JP2009054615A - Powder magnetic core, and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a powder magnetic core of which core characteristics are improved, especially by introducing parameters of frequency and cumulation of particle diameters and increasing a filling factor of amorphous soft magnetic alloy powder, and to provide a manufacturing method thereof. <P>SOLUTION: Frequency of the particle diameters in an cumulation range 10-90% is suppressed to be not higher than 8% by mixing 4 μm classified powder 5-50 mass% in reference powder (D50=12.25 μm) of amorphous soft magnetic alloy power, for example, mainly containing Fe and further containing at least two out of P, C, B, Si. As a result, the filling factor of the amorphous soft magnetic alloy powder with respect to the powder magnetic core can be increased as compared with the powder magnetic core containing only the reference powder, core loss can be reduced, and furthermore, magnetic permeability can be increased. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a dust core in which an amorphous soft magnetic alloy powder is solidified by a binder, and in particular, the core characteristics are improved by increasing the filling rate of the amorphous soft magnetic alloy powder. The present invention relates to a dust core and a method for producing the same.

  In the powder core using the amorphous soft magnetic alloy powder shown in Patent Document 1 below, the structure is relaxed by heat treatment at a lower temperature than the Fe-Al-Si alloy (Sendust (registered trademark)). Since distortion during molding can be released, core loss can be appropriately reduced by restoring sufficient magnetic properties of the powder and maintaining insulation between the powders.

  In a dust core, it is extremely important to improve core characteristics by reducing core loss and increasing permeability.

In order to improve the core characteristics, it was important to improve the filling rate of the amorphous soft magnetic alloy powder in the powder core.
JP 2005-307291 A JP 2004-349585 A Japanese Patent Laid-Open No. 2000-114022 JP 2004-273564 A JP-A-5-299232 JP-A-4-343207 JP 2001-196216 A

  As shown in Patent Document 2 to Patent Document 7, by mixing magnetic powders having different average particle diameters, the filling rate is improved by interposing small-diameter magnetic powder in the gap between large-diameter magnetic powders. There are many ideas from the past.

  However, in the conventional methods for improving the filling rate described in Patent Documents 2 to 7, the parameters of the frequency distribution and accumulation of the particle size distribution are not considered.

  Therefore, the present invention is to solve the above-described conventional problems, and in particular, by introducing the frequency distribution and accumulation parameters of the particle size distribution, the filling rate of the amorphous soft magnetic alloy powder is increased, and the core characteristics are improved. An object of the present invention is to provide a pressed powder core and a manufacturing method thereof.

The present invention provides a powder core in which amorphous soft magnetic alloy powder is solidified and formed by a binder,
The amorphous magnetic alloy powder is mainly composed of Fe, and includes at least two of P, C, B, and Si,
The frequency of the particle size distribution of the amorphous magnetic alloy powder is 8% or less in a cumulative range of 10% to 90%.

  As a result, the filling rate of the amorphous soft magnetic alloy powder can be effectively improved, and the core characteristics can be improved by reducing the core loss and increasing the magnetic permeability.

  In the present invention, the difference between the maximum frequency and the minimum frequency of the particle size distribution is preferably 4% or less. If the difference between the maximum frequency and the minimum frequency of the particle size distribution becomes large, the filling rate of the amorphous soft magnetic alloy powder cannot be sufficiently improved, so the difference between the maximum frequency and the minimum frequency of the particle size can be reduced. Is preferred.

  In the present invention, the frequency of the particle size distribution is more preferably 6% or less, the frequency of the particle size distribution is 4% or less, and the difference between the maximum frequency and the minimum frequency of the particle size is 2% or less. More preferably it is. Thereby, the filling rate of the amorphous soft magnetic alloy powder can be improved more effectively, and the core loss can be reduced more appropriately, and the magnetic permeability can be increased.

  In the present invention, the amorphous soft magnetic alloy powder is preferably represented by the following composition formula.

_{Fe 100-a-b-x} -y-z-w-t Co a Ni b M x P y C z B w Si t
However, M is one or more elements selected from Cr, Mo, W, V, Nb, Ta, Ti, Zr, Hf, Pt, Pd, Au, Sn, and Al, and shows a composition ratio a , B, x, y, z, w, and t are 0 atomic% ≦ x ≦ 5 atomic%, 0 atomic% ≦ y ≦ 15 atomic%, 0 atomic% <z ≦ 8 atomic%, 1 atomic% ≦ w ≦ 15 atomic%, 0 atomic% ≦ t ≦ 12 atomic%, 0 atomic% ≦ a ≦ 20 atomic%, 0 atomic% ≦ b ≦ 5 atomic%, 70 atomic% ≦ (100-ab-xyz) −w−t) ≦ 83 atomic%. In the above composition, the addition amount y of P is more preferably 2 atomic percent or more, and the addition amount w of B is more preferably 12 atomic percent or less. The addition amount t of Si is more preferably 0.5 atomic% ≦ t ≦ 8 atomic%.

The present invention also relates to a method for producing a dust core obtained by solidifying and molding an amorphous soft magnetic alloy powder with a binder.
A first step of forming the amorphous soft magnetic alloy powder containing Fe as a main component and containing at least two of P, C, B, and Si by an atomizing method;
A second step of adjusting the frequency of the particle size distribution of the amorphous magnetic alloy powder to 8% or less in the cumulative range of 10% to 90% during the first step or after the first step;
A third step in which the amorphous soft magnetic alloy powder and an additive containing a binder and a lubricant are mixed and granulated to form a granulated powder;
A fourth step of compression-molding the granulated powder to form a core precursor of a predetermined shape;
A fifth step of heat-treating the core precursor and removing strain generated in the amorphous soft magnetic alloy powder by compression molding;
It is characterized by having.

  As a result, a compact core having a high filling ratio of the amorphous soft magnetic alloy powder and excellent core characteristics can be easily and appropriately manufactured.

In the present invention, when the amorphous soft magnetic alloy powder obtained in the first step is used as a reference powder, it has an average particle diameter (D50) smaller than the average particle diameter (D50) of the reference powder, An amorphous soft magnetic alloy powder (adjusted powder) formed by an atomizing method containing at least two of P, C, B, and Si as a main component is prepared.
In the second step, the reference powder and an appropriate amount of the adjusted powder are mixed so that the frequency of the particle size distribution of the amorphous magnetic alloy powder is 8% or less in a cumulative range of 10% to 90%. It is preferable to do. Thereby, the filling rate of the amorphous soft magnetic alloy powder can be easily increased as compared with the reference powder.

  Further, it is preferable that the adjustment powder is mixed within the range of 5% by mass to 50% by mass because the filling rate of the amorphous soft magnetic alloy powder can be effectively increased as compared with the reference powder.

  Moreover, it is more preferable to mix the said adjustment powder within the range of 10 mass%-20 mass%.

In the present invention, when the amorphous soft magnetic alloy powder obtained in the first step is used as a reference powder, it has an average particle diameter (D50) larger than the average particle diameter (D50) of the reference powder, and Fe Amorphous soft magnetic alloy powder (adjusted powder) formed by an atomizing method containing at least two of P, C, B, and Si as a main component,
In the second step, the reference powder and an appropriate amount of the adjusted powder are mixed so that the frequency of the particle size distribution of the amorphous magnetic alloy powder is 8% or less in a cumulative range of 10% to 90%. May be. In such a case, it is preferable to mix the adjusted powder within a range of 5% by mass to 20% by mass.

  In the present invention, it is preferable that in the second step, the difference between the maximum frequency and the minimum frequency of the particle size is adjusted to 4% or less.

  In the present invention, in the second step, the frequency of the particle size distribution is more preferably 6% or less, the frequency of the particle size distribution is 4% or less, and the maximum frequency and the minimum frequency of the particle size distribution. It is more preferable to adjust the difference to 2% or less.

  In the present invention, it is preferable to form the amorphous magnetic alloy powder represented by the following composition formula.

_{Fe 100-a-b-x} -y-z-w-t Co a Ni b M x P y C z B w Si t
However, M is one or more elements selected from Cr, Mo, W, V, Nb, Ta, Ti, Zr, Hf, Pt, Pd, Au, Sn, and Al, and shows a composition ratio a , B, x, y, z, w, and t are 0 atomic% ≦ x ≦ 5 atomic%, 0 atomic% ≦ y ≦ 15 atomic%, 0 atomic% <z ≦ 8 atomic%, 1 atomic% ≦ w ≦ 15 atomic%, 0 atomic% ≦ t ≦ 12 atomic%, 0 atomic% ≦ a ≦ 20 atomic%, 0 atomic% ≦ b ≦ 5 atomic%, 70 atomic% ≦ (100-ab-xyz) −w−t) ≦ 83 atomic%.

  According to the dust core of the present invention, the filling rate of the amorphous soft magnetic alloy powder can be effectively improved, and the core characteristics can be improved by reducing the core loss and increasing the magnetic permeability.

  Further, according to the method for producing a dust core of the present invention, a dust core having a high filling rate of the amorphous soft magnetic alloy powder and excellent core characteristics can be produced easily and appropriately.

(Amorphous soft magnetic alloy powder and compacted core form)
The dust core in the present invention is obtained by solidifying and molding an amorphous soft magnetic alloy powder with a binder.

  The amorphous soft magnetic alloy powder has a substantially spherical or ellipsoidal shape. A large number of the amorphous soft magnetic alloy powders exist in the structure, and the amorphous soft magnetic alloy powders are insulated from each other by the binder.

  The amorphous magnetic alloy powder contains Fe as a main component and contains at least P, C, B, and Si. The amorphous soft magnetic alloy powder is preferably represented by the following composition formula.

_{Fe 100-a-b-x} -y-z-w-t Co a Ni b M x P y C z B w Si t
However, M is one or more elements selected from Cr, Mo, W, V, Nb, Ta, Ti, Zr, Hf, Pt, Pd, Au, Sn, and Al, and shows a composition ratio a , B, x, y, z, w, and t are 0 atomic% ≦ x ≦ 5 atomic%, 0 atomic% ≦ y ≦ 15 atomic%, 0 atomic% <z ≦ 8 atomic%, 1 atomic% ≦ w ≦ 15 atomic%, 0 atomic% ≦ t ≦ 12 atomic%, 0 atomic% ≦ a ≦ 20 atomic%, 0 atomic% ≦ b ≦ 5 atomic%, 70 atomic% ≦ (100-ab-xyz) −w−t) ≦ 83 atomic%.

  Since the amorphous soft magnetic alloy powder of the present embodiment includes Fe exhibiting magnetism and metalloid elements such as P, C, and B having an amorphous forming ability, the amorphous phase is the main phase. In addition, it exhibits excellent soft magnetic properties.

  Further, by adding an element M (one or more element elements of Cr, Mo, W, V, Nb, Ta, Ti, Zr, Hf, Pt, Pd, Au, Sn, and Al). Corrosion resistance can be improved.

  Furthermore, in the above composition, the amorphous soft magnetic alloy powder has a P addition amount y of more preferably 2 atomic% or more, and a B addition amount w of 12 atomic% or less. The addition amount t of Si is more preferably 0.5 atomic% ≦ t ≦ 8 atomic%. By setting it as such a composition, the temperature interval (DELTA) Tx of the supercooling liquid represented by the type | formula of (DELTA) Tx = Tx-Tg (however, Tx shows crystallization start temperature and Tg shows glass transition temperature) shows 20K or more. However, depending on the composition, ΔTx has a remarkable temperature interval of 30K or more, and further 50K or more, and it becomes easier to become amorphous.

  The Fe amount (100-abxxyz-wt) of the magnetic powder of the present embodiment is preferably 70 atom% or more and 83 atom% or less, and 72 atom% or more and 82 atom% or less. It is more preferable that it is 73 atomic% or more and 80 atomic% or less. Thus, high saturation magnetization is shown by the high amount of Fe. If the amount of Fe exceeds 83 atomic%, the converted vitrification temperature (Tg / Tm) indicating the degree of amorphous forming ability of the alloy becomes less than 0.50, and the amorphous forming ability is reduced. It is not preferable. In the above formula, Tm represents the melting point of the magnetic powder.

The Co amount a of the amorphous soft magnetic alloy powder can be in the range of 0 to 20 atomic%, and the Ni amount b can be in the range of 0 to 5 atomic%. Co has the effect of increasing the Curie temperature Tc and enhancing the corrosion resistance. However, if it exceeds 20 atomic%, the amount of Fe is reduced correspondingly, the saturation magnetization becomes 180 × 10 ⁻⁶ Wbm / Kg or less, and Tc rises to a temperature near Tg, which makes it difficult to perform heat treatment. Ni improves corrosion resistance (highest corrosion resistance among ferromagnetic elements), but saturation magnetization tends to decrease at 6 atomic% or more.

  C, P, B, and Si are elements that increase the ability to form an amorphous material, and it is preferable to add at least two of these elements. By adding these elements to Fe and the element M to form a multi-component system, an amorphous phase is formed more stably than in the case of a binary system including only Fe and the element M.

  In particular, since P has a eutectic composition with Fe at a low temperature (about 1050 ° C.), the entire structure tends to form an amorphous state. Further, when P and Si are added simultaneously, the temperature interval ΔTx of the supercooled liquid is easily expressed, the amorphous forming ability is improved, and the production conditions for obtaining an amorphous single phase structure are relatively simple. Can relax in the direction.

  When the composition ratio y of P is in the above range, the temperature interval ΔTx of the supercooled liquid is developed and the amorphous forming ability of the alloy powder is improved.

  Further, the element M represented by Cr, Mo, W, V, Nb, Ta, Ti, Zr, and Hf can form a passivated oxide film on the alloy powder, and can improve the corrosion resistance of the alloy powder. Among these elements, Cr is most effective for improving the corrosion resistance. In the water atomization method, when the molten alloy is in direct contact with water, it is possible to prevent the occurrence of a corroded portion that occurs in the drying step of the alloy powder (visual level). These elements may be added alone or in combination of two or more, for example, in combination of Mo, V and Mo, Cr and V, Cr and Cr, Mo, V, etc. You may do it. Among these elements, Mo and V are slightly inferior in corrosion resistance to Cr, but the amorphous forming ability is improved. Therefore, these elements are selected as necessary. On the other hand, when the addition amount of an element selected from Cr, Mo, W, V, Nb, and Ta exceeds 8 atomic%, the magnetic characteristics (saturation magnetization) deteriorate.

  Of the elements employed as the element M in the composition formula, Zr and Hf have the highest glass-forming ability. Since Ti, Zr, and Hf have strong oxidizing properties, if these elements are added in excess of 8 atomic%, melting the alloy powder raw material in the atmosphere will oxidize the molten metal during melting of the raw material, resulting in magnetic properties (saturation). Magnetization) decreases. These elements also contribute to the formation of a passive film on the powder surface and improve the corrosion resistance.

  Further, the effect of improving the corrosion resistance as the magnetic powder can be obtained by adding one or more kinds of noble metal elements selected from Pt, Pd and Au, and by dispersing these noble metal elements on the powder surface, Corrosion resistance is improved. These noble metal elements may be added alone or in combination with the above-described elements having an effect of improving corrosion resistance such as Cr. Since the above precious metal element does not mix with Fe, if it is added in excess of 8 atomic%, the glass forming ability is lowered, and the magnetic properties (saturation magnetization) are also lowered.

  In order to give the amorphous soft magnetic alloy powder corrosion resistance, the amount of the element M added needs to be 0.5 atomic% or more.

  Of the M in the composition formula, Sn is a low melting point metal, the effect of softening the alloy by adding Sn, the effect of making it easier to obtain a spherical powder when forming the alloy powder by atomization In order to promote such effects, it may be added as necessary. Although not shown for the element M, In, Zn, and Ga can be expected to have the same effect.

  Next, when Si is added, the thermal stability is improved. Therefore, if necessary, 0.5 atomic% or more may be added. On the other hand, if the amount of Si added exceeds 8 atomic%, the melting point increases. Accordingly, the Si amount t needs to be 0.5 atomic% or more and 8 atomic% or less, preferably 2 to 8 atomic%, more preferably 3 atomic% or more and 7 atomic% or less.

  This Si is an important element in the amorphous soft magnetic alloy powder of the present embodiment, and in the process where the molten alloy is rapidly cooled in the presence of water by the water atomization method to form an amorphous alloy, Si prevents the alloy powder from being corroded in addition to the elements that have the effect of improving the corrosion resistance.

  Next, when the B amount w is less than 1 atomic%, it is difficult to obtain a magnetic powder, and when it exceeds 15 atomic%, the melting point increases. Therefore, the B amount w is preferably 1 atom% or more and 15 atom% or less, preferably 2 atom% or more and 10 atom%, and more preferably 4 atom% or more and 9 atom% or less.

  Moreover, since thermal stability improves when C is added, C is preferably added. On the other hand, when the C content z exceeds 8 atomic%, the melting point increases. Accordingly, the C amount z is preferably 8 atomic% or less, more preferably 0 atomic% to 6 atomic% or less, and further preferably 1 atomic% or more and 4 atomic% or less.

  The total composition ratio (y + z + w + t) of these metalloid elements C, P, B and Si is preferably 17 atomic percent or more and 25 atomic percent or less, and more preferably 18 atomic percent or more and 25 atomic percent or less. .

  If the total composition ratio of the metalloid elements exceeds 25 atomic%, the composition ratio of Fe is particularly lowered and the saturation magnetization is lowered, which is not preferable. When the total composition ratio of the metalloid elements is less than 17 atomic%, the amorphous forming ability is lowered and it is difficult to obtain an amorphous phase single phase structure.

  In the magnetic powder of this embodiment, Ge may be contained in the above composition in an amount of 4 atomic% or less.

In any of the above compositions, in this embodiment, the value of Tx / Tm is 0.5 or more, and depending on the composition, 0.55 or more is obtained.
Further, inevitable impurities may be included in addition to the elements represented by the above composition.

  Next, the amorphous soft magnetic alloy powder of the present embodiment preferably has an average aspect ratio of 1 or more and 3.5 or less, more preferably 1 or more and 3 or less. More preferably, it is 2 or more and 2.5 or less. If the average aspect ratio exceeds 3.5, the amount of amorphous powder increases and the molding density decreases. Moreover, it becomes difficult to take insulation between the amorphous soft magnetic alloy powders when the core is formed.

Examples of the binder include epoxy resin, silicone resin, silicone rubber, phenol resin, urea resin, melamine resin, liquid or powdery resin such as PVA (polyvinyl alcohol) or rubber, water glass (Na ₂ O—SiO _{2). 2} ), oxide glass powder (Na ₂ O—B ₂ O ₃ —SiO ₂ , PbO—B ₂ O ₃ —SiO ₂ , PbO—BaO—SiO ₂ , Na ₂ O—B ₂ O ₃ —ZnO, CaO— BaO—SiO ₂ , Al ₂ O ₃ —B ₂ O ₃ —SiO ₂ , B ₂ O ₃ —SiO ₂ ), glassy substances produced by the sol-gel method (SiO ₂ , Al ₂ O ₃ , ZrO ₂ , TiO _2, etc.) As a main component).

(About the frequency and cumulative value of the particle size distribution of the powder)
The characteristic part of the dust core of the present embodiment is that the frequency of the particle size distribution of the amorphous soft magnetic alloy powder is 8% or less, preferably 6% or less in a cumulative range of 10% to 90%. It is in.

  "Powder particle size distribution" can be measured with a particle size distribution measuring device. The particle size distribution can be measured, for example, using a Microtrac particle size distribution measuring device MT3300EX manufactured by Nikkiso Co., Ltd. For example, as a condition of the microtrack particle size distribution measuring device, “volume” is selected for “distribution display”, “standard” is selected for “particle size category selection”, and “1408 μm” is selected for “upper limit of measurement”. “0.021 μm” is selected as the measurement lower limit, “128” is selected as the “number of channels”, and “30 seconds” is selected as the “measurement time”. The measurement principle of this particle size distribution measuring apparatus is a laser diffraction scattering method (microtrack method).

  “Powder particle size distribution” is a number ratio of a large number of amorphous soft magnetic alloy powders having different particle sizes for each particle size category. “Powder particle size distribution” is obtained by accumulating “frequency” from the smaller particle size classification. “Frequency” and “Powder size distribution” are both expressed in%.

  The average particle diameter (D50) of the amorphous soft magnetic alloy powder of this embodiment is in the range of 4 to 55 μm, preferably 4 to 35 μm. The average particle diameter (D50) refers to the particle diameter at a cumulative value of 50%.

  Normally, the “frequency” is very large in the vicinity of the average particle diameter (D50), but in this embodiment, the frequency in the particle size distribution of the amorphous soft magnetic alloy powder is set so that the particle diameter exists uniformly over a wide range. The cumulative range of 10% to 90% is adjusted to 8% or less. As a result, according to the experimental results to be described later, it is possible to improve the decrease in filling rate caused by the high hardness of the amorphous alloy powder without using plastic deformation of the powder. As a result, the core density can be increased while maintaining the insulation between the particles, the core loss can be reduced, and the permeability can be increased to improve the core characteristics. It becomes possible.

  The cumulative range of 0% to 10% (not including 10%) and 90% to 100% (not including 90%) is excluded, but the frequency in this range is usually less than 8%. If this range is included, the “difference between the maximum frequency and the minimum frequency” specified below is 0%, and the “difference between the maximum frequency and the minimum frequency” cannot be properly specified. The cumulative ranges of 0% to 10% (not including 10%) and 90% to 100% (not including 90%) are excluded.

  In the present embodiment, it is preferable that the difference between the maximum frequency and the minimum frequency is 6% or less, more preferably 4% or less, in a cumulative range of 10% to 90%. Thereby, the filling rate of the amorphous soft magnetic alloy powder can be improved more effectively.

  In the present embodiment, it is more preferable that the frequency is 4% or less and the difference between the maximum frequency and the minimum frequency is 2% or less in a cumulative range of 10% to 90%.

(Manufacturing method of the powder core of this embodiment)
First, an amorphous soft magnetic alloy powder having the above composition is formed by an atomizing method (first step). As the atomization method, it is preferable to use a water atomization method or a gas atomization method. Here, for example, when producing the amorphous soft magnetic alloy powder by the water atomization method, the target amorphous soft magnetic alloy is controlled by controlling the water injection pressure, the injection flow rate, the molten alloy flow rate, etc. The aspect ratio and average particle size (D50) of the powder can be obtained.

  The amorphous soft magnetic alloy powder obtained in the first step is referred to as “reference powder”. If the frequency in the particle size distribution of the reference powder is 8% or less in the cumulative range of 10% to 90%, it is not necessary to perform the next second step. I do.

  That is, an amorphous soft magnetic alloy powder (conditioning powder) having an average particle size (D50) smaller than the average particle size (D50) of the reference powder and having the above-described composition is prepared. The reference powder and an appropriate amount of the adjusted powder are mixed so that the frequency in the particle size distribution of the powder is 8% or less in a cumulative range of 10% to 90% (second step).

  At this time, it is preferable to mix the said adjustment powder within the range of 5 mass%-50 mass% in the total mass of the mixed powder of the said reference | standard powder and adjustment powder. Moreover, it is more preferable to mix the said adjustment powder within the range of 10 mass%-20 mass%.

  Here, the average particle diameter (D50) of the reference powder is 4 to 55 μm, particularly in the range of 4 to 35 μm when the water atomization method is used, and the average particle diameter (D50) of the adjusted powder smaller than the reference powder is When using the water atomization method, it is preferable to be in the range of 4 to 30 μm.

  Even if the average particle diameter (D50) of the adjustment powder is larger than the average particle diameter (D50) of the reference powder, the filling rate of the amorphous soft magnetic alloy powder (mixed powder of the reference powder and the adjustment powder) is the reference Although it can be increased from the filling rate of the powder, it has been found by experiments to be described later that it is difficult to obtain the effect of reducing the core loss as compared with the dust core using only the reference powder as the amorphous soft magnetic alloy powder. Therefore, in order to reduce the core loss as compared with the reference powder and further increase the magnetic permeability as compared with the reference powder, the average particle diameter (D50) of the adjusted powder is set higher than the average particle diameter (D50) of the reference powder. It is preferable to make it small.

  When the average particle diameter (D50) of the adjusted powder is larger than the average particle diameter (D50) of the reference powder, the adjusted powder is 5 mass in the total mass of the mixed powder of the reference powder and the adjusted powder. It is preferable to mix within the range of% -20 mass%.

  Here, the average particle diameter (D50) of the reference powder is 4 to 55 μm, particularly in the range of 4 to 35 μm when the water atomization method is used, and the average particle diameter (D50) of the adjusted powder larger than the reference powder is In the case of using a water atomizing method, it is preferably in the range of 6 to 50 μm.

  The adjusted powder is preferably classified by a classifier so that the average particle diameter (D50) of the adjusted powder falls within the above range. For example, classification is carried out using a precision air classifier of Nissin Engineering Co., Ltd. trade name: Turbo Classifier TC40.

  In the second step, the difference between the maximum frequency and the minimum frequency of the particle size distribution of the amorphous soft magnetic alloy powder (mixed powder of the reference powder and the adjustment powder) is 10% to 90% in the cumulative range. % Or less, more preferably 4% or less.

  Further, in the second step, the amorphous soft magnetic alloy powder (a mixture of the reference powder and the adjustment powder) has a particle size distribution frequency of 4% or less in a cumulative range of 10% to 90%, and More preferably, the difference between the maximum frequency and the minimum frequency is adjusted to 2% or less.

  Subsequently, the amorphous soft magnetic alloy is mixed with an additive having a binder and a lubricant. The mixing ratio of the insulating material in the mixture is preferably in the range of 0.3% by mass to 5% by mass. The mixing ratio of the lubricant in the mixture is preferably in the range of 0.1% by mass to 2% by mass. For example, zinc stearate can be used as the lubricant.

  The amorphous soft magnetic alloy and the additive are mixed and then dried and pulverized to obtain a granulated powder (third step).

  The granulated powder is classified so as to be easily filled in a press mold. For example, a 300 to 850 μm granulated powder obtained by dispensing using a sieve having an opening of 300 μm or more and 850 μm or less is used.

Subsequently, the granulated powder is filled into a mold, heated to room temperature or a predetermined temperature while applying pressure, and compression molded to obtain a core precursor having a predetermined shape (fourth step). For example, the press pressure is 20 t / cm ² . The core precursor has, for example, a substantially ring shape. For example, the core precursor has an outer diameter of 20 mm, an inner diameter of 12 mm, and a height of 6.8 mm.

Subsequently, the core precursor is heat-treated (fifth step). As an example of the heat treatment conditions, heating is performed at 510 ° C. for 1 hour under a N ₂ gas atmosphere with a temperature increase rate of 40 ° C./min. Thereby, the distortion produced in the amorphous soft magnetic alloy powder by compression molding can be removed.

[Measurement of particle size distribution]
In the experiment, Fe _{74.43 at%} Cr _{1.96 at%} P _{9.04 at%} C _{2.16 at%} B _{7.54 at%} Si _{4.87 at%} Si _{4.87 at%} by a water atomization method (reference powder) Formed.

  The molten metal temperature (temperature of the melted alloy) at the time of obtaining the reference powder was 1550 ° C., and the water ejection pressure was 68.6 MPa.

  The reference powder used was a powder classified with a sieve having an opening of 180 μm for the purpose of removing the coarse powder and then classified with a sieve having an opening of 32 μm for the purpose of removing the irregularly shaped powder.

Subsequently, apart from the above reference powder, a substantially spherical amorphous _material of Fe _{74.43 at%} Cr _{1.96 at%} P _{9.04 at%} C _{2.16 at%} B _{7.54 at%} Si _{4.87 at% was} obtained by the water atomization method. Using a precision air classifier of Nissin Engineering Co., Ltd. product name: Turbo Classifier TC40, 4 μm classified powder, 6 μm classified powder, 8 μm classified powder, and 8 μm classified residual powder were obtained. .

  Here, the 4 μm classified powder means powder classified so that the average particle diameter (D50) is about 4 μm, and the 6 μm classified powder and the 8 μm classified powder are classified so as to be about 6 μm and about 8 μm, respectively. Powder. The 8 μm classified residual powder means a residual powder obtained by removing the amorphous soft magnetic alloy powder classified as an 8 μm classified powder from the produced amorphous magnetic powder.

The particle size distributions of the reference powder, 4 μm classified powder, 6 μm classified powder, 8 μm classified powder, and 8 μm classified residual powder were measured using a Microtrac particle size distribution measuring device MT3300EX manufactured by Nikkiso Co., Ltd.
The experimental results are shown in Tables 1 and 2 below.

  Table 1 shows the particle diameter, frequency, and accumulation of the reference powder and 4 μm classified powder. Since “4 μm classified powder 20% mixed” shown in Table 1 is the result of the next experiment, it will be described later.

  FIG. 1 is a graph (particle size distribution diagram) showing the relationship between the frequency and accumulation of the particle size distribution of the reference powder shown in Table 1.

  FIG. 4 is a graph showing the relationship between the cumulative particle size distribution of the reference powder shown in Table 2 and the frequency.

  FIG. 2 is a graph (particle size distribution diagram) showing the relationship between the particle size of 4 μm classified powder shown in Table 1, the frequency of particle size distribution, and the accumulation.

  In Table 2, “cumulative vs frequency (%)” and “cumulative vs particle size (μm)” are shown in the powder particle size distribution column. Each data of the 4 μm classified powder, 6 μm classified powder, 8 μm classified powder, and 8 μm classified residual powder is shown in the column of the mixing amount of 100 mass%. In addition, all the other data columns except the column of the reference | standard powder and the amount of mixing of 100 mass% are the data in the mixed powder which mixed the reference | standard powder and adjustment powder (classified powder).

  As shown in FIGS. 1, 4, 1, and 2, the particle size distribution of the reference powder was found to have a cumulative value in the range of 10% to 90% and a particle size frequency of 6% or less.

  On the other hand, as shown in FIG. 2, Table 1 and Table 2 (100% by mass mixing column), the particle size distribution of the 4 μm classified powder has a cumulative value in the range of about 40% to about 60%, and the frequency exceeds 8%. It was found that the frequency exceeded 6% in the range from about 40% to about 80%.

  The particle size distribution data of 6 μm classified powder and 8 μm classified residual powder are all shown in Table 2 (100% by mass mixing column). Even with 6 μm classified powder and 8 μm classified residual powder, the cumulative value ranges from about 40% to about 60%, the frequency of particle size exceeds 8%, and the frequency ranges from about 40% to about 80% with a frequency of 6%. It was found that

  Further, in the 8 μm classified powder, the frequency of the particle size distribution does not exceed 8%, but it was found that the frequency exceeded 6% in the range of about 40% to about 80%.

  The average particle size (D50) is shown in the 50% column of “cumulative vs particle size (μm)” of “powder particle size distribution” shown in Table 2. That is, the average particle diameter (D50) of the reference powder is 12.25 μm, the average particle diameter (D50) of the 4 μm classified powder is 4.11 μm, and the average particle diameter (D50) of the 6 μm classified powder is 5.83 μm, 8 μm classified powder. The average particle size (D50) was 8.45 μm, and the average particle size (D50) of the 8 μm classified residual powder was 19.59 μm.

[Results of mixing reference powder and adjustment powder]
Subsequently, the above-mentioned 4 μm classified powder, 6 μm classified powder, 8 μm classified powder, and 8 μm classified residual powder were mixed with the reference powder as adjusted powders. The said adjustment powder was mixed in 5 mass%, 10 mass%, 20 mass%, or 50 mass% in the total mass of the mixed powder of the said reference | standard powder and adjustment powder. The particle size distribution data of the mixed powder is described in the “powder particle size distribution” column of Table 2 described above.

  In addition, about the result of having mixed 20 mass% of 4 micrometer classification powder which could improve the core characteristic most, Table 1 and FIG. 3 also showed the relationship between a particle size, frequency, and accumulation.

  First, the experimental results of the mixed powder obtained by mixing 5% by mass to 50% by mass of 4 μm classified powder with respect to the reference powder will be considered.

  FIG. 5 is a graph of the “cumulative vs frequency (%)” column of “powder particle size distribution” of “4 μm classified powder” shown in Table 2. FIG. 5 also shows data of only 4 μm classified powder (mixing amount 100% by mass), but as shown in FIG. 5 and Table 2, 4 μm classified powder is mixed with 5 to 50% by mass of 4 μm classified powder. As a result, it can be seen that the cumulative value of the particle size distribution is in the range of 10% to 90%, and the frequency of the particle size can be suppressed to 8% or less. In particular, the 4 μm classified powder is 10% to 50% by weight. It has been found that the mixed product can suppress the cumulative value of the particle size distribution to 6% or less.

As shown in Table 2, the filling rate of the amorphous soft magnetic alloy powder is more than 80% even in the reference powder, but by making a mixed powder in which 5 μm to 50% by weight of 4 μm classified powder is mixed, It was found that the filling rate of the amorphous soft magnetic alloy powder was higher than that of the reference powder. In the core characteristic column shown in Table 2, the core loss W and the magnetic permeability _{μ ′} DC superposition characteristic _{μ ′ (5500 A / m)} are described.

The core characteristics were measured with the above-described reference powder or a powder core provided with a mixed powder. The powder core is prepared by mixing, drying and pulverizing the above-mentioned reference powder or mixed powder, silicone resin (1.4% by mass) and zinc stearate (0.3% by mass), with an opening of 300 μm and an opening of 300 μm. A granulated powder is formed by classification to 300 to 850 μm using a 850 μm sieve, and at a press pressure of 20 t / cm ² , the outer diameter is 20 mm, the inner diameter is 12 mm, and the height is 6.8 mm. The core precursor was formed and obtained by heating at 510 ° C. for 1 hour under a N ₂ gas atmosphere at a rate of temperature increase of 40 ° C./minm.

  As shown in Table 2, the core loss is higher in the dust core provided with the mixed powder in which 5 to 50% by mass of 4 μm classified powder is mixed as compared with the dust core provided with only the reference powder. Became smaller.

  Regarding the magnetic permeability μ ′, the mixed powder obtained by mixing 5% by mass of 4 μm classified powder and the dust core provided with the mixed powder obtained by mixing 50% by mass of 4 μm classified powder were smaller than the reference powder.

  Therefore, in order to obtain a high magnetic permeability μ ′ as well as an effect of reducing the core loss with respect to the reference powder, it is more preferable to use a dust core including a mixed powder obtained by mixing 10% by mass to 20% by mass of 4 μm classified powder. It turned out to be preferable. Moreover, as shown in Table 2, it turned out that it is most preferable to set it as the compacting core provided with the mixed powder which mixed 20 mass% 4 micrometers classification powder from the result of the core characteristic.

  FIG. 6 is a graph of the “cumulative vs frequency (%)” column of “powder particle size distribution” of “6 μm classified powder” shown in Table 2. FIG. 7 is a graph of the “cumulative vs frequency (%)” column of “powder particle size distribution” of “8 μm classified powder” shown in Table 2. 6 and 7 also show data of 6 μm classified powder only (mixing amount 100% by mass) or 8 μm classified powder only (mixing amount 100% by mass). As shown in FIGS. 6, 7, and 2, the particle size is within a range of 10% to 90% by mixing 5 μm to 50% by weight of 6 μm classified powder or 8 μm classified powder with the reference powder. The frequency of distribution can be suppressed to 8% or less. In the case of 6 μm classified powder, by mixing 5% by mass to 50% by mass, the cumulative value ranges from 10% to 90%, and the frequency of particle size distribution It was found that the frequency of the particle size distribution can be suppressed to 6% or less except in the case of mixing 8% by mass in the case of 8 μm classified powder.

  And as shown in Table 2, about the filling rate of the powder core provided with the mixed powder obtained by mixing 5 to 50% by mass of 6 μm classified powder or 8 μm classified powder, and the core characteristics, the mixed powder of 4 μm classified powder is used. The same result as that of the compacted core provided was obtained.

  Each of the average particle diameter (D50) of the 4 μm classified powder, 6 μm classified powder, and 8 μm classified powder is smaller than the average particle diameter (D50) of the reference powder.

  On the other hand, the average particle size (D50) of the 8 μm classified residual powder is larger than the average particle size (D50) of the reference powder.

  FIG. 8 is a graph of the “cumulative vs frequency (%)” column of “powder particle size distribution” of “8 μm classified residual powder” shown in Table 2. FIG. 8 also shows data of only 8 μm classification residual powder (mixing amount: 100 mass%). As shown in FIG. 8 and Table 2, by mixing 5 to 50% by weight of 8 μm classified residual powder with the reference powder, the cumulative value ranges from 10% to 90%, and the frequency of particle size distribution is 8% or less. It was found that by mixing 5% by mass to 20% by mass, the frequency of the particle size distribution can be suppressed to 6% or less when the cumulative value is in the range of 10% to 90%. .

  As shown in Table 2, it was found that the filling rate of the amorphous soft magnetic alloy powder can be made larger than that of the reference powder even when the adjustment powder having an average particle size (D50) larger than that of the reference powder is mixed.

  As shown in Table 2, in the powder core provided with the mixed powder in which 50% by mass of 8 μm classified residual powder is mixed, the cumulative value is around 50% and the frequency of particle size distribution is 8% or less, but it exceeds 6%. In addition, the packing ratio was almost the same as that of the powder core having only the reference powder as the amorphous soft magnetic alloy powder. On the other hand, in the powder core provided with the mixed powder in which 5 to 20% by mass of 8 μm classification residual powder is mixed, the cumulative value is 6% or less in the range of 10% to 90%, and the amorphous soft magnetic alloy powder As a result, it was found that the filling rate can be increased as compared with the powder core provided with only the reference powder. However, considering the core characteristics, in the dust core provided with the mixed powder in which 5 to 50% by mass of 8 μm classified residual powder is mixed, the magnetic permeability is higher than that of the dust core having only the reference powder as the amorphous soft magnetic alloy powder. It can be seen that the core loss increases although μ ′ increases.

  Therefore, the adjustment powder to be mixed with the reference powder has an average particle size (D50) smaller than that of the reference powder, and the mixing ratio is 5% by mass to 50% by mass, preferably 10% by mass to 20% by mass. Forming can improve the filling rate as compared with the dust core having only the reference powder as the amorphous soft magnetic alloy powder, and the core loss W compared to the dust core having only the reference powder as the amorphous soft magnetic alloy powder. It was found that can be improved.

  Further, as shown in Table 2, it was found that the difference between the maximum frequency and the minimum frequency of the particle size is preferably 4% or less.

  Moreover, in the powder core provided with the mixed powder in which 20% by mass of 4 μm classified powder is mixed, the core loss reduction effect and the permeability increase effect with respect to the reference powder are more effectively increased than those of other samples. In the range of 10% to 90% of the cumulative value, the frequency of the particle size distribution is 4% or less, and the difference between the maximum frequency and the minimum frequency of the particle size distribution is more preferably 2% or less. .

[Experiment of Compact Core (Comparative Example) with Fe-Al-Si Alloy]
In the experiment, a substantially spherical crystalline magnetic powder (reference powder) of an Fe—Al—Si based alloy was formed by a water atomization method.

  In addition to the above-mentioned standard powder, a substantially spherical crystalline magnetic powder of Fe-Al-Si alloy is formed by water atomization method, and Nisshin Engineering Co., Ltd. trade name: Turbo Classifier TC40 precision air classifier Was used to obtain 4 μm classified powder.

The particle size distributions of the reference powder and the 4 μm classified powder were measured using a Microtrac particle size distribution measuring device MT3300EX manufactured by Nikkiso Co., Ltd., respectively.
The experimental results are shown in Table 3 below.

  Table 3 shows experimental results of “powder particle size distribution vs. particle size (μm)”. The average particle diameter (D50) of the reference powder was 11.65 μm. Moreover, the average particle diameter (D50) of 4 micrometers classification powder (100 mass% mixing amount of 4 micrometers classification powder of Table 3) was 4.75 micrometers.

  Then, the reference powder and 4 μm classified powder were mixed. The 4 μm mixed powder was mixed in the range of 10% by mass to 50% by mass in the total mass of the reference powder and the 4 μm classified powder. And the dust core provided with the mixed powder which mixed the reference | standard powder and 4 micrometer classification powder in the range of 10 mass%-50 mass% was formed. The production conditions of the dust core were the same except for the production conditions of the dust core shown in Table 2 and the heating temperature for the core precursor. The heating temperature for the core precursor including the Fe—Al—Si based alloy was specified at 600 ° C. for 1 hour.

  As shown in Table 3, the core loss of the dust core comprising the Fe—Al—Si alloy is much higher than that of the dust core of this example shown in Table 2, and the core characteristics are the same as in this example. It turned out to be extremely bad. Moreover, although the core loss of the mixed powder was slightly improved, it was found that the improvement effect was not as good as that of the powder core of this example.

[SEM photograph of powder core cross section]
FIG. 9A is an SEM photograph of a cross-section of a dust core provided with an Fe—Al—Si alloy containing only a reference powder as the magnetic powder shown in Table 3, and FIG. 9B is a 4 μm classified powder shown in Table 3. The SEM photograph of the cross section of the dust core provided with the Fe-Al-Si alloy mixed with 10% by mass, FIG. 9C, includes the Fe-Al-Si alloy mixed with 20% of the 4 μm classified powder shown in Table 3. FIG. 9D is a SEM photograph of a powder core cross section provided with an Fe—Al—Si alloy in which 50% by mass of the 4 μm classified powder shown in Table 3 is mixed.

  FIG. 9 (e) is an SEM photograph of a cross-section of the dust core of the example having only the reference powder as the amorphous soft magnetic alloy powder shown in Table 2, and FIG. 9 (f) is a 4 μm classified powder shown in Table 2. SEM photograph of the cross-section of the powder core of the example provided with 10% by mass of the mixed powder, FIG. 9 (g) shows the powder of the example provided with the mixed powder of 20% by mass of the 4 μm classified powder shown in Table 2. The SEM photograph of the core cross section, FIG. 9 (h) is a SEM photograph of the powder core cross section of the example including the mixed powder obtained by mixing 50% by mass of the 4 μm classified powder shown in Table 2.

  As shown in FIGS. 9A to 9D, in the dust core of the comparative example including the Fe—Al—Si alloy, each magnetic powder is deformed, and there are many places where the magnetic powders are in contact with each other. I found out that Thereby, even if a filling rate can be raised in a comparative example, it is estimated that a core loss cannot be reduced as much as the said Example.

  On the other hand, as shown in FIGS. 9E to 9H, no deformation of the amorphous soft magnetic alloy powder was observed in the dust core of this example. It was also found that the gap between the amorphous soft magnetic alloy powders was reduced by mixing 4 μm classified powder with the reference powder. Therefore, it is presumed that the filling rate is increased and the amorphous soft magnetic alloy powder is not deformed and the insulation between the respective powders is appropriately maintained, so that the core loss can be appropriately reduced.

[Production of amorphous soft magnetic alloy powder of this example]
As shown in Table 4 below, it was found that an amorphous soft magnetic alloy having an average particle size (D50) of 4 to 55 μm can be produced regardless of the gas atomization method and the water atomization method and regardless of the composition. The classification shown in Table 4 was performed using a precision air classifier of Nissin Engineering Co., Ltd. trade name: Turbo Classifier TC40.

  As shown in Table 4, in this example, amorphous soft magnetic alloy powders having various average particle diameters (D50) can be produced. Therefore, amorphous soft magnetic alloys having different average particle diameters (D50). It is possible to easily adjust the particle size distribution frequency of the amorphous magnetic alloy powder to 8% or less, preferably 6% or less in the cumulative range of 10% to 90% by mixing the powder. I understood.

A graph (particle size distribution diagram) showing the relationship between the particle size, frequency and accumulation of the reference powder of this example shown in Table 1, A graph (particle size distribution diagram) showing the relationship between the particle size, frequency and accumulation of the 4 μm classified powder shown in Table 1, A graph (particle size distribution diagram) showing the relationship between the particle size, frequency and accumulation of this example in which 20% by mass of 4 μm classified powder was mixed, A graph showing the relationship between the cumulative particle size and frequency of the reference powder shown in Table 2, Graph of “cumulative vs frequency (%)” column of “powder particle size distribution” of “4 μm classified powder” shown in Table 2, Graph of “cumulative vs frequency (%)” column of “powder particle size distribution” of “6 μm classified powder” shown in Table 2, Graph of “cumulative vs frequency (%)” column of “powder particle size distribution” of “8 μm classified powder” shown in Table 2, Graph of “cumulative vs frequency (%)” column of “powder particle size distribution” of “8 μm classification residual powder” shown in Table 2, (A) is an SEM photograph of a cross-section of a dust core provided with an Fe—Al—Si alloy containing only a reference powder as the magnetic powder shown in Table 3, and (b) is a mixture of 10% of 4 μm classified powder shown in Table 3. An SEM photograph of a cross section of a dust core provided with an Fe-Al-Si alloy, (c) is an SEM photograph of a cross section of a powder core provided with an Fe-Al-Si alloy mixed with 20% of 4 μm classified powder shown in Table 3. , (D) is a SEM photograph of a cross-section of a dust core comprising a Fe-Al-Si alloy mixed with 50% of 4 μm classified powder shown in Table 3, and (e) is an amorphous soft magnetic alloy shown in Table 2. SEM photograph of the cross-section of the dust core of the example having only the reference powder as a powder, (f) is an SEM photograph of the cross-section of the dust core of the example having a mixed powder in which 10% of the 4 μm classified powder shown in Table 2 is mixed, (G) is a mixed powder prepared by mixing 20% of the 4 μm classified powder shown in Table 2. The SEM photograph of the cross-section of the dust core of the embodiment, (h) is the SEM photograph of the cross-section of the dust core of the embodiment comprising a mixed powder obtained by mixing 50% of the 4 μm classified powder shown in Table 2.

Claims (15)

In a powder core in which amorphous soft magnetic alloy powder is solidified and formed by a binder,
The amorphous magnetic alloy powder is mainly composed of Fe, and includes at least two of P, C, B, and Si,
The powder core according to claim 1, wherein a frequency of a particle size distribution of the amorphous magnetic alloy powder is 8% or less in a cumulative range of 10% to 90%.   The powder core according to claim 1, wherein the frequency in the particle size distribution is 6% or less.   The powder core according to claim 1 or 2, wherein a difference between the maximum frequency and the minimum frequency of the particle size distribution is 4% or less.   The dust core according to claim 1, wherein the frequency of the particle size distribution is 4% or less, and the difference between the maximum frequency and the minimum frequency of the particle size distribution is 2% or less. The powdered core according to any one of claims 1 to 4, wherein the amorphous soft magnetic alloy powder is represented by the following composition formula.
_{Fe 100-a-b-x} -y-z-w-t Co a Ni b M x P y C z B w Si t
However, M is one or more elements selected from Cr, Mo, W, V, Nb, Ta, Ti, Zr, Hf, Pt, Pd, Au, Sn, and Al, and shows a composition ratio a , B, x, y, z, w, and t are 0 atomic% ≦ x ≦ 5 atomic%, 0 atomic% ≦ y ≦ 15 atomic%, 0 atomic% <z ≦ 8 atomic%, 1 atomic% ≦ w ≦ 15 atomic%, 0 atomic% ≦ t ≦ 12 atomic%, 0 atomic% ≦ a ≦ 20 atomic%, 0 atomic% ≦ b ≦ 5 atomic%, 70 atomic% ≦ (100-ab-xyz) −w−t) ≦ 83 atomic%. In the method for producing a powder core obtained by solidifying and molding an amorphous soft magnetic alloy powder with a binder,
A first step of forming the amorphous soft magnetic alloy powder containing Fe as a main component and containing at least two of P, C, B, and Si by an atomizing method;
A second step of adjusting the frequency of the particle size distribution of the amorphous magnetic alloy powder to 8% or less in the cumulative range of 10% to 90% during the first step or after the first step;
A third step in which the amorphous soft magnetic alloy powder and an additive containing a binder and a lubricant are mixed and granulated to form a granulated powder;
A fourth step of compression-molding the granulated powder to form a core precursor of a predetermined shape;
A fifth step of heat-treating the core precursor and removing strain generated in the amorphous soft magnetic alloy powder by compression molding;
A method for producing a dust core, comprising: When the amorphous soft magnetic alloy powder obtained in the first step is used as a reference powder, it has an average particle size (D50) smaller than the average particle size (D50) of the reference powder, Fe is the main component, Prepare an amorphous soft magnetic alloy powder (adjusted powder) formed by an atomizing method containing at least two of P, C, B, and Si,
In the second step, the reference powder and an appropriate amount of the adjusted powder are mixed so that the frequency of the particle size distribution of the amorphous magnetic alloy powder is 8% or less in a cumulative range of 10% to 90%. The manufacturing method of the powder core of Claim 6.   The manufacturing method of the powder core of Claim 7 which mixes the said adjustment powder within the range of 5 mass%-50 mass%.   The manufacturing method of the powder core of Claim 8 which mixes the said adjustment powder within the range of 10 mass%-20 mass%. When the amorphous soft magnetic alloy powder obtained in the first step is used as a reference powder, it has an average particle size (D50) larger than the average particle size (D50) of the reference powder, Fe is the main component, Prepare an amorphous soft magnetic alloy powder (adjusted powder) formed by an atomizing method containing at least two of P, C, B, and Si,
In the second step, the reference powder and an appropriate amount of the adjusted powder are mixed so that the frequency of the particle size distribution of the amorphous magnetic alloy powder is 8% or less in a cumulative range of 10% to 90%. The manufacturing method of the powder core of Claim 6.   The manufacturing method of the powder core of Claim 10 which mixes the said adjustment powder within the range of 5 mass%-20 mass%.   The method for producing a dust core according to any one of claims 6 to 11, wherein the frequency of the particle size distribution is adjusted to 6% or less in the cumulative range of 10% to 90% in the second step.   The method for producing a dust core according to any one of claims 6 to 12, wherein in the second step, a difference between the maximum frequency and the minimum frequency of the particle size distribution is adjusted to 4% or less.   The powder compact according to any one of claims 6 to 11, wherein in the second step, the frequency of the particle size distribution is adjusted to 4% or less, and the difference between the maximum frequency and the minimum frequency of the particle size is adjusted to 2% or less. Core manufacturing method. The method for producing a dust core according to any one of claims 6 to 14, wherein the amorphous magnetic alloy powder represented by the following composition formula is formed.
_{Fe 100-a-b-x} -y-z-w-t Co a Ni b M x P y C z B w Si t
However, M is one or more elements selected from Cr, Mo, W, V, Nb, Ta, Ti, Zr, Hf, Pt, Pd, Au, Sn, and Al, and shows a composition ratio a , B, x, y, z, w, and t are 0 atomic% ≦ x ≦ 5 atomic%, 0 atomic% ≦ y ≦ 15 atomic%, 0 atomic% <z ≦ 8 atomic%, 1 atomic% ≦ w ≦ 15 atomic%, 0 atomic% ≦ t ≦ 12 atomic%, 0 atomic% ≦ a ≦ 20 atomic%, 0 atomic% ≦ b ≦ 5 atomic%, 70 atomic% ≦ (100-ab-xyz) −w−t) ≦ 83 atomic%.

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