A MHz-level low-loss sendust magnetic powder core and its preparation method

Abstract

The present invention discloses a MHz-level low-loss sendust magnetic powder core and a preparation method thereof, comprising the following steps: (1) insulation coating: adding a coating agent, zinc acetate solution, to sendust alloy powder, stirring evenly, then frying on a heating furnace to dry, cooling, forming a passivated powder, then adding a binder, stirring evenly, heating and frying to dry, and cooling; (2) pressing and molding: adding a release agent to the coated powder, stirring evenly, and pressing into a green part; (3) heat treatment: annealing the green part in step (2) under a protective atmosphere, cooling, and obtaining a MHz-level low-loss sendust magnetic powder core. This technical solution creatively uses zinc acetate as a coating agent to passivate and coat sendust powder, thereby increasing its operating frequency to the high-frequency MHz range while maintaining a relatively low loss. At the same time, it also has a high effective magnetic permeability and magnetic flux density BS, suitable for MHz working conditions, and stable performance.

Description

Technical Field

[0001] The present invention relates to the technical field of sendust magnetic powder core materials, and in particular to a MHz-level low-loss sendust magnetic powder core and a preparation method thereof. Background Art

[0002] In recent years, the rapid development of new energy vehicles, artificial intelligence, and robotics has accelerated the development of power electronics toward higher frequencies, miniaturization, and increased energy efficiency. Although third-generation wide-bandgap semiconductors such as SiC and GaN enable power electronics to operate at higher megahertz (MHz) frequencies, no soft magnetic material has yet fully realized the potential of wide-bandgap semiconductors. Therefore, the development of high-frequency, low-loss soft magnetic materials has become a top priority. Sendust metal powder cores, with their advantages such as high flux density, high DC bias, and low loss, are widely used in power electronics and can adapt to the trend toward higher frequencies. However, at MHz frequencies, Sendust metal powder cores experience significant increases in hysteresis and eddy current losses, severely limiting the efficiency of high-frequency power electronics.

[0003] There are already a number of technologies that can increase the operating frequency of Sendust magnetic powder core materials and reduce their power loss, but the operating frequency is mostly only in the range of 100kHz-500kHz and cannot be increased to 1MHz. Moreover, at high frequencies of MHz, the loss of the core increases sharply. If the core loss is too large, it will affect the service life of the core. Therefore, how to significantly reduce the core loss at high frequencies of MHz is a problem that still needs to be solved in this field.

[0004] Patent application number CN117476304A discloses a high-frequency, low-loss metal soft magnetic powder core and its preparation method. Through methods such as particle size classification and optimized coating process, the metal magnetic powder core prepared has a power loss of 518W / kg at 100kHz / 100mT and an effective magnetic permeability of 62. However, the metal magnetic powder core prepared by this method has an operating frequency that is too low and cannot maintain low loss and effective magnetic permeability in the megahertz frequency band. Patent application number CN116313358A discloses a method for preparing a FeSiAl magnetic powder core coated with multiple ferrites. By coating the outer surface of the FeSiAl magnetic powder core with NiZn ferrite powder and MnZn ferrite powder, the performance of the composite magnetic powder core is improved, thereby reducing its power loss while increasing the magnetic permeability of the magnetic powder core. However, the magnetic powder core prepared by this method has a power loss of 680.16mW / cm at 100kHz / 100mT. 3The operating frequency is too low to maintain low loss and permeability in the megahertz frequency band. Patent application number CN115565773A discloses a method for preparing MHz-level high-stability soft magnetic powder cores. The method uses a sol-gel method to insulate and coat pretreated metal soft magnetic powder, and finally presses and forms a composite powder core. The prepared metal soft magnetic composite powder core material has an effective permeability stability of 99.1% within the 1MHz range, but at 100kHz / 100mT, the power loss is 926.94mW / cm 3 , the effective magnetic permeability is 48.6, the loss is large and the magnetic permeability is low, which cannot be used in the MHz frequency band. Patent application with publication number CN113674979A discloses a method for preparing a metal soft magnetic core for ultra-high frequency and its materials. By selecting fine powder and performing surface active treatment, the sendust magnetic powder core prepared has a power loss of 1996.8kW / m under 500kHz / 100mT conditions. 3 , with an effective magnetic permeability of 60.2. Although the metal soft magnetic core has a certain improvement in operating frequency, the power loss of the metal soft magnetic core is also high. Patent application with publication number CN119296948A discloses a method for simultaneously reducing the hysteresis loss and eddy current loss of FeSiAl magnetic powder cores. The method involves adding a salt solution containing metal M to the FeSiAl magnetic powder core, drying it to obtain an insulating coated magnetic powder core, and finally pressing it to obtain FeSiAl:M / Al2O3. The magnetic powder core prepared by this method has a core loss reduced to 1120-1620mW / cm3 at 1MHz / 0.05T. 3 , and the magnetic permeability is about 60. Although the magnetic powder core can be used at 1 MHz, the magnetic permeability of the obtained magnetic powder core is low, and during the preparation process, the salt solution containing metal M needs to be stirred in a closed container, which takes a long time and has strict preparation conditions. Summary of the Invention

[0005] In order to solve the above technical problems, the purpose of the present invention is to provide a MHz-level low-loss Sendust magnetic powder core and its preparation method, which can increase the operating frequency of the Sendust magnetic powder core material to MHz while also having a higher effective magnetic permeability and saturation magnetic induction intensity B. S performance.

[0006] In order to achieve the above-mentioned purpose, the present invention adopts the following technical solutions:

[0007] A method for preparing a MHz-level low-loss Sendust magnetic powder core comprises the following steps:

[0008] (1) Insulation coating: Add zinc acetate solution as coating agent to the iron-silicon-aluminum alloy powder, stir evenly, then place it on a heating furnace to fry and dry, cool to form passivated powder, then add a binder, stir evenly, heat and fry until dry, and cool;

[0009] (2) Compression molding: Add a release agent to the coated powder, stir evenly, and press into a green part;

[0010] (3) Heat treatment: The green part in step (2) is annealed in a protective atmosphere and cooled to obtain a MHz-level low-loss Sendust magnetic powder core.

[0011] Preferably, the composition of the Sendust alloy powder in step (1) is as follows, in mass percentage: Fe: 84.6%-84.8%, Si: 9.6%, and the remainder is Al.

[0012] Preferably, in step (1), the zinc acetate solution consists of the following components: zinc acetate: 0.3wt%-0.8wt%, and the solvent is deionized water.

[0013] Preferably, in step (1), the binder is a methyl acetate solution of a silicone resin or an acetone solution of a silicone resin.

[0014] Preferably, in step (1), the temperature for frying to dryness is 130°C to 180°C.

[0015] Preferably, in step (2), the release agent is selected from one or more of zinc stearate, calcium stearate, barium stearate and paraffin, and the amount of the release agent added is 0.3 wt%-0.4 wt%.

[0016] Preferably, in step (3), the annealing temperature is 700°C to 750°C, the heating rate is 8°C / min to 10°C / min, the holding time is 1 hour, and the annealing atmosphere is nitrogen.

[0017] Preferably, in step (1), the Sendust aluminum alloy powder synthesized by metal atomization is selected, sieved to 600 mesh, and stress annealed in advance at a temperature of 780°C-810°C for a time of 1h-1.5h.

[0018] As a preference, in step (2), the green piece is pressed into a ring shape, and the unit molding pressure is 18t / cm 3 -20t / cm 3 .

[0019] A MHz-level low-loss Sendust magnetic powder core prepared by the method described above.

[0020] The present invention has the following beneficial effects due to the adoption of the above technical solution:

[0021] 1. The present invention creatively uses zinc acetate as a coating agent to passivate and coat Sendust powder. The resulting Sendust magnetic powder core material is suitable for MHz operating conditions and has stable performance, filling the gap in domestic Sendust magnetic powder core materials that are almost completely used at this operating frequency. At the same time, under this operating condition, the loss of the present invention is greatly reduced, far superior to ordinary Sendust magnetic powder core materials;

[0022] 2. The sendust soft magnetic metal powder in the present invention is obtained by 600-mesh screening. Compared with the prior art method of reducing core loss by particle size classification and using ultra-fine powder, the powder preparation process of the sendust soft magnetic metal powder in the present invention is simpler, the utilization rate of the finished powder is higher, and the preparation cost of the material is effectively reduced;

[0023] 3. Compared to directly adding an inorganic coating agent, the present invention uses zinc acetate sintering to form a coating layer, which not only produces a more uniform and dense insulating layer but also offers advantages such as higher bonding strength and oxidation resistance, while simplifying the passivation and coating process. The use of zinc acetate as a coating agent can reduce magnetic domain displacement resistance, lower hysteresis loss, and increase effective magnetic permeability. The increased coating layer resistance reduces eddy current loss at high frequencies, allowing the Sendust magnetic powder core prepared by the present invention to maintain relatively low loss characteristics even under high-frequency MHz operating conditions.

[0024] 4. The Sendust magnetic powder core material of the present invention increases its operating frequency to the high frequency MHz range and maintains a relatively low loss. At the same time, it also has a higher effective magnetic permeability and magnetic flux density B S Under the conditions of 1MHz / 50mT, the Sendust magnetic powder core material prepared by the present invention not only has a loss as low as 945.6kW / m 3 , and the effective magnetic permeability is higher than 75, under the condition of 10kOe, B S Higher than 900mT. Moreover, it is low-cost, simple to operate, and easy to mass-produce. Therefore, this material can be well applied in the MHz high-frequency field. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a microscopic morphology of the Sendust magnetic powder core material prepared in Example 3 and a corresponding Zn element distribution diagram. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solutions and advantages of this application more clear, the technical solutions of this application will be clearly and completely described below in conjunction with specific embodiments. Obviously, the embodiments described are only part of the embodiments of this application, not all of them. In the present invention, unless otherwise specified, all parts and percentages are by weight, and all equipment and raw materials can be purchased from the market or are commonly used in the industry.

[0027] The endpoints of the ranges and any values ​​disclosed in this application are not limited to the exact ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range or the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges.

[0028] The present invention discloses a method for preparing a MHz-level low-loss Sendust magnetic powder core, comprising the following steps:

[0029] (1) Insulation coating: Add zinc acetate solution as coating agent to the iron-silicon-aluminum alloy powder, stir evenly, then place it on a heating furnace to fry and dry, cool to form passivated powder, then add a binder, stir evenly, heat and fry until dry, and cool;

[0030] (2) Compression molding: Add a release agent to the coated powder, stir evenly, and press into a green part;

[0031] (3) Heat treatment: The green part in step (2) is annealed in a protective atmosphere and cooled to obtain a MHz-level low-loss Sendust magnetic powder core.

[0032] The composition of the iron-silicon-aluminum alloy powder in step (1), in terms of mass percentage, is as follows: Fe: 84.6%-84.8%, Si: 9.6%, and the remainder Al. The proportion of Fe can be selected from 84.6%, 84.7%, 84.8%, or other values ​​within the range. The selection can be based on actual needs and is not limited here. The sendust aluminum alloy powder is a sendust aluminum alloy powder synthesized by metal atomization, and can be prepared by the following steps: weighing corresponding weights of iron blocks, silicon ingots and aluminum blocks according to the designed alloy component ratio, placing them in a vacuum medium frequency furnace for smelting, pouring the molten steel into an atomizing device, and simultaneously impacting the molten steel with high-pressure nitrogen. After rapid cooling, the sendust aluminum alloy powder is obtained, and the obtained sendust aluminum alloy powder is sieved for particle size, and sendust aluminum alloy powder with a mesh size of 600 is selected, and then stress annealing is performed. The annealing temperature is 780°C-810°C, specifically selected from 780°C, 790°C, 800°C, and 810°C, or other values ​​within the range, which can be selected according to actual needs and is not limited here; the annealing time is 1h-1.5h, specifically selected from 1h, 1.1h, 1.2h, 1.3h, 1.4h, and 1.5h, or other values ​​within the range, which can be selected according to actual needs and is not limited here.

[0033] In some embodiments, based on the Sendust alloy powder, the zinc acetate solution comprises the following components: 0.3 wt% to 0.8 wt% zinc acetate, and the solvent is deionized water. The mass ratio of zinc acetate to the Sendust alloy powder can be specifically selected from 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, and 0.8 wt%, or other values ​​within the range. The selection is based on actual needs and is not limited herein.

[0034] In some embodiments, the binder is a methyl acetate solution of a silicone resin or an acetone solution of a silicone resin. The binder may also be other conventional binders used in the art. Based on the Sendust alloy powder, the binder used in the present invention is composed of 0.5 wt% silicone resin and 5 wt% methyl acetate / acetone.

[0035] In some embodiments, the temperature for frying in step (1) is 130°C to 180°C, which can be specifically selected from 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, or other values ​​within the range. The selection can be made based on actual needs and is not limited here.

[0036] In some embodiments, the release agent is selected from one or more of zinc stearate, calcium stearate, barium stearate and paraffin. Based on the sendust alloy powder, the amount of the release agent added is 0.3wt%-0.4wt%, specifically selected from 0.3wt%, 0.32wt%, 0.34wt%, 0.36wt%, 0.38wt%, 0.4wt%, or other values ​​within the range. It can be selected according to actual needs and is not limited here.

[0037] In some embodiments, the green part is pressed into a ring shape with a unit forming pressure of 18t / cm 3 -20t / cm 3 , specifically 18t / cm 3 、19t / cm 3 、20t / cm 3 , or other values ​​within the range, which can be selected according to actual needs and are not limited here.

[0038] In some embodiments, the annealing temperature in step (3) is 700°C~750°C, which can be specifically selected from 700°C, 710°C, 720°C, 730°C, 740°C, 750°C, or other values ​​within the range, which can be selected according to actual needs and is not limited here; the heating rate is 8°C / min-10°C / min, which can be specifically selected from 8°C / min, 8.5°C / min, 9°C / min, 9.5°C / min, 10°C / min, or other values ​​within the range, which can be selected according to actual needs and is not limited here; the holding time is 1 hour, the annealing atmosphere is nitrogen, and the MHz-level low-loss sendust magnetic powder core is obtained by rapid cooling after the holding is completed.

[0039] Generally speaking, the prepared MHz-level low-loss sendust magnetic powder core needs to be placed in an impregnation liquid, soaked for a certain period of time, cleaned, placed in an oven for baking, and then placed in a coating machine for spraying to obtain a finished magnetic powder core. The impregnation liquid can be a conventional impregnation liquid of 0.5% mixture of epoxy resin and methyl acetate, or other conventional impregnation liquids used in this field.

[0040] The invention also discloses a MHz-level low-loss Sendust magnetic powder core prepared by the method described above.

[0041] The following is further explained with reference to the examples. The "mass ratio" referred to below is based on the Sendust alloy powder.

[0042] Example 1:

[0043] A method for preparing a MHz-level low-loss Sendust magnetic powder core comprises the following steps:

[0044] (1) Insulation coating: Add zinc acetate solution as coating agent to the sendust alloy powder, wherein the mass ratio of zinc acetate is 0.3%; stir evenly, heat and fry until dry while stirring, and keep the temperature between 100-130℃, cool to form passivated powder, and then add binder, which is composed of 0.5wt% silicone resin and 5wt% acetone, stir evenly and heat and fry until dry, and keep the temperature between 100℃-130℃, and then let it cool;

[0045] (2) Pressing: Add a release agent (0.4 wt% zinc stearate) to the coated powder and stir evenly. 3 -20t / cm 3 Pressing into a ring-shaped green part;

[0046] (3) Heat treatment: The green part in step (2) was sintered in a nitrogen atmosphere furnace at 730°C for 1 hour, cooled, impregnated, baked, and sprayed to prepare a magnetic powder core sample.

[0047] In this embodiment, the Sendust alloy powder is a 600-mesh Sendust alloy powder synthesized by metal atomization. The Sendust alloy powder contains, by mass percentage, 84.6% Fe, 9.6% Si, and the remainder Al.

[0048] Example 2:

[0049] The difference between this embodiment and embodiment 1 is that in step (1), the mass ratio of zinc acetate is 0.4%, and other conditions are consistent with those in embodiment 1.

[0050] Example 3:

[0051] The difference between this embodiment and embodiment 1 is that in step (1), the mass ratio of zinc acetate is 0.5%, and other conditions are consistent with those in embodiment 1.

[0052] Example 4:

[0053] The difference between this embodiment and embodiment 1 is that in step (1), the mass ratio of zinc acetate is 0.6%, and other conditions remain the same as those in embodiment 1.

[0054] Example 5:

[0055] The difference between this embodiment and embodiment 1 is that in step (1), the mass ratio of zinc acetate is 0.7%, and other conditions are consistent with those in embodiment 1.

[0056] Example 6:

[0057] The difference between this embodiment and embodiment 1 is that in step (1), the mass ratio of zinc acetate is 0.8%, and other conditions remain the same as those in embodiment 1.

[0058] Example 7:

[0059] The difference between this embodiment and embodiment 3 is that, in this embodiment, the contents of the components in the sendust alloy powder are, by mass percentage, 84.8% Fe, 9.6% Si, and the remainder Al. Other conditions remain the same as those in embodiment 1.

[0060] Comparative Example 1:

[0061] The difference between this comparative example and Example 1 is that in step (1), the mass ratio of zinc acetate is 0.1%, and other conditions are consistent with Example 1.

[0062] Comparative Example 2:

[0063] The difference between this comparative example and Example 1 is that in step (1), the mass ratio of zinc acetate is 0.2%, and other conditions are consistent with Example 1.

[0064] Comparative Example 3:

[0065] The difference between this comparative example and Example 1 is that in step (1), the mass ratio of zinc acetate is 0.9%, and other conditions are consistent with Example 1.

[0066] Comparative Example 4:

[0067] The difference between this comparative example and Example 1 is that in step (1), the coating agent is zinc ferrite, the mass ratio of zinc ferrite is 0.5%, and the average particle size of zinc ferrite is 1 μm. Other conditions remain the same as in Example 1.

[0068] In the above Examples 1-7 and Comparative Examples 1-4, the final composition of the sendust powder was consistent with the designed composition as determined by a Rigaku Primus II XRF analyzer. The micromorphology and element distribution of the magnetic powder core sample prepared in Example 3 were observed using a Thermo Fisher Apreo scanning electron microscope. The results are as follows: Figure 1 As shown, it can be seen that Zn is evenly distributed on the surface of the Sendust magnetic powder core.

[0069] Performance tests were performed on the magnetic powder core samples prepared in Examples 1-7 and Comparative Examples 1-4. The inductance of the Sendust magnetic powder core samples was measured using an LCR meter and converted to magnetic permeability using a formula. The power loss of the Sendust magnetic powder cores was measured using an Iwasaki SY-8218 AC BH analyzer at 1 MHz / 50 mT. The saturation magnetic induction intensity of the Sendust magnetic powder core samples was measured using a METRONSK-110 DC BH analyzer at 10 kOe. The test results are shown in Table 1 below:

[0070] Table 1: Performance test results of magnetic powder core samples prepared in Examples 1-7 and Comparative Examples 1-4

[0071] Group <![CDATA[P cv (kW / m 3 )(1MHz / 50mT)]]> Magnetic permeability <![CDATA[B s (mT)]]> Example 1 1106.7 71.7 910 Example 2 970.7 75.6 905 Example 3 945.6 78.5 903 Example 4 965.8 80.8 900 Example 5 1183.8 80.1 895 Example 6 1192.1 80.6 890 Example 7 1079.2 82.2 896 Comparative Example 1 1503.1 72.4 912 Comparative Example 2 1327.3 73.1 912 Comparative Example 3 1765 70.2 889 Comparative Example 4 3263.1 62.3 897

[0072] Results analysis: From Table 1 above, it can be seen that in the MHz frequency band, the core loss P of the magnetic powder cores prepared in Examples 1-7 is cv Less than 1200kW / m 3 , which is much lower than the core loss of the magnetic powder core prepared by directly adding inorganic coating agent zinc ferrite in Comparative Example 4. This is because in the preparation process of the present invention, zinc acetate is weakly acidic after hydrolysis, and during the sintering process, zinc oxide is first decomposed and then evenly distributed on the surface of the sendust matrix through diffusion reaction, and further reacts with the matrix in situ at high temperature to form a zinc ferrite spinel layer. The in-situ reaction can form a uniformly distributed zinc ferrite spinel layer. Since the spinel structure layer has better insulation, acid and alkali resistance and oxidation resistance than metal, this method of forming a coating layer by sintering zinc acetate can not only obtain a more uniform insulating layer, but also has the advantages of higher bonding strength and oxidation resistance, compared with directly adding an inorganic coating agent, while simplifying the passivation and coating process flow. Since the coating structure layer is more uniform and dense, it can reduce the resistance to magnetic domain displacement, reduce hysteresis loss, and improve effective magnetic permeability. Since the coating layer resistance is increased, the eddy current loss at high frequency is reduced. This allows the present invention to maintain a relatively low loss characteristic even under high-frequency megahertz operating conditions. However, the magnetic powder core prepared in Comparative Example 4 exhibited significantly higher losses and decreased magnetic permeability at 1 MHz / 50 mT. This is because in Comparative Example 4, the inorganic coating agent zinc ferrite was directly used to passivate and coat the sendust magnetic powder core. This resulted in poor coating uniformity and low inter-particle bonding, increasing magnetic anisotropy and hysteresis losses, ultimately leading to higher losses and lower magnetic permeability.

[0073] As shown in Table 1, the mass ratio of zinc acetate should be added in the range of 0.3wt%-0.8wt%. Too much or too little zinc acetate addition will lead to an increase in the core loss of the prepared Sendust magnetic powder core sample and a decrease in the magnetic permeability.

[0074] Overall, the performance of the magnetic powder core prepared under the preparation conditions of Example 3 is the best. Under the conditions of 1MHz / 50mT, the loss is as low as 945.6kW / m 3 , and the effective magnetic permeability is higher than 75, under the condition of 10kOe, B S Above 900mT.

[0075] Although the embodiments of the present invention have been shown and described above, it is understandable that the above embodiments are illustrative and cannot be understood as limiting the present invention. Those skilled in the art may change, modify, replace, modify, delete some features, add features, or re-combine features to form a technical solution within the scope of the present invention without departing from the principles and purpose of the present invention. Any simple modifications, equivalent changes, and modifications made to the above embodiments based on the innovative principles of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a MHz-level low-loss Sendust magnetic powder core, characterized in that: The following steps are involved: (1) Insulation coating: Add zinc acetate solution as coating agent to the iron-silicon-aluminum alloy powder, stir evenly, then place it on a heating furnace to fry and dry, cool to form passivated powder, then add a binder, stir evenly, heat and fry until dry, and cool; (2) Compression molding: Add a release agent to the coated powder, stir evenly, and press into a green part; (3) Heat treatment: annealing the green part in step (2) under a protective atmosphere. Zinc acetate decomposes zinc oxide during the sintering process and reacts with the matrix in situ to form a zinc ferrite spinel layer. Cooling is performed to obtain a MHz-level low-loss sendust magnetic powder core. The components of the iron-silicon-aluminum alloy powder in step (1) are, by mass percentage, 84.6%-84.8% Fe, 9.6% Si, and the remainder Al; the zinc acetate solution is composed of 0.3 wt %-0.8 wt % zinc acetate, and the solvent is deionized water.

2. The method for preparing a MHz-level low-loss Sendust magnetic powder core according to claim 1, characterized in that: In step (1), the binder is a methyl acetate solution of a silicone resin or an acetone solution of a silicone resin.

3. The method for preparing a MHz-level low-loss Sendust magnetic powder core according to claim 1, characterized in that: In step (1), the temperature for frying is 130°C to 180°C.

4. The method for preparing a MHz-level low-loss Sendust magnetic powder core according to claim 1, characterized in that: In step (2), the release agent is selected from one or more of zinc stearate, calcium stearate, barium stearate and paraffin, and the added amount of the release agent is 0.3 wt%-0.4 wt%.

5. The method for preparing a MHz-level low-loss Sendust magnetic powder core according to claim 1, characterized in that: In step (3), the annealing temperature is 700°C to 750°C, the heating rate is 8°C / min to 10°C / min, the holding time is 1h, and the annealing atmosphere is nitrogen.

6. The method for preparing a MHz-level low-loss Sendust magnetic powder core according to claim 1, characterized in that: In step (1), the iron-silicon-aluminum alloy powder synthesized by metal atomization is selected, sieved with 600 mesh, and stress annealed in advance at a temperature of 780° C. to 810° C. for 1 h to 1.5 h.

7. The method for preparing a MHz-level low-loss Sendust magnetic powder core according to claim 1, characterized in that: In step (2), the green part is pressed into a ring shape with a unit forming pressure of 18 t / cm 3 -20t / cm 3 .

8. A MHz-level low-loss Sendust magnetic powder core, characterized in that: The MHz-level low-loss Sendust magnetic powder core is prepared by the preparation method of any one of claims 1 to 7.

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