Soft magnetic powder, dust core, magnetic element, and electronic device

Abstract

Provided are a soft magnetic powder, a dust core, a magnetic element, and an electronic device with which it is possible to produce a dust compact having excellent oxidation resistance and good density, coercive force, and DC superposition characteristics. The soft magnetic powder is composed of a composition represented by the compositional formula FexCuaNbb (Si1-y (B1-zCrz) y) 100-x-a-b [a, b, x, y, and z are 0.3 < = a < = 2.0, 2.0 < = b < = 4.0, 75.5 < = x < = 79.5, 0.55 < = y < = 0.91, and 0.015 < = z < = 0.185], and has an average particle diameter of 5.0 [mu] m to 45.0 [mu] m, a crystallite diameter measured by X-ray diffraction of 5.0 nm to 20.0 nm, and a magnetic permeability reduction rate d represented by the following formula of 3.0% or less. D = [mu] 1-[mu] 100 / [mu] 1 * 100 ([mu] 1 and [mu] 100 are the magnetic permeability measured at 1 MHz and 100 MHz, respectively).

Description

Technical Field

[0001] The present invention relates to soft magnetic powder, pressed powder magnetic core, magnetic element and electronic equipment. Background Art

[0002] Patent Document 1 discloses a soft magnetic powder comprising amorphous metal particles having a composition formula of Fe 100-a-b-c-d-e-f-g Cr a Si b B c C d Al e Ti f Co g [Wherein, a, b, c, d, e, f, and g are numbers representing atomic % and satisfy 0 < a ≤ 3.0, 5.0 ≤ b ≤ 15.0, 7.0 ≤ c ≤ 15.0, 0.1 ≤ d ≤ 3.0, 0 < e ≤ 0.016, 0 < f ≤ 0.009, and 0 ≤ g ≤ 0.025.] This structure produces a soft magnetic powder that has excellent magnetic properties derived from an amorphous alloy and achieves low coercivity.

[0003] Patent Document 1 also discloses heat treatment during the production of soft magnetic powder. This heat treatment can reduce various defects and anisotropy (stress-induced anisotropy) introduced during the production of soft magnetic powder. This can lower the coercivity. Furthermore, Patent Document 1 discloses setting the heating temperature during the heat treatment to a temperature lower than the crystallization temperature of the amorphous metal particles.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2022-175110.

[0007] However, from the perspective of reliably achieving further reductions in coercivity, the method for producing soft magnetic powder described in Patent Document 1 still leaves room for improvement. For example, even after heat treatment, the coercivity of some particles may not be sufficiently reduced. Therefore, achieving a soft magnetic powder with reliably reduced coercivity remains a technical challenge.

[0008] Furthermore, a decrease in the density of the powder compact and a decrease in the DC superposition characteristics due to oxidation cause a decrease in the operational stability of a magnetic component using the powder compact.

[0009] Therefore, it has become a technical problem to realize a soft magnetic powder capable of producing a green compact having excellent oxidation resistance, density, coercive force, and DC superposition characteristics. Summary of the Invention

[0010] The soft magnetic powder according to the application example of the present invention is

[0011] Composition formula expressed by atomic ratio Fe x Cu a Nb b (Si 1-y (B 1-z Cr z ) y ) 100-x-a-b The composition and impurity composition of

[0012] [a, b, x, y, z satisfy

[0013] 0.3≤a≤2.0,

[0014] 2.0≤b≤4.0,

[0015] 75.5≤x≤79.5,

[0016] 0.55≤y≤0.91,

[0017] 0.015≤z≤0.185.]

[0018] The average particle size is 5.0 μm or more and 45.0 μm or less,

[0019] The crystallite diameter measured by X-ray diffraction is 5.0 nm or more and 20.0 nm or less,

[0020] By mixing with epoxy resin with a mass ratio of 2.0 mass%, and 2 ) pressure to obtain a first annular molded body with an outer diameter of 14 mm, an inner diameter of 8 mm and a thickness of 3 mm, and then 7 turns of a 0.6 mm diameter wire are wound around the first molded body to produce a first test body. The reduction rate d of the magnetic permeability expressed by the following formula is less than 3.0%.

[0021] d=|μ1-μ 100 | / μ1×100

[0022] [In the above formula, μ1 is the magnetic permeability of the first test object measured at a frequency of 1 MHz, μ 100 is the magnetic permeability of the first test object measured at a frequency of 100 MHz.]

[0023] The dust core according to the application example of the present invention contains the soft magnetic powder according to the application example of the present invention.

[0024] A magnetic element according to an application example of the present invention includes the powder magnetic core according to the application example of the present invention.

[0025] An electronic device according to an application example of the present invention includes the magnetic element according to the application example of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is an example of a DSC curve obtained from the metal powder according to the embodiment.

[0027] Figure 2 It is a plan view schematically showing a ring-shaped coil component.

[0028] Figure 3 It is a perspective view schematically showing a closed magnetic circuit type coil component.

[0029] Figure 4 It is a perspective view showing the structure of a mobile personal computer as an electronic device according to the embodiment.

[0030] Figure 5 It is a plan view showing the structure of a smartphone as an electronic device according to the embodiment.

[0031] Figure 6 It is a perspective view showing the structure of a digital camera as an electronic device according to the embodiment.

[0032] Explanation of symbols

[0033] 10. Coil component; 11. Pressed powder core; 12. Conductive wire; 20. Coil component; 21. Pressed powder core; 22. Conductive wire; 100. Display unit; 1000. Magnetic element; 1100. Personal computer; 1102. Keyboard; 1104. Main body; 1106. Display unit; 1200. Smart phone; 1202. Operation button; 1204. Earpiece; 1206. Microphone; 1300. Digital camera; 1302. Housing; 1304. Light receiving unit; 1306. Shutter button; 1308. Memory; L1. DSC curve; L2. DSC curve; L3. DSC curve; L4. DSC curve; L5. DSC curve; P1. First heating peak; P2. Second heating peak; Tx1. Temperature; Tx2. Temperature. DETAILED DESCRIPTION

[0034] Hereinafter, the soft magnetic powder, metal powder, powder magnetic core, magnetic element, and electronic device of the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.

[0035] 1. Soft magnetic powder

[0036] The soft magnetic powder according to the embodiment is a metal powder exhibiting soft magnetism. This soft magnetic powder can be used for any purpose, but is used, for example, to manufacture various powder compacts such as powder cores and electromagnetic wave absorbers by binding particles together with a binder.

[0037] The soft magnetic powder according to the embodiment is composed of a composition formula of Fe x Cu a Nb b (Si 1-y (B 1-z Cr z ) y ) 100-x-a-b Indicates the composition and impurity composition.

[0038] [a, b, x, y, z satisfy

[0039] 0.3≤a≤2.0,

[0040] 2.0≤b≤4.0,

[0041] 75.5≤x≤79.5,

[0042] 0.55≤y≤0.91,

[0043] 0.015≤z≤0.185.]

[0044] Furthermore, the average particle size of the soft magnetic powder according to the embodiment is 5.0 μm or more and 45.0 μm or less.

[0045] Furthermore, the soft magnetic powder according to the embodiment has a crystallite (ie, fine single crystal) diameter of 5.0 nm or more and 20.0 nm or less as measured by X-ray diffraction.

[0046] By primarily adding an optimal amount of Cr (chromium) to this soft magnetic powder, the powder's oxidation resistance is enhanced. As a result, when the soft magnetic powder is compacted, the density of the compacted powder, which is reduced by oxides, can be suppressed. Furthermore, by optimizing the amounts of each element added, the crystallite diameter in the soft magnetic powder is controlled to be neither too small nor too large. Consequently, an increase in the coercivity of the soft magnetic powder can be suppressed.

[0047] Furthermore, the soft magnetic powder according to the embodiment is a powder such that when formed into a first ring-shaped compact together with a binder, the magnetic permeability of the first compact satisfies a predetermined value. The magnetic permeability is evaluated as follows.

[0048] First, an epoxy resin in an amount corresponding to 2.0% by mass of the soft magnetic powder according to the embodiment is mixed with the soft magnetic powder, and the obtained mixture is heated at 294.2 MPa (3t / cm 2 ) is stamped under a pressure of . Thus, a first molded body with an outer diameter of 14 mm, an inner diameter of 8 mm, a thickness of 3 mm and a relative density of 66% is obtained. It should be noted that the relative density refers to the relative value obtained by dividing the density obtained by dividing the mass of the first molded body by the volume by the true density of the soft magnetic powder. Then, 7 turns of a wire with a wire diameter of 0.6 mm are wound on the obtained first molded body to produce a first test body. Then, the magnetic permeability of the first test body is measured at a frequency of 1 MHz and a frequency of 100 MHz respectively. In addition, in the soft magnetic powder involved in the embodiment, the reduction rate d of the magnetic permeability expressed by the following formula is less than 3.0%.

[0049] d=|μ1-μ 100 | / μ1×100

[0050] [In the above formula, μ1 is the magnetic permeability of the first test object measured at a frequency of 1 MHz, μ 100 is the magnetic permeability of the first test object measured at a frequency of 100 MHz.]

[0051] This structure makes it difficult for magnetic elements made of soft magnetic powder to experience magnetic saturation even when a DC current is applied to the coil. Therefore, using the soft magnetic powder of the embodiment enables the manufacture of magnetic elements with good DC superposition characteristics and excellent operational stability.

[0052] Hereinafter, the soft magnetic powder according to the embodiment will be described in detail.

[0053] 1.1. Composition

[0054] Fe (iron) has a significant influence on the basic magnetic properties and mechanical properties of the soft magnetic powder according to the embodiment.

[0055] The Fe content x is 75.5 atomic % or more and 79.5 atomic % or less, preferably 76.0 atomic % or more and 78.5 atomic % or less, and more preferably 76.5 atomic % or more and 78.0 atomic % or less. It should be noted that if the Fe content x is below the lower limit, the saturation magnetic flux density of the soft magnetic powder decreases. On the other hand, if the Fe content x is above the upper limit, an amorphous structure cannot be stably formed during the production of the soft magnetic powder, and the crystallite diameter becomes too large, resulting in an increase in coercivity.

[0056] Cu (copper) tends to separate from Fe when producing the soft magnetic powder of the embodiment from raw materials. Therefore, the inclusion of Cu causes fluctuations in the composition, creating regions within the particles that are prone to partial crystallization. This results in the precipitation of the relatively easily crystallized body-centered cubic Fe phase, facilitating the formation of grains with the aforementioned crystallite diameter.

[0057] The Cu content a is from 0.3 atomic % to 2.0 atomic %, preferably from 0.5 atomic % to 1.5 atomic %, and more preferably from 0.7 atomic % to 1.3 atomic %. It should be noted that if the Cu content a is below the lower limit, grain refinement is impaired, and grains with a crystallite diameter within the aforementioned range cannot be formed. On the other hand, if the Cu content a exceeds the upper limit, the mechanical properties of the soft magnetic powder are reduced, resulting in brittleness.

[0058] When Nb (niobium) is subjected to heat treatment from a state containing a large amount of amorphous structure, it contributes to the refinement of crystal grains together with Cu, thereby easily forming crystal grains having the aforementioned crystallite diameter.

[0059] The Nb content b is from 2.0 atomic % to 4.0 atomic %, preferably from 2.5 atomic % to 3.5 atomic %, and more preferably from 2.7 atomic % to 3.3 atomic %. It should be noted that if the Nb content b is below the lower limit, grain refinement is impaired, and grains with a crystallite diameter within the aforementioned range cannot be formed. On the other hand, if the Nb content b exceeds the upper limit, the mechanical properties of the soft magnetic powder deteriorate, resulting in brittleness. Furthermore, the magnetic permeability of the soft magnetic powder decreases.

[0060] Si (silicon) promotes amorphization when manufacturing the soft magnetic powder of the embodiment from raw materials. Therefore, when manufacturing the soft magnetic powder of the embodiment, a homogeneous amorphous structure is temporarily formed. Subsequently, crystallization facilitates the formation of grains with more uniform crystallite diameters. A uniform crystallite diameter helps average out the crystalline magnetic anisotropy within each grain, thereby reducing coercivity and increasing magnetic permeability, contributing to improved soft magnetic properties.

[0061] Boron (B) promotes amorphization when manufacturing the soft magnetic powder of the embodiment from raw materials. Therefore, when manufacturing the soft magnetic powder of the embodiment, a homogeneous amorphous structure is temporarily formed. Subsequently, crystallization facilitates the formation of grains with more uniform crystallite diameters. As a result, coercivity can be reduced and magnetic permeability increased, achieving improved soft magnetic properties. Furthermore, the combined use of Si and B can synergistically promote amorphization due to the difference in their atomic radii.

[0062] Cr (chromium) improves the oxidation resistance of soft magnetic powder. This prevents the density of the compacted powder from decreasing due to oxides when the soft magnetic powder is compacted. Consequently, the influence of oxides on magnetic properties can be suppressed. Furthermore, by optimizing the Cr content, the crystallite diameter in the soft magnetic powder can be controlled so that it is neither too small nor too large. Consequently, an increase in the coercive force of the soft magnetic powder can be suppressed. Furthermore, by adding Cr, the Si content is relatively reduced, stabilizing the magnetic permeability over a wide frequency range. This improves the DC superposition characteristics.

[0063] Furthermore, the total content of Si, B, and Cr (Si+B+Cr) is set to 1, and the ratio of the total content of B and Cr (B+Cr) to the total content (Si+B+Cr) is set to y.

[0064] y satisfies 0.55 ≤ y ≤ 0.91, preferably 0.60 ≤ y ≤ 0.90, and more preferably 0.65 ≤ y ≤ 0.80. This allows for a balanced amount of Si, B, and Cr. Consequently, the oxidation resistance and magnetic permeability of the soft magnetic powder can be improved in a well-balanced manner.

[0065] If y is below the lower limit, oxidation resistance decreases, the crystallite diameter becomes too small, and the magnetic permeability decreases. On the other hand, if y is above the upper limit, the crystallite diameter becomes too large, and the coercivity increases.

[0066] In addition, the ratio of the Cr content to the total content (B+Cr) is represented by z.

[0067] z satisfies 0.015 ≤ z ≤ 0.185, preferably 0.030 ≤ z ≤ 0.150, and more preferably 0.045 ≤ z ≤ 0.120. This allows for a balanced balance between the amounts of B and Cr. Consequently, both the oxidation resistance and magnetic permeability of the soft magnetic powder can be improved in a well-balanced manner.

[0068] If z is below the lower limit, oxidation resistance decreases, the crystallite diameter becomes too small, and the magnetic permeability decreases. On the other hand, if z is above the upper limit, the crystallite diameter becomes too large, and the coercivity increases.

[0069] The Si content is preferably 1.5 atomic % to 14.0 atomic %, more preferably 3.0 atomic % to 10.0 atomic %, and even more preferably 4.0 atomic % to 8.0 atomic %. This allows for the production of a soft magnetic powder that can produce a green compact with lower coercivity and improved DC superposition characteristics.

[0070] The B content is preferably 5.0 atomic % to 17.0 atomic %, more preferably 7.0 atomic % to 16.0 atomic %, and even more preferably 9.0 atomic % to 13.5 atomic %. This allows for the production of a soft magnetic powder having a lower coercive force and improved DC superposition characteristics.

[0071] The Cr content is preferably from 0.3 atomic % to 2.7 atomic %, more preferably from 0.5 atomic % to 2.2 atomic %, and even more preferably from 0.8 atomic % to 1.8 atomic %. This further improves the oxidation resistance of the soft magnetic powder and minimizes the formation of oxides. Consequently, the crystallite diameter of the grains contained in each particle can be appropriately controlled.

[0072] The soft magnetic powder according to the embodiment has the composition formula Fe x Cu a Nb b (Si 1-y (B 1-z Cr z ) y ) 100-x-a-b In addition to the composition shown, impurities may also be contained. As impurities, all elements other than the above can be listed, but the total content of the impurities is preferably 0.50 atomic % or less. If within this range, even if impurities are mixed in, it is difficult to hinder the above effect, so it is allowed to contain.

[0073] Furthermore, the content of each element included in the impurities is preferably 0.05 atomic % or less. Within this range, the impurities are unlikely to inhibit the above-mentioned effects, and thus their inclusion is permitted.

[0074] Furthermore, among the impurities, the oxygen content is preferably 1500 ppm or less, more preferably 800 ppm or less. When the oxygen content is within the above range, the generation of oxides that may cause a decrease in the density of the molded body can be suppressed to a very low level.

[0075] As mentioned above, the soft magnetic powder according to the embodiment has been described. The above-mentioned composition and impurities are determined by the following analysis method.

[0076] Examples of the analysis method include the atomic absorption spectrometry for iron and steel specified in JIS G 1257:2000, the inductively coupled plasma emission spectrometry for iron and steel specified in JIS G 1258:2007, the spark discharge emission spectrometry for iron and steel specified in JIS G 1253:2002, the fluorescent X-ray analysis for iron and steel specified in JIS G 1256:1997, and the gravimetric titration-absorptiometry specified in JIS G1211 to G1237.

[0077] Specifically, for example, there can be mentioned a solid-state emission spectrometer manufactured by SPECTRO, particularly a spark discharge emission spectrometer (model: SPECTROLAB, type: LAVMB08A), or an inductively coupled plasma analyzer CIROS120 manufactured by Rigaku Corporation.

[0078] In particular, when determining C (carbon) and S (sulfur), the oxygen stream combustion (high-frequency induction heating furnace combustion)-infrared absorption method specified in JIS G 1211: 2011 may be used. Specifically, the carbon and sulfur analyzer CS-200 manufactured by LECO Corporation can be used.

[0079] In particular, when determining N (nitrogen) and O (oxygen), the Nitrogen Quantification Method for Iron and Steel specified in JIS G 1228:1997 and the General Rules for Oxygen Quantification Method for Metal Materials specified in JIS Z 2613:2006 can also be used. Specific examples include the TC-300 / EF-300 oxygen and nitrogen analyzer manufactured by LECO and the ONH836 oxygen, nitrogen, and hydrogen analyzer manufactured by LECO.

[0080] Particle size

[0081] The average particle size of the soft magnetic powder according to the embodiment is 5.0 μm or more and 45.0 μm or less, preferably 7.0 μm or more and 30.0 μm or less, and more preferably 10.0 μm or more and 20.0 μm or less.

[0082] By using soft magnetic powder with such an average particle size, the path through which eddy currents flow can be shortened, thereby enabling the manufacture of magnetic components that can effectively suppress eddy current losses. Furthermore, the filling rate of the soft magnetic powder in the powder compact can be increased, facilitating the improvement of the magnetic permeability and saturation magnetic flux density of the powder core.

[0083] Furthermore, when the soft magnetic powder has an average particle size of 10 μm or greater, mixing it with a soft magnetic powder having a smaller average particle size than the soft magnetic powder of the embodiment can achieve a higher compact density, thereby facilitating further improvement in the saturation magnetic flux density and magnetic permeability of the dust core.

[0084] The average particle size of the soft magnetic powder refers to a particle size D50 at which the cumulative frequency from the smaller diameter side is 50% in the volume-based cumulative particle size distribution of the soft magnetic powder obtained using a laser diffraction particle size distribution analyzer.

[0085] If the average particle size of the soft magnetic powder is below the lower limit, the soft magnetic powder becomes too fine, which may reduce the filling capacity of the soft magnetic powder. This reduces the compact density of the dust core, and depending on the composition and mechanical properties of the soft magnetic powder, the magnetic permeability and saturation flux density of the dust core may also decrease. On the other hand, if the average particle size of the soft magnetic powder is above the upper limit, depending on the composition and mechanical properties of the soft magnetic powder, eddy current losses generated within the particles may not be sufficiently suppressed, which may increase the iron loss of the magnetic element.

[0086] 1.3. Crystallite diameter

[0087] The soft magnetic powder involved in the embodiment has a crystallite diameter of 5.0 nm or more and 20.0 nm or less as measured by X-ray diffraction. If the crystallite diameter is within this range, the crystallite diameter of the soft magnetic powder is optimized, so even if the content of Si, which has the effect of increasing magnetic permeability, is relatively low, the reduction in magnetic permeability can be suppressed. In addition, the crystalline magnetic anisotropy of each grain is easily averaged, and a soft magnetic powder with low coercive force can be obtained. In addition, a soft magnetic powder with stable magnetic permeability in a wide frequency range can be achieved. As a result, magnetic saturation is difficult to occur, and thus a soft magnetic powder that can realize a magnetic element with good DC superposition characteristics and excellent operational stability can be obtained.

[0088] The crystallite diameter in the soft magnetic powder is preferably 6.0 nm or more and 13.0 nm or less, and more preferably 8.0 nm or more and 11.0 nm or less.

[0089] The crystallite diameter is measured using X-ray diffraction. X-ray diffraction patterns are obtained for the soft magnetic powder and a standard sample, and the diffraction line width attributed to Fe is estimated. The crystallite diameter is then calculated using the Scherrer method. The X-ray diffraction pattern obtained for the standard sample is used to estimate the diffraction line width attributed to the instrument. This diffraction line width is used to calibrate the crystallite diameter calculated from the soft magnetic powder.

[0090] The individual particles comprising the soft magnetic powder according to the embodiments contain crystal grains having the aforementioned crystallite diameter, but may also contain an amorphous structure. The coexistence of crystal grains and an amorphous structure further reduces the magnetostriction of the soft magnetic powder. As a result, a soft magnetic powder can be obtained whose magnetic permeability is not easily reduced, even with a low Si content.

[0091] 1.4 Magnetic permeability

[0092] In the soft magnetic powder according to the embodiment, when the magnetic permeability of the first test object is measured at a frequency of 1 MHz, the magnetic permeability is preferably 15 or more and less than 21, more preferably 16 or more and less than 20, and even more preferably 17 or more and less than 20.

[0093] This structure, by primarily optimizing the Si content in the soft magnetic powder, is believed to reduce the occurrence of magnetic saturation over a wide frequency range. Consequently, magnetic elements manufactured using soft magnetic powders can achieve excellent DC superposition characteristics when a DC current is superimposed on the coil.

[0094] The magnetic permeability is measured using an impedance analyzer (4294A, manufactured by Keysight Technology Co., Ltd.) or the like.

[0095] In addition, in the soft magnetic powder involved in the embodiment, when the magnetic permeability of the aforementioned first test body is measured at a frequency of 100 MHz, the magnetic permeability is preferably 15 or more and less than 21, more preferably 16 or more and less than 20, and even more preferably 17 or more and less than 20.

[0096] With such a structure, it is possible to obtain a soft magnetic powder that can realize a magnetic element that can be used in a wide frequency range and can be miniaturized.

[0097] In the soft magnetic powder according to the embodiment, the decrease rate of magnetic permeability when the frequency is increased from 1 MHz to 100 MHz is 3.0% or less, preferably 2.5% or less, and more preferably 2.0% or less, as described above.

[0098] 1.5 DC superposition characteristics

[0099] When the soft magnetic powder according to the embodiment is molded together with a binder to produce a second ring-shaped molded body, the DC superposition characteristics of the second molded body preferably satisfy predetermined conditions. The DC superposition characteristics are evaluated as follows.

[0100] First, an epoxy resin in an amount corresponding to 2.0% by mass of the soft magnetic powder according to the embodiment is mixed with the soft magnetic powder, and the obtained mixture is heated at 294.2 MPa (3t / cm 2) is stamped under pressure. Thus, a second molded body in the shape of a ring with an outer diameter of 28 mm, an inner diameter of 14 mm, and a thickness of 5 mm is obtained. Next, after placing the obtained second molded body in a resin shell, 50 turns of a wire with a wire diameter of 1.25 mm are wound on the shell to make a second test body. Next, an AC signal with a frequency of 10 kHz is passed through the second test body, and the inductance when no DC bias current is superimposed is used as a reference value. Next, the inductance is measured while gradually increasing the DC bias current superimposed on the second test body. In addition, when the measured value drops to 80% of the reference value (the reference value is regarded as 100%, and the measured value drops to 80%), the DC bias current superimposed on the second test body is measured. In this specification, the DC bias current at this time is referred to as "DC superimposition allowable current" as an indicator for evaluating DC superimposition characteristics.

[0101] In the soft magnetic powder according to the embodiment, the DC bias current is preferably 17 A or greater, more preferably 18 A or greater and 24 A or less, and even more preferably 19 A or greater and 22 A or less. If the DC bias current is within this range, it is considered that a sufficiently high DC bias current can be applied. Therefore, a soft magnetic powder with a DC bias current within this range can achieve a magnetic element with sufficiently high DC bias characteristics and excellent operational stability.

[0102] It should be noted that the DC superposition allowable current may be higher than the upper limit value. However, in this case, the production difficulty of the soft magnetic powder becomes higher, which may lead to an increase in production cost and a decrease in production yield.

[0103] As the DC power supply, two DC stabilized power supplies (EX-1500H manufactured by Takasago, Ltd.) connected in parallel were used. As the inductance measurement device, an impedance analyzer (4294A manufactured by Keysight Technology, Ltd.) was used.

[0104] 1.6 Coercive force

[0105] The coercivity of the soft magnetic powder according to the embodiment is not particularly limited, but is preferably less than 2.00 [Oe] (less than 160 [A / m]), and more preferably is greater than or equal to 0.10 [Oe] and less than or equal to 1.67 [Oe] (greater than or equal to 39.9 [A / m] and less than or equal to 133 [A / m]). By using such a soft magnetic powder with a low coercivity, it is possible to manufacture a magnetic element that can sufficiently suppress hysteresis loss even at high frequencies.

[0106] The coercive force of the soft magnetic powder can be measured by, for example, a vibrating sample magnetometer such as TM-VSM1230-MHHL manufactured by Tamagawa Seisakusho Co., Ltd.

[0107] 1.7. Saturation magnetic flux density

[0108] The saturation magnetic flux density of the soft magnetic powder according to the embodiment is preferably 1.20 [T] or higher, more preferably 1.25 [T] or higher, further preferably 1.28 [T] or higher, and particularly preferably 1.30 [T] or higher. This allows for the production of a magnetic element that is less susceptible to saturation even under high current.

[0109] The saturation magnetic flux density of the soft magnetic powder is measured, for example, by the following method.

[0110] First, the true specific gravity (ρ) of the soft magnetic powder was measured using a fully automatic gas displacement densitometer (AccuPyc 1330, manufactured by Micromeritics). Next, the maximum magnetization (Mm) of the soft magnetic powder was measured using a vibrating sample magnetometer (VSM system, TM-VSM1230-MHHL, manufactured by Tamagawa Seisakusho Co., Ltd.). The saturation magnetic flux density (Bs) was then calculated using the following formula.

[0111] Bs=4π / 10000×ρ×Mm

[0112] 1.8. Density of molded body

[0113] The soft magnetic powder according to the embodiment is mixed with an epoxy resin in an amount corresponding to 2.0% by mass of the epoxy resin, and the obtained mixture is heated at 294.2 MPa (3t / cm 2 The density of the third molded body obtained by stamping under the pressure of ) is preferably 4.99 g / cm 3 More than 5.01 g / cm 3 Above and 5.20g / cm 3 If the density of the third compact is within the above range, the oxide content in the third compact is sufficiently suppressed, resulting in a sufficient alloy content. This further improves the magnetic permeability and saturation magnetic flux density of the magnetic element.

[0114] It should be noted that the soft magnetic powder according to the embodiment may be mixed with other soft magnetic powders and non-soft magnetic powders to be used as mixed powder for various applications.

[0115] 2. Method for producing soft magnetic powder

[0116] Next, an example of a method for producing the soft magnetic powder according to the above embodiment will be described.

[0117] Soft magnetic powders can be produced by any method. Examples of production methods include various atomization methods, such as water atomization, rotating water flow atomization, and gas atomization, as well as pulverization methods. Of these, atomization is preferred. Atomization effectively produces high-quality metal powders with a particle shape closer to a true sphere and less formation of oxides. Therefore, atomization can produce metal powders with a smaller specific surface area.

[0118] The atomization method produces metal powder by pulverizing molten metal with a high-speed jet of liquid or gas, which then cools the molten metal. In the atomization method, the molten metal is pulverized and then sphericalized during solidification, resulting in the production of particles that are closer to true spherical shapes.

[0119] Among them, the water atomization method is a method of producing metal powder from molten metal by using a liquid such as water as a coolant, spraying it in an inverted cone shape that converges at a point, and causing molten metal to flow down and collide with the convergence point.

[0120] In addition, the rotating water flow atomization method is a method of supplying coolant along the inner circumference of a cooling cylinder and causing it to rotate along the inner circumference. On the other hand, liquid or gas is sprayed onto the molten metal to take the scattered molten metal into the coolant, thereby producing metal powder.

[0121] The gas atomization method is a method of producing metal powder from molten metal by using gas as a cooling medium, spraying it in an inverted cone shape that converges at one point, and causing molten metal to flow down and collide with the convergence point.

[0122] Each particle of the metal powder obtained in this manner is composed of an amorphous structure. By subjecting such metal powder to a crystallization treatment (heat treatment) described later, the soft magnetic powder according to the above embodiment can be obtained.

[0123] The metal powder according to the embodiment is a metal powder that is intended to be subjected to a crystallization process, and is composed of the same composition and impurities as the soft magnetic powder described above.

[0124] A DSC (Differential Scanning Calorimeter) curve was obtained for such metal powder by differential scanning calorimetry. The mass of the sample in the differential scanning calorimetry was 20 mg, and the measurement atmosphere was a nitrogen atmosphere.

[0125] Figure 1 This is an example of a DSC curve obtained from the metal powder used in the production of the soft magnetic powder according to the embodiment.

[0126] Figure 1The DSC curves L1 to L5 shown have a first exothermic peak P1 and a second exothermic peak P2, respectively. The second exothermic peak P2 is located on the high temperature side of the first exothermic peak P1. The DSC curves L1 to L5 are obtained by making the Cr content as Figure 1 DSC curves obtained from metal powders that varied as shown. Specifically, DSC curves L1, L2, L3, L4, and L5 were obtained from metal powders having Cr contents of 0.0 atomic %, 0.5 atomic %, 1.0 atomic %, 1.5 atomic %, and 2.0 atomic %. Note that these metal powders had an Fe content of 77.0 atomic %, a Cu content of 1.0 atomic %, and a Nb content of 3.0 atomic %. Furthermore, the B content was adjusted so that, together with the Cr content, the total was 13.3 atomic %.

[0127] The first exothermic peak P1 is a peak with a peak top temperature Tx1 within a range of 450°C to 550°C. The first exothermic peak P1 is a peak of heat generated when the crystal grains of the soft magnetic powder are generated. Therefore, it can be said that the first exothermic peak P1 is a peak caused by the crystallization necessary for the production of soft magnetic powder. Through such crystallization, crystal grains having, for example, a body-centered cubic lattice (Bcc-Fe) structure are generated. Hereinafter, these are simply referred to as "crystal grains."

[0128] The second exothermic peak P2 is a peak whose top temperature Tx2 is within the range of 600°C to 700°C. The second exothermic peak P2 is a peak of heat generation associated with the formation of a crystalline structure different from the grains of the soft magnetic powder. This crystalline structure, for example, primarily composed of an Fe-B alloy, deteriorates the soft magnetic properties of the soft magnetic powder. Therefore, the second exothermic peak P2 can be considered to be a peak caused by a crystalline structure that is unnecessary in the production of the soft magnetic powder. Hereinafter, this is also referred to as "unnecessary crystalline structure."

[0129] Furthermore, in the metal powder according to the embodiment, the temperature difference Tx2-Tx1 between the first exothermic peak P1 and the second exothermic peak P2 is greater than or equal to 125°C and less than or equal to 180°C. This structure ensures a sufficient temperature difference, making it easier to impart the necessary heat to the metal powder to form the aforementioned crystal grains when heat-treating the metal powder between the temperatures of the first exothermic peak P1 and the second exothermic peak P2. Therefore, by enabling crystallization at higher temperatures, the formation of unnecessary crystalline structures can be avoided, and appropriate grain growth can be achieved. As a result, it is easier to produce a soft magnetic powder with a crystallite diameter controlled within the aforementioned range.

[0130] Furthermore, the temperature difference Tx2-Tx1 between the first exothermic peak P1 and the second exothermic peak P2 is preferably 130°C or higher and 165°C or lower, and more preferably 135°C or higher and 155°C or lower.

[0131] It should be noted that if the temperature difference is below the lower limit, when fully generating grains within the aforementioned crystallite diameter range, that is, when heat treatment is performed at a temperature sufficiently higher than the temperature of the first exothermic peak P1, crystallization corresponding to the second exothermic peak P2 may unexpectedly occur. On the other hand, the temperature difference can be higher than the upper limit, but depending on the temperature of the second exothermic peak P2, the temperature of the first exothermic peak P1 becomes too low, which can easily lead to deviations in the grain size, and the crystallite diameter of the generated grains may easily deviate from the aforementioned range.

[0132] It should be noted that the temperature difference depends on the composition of the metal powder, especially the Cr content. Figure 1 As shown, the temperature difference tends to increase as the Cr content increases from 0 atomic % to 2.0 atomic %. Furthermore, it is believed that the state of the amorphous structure in the metal powder is also affected. For example, if the cooling rate during the formation of the amorphous structure is slow, the temperature difference tends to decrease. Therefore, when producing metal powder, it is preferable to use a production method that achieves a fast cooling rate from the molten metal, such as the rotating water atomization method.

[0133] The above metal powder is subjected to a crystallization treatment (heat treatment), whereby at least a portion of the amorphous structure is crystallized to form crystal grains.

[0134] The crystallization treatment can be performed by heat treating the soft magnetic powder containing the amorphous structure. The temperature of the heat treatment is not particularly limited, but is preferably 520°C or higher and 640°C or lower, more preferably 530°C or higher and 630°C or lower, and further preferably 540°C or higher and 620°C or lower. In addition, the heat treatment time is preferably such that the time maintained at the temperature is 1 minute or higher and 180 minutes or lower, more preferably 3 minutes or higher and 120 minutes or lower, and further preferably 5 minutes or higher and 60 minutes or lower. By setting the temperature and time of the heat treatment within the range, grains with a more appropriate and uniform crystallite diameter can be generated.

[0135] It should be noted that if the temperature or time of the heat treatment is lower than the lower limit, depending on the composition of the soft magnetic powder, crystallization may become insufficient, the crystallite diameter may become too small, or the uniformity of the crystallite diameter may deteriorate. On the other hand, if the temperature or time of the heat treatment is higher than the upper limit, depending on the composition of the soft magnetic powder, crystallization may proceed excessively, the crystallite diameter may become too large, or the uniformity of the crystallite diameter may deteriorate.

[0136] The crystallization atmosphere is not particularly limited, but is preferably an inert gas atmosphere such as nitrogen or argon; a reducing gas atmosphere such as hydrogen or ammonia decomposition gas; or a reduced pressure atmosphere thereof. This can inhibit oxidation of the metal while allowing crystallization, resulting in a soft magnetic powder with excellent magnetic properties.

[0137] The oxygen concentration of the crystallization atmosphere affects the amount of oxides generated. Therefore, the oxygen concentration of the crystallization atmosphere is preferably 1000 ppm or less by volume, more preferably 5 ppm to 500 ppm, and even more preferably 10 ppm to 200 ppm. This can suppress the generation of oxides and produce a soft magnetic powder capable of producing a high-density green compact.

[0138] The cooling rate in the crystallization treatment is preferably 1°C / minute or more and 100°C / minute or less, more preferably 2°C / minute or more and 30°C / minute or less, and further preferably 4°C / minute or more and 20°C / minute or less. By setting the cooling rate within the range, it is easy to control the crystallite diameter of the soft magnetic powder within the range. In addition, the deviation of the crystallite diameter can also be suppressed. It should be noted that if the cooling rate is lower than the lower limit, the crystallite diameter of the soft magnetic powder is likely to become too large. On the other hand, if the cooling rate is higher than the upper limit, the deviation of the crystallite diameter of the soft magnetic powder is likely to become large.

[0139] As described above, the soft magnetic powder according to this embodiment can be produced.

[0140] The produced soft magnetic powder may be classified as needed. Examples of the classification method include dry classification such as sieving classification, inertial classification, and centrifugal classification, and wet classification such as sedimentation classification.

[0141] Furthermore, if necessary, an insulating film may be formed on the surface of each particle of the obtained soft magnetic powder. Examples of materials constituting this insulating film include phosphates such as magnesium phosphate, calcium phosphate, zinc phosphate, manganese phosphate, and cadmium phosphate; inorganic materials such as silicates such as sodium silicate; ceramic materials such as silicon dioxide, aluminum oxide, magnesium oxide, zirconium oxide, and titanium dioxide; and glass materials such as borosilicate glass and silica glass.

[0142] 3.Powder cores and magnetic components

[0143] Next, the dust core and the magnetic element according to the embodiment will be described.

[0144] The magnetic components according to the embodiments can be applied to various magnetic components including magnetic cores, such as choke coils, inductors, noise filters, reactors, transformers, motors, actuators, solenoid valves, and generators. Furthermore, the powder magnetic cores according to the embodiments can be applied to the magnetic cores included in these magnetic components.

[0145] Hereinafter, two types of coil components will be described as representative examples of magnetic elements.

[0146] 3.1. Ring type

[0147] First, a ring-shaped coil component as a magnetic element according to the embodiment will be described.

[0148] Figure 2 It is a plan view schematically showing the ring-shaped coil component 10 . Figure 2 The coil component 10 shown includes an annular powder magnetic core 11 and a conductive wire 12 wound around the powder magnetic core 11 .

[0149] The dust core 11 is formed by mixing the soft magnetic powder according to the embodiment with a binder and then molding the resulting mixture. Because the dust core 11 is a compact containing the soft magnetic powder according to the embodiment, it has a high molding density and excellent coercive force and DC superposition characteristics. Therefore, when the coil component 10 including the dust core 11 is incorporated into an electronic device, the device can achieve both enhanced performance and reduced size.

[0150] As the constituent materials of the adhesive used in the production of the pressed powder magnetic core 11, for example, there can be listed organic materials such as silicone resins, epoxy resins, phenolic resins, polyamide resins, polyimide resins, and polyphenylene sulfide resins; inorganic materials such as phosphates such as magnesium phosphate, calcium phosphate, zinc phosphate, manganese phosphate, and cadmium phosphate; and silicates such as sodium silicate.

[0151] Examples of the material constituting the conductive wire 12 include highly conductive materials, such as metal materials containing Cu, Al, Ag, Au, Ni, etc. Furthermore, an insulating film is provided on the surface of the conductive wire 12 as necessary.

[0152] It should be noted that the shape of the powder core 11 is not limited to Figure 2 The ring shape shown may be, for example, a shape in which a portion of the ring is missing, or a shape in which the longitudinal direction is a straight line.

[0153] Furthermore, the powder core 11 may contain soft magnetic powder and non-magnetic powder other than the soft magnetic powder according to the above-described embodiment, as needed.

[0154] 3.2 Closed magnetic circuit type

[0155] Next, a closed magnetic circuit type coil component as a magnetic element according to an embodiment will be described.

[0156] Figure 3 It is a perspective view schematically showing a closed magnetic circuit type coil component 20 .

[0157] The closed magnetic circuit type coil component 20 will be described below. However, the following description will focus on differences from the ring type coil component 10 , and descriptions of the same matters will be omitted.

[0158] Figure 3 The coil component 20 shown is made by embedding a coiled conductive wire 22 within a powder core 21. Because the powder core 21 is a compact containing the soft magnetic powder of the embodiment, it has a high compact density and excellent coercivity, magnetic permeability, and DC superposition characteristics. Therefore, when the coil component 20 including the powder core 21 is incorporated into electronic equipment, it can achieve both enhanced performance and reduced size.

[0159] It should be noted that the powder core 21 may contain soft magnetic powder and non-magnetic powder other than the soft magnetic powder according to the above-mentioned embodiment as needed.

[0160] 4. Electronic devices

[0161] Then, based on Figures 4 to 6 An electronic device including the magnetic element according to the embodiment will be described.

[0162] Figure 4 It is a perspective view showing the structure of a mobile personal computer 1100 as an electronic device according to the embodiment. Figure 4 The illustrated personal computer 1100 includes a main body 1104 with a keyboard 1102 and a display unit 1106 with a display unit 100. The display unit 1106 is rotatably supported on the main body 1104 via a hinge structure. Such a personal computer 1100 incorporates magnetic components 1000, such as a choke coil for a switching power supply, an inductor, and a motor.

[0163] Figure 5 1 is a plan view showing the structure of a smartphone 1200 as an electronic device according to the embodiment. Figure 5 The smartphone 1200 shown includes a plurality of operation buttons 1202, an earpiece 1204, and a microphone 1206. The display unit 100 is disposed between the operation buttons 1202 and the earpiece 1204. Such a smartphone 1200 has built-in magnetic components 1000 such as an inductor, a noise filter, and a motor.

[0164] Figure 6 1 is a perspective view showing the structure of a digital camera 1300 as an electronic device according to an embodiment. The digital camera 1300 generates an imaging signal by photoelectrically converting an optical image of a subject using an imaging element such as a CCD (Charge Coupled Device).

[0165] Figure 6 The digital camera 1300 shown includes a display unit 100 disposed on the back of a housing 1302. The display unit 100 functions as a viewfinder that displays an electronic image of a subject. Furthermore, a light receiving unit 1304 including an optical lens, a CCD, and the like is disposed on the front side of the housing 1302, i.e., the back side in the figure.

[0166] When the photographer checks the subject image displayed on the display unit 100 and presses the shutter button 1306, the imaging signal of the CCD at that time is transmitted and stored in the memory 1308. Such a digital camera 1300 also has a built-in magnetic element 1000 such as an inductor or a noise filter.

[0167] As the electronic device involved in the embodiment, in addition to Figure 4 Personal computer 1100, Figure 5 Smartphone 1200, Figure 6 In addition to the digital camera 1300, examples thereof include mobile phones, tablet terminals, watches, inkjet printers and other inkjet ejection devices, notebook personal computers, televisions, cameras, video tape recorders, car navigation devices, pagers, electronic notepads, electronic dictionaries, calculators, electronic game consoles, word processors, workstations, videophones, anti-theft TV monitors, electronic binoculars, POS terminals, electronic thermometers, blood pressure monitors, blood glucose meters, electrocardiogram measuring devices, ultrasonic diagnostic equipment, electronic endoscopes and other medical equipment, fish finders, various measuring equipment, measuring instruments for vehicles, aircraft, and ships, mobile body control equipment such as motor vehicle control equipment, aircraft control equipment, railway vehicle control equipment, and ship control equipment, flight simulators, etc.

[0168] Such an electronic device includes the magnetic element according to the embodiment. Thus, the effect of the magnetic element can be utilized, and the performance and size of the electronic device can be improved.

[0169] 5. Effects of implementation methods

[0170] As described above, the soft magnetic powder according to the embodiment is represented by the composition formula Fe x Cu a Nb b (Si 1-y(B 1-z Cr z ) y ) 100-x-a-b The composition and impurity composition of [a, b, x, y, and z satisfy 0.3≤a≤2.0, 2.0≤b≤4.0, 75.5≤x≤79.5, 0.55≤y≤0.91, and 0.015≤z≤0.185.], the average particle size is 5.0 μm to 45.0 μm, and the crystallite diameter measured by X-ray diffraction is 5.0 nm to 20.0 nm.

[0171] In addition, the soft magnetic powder according to the embodiment is mixed with 2.0% by mass of epoxy resin, and the obtained mixture is subjected to a pressure drop of 294.2 MPa (3t / cm 2 ) is stamped under a pressure of 1.50 ℃ to obtain a first annular formed body with an outer diameter of 14 mm, an inner diameter of 8 mm and a thickness of 3 mm. When the first test body is made by winding 7 turns of a wire with a wire diameter of 0.6 mm on the first formed body, the reduction rate d of the magnetic permeability expressed by the following formula is less than 3.0%.

[0172] d=|μ1-μ 100 | / μ1×100

[0173] [In the above formula, μ1 is the magnetic permeability of the first test object measured at a frequency of 1 MHz, μ 100 is the magnetic permeability of the first test object measured at a frequency of 100 MHz.]

[0174] With such a structure, a soft magnetic powder can be obtained that is excellent in oxidation resistance and can produce a green compact having good density, coercive force, and DC superposition characteristics.

[0175] In the soft magnetic powder according to the above embodiment, the magnetic permeability μ1 is 15 or more and less than 21.

[0176] With this structure, it is thought that by optimizing the Si content in the soft magnetic powder, magnetic saturation is less likely to occur, thereby obtaining a soft magnetic powder capable of realizing a magnetic element with excellent DC superposition characteristics.

[0177] The soft magnetic powder according to the embodiment is mixed with 2.0 mass % of epoxy resin, and the obtained mixture is subjected to a pressure drop of 294.2 MPa (3t / cm 2) was pressed under pressure to obtain a second annular molded body having an outer diameter of 28 mm, an inner diameter of 14 mm, and a thickness of 5 mm. When a second test object was produced by winding 50 turns of a 1.25 mm diameter wire around the second molded body, the DC bias current measured for the second test object was 17 A or greater. This DC bias current refers to the DC bias current applied to the second test object when the inductance is reduced to 80% of the baseline value, measured when an AC signal with a frequency of 10 kHz is passed through the second test object and the inductance without DC bias current is used as the baseline value.

[0178] With such a structure, it is possible to obtain a soft magnetic powder capable of realizing a magnetic element having sufficiently high DC superposition characteristics and excellent operational stability.

[0179] In the soft magnetic powder according to the embodiment, the Si content is 4.0 atomic % to 8.0 atomic %, the B content is 9.0 atomic % to 13.5 atomic %, and the Cr content is 0.5 atomic % to 2.2 atomic %.

[0180] This structure allows for the production of soft magnetic powders that exhibit lower coercivity and improved DC superposition characteristics. Furthermore, the oxidation resistance of the soft magnetic powder can be further improved, minimizing the generation of oxides. Consequently, the crystallite diameter of each particle can be appropriately controlled.

[0181] In the soft magnetic powder according to the above embodiment, the oxygen content is 1500 ppm or less.

[0182] With such a structure, the generation of oxides that would cause a decrease in the density of the molded body can be suppressed to a very low level.

[0183] In the soft magnetic powder according to the embodiment, the maximum magnetization measured by a vibrating sample magnetometer is defined as Mm [emu / g], the true density is defined as ρ [g / cm 3 ], the saturation magnetic flux density Bs[T] calculated by 4π / 10000×ρ×Mm=Bs is greater than 1.20[T].

[0184] With this structure, a magnetic element that is unlikely to saturate even at high current can be obtained.

[0185] The powder magnetic core according to the above embodiment contains the soft magnetic powder according to the above embodiment.

[0186] With such a structure, a powder magnetic core having good density, coercive force, and DC superposition characteristics can be obtained.

[0187] The magnetic element according to the above embodiment includes the powder magnetic core according to the above embodiment.

[0188] With such a structure, it is possible to obtain a magnetic element capable of achieving higher performance and smaller size of electronic equipment etc. in which the magnetic element is mounted.

[0189] The electronic device according to the above embodiment includes the magnetic element according to the above embodiment.

[0190] With such a structure, it is possible to obtain an electronic device that achieves both high performance and miniaturization.

[0191] As mentioned above, the soft magnetic powder, metal powder, powder magnetic core, magnetic element, and electronic device of the present invention have been described based on preferred embodiments, but the present invention is not limited thereto.

[0192] For example, in the above embodiments, compressed powder bodies such as powdered magnetic cores are described as examples of applications of the soft magnetic powder of the present invention. However, these applications are not limited to these applications. For example, magnetic devices such as magnetic fluids and magnetic heads may also be used. Furthermore, the shapes of the powdered magnetic cores and magnetic components are not limited to those shown in the figures and may be any shape.

[0193] Example

[0194] Next, specific examples of the present invention will be described.

[0195] 6. Preparation of soft magnetic powder

[0196] 6.1. Sample No. 1

[0197] First, the raw materials are melted in a high-frequency induction furnace and pulverized by a rotating water atomization method to obtain metal powder.

[0198] The resulting metal powder was then subjected to a crystallization treatment by heating in a nitrogen atmosphere. The heating temperatures during the heat treatment are shown in Table 1. The cooling rate after heating was 10°C / minute, and the oxygen concentration in the crystallization atmosphere was 100 ppm. The heating temperatures shown in Table 1 were determined by previously investigating the heating temperature at which the coercivity of the soft magnetic powder was minimized.

[0199] The powder was then classified using an air classifier. This yielded soft magnetic powder, Sample No. 1. The composition of the resulting soft magnetic powder, the structure of the metal powder before heat treatment, the crystallization temperature of the metal powder, and the heating temperature during heat treatment are shown in Table 1.

[0200] 6.2. Samples No. 2 to 16

[0201] Soft magnetic powder was obtained in the same manner as in Sample No. 1 except that the production conditions of the soft magnetic powder were changed as shown in Table 1.

[0202] Note that the soft magnetic powder of Sample No. 16 was not subjected to heat treatment.

[0203] [Table 1]

[0204]

[0205] In Table 1 and Table 2 described later, among the soft magnetic powders of each sample No., those corresponding to the present invention are designated as “Examples”, and those not corresponding to the present invention are designated as “Comparative Examples”.

[0206] 7. Evaluation of soft magnetic powder and molded body

[0207] 7.1. Average particle size of soft magnetic powder

[0208] The average particle size of the soft magnetic powder of each Example and each Comparative Example was measured. The measurement results are shown in Table 2.

[0209] 7.2. Crystallite diameter of soft magnetic powder

[0210] The crystallite diameter of the soft magnetic powder of each example and each comparative example was measured by X-ray diffraction. The measurement results are shown in Table 2.

[0211] 7.3. Oxygen content of soft magnetic powder

[0212] The oxygen content of the soft magnetic powder of each Example and each Comparative Example was measured using an oxygen, nitrogen, and hydrogen analyzer, ONH836, manufactured by LECO. The measurement results are shown in Table 2.

[0213] 7.4. Coercivity of Soft Magnetic Powders

[0214] The coercive force of the soft magnetic powders of each Example and each Comparative Example was measured by the aforementioned method. The coercive force was then evaluated according to the following evaluation criteria. The evaluation results are shown in Table 2.

[0215] A: Coercive force is less than 0.90Oe

[0216] B: Coercive force is 0.90 Oe or more and less than 1.33 Oe

[0217] C: Coercive force is 1.33 Oe or more and less than 1.67 Oe

[0218] D: Coercive force is 1.67 Oe or more and less than 2.00 Oe

[0219] E: Coercive force is 2.00 Oe or more and less than 2.33 Oe

[0220] F: Coercive force is 2.33Oe or more

[0221] 7.5. Saturation flux density of soft magnetic powder

[0222] The saturation magnetic flux density of the soft magnetic powder obtained in each example and each comparative example was calculated using the aforementioned method. The calculation results are shown in Table 2.

[0223] 7.6. Molded body density

[0224] The density of the molded bodies produced using the soft magnetic powders of each Example and Comparative Example was measured using the aforementioned method. The density of the molded bodies was then evaluated according to the following evaluation criteria. The measurement results are shown in Table 2.

[0225] A: Molded body density is 5.01 g / cm 3 above

[0226] B: Molded body density is 4.99 g / cm 3 Above and less than 5.01g / cm 3

[0227] C: Molded body density is less than 4.99 g / cm 3

[0228] 7.7. Magnetic permeability of molded bodies

[0229] The magnetic permeabilities of the molded articles produced using the soft magnetic powders obtained in each of the Examples and Comparative Examples were measured at frequencies of 1 MHz and 100 MHz using the aforementioned method. Furthermore, the rate of decrease in magnetic permeability when the frequency was increased from 1 MHz to 100 MHz was calculated. The measured and calculated results are shown in Table 2.

[0230] 7.8. DC Superposition Characteristics of Molded Products

[0231] The molded articles produced using the soft magnetic powders obtained in each Example and Comparative Example had their DC bias currents measured using the aforementioned method. The DC bias characteristics were then evaluated by comparing the measurement results with the following evaluation criteria. The evaluation results are shown in Table 2.

[0232] A: Particularly good DC superposition characteristics (DC superposition allowable current is 19A or more and 22A or less)

[0233] B: Good DC superposition characteristics (DC superposition allowable current is 18A or more and less than 19A or more than 22A and less than 24A)

[0234] C: Slightly better DC superposition characteristics (DC superposition allowable current is 17A or more and less than 18A or more than 24A)

[0235] D: DC superposition characteristics are poor (DC superposition allowable current is less than 17A)

[0236] [Table 2]

[0237]

[0238] As shown in Table 2, the soft magnetic powders of each example exhibit excellent oxidation resistance despite a high Fe content, and their oxygen content is kept relatively low. Furthermore, the soft magnetic powders of each example exhibit low coercivity. Furthermore, the molded articles produced using the soft magnetic powders of each example exhibit excellent density and DC superposition characteristics.

Claims

1. A soft magnetic powder, characterized in that Composition formula expressed by atomic ratio Fe x Cu a Nb b (Si 1-y (B 1-z Cr z ) y ) 100-x-a-b The composition and impurity composition of a, b, x, y, z satisfy 0.3≤a≤2.0、 2.0≤b≤4.0、 75.5≤x≤79.5、 0.55≤y≤0.91、 0.015≤z≤0.185， The average particle size is 5.0 μm or more and 45.0 μm or less, The crystallite diameter measured by X-ray diffraction is 5.0 nm or more and 20.0 nm or less, By mixing with epoxy resin at a mass ratio of 2.0 mass%, and 2 The obtained mixture was press-formed at a pressure of 100° to obtain a first annular molded body having an outer diameter of 14 mm, an inner diameter of 8 mm, and a thickness of 3 mm. When a first test object was produced by winding a wire having a diameter of 0.6 mm seven times around the first molded body, the reduction rate d of the magnetic permeability expressed by the following formula was 3.0% or less. d=|μ1-μ 100 | / μ1×100 In the above formula, μ1 is the magnetic permeability of the first test object measured at a frequency of 1 MHz, μ 100 It is the magnetic permeability of the first test object measured at a frequency of 100 MHz.

2. The soft magnetic powder according to claim 1, wherein The magnetic permeability μ1 is greater than or equal to 15 and less than 21.

3. The soft magnetic powder according to claim 1 or 2, characterized in that By mixing with 2.0% by mass of epoxy resin, the obtained mixture has a viscosity of 294.2 MPa (3t / cm 2 After being stamped under a pressure of , a second annular molded body with an outer diameter of 28 mm, an inner diameter of 14 mm, and a thickness of 5 mm is obtained, 50 turns of a 1.25 mm diameter wire are wound around the second molded body to make a second test body, and an AC signal with a frequency of 10 kHz is passed through the second test body. When the inductance without superimposed DC bias current is used as a reference value, when the inductance measured while gradually increasing the DC bias current superimposed on the second test body is reduced to 80% of the reference value, the DC bias current superimposed on the second test body is greater than 17 A.

4. The soft magnetic powder according to claim 1 or 2, characterized in that The Si content is 4.0 atomic % or more and 8.0 atomic % or less, The content of B is 9.0 atomic % or more and 13.5 atomic % or less, The Cr content is 0.5 atomic % or more and 2.2 atomic % or less.

5. The soft magnetic powder according to claim 1 or 2, characterized in that The oxygen content is below 1500ppm.

6. The soft magnetic powder according to claim 1 or 2, characterized in that The maximum magnetization measured using a vibrating sample magnetometer is defined as Mm. When the true density is set to ρ, The saturation magnetic flux density Bs obtained by 4π / 10000×ρ×Mm=Bs is greater than 1.20, where the unit of maximum magnetization Mm is emu / g and the unit of true density ρ is g / cm 3 , the unit of saturation magnetic flux density Bs is T.

7. A pressed powder magnetic core, characterized in that: Contains the soft magnetic powder according to claim 1 or 2.

8. A magnetic element, characterized in that: A powder magnetic core according to claim 7 is provided.

9. An electronic device, characterized in that: A magnetic element according to claim 8 is provided.

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