WO2006006545A1 - Dust core and its manufacturing method - Google Patents

Abstract

A dust core formed by press-forming a magnetic core powder produced by coating magnetic powder containing Fe as a main component with an insulating film. The dust core is characterized in that the magnetic powder contains 1.5 mass% or less of Si, the volume average particle size is 80 to 300 μm, the density ratio is 96% or more, and the dust core is used in an alternating magnetic field of a frequency of 100 to 2,000 Hz. The dust core exhibits a low iron loss and high magnetic flux density equivalent or superior to those of conventionally used magnetic steel sheets when the dust core is used at such a frequency.

Description

 Specification

 Powder magnetic core and manufacturing method thereof

Technical field

 [0 0 0 1]

 The present invention relates to a dust core having low loss and excellent magnetic properties, and a method for producing the same. Background art

 [0 0 0 2]

 There are many products that use electromagnetism around us, such as transformers, motors, generators, speakers, induction heaters, and various types of actuators. Many of these products use an alternating magnetic field, and in order to obtain a large alternating magnetic field efficiently, a magnetic core (soft magnet) is usually provided in the alternating magnetic field.

 [0 0 0 3]

 Due to the nature of such a magnetic core, it is first required that a large magnetic flux density be obtained in an alternating magnetic field. Next, when it is used in an alternating magnetic field, it is required that the high-frequency loss (hereinafter simply referred to as “iron loss”) regardless of the material of the magnetic core is reduced. This iron loss includes eddy current loss, hysteresis loss and residual loss, but the main problems are eddy current loss and hysteresis loss. It is also important that the coercive force is small in order for the magnetic core to follow the alternating magnetic field and quickly reach a high magnetic flux density. By reducing this coercive force, it is possible to improve both (initial) permeability and hysteresis loss.

 [0 0 0 4]

 However, it is not easy to simultaneously achieve high magnetic flux density, low eddy current loss, and low hysteresis loss. In addition to simple iron ingots, eddy current loss and hysteresis loss increase even if a high magnetic flux density is obtained when thin steel sheets are laminated.

 [0 0 0 5]

Recently, it was obtained by pressure molding magnetic powder (magnetic core powder) coated with an insulating film. Dust cores with high magnetic properties and low loss are being developed (Patent Document 1, Patent Document 2). In order to further reduce the iron loss of the dust core, magnetic powders and insulating coatings having various forms and compositions have been developed (Patent Documents 3 to 13).

 [0006]

 [Patent Document 1] Special Table 2000 1 5 04785 Publication

 [Patent Document 2] Japanese Patent Laid-Open No. 2003-97624

 [Patent Document 3] JP 2001-8521 1

 [Patent Document 4] Japanese Patent Laid-Open No. 2003 03 03711

 [Patent Document 5] Japanese Patent No. 2710 1 5 2

 [Patent Document 6] Japanese Patent Application Laid-Open No. 2000-3 0924

 [Patent Document 7] Japanese Patent Laid-Open No. 11-54314

 [Patent Document 8] Japanese Patent Application Laid-Open No. 2002-43113

 [Patent Document 9] Japanese Patent Application Laid-Open No. 2002-1 41213

 [Patent Document 10] Japanese Patent Publication No. 7-1 5 124

 [Patent Document 1 1] Japanese Unexamined Patent Publication No. 2003-272909

 [Patent Document 12] Japanese Patent Application Laid-Open No. 2003-105403

 [Patent Document 13] Japanese Patent Laid-Open No. 2001-102207 Disclosure of Invention

 【Task】

 [0007]

 However, even though there are individual proposals for magnetic powder and insulation coating, when it comes to dust cores used in the low frequency range where the operating frequency range is about several kHz or less, the improvement in overall magnetic properties and iron Until now, there has never been a combination of reducing loss at a high level.

 [0008]

Conventionally, as described in the above Patent Documents 6, 9, 11, 12, 13, etc., the high magnetic flux density of the powder magnetic core is used for reactors used in the high frequency range around 20 to 100 kHz. Most of them were designed to reduce the loss and loss. Such high frequency In order to reduce the iron loss of dust cores used in several regions, it was important to reduce the eddy current loss, which increases in proportion to the square of the frequency.

 [0009]

 On the other hand, in order to reduce the iron loss of the dust core used in the low frequency range, it is important to reduce the hysteresis loss that increases in proportion to the frequency. Even if a conventional dust core developed on the premise of use in a high frequency range is applied to a dust core used in a low frequency range as it is, preferable characteristics cannot be obtained.

 [0010]

 The present invention has been made in view of such circumstances, and on the premise that it is used in a relatively low frequency range, a high magnetic property (high magnetic flux density) and a low loss dust core and its manufacture It aims to provide a method.

 [Means and effects]

 [001 1]

 The present inventor has intensively studied to solve this problem, and as a result of repeated trial and error, the present inventor is suitable for increasing the magnetic flux density and reducing the loss of the dust core used in the low frequency range. The inventors have newly found the particle form and composition of the magnetic powder and have completed the present invention.

 [001 2]

 (Dust core)

 That is, the powder magnetic core of the present invention is a powder magnetic core obtained by pressure-molding a magnetic core powder in which a magnetic powder mainly composed of iron (F e) is coated with an insulating film.

 The magnetic powder contains 1.5% by mass or less of silicon (S i), has a volume average particle size of 80 to 300 μm, and has a powder magnetic core with respect to the true density (p.) Of the magnetic powder. It is characterized by being used in an alternating magnetic field having a density ratio (/.:/.), Which is a ratio of bulk density (P), of 96% or more and a frequency of 100 to 2000 Hz.

 [0013]

The dust core of the present invention has not only excellent magnetic properties but also very low iron loss when used in an alternating magnetic field of a relatively low frequency range of 100 to 2000 Hz. The reason why the dust core of the present invention exhibits such excellent characteristics is not necessarily clear. However, the current situation is considered as follows.

 [0 0 1 4]

 First, the magnetic powder composing the powder magnetic core of the present invention is mainly composed of Fe exhibiting ferromagnetism and has a small content of Si, which is paramagnetic. Furthermore, the density ratio of the dust core is very high, 96% or more. It is considered that by the fusion of both, the dust core of the present invention has developed excellent magnetic properties.

 [0 0 1 5]

 Next, since the magnetic powder constituting the dust core of the present invention has a relatively large particle size, the coercive force of the magnetic powder is reduced. As a result, the hysteresis loss of the dust core can be reduced. For example, when the magnetic powder is atomized powder, the larger the grain size, the larger the crystal grain size, which facilitates the movement of the domain wall when magnetized, further reducing the coercive force and thus reducing the hysteresis loss.

 [0 0 1 6]

 Increasing the particle size of the magnetic powder lowers the volume resistivity (hereinafter simply referred to as “resistivity” as appropriate) and increases eddy current loss. However, since the dust core of the present invention is premised on the use in the low frequency range described above, its influence on the total iron loss is small. That is, according to the dust core of the present invention, by setting the particle size of the magnetic powder within the above-described range, the hysteresis loss is greatly reduced, and as a result, the iron loss is sufficiently reduced as a whole.

 [0 0 1 7]

 (Production method of dust core)

The present invention can be grasped not only as the dust core but also as a manufacturing method thereof. That is, the present invention provides a magnetic core powder in which a magnetic powder having Fe as a main component and having Si of 1.5% by mass or less and having a volume average particle size of 80 to 300 μm is coated with an insulating coating. A powder magnetic core comprising: a filling step of filling a powder into a mold; and a molding step of pressure-molding a powder for a magnetic core in the mold, wherein the above-described dust core of the present invention is obtained. It is good also as a manufacturing method. Brief Description of Drawings Figure 1 is a graph showing the relationship between the particle size of magnetic powder and iron loss.

 Figure 2 is a graph showing the relationship between the particle size of magnetic powder and eddy current loss.

 Fig. 3 is a draft showing the relationship between the crystal grain size of magnetic powder and the coercive force. BEST MODE FOR CARRYING OUT THE INVENTION

 Embodiment

 [0018]

 Next, the present invention will be described in more detail with reference to embodiments. It should be noted that the contents described in this specification, including the following embodiments, are applicable not only to the dust core of the present invention but also to the manufacturing method thereof.

 [0019]

 (1) Magnetic powder

The magnetic powder according to the present invention is composed of a powder containing Fe as a main component and containing 1.5% by mass or less of Si. Si is an element that increases the electrical resistivity of the powder particles. A dust core made of magnetic powder containing Si has a high specific resistance and reduces eddy current loss. However, when the Si content increases, the magnetic properties (magnetic flux density) of the dust core are likely to decrease. Therefore, in the present invention, the Si content in the magnetic powder is suppressed to increase the magnetic flux density of the dust core. Here, in the case of the present invention, even if the Si content in the magnetic powder is reduced, the magnetic powder itself is covered with the insulating coating, so that the eddy current loss of the dust core increases rapidly. There is no. Furthermore, the eddy current loss increases in proportion to the square of the frequency (f) of the alternating magnetic field (f ² ). However, in the case of the dust core of the present invention, the operating frequency range is low, so the eddy current loss itself is In the first place, the ratio of the total iron loss is low.

 [0020]

The Si content in the magnetic powder is 1.5% by mass or less, 1.2% by mass or less, 1.0% by mass or less, 0.8% by mass, or 0.5% by mass with respect to 100% by mass of the entire magnetic powder. % Is preferred. From the viewpoint of enhancing the magnetic properties of the dust core, the magnetic powder is preferably pure iron powder with a purity of 99.5% or more, 99.7% or more, and 99.8% or more. The magnetic powder may be composed of Si, the balance being Fe and inevitable impurities, and may contain a magnetic property improving element or an iron loss reducing element as appropriate. Examples of such elements include aluminum (A 1), nickel (N i), and cobalt (Co).

 [0021]

 The magnetic powder of the present invention comprises particles having a volume average particle size of 80 to 300 μm. This makes it possible to significantly reduce the hysteresis loss while suppressing the eddy current loss of the dust core used in the low frequency range. If the volume average particle size is too small, it is difficult to reduce the hysteresis loss. On the other hand, an excessive volume average particle size is not preferable because the specific resistance value decreases and eddy current loss increases. The lower limit of the volume average particle diameter is preferably 100 μπι, 120 im, and further preferably 150 μπι. The upper limit of the volume average particle diameter is preferably 280 μηι, 250 μπι, or even 200 μπι.

 [0022]

The volume average particle diameter referred to in this specification is an average value (∑ d./N) of volume particle diameters (d.) Obtained for each of a predetermined number (Ν = 100) of the constituent particles. The volume particle size (d.) Is defined as the diameter of a solid sphere with the same mass as the mass per constituent particle (m). D. = (3m / 4πo) ^1/3 . Where p. Is the true density determined from the composition of the magnetic powder.

 [0023]

 The particle shape of the magnetic powder is not particularly limited, but it is preferably composed of flat particles having an average thickness of 20 to 100 m, more preferably 20 to 50 m. This is because, when magnetic powder made of flat particles is used, eddy current generation can be suppressed with respect to the magnetic flux flowing in the longitudinal direction of the flat powder of the dust core, and eddy current loss can be further reduced.

 [0024]

The thickness (h.) Of the flat particle is obtained from the average ((hi + h ₂ ) / 2) of the maximum thickness (h and minimum thickness (ha), and the average thickness is a predetermined number (N = 100) of flat particles It is obtained as the average value (∑h. ノ N) of the thickness (h.) Obtained for each.

 [0025]

The flat particles can be produced, for example, by crushing substantially spherical powder particles by rolling, forging, or the like. When the powder particles having the above volume average particle size are formed into a substantially oval shape with an average thickness of 20 to 100 μm, the two-dimensional average particle size is 80 to 1 500 μηι. It will be about. The two-dimensional average particle diameter is the average value of the major axis (d, i) and minor axis (d, ₂ ) for each of a predetermined number (N) of the constituent particles (d,. = ( d, ι + d ' ₂ ) / 2), and the average value (∑ d' .ZN) for a given number (N). The major axis is the longest diameter of the constituent particles, and the minor axis is the length measured in the direction perpendicular to the major axis direction through the midpoint of the major axis. The measurement surface for the two-dimensional particle diameter is the plane perpendicular to the thickness direction of the flat particles.

 [00 26]

Magnetic powder is flat Hitoshihi surface area obtained by averaging the specific surface area is the surface area per unit mass of constituent particles 5 X 1 0 one ³

In the following, it is preferable that it is 3 X 10 − ³ m ² Z g or less. When the average specific surface area is excessive, the total amount of the insulating coating covering the surface of the constituent particles increases with respect to the film thickness, and the magnetic properties of the dust core are deteriorated. If the total amount of the insulating film is considered constant, the film thickness becomes relatively thin. As a result, the specific resistance of the dust core decreases and eddy current loss increases. In any case, an increase in the average specific surface area is not preferable.

 [00 2 7]

The average specific surface area as used herein is an average value of specific surface areas obtained for a predetermined number (N = 1100) of constituent particles. The specific surface area is determined by (∑ S. ') ZN. _{Here, S 0, = S / (} V · p) = 4 π r (4 π r 3 p / 3) = 3 / (p · r), r: powder radius, p: a powder constant.

 [0 0 28]

 The closer the shape of the constituent particles of the magnetic powder is to a spherical shape, the smaller the surface area per unit mass. An example of such magnetic powder is atomized powder. In particular, water gas atomized powder having a low cooling rate and gas atomized powder are more preferable than water atomized powder having a high cooling rate because particles having a nearly spherical shape can be obtained.

 [00 29]

The magnetic powder preferably has an average crystal grain size of the constituent particles of 50 / m or more, further 200 Xm or more. The larger the crystal grain size of the constituent particles, the easier the movement of the domain wall and the lower the coercive force, making it easier to reduce the hysteresis loss. The average crystal grain size here is an average value of crystal grain sizes obtained for a predetermined number (N = 1100) of constituent particles. is there. The crystal grain size per each constituent particle was obtained from image analysis of all phase observation.

 [0 0 3 0]

 The crystal grain size of the constituent particles of the magnetic powder is larger as the crystal grows easily. Taking atomized powder as an example, water gas atomized powder having a low cooling rate and gas atomized powder are more preferable than water atomized powder having a large cooling rate. In view of both the specific surface area and the crystal grain size described above, it is highly preferred that the magnetic powder is made of gastomized powder.

 [0 0 3 1]

 Even if the magnetic powder is made of gas atomized powder, the magnetic powder is not necessarily in the form at the time of gas atomization. That is, the magnetic powder may be a powder composed of the above-described flat particles obtained by rolling a gas atomized powder. By subjecting the gas atomized powder to rolling or the like, the specific surface area of the constituent particles can be slightly increased compared to the gas atomized powder before the treatment. However, the specific surface area of the constituent particles made of gas atomized powder is much smaller than that of water atomized powder with a distorted particle surface.

 [0 0 3 2]

 Furthermore, considering the case of high-pressure molding of magnetic powder, in addition to the reasons described above, eddy current loss and hysteresis loss can be further reduced by using smooth particles with a surface shape such as gasified powder. Therefore, it is preferable. This is because, when the magnetic powder is pressed, if the surface of the constituent particles is smooth, the aggression between the particles in contact with each other decreases. For example, it is possible to avoid a situation in which a projection or the like of a certain particle pierces another adjacent particle, and the insulating coating formed on the surface of each particle is destroyed. As a result, it is easy to obtain the originally designed specific resistance, and it is easy to reduce the eddy current loss of the dust core.

 [0 0 3 3]

 If the surface of the constituent particles is smooth, it is possible to suppress large strain and stress from being applied only to a part of the constituent particles, so that the increase in coercive force and hysteresis loss due to residual strain and residual stress is reduced. . Such a situation is the same even when the magnetic powder is composed of the above-described flat particles.

[0 0 3 4] An example of the above-described method for producing atomized powder will be described. Gas atomized powder can be obtained by a gas spray atomization method in which gas is sprayed onto a molten metal stream having a predetermined composition to make a atomized powder. Water atomized powder is obtained by a water spray atomization method in which water is sprayed onto the molten metal stream to atomize it.

 [0 0 3 5]

 Of course, a powder other than the atomized powder described above may be used as the magnetic powder. For example, powdered powder obtained by grinding an alloy ingot with a ball mill or the like may be used. When pulverized powder is used, the crystal grain size can be increased by subsequent heat treatment (for example, heat treatment at 800 ° C or higher in an inert atmosphere (N 2 gas, Ar gas, etc.)) However, it is also possible to obtain a powder composed of flat particles having a relatively smooth surface shape by rolling or the like.

 [0 0 3 6]

 (2) Insulation coating

The insulating coating covering the surface of the magnetic powder increases the specific resistance of the dust core and reduces its eddy current loss. The thicker the insulation film, the greater the specific resistance of the dust core. However, if the insulating coating is too thick, the magnetic flux density of the dust core will decrease. From the viewpoint of ensuring the magnetic flux density and specific resistance of the dust core, the film thickness is preferably 10 to 100 nm, more preferably 10 to 50 nm. In terms of the mass ratio, the insulating coating film is preferably 0.1 to 0.3 mass% when the entire powder magnetic core is 10 mass%. Converting this to volume%, the insulating coating is 1 to 3 volume when the entire powder magnetic core is 100 volume%. / ₀ Furthermore, it is preferable that it is 1.5 to 2.5% by volume. Needless to say, it is ideal that the insulating coating is originally formed for each powder particle. However, in fact, of course, there are cases where several particles are solidified and an insulating film is formed around them, and this state is also assumed by the present invention.

 [0 0 3 7]

Insulating coatings include oxide coatings, phosphate coatings, and resin coatings (coating of silicone resin, amide resin, imide resin, phenol resin, etc.). Any of the insulating coatings of the present invention may be used, but an oxide coating or a phosphate coating is preferable in view of heat resistance. [0038]

In addition to the typical S i 0 ₂ coating, the oxide coating includes A 1 ₂ 0 ₃ coating, T i 0 ₂ coating, Z r 0 ₂ , and these complex oxide insulating coatings (F e S i 0 ₃ , F eA l ₂ 0 ₄ , Ni F e ₂ 0 ₄ etc.). When the magnetic powder contains 0.3 to 1.5 mass% of Si, the S i O ₂ coating can also be formed by surface oxidation of the magnetic powder. However, it is preferable to the provision to ensure a predetermined amount of S i O ₂ film on the surface of the magnetic powder, Ru a silicone resin.

 [0039]

Silicone resin is a synthetic resin having a siloxane bond. The silicone resin coating itself functions as an insulating coating. When it is heated to a high temperature (700-900 ° C), it changes to an S i O ₂ coating with excellent heat resistance. The silicone resin is preferably heated after the dust core is formed. By pressurizing heat after molding, in conjunction with the formation of S I_〇 ₂ coating, residual strain or residual stress in the powder compact that has been introduced in the molding (magnetic powder) is removed, low-les coercivity and hysteresis loss This is because a dust core is obtained.

 [0040]

By the way, in order to form the S i O ₂ coating directly and stably on the surface of the magnetic powder, it is better that the magnetic powder contains 0.8 mass% or more of Si. The reason is not clear, but it seems that the silicone resin is easy to chemisorb to Si atoms on the surface of the magnetic powder.

[0041]

On the other hand, when the Si content in the magnetic powder is low (when the magnetic powder is pure iron powder, for example), the sio ₂ coating that directly coats the surface of the magnetic powder has durability (not only aged deterioration) Durability not to be broken during molding) is not always sufficient. Here, the case where the amount of Si is small is specifically the case where the amount of 3 i is 0.8 mass% or less and further 0.5 mass% or less when the entire magnetic powder is 100 mass%.

 [0042]

In order to stably form a silicone resin coating (or Si02 coating) on the surface of the magnetic powder, the present inventor has used a phosphate coating on the surface of the magnetic powder as a base treatment. It was newly found that it is preferable to provide. Therefore, the insulating coating of the present invention has a first insulating layer composed of a phosphate coating and a silicone resin covering the first insulating layer when the Si amount in the magnetic powder is 0.8% or less. Preferably, it is formed of two insulating layers.

 [0 0 4 3]

 The insulating film composed of the first insulating layer and the second insulating layer is very excellent in heat resistance. Even when a powder magnetic core made of magnetic powder coated with this insulating film is annealed at a high temperature of 400 ° C. or higher, 45 ° C. or higher, or even 500 ° C. or higher, the insulating coating exists. Even if it can change its form, it will not be completely destroyed. In other words, the dust core exhibits sufficient specific resistance even after annealing. The heat resistance of such an insulating film is very important even in a dust core used in a relatively low frequency region as in the present invention. Even if the powder core is annealed to remove residual strain and residual stress accumulated inside it, and the hysteresis loss of the powder core is reduced, the insulation coating is greatly destroyed during annealing. If the specific resistance decreases rapidly, the iron loss increases even though it is a dust core used in the low frequency range. Therefore, even in the case of a dust core used in a relatively low frequency region as in the present invention, the higher the heat resistance of the insulating film, the better. If the heat resistance of the insulating coating is high, annealing can be performed at a higher temperature while suppressing a decrease in specific resistance. This is because residual strain and the like accumulated inside the dust core can be more easily removed, and hysteresis loss can be further reduced.

 [0 0 4 4]

Furthermore, the present inventor has newly developed an insulating film having excellent heat resistance, in which oxide particles are combined with the first insulating layer and the second insulating layer. The following combinations of oxide particles can be considered. One is a case where the second insulating layer is formed of a composite insulating layer in which oxide particles are dispersed in the silicone resin. The other is a case where a third insulating layer mainly composed of oxide particles is further provided on the second insulating layer made of the silicone resin coating alone or a composite insulating layer thereof. However, in any case, what is important is not the structure or form of the insulating coating itself, but that the specific resistance of the dust core is stably maintained even after heating, and eddy current loss is suppressed. . Present As a matter of fact, the film thickness of the insulation film covering the surface of magnetic powder around 10 ° ^ m is very thin, around 100 nm, so it is difficult to clearly identify the structure of the insulation film. is there. In addition, when the powder magnetic core immediately after molding is annealed or used in a high-temperature atmosphere, the presence of the insulating coating covering the magnetic powder is expected to change significantly from the initial state. The From this point of view, the structure and form of the insulating film itself is not meaningful, and as a result, an insulating film that can ensure a sufficient specific resistance is sufficient.

 The first insulating layer, second insulating layer, third insulating layer, and oxide particles described above will be described in more detail.

 [0 0 4 5]

 (a) First insulation layer

 The type of the phosphate coating that is the first insulating layer is not limited. For example, as disclosed in Patent Document 1, the first insulating layer may be a phosphate coating formed by bringing a magnetic powder into contact with a predetermined concentration of phosphoric acid to form iron phosphate on the surface of the magnetic powder. Further, an Mg- (F e) —B—P—O-based insulating layer as described in Patent Document 6 may be used.

 [0 0 4 6]

 However, the present inventors have newly developed a phosphate coating that is more excellent in heat resistance, unlike these phosphate coatings. Then, it has been confirmed that when this phosphate coating is used as the first insulating layer, and the second insulating layer and further the third insulating layer are formed thereon, an insulating coating having extremely excellent heat resistance can be obtained. . This first insulating layer has a 6-coordinate ion radius of 0.07 3 nm defined by a first element group consisting of at least phosphorus (P) and oxygen (O) and Shannon (Shannon, R, D). And a second element capable of producing a cation having a valence of 2 or more. This first insulating layer may contain Fe dissolved from the magnetic powder. In addition, a borophosphate coating containing boron (B) (in this specification, such a coating is also included in the “phosphate coating”) is more excellent in heat resistance than a simple phosphate coating.

 [0 0 4 7]

By the way, the first insulating layer in this case is considered to be an amorphous phosphate glass coating. Therefore, network formers (network-forming ions) that make up glass and network modifications The second element should be extracted and selected appropriately according to the Zacca Raisen rule, which is the law for the body (network-modified ions). An amorphous glass-like insulating layer composed of a network forming body consisting of the first element group and a network modification body, which is the second element having a large ionic radius, is difficult to crystallize, increases in viscosity, and burns. Condensation is less likely to occur. The reason why the cation of the second element is divalent or higher is that monovalent cations (eg, Na ⁺ , K ⁺ ) are easy to react with water, and it is preferable that they do not exist in consideration of long-term stability. It is. The reason why Shannon's ionic radius is used as the ionic radius of the second element is that it is currently most widely used. Among them, the 6-coordinate ion radius was chosen because the ion radius differs depending on the coordination number, so that the comparison object is clear. The present inventor examined various elements and found that when the ion radius of the second element was 0.073 nm or more, the coating exhibited excellent heat resistance. Conversely, if the ionic radius is less than 0.073 nm, the heat resistance is at a conventional level, and the heat resistance cannot be improved. The ion radius is preferably 0.075 nm or more, and more preferably 0.08 nm or more. In addition, the upper limit of the ion radius is preferably 0.170 nm or less in consideration of handling properties.

 [0048]

Specific examples of such a second element include alkaline earth metal elements and rare earth elements (RE). Alkaline earth metal elements include beryllium (B e), Mg, C a, S r, barium (B a), and radium (R a), but Be eop Mg is 6-coordinated Is excluded because the ionic radius of is less than 0.073 nm. Considering handling, safety, environmental friendliness, etc., Ca or Sr is preferable as the second element from the alkaline earth metal element. In addition, the rare earth elements include scandium (Sc), Y, lanthanide elements, and lactide elements. Similarly, in consideration of handling properties, soot is preferable. Other elements that can be the second element include lanthanoids (La to Lu) and bismuth (Bi). Table 6 shows the ionic radii of each of these elements together with their valences. Needless to say, these second elements may be not only one kind of element but also plural kinds of elements. Thus, an insulating film (first insulating layer) excellent in heat resistance constituting the first layer of the present invention was obtained. [0 0 4 9]

 (b) Second insulating layer

 The second insulating layer is formed on the first insulating layer and is made of silicone resin. Due to the presence of the second insulating layer, the insulating coating of the present invention exhibiting higher heat resistance than the first insulating layer alone was obtained. Although the detailed mechanism for realizing this excellent effect is unknown at present, the heat resistance is not improved by mere duplication of the insulating layer, but the insulation is achieved by the synergistic effect of the first insulating layer and the second insulating layer. It is thought that the heat resistance of the coating was further improved.

 [0 0 5 0]

 The silicone resin is preferably contained in a proportion of from 0.05 to 0.8 mass%, more preferably from 0.1 to 0.3 mass%, based on 100 mass% of the entire magnetic powder. This is because if the silicone resin is too small, the effect of improving the heat resistance of the insulating coating is small, and if the silicone resin is excessive, the magnetic flux density of the dust core is reduced, which is not preferable. The amount of the silicone resin is almost the same even in the case of containing the oxide particles to be described later, but the ratio may be slightly changed depending on the presence or absence of the oxide particles.

 [0 0 5 1]

 Silicone resin is a polyorganosiloxane containing monofunctional (M units), bifunctional (D units), 3 functional (T units), or tetrafunctional (Q units) siloxane units in the molecule. Sure. This silicone resin is characterized by a higher crosslink density than silicone oil and silicone rubber, and is hard when cured. Silicone resins are roughly classified into straight silicone resins whose components are composed solely of silicones, and silicone-modified organic resins that are copolymers of silicone components and organic resins. Either is fine.

 [0 0 5 2]

 Straight silicone resins can be broadly classified into MQ resin and DT resin, and either can be used. Examples of the silicone-modified organic resin include alkyd modification, epoxy modification, polyester modification, acrylic modification, and phenol modification.

[0 0 5 3] There are two types of silicone resins: a type that cures by heating (heat curing type) and a type that cures even at room temperature (room temperature curing type). The curing mechanisms of heat-curing silicone resins can be broadly divided into dehydration condensation reaction, addition reaction, peroxide reaction, etc. The curing mechanisms of room temperature-curing silicone resin are deoximation reaction, dealcoholization. Some are due to reactions. Any silicone resin may be used in the present invention.

 [0 0 5 4]

 Specific examples of such silicone resins include, for example, SH 805, SH 806A, SH 840, SH 997, SR 620, SR 2306, SR 2309, SR 2310, SR 2316, DC12577, manufactured by Toray Dow Co., Ltd. SR2400, SR2402, SR2404, SR2405, SR2406, SR2410, SR2411, SR2416, SR2420, SR2107, SR2115, SR2145, SH6018, DC-2230, DC3037, QP8-5314, etc. Also, manufactured by Shin-Etsu Chemical Co., Ltd., KR251, KR255, KR 114A, KR112, KR2610B, KR2621-1, KR230B, KR220, KR285, K295, KR2019, KR27 06, KR165, KR166, KR169, KR2038, KR221, KR155 , KR240, KR101-10, KR120, K R105, KR271, KR282, KR311, KR211, KR212, KR216, KR213, KR217, KR9218, SA-4, KR206, ES1001N, ES1002T, ES1004, KR9706, KR5203, KR5221, etc. . Of course, silicone resins other than these brands may be used.

 [0 0 5 5]

 The silicone resin used in the present invention may be a finely divided silicone resin dispersed in a solvent to form a colloidal shape, or may be a silicone resin obtained by modifying the raw material. Furthermore, a silicone resin in which two or more types of silicone resins having different types, molecular weights, and functional groups are mixed at an appropriate ratio may be used.

 [0 0 5 6]

 By the way, in the case of the second insulating layer in which oxide particles are dispersed in such a silicone resin, as described above, the heat resistance of the insulating coating is further improved. The reason for this is not always clear, but at present it can be considered as follows.

 [0 0 5 7]

The present inventors have variously experiments, silicone resin solution into fine oxide particles (S I_〇 ₂₎ was添Ka卩treatment liquid, the fluidity becomes higher than the silicone resin solution alone . By using the treatment liquid to which the oxide particles were added, the second insulating layer was easily formed on the surface of the magnetic powder on which the first insulating layer was formed. This is considered to have contributed to the uniformity of the second insulating layer formed on the first insulating layer, and consequently the uniformity of the insulating film. Here, the uniformity of the insulation coating is necessary because, for example, if the coating state by the insulation coating is non-uniform, for example, a thin part is attacked preferentially, and particles of magnetic powder are This is because the specific resistance value of the powder magnetic core decreases due to direct contact of the powder and further sintering.

 [0058]

 Oxide particles are extremely excellent in heat resistance (high temperature insulation). The oxide particles are present uniformly on the surface of the magnetic powder, and the direct contact between these particles is positively suppressed, and the heat resistance of the insulating coating of the present invention is further improved. It is done.

 [0059]

The oxide constituting the oxide particles is not limited as long as it has high insulation and heat resistance. Examples of such oxides include Si 0 ₂ , A 12 O 3, Zr 0 ₂ , Mg ₂ O, composite oxide spinel, and garnet. In consideration of its availability, cost, etc., one or more oxides of Si, Zr, Mg or A 1 are suitable for the oxide particles. The oxide particles may be an oxide obtained by alloying two or more metals. A colloidal oxide may be used.

 [0060]

 The average particle size of the oxide particles is preferably 100 nm or less, more preferably 70 nm or less. On the other hand, considering the manufacturability and availability of oxide particles, the lower limit of the particle size is preferably 50 nm or even 30 nm. In particular, the particle size ratio (dZD) between the volume average particle size (D) of the magnetic powder and the particle size (d) of the oxide particles is lZl 0 ~: ίΖΐ 00000 or even 1 Z100 ~: L / 10000 preferable.

 [0061]

 The mixing ratio of the oxide particles to the silicone resin (oxide particles Z silicone resin) is preferably 0.1 to 10 and more preferably 0.3 to 3 by weight.

[0062] The average particle diameter of the acid particles referred to in the present invention is the number average particle diameter of the fixed direction diameter observed with a microscope.

 [0 0 6 3]

 (c) Third insulation layer

 It is preferable that a third insulating layer mainly composed of the above-described oxide particles is formed on the second insulating layer.

 [0 0 6 4]

 The second insulating layer, which is the lower layer of the third insulating layer, may be an insulating layer made only of a silicone resin, or a composite insulating layer in which oxide particles are dispersed in the silicone resin. In this case, the reason why the heat resistance of the insulating film of the present invention is improved is not necessarily clear, but at present, it is considered to be almost the same as the reason described above.

 As a method of forming the third insulating layer mainly composed of oxide particles on the second insulating layer, mechanical mixing, a method of adding oxide particles to various coating liquids in advance, and the like can be considered.

 [0 0 6 5]

 By the way, when considering the powder for the magnetic core, regardless of whether the oxide particles are mixed in the second insulating layer or dispersed on the second insulating layer, the oxide particles comprise 100 mass% of the entire magnetic powder. As a content of 0.05 to 0.5% by mass, further 0.08 to 0.3% by mass is preferable. If the amount of oxide particles is too small, the effect of improving the heat resistance of the insulating coating is small. The amount of silicone resin at this time is as described above.

 [0 0 6 6]

 The insulating coating according to the present invention may have the first insulating layer and the second insulating layer described above at the time of coating. Furthermore, from the stage of coating, both layers may be integrated together to form a single insulating film as a whole. In any case, the insulating coating does not necessarily maintain the initial state of the coating. The insulating coating may be one in which the first insulating layer and the second insulating layer are changed, altered or transformed by subsequent heating or the like. The dust core obtained as such a product is also included in the scope of the present invention.

[0 0 6 7] Note that the above-described insulating coating is not premised on the assumption that it is exposed to a high temperature state by annealing or the like. It may be used in an unheated state or a room temperature range. In that case, needless to say, the insulating coating of the present invention stably exhibits a very high insulating property (high resistance value).

 [0 0 6 8]

 (3) Insulating coating formation method (Magnetic core powder manufacturing method)

The insulating film is formed on the surface of the magnetic powder by an appropriate method according to the type. For example, in the case of a silicone resin coating, it is formed by adding a silicone resin solution to magnetic powder and stirring, kneading, or the like. As a result, a magnetic core powder in which the surface of the magnetic powder is coated with a silicone resin is obtained. In the case of the S i 0 ₂ coating, the magnetic powder coated with the silicone resin is formed by heating at a high temperature. In addition, by oxidizing the magnetic powder itself in an appropriate oxidizing atmosphere, an oxide film can be formed on the surface. Such a method for forming an insulating film is conventionally well known. In the following, a method for forming an insulating film composed of the first insulating layer, the second insulating layer, and the third insulating layer will be described.

 [0 0 6 9]

 This method of forming an insulating film (even if considered as a method of manufacturing a magnetic core powder) basically comprises a first insulating layer forming step and a second insulating layer forming step. Of course, when the insulating coating includes the third insulating layer, a third insulating layer forming step of forming the third insulating layer on the second insulating layer of magnetic powder is provided.

 [0 0 7 0]

 (a) First insulating layer formation process

 The first insulating layer forming step includes a contact step in which the first coating treatment liquid is brought into contact with the magnetic powder, and a drying step in which the magnetic powder is subsequently dried.

 [0 0 7 1]

First, the first coating treatment liquid is a solution containing phosphoric acid and the second element referred to in the present invention. This is not limited to an aqueous solution, but may be a solution using an organic solvent such as ethanol, methanol, isopropyl alcohol, acetone, or glycerin. In any case, the first coating solution is prepared by mixing phosphoric acid in these solvents, It dissolves compounds and salts of elements and rare earth elements. Other, magnetic powder (for example,

Surfactant effective for improving wettability with Fe powder and forming a uniform film, and anti-mold agent for preventing oxidation of magnetic powder (eg Fe powder) are added as appropriate. You may do it.

 [0 0 7 2]

 The contact process includes various methods (processes) such as a solution spraying method (spraying process) in which the first coating treatment liquid is sprayed on the material to be treated and a solution immersion method (immersion process) in which the first coating treatment liquid is immersed in the first coating treatment liquid. Can be done. The solution spraying method and the solution dipping method can be processed in large quantities and are industrially effective. In addition to these methods, a thin and uniform insulating film may be formed on the surface of the material to be processed using an electrochemical reaction such as plating. In this case, since the surface of the material to be treated coated with the insulating film is electrically insulated, the uncoated surface part (exposed part) force naturally reacts with the first coating treatment liquid preferentially. . As a result, the surface of the material to be treated (magnetic powder) is sequentially coated, and the entire surface of the material to be treated is uniformly coated without pinholes.

 [0 0 7 3]

 By changing the concentration of the first coating treatment liquid used in this contact step, it is possible to adjust the film thickness of the insulating film to be formed. Increasing the concentration of the first coating treatment liquid

A thick insulating film can be obtained, and a thin insulating film can be obtained when the film is thinned. Of course, a thin insulating film may be formed as a whole by forming thin film thicknesses. The contact time between the material to be treated and the first coating treatment liquid may also affect the film thickness. However, in reality, the reaction time between the two may be short, and once the surface of the material to be treated is covered, the change in film thickness is small even if the contact time is increased.

 [0 0 7 4]

 The drying process is a process of diverging excess first coating treatment liquid and its solvent adhering to the material to be treated. This drying step may be natural drying as well as heat drying. However, in order to stably and quickly fix the insulating film on the surface of the material to be treated, heat drying

(Heat drying step) is preferable. The heating temperature is preferably about 80 to 35 ° C., and the heating time is preferably about 10 to 18 O min. The heating atmosphere may be during vacuum degassing, nitrogen, or air. [0 0 7 5]

 (b) Second insulating layer formation process

 The second insulating layer forming step is a step of forming a second insulating layer made of silicone resin on the first insulating layer of the material to be processed. At this time, in order to form the second insulating layer uniformly, it is preferable to use a second coating treatment liquid in which silicone resin is dissolved or dispersed in a solvent or the like. Examples of such solvents include alcohol solvents such as ethanol and methanol, ketone solvents such as acetone and methyl ethyl ketone, and fragrances such as benzene, toluene, xylene, phenol, and benzoic acid. Family solvents, petroleum solvents such as rigging and kerosene. In particular, an aromatic solvent that easily dissolves the silicone resin is preferable. If the silicone resin is soluble or dispersible, water may be used as a solvent. Treatment liquid in which silicone resin is dissolved in a solvent

The concentration of the (second coating treatment liquid) may be determined in consideration of ease of construction and drying time.

 [0 0 7 6]

 The second insulating layer forming step also includes the contact step of bringing the second coating treatment liquid into contact with the magnetic powder on which the first insulating layer is formed, and the subsequent drying step of drying it. This is the same as the layer forming step. The contents of the contact process and the drying process are almost the same. However, if a volatile solvent (such as ethanol) is used as the solvent for the silicone resin, the solvent will naturally volatilize and the drying process will be substantially completed, without needing to heat dry. Become. In the case where the oxide particles are mixed in the second insulating layer, the oxide particles may be added to the solvent together with the silicone resin and stirred and mixed.

 [0 0 7 7]

 (c) Third insulating layer formation process

 The third insulating layer forming step is a step of forming a third insulating layer made of oxide particles on the second insulating layer of the material to be processed.

 [0 0 7 8]

The third insulating layer forming step also includes the contact step of bringing the third coating treatment liquid into contact with the magnetic powder on which the second insulating layer is formed, and the subsequent drying step of drying it. This is the same as the first insulating layer forming step and the second insulating layer forming step. The contents of the contact process and the drying process can be made almost the same as those cases.

 [0 0 7 9]

 (4) Manufacturing method of dust core

 The method for manufacturing a dust core is basically based on a filling process in which the above-described magnetic core powder is filled in a molding die (simply referred to as “mold”) and a molding process in which the filled magnetic core powder is pressure-molded. Become. This molding process may be performed in a magnetic field or in a non-magnetic field, but in any case, it greatly affects the magnetic properties of the dust core. In particular, the molding pressure greatly affects the increase in the density of the dust core and the accompanying increase in the magnetic flux density of the dust core. However, when the molding pressure is increased, galling is likely to occur between the inner surface of the mold and the magnetic core powder, the release pressure is excessive, and the mold life is extremely reduced. For this reason, in the conventional molding method, it was actually difficult to increase the molding pressure.

 [0 0 8 0]

 The present inventor has established an innovative warm high pressure molding method and has solved these problems. In this warm high-pressure molding method, the filling step is a step of filling a metal mold coated with a higher fatty acid-based lubricant with a magnetic core powder, and the molding step is performed between the magnetic core powder and the inner surface of the mold. This is a warm high pressure forming process in which a metal sarcophagus film is formed.

 [0 0 8 1]

 For example, if the magnetic powder is a powder containing Fe as a main component and the higher fatty acid lubricant is lithium stearate, the outer surface of the powder magnetic core in contact with the inner surface of the mold has lubricity. A metal sarcophagus film composed of excellent iron stearate is formed. Due to the presence of this iron stearate film, no galling or the like occurs, and the dust core is removed from the mold with a very low pressure. In addition, the tool life can be extended.

 [0 0 8 2]

 Next, this manufacturing method will be described in more detail.

 (a) Filling process

During the filling process, it is necessary to apply a higher fatty acid lubricant to the inner surface of the mold (application process). The higher fatty acid lubricant to be applied is preferably a metal salt of a higher fatty acid in addition to the higher fatty acid itself. Examples of higher fatty acid metal salts include lithium salts, calcium salts, and zinc salts. In particular, lithium stearate, calcium stearate, and zinc stearate are preferable. In addition, barium stearate, lithium palmitate, lithium oleate, calcium palmitate, calcium oleate, and the like can also be used.

 [0 0 8 3]

 This coating step is preferably a step of spraying a higher fatty acid-based lubricant dispersed in water or an aqueous solution into a heated mold.

 [0 0 8 4]

 When the higher fatty acid lubricant is dispersed in water or the like, it becomes easy to uniformly spray the higher fatty acid lubricant on the inner surface of the mold. Furthermore, when it is sprayed into the heated mold, the water quickly evaporates, and the higher fatty acid lubricant can be uniformly adhered to the inner surface of the mold. The heating temperature of the mold at that time needs to take into account the temperature of the molding process described later. For example, it is sufficient to heat to 10 ° C. or higher. However, in order to form a uniform film of a higher fatty acid-based lubricant, it is preferable that the heating temperature be lower than the melting point of the higher fatty acid-based lubricant. For example, when lithium stearate is used as the higher fatty acid-based lubricant, the heating temperature should be less than 220 ° C.

 [0 0 8 5]

 When the higher fatty acid-based lubricant is dispersed in water or the like, the higher fatty acid-based lubricant is from 0.1 to 5% by mass, and more preferably from 0. When included in a ratio of 5 to 2% by mass, a uniform lubricating film is preferably formed on the inner surface of the mold.

 [0 0 8 6]

In addition, when a higher fatty acid lubricant is dispersed in water or the like, if a surfactant is added to the water, the higher fatty acid lubricant can be uniformly dispersed. Examples of such surfactants include alkylphenol-based surfactants, polyoxyethylene nonenophenolatenore (EO) 6, polyoxyethylene noninorephenyl etherenole (EO) 10, and cation-based nonionics. Type surfactant, borate ester Emulbon T -80, etc. can be used. Two or more of these may be used in combination. For example, when lithium stearate is used as a higher fatty acid-based lubricant, polyoxyethylene noninorephenolatenore (EO) 6, polyoxyethylene nonenolephenyletherenore (EO) 10 and borate ester emulbon T 1 8 It is preferable to use three types of surfactants at the same time. This is because the dispersion of lithium stearate in water or the like is further activated when it is added in combination as compared with the case where only one of them is added.

 [0 0 8 7]

 In addition, in order to obtain an aqueous solution of a higher fatty acid-based lubricant having a viscosity suitable for spraying, assuming that the entire aqueous solution is 100% by volume, the ratio of the surfactant is 1.5 to 15% by volume. preferable.

 [0 0 8 8]

In addition, a small amount of antifoaming agent (for example, silicon-based antifoaming agent) may be added. This is because when the foaming of the aqueous solution is intense, it is difficult to form a uniform higher fatty acid-based lubricant film on the inner surface of the mold when it is fogged. The defoamer addition ratio is 100 volume of the total volume of the aqueous solution. / ₀ and the when, for example, 0. 1 have good be about 1% by volume.

 The higher fatty acid-based lubricant particles dispersed in water or the like preferably have a maximum particle size of less than 30 μιη.

 [0 0 8 9]

 When the maximum particle size is 30 m or more, the particles of the higher fatty acid lubricant are likely to settle in the aqueous solution, and it becomes difficult to uniformly apply the higher fatty acid lubricant to the inner surface of the mold. .

 Application of the aqueous solution in which the higher fatty acid-based lubricant is dispersed can be performed using, for example, a spray gun for coating or an electrostatic gun.

 [0 0 9 0]

As a result of an experiment conducted by the inventor on the relationship between the application amount of the higher fatty acid-based lubricant and the extraction pressure of the powder compact, it was found that the film thickness was about 0.5 to 1.5 μπι. It has been found that it is preferable to attach a higher fatty acid-based lubricant to the inner surface of the mold. [0 0 9 1]

 (b) Molding process

 Although the details are not clear, it is thought that in this process, the metal sarcophagus film is formed by mechanochemical reaction.

 [0 0 9 2]

 That is, the reaction causes the magnetic core powder (especially the insulating coating) to chemically bond with the higher fatty acid-based lubricant, and the metal sarcophagus coating (for example, the higher fatty acid iron salt coating) forms the magnetic core powder. Formed on the body surface. This metal sarcophagus coating is firmly bonded to the surface of the powder compact and exhibits a lubricating performance far superior to that of higher fatty acid lubricants adhering to the inner surface of the mold. As a result, the frictional force between the contact surface between the inner surface of the mold and the outer surface of the powder compact is remarkably reduced, and high pressure molding is possible.

[0 0 9 3]

 Each particle of the magnetic core powder is coated with an insulating coating, but an element that promotes the formation of a metal sarcophagus coating in the insulating coating (for example, Fe as the main component of the magnetic powder or the first mentioned in the present invention). 2 elements) as the main components, it is considered that a metal salt coating (metal sarcophagus coating) of higher fatty acids is formed based on them.

 [0 0 9 4]

 “Warm” in the molding process means that the molding process is performed under appropriate heating conditions according to each situation. However, in order to promote the reaction between the magnetic core powder and the higher fatty acid-based lubricant, it is generally preferable that the molding temperature is 10 ° C. or higher. Also, in order to prevent the breakdown of the insulating coating and the alteration of the higher fatty acid lubricant, the molding temperature is generally reduced.

It is preferable that the temperature is 200 ° C. or lower. It is more preferable that the molding temperature is 120 to 180 ° C.

 [0 0 9 5]

The degree of "pressurization" in the molding process is also appropriately determined according to the desired properties of the powder magnetic core, the magnetic core powder, the insulation coating, the type of higher fatty acid lubricant, the material of the mold and the internal surface properties, etc. However, when this manufacturing method is used, molding can be performed under high pressure exceeding the conventional molding pressure. For this reason, for example, the molding pressure is 70 OMPa or more, 7 85MPa or higher, lOO OMPa or higher, or 2000MPa. The higher the molding pressure, the higher the density magnetic core. However, in consideration of the life and productivity of the mold, the molding pressure should be 200 OMPa or less, more preferably 150 OMPa or less.

 [0096]

 In addition, the present inventor confirmed by experiments that when this warm high-pressure molding method is used, the extraction pressure becomes maximum when the molding pressure is about 600 MPa, and the extraction pressure decreases rather than that. ing. Even when the molding pressure was changed in the range of 900 to 200 OMPa, the extraction pressure remained at a very low value of about 5 MPa. This also shows how the metal sarcophagus film formed by the warm high pressure forming method, which is one of the production methods of the present invention, is excellent in lubricity. It can be seen that this warm high-pressure forming method is optimal as a method for manufacturing a dust core that requires high density by high-pressure forming. Such a phenomenon can occur not only when lithium stearate is used as the higher fatty acid-based lubricant, but also when calcium stearate or zinc stearate is used.

 [0097]

 (c) Heating process, annealing process

 The method for producing a dust core according to the present invention preferably further includes a heating step or an annealing temperature for heating the powder compact obtained after the molding step. The heating temperature and heating time of the heating process and annealing temperature may be appropriately selected according to the specifications of the powder magnetic core. In this respect, there is no essential difference between the heating process and the annealing temperature, but both have different purposes.

 [0098]

Heating step, when the insulating coating was a silicone resin film, by heating the Tokura powder molded body after the molding step is a step for the silicone resin coating and s io ₂ coating. On the other hand, the annealing process is a process for removing the strain (residual strain) and stress (residual stress) accumulated in the powder compact obtained after the molding process for the purpose of reducing coercive force and hysteresis loss. is there. Of course, the heating process may also serve as the annealing temperature by appropriately selecting the heating temperature, heating time, and heating atmosphere. The degree may also serve as a heating step.

 [0 0 9 9]

 Note that the insulating film having a multilayer structure including the first insulating layer made of the phosphate film and the second insulating layer made of the silicone resin covering the first insulating layer is extremely excellent in heat resistance as described above. It is preferable to perform an annealing step on the powder compact provided with this insulating film, since hysteresis loss is sufficiently reduced while suppressing reduction of eddy current loss. The composition of the magnetic powder on which the insulating coating is formed is not particularly limited, but as described above, it is particularly effective in the case of pure iron powder having an Si content of 0.8% or less.

 [0 1 0 0]

 In the heating and annealing step, it is preferable to heat at 300 to 900 ° C, more preferably 50000 to 700 ° C for 0.:! To 10 hours, and further 0.5 to 2.0 hours. . The atmosphere at this time is preferably an inert atmosphere. Again, by performing such a heating or annealing step, the insulating coating can change at least partially from its original state. However, even the dust core after such a heating step or annealing step is the dust core of the present invention.

[0 1 0 1]

 (5) Powder magnetic core

The dust core of the present invention is a high-density molding of the above-described magnetic core powder. The density ratio ( _P ) is the ratio of the bulk density ( _P ) of the dust core to the true density ( _p .) Of the magnetic powder. / po) is 96% or more. Such a high-density powder magnetic core generates a very high magnetic flux density. This is equivalent to or better than conventional electromagnetic steel sheets used in high performance motors. The higher the density ratio is 97% or more, 98% or more, and 99% or more, it is preferable because a higher magnetic flux density can be obtained. Further, the magnetic powder constituting the dust core of the present invention has a relatively small amount of Si contained. Accordingly, the dust core of the present invention exhibits a higher magnetic flux density than a dust core using a magnetic powder such as general Fe-3% Si.

 [0 1 0 2]

In the present invention, the magnetic properties of the dust core are indirectly indicated by the density ratio. For example, the magnetic density of the dust core is determined by the magnetic flux density when placed in a magnetic field of a specific strength. The characteristics may be specified directly. In addition, although there is magnetic permeability as an index for the magnetic characteristics of the dust core, the magnetic permeability is not constant as can be seen from a general BH curve. The magnetic properties of the dust core are evaluated by the magnetic flux density.

 [0103]

The specific magnetic field may be appropriately selected from 1 to 20 kA / m. For example, 2 k A / m, 5 k AZm, 8 k A / m, 10 k A / m, 16 k A / m, 20 k A / m, and the like. B _2k , B _5k , B _8k , B ₁₀ k, B _16k , B ₂ are the magnetic flux densities that can be generated when the dust core is placed in the magnetic field. The dust core of the present invention can be evaluated by expressing _{k and the} like. In the case of the dust core of the present invention, for example, B ₂ . High magnetic flux density such as _k ≥ l. 7T, 1.8 Τ, 1.9 2. or even 2.0 T, B iok ≥ 1.5 Τ, 1. 6 Τ, 1. 7 Τ or even 1.8 Τ.

 [0104]

 If the saturation magnetization Ms is small, a large magnetic flux density cannot be obtained in a high magnetic field. However, in the dust core of the present invention, for example, the saturation magnetization Ms ≥1.9 T in a magnetic field of 1.6 MAZm 2. Since it is over 0T, a stable high magnetic flux density can be obtained even in a high magnetic field.

 [0105]

 Furthermore, there is a coercive force as an index of the magnetic characteristics of the dust core. The smaller the coercive force, the better the followability of the dust core to the AC magnetic field, and the smaller the hysteresis loss. In the case of the dust core of the present invention, the coercive force b H c can be 150 A / m or less, 130 A / m or less, or even 100 AZm or less. The coercive force b He referred to in this specification is defined as a value measured from a magnetization curve with a maximum magnetic field of 2 kAZm.

 [0106]

 Incidentally, as the amount of Si in the magnetic powder increases, the coercive force of the dust core tends to decrease. From this viewpoint, the Si amount of the magnetic powder according to the present invention is preferably 0.8 to 1.5 mass%.

[0107] Next, the electrical characteristics (ie, specific resistance) of the dust core will be described. The specific resistance is, in principle, an eigenvalue for each dust core that does not depend on the shape. For a dust core having the same shape, the larger the specific resistance, the lower the eddy current loss. The specific resistance varies depending on the type of insulating coating, the amount of insulating coating (film thickness), and the presence or absence of annealing, but the specific resistance is 50 μΩηι or more, Ο Ο Ο μΩηι or more, 300 μΩm or more, and 1000 μ If it is Ω m or more, eddy current loss can be sufficiently reduced.

 [0108]

 Note that the relationship between the specific resistance of the dust core and the magnetic flux density varies depending on the amount of insulation coating on the entire dust core. Specifically, as the amount of insulating film increases, the specific resistance increases and the magnetic flux density decreases. Conversely, as the amount of insulating film decreases, the specific resistance decreases and the magnetic flux density increases. This tendency is basically the same even with an annealed powder magnetic core. By using the above-described insulating film excellent in durability, heat resistance, etc. and reducing the amount of use, a dust core excellent in both magnetic characteristics and electrical characteristics can be obtained.

 [0109]

 The mechanical properties (particularly strength) of the dust core are also important when considering actual use. Unlike a forged product or a sintered product, a dust core is composed only of mechanically bonded constituent particles covered with an insulating film mainly by plastic deformation, and its strength is not high. However, since the density ratio of the dust core of the present invention is as high as 96% or more, it has practically sufficient strength. For example, it has a 4 point bending strength σ of 5 OMPa or higher, or 10 OMPa or higher. This four-point bending strength σ is not specified in JIS, but can be determined by the green compact test method.

 [01 10]

 (6) Application of dust core

The dust core of the present invention can be used for various electromagnetic devices such as motors, actuators, transformers, induction heaters (IH), speakers, and rear tuttles. Among them, it is preferable to be used for an electromagnetic device that operates in a low frequency range of 2000 Hz or less (for example, 100 to 2000 Hz). When used in such a low frequency range, the dust core of the present invention exhibits high magnetic properties while significantly suppressing iron loss. As an electromagnetic device used in such a low frequency range, an electric motor (motor) or power generation There is a machine. That is, the dust core of the present invention is preferably an iron core constituting a field or an armature of an electric motor or a generator. In particular, the dust core of the present invention is suitable for a drive motor that requires low loss and high output (high magnetic flux density). Such a drive motor is used in, for example, a hybrid vehicle or an electric vehicle. An example of the iron loss of the dust core of the present invention will be given. When the dust core of the present invention is used in an alternating magnetic field with an operating frequency of 800 Hz and a magnetic flux density of 1.0 T, the iron loss is as small as 55 W / kg or less, 53 WZkg or less, or 38 W / kg or less. This iron loss is much smaller than the conventional dust core, and is equivalent to or less than the high-performance electrical steel sheet (20 J NEH 1200 (manufactured by JFE Schinole)) used in motors. Of the above iron losses, the hysteresis loss is sufficiently low, 37W / kg or less, 34W / kg or less, and 32W / kg or less. Of course, of the above iron loss, the eddy current loss is 21 W / kg or less, 16 WZkg or less, and further 6 W / kg or less.

 [011 1]

 【Example】

 The present invention will be described more specifically with reference to examples.

 (First example)

 (1) Formation of insulating coating (Manufacture of magnetic core powder)

 As raw material powder (magnetic powder), commercially available with a composition of pure Fe (purity: 99.8%, ABC 100.30 from Heganes), Fe—l% S i and Fe—3 %% Si Atomized powder was prepared. The unit is mass% (hereinafter the same). The brand name and production of each powder are as follows.

 [0112]

 The volume average particle diameter of each powder was pure iron powder 80 m, Fe-1% Si powder 80 μm, and Fe-3% Si powder 80 μm.

 [0113]

 Each of these powders was coated with a silicone resin film (insulating film) as follows.

 [0114]

Commercially available silicone resin (Toray 'Dow Corning' manufactured by Silicone, “SR-2 400 ”) was dissolved in 5 times the organic solvent (toluene) to prepare a coating treatment solution. This coating solution was added to the magnetic powder, mixed and stirred, and then dried at 150 ° C. for 2 hours. Thus, a magnetic powder (magnetic core powder) whose surface was covered with a silicone resin coating was obtained. The coating treatment solution was added so that the amount of the silicone resin was 0.2% by mass with respect to 100% by mass of the magnetic powder. In addition, since the mass% of the silicone resin is very small, the above ratio hardly changes even if the entire coated magnetic core powder (or powder magnetic core) is considered to be 100 mass% (the same applies hereinafter). Incidentally, the silicone resin decomposes when heated to 750 ° C., and forms a SiO ₂ oxide film (insulating film) on the surface of the magnetic powder.

 [01 1 5]

 (2) Manufacturing of dust core

 Applying the die lubrication warm high pressure molding method to each magnetic core powder, ring-shaped (outer diameter: Φ 39 mm x inner diameter φ 3 Omm x thickness 5 mm) and plate-shaped (5 mm x 10 mm x 55 mm) 2 Each type of specimen was made. This ring-shaped specimen is for magnetic property evaluation, and the plate-shaped specimen is for electrical resistance evaluation. No internal lubricant or resin binder was used in molding each specimen (dust core).

 [01 16]

 Specifically, the mold lubrication warm high pressure molding method was performed as follows.

 [01 1 7]

 (a) A cemented carbide mold having a cavity corresponding to each test piece shape was prepared. This mold was preheated to 150 ° C. with a band heater. In addition, the inner peripheral surface of this mold was pre-treated with TiN coating, and the surface roughness was set to 0.4 Z.

 [01 18]

Lithium stearate dispersed in an aqueous solution was uniformly applied at a rate of about 10 cm ³ / min to the inner peripheral surface of the heated mold with a spray gun (application process). The aqueous solution used here is obtained by adding a surfactant and an antifoaming agent to water. The surface active agent include polyoxyethylene Roh loose phenyl ether (EO) 6, with respect to (EO) 10 using及Pi borate Emar Bonn T one 80, respectively entire solution (100 body product _^0/0) It was added in increments of 1% by volume. In addition, for antifoaming agent, FS Antifoam Using 80, 0.2% by volume was added to the whole aqueous solution (100% by volume).

 [01 19]

In addition, lithium stearate having a melting point of about 225 ° C and a particle size of 20 μηι was used. The amount of dispersion was 25 g with respect to 100 cm ^{3 of the} aqueous solution. Then, this was further refined with a ball mill type powder mill (Teflon-coated steel balls: 100 hours), and the resulting stock solution was diluted 20 times to give an aqueous solution having a final concentration of 1% for the application step. did.

 [0120]

 (b) A magnetic core powder that had been heated to 15 ° C. at the same temperature was filled into the mold coated with lithium stearate on the inner surface (filling step).

 [0121]

 (c) While maintaining the mold at 150 ° C., the core powder filled in the mold was warm-pressed basically at a molding pressure of 1568 MPa (molding process).

 In this warm high-pressure molding, none of the powders for the magnetic core cause galling or the like, and it is possible to take out the powder compact from the mold with a low pressure of about 5 MPa and a depressurization pressure. did it.

 [0122]

(d) Each of the obtained powder compacts was subjected to a heat treatment (annealing treatment) at 750 ° C. for 30 minutes in a nitrogen atmosphere (heating step or annealing step). Thus, distortion and stress remaining in the powder compact with a silicone榭fat coating becomes S i 0 ₂ coating is removed.

 [0123]

 (Second embodiment)

 The above-described Fe-1% Si magnetic powder (volume average particle size: 80 μm) was coated with a silicone resin film (insulating film) in the same manner as in the first example. However, the amount of the silicone resin was 0.1% by mass, 0.2% by mass and 0.5% by mass with respect to 100% by mass of the magnetic powder. In this way, three types of magnetic core powders with different amounts of insulating coating were obtained.

[0124] Each of the obtained magnetic core powders was subjected to warm high pressure molding similar to that of the first example, and each of the obtained powder compacts was subjected to the heat treatment described above (7500 ° Cx 3 in nitrogen atmosphere). 0 minutes).

 [0 1 2 5]

 (Third example)

 Fe-1% Si magnetic powder classified into 8 stages by sieving method was prepared. Specifically, (a) 4 5 ~ 6 3 μ πα (b) 6 3 ~ 74 μ πι, (c) 7 4 ~ 1 0 5 μ πι, (d) 1 0 5 ~ 1 5 0 μ ηι, (e) 1 5 0 to 2 1 2 μ πι, (f) 2 1 2 to 2 5 0 μ πι, (g) 2 5 0 to 3 0 0, (h) 3 0 0 to 3 5 5 μ πι Classified. In terms of the volume average particle diameter according to the present invention, (a) 5 0 to 60 μ πι (1)) 6 5 to 70 μm, (c) 8 0 to 100 μπι, ( d) 1 2 0 to 1 4 0 / m, (e) 1 7 0 to: 1 9 0 μ μη, (f) 2 2 0 to 24 0 μΐη, (g) 2 7 0 to 2 9 0 μπι, ( h) 3 2 0 to 3 4 0 μ ιη. The Fe 1% Si magnetic powder used was the same atomized powder as in the first example.

 [0 1 2 6]

 A silicone resin film was formed on each of these magnetic powders in the same manner as in the first example. The amount of silicone resin was 0.2% by mass with respect to 100% by mass of the magnetic powder. In this way, eight kinds of magnetic core powders having different particle diameters were obtained.

 Each of the obtained magnetic core powders was subjected to warm high pressure molding similar to that of the first example, and each of the obtained powder compacts was subjected to the heat treatment described above (7500 ° Cx 3 in nitrogen atmosphere). 0 minutes).

 [0 1 2 7]

 (Example 4)

 F e-1% Si magnetic powder classified into 11 steps by a sieving method was prepared. These classifications are the 8-stage classifications shown in the third embodiment. The Fe-1% Si magnetic powder used is the same atomized powder as in the first example.

 [0 1 2 8]

Each of these powders was rolled to a thickness of 0.05 mm and 0.1 mm with a small rolling mill (DBR-50 S (manufactured by Daito Seisakusho)). About) In this way, oblate flat particles having different particle sizes or thicknesses were obtained. The classification before rolling can be divided into 8 stages, and the thickness after rolling can be divided into 2 stages. Therefore, a total of 22 types of magnetic powder were obtained.

 [0129]

 A silicone resin film was formed on each of these magnetic powders in the same manner as in the first example. The amount of silicone resin was 0.2% by mass with respect to 100% by mass of the magnetic powder. Using each of the obtained magnetic core powders, warm high-pressure molding similar to that of the first example was carried out, and each of the obtained powder compacts was subjected to the heat treatment described above (750 ° C x 30 minutes in a nitrogen atmosphere). Was given.

 [0130]

 (Fifth embodiment)

 (1) Manufacture of magnetic core powder

 Two types of pure iron powder, which are commercially available as magnetic powder, have been facilitated. One is water atomized powder (KIP-304 AS from Kawasaki Steel) and the other is gas atomized powder (manufactured by Sanyo Special Steel). These powders were not used for classification and were used as received. The particle size was 100-200 μm. This is 130 to 170 μηι in terms of the volume average particle size of the present invention.

 [0131]

(a) The first insulating layer was coated on the magnetic powder by the following method. Sr C0 ₃ (alkaline earth metal oxide): 1 1 g, boric acid (H ₃ B0 ₃ ): 3 g, phosphoric acid (H ₃ P0 ₄ ): ■ · 19 g was added to 200 ml of ion-exchanged water and dissolved by stirring to obtain a coating solution (first coating treatment solution). These mixing ratios are Sr: B: P = 1.5: 1: 4 in molar ratio.

 [0132]

2 Oml of the coating solution was dropped onto 100 g of each magnetic powder in a 100 ml beaker (first contact step). This was put in an electric furnace and dried by heating in the atmosphere for 200 minutes at 200 ° C (first drying step). Thus, the first insulating layer (Sr—B—P—O type insulating layer, strontium phosphate type glassy insulating layer) was fixed and formed on the surface of the magnetic powder (first insulating layer forming step). This first insulating layer The ratio was 3% by mass for water atomized powder and 2% by mass for gas atomized powder with respect to the total magnetic powder (100% by mass) before treatment.

 [01 33]

 (b) The second insulating layer was coated on the magnetic powder (hereinafter simply referred to as “first magnetic powder”) on which the first insulating layer was formed by the following method.

Silicone resin solution (E Redaukoyungu Co. SR 2400), silica oxide particles (S I_〇 ₂₎ particles (Admatechs Co., 50 nm particle size) were prepared and. The silicone resin solution (SR2400) is a solution in which a silicone resin is dissolved at a ratio of 50% by mass in toluene as a solvent.

 [0 1 34]

 The second insulating layer (or third insulating layer) is formed on the first magnetic powder as follows. When forming the second insulating layer made of silicone resin, 50 g of each first magnetic powder is placed in a 100 ml beaker. From above, the silicone resin solution was added so that the amount of silicone resin reached the ratio shown in Table 2 (second contact step). In addition, when forming the composite insulating layer of the silicone resin and the silica particles, the silicone resin solution was further added, and then the silicon force particles were added to the ratio shown in Table 2 (No. 1). 2 contact process).

 [01 35]

 Add ethanol 3 Om 1 to each of the first magnetic powder and various ratios of silicone resin solution added, and stir in the atmosphere at 60 ° C or higher for 30 minutes. (Second contact process).

 [01 36]

 Thus, on the magnetic powder on which the first insulating layer composed of the Sr—B—P—O-based insulating layer is formed, the second insulating layer composed of the silicone resin or the second composed of the silicone resin op-silica particles. Two insulating layers (composite insulating layers) were formed (second insulating layer forming step). Thus, various magnetic core powders coated with the first insulating layer and the second insulating layer were obtained.

 [01 37]

(2) Manufacturing of dust core Using each of these magnetic core powders, warm high pressure molding similar to that of the first example was performed. The obtained powder compact was appropriately subjected to annealing in the air at an annealing temperature of 500 ° C or 600 ° C and an annealing time of 30 minutes. Some test pieces were annealed in an antioxidant atmosphere (Ar gas atmosphere) at an annealing temperature of 650 ° C.

 [0138]

 (Measurement)

 (1) The specific resistance was measured using a plate-shaped test piece. The specific resistance was measured by a four-terminal method using a micro-ohm meter (manufacturer: Hyuetsu Packard (HP), model number: 3442 OA) (hereinafter the same).

 [0139]

 (2) Using a ring-shaped specimen and a plate-shaped specimen, their magnetic properties and density were measured.

 Among the magnetic characteristics, the static magnetic field characteristics were measured with a DC self-recording magnetometer (manufacturer: Toei Kogyo, model number: MO DEL-TRF). The AC magnetic field characteristics were measured with an AC B-H curve tracer (manufacturer: Iwasaki Tsushinki Co., Ltd., model number: SY-8232). The AC magnetic field characteristics in each table are the measured iron loss when the dust core is placed in a magnetic field of 1.0T at 400Hz or 800Hz. Ph in the table is hysteresis loss, Pe is eddy current loss, Pc is iron loss (Pe + Ph), and Pcm is iron loss by weight.

 [0140]

The magnetic flux density in a static magnetic field indicates the magnetic flux density that can be generated when the magnetic field strength is changed sequentially to 2, 5, 8, 10, 16, and 20 kA / m. In each table, B ₂ k, B sk, B sk, Bi respectively. k ゝ B i 6 k _s B _20k . Μπι in the table is the maximum permeability. In this specification, the coercive force b He is a value measured from a magnetization curve at a maximum magnetic field of 2 kA / m. The density was measured by the Archimedes method.

 [0141]

The results thus obtained are also shown in Tables 1 to 4 and Tables 5A and 5B. Table 1 shows the results of the first example, Table 2 shows the results of the second example, Table 3 shows the results of the third example, Table 4 shows the results of the fourth example, Table 5 Table 5B shows the results of the fifth example. Show.

 [0142]

 (Evaluation)

 (1) First example

 As can be seen from the results shown in Table 1, as the Si content in the magnetic powder increases, the coercive force b He decreases and the hysteresis loss Ph also decreases. As the Si content in the magnetic powder increases, the specific resistance increases and the eddy current loss Pe decreases. Therefore, the iron loss decreases as the test piece with a larger amount of Si in the magnetic powder. On the other hand, the magnetic flux density decreases as the Si amount increases. Therefore, in order to achieve a high balance between low iron loss and high magnetic flux density, it is preferable that Si is contained in the magnetic powder at about 1% by mass (1.5% by mass or less).

 [0143]

 When pure iron powder is used as the magnetic powder, the specific resistance and eddy current loss of the test piece are relatively large because the insulating coating easily breaks, decomposes and disappears during molding and heating. I think that. In other words, it seems that the stability of the silicone resin coating covering the surface of pure iron powder was weak.

 [0 144]

 (2) Second embodiment

 As can be seen from the results shown in Table 2, as the amount of silicone resin increases, the specific resistance increases and the eddy current loss Pe decreases. At this time, the coercive force bHc and the hysteresis loss Ph are almost constant. As a result, the iron loss decreases as the amount of silicone resin increases. On the other hand, as the amount of silicone resin increases, the magnetic flux density decreases as a whole. Accordingly, in order to achieve a high balance between low iron loss and high magnetic flux density, the amount of silicone resin is preferably 0.1 to 0.3% by mass.

 [0145]

 (3) Third embodiment

As can be seen from the results shown in Table 3, the eddy current loss increased and the hysteresis loss decreased as the particle size of the magnetic powder increased. When the magnetic field is 1.0 T and the frequency is 800 Hz, the iron loss, which is the sum of eddy current loss and hysteresis loss, is the particle size of the magnetic powder. The value was stably low at 80 to 300 / m. This is shown in Fig. 1. [0146]

 (4) Fourth embodiment

 As can be seen from the results shown in Table 4, when magnetic powder composed of flat particles (thickness 0.05 mm) was used, eddy current loss was greatly reduced. The rate of decrease was more pronounced as the particle size of the magnetic powder was larger. Iron loss showed a similar trend. Conversely, it can be said that the hysteresis loss itself hardly changed depending on the shape of the constituent particles of the powder. This is shown superimposed on Figure 1.

 [0147]

 Figure 2 shows the effect of the particle shape and composition of the magnetic powder on the relationship between particle size and eddy current loss. It was found that the eddy current loss becomes smaller as the magnetic powder is made of flat particles and the thickness is smaller.

 [0148]

 (5) Fifth embodiment

Table 5 A and as can be seen from the results shown in Table 5 B, when the dust core including insulating film of a multilayer structure, specific resistance even after 500 ° C annealing was as large as ₁₀₀ μ Ωπι greater. It was found that if magnetic powder coated with this insulating film was used, even if the magnetic powder was pure iron powder, not only hysteresis loss but also eddy current loss could be reduced at the same time. That is, it was found that a dust core with low iron loss can be obtained.

 [0149]

 In particular, when the insulating coating contains silica particles, the specific resistance of the specimen showed a sufficiently high value not only after annealing at 500 ° C but also after annealing at 600 ° C.

 [0150]

Comparing the case where the AC frequency is 40 OH _Z and 80 OH _Z , when the frequency is low (400 Hz), the effect of hysteresis loss is larger, and the annealing temperature rises (500 ° C → 600 ° C) The rate of decrease in iron loss due to the was also large.

 [0151]

The test piece made of gas atomized powder generally had a higher specific resistance than the test piece made of water atomized powder, despite the small amount of the first insulating layer. Therefore, gas at It has been found that a powder core having a low magnetic loss and a high magnetic flux density can be obtained while using a small amount of insulating coating while reducing the amount of insulating coating.

 [0152]

 (6) Other

 The relationship between the crystal grain size and the coercive force will be added. Pure Fe magnetic powder and Fe-l Si magnetic powder were heat-treated at 900 ° C and 1250 ° C, respectively, and the relationship between crystal grain size and coercive force was investigated. The results are shown in Fig. 3.

 [0153]

 Each crystal grain size is an average value of crystal grain sizes obtained for a predetermined number (N = 100) of constituent particles.

 [0154]

 As is clear from Fig. 3, the coercive force decreased as the crystal grain size increased. Therefore, hysteresis loss can be further reduced by using a magnetic powder having a large crystal grain size (for example, a gas atomized powder having a relatively low cooling rate). As a result, when the crystal grain size exceeds 2 ° 0 μm, the decrease in coercive force approaches saturation. Considering eddy current loss, it is preferable to use magnetic powder having a crystal grain size of 50 to 250 μm.

 [0155]

So far, the AC frequency is 800Hz, but the same applies to other frequencies (2000Hz or less).

AC magnetic field characteristics AC magnetic field characteristics

 Volume resistivity Static magnetic field characteristics

 Test (1.0T / 400Hz) (1.0T / 800Hz)

 Magnetic mean particle size P

 Fragment

 No. Powder bHc Pcv Phv Pev Pcm Pcv Phv Pev Pcm

(m) (U Qm) ^B 2k 曰 5k ^B 8k ^D 10k ^D 16k ^B Z0k

 μm

 (T) (A / m) (kW / m3) (W / kg) (k / m3) (W / kg)

1 -1 Pure iron 80 5 1.00 1.50 1.63 1.67 1.80 1.90 800 200 8970 878 8170 1164 34436 1756 32680 4472

1 -2 Fe-1% S 80 1500 0.76 1.36 1.53 1.60 1.73 1.81 300 120 174 143 30 23 403 287 120 53

1 -3 Fe— 3% Si 80 2000 0.35 0.76 1.08 1.22 1.45 1.56 250 100 154 147 7 21 323 294 29 44 Silicone resin content: 0.2% by mass,

Heating process: 750 ° C x 30 minutes (nitrogen atmosphere)

¾1

[W 10 Magnetic field characteristics '' AC magnetic field characteristics Silicone resistivity Static magnetic field characteristics AC

 Test density ratio (1.0T / 400Hz) (1.OT / 800Hz)

 Resin P

 Fragment

 No. (%) bHc

^B 2k ^B 5k ^B 8k ^B 10k ^B 16k ^B 20k Pcv Phv Pev Pcm Pcv Phv Pev Pcm

(Mass ⁰ / o) (jU Q m) U m

 (T) (A / m) (kW / m3) (W / kg) (kW / m3) (W / kg)

2- 1 0.1 300 98 1.00 1.46 1.59 1.65 1.77 1.85 450 120 179 144 35 24 428 288 140 57

2-2 0.2 1500 98 0.76 1.36 1.53 1.60 1.73 1.81 300 120 174 143 30 23 406 286 120 53

2-3 0.5 5000 98 0.31 0.67 0.94 1.07 1.32 1.43 150 120 168 140 28 23 392 280 112 52 Magnetic powder: Fe— 1% Si, Volume average particle size 80〃 m

Heating process: Ί 50 ° C x 30 minutes (nitrogen atmosphere)

] ¾2

【1 ^ 〇

AC magnetic field characteristics AC magnetic field characteristics

 Body !! ¾ Resistivity Static magnetic field characteristics

 Experimental density ratio (1.0T / 400Hz) (1.0T / 800Hz)

 Average particle size

 Piece P

 No. (%) bHc Pcv Phv Pev Pom Pcv Phv Pev Pcm

(jU m) (Q m) ^B 2k ^B 5k ^B 8k ^B 10k ^B 16k ^B 20k

(T) (AZm) (kW / m ³ ) (W / kg) (kW / m ³ ) (W / kg)

3-1 320 -340 310 98.4 0.79 1.38 1.55 1.61 1.72 1.81 330 105 181 133 43 24 454 266 171 60

3 -2 270 to 290 360 98.5 0.73 1.36 1.54 1.60 1.72 1.81 300 105 177 133 34 23 420 267 136 55

3 -3 220-240 400 98.4 0.80 1.39 1.55 1.62 1.74 1.82 340 110 171 136 28 23 402 273 1 14 53

3 -4 170 ~ 190 500 97.9 0.70 1.33 1.52 1.58 1.70 1.79 290 120 178 149 21 23 398 299 84 53

3-5 120-1 0 600 98.0 0.86 1.41 1.56 1.62 1.74 1.82 360 130 186 164 15 25 399 328 58 53

3 -6 80 ~ 100 1500 98.2 0.76 1.35 1.53 1.60 1.72 1.81 320 160 203 182 12 27 412 364 47 54

 3-7 65-70 2000 97.9 0.57 1.17 1.43 1.52 1.68 1.75 230 180 227 209 8 30 464 418 33 61

3-8 50-60 3000 97.2 0.44 1.00 1.32 1.43 1.62 1J1 180 210 248 233 8 33 534 466 33-—It— Magnetic powder: Fe— 1% Si

Silicone resin content: 0.2% by mass,

Heating process: 750 ° C x 30 minutes (nitrogen atmosphere)

1

 Magnetic powder: Fe— 1% Si, flat particles

 Silicone resin content: 0.2% by mass,

 Heating process: 750 ° C x 30 minutes (nitrogen atmosphere)

【 Ten [0 1 6 0]

 [Table 5 A]

rOverJ means that the specific resistance value has exceeded the measurement range. (*) Means annealing in an Ar atmosphere in a vacuum furnace.

[0 1 6 2]

]

Six-coordinate network modifier element Ion radius

(nm) a Mg ²⁺ 0.0720 le

Gold Power Ca ²⁺ 0.1000 Genus

Sr ²⁺ 0.1180 Mainland

Element Ba ²⁺ 0.1350 Noble Sc ³⁺ 0.0745 Sat

 γ3 + 0.0900 兀

La ³⁺ 0.1032

By Bi ³⁺ 0.1030 other

Claims

The scope of the claims

1. In a powder magnetic core formed by press-molding a magnetic core powder in which a magnetic powder mainly composed of iron (F e) is coated with an insulating film,

 The magnetic powder contains 1.5% by mass or less of key element (S i) and has a volume average particle size of 80 to 300 μπι,

Density ratio ρ / _Ρ, which is the ratio of the bulk density (ρ) of the dust core to the true density (ρ.) Of the magnetic powder. %) Is 96% or more,

 A dust core that is used in an alternating magnetic field with a frequency of 100 to 2000 Hz.

2. Magnetic flux density B ₂ generated in a magnetic field of 20 kA / m. The dust core according to claim 1, wherein _k is 1.7 T or more.

3. The powder magnetic core according to claim 1, wherein the magnetic powder is made of flat particles having a substantially oval shape with an average thickness of 20 to 100 μm.

4. The magnetic powder, a dust core according to claim 1, wherein the average specific surface area was leveling a specific surface area is the surface area per unit mass of constituent particles flat is less than 5 X 10- ³ m ² / g

5. The dust core according to claim 1, wherein the magnetic powder has an average crystal grain size of 50 μm or more.

6. The dust core according to claim 1, wherein the magnetic powder is a gas atomized powder.

7. The dust core according to claim 1, wherein the insulating coating is a silicone resin coating or a silicon dioxide (S i 0 ₂ ) coating.

8. The magnetic powder is pure iron powder having a Si of 0.8% or less,

 2. The dust core according to claim 1, wherein the insulating film is composed of a first insulating layer made of a phosphate film, a second insulating layer made of silicone resin covering the first insulating layer, and a force.

9. The dust core according to claim 8, wherein the second insulating layer is a composite insulating layer in which oxide particles are dispersed in the silicone resin.

10. The dust core according to claim 8, further comprising a third insulating layer provided on the second insulating layer and mainly made of oxide particles.

11. The dust core according to claim 9 or 10, wherein the oxide particles have an average particle size of 10 to 100 nm.

12. The dust core according to claim 1, wherein the insulating coating is 0.1 to 0.3% by mass when the entire powder magnetic core is 100% by mass.

1 3. The coercive force is 1 5 0 A / m or less,

 2. The dust core according to claim 1, wherein the volume resistivity value is 20 μΩΩπι or more.

14. The dust core according to claim 1, which is an iron core constituting a field or armature of an electric motor or a generator.

15. The dust core according to claim 14, wherein the electric motor is for a hybrid vehicle or an electric vehicle.

1 6. Magnetic core powder in which die is coated with magnetic powder having Fe as a main component and having Si of 1.5% by mass or less and volume average particle diameter of 80 to 300 / zm. Filling process to fill in, A molding step of pressure molding the magnetic core powder in the mold,

 A method for producing a dust core, wherein the dust core according to claim 1 is obtained.

1 7. The filling step is a step of filling the magnetic core powder into the mold in which a higher fatty acid-based lubricant is applied to the inner surface,

 17. The method of manufacturing a dust core according to claim 16, wherein the forming step is a warm high-pressure forming step in which a metal sarcophagus film is formed between the magnetic core powder and the inner surface of the mold.

1 8. The insulating coating is a silicone resin coating,

Furthermore, manufacturing how the dust core according to claim 1 6, comprising a heating step of the silicone resin to be film as S i 0 ₂ coating by heating the powder compact obtained after the molding process.

1 9. The magnetic 1 "raw powder is pure iron powder with 3 1 0.8% or less,

 The insulating coating comprises a first insulating layer made of a phosphate coating and a second insulating layer made of a silicone resin that covers the first insulating layer,

 Furthermore, the manufacturing method of the powder magnetic core of Claim 16 provided with the annealing process which anneals the powder compact obtained after the said shaping | molding process.

20. A powder magnetic core obtained by the method for manufacturing a powder magnetic core according to any one of claims 18 and 19.