Soft magnetic alloy and magnetic component

Abstract

The present invention provides a soft magnetic alloy having: an inner region having a soft magnetic alloy composition containing Fe and Co; and a Co concentration region present on a surface side than the inner region, the Co concentration being higher than that of the inner region. Furthermore, the Co concentration degree in the Co concentration region is greater than 1.2.

Description

Technical Field

[0001] This invention relates to soft magnetic alloys and magnetic components using the soft magnetic alloys. Background Technology

[0002] Soft magnetic alloys, as shown in Patent Documents 1-3, are known as magnetic materials used in various magnetic components such as inductors. These soft magnetic alloys have a higher saturation magnetic flux density (Bs) than ferrite materials and possess excellent soft magnetic properties. However, soft magnetic alloys sometimes corrode due to storage conditions or the environment in which they are used, such as rusting, requiring improved corrosion resistance.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2009-293099

[0006] Patent Document 2: Japanese Patent Application Publication No. 2007-231415

[0007] Patent Document 3: Japanese Patent Application Publication No. 2014-167139 Summary of the Invention

[0008] The technical problem that the invention aims to solve

[0009] The present invention was made in view of the above circumstances, and its object is to provide a soft magnetic alloy with high corrosion resistance and a magnetic component using the soft magnetic alloy.

[0010] Technical solutions for solving technical problems

[0011] To achieve the above objectives, the present invention provides a soft magnetic alloy having:

[0012] The internal region is composed of a soft magnetic alloy containing Fe and Co;

[0013] The Co concentration region exists on the surface side, which is higher than the aforementioned internal region.

[0014] The Co concentration in the aforementioned Co concentration region is greater than 1.2.

[0015] The inventors of this invention conducted in-depth research and found that by using a soft magnetic alloy with the above-mentioned characteristics, it is possible to suppress rusting when immersed in water and improve corrosion resistance.

[0016] Preferably, the Co-concentrated region is a metallic phase.

[0017] Preferably, the degree of amorphization of the above-mentioned soft magnetic alloy is 85% or higher.

[0018] In addition, the aforementioned soft magnetic alloys can be in the form of strips or powders.

[0019] The soft magnetic alloy of the present invention has no particular limitations in its application; for example, it can be used in various magnetic components such as coil parts for inductors, filters, and antennas. The soft magnetic alloy of the present invention is also suitable as a magnetic core material for coil parts and the like in the aforementioned applications. Attached Figure Description

[0020] Figure 1A This is an enlarged cross-sectional view of the main part of the soft magnetic alloy 1 according to one embodiment of the present invention.

[0021] Figure 1B This is an example of an enlarged cross-sectional view of the main part of a soft magnetic alloy 1a according to one embodiment of the present invention.

[0022] Figure 2A This is an example of a diagram obtained through X-ray crystal structure analysis.

[0023] Figure 2B Yes Figure 2A The image shown is an example of a pattern obtained by performing graphic fitting.

[0024] Figure 3A It is along Figure 1A The measurement line L shown M An example of a curve obtained by using EDX for line analysis.

[0025] Figure 3B It is along Figure 1B The measurement line L shown M a, An example of a curve obtained by using EDX for line analysis.

[0026] Figure 4A This is a cross-sectional view of a soft magnetic alloy 1b according to one embodiment of the present invention.

[0027] Figure 4B It is Figure 4A The area shown is an enlarged cross-sectional view of IVB.

[0028] Figure 5A yes Figure 1A An example of an EELS image of the soft magnetic alloy 1 shown.

[0029] Figure 5B yes Figure 1B An example of an EELS image of the soft magnetic alloy 1a shown.

[0030] Figure 5C yes Figure 4AAn example of a STEM image of the soft magnetic alloy 1b shown.

[0031] Explanation of reference numerals in the attached figures

[0032] 1, 1a, 1b: Soft magnetic alloy; 2: Internal region; 10: Outer surface; 11: Co-concentrated region; 12: SB oxide layer; 13: Fe oxide layer; 20: Covering layer. Detailed Implementation

[0033] The present invention will now be described in detail based on the embodiments shown in the accompanying drawings.

[0034] The soft magnetic alloy 1 of this embodiment can have a strip shape, a powder shape, or other bulk shapes, and the shape of the soft magnetic alloy 1 is not particularly limited. Furthermore, the size of the soft magnetic alloy 1 is not particularly limited. For example, when the soft magnetic alloy 1 is in the shape of a strip, the thickness of the strip can be 15 μm to 100 μm; when the soft magnetic alloy 1 is in the shape of a powder, the average particle size of the soft magnetic alloy powder can be 0.5 μm to 150 μm, preferably 0.5 μm to 25 μm.

[0035] The average particle size mentioned above can be determined by various particle size analysis methods such as laser diffraction, preferably using a particle image analysis device, the Morphologi G3 (manufactured by Malvern Panalytical). Using the Morphologi G3, the soft magnetic alloy powder is dispersed using air, and the projected area of ​​the particles constituting the powder is measured. The particle size distribution with a circular equivalent diameter is obtained based on this projected area. Then, in the obtained particle size distribution, the particle size at which the cumulative relative degree based on volume or number reaches 50% is calculated as the average particle size. Where the soft magnetic alloy 1 is contained within a magnetic core, the average particle size of the soft magnetic alloy 1 (powder) can be calculated by measuring the circular equivalent diameter of the particles included in the cross-section using cross-sectional observation with an electron microscope (SEM, STEM, etc.).

[0036] Figure 1A This is an enlarged cross-sectional view of the area near the surface of the soft magnetic alloy 1. For example... Figure 1A As shown, the soft magnetic alloy 1 has an inner region 2 and a Co-enriched region 11 located on the surface side of the soft magnetic alloy 1, which is closer to the inner region 2. In this embodiment, "inner side" refers to the side closer to the center of the soft magnetic alloy 1, and "surface side" or "outer side" refers to the side further away from the center of the soft magnetic alloy 1.

[0037] (Internal Area 2)

[0038] The internal region 2 is the matrix portion of the soft magnetic alloy 1, comprising at least 90 vol% of its volume. Therefore, the average composition of the soft magnetic alloy 1 can be considered as the composition of the internal region 2, and the crystal structure of the soft magnetic alloy 1 can be considered as the crystal structure of the internal region 2. Furthermore, the volume ratio of the internal region 2 described above can replace the area ratio, and at least 90% of the cross-sectional area of ​​the soft magnetic alloy 1 is the internal region 2.

[0039] The inner region 2 (i.e., soft magnetic alloy 1) has a soft magnetic alloy composition containing Fe and Co, and the specific alloy composition is not particularly limited. For example, the inner region 2 can be a soft magnetic alloy with a crystalline system such as Fe-Co alloy, Fe-Co-V alloy, Fe-Co-Si alloy, or Fe-Co-Si-Al alloy. Furthermore, it is preferable that the inner region 2 contains P. Examples of soft magnetic alloys with a P-containing crystalline system include Fe-Co-Si-P alloys and Fe-Co-Si-P-Cr alloys. By containing P in the inner region 2, Co tends to concentrate at the outer edge of the inner region 2.

[0040] Furthermore, from the viewpoint of reducing coercivity, the internal region 2 preferably has an amorphous or nanocrystalline alloy composition. Examples of amorphous or nanocrystalline soft magnetic alloys include Fe-Co-PC alloys, Fe-Co-B alloys, or Fe-Co-B-Si alloys. More specifically, the internal region 2 preferably has a composition satisfying the formula ((Fe... (1-(α+β)) Co α Ni β )1 -γ X1 γ ) (1-(a+b+c+d+e)) B a P b Si c C d Cr e The alloy composition, by having the above composition, easily yields amorphous, heteroamorphous, or nanocrystalline crystalline structures.

[0041] In the above composition, B represents boron, P represents phosphorus, C represents carbon, and X1 is one or more elements selected from Ti, Zr, Hf, Nb, Ta, Mo, W, Al, Ga, Ag, Zn, S, Ca, Mg, V, Sn, As, Sb, Bi, N, O, Au, Cu, rare earth elements, and platinum group elements. Rare earth elements include Sc, Y, and lanthanides, while platinum group elements include Ru, Rh, Pd, Os, Ir, and Pt. Furthermore, α, β, γ, a, b, c, d, and e are atomic ratios, which preferably satisfy the following conditions.

[0042] The Co content relative to Fe (α) is 0.005 ≤ α ≤ 0.700, which can be 0.010 ≤ α ≤ 0.600, 0.030 ≤ α ≤ 0.600, or 0.050 ≤ α ≤ 0.600. Within the above ranges for α, both Bs and corrosion resistance are improved. From the viewpoint of increasing Bs, 0.050 ≤ α ≤ 0.500 is preferred. Although there is a tendency for higher corrosion resistance with larger α, Bs tends to decrease when α is too large.

[0043] Furthermore, the Ni content relative to Fe (β) is 0 ≤ β ≤ 0.200. That is, it can be Ni-free, or it can be 0.005 ≤ β ≤ 0.200. From the perspective of increasing Bs, it can be 0 ≤ β ≤ 0.050, 0.001 ≤ β ≤ 0.050, or 0.005 ≤ β ≤ 0.010. Although there is a tendency for higher β to result in higher corrosion resistance, Bs decreases when β is too high.

[0044] X1 can be present as an impurity or intentionally added. The content (γ) of X1 is 0 ≤ γ < 0.030. That is, relative to the combined content of Fe, Co, and Ni, less than 3.0% can be replaced by X1.

[0045] Furthermore, when the sum of the atomic ratios of the elements constituting the soft magnetic alloy is set to 1, the atomic ratio of the total content of Fe, Co, Ni, and X1 (1-(a+b+c+d+e)) is preferably 0.720≤(1-(a+b+c+d+e))≤0.950, more preferably 0.780≤(1-(a+b+c+d+e))≤0.890. By satisfying this condition, Bs can be easily increased. In addition, by setting it to 0.720≤(1-(a+b+c+d+e))≤0.890, an amorphous alloy is easily obtained.

[0046] a is the ratio of the number of atoms of B, preferably 0≤a≤0.200, and more preferably 0≤a≤0.150 from the viewpoint of increasing Bs.

[0047] b is the atomic ratio of P, preferably 0 ≤ b ≤ 0.100. That is, it may not contain P. From the viewpoint of simultaneously improving Bs and corrosion resistance, it is more preferably 0.001 ≤ b ≤ 0.100, further preferably 0.005 ≤ b ≤ 0.080, and particularly preferably 0.005 ≤ b ≤ 0.050.

[0048] c is the atomic ratio of Si, preferably 0 ≤ c ≤ 0.150. That is, it can be Si-free, but from the viewpoint of simultaneously improving Bs and corrosion resistance, it is more preferably 0.001 ≤ c ≤ 0.070.

[0049] d is the atomic ratio of C, preferably 0 ≤ d ≤ 0.050. That is, it can be C-free, but from the viewpoint of simultaneously improving Bs and corrosion resistance, 0 ≤ d ≤ 0.020 is more preferred.

[0050] e is the atomic ratio of Cr, preferably 0 ≤ e ≤ 0.050. That is, from the viewpoint of improving Bs, it is possible to have no Cr, but from the viewpoint of simultaneously improving Bs and corrosion resistance, it is more preferably 0.001 ≤ e ≤ 0.020.

[0051] The composition of the aforementioned internal region 2 (i.e., the composition of the soft magnetic alloy 1) can be analyzed using, for example, inductively coupled plasma atomic emission spectrometry (ICP). In cases where it is difficult to determine the oxygen content using ICP, a pulsed heating melting extraction method can be used. Furthermore, in cases where it is difficult to determine the carbon and sulfur content using ICP, infrared absorption spectrometry can be used.

[0052] In addition to ICP, compositional analysis can also be performed using EDX (energy-dispersive X-ray diffraction) or EPMA (electron probe microanalysis) attached to an electron microscope. For example, for soft magnetic alloy 1 contained in a resin-containing magnetic core, it is sometimes difficult to perform compositional analysis using ICP. In such cases, EDX or EPMA can be used. Furthermore, if detailed compositional analysis is difficult to perform using either of the above methods, 3DAP (three-dimensional atomic probe microanalysis) can be used. When using 3DAP, the influence of resin components or surface oxidation in the analyzed area can be eliminated, allowing for the determination of the composition of the soft magnetic alloy 1, i.e., the internal region 2. This is because when using 3DAP, a small region (e.g., a region of Φ20nm × 100nm) can be defined within the soft magnetic alloy 1, and the average composition can be measured.

[0053] Furthermore, when performing line analysis of the cross-section near the surface of the soft magnetic alloy 1 using EDX or EELS (electron energy loss spectroscopy), the internal region 2 can be identified as a region with stable Fe and Co concentrations (see reference). Figure 3A Alternatively, for example, the average composition obtained through mapping analysis in the inner region 2 can be used as the composition of the soft magnetic alloy 1. In this case, the mapping analysis is performed using EDX or EELS, and the measurement site can be a region of the soft magnetic alloy 1 at least 100 nm from the surface in the depth direction (equivalent to the inner region 2), and the measurement field of view can be set to approximately 256 nm × 256 nm.

[0054] The crystalline structure of the internal region 2 (i.e., the crystalline structure of the soft magnetic alloy 1) can be crystalline, nanocrystalline, or amorphous, and more preferably amorphous. In other words, the degree of amorphization X of the internal region 2 (i.e., the degree of amorphization X of the soft magnetic alloy 1) is preferably 85% or more. A crystalline structure with a degree of amorphization X of 85% or more is a structure that is substantially composed of amorphous material or a structure composed of heteroamorphous material. Here, a structure composed of heteroamorphous material refers to a structure in which trace amounts of crystals exist within the amorphous material. That is, in this embodiment, "amorphous crystalline structure" refers to a crystalline structure with a degree of amorphization X of 85% or more, and may also include crystals within the range that satisfies this degree of amorphization X.

[0055] Furthermore, in the case of a structure composed of heteromorphic amorphous materials, the average crystal grain size of the crystals present in the amorphous material is preferably 0.1 nm or more and 10 nm or less. In addition, in this embodiment, "nanocrystalline" refers to a crystalline structure with an amorphization degree X of less than 85% and an average crystal grain size of 100 nm or less (preferably 3 nm to 50 nm), and "crystalline material" refers to a crystalline structure with an amorphization degree X of less than 85% and an average crystal grain size of more than 100 nm.

[0056] The degree of amorphization X can be determined by X-ray crystallographic analysis using XRD. Specifically, the soft magnetic alloy 1 of this embodiment is subjected to 2θ / θ measurement using XRD, and the results are obtained. Figure 2A The figure shown is an example of this. In this case, the measurement range of the diffraction angle 2θ is set to a range that allows confirmation of halos originating from amorphous materials, preferably a range of 2θ = 30° to 60°.

[0057] Next, using the Lorentz function shown in equation (2) below, for Figure 2A The graph shown is subjected to graph fitting. In this graph fitting, it is preferable to set the error between the measured integral intensity of XRD and the integral intensity calculated using the Lorentz function to within 1%. Through this graph fitting, the following is obtained: Figure 2B The crystalline composition pattern α shown represents the crystalline scattering integral intensity Ic. c α represents the amorphous composition pattern representing the amorphous scattering integral intensity Ia. a and the pattern α that combines them c+a Then, the crystalline scattering integral intensity Ic and the amorphous scattering integral intensity Ia obtained here are introduced into the following equation (1) to calculate the degree of amorphization X.

[0058] X=100-(Ic / (Ic+Ia)×100)...(1)

[0059] Ic: Integral intensity of crystalline scattering

[0060] Ia: Integral intensity of amorphous scattering

[0061]

[0062] h: Peak height

[0063] u: Peak position

[0064] w: half-width

[0065] b: Background height

[0066] Furthermore, the method for determining the degree of amorphization X is not limited to the XRD method mentioned above; it can also be determined by EBSD (crystallization orientation analysis) or electron X-ray diffraction.

[0067] (Co Concentration Zone 11)

[0068] The Co-enriched region 11 is a region where the Co concentration is higher than that of the internal region 2 described above. In this embodiment, the Co-enriched region 11 is preferably a continuous amorphous metallic phase extending from the internal region 2, covering at least a portion of the outer periphery of the internal region 2. The coverage of the Co-enriched region 11 relative to the internal region 2 in the cross-section of the soft magnetic alloy 1 is not particularly limited, but can be, for example, 50% or more, more preferably 80% or more.

[0069] The presence and coverage of the Co-concentrated region 11 can be confirmed by observing the cross-section near the surface of the soft magnetic alloy 1 using STEM (scanning transmission electron microscopy) or TEM (transmission electron microscopy) and performing mapping analysis using EDX or EELS at the same time. For example, Figure 5A The image shown (EELS image) is an example of the mapping analysis results of EELS. This EELS image represents the distribution of Co, with the intensity of Co represented by the contrast between light and dark areas. Figure 5A In the image, inner region 2 can be identified as a region where there is almost no variation in Co concentration. Furthermore, it is evident that the contrast brightens at the edge of inner region 2, indicating a higher Co concentration than in inner region 2. This region with high Co concentration is designated as Co-concentrated region 11, and its presence can be confirmed using Co-related EELS images.

[0070] The average thickness t1 of the Co-concentrated region 11 determined by this mapping analysis is preferably 0.3 nm or more. There is no particular upper limit to t1; for example, it can be 30.0 nm or less. Increasing t1 within this appropriate range yields better results for corrosion resistance. Preferably, the average thickness t1 is measured and calculated at at least three locations by varying the measurement field of view.

[0071] As mentioned above, the Co concentration region 11 is sometimes extremely thin. When determining the Co concentration region 11, it is preferable to use not only mapping analysis but also line analysis. Figure 3A Is the example along Figure 1A The measurement line L shown M A schematic diagram of the results of line analysis, with the vertical axis representing the detection intensity of each element (i.e., the intensity of characteristic X-rays) and the horizontal axis representing the distance (depth) from the outermost surface (10). For example... Figure 3A As shown in the online analysis results, a peak indicating a higher Co concentration can be identified at the edge of the inner region 2 where the Fe or Co concentration is stable. The location of this Co peak is the Co concentration region 11. In other words, the maximum Co concentration exists in the Co concentration region 11. The presence or absence of the aforementioned peak confirms the existence of the Co concentration region 11.

[0072] Furthermore, as described above, the Co-enriched region 11 containing the aforementioned peaks is preferably a metallic phase. The phase state of the Co-enriched region 11 can be confirmed by the aforementioned line analysis, mapping analysis, or analysis using a STEM or an EELS (electron energy loss spectroscopy) detector attached to a TEM. For example, when analyzing the spectrum obtained by EELS, the ratio of Co in the oxide to metallic Co in the Co-enriched region 11 can be calculated. If the ratio of metallic Co is greater than that of the oxide, the Co-enriched region 11 is defined as a metallic phase. Additionally, if an oxide layer (such as the SB oxide layer 12, Fe oxide layer 13, or capping layer 20 described later) exists outside the Co-enriched region 11, the detection intensity of oxygen in the Co-enriched region 11 is lower than that in the oxide layer during mapping analysis or line analysis. This analysis confirms that the Co-enriched region 11 is a metallic phase.

[0073] Furthermore, in this embodiment, the Co concentration in the Co concentration region 11 is defined as the molar ratio of Co in the Co concentration region 11 (C11). Co The molar ratio of Co to internal region 2 (C2) Co The ratio of (C11) Co / C2 co The Co concentration is preferably greater than 1.20, more preferably greater than 1.50. Furthermore, there is no particular upper limit to the Co concentration; for example, it can be set to below 20.

[0074] When a soft magnetic alloy consisting of internal regions 2 without the formation of Co-concentrated regions 11 is used as a reference alloy, there is a tendency that the higher the Co concentration, the better the corrosion resistance of the soft magnetic alloy 1 of this embodiment compared to the reference alloy. That is, there is a positive correlation between Co concentration and corrosion resistance. In addition, since the internal regions 2 of the soft magnetic alloy 1 contain a predetermined amount of P, there is a tendency that the Co concentration can easily increase, and the corrosion resistance can be further improved.

[0075] C2 used to calculate Co concentration Co and C11 Co The composition was determined using EELS analysis. Specifically, C2 Co This is the molar ratio of Co to the total of Fe and Co detected in internal region 2, calculated through analysis of the EELS spectrum. Similarly, C11 Co This refers to the molar ratio of Co to the total amount of Fe and Co detected in the Co concentration region 11. That is, the molar ratio of Co in each region is expressed as Co / (Fe+Co), and to exclude the influence of impurities (elements introduced during sample preparation, etc.), the denominator is set to (Fe+Co). Furthermore, the resolution in this analysis is preferably set to 0.5 nm or less. Co Preferably, the measurement is performed at a depth of 0.2 μm or more from the outermost surface 10 of the soft magnetic alloy 1 inward. Furthermore, the Co concentration is preferably measured at at least five locations within a field of view, and the average value is calculated.

[0076] Furthermore, in the Co-enriched region 11, Co is detected as the main constituent element, in addition to elements such as Fe that constitute the internal region 2. Moreover, in the Co-enriched region 11, similar to the enrichment of Co, the enrichment of other elements can also occur; for example, P can be cited as another element. In this case, during mapping analysis or line analysis, a high concentration region of P is sometimes observed, coinciding with the region of high Co enrichment in the depth direction of the soft magnetic alloy 1.

[0077] As described above, the soft magnetic alloy 1 has a characteristic surface microstructure including a Co-concentrated region 11. Especially in this embodiment, such as Figure 1A and Figure 3A As shown, the Co-enriched region 11 is located on the outermost surface and constitutes the outermost surface 10 of the soft magnetic alloy 1. However, other surface structures may also exist outside the Co-enriched region 11.

[0078] For example, it can also be like Figure 1B The soft magnetic alloy 1a shown has an SB oxide layer 12 containing Si and / or B formed to cover the surface side of the Co-enriched region 11. The SB oxide layer 12 is a region in which the concentration of at least one element selected from Si and B is higher than that of the inner region 2, and either Si or B or both Si and B are enriched.

[0079] In fact, Figure 5B for Figure 1B An example of an EELS image of the soft magnetic alloy 1a shown. Figure 5B The three EELS images shown are all measurements from the same location. Figure 5B In the EELS image of B (center: BK), it can be confirmed that the contrast is brighter on the surface side of the Co-concentrated region 11, which is more concentrated than Co, and the concentration of B in this region is higher than that in the inner region 2 and the Co-concentrated region 11. Figure 5B In this case, the region with high B concentration is SB oxide layer 12.

[0080] When the inner region 2 contains Si and / or B, the SB oxide layer 12 is sometimes formed during the formation of the Co-enriched region 11, and is preferably an amorphous oxide phase. Furthermore, the average thickness t2 of the SB oxide layer 12 is preferably 0.5 nm or more. There is no particular upper limit to t2; for example, it can be set to 30 nm or less.

[0081] Alternatively, an Fe oxide layer 13 containing Fe can be formed on the outer side of the Co concentration region 11. This Fe oxide layer 13 is sometimes formed together with the Co concentration section 11 during the formation of the Co concentration region 11, and the Fe concentration in the Fe oxide layer 13 is higher than that in the Co concentration section 11 and the inner region 2. Furthermore, as... Figure 1B As shown, in the presence of SB oxide layer 12, Fe oxide layer 13 is preferably located on the surface side of SB oxide layer 12, and more preferably, the crystallization area is higher than that of SB oxide layer 12.

[0082] In fact, Figure 5B In the EELS image of Fe (right: Fe-L), it can be confirmed that the contrast brightens on the surface side closer to the SB oxide layer 12, indicating a region with a high Fe concentration on the outermost surface of the soft magnetic alloy 1a. Figure 5B In this region, the Fe oxide layer 13 forms the outermost surface 10 of the soft magnetic alloy 1a. In this embodiment, the average thickness t3 of the Fe oxide layer 13 is preferably 1 nm or more. There is no particular upper limit to t3; for example, it can be set to 50 nm or less.

[0083] Figure 3B It is a simulated representation along Figure 1B The measurement line L shown M a. A graph showing the results of line analysis using EDX. In the presence of SB oxide layer 12, as... Figure 3B As shown, peaks of Si and / or B are observed on the surface side of the Co peak, and the detection intensity of oxygen increases in a manner that coincides with these Si and / or B peaks. Furthermore, when an Fe oxide layer 13 is also present on the surface side of the SB oxide layer 12, a Fe peak can be confirmed on the surface side of the Si and / or B peak. Thus, the presence or absence of the SB oxide layer 12 and the Fe oxide layer 13 can be confirmed by line analysis using EDX or EELS, or alternatively by... Figure 5BThe mapping analysis shown is confirmed.

[0084] In addition, such as Figure 4A and Figure 4B The soft magnetic alloy 1b shown can have an insulating capping layer 20 formed on the outer side of the Co-enriched region 11. This capping layer 20 is a film formed after the Co-enriched region 11 is formed, through surface treatment such as coating, and its average thickness is preferably 5 nm to 100 nm, more preferably 50 nm or less. That is, when the capping layer 20 is formed, the outermost surface 10 of the soft magnetic alloy 1b is composed of the capping layer 20, and the capping layer 20 is located on the surface side of the soft magnetic alloy 1b closer to the Co-enriched region 11, the SB oxide layer 12, and the Fe oxide layer 13. In fact, Figure 5C for Figure 4A An example of a STEM image of the soft magnetic alloy 1b is shown. In this STEM image, a region of bright contrast can be identified on the outermost surface 10 of the soft magnetic alloy 1b, which is the overlay layer 20.

[0085] Thus, in the surface structure of the soft magnetic alloy 1, in addition to the Co-enriched region 11, other layers (SB oxide layer 12, Fe oxide layer 13, capping layer 20, etc.) may be included. However, even in the presence of other layers, the Co-enriched region 11 exists on the side connected to the inner region 2. Moreover, the perpendicular distance d1 from the outermost surface to the Co-enriched region 11 (refer to...) Figure 1B , Figure 4B The distance d1 is preferably 200 nm or less, more preferably 100 nm or less, and even more preferably 50 nm or less. In particular, when there is no capping layer 20 and the outermost surface 10 is composed of SB oxide layer 12 or Fe oxide layer 13, the above-mentioned vertical distance d1 is preferably 30 nm or less, more preferably 20 nm or less.

[0086] Furthermore, the sample used for analysis of the Co-concentrated region 11 is preferably prepared using a microsampling method employing FIB (Focused Ion Beam). For example, a Pt film of approximately 30 nm thickness for surface protection during processing is formed on the outermost surface 10 of the soft magnetic alloy 1 by sputtering. Then, a section approximately 2 μm deep from the outermost surface is cut using FIB to obtain a thin-film sample. This thin-film sample is then processed to reduce its thickness in the direction orthogonal to the depth direction to less than 20 nm. This thin-film sample can then be used as a measurement sample for TEM or HRTEM observation.

[0087] The manufacturing method of the soft magnetic alloy 1 of this embodiment will be described below.

[0088] The matrix portion (internal region 2) of the soft magnetic alloy 1 can be manufactured by various melting methods, and is particularly preferred by quenching molten metal (molten liquid). This is because quenching readily yields an amorphous soft magnetic alloy 1. For example, the soft magnetic alloy 1 in strip shape can be manufactured by a single-roll method, and the soft magnetic alloy 1 in powder shape can be manufactured by an atomization method. Hereinafter, methods for obtaining soft magnetic alloy strips by the single-roll method and methods for obtaining soft magnetic alloy powder by gas atomization, as an example of an atomization method, will be described.

[0089] When using the single-roller method, firstly, the raw materials (pure metals, etc.) constituting the soft magnetic alloy 1 are prepared and weighed in a manner that makes up the desired alloy composition. Then, the raw materials of each element are melted to produce a master alloy. There are no particular limitations on the melting method used to produce the master alloy; for example, there is a method of melting it in a chamber with a specified vacuum degree by high-frequency heating.

[0090] Next, the aforementioned master alloy is heated to melt it, yielding molten metal. The temperature of the molten metal can be set considering the melting point of the target alloy composition, for example, it can be set to 1200–1600°C. Using the single-roll method, the molten metal is supplied to a cooled rotating roll using a nozzle or similar means, and a thin strip of soft magnetic alloy is manufactured in the direction of the roll's rotation. At this time, the thickness of the resulting strip can be adjusted by controlling the roll's rotational speed, the distance between the nozzle and the roll, and the temperature of the molten metal. Furthermore, the roll's temperature and rotational speed can be set to conditions that facilitate the soft magnetic alloy becoming amorphous; for example, the roll temperature is preferably 20–30°C, and the rotational speed is preferably 20–30 m / sec. In addition, the atmosphere within the chamber is not particularly limited; for example, it can be an atmospheric atmosphere or an inert gas atmosphere.

[0091] Similar to the single-roller method described above, when using the gas atomization method, molten metal at 1200–1600°C is obtained and then sprayed into a chamber to produce powder. Specifically, molten metal is sprayed from the nozzle into the cooling section within the chamber, while high-pressure gas is injected into the sprayed molten metal. Through the injection of high-pressure gas, the molten metal is dispersed within the chamber and then collides with the cooling section (cooling water), thereby being rapidly cooled and solidified into soft magnetic alloy powder. The soft magnetic alloy powder obtained by this gas atomization method typically has a spherical particle shape, and the average sphericity of the soft magnetic alloy powder is preferably 0.8 or more, more preferably 0.9 or more, and even more preferably 0.95 or more.

[0092] As the high-pressure gas, inert gases such as nitrogen, argon, and helium, or reducing gases such as ammonia decomposition gases, are preferably used. The pressure of the injected high-pressure gas is preferably 2.0 MPa to 10 MPa. Furthermore, the injection rate of the molten metal is preferably 0.5 kg / min to 4.0 kg / min. When using this gas atomization method, the particle size and shape of the soft magnetic alloy powder can be adjusted according to the ratio of the high-pressure gas pressure to the injection rate of the molten metal.

[0093] After obtaining a thin strip or powdered soft magnetic alloy as described above, the soft magnetic alloy is heat-treated at low temperature in an oxygen concentration atmosphere under a specified pressure state, thereby forming a Co-enriched region 11.

[0094] Specifically, the holding temperature during heat treatment is preferably a temperature at which the soft magnetic alloy does not crystallize, for example, preferably 200°C to 400°C, more preferably 200°C to 300°C. Furthermore, the temperature holding time is preferably set to 0.5 hours to 3.0 hours. The oxygen concentration in the heating furnace is preferably set to 20 ppm to 2000 ppm, more preferably 100 ppm to 1000 ppm. Additionally, in the heating furnace, the oxygen concentration is preferably managed as described above, and an inert gas such as argon or nitrogen is introduced to create a positive pressure; the gauge pressure in the heating furnace is set to 0.15 kPa to 0.50 kPa, preferably 0.30 kPa to 0.45 kPa. Here, gauge pressure refers to the absolute pressure (pressure when absolute vacuum is set to 0 Pa) minus atmospheric pressure.

[0095] By performing heat treatment under such conditions, a Co-enriched region 11 with defined characteristics is formed on the surface side of the soft magnetic alloy 1. Furthermore, when the soft magnetic alloy 1 contains Si and / or B, the aforementioned heat treatment sometimes forms an SB oxide layer 12, and depending on the heat treatment conditions, sometimes forms an Fe oxide layer 13. Moreover, in cases where the soft magnetic alloy 1 is formed as a crystalline or nanocrystalline material (i.e., where the degree of amorphization X is less than 85%), a pre-process heat treatment for controlling crystallinity may be performed before performing the heat treatment for forming the aforementioned Co-enriched region 11.

[0096] In such Figure 4A and Figure 4BWhen the capping layer 20 is formed as shown, after forming the Co-enriched region 11 through the above-described heat treatment, film-forming treatments such as phosphate treatment, mechanical alloying, silane coupling treatment, and hydrothermal synthesis can be performed. Examples of types of capping layer 20 include phosphates, silicates, soda-lime glass, borosilicate glass, lead glass, aluminosilicate glass, borate glass, and sulfate glass. Examples of phosphates include magnesium phosphate, calcium phosphate, zinc phosphate, manganese phosphate, and cadmium phosphate; examples of silicates include sodium silicate. When the capping layer 20 is formed, improvements in the voltage withstand capability of the magnetic core containing the soft magnetic alloy 1 can be expected.

[0097] Through the above processes, a soft magnetic alloy 1 having a defined Co-concentration region 11 can be obtained. The soft magnetic alloy 1 of this embodiment can be applied to various magnetic components such as coil components of inductors, filters, and antennas, and is particularly suitable for magnetic cores of coil components such as inductors. Furthermore, the magnetic core containing the soft magnetic alloy 1 may contain a resin component, or the soft magnetic alloy 1 may be mixed with other magnetic particles to form the magnetic core.

[0098] (Summary of Implementation Methods)

[0099] In the soft magnetic alloy 1 of this embodiment, a Co-enriched region 11 with defined characteristics is formed on the outer side of the internal region 2, which is composed of a soft magnetic alloy containing Fe and Co. The Co concentration in the Co-enriched region 11 exceeds 1.20. By having this characteristic, rusting of the soft magnetic alloy 1 when immersed in water can be suppressed, and corrosion resistance can be improved.

[0100] Furthermore, by forming a Co-enriched region 11 in an amorphous soft magnetic alloy 1 with an amorphization degree of 85% or more, a high saturation magnetic flux density Bs can be ensured, and the corrosion resistance of the soft magnetic alloy 1 can be further improved.

[0101] The embodiments of the present invention have been described above, but the present invention is not limited to the above embodiments, and various changes can be made within the scope of the present invention.

[0102] Example

[0103] The present invention will now be described in more detail based on specific embodiments. However, the present invention is not limited to the following embodiments. In the tables shown below, the sample numbers marked with ※ are comparative examples.

[0104] Experiment 1

[0105] In Experiment 1, soft magnetic alloy powder was prepared by gas atomization. During gas atomization, the following settings were used: molten metal injection temperature: 1500℃; molten metal injection rate: 1.2 kg / min; high-pressure gas pressure: 7.0 MPa; cooling water pressure: 10 MPa. This yielded soft magnetic alloy powder with a volumetric average particle size (D50) ranging from 15 to 30 μm. The powder was then heat-treated under the conditions shown in Table 1 to obtain samples 2–5 and 7–16. Additionally, samples 1 and 6, which were not heat-treated, were also prepared in Experiment 1. The following evaluations were performed using sample 1 or sample 6 as a reference.

[0106] Composition and Crystalline Structure of Soft Magnetic Alloy Powders

[0107] The composition of the soft magnetic alloy powder obtained by gas nebulization was determined using ICP. The results confirmed that in samples 1-5 of Experiment 1, the soft magnetic alloy powder (i.e., internal region 2) contained Fe. 0.07 Co 0.3 The average composition. On the other hand, it was confirmed that in samples 6-16 of Experiment 1, the soft magnetic alloy powder (i.e., internal region 2) had a composition that satisfied the formula: (Fe 0.7 Co 0.3 ) 0.82 B 0.11 P 0.02 Si 0.03 C0. 01 Cr 0.01 The alloy composition has the following atomic ratios: α = 0.300, β = 0, γ = 0, a = 0.110, b = 0.020, c = 0.030, d = 0.010, e = 0.010.

[0108] Furthermore, X-ray crystallographic analysis of the soft magnetic alloy powder in Experiment 1 confirmed that in samples 1-5 of Experiment 1, the soft magnetic alloy powder (i.e., internal region 2) was a crystalline material with an amorphization degree X of less than 85%. On the other hand, in samples 6-16 of Experiment 1, the soft magnetic alloy powder (i.e., internal region 2) was confirmed to be an amorphous material with an amorphization degree X of more than 85%.

[0109] <Analysis of Surface Tissue>

[0110] For the soft magnetic alloys of each sample in Experiment 1, thin sheet samples were taken near the surface using the FIB microsampling method. Then, using these thin sheet samples, TEM-EDX mapping analysis was performed to investigate the presence or absence of Co-enriched regions 11. Furthermore, TEM-EELS was used to perform compositional analysis in specific regions to determine the Co concentration in Co-enriched regions 11. The results of the surface microstructure analysis are shown in Table 1. Moreover, EELS analysis confirmed that Co-enriched regions 11 are amorphous metallic phases.

[0111] <Saturation magnetic flux density Bs>

[0112] The Bs of the soft magnetic alloys in each sample were measured using a vibrating sample magnetometer (VSM) under a magnetic field of 1000 kA / m. The measurement results are shown in Table 1. For this Bs, Bs above 1.50 T were considered good, and Bs above 1.70 T were considered better.

[0113] <Immersion Test>

[0114] First, before conducting the immersion test, magnetic core samples were prepared using the soft magnetic alloy of each specimen. The magnetic core samples were prepared according to the following steps: 3 parts by mass of epoxy resin were mixed with 100 parts by mass of the soft magnetic alloy to obtain granules. Then, these granules were filled into a mold at a pressure of 4 tons / cm³. 2 The pressure is applied to form the shape. inner diameter A toroidal magnetic core sample with a height of 1.0 mm.

[0115] To evaluate the corrosion resistance of the obtained magnetic core samples, an immersion test was conducted. In the immersion test, the magnetic core samples were immersed in tap water, and the time until rust was visually observed (rusting time) was measured. In Experiment 1, the rusting time T1 of sample 1 or sample 6 (which did not undergo heat treatment) was used as a benchmark to evaluate the corrosion resistance of each sample. Specifically, in Experiment 1, samples with a rusting time less than 1.2 times T1 (rusting time of sample 1 or sample 6) were classified as "F (Unacceptable)", and samples with a rusting time greater than 1.2 times T1 were classified as "G (Good)". The evaluation results of the two levels, "F" and "G", are shown in Table 1.

[0116]

[0117] As shown in Table 1, it can be confirmed that the samples (3-5, 8-16) with the formation of Co-enriched regions 11 and a Co concentration exceeding 1.20 exhibit good corrosion resistance relative to the reference alloy (sample 1 or sample 6). Furthermore, it can be confirmed that in samples 3-5 and 8-16, the vertical distance d1 from the outermost surface 10 to the Co-enriched region 11 is less than 30 nm. These results confirm that by forming Co-enriched regions 11 with specified characteristics on the surface side of the soft magnetic alloy, high Bs can be maintained and corrosion resistance can be improved.

[0118] Furthermore, while specific values ​​for rusting time are omitted in Table 1, it is evident that a higher Co concentration tends to result in better relative corrosion resistance compared to the reference alloy. It is known that a Co concentration of 1.25 or higher is preferred, and more preferably 1.50 or higher.

[0119] Experiment 2

[0120] In Experiment 2, the alloy composition was changed to obtain soft magnetic alloys for samples 2-1 to 2-90. The alloy compositions of each sample obtained by ICP analysis are shown in Tables 2 to 7.

[0121] Specifically, in samples 2-1 to 2-14 shown in Table 2, samples were prepared that satisfy the composition formula: (Fe 1-α Co α ) 0.84 B 0.11 Si 0.03 C 0.01 Cr 0.01 (Atomic ratios: β=0, γ=0, a=0.110, b=0, c=0.030, d=0.010, e=0.010), and a soft magnetic alloy with a changed atomic ratio α of Co.

[0122] In addition, in samples 2-15 to 2-34 shown in Table 3, soft magnetic alloys were prepared by fixing the atomic ratios of Co, Ni, and Xl to α = 0.300, β = 0, and γ = 0, and changing the atomic ratios of nonmetals (B, P, Si, C) and Cr.

[0123] In addition, in samples 2-35 to 2-38 shown in Table 4, samples were prepared that satisfy the composition formula: (Fe (1-(0.3+β) Co 0.3 Ni β ) 0.84 B 0.11 Si 0.03 C 0.01 Cr 0.01(Atomic ratio: α=0.300, γ=0, a=0.110, b=0, c=0.030, d=0.010, e=0.010), and a soft magnetic alloy with a changed atomic ratio β of Ni.

[0124] In addition, among samples 2-39 to 2-90 shown in Tables 5 to 7, samples satisfying the composition formula ((Fe) were prepared. 0.7 Co 0.3 ) 0.975 X1 0.025 ) 0.84 B 0.11 Si 0.03 C 0.01 Cr 0.01 (Atomic ratio: α=0.300, β=0, γ=0.025, a=0.110, b=0, c=0.030, d=0.010, e=0.010), and a soft magnetic alloy with changed element types of X1.

[0125] Furthermore, it was confirmed that the degree of amorphization X of each soft magnetic alloy in Experiment 2 was above 85%. In Experiment 2, for each alloy composition, samples subjected to the prescribed heat treatment and samples without heat treatment were prepared. In Tables 2 to 7, the cases with heat treatment are recorded as "Y", and the cases without heat treatment are recorded as "N". The heat treatment conditions for Experiment 2 were set as follows: holding temperature: 200°C, holding time: 1 h, oxygen concentration in the furnace: 100 ppm, and gauge pressure in the furnace: 0.30 kPa.

[0126] In addition, in Experiment 2, samples 2-1 to 2-90 were subjected to Bs determination and immersion tests, similar to those in Experiment 1. In the immersion test of Experiment 2, the rusting time T of samples with the same composition that had not undergone heat treatment was measured. N As a benchmark, the rusting time of the heat-treated specimen was set as T. Y , will T Y / T N Samples with a value < 1.2 are judged as "F (unacceptable)", and samples with a value 1.2 ≤ T are judged as "F (unacceptable)". Y / T N The sample was judged as "G (Good)". The evaluation results are shown in Tables 2 to 7.

[0127]

[0128]

[0129]

[0130]

[0131]

[0132]

[0133] As shown in Tables 2 to 7, the samples that underwent the specified heat treatment exhibited higher corrosion resistance than those that did not. Based on these results, it can be concluded that within the alloy composition range shown in Experiment 2, by forming the Co-enriched region 11 with the specified characteristics, high Bs levels can be maintained and corrosion resistance can be improved.

[0134] Furthermore, as a supplement to the results in Table 2, there is a tendency that the higher the Co content in internal region 2 (i.e., the Co content of the soft magnetic alloy), the longer the rusting time. That is, the higher the Co content in internal region 2, the higher the corrosion resistance as an absolute evaluation. However, as shown in sample 2-14 of Table 2, when the Co content in internal region 2 is high, there is a tendency for the Co concentration to decrease. Moreover, regarding the relative improvement effect on corrosion resistance (i.e., corrosion resistance relative to the reference alloy), compared with sample 2-14, other samples 2-2, 4, 6, 8, 10, and 12 with higher Co concentrations show good results. That is, based on these results, it can be confirmed that the higher the Co concentration, the greater the improvement effect on corrosion resistance relative to the reference alloy (samples that do not undergo heat treatment to form the concentration region).

[0135] Experiment 3

[0136] In Experiment 3, soft magnetic alloy powders with an amorphous degree X of over 85% (samples 3-1 and 3-2), soft magnetic alloy powders with amorphous degree X of less than 85% and nanocrystalline structure (samples 3-3 and 3-4), and soft magnetic alloy powders with amorphous degree X of less than 85% and crystalline structure (samples 3-5 and 3-6) were manufactured to investigate the effect of different crystal structures of soft magnetic alloys on corrosion resistance.

[0137] In Experiment 3, the crystal structure of each sample was controlled by a pre-process heat treatment. Specifically, in samples 3-1 and 3-2 of Experiment 3, amorphous soft magnetic alloy powders were obtained because no pre-process heat treatment was performed. Samples 3-1 and 3-2 correspond to samples 6 and 14 of Experiment 1. In addition, in samples 3-3 and 3-4 of Experiment 3, nanocrystalline soft magnetic alloy powders were obtained by performing a pre-process heat treatment at a holding temperature of 500°C. Furthermore, in samples 3-5 and 3-6 of Experiment 3, crystalline soft magnetic alloy powders were obtained by performing a pre-process heat treatment at a holding temperature of 650°C. Furthermore, other conditions in the above-mentioned pre-process heat treatment were set as follows: heating rate: 100°C / min, furnace atmosphere: Ar atmosphere, and gauge pressure in the furnace: 0.0 kPa, controlling the crystal structure without forming the Co-enriched region 11.

[0138] The composition of the soft magnetic alloy in each sample of Experiment 3 was (Fe) 0.7 Co 0.3 ) 0.82 B 0.11 P 0.02 Si 0.03 C 0.01 Cr 0.01 The results are the same. Furthermore, in Experiment 3, for each crystal structure, samples subjected to heat treatment to form the Co enrichment region 11 and samples without heat treatment were prepared. In Table 8, the cases with heat treatment are recorded as "Y", and the cases without heat treatment are recorded as "N". In addition, in the samples (3-4, 3-5) that underwent the previous heat treatment, heat treatment to form the Co enrichment region 11 was performed after the previous heat treatment. The conditions for this heat treatment in Experiment 3 were set as follows: holding temperature: 200°C, holding time: 1.0 h, oxygen concentration in the furnace: 100 ppm, gauge pressure in the furnace: 0.3 kPa.

[0139] In addition, in Experiment 3, the Bs content and immersion test were performed in the same manner as in Experiment 2. In the immersion test of Experiment 3, within the same crystal structure, the rusting time T of the untreated sample was measured. N As a benchmark, the rusting time of the heat-treated specimen was set as T. Y , will T Y / T N Samples with a value < 1.2 are judged as "F (unacceptable)", and samples with a value 1.2 ≤ T are judged as "F (unacceptable)". Y / T N The sample was judged as "G (Good)". The evaluation results of Experiment 3 are shown in Table 8.

[0140]

[0141] As shown in Table 8, even for nanocrystalline or crystalline soft magnetic alloys, similar to amorphous alloys, the corrosion resistance of samples 3-4 and 3-6, which formed the Co-enriched region 11b through specified heat treatment, was improved compared to samples 3-3 and 3-5, which did not undergo heat treatment. Furthermore, comparing the results of samples 3-3 to 3-5 with those of samples 3-1 and 3-2 in Table 8, it can be seen that in the case of amorphous soft magnetic alloys, the rusting time is longer compared to the reference alloy, and the improvement in corrosion resistance is particularly good.

[0142] Experiment 4

[0143] In Experiment 4, thin strip-shaped soft magnetic alloy samples (samples 4-1 and 4-2) were fabricated using the single-roller method. The fabrication conditions were set as follows: molten metal temperature sprayed onto the roll: 1300℃; roll temperature: 30℃; roll speed: 25 m / sec. The chamber was set to atmospheric atmosphere. The resulting soft magnetic alloy strips had a thickness of 20–25 μm, a width of approximately 5 mm along the short side, and a length of approximately 10 m.

[0144] In addition, in Experiment 4, the alloy composition of samples 4-1 and 4-2 was determined by ICP, similar to that in Experiment 1, and it was confirmed that both met the composition formula: (Fe 0.7 Co 0.3 ) 0.82 B 0.11 P 0.02 Si 0.03 C 0.01 Cr 0.01 (Atomic ratio: α=0.300, β=0, γ=0, a=0.110, b=0.020, c=0.030, d=0.010, e=0.010). Furthermore, XRD analysis of the crystal structure of the soft magnetic alloy ribbons in samples 4-1 and 4-2 confirmed that both were amorphous with a degree of amorphization X: ≥ 85%.

[0145] For the soft magnetic alloy strip of sample 4-1, no heat treatment was performed; instead, surface microstructure analysis, Bs determination, and a water immersion test were conducted. On the other hand, for the soft magnetic alloy strip of sample 4-2, heat treatment was performed under the conditions shown in Table 9, followed by the same evaluation as sample 4-1. Furthermore, in the water immersion test of the soft magnetic alloy strip, test samples were prepared by cutting the strip into arbitrary sizes (approximately 4 cm in length × approximately 5 mm in width), and the strip-shaped test samples were immersed in tap water. The method for determining whether an item passed in Experiment 4 was the same as in Experiment 1. The evaluation results for each sample in Experiment 4 are shown in Table 9. Additionally, Table 9 also shows the experimental results for soft magnetic alloy powder with the same alloy composition as samples 4-1 and 4-2 (samples 6 and 14 of Experiment 1).

[0146]

[0147] As shown in Table 9, it can be confirmed that even when the soft magnetic alloy has a thin strip shape, high Bs and improved corrosion resistance can be maintained by forming the Co enrichment region 11b using a specified heat treatment.

Claims

1. A soft magnetic alloy, characterized in that, have: The internal region has a soft magnetic alloy composition containing Fe and Co; and A Co-concentrated region exists on the surface side of the region, where the Co concentration is higher than in the internal region. The Co concentration in the Co concentration region is greater than 1.

25. The Co concentration in the Co concentration region is the ratio of the amount of Co in the Co concentration region to the amount of Co in the inner region.

2. The soft magnetic alloy according to claim 1, characterized in that: The Co-concentrated region is a metallic phase.

3. The soft magnetic alloy according to claim 1 or 2, characterized in that: The degree of amorphization is above 85%.

4. The soft magnetic alloy according to claim 1 or 2, characterized in that: The soft magnetic alloy has a thin strip shape.

5. The soft magnetic alloy according to claim 1 or 2, characterized in that: The soft magnetic alloy is in powder form.

6. A magnetic component, characterized in that: The soft magnetic alloy included in any one of claims 1 to 5.

Images