Soft magnetic powder, magnetic cores, magnetic component, and electronic device

Abstract

To provide a soft magnetic powder, a magnetic core, a magnetic component, and an electronic device.SOLUTION: A soft magnetic powder contains at least one element selected from the group consisting of Fe, Co, and Ni as its main component. The glass transition temperature Tg, Curie temperature Tc, and first crystallization temperature Tx satisfy the relationship Tg≤Tc<Tx.SELECTED DRAWING: Figure 1A

Description

[Technical Field]

[0001] The present invention relates to a soft magnetic powder, a magnetic core, a magnetic component, and an electronic component. [Background technology]

[0002] Magnetic components such as inductors are required to be highly efficient in order to save energy. Therefore, materials that can achieve low loss are also required for inductors. One method for reducing loss is heat treatment, which aims to remove distortion from the material.

[0003] Conventionally, it is common to perform heat treatment on soft magnetic materials whose Curie point (Tc) is lower than their glass transition point (Tg) (for example, Patent Document 1 listed below). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-307291 Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a soft magnetic powder, a magnetic core, a magnetic component, and an electronic device that are capable of reducing core loss. [Means for solving the problem]

[0006] As a result of intensive studies on soft magnetic powders capable of reducing core loss, the inventors have found that when the Curie point (Tc) is higher than the crystallization temperature (Tx) of the soft magnetic powder, magnetic order cannot be eliminated by heat treatment and it is difficult to reduce the loss. On the other hand, when the Curie point (Tc) of the soft magnetic powder is lower than the glass transition point (Tg), it has been found that magnetic order is reproduced during the cooling process after heat treatment and there is a limit to reducing the loss.

[0007] That is, the soft magnetic powder according to one embodiment of the present invention is a soft magnetic powder containing, as a main component, one or more elements selected from Fe, Co, and Ni, where the glass transition point of the soft magnetic powder is denoted as Tg, the Curie point is denoted as Tc, and the first crystallization temperature is denoted as Tx, satisfies Tg ≦ Tc < Tx.

[0008] In the soft magnetic powder that satisfies Tg ≦ Tc < Tx, even if the composition is the same as that of the soft magnetic powder that does not satisfy Tg ≦ Tc < Tx, loss reduction can be achieved by heat treatment. The reason is considered to be that, for example, by controlling the Tg of the soft magnetic powder, structural relaxation and magnetic disordering can occur simultaneously by heat treatment, and low core loss can be realized.

[0009] Preferably, the main component of the soft magnetic powder is Fe 1-( α + β ) Coα Niβ has a composition represented as (atomic ratio), 0 ≦ α + β < 1 0 ≦ α ≦ 0.6 0 ≦ β ≦ 0.6 and satisfies.

[0010] Preferably, the soft magnetic powder is the formula (Fe 1-( α + β ) Coα Niβ )1-(a+b+c+d) B a P b Si c C d X1 e (atomic ratio), X1 is one or more selected from Ti, Zr, Hf, Nb, Ta, Mo, W, Al, Ga, Ag, Zn, Cr, Mn, V, Sn, As, Sb, Bi, Au, Cu, rare earth elements, and platinum group elements; 0.020≦a≦0.16, 0.01≦b≦0.16, 0≦c≦0.100, 0≦d≦0.07, 0≦e≦0.07, 0≦α≦0.600, 0 ≤ β ≤ 0.600, and 0.760≦1-(a+b+c+d+e)≦0.840, Satisfy.

[0011] Preferably, Tc-Tg≧1, Tc-Tg≧3, Tc-Tg≧9. Also preferably, Tx-Tc≧1, Tx-Tc≧3, Tx-Tc≧5.

[0012] A magnetic core according to one embodiment of the present invention contains any of the soft magnetic powders described above.

[0013] A magnetic component according to one embodiment of the present invention includes any of the soft magnetic powders described above.

[0014] An electronic device according to one embodiment of the present invention includes any of the soft magnetic powders described above.

[0015] A method for producing a soft magnetic powder according to one embodiment of the present invention includes the steps of: A step of obtaining a soft magnetic ribbon before cooling and hardening, the soft magnetic ribbon containing one or more elements selected from Fe, Co, and Ni as a main component; It is preferable to have a step of spraying a cooling liquid (for example, cooling water) onto the soft magnetic ribbon before cooling and hardening, to cool the soft magnetic ribbon, and pulverizing the soft magnetic ribbon, thereby obtaining the soft magnetic powder.

[0016] A method for manufacturing a magnetic component according to an embodiment of the present invention includes: obtaining a molded body by molding the soft magnetic powder obtained by the above-described method for manufacturing soft magnetic powder into a predetermined shape; and heat-treating the molded body. Let the temperature for heat-treating the molded body be Ta, the Curie point of the soft magnetic powder be Tc, and the first crystallization temperature be Tx. It is preferable that Tx - Ta ≥ 1 and Ta - Tc ≥ 1.

Brief Description of the Drawings

[0017] [Figure 1A] FIG. 1A is a graph showing a DSC curve and an average DDDSC curve of soft magnetic powder according to an embodiment of the present invention. [Figure 1B] FIG. 1B is a graph showing a DSC curve and an average DDDSC curve of soft magnetic powder according to a comparative example of the present invention. [Figure 2] FIG. 2 is a schematic explanatory view for manufacturing soft magnetic powder according to an embodiment of the present invention. [Figure 3] FIG. 3 is a schematic perspective view of a magnetic core made of soft magnetic powder according to an embodiment of the present invention.

Embodiments for Carrying Out the Invention

[0018] Hereinafter, embodiments of the present invention will be described. First, the soft magnetic powder according to this embodiment will be described.

[0019] For the soft magnetic powder according to this embodiment, let the glass transition point of the soft magnetic powder be Tg, the Curie point be Tc, and the first crystallization temperature be Tx, and Tg ≤ Tc < Tx is satisfied.

[0020] The glass transition temperature Tg, Curie point Tc, and first crystallization temperature Tx of the soft magnetic powder can be determined, for example, from the differential scanning calorimetry curve (DSC curve) shown in FIG. 1A(a) and the curve obtained by second-order differentiation of the DSC curve (referred to as the DDSC curve). The DSC curve is measured during the heating process of the soft magnetic powder. The horizontal axis of the DSC curve indicates the temperature of the soft magnetic powder (unit: °C). The vertical axis of the DSC curve indicates the heat flow per unit mass of the soft magnetic powder (unit: mW / mg). A positive heat flow indicates heat generation by the soft magnetic powder. A negative heat flow indicates heat absorption by the soft magnetic powder. The baseline of the DSC curve may be corrected as appropriate. The heating rate of the soft magnetic powder in measuring the DSC curve is 40°C / min.

[0021] The Tx of soft magnetic powder is defined as the crystallization temperature of the alloy powder that exhibits a glass transition, and can be defined as the temperature on the horizontal axis at which the vertical axis reaches 0 when the DSC curve changes significantly from negative to positive, as shown in Figure 1A(a). At Tx, it is thought that the supercooled liquid (metallic glass) in the alloy particles that make up the soft magnetic powder begins to crystallize, and the soft magnetic powder begins to generate heat due to crystallization.

[0022] Furthermore, Tc can be determined by averaging the DDDSC curves shown in Figure 1A(b), which are second-order derivatives of the DSC curves, over a temperature range of ±2°C. When the largest peak can be identified on the lower temperature side than Tx in the average DDDSC curve, that peak indicates Tc, and the temperature corresponding to that peak can be defined as Tc.

[0023] Furthermore, Tg can be defined as the point on a DSC curve where DSC changes from 0 to a negative value. Because the reaction at the Curie point Tc is an endothermic reaction, the value is negative near the Curie point Tc. When the temperature is raised from a low temperature, at Tg, the metallic glass component contained in the particles that make up the soft magnetic powder absorbs heat and gains fluidity. At temperatures above Tg, the metallic glass is thought to begin to become a supercooled liquid.

[0024] As shown in (b) of FIG. 1A, the peak related to Tc changes rapidly from a minimum value to a maximum value. Considering the half-width of the peak, etc., when obtaining the slope (SLOPE1) of the average DDDSC curve in the range from the minimum value of -15°C to the minimum value of -25°C and the slope SLOPE2 of the average DDDSC curve in the range from the maximum value of +15°C to the maximum value of +25°C, when the relationship between SLOPE1 and SLOPE2 satisfies any of the following conditions, it means that there is Tc in the supercooled liquid region (between Tg and Tx). (Condition 1) SLOPE1 ≤ -0.0015 and SLOPE2 ≤ -0.0015 (Condition 2) |SLOPE2| / |SLOPE1| ≥ 2 (Condition 3) SLOPE1 ≤ 0.0015 and SLOPE2 > -0.015

[0025] In this embodiment, Tg may be, for example, 350 to 500°C, and Tx may be Tg + 15°C or more and Tg + 100°C or less.

[0026] Note that (a) of FIG. 1B shows the DSC curve of a conventional soft magnetic powder, and (b) of FIG. 1B shows the average DDDSC curve of a conventional soft magnetic powder. As shown in FIG. 1B, Tg ≤ Tc < Tx is not satisfied.

[0027] In this embodiment, preferably, Tc - Tg ≥ 1, Tc - Tg ≥ 3, Tc - Tg ≥ 9. Also, preferably, Tx - Tc ≥ 1, Tx - Tc ≥ 3, Tx - Tc ≥ 5.

[0028] In the soft magnetic powder that satisfies Tg ≤ Tc < Tx, even if the composition is the same as that of the soft magnetic powder that does not satisfy Tg ≤ Tc < Tx, heat treatment can reduce the loss. The reason is considered to be that, for example, by controlling the Tg of the soft magnetic powder, structural relaxation and magnetic disordering can occur simultaneously by heat treatment, and low core loss can be realized.

[0029] The relationship between Tg, Tx and Tc described above can be realized particularly by a new manufacturing method as described below, but it also changes depending on the ratio of magnetic elements (for example, Fe, Co, Ni, etc.).

[0030] The material and composition of the soft magnetic powder according to this embodiment are not particularly limited as long as it has soft magnetic properties. The soft magnetic powder may be composed of, for example, a hetero-amorphous Fe-Si-B alloy, an Fe-Co-Si-B alloy, a nanocrystalline Fe-Si-B-Nb-Cu alloy, or an Fe-B-Nb alloy.

[0031] The microstructure of the soft magnetic powder according to this embodiment is not particularly limited. For example, the soft magnetic powder according to this embodiment may have a structure consisting solely of amorphous material, or may have a nanoheterostructure in which primary crystallites exist in an amorphous state. The primary crystallites may have an average particle size of 0.3 to 10 nm. Alternatively, the particles of the soft magnetic powder according to this embodiment may be particles consisting of a nanocrystalline phase, or particles in which an amorphous phase and a nanocrystalline phase are mixed. Furthermore, among structures consisting of nanocrystals, the soft magnetic powder according to this embodiment may particularly have a structure consisting of Fe-based nanocrystals. Furthermore, the particles of the soft magnetic powder according to this embodiment may contain nanocrystals and metallic glass, or both nanocrystals and metallic glass may exist in soft magnetic alloy particles consisting of a single alloy composition.

[0032] Nanocrystals refer to crystals with a particle size on the nanometer order. Fe-based nanocrystals are crystals with a particle size on the nanometer order, mainly composed of Fe, and with a bcc (body-centered cubic lattice) crystal structure. In this embodiment, it is preferable to precipitate Fe-based nanocrystals with an average particle size of 5 to 30 nm.

[0033] Hereinafter, a method for confirming whether the soft magnetic powder of this embodiment has an amorphous structure (a structure consisting only of amorphous or a nanoheterostructure) or a crystalline structure will be described. In this embodiment, a soft magnetic alloy ribbon having an amorphous ratio X shown in the following formula (1) of 85% or more has an amorphous structure, and a soft magnetic alloy ribbon having an amorphous ratio X of less than 85% has a crystalline structure.

[0034] X = 100 - (Ic / (Ic + Ia) × 100) ... (1) Ic: Crystalline scattering integrated intensity Ia: Amorphous scattering integrated intensity

[0035] The amorphous ratio X is calculated by performing a crystal structure analysis on the soft magnetic alloy ribbon by X-ray diffraction (XRD), identifying the phase, reading the peaks of crystallized Fe or a compound (Ic: crystalline scattering integrated intensity, Ia: amorphous scattering integrated intensity), determining the crystallization ratio from the peak intensity, and then calculating the crystallization ratio X using the above formula (1). The calculation method will be described in more detail below.

[0036] The soft magnetic powder according to this embodiment is subjected to crystal structure analysis by XRD, and profile fitting is performed using a Lorentz function to obtain a crystalline component pattern showing the crystalline scattering integrated intensity, an amorphous component pattern showing the amorphous scattering integrated intensity, and a combined pattern of these. The amorphous fraction X is calculated from the crystalline scattering integrated intensity and the amorphous scattering integrated intensity of the obtained pattern using the above formula (1). The measurement range is a diffraction angle 2θ of 30° to 60°, in which an amorphous-derived halo can be confirmed. Within this range, the error between the integrated intensity measured by XRD and the integrated intensity calculated using the Lorentz function is set to within 1%.

[0037] Furthermore, when evaluating the amorphous nature of a magnetic core, it can be confirmed by observing the microstructure using a scanning transmission electron microscope (STEM). In other words, it can be determined by analyzing the area ratio of the amorphous part to the nanocrystalline or crystalline part. In other words, if the area ratio of the amorphous part is 85% or more, it is defined as amorphous, and if primary microcrystals of about 0.1 to 10 nm are observed in a high-resolution image, it can be said to have a nanoheterostructure.

[0038] The soft magnetic powder of this embodiment preferably contains one or more elements selected from the group consisting of Fe, Co, and Ni as a main component. Preferably, the main component of the soft magnetic powder is Fe 1-( α + β ) Coα Niβ (atomic ratio), The following conditions are satisfied: 0≦α+β<1, 0≦α≦0.6, and 0≦β≦0.6.

[0039] More preferably, the soft magnetic powder is Formula (Fe 1-( α + β ) Coα Niβ ) 1-(a+b+c+d) B a P b Si c C d X1 e (atomic ratio), where X1 is one or more elements selected from Ti, Zr, Hf, Nb, Ta, Mo, W, Al, Ga, Ag, Zn, Cr, Mn, V, Sn, As, Sb, Bi, Au, Cu, rare earth elements, and platinum group elements.

[0040] Preferably, 0.020≦a≦0.16, 0.01≦b≦0.16, 0≦c≦0.100, 0≦d≦0.07, 0≦e≦0.07, 0≦α≦0.600, 0 ≤ β ≤ 0.600, and Satisfies 0.760≦1-(a+b+c+d+e)≦0.840.

[0041] The soft magnetic powder of this embodiment may contain elements other than those mentioned above as inevitable impurities. For example, the soft magnetic powder may contain inevitable impurities, preferably at 1 atomic % or less. Examples of inevitable impurities include, but are not limited to, O, N, S, Mg, Ca, and Na.

[0042] The average particle size (D50) of the soft magnetic particles constituting the soft magnetic powder according to this embodiment is not particularly limited, but is preferably 1.0 to 200 μm. The circularity of the particles is also not particularly limited, and is, for example, about 0.4 to 1.0.

[0043] The circularity of particles can be determined using, for example, a Morphologi G3 (Malvern Panatical) as follows: The Morphologi G3 is an instrument that disperses powder using air and projects and evaluates the shape of each particle.

[0044] Morphologi G3 can create and evaluate projection images of many particles at once, allowing it to evaluate the shapes of many particles in a shorter time than evaluation methods such as conventional scanning electron microscope (SEM) observation. For example, it can create projection images of more than 20,000 particles, automatically calculate the circularity of each particle, and calculate the average circularity based on the number of particles.

[0045] The Morphologi G3 can also be used to determine the average particle size, D50 particle size, average aspect ratio, and the proportion of particles with a particle size of 160 μm or more. Here, D50 refers to the particle size when the cumulative number-based particle size of the particles contained in the soft magnetic powder is 50%.

[0046] As a method other than Morphologi G3, for example, an SEM image of the soft magnetic powder is taken with a scanning electron microscope (SEM), and from the obtained SEM image, the circle-equivalent diameters of 200 or more soft magnetic particles that make up the soft magnetic powder are calculated using image analysis software, and the arithmetic average value can be used as the particle size D50 of the soft magnetic powder. Also, using a similar method, the circularity of each soft magnetic particle can be calculated, and the arithmetic average value can be used as the average circularity.

[0047] The method for producing the soft magnetic powder of this embodiment will be described below with reference to FIG. 2 as needed.

[0048] First, the pure raw materials of each element contained in the soft magnetic powder to be finally obtained are prepared and weighed so as to have the same composition as the soft magnetic powder to be finally obtained. Then, the pure raw materials of each element are melted and mixed to prepare a master alloy. Note that any method for melting the pure raw materials can be used, but one method is to melt them by high-frequency heating after evacuating a chamber. Note that the master alloy and the soft magnetic powder to be finally obtained usually have the same composition.

[0049] Next, the produced master alloy is heated and melted, for example, in a container 21 shown in Fig. 2, to obtain a molten metal (molten metal). There are no particular restrictions on the temperature of the molten metal, but it can be set to, for example, 1100 to 1600°C.

[0050] In a chamber (not shown), molten metal 22 is sprayed as a continuous liquid from a container 21 through a slit nozzle formed at the bottom of the container 21 onto a roll 23 rotating in the direction of the arrow. As a result, a thin ribbon 20 is stretched uniformly in the rotation direction of the roll 23.

[0051] High-pressure water W is sprayed from a cooling nozzle 30 onto this ribbon (before cooling and hardening) 20 to rapidly cool and pulverize the ribbon 20, and the resulting pulverized powder 20a is poured into a water flow tank 34 together with the water W to convert the ribbon 20 into soft magnetic powder composed of the pulverized powder 20a. The water flow tank 34 is disposed inside the powder production chamber 32, and a mesh 36 is attached downstream of the water flow tank 34, allowing the water flowing inside the water flow tank 34 and the pulverized powder 20a to pass through the mesh 36 for classification. The classified soft magnetic powder 20b that flows out together with the water through the mesh 36 is separated from the water and collected, for example, by a magnetic collection roll 38, to obtain the soft magnetic powder 20b of this embodiment.

[0052] In this embodiment, the material of the roll 23 is not particularly limited, but is, for example, Cu. There are no particular limitations on the atmosphere inside the chamber 32, but an air atmosphere is particularly suitable for mass production.

[0053] There are no particular limitations on the shape or dimensions of the injection port of the cooling nozzle 30, and various shapes such as circular, elliptical, and rectangular can be used, but it is preferable that the injection port has a width or diameter (including the major axis) equal to or greater than the width (perpendicular to the paper surface of FIG. 2) of the ribbon 20. It is preferable to apply water W across the entire width of the ribbon 20 to crush the entire width of the ribbon.

[0054] The pressure of the sprayed water is not particularly limited as long as it can rapidly cool and pulverize the ribbon 20. However, from the viewpoint of sufficiently reducing the particle size of the soft magnetic powder, the water pressure is preferably 0.5 MPa or more, 2 MPa or more, 4 MPa or more, or 7 MPa or more. From the viewpoint of lowering Tg, the water pressure is preferably 0.5 MPa or more, 2 MPa or more, 4 MPa or more, or 7 MPa or more. It is believed that increasing the water pressure expands the supercooled liquid region and lowers Tg. Note that, from the viewpoint of recovering the pulverized soft magnetic powder 20b, the water pressure may be 10 MPa or less. The temperature of the sprayed water is not particularly limited, but from the viewpoint of rapidly cooling and pulverizing the ribbon 20, it is preferably 10 to 50°C, for example.

[0055] The quenched and pulverized ribbon becomes powder (pulverized powder) and flows to the recovery section together with the cooling water in the water flow tank 34. The recovery section is not particularly limited as long as it is equipped with a mechanism that can separate the cooling water from the soft magnetic powder. For example, as shown in FIG. 2, only the soft magnetic powder 20b may be recovered by a magnetic recovery roll 38 or the like, or by a sieve or the like. The recovery section may also be equipped with a sieve or the like to remove large particles that have not been sufficiently pulverized.

[0056] There are no particular limitations on the applications of the soft magnetic powder according to the embodiment described above. The soft magnetic powder according to the embodiment may be used alone or mixed with other soft magnetic powders to produce, for example, a toroidal magnetic core 2 as shown in FIG. 2, or a magnetic core or magnetic component having another shape.

[0057] The magnetic core may be wound with a wire and used as an inductor (particularly a power device such as a power inductor) or an electronic device such as a voltage transformer. Alternatively, the soft magnetic powder according to the above-described embodiment may be used alone or mixed with other soft magnetic powders to form a dust core with a built-in coil.

[0058] Other soft magnetic powders that may be mixed with the soft magnetic powder according to the above-described embodiment include soft magnetic powders produced by atomization, soft magnetic powders produced by spray pyrolysis, and soft magnetic powders produced by the carbonyl method.

[0059] Furthermore, examples of the soft magnetic powder composition include Fe-based crystalline compositions such as Fe, Fe-Co, Fe-Si, Fe-Ni, Fe-Ni-Mo, Fe-Si-Cr, Fe-Si-Al, Fe-Si-Al-Ni, and Fe-Ni-Si-Co; Fe-based amorphous alloy compositions; and Fe-based nanocrystalline alloy compositions such as Fe-Nb-BP-Si, Fe-Nb-B-Si-Cu, Fe-Nb-B, Fe-Si-B, Fe-Si-Cr-BC, and Fe-Si-BC.

[0060] The content of the other soft magnetic powders is preferably about 30% by mass or less of the total mass of the powder including the soft magnetic powder according to the embodiment, and is preferably 30% by area or less of the cross-sectional area of the magnetic core occupied by the total powder including the soft magnetic powder according to the embodiment.

[0061] Electronic components such as inductors having a magnetic core containing the soft magnetic powder according to the embodiment are incorporated into and used in electronic devices such as mobile phones, personal computers, etc. Examples of magnetic components other than the magnetic core include thin film inductors, magnetic heads, and magnetic shielding sheets, which are incorporated into and used in electronic devices.

[0062] There are no particular limitations on the method for obtaining the magnetic core and inductor, and one example is a method in which the soft magnetic powder according to this embodiment is mixed with a binder, a curing agent, a catalyst, a solvent, etc., and then molded using a mold. Furthermore, before mixing with the binder, the powder surface may be subjected to an oxidation treatment or an insulating coating, etc.

[0063] There are no particular restrictions on the molding method, and examples include molding using a metal mold and mold molding. There are no particular restrictions on the type of binder, and examples include epoxy resin and silicone resin. The solvent is determined depending on the type of resin, and acetone is used, for example. There are no particular restrictions on the mixing ratio of the soft magnetic powder and binder, either. For example, 100% by mass of soft magnetic powder is mixed with 1 to 10% by mass of binder.

[0064] Furthermore, in this embodiment, it is preferable to heat treat the compact for forming the magnetic core after molding. In this embodiment, it is preferable to remove distortion from the compact by heat treatment. From the viewpoint of simultaneously causing magnetic disordering and structural relaxation by heat treatment, it is preferable that the heat treatment temperature Ta is equal to or higher than the Curie temperature Tc and lower than the first crystallization temperature Tx. Tx - Ta is preferably 1°C or higher, more preferably 5°C or higher. Ta - Tc is preferably 1°C or higher, more preferably 2°C or higher, and even more preferably 4°C or higher.

[0065] The soft magnetic powder of this embodiment can reduce core loss by being heat-treated under these conditions. The heat treatment may be performed on the soft magnetic powder before it is made into a compact, and then the compact is formed. However, it is preferable to perform the heat treatment on the compact after the soft magnetic powder according to this embodiment is formed into a predetermined shape.

[0066] Furthermore, soft magnetic powder can be compacted and integrated with a magnetic body to produce an inductance component, which can easily handle high frequencies and large currents.

[0067] Furthermore, when a soft magnetic powder is used, an inductance component can be obtained by alternately printing and laminating a soft magnetic powder-containing paste prepared by adding a binder and a solvent to the soft magnetic powder and a conductive paste prepared by adding a binder and a solvent to a conductive metal for the coil, followed by heating and firing. Alternatively, an inductance component having a coil built into a magnetic body can be obtained by preparing a soft magnetic sheet using the soft magnetic powder-containing paste, printing the conductive paste on the surface of the soft magnetic sheet, laminating these to form a laminate, and firing the laminate.

[0068] The present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the present invention.

[0069] For example, the magnetic core 2 shown in Fig. 3 as an example of a magnetic component is a toroidal (ring-shaped) core, but the shape of the core is not particularly limited and can be various shapes such as a drum core, an E-shaped core, an I-shaped core, etc. These are used as magnetic cores for inductors, motors, transformers, noise suppression components, etc. [Example]

[0070] Examples of the present invention will be described below, but the present invention is not limited to these examples.

[0071] Example 1 Fe 64 Co 16 B 11 The raw materials were weighed to have a composition of P7Si2 and melted by high-frequency heating to produce a master alloy. The produced master alloy was then heated and melted using the apparatus 10 shown in Figure 2, and the temperature of the molten metal was adjusted to 1100 to 1600°C according to the alloy composition using the container 21 of the apparatus 10 shown in Figure 3. The molten metal was then sprayed onto the roll 23. The roll 23 was made of Cu, had a diameter of 250 mm, and was rotated at 1800 rpm.

[0072] The drawn metal ribbon (before cooling and hardening) was immediately cooled and pulverized by water W sprayed from a high-pressure nozzle 30, and collected by a recovery roll 38 serving as a recovery section to obtain soft magnetic powder. The nozzle opening of the high-pressure nozzle 30 was rectangular with long sides of 10 mm and short sides of 0.1 mm, and the water pressure was 0.5 MPa and the water temperature was 20°C. In other words, the soft magnetic powder was produced under the conditions listed in Table 1A. The width of the ribbon 20 was 5 mm, with the long sides of the nozzle opening of the high-pressure nozzle 30 being 10 mm or less.

[0073] The soft magnetic powder thus obtained was evaluated as follows.

[0074] (D50, circularity) SEM images of the soft magnetic powder were taken using a scanning electron microscope (SEM). From the obtained SEM images, the equivalent circle diameters of 200 or more soft magnetic particles constituting the soft magnetic powder were calculated using image analysis software, and the arithmetic mean value was used as the particle size D50 of the soft magnetic powder. In addition, the circularity of each soft magnetic particle was calculated, and the arithmetic mean value was used as the average circularity. The results are shown in Table 1B.

[0075] (Tc, Tg, Tx) The Curie temperature Tc, glass transition temperature Tg, and first crystallization temperature Tx were determined by DSC (differential scanning calorimetry) analysis using the method described above. The results are shown in Table 1B.

[0076] Furthermore, dust cores were produced using the obtained soft magnetic powders according to the following procedure, and the core loss was evaluated.

[0077] (Preparation of powder core) To 100% by mass of the obtained soft magnetic powder, 1.0% by mass of silicone resin was added and kneaded in a kneader to produce granules. This was filled into a toroidal mold with an outer diameter of 17.5 mm and an inner diameter of 11.0 mm and pressed at a molding pressure of 1180 MPa to obtain a compact. The core weight was 1 g. The obtained compact was heat-treated in a belt furnace at 485°C for 30 minutes in a nitrogen atmosphere to produce a powder core.

[0078] The core loss of the powder cores before and after the heat treatment was measured using a BH analyzer at a measurement frequency of 100 kHz and a magnetic flux density of 50 mT. The reduction rate of core loss due to the heat treatment was calculated. The results are shown in Table 1B.

[0079] Examples 2 to 9 As shown in Table 1A, except that the water pressure used to pulverize the ribbon was changed to 1 to 10 MPa, soft magnetic powders and dust cores were produced and evaluated in the same manner as in Example 1. The results are shown in Table 1B.

[0080] [Table 1A]

[0081] [Table 1B]

[0082] Comparative Example 1 An alloy ribbon having the same composition as in Example 1 was obtained by a conventional single-roll method (roll rotation speed: 1800 rpm). For the obtained alloy ribbon, Tc, Tg, and Tx were measured in the same manner as in Example 1, except that the powder was replaced with a ribbon. The results are shown in Table 1B.

[0083] Comparative Example 2 The alloy ribbon after cooling and hardening shown in Comparative Example 1 was pulverized in a ball mill, and the pulverization conditions were changed and the resultant was classified so as to obtain a soft magnetic powder having a D50 and circularity equivalent to those of Example 4. The obtained soft magnetic powder was used to prepare a dust core in the same manner as in Example 1. The obtained soft magnetic powder and dust core were evaluated in the same manner as in Example 1. The results are shown in Table 1B.

[0084] Comparative Examples 3 to 11 Soft magnetic powders having the same composition and equivalent D50 as those in Examples 1 to 9 were produced by gas atomization or water atomization. The obtained soft magnetic powders were used to produce dust cores in the same manner as in Example 1. The obtained soft magnetic powders and dust cores were evaluated in the same manner as in Example 1. The results are shown in Table 1B.

[0085] Rating 1 The results shown in Table 1B indicate that the soft magnetic powders of each example can reduce core loss by heat treatment compared to comparative examples with equivalent D50 and circularity. This is thought to be because, when removing distortion during compaction by heat treatment, Tc, Tg, and Tx satisfy a predetermined relationship, which makes it possible to simultaneously achieve magnetic disordering and structural relaxation.

[0086] It was also found that as the water pressure during pulverization was increased, the ribbons were pulverized more finely, the particle size became smaller, and the circularity tended to increase. It was also found that as the water pressure increased, the Tg of the soft magnetic powder tended to decrease. This is thought to be because the soft magnetic powder was cooled more rapidly.

[0087] Examples 10 to 12 In Examples 10 to 12, soft magnetic powders and dust cores were produced in the same manner as in Example 7, and evaluations were performed in the same manner as in Example 7, except that the temperature of the water used to pulverize and cool the ribbon was varied within the range of 10 to 50°C as shown in Table 2A. The results are shown in Table 2B.

[0088] [Table 2A]

[0089] [Table 2B]

[0090] Examples 13 to 15 In Examples 13 to 15, except that the shape of the nozzle for spraying water to pulverize and cool the ribbon was changed as shown in Table 2A, soft magnetic powders and dust cores were produced in the same manner as in Example 7, and evaluations were performed in the same manner as in Example 1. The results are shown in Table 2B.

[0091] Examples 16 to 18 In Examples 16 to 18, soft magnetic powders and dust cores were prepared in the same manner as in Example 7, except that the roll rotation speed was changed within the range of 1600 to 2200 rpm as shown in Table 2A, and evaluations were carried out in the same manner as in Example 7. The results are shown in Table 2B.

[0092] Rating 2 From the results of each example shown in Table 2B, it was found that when Tc, Tg, and Tx satisfy a predetermined relationship, the core loss can be effectively reduced by heat treatment in all cases.

[0093] Furthermore, the results of Examples 10 to 12 show that core loss can be effectively reduced even if the temperature of water used to pulverize the ribbon is varied within the range shown in Table 2A. The results of Examples 13 to 15 show that the particle size of the soft magnetic powder can be adjusted by the nozzle shape. The results of Examples 16 to 18 show that the particle size of the soft magnetic powder can be adjusted by the roll rotation speed.

[0094] Examples 19 to 23 The soft magnetic powder obtained in Example 1 was further classified and adjusted so that the average particle size D50 would be the value shown in Table 3, thereby obtaining soft magnetic powders according to Examples 19 to 23. Dust cores were produced using the obtained soft magnetic powder, and the soft magnetic powder and dust cores were evaluated in the same manner as in Example 1. The results are shown in Table 3.

[0095] Examples 24-25 The soft magnetic powder obtained in Example 7 was further classified and the average particle size D50 was adjusted to the values shown in Table 3, thereby obtaining soft magnetic powders according to Examples 24 and 25. Dust cores were produced using the obtained soft magnetic powder, and the soft magnetic powder and dust cores were evaluated in the same manner as in Example 1. The results are shown in Table 3.

[0096] [Table 3]

[0097] Rating 3 The results shown in Table 3 show that even when the particle size is adjusted by classification or other means, the soft magnetic powder has similar thermodynamic properties, i.e., Tc, Tg, and Tx satisfy the specified relationships, and that core loss can be effectively reduced in all cases by heat treatment.

[0098] Examples 26 to 34 Except that the raw materials were weighed so that the master alloy had the composition shown in Table 4 and the heat treatment temperature of the compacted core was adjusted to Tx - 5°C, soft magnetic powder and compacted core were produced and evaluated in the same manner as in Example 7. The results are shown in Table 4.

[0099]

Table 4

[0100] Examples 35 to 51 Except that the raw materials were weighed so that the master alloy had the composition shown in Table 5 and the heat treatment temperature of the compacted core was adjusted to Tx - 5°C, soft magnetic powder and compacted core were produced in the same manner as in Example 7, and evaluated in the same manner as in Example 1. The results are shown in Table 5.

[0101]

Table 5

[0102] Examples 52 to 66 Except that the raw materials were weighed so that the master alloy had the composition shown in Table 6 and the heat treatment temperature of the compacted core was adjusted to Tx - 5°C, soft magnetic powder and compacted core were produced in the same manner as in Example 7, and evaluated in the same manner as in Example 1. The results are shown in Table 6.

[0103]

Table 6

[0104] Rating 4 From the results of each example shown in Tables 4 to 6, it was found that even when the soft magnetic powder has various compositions (variables of B, P, Si and / or Nb), the core loss can be reduced by satisfying a predetermined structure (Tg ≤ Tc < Tx).

[0105] Examples 67 to 88 Comparing with Example 7, soft magnetic powder and a compacted core were produced in the same manner as in Example 64, except that raw materials were weighed so that the master alloy had the composition shown in Table 7, and the same evaluation as in Example 1 was performed. The results are shown in Table 7.

[0106] [Table 7]

[0107] Rating 5 From the results shown in Table 7, it was found that even when the soft magnetic powder contains various X1, the core loss can be reduced by satisfying a predetermined configuration (Tg ≤ Tc < Tx).

[0108] Examples 90 to 125 Soft magnetic powder and a compacted core were produced in the same manner as in Example 7, except that raw materials and additives were changed so that the elements shown in Table 8 were contained at 0.01 to 1.0 at% based on the total number of atoms of the soft magnetic powder, and the same evaluation as in Example 1 was performed. The results are shown in Table 8.

[0109] [Table 8]

[0110] Rating 6 From the results shown in Table 8, it was found that even when the soft magnetic powder contains impurities within a predetermined range (for example, 1.0 at% or less), the core loss can be reduced by satisfying a predetermined configuration (Tg ≤ Tc < Tx). [Explanation of Signs]

[0111] 2... Magnetic core 20... Thin strip 20a... Pulverized powder 20b... Soft magnetic powder 21... Container 22... Molten metal 23... Roll 30... Water flow nozzle 32...Chamba 34…water tank 36...Mesh 38... Recovery roll

Claims

1. A soft magnetic powder containing one or more elements selected from the group consisting of Fe, Co, and Ni as a main component, The glass transition temperature of the soft magnetic powder is represented by Tg, the Curie point by Tc, and the first crystallization temperature by Tx, A soft magnetic powder that satisfies Tg≦Tc<Tx.

2. The main component of the soft magnetic powder is Fe. 1-( α + β ) Coα Niβ (atomic ratio), ０≦α＋β＜１ ０≦α≦０．６ ０≦β≦０．６ 2. The soft magnetic powder according to claim 1, which satisfies the following:

3. Formula (Fe 1-( α + β ) Coα Niβ ) 1-(a+b+c+d) B a P b Si c C d X1 e (atomic ratio), X1 is one or more selected from Ti, Zr, Hf, Nb, Ta, Mo, W, Al, Ga, Ag, Zn, Cr, Mn, V, Sn, As, Sb, Bi, Au, Cu, rare earth elements, and platinum group elements; 0.020≦a≦0.16, 0.01≦b≦0.16, 0≦c≦0.100, 0≦d≦0.07, 0≦e≦0.07, ０≦α≦０．６００、 0≦β≦0.600, and 0.760≦1-(a+b+c+d+e)≦0.840, 2. The soft magnetic powder according to claim 1, which satisfies the following:

4. Tc-Tg≧1 2. The soft magnetic powder according to claim 1, further satisfying the above.

5. Tx-Tc≧1 2. The soft magnetic powder according to claim 1, further satisfying the above.

6. A magnetic core comprising the soft magnetic powder according to any one of claims 1 to 5.

7. A magnetic part comprising the soft magnetic powder according to any one of claims 1 to 5.

8. An electronic device comprising the soft magnetic powder according to any one of claims 1 to 5.

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