Soft magnetic alloy and method for producing soft magnetic alloy

Abstract

To provide a soft magnetic alloy based on an Fe-Si-B-Cu-Nb alloy system that achieves coexistence of high saturation magnetic flux density and high punchability, and a method for producing the soft magnetic alloy.SOLUTION: A soft magnetic alloy contains, in atomic%, 7.0%≤Si≤15.0%, 7.0%≤B≤10.0%, 0.5%≤Cu≤2.0%, 0.03%≤C≤0.30%, 0.005%≤S≤0.050%, and 3.0%<X≤5.0%, where X is at least one element selected from Ti, Nb, V, Zr, Hf, Ta, and W, the balance being Fe or Fe in which a part thereof is replaced with at least one of Ni and Co, and unavoidable impurities. In addition, by rapidly cooling an alloy melt, an amorphous alloy ribbon having the above component composition is produced, and heat treatment of the alloy ribbon is performed using, as a target temperature, a range of ±15°C from a temperature 30°C higher than the crystallization-start temperature of the alloy ribbon.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a soft magnetic alloy and a method for producing the same, and more particularly to a soft magnetic alloy based on an Fe-Si-B-Cu-Nb alloy and a method for producing the same. [Background technology]

[0002] Materials based on Fe-Si-B-Cu-Nb alloys are known as a type of soft magnetic alloy used in high-frequency transformers, choke coils, motor cores, etc. Such materials are disclosed in the following Patent Documents 1 to 3, etc. An alloy based on Fe-Si-B-Cu-Nb alloys is obtained as an amorphous phase and then heat-treated to obtain a structure containing nanocrystals. The generation of nanocrystals allows for the attainment of good soft magnetic properties.

[0003] The composition of soft magnetic alloys based on Fe-Si-B-Cu-Nb alloys is adjusted to achieve desired properties. For example, elements such as B, C, and P are added to promote the amorphization necessary for obtaining nanocrystals through heat treatment. Furthermore, the addition of elements such as Cu, Nb, V, Ti, W, Hf, and Ta can refine the nanocrystals obtained through heat treatment. Furthermore, the addition of Si increases magnetic permeability. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-195936 [Patent Document 2] Japanese Patent Application Publication No. 2019-148004 [Patent Document 3] Japanese Patent Application Publication No. 2019-131853 Summary of the Invention [Problem to be solved by the invention]

[0005] Soft magnetic alloys based on Fe-Si-B-Cu-Nb alloys are materials with an excellent balance between coercive force and saturation magnetic flux density. However, when used in high-frequency transformers or the like, from the perspective of miniaturization, it is particularly required to have a particularly high saturation magnetic flux density. Also, in applications such as motor cores, there are cases where sheet materials of soft magnetic alloys are punched and a large number of the obtained punched bodies are laminated. However, soft magnetic alloys based on Fe-Si-B-Cu-Nb alloys have very high strength both in the amorphous state and in the nanocrystalline alloy state, so the punching property is low. Improving the punching property is important in order to suppress the manufacturing cost of products that require punching of soft magnetic alloys, such as motor cores. However, in the component compositions of soft magnetic alloys based on Fe-Si-B-Cu-Nb alloys generally adopted, it is difficult to achieve both high saturation magnetic flux density and high punching property.

[0006] The problem to be solved by the present invention is to provide a soft magnetic alloy based on Fe-Si-B-Cu-Nb alloy that can achieve both high saturation magnetic flux density and high punching property, and a method for manufacturing such a soft magnetic alloy.

Means for Solving the Problem

[0007] In order to solve the above problems, the soft magnetic alloy and the method for manufacturing the soft magnetic alloy of the present invention have the following configurations.

[0008] [1] The soft magnetic alloy of the present invention contains, in atomic%, ≦Si≦15.0%, ≦B≦10.0%, ≦Cu≦2.0%, ≦C≦0.30%, ≦S≦0.050%, and at least one element selected from Ti, Nb, V, Zr, Hf, Ta, W as X, <X≦5.0%, and the balance consists of Fe, or Fe partially substituted with at least one of Ni and Co, and inevitable impurities.

[0009] [2] In the aspect of [1] above, the soft magnetic alloy may further contain at least one of 0% < P ≤ 2.0%, 0% < Cr ≤ 3.0%, and 0% < Mo ≤ 3.0% in atomic percentage.

[0010] [3] In the aspect of [1] or [2] above, the soft magnetic alloy may constitute a nanocrystalline alloy containing nanocrystals with an average crystal grain size of 30 nm or less.

[0011] [4] The method for manufacturing the soft magnetic alloy of the present invention includes rapidly cooling an alloy melt to produce an amorphous alloy ribbon having the component composition of [1] or [2] above, and then performing heat treatment on the alloy ribbon with a target temperature in the range of ±15°C from a temperature 30°C higher than the crystallization start temperature of the alloy ribbon.

Advantages of the Invention

[0012] The soft magnetic alloy according to the present invention having the configuration of [1] above has a high saturation magnetic flux density and high punching property by having the above component composition. In particular, since the amount of each additive element is suppressed within a range where it does not become too large, the content of Fe (and Ni, Co) can be ensured relatively high, and the saturation magnetic flux density can be effectively improved. Also, by containing appropriate amounts of C and S, the punching property is improved while maintaining high magnetic properties such as saturation magnetic flux density in the soft magnetic alloy.

[0013] In the aspect of [2] above, at least one of a predetermined amount of P, Cr, and Mo is added to the soft magnetic alloy. P has a high effect on refining the crystal grains of the soft magnetic alloy when coexisting with Cu. Also, Cr and Mo improve the corrosion resistance of the soft magnetic alloy.

[0014] In the above aspect [3], the soft magnetic alloy is a nanocrystalline alloy containing nanocrystals with an average crystal grain size of 30 nm or less. Nanocrystalline alloys are obtained by heat treating amorphous alloys, and if the formed nanocrystals have an average grain size of 30 nm or less, they are highly effective in improving soft magnetic properties. By having the soft magnetic alloy have the above component composition, the effect of miniaturizing the nanocrystals is obtained, making it easy to obtain a nanocrystalline alloy with an average grain size of 30 nm or less.

[0015] In the method for producing a soft magnetic alloy according to the present invention having the configuration [4] above, an amorphous alloy ribbon obtained as having the component composition [1] or [2] above is heat-treated at a predetermined target temperature, and a nanocrystalline alloy is obtained through this heat treatment. When the soft magnetic alloy has the component composition [1] or [2], the obtained nanocrystalline alloy exhibits both a high saturation magnetic flux density and high punchability, as described above. Furthermore, when heat-treated at the target temperature, a nanocrystalline alloy containing fine nanocrystals is obtained. DETAILED DESCRIPTION OF THE INVENTION

[0016] A soft magnetic alloy according to one embodiment of the present invention and a method for manufacturing the same will be described in detail below. The soft magnetic alloy according to this embodiment is configured as an alloy material having a predetermined component composition. In this specification, the content of each element is expressed in atomic percent. Furthermore, various properties refer to values ​​at room temperature in the atmosphere.

[0017] [Soft magnetic alloy composition] A soft magnetic alloy according to one embodiment of the present invention contains the following predetermined amounts of Si, B, Cu, C, S, and element X, with the balance consisting of Fe or Fe partially substituted with at least one of Ni and Co, and unavoidable impurities. Here, element X refers to at least one element selected from Ti, Nb, V, Zr, Hf, Ta, and W.

[0018] 7.0%≦Si≦15.0% In soft magnetic alloys, Si has the effects of improving magnetic permeability, reducing magnetostriction, and reducing eddy current loss. By setting the Si content at 7.0% or less, these effects can be fully obtained. Setting the Si content at 8.0% or less, or even 9.0% or less, is more preferable.

[0019] On the other hand, if too much Si is added, the Fe (and Ni, Co) content in the soft magnetic alloy will be relatively reduced. This will lead to deterioration of magnetic properties, such as making it difficult to obtain a sufficiently high saturation magnetic flux density. Furthermore, if too much Si is added, it will actually make it difficult to reduce magnetostriction. To prevent these problems, the Si content is set to Si≦15.0%. Si≦12.0% is more preferable.

[0020] 7.0%≦B≦10.0% B is effective in amorphizing soft magnetic alloys before heat treatment. By subjecting amorphous soft magnetic alloys to heat treatment, nanocrystals can be generated. From the viewpoint of sufficiently promoting the amorphization of soft magnetic alloys, the B content is set to 7.0% or less. 7.5% or less, or even 8.0% or less, is more preferable.

[0021] On the other hand, if a soft magnetic alloy contains a large amount of B, FeB compounds are likely to be formed when the amorphous alloy is heat-treated to form a nanocrystalline alloy. The FeB compounds deteriorate the magnetic properties of the soft magnetic alloy. To suppress the formation of FeB compounds, the B content is set to B≦10.0%. B≦9.0% is more preferable.

[0022] 0.5%≦Cu≦2.0% In soft magnetic alloys, Cu promotes the formation of clusters that become nuclei for nanocrystal formation after heat treatment. To ensure a sufficient effect in promoting cluster formation, the Cu content is set to 0.5% or less. 0.7% or less, or even 0.8% or less, is more preferable.

[0023] However, adding too much Cu causes the clusters to become coarse, which actually hinders the refinement of Fe-containing crystals. Furthermore, adding too much Cu reduces the relative content of Fe (and Ni and Co) in the soft magnetic alloy. To prevent these phenomena, Cu is set to 2.0% or less. Cu 1.2% or even 1.0% is more preferable.

[0024] 0.03%≦C≦0.30% When added to a soft magnetic alloy, C reduces the ductility of the amorphous phase and improves punchability. To fully obtain this effect, the C content is set to 0.03% or less. 0.04% or less, or even 0.05% or less, is more preferable.

[0025] On the other hand, adding a large amount of C makes it easier for FeC compounds to form when the amorphous alloy is heat-treated to form a nanocrystalline alloy. The formation of FeC compounds leads to a deterioration of magnetic properties. To prevent the formation of FeC compounds and the resulting deterioration of magnetic properties, the C content is set to 0.30% or less. C 0.20% or even C 0.10% is more preferable.

[0026] 0.005%≦S≦0.050% Like C, when added to a soft magnetic alloy, S reduces the ductility of the amorphous phase and improves punchability. To fully obtain this effect, the S content is set to 0.005% or less. 0.008% or less, or even 0.010% or less, is more preferable.

[0027] On the other hand, adding a large amount of S leads to a deterioration in magnetic properties. From the viewpoint of suppressing the deterioration in magnetic properties, the S content is set to 0.050% or less. It is more preferable that S 0.030% or more preferably C 0.020% or less.

[0028] 3.0% <X≦5.0% The soft magnetic alloy according to this embodiment contains at least one element X, that is, at least one selected from Ti, Nb, V, Zr, Hf, Ta, and W, and the total content thereof is 3.0% < X ≦ 5.0%. Any of Ti, Nb, V, Zr, Hf, Ta, and W has an effect of suppressing the coarsening of nanocrystals and facilitating the generation of fine nanocrystals in the soft magnetic alloy. The soft magnetic alloy may contain any one or several of the element X, but it is particularly preferable to contain Nb.

[0029] From the viewpoint of sufficiently obtaining the effect of refining nanocrystals, the content of element X in the soft magnetic alloy is 3.0% < X. It is more preferable that 3.1% ≦ X, and further 3.2% ≦ X.

[0030] However, if too much element X is added, the content of Fe (and Ni, Co) in the soft magnetic alloy will relatively decrease. Then, it becomes difficult to obtain a sufficiently high saturation magnetic flux density, etc., leading to deterioration of magnetic properties. From the viewpoint of suppressing the deterioration of magnetic properties, the content of element X can be suppressed to X ≦ 5.0%. With an element X content of 5.0% or less, a sufficiently high effect can be obtained for suppressing the coarsening of nanocrystals. It is more preferable that X ≦ 4.0%.

[0031] ·Fe, Ni, Co The soft magnetic alloy according to this embodiment consists of the remaining parts of the above-described predetermined amounts of Si, B, Cu, C, S, and element X, excluding inevitable impurities, being Fe, or Fe with a part of it replaced by Ni and Co. Ni and Co are magnetic elements like Fe and are added in a form that replaces Fe in the soft magnetic alloy. The addition amounts of Ni and Co are not particularly limited, but it is preferable to suppress them to Ni ≦ 20% and Co ≦ 20%.

[0032] The soft magnetic alloy according to this embodiment may contain, in addition to Fe (and Ni, Co) as essential elements, only at least one of the above-described predetermined amounts of Si, B, Cu, C, S, and at least one of Ti, Nb, V, Zr, Hf, Ta, and W, or may further contain, as optional elements, at least one of the following predetermined amounts of P, Cr, and Mo.

[0033] 0% <P≦2.0% P coexists with Cu in soft magnetic alloys to form Cu3P clusters, which have the effect of suppressing the coarsening of the clusters formed by Cu. Cu3P clusters are more finely dispersed than Cu clusters. Therefore, they are highly effective in refining nanocrystalline grains in nanocrystalline alloys. Even a small amount of P is effective in suppressing the coarsening of clusters, so there is no specific lower limit for its content. However, a high addition effect can be achieved by setting the content at 0.01% or less, or even 0.02% or less. Note that P less than 0.01% can be considered an unavoidable impurity.

[0034] On the other hand, adding a large amount of P makes it easier for FeP compounds to form when the amorphous alloy is heat-treated to form a nanocrystalline alloy. The formation of FeP compounds leads to a deterioration of magnetic properties. From the viewpoint of suppressing the formation of FeP compounds, P is set to 2.0% or less. P 1.6% or less is more preferable.

[0035] 0% <Cr≦3.0% 0% <Mo≦3.0% Cr and Mo contribute to improving corrosion resistance when added to soft magnetic alloys. Even small amounts of Cr and Mo are effective in improving corrosion resistance, so there is no specific lower limit for their content. However, a high addition effect can be achieved by setting the content within the ranges 0.02%≦Cr and 0.02%≦Mo, or even 0.05%≦Cr and 0.05%≦Mo. Note that Cr and Mo in amounts less than 0.02% each can be considered unavoidable impurities.

[0036] On the other hand, adding large amounts of Cr and Mo reduces the Fe (and Ni and Co) content in the soft magnetic alloy. This leads to deterioration of magnetic properties, such as making it difficult to obtain a sufficiently high saturation magnetic flux density. To prevent deterioration of magnetic properties, the Cr contents are set to 3.0% or less and Mo contents are set to 3.0% or less. Cr contents are more preferably set to 2.5% or less and Mo contents are more preferably set to 2.5% or less.

[0037] As described above, the soft magnetic alloy according to this embodiment contains the predetermined amounts of Si, B, Cu, C, S, and at least one of Ti, Nb, V, Zr, Hf, Ta, and W, with the remainder consisting of Fe (and Ni and Co) and unavoidable impurities. The soft magnetic alloy may further contain the predetermined amount of at least one of P, Cr, and Mo as an optional element. The unavoidable impurities are permitted to be present within a range that does not significantly impair the properties of the soft magnetic alloy, such as magnetic properties. Specific examples of unavoidable impurities include Mn<0.10%, Al<0.50%, O<0.05%, N<0.05%, and a total of Mg and Ca of 0.05% or less. By allowing the inclusion of impurities within the above content ranges, it is possible to avoid increases in production costs due to excessive elimination of impurities in the production of the soft magnetic alloy. It should be noted that Al has the effect of reducing eddy current loss, and therefore may be contained in the soft magnetic alloy within the range of Al<0.50%.

[0038] The shape of the soft magnetic alloy according to this embodiment is not particularly limited and may be any shape. However, it is preferable that the alloy ribbon be in the form of an alloy ribbon. The alloy ribbon may be configured as an amorphous alloy or a nanocrystalline alloy containing nanocrystals. As will be explained next in connection with a method for producing a soft magnetic alloy, a nanocrystalline alloy can be obtained by heat treating an amorphous alloy. The properties of the soft magnetic alloy will be explained after the method for producing a soft magnetic alloy.

[0039] [Method of manufacturing soft magnetic alloys] Here, a method for producing a soft magnetic alloy according to one embodiment of the present invention will be described. Here, the soft magnetic alloy according to one embodiment of the present invention described above is produced as an alloy ribbon.

[0040] In this manufacturing method, first, a molten alloy is quenched to produce an amorphous alloy ribbon having the above-described composition. A ribbon of a soft magnetic alloy can be manufactured, for example, by a single-roll liquid quenching method. That is, a molten alloy having a predetermined composition is discharged onto the surface of a copper roll rotating at high speed, and then quenched and solidified to obtain an alloy ribbon. The alloy ribbon is preferably manufactured in an inert atmosphere such as an Ar atmosphere. The manufacturing conditions may be adjusted so that the resulting alloy ribbon has a width of approximately 10 to 200 mm and a thickness of approximately 10 to 50 μm. Examples of manufacturing conditions include heating the molten alloy to a temperature 200°C or higher than the melting point, setting the difference between the internal pressure of the nozzle discharging the molten alloy and the external pressure of the space containing the copper roll to 1 atmosphere or more, and setting the gap between the nozzle and the roll to 1 mm or less.

[0041] In this way, the ribbon-shaped soft magnetic alloy obtained by rapid cooling of the molten alloy is amorphous. By heat treating this amorphous alloy ribbon, a nanocrystalline alloy can be obtained. A nanocrystalline alloy contains nanocrystals in an amorphous matrix.

[0042] When heat treatment is performed, the amorphous alloy ribbon is heated to a target temperature. The target temperature may be set to a temperature 30°C higher than the crystallization start temperature of the soft magnetic alloy constituting the alloy ribbon. Alternatively, a tolerance of ±15°C may be set for the target temperature. The crystallization start temperature can be measured by differential scanning calorimetry (DSC). Note that, within the above-described range of the component composition of the soft magnetic alloy, the temperature 30°C higher than the crystallization start temperature falls within the range of 465°C to 500°C, and therefore the target temperature may be set within this range. It is preferable not to heat the alloy ribbon to a temperature higher than 500°C throughout the entire heat treatment period.

[0043] During the heat treatment, the temperature of the alloy ribbon is increased to a target temperature at a rate of, for example, 1°C / min or more and 30°C / min or less. The heating time at the target temperature is, for example, 0.5 hours or more and 3.0 hours or less. The heat treatment is preferably performed in an inert atmosphere such as an Ar atmosphere. After the heat treatment, the alloy ribbon is naturally cooled in an inert gas.

[0044] [Characteristics of soft magnetic alloys] The soft magnetic alloy according to the embodiment of the present invention has the above-described composition, which allows it to have excellent soft magnetic properties such as high magnetic permeability, as well as high saturation magnetic flux density. At the same time, the soft magnetic material also has excellent punchability. The high saturation magnetic flux density is achieved by, in particular, ensuring that the content of each additive element is not excessive, ensuring a sufficient content of the magnetic element Fe (and Ni and Co), and by limiting the content of elements that may adversely affect the magnetic properties to a range where their adverse effects are not significant. The high punchability is also achieved primarily by the combined addition of appropriate amounts of C and S, which reduces the ductility of the amorphous phase. Thus, the soft magnetic alloy according to the embodiment of the present invention achieves a good balance between high saturation magnetic flux density and high punchability due to the effect of the composition.

[0045] Furthermore, the inclusion of B, Cu, and element X, and optionally P, in this soft magnetic alloy effectively refines the nanocrystals in the nanomagnetic alloy obtained by heat-treating the amorphous alloy. Furthermore, the composition of the components allows for a high degree of robustness to manufacturing conditions, resulting in a nanocrystalline alloy containing such fine nanocrystals. That is, even if manufacturing conditions for the soft magnetic alloy, such as the heating rate, target temperature, and heating time during heat treatment, vary, nanocrystalline alloys containing fine nanocrystals can be produced. In nanocrystalline alloys obtained by heat-treating an amorphous alloy, the smaller the nanocrystal grain size, the better the soft magnetic properties can be obtained. Preferably, the average grain size of the nanocrystals is 30 nm or less, or even 25 nm or less, or even 20 nm or less. Because this soft magnetic alloy exhibits high robustness to heat treatment conditions, nanocrystalline alloys containing fine nanocrystals can be reliably obtained by heat treatment under a wide range of conditions, including the target temperature, heating rate, and heating time described above for the manufacturing method. In particular, as adopted in the examples below, it is preferable to obtain a nanocrystalline alloy with an average crystal grain size of 30 nm or less by heat treatment with a target temperature 30°C higher than the crystallization onset temperature, a heating rate of 2.5°C / min, and a heating time of 60 minutes.

[0046] As described above, the soft magnetic alloy according to this embodiment has a high saturation magnetic flux density, preferably 1.4 T or more. The soft magnetic alloy also exhibits good soft magnetic properties, preferably having a core loss of less than 5.0 W / kg at an applied magnetic flux density of 0.1 T and a frequency of 20 kHz. The saturation magnetic flux density and core loss are measured for a nanocrystalline alloy obtained by heat-treating an amorphous alloy. [Example]

[0047] The present invention will be described in more detail below using examples, but the present invention is not limited to these examples.

[0048] [Sample preparation] As the soft magnetic alloys according to Examples 1 to 19 and Comparative Examples 1 to 6, alloy ribbons were prepared containing each component element at the concentration shown in Table 1, with the remainder consisting of unavoidable impurities and Fe. A molten alloy having a predetermined component composition ratio was prepared, and a ribbon was produced by a single-roll liquid quenching method. That is, the molten alloy was discharged onto the surface of a rotating copper roll, where it was rapidly cooled and solidified. The obtained alloy ribbons had widths of 30 to 120 mm and thicknesses of 10 to 30 μm.

[0049] Furthermore, for the samples of each Example and Comparative Example, the alloy ribbons produced by the single-roll liquid quenching method described above were subjected to heat treatment. The crystallization onset temperature of each sample alloy was measured in advance by DSC, and the target temperature for each sample was set to a temperature 30°C higher than the crystallization onset temperature. The target temperature for each sample was within the range of 465 to 500°C. For the heat treatment, the alloy ribbon was heated in a heating furnace in an Ar atmosphere from room temperature to the target temperature set above at a heating rate of 2.5°C / min. The target temperature was then maintained for 60 minutes. Thereafter, heating was stopped, and the alloy ribbon was allowed to cool naturally in the furnace. Additionally, as Reference Example 1, instead of the heat treatment under the above conditions, the same sample as in Example 1 was subjected to a two-stage heat treatment, in which heating was performed at a target temperature of 450°C for 60 minutes and then at 650°C for 1 hour. For the samples used to evaluate the saturation magnetic flux density and core loss, the alloy ribbon produced by the single-roll liquid quenching method described above was cut into ribbons with a width of 5 mm, and processed into toroidal cores (outer diameter 21 mm, inner diameter 20 mm) wound 30 times, which were then heat-treated under the conditions described above.

[0050] [Evaluation method] The soft magnetic alloys produced above were subjected to the following evaluations. Each evaluation was carried out at room temperature.

[0051] (1) Confirmation of amorphization X-ray diffraction was used to confirm whether the structure of the alloy ribbon before heat treatment had become amorphous. Specifically, X-rays were incident on the free surface (the surface that was not in contact with the roll during quenching) of the alloy ribbon before heat treatment, and X-ray diffraction measurement was performed. Cu Kα rays were used as the X-ray source. In the obtained diffraction pattern, the integrated intensity (A cry ) and the integrated intensity of the peaks derived from the amorphous phase (A amo The crystallinity was calculated from the cry / (A amo +A cry ) × 100%). When the obtained crystallinity was less than 5%, it was judged that the amorphization was sufficient (◯). On the other hand, when the crystallinity was 5% or more, it was judged that the amorphization was insufficient (×). Here, the peak derived from the crystalline phase was the peak corresponding to the (220) plane of the α phase, and the peak derived from the amorphous phase was the peak where the diffraction angle 2θ was 30°≦2θ≦60° and the half-width was ≧3°.

[0052] (2) Crystal grain size The heat-treated alloy ribbon was subjected to X-ray diffraction measurement in the same manner as in the test (1) above. In the obtained X-ray diffraction pattern, the average grain size of the crystal grains was calculated from the width of the peak corresponding to the (110) plane of the α phase using the following Scherrer equation. D= Kλ / Bcosθ Here, D is the crystal grain size, K is the Scherrer constant, which is set to 0.9, λ is the wavelength of the X-ray, B is the width of the diffraction peak, and θ is the Bragg angle. If the average crystal grain size is 30 nm or less, it can be considered that the nanocrystals have been sufficiently refined.

[0053] (3) Punchability A punching test was conducted on the alloy ribbon before heat treatment. Specifically, a 20 μm-thick alloy ribbon before heat treatment was punched into φ10 mm disks using an SKD11 die and a cemented carbide punch. If no defective disk shape or tool wear occurred even after punching 3,000 disks, the punchability was judged to be high (◯). On the other hand, if at least one of defective disk shape and tool wear occurred before punching 3,000 disks, the punchability was judged to be low (×).

[0054] (4) Saturation magnetic flux density The saturation magnetic flux density of the heat-treated toroidal core was measured. Specifically, a DC BH measurement was performed to obtain a BH curve with a maximum magnetic field Hm of 3000 A / m, and the magnetic flux density value at H=3000 A / m was recorded as the saturation magnetic flux density (Bs). A measured value of 1.4 T or higher can be considered to have a sufficiently high saturation magnetic flux density.

[0055] (5) Core loss The core loss of the heat-treated toroidal core was measured. Specifically, AC BH measurements were performed to evaluate the core loss at an applied magnetic flux density of 0.1 T and a frequency of 20 kHz. If the measured value is less than 5.0 W / kg, the core loss can be considered to be sufficiently small.

[0056] [Test Results] Table 1 shows the component compositions and evaluation results for Examples 1 to 19, Comparative Examples 1 to 6, and Reference Example 1. In the table, a column marked with "-" indicates that the element is not contained except as an unavoidable impurity. For Mg and Ca, the total amount is shown.

[0057] [Table 1]

[0058] In Table 1, the soft magnetic alloys of Examples 1 to 19 contain 7.0%≦Si≦15.0%, 7.0%≦B≦10.0%, 0.5%≦Cu≦2.0%, 0.03%≦C≦0.30%, and 0.005%≦S≦0.050%, with the remainder consisting of Fe (and Ni and Co) and unavoidable impurities. Correspondingly, in each soft magnetic alloy, the alloy ribbon is amorphous before heat treatment, and after heat treatment, a nanocrystalline alloy with an average crystal grain size of 30 nm or less is obtained. High punchability is also achieved. Furthermore, a saturation magnetic flux density of 1.4 T or more is obtained, and core loss is suppressed to less than 5.0 W / kg. Thus, high punchability and high saturation magnetic flux density are simultaneously achieved. Furthermore, finer nanocrystals are achieved in the nanocrystalline alloy, and high soft magnetic properties indicated by low core loss are obtained.

[0059] In Comparative Example 1, the C content is too low. In Comparative Example 3, the S content is too low. In Comparative Examples 1 and 3, the punchability is poor due to the lack of C and S. On the other hand, in Comparative Example 2, the C content is too high. In Comparative Example 4, the S content is too high. In Comparative Examples 2 and 4, the C and S content is excessive, resulting in a low saturation magnetic flux density significantly below 1.4 T. Furthermore, in Comparative Example 4, the core loss is also large. From these results, it can be said that adding appropriate amounts of C and S to a soft magnetic material can achieve both high saturation magnetic flux density and high punchability.

[0060] In Comparative Example 5, the Cu content is too low. The crystal grain size after heat treatment exceeds 30 nm. This can be interpreted as being due to the low Cu content, which prevents sufficient formation of clusters in the amorphous alloy that are effective in refining nanocrystals. Core loss also increases because the nanocrystals are not sufficiently refined. In Comparative Example 6, the content of element X (Nb) is too low. In this case, the nanocrystal grain size after heat treatment exceeds 30 nm because the effect of element X in refining nanocrystals is not sufficient. Core loss also increases.

[0061] In Reference Example 1, the soft magnetic alloy has the same composition as in Example 1, but is heat-treated in two stages, with the second stage being performed at a high temperature of 650°C. Due to the effect of the composition, the soft magnetic alloy according to the embodiment of the present invention exhibits high robustness to heat treatment conditions, and after heat treatment under a wide range of conditions, a nanocrystalline alloy containing fine nanocrystals is obtained. However, heat treatment at extremely high temperatures, as in Reference Example 1, causes coarsening of the nanocrystals. In Reference Example 1, the core loss is significantly increased, which is thought to be due to the coarsening of the nanocrystals as well as the precipitation of borides during heat treatment. Based on these results, it is preferable to avoid raising the heating temperature during heat treatment too high, and keep it at around 500°C or less. The two-stage heat treatment, particularly the high-temperature second heat treatment, is adopted in Patent Document 3.

[0062] The embodiments and examples of the present invention have been described above. The present invention is not particularly limited to these embodiments and examples, and various modifications can be made.

Claims

1. In atomic percent, 7.0%≦Si≦15.0%, 7.0%≦B≦10.0%, 0.5%≦Cu≦2.0%, 0.03%≦C≦0.30%, 0.005%≦S≦0.050%; X is at least one element selected from Ti, Nb, V, Zr, Hf, Ta, and W, 3.0%<X≦5.0%; The balance of the soft magnetic alloy is Fe, or a portion of the Fe is substituted with at least one of Ni and Co, and unavoidable impurities.

2. Furthermore, in atomic percent, 0%<P≦2.0%, 0%<Cr≦3.0%, 0%<Mo≦3.0% The soft magnetic alloy according to claim 1, comprising at least one of the following:

3. 3. The soft magnetic alloy according to claim 1, which is a nanocrystalline alloy containing nanocrystals having an average crystal grain size of 30 nm or less.

4. The molten alloy is rapidly cooled to produce an amorphous alloy ribbon having the component composition of claim 1 or claim 2, and then A method for producing a soft magnetic alloy, comprising heat-treating the alloy ribbon at a target temperature within a range of ±15°C from a temperature 30°C higher than the crystallization start temperature of the alloy ribbon.

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