Fe-based nanocrystalline soft magnetic alloy and magnetic components

Abstract

Provided is an Fe-based nanocrystal soft magnetic alloy containing an amorphous phase and crystal grains, and having a composition represented by (Fe1-x-ySixAly)100-a-b-cMaM'bCuc (M represents at least one element selected from the group consisting of Nb, W, Zr, Hf, Ti, and Mo; M' represents at least one element selected from the group consisting of B, C, and P; a, b, and c represent 2.0≤a≤5.0, 3.0<b<10.0, and 0<c<3.0, in atomic% respectively; and x and y represent 0.15≤x≤0.25 and 0.012≤y≤0.10, and satisfy 0.19≤x＋y≤0.29), wherein clusters are dispersed in the amorphous phase.

Description

Technical Field

[0001] The present disclosure relates to Fe-based nanocrystalline soft magnetic alloys and magnetic components.

Background Art

[0002] With the active promotion of the high performance, miniaturization, and weight reduction of electric and electronic devices and information and communication equipment, miniaturization and high efficiency of power supply devices used in these various devices are desired. Magnetic components used in power conversion devices can generally be miniaturized by increasing the conversion frequency. However, magnetic components for noise filters, such as common mode choke coils, cannot be miniaturized other than by increasing the magnetic permeability of the material. In recent years, with the trend towards thinner, lighter, and more compact electronic devices, miniaturization of power conversion parts such as noise filters has been required. Therefore, in particular, an improvement in the magnetic permeability in the high-frequency range of magnetic materials used for common mode choke coils and the like is strongly desired. So far, the development of magnetic materials showing excellent high-frequency characteristics has been underway. For example, Fe-Si-B-Cu-Nb-based nanocrystalline soft magnetic materials mainly composed of Fe are widely known (Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Magnetic materials generally have high magnetic permeability by making both the magnetostriction λ and the crystalline magnetic anisotropy K close to zero. In Patent Document 1, by making the magnetic material have a nanocrystalline structure, the crystalline magnetic anisotropy is averaged and reduced, and the magnetic permeability is significantly improved compared to conventional materials. However, the composition within the crystal is Fe-Si, and the crystalline magnetic anisotropy within each crystal is not zero, and it does not necessarily become zero even after averaging.

[0005] As a magnetic material in which both magnetic distortion and crystal magnetic anisotropy become zero, an Fe-Si-Al-based magnetic material called Sendust is known. However, in a magnetic material having a nanocrystalline structure, where the relative volume ratio of the grain boundary layer (amorphous phase) to the nanocrystals is large, since this amorphous phase has positive magnetic distortion, even if the composition of Sendust is applied to a nanocrystalline soft magnetic material, the magnetic distortion of the entire material does not become zero.

[0006] The present invention has been made in view of the above problems, and an object thereof is to provide a nanocrystalline soft magnetic material that exhibits high magnetic permeability in a high-frequency region.

Means for Solving the Problems

[0007] As a result of repeated studies to solve the above problems, the present inventor has found that an Fe-based nanocrystalline soft magnetic alloy having a specific composition and in which clusters are dispersed exhibits high magnetic permeability in a high-frequency region, and has reached the present invention. That is, the gist of the present invention is as follows.

[0008] [1] An Fe-based nanocrystalline soft magnetic alloy containing an amorphous phase and crystal grains, in which clusters are dispersed in the amorphous phase and having a composition represented by the following general formula (I), an Fe-based nanocrystalline soft magnetic alloy. (Fe Si x Al y ) 100-a-b-c M a M’ b Cu c (I) (M represents one or more elements selected from the group consisting of Nb, W, Zr, Hf, Ti, and Mo; M’ represents one or more elements selected from the group consisting of B, C, and P; a, b, and c are each in atomic %, representing 2.0 ≦ a ≦ 5.0, 3.0 < b < 10.0, and 0 < c < 3.0; x and y represent 0.150 ≦ x ≦ 0.250 and 0.012 ≦ y ≦ 0.100, and satisfy 0.190 ≦ x + y ≦ 0.290.) [2] In the general formula (I), a represents, in atomic %, 2.0 < a < 5.0, x and y represent 0.160 ≤ x ≤ 0.250 and 0.023 ≤ y ≤ 0.090, and satisfy 0.210 ≤ x + y ≤ 0.280. The Fe-based nanocrystalline soft magnetic alloy according to [1]. [3] In the general formula (I), x and y represent 0.170 ≤ x ≤ 0.240 and 0.040 ≤ y ≤ 0.070, and satisfy 0.210 ≤ x + y ≤ 0.280. The Fe-based nanocrystalline soft magnetic alloy according to [1]. [4] The Fe-based nanocrystalline soft magnetic alloy according to any one of [1] to [3], wherein M is Nb and M' is B. [5] The Fe-based nanocrystalline soft magnetic alloy according to any one of [1] to [4], wherein the atoms constituting the cluster are either one or both of Cu and Al. [6] The Fe-based nanocrystalline soft magnetic alloy according to [5], wherein the atoms constituting the cluster are both Cu and Al, and each cluster contains both Cu and Al. [7] The Fe-based nanocrystalline soft magnetic alloy according to any one of [1] to [6], wherein the average crystal grain size of the crystal grains is 11.3 nm or less. [8] In the general formula (I), c and y satisfy c ≥ -34y + 1.7. The Fe-based nanocrystalline soft magnetic alloy according to [7]. [9] The number density of the clusters is 1.65×10 -4 / nm 3 or more and 7.3×10 -4 / nm 3 or less. The Fe-based nanocrystalline soft magnetic alloy according to any one of [1] to [8].

[10] The number of magnetic walls is 15 / mm or more and 50 / mm or less. The Fe-based nanocrystalline soft magnetic alloy according to any one of [1] to [9].

[11] A magnetic component including the Fe-based nanocrystalline soft magnetic alloy according to any one of [1] to

[10] .

[12] An amorphous alloy manufacturing process is performed by rapidly cooling and solidifying a molten metal having the composition represented by the general formula (I) using an ultra-rapid cooling method to produce an amorphous alloy. A heat treatment step is performed to nanocrystallize the amorphous alloy by heat treatment at 500°C to 700°C for 5 minutes to 5 hours. A method for producing an Fe-based nanocrystalline soft magnetic alloy, as described in any of [1] to

[10] , including the above.

[13] A method for producing an Fe-based nanocrystalline soft magnetic alloy according to

[12] , wherein a magnetic field is applied to the amorphous alloy during the heat treatment step of the heat treatment step.

[14] A method for producing an Fe-based nanocrystalline soft magnetic alloy according to

[13] , wherein the angle between the magnetic path of the amorphous alloy and the direction of magnetic field application is within the range of 90°±15° when the magnetic field is applied.

[15] A method for producing an Fe-based nanocrystalline soft magnetic alloy according to

[13] or

[14] , wherein the magnetic field strength in the application of the magnetic field is 8 kA / m or more and 400 kA / m or less.

[16] An amorphous alloy manufacturing process is performed by rapidly cooling and solidifying a molten metal having a composition represented by general formula (II) using an ultra-rapid cooling method to produce an amorphous alloy. A heat treatment step is performed to nanocrystallize the amorphous alloy by heat treatment at 500°C to 700°C for 5 minutes to 5 hours. Includes, A method for producing an Fe-based nanocrystalline soft magnetic alloy, comprising applying a magnetic field to the amorphous alloy during the heat treatment step. (Fe 1-p-q Si p Al q ) 100-d-e-f Q d Q' e Cu f (II) (Q represents one or more elements selected from the group consisting of Nb, W, Zr, Hf, Ti, and Mo; Q' represents one or more elements selected from the group consisting of B, C, and P; d, e, and f are in atomic %, representing 2.0 ≤ d ≤ 5.0, 3.0 < e < 10.0, and 0 < f < 3.0 respectively; p and q represent 0.150 ≤ p ≤ 0.250 and 0.0020 ≤ q < 0.012, and satisfy 0.190 ≤ p + q ≤ 0.290.)

[17] The method for producing an Fe-based nanocrystalline soft magnetic alloy according to

[14] , wherein the angle formed by the magnetic path of the amorphous alloy and the magnetic field application direction in the magnetic field application is within the range of 90° ± 15°.

[18] The method for producing an Fe-based nanocrystalline soft magnetic alloy according to

[16] or

[17] , wherein the magnetic field strength in the magnetic field application is 8 kA / m or more and 400 kA / m or less. [Advantages of the Invention]

[0009] According to the present invention, a nanocrystalline soft magnetic material showing high magnetic permeability in the high frequency region can be provided. [Brief Description of the Drawings]

[0010] [Figure 1] It is a diagram showing the relationship between the content ratios of Fe, Si, and Al and the relative magnetic permeability in the Fe-based nanocrystalline soft magnetic alloys obtained in Examples 1 to 27 and Comparative Examples 1 to 14. [Figure 2] It is the result of observing the distribution of Si, Al, B, and Cu in the Fe-based nanocrystalline soft magnetic alloy obtained in Example 11 by three-dimensional atom probe (substitute photograph of the drawing).[[ID=Q27]] [Figure 3] It is the result of observing the distribution of each element contained in the Fe-based nanocrystalline soft magnetic alloy obtained in Example 11 by three-dimensional atom probe (substitute photograph of the drawing). [Figure 4] It is the result of observing the distribution of each element contained in the Fe-based nanocrystalline soft magnetic alloy obtained in Example 11 by three-dimensional atom probe (substitute photograph of the drawing). [Figure 5](a) to (h) are polarized light microscope images showing the magnetic domain structure of the Fe-based nanocrystalline soft magnetic alloys obtained in Comparative Example 18, Examples 38, 39, 41, 44, 45, 46, and 47, respectively (photographs used as substitutes for drawings). [Figure 6] This graph shows the relationship between the Al content, the number of magnetic domain walls, and the relative permeability of the Fe-based nanocrystalline soft magnetic alloys obtained in Comparative Example 18, Examples 38, 39, 41, and 43-47. [Figure 7] This graph shows the relationship between ambient temperature and the rate of change in inductance for the Fe-based nanocrystalline soft magnetic alloys obtained in Examples 1, 6, and 11, and Comparative Example 14. [Figure 8] This graph shows the relationship between the Cu and Al content and the average grain size of crystal grains in Fe-based nanocrystalline soft magnetic alloys obtained in Examples 6, 11, 12, 39, 41, 43-46 and 60-71, Reference Examples 1-4, and Comparative Examples 30-33. [Figure 9] (a) and (b) are schematic diagrams showing the shape of the core. [Modes for carrying out the invention]

[0011] Embodiments of the present invention will be described in detail below. The following description of the constituent elements is an example (representative example) of an embodiment of the present invention, and the present invention is not limited to these contents unless it exceeds the gist of the invention.

[0012] 1. Fe-based nanocrystalline soft magnetic alloy A first embodiment of the present invention is an Fe-based nanocrystalline soft magnetic alloy comprising an amorphous phase and crystalline grains, with clusters dispersed in the amorphous phase, and having a composition represented by the following general formula (I). (Fe 1-x-y Si x Al y ) 100-a-b-c M a M' b Cu c (I) In the general formula (I), M represents one or more elements selected from the group consisting of Nb, W, Zr, Hf, Ti, and Mo; M' represents one or more elements selected from the group consisting of B, C, and P; a, b, and c are in atomic %, representing 2.0 ≤ a ≤ 5.0, 3.0 < b < 10.0, and 0 < c < 3.0, respectively; x and y represent 0.150 ≤ x ≤ 0.250 and 0.012 ≤ y ≤ 0.100, and satisfy 0.190 ≤ x + y ≤ 0.290.

[0013] That is, the Fe-based nanocrystalline soft magnetic alloy according to this embodiment is a soft magnetic material in which crystal grains and atomic clusters composed of a crystal phase are formed in an amorphous phase, and exhibits a high magnetic permeability even in a high-frequency region. In this specification, "specific magnetic permeability" may be used as an evaluation index of "magnetic permeability". In this specification, the high-frequency region means, for example, a frequency region of 100 kHz or higher. The Fe-based nanocrystalline soft magnetic alloy according to this embodiment exhibits a high specific magnetic permeability, such as 21,000 or higher, 25,000 or higher, or 30,000 or higher, in this frequency region.

[0014] The specific magnetic permeability of the Fe-based nanocrystalline soft magnetic alloy can be calculated based on the following formula (1) by measuring the inductance of a coil wound around the core of the Fe-based nanocrystalline soft magnetic alloy. μr = μ / μ0 (1) μr: specific magnetic permeability μ0: magnetic permeability of vacuum = 4π×10 -7 [H / m] μ: magnetic permeability [H / m] = Ll / A / N 2 L: inductance [H] l: magnetic path length [m] A: core effective cross-sectional area [m 2 N: number of turns

[0015] 1-1. Composition The Fe-based nanocrystalline soft magnetic alloy according to this embodiment has a composition represented by the following general formula (I). However, this composition may contain inevitable impurities. (Fe​1-x-y Si x Al y ) 100-a-b-c M a M' b Cu c (I)

[0016] (M and M') In general formula (I), M represents one or more elements selected from the group consisting of Nb, W, Zr, Hf, Ti, and Mo, and is preferably Nb. Nb has the effect of raising the crystallization initiation temperature of the alloy, but it is also thought to have the effect of refining the precipitated crystal grains by forming an amorphous phase grain boundary layer together with B during the crystallization process, or by suppressing the growth of crystal grains through interaction with elements such as Cu that can form clusters and lower the crystallization initiation temperature.

[0017] In general formula (I), M' represents one or more elements selected from the group consisting of B, C, and P. One or more elements selected from the group consisting of B, C, and P are necessary in a certain amount together with Si to facilitate the formation of an amorphous structure in which the constituent elements are uniformly dispersed. Of these, B is considered to be an effective element for forming grain boundary layers together with Nb during the crystallization process to form fine crystal grains, so it is preferable that M' is B. From the above, in general formula (I), it is particularly preferable that M is Nb and M' is B, from the viewpoint of obtaining fine crystal grains.

[0018] (a, b, and c) a is usually 2.0 or higher, preferably greater than 2.0, more preferably 2.5 or higher, and even more preferably 3.0 or higher, and also usually 5.0 or lower, preferably less than 5.0, more preferably 4.5 or lower, and even more preferably 4.0 or lower. It is most preferable that a be around 3.0. b is usually greater than 3.0, preferably 4.0 or more, more preferably 4.5 or more, and even more preferably 5.0 or more, and is also usually less than 10.0, preferably 9.5 or less, more preferably 9.0 or less, and even more preferably 7.0 or less. c is usually greater than 0, preferably 0.3 or more, more preferably 0.5 or more, even more preferably 0.7 or more, and usually less than 3.0, preferably 2.5 or less, more preferably 2.0 or less, even more preferably 1.5 or less, and particularly preferably 1.2 or less. c is most preferably around 1.0.

[0019] By setting a to c within the above range, it becomes easier to form crystal grains with a small average grain size, thereby reducing the magnetic anisotropy of the Fe-based nanocrystalline soft magnetic alloy, and thus enabling the production of an Fe-based nanocrystalline soft magnetic alloy exhibiting high specific permeability. Furthermore, because the crystal grains can be refined in this way, the soft magnetic properties such as permeability and coercivity of the Fe-based nanocrystalline soft magnetic alloy can also be improved.

[0020] When M' is B, setting b to the above range ensures amorphous formation ability, suppresses the deposition of Fe-B binary compounds with inferior magnetic properties, and enables the realization of excellent soft magnetic properties. Furthermore, since c is within the above range, amorphous formation ability is ensured, making it easier to produce amorphous alloys by the ultra-rapid cooling method described later. In addition, since c is within the above range, Cu-containing clusters are more easily formed uniformly in the amorphous phase prior to the crystallization of α-Fe(Si,Al), and these clusters can act as crystal nuclei to form fine crystal grains.

[0021] In this embodiment, the composition of the alloy used as a raw material for the Fe-based nanocrystalline soft magnetic alloy (i.e., the composition of the molten metal) and the composition of the resulting Fe-based nanocrystalline soft magnetic alloy are assumed to be the same.

[0022] (x and y) x and y represent the molar amounts of Si and Al, respectively, when the molar amounts of Fe, Si, and Al in the Fe-based nanocrystalline soft magnetic alloy are set to 1. Furthermore, the molar amount of Fe when the molar amounts of Fe, Si, and Al in the Fe-based nanocrystalline soft magnetic alloy are set to 1 is expressed as 1-(x+y).

[0023] x is usually 0.150 or higher, preferably 0.160 or higher, more preferably 0.170 or higher, and also usually 0.250 or lower, preferably 0.245 or lower, more preferably 0.240 or lower, and even more preferably 0.220 or lower. y is usually 0.012 or higher, preferably 0.020 or higher, more preferably 0.023 or higher, and even more preferably 0.040 or higher, and may also be 0.050 or higher, and is usually 0.100 or lower, preferably 0.090 or lower, and more preferably 0.070 or lower. Furthermore, x+y is usually 0.190 or higher, preferably 0.210 or higher, more preferably 0.215 or higher, and also usually 0.290 or lower, preferably 0.280 or lower, more preferably 0.275 or lower, even more preferably 0.270 or lower, and particularly preferably 0.265 or lower.

[0024] By keeping x within the above range, amorphous formation ability is ensured, facilitating the production of amorphous alloys by the ultra-rapid cooling method described later. Furthermore, it is possible to suppress increases in crystal magnetic anisotropy within the crystal grains and excessive negative magnetostriction, thereby achieving good soft magnetic properties. Furthermore, when y satisfies the above numerical range, the crystalline magnetic anisotropy of the crystalline phase of the Fe-Si-Al ternary alloy within the crystal grains is reduced, and a sufficient number of Al-containing clusters are formed, making it easier to form crystal grains with a small average grain size. This reduces the crystalline magnetic anisotropy of the Fe-based nanocrystalline soft magnetic alloy and improves soft magnetic properties such as permeability and coercivity. In addition, it can reduce the magnetostriction of the Fe-based nanocrystalline soft magnetic alloy. Therefore, by setting x and y within the above range, an Fe-based nanocrystalline soft magnetic alloy exhibiting high specific permeability can be obtained.

[0025] 1-2. Amorphous phase and crystal grains In this embodiment, the Fe-based nanocrystalline soft magnetic alloy has crystal grains formed from the crystalline phase, with the remainder being an amorphous phase in which clusters are dispersed. More specifically, in the alloy structure, crystal grains typically account for 50% or more by volume, preferably 65% ​​or more, more preferably 69% or more, and typically 90% or less, preferably 85% or less, more preferably 80% or less, with the remainder being an amorphous phase in which clusters are dispersed.

[0026] The volume fraction of crystal grains can be determined by the following method: analysis using an X-ray diffractometer (XRD) is performed, and the fraction is determined according to the following formula (2). X = Ic / (Ic + Ia) × 100 (2) X: Volume fraction of the crystalline phase Ic: Crystalline product scattering intensity Ia: Amorphous product scattering intensity

[0027] The crystal grains consist of a crystalline phase of an Fe-Si-Al ternary alloy having a body-centered cubic (bcc) structure, in which Si and Al are dissolved in the main Fe, and other elements may also be dissolved. Fe-based nanocrystalline soft magnetic alloys can reduce crystalline magnetic anisotropy by including a specific amount of Al in their composition, and furthermore, because the crystalline magnetic anisotropy is averaged out and reduced due to the fineness of the crystal grains, it is thought that the relative permeability is improved. Furthermore, the crystal structure of the crystalline phase constituting the crystal grains can be identified by X-ray diffraction (XRD).

[0028] The average grain size of the crystal grains is not particularly limited if it is on a nanoscale, and is usually 9.0 nm or larger, and is usually 20.0 nm or smaller, preferably 12.0 nm or smaller, more preferably 11.3 nm or smaller, even more preferably 11.0 nm or smaller, and particularly preferably 10.0 nm or smaller. Alternatively, it is usually 9 nm or larger, and is usually 20 nm or smaller, preferably 12 nm or smaller, and more preferably 11 nm or smaller. By keeping the average grain size of the crystal grains within the above range, the crystalline magnetic anisotropy is averaged out and reduced, and the effect of improving relative permeability tends to be greater. Furthermore, because the crystal grains are so fine, it is also possible to improve the soft magnetic properties such as permeability and coercivity of the Fe-based nanocrystalline soft magnetic alloy.

[0029] The average grain size of the crystal grains can be determined by analyzing the Fe-based nanocrystalline soft magnetic alloy using an X-ray diffractometer (XRD) and following the formula (3) below. D = (K × λ) / (β × cosθ) (3) D: Crystal grain size [nm] K: Scherrer constant λ: Wavelength of X-ray [nm] β: Half-width [rad] θ: Bragg angle [rad]

[0030] A phase relationship is observed between the average grain size of the crystal grains and the composition represented by general formula (I). In particular, when the relationship between c and y regarding the Cu and Al content is expressed by the following formula (4), the average grain size of the crystal grains tends to vary depending on Z in formula (4). More specifically, when Z is 1.7, 2.2, and 3.2 in formula (4), the average grain size of the crystal grains tends to be approximately 11.3 nm, approximately 11.0 nm, and approximately 10.0 nm, respectively. c = -34y + Z (4) Furthermore, when c and y satisfy the relationship c≧-34y+2.2, the average grain size of the crystal grain tends to be 11.0 nm or less, and when c≧-34y+3.2, the average grain size of the crystal grain tends to be 10.0 nm or less. Also, when c≦-34y+4.5, the average grain size of the crystal grain tends to be 9.0 nm or more.

[0031] 1-3. Clusters In this embodiment, the Fe-based nanocrystalline soft magnetic alloy has clusters dispersed in the amorphous phase. In this specification, a cluster refers to an aggregate of atoms observed by a three-dimensional atom probe (3DAP). The clusters may be uniformly distributed or unevenly distributed in the Fe-based nanocrystalline soft magnetic alloy, but a uniform distribution is preferred.

[0032] The types of atoms constituting the clusters are not particularly limited as long as they are atoms other than Fe, which is the main component of the Fe-based nanocrystalline soft magnetic alloy, and may be one or more atoms selected from the group consisting of Si, Al, Nb, W, Zr, Hf, Ti, Mo, B, C, P, and Cu. Of these, it is preferable that the atoms constituting the clusters be either Cu or Al, or both, and more preferably both Cu and Al. Cu is an element that does not form a solid solution with Fe and therefore forms clusters, and Al is an element that readily forms a solid solution or compound with Cu and thus forms clusters.

[0033] When a cluster is composed of two or more types of atoms, each cluster may be an aggregate of one type of atom or an aggregate of two or more types of atoms, but it is preferable that it is an aggregate of two or more types of atoms. More specifically, when the atoms that make up a cluster include both Cu and Al, Cu clusters and Al clusters may be dispersed in the amorphous phase of the Fe-based nanocrystalline soft magnetic alloy, or clusters containing both Cu and Al may be dispersed, but it is preferable that clusters containing both Cu and Al are dispersed.

[0034] Furthermore, as shown in the example described later (Figure 2), if microstructural observation using a three-dimensional atom probe (3DAP) reveals that the portion of the Cu distribution corresponding to a cluster overlaps with the portion of the Al distribution corresponding to a cluster, it can be considered that clusters containing both Cu and Al are dispersed in the amorphous phase of the Fe-based nanocrystalline soft magnetic alloy.

[0035] As will be described later, Fe-based nanocrystalline soft magnetic alloys are manufactured by heat-treating an amorphous alloy to form clusters and crystal grains in the microstructure. The clusters are formed in the amorphous alloy in the initial stages of heat treatment, and in addition to growing the crystal phase as crystal nuclei, they can also be dispersed around the crystal phase to suppress excessive crystal growth. This is thought to result in an Fe-based nanocrystalline soft magnetic alloy containing crystal grains with small grain sizes. Furthermore, it is thought that the dispersion of fine clusters in the amorphous phase reduces the crystalline magnetic anisotropy, resulting in an Fe-based nanocrystalline soft magnetic alloy with high relative permeability. Clusters composed of either or both Cu and Al are preferred because they exhibit these effects to a high degree.

[0036] The cluster number density in Fe-based nanocrystalline soft magnetic alloys is typically 1.65 × 10⁻⁶. -4 / nm 3 Preferably 1.90 × 10 -4 / nm 3 The above is more 2.15 × 10 -4 / nm 3 More preferably 2.50 × 10 -4 / nm 3 That concludes my explanation. Normally 7.30×10 -4 / nm 3 The following is preferably 5.50 × 10 -4 / nm 3 More preferably, 3.00 × 10 -4 / nm 3 That's all. The number density of clusters is in Fe-based nanocrystalline soft magnetic alloys. of Using the 3D mapping obtained by 3D atom probe (3DAP) analysis, body This can be determined by checking the number of clusters per unit product. In this case, if one type of atom accounts for 20% or more of the atoms constituting a cluster, it shall be counted as one cluster of that atom. Also, if two types of atoms account for 20% or more of the atoms constituting a cluster, it shall be counted as one cluster containing both of those two types of atoms.

[0037] By keeping the average size and number density of clusters within the above range, that is, by allowing many small clusters to exist, the spacing between clusters becomes narrower. As a result, the growth of the crystalline phase that forms with the clusters as crystal nuclei is suppressed, and an Fe-based nanocrystalline soft magnetic alloy containing crystal grains with a small average grain size can be obtained. Consequently, a high relative permeability can be achieved. The average size and number density of clusters, particularly the number density, can be adjusted by varying the composition represented by general formula (I). For example, to form clusters containing both Cu and Al, this can be adjusted by changing c, y, and y × (100 - abc) in general formula (I).

[0038] 1-4. Domain wall The Fe-based nanocrystalline soft magnetic alloy according to this embodiment has a greater number of domain walls, which are spaces between magnetic domains where the magnetic moments of atoms continuously reverse, than conventional Fe-based nanocrystalline soft magnetic alloys. Specifically, the number of domain walls in the Fe-based nanocrystalline soft magnetic alloy according to this embodiment is usually 10 / mm or more, preferably 15 / mm or more, more preferably 20 / mm or more, and usually 50 / mm or less, preferably 40 / mm or less. The number of magnetic domain walls is determined by observing the magnetic domain structure of Fe-based nanocrystalline soft magnetic alloys using a polarizing microscope that utilizes the magnetic Kerr effect. The number of magnetic domain walls present per 1 mm is measured at 5 to 10 locations, and the average value is calculated.

[0039] The number of magnetic domain walls depends on the composition of the soft magnetic alloy. Therefore, in this embodiment, the number of magnetic domain walls varies depending on the composition represented by general formula (I), particularly the Al content. In particular, when the Al content in the three-element ratio of Fe, Si, and Al, i.e., when y in general formula (I) is in the range of 0.012 to 0.100, the number of magnetic domain walls becomes 10 / mm or more, which is greater than when the Al content is 0, as shown in the examples described later. Furthermore, if y in general formula (I) is in the preferred range of 0.023 to 0.090, the number of magnetic domain walls becomes even greater, at 15 / mm or more. Alternatively, when the Al content in the composition represented by general formula (I) is greater than 0 atomic%, preferably 1.0 atomic%, the number of magnetic domain walls becomes 10 / mm or more. Furthermore, when the Al content in the composition represented by general formula (I) is 3.0 atomic%, preferably 4.0 atomic%, or 7.5 atomic%, preferably 7.0 atomic%, the number of magnetic domain walls becomes 15 / mm or more. Furthermore, as shown in the examples described later, Fe-based nanocrystalline soft magnetic alloys with a magnetic domain wall number of 15 / mm or more also have high relative permeability.

[0040] The inventors of this invention speculate that the reason for the large number of magnetic domain walls in the Fe-based nanocrystalline soft magnetic alloy according to this embodiment is as follows. Factors influencing the magnetic domain structure include magnetostatic energy, magnetic anisotropy energy, elastic energy due to magnetostriction, domain wall energy, and exchange energy. Of these, domain wall energy increases as the magnetic domains are subdivided and the number of domain walls increases. On the other hand, in the Fe-based nanocrystalline soft magnetic alloy according to this embodiment, the crystal structure is refined, particularly due to the Al content being within a specific range, which averages out the crystalline magnetic anisotropy to near zero. This reduction in crystalline magnetic anisotropy leads to a decrease in domain wall energy. Furthermore, the magnetostatic energy is also reduced due to the subdivision of the magnetic domains. From these observations, it is considered that in this embodiment, the amount of magnetostatic energy reduced by the subdivision of the magnetic domains is greater than the amount of increase in domain wall energy due to the increase in domain walls, so the subdivision of the magnetic domains, which is energetically more stable, progresses. As a result, it is inferred that the number of domain walls in the Fe-based nanocrystalline soft magnetic alloy according to this embodiment increases.

[0041] 2. Method for manufacturing Fe-based nanocrystalline soft magnetic alloy The method for producing the Fe-based nanocrystalline soft magnetic alloy according to this embodiment is not particularly limited and may include, for example, an amorphous alloy production step in which an amorphous alloy is produced by rapidly solidifying a molten metal having a composition represented by general formula (I) using an ultra-rapid cooling method, and a heat treatment step in which nanocrystallization is performed by heat treating the amorphous alloy at a temperature above the crystallization initiation temperature.

[0042] In the above method, the composition of the alloy subjected to the ultra-rapid cooling method is expressed by general formula (I), similar to the Fe-based nanocrystalline soft magnetic alloy obtained, and is selected according to the properties of the desired Fe-based nanocrystalline soft magnetic alloy. For example, c and y in general formula (I) may be determined based on formula (4) above from the viewpoint of adjusting the average grain size of the crystal grains to a desired size, or the Al content may be determined from the viewpoint of adjusting the number of magnetic domain walls to a desired range.

[0043] Furthermore, it is desirable that the temperature of the molten metal during rapid cooling be 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-based prevention method, gas atomization method, and water atomization method can be employed. The preparation of amorphous alloys by the ultra-rapid quenching 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. The shape of the resulting amorphous alloy is not particularly limited, but is usually ribbon-shaped. It is preferable that the amorphous alloy obtained by rapid cooling of the molten metal does not contain a crystalline phase, but it may contain a portion of the crystalline phase.

[0044] The amorphous alloy obtained by the above-described ultra-rapid cooling method can be processed into the desired shape as needed before heat treatment. Specific processing methods include winding, punching, and etching. Processing to obtain the desired shape of the magnetic material may be performed after heat treatment, but it is preferable to perform it before heat treatment. This is because although the alloy exhibits good processability in the amorphous alloy stage, its processability decreases once it undergoes nanocrystallization due to heat treatment.

[0045] The heat treatment temperature is above the crystallization start temperature of the alloy, specifically, usually 500°C or higher, preferably 530°C or higher, more preferably 550°C or higher, and usually 700°C or lower, preferably 650°C or lower, and more preferably 600°C or lower. Note that the heat treatment temperature refers to the highest temperature reached during the heat treatment. The holding time at the heat treatment temperature depends on the shape of the amorphous alloy, etc., but from the viewpoint of uniformly heating the entire alloy and productivity, it is usually 5 minutes or more, preferably 8 minutes or more, more preferably 10 minutes or more, and usually 5 hours or less, preferably 3 hours or less, more preferably 2 hours or less, and even more preferably 1 hour or less. The heat treatment may be carried out in an oxidizing atmosphere such as air, in an inert gas atmosphere such as argon, helium, or nitrogen, or under vacuum conditions, but it is preferable to carry it out in an inert gas atmosphere.

[0046] In the initial stages of heat treatment, clusters are formed in the amorphous alloy, and crystal grains grow using these clusters as crystal nuclei. In this embodiment, the Fe-based nanocrystalline soft magnetic alloy has a composition represented by general formula (I), which allows for the formation of a sufficient number of clusters. As a result, the spacing between clusters becomes narrower, suppressing crystal growth and enabling the refinement of crystal grains.

[0047] Furthermore, in the heat treatment process, it is preferable to apply a magnetic field to the amorphous alloy during heat treatment from the viewpoint of obtaining the effect of improving permeability by refining the magnetic domains. By applying a magnetic field during the heat treatment of an amorphous alloy having a composition represented by general formula (I), further improvement in permeability can be achieved. Note that nanocrystallization occurs during heat treatment, and the formation of fine crystal grains progresses in the amorphous alloy, but in this specification, amorphous alloys containing such growing crystal grains are also referred to as "amorphous alloys" for convenience.

[0048] The timing of magnetic field application may be part of the time from the start to the end of the heat treatment, or it may be for the entire duration. Furthermore, if magnetic field application is performed for part of the time from the start to the end of the heat treatment, it may be performed continuously or intermittently. Alternatively, if magnetic field application is performed for part of the time from the start to the end of the heat treatment, it may be performed after a predetermined time has elapsed from the start of the heat treatment and crystal grains have formed. In this case, after crystal grain formation, the amorphous alloy may be cooled and reheated before applying the magnetic field. Preferably, magnetic field application is performed for part of the time or for the entire duration while the material is held at the heat treatment temperature.

[0049] The strength of the magnetic field applied to the amorphous alloy is not particularly limited as long as it is sufficient to magnetically saturate the amorphous alloy, and is usually 8 kA / m or more, more preferably 16 kA / m or more, and most preferably 24 kA / m or more, and also usually 400 kA / m or less, more preferably 320 kA / m or less, more preferably 240 kA / m or less, even more preferably 160 kA / m or less, and most preferably 80 kA / m or less.

[0050] The direction in which the magnetic field is applied is not particularly limited and may be any direction. For example, if a ribbon-shaped amorphous alloy is produced by an ultra-rapid cooling method and the ribbon is wound before heat treatment, applying the magnetic field in the diametrical direction of the winding (i.e., parallel to the magnetic path) improves the angularity ratio of the magnetization curve and improves the magnetic properties at low frequencies. However, it is preferable to apply the magnetic field in the height direction of the winding (i.e., the width direction of the ribbon). In other words, when the angle between the magnetic path of the amorphous alloy and the direction of magnetic field application is applied, it is usually within the range of 90°±15°, preferably 90°±10°, and more preferably 90°±5°. This reduces the angularity ratio of the magnetization curve, but improves the permeability in the high-frequency range. In particular, in the Fe-based nanocrystalline soft magnetic alloy according to this embodiment, the permeability is improved not only in the high-frequency range but also in the low-frequency range of 100 kHz or less. This makes it possible to manufacture a magnetic core of Fe-based nanocrystalline soft magnetic alloy with high permeability from the low-frequency range to the high-frequency range. This is thought to be because the magnetic domains are subdivided by the application of a magnetic field, and the permeability improves due to the movement of magnetic domain walls.

[0051] 3. Method for manufacturing Fe-based nanocrystalline soft magnetic alloy A second embodiment of the present invention is a method for producing an Fe-based nanocrystalline soft magnetic alloy represented by the following general formula (II), comprising: an amorphous alloy production step of producing an amorphous alloy by rapidly solidifying a molten metal having the composition represented by general formula (II) using an ultra-rapid cooling method; and a heat treatment step of performing nanocrystallization by heat treatment of the amorphous alloy at a temperature above the crystallization initiation temperature, wherein a magnetic field is applied to the amorphous alloy during the heat treatment. According to the production method of this embodiment, an Fe-based nanocrystalline soft magnetic alloy having the same composition as general formula (II) is obtained, in which clusters are dispersed in the amorphous phase. Note that the composition represented by general formula (II) may contain unavoidable impurities. (Fe 1-p-q Si p Al q ) 100-d-e-f Q d Q' e Cu f (II)

[0052] (Q and Q') In general formula (II), Q represents one or more elements selected from the group consisting of Nb, W, Zr, Hf, Ti, and Mo, and is preferably Nb. Nb has the effect of raising the crystallization initiation temperature of the alloy, but it is also thought to have the effect of refining the precipitated crystal grains by forming an amorphous phase grain boundary layer together with B during nanocrystallization, or by suppressing the growth of crystal grains through interaction with elements such as Cu that can form clusters and lower the crystallization initiation temperature. When the crystal grains are refined, the crystal magnetic anisotropy is averaged out and reduced, so it is thought that an Fe-based nanocrystalline soft magnetic alloy with high relative permeability can be manufactured.

[0053] In general formula (II), Q' represents one or more elements selected from the group consisting of B, C, and P. One or more elements selected from the group consisting of B, C, and P are necessary in a certain amount together with Si to facilitate the formation of an amorphous structure in which the constituent elements are uniformly dispersed. Of these, B is considered to be an effective element for forming grain boundary layers together with Nb during nanocrystallization to form fine crystal grains, so Q' is preferably B. From the above, in general formula (II), it is particularly preferable that Q is Nb and Q' is B, from the viewpoint of obtaining fine crystal grains.

[0054] (d, e, and f) d is usually 2.0 or higher, preferably greater than 2.0, more preferably 2.5 or higher, and even more preferably 3.0 or higher, and also usually 5.0 or lower, preferably less than 5.0, more preferably 4.5 or lower, and even more preferably 4.0 or lower. Most preferably d is around 3.0. e is usually greater than 3.0, preferably 4.0 or more, more preferably 4.5 or more, and even more preferably 5.0 or more, and is also usually less than 10.0, preferably 9.5 or less, more preferably 9.0 or less, and even more preferably 7.0 or less. f is usually greater than 0, preferably 0.3 or more, more preferably 0.5 or more, even more preferably 0.7 or more, and usually less than 3.0, preferably 2.5 or less, more preferably 2.0 or less, even more preferably 1.5 or less, and particularly preferably 1.2 or less. It is most preferable that f be around 1.0.

[0055] By setting d to f within the above range, it becomes easier to form crystal grains with a small average grain size during nanocrystallization, thereby reducing crystalline magnetic anisotropy. This makes it possible to manufacture Fe-based nanocrystalline soft magnetic alloys exhibiting high specific permeability. Furthermore, if grain refinement is achieved, the soft magnetic properties such as permeability and coercivity of the Fe-based nanocrystalline soft magnetic alloy can also be improved.

[0056] When Q' is B, setting e to the above range ensures amorphous formation ability, suppresses the precipitation of Fe-B binary compounds which have inferior magnetic properties, and is thought to improve soft magnetic properties. Furthermore, since f is within the above range, amorphous formation ability is ensured, making it easier to produce amorphous alloys by the ultra-rapid cooling method. In addition, since f is within the above range, it is thought that Cu-containing clusters are more easily formed uniformly in the amorphous phase prior to the crystallization of α-Fe(Si,Al), and these clusters can act as crystal nuclei to form fine crystal grains.

[0057] (p and q) p and q represent the molar amounts of Si and Al, respectively, when the molar amounts of Fe, Si, and Al in the composition represented by general formula (II) are set to 1. Furthermore, the molar amount of Fe when the molar amounts of Fe, Si, and Al in the composition represented by general formula (II) are set to 1 is expressed as 1-(p+q).

[0058] p is usually 0.150 or higher, preferably 0.160 or higher, more preferably 0.170 or higher, and also usually 0.250 or lower, preferably 0.245 or lower, more preferably 0.240 or lower, and even more preferably 0.220 or lower. q is usually 0.0020 or higher, preferably 0.0050 or higher, more preferably 0.010 or higher, and also usually less than 0.012, preferably 0.011 or lower. Furthermore, p+q is usually 0.190 or higher, preferably 0.210 or higher, more preferably 0.215 or higher, and also usually 0.290 or lower, preferably 0.280 or lower, more preferably 0.275 or lower, even more preferably 0.270 or lower, and particularly preferably 0.265 or lower.

[0059] The conditions for rapid solidification by the ultra-rapid cooling method in this embodiment, the shape of the amorphous alloy produced by rapid solidification, the processing of the amorphous alloy that can be performed before heat treatment, the heat treatment conditions, and the conditions for applying a magnetic field are described by referring to the explanation in section "2. Method for producing an Fe-based nanocrystalline soft magnetic alloy" relating to the Fe-based nanocrystalline soft magnetic alloy according to the first embodiment of the present invention.

[0060] 4. Magnetic components The Fe-based nanocrystalline soft magnetic alloy obtained by the first embodiment of the present invention and the manufacturing method obtained by the second embodiment of the present invention can be used in various magnetic components such as reactors, common mode choke coils, transformers, communication pulse transformers, motor or generator cores, yoke materials, current sensors, magnetic sensors, antenna cores, and electromagnetic wave absorbing sheets. Of these, the Fe-based nanocrystalline soft magnetic alloy is particularly suitable for applications requiring high relative permeability at high frequencies, such as common mode choke coils, zero-phase reactors, current transformers, and ground fault sensors.

[0061] Here, common mode choke coils are required to be miniaturized to conserve resources, reduce costs, and conserve energy and CO2 emissions through reduced losses, without compromising their inductance performance. Miniaturizing common mode choke coils requires the use of a material with high magnetic permeability for the core. The Fe-based nanocrystalline soft magnetic alloy obtained by the manufacturing method according to the first embodiment of the present invention and the Fe-based nanocrystalline soft magnetic alloy obtained by the manufacturing method according to the second embodiment of the present invention are useful because they exhibit high magnetic permeability. Furthermore, to reduce manufacturing costs and losses, it is effective to reduce the number of turns in the winding and shorten the winding length, which is the cause of copper loss. The inductance of a common mode choke coil is shown by the following equation (5). From this equation (5), it can be seen that in order to reduce the number of turns without compromising the inductance, the magnetic permeability should be increased, the cross-sectional area should be increased, and the magnetic path length should be shortened.

[0062] L=μ(Ae / le)N 2 (5) L: Inductance [H] le: Magnetic path length [m] Ae: Core cross-sectional area [m²] 2 ] N: Number of turns

[0063] An example of a core shape with a large cross-sectional area and short magnetic path length is the cylindrical shape shown in Figure 9(a). However, shortening the magnetic path length necessitates extending the length in the long axis direction (direction A in Figure 9(a)) of the cylindrical shape in order to increase the cross-sectional area, thus failing to meet the requirement for miniaturization of the core. Thus, since there are limits to shortening the magnetic path length and expanding the cross-sectional area, it is necessary to form the core with a material with high magnetic permeability in order to reduce the number of turns in a small core. Conventional materials do not have sufficient magnetic permeability, and it was not possible to achieve practical levels of inductance by reducing the number of turns. However, the Fe-based nanocrystalline soft magnetic alloy obtained by the first embodiment of the present invention and the manufacturing method of the second embodiment of the present invention have higher magnetic permeability than conventional materials, so it is possible to achieve both high inductance and a reduction in the number of turns in a small core.

[0064] However, by using the Fe-based nanocrystalline soft magnetic alloy according to the first embodiment of the present invention, and the Fe-based nanocrystalline soft magnetic alloy obtained by the manufacturing method according to the second embodiment of the present invention, as the core material, the number of turns can be reduced to a number less than conventional products, specifically 8, 6, 4, 2, etc., without impairing the characteristics of the common mode choke coil. For example, as shown in the examples described later, a common mode choke coil with a 2-turn structure (2 turns) having a core of the shape shown in Figure 9(a) formed from the Fe-based nanocrystalline soft magnetic alloy according to the first embodiment of the present invention is smaller, lighter, and has lower losses compared to a general-purpose common mode choke coil having a core of the shape shown in Figure 9(b), and also exhibits equivalent inductance.

[0065] Based on the above, by using the Fe-based nanocrystalline soft magnetic alloy obtained by the manufacturing method according to the first embodiment of the present invention and the Fe-based nanocrystalline soft magnetic alloy obtained by the manufacturing method according to the second embodiment of the present invention as the material for a core with the shape shown in Figure 9(a), and by reducing the number of windings, it is possible to miniaturize, reduce the cost of, and reduce the loss of common mode choke coils. Furthermore, because the number of windings is small, material costs are reduced, winding processing is made easier and the manufacturing load is reduced, and disassembly at the time of disposal is also made easier, thus promoting material recycling. Therefore, according to the first and second embodiments of the present invention, it is possible to provide an environmentally friendly Fe-based nanocrystalline soft magnetic alloy that contributes to the SDGs. [Examples]

[0066] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist of the invention.

[0067] <Examples 1-27, Comparative Examples 1-13> Alloy ribbons were prepared from molten metal with the composition shown in Table 1 using the single-roll method. Specifically, a master alloy was obtained by melting and mixing pure metals of each element, weighed to achieve the composition shown in Table 1, using the arc melting method. The resulting molten alloy was then ejected onto a roll rotating at a peripheral speed of 50 m / s under reduced pressure in an argon gas atmosphere to produce ribbons with a width of 5 mm and a thickness of 10 μm. Next, the obtained ribbon was wound to produce a wound magnetic core with an outer diameter of 13 mm, an inner diameter of 12 mm, and a height of 5 mm. The obtained wound magnetic core was heat-treated at 550°C for 1 hour under a nitrogen atmosphere to produce a core of Fe-based nanocrystalline soft magnetic alloy.

[0068] <Comparative Example 14> Fe 73.5 Si 16.5 The core was prepared in the same manner as in Example 1, except that a molten metal with the composition represented by Nb3B6Cu1 was used. Furthermore, Fe 73.5 Si 16.5An alloy having the composition represented by Nb3B6Cu1 is a conventional soft magnetic material described in Patent Document 1.

[0069] <Comparative Example 15> A wound magnetic core was obtained in the same manner as in Example 1, except that a molten metal with the composition shown in Table 1 was used. The obtained wound magnetic core was subjected to heat treatment at 545°C for 60 minutes under a nitrogen atmosphere to produce a core of Fe-based nanocrystalline soft magnetic alloy.

[0070] <Examples 29-37, Comparative Examples 16-17> A wound magnetic core was obtained in the same manner as in Example 1, except that a molten metal with the composition shown in Table 1 was used. The obtained wound magnetic core was then heat-treated under the heat treatment conditions shown in Table 1 in a nitrogen atmosphere to produce a core of Fe-based nanocrystalline soft magnetic alloy.

[0071] <Comparative Example 18> A wound magnetic core was obtained in the same manner as in Example 1, except that a molten metal with the composition shown in Table 1 was used. The obtained wound magnetic core was heat-treated at 545°C for 60 minutes under a nitrogen atmosphere, and from 50 minutes after the start of the heat treatment until the end of the heat treatment, a magnetic field with a magnetic field strength of 120 kA / m was applied to the wound magnetic core in the height direction of the wound magnetic core (i.e., in the width direction of the ribbon constituting the wound magnetic core) to fabricate a core of Fe-based nanocrystalline soft magnetic alloy.

[0072] <Examples 38-47, Comparative Examples 19-20> A wound magnetic core was obtained in the same manner as in Example 1, except that a molten metal with the composition shown in Table 1 was used. The obtained wound magnetic core was heat-treated under the heat treatment conditions shown in Table 1 in a nitrogen atmosphere, and a magnetic field with a magnetic field strength of 240 kA / m was applied to the wound magnetic core in the height direction of the wound magnetic core (i.e., in the width direction of the ribbon constituting the wound magnetic core) for the entire duration of holding at the holding temperature shown in Table 1, thereby fabricating a core of Fe-based nanocrystalline soft magnetic alloy.

[0073] [Evaluation of relative permeability] The cores of Examples 1-47 and Comparative Examples 1-20 were each loaded into a resin case, and then coils were fabricated by winding 0.5 mm diameter copper wire three times around the resin case. Using an impedance analyzer (Keysight, E4990A), the inductance of the obtained coils was measured at frequencies of 1 kHz or 100 kHz and Hm = 0.4 A / m or less, and the relative permeability of the Fe-based nanocrystalline soft magnetic alloy was determined based on the above formula (1). The magnetic path length l was 39 mm, and the effective cross-sectional area A was 1.8 mm². 2 The number of turns N is 3. The results are shown in Table 1 and Figure 1.

[0074] [Table 1-1]

[0075] [Table 1-2]

[0076] [Table 1-3]

[0077] From Table 1 and Figure 1, the Fe-based nanocrystalline soft magnetic alloys of Examples 1-27 and 29-37, having a composition represented by general formula (I), exhibited high relative permeability of 21,000 or more at a frequency of 100 kHz. Furthermore, from Examples 38-47, it was confirmed that applying a magnetic field during heat treatment could achieve a higher relative permeability than when no magnetic field was applied.

[0078] On the other hand, the Fe-based nanocrystalline soft magnetic alloys of Comparative Examples 5 to 13, in which the content ratios of Fe, Si, and Al were within the range of general formula (I), but the amounts of Nb, B, and Cu were outside the range of general formula (I), had a relative permeability of 20,000 or less at a frequency of 100 kHz (indicated by "×" in Figure 1). From this, it can be said that in order for Fe-based nanocrystalline soft magnetic alloys to exhibit high relative permeability, it is important that not only the conditions related to x and y in general formula (I) but also a, b, and c are all satisfied.

[0079] Furthermore, Examples 28 and 38, which differ only in the presence or absence of magnetic field application during heat treatment, are examples relating to a composition represented by general formula (II), in which the Al content in the three-element ratio of Fe, Si, and Al is smaller than that of the composition represented by general formula (I). Comparing these examples, it was shown that even with the composition represented by general formula (II), applying a magnetic field during heat treatment improves the relative permeability at a frequency of 100 kHz compared to when no magnetic field was applied, thus achieving a higher relative permeability.

[0080] On the other hand, by comparing Comparative Examples 16 and 19, and Comparative Examples 17 and 20, it was found that if the composition represented by general formula (I) satisfies the requirement of y, which is the Al content ratio in the three-element ratio of Fe, Si, and Al, but does not satisfy the requirements of 1-xy and x, which are the Fe and Si content ratios in the three-element ratio, then applying a magnetic field during heat treatment does not improve the relative permeability.

[0081] Furthermore, Table 1 shows that if the alloy composition is represented by general formula (I) or (II), applying a magnetic field during heat treatment tends to improve not only the relative permeability in the high-frequency region but also the relative permeability in the low-frequency region.

[0082] [Evaluation of compositional distribution] A ribbon was unwound from the core prepared in Example 11 and processed to obtain a needle-shaped sample with a tip coefficient of approximately 10 nm. The distribution of Si, Al, B, and Cu was evaluated in a range of approximately 30 nm × 30 nm × 70 nm of the obtained needle-shaped sample by microstructural observation using a 3D atom probe. The results are shown in Figure 2.

[0083] Figure 2 shows the concentration of each atom using light and dark areas. That is, dark areas indicate low concentration, and bright areas indicate high concentration. In Figure 2, areas with a high Si distribution are crystal grains, and areas with a high B distribution are amorphous phases. Figure 2 confirms that the Fe-based nanocrystalline soft magnetic alloy of Example 11 has clusters dispersed in the amorphous phase. Since the distribution of Cu clusters and Al clusters was observed at almost the same location, it is considered that each cluster is an aggregate containing both Cu and Al. Furthermore, Figure 2 confirms that Al exists not only as clusters in the amorphous phase but is also widely distributed within the crystal grains.

[0084] [Evaluation of crystal grain size I] Ribbons were unwound from the cores prepared in Examples 6, 11, 12, 39, and 43-46, and Comparative Example 14. Analysis was performed using an X-ray diffractometer (XRD), and the average grain size of the crystal grains was determined by averaging according to formula (3) above. The results are shown in Table 2.

[0085] [Table 2]

[0086] As shown in Table 2, the alloy of Comparative Example 14, which does not contain Al in its composition, had an average grain size exceeding 12.0 nm, while the Fe-based nanocrystalline soft magnetic alloys of Examples 6, 11, 12, 39, and 43-46, which have a composition represented by general formula (I), had an average grain size of 11.3 nm or less. This indicates that the grain size is refined by using an alloy composition represented by general formula (I). In Fe-based nanocrystalline soft magnetic alloys having a composition represented by general formula (I), clusters of Cu and Al are formed, and the spacing between these clusters becomes narrower, which suppresses crystal growth. As a result, it is thought that crystal grains with a smaller average grain size are formed compared to alloys that do not contain Al in their composition.

[0087] [Evaluation of Composition Distribution II] Ribbons were unwound and processed from the cores prepared in Example 11 and Comparative Example 14 to obtain needle-shaped samples with a tip coefficient of approximately 10 nm. The distribution of Fe, Si, Al, Nb, B, and Cu was evaluated by microstructural observation using a 3D atom probe (CAMECA, EIKOS-UV) in a range of approximately 30 nm × 30 nm × 70 nm of the obtained needle-shaped samples. The evaluation results are shown in Table 3. Furthermore, the 3D map of the Fe-based nanocrystalline soft magnetic alloy obtained in Example 11 is shown in Figure 3, and the sliced ​​3D map is shown in Figure 4.

[0088] [Table 3]

[0089] From Table 3, Figure 3, and Figure 4, it can be seen that the Fe-based nanocrystalline soft magnetic alloy of Example 11 had a smaller average cluster size and a higher cluster number density than Comparative Example 14. Furthermore, as can be seen from Table 2, the Fe-based nanocrystalline soft magnetic alloy of Example 11 had a smaller average grain size and higher relative permeability than Comparative Example 14. From the above, it can be seen that Fe-based nanocrystalline soft magnetic alloys containing small clusters at a sufficient number density have a smaller average grain size and higher relative permeability.

[0090] [Evaluation of magnetic domain wall count] The magnetic domain structures of the Fe-based nanocrystalline soft magnetic alloys obtained in Comparative Example 18 and Examples 38, 39, 41, and 43-47 were observed using a polarizing microscope employing the magnetic Kerr effect (magnetic domain observation device, BH-782PI-NCC, manufactured by NeoArk Corporation). Polarizing microscope images of the magnetic domain structures of the Fe-based nanocrystalline soft magnetic alloys of Comparative Example 18 and Examples 38, 39, 41, 44, 45, 46, and 47 are shown in Figures 5(a) to (h), respectively. In addition, the number of magnetic domain walls per 1 mm was measured at 5 to 10 arbitrary locations in the polarizing microscope images, and the average value was determined as the number of magnetic domain walls. The results are shown in Table 4. Furthermore, the relationship between the Al content, the number of magnetic domain walls, and the relative permeability is shown in Figure 6.

[0091] [Table 4]

[0092] Table 4 and Figure 6 show that the number of magnetic domain walls in the Fe-based nanocrystalline soft magnetic alloy without Al (Comparative Example 18) was 4.2 / mm, while the number of magnetic domain walls in the Fe-based nanocrystalline soft magnetic alloys where y in general formula (I) was in the range of 0.012 to 0.100 (Examples 38, 39, 41, 43-47) was 10 / mm or more. Furthermore, when y in general formula (I) was in the range of 0.040 to 0.100 (Examples 43-47), the number of magnetic domain walls was even higher, at 15 / mm or more. Also, from Figure 6, it was confirmed that the relationship between Al content and the number of magnetic domain walls behaved similarly to the relationship between Al content and relative permeability. Therefore, from Figure 6, it is considered that there is also a relationship between the number of magnetic domain walls and relative permeability, and that relative permeability improves with increasing number of magnetic domain walls. These results show that having a composition represented by general formula (I) increases the number of magnetic domain walls and improves relative permeability. Furthermore, it was found that adjusting the Al content makes it possible to subdivide the magnetic domain walls.

[0093] <Examples 48-59, Comparative Examples 21-29> Cores were prepared in the same manner as in Example 1, except that the molten metal composition, heat treatment temperature, and heat treatment time were changed as shown in Table 5, and the relative permeability was calculated. Magnetostriction was also measured according to the measurement method described below. The results are shown in Table 5. The molten compositions used in Comparative Examples 24-29 are the same as those of the conventional soft magnetic materials described in Patent Document 1.

[0094] [Method for measuring magnetostriction] When an external force is applied to a metal (resistor), causing it to expand or contract, its resistance increases or decreases. The strain gauge method utilizes this principle. Strain gauges are attached to a ribbon wound from a core via a polyimide film, which is an electrical insulator. Magnetostriction is determined by measuring the relative strain measured by the strain gauges when the material is magnetized to magnetic saturation in a solenoid magnet.

[0095] [Table 5]

[0096] Table 5 shows that an amorphous alloy obtained from molten metal with the composition represented by general formula (I) can be heat-treated at 530-590°C for 10 minutes to obtain an Fe-based nanocrystalline soft magnetic alloy with near-zero magnetostriction and a high specific permeability of over 26,000 at a frequency of 100 kHz. On the other hand, when no heat treatment was performed (Comparative Examples 15-17), the relative permeability was a very low value of 2,000. In alloys that did not satisfy the composition represented by general formula (I) (Comparative Examples 18-23), when heat treatment was performed at 520°C or 550°C, similar to that of Examples 28-39, it was found that even if the heat treatment time was extended, Fe-based nanocrystalline soft magnetic alloys exhibiting a relative permeability of 20,000 or more could not be obtained.

[0097] [Evaluation of crystalline magnetic anisotropy] The cores prepared in Examples 1, 6, and 11, and Comparative Example 14, were each loaded into a resin case, and then coils were fabricated by winding 0.5 mm diameter copper wire three times around the resin case. The inductance Ls of the obtained coils was measured using an impedance analyzer (Keysight, E4990A) at a frequency of 1 kHz and Hm = 0.4 A / m or less, under different ambient temperatures. The results are shown in Table 6. Furthermore, the rate of change ΔLs of inductance Ls at each ambient temperature was calculated, using the inductance Ls at room temperature (20°C) as the baseline. The relationship between ambient temperature and the rate of change ΔLs (%) of inductance is shown in Figure 7.

[0098] [Table 6]

[0099] In Comparative Example 14, which does not contain Al, the change in inductance Ls relative to the value of inductance Ls at room temperature (20°C) tends to decrease as the ambient temperature decreases, but it is observed that there is no maximum point. From equation (1) above, if the rate of change of inductance increases, the relative permeability increases. In other words, as shown in Figure 7, temperature dependence is observed in relative permeability, and a maximum point of inductance is observed at a specific ambient temperature. Furthermore, from the results of Examples 1, 6 and 11, it is observed that in compositions with different Al content, as the Al concentration decreases, the temperature at which the maximum point occurs shifts to the lower temperature side.

[0100] Here, from Fig. 3 in Ken Takahashi, Hideo Arai, Toshiro Tanaka, and Tokuo Wakiyama, "Ordered Structure and Magnetic Anisotropy of Sendust Alloy Single Crystals," Journal of the Japan Society of Applied Magnetics, 1986, Vol. 10, No. 2, pp. 221-224 (hereinafter referred to as "References"), it is clearly shown that magnetic anisotropy K has a temperature dependence, and that as the temperature decreases, positive magnetic anisotropy K decreases to zero, and further to a negative value. Generally, it is expected that the permeability will be at its maximum when the magnetic anisotropy K is zero. In other words, when the temperature is lowered from room temperature, K is positive above a certain temperature, and after K becomes zero at that temperature, the magnetic anisotropy K becomes negative when the temperature is lowered further. That is, K ≠ 0 outside of that temperature, so the relative permeability decreases. It can be seen that the relative permeability at that temperature is higher than before and after that temperature. Furthermore, the above references show that as the Al concentration decreases and the magnetic anisotropy K at room temperature increases, the temperature at which the magnetic anisotropy K becomes zero (K=0) shifts to the lower temperature side.

[0101] From Figure 7 and Fig. 3 of the above-mentioned reference, it can be said that the trend in ambient temperature at which the maximum inductance point is shown for different Al addition amounts in Examples 1, 6, and 11 is almost identical to the trend in temperature at which the crystalline magnetic anisotropy K becomes zero in the reference. From this, it can be said that the crystalline magnetic anisotropy K of Fe-Si-Al ternary alloys and the relative permeability of the Fe-based nanocrystalline soft magnetic alloys obtained in the examples show similar temperature dependence, indicating that the crystalline magnetic anisotropy K within the crystal grains is strongly correlated with the relative permeability in Fe-based nanocrystalline soft magnetic alloys as well. Therefore, it can be seen that there is a relationship between making the crystalline magnetic anisotropy K zero and increasing the relative permeability. Furthermore, it can be inferred that the relative permeability is improved by including Al, and that it is possible to make the crystalline magnetic anisotropy K zero.

[0102] <Examples 60-71, Reference Examples 1-4, Comparative Examples 30-33> A wound magnetic core was obtained in the same manner as in Example 1, except that a molten metal with the composition shown in Table 7 was used. The obtained wound magnetic core was heat-treated under the heat treatment conditions shown in Table 7 in a nitrogen atmosphere, and a magnetic field with a magnetic field strength of 240 kA / m was applied to the wound magnetic core in the height direction of the wound magnetic core (i.e., in the width direction of the ribbon constituting the wound magnetic core) for the entire duration of holding at the holding temperature shown in Table 7, thereby fabricating a core of Fe-based nanocrystalline soft magnetic alloy.

[0103] [Evaluation of crystal grain size II] Ribbons were unwound from the cores prepared in Examples 6, 11, 12, 39, 41, 43-46 and 60-71, Reference Examples 1-4, and Comparative Examples 14 and 30-33. Analysis was performed using an X-ray diffractometer (XRD), and the average grain size of the crystal grains was determined by averaging according to the above formula (3). The results are shown in Table 7 and Figure 8.

[0104] [Table 7]

[0105] Table 7 and Figure 8 show that there is a correlation between the average grain size of the crystal grains and the content of c and y in the composition represented by general formula (I), i.e., the content of Cu and Al that constitute the clusters. For example, the average grain size of the crystal grains is approximately 11.3 nm if c = -34y + 1.7, approximately 11.0 nm if c = -34y + 2.2, and approximately 10.0 nm if c = -34y + 3.2. Therefore, based on the above formula, it is possible to manufacture Fe-based nanocrystalline soft magnetic alloys containing crystal grains of a desired average grain size.

[0106] <Example 72> A core of Fe-based nanocrystalline soft magnetic alloy was obtained in the same manner as in Example 45, except that the ribbon width was set to 45 mm. After loading each of the obtained cores into a resin case, a common mode choke coil with a two-turn structure was fabricated by winding a 1.6 mm diameter copper wire two turns around the resin case.

[0107] [Evaluation of magnetic components] Table 8 shows the catalog values ​​for dimensions, number of turns, inductance, rated current, and DC resistance of a general-purpose common mode choke coil with a ferrite core (Tokin Corporation, Ferrite Tokin SC-15-100). Furthermore, the DC resistance of the common mode choke coil in Example 72 was measured using a DC resistance meter (HIOKI RM3545, manufactured by HIOKI E.E. CORPORATION). The dimensions, number of turns, inductance, rated current, and DC resistance of the common mode choke coil in Example 72 are shown in Table 8. The dimensions in Example 72 were set to have the same inductance and rated current as the general-purpose common mode choke coil described above.

[0108] [Table 8]

[0109] Table 8 shows that the common mode choke coil of Example 72, which has a core made of Fe-based nanocrystalline soft magnetic alloy, can achieve the same inductance and rated current as a general-purpose common mode choke coil, even though it is smaller in size. Furthermore, the common mode choke coil of Example 72 is lighter, weighing less than half the weight of a general-purpose common mode choke coil, and has lower resistance, with copper loss being less than 1 / 10 the weight. From the above, it has been shown that the common mode choke coil using Fe-based nanocrystalline soft magnetic alloy as the core according to the present invention is compact and high-performance, and can be used as a practical replacement for conventional common mode choke coils.

Claims

1. An Fe-based nanocrystalline soft magnetic alloy containing an amorphous phase and crystalline grains, Clusters, which are aggregates of atoms observed by a three-dimensional atom probe, are dispersed in the amorphous phase, and have a composition represented by the following general formula (I). The average grain size of the aforementioned crystal grains is 11.3 nm or less. An Fe-based nanocrystalline soft magnetic alloy having a magnetic domain wall count of 15 / mm or more and 50 / mm or less. (F%) １－ｘ－ｙ Yes ｘ Al ｙ ) １００－ａ－ｂ－ｃ M ａ M' ｂ Cổ ｃ (I) (M represents one or more elements selected from the group consisting of Nb, W, Zr, Hf, Ti, and Mo, and includes at least Nb; M' represents one or more elements selected from the group consisting of B, C, and P, and includes at least B; a, b, and c represent atomic percent values ​​of 2.0 ≤ a ≤ 5.0, 3.0 < b < 10.0, and 0 < c < 3.0, respectively; x and y represent 0.150 ≤ x ≤ 0.250 and 0.012 ≤ y ≤ 0.100, and satisfy 0.190 ≤ x + y ≤ 0.290.)

2. The Fe-based nanocrystalline soft magnetic alloy according to claim 1, wherein in the general formula (I), a represents 2.0 < a < 5.0 in atomic percent, x and y represent 0.160 ≤ x ≤ 0.250 and 0.023 ≤ y ≤ 0.090, and satisfies 0.210 ≤ x + y ≤ 0.

280.

3. The Fe-based nanocrystalline soft magnetic alloy according to claim 1, wherein in the general formula (I), x and y represent 0.170 ≤ x ≤ 0.240 and 0.040 ≤ y ≤ 0.070, and satisfy 0.210 ≤ x + y ≤ 0.

280.

4. The Fe-based nanocrystalline soft magnetic alloy according to any one of claims 1 to 3, wherein M is Nb and M' is B.

5. The Fe-based nanocrystalline soft magnetic alloy according to any one of claims 1 to 4, wherein the atoms constituting the cluster are either Cu and Al or both.

6. The Fe-based nanocrystalline soft magnetic alloy according to claim 5, wherein the atoms constituting the cluster are both Cu and Al, and each cluster contains both Cu and Al.

7. The Fe-based nanocrystalline soft magnetic alloy according to any one of claims 1 to 6, wherein c and y satisfy c ≥ -34y + 1.7 in the general formula (I).

8. The number density of the clusters is 1.65 × 10 －４ / nm ３ or more and 7.3 × 10 －４ / nm ３ or less, and The Fe-based nanocrystalline soft magnetic alloy according to any one of claims 1 to 7, wherein the number density of the clusters is the number of clusters per unit volume in a three-dimensional mapping obtained by three-dimensional atom probe analysis of the Fe-based nanocrystalline soft magnetic alloy.

9. A magnetic component comprising the Fe-based nanocrystalline soft magnetic alloy described in any one of claims 1 to 8.

10. An amorphous alloy manufacturing process is performed by rapidly cooling and solidifying a molten metal having the composition represented by the general formula (I) using an ultra-rapid cooling method to produce an amorphous alloy. A heat treatment step is performed to nanocrystallize the amorphous alloy by heat treatment at 500°C to 700°C for 5 minutes to 5 hours. Includes, During the heat treatment process described above, a magnetic field is applied to the amorphous alloy. In the aforementioned magnetic field application, the angle between the magnetic path of the amorphous alloy and the direction of the applied magnetic field is within the range of 90° ± 15°. A method for producing an Fe-based nanocrystalline soft magnetic alloy according to any one of claims 1 to 8, wherein the magnetic field strength in the application of the magnetic field is 8 kA / m or more and 400 kA / m or less.

11. A method for producing an Fe-based nanocrystalline soft magnetic alloy containing an amorphous phase and crystal grains, The average grain size of the aforementioned crystal grains is 12.3 nm or less. An amorphous alloy manufacturing process is performed by rapidly cooling and solidifying a molten metal having a composition represented by general formula (II) using an ultra-rapid cooling method to produce an amorphous alloy. A heat treatment step is performed to nanocrystallize the amorphous alloy by heat treatment at 500°C to 700°C for 5 minutes to 5 hours. Includes, During the heat treatment process described above, a magnetic field is applied to the amorphous alloy. In the application of the magnetic field, the angle between the magnetic path of the amorphous alloy and the direction of the applied magnetic field is within the range of 90° ± 15°. A method for producing an Fe-based nanocrystalline soft magnetic alloy, wherein the magnetic field strength during the application of the magnetic field is 8 kA / m or more and 400 kA / m or less. (Fe １－ｐ－ｑ Si ｐ Al ｑ ) １００－ｄ－ｅ－ｆ Q ｄ Q' ｅ Cu ｆ (II) (Q represents one or more elements selected from the group consisting of Nb, W, Zr, Hf, Ti, and Mo, and including at least Nb; Q' represents one or more elements selected from the group consisting of B, C, and P, and including at least B; d, e, and f represent 2.0 ≤ d ≤ 5.0, 3.0 < e < 10.0, and 0 < f < 3.0 in atomic percent, respectively; p and q represent 0.150 ≤ p ≤ 0.250 and 0.0020 ≤ q < 0.012, and satisfying 0.190 ≤ p + q ≤ 0.290.)

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