Method for manufacturing Fe-based nanocrystalline alloy core and Fe-based nanocrystalline alloy core

Abstract

A method for manufacturing an Fe-based nanocrystalline alloy core, comprising: an oxide film forming process in which a core material formed by winding a ribbon of a nanocrystalline Fe-based alloy is heat-treated under an oxidizing atmosphere; and a nanocrystallization process in which the core material after the oxide film forming process is heat-treated under a non-oxidizing atmosphere to perform nanocrystallization of the nanocrystalline Fe-based alloy, wherein the maximum temperature of the heat treatment in the oxide film forming process is a temperature lower than the crystallization start temperature of the nanocrystalline Fe-based alloy, and the maximum temperature of the heat treatment in the nanocrystallization process is a temperature higher than the crystallization start temperature of the nanocrystalline Fe-based alloy.

Description

Technology Field

[0001] The present invention relates to a method for manufacturing an Fe-based nanocrystalline alloy core and an Fe-based nanocrystalline alloy core. Background Technology

[0002] Fe-based nanocrystalline alloys are used as cores for common mode chokes, high-frequency transformers, etc., because they possess excellent soft magnetic properties capable of realizing high permeability.

[0003] As a representative composition of Fe-based nanocrystalline alloys, a magnetic material of Fe-Si-B-Cu-Nb nanocrystalline structure with Fe as the main component is known (Patent Document 1). A coil or magnetic core using such a magnetic material is generally obtained by winding a ribbon of a nanocrystallizable Fe-based amorphous alloy to form a cylindrical wound core and heat treating it.

[0004] Higher permeability is required for cores, and in addition to material selection, technologies to improve permeability are being actively developed.

[0005] For example, Patent Documents 2 and 3 disclose a technique for improving permeability in a high-frequency region by forming an oxide film on the surface of a magnetic ribbon in a magnetic core formed by winding or stacking a ribbon of an amorphous magnetic alloy. This technique involves insulating the ribbon layers of a magnetic core formed by winding or stacking magnetic ribbons with an oxide film, thereby suppressing the generation of eddy currents flowing between the ribbon layers and reducing eddy current losses, resulting in improved permeability.

[0006] In addition, Patent Document 4 discloses a technology that improves permeability by adjusting the crystal magnetic anisotropy by applying a magnetic field while performing heat treatment on a magnetic core using a nanocrystalline alloy material.

[0007] [Prior Art Literature]

[0008] [Patent Literature]

[0009] [Patent Document 1] Patent Publication No. 64-79342

[0010] [Patent Document 2] JPA No. 6-346219

[0011] [Patent Document 3] Patent Publication No. 57-169207

[0012] [Patent Document 4] Patent Publication No. JPA 2-77105 The problem to be solved

[0013] Recently, for example, cores for common mode chokes are required to be able to adequately handle low frequencies.

[0014] In a magnetic core formed by winding or laminating nanocrystalline alloy magnetic ribbons, the generation of eddy currents flowing between ribbon layers can be suppressed by forming an oxide film on the surface of the magnetic ribbons, thereby improving permeability in the high-frequency region. However, unlike the amorphous alloy magnetic cores described in Patent Documents 2 and 3, nanocrystalline alloy magnetic cores tend to have a lower permeability in the low-frequency region due to the formation of an oxide film. Although it is possible to improve permeability in the low-frequency region by applying a magnetic field in nanocrystalline alloy magnetic cores, the problem remains that the degree of improvement is insufficient.

[0015] The present invention aims to provide a method for manufacturing an Fe-based nanocrystalline alloy core that exhibits high permeability in the low-frequency region, taking into account the above-mentioned problems. means of solving the problem

[0016] As a result of repeated investigations to solve the above problem, the inventors discovered that by forming an oxide film on the surface of an Fe-based alloy ribbon of a core material formed by winding an Fe-based alloy ribbon, and then nanocrystallizing the Fe-based alloy in an environment where the oxide film is not formed, an Fe-based nanocrystalline alloy core exhibiting high permeability even in the low-frequency region is obtained, thereby arriving at the present invention. In other words, the gist of the present invention is as follows.

[0017] [1]

[0018] An oxide film formation process in which a core material formed by winding a ribbon of a nanocrystallizable Fe-based alloy is heat-treated under an oxidizing atmosphere, and

[0019] The nanocrystallization process comprises performing nanocrystallization of the nanocrystallizable Fe-based alloy by heat-treating the core material after the oxide film formation process under a non-oxidizing atmosphere.

[0020] The maximum temperature of the heat treatment in the above oxide film formation process is a temperature lower than the crystallization initiation temperature of the nanocrystallizable Fe-based alloy, and

[0021] A method for manufacturing an Fe-based nanocrystalline alloy core in which the maximum temperature of the heat treatment in the above nanocrystalline process is a temperature greater than or equal to the crystallization initiation temperature of the above nanocrystalline Fe-based alloy.

[0022] [2]

[0023] It includes a magnetic field application process that applies a magnetic field in the height direction of the magnetic core material while performing heat treatment on the magnetic core material after the above nanocrystallization process,

[0024] A method for manufacturing an Fe-based nanocrystalline alloy core as described in [1], wherein the maximum temperature of the heat treatment in the above magnetic field application process is lower than the crystallization start temperature of the above nanocrystalline Fe-based alloy.

[0025] [3]

[0026] A method for manufacturing a Fe-based nanocrystalline alloy core as described in [1] or [2], wherein the above nanocrystalline Fe-based alloy has a composition represented by the following general formula (I).

[0027] Fe x Si a B b Cu C Nb d (I)

[0028] (In general formula (I), a to d (atomic %) represent 3.0≤a≤12.0, 1.0≤b≤7.0, 1.0≤c≤5.0, and 1.0≤d≤9.0, respectively; x (atomic %) is the remainder excluding Si, B, Cu, and Nb, satisfying 73.0≤x≤92.0.)

[0029] [4]

[0030] The ribbon is a self-reinforced heart,

[0031] The above ribbon has a first oxide film layer, a second oxide film layer, and a base material formed of an Fe-based nanocrystalline alloy including an amorphous phase and crystal grains in this order, and

[0032] The above Fe-based nanocrystalline alloy has a composition represented by the following general formula (I), and

[0033] Fe-based nanocrystalline alloy core satisfying (A) and (B) below in the depth profile by X-ray photoelectron spectroscopy of sample X below.

[0034] Fe x Si a B b Cu C Nb d (I)

[0035] (In general formula (I), a to d (atomic %) represent 3.0≤a≤12.0, 1.0≤b≤7.0, 1.0≤c≤5.0, and 1.0≤d≤9.0, respectively; x (atomic %) is the remainder excluding Si, B, Cu, and Nb, satisfying 73.0≤x≤92.0.)

[0036] (A) Cu in a depth range corresponding to the first oxide film layer above 2p A peak appears.

[0037] (B) In the depth range corresponding to the first oxide film layer, Cu 2p The peak intensity of O derived from SiO2 1S It is stronger than the intensity of.

[0038] (Sample X) When the area between the inner surface and the outer surface of the Fe-based nanocrystalline alloy core is virtually divided into three regions, a first region, a second region, and a third region, extending from the inner surface toward the outer surface, a ribbon located within the second region is cut and used as a sample. The first region, the second region, and the third region are regions that divide the radial length between the inner surface and the outer surface into 40 / 20 / 40. X-ray photoelectron spectroscopy analysis is performed on the surface of the sample that was facing the outer surface when it was wound to form the Fe-based nanocrystalline alloy core.

[0039] [5]

[0040] In the depth profile above, the Fe-based nanocrystalline alloy core described in [4] further satisfies (C) and (D) below.

[0041] (C) O of SiO2 in a depth range corresponding to the second oxide film layer above 1S and Si 2p A peak appears.

[0042] (D) In ​​the depth range corresponding to the second oxide film layer above, O of SiO2 1S The peak intensity of Cu 2p It is stronger than the intensity of.

[0043] [6]

[0044] In the depth profile above, the Fe-based nanocrystalline alloy core described in [4] or [5] further satisfies (E) below.

[0045] (E) Cu in the depth range corresponding to the first oxide film layer above 2p Cu in the depth range corresponding to the above base material, where the peak intensity is 2p It is stronger than the intensity of. Effects of the invention

[0046] According to the present invention, a method for manufacturing an Fe-based nanocrystalline alloy core that exhibits high permeability in the low frequency region can be provided.

[0047] In addition, according to a preferred embodiment of the present invention, a method for manufacturing an Fe-based nanocrystalline alloy core that exhibits high permeability in both low-frequency and high-frequency regions can be provided.

[0048] In addition, according to the present invention, the above manufacturing method can provide an Fe-based nanocrystalline alloy core exhibiting high permeability in the low frequency region. Brief explanation of the drawing

[0049] Figure 1 is a graph showing the relative permeability at a frequency of 10 kHz of Fe-based nanocrystalline alloy cores obtained in experimental and comparative examples. Figure 2 is a graph showing the relative permeability at a frequency of 100 kHz of Fe-based nanocrystalline alloy cores obtained in experimental and comparative examples. Figure 3 is a schematic diagram illustrating sample X for X-ray photoelectron spectroscopy analysis. Figure 4 is a TEM image of the cross-section of a ribbon forming an Fe-based nanocrystalline alloy core obtained in Example 2, Comparative Example 2, and Comparative Example 4 (photograph for drawing). Figure 5 is a depth profile obtained by X-ray photoelectron spectroscopy of the Fe-based nanocrystalline alloy core obtained in Example 2. Figure 6 is a depth profile obtained by X-ray photoelectron spectroscopy of the Fe-based nanocrystalline alloy core obtained in Comparative Example 2. Figure 7 is a depth profile obtained by X-ray photoelectron spectroscopy of the Fe-based nanocrystalline alloy core obtained in Comparative Example 4. Specific details for implementing the invention

[0050] Embodiments of the present invention will be described in detail below. The description of the constituent elements described below is merely an example (representative example) of an embodiment of the present invention, and the present invention is not specified in these details unless it exceeds the gist thereof.

[0051] In addition, in this specification, when "~" is used to express numerical values ​​or physical properties placed before and after it, it shall be used to include the values ​​before and after it.

[0052] <1. Method for manufacturing Fe-based nanocrystalline alloy core>

[0053] A method for manufacturing an Fe-based nanocrystalline alloy core according to a first embodiment of the present invention comprises an oxide film formation process in which a core material formed by winding a ribbon of a nanocrystalline Fe-based alloy is heat-treated under an oxidizing atmosphere, and a nanocrystallization process in which nanocrystallization of the nanocrystalline Fe-based alloy is performed by heat-treating the core material after the oxide film formation process under a non-oxidizing atmosphere. Here, the maximum temperature of the heat treatment in the oxide film formation process is a temperature below the crystallization initiation temperature of the nanocrystalline Fe-based alloy, and the maximum temperature of the heat treatment in the nanocrystallization process is a temperature above the crystallization initiation temperature of the nanocrystalline Fe-based alloy.

[0054] Unless otherwise specified, the heat treatment temperature mentioned in this specification refers to the set temperature of the heat treatment furnace used for heat treatment of the core material. In addition, the temperature of the core material itself is about 5°C to 10°C higher than the set temperature of the heat treatment furnace, and can be measured by attaching a thermocouple to the core material.

[0055] The Fe-based nanocrystalline alloy core obtained by the manufacturing method according to the present embodiment exhibits high permeability in the low-frequency region. Additionally, in this specification, "relative permeability" may be used as an indicator for evaluating "permeability."

[0056] In this specification, the permeability in the low-frequency region is evaluated based on the permeability at a frequency of 10 kHz. In addition, the permeability in the high-frequency region is evaluated based on the permeability at a frequency of 100 kHz.

[0057] The relative permeability of the Fe-based nanocrystalline alloy core can be calculated by measuring the inductance of a coil wound on the Fe-based nanocrystalline alloy core and based on the following equation (1).

[0058] μr = μ / μ0 (1)

[0059] μr: Relative permeability

[0060] μ0 : Vacuum permeability = 4π × 10 -7 [H / m]

[0061] μ: Permeability [H / m] = Ll / A / N 2

[0062] L : Inductance [H]

[0063] l : Length [m]

[0064] A : Core effective cross-sectional area [㎡]

[0065] N : Volume

[0066] The manufacturing method according to the present embodiment is similar to the conventional manufacturing method (e.g., see Patent Documents 2 and 3) in that it is a method for manufacturing an Fe-based nanocrystalline alloy core with an oxide film formed to suppress eddy currents, but unlike the conventional manufacturing method, it can achieve an improvement in permeability in the low-frequency region.

[0067] In conventional manufacturing methods, heat treatment is performed under an oxidizing atmosphere, thereby allowing the formation of an oxide film and nanocrystallization to proceed simultaneously. In contrast, the manufacturing method according to the present embodiment is a method for forming an oxide film without causing nanocrystallization during the oxide film formation process, and for performing nanocrystallization of an Fe-based alloy without forming an oxide film that affects permeability during the nanocrystallization process. The inventors speculate that in the manufacturing method according to the present embodiment, the formation of the oxide film and nanocrystallization are performed separately in this order, thereby preventing the formation of the oxide film and nanocrystallization from proceeding simultaneously, which can improve permeability in the low-frequency region.

[0068] <1-1. Oxide Film Formation Process>

[0069] The oxide film formation process is a process of forming an oxide film on the surface of an Fe-based alloy ribbon by heat-treating a core material, which is formed by winding a ribbon of a nanocrystallizable Fe-based alloy (hereinafter simply referred to as "Fe-based alloy"), under an oxidizing atmosphere. The maximum temperature of the heat treatment in the oxide film formation process is a temperature lower than the crystallization initiation temperature of the Fe-based alloy.

[0070] The Fe-based alloy constituting the Fe-based alloy ribbon is not particularly limited as long as it is an Fe-based alloy capable of nanocrystallization by heat treatment, and examples include Fe-Si-B-Cu-Nb alloys. As a specific composition of the Fe-Si-B-Cu-Nb alloy, a composition represented by the following general formula (I) is preferably exemplified.

[0071] Fe x Si a B b Cu C Nb d (I)

[0072] In general formula (I), a to d (atomic %) represent 3.0≤a≤12.0, 1.0≤b≤7.0, 1.0≤c≤5.0, and 1.0≤d≤9.0, respectively; x (atomic %) is the remainder other than Si, B, Cu, and Nb, satisfying 73.0≤x≤92.0. In addition, this remainder may contain unavoidable impurities.

[0073] The crystallization initiation temperature of a nanocrystallizable Fe-based alloy is typically 350°C or higher and 520°C or lower, and in the case of an Fe-Si-B-Cu-Nb alloy having a composition represented by the general formula (I) above, the crystallization initiation temperature is typically 480°C or higher and 520°C or lower.

[0074] In addition, in this specification, the crystallization initiation temperature is defined as the temperature at which an exothermic reaction is detected due to the initiation of nanocrystallization when the measurement conditions of the differential scanning calorimeter (DSC) are set at a heating rate of 10°C / min.

[0075] The thickness and width of the Fe-based alloy ribbon are not particularly limited as long as they can be wound to form a magnetic core of a practical shape. Specifically, the thickness of the ribbon is typically 8 μm or more and 25 μm or less, and the width of the ribbon is typically 5 mm or more and 25 mm or less.

[0076] As for the core material, commercially available core material may be used as is, or a core material produced by winding a commercially available Fe-based alloy ribbon may be used. Alternatively, a core material may be used by producing an Fe-based alloy ribbon by rapidly cooling and solidifying a molten Fe-based alloy using the ultra-rapid cooling method, and then winding said ribbon.

[0077] In the above ultra-rapid cooling method, it is preferable to set the temperature of the molten metal during rapid cooling to a temperature approximately 50°C to 300°C higher than the melting point of the alloy. The ultra-rapid cooling method is not particularly limited, and known methods such as the single-roll method, double-roll method, rotating liquid prevention method, gas atomization method, and water atomization method may be adopted. The production of Fe-based alloy ribbons by the ultra-rapid cooling method may be carried out under an oxidizing atmosphere such as air, under an inert gas atmosphere such as argon, helium, or nitrogen, or under vacuum conditions.

[0078] In addition, Fe-based alloy ribbons are typically composed of an amorphous phase. While it is preferable that Fe-based alloy ribbons not contain a crystalline phase, they may contain a crystalline phase in some parts as long as it does not impede the effects of the present invention.

[0079] As an oxidation atmosphere, an oxygen-containing atmosphere such as oxygen gas or air may be used. The lower limit of the oxygen concentration in the oxygen-containing atmosphere is not particularly limited as long as an oxide film can be formed on the surface of the Fe-based alloy ribbon, and is typically 0.1 vol% or more, and may be 0.2 vol% or more, 0.3 vol% or more, 1.0 vol% or more, 10.0 vol% or more, or 20.0 vol% or more. In addition, the upper limit of the oxygen concentration in the oxygen-containing atmosphere is typically 100% or less, and may be 80.0 vol% or less, 60.0 vol% or less, or 40.0 vol% or less. That is, suitable ranges for the oxygen concentration of the oxygen-containing atmosphere include 0.1 vol% or more and 80.0 vol% or less, 0.2 vol% or more and 100% or less, 0.3 vol% or more and 60.0 vol% or less, 1.0 vol% or more and 60.0 vol% or less, 10.0 vol% or more and 40.0 vol% or less, and 20.0 vol% or more and 40.0 vol% or less. Moisture may be added to the oxidation atmosphere by means of humidifying gas, superheated steam, etc. In addition, in the oxide film formation process, boiling treatment may be performed on the core material before heat treatment under an oxidation atmosphere.

[0080] The maximum temperature of the heat treatment in the oxide film formation process varies depending on the type of oxidizing atmosphere, the heat treatment time, etc., but is typically 300°C or higher, preferably 400°C or higher. In addition, it is typically lower than the crystallization start temperature of the Fe-based alloy, preferably lower than 50°C below the crystallization start temperature of the Fe-based alloy, more preferably lower than 60°C below the crystallization start temperature of the Fe-based alloy, and even more preferably lower than 70°C below the crystallization start temperature of the Fe-based alloy. That is, suitable ranges for the maximum temperature of the heat treatment include 400°C or higher and lower than 50°C below the crystallization start temperature of the Fe-based alloy, 300°C or higher and lower than the crystallization start temperature of the Fe-based alloy, 400°C or higher and lower than 60°C below the crystallization start temperature of the Fe-based alloy, and 400°C or higher and lower than 70°C below the crystallization start temperature of the Fe-based alloy. By keeping the maximum temperature within the above range, the simultaneous progression of oxide film formation and nanocrystallization of the Fe-based alloy can be suppressed while forming an oxide film on the surface of the Fe-based alloy ribbon constituting the core material, thereby improving the permeability of the Fe-based nanocrystal alloy core in the low-frequency region.

[0081] The rate of increase in temperature to reach the maximum temperature and the rate of decrease in temperature after the maintenance at the maximum temperature is terminated are not particularly limited as long as they do not impede the effects of the present invention, and rates generally adopted for heat treatment in the technical field of the present invention may be applied.

[0082] The holding time at the maximum temperature above varies depending on the type of oxidizing atmosphere, heat treatment temperature, etc., but is typically 1 hour or more, preferably 2 hours or more, more preferably 3 hours or more, and also typically 30 hours or less, preferably 20 hours or less, more preferably 10 hours or less. That is, suitable ranges for the holding time at the maximum temperature above include 1 hour or more and 20 hours or less, 2 hours or more and 30 hours or less, and 3 hours or more and 10 hours or less.

[0083] <1-2. Nanocrystallization Process>

[0084] The nanocrystallization process is a process for nanocrystallizing a nanocrystallizable Fe-based alloy by heat-treating the core material after the oxide film formation process under a non-oxidizing atmosphere. The maximum temperature of the heat treatment in the nanocrystallization process is a temperature higher than the crystallization initiation temperature of the nanocrystallizable Fe-based alloy. Through the nanocrystallization process, an Fe-based nanocrystalline alloy containing crystal grains consisting of a crystalline phase (bcc phase) and an amorphous phase is formed.

[0085] In this specification, a non-oxidizing atmosphere refers to an atmosphere capable of suppressing the formation of an oxide film to an extent that does not affect the permeability. Specifically, examples of such a non-oxidizing atmosphere include inert gas atmospheres such as argon, helium, and nitrogen. A non-oxidizing atmosphere may contain a trace amount of oxygen. When a non-oxidizing atmosphere contains oxygen, the oxygen concentration is typically less than 0.1 vol%, preferably 0.01 vol% or less, and more preferably 0.001 vol% or less.

[0086] The lower limit of the maximum temperature for heat treatment in the nanocrystallization process is not particularly limited as long as it is above the crystallization start temperature of the Fe-based alloy, and preferably, it is above a temperature 14°C higher than the crystallization start temperature of the Fe-based alloy. In addition, the upper limit of the maximum temperature for heat treatment in the nanocrystallization process is typically below a temperature 59°C higher than the crystallization start temperature of the Fe-based alloy, preferably below a temperature 44°C higher than the crystallization start temperature of the Fe-based alloy. More specifically, when the crystallization start temperature of the Fe-based alloy is about 516°C, the heat treatment temperature in the nanocrystallization process is typically 516°C or higher, preferably 530°C or higher, and also typically 575°C or lower, preferably 560°C or lower. That is, suitable ranges for the maximum temperature of the heat treatment include a temperature 14°C higher than the crystallization start temperature of the Fe-based alloy and a temperature 59°C higher than the crystallization start temperature of the Fe-based alloy and a temperature 14°C higher than the crystallization start temperature of the Fe-based alloy and a temperature 44°C higher than the crystallization start temperature of the Fe-based alloy, and more specifically, a range of 516°C to 560°C and 530°C to 575°C.

[0087] The rate of increase in temperature to reach the maximum temperature and the rate of decrease in temperature after the maintenance at the maximum temperature is terminated are not particularly limited as long as they do not impede the effects of the present invention, and rates generally adopted for heat treatment in the technical field of the present invention may be applied.

[0088] The holding time at the maximum temperature above varies depending on the composition of the Fe-based alloy, the size of the core, etc., but from the perspective of uniformly heating the entire alloy and productivity, it is typically 30 minutes or more, preferably 50 minutes or more, more preferably 90 minutes or more, and typically 10 hours or less, preferably 2 hours or less. That is, suitable ranges for the holding time at the maximum temperature above include 30 minutes or more and 2 hours or less, 50 minutes or more and 10 hours or less, and 90 minutes or more and 10 hours or less.

[0089] The nanocrystallization process may further include a heat retention process in which, during the process of raising the temperature to the aforementioned maximum temperature, the temperature is temporarily stopped at the point where the heat treatment temperature is reached below the maximum temperature, and the heat treatment temperature is maintained.

[0090] During the nanocrystallization of Fe-based alloys, overshoot may occur, where the temperature of the core material rises above the set temperature of the heat treatment furnace due to self-heating during the precipitation of crystal phases; however, this overshoot can be suppressed through a thermal holding process. Overshoot causes variations in the permeability of the Fe-based nanocrystalline alloy core. Therefore, by suppressing overshoot, the internal temperature of the core material becomes uniform, and as a result, variations in the permeability of the Fe-based nanocrystalline alloy core can be suppressed. Furthermore, the suppression of overshoot indicates that when the thermal holding process is performed, the difference between the set temperature of the heat treatment furnace during nanocrystallization and the actual temperature of the core material becomes smaller than when the thermal holding process is not performed.

[0091] The inventors speculate as follows as the reason why overshoot in nanocrystallization is suppressed and furthermore the variation in permeability of the Fe-based nanocrystalline alloy core is suppressed by performing a thermal insulation process.

[0092] If overshoot occurs during the nanocrystallization of Fe-based alloys, a temperature exceeding the set temperature of the heat treatment furnace is applied to the core, causing excessive precipitation of crystalline phases and potentially leading to deviations in the permeability of the Fe-based nanocrystalline alloy core. However, if a heat retention process is performed prior to nanocrystallization, the amount of thermal energy applied to the core material wound with Fe-based alloy ribbons is suppressed. Consequently, the rate of crystalline phase precipitation slows down, thereby suppressing self-heating associated with the precipitation. As a result, it is presumed that overshoot is suppressed, and furthermore, deviations in the permeability of the Fe-based nanocrystalline alloy core are contained.

[0093] The heat treatment temperature in the thermal insulation process is not particularly limited as long as it is a temperature below the maximum temperature of the nanocrystallization process, and is typically 65°C lower than the crystallization start temperature of the Fe-based alloy, preferably 60°C lower than the crystallization start temperature of the Fe-based alloy, and also 45°C lower than the crystallization start temperature of the Fe-based alloy, preferably 40°C lower than the crystallization start temperature of the Fe-based alloy. That is, suitable ranges for the heat treatment temperature include a temperature 65°C lower than the crystallization start temperature of the Fe-based alloy, a temperature 40°C lower than the crystallization start temperature of the Fe-based alloy, and a range of 60°C lower than the crystallization start temperature of the Fe-based alloy and 45°C lower than the crystallization start temperature of the Fe-based alloy.

[0094] The heat treatment time in the heat retention process varies depending on the heat treatment temperature and the size of the core material, but from the perspective of homogenizing the temperature inside the heat treatment furnace, it is typically 30 minutes or more, preferably 60 minutes or more, and more preferably 100 minutes or more; and typically 5 hours or less, preferably 4 hours or less, and more preferably 3 hours or less. That is, suitable ranges for the heat treatment time include 30 minutes or more and 4 hours or less, 60 minutes or more and 5 hours or less, and 100 minutes or more and 3 hours or less. After the above heat treatment time has elapsed, that is, after the heat retention process is completed, the temperature is raised to the maximum temperature of the heat treatment in the nanocrystallization process to sufficiently promote the nanocrystallization of the Fe-based alloy.

[0095] <1-3. Magnetic Field Application Process>

[0096] The manufacturing method according to the present embodiment may further include a magnetic field application process in which a magnetic field is applied in the height direction of the core material while performing heat treatment on the core material after the nanocrystallization process. It is preferable to perform the magnetic field application process from the perspective of improving the permeability of the Fe-based nanocrystalline alloy core in the high-frequency region.

[0097] The maximum temperature of the heat treatment in the magnetic field application process is not particularly limited, but is typically 300°C or higher, preferably 400°C or higher, and is also typically lower than the crystallization start temperature of the Fe-based alloy, preferably lower than 50°C lower than the crystallization start temperature of the Fe-based alloy, and more preferably lower than 60°C lower than the crystallization start temperature of the Fe-based alloy. That is, suitable ranges for the maximum temperature of the heat treatment include 400°C or higher and lower than the crystallization start temperature of the Fe-based alloy, 300°C or higher and lower than 50°C lower than the crystallization start temperature of the Fe-based alloy, and 400°C or higher and lower than 60°C lower than the crystallization start temperature of the Fe-based alloy.

[0098] The rate of increase in temperature to the maximum temperature and the rate of decrease in temperature after the maintenance at the maximum temperature is terminated are not particularly limited as long as they do not impede the effects of the present invention, and rates generally adopted in heat treatment in the technical field of the present invention may be applied.

[0099] The holding time at the maximum temperature above varies depending on the maximum temperature, the size of the core material, etc., but from the perspective of homogenizing the temperature inside the heat treatment furnace, it is typically 20 minutes or more, preferably 30 minutes or more, and also typically 5 hours or less, preferably 2 hours or less, more preferably 1 hour or less. That is, suitable ranges for the holding time at the maximum temperature above include 20 minutes or more and 2 hours or less, 30 minutes or more and 5 hours or less, and 30 minutes or more and 1 hour or less.

[0100] In the magnetic field application process, the magnetic field is applied to the magnetic core material in the height direction of the magnetic core material, that is, in the width direction of the Fe-based alloy ribbon constituting the magnetic core material. The strength of the magnetic field applied to the magnetic core material is not particularly limited as long as it is high enough to magnetically saturate the magnetic core, and is typically 50 mT or more, preferably 80 mT or more, more preferably 100 mT or more, and also typically 150 mT or less. That is, suitable ranges for magnetic field strength include 50 mT or more and 150 mT or less, 80 mT or more and 150 mT or less, and 100 mT or more and 150 mT or less.

[0101] The magnetic field application process may be carried out under an oxidizing atmosphere such as air, under an inert gas atmosphere such as argon, helium, or nitrogen, or under vacuum conditions, but it is preferable to carry out the process under an inert gas atmosphere.

[0102] In addition, although the above description mentions that the heat treatment in the oxide film formation process, the nanocrystallization process, and the magnetic field application process includes raising the temperature, holding at the maximum temperature, and lowering the temperature, raising the temperature or lowering the temperature is not necessarily required. For example, after the heat treatment in the oxide film formation process, the atmosphere of the heat treatment furnace may be changed from an oxidizing atmosphere to a non-oxidizing atmosphere, and the nanocrystallization process may be performed by further raising the temperature. However, considering the necessity of changing the atmosphere inside the heat treatment furnace, the necessity of applying a magnetic field, and the manufacturing equipment, it is desirable that the heat treatment in each process include a series of operations such as raising the temperature, holding at the maximum temperature, and lowering the temperature.

[0103] <2. Fe-based nanocrystalline alloy core>

[0104] The Fe-based nanocrystalline alloy core according to the second embodiment of the present invention is a core formed by winding a ribbon, said ribbon having a first oxide film layer, a second oxide film layer, and a base material formed of an Fe-based nanocrystalline alloy including an amorphous phase and crystal grains in this order, and said Fe-based nanocrystalline alloy having a composition represented by the following general formula (I). When X-ray photoelectron spectroscopy (XPS) analysis is performed on a specific sample sampled from the Fe-based nanocrystalline alloy core according to the present embodiment, a characteristic depth profile described below is obtained.

[0105] Fe x Si a B b Cu C Nb d (I)

[0106] General formula (I) is the same as General formula (I) described in <1-1. Oxide Film Formation Process> above. Accordingly, the definitions of a~d (atomic %) and x (atomic %) and preferred embodiments are as described in <1-1. Oxide Film Formation Process>.

[0107] The Fe-based nanocrystalline alloy core according to the present embodiment is a core obtained using an Fe-Si-B-Cu-Nb alloy having a composition represented by general formula (I) as a nanocrystalline Fe-based alloy in the manufacturing method according to the first embodiment of the present invention, and exhibits high permeability in the low-frequency region. In manufacturing the Fe-based nanocrystalline alloy core according to the present embodiment, it is not necessary to perform the magnetic field application process described in <1-3. Magnetic Field Application Process> above. This is because the magnetic field application does not affect or only slightly affects the structure and composition of the oxide film described above. However, since the Fe-based nanocrystalline alloy core exhibits high permeability in both the low-frequency and high-frequency regions by undergoing the magnetic field application process, it is preferable that it be manufactured by a manufacturing method including the magnetic field application process.

[0108] <2-1. First oxide layer, second oxide layer and base material>

[0109] Since the Fe-based nanocrystalline alloy core according to the present embodiment is manufactured by the manufacturing method according to the first embodiment of the present invention, the ribbon constituting the core has a first oxide film layer, a second oxide film layer, and a base material formed of an Fe-based nanocrystalline alloy including an amorphous phase and crystal grains in this order. The first oxide film layer is the outermost surface layer of the ribbon.

[0110] The first oxide film layer and the second oxide film layer are formed by the oxide film formation process in the above manufacturing method. In addition, the base material is formed by nanocrystallizing a nanocrystallizable Fe-Si-B-Cu-Nb alloy having a composition represented by general formula (I) in the nanocrystallization process in the above manufacturing method. The base material may contain components other than the Fe-based nanocrystalline alloy, for example, components incorporated during the ribbon forming process and the oxide film formation process.

[0111] In the present embodiment, the first oxide film layer and the second oxide film layer may be formed on at least one surface of the ribbon, but are typically formed on both surfaces of the ribbon. Additionally, the first oxide film layer and the second oxide film layer may be formed on at least a part of the surface of the ribbon, but are typically formed over the entire surface of the ribbon.

[0112] The total thickness of the first oxide film layer and the second oxide film layer is not particularly limited, but since an oxide film having a thickness of about 4 nm is formed by natural oxidation, it is typically 5.0 nm or more, preferably 8.0 nm or more, more preferably 10 nm or more, and even more preferably 12 nm or more, and is also typically 25 nm or less, preferably 20 nm or less. That is, suitable ranges for the total thickness of the first oxide film layer and the second oxide film layer include 5.0 nm or more and 20 nm or less, 8.0 nm or more and 20 nm or less, 10 nm or more and 25 nm or less, and 12 nm or more and 25 nm or less.

[0113] The presence or absence of the first oxide layer and the second oxide layer can be confirmed by transmission electron microscopy (TEM) observation of the ribbon cross-section. Additionally, the thickness of the first oxide layer and the second oxide layer can be measured from the TEM image. TEM imaging is performed to obtain a TEM image near the ribbon surface subject to XPS analysis in order to compare the TEM observation results of the first oxide layer and the second oxide layer with the XPS analysis results. During TEM observation, a protective layer may be formed on the first oxide layer to improve the visibility of the first oxide layer and the second oxide layer in the TEM image. The protective layer can be formed by known methods, for example, by deposition. Carbon, platinum, tungsten, etc., may be used as the material for the protective layer. Furthermore, the sample for observing the ribbon cross-section can be prepared by cutting the ribbon using, for example, the convergent ion beam method (FIB method). An example of TEM measurement conditions is shown below.

[0114] (TEM measurement conditions)

[0115] ㆍDevice: JEM-2100 (Manufactured by Nihon Electronics Co., Ltd.)

[0116] ㆍAcceleration voltage: 200kV

[0117] Magnification: 100,000x or 200,000x

[0118] <2-2. Depth Profile by XPS Analysis>

[0119] When XPS analysis is performed on the surface structure of a ribbon comprising a first oxide film layer, a second oxide film layer, and a base material of the Fe-based nanocrystalline alloy core according to the present embodiment, a characteristic depth profile satisfying (A) and (B) below is obtained.

[0120] (A) Cu in the depth range corresponding to the first oxide film layer 2p A peak appears.

[0121] (B) In the depth range corresponding to the first oxide film layer, Cu 2p The peak intensity of O derived from SiO2 1S It is stronger than the intensity of.

[0122] As shown in the examples described below, in the depth profile of a conventional Fe-based nanocrystalline alloy core, Cu 2p The peak (maximum value) is observed in a depth range corresponding to the space between the second oxide film layer and the base material, rather than in a depth range corresponding to the first oxide film layer (i.e., the outermost surface layer). For this reason, conventional Fe-based nanocrystalline alloy cores do not satisfy (A) and (B). Therefore, a depth profile satisfying (A) and (B) is unique to the Fe-based nanocrystalline alloy core according to the present embodiment.

[0123] In addition, the Fe-based nanocrystalline alloy core according to the present embodiment preferably further satisfies (C) and (D) below in the depth profile by XPS analysis.

[0124] (C) O of SiO2 in the depth range corresponding to the second oxide film layer 1S and Si 2p A peak appears.

[0125] (D) O of SiO2 in the depth range corresponding to the second oxide film layer 1S The peak intensity of Cu 2p It is stronger than the intensity of.

[0126] As shown in the examples described below, in the depth profile when an oxide film is formed on the ribbon surface by natural oxidation, O of SiO2 1S and Si 2p The peak is observed in the depth range corresponding to the first oxide film layer. Therefore, in addition to (A) and (B), a depth profile satisfying (C) is also unique to the Fe-based nanocrystalline alloy core according to the present embodiment.

[0127] In addition, the Fe-based nanocrystalline alloy core according to the present embodiment preferably further satisfies the following (E) in the depth profile by XPS analysis.

[0128] (E) Cu in the depth range corresponding to the first oxide film layer 2p Cu in the depth range corresponding to the base material where the peak intensity is 2p It is stronger than the intensity of.

[0129] As shown in the embodiments described below, in the depth profile of a conventional Fe-based nanocrystalline alloy core, Cu in the depth range corresponding to the first oxide film layer 2p No peak (maximum) appears, and weak intensity Cu 2p A signal is observed. Additionally, in the depth range corresponding to the base material, Cu, which has a stronger strength than in the depth range corresponding to the first oxide film layer, 2p A signal is observed. For this reason, the depth profile satisfying (E) is also unique to the Fe-based nanocrystalline alloy core according to the present embodiment.

[0130] In addition, in this specification, the depth range corresponding to the first oxide film layer and the second oxide film layer is a range based on the thickness of the first oxide film layer and the second oxide film layer measured from TEM, respectively. In addition, the Cu of the depth range corresponding to the base material 2p Cu at a depth where the influence of the oxide film is not visible in terms of intensity 2p It adopts the strength of. More specifically, within a depth range of 5 nm, Cu 2p Cu for the maximum strength of 2p Select a depth range with small variation in signal intensity where the ratio of the minimum intensity is typically 0.80 or higher, preferably 0.85 or higher, and more preferably 0.90 or higher, and Cu within this depth range 2p The strength of Cu within a depth range equivalent to the base material 2p The range of depths in which such signal strength variation is small is referred to as the range of depth 15 nm or more in Example 2 described later, the range of depth 28 nm or more in Comparative Example 2, and the range of depth 21 nm or more in Comparative Example 4 (the range indicated by arrows in FIGS. 5 to 7).

[0131] In this embodiment, the specific sample subjected to XPS analysis is the following sample X.

[0132] (Sample X) When the inner and outer surfaces of an Fe-based nanocrystalline alloy core are virtually divided into three regions, a first region, a second region, and a third region, extending from the inner surface toward the outer surface, a ribbon located within the second region is cut and used as a sample. The first, second, and third regions are regions that divide the radial length between the inner and outer surfaces into 40 / 20 / 40. X-ray photoelectron spectroscopy analysis is performed on the surface of the sample that was facing the outer surface when the wound Fe-based nanocrystalline alloy core was formed.

[0133] The reason for using a ribbon located within the second region as a sample is as follows.

[0134] In a magnetic core formed by winding ribbons, the permeability is influenced by the oxide film layer formed on the surface of a ribbon located near the midpoint between the inner and outer surfaces with respect to the radial direction of the magnetic core, or on a ribbon located slightly towards the inner surface side than the midpoint. Furthermore, the oxide film layer formed on the surface of a ribbon located on the outer surface side with respect to the radial direction of the magnetic core may be affected by the surrounding environment during the manufacturing process of the magnetic core. Therefore, a specific oxide film layer is stably formed regardless of the surrounding environment on the surface of a ribbon located near the midpoint in the radial direction of the magnetic core, or on a ribbon located slightly towards the inner surface side than the midpoint. Accordingly, to evaluate the composition of the oxide film that contributes to the improvement of permeability, it is necessary to analyze the oxide film layer formed on the surface of a ribbon located near the midpoint between the inner and outer surfaces, or on a ribbon located slightly towards the inner surface side than the midpoint.

[0135] Sample X for XPS analysis will be described in more detail with reference to FIG. 3. FIG. 3(a) is a perspective view of an Fe-based nanocrystalline alloy core, and FIG. 3(b) is a cross-sectional perspective view of an Fe-based nanocrystalline alloy core. As shown in FIG. 3(a), the Fe-based nanocrystalline alloy core (10) according to the present embodiment is a core in which a ribbon is wound in a toroidal shape. The ribbon is wound and stacked between the inner surface (11) and the outer surface (12) of the Fe-based nanocrystalline alloy core (10). Here, as shown in FIG. 3(b), the radial length between the inner surface (11) and the outer surface (12) of the Fe-based nanocrystalline alloy core (10) is virtually divided into three regions, which are designated as the first region (21), the second region (22), and the third region (23) in order from the inner surface (11) toward the outer surface (12). The first region (21), the second region (22), and the third region (23) are regions that divide the radial length between the inner surface (11) and the outer surface (12) into l1 / l2 / l3. l1 / l2 / l3 can typically be 40 / 20 / 40, 40 / 15 / 45, or 45 / 10 / 45. For XPS analysis, a ribbon located in the second region (22), that is, the central part between the inner surface (11) and the outer surface (12) of the Fe-based nanocrystalline alloy core (10), is cut, and the surface of the ribbon that was facing the outer surface (12) when wound is used as the analysis surface. In addition, for XPS analysis, the photoelectron intensity is measured at each depth from the ribbon surface while sputtering the analysis surface. An example of the conditions for XPS analysis is shown below.

[0136] (XPS Analysis Conditions)

[0137] ㆍDevice: PHI5000 VersaProbe (Manufactured by R-Back Pie Co., Ltd.)

[0138] ㆍAchieved vacuum: 6.7×10 -8 Pa or less

[0139] Source: Monocolor Al-Kα X-rays

[0140] ㆍOutput: 25W

[0141] ㆍDetection area: 100㎛φ

[0142] Angle of incidence: 45°

[0143] ㆍEjection angle: 45°

[0144] (Sputter conditions)

[0145] ㆍIonic species: Argon

[0146] ㆍAcceleration voltage: 1kV

[0147] ㆍSmall area: 2mm × 2mm

[0148] ㆍSputtering rate: 2.27 nm / min

[0149] In XPS analysis, a depth profile is obtained by creating a chart with the depth (nm) equivalent to SiO2 calculated using the sputter etching rate of the SiO2 standard sample from the sputtering time on the horizontal axis and the photoelectron intensity (cps) on the vertical axis, and it is determined whether the above (A) to (E) are satisfied.

[0150] <3. Applications of Fe-based nanocrystalline alloy cores>

[0151] The Fe-based nanocrystalline alloy core produced by the manufacturing method according to the first embodiment of the present invention and the Fe-based nanocrystalline alloy core according to the second embodiment of the present invention can be suitably used as a core for a reactor, a common mode choke coil, a transformer, a pulse transformer for communication, a motor, or a generator.

[0152] [Example]

[0153] The present invention will be explained in more detail below by way of examples, but the present invention is not limited to the description of the following examples as long as it does not exceed the gist thereof.

[0154] <Example 1>

[0155] An Fe-based alloy ribbon with a width of 12.5 mm and a thickness of 14 μm, made of an Fe-Si-B-Cu-Nb alloy having a composition represented by the general formula (I) above, was wound, and an Fe-based alloy core material with an outer diameter of 25 mm, an inner diameter of 15 mm, and a height of 12.5 mm was produced. In addition, the crystallization initiation temperature of the Fe-based alloy constituting the Fe-based alloy ribbon was determined by differential scanning calorimetry (DSC) and was found to be 516°C.

[0156] (Oxide film formation process)

[0157] An Fe-based alloy core material was placed in a heat treatment furnace, and an oxide film was formed by heating at a maximum temperature of 440°C for 180 minutes under an oxidizing atmosphere with an oxygen concentration of 0.4 vol%.

[0158] (Nanocrystallization process)

[0159] After the oxide film formation process, the Fe-based alloy core material was placed in a heat treatment furnace and heated at 470°C for 120 minutes under a nitrogen atmosphere (oxygen concentration 0 vol%), and then heated at 550°C for 100 minutes to perform nanocrystallization of the Fe-based alloy. By cooling the core material after nanocrystallization to room temperature (20°C), the Fe-based nanocrystalline alloy core of Example 1 was obtained.

[0160] <Example 2>

[0161] (Magnetic field application process)

[0162] The Fe-based nanocrystalline alloy core obtained in Example 1 was placed in a heat treatment furnace, and a magnetic field with a magnetic field strength of 100 mT was applied to the core in the height direction of the core while heat treatment was performed under a nitrogen atmosphere (oxygen concentration 0 vol%). The Fe-based nanocrystalline alloy core was obtained by cooling the core to room temperature (20°C) after the application of the magnetic field. In addition, the heat treatment was performed under conditions where the holding time at the maximum temperature of 450°C was 30 minutes.

[0163] <Comparative Example 1>

[0164] An Fe-based nanocrystalline alloy core was obtained in the same manner as in Example 1, except that the oxide film formation process was not performed and the nanocrystallization process was performed under an oxidizing atmosphere with an oxygen concentration of 0.4 vol%.

[0165] <Comparative Example 2>

[0166] An Fe-based nanocrystalline alloy core was obtained in the same manner as in Example 2, except that the oxide film formation process was not performed and the nanocrystallization process was performed under an oxidizing atmosphere with an oxygen concentration of 0.4 vol%.

[0167] <Comparative Example 3>

[0168] An Fe-based nanocrystalline alloy core was obtained in the same manner as in Example 1, except that the oxide film formation process was not performed.

[0169] <Comparative Example 4>

[0170] An Fe-based nanocrystalline alloy core was obtained in the same manner as in Example 2, except that the oxide film formation process was not performed.

[0171] [Evaluation of Non-investment Rate]

[0172] A hollow core was fabricated by loading the Fe-based nanocrystalline alloy core obtained from the examples and comparative examples into a resin case. A 1-turn core was fabricated by passing a coated copper wire with a diameter of 0.5 mm through the hollow part of the fabricated core. The inductance of the core obtained at frequencies of 10 kHz and 100 kHz was measured using an impedance analyzer (manufactured by Agilent Technologies, 4294A), and the relative permeability of the Fe-based nanocrystalline alloy core was calculated based on the following equation (1). In addition, the magnetic length (l) was 6.3 × 10 -2 m, the effective cross-sectional area (A) is 4.8×10 -5 m 2 , the number of volumes (N) was set to 1. The results are shown in Table 1, Figure 1, and Figure 2.

[0173] μr = μ / μ0 (1)

[0174] μr: Relative permeability

[0175] μ0 : Vacuum permeability = 4π × 10 -7 [H / m]

[0176] μ: Permeability [H / m] = Ll / A / N 2

[0177] L : Inductance [H]

[0178] l : Length [m] = 6.3 × 10 -2 [m]

[0179] A : Core effective cross-sectional area [㎡] = 4.8×10 -5 [m 2 ]

[0180] N : Number of volumes = 1

[0181] Oxide film formation process Nanocrystallization process oxygen concentration (vol%) Magnetic field processing Non-permeability 10 kHz 100 kHz Example 1 is available 0 doesn't exist 117,225 - Example 2 is available 0 is available 118,139 36,355 Comparative Example 1 doesn't exist 0.4 doesn't exist 78,406 31,717 Comparative Example 2 doesn't exist 0.4 is available 94,322 37,847 Comparative Example 3 doesn't exist 0 doesn't exist 89,595 21,747 Comparative Example 4 doesn't exist 0 is available 106,794 31,891

[0182] From Table 1 and Figure 1, it was confirmed that the Fe-based nanocrystalline alloy core obtained by simultaneously proceeding with the formation of an oxide film and nanocrystallization (Comparative Example 1) has a lower relative permeability at a frequency of 10 kHz than the Fe-based nanocrystalline alloy core obtained by performing only nanocrystallization without forming an oxide film (Comparative Example 3), and that the permeability of the Fe-based nanocrystalline alloy core in the low-frequency region is reduced due to the formation of an oxide film.

[0183] Meanwhile, the Fe-based nanocrystalline alloy core (Example 1) obtained by forming an oxide film under conditions where nanocrystalline formation does not occur, and then performing nanocrystalline formation under a non-oxidizing atmosphere where an oxide film is not formed, had an oxide film similar to the Fe-based nanocrystalline alloy core obtained in Comparative Example 1, but the relative permeability at a frequency of 10 kHz was significantly improved and was higher than that of the Fe-based nanocrystalline alloy core obtained in Comparative Example 3.

[0184] From these results, it was found that when oxide film formation and nanocrystallization are performed separately in this order, the permeability of the Fe-based nanocrystal alloy core in the low-frequency range is enhanced, contrary to the technical common knowledge that the permeability of the nanocrystal alloy core in the low-frequency range decreases due to the formation of the oxide film.

[0185] In addition, it was confirmed from Table 1 and Figure 1 that the permeability of the Fe-based nanocrystalline alloy core in the low-frequency region is improved by applying a magnetic field.

[0186] From Table 1 and Figure 2, the relative permeability at a frequency of 100 kHz of the Fe-based nanocrystalline alloy core (Example 2), obtained by sequentially performing oxide film formation, nanocrystallization, and magnetic field application, was a high value comparable to that of the Fe-based nanocrystalline alloy core (Comparative Example 2), obtained by applying a magnetic field to a core material fabricated by simultaneously performing oxide film formation and nanocrystallization.

[0187] From these results, it can be seen that by performing a magnetic field application process, it is possible to manufacture Fe-based nanocrystalline alloy cores that exhibit high permeability even in the high-frequency region.

[0188] [TEM Observation]

[0189] From the Fe-based nanocrystalline alloy cores obtained in Example 2, Comparative Example 2, and Comparative Example 4, a ribbon identical to Sample X for XPS analysis was cut (where l1 / l2 / l3 = 45 / 10 / 45). Subsequently, a protective layer was formed by deposition on the surface identical to the analysis surface for XPS analysis among the two surfaces of the ribbon. The ribbon coated with this protective layer was cut perpendicularly to the surface to obtain a sample for TEM observation. TEM measurements were performed on the obtained sample for TEM observation under the following measurement conditions. The obtained TEM images are shown in Fig. 4.

[0190] (TEM measurement conditions)

[0191] ㆍDevice: JEM-2100 (Manufactured by Nihon Electronics Co., Ltd.)

[0192] ㆍAcceleration voltage: 200kV

[0193] ㆍMagnification: 100,000x (Example 2, Comparative Example 4) or 200,000x (Comparative Example 2)

[0194] In FIG. 4, it can be seen that the Fe-based nanocrystalline alloy cores obtained in Example 2, Comparative Example 2, and Comparative Example 4 all have two oxide film layers on the ribbon surface. The thickness of each oxide film layer measured in FIG. 4 is shown in Table 2.

[0195] Thickness of the first oxide film layer (nm) Thickness of the second oxide film layer (nm) Example 2 7.70 6.20 Comparative Example 2 7.29 2.37 Comparative Example 4 3.52 0.89

[0196] In Figure 4 and Table 2, in Example 2, in which an oxide film was formed prior to nanocrystallization and then nanocrystallization was performed under a non-oxidizing atmosphere, it can be seen that the first oxide film layer and the second oxide film layer have the same thickness. In contrast, in Comparative Example 2, in which an oxide film was formed while nanocrystallizing was performed, and Comparative Example 4, in which the oxide film formation process was not performed and nanocrystallization was also performed under a non-oxidizing atmosphere, it can be seen that the first oxide film layer has a thickness of more than twice that of the second oxide film layer.

[0197] In Comparative Example 4, since an oxide film is not intentionally formed, the oxide film layer formed on the ribbon surface is due to natural oxidation. Therefore, the total thickness of the two oxide film layers in Comparative Example 4 is less than 5 nm, and is significantly thinner than the total thickness of the first oxide film layer and the second oxide film layer in Example 2, in which an oxide film was intentionally formed.

[0198] [Measurement of Depth Profile by XPS Analysis]

[0199] A ribbon located within the second region (l1 / l2 / l3 = 45 / 10 / 45) was cut from the Fe-based nanocrystalline alloy core obtained in Example 2, Comparative Example 2, and Comparative Example 4, and designated as Sample X. Of the two surfaces of Sample X, the surface facing the outer circumference when wound to form the core was designated as the analysis surface, and a depth profile was obtained by performing XPS analysis while sputtering this analysis surface. The XPS analysis conditions are as follows. The results are shown in FIGS. 5 to 7. In FIGS. 5 to 7, the horizontal axis of the XPS analysis chart was set to the depth (nm) converted to SiO2, calculated using the sputter etching rate of the SiO2 standard sample from the sputtering time.

[0200] (XPS Analysis Conditions)

[0201] ㆍDevice: PHI5000 VersaProbe (Manufactured by R-Back Pie Co., Ltd.)

[0202] ㆍAchieved vacuum: 6.7×10 -8 Pa or less

[0203] Source: Monocolor Al-Kα X-rays

[0204] ㆍOutput: 25W

[0205] ㆍDetection area: 100㎛φ

[0206] Angle of incidence: 45°

[0207] ㆍEjection angle: 45°

[0208] (Sputter conditions)

[0209] ㆍIonic species: Argon

[0210] ㆍAcceleration voltage: 1kV

[0211] ㆍSmall area: 2mm × 2mm

[0212] ㆍSputtering rate: 2.27 nm / min

[0213] As can be seen from FIG. 5, in the depth profile of Example 2, Cu is located at a depth of approximately 2.27 nm corresponding to the first oxide film layer. 2pA peak (maximum value) of Cu was observed in the depth range corresponding to the first oxide film layer. 2p The peak intensity of O derived from SiO2 1S It was found that it was stronger than the intensity of. In addition, in the depth profile of Example 2, O derived from SiO2 was found at a depth of approximately 11.35 nm, corresponding to the second oxide film layer. 1S and Si 2p A peak was observed, indicating O of SiO2 origin in the depth range corresponding to the second oxide film layer. 1S The peak intensity of Cu 2p It was found that it was stronger than the strength of. In addition, Cu in the depth range corresponding to the first oxide film layer 2p The peak intensity is Cu in the depth range corresponding to the base material. 2p It was stronger than the intensity of.

[0214] Meanwhile, in the depth profiles of Comparative Examples 2 and 4, Cu 2p The intensity reached a maximum value in the depth range corresponding to the space between the second oxide film layer and the base material, was weak in the depth range corresponding to the base material, and was even weaker in the depth range corresponding to the first oxide film layer. Furthermore, in the depth profile of Comparative Example 2, O derived from SiO2 at a depth of 9.08 nm corresponding to the second oxide film layer 1S and Si 2p Although a peak was observed, the depth profile of Comparative Example 4 is O derived from SiO2 1S and Si 2p A peak was observed at a depth of 2.27 nm corresponding to the first oxide film layer. Explanation of the symbols

[0215] 10 Fe-based nanocrystalline alloy core If you give 11 12 outsourced 21 Area 1 22 Second Area 23 Third Area

Claims

Claim 1 delete Claim 2 delete Claim 3 delete Claim 4 Fe-based nanocrystalline alloy core, wherein the core is wound with ribbons, said ribbons having a first oxide film layer, a second oxide film layer, and a base material formed of an Fe-based nanocrystalline alloy including an amorphous phase and crystal grains in this order, said Fe-based nanocrystalline alloy having a composition represented by the following general formula (I), and satisfying (A) and (B) below in the depth profile by X-ray photoelectron spectroscopy of the following sample X. x Si a B b Cu C Nb d (I) (In general formula (I), a to d (atomic %) represent 3.0 ≤ a ≤ 12.0, 1.0 ≤ b ≤ 7.0, 1.0 ≤ c ≤ 5.0, and 1.0 ≤ d ≤ 9.0, respectively; x (atomic %) is the remainder other than Si, B, Cu, and Nb, satisfying 73.0 ≤ x ≤ 92.0.) (A) Cu in the depth range corresponding to the first oxide film layer 2p A peak of appears. (B) In the depth range corresponding to the first oxide film layer, Cu 2p The peak intensity of O derived from SiO2 1S It is stronger than the strength of (Sample X). When the area between the inner surface and the outer surface of the Fe-based nanocrystalline alloy core is virtually divided into three regions, a first region, a second region, and a third region, extending from the inner surface toward the outer surface, a ribbon located within the second region is cut and used as a sample. The first region, the second region, and the third region are regions that divide the radial length between the inner surface and the outer surface into 40 / 20 / 40. X-ray photoelectron spectroscopy analysis is performed on the surface of the sample that was facing the outer surface when it was wound to form the Fe-based nanocrystalline alloy core. Claim 5 In claim 4, an Fe-based nanocrystalline alloy core further satisfying (C) and (D) in the depth profile above. (C) O of SiO2 in a depth range corresponding to the second oxide film layer. 1S and Si 2p A peak of appears. (D) O of SiO2 in the depth range corresponding to the second oxide film layer. 1S The peak intensity of Cu 2p It is stronger than the intensity of. Claim 6 In claim 4 or 5, an Fe-based nanocrystalline alloy core further satisfying (E) in the depth profile. (E) Cu in the depth range corresponding to the first oxide film layer. 2p Cu in the depth range corresponding to the above base material, where the peak intensity is 2p It is stronger than the intensity of.

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