Cut core and noise countermeasure member using same

Abstract

Provided is a means by which, even when it is difficult to provide a surface oxide film on a contact surface of a cut core by means of heat treatment at a crystallisation heat treatment temperature, the magnetic characteristics of the cut core are stably maintained for a long period of time. A cut core according to the present invention comprises two or more laminates in which a soft-magnetic alloy ribbon is laminated in the thickness direction. The laminates each comprise at least one contact surface and are in contact with one another at the contact surfaces. The soft-magnetic alloy ribbon includes a composition represented by Fe100-x-y-z-a-bSixByCuzCraMb (where M represents at least one element selected from Nb and Mo, and x, y, z, a and b represent atomic percentages of Si, B, Cu, Cr and M and satisfy 11.0 ≤ x ≤ 17.0, 5.0 ≤ y ≤ 10.0, 0.5 ≤ z ≤ 2.0, 0.5 ≤ a ≤ 4.0, 1.0 ≤ b ≤ 5.0, and 65 ≤ 100-x-y-z-a-b ≤ 75).

Description

Cut core and noise suppression member using the same

[0001] The present invention relates to a cut core and a noise suppression member using the same.

[0002] A magnetic core is a ring-shaped or rod-shaped component made of a soft magnetic material. Magnetic cores are used in transformers and reactors in combination with coils to increase magnetic permeability, and are also used as noise filters placed around cables. Soft magnetic materials used in magnetic cores include ferrite, silicon steel plate, and soft magnetic alloy ribbon. Silicon steel plate and soft magnetic alloy ribbon are often used in the form of a laminate formed by winding the material into a ring shape and stacking it in the thickness direction.

[0003] Patent Document 1 describes an invention for a magnetic core called a cut core, which has a structure in which a soft magnetic alloy ribbon made of an Fe-based nanocrystalline alloy is wound and at least a portion of the magnetic path is cut. Cut cores are widely used because they are convenient for placing around a wired cable as a noise suppression member or for use in combination with a manufactured coil. Patent Document 1 describes that by polishing the cut surface of the cut core and then etching it to remove burrs from the cut surface, conduction in the stacking direction of the laminate is prevented, resulting in a cut core with low hysteresis loss.

[0004] On the other hand, attempts have been made to improve the corrosion resistance of soft magnetic alloy ribbons. For example, Patent Document 2 describes an invention of a soft magnetic alloy with excellent corrosion resistance obtained by heat treating an amorphous alloy containing 2 to 5 atomic % of Cr. Furthermore, Patent Document 3 describes an invention of a soft magnetic alloy ribbon with excellent corrosion resistance, in which an oxide film is formed on the surface of a primary microcrystalline alloy ribbon by heat treating the primary microcrystalline alloy ribbon in an atmosphere having an oxygen concentration of 6 to 18%. The heat treatments described in Patent Documents 2 and 3 are both performed for the purpose of precipitating microcrystals in the alloy ribbon. The heat treatment temperature is 550°C in Patent Document 2 and 420°C in Patent Document 3.

[0005] JP-A-9-27412, JP-A-3-24252, JP-A-2011-149045

[0006] In cut cores, the cut surfaces of the laminates serve as contact surfaces, and adjacent laminates are magnetically connected by tight contact through the contact surfaces. However, if rust occurs on the contact surfaces, the volume of the rust expands, creating gaps at the contact surfaces, disrupting magnetic continuity and potentially significantly reducing the magnetic permeability of the entire cut core. For this reason, special care must be taken to prevent rust from forming on the contact surfaces of cut cores.

[0007] Patent Documents 2 and 3 describe findings related to the corrosion resistance of soft magnetic alloy ribbons having a surface oxide film formed by heat treatment for the purpose of precipitating microcrystals in the alloy ribbon. On the other hand, in the contact surface of the cut core described in Patent Document 1, the surface oxide film formed by heat treatment is stripped away by processing, resulting in the formation of a contact surface without a surface oxide film. The findings described in Patent Documents 2 and 3 cannot be applied to the corrosion resistance of such a contact surface without a surface oxide film.

[0008] In the cut core manufacturing method described in Patent Document 1, a laminate formed by winding an alloy ribbon is subjected to a crystallization heat treatment, and then the laminate is impregnated with an adhesive and fixed. The heat resistance temperature of the adhesive is lower than the temperature of the crystallization heat treatment. If the laminate is cut after being fixed with the adhesive, and then heat treated again at the temperature of the crystallization heat treatment in order to provide a surface oxide film on the contact surfaces formed by the cutting, a new problem arises: the adhesive fixing the laminate is thermally decomposed.

[0009] On the other hand, when cutting and crystallization heat treatment are performed prior to fixing the laminate by impregnation with an adhesive, the laminate is cut before being fixed with an adhesive, which causes other problems, such as the cutting process being unable to be performed accurately or the position of the alloy ribbon being shifted during fixing, resulting in a loss of flatness of the contact surface.

[0010] The present invention was made in consideration of these problems specific to cut cores, and aims to provide a cut core that can maintain stable magnetic properties for a long period of time, even when it is difficult to form a surface oxide film on the contact surface of the cut core by heat treatment at the crystallization heat treatment temperature.

[0011] The gist and configuration of the present invention are as follows.

[0012] [1] A cut core including two or more laminates in which soft magnetic alloy ribbons are laminated in a thickness direction, wherein the laminates have at least one contact surface per laminate and are in contact with each other at the contact surfaces, and the soft magnetic alloy ribbons are Fe100-x-y-z-a-bSi ｘ B ｙ Cu ｚ Cr ａ M ｂ (wherein M represents at least one element selected from Nb and Mo, and x, y, z, a, and b represent the atomic percentages of Si, B, Cu, Cr, and M, respectively, and satisfy the following: 11.0≦x≦17.0, 5.0≦y≦10.0, 0.5≦z≦2.0, 0.5≦a≦4.0, 1.0≦b≦5.0, and 65≦100-x-y-z-a-b≦75.)

[0013] [2] The cut core according to the above-mentioned [1], wherein, at the contact surface, the soft magnetic alloy ribbon includes: a substrate having the above-mentioned component composition; an intermediate diffusion layer located outside the substrate, the intermediate diffusion layer being enriched in Si and depleted in Fe compared to the component composition of the soft magnetic alloy ribbon; and a surface oxide layer located outside the intermediate diffusion layer, the surface oxide layer being enriched in Si and depleted in Fe and Cr compared to the component composition of the soft magnetic alloy ribbon and newly containing O.

[0014] [3] The cut core according to the above [1] or [2], wherein the soft magnetic alloy ribbon contains an Fe-based nanocrystalline alloy.

[0015] [4] The cut core according to the above [3], wherein the oxygen concentration at the outermost surface of the surface oxide layer is 43.0 atomic % or more.

[0016] [5] The impedance at a frequency of 100 kHz is measured before and after immersing the cut core in ion-exchanged water for 100 hours, and the measured value before immersion is taken as Z Ａ , the measured value after immersion is Z Ｂ When this is done, (Z Ｂ -Z Ａ ) / Z Ａ The cut core according to any one of [1] to [4] above, wherein the absolute value of the impedance change rate ΔZ calculated by multiplying the absolute value by 100 is 15% or less.

[0017] [6] A cut core according to any of the above [1] to [5], comprising n laminates formed by cutting a single annular body formed by winding the soft magnetic alloy ribbon into a ring shape at n locations (where n is an integer of 2 or more) perpendicular to the circumferential direction of the annular body, wherein the cut surfaces of the (n x 2) faces of the n laminates serve as the contact surfaces, and two adjacent laminates of the n laminates come into contact with each other at the cut surfaces that serve as the contact surfaces, thereby forming a magnetic circuit as a whole.

[0018] [7] A cut core according to any of [1] to [5] above, comprising two or more laminates formed by providing a discontinuous portion in a part of the circumferential direction of one annular body formed by winding the soft magnetic alloy ribbon in a ring shape, at least one of two widthwise end faces of each of the two or more laminates being the contact surface, and two adjacent laminates of the two or more laminates being in contact with each other at the widthwise end face as the contact surface so that the discontinuous portions of each laminate do not overlap in the circumferential direction, thereby forming a magnetic circuit as a whole.

[0019] [8] A noise suppression member using the cut core according to any one of [1] to [7] above.

[0020] According to the present invention, rust is less likely to occur on the contact surface of the cut core than in the prior art, and therefore, the magnetic permeability of the cut core can be prevented from decreasing over a long period of time even in environments where rust is likely to occur, such as high temperature and humidity.

[0021] 1 is a graph showing the relationship between the distance from the surface of the contact surface of a soft magnetic alloy ribbon after grinding without heat treatment for crystallization and the ratio of elements. 2 is a graph showing the relationship between the distance from the surface of the contact surface of a soft magnetic alloy ribbon containing an Fe-based nanocrystalline alloy that has been ground after heat treatment for crystallization. 3 is a graph showing the relationship between the distance from the surface of the contact surface of a soft magnetic alloy ribbon containing an Fe-based nanocrystalline alloy that has been ground after heat treatment for crystallization and further subjected to heating treatment in air at 130° C. for 8 hours. 4 is a schematic diagram showing an example of one embodiment of a cut core. 5 is a schematic diagram showing an example of another embodiment of a cut core.

[0022] Hereinafter, embodiments of the present invention will be described in detail.

[0023] [Cut Core] In one embodiment, the present invention relates to a cut core including two or more laminates formed by laminating soft magnetic alloy ribbons in a thickness direction, and the laminates each have at least one contact surface, and the contact surfaces are in contact with each other.

[0024] The soft magnetic alloy ribbon used in the cut core according to the present invention can be produced, for example, by spraying a molten alloy having a predetermined composition onto the surface of a chill roll and rapidly solidifying it. The metal structure of the alloy ribbon obtained by this method may be amorphous or crystalline, or may be crystallized by heat treatment after rapid solidification. The thickness of the soft magnetic alloy ribbon is preferably 10 μm or more and 40 μm or less, since a thickness of 10 μm or more does not significantly reduce the packing ratio when the cut core is formed, and a thickness of 40 μm or less makes the ribbon less likely to break during winding. A more preferred thickness is 15 μm or more and 25 μm or less. The width of the soft magnetic alloy ribbon is not particularly limited, as it varies greatly depending on the application of the cut core. For example, in the case of a cut core for a noise filter, the width of the soft magnetic alloy ribbon is preferably 5.0 mm or more and 50 mm or less.

[0025] The cut core according to the present invention includes two or more laminates in which soft magnetic alloy ribbons are laminated in the thickness direction. By laminating the soft magnetic alloy ribbons in the thickness direction, the cross-sectional area of ​​the magnetic path of the cut core can be increased, thereby increasing the magnetic flux. The direction of the magnetic flux in the cut core coincides with the in-plane direction of the soft magnetic alloy ribbons. By configuring the magnetic circuit of the cut core with two or more laminates, it is possible to separate at least one laminate from the magnetic circuit and reintegrate the separated laminates to reconstruct the magnetic circuit. This makes it possible to later arrange the cut core around an already-wired cable or later combine the cut core with an already-manufactured coil.

[0026] In the cut core according to the present invention, the laminates have at least one contact surface per laminate. The contact surfaces of the laminates are preferably arranged parallel to the thickness direction of the soft magnetic alloy ribbons constituting the laminate. In such a case, a cross section of the soft magnetic alloy ribbon cut at the contact surface is exposed at the contact surface. When the cut core is separated, the magnetic circuit is interrupted at the contact surface. When the cut core is reassembled, the contact surfaces of the two or more laminates come into contact with each other, so that the entire cut core appears to be a continuous magnetic body, and the once interrupted magnetic circuit is re-established.

[0027] The laminate can be manufactured by bundling or winding soft magnetic alloy ribbons arranged in a predetermined shape into a roll. The ratio of the volume of the soft magnetic alloy ribbons to the total volume of the laminate, i.e., the packing rate, is preferably 65 vol% or more and 85 vol% or less, since the magnetic permeability does not decrease significantly if the packing rate is 65 vol% or more, and the residual strain does not increase if the packing rate is 85 vol% or less, and impregnation with an adhesive, which will be described later, is easy. The packing rate can be adjusted by the restraining force when bundling the soft magnetic alloy ribbons or the tension when winding them.

[0028] After producing the laminate, it is preferable to perform a heat treatment before impregnating with an adhesive to remove residual strain generated in the soft magnetic alloy ribbon. The heat treatment temperature is preferably 350° C. or higher and 700° C. or lower. The heat treatment atmosphere is preferably an inert atmosphere such as nitrogen or argon, or a vacuum.

[0029] The soft magnetic alloy ribbons constituting the heat-treated laminate are impregnated with an adhesive to fix the soft magnetic alloy ribbons and maintain the shape of the laminate. As the adhesive, organic adhesives such as acrylic resins, epoxy resins, polyimide resins, silicone resins, and silicone elastomers can be used, and inorganic adhesives such as water glass, bentonite solvents, alumina solvents, and silica solvents can be used.

[0030] The viscosity of the adhesive is preferably, for example, 2000 mPa·s or less in order to allow the adhesive to penetrate evenly into the voids of the soft magnetic alloy ribbons. If the viscosity of the adhesive is higher than 2000 mPa·s, the adhesive can be allowed to penetrate evenly into the voids of the soft magnetic alloy ribbons by adjusting the viscosity by adjusting the temperature or adding a diluent such as an organic solvent, or by performing vacuum impregnation. In addition, the adhesive may be applied to the surface before laminating the soft magnetic alloy ribbons.

[0031] When the adhesive used is a thermosetting resin, the adhesive is impregnated into the voids of the soft magnetic alloy ribbons, and then the entire laminate is heated to harden the adhesive. For example, in the case of an epoxy resin, the hardening temperature is preferably 50° C. or higher and 180° C. or lower.

[0032] Cut surfaces and discontinuous portions can be created by cutting the laminate fixed with adhesive. For example, a wet peripheral slicer equipped with a cutting wheel can be used for the cutting process. For example, a GC grinding wheel using a resinoid binder is suitable for the cutting wheel. The GC grinding wheel used preferably has a bond strength of K to P, a grit size of 80 to 150, and a thickness in the range of approximately 0.5 to 1.5 mm.

[0033] The cut surface or the surface of the discontinuous portion can be polished to make the surface smooth. In particular, when the cut surface or the surface of the discontinuous portion is used as the contact surface of the present invention, the arithmetic mean roughness Ra of the polished surface is preferably 0.70 μm or less, and the maximum height roughness Rz is preferably 10 μm or less. This allows the contact surfaces to closely contact each other, reducing gaps and preventing the flow of magnetic flux, thereby suppressing the decrease in magnetic permeability caused by forming a cut core. The arithmetic mean roughness Ra of the polished surface is more preferably 0.35 μm or less, and even more preferably 0.16 μm or less. The maximum height roughness Rz is more preferably 5.0 μm or less. The lower limits of the arithmetic mean roughness Ra and the maximum height roughness Rz are not particularly limited, but should be within the range possible for mass production.

[0034] The flatness of the polished surface is preferably 2.5 μm or less. This allows the contact surfaces to adhere closely to each other, reducing gaps and preventing the flow of magnetic flux, thereby suppressing the decrease in magnetic permeability caused by forming a cut core. There is no particular limit to the lower limit of the flatness of the polished surface, but it should be within the range possible for mass production. When two or more contact surfaces are provided per laminate, it is preferable to appropriately adjust the angle between the two or more contact surfaces so that no gaps are generated at the contact surfaces when assembled into a cut core.

[0035] The area ratio of the cross section of the soft magnetic alloy ribbon exposed at the contact surface of the laminate formed by cutting and polishing depends on the packing ratio of the soft magnetic alloy ribbon in the laminate. For example, when the thickness of the soft magnetic alloy ribbon is 18 μm and the thickness of the adhesive layer is 4 to 5 μm on average, the area ratio of the cross section of the soft magnetic alloy ribbon at the contact surface is about 75 to 80%. In this case, the cross section of the soft magnetic alloy ribbon occupies most of the contact surface, so that magnetic continuity is always maintained even when the positions of two or more laminates in contact at the contact surface are shifted in a direction parallel to the contact surface.

[0036] In the cut core according to the present invention, it is preferable that the shapes and sizes of the two contact surfaces of the two or more laminations that come into contact with each other are identical, and that the shapes of the two contact surfaces are made to fit together perfectly except for discontinuous portions, thereby reducing magnetic flux leakage from the magnetic path and increasing the magnetic permeability of the reconstructed magnetic circuit.

[0037] Even if the cut surface or the surface of the discontinuous portion produced by cutting is not used as the contact surface of the present invention, it is preferable to remove burrs produced on the cut surface or the surface of the discontinuous portion by polishing in order to improve the corrosion resistance of the surface. In this case, it is preferable to finish the polished surface to have the same level of arithmetic mean roughness Ra and maximum height roughness Rz as the contact surface.

[0038] [Component Composition] The soft magnetic alloy ribbon used in the cut core according to the present invention is Fe100-x-y-z-a-bSi ｘ B ｙ Cu ｚ Cr ａ M ｂ where M represents at least one element selected from Nb and Mo, and x, y, z, a, and b represent the atomic percentages of Si, B, Cu, Cr, and M, respectively, and satisfy the following conditions: 11.0≦x≦17.0, 5.0≦y≦10.0, 0.5≦z≦2.0, 0.5≦a≦4.0, 1.0≦b≦5.0, and 65≦100-x-y-z-a-b≦75. Unless otherwise specified, the component compositions in this specification are expressed in atomic percentages.

[0039] Si, together with B, is an element that promotes the amorphization of Fe-based alloys. The atomic percentage x of Si is set to 11.0 or more to promote amorphization, while the magnetization is not significantly impaired if it is 17.0 or less. Similarly, the atomic percentage y of B is set to 5.0 or more to promote amorphization, while the magnetization is not significantly impaired if it is 10.0 or less. Therefore, the atomic percentage y of B is set to 5.0 or more to 10.0.

[0040] Cu is an element that tends to separate from Fe and forms nuclei during crystallization heat treatment to promote the refinement of crystals. If the atomic percentage z of Cu is 0.5 or more, the refinement of crystals is promoted, and if it is 2.0 or less, the magnetization is not significantly impaired. Therefore, the atomic percentage z of Cu is set to 0.5 or more and 2.0 or less.

[0041] Cr is an element that has the effect of increasing the corrosion resistance of the contact surface. If the atomic percentage a of Cr is 0.5 or more, the corrosion resistance of the contact surface is increased, and if it is 4.0 or less, the magnetization is not significantly impaired, so the atomic percentage a of Cr is set to 0.5 or more and 4.0 or less. From the viewpoint of improving corrosion resistance, the atomic percentage a of Cr is preferably set to 2.5 or more.

[0042] The symbol M represents at least one element selected from Nb and Mo. The atomic percentage b of M represents the sum of the atomic percentages of Nb and Mo. Nb and Mo are elements that increase the crystallization temperature, suppress grain growth, and promote refinement of crystals. If the atomic percentage b of M is 1.0 or more, refinement of crystals is promoted, and if it is 5.0 or less, magnetization is not significantly impaired, so it is set to 1.0 or more and 5.0 or less.

[0043] Fe is the main component that forms the base of the soft magnetic alloy ribbon according to the present invention, and is the only element in the component composition that is the source of ferromagnetism. In the above-mentioned component composition notation, the atomic percentage of Fe is expressed as the difference obtained by subtracting the total atomic percentage of elements other than Fe from 100. If the atomic percentage of Fe is 65 or more, the magnitude of magnetization is sufficient, and if it is 75 or less, the function of the added element is exhibited without impairing the balance with other added elements, so it is set to 65 or more and 75 or less.

[0044] The cut core according to the present invention has the above-mentioned component composition, which improves the corrosion resistance of the contact surface compared to the cut core according to the prior art. This prevents rust from forming on the contact surface, so that the magnetic coupling due to the close contact at the contact surface is maintained even after long-term use, and the magnetic permeability of the magnetic circuit does not decrease.

[0045] [Intermediate Diffusion Layer and Surface Oxide Layer] In a preferred embodiment, the cut core according to the present invention includes, at the contact surface, a substrate having the above-described composition of the soft magnetic alloy ribbon; an intermediate diffusion layer located outside the substrate and enriched in Si and depleted in Fe compared to the composition of the soft magnetic alloy ribbon; and a surface oxide layer located outside the intermediate diffusion layer and newly containing O (oxygen), enriched in Si, and depleted in Fe and Cr compared to the composition of the soft magnetic alloy ribbon. In this specification, the phrase "the intermediate diffusion layer is located outside the substrate" refers to the intermediate diffusion layer being located on the surface of the substrate or farther from the center of the substrate as viewed from the substrate. Similarly, in this specification, the phrase "the surface oxide layer is located outside the intermediate diffusion layer" refers to the surface of the intermediate diffusion layer or farther from the center of the substrate as viewed from the intermediate diffusion layer located outside the substrate.

[0046] The intermediate diffusion layer and the surface oxidation layer will be described below using actual data. FIG. 1 is a graph showing the relationship between the distance from the surface and the ratio of elements at the contact surface of a soft magnetic alloy ribbon according to Example 3 of the present invention, which is shown in Example 1 described later. The surface of the side not in contact with the chill roll was polished with No. 600 abrasive paper without heat treatment for crystallization, thereby removing any products produced during ribbon production. The ratios of elements were measured by glow discharge optical emission spectroscopy (GD-OES). The composition of the soft magnetic alloy ribbon according to Example 3 was Fe: 69.5%, Si: 15.5%, B: 7.0%, Cu: 1.0%, Cr: 4.0%, and Nb: 3.0%. The horizontal axis of FIG. 1 represents the distance (nm) from the surface, and the vertical axis represents the ratio (at %) of elements at each distance. FIG. 1 also shows the ratios of Fe, Si, Cr, and O (oxygen) among the measured ratios of elements. Of these, for Fe, the analytical value is multiplied by 1 / 2 (Fe / 2) and displayed.

[0047] According to FIG. 1 , in the region indicated by symbol C at a distance of 50 nm or more from the surface of the soft magnetic alloy ribbon of Example 3, the ratios of elements are almost constant. This region C corresponds to the substrate having the above-described composition. The region indicated by symbol B at a distance of 8 nm or more and 50 nm or less from the surface is located outside the substrate, and the ratio of Si gradually increases and the ratio of Fe gradually decreases as the distance from the surface approaches. This region B corresponds to an intermediate diffusion layer in which Si is enriched and Fe is depleted compared to the composition of the soft magnetic alloy ribbon. The region indicated by symbol A at a distance of 0 nm or more and 8 nm or less from the surface is located outside the intermediate diffusion layer, and the ratios of Si and O are extremely high and the ratios of Fe and Cr are reduced compared to the substrate. This region A corresponds to a surface oxide layer that additionally contains O (oxygen) compared to the composition of the soft magnetic alloy ribbon, and is enriched in Si and depleted in Fe and Cr.

[0048] In the graph showing the change in element ratios exemplified in FIG. 1 , the method for determining the position of the boundary between the substrate (region C) and the intermediate diffusion layer (region B) and the position of the boundary between the intermediate diffusion layer (region B) and the surface oxide layer (region A) is not particularly limited. For example, the point on the graph where the element ratio value changes from the region of the substrate, where the element ratio value is constant and the same value as the component composition of the soft magnetic alloy ribbon, to increase or decrease can be determined as the boundary between the substrate and the intermediate diffusion layer. Furthermore, for example, the point where the second derivative coefficient of the element ratio value with respect to the distance from the surface changes significantly can be determined as the boundary between the intermediate diffusion layer and the surface oxide layer. If it is not possible to clearly determine these points for all elements, these points may be determined using the ratio of at least one element among the element ratios shown in the graph.

[0049] In this preferred embodiment, the mechanism by which the surface oxide layer and the intermediate diffusion layer are formed on the contact surface is not clearly understood, but the following is likely to be the case. As described above, the contact surface is formed by processing a laminate of soft magnetic alloy ribbons by cutting, polishing, etching, or the like. For example, when wet polishing is performed, the contact surface formed during the polishing process comes into contact with water or other media used for polishing and cleaning. Furthermore, when the polished surface is dried after cleaning, the contact surface comes into contact with heated air. It is believed that O taken into the surface of the contact surface during these processes generates oxides of Si, resulting in the formation of a surface oxide layer that contains O, is concentrated in Si, and is depleted in Fe and Cr. The O contained in the surface oxide layer is not contained in the substrate, but is taken into the soft magnetic alloy ribbon after the contact surface is formed. On the other hand, it is believed that the intermediate diffusion layer is formed as a result of the diffusion of Si and O driven by the difference in concentration of Si and O between the substrate and the surface oxide layer.

[0050] Although the mechanism by which rusting of the contact surface is prevented in this preferred embodiment is not clearly understood, it is believed that the corrosion resistance of the contact surface is improved and rusting is prevented by the presence of an intermediate diffusion layer (area B) outside the base material (area C) and a surface oxide layer (area A) further outside that. Note that the surface oxide layer and intermediate diffusion layer are deficient in Cr compared to the base material, and therefore the above-mentioned rust prevention effect is believed to be due to a mechanism different from rust prevention by the formation of a passive film, which is generally known for Fe-Cr alloys.

[0051] Regarding the cut core according to the present invention, the processing method for forming the contact surface on the laminate may be any type as long as the substrate is exposed. As described above, the processing of the laminate can be performed by cutting, polishing, etching, etc., but the processing method is not limited to these.

[0052] [Fe-based nanocrystalline alloy] In a preferred embodiment, in the cut core according to the present invention, the soft magnetic alloy ribbon contains an Fe-based nanocrystalline alloy.

[0053] The Fe-based nanocrystalline alloy is a soft magnetic alloy that can be obtained by spraying a molten alloy containing Fe as a main component onto the surface of a chill roll, rapidly solidifying the quenched ribbon, and then heat-treating the quenched ribbon. The quenched ribbon before heat treatment is in an amorphous state due to the action of Si and B contained in the component composition in the above-mentioned predetermined proportions. By heat-treating the quenched ribbon, fine crystals with a grain size of more than 0 nm and not more than 60 nm are crystallized in the amorphous base. This results in a soft magnetic alloy ribbon with a fine crystalline structure and uniform grain size, and excellent soft magnetic properties. Furthermore, in the Fe-based nanocrystalline alloy, uncrystallized portions remain in an amorphous state even after heat treatment.

[0054] The heat treatment temperature for crystallizing the quenched ribbon is preferably 350° C. to 700° C. The heat treatment is preferably carried out in an inert atmosphere such as nitrogen or argon, or in a vacuum.

[0055] The heat treatment of the quenched ribbons is preferably carried out after the quenched ribbons are stacked. This is because the soft magnetic alloy ribbons after the heat treatment of the quenched ribbons are brittle and easily cracked, making them difficult to handle. By stacking the quenched ribbons in advance to form a laminate and then carrying out the heat treatment, damage to the laminate due to cracking of the soft magnetic alloy ribbons can be prevented. By carrying out the heat treatment for crystallization, it is also possible to simultaneously remove residual strain introduced during the production of the quenched ribbons and the assembly of the laminate. When carrying out the heat treatment after stacking the quenched ribbons, it is preferable to fix the laminate using a jig or the like to prevent it from separating into the original quenched ribbons.

[0056] As in the case of a soft magnetic alloy ribbon that is not subjected to heat treatment for crystallization, even when the soft magnetic alloy ribbon contains an Fe-based nanocrystalline alloy, it is preferable from the viewpoint of corrosion resistance that the soft magnetic alloy ribbon at the contact surface comprises a substrate, an intermediate diffusion layer located outside the substrate, and a surface oxidation layer located outside the intermediate diffusion layer.

[0057] Below, the intermediate diffusion layer and the surface oxidation layer when the soft magnetic alloy ribbon contains an Fe-based nanocrystalline alloy will be described using actual data. FIG. 2 is a graph showing the relationship between the distance from the surface at the contact surface and the ratio of elements for a soft magnetic alloy ribbon containing an Fe-based nanocrystalline alloy, which was crystallized by heat treatment of the soft magnetic alloy ribbon of Example 3 shown in Example 2 described later at 550°C for 90 minutes in an argon atmosphere. As in FIG. 1 , the ratio of elements was measured by glow discharge optical emission spectroscopy (GD-OES). As in FIG. 1 , the soft magnetic alloy ribbon containing an Fe-based nanocrystalline alloy shown in FIG. 2 also shows a region C corresponding to the substrate, a region B corresponding to the intermediate diffusion layer, and a region A corresponding to the surface oxidation layer. The boundary between the substrate and the intermediate diffusion layer is not very clear, but appears to be located approximately 50 nm from the surface. As in FIG. 1 , the boundary between the intermediate diffusion layer and the surface oxidation layer is located 8 nm from the surface. Furthermore, the ratio of O at the outermost surface is higher than that in FIG. 1, and conversely, the ratio of Si is lower than that in FIG.

[0058] [Oxygen Concentration at the Outermost Surface of the Surface Oxidized Layer] In a preferred embodiment, in the cut core according to the present invention, the soft magnetic alloy ribbon contains an Fe-based nanocrystalline alloy, and the oxygen concentration at the outermost surface of the surface oxide layer is 43.0 atomic % or more. When the oxygen concentration at the outermost surface of the surface oxide layer is 43.0 atomic % or more, the corrosion resistance of the contact surface of the laminate is particularly excellent. Although there is no particular upper limit for the oxygen concentration at the outermost surface of the surface oxide layer, it is preferably 60.0 atomic % or less.

[0059] The method for increasing the oxygen concentration at the outermost surface of the surface oxide layer to 43.0% or more is not particularly limited. For example, in the case of a soft magnetic plywood ribbon containing an Fe-based nanocrystalline alloy having the component composition specified in the present invention and obtained by heat treatment for crystallization, the oxygen concentration at the outermost surface of the surface oxide layer can be increased to 43.0% or more by carrying out a heating treatment in which a laminate having contact surfaces formed thereon after the heat treatment is held in air at 130°C for 8 hours. The temperature of this heating treatment is lower than the heat resistance temperature of the adhesive that fixes the laminate.

[0060] As shown in Fig. 2, in the case of a soft magnetic plywood ribbon containing an Fe-based nanocrystalline alloy that has been heat-treated for crystallization, the oxygen concentration at the outermost surface of the surface oxide layer immediately after the contact surface is formed is less than 40.0 atomic %, and it is difficult to increase the oxygen concentration to 43.0% or more. In addition, in the case of a soft magnetic plywood ribbon containing an Fe-based nanocrystalline alloy that has been heat-treated for crystallization in an argon atmosphere and before the contact surface is formed, the oxygen concentration at the outermost surface of the surface oxide layer is approximately 37.0 atomic %, and it is also difficult to increase the oxygen concentration to 43.0% or more. Therefore, in order to increase the oxygen concentration at the outermost surface of the surface oxide layer to 43.0% or more, it is preferable to perform a heating treatment in which the laminate containing the Fe-based nanocrystalline alloy obtained by the heat treatment for crystallization and the contact surface formed after the heat treatment is held in air at 130 ° C. for 8 hours.

[0061] If the temperature of the heat treatment performed in the atmosphere is too low, the oxygen concentration at the outermost surface of the surface oxide layer cannot be increased to 43.0 atomic % or more. Therefore, the heat treatment temperature is preferably 100°C or higher, more preferably 120°C or higher. On the other hand, if the heat treatment temperature is too high, the oxygen concentration at the outermost surface of the surface oxide layer will exceed 60.0 atomic %. Therefore, the heat treatment temperature is preferably 160°C or lower, more preferably 140°C or lower. The preferred treatment time for the heat treatment should be the time required to achieve an oxygen concentration of 43.0 atomic % or more at the outermost surface of the surface oxide layer within the above preferred temperature range, taking into account the heat capacity of the laminate and other conditions.

[0062] FIG. 3 is a graph showing the relationship between the distance from the surface at the contact interface and the ratio of elements in a soft magnetic alloy ribbon containing an Fe-based nanocrystalline alloy, which was crystallized by heat treatment at 550°C for 90 minutes in an argon atmosphere for the soft magnetic alloy ribbon of Inventive Example 14 shown in Example 2 below. The soft magnetic alloy ribbon was further subjected to a heating treatment of holding the soft magnetic alloy ribbon in air at 130°C for 8 hours. The component composition of the soft magnetic alloy ribbon of Inventive Example 14 is the same as that of the soft magnetic alloy ribbon of Inventive Example 3 shown in FIGS. 1 and 2. As in FIGS. 1 and 2, the component ratios were measured by glow discharge optical emission spectroscopy (GD-OES). The component ratios in the intermediate diffusion layer of this sample are not significantly different from those in the intermediate diffusion layer shown in FIG. 2. On the other hand, in the surface oxidation layer of FIG. 3, the oxygen concentration at the outermost surface reaches 44.6 atomic %, while the Si concentration at the outermost surface is lower than that shown in FIG. 2. Furthermore, the boundary between the intermediate diffusion layer and the surface oxide layer is located 10 nm away from the surface, and the thickness of the surface oxide layer is slightly increased compared to Figures 1 and 2. As shown in Example 3 described below, in Example 14, in which the oxygen concentration at the outermost surface of the surface oxide layer is 43.0 atomic % or more, the corrosion resistance of the contact surface of the laminate was particularly superior to that of Comparative Example 2, in which the oxygen concentration was 42.6 atomic %.

[0063] [Rate of Impedance Change] In a preferred embodiment, the cut core according to the present invention has a soft magnetic alloy ribbon containing an Fe-based nanocrystalline alloy, and the impedance at a frequency of 100 kHz is measured before and after immersion of the cut core in ion-exchanged water for 100 hours, and the measured value before immersion is expressed as Z Ａ , the measured value after immersion is Z Ｂ When this is done, (Z Ｂ -Z Ａ ) / Z ＡThe absolute value of the impedance change rate ΔZ calculated by multiplying the surface oxidized layer and the intermediate diffusion layer by 100 is 15% or less. Generally, when a cut core is immersed in ion-exchanged water, red rust forms on the contact surface. This causes the impedance after immersion to decrease compared to the impedance before immersion. In this case, the impedance change rate ΔZ is a negative value, and the larger the absolute value of ΔZ, the greater the degree of rusting. In the cut core according to the present invention, the corrosion resistance of the contact surface is improved by the presence of the surface oxide layer and intermediate diffusion layer, so the absolute value of the impedance change rate ΔZ under the above evaluation conditions does not exceed 15%. More preferably, the absolute value of the impedance change rate ΔZ is 12% or less.

[0064] The temperature of the ion-exchanged water when the cut core is immersed is not particularly limited, but the temperature of the ion-exchanged water is preferably room temperature. Room temperature is, for example, 25° C. Furthermore, the temperature when measuring the impedance of the cut core is not particularly limited, but the temperatures of the cut core and the surrounding environment are preferably room temperature.

[0065] [Cut Surface Contact Type Cut Core] In a preferred embodiment, the cut core according to the present invention includes n laminates formed by cutting an annular body formed by winding a soft magnetic alloy ribbon into an annular shape at n locations (n ​​is an integer of 2 or more) perpendicular to the circumferential direction of the annular body, the (n × 2) cut surfaces of the n laminates being contact surfaces, and two adjacent laminates among the n laminates being in contact with each other at the cut surfaces serving as contact surfaces, thereby forming a magnetic circuit as a whole. Fig. 4 is a schematic diagram showing an example of the shape of the cut core according to this preferred embodiment.

[0066] The cut core 1 illustrated in Fig. 4 includes two laminates 2 obtained by dividing a single annular body formed by annularly winding a soft magnetic alloy ribbon into two equal parts. Each laminate 2 has two cut surfaces perpendicular to the circumferential direction. The soft magnetic alloy ribbon can be wound in multiple layers around the outer circumferential surface of a cylindrical jig while applying tension to the long soft magnetic alloy ribbon.

[0067] The shape of the cut core before cutting may be any shape as long as it is closed annularly, and may be any shape such as a circle, the shape of an athletics track, a rectangle with rounded corners, etc. However, since there is a limit to the deformability of a soft magnetic alloy ribbon in bending processing, the radius of curvature of the curved surface needs to be equal to or greater than the limit.

[0068] As shown in FIG. 4 , the cut surface can be provided, for example, perpendicular to the circumferential direction of the soft magnetic alloy ribbon. In this specification, the "circumferential direction" refers to the direction in which the soft magnetic alloy ribbon is wound. More strictly, it refers to the direction of the tangent of the soft magnetic alloy ribbon at the position where the soft magnetic alloy ribbon contacts the outermost surface of the already wound laminate. By using the cut surface perpendicular to the circumferential direction as the contact surface, the area of ​​the contact surface can be reduced. In addition, the fact that the contact surface is perpendicular to the circumferential direction is convenient when applying a force perpendicular to the contact surface to achieve close contact. However, the direction of the cut surface does not necessarily have to be perpendicular to the circumferential direction and can be provided in any direction.

[0069] Two or more laminations 2 contact each other at their contact surfaces 2a, forming a magnetic circuit as a whole. The magnetic circuit is reconstructed by closing the magnetic path formed by successive laminations in a ring shape. In Fig. 4, the cut core 1 is made up of two laminations 2, but the number of laminations 2 may be three or more. Also, in Fig. 4, the two laminations 2 making up the cut core 1 are the same size, but the magnetic path length of one of the two laminations 2 may be longer and the magnetic path length of the other may be shorter.

[0070] [End Face Contact Type Cut Core] In a preferred embodiment, the cut core according to the present invention includes two or more laminates formed by providing a discontinuous portion at a circumferential portion of a single annular body formed by winding a soft magnetic alloy ribbon in an annular shape, at least one of two widthwise end faces of each of the two or more laminates serves as a contact surface, and two adjacent laminates of the two or more laminates contact each other at the widthwise end face as the contact surface so that the discontinuous portions do not overlap in the circumferential direction, thereby forming a magnetic circuit as a whole. Fig. 5 is a schematic diagram showing an example of the shape of the cut core according to this preferred embodiment.

[0071] In the cut core 1 illustrated in FIG. 5 , each laminate 2 has one discontinuous portion 2 b. In this specification, the term "discontinuous portion" refers to a portion where the continuity in the winding direction of the soft magnetic alloy ribbon wound in an annular shape is broken due to the absence of a portion of the annular body. The width of the discontinuous portion 2 b need only be large enough to allow a cable or the like to pass through. The magnetic path of one laminate 2 is interrupted at the discontinuous portion 2 b. By providing the discontinuous portion 2 b in the laminate 2, when the two laminates 2 are separated, for example, a cable can be moved from the outside to the inside of the annular laminate through the discontinuous portion 2 b.

[0072] In this preferred embodiment, the discontinuous portion 2b can be provided in the laminate 2 by, for example, impregnating a soft magnetic alloy wound into an annular shape with an adhesive, fixing the soft magnetic alloy, and then cutting the soft magnetic alloy to remove a portion of the laminate 2. Alternatively, the discontinuous portion 2b can be provided in an annular shape by laminating flat soft magnetic alloy ribbons that have been cut into a predetermined shape, and then bending the entire laminate.

[0073] In this preferred embodiment, the discontinuous portion 2 b is not a contact surface. The pair of cross sections constituting the discontinuous portion 2 b does not need to be perpendicular to the winding direction of the soft magnetic alloy ribbon, and may have any angle with respect to the winding direction. However, from the viewpoint of ease of movement of the cable, it is preferable that the pair of cross sections constituting the discontinuous portion 2 b are parallel to each other.

[0074] The laminates 2 have at least one of two widthwise end faces as a contact surface 2a, and the laminates 2 are in contact with each other at the contact surface 2a so that the discontinuous portions 2b do not overlap, thereby forming a magnetic circuit as a whole. The "widthwise end faces" of the laminate 2 refer to the two end faces perpendicular to the central axis 2c of the winding in the laminate 2 obtained by winding the soft magnetic alloy ribbon into a ring shape. As a result of winding the soft magnetic alloy ribbon, the widthwise ends of the soft magnetic alloy ribbon are stacked at the end faces of the laminate. By bringing two or more laminates 2 into contact with each other at the contact surface 2a so that the discontinuous portions 2b do not overlap, the magnetic path interrupted by the discontinuous portions 2b in one laminate 2 is connected by the adjacent laminate 2, thereby reconstructing a closed magnetic circuit as a whole. As described above, it is preferable to polish the contact surface 2a to smooth the contact surface 2a. The contact surface 2a does not need to be strictly perpendicular to the central axis 2c of the winding, and may have a slight angle with respect to the winding direction.

[0075] In Figure 5, the number of laminates 2 constituting the cut core 1 is two, but the number of laminates 2 may be three or more. In Figure 5, the two laminates 2 constituting the cut core 1 are the same size, but one of the two laminates 2 may be thicker and the other thinner. When the number of laminates 2 is three or more, the widthwise end faces of the intermediate laminate 2 perpendicular to the central axis of winding become contact surfaces 2a. Furthermore, when the number of laminates 2 is three or more, it is sufficient that the discontinuous portions 2b do not overlap between two adjacent laminates 2 that are in contact with each other, but the discontinuous portions 2b may overlap between laminates 2 that are located farther apart.

[0076] [Case] ​​The cut core can be housed in a case (not shown) for use. In this case, it is preferable to house one laminate 2 in one case so that all of the contact surfaces 2a of the laminate 2 are exposed from the case. This allows the contact surfaces 2a of the laminate 2 to come into contact with each other by fitting the cases together, thereby reconfiguring the magnetic circuit. Materials that can be used to form the case include PBT (polybutylene terephthalate), PA (polyamide), PPS (polyphenylene sulfide), ABS (acrylonitrile butadiene styrene), ASA (acrylonitrile styrene acrylic rubber), silicone resins, silicone elastomers, etc.

[0077] The case preferably includes a load mechanism that can tightly press the opposing contact surfaces 2 a together by fitting them together. The load mechanism may have any structure as long as it can maintain tight contact between the contact surfaces 2 a. Examples of the load mechanism that can be included in the case include a leaf spring, protrusion, or band made of resin or metal.

[0078] If the load applied to the contact surface 2a by the load mechanism provided in the case is at least five times the mass of the laminate 2, it is possible to prevent the contact surface 2a from separating due to vibrations or impacts during use of the cut core 1. If the load is no more than 100 times the mass of the laminate 2, it is possible to prevent the soft magnetic properties from being impaired due to distortion caused by deformation of the laminate 2. Therefore, it is preferable that the load applied to the contact surface 2a be at least five times but no more than 100 times the mass of the laminate 2. The means for applying a load to the contact surface 2a does not necessarily have to be by fitting the case together, and a simple means such as fastening two or more laminates 2 together with vinyl tape or a cable tie may be used.

[0079] [Anti-Noise Member] In another embodiment, the present invention relates to an anti-noise member. The anti-noise member according to the present invention is a noise countermeasure member that uses the cut core according to the present invention. As described above, the cut core 1 according to the present invention can be separated or combined at the contact surface 2a. When the cut core 1 is separated into two or more laminated bodies 2, the laminated bodies 2 can be subsequently placed at any position on, for example, an already-wired cable. Then, by combining the laminated bodies 2, the magnetic circuit that was interrupted by the separation can be easily reconstituted.

[0080] As described above, the cut core 1 according to the present invention has excellent corrosion resistance at the contact surface 2a, and therefore can maintain its noise-reducing performance for a long period of time even after being installed as a noise suppression member around cables, etc. Therefore, the noise suppression member according to the present invention can be suitably used, for example, in electrical equipment or electronic devices in which the noise suppression member cannot be easily replaced after installation.

[0081] The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

[0082] [Example 1] (Evaluation of Alloy Ribbons) Molten alloys having the composition of Inventive Examples 1-11 and Comparative Example 1 listed in Table 1 were quenched by a single roll method to obtain alloy ribbons made of Fe-based amorphous alloys with a width of 10 mm and a thickness of 23 μm. The obtained alloy ribbons were cut into lengths of 15 mm, and the surface on the side not in contact with the chill roll, i.e., the free surface, was polished with No. 600 abrasive paper to remove any products produced during ribbon production, thereby preparing test specimens simulating contact surfaces exposed by processing. In addition to these test specimens, test specimens having the composition of Inventive Examples 12-22 and Comparative Example 2 listed in Table 1 were produced by the same process, and after exposing the contact surfaces, test specimens were also prepared by heating the exposed surfaces in air at 130°C for 8 hours.

[0083] Next, all the obtained test pieces were immersed in ion-exchanged water at 25°C for 24 hours, and the polished surfaces of the test pieces after immersion were visually observed to evaluate the corrosion resistance based on the presence or absence of discoloration and rust. The evaluation results were as follows: no discoloration at all was rated "excellent," whitish discoloration but no red rust was rated "good," red rust occurred on 20% or less of the entire observed surface was rated "passing," and red rust occurred on more than 20% of the entire observed surface was rated "failing." The evaluation results are shown in Table 1.

[0084]

[0085] According to the corrosion resistance evaluation results shown in Table 1, the specimens of Examples 1 to 11, which had a Cr content of 0.5 to 4.0 atomic percent, exhibited less rusting on the polished surface simulating the contact surface of the cut core according to the present invention, than the specimen of Comparative Example 1, which contained no Cr. In particular, when the Cr content was 2.5 or more atomic percent, the evaluation results were "good" or "excellent," and no red rust was observed. Furthermore, the specimens of Examples 12 to 22, which had a Cr content of 0.5 to 4.0 atomic percent and were subjected to heating treatment in air at 130°C for 8 hours after polishing, showed no discoloration or rusting, unlike the specimen of Comparative Example 2, which did not contain Cr and exhibited red rust.

[0086] [Example 2] (Oxygen Concentration at the Outermost Surface of the Surface Oxidized Layer) Alloy ribbons having the component compositions of Inventive Examples 1-3 and Comparative Example 1 listed in Table 1 were produced by the same process as in Example 1, and were crystallized by heat treatment at 550°C for 90 minutes in an argon atmosphere to obtain soft magnetic alloy ribbons containing an Fe-based nanocrystalline alloy. The obtained alloy ribbons were cut into lengths of 15 mm, and the surface not in contact with the chill roll, i.e., the free surface, was polished with No. 600 abrasive paper to remove any products produced during ribbon production, thereby obtaining test specimens simulating contact surfaces exposed by processing. In addition to these test specimens, test specimens having the component compositions of Inventive Examples 12-14 and Comparative Example 2 listed in Table 1 were produced by the same process, and after the contact surfaces were exposed, test specimens were also prepared by heating the exposed surfaces in air at 130°C for 8 hours.

[0087] Next, the oxygen concentration on the polished outermost surface of each test piece was measured by glow discharge optical emission spectroscopy (GD-OES). For the measurement, a GD-Profiler 2 manufactured by Horiba, Ltd. was used. The measurement results are shown in Table 2.

[0088]

[0089] According to the measurement results shown in Table 2, in the soft magnetic plywood ribbon containing the Fe-based nanocrystalline alloy that had been subjected to heat treatment for crystallization, the oxygen concentration at the outermost surface of the surface oxide layer of the test piece immediately after the contact surface was exposed was 39.5 atomic % or less. On the other hand, in the test piece that had been subjected to heat treatment in air at 130°C for 8 hours after the contact surface was exposed, the oxygen concentration at the outermost surface of the surface oxide layer was 43.0 atomic % or more, except for Comparative Example 2. In contrast, the oxygen concentration at the outermost surface of the surface oxide layer of the test piece of Comparative Example 2 was 42.6 atomic %.

[0090] [Example 3] (Evaluation of magnetic core) Using the same method as in Example 1, a molten alloy having the composition shown in Table 1 was quenched by a single roll method to obtain an alloy ribbon made of an Fe-based amorphous alloy with a width of 10 mm and a thickness of 23 μm. The obtained alloy ribbon was wound into a cylindrical laminate with an outer diameter of 28.5 mm, an inner diameter of 18.0 mm, and a height of 10 mm. However, the laminate according to this example did not have the discontinuous portion 2b shown in FIG. 4, and the entire laminate was continuous without any seams. Next, the cylindrical laminate made of the Fe-based amorphous alloy was heat-treated at 550 ° C. for 90 minutes in an argon atmosphere to crystallize it, and a magnetic core made of an Fe-based nanocrystalline alloy was produced.

[0091] Next, the obtained magnetic core was immersed in a solution in which epoxy resin 801N manufactured by Mitsubishi Chemical and curing agent ST12 were mixed in a specified ratio, and the solution was evacuated to -0.1 MPaG and held for 10 minutes, after which the atmospheric pressure was released and the magnetic core was impregnated with the epoxy resin. The magnetic core impregnated with the epoxy resin was left at room temperature for 24 hours, and then held in the air at 80°C for 3 hours to cure the epoxy resin and fix the Fe-based nanocrystalline alloy ribbon.

[0092] Next, the end face perpendicular to the central axis of the winding of the magnetic core, i.e., the plane parallel to the thickness direction of the soft magnetic alloy ribbon, was polished. The polished plane of the magnetic core corresponds to the contact surface 2a in the end-face contact type cut core 1 shown in FIG. 5. A Tegramin-25 manufactured by Struers was used to polish the plane. The polishing conditions were a revolution of 100 rpm, a rotation of 50 rpm in the same direction, and a load of 15 N. The grit of the abrasive paper was gradually reduced from 220 to 320, 500, 800, 1200, and 2000, and magnetic cores (Invention Examples 1-11 and Comparative Example 1) were prepared by polishing the plane on one side. In addition, magnetic cores (Invention Examples 12-22 and Comparative Example 2) were also prepared by heating the obtained magnetic cores in air at 130°C for 8 hours. The coercivity of the obtained magnetic cores was measured using an automatic coercivity meter K-HC1000 manufactured by Tokyo Tokushu Kogyo Co., Ltd. For each magnetic core, the magnetic core was immersed in water and the polished flat surface was subjected to an evaluation of corrosion resistance in the same manner as in Example 1. The results obtained are shown in Table 3.

[0093]

[0094] According to the evaluation results shown in Table 3, the coercive force of the magnetic cores was lower than 15.0 A / m, except for invention examples 6 and 17, indicating good soft magnetic properties. Furthermore, with regard to corrosion resistance, similar to the evaluation results of Example 1, it can be seen that the magnetic cores of invention examples 1 to 11, which contain Cr in their composition, exhibit good corrosion resistance, and the magnetic cores of invention examples 12 to 22, which were subjected to heat treatment, exhibit particularly excellent corrosion resistance.

[0095] Comparing the results of Example 2 shown in Table 2 with the results of Example 3 shown in Table 3, the following can be seen. According to Table 3, in the magnetic cores of Examples 12 to 22 that underwent heating treatment, no discoloration was observed on the surface of the test piece simulating the contact surface, demonstrating particularly excellent corrosion resistance. According to Table 2, in the soft magnetic plywood strips containing an Fe-based nanocrystalline alloy of Examples 12 to 22 that constitute these magnetic cores, the oxygen concentration at the outermost surface of the surface oxidation layer was 43.0 atomic % or more. On the other hand, according to Table 3, in the magnetic core of Comparative Example 2 that also underwent heating treatment, red rust occurred over more than 20% of the surface area of ​​the test piece. According to Table 2, in the soft magnetic plywood strip containing an Fe-based nanocrystalline alloy of Comparative Example 2 that constitutes this magnetic core, the oxygen concentration at the outermost surface of the surface oxidation layer was 42.6 atomic %, which is lower than 43.0 atomic %. These results show that in a soft magnetic plywood ribbon containing an Fe-based nanocrystalline alloy, when the oxygen concentration at the outermost surface of the surface oxide layer formed on the contact surface is 43.0 atomic % or more, the contact surface exhibits particularly excellent corrosion resistance.

[0096] [Example 4] (Effect of Surface Roughness) Using the same method as in Example 2, an Fe-based nanocrystalline alloy ribbon having the component composition listed in Table 1 was wound to form a laminate, and then impregnated with epoxy resin to form a fixed magnetic core. The end faces perpendicular to the central axis of the winding of the obtained magnetic core were polished. In the flat surface polishing process, the polishing was stopped at each of the stages of using abrasive paper with grits of 220, 320, 800, and 2000. Next, a portion of the obtained magnetic core was subjected to heating treatment in air at 130°C for 8 hours. The arithmetic mean roughness Ra of the polished surface was measured using a Keyence VK-X3000 laser microscope. The measurement magnification was 480x, the objective lens magnification was 20x, and the cutoff wavelengths were set to 2.75 μm for the S-filter and 0.8 mm for the L-filter. One line was measured from the inner periphery to both end faces. For each test piece, the magnetic core was immersed in water, and the polished flat surface was subjected to an evaluation of corrosion resistance in the same manner as in Example 1. The results are shown in Table 4.

[0097]

[0098] According to the evaluation results shown in Table 4, for all samples of the polished surface simulating the contact surface of the cut core according to the present invention, the arithmetic mean roughness (Ra) of the polished surface decreased with increasing grit size of the abrasive paper used for polishing. Furthermore, for the samples of Examples 1 to 11, in which the Cr content was 0.5 or more and 4.0 or less in atomic percent, the corrosion resistance tended to improve with decreasing arithmetic mean roughness (Ra). In particular, for the samples using the 2000 grit abrasive paper, the area of ​​the area where red rust occurred was 20% or less of the entire observed surface (excellent, good, or fair). Furthermore, for the samples of Examples 12 to 22, which were subjected to heat treatment after polishing, no discoloration or rusting was observed (excellent). In contrast, for the samples of Comparative Examples 1 and 2, which did not contain Cr, the area of ​​the area where red rust occurred exceeded 20% of the entire observed surface (failure) for all grit sizes of abrasive paper.

[0099] [Example 5] (Evaluation of Cut Core) Using the same method as in Example 3, an Fe-based nanocrystalline alloy ribbon having the component composition shown in Table 1 was impregnated with epoxy resin and wound to form a laminate, and then impregnated with epoxy resin to form a fixed magnetic core. Next, the obtained magnetic core was cut so that the shape of the laminate became the shape shown in Figure 5, thereby providing discontinuous portions. Cutting was performed manually using a high-speed precision cutting machine Finecut HS-100 manufactured by Heiwa Technica Co., Ltd., and a grinding wheel (outer diameter φ205 mm, inner diameter φ25.4 mm, thickness 0.7 mm) manufactured by Heiwa Technica Co., Ltd., Tokusutoshisuten B, to provide discontinuous portions with a width of 10 mm.

[0100] Next, using the same method as in Example 3, one end face of the magnetic core having discontinuous portions, perpendicular to the central axis of the winding, was polished using up to #2000 abrasive paper. Then, heating treatment was performed in air at 130°C for 8 hours. The surface roughness of the polished surface was Ra 0.1 μm and Rz 1.0 μm. Two of the resulting polished magnetic cores were brought into contact with each other so that the center positions of the discontinuous portions formed an angle of 180°, as shown in Figure 5, and then fixed with heat-resistant tape to form a cut core. The coercivity of the resulting cut core was measured using the same method as in Example 3.

[0101] Next, in the same manner as in Example 1, the cut core was immersed in ion-exchanged water at 25°C for 100 hours, and the impedance at a frequency of 100 kHz was measured before and after immersion. The measured value before immersion was taken as Z Ａ , the measured value after immersion is Z Ｂ When this is done, (Z Ｂ -Z Ａ ) / Z Ａ The impedance change rate ΔZ (%) was calculated by multiplying the impedance by 100 times. A Keysight impedance analyzer 4294A was used to measure the impedance. The temperature of the cut core and the surrounding environment when measuring the impedance was 25°C. One turn of a lead wire H-PVC, Φ0.5 mm solid wire manufactured by Tanaka Electric Wire Co., Ltd. was passed through the cut core, and the cut core was fixed using a Keysight lead wire fixture 16047E for measurement. At this time, a weight with a mass of 100 g was placed on the cut core to apply a load to the contact surface and bring them into close contact.

[0102] Next, a cut core other than the one used for water immersion was held in an environment of 85°C and 85% RH for 1000 hours using an Espec SH-222 small environmental tester, and the rate of change in impedance at a frequency of 100 kHz, ΔZ, before and after the test was calculated in the same manner as for water immersion. These evaluation results are shown in Table 5.

[0103]

[0104] According to the evaluation results shown in Table 5, under both the water immersion and 85°C / 85% RH test conditions, the absolute values ​​of the impedance change rate ΔZ for the cut cores of Examples 12 to 22 according to the present invention were smaller than those for Comparative Example 2 and never exceeded 15%. It is believed that the formation of red rust on the contact surfaces impaired adhesion of the contact surfaces, as in Example 2, and reduced magnetic permeability, resulting in a larger absolute value of the impedance change rate ΔZ. In contrast, it is believed that the formation of red rust on the contact surfaces was suppressed compared to Comparative Example 2, resulting in a smaller absolute value of the impedance change rate ΔZ than in Comparative Example 2.

[0105] This cut core can be attached to the power cables of electronic devices such as automobiles, power generation / power supply equipment, communication equipment, and office / factory automation equipment, and can be used as a noise suppression core to suppress noise generated within these electronic devices or generated externally and propagating within the cable.

[0106] A: Surface oxidation layer B: Intermediate diffusion layer C: Substrate 1: Cut core 2: Laminate 2a: Contact surface 2b: Discontinuous portion 2c: Central axis of winding

Claims

1. A cut core comprising two or more laminates in which soft magnetic alloy ribbons are laminated in the thickness direction, wherein each laminate has at least one contact surface and the contact surfaces are in contact with each other, and the soft magnetic alloy ribbon is Fe100−x−y−z−a−bSi ｘ B ｙ Cu ｚ Cr ａ M ｂ (where M represents at least one element selected from Nb and Mo, x, y, z, a and b represent the atomic percentages of Si, B, Cu, Cr and M respectively, 11.0 ≦ x ≦ 17.0, 5.0 ≦ y ≦ 10.0, 0.5 ≦ z ≦ 2.0, 0.5 ≦ a ≦ 4.0, 1.0 ≦ b ≦ 5.0 and 65 ≦ 100−x−y−z−a−b ≦ 75 are satisfied.) The cut core is characterized by having a component composition represented by this.

2. On the contact surface, the soft magnetic alloy ribbon includes a base material having the above composition, an intermediate diffusion layer located outside the base material, in which Si is concentrated and Fe is deficient compared to the above composition, and a surface oxide layer located outside the intermediate diffusion layer, which newly contains O (oxygen) compared to the above composition, in which Si is concentrated and Fe and Cr are deficient. The cut core according to claim 1.

3. The soft magnetic alloy ribbon includes an Fe-based nanocrystalline alloy. The cut core according to claim 1 or 2.

4. The oxygen concentration on the outermost surface of the surface oxide layer is 43.0 atomic % or more. The cut core according to claim 3.

5. Measure the impedance at a frequency of 100 kHz before and after immersing the cut core in ion-exchanged water for 100 hours. Let the measured value before immersion be Z Ａ , and the measured value after immersion be Z Ｂ . When (Z Ｂ - Z Ａ ) / Z Ａ × 100 is calculated, the absolute value of the impedance change rate ΔZ is 15% or less. The cut core according to any one of claims 1 to 4 6. The soft magnetic alloy ribbon is wound into an annular shape, and n laminates formed by cutting the annular body at n locations (where n is an integer of 2 or more) perpendicular to the circumferential direction thereof are provided. The (n×2) cut surfaces of the n laminates serve as the contact surfaces, and two adjacent laminates among the n laminates are in contact with each other at the cut surfaces as the contact surfaces to form a magnetic circuit as a whole. The cut core according to any one of claims 1 to 5.

7. For one annular body formed by winding the soft magnetic alloy ribbon into an annular shape, two or more laminates formed by providing one discontinuity in a part of the circumferential direction thereof are provided. At least one of the two widthwise end faces of each of the two or more laminates serves as the contact surface, and two adjacent laminates among the two or more laminates are in contact with each other at the widthwise end faces as the contact surfaces so that the respective discontinuities do not overlap in the circumferential direction to form a magnetic circuit as a whole. The cut core according to any one of claims 1 to 5.

8. A noise countermeasure member using the cut core according to any one of claims 1 to 7.

Images