Alloy particles

Abstract

To provide an alloy particle having a high saturation magnetic flux density and excellent corrosion resistance.SOLUTION: An alloy particle of the present invention is an alloy particle in which the total of Fe and Co is 82.2 pts.mass or more and 96.5 pts.mass or less, Co is 0 pts.mass or more and 30.0 pts.mass or less, P is 0 pts.mass or more and 4.5 pts.mass or less, B is more than 0 pts.mass and 5.0 pts.mass or less, C is 0 pts.mass or more and 3.0 pts.mass or less, Si is 0 pts.mass or more and 6.7 pts.mass or less, Ni is more than 0 pts.mass and 12.0 pts.mass or less, Cr is more than 0 pts.mass and 4.2 weight mass% or less, the total of Mo, W, Zr, and Nb is 0 pts.mass or more and 4.2 pts.mass or less, the sum of pts.mass of P and pts.mass of Cr is 7.4 pts.mass or less, the product of pts.mass of Ni and pts.mass of Cr is 0.5 or more, and the total of Fe, Co, and Ni is 97.0 pts.mass or less. The alloy particle contains an amorphous phase, and the volume ratio of the amorphous phase is 70% or more.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to alloy particles. More specifically, it relates to soft magnetic alloy particles having a high saturation magnetic flux density and excellent corrosion resistance.

Background Art

[0002] There is an increasing need for miniaturization of coil components such as inductors and reactors (hereinafter also referred to as components). These components include a coil and a magnetic core and convert current and magnetic flux. For miniaturization, for example, it is necessary to reduce the number of turns and the radius of the coil, but these reductions result in a decrease in the inductance of the component (the number of magnetic fluxes decreases). This decrease in inductance can be compensated by increasing the frequency of the current (switching frequency). Therefore, the components are required to operate at high frequencies.

[0003] In addition, for small components, in order to dramatically increase the inductance, a magnetic core containing a soft magnetic material with a high magnetic permeability is usually used. This magnetic core generates energy loss (iron loss) associated with changes in the magnetic field, and this energy loss increases with the increase in frequency. In particular, when the magnetic field in the magnetic core changes at a high frequency, a large eddy current is generated in the magnetic core by magnetic induction. As a result, at high frequencies, the influence of Joule heat (eddy current loss) caused by the eddy current on the total energy loss becomes large, and it is difficult to operate the components at high frequencies. Therefore, as a solution for reducing the eddy current loss, reducing the size of the soft magnetic material can be mentioned. For this reason, at high frequencies, powder (also referred to as powder or alloy particles) is often used as the soft magnetic material for the magnetic core.

[0004] Furthermore, using a material with a high volume resistivity for the magnetic core can reduce the eddy current loss. Since the volume resistivity of the amorphous phase (amorphous phase) is higher than that of the crystalline phase for the same chemical composition, a material containing the amorphous phase is suitable at high frequencies.

[0005] A technique using such a powder containing an amorphous phase for components is disclosed in Patent Document 1. In this technique, the magnetic permeability of the powder is increased to improve the magnetic properties.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, in addition to the large specific surface area of the powder, the amorphous phase of the metal is easily oxidized. Therefore, the powder containing the amorphous phase tends to have low corrosion resistance. In particular, when the particle size of the powder is reduced for high-frequency applications, the corrosion resistance of the powder is significantly reduced.

[0008] Patent Document 1 discloses a powder containing Si as an element for enhancing corrosion resistance and having a high-concentration layer of Si on the surface portion. Although Cr, Mo, W, V, Nb, Ta, Ti, Zr, Hf, Pt, Pd, and Au are also disclosed in Patent Document 1 as optional elements for enhancing the corrosion resistance of this powder, even when these elements are included, this powder did not have sufficient corrosion resistance in a wet atmosphere. Thus, it has not been known as a problem that simply containing an element for enhancing the corrosion resistance of the powder does not increase the required corrosion resistance depending on the chemical composition.

[0009] In recent years, components that can operate even with a large current have been demanded. When a large alternating current is passed through a coil, a larger magnetic field can be generated. However, if the saturation magnetic flux density of the material is small, it becomes difficult to operate the component due to magnetic saturation. However, there has been a problem in that when the powder contains a large amount of an amorphous phase that increases the volume resistivity or a large amount of an element that enhances the corrosion resistance, the saturation magnetic flux density decreases.

[0010] Therefore, in the prior art, it was impossible to obtain a powder having a high saturation magnetic flux density and excellent corrosion resistance.

[0011] The present invention has been made in view of the above problems, and an object thereof is to provide alloy particles having a high saturation magnetic flux density and excellent corrosion resistance. The present invention also aims to provide a coil component containing the above alloy particles.

Means for Solving the Problems

[0012] The alloy particles according to the first embodiment of the present invention are alloy particles containing Fe, B, Ni, and Cr, and optionally containing Mo, W, Zr, Nb, Co, P, C, and Si. When the total content of Fe, Co, B, Ni, P, C, Si, Nb, Cr, Mo, W, and Zr is 100 parts by mass, the total of Fe and Co: 82.2 parts by mass or more and 96.5 parts by mass or less, Co: 0 parts by mass or more and 30.0 parts by mass or less, P: 0 parts by mass or more and 4.5 parts by mass or less, B: more than 0 parts by mass and 5.0 parts by mass or less, C: 0 parts by mass or more and 3.0 parts by mass or less, Si: 0 parts by mass or more and 6.7 parts by mass or less, Ni: more than 0 parts by mass and 12.0 parts by mass or less, Cr: more than 0 parts by mass and 4.2 parts by mass or less, the total of Mo, W, Zr, and Nb: 0 parts by mass or more and 4.2 parts by mass or less, the sum of the mass parts of P and the mass parts of Cr is 7.4 parts by mass or less, the product of the mass parts of Ni and the mass parts of Cr is 0.5 or more, the total of Fe, Co, and Ni: 97.0 parts by mass or less, and when Ni is more than 0 parts by mass and 7.4 parts by mass or less, the total of Fe, Co, and Ni satisfies 89.6 parts by mass or more, and when Ni is more than 7.4 parts by mass and 12.0 parts by mass or less, the difference obtained by subtracting 0.5 times the mass parts of Ni from the sum of the mass parts of Fe and Co satisfies 78.5 parts by mass or more. The above alloy particles contain an amorphous phase, and the volume ratio of the amorphous phase is 70% or more.

[0013] The alloy particles according to the second embodiment of the present invention are alloy particles containing an amorphous phase. The alloy particles contain Fe, B, Ni, and Cr, and optionally contain Mo, W, Zr, Nb, Co, P, C, and Si. In the concentration profile of the components in the depth direction of the alloy particles, N1 > N2, and the average distance D from the surface where the Ni concentration becomes (N1 + N2) × 0.5 is 1.3 nm or more (where N1 is the Ni concentration at a depth of 0 nm from the surface, and N2 is the average Ni concentration in the region from a depth of 10 nm to 100 nm from the surface).

[0014] Note that the alloy particles according to the second embodiment of the present invention may include the characteristic points of the alloy particles according to the first embodiment of the present invention.

[0015] The coil component of the present invention includes a core containing the alloy particles of the present invention and a coil.

Advantages of the Invention

[0016] According to the present invention, alloy particles having a high saturation magnetic flux density and excellent corrosion resistance can be provided. Therefore, a small coil component operating at high frequency and high current can be provided stably and flexibly. Accordingly, the size of electronic devices that can be used with high current can be reduced.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0018] The inventors have newly found that the corrosion resistance of the powder can be greatly enhanced by the combination of Ni and Cr. Further, the inventors have newly found that in the depth-direction concentration profile by Auger electron spectroscopy, when Ni is concentrated near the surface of the powder, the corrosion resistance of the powder can be greatly enhanced. From these findings, the inventors have derived that high corrosion resistance can be imparted to the powder even with the same amount of ferromagnetic elements, and that high saturation magnetic flux density can be imparted to the powder even with the same corrosion resistance, thereby completing the present invention.

[0019] Hereinafter, alloy particles according to a first embodiment, which is one embodiment of the present invention, will be described.

[0020] First, the chemical composition of the alloy particles according to the present embodiment will be described. The alloy particles according to the present embodiment contain Fe, B, Ni, and Cr, and optionally contain Mo, W, Zr, Nb, Co, P, C, and Si. The following description is based on the premise of the above-described element content conditions.

[0021] In the following description, unless otherwise specified, "parts by mass" means parts by mass when the total content of Fe, Co, B, Ni, P, C, Si, Nb, Cr, Mo, W, and Zr is 100 parts by mass. Similarly, unless otherwise specified, "parts by mole" means parts by mole when the total content of Fe, Co, B, Ni, P, C, Si, Nb, Cr, Mo, W, and Zr is 100 parts by mole.

[0022] Total of Fe and Co: 82.2 parts by mass or more and 96.5 parts by mass or less, Co: 0 parts by mass or more and 30.0 parts by mass or less.

[0023] Fe (iron) and Co (cobalt) have ferromagnetism and increase the saturation magnetic flux density. Therefore, in order to obtain a sufficient saturation magnetic flux density, the total of Fe and Co needs to be 82.2 parts by mass or more. From the viewpoint of obtaining a higher saturation magnetic flux density, it is preferable that the total of Fe and Co is 82.5 parts by mass or more, and more preferably 84.9 parts by mass or more. On the other hand, in order to obtain sufficient thermal stability of the amorphous phase, the total of Fe and Co needs to be 96.5 parts by mass or less. From the viewpoint of obtaining higher thermal stability of the amorphous phase, it is preferable that the total of Fe and Co is 92.5 parts by mass or less, and more preferably 91.5 parts by mass or less. In particular, Fe is an essential element for obtaining a high saturation magnetic flux density without increasing the cost. Therefore, the amount of Fe needs to be 52.2 parts by mass or more. Since Co is expensive, it may be 0 parts by mass. That is, the alloy particles may not contain Co. Although Co has a smaller saturation magnetic flux density alone than Fe, the saturation magnetic flux density is greatly increased by the interaction with Fe. Therefore, from the viewpoint of increasing the saturation magnetic flux density, the amount of Co is preferably 1.0 part by mass or more, and more preferably 2.0 parts by mass or more. On the other hand, as the amount of Co increases, the increase amount of the saturation magnetic flux density per Co content decreases. Therefore, the amount of Co needs to be 30.0 parts by mass or less. In particular, the amount of Co is preferably 12.0 parts by mass or less, and more preferably 10.0 parts by mass or less.

[0024] P: 0 part by mass or more and 4.5 parts by mass or less.

[0025] P (phosphorus) enhances the thermal stability of the amorphous phase. The lower limit of the amount of P is 0 part by mass. That is, the alloy particles may not contain P. In order to sufficiently enhance the thermal stability of the amorphous phase, the amount of P is preferably 0.3 part by mass or more, and more preferably 0.6 part by mass or more. On the other hand, in order to obtain a sufficient saturation magnetic flux density, the amount of P needs to be 4.5 parts by mass or less. From the viewpoint of obtaining a higher saturation magnetic flux density, the amount of P is preferably 3.0 parts by mass or less, and more preferably 1.4 parts by mass or less. The amount of P may be 0.1 part by mass or more.

[0026] B: More than 0 parts by mass and 5.0 parts by mass or less.

[0027] B (boron) is an essential element for enhancing the thermal stability of the amorphous phase. From the viewpoint of obtaining higher thermal stability of the amorphous phase, the amount of B is preferably 1.0 part by mass or more, and more preferably 1.2 parts by mass or more. On the other hand, in order to obtain a sufficient saturation magnetic flux density, it is necessary that the amount of B is 5.0 parts by mass or less. From the viewpoint of obtaining a higher saturation magnetic flux density, it is preferable that the amount of B is 4.0 parts by mass or less. The amount of B may be 0.1 part by mass or more.

[0028] C: 0 parts by mass or more and 3.0 parts by mass or less.

[0029] C (carbon) enhances the thermal stability of the amorphous phase. The lower limit of the amount of C is 0 parts by mass. That is, the alloy particles may not contain C. In order to sufficiently enhance the thermal stability of the amorphous phase, the total of B and C is preferably 1.0 part by mass or more. From the viewpoint of obtaining higher thermal stability of the amorphous phase, it is preferable that the amount of C is 1.0 part by mass or more, and more preferably the total of B and C is 2.0 parts by mass or more. On the other hand, in order to obtain a sufficient saturation magnetic flux density, it is necessary that the amount of C is 3.0 parts by mass or less. Also, if C is too much, Fe 3 The C phase is likely to be formed. Therefore, in order to obtain the thermal stability of the amorphous phase, it is necessary that the amount of C is 3.0 parts by mass or less. From the viewpoint of obtaining a higher saturation magnetic flux density, it is preferable that the amount of C is 2.5 parts by mass or less, and more preferably 2.0 parts by mass or less. The total of B and C is preferably 8.0 parts by mass or less, more preferably 7.0 parts by mass or less, and even more preferably 4.2 parts by mass or less. The amount of C may be 0.1 part by mass or more.

[0030] Si: 0 parts by mass or more and 6.7 parts by mass or less.

[0031] Si (silicon) enhances the thermal stability of the amorphous phase. The lower limit of the amount of Si is 0 parts by mass. That is, the alloy particles may not contain Si. From the viewpoint of obtaining higher thermal stability of the amorphous phase, the amount of Si is preferably 0.5 parts by mass or more, and more preferably 1.0 parts by mass or more. On the other hand, in order to obtain a sufficient saturation magnetic flux density, it is necessary that the amount of Si is 6.7 parts by mass or less. From the viewpoint of obtaining a higher saturation magnetic flux density, it is preferable that the amount of Si is 4.0 parts by mass or less. The amount of Si may be 0.1 parts by mass or more.

[0032] Ni: More than 0 parts by mass and 12.0 parts by mass or less, Total of Fe, Co and Ni: 97.0 parts by mass or less, When Ni is more than 0 parts by mass and 7.4 parts by mass or less: Total of Fe, Co and Ni: 89.6 parts by mass or more, When Ni is more than 7.4 parts by mass and 12.0 parts by mass or less: The difference obtained by subtracting 0.5 times the mass part of Ni from the sum of the mass parts of Fe and Co is 78.5 parts by mass or more.

[0033] Ni (nickel) is an essential element for enhancing corrosion resistance. Ni has a remarkable corrosion resistance effect when added to the chemical composition containing B. From the viewpoint of obtaining higher corrosion resistance, the amount of Ni is preferably 2.0 parts by mass or more, and more preferably 3.6 parts by mass or more. The amount of Ni may be 0.1 parts by mass or more.

[0034] If there is too much Ni, the saturation magnetic flux density and the Curie point will decrease. Furthermore, if there is too much Ni, the amorphous forming ability will decrease. Therefore, the amount of Ni needs to be 12.0 parts by mass or less. In order to sufficiently enhance the thermal stability of the amorphous phase, the total of Fe, Co, and Ni needs to be 97.0 parts by mass or less. From the viewpoint of obtaining a higher saturation magnetic flux density, the amount of Ni is preferably 10.0 parts by mass or less, and more preferably 9.0 parts by mass or less. In particular, when Ni is more than 7.4 parts by mass and 12.0 parts by mass or less, in order to obtain a high magnetic flux density, the difference obtained by subtracting 0.5 times the mass part of Ni from the sum of the mass parts of Fe and Co needs to be 78.5 parts by mass or more. When Ni is more than 0 parts by mass and 7.4 parts by mass or less, the total of Fe, Co, and Ni needs to be 89.6 parts by mass or more.

[0035] Cr: More than 0 parts by mass and 4.2 parts by mass or less, The sum of the mass part of P and the mass part of Cr is 7.4 parts by mass or less, The product of the mass part of Ni and the mass part of Cr is 0.5 or more.

[0036] Cr (chromium) greatly enhances the corrosion resistance in combination with P. Therefore, Cr is essential. Furthermore, by including Cr, Ni can be concentrated near the surface of the alloy particles to obtain higher corrosion resistance. Therefore, it is necessary that the product of the mass part of Cr and the mass part of Ni is 0.5 or more. On the other hand, in order to obtain a sufficient saturation magnetic flux density, Cr needs to be 4.2 parts by mass or less. From the viewpoint of obtaining a higher saturation magnetic flux density, Cr is preferably 3.5 parts by mass or less, and more preferably 2.5 parts by mass or less. In order to obtain a sufficient saturation magnetic flux density Bs, the sum of the mass part of P and the mass part of Cr needs to be 7.4 parts by mass or less.

[0037] The total of Mo, W, Zr, and Nb: 0 parts by mass or more and 4.2 parts by mass or less.

[0038] Mo, W, Zr, and Nb are optional elements that enhance corrosion resistance. On the other hand, if the total amount of Mo, W, Zr, and Nb is too large, the saturation magnetic flux density will decrease. Therefore, the total amount of Mo, W, Zr, and Nb needs to be 4.2 parts by mass or less. From the perspective of obtaining a higher saturation magnetic flux density Bs, the total amount of Mo, W, Zr, and Nb is preferably 2.0 parts by mass or less.

[0039] The alloy particles according to this embodiment may contain elements other than Fe, Co, B, P, C, Si, Ni, Cr, Mo, W, Zr, and Nb as impurities. To increase the saturation magnetic flux density, the amount of impurities is preferably 1.0 part by mass or less, and more preferably 0.50 part by mass or less. Further, the amount of impurities is preferably 1.0 mole part or less, and more preferably 0.50 mole part or less. For example, as impurities, N, O, Al, S, Ca, Ti, V, Cu, Mn, Zn, As, Ag, Sn, Sb, Hf, Ta, Bi, and rare earth elements (REM) can be mentioned. REM are Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu. In particular, in order to reduce the hysteresis loss and enhance the thermal stability of the amorphous phase, Ca, Ti, and Al are each preferably 0.1 part by mass or less. Similarly, from the perspective of enhancing the thermal stability of the amorphous phase, the amount of Cu is preferably 0.04 part by mass or less or 0.04 mole part or less, and more preferably 0.02 part by mass or less or 0.02 mole part or less. From the perspective of increasing the saturation magnetic flux density, the amount of O is preferably 0.1 part by mass or less, and more preferably 0.05 part by mass or less. The amount of impurities may be 0 part by mass. That is, the alloy particles may not contain impurities.

[0040] For the measurement of the amount of each element, a method that can obtain the accuracy of the above significant digits is used. Specifically, the measurement methods described in the examples below and equivalent measurement methods are applied to the quantification.

[0041] Next, the internal structure of the alloy particles according to this embodiment will be described.

[0042] The amorphous phase increases the volume resistivity and permeability of the alloy particles and decreases the magnetic anisotropy and coercive force. Therefore, it is necessary for the alloy particles to contain the amorphous phase. The average volume ratio of this amorphous phase needs to be 70% or more, preferably 80% or more. The average volume ratio of the amorphous phase may be 100%. That is, the structure within the alloy particles is a structure composed of one or more amorphous phases, or a duplex structure of an amorphous phase and a crystalline phase. When the alloy particles contain a crystalline phase, in order to decrease the coercive force, it is preferable that the average crystal grain size of each phase of the crystalline phase obtained by the Scherrer formula is 30 nm or less, and more preferably 25 nm or less. Also, the crystalline phase is classified into an alloy phase and a compound phase. The alloy phase is, for example, a phase of Fe with a body-centered cubic structure or a phase of Fe-Si. In order to increase the saturation magnetic flux density, the average volume ratio of the alloy phase may be 10% or more. Also, in order to decrease the coercive force, the average volume ratio of the compound phase is preferably 10% or less, preferably 2% or less, and particularly preferably 1% or less. The average volume ratio of the compound phase may be 0%. Examples of the compound phase include compounds such as Fe 3 P, Fe 3 B, Fe 3 C, Fe 2 B, oxides and phases of such compounds and their solid solutions. The volume ratio of each phase is determined by peak analysis of the data obtained by the X-ray diffraction method (XRD). This peak analysis uses the method described in the examples below. Here, as the XRD sample, the alloy particles are used as they are without being crushed or the like. Also, the fact that the alloy particles contain an amorphous phase is defined as the amount of the amorphous phase being calculable by the method described in the examples below.

[0043] Hereinafter, alloy particles according to a second embodiment, which is another embodiment of the present invention, will be described.

[0044] The surface structure of the alloy particles according to this embodiment will be described.

[0045] In the depth-direction concentration profile obtained by Auger electron spectroscopy, when Ni is concentrated near the surface of the powder, the corrosion resistance of the powder can be greatly enhanced. Specifically, in the concentration profile of the components in the depth direction of the alloy particles determined by repeating in this order the analysis of the surface of the alloy particles by Auger electron spectroscopy and the removal of the surface by irradiation with argon ions, N1 > N2. Here, N1 is the Ni concentration at a depth of 0 nm from the surface, and N2 is the average Ni concentration in the region from a depth of 10 nm to 100 nm from the surface. Further, it is necessary that the average distance D from the surface at which the Ni concentration of the above alloy particles becomes (N1 + N2) × 0.5 is 1.3 nm or more. On the other hand, the above distance D is, for example, 6.0 nm or less. Note that the concentration profile is measured as the content (parts by mass) of each component when the total content of Fe, Co, Ni, P, B, C, Si, Nb, Cr, Mo, W, Zr, and O is 100 parts by mass. The concentration profile of the components in the depth direction of the alloy particles is, for example, measured at intervals of 1.1 nm in the range from a depth of 0 nm to less than 11 nm, and at intervals of 2.2 nm in the range from a depth of 11 nm to 100 nm, and is obtained by connecting the concentration data adjacent to each other in the depth direction with a linear equation (straight line). When measuring using Auger electron spectroscopy (AES), in the acquisition of the spectroscopic spectrum, the variation in the measured values at the position of a depth of 0 nm is large. For this reason, it is preferable to measure only at the position of a depth of 0 nm twice and obtain the average value thereof. Further, in order to improve the SN ratio, the number of measurements may be increased to obtain the average value.

[0046] When the surface structure of the alloy particles has the above characteristic points, elements included in the group consisting of Ni and Cr form a sound passive film, and the corrosion resistance is remarkably improved.

[0047] Here, the number of alloy particles measured by Auger electron spectroscopy is 10, and the concentration profiles of these 10 alloy particles are averaged and used.

[0048] The internal structure of the alloy particles according to the present embodiment will be described.

[0049] Also in this embodiment, similar to the first embodiment, the alloy particles contain an amorphous phase.

[0050] Note that as a modification of the second embodiment, the second embodiment may include the characteristic points of the first embodiment.

[0051] Furthermore, more preferable embodiments of the first embodiment, the second embodiment, and the modification of the second embodiment will be described.

[0052] The size and shape of the alloy particles according to this embodiment will be described.

[0053] The size of the alloy particles is arbitrary. In order to increase the energy efficiency in the frequency band applied to the coil component and the effective magnetic permeability of the magnetic core, the D50 of the alloy particles is preferably 1 μm or more and 50 μm or less, and more preferably 20 μm or more and 40 μm or less. In particular, when emphasizing the energy efficiency at a high frequency and when emphasizing the filling rate of the alloy particles, the D50 of the alloy particles is preferably 1 μm or more and 10 μm or less, and more preferably 1 μm or more and 6 μm or less. Also, in order to facilitate the molding of the magnetic core or ensure the insulation of the coil component, the D90 of the alloy particles is preferably 100 μm or less, more preferably 80 μm or less, and particularly preferably 60 μm or less. The D90 of the alloy particles may be 1 μm or more. Here, D50 and D90 respectively mean the particle diameters at which the cumulative frequency from the smaller particle diameters in the particle diameter distribution of the volume distribution becomes 50% and 90%.

[0054] Similarly, the shape of the alloy particles is arbitrary. For example, when actively utilizing shape magnetic anisotropy, the aspect ratio may be 0.10 or more and 0.70 or less. On the other hand, the aspect ratio may be 0.70 or more and 1.0 or less so that the magnetic permeability of the coil component can be increased without considering anisotropy. When emphasizing the filling rate of the alloy particles, the aspect ratio is preferably 0.70 or more and 0.95 or less, and more preferably 0.75 or more and 0.90 or less. Here, the aspect ratio is the ratio of the minor axis length to the major axis length in the two-dimensional projection image of the alloy particles, and is obtained by averaging the values obtained from at least 10 or more alloy particles.

[0055] The surface structure and surface coating of the alloy particles according to this embodiment will be described.

[0056] In addition to the passive film, a separate film may be formed on the surface of the alloy particles as required. In order to enhance the insulation between the alloy particles, the film may be an oxide or a nitride. The film is preferably a phosphate or an oxide containing Si. The method for forming the film is not limited, but the sol-gel method or the mechanochemical reaction method is preferred to obtain high insulation.

[0057] The internal stress of the alloy particles according to this embodiment will be described.

[0058] In order to reduce the coercive force, it is desirable that the internal stress of the alloy particles be small, but it is difficult to quantify the internal stress. Therefore, considering the influence of the internal stress on the coercive force, the coercive force of the alloy particles is preferably 500 A / m or less, more preferably 200 A / m or less, and even more preferably 100 A / m or less. The coercive force of the alloy particles may be 0.0 A / m or more, or may be 0.1 A / m or more.

[0059] Hereinafter, a magnetic core according to an embodiment of the present invention will be described.

[0060] The magnetic core according to this embodiment contains the alloy particles according to the above embodiment. For stable bonding, the magnetic core may contain resin. Further, the resin may be at least one selected from the group consisting of epoxy resin, phenolic resin, and silicone resin. Furthermore, the magnetic core may contain a magnetic material other than the alloy particles of the above embodiment, and may contain a non-magnetic material such as an oxide.

[0061] Hereinafter, a coil component according to an embodiment of the present invention will be described.

[0062] The coil component according to this embodiment includes the magnetic core and the coil according to the above embodiment. The coil may be wound around the outer periphery of the magnetic core or may be encapsulated in the magnetic core. Examples of the coil component include an inductor, a reactor, and components including these (for example, a DC-DC converter).

[0063] FIG. 1 is a perspective view schematically showing an example of an inductor as an embodiment of the coil component of the present invention.

[0064] In the inductor shown in FIG. 1, a protective layer 15 is formed at a substantially central portion of the surface of the magnetic core 14 formed in a rectangular shape, and a pair of external electrodes 16a and 16b are formed at both end portions of the surface of the magnetic core 14 so as to sandwich the protective layer 15.

[0065] FIG. 2 is a perspective view showing the internal structure of the inductor shown in FIG. 1. In FIG. 2, for convenience of explanation, the protective layer 15, the external electrode 16a, and the external electrode 16b are omitted.

[0066] The magnetic core 14 is formed of a composite material containing, for example, the alloy particles of the present invention as a main component and containing a resin material such as epoxy resin. A coil 17 is embedded in the magnetic core 14.

[0067] Incidentally, the content of the alloy particles in the composite material is not particularly limited, but is preferably 60% by volume or more in terms of volume ratio. If the content of the alloy particles is less than 60% by volume, the magnetic permeability and saturation magnetic flux density may decrease due to the excessively small content of the alloy particles, leading to a deterioration in magnetic properties. Also, the upper limit of the content of the alloy particles is preferably 99% by volume or less because the resin material only needs to be contained to such an extent that the desired effects are achieved.

[0068] The coil 17 has, for example, a cylindrical shape in which a rectangular wire is wound in a coil shape. The end portions 17a and 17b of the coil 17 are exposed on the end face of the magnetic core 14 so as to be electrically connectable to the external electrodes 16a and 16b, respectively. The coil 17 is formed by coating, for example, a rectangular wire made of copper or the like with an insulating resin such as a polyester resin or a polyamide-imide resin, forming it in a strip shape, and winding it in a coil shape so as to have a hollow core.

[0069] The inductor shown in FIG. 1 can be manufactured, for example, by the following method.

[0070] First, the alloy particles and the resin material of the present invention are kneaded and dispersed to produce a composite material. Next, the coil 17 is embedded in the composite material so that the coil 17 is sealed with the composite material. Then, for example, a compression molding method is used for molding to obtain a molded body in which the coil 17 is embedded. After the obtained molded body is taken out of the molding die, heat treatment is performed, surface polishing is performed, and the magnetic core 14 in which the end portions 17a and 17b of the coil 17 are exposed on the end face is obtained.

[0071] Next, an insulating resin is applied to the surface of the magnetic core 14 other than the formation sites of the external electrodes 16a and 16b and cured to form a protective layer 15.

[0072] Thereafter, external electrodes 16a and 16b mainly composed of a conductive material are formed at both ends of the magnetic core 14. Thus, the inductor is manufactured.

[0073] The method for forming the external electrodes 16a and 16b is not particularly limited, and for example, it can be formed by any method such as a coating method, a plating method, a thin film forming method, etc.

[0074] In the inductor shown in FIG. 1, since the coil 17 is embedded in the magnetic core 14 and the magnetic core 14 contains the above-described alloy particles as a main component, it has a high saturation magnetic flux density and low magnetic loss, and has good soft magnetic properties with ferromagnetism and small hysteresis characteristics. A high-purity and high-quality coil component can be obtained with high efficiency.

[0075] In the above embodiment, a coil component such as an inductor is exemplified as a device using the alloy particles of the present invention. However, since the alloy particles of the present invention have a high saturation magnetic flux density and low magnetic loss, they can also be applied to a stator core or a rotor core equipped in a motor. A motor usually includes a stator core in which a plurality of armature teeth are provided at equal intervals on the same circumference, a coil wound around the armature teeth, and a rotor core rotatably disposed inside the stator core. As described above, since the alloy particles of the present invention have a high saturation magnetic flux density and low magnetic loss, at least one of, preferably both, the stator core and the rotor core contains the alloy particles of the present invention as a main component, thereby making it possible to obtain a high-quality motor with low power loss.

[0076] Hereinafter, an electronic device according to an embodiment of the present invention will be described.

[0077] The electronic device according to the present embodiment includes the coil component according to the above embodiment. Examples of the electronic device include a smartphone, a tablet, a personal computer, a server device, a communication device, etc. Further, examples of the mobility including the electronic device include an electric vehicle, a hybrid vehicle, a two-wheeled vehicle, an aircraft, a railway, etc.

[0078] Hereinafter, a method for manufacturing alloy particles according to an embodiment of the present invention will be described.

[0079] The method for manufacturing alloy particles according to this embodiment includes a melting step and a solidification step.

[0080] In the melting step, the raw materials are heated and melted to prepare a molten metal. The chemical composition of the molten metal can be controlled by selecting and blending a plurality of raw materials or refining the molten metal so as to satisfy a predetermined chemical composition. Further, in order to facilitate the moderation of the chemical composition, a master alloy prepared by previously melting and solidifying or a pulverized product thereof may be used as a raw material. Also, molten metals having different chemical compositions from each other may be mixed to prepare a target molten metal. Examples of the raw materials include pure iron, pig iron, iron-based scrap, ferroalloys (ferroboron, ferrophosphorus, ferrosilicon, ferrochrome), graphite, phosphorus monomer, and metallic chromium. In particular, the chemical composition of the molten metal may be the chemical composition described in the first embodiment. This molten metal with this chemical composition is particularly effective in significantly reducing the oxidation of the alloy particles after atomization with water. The heating method may be indirect resistance heating, induction heating, or arc heating.

[0081] In order to obtain alloy particles having a uniform chemical composition and containing an amorphous phase, the temperature of the molten metal needs to be higher than the liquidus temperature. Also, in order to increase the cooling efficiency in the solidification step and stably generate an amorphous phase, the temperature of the molten metal is preferably lower than the temperature obtained by adding 500°C to the liquidus temperature.

[0082] In order to make the chemical composition of the molten metal uniform, it is preferable that the melting step has a time for maintaining the molten metal at the target molten metal temperature. For example, this time is preferably 1 minute or more, and more preferably 5 minutes or more. Also, in order to reduce the dissipation of elements with high vapor pressure and the dissolution of gases in the atmosphere into the molten metal, the time is preferably 60 minutes or less, and more preferably 30 minutes or less.

[0083] The atmosphere in contact with the molten metal may be air. In order to increase the yield of alloy particles, the atmosphere may be an inert gas atmosphere containing nitrogen or argon, or an atmosphere with a controlled oxygen potential.

[0084] In the solidification step, the molten metal is pulverized to form droplets, and these droplets are solidified to produce alloy particles. The atomization method can be applied to the pulverization and solidification of the molten metal. As this atomization method, for example, the water atomization method, the gas atomization method, the disk atomization method, the atomization method using a combustion flame jet, and combinations thereof can be selected. Further, for example, after pulverizing the molten metal by the gas atomization method and the atomization method using a combustion flame jet, the molten metal may be rapidly cooled by the water atomization method. The fluid used in the atomization method may be water, a gas such as an inert gas, or a gas containing mist. The supply rate of the fluid is set in a range sufficient to deprive the molten metal of the heat quantity it has and to cause an amorphous phase to occur during the solidification of the molten metal. In particular, in order to stably form the amorphous phase, the fluid is particularly preferably water having a high cooling capacity.

[0085] When the solidification step is the water atomization method, the water pressure needs to be 20 MPa or more and 250 MPa or less. If the water pressure is lower than 20 MPa, the volume ratio of the amorphous phase of the obtained alloy particles is low and the coercive force becomes high. If the water pressure exceeds 250 MPa, the average particle diameter of the alloy particles becomes too small, so the space filling rate of the alloy particles becomes low and the inductance of the coil component decreases. In the case of a chemical composition with a low amorphous forming ability, it is preferable to pulverize the molten metal at a high water pressure. Therefore, the water pressure is preferably 50 MPa or more and 250 MPa or less. Further, in the case of a chemical composition with a low amorphous forming ability, the water pressure is preferably 70 MPa or more and 250 MPa or less.

[0086] The method for manufacturing alloy particles according to this embodiment may further include a drying step after the solidification step. This drying step is preferably immediately after the solidification step. For example, when water is used during the solidification step, in order to improve the energy efficiency of drying, wet alloy particles (slurry) may be obtained from the mixture of water and alloy particles by a separation method such as cyclone, filtration, or sedimentation. In this slurry, since the alloy particles are in contact with both water and gas, corrosion is likely to progress when the gas contains oxygen gas. Therefore, it is preferable to reduce the oxygen partial pressure to 40 Pa or less. Also, in order to reduce the oxygen dissolved in water, an inert gas may be blown into the water used in the atomization method or the mixture of water and alloy particles. In order to reduce the area of direct contact between the oxygen gas in the atmosphere and the alloy particles, when the mass of the alloy particles in the slurry is 100, it is preferable that the mass of water in the slurry is 5 or more and 100 or less, and more preferably 20 or more and 80 or less.

[0087] The alloy particles can be dried by heating, reducing pressure, and combinations thereof. When drying is performed by heating, in order to avoid a decrease in the saturation magnetic flux density due to an increase in the amount of oxide, it is preferable that the oxygen partial pressure is 20 Pa or less and the temperature is 100°C or more and 250°C or less, and more preferably the oxygen partial pressure is 2 Pa or less and the temperature is 120°C or more and 200°C or less. Stirring may be performed during drying to prevent particle aggregation, caking, or adhesion of the particles to the drying container. Also, stress may be applied to the alloy particles after drying to break up aggregated or caked particles or particles adhered to the drying container. Also, the drying step may be performed multiple times. It is considered that a passive film is formed on the surface of the alloy particles between the solidification step and the drying step.

[0088] The method for manufacturing alloy particles according to this embodiment may further include a classification step after the solidification step. This classification step may be immediately after any of the solidification step, the drying step, the compounding step described below, the heat treatment step described below, and the surface treatment step described below. In the classification step, the particle size distribution of the alloy particles is adjusted. For adjusting the particle size distribution, for example, a vibrating sieve, an ultrasonic sieve, an air classification, etc. can be used. The classification method may be based on the differences in inertial force, weight ratio, and fluidity between particles. The target particle size distribution preferably satisfies, for example, the preferable ranges of D50 and D90 in the above embodiment. Also, the classification step may be performed multiple times.

[0089] The method for manufacturing alloy particles according to this embodiment may further include a compounding step after the solidification step. This compounding step may be immediately after any of the solidification step, the drying step, the classification step, the heat treatment step described below, and the surface treatment step described below. In this compounding step, one or more kinds of powders are mixed. The combination of powders to be mixed is arbitrary as long as at least one kind of powder is obtained by the method for manufacturing alloy particles according to this embodiment. Two or more kinds of powders having different chemical compositions, structures, and particle size distributions may be mixed. For example, alloy particles with D50 of 50 μm and alloy particles with D50 of 4 μm may be mixed. As the soft magnetic material, for example, Fe-Si-based crystalline powder, Fe-Si-Cr-based crystalline powder, Fe-B-based amorphous powder, Fe-Si-B-based amorphous powder, Fe-Si-B-P-based amorphous powder, iron powder, or nanocrystalline powder may be mixed with the alloy particles. As the non-magnetic material, an inorganic filler may be mixed with the alloy particles.

[0090] The method for manufacturing alloy particles according to this embodiment may further include a heat treatment step after the solidification step. This heat treatment step may be immediately after any of the solidification step, drying step, classification step, compounding step, and surface treatment step described later. In the heat treatment step, the alloy particles are heated to reduce the internal stress (internal strain) contained in the alloy particles. In order to ensure a sufficient amount of the amorphous phase of the alloy particles, the heat treatment temperature needs to be lower than the crystallization start temperature. The heat treatment temperature is preferably 20°C or more lower than the crystallization start temperature. Also, in order to sufficiently reduce the internal stress, the heat treatment temperature is preferably 300°C or more. For example, the heat treatment temperature may be 300°C or more and 550°C or less. The heating rate may be 1°C / min or more and 5000°C / min or less. Since the crystallization start temperature changes according to the heating rate, the crystallization start temperature corresponding to the heating rate is specified and determined by differential scanning calorimetry (DSC). For heating rates that cannot be reached by DSC, the relationship between the heating rate measured by DSC and the crystallization start temperature is extended to the high heating rate side to determine the crystallization start temperature. Also, in order to sufficiently reduce the internal stress, the time for which the alloy particles are maintained at a temperature of 300°C or more is preferably 1 minute or more. This time is preferably 120 minutes or less in order to prevent the formation of coarse crystal grains. In order to avoid a decrease in the saturation magnetic flux density due to an increase in the amount of oxide, the atmosphere for the heat treatment is preferably an inert gas atmosphere in which the oxygen potential is controlled. For example, the oxygen partial pressure in the atmosphere is preferably 100 Pa or less. As the heating method, for example, electromagnetic waves such as infrared rays may be used, or induction heating may be used. Also, the alloy particles may be heated by bringing them into contact with or close to a heated medium (solid, liquid, gas, mixture).

[0091] The method for manufacturing alloy particles according to this embodiment may further include a surface treatment step after the solidification step. This surface treatment step may be immediately after any of the solidification step, drying step, classification step, blending step, and heat treatment step. In the surface treatment step, for example, a chemical conversion treatment, a mechanochemical reaction, a sol-gel reaction, or the like can be utilized. By the surface treatment step, a film that can be separately formed as necessary can be formed on the surface of the alloy particles.

[0092] The alloy particles according to the first and second embodiments, and the alloy particles according to these preferred embodiments can be preferably manufactured by the method for manufacturing alloy particles according to this embodiment, but they may also be manufactured by manufacturing methods other than this embodiment.

[0093] Hereinafter, a method for manufacturing a magnetic core according to an embodiment of the present invention will be described.

[0094] In the method for manufacturing a magnetic core according to an embodiment of the present invention, the alloy particles according to the above-described embodiment are used. As the molding method, for example, press molding or mold molding can be used. Specifically, it can be selected from molding methods such as cold uniaxial pressing, hot uniaxial pressing, spark plasma sintering (SPS), cold isostatic pressing, hot isostatic pressing, sheet molding, potting molding, transfer molding, and injection molding. Further, additives such as a binder may be mixed with the alloy particles according to the above-described embodiment. The binder may be at least one selected from the group consisting of an epoxy resin, a phenol resin, and a silicone resin. Other additives may be a silane coupling agent, a lubricant, a curing accelerator, a curing retarder, or the like.

Examples

[0095] Hereinafter, examples that more specifically disclose the present invention will be shown. Note that the present invention is not limited only to these examples.

[0096] (Production of alloy particles) The raw materials were weighed so that the alloy particles would have the chemical compositions shown in Table 1 and Table 3, taking into account the changes in chemical composition due to slag generation during dissolution. The total weight of the raw materials was set to 150 g. As the Fe source, Myron (purity 99.95 wt%) manufactured by Toho Zinc Co., Ltd. was used. Also, as the B source, C source, Si source, Ni source, Cr source, Mo source, W source, Zr source, Nb source, and Co source, materials manufactured by High Purity Chemical Laboratory Co., Ltd. were used. As the P source and Fe source, massive iron phosphide Fe 3 P (purity 99 wt%) was used. As the B source, granular boron (purity 99.5 wt%) was used. As the C source, powdered graphite (purity 99.95 wt%) was used. As the Si source, Ni source, Cr source, Mo source, W source, Zr source, Nb source, and Co source, pure metals (purity 99 wt% or more) were used.

[0097] The above raw materials were placed in an alumina crucible and heated to 1400 °C in an argon gas atmosphere of 1.0 atm by high-frequency induction heating. The raw materials were held at 1400 °C for 10 minutes to prepare a molten metal. This molten metal was allowed to flow down through a hole at the bottom of the crucible, and alloy particles were produced from the molten metal by the water atomization method, and the alloy particles were collected in a sedimentation tank. The water pressure in the water atomization method was set to 80 MPa.

[0098] In Comparative Example 30, the chemical composition of the raw materials was the same as that of Example 30, but among the atomization operating conditions, the water pressure was set to 0.5 times (40 MPa) that of Example 30.

[0099] After atomization, the sedimentation tank was allowed to stand for 30 minutes to sediment the alloy particles in the dissolution tank, and the muddy alloy particles were collected. In these muddy alloy particles, the mass of water was 50 with respect to the mass of the alloy particles of 100. The muddy alloy particles were heated to 200 °C at a pressure of 1 Pa or less and then maintained at 200 °C for 180 minutes to dry the alloy particles. The dried alloy particles were classified using a vibrating sieve, and the alloy particles between a sieve with an opening of 20 μm and a sieve with an opening of 53 μm were collected.

[0100] (Measurement of D50) The average particle diameter D50 of the alloy particles was measured using a laser diffraction particle size distribution analyzer (HELOS / RODOS manufactured by Sympatec). The dispersion pressure condition was set to 2 bar (200 kPa).

[0101] (Quantification of Chemical Composition) The amounts of B and C contained in the alloy particles were measured by atomic absorption spectrometry. The amounts of elements other than B and C (Fe, P, Si, Ni, Cr, Mo, W, Zr, Nb, Co) were measured by inductively coupled plasma mass spectrometry (ICP-MS method).

[0102] (Measurement of Volume Fraction Va of Amorphous Phase) The alloy particles were directly measured by the θ-2θ method using an X-ray diffractometer Miniflex (Cu tube) manufactured by Rigaku Corporation to obtain a diffraction intensity profile. The step size was set to 0.01°, the scan speed was set to 5° / min, and the 2θ scan range was 25° or more and 90° or less. In the diffraction intensity profile, a halo derived from the amorphous phase, a (110) peak derived from the (110) plane of the crystal phase having a body-centered cubic structure, and a peak of the compound phase may occur in the vicinity of 2θ = 44°. The area intensity Ia of the halo, the area intensity Ic of the (110) peak, and the area intensity Ic' of the compound phase peak were calculated from the diffraction intensity profile by the method described in Japanese Patent Application No. 2017-532527, and the volume fraction Va of the amorphous phase was determined by the following formula (1). Incidentally, the volume fraction Vc of the crystal phase having a body-centered cubic structure can be determined by the following formula (2). Va = Ia / (Ia + Ic + Ic') (1) Vc = Ic / (Ia + Ic + Ic') (2)

[0103] (Determination of Surface Concentration Profile) For some of the examples and comparative examples, the change in the chemical composition in the depth direction from the surface to the inside of the alloy particles was measured by Auger electron spectroscopy (AES). In this measurement, surface analysis and removal of the surface by irradiation with argon ions were repeated in this order. The measurement was performed at intervals of 1.1 nm in the range of a depth of 0 nm or more and less than 11 nm, and at intervals of 2.2 nm in the range of a depth of 11 nm or more and 100 nm or less. The measurement was performed twice only at the position of a depth of 0 nm, and the average value was obtained. The measurement at positions other than a depth of 0 nm was performed once each. The number of alloy particles measured by AES was 10, and the concentration profiles of these 10 alloy particles were averaged and used.

[0104] (Measurement of saturation magnetic flux density Bs) The alloy particles were densely packed into a cylinder case for powder. The saturation mass magnetization Ms of these alloy particles was measured by a vibrating sample type magnetometer (VSM-5-15 manufactured by Toei Industry Co., Ltd.) at a maximum magnetic field of 10 kOe. Also, the apparent density ρ was measured by the pycnometer method (AccuPycII1340 manufactured by Shimadzu Corporation). He was used as the substitution gas, and 25 g of alloy particles were used as the sample. The saturation magnetic flux density Bs was calculated from the above saturation mass magnetization Ms and the above apparent density ρ using the following formula (3). Bs = 4π × Ms × ρ (3)

[0105] (Measurement of coercive force Hc) The alloy particles were filled into a capsule for powder measurement, and this capsule was consolidated so that the alloy particles did not move when a magnetic field was applied. The coercive force Hc of the alloy particles in this capsule was measured with a coercive force meter K-HC1000 manufactured by Tohoku Special Steel Co., Ltd.

[0106] (Corrosion potential E corr and corrosion current density i corr in alloy particles) The corrosion potential (natural potential) E corr and corrosion current density i corrThese were measured using an electrochemical measurement system (HZ-5000 manufactured by Hokuto Denko Corporation). For the working electrode, reference electrode, and counter electrode, GRC-3155, RE-2, and CE-2 manufactured by ECS Frontier Co., Ltd. were used, respectively. A mixture obtained by mixing alloy particles and carbon paste (CPO [model number 001010] manufactured by BASF Japan Ltd.) at a mass ratio of 2:1 was packed into the hole of a cylindrical working electrode. After immersing this working electrode in a 3 mass% NaCl aqueous solution for 1 hour, the natural potential E corr was measured. Thereafter, a voltage was applied to the working electrode from the natural potential up to +300 mV to obtain an anodic polarization curve. The scan speed was set to 2 mV / s and the sampling interval was set to 2 s. The corrosion current obtained from the anodic polarization curve was divided by the cross-sectional area of the reference electrode, 0.0176 cm 2 to obtain the corrosion current density i corr . Note that this corrosion current density i corr was defined as the current density at a potential obtained by adding 100 mV to the corrosion potential. As an index of corrosion resistance, the corrosion potential was used.

[0107] Table 2 and Table 3 show the D50, Va, Bs, Hc, E corr and i corr of the alloy particles.

[0108]

Table 1

[0109]

Table 2

[0110]

Table 3

[0111] In Examples 1 to 55, the alloy particles have the chemical composition and structure of the present invention and have a high saturation magnetic flux density Bs and excellent corrosion resistance.

[0112] In Comparative Example 1, since the total of the parts by mass of P and the parts by mass of Cr is large, the saturation magnetic flux density Bs is small.

[0113] In Comparative Examples 2 to 3, since the total of the parts by mass of Fe and the parts by mass of Co is small, the saturation magnetic flux density Bs is small.

[0114] In Comparative Example 4, since the total of the parts by mass of Fe and the parts by mass of Co is large, the coercive force Hc is large.

[0115] In Comparative Examples 5 to 6, 8 to 9, and 24, since the parts by mass of any one of P, B, C, and Si are large, the saturation magnetic flux density Bs is small.

[0116] In Comparative Example 7, since the parts by mass of C are large, the saturation magnetic flux density Bs is small and the coercive force Hc is large.

[0117] In Comparative Example 8, since the parts by mass of C are large, the saturation magnetic flux density Bs is small. Since the parts by mass of C are smaller than those in Comparative Example 7, the volume fraction Va of the amorphous phase is 70% or more and the coercive force Hc is small.

[0118] In Comparative Example 9, since the parts by mass of Si are large, the saturation magnetic flux density Bs is small.

[0119] In Comparative Examples 10 to 11, since the amount of Ni is large, the saturation magnetic flux density Bs is small and the coercive force Hc is large.

[0120] In Comparative Examples 12 to 13 and 15, since the amount of Cr is large, the saturation magnetic flux density Bs is small.

[0121] In Comparative Example 14, since the amount of Cr is large and the total amount of the parts by weight of P and the parts by weight of Cr is large, the saturation magnetic flux density Bs is small and the coercive force Hc is large.

[0122] In Comparative Examples 16 to 18, the product of the parts by mass of Ni and the parts by mass of Cr is small, and the corrosion potential E corr which is an index of corrosion resistance is low. Also, the corrosion current density i corr is high.

[0123] In Comparative Examples 19 and 20, the sum of the parts by mass of Fe, Co, and Ni is large, and the coercive force Hc is large.

[0124] In Comparative Examples 21 and 22, Ni is less, and the sum of the parts by mass of Fe, Co, and Ni is small, and the saturation magnetic flux density Bs is small.

[0125] In Comparative Example 23, the difference obtained by subtracting 0.5 times the part by mass of Ni from the sum of the parts by mass of Fe and Co is small, and the saturation magnetic flux density Bs is small.

[0126] In Comparative Example 24, since the part by mass of C is large, the saturation magnetic flux density Bs is small. Compared with Comparative Example 7, the part by mass of C is less, compared with Comparative Example 8, the part by mass of Fe is less, and the part by mass of B is large. Therefore, the volume ratio Va of the amorphous phase is 100%, and the coercive force Hc is small.

[0127] In Comparative Example 25, since the amount of Nb is large, the saturation magnetic flux density Bs is small.

[0128] In Comparative Example 26, since it does not contain Cr, the corrosion potential E corr which is an index of corrosion resistance is low.

[0129] In Comparative Example 27, since the amount of Co is large, the coercive force Hc is large.

[0130] In Comparative Example 28, since it does not contain B, the coercive force Hc is large.

[0131] In Comparative Example 29, since the product of the part by mass of Ni and the part by mass of Cr is small, the corrosion potential E corr which is an index of corrosion resistance is low.

[0132] In Comparative Example 30, the chemical composition of the alloy particles is the same as that in Example 30, but it is a composition with low amorphous forming ability. Among the atomization operation conditions, since the water pressure was set to 0.5 times (40 MPa) that of Example 30, the volume ratio of the amorphous phase is small, and the coercive force Hc is large.

[0133] Comparative Example 31 is an alloy ribbon with the same composition as that of Example 5 prepared by the single-roll liquid quenching method. The same raw materials as those in Example 5 were placed in a quartz crucible and heated to 1400°C in an argon gas atmosphere of 1.0 atm by high-frequency induction heating. The raw materials were held at 1400°C for 10 minutes to prepare a molten metal. This molten metal was discharged from a slit nozzle attached to the lower part of a quartz nozzle onto the surface of a copper roll for cooling at a pressure of 0.015 MPa. The copper roll for cooling was rotating at a peripheral speed of 25 m / s, and the molten metal was rapidly solidified to obtain a ribbon with an average width of 10 mm and an average thickness of 24 μm.

[0134] (Measurement of corrosion potential E corr and corrosion current density i corr in the alloy ribbon) The corrosion potential (natural potential) E corr of alloy particles and corrosion current density i corr were measured with an electrochemical measurement system (HZ-5000 manufactured by Hokuto Denko Corporation). RE-2 and CE-2 manufactured by ECC Frontier Co., Ltd. were used as the reference electrode and counter electrode, respectively. One end of the alloy ribbon with a width of 10 mm and a length of 60 mm up to 20 mm was immersed in a 3 mass% NaCl aqueous solution, and the natural potential E corr was measured with the alloy ribbon as the working electrode. Then, a voltage was applied to the working electrode from the natural potential up to +300 mV to obtain an anodic polarization curve. The scan speed was 2 mV / s, and the sampling interval was 2 s. The corrosion current obtained from the anodic polarization curve was divided by the surface area of the alloy ribbon of 4.0 cm 2 to obtain the corrosion current density i corr . Note that this corrosion current density i corr was defined as the current density at a potential obtained by adding 100 mV to the corrosion potential. The corrosion potential was used as an index of corrosion resistance.

[0135] Table 4 shows Va, Bs, Hc, E corr and i corr of the alloy ribbon of Comparative Example 31.

[0136]

Table 4

[0137] Table 5 shows the AES results for the alloy particles of Example 5 and Comparative Example 26 and the alloy ribbon of Comparative Example 31.

[0138] [Table 5]

[0139] The AES data of Example 5 and Comparative Example 31 are shown in FIGS. 3 and 4.

[0140] In Example 5, the Ni concentration N1 at a depth of 0 nm from the surface of the alloy particles and the average Ni concentration N2 from a depth of 10 nm to 100 nm from the surface of the alloy particles are in the relationship of N1 > N2, and the average distance D from the surface of the alloy particles at the Ni concentration of (N1 + N2) × 0.5 obtained by multiplying the sum of N1 and N2 by 0.5 is 1.3 nm or more. Therefore, the corrosion potential E, which is an index of corrosion resistance corr is high.

[0141] In Comparative Example 26, the Ni concentration N1 at a depth of 0 nm from the surface of the alloy particles and the average Ni concentration N2 from a depth of 10 nm to 100 nm from the surface of the alloy particles are in the relationship of N1 > N2, but the average distance D from the surface of the alloy particles at the Ni concentration of (N1 + N2) × 0.5 obtained by multiplying the sum of N1 and N2 by 0.5 is less than 1.3 nm. Therefore, the corrosion potential E, which is an index of corrosion resistance corr is low.

[0142] In Comparative Example 31, the Ni concentration N1 at a depth of 0 nm from the surface of the alloy ribbon and the average Ni concentration N2 from a depth of 10 nm to 100 nm from the surface of the alloy ribbon are in the relationship of N1 < N2. Therefore, the corrosion potential E, which is an index of corrosion resistance corr is low.

[0143] The preferred embodiments of the present invention have been described above, but the present invention is not limited to these embodiments. Additions, omissions, substitutions, and other changes can be made without departing from the spirit of the present invention. Further, the present invention is not limited by the foregoing description, but is limited by the scope of the claims. [Explanation of Reference Numerals]

[0144] 14 Core 15 Protective layer 16a, 16b External electrodes 17 Coil 17a, 17b Ends

Claims

1. Alloy particles containing an amorphous phase, containing Fe, B, Ni, and Cr, and optionally containing Mo, W, Zr, Nb, Co, P, C, and Si, In the concentration profile of the components in the depth direction of the alloy particles, N1 > N2, and the average distance D from the surface where the Ni concentration is (N1 + N2) × 0.5 is 1.3 nm or more (where N1 is the Ni concentration at a depth of 0 nm from the surface and N2 is the average Ni concentration in the region from a depth of 10 nm to 100 nm from the surface).

2. When the total content of Fe, Co, B, Ni, P, C, Si, Nb, Cr, Mo, W, and Zr is 100 parts by mass, Total of Fe and Co: 82.2 parts by mass or more and 96.5 parts by mass or less, Co: 0 parts by mass or more and 30.0 parts by mass or less, P: 0 parts by mass or more and 4.5 parts by mass or less, B: More than 0 parts by mass and 5.0 parts by mass or less, C: 0 parts by mass or more and 3.0 parts by mass or less, Si: 0 parts by mass or more and 6.7 parts by mass or less, Ni: More than 0 parts by mass and 12.0 parts by mass or less, Cr: More than 0 parts by mass and 4.2 parts by mass or less, Total of Mo, W, Zr, and Nb: 0 parts by mass or more and 4.2 parts by mass or less, Sum of the parts by mass of P and the parts by mass of Cr is 7.4 parts by mass or less, Product of the parts by mass of Ni and the parts by mass of Cr is 0.5 or more, Total of Fe, Co, and Ni: 97.0 parts by mass or less, and When Ni is more than 0 parts by mass and 7.4 parts by mass or less, the total of Fe, Co, and Ni satisfies 89.6 parts by mass or more. When Ni is more than 7.4 parts by mass and 12.0 parts by mass or less, the difference obtained by subtracting Ni × 0.5 from the sum of the parts by mass of Fe and Co satisfies 78.5 parts by mass or more. The alloy particles according to claim 1, wherein the alloy particles contain an amorphous phase and the volume ratio of the amorphous phase is 70% or more.

3. A coil component including a magnetic core containing the alloy particles according to claim 1 or 2 and a coil.

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