Magnetic thin ribbon and magnetic core using the same

Abstract

The present invention relates to a magnetic ribbon and a magnetic core using the same. An embodiment of the present invention generally relates to a magnetic ribbon and a magnetic core using the same. The magnetic ribbon of the embodiment of the present invention has a crystallinity of 0.05 to 0.4 when XRD analysis is performed on the Fe-Nb-Cu-Si-B magnetic ribbon, as shown by the total peak area of ​​the crystalline phase / (the peak area of ​​the amorphous phase + the total peak area of ​​the crystalline phase). In addition, the magnetic ribbon preferably has an area where a KIKUCHI pattern is detected when EBSD analysis is performed on the crystalline phase. In addition, the thickness of the magnetic ribbon is preferably 25 μm or less.

Description

[0001] This application is an application that has entered the Chinese domestic phase of international application PCT / JP2020 / 034201 (international application date: September 9, 2020), and the above-mentioned international application is incorporated into this specification by reference. In addition, this application is based on Japanese patent application 2019-164598 (filing date: September 10, 2019) and enjoys priority from the above-mentioned application. This application incorporates the entire contents of the above-mentioned application by reference. Technical Field

[0002] The embodiments generally relate to a magnetic ribbon and a magnetic core using the same. Background Art

[0003] For the input and output of power conversion devices such as switching regulators, noise filters combining inductors and capacitors are used. These inductors are equipped with common-mode choke coils to eliminate common-mode noise. A common-mode choke coil is a coil wound around a magnetic core.

[0004] Magnetic materials used in magnetic cores include ferrite, amorphous alloys, and Fe-based microcrystalline materials. Among them, Fe-based microcrystalline materials are becoming popular from the perspective of miniaturization and lightness. Fe-based fine crystalline materials are obtained by heat-treating Fe-based amorphous alloys containing Cu above the crystallization temperature. By using Fe-based microcrystalline materials, the inductance value of the components is reduced due to the high magnetic permeability, so they can be miniaturized and lightweight. In addition, Fe-based microcrystalline materials are used mainly for applications that require high voltage pulse attenuation energy or large current applications because they have high magnetic flux density and low loss.

[0005] For example, International Publication No. 2018 / 062409 discloses a magnetic core with a magnetic permeability of 25,000 or higher at a frequency of 100 kHz. Furthermore, the aforementioned patent document discloses a magnetic core wound with an iron-based soft magnetic alloy sheet having a crystal structure with an average grain size of 100 nm or less. In this patent document, the magnetic permeability is improved by controlling the thickness of the insulating layer, for example. Specifically, the magnetic permeability is increased by controlling the insulating layer to increase the occupancy rate of the magnetic ribbon.

[0006] On the other hand, the Radio Act stipulates that installation permits must be applied for in equipment using high-frequency currents of 10kHz or higher. Furthermore, the Radio Act stipulates installation conditions. To meet these conditions, miniaturization of power conversion devices is essential. Power conversion devices primarily operate in the 100kHz to 1MHz range. Therefore, there is a demand for magnetic cores that can be miniaturized in frequencies above 10kHz, and further in the 100kHz to 1MHz range. Summary of the Invention

[0007] To achieve miniaturization of magnetic cores, increasing magnetic permeability is effective. While the magnetic cores described in the aforementioned patent documents exhibit good permeability, there are limits to achieving higher permeability. In particular, there are limits to achieving higher permeability above 10 kHz, and further within the 100 kHz to 1 MHz range. Investigation into the reasons for this has revealed that the amount of crystalline phase present in the Fe-based amorphous alloy ribbon before heat treatment is crucial.

[0008] When manufacturing Fe-based fine-crystalline alloy ribbons, the Fe-based amorphous alloy ribbons are heat-treated to crystallize. Before heat treatment, the Fe-based amorphous alloy ribbons are essentially free of crystals. It has been found that there are limits to achieving higher magnetic permeability when heat-treating amorphous alloys that are essentially free of crystals.

[0009] In one aspect, the present invention is an invention for addressing such a problem, and an object of the present invention is to provide a magnetic ribbon capable of increasing magnetic permeability.

[0010] The magnetic ribbon of the embodiment is characterized in that, when the Fe-Nb-Cu-Si-B magnetic ribbon is subjected to XRD analysis, the crystallinity indicated by the total peak area of ​​the crystalline phase / (the peak area of ​​the amorphous phase + the total peak area of ​​the crystalline phase) is 0.05 to 0.4.

[0011] According to the magnetic thin ribbon and the magnetic core using the same according to the embodiment, it is possible to obtain a magnetic thin ribbon capable of increasing magnetic permeability. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is a diagram showing an example of a magnetic ribbon according to an embodiment.

[0013] Figure 2 This is a diagram showing an example of a magnetic core according to an embodiment.

[0014] Figure 3 It is a diagram showing another example of the magnetic core according to the embodiment. DETAILED DESCRIPTION

[0015] The magnetic ribbon of the embodiment is characterized in that, when the Fe-Nb-Cu-Si-B magnetic ribbon is subjected to XRD analysis, the crystallinity indicated by the total peak area of ​​the crystalline phase / (the peak area of ​​the amorphous phase + the total peak area of ​​the crystalline phase) is 0.05 to 0.4.

[0016] The Fe-Nb-Cu-Si-B system is an iron alloy containing iron (Fe), niobium (Nb), copper (Cu), silicon (Si), and boron (B) as constituent elements.

[0017] The composition of the iron alloy is represented by, for example, the following general formula (composition formula).

[0018] General formula: Fe aCu b Nb c M d Si e B f

[0019] a is a number satisfying a+b+c+d+e+f=100 atomic %, b is a number satisfying 0.01≤b≤8 atomic %, c is a number satisfying 0.01≤c≤10 atomic %, d is a number satisfying 0≤d≤20 atomic %, e is a number satisfying 10≤e≤25 atomic %, and f is a number satisfying 3≤f≤12 atomic %. Furthermore, in the formula, M is at least one element selected from the group consisting of Group 4 elements, Group 5 elements (excluding Nb), Group 6 elements, and rare earth elements of the periodic table.

[0020] Iron (Fe) is an element that forms a crystalline phase with silicon (Si). Using Fe as a main component allows for a low-cost material.

[0021] Copper (Cu) is effective in improving corrosion resistance, preventing grain coarsening, and improving soft magnetic properties such as iron loss and magnetic permeability. The Cu content is preferably between 0.01 atomic % and 8 atomic % (0.01 ≤ b ≤ 8). When the content is less than 0.01 atomic %, the effect of addition is minimal, while when it exceeds 8 atomic %, the magnetic properties deteriorate.

[0022] Niobium (Nb) is effective for uniformizing the crystal grain size and stabilizing the magnetic properties against temperature changes. The content of the M element is preferably 0.01 atomic % to 10 atomic % (0.01≤c≤10).

[0023] Silicon (Si) and boron (B) promote the amorphization of the alloy or the precipitation of microcrystals during manufacturing. Si and B are effective for improving the crystallization temperature and heat treatment for improving magnetic properties. In particular, Si dissolves in Fe, the main component of fine crystal grains, and is effective for reducing magnetic strain and magnetic anisotropy. The Si content is preferably 10 atomic% to 25 atomic% (10≤e≤25). The B content is preferably 3 atomic% to 12 atomic% (3≤f≤12).

[0024] M is at least one element selected from the group consisting of Group 4 elements, Group 5 elements (excluding Nb), Group 6 elements, and rare earth elements of the periodic table. Examples of Group 4 elements include Ti (titanium), Zr (zirconium), Hf (hafnium), etc. Examples of Group 5 elements include V (vanadium), Ta (tantalum), etc. Examples of Group 6 elements include Cr (chromium), Mo (molybdenum), W (tungsten), etc. Examples of rare earth elements include Y (yttrium), lanthanides, actinides, etc. Element M is effective for homogenizing the crystal grain size and stabilizing the magnetic properties with respect to temperature changes. The content of element M is preferably 0 atomic % to 20 atomic % (0≤d≤20).

[0025] In addition, the general formula preferably includes Fe, Nb, Cu, Si, and B (d = 0 atomic %). Furthermore, when the above general formula is satisfied, an Fe3Si phase is formed. The Fe3Si phase is a type of α'-Fe phase. The α'-Fe phase is broadly included in the α-Fe phase. The fine crystal grains mainly have at least one phase selected from the group consisting of the α-Fe phase, the Fe3Si phase, and the Fe2B phase. Each crystal may also contain constituent elements that satisfy the general formula.

[0026] The term "magnetic ribbon" refers to a long ribbon after casting or a ribbon obtained by cutting the long ribbon into a predetermined size. The ribbon obtained by cutting the long ribbon into a predetermined size may have any size.

[0027] Furthermore, the magnetic ribbon of the embodiment is characterized in that, when subjected to XRD analysis (X-ray Diffraction), the crystallinity indicated by total peak area of ​​the crystalline phase / (peak area of ​​the amorphous phase + total peak area of ​​the crystalline phase) is 0.1 to 0.4. Figure 1 An example of a magnetic ribbon is shown in FIG. In the figure, 1 is a magnetic ribbon.

[0028] First, the XRD analysis conditions will be described. XRD analysis was performed using a Cu target, a tube voltage of 40 kV, a tube current of 40 mA, and a slit width (RS) of 0.40 mm. Furthermore, the measurement conditions were set to out-of-plane (θ / 2θ), with the diffraction angle 2θ ranging from 5° to 140°.

[0029] The peak with the strongest peak at a diffraction angle (2θ) of 30° to 60° and a half-value width of 3° or more was set as the peak of the amorphous phase. The area of ​​the amorphous phase peak was set as the peak area of ​​the amorphous phase. All peaks other than the amorphous phase peak detected at 5° to 140° were set as peaks of the crystalline phase. The total area of ​​the crystalline phase peaks was set as the total peak area of ​​the crystalline phase.

[0030] Under the above-mentioned XRD analysis conditions, peaks of the amorphous phase are detected at 22°±1° and 44°±1°. In other words, peaks other than these are counted as peaks of the crystalline phase.

[0031] Crystallinity = total peak area of ​​crystalline phase / (peak area of ​​amorphous phase + total peak area of ​​crystalline phase). The so-called crystallinity of 0.05 to 0.4 indicates that a specified amount of crystalline phase exists in the magnetic ribbon. As described below, the magnetic core wound with the magnetic ribbon is heat-treated to form a fine crystal structure. Therefore, it means that the crystallinity of the magnetic core (or magnetic ribbon) before the heat treatment for forming the fine crystal structure is 0.05 to 0.4. In addition, since the above-mentioned magnetic core is a magnetic core (or magnetic ribbon) before the heat treatment for forming the fine crystal structure, it means that a crystalline phase exists in the magnetic ribbon after casting.

[0032] The fine crystal grains primarily contain at least one crystalline phase selected from the group consisting of an α-Fe phase, an Fe3Si phase, and an Fe2B phase. These crystalline phases are preferably formed in the cast magnetic ribbon. By forming crystalline phases in the cast magnetic ribbon, the pre-existing crystalline phases can serve as nuclei during heat treatment to form a fine crystal structure. This allows for increased magnetic permeability.

[0033] In addition, if the crystallinity is lower than 0.05, the effect of setting the crystalline phase is small. In addition, if the crystallinity exceeds 0.4, it is possible that the miniaturization of the crystals becomes difficult. In addition, the possibility of breakage when winding onto the core becomes higher. Therefore, the crystallinity is preferably in the range of 0.05 to 0.4, more preferably in the range of 0.05 to 0.3, and further preferably in the range of 0.1 to 0.3. If the crystallinity is set to less than 0.3, the strength of the magnetic ribbon is improved. By setting the crystallinity to more than 0.1, the crystallinity is stabilized. In addition, the magnetic ribbon of the embodiment, for example, regardless of where the XRD analysis is performed on the ribbon surface, the crystallinity is within the range of 0.05 to 0.4.

[0034] In addition, when performing EBSD analysis on a crystalline phase, it is preferred to have an area where a KIKUCHI pattern is detected. EBSD analysis is an electron backscatter diffraction method (Electron Backscatter Diffraction Pattern). Crystal orientation can be analyzed in EBSD analysis. In addition, the KIKUCHI pattern (Kikuchi image) is a line or band seen in addition to the diffraction points. It is also called a Kikuchi figure. The KIKUCHI pattern is a pattern produced by Bragg reflection caused by inelastic scattering of incident electrons caused by thermal vibrations of atoms in the crystal.

[0035] Regarding the light and dark lines of the KIKUCHI pattern, the lines closer to the incident line appear darker, and the lines farther away become brighter. The better the crystallinity, the brighter the lines will be. This also allows the growth direction of the crystal to be determined. Therefore, generally speaking, if the KIKUCHI pattern is detected, it indicates the presence of crystal orientation. <111> <120> <110> wait.

[0036] The so-called region where the KIKUCHI pattern is detected indicates the presence of a crystalline phase. By heat treatment, a fine crystal structure can be formed using the crystalline phase as a core. Therefore, it is preferred that the region where the KIKUCHI pattern is detected be present regardless of where the crystalline phase of the magnetic ribbon is measured.

[0037] EBSD analysis was performed using an electron beam condition set to 15 kV. The EBSD analysis instrument used was the Hikari High Speed ​​EBSD Detector OIM Analysis Software version 7, manufactured by EDAX (TSL). The measurement field of view was set to five or more points. Measurements were terminated if a Kikuchi pattern was detected within five or fewer times.

[0038] The thickness of the magnetic ribbon is preferably 25 μm or less. Reducing the thickness of the magnetic ribbon can reduce eddy current losses. Therefore, the thickness of the magnetic ribbon is preferably 25 μm or less, and more preferably 20 μm or less. It should be noted that the thickness of the magnetic ribbon is the average thickness. The average thickness is determined by averaging the thicknesses at five random locations when observing a cross-section of the magnetic ribbon using a micrometer.

[0039] Furthermore, the surface roughness Ra of the magnetic ribbon is preferably 1.0 μm or less. A low surface roughness Ra can prevent breakage of the magnetic ribbon during winding. Furthermore, the thickness of the insulating layer used for interlayer insulation in the magnetic core can be made uniform. Furthermore, the formation of gaps between the insulating layer and the magnetic ribbon can be suppressed, thereby improving the space utilization ratio.

[0040] In addition, when comparing the area of ​​the crystalline phase at the surface and center of the magnetic ribbon, it is preferred that there are more crystalline phases in the surface. In this case, it is sufficient as long as there are crystalline phases in the surface of either side of the magnetic ribbon. The so-called surface portion is an area within 2 μm from the concave portion of the surface of the magnetic ribbon. The so-called center portion is an area of ​​±2 μm from the center in the thickness direction of the magnetic ribbon. The concave portion of the surface is set to the most concave part of the surface convexity and concavity of the measurement area. The so-called crystalline phase is a phase in which one or more selected from α-Fe phase, Fe3Si phase and Fe2B phase become the main body. By increasing the crystalline phase in the surface of the magnetic ribbon, fine crystals can be obtained by the crystallization heat treatment described later. In this way, the magnetic properties can be improved. In addition, it is preferred that there is no crystalline phase in the center of the magnetic ribbon. By performing EBSD analysis on the cross section of the magnetic ribbon, the area ratio of the crystalline phase on the surface and in the center can be investigated.

[0041] The magnetic core is formed by winding or stacking the above-mentioned magnetic thin ribbons. The magnetic thin ribbons are processed into the required size and then wound or stacked. In addition, interlayer insulation is provided as needed.

[0042] Figure 2 and Figure 3 An example of a magnetic core is shown in FIG. Figure 2 is an example of a wound core. Figure 3 This is an example of a laminated core. In the figure, 2-1 is a wound core and 2-2 is a laminated core.

[0043] The wound core 2-1 is a core formed by winding a magnetic thin strip 1. The wound core 2-1 has a ring shape with a hollow center. In addition, an insulating layer may be provided on the surface of the magnetic thin strip 1. Figure 2 Although a circular core is shown as an example, a core wound into a square shape, an elliptical shape, or a U-shape may also be used.

[0044] The laminated magnetic core 2-2 is formed by laminating magnetic ribbons 1. The number of laminated ribbons is arbitrary. Furthermore, an insulating layer may be provided on the surface of the magnetic ribbons 1. The shapes of the magnetic ribbons 1 include various shapes, such as rectangular, square, H-shaped, U-shaped, triangular, and circular.

[0045] After forming the magnetic core, it is preferably heat-treated to obtain a crystal structure with an average grain size of 200 nm or less. Furthermore, the magnetic core after heat treatment preferably has a crystallinity of 0.9 or greater. The heat treatment temperature is set to a temperature higher than the first crystallization temperature, which is approximately 500°C to 520°C.

[0046] The crystallization temperature is the temperature at which crystals begin to precipitate. Crystals can be precipitated by performing heat treatment near the crystallization temperature. Fe-Nb-Cu-Si-B magnetic thin ribbons have a first crystallization temperature and a second crystallization temperature. The first crystallization temperature is around 500°C to 520°C. In addition, the second crystallization temperature is above 600°C. Crystals can be precipitated by performing heat treatment near the first crystallization temperature or at a temperature higher than the first crystallization temperature. In addition, crystals can be precipitated by performing heat treatment near the second crystallization temperature or at a temperature higher than the second crystallization temperature.

[0047] Heat treatment at a temperature near or higher than the first crystallization temperature is referred to as the first heat treatment. Furthermore, heat treatment at a temperature near or higher than the second crystallization temperature is referred to as the second heat treatment. By combining the first and second heat treatments, the degree of crystallinity can be controlled.

[0048] In addition, the average crystal particle size is calculated by the Scherrer formula of the half-value width of the diffraction peak obtained by XRD analysis. The Scherrer formula is expressed as D = (K·λ) / (βcosθ). Here, D is the average crystal particle size, K is the shape factor, λ is the wavelength of the X-ray, β is the full width at half maximum (FWHM) of the peak, and θ is the Bragg angle. The shape factor K is set to 0.9. The Bragg angle is half of the diffraction angle 2θ. It should be noted that the conditions for XRD analysis are the same as the conditions for measuring the crystallinity mentioned above.

[0049] The average crystal grain size is preferably 200 nm or less, more preferably 50 nm or less. By reducing the average crystal grain size, it is possible to reduce iron loss and improve magnetic permeability.

[0050] Furthermore, the crystallinity is preferably 0.9 or higher, more preferably 0.95 to 1.0. The higher the crystallinity, the higher the proportion of crystals in the magnetic ribbon. In other words, heat treating the magnetic core increases the proportion of crystals. Furthermore, after heat treatment, the average crystal grain size of the magnetic core is preferably smaller than the average crystal grain size of the magnetic ribbon.

[0051] The magnetic core described above is designed to be insulated, such as by being housed in a resin mold or an insulating housing. Furthermore, it is preferably wound with a coil. By winding the coil, a magnetic component such as a choke coil is formed. Furthermore, by insulating the core, insulation from the coil can be achieved. Furthermore, damage to the core during coil winding can be prevented.

[0052] It should be noted that the magnetic core of the embodiment is also intended to include a magnetic core that has been subjected to insulation treatment or coil winding.

[0053] The magnetic core described above can achieve high magnetic permeability, particularly high magnetic permeability in the frequency range of 10 kHz or higher, and further in the range of 100 kHz to 1 MHz.

[0054] In addition, when the inductance at 10kHz is set to L 10 , set the inductance at 100kHz to L 100 When L 10 / L 100 is less than 1.5, and the magnetic permeability at 100kHz is more than 15000. In addition, when the inductance of 100kH is set to L 100 , set the 1MHz inductor to L 1M When L 100 / L 1M The magnetic permeability at 100 kHz is 15,000 or more.

[0055] L 10 / L 1001.5 or less indicates that the inductance fluctuation at 10kHz to 100kHz is suppressed. 100 / L 1M A value of 11 or less indicates that a decrease in inductance at 100 kHz to 1 MHz is suppressed. Furthermore, the magnetic permeability at 100 kHz is 15,000 or more.

[0056] For example, Table 5 of the above-mentioned International Publication No. 2018 / 062409 shows the magnetic permeability at 10kHz and 100kHz. According to Table 5 of the above-mentioned patent document, if the frequency rises, the magnetic permeability becomes about half. As the microcrystalline material in the past becomes higher in magnetic permeability, the magnetic permeability decreases. The same is true for the inductance value. In order to cope with it, it is necessary to increase the number of turns of the coil and enlarge the magnetic core. On the other hand, if the number of turns is increased or the core size is increased, there is a problem of increasing the imbalance caused by the increase in inductance on the low-frequency side below 100kHz.

[0057] The magnetic core of the embodiment suppresses fluctuations in inductance and permeability between 10 kHz and 1 MHz. Consequently, it is possible to provide a magnetic core with stably high permeability within the 10 kHz to 1 MHz range. This improves the core's frequency dependence. It should be noted that the magnetic core of the embodiment is designed to be usable even in frequencies exceeding 1 MHz.

[0058] In addition, L 10 / L 100 The lower limit of L is not particularly limited, but is preferably 1.1 or more. 100 / L 1M The lower limit of L is not particularly limited, but is preferably 6 or more. 10 / L 100 or L 100 / L 1M If it is too small, the magnetic permeability may be too low.

[0059] The inductance and magnetic permeability were measured using an impedance analyzer (Hewlett Packard Japan, YHP4192A) at room temperature, 1 turn, and 1 V. The magnetic permeability was determined from the inductance at frequencies of 10 kHz, 100 kHz, and 1 MHz.

[0060] In the magnetic core of the embodiment, the AL value can be increased. The AL value satisfies the relationship: AL value ∝ μ × Ae / Le. μ represents magnetic permeability, Le represents the average magnetic path length, and Ae represents the effective cross-sectional area. The AL value is an indicator of the performance of the magnetic core. A higher AL value indicates a higher inductance.

[0061] When the core dimensions (Ae / Le) are the same, the AL value increases as the permeability μ increases. The AL value decreases by increasing the average magnetic path length Le. The AL value decreases by decreasing the effective cross-sectional area Ae.

[0062] If the magnetic core is enlarged, the AL value becomes larger. On the other hand, the enlargement of the magnetic core will cause problems with the configuration space within the electronic device. In the magnetic core of the embodiment, the frequency dependence of the inductance value and the magnetic permeability μ is suppressed. As a result, the average magnetic path length Le of the magnetic core can be reduced. The increase in the AL value can achieve the miniaturization of the magnetic core. As a result, it becomes easier to lighten the magnetic core and ensure the configuration space in the electronic device. Therefore, the degree of freedom of design within the electronic device can be increased.

[0063] If the magnetic core is miniaturized, fewer thin magnetic strips are needed to form the core, which can also reduce costs. Furthermore, even if the number of windings is reduced, equivalent properties can be achieved. Reducing the number of windings can reduce the amount of windings used, thereby reducing costs. Furthermore, reducing the number of windings can reduce the probability of core damage during the winding process. Therefore, the yield rate during the winding process can be improved. Furthermore, reducing the number of windings can reduce the heat generated by the windings.

[0064] The miniaturization of the magnetic core also leads to lightweighting. That is, when the characteristics of the magnetic core are the same as those of the previous magnetic core, miniaturization and lightweighting can be achieved. The miniaturization and lightweighting of the magnetic core will lead to miniaturization and lightweighting of electronic devices such as switching power supplies, antenna devices, and converters. In addition, as described above, the heat generation can be suppressed in the magnetic core of the embodiment. Therefore, it is suitable for fields with large temperature changes in the use environment or large current fields (more than 20 amperes). Examples of such fields include solar converters, converters for EV motor drives, etc.

[0065] The following is a description of a method for producing the magnetic ribbon according to the embodiment. The method for producing the magnetic ribbon according to the embodiment is not particularly limited as long as it has the above-described configuration, but the following methods can be cited as methods for obtaining the magnetic ribbon with a high yield.

[0066] First, a process for manufacturing a magnetic ribbon is performed. First, a raw material powder obtained by mixing the constituent components is prepared in a manner that satisfies the above-mentioned general formula (composition formula). Next, the raw material powder is melted to produce a raw material molten metal. The raw material molten metal is used to manufacture a long magnetic ribbon by a roller quenching method. The roller quenching method is a method of ejecting the raw material molten metal onto a high-speed rotating cooling roller. When performing the roller quenching method, it is preferred that the surface roughness Ra of the cooling roller be set to less than 1 μm.

[0067] Furthermore, when using the roller quenching method, it is preferable to clean the roller surface. Cleaning the roller surface stabilizes the contact between the chill roller and the raw molten metal. For example, it is preferable to set the contact surface of the chill roller to half its circumference, and to clean the surface of the chill roller that is not in contact with the raw molten metal during rotation. Cleaning the rotating chill roller stabilizes the contact between the chill roller and the raw molten metal. Examples of cleaning methods include brush pressure, cotton pressure, and gas jets.

[0068] Cleaning improves cooling efficiency and enables control of crystallinity. Consequently, it is possible to produce magnetic ribbons with crystallinity of 0.05 to 0.4. Furthermore, the surface roughness Ra can be set to 1 μm or less.

[0069] Furthermore, when the crystallinity of the magnetic ribbon after the roll quenching method is less than 0.05, a method of adjusting the crystallinity by laser treatment is also adopted.

[0070] Through this process, the magnetic thin ribbon of the embodiment can be obtained. Next, a method for manufacturing the magnetic core will be described.

[0071] The insulating layer is then formed on the obtained magnetic ribbon. The magnetic ribbon may be a magnetic tape processed to a desired size, or a long ribbon may be provided with the insulating layer.

[0072] Next, the process of manufacturing the magnetic core is carried out. In the case of a wound magnetic core, a long magnetic thin strip provided with an insulating layer is wound to produce the core. The outermost periphery of the winding is fixed by spot welding or adhesive.

[0073] In the case of a laminated magnetic core, one method involves stacking long thin magnetic strips with an insulating layer and then cutting them into the necessary size. Alternatively, the long thin magnetic strips with an insulating layer can be cut into the necessary size and then stacked. The sides of the stack are secured with an adhesive. Preferably, the surface of the magnetic core is coated with resin. This resin coating can increase the strength of the magnetic core.

[0074] Next, the core is heat-treated to precipitate fine crystals and form a fine crystalline structure. Since the magnetic ribbon becomes brittle due to the precipitation of fine crystals, it is preferable to heat-treat it after forming it into a core.

[0075] The heat treatment temperature is preferably a temperature near the crystallization temperature (first crystallization temperature) or a temperature higher than it. In this case, a temperature higher than -20°C of the crystallization temperature is preferred. If the magnetic ribbon is an iron-based soft magnetic alloy plate that satisfies the above general formula, the crystallization temperature is 500°C to 520°C. Therefore, the heat treatment temperature is preferably 480°C to 600°C. The heat treatment temperature is more preferably 510°C to 560°C. Heat treatment at a temperature near the first crystallization temperature or a temperature higher than it is referred to as the first heat treatment.

[0076] The heat treatment time is preferably 30 hours or less. The heat treatment time is the time when the temperature of the magnetic core is 480°C to 600°C. If it exceeds 40 hours, the average particle size of the fine crystal grains may exceed 200nm. The heat treatment time is more preferably 20 minutes to 25 hours. The heat treatment time is even more preferably 1 hour to 10 hours. Within this range, it is easy to control the average crystal grain size to 50nm or less.

[0077] In addition, heat treatment at a temperature near or above the second crystallization temperature is referred to as a second heat treatment. The second heat treatment temperature is preferably above 600°C. The second crystallization temperature is a temperature at which crystallization is promoted in a temperature region higher than the first crystallization temperature. By performing the second heat treatment, crystallization can be further promoted. That is, for example, crystallization can be performed in regions that were not precipitated in the first heat treatment. In addition, further crystals can be precipitated from the crystals precipitated in the first heat treatment. Therefore, the degree of crystallinity can be increased.

[0078] Furthermore, under the above heat treatment conditions, the crystallinity of the magnetic core can be set to 0.9 or higher. That is, by XRD analysis, for example, the crystallinity can be set to 0.9 or higher regardless of where the measurement is performed.

[0079] In addition, heat treatment in a magnetic field may be performed as needed. In the heat treatment in a magnetic field, it is preferred to apply a magnetic field along the short side direction of the magnetic core. For a wound magnetic core, a magnetic field is applied along the width direction. For a laminated magnetic core, a magnetic field is applied along the short side direction of the laminate. By applying a magnetic field along the short side direction of the magnetic core while performing heat treatment, the magnetic domain walls of the magnetic ribbon can be reduced or eliminated. By reducing the magnetic domain walls, the loss is reduced, and thus the magnetic permeability is improved. The applied magnetic field is preferably 80 kA / m or more, more preferably 100 kA / m or more. The heat treatment temperature is preferably 200°C to 700°C. The heat treatment time for heat treatment in a magnetic field is preferably 20 minutes to 10 hours. Heat treatment in a magnetic field may also be performed in one step with the heat treatment for precipitation of fine crystals described above. It is set to perform insulation treatment such as housing the magnetic core in an insulating housing as needed. When mounted in various electronic devices, it is set to perform coil winding treatment, i.e., winding treatment, as needed.

[0080] Example

[0081] (Examples 1 to 3, Comparative Examples 1 and 2, Reference Example 1)

[0082] As the first magnetic thin ribbon, Fe 73.5 Cu 1.0 Nb 3.0 Si 16.0 B 6.5 The raw material powder is prepared in such a way that the ratio (atomic %) of Fe 73.4 Cu 1.0 Nb 2.6 Si 14.0 B 9.0 The total atomic % of each component is 100%.

[0083] Next, the raw material powder is melted to produce a raw material molten metal. The raw material molten metal is then used to produce a long magnetic ribbon by a roll quenching method. When using the roll quenching method, a cooling roll with a surface roughness Ra of 1 μm or less is used.

[0084] In the examples, the roller quenching method was used to clean the cooling roller surface. In Comparative Example 1, the cooling roller surface was not cleaned. Furthermore, in Comparative Example 2, the magnetic ribbon of Comparative Example 1 was heat-treated to reduce the crystallinity to 0.62.

[0085] The crystallinity of the magnetic ribbons of Examples and Comparative Examples was measured.

[0086] The crystallinity was measured by XRD analysis using a Cu target, a tube voltage of 40 kV, a tube current of 40 mA, and a slit width (RS) of 0.40 mm. The measurement was performed within a diffraction angle 2θ range of 5° to 140°.

[0087] The peak with the strongest peak at a diffraction angle (2θ) of 30° to 60° and a half-value width of 3° or more was set as the peak of the amorphous phase. The area of ​​the amorphous phase peak was set as the peak area of ​​the amorphous phase. All peaks other than the amorphous phase peak detected at 5° to 140° were set as peaks of the crystalline phase. The total area of ​​the crystalline phase peaks was set as the total peak area of ​​the crystalline phase.

[0088] The crystallinity was determined by total peak area of ​​the crystalline phase / (peak area of ​​the amorphous phase + total peak area of ​​the crystalline phase).

[0089] Furthermore, the presence or absence of a Kikuchi pattern was determined by performing EBSD analysis on the crystal phase. Three arbitrary locations were measured in the EBSD analysis, and if a Kikuchi pattern was observed at least once, it was considered "present." If not, it was considered "absent."

[0090] The plate thickness was set as a peak-to-peak value evaluated using a micrometer. Measurements were made at five arbitrary locations, and the average value was set as the average plate thickness.

[0091] In addition, the average crystal particle size of the crystalline phase was determined. The average crystal particle size was determined by XRD analysis using the Scherrer equation. The XRD analysis conditions were the same as those used to measure the crystallinity.

[0092] The results are shown in Table 1.

[0093] Table 1

[0094]

[0095] Furthermore, cross-sections of the magnetic ribbons from the Examples and Comparative Examples were examined for the presence of crystalline phases in the surface and central regions. EBSD analysis was performed on the cross-sections of the magnetic ribbons. The presence of crystalline phases within 2 μm of a concave portion of the surface of the magnetic ribbons was examined. Furthermore, the presence of crystalline phases in the central region within ±2 μm from the center of the magnetic ribbons was examined. The results are shown in Table 2.

[0096] Table 2

[0097] The presence or absence of a crystalline phase on the surface The presence or absence of a crystalline phase in the center Example 1 have none Example 2 have none Example 3 have none Example 4 have none Example 5 have none Comparative Example 1 have none Comparative Example 2 have have

[0098] Magnetic cores were fabricated using the magnetic ribbons from the examples and comparative examples. The cores were wound cores with an outer diameter of 37 mm, an inner diameter of 23 mm, and a width of 15 mm. SiO2 films were used for interlayer insulation. The first crystallization temperature of the magnetic ribbons was measured using a differential scanning calorimeter (DSC) and was found to be 509°C. The second crystallization temperature was 710°C.

[0099] A fine crystalline structure was obtained by subjecting the core to heat treatment at 530°C in a nitrogen atmosphere for 1 to 10 hours. This heat treatment is referred to as the first heat treatment. Next, as the second heat treatment, the core was subjected to heat treatment at 530°C in an air atmosphere for 1 to 10 hours to obtain a fine crystalline structure. Furthermore, Example 1 was treated with air heat treatment as the second heat treatment, which is referred to as Reference Example 1. Through this process, magnetic cores for Examples and Comparative Examples were produced.

[0100] The crystallinity and average grain size of each magnetic core were measured using the same method as for the magnetic ribbon.

[0101] The inductance and magnetic permeability of the magnetic core were also measured. The inductance was measured using a core housed in an insulating case. The coil was set to one turn and the measurement was performed at an open-circuit voltage of 1V. The measurement equipment used was a YHP 4192A. The inductance was measured at frequencies of 10kHz, 100kHz, and 1MHz. Furthermore, the magnetic permeability was determined from the inductance value.

[0102] The results are shown in Tables 3, 4, and 5.

[0103] Table 3

[0104]

[0105] Table 4

[0106]

[0107] Table 5

[0108]

[0109] As can be seen from Tables 3 to 5, the magnetic cores of the examples suppress changes in inductance and permeability due to frequency, and therefore exhibit excellent characteristics as magnetic cores used in the 10 kHz to 1 MHz range.

[0110] While several embodiments of the present invention have been illustrated above, these embodiments are provided as examples and are not intended to limit the scope of the invention. These novel embodiments may be implemented in various other ways, and various omissions, substitutions, and modifications may be made without departing from the spirit of the invention. These embodiments and their variations are intended to be included within the scope and spirit of the invention, and are also intended to be included within the scope of the invention set forth in the claims and their equivalents. The above embodiments may be implemented in combination with one another.

[0111] Explanation of symbols

[0112] 1…Magnetic ribbon

[0113] 2-1…Wound core

[0114] 2-2…Laminated core

Claims

1. A magnetic ribbon, characterized in that: When the Fe-Nb-Cu-Si-B magnetic ribbon is subjected to XRD analysis, the crystallinity indicated by the total peak area of ​​the crystalline phase / (the peak area of ​​the amorphous phase + the total peak area of ​​the crystalline phase) is 0.05 to 0.

4. XRD analysis was performed with a Cu target, a tube voltage of 40 kV, a tube current of 40 mA, and a slit width RS of 0.40 mm. The measurement conditions were set to out-of-plane θ / 2θ, and the diffraction angle 2θ was measured in the range of 5° to 140°. The strongest peak is at a diffraction angle 2θ of 30° to 60°, and a peak with a half-value width of 3° or more is set as the peak of the amorphous phase, the area of ​​the peak of the amorphous phase is set as the peak area of ​​the amorphous phase, all peaks other than the peak of the amorphous phase detected at 5° to 140° are set as peaks of the crystalline phase, and the total area of ​​the peaks of the crystalline phase is set as the total peak area of ​​the crystalline phase. Under the above-mentioned XRD analysis conditions, peaks of the amorphous phase are detected at 22°±1° and 44°±1°, and peaks other than these are counted as peaks of the crystalline phase.

2. The magnetic ribbon according to claim 1, characterized in that When the crystalline phase was subjected to EBSD analysis, there was a region where a KIKUCHI pattern was detected.

3. The magnetic ribbon according to claim 1 or claim 2, characterized in that: The magnetic thin ribbon has a thickness of 25 μm or less.

4. A magnetic core, characterized in that: The magnetic thin ribbon according to claim 1 is wound or stacked.

5. The magnetic core according to claim 4, characterized in that The magnetic core according to claim 4 is heat-treated to obtain a crystal structure having an average crystal grain size of 200 nm or less.

6. The magnetic core according to claim 4 or claim 5, characterized in that: When the magnetic core was subjected to XRD analysis, the value of crystallinity was 0.9 or more.

7. The magnetic core according to claim 4, characterized in that The coil is wound.

8. The magnetic core according to claim 4, wherein When the inductance at 10kHz is set to L 10 , set the inductance at 100kHz to L 100 When L 10 / L 100 The magnetic permeability at 100kHz is 15000 or more.

9. The magnetic core according to claim 4, wherein When the inductor is set to 100kH, 100 , set the 1MHz inductor to L 1M When L 100 / L 1M The magnetic permeability at 100 kHz is 15,000 or more.

10. A magnetic core, characterized in that: A magnetic core obtained by winding or laminating the magnetic thin ribbons according to claim 3 is heat-treated to obtain a crystal structure having an average crystal grain size of 200 nm or less. When the magnetic core is subjected to XRD analysis, the crystallinity value is greater than 0.

9. When the inductance at 10kHz is set to L 10 , set the inductance at 100kHz to L 100 When L 10 / L 100 The magnetic permeability at 100kHz is 15000 or more.

11. A magnetic core, characterized in that: A magnetic core obtained by winding or laminating the magnetic thin ribbons according to claim 3 is heat-treated to obtain a crystal structure having an average crystal grain size of 200 nm or less. When the magnetic core is subjected to XRD analysis, the crystallinity value is greater than 0.

9. When the inductance at 100kHz is set to L 100 , set the 1MHz inductor to L 1M When L 100 / L 1M The magnetic permeability at 100 kHz is 15,000 or more.

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