Wound magnetic core and alloy core

Abstract

The present application provides a manufacturing method of a wound core of a nanocrystalline soft magnetic alloy ribbon, comprising: a first heat treatment process, in which a first inner shape correction jig for maintaining the wound core as a non-circular shape is arranged in an inner space of the wound core formed by winding an amorphous soft magnetic alloy ribbon that can be nanocrystallized, and the wound core is heat treated at a temperature of 300°C or higher and lower than a crystallization start temperature; and a second heat treatment process, in which the first inner shape correction jig is removed, at least one second inner shape correction jig is arranged in the inner space of the wound core, and the wound core is heat treated at a temperature of the crystallization start temperature or higher for nanocrystallization, a cross section of the second inner shape correction jig perpendicular to an extension direction is smaller than a cross section of the first inner shape correction jig perpendicular to the extension direction, and a magnetic field is applied to the wound core during a part of the second heat treatment process.

Description

[0001] This application is a divisional application; its parent application number is "2020800110772", and the invention title is "Winded magnetic core, alloy core and method for manufacturing wound magnetic core". Technical Field

[0002] This disclosure relates to a non-circular wound magnetic core, an alloy core, and a method for manufacturing the wound magnetic core, which is wound with a soft magnetic alloy strip made of nanocrystalline alloy. Background Technology

[0003] The increasing frequency of inverters, which accompanies the improvement in the performance of power semiconductor devices, enhances current and voltage control capabilities. Conversely, high-frequency leakage current caused by the common-mode voltage generated by the inverter becomes a problem. A common-mode choke coil is used as a method to suppress this leakage. The common-mode choke coil has a core made of a soft magnetic material. As for the core used, Patent Document 1 discloses that a core made of a thin strip of Fe-based or Co-based nanocrystalline alloy is suitable. Nanocrystalline alloys exhibit higher saturation magnetic flux density compared to permalloy and Co-based amorphous alloys, and have higher permeability than Fe-based amorphous alloys.

[0004] Representative compositions of nanocrystalline alloys are disclosed, for example, in Patent Document 2. Typical examples of manufacturing methods for magnetic cores using nanocrystalline alloys include: a step of rapidly cooling molten metal of a raw material alloy having a desired composition to form an amorphous alloy strip; a step of winding the amorphous alloy strip to form a ring-shaped wound magnetic core; and a step of crystallizing the amorphous alloy strip by heat treatment to obtain a magnetic core having a nanocrystalline structure.

[0005] Magnetic cores made of nanocrystalline alloys can have their magnetic properties, such as permeability μ and rectangularity ratio, significantly altered by adjusting the temperature profile during heat treatment and applying a magnetic field in a specific direction during heat treatment. For example, Patent Document 3 describes a magnetic core with high permeability and low rectangularity ratio: by applying a magnetic field in the direction of the core's height or radial direction, the permeability μ (50Hz to 1kHz) is 70,000 or higher, and the rectangularity ratio is 30% or lower.

[0006] Magnetic cores made of nanocrystalline alloys are usually circular. Circular magnetic cores are manufactured by winding a thin strip of amorphous alloy into a circular, toroidal core, followed by a heat treatment that accompanies nanocrystallization (hereinafter referred to as nanocrystallization heat treatment).

[0007] On the other hand, depending on the space where the magnetic core is used, sometimes non-circular magnetic cores such as rectangular or elliptical ones are required. In the case of manufacturing non-circular magnetic cores, nanocrystallization heat treatment is performed while the inner circumference of the wound magnetic core is corrected to be non-circular using a non-circular inner shape correction jig.

[0008] Patent Document 4 discloses a nanocrystallization heat treatment method as follows: After winding an amorphous alloy strip into a core, the stress within the strip is relieved by a primary heat treatment held at a temperature below the crystallization initiation temperature. The core is then removed, and a secondary heat treatment for nanocrystallization of the strip is performed at a temperature above the crystallization initiation temperature. According to Patent Document 4, this method can suppress the decrease in magnetic properties caused by stress generated during heat treatment.

[0009] Existing technical documents

[0010] Patent documents

[0011] Patent Document 1: Japanese Patent No. 2501860

[0012] Patent Document 2: Japanese Patent Publication No. 4-4393

[0013] Patent Document 3: Japanese Patent Application Publication No. 7-278764

[0014] Patent Document 4: Japanese Patent Application Publication No. 1-247557 Summary of the Invention

[0015] The problem that the invention aims to solve

[0016] In applications such as electric vehicles, the wound cores of common-mode choke coils are sometimes installed in devices containing multiple wiring and electronic components. In such cases, the wound core is sometimes designed to be spatially independent of the wiring and electronic components. Specifically, there are cases where non-circular wound cores are required. In recent years, the demand for such non-circular wound cores has also increased.

[0017] This disclosure provides a wound magnetic core, an alloy core, and a method for manufacturing the wound magnetic core, which are non-circular but have impedance characteristics equivalent to those of a circle.

[0018] Solution for solving the problem

[0019] A method for manufacturing a wound magnetic core of a nanocrystalline soft magnetic alloy strip according to one embodiment of the present invention includes: a first heat treatment step in which, with a first inner shape correction fixture for holding the wound magnetic core as non-circular is disposed in the inner space of a wound magnetic core formed by winding a nanocrystalline amorphous soft magnetic alloy strip, the wound magnetic core is heat-treated at a temperature of 300°C or higher and lower than the crystallization start temperature; and a second heat treatment step in which the first inner shape correction fixture is removed, and with at least one second inner shape correction fixture disposed in the inner space of the wound magnetic core, the wound magnetic core is heat-treated at a temperature of 300°C or higher than the crystallization start temperature, wherein the cross section of the second inner shape correction fixture perpendicular to the extension direction is smaller than the cross section of the first inner shape correction fixture perpendicular to the extension direction, and a magnetic field is applied to the wound magnetic core during a portion of the second heat treatment step.

[0020] Alternatively, in the second heat treatment process described above, after the above-mentioned nanocrystallization heat treatment, the above-mentioned magnetic field is applied during cooling.

[0021] Alternatively, in the first heat treatment process described above, a shape correction fixture for keeping the wound magnetic core non-circular can be disposed on the outside of the wound magnetic core.

[0022] Alternatively, in the second heat treatment process, a second inner shape correction fixture may be placed in the inner space of the wound magnetic core.

[0023] Alternatively, before the aforementioned nanocrystallization heat treatment, the second inner shape correction fixture is positioned within the inner space of the wound magnetic core in a position that does not contact the wound magnetic core.

[0024] Alternatively, the outer periphery shape of the cross section of the second inner shape correction fixture may be similar to the outer periphery shape of the cross section of the first inner shape correction fixture.

[0025] Alternatively, the outer periphery of the aforementioned second inner shape correction fixture may have an area that is more than 0.5 times and less than 0.9 times the outer periphery of the aforementioned first inner shape correction fixture.

[0026] Alternatively, in the second heat treatment process, multiple second inner shape correction fixtures may be arranged in the inner space of the wound magnetic core.

[0027] Alternatively, the aforementioned plurality of second inner shape correction jigs can move within the inner space of the aforementioned wound magnetic core.

[0028] Alternatively, in the state prior to the aforementioned nanocrystallization heat treatment, the plurality of second inner shape correction fixtures are positioned within the inner space of the aforementioned wound magnetic core in a position that does not contact the aforementioned wound magnetic core.

[0029] Alternatively, the plurality of second inner shape correction fixtures may be inscribed in a cross section perpendicular to the axis of the winding magnetic core, in a shape similar to the outer periphery shape of the cross section of the first inner shape correction fixture, wherein the similar shape has an area of ​​0.5 times or more and 0.9 times or less than the outer periphery shape of the first inner shape correction fixture.

[0030] Alternatively, it may also include an impregnation process in which resin is impregnated in the wound magnetic core after the second heat treatment process described above.

[0031] In one embodiment of this disclosure, the wound magnetic core of the nanocrystalline soft magnetic alloy strip is a wound magnetic core of the nanocrystalline soft magnetic alloy strip, and the wound magnetic core has a non-circular shape.

[0032] The impedance relative permeability μrz of the aforementioned wound magnetic core at 100kHz is above 45000.

[0033] The aforementioned wound magnetic core does not have a portion in which the thickness t of the aforementioned nanocrystalline soft magnetic alloy strip is 0.1t or more relative to the aforementioned stacking direction of the aforementioned wound magnetic core, where the separation between the aforementioned nanocrystalline soft magnetic alloy strip and the adjacent nanocrystalline soft magnetic alloy strip in the stacking direction is 0.1t or more.

[0034] Alternatively, the wound magnetic core may be in the shape of a racetrack, or at least one of the straight sections of the racetrack shape may have irregularities.

[0035] Alternatively, the above-mentioned wound magnetic core, when subjected to an AC magnetic field with a frequency of f = 10 kHz and an amplitude of H = 0.05 A / m, has a relative permeability μ (10 kHz) of 80,000 or more, a rectangularity ratio Br / Bm of the DC hysteresis loop (DC BH loop) of 50% or less, and a coercivity of 1.1 A / m or less.

[0036] Alternatively, the wound magnetic core may not have a portion in which the thickness t of the nanocrystalline soft magnetic alloy strip separated from the adjacent nanocrystalline soft magnetic alloy strip in the stacking direction is 0.1t or more relative to the stacking direction of the wound magnetic core.

[0037] One embodiment of the alloy core disclosed herein comprises: a wound magnetic core of a nanocrystalline soft magnetic alloy strip as described in any of the preceding claims; and a resin impregnated in the wound magnetic core.

[0038] The effects of the invention are as follows.

[0039] According to this disclosure, a wound magnetic core, an alloy core, and a method for manufacturing the wound magnetic core are provided, which are non-circular but have impedance characteristics equivalent to those of a circle. Attached Figure Description

[0040] Figure 1 This is a diagram showing the state after the amorphous ribbon is wound up.

[0041] Figure 2 This is a diagram showing a non-circular wound magnetic core formed by an external shape correction fixture and a first internal shape correction fixture.

[0042] Figure 3 This diagram illustrates the state of a wound magnetic core after heat treatment in a magnetic field without a second internal shape correction fixture.

[0043] Figure 4 This is a diagram used to illustrate the shape of the second internal shape correction fixture.

[0044] Figure 5 This is a diagram used to illustrate the shape of other second internal shape correction fixtures.

[0045] Figure 6 This is a diagram used to illustrate the shape of other second internal shape correction fixtures.

[0046] Figure 7 This is a diagram used to illustrate the heat treatment conditions of the first heat treatment process.

[0047] Figure 8 This is a diagram used to illustrate the heat treatment conditions for the second heat treatment process.

[0048] Figure 9 This is a diagram showing the heat treatment conditions of the first heat treatment step in Example 1.

[0049] Figure 10 This is a diagram showing the heat treatment conditions of the second heat treatment process in Example 1.

[0050] Figure 11 This is a graph showing the frequency characteristics of impedance relative to permeability.

[0051] Figure 12 This is a graph showing the DC BH characteristics.

[0052] Figure 13 This is a schematic diagram illustrating the size of the second internal shape correction fixture.

[0053] Figure 14 This is a diagram used to illustrate the shape and configuration of other second internal shape correction fixtures. Detailed Implementation

[0054] The inventors of this application have conducted a detailed study on a method for manufacturing a wound magnetic core composed of a non-circular nanocrystalline soft magnetic alloy strip. The circular and non-circular wound magnetic cores described in this application refer to the shape of the wound magnetic core in a cross-section parallel to the stacking direction of the strip. The stacking direction of the strip is perpendicular to the main surface of the strip. Furthermore, the cross-section of the wound magnetic core parallel to the stacking direction of the strip is also perpendicular to the axis of the wound magnetic core. Since each wound magnetic core has an internal space, the cross-section has a non-circular annular shape. In other words, the non-circular wound magnetic core disclosed herein has a non-circular annular cross-section, with its outer and inner circumferences having approximately similar non-circular shapes.

[0055] Generally, amorphous alloy ribbons shrink during nanocrystallization, with a volume reduction of approximately 1%. In the case of a wound magnetic core composed of a circular nanocrystalline soft magnetic alloy ribbon, the cross-section of the wound core parallel to the stacking direction is circular. Therefore, the stress generated by the ribbon's shrinkage acts uniformly in a circular manner, resulting in minimal ribbon deformation. In contrast, in the case of a non-circular wound magnetic core, the stress generated by the ribbon's shrinkage acts unevenly, potentially leading to deformation. Therefore, to prevent deformation, nanocrystallization heat treatment is considered with an internal shape-correcting fixture positioned on the inner circumference of the wound magnetic core. However, in this case, because the ribbon's shrinkage is suppressed, if nanocrystallization progresses, the suppressed shrinkage generates an internal magnetic field within the ribbon. This imparts unexpected induced magnetic anisotropy, potentially leading to performance degradation.

[0056] According to Patent Document 4, the above two-stage heat treatment can suppress the effect of characteristic deterioration caused by the core, and significant effects can be obtained, especially in the case of manufacturing rectangular magnetic cores.

[0057] On the other hand, in the manufacture of common-mode choke coils, sometimes magnetic field heat treatment is performed by applying a magnetic field in a specific direction during heat treatment in order to adjust the electrical and magnetic characteristics. The magnetic field is applied during heat treatment and at the temperatures before and after nanocrystallization, and during cooling after nanocrystallization. As a result, for example, the impedance of the wound magnetic core at a frequency of 100 kHz can be increased.

[0058] However, as can be seen from the method in Patent Document 4, when a magnetic field is applied during the secondary heat treatment, since there is no internal shape correction fixture, the repulsive force generated by magnetization between the layers of the wound strip may cause significant deformation of the wound magnetic core. In view of this problem, this disclosure provides a manufacturing method and product for a wound magnetic core made of nanocrystalline soft magnetic alloy strip, which, although non-circular, has impedance characteristics equivalent to those of a circle.

[0059] The embodiments of this disclosure will be described below, but this disclosure is not limited to the following embodiments. Furthermore, in this specification, the numerical range indicated by “~” refers to the range including the values ​​before and after the “~” as the minimum and maximum values, respectively.

[0060] This disclosure discloses a method for manufacturing a wound magnetic core of a nanocrystalline soft magnetic alloy strip, comprising: a first heat treatment step, wherein, with a first internal shape correction fixture for holding the wound magnetic core as non-circular is disposed in the internal space of the wound magnetic core formed by winding a nanocrystalline amorphous soft magnetic alloy strip, the wound magnetic core is heat-treated at a temperature of 300°C or higher and lower than the crystallization initiation temperature; and

[0061] In the second heat treatment step, the first inner shape correction fixture is removed, and with at least one second inner shape correction fixture positioned in the inner space of the wound magnetic core, the wound magnetic core is subjected to nanocrystallization heat treatment at a temperature above the crystallization initiation temperature.

[0062] The cross-section perpendicular to the extension direction of the second internal shape correction fixture is smaller than the cross-section perpendicular to the extension direction of the first internal shape correction fixture.

[0063] During a portion of the second heat treatment process described above, a magnetic field is applied to the wound magnetic core.

[0064] In the manufacture of non-circular wound magnetic cores using nanocrystalline alloy strips, if heat treatment accompanying nanocrystallization is performed while maintaining a corrective fixture for keeping the shape non-circular, the magnetic properties deteriorate as the volume of the soft magnetic alloy strip decreases during nanocrystallization and unexpected stress occurs between the strips.

[0065] To reduce the degradation of such magnetic properties, it is effective to obtain a wound magnetic core of nanocrystalline soft magnetic alloy strip by using a manufacturing method that includes the first heat treatment process and the second heat treatment process described above.

[0066] <Nanocrystalline amorphous soft magnetic alloy ribbon>

[0067] The method for manufacturing the wound magnetic core in this embodiment uses a nanocrystalline amorphous soft magnetic alloy strip. This soft magnetic alloy strip is essentially obtained by rapidly cooling molten alloy metal to obtain an amorphous alloy strip with a predetermined composition. By subjecting the amorphous alloy strip to a heat treatment at a temperature above the crystallization initiation temperature to nanocrystallization, a nanocrystalline soft magnetic alloy strip is obtained.

[0068] Analysis based on X-ray diffraction and transmission electron microscopy revealed that the fine grains are Fe with a body-centered cubic lattice structure after solution treatment of Si, etc. At least 30% by volume of the Fe-based nanocrystalline alloy consists of fine grains with an average particle size of less than 100 nm, measured at the maximum size. Furthermore, the portion of the Fe-based nanocrystalline alloy excluding the fine grains is primarily amorphous. The proportion of fine grains can be 80% by volume or more, or substantially 100% by volume.

[0069] The composition of the Fe-based nanocrystalline alloy used in the embodiments of this disclosure is preferably represented by the following general formula.

[0070] General formula: (Fe 1－a M a ) 100－x－y－z－α－β－γ Cu x Si y B z M' α M” β X γ (atom%)

[0071] Here, M is at least one element selected from Co and Ni, M' is at least one element selected from Nb, Mo, Ta, Ti, Zr, Hf, V, Cr, Mn and W, M” is at least one element selected from Al, platinum group elements, Sc, rare earth elements, Zn, Sn and Re, and X is at least one element selected from C, Ge, P, Ga, Sb, In, Be and As.

[0072] The given composition ratios a, x, y, z, α, β, and γ can satisfy the following relationships.

[0073] 0 ≤ a < 0.5

[0074] 0.1≤x≤3

[0075] 10≤y≤20

[0076] 5≤z≤10

[0077] 0.1≤α≤5

[0078] 0≤β≤10

[0079] 0≤γ≤10

[0080] The following is a detailed explanation of the preferred composition.

[0081] This Fe-based nanocrystalline alloy contains 0.1 to 3 atomic percent Cu. If the Cu content is less than 0.1 atomic percent, the reduction in core loss and the achievement of the desired μ' effect due to the addition of Cu are almost negligible. On the other hand, if the Cu content is more than 3 atomic percent, the core loss sometimes increases compared to the alloy without Cu. Furthermore, μ' decreases, and the desired μ' is not achieved. In this disclosure, a Cu content x of 0.5 to 2 atomic percent is particularly preferred. Within this range, the core loss is particularly low.

[0082] The addition of Cu results in grain refinement. The reason for this is not yet clear, but it is believed to be as follows: Cu and Fe have a positive interaction parameter and low solid solubility, exhibiting a tendency to separate. Therefore, when an amorphous alloy is heated, Fe atoms or Cu atoms tend to aggregate and form clusters, creating compositional fluctuations. This results in multiple readily crystallizable regions, generating fine grains around these clusters. This crystallization is predominantly Fe with almost no Cu solid solution. Therefore, through crystallization, Cu migrates to the vicinity of the fine grains, increasing the Cu concentration around the grain periphery. Consequently, grain growth is considered difficult.

[0083] The grain refinement effect brought about by the addition of Cu is considered to be particularly significant due to the presence of at least one element selected from Nb, Mo, Ta, Ti, Zr, Hf, V, Cr, Mn, and W. The grain refinement-promoting effect of these elements is especially pronounced among Nb, Mo, Ta, Zr, and Hf. Among these elements, the addition of Nb makes it particularly easy for the grains to become finer, resulting in alloys with excellent soft magnetic properties. Furthermore, the addition of Nb produces a microcrystalline phase with Fe as the main component. Therefore, compared to Fe-based amorphous alloys, magnetostriction is reduced, and unexpected magnetic anisotropy caused by stress applied to Fe-based nanocrystalline alloys during operation can be decreased. These phenomena are considered one of the reasons for the improved soft magnetic properties. The above elements are contained in the range of 0.1 to 5 atomic percent. Preferably, the range is 2 to 5 atomic percent. If less than 0.1 atomic percent, grain refinement may become insufficient. If more than 5 atomic percent, the saturation magnetic flux density decreases significantly.

[0084] Si and B are particularly useful elements for grain refinement in Fe-based nanocrystalline alloys. For example, after obtaining an amorphous alloy through the addition of Si and B, fine grains are formed by heat treatment, thereby obtaining an Fe-based nanocrystalline alloy. The Si content is in the range of 10 to 20 atomic percent. When the Si content is less than 10 atomic percent, the amorphous forming ability of the alloy is low, and it is difficult to stably obtain an amorphous alloy. Furthermore, due to insufficient reduction in the crystal magnetic anisotropy of the alloy, it is difficult to obtain excellent soft magnetic properties (e.g., low coercivity). When the Si content exceeds 20 atomic percent, the reduction in the saturation magnetic flux density of the alloy becomes larger, and the resulting alloy is prone to embrittlement. A preferred lower limit for Si is 14 atomic percent. On the other hand, a preferred upper limit for Si is 18 atomic percent.

[0085] Furthermore, the content of B is in the range of 5 to 10 atomic percent. B is an essential element for the formation of amorphous materials; when the B content is below 5 atomic percent, the ability to form amorphous materials is low, and it is difficult to stably obtain amorphous materials. When the B content exceeds 10 atomic percent, the decrease in saturation magnetic flux density becomes greater. The preferred lower limit for B is 6 atomic percent. On the other hand, the preferred upper limit for B is 8.5 atomic percent.

[0086] This Fe-based nanocrystalline alloy may contain less than 10 atomic percent of at least one element selected from C, Ge, P, Ga, Sb, In, Be, and As, or it may contain 0 atomic percent. These elements are effective for amorphization in the formation of amorphous alloy ribbons. Adding these elements together with Si and B helps to amorphize the alloy and also achieves the effect of adjusting magnetostriction and Curie temperature.

[0087] Furthermore, it may contain at least 10 atomic percent or less of an element selected from Al, platinum group elements, Sc, rare earth elements, Zn, Sn, and Re, or it may contain 0 atomic percent. These elements have the effects of improving corrosion resistance, improving magnetic properties, and adjusting magnetostriction. If the content exceeds 10 atomic percent, it leads to a significant decrease in saturation magnetic flux density. The content of these elements is particularly preferred to be 8 atomic percent or less. When at least one element selected from the group consisting of Ru, Rh, Pd, Os, Ir, and Pt is added to the above elements, a nanocrystalline soft magnetic alloy with particularly excellent corrosion resistance is obtained.

[0088] The remaining portion, excluding impurities, is essentially Fe. A portion of the Fe may also be replaced by Co or Ni. The content a of M (Co and / or Ni) in the above formula is 0 ≤ a < 0.5. If a exceeds 0.3, core loss increases; therefore, 0 ≤ a ≤ 0.3 is preferred. Here, to obtain high μ', a = 0 is preferred.

[0089] The soft magnetic alloy strips made of nanocrystalline alloys disclosed herein can, for example, use soft magnetic alloy strips with a thickness of 10 μm to 25 μm. These soft magnetic alloy strips are typically manufactured continuously by rolling molten alloy metal. In the state of being manufactured by this rolling cooling, they are in the state of an amorphous alloy strip. The amorphous alloy strips manufactured by this rolling cooling are elongated during manufacturing. Therefore, they are typically transported in a wound state. Then, they are cut to a predetermined width as needed.

[0090] <First Heat Treatment Process>

[0091] In the first heat treatment process, a winding process is first performed, in which amorphous alloy strips cut to a predetermined width are wound... Figure 1 The wound magnetic core 11 with axis A is formed by winding it into a circular shape as shown. Then, the wound magnetic core 11 is deformed in a manner that results in a desired shape, such as... Figure 2 As shown, a first internal shape correction fixture 31 is arranged within the inner space 11i of the wound magnetic core 11 to form a non-circular wound magnetic core 12 and maintain its shape. At this time, it can also be done as follows: Figure 2 The shape correction fixtures 2a and 2b are configured as shown. In this state, the wound magnetic core 12 has a non-circular shape due to elastic deformation. If the first inner shape correction fixture 31 and the shape correction fixtures 2a and 2b are removed, the wound magnetic core 12 is to be restored to a circular shape. Preferably, the first inner shape correction fixture 31, when inserted into the wound magnetic core 11, has a non-circular shape in its cross-section perpendicular to the extension direction B, similar to the desired non-circular shape of the wound magnetic core to be manufactured. Here, the extension direction B of the first inner shape correction fixture 31 refers to the direction parallel to the axis A of the wound magnetic core 12 when the first inner shape correction fixture 31 is inserted into the wound magnetic core 11. The extension directions of the second inner shape correction fixtures 32a, 32b, and 32c described below are also defined in the same way.

[0092] In this embodiment, after the amorphous alloy strip is wound into a circle, it is held in a non-circular shape using a first inner shape correction jig 31. However, it is also possible to directly wind the amorphous alloy strip into a non-circular first inner shape correction jig 31 to form a non-circular wound magnetic core 12. Furthermore, in this embodiment, an example of a non-circular cross-section is shown with a roughly triangular shape, but the wound magnetic core of this disclosure is not limited to this shape. The wound magnetic core may also have a roughly rectangular, elliptical, or other shapes. That is, the wound magnetic core 11 may also have any non-circular shape that can be held using a first inner shape correction jig, or a combination of a first inner shape correction jig and an outer shape correction jig. Furthermore, when viewed as a cross-sectional shape, the wound magnetic core may have a racetrack shape formed by connecting two semicircles with two straight sections, or it may have a shape in which one or both of the two straight sections of the racetrack shape have outward-facing concave or convex portions.

[0093] Subsequently, with a first internal shape correction fixture 31 for holding the wound magnetic core 12 in a non-circular state disposed in the inner space (hole) 12i of the wound magnetic core 12, the wound magnetic core 12 is heat-treated at a temperature of 300°C or higher but lower than the crystallization initiation temperature. According to this first heat treatment step, the shape of the wound magnetic core 12 of the amorphous alloy strip is fixed as non-circular. Thus, the shape can be maintained even without the internal shape correction fixture 31.

[0094] The first heat treatment process, by heating in a non-reactive atmosphere, easily alleviates the stress caused by deformation into a non-circular shape. In this first heat treatment process, nitrogen is essentially used as the non-reactive atmosphere. Inert gases can also be used as the non-reactive atmosphere. Furthermore, reducing gases such as hydrogen can also be used. Additionally, heat treatment can be performed in a vacuum.

[0095] The heat treatment temperature of the first heat treatment step (hereinafter referred to as the first heat treatment temperature) is selected within the range of 300°C or higher and below the crystallization initiation temperature. If the temperature is below 300°C, it is impossible to fix the shape as non-circular. Furthermore, if the temperature is above the crystallization initiation temperature, a nanocrystalline phase is formed, the volume of the amorphous alloy strip decreases, and thus unexpected stress is generated between it and the straightening fixture, leading to the deterioration of magnetic properties.

[0096] Furthermore, in this application, the crystallization onset temperature is defined as the temperature at which the exothermic reaction caused by the initiation of nanocrystallization is detected under the measurement conditions of differential scanning calorimetry (DSC) at a heating rate of 10 °C / min.

[0097] The crystallization initiation temperature of the soft magnetic alloy strip composed of Fe-based nanocrystalline alloy is approximately in the range of 510 to 550°C. Therefore, the first heat treatment temperature is preferably carried out at a temperature below 510°C. Figure 7 A summary of the temperature profile for the first heat treatment step is shown. The upper limit of the first heat treatment temperature is preferably 500°C, more preferably 480°C. If the first heat treatment temperature is too low, stress relief becomes slow, thus the heat treatment takes longer, which is not recommended from a productivity point of view. The lower limit of the first heat treatment temperature is 300°C, preferably 350°C.

[0098] Regarding the holding time within the first heat treatment temperature range, sufficient time is required for the aforementioned stress relief, with a lower limit preferably of 10 minutes, and more preferably 30 minutes. There is no particular upper limit, but excessively long holding times are not recommended for productivity. Therefore, the upper limit of the holding time is preferably 180 minutes, and more preferably 90 minutes.

[0099] <Second heat treatment process>

[0100] After the first heat treatment process, remove the first internal shape straightening fixture 31, as follows: Figure 4 As shown, a second inner shape correction fixture 32a, smaller than the first inner shape correction fixture 31, is disposed in the inner space 12i of the wound magnetic core 12'. In this state, a second heat treatment process is performed to nanocrystallize the wound magnetic core 12' at a temperature above the crystallization start temperature. At this time, the outer shape correction fixture can also be disposed on the outer periphery of the wound magnetic core 12. According to the first heat treatment process, even without the inner shape correction fixture 31, the wound magnetic core 12' maintains the desired non-circular shape. In other words, according to the first heat treatment, the wound magnetic core 11 is plastically deformed to obtain a wound magnetic core 12' with the desired non-circular shape.

[0101] If a second heat treatment process accompanying nanocrystallization is performed, the thin strip constituting the wound magnetic core shrinks. Specifically, the amorphous alloy thin strip shrinks in three dimensions along both the thickness direction and the orthogonal direction perpendicular to the thickness direction as it nanocrystallizes. For example, in the length direction of the amorphous alloy thin strip, it decreases by approximately 1% in length conversion. Therefore, if the second heat treatment is performed while maintaining the inner shape correction fixture 31 used in the first heat treatment process, stress is applied to the wound magnetic core during nanocrystallization. In contrast, if the inner shape correction fixture 31 is removed, the effect of the stress applied during nanocrystallization can be avoided. However, if a magnetic field is applied to the wound magnetic core during the second heat treatment, as... Figure 3As shown, deformation of the wound magnetic core occurs. Specifically, a gap is created on the inner circumferential side by the thin strip separating from the adjacent thin strip in the stacking direction. For example, one or more portions (of the thin strip deviation) are created where, relative to the thickness t in the stacking direction of the wound magnetic core 12', the thin strip separates from the adjacent thin strip in the stacking direction with a gap S of 0.1t or more. This is because the amorphous thin strip is magnetized by the applied magnetic field, and a repulsive force generated by magnetization acts between the amorphous thin strips. In particular, in the straight section L of the wound magnetic core, there is a greater degree of freedom for the deformation of the amorphous thin strip compared to the corner section C, and this deformation occurs significantly in the straight section L.

[0102] Therefore, in this disclosure, after the first heat treatment process, the first inner shape correction fixture is removed, and at least one second inner shape correction fixture smaller than the first inner shape correction fixture is disposed in the inner space of the wound magnetic core. This reduces the deformation of the wound magnetic core during heat treatment in the magnetic field caused by the second heat treatment process, and also reduces the stress caused by the reduction in the size of the wound magnetic core accompanying nanocrystallization.

[0103] Based on the reasons for the aforementioned deformation, this invention is particularly effective for wound magnetic cores with non-circular cross-sections, especially for wound magnetic cores whose cross-sections include a large proportion of straight sections. This invention is applicable to wound magnetic cores having, for example, a curvature of 10m in the inner circumferential shape of the cross-section. －1 The following straight or curved sections (arcs or straight lines with a radius greater than 10 cm) are particularly effective for wound magnetic cores with a cross-section that is more than 10% of the total length of the inner circumference.

[0104] The second inner shape straightening fixture has the effect of suppressing deformation of the inner diameter portion of the wound magnetic core, but its deformation suppression effect is smaller than that of the first inner shape straightening fixture. In other words, compared to the first inner shape straightening fixture, the second inner shape straightening fixture allows for shrinkage deformation of the wound magnetic core. During the second heat treatment process, the wound magnetic core undergoes deformation in the shrinkage direction. In this case, if the first inner shape straightening fixture, which has a greater effect on suppressing deformation, is still used, unwanted stress is imposed on the wound magnetic core due to the suppression of deformation, leading to a deterioration in the magnetic properties of the wound magnetic core. Therefore, in this disclosure, a second inner shape straightening fixture, although having a deformation suppression effect, but with a smaller effect than the first inner shape straightening fixture, is used. Thus, the amount of deformation of the wound magnetic core can be adjusted in two stages, and the deterioration of the magnetic properties of the wound magnetic core can be suppressed by changing the heat treatment temperature in the first and second heat treatment processes.

[0105] To achieve this effect, the second internal shape correction fixture preferably has a smaller overall size than the first internal shape correction fixture. Specifically, the cross-section of the second internal shape correction fixture perpendicular to its extension direction is smaller than the cross-section of the first internal shape correction fixture perpendicular to its extension direction. For example, the size of the second internal shape correction fixture is preferably 0.5% to 20% smaller than that of the first internal shape correction fixture 31. This ratio is not an area ratio, but a ratio relative to length. More specifically, it is expressed as the ratio of the length of the outer periphery (outer edge) of the cross-section of the first internal shape correction fixture 31 and the second internal shape correction fixture 32a perpendicular to its extension direction (the direction that becomes the axis of the winding magnetic core when inserted into the winding magnetic cores 12, 12'). When the first internal shape correction fixture 31 and the second internal shape correction fixture 32a are inserted into the winding magnetic cores 12, 12', this cross-section is parallel to the surface that defines the shape of the winding magnetic cores 12, 12'. Hereinafter, the shape of the cross-section of the internal shape correction fixture refers to the cross-section based on this definition.

[0106] If the lower limit of the reduction ratio of the length is less than 0.5%, unwanted stress will be applied to the wound core 12' in the second heat treatment process, and the magnetic properties of the manufactured wound core will easily deteriorate. The lower limit is preferably 0.8%, more preferably 1.0%, and more preferably 1.5%. On the other hand, if the upper limit exceeds 20%, it will be difficult to obtain a wound core of the desired size. The upper limit is preferably 15%, and more preferably 10%.

[0107] One or more second inner shape correction fixtures can be configured within the inner space of the wound magnetic core. When one second inner shape correction fixture is configured, the cross-sectional shapes of the first and second inner shape correction fixtures can be similar to each other. When multiple second inner shape correction fixtures are configured, the cross-sectional shape of the second inner shape correction fixtures can be different from that of the first inner shape correction fixture. Figure 4 A second internal shape correction fixture 32a, which has a similar shape to the first internal shape correction fixture 32, is shown. Figure 5 , Figure 6 An example of a configuration of multiple second internal shape correction clamps 32b, 32c is shown.

[0108] like Figure 4 As shown, when a second inner shape correction fixture 32a is configured, in the state before nanocrystallization heat treatment, the second inner shape correction fixture 32a can also be configured and fixed in the inner space 12i of the wound magnetic core 12' in a manner that does not contact the wound magnetic core.

[0109] Figure 5 , Figure 6An example of configuring multiple second inner shape correction clamps 32b and 32c is shown. When multiple second inner shape correction clamps 32b and 32c are configured, in the state prior to nanocrystallization heat treatment, the second inner shape correction clamps 32b and 32c can also be configured and fixed within the inner space 12i of the wound magnetic core 12' without contacting it. Specifically, the second inner shape correction clamps 32b and 32c can also be grounded within a shape 32p' similar to the outer periphery shape of the cross-section of the first inner shape correction clamp in a cross-section perpendicular to the axis of the wound magnetic core. The multiple second inner shape correction clamps 32b and 32c can each have the same cross-sectional shape, or they can have partially different cross-sectional shapes. Each of the second inner shape correction clamps 32a to 32c is specifically configured in the straight portion of the cross-sectional shape of the wound magnetic core to suppress deformation when a magnetic field is applied in the aforementioned portion. Specifically, it is possible to obtain a wound magnetic core in which no thin strip leaves the adjacent thin strip in the stacking direction with a gap S of more than 0.1t.

[0110] In the above situations, such as Figure 13 As shown, the outer periphery shape 32p of the cross-section of the second inner shape straightening fixture 32a and the shape 32p' formed by the second inner shape straightening fixtures 32b and 32c, which is similar to the outer periphery shape of the cross-section of the first inner shape straightening fixture, are preferably located in a region R with an area ratio of 0.5 times or more and 0.9 times or less relative to the outer periphery shape of the first inner straightening fixture, i.e., the inner periphery shape of the wound magnetic core after the first heat treatment. More preferably, the shape 32p and the shape 32p' have an area ratio of 0.8 times or more and 0.9 times or less relative to the outer periphery shape of the first inner straightening fixture.

[0111] Furthermore, when multiple second inner shape correction jigs are arranged within the inner space of the wound magnetic core, if these jigs can move, even if the thin strip of the wound magnetic core shrinks due to nanocrystallization, it is possible to suppress the application of unwanted stress to the wound magnetic core, thus preventing the deterioration of its magnetic properties. Therefore, for example, it is also possible to... Figure 14 As shown, the second inner shape correction fixture 32d is configured in a movable state within the inner space 12i of the wound magnetic core 12'.

[0112] In the second heat treatment process, the wound magnetic core 12' is subjected to nanocrystallization heat treatment. Figure 8An example of a temperature profile for nanocrystallization heat treatment is shown. The nanocrystallization heat treatment includes a period t' from a temperature Ts lower than the crystallization initiation temperature to a temperature Te higher than the crystallization initiation temperature. The heating temperature can be set in a range of 510°C or higher and 600°C or lower. If the heat treatment temperature is lower than 510°C or higher than 600°C, magnetostriction tends to increase. If the heat treatment temperature is 550°C or higher and 600°C or lower, magnetostriction can be further reduced. Specifically, it is also possible to make the saturation magnetostriction constant of the wound magnetic core 3 ppm or lower, further 2 ppm or lower, and further 1 ppm or lower.

[0113] Furthermore, in the nanocrystallization heat treatment, when heating from a temperature lower than the crystallization initiation temperature to a temperature higher than it, the heating rate at the crystallization initiation temperature is preferably a slow rate of 0.2 to 1.2 °C / min. This suppresses the formation of coarse grains caused by the self-heating of thin bands during nanocrystallization, thereby enabling stable nanocrystallization. Alternatively, the heating rate can be relatively rapid, for example, 3 to 5 °C / min, up to 20 °C lower than the crystallization initiation temperature. This shortens the heat treatment time and increases productivity.

[0114] Regarding the holding time at the highest temperature during the nanocrystallization heat treatment, sufficient time is required for the cultivation of the nanocrystalline phase, preferably 10 minutes or more, more preferably 15 minutes or more. There is no particular upper limit to the holding time during the nanocrystallization heat treatment, but excessively long holding times degrade productivity and are therefore not recommended. Therefore, the upper limit for the holding time during the nanocrystallization heat treatment is preferably 180 minutes, more preferably 120 minutes. It is preferable that no magnetic field is applied during the nanocrystallization heat treatment.

[0115] <Magnetic field application process>

[0116] During a portion of the second heat treatment process, a magnetic field is applied to the wound magnetic core. For example, after sufficient cultivation of the nanocrystalline phase, the core is cooled to a temperature lower than the maximum temperature, and a magnetic field is applied to impart induced magnetic anisotropy during cooling. Specifically, the temperature can be maintained at a temperature during cooling, and then the magnetic field is applied while the temperature is decreasing. The higher the holding temperature, the stronger the induced magnetic anisotropy is imparted, and the lower the permeability. In other words, the permeability can be controlled by changing the holding temperature before applying the magnetic field. However, at temperatures below 200°C, induced magnetic anisotropy cannot be sufficiently imparted, and at temperatures above 500°C, grain growth of the nanocrystalline phase is promoted, thus increasing the coercivity and leading to deterioration of the soft magnetic properties. Therefore, the holding temperature before applying the magnetic field is preferably 200°C or higher and 500°C or lower.

[0117] The temperature holding time before applying the magnetic field is preferably 5 minutes or more, and more preferably 10 minutes or more. There is no particular upper limit to the holding time, but if it is less than 10 hours, the time required for heat treatment can be shortened, thereby increasing productivity.

[0118] The direction of the applied magnetic field can be set to be orthogonal to the magnetic circuit of the wound magnetic core. Then, cooling can be performed while the magnetic field is being applied.

[0119] The applied magnetic field strength is preferably 60 kA / m or more, more preferably 100 kA / m or more. Furthermore, there is no particular upper limit to the magnetic field strength, but even if it exceeds 400 kA / m, it will not further impart magnetic anisotropy to the induced magnetic field, so it is preferably 400 kA / m or less.

[0120] When cooling is performed while a magnetic field is applied, the magnetic field needs to be continuously applied until the temperature drops to a sufficiently low level. Preferably, the magnetic field is continuously applied until the temperature drops below 200°C, more preferably below 100°C. Furthermore, the magnetic field can be any of a direct current magnetic field, an alternating current magnetic field, or a pulsed magnetic field.

[0121] The first and second heat treatment steps are preferably performed in a non-reactive atmosphere. When heat treatment is performed in nitrogen, sufficient magnetic permeability is obtained, essentially treating nitrogen as a non-reactive gas. Inert gases can also be used as non-reactive gases. Furthermore, a hydrogen-based reducing atmosphere can also be used. Alternatively, heat treatment can be performed in a vacuum. Specifically, the first and second heat treatment steps are preferably performed in an atmosphere with an oxygen concentration of 10 ppm or less.

[0122] <Wound magnetic core of nanocrystalline soft magnetic alloy strip>

[0123] The first embodiment of this disclosure provides a wound magnetic core with a structure in which a nanocrystalline soft magnetic alloy strip is wound. Furthermore, as described above, the non-circular wound magnetic core of this disclosure has a non-circular ring shape, with its outer and inner edges having substantially similar non-circular shapes. Moreover, the wound magnetic core of this disclosure exhibits excellent impedance characteristics when its impedance relative permeability μrz is 45,000 or higher at 100 kHz. Furthermore, the wound magnetic core of this disclosure can also achieve a high impedance relative permeability μrz over a wide frequency range when its impedance relative permeability is 80,000 or higher at 10 kHz and 10,000 or higher at 1 MHz.

[0124] Thus, the reason for the higher impedance relative to permeability μrz of the wound magnetic core of the non-circular nanocrystalline soft magnetic alloy strip disclosed herein is that, by reducing the stress caused by the internal shape-correcting fixture during the heat treatment accompanying crystallization, the unexpected induced magnetic anisotropy generated inside the amorphous strip can be mitigated, thereby achieving uniform induced magnetic anisotropy even in non-circular shapes. Since the induced magnetic anisotropy becomes uniform, there is less domain wall movement during magnetization, thus it is inferred that the magnetic moment can follow at higher frequencies.

[0125] The aforementioned magnetic cores with relatively high impedance relative to permeability μrz are useful as cores for common-mode chokes, for example, by winding or passing wires to enable them to function as common-mode chokes.

[0126] The impedance relative permeability μrz is often used as a characteristic parameter for common-mode chokes. The impedance relative permeability μrz is described, for example, in JIS standard C2531 (revised in 1999). The impedance relative permeability μrz can be considered to be equal to the absolute value of the complex relative permeability (μr'-iμr”) as shown in the following equation (1) (e.g., “Key Points for the Selection of Magnetic Materials”, published on November 10, 1989, edited by Keizo Ota).

[0127] μrz=(μr'2+μr” 2 ) 1 / 2 …(1)

[0128] In equation (1) above, the real part μr' of the complex relative permeability represents the magnetic flux density component without phase delay relative to the magnetic field, which generally corresponds to the magnitude of the impedance relative permeability μrz in the low-frequency region. On the other hand, the imaginary part μr” represents the magnetic flux density component including phase delay relative to the magnetic field, which is equivalent to the amount of magnetic energy loss. The impedance of the wound magnetic core is proportional to the impedance relative permeability μrz. If the impedance relative permeability μrz is a high value in a wide frequency band, a high impedance can be obtained, and the ability to remove common-mode noise is excellent.

[0129] Furthermore, the wound magnetic core disclosed herein can also be a wound magnetic core with the following characteristics: when an AC magnetic field with frequency f = 10 kHz and amplitude H = 0.05 A / m is applied, the relative permeability μ (10 kHz) measured at room temperature is 80,000 or more, the rectangularity ratio Br / Bm of the DC hysteresis loop is 50% or less, and the coercivity is 1.1 A / m or less.

[0130] Furthermore, the wound magnetic core disclosed herein can be impregnated with resin. Since nanocrystalline wound magnetic cores become brittle during the heat treatment used for nanocrystallization, resin impregnation is sometimes used to improve mechanical stability. Additionally, resin impregnation is sometimes used to maintain a non-circular shape. In this case, a design challenge arises: if resin is impregnated, stress is applied to the nanocrystalline alloy strip, causing a change in the impedance of the wound magnetic core that does not meet customer requirements.

[0131] The nanocrystalline alloy magnetic core disclosed herein can minimize changes in impedance characteristics even when impregnated with resin. Epoxy-based, acrylic-based, and other resins can be appropriately used as the impregnating resin. Furthermore, the volume of the resin solvent used in the above-mentioned resin impregnation is typically about 5 wt% to 40 wt% relative to the weight of the resin. In the case of resin impregnation, after the second heat treatment step, the nanocrystalline alloy magnetic core is immersed in a container filled with a solution containing the above-mentioned resin, the nanocrystalline alloy magnetic core is removed from the container, and the solvent is dried, thereby obtaining an alloy core comprising a nanocrystalline alloy magnetic core and resin impregnated in the core.

[0132] <Permeability>

[0133] In this application, the term "permeability" is synonymous with "relative permeability". Furthermore, the relative permeability measured at room temperature under conditions of an applied alternating magnetic field with frequency f = 1 kHz and amplitude H = 0.05 amperes per meter (A / m) is denoted as μr (1 kHz).

[0134] Furthermore, the impedance relative permeability is denoted as μrz. Additionally, the impedance relative permeability was measured using an impedance / gain phase analyzer (model 4194A) manufactured by Keysight Technologies. The measurement was performed by passing an insulated wire through the center of the wound magnetic core and connecting it to the input / output terminals.

[0135] (Example 1)

[0136] A Fe-based amorphous alloy strip, containing 1% Cu, 3% Nb, 15.5% Si, 6.5% B (atomic percent), the remainder Fe, and unavoidable impurities, was rapidly cooled using a single-roll method to obtain a 50 mm wide and 14 μm thick Fe-based amorphous alloy strip. This Fe-based amorphous alloy strip was then cut (trimmed) into 35 mm wide pieces.

[0137] The cut Fe-based amorphous alloy strip was wound into a circle with an outer diameter of 90 mm and an inner diameter of 80 mm (height 35 mm) to form a wound magnetic core. Differential scanning calorimetry (DSC) determined that the crystallization initiation temperature of this alloy was 529 °C.

[0138] Then, relative to the wound magnetic core that is wound into a circle, such as Figure 2 As shown, a first inner shape correction fixture 31 is arranged on the inner periphery, and outer shape correction fixtures 2a and 2b are arranged on the outer periphery, thereby deforming into a roughly triangular non-circular shape. The first inner shape correction fixture 31 and the outer shape correction fixtures 2a and 2b are made of SUS304, a non-magnetic metal.

[0139] Then, relative to the non-circular wound magnetic core that has been corrected, according to Figure 9 The temperature curves shown indicate the heat treatment process. Furthermore, the temperatures shown here are the atmosphere temperatures within the heat treatment furnace, controlled by a temperature controller (KP1000C manufactured by Chino Corporation). The first heat treatment was conducted in a nitrogen atmosphere with an oxygen concentration of 10 ppm or less (2 ppm).

[0140] The temperature controller settings for the first heat treatment are as follows: the wound magnetic core is heated from room temperature to 450°C in 90 minutes (heating rate is 4.8°C / min), held for 30 minutes, and then cooled to below 100°C in 220 minutes (cooling rate is 1.6°C / min).

[0141] Then, a second heat treatment process is carried out.

[0142] First, the first internal shape-correcting fixture is removed. Because the first heat treatment instills curl marks on the wound magnetic core made of amorphous alloy strip, the shape of the wound magnetic core is maintained even after the first internal shape-correcting fixture is removed. Next, as... Figure 4 As shown, a second inner shape correction fixture, smaller than the first inner shape correction fixture, is positioned within the inner space of the wound magnetic core. The second inner shape correction fixture is a fixture whose external dimensions, when viewed axially, are 1% smaller than the first inner shape correction fixture. Therefore, a gap is created between the inner circumference of the wound magnetic core, made of amorphous alloy strip, and the second inner shape correction fixture. Furthermore, the outer correction fixture is not removed, and the outer correction fixture remains in place.

[0143] After that, according to Figure 10The temperature curves shown are used for heat treatment. As a temperature controller setting, the temperature was first increased from room temperature to 450°C over 90 minutes (heating rate 4.8°C / min), and held for 30 minutes. This resulted in a uniform temperature distribution inside the wound core at 450°C. Then, the temperature was increased to 580°C over 240 minutes (heating rate 0.5°C / min). During this heating, nanocrystallization began around 529°C, and the volume of the wound core shrank by approximately 1%. At this point, because a gap was provided between the wound core and the second inner shape correction fixture, the resulting wound core did not experience stress associated with shrinkage. Furthermore, the low heating rate of 0.5°C / min suppressed the formation of coarse grains caused by self-heating during nanocrystallization, thus enabling stable nanocrystallization. Afterward, the temperature was held at 580°C for 30 minutes, and then cooled to 400°C over 160 minutes (cooling rate 1.1°C / min). Subsequently, the temperature distribution inside the wound magnetic core was made uniform at 400°C by holding it at 400°C for 80 minutes. This heat treatment was carried out in a nitrogen atmosphere with an oxygen concentration of less than 10 ppm (2 ppm).

[0144] After being held at 400°C, the core is cooled while a magnetic field is applied (cooling rate is 1.4°C / min). A magnetic field is applied in a direction orthogonal to the magnetic circuit direction in the wound core (in this embodiment, the axial direction of the wound core). The applied magnetic field strength is 160 kA / m. Anisotropy of the induced magnetic field is imparted by applying the magnetic field until the temperature drops below 100°C. Then, the second inner shape correction fixture and the outer shape correction fixture are removed. This yields a non-circular wound core of this embodiment. The relative permeability μr' (10 kHz) of this wound core is 86,000. The magnetostriction is below 1 ppm.

[0145] Figure 11 This is a graph showing the frequency characteristics of the impedance relative permeability μrz of the wound magnetic core obtained through this embodiment. The impedance relative permeability μrz (100kHz) is 45,000 or higher (45,441). Figure 12 This is a graph showing the DC BH curve of the wound magnetic core obtained through this embodiment. The coercivity is less than 1 A / m (0.95 A / m).

[0146] Table 1 records the measured values ​​of the impedance relative permeability μrz in this embodiment, and Table 2 records the saturation magnetic flux density Bm, residual magnetic flux density Br, and the rectangularity ratio Br / Bm of the DC hysteresis loop as other characteristics.

[0147] Table 1

[0148]

[0149] Table 2

[0150]

[0151] (Comparative Example 1)

[0152] As Comparative Example 1, a circular wound magnetic core was fabricated. After winding an amorphous alloy strip into a circle to form a wound magnetic core, without setting out shape correction fixtures or internal shape correction fixtures, nanocrystallization heat treatment was performed in the circular state to obtain the wound magnetic core. The heat treatment conditions were the same as those for the nanocrystallization heat treatment in the second heat treatment step of Example 1.

[0153] exist Figure 11 , Figure 12 Tables 1 and 2 together record the characteristics of the wound magnetic core obtained by Comparative Example 1. The frequency characteristics and BH curves are substantially the same in Example 1 and Comparative Example 1. Figure 11 , Figure 12 The graph in this embodiment repeats the graph of Example 1. Therefore, it can be seen that the non-circular wound magnetic core of Example 1 in this embodiment can achieve the same characteristics as a circular magnetic core.

[0154] (Comparative Example 2)

[0155] As a comparative example 2, in the second heat treatment process, the first inner shape correction fixture was not removed, and nanocrystallization heat treatment was performed with the first inner shape correction fixture still in place to produce a wound magnetic core. Otherwise, the manufacturing conditions were the same as in Example 1.

[0156] exist Figure 11 , Figure 12 The characteristics of the magnetic core obtained by Comparative Example 2 are recorded in Tables 1 and 2. The coercivity of the wound magnetic core of Comparative Example 2 is 1.17 A / m, which is a larger value than that of Example 1. The impedance relative permeability μrz (100kHz) of the wound magnetic core of Comparative Example 2 is only 37,808, which is lower than that of Example 1. Furthermore, the impedance relative permeability μrz of the wound magnetic core of Comparative Example 2 is lower than that of Example 1 over a relatively wide frequency range of 1kHz to 10MHz. It can be seen that by using the method shown in Example 1, it is possible to obtain a non-circular wound magnetic core with an impedance relative permeability μrz that is higher than that of Comparative Example 2.

[0157] Symbol Explanation

[0158] 11—Circular wound magnetic core, 12—Non-circular wound magnetic core, 2a, 2b—Shape correction fixture, 31—First inner shape correction fixture, 32a, 32b, 32c—Second inner shape correction fixture.

Claims

1. A wound magnetic core of a nanocrystalline soft magnetic alloy strip, characterized in that, The aforementioned wound magnetic core has a non-circular shape. The impedance relative permeability μrz of the aforementioned wound magnetic core at 100kHz is above 45000. The aforementioned wound magnetic core does not have a portion in which the thickness t of the aforementioned nanocrystalline soft magnetic alloy strip is 0.1t or more relative to the aforementioned stacking direction of the aforementioned wound magnetic core, where the separation between the aforementioned nanocrystalline soft magnetic alloy strip and the adjacent nanocrystalline soft magnetic alloy strip in the stacking direction is 0.1t or more.

2. The wound magnetic core of the nanocrystalline soft magnetic alloy strip according to claim 1, characterized in that, The aforementioned wound magnetic core is in the shape of a racetrack, or the straight portion of at least one of the racetrack shapes has irregularities.

3. The wound magnetic core of the nanocrystalline soft magnetic alloy strip according to claim 1 or 2, characterized in that, The above-mentioned wound magnetic core, under the condition of being subjected to an AC magnetic field with frequency f = 10 kHz and amplitude H = 0.05 A / m, has a relative permeability μ of 80,000 or more, a rectangularity ratio Br / Bm of DC hysteresis loop of 50% or less, and a coercivity of 1.1 A / m or less, as measured at room temperature.

4. An alloy core, characterized in that, have: The wound magnetic core of the nanocrystalline soft magnetic alloy strip as described in any one of claims 1 to 3; and The resin impregnated in the above-mentioned wound magnetic core.

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