JPH0927412A - Cut core and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a cut core, having low magnetic loss, which is used for a high frequency transformer and a choke coil etc. SOLUTION: This cut core of a structure which has a winding of a nanocrystal alloy strip, containing at least a kind of element selected from Cu and Au, at least a kind of element selected from the group consisting of Nb, Mo, Ta Ti, Zr, Hf, V and W, at least a kind of element, which is selected from the group of Si and B, and Fe as essential element, with at least 50% of its structure composed of the crystal grain of 50nm or smaller in grain diameter, and with at least a part of magnetic path cut has a resistance value of 1Ω or higher per 10mm thickness between the inner circumferential part and the outer circumferential part of the cut core.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cut core using a nanocrystalline soft magnetic alloy used for a high frequency transformer, a choke coil, etc., and having a particularly low core loss, and a method for manufacturing the cut core.

[0002]

2. Description of the Related Art Conventionally, as a magnetic core used in a high frequency transformer or the like, a magnetic core made of silicon steel or ferrite has been mainly used. Ferrite cores are used especially in the high frequency region of 100 kHz or higher because they have low core loss at high frequencies. On the other hand, the silicon steel core has a high saturation magnetic flux density and can be made smaller than other materials in the low frequency range, so it is several kHz.
It is mainly used in the following frequency bands. Generally, the metal magnetic cores used for these applications are often used in the form of cut cores. For the cut core, the winding coil is separately and automatically wound separately, and then the cut core is inserted to manufacture the transformer or the choke coil. On the other hand, in a closed magnetic circuit core that is not a cut core, it is not possible to manufacture the winding coil in advance and insert the core, which makes it difficult to automate the winding work for the core. In this case, the cost is significantly increased, so that it is rarely used except for some applications such as a pulse transformer that requires high inductance in a form other than the cut core.

By the way, in recent years, the drive frequency of inverters and the like has been designed to be several tens of kHz higher than the audible frequency for the purpose of preventing noise and downsizing of the transformer. However, since the cut core using silicon steel has too large a core loss, it generates a large amount of heat and is difficult to use. Recently, a cut core using an Fe-based amorphous alloy having a high saturation magnetic flux density and a relatively high frequency characteristic has been commercialized. When manufacturing a cut core using an alloy ribbon, impregnation is essential. this is,
The purpose is to prevent the ribbon from peeling off during cutting. However, the Fe-based amorphous alloy has a remarkably large magnetostriction, and when resin impregnation is performed to form a cut core, the core loss is remarkably increased and the characteristics of the material cannot be utilized at present. Therefore, the transformer using the Fe-based amorphous cut core cannot fully utilize the characteristics of the material,
The amount of heat generated increases, and the efficiency of the circuit deteriorates. Co
The base amorphous alloy is suitable in terms of characteristics because it has a low magnetic core loss and a small magnetostriction, but it has a large change over time and is problematic for practical use. Further, as described in JP-A 1-110707, an Fe-based nanocrystal alloy having fine crystal grains has been developed in recent years, and since it has a small magnetostriction and a small deterioration of magnetic properties due to impregnation, it is suitable for these applications. It has been reported.

[0004]

However, the cut cores using these Fe-based nanocrystalline alloys have remarkably lower magnetic core loss than the cut cores using silicon steel or Fe-based amorphous alloys, but the cut cores after cutting are impregnated. Compared with the previous core loss, the core loss after cutting was large, and there was a problem that the characteristics originally possessed by the material could not be fully utilized.

[0005]

In order to solve the above problems, the inventors of the present invention have conducted diligent studies and, as a result, have found that the main cause of the increase in the core loss after cutting is the burr generated on the cutting surface during cutting. Further, they found out that the magnetic core loss is related to the resistance value between the inner peripheral portion and the outer peripheral portion of the cut core, and arrived at the present invention. That is, the present invention is Cu,
At least one element selected from Au, Nb, Mo, Ta, Ti, Z
At least one element selected from the group consisting of r, Hf, V and W, at least one element selected from the group consisting of Si, B and Fe as essential elements, and at least 50% of the texture is a grain In a cut core having a structure in which a nanocrystalline alloy ribbon made of crystal grains with a diameter of 50 nm or less is wound and at least part of the magnetic path is cut, the resistance value between the inner and outer circumferences of the cut core Is 1 Ω or more per 10 mm thickness, which is a cut core. Furthermore, if the resistance value between the inner peripheral portion and the outer peripheral portion of the cut core is 5 Ω or more per 10 mm thickness, the core loss is also significantly reduced, which is preferable. In addition, 1
The effective relative permeability μ _{e at} kHz is preferably 5000 or more, and the core loss at 20 kHz, 0.2T is 20 W / kg or less, which is suitable as a cut core. When the thickness of the nanocrystalline ribbon is 3 μm to 50 μm, a cut core having excellent magnetic properties can be obtained.

Yet another invention is Cu, at least one element selected from Au, at least one element selected from the group consisting of Nb, Mo, Ta, Ti, Zr, Hf, V and W, Si, At least one element selected from the group consisting of B and the step of winding an amorphous alloy ribbon containing Fe as an essential element into a toroidal shape, and at least 50 of the structure by heat treatment
%, A step of forming a magnetic core made of a nanocrystalline alloy ribbon made of crystal grains having a particle size of 50 nm or less, a step of impregnating with a resin and hardening the resin, a step of cutting at least a part of a magnetic path, and a step after cutting It is a method of manufacturing a cut core, which comprises a step of polishing a cut surface, and it is preferable that the cut core after the cutting is polished and further etched.
Another invention is Cu, at least one element selected from Au, at least one element selected from the group consisting of Nb, Mo, Ta, Ti, Zr, Hf, V and W, a group consisting of Si and B. A step of winding an amorphous alloy ribbon containing at least one element selected from the above and Fe as an essential element into a toroidal shape, and heat-treating this to form a nano-particle composed of crystal grains with a grain size of 50 nm or less at least 50% It comprises a step of forming a magnetic core made of a crystalline alloy ribbon, a step of impregnating with a resin and hardening the resin, a step of cutting at least a part of the magnetic path, and a step of etching the cut surface after cutting. It is a characteristic method of manufacturing a cut core.

Hereinafter, the present invention will be described in detail. The cut core of the present invention is Cu, at least one element selected from Au, Nb, Mo, Ta, Ti, Zr, Hf, at least one element selected from the group consisting of V and W, Si, consisting of B A nanocrystalline alloy ribbon is used which contains at least one element selected from the group and Fe as essential elements, and in which at least 50% of the structure is composed of crystal grains having a grain size of 50 nm or less. FIG. 1 shows a schematic diagram when the cut core according to the present invention is divided into two. When actually using, winding is done separately, a coil is created, and it is inserted into the core and the two cores are used by abutting at the cut surface. As a result of diligent studies by the present inventors, the cut core using the nanocrystalline alloy cut with a GC grindstone or the like remains burrs on the thin ribbon of the cut surface, and each thin ribbon layer is electrically conducted and the interlayer of the thin ribbon is electrically connected. Since eddy current flows in the core, it was found that the magnetic core loss increased significantly when the cut core was used due to the increase in eddy current loss caused by this. It was also found that the effect of conduction on the cut surface is much larger than the effect of conduction on an incomplete portion of interlayer insulation inside the core. It is considered that this electrical continuity of the cut surface is related to the fact that the thin strips come into contact with each other at the cut surface and become electrically conductive due to the clogging of the grindstone, but this is completely eliminated even if the cutting conditions are changed. It was difficult to do. Therefore, as a result of examining this burr removal method,
It has been found that this burr can be removed by polishing or etching the cut surface, and the electrical conduction of the cut surface is reduced by performing these methods. Furthermore, it was also found that the electrical conductivity of the cut surface is reduced, that is, the core resistance of the core is reduced when the resistance of the cut surface is increased.

FIG. 4 shows the results of measuring the core loss of the cut core at room temperature of 20 kHz and 0.2 T and the resistance between the inner and outer peripheral portions of the core by changing the polishing conditions and etching time of the cut surface. The resistance value R is shown as a value per 10 mm thickness. R is 1
It can be seen that the magnetic core loss is remarkably increased when it is less than Ω. The core having a particularly low R is a core that has not been polished or etched. When the core has a resistance of 1 Ω or more per 10 mm thickness, the core loss of the core becomes extremely small. Ten
1 Ω per mm thickness means that the resistance value between the inner and outer circumferences is 1 Ω when the distance between the inner and outer circumferences is 10 mm, and it is 2 Ω for a 20 mm thick core and 5 Ω for a 5 mm thick core. 0.5 Ω
Means that The resistance value is measured with a resistance measuring instrument by contacting the measuring terminals with two points on the cut surface, that is, the inner peripheral portion and the outer peripheral portion side. This effect is also observed in the case of a cut core using a thin strip with interlayer insulation such as SiO2. In this case, the change in resistance value due to polishing and etching is larger than that when interlayer insulation is performed, and it is 1 per 10 mm before polishing and etching.
The resistance value reaching Ω increases to 5Ω or more. Along with this, the magnetic core loss is also significantly reduced, and more preferable results are obtained.
In use, a spacer may be sandwiched between the abutting portions in order to adjust the effective relative magnetic permeability. Further, the core body is often fastened and fixed with a fixing band or the like. Further, in many cases, the butted portion is fixed by adhering it with resin or the like so that the core does not move. If necessary, impregnate the coil with varnish or the like.

Next, the method of manufacturing the cut core according to the present invention will be described in detail. The alloy ribbon is usually manufactured as follows. First, by a liquid quenching method such as a single roll method or a twin roll method, a plate thickness of about 3 to 100 μm Cu, at least one element selected from Au, and Nb, Mo, Ta, Ti, Zr, Hf, At least one element selected from the group consisting of V and W, at least one element selected from the group consisting of Si, B, and an amorphous alloy ribbon containing Fe as an essential element in the atmosphere, argon or It is produced in an inert gas atmosphere such as helium or in a reduced pressure atmosphere such as helium. Next, this alloy ribbon is wound into a toroidal shape and then heat-treated in an atmosphere of an inert gas such as argon gas or nitrogen gas or in a vacuum so that at least 50% of the structure consists of crystal grains having a grain size of 500 angstroms or less. A magnetic core composed of a nanocrystalline alloy ribbon is prepared. At this time, if the surface of the alloy ribbon is covered with an oxide such as SiO ₂ or Al ₂ O ₃ to perform interlayer insulation, particularly preferable results can be obtained in a wide material. Further, the effect of improving the characteristics of the manufacturing method of the present invention becomes more remarkable. As a method of interlayer insulation, a method of depositing an oxide such as MgO by an electrophoretic method, a method of forming a film of an oxide such as SiO ₂ , Li ₂ O and MgO by applying a metal alkoxide solution on the surface and subjecting it to heat treatment, There are a method of applying a phosphate or chromate treatment to coat the surface with an oxide, and a method of flowing fine ceramic powder and passing it through a thin ribbon to adhere it.

Next, impregnation is carried out in order to prevent the ribbon from peeling off during cutting. As the impregnating resin, an epoxy resin, a polyimide resin, an acrylic resin, or the like can provide preferable results in terms of heat resistance, temperature characteristics, and adhesive strength. The impregnation is preferably vacuum impregnation so that the resin can be inserted between the layers as completely as possible. However, the impregnation is not limited to this, and the vacuum impregnation is not necessarily required if the resin enters the layers. Then the cutting is performed. The cutting is usually performed with a peripheral slicer or the like. The cutting grindstone is not particularly limited, but is GC
The grindstone is most suitable because it does not fall off. As a grindstone used for cutting, a GC grindstone using a resinoid binder is suitable, and a grindstone having a bond degree of K to P and a grain size of 80 to 150 is desirable. The cutting conditions include a feed rate of 0.5 to 30 mm /
A min of about 1000 to 4000 rpm is suitable for the whetstone. A grindstone thickness of 0.5 mm to 1.5 mm is suitable. If it exceeds this range, peeling of the ribbon and flaws on the cut surface are likely to occur. Further, the grindstone is easily worn or damaged.

Next, the cut surface is polished or etched.
Polishing the cut surface increases the effective relative magnetic permeability, and when the surfaces are abutted without a spacer or the like, the effective relative magnetic permeability μ _e at 1 kHz shows 5000 or more. This is because in a cut core that has been cut, the core is deformed, so that voids occur at the abutting surfaces and the effective relative magnetic permeability is low. However, if this is ground, the voids decrease and μ _e is considered to increase. 15,000 when completely polished
It is possible to realize a degree of μe. When such a cut core is used for a transformer, it is possible to reduce the exciting current, and therefore more preferable results can be obtained depending on the usage. Further, in such a cut core, the leakage magnetic flux having a vertical component in the ribbon decreases, and the eddy current in the ribbon surface also decreases. Therefore, a cut core with a large μe has a frequency of 20 kHz,
A cut core having a magnetic core loss at 0.2 T of 20 W / kg or less can be obtained more easily. In the core with interlayer insulation
It is also possible to obtain characteristics of 5 W / kg or less. When polishing, the effect is more remarkable than when polishing in the width direction of the ribbon. Further, rough polishing may be performed at the initial polishing, but smoother final polishing at the final stage gives more preferable results. As a polishing method, for example, a method such as polishing with emery paper or buffing can be performed.

Further, as an example of the etching liquid for the etching treatment, a diluting liquid such as nitric acid or sulfuric acid may be mentioned, but other etching liquids may be used. Further, electrolytic etching may be performed. After etching, the core is washed with water and dried, and a rust-preventing oil or rust-preventive agent is applied to prevent rusting, so that a more reliable product can be obtained. Also, a ceramic or resin film may be formed on the cut surface for electrical insulation. Further, after cutting, if the cut surface is polished and further etched, a cut core having a lower magnetic core loss and a higher effective relative magnetic permeability can be realized.

[0013] general formula as preferred alloy system used in the present _{invention: (Fe 1-a M a} ) is represented by _{100-xyzb A x M 'y} M''z X b ( atomic%), M in the formula is At least one element selected from Co, Ni, A is at least one element selected from Cu, Au, M'is selected from Ti, V, Zr, Nb, Mo, Hf, Ta and W. At least one element, M '' is at least selected from Cr, Mn, Al, Sn, Zn, Ag, In, white metal elements, Mg, Ca, Sr, Y, rare earth elements, N, O and S One element, X represents at least one element selected from B, Si, C, Ge, Ga and P, and a, x, y, z and b are 0 ≦ a <0.5 and 0 ≦ x, respectively. ≦ 10, 0.1 ≦ y ≦ 20, 0 ≦ z ≦ 2
An alloy having a composition represented by a number satisfying 0 and 2 ≦ b ≦ 30 can be mentioned. The content x of at least one element selected from the additive elements Cu and Au represented by A in the above alloy is in the range of 0 to 10 atomic%. These elements are added for the purpose of improving the magnetic permeability, but if it is more than 10 atomic%, the saturation magnetic flux density and the magnetic permeability are significantly lowered, which is not preferable. A more preferable range is 0.1 to 3 atomic%, and a particularly preferable range is 0.5 to 2 atomic%. In this range, particularly high magnetic permeability is obtained. M'is at least one element selected from the group consisting of Ti, V, Zr, Nb, Mo, Hf, Ta and W, and is Cu, Au.
And the like have the effect of making crystal grains finer and improving soft magnetic properties. The content y of M'is 0.1 to 20 atomic%. If it is less than 0.1 atomic%, the effect of grain refinement is insufficient, and if it exceeds 20 atomic%, the saturation magnetic flux density is remarkably lowered. The preferable content y of M'is 2 to 8 atom%. Ti, Zr,
When Nb, Mo, Hf, Ta and W are not present, the crystal grains are not refined so much and the soft magnetic properties are poor. Nb, Mo, and Ta are particularly effective, but when Nb is added among these elements, the crystal grains tend to become finer and soft magnetic characteristics are excellent.

The reason why the magnetic permeability is increased by the combined addition of Cu, Au and Ti, Zr, Nb, Mo, Hf, Ta and W is not clear, but it is considered as follows. Since the interaction parameters of Cu, Au and Fe tend to be positive and tend to separate, when the alloy in the amorphous state is heated, Fe atoms or both Cu and Au atoms gather together to form clusters, resulting in composition fluctuations. Occurs. For this reason, there are many regions that are easy to partially crystallize,
A large number of fine crystal grains are formed from the nuclei. This crystal grain contains Fe as a main component, and since there is almost no solid solubility of Fe, Cu, and Au, the Cu and Au concentrations around the crystal grain become high. In addition, there are many Si etc. around this crystal grain, and Ti, Zr, Nb, M
When o, Hf, Ta, W, etc. are present, it is difficult to crystallize and it is considered that the crystal grains are difficult to grow. Therefore, it is considered that the crystal grains are made finer. As the crystal grains are made finer in this way, the magnetocrystalline anisotropy apparently cancels each other out, and the crystal phase is mainly Fe solid solution of bcc structure and the magnetostriction is small. It is considered that the soft magnetic properties are improved and the high magnetic permeability is obtained due to the reduced magnetic properties.

The additive elements represented by M "are Cr, Mn, Sn, Zn,
Ag, In, white metal element, Mg, Ca, Sr, Y, rare earth element, N, O and S
At least one element selected from the group consisting of has the effect of improving corrosion resistance, improving magnetic properties, adjusting magnetostriction, etc., but its content is at most 10 atomic% or less. is there. The above alloy may contain 2 to 20 atom% or less of at least one element selected from the group consisting of Si, B, C, Ge, Ga, Al and P represented by X. Si and B
Is an element particularly useful for refining the alloy. Fe of the present invention
The base soft magnetic alloy film is preferably obtained by once forming an amorphous alloy film by the effect of adding Si and B and then forming fine crystal grains by heat treatment. At least one element selected from the group consisting of C, Ge, Ga, Al and P is an element effective for amorphization, and it is added together with Si and B to help amorphization of the alloy. , Effective in adjusting magnetostriction and Curie temperature. Also, if the content b of X is less than 2 at%, there is no effect of grain refinement, and if it is more than 20 at%, the saturation magnetic flux density decreases and the soft magnetic properties deteriorate.

The balance consists essentially of Fe except for impurities, but part of Fe may be replaced by the component M (Co and / or Ni). The content a of M is 0 ≦ a <0.5,
Preferably 0 ≦ a ≦ 0.3. This is because if a exceeds 0.3, the magnetic permeability may decrease. More preferably a
Is less than or equal to 0.1. Co substitution also has the effect of increasing the saturation magnetic flux density, and is more advantageous as a smooth choke coil and a low frequency transformer material used in a high coercive force recording medium.

[0017]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited thereto. (Example 1) Fe having a width of 25 mm and a thickness of 17 μm was formed by a single roll method.
_bal. Cu ₁ Nb ₃ Si _15.5 B ₇ Amorphous alloy ribbon was prepared.
Next, this alloy ribbon was passed through a lithium silicate solution and then dried at 200 ° C to form an insulating layer with a thickness of about 0.5 μm on both sides of the ribbon, and a stainless steel ring was used as a core to form the corners of the shape shown in FIG. A wound magnetic core having a shape was produced. Next, this magnetic core was heat-treated at 550 ° C for 1 hour in a nitrogen gas atmosphere. Temperature rising rate is 10 ° C / mi
The cooling rate was 20 ° C / min. 20kHz, 0.2T of this magnetic core
After measuring the magnetic core loss, vacuum-impregnate this magnetic core with three-bond epoxy resin 2287B, press the outside of the core with a plate, and then hold it for 2 hours at 120 ° C and 5h at 150 ° C to cure it for 20kH
The magnetic core loss of z and 0.2T was measured. Next, the magnetic core was cut with a GC grindstone to produce a cut core. As a result of observing the structure of the alloy with a transmission electron microscope, the average crystal grain size was 13 nm and the proportion of crystal grains was 80% or more. Next, before and after polishing the cut surface and before and after etching,
The core loss and the resistance between the inner and outer circumferences of the core at room temperature of 20 kHz and 0.2 T were measured. Here, the resistance value R is shown as a value per 10 mm thickness. Table 1 shows the obtained results and the core loss of the cut core using the nanocrystalline alloy which has not been conventionally polished or etched and the cut core made of silicon steel or Fe-based amorphous alloy.

[0018]

[Table 1]

It can be seen that the cut core of the present invention has a low core loss of about one order and a remarkably low core loss. The results of applying the same process as the present invention to a cut core using an Fe-based amorphous alloy are also shown in Table 1, but it can be seen that the effect of reducing the core loss is small. From this, it was confirmed that the manufacturing method of the present invention is remarkable in the cut core using the nanocrystalline alloy and has a large R and a low core loss. FIG. 3 shows a conventional manufacturing process of a cut core and the manufacturing process of the present invention.

Example 2 Fe _bal. Cu ₁ Ta ₃ Si _15.5 B _6.5 (at
%), And an amorphous alloy ribbon with a width of 25 mm and a thickness of 17 μm was prepared by the single roll method. Next, a toroidal magnetic core having the shape shown in FIG. 2 was produced while forming an insulating layer on the surface of this alloy ribbon by an electrophoresis method using MgO. Next, this magnetic core was heat-treated at 550 ° C. for 1 hour in an argon gas atmosphere. The temperature rising rate was 15 ° C / min and the cooling rate was 10 ° C / min. After measuring the core loss of this core at 20 kHz and 0.2 T, this core was vacuum impregnated with three-bond acrylic resin TB3934B, left standing at 150 ° C. for 3 hours to cure, and the core loss at 20 kHz and 0.2 T was measured. Next, the magnetic core was cut with a GC grindstone to produce a cut core. As a result of observing the structure of the alloy with a transmission electron microscope, the crystal grain size was 12 nm and the crystal grain ratio was 80.
It was over%. Next, while changing the polishing conditions and etching time of the cut surface, the core loss of the cut core at room temperature of 20 kHz and 0.2 T and the resistance between the inner and outer peripheral portions of the core were measured. The resistance value R is shown as a value per 10 mm thickness. The relationship between R and the core loss is shown in FIG. It can be seen that when R is less than 1Ω, the core loss is significantly increased. It can be seen that the R is particularly low in the core that has not been polished or etched. The cut core of the present invention has a lower magnetic core loss and is superior to the conventional cut core that is not polished or etched, and the effectiveness of the present invention was confirmed.

(Example 3) Width 20 mm thickness of the composition shown in Table 2
A 15 μm amorphous alloy ribbon was prepared by the single roll method. Next, this alloy ribbon was wound into a shape shown in FIG. 5 to produce a wound magnetic core. Next, this magnetic core is placed in an argon gas atmosphere 55
Heat treatment was performed at 0 ° C for 1 hour. The temperature rising rate was 20 ° C / min and the cooling rate was 20 ° C / min. We also examined the cases where the ribbon was not insulated between layers or when it was insulated. This magnetic core is vacuum impregnated with various resins and hardened, and the GC is
It cut with the grindstone and produced the cut core. Next, 20kH of the cut core before and after polishing the cut surface and before and after etching
The core loss at room temperature of z and 0.2T and the resistance between the inner and outer circumferences of the core were measured. The resistance value R is shown as a value per 10 mm thickness. Table 2 shows the obtained results. Even when the interlayer insulation was not performed, reduction of magnetic core loss and improvement of R were recognized by polishing and etching. In the case of interlayer insulation, the improvement effect is more remarkable. The cut core of the present invention has a low core loss and is superior to the conventional cut core. In particular, the ground core has a high effective relative magnetic permeability of 5000 or more and can realize a transformer with a small exciting current.

[0022]

[Table 2]

[0023]

According to the present invention, a cut core having a low magnetic core loss suitable for a high frequency transformer, a choke coil and the like and a method for manufacturing the cut core can be realized.

[Brief description of drawings]

FIG. 1 is a schematic diagram when a cut core according to the present invention is divided into two.

FIG. 2 is a diagram showing an example of a shape of a cut core according to the present invention before being cut.

FIG. 3 is a diagram showing a conventional manufacturing method of a cut core using a nanocrystalline alloy and a manufacturing method of the present invention.

FIG. 4 is a diagram showing an example of the relationship between the core loss of a cut core and R according to the present invention.

FIG. 5 is a diagram showing an example of a shape of a cut core according to the present invention before being cut.

Claims (9)

[Claims] 1. A group consisting of at least one element selected from Cu and Au, at least one element selected from the group consisting of Nb, Mo, Ta, Ti, Zr, Hf, V and W, and Si and B. A nanocrystalline alloy ribbon containing at least one element selected from among Fe and Fe as an essential element, at least 50% of which has a grain size of 50 nm or less, and at least a part of a magnetic path A cut core having a cut structure, wherein a resistance value between an inner peripheral portion and an outer peripheral portion of the cut core is 1 Ω or more per 10 mm thickness. 2. The cut core according to claim 1, wherein a resistance value between an inner peripheral portion and an outer peripheral portion of the cut core is 5 Ω or more per 10 mm thickness. 3. The effective relative permeability μ _{e at} 1 kHz is 5000.
It is above, The cut core of Claim 1 or Claim 2 characterized by the above-mentioned. 4. The core loss at 20 kHz, 0.2T is 20 W /
The cut core according to any one of claims 1 to 3, which has a weight of not more than kg. 5. The thickness of the nanocrystalline ribbon is 3 μm to 50 μm.
It is m, The cut core in any one of Claim 1 thru | or 4 characterized by the above-mentioned. 6. A group consisting of at least one element selected from Cu and Au, at least one element selected from the group consisting of Nb, Mo, Ta, Ti, Zr, Hf, V and W, and Si and B. A step of winding an amorphous alloy ribbon containing at least one element selected from the above and Fe as an essential element into a toroidal shape, and heat-treating this to form a nano-particle composed of crystal grains with a grain size of 50 nm or less at least 50% Characterized by comprising a step of forming a magnetic core made of a crystal alloy ribbon, a step of impregnating with a resin and hardening the resin, a step of cutting at least a part of a magnetic path, and a step of polishing a cut surface after cutting. And a method for manufacturing a cut core. 7. A group consisting of at least one element selected from Cu and Au, at least one element selected from the group consisting of Nb, Mo, Ta, Ti, Zr, Hf, V and W, and Si and B. A step of winding an amorphous alloy ribbon containing at least one element selected from the above and Fe as an essential element into a toroidal shape, and heat-treating this to form a nano-particle composed of crystal grains with a grain size of 50 nm or less at least 50% It comprises a step of forming a magnetic core made of a crystalline alloy ribbon, a step of impregnating with a resin and hardening the resin, a step of cutting at least a part of the magnetic path, and a step of etching the cut surface after cutting. A method of manufacturing a cut core having the characteristics. 8. The method for manufacturing a cut core according to claim 6, comprising a step of polishing the cut surface after cutting and further performing etching treatment. 9. The amorphous alloy ribbon has a thickness of 3 μm.
To 50 μm, the method for producing a cut core according to any one of claims 6 to 8.