JP2013089929A - Soft magnetic powder, powder magnetic core, and magnetic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a soft magnetic powder having a small core loss and low frequency dependence thereof, and capable of manufacturing a powder magnetic core having a small core loss even if it is driven with a high frequency of 1 MHz or higher, and to provide a powder magnetic core having a small core loss and low frequency dependence thereof, and a magnetic device.SOLUTION: The soft magnetic powder of Fe or an Fe-Ni-based alloy has a primary particle size of 0.01-5 μm, and an average value of the product of aspect ratio and area ratio of 1.0-4.0.

Description

  The present invention relates to a soft magnetic powder, a dust core, and a magnetic device.

  Conventionally, a dust core has been widely used as a magnetic core provided in an inductor or the like. The performance required for the dust core is high electrical resistance and small core loss (magnetic core loss). In order to realize such a dust core, the atomizing method is used as a material for the dust core. Various attempts have been made to use metal magnetic powders such as FeSi-based and FeNi-based alloy powders manufactured by the above, and pure iron powders (high-purity iron powders) manufactured by the carbonyl method.

  In recent years, miniaturization and high output of electronic devices have progressed, and high integration of various parts and high-speed signal processing have progressed. Along with this, miniaturization of power supply lines for supplying power and an increase in current are required. For example, in a power inductor used for a power supply or the like, it is required to have a small inductance drop under DC current superposition, and in order to realize this, a magnetic material having high saturation magnetization as a material for a dust core, For example, pure iron powder (high purity iron powder) is widely used.

  On the other hand, since the inductor and the like can be miniaturized by driving the power supply circuit at a high frequency, development of a magnetic material with a high frequency and a small core loss is required. The core loss includes a hysteresis loss and an eddy current loss. To manufacture a magnetic material with a small core loss, it is essential to reduce the hysteresis loss and the eddy current loss. In order to reduce the hysteresis loss, a material having a small coercive force is required. In addition, reduction of eddy current loss requires reduction of eddy current between particles (improvement of insulation between particles) and reduction of eddy current in particles (fine particle). In particular, since the eddy current loss tends to increase in proportion to the square of the driving frequency, the eddy current loss is required to be small in the dust core used in the high frequency range. For this reason, it is considered that miniaturization of the magnetic material is effective in order to cope with a higher driving frequency, for example, several MHz.

In many cases, it is necessary to crush necking (connection) generated between particles in order to make the magnetic material finer. As the crushing technique, for example, those disclosed in Patent Literature 1 and Patent Literature 2 are disclosed. can give. Patent Document 1 describes that a pulverized magnetic powder can be obtained by applying an impact or vibration to the magnetic powder using a V-type or W-cone mixer or ball mill (see Patent Document 1). ). Moreover, in patent document 2, the magnetic powder for powder magnetic cores can be obtained by performing the crushing of the magnetic powder in the reduction annealing step by inserting ceramic balls together with the magnetic powder in the rotary reduction furnace. (See Patent Document 2).

Japanese Patent No. 0421944 JP 2009-001868 A

  By the methods described in Patent Document 1 and Patent Document 2, so-called coarse particles having a primary particle size of several tens of μm or more can be obtained. When a powder magnetic core was produced using the iron powder obtained by the methods described in Patent Documents 1 and 2, the core loss was large, and there was a problem that the core loss was particularly large when driven at a high frequency of 1 MHz or higher. .

The details of the mechanism of action in which such problems occur are not yet clear, but are estimated as follows, for example. According to the knowledge of the present inventors, the raw material powder used when producing a soft magnetic powder such as reduced powder is composed of secondary particles enclosing the necking (connection) between particles. The secondary particles are pulverized by the above-described conventional technique to become primary particles. In the crushing, the soft soft magnetic powder having a low Vickers hardness is likely to be deformed and the resulting coarse particles. Soft magnetic powders with a primary particle size of several tens of μm or more have a relatively large particle weight and a relatively large drop energy. Therefore, when a particle collides with each other using its own weight, such as a V mixer, deformation occurs. It is possible to disintegrate easily.

However, secondary particles formed by agglomeration of primary particles having an average particle size of several μm to sub-micron order have a relatively small particle weight and a relatively small particle drop energy. Crushing at the collision of the used particles is insufficient. Further, in a ball mill using media, since the impact energy of the media is too large, particle deformation and accompanying particle coarsening are inevitable.
For this reason, it can be said that the conventional magnetic material miniaturization method is insufficient.

  As described above, in order to provide a dust core with a small core loss even in a high frequency band, it is necessary to produce a magnetic powder with a fine particle diameter, but at present, it is sufficient to provide this fine magnetic powder. No cracking technology has been found.

  The present invention has been made in view of the above problems, and its object is to provide a soft core that has a small core loss and its frequency dependency and can produce a dust core with a small core loss even when driven at a high frequency of 1 MHz or higher. An object of the present invention is to provide a magnetic powder, a dust core having a small core loss and its frequency dependency, and a magnetic device.

  In order to solve the above-mentioned problems, the present inventors have conducted extensive research. As a result, in the soft magnetic powder of Fe or Fe—Ni alloy, not only the primary particle diameter but also the shape of the primary particles is obtained. It has been found that there is a correlation with the core loss of the magnetic core and its frequency dependence, and the present invention has been completed.

  That is, the soft magnetic powder of the present invention is a soft magnetic powder of Fe or Fe—Ni alloy, and the primary particle diameter of the soft magnetic powder is 0.01 to 5 μm, and the aspect ratio and area ratio of the primary particles. The average value of the products is 1.0 to 4.0.

  Here, in this specification, “primary particles” mean particles that are the smallest unit contained in powder, and “primary particle diameter” means “particles” calculated for 200 randomly selected particles. The average value of “diameter”. The “particle diameter” is a value obtained by measuring the Haywood diameter of the particle cross section, and can be measured, for example, by SEM observation of a particle cross section obtained by embedding particles in a resin and polishing.

On the other hand, particles formed by agglomeration of such primary particles by intermolecular force or the like or connection by gentle necking are referred to as “secondary particles”. In general, since the reduced powder exists in the form of secondary particles, the particle size distribution graph of the reduced powder shows the distribution of secondary particles. Further, the secondary particle diameter means a median diameter in a cumulative distribution on a volume basis, and can be measured using, for example, a laser diffraction dry particle size measuring apparatus.

The “average value of the product of the primary particle aspect ratio and the area ratio” is the average value of the “product of the primary particle aspect ratio and the area ratio” calculated for 200 randomly selected particles. The “product of the primary particle aspect ratio and the area ratio” is a value obtained by multiplying the “aspect ratio” of each particle by the “area ratio”. The “aspect ratio” is a value obtained by measuring the major axis length and minor axis length of a particle cross section and gradually increasing the major axis length by the minor axis length. The “area ratio” is a value obtained by dividing the area value of the particle cross section by the average value of the area values of 200 particles. The major axis length, minor axis length, and cross-sectional area of each particle can be measured, for example, by SEM observation of a particle cross-section obtained by embedding the particles with a resin and polishing

  The inventors of the present invention have measured the characteristics of the dust core produced by using the soft magnetic powder configured as described above. As a result, the core loss when driven at a high frequency of 1 MHz or higher is exceptional as compared with the conventional case. I found it to be smaller. The details of the mechanism of action that produces this effect are not yet clear, but are estimated as follows, for example.

The soft magnetic powder having the above structure has a secondary particle size similar to that of the prior art, but the average product of the aspect ratio and area ratio of the primary particles is in the range of 1.0 to 4.0. And
This indicates that there are few primary particles with large (abnormal) aspect ratio and area. That is, the deformation of the primary particles and the accompanying coarsening of the primary particles are small, and thus the magnetic powder has a small distortion and a small coercive force. For this reason, the dust core produced using this has a sufficiently reduced hysteresis loss as well as an eddy current loss. As a result, the core loss is significantly reduced from the low frequency range to the high frequency range. Conceivable. However, the action is not limited to these.

In general, the aspect ratio is often expressed as an overall average value based on the values of a large number of particles. Particles with a large aspect ratio are thought to have undergone plastic deformation and accompanying particle coarsening, but using this general average aspect ratio reduces the contribution (presence) of coarse particles. It is difficult to detect the presence of coarse particles. However, since the volume ratio (area ratio of the cross section) of the coarsened particles increases with the coarsening, the characteristics of the soft magnetic powder and the characteristics when the soft magnetic powder is used as a dust core are obtained. The effect will be greater. On the other hand, in this case, the “aspect ratio” uses the value of each particle as it is. Further, the “area ratio” of the individual particles is calculated, and the product of the “aspect ratio” and the “area ratio” of each particle is calculated. The average value of the products, that is, the “aspect ratio of the primary particles and the area ratio” is calculated. The “average value of the product” is defined as a parameter for detecting the presence of coarse particles. By defining in this way, it becomes possible to represent the influence of coarse particles that could not be expressed only by a general aspect ratio.

The soft magnetic powder of the present invention preferably has a coercive force of 25 Oe (1989 A / m) or less, more preferably 5 to 25 Oe (398 to 1989 A / m). With the soft magnetic powder, the hysteresis loss is sufficiently reduced, and as a result, the core loss is significantly reduced from the low frequency region to the high frequency region. However, the action is not limited to these.

The soft magnetic powder of the present invention is preferably a reduced powder produced by a reduction method. For example, in the case of a powder produced by the water atomization method, it is relatively easy to produce primary particles of several tens of μm, but it is difficult to produce primary particles of several μm, classification is necessary, and production is difficult. In addition, the cost is high. On the other hand, in the reduction method, it is relatively easy to produce primary particles of several μm or less by adjusting the primary particle diameter of the raw material. With such a method, secondary particles formed by agglomerating primary particles on the order of several μm to sub-micron can be easily and inexpensively manufactured with good reproducibility.

  The soft magnetic powder of the present invention is preferably crushed with a wet medialess atomizer. When it is dry, the soft magnetic powder becomes high temperature due to heat generated during crushing, which may cause sintering, alteration, and characteristic deterioration. If it is wet, since cooling with a solvent can be efficiently performed even if heat is generated during crushing, it is possible to suppress sintering, alteration and deterioration of characteristics of the soft magnetic powder. In addition, when the media is used, the collision energy of the media tends to increase, so that characteristic deterioration due to particle deformation and distortion is likely to occur. In addition, contamination from the media is unavoidable and causes deterioration of the properties of the soft magnetic powder. On the other hand, in the case of medialess, the primary particles are deformed and the secondary particles are effectively crushed (reduced in diameter) without causing deterioration of characteristics due to strain, and contamination from media is mixed. Can be eliminated. Therefore, if it is a crushing method with such an apparatus, it is possible to easily and inexpensively manufacture soft magnetic powder capable of producing a dust core having a sufficiently reduced core loss from a low frequency region to a high frequency region. Become. In addition, productivity and economy are further improved.

  The soft magnetic powder preferably includes surface-treated powder that has been surface-treated so as to include a coating of an insulating layer on at least a part of the surface thereof. As a result, the insulation between the particles is enhanced, the path through which the eddy current flows is blocked, and the eddy current loss is further reduced.

  The soft magnetic powder can be mixed with a resin and / or a lubricant and pressure-molded to obtain a dust core. As a result, the insulation between the particles is enhanced, the path through which the eddy current flows is blocked, and the eddy current loss is further reduced. Further, the moldability is improved and the utility is excellent.

  The soft magnetic powder of the present invention can also be used for magnetic devices such as inductors, generators, reactors, motors, various transformers, antennas, EMI countermeasure parts, magnetic shield materials and the like.

  ADVANTAGE OF THE INVENTION According to this invention, a core loss is fully reduced from a low frequency area | region to a high frequency area | region, the dust core which can respond also to the high frequency of 1 MHz or more, and the soft magnetic powder which can produce this easily are provided. The In addition, since the drive frequency can be increased, the inductor and the like can be reduced in size.

It is a schematic diagram which shows notionally the aggregation state of the secondary particle and primary particle of the surface treatment reduction iron powder of this embodiment. It is a flowchart which shows the manufacturing method of the soft magnetic powder of this embodiment, or surface treatment powder, and the manufacturing method of a powder magnetic core.

  Embodiments of the present invention will be described below. In addition, the following embodiment is an illustration for demonstrating this invention, and this invention is not limited only to the embodiment. In the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. Further, the positional relationship such as up, down, left and right is based on the positional relationship shown in the drawings unless otherwise specified. Further, the dimensional ratios in the drawings are not limited to the illustrated ratios.

FIG. 1 is a schematic view conceptually showing the aggregation state of secondary particles and primary particles of the soft magnetic powder of this embodiment.
The soft magnetic powder 100 is Fe powder or Fe—Ni alloy powder , and has a primary particle diameter of 0.01 to 5 μm, preferably 0.01 to 3 μm, more preferably 0.01 to 2 μm. Have secondary particles 12 having an average particle diameter of 1 to 15 μm, preferably 1 to 10 μm, more preferably 1 to 5 μm. The soft magnetic powder 100 is preferably obtained by crushing with a wet medialess atomizer. Further, the soft magnetic powder 100 is preferably a reduced powder produced by a reduction method. It is preferable that at least a part of the surface of the primary particle 11 is covered with the insulating layer 13. As shown in the figure, the secondary particles 12 have a spongy structure by aggregating or connecting a plurality of primary particles 11. Hereinafter, the manufacturing method of the soft magnetic powder 100 of this embodiment and the manufacturing method of the dust core will be described, and the soft magnetic powder 100 of this embodiment will be described in detail.

FIG. 2 is a flowchart showing a method of manufacturing the soft magnetic powder and the dust core of the present embodiment.
The soft magnetic powder of this embodiment is manufactured through a step (S1) of producing a secondary particle powder formed by agglomerating primary particles and a step (S2) of crushing the secondary particle powder. can do. The soft magnetic powder of the present embodiment may include surface-treated powder in which at least a part of the surface of the soft magnetic powder is covered with an insulating layer as necessary. Furthermore, an insulating resin and / or a lubricant may be included. In such a case, following the steps of S1 and S2, the step of surface treatment (S3a) and / or the step of adding an insulating resin and / or the step of adding a lubricant (S3b) are performed. After that, it can be manufactured.
Moreover, the powder magnetic core of the present embodiment can be manufactured by subjecting the surface-treated powder (soft magnetic powder S3) obtained as described above to a pressure treatment and then a heat treatment process (S4-S5). .

  In the step (S1) of producing secondary particle powder formed by agglomerating primary particles, secondary particle powder containing primary particles having an average particle diameter of 0.01 to 5 μm is produced. In this embodiment, the Fe powder containing primary particles having an average particle diameter of 0.01 to 5 μm or the Fe—Ni alloy powder is a dust core in which the core loss is sufficiently reduced from the low frequency region to the high frequency region. In order to obtain, it is preferable that it was manufactured by the reduction method.

  A well-known thing can be used as iron oxide used as the raw material of reduced iron Fe powder. Specific examples thereof include iron oxides (including iron hydrated oxides) such as hematite, maghematite, magnetite, wustite, beltlite, goethite, akaganite and lepidocrotite, but are not particularly limited to these. Not. Each of these can be used alone or in combination of two or more. Among these, since hematite produced by recovering from the acid used for the pickling treatment in the pretreatment of the rolling process of the steel sheet can be easily obtained at a low cost, iron oxide as a raw material for reduced iron Fe powder As preferred.

  The iron oxide used as a raw material for the reduced Fe—Ni alloy powder is the same as that for the reduced Fe powder. Known nickel oxide can be used. Specific examples thereof include nickel (II) oxide and nickel (III) oxide. Among these, nickel (II) oxide is preferable as the nickel oxide that is a raw material for the reduced Fe—Ni alloy powder.

  Powdered iron oxide and nickel oxide used as raw materials for reduced Fe powder or reduced Fe—Ni alloy powder are used. The particle size of the primary particles is preferably smaller than the particle size of the primary particles of the desired surface-treated reduced powder. In the production of reduced Fe powder or reduced Fe-Ni alloy powder by the reduction method, the primary particle size can be increased by appropriately setting the reduction conditions, but the iron oxide powder having a large particle size, or It tends to be difficult to obtain a reduced powder having a small particle diameter from a mixture of iron oxide and nickel oxide.

The step of reducing iron oxide or a mixture of iron oxide and nickel oxide (S1a) may be performed based on known conditions in the reduction method, and is not particularly limited. It can be appropriately set according to the performance of the furnace to be used, a reaction method such as a falling type, a fluidized bed type, a rotary type or a fixed bed type, a processing amount of iron oxide and the like. Generally, in a fixed or rotary furnace, about 20 to 100 g of iron oxide is reduced at a reducing temperature of about 200 to 650 ° C. for about 1 to 6 hours in a reducing gas atmosphere having a low oxygen concentration. Process. Usually, when the oxygen partial pressure exceeds 10%, the oxidation proceeds rapidly and is oxidized to the inside of the particles, and the reduction does not tend to proceed sufficiently. On the other hand, if the reduction temperature is less than 200 ° C., the treatment time becomes long and the reduction does not proceed sufficiently. On the other hand, if the reduction temperature exceeds 700 ° C., sintering tends to occur and the particle size tends to increase. Therefore, a preferable reduction temperature is 400 to 650 ° C. Examples of the reducing gas include CO, H ₂ S, SO ₂ , and H _2. Among these, H ₂ is preferable.

  The step of slowly and slowly oxidizing the surface of the Fe powder obtained by the reduction treatment may be performed based on known conditions in the reduction method, and performs mild surface oxidation to such an extent that the oxidation does not proceed to the inside of the Fe powder. As long as it is not particularly limited. The treatment temperature, treatment time, oxygen concentration, etc. can be appropriately set according to the treatment amount of iron oxide and the like. Generally, in a furnace, about 20 to 100 g of iron oxide is treated in an oxygen-containing atmosphere with an oxygen partial pressure of about 1 to 5% at a temperature of about 20 to 100 ° C. for about 5 minutes to 1 hour. I do.

  As an example of preferable processing conditions in the present embodiment, iron oxide powder as a raw material is charged into a fixed or rotary furnace, and dried hydrogen gas is introduced at a temperature of about 500 to 600 ° C. for about 3 to 5 hours. After reducing to room temperature, the temperature is kept at about 30 to 80 ° C. for about 5 to 30 minutes in an inert gas atmosphere with an oxygen partial pressure of about 1 to 3%, and then a gradual oxidation treatment is performed. A method is mentioned.

  Next, the reduced powder containing primary particles having an average particle diameter of 0.01 to 5 μm manufactured by the reduction method thus obtained is crushed (S2). Thereby, the soft magnetic powder of this embodiment can be obtained (S3).

The pulverization treatment is preferably performed with a wet medialess atomization apparatus in which a solvent is added to the reduced powder. Since the primary particles are coated with the added solvent, the secondary particles can be prevented from re-forming due to the re-aggregation of the primary particles, so that the crushing can be performed with high efficiency and the reduction powder can be prevented from being oxidized by the atmosphere. it can. Examples of the solvent that can be used include aqueous solutions such as acids and alkalis, mineral oils, synthetic oils, vegetable oils, and other organic solvents, and organic solvents such as acetone and alcohols, but are not particularly limited thereto. These can be used individually by 1 type and can be used in combination of 2 or more type.
The crushing process is preferably performed with a medialess atomizer. By making it medialess, plastic deformation of particles and accompanying particle coarsening can be prevented. Furthermore, contamination from media can be prevented.
Available wet medialess atomizers include ultrasonic homogenizer, high pressure homogenizer (wet cavitation mill), colloid mill, wet jet mill, wet atomizer using high pressure, wet atomizer using sonic air jet. However, it is not particularly limited to these. By the above method, the aggregation of the primary particles is released, and as a result, a reduced powder in which the average particle diameter of the secondary particles is reduced to 1 to 15 μm or less can be obtained.

  The pulverization treatment is preferably performed in an inert gas atmosphere such as nitrogen having an oxygen concentration of 500 ppm or less in order to prevent the reduced powder from being oxidized by the atmosphere.

  The surface treatment is not particularly limited as long as it is an insulating layer that imparts insulation to the surface of the soft magnetic powder. Specific examples of the insulating layer include inorganic compounds such as iron phosphate, iron borate, iron sulfate, iron nitrate, iron acetate, iron carbonate, silica, titania, zirconia, magnesia, alumina, chromium oxide, and zinc oxide. Can be mentioned. These can be used alone or in combination of two or more. From the viewpoint of heat resistance, preferable insulating layers are iron phosphate, silica, titania, zirconia, magnesia, alumina, chromium oxide, zinc oxide, and the like, and more preferably iron phosphate. Iron phosphate formed by phosphoric acid treatment or the like does not have ferromagnetism, and thus has a small magnetic adverse effect. Further, since it is stable as a compound, it can be expected to have an antirust effect.

  The soft magnetic powder of this embodiment may contain an insulating resin. By coating part or all of the surface of the soft magnetic powder with an insulating resin, it is possible to improve the insulation between the particles and to improve the moldability at the time of molding the dust core. The insulating resin is appropriately selected according to the required characteristics. Specific examples thereof include various organic polymer resins such as silicone resin, phenol resin, acrylic resin, and epoxy resin, but are not particularly limited thereto. These can be used individually by 1 type and can be used in combination of 2 or more type. Moreover, you may contain a well-known hardening | curing agent and a crosslinking agent as needed.

  The mixing of the soft magnetic powder with the insulating resin or the like is preferably performed using a stirrer / mixer such as a pressure kneader or a ball mill. Preferably, the coated surface-treated powder is easily obtained from the insulating resin by mixing at room temperature for 20 to 60 minutes. In particular, for the purpose of improving wettability, it is preferable to perform mixing in the presence of the organic solvent described above. Specifically, preferably by mixing at room temperature for 20 to 60 minutes, the resulting mixture is preferably dried at about 50 to 100 ° C. for 10 minutes to 10 hours, and then the organic solvent is volatilized or removed, A soft magnetic powder coated with an insulating resin is obtained.

  The blending amount of the insulating resin is not particularly limited, but an increase in the insulating resin, which is a non-magnetic component, causes a decrease in inductance when used as a dust core. It is preferable that it is 0.1-5 mass%.

  The soft magnetic powder of this embodiment may contain a lubricant. By adhering to a part or all of the surface of the soft magnetic powder, the lubricity between the particles and between the mold and the particles is improved, and the moldability during molding of the dust core is improved. The lubricant is appropriately selected as necessary. Specific examples thereof include, but are not particularly limited to, metal soaps such as lithium stearate, zinc stearate, aluminum stearate, calcium stearate, copper stearate, and zinc oleate. These can be used individually by 1 type and can be used in combination of 2 or more type.

In mixing the soft magnetic powder and the lubricant, it is preferable to knead the mixture in order to distribute the added lubricant uniformly to the raw material powder. The kneading may be performed by a known method, and is not particularly limited. However, a mixer (for example, an attawriter, a vibration mill, a ball mill, a V mixer, etc.) or a granulator (for example, a fluid granulator, a rolling granulator, etc. Etc.) is preferable.

  The blending amount of the lubricant is not particularly limited, but an increase in the lubricant that is a non-magnetic component can cause a decrease in inductance when used as a dust core. It is preferable that it is 0.02-1 mass%.

The surface-treated powder of the present embodiment may contain known additives such as inorganic materials such as SiO ₂ and Al ₂ O ₃ , lubricants, molding aids, and the like as necessary.

  The powder magnetic core of the present embodiment can be manufactured by subjecting the soft magnetic powder of the present embodiment to pressure forming and then heat treatment (S4-S5). The dust core of the present embodiment can be manufactured by a known manufacturing method by using the soft magnetic powder of the present embodiment as the core material.

  In the pressure molding step, the surface-treated powder is filled in a molding die of a press machine, and then the surface-treated powder is pressurized and subjected to compression molding to obtain a molded body. The molding conditions in this compression molding are not particularly limited, and are appropriately set according to the bulk density and viscosity of the surface-treated powder, the desired shape, size and density of the dust core. For example, the molding pressure is usually about 392 to 1177 MPa, preferably about 588 to 785 MPa, and the time for maintaining the maximum pressure is about 0.1 second to 1 minute.

  In the heat treatment step, the molded body obtained as described above is held, for example, at a temperature of 150 to 300 ° C. for about 15 to 120 minutes. Thereby, the resin as the insulator in the molded body is cured, and a dust core (powder) is obtained.

  In addition, you may pass through the rust prevention process process which performs a rust prevention process to a dust core after a heat treatment process as needed. The rust prevention treatment may be performed according to a known method, for example, by spray coating an epoxy resin or the like. The film thickness by spray coating is usually about several tens of μm. It is desirable to perform heat treatment after the rust prevention treatment.

  The preferred embodiment of the present invention has been described above, but the present invention is not limited to the above embodiment. The present invention can be variously modified without departing from the gist thereof.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples.

In addition, the measuring method of the various performance in an Example and a comparative example is as follows.
<Vickers hardness>
According to the method of JISZ2244, it was measured with a micro hardness meter (manufactured by Shimadzu Corporation).

<Aspect ratio and area ratio>
Using a scanning electron microscope (SEM), the cross section of the soft magnetic powder embedded in the resin was observed, and the aspect ratio and area ratio of 200 randomly selected particles were measured.

<Primary particle size>
Using a scanning electron microscope (SEM), the cross-section of the soft magnetic powder embedded in the resin was observed, the Haywood diameter was measured for 200 randomly selected particles, and the number average particle diameter was defined as the primary particle diameter. .

<Secondary particle size>
The secondary particle size (D50% particle size) of the soft magnetic powder was measured using a laser diffraction dry particle size measuring device (HELOS system, manufactured by Sympatec).

<Coercivity>
20 mg of soft magnetic powder was put in a non-magnetic case and hardened with paraffin, and a magnetic field of 1850 Oe (147.2 kA / m) was applied to the soft magnetic powder using an Hc meter (K-HC1000, manufactured by Tohoku Special Steel) The coercivity was measured.

<Core loss of dust core>
The core loss (magnetic core loss: Pcv) of the dust core was measured under the measurement conditions: applied magnetic field Bm = 10 mT, f = 1 MHz, and f = 3 MHz using a BH analyzer (SY-8218, manufactured by Iwatori). .

<Ratio of 1 MHz core loss to 3 MHz core loss (frequency dependence of core loss)>
The calculation was performed by dividing the 3 MHz core loss by the 1 MHz core loss. This evaluation of the frequency dependence of the core loss indicates the degree of increase in the core loss with respect to the frequency rise, and the larger the value, the larger the core loss at high frequency, meaning that it is not suitable for use in high frequency applications. To do.

(Comparative Example 1)
First, hematite (CSR-900, manufactured by Chemilite Co., Ltd.) was used as a raw material powder, and after filling this into a stainless steel container, the stainless steel container was charged into a box-type batch furnace. Next, after exhausting the air in the system with a vacuum pump, hydrogen gas was introduced at a flow rate of 1 L / min to replace the inside of the furnace with a hydrogen atmosphere of positive pressure (1 atm or more), and a temperature of 500 ° C. Heat treatment for hours was performed. After cooling, the hydrogen gas in the furnace was exhausted at 100 ° C. or lower, and then argon gas and air were introduced, and the atmosphere in the furnace was replaced with an atmosphere having an oxygen partial pressure of 2%. Hold for 15 minutes at temperature to effect gentle surface oxidation. Thereafter, the stainless steel container in the furnace was taken out to obtain reduced iron Fe powder.
5 g of this reduced Fe powder is put into a 250 ml polybin (polypropylene bottle), 50 g of steel balls (Φ3.2 mm, 0.16 g / pc) and 20 g of an organic solvent are added, and then placed in a uniaxial ball mill under an Air atmosphere. For 6 hours. Thereafter, the reduced Fe powder after the pulverization treatment is taken out, the steel balls are separated with a sieve having a mesh opening of 2 mm, and further heated to vaporize the organic solvent and dried. Finished).

(Comparative Example 2)
A reduced Fe powder was obtained by performing the same reduction treatment as in Comparative Example 1 except that the heat treatment was performed at a temperature of 600 ° C. for 5 hours. The reduced Fe powder was subjected to the same pulverization treatment as in Comparative Example 1 to obtain the reduced Fe powder of Comparative Example 2 (after the pulverization treatment).

(Comparative Example 3)
A reduced Fe—Ni alloy powder was obtained by carrying out the same reduction treatment as in Comparative Example 1 except that raw material powder in which iron oxide and nickel oxide were mixed at a mass ratio of 100: 74 was used. The reduced Fe—Ni alloy powder was crushed in the same manner as in Comparative Example 1 to obtain a reduced Fe—Ni alloy powder (compared with pulverized treatment) in Comparative Example 3.

(Comparative Example 4)
A reduced Fe—Ni alloy powder was obtained by performing the same reduction treatment as in Comparative Example 2 except that raw material powder in which iron oxide and nickel oxide were mixed at a mass ratio of 100: 74 was used. The reduced Fe—Ni alloy powder was subjected to the same pulverization treatment as in Comparative Example 1 to obtain the reduced Fe—Ni alloy powder (compared with pulverization treatment) of Comparative Example 4.

(Comparative Example 5)
After melting the molten metal made of pure iron, the molten metal is made to flow down from the nozzle, and the soft magnetic powder made of water atomized powder is manufactured by spraying water toward the molten metal flow, and the particle size is adjusted by classification. The water atomized Fe powder was obtained. This water atomized Fe powder was subjected to the same crushing treatment as in Comparative Example 1 to obtain a water atomized Fe powder (compared with crushing treatment) of Comparative Example 5.

Example 1
The same reduction treatment as in Comparative Example 1 was performed to obtain reduced Fe powder. A slurry was prepared by adding an organic solvent to the reduced Fe powder, and pulverized with a high-pressure homogenizer using a known method. Thereafter, the obtained slurry was heated in a nitrogen atmosphere, and the organic solvent was evaporated and dried to obtain reduced Fe powder of Example 1 (disintegrated).

(Example 2)
The same reduction treatment as in Comparative Example 2 was performed to obtain reduced Fe powder. This reduced Fe powder was crushed in the same manner as in Example 1 to obtain reduced Fe powder in Example 2 (crushed).

(Example 3)
The reduction process similar to the comparative example 3 was performed, and the reduced Fe-Ni alloy powder was obtained. This reduced Fe—Ni alloy powder was crushed in the same manner as in Example 1 to obtain reduced Fe—Ni alloy powder in Example 3 (having been crushed).

Example 4
The reduction process similar to the comparative example 4 was performed, and the reduced Fe-Ni alloy powder was obtained. This reduced Fe—Ni alloy powder was crushed in the same manner as in Example 1 to obtain reduced Fe—Ni alloy powder in Example 4 (pulverized).

(Example 5)
The water atomization process similar to the comparative example 5 was performed, and water atomized Fe powder was obtained. This water atomized iron Fe powder was crushed in the same manner as in Example 1 to obtain the water atomized iron Fe powder of Example 5 (disintegrated).

Table 1 shows the powder evaluation and magnetic properties of the soft magnetic powders of Examples 1 to 5 and Comparative Examples 1 to 5.

As is apparent from Table 1, it was confirmed that the soft magnetic powders of Comparative Examples 1 to 5 had a large coercive force. This is because the product of the aspect ratio and the area ratio is large, and it can be said that the coercive force is increased due to distortion caused by plastic deformation. On the other hand, in the soft magnetic powders of Examples 1 to 5, since the product of the aspect ratio and the area ratio is small and the plastic deformation of the particles is small, it is confirmed that the coercive force is as small as 25 Oe (1989 A / m) or less. It was. The dust core produced using this soft magnetic powder was confirmed to be suitable for high-frequency driving in the MHz band, and it was confirmed that the object of the present invention could be achieved.

(Comparative Example 6)
The reduced Fe powder of Comparative Example 1 was mixed with an organic solvent and 1.00% by mass of phosphoric acid with respect to the reduced iron Fe powder, and then dried to obtain reduced Fe powder (surface treated).
An epoxy resin (N-695, manufactured by Dainippon Ink Co., Ltd.) and a curing agent were mixed, and the mixture was dissolved in an organic solvent to prepare a liquid composition. Next, both the reduced Fe powder (surface-treated) and the liquid composition weighed to be 3.0% by mass with respect to the reduced Fe powder (surface-treated) are put into a polybin, The mixture was thoroughly stirred and mixed while rotating on a gantry. Thereafter, the stirred mixture was taken out into a beaker and heated to evaporate the organic solvent and dry to obtain granular reduced Fe powder.
To the obtained granular reduced Fe powder, 0.3% by mass of zinc stearate is added as a lubricant, and the mixture is put into a mixer (V mixer, manufactured by Tsutsui Rika Kikai Co., Ltd.) for 10 minutes at a rotational speed of 12 rpm. Kneaded.
The obtained mixture (kneaded material) was filled into a toroidal mold having an outer diameter of 11.0 mm, an inner diameter of 6.5 mm, and a thickness of 3.0 mm, and pressure-molded at a molding pressure of 588 MPa, A molded body was obtained. Then, the obtained toroidal molded object was hold | maintained at 180 degreeC for 1 hour in the thermostat, and the dust core of the comparative example 6 was obtained.

(Comparative Examples 7 to 10)
Except for using the reduced Fe powder, reduced Fe—Ni alloy powder and water atomized Fe powder obtained in Comparative Examples 2 to 5, the same operation as in Comparative Example 6 was performed.
The dust cores of Comparative Examples 7 to 10 were obtained.

(Examples 6 to 10)
Except using the reduced iron Fe powder, reduced Fe-Ni alloy powder, and water atomized Fe powder obtained in Examples 1 to 5, the same operation as in Comparative Example 6 was performed, and the dust magnets of Examples 6 to 10 were used. I got a wick.

Table 2 shows the performance evaluation of the dust cores of Examples 6 to 10 and Comparative Examples 6 to 10.

As is clear from Table 2, it was confirmed that the dust cores of Comparative Examples 6 to 10 had a very large core loss at driving frequencies of 1 MHz and 3 MHz and were not practically usable. On the other hand, the dust cores of Examples 6 to 10 have a core loss at 1 MHz of 170 kW / m ³ or less and a core loss at 3 MHz of 700 kW / m ³ or less, and are suitable for high-frequency driving in the MHz band. It was confirmed that the core loss and its frequency dependence were excellent.

  As described above, the soft magnetic powder, the dust core, and the magnetic device of the present invention can cope with a high frequency of 1 MHz or more by significantly reducing the core loss from the low frequency region to the high frequency region. It is possible to reduce the size of magnetic devices, so it is widely used in inductors, generators, reactors, motors, various transformers, antennas, EMI countermeasure parts, magnetic devices such as magnetic shielding materials, and various equipment, facilities, and systems equipped with them. And can be used effectively.

  11 ... primary particles, 12 ... secondary particles, 13 ... insulating layer, 100 ... soft magnetic powder.

Claims (7)

A soft magnetic powder of Fe or Fe-Ni alloy,
A soft magnetic powder having a primary particle diameter of 0.01 to 5 µm and an average product of an aspect ratio and an area ratio of the primary particles of 1.0 to 4.0. The soft magnetic powder according to claim 1, wherein the soft magnetic powder has a coercive force of 25 Oe or less. The soft magnetic powder according to claim 1 or 2, wherein the soft magnetic powder is a reduced powder produced by a reduction method. The soft magnetic powder according to any one of claims 1 to 3, wherein the soft magnetic powder is obtained by pulverization with a wet medialess atomizer. The soft magnetic powder according to claim 1, wherein at least a part of the surface is covered with an insulating layer. A powder magnetic core obtained by mixing the soft magnetic powder according to any one of claims 1 to 5 with a resin and / or a lubricant and press-molding the mixture. A magnetic device obtained by using the soft magnetic powder according to claim 1.