Manufacturing method for Fe-based nanocrystalline alloy ribbon and manufacturing method for magnetic core

Abstract

A method for producing a thin Fe-based nanocrystalline alloy ribbon that is thin and suppresses the generation of protrusions on the free solidification surface is provided. [Solution] A method for producing an Fe-based nanocrystalline alloy ribbon includes the steps of: supplying an Fe-based alloy melt onto a rotating chill roll; and rapidly solidifying the Fe-based alloy melt supplied onto the chill roll to obtain an Fe-based amorphous alloy ribbon having a free solidification surface and a roll contact surface; and heat treating the Fe-based amorphous alloy ribbon to obtain an Fe-based nanocrystalline alloy ribbon, wherein the outer periphery of the chill roll is made of a Cu alloy, and the thermal conductivity of the outer periphery is 70 W / (m·K) or more and 225 W / (m·K) or less.

Description

[Technical Field]

[0001] The present disclosure relates to a method for producing an Fe-based nanocrystalline alloy ribbon, a method for producing a magnetic core, an Fe-based nanocrystalline alloy ribbon, and a magnetic core. [Background technology]

[0002] Fe-based nanocrystalline alloys have excellent magnetic properties, such as low loss and high magnetic permeability, and are therefore used as materials for magnetic components (such as magnetic cores). A magnetic core including an Fe-based nanocrystalline alloy ribbon is manufactured, for example, by rapidly solidifying an Fe-based alloy melt by a single roll method to obtain an Fe-based amorphous alloy ribbon, and then winding or stacking the obtained Fe-based amorphous alloy ribbon and heat treating it to precipitate nanocrystalline grains in the alloy structure of the Fe-based amorphous alloy ribbon, thereby forming an Fe-based nanocrystalline alloy ribbon (see, for example, Patent Document 1).

[0003] As an example of a magnetic core including an Fe-based nanocrystalline alloy ribbon, Patent Document 2 discloses a low-loss magnetic core for use in a radio frequency acceleration cavity, which is formed by winding an Fe-based nanocrystalline alloy ribbon having a roll contact surface and a free surface by a single roll method via an insulating layer, and which is characterized in that protrusions of a predetermined shape are dispersed on the free surface of the Fe-based nanocrystalline alloy ribbon, and the tops of the protrusions are polished to be blunt. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 4-4393 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-167228 Summary of the Invention [Problem to be solved by the invention]

[0005] Patent Document 2 describes a problem in that, when a conventional alloy ribbon having a thickness exceeding 15 μm is thinned, protrusions are formed on one main surface of the alloy ribbon, and an insulating layer is not formed at the protrusions, resulting in contact and conduction between adjacent alloy ribbons in the magnetic core via the insulating layer, resulting in a decrease in insulation. Patent Document 2 describes that the above problem can be solved by polishing and blunting the tops of the protrusions.

[0006] However, the method of polishing the tops of the protrusions to blunt them, as described in Patent Document 2, has the problem of increasing the number of production steps. It also has the problem of requiring a large number of steps to maintain and manage the polishing capacity. It is also difficult to continuously and effectively polish the Fe-based nanocrystalline alloy ribbon over almost the entire surface without bias, which limits the ability to continuously and stably ensure high insulation. Therefore, in order to improve the protrusions of thin Fe-based nanocrystalline alloy ribbons (specifically, those with a thickness of 15 μm or less), a technology is required that can suppress the occurrence of the protrusions themselves, without relying on a technology for polishing the tops of the protrusions.

[0007] An object of a first aspect of the present disclosure is to provide a method for producing an Fe-based nanocrystalline alloy ribbon, which is a thin Fe-based nanocrystalline alloy ribbon in which the generation of protrusions on the free solidification surface is suppressed. An object of a second aspect of the present disclosure is to provide a method for manufacturing a magnetic core, which includes a wound body in which thin Fe-based nanocrystalline alloy ribbons are wound with an insulating layer interposed therebetween, and which can manufacture a magnetic core having excellent insulation between adjacent Fe-based nanocrystalline alloy ribbons with the insulating layer interposed therebetween. An object of a third aspect of the present disclosure is to provide a thin Fe-based nanocrystalline alloy ribbon in which the generation of protrusions on the free solidification surface is suppressed. An object of the fourth aspect of the present disclosure is to provide a magnetic core including a wound body in which thin Fe-based nanocrystalline alloy ribbons are wound with an insulating layer interposed therebetween, and which has excellent insulation between adjacent Fe-based nanocrystalline alloy ribbons with the insulating layer interposed therebetween. [Means for solving the problem]

[0008] Specific means for solving the above problems are as follows. <1> supplying a molten Fe-based alloy onto a rotating chill roll and rapidly solidifying the molten Fe-based alloy supplied onto the chill roll to obtain an Fe-based amorphous alloy ribbon having a free solidification surface and a roll contact surface, a width of 5 mm to 65 mm, and a thickness of 10 μm to 15 μm; heat-treating the Fe-based amorphous alloy ribbon to obtain an Fe-based nanocrystalline alloy ribbon; Including, the outer periphery of the cooling roll is made of a Cu alloy, and the thermal conductivity of the outer periphery is 70 W / (m K) or more and 225 W / (m K) or less; A manufacturing method for Fe-based nanocrystalline alloy ribbons. <2> The Vickers hardness of the outer periphery is 250 HV or more. <1> 1. A method for producing the Fe-based nanocrystalline alloy ribbon according to claim 1 . <3> The molten Fe-based alloy has an alloy composition represented by the following composition formula (A): <1> or <2> 1. A method for producing the Fe-based nanocrystalline alloy ribbon according to claim 1 . Fe 100-a-b-c-d-e Cu a Si b B c Nb d Ce … Composition formula (A) In composition formula (A), 100-abcde, a, b, c, d, and e respectively represent the atomic percentage of each element when the total of Fe, Cu, Si, B, Nb, and C is 100 atomic percent, and a, b, c, d, and e respectively satisfy 0.30≦a≦2.00, 13.00≦b≦16.00, 6.00≦c≦11.00, 2.00≦d≦4.00, and 0.04≦e≦0.40.

[0009] <4> A method for manufacturing a magnetic core including a wound body C in which an Fe-based nanocrystalline alloy ribbon is wound with an insulating layer interposed therebetween, supplying a molten Fe-based alloy onto a rotating chill roll and rapidly solidifying the molten Fe-based alloy supplied onto the chill roll to obtain an Fe-based amorphous alloy ribbon having a free solidification surface and a roll contact surface, a width of 5 mm to 65 mm, and a thickness of 10 μm to 15 μm; forming the insulating layer on the free solidification surface of the Fe-based amorphous alloy ribbon; a step of winding the Fe-based amorphous alloy ribbon on which the insulating layer has been formed, to obtain a wound body A in which the Fe-based amorphous alloy ribbon is wound with the insulating layer interposed therebetween; a step of obtaining the wound body C by heat treating the wound body A; Including, the outer periphery of the cooling roll is made of a Cu alloy, and the thermal conductivity of the outer periphery is 70 W / (m K) or more and 225 W / (m K) or less; Manufacturing method of magnetic core. <5> The Vickers hardness of the outer periphery is 250 HV or more. <4> A method for manufacturing the magnetic core described in <6> The molten Fe-based alloy has an alloy composition represented by the following composition formula (A): <4> or <5> A method for manufacturing the magnetic core described in Fe 100-a-b-c-d-e Cu a Si b B c Nb d Ce … Composition formula (A) In composition formula (A), 100-abcde, a, b, c, d, and e respectively represent the atomic percentage of each element when the total of Fe, Cu, Si, B, Nb, and C is 100 atomic percent, and a, b, c, d, and e respectively satisfy 0.30≦a≦2.00, 13.00≦b≦16.00, 6.00≦c≦11.00, 2.00≦d≦4.00, and 0.04≦e≦0.40.

[0010] <7> having a free solidification surface and a roll contact surface, The number of protrusions P on the free solidification surface, each having a depression in the center, is determined based on an area of 100 mm 2 1.2 or less per The width is between 5mm and 65mm, The thickness is 10 μm or more and 15 μm or less, Fe-based nanocrystalline alloy ribbon. <8> The warpage in the width direction is 0.30 mm or less per 10 mm width. <7> The Fe-based nanocrystalline alloy ribbon according to claim 1. <9> The alloy has a composition represented by the following composition formula (A): <7> or <8> The Fe-based nanocrystalline alloy ribbon according to claim 1. Fe 100-a-b-c-d-e Cu a Si b B c Nb d Ce … Composition formula (A) In composition formula (A), 100-abcde, a, b, c, d, and e respectively represent the atomic percentage of each element when the total of Fe, Cu, Si, B, Nb, and C is 100 atomic percent, and a, b, c, d, and e respectively satisfy 0.30≦a≦2.00, 13.00≦b≦16.00, 6.00≦c≦11.00, 2.00≦d≦4.00, and 0.04≦e≦0.40.

[0011] <10> <7> ~ <9> 10. A magnetic core including a wound body C1 in which the Fe-based nanocrystalline alloy ribbon according to any one of 1 to 9 is wound with an insulating layer interposed therebetween. <11> The insulation ratio RI expressed by the following formula (1) is 80% or more. <10> The magnetic core described in RI=Rr / (Ru·Lr)×100(%) … Formula (1) In formula (1), Rr is a DC electrical resistance value (Ω) between two ends, that is, one end of the innermost periphery and the other end of the outermost periphery, of the Fe-based nanocrystalline alloy ribbon; Ru is the DC electrical resistance (Ω) per meter of the Fe-based nanocrystalline alloy ribbon in the longitudinal direction, Lr is the length (m) of the Fe-based nanocrystalline alloy ribbon in the longitudinal direction. [Effects of the Invention]

[0012] According to a first aspect of the present disclosure, there is provided a method for producing an Fe-based nanocrystalline alloy ribbon, which is a thin Fe-based nanocrystalline alloy ribbon in which the generation of protrusions on the free solidification surface is suppressed. According to a second aspect of the present disclosure, there is provided a method for manufacturing a magnetic core, which includes a wound body in which a thin Fe-based nanocrystalline alloy ribbon is wound with an insulating layer interposed therebetween, and which can produce a magnetic core having excellent insulation between adjacent Fe-based nanocrystalline alloy ribbons interposed therebetween. According to a third aspect of the present disclosure, there is provided a thin Fe-based nanocrystalline alloy ribbon in which the generation of protrusions on the free solidification surface is suppressed. According to a fourth aspect of the present disclosure, there is provided a magnetic core including a wound body in which a thin Fe-based nanocrystalline alloy ribbon is wound with an insulating layer interposed therebetween, and the magnetic core has excellent insulation between adjacent Fe-based nanocrystalline alloy ribbons with the insulating layer interposed therebetween. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a laser microscope image (magnification 50x) of two protrusions P (i.e., protrusions P having a depression in the center) in the Fe-based amorphous alloy ribbon of Comparative Example 1, observed from a direction perpendicular to the free solidification surface. [Figure 2] FIG. 2 is a 3D view of FIG. 1. DETAILED DESCRIPTION OF THE INVENTION

[0014] In the present disclosure, the term "process" includes not only an independent process but also a process that cannot be clearly distinguished from other processes as long as the intended purpose of the process is achieved. In this disclosure, the term "nanocrystalline alloy" refers to an alloy that includes a nanocrystalline phase (i.e., a phase consisting of nanocrystalline grains). The "nanocrystalline alloy" may also include phases other than the nanocrystalline phase (e.g., an amorphous phase). In the present disclosure, "Fe-based" means that the main component (i.e., the component with the largest mass content) is Fe.

[0015] [Method for producing Fe-based nanocrystalline alloy ribbon] The method for producing an Fe-based nanocrystalline alloy ribbon according to the present disclosure (hereinafter also referred to as "the method for producing an Fe-based nanocrystalline alloy ribbon according to the present disclosure") comprises: supplying a molten Fe-based alloy onto a rotating chill roll and rapidly solidifying the molten Fe-based alloy supplied onto the chill roll to obtain an Fe-based amorphous alloy ribbon having a free solidification surface and a roll contact surface, a width of 5 mm to 65 mm, and a thickness of 10 μm to 15 μm; a step of heat-treating the Fe-based amorphous alloy ribbon to obtain an Fe-based nanocrystalline alloy ribbon; Including, The outer periphery of the chill roll is made of a Cu alloy, and the thermal conductivity of the outer periphery is 70 W / (m·K) or more and 225 W / (m·K) or less. The method for producing an Fe-based nanocrystalline alloy ribbon according to the present disclosure may include other steps as necessary.

[0016] In the present disclosure, the free solidification surface of the Fe-based amorphous alloy ribbon means one of the two main surfaces of the Fe-based amorphous alloy ribbon that is not in contact with a chill roll and is exposed to the atmosphere during the production of the Fe-based amorphous alloy ribbon. The same applies to the free solidification surface of an Fe-based nanocrystalline alloy ribbon obtained by heat treating the Fe-based amorphous alloy ribbon. In the present disclosure, the roll contact surface of the Fe-based amorphous alloy ribbon means one of the two main surfaces of the Fe-based amorphous alloy ribbon that was in contact with a cooling roll in the stage of producing the Fe-based amorphous alloy ribbon. The same applies to the roll contact surface of an Fe-based nanocrystalline alloy ribbon obtained by heat treating the Fe-based amorphous alloy ribbon. The alloy ribbon having a free solidification surface and a roll contact surface means that the alloy ribbon is an alloy ribbon obtained by the single roll method.

[0017] Through investigations by the present inventors, it has been found that in the case where a molten Fe-based alloy is supplied onto a rotating chill roll, the supplied molten Fe-based alloy is rapidly solidified to obtain an Fe-based amorphous alloy ribbon having a free solidification surface and a roll contact surface (hereinafter, the operations up to this point are also referred to as "casting"), and the obtained Fe-based amorphous alloy ribbon is heat-treated to obtain an Fe-based nanocrystalline alloy ribbon, protrusions are likely to be generated on the free solidification surface of the Fe-based nanocrystalline alloy ribbon, particularly when the thickness of the Fe-based amorphous alloy ribbon is 15 μm or less, and the outer periphery of the chill roll is made of a Cu alloy and has a thermal conductivity of more than 225 W / (m·K). The reason for this is not clear, but is presumed to be as follows. The casting of the Fe-based amorphous alloy ribbon is usually performed while polishing the outer peripheral surface (i.e., the surface of the outer peripheral portion) of the chill roll. This polishing of the outer peripheral surface is usually performed after the cast Fe-based amorphous alloy ribbon is peeled from the outer peripheral surface and before the next molten Fe-based alloy is supplied to the outer peripheral surface. Here, if the outer peripheral portion of the chill roll is made of a Cu alloy and has a thermal conductivity of more than 225 W / (m·K), the Vickers hardness of the outer peripheral portion tends to be low. As a result, when the outer peripheral surface of the chill roll is polished, deep scratches are formed on the outer peripheral portion, generating coarse polishing powder, which is thought to easily adhere to the outer peripheral surface. When the molten Fe-based alloy is supplied onto the outer peripheral surface with the polishing powder attached, air is likely to be entrained in the supplied molten Fe-based alloy, resulting in localized areas with insufficient cooling rate and prone to crystallization, which are thought to become protrusions. When the thickness of the Fe-based amorphous alloy ribbon to be cast is thin (specifically, 15 μm or less), it is more susceptible to the influence of polishing powder, and it is thought that protrusions are more likely to occur. It is thought that the generated protrusions are also maintained on the free solidification surface of the Fe-based nanocrystalline alloy ribbon obtained by heat treating the Fe-based amorphous alloy ribbon.

[0018] Regarding the above-mentioned problem, the manufacturing method of the Fe-based nanocrystalline alloy ribbon of the present disclosure can suppress the generation of protrusions on the free solidification surface even when casting an Fe-based amorphous alloy ribbon with a thickness of 15 μm or less. The effect of suppressing the generation of protrusions on the free solidification surface is contributed by the fact that the thermal conductivity of the outer peripheral portion of the cooling roll (i.e., the outer peripheral portion made of a Cu alloy) is 225 W / (m·K) or less. Specifically, when the thermal conductivity of the outer peripheral portion is 225 W / (m·K) or less, the Vickers hardness of the outer peripheral portion increases (i.e., the outer peripheral portion becomes hard), the generation of the above-mentioned coarse abrasive powder is suppressed, and as a result, it is considered that the generation of protrusions is suppressed.

[0019] Hereinafter, each step of the method for manufacturing the Fe-based nanocrystalline alloy ribbon of the present disclosure will be described.

[0020] <Step of obtaining an Fe-based amorphous alloy ribbon> The step of obtaining an Fe-based amorphous alloy ribbon is a step of supplying an Fe-based alloy melt onto a rotating cooling roll and rapidly solidifying the Fe-based alloy melt supplied onto the cooling roll, thereby obtaining an Fe-based amorphous alloy ribbon having a free solidification surface and a roll contact surface, a width of 5 mm or more and 65 mm or less, and a thickness of 10 μm or more and 15 μm or less.

[0021] (Preferred alloy composition of the Fe-based alloy melt) The preferred alloy composition of the Fe-based alloy melt is an alloy composition represented by the following composition formula (A) in terms of being likely to form a nanocrystalline phase in the alloy structure by heat treatment.

[0022] Each step in the method for manufacturing the Fe-based nanocrystalline alloy ribbon of the present disclosure does not affect the alloy composition of the alloy. Therefore, the alloy composition of the Fe-based alloy melt is maintained as it is in the Fe-based amorphous alloy ribbon and the Fe-based nanocrystalline alloy ribbon manufactured using the Fe-based alloy melt. That is, the alloy composition represented by the following composition formula (A) is the preferred chemical composition of the Fe-based alloy melt, and also the preferred chemical composition of the Fe-based amorphous alloy ribbon, and also the preferred chemical composition of the Fe-based nanocrystalline alloy ribbon.

[0023] Fe 100-a-b-c-d-e Cu a Sib B c Nb d Ce … Composition formula (A) In composition formula (A), 100-abcde, a, b, c, d, and e respectively represent the atomic percentage of each element when the total of Fe, Cu, Si, B, Nb, and C is 100 atomic percent, and a, b, c, d, and e respectively satisfy 0.30≦a≦2.00, 13.00≦b≦16.00, 6.00≦c≦11.00, 2.00≦d≦4.00, and 0.04≦e≦0.40.

[0024] The alloy composition represented by composition formula (A) will be described below. Hereinafter, the atomic % indicating the content of each element means the atomic % of each element when the total of Fe, Cu, Si, B, Nb, and C is taken as 100 atomic %.

[0025] Fe is the element that is responsible for the soft magnetic properties. From the viewpoint of obtaining a high saturation magnetic flux density Bs, the Fe content (atomic %) (that is, "100-abcde" in composition formula (A)) is preferably 72.00 atomic % or more, and more preferably 74.00 atomic % or more.

[0026] Cu is an element that becomes the nucleus of nanocrystalline grains when an Fe-based amorphous alloy ribbon is heat-treated to obtain an Fe-based nanocrystalline alloy ribbon. This heat treatment causes nanocrystalline grains to precipitate within the alloy structure. From the viewpoint of such effects, the Cu content (that is, "a" in composition formula (A)) is 0.30 atomic % or more, preferably 0.80 atomic % or more, and more preferably 0.90 atomic % or more. On the other hand, if the Cu content exceeds 2.00 atomic %, there is a high possibility that nanocrystalline nuclei exist in the Fe-based amorphous alloy ribbon before the heat treatment, and the crystals formed from the nanocrystalline nuclei by the heat treatment grow large and coarse, which may result in deterioration of the magnetic properties. Therefore, the Cu content is 2.00 atomic % or less, preferably 1.50 atomic % or less, and more preferably 1.30 atomic % or less.

[0027] Si reduces the magnetocrystalline anisotropy of Fe to improve soft magnetic properties, and together with B (boron), is an element effective in improving amorphous forming ability. If the Si content is 13.00 atomic % or more, high amorphous forming ability can be obtained in the production of an Fe-based amorphous alloy ribbon. Also, low saturation magnetostriction can be obtained in the nanocrystalline alloy ribbon obtained by heat treatment. Therefore, the Si content (i.e., "b" in composition formula (A)) is 13.00 atomic % or more, preferably 13.40 atomic % or more, and more preferably 13.50 atomic % or more. On the other hand, if the Si content exceeds 16.00 atomic %, the viscosity of the molten alloy decreases, and therefore, when the molten alloy is discharged onto the outer peripheral surface of a chill roll and rapidly solidified to obtain an Fe-based amorphous alloy ribbon, the smoothness of the free solidification surface of the Fe-based amorphous alloy ribbon may be deteriorated. Therefore, the Si content is 16.00 atomic % or less, preferably 15.5 atomic % or less.

[0028] As mentioned above, B (boron) is an element that, together with Si, is effective in amorphous formation. Furthermore, when a nanocrystalline phase (i.e., a phase consisting of nanocrystalline grains) is formed in the alloy structure by heat treatment, B is an element that determines the volume fraction of the amorphous phase, which is a phase that does not crystallize. In other words, B is an element that determines the volume ratio of the nanocrystalline phase to the amorphous phase after heat treatment.

[0029] The magnetostriction of the nanocrystalline phase is negative, while that of the amorphous phase is positive, and the ratio of the two determines the magnetostriction of the entire alloy. If the B content is high, the volume fraction of the amorphous phase increases compared to the nanocrystalline phase after heat treatment, resulting in a larger saturation magnetostriction. The saturation magnetostriction is 5×10 -6 The following is considered preferable. From the viewpoint of achieving saturation magnetostriction or less, the B content (i.e., "c" in composition formula (A)) is 11.00 atomic % or less, and preferably 9.00 atomic % or less. When the saturation magnetostriction is small, deterioration of the magnetic properties is suppressed even if the magnetic core is subjected to mechanical stress when storing the produced magnetic core in a case or when winding a wire around the magnetic core to form a coil. On the other hand, if the B content is low, it becomes difficult to stably obtain an amorphous phase when the molten alloy is quenched to produce an alloy ribbon. From the viewpoint of stably obtaining an amorphous phase, the B content is 6.00 atomic % or more, preferably 6.50 atomic % or more.

[0030] Nb is an element that is effective in distributing the nanocrystalline grains that precipitate after heat treatment uniformly within the alloy structure, suppressing the generation of coarse crystal grains, and precipitating fine nanocrystalline grains. From the viewpoint of such effects, the Nb content (i.e., "d" in composition formula (A)) is 2.00 atomic % or more, preferably 2.40 atomic % or more, more preferably 2.50 atomic % or more, and even more preferably 2.80 atomic % or more. On the other hand, since Nb does not contribute to the magnetic properties, the content is preferably 4.00 atomic % or less, more preferably 3.50 atomic % or less, and even more preferably 3.20 atomic % or less.

[0031] Carbon (C) is effective in stabilizing the viscosity of a molten Fe-based alloy. From the viewpoint of this effect, the C content (i.e., "e" in composition formula (A)) is 0.04 atomic % or more, preferably 0.05 atomic % or more, more preferably 0.10 atomic % or more, and even more preferably 0.12 atomic % or more. On the other hand, from the viewpoint of suppressing embrittlement of the alloy ribbon, the C content is preferably 0.40 atomic % or less, more preferably 0.35 atomic % or less, and even more preferably 0.30 atomic % or less.

[0032] The molten Fe-based alloy having an alloy composition represented by the composition formula (A) may contain at least one impurity element in addition to this alloy composition (the same applies to the Fe-based amorphous alloy ribbon having the alloy composition represented by the composition formula (A) and the Fe-based nanocrystalline alloy ribbon having the alloy composition represented by the composition formula (A)). Here, the impurity elements refer to elements other than the elements in the alloy composition represented by composition formula (A). When the entire alloy composition represented by composition formula (A) (i.e., the sum of Fe, Cu, Si, B, Nb, and C) is taken as 100 atomic %, the total content of impurity elements is preferably 0.20 atomic % or less, and more preferably 0.10 atomic % or less.

[0033] (Cooling roll) In the step of obtaining the Fe-based amorphous alloy ribbon, the molten Fe-based alloy is supplied onto a chill roll, and the molten Fe-based alloy supplied onto the chill roll is quenched to obtain the Fe-based amorphous alloy ribbon. The outer periphery of the chill roll (that is, the portion including the outer periphery surface) is made of a Cu alloy. The thermal conductivity of the outer periphery made of Cu alloy is 70 W / (m·K) or more and 225 W / (m·K) or less.

[0034] By keeping the thermal conductivity of the outer periphery made of Cu alloy at 225 W / (m·K) or less, the generation of protrusions on the free solidification surface of the final Fe-based nanocrystalline alloy ribbon is suppressed. From the viewpoint of further suppressing the occurrence of protrusions, the thermal conductivity of the outer periphery is preferably 220 W / (m·K) or less, more preferably 200 W / (m·K) or less, even more preferably 170 W / (m·K) or less, even more preferably 150 W / (m·K) or less, and even more preferably 130 W / (m·K) or less. On the other hand, from the viewpoint of the performance of quenching the molten Fe-based alloy supplied onto the chill roll, the thermal conductivity of the outer periphery is 70 W / (m K) or more. From the viewpoint of further improving the above performance, the thermal conductivity of the outer periphery is preferably 90 W / (m K) or more, and more preferably 110 W / (m K) or more.

[0035] The thermal conductivity of the outer periphery can be controlled by the type and amount of metal elements other than Cu contained in the Cu alloy that constitutes the outer periphery. For example, in a Cu-Be alloy, the thermal conductivity can be controlled by the Be content. An example of a Cu alloy with a thermal conductivity of 70 W / (m K) or more and 225 W / (m K) or less is a Cu-Be alloy containing 1.6 to 2.2 mass% Be with respect to the entire Cu-Be alloy. In the Cu-Be alloy, the remainder excluding Be is Cu and impurities. The impurities in the Cu-Be alloy are at least one element other than Cu and Be. Examples of impurities in the Cu-Be alloy include Ni and Co. The total content of impurities is, for example, 1.0 mass % or less. Furthermore, examples of Cu alloys constituting the outer periphery include Cu-Ni alloys and Cu-Ni-Be alloys. These Cu alloys may also contain impurities, such as Si, Cr, Ag, and Zr.

[0036] The Vickers hardness of the outer periphery of the chill roll is preferably 250 HV or more, which further suppresses the generation of protrusions on the free solidification surface. From the viewpoint of further suppressing the generation of protrusions on the free solidification surface, the Vickers hardness of the outer periphery of the chill roll is more preferably 260 HV or more, and even more preferably 300 HV or more. There is no particular need to limit the upper limit of the Vickers hardness of the outer periphery of the chill roll. The Vickers hardness of the outer periphery of the chill roll can be, for example, 400 HV or less, which makes it easier to polish the outer periphery of the chill roll during casting (i.e., during production of the Fe-based amorphous alloy ribbon), improves the removal of deposits adhering to the outer periphery surface of the chill roll (i.e., the outer surface of the outer periphery), and further suppresses crystallization of the Fe-based amorphous alloy ribbon caused by the deposits.

[0037] In the present disclosure, Vickers hardness refers to a value measured under a test load of 20 kgf.

[0038] The chill roll preferably has a structure inside it for cooling the outer periphery, which further suppresses the temperature rise on the outer periphery due to contact with the molten Fe-based alloy and more effectively maintains the cooling capacity on the outer periphery. A preferred structure for cooling the outer periphery is one in which temperature-controlled water is brought into contact with and circulated on the cooling roll rotation axis side of the outer periphery (that is, the inner surface of the outer periphery). In this case, it is structurally preferable to use a different alloy for the material of the portion of the chill roll that is located on the rotation axis side of the outer periphery. The different alloy does not need to take into consideration the thermal conductivity. Examples of the different alloy include stainless steel and cast iron.

[0039] The thickness of the outer periphery of the chill roll is preferably 15 mm or more and 40 mm or less from the viewpoint of ensuring cooling capacity for the Fe-based alloy melt and from the viewpoint of easily maintaining and controlling the surface condition of the outer periphery of the chill roll. The thickness of the outer periphery is more preferably 17 mm or more, and even more preferably 20 mm or more. The thickness of the outer periphery is more preferably 30 mm or less.

[0040] From the viewpoint of maintenance of the chill roll body, the diameter of the chill roll is preferably 300 mm or more, and more preferably 400 mm or more. The diameter of the cooling roll is preferably 1000 mm or less, and more preferably 900 mm or less. In order to obtain a more stable cooling capacity for the molten Fe-based alloy, the width of the chill roll is preferably 2.5 times or more the maximum width of the Fe-based amorphous alloy ribbon to be produced, and more preferably 3.0 times or more the maximum width of the Fe-based amorphous alloy ribbon. On the other hand, the width of the chill roll is preferably 10.0 times or less the maximum width of the Fe-based amorphous alloy ribbon in terms of maintaining and controlling the surface condition of the outer peripheral surface of the chill roll.

[0041] From the viewpoint of further increasing the cooling rate of the Fe-based alloy melt and more stably producing an Fe-based amorphous alloy ribbon, the peripheral speed of the rotating chill roll is preferably 20 m / s or more and 35 m / s or less, more preferably 25 m / s or more and 35 m / s or less, and even more preferably 27 m / s or more and 30 m / s or less.

[0042] (Width and thickness of Fe-based amorphous alloy ribbon) In the step of obtaining an Fe-based amorphous alloy ribbon, an Fe-based amorphous alloy ribbon having a width of 5 mm or more and 65 mm or less and a thickness of 10 μm or more and 15 μm or less is obtained.

[0043] The width and thickness of the Fe-based amorphous alloy ribbon are not changed by the heat treatment described below. Therefore, the width of the Fe-based nanocrystalline alloy ribbon obtained by heat treating the Fe-based amorphous alloy ribbon is also 5 mm or more and 65 mm or less, and the thickness of the Fe-based nanocrystalline alloy ribbon is also 10 μm or more and 15 μm or less.

[0044] When the thickness of the Fe-based amorphous alloy ribbon is 15 μm or less, eddy current loss is suppressed in a magnetic core manufactured using the Fe-based amorphous alloy ribbon. Furthermore, as described above, when the thickness of an Fe-based amorphous alloy ribbon is 15 μm or less, protrusions tend to be generated on the free solidification surface. However, according to the manufacturing method of an Fe-based nanocrystalline alloy ribbon of the present disclosure, an Fe-based amorphous alloy ribbon and an Fe-based nanocrystalline alloy ribbon can be obtained in which the generation of protrusions on the free solidification surface is suppressed, even though the thickness is 15 μm or less. The thickness of the Fe-based amorphous alloy ribbon is preferably 14.7 μm or less, more preferably 14.5 μm or less, even more preferably 14 μm or less, and still more preferably 13.5 μm or less.

[0045] On the other hand, the thickness of the Fe-based amorphous alloy ribbon is 10 μm or more. This allows for stable production of long Fe-based amorphous alloy ribbons and long Fe-based nanocrystalline alloy ribbons. Furthermore, the mechanical strength is ensured to prevent breakage due to handling in subsequent processes. The thickness of the Fe-based amorphous alloy ribbon is preferably 11 μm or more.

[0046] Furthermore, when the width of the Fe-based amorphous alloy ribbon is 65 mm or less, a long Fe-based amorphous alloy ribbon and a long Fe-based nanocrystalline alloy ribbon can be stably obtained. The width of the Fe-based amorphous alloy ribbon is preferably 63 mm or less, more preferably 60 mm or less, and even more preferably 55 mm or less. On the other hand, productivity (economic rationality) is ensured by making the width of the Fe-based amorphous alloy ribbon 5 mm or more. The width of the Fe-based amorphous alloy ribbon is preferably 10 mm or more, and more preferably 15 mm or more.

[0047] In this step, the width of the Fe-based amorphous alloy ribbon may be adjusted to 5 mm or more and 65 mm or less by slitting the Fe-based amorphous alloy ribbon. Alternatively, a plurality of thin strips of Fe-based amorphous alloy having a width of 5 mm or more and 65 mm or less may be obtained by slitting.

[0048] The width and thickness of the Fe-based amorphous alloy ribbon are also maintained in the Fe-based nanocrystalline alloy ribbon obtained by heat-treating the Fe-based amorphous alloy ribbon. Therefore, the preferred ranges of the width and thickness of the Fe-based nanocrystalline alloy ribbon are the same as the preferred ranges of the width and thickness of the Fe-based amorphous alloy ribbon.

[0049] (Warping of Fe-based amorphous alloy ribbon) The warpage of the Fe-based amorphous alloy ribbon is preferably 0.30 mm or less per 10 mm width of the Fe-based amorphous alloy ribbon. This further improves the uniformity of the thickness of the insulating layer (specifically, the uniformity in the width direction of the Fe-based amorphous alloy ribbon) when the insulating layer is formed on the Fe-based amorphous alloy ribbon. As a result, the insulating layer is further prevented from falling off from the Fe-based amorphous alloy ribbon on which the insulating layer is formed (or the Fe-based nanocrystalline alloy ribbon obtained by the heat treatment). This effectively prevents a decrease in insulation between adjacent Fe-based nanocrystalline alloy ribbons (that is, a decrease in insulation caused by the falling off of an insulating layer) in a magnetic core, which will be described later. The warp of the Fe-based amorphous alloy ribbon per 10 mm width of the Fe-based amorphous alloy ribbon is more preferably 0.25 mm or less, still more preferably 0.20 mm or less, and still more preferably 0.10 mm or less.

[0050] The thermal conductivity of the outer peripheral part of the cooling roll being 70 W / (m·K) or more and 225 W / (m·K) or less also contributes to reducing the warp of the Fe-based amorphous alloy ribbon. When the Vickers hardness of the outer peripheral part of the cooling roll is 250 HV or more, the warp of the Fe-based amorphous alloy ribbon is further reduced.

[0051] The warp of the Fe-based amorphous alloy ribbon is measured on a flat plate by placing the Fe-based amorphous alloy ribbon with the convex side of the warp facing up and using a device having a laser light emitting part and a laser light receiving part. As the device, for example, LB-300 manufactured by Keyence Corporation is used.

[0052] The warp of the Fe-based amorphous alloy ribbon is also maintained in the Fe-based nanocrystalline alloy ribbon obtained by heat-treating the Fe-based amorphous alloy ribbon. Therefore, the preferable range of the warp of the Fe-based nanocrystalline alloy ribbon is the same as the preferable range of the warp of the Fe-based amorphous alloy ribbon. The method for measuring the warp of the Fe-based nanocrystalline alloy ribbon is the same as the method for measuring the warp of the Fe-based amorphous alloy ribbon.

[0053] <Process for obtaining Fe-based nanocrystalline alloy ribbon> In the process for obtaining the Fe-based nanocrystalline alloy ribbon, the above-described Fe-based amorphous alloy ribbon is heat-treated to obtain the Fe-based nanocrystalline alloy ribbon. By the heat treatment, at least a part of the alloy structure of the Fe-based amorphous alloy ribbon is nanocrystallized (that is, nanocrystalline grains are generated), and as a result, the Fe-based nanocrystalline alloy ribbon is obtained.

[0054] In the manufacturing method of the Fe-based nanocrystalline alloy ribbon according to the present disclosure, the Fe-based amorphous alloy ribbon obtained in the step of obtaining the Fe-based amorphous alloy ribbon may be heat-treated as it is, or the Fe-based amorphous alloy ribbon obtained in the step of obtaining the Fe-based amorphous alloy ribbon may be stacked or wound, and the resulting stacked body or wound body may be heat-treated. The embodiment of heat-treating the wound body obtained by winding the Fe-based amorphous alloy ribbon includes the manufacturing method of the magnetic core of the present disclosure, which will be described later.

[0055] The maximum temperature in the heat treatment is preferably 500°C or higher and 700°C or lower, and more preferably 550°C or higher and 600°C or lower. In the heat treatment, the holding time at the maximum temperature is preferably 0.3 hours or more and 5 hours or less, more preferably 0.5 hours or more and 3 hours or less, and even more preferably 1 hour or more and 2 hours or less. The atmosphere in the heat treatment may be a non-oxidizing atmosphere such as nitrogen or an air atmosphere, but from the viewpoint of stabilizing quality, a non-oxidizing atmosphere is preferred. The heat treatment is carried out using, for example, a heat treatment furnace. The heat treatment may be carried out in a magnetic field.

[0056] [Method for manufacturing magnetic core] The method for manufacturing a magnetic core according to the present disclosure includes: A method for manufacturing a magnetic core including a wound body C in which an Fe-based nanocrystalline alloy ribbon is wound with an insulating layer interposed therebetween, supplying a molten Fe-based alloy onto a rotating chill roll and rapidly solidifying the molten Fe-based alloy supplied onto the chill roll to obtain an Fe-based amorphous alloy ribbon having a free solidification surface and a roll contact surface, a width of 5 mm to 65 mm, and a thickness of 10 μm to 15 μm; forming an insulating layer on a free solidification surface of the Fe-based amorphous alloy ribbon; a step of winding the Fe-based amorphous alloy ribbon on which the insulating layer has been formed, to obtain a wound body A in which the Fe-based amorphous alloy ribbon is wound with the insulating layer interposed therebetween; a step of heat-treating the wound body A to obtain a wound body C (i.e., a wound body C in which the Fe-based nanocrystalline alloy ribbon is wound with an insulating layer interposed therebetween); Including, The outer periphery of the chill roll is made of a Cu alloy, and the thermal conductivity of the outer periphery is 70 W / (m·K) or more and 225 W / (m·K) or less. The method for manufacturing a magnetic core according to the present disclosure may include other steps as necessary.

[0057] In the manufacturing method of the magnetic core according to the present disclosure, the steps of forming an insulating layer, obtaining the wound body A, and obtaining the wound body C are all included in the concept of "a step of obtaining an Fe-based nanocrystalline alloy ribbon" in the manufacturing method of the Fe-based nanocrystalline alloy ribbon according to the present disclosure. Except for this point, the method for producing the magnetic core of the present disclosure is the same as the method for producing the Fe-based nanocrystalline alloy ribbon of the present disclosure described above.

[0058] The "step of obtaining an Fe-based amorphous alloy ribbon" in the manufacturing method of the magnetic core of the present disclosure is the same as the "step of obtaining an Fe-based amorphous alloy ribbon" in the manufacturing method of the Fe-based nanocrystalline alloy ribbon of the present disclosure described above. Therefore, the "step of obtaining an Fe-based amorphous alloy ribbon" in the manufacturing method of the magnetic core of the present disclosure also provides an Fe-based amorphous alloy ribbon in which the generation of protrusions on the free solidification surface is suppressed. In the method for manufacturing a magnetic core according to the present disclosure, a wound body A in which an Fe-based amorphous alloy ribbon is wound with an insulating layer interposed therebetween is heat-treated. This heat treatment causes the Fe-based amorphous alloy ribbon in the wound body A to become an Fe-based nanocrystalline alloy ribbon, thereby obtaining a magnetic core including a wound body C in which the Fe-based nanocrystalline alloy ribbon is wound with an insulating layer interposed therebetween. As described above, the generation of protrusions on the free solidification surface of the Fe-based amorphous alloy ribbon in the winding A is suppressed, and therefore, in the winding C, the deterioration of the insulation between the adjacent Fe-based nanocrystalline alloy ribbons with the insulating layer interposed therebetween is suppressed.

[0059] As described above, the magnetic core manufactured by the method for manufacturing a magnetic core according to the present disclosure has excellent insulation between adjacent Fe-based nanocrystalline alloy ribbons with an insulating layer interposed therebetween. Therefore, eddy current loss is reduced in a magnetic core manufactured by the magnetic core manufacturing method of the present disclosure. Generally, the loss of a magnetic core is determined by hysteresis loss and eddy current loss. The eddy current loss is frequency dependent, and there is a clear tendency for it to increase as the applied frequency increases. From the above perspective, the method for manufacturing a magnetic core according to the present disclosure is particularly suitable as a method for manufacturing a magnetic core to be used under high frequency conditions (particularly high frequency conditions on the order of MHz or higher).

[0060] From the viewpoint of further suppressing eddy current loss, it is preferable that the magnetic core manufactured by the magnetic core manufacturing method of the present disclosure satisfy the insulation ratio RI described below of 80% or more. A more preferable range of the insulation ratio RI is the same as the more preferable range of the insulation ratio RI for a magnetic core according to an example of the present disclosure described below.

[0061] Hereinafter, steps other than the step of obtaining an Fe-based amorphous alloy ribbon in the method for producing a magnetic core according to the present disclosure will be described.

[0062] <Step of forming insulating layer> In the step of forming an insulating layer in the method for manufacturing a magnetic core according to the present disclosure, the insulating layer is formed on the free solidification surface of the Fe-based amorphous alloy ribbon. The insulating layer preferably comprises a metal oxide such as heat-treated silica (silicon oxide), alumina (aluminum oxide), and magnesia (magnesium oxide). In this case, the insulating layer may contain only one type of metal oxide, or two or more types of metal oxides. When the insulating layer contains a metal oxide, the influence of the heat treatment in the step of obtaining the wound body C on the insulating layer is further reduced. For example, the maximum temperature of the heat treatment at 550°C to 600°C exceeds the heat resistance temperature of organic materials such as polymers. Even when the heat treatment is performed at this maximum temperature, if the insulating layer contains a metal oxide, the influence of the heat treatment on the insulating layer is reduced, and the insulating properties of the insulating layer are effectively obtained.

[0063] The thickness of the insulating layer is preferably 1.5 to 2.5 μm.

[0064] Although the insulating layer may be provided on both the free solidification surface and the roll contact surface of the Fe-based amorphous alloy ribbon, it is preferable that the insulating layer be provided on the free solidification surface of the Fe-based amorphous alloy ribbon and not on the roll contact surface, which prevents contact between the insulating layers during and after the step of obtaining the wound body, thereby further suppressing the falling off of the insulating layers due to contact between the insulating layers.

[0065] The insulating layer can be formed, for example, as follows. A suspension is prepared by suspending a powdered metal oxide (hereinafter also referred to as metal oxide powder) in an organic solvent such as alcohol. An Fe-based amorphous alloy ribbon is immersed in the obtained suspension for a certain period of time to adhere the suspension to the Fe-based amorphous alloy ribbon. Then, the suspension adhering to the Fe-based amorphous alloy ribbon is dried, thereby forming an insulating layer on the free solidification surface and the roll contact surface of the Fe-based amorphous alloy ribbon. The thickness of the insulating layer can be determined by controlling the content of metal oxide powder in the suspension, the immersion time, and the like. Here, if the suspension adhering to the roll contact surface is removed after removal and before drying, an insulating layer can be formed only on the free solidification surface of the Fe-based amorphous alloy ribbon.

[0066] <Step of obtaining wound body A> In the step of obtaining the wound body A, the Fe-based amorphous alloy ribbon on which the insulating layer is formed is wound to obtain the wound body A in which the Fe-based amorphous alloy ribbon is wound with the insulating layer interposed therebetween. The Fe-based amorphous alloy ribbon on which the insulating layer has been formed can be wound according to a known method. At this time, the wound body A may be temporarily fixed with a Cu wire or the like having a diameter of about 0.5 mm to maintain its shape.

[0067] <Step of obtaining wound body C> In the step of obtaining the wound body C, the wound body A is heat-treated to obtain the wound body C (that is, the wound body C in which the Fe-based nanocrystalline alloy ribbon is wound with an insulating layer interposed therebetween). In the step of obtaining the wound body C, the Fe-based amorphous alloy ribbon in the wound body A is heat-treated to become an Fe-based nanocrystalline alloy ribbon. This is the same as the "step of obtaining an Fe-based nanocrystalline alloy ribbon" in the above-described method of producing an Fe-based nanocrystalline alloy ribbon according to the present disclosure. The preferred conditions for the heat treatment in the step of obtaining the wound body C are the same as the preferred conditions for the heat treatment in the "step of obtaining an Fe-based nanocrystalline alloy ribbon" in the manufacturing method of an Fe-based nanocrystalline alloy ribbon according to the present disclosure.

[0068] As mentioned above, the heat treatment may be carried out in a magnetic field. The magnetic field is preferably applied in two directions: the circumferential direction of the magnetic core and the height direction of the magnetic core (the width direction of the alloy ribbon). The strength of the applied magnetic field and / or the temperature range in which the magnetic field is applied can be appropriately optimized depending on the application of the magnetic core. Furthermore, the two magnetic field directions may be alternated.

[0069] [Fe-based nanocrystalline alloy ribbon, magnetic core] An Fe-based nanocrystalline alloy ribbon according to an example of the present disclosure comprises: having a free solidification surface and a roll contact surface, The number of protrusions P on the free solidification surface, each having a depression in the center, is determined based on an area of 100 mm 2 1.2 or less per The width is between 5mm and 65mm, The thickness is 10 μm or more and 15 μm or less. As described above, in the Fe-based nanocrystalline alloy ribbon according to the example of the present disclosure, the generation of protrusions on the free solidification surface is suppressed.

[0070] The magnetic core according to the example of the present disclosure includes a wound body C1 in which the Fe-based nanocrystalline alloy ribbon according to the example of the present disclosure is wound with an insulating layer interposed therebetween. A magnetic core according to an example of the present disclosure has excellent insulation between adjacent Fe-based nanocrystalline alloy ribbons with an insulating layer interposed therebetween.

[0071] As mentioned above, in an Fe-based nanocrystalline alloy ribbon having a thickness of 15 μm or less, protrusions are likely to occur on the free solidification surface, and among the protrusions, protrusions P having a depression in the center are particularly likely to occur. According to the study by the inventors, protrusions P on the free solidification surface of an Fe-based nanocrystalline alloy ribbon with a thickness of 15 μm or less were formed on a surface of 100 mm 2 It has been revealed that by limiting the number of ribbons per ribbon to 1.2 or less, the insulation between the Fe-based nanocrystalline alloy ribbons is significantly improved in a magnetic core including a winding body C1 in which the Fe-based nanocrystalline alloy ribbon is wound with an insulating layer interposed therebetween. The Fe-based nanocrystalline alloy ribbon and magnetic core according to this example were made based on this knowledge.

[0072] In the present disclosure, "a wound body in which an Fe-based nanocrystalline alloy ribbon is wound with an insulating layer interposed therebetween" (winding body C1, winding body C) means a wound body in which an Fe-based nanocrystalline alloy ribbon is wound with an insulating layer interposed therebetween. Therefore, the "wound body in which an Fe-based nanocrystalline alloy ribbon is wound via an insulating layer" is not limited to a wound body obtained by winding an Fe-based nanocrystalline alloy ribbon on which an insulating layer is formed. For example, as in the manufacturing method of the magnetic core of the present disclosure, a wound body obtained by winding an Fe-based amorphous alloy ribbon on which an insulating layer has been formed is heat-treated under predetermined conditions to obtain a wound body in which the Fe-based nanocrystalline alloy ribbon is wound with the insulating layer interposed therebetween. Such a wound body is also included in the concept of "a wound body in which the Fe-based nanocrystalline alloy ribbon is wound with the insulating layer interposed therebetween."

[0073] There is no particular limitation on the method for producing the Fe-based nanocrystalline alloy ribbon and magnetic core according to this example. For example, according to the above-described method for producing an Fe-based nanocrystalline alloy ribbon of the present disclosure, the Fe-based nanocrystalline alloy ribbon according to this example can be suitably produced. In particular, the magnetic core according to this example can be suitably manufactured by the method for manufacturing a magnetic core according to the present disclosure described above. In this case, the wound body C1 in the magnetic core according to this example is obtained as the wound body C in the method for manufacturing a magnetic core according to the present disclosure.

[0074] In this example, the protrusion P having a depression in the center (hereinafter also simply referred to as "protrusion P") means a protrusion having a depression in the center when observed from a direction perpendicular to the free solidification surface.

[0075] In this example, the area is 100 mm 2 Observation to determine the number of hit protrusions P is carried out using a stereomicroscope at a magnification of 40 times.

[0076] Free solidification surface area: 100mm 2 The number of the landing protrusions P is 1.2 or less as described above. The number of the landing protrusions P may be 0. The number of the protrusions P is preferably 1.0 or less, from the viewpoint of further improving the insulation between the Fe-based nanocrystalline alloy ribbons in the magnetic core.

[0077] The preferred aspects of the Fe-based nanocrystalline alloy ribbon according to this example (e.g., preferred aspects of alloy composition, width, thickness, warpage, etc.) are the same as the preferred aspects of the Fe-based nanocrystalline alloy ribbon obtained by the manufacturing method of the Fe-based nanocrystalline alloy ribbon according to the present disclosure. A preferred aspect of the magnetic core according to this example is the same as a preferred aspect of the magnetic core obtained by the magnetic core manufacturing method of the present disclosure.

[0078] <Insulation Ratio RI> As described above, the magnetic core according to this example has excellent insulation between the Fe-based nanocrystalline alloy ribbons, which reduces eddy current loss. From the viewpoint of further reducing eddy current loss, the magnetic core according to this example preferably has an insulation ratio RI expressed by the following formula (1) of 80% or more.

[0079] RI=Rr / (Ru·Lr)×100(%) … Formula (1) In formula (1), Rr is the DC electrical resistance (Ω) between one end of the innermost circumference and the other end of the outermost circumference in the Fe-based nanocrystalline alloy ribbon, Ru is the DC electrical resistance (Ω) per meter of the Fe-based nanocrystalline alloy ribbon in the longitudinal direction, Lr is the length (m) of the Fe-based nanocrystalline alloy ribbon.

[0080] The insulation ratio RI expressed by the formula (1) will be explained below. In the magnetic core according to this example, when the Fe-based nanocrystalline alloy ribbons are completely insulated from each other, the product of Ru and Lr in formula (1) (i.e., "Ru·Lr") is the same value as Rr in formula (1). In this case, the insulation ratio RI is 100%. On the other hand, if there is a location where the insulation is broken down (i.e., a short circuit) between the Fe-based nanocrystalline alloy ribbons, Rr will be smaller than "Ru·Lr." In this case, the insulation ratio RI will be less than 100%.

[0081] Ru in formula (1) is calculated based on the diameter of the magnetic core according to this example by estimating a position 1 m from the outermost edge of the magnetic core and measuring the DC electrical resistance (Ω) between the outermost edge and a position 1 m from the outermost edge.

[0082] From the viewpoint of further reducing eddy current loss, the insulation ratio RI of the magnetic core according to this example is preferably 85% or more, and more preferably 90% or more. Furthermore, the insulation ratio RI of the magnetic core according to this example may be 100%, but is preferably less than 100% from the viewpoint of the manufacturability (ease of manufacturing) of the magnetic core. [Example]

[0083] Examples of the present disclosure will be described below, but the present disclosure is not limited to the following examples.

[0084] Example 1 -Manufacturing (casting) of Fe-based amorphous alloy ribbons- Fe bal. Cu 0.98 Si 14.99 B 6.68 Nb 2.89 C 0.05 A molten Fe-based alloy (9.1 kg) having an alloy composition expressed as (atomic %) was supplied onto a rotating chill roll, and the supplied molten Fe-based alloy was rapidly solidified to obtain an Fe-based amorphous alloy ribbon having a free solidification surface and a roll contact surface, a width of 25 mm, and a thickness of 13.4 μm. Here, "bal." (balance) is the value corresponding to "100-abcde" in the composition formula (A). It was confirmed by observing the cross section of the ribbon with a scanning electron microscope (SEM) that the obtained Fe-based alloy ribbon was an Fe-based amorphous alloy ribbon, that is, that the alloy structure was composed of an amorphous phase.

[0085] The alloy composition of the Fe-based alloy does not change throughout all the steps of this example, and therefore the alloy compositions of the Fe-based alloy molten metal, the Fe-based amorphous alloy ribbon, and the Fe-based nanocrystalline alloy ribbon described below are the same. Furthermore, the size (thickness, width, and length) of the ribbon does not change throughout the entire process of this example. Therefore, the size (thickness, width, and length) of the Fe-based nanocrystalline alloy ribbon described later is the same as the size (thickness, width, and length) of the Fe-based amorphous alloy ribbon.

[0086] In the following description, the term "ribbon" simply means an Fe-based nanocrystalline alloy ribbon or an Fe-based amorphous alloy ribbon.

[0087] The rotation speed of the cooling roll was set to 28 m / sec as the peripheral speed of the outer periphery. The following cooling rolls were used. This cooling roll has a water channel inside for circulating cooling water as a structure for cooling the outer periphery.

[0088] -Cooling Roll- ·Diameter: 800mm ·Width: 150mm Outer thickness: 20mm Outer material: Cu-Be alloy (Be: 1.9 mass%, balance Cu and impurities) Thermal conductivity of outer periphery: 124W / (m·K)

[0089] -Vickers height of outer periphery- The Vickers hardness of the outer periphery was measured using a Vickers hardness tester under a test load of 20 kgf. The results are shown in Table 1.

[0090] - Area of free solidification surface 100mm 2 Measurement of the number of protrusions P per In order to evaluate the number of protrusions P on the free solidification surface of the obtained Fe-based amorphous alloy ribbon, the free solidification surface was observed with a stereomicroscope at a magnification of 40 times in 30 fields of view (area 1154 mm 2 ) was observed. Based on the observation results, the area is 100 mm 2 The number of hit protrusions P was calculated. The results are shown in Table 1. The number of protrusions P on the free solidification surface of the Fe-based amorphous alloy ribbon (that is, the ribbon before the heat treatment) does not change in the subsequent steps. That is, the number of protrusions P on the free solidification surface of the Fe-based nanocrystalline alloy ribbon (i.e., the ribbon after heat treatment) described below is the same as the number of protrusions P on the free solidification surface of the Fe-based amorphous alloy ribbon (i.e., the ribbon before heat treatment).

[0091] -Warp in the width direction- The warpage of the Fe-based amorphous alloy ribbon in the width direction was measured as follows. A sample having a length of 100 mm was taken from each of the ends of the Fe-based amorphous alloy ribbon at the beginning of casting and at the end of casting. Each sample was placed on a surface plate with the convex side of the warp facing upward, and the height of the top of the sample was measured using an LB-300 made by Keyence Corporation. The maximum top height for the two samples was 0.10 mm. Since the width of the sample was 25 mm, the warpage in the width direction of the Fe-based amorphous alloy ribbon was calculated to be 0.04 mm per 10 mm of width (see Table 1).

[0092] - Formation of insulating layer - An insulating layer having a thickness of 2.1 μm was formed on the free solidification surface of the Fe-based amorphous alloy ribbon as follows. A suspension was prepared by suspending silica powder having an average particle size of 0.5 μm in isopropyl alcohol (IPA). The Fe-based amorphous alloy ribbon obtained above was passed through this suspension, and then the suspension adhering to the roll contact surface of the Fe-based amorphous alloy ribbon was removed. The suspension adhered to the free solidification surface of the Fe-based amorphous alloy ribbon was dried to obtain an insulating layer with a thickness of 2.1 μm.

[0093] -Making of wound body A- The Fe-based amorphous alloy ribbon (length: 264 m) on which the insulating layer was formed was wound to obtain a wound body A having an inner diameter of 60.5 mm and an outer diameter of 100.0 mm (i.e., wound body A in which the Fe-based amorphous alloy ribbon was wound with the insulating layer interposed therebetween).

[0094] -Making the wound body C (magnetic core)- The above-mentioned wound body A was heat-treated under conditions of a maximum holding temperature of 580°C and a holding time of 2 hours, thereby obtaining wound body C (i.e., wound body C in which an Fe-based nanocrystalline alloy ribbon was wound with an insulating layer interposed therebetween) as a magnetic core. The cross section of the ribbon in the wound body C was observed with a scanning electron microscope (SEM) to confirm that the Fe-based alloy ribbon in the wound body C was an Fe-based nanocrystalline alloy ribbon, i.e., that nanocrystalline grains were generated in the alloy structure.

[0095] -Measurement of insulation ratio RI- The insulation ratio RI of the magnetic core obtained above (that is, the insulation ratio RI expressed by the formula (1)) was measured by the method described above. The results are shown in Table 1.

[0096] (Examples 2 to 4 and Comparative Example 1) The same operations as in Example 1 were carried out except that the production conditions for the Fe-based amorphous alloy ribbon (including the alloy composition of the molten Fe alloy) were changed as shown in Table 1. However, in Examples 3 and 4, the maximum holding temperature of the heat treatment for the wound body A was further changed to 550°C. The results are shown in Table 1.

[0097] In Example 2, the following cooling roll was used. The cooling roll of Example 2 also has a water channel for circulating cooling water inside as a structure for cooling the outer periphery.

[0098] -Cooling Roll of Example 2- ·Diameter: 800mm ·Width: 150mm Outer thickness: 20mm Outer material: Cu-Be alloy (Be: 2.0 mass%, balance Cu and impurities) Thermal conductivity of outer periphery: 120W / (m·K)

[0099] In Example 3, the following chill rolls were used. The cooling roll of Example 3 also has a water channel for circulating cooling water inside as a structure for cooling the outer periphery.

[0100] -Cooling Roll of Example 3- ·Diameter: 450mm ·Width: 300mm Outer thickness: 17mm Outer periphery material: Cu-Ni alloy (Cu: 90% or more by mass, the remainder being impurities (including Ni, Si, and Cr)) Thermal conductivity of outer periphery: 168W / (m·K)

[0101] In Example 4, the following chill rolls were used. The cooling roll of Example 4 also has a water channel for circulating cooling water inside as a structure for cooling the outer periphery.

[0102] -Cooling Roll of Example 4- ·Diameter: 650mm ·Width: 300mm Outer thickness: 17mm Outer periphery material: Cu-Ni-Be alloy (Cu: 90% by mass or more, Ni: 7% by mass, Be: 0.3% by mass, balance impurities (including Ag, Cr, and Zr)) Thermal conductivity of outer periphery: 212 W / (m K)

[0103] In Comparative Example 1, the following cooling roll was used. The cooling roll of Comparative Example 1 also has water channels inside for circulating cooling water as a structure for cooling the outer periphery.

[0104] -Cooling Roll of Comparative Example 1- ·Diameter: 800mm ·Width: 150mm Outer thickness: 20mm Outer material: Cu-Be alloy (Be: 0.3 mass%, balance Cu and impurities) Thermal conductivity of outer periphery: 240W / (m·K)

[0105] [Table 1]

[0106] As shown in Table 1, in Examples 1 to 4 in which the thermal conductivity of the outer periphery of the chill roll was 70 W / (m·K) or more and 225 W / (m·K) or less, the free solidification surface of the ribbon was 100 mm 2 The number of contact protrusions P was reduced, and the insulation ratio RI of the magnetic core was excellent. In contrast, in the comparative example where the thermal conductivity of the outer periphery of the chill roll is more than 225 W / (m K), the free solidification surface of the ribbon is 100 mm 2 The number of protrusions P on the bearing surface increased significantly, and the insulation factor RI of the magnetic core deteriorated significantly.

[0107] Fig. 1 is a laser microscope image (magnification 50x) of two protrusions P (i.e., protrusions P having a depression in the center) in the Fe-based amorphous alloy ribbon of Comparative Example 1, observed from a direction perpendicular to the free solidification surface, and Fig. 2 is a 3D (three-dimensional) display diagram of Fig. 1. Here, a laser microscope "VK-8716" manufactured by Keyence Corporation was used as the laser microscope, and analysis to obtain a three-dimensional image was performed using analysis software "VK Analyzer ver. 2.4.0.0" manufactured by the same company. In Comparative Example 1, many such protrusions P were generated, but in Examples 1 to 4, the number of such protrusions P was reduced.

[0108] The disclosure of Japanese Patent Application No. 2018-180031, filed on September 26, 2018, is incorporated herein by reference in its entirety. All publications, patent applications, and technical standards mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication, patent application, or technical standard was specifically and individually indicated to be incorporated by reference.

Claims

1. a step of supplying a molten Fe-based alloy onto a rotating chill roll, and rapidly solidifying the molten Fe-based alloy supplied onto the chill roll, thereby obtaining an Fe-based amorphous alloy ribbon having a free solidification surface and a roll contact surface, a width of 5 mm to 65 mm, and a thickness of 10 μm to 14 μm; heat-treating the Fe-based amorphous alloy ribbon to obtain an Fe-based nanocrystalline alloy ribbon; Including, the outer periphery of the chill roll is made of a Cu alloy, the thermal conductivity of the outer periphery is 110 W / (m K) or more and 225 W / (m K) or less, and the Vickers hardness of the outer periphery is 250 HV or more; The diameter of the cooling roll is 300 mm or more and 1000 mm or less, The thickness of the outer circumferential portion of the cooling roll is 15 mm or more and 40 mm or less, the peripheral speed of the cooling roll is 20 m / sec or more and 35 m / sec or less, the number of protrusions P having a depression in the center on the free solidification surface of the Fe-based nanocrystalline alloy ribbon is 1.2 or less per 100 mm2 area; A method for producing an Fe-based nanocrystalline alloy ribbon.

2. 2. The method for producing an Fe-based nanocrystalline alloy ribbon according to claim 1, wherein the Fe-based alloy molten metal has an alloy composition represented by the following composition formula (A): Fe100-a-b-c-d-eCuaSibBcNbdCe... Composition formula (A) In the composition formula (A), 100-a-b-c-d-e, a, b, c, d, and e respectively represent the atomic percentage of each element when the total of Fe, Cu, Si, B, Nb, and C is 100 atomic percent, and a, b, c, d, and e respectively satisfy 0.30≦a≦2.00, 13.00≦b≦16.00, 6.00≦c≦11.00, 2.00≦d≦4.00, and 0.04≦e≦0.

40.

3. A method for manufacturing a magnetic core including a wound body C in which an Fe-based nanocrystalline alloy ribbon is wound with an insulating layer interposed therebetween, comprising: a step of supplying a molten Fe-based alloy onto a rotating chill roll, and rapidly solidifying the molten Fe-based alloy supplied onto the chill roll, thereby obtaining an Fe-based amorphous alloy ribbon having a free solidification surface and a roll contact surface, a width of 5 mm to 65 mm, and a thickness of 10 μm to 14 μm; forming the insulating layer on the free solidification surface of the Fe-based amorphous alloy ribbon; a step of winding the Fe-based amorphous alloy ribbon on which the insulating layer has been formed, to obtain a wound body A in which the Fe-based amorphous alloy ribbon is wound with the insulating layer interposed therebetween; a step of obtaining the wound body C by heat treating the wound body A; Including, the outer periphery of the chill roll is made of a Cu alloy, the thermal conductivity of the outer periphery is 110 W / (m K) or more and 225 W / (m K) or less, and the Vickers hardness of the outer periphery is 250 HV or more; The diameter of the cooling roll is 300 mm or more and 1000 mm or less, The thickness of the outer circumferential portion of the cooling roll is 15 mm or more and 40 mm or less, the peripheral speed of the cooling roll is 20 m / sec or more and 35 m / sec or less, The method for manufacturing a magnetic core, wherein the number of protrusions P having a depression in the center on the free solidification surface of the Fe-based nanocrystalline alloy ribbon is 1.2 or less per 100 mm2 area.

4. The method for producing a magnetic core according to claim 3, wherein the molten Fe-based alloy has an alloy composition represented by the following composition formula (A): Fe100-a-b-c-d-eCuaSibBcNbdCe... Composition formula (A) In the composition formula (A), 100-a-b-c-d-e, a, b, c, d, and e respectively represent the atomic percentage of each element when the total of Fe, Cu, Si, B, Nb, and C is 100 atomic percent, and a, b, c, d, and e respectively satisfy 0.30≦a≦2.00, 13.00≦b≦16.00, 6.00≦c≦11.00, 2.00≦d≦4.00, and 0.04≦e≦0.40.

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