TW202105421A - Insulation coated soft magnetic alloy powder - Google Patents

Abstract

Provided is soft magnetic alloy powder having both magnetic properties, and reliability such as insulation and corrosion resistance. Provided is the insulating film soft magnetic alloy powder in which an oxide film having a thickness of 1 to 10 nm is formed on the surface of iron-based soft magnetic alloy powder and a ratio of the particle diameter (D50) to the film thickness of the oxide film is 100 to 21000.

Description

Insulating film soft magnetic alloy powder

The present invention relates to soft magnetic alloy powders for insulating coatings.

In recent years, due to the demand for miniaturization and thinning, it is desired that power inductors used in power circuits are soft magnetic materials that can be used at large currents and high frequencies. It is known that ferrite-based materials belonging to oxides can be used as the main material of inductors, but due to their low saturation magnetization, they are not conducive to miniaturization; in recent years, the use of high saturation magnetization is conducive to miniaturization and thinness. The number of metal inductors made of alloy-based materials is increasing rapidly. As a metal inductor, there is known a powder core formed by using soft magnetic alloy powder (hereinafter also referred to as iron-based soft magnetic alloy powder) containing iron as a main material, mixing the soft magnetic alloy powder and resin, and compression molding. The magnetic properties (saturation magnetization, permeability, core loss, frequency characteristics, etc.) of the powder magnetic core depend on the magnetic properties, particle size distribution, filling and electrical resistance of the soft magnetic alloy powder used.

Since the conventionally used ferrite-based materials are oxides, they have high reliability in insulation and corrosion resistance. However, the reliability of the above-mentioned characteristics of alloy-based materials is lower than that of ferrous-iron-based materials, which is used to improve soft magnetic alloy As a technique for powder insulation and corrosion resistance, for example, a film formation method by phosphoric acid treatment is known (Patent Documents 1 and 2). However, when the coating is formed by phosphoric acid treatment, since the thickness of the coating is on the order of micrometers, the magnetic properties of the powder are reduced, the coating is easily peeled off by external force, and when it is used as an inductor material, the magnetic body in the inductor Caused by electricity or rust Deterioration of the characteristics and other issues. In order to have both reliability and magnetic properties such as insulation and corrosion resistance, a thinner and hard-to-peel film is required.

[Prior Technical Literature]

[Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2003-272911

[Patent Document 2] Japanese Patent Laid-Open No. 2008-63651

The object of the present invention is to provide a soft magnetic alloy powder that has both reliability such as insulation and corrosion resistance and high magnetic properties.

The present inventors obtained the following findings from the results of various studies conducted, thereby completing the present invention: a thin oxide film with a thickness of nanometers is formed on the iron-based soft magnetic alloy powder, and as a result, a suppressable oxide film is formed. Iron-based soft magnetic alloy powder (hereinafter also referred to as insulating film soft magnetic alloy powder) that has reduced magnetic properties and also has high insulation and corrosion resistance.

That is, the present invention is a soft insulating film in which an oxide film with a film thickness of 1-10 nm is formed on the surface of iron-based soft magnetic alloy powder, and the ratio of particle diameter (D50)/oxide film thickness is 100-21000 Magnetic alloy powder.

One aspect of the present invention provides the above-mentioned insulating coating soft magnetic alloy powder, the oxide coating of which has a film thickness of 1 to 6 nm.

One aspect of the present invention provides the above-mentioned insulating coating soft magnetic alloy powder, the ratio of the particle size (D50)/the film thickness of the oxide coating is 150 to 3000.

One aspect of the present invention provides the above-mentioned insulating coating soft magnetic alloy powder, the particle size (D50) of the iron-based soft magnetic alloy powder is 0.7 to 5.0 μm.

One aspect of the present invention provides the above-mentioned insulating coating soft magnetic alloy powder, wherein the iron-based soft magnetic alloy powder is iron-based amorphous alloy powder or iron-based crystalline alloy powder.

One aspect of the present invention provides the above-mentioned insulating coating soft magnetic alloy powder, and the above-mentioned iron-based soft magnetic alloy powder is an iron-based amorphous alloy powder having a composition represented by the following composition formula:

(Fe _1-st Co _s Ni _t ) _100-xy {(Si _a B _b ) _m (P _c C _d ) _n } _x M _y

[In the formula, the composition ratio of Fe, Co and Ni is

x

22、 19

x

twenty two,

y

6.0、 0

y

6.0,

s

0.35、 0

s

0.35,

t

0.35、以及 0

t

0.35, and

0.35、 s+t

0.35,

The composition ratio of Si, B, P and C is

(m：n)

(6：1)、 (0.5:1)

(m: n)

(6:1),

(a：b)

(5.5：4.5)、以及 (2.5: 7: 5)

(a:b)

(5.5:4.5), and

(c：d)

(9.5：0.5)； (5.5: 4.5)

(c:d)

(9.5:0.5);

M is Nb or Mo].

One aspect of the present invention provides the above-mentioned insulating coating soft magnetic alloy powder, and the iron-based soft magnetic alloy powder is Fe-Si-Cr series crystalline alloy powder.

One aspect of the present invention provides the above-mentioned insulating coating soft magnetic alloy powder, which contains 5% by weight or less of Cr.

One aspect of the present invention provides the aforementioned insulating coating soft magnetic alloy powder, the oxide coating of which is an SiO ₂ film.

According to the present invention, it is possible to provide a soft magnetic alloy powder that has both reliability such as insulation and corrosion resistance and high magnetic properties.

Fig. 1 is a transmission electron micrograph of the insulating coating soft magnetic alloy powder of the present invention.

2 is a scanning electron micrograph showing the insulating film soft magnetic alloy powder of the present invention and the iron-based amorphous alloy powder without oxide film formation, and a line scan of oxygen obtained by an energy dispersive X-ray analyzer Graph of results.

3 is a graph showing the relationship between the film thickness of the oxide film of Comparative Example 5 and Examples 11 to 17, the particle size of the soft magnetic alloy powder of the insulating film, and the amount of oxygen.

4 is a graph showing the relationship between the film thickness and the resistivity of the oxide coatings of Comparative Example 5 and Examples 11-17.

Fig. 5 is a photograph showing the presence or absence of rust after the salt spray test in Examples and Comparative Examples.

FIG. 6 is a graph showing the relationship between the film thickness and the magnetic permeability of the oxide film of Comparative Example 5 and Examples 11-17.

An embodiment of the present invention will be described in detail later. The present invention is not limited to the following embodiments, and can be implemented with appropriate changes within a range that does not impair the effects of the present invention.

The insulating film soft magnetic alloy powder-based oxide film of this embodiment is formed on the surface of the iron-based soft magnetic alloy powder, and the thickness of the oxide film is 1 to 10 nm. In the insulating coating soft magnetic alloy powder of this embodiment, the thickness of the oxide coating is 1-10 nm, preferably 1-9 nm, more preferably 1-8 nm, most preferably 1-6 nm. By forming an oxide film with a thickness of nanometers in the above range on the surface of the iron-based soft magnetic alloy powder, it is possible to suppress the decrease in the magnetic properties of the insulating film soft magnetic alloy powder and at the same time obtain high insulation. And corrosion resistance.

[Film Thickness]

The film thickness of the oxide film of the insulating film soft magnetic alloy powder in this embodiment refers to the actual value of the film thickness measured using a transmission electron microscope or the like.

[Oxide Coating]

In this specification, the "oxide film" refers to an insulating film containing an oxide formed in the form of an iron-based soft magnetic alloy powder, and the oxide is not particularly limited as long as the film is made insulating.

[Fe-based soft magnetic alloy powder]

In this specification, "iron-based soft magnetic alloy powder" refers to a conventionally known soft magnetic alloy powder that uses iron as a main material. From the viewpoint of magnetic properties and productivity, the iron-based soft magnetic alloy powder is preferably iron-based amorphous alloy powder or iron-based crystalline alloy powder produced by a water atomization method. The particle size of the iron-based soft magnetic alloy powder is not particularly limited, and can be adjusted according to the desired magnetic properties.

[Ratio of particle size (D50)/thickness of oxide film]

In the insulating film soft magnetic alloy powder of this embodiment, the ratio of the particle diameter (D50) of the insulating film soft magnetic alloy powder/the film thickness of the oxide film is 100~21000, preferably 100~10000, more preferably 150~ 5000, the best is 150~3000. "The ratio of particle size (D50)/oxide film thickness" refers to the median diameter of the insulating film soft magnetic alloy powder: the ratio of the measured value of D50 to the measured value of the oxide film thickness, and it has no unit. The dimensionless quantity. By setting the ratio of particle diameter (D50)/oxide film thickness within the above range, the soft magnetic alloy powder of the insulating film is excellent as a material for the powder magnetic core and can simultaneously possess magnetic properties, insulation and corrosion resistance. .

The particle size of the iron-based soft magnetic alloy powder of this embodiment is preferably 0.1 to 210 μm, more preferably 0.2 to 100 μm, still more preferably 0.5 to 50 μm, still more preferably 0.5 to 30 μm, particularly preferably 0.7 to 5 μm.

[Particle size]

In this specification, the "particle size" refers to the median particle size: D50, the above-mentioned particle size is measured by conventional and well-known methods, such as by laser refraction. Measured by scattering method.

In the insulating coating soft magnetic alloy powder of this embodiment, the iron-based soft magnetic alloy powder is preferably an iron-based amorphous alloy powder or an iron-based crystalline alloy powder. By using iron-based amorphous alloy powder or iron-based crystalline alloy powder, it has excellent soft magnetic properties.

Among the insulating coating soft magnetic alloy powders of this embodiment, the iron-based soft magnetic alloy powder is preferably an iron-based amorphous alloy powder having a composition represented by the following composition formula:

(Fe _1-st Co _s Ni _t ) _100-xy {(Si _a B _b ) _m (P _c C _d ) _n } _x M _y

[In the formula, the composition ratio of Fe, Co and Ni is

x

22、 19

x

twenty two,

y

6.0、 0

y

6.0,

s

0.35、 0

s

0.35,

t

0.35、以及 0

t

0.35, and

0.35、 s+t

0.35,

The composition ratio of Si, B, P and C is

(m：n)

(6：1)、 (0.5:1)

(m: n)

(6:1),

(a：b)

(5.5：4.5)、以及 (2.5: 7: 5)

(a:b)

(5.5:4.5), and

(c：d)

(9.5：0.5)； (5.5: 4.5)

(c:d)

(9.5:0.5);

M is Nb or Mo].

When the iron-based soft magnetic alloy powder is an iron-based amorphous alloy powder having the above composition, in addition to having excellent soft magnetic properties, it also has flame retardancy.

In the insulating coating soft magnetic alloy powder of this embodiment, the iron-based soft magnetic alloy powder is preferably an iron-based crystalline alloy powder of Fe-Si-Cr-based crystalline alloy powder. By making the iron-based soft magnetic alloy powder Fe-Si-Cr series crystalline alloy powder, it can have excellent soft magnetic properties and corrosion resistance.

In the insulating coating soft magnetic alloy powder of the present embodiment, the iron-based soft magnetic alloy powder preferably contains 5% by weight or less of Cr. By containing Cr, an oxide film is formed on the surface of the iron-based soft magnetic alloy powder itself, which can further improve the corrosion resistance of the insulating soft magnetic alloy powder. Not limited to Cr, Al, Zn, etc. can also contribute to the formation of the oxide film on the surface of the iron-based soft magnetic alloy powder itself, and the same effect can be obtained. Al can increase the hardness of the oxide film formed by Cr and/or Zn, and has the effect of improving corrosion resistance. Therefore, by also including Cr And/or Zn and Al can obtain a synergistic effect.

The oxide coating of the insulating coating soft magnetic alloy powder of this embodiment is preferably an SiO ₂ film. By making the oxide film a dense and chemically very stable SiO ₂ film, it is possible to obtain an insulating film soft magnetic alloy powder that is difficult to peel and has high insulation and corrosion resistance.

[Production method]

The insulating coating soft magnetic alloy powder of this embodiment is produced by forming an oxide coating on the iron-based soft magnetic alloy powder.

The iron-based soft magnetic alloy powder as a material can be prepared by a conventionally known melting process, a mechanical process, or a chemical process, but it is preferably manufactured by an atomization method. The powder is obtained by the following atomization method, and then the above powder is dried to obtain the target iron-based soft magnetic alloy powder; the above atomization method is obtained by melting the material that has been adjusted to the desired composition The parameters of the melt are set to achieve the required cooling conditions and the required particle size. Among the atomization methods, the water atomization method is preferred, because the water atomization method can be manufactured in an atmospheric environment, so the equipment cost and manufacturing cost are low, and a small particle size powder can be obtained. Because the powder has a small particle size, it is possible to produce a powder magnetic core that suppresses eddy current loss and has excellent magnetic properties.

The oxide film can be formed by conventionally known methods, for example, chemical vapor deposition (CVD) and physical vapor deposition (PVD) and other vapor-phase methods, thermal spraying (thermal spraying), and the like. In particular, from the viewpoint of productivity and cost, it is preferably carried out by a sol-gel method. In the sol-gel method, a solution containing metal alkoxide or metal acetate as the raw material of the oxide of the coating component, water for hydrolysis, alcohol as a solvent, acid or alkali as a catalyst, and the like are combined with the iron obtained above Base soft magnetic alloy After the powders are mixed, the oxide film is formed by heating and removing the solvent. The mixing system can be performed using, for example, a planetary mixer, a mixing mill, a tossing machine, a ribbon mixer, and the like. As long as it has a structure for mixing the powder and the solution, the device used for mixing is not particularly limited. In the sol-gel method, the oxide film thickness can be adjusted to the desired thickness by adjusting the conditions such as the amount of oxide blended, the mixing time, the method of dropping the solution, the amount of dropping, and the temperature. .

After the oxide film is formed, classification can be performed to obtain an insulating film soft magnetic alloy powder with a target particle size corresponding to the required magnetic properties.

[Example]

The following shows examples of the present invention. The content of the present invention should not be construed as being limited to these embodiments only.

[Manufacturing of soft magnetic alloy powder for insulating coating]

1. Preparation of raw alloy powder

A high-frequency induction furnace is used to melt the raw material mixture prepared to have the following composition, and the iron-based amorphous alloy powder and the iron-based crystalline alloy powder are prepared by the water atomization method.

<Iron-based amorphous alloy powder>

(Fe _1-st Co _s Ni _t ) _100-xy {(Si _a B _b ) _m (P _c C _d ) _n } _x M _y

Where s=0, t=0, x=22, y=0.89, m: n=3:1, a: b=3.8: 6.2, c: d=7.8: 2.2, Cr: 0wt%~3.0wt% .

<Iron-based crystalline alloy powder>

‧(92)Fe3.5Si4.5Cr(wt%),

‧(95)Fe2Si3Cr(wt%),

‧(92)Fe5Si3Cr(wt%),

‧(90)Fe7Si3Cr(wt%),

‧(92)Fe7Si1Cr(wt%), and

‧(91)Fe7Si2Cr(wt%)

The water atomization conditions for preparing iron-based amorphous alloy powder and iron-based crystalline alloy powder are as follows:

<Iron-based amorphous alloy powder-water atomization conditions>

‧Water pressure: 100MPa

‧Water volume: 100L/min

‧Water temperature: 20℃

4mm ‧Aperture:

4mm

‧Molten temperature: 1500℃

<Iron-based crystalline alloy powder-water atomization conditions>

‧Water pressure: 100MPa

‧Water volume: 100L/min

‧Water temperature: 20℃

4mm ‧Aperture:

4mm

‧Molten temperature: 1800℃

The obtained iron-based amorphous alloy powder and iron-based crystalline alloy powder were dried by a vibration vacuum dryer (central processing mechanism: VU-60). The drying conditions are as follows.

<Drying conditions>

‧Temperature: 100℃

‧Pressure: below 10kPa

‧Time: 60 minutes

An ICP emission analyzer (SPS3500D: manufactured by Hitachi High-Technologies) was used to analyze the composition of the dried iron-based amorphous alloy powder and the iron-based crystalline alloy powder to confirm that it had the target composition.

2. Coating treatment

The dried iron-based amorphous alloy powder and iron-based crystalline alloy powder are mixed with a coating solution that has the components required to _{form a SiO 2 film under the conditions to obtain the target film thickness, and the solvent is heated} At the same time as it is completely removed, the oxide film is hardened to form oxide films of various film thicknesses. The conditions for controlling the film thickness are calculated and determined from the coating component concentration of the coating liquid (solid content concentration of the coating liquid), the specific gravity of the coating component, and the specific surface area of each powder.

For example, in the case of obtaining an oxide film with a film thickness of 5 nm, 10.98 g of a coating solution with a concentration of 10% is mixed with respect to 1 kg of each powder.

3. Hierarchical processing

The coated and dried iron-based amorphous alloy powder and iron-based crystalline alloy powder are classified by an air current classification device (manufactured by Nissin Engineering: Turbo classifier) to obtain the target insulating coating soft magnetic alloy powder. The particle diameter (D50) of the obtained insulating coating soft magnetic alloy powder was measured using a wet particle size distribution measuring machine (MT3300EX II: manufactured by Microchick Bayer).

For the insulating coating soft magnetic alloy powder prepared using iron-based amorphous alloy powder (Examples 1 to 32 and Comparative Examples 1 to 16) and the insulating coating soft magnetic alloy powder prepared using iron-based crystalline alloy powder (implementation Examples 33-50 and Comparative Examples 17-28) were evaluated as follows.

[Evaluation item]

1. Powder physical properties

1-1. Observe the envelope

Use a scanning electron microscope (SEM) (JSM7200: manufactured by JEOL) to observe the shape of the soft magnetic alloy powder of the insulating coating, use an energy dispersive X-ray analyzer (EDS) (X-MAX50: manufactured by Oxford Instruments) and a transmission type The oxide film was observed with an electron microscope (TEM) (H-9500: manufactured by Hitachi High-Technologies).

1-2. Oxygen measurement

An oxygen analyzer (EMGA823: manufactured by Horiba Manufacturing Co., Ltd.) was used to measure the amount of oxygen contained in the insulating coating soft magnetic alloy powder.

2. Film performance

The insulating coating soft magnetic alloy powder and epoxy resin were mixed to prepare granulated powder, and the powder was pressed into a cylindrical shape to prepare pellets (diameter: 12 mm, height: 5 mm), and the following evaluations were performed.

2-1. Evaluation of insulation

Using a withstand voltage insulation resistance meter (TOS9201: Kikusui Electric Co., Ltd.), the two sides of the pellets were sandwiched between copper plates, the resistance value was measured by the two-terminal method, and the volume resistivity was calculated from the outer dimensions and resistance value of the pellets.

2-2. Evaluation of corrosion resistance

A salt water spray tester (STP-90V-4: manufactured by Suga Tester) was used to perform a salt water spray test in accordance with American Standard ASTM-B117. Visually confirm the rust on the surface of the particles every 24 hours until 96 hours.

3. Magnetic properties

The above-mentioned granulated powder compressed powder is formed into a ring shape (forming pressure: 5MPa) to form a powder magnetic core (outer diameter: 15mm, inner diameter: 9mm, thickness: 3mm), and a copper wire with a wire diameter of 0.3mm is doubled Wire winding method is used to produce toroidal cores and used as evaluation data. Using a BH analyzer (SY8258: manufactured by Iwatoki), the magnetic permeability was measured under the conditions of a measurement frequency of 1000kHz and a maximum magnetic flux density of 40mT.

[Evaluation results]

1. Powder physical properties

FIG. 1 is a transmission electron microscope (TEM) photograph of an insulating film soft magnetic alloy powder in which an oxide film is formed on an iron-based amorphous alloy powder in Example 16. FIG. As shown in FIG. 1, it was confirmed that a film (film thickness: 5 nm) was indeed formed on the iron-based amorphous alloy powder. In addition, it was also confirmed that the film thickness calculated from the film treatment conditions of the oxide film basically coincided with the actual film thickness.

Figure 2 is a scanning electron micrograph (SEM) of the insulating coating soft magnetic alloy powder of Example 15 (right side of Figure 2) and the iron-based amorphous alloy powder without oxide coating (left side of Figure 2) of Comparative Example 5 And the line scan result of oxygen obtained by energy dispersive X-ray analyzer (EDS). The vertical axis is the count value per hour of the Kα line of oxygen. The higher the value, the presence of oxygen, that is, the formation of an oxide film. It can be seen from the comparison of the left and right parts of FIG. 2 that by performing the coating treatment, it was confirmed that an oxide coating was indeed formed on the iron-based amorphous alloy powder.

Fig. 3 shows the thickness of the oxide film (nm) and the particle size of the insulating film soft magnetic alloy powder (D50: μm) calculated from the formation conditions of the oxide film And an example of the relationship graph between oxygen content (wt%) (Comparative Example 5 and Examples 11 to 17). As shown in FIG. 3, as the film thickness increases, the amount of oxygen also increases proportionally, which means that an oxide film is formed on the iron-based amorphous alloy powder and the oxide film can be adjusted to the target film thickness.

2. Film performance

4 is an example of a graph showing the relationship between the film thickness of the oxide film of the insulating film soft magnetic alloy powder and the resistivity (Comparative Example 5 and Examples 11 to 17). The resistivity of the iron-based amorphous alloy powder without oxide coating is about 1.0×10 ⁴ Ω‧m, and even if the thickness of the oxide coating is only 1nm, the resistivity is increased by about 100 times; when the oxide coating is When the film thickness is 2nm, a high resistivity of ^{about 1.0×10 7 Ω‧m can be achieved.}

Fig. 5 is an example of a photograph showing the presence or absence of rust after the salt spray test. The black dots in the photograph enclosed by the dotted line indicate that rust has occurred. The iron-based amorphous alloy powder without an oxide coating rusted after 48 hours. On the other hand, in the iron-based amorphous alloy powder with an oxide film, when the film thickness is 2.5nm, rust is first observed after 96 hours; and when the film thickness is 3nm, even after 96 hours No rust was observed. It can be seen that even when the thickness of the oxide coating of the insulating coating soft magnetic alloy powder of the present embodiment is as thin as the nanometer order, the corrosion resistance can be greatly improved.

3. Magnetic properties

Fig. 6 is an example of a graph showing the relationship between the film thickness of the oxide film and the magnetic permeability (Comparative Example 5 and Examples 11 to 17). It can be seen that since the film thickness of the oxide film is on the order of nanometers, even if the film thickness is increased, the decrease in magnetic permeability is reduced, and the decrease in magnetic permeability is also Slower.

The evaluation results of the insulating coating soft magnetic alloy powders (Examples 1 to 32, Comparative Examples 1 to 16) made of iron-based amorphous alloy powders are shown in Table 1; Table 2 shows the evaluation results of the produced insulating coating soft magnetic alloy powders (Examples 33 to 50, Comparative Examples 17 to 28).

[Table 1]

[Table 2]

In Tables 1 and 2, the "reduction rate (%)" refers to the rate of decrease in magnetic permeability compared with the alloy powder without an oxide film formed without coating treatment, and the "corrosion resistance (hours)" is Refers to the result of rusting confirmed by visual inspection every 24 hours in the above salt spray test. "-48" means that rust was confirmed within 48 hours, and "48-72" means that rust was confirmed within 48 to 72 hours. , "72-96" means that rust was confirmed within 72 to 96 hours, and "96-" means that rust was not confirmed even after 96 hours.

As shown in Table 1 and Table 2, the insulating coating soft magnetic alloy powders of the examples suppressed the reduction rate of magnetic permeability to less than 20% regardless of whether they were amorphous or crystalline, which was compared with the comparative example where the coating was not formed. Compared with, the resistivity and corrosion resistance are improved. For Examples 11, 24, and 27 in Table 1, all have the same corrosion resistance evaluation result "-48" as that of Comparative Examples 5, 11, and 13, but the resistivity is compared with Comparative Examples 5, 11, and 13. In the case of a large improvement, it is clear that an oxide film is formed, and there is no difference when observed every 24 hours. Compared with the comparative example where the oxide film is not formed, the corrosion resistance is significantly improved. From this result, the insulating coating soft magnetic alloy powder of the example has excellent characteristics as a material of the powder magnetic core. In particular, the insulating coating soft magnetic alloy powders of Examples 1-9, 11-15, 18, 19, 21, 22, 24, 25, 27, 28, 30, and 31 have a magnetic permeability reduction rate of less than 10% Excellent magnetic properties. Among them, in particular, the insulating coating soft magnetic alloy powders of Examples 1, 2, 5 to 9, 14, 15, 19, and 31 also have high resistivity and high corrosion resistance at the same time. The insulating coating soft magnetic alloy powder of the embodiment has very excellent characteristics as the material of the powder magnetic core.

As shown in Table 1 and Table 2, the insulating film soft magnetic alloy powder of the example forms an oxide film on the surface of the iron-based soft magnetic alloy powder itself, even if the content of Cr, which has the effect of improving corrosion resistance, is small, Can improve corrosion resistance. That is, with the present invention, the amount of Cr used can be reduced, and the insulating film can be manufactured at a lower cost Soft magnetic alloy powder.

In this embodiment, although _{each powder is coated with a SiO 2} film, the same result can be obtained even if the powder is coated with an Al ₂ O _{3 film.}

Claims (9)

An insulating film soft magnetic alloy powder, characterized in that an oxide film with a thickness of 1-10 nm is formed on the surface of the iron-based soft magnetic alloy powder, and the ratio of particle diameter (D50)/film thickness of the oxide film is 100 ~21000. The insulating coating soft magnetic alloy powder of claim 1, wherein the thickness of the oxide coating is 1 to 6 nm. The insulating coating soft magnetic alloy powder of claim 1 or 2, wherein the ratio of the particle diameter (D50)/the film thickness of the oxide coating is 150 to 3000. The insulating coating soft magnetic alloy powder according to any one of claims 1 to 3, wherein the particle size (D50) of the iron-based soft magnetic alloy powder is 0.7-5 μm. The insulating coating soft magnetic alloy powder of any one of claims 1 to 4, wherein the iron-based soft magnetic alloy powder is an iron-based amorphous alloy powder or an iron-based crystalline alloy powder. According to claim 5, the insulating coating soft magnetic alloy powder, wherein the iron-based soft magnetic alloy powder is an iron-based amorphous alloy powder having a composition represented by the following composition formula: (Fe _1-st Co _s Ni _t ) _100-xy {(Si _a B _b ) _m (P _c C _d ) _n } _x M _y [In the formula, the composition ratio of Fe, Co and Ni is 19

x

twenty two, 0

y

6.0, 0

s

0.35, 0

t

0.35, and s+t

0.35, The composition ratio of Si, B, P and C is (0.5:1)

(m: n)

(6:1), (2.5: 7: 5)

(a:b)

(5.5:4.5), and (5.5: 4.5)

(c:d)

(9.5:0.5); M is Nb or Mo]. According to claim 5, the insulating coating soft magnetic alloy powder, wherein the iron-based soft magnetic alloy powder is Fe-Si-Cr series crystalline alloy powder. The insulating coating soft magnetic alloy powder according to any one of claims 1 to 7, which contains 5% by weight or less of Cr. The insulating coating soft magnetic alloy powder according to any one of claims 1 to 8, wherein the oxide coating is a SiO ₂ film.

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