WO2021241466A1

WO2021241466A1 - Soft magnetic powder, method for producing soft magnetic powder, soft magnetic material, powder magnetic core, and method for producing powder magnetic core

Info

Publication number: WO2021241466A1
Application number: PCT/JP2021/019492
Authority: WO
Inventors: 岳志河内; 悠介飯田
Original assignee: Ｄｏｗａエレクトロニクス株式会社
Priority date: 2020-05-27
Filing date: 2021-05-24
Publication date: 2021-12-02
Also published as: JP2021188131A; KR20220129623A; TW202206619A; CN115605303A

Abstract

A soft magnetic powder composed of an Fe alloy including 0.1-15 mass% of Si and at least 1 ppm to less than 1,000 ppm of an alkali metal and/or an alkaline earth metal.

Description

Soft magnetic powder, manufacturing method of soft magnetic powder, soft magnetic material, powder magnetic core and powder magnetic core manufacturing method

The present invention relates to a soft magnetic powder, a method for producing 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. In electronic devices, the frequency is increased in order to improve the performance and the size, and along with this, the dust core constituting the magnetic component is also required to cope with the frequency.

The dust core is generally manufactured by compounding soft magnetic powder with a binder such as resin as necessary and then compression molding. 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 a loss is divided into a hysteresis loss and an eddy current loss, and in particular, in order to reduce the hysteresis loss, a soft magnetic powder capable of providing a dust core having a high magnetic permeability is required. Hereinafter, the soft magnetic powder capable of forming a powder magnetic core having a high magnetic permeability may be expressed as "a soft magnetic powder having a high magnetic permeability".

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).

In Patent Document 1, a soft magnetic powder capable of producing a powder magnetic core having a high magnetic permeability, a powder magnetic core having a high magnetic permeability manufactured by using the soft magnetic powder, and high-performance magnetism having the powder magnetic core. The subject is to provide an element. In order to solve this problem, Fe, Si and Mn are contained, Fe is the main component, the content of Si is 1 wt% or more and 8 wt% or less, and the content of Mn is more than 0.2 wt% and 1 wt% or less. Patent Document 1 describes a soft magnetic powder that satisfies all of the requirements.

It is also important that the dust core does not easily deteriorate over time. The amount of oxidation over time (oxidation resistance) can be used as one index of deterioration over time. This is because when the powder (which constitutes the dust core) is oxidized, it generally adversely affects the magnetic properties such as magnetic permeability.

Japanese Unexamined Patent Publication No. 2008-255384

It is an object of the present invention to provide a soft magnetic powder composed of an alloy containing Fe and Si, which is excellent in magnetic permeability and oxidation resistance, and a method for producing such a soft magnetic powder. And.

As a result of diligent studies to solve the above problems, the present inventors have found that a soft magnetic powder containing a predetermined amount of an alkali metal and / or an alkaline earth metal is excellent in magnetic permeability and oxidation resistance, and the present invention has been made. Has been completed.

That is, the present invention is as follows.
A soft magnetic powder composed of an Fe alloy containing 0.1 to 15% by mass of Si and containing 1 ppm or more and less than 1000 ppm of an alkali metal and / or an alkaline earth metal.

It is preferable that the cumulative 50% particle size (D50) based on the volume measured by the laser diffraction type particle size distribution measuring device of this soft magnetic powder is 0.1 to 15 μm.

The soft magnetic powder preferably contains 84 to 99.7% by mass of Fe, preferably 0.2 to 10% by mass of Si, and contains 10 to 800 ppm of an alkali metal and / or an alkaline earth metal. preferable.

It is preferable that the soft magnetic powder further contains Cr, and the Cr content is 0.1 to 8% by mass. Further, it is preferable that the total content of Fe, Si and Cr in the powder is 97.8% by mass or more.

The Mn content of the soft magnetic powder is preferably 1000 ppm or less, more preferably 800 ppm or less, and further preferably 15 to 400 ppm.

As a preferred embodiment, the soft magnetic powder of the present invention is a soft magnetic powder composed of an Fe alloy containing 0.1 to 15% by mass of Si and 1 to 950 ppm of Na.

The method for producing a soft magnetic powder of the present invention comprises a step 1 of heating and melting an Fe raw material and a Si raw material to prepare a molten metal containing Fe and Si and having a Si content of 0.1 to 15% by mass.
Step 2 to obtain a soft magnetic powder composed of an Fe alloy containing Si by spraying a fluid onto the molten metal while dropping the molten metal to crush and solidify the molten metal.
It has a step 3 of adding an alkali metal source and / or an alkaline earth metal source to the soft magnetic powder so that the soft magnetic powder contains an alkali metal and / or an alkaline earth metal at 1 ppm or more and less than 1000 ppm.

The Mn content in the molten metal is preferably 1000 ppm or less.

By further heating and melting the Cr raw material in addition to the Fe raw material and the Si raw material, a molten metal containing Fe, Si and Cr is prepared as the molten metal, and the Cr content in the molten metal is 0.1 to 8% by mass. Is preferable.

In step 3, an alkali metal source and / or an alkaline earth metal source is added to the soft magnetic powder so that the soft magnetic powder contains 10 to 800 ppm of an alkali metal and / or an alkaline earth metal. preferable.

Water was used as the fluid in the step 2, and in the step, a slurry in which the soft magnetic powder and water were mixed was obtained.
In the step 3, it is preferable to add the alkali metal source and / or the alkaline earth metal source to the slurry.

It is preferable that the alkali metal and / or alkaline earth metal source is an alkali metal, and is sodium hydroxide or potassium hydroxide.

It is preferable to use electrolytic iron having a Mn content of 100 ppm or less as the Fe raw material.

In a preferred embodiment, the method for producing a soft magnetic powder of the present invention heats and melts an Fe raw material and a Si raw material to prepare a molten metal containing Fe and Si and having a Si content of 0.1 to 15% by mass. Step 1 and
Step 2 to obtain a soft magnetic powder composed of an Fe alloy containing Si by spraying a fluid onto the molten metal while dropping the molten metal to crush and solidify the molten metal.
It has a step 3 of adding a Na source to the soft magnetic powder so that the soft magnetic powder contains 1 to 950 ppm of Na.

The soft magnetic material of the present invention includes, for example, the above-mentioned soft magnetic powder and a binder. The dust core of the present invention includes the above-mentioned soft magnetic powder. This dust core can be produced, for example, by molding the above-mentioned soft magnetic powder or the above-mentioned soft magnetic material into a predetermined shape and heating the obtained molded product.

According to the present invention, there is provided a soft magnetic powder having excellent magnetic permeability and oxidation resistance, which is composed of an alloy containing Fe and Si, and a method for producing such a soft magnetic powder.

Hereinafter, embodiments of the soft magnetic powder of the present invention and the method for producing the same will be described.

<Soft magnetic powder>
The embodiment of the soft magnetic powder of the present invention is composed of an Fe (iron) alloy containing Si (silicon).

(Alloy composition)
The soft magnetic powder contains Si in the range of 0.1 to 15% by mass, and preferably contains Fe as a main component. Fe is an element that contributes to the magnetic and mechanical properties of the soft magnetic powder. Si is an element that enhances magnetic properties such as magnetic permeability of soft magnetic powder. The "main component" of Fe means the element having the highest content among the elements constituting the soft magnetic powder. The content of Fe in the soft magnetic powder is preferably 84 to 99.7% by mass, more preferably 88 to 98.2% by mass, from the viewpoint of magnetic properties and mechanical properties. 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 this viewpoint, the Si content is preferably 0.2 to 10% by mass (preferably 0.2% by mass or more and less than 10% by mass), and more preferably 1.2 to 8% by mass. Further, the total content of Fe and Si in the soft magnetic powder is preferably 90% by mass or more, more preferably 92% by mass or more (usually, from the viewpoint of suppressing deterioration of magnetic properties due to the inclusion of impurities). 99.8% by mass or less).

The embodiment of the soft magnetic powder of the present invention preferably contains Cr (chromium) from the viewpoint of lowering the oxygen content of the powder, enhancing magnetic properties such as saturation magnetization, and enhancing the oxidation resistance of the powder. .. From the above viewpoint, the Cr content of this soft magnetic powder is preferably 0.1 to 8% by mass, more preferably 0.5 to 7% by mass.

Further, the total content of Fe, Si and Cr in this soft magnetic powder is preferably 97.8% by mass or more (usually 99.8% by mass or less). By adopting this configuration, the soft magnetic powder becomes crystalline and therefore softer than the amorphous alloy powder, and when the powder magnetic core is manufactured using the soft magnetic powder, the packing density of the powder is increased. High magnetic permeability can be achieved.

The embodiment of the soft magnetic powder of the present invention contains 1 ppm or more and less than 1000 ppm of an alkali metal and / or an alkaline earth metal. By containing such a trace amount of alkali metal and / or alkaline earth metal, the soft magnetic powder is excellent in magnetic permeability and also in oxidation resistance. The oxidation resistance can be evaluated by an accelerated test in which the powder is stored for a certain period of time under high temperature and high humidity.

Regarding the content of the alkali metal and / or alkaline earth metal, when the soft magnetic powder contains a plurality of types of alkali metals and / or alkaline earth metals (for example, when Na and K are contained), these contents are It means that the total is 1 ppm or more and less than 1000 ppm. From the viewpoint of the oxidation resistance of the soft magnetic powder, the content of the alkali metal and / or the alkaline earth metal in the soft magnetic powder is preferably 1 to 950 ppm, more preferably 10 to 950 ppm, as a specific range. It is 800 ppm, more preferably 15 to 500 ppm, and particularly preferably 50 to 200 ppm. The alkali metal and / or alkaline earth metal is assumed to be present on the particle surface of the soft magnetic powder, for example, when the soft magnetic powder is produced by the embodiment of the method for producing the soft magnetic powder of the present invention described later. Conceivable.

As the alkali metal and / or alkaline earth metal, Na (sodium) and K (potassium) are preferable, and Na is particularly preferable, from the viewpoint of magnetic permeability and oxidation resistance of the soft magnetic powder.

In addition to the above Fe, Si, Cr, and alkali metals and / or alkaline earth metals, the soft magnetic powder of the present embodiment may contain other elements as long as the effects of the present invention are exhibited. Examples are Pd (palladium), Co (cobalt), Mo (molybdenum), Zr (zirconium), C (carbon), N (nitrogen), O (oxygen), P (phosphorus), Cl (chlorine), Mn (manganese), Ni (nickel), Cu (copper), S (sulfur), As (arsenic), B (boron), Sn (tin), Ti (titanium), V (vanadium), Al (aluminum) Can be mentioned. Of these, the content excluding oxygen is preferably 1% by mass or less in total, and more preferably 10 to 5000 ppm. The soft magnetic powder of the present embodiment can be produced, for example, by the embodiment of the method for producing a soft magnetic powder of the present invention, which will be described later. In such a case, the amount of each element mentioned above is small. Excellent magnetic properties, etc.

Of these, the content of Mn contained as an impurity in the Fe raw material and Si raw material, which are the raw materials for producing the soft magnetic powder of the present invention, is the magnetic permeability of the embodiment of the soft magnetic powder of the present invention. From the viewpoint of oxidation resistance, less is preferable. In order to reduce the Mn content to 0, a manufacturing raw material having a reduced Mn as much as possible may be used, but it is very difficult in terms of cost. Considering the balance between cost and characteristics (permeability, etc.), the allowable content of Mn in the soft magnetic powder is preferably 1000 ppm or less, more preferably 800 ppm or less, and further preferably 0. It is 1 to 800 ppm, more preferably 10 to 500 ppm, particularly preferably 15 to 400 ppm, and most preferably 50 to 300 ppm.

In the embodiment of the soft magnetic powder of the present invention, the oxygen content is preferably 2.0% by mass or less from the viewpoint of magnetic permeability (the oxygen content is usually 0.05% by mass or more). From the same viewpoint, the oxygen content is more preferably 0.1 to 1.5% by mass. Since the oxygen content increases as the particle size of the powder decreases, the oxygen content (O) and the laser diffraction type particle size distribution measuring device for the soft magnetic powder are used to correct the fluctuation of the oxygen content due to the particle size. It is desirable to adopt the product (O × D ₅₀ (mass% · μm)) with the cumulative 50% particle size (D _{50) based on the measured volume.} The product (O × D ₅₀ (mass% · μm)) is preferably 12 (mass% · μm) or less, preferably 0.40 to 8.50, from the viewpoint of obtaining good saturation magnetization of the soft magnetic powder. It is more preferably (% by mass · μm).

(Average particle size (D ₅₀ ))
Cumulative 50% particle diameter on a volume basis as measured by a laser diffraction type particle size distribution measuring apparatus of the embodiment of the soft magnetic powder of the present invention (D ₅₀₎ is not particularly limited, from the viewpoint that corresponds to the size of electronic equipment , 0.1 to 15 μm, more preferably 0.5 to 10 μm.

(BET specific surface area)
The specific surface area (BET specific surface area) measured by the BET one-point method according to 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. preferably 0.15 ~ 3.00m ² / g, more preferably 0.20 ~ 2.50m ² / g.

(Tap density)
The tap density 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, and more preferably. It is 2.8 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 (flake-shaped), or distorted shape (indeterminate form). good. More preferably, it is a powder having a high degree of sphericity.

<Manufacturing method of soft magnetic powder>
The embodiment of the soft magnetic powder of the present invention described above can be produced by the embodiment of the method for producing a soft magnetic powder of the present invention. This production method includes a molten metal preparation step 1, an atomizing step 2, and an alkali metal source and / or an alkaline earth metal source addition step 3. Hereinafter, this manufacturing method will be described.

(Melted metal preparation step 1)
In the molten metal preparation step, the Fe raw material and the Si raw material are heated and melted to prepare the molten metal. At this time, the amount of Si raw material used is adjusted so that the content of Si in the molten metal is 0.1 to 15% by mass. The content of each element in the molten metal shall be calculated from the amount of the raw material charged (multiplied by the ratio and purity of each element in the raw material).

The content of Si in the molten metal is preferably 0.2 to 10% by mass (preferably 0.2% by mass or more and less than 10% by mass), and more preferably 1.2 to 8% by mass. Further, the total content of Fe and Si in the molten metal is preferably 90% by mass or more, more preferably 92% by mass or more (usually 99.8% by mass or less). Examples of Fe raw materials include pure iron and electrolytic iron, and examples of Si raw materials include silicon metal and semiconductor scrap.

Further, as described above, the content of Mn in the powder is preferably 1000 ppm or less, more preferably 800 ppm or less, still more preferably 0.1 to 800 ppm, still more preferably, from the viewpoint of magnetic permeability and oxidation resistance of the soft magnetic powder. It is preferably 10 to 500 ppm, particularly preferably 15 to 400 ppm, most preferably 50 to 300 ppm, and for that purpose, the Mn content in the molten metal is preferably 1000 ppm or less, more preferably 800 ppm or less, still more preferably. The type and amount of the raw material for preparing the molten metal are adjusted so as to be 0.1 to 800 ppm, more preferably 10 to 500 ppm, particularly preferably 15 to 400 ppm, and most preferably 50 to 300 ppm.

For example, as the Fe raw material, electrolytic iron having high purity and low content of Mn as an impurity is used. The Fe content of the electrolytic iron is preferably 99.90% by mass or more (usually 99.999% by mass or less), and the Mn content is 100 ppm or less, preferably 50 ppm or less, more preferably 25 ppm or less, still more preferably. It is 10 ppm or less, particularly preferably 5 ppm or less, and most preferably 3 ppm or less (usually 0.001 ppm or more). Similarly, it is preferable to use a Si raw material having a low Mn content. Further, with respect to the Fe raw material (the Mn content is not small) and the Si raw material, measures may be taken to reduce the Mn content by refining technology.

Further, when the soft magnetic powder is set to further contain Cr, the Cr raw material is further heated and melted in addition to the Fe raw material and the Si raw material in the main molten metal preparation step 1. Examples of Cr raw materials include ferrochrome and electrolytic metal chromium. The Cr content in the molten metal should be 0.1 to 8% by mass from the viewpoint of lowering the oxygen content of the soft magnetic powder, enhancing magnetic properties such as saturation magnetization, and enhancing the oxidation resistance of the powder. Is preferable, and 0.5 to 7% by mass is more preferable. The total content of Fe, Si and Cr in the molten metal is preferably 97.8% by mass or more (usually 99.8% by mass or less). Further, when trying to produce a soft magnetic powder having a low Mn content, a Cr raw material having a low Mn content may be used, or a Cr raw material (not having a low Mn content) may be refined by refining technology. You may take measures to reduce the content of.

(Atomizing process 2)
In the atomizing step 2, a fluid is sprayed onto the molten metal while dropping the molten metal prepared in the molten metal preparation step 1, and the molten metal is crushed and solidified to be composed of an Fe alloy containing Si (optionally further containing Cr). To obtain a soft magnetic powder. Examples of such fluids include gas, water and frames. From the viewpoint of producing a soft magnetic powder having a high degree of sphericity, gas is preferable as a fluid, and from the viewpoint of producing a soft magnetic powder having a small particle size in good yield, water is preferable as a fluid. When water is used as the fluid, the atomizing step 2 is carried out to obtain a slurry in which the soft magnetic powder and water are mixed.

(Alkali metal source and / or alkaline earth metal source addition step 3)
In the alkali metal source and / or alkaline earth metal source addition step 3, the alkali metal source and / or the alkaline earth metal source is added to the soft magnetic powder obtained in the atomizing step 2. The amount of the alkali metal source and / or the alkaline earth metal source added may accelerate the progress of corrosion in the final product from the viewpoint of magnetic permeability and oxidation resistance, and if the amount added is too large, it is a soft magnetic powder. The content of the alkali metal and / or alkaline earth metal in the metal is 1 ppm or more and less than 1000 ppm. This addition amount can be experimentally determined according to the embodiment of the alkali metal source and / or alkaline earth metal source addition step 3.

From the viewpoint of the oxidation resistance of the soft magnetic powder, the amount of the alkali metal source and / or the alkaline earth metal source added is preferably 1 to 1 to the content of the alkali metal and / or the alkaline earth metal in the soft magnetic powder. The amount is 950 ppm, more preferably 10 to 800 ppm, still more preferably 15 to 500 ppm, and particularly preferably 50 to 200 ppm.

Examples of alkali metal sources and / or alkaline earth metal sources include sodium hydroxide, sodium hydrogen carbonate (Na source), and potassium hydroxide (K source). Among these, sodium hydroxide and potassium hydroxide are preferable, and sodium hydroxide is more preferable, because constituent elements other than alkali metal and / or alkaline earth metal are less likely to be involved in the soft magnetic powder as impurities.

The method of adding the alkali metal source and / or the alkaline earth metal source to the soft magnetic powder is not particularly limited, but in a wet manner so that the alkali metal and / or the alkaline earth metal adheres evenly to the constituent particles of the powder. Addition is preferred. For example, when water is used as a fluid in the atomizing step 2, a slurry in which soft magnetic powder and water are mixed can be obtained. An alkali metal source and / or an alkaline earth metal source is added to the slurry, and the slurry is stirred. do. Further, for example, when a dry soft magnetic powder is obtained in the atomizing step 2 by using a gas as a fluid, the alkali metal and / or the alkaline earth metal source, water and the powder are mixed and stirred. An alkali metal and / or an alkaline earth metal source may be dissolved in water to form an aqueous solution, and the powder may be mixed and stirred.

(Other processes (solid-liquid separation process, drying process, crushing process, etc.))
When water is used as the fluid in the atomizing step 2, or when the alkali metal source and / or the alkaline earth metal source is wetly added in the alkali metal source and / or the alkaline earth metal source addition step 3, the (alkaline metal source and / or the alkaline earth metal source is added. When the soft magnetic powder (containing an alkali metal and / or an alkaline earth metal) is obtained in the form of a slurry mixed with water, the soft magnetic powder is recovered as a solid content by solid-liquid separation. .. The soft magnetic powder obtained in the dry state in the alkali metal source and / or the alkaline earth metal source addition step 3 and the powder obtained by the above-mentioned solid-liquid separation are further washed with water and then dried, if necessary. May be good.

Further, the soft magnetic powder may be crushed or classified by sieving or wind power classification as necessary to adjust the particle size (particle size distribution).

Further, the soft magnetic powder produced according to the embodiment of the method for producing a soft magnetic powder of the present invention described above may be heat-treated. The heat treatment is carried out at a temperature of about 400 to 1100 ° C. in a reducing atmosphere such as a hydrogen atmosphere or an inert atmosphere such as a nitrogen atmosphere. This makes it possible to remove the residual stress and strain of the soft magnetic powder while preventing oxidation of the soft magnetic powder, and improve the magnetic properties. Further, the heat treatment may be carried out before or after the particle size adjusting process such as the above-mentioned crushing.

<Soft magnetic material>
The embodiment of the soft magnetic powder of the present invention described above is excellent in magnetic permeability and oxidation resistance as described above.

From such characteristics, the embodiment of the soft magnetic powder of the present invention can be suitably applied to the soft magnetic material. The soft magnetic powder itself can be used as a soft magnetic material, or 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 in the case of a soft magnetic powder alone and in the case of a mixture of powder and 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 the obtained molded product, a dust core including the embodiment of the soft magnetic powder of the present invention can be produced. More specifically, a powder magnetic core is obtained by placing a soft magnetic material in a mold having a predetermined shape, pressurizing the material, and heating the material.

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited thereto.

[Example 1]
In a tundish furnace, 26.9 kg of electrolytic iron (purity: about 99.99% by mass. Mn content: 1 ppm), silicon metal (purity: 99% by mass or more, Mn content: 770 ppm) 1.1 kg and ferrochrome ( Fe content: 31.3% by mass. Cr content: 66.8% by mass. Mn content: 3600ppm) 2.0 kg is heated and dissolved at 1700 ° C. in a nitrogen atmosphere to dissolve the molten metal in a nitrogen atmosphere (oxygen concentration). While dropping from the bottom of the tundish furnace at 0.001 ppm or less), high-pressure water (pH 6) was sprayed at a water pressure of 150 MPa and a water volume of 160 L / min to pulverize and solidify to obtain a slurry containing a soft magnetic powder.

A 25% by mass NaOH aqueous solution was added to the obtained slurry (containing 30 kg of the soft magnetic powder) at a ratio of 3 kg to 100 kg of the soft magnetic powder, and the mixture was stirred and mixed. Then, the slurry was separated into solid and liquid, and the solid was dried in vacuum at 40 ° C. for 30 hours to obtain FeSiCr alloy powder 1.

It should be noted that the measurement results of the alkali metal and alkaline earth metal contents of the FeSiCr alloy 5 obtained in Comparative Example 1 described later and the alkali metals and alkalis of the FeSiCr alloy powders 1 and 2 obtained in Examples 1 and 2 were obtained. Since the content of the earth metal is the same, the electrolytic iron and the pure iron, silicon metal and ferrochrome used in Example 2 and the like are said to contain substantially neither alkali metal nor alkaline earth metal. Conceivable.

For the substantially spherical FeSiCr alloy powder 1 thus obtained, the composition (amount of Fe, Si, Cr, O, Mn and alkali metal and alkaline earth metal), particle size distribution, magnetic properties and oxidation resistance were determined. rice field. The results are shown in Table 2 below. Further, the raw materials for producing the powder and the amount of the NaOH aqueous solution added are summarized in Table 1 below.

[composition]
The composition of FeSiCr alloy powder 1 was measured as follows.
Si was analyzed by the gravimetric method as follows. First, hydrochloric acid and perchloric acid were added to the sample (FeSiCr alloy powder 1) and decomposed by heating, and the sample (FeSiCr alloy powder 1) was heated until white smoke of perchloric acid was generated. Continued heating to dry. 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 ignited. 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.

The contents of Cr, Mn and alkaline earth metals were determined by quantitative analysis using an inductively coupled plasma (ICP) emission spectrometer (SPS3520V manufactured by Hitachi High-Tech Science Co., Ltd.).
The content of the alkali metal was determined by quantitative analysis using an atomic absorption spectrophotometer (Hitachi High-Tech Science, ZA3300 type frame dedicated machine).

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

[Particle size distribution]
For the particle size distribution, use a laser diffraction 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. rice field.

[Measurement of magnetic properties (permeability μ')]
FeSiCr 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 complex powder was placed in a toroidal-shaped container, and a load of 9800 N (1 Ton) was applied by a hand press to obtain a toroidal-shaped molded body having an outer diameter of 7 mm and an inner diameter of 3 mm. For this molded body, 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). .. The packing density was obtained by dividing the weight of the FeSiCr alloy powder 1 (97% of the weight of the composite powder) in the obtained toroidal-shaped molded body by the volume measured for the molded body. The packing density was 5.4 g / cm ³ .

[Evaluation of oxidation resistance]
A test was conducted in which 30 g of FeSiCr alloy powder 1 (gray) was placed in an aluminum cup and stored at 85 ° C. in an 85% RH environment for 3 days. Further, after the FeSiCr alloy powder 1 after the storage test was granulated in a mortar and mixed uniformly, the oxygen content of the FeSiCr alloy powder 1 was determined to determine the amount of increase in the oxygen content by the storage test. The oxygen content of the alloy powder after the storage test was measured by an oxygen / nitrogen / hydrogen analyzer (EMGA-920 manufactured by HORIBA, Ltd.).

[Example 2]
FeSiCr alloy powder according to Example 2 in the same manner as in Example 1 except that pure iron (purity: about 99.94% by mass, Mn content: 200 ppm) was used instead of electrolytic iron in Example 1. 2 was manufactured. The FeSiCr alloy powder 2 was evaluated in the same manner as in Example 1. The results are shown in Table 2 below.

[Example 3]
In Example 2, the FeSiCr alloy powder 3 was produced by the same method as in Example 2 except that the amount of the 25 mass% NaOH aqueous solution added to the slurry was changed to 240 g with respect to 100 kg of the soft magnetic powder. The FeSiCr alloy powder 3 was evaluated in the same manner as in Example 1. The results are shown in Table 2 below.

[Example 4]
In Example 2, the FeSiCr alloy powder 4 was produced by the same method as in Example 2 except that the amount of the 25 mass% NaOH aqueous solution added to the slurry was changed to 36 kg in proportion to 100 kg of the soft magnetic powder. The FeSiCr alloy powder 4 was evaluated in the same manner as in Example 1. The results are shown in Table 2 below.

[Comparative Example 1]
The FeSiCr alloy powder 5 was produced in the same manner as in Example 2 except that the 25% by mass NaOH aqueous solution was not added to the slurry in Example 2. The FeSiCr alloy powder 5 was evaluated in the same manner as in Example 1. The results are shown in Table 2 below. In the evaluation of oxidation resistance, the FeSiCr alloy powder 5 changed its color from gray to reddish brown.

[Comparative Example 2]
In Example 2, the FeSiCr alloy powder 6 was produced by the same method as in Example 2 except that the amount of the 25 mass% NaOH aqueous solution added to the slurry was changed to 90 kg in proportion to 100 kg of the soft magnetic powder. The FeSiCr alloy powder 6 was evaluated in the same manner as in Example 1. The results are shown in Table 2 below. In the evaluation of oxidation resistance, the FeSiCr alloy powder 6 changed its color from gray to reddish brown.

For Examples 1 to 4 and Comparative Examples 1 and 2 above, the types of raw materials, the amount charged, and the amount of the NaOH aqueous solution added are shown in Table 1 below, and the composition, particle size distribution, magnetic properties, and oxidation resistance of the produced FeSiCr alloy powder are shown. The sexes are shown in Table 2 below. In Table 2, for example, in the column of "alkali metal / alkaline earth metal", in Example 1 "Na: 90", 90 ppm of Na is detected, and other alkali metals / alkaline earth metals are detected. It means that it wasn't. The same applies to the following Examples and Comparative Examples, and the “−” in Comparative Example 1 means that neither an alkali metal nor an alkaline earth metal was detected.

The FeSiCr alloy powders 1 to 4 of Examples 1 to 4 containing a predetermined amount of an alkali metal and / or an alkaline earth metal (Na) show an excellent magnetic permeability of 15.5 or more, and are stored to evaluate oxidation resistance. No discoloration was observed in the test, and the increase in oxygen content was smaller than that in the comparative example.

The FeSiCr alloy powders 1 and 2 of Examples 1 and 2 in which the amount of the alkali metal and / or the alkaline earth metal is 90 ppm are particularly excellent in oxidation resistance (the amount of increase in the oxygen content is small), and among these, Mn The FeSiCr alloy powder of Example 1 having the lowest content had particularly excellent magnetic permeability and also had the highest oxidation resistance.

Claims

A soft magnetic powder composed of an Fe alloy containing 0.1 to 15% by mass of Si and containing an alkali metal and / or an alkaline earth metal of 1 ppm or more and less than 1000 ppm.
The soft magnetic powder according to claim 1, wherein the cumulative 50% particle size (D50) on a volume basis measured by a laser diffraction type particle size distribution measuring device is 0.1 to 15 μm.
The soft magnetic powder according to claim 1 or 2, which contains 84 to 99.7% by mass of Fe.
The soft magnetic powder according to any one of claims 1 to 3, which contains 0.2 to 10% by mass of Si.
The soft magnetic powder according to any one of claims 1 to 4, which contains 10 to 800 ppm of an alkali metal and / or an alkaline earth metal.
The soft magnetic powder according to any one of claims 1 to 5, wherein the soft magnetic powder further contains Cr, and the Cr content is 0.1 to 8% by mass.
The soft magnetic powder according to claim 6, wherein the total content of Fe, Si and Cr is 97.8% by mass or more.
The soft magnetic powder according to any one of claims 1 to 7, wherein the Mn content is 1000 ppm or less.
The soft magnetic powder according to any one of claims 1 to 8, wherein the Mn content is 800 ppm or less.
The soft magnetic powder according to any one of claims 1 to 9, wherein the Mn content is 15 to 400 ppm.
A soft magnetic powder composed of an Fe alloy containing 0.1 to 15% by mass of Si and 1 to 950 ppm of Na.
Step 1 of preparing a molten metal containing Fe and Si and having a Si content of 0.1 to 15% by mass by heating and melting the Fe raw material and the Si raw material.
Step 2 to obtain a soft magnetic powder composed of an Fe alloy containing Si by spraying a fluid onto the molten metal while dropping the molten metal to crush and solidify the molten metal.
It has a step 3 of adding an alkali metal source and / or an alkaline earth metal source to the soft magnetic powder so that the soft magnetic powder contains 1 ppm or more and less than 1000 ppm of the alkali metal and / or the alkaline earth metal. A method for producing soft magnetic powder.
The method for producing a soft magnetic powder according to claim 12, wherein the Mn content in the molten metal is 1000 ppm or less.
By further heating and melting the Cr raw material in addition to the Fe raw material and the Si raw material, a molten metal containing Fe, Si and Cr is prepared as the molten metal, and the Cr content in the molten metal is 0.1 to 8% by mass. The method for producing a soft magnetic powder according to claim 12 or 13.
In step 3, an alkali metal source and / or an alkaline earth metal source is added to the soft magnetic powder so that the soft magnetic powder contains 10 to 800 ppm of an alkali metal and / or an alkaline earth metal. Item 6. The method for producing a soft magnetic powder according to any one of Items 12 to 14.
Water was used as the fluid in the step 2, and in the step, a slurry in which the soft magnetic powder and water were mixed was obtained.
The method for producing a soft magnetic powder according to any one of claims 12 to 15, wherein in the step 3, the alkali metal source and / or the alkaline earth metal source is added to the slurry.
The method for producing a soft magnetic powder according to any one of claims 12 to 16, wherein the alkali metal source and / or the alkaline earth metal source is sodium hydroxide or potassium hydroxide.
The method for producing a soft magnetic powder according to any one of claims 12 to 17, wherein an electrolytic iron having a Mn content of 100 ppm or less is used as the Fe raw material.
Step 1 of preparing a molten metal containing Fe and Si and having a Si content of 0.1 to 15% by mass by heating and melting the Fe raw material and the Si raw material.
Step 2 to obtain a soft magnetic powder composed of an Fe alloy containing Si by spraying a fluid onto the molten metal while dropping the molten metal to crush and solidify the molten metal.
A method for producing a soft magnetic powder, which comprises a step 3 of adding a Na source to the soft magnetic powder so that the soft magnetic powder contains 1 to 950 ppm of Na.
A soft magnetic material containing the soft magnetic powder according to any one of claims 1 to 11 or the soft magnetic powder produced by the production method according to any one of claims 12 to 19 and a binder.
A dust core containing the soft magnetic powder according to any one of claims 1 to 11 or the soft magnetic powder produced by the production method according to any one of claims 12 to 19.
The soft magnetic powder according to any one of claims 1 to 11 or the soft magnetic material according to claim 20 is molded into a predetermined shape, and the obtained molded product is heated to obtain a dust core. Manufacturing method of powder magnetic core.