Iron-based magnetic powder core, method for manufacturing the same, and electromagnetic induction device

Abstract

The application provides an iron-based magnetic powder core, a preparation method thereof and an electromagnetic induction device. The preparation method of the iron-based magnetic powder core comprises the following steps: performing surface passivation treatment on an iron-nickel alloy and a flaky iron-silicon-aluminum alloy to obtain an iron-based composite magnetic material; and mixing the iron-based composite magnetic material with a binder and a release agent, and performing compression molding treatment in an inert atmosphere or a reducing atmosphere to obtain the iron-based magnetic powder core. The iron-based magnetic powder core prepared by using the preparation method has high magnetic permeability and a quality factor, and has the advantages of small power loss and the like. In addition, the compression molding treatment is performed in the inert atmosphere or the reducing atmosphere, which can inhibit oxidation of the iron-based magnetic powder core in an annealing process and inhibit deterioration of soft magnetic properties of the magnetic powder core.

Description

Technical Field

[0001] This invention relates to the field of metal soft magnetic material preparation technology, and more specifically, to an iron-based magnetic powder core, its preparation method, and an electromagnetic induction device. Background Technology

[0002] With the upgrading of electronic products, the demand for small-volume, high-power inductors is increasing, which requires magnetic powder cores to have high magnetic density, high permeability, and low loss performance.

[0003] Iron-nickel soft magnetic alloy powder cores can achieve a saturation magnetic flux density of around 1.3T and a permeability exceeding 200, exhibiting excellent DC superposition characteristics. However, they experience significant eddy current losses at high frequencies. This is because the resistivity of the iron-nickel soft magnetic alloy powder core is low, leading to high energy losses (i.e., eddy current losses) due to induced currents at high frequencies. Iron-silicon-aluminum soft magnetic alloys, on the other hand, possess advantages such as high effective permeability, stable magnetic properties, high saturation magnetic intensity, and low losses. To reduce eddy current losses, surface passivation and coating treatments are typically applied to the iron-nickel alloy powder to increase its resistivity, thereby reducing eddy current losses.

[0004] Existing literature (patent number CN102306528B) discloses a soft magnetic material of iron-nickel alloy with a permeability μ = 125 H / m and its manufacturing method. The preparation method of the aforementioned soft magnetic material of iron-nickel alloy includes: surface treatment of iron-nickel powder with phosphoric acid, followed by addition of phenolic resin, calcination until dry, pressing and molding, heat treatment, and then coating the surface of the soft magnetic material with epoxy resin paint. The loss of the obtained soft magnetic material of iron-nickel alloy is 350 mW / cm. 3 (50kHz, 100mT).

[0005] Iron-nickel magnetic powder is widely used in switching power supplies and electronic communications. Currently, the application frequencies of iron-nickel or iron-nickel composites with other soft magnetic powders are generally below 200kHz, and they suffer from high losses, making them unsuitable for the MHz-level high frequencies required by 5G inductors. Therefore, it is of great significance to research and develop a soft magnetic alloy powder or magnetic powder composite material with application frequencies reaching 100kHz or even MHz levels while exhibiting low-loss performance. Summary of the Invention

[0006] The main objective of this invention is to provide an iron-based magnetic powder core, its preparation method, and an electromagnetic induction device to solve the problem of high eddy current loss of existing soft magnetic alloy magnetic powder or magnetic powder composite materials under high frequency conditions (100kHz and 1MHz).

[0007] To achieve the above objectives, the present invention provides a method for preparing an iron-based magnetic powder core, the method comprising: performing surface passivation treatment on an iron-nickel alloy and a sheet-like iron-silicon-aluminum alloy to obtain an iron-based composite magnetic material; mixing the iron-based composite magnetic material with a binder and a release agent, and performing pressing molding treatment under an inert atmosphere or a reducing atmosphere to obtain an iron-based magnetic powder core.

[0008] Furthermore, the iron-nickel alloy is spherical, and the D50 is 15–29 μm.

[0009] Furthermore, the thickness of the sheet-like iron-silicon-aluminum alloy is ≤5μm, and the projected area of ​​the iron-nickel alloy on the plane containing the sheet-like iron-silicon-aluminum alloy is larger than the area of ​​the sheet-like iron-silicon-aluminum alloy.

[0010] Furthermore, the sheet-like iron-silicon-aluminum alloy is elliptical or circular. Preferably, the thickness of the sheet-like iron-silicon-aluminum alloy is 0.3–3 μm, and the D50 is 40–60 μm.

[0011] Further, the amount of the sheet iron-silicon-aluminum alloy is 0.1 to 30 wt% based on the percentage of the total weight of the sheet iron-silicon-aluminum alloy and the iron-nickel alloy; preferably, the amount of the sheet iron-silicon-aluminum alloy is 1 to 20 wt% based on the percentage of the total weight of the sheet iron-silicon-aluminum alloy and the iron-nickel alloy.

[0012] Further, the surface passivation process includes: mixing a passivating agent, an iron-nickel alloy, and a sheet-like iron-silicon-aluminum alloy to obtain an iron-based composite magnetic material; the amount of passivating agent used is 0.01 to 5 wt%, preferably 0.1 to 3 wt%, based on the percentage of the total weight of the passivating agent, the iron-nickel alloy, and the sheet-like iron-silicon-aluminum alloy; preferably, the passivating agent is selected from one or more of the group consisting of phosphoric acid, chromic acid, and aluminum dihydrogen phosphate.

[0013] Furthermore, the binder is selected from one or more of the group consisting of silicone resin, phenolic resin, epoxy resin, glass powder and water glass; preferably, the weight of the binder accounts for 0.3 to 3 wt% of the total weight of the iron-based composite magnetic material and the binder.

[0014] Furthermore, the release agent is selected from one or more of the group consisting of stearic acid compounds, talc powder and release oil; preferably, the weight of the release agent accounts for 0.1 to 0.4 wt% of the total weight of the iron-based composite magnetic material and the binder.

[0015] To achieve the above objectives, another aspect of the present invention provides an iron-based magnetic powder core, wherein the magnetic permeability of the iron-based magnetic powder core is 100–160 H / m, the quality factor is 81–156, and the power loss is 2180–3150 mW / cm. 3 Alternatively, the iron-based magnetic powder core may be prepared by the iron-based magnetic powder core preparation method provided in this application.

[0016] Another aspect of the present invention provides an electromagnetic induction device, including an electromagnetic induction unit, wherein the electromagnetic induction unit is made from the iron-based magnetic powder core provided in this application.

[0017] Applying the technical solution of this invention, on the one hand, after surface passivation treatment and pressing molding of the sheet-like iron-silicon-aluminum alloy and iron-nickel alloy, the sheet-like iron-silicon-aluminum alloy adheres to the surface of the iron-nickel alloy. The high aspect ratio of the sheet-like iron-silicon-aluminum alloy not only has high permeability and resistivity, but its sheet-like structure also provides spatial isolation. The synergistic effect of the two can improve the permeability of the obtained iron-based magnetic powder core, while reducing eddy current losses between different alloys in the iron-based composite magnetic material. On the other hand, the surface passivation treatment can form a passivation film on the surface of the iron-based composite magnetic material. The passivation film has good insulation properties, which is beneficial to further reduce the eddy current losses of the iron-based composite magnetic material. The addition of a binder can make the particles inside the iron-based composite magnetic material adhere to each other, so as to facilitate the subsequent pressing molding effect. The addition of a release agent can reduce the friction between the iron-based composite magnetic material and the mold, increase the compaction density, and extend the mold life. The iron-based magnetic powder core prepared by the above method has high permeability and quality factor (Q value), while having low power loss. Furthermore, pressing and molding under an inert or reducing atmosphere can suppress the oxidation of the iron-based magnetic powder core during the annealing process, and at the same time suppress the deterioration of the soft magnetic properties of the magnetic powder core. Attached Figure Description

[0018] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0019] Figure 1 An SEM image (magnification 1000x) of the iron-nickel alloy involved in Embodiment 1 of the present invention is shown;

[0020] Figure 2 An SEM image (magnification 500x) of the sheet-like iron-silicon-aluminum alloy involved in Embodiment 1 of the present invention is shown.

[0021] Figure 3 The image shows a SEM image (magnification of 500x) of the iron-based magnetic powder core prepared in Example 1 of the present invention.

[0022] Figure 4 The image shown is a SEM image (magnification of 1000x) of the iron-based magnetic powder core prepared in Example 1 of the present invention. Detailed Implementation

[0023] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the embodiments.

[0024] As described in the background section, existing soft magnetic alloy powders or magnetic powder composites suffer from high eddy current losses under high-frequency conditions (100kHz and 1MHz). To address this technical problem, this application provides a method for preparing an iron-based magnetic powder core. The method includes: surface passivation treatment of an iron-nickel alloy and a sheet-like iron-silicon-aluminum alloy to obtain an iron-based composite magnetic material; mixing the iron-based composite magnetic material with a binder and a release agent; and pressing and molding the mixture under an inert or reducing atmosphere to obtain the iron-based magnetic powder core.

[0025] On the one hand, after surface passivation and pressing of the sheet-like iron-silicon-aluminum alloy and iron-nickel alloy, the sheet-like iron-silicon-aluminum alloy adheres to the surface of the iron-nickel alloy. The high aspect ratio of the sheet-like iron-silicon-aluminum alloy not only results in high permeability and resistivity, but its sheet-like structure also provides spatial isolation. The synergistic effect of these two processes improves the permeability of the resulting iron-based magnetic powder core while reducing eddy current losses between different alloys in the iron-based composite magnetic material. On the other hand, surface passivation forms a passivation film on the surface of the iron-based composite magnetic material. This passivation film has good insulation properties, which further helps to reduce eddy current losses in the iron-based composite magnetic material. The addition of a binder enables the particles within the iron-based composite magnetic material to adhere to each other, facilitating subsequent pressing. The addition of a release agent reduces friction between the iron-based composite magnetic material and the mold, increasing compaction density and extending mold life. Furthermore, pressing and molding under an inert or reducing atmosphere can suppress oxidation of the iron-based magnetic powder core during annealing, and also inhibit the deterioration of the soft magnetic properties of the magnetic powder core. The iron-based magnetic powder core prepared by the above method has high permeability and quality factor (Q value), while also exhibiting low power loss.

[0026] In a preferred embodiment, the iron-nickel alloy is spherical with a D50 of 15–29 μm. Compared to other ranges, limiting the D50 of the iron-nickel alloy to the above range is beneficial for giving the iron-nickel alloy a suitable specific surface area, facilitating the subsequent attachment of sheet-like iron-silicon-aluminum alloys to its outer surface, and reducing the likelihood of agglomeration. Simultaneously, the iron-nickel alloy with the above particle size range has a higher saturation magnetization. Surface passivation treatment under the premise of higher saturation magnetization reduces its eddy current losses at high frequencies.

[0027] In order to reduce the impurity content in the obtained iron-based magnetic powder core and improve the electromagnetic performance of the iron-based magnetic powder core, preferably, the iron-nickel alloy is prepared by gas atomization, and the weight percentage of Fe in the iron-nickel alloy is 49-51 wt%, and the weight percentage of Ni is 47-50 wt%; the sheet-like iron-silicon-aluminum alloy is Sendust alloy.

[0028] To further facilitate the subsequent attachment of the sheet-like iron-silicon-aluminum alloy to the outer surface of the spherical iron-nickel alloy, in a preferred embodiment, the thickness of the sheet-like iron-silicon-aluminum alloy is ≤5μm, and the projected area of ​​the iron-nickel alloy on the plane where the sheet-like iron-silicon-aluminum alloy is located is larger than the area of ​​the sheet-like iron-silicon-aluminum alloy.

[0029] The magnitude of the demagnetizing magnetic field is related to the shape and magnetization of the magnet. In a preferred embodiment, the cross-section of the sheet-like iron-silicon-aluminum alloy is elliptical or circular. When the cross-section is circular, an excessively large diameter of the sheet-like iron-silicon-aluminum alloy can lead to a decrease in the demagnetizing magnetic field, thereby reducing the superposition characteristics. To further suppress the decrease in the demagnetizing magnetic field strength and the reduction in superposition characteristics, the shape and size of the sheet-like iron-silicon-aluminum alloy need to be limited to a suitable range. Preferably, the thickness of the sheet-like iron-silicon-aluminum alloy is 0.3–3 μm, and the D50 is 40–60 μm.

[0030] If the amount of sheet-like iron-silicon-aluminum alloy used is too small, it will be insufficient to coat the surface of the iron-nickel alloy; if the amount is too large, the resistivity will be too high, affecting the superposition performance. In a preferred embodiment, the amount of sheet-like iron-silicon-aluminum alloy used is 0.1–30 wt%, based on the total weight of the sheet-like iron-silicon-aluminum alloy and the iron-nickel alloy. Compared to other ranges, limiting the amount of sheet-like iron-silicon-aluminum alloy to the above range is beneficial to improving the resistivity of the nickel-based magnetic composite material, thereby reducing eddy current losses at high frequencies, without affecting its superposition characteristics.

[0031] In order to further improve the resistivity of nickel-based magnetic composite material without affecting the superposition characteristics, preferably, the amount of sheet iron-silicon-aluminum alloy is 1 to 20 wt% based on the percentage of the total weight of sheet iron-silicon-aluminum alloy and iron-nickel alloy.

[0032] Surface passivation treatment can form a passivation film on the surface of iron-based composite magnetic materials. This passivation film has good insulation properties, thus helping to reduce eddy current losses in the iron-based composite magnetic materials. In a preferred embodiment, the surface passivation treatment process includes: mixing a passivating agent, an iron-nickel alloy, and a sheet-like iron-silicon-aluminum alloy to obtain the iron-based composite magnetic material; the amount of passivating agent used is 0.01–5 wt% of the total weight of the passivating agent, iron-nickel alloy, and sheet-like iron-silicon-aluminum alloy. Compared to other ranges, limiting the amount of passivating agent within the above range is beneficial for improving raw material utilization and increasing the yield of the passivation film during the surface passivation treatment, thereby further reducing the eddy current losses of the iron-based composite magnetic materials. To further improve raw material utilization and simultaneously increase the yield of the passivation film and reduce eddy current losses, the amount of passivating agent used is preferably 0.1–3 wt%.

[0033] In order to improve the insulation of iron-nickel alloys and iron-silicon-aluminum alloys, and thereby reduce the eddy current loss of iron-based magnetic composite materials, the passivating agent preferably includes, but is not limited to, one or more of the group consisting of phosphoric acid, chromic acid and aluminum dihydrogen phosphate.

[0034] A second aspect of this application also provides a method for preparing a magnetic powder core. The method includes: after the surface passivation treatment step in the preparation method of the iron-based composite magnetic material, mixing the iron-based composite magnetic material with a binder and a release agent, and then performing a pressing and molding process to obtain the magnetic powder core. The addition of the binder enables the particles within the iron-based composite magnetic material to adhere to each other, which affects the effect of the subsequent pressing and molding process. The addition of the release agent reduces the friction between the iron-based composite magnetic material and the mold, thereby increasing the compaction density and extending the mold life.

[0035] The pressing process requires pressurizing and annealing a mixture of iron-based composite magnetic materials, binders, and release agents. Higher pressing pressure results in greater compaction density, internal stress, and higher magnetic density in the pressed magnetic powder core. However, excessive pressure increases defects and dislocations in the magnetic powder core and can damage the mold. In a preferred embodiment, the pressing pressure during the pressing process is 500–2200 MPa. Compared to other ranges, limiting the pressing pressure within this range is beneficial for increasing the magnetic density of the magnetic powder core and for suppressing the deterioration of its soft magnetic properties.

[0036] Annealing refers to heat treatment of pressed magnetic powder cores at a specific temperature. This releases the internal stress generated in the iron-based magnetic composite material during pressing. A suitable annealing temperature plays a crucial role in releasing this stress. If the annealing temperature is too low, the internal stress cannot be released; if the annealing temperature is too high, it may burn the binder and release agent inside the iron-based magnetic composite material, and may even damage the mechanical structure of the composite material. In a preferred embodiment, the annealing temperature is 400–900°C. Compared to other ranges, limiting the annealing temperature within this range is beneficial for releasing the internal stress of the magnetic powder core, increasing its mechanical strength, and simultaneously suppressing the deterioration of the soft magnetic properties of the magnetic powder core. To further enhance the stress release effect, the annealing temperature is preferably 600–900°C.

[0037] In a preferred embodiment, the annealing process is performed in an inert or reducing atmosphere, such as nitrogen, argon, or hydrogen. This suppresses oxidation of the iron-based magnetic powder core during the annealing process and also inhibits the deterioration of the soft magnetic properties of the magnetic powder core.

[0038] This application employs binders commonly used in the art. In a preferred embodiment, the binder includes, but is not limited to, one or more of the group consisting of silicone resin, phenolic resin, epoxy resin, glass powder, and water glass. Using the above-mentioned types of binders can improve the bonding strength between particles within the iron-based composite magnetic material, a process that affects the effect of subsequent pressing and molding processes. Specifically, when using high-temperature binders such as silicone resin and water glass, the bonding strength can be further enhanced during subsequent annealing; when using low-temperature binders such as epoxy resin, it is more suitable for application in magnetic devices containing coils and the aforementioned magnetic powder core.

[0039] To further improve the bonding strength between particles within the iron-based composite magnetic material, thereby enhancing the effect of subsequent pressing and molding, preferably, the weight of the binder accounts for 0.3 to 3 wt% of the total weight of the iron-based composite magnetic material and the binder.

[0040] In a preferred embodiment, the release agent includes, but is not limited to, one or more of the group consisting of stearic acid compounds, talc, and release oil. Using release agents of the above types helps enhance the sliding between particles within the iron-based composite magnetic material and can reduce friction between the iron-based composite magnetic material and the mold, thereby increasing compaction density and extending mold life.

[0041] To further reduce friction between the iron-based composite magnetic material and the mold, thereby increasing compaction density and extending mold life, preferably, the weight of the release agent accounts for 0.1 to 0.4 wt% of the total weight of the iron-based composite magnetic material and the binder.

[0042] The second aspect of this application also provides an iron-based magnetic powder core, wherein the magnetic permeability of the iron-based magnetic powder core is 100-160 H / m, the quality factor is 81-156, and the power loss is 2180-3150 mW / cm. 3 It can be prepared by the above-mentioned method for preparing magnetic powder cores.

[0043] Compared with magnetic powder cores prepared by other methods, magnetic powder cores prepared by the above method have excellent permeability, high quality factor (Q value) and low power loss (power loss includes eddy current loss).

[0044] A third aspect of this application also provides an electromagnetic induction device, including an electromagnetic induction part, which is made from the iron-based magnetic powder core provided in this application.

[0045] The iron-based magnetic powder cores prepared using the iron-based magnetic powder cores provided in this application have high permeability and quality factor (Q value), while exhibiting low power loss. Therefore, the electromagnetic induction devices including the aforementioned electromagnetic induction section have low power loss, and their application frequencies can reach 100kHz or even MHz. Preferably, the aforementioned electromagnetic induction devices include, but are not limited to, switching power supplies, high-power filters and antenna tuning circuits, and high-performance EMI filters.

[0046] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0047] It should be noted that the magnetic rings prepared in all embodiments and comparative examples of this application were tested with 20×5 turns. An impedance analyzer was used to test the permeability, Q value, and DC superposition characteristics, and a BH analyzer was used to test the power loss (P). cv ).

[0048] Example 1

[0049] 100g of gas-atomized iron-silicon-aluminum alloy with a D50 of 30μm was placed in a ball mill jar, along with 3000g of zirconium balls and 300g of anhydrous ethanol. The jar was then placed in a planetary ball mill and milled for 3 hours at 200rpm. After ball milling, a sheet-like iron-silicon-aluminum alloy with a thickness of 2μm and a D50 of 60μm was obtained.

[0050] The above-mentioned sheet-like iron-silicon-aluminum alloy was mixed evenly with a gas-atomized iron-nickel alloy with a D50 of 25 μm, and the weight ratio of sheet-like iron-silicon-aluminum alloy to iron-nickel alloy was 1:99 (i.e., the amount of sheet-like iron-silicon-aluminum alloy was 1 wt%). A specific amount of phosphoric acid was used as a passivating agent (i.e., the amount of phosphoric acid was 0.2 wt% based on the total weight of phosphoric acid, iron-nickel alloy and sheet-like iron-silicon-aluminum alloy). The phosphoric acid was then diluted 25 times with acetone to obtain a phosphoric acid dilution. The mixed magnetic powder was added to the phosphoric acid dilution for surface passivation treatment. After treatment for 30 minutes, an iron-based composite magnetic material was obtained.

[0051] The above-mentioned gas-atomized iron-nickel alloy contains 50 wt% Fe and 50 wt% Ni by weight. For example... Figure 1 As shown, the gas-atomized iron-nickel alloy consists of spherical particles. The sheet-like iron-silicon-aluminum alloy is made from Sendust alloy (manufactured by Ansteel Technology Co., Ltd.). The microstructure of the sheet-like iron-silicon-aluminum alloy is shown below. Figure 2 As shown.

[0052] The aforementioned iron-based composite magnetic material was mixed with epoxy resin and release powder, wherein the epoxy resin accounted for 0.5 wt% of the total weight of the iron-based composite magnetic material and epoxy resin, and the release powder accounted for 0.2 wt% of the total weight of the iron-based composite magnetic material and binder. The mixture of the iron-based composite magnetic material, epoxy resin, and release powder was pressed into a magnetic ring with an outer diameter, inner diameter, and height of 8.0 mm, 5 mm, and 3 mm, respectively, under a pressure of 1000 MPa. This magnetic ring was then annealed in a nitrogen atmosphere at 600°C for 2 hours to obtain a ring-shaped magnetic powder core. Figure 3 As shown in the SEM image of the cross-section of the annular magnetic powder core, rough wrinkles can be seen, indicating that the sheet-like iron-silicon-aluminum was successfully attached to the surface of the iron-nickel alloy magnetic powder.

[0053] The electromagnetic performance test results of the prepared annular magnetic powder core are shown in Table 1.

[0054] Example 2

[0055] The difference from Example 1 is that the amount of sheet-like iron-silicon-aluminum alloy used is 0.1 wt%.

[0056] The electromagnetic performance test results of the prepared annular magnetic powder core are shown in Table 1.

[0057] Example 3

[0058] The difference from Example 1 is that the amount of sheet-like iron-silicon-aluminum alloy used is 1 wt%.

[0059] The electromagnetic performance test results of the prepared annular magnetic powder core are shown in Table 1.

[0060] Example 4

[0061] The difference from Example 1 is that the weight ratio of sheet iron-silicon-aluminum alloy to iron-nickel alloy is 1:10, that is, the amount of sheet iron-silicon-aluminum alloy used is 9.1 wt%.

[0062] The electromagnetic performance test results of the prepared annular magnetic powder core are shown in Table 1.

[0063] Example 5

[0064] The difference from Example 1 is that the weight ratio of sheet iron-silicon-aluminum alloy to iron-nickel alloy is 1:5, that is, the amount of sheet iron-silicon-aluminum alloy used is 16.7wt%.

[0065] The electromagnetic performance test results of the prepared annular magnetic powder core are shown in Table 1.

[0066] Example 6

[0067] The difference from Example 1 is that the amount of sheet-like iron-silicon-aluminum alloy used is 20 wt%.

[0068] The electromagnetic performance test results of the prepared annular magnetic powder core are shown in Table 1.

[0069] Example 7

[0070] The difference from Example 1 is that the amount of sheet-like iron-silicon-aluminum alloy used is 30 wt%.

[0071] The electromagnetic performance test results of the prepared annular magnetic powder core are shown in Table 1.

[0072] Example 8

[0073] The difference from Example 1 is that the amount of sheet-like iron-silicon-aluminum alloy used is 40 wt%.

[0074] The electromagnetic performance test results of the prepared annular magnetic powder core are shown in Table 1.

[0075] Example 9

[0076] The difference from Example 4 is that the amount of phosphoric acid used is 0.01 wt%, which is the percentage of the total weight of phosphoric acid, iron-nickel alloy and sheet iron-silicon-aluminum alloy.

[0077] The electromagnetic performance test results of the prepared annular magnetic powder core are shown in Table 1.

[0078] Example 10

[0079] The difference from Example 4 is that the amount of phosphoric acid used is 0.1 wt%, based on the percentage of the total weight of phosphoric acid, iron-nickel alloy and sheet iron-silicon-aluminum alloy.

[0080] The electromagnetic performance test results of the prepared annular magnetic powder core are shown in Table 1.

[0081] Example 11

[0082] The difference from Example 4 is that the passivating agent used is 1 wt% aluminum dihydrogen phosphate.

[0083] The electromagnetic performance test results of the prepared annular magnetic powder core are shown in Table 1.

[0084] Example 12

[0085] The difference from Example 1 is that the passivating agent used is 2wt% chromic acid.

[0086] The electromagnetic performance test results of the prepared annular magnetic powder core are shown in Table 1.

[0087] Example 13

[0088] The difference from Example 4 is that the amount of phosphoric acid used is 3 wt%, based on the percentage of the total weight of phosphoric acid, iron-nickel alloy and sheet iron-silicon-aluminum alloy.

[0089] The electromagnetic performance test results of the prepared annular magnetic powder core are shown in Table 1.

[0090] Example 14

[0091] The difference from Example 4 is that the amount of phosphoric acid used is 5 wt%, based on the percentage of the total weight of phosphoric acid, iron-nickel alloy, and sheet iron-silicon-aluminum alloy.

[0092] The electromagnetic performance test results of the prepared annular magnetic powder core are shown in Table 1.

[0093] Example 15

[0094] The difference from Example 4 is that the amount of phosphoric acid used is 7 wt%, based on the percentage of the total weight of phosphoric acid, iron-nickel alloy and sheet iron-silicon-aluminum alloy.

[0095] The electromagnetic performance test results of the prepared annular magnetic powder core are shown in Table 1.

[0096] Example 16

[0097] The difference from Example 4 is that the adhesive used is 3% silicone resin.

[0098] The electromagnetic performance test results of the prepared annular magnetic powder core are shown in Table 1.

[0099] Example 17

[0100] The difference from Example 4 is that the ball milling time of the iron-silicon-aluminum alloy is 10 hours, and the resulting sheet-like iron-silicon-aluminum alloy is in the form of a thin sheet with a thickness of 1 μm.

[0101] The electromagnetic performance test results of the prepared annular magnetic powder core are shown in Table 1.

[0102] Example 18

[0103] The difference from Example 4 is that the molding pressure is 2000MPa and the adhesive is 3% silicone resin.

[0104] The electromagnetic performance test results of the prepared annular magnetic powder core are shown in Table 1.

[0105] Example 19

[0106] The difference from Example 5 is that the adhesive used is 3% silicone resin, the pressure is 1500 MPa, and the annealing temperature is 900°C.

[0107] The electromagnetic performance test results of the prepared annular magnetic powder core are shown in Table 1.

[0108] Example 20

[0109] The difference from Example 4 is that the annealing temperature is 900°C.

[0110] The electromagnetic performance test results of the prepared annular magnetic powder core are shown in Table 1.

[0111] Example 21

[0112] The difference from Example 4 is that the annealing temperature is 400°C.

[0113] The electromagnetic performance test results of the prepared annular magnetic powder core are shown in Table 1.

[0114] Example 22

[0115] The difference from Example 19 is that the annealing atmosphere is hydrogen.

[0116] The electromagnetic performance test results of the prepared annular magnetic powder core are shown in Table 1.

[0117] Comparative Example 1

[0118] The difference from Example 4 is that the ball milling time for the gas-atomized iron-silicon-aluminum alloy is 30 minutes, and the iron-silicon-aluminum alloy obtained after ball milling has an irregular particle shape.

[0119] The electromagnetic performance test results of the prepared annular magnetic powder core are shown in Table 1.

[0120] Comparative Example 2

[0121] The difference from Example 1 is that: the iron-silicon-aluminum alloy was directly atomized and was not ball-milled into a sheet structure.

[0122] The electromagnetic performance test results of the prepared annular magnetic powder core are shown in Table 1.

[0123] Comparative Example 3

[0124] The difference from Example 1 is that the passivating agent phosphoric acid was not added.

[0125] The electromagnetic performance test results of the prepared annular magnetic powder core are shown in Table 1.

[0126] Comparative Example 4

[0127] The difference from Example 4 is that the annealing atmosphere is air.

[0128] The electromagnetic performance test results of the prepared annular magnetic powder core are shown in Table 1.

[0129] Table 1

[0130]

[0131] As can be seen from the above description, the embodiments of the present invention achieve the following technical effects:

[0132] Comparing Examples 1 to 8, it can be seen that, compared with other ranges, limiting the amount of sheet-like iron-silicon-aluminum alloy to the preferred range of this application is beneficial to improving the resistivity of nickel-based magnetic composite materials, thereby reducing eddy current losses at high frequencies, while not affecting their superposition characteristics.

[0133] Comparing Examples 1 and 12, and Examples 4 and 11, it can be seen that using the passivating agent of the preferred type of this application is beneficial to improving the insulation of iron-nickel alloys and iron-silicon-aluminum alloys, thereby reducing the eddy current loss of iron-based magnetic composite materials.

[0134] Comparing Examples 4, 9, and 10 with Examples 13 to 15, it can be seen that, compared with other ranges, limiting the amount of passivating agent to the preferred range of this application is beneficial to improving the utilization rate of raw materials. At the same time, it improves the yield of passivation film in surface passivation treatment, which in turn is beneficial to further reduce the eddy current loss of iron-based composite magnetic materials.

[0135] Comparing Examples 4 and 16, it can be seen that using the preferred type of binder of this application can improve the bonding strength between the internal particles of the iron-based composite magnetic material, which will affect the effect of subsequent pressing and molding processes.

[0136] Comparing Examples 4 and 17 with Comparative Examples 1 and 2, it can be seen that the sheet-like iron-silicon-aluminum alloy not only has high permeability and resistivity, but its sheet-like structure can also play a role in spatial isolation. The synergistic effect of the two can improve the permeability of the iron-based magnetic powder core and reduce the eddy current loss between different alloys in the iron-based composite magnetic material.

[0137] Comparing Examples 4, 20, and 21, it can be seen that, compared to other ranges, limiting the annealing temperature to the preferred range of this application is beneficial to releasing the internal stress of the magnetic powder core, increasing its mechanical strength, and suppressing the deterioration of the soft magnetic properties of the magnetic powder core.

[0138] Comparing Examples 19 and 22, and Examples 4 and Comparative Example 4, it is evident that the annealing treatment is carried out in an inert gas atmosphere or a reducing atmosphere, such as nitrogen, argon, or hydrogen. This helps to suppress the oxidation of the magnetic powder core during the annealing process and inhibits the deterioration of the soft magnetic properties of the magnetic powder core.

[0139] Comparing all embodiments and comparative examples, it can be seen that, on the one hand, after surface passivation treatment and pressing molding of the sheet-like iron-silicon-aluminum alloy and iron-nickel alloy, the sheet-like iron-silicon-aluminum alloy adheres to the surface of the iron-nickel alloy. The high aspect ratio of the sheet-like iron-silicon-aluminum alloy not only has high permeability and resistivity, but its sheet-like structure also provides spatial isolation. The synergistic effect of the two can improve the permeability of the obtained iron-based magnetic powder core, while reducing eddy current losses between different alloys in the iron-based composite magnetic material. On the other hand, surface passivation treatment can form a passivation film on the surface of the iron-based composite magnetic material. The passivation film has good insulation properties, which is beneficial to further reduce the eddy current losses of the iron-based composite magnetic material. The addition of binder can make the particles inside the iron-based composite magnetic material adhere to each other, so as to facilitate the subsequent pressing molding effect. The addition of release agent can reduce the friction between the iron-based composite magnetic material and the mold, increase the compaction density, and extend the mold life. Furthermore, pressing and molding under an inert or reducing atmosphere can suppress oxidation of the iron-based magnetic powder core during annealing, and also inhibit the deterioration of the soft magnetic properties of the magnetic powder core. The iron-based magnetic powder core prepared by the above method has high permeability and quality factor (Q value), while also exhibiting low power loss.

[0140] It should be noted that the terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate so that the embodiments of this application described herein can be implemented, for example, in a sequence other than those described herein.

[0141] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing an iron-based magnetic powder core, characterized in that, The method for preparing the iron-based magnetic powder core includes: Iron-based composite magnetic materials are obtained by surface passivation treatment of iron-nickel alloy and sheet-like iron-silicon-aluminum alloy. The iron-based composite magnetic material is mixed with a binder and a release agent, and then pressed and molded under an inert or reducing atmosphere to obtain the iron-based magnetic powder core. The iron-nickel alloy is spherical with a D50 of 15–29 μm; the sheet-like iron-silicon-aluminum alloy has a thickness of 0.3–3 μm and a D50 of 40–60 μm; the projected area of ​​the iron-nickel alloy on the plane containing the sheet-like iron-silicon-aluminum alloy is larger than the area of ​​the sheet-like iron-silicon-aluminum alloy; the amount of the sheet-like iron-silicon-aluminum alloy is 1–20 wt% of the total weight of the sheet-like iron-silicon-aluminum alloy and the iron-nickel alloy. The surface passivation process includes: The passivating agent, the iron-nickel alloy, and the sheet-like iron-silicon-aluminum alloy are mixed to obtain the iron-based composite magnetic material; the amount of the passivating agent is 0.1-3 wt% based on the percentage of the total weight of the passivating agent, the iron-nickel alloy, and the sheet-like iron-silicon-aluminum alloy; the passivating agent is selected from one or more of the group consisting of phosphoric acid, chromic acid, and aluminum dihydrogen phosphate.

2. The method for preparing an iron-based magnetic powder core according to claim 1, characterized in that, The sheet-like iron-silicon-aluminum alloy is elliptical or circular.

3. The method for preparing an iron-based magnetic powder core according to claim 1, characterized in that, The adhesive is selected from one or more of the group consisting of silicone resin, phenolic resin, epoxy resin, glass powder, and water glass.

4. The method for preparing an iron-based magnetic powder core according to claim 1, characterized in that, The weight of the binder accounts for 0.3 to 3 wt% of the total weight of the iron-based composite magnetic material and the binder.

5. The method for preparing an iron-based magnetic powder core according to claim 1, characterized in that, The release agent is selected from one or more of the group consisting of stearic acid compounds, talc, and release oil.

6. The method for preparing an iron-based magnetic powder core according to claim 1, characterized in that, The release agent accounts for 0.1 to 0.4 wt% of the total weight of the iron-based composite magnetic material and the binder.

7. A type of iron-based magnetic powder core, characterized in that, The iron-based magnetic powder core has a permeability of 100–160 H / m, a quality factor of 81–156, and a power loss of 2180–3150 mW / cm. 3 The iron-based magnetic powder core is prepared by the method for preparing iron-based magnetic powder core according to any one of claims 1 to 6.

8. An electromagnetic induction device, comprising an electromagnetic induction unit, characterized in that, The electromagnetic induction unit is made from the iron-based magnetic powder core as described in claim 7.

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