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 refinement of nanocrystals, and a method for producing the soft magnetic alloy.SOLUTION: A soft magnetic alloy contains, in atomic%, 7.0%≤Si≤12.0%, 7.0%≤B≤10.0%, 0.5%≤Cu≤2.0%, 0.5%≤P≤2.0%, 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, and, with the contents of Cu and P in atomic% being denoted as Cu and P, respectively, satisfies 0.40≤Cu / P<1.0.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. To improve the saturation magnetic flux density, it is effective to increase the content of Fe or Ni and Co that can replace Fe. However, if this is done, the amount of various elements that can be added, which are effective for the amorphization of the material and the refinement of nanocrystals in the nanocrystalline alloy formed by heat treatment, will relatively decrease. Then, it becomes difficult to obtain a nanocrystalline alloy containing fine nanocrystals. In particular, as the content of additive elements such as Cu and Nb, which have a high effect on the refinement of nanocrystals, decreases, coarsening of nanocrystals during heat treatment is likely to occur.

[0006] The problem to be solved by the present invention is to provide a soft magnetic alloy based on an Fe-Si-B-Cu-Nb alloy, which can achieve both a high saturation magnetic flux density and refinement of nanocrystals, and a method for producing such a soft magnetic alloy.

Means for Solving the Problem

[0007] To solve the above problems, the soft magnetic alloy and the method for producing a soft magnetic alloy of the present invention have the following configurations.

[0008] [1] The soft magnetic alloy of the present invention contains, in atomic percentage, 7.0% ≤ Si ≤ 12.0%, 7.0% ≤ B ≤ 10.0%, 0.5% ≤ Cu ≤ 2.0%, 0.5% ≤ P ≤ 2.0%, and at least one element selected from Ti, Nb, V, Zr, Hf, Ta, and W as X, 3.0% < X ≤ 5.0%, and the balance consists of Fe or Fe in which a part of Fe is replaced by at least one of Ni and Co, and inevitable impurities. The contents of Cu and P in atomic percentage are denoted as Cu and P, respectively, and 0.40 ≤ Cu / P < 1.0.

[0009] [2] In the aspect of [1] above, the soft magnetic alloy may further contain at least one of 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 be configured as 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 manufactures an amorphous alloy ribbon having the component composition of [1] or [2] above by rapidly cooling an alloy melt, and then performs 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.

[0012] [5] In the aspect of [4] above, it is preferable to raise the temperature to the target temperature at a heating rate of 1°C / min or more and 30°C / min or less, and then heat the alloy ribbon at the target temperature for 0.5 hours or more and 3.0 hours or less.

Effect of the Invention

[0013] The soft magnetic alloy according to the present invention having the configuration of [1] above has a high saturation magnetic flux density and enables both the refinement of nanocrystals by having the above component composition. In particular, when the soft magnetic alloy contains a predetermined amount of Cu and P and their mass ratio satisfies 0.40 ≤ Cu / P < 1.0, a high effect on the refinement of nanocrystals when heat-treating an amorphous alloy can be obtained. On the other hand, the addition amount of an element X or the like having an effect of refining nanocrystals can be suppressed low, and accordingly, the content of Fe (and Ni, Co) can be ensured relatively high, and the saturation magnetic flux density can be effectively improved.

[0014] Furthermore, because the component composition of the soft magnetic alloy is highly effective in refining nanocrystals, a nanocrystalline alloy containing fine nanocrystals can be obtained even if the conditions during heat treatment, such as the heating rate, heating temperature, heating time, etc., vary to some extent. In other words, fine nanocrystals can be stably generated with high robustness against variations in manufacturing conditions, such as the heating rate, heating temperature, and heating time during heat treatment, and the stability of the properties of the soft magnetic alloy can be improved.

[0015] In the above embodiment [2], at least one of Cr and Mo is added to the soft magnetic alloy. Cr and Mo improve the corrosion resistance of the soft magnetic alloy.

[0016] 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, it is possible to obtain a nanocrystalline alloy with high robustness against manufacturing conditions, in which the average grain size of the nanocrystals is kept small, at 30 nm or less.

[0017] In the method for producing a soft magnetic alloy according to the present invention, which has the above-mentioned configurations [4] and [5], an amorphous alloy ribbon obtained as having the above-mentioned composition [1] or [2] is heat-treated under specified conditions, and a nanocrystalline alloy is obtained through this heat treatment. When the soft magnetic alloy has the composition [1] or [2], the obtained nanocrystalline alloy achieves both a high saturation magnetic flux density and fine nanocrystals, as described above. Because the composition of the soft magnetic alloy is highly effective in fine nanocrystals, a nanocrystalline alloy containing fine nanocrystals can be obtained with high robustness even when the heating rate, target temperature, and heating time during heat treatment are changed within the above-mentioned ranges. DETAILED DESCRIPTION OF THE INVENTION

[0018] 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.

[0019] [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, P, 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. Furthermore, the Cu and P satisfy a predetermined quantitative ratio.

[0020] 7.0%≦Si≦12.0% 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.

[0021] On the other hand, if too much Si is added, the content of Fe (and Ni and Co) 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≦12.0%. Si≦11.0% is more preferable.

[0022] 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.

[0023] 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.

[0024] 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. 0.6% or less, or even 0.7% or less, is more preferable.

[0025] 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≦2.0% is recommended. Cu≦1.5%, or even Cu≦1.2%, is more preferable.

[0026] 0.5%≦P≦2.0% P coexists with Cu in soft magnetic alloys to form Cu3P clusters, thereby suppressing the coarsening of the clusters formed by Cu. The Cu3P clusters are finer and more dispersed than the Cu clusters. To fully enhance the effect of Cu3P cluster formation, the P content is set to 0.5% or less. 0.8% or less, or even 1.0% or less, is more preferable.

[0027] 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.

[0028] ·0.40 ≦ Cu / P < 1.0 The soft magnetic alloy contains the above-mentioned predetermined amounts of Cu and P respectively, and further, Cu and P satisfy a predetermined quantitative ratio. That is, when the contents of Cu and P in atomic % are represented as Cu and P respectively, 0.40 ≦ Cu / P < 1.0 is satisfied.

[0029] If P is too much with respect to Cu, that is, if Cu / P is too small, surplus P that does not contribute to the formation of Cu3P clusters occurs, and it is difficult for the refinement of nanocrystals due to the generation of Cu3P clusters to occur effectively. Moreover, the surplus P deteriorates the magnetic properties of the soft magnetic alloy. However, by setting 0.40 ≦ Cu / P and suppressing the amount of P with respect to Cu, the generation of surplus P can be suppressed. It is more preferable that 0.50 ≦ Cu / P, and further 0.60 ≦ Cu / P.

[0030] On the other hand, if P is too little with respect to Cu, that is, if Cu / P is too large, the formation of Cu3P clusters does not occur sufficiently, and sufficient contribution cannot be obtained for promoting the fine dispersion of the clusters. However, by setting Cu / P < 1.0 and ensuring the amount of P with respect to Cu, the promoting effect of the fine dispersion of the clusters due to the formation of Cu3P clusters can be enhanced. It is more preferable that Cu / P < 0.90, and further Cu / P < 0.80.

[0031] ·3.0% < X ≦ 5.0% The soft magnetic alloy according to this embodiment contains at least one element X selected from Ti, Nb, V, Zr, Hf, Ta, and W, and the total content thereof is 3.0% < X ≦ 5.0%. Ti, Nb, V, Zr, Hf, Ta, and W all have the effect of suppressing the coarsening of nanocrystals and making it easy to generate fine nanocrystals in the soft magnetic alloy. The soft magnetic alloy may contain any one or any number of elements X, but it is particularly preferable to contain Nb.

[0032] From the viewpoint of sufficiently obtaining the effect of refinement of nanocrystals, the content of element X in the soft magnetic alloy is set to 3.0% < X. It is more preferable that 3.1% ≦ X, and further 3.2% ≦ X.

[0033] However, adding too much element X reduces the relative content of Fe (and Ni and Co) 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 content of element X is limited to X≦5.0%. A content of element X of 5.0% or less is sufficiently effective in suppressing coarsening of nanocrystals. X≦4.0% is more preferable.

[0034] Fe, Ni, Co The soft magnetic alloy according to this embodiment is composed of the above-described predetermined amounts of Si, B, Cu, P, and element X, with the remainder consisting of Fe or Fe partially substituted with Ni and Co, excluding unavoidable impurities. Ni and Co are magnetic elements like Fe, and are added to the soft magnetic alloy to replace Fe. The amounts of Ni and Co added are not particularly limited, but it is preferable to limit Ni≦20% and Co≦20%.

[0035] The soft magnetic alloy according to this embodiment may contain, as essential elements, Fe (and Ni and Co), the above-mentioned predetermined amounts of at least one of Si, B, Cu, P, and Ti, Nb, V, Zr, Hf, Ta, and W, and may further contain, as optional elements, the following predetermined amounts of at least one of Cr, Mo, and C. In particular, an embodiment containing at least one of Cr and Mo is preferred.

[0036] 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.

[0037] 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.

[0038] 0% <C≦1.0% When added to soft magnetic alloys, C has the effect of improving punchability. Since even a small amount of C exerts this effect, there is no specific lower limit for its content. However, if the C content is set to 0.01% or less, a high addition effect can be obtained. Note that C less than 0.01% can be considered an unavoidable impurity.

[0039] 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 suppress the formation of FeC compounds, the C content is set at 1.0% or less.

[0040] As described above, the soft magnetic alloy according to this embodiment contains the predetermined amounts of Si, B, Cu, P, 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 Cr, Mo, and C as an optional element. The unavoidable impurities are permitted to be contained 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 manufacturing costs due to excessive elimination of impurities during the production of the soft magnetic alloy. Al has the effect of reducing eddy current loss, so it may be contained in the soft magnetic alloy within the range of Al<0.50%.

[0041] 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.

[0042] [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.

[0043] 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.

[0044] 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.

[0045] When performing the heat treatment, the amorphous alloy ribbon is heated to a target temperature at a predetermined heating rate and maintained at the target temperature for a predetermined time. 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 that the alloy ribbon not be heated to a temperature higher than 500°C throughout the entire heat treatment period.

[0046] The temperature rise rate during the heat treatment may be, for example, 1°C / min or more and 30°C / min or less. The heating time at the target temperature may be, 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 may be naturally cooled in an inert gas.

[0047] [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 a high saturation magnetic flux density. At the same time, nanocrystalline refinement can be achieved in the nanomagnetic alloy obtained by heat-treating the amorphous alloy. In particular, when the soft magnetic alloy contains predetermined amounts of Cu and P, with the ratio of these elements being in the range of 0.40≦Cu / P<1.0, the formation of finely dispersed clusters is highly effective in refining the nanocrystalline refinement. Therefore, even if the content of elements X, such as B and Nb, which are effective in refining the nanocrystalline refinement, is kept to a certain level, sufficient nanocrystalline refinement can be achieved. By keeping the content of these elements and Si to a minimum, the content of the magnetic elements Fe (and Ni and Co) is sufficiently ensured, resulting in a high saturation magnetic flux density. Thus, the soft magnetic alloy according to the embodiment of the present invention achieves a good balance between high saturation magnetic flux density and nanocrystalline refinement due to the effect of the composition.

[0048] Furthermore, because the soft magnetic alloy has an excellent effect of refining nanocrystals due to its component composition, a nanocrystalline alloy containing fine nanocrystals can be obtained with high robustness against manufacturing conditions. In other words, even if the manufacturing conditions of the soft magnetic alloy, including the heating rate, target temperature, and heating time during heat treatment, vary, a nanocrystalline alloy containing fine nanocrystals can be manufactured. This makes it easier to manage the manufacturing conditions, and the properties of the manufactured soft magnetic alloy are also stable. In particular, when performing heat treatment on large soft magnetic alloy materials or large quantities of soft magnetic alloy materials, it is difficult to increase the heating rate. However, even in such cases, coarsening of nanocrystals due to a slow heating rate can be suppressed, making it easier to consistently obtain good magnetic properties.

[0049] In nanocrystalline alloys obtained by heat treatment of amorphous alloys, the smaller the grain size of the nanocrystals, the better the soft magnetic properties. Preferably, the average grain size of the nanocrystals in the nanocrystalline alloy obtained by heat treatment is 30 nm or less, further 25 nm or less, or even 20 nm or less. This soft magnetic alloy exhibits high robustness to heat treatment conditions, allowing nanocrystalline alloys with fine nanocrystals to be stably obtained by heat treatment under a wide range of conditions, including the target temperature, heating rate, and heating time ranges listed above for the manufacturing method. In particular, as used in the examples below, it is preferable to obtain nanocrystalline alloys with an average grain size of 30 nm or less by heat treatment at a target temperature 30°C higher than the crystallization onset temperature, at a heating rate of 10°C / min, and for a heating time of 60 minutes.

[0050] 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]

[0051] The present invention will be described in more detail below using examples, but the present invention is not limited to these examples.

[0052] [Sample preparation] As the soft magnetic alloys according to Examples 1 to 15 and Comparative Examples 1 to 9, 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.

[0053] 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 10°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, a two-stage heat treatment was performed on the same sample as in Example 1, 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.

[0054] [Evaluation method] The soft magnetic alloys produced above were subjected to the following evaluations. Each evaluation was carried out at room temperature.

[0055] (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°.

[0056] (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.

[0057] (3) Saturation magnetic flux density The saturation magnetic flux density of the toroidal core after heat treatment was measured. Specifically, DC B-H measurement was carried out to obtain the B-H curve with the maximum magnetic field Hm = 3000 A / m, and the value of the magnetic flux density at H = 3000 A / m was recorded as the saturation magnetic flux density (Bs). If the measured value is 1.4 T or more, it can be considered that the saturation magnetic flux density is sufficiently high.

[0058] (4) Core loss The core loss of the toroidal core after heat treatment was measured. Specifically, AC B-H measurement was carried out 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, it can be considered that the core loss is sufficiently small.

[0059] [Test results] Table 1 shows the component compositions and the results of each evaluation for Examples 1 to 15, Comparative Examples 1 to 9, and Reference Example 1. As the component compositions, the quantity ratio Cu / P is also shown together. In the table, the columns indicated by "-" mean that they are not contained except for inevitable impurities. For Mg and Ca, the total amounts are shown.

[0060]

Table 1

[0061] In Table 1, the soft magnetic alloys of Examples 1 to 15 contain 7.0% ≤ Si ≤ 12.0%, 7.0% ≤ B ≤ 10.0%, 0.5% ≤ Cu ≤ 2.0%, 0.5% ≤ P ≤ 2.0%, 3.0% < X ≤ 5.0%, and the balance consists of Fe (and Ni, Co) and inevitable impurities. And 0.40 ≤ Cu / P < 1.0. Correspondingly, in any of the soft magnetic alloys, the alloy ribbon before heat treatment is amorphous, and through heat treatment, a nanocrystalline alloy having an average crystal grain size of 30 nm or less is obtained. Also, a saturation magnetic flux density of 1.4 T or more is obtained, and the core loss is suppressed to less than 5.0 W / kg. Thus, the refinement of the nanocrystals and the increase in the saturation magnetic flux density in the nanocrystalline alloy are compatible. Also, high soft magnetic properties shown by low core loss are obtained.

[0062] In Comparative Example 1, the Si content is too low, resulting in large core loss. Meanwhile, in Comparative Example 2, the Si content is too high, resulting in a small Fe content, and a saturation magnetic flux density of 1.4 T or more is not achieved. In Comparative Example 3, the B content is too low. Accordingly, an amorphous structure is not obtained before heat treatment, and a nanocrystalline alloy containing nanocrystals is not obtained even after heat treatment. Therefore, sufficient soft magnetic properties are not obtained, resulting in large core loss. Meanwhile, in Comparative Example 4, the B content is too high, resulting in a small Fe content, similar to Comparative Example 2, and a saturation magnetic flux density of 1.4 T or more is not achieved.

[0063] 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. The core loss also increases, corresponding to the insufficient refinement of the nanocrystals. In Comparative Example 6, the Cu content is sufficient, but the Cu / P ratio is too small. Meanwhile, in Comparative Example 7, the Cu / P ratio is too large. In both Comparative Examples 6 and 7, the crystal grain size after heat treatment exceeds 30 nm. From these results, it can be said that unless the Cu / P ratio is within an appropriate range and Cu and P are contained in a balanced manner, the refinement of nanocrystals by the formation of CuP clusters does not function sufficiently effectively. In Comparative Examples 6 and 7, the core loss also increases, corresponding to the insufficient refinement of the nanocrystals.

[0064] In both Comparative Examples 8 and 9, the content of element X (Nb) was too low. In these Comparative Examples, the effect of element X in refining the nanocrystals was insufficient, and the particle size of the nanocrystals after heat treatment exceeded 30 nm. In addition, the core loss was also large.

[0065] 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.

[0066] 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≦12.0%, 7.0%≦B≦10.0%, 0.5%≦Cu≦2.0%, 0.5%≦P≦2.0%; X is at least one element selected from Ti, Nb, V, Zr, Hf, Ta, and W, 3.0%<X≦5.0%; the balance being Fe, or Fe partially substituted with at least one of Ni and Co, and unavoidable impurities; The contents of Cu and P in atomic % are represented as Cu and P, respectively. A soft magnetic alloy, wherein 0.40≦Cu / P<1.

0.

2. Furthermore, in atomic percent, 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.

5. 5. The method for producing a soft magnetic alloy according to claim 4, wherein the temperature is increased to the target temperature at a temperature increase rate of 1° C. / min or more and 30° C. / min or less, and the alloy ribbon is heated at the target temperature for 0.5 hours or more and 3.0 hours or less.

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