Magnetic powder

Abstract

Providing a magnetic sheet that can sufficiently absorb electromagnetic waves in the high-frequency range. 【Solution means】The magnetic sheet 2 has a matrix 4 and powder dispersed in this matrix. The powder is an aggregate of a large number of flat particles 6. The material of these flat particles 6 is an Fe-based alloy. This alloy Ni: 25.0 mass% or more and 40.0 mass% or less Al: 3.0 mass% or more and 15.0 mass% or less Ti: 0.1 mass% or more and 10.0 mass% or less Cu: 0 mass% or more and 10.0 mass% or less and contains inevitable impurities. The ratio RA calculated by the following formula is 0.980 or more and 1.020 or less. RA = Fe% / (Ni% + Al% + Ti% + Cu%) In this formula, Fe%, Ni%, Al%, Ti%, and Cu% respectively represent the atomic contents of Fe, Ni, Al, Ti, and Cu in the Fe-based alloy.

Description

Technical Field

[0001] This specification relates to a powder whose particles are flat and have magnetism.

Background Art

[0002] Electronic devices such as personal computers and mobile phones have circuits. Due to radio wave noise radiated from electronic components mounted on this circuit, radio wave interference occurs between electronic components and between electronic circuits. Radio wave interference causes malfunction of electronic devices. For the purpose of suppressing malfunctions, a magnetic sheet (electromagnetic wave absorption sheet) is inserted into the electronic device. General magnetic sheets contain magnetic powder.

[0003] Japanese Patent Application Laid-Open No. 2018-085438 discloses magnetic powder whose composition is Fe-Co-C-Ni or Fe-Co-C-Mn. Japanese Patent Application Laid-Open No. 2018-125480 discloses magnetic powder whose composition is Fe-Cr-C or Fe-C-Cr-N.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In recent years, electronic devices have been aiming to increase communication speed. High-frequency radio waves are used for high-speed communication. Suppressing malfunctions caused by electromagnetic wave noise in the high-frequency range is important.

[0006] What the applicant intends is to provide a magnetic member that can sufficiently absorb electromagnetic waves in the high-frequency range. [Means for solving the problem]

[0007] The magnetic powder disclosed herein has a large number of flattened particles. The material of these particles is Ni: 25.0 mass% or more and 40.0 mass% or less Al: 3.0 mass% or more and 15.0 mass% or less Ti: 0.1% by mass or more and 10.0% by mass or less Cu: 0 mass% or more and 10.0 mass% or less and Inevitable impurities It is an Fe-based alloy containing [the specified element]. The ratio RA calculated using the following formula is between 0.980 and 1.020. RA = Fe% / (Ni% + Al% + Ti% + Cu%) In this formula, Fe%, Ni%, Al%, Ti%, and Cu% represent the atomic content of Fe, Ni, Al, Ti, and Cu in the Fe-based alloy, respectively.

[0008] Preferably, this Fe-based alloy has a structure obtained by spinodal decomposition. This structure may have a ferromagnetic phase α1 containing Fe and a weakly magnetic phase α2 containing Ni, Al, and Ti.

[0009] Preferably, the average particle thickness Tav of the magnetic powder is 3.0 μm or less. Preferably, the saturation magnetization Ms of the magnetic powder is 0.8 T or more. Preferably, the coercivity iHc of the magnetic powder is 20 kA / m or more.

[0010] The polymer composition disclosed herein comprises a base polymer and a powder dispersed in the base polymer. The powder has numerous flattened particles. The material of these particles is: Ni: 25.0 mass% or more and 40.0 mass% or less Al: 3.0 mass% or more and 15.0 mass% or less Ti: 0.1% by mass or more and 10.0% by mass or less Cu: 0 mass% or more and 10.0 mass% or less and Inevitable impurities is an Fe-based alloy containing . The ratio RA calculated by the following formula of this polymer composition is 0.980 or more and 1.020 or less. RA = Fe% / (Ni% + Al% + Ti% + Cu%) In this formula, Fe%, Ni%, Al%, Ti%, and Cu% represent the atomic contents of Fe, Ni, Al, Ti, and Cu in the Fe-based alloy, respectively.

Advantages of the Invention

[0011] The magnetic member containing this powder sufficiently absorbs electromagnetic wave noise in the high-frequency range. This magnetic member can suppress malfunction of electronic devices.

Brief Description of the Drawings

[0012] [Figure 1] FIG. 1 is a schematic cross-sectional view showing a part of a magnetic member according to an embodiment. [Figure 2] FIG. 2 is an enlarged view showing flat particles included in the magnetic member of FIG. 1.

Embodiments for Carrying Out the Invention

[0013] Hereinafter, preferred embodiments will be described in detail with reference to the drawings as appropriate.

[0014] [Magnetic Sheet] In FIG. 1, a magnetic sheet 2 (magnetic member) is shown. This magnetic sheet 2 has a matrix 4 and magnetic powder dispersed in this matrix 4. The matrix 4 is a polymer composition. A typical base material of this polymer composition is rubber or resin. This powder is an aggregate of a large number of particles 6.

[0015] In the production of this magnetic sheet 2, the powder is kneaded with various chemicals into the base polymer to obtain a polymer composition. Known methods can be adopted for kneading. For example, kneading can be carried out using a closed kneader, open rolls, etc. Examples of the chemicals include processing aids such as lubricants and binders. The polymer composition may contain a flame retardant.

[0016] Next, the magnetic sheet 2 is formed from this polymer composition. Known methods can be adopted for forming. Forming can be carried out by methods such as compression molding, injection molding, extrusion molding, rolling, etc.

[0017] The shape of the magnetic member is not limited to sheet form. The magnetic member can have shapes such as ring shape, cube shape, rectangular parallelepiped shape, cylindrical shape, etc. This powder is also suitable for magnetic members having even more complex shapes.

[0018] The frequency FR at which tanδ (μ” / μ’), represented by the ratio of the real part permeability μ’ to the imaginary part permeability μ” in the magnetic sheet 2 (magnetic member), reaches 0.1 is preferably 800 MHz or higher. The magnetic sheet 2 with this frequency FR of 800 MHz or higher sufficiently absorbs electromagnetic wave noise in the high-frequency range. From this perspective, this frequency FR is preferably 90 MHz or higher, and particularly preferably 965 MHz or higher.

[0019] [Particle Shape] In FIG. 2, a cross-section of one particle 6 is shown. In FIG. 1, what is indicated by reference sign L1 is the length of the long axis of the particle 6, and what is indicated by reference sign T1 is the thickness of the particle 6. The length L1 is larger than the thickness T1. In other words, the shape of this particle 6 is flat.

[0020] The flattened particles 6 exhibit shape anisotropy. This anisotropy can contribute to the high real permeability μ' of the magnetic sheet 2. Moreover, in a magnetic sheet 2 containing flattened particles 6 with a small thickness T1, eddy current losses are suppressed, making relaxation of the real permeability μ' less likely. In this magnetic sheet 2, the frequency FR at which tanδ(μ'' / μ'), expressed as the ratio of the real permeability μ' to the imaginary permeability μ'', reaches 0.1 is high. This magnetic sheet 2 can absorb electromagnetic noise in the high-frequency range.

[0021] The average Tav of the thickness T1 is preferably 3.0 μm or less. Eddy current loss is suppressed in magnetic sheet 2 containing powder with an average thickness Tav of 3.0 μm or less. The frequency FR at which tanδ(μ'' / μ') reaches 0.1 in this magnetic sheet 2 is high. From this viewpoint, an average thickness Tav of 2.5 μm or less is more preferable, and 2.0 μm or less is particularly preferable. From the viewpoint of ease of powder manufacturing, an average thickness Tav of 0.1 μm or more is preferred, 0.5 μm or more is more preferable, and 1.0 μm or more is particularly preferable.

[0022] The aspect ratio of this powder is preferably between 1.5 and 100. In a magnetic sheet 2 containing powder with an aspect ratio of 1.5 or more, the real permeability μ' and imaginary permeability μ'' in the high-frequency range are sufficiently large. From this viewpoint, an aspect ratio of 5 or more is particularly preferred. In a magnetic sheet 2 containing powder with an aspect ratio of 100 or less, the areas where particles 6 come into contact with each other are suppressed, and losses due to eddy currents are suppressed. From this viewpoint, an aspect ratio of 80 or less is particularly preferred.

[0023] For measuring the length L1, thickness T1, and aspect ratio, a resin-embedded sample is used that allows observation of the thickness direction of the flattened particles 6. This sample is polished, and the polished surface is observed using a scanning electron microscope (SEM). The magnification of the image during observation is 500x. In the analysis of this image, the image data is binarized. When the binarized image is approximated as an ellipse, the length of the major axis is the length L1, the length of the minor axis is the thickness T1, and the ratio of the two (length of the major axis / length of the minor axis) is the aspect ratio of each particle 6. These results are given an arithmetic mean to calculate the average thickness Tav and aspect ratio of the powder.

[0024] [Particle material] The material of the flattened particle 6 is an Fe-based alloy. This Fe-based alloy is Ni: 25.0 mass% or more and 40.0 mass% or less Al: 3.0 mass% or more and 15.0 mass% or less Ti: 0.1% by mass or more and 10.0% by mass or less Cu: 0 mass% or more and 10.0 mass% or less and Inevitable impurities It contains.

[0025] Ni: 25.0 mass% or more and 40.0 mass% or less Al: 3.0 mass% or more and 15.0 mass% or less Ti: 0.1% by mass or more and 10.0% by mass or less and Cu: 0 mass% or more and 10.0 mass% or less Fe-based alloys containing the above, with the remainder being Fe and unavoidable impurities, are preferred.

[0026] [Method for producing powder] In powder production, the raw material powder is first prepared. The raw material powder can be obtained by gas atomization, water atomization, disc atomization, grinding, etc. Gas atomization and disc atomization are preferred. In gas atomization, the raw material metal is heated and melted to obtain molten metal. This molten metal flows out of a nozzle. Gas (argon gas, nitrogen gas, etc.) is blown onto this molten metal. Due to the energy of this gas, the molten metal is pulverized into droplets, which are cooled as they fall. These droplets solidify, forming particles. In this gas atomization method, the molten metal instantly condenses into droplets and cools simultaneously, resulting in a uniform microstructure. Moreover, since droplets are formed continuously, the compositional difference between particles is extremely small. In disc atomization, the raw material metal is heated and melted to obtain molten metal. This molten metal flows out of a nozzle. This molten metal is dropped onto a rapidly rotating disc. The molten metal is rapidly cooled and solidifies, yielding particles.

[0027] This raw material powder is subjected to classification and heat treatment as needed. Furthermore, this raw material powder is flattened. Typical flattening is performed using an attritor. The flattened powder is then subjected to classification and other treatments as needed.

[0028] This powder is subjected to heat treatment. The preferred heat treatment is aging treatment. In aging treatment, the powder is held at a high temperature. The holding temperature is preferably 500°C to 800°C, and particularly preferably 550°C to 750°C. The holding time is preferably 1 hour to 6 hours, and particularly preferably 1 hour to 5 hours. After holding, the powder is slowly cooled. Aging treatment may be performed prior to flattening.

[0029] [Metal structure] The microstructure of the alloy before aging is martensite. This martensite is a supersaturated solid solution. Through aging, the microstructure decomposes into a ferromagnetic phase α1 containing a large amount of Fe and a weakly magnetic phase α2 containing Ni, Al, and Ti. This decomposition is called spinodal decomposition. The microstructure after spinodal decomposition has a periodic modulated structure. The period of this microstructure is on the nano-order. The period of this microstructure is smaller than that of a precipitated microstructure. In powders with this microstructure, the ferromagnetic phase α1 is separated by the weakly magnetic phase α2, thus preventing the reversal of the magnetic moment. The coercivity of this powder is high. The frequency FR at which tanδ(μ” / μ') of the magnetic sheet 2 containing this powder reaches 0.1 is high. This magnetic sheet 2 can absorb electromagnetic noise in the high-frequency range.

[0030] During flattening, stress is applied to the particle structure. When spinodal decomposition occurs in the flattened particles, a large magnetoelastic effect is achieved due to the stress applied to the ferromagnetic phase α1, resulting in a large coercivity. A magnetic component containing this powder can achieve a high frequency FR.

[0031] [Ratio RA] The ratio RA of magnetic powders is calculated using the following formula. RA = Fe% / (Ni% + Al% + Ti% + Cu%) In this formula, Fe%, Ni%, Al%, Ti%, and Cu% represent the atomic content of Fe, Ni, Al, Ti, and Cu in the Fe-based alloy, respectively.

[0032] The ratio RA is preferably between 0.980 and 1.020. In powders with a ratio RA of 0.980 or higher, a sufficient ferromagnetic phase α1 is generated by spinodal decomposition. This powder has excellent magnetic properties. From this viewpoint, a ratio RA of 0.985 or higher is more preferable, and 0.990 or higher is particularly preferable. In powders with a ratio RA of 1.020 or lower, the ferromagnetic phase α1 generated by spinodal decomposition is not excessive. Magnetization reversal is less likely to occur in this powder. From this viewpoint, a ratio RA of 1.015 or lower is more preferable, and 1.010 or lower is particularly preferable.

[0033] [Saturation magnetization Ms] The saturation magnetization Ms of the magnetic powder is preferably 0.8T or higher. The frequency FR at which the tanδ(μ'' / μ') of the magnetic sheet 2 containing this powder reaches 0.1 is high. This magnetic sheet 2 can absorb electromagnetic noise in the high-frequency range. From this viewpoint, the saturation magnetization Ms is more preferably 0.9T or higher, and particularly preferably 1.0T or higher. The saturation magnetization Ms is measured using a vibrating sample magnetometer (VSM). The measurement conditions are as follows. Maximum applied magnetic field: 1204kA / m Powder mass: approximately 70 mg

[0034] [Coercivity iHc] The coercivity iHc of the magnetic powder is preferably 20 kA / m or higher. The frequency FR at which tanδ(μ” / μ') reaches 0.1 for the magnetic sheet 2 containing this powder is high. This magnetic sheet 2 can absorb electromagnetic noise in the high-frequency range. From this viewpoint, the coercivity iHc is more preferably 22 kA / m or higher, and particularly preferably 24 kA / m or higher. The coercivity iHc is the strength of the external magnetic field required to return a magnetized magnetic material to an unmagnetized state. The coercivity is measured using a vibrating sample magnetometer (VSM). The measurement conditions are the same as those for measuring saturation magnetization Ms. The direction of the applied magnetic field is the longitudinal direction of the flattened particle 6.

[0035] [Median diameter D50] From the viewpoint of obtaining a homogeneous magnetic sheet 2 with a smooth surface, the median diameter D50 of the powder is preferably 90 μm or less, more preferably 80 μm or less, and particularly preferably 70 μm or less. A median diameter D50 of 10 μm or more is preferred. The median diameter D50 is the particle diameter at the point where the cumulative curve reaches 50% when the total volume of the powder is set to 100%. The median diameter D50 is measured, for example, by Nikkiso's laser diffraction / scattering particle size distribution analyzer "Microtrac MT3000". The powder is poured into the cell of this device together with pure water, and the median diameter D50 is detected based on the light scattering information of the particles 6.

[0036] [Tap Density TD] From the viewpoint of obtaining a homogeneous magnetic sheet 2 with a smooth surface, the tap density TD of the powder is 2.5 g / cm³. 3 The following is preferable: 2.3 g / cm³ 3 The following is more preferable: 2.1 g / cm³ 3 The following is particularly preferable: Tap density TD is 0.3 g / cm³. 3 The above is preferable. The tap density TD is measured in accordance with the provisions of "JIS Z 2512". In the measurement, approximately 40g of powder is used in a volume of 100cm³. 3 It is filled into the cylinder. The measurement conditions are as follows: Drop height: 50mm Number of taps: 200

[0037] [element] The roles of each element are explained in detail below.

[0038] [Ni (Nickel)] Ni forms the Fe-Ni martensite phase. Ni is essential for the formation of the weakly magnetic phase α2. The coercivity iHc of Ni-containing powder is high. From this viewpoint, the Ni content is preferably 25.0 mass% or more, more preferably 28.0 mass% or more, and particularly preferably 30.0 mass% or more. Excess Ni leads to retained austenite after aging treatment. Retained austenite reduces the saturation magnetization Ms of the powder and reduces the frequency FR of the magnetic sheet 2. From the viewpoint of achieving a high frequency FR, the Ni content is preferably 40.0 mass% or less, more preferably 38.0 mass% or less, and particularly preferably 36.0 mass% or less.

[0039] [Al (Aluminum)] Al is essential for the formation of the weakly magnetic phase α2. Al increases the resistivity of particle 6 and reduces eddy current losses. From this viewpoint, the Al content is preferably 3.0 mass% or more, more preferably 4.0 mass% or more, and particularly preferably 5.0 mass% or more. Excess Al lowers the saturation magnetization Ms and lowers the frequency FR. From the viewpoint of achieving a high frequency FR, the Al content is preferably 15.0 mass% or less, more preferably 14.0 mass% or less, and particularly preferably 13.0 mass% or less.

[0040] [Ti (Titanium)] Ti primarily dissolves in the weakly magnetic phase α2. The saturation magnetization of the weakly magnetic phase α2 with dissolved Ti is low. In alloys containing Ti, the difference between the saturation magnetization of the ferromagnetic phase α1 and the saturation magnetization of the weakly magnetic phase α2 is large. The coercivity iHc of this powder is high. This powder can be used to obtain a magnetic member with a high frequency FR. From this viewpoint, the Ti content is preferably 0.1 mass% or more, more preferably 0.2 mass% or more, and particularly preferably 0.5 mass% or more. Excess Ti leads to a rapid decrease in the saturation magnetization Ms of the powder, which lowers the frequency FR of the magnetic sheet 2. From the viewpoint of achieving a high frequency FR, the Ti content is preferably 10.0 mass% or less, more preferably 9.0 mass% or less, and particularly preferably 8.0 mass% or less.

[0041] [Cu (copper)] Like Ti, Cu primarily dissolves in the weakly magnetic phase α2. The saturation magnetization of the weakly magnetic phase α2 in which Cu is dissolved is low. In alloys containing Cu, the difference between the saturation magnetization of the ferromagnetic phase α1 and the saturation magnetization of the weakly magnetic phase α2 is large. The coercivity iHc of this powder is large. This powder can be used to obtain magnetic members with a high frequency FR. From these viewpoints, the Cu content is preferably 0 mass% or more, more preferably 1.0 mass% or more, and particularly preferably 2.0 mass% or more. Excess Cu leads to retained austenite after aging. Retained austenite reduces the saturation magnetization Ms of the powder and reduces the frequency FR of the magnetic sheet 2. From the viewpoint of achieving a high frequency FR, the Cu content is preferably 10.0 mass% or less, more preferably 9.0 mass% or less, and particularly preferably 8.0 mass% or less. Cu is not essential in this alloy. Therefore, the alloy does not need to contain Cu other than unavoidable impurities. In other words, the copper content can be virtually zero.

[0042] [Fe (iron)] Fe is the main component of this alloy. Fe is dissolved in the ferromagnetic phase α1. Fe can contribute to the magnetic properties of the powder. From this viewpoint, the Fe content is preferably 30% by mass or more, more preferably 40% by mass or more, and particularly preferably 45% by mass or more. From the viewpoint that the alloy can sufficiently contain Ni, Al, Ti, or Cu, the Fe content is preferably 70% by mass or less, more preferably 65% ​​by mass or less, and particularly preferably 60% by mass or less.

[0043] [Other perspectives] This specification is also directed to a method for producing magnetic powder. This method is (1) The material is, Ni: 25.0 mass% or more and 40.0 mass% or less Al: 3.0 mass% or more and 15.0 mass% or less Ti: 0.1% by mass or more and 10.0% by mass or less Cu: 0 mass% or more and 10.0 mass% or less and Inevitable impurities The process of preparing a raw material powder which is an Fe-based alloy containing the following: (2) A process of flattening this powder, and (3) A process in which the powder is subjected to aging treatment to induce spinodal decomposition in the metal structure of the powder. Includes.

[0044] This specification is also directed to magnetic members. These magnetic members have a matrix 4 with a polymer as the base material, and magnetic powder dispersed in the matrix 4. The magnetic powder contains a large number of flattened particles 6. The material of these particles 6 is: Ni: 25.0 mass% or more and 40.0 mass% or less Al: 3.0 mass% or more and 15.0 mass% or less Ti: 0.1% by mass or more and 10.0% by mass or less Cu: 0 mass% or more and 10.0 mass% or less and Inevitable impurities It is an Fe-based alloy containing [a specific compound]. The ratio RA of this magnetic material, calculated using the following formula, is between 0.980 and 1.020. RA = Fe% / (Ni% + Al% + Ti% + Cu%) In this formula, Fe%, Ni%, Al%, Ti%, and Cu% represent the atomic content of Fe, Ni, Al, Ti, and Cu in the Fe-based alloy, respectively. [Examples]

[0045] The effects of the magnetic powders described in the following examples will be clarified, but the scope disclosed herein should not be interpreted as limiting based on the description of these examples.

[0046] [Example 1] Raw material powder was obtained by gas atomization and classification. This raw material powder was flattened using a wet attritor. Furthermore, this powder was subjected to aging treatment to produce the powder of Example 1 having the composition shown in Table 1 below. Spinodal separation occurred during the aging treatment, resulting in the formation of a ferromagnetic phase α1 and a weakly magnetic phase α2. The median diameter D50, tap density TD, average thickness Tav, saturation magnetization Ms, and coercivity iHc of this powder are shown in Table 2 below.

[0047] [Examples 2-9 and Comparative Examples 1-9] Powders for Example 2-9 and Comparative Example 1-9 were prepared in the same manner as in Example 1, except that the composition was as shown in Table 1 below.

[0048] [Frequency FR measurement] A resin composition was obtained by mixing 20 parts by mass of powder with 100 parts by mass of a base resin. A sheet for magnetic components was molded from this resin composition. Strip-shaped test pieces with a width of 4 mm and a length of 35 mm were cut from this magnetic sheet. Using these test pieces, the relative permeability at room temperature from 1 MHz to 9 GHz was measured with a PMM-9G1 (manufactured by Ryowa Electronics), and the frequency FR at which tanδ(μ” / μ') reached 0.1 was calculated. The results are shown in Table 2 below.

[0049] [Table 1]

[0050] [Table 2]

[0051] As shown in Table 2, magnetic members with high frequency FR can be obtained from the powders of each example. The superiority of this magnetic powder is clear from these evaluation results. [Industrial applicability]

[0052] The powders described above are suitable for various magnetic materials. [Explanation of Symbols]

[0053] 2. Magnetic sheet 4. The Matrix 6...particles

Claims

1. It has many flattened particles, The material of these particles is Ni: 25.0% by mass or more and 40.0% by mass or less Al: 3.0% by mass or more and 15.0% by mass or less Ti: 0.1% by mass or more and 10.0% by mass or less Cu: 0 mass% or more and 10.0 mass% or less and Inevitable impurities It is an Fe-based alloy containing, A magnetic powder having a ratio RA of 0.980 or more and 1.020 or less, calculated using the following formula. RA = Fe% / (Ni% + Al% + Ti% + Cu%) (In this formula, Fe%, Ni%, Al%, Ti%, and Cu% represent the atomic content of Fe, Ni, Al, Ti, and Cu in the Fe-based alloy, respectively.)

2. The magnetic powder according to claim 1, wherein the above Fe-based alloy has a structure obtained by spinodal decomposition.

3. The magnetic powder according to claim 2, wherein the above structure comprises a ferromagnetic phase α1 containing Fe and a weakly magnetic phase α2 containing Ni, Al, and Ti.

4. The magnetic powder according to claim 1 or 2, wherein the average thickness Tav of the above particles is 3.0 μm or less.

5. The magnetic powder according to claim 1 or 2, wherein the saturation magnetization Ms is 0.8 T or higher.

6. The magnetic powder according to claim 1 or 2, wherein the coercivity iHc is 20 kA / m or more.

7. It comprises a base polymer and a powder dispersed in this base polymer. The above powder has a large number of flattened particles, The material of these particles is Ni: 25.0% by mass or more and 40.0% by mass or less Al: 3.0% by mass or more and 15.0% by mass or less Ti: 0.1% by mass or more and 10.0% by mass or less Cu: 0 mass% or more and 10.0 mass% or less and Inevitable impurities It is an Fe-based alloy containing, A polymer composition having a ratio RA of 0.980 or more and 1.020 or less, calculated using the following formula. RA = Fe% / (Ni% + Al% + Ti% + Cu%) (In this formula, Fe%, Ni%, Al%, Ti%, and Cu% represent the atomic content of Fe, Ni, Al, Ti, and Cu in the Fe-based alloy, respectively.)

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