Iron-silicon magnetic powder core and preparation method thereof

Abstract

The invention discloses an iron-silicon magnetic powder core and a preparation method thereof, and belongs to the technical field of soft magnetic materials and powder metallurgy. The preparation method comprises the following steps: fully mixing a phosphoric acid metal ion solution containing phosphoric acid and metal acid phosphate with iron-silicon alloy powder; the mass ratio of the phosphoric acid solution to the metal acid phosphate to the iron-silicon alloy powder is (0.25-1.5): (0.5-3): 100, and the mass ratio of the phosphoric acid solution to the metal acid phosphate to the iron-silicon alloy powder is (0.25-1.5): (0.5-3): 100; and the coated iron-silicon alloy powder is pressed, and the iron-silicon magnetic powder core is prepared. According to the scheme, the iron-silicon alloy powder is added into the weak acid mixed solution of the phosphoric acid and the metal acid phosphate, so that the dosage of the phosphoric acid in the passivation process is reduced, the passivation speed of the iron-silicon alloy powder is slowed down, and a more uniform insulating coating layer can be formed; meanwhile, by adding metal acid phosphate, acid radical ions are provided in the passivation process, and corresponding orthophosphoric acid metal is generated on the outer surface of the iron-silicon alloy powder.

Description

Technical Field

[0001] This invention relates to the fields of soft magnetic materials and powder metallurgy, and more specifically, to an iron-silicon magnetic powder core and its preparation method. Background Technology

[0002] Metal powder cores are soft magnetic composite materials prepared through a series of processes including mixing ferromagnetic particles with insulating dielectric materials, pressing, and heat treatment. Common metal powder cores include ferromagnetic powder cores, iron-silicon alloy powder cores, iron-silicon-aluminum powder cores, and iron-nickel powder cores. Among these, iron-silicon alloy powder cores have become the preferred material for motor cores due to their high saturation magnetic induction of up to 1.6T, near-zero magnetostriction coefficient, excellent DC bias performance, and low cost. Furthermore, their unique three-dimensional flux path design overcomes the structural limitations of traditional two-dimensional cores (such as laminated silicon steel and amorphous ribbon), improving design flexibility and efficiency, and providing new possibilities for motor miniaturization. However, under high energy density input conditions, the energy loss problem of ferromagnetic powder cores is particularly prominent, especially in mid-to-high frequency scenarios exceeding 100kHz, where iron losses increase significantly. This characteristic contradicts the development trend of motor technology towards higher power, higher speed, lower energy consumption, and higher frequency.

[0003] Under the influence of an alternating magnetic field, the iron losses of soft magnetic materials mainly include hysteresis loss, eddy current loss, and residual loss. When the operating frequency exceeds 100kHz, the induced current generated by the applied magnetic field will form a local magnetic field distortion within the material, causing the skin effect and reducing the magnetization efficiency, making eddy current loss the dominant factor limiting high-frequency performance. Eddy current loss can be further divided into intraparticle (microscopic) eddy current loss and interparticle (macroscopic) eddy current loss. Studies have shown that there are two core strategies for reducing high-frequency eddy current loss: one is to reduce microscopic eddy current loss by refining the particle size to less than the skin depth; the other is to suppress macroscopic eddy current loss by increasing the interparticle resistivity. However, excessively increasing the proportion of fine powder in the raw materials will reduce the green density of iron-silicon soft magnetic composite materials, thereby affecting the permeability and saturation magnetic induction. Therefore, the insulating coating process, which uses an insulating medium to construct high-resistivity grain boundaries on the surface of iron-silicon alloy powder to block the eddy current path induced by the alternating magnetic field, has become the core link in the performance control of iron-silicon soft magnetic composite materials.

[0004] Common organic insulating materials, such as epoxy resin, acrylic resin, and polyurethane, were once widely used due to their good adhesion and flexibility. However, due to their poor heat resistance, they are prone to carbonization and decomposition at high temperatures approaching 550°C, making it difficult to meet the requirements of heat treatment processes at 500~800°C.

[0005] Inorganic insulating materials, with their excellent thermal stability and high resistivity, have become a current research hotspot. Inorganic insulating media, represented by ceramic oxides such as MgO, Al2O3, and SiO2, and ferrites such as Mn-Zn and Mg-Zn, can maintain their insulation properties and alleviate internal stress at higher temperatures. However, their hardness and brittleness may lead to cracks and porosity during the molding process, affecting the final magnetic and mechanical properties. Furthermore, the coating technology for these inorganic insulating media has not yet achieved large-scale industrial application due to high cost, complex processes, and insufficient technological maturity, and remains mainly in the laboratory research stage.

[0006] Phosphoric acid passivation has become the most widely used inorganic insulating coating technology in commercial iron-silicon soft magnetic composites due to its low cost, high efficiency, and simple process. This technology forms a dense, high-resistivity phosphate insulating layer on the powder surface through an interfacial chemical reaction between phosphoric acid and iron-silicon alloy powder. Furthermore, the thermal expansion coefficient of the phosphate layer is similar to that of the iron-silicon matrix, which helps reduce interfacial stress and delamination during heat treatment.

[0007] For example, Chinese patent application CN119008160A discloses a method for preparing a high-permeability ferromagnetic powder core material. The method involves first inorganically coating the raw iron-silicon metal magnetic powder core with phosphoric acid to form a phosphide film on the powder surface, then adding resin for organic coating, and finally adding an appropriate amount of lubricant to prepare a high-permeability ferromagnetic powder core. In this application, the amount of phosphoric acid used needs to be strictly controlled during the preparation process, and the phosphoric acid reaction can cause uneven surface morphology of the microparticles.

[0008] For example, Chinese patent application CN120072495A discloses an iron-based magnetic powder core, its preparation method, and its application. The method involves pre-coating the core with a mixed solution of silica sol, silane coupling agent, and polyurethane to obtain modified iron-silicon alloy powder. Then, phosphoric acid and / or aluminum dihydrogen phosphate solution are used as passivating agents to treat the modified iron-silicon alloy powder, resulting in an insulatingly coated passivated magnetic powder. This application uses a modified insulating adhesive to pre-coat the iron-silicon magnetic powder. Although the insulating particles in the modified insulating adhesive are fine and easily adsorbed onto the magnetic powder surface, and the subsequent insulating coating treatment makes the particle distribution on the magnetic powder surface more uniform, achieving better insulation and effectively reducing the loss of the magnetic powder core, the introduction of the modified insulating adhesive increases the thickness of the coating layer, reduces the magnetic permeability of the magnetic powder core, and the method has many influencing factors in its operation, making it unsuitable for large-scale production. Summary of the Invention

[0009] 1. Technical problems to be solved To address the technical problems of complex preparation processes and the need for further optimization of the coating thickness in existing phosphoric acid passivation processes, this invention provides an iron-silicon magnetic powder core and its preparation method. This method reduces the amount of passivating phosphoric acid used by adding iron-silicon alloy powder to a phosphoric acid and metal acid phosphate solution, thereby slowing down the passivation rate of the iron-silicon alloy powder and facilitating the formation of a more uniform insulating coating layer. Simultaneously, the addition of metal acid phosphate provides anion ions during the passivation process, generating corresponding orthophosphate metal salts on the outer surface of the iron-silicon alloy powder.

[0010] 2. Technical solutions adopted To achieve the above objectives, the technical solution provided by the present invention is as follows: The first aspect of this invention provides a method for preparing an iron-silicon magnetic powder core, comprising the following steps: thoroughly mixing an iron-silicon alloy powder with a phosphoric acid metal ion solution containing phosphoric acid and a metal acid phosphate, so as to passivate the outer surface of the iron-silicon alloy powder and form an insulating coating layer, wherein the mass ratio of the phosphoric acid solution, the metal acid phosphate and the iron-silicon alloy powder is 0.25~1.5:0.5~3:100; and pressing the coated iron-silicon alloy powder to prepare an iron-silicon magnetic powder core.

[0011] It should be noted that when using only phosphoric acid solution for passivation, the amount of phosphoric acid solution used during the passivation process needs to be precisely calculated. If the amount is too large, the passivation rate will be too fast, easily forming a thick insulating coating layer on the outer layer of the iron-silicon alloy powder, and increasing the unevenness of corrosion on the surface of the iron-silicon alloy powder. Conversely, if the amount of phosphoric acid solution is too small, the passivation layer will not be able to completely coat the outer surface of the iron-silicon alloy powder. However, it is usually difficult to accurately control the amount of phosphoric acid solution using existing processes, thus affecting the coating effect. Based on the above, this application uses a mixed solution containing phosphoric acid and metal acid phosphate as the insulating coating solution, and the mass ratio of phosphoric acid solution, metal acid phosphate, and iron-silicon alloy powder is 0.25~1.5:0.5~3:100, thereby enabling slow corrosion of the iron-silicon alloy powder surface during the passivation process and achieving adjustable passivation process.

[0012] Specifically, metal acid phosphates can provide acid radicals and metal cations, which can not only reduce the amount of phosphoric acid used, but also combine with phosphate radicals during the passivation process to form more stable orthophosphates corresponding to the metal ions. This can reduce the supersaturation of crystallization, promote the precipitation and crystallization of iron phosphate and orthophosphates corresponding to the metal ions, and generate a composite passivation layer with an amorphous crystalline mixed phase in situ on the outer surface of the iron-silicon alloy powder.

[0013] It should be further explained that the passivation coating preparation method of this invention has several advantages. Firstly, compared with existing methods that use strong acids, such as concentrated sulfuric acid or strong oxidizing solutions, as passivating agents, the passivation process is slower, making it suitable for industrial applications and reducing uneven corrosion or preventing excessive corrosion. Secondly, in the phosphoric acid passivation process, if metal oxides are directly added, even if the particle size of the metal oxides is limited to the nanometer scale, the low solubility of metal oxides makes it difficult for them to react in a phosphoric acid solution of a limited concentration. Furthermore, even if the metal oxides react with phosphoric acid, a dense passivation film is formed on the surface of the metal oxides, hindering further passivation reactions and making it difficult for the reaction to continue. Therefore, it is difficult to generate phosphoric acid in situ to participate in the passivation process of iron-silicon alloy powder; the passivation film can only adhere to the outer surface of the iron-silicon alloy powder in the form of particles. Moreover, the passivation film on the outer surface of the metal oxides limits its adhesion strength to the iron-silicon alloy powder, resulting in poor uniformity in this coating method. In addition, compared with existing multilayer coatings, the preparation process of this application is simpler, and the resulting coating layer is thinner and more uniform.

[0014] When the mass ratio of metal acid phosphate to iron-silicon alloy powder is between 0.5 and 3:100, as the proportion of metal acid phosphate increases, the thickness of the insulating layer covering the iron-silicon alloy powder gradually increases. This leads to a decrease in saturation magnetization, a reduction in the loss of the magnetic powder core, and an increase in resistivity. However, if the mass ratio exceeds 3:100, the saturation magnetization will significantly decrease, reducing the overall performance of the iron-silicon magnetic powder core. Therefore, the mass ratio of metal acid phosphate to iron-silicon alloy powder should not exceed 3%.

[0015] Furthermore, the mass ratio of the phosphoric acid solution, the metal acid phosphate, and the iron-silicon alloy powder is 0.25~0.5:1.5~2:100. Within this range of addition proportions, the loss-saturation magnetization of the prepared iron-silicon magnetic powder core reaches the optimal overall performance.

[0016] Furthermore, the phosphate metal ion solution is mixed uniformly with the iron-silicon alloy powder, specifically including the following steps: adding the iron-silicon alloy powder into a rotary reactor and introducing a protective gas into it, then adding the phosphate metal ion solution; starting the rotary reactor and assisting microwave heating to 100~200℃; wherein the rotation speed of the rotary reactor is 400~800 r / min, the passivation treatment time is 0.5h~3h, obtaining a solution containing passivated iron-silicon alloy powder, adsorbing the passivated iron-silicon alloy powder, and washing it until neutral; further including performing the following operation on the neutral iron-silicon alloy powder: vacuum drying at a temperature of 80℃~100℃ to obtain iron-silicon alloy powder with an insulating coating layer.

[0017] The protective gas is preferably a mixture of Ar and N2, with a volume ratio of 95:5.

[0018] Microwave heating can raise the reaction temperature more quickly, thereby increasing the reaction rate. It can also improve the diffusion ability of metal ions and stimulate the OH bonds and PO4 bonds in H3PO4. 3- Group vibrations reduce the phosphate dissociation energy barrier by 40%, making it easier for iron-silicon alloy powder to react with phosphate ions, significantly improving the density, uniformity, and reaction efficiency of the passivation film.

[0019] The passivated iron-silicon alloy powder is vacuum dried at a temperature of 80℃~100℃ to further remove the solvent on the surface of the iron-silicon alloy powder and reduce its dryness.

[0020] Furthermore, the phosphate metal ion solution also includes a solvent, which is any one or a combination of two or more of anhydrous ethanol, acetone, ethylene glycol, and deionized water.

[0021] The solvent acts as a dispersant to ensure thorough mixing of the phosphoric acid solution and the metal acid phosphate; it also acts as a diluent to adjust the acidity of the mixed solution.

[0022] Furthermore, the specific preparation method of the phosphate metal ion solution is as follows: the solvent used is anhydrous ethanol, which is heated to 40~70℃, and then a phosphoric acid solution is added to it and stirred for 4~8 min to obtain a phosphate ethanol solution; then, metal acid phosphate powder is added to the obtained phosphate ethanol solution, and stirring is continued for 0.5~2 h with the aid of ultrasonic dispersion; wherein the stirring speed is 300~500 / min, the interval between each ultrasonic dispersion treatment is 1~5 min, and the duration of each treatment is 4~10 min / time.

[0023] Furthermore, the metal acid phosphate is any one of magnesium dihydrogen phosphate, zinc dihydrogen phosphate, calcium dihydrogen phosphate, manganese dihydrogen phosphate, or aluminum dihydrogen phosphate. Preferably, the metal acid phosphate is a dihydrogen phosphate of the corresponding metal, which is adaptable to acidic environments, has advantages in film-forming quality, and its hydrolysis gradient is gradually controllable by the chemical reaction.

[0024] Furthermore, the particle size of the iron-silicon alloy powder used is 30~100μm, and the Si content is 4.5~7.5wt%.

[0025] A second aspect of the present invention provides an iron-silicon magnetic powder core prepared by the above-described preparation method, wherein the resistivity of the iron-silicon magnetic powder core is greater than 8.1 × 10⁻⁶. -2 Ω·m, iron loss P 10 / 50 The concentration is 1.2~1.8 W / kg, P10 / 400 The concentration is 17.4~24.2 W / kg, P 1 / 10k It ranges from 10.3 to 16.2 W / kg.

[0026] Furthermore, the insulation layer thickness of the coated iron-silicon alloy powder used in the pressing raw material of the iron-silicon magnetic powder core is 2.1~4.9μm; the external insulation layer of the iron-silicon alloy powder is a composite passivation layer composed of iron phosphate and orthophosphate corresponding to metal acid phosphate.

[0027] The third aspect of the present invention provides an iron-silicon magnetic powder core, wherein the outer insulating layer of the iron-silicon alloy powder in the pressed raw material is a composite passivation layer composed of iron phosphate and orthophosphate corresponding to metal acid phosphate.

[0028] Subsequently, the technical solution provided by this invention, compared with the prior art, has the following beneficial effects: (1) The present invention optimizes the passivation coating process of iron-silicon alloy powder. Specifically, the solution of phosphoric acid metal ions containing phosphoric acid and metal acid phosphate is fully mixed with iron-silicon alloy powder. During the passivation process, the outer surface of iron-silicon alloy powder can be slowly corroded, and the passivation process can be adjusted. Metal acid phosphate provides acid radical ions and metal ions, which can not only reduce the amount of phosphoric acid, but also combine with phosphate radicals during the passivation process to form more stable orthophosphates corresponding to the metal ions, thereby reducing the supersaturation of crystallization and promoting the precipitation and crystallization of iron phosphate and orthophosphates corresponding to the metal ions, and generating a composite passivation layer with an amorphous crystalline mixed phase on the outer surface of iron-silicon alloy powder.

[0029] (2) The mass ratio of each raw material in the further passivation process of this invention is optimized. Specifically, the mass ratio of phosphoric acid solution, metal acid phosphate, and iron-silicon alloy powder is 0.25~6:0.5~3:100. Within this range, as the proportion of metal acid phosphate increases, the thickness of the insulating layer covering the outer surface of the iron-silicon alloy powder gradually increases. At this time, the saturation magnetization decreases, the core loss of the iron-silicon magnetic powder core decreases, and the resistivity increases. When the mass ratio of metal acid phosphate to iron-silicon alloy powder exceeds 3:100, the saturation magnetization will be significantly reduced, and the overall performance of the iron-silicon magnetic powder core will be reduced. Therefore, the above range is preferred. Attached Figure Description

[0030] Figure 1 The images show the SEM morphology of the iron-silicon alloy powders prepared in Comparative Example 1, Example 1, and Comparative Example 3 of this invention.

[0031] Figure 2 The images show the cross-sectional SEM morphology and elemental distribution of the iron-silicon alloy powders prepared in Comparative Examples 1, 3, and 1 of this invention.

[0032] Figure 3 for Figure 2 Local SEM morphology and elemental distribution of the iron-silicon alloy powder insulation layer in c.

[0033] Figure 4 The image shows the XRD pattern of the iron-silicon alloy powder prepared in Example 1 of this invention.

[0034] Figure 5 This is a SEM image of the iron-silicon alloy powder prepared in Comparative Example 2 of this invention.

[0035] Figure 6 This is a partial SEM image showing the morphology and elemental distribution of the iron-silicon alloy powder insulating layer prepared in Comparative Example 2 of this invention.

[0036] Figure 7 This is a SEM image of the iron-silicon alloy powder prepared in Comparative Example 4 of this invention.

[0037] Figure 8 This is a partial SEM image showing the morphology and elemental distribution of the iron-silicon alloy powder insulating layer prepared in Comparative Example 4 of this invention. Detailed Implementation

[0038] To further understand the content of this invention, the invention will be described in detail with reference to the embodiments.

[0039] The solvent used in the following examples is anhydrous ethanol, which should not be construed as a limitation on the types of solvents applicable to the preparation method of the present invention. Other solvents, such as acetone, ethylene glycol, deionized water, etc., can also be used.

[0040] The phosphoric acid solution used in the following examples has a concentration of 1 mol / L, which is a commonly used concentration of commercially available phosphoric acid solutions. When using other concentrations, the amount of phosphoric acid contained in the solution should be converted into the corresponding amount of phosphoric acid solution.

[0041] The following examples use zinc dihydrogen phosphate or aluminum dihydrogen phosphate as examples for illustration. This should not be construed as a limitation on the types of metal acid phosphates applicable to the preparation method of the present invention. Magnesium dihydrogen phosphate, calcium dihydrogen phosphate, and manganese dihydrogen phosphate can also be used.

[0042] Example 1 This embodiment provides a method for preparing an iron-silicon magnetic powder core. The amount of various raw materials used in the preparation process is calculated based on 20g of iron-silicon alloy powder as 100%, and the amount of other raw materials is converted into a percentage of the iron-silicon alloy powder used. The particle size of the iron-silicon alloy powder used is 30~100μm, and the mass ratio of silicon is 4.5%. The preparation method includes the following steps: First stage: Preparation of phosphate metal ion solution a. Weigh out 30% of anhydrous ethanol and heat it to 50°C in a constant temperature water bath; b. Add 0.25% (w / w) of 1 mol / L phosphoric acid solution to the heated anhydrous ethanol and stir at 400 r / min for 5 min to obtain a phosphoric acid ethanol solution; then add 1.0% (w / w) of zinc dihydrogen phosphate powder and ultrasonically disperse until the zinc dihydrogen phosphate powder is completely dissolved in the phosphoric acid ethanol solution. The interval between each ultrasonic dispersion treatment is 1 min and the duration of each treatment is 4 min, to obtain a zinc dihydrogen phosphate ethanol mixed solution with a pH of 2-3.

[0043] The second stage involves insulating the iron-silicon alloy powder using a metal phosphate ion solution. c. Weigh 20g of iron-silicon alloy powder and add it to a rotary reactor. Introduce a mixed inert gas with a volume ratio of 95% Ar and 5% N2 into the rotary reactor as a protective atmosphere. Then add the zinc dihydrogen phosphate ethanol mixed solution prepared in step b. The stirring speed inside the rotary reactor is 400 r / min. The rotary reactor is heated to 150°C using a microwave heating device. A solvent reflux mechanism is added. The passivation time is 30 min to obtain a solution containing passivated iron-silicon alloy powder. d. The solution containing the passivated iron-silicon alloy powder is filtered to obtain the passivated iron-silicon alloy powder, and washed with anhydrous ethanol until the solution is neutral. Then it is filtered again to obtain the washed iron-silicon alloy powder. e. Place the washed and passivated iron-silicon alloy powder into a vacuum drying oven at 80°C and dry it, with the vacuum degree controlled at -0.05~-0.06MPa; to obtain iron-silicon alloy powder with zinc ion-optimized phosphate passivation layer.

[0044] The third stage involves preparing iron-silicon-silicon magnetic powder cores using iron-silicon alloy powder with insulating coating. f. The iron-silicon alloy powder with a passivation layer prepared in step e is mixed with silicone resin and zinc stearate, wherein the mass ratio of the three is 100:1.0:0.5. g. Cold pressing is performed using a press, with a pressure of 1200 MPa. h. After pressing, the core is sent to a tubular atmosphere furnace for heat treatment under Ar protection. The heat treatment temperature is 500℃ and the holding time is 2h. After that, it is cooled to room temperature with the furnace to obtain the iron-silicon magnetic powder core after zinc salt optimized phosphate insulation layer.

[0045] The microstructure of the iron-silicon alloy powder with zinc ion-optimized phosphoric acid passivation layer prepared in step e is shown in the figure below. Figure 1 As shown in Figures c and d; the SEM morphology and elemental distribution of their cross-sections are shown in Figures c and d. Figure 2 As shown in Figure c; the local SEM morphology and elemental distribution of its insulating layer are shown in Figure c. Figure 3 As shown; its XRD pattern is as follows. Figure 4 As shown, from Figure 4 It is known that the insulating coating layer on the outer surface of the iron-silicon alloy powder contains zinc phosphate and iron phosphate.

[0046] Comparative Example 1 This comparative example provides a method for preparing an iron-silicon magnetic powder core. The difference between this comparative example and Example 1 is that only phosphoric acid solution is added in step b, and zinc dihydrogen phosphate powder is not added. The amount of phosphoric acid solution used is the same as in Example 1. At this time, the pH of the solution is 2~3. The rest of the operations are basically the same.

[0047] The microstructure of the iron-silicon alloy powder with a phosphate passivation layer prepared in step e of this comparative example is shown in the figure below. Figure 1 As shown in Figures a and b; the SEM morphology and elemental distribution of their cross-sections are shown in Figures 1-2. Figure 2 As shown in Figure a.

[0048] Comparative Example 2 This comparative example provides a method for preparing an iron-silicon magnetic powder core. The difference between this comparative example and Example 1 is that the amount of phosphoric acid is increased in step b. Specifically, a 20% phosphoric acid solution with a mass concentration of 2 mol / L is used, and the pH of the resulting phosphoric acid metal ion solution is 1.8. The remaining operations are basically the same.

[0049] The microstructure of the iron-silicon alloy powder with a phosphate passivation layer prepared in step e of this comparative example is shown in the figure below. Figure 5 As shown; its cross-sectional SEM morphology and elemental distribution diagram are as follows. Figure 6 As shown.

[0050] The microscopic morphology diagram shows that when a high amount of phosphoric acid solution is used to passivate the iron-silicon alloy powder, the phosphoric acid passivation reaction on the surface of the iron-silicon alloy powder is intense, resulting in excessive corrosion of the iron-silicon alloy powder. This leads to the formation of a thick phosphoric acid passivation insulating layer on the surface, which, although increasing the resistivity, causes a serious decrease in the overall magnetic properties.

[0051] Comparative Example 3 This comparative example provides a method for preparing an iron-silicon magnetic powder core. The difference between this comparative example and Example 1 is that in step b, a phosphoric acid solution and 1.0% by mass of zinc oxide powder are added. The amount of phosphoric acid solution used is the same as in Example 1. At this time, the pH of the solution is 2-3. The rest of the operations are basically the same.

[0052] The microstructure of the iron-silicon alloy powder with zinc oxide-optimized phosphate passivation layer prepared in step e of this comparative example is shown in the figure below. Figure 1 As shown in e and f; the SEM morphology and elemental distribution of their cross-sections are as follows. Figure 2 As shown in b.

[0053] Comparative Example 4 This comparative example provides a method for preparing an iron-silicon magnetic powder core. The difference between this comparative example and Example 1 is that in step b, a phosphoric acid solution is added but zinc dihydrogen phosphate powder is not added. The amount of phosphoric acid solution used is 7.5% by mass. The rest of the operations are basically the same.

[0054] The anions in this comparative example are essentially the same as those in Example 1, that is, providing the same acidic corrosion conditions as in Example 1. Its microstructure, as well as the SEM morphology and elemental distribution of its cross-section, are referenced. Figure 7 , Figure 8 As shown.

[0055] Example 2 This embodiment provides a method for preparing an iron-silicon magnetic powder core. The amount of all raw materials used in the preparation process is calculated based on 20g of iron-silicon alloy powder as 100%. The amounts of other raw materials are converted into percentages of the iron-silicon alloy powder used. The particle size of the iron-silicon alloy powder used is 30~100μm, and the mass percentage of silicon is 5%. The preparation method includes the following steps: First stage: Preparation of phosphate metal ion solution a. Weigh out the corresponding 30% mass of anhydrous ethanol and heat it to 60℃ in a constant temperature water bath; b. Under mechanical stirring, add 1.5% (w / w) of 1 mol / L phosphoric acid solution to the heated anhydrous ethanol and stir at 300 r / min for 6 min to obtain a phosphoric acid ethanol solution; then add 0.5% (w / w) of zinc dihydrogen phosphate powder and ultrasonically disperse until the zinc dihydrogen phosphate powder is completely dissolved in the phosphoric acid ethanol solution, wherein the interval between each ultrasonic dispersion treatment is 1 min and the duration of each treatment is 5 min; to obtain a zinc dihydrogen phosphate ethanol mixed solution with a pH of 2-3.

[0056] The second stage involves insulating the iron-silicon alloy powder using a metal phosphate ion solution. c. Weigh 20g of iron-silicon alloy powder and add it to a rotary reactor. Introduce a mixed inert gas with a volume ratio of 95% Ar and 5% N2 into the rotary reactor as a protective atmosphere. Then add the zinc dihydrogen phosphate ethanol mixed solution prepared in step b. The stirring speed inside the rotary reactor is 400r / min, and the reactor is heated to 100℃ using a microwave heating device. A solvent reflux mechanism is added, and the passivation time is 60min to obtain a solution containing passivated iron-silicon alloy powder. d. The solution containing the passivated iron-silicon alloy powder is filtered to obtain the passivated iron-silicon alloy powder, and washed with anhydrous ethanol until the solution is neutral. Then it is filtered again to obtain the washed iron-silicon alloy powder. e. Place the washed and passivated iron-silicon alloy powder into a vacuum drying oven and dry it at 70°C, with the vacuum degree controlled at -0.05~-0.06MPa; to obtain iron-silicon alloy powder with zinc ion-optimized phosphate passivation layer.

[0057] The third stage involves preparing iron-silicon magnetic powder cores using iron-silicon alloy powder with insulating coating. f. The iron-silicon alloy powder with passivation layer prepared in step e is mixed with silicone resin and zinc stearate, wherein the mass ratio of the three is 100:1.5:1. g. Cold pressing is performed using a press, with a pressure of 1200 MPa. h. After pressing, the core is sent to a tubular atmosphere furnace for heat treatment under Ar protection. The heat treatment temperature is 600℃ and the holding time is 1h. After that, it is cooled to room temperature with the furnace to obtain the iron-silicon magnetic powder core after zinc salt optimized phosphate insulation layer.

[0058] Example 3 This embodiment provides a method for preparing an iron-silicon magnetic powder core. The amount of all raw materials used in the preparation process is calculated based on 20g of iron-silicon alloy powder as 100%. The amounts of other raw materials are converted into percentages of the iron-silicon alloy powder used. The particle size of the iron-silicon alloy powder used is 30~100μm, and the mass percentage of silicon is 6%. The preparation method includes the following steps: First stage: Preparation of phosphate metal ion solution a. Weigh out 40% of anhydrous ethanol and heat it to 70°C in a constant temperature water bath; b. Add 0.75% by mass of 1 mol / L phosphoric acid solution to the heated anhydrous ethanol and stir at 400 r / min for 4 min to obtain a phosphoric acid ethanol solution; then add 1.5% by mass of zinc dihydrogen phosphate powder and ultrasonically disperse until the zinc dihydrogen phosphate powder is completely dissolved in the phosphoric acid ethanol solution. The interval between each ultrasonic dispersion treatment is 3 min and the duration of each treatment is 8 min, to obtain a zinc dihydrogen phosphate ethanol mixed solution with a pH of 2-3.

[0059] The second stage involves insulating the iron-silicon alloy powder using a metal phosphate ion solution. c. Weigh 20g of iron-silicon alloy powder and add it to a rotary reactor. Introduce a mixed inert gas with a volume ratio of 95% Ar and 5% N2 into the rotary reactor as a protective atmosphere. Then add the zinc dihydrogen phosphate ethanol mixed solution prepared in step b. The stirring speed inside the rotary reactor is 600 r / min, and the rotary reactor is heated to 200℃ using a microwave heating device. The passivation time is 10 min to obtain a solution containing passivated iron-silicon alloy powder. d. The solution containing the passivated iron-silicon alloy powder is filtered to obtain the passivated iron-silicon alloy powder, and washed with ethanol-free solution until the solution is neutral, and then filtered again to obtain the washed iron-silicon alloy powder. e. Place the washed and passivated iron-silicon alloy powder into a vacuum drying oven and dry it at 90°C, with the vacuum degree controlled at -0.05~-0.06MPa; to obtain iron-silicon alloy powder with zinc ion-optimized phosphate passivation layer.

[0060] The third stage involves preparing iron-silicon magnetic powder cores using iron-silicon alloy powder with insulating coating. f. The iron-silicon alloy powder with a passivation layer prepared in step e is mixed with silicone resin and zinc stearate, wherein the mass ratio of the three is 100:1.2:0.8. g. Cold pressing is performed using a press, with a pressure of 800 MPa. h. After pressing, the core is sent to a tubular atmosphere furnace for heat treatment under Ar protection. The heat treatment temperature is 700℃ and the holding time is 0.5h. Then, it is cooled to room temperature with the furnace to obtain the iron-silicon magnetic powder core with zinc salt optimized phosphate insulation layer.

[0061] Example 4 This embodiment provides a method for preparing an iron-silicon magnetic powder core. The amount of all raw materials used in the preparation process is calculated based on 20g of iron-silicon alloy powder as 100%. The amounts of other raw materials are converted into percentages of the iron-silicon alloy powder used. The particle size of the iron-silicon alloy powder used is 30~100μm, and the mass percentage of silicon is 7.5%. The preparation method includes the following steps: First stage: Preparation of phosphate metal ion solution a. Weigh out 40% of anhydrous ethanol and heat it to 50°C in a constant temperature water bath; b. Add 1.0% (w / w) of 1 mol / L phosphoric acid solution to the heated anhydrous ethanol and stir at 400 r / min for 8 min to obtain a phosphoric acid ethanol solution; then add 2.0% (w / w) of zinc dihydrogen phosphate powder and ultrasonically disperse until the zinc dihydrogen phosphate powder is completely dissolved in the phosphoric acid ethanol solution. The interval between each ultrasonic dispersion treatment is 4 min and the duration of each treatment is 8 min, to obtain a zinc dihydrogen phosphate ethanol mixed solution with a pH of 2-3.

[0062] The second stage involves insulating the iron-silicon alloy powder using a metal phosphate ion solution. c. Weigh 20g of iron-silicon alloy powder and add it to a rotary reactor. Introduce a mixed inert gas with a volume ratio of 95% Ar and 5% N2 into the rotary reactor as a protective atmosphere. Then add the zinc dihydrogen phosphate ethanol mixed solution prepared in step b. The stirring speed inside the rotary reactor is 600 r / min, and the rotary reactor is heated to 150°C using a microwave heating device. A solvent reflux mechanism is added, and the passivation time is 45 min to obtain a solution containing passivated iron-silicon alloy powder. d. The solution containing the passivated iron-silicon alloy powder is filtered to obtain the passivated iron-silicon alloy powder, and washed with anhydrous ethanol until the solution is neutral. Then it is filtered again to obtain the washed iron-silicon alloy powder. e. Place the washed and passivated iron-silicon alloy powder into a vacuum drying oven at 80°C and dry it, with the vacuum degree controlled at -0.05~-0.06MPa; to obtain iron-silicon alloy powder with zinc ion-optimized phosphate passivation layer.

[0063] The third stage involves preparing iron-silicon magnetic powder cores using iron-silicon alloy powder with insulating coating. f. The iron-silicon alloy powder with a passivation layer prepared in step e is mixed with silicone resin and zinc stearate, wherein the mass ratio of the three is 100:1.0:0.5. g. Cold pressing is performed using a press, with a pressure of 800 MPa. h. After pressing, the core is sent to a tubular atmosphere furnace for heat treatment under Ar protection. The heat treatment temperature is 500℃ and the holding time is 1.5h. Then, it is cooled to room temperature with the furnace to obtain the iron-silicon magnetic powder core with zinc salt optimized phosphate insulation layer.

[0064] Example 5 This embodiment provides a method for preparing an iron-silicon magnetic powder core. The amount of all raw materials used in the preparation process is calculated based on 20g of iron-silicon alloy powder as 100%. The amounts of other raw materials are converted into percentages of the iron-silicon alloy powder used. The particle size of the iron-silicon alloy powder used is 30~100μm, and the mass percentage of silicon is 4.5%. The preparation method includes the following steps: First stage: Preparation of phosphate metal ion solution a. Weigh out 50% of anhydrous ethanol and heat it to 40°C in a constant temperature water bath; b. Add 1.0% (w / w) of 1 mol / L phosphoric acid solution to the heated anhydrous ethanol and stir at 400 r / min for 5 min to obtain a phosphoric acid ethanol solution; then add 2.5% (w / w) of zinc dihydrogen phosphate powder and ultrasonically disperse until the zinc dihydrogen phosphate powder is completely dissolved in the phosphoric acid ethanol solution. The interval between each ultrasonic dispersion treatment is 5 min and the duration of each treatment is 10 min, to obtain a zinc dihydrogen phosphate ethanol mixed solution with a pH of 2-3.

[0065] The second stage involves insulating the iron-silicon alloy powder using a metal phosphate ion solution. c. Weigh 20g of iron-silicon alloy powder and add it to a rotary reactor. Introduce a mixed inert gas with a volume ratio of 95% Ar and 5% N2 into the rotary reactor as a protective atmosphere. Then add the zinc dihydrogen phosphate ethanol mixed solution prepared in step b. The stirring speed inside the rotary reactor is 800 r / min. The rotary reactor is heated to 120°C using a microwave heating device. A solvent reflux mechanism is added. The passivation time is 30 min to obtain a solution containing passivated iron-silicon alloy powder. d. The solution containing the passivated iron-silicon alloy powder is filtered to obtain the passivated iron-silicon alloy powder, and washed with anhydrous ethanol until the solution is neutral. Then it is filtered again to obtain the washed iron-silicon alloy powder. e. Place the washed and passivated iron-silicon alloy powder into a vacuum drying oven and dry at 80°C to obtain iron-silicon alloy powder with zinc ion-optimized phosphate passivation layer.

[0066] The third stage involves preparing iron-silicon magnetic powder cores using iron-silicon alloy powder with insulating coating. f. The iron-silicon alloy powder with a passivation layer prepared in step e is mixed with silicone resin and zinc stearate, wherein the mass ratio of the three is 100:1.0:0.5. g. Cold pressing is performed using a press, with a pressure of 1600 MPa. h. After pressing, the powder is sent to a tubular atmosphere furnace for heat treatment under Ar protection. The heat treatment temperature is 700℃ and the holding time is 1h. After that, it is cooled to room temperature with the furnace to obtain the iron-silicon powder core after zinc salt optimized phosphate insulation layer.

[0067] Example 6 This embodiment provides a method for preparing an iron-silicon magnetic powder core. The amount of all raw materials used in the preparation process is calculated based on 20g of iron-silicon alloy powder as 100%. The amounts of other raw materials are converted into percentages of the iron-silicon alloy powder used. The particle size of the iron-silicon alloy powder used is 30~100μm, and the mass percentage of silicon is 4.5%. The preparation method includes the following steps: First stage: Preparation of phosphate metal ion solution a. Weigh out 50% of anhydrous ethanol and heat it to 50°C in a constant temperature water bath; b. Add 1.0% pure phosphoric acid by mass to the heated anhydrous ethanol and stir at 500 r / min for 5 min to obtain a phosphoric acid ethanol solution; then add 3% zinc dihydrogen phosphate powder by mass and ultrasonically disperse until the zinc dihydrogen phosphate powder is completely dissolved in the phosphoric acid ethanol solution, wherein the interval between each ultrasonic dispersion treatment is 5 min and the duration of each treatment is 10 min, to obtain a zinc dihydrogen phosphate ethanol mixed solution with a pH of 2~3.

[0068] The second stage involves insulating the iron-silicon alloy powder using a metal phosphate ion solution. c. Weigh 20g of iron-silicon alloy powder and add it to a rotary reactor. Introduce a mixed inert gas with a volume ratio of 95% Ar and 5% N2 into the rotary reactor as a protective atmosphere. Then add the zinc dihydrogen phosphate ethanol mixed solution prepared in step b. The stirring speed inside the rotary reactor is 800 r / min. The rotary reactor is heated to 200°C using a microwave heating device. A solvent reflux mechanism is added. The passivation time is 20 min to obtain a solution containing passivated iron-silicon alloy powder. d. The solution containing the passivated iron-silicon alloy powder is filtered to obtain the passivated iron-silicon alloy powder, and washed with anhydrous ethanol until the solution is neutral. Then it is filtered again to obtain the washed iron-silicon alloy powder. e. Place the washed and passivated iron-silicon alloy powder into a vacuum drying oven and dry at 80°C to obtain iron-silicon alloy powder with zinc ion-optimized phosphate passivation layer.

[0069] The third stage involves preparing iron-silicon magnetic powder cores using iron-silicon alloy powder with insulating coating. f. The iron-silicon alloy powder with a passivation layer prepared in step e is mixed with silicone resin and zinc stearate, wherein the mass ratio of the three is 100:1.0:0.5. g. Cold pressing is performed using a press, with a pressure of 1600 MPa. h. After pressing, the core is sent to a tubular atmosphere furnace for heat treatment under Ar protection. The heat treatment temperature is 700℃ and the holding time is 1h. After that, it is cooled to room temperature with the furnace to obtain the iron-silicon magnetic powder core after zinc salt optimized phosphate insulation layer.

[0070] Example 7 This embodiment provides a method for preparing an iron-silicon magnetic powder core. The amount of all raw materials used in the preparation process is calculated based on 20g of iron-silicon alloy powder as 100%. The amounts of other raw materials are converted into percentages of the iron-silicon alloy powder used. The particle size of the iron-silicon alloy powder used is 30~100μm, and the mass percentage of silicon is 4.5%. The preparation method includes the following steps: First stage: Preparation of phosphate metal ion solution a. Weigh out 30% of anhydrous ethanol and heat it to 50°C in a constant temperature water bath; b. Add 0.75% (w / w) of 1 mol / L phosphoric acid solution to the heated anhydrous ethanol and stir at 400 r / min for 4 min to obtain a phosphoric acid ethanol solution; then add 1% (w / w) of calcium dihydrogen phosphate powder and ultrasonically disperse until the calcium dihydrogen phosphate powder is completely dissolved in the phosphoric acid ethanol solution. The interval between each ultrasonic dispersion treatment is 1 min and the duration of each treatment is 4 min, to obtain a calcium dihydrogen phosphate ethanol mixed solution with a pH of 2-3.

[0071] The second stage involves insulating the iron-silicon alloy powder using a metal phosphate ion solution. c. Weigh 20g of iron-silicon alloy powder and add it to a rotary reactor. Introduce a mixed inert gas with a volume ratio of 95% Ar and 5% N2 into the rotary reactor as a protective atmosphere. Then add the calcium dihydrogen phosphate solution prepared in step b. The stirring speed inside the rotary reactor is 400 r / min. The rotary reactor is heated to 150°C using a microwave heating device. A solvent reflux mechanism is added. The passivation time is 40 min to obtain a solution containing passivated iron-silicon alloy powder. d. The solution containing the passivated iron-silicon alloy powder is filtered to obtain the passivated iron-silicon alloy powder, and washed with anhydrous ethanol until the solution is neutral. Then it is filtered again to obtain the washed iron-silicon alloy powder. e. Place the washed and passivated iron-silicon alloy powder into a vacuum drying oven and dry it at 80°C, with the vacuum degree controlled at -0.05~-0.06MPa; to obtain iron-silicon alloy powder with calcium ion-optimized phosphate passivation layer.

[0072] The third stage involves preparing iron-silicon magnetic powder cores using iron-silicon alloy powder with insulating coating. f. The iron-silicon alloy powder with a passivation layer prepared in step e is mixed with silicone resin and zinc stearate, wherein the mass ratio of the three is 100:1.0:0.5. g. Cold pressing is performed using a press, with a pressure of 1000 MPa. h. After pressing, the core is sent to a tubular atmosphere furnace for heat treatment under Ar protection. The heat treatment temperature is 600℃ and the holding time is 1h. After that, it is cooled to room temperature with the furnace to obtain the iron-silicon magnetic powder core after calcium salt optimized phosphate insulation layer.

[0073] Example 8 This embodiment provides a method for preparing an iron-silicon magnetic powder core. The amount of all raw materials used in the preparation process is calculated based on 20g of iron-silicon alloy powder as 100%. The amounts of other raw materials are converted into percentages of the iron-silicon alloy powder used. The particle size of the iron-silicon alloy powder used is 30~100μm, and the mass percentage of silicon is 4.5%. The preparation method includes the following steps: First stage: Preparation of phosphate metal ion solution a. Weigh out 30% of anhydrous ethanol and heat it to 50°C in a constant temperature water bath; b. Add 1.0% by mass of a 1 mol / L phosphoric acid solution to the heated anhydrous ethanol and stir at 400 r / min for 6 min to obtain a phosphoric acid ethanol solution; then add 1% by mass of aluminum dihydrogen phosphate powder and ultrasonically disperse until the aluminum dihydrogen phosphate powder is completely dissolved in the phosphoric acid ethanol solution, wherein the interval between each ultrasonic dispersion treatment is 1 min and the duration of each treatment is 4 min, to obtain a mixed solution of aluminum dihydrogen phosphate and ethanol with a pH of 2~3.

[0074] The second stage involves using a metal phosphate ion solution to perform an insulating coating treatment on the iron-silicon alloy powder. c. Weigh 20g of iron-silicon alloy powder and add it to a rotary reactor. Introduce a mixed inert gas with a volume ratio of 95% Ar and 5% N2 into the rotary reactor as a protective atmosphere. Then add the aluminum dihydrogen phosphate ethanol mixed solution prepared in step b. The stirring speed inside the rotary reactor is 400 r / min, and the rotary reactor is heated to 150°C using a microwave heating device. A solvent reflux mechanism is added, and the passivation time is 40 min to obtain a solution containing passivated iron-silicon alloy powder. d. The solution containing the passivated iron-silicon alloy powder is filtered to obtain the passivated iron-silicon alloy powder, and washed with anhydrous ethanol until the solution is neutral. Then it is filtered again to obtain the washed iron-silicon alloy powder. e. Place the washed and passivated iron-silicon alloy powder into a vacuum drying oven and dry it at 100°C to obtain iron-silicon alloy powder with a calcium ion-optimized phosphate passivation layer.

[0075] The third stage involves preparing iron-silicon magnetic powder cores using iron-silicon alloy powder with insulating coating. f. The iron-silicon alloy powder with a passivation layer prepared in step e is mixed with silicone resin and zinc stearate, wherein the mass ratio of the three is 100:1.0:0.5. g. Cold pressing is performed using a press, with a pressure of 1000 MPa. h. After pressing, the core is sent to a tubular atmosphere furnace for heat treatment under Ar protection. The heat treatment temperature is 600℃ and the holding time is 1h. After that, it is cooled to room temperature with the furnace to obtain the iron-silicon magnetic powder core after calcium salt optimized phosphate insulation layer.

[0076] Performance Comparison Table 1 Performance data of the iron-silicon magnetic powder cores prepared in Examples 1-8 and Comparative Examples 1-4

[0077] The performance data of the iron-silicon magnetic powder cores prepared in Examples 1-8 and Comparative Examples 1-4 are detailed in Table 1.

[0078] Combined with Table 1 Figure 1-8 As shown, the following conclusions can be drawn: (1) From the microstructure diagrams and elemental distribution diagrams of Example 1, Comparative Example 1, and Comparative Example 3, it can be seen that the addition of zinc dihydrogen phosphate helps to form a phosphoric acid passivation insulating layer, making the insulating layer more uniform and dense, and significantly improving the resistivity of the iron-silicon magnetic powder core, thus reducing its core loss. Compared with the direct addition of zinc oxide in Comparative Example 3, the zinc dihydrogen phosphate added in Example 1 will directly ionize into phosphate in the ethanol solution. and Ions participate instantaneously in film formation, avoiding the lag required for zinc oxide to first form zinc dihydrogen phosphate, and at the same time avoiding the crystallization defects caused by undissolved zinc oxide particles in the comparative example, thus forming a dense zinc phosphate and iron phosphate deposition film.

[0079] (2) When the metal acid phosphate is zinc dihydrogen phosphate, it can be seen from Examples 1-6 and Table 1 that when the amount of zinc dihydrogen phosphate added is 1.5%, the iron-silicon magnetic powder core prepared in Example 3 has better overall performance. At this time, the insulation layer thickness on the outer surface of the iron-silicon alloy powder is uniform, and the element distribution in the insulation layer is more uniform.

[0080] (3) As can be seen from Examples 1, 7, and 8, the test results are detailed in Table 1. Table 1 shows that zinc dihydrogen phosphate has a better optimizing effect on the phosphoric acid process than aluminum dihydrogen phosphate and calcium dihydrogen phosphate. The reason is that aluminum dihydrogen phosphate contains... It will form a colloidal state This hinders Fe dissolution, thus resulting in poor film continuity; while calcium dihydrogen phosphate... It will generate loose It has no chemical bond with iron-silicon alloy powder.

[0081] (4) As can be seen from the microstructure diagrams and elemental distribution diagrams of Example 1 and Comparative Example 4, compared with the passivation treatment using only phosphoric acid solution, the method of using phosphoric acid combined with dihydrogen phosphate can achieve the same phosphate concentration with less dosage and faster speed. At the same time, its surface passivation layer is more uniform and dense, avoiding the problem of excessive corrosion of iron powder by high concentration of phosphoric acid leading to the cracking of the phosphoric acid passivation layer. Meanwhile, Example 1 demonstrates better comprehensive magnetic properties while ensuring a high-quality insulation layer.

Claims

1. A method for preparing an iron-silicon magnetic powder core, characterized in that, include: A phosphoric acid metal ion solution containing phosphoric acid and metal acid phosphate is thoroughly mixed with iron-silicon alloy powder to passivate the outer surface of the iron-silicon alloy powder and form an insulating coating layer. The mass ratio of phosphoric acid solution, metal acid phosphate and iron-silicon alloy powder is 0.25~1.5:0.5~3:

100. The coated iron-silicon alloy powder is pressed to prepare an iron-silicon magnetic powder core.

2. The method for preparing the iron-silicon magnetic powder core according to claim 1, characterized in that, The phosphate metal ion solution is mixed evenly with the iron-silicon alloy powder, specifically including the following steps: Iron-silicon alloy powder is added to a rotary reactor, and a protective gas is introduced into it. Then, a metal phosphate ion solution is added. The rotary reactor is started and assisted by microwave heating to 100~200℃. The rotation speed of the rotary reactor is 400~800 r / min, and the passivation treatment time is 10~60 min. A solution containing passivated iron-silicon alloy powder is obtained. The passivated iron-silicon alloy powder is adsorbed and washed until neutral. It also includes performing the following operation on neutral iron-silicon alloy powder: vacuum drying at a temperature of 80℃~100℃ to obtain iron-silicon alloy powder with an insulating coating layer.

3. The method for preparing the iron-silicon magnetic powder core according to claim 1, characterized in that, The phosphate metal ion solution also includes a solvent, which is any one or a combination of two or more of the following solvents: anhydrous ethanol, acetone, ethylene glycol, and deionized water.

4. The method for preparing the iron-silicon magnetic powder core according to claim 3, characterized in that, The specific preparation method of the phosphate metal ion solution is as follows: The solvent used is anhydrous ethanol, which is heated to 40~70℃, and then phosphoric acid solution is added to it. The mixture is stirred for 4~8 min to obtain a phosphoric acid ethanol solution. Then, metal acid phosphate powder is added to the obtained phosphoric acid ethanol solution, and the mixture is stirred for 0.5~2 h with the aid of ultrasonic dispersion. The stirring speed is 300~500 / min, the interval between each ultrasonic dispersion treatment is 1~5min, and the duration of each treatment is 4~10min / time.

5. The method for preparing an iron-silicon magnetic powder core according to any one of claims 1-4, characterized in that, The metal acid phosphate is any one of magnesium dihydrogen phosphate, zinc dihydrogen phosphate, calcium dihydrogen phosphate, manganese dihydrogen phosphate, or aluminum dihydrogen phosphate.

6. The method for preparing the iron-silicon magnetic powder core according to claim 5, characterized in that, The iron-silicon alloy powder used has a particle size of 30~100μm and a Si content of 4.5~7.5wt%.

7. A ferrosilicon magnetic powder core prepared by the preparation method according to any one of claims 1-6, characterized in that, The resistivity of the iron-silicon magnetic powder core is greater than 8.1 × 10⁻⁶. -2 Ω·m, iron loss P 10 / 50 The concentration is 1.2~1.8 W / kg, P 10 / 400 The concentration is 17.4~24.2 W / kg, P 1 / 10k It ranges from 10.3 to 16.2 W / kg.

8. The iron-silicon magnetic powder core according to claim 7, characterized in that, The insulation layer thickness of the coated iron-silicon alloy powder used in the pressing raw material of the iron-silicon magnetic powder core is 2.1~4.9μm; the outer insulation layer of the iron-silicon alloy powder is a composite passivation layer composed of iron phosphate and orthophosphate corresponding to metal acid phosphate.

9. A type of iron-silicon magnetic powder core, characterized in that, The outer insulating layer of the iron-silicon alloy powder in the pressed raw material is a composite passivation layer composed of iron phosphate and orthophosphate corresponding to metal acid phosphate.

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