JP2020152947A - Soft-magnetic powder, heat-treatment method for soft-magnetic powder, soft-magnetic material, powder magnetic core, and manufacturing method for powder magnetic core - Google Patents

Abstract

To provide a soft-magnetic powder based on a FeSi(P) alloy that is excellent in humidity resistance.SOLUTION: A soft-magnetic powder contains 89.5-99.6 mass% of Fe, 0.2-9.0 mass% of Si, and 0-1.0 mass% of P. The soft-magnetic powder has a crystallite diameter on a plane (111) of 95 nm or greater.SELECTED DRAWING: None

Description

The present invention relates to a soft magnetic powder, a heat treatment method for a soft magnetic powder, a soft magnetic material, a powder magnetic core, and a method for producing a powder magnetic core.

A magnetic component having a dust core, such as an inductor, is attached to the electronic device. The dust core is generally manufactured by compounding a soft magnetic powder with a binder such as a resin and then compression molding it. When an AC magnetic flux is passed through this dust core, some energy is lost and heat is generated, which poses a problem in electronic devices. Such iron loss is composed of hysteresis loss and eddy current loss. In order to reduce the hysteresis loss, it is required to reduce the coercive force Hc of the dust core and increase the magnetic permeability μ.

As the soft magnetic powder, a FeSi alloy powder containing Si has been proposed because a high magnetic permeability can be obtained (see, for example, Patent Document 1). Patent Document 1 describes that the soft magnetic properties can be improved by blending 5 to 7% by mass of Si.

Further, Patent Document 2 describes that by adding a small amount of P to FeSi alloy powder, the specific resistance thereof is increased and effects such as reduction of eddy current loss can be obtained.

Japanese Unexamined Patent Publication No. 2016-171167 Japanese Unexamined Patent Publication No. 2017-224717

As shown in Patent Documents 1 and 2, the soft magnetic powder containing Fe and Si (further P) is excellent in magnetic properties. Moisture resistance is required for the dust core produced from such soft magnetic powder. Therefore, the soft magnetic powder itself is also required to have moisture resistance.

Therefore, an object of the present invention is to provide a FeSi (P) alloy-based soft magnetic powder having excellent moisture resistance.

Further, in the compression during the production of the dust core, the binder is decomposed and volatilized and removed by heating at a high temperature to obtain a dust core substantially composed of only the soft magnetic powder component. There is. From the viewpoint of cost, it is desirable that this heating can be performed in an air atmosphere. For that purpose, the soft magnetic powder is required to have oxidation resistance. Further, the soft magnetic powder is required to have oxidation resistance because the reactivity generally increases at a high temperature.

Therefore, it is an object of the present invention to preferably provide a FeSi (P) alloy-based soft magnetic powder having excellent moisture resistance and oxidation resistance.

As a result of diligent studies to solve the above problems, the present inventors have found that FeSi (P) alloy-based soft magnetic powder having a large crystallite diameter has excellent moisture resistance, and such soft magnetic powder is obtained from FeSi ( P) It has been found that a soft magnetic powder made of an alloy can be produced by heat treatment at a specific temperature. In addition, the present inventors have excellent moisture resistance and oxidation resistance of FeSi (P) alloy-based soft magnetic powder having a large crystallite diameter and a predetermined relationship between the amount of oxygen and the average particle size. It has been found that such a soft magnetic powder can be produced by heat-treating a soft magnetic powder made of a FeSi (P) alloy at a specific temperature and in a specific atmosphere. As described above, the present inventors have completed the present invention.

That is, the present invention is as follows.
[1] A soft magnetic powder containing 89.5 to 99.6% by mass of Fe, 0.2 to 9.0% by mass of Si, and 0 to 1.0% by mass of P, and crystals on the (111) plane. A soft magnetic powder having a child diameter of 95 nm or more.

[2] The soft magnetic powder according to [1], wherein the N content is 800 ppm or less.

[3] The soft magnetic powder according to [1] or [2], wherein the total content of Fe, Si and P in the soft magnetic powder is 97.5% by mass or more.

[4] The product (O × D50) of the oxygen content (O) of the soft magnetic powder and the cumulative 50% particle diameter (D50) based on the volume measured by the laser diffraction / scattering type particle size distribution measuring device is 3.00. The soft magnetic powder according to any one of [1] to [3], which is (mass% · μm) or less.

[5] The soft magnetic powder according to [4], wherein the product (O × D50) is 2.30 (mass% · μm) or less.

[6] The soft magnetic powder according to [5], wherein the product (O × D50) is 1.70 to 2.00 (mass% · μm).

[7] The soft magnetic powder according to any one of [1] to [6], which contains 0.02 to 0.5% by mass of P.

[8] A step of heat-treating a soft magnetic powder containing 89.5 to 99.6% by mass of Fe, 0.2 to 9.0% by mass of Si, and 0 to 1.0% by mass of P at 500 to 950 ° C. A method for heat-treating a soft magnetic powder.

[9] The method for heat-treating a soft magnetic powder according to [8], wherein the heat treatment is performed at 500 to 850 ° C.

[10] The heat treatment is performed under the condition that the product (heat treatment temperature x atmospheric oxygen concentration) of the heat treatment temperature (° C.) and the oxygen concentration (ppm) in the atmosphere in which the heat treatment is performed is 700,000 (° C. ppm) or less. The heat treatment method for soft magnetic powder according to [8] or [9], which is carried out.

[11] The method for heat-treating a soft magnetic powder according to [8] or [9], wherein the heat treatment is performed in an atmosphere having an oxygen concentration of 500 ppm or less.

[12] The method for heat-treating a soft magnetic powder according to any one of [8] to [11], wherein the heat treatment is performed at 700 to 850 ° C. in an atmosphere having an oxygen concentration of 50 to 400 ppm.

[13] A soft magnetic material containing the soft magnetic powder according to any one of [1] to [7] and a binder.

[14] A dust core containing the soft magnetic powder according to any one of [1] to [7].

[15] The soft magnetic powder according to any one of [1] to [7] or the soft magnetic material according to [13] is molded into a predetermined shape, and the obtained molded product is heated to obtain a dust core. A method of manufacturing a dust core.

According to the present invention, a FeSi (P) alloy-based soft magnetic powder having excellent moisture resistance is provided. The soft magnetic powder of a preferred embodiment of the present invention is further excellent in oxidation resistance.

Hereinafter, embodiments of the soft magnetic powder of the present invention and a method for producing the same (heat treatment method for the soft magnetic powder) will be described.

[Soft magnetic powder]
An embodiment of the soft magnetic powder of the present invention is a powder having an alloy composition containing Fe (iron) and Si (silicon) and may contain a specific amount of P (phosphorus). This soft magnetic powder is also referred to as a FeSi (P) alloy-based soft magnetic powder. When P is contained, it is described as FeSiP. Hereinafter, this soft magnetic powder will be described.

<Alloy composition>
Embodiments of the soft magnetic powder of the present invention contain 89.5-99.6% by mass of Fe. The content of Fe in the soft magnetic powder is in such a range from the viewpoint of magnetic properties and mechanical properties, preferably 90.0 to 99.0% by mass, and more preferably 90.5 to 95.5. It is mass%.

The embodiment of the soft magnetic powder of the present invention contains 0.2 to 9.0% by mass of Si. The Si content in the soft magnetic powder is within the above range from the viewpoint of improving magnetic properties such as magnetic permeability without impairing the magnetic properties and mechanical properties due to Fe. From the viewpoint of this magnetic property, the Si content is preferably 0.5 to 8.8% by mass, more preferably 4.0 to 8.6% by mass.

Embodiments of the soft magnetic powder of the present invention contain 0 to 1.0% by mass of P (that is, may not be contained). The presence of a small amount of P enhances the insulating property of the soft magnetic powder, and can reduce the eddy current loss when the powder magnetic core is used. From the viewpoint of reducing the eddy current loss, the P content is preferably 0.02 to 0.5% by mass, more preferably 0.03 to 0.4% by mass.

Further, in the embodiment of the soft magnetic powder of the present invention, the total content of Fe, Si and P is preferably 97.5% by mass or more from the viewpoint of suppressing deterioration of magnetic properties due to the inclusion of impurities. , More preferably 98.0% by mass or more.

The embodiment of the soft magnetic powder of the present invention may contain impurities in addition to the above Fe, Si and P as long as the effects of the present invention are exhibited. Examples of impurities are Na (sodium), K (potassium), Ca (calcium), Pd (palladium), Mg (magnesium), Co (cobalt), Mo (molybdenum), Zr (zirconium), C (carbon). , N (nitrogen), O (oxygen), Cl (chlorine), Mn (manganesium), Ni (nickel), Cu (copper), S (sulfur), As (arsenic), B (boron), Sn (tin) , Ti (titanium), V (vanadium), Al (aluminum). Of these, the content excluding oxygen is preferably 1% by mass or less in total, and more preferably 10 to 6000 ppm.

In the embodiment of the soft magnetic powder of the present invention, a small amount of elements may be added in order to impart some property such as insulating property to the soft magnetic powder. Examples of such trace-added elements include Na, K, Ca, Pd, Mg, Co, Mo, Zr, C, N, Cl, Mn, Ni, Cu, S, As, B, Sn, Ti, V. , Al. The total amount of these additions is preferably 1% by mass or less, and more preferably 10 to 6000 ppm.

<Crystalline diameter>
The crystallite diameter on the (111) plane of the embodiment of the soft magnetic powder of the present invention is 95 nm or more. Due to the large crystallite diameter as described above, the soft magnetic powder has excellent moisture resistance, and a dust core having excellent moisture resistance can be produced from the powder. Considering that it is difficult to produce a soft magnetic powder having a very large crystallite diameter and the above-mentioned moisture resistance, the crystallite diameter of the soft magnetic powder is preferably 96 to 250 nm, more preferably 99 to 99. It is 180 nm. The crystallite diameter can be measured by an X-ray diffraction method. In the case of the alloy composition of the embodiment of the soft magnetic powder of the present invention, a peak of the (111) plane appears in or near the range of 2θ = 51.5 ° to 53.5 ° with respect to the diffraction angle θ, and from this The crystallite diameter can be calculated. The details of the method for measuring the crystallite diameter will be described in Examples described later.

<Product of oxygen content of soft magnetic powder and average particle size>
As a result of the study by the present inventors, it was found that the oxygen content (O) in the soft magnetic powder affects the moisture resistance and oxidation resistance of the soft magnetic powder, as well as the magnetic properties. Since the oxygen content increases as the particle size of the powder decreases, in the present invention, the oxygen content (O) and the laser diffraction / scattering type of the soft magnetic powder are used to correct the fluctuation of the oxygen content due to the particle size. The product (O × D50 (mass% · μm)) with the cumulative 50% particle diameter (D50) based on the volume measured by the particle size distribution measuring device is adopted. The product (O × D50 (mass% · μm)) is preferably 3.00 (mass% · μm) or less from the viewpoint of moisture resistance of the soft magnetic powder, and has moisture resistance and magnetic properties (particularly magnetic permeability). From the viewpoint of moisture resistance and oxidation resistance, it is more preferably 2.30 (mass% · μm) or less, and particularly preferably 1.70 to 2.00 (mass% · μm).

<Oxygen content (O)>
The oxygen content (O) of the embodiment of the soft magnetic powder of the present invention is preferably 0.1 to 1.5% by mass, more preferably 0.15 to 0.85, from the viewpoint of excellent magnetic properties. It is mass%.

<Nitrogen content>
The content of N (nitrogen) in the embodiment of the soft magnetic powder of the present invention is preferably 800 ppm or less from the viewpoint of excellent magnetic properties. Considering that it is difficult to completely remove N from the soft magnetic powder, the content of N is more preferably 1 to 700 ppm.

<Average particle size (D50)>
The cumulative 50% particle size (D50) based on the volume measured by the laser diffraction / scattering type particle size distribution measuring device according to the embodiment of the soft magnetic powder of the present invention is not particularly limited, but the eddy current loss can be reduced by reducing the particle size. Therefore, it is preferably 0.1 to 10 μm, and more preferably 0.5 to 5 μm.

<BET specific surface area>
The specific surface area (BET specific surface area) measured by the BET one-point method of the embodiment of the soft magnetic powder of the present invention is from the viewpoint of suppressing the generation of oxides on the particle surface of the powder and exhibiting good magnetic properties. It is preferably 0.15 to 3.00 m ² / g, and more preferably 0.25 to 2.50 m ² / g.

<Tap Density (TAP)>
The tap density (TAP) of the embodiment of the soft magnetic powder of the present invention is preferably 2.0 to 7.5 g / cm ³ from the viewpoint of increasing the packing density of the powder and exhibiting good magnetic properties. More preferably, it is 2.5 to 6.5 g / cm ³ .

<Shape>
The shape of the embodiment of the soft magnetic powder of the present invention is not particularly limited, and may be spherical or substantially spherical, and may be granular, flaky (flakes), or distorted (indeterminate). Good.

[Method for producing soft magnetic powder of the present invention (heat treatment method for soft magnetic powder)]
The soft magnetic powder of the present invention described above can be produced according to the embodiment of the heat treatment method for the soft magnetic powder of the present invention. The heat treatment method includes a step (heat treatment step) of heat-treating a specific soft magnetic powder under specific conditions.

<Raw material powder>
In the embodiment of the heat treatment method for soft magnetic powder of the present invention, the soft magnetic powder (hereinafter, also referred to as “raw material powder”) applied to the heat treatment step is the embodiment of the soft magnetic powder of the present invention, and the particle size and shape. Etc. are substantially the same, but the crystallite diameters are different, and the characteristics regarding the oxygen content are also slightly different.

That is, the raw material powder is a soft magnetic powder containing Fe and Si and may contain P, and contains Fe in an amount of 89.5 to 99.6% by mass, preferably 90.0 to 99.0% by mass, more preferably. Containing 90.5 to 95.5% by mass, 0.2 to 9.0% by mass of Si, preferably 0.5 to 8.8% by mass, and more preferably 4.0 to 8.6% by mass. P is contained in an amount of 0 to 1.0% by mass, preferably 0.02 to 0.5% by mass, more preferably 0.03 to 0.4% by mass, and the content of Fe, Si and P in the soft magnetic powder. The total is preferably 97.5% by mass or more, and more preferably 98.0% by mass or more. The raw material powder may usually contain impurities in addition to Fe, Si, and P. Examples thereof include Na (sodium), K (potassium), Ca (calcium), Pd (palladium), Mg (magnesium), and so on. Co (cobalt), Mo (molybdenum), Zr (zirconium), C (carbon), N (nitrogen), O (oxygen), Cl (chlorine), Mn (manganesium), Ni (nickel), Cu (copper), Examples include S (sulfur), As (arsenic), B (boron), Sn (tin), Ti (titanium), V (vanadium), and Al (aluminum), and the content of these excluding oxygen is The total is preferably 1% by mass or less, and more preferably 10 to 6000 ppm. Examples of trace elements added in the raw material powder are Na, K, Ca, Pd, Mg, Co, Mo, Zr, C, N, Cl, Mn, Ni, Cu, S, As, B, Sn, Ti, V. , Al. The total amount of these additions is preferably 1% by mass or less, and more preferably 10 to 6000 ppm.

The N (nitrogen) content of the raw material powder is preferably 800 ppm or less, more preferably 1 to 700 ppm. The volume-based cumulative 50% particle size (D50) measured by the laser diffraction scattering type particle size distribution measuring device of the raw material powder is preferably 0.1 to 10 μm, more preferably 0.5 to 5 μm, and is measured by the BET 1-point method. The measured specific surface area (BET specific surface area) is preferably 0.15 to 3.00 m ² / g, more preferably 0.25 to 2.50 m ² / g, and the tap density (TAP) is preferably 2. .0 to 7.5 g / cm ³ , more preferably 2.5 to 6.5 g / cm ³ . The shape of the raw material powder is not particularly limited, and may be spherical or substantially spherical, and may be granular, flaky (flake-shaped), or distorted (amorphous).

(Crystall diameter)
The crystallite diameter on the (111) plane of the raw material powder is not particularly limited, but the crystallite diameter of the conventional FeSi (P) soft magnetic powder (that is, the raw material powder) that has not been treated according to the heat treatment embodiment of the present invention is Usually, it is about 50 to 92 nm, and by carrying out the heat treatment specified in the present invention, the crystallite diameter thereof can be grown to 95 nm or more.

(Product of oxygen content and average particle size)
The embodiment of the heat treatment method for soft magnetic powder of the present invention preferably heat-treats the raw material powder in an atmosphere having a specific oxygen concentration, and the heat treatment of the raw material powder increases the oxygen content (O) in the powder. May be slightly affected. The product (O × D50 (mass% · μm)) of the oxygen content (O) of the raw material powder and the cumulative 50% particle diameter (D50) based on the volume measured by the laser diffraction / scattering type particle size distribution measuring device is particularly limited. Although not, it is usually in the range of 1.10 to 3.50 (mass% · μm).

(Oxygen content (O))
As described above, the oxygen content (O) in the powder may be slightly affected by carrying out the embodiment of the heat treatment method for the soft magnetic powder of the present invention on the raw material powder. The oxygen content (O) of the raw material powder is not particularly limited, but is usually 0.05 to 1.4% by mass.

The raw material powder described above can be produced by a known method, for example, a gas atomization method, a water atomization method, a vapor phase method using plasma, or the like, or can be purchased as a commercially available product.

<Heat treatment process>
In the heat treatment step in the embodiment of the heat treatment method for soft magnetic powder of the present invention, the raw material powder described above is heat-treated at 500 to 950 ° C. By heat-treating at such a high temperature, the crystallites of the raw material powder are grown, and the soft magnetic powder having a large crystallite diameter specified in the present invention, having excellent moisture resistance, and being useful as a raw material for producing a dust core. Is obtained.

Regarding the conditions of this heat treatment, the heat treatment is performed under the condition that the product (heat treatment temperature x atmospheric oxygen concentration) of the heat treatment temperature (° C) and the oxygen concentration (ppm) in the atmosphere in which the heat treatment is performed is 700,000 (° C · ppm) or less. When the above is carried out, a soft magnetic powder having excellent moisture resistance can be obtained. The product (heat treatment temperature × atmospheric oxygen concentration) is preferably 5 to 650,000 (° C. ppm).

In the heat treatment step of the embodiment of the heat treatment method of the present invention, the heat treatment is performed at a temperature of 500 to 850 ° C. while satisfying the product (heat treatment temperature × atmospheric oxygen concentration), so that the oxidation resistance is also excellent. A soft magnetic powder can be obtained.

The oxygen concentration in the atmosphere in which the heat treatment is performed in the heat treatment step is preferably 500 ppm or less because high oxygen concentration causes oxidation of the powder and adversely affects the magnetic properties. In particular, when the oxygen concentration in the atmosphere is set to 50 to 400 ppm and the heat treatment is performed at 700 to 850 ° C., a soft magnetic powder having excellent moisture resistance, oxidation resistance and magnetic properties (particularly magnetic permeability) is obtained. Obtainable. The preferable oxygen concentration in the atmosphere in which the heat treatment is performed is as described above, but the balance, that is, the composition other than oxygen in the atmosphere is not particularly limited as long as it does not substantially show reactivity with the raw material powder. From the viewpoint of preferably exerting the effects of the present invention, the atmosphere is preferably substantially composed of only oxygen and an inert element (the total of oxygen and the inert element is 99.5% by volume or more). Examples of the inert element include helium, neon, argon, nitrogen and the like. Among these, nitrogen is preferable from the viewpoint of cost.

Further, the heat treatment in the heat treatment step is preferably carried out for 10 to 1800 minutes, preferably for 20 to 1200 minutes, from the viewpoint of improving the electrical insulation of the powder after the heat treatment and preventing the deterioration of the magnetic properties due to productivity and oxidation. It is more preferable to do so.

<Other processes>
For the soft magnetic powder that has undergone the heat treatment step, other steps may be carried out. For example, when powder agglomeration occurs due to heat treatment, a crushing step may be carried out for this.

<Soft magnetic material>
The embodiment of the soft magnetic powder of the present invention described above can be used as a soft magnetic material which is a raw material for producing a dust core, and the material is used to produce a powder magnetic core having excellent moisture resistance. be able to.

The soft magnetic powder itself can be used as a soft magnetic material, or it can be a soft magnetic material mixed with a binder. In the latter case, for example, a soft magnetic powder is mixed with a binder (insulating resin and / or an inorganic binder) and granulated to obtain a granular composite powder (soft magnetic material). The content of the soft magnetic powder in this soft magnetic material is preferably 80 to 99.9% by mass from the viewpoint of achieving good magnetic properties. From the same viewpoint, the content of the binder in the soft magnetic material is preferably 0.1 to 20% by mass.

Specific examples of the insulating resin include (meth) acrylic resin, silicone resin, epoxy resin, phenol resin, urea resin, and melamine resin. Specific examples of the inorganic binder include a silica binder and an alumina binder. Further, the soft magnetic material (both the soft magnetic powder alone and the mixture of the powder and the binder) may contain other components such as wax and lubricant, if necessary.

<Powder magnetic core>
By molding the soft magnetic material described above into a predetermined shape and heating it, a powder magnetic core including the embodiment of the soft magnetic powder of the present invention can be produced. More specifically, the soft magnetic material is placed in a mold having a predetermined shape, pressurized and heated (the heating temperature is preferably 200 to 1200 ° C., more preferably 300 to 1000 ° C.) to obtain a dust core. To get. Moreover, since the soft magnetic powder of the present invention has excellent oxidation resistance, the work of obtaining the dust core can be performed in an air atmosphere.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

[Reference Example 1 (Ref. 1)]
In a tundish furnace, 14.5 kg of electrolytic iron (purity: 99.95% by mass or more), 1.01 kg of silicon metal (purity: 99% by mass or more), and 28.5 g of FeP alloy (Fe 72 wt%, P 26 wt%) were added. The molten metal heated and melted at 1700 ° C. in a nitrogen atmosphere is rapidly cooled and solidified by spraying high-pressure water (pH 10.3) at a water pressure of 150 MPa and a water volume of 160 L / min while dropping from the bottom of the tundish furnace in a nitrogen atmosphere. The resulting slurry was separated into solid and liquid, the solid was washed with water, and dried in vacuum at 40 ° C. for 30 hours.

With respect to the substantially spherical FeSiP alloy powder 1 thus obtained, the composition (Fe, Si, P content, oxygen content, carbon content and nitrogen content), BET specific surface area, tap density (TAP), The particle size distribution, crystallite diameter and magnetic properties were determined, and the moisture resistance and oxidation resistance were evaluated. The results are shown in Tables 1 and 2 below. The details of these measurement and evaluation methods will be described below.

[composition]
The composition of FeSiP alloy powder 1 was measured as follows.

Fe was analyzed by the titration method according to JIS M8263 (chromium ore-iron quantification method) as follows. First, sulfuric acid and hydrochloric acid were added to 0.1 g of a sample (FeSiP alloy powder 1), and the mixture was heated and decomposed, and heated until white smoke of sulfuric acid was generated. After allowing to cool, water and hydrochloric acid were added and heated to dissolve soluble salts. Then, warm water is added to the obtained sample solution to adjust the liquid volume to about 120 to 130 mL, the liquid temperature is adjusted to about 90 to 95 ° C., a few drops of the indigo carmine solution are added, and the titanium (III) chloride solution is added to the sample solution. Add until the color changed from yellow-green to blue, then colorless and transparent. The potassium dichromate solution was subsequently added until the sample solution remained blue for 5 seconds. Iron (II) in this sample solution was titrated with a potassium dichromate standard solution using an automatic titrator to determine the amount of Fe.

Si was analyzed by the gravimetric method as follows. First, hydrochloric acid and perchloric acid were added to the sample (FeSiP alloy powder 1) to decompose it by heating, and the sample (FeSiP alloy powder 1) was heated until white smoke of perchloric acid was generated. It was subsequently heated to dryness. After allowing to cool, water and hydrochloric acid were added and heated to dissolve soluble salts. Subsequently, the insoluble residue was filtered using a filter paper, and the residue was transferred to a crucible together with the filter paper, dried and incinerated. After allowing to cool, the crucible was weighed together. A small amount of sulfuric acid and hydrofluoric acid were added, and the mixture was heated to dryness and then heated strongly. After allowing to cool, the crucible was weighed together. Then, the second weighing value was subtracted from the first weighing value, and the weight difference was calculated as SiO ₂ to obtain the Si amount.

P was analyzed using an inductively coupled plasma (ICP) emission spectrometer (SPS3520V manufactured by Hitachi High-Tech Science Corporation). As a result, the amount of P was 0.057% by mass.

The oxygen content and nitrogen content were measured by an oxygen / nitrogen / hydrogen analyzer (EMGA-920 manufactured by HORIBA, Ltd.).

The carbon content was measured with a carbon / sulfur analyzer (EMIA-22V manufactured by HORIBA, Ltd.).

[BET specific surface area]
For the BET specific surface area, a BET specific surface area measuring device (Macsorb manufactured by Mountech Co., Ltd.) was used to flow nitrogen gas into the measuring device at 105 ° C. for 20 minutes to degas, and then a mixed gas of nitrogen and helium (N). ₂ :30% by volume, He: 70% by volume) was measured by the BET 1-point method.

[Tap density]
The tap density (TAP) is the same as the method described in JP-A-2007-263860, in which FeSiP alloy powder 1 is filled into a bottomed cylindrical die having an inner diameter of 6 mm and a height of 11.9 mm up to 80% of the volume. To form an alloy powder layer, a pressure of 0.160 N / m ² was uniformly applied to the upper surface of the alloy powder layer, and the alloy powder layer was compressed at this pressure until the alloy powder was no longer densely packed. After that, the height of the alloy powder layer is measured, the density of the alloy powder is obtained from the measured value of the height of the alloy powder layer and the weight of the filled alloy powder, and this is calculated as the tap density of FeSiP alloy powder 1. And said.

[Particle size distribution]
For the particle size distribution, use a laser diffraction / scattering type particle size distribution measuring device (SIMPATEC's Heros particle size distribution measuring device (HELOS & RODOS (air flow type dispersion module))) to obtain a volume-based particle size distribution at a dispersion pressure of 5 bar. I asked.

[Measurement of crystallite diameter]
The crystallite diameter on the (111) plane of the FeSiP alloy powder 1 was measured using an X-ray diffractometer (manufactured by Rigaku, model RINT-Ultima III). Cobalt was used as the X-ray source, and X-rays were generated at an accelerating voltage of 40 kV and a current of 30 mA. The divergent slit opening angle is 1/3 °, the scattering slit opening angle is 2/3 °, and the light receiving slit width is 0.3 mm. In order to accurately measure the half-value range, a step scan was performed in a range of 2θ of 51.5 to 53.5 ° with a measurement interval of 0.02 °, a counting time of 5 seconds, and an integration number of 3 times.

From the obtained diffraction chart, the crystallite diameter was determined by Scheller's equation (Dhkl = Kλ / βcosθ) using the powder X-ray analysis software PDXL2. In this formula, Dhkl is the crystallite diameter (size of the crystallite in the direction perpendicular to hkl) (Å), λ is the wavelength of the measured X-ray (Angstrom) (Cu target; 1.54059Å), and β is the crystallite. The spread of the diffraction line according to the magnitude (rad) (expressed using the half-value width), θ is the Bragg angle (rad) of the diffraction angle (the angle when the incident angle and the reflection angle are equal, and the peak top angle is used. ), K is a Scherrer constant (K = 0.9, although it depends on the definition of D and β). The peak data of the (111) plane was used for the calculation.

[Measurement of magnetic properties (permeability, holding power, and saturation magnetization)]
FeSiP alloy powder 1 and bisphenol F type epoxy resin (manufactured by TISC Co., Ltd .; one-component epoxy resin B-1106) are weighed at a mass ratio of 97: 3, and vacuum stirring / defoaming mixer (manufactured by EME; V-mini300). ) Was kneaded to obtain a paste in which the test powder was dispersed in the epoxy resin. This paste was dried on a hot plate at 30 ° C. for 2 hours to form a composite of an alloy powder and a resin, and then granulated into a powder to obtain a composite powder. 0.2 g of this composite powder was placed in a donut-shaped container, and a load of 9800 N (1 Ton) was applied by a hand press to obtain a toroidal molded product having an outer diameter of 7 mm and an inner diameter of 3 mm. For this molded product, the real part μ'of the complex relative permeability at 10 MHz was measured using an RF impedance / material analyzer (manufactured by Agilent Technologies; E4991A) and a test fixture (manufactured by Agilent Technologies; 16454A). ..

In addition, using a high-sensitivity vibrating sample magnetometer (manufactured by Toei Kogyo Co., Ltd .: VSM-P7-15 type), applied magnetic field (10 kOe), M measurement range (50 emu), step bit 100 bits, time constant 0.03 sec. The magnetic properties of the FeSiP alloy powder 1 were measured with a weight time of 0.1 sec. The saturation magnetization σs and the coercive force Hc were determined from the BH curve. The processing constants were specified by the manufacturer. Specifically, it is as follows.

Intersection detection: least squares method M average score 0 H average score 0
Ms With: 8 Mr With: 8 Hc With: 8 SFD With: 8 S.M. Star With: 8
Sampling time (seconds): 90
2-point correction P1 (Oe): 1000
2-point correction P2 (Oe): 4500

[Evaluation of moisture resistance]
The moisture resistance of FeSiP alloy powder 1 was evaluated as follows using Δσs as an index.
After storing the powder in an atmospheric atmosphere (temperature: 60 ° C., relative humidity: 90%) in which temperature and humidity are controlled for 7 days, a high-sensitivity vibrating sample magnetometer (manufactured by Toei Kogyo Co., Ltd .: VSM-) Using a P7-15 type), the saturated magnetization σs of the FeSiP alloy powder 1 (when the applied magnetic field is 10 kOe), the applied magnetic field (10 kOe), the M measurement range (50 emu), the step bit 100 bits, the time constant 0.03 sec, and the weight time 0.1 sec. Magnetization per gram) was measured. The difference between the obtained σs (A) and σs (B) before storage in the above atmosphere was defined as Δσs.
Δσs = σs (B) -σs (A)

[Evaluation of oxidation resistance]
The oxidation resistance of FeSiP alloy powder 1 was evaluated as follows.

The weight increase rate during heating was determined by a differential thermogravimetric simultaneous measuring device (EXATERT G / DTA6300 type of SII Nanotechnology Co., Ltd.). Specifically, 20 mg of FeSiP alloy powder 1 is placed in a sample container (alumina open type sample container φ5.2 mm, height 2.5 mm), the container is set in the holder of the measuring device, and the flow rate is set in the measuring device. The analysis was carried out by flowing Air at 200 ml / min (that is, in an air atmosphere) and raising the temperature from room temperature (25 ° C.) to 800 ° C. at a heating rate of 5 ° C./min. The weight of the alloy powder before heating, which is the difference (weight increased by heating) between the weight (C) of the alloy powder in the sample container and the weight (D) of the alloy powder before heating measured by raising the temperature to 700 ° C. The rate of increase (%) with respect to (D) was calculated.
Rate of increase (%) = {(C)-(D)} / (D) x 100

[Example 1]
The FeSiP alloy powder 1 obtained in Reference Example 1 (Ref. 1) was heated to 600 ° C. at a heating rate of 10 ° C./min in a nitrogen atmosphere containing 1.0 ppm of oxygen using a furnace. The heat treatment was carried out at this heat treatment temperature of 600 ° C. for 30 minutes to obtain a substantially spherical FeSiP alloy powder 2. The composition (Fe, Si, P content, oxygen content, carbon content and nitrogen content), BET specific surface area, and tap density of this alloy powder 2 in the same manner as in Reference Example 1 (Ref. 1). (TAP), particle size distribution, crystallite diameter and magnetic properties were determined, and moisture resistance and oxidation resistance were evaluated. The amount of P in the FeSiP alloy powder 2 was almost the same as that in the FeSiP alloy powder 1.

[Examples 2 to 6, Comparative Examples 1 to 4]
Substantially spherical FeSiP alloy powders 3 to 11 were obtained in the same manner as in Example 1 except that the heat treatment temperature and the oxygen concentration in the nitrogen atmosphere were changed as shown in Table 1 below. For these alloy powders, the composition (Fe, Si, P content, oxygen content, carbon content and nitrogen content), BET specific surface area, and tap density are the same as in Reference Example 1 (Ref. 1). (TAP), particle size distribution, crystallite diameter and magnetic properties were determined, and moisture resistance and oxidation resistance were evaluated. The amount of P in the FeSiP alloy powders 3 to 11 was almost the same as that in the FeSiP alloy powder 1.

[Reference Example 2 (Ref. 2)]
FeSi of Reference Example 2 in the same manner as in Reference Example 1 except that the raw materials for the molten metal were electrolytic iron (purity: 99.95% by mass or more) 14.03 kg and silicon metal (purity: 99% by mass or more) 0.975 kg. Alloy powder 1 was obtained.

The substantially spherical FeSi alloy powder 1 thus obtained has a composition (Fe, Si content, oxygen content, carbon content and nitrogen content) in the same manner as in Reference Example 1 (Ref. 1). ), BET specific surface area, tap density (TAP), particle size distribution, crystallite diameter and magnetic properties were determined, and moisture resistance and oxidation resistance were evaluated.

[Example 7]
The FeSi alloy powder 1 obtained in Reference Example 2 (Ref. 2) was heat-treated in the same manner as in Example 1 to obtain a substantially spherical FeSi alloy powder 2. The composition (Fe, Si content, oxygen content, carbon content and nitrogen content), BET specific surface area, and tap density (TAP) of this alloy powder in the same manner as in Reference Example 1 (Ref. 1). , Particle size distribution, crystallite diameter and magnetic properties were obtained, and moisture resistance and oxidation resistance were evaluated.

The above results are summarized in Tables 1 and 2 below.

From the comparison between Comparative Examples and Examples, the soft magnetic powder obtained by heat-treating the FeSi (P) alloy-based soft magnetic powder having a specific composition at a high temperature of 600 ° C. or higher has a large crystallite diameter of 99 nm or more. It can be seen that when the moisture resistance is evaluated using this as a molded product (Δσs), excellent results are shown.

Further, from the comparison between Example 3 and other Examples, it can be seen that a soft magnetic powder having a low nitrogen content can be obtained by setting the heat treatment temperature to less than 900 ° C.

From the comparison between Example 6 and other examples, when the FeSi (P) alloy-based soft magnetic powder is heat-treated under the condition that the product of the heat treatment temperature and the oxygen concentration in the heat treatment atmosphere is 600,000 (° C. ppm) or less. The obtained soft magnetic powder has a product of the oxygen content (O) and the average particle size (D50) of 2.62 (mass% · μm) or less, and the moisture resistance for this may be particularly good. Recognize.

From the comparison between Examples 5 and 6 and other Examples, the product of the oxygen content (O) and the average particle size (D50) is 2.10 (mass%) by setting the oxygen concentration in the heat treatment atmosphere to 100 ppm or less. A soft magnetic powder of μm) or less is obtained, and it can be seen that the magnetic permeability (μ') of the molded product thereof is excellent.

From the comparison between Example 4 and other examples, by setting the heat treatment temperature to 800 ° C. and the oxygen concentration in the heat treatment atmosphere to 100 ppm, the product of the oxygen content (O) and the average particle size (D50) is 1. A soft magnetic powder larger than .68 (mass% μm) and smaller than 2.10 (mass% μm) was obtained, which has excellent oxidation resistance, moisture resistance, and magnetic permeability (μ'). It turns out to be excellent.

Claims (15)

A soft magnetic powder containing 89.5 to 99.6% by mass of Fe, 0.2 to 9.0% by mass of Si, and 0 to 1.0% by mass of P.
A soft magnetic powder having a crystallite diameter of 95 nm or more on the (111) plane. The soft magnetic powder according to claim 1, wherein the content of N is 800 ppm or less. The soft magnetic powder according to claim 1 or 2, wherein the total content of Fe, Si and P in the soft magnetic powder is 97.5% by mass or more. The product (O × D50) of the oxygen content (O) of the soft magnetic powder and the cumulative 50% particle diameter (D50) on a volume basis measured by a laser diffraction / scattering particle size distribution measuring device is 3.00 (mass%). The soft magnetic powder according to any one of claims 1 to 3, which is μm) or less. The soft magnetic powder according to claim 4, wherein the product (O × D50) is 2.30 (mass% · μm) or less. The soft magnetic powder according to claim 5, wherein the product (O × D50) is 1.70 to 2.00 (mass% · μm). The soft magnetic powder according to any one of claims 1 to 6, which contains 0.02 to 0.5% by mass of P. It has a step of heat-treating a soft magnetic powder containing 89.5 to 99.6% by mass of Fe, 0.2 to 9.0% by mass of Si, and 0 to 1.0% by mass of P at 500 to 950 ° C. Heat treatment method for soft magnetic powder. The method for heat-treating a soft magnetic powder according to claim 8, wherein the heat treatment is performed at 500 to 850 ° C. The heat treatment is carried out under the condition that the product (heat treatment temperature x atmospheric oxygen concentration) of the heat treatment temperature (° C.) and the oxygen concentration (ppm) in the atmosphere in which the heat treatment is performed is 700,000 (° C. ppm) or less. The method for heat-treating a soft magnetic powder according to claim 8 or 9. The method for heat-treating a soft magnetic powder according to claim 8 or 9, wherein the heat treatment is performed in an atmosphere having an oxygen concentration of 500 ppm or less. The method for heat-treating a soft magnetic powder according to any one of claims 8 to 11, wherein the heat treatment is performed at 700 to 850 ° C. in an atmosphere having an oxygen concentration of 50 to 400 ppm. A soft magnetic material containing the soft magnetic powder according to any one of claims 1 to 7 and a binder. A powder magnetic core containing the soft magnetic powder according to any one of claims 1 to 7. A dust compact obtained by molding the soft magnetic powder according to any one of claims 1 to 7 or the soft magnetic material according to claim 13 into a predetermined shape and heating the obtained molded product to obtain a dust core. How to make a magnetic core.