An iron-based amorphous composite magnetic powder core and preparation method thereof

Abstract

The present invention provides an iron-based amorphous composite magnetic powder core and a preparation method thereof, belonging to the field of power electronics technology, including: ball-milling FeSiBC amorphous flake powder; mixing the ball-milled FeSiBC amorphous flake powder with FeSiBCCr amorphous spherical powder in a certain proportion to obtain a mixed powder, wherein the mass of the FeSiBC amorphous flake powder accounts for 85%-90% of the total mass of the mixed powder; putting the mixed powder into a phosphoric acid solution for passivation treatment; putting the passivated mixed powder into a mold for preliminary pressing to form a preform; performing vacuum impregnation and pressure impregnation on the preform with a resin solution, baking it and then putting it into a mold for final pressing to obtain the product. The prepared magnetic powder core has high magnetic permeability, low loss, stability with frequency change, and high DC bias performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of power electronics, and particularly relates to an iron-based amorphous composite magnetic powder core and a preparation method thereof. Background Art

[0002] In the context of the increasing development of power electronics and communication technologies, amorphous soft magnetic alloys have become important research materials due to their excellent magnetic properties, and soft magnetic powder cores are one of their application fields. Compared with silicon steel and ferrite, soft magnetic powder cores have both high saturation magnetization intensity, high magnetic permeability, and low loss, and are medium-high frequency soft magnetic composites that bridge the gap between low frequency and high frequency.

[0003] According to different shapes, amorphous soft magnetic powders can be divided into flake powders and spherical powders. Flake amorphous powders show significant potential in electromagnetic applications due to their unique shape and microstructural characteristics, and have gradually become a research hotspot in academic and industrial fields in recent years. Spherical amorphous powders are usually prepared by a combined gas and water atomization process, and the particle size distribution is relatively uniform and regular. Such powders can provide better magnetic uniformity when preparing magnetic powder cores. Due to the larger surface area to volume ratio, flake powders can more easily form an optimized magnetic flux path during the pressing process. The advantages of this structure may lead to magnetic cores prepared from flake powders having higher magnetic permeability and lower loss, especially in high-frequency applications. Therefore, understanding the performance differences between spherical and flake powders when preparing magnetic powder cores, and exploring the microscopic mechanisms behind these differences, is of great significance for the optimization and application of amorphous soft magnetic materials.

[0004] In the prior art, a Chinese invention patent with the publication number CN112908604B discloses an iron-based amorphous composite magnetic powder core and a preparation method thereof. The insulated coated composite powder is pressed into shape in a mold, and after stress relief annealing, the iron-based amorphous composite magnetic powder core is obtained. This technical solution improves the soft magnetic properties of the magnetic powder core by increasing the density and microcrystallization, and does not consider the relationship between the orientation of flake powders and the properties of the composite magnetic powder core. Therefore, the improvement of the soft magnetic properties of the magnetic powder core is limited. Summary of the Invention

[0005] To solve the above problems, the present invention provides an iron-based amorphous composite magnetic powder core and a preparation method thereof. By ball milling FeSiBC amorphous flake powders, deformation-induced nanocrystals are generated, and at the same time, the edges and corners of the flake powders are polished to improve the insulation performance between the powders. Combined with the improved pressing process, the prepared magnetic powder core has high magnetic permeability, low loss, stability with frequency change, and high DC bias performance.

[0006] To achieve the above object, the technical solutions adopted by the present invention are as follows:

[0007] On the one hand, the present invention provides a method for preparing an iron-based amorphous composite magnetic powder core, comprising: ball-milling FeSiBC amorphous flake powder; mixing the ball-milled FeSiBC amorphous flake powder with FeSiBCCr amorphous spherical powder in a certain proportion to obtain a mixed powder, wherein the mass of the FeSiBC amorphous flake powder accounts for 85%-90% of the total mass of the mixed powder; putting the mixed powder into a phosphoric acid solution for passivation treatment; putting the passivated mixed powder into a mold for preliminary pressing to form a preform; performing vacuum impregnation and pressure impregnation on the preform with a resin solution, baking, and then putting it into a mold for final pressing to obtain the product.

[0008] Further, the average particle size of the FeSiBC amorphous flake powder before ball-milling is 80μm-110μm, and the ratio of the average particle size of the FeSiBCCr amorphous spherical powder to that of the FeSiBC amorphous flake powder before ball-milling is 1: (3.5-4.5).

[0009] Further, the average particle size of the FeSiBC amorphous flake powder before ball-milling is 90μm-100μm.

[0010] Further, the ball-milling process is: maintaining a rotation speed of 50r / min-80r / min for 10min-20min; maintaining a rotation speed of 90r / min-120r / min for 5min-10min.

[0011] Further, before the passivation treatment, the mixed powder is cleaned, and the cleaning process is: soaking the mixed powder in an alkaline solution with a pH of 8-9 for at least 20min; secondly, soaking it in an acidic solution with a pH of 5-6 for at least 5min; and then cleaning it with deionized water after completion.

[0012] Further, the passivation treatment process is: soaking treatment is carried out with an aqueous solution of phosphoric acid and sodium nitrate, wherein the volume concentration of phosphoric acid is 12%-16%, the volume concentration of sodium nitrate is 2%-5%, and the rest is deionized water; the pH is maintained at 2-3 and the temperature is 60℃-80℃ during the soaking process for passivation for 10min-20min, and then passivation is carried out at a temperature of 30℃-40℃ for 10min-20min. Stirring is carried out at 50r / min-60r / min during the passivation process, and cleaning can be carried out after completion.

[0013] Further, the preliminary pressing process is: putting the passivated mixed powder into a mold and pressing it at a pressure of 0.8GPa-1.0GPa.

[0014] Further, the vacuum infiltration and pressure infiltration processes are as follows: evacuate to a vacuum degree not exceeding 0.2 Pa, pour in the resin solution, and maintain for at least 10 min; subsequently, apply a pressure of at least 5 Mpa to the system and maintain for at least 10 min.

[0015] Further, the pressure for the final pressing and forming is 1.5 GPa - 2.0 GPa.

[0016] On the other hand, the present invention provides an iron-based amorphous composite magnetic powder core, which is prepared by the above preparation method.

[0017] The beneficial effects brought by the technical solutions provided by the embodiments of the present invention include:

[0018] (1). By ball-milling the FeSiBC amorphous flake powder, first, the sharp edges and corners of the amorphous flake powder are impacted and passivated to avoid piercing the subsequent insulation coating layer; second, by hammering the relatively passivated positions, that is, the positions with a curvature greater than 1 mm, nanocrystals are induced to form on the powder surface. Especially, the nanocrystals are formed on the powder surface, improving the magnetic coupling between the amorphous matrix and the nanocrystals, increasing the magnetic permeability of the prepared magnetic powder core, and reducing the loss; finally, the formation of nanocrystals helps the sliding between the FeSiBC amorphous flake powder and the FeSiBCCr amorphous spherical powder during the pre-forming process, enabling the long axis of the amorphous flake powder to be arranged in a certain orientation, avoiding piercing the insulation layer during the sliding process, and improving the soft magnetic properties of the magnetic powder core.

[0019] (2). In order to improve the sliding effect between the FeSiBC amorphous flake powder and the FeSiBCCr amorphous spherical powder, the present application limits the mass ratio of the two. If the content of the FeSiBC amorphous flake powder is relatively high, the sliding is poor and it is difficult to form an arrangement with a certain orientation. If the content of the FeSiBC amorphous flake powder is relatively low, that is, the content of the FeSiBCCr amorphous spherical powder is high, it will lead to an increase in the aggregation degree of the amorphous spherical powder, reducing the soft magnetic properties of the magnetic powder core.

[0020] (3) The compacting process is defined. Double compaction is adopted. For the preliminary compaction, considering the sliding between the FeSiBC amorphous flake powder and the FeSiBCCr amorphous spherical powder, in order to make them slide to the desired orientation. During the sliding process, there is a possibility that the passivation film passivated by phosphoric acid solution breaks. Based on this consideration, the voids between the powders or the gaps of the broken passivation film are filled by vacuum impregnation and pressure impregnation of resin solution, which improves the strength of the magnetic powder core while ensuring the insulation performance. Secondly, compared with the one-step compaction of the prior art, the filling amount of the resin solution is reduced, and the density of the magnetic powder core is increased. Specifically, resin needs to be added in the early stage of one-step compaction. During the direct compaction process, there is a problem that the internal resin cannot be effectively discharged, resulting in a small density of the prepared magnetic powder core. However, in this application, through the powder mass ratio and sliding relationship, the preform prepared has a passage for filling the resin solution, reducing the filling amount of the resin solution and increasing the density of the magnetic powder core. Description of the Drawings

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0022] Figure 1 Schematic diagram of the iron-based amorphous composite magnetic powder core prepared in the embodiment of the present invention;

[0023] Figure 2 SEM diagram of the amorphous powder provided in Embodiment 1 of the present invention. a is the FeSiBC amorphous flake powder after ball milling, and b is the FeSiBCCr amorphous spherical powder;

[0024] Figure 3 EDS P element distribution detection diagram after passivation treatment of the mixed powder provided in Embodiment 1 of the present invention. a is the FeSiBC amorphous flake powder, and b is the FeSiBCCr amorphous spherical powder;

[0025] Figure 4 Side morphology diagram of the iron-based amorphous composite magnetic powder core provided in Embodiment 1 of the present invention;

[0026] Figure 5 Side morphology diagram of the iron-based amorphous composite magnetic powder core provided in Embodiment 2 of the present invention;

[0027] Figure 6 Side morphology diagram of the iron-based amorphous composite magnetic powder core provided in Comparative Example 1 of the present invention;

[0028] Figure 7Graph showing the relationship between the magnetic permeability and frequency of the iron-based amorphous composite magnetic powder cores provided in the embodiments and comparative examples of the present invention;

[0029] Figure 8 Graph showing the relationship between the density of the iron-based amorphous composite magnetic powder cores provided in the embodiments and comparative examples of the present invention and the addition amount of FeSiBCCr amorphous spherical powder;

[0030] Figure 9 Graph showing the relationship between the loss and frequency of the iron-based amorphous composite magnetic powder cores provided in the embodiments and comparative examples of the present invention. Detailed implementation manners

[0031] The present invention will be further described in detail below through specific implementation manners. However, those skilled in the art will understand that the following embodiments are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention. For those not specified in the embodiments regarding specific technologies or conditions, the technologies or conditions described in the literature in this field or according to the product specifications shall be followed. For reagents or instruments whose manufacturers are not specified, they are all conventional products that can be obtained through commercial purchases.

[0032] As used herein, the words "comprising", "including", "having" or any other variants thereof are intended to cover non-exclusive inclusion. For example, a process, method, article or device including listed elements does not necessarily have to be limited to those elements, but may include other elements not explicitly listed or inherent to such process, method, article or device. Unless otherwise clearly specified in the context, the singular forms "a / an" and "the" include plural referents.

[0033] Unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those skilled in the art. In addition to the specific methods, devices, and materials used in the embodiments, according to the knowledge of those skilled in the art regarding the prior art and the description of the present invention, any methods, devices, and materials of the prior art similar to or equivalent to those described in the embodiments of the present invention can also be used to implement the present invention.

[0034] Without specific description, in the embodiments of the present invention, each process is carried out at room temperature, and the measurement is in mass percentage or mass percent content.

[0035] The present invention provides a method for preparing an iron-based amorphous composite magnetic powder core, including:

[0036] S1. Ball-milling FeSiBC amorphous flake powder;

[0037] S2. Mix the ball-milled FeSiBC amorphous flake powder and FeSiBCCr amorphous spherical powder in a certain proportion to obtain a mixed powder. The mass of the FeSiBC amorphous flake powder is 85%-90% of the total mass of the mixed powder, such as 85%, 86%, 87%, 88%, 89%, 90%.

[0038] S3. Put the mixed powder into a phosphoric acid solution for passivation treatment.

[0039] S4. Put the passivated mixed powder into a mold for preliminary pressing to obtain a preform.

[0040] S5. Carry out vacuum infiltration and pressure infiltration of the resin solution on the preform, bake it, and then put it into a mold for final pressing to obtain the product.

[0041] In the present invention, the FeSiBC amorphous flake powder is ball-milled. First, the sharp edges and corners of the amorphous flake powder are impacted and passivated to avoid piercing the insulation coating layer subsequently. Second, the relatively passivated positions, i.e., the parts with a curvature greater than 1 mm, are hammered to induce the formation of nanocrystals on the powder surface. In particular, the nanocrystals are formed on the powder surface, improving the magnetic coupling between the amorphous matrix and the nanocrystals, increasing the magnetic permeability of the prepared magnetic powder core, and reducing the loss. Finally, the formation of nanocrystals contributes to the subsequent sliding between the FeSiBC amorphous flake powder and the FeSiBCCr amorphous spherical powder during the pre-forming process, enabling the long axis of the amorphous flake powder to be arranged in a certain orientation, avoiding piercing the insulation layer during the sliding process, and improving the soft magnetic properties of the magnetic powder core. To improve the sliding effect between the FeSiBC amorphous flake powder and the FeSiBCCr amorphous spherical powder, the mass ratio of the two is limited in this application. If the content of the FeSiBC amorphous flake powder is relatively high, the sliding is poor and it is difficult to form an arrangement with a certain orientation. If the content of the FeSiBC amorphous flake powder is relatively low, i.e., the content of the FeSiBCCr amorphous spherical powder is high, it will lead to an increase in the aggregation degree of the amorphous spherical powder and reduce the soft magnetic properties of the magnetic powder core. The pressing and forming process is limited. Two-step pressing and forming is adopted. For the preliminary pressing and forming, considering the sliding between the FeSiBC amorphous flake powder and the FeSiBCCr amorphous spherical powder, with the expectation that the two slide to the desired orientation. During the sliding process, there is a possibility that the passivation film passivated with a phosphoric acid solution breaks. Based on this consideration, the voids between the powders or the gaps of the broken passivation film are filled by vacuum impregnation and pressure impregnation of the resin solution, improving the strength of the magnetic powder core while ensuring the insulation performance. Second, compared with the one-step pressing and forming of the prior art, the filling amount of the resin solution is reduced, and the density of the magnetic powder core is increased. Specifically, in the prior art of one-step pressing and forming, resin needs to be added in the early stage. During the direct pressing and forming process, there is a problem that the internal resin cannot be effectively discharged, resulting in a relatively small density of the prepared magnetic powder core. However, in this application, through the powder mass ratio and sliding movement, the prepared preform has a passage for filling the resin solution, reducing the filling amount of the resin solution and increasing the density of the magnetic powder core.

[0042] It should be noted that the baking temperature is based on the temperature required for the curing of the resin solution, which is common knowledge. For illustration purposes, epoxy resin is used in the present invention, and the baking temperature is 70 °C.

[0043] The average particle size of the FeSiBC amorphous flake powder is 80 μm - 110 μm, such as 80 μm, 90 μm, 100 μm, 110 μm. The ratio of the average particle size of the FeSiBCCr amorphous spherical powder to the FeSiBC amorphous flake powder before ball milling is 1:(3.5 - 4.5), such as 1:3.5, 1:4.0, 1:4.5. Through the above limitations, the sliding motion ability of the FeSiBC amorphous flake powder and the FeSiBC amorphous flake powder is improved.

[0044] Preferably, the average particle size of the FeSiBC amorphous flake powder is 90 μm - 100 μm.

[0045] The ball milling process is: maintaining at a rotation speed of 50 r / min - 80 r / min for 15 min - 30 min.

[0046] Preferably, the ball milling process is: maintaining at a rotation speed of 50 r / min - 80 r / min for 10 min - 20 min; maintaining at a rotation speed of 90 r / min - 120 r / min for 5 min - 10 min. In the early stage, the sharp parts of the FeSiBC amorphous flake powder are polished at a small rotation speed to avoid the amorphous flake powder being broken into smaller particle sizes due to too high a ball milling speed, and at the same time, the surface modification of the amorphous flake powder is realized; in the later stage, ball milling is carried out at a larger rotation speed to form nanocrystals in the deeper parts of the powder particles, such as forming nanocrystals at a depth of at least 10 nm, so as to improve the integrity and strength of the phosphoric acid passivation film in the subsequent preliminary pressing process.

[0047] Before passivation treatment, the mixed powder is cleaned. The cleaning process is: soaking the mixed powder in an alkaline solution with a pH of 8 - 9 for at least 20 min to remove the oil stains, etc. of the mixed powder; secondly, soaking it in an acidic solution with a pH of 5 - 6 for at least 5 min to remove the oxides on the powder surface, so that the prepared passivation film is tightly combined with the substrate; after completion, it is cleaned with deionized water.

[0048] The passivation treatment process is as follows: Soak in an aqueous solution of phosphoric acid and sodium nitrate, where the volume concentration of phosphoric acid is 12% - 16%, the volume concentration of sodium nitrate is 2% - 5%, and the rest is deionized water; maintain the pH at 2 - 3 and the temperature at 60°C - 80°C during soaking for 10 min - 20 min, and then passivate at a temperature of 30°C - 40°C for 10 min - 20 min. Stir at 50 r / min - 60 r / min during the passivation process, and then perform cleaning. Adding sodium nitrate as an oxidant accelerates the passivation reaction, and adding ammonia water adjusts the pH value of the solution. A relatively loose passivation film is formed at a higher temperature in the early stage, and then a complete and dense passivation film is formed at a lower temperature. The loose passivation film is beneficial for the sliding movement between powders, while the dense passivation film ensures good insulation performance between powder particles. The passivation time should not be too long, as excessive time will cause partial dissolution of the film layer. Ultrasonic vibration is strictly prohibited in this process. Since a loose passivation film is formed in the early stage, if ultrasonic vibration is used, there is a possibility of the loose passivation film falling off, and the stirring speed should not be too high.

[0049] The preliminary pressing and forming process is as follows: Put the passivated mixed powder into a mold and press it into shape under a pressure of 0.80 GPa - 1.0 GPa, preferably with a holding pressure of at least 5 min.

[0050] Preferably, during the pressing and forming process, additional vibration is applied, and the vibration frequency is 50 Hz - 100 Hz. It is necessary to limit the vibration frequency. If the vibration frequency is too small, it will not promote the sliding movement; if the vibration frequency is too high, the additional wear between powders will increase, reducing the insulation performance between different powder particles.

[0051] The vacuum impregnation and pressure impregnation process is as follows: Evacuate to a vacuum degree not exceeding 0.2 Pa, pour in the resin solution, and keep it for at least 10 min; then, apply a pressure of at least 5 Mpa to the system and keep it for at least 10 min.

[0052] The pressure for the final pressing and forming is 1.5 GPa - 2.0 GPa, preferably with a holding pressure of at least 5 min.

[0053] The embodiment of the present invention also provides an iron-based amorphous composite magnetic powder core prepared by the above preparation method.

[0054] The magnetic powder core prepared by the present invention is an annular magnetic powder core with an outer diameter of 40 mm, an inner diameter of 24 mm, and a height of 21 mm, as Figure 1 shown, and the pressing direction is perpendicular to the paper surface direction.

[0055] For illustration, in the embodiment of the present invention, the FeSiBC amorphous flake powder is made of Fe 93.1 Si 4.3 B2.4 C 0.2 The FeSiBCCr amorphous spherical powder is made of Fe 85.7 Si 7.9 B 3.6 C 0.8 Cr 2.0 。

[0056] To better illustrate the purpose, technical solution and advantages of the present invention, the present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0057] Example 1

[0058] The embodiment of the present invention provides a preparation method of an iron-based amorphous composite magnetic powder core, and a magnetic powder core prepared by using this method, including:

[0059] S1. Ball-mill the FeSiBC amorphous flake powder. The ball-milling process is as follows: maintain at a speed of 50 r / min for 15 min. The FeSiBC amorphous flake powder after ball-milling is as shown in Figure 2 (a) below. It can be seen that the edges and corners of the FeSiBC amorphous flake powder after ball-milling are round.

[0060] S2. Mix the ball-milled FeSiBC amorphous flake powder with the FeSiBCCr amorphous spherical powder in a certain proportion to obtain a mixed powder. The mass of the FeSiBC amorphous flake powder is 85% of the total mass of the mixed powder. The FeSiBCCr amorphous spherical powder is as shown in Figure 2 (b) below. The average particle size of the FeSiBC amorphous flake powder is 92.3 μm, and the average particle size of the FeSiBCCr amorphous spherical powder is 23.1 μm.

[0061] S3. Put the mixed powder into a phosphoric acid solution for passivation treatment. After cleaning the mixed powder, soak it in an aqueous solution of phosphoric acid and sodium nitrate. The volume concentration of phosphoric acid is 12%, and the volume concentration of sodium nitrate is 2%, and the rest is deionized water; maintain the pH at 2.0 and the temperature at 60 °C for passivation for 10 min during the soaking process, and then passivate at a temperature of 30 °C for 10 min. Stir at 50 r / min during the passivation process, and then perform cleaning. It can be seen from Figure 3 (a) below and Figure 3 (b) below that the P element is evenly distributed on the surface of the two amorphous powders, forming a uniform insulating layer.

[0062] S4. Put the passivated mixed powder into a mold for preliminary pressing and forming at a pressure of 0.8 GPa to obtain a preform.

[0063] S5. The preform is subjected to vacuum impregnation and pressure impregnation with a resin solution, baked and then placed in a mold for final compression molding to obtain the product. The vacuum impregnation and pressure impregnation process is as follows: evacuate to a vacuum degree of 0.2 Pa, pour in the resin solution and keep it for 10 min; then, apply pressure to the system to 5 Mpa and keep it for 10 min, and then perform compression molding at a pressure of 1.5 GPa. The side view of the prepared magnetic powder core is as shown in Figure 4 shown, that is Figure 1 the side view of the magnetic powder core in Figure 4 . The upper and lower parts of

[0064] Example 2

[0065] The embodiment of the present invention provides a preparation method of an iron-based amorphous composite magnetic powder core and a magnetic powder core prepared by using this method, including:

[0066] S1. Ball-mill the FeSiBC amorphous flake powder. The ball-milling process is as follows: keep the rotation speed at 80 r / min for 30 min.

[0067] S2. Mix the ball-milled FeSiBC amorphous flake powder and FeSiBCCr amorphous spherical powder in a certain proportion to obtain a mixed powder. The mass of the FeSiBC amorphous flake powder is 90% of the total mass. The average particle size of the FeSiBC amorphous flake powder is 100 μm, and the ratio of the average particle size of the FeSiBCCr amorphous spherical powder to that of the FeSiBC amorphous flake powder is 1:4.5.

[0068] S3. Put the mixed powder into a phosphoric acid solution for passivation treatment. After cleaning the mixed powder, soak it in an aqueous solution of phosphoric acid and sodium nitrate. The volume concentration of phosphoric acid is 16%, and the volume concentration of sodium nitrate is 5%, and the rest is deionized water; keep the pH at 3.0 and the temperature at 80 °C during the soaking process for 20 min, and then passivate it at a temperature of 40 °C for 20 min. Stir at 60 r / min during the passivation process, and then perform cleaning after completion.

[0069] S4. Put the passivated mixed powder into a mold for preliminary compression molding at a pressure of 1.0 GPa to obtain a preform.

[0070] S5. The preform is subjected to vacuum impregnation and pressure impregnation with a resin solution, baked and then placed in a mold for final compression molding to obtain the product. The vacuum impregnation and pressure impregnation process is as follows: evacuate to a vacuum degree of 0.2 Pa, pour in the resin solution and keep it for 10 min; then, apply pressure to the system to 5 Mpa and keep it for 10 min, and then perform compression molding at a pressure of 2 GPa.

[0071] The side view of the prepared magnetic powder core is as shown in Figure 5 . It can be seen that the FeSiBC amorphous flake powders are arranged along a certain orientation, and the long axis is approximately perpendicular to the pressure direction.

[0072] Example 3

[0073] An embodiment of the present invention provides a preparation method of an iron-based amorphous composite magnetic powder core and a magnetic powder core prepared by using this method, including:

[0074] S1. Ball-mill the FeSiBC amorphous flake powders, and the ball-milling process is: maintain at a rotation speed of 50 r / min for 15 min.

[0075] S2. Mix the ball-milled FeSiBC amorphous flake powders and FeSiBCCr amorphous spherical powders in a certain proportion to obtain a mixed powder. The mass of the FeSiBC amorphous flake powders is 85% of the total mass. The average particle size of the FeSiBC amorphous flake powders is 90 μm, and the ratio of the average particle size of the FeSiBCCr amorphous spherical powders to that of the FeSiBC amorphous flake powders is 1:3.5.

[0076] S3. Put the mixed powder into a phosphoric acid solution for passivation treatment. After cleaning the mixed powder, soak it in an aqueous solution of phosphoric acid and sodium nitrate, where the volume concentration of phosphoric acid is 12%, the volume concentration of sodium nitrate is 2%, and the rest is deionized water; maintain the pH at 2.0 and the temperature at 60 °C for passivation for 10 min during the soaking process, and then passivate at a temperature of 30 °C for 10 min. Stir at 50 r / min during the passivation process, and then perform cleaning after completion.

[0077] S4. Put the passivated mixed powder into a mold for preliminary pressing and forming at a pressure of 0.8 GPa to obtain a preform.

[0078] S5. Perform vacuum infiltration and pressure infiltration of the resin solution on the preform, bake it, and then put it into a mold for final pressing and forming to obtain the product. The vacuum infiltration and pressure infiltration process is: evacuate to a vacuum degree of 0.2 Pa, pour in the resin solution, and maintain for 10 min; then, apply a pressure of 5 Mpa to the system and maintain for 10 min, and then press and form at a pressure of 1.5 GPa.

[0079] In the prepared magnetic powder core, the FeSiBC amorphous flake powders are arranged along a certain orientation, and the long axis is approximately perpendicular to the pressure direction.

[0080] Example 4

[0081] Different from Example 3, in step S2 of this example, the average particle size of the FeSiBC amorphous flake powder is 80 μm, and the ratio of the average particle size of the FeSiBCCr amorphous spherical powder to that of the FeSiBC amorphous flake powder is 1:4.

[0082] In the prepared magnetic powder core, the FeSiBC amorphous flake powder is arranged along a certain orientation, and the long axis is approximately perpendicular to the pressure direction.

[0083] Example 5

[0084] Different from Example 3, in step S2 of this example, the average particle size of the FeSiBC amorphous flake powder is 110 μm, and the ratio of the average particle size of the FeSiBCCr amorphous spherical powder to that of the FeSiBC amorphous flake powder is 1:4.

[0085] In the prepared magnetic powder core, the FeSiBC amorphous flake powder is arranged along a certain orientation, and the long axis is approximately perpendicular to the pressure direction.

[0086] Example 6

[0087] Different from Example 1, in step S1 of this example, the ball milling process is as follows: maintaining at a rotation speed of 50 r / min for 10 min; maintaining at a rotation speed of 90 r / min for 5 min.

[0088] In the prepared magnetic powder core, the FeSiBC amorphous flake powder is arranged along a certain orientation, and the long axis is approximately perpendicular to the pressure direction.

[0089] Example 7

[0090] Different from Example 1, in step S1 of this example, the ball milling process is as follows: maintaining at a rotation speed of 80 r / min for 20 min; maintaining at a rotation speed of 120 r / min for 10 min.

[0091] In the prepared magnetic powder core, the FeSiBC amorphous flake powder is arranged along a certain orientation, and the long axis is approximately perpendicular to the pressure direction.

[0092] Comparative Example 1

[0093] Different from Example 1, in step S2 of this comparative example, the mass of the FeSiBC amorphous flake powder is 95% of the total mass.

[0094] The side view of the prepared magnetic powder core is as Figure 6 shown. It can be seen that the FeSiBC amorphous flake powder is arranged along a certain orientation, and the long axis is arranged at an acute angle to the pressure direction.

[0095] Comparative Example 2

[0096] Different from Example 1, in step S2 of this comparative example, the mass of the FeSiBC amorphous flake powder is 80% of the total mass.

[0097] Comparative Example 3

[0098] Different from Example 1, this comparative example omits step S1.

[0099] Comparative Example 4

[0100] Different from Example 1, in step S3 of this comparative example, passivation is carried out at a temperature of 30 °C for 20 min.

[0101] Comparative Example 5

[0102] Different from Example 1, in step S3 of this comparative example, 1 wt% epoxy resin is added to the mixed powder after passivation, and then it is pressed into shape at a pressure of 1.5 GPa.

[0103] Effect verification

[0104] Typically, Examples 1 and 2 (the results of Examples 1 and 2 are similar to those of other examples), Comparative Examples 1 and 2, the changes in the magnetic permeability of the magnetic powder cores prepared from pure FeSiBC amorphous flake powder and pure FeSiBCCr amorphous spherical powder with frequency are as follows Figure 7 shown. It can be seen from Figure 7 that the magnetic permeability of Examples 1 and 2 has no obvious change in the frequency range of 0 - 1000 kHz, and the magnetic permeability of Examples 1 and 2 is significantly higher than that of Comparative Examples 1 and 2. It can be seen from Figure 8 that the density of the composite magnetic powder core shows a trend of first increasing and then decreasing with the addition amount of FeSiBCCr amorphous spherical powder. This is because a reasonable mass ratio of FeSiBC amorphous flake powder and FeSiBCCr amorphous spherical powder promotes the movement during the pressing process, resulting in a higher density of the prepared magnetic powder core, while an increase in the mass ratio of FeSiBCCr amorphous spherical powder leads to serious agglomeration and reduces the density of the magnetic powder core.

[0105] Examples 1 and 2 (the results of Examples 1 and 2 are similar to those of other examples), Comparative Examples 1 and 2, the changes in the loss of the magnetic powder cores prepared from pure FeSiBC amorphous flake powder and pure FeSiBCCr amorphous spherical powder with frequency are as follows Figure 9 shown. It can be seen from Figure 9 that the losses of Examples 1 and 2 are lower than those of Comparative Examples 1 and 2 in the frequency range of 25 - 125 kHz.

[0106] In order to compare the performance of each embodiment and comparative example, the permeability of the amorphous composite magnetic powder core of the present invention was measured under the test conditions of Bm = 0.05 T and 1 - 1000 kHz; the loss was measured under the test conditions of Bm = 0.05 T and 1000 kHz. The following parameters were detected respectively, and the detection results are shown in Table 1.

[0107] Table 1 Measurement data of soft magnetic properties of each embodiment and comparative example

[0108]

[0109] The above are only the embodiments of the present application and are not used to limit the protection scope of the present application. For those skilled in the art, various changes and modifications can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing an iron-based amorphous composite magnetic powder core, characterized in that: include: The FeSiBC amorphous sheet-like powder was ball-milled; The ball-milled FeSiBC amorphous sheet-shaped powder and the FeSiBCCr amorphous spherical powder are mixed in a certain proportion to obtain a mixed powder, wherein the mass of the FeSiBC amorphous sheet-shaped powder accounts for 85%-90% of the total mass of the mixed powder; placing the mixed powder into a phosphoric acid solution for passivation treatment; The mixed powder after passivation is placed in a mold for preliminary pressing to obtain a preform; The resin solution is vacuum impregnated and pressure impregnated, and then placed in a mold for final compression molding after baking. The passivation process is as follows: immersion treatment is performed using phosphoric acid and sodium nitrate aqueous solutions, wherein the volume ratio of phosphoric acid is 12%-16%, the volume ratio of sodium nitrate is 2%-5%, and the rest is deionized water; during the immersion process, the pH is maintained at 2-3, the temperature is 60°C-80°C, and the passivation is performed for 10min-20min, followed by passivation at a temperature of 30°C-40°C for 10min-20min, stirring at 50r / min-60r / min during the passivation process, and washing is performed after completion; Ultrasonic vibration is not used during the passivation process.

2. The preparation method according to claim 1, characterized in that: The average particle size of the FeSiBC amorphous sheet-like powder before ball milling is 80 μm-110 μm, and the ratio of the average particle size of the FeSiBCCr amorphous spherical powder to the FeSiBC amorphous sheet-like powder before ball milling is 1:(3.5-4.5).

3. The preparation method according to claim 2, characterized in that: The average particle size of the FeSiBC amorphous sheet powder before ball milling is 90 μm-100 μm.

4. The preparation method according to claim 1, characterized in that: The ball milling process is: maintaining a rotation speed of 50r / min-80r / min for 10min-20min; maintaining a rotation speed of 90r / min-120r / min for 5min-10min.

5. The preparation method according to claim 1, characterized in that: Before the passivation treatment, the mixed powder is cleaned, and the cleaning process is as follows: soaking the mixed powder in an alkaline solution with a pH of 8-9 for at least 20 minutes; secondly, soaking in an acidic solution with a pH of 5-6 for at least 5 minutes; after completion, washing with deionized water.

6. The preparation method according to claim 1, characterized in that: The preliminary pressing process is: placing the passivated mixed powder into a mold and pressing it at a pressure of 0.8 GPa-1.0 GPa.

7. The preparation method according to claim 1, characterized in that: The vacuum infiltration and pressure infiltration processes are as follows: evacuate the system to a vacuum degree not exceeding 0.2 Pa, pour in the resin solution, and maintain for at least 10 minutes; then, apply a pressure of at least 5 MPa to the system and maintain for at least 10 minutes.

8. The preparation method according to claim 1, characterized in that: The final compression molding pressure is 1.5 GPa-2.0 GPa.

9. An iron-based amorphous composite magnetic powder core, characterized in that: The iron-based amorphous composite magnetic powder core is prepared by the preparation method described in any one of claims 1-8.

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