阅读说明：本技术 软磁性粉末、软磁性粉末的热处理方法、软磁性材料、压粉磁芯和压粉磁芯的制造方法 (Soft magnetic powder, method for heat treatment of soft magnetic powder, soft magnetic material, dust core, and method for producing dust core ) 是由 河内岳志 饭田悠介 井上健一 于 2019-12-25 设计创作，主要内容包括：一种软磁性粉末,其包含89.5～99.6质量％的Fe、0.2～9.0质量％的Si、0～1.0质量％的P,所述软磁性粉末的(111)面的微晶直径为95nm以上。(A soft magnetic powder comprising 89.5-99.6 mass% of Fe, 0.2-9.0 mass% of Si, and 0-1.0 mass% of P, wherein the crystallite diameter of the (111) plane of the soft magnetic powder is 95nm or more.)

1. A soft magnetic powder comprising 89.5 to 99.6 mass% of Fe, 0.2 to 9.0 mass% of Si, and 0 to 1.0 mass% of P,

the crystallite diameter on the (111) surface of the soft magnetic powder is 95nm or more.

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

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

4. The soft magnetic powder according to any one of claims 1 to 3, wherein the product (O x D50) of the oxygen content (O) of the soft magnetic powder and the volume-based cumulative 50% particle diameter (D50) measured by a laser diffraction/scattering particle size distribution measuring apparatus is 3.00 (mass%. mu.m) or less.

5. The soft magnetic powder according to claim 4, wherein the product (O x D50) is 2.30 (mass%. mu.m) or less.

6. The soft magnetic powder according to claim 5, wherein the product (OxD 50) is 1.70 to 2.00 (mass%. mu.m).

7. A soft magnetic powder according to any one of claims 1 to 6, which contains 0.02 to 0.5 mass% of P.

8. A method for heat-treating a soft magnetic powder, comprising: and (3) heat-treating soft magnetic powder containing 89.5 to 99.6 mass% of Fe, 0.2 to 9.0 mass% of Si, and 0 to 1.0 mass% of P at 500 to 950 ℃.

9. A method for heat-treating a soft magnetic powder according to claim 8, wherein the heat treatment is performed at 500 to 850 ℃.

10. The method for heat-treating soft magnetic powder according to claim 8 or 9, wherein the heat treatment is performed under a condition that the product of the heat treatment temperature (° c) and the oxygen concentration (ppm) in the atmosphere in which the heat treatment is performed (heat treatment temperature x atmospheric oxygen concentration) is 70 ten thousand (° c-ppm) or less.

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

12. A 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 ℃ in an atmosphere having an oxygen concentration of 50 to 400 ppm.

13. A soft magnetic material comprising the soft magnetic powder according to any one of claims 1 to 7 and a binder.

14. A dust core comprising the soft magnetic powder according to any one of claims 1 to 7.

15. A method for producing a powder magnetic core, wherein the soft magnetic powder according to any one of claims 1 to 7 or the soft magnetic material according to claim 13 is molded into a predetermined shape, and the molded product obtained is heated to obtain a powder magnetic core.

Technical Field

The present invention relates to a soft magnetic powder, a method of heat-treating a soft magnetic powder, a soft magnetic material, a dust core, and a method of manufacturing a dust core.

Background

A magnetic component having a dust core, such as an inductor, is mounted in an electronic device. The dust core is generally produced by combining a soft magnetic powder with a binder such as a resin as needed, and then compression molding the resultant. When an ac magnetic flux flows through the powder magnetic core, a part of the energy is lost to generate heat, which is a problem for electronic devices. This 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 permeability μ.

As soft magnetic powder, FeSi alloy powder containing Si has been proposed because of its ability to obtain high magnetic permeability (for example, see patent document 1). Patent document 1 describes that magnetic properties can be improved by adding 5 to 7 mass% of Si.

Patent document 2 describes that the addition of a small amount of P to the FeSi alloy powder can improve the resistivity thereof and reduce eddy current loss and the like.

Documents of the prior art

Patent document

Patent document 1 Japanese patent laid-open publication No. 2016-171167

Patent document 2 Japanese patent laid-open publication No. 2017-224717

Disclosure of Invention

Problems to be solved by the invention

As shown in patent documents 1 and 2, soft magnetic powder containing Fe and Si (further containing P) is excellent in magnetic properties. Moisture resistance is required for a dust core made of such soft magnetic powder. Therefore, the soft magnetic powder itself also needs moisture resistance.

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

In addition, in the compression in the production of the powder magnetic core, the binder is decomposed and volatilized by heating at a high temperature to remove the binder, and the powder magnetic core substantially composed only of the soft magnetic powder component is produced. From the viewpoint of cost, it is desirable that the heating be performed in an atmospheric atmosphere. Therefore, the soft magnetic powder is required to have oxidation resistance. In addition, since reactivity is generally increased at high temperatures, the soft magnetic powder is required to have oxidation resistance.

Accordingly, it is an object of the present invention to provide a fesi (p) alloy-based soft magnetic powder having excellent moisture resistance and excellent oxidation resistance.

Means for solving the problems

The present inventors have conducted intensive studies to solve the above problems, and as a result, have found that: soft magnetic powder of fesi (p) -alloy type having a large crystallite diameter is excellent in moisture resistance, and such soft magnetic powder can be produced by heat-treating soft magnetic powder of fesi (p) -alloy at a specific temperature. The present inventors have also found that a soft magnetic powder of an fesi (p) alloy type having a large crystallite diameter and a predetermined relationship between oxygen content and average particle size is excellent in moisture resistance and also excellent in oxidation resistance, and that such a soft magnetic powder can be produced by heat-treating a soft magnetic powder of an fesi (p) alloy at a specific temperature in a specific atmosphere. As described above, the present inventors have completed the present invention.

Namely, the present invention is as follows.

[1] A soft magnetic powder comprising 89.5-99.6 mass% of Fe, 0.2-9.0 mass% of Si, and 0-1.0 mass% of P, wherein the crystallite diameter of the (111) plane of the soft magnetic powder is 95nm or more.

[2] The soft magnetic powder according to [1], wherein the content of N is 800ppm 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 soft magnetic powder according to any one of [1] to [3], wherein the product (O × D50) of the oxygen content (O) of the soft magnetic powder and the volume-based cumulative 50% particle diameter (D50) measured by a laser diffraction/scattering particle size distribution measuring apparatus is 3.00 (mass%. mu.m) or less.

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

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

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

[8] A method for heat-treating a soft magnetic powder, comprising: and (3) heat-treating soft magnetic powder containing 89.5 to 99.6 mass% of Fe, 0.2 to 9.0 mass% of Si, and 0 to 1.0 mass% of P at 500 to 950 ℃.

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

[10] The method for heat-treating a soft magnetic powder according to [8] or [9], wherein the heat treatment is performed under a condition that a product of a heat treatment temperature (DEG C.) and an oxygen concentration (ppm) in an atmosphere in which the heat treatment is performed (heat treatment temperature x atmospheric oxygen concentration) is 70 ten thousand (DEG C. ppm) or less.

[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 500ppm 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 ℃ in an atmosphere having an oxygen concentration of 50 to 400 ppm.

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

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

[15] A method for producing a dust core, wherein 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 molded product is heated to obtain a dust core.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, a fesi (p) alloy-based soft magnetic powder having excellent moisture resistance can be provided. The soft magnetic powder according to a preferred embodiment of the present invention further has excellent oxidation resistance.

Detailed Description

Hereinafter, embodiments of the soft magnetic powder and the method for producing the same (method for heat-treating the soft magnetic powder) according to the present invention 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 referred to as FeSiP. The soft magnetic powder will be described below.

< composition of alloy >

Embodiments of the soft magnetic powder of the present invention contain 89.5 to 99.6 mass% of Fe. From the viewpoint of magnetic properties and mechanical properties, the content of Fe in the soft magnetic powder is preferably 90.0 to 99.0 mass%, more preferably 90.5 to 95.5 mass%.

Embodiments of the soft magnetic powder of the present invention include 0.2 to 9.0 mass% of Si. The content of Si in the soft magnetic powder is in the above range from the viewpoint of not impairing the magnetic properties and mechanical properties due to Fe and improving the magnetic properties such as magnetic permeability. From the viewpoint of the magnetic properties, the content of Si is preferably 0.5 to 8.8 mass%, more preferably 4.0 to 8.6 mass%.

Embodiments of the soft magnetic powder of the present invention may contain 0 to 1.0 mass% of P (that is, may not be contained). The presence of a small amount of P increases the insulation of the soft magnetic powder, and thus reduces the eddy current loss when the powder magnetic core is produced. From the viewpoint of reducing the eddy current loss, the content of P is preferably 0.02 to 0.5 mass%, more preferably 0.03 to 0.4 mass%.

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

Embodiments of the soft magnetic powder of the present invention may contain impurities in addition to Fe, Si, and P in the range in which the effects of the present invention are exhibited. Examples of the impurities include 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 (manganese), Ni (nickel), Cu (copper), S (sulfur), As (arsenic), B (boron), Sn (tin), Ti (titanium), V (vanadium), and Al (aluminum). Of these, the total content of oxygen-removed substances is preferably 1 mass% or less, and more preferably 10 to 6000 ppm.

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

< crystallite diameter >

The crystallite diameter of the (111) plane of the embodiment of the soft magnetic powder of the present invention is 95nm or more. Thus, the soft magnetic powder has excellent moisture resistance due to the large crystallite diameter, and a dust core having excellent moisture resistance can be produced from the powder. In view of the difficulty in producing soft magnetic powder having a very large crystallite diameter and the moisture resistance, the crystallite diameter of the soft magnetic powder is preferably 96 to 250nm, more preferably 99 to 180 nm. The crystallite diameter can be measured by X-ray diffraction. In the case of the alloy composition of the embodiment of the soft magnetic powder of the present invention, the crystallite diameter can be calculated by causing a peak of the (111) plane to appear in the range of or in the vicinity of 51.5 ° to 53.5 ° with respect to the diffraction angle θ. The detailed method for measuring the crystallite diameter will be described in the following examples.

< product of oxygen content and average particle diameter of Soft magnetic powder >

As a result of the studies by the present inventors, it is found that the oxygen content (O) in the soft magnetic powder affects the moisture resistance, oxidation resistance and magnetic characteristics of the soft magnetic powder. In the present invention, in order to correct the variation in oxygen content due to the particle size, the product (O × D50 (mass%. μm)) of the oxygen content (O) and the volume-based cumulative 50% particle size (D50) of the soft magnetic powder measured by a laser diffraction scattering particle size distribution measuring apparatus is used. 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, more preferably 2.30 (mass%. μm) or less from the viewpoint of moisture resistance and magnetic characteristics (particularly magnetic permeability), and particularly preferably 1.70 to 2.00 (mass%. μm) from the viewpoint of moisture resistance and oxidation resistance.

< oxygen content (O) >

From the viewpoint of excellent magnetic properties, the oxygen content (O) in the embodiment of the soft magnetic powder of the present invention is preferably 0.1 to 1.5 mass%, more preferably 0.15 to 0.85 mass%.

< Nitrogen content >

From the viewpoint of excellent magnetic properties, the content of N (nitrogen) in the soft magnetic powder of the embodiment of the present invention is preferably 800ppm or less. In consideration of the difficulty in completely removing N from the soft magnetic powder, the content of N is more preferably 1 to 700 ppm.

< average particle diameter (D50) >)

The volume-based cumulative 50% particle diameter (D50) measured by a laser diffraction scattering particle size distribution measuring apparatus according to an embodiment of the soft magnetic powder of the present invention is not particularly limited, and is preferably 0.1 to 10 μm, and more preferably 0.5 to 5 μm, in terms of reducing eddy current loss when the particle diameter is reduced.

< BET specific surface area >

From the viewpoint of suppressing the generation of oxides on the particle surfaces of the powder and exerting good magnetic properties, the specific surface area (BET specific surface area) measured by the BET single-point method of an embodiment of the soft magnetic powder of the present invention is preferably 0.15 to 3.00m²A more preferable range is 0.20 to 2.50 m/g²/g。

TAP

The TAP density (TAP) of an embodiment of the soft magnetic powder of the present invention is preferably 2.0 to 7.5g/cm from the viewpoint of enhancing the filling density of the powder to exhibit good magnetic properties³More preferably 2.5 to 6.5g/cm³。

< shape >

The shape of the embodiment of the soft magnetic powder of the present invention is not particularly limited, and may be spherical, substantially spherical, granular, flaky (scaly), or distorted (irregular).

[ method for producing Soft magnetic powder of the present invention (method for Heat-treating Soft magnetic powder) ]

The soft magnetic powder of the present invention described above can be produced by an embodiment of the heat treatment method of the soft magnetic powder of the present invention. This heat treatment method has a step (heat treatment step) of heat-treating a specific soft magnetic powder under specific conditions.

< raw material powder >

In the embodiment of the method for heat-treating a soft magnetic powder according to the present invention, the soft magnetic powder (hereinafter also referred to as "raw material powder") subjected to the heat-treatment step has substantially the same particle size, shape, and the like as those of the embodiment of the soft magnetic powder according to the present invention, but the crystallite diameter is different and the characteristics relating to the oxygen content are slightly different.

That is, the raw material powder is a soft magnetic powder containing Fe and Si, and may contain P, and contains 89.5 to 99.6 mass% of Fe, preferably 90.0 to 99.0 mass%, more preferably 90.5 to 95.5 mass%, 0.2 to 9.0 mass% of Si, preferably 0.5 to 8.8 mass%, more preferably 4.0 to 8.6 mass%, and 0 to 1.0 mass% of P, preferably 0.02 to 0.5 mass%, more preferably 0.03 to 0.4 mass%, and the total content of Fe, Si, and P in the soft magnetic powder is preferably 97.5 mass% or more, more preferably 98.0 mass% or more. The raw material powder may contain impurities in addition to Fe, Si, and P, and examples thereof include 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 (manganese), Ni (nickel), Cu (copper), S (sulfur), As (arsenic), B (boron), Sn (tin), Ti (titanium), V (vanadium), and Al (aluminum), and the total content of oxygen-removed substances among these is preferably 1 mass% or less, and more preferably 10 to 6000 ppm. Examples of the trace additive elements in the raw material powder include Na, K, Ca, Pd, Mg, Co, Mo, Zr, C, N, Cl, Mn, Ni, Cu, S, As, B, Sn, Ti, V, and Al. The total amount of these additives is preferably 1 mass% or less, and more preferably 10 to 6000 ppm.

The N (nitrogen) content of the raw material powder is preferably 800ppm or less, and more preferably 1 to 700 ppm. The raw material powder preferably has a cumulative 50% particle diameter (D50) on a volume basis measured by a laser diffraction scattering particle size distribution measuring apparatus of 0.1 to 10 μm, more preferably 0.5 to 5 μm, and a specific surface area (BET specific surface area) measured by a BET single-point method of 0.15 to 3.00m²A concentration of 0.20 to 2.50m²The TAP density is preferably 2.0 to 7.5g/cm³More preferably 2.5 to 6.5g/cm³. The shape of the raw material powder is not particularly limited, and may be spherical, substantially spherical, granular, flaky (scaly), or distorted (irregular).

(crystallite diameter)

The crystallite diameter of the (111) plane of the raw material powder is not particularly limited, and the crystallite diameter of a conventional fesi (p) soft magnetic powder (i.e., raw material powder) which has not been subjected to the treatment according to the embodiment of the heat treatment of the present invention is generally about 50 to 92nm, whereas the crystallite diameter can be grown to 95nm or more by performing the heat treatment defined in the present invention.

(product of oxygen content and average particle diameter)

In the embodiment of the method for heat-treating a soft magnetic powder of the present invention, the raw material powder is preferably heat-treated in an atmosphere having a specific oxygen concentration, and the oxygen content (O) in the powder may be affected by the heat treatment of the raw material powder. The product (O × D50 (mass%. μm)) of the oxygen content (O) of the raw material powder and the volume-based cumulative 50% particle diameter (D50) measured by a laser diffraction scattering particle size distribution measuring apparatus is not particularly limited, and is usually in the range of 1.10 to 3.50 (mass%. μm).

(oxygen content (O))

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

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

< Heat treatment Process >

In the heat treatment step in the embodiment of the method for heat-treating soft magnetic powder according to the present invention, the raw material powder described above is heat-treated at 500 to 950 ℃. By performing the heat treatment at such a high temperature, crystallites of the raw material powder can be grown, and a soft magnetic powder having a large crystallite diameter defined in the present invention, excellent in moisture resistance, and useful as a raw material for producing a dust core can be obtained.

Under the conditions of this heat treatment, if the heat treatment is performed under the condition that the product of the heat treatment temperature (. degree. C.) and the oxygen concentration (ppm) in the atmosphere in which the heat treatment is performed (heat treatment temperature. times. atmospheric oxygen concentration) is 70 ten thousand (. degree. C. ppm) or less, soft magnetic powder having excellent moisture resistance can be obtained. The product (heat treatment temperature x atmospheric oxygen concentration) is preferably 500 to 65 ten thousand (DEG C. ppm).

In the heat treatment step of the embodiment of the heat treatment method of the present invention, by performing heat treatment at a temperature of 500 to 850 ℃ while satisfying the above-described product (heat treatment temperature × ambient oxygen concentration), it is possible to obtain a soft magnetic powder having excellent oxidation resistance.

When the oxygen concentration in the atmosphere in which the heat treatment in the heat treatment step is performed is high, oxidation of the powder occurs and the magnetic properties are adversely affected, and therefore, it is preferably 500ppm or less. In particular, when the oxygen concentration in the atmosphere is set to 50 to 400ppm and heat treatment is performed at 700 to 850 ℃, soft magnetic powder having excellent moisture resistance, oxidation resistance, and magnetic properties (particularly magnetic permeability) can be obtained. The preferred oxygen concentration in the atmosphere in which the heat treatment is performed is as described above, but the composition other than oxygen in the atmosphere is not particularly limited as long as the composition does not substantially exhibit reactivity with the raw material powder. The atmosphere is preferably substantially composed of only oxygen and an inactive element (the total of oxygen and the inactive element is 99.5 vol% or more) from the viewpoint of suitably exhibiting the effects of the present invention. Examples of the inert element include helium, neon, argon, and nitrogen. Among them, nitrogen is preferable from the viewpoint of cost.

The heat treatment in the heat treatment step is preferably performed for 10 to 1800 minutes, and more preferably for 20 to 1200 minutes, from the viewpoints of improving the electrical insulation of the powder after the heat treatment and preventing the productivity and the deterioration of the magnetic properties due to oxidation.

< other working procedures >

The soft magnetic powder subjected to the heat treatment step may be subjected to another step. For example, when aggregation of the powder occurs by the heat treatment, the crushing step may be performed.

< Soft magnetic Material >

The soft magnetic powder of the embodiment of the present invention described above can be used as a soft magnetic material that is a raw material for producing a powder magnetic core, and a powder magnetic core having excellent moisture resistance can be produced using this material.

The soft magnetic powder itself may be used as a soft magnetic material, or may be mixed with a binder to obtain a soft magnetic material. In the latter case, for example, the soft magnetic powder is mixed with a binder (insulating resin and/or inorganic binder) and granulated to obtain a granular composite powder (soft magnetic material). From the viewpoint of achieving good magnetic properties, the content of the soft magnetic powder in the soft magnetic material is preferably 80 to 99.9 mass%. 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 resins, silicone resins, epoxy resins, phenol resins, urea resins, and melamine resins. Specific examples of the inorganic binder include a silica binder and an alumina binder. Further, the soft magnetic material (both of the case of the soft magnetic powder alone and the case of the mixture of the powder and the binder) may contain other components such as wax, lubricant, and the like as necessary.

< powder magnetic core >

The powder magnetic core according to the embodiment including the soft magnetic powder of the present invention can be produced by molding the soft magnetic material described above into a predetermined shape and heating the molded material. More specifically, a soft magnetic material is put in a mold having a predetermined shape, and the mold is pressurized and heated (the heating temperature is preferably 200 to 1200 ℃, and more preferably 300 to 1000 ℃) to obtain a powder magnetic core. Further, since the soft magnetic powder of the present invention is excellent in oxidation resistance, the operation for obtaining the powder magnetic core can be performed in an atmospheric atmosphere.

Examples

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

Reference example 1(Ref.1)

In a tundish furnace, high-pressure water (pH10.3) was blown at a water pressure of 150MPa and a water amount of 160L/min to rapidly solidify the molten steel obtained by heating and melting 14.5kg of electrolytic iron (purity: 99.95% by mass or more), 1.01kg of silicon metal (purity: 99% by mass or more), and 28.5g of FeP alloy (Fe72 wt%, P26 wt%) at 1700 ℃ in a nitrogen atmosphere, from the bottom of the tundish furnace, while dropping the molten steel from the bottom of the tundish furnace in a nitrogen atmosphere, the obtained slurry was subjected to solid-liquid separation, the solid was washed with water, and dried under vacuum conditions of 40 ℃ and 30 hours.

The substantially spherical FeSiP alloy powder 1 thus obtained was evaluated for composition (Fe, Si, P content, oxygen content, carbon content, and nitrogen content), BET specific surface area, TAP density (TAP), particle size distribution, crystallite diameter, and magnetic properties, and further for moisture resistance and oxidation resistance. The results are shown in tables 1 and 2 below. The methods for these measurements and evaluations will be described in detail below.

[ composition ]

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

Fe was analyzed by the titration method in accordance with JIS M8263 (method for quantifying chromium ore-iron) in the following manner. First, 0.1g of a sample (FeSiP alloy powder 1) was added with sulfuric acid and hydrochloric acid to be thermally decomposed, and heated until white smoke of sulfuric acid was generated. After natural cooling, water and hydrochloric acid were added and heated to dissolve soluble salts. Then, warm water is added to the obtained sample solution so that the liquid volume is about 120 to 130mL and the liquid temperature is about 90 to 95 ℃, then a few drops of an acidic indigo solution are added, and a titanium (III) chloride solution is added until the color of the sample solution changes from yellow green to blue, and then changes to colorless and transparent. Next, the potassium dichromate solution was added until the sample solution remained in a blue state for 5 seconds. The amount of Fe was determined by titrating iron (II) in the sample solution with a potassium dichromate standard solution using an automatic titrator.

Si was analyzed by the gravimetric method in the following manner. First, hydrochloric acid and perchloric acid are added to a sample (FeSiP alloy powder 1) and thermally decomposed until white smoke of perchloric acid is generated. Subsequently, the mixture is heated to be dried and solidified. After natural cooling, water and hydrochloric acid were added and heated to dissolve soluble salts. Next, insoluble residues were filtered off using filter paper, and the residues were transferred to a crucible together with the filter paper, dried, and ashed. After natural cooling, the mixture was weighed together with the crucible. A small amount of sulfuric acid and hydrofluoric acid was added, and after drying and solidification by heating, heating was performed. After natural cooling, the mixture was weighed together with the crucible. Then, the second weighed value was subtracted from the first weighed value to obtain SiO₂The weight difference was calculated to determine the Si amount.

P was analyzed by using an Inductively Coupled Plasma (ICP) emission analyzer (SPS 3520V, product of hitachi high and new technologies). As a result, the P content was 0.057 mass%.

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

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

[ BET specific surface area ]

BET specific surface area A BET specific surface area meter (Macsorb manufactured by MOUNTECH) was used, nitrogen gas was passed through the meter at 105 ℃ for 20 minutes and then degassed, and a mixed gas (N) of nitrogen gas and helium gas was passed through the meter₂: 30 vol%, He: 70 vol.%), by the BET single point method.

[ tap Density ]

TAP the FeSiP alloy powder 1 was filled in a bottomed cylindrical mold having an inner diameter of 6mm × a height of 11.9mm to 80% of the volume to form an alloy powder layer, and 0.160N/m was uniformly applied to the upper surface of the alloy powder layer in the same manner as in the method described in jp 2007-263860 a²The alloy powder layer is compressed by the pressure until the alloy powder is not densely filled any more, and then the height of the alloy powder layer is measured, and the density of the alloy powder is determined from the measured value of the height of the alloy powder layer and the weight of the filled alloy powder, and this is taken as the tap density of the FeSiP alloy powder 1.

[ particle size distribution ]

The particle size distribution was measured on a volume basis at a dispersion pressure of 5 bar using a laser diffraction scattering particle size distribution measuring apparatus (HELOS & RODOS (air flow type dispersion module)) manufactured by SYMPATEC.

[ measurement of crystallite diameter ]

The crystallite diameter on the (111) plane of the FeSiP alloy powder 1 was measured using an X-ray diffraction apparatus (model: RINT-UltimaIII, manufactured by Kiyobo Co., Ltd.). The X-ray source uses cobalt and generates X-rays under the conditions that the acceleration voltage is 40kV and the current is 30 mA. The divergent slit opening angle was 1/3 °, the scattering slit opening angle was 2/3 °, and the light-receiving slit width was 0.3 mm. In order to accurately measure the half-value width, the range of 51.5-53.5 degrees of 2 theta is measured by step scanning under the conditions that the measurement interval is 0.02 degrees, the counting time is 5 seconds, and the cumulative number is 3 times.

From the obtained diffraction pattern, the crystallite diameter was determined by the scherrer equation (Dhkl ═ K λ/β cos θ) using powder X-ray analysis software PDXL 2. In this formula, Dhkl is the crystallite diameter (the size of the crystallite in the direction perpendicular to hkl)λ is the wavelength (angstrom) of the measurement X-rays (Cu target;) β represents a width (rad) of a diffraction line based on a size of a crystallite (represented by a half-value width), θ represents a bragg angle (rad) of a diffraction angle (angle when an incident angle is equal to a reflection angle, angle of a peak top is used), and K represents a scherrer constant (K is 0.9 although it differs depending on the definition of D, β, and the like). The peak data of the (111) plane is used for the calculation.

[ measurement of magnetic characteristics (permeability, coercive force, and saturation magnetization) ]

FeSiP alloy powder 1 and bisphenol F type epoxy resin (TESK CO., LTD., manufactured by LTD.; one-pack epoxy resin B-1106) were mixed in a ratio of 97: 3, and kneading them with a vacuum mixer (manufactured by EME corporation; V-mini300) to prepare a paste in which the test powder was dispersed in the epoxy resin. The paste was dried on a hot plate at 30 ℃ for 2 hours to prepare a composite of alloy powder and resin, and then granulated into powder to prepare composite powder. 0.2g of the composite powder was charged into an annular container, and a load of 9800N (1 ton) was applied thereto by a manual pressure machine, whereby an annular molded body having an outer diameter of 7mm and an inner diameter of 3mm was obtained. The real part μ' of the complex relative permeability at 10MHz was measured for the molded article using an RF impedance/material analyzer (manufactured by Agilent Technologies, Inc.; E4991A) and a test jig (manufactured by Agilent Technologies, Inc.; 16454A).

The magnetic properties of the FeSiP alloy powder 1 were measured using a high-sensitivity vibration sample type magnetometer (model VSM-P7-15, manufactured by Toyoto K.K.) under the conditions of an applied magnetic field (10kOe), an M measurement range (50emu), a step bit of 100bit, a time constant of 0.03 second, and a waiting time of 0.1 second. The saturation magnetization σ s and the coercive force Hc were obtained from the B-H curve. The process constant is set by the manufacturer. The details are as follows.

And (3) cross point detection: least square method M average point number 0H average point number 0

Ms Width：8 Mr Width：8 Hc Width：8 SFD Width：8 S.Star Width：8

Sampling time (sec): 90

Point 2 correction P1 (Oe): 1000

Point 2 correction P2 (Oe): 4500

[ evaluation of moisture resistance ]

The moisture resistance of the FeSiP alloy powder 1 was evaluated as follows using Δ σ s as an index.

After the powder was stored in an atmosphere of controlled temperature and humidity (temperature: 60 ℃ C., relative humidity: 90%) for 7 days, the saturation magnetization σ s of the FeSiP alloy powder 1 (magnetization per 1g when a magnetic field of 10kOe was applied) was measured using a high-sensitivity vibration sample type magnetometer (VSM-P7-15 type, manufactured by Dongxin industries, Ltd.) under the conditions of an applied magnetic field (10kOe), an M measurement range (50emu), a step bit of 100bit, a time constant of 0.03 second, and a waiting time of 0.1 second. The difference between σ s (A) thus obtained and σ s (B) before storage in the atmosphere is referred to as Δ σ s.

Δσs＝σs(B)-σs(A)

[ evaluation of Oxidation resistance ]

The oxidation resistance of the FeSiP alloy powder 1 was evaluated as follows.

The weight gain rate during heating was determined using a differential thermal gravimetric simultaneous measurement apparatus (model EXATERTG/DTA6300 of SII NanoTechnology Inc.). Specifically, 20mg of the FeSiP alloy powder 1 was charged into a sample vessel (an alumina open type sample vessel, i.e., 5.2mm in diameter and 2.5mm in height), the vessel was placed on a holder of the measuring apparatus, air was passed through the measuring apparatus at a flow rate of 200 ml/min (i.e., under an atmospheric atmosphere), and the temperature was raised from room temperature (25 ℃) to 800 ℃ at a temperature raising rate of 5 ℃/min for analysis. The increase rate (%) of the difference (weight increased by heating) between the weight (C) of the alloy powder in the sample container measured by raising the temperature to 700 ℃ and the weight (D) of the alloy powder before heating to the weight (D) of the alloy powder before heating was determined.

Increase rate (%) { (C) - (D) }/(D) × 100

[ example 1]

The FeSiP alloy powder 1 obtained in reference example 1(ref.1) was heated to 600 ℃ at a heating rate of 10 ℃/min in a nitrogen atmosphere containing 1.0ppm of oxygen using a furnace, and heat-treated at 600 ℃ for 30 minutes to obtain a substantially spherical FeSiP alloy powder 2. With respect to this alloy powder 2, the composition (content of Fe, Si, P, oxygen content, carbon content, and nitrogen content), BET specific surface area, TAP density (TAP), particle size distribution, crystallite diameter, and magnetic characteristics were determined in the same manner as in reference example 1(ref.1), and further moisture resistance and oxidation resistance were evaluated. The amount of P in the FeSiP alloy powder 2 was substantially equal to that in the FeSiP alloy powder 1.

Examples 2 to 6 and 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. With respect to these alloy powders, the composition (Fe, Si, P content, oxygen content, carbon content, and nitrogen content), BET specific surface area, TAP density (TAP), particle size distribution, crystallite diameter, and magnetic characteristics were determined in the same manner as in reference example 1(ref.1), and further moisture resistance and oxidation resistance were evaluated. The P content of the FeSiP alloy powder is 3-11 which is approximately equal to that of the FeSiP alloy powder 1.

Reference example 2(Ref.2)

FeSi alloy powder 1 of reference example 2 was obtained in the same manner as in reference example 1, except that 14.03kg of electrolytic iron (purity: 99.95% by mass or more) and 0.975kg of silicon metal (purity: 99% by mass or more) were used as molten steel raw materials.

The composition (Fe and Si contents, oxygen content, carbon content, and nitrogen content), BET specific surface area, TAP density (TAP), particle size distribution, crystallite diameter, and magnetic properties were determined for the thus obtained substantially spherical FeSi alloy powder 1 in the same manner as in reference example 1(ref.1), and further moisture resistance and oxidation resistance were evaluated.

[ example 7]

The FeSi alloy powder 1 obtained in the above 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. With respect to this alloy powder, the composition (Fe and Si contents, oxygen content, carbon content, and nitrogen content), BET specific surface area, TAP density (TAP), particle size distribution, crystallite diameter, and magnetic characteristics were determined in the same manner as in reference example 1(ref.1), and further moisture resistance and oxidation resistance were evaluated.

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

[ Table 1]

[ Table 2]

As is clear from comparison between the comparative examples and examples, the soft magnetic powder obtained by heat-treating the fesi (p) alloy-based soft magnetic powder of a specific composition at a high temperature of 600 ℃ or higher has a crystallite diameter of 99nm or more, and shows excellent results when the moisture resistance (Δ σ s) is evaluated as a molded article.

Further, as is clear from comparison of example 3 with other examples, by setting the heat treatment temperature to less than 900 ℃, soft magnetic powder with a small nitrogen content can be obtained.

As is clear from comparison between example 6 and other examples, when 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 60 ten thousand (deg.c · ppm) or less, the product of the oxygen content (O) and the average particle diameter (D50) of the obtained soft magnetic powder is 2.62 (mass%. mu.m) or less, and the above-mentioned moisture resistance is particularly good.

As is clear from comparison of examples 5 and 6 with other examples, by setting the oxygen concentration in the heat treatment atmosphere to 100ppm or less, a soft magnetic powder having a product of the oxygen content (O) and the average particle diameter (D50) of 2.10 (mass%. mu.m) or less can be obtained, and the magnetic permeability (mu') of the molded article thereof is excellent.

As is clear from comparison of example 4 with other examples, by setting the heat treatment temperature to 800 ℃ and the oxygen concentration in the heat treatment atmosphere to 100ppm, a soft magnetic powder having a product of the oxygen content (O) and the average particle diameter (D50) of more than 1.68 (mass%. μm) and less than 2.10 (mass%. μm) can be obtained, which is excellent in oxidation resistance, particularly excellent in moisture resistance, and also excellent in magnetic permeability (μ').