JP2005206880A - Soft magnetic material and production method therefor, and dust core containing the soft magnetic material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide soft magnetic material for a dust core, the material which is excellent in compressibility and fluidity, and undergoes little change in electric resistance value even when fired at high temperature, and to provide a dust core containing the soft magnetic material for a dust core and having high electric resistance value. <P>SOLUTION: The soft magnetic material for a dust core is composed of composite particle powder in which an inorganic compound selected from one or more metals selected from aluminum, zirconium, titanium, silicon, magnesium and iron formed from metal alkoxide and/or an inorganic compound such as a phosphorous compound is stuck to or covered on the surface of each particle of soft magnetic particle powder. The dust core is obtained by subjecting the soft magnetic material for a dust core to compression molding. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention provides a soft magnetic material that is excellent in compressibility and fluidity and has little change in electrical resistance even when fired at high temperatures, and a dust core having a high electrical resistance containing the soft magnetic material. .

  In recent years, along with energy saving and miniaturization of home appliances and electronic devices, there is an increasing demand for miniaturization, high output, and high efficiency of power conversion efficiency for magnetic core materials used for these. Higher operating frequency is known to be effective in reducing the size of equipment, increasing output, and increasing power conversion efficiency. Even in the high frequency range, high magnetic flux density, magnetic permeability, and low iron loss. There is a strong need for magnetic core materials.

  Conventionally, as such a magnetic core material, a laminated magnetic core using a silicon steel plate or the like has been used. However, a laminated magnetic core has a disadvantage that eddy current loss generated inside the magnetic core increases as the operating frequency increases. have.

  For this reason, in recent years, a powder core in which a soft magnetic powder is coated with an insulating resin such as a phenol resin or an epoxy resin and is compression-molded has a low iron loss in a high frequency region as compared with a laminated magnetic core and has excellent moldability. However, it is widely used as a substitute for a laminated magnetic core.

  On the other hand, further miniaturization and higher performance, that is, higher magnetic flux density is desired for the powder magnetic core. For such higher magnetic flux density, the packing density of the soft magnetic powder is increased. Things have been done.

  However, it is known that since compression molding is performed at a high pressure in order to highly fill the soft magnetic powder, strain remains in the soft magnetic powder, leading to an increase in hysteresis loss. Therefore, in order to reduce the hysteresis loss due to strain, the molded product is usually annealed.

  By the way, in general, hysteresis loss and eddy current loss are known as main causes of iron loss of a dust core. As described above, it is known that the removal of strain due to annealing is effective as a method for reducing hysteresis loss. On the other hand, as a method for reducing eddy current loss, an insulating resin or the like is used between particles. It is done by insulating.

  However, annealing is generally effective at a temperature of 500 ° C. or higher, preferably 600 ° C. or higher. However, the bonding resin as a binder of the soft magnetic particle powder and the insulation between the particles are not effective. Therefore, when an insulating resin is used, annealing at a high temperature will cause the resin to decompose and the molded body will become brittle, or the insulation will be degraded, so annealing at a high temperature is difficult. It was difficult to reduce both hysteresis loss and eddy current loss at the same time.

  Up to now, soft magnetic metal powder (Patent Document 1) in which a phosphate film and a sodium silicate film are formed on the surface of the soft magnetic metal powder, or a magnetic powder in which the magnetic powder surface is coated with a silica-based sol film A technique using (Patent Document 2) as a powder for a powder magnetic core is disclosed.

  Moreover, the technique which uses the iron-base powder coat | covered with the film containing an epoxy resin and an alumina containing silica as powder for powder magnetic cores is disclosed (patent document 3).

  Moreover, the powder magnetic core which combined the iron powder which gave the iron powder or the phosphate compound film on the surface with resin was disclosed (patent document 4).

  Further, a dust core having an insulating layer containing a silicone skeleton and a pigment between magnetic powder particles is disclosed (Patent Document 5).

  On the other hand, it is preferable that the electric resistance value of the dust core is high. If the electric resistance of the dust core is high, the permeability hardly changes even in a high frequency range, but if the electric resistance value is low, the permeability is high in the high frequency range. Tend to drop sharply.

  As means for increasing the electrical resistance value, the surface of the metal powder is obtained by hydrolyzing the soft magnetic powder (Patent Documents 6 to 7) and the metal alkoxide obtained by subjecting the soft magnetic metal powder to a phosphate treatment to form a phosphate coating. Discloses a magnetic material powder in which a hydroxide is adsorbed on (Patent Document 8).

  For the purpose of improving fluidity and moldability, at least one selected from iron-based powders, lubricants and powders for alloys is an organoalkoxysilane, an organosilazane, a titanate coupling agent, a fluorine coupling. A powder coated with one or more surface treatment agents selected from agents is disclosed (Patent Document 9).

JP 2002-170707 A JP 2001-196217 A JP 2003-166004 A JP 2002-246219 A JP 2002-343657 A JP-A-62-222410 JP-A-63-70504 JP-A-9-125111 JP 10-31001 A

  A dust core soft magnetic material that is excellent in compressibility and fluidity and has a small change in electrical resistance even when fired at high temperature is currently most demanded, but has not yet been obtained.

  That is, in Patent Documents 1 and 2, a soft magnetic metal powder magnetic powder in which a phosphate film and a sodium silicate film or a silica-based sol film are formed on the surface of a soft magnetic metal powder is used for a dust core. Although it is described that it is used as a powder, the compressibility is not taken into consideration, and as shown in a comparative example described later, the change rate (%) of the compressive density indicating compressibility is as bad as 5.2%. there were.

  Patent Document 3 describes that an iron-based powder coated with a coating containing an epoxy resin and alumina-containing silica is used as a powder for a powder magnetic core. Patent Document 4 describes iron powder or phosphorus. Although the powder magnetic core which combined the iron powder which gave the acid compound film on the surface with the resin is described, the rate of change of the specific resistance value before and after annealing of the pressure-molded body is 10 to 94%, both It is expensive.

  Patent Document 5 describes a dust core having an insulating layer containing a silicone skeleton and a pigment between magnetic powder particles. However, since a silicone resin is used for the insulating layer, depending on the pressure, Compressed. For this reason, the rate of change in compression density showing compressibility is high, and distortion of the magnetic particles tends to remain during pressure molding.

  Patent Documents 6 to 7 describe amorphous magnetic alloy powders in which a phosphate coating such as zinc phosphate, magnesium phosphate, calcium phosphate, and iron phosphate is formed. The heat resistance temperature of the salt coating is about 500 ° C., and if it is annealed at a temperature higher than that, it is difficult to maintain the insulating properties.

  Patent Document 8 describes a magnetic material powder in which a metal alkoxide is hydrolyzed and a hydroxide is adsorbed on the surface of the metal powder, but hydrolysis is caused by adding distilled water to the metal alkoxide. Advances rapidly, and the resulting hydroxide particles become coarse and it becomes difficult to provide a dense coating, so it is difficult to obtain good compressibility.

  Patent Document 9 discloses that at least one surface selected from iron-based powders, lubricants and alloy powders is at least one surface selected from organoalkoxysilanes, organosilazanes, titanate coupling agents, and fluorine coupling agents. Although powder coated with a treating agent is described, it is not preferable because it is weak against heat because it treats organic matter, and the volume resistivity value before and after heating becomes large.

  Therefore, the present invention has a technical problem to obtain a soft magnetic material that has excellent fluidity, can be compression-molded at a low pressure, and has a small volume resistivity change even when fired at a high temperature. To do.

  As a result of intensive research to solve the above problems, the present inventors have found that the soft magnetic particle powder having an inorganic compound attached or coated on the particle surface has excellent fluidity and can be compression-molded at a low pressure. In addition, even when fired at a high temperature, there is little change in the electric resistance value, and by using the soft magnetic particle powder as a soft magnetic material for a dust core, a dust core having a high electric resistance value can be obtained. As a result, the present invention has been found.

  That is, the present invention is a soft magnetic material characterized by comprising a composite particle powder in which an inorganic compound is adhered or coated on the surface of the soft magnetic particle powder (Invention 1).

  The present invention provides the soft magnetic material, wherein the inorganic compound comprises a compound containing one or more metal elements selected from aluminum, zirconium, titanium, silicon, magnesium, iron and phosphorus. (Invention 2).

  Moreover, this invention is an inorganic compound and / or phosphorus compound which an inorganic compound produces | generates from the metal alkoxide containing 1 type, or 2 or more types of metal elements chosen from aluminum, zirconium, titanium, silicon, magnesium, or iron. This is the soft magnetic material of the present invention 1 or 2 (Invention 3).

  In addition, the present invention is the soft magnetic material according to any one of the first to third aspects, wherein the change rate of the compression density of the composite particle powder is less than 5% (the present invention 4).

  Further, the present invention is the soft magnetic material according to any one of the present inventions 1 to 4, wherein the change rate of the volume resistivity before and after the heating of the composite particle powder is 20% or less (the present invention 5). .

  In the present invention, the metal alkoxide solution is added to a suspension obtained by dispersing soft magnetic particle powder in an organic solvent, followed by air drying and then drying at 60 to 120 ° C. This is a method for producing any one of the soft magnetic materials (Invention 6).

  In addition, the present invention is characterized in that a metal alkoxide solution is added to a suspension in which soft magnetic particle powder is dispersed in an organic solvent, a phosphoric acid solution is added, air-dried, and then dried at 60 to 120 ° C. A method for producing a soft magnetic material according to any one of Inventions 1 to 5 (Invention 7).

  In addition, the present invention is a dust core formed by compression molding the soft magnetic material according to any one of the first to fifth aspects (Invention 8).

  The soft magnetic material according to the present invention is excellent in fluidity, can be compression-molded at a low pressure, and has a small change in electric resistance even when fired at a high temperature. Is preferred.

  The powder magnetic core according to the present invention is suitable as a high-performance powder magnetic core because the soft magnetic material is used so that the electric resistance value is high and the electric resistance value hardly changes even when fired at a high temperature. Is

  The configuration of the present invention will be described in more detail as follows.

  First, the soft magnetic material according to the present invention will be described.

  The soft magnetic material according to the present invention is an inorganic material produced from a metal alkoxide containing one or more metal elements selected from aluminum, zirconium, titanium, silicon, magnesium or iron on the particle surface of the soft magnetic particle powder. It consists of composite particle powder to which a compound and / or a phosphorus compound adheres or is coated.

  The coating amount of the inorganic compound generated from the metal alkoxide of the soft magnetic material according to the present invention is preferably 0.001 to 100% by weight in terms of each element. When the amount is less than 0.001% by weight, the effect of the present invention cannot be obtained. Since the effect of the present invention can be sufficiently obtained by the addition amount of 0.001 to 100% by weight, it is meaningless to add more than necessary exceeding 100% by weight. When considering the compressibility and fluidity of the obtained soft magnetic material, the content is more preferably 0.002 to 75% by weight, and still more preferably 0.005 to 50% by weight.

  The coating amount of the phosphorus compound of the soft magnetic material according to the present invention is preferably 0.001 to 100% by weight in terms of P. When the amount is less than 0.001% by weight, the effect of the present invention cannot be obtained. Since the effect of the present invention can be sufficiently obtained by the addition amount of 0.001 to 100% by weight, it is meaningless to add more than necessary exceeding 100% by weight. In consideration of the compressibility and fluidity of the obtained soft magnetic material and the filling rate of the soft magnetic particle powder when used in a dust core, 0.002 to 75% by weight is more preferable, and still more preferably 0.005. ~ 50% by weight.

  The average particle size of the soft magnetic material according to the present invention may be selected according to the application and characteristics, but is preferably in the range of 1.0 to 500.0 μm. When the average particle size is 500.0 μm or more, the particle size is too large, and when used in a dust core, the packing density is lowered, which is not preferable. An average particle size of 1.0 μm or less is not preferable because the particle size is too small and fluidity is lowered. More preferably, it is 5.0-400.0 micrometers, More preferably, it is 10.0-300.0 micrometers.

  Regarding the compressibility of the soft magnetic material according to the present invention, the rate of change in compression density is preferably less than 5% in the evaluation method described later. If the change rate of the compression density is 5% or more, it is not preferable because a high pressure is required when producing a dust core. More preferably, it is 4% or less, and still more preferably 3% or less.

  The volume resistivity value of the soft magnetic material according to the present invention is preferably 1.0 mΩ · cm or more, more preferably 2.0 mΩ · cm or more. Further, the rate of change in volume resistivity value before and after heating at 500 ° C. for 1 hour is preferably 20% or less, more preferably 15% or less, and even more preferably 10% or less. When the rate of change of the volume resistivity value before and after heating exceeds 20%, the specific resistance value of the dust core obtained by using this tends to be lowered by annealing, which is not preferable.

  The fluidity of the soft magnetic material according to the present invention is preferably a fluidity index of 70 or more. When the fluidity index is less than 70, the filling property to the mold is not improved during the production of the dust core, and therefore the filling rate of the soft magnetic particle powder in the dust core is poor. More preferably, it is 75-95.

  Next, a method for producing a soft magnetic material according to the present invention will be described.

  The soft magnetic material according to the present invention is obtained by adding a metal alkoxide solution and / or a phosphoric acid aqueous solution to a suspension obtained by dispersing soft magnetic particle powder, which is a particle powder to be treated, in a water-soluble organic solvent. It can be obtained by drying at 60 to 120 ° C.

  As the soft magnetic particle powder in the present invention, iron powder, ferrite powder, sendust powder, permalloy powder, and the like by various production methods such as atomized iron powder, reduced iron powder, and carbonyl iron powder can be used. Considering the permeability and magnetic flux density of the obtained dust core, iron powder is preferred. The average particle size of the soft magnetic particle powder is preferably 1.0 to 500.0 μm, more preferably 5.0 to 400.0 μm, and still more preferably 10.0 to 300.0 μm.

  The compressibility of the soft magnetic particle powder in the present invention has a compression density change rate of 5% or more in an evaluation method described later.

  In general, the volume resistivity value of the soft magnetic particle powder in the present invention is preferably 0.1 mΩ · cm or more, more preferably 0.5 mΩ · cm or more. Moreover, the change rate of the volume resistivity value before and after heating for 1 hour at 500 ° C. is usually 25% or more.

  The fluidity of the soft magnetic particle powder in the present invention usually has a fluidity index of 50 or more, preferably 55-80.

  Any organic solvent may be used as long as it is generally used, but a water-soluble organic solvent is preferable. Specifically, alcohol solvents such as ethyl alcohol, propyl alcohol or butyl alcohol, ketone solvents such as acetone or methyl ethyl ketone, glycol ether solvents such as methyl cellosolve, ethyl cellosolve, propyl cellosolve or butyl cellosolve, diethylene glycol, triethylene glycol , Oxyethylene such as polyethylene glycol, dipropylene glycol or tripropylene glycol, polypropylene glycol, oxypropylene addition polymer, alkylene glycol such as ethylene glycol, propylene glycol or 1,2,6-hexanetriol, glycerin, 2-pyrrolidone, etc. Can be preferably used, but more preferably ethyl alcohol, propyl alcohol, butyl alcohol, etc. Alcohol solvents, acetone, ketone solvents such as methyl ethyl ketone.

  As the metal element constituting the metal alkoxide used in the present invention, aluminum, zirconium, titanium, silicon, magnesium, iron, vanadium, germanium, tantalum, tungsten, indium, molybdenum, barium and the like can be used, preferably aluminum, Zirconium, titanium, silicon, magnesium and iron. Moreover, as a kind of alkoxide, methoxide, ethoxide, propoxide, isopropoxide, oxyisopropoxide, butoxide, etc. can be used. Considering the uniformity of treatment and the treatment effect, tetraethoxysilane, aluminum triisopropoxide, zirconium tetraisopropoxide, titanium tetraisopropoxide and the like are preferable.

  The metal alkoxide is preferably used after being dispersed or dissolved in advance in the above-mentioned organic solvent in order to perform a more uniform treatment.

  In addition, the hydrolysis of the metal alkoxide does not require any particular addition of water in order to attach or cover a finer inorganic compound to the particle surface of the soft magnetic particles. It is preferable to perform hydrolysis with moisture.

  The addition amount of the metal alkoxide varies depending on the specific surface area of the soft magnetic particle powder, but is usually 0.001 to 100 parts by weight in terms of each element per 100 parts by weight of the soft magnetic particle powder. When the amount is less than 0.001 part by weight, the effect of the present invention cannot be obtained. Since the effect of this invention is fully acquired by the addition amount of 0.001-100 weight part, it is meaningless to add more than necessary exceeding 100 weight part. When considering the compressibility and fluidity of the obtained soft magnetic material, the amount is preferably 0.002 to 75 parts by weight, more preferably 0.005 to 50 parts by weight.

  In the present invention, a phosphoric acid solution or a phosphate solution may be added instead of the metal alkoxide. More preferably, the phosphoric acid solution or the phosphate solution is added to the suspension to which the metal alkoxide solution is added.

  The amount of phosphoric acid or phosphate added in the present invention varies depending on the specific surface area of the soft magnetic particle powder, but is usually 0.001 to 100 parts by weight in terms of P per 100 parts by weight of the soft magnetic particle powder. When the amount is less than 0.001 part by weight, the effect of the present invention cannot be obtained. Since the effect of this invention is fully acquired by the addition amount of 0.001-100 weight part, it is meaningless to add more than necessary exceeding 100 weight part. When considering the compressibility and fluidity of the resulting soft magnetic material and the filling rate of the soft magnetic particle powder when used in a dust core, 0.002 to 75 parts by weight is preferable, and 0.005 to 50 is more preferable. Parts by weight.

  The equipment for mixing the soft magnetic particle powder with the metal alkoxide solution and / or phosphoric acid or phosphate solution includes a high-speed agitate mixer, specifically a Henschel mixer, a speed mixer, a ball cutter, a power mixer, and a hybrid. Use a mixer.

  When adding phosphoric acid or phosphate as an aqueous solution, it is preferable to add a small amount in order to prevent hydrolysis from proceeding rapidly.

  The obtained soft magnetic particle powder can be obtained by drying in a draft at room temperature for 3 to 24 hours and then drying in a temperature range of 60 to 120 ° C. for 1 to 24 hours.

  Next, the dust core according to the present invention will be described.

  The powder magnetic core according to the present invention is obtained by mixing the soft magnetic material according to the present invention with additives such as a binder resin and a lubricant, if necessary, and compression-molding the mixed particle powder, followed by heat treatment. Can be obtained.

  As the binder resin, an epoxy resin, an imide resin, a phenol resin, a silicone resin, or the like can be used alone or in combination.

  The compression molding can be performed by a compression molding method using a mold that is usually performed. In addition, what is necessary is just to select a shaping | molding pressure suitably according to a use.

  The heat treatment temperature after compression molding may be appropriately adjusted according to the type of binder resin and the required properties, and the upper limit of the heat treatment temperature is not higher than the decomposition temperature of the inorganic compound coating.

  The volume occupancy (vol%) of the soft magnetic particle powder in the dust core according to the present invention is 90% or more, preferably 91%, more preferably 92% or more.

  The specific resistance value of the dust core according to the present invention is 2.0 mΩ · cm or more, preferably 3.0 mΩ · cm or more, more preferably 4.0 mΩ · cm or more. Further, the change rate of the specific resistance value before and after the heat treatment is preferably less than 30%, more preferably less than 20%, and still more preferably less than 10%.

<Action>
The most important point in the present invention is that the soft magnetic material composed of the composite particle powder in which the inorganic compound adheres or is coated on the surface of the soft magnetic particle powder is excellent in compressibility and fluidity and fired at a high temperature. This is also the fact that there is little change in the volume resistivity value.

  As the reason why the fluidity of the soft magnetic material according to the present invention is excellent, the present inventor has produced an inorganic compound adhering to or covering the particle surface of the soft magnetic particle powder from the metal alkoxide, thereby forming the particle surface. It is estimated that very fine protrusions were generated.

  As a reason why the compressibility of the soft magnetic material according to the present invention is excellent, the present inventors have improved the fluidity of the soft magnetic material for the above reasons, so that the filling property is improved. As a result, even a low pressure is sufficient. It is presumed that compression density can be obtained.

  As a reason why the volume resistivity of the soft magnetic material according to the present invention is small even when fired at a high temperature, the present inventor has determined that the inorganic compound adhering to or covering the particle surface of the soft magnetic particle powder is from a metal alkoxide. It is presumed that by forming the particles, the fine particles can be adhered or covered with fine particles, and the soft magnetic particle powder as the core particles is hardly affected by heat.

  Moreover, it is a fact that the dust core obtained by using the soft magnetic material according to the present invention has a high specific resistance value.

  The reason why the powder magnetic core according to the present invention has a high specific resistance value is that the present inventor used the soft magnetic material according to the present invention as a soft magnetic material, which has little change even when the volume resistivity value is fired at a high temperature. Therefore, it is considered that the specific resistance value, which is largely reduced by performing the heat treatment, can be maintained at substantially the same value as before the heat treatment.

  Examples of the present invention will be described below to specifically explain the present invention.

  The average particle diameter of each particle powder was measured by measuring the particle diameter of 350 particles shown in the electron micrograph, and the average value was shown.

  The coating amount of the insulating layer adhered to or coated on the surface of the soft magnetic particle powder is “fluorescence X-ray analyzer 3063M type” (manufactured by Rigaku Denki Kogyo Co., Ltd.). It was measured according to the “General Rules of Analysis”.

For the volume resistivity of each particle powder, first, 0.5 g of the particle powder was measured and subjected to pressure molding at a pressure of 1.372 × 10 ⁷ Pa using a KBr tablet molding machine (Shimadzu Corporation). A cylindrical sample to be measured was prepared.

  Next, after the sample to be measured was exposed to an environment of 25 ° C. and a relative temperature of 60% for 12 hours or more, the sample to be measured was set between stainless steel electrodes, and an electric resistance measuring device (model 4329A Yokogawa Hokushin Electric Co., Ltd. The resistance value R (mΩ) was measured by applying a voltage of 15V.

Next, the area A (cm ² ) and the thickness t ₀ (cm) of the upper surface of the sample to be measured (cylindrical) are measured, and each measured value is inserted into the following Equation 1 to determine the volume resistivity (mΩ · cm )

<Equation 1>
Volume resistivity (mΩ · cm) = R × (A / t ₀ )

  The rate of change (%) in volume resistivity before and after heating of each particle powder is the same as described above after heating the column-shaped sample for volume resistivity measurement prepared above at 500 ° C. for 1 hour. Then, the volume resistivity value was measured, and the volume resistivity value before and after heating was inserted into the following formula 2 to obtain the rate of change of the volume resistivity value.

<Equation 2>
Change rate (%) of volume resistivity before and after heating = {volume resistivity (before heating) −volume resistivity (after heating)} / volume resistivity (before heating) × 100

  The fluidity of each particle powder is measured using powder testers (trade name, manufactured by Hosokawa Micron Co., Ltd.) by measuring the powder characteristic values of angle of repose (degree), degree of compression (%), spatula angle (degree), and degree of aggregation. Then, each index obtained by replacing each measured value with a numerical value of the same standard was obtained, and each index was indicated as a total liquidity index. The closer the fluidity index is to 100, the better the fluidity.

The rate of change in the compression density of each particle powder was determined by first measuring 0.3 g of the sample powder, placing it in a cylindrical mold having a diameter of 13 mm, and using a KBr tablet molding machine (Shimadzu Corporation), 9.8. From the thickness of the powder layer obtained by pressure molding at pressures of × 10 ⁷ Pa and 4.9 × 10 ⁸ Pa, the compression densities CD ₁ (g / cm ³ ) and CD ₅ (g / Cm ³ ) and the respective measured values were inserted into the following formula 3 to determine the rate of change (%) in compression density.

<Equation 3>
Change rate of compression density (%) = {(CD ₁ −CD ₅ ) / CD ₁ )} × 100

The volume occupancy of the soft magnetic particle powder contained in the powder magnetic core is determined from the true specific gravity of each sample powder and the weight of each sample powder used for compression molding. The volume was determined. Subsequently, the powder mixture for the dust core described later is compression-molded into a cylindrical shape (φ23 × 5 mm) at a molding pressure of 4.9 × 10 ⁸ Pa, and the volume of the sample powder contained in the dust core and after the compression molding It was obtained from the volume of the cylinder.

The specific resistance value of the powder magnetic core was measured using an electric resistance measuring device (model 4329A Kita Yokogawa) in the same manner as the volume resistivity of each particle powder was measured using a powder magnetic core produced by the method described later. Electric resistivity) was used to measure the specific resistance value before and after the heat treatment. Further, the change rate of the specific resistance value before and after the heat treatment is expressed by the following equation 4 using the specific resistance value R ₀ (mΩ · cm) before the heat treatment and the specific resistance value R ₁ (mΩ · cm) after the heat treatment. Each measurement value was inserted, and the change rate (%) of the specific resistance value was obtained.

<Equation 4>
Specific resistance change rate (%) = {(R ₀ −R ₁ ) / R ₀ )} × 100

<Example 1-1: Production of soft magnetic material>
Iron powder (particle shape: granular, average particle diameter 20.1 μm, volume resistivity 315.1 mΩ · cm, volume resistivity change before and after heating 35.8%, fluidity 59, compression density change 7 0.5%) was poured into 500 ml of acetone using a stirrer to obtain an acetone slurry containing iron powder.

  Next, 200 ml of an acetone solution in which 10.0 g of aluminum isopropoxide was dispersed was added to the acetone slurry containing the iron powder, and the mixture was stirred and mixed for 60 minutes.

  Next, 6.0 g of an aqueous phosphoric acid solution (phosphoric acid content: 85% by weight) was added to the mixed solution over 10 minutes, and the mixture was further stirred and mixed for 20 minutes.

  The obtained mixed solution was air-dried in a fume hood for 3 hours and then dried at 80 ° C. for 60 minutes using a dryer to obtain a soft magnetic material.

  The obtained soft magnetic material was granular particles having an average particle diameter of 20.3 μm. The volume resistivity value was 411.2 mΩ · cm, the rate of change in volume resistivity value before and after heating was 8.3%, the fluidity was 82, and the rate of change in compression density was 1.8%. The surface treated product adhered or coated was 0.26% by weight in terms of Al and 0.32% by weight in terms of P.

<Example 2-1: Production of dust core>
Using a mold in which 100 parts by weight of the soft magnetic material and 0.6 parts by weight of an epoxy resin are mixed and zinc stearate is applied, the mixed powder is ring-shaped (10 × φ23 × at a molding pressure of 4.9 × 10 ⁸ Pa). 5 mm). The compact was heated in air at 200 ° C. for 30 minutes and then cooled to obtain a dust core.

  The volume occupancy of the soft magnetic particle powder of the obtained dust core is 92.4 vol%, the specific resistance value before heat treatment is 463.9 mΩ · cm, the specific resistance value after heat treatment is 423.5 mΩ · cm, The rate of change of the specific resistance value was 8.7%.

  A soft magnetic material and a dust core were prepared according to Examples 1-1 and 2-1. Various characteristics of each production condition and the obtained soft magnetic particle powder and dust core are shown.

Soft magnetic particles A to E:
A soft magnetic particle powder having the characteristics shown in Table 1 was prepared as a particle to be treated.

Examples 1-2 to 1-7, Comparative Examples 1 and 2:
A soft magnetic material for a dust core was prepared in the same manner as in Example 1-1 except that the type of soft magnetic particle powder, the type of organic solvent in the surface treatment step, the type of surface treatment agent, and the amount added were varied. Obtained.

  The production conditions at this time are shown in Table 2, and the characteristics of the obtained soft magnetic particle powder are shown in Table 3.

In Comparative Example 2, a commercially available silica sol (average particle size 10 to 20 nm, SiO ₂ content 20% by weight) dispersed in acetone was used for the treatment.

Comparative example 3 (JP 2001-196217 A Example additional test)
30 parts by weight of modified aluminum silicate sol (organic solvent: methanol, solid content 50% by weight) is charged into a mixer with respect to 100 parts by weight of iron powder (Table 1 soft magnetic particles B) having an average particle size of 35.3 μm. Mixed for hours. Next, the mixture was heated at 100 ° C. and mixed for about 1 hour, and then filtered to obtain iron powder.

  Table 3 shows various properties of the obtained iron powder.

Comparative Example 4 (Japanese Patent Laid-Open No. 9-125111, Example Additional Test)
After adding 18.58 g of sodium methoxide and 160.85 g of tetraethoxysilane to 500 ml of ethanol and stirring well, 1000 g of carbonyl iron powder (average particle size: 3.2 μm) was added to the solution while stirring. Next, the mixed solution was stirred with an ultrasonic disperser and heated in an oven while being uniformly dispersed. When distilled water was gradually added to the dispersion, a precipitate was formed at the bottom of the container, and the precipitate was filtered, dried, and heated at 300 ° C. for 30 minutes to obtain a metal powder.

  Table 3 shows various properties of the obtained metal powder.

Examples 2-2 to 2-9, Comparative Examples 5 to 13:
A dust core was obtained in the same manner as in Example 2-1, except that various types of soft magnetic materials were used.

  Table 4 shows various characteristics of the obtained dust core.

  The soft magnetic material according to the present invention has excellent fluidity, can be compression-molded at a low pressure, and has little change in electric resistance even when fired at a high temperature. Is preferred.

  The powder magnetic core according to the present invention is suitable as a high-performance powder magnetic core because the soft magnetic material is used so that the electric resistance value is high and the electric resistance value hardly changes even when fired at a high temperature. It is.

Claims (8)

A soft magnetic material comprising a composite particle powder in which an inorganic compound adheres to or covers the particle surface of the soft magnetic particle powder. 2. The soft magnetic material according to claim 1, wherein the inorganic compound comprises a compound containing one or more elements selected from aluminum, zirconium, titanium, silicon, magnesium, iron and phosphorus. The inorganic compound is an inorganic compound and / or a phosphorus compound produced from a metal alkoxide containing one or more metal elements selected from aluminum, zirconium, titanium, silicon, magnesium or iron. Item 3. The soft magnetic material according to item 1 or 2. The soft magnetic material according to any one of claims 1 to 3, wherein a rate of change in compression density of the composite particle powder is less than 5%. The soft magnetic material according to any one of claims 1 to 4, wherein a change rate of a volume resistivity value before and after heating of the composite particle powder is 20% or less. The metal alkoxide solution is added to a suspension in which soft magnetic particle powder is dispersed in an organic solvent, and then air-dried and then dried at 60 to 120 ° C. The manufacturing method of the soft-magnetic material of description. A metal alkoxide solution is added to a suspension of soft magnetic particle powder dispersed in an organic solvent, a phosphoric acid solution is added, air-dried, and dried at 60 to 120 ° C. Item 6. A method for producing a soft magnetic material according to Item 5. A dust core formed by compression-molding the soft magnetic material according to any one of claims 1 to 5.