Method for producing Fe-based nanocrystalline alloy thin strip, method for producing magnetic core, Fe-based nanocrystalline alloy thin strip, and magnetic core
阅读说明：本技术 Fe基纳米晶合金薄带的制备方法、磁芯的制备方法、Fe基纳米晶合金薄带以及磁芯 (Method for producing Fe-based nanocrystalline alloy thin strip, method for producing magnetic core, Fe-based nanocrystalline alloy thin strip, and magnetic core ) 是由 砂川淳 森次仲男 于 2019-09-24 设计创作，主要内容包括：提供一种Fe基纳米晶合金薄带的制备方法,包括如下步骤：向旋转的冷却辊上提供Fe基合金熔融液体,通过使提供至所述冷却辊上的所述Fe基合金熔融液体急冷凝固,得到具有自由凝固面和辊接触面的Fe基非晶合金薄带的步骤,对所述Fe基非晶合金薄带进行热处理得到Fe基纳米晶合金薄带的步骤,其中,所述冷却辊的外周部由Cu合金构成,且所述外周部的导热系数为70W/(m·K)以上225W/(m·K)以下。(The preparation method of the Fe-based nanocrystalline alloy thin strip comprises the following steps: and a step of providing a molten Fe-based alloy on a rotating cooling roll, rapidly cooling and solidifying the molten Fe-based alloy on the cooling roll to obtain a thin Fe-based amorphous alloy ribbon having a free solidification surface and a roll contact surface, and a step of heat-treating the thin Fe-based amorphous alloy ribbon to obtain a thin Fe-based nanocrystalline alloy ribbon, wherein an outer peripheral portion of the cooling roll is made of a Cu alloy, and a thermal conductivity of the outer peripheral portion is 70W/(m · K) to 225W/(m · K).)
1. A preparation method of a Fe-based nanocrystalline alloy thin strip comprises the following steps:
a step of supplying an Fe-based alloy molten liquid onto a rotating chill roll so that the Fe-based alloy molten liquid supplied onto the chill roll is rapidly solidified, thereby obtaining an Fe-based amorphous alloy thin strip having a free solidification surface and a roll contact surface, a width of 5mm or more and 65mm or less, and a thickness of 10 μm or more and 15 μm or less, and
performing heat treatment on the Fe-based amorphous alloy thin strip to obtain a Fe-based nanocrystalline alloy thin strip;
wherein an outer peripheral portion of the cooling roll is made of a Cu alloy, and a thermal conductivity of the outer peripheral portion is 70W/(m.K) to 225W/(m.K).
2. The method for producing an Fe-based nanocrystalline alloy ribbon according to claim 1, wherein the vickers hardness of the outer peripheral portion is 250HV or more.
3. The method for producing the Fe-based nanocrystalline alloy ribbon according to claim 1 or 2, the Fe-based alloy molten liquid having an alloy composition represented by the following composition formula (a),
Fe100-a-b-c-d-eCuaSibBcNbdCe… component formula (A)
In the compositional formula (A), 100-a-B-C-d-e, a, B, C, d and e respectively represent atomic% of each element when Fe, Cu, Si, B, Nb and C are 100 atomic% in total, and a, B, C, d and e 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, respectively.
4. A method for producing a magnetic core including a wound body C obtained by winding a thin strip of Fe-based nanocrystalline alloy with an insulating layer interposed therebetween, comprising the steps of:
a step of supplying an Fe-based alloy molten liquid onto a rotating chill roll, and rapidly cooling and solidifying the Fe-based alloy molten liquid supplied onto the chill roll, thereby obtaining an Fe-based amorphous alloy thin strip having a free solidification surface and a roll contact surface, a width of 5mm to 65mm, and a thickness of 10 μm to 15 μm,
a step of forming the insulating layer on the free solidification surface of the thin strip of Fe-based amorphous alloy,
a step of obtaining a wound body A in which the Fe-based amorphous alloy ribbon is wound with the insulating layer interposed therebetween by winding the Fe-based amorphous alloy ribbon on which the insulating layer is formed, and
a step of heat-treating the wound body a to obtain a wound body C;
wherein an outer peripheral portion of the cooling roll is made of a Cu alloy, and a thermal conductivity of the outer peripheral portion is 70W/(m.K) to 225W/(m.K).
5. The method for producing a magnetic core according to claim 4, wherein the Vickers hardness of the outer peripheral portion is 250HV or more.
6. The method for producing a magnetic core according to claim 4 or 5, the Fe-based alloy molten liquid having an alloy composition represented by the following composition formula (A),
Fe100-a-b-c-d-eCuaSibBcNbdCe… component formula (A)
In the compositional formula (A), 100-a-B-C-d-e, a, B, C, d and e respectively represent atomic% of each element when Fe, Cu, Si, B, Nb and C are 100 atomic% in total, and a, B, C, d and e 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, respectively.
7. A Fe-based nanocrystalline alloy thin strip,has a free solidification surface and a roller contact surface, wherein the number of the protrusions P having the pits at the central part of the free solidification surface is 100mm2The Fe-based nanocrystalline alloy ribbon has a width of 5mm to 65mm and a thickness of 10 μm to 15 μm, respectively, of 1.2 or less in area.
8. The Fe-based nanocrystalline alloy thin strip according to claim 7, having a warpage in the width direction of 0.30mm or less per 10mm width.
9. The Fe-based nanocrystalline alloy ribbon according to claim 7 or 8, having an alloy composition represented by the following composition formula (A),
Fe100-a-b-c-d-eCuaSibBcNbdCe… component formula (A)
In the compositional formula (A), 100-a-B-C-d-e, a, B, C, d and e respectively represent atomic% of each element when Fe, Cu, Si, B, Nb and C are 100 atomic% in total, and a, B, C, d and e 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, respectively.
10. A magnetic core comprising a roll C1 formed by winding the Fe-based nanocrystalline alloy ribbon according to any one of claims 7 to 9 with an insulating layer interposed therebetween.
11. The magnetic core according to claim 10, wherein an insulation rate RI represented by the following formula (1) is 80% or more,
RI ═ Rr/(Ru · Lr) × 100 (%) formula (1)
In the formula (1), Rr represents a dc resistance value in Ω between one end of the innermost circumference and the other end of the outermost circumference in the Fe-based nanocrystalline alloy ribbon, Ru represents a dc resistance value in Ω per 1m length of the Fe-based nanocrystalline alloy ribbon in the longitudinal direction, and Lr represents a length in m in the longitudinal direction of the Fe-based nanocrystalline alloy ribbon.
Technical Field
The present disclosure relates to a method for producing a Fe-based nanocrystalline alloy thin strip, a method for producing a magnetic core, a Fe-based nanocrystalline alloy thin strip, and a magnetic core.
Background
Fe-based nanocrystalline alloys have excellent magnetic properties such as low loss and high magnetic permeability, and are therefore used as materials for magnetic parts (e.g., magnetic cores).
A magnetic core including an Fe-based nanocrystalline alloy ribbon is produced, for example, by a method in which an Fe-based alloy molten liquid is rapidly solidified by a single-roll method to obtain an Fe-based amorphous alloy ribbon, and the obtained Fe-based amorphous alloy ribbon is wound or laminated and then subjected to a heat treatment to precipitate nanocrystalline grains in the alloy structure of the Fe-based amorphous alloy ribbon as an Fe-based nanocrystalline alloy ribbon (for example, refer to patent document 1).
As a magnetic core containing a Fe-based nanocrystalline alloy ribbon, for example, patent document 2 discloses a low-loss high-frequency acceleration cavity magnetic core used as a high-frequency acceleration cavity magnetic core having a shape in which a Fe-based nanocrystalline alloy ribbon having a roll contact surface and a free surface obtained by a single roll method is wound via an insulating layer, and projections having a predetermined shape are dispersed on the free surface of the Fe-based nanocrystalline alloy ribbon, and the tops of the projections are polished and passivated.
Patent document 1: japanese examined patent publication (Kokoku) No. 4-4393
Patent document 2: japanese patent laid-open publication No. 2015-167228
Disclosure of Invention
Problems to be solved by the invention
Patent document 2 describes that when the thickness of a conventional alloy ribbon having a thickness of more than 15 μm is reduced, there is a protrusion on one main surface of the alloy ribbon, and an insulating layer is not formed on the protrusion, and as a result, there is a problem that the insulating properties are reduced by causing contact and conduction between adjacent alloy ribbons in a magnetic core via the insulating layer. Patent document 2 describes that the above problem can be solved by polishing and passivating the top of the protrusion.
However, the method of polishing and passivating the top of the protrusion described in patent document 2 has a problem of increasing the number of production steps. Further, there is a problem that the man-hours for maintaining and managing the polishing ability are large. Further, it is difficult to continuously and effectively polish the Fe-based nanocrystalline alloy ribbon over almost the entire surface thereof without variation, and therefore, there is a limit to ensuring a continuous stable high insulation property.
Therefore, as a technique for improving the projections of a thin Fe-based nanocrystalline alloy ribbon having a small thickness (specifically, a thickness of 15 μm or less), a technique that does not rely on polishing the top of the projections but suppresses the occurrence of the projections itself is required.
An object of the first aspect of the present disclosure is to provide a method for producing a thin Fe-based nanocrystalline alloy ribbon that is thin, and that can produce a thin Fe-based nanocrystalline alloy ribbon that suppresses the occurrence of projections in the free solidified surface.
A second aspect of the present disclosure is directed to a method for producing a magnetic core including a wound body obtained by winding a thin Fe-based nanocrystalline alloy ribbon having a small thickness with an insulating layer interposed therebetween, the method being capable of producing a magnetic core having excellent insulation between adjacent Fe-based nanocrystalline alloy ribbons with an insulating layer interposed therebetween.
A third aspect of the present disclosure is to provide a thin Fe-based nanocrystalline alloy ribbon that is thin and in which the occurrence of projections in the free solidification surface is suppressed.
A fourth aspect of the present disclosure is directed to provide a magnetic core including a wound body obtained by winding a thin Fe-based nanocrystalline alloy ribbon with an insulating layer interposed therebetween, the magnetic core having excellent insulation between adjacent Fe-based nanocrystalline alloy ribbons with an insulating layer interposed therebetween.
Means for solving the problems
Specific methods for solving the above problems are as follows:
<1> a method for preparing a Fe-based nanocrystalline alloy ribbon, comprising the following steps:
a step of supplying an Fe-based alloy molten liquid onto a rotating chill roll so that the Fe-based alloy molten liquid supplied onto the chill roll is rapidly solidified, thereby obtaining an Fe-based amorphous alloy thin strip having a free solidification surface and a roll contact surface, a width of 5mm or more and 65mm or less, and a thickness of 10 μm or more and 15 μm or less, and
performing heat treatment on the Fe-based amorphous alloy thin strip to obtain a Fe-based nanocrystalline alloy thin strip;
wherein an outer peripheral portion of the cooling roll is made of a Cu alloy, and a thermal conductivity of the outer peripheral portion is 70W/(m.K) to 225W/(m.K).
<2> the method of producing a Fe-based nanocrystalline alloy ribbon according to the above <1>, wherein the Vickers hardness of the outer peripheral portion is 250HV or more.
<3> the method for producing a thin strip of Fe-based nanocrystalline alloy according to the above <1> or <2>, the Fe-based alloy molten liquid having an alloy composition represented by the following composition formula (a),
Fe100-a-b-c-d-eCuaSibBcNbdCe… component formula (A)
In the compositional formula (A), 100-a-B-C-d-e, a, B, C, d and e respectively represent atomic% of each element when Fe, Cu, Si, B, Nb and C are 100 atomic% in total, and a, B, C, d and e 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, respectively.
<4> a method for producing a magnetic core comprising a wound body C obtained by winding a thin strip of Fe-based nanocrystalline alloy with an insulating layer interposed therebetween, comprising the steps of:
a step of supplying an Fe-based alloy molten liquid onto a rotating chill roll, and rapidly cooling and solidifying the Fe-based alloy molten liquid supplied onto the chill roll, thereby obtaining an Fe-based amorphous alloy thin strip having a free solidification surface and a roll contact surface, a width of 5mm to 65mm, and a thickness of 10 μm to 15 μm,
a step of forming the insulating layer on the free solidification surface of the thin strip of Fe-based amorphous alloy,
a step of obtaining a wound body A in which the Fe-based amorphous alloy ribbon is wound with the insulating layer interposed therebetween by winding the Fe-based amorphous alloy ribbon on which the insulating layer is formed, and
a step of heat-treating the wound body A to obtain the wound body C,
wherein an outer peripheral portion of the cooling roll is made of a Cu alloy, and a thermal conductivity of the outer peripheral portion is 70W/(m.K) to 225W/(m.K).
<5> the method of manufacturing a magnetic core according to <4>, wherein the Vickers hardness of the outer peripheral portion is 250HV or more.
<6> the production method for a magnetic core according to <4> or <5>, the Fe-based alloy molten liquid having an alloy composition represented by the following composition formula (A),
Fe100-a-b-c-d-eCuaSibBcNbdCe… component formula (A)
In the compositional formula (A), 100-a-B-C-d-e, a, B, C, d and e respectively represent atomic% of each element when Fe, Cu, Si, B, Nb and C are 100 atomic% in total, and a, B, C, d and e 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, respectively.
<7>A Fe-based nanocrystalline alloy ribbon having a free solidified surface and a roll contact surface, wherein the number of projections P having a dimple in the central portion of the free solidified surface is 100mm per 100mm2Less than 1.2 in area, and the width of the Fe-based nanocrystalline alloy thin strip is 5mmAbove 65mm, and the thickness is 10 μm to 15 μm.
<8> the thin strip of Fe-based nanocrystalline alloy according to <7>, wherein the warpage in the width direction (inverse り) is 0.30mm or less per 10mm width.
<9> the Fe-based nanocrystalline alloy ribbon according to <7> or <8> having an alloy composition represented by the following composition formula (A),
Fe100-a-b-c-d-eCuaSibBcNbdCe… component formula (A)
In the compositional formula (A), 100-a-B-C-d-e, a, B, C, d and e respectively represent atomic% of each element when Fe, Cu, Si, B, Nb and C are 100 atomic% in total, and a, B, C, d and e 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, respectively.
<10> a magnetic core comprising a roll C1 formed by winding the Fe-based nanocrystalline alloy ribbon described in any one of <7> to <9> with an insulating layer interposed therebetween.
<11> the magnetic core according to <10>, having an insulation rate RI represented by the following formula (1) of 80% or more,
RI ═ Rr/(Ru · Lr) × 100 (%) … formula (1)
In the formula (1), Rr represents a direct current resistance value (Ω) between one end of the innermost circumference and both ends of the other end of the outermost circumference in the Fe-based nanocrystalline alloy ribbon, Ru represents a direct current resistance value (Ω) per 1m length of the Fe-based nanocrystalline alloy ribbon in the longitudinal direction, and Lr represents a length (m) of the Fe-based nanocrystalline alloy ribbon in the longitudinal direction.
Effects of the invention
According to the first aspect of the present disclosure, there is provided a production method of a thin strip of Fe-based nanocrystalline alloy that is a thin strip of Fe-based nanocrystalline alloy of a small thickness, the production method being capable of producing a thin strip of Fe-based nanocrystalline alloy that suppresses the occurrence of projections in a free solidification surface.
According to the second aspect of the present disclosure, there is provided a method for producing a magnetic core including a wound body obtained by winding a thin Fe-based nanocrystalline alloy ribbon having a small thickness with an insulating layer interposed therebetween, the method being capable of producing a magnetic core having excellent insulation between adjacent Fe-based nanocrystalline alloy ribbons with an insulating layer interposed therebetween.
According to a third aspect of the present disclosure, there is provided a thin Fe-based nanocrystalline alloy ribbon, which is thin and in which the occurrence of projections in the free solidified surface is suppressed.
According to a fourth aspect of the present disclosure, there is provided a magnetic core including a wound body obtained by winding a thin Fe-based nanocrystalline alloy ribbon with an insulating layer interposed therebetween, the magnetic core having excellent insulation between adjacent Fe-based nanocrystalline alloy ribbons with an insulating layer interposed therebetween.
Drawings
Fig. 1 is a laser microscope image (50-fold magnification) of 2 projections P (i.e., projections P having a pit in the central portion) in the Fe-based amorphous alloy ribbon of comparative example 1, when viewed from a direction perpendicular to the free solidification surface.
Fig. 2 is a three-dimensional view of fig. 1.
Detailed Description
In the present disclosure, the designation of "step" is not only a separate step, but is also included in the present application as long as the intended purpose of the step is included even in the case of an alloy that cannot be distinguished from other steps.
In the present disclosure, the term "nanocrystalline alloy" refers to an alloy containing a nanocrystalline phase (i.e., a phase formed by nanocrystalline particles). The "nanocrystalline alloy" may also contain phases other than nanocrystalline phases (e.g., amorphous phases).
In the present disclosure, the term "Fe-based" means that the main component (i.e., the component having the largest mass content) is Fe.
[ method for producing Fe-based nanocrystalline alloy thin strip ]
The method for producing a Fe-based nanocrystalline alloy thin strip according to the present disclosure (hereinafter also referred to as "the method for producing a Fe-based nanocrystalline alloy thin strip according to the present disclosure") includes the steps of:
a step of supplying an Fe-based alloy molten liquid onto a rotating chill roll so that the Fe-based alloy molten liquid supplied onto the chill roll is rapidly solidified, thereby obtaining an Fe-based amorphous alloy thin strip having a free solidification surface and a roll contact surface, a width of 5mm or more and 65mm or less, and a thickness of 10 μm or more and 15 μm or less, and
performing heat treatment on the Fe-based amorphous alloy thin strip to obtain a Fe-based nanocrystalline alloy thin strip;
wherein an outer peripheral portion of the cooling roll is made of a Cu alloy, and a thermal conductivity of the outer peripheral portion is 70W/(m.K) to 225W/(m.K).
The method for producing the Fe-based nanocrystalline alloy thin strip of the present disclosure may further include other steps as necessary.
In the present disclosure, the free solidification surface of the Fe-based amorphous alloy ribbon refers to the major surface exposed to the atmosphere without contacting the cooling roll at the stage of producing the Fe-based amorphous alloy ribbon, out of 2 major surfaces of the Fe-based amorphous alloy ribbon. The meaning of the free solidification surface of the Fe-based nanocrystalline alloy ribbon obtained by heat-treating the Fe-based amorphous alloy ribbon is also the same.
In the present disclosure, the roll contact surface of the Fe-based amorphous alloy thin strip means a major surface that contacts the cooling roll at the stage of producing the Fe-based amorphous alloy thin strip, among 2 major surfaces of the Fe-based amorphous alloy thin strip. The roll contact surface of the Fe-based nanocrystalline alloy thin strip obtained by heat-treating the Fe-based amorphous alloy thin strip is also equivalent.
The alloy thin strip having a free solidification surface and a roll contact surface means an alloy thin strip obtained by a single-roll method.
As a result of the studies by the present inventors, it was found that, when an Fe-based alloy molten liquid is supplied to a rotating cooling roll and rapidly solidified to obtain an Fe-based amorphous alloy ribbon having a free solidification surface and a roll contact surface (hereinafter, the operation up to this point is also referred to as "casting") and the obtained Fe-based amorphous alloy ribbon is subjected to heat treatment to obtain an Fe-based nanocrystalline alloy ribbon, particularly, when the thickness of the Fe-based amorphous alloy ribbon is 15 μm or less, the outer circumferential portion of the cooling roll is made of a Cu alloy, and the thermal conductivity of the outer circumferential portion exceeds 225W/(m · K), projections are likely to be generated on the free solidification surface of the Fe-based nanocrystalline alloy ribbon.
The reason is not clear, but is presumed as follows:
the casting of the Fe-based amorphous alloy thin strip is generally performed while polishing the outer peripheral surface (i.e., the surface of the outer peripheral portion) of the cooling roll. The outer peripheral surface is usually polished between the time when the cast Fe-based amorphous alloy thin strip is peeled off from the outer peripheral surface and the time when the subsequent Fe-based alloy molten liquid is supplied to the outer peripheral surface. Here, when the outer peripheral portion of the cooling roll is made of a Cu alloy and the thermal conductivity of the outer peripheral portion exceeds 225W/(m · K), the vickers hardness of the outer peripheral portion tends to be low. As a result, it is considered that when the outer peripheral surface of the cooling roll is polished, a deep flaw is easily formed on the outer peripheral surface, and coarse abrasive powder is easily generated, and the generated abrasive powder is easily attached to the outer peripheral surface. When the Fe-based alloy molten liquid is supplied to the outer peripheral surface to which the abrasive powder is attached, air is likely to be entrained in the supplied Fe-based alloy molten liquid, and as a result, a portion which is likely to be crystallized due to insufficient cooling rate is locally generated, and this portion is considered to be a protrusion. When the thickness of the Fe-based amorphous alloy ribbon to be cast is thin (specifically, 15 μm or less), it is considered that the Fe-based amorphous alloy ribbon is more likely to be affected by the abrasive powder, and therefore, the protrusion is more likely to occur. It is considered that the generated projections are maintained on the free solidification surface of the Fe-based nanocrystalline alloy thin strip obtained by heat-treating the Fe-based amorphous alloy thin strip.
In relation to the above problems, the method for producing the Fe-based nanocrystalline alloy ribbon according to the present disclosure is not limited to casting the Fe-based amorphous alloy ribbon having a thickness of 15 μm or less, and can suppress the generation of the protrusion in the free solidified surface.
In order to effectively suppress the generation of the protrusion on the free solidification surface, it is advantageous that the thermal conductivity of the outer periphery of the cooling roll (i.e., the outer periphery made of the Cu alloy) is 225W/(m · K) or less. Specifically, when the thermal conductivity of the outer peripheral portion is 225W/(m · K) or less, the vickers hardness of the outer peripheral portion increases (that is, the outer peripheral portion becomes hard), and the generation of the coarse abrasive powder is suppressed, and as a result, it is considered that the generation of the protrusion can be suppressed.
Hereinafter, each step of the method for producing the Fe-based nanocrystalline alloy thin strip according to the present disclosure will be described.
< step of obtaining Fe-based amorphous alloy thin strip >
The step of obtaining the Fe-based amorphous alloy thin strip is a step of providing a molten Fe-based alloy on a rotating cooling roll, and rapidly cooling and solidifying the molten Fe-based alloy on the cooling roll, thereby obtaining the Fe-based amorphous alloy thin strip having a free solidification surface and a roll contact surface, a width of 5mm to 65mm, and a thickness of 10 μm to 15 μm.
(preferred alloy composition of Fe-based alloy molten liquid)
The preferred alloy composition of the Fe-based alloy molten liquid is an alloy composition represented by the following composition formula (a) from the viewpoint that a nanocrystalline phase is easily formed in the alloy structure by heat treatment.
The steps in the preparation method of the Fe-based nanocrystalline alloy thin strip disclosed by the invention have no influence on the alloy composition of the alloy.
Therefore, the alloy composition of the Fe-based alloy molten liquid remains as it is in the production of the Fe-based amorphous alloy thin strip and the Fe-based nanocrystalline alloy thin strip using the Fe-based alloy molten liquid.
That is, the alloy composition represented by the following composition formula (a) is a preferable chemical composition of the Fe-based alloy molten liquid, and is a preferable chemical composition of the Fe-based amorphous alloy ribbon, and is a preferable chemical composition of the Fe-based nanocrystalline alloy ribbon.
Fe100-a-b-c-d-eCuaSibBcNbdCe… component formula (A)
In the compositional formula (A), 100-a-B-C-d-e, a, B, C, d, and e each represent an atomic% of each element when the total of Fe, Cu, Si, B, Nb, and C is 100 at%, and a, B, C, d, and e 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, respectively.
The alloy composition represented by the 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 100 atomic%.
Fe is an element that becomes a main body of soft magnetic characteristics.
From the viewpoint of obtaining a high saturation magnetic flux density Bs, the content (at%) of Fe (i.e., "100-a-b-c-d-e" in the composition formula (a)) is preferably 72.00 at% or more, and more preferably 74.00 at% or more.
Cu is an element which becomes a nucleus of a nanocrystal when a Fe-based amorphous alloy thin strip is subjected to heat treatment to obtain a Fe-based nanocrystalline alloy thin strip. By this heat treatment, nanocrystalline grains are precipitated in the alloy structure.
From the viewpoint of the effect, the content of Cu (i.e., "a" in the composition formula (a) is 0.30 at% or more, preferably 0.80 at% or more, and more preferably 0.90 at% or more).
On the other hand, if the Cu content exceeds 2.00 atomic%, the possibility of nanocrystalline nuclei existing in the Fe-based amorphous alloy ribbon before heat treatment increases, and the nanocrystalline nuclei grow and coarsen by heat treatment, which may deteriorate 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.
Si is an effective element that reduces the crystal magnetic anisotropy of Fe, improves soft magnetic properties, and is capable of forming an amorphous together with B (boron).
When the content of Si is 13.00 atomic% or more, a high amorphous forming ability can be obtained when an Fe-based amorphous alloy ribbon is produced. In addition, in the nanocrystalline alloy ribbon obtained by the heat treatment, lower saturation magnetostriction can be obtained. Therefore, the content of Si (i.e., "b" in the 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, when the Si content exceeds 16.00 atomic%, the viscosity of the alloy molten liquid decreases, and therefore, when the alloy molten liquid is poured onto the outer peripheral surface of the cooling roll and rapidly solidified to obtain an Fe-based amorphous alloy thin strip, there is a risk that the smoothness of the free solidification surface of the Fe-based amorphous alloy thin strip deteriorates. Therefore, the Si content is 16.00 atomic% or less, preferably 15.5 atomic% or less.
As described above, B (boron) is an effective element having an amorphous forming ability together with Si. Further, when a nanocrystalline phase (i.e., a phase formed of nanocrystalline particles) is formed in the alloy structure by heat treatment, it is an element that determines the volume fraction of an amorphous phase as an uncrystallized phase. That is, B is an element that determines the volume ratio of the nanocrystalline phase to the amorphous phase after the heat treatment.
Compared with the nano-crystalline phase, the magnetostriction is negative, and the amorphous phase is positive, and the proportion of the magnetostriction of the whole alloy is determined by the proportion of the magnetostriction of the nano-crystalline phase to the amorphous phase. When the content of B is large, the volume fraction of the amorphous phase becomes large as compared with the nanocrystal after heat treatment, resulting in an increase in saturation magnetostriction. The saturation magnetostriction is preferably 5 × 10-6The following. From the viewpoint of obtaining a saturated magnetostriction or less, the content of B (i.e., "c" in the composition formula (a)) is 11.00 atomic% or less, preferably 9.00 atomic% or less. When the saturation magnetostriction is small, when the prepared core is stored in a case or the like, or when a coil is formed by winding a coil around the core, deterioration of magnetic characteristics can be suppressed even if the core is subjected to mechanical stress.
On the other hand, when the content of B is small, it becomes difficult to stably obtain an amorphous phase when an alloy molten liquid is quenched to produce an alloy thin strip. From the viewpoint of stably obtaining an amorphous phase, the content of B is 6.00 atomic% or more, preferably 6.50 atomic% or more.
Nb is an effective element for uniformly distributing the nanocrystalline grains precipitated after the heat treatment in the alloy structure, suppressing the formation of coarse grains, and precipitating fine nanocrystalline grains.
From the viewpoint of the above-mentioned effects, the content of Nb (i.e., "d" in the composition formula (a)) is 2.00 at% or more, preferably 2.40 at% or more, more preferably 2.50 at% or more, and still more preferably 2.80 at% or more.
On the other hand, Nb does not contribute to the magnetic properties, and is preferably 4.00 at% or less, more preferably 3.50 at% or less, and further preferably 3.20 at% or less.
C (carbon) is effective in stabilizing the viscosity of the Fe-based alloy molten liquid. From the viewpoint of the above-mentioned effects, the content of C (i.e., "e" in the composition formula (a)) is 0.04 at% or more, preferably 0.05 at% or more, more preferably 0.10 at% or more, and still more preferably 0.12 at% or more.
On the other hand, the content of C is preferably 0.40 atomic% or less, more preferably 0.35 atomic% or less, and further preferably 0.30 atomic% or less, from the viewpoint of suppressing embrittlement of the alloy ribbon.
The Fe-based alloy molten liquid having the alloy composition represented by the composition formula (a) may contain at least 1 impurity element in addition to the 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 element means an element other than the elements in the alloy composition represented by the composition formula (a).
The total content of impurity elements when the entire alloy composition represented by the composition formula (a) (i.e., the total of Fe, Cu, Si, B, Nb, and C) is 100 atomic% is preferably 0.20 atomic% or less, and more preferably 0.10 atomic% or less.
(Cooling roll)
In the step of obtaining the Fe-based amorphous alloy ribbon, the Fe-based alloy molten liquid is supplied onto the cooling roll, and the Fe-based alloy molten liquid supplied onto the cooling roll is rapidly cooled, thereby obtaining the Fe-based amorphous alloy ribbon.
The outer periphery of the cooling roll (i.e., the portion including the outer periphery) is made of a Cu alloy.
The outer peripheral part made of a Cu alloy has a thermal conductivity of 70W/(m.K) to 225W/(m.K).
By setting the thermal conductivity of the outer peripheral portion of the Cu alloy to 225W/(m · K) or less, the formation of projections on the free solidification surface of the finally obtained Fe-based nanocrystalline alloy ribbon can be suppressed.
From the viewpoint of further suppressing the generation of the protrusion, the thermal conductivity of the outer peripheral portion is preferably 220W/(m · K) or less, more preferably 200W/(m · K) or less, still more preferably 170W/(m · K) or less, still more preferably 150W/(m · K) or less, and still more preferably 130W/(m · K) or less.
On the other hand, from the viewpoint of the ability to quench the Fe-based alloy molten liquid supplied to the chill roll, the thermal conductivity of the outer peripheral portion is 70W/(m · K) or more. From the viewpoint of further improving the above performance, the thermal conductivity of the outer peripheral portion is preferably 90W/(m · K) or more, and more preferably 110W/(m · K) or more.
The thermal conductivity of the outer peripheral portion can be controlled by the type and amount of the metal element contained in the Cu alloy constituting the outer peripheral portion, excluding Cu.
For example, Cu-Be alloy can Be controlled by the Be content. Examples of the Cu alloy having a thermal conductivity of 70W/(m.K) to 225W/(m.K) include Cu-Be alloys containing Be in an amount of 1.6 to 2.2 mass% based on the entire Cu-Be alloy.
In the above Cu — Be alloy, the balance other than Be is Cu and impurities. The impurities in the Cu-Be alloy are at least 1 of Cu and elements other than Be. Examples of the impurities in the Cu-Be alloy include Ni and Co. The total content of impurities is, for example, 1.0 mass% or less.
Further, examples of the Cu alloy constituting the outer peripheral portion include a Cu — Ni alloy, a Cu — Ni — Be alloy, and the like. These Cu alloys may contain impurities, and examples of the impurities include Si, Cr, Ag, Zr, and the like.
The Vickers hardness of the outer periphery of the cooling roller is preferably 250HV or more. This can further suppress the occurrence of projections on the free solidified surface.
From the viewpoint of further suppressing the generation of projections on the free solidified surface, the vickers hardness of the outer peripheral portion of the cooling roller is more preferably 260HV or more, and still more preferably 300HV or more.
The upper limit of the vickers hardness of the outer peripheral portion of the cooling roller is not particularly limited.
The vickers hardness of the outer peripheral portion of the cooling roller may be, for example, 400HV or less. This makes it easier to grind the outer peripheral portion of the cooling roll during casting (i.e., during production of the Fe-based amorphous alloy ribbon), and can further improve the removability of the deposit adhering to the outer peripheral surface of the cooling roll (i.e., the outer surface of the outer peripheral portion), thereby further suppressing crystallization of the Fe-based amorphous alloy ribbon due to the deposit.
In the present disclosure, the vickers hardness refers to a value measured at a test load of 20 kgf.
The cooling roll preferably has a structure for cooling the outer peripheral portion inside the cooling roll. This can further suppress the temperature rise of the outer peripheral surface caused by contact with the molten Fe-based alloy liquid, and can more effectively maintain the cooling capacity of the outer peripheral surface.
As a structure for cooling the outer peripheral portion, a structure in which the cooling roll rotating shaft side of the outer peripheral portion (i.e., the inner surface of the outer peripheral portion) is brought into contact with temperature-controlled water and circulated is preferable.
In this case, it is preferable to use another alloy as the material of the portion of the cooling roll located on the side of the rotational axis of the cooling roll as viewed from the outer peripheral portion. For other alloys, no special consideration of thermal conductivity is required. Examples of the other alloy include stainless steel and cast iron.
The thickness of the outer peripheral portion of the cooling roll is preferably 15mm to 40mm from the viewpoint of ensuring cooling energy for the Fe-based alloy molten liquid and from the viewpoint of facilitating maintenance and management of the surface state of the outer peripheral surface of the cooling roll.
The thickness of the outer peripheral portion is more preferably 17mm or more, and still more preferably 20mm or more.
Further, the thickness of the outer peripheral portion is more preferably 30mm or less.
The diameter of the cooling roll is preferably 300mm or more, and more preferably 400mm or more, from the viewpoint of maintenance and control of the cooling roll main body.
The diameter of the cooling roll is preferably 1000mm or less, more preferably 900mm or less.
The width of the cooling roll is preferably 2.5 times or more the maximum width of the Fe-based amorphous alloy ribbon to be produced, from the viewpoint of more stably obtaining the cooling energy of the molten Fe-based alloy. The width of the cooling roll is more preferably 3.0 times or more the maximum width of the Fe-based amorphous alloy thin strip.
On the other hand, the width of the cooling roll is preferably 10.0 times or less the maximum width of the Fe-based amorphous alloy ribbon from the viewpoint of maintaining and controlling the surface state of the outer peripheral surface of the cooling roll.
From the viewpoint of further increasing the cooling rate of the molten Fe-based alloy and more stably producing the Fe-based amorphous alloy ribbon, the peripheral speed of the outer periphery of the rotating cooling roll is preferably 20 m/sec to 35 m/sec. The peripheral speed of the outer periphery of the rotating cooling roll is more preferably 25 m/sec to 35 m/sec, and still more preferably 27 m/sec to 30 m/sec.
(Width and thickness of Fe-based amorphous alloy thin strip)
In the step of obtaining the Fe-based amorphous alloy ribbon, the Fe-based amorphous alloy ribbon with the width of 5mm to 65mm and the thickness of 10 μm to 15 μm is obtained.
The width and thickness of the Fe-based amorphous alloy thin strip are not changed by the heat treatment described later. Therefore, the width of the Fe-based nanocrystalline alloy ribbon obtained by heat treatment of the Fe-based amorphous alloy ribbon is also 5mm to 65mm, and the thickness of the Fe-based nanocrystalline alloy ribbon is also 10 μm to 15 μm.
By making the thickness of the Fe-based amorphous alloy thin strip 15 μm or less, eddy current loss in the magnetic core produced using the Fe-based amorphous alloy thin strip can be suppressed.
As described above, when the thickness of the Fe-based amorphous alloy ribbon is 15 μm or less, the free solidification surface tends to be easily protruded. However, according to the method for producing the Fe-based nanocrystalline alloy ribbon of the present disclosure, even if the thickness is 15 μm or less, it is possible to obtain an Fe-based amorphous alloy ribbon and an Fe-based nanocrystalline alloy ribbon in which the generation of free solidification surface projections is suppressed.
The thickness of the Fe-based amorphous alloy ribbon is preferably 14.7 μm or less, more preferably 14.5 μm or less, still more preferably 14 μm or less, and still more preferably 13.5 μm or less.
On the other hand, the thickness of the Fe-based amorphous alloy ribbon is 10 μm or more. Thus, a long Fe-based amorphous alloy ribbon and a long Fe-based nanocrystalline alloy ribbon can be stably obtained. Further, mechanical strength for suppressing breakage or the like due to processing or the like of a subsequent step is secured.
The thickness of the thin strip of Fe-based amorphous alloy is preferably 11 μm or more.
Further, by setting the width of the Fe-based amorphous alloy ribbon to 65mm 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 thin ribbon of the Fe-based amorphous alloy is preferably 63mm or less, more preferably 60mm or less, and further preferably 55mm or less.
On the other hand, the productivity (economic rationality) can be ensured by setting the width of the Fe-based amorphous alloy thin strip to 5mm or more. The width of the thin strip of Fe-based amorphous alloy is preferably 10mm or more, and more preferably 15mm or more.
In this step, the Fe-based amorphous alloy thin strip may be cut, and the width of the Fe-based amorphous alloy thin strip may be adjusted to be 5mm to 65 mm.
Furthermore, a plurality of Fe-based amorphous alloy ribbons with a width of 5mm to 65mm can be obtained by cutting.
The width and thickness of the Fe-based amorphous alloy ribbon are maintained in the Fe-based nanocrystalline alloy ribbon obtained by heat-treating the Fe-based amorphous alloy ribbon.
Therefore, the preferable ranges of the width and thickness of the Fe-based nanocrystalline alloy thin strip are the same as those of the Fe-based amorphous alloy thin strip.
(warping of thin Fe-based amorphous alloy strip)
The warpage of the thin ribbon of Fe-based amorphous alloy is preferably 0.30mm or less per 10mm width of the thin ribbon of Fe-based amorphous alloy.
Thus, when the insulating layer is formed on the Fe-based amorphous alloy thin strip, the uniformity of the thickness of the insulating layer (specifically, the uniformity of the width direction of the Fe-based amorphous alloy thin strip) can be further improved.
As a result, the separation of the insulating layer from the Fe-based amorphous alloy ribbon (or Fe-based nanocrystalline alloy ribbon obtained by heat treatment) on which the insulating layer is formed can be further suppressed.
In this way, in the magnetic core described later, it is possible to effectively suppress a decrease in insulation between adjacent Fe-based nanocrystalline alloy ribbons (i.e., a decrease in insulation due to the peeling of the insulating layer).
The warpage of the Fe-based amorphous alloy thin strip per 10mm width of the Fe-based amorphous alloy thin strip is more preferably 0.25mm or less, still more preferably 0.20mm or less, and still more preferably 0.10mm or less.
The outer peripheral part of the cooling roller has a thermal conductivity of 70W/(m.K) to 225W/(m.K), which also contributes to reducing the warpage of the Fe-based amorphous alloy ribbon.
When the vickers hardness of the outer periphery of the cooling roll is 250HV or more, the warpage of the Fe-based amorphous alloy ribbon is further reduced.
The warpage of the Fe-based amorphous alloy thin strip was measured by placing the Fe-based amorphous alloy thin strip on a platen with the convex side of the warpage as the upper surface, using a device having a laser light emitting section and a laser light receiving section.
As the apparatus, for example, LB-300 manufactured by Kenzy corporation was used.
The warpage of the Fe-based amorphous alloy thin strip is maintained in the Fe-based nanocrystalline alloy thin strip obtained by heat-treating the Fe-based amorphous alloy thin strip.
Therefore, the preferable range of the warpage of the Fe-based nanocrystalline alloy thin strip is the same as the preferable range of the warpage of the Fe-based amorphous alloy thin strip.
The method for measuring the warpage of the Fe-based nanocrystalline alloy thin strip is the same as the method for measuring the warpage of the Fe-based amorphous alloy thin strip.
< step of obtaining Fe-based nanocrystalline alloy thin strip >
And in the step of obtaining the Fe-based nanocrystalline alloy thin strip, carrying out heat treatment on the Fe-based amorphous alloy thin strip to obtain the Fe-based nanocrystalline alloy thin strip.
The heat treatment causes nanocrystallization (i.e., nanocrystalline grains) of at least a part of the alloy structure of the Fe-based amorphous alloy ribbon, resulting in the Fe-based nanocrystalline alloy ribbon.
In the method for producing 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 directly heat-treated, or the Fe-based amorphous alloy ribbon obtained in the step of obtaining the Fe-based amorphous alloy ribbon may be laminated or wound, and the obtained laminate or wound body may be heat-treated.
The method of heat-treating the wound body obtained by winding the Fe-based amorphous alloy thin strip includes a method of manufacturing a magnetic core of the present disclosure described later.
The maximum temperature in the heat treatment is preferably 500 ℃ to 700 ℃ inclusive, and more preferably 550 ℃ to 600 ℃ inclusive.
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 further preferably 1 hour or more and 2 hours or less.
The atmosphere during the heat treatment may be a non-oxidizing atmosphere such as nitrogen or an atmospheric atmosphere, and is preferably a non-oxidizing atmosphere from the viewpoint of quality stabilization.
The heat treatment is performed, for example, using a heat treatment furnace.
The heat treatment can also be carried out in a magnetic field.
[ method for producing magnetic core ]
The method for producing a magnetic core of the present disclosure is a method for producing a magnetic core including a wound body C obtained by winding a Fe-based nanocrystalline alloy thin strip with an insulating layer interposed therebetween, and includes the steps of:
a step of supplying an Fe-based alloy molten liquid onto a rotating chill roll, and rapidly cooling and solidifying the Fe-based alloy molten liquid supplied onto the chill roll, thereby obtaining an Fe-based amorphous alloy thin strip having a free solidification surface and a roll contact surface, a width of 5mm to 65mm, and a thickness of 10 μm to 15 μm,
a step of forming the insulating layer on the free solidification surface of the thin strip of Fe-based amorphous alloy,
a step of winding the Fe-based amorphous alloy ribbon on which the insulating layer is formed to obtain a wound body A in which the Fe-based amorphous alloy ribbon is wound with the insulating layer interposed therebetween, and
a step of heat-treating the wound body a to obtain a wound body C (i.e., a wound body C obtained by winding a Fe-based nanocrystalline alloy ribbon with an insulating layer interposed therebetween);
wherein an outer peripheral portion of the cooling roll is made of a Cu alloy, and a thermal conductivity of the outer peripheral portion is 70W/(m.K) to 225W/(m.K).
The method of manufacturing the magnetic core of the present disclosure may also include other steps as needed.
In the method for producing a magnetic core according to the present disclosure, the step of forming the insulating layer, the step of obtaining the wound body a, and the step of obtaining the wound body C are all included in the concept of the "step of obtaining the Fe-based nanocrystalline alloy ribbon" in the method for producing the Fe-based nanocrystalline alloy ribbon according to the present disclosure.
The method for producing the magnetic core of the present disclosure is the same as the method for producing the Fe-based nanocrystalline alloy thin strip of the present disclosure described above, except for this point.
The "step of obtaining the Fe-based amorphous alloy thin strip" in the manufacturing method of the magnetic core of the present disclosure is the same as the "step of obtaining the Fe-based amorphous alloy thin strip" in the above-described manufacturing method of the Fe-based nanocrystalline alloy thin strip of the present disclosure. Therefore, in the "step of obtaining an Fe-based amorphous alloy thin strip" in the method for producing a magnetic core according to the present disclosure, an Fe-based amorphous alloy thin strip in which the generation of the protrusion in the free solidification surface is suppressed can be obtained.
In the method for manufacturing a magnetic core of the present disclosure, a wound body a formed by winding a Fe-based amorphous alloy thin strip with an insulating layer interposed therebetween is subjected to a heat treatment. By this heat treatment, the Fe-based amorphous alloy ribbon in the roll a is changed into an Fe-based nanocrystalline alloy ribbon, and as a result, a magnetic core including a roll C formed by winding the Fe-based nanocrystalline alloy ribbon with an insulating layer interposed therebetween is obtained.
In the Fe-based amorphous alloy thin strip in the jelly roll a, as described above, the generation of the protrusion in the free solidification surface is suppressed. Therefore, in the roll C, the decrease in the insulation between the adjacent Fe-based nanocrystalline alloy ribbons with the insulating layer interposed therebetween is suppressed.
As described above, in the magnetic core produced by the method for producing a magnetic core according to the present disclosure, the insulating property between the adjacent Fe-based nanocrystalline alloy thin strips through the insulating layer is excellent.
Therefore, in the magnetic core produced by the production method of the magnetic core of the present disclosure, eddy current loss is reduced.
In general, the core loss is determined by the hysteresis loss and the eddy current loss.
The eddy current loss is frequency-dependent, and tends to increase significantly as the applied frequency increases.
From the above viewpoint, the method for producing a magnetic core of the present disclosure is particularly suitable for a method for producing a magnetic core used under high-frequency conditions (in particular, high-frequency conditions of MHz order or higher).
From the viewpoint of further suppressing eddy current loss, the magnetic core produced by the production method of a magnetic core of the present disclosure preferably satisfies an insulation rate RI described later of 80% or more. A more preferable range of the insulation rate RI is the same as a more preferable range of the insulation rate RI of the magnetic core according to an example of the present disclosure described later.
Hereinafter, the steps other than the step of obtaining the Fe-based amorphous alloy thin strip in the method for producing a magnetic core of the present disclosure will be described.
< step of Forming insulating layer >
In the step of forming the insulating layer in the method of manufacturing a magnetic core of the present disclosure, the insulating layer is formed on the free solidification surface of the thin ribbon of the Fe-based amorphous alloy.
The insulating layer preferably contains a metal oxide such as heat-treated silicon oxide (silicon oxide), aluminum oxide (aluminum oxide), or magnesium oxide (magnesium oxide).
In this case, the number of the metal oxides contained in the insulating layer may be 1, or 2 or more.
In the case where the insulating layer contains a metal oxide, the influence of the heat treatment in the step of obtaining the roll C on the insulating layer is further reduced.
For example, the maximum temperature of the heat treatment at 550 to 600 ℃ exceeds the heat resistance temperature of an organic material such as a polymer. Even when the heat treatment is performed at the highest temperature, when the insulating layer contains a metal oxide, the influence of the heat treatment on the insulating layer can be reduced, and the insulating property of the insulating layer can be effectively obtained.
The thickness of the insulating layer is preferably 1.5 to 2.5 μm.
The insulating layer may be provided on both the free solidification surface and the roll contact surface of the Fe-based amorphous alloy ribbon, but is preferably provided on the free solidification surface of the Fe-based amorphous alloy ribbon and not provided on the roll contact surface. This can prevent contact between the insulating layers in the step of obtaining the wound body and in the subsequent steps, and as a result, can further suppress peeling of the insulating layers due to contact between the insulating layers.
The insulating layer can be formed, for example, as follows.
A suspension is prepared by suspending a metal oxide powder (hereinafter also referred to as metal oxide powder) in an organic solvent such as alcohol. In the obtained suspension, the Fe-based amorphous alloy ribbon is immersed for a certain period of time to adhere the suspension to the Fe-based amorphous alloy ribbon, and then the suspension adhering to the Fe-based amorphous alloy ribbon is dried, whereby an insulating layer can be formed 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 the metal oxide powder in the suspension, the dipping time, and the like.
Here, when the suspension adhering to the roller contact surface is removed after the taking-out and before the drying, the insulating layer may be formed only on the free solidified surface of the Fe-based amorphous alloy ribbon.
< step of obtaining roll A >
In the step of obtaining the roll a, the Fe-based amorphous alloy ribbon on which the insulating layer is formed is wound to obtain the roll a in which the Fe-based amorphous alloy ribbon is wound with the insulating layer interposed therebetween.
The winding of the Fe-based amorphous alloy ribbon with the insulating layer formed thereon can be performed by a known method.
At this time, the wound body a may be temporarily fixed by a Cu wire or the like having a diameter of about 0.5mm to maintain the shape.
< step of obtaining roll C >
In the step of obtaining the roll C, the roll a is heat-treated to obtain the roll C (that is, the roll C in which the Fe-based nanocrystalline alloy ribbon is wound with the insulating layer interposed therebetween).
In the step of obtaining the roll C, the Fe-based amorphous alloy ribbon in the roll a is heat-treated to become an Fe-based nanocrystalline alloy ribbon. This is the same as the "step of obtaining the Fe-based nanocrystalline alloy ribbon" in the method for producing the Fe-based nanocrystalline alloy ribbon of the present disclosure.
The preferable conditions of the heat treatment in the step of obtaining the wound body C are the same as those of the heat treatment in the "step of obtaining an Fe-based nanocrystalline alloy ribbon" in the above-described method of producing an Fe-based nanocrystalline alloy ribbon of the present disclosure.
As indicated above, the heat treatment may be carried out in a magnetic field.
The magnetic field direction is preferably 2 directions of the circumferential direction of the magnetic core and the height direction of the magnetic core (width of the alloy ribbon).
The strength of the applied magnetic field and/or the temperature region of the applied magnetic field may be appropriately adjusted depending on the use of the magnetic core.
Further, the order of the above 2 magnetic field directions may be changed.
[ Fe-based nanocrystalline alloy thin strip, magnetic core ]
An Fe-based nanocrystalline alloy ribbon according to one example of the present disclosure has a free solidified surface in which the number of projections P having a pit in the central portion is 100mm per 100mm, and a roll contact surface2The area is less than 1.2, the width of the Fe-based nanocrystalline alloy thin strip is more than 5mm and less than 65mm, and the thickness of the Fe-based nanocrystalline alloy thin strip is more than 10 mu m and less than 15 mu m.
As described above, in the Fe-based nanocrystalline alloy ribbon according to one example of the present disclosure, the generation of the projections in the free solidification surface is suppressed.
A magnetic core according to an example of the present disclosure includes a wound body C1 formed by winding an Fe-based nanocrystalline alloy ribbon according to an example of the present disclosure with an insulating layer interposed therebetween.
In the magnetic core according to one example of the present disclosure, the insulating property between the adjacent Fe-based nanocrystalline alloy ribbons with the insulating layer interposed therebetween is excellent.
As described above, in the Fe-based nanocrystalline alloy ribbon having a thickness of 15 μm or less, projections tend to be formed on the free solidification surface, and among the projections, particularly, projections P having a pit in the central portion tend to be formed.
According to the studies of the present inventors, it was confirmed that the projections P in the free solidification surface of the Fe-based nanocrystalline alloy thin strip having a thickness of 15 μm or less were restricted to every 100mm2In a magnetic core including a wound body C1 formed by winding the Fe-based nanocrystalline alloy ribbon with an insulating layer interposed therebetween, the insulating properties between the Fe-based nanocrystalline alloy ribbons are significantly improved, the area of which is 1.2 or less.
The Fe-based nanocrystalline alloy ribbon and the magnetic core according to one example of the present disclosure have been completed based on this finding.
In the present disclosure, the "wound body formed by winding the Fe-based nanocrystalline alloy ribbon with the insulating layer interposed therebetween" (wound body C1, wound body C) refers to a wound body in which the Fe-based nanocrystalline alloy ribbon is wound with the insulating layer interposed therebetween.
Therefore, the "wound body formed by winding the Fe-based nanocrystalline alloy thin strip with the insulating layer interposed therebetween" is not limited to a wound body formed by winding an Fe-based nanocrystalline alloy thin strip with an insulating layer formed thereon.
For example, in the method for producing a magnetic core according to the present disclosure, a wound body obtained by winding an Fe-based amorphous alloy thin strip having an insulating layer formed thereon is subjected to a heat treatment under predetermined conditions, thereby obtaining a wound body in which an Fe-based nanocrystalline alloy thin strip is wound with the insulating layer interposed therebetween. Such a wound body is also included in the concept of "a wound body formed by winding an Fe-based nanocrystalline alloy ribbon with an insulating layer interposed therebetween".
The method of preparing the Fe-based nanocrystalline alloy ribbon and the magnetic core according to an example of the present disclosure is not particularly limited.
For example, according to the method for producing the Fe-based nanocrystalline alloy ribbon according to the present disclosure, the Fe-based nanocrystalline alloy ribbon according to an example of the present disclosure can be produced.
In particular, according to the method for producing a magnetic core of the present disclosure, a magnetic core according to an example of the present disclosure can be suitably produced. In this case, as the wound body C in the method for producing a magnetic core of the present disclosure, a wound body C1 in a magnetic core according to an example of the present disclosure was obtained.
In the example of the present disclosure, the protrusion P having a recess in the central portion (hereinafter, simply referred to as "protrusion P") is a protrusion having a recess in the central portion when viewed from a direction perpendicular to the free solidification surface.
According to an example of the present disclosure, to calculate per 100mm2The number of protrusions P in the area was observed by using a solid microscope at a magnification of 40 times.
Per 100mm of free setting surface2The number of the protrusions P in the area is 1.2 or less as described above. The number of the projections P may be 0.
The number of the projections P is preferably 1.0 or less from the viewpoint of further improving the insulation between the Fe-based nanocrystalline alloy thin strips in the magnetic core.
Preferred embodiments (for example, preferred embodiments of alloy composition, width, thickness, warpage, and the like) of the Fe-based nanocrystalline alloy ribbon according to an example of the present disclosure are the same as the preferred embodiments of the Fe-based nanocrystalline alloy ribbon obtained by the method for producing an Fe-based nanocrystalline alloy ribbon according to the present disclosure.
A preferred embodiment of the magnetic core according to an example of the present disclosure is the same as that of the magnetic core obtained by the method for producing a magnetic core of the present disclosure.
< insulation ratio RI >
As described above, the magnetic core according to the example of the present disclosure has excellent insulation between the Fe-based nanocrystalline alloy thin strips. This can reduce eddy current loss.
From the viewpoint of further reducing eddy current loss, the insulation rate RI represented by the following formula (1) of the magnetic core according to an example of the present disclosure is preferably 80% or more.
RI ═ Rr/(Ru · Lr) × 100 (%) … formula (1)
In the formula (1), Rr is a direct current resistance value (Ω) between 2 ends of one end of the innermost circumference and the other end of the outermost circumference in the Fe-based nanocrystalline alloy ribbon, Ru is a direct current resistance value (Ω) per 1m length in the length direction of the Fe-based nanocrystalline alloy ribbon, and Lr is a length (m) of the Fe-based nanocrystalline alloy ribbon.
The insulation rate RI represented by formula (1) will be described below.
In the magnetic core according to one example of the present disclosure, when the Fe-based nanocrystalline alloy thin strips are completely insulated from each other, the product between Ru and Lr in expression (1) (i.e., "Ru · Lr") has the same value as Rr in expression (1). In this case, the insulation rate RI is 100%.
On the other hand, in the case where there is a portion where insulation is broken (i.e., a portion where short circuit occurs) between the Fe-based nanocrystalline alloy thin strips, Rr becomes smaller than "Ru · Lr". In this case, the insulation rate RI is less than 100%.
Ru in formula (1) can be calculated by: based on the diameter of the magnetic core according to an example of the present disclosure, the position 1m from the outermost peripheral end of the magnetic core is estimated, and the dc resistance value (Ω) between the outermost peripheral end and the position 1m from the outermost peripheral end is measured.
From the viewpoint of further reducing eddy current loss, the insulation rate RI of the magnetic core according to an example of the present disclosure is preferably 85% or more, and more preferably 90% or more.
The insulation rate RI of the magnetic core according to an example of the present disclosure may be 100%, and is preferably less than 100% from the viewpoint of the manufacturing suitability (ease of production) of the magnetic core.
Examples
Examples of the present disclosure are given below, but the present disclosure is not limited to the following examples.
(example 1)
Preparation (casting) of Fe-based amorphous alloy thin strip
Will have a composition of Febal.Cu0.98Si14.99B6.68Nb2.89C0.05An Fe-based alloy molten liquid (9.1kg) having an alloy composition represented by (atomic%) was supplied onto a rotating cooling roll, and the supplied Fe-based alloy molten liquid was rapidly solidified to obtain an Fe-based amorphous alloy ribbon having a free solidified surface and a roll contact surface, a width of 25mm, and a thickness of 13.4. mu.m.
Here, "bal." (balance) is a value corresponding to "100-a-b-c-d-e" in the composition formula (A).
The obtained Fe-based alloy ribbon is an Fe-based amorphous alloy ribbon, i.e., the alloy structure is formed of an amorphous phase, which can be confirmed by observing the cross section of the ribbon by a Scanning Electron Microscope (SEM).
The alloy composition of the Fe-based alloy did not change throughout all the steps of the present example. Therefore, the alloy compositions of the Fe-based alloy molten liquid, the Fe-based amorphous alloy ribbon, and the Fe-based nanocrystalline alloy ribbon described later are the same.
In addition, the dimensions (thickness, width and length) of the ribbon are not changed in all steps of the present embodiment. Therefore, the dimensions (thickness, width, and length) of the Fe-based nanocrystalline alloy ribbon described later are the same as those of the Fe-based amorphous alloy ribbon.
Hereinafter, the term "thin strip" refers to a thin strip of Fe-based nanocrystalline alloy or a thin strip of Fe-based amorphous alloy.
The rotational speed of the cooling roll was 28 m/sec in terms of the peripheral speed of the outer periphery.
As the cooling roll, the following cooling roll was used.
The cooling roller has a water channel for circulating cooling water as a structure for cooling the outer periphery inside.
Cooling roller
Diameter: 800mm
Width: 150mm
Thickness of outer peripheral portion: 20mm
Raw material for outer periphery: Cu-Be alloy (Be: 1.9 mass%, the balance being Cu and impurities)
Thermal conductivity of the outer peripheral portion: 124W/(m.K)
Vickers hardness of the peripheral portion-
The vickers hardness of the outer peripheral portion was measured using a vickers hardness tester under a test load of 20 kgf.
The results are shown in Table 1.
Per 100mm of free setting surface2Determination of the number of protrusions P in the area-
In order to evaluate the number of projections P on the free solidified surface of the obtained Fe-based amorphous alloy ribbon, 30 fields (area 1154 mm) were observed with a solid microscope at a magnification of 40 times2) The free solidified surface was observed.
Based on the observation results, the average particle diameter was determined for each 100mm2The number of protrusions P in the area.
The results are shown in Table 1.
The number of projections P on the free solidification surface of the Fe-based amorphous alloy ribbon (i.e., the ribbon before heat treatment) does not change in the subsequent steps.
That is, the number of projections P in the free solidified surface of the Fe-based nanocrystalline alloy ribbon (i.e., the ribbon after heat treatment) described later is the same as the number of projections P in the free solidified surface of the Fe-based amorphous alloy ribbon (i.e., the ribbon before heat treatment).
Warpage in the width direction
The warpage in the width direction of the Fe-based amorphous alloy ribbon was measured as follows.
A sample 1 piece having a length of 100mm was cut from each of the casting start side end portion and the casting end side end portion of the Fe-based amorphous alloy thin strip.
Each sample was placed on the platen so that the warped convex side was on the upper surface side, and in this state, the height of the uppermost portion of the upper surface of the sample was measured. The height of the uppermost portion was measured using LB-300 manufactured by Kenz.
The maximum height of the uppermost part in the 2 samples was 0.10 mm.
The width of the sample was 25mm, and the width-direction warpage of the Fe-based amorphous alloy thin strip was determined to be 0.04mm per 10mm width (see table 1).
Formation of an insulating layer
An insulating layer having a thickness of 2.1 μm was formed on the free solidified surface of the thin ribbon of Fe-based amorphous alloy.
Silica powder having an average particle size of 0.5 μm was suspended in isopropyl alcohol (IPA) to prepare a suspension.
The Fe-based amorphous alloy ribbon obtained as described above is passed through the suspension, and thereafter the suspension adhering to the roll contact surface of the Fe-based amorphous alloy ribbon is removed.
The suspension attached to the free solidified surface of the Fe-based amorphous alloy ribbon was dried, thereby obtaining an insulating layer having a thickness of 2.1. mu.m.
Preparation of the coil A
The Fe-based amorphous alloy ribbon (length 264m) on which the insulating layer was formed was wound, thereby obtaining a wound body A having an inner diameter of 60.5mm and an outer diameter of 100.0mm (i.e., a wound body A in which the Fe-based amorphous alloy ribbon was wound with the insulating layer interposed therebetween).
Preparation of the coil C (magnetic core)
The wound body a was heat-treated at a maximum holding temperature of 580 ℃ for 2 hours, to obtain a wound body C (i.e., a wound body C in which a Fe-based nanocrystalline alloy ribbon was wound with an insulating layer interposed therebetween) as a magnetic core.
When the cross section of the ribbon in the roll C was observed with a Scanning Electron Microscope (SEM), it was confirmed that the Fe-based alloy ribbon in the roll C was an Fe-based nanocrystalline alloy ribbon, that is, nanocrystalline grains were generated in the alloy structure.
Determination of the insulation Rate RI-
The insulation rate RI of the obtained magnetic core (i.e., the insulation rate RI represented by formula (1)) was measured by the method described above.
The results are shown in Table 1.
(examples 2 to 4 and comparative example 1)
The same operation as in example 1 was carried out except that the conditions for producing the Fe-based amorphous alloy ribbon (alloy composition including the Fe-based alloy molten liquid) were changed as shown in table 1.
However, in examples 3 and 4, the maximum holding temperature for the heat treatment of the wound body a was changed to 550 ℃.
The results are shown in Table 1.
The following chill roll was used in example 2.
The cooling roller of example 2 also has a water channel for circulating cooling water as a structure for cooling the outer peripheral portion inside.
Cooling roller of example 2
Diameter: 800mm
Width: 150mm
Thickness of outer peripheral portion: 20mm
Raw material for outer periphery: Cu-Be alloy (Be: 2.0 mass%, the balance being Cu and impurities)
Thermal conductivity of the outer peripheral portion: 120W/(m.K)
The following chill roll was used in example 3.
The cooling roller of example 3 also has a water channel for circulating cooling water as a structure for cooling the outer peripheral portion inside.
Cooling roller of example 3
Diameter: 450mm
Width: 300mm
Thickness of outer peripheral portion: 17mm
Raw material for outer periphery: Cu-Ni alloy (Cu: 90 mass% or more, balance being impurities (containing Ni, Si and Cr))
Thermal conductivity of the outer peripheral portion: 168W/(m.K)
The following chill roll was used in example 4.
The cooling roller of example 4 also has a water channel for circulating cooling water as a structure for cooling the outer peripheral portion inside.
Cooling roller of example 4
Diameter: 650mm
Width: 300mm
Thickness of outer peripheral portion: 17mm
Raw material for outer periphery: Cu-Ni-Be alloy (Cu: 90 mass% or more, Ni: 7 mass%, Be: 0.3 mass%, balance impurities (including Ag, Cr, and Zr))
Thermal conductivity of the outer peripheral portion: 212W/(m.K)
The following chill roll was used in comparative example 1.
The cooling roller of comparative example 1 also has a water channel for circulating cooling water as a structure for cooling the outer peripheral portion inside.
Cooling roller of comparative example 1
Diameter: 800mm
Width: 150mm
Thickness of outer peripheral portion: 20mm
Raw material for outer periphery: Cu-Be alloy (Be: 0.3 mass%, the balance being Cu and impurities)
Thermal conductivity of the outer peripheral portion: 240W/(m.K)
[ Table 1]
As shown in Table 1, in examples 1 to 4 in which the thermal conductivity of the outer periphery of the cooling roll was 70W/(mK) to 225W/(mK), the free solidified surface of the ribbon was reduced per 100mm2The number of the protrusions P in (2) and the insulation rate RI of the magnetic core are excellent.
On the other hand, in comparative example 1 in which the thermal conductivity of the outer periphery of the cooling roll exceeded 225W/(mK), the free solidified surface of the ribbon was 100mm per 100mm2The number of the projections P in (b) is greatly increased, and the insulation rate RI of the core is greatly deteriorated.
Fig. 1 is a laser microscope image (50-fold magnification) of 2 projections P (i.e., projections P having a pit in the central portion) in the Fe-based amorphous alloy ribbon of comparative example 1, when viewed from a direction perpendicular to the free solidification surface, and fig. 2 shows a Three-dimensional (Three Dimension) display image of fig. 1. Here, as the laser microscope, a laser microscope "VK-8716" manufactured by keyins corporation was used, and analysis for obtaining a three-dimensional image was performed using analysis software "VK Analyzer ver.2.4.0.0" of the corporation.
In comparative example 1, a large number of such projections P were generated, but in examples 1 to 4, such projections P were reduced.
The disclosure of japanese patent application No. 2018-180031, applied for 26.9.2018, is incorporated by reference in its entirety into this specification.
All documents, patent applications, and technical standards described in the present specification are incorporated by reference into the present specification as if each document, patent application, and technical standard were specifically and individually indicated to be incorporated by reference.