Low-loss high-superposition Fe-Si-Al magnetic powder core and preparation method thereof

Abstract

The invention belongs to the field of soft magnetic functional materials, and particularly relates to a low-loss high-superposition Fe-Si-Al magnetic powder core and a preparation method thereof, and the preparation method comprises the following steps: preparing a coating agent, passivating coated powder, bonding and lubricating, and pressing and annealing. According to the method, based on the hydrolysis characteristic of metasilicic acid and the hydrolysis promotion effect of the alkaline catalyst, nano-porous silicon dioxide is prepared as a coating agent, meanwhile, the etching effect of alkaline matter on silicon dioxide can effectively increase the specific surface area of the nano-porous silicon dioxide, and the bonding strength of the nano-porous silicon dioxide and iron-silicon-aluminum powder is improved; the vacuum calcination treatment not only removes residual reagents, but also promotes sufficient thermal decomposition of metasilicic acid into silicon dioxide for in-situ coating, and stabilizes the lattice structure of the metasilicic acid. The coating layer of the low-loss high-superposition Fe-Si-Al magnetic powder core is firm in combination, thin and uniform in thickness and stable and compact in structure, the hysteresis loss of the Fe-Si-Al magnetic powder core can be effectively reduced, the direct-current bias performance is improved, and rising of eddy-current loss is avoided.

Description

Technical Field

[0001] The present invention belongs to the field of soft magnetic functional materials, and particularly relates to a low-loss and high-superposition iron-silicon-aluminum magnetic powder core and a preparation method thereof. Background Art

[0002] Since the successful development of iron-silicon-aluminum magnetic powder cores in the 1980s, they have been widely used and occupied a large market share in the mid- to low-end market. They are widely used in energy storage inductors, filter inductors, switching power supplies, etc. However, iron-silicon-aluminum magnetic powder cores have a significant drawback, that is, the saturation magnetic induction intensity is relatively low, which results in poor DC bias performance. In the 5G era today, magnetic powders are generally used in high-power environments. While the powder cores are magnetized by high-frequency alternating current, they are also affected by the superposition of DC components. Under a large DC bias current, the magnetic powder cores are prone to saturation, leading to a decline in the overall performance of the magnetic powder cores; at the same time, the magnetic powder cores will generate greater eddy current losses in a high-frequency environment. Therefore, ensuring that the iron-silicon-aluminum magnetic powder cores have low high-frequency losses while improving the DC bias performance is a current research hotspot.

[0003] At present, the insulation coating processes of iron-silicon-aluminum magnetic powder cores can be divided into chemical coating, physical coating, and physical-chemical hybrid coating. In chemical coating, a chemical reaction occurs between acidic or alkaline auxiliary materials and iron-silicon-aluminum powder to form a coating film on the surface. The coating quality is closely related to the concentration and content of the acid-base agents, which is extremely likely to cause problems such as uneven coating and acid-base residues, ultimately leading to the deterioration of the electromagnetic properties of the magnetic powder cores; in physical coating, the coating agent does not react with the iron-silicon-aluminum powder, and inorganic oxides or organic resins are directly coated on the powder surface. However, the binding strength between inorganic oxides and soft magnetic powders is poor and they are extremely likely to fall off during the mixing and pressing processes, and organic resins are extremely likely to decompose during the high-temperature annealing process, both of which expose the powder surface and exacerbate the eddy current losses; in physical-chemical hybrid coating, the iron-silicon-aluminum powder not only needs to undergo a passivation reaction but also needs to be coated twice, and the process is relatively complex. In addition, the coating layers obtained by these three insulation coating methods currently have different thicknesses, it is difficult to form a uniform bread coating, and the DC bias performance and loss performance of the obtained iron-silicon-aluminum magnetic powder cores cannot meet the requirements of high-performance magnetic powder cores at the same time.

[0004] Chinese Patent No. CN111192735A discloses an insulated-coated metal soft magnetic powder and its preparation method, which mainly uses organic resin for direct coating. However, after high-temperature sintering, the coating layer is easily damaged, and part of the surface of the magnetic powder core is exposed, greatly increasing the eddy current loss. Chinese Patent No. CN107464650A discloses a preparation method of a metal soft magnetic powder core with high-temperature heat treatment resistance. By improving the process of silicone resin, the high-temperature resistance of the silicone resin coating layer is improved. However, it still decomposes during the reaction at high temperature, and the formed silicon oxide does not completely coat the magnetic powder core tightly, resulting in increased loss. Chen Yuanxing et al. mentioned in "Effect of Fe-6.5Si Alloy Powder Morphology on the Performance of Magnetic Powder Cores" that only using metasilicic acid as a binder is convenient for pressing iron-silicon powder into shape, but the hydrolysis effect of metasilicic acid is not reflected, less silicon dioxide is generated by hydrolysis, and the coating effect is poor, so there is no superiority in performance.

[0005] Therefore, there is an urgent need for a new insulation coating method to improve the performance of metal soft magnetic powder cores. Summary of the Invention

[0006] The present invention provides a low-loss and high-superposition Fe-Si-Al magnetic powder core and its preparation method, aiming to solve at least one of the technical problems existing in the above prior art.

[0007] The preparation method of the low-loss and high-superposition Fe-Si-Al magnetic powder core of the present invention is based on the hydrolysis characteristics of metasilicic acid, and with the help of the hydrolysis promotion effect of an alkaline catalyst, nano-porous silica is prepared as a coating agent for Fe-Si-Al powder; at the same time, the etching effect of the alkaline substance on silica can effectively increase the specific surface area of nano-porous silica and enhance the bonding strength with Fe-Si-Al powder; vacuum calcination treatment not only removes residual reagents but also promotes the full thermal decomposition of metasilicic acid into silica for in-situ coating. The low-loss and high-superposition Fe-Si-Al magnetic powder core of the present invention: 1. By coating nano-porous silica with strong adsorption, the bonding strength between the coating layer and Fe-Si-Al powder is enhanced. The formed coating layer is uniform and thin (with a thickness of only 10-50 nm), which can effectively reduce the hysteresis loss of the magnetic powder core and improve the DC bias performance; 2. Through vacuum calcination treatment, residual alkaline catalysts are removed, and residual metasilicic acid is promoted to fully decompose into silica for in-situ coating. At the same time, the lattice structure of nano-porous silica is stabilized, the density and stability of the coating layer are improved, and the increase of eddy current loss is effectively avoided.

[0008] A preparation method of a low-loss and high-superposition Fe-Si-Al magnetic powder core includes the following steps:

[0009] S1: Prepare the coating agent. Disperse metasilicic acid in absolute ethanol. Under stirring, add a mixed solution of an alkaline catalyst and deionized water to adjust the pH, and continue stirring to form a sol to obtain the nano-porous silica coating solution.

[0010] S2: Passivate and coat the powder. Mix the nano-porous silica coating solution obtained in step S1 with the iron-silicon-aluminum powder, stir evenly, bake and dry, and then place it in a tube furnace for vacuum calcination to obtain the iron-silicon-aluminum powder coated with nano-porous silica.

[0011] S3: Bond and lubricate. Mix the iron-silicon-aluminum powder coated with nano-porous silica obtained in step S2 with a composite water-soluble binder, stir evenly and dry, then add a lubricant, mix evenly and screen to obtain the composite iron-silicon-aluminum powder.

[0012] S4: Press and anneal. Press the composite iron-silicon-aluminum powder obtained in step S3, and perform high-temperature annealing in a nitrogen atmosphere after pressing to obtain the low-loss and high-superposition iron-silicon-aluminum magnetic powder core.

[0013] Preferably, in step S1, the mass ratio of metasilicic acid to ethanol is (3 - 5):10.

[0014] Preferably, in step S1, the alkaline catalyst is at least one of concentrated ammonia water, urea, hydrazine, ammonium bicarbonate, and sodium bicarbonate.

[0015] Further, in step S1, the alkaline catalyst is more preferably concentrated ammonia water.

[0016] Preferably, in step S1, the mass ratio of the alkaline catalyst to deionized water is (1 - 4):20, and the pH is adjusted to 8 - 10.

[0017] Preferably, in step S1, the stirring speed is 200 - 400 rpm, more preferably 300 rpm, and the stirring time after adjusting the pH to 8 - 10 is 30 - 90 min.

[0018] Preferably, in step S2, the particle size of the iron-silicon-aluminum powder is 200 mesh - 800 mesh, and the mass ratio of the iron-silicon-aluminum powder to the nano-porous silica coating solution in step S1 is 10:(1 - 3).

[0019] Preferably, in step S2, the stirring speed is 200 - 400 rpm, and the stirring time is 30 min - 60 min.

[0020] Preferably, in step S2, the baking temperature is 80 - 120 °C, and the baking time is 60 - 90 min.

[0021] Preferably, in step S2, the vacuum calcination temperature is 350 - 550°C, the heating rate is 2 - 6°C / min, and the heat preservation time is 1 - 3 h.

[0022] Preferably, in step S3, the composite water-soluble binder includes an aqueous polyurethane emulsion and an acrylate water-based adhesive. Based on the iron-silicon-aluminum powder coated with nano-porous silica in step S2, it includes 0.3 - 0.6 wt% of the aqueous polyurethane emulsion, 0.2 - 0.5 wt% of the acrylate water-based adhesive, and 4 - 8 wt% of deionized water.

[0023] Preferably, in step S3, the drying temperature is 80 - 120°C, and the drying time is 60 - 120 min.

[0024] Preferably, in step S3, based on the iron-silicon-aluminum powder coated with nano-porous silica in S2, the addition amount of the lubricant is 0.3 - 0.6 wt%, and the lubricant is at least one of aluminum stearate, magnesium stearate, and stearic acid amide.

[0025] Preferably, in step S4, the pressing pressure is 18 - 20 t / cm 2 , the annealing temperature is 700 - 750°C, and the annealing time is 1 - 3 h.

[0026] A low-loss and high-superposition iron-silicon-aluminum magnetic powder core is prepared by the above method.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1. In the present invention, the silica prepared by the hydrolysis of metasilicic acid is at the nano level, with a particle size of 10 - 50 nm. The coating layer formed on the surface of the iron-silicon-aluminum particles is relatively thin. On the one hand, during the process of pressing the magnetic powder core, there are more distributed air gaps per unit volume, and the DC bias performance is better. On the other hand, the relatively thin coating layer is beneficial to reducing the hysteresis loss of the magnetic powder core;

[0029] 2. In the present invention, at least one of concentrated ammonia water, urea, hydrazine, ammonium bicarbonate, and sodium bicarbonate is used as the catalyst for the hydrolysis of metasilicic acid. On the one hand, it can adjust the pH of the system and promote the hydrolysis of metasilicic acid. On the other hand, the etching effect of the alkaline catalyst on the hydrolysis product nano-porous silica increases its specific surface area and enhances its adsorption effect on the iron-silicon-aluminum powder particles, effectively improving the bonding strength between the coating layer and the iron-silicon-aluminum powder. The obtained coating layer is more dense and not easily damaged, effectively avoiding the increase in eddy current loss;

[0030] 3. In the present invention, by optimizing the calcination process in vacuum, on the one hand, the residual alkaline catalyst and impurities in the iron silicon aluminum powder can be removed. On the other hand, the unhydrolyzed metasilicic acid decomposes into nano-silica, which in-situ coats the iron silicon aluminum particles, and at the same time makes the generated nano-porous silica lattice more stable, thus making the coating layer more stable. Detailed Embodiment

[0031] The technical solution of the present invention will be further described in detail below through specific embodiments. Based on the embodiments of the present invention, all other embodiments obtained by other technical personnel without creative work fall within the protection scope of the present invention.

[0032] Example 1.

[0033] S1: Prepare the coating agent. Disperse 40 g of metasilicic acid in 100 g of absolute ethanol, and while stirring at a speed of 300 rpm, add an appropriate amount of ammonia water solution (prepared from 4 g of concentrated ammonia water and 20 g of deionized water) to adjust the pH to 9. Then continue to stir at a speed of 300 rpm for 1 h. After stirring to form a sol, a nano-porous silica coating solution is obtained.

[0034] S2: Passivate the coated powder. Mix 143 g of the nano-porous silica coating solution obtained in step S1 with 1000 g of 200-mesh iron silicon aluminum powder evenly, with a stirring speed of 200 rpm and a stirring time of 60 min. After stirring, place it in an oven at 100 °C and bake for 70 min to obtain a dry powder. Place the dry powder in a tubular furnace. After evacuating to vacuum with a vacuum pump, heat it to 450 °C at a heating rate of 5 °C / min and keep it warm for 2 h. After cooling to room temperature, nano-porous silica-coated iron silicon aluminum powder is obtained.

[0035] S3: Bond and lubricate. Mix the nano-porous silica-coated iron silicon aluminum powder obtained in step S2 with 0.4% of water-based polyurethane emulsion, 0.3% of acrylate water-based glue, and 5% of deionized water based on the mass of the powder. Stir for 20 min and then place it in an oven at 100 °C to dry for 90 min. After cooling to room temperature, add 0.4 wt% of stearic acid amide and stir and mix evenly to obtain composite iron silicon aluminum powder.

[0036] S4: Press and anneal. Press the composite iron silicon aluminum powder obtained in step S3 at 20 t / cm 2 Press. After pressing, anneal at a high temperature of 730 °C for 3 h to obtain a low-loss and high-superposition iron silicon aluminum magnetic powder core.

[0037] Example 2

[0038] S1: Prepare the coating agent. Disperse 30 g of metasilicic acid in 100 g of absolute ethanol, and while stirring at a speed of 200 rpm, add an appropriate amount of urea solution (prepared from 2 g of urea and 20 g of deionized water) to adjust the pH to 9. Then continue to stir at a speed of 200 rpm for 90 min. After stirring to form a sol, a nano-porous silica coating solution is obtained;

[0039] S2: Passivate and coat the powder. Mix 125 g of the nano-porous silica coating solution obtained in step S1 with 1000 g of 400-mesh iron-silicon-aluminum powder evenly, with a stirring speed of 300 rpm and a stirring time of 40 min. After stirring, place it in an 80 °C oven and bake for 90 min to obtain a dry powder; Place the dry powder in a tubular furnace. After evacuating to vacuum with a vacuum pump, heat it to 400 °C at a heating rate of 4 °C / min and hold for 1.5 h. After cooling to room temperature, nano-porous silica-coated iron-silicon-aluminum powder is obtained;

[0040] S3: Bond and lubricate. Mix the nano-porous silica-coated iron-silicon-aluminum powder obtained in step S2 with 0.3% of aqueous polyurethane emulsion, 0.3% of acrylate water-based glue, and 4% of deionized water based on the mass of the powder. After stirring for 20 min, place it in an 80 °C oven and dry for 60 min. After cooling to room temperature, add 0.4 wt% of stearic acid amide and stir and mix evenly to obtain composite iron-silicon-aluminum powder;

[0041] S4: Press and anneal. Press the composite iron-silicon-aluminum powder obtained in step S3 at 18 t / cm 2 Press. After pressing, anneal at a high temperature of 700 °C for 3 h to obtain a low-loss and high-superposition iron-silicon-aluminum magnetic powder core.

[0042] Example 3

[0043] S1: Prepare the coating agent. Disperse 30 g of metasilicic acid in 100 g of absolute ethanol, and while stirring at a speed of 400 rpm, add an appropriate amount of hydrazine solution (prepared from 1 g of hydrazine and 20 g of deionized water) to adjust the pH to 8. Then continue to stir at a speed of 400 rpm for 30 min. After stirring to form a sol, a nano-porous silica coating solution is obtained;

[0044] S2: Passivate and coat the powder. Mix 100 g of the nano-porous silica coating solution obtained in step S1 with 1000 g of 200-mesh iron-silicon-aluminum powder evenly, with a stirring speed of 300 rpm and a stirring time of 40 min. After stirring, place it in a 100 °C oven and bake for 70 min to obtain a dry powder; Place the dry powder in a tubular furnace. After evacuating to vacuum with a vacuum pump, heat it to 550 °C at a heating rate of 6 °C / min and hold for 1 h. After cooling to room temperature, nano-porous silica-coated iron-silicon-aluminum powder is obtained;

[0045] S3: Bonding and lubricating, mix the iron-silicon-aluminum powder coated with nano-porous silica obtained in step S2 with 0.6% aqueous polyurethane emulsion, 0.2% acrylate water-based adhesive, and 8% deionized water based on the mass of the powder, stir for 20 min, then place it in an oven at 100 °C for drying for 90 min. After cooling to room temperature, add 0.4 wt% stearic acid amide, and stir and mix evenly to obtain composite iron-silicon-aluminum powder;

[0046] S4: Pressing and annealing, press the composite iron-silicon-aluminum powder obtained in step S3 at 18 t / cm 2 Pressing. After the pressing is completed, anneal at a high temperature of 700 °C for 2 h to obtain a low-loss and high-superposition iron-silicon-aluminum magnetic powder core.

[0047] Example 4

[0048] S1: Prepare the coating agent, disperse 50 g of metasilicic acid in 100 g of absolute ethanol, while stirring at a speed of 400 rpm, add an appropriate amount of ammonium bicarbonate aqueous solution (prepared from 2 g of ammonium bicarbonate and 20 g of deionized water) to adjust the pH to 8, and then continue to stir at a speed of 400 rpm for 1 h. After stirring to form a sol, obtain a nano-porous silica coating solution;

[0049] S2: Passivate and coat the powder, mix 132 g of the nano-porous silica coating solution obtained in step S1 with 1000 g of 200-mesh iron-silicon-aluminum powder evenly, stir at a speed of 400 rpm for 30 min, and after the stirring is completed, place it in an oven at 120 °C for baking for 60 min to obtain a dry powder; place the dry powder in a tubular furnace, evacuate to vacuum with a vacuum pump, then heat it to 350 °C at a heating rate of 3 °C / min, and keep it at this temperature for 3 h. After cooling to room temperature, obtain iron-silicon-aluminum powder coated with nano-porous silica;

[0050] S3: Bonding and lubricating, mix the iron-silicon-aluminum powder coated with nano-porous silica obtained in step S2 with 0.3% aqueous polyurethane emulsion, 0.5% acrylate water-based adhesive, and 5% deionized water based on the mass of the powder evenly, stir for 20 min, then place it in an oven at 120 °C for drying for 60 min. After cooling to room temperature, add 0.4 wt% stearic acid amide, and stir and mix to obtain composite iron-silicon-aluminum powder;

[0051] S4: Pressing and annealing, press the composite iron-silicon-aluminum powder obtained in step S3 at 18 t / cm 2 Pressing. After the pressing is completed, anneal at a high temperature of 750 °C for 1 h to obtain a low-loss and high-superposition iron-silicon-aluminum magnetic powder core.

[0052] Comparative Example 1

[0053] Compared with Example 1, in Comparative Example 1, only the ammonia aqueous solution is not added, and other steps are the same.

[0054] Comparative Example 2

[0055] Compared with Example 1, in Comparative Example 2, only the vacuum calcination treatment is not carried out, and other steps are the same.

[0056] Comparative Example 3

[0057] Compared with Example 2, in Comparative Example 3, only the urea solution is not added, and other steps are the same.

[0058] Comparative Example 4

[0059] Compared with Example 2, in Comparative Example 4, only the vacuum calcination treatment is not carried out, and other steps are the same.

[0060] Comparative Example 5

[0061] For Example 1, in Comparative Example 5, the purchased nano-silica solution is used for coating. 100 g of nano-silica solution is mixed with 1000 g of 200-mesh iron-silicon-aluminum powder, and the S3 bonding and lubricating step and the S4 pressing and annealing step are the same.

[0062] The composite iron-silicon-aluminum powders obtained from Examples 1-4 and Comparative Examples 1-5 are pressed into magnetic rings with an outer diameter of 27.00 mm, an inner diameter of 14.70 mm, and a height of 11.10 ± 0.10 mm. After heat treatment, coils are wound around the magnetic rings, and the inductance values of the magnetic rings are measured to calculate the magnetic permeability and DC bias performance; the power loss of the magnetic rings is measured.

[0063] The performance test results of Examples 1-4 and Comparative Examples 1-5 are shown in Table 1:

[0064] Table 1 Magnetic properties of materials in Examples and Comparative Examples

[0065] It can be seen from the test results that compared with Comparative Examples 1 and 2, Examples 1, 3, and 4 have better DC bias performance and lower power loss; compared with Comparative Examples 3 and 4, Example 2 has better DC bias performance and lower power loss; compared with Comparative Example 5, Examples 1-4 have obvious advantages and better comprehensive electromagnetic performance. This is because the iron-silicon-aluminum magnetic powder cores of Examples 1-4 are uniformly coated with a thin and dense nano-porous silica layer, and this nano-porous silica is prepared by promoting the hydrolysis of metasilicic acid with an alkaline substance. The alkaline substance not only acts as a catalyst to ionize or hydrolyze to produce hydroxide ions (OH -It promotes the hydrolysis of metasilicic acid and, at the same time, acts as an etchant to etch the surface of silica, increasing the specific surface area and enhancing the bonding strength between nano-porous silica and iron-silicon-aluminum powder. The vacuum calcination treatment effectively improves the crystallinity of silica and forms a dense and thin silica coating layer on the surface of iron-silicon-aluminum particles. On the one hand, during the process of pressing the magnetic powder core, there are more distributed air gaps per unit volume, and the DC bias performance is better. On the other hand, the thin coating layer is beneficial to reducing the hysteresis loss of the magnetic powder core. Therefore, the obtained iron-silicon-aluminum powder has excellent performance.

[0066] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that modifications or equivalent replacements can still be made to the specific implementation manners of the present invention. Any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention should be covered by the scope of the claims of the present invention.

Claims

1. A preparation method of a low-loss and high-superposition iron-silicon-aluminum magnetic powder core, characterized in that, It includes the following steps: S1: Prepare a coating agent. Disperse metasilicic acid in absolute ethanol, add an aqueous solution of an alkaline catalyst while stirring to adjust the pH, and continue stirring to form a sol, and then obtain a nano-porous silica coating solution. S2: Passivate the coated powder. Mix the nano-porous silica coating solution obtained in step S1 with an iron-silicon-aluminum powder, stir evenly, bake and dry, and then place it in a tube furnace for vacuum calcination to obtain an iron-silicon-aluminum powder coated with nano-porous silica. S3: Bond and lubricate. Mix the iron-silicon-aluminum powder coated with nano-porous silica obtained in step S2 with a composite water-soluble binder, stir evenly and dry, then add a lubricant and mix, and after mixing evenly, sieve to obtain a composite iron-silicon-aluminum powder. S4: Press and anneal. Press the composite iron-silicon-aluminum powder obtained in step S3, and then perform high-temperature annealing in a nitrogen atmosphere to obtain a low-loss and high-superposition iron-silicon-aluminum magnetic powder core.

2. The preparation method according to claim 1, wherein In the step S1, the mass ratio of metasilicic acid to absolute ethanol is (3 - 5):

10.

3. The preparation method according to claim 1, characterized in that, In the step S1, the alkaline catalyst is at least one of concentrated ammonia water, urea, hydrazine, ammonium bicarbonate, and sodium bicarbonate.

4. The preparation method according to claim 1, characterized in that, In the step S1, the mass ratio of the alkaline catalyst to deionized water in the aqueous solution of the alkaline catalyst is (1 - 4):20, adjust the pH to 8 - 10, the stirring speed is 200 - 400 rpm, and the continuous stirring time after adjusting the pH to 8 - 10 is 30 - 90 min.

5. The preparation method according to claim 1, characterized in that, In the step S2, the particle size of the iron-silicon-aluminum powder is 200 mesh to 800 mesh, and the mass ratio of the iron-silicon-aluminum powder to the nano-porous silica coating solution in step S1 is 100:(10 - 15).

6. The preparation method according to claim 1, characterized in that, In the step S2, the stirring speed is 200 - 400 rpm, the stirring time is 30 - 60 min, the baking temperature is 80 - 120 °C, and the baking time is 60 - 90 min; the vacuum calcination temperature is 350 - 550 °C, the heating rate is 2 - 6 °C / min, and the holding time is 1 - 3 h.

7. The preparation method according to claim 1, characterized in that, In the step S3, based on the iron-silicon-aluminum powder coated with nano-porous silica, the composite water-soluble binder includes 0.3 - 0.6 wt% of an aqueous polyurethane emulsion, 0.2 - 0.5 wt% of an acrylate water-based adhesive, and 4 - 8 wt% of deionized water; the drying temperature is 80 - 120 °C, and the drying time is 60 - 120 min.

8. The preparation method according to claim 1, characterized in that, The lubricant in the step S3 is at least one of aluminum stearate, magnesium stearate, and stearamide.

9. The preparation method according to claim 1, characterized in that, In the step S4, the pressing pressure is 18 - 20 t / cm 2 , the annealing temperature is 700 - 750 °C, and the annealing time is 1 - 3 h.

10. A low-loss and high-superposition iron-silicon-aluminum magnetic powder core, characterized in that, It is prepared by using the preparation method described in any one of claims 1 - 9.

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