicon oxide, which is a nonmagnetic material, in the soft magnetic particles increases, and the magnetic properties of the soft magnetic material obtained from the soft magnetic particles may be deteriorated. is there. The thickness of the silicon oxide film can be adjusted by, for example, the composition of the Fe—Si alloy constituting the Fe—Si-based iron-based soft magnetic particles, the temperature and time of heat treatment for forming the silicon oxide film, and the like.

  The coating amount of the magnesium-containing ferrite film formed on the surface of the silicon oxide film is preferably 0.5% by mass or more and 4.0% by mass or less with respect to the Fe—Si-based iron-based soft magnetic particles. . If the coating amount of the ferrite film is less than 0.5% by mass, it is difficult to form a continuous film, and it becomes difficult to ensure insulation between the Fe—Si-based iron-based soft magnetic particles. On the other hand, when the coating amount of the ferrite film exceeds 4.0% by mass, the thickness of the insulating film becomes excessive, and the Fe—Si-based iron-based soft magnetic particles occupying per unit volume of the soft magnetic material made of the soft magnetic powder. The ratio may decrease, leading to a decrease in magnetic permeability as a whole of the soft magnetic material and an increase in hysteresis loss.

  Also, the coating thickness of the magnesium-containing ferrite film is preferably 0.1 μm or more and 10 μm or less. If the coating film thickness of the magnesium-containing ferrite film is less than 0.1 μm, the thickness as the insulating film is too thin, and it becomes difficult to ensure the insulation between the Fe—Si-based iron-based soft magnetic particles. On the other hand, when the coating thickness of the ferrite film exceeds 10 μm, the thickness of the insulating film becomes excessive, and the proportion of Fe—Si based iron-based soft magnetic particles occupying per unit volume of the soft magnetic material made of the soft magnetic powder is There is a risk that the magnetic permeability of the soft magnetic material as a whole decreases and the hysteresis loss increases.

  In addition, the coating thickness of the magnesium-containing ferrite film in the soft magnetic material according to the present invention can be appropriately adjusted according to, for example, the use of the soft magnetic material. For example, when the soft magnetic material according to the present invention is used as the core of a motor that requires high magnetic permeability, the coating thickness of the magnesium-containing ferrite film is as long as it is possible to ensure insulation. It is desirable to make it as thin as possible.

  The magnesium-containing ferrite film is made of a general ferrite having a spinel crystal structure such as manganese zinc ferrite, nickel zinc ferrite, copper zinc ferrite, etc., and is a soft magnetic ferrite ( Soft ferrite). Since the specific resistance of soft magnetic ferrite is high, the Fe—Si based iron-based soft magnetic particles having a magnesium-containing ferrite film formed on the surface are electrically isolated. That is, the magnesium-containing ferrite film functions as an insulating film, and conduction between the Fe—Si-based iron-based soft magnetic particles is interrupted (insulation is ensured). Thereby, the fall of the electrical resistance of a soft magnetic body resulting from conduction | electrical_connection between Fe-Si type iron group soft magnetic particles can be prevented. Furthermore, by covering the soft magnetic ferrite having magnetism in this way, it is possible to suppress a decrease in the magnetic properties of the soft magnetic material, compared to the case of coating an insulating film having no magnetism.

  However, the ferrite film included in the soft magnetic powder according to the present invention as an insulating film is made of magnesium-containing ferrite containing Mg (magnesium) in its crystal structure. Magnesium-containing ferrite contains a stable oxide (MgO) and thus is not easily reduced and has low reactivity with Fe (iron). As a result, the possibility of an increase in eddy current loss due to a decrease in insulation due to reaction with soft magnetic particles during the annealing treatment is reduced.

Typically, the magnesium-containing ferrite film comprises a compound represented by the composition formula Mg _x M _1-x Fe ₂ O ₄ . In the formula, M represents a metal element other than Mg and Fe. Specifically, M represents one or more metal elements selected from, for example, Mn (manganese), Zn (zinc), Ni (nickel), Cu (copper), and the like. x represents the proportion of Mg in the metal elements other than Fe constituting the compound, and is preferably 0.1 or more and 0.5 or less. If x is less than 0.1, the effect of reducing the reactivity between the ferrite and Fe (iron) resulting from the inclusion of Mg in the ferrite film cannot be sufficiently obtained. On the other hand, if x exceeds 0.5, the magnetic properties of the ferrite are lowered, and as a result, the magnetic properties of the soft magnetic material obtained from the soft magnetic powder may be lowered.

  As described above, according to the soft magnetic powder according to the present invention, in the soft magnetic body (core) obtained from the soft magnetic powder, low iron loss can be achieved while maintaining low coercive force and high magnetic permeability. it can.

(2) Soft magnetic body The soft magnetic body according to the present invention can be obtained by pressing the soft magnetic powder according to the present invention as described above to produce a compacted body. Such a powder compact is used as a soft magnetic material that becomes a core (a powder magnetic core) such as a transformer and a motor. However, the soft magnetic material has inherent distortion caused by, for example, stress acting upon forming the magnesium-containing ferrite film and / or compacting the soft magnetic powder. Such a distortion may lead to a hysteresis loss when the soft magnetic material is used as a core, for example, and may increase the iron loss of the entire core.

  However, the soft magnetic material according to the present invention obtained from the soft magnetic powder according to the present invention as described above can achieve a remarkably low iron loss by heat treatment (annealing treatment) under predetermined conditions. Specifically, in the annealing treatment, the soft magnetic material is subjected to a heat treatment in an inert atmosphere at a temperature of 900 ° C. or more and 1200 ° C. or less (details of the annealing treatment will be described later). The soft magnetic material that has undergone such heat treatment exhibits an iron loss of 75 W / kg or less when an AC magnetic field having an amplitude of 0.2 T and a frequency of 10 kHz is applied at room temperature. This “iron loss” is the sum of hysteresis loss and eddy current loss, as is well known to those skilled in the art.

  By the annealing treatment, hysteresis loss can be reduced, and iron loss as a whole core made of the soft magnetic material according to the present invention can be reduced. Moreover, since the soft magnetic powder according to the present invention has the above-described configuration, a low coercive force and a high magnetic permeability can be achieved. In addition, since the insulating property of the magnesium-containing ferrite film is not lowered even by the annealing treatment, a low iron loss can be achieved without causing an increase in eddy current loss accompanying the annealing treatment.

  As described above, the soft magnetic material according to the present invention can achieve a low iron loss while maintaining a low coercive force and a high magnetic permeability.

  More preferably, the soft magnetic material according to the present invention obtained from the soft magnetic powder according to the present invention has an amplitude of 0.2 T and a frequency of 10 kHz after heat treatment in an inert atmosphere at a temperature of 1000 ° C. or higher and 1200 ° C. or lower. The iron loss measured at room temperature when an alternating magnetic field having a current density of 50 W / kg is applied.

(3) Method for producing soft magnetic powder The method for producing soft magnetic powder according to the present invention comprises:
A silicon oxide film is formed on the surface of the Fe—Si-based iron-based soft magnetic particles by subjecting the Fe—Si-based iron-based soft magnetic particles to a heat treatment in an inert atmosphere at a temperature of 900 ° C. or higher and 1100 ° C. or lower. An oxide film forming step;
An insulating film forming step of forming a magnesium-containing ferrite film on the surface of the silicon oxide film;
including.

  As the Fe—Si-based iron-based soft magnetic particles, as described above, Fe—Si-based iron-based soft magnetic particles widely used as a constituent material of a dust core can be used. Typically, Fe—Si-based iron-based soft magnetic particles produced by a water atomization method are used.

  In the oxide film forming step, the Fe—Si-based iron-based soft magnetic particles are subjected to a heat treatment in an inert atmosphere at a temperature of 900 ° C. or higher and 1100 ° C. or lower. Thereby, a silicon oxide film can be formed on the surface of the Fe—Si-based iron-based soft magnetic particles. As described above, this silicon oxide film is composed of an oxide that forms an oxide film that covers the surface of the Fe-Si-based iron-based soft magnetic particles, and oxygen that forms a relatively unstable iron oxide among silicon oxide and the particles. It is formed by the reaction with silicon present in the interior of the substrate.

  More specifically, oxygen constituting the iron oxide existing on the surface of the Fe—Si-based iron-based soft magnetic particles reacts with Si (silicon) in the Fe—Si alloy while diffusing into the inside of the particles, and silicon oxide ( Si oxide) is generated. Along with this, the Si concentration in the vicinity of the surface of the particle decreases, and a Si concentration gradient is generated inside the particle. For this reason, Si existing inside the particles diffuses to the vicinity of the surface, and the concentration gradient is relaxed. With such a mechanism, the surface of the Fe—Si based iron-based soft magnetic particles can be covered with the silicon oxide film.

  If the temperature of the heat treatment is less than 900 ° C., it is difficult to form a silicon oxide film. On the other hand, when the temperature of the heat treatment exceeds 1200 ° C., it becomes difficult to maintain the powder state by, for example, fusion of Fe—Si based iron-based soft magnetic particles. The inert atmosphere means not only a rare gas atmosphere such as Ar (argon) but also an atmosphere capable of suppressing oxidation of Fe—Si based iron-based soft magnetic particles such as a nitrogen atmosphere and a vacuum atmosphere.

  In the insulating film forming step, a magnesium-containing ferrite film is formed on the surface of the silicon oxide film formed on the surface of the Fe—Si based iron-based soft magnetic particles as described above. The constituent material of the magnesium-containing ferrite film is as described above. A specific method for forming a magnesium-containing ferrite film is to form a magnesium-containing ferrite film having a sufficient thickness continuously and uniformly to achieve sufficient insulation between Fe-Si-based iron-based soft magnetic particles. As long as it is possible, it is not particularly limited.

  That is, in the insulating film forming step, for example, a coating method in which mechanical energy such as compression, shear, and friction is applied to Fe-Si based iron-based soft magnetic particles and magnesium-containing ferrite powder, and a magnesium-containing ferrite slurry are prepared. A wet coating method applied to the Fe—Si-based iron-based soft magnetic particles can be employed.

  As described above, according to the method for producing a soft magnetic powder according to the present invention, a soft magnetic material constituting a soft magnetic body (core) capable of achieving a low iron loss while maintaining a low coercive force and a high magnetic permeability. A powder can be obtained.

  From the standpoint of achieving sufficient insulation between the Fe-Si-based iron-based soft magnetic particles by continuously and uniformly forming a magnesium-containing ferrite film having a thickness on the order of μm, a coating using mechanical energy The method is desirable. In this case, the insulating film forming step includes a mixing step of preparing a mixed powder that is a mixture of the Fe-Si-based iron-based soft magnetic particles and the magnesium-containing ferrite particles on which the silicon oxide film is formed; A film forming step of forming a magnesium-containing ferrite film on the surface of the silicon oxide film formed on the surface of the Fe—Si-based iron-based soft magnetic particles by applying mechanical energy to the mixed powder.

  As a specific method for forming a magnesium-containing ferrite film on the surface of the silicon oxide film formed on the surface of the Fe—Si-based iron-based soft magnetic particles in the film forming step, for example, a mechano-fusion method is cited. Can do. As is well known to those skilled in the art, the mechano-fusion method is a dry processing method in which a certain substance is fused to the surface of another substance using mechanical energy. In the following description, the film formation process by the mechanofusion method may be referred to as “mechanofusion process”.

  Specifically, Fe—Si-based iron-based soft magnetic particles and magnesium-containing ferrite particles are mixed at a ratio corresponding to the thickness (coating amount) necessary to achieve insulation, and a press head is disposed inside. The mixed powder is filled into the rotor. Then, by rotating the rotor under predetermined conditions (for example, the rotational speed of the rotor, temperature, and ambient atmosphere), the mixed powder is compressed, sheared, frictioned, etc. between the press head and the inner wall of the rotor. Mechanical energy is applied to the mixture. As a result, a magnesium-containing ferrite film having a desired thickness can be formed on the surface of the Fe—Si-based iron-based soft magnetic particles while suppressing damage and / or peeling of the silicon oxide film.

(4) Method for producing soft magnetic material The method for producing a soft magnetic material according to the present invention comprises:
A powder production process for producing a soft magnetic powder by the method for producing a soft magnetic powder according to the present invention;
A compacting step of pressurizing the soft magnetic powder to produce a compacted compact;
A sintering step of sintering the green compact to obtain a sintered body;
including.

  The method for producing the soft magnetic powder according to the present invention, which is executed in the above powder production process, has already been described above. Since the soft magnetic powder according to the present invention has the above-described configuration, a low coercive force and a high magnetic permeability can be achieved.

  In the compacting process, for example, the soft magnetic powder (comprising Fe-Si based iron-based soft magnetic particles having a magnesium-containing ferrite film formed on the surface) manufactured in the powder manufacturing process is placed in the cavity of the mold. Fill. And a compacting body is produced by pressurizing the soft magnetic powder filled in the cavity. At this time, for example, a warm lubrication molding method using a lubricant such as an aqueous solution of zinc stearate may be employed. Pressurization of the soft magnetic powder can be performed by a known pressurizing apparatus. The higher the load at the time of pressurization (pressing force), the higher the density of the green compact.

  The higher the density of the soft magnetic material, the better the magnetic properties and mechanical strength of the soft magnetic material. Therefore, in the compacting process, compacting is performed with a high load in order to increase the density of the compacted product. However, the higher the load at the time of compacting, the more prominent the deformation of the particles constituting the soft magnetic powder constituting the compact. Therefore, when the magnesium-containing ferrite film as the insulating film cannot follow the deformation of the Fe—Si based iron-based soft magnetic particles in the compacting process, the insulating film is damaged and / or peeled off, thereby causing the Fe—Si based iron group. There is a possibility that the insulation between the soft magnetic particles may be lowered.

  However, as will be described in detail later, in the soft magnetic powder according to the present invention, the magnesium-containing ferrite film is composed of powdered ferrite particles. Therefore, even if the Fe-Si iron-based soft magnetic particles are deformed in the compacting process, the ferrite particles constituting the magnesium-containing ferrite film flow, so that the magnesium-containing ferrite film is also Fe-Si-based iron-based soft magnetic particles. It can be easily deformed following the deformation. As a result, it is possible to prevent the magnesium-containing ferrite film as the insulating film from being destroyed by pressure deformation, and to more reliably achieve insulation between adjacent Fe-Si-based iron-based soft magnetic particles. .

  In the sintering step, the green compact is sintered into a sintered body. Only the pressurization in the compacting process cannot achieve a strong bonding force between the Fe-Si-based iron-based soft magnetic particles through the magnesium-containing ferrite film, and the mechanical strength of the soft magnetic material is low. However, the mechanical strength of the soft magnetic material can be increased by strengthening the bond between the particles by sintering. In addition, the soft magnetic ferrite layer covering the surface of the Fe—Si-based iron-based soft magnetic particles is formed of ferrite particles as described above. In the sintering process, bonding between these ferrite particles and particle growth occur. This also contributes to the improvement of the mechanical strength of the soft magnetic material.

  Moreover, in the said compacting body, since the distortion resulting from the pressurization at the time of compacting is accumulate | stored, a hysteresis loss is large in the state as it is. The sintering process is also positioned as an annealing process for removing this distortion. Thereby, a hysteresis loss can be reduced and the iron loss as the whole core which consists of a soft-magnetic body based on this invention can be reduced.

  By the way, in general, in a green compact made of iron-based soft magnetic particles coated with a ferrite film, the higher the heat treatment temperature (sintering temperature) in the sintering step, the greater the mechanical strength of the sintered body. However, the coercive force tends to decrease. Therefore, if the sintering temperature is excessively low, such an effect cannot be obtained sufficiently. On the other hand, when the sintering temperature is excessively high, the reduction of ferrite proceeds and the internal oxidation of the iron-based soft magnetic particles proceeds to produce FeO (iron oxide). FeO is paramagnetic at room temperature, has electrical conductivity, and has low strength. Therefore, when a large amount of FeO phase is present in a soft magnetic material, the permeability decreases, the eddy current loss increases, and the mechanical strength increases. Incurs a decline. That is, when the sintering temperature is increased, a large amount of FeO is generated at the grain boundaries of the iron-based soft magnetic particles, and the ferrite film (insulating film) is deteriorated. When the insulating film is deteriorated in this way, the insulating property between the iron-based soft magnetic particles cannot be maintained, and there is a risk of increasing the eddy current loss of the soft magnetic material.

  On the other hand, since the soft magnetic powder according to the present invention used in the method for producing a soft magnetic material according to the present invention contains a stable oxide (MgO), it is difficult to be reduced and has a reactivity with Fe (iron). A low magnesium-containing ferrite film is provided as an insulating film. Further, in the soft magnetic powder, a silicon oxide film is interposed between the insulating film and the Fe—Si-based iron-based soft magnetic particles. Therefore, since the decrease in insulation of the magnesium-containing ferrite film accompanying the sintering of the green compact in the sintering step is suppressed, low iron loss can be achieved without causing an increase in eddy current loss. .

  According to the method for manufacturing a soft magnetic body according to a preferred embodiment of the present invention, when an AC magnetic field having an amplitude of 0.2 T and a frequency of 10 kHz is applied to the sintered body, the iron loss measured at room temperature is 75 W / A soft magnetic material having a weight of kg or less can be obtained. A soft magnetic body having such a low iron loss is produced, for example, by sintering the green compact in an inert atmosphere at a temperature of 900 ° C. or higher and 1200 ° C. or lower in the sintering step. be able to.

  According to the method of manufacturing a soft magnetic material according to a more preferable aspect of the present invention, the iron loss measured at room temperature when an AC magnetic field having an amplitude of 0.2 T and a frequency of 10 kHz is applied to the sintered body is 50 W. / Kg or less of a soft magnetic material can be obtained. A soft magnetic body having such a low iron loss is produced, for example, by sintering the green compact in an inert atmosphere at a temperature of 1000 ° C. or higher and 1200 ° C. or lower in the sintering step. be able to.

  As described above, the inert atmosphere also oxidizes not only a rare gas atmosphere such as Ar (argon) but also a nitrogen atmosphere and a vacuum atmosphere such as Fe-Si based iron-based soft magnetic particles and a magnesium-containing ferrite film. It means an atmosphere that can be suppressed.

  As described above, according to the method for manufacturing a soft magnetic body according to the present invention, a soft magnetic body (core) capable of achieving a low iron loss while maintaining a low coercive force and a high magnetic permeability can be obtained. .

<Preliminary experiment>
In this embodiment, for the purpose of promoting the understanding of the present invention, first, ferrite containing no Mg (magnesium) is used as a material for forming an insulating film, and the above-described soft magnetic powder, soft magnetic material, and These manufacturing methods will be described.

1. Soft Magnetic Powder (a) Formation of Silicon Oxide Film First, the silicon oxide film formed on the surface of the Fe—Si based iron-based soft magnetic particles will be described below. In this example, water atomized powder of Fe-Si alloy (Fe-3.0% Si) containing 3.0% by mass of Si is used as Fe-Si-based iron-based soft magnetic particles. Heat treatment was performed under various conditions.

P1: No heat treatment.
P2: Heat treatment at 900 ° C. for 10 minutes in N ₂ (nitrogen) atmosphere.
P3: Heat treatment at 900 ° C. for 20 minutes in N ₂ (nitrogen) atmosphere.

  In the following description, the powder samples that have been heat-treated under the conditions P1 to P3 are also referred to as P1 to P3, respectively. Table 1 below shows the results of quantitative analysis of the composition of the outermost surfaces of the powder samples P1 to P3 by X-ray photoelectron spectroscopy (XPS).

  As is clear from the analysis results shown in Table 1, the presence of Fe and Si oxides was confirmed on the surface of the powder sample P1 that had not been heat-treated. Compared with the powder sample P1, in the powder samples P2 and P3, the Fe concentration is lower and the Si concentration is higher. That is, it was confirmed that a silicon oxide film was formed in the powder samples P2 and P3.

  Therefore, the composition distribution in the depth direction was analyzed for the powder samples P2 and P3 having the silicon oxide film formed on the surface as described above. The analysis results are shown in FIG. 1 (P2) and FIG. 2 (P3), respectively. Based on the concentration distribution of O (oxygen) indicated by the solid line, the thickness of the silicon oxide film formed in the powder sample P2 having a short heat treatment time is determined to be about 300 nm at the thick portion. On the other hand, in the powder sample P3 having a long heat treatment time, the thickness of the silicon oxide film is determined to be about 600 nm.

(B) Formation of ferrite film Next, ferrite films were formed on the surfaces of the powder samples P2 and P3 on which the silicon oxide film was formed by the heat treatment. Specifically, for each of the powder samples P2 and P3 (Fe—Si based iron-based soft magnetic particles) prepared as described above, 60 g of soft magnetic ferrite (Ni—Zn) with respect to 1500 g of soft magnetic particles. -Cu ferrite: manufactured by Toda Kogyo Co., Ltd.) was mixed in an Ar atmosphere glove box to prepare a mixed powder.

  Thereafter, the mixed powder is taken out from the glove box and filled in a mechanofusion apparatus (manufactured by Hosokawa Micron Corporation), and the surface of each Fe-Si-based iron-based soft magnetic particle is coated with the apparatus by the apparatus. An insulating film was formed. For both powder samples P2 and P3, a ferrite coating treatment was performed for 40 minutes in a rotor rotational speed of 1000 rpm, room temperature (water cooling), and an Ar flow atmosphere. Scanning electron microscope (SEM) photographs of the appearance (a) and the cross section (b) of the ferrite-coated powder samples MP2 and MP3 corresponding to the powder samples P2 and P3, respectively, are shown in FIGS. 3 and 4, respectively.

  In the SEM photographs showing the appearance of the particles constituting the ferrite-coated powder samples MP2 and MP3 ((a) of FIG. 3 and (a) of FIG. 4), both of the powder samples MP2 and MP3 include some uneven portions. It looks the same for the point that the entire surface of the particle is covered with ferrite powder. However, in the SEM photographs (FIG. 3 (b) and FIG. 4 (b)) showing the cross sections of the particles constituting the powder samples MP2 and MP3, a ferrite film (insulation) is formed between the ferrite-coated powder samples MP2 and MP3. Differences in the structure of the membrane were observed.

  Specifically, in the powder sample MP2, the ferrite powders constituting the insulating film or the sample powder (Fe—Si iron-based soft magnetic particles) and the ferrite powder are fused to form an integral film-like structure. Was forming. On the other hand, in the powder sample MP3, individual ferrite powders can be confirmed, and a structure in which powders are laminated is formed.

  In the above, since the silicon oxide film of the powder sample P2 is thin (about 300 nm), it is considered that the silicon oxide film is damaged and / or peeled off when the ferrite powder is rubbed against the Fe—Si alloy powder in the mechanofusion process. . That is, since the silicon oxide film was damaged and / or peeled, the ferrite powder and the Fe—Si alloy powder came into direct contact with each other, and they were mixed and changed into an integral film structure. It is done.

  On the other hand, since the silicon oxide film of the powder sample P3 is thick (about 600 nm), the silicon oxide film is not broken and / or peeled off even in the mechanofusion process, and the silicon oxide film is amorphous and hard, so the ferrite powder It is considered that a structure in which powders are laminated is formed.

2. Production of soft magnetic body (a) Using the ferrite-coated powder samples MP2 and MP3 prepared as described above, a ring-shaped soft magnetic body sample (outer diameter: about 20 mmφ, inner diameter: about 14 mmφ, thickness: about 3 mm) was compacted. For the compacting, a warm lubrication molding method (temperature: 130 ° C., pressure: 1200 MPa, lubricant: zinc stearate aqueous solution) was employed. Sintered bodies corresponding to the ferrite-coated powder samples MP2 and MP3 by subjecting these green compacts to heat treatment (annealing treatment) at 900 ° C. for 10 minutes in an inert gas (Ar) atmosphere. (Soft magnetic materials) were produced. In the following description, samples of soft magnetic bodies (sintered bodies) corresponding to the ferrite-coated powder samples MP2 and MP3 are also referred to as soft magnetic bodies MP2 and MP3, respectively.

(B) Magnetic characteristics For each of the soft magnetic materials MP2 and MP3, a magnetic flux density Bm [T] in an external magnetic field (Hm) of 8 kA / m using a direct current BH curve tracer (manufactured by Riken Denshi Co., Ltd.). The coercive force Hc [A / m] was measured. It can be determined that the larger the magnetic flux density Bm, the higher the magnetic permeability, and the smaller the coercive force Hc, the lower the iron loss (hysteresis loss). In addition, using an AC B-H analyzer (manufactured by Iwatsu Measurement Co., Ltd.), the iron loss was measured when an AC magnetic field having an amplitude of 0.2T and a frequency of 10 kHz was applied to each sample, and hysteresis loss ( His loss) and eddy current loss (eddy current loss). The material composition, manufacturing conditions (annealing temperature), density (core density), and magnetic properties (magnetic flux density, coercive force, iron loss, hiss loss, and eddy current loss) of each soft magnetic material sample are listed in Table 2 below. To do.

  As shown in Table 2, regarding the density of the soft magnetic body (sintered body), no significant difference was observed depending on the thickness of the silicon oxide film. On the other hand, the eddy current loss was large in the soft magnetic body MP2 having a thin (about 300 nm) silicon oxide film and small in the soft magnetic body MP3 having a thick (about 600 nm) silicon oxide film. This is because, in the soft magnetic material MP2, the insulation between the soft magnetic powders is reduced because the silicon oxide film is thin, whereas in the soft magnetic material MP3, the insulation between the soft magnetic powders is caused because the silicon oxide film is thick. As a result, it is considered that the eddy current loss is reduced.

(C) Structure Next, a part of the ring-shaped samples of the soft magnetic bodies MP2 and MP3 after the above magnetic property evaluation was cut out, and the structure was observed. SEM image (a) of cross-sectional structure of soft magnetic materials MP2 and MP3, and graph (b) showing an analysis result by energy dispersive X-ray spectroscopy (EDX: Energy Dispersive X-ray Spectrometry) in a linear portion shown in the SEM image Are shown in FIGS. 5 and 6, respectively.

  First, the soft magnetic material MP2 will be examined with reference to FIG. According to the SEM image (a) of the cross-sectional structure of the soft magnetic material MP2, the oxidation phase spreads from the ferrite coating at the grain boundary of the soft magnetic powder shown in the center to the inside of the soft magnetic powder. According to the EDX analysis result (b), a large number of spherical silicon oxides (Si oxides) are observed in the ferrite coating at the grain boundaries and in the oxidized phase inside the powder, whereas between the ferrite coating and the soft magnetic powder. The silicon oxide film is not clearly recognized.

  The silicon oxide film of the soft magnetic material MP2 had already disappeared by the above-mentioned mechanofusion treatment, or because the film thickness was thin, Fe—Si based iron-based soft magnetic particles (soft) by oxygen supplied from the ferrite coating. It is thought that it disappeared with the progress of internal oxidation of the magnetic powder. From the fact that the oxide phase of Mn, which is a trace element added to the soft magnetic powder, can be confirmed near the center of the ferrite coating by EDX analysis, as described above, there is a wide range of active activity between the ferrite coating and the soft magnetic powder. Interdiffusion is considered to have occurred. Moreover, since the oxygen concentration is low and covers a wide range in the result of EDX analysis, it is presumed that the internal oxidation of the soft magnetic powder has progressed remarkably as described above. Along with this, FeO (wustite) having low insulation is generated in the ferrite coating, and it is considered that the insulation of the soft magnetic body MP2 as a whole cannot be maintained in combination with the disappearance of the silicon oxide film described above. .

  On the other hand, according to the SEM image (a) of the cross-sectional structure of the soft magnetic material MP3, the expansion of the oxidized phase into the soft magnetic powder is not recognized, and according to the EDX analysis result (b), the film thickness is at least 1 μm. It has been confirmed that a silicon oxide film having bismuth exists between the ferrite coating and the soft magnetic powder. That is, in the soft magnetic material MP3, the thickness of the silicon oxide film is increased as compared with that before sintering (annealing treatment). This is because, as the reduction reaction of ferrite proceeds, oxygen diffuses through the silicon oxide film toward the Fe-Si-based iron-based soft magnetic particles (soft magnetic powder), and the interface between the silicon oxide film and the soft magnetic powder. It is considered that this is because silicon oxide (Si oxide) was newly generated in step (b). In addition, it is considered that the island-like regions having a low oxygen concentration scattered inside the ferrite coating are generated as a result of the ferrite reduction reaction as described above.

  As described above, in the soft magnetic body MP3, a thick silicon oxide film is interposed between the soft magnetic particles and the ferrite coating, so that the ferrite coating and the soft magnetic powder as observed in the soft magnetic body MP2 are interposed. It is thought that active interdiffusion over a wide area did not occur. As a result, it is considered that the reaction between the ferrite coating and the soft magnetic powder (Fe) was suppressed, and the increase in eddy current loss accompanying the annealing treatment was suppressed.

  From the above, the silicon oxide film formed on the surface of the Fe—Si-based iron-based soft magnetic particles has a silicon oxide film formed on the surface of the soft magnetic particles, and the surface of the silicon oxide film is covered with ferrite. It has been confirmed that it has a function of maintaining the layer structure in which is formed. As a result, the direct reaction between the ferrite coating and the soft magnetic powder can be prevented or suppressed during annealing (sintering), and the insulation between the Fe-Si-based iron-based soft magnetic particles can be maintained. it can. It is also confirmed that the silicon oxide film needs to have a thickness that can withstand the ferrite powder coating process (mechanofusion process) and the annealing process (sintering) in order to exhibit the function as described above. It was.

<This experiment>
In the present embodiment, based on the knowledge obtained in the preliminary experiment described above, the soft magnetic material according to the embodiment of the present invention that uses ferrite containing Mg (magnesium) as a material for forming the insulating film, and the insulating film And a soft magnetic material according to a comparative example using a ferrite not containing Mg (magnesium) as a material for forming the magnetic material, and comparatively examining their magnetic properties.

1. Comparative Example By the way, in an Fe—Si alloy, it is said that hysteresis loss (his loss) can be reduced by suppressing the coercive force (Hc) to 100 A / m or less. As described above, in the soft magnetic material MP3, since the silicon oxide film has a suitable thickness, an increase in eddy current loss accompanying the annealing process is suppressed. However, as shown in Table 2, even in such a soft magnetic material MP3, the coercive force Hc exceeds 200 A / m, and the loss cannot be sufficiently reduced. In the following description, the soft magnetic material MP3 is referred to as “Comparative Example CE1”.

  Therefore, in order to lower the coercive force Hc, annealing (sintering) was performed on the soft magnetic material having the same configuration as that of Comparative Example 1 at a higher temperature (1000 ° C.). However, as a result of annealing and raising the temperature in this way, eddy current loss increased, and the insulation between soft magnetic powders deteriorated. This is because the amount of oxygen supplied by the reduction of Ni—Zn—Cu ferrite is increased by annealing treatment at a higher temperature, and the structure of the silicon oxide film and the ferrite coating is destroyed. This is presumably because even the soft magnetic material can no longer maintain the insulation between the soft magnetic powders. In the following description, the soft magnetic material MP3 that has been annealed and raised in temperature to 1000 ° C. will be referred to as “Comparative Example CE2”. Furthermore, as Comparative Example CE3, a soft magnetic material using commercially available pure iron powder was also prepared.

2. Example As a countermeasure against the above, it is conceivable to further increase the thickness of the silicon oxide film, but as described above, the oxygen supply source for forming the silicon oxide film is Fe-Si (formed by the water atomization method). Fe oxide present on the surface of the iron-based soft magnetic particles. Therefore, even if the conditions (high temperature and time) of the heat treatment for forming the silicon oxide film are made stricter, the effect of increasing the thickness of the silicon oxide film is small. In addition, if the silicon oxide film is too thick, the moldability during compacting may be reduced.

  Therefore, as a result of intensive research, the inventor formed an insulating film with Mg (magnesium) -containing ferrite that has low reactivity with Fe at high temperatures, thereby performing annealing treatment at a temperature of 1000 ° C. or higher. It was also found that the insulation between soft magnetic powders can be maintained.

  Based on the above knowledge, as listed in Table 3 below, Fe-Si alloy is used as soft magnetic particles, Mg-containing ferrite is used as a material for forming an insulating film, and the coating amount and annealing temperature are variously changed. Samples of various soft magnetic materials according to the modified examples WE1 to WE9 were prepared. In Table 3 below, the above-described comparative examples CE1 to CE3 are also listed.

(A) Constituent material and manufacturing method As shown in Table 3, in Examples WE1 to WE7, Fe-6.5% Si containing 6.5% by mass of Si as Fe-Si based iron-based soft magnetic particles. An alloy was used, and for Examples WE8 and WE9, an Fe-3.0% Si alloy containing 3.0% by mass of Si was used as the Fe—Si-based iron-based soft magnetic particles.

In any of Examples WE1 to WE9, a silicon oxide film was formed by performing heat treatment under the above-described condition P3 (at 900 ° C. for 20 minutes in an N ₂ (nitrogen) atmosphere). Further formed in any of the embodiments WE1 to WE9, by mechanofusion processing described above, at coating amount shown in Table 3, MgZn ferrite _{(Mg 0.6 Zn 0.4 Fe 2 O} 4) as a ferrite film did.

  Also for compacting, a ring-shaped sample was prepared by the above-described warm-type lubrication molding method (temperature: 130 ° C., pressure: 1200 MPa, lubricant: zinc stearate aqueous solution), and the annealing temperatures shown in Table 3 (annealing) Temperature) and sintering while performing the annealing treatment.

(B) Magnetic characteristics The results of measuring various magnetic characteristics of the samples of various soft magnetic materials according to the above-described comparative examples CE1 to CE3 and examples WE1 to WE9 are also listed in Table 3 above. The measurement of the magnetic flux density Bm [T] and the coercive force Hc [A / m] with the direct current BH curve tracer and the measurement of the iron loss with the alternating current BH analyzer are performed in the same manner as the procedure described above for the preliminary experiment. It was. However, in Table 3, iron loss is not separated into hysteresis loss (his loss) and eddy current loss (eddy current loss), and only iron loss is shown.

  On the other hand, in this experiment, in order to evaluate the DC superposition characteristics of various samples, the relative permeability (μr) in a minor loop on which a DC magnetic field was superimposed was further measured. In Table 3, μr0 is the relative permeability when the DC superimposed magnetic field is 0 (zero) A / m, and μr10 kA is the relative permeability when the DC superimposed magnetic field is 10 kA / m. The smaller the decrease in relative permeability μr (Δμr = μr0−μr10 kA) with respect to the increase in DC magnetic field from 0 (zero) A / m to 10 kA / m, the better the DC superposition characteristics. The measurement results of these magnetic properties are also listed in Table 3 above, and the soft magnetic samples according to Examples WE3, WE5, and WE7 and Comparative Example CE3 are also shown in the graph of FIG.

  As is clear from Table 3, in the samples of various soft magnetic materials according to Examples WE1 to WE9, a silicon oxide film having the same thickness as Comparative Examples CE1 and CE2 is formed by coating MgZn ferrite as an insulating film. Despite being provided, the coercive force could be suppressed to less than 200 A / m while suppressing the iron loss to 75 W / kg or less by annealing at a temperature of 900 ° C. or higher.

  Further, in Example WE2 and Examples WE4 to We9 in which the annealing temperature was increased to 1000 ° C. or higher, the iron loss increased due to the increase in eddy current loss, while the coercive force was suppressed to 50 W / kg or less. It could be suppressed to less than 100 A / m. In particular, Example WE5 showed the lowest iron loss among the various Examples. Specifically, the iron loss of the soft magnetic material sample according to Example WE5 was reduced to 36 W / kg. This is a value less than half of the iron loss (78 W / kg) of a commercially available pure iron powder core (corresponding to Comparative Example CE3).

  Regarding the DC superposition characteristics, in all the examples WE1 to WE9, the decrease Δμr in relative permeability μr due to the increase in the DC magnetic field described above is smaller than that of a commercially available pure iron powder core (corresponding to the comparative example CE3). It was confirmed that the direct current superposition characteristics were excellent.

  From the above, according to the present invention, it was confirmed that a soft magnetic powder capable of achieving a low iron loss while maintaining a low coercive force and a high magnetic permeability can be provided. Furthermore, in the soft magnetic material molded with the soft magnetic powder according to the present invention, even if it is subjected to annealing at a higher temperature to further reduce the hysteresis loss, it is further reduced without increasing the eddy current loss. Iron loss could be achieved. In addition, it was also confirmed that the soft magnetic material molded with the soft magnetic powder according to the present invention has excellent direct current superposition characteristics.

  While several embodiments and examples having specific configurations have been described above and sometimes with reference to the accompanying drawings for the purpose of illustrating the present invention, the scope of the present invention is limited to these illustrative examples. It should be understood that the present invention should not be construed as being limited to the embodiments and examples, and that modifications can be made as appropriate within the scope of the matters described in the claims and the specification.

Claims (7)

A silicon oxide film is formed on the surface of the Fe—Si-based iron-based soft magnetic particles by subjecting the Fe—Si-based iron-based soft magnetic particles to a heat treatment in an inert atmosphere at a temperature of 900 ° C. or higher and 1100 ° C. or lower. An oxide film forming step;
An insulating film forming step of forming a magnesium-containing ferrite film on the surface of the silicon oxide film;
A method for producing soft magnetic powder, comprising: In the manufacturing method of the soft-magnetic powder of Claim 1 ,
The insulating film forming step includes
A mixing step of preparing a mixed powder that is a mixture of the Fe-Si-based iron-based soft magnetic particles and the magnesium-containing ferrite particles on which the silicon oxide film is formed;
A film forming step of forming a magnesium-containing ferrite film on the surface of the silicon oxide film formed on the surface of the Fe-Si-based iron-based soft magnetic particles by applying mechanical energy to the mixed powder;
A method for producing soft magnetic powder, comprising: A powder production process for producing a soft magnetic powder by the method for producing a soft magnetic powder according to claim 1 or 2 ,
A compacting step of pressurizing the soft magnetic powder to produce a compacted compact;
A sintering step of sintering the green compact to obtain a sintered body;
A method for producing a soft magnetic material. In the manufacturing method of the soft-magnetic body of Claim 3 ,
In the sintering step, the green compact is sintered in an inert atmosphere at a temperature of 900 ° C. or higher and 1200 ° C. or lower.
A method for producing a soft magnetic material. In the manufacturing method of the soft-magnetic body of Claim 3 or Claim 4 ,
In the sintering step, the compacted body is such that an iron loss measured at room temperature when an AC magnetic field having an amplitude of 0.2 T and a frequency of 10 kHz is applied to the sintered body is 75 W / kg or less. Is a process of sintering
A method for producing a soft magnetic material. In the manufacturing method of the soft-magnetic body of Claim 3 ,
In the sintering step, the green compact is sintered in an inert atmosphere at a temperature of 1000 ° C. or more and 1200 ° C. or less.
A method for producing a soft magnetic material. In the manufacturing method of the soft-magnetic body of Claim 3 or Claim 6 ,
In the sintering step, the compacted body is such that an iron loss measured at room temperature is 50 W / kg or less when an alternating magnetic field having an amplitude of 0.2 T and a frequency of 10 kHz is applied to the sintered body. Is a process of sintering
A method for producing a soft magnetic material.