JP2007042883A - Soft magnetic material, its manufacturing method, and dust core containing same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a soft magnetic material having excellent oxidation resistance, compressibility and fluidity while reducing the change of an electric resistance value even when baked at a high temperature, and a dust core containing the soft magnetic material and having a superior magnetic stability and the high electric resistance value. <P>SOLUTION: The soft magnetic material is composed of composite particle powder in which an inorganic compound consisting of silicon, the inorganic compound consisting of phosphorus, and the inorganic compound consisting of aluminum as required, are attached or coated on the particle surfaces of soft-magnetic particle powder. The soft magnetic material is obtained in such a manner that silicon alcoxide is added into a suspension in which soft-magnetic particle powder is dispersed in an organic solvent, and a phosphoric-acid solution is added, mixed/agitated and dried at 30 to 120°C. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention is excellent in oxidation resistance, compressibility, and fluidity, and has excellent magnetic stability including a soft magnetic material having little change in electrical resistance even when baked at a high temperature, and the magnetic stability containing the soft magnetic material. A dust core having a high electric resistance value is provided.

  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.

  Soft magnetic metal powder is easily oxidized and corroded when exposed to air and moisture in the air, and the metal part of the particle surface is gradually oxidized to deteriorate the magnetic properties. Therefore, it is necessary to coat the particle surface with an oxide or the like. However, if a sufficient antioxidation effect is obtained, the coating becomes thick, and when the powder magnetic core is formed, the proportion of the soft magnetic particle powder in the powder magnetic core is reduced, which makes it difficult to increase the magnetic flux density. .

  Conventionally, a composite magnetic particle having an insulating coating containing at least one of a metal phosphate and an oxide and a lubricant coating containing a metal soap surrounding the surface of the insulating coating on the surface of the metal magnetic particle (patent) A technique using Document 1) as a powder for a dust core is disclosed.

  Also, a soft magnetic metal powder (Patent Document 2 and Patent Document 3) in which a phosphate film and a sodium silicate film are formed on the surface of the soft magnetic metal powder, or the surface of the magnetic powder is coated with a silica-based sol film. A technique of using the magnetic powder (Patent Document 4) as a powder for a powder magnetic core is disclosed.

  Further, a coated metal powder for dust core (Patent Document 5) in which the surface of a ferromagnetic metal powder is coated with a phosphate or a phosphorus compound containing aluminum is disclosed.

  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, a magnetic material powder (Patent Document 6) is disclosed in which a metal alkoxide is hydrolyzed and a hydroxide is adsorbed on the surface of the metal powder.

JP 2005-129716 A JP 2002-170707 A JP 2003-197416 A JP 2001-196217 A JP 2005-113258 A JP-A-9-125111

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

  That is, Patent Document 1 has an insulating coating containing at least one of a metal phosphate and an oxide and a lubricant coating containing metal soap surrounding the surface of the insulating coating on the surface of the metal magnetic particles. Although it is described that composite magnetic particles are used as powders for powder magnetic cores, silicon oxide is used as insulating coatings or lubricant particles, compared with coatings of inorganic compounds made of silicon having silanol groups. Since the affinity between water and water is low and the ability to trap moisture and oxygen is poor, it is difficult to obtain high oxidation resistance.

  In Patent Documents 2 to 4, 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 the soft magnetic metal powder is used for a dust core. Although it is described that it is used as a powder, compressibility is not taken into consideration, and as shown in a later-described comparative example, the rate of change in compression density indicating compressibility is as bad as 5.3%.

  Patent Document 5 discloses a coated metal powder for a dust core in which the surface of a ferromagnetic metal powder is coated with a phosphate or a phosphorus compound containing aluminum. Since a compound has a low ability to trap oxygen and moisture in the air, it is difficult to obtain high oxidation resistance.

  Patent Document 6 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.

  Therefore, the present invention is to obtain a soft magnetic material that is excellent in oxidation resistance and fluidity, can be compression-molded at a low pressure, and has a small volume resistivity change even when fired at a high temperature. Technical issue.

  As a result of intensive studies to solve the above problems, the present inventors have found that the soft magnetic particle powder having an inorganic compound composed of silicon and phosphorus adhered or coated on the particle surface is resistant to oxidation and Excellent fluidity, compression molding is possible at low pressure, and there is little change in electrical resistance value even when fired at high temperature, and the soft magnetic particle powder is used as a soft magnetic material for a dust core. As a result, it was found that a dust core having a high electric resistance value was obtained, and the present invention was achieved.

  That is, the present invention is characterized in that the soft magnetic particle powder is composed of an inorganic compound made of silicon and an inorganic compound made of phosphorus, or a composite particle powder in which a composite of the inorganic compound is adhered or coated. It is a soft magnetic material (Invention 1).

  The present invention also provides an inorganic compound composed of aluminum, an inorganic compound composed of silicon and an inorganic compound composed of phosphorus, or a composite particle powder in which a composite of the inorganic compound is attached to or coated on the particle surface of the soft magnetic particle powder. A soft magnetic material characterized in that (Invention 2).

  The present invention is the soft magnetic material according to any one of the first and second aspects, wherein the inorganic compound comprising silicon contains a silanol group (the third aspect).

  Further, the present invention is the soft magnetic material according to any one of the present inventions 1 to 3, wherein the oxidation resistance of the composite particle powder is 10% or less (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 compression density of the composite particle powder is less than 5% (Invention 5).

  Further, the present invention is the soft magnetic material according to any one of the present inventions 1 to 5, 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 6). .

  Further, the present invention is characterized in that after adding silicon alkoxide to a suspension in which soft magnetic particle powder is dispersed in an organic solvent, a phosphoric acid solution is added, and after mixing and stirring, drying is performed at 30 to 120 ° C. This is a method for producing a soft magnetic material according to any one of Invention 1 or Inventions 3 to 6 (Invention 7).

  In the present invention, after adding a solution in which aluminum alkoxide is dispersed or dissolved in an organic solvent to soft magnetic particle powder, silicon alkoxide is added, then a phosphoric acid solution is added, and after mixing and stirring, 30 to A method for producing a soft magnetic material according to any one of the present inventions 2 to 6, wherein the soft magnetic material is dried at 120 ° C. (Invention 8).

  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 sixth aspects (Invention 9).

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

  The dust core according to the present invention uses the soft magnetic material, so that there is little deterioration in the magnetic properties due to oxidation, the electrical resistance value is high, and the electrical resistance value changes even when fired at a high temperature. Because there are few, it is suitable as a high-performance dust core.

  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 includes an inorganic compound composed of silicon and an inorganic compound composed of phosphorus or a composite of these inorganic compounds, an inorganic compound composed of aluminum, an inorganic compound composed of silicon, and the surface of the soft magnetic particle powder. It consists of a composite particle powder to which an inorganic compound comprising phosphorus or a composite of these inorganic compounds adheres or is coated.

  The coating amount of the inorganic compound generated from the silicon alkoxide of the soft magnetic material according to the present invention depends on the specific surface area of the soft magnetic particle powder as the particles to be treated, but is 0.0005 to 5.0% by weight in terms of Si. preferable. When the amount is less than 0.0005% by weight, the amount of the inorganic compound composed of silicon to be attached or coated is too small, so that the effect of improving the oxidation resistance, compressibility and fluidity which is the object of the present invention cannot be obtained. When the amount exceeds 5.0% by weight, the number of inorganic compounds not involved in magnetism increases, and thus magnetic characteristics are deteriorated. When considering the oxidation resistance, compressibility, fluidity and magnetic properties of the obtained soft magnetic material, 0.00075 to 2.5 wt% is more preferable, and still more preferably 0.001 to 1.0 wt%. is there.

  The coating amount of the phosphorus compound of the soft magnetic material according to the present invention is preferably 0.0005 to 10.0% by weight in terms of P, although it depends on the specific surface area of the soft magnetic particle powder that is the particle to be treated. When the amount is less than 0.0005% by weight, the amount of the inorganic compound composed of phosphorus to be adhered or coated is too small, so that the effect of improving the compressibility and fluidity of the present invention cannot be obtained. When the content exceeds 10.0% by weight, the number of inorganic compounds not involved in magnetism increases, and thus magnetic characteristics deteriorate, which is not preferable. When considering the compressibility, fluidity and magnetic properties of the resulting soft magnetic material, it is more preferably 0.00075 to 7.5% by weight, still more preferably 0.001 to 5.0% by weight.

  The coating amount of the inorganic compound made of aluminum generated from the aluminum alkoxide of the soft magnetic material according to the present invention depends on the specific surface area of the soft magnetic particle powder as the particles to be treated, but is 0.0005 to 5.0 in terms of Al. % By weight is preferred. It is superior in compressibility and fluidity by adhering or coating an inorganic compound made of silicon in addition to an inorganic compound made of silicon and an inorganic compound made of aluminum in the range of 0.0005 to 5.0% by weight in terms of Al. Improvement effect is obtained. When the amount exceeds 5.0% by weight, the increase in the number of inorganic compounds not involved in magnetism decreases the magnetic properties, which is not preferable. When considering the compressibility, fluidity and magnetic properties of the resulting soft magnetic material, the amount is more preferably 0.0075 to 4.0% by weight, and still more preferably 0.001 to 3.0% 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 diameter exceeds 500.0 μm, the particle diameter is too large, and when used in a dust core, the packing density is lowered, which is not preferable. An average particle size of less than 1.0 μm 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. When the change rate of the compression density is 5.0% or more, a high pressure is required when producing a dust core, which is not preferable. More preferably, it is 4.0% or less, More preferably, it is 3.0% or less.

  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.

  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.

  In the soft magnetic material according to the present invention, the inorganic compound made of silicon contains a silanol group. By containing silanol groups, the affinity with moisture and oxygen in the air is increased, and moisture and oxygen can be trapped effectively, thereby suppressing the corrosion of soft magnetic particle powder caused by moisture and oxygen. be able to.

  The oxidation resistance of the soft magnetic material according to the present invention is preferably 10.0% or less in the evaluation method described later. When the oxidation resistance exceeds 10.0%, the deterioration of the magnetic characteristics over time is too large, which is not preferable. More preferably, it is 9.0% or less, More preferably, it is 8.0% or less.

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

  The soft magnetic material according to the first aspect of the present invention is obtained by adding silicon alkoxide to a suspension obtained by dispersing soft magnetic particle powder, which is a particle powder to be treated, in an organic solvent, adding a phosphoric acid solution, mixing and stirring, and then adding 30 It can be obtained by drying at ~ 120 ° C. As a method for adding silicon alkoxide, in addition to the above addition method, a silicon alkoxide solution dispersed or dissolved in an organic solvent may be added to the soft magnetic particle powder.

  In addition, the soft magnetic material according to the second aspect of the present invention includes adding a solution in which an aluminum alkoxide is dispersed or dissolved in an organic solvent to a soft magnetic particle powder that is a particle to be treated, then adding a silicon alkoxide, It can be obtained by adding an acid solution, mixing and stirring, and drying at 30 to 120 ° C. As a method for adding aluminum alkoxide and silicon alkoxide, in addition to the above addition method, a solution in which aluminum alkoxide is dispersed or dissolved in an organic solvent may be added to a suspension obtained by dispersing soft magnetic particle powder in an organic solvent. Alternatively, a solution obtained by adding silicon alkoxide to a solution in which aluminum alkoxide is dispersed or dissolved in an organic solvent may be added simultaneously.

  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.

  In the evaluation method described later, the compressibility of the soft magnetic particle powder in the present invention usually has a value at which the rate of change in compression density exceeds 5%.

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

  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 oxidation resistance of the soft magnetic particle powder in the present invention usually has a value exceeding 10% in the evaluation method described later.

  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 kind of alkoxide constituting the silicon alkoxide used in the present invention, methoxide, ethoxide, propoxide, isopropoxide, oxyisopropoxide, butoxide and the like can be used. Further, ethyl silicate and methyl silicate obtained by partially hydrolyzing and condensing tetraethoxysilane or tetramethoxysilane can be used. Considering the uniformity of treatment and treatment effect, the silicon alkoxide is preferably tetraethoxysilane, tetramethoxysilane, methyl silicate or the like.

  As the kind of alkoxide constituting the aluminum alkoxide used in the present invention, methoxide, ethoxide, propoxide, isopropoxide, oxyisopropoxide, butoxide and the like can be used. Considering the uniformity of treatment and the treatment effect, the aluminum alkoxide is preferably aluminum triisopropoxide, aluminum tributoxide or the like.

  Moreover, when the said silicon alkoxide and aluminum alkoxide are solid, in order to perform a more uniform process, it is preferable to disperse | distribute or dissolve in the above-mentioned organic solvent beforehand, and to use.

  In addition, hydrolysis of the silicon alkoxide and aluminum alkoxide does not require any particular addition of water in order to attach or coat a finer inorganic compound to the surface of the soft magnetic particles. It is preferable to carry out hydrolysis with moisture contained in the particles.

  The amount of silicon alkoxide added varies depending on the specific surface area of the soft magnetic particle powder, but is usually 0.0005 to 5.0 parts by weight in terms of Si per 100 parts by weight of the soft magnetic particle powder, preferably 0.00075 to 2.5 parts by weight, more preferably 0.001 to 1.0 parts by weight.

  The amount of aluminum alkoxide added varies depending on the specific surface area of the soft magnetic particle powder, but is usually 0.0005 to 5.0 parts by weight in terms of Al per 100 parts by weight of the soft magnetic particle powder, preferably 0.0075 to 4.0 parts by weight, more preferably 0.001 to 3.0 parts by weight.

  The phosphoric acid used in the present invention is an acid formed by hydrating diphosphorus pentoxide, and metaphosphoric acid, pyrophosphoric acid, orthophosphoric acid, triphosphoric acid, and tetraphosphoric acid can be used, preferably orthophosphoric acid. is there.

  The addition amount of phosphoric acid in the present invention varies depending on the specific surface area of the soft magnetic particle powder, but is usually 0.0005 to 10.0 parts by weight in terms of P per 100 parts by weight of the soft magnetic particle powder, preferably 0. 0.005 to 7.5 parts by weight, more preferably 0.001 to 5.0 parts by weight.

  As equipment for mixing soft magnetic particle powder with silicon alkoxide solution, aluminum alkoxide solution and phosphoric acid solution, there are high-speed agitate type mixers, specifically Henschel mixer, speed mixer, ball cutter, power mixer, hybrid mixer, A cone blender or the like may be used.

  When phosphoric acid is added as an aqueous solution, it is preferably added in small amounts in order to prevent hydrolysis from proceeding rapidly.

The mixing / stirring of the soft magnetic particle powder with the silicon alkoxide solution, the aluminum alkoxide solution and the phosphoric acid solution is preferably performed at room temperature to the boiling point of the organic solvent used. From the viewpoint of preventing oxidation of the soft magnetic particles, it is preferable to perform the reactions under an inert gas atmosphere such as N ₂ gas.

The obtained soft magnetic particle powder is dried in a draft at room temperature for 3 to 24 hours, and then dried in a temperature range of 60 to 120 ° C, or dried under reduced pressure in a temperature range of 30 to 80 ° C. Can be obtained. When the above temperature range is exceeded, silanol groups of the inorganic compound made of silicon decrease, which makes it difficult to suppress corrosion of the soft magnetic particle powder due to moisture and oxygen, and is not preferable because the oxidation resistance decreases. . Drying can be performed in air or in an inert gas atmosphere such as N ₂ gas, but from the same viewpoint as described above, it is preferably in an inert gas atmosphere such as N ₂ gas.

  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. Obtainable.

  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 90.0% or more, preferably 91.0%, more preferably 92.0% 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%.

  The change rate (%) of the magnetic flux density of the dust core according to the present invention is preferably 2.0% or less, more preferably 1.5% or less, and even more preferably 1.0% or less.

<Action>
The most important point in the present invention is that the surface of the soft magnetic particle powder is adhered or coated with an inorganic compound composed of silicon and an inorganic compound composed of phosphorus or an inorganic compound composed of aluminum, an inorganic compound composed of silicon, and an inorganic compound composed of phosphorus. This is the fact that the soft magnetic material comprising the composite particle powder is excellent in oxidation resistance, compressibility and fluidity, and has little change in volume resistivity even when fired at high temperature.

  As the reason why the fluidity of the soft magnetic material according to the present invention is excellent, the present inventor considered that the inorganic compound composed of silicon and the inorganic compound composed of aluminum attached to or coated on the surface of the soft magnetic particle powder are organic solvents. It is presumed that very fine protrusions were produced on the surface of the particles by forming from metal alkoxide using.

  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 the 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 said that the inorganic compound comprising silicon adhering to or covering the particle surface of the soft magnetic particle powder and By forming an inorganic compound made of aluminum from a metal alkoxide using an organic solvent, it becomes possible to attach or coat with fine and fine particles, and the soft magnetic particle powder, which is a particle to be treated, is affected by heat. It is estimated that it became difficult.

  The reason for the superior oxidation resistance of the soft magnetic material according to the present invention is that the present inventor has an affinity for moisture and oxygen in the air because the silicon-containing inorganic compound contains a silanol group. It is presumed that the corrosion of the soft magnetic particle powder due to moisture and oxygen could be suppressed because the moisture and oxygen can be effectively trapped. Further, by adding phosphoric acid during production, the surface of the soft magnetic particles reacts with phosphorus to form an inorganic compound composed of phosphorus such as iron phosphate, thereby forming an inorganic composed of silicon containing a silanol group. It is considered that the moisture adhering to the compound or trapped from the coating layer is less likely to enter the soft magnetic particles and is less likely to be oxidized due to its synergistic effect.

  Moreover, it is the fact that the dust core obtained by using the soft magnetic material according to the present invention is excellent in magnetic stability and 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.

  As the reason why the dust core according to the present invention is excellent in magnetic stability, the present inventor used the soft magnetic material according to the present invention having excellent oxidation resistance as a soft magnetic material, so that moisture in the air This is thought to be because corrosion due to oxygen and oxygen could be effectively suppressed.

  Hereinafter, the present invention will be described in detail with reference to examples.

  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 inorganic compound made of aluminum, the inorganic compound made of silicon, and the inorganic compound made of phosphorus adhered or coated on the surface of the soft magnetic particle powder is “X-ray fluorescence analyzer 3063M type” (Rigaku Denki Kogyo Co., Ltd.) Measured in accordance with JIS K0119 “General Rules for Fluorescence X-ray Analysis”.

Silanol groups inorganic compound consisting of silicon soft magnetic particulate material is contained, "Infrared absorption spectrum FTIR-8700" used (manufactured by Shimadzu Corporation), silanol groups found in the vicinity of 3250cm ^-1 (Si-OH) This was performed by confirming the presence or absence of absorption of Si-OH stretching vibration.

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 1 to determine the rate of change (%) in compression density.

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

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 2 to obtain a volume resistivity (mΩ · cm )

<Equation 2>
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 Equation 3 to obtain the rate of change of the volume resistivity value.

<Equation 3>
Change rate (%) of volume resistivity before and after heating = {volume resistivity (before heating) −volume resistivity (after heating)} / volume resistivity (before heating) × 100

  The oxidation resistance (%) of each particle powder is determined by first subjecting the sample to be measured to an environment of 60 ° C. and a relative temperature of 90% for 14 days, and then performing pressure molding in the same manner as the volume resistivity measurement. A cylindrical sample to be measured was prepared. A similar columnar sample was prepared for the measured use before exposure, and each volume specific resistance value before and after exposure was measured.

<Equation 4>
Oxidation resistance (%) = {volume specific resistance value (before exposure) −volume specific resistance value (after exposure)} / volume specific resistance value (before exposure) × 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 measurement 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 rate of change of specific resistance values before and after heat treatment using the heat treatment before the specific resistance R _{0 (mΩ} · cm), and after heat treatment of the specific resistance R _{1 (mΩ} · cm), the following Expression 5 Each measurement value was inserted, and the change rate (%) of the specific resistance value was obtained.

<Equation 5>
Specific resistance change rate (%) = {(R ₀ −R ₁ ) / R ₀ )} × 100

  The rate of change (%) in the magnetic flux density of the dust core is determined by the method described later for the soft magnetic material exposed for 14 days in an environment at a temperature of 60 ° C. and a relative temperature of 90%, and before the exposure. The magnetic flux density before and after exposure was measured at a magnetic field H of 10 kA / m, and the rate of change of the magnetic flux density was determined by the following equation (6).

<Equation 6>
Change rate of magnetic flux density (%) = {magnetic flux density (before exposure) −magnetic flux density (after exposure)} / magnetic flux density (before exposure) × 100

<Example 1-1: Production of soft magnetic material>
Iron powder (particle shape: granular, average particle diameter 65.4 μm, rate of change in compression density 5.9%, fluidity 53, volume resistivity 183.2 mΩ · cm, rate of change in volume resistivity 36 before and after heating 36 .3%, oxidation resistance 16.6%) To 10 kg, an acetone solution in which 2.6 g of aluminum isopropoxide is dispersed was added, 0.9 g of tetraethoxysilane was added, and then, into the mixed solution, 3.7 g of an aqueous phosphoric acid solution (phosphoric acid content: 85 wt%) was added dropwise, and the mixture was stirred and mixed for 20 minutes at a reaction temperature of 45 ° C. under a N ₂ stream.

  The obtained mixed solution was dried under reduced pressure at 45 ° C. to obtain a soft magnetic material.

The obtained soft magnetic material was granular particles having an average particle diameter of 65.5 μm. The rate of change in compression density is 2.5%, the fluidity is 79, the volume resistivity is 219.5 mΩ · cm, the rate of change in volume resistivity before and after heating is 6.7%, and the oxidation resistance is 7.6. %Met. The surface treated product adhered or coated was 0.003% by weight in terms of Al, 0.001% by weight in terms of Si, and 0.010% by weight in terms of P. When an infrared absorption spectrum of the obtained soft magnetic material was measured, absorption was observed in the vicinity of 3250 cm ⁻¹ , and it was confirmed that a silanol group was present.

<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 92.7 vol%, the specific resistance value before heat treatment is 247.7 mΩ · cm, the specific resistance value after heat treatment is 225.2 mΩ · cm, The change rate of the specific resistance value was 8.1%, and the change rate of the magnetic flux density was 0.6%.

  A soft magnetic material and a dust core were prepared according to Examples 1-1 and 2-1. Various characteristics of each manufacturing condition and the obtained soft magnetic material 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 1-3:
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. When the infrared absorption spectrum of each soft magnetic material obtained in Examples 1-2 to 1-7 was measured, absorption was observed in the vicinity of 3250 cm ⁻¹ , and a silanol group may be present in any soft magnetic material. confirmed.

In Comparative Example 2, a commercially available silica sol (average particle size 10 to 20 nm, SiO ₂ content 20% by weight) dispersed in ethanol 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 having an average particle size of 65.4 μm (Table 1 soft magnetic particles A). 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. When the infrared absorption spectrum of each soft magnetic material obtained in Comparative Examples 2 and 3 was measured, no absorption was observed in the vicinity of 3250 cm ⁻¹ , and the presence of silanol groups was not confirmed in any soft magnetic material.

Examples 2-2 to 2-9, comparative examples 4 to 11:
A dust core was obtained in the same manner as in Example 2-1, except that the type of the soft magnetic material was variously changed.

  Table 4 shows various characteristics of the obtained dust core.

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

The dust core according to the present invention uses the soft magnetic material, so that there is little deterioration in the magnetic properties due to oxidation, the electrical resistance value is high, and the electrical resistance value changes even when fired at a high temperature. Since there are few, it is suitable as a high performance dust core.

Claims (9)

A soft magnetic material comprising: an inorganic compound comprising silicon and an inorganic compound comprising phosphorus, or a composite particle powder having a composite of the inorganic compound attached or coated on the surface of the soft magnetic particle powder. The surface of the soft magnetic particle powder is composed of an inorganic compound composed of aluminum, an inorganic compound composed of silicon and an inorganic compound composed of phosphorus, or a composite particle powder in which a composite of the inorganic compound is attached or coated. Soft magnetic material. 3. The soft magnetic material according to claim 1, wherein the inorganic compound made of silicon contains a silanol group. The soft magnetic material according to any one of claims 1 to 3, wherein the oxidation resistance of the composite particle powder is 10% or less. The soft magnetic material according to any one of claims 1 to 4, 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 5, wherein a rate of change of the volume resistivity value before and after the heating of the composite particle powder is 20% or less. The silicon alkoxide is added to a suspension in which soft magnetic particle powder is dispersed in an organic solvent, and then a phosphoric acid solution is added thereto, followed by mixing and stirring, followed by drying at 30 to 120 ° C. A method for producing a soft magnetic material according to any one of claims 3 to 6. After adding a solution in which aluminum alkoxide is dispersed or dissolved in an organic solvent to soft magnetic particle powder, add silicon alkoxide, then add a phosphoric acid solution, and after mixing and stirring, drying at 30 to 120 ° C. The method for producing a soft magnetic material according to claim 2, wherein: A dust core formed by compression-molding the soft magnetic material according to any one of claims 1 to 6.