A MHz-level low-loss Fe-Si-Al magnetic powder core and a sintering diffusion preparation method thereof

Abstract

The application discloses a MHz-level low-loss FeSiAl magnetic powder core and a sintering diffusion preparation method thereof, and comprises the following steps: (1) powder immersion: completely immerse FeSiAl alloy powder in molten Sn-based metal material, and take out after sufficient wetting; (2) diffusion annealing: perform diffusion annealing on the wet FeSiAl powder in an annealing atmosphere; (3) pressing forming: add a binder, uniformly stir, heat and dry, then add a release agent, uniformly stir, and then press into a green part; (4) heat treatment: perform annealing on the green part in the step (3) in a protective atmosphere, and cool to obtain the MHz-level low-loss FeSiAl magnetic powder core. According to the scheme, the working frequency of the FeSiAl magnetic powder core material is increased to MHz, and meanwhile, the effective permeability is relatively high and the power loss is relatively low.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of soft magnetic composite materials, and particularly relates to an MHz-level low-loss iron-silicon-aluminum magnetic powder core and a melt diffusion preparation method thereof. BACKGROUND

[0002] In recent years, with the increasing demand for high-power density and high-frequency applications such as AI servers, GPU chips, humanoid robots, flying cars, drones and intelligent driving, power soft magnetic materials are required to develop towards high frequency, miniaturization and high energy efficiency. Although the third-generation wide-bandgap semiconductors such as SiC and GaN can enable power electronics to work at a higher frequency of megahertz (MHz), so far there is no soft magnetic material that can fully exploit the potential of wide-bandgap semiconductors. This severely limits the power electronic devices for high-frequency applications, so the development of MHz-level low-loss soft magnetic materials is the key to breaking through the industry bottleneck. Iron-silicon-aluminum soft magnetic composites have the performance advantages of high magnetic flux density, high DC bias and low loss, and are widely used in power electronic devices, and are expected to develop into the next generation of materials for high-frequency application scenarios in performance iteration. However, only the adjustment of composition or improvement of process can hardly solve the problem of rapid performance degradation at MHz frequency.

[0003] There are many technologies that can improve the application frequency of soft magnetic composites or reduce their power loss, but the application scenarios are often limited to the range of 100k-500kHz, and cannot be improved to a usage frequency of 1MHz, or at high frequency MHz, the loss of the magnetic core increases sharply, and its wide application cannot be realized, therefore, how to greatly reduce the loss of the magnetic core at high frequency MHz is still a problem to be solved in the field.

[0004] The patent application with publication number CN119296948A discloses a method for simultaneously reducing the hysteresis loss and eddy current loss of a FeSiAl magnetic powder core, a salt solution containing metal M is added to the FeSiAl magnetic powder core, and after drying, an insulating coated magnetic powder core is obtained, and finally a FeSiAl:M / Al2O3 is obtained by pressing. The magnetic powder core prepared by the method has a magnetic core loss of 1120-1620mW / cm 3 at 1MHz / 0.05T, and a magnetic permeability of about 60. However, this method requires the use of a sealed container to configure strong acid groups (Cl - , SO4 2- , NO3 -) metal salt solution, high cost, long time, strict requirements for preparation conditions and easy to discharge acid gas. Patent application No. CN117476304A discloses a high-frequency low-loss metal soft magnetic powder core and a preparation method thereof. The metal magnetic powder core prepared by particle size grading and optimization of coating process has a power loss of 518 W / kg and an effective permeability of 62 under the condition of 100 kHz / 100 mT. However, the metal magnetic powder core prepared by the method has a very low frequency and cannot still maintain low loss and effective permeability in the megahertz frequency band. Patent application No. CN116313358A discloses a preparation method of FeSiAl magnetic powder core coated with NiZn and MnZn ferrite powders. The performance of the composite magnetic powder core is improved by coating the outer side of the FeSiAl magnetic powder core with NiZn and MnZn ferrite powders, thereby reducing the power loss and simultaneously improving the permeability of the magnetic powder core. However, the magnetic powder core prepared by the method has a permeability of >70, but a power loss of 680.16 mW / cm 3 at 100 kHz / 100 mT, and a very low frequency, which cannot still maintain low loss and permeability in the megahertz frequency band. SUMMARY

[0005] To solve the above technical problems, the purpose of the present application is to provide an MHz-level low-loss FeSiAl magnetic powder core and a preparation method thereof, which can increase the working frequency of the FeSiAl magnetic powder core material to MHz while still having high effective permeability and low power loss.

[0006] To achieve the above purpose, the present application adopts the following technical solutions:

[0007] A preparation method of an MHz-level low-loss FeSiAl magnetic powder core, comprising the following steps:

[0008] (1) Powder soaking: completely immerse the FeSiAl alloy powder in molten tin-based metal material, and take it out after sufficient wetting;

[0009] (2) Diffusion annealing: diffuse anneal the wetted FeSiAl powder in an annealing atmosphere;

[0010] (3) Pressing: add a binder, stir uniformly, heat and dry, then add a release agent, stir uniformly, and press into a green body;

[0011] (4) Heat treatment: anneal the green body in step (3) in a protective atmosphere, cool, and obtain the MHz-level low-loss FeSiAl magnetic powder core.

[0012] Preferably, in step (1), the melting point of the tin-based metal material is not higher than 300℃.

[0013] As a preference, the tin-based metal material is tin or a tin-based alloy, which includes tin and at least one metal selected from iron, copper, cadmium, silver and lead.

[0014] As a preference, in step (1), the holding temperature of the molten tin-based metal material is 300-400℃, and the infiltration time is 0.5-2h.

[0015] As a preference, in step (1), the composition of the iron-silicon-aluminum alloy powder, in terms of mass percentage, is as follows: Fe: 84.5-84.9%, Si: 9.6%, and the rest is Al.

[0016] As a preference, in step (2), the diffusion annealing temperature is 850-1000℃, the heating rate is 10-12℃ / min, the holding time is 1-2h, and the annealing atmosphere is hydrogen.

[0017] As a preference, in step (3), the binder is a methyl acetate solution of silicone resin or an acetone solution of silicone resin, the drying temperature is 130-180℃, the drying time is 10min, the release agent is selected from one or more of zinc stearate, calcium stearate, barium stearate and paraffin wax, and the addition amount of the release agent is 0.3-0.4wt%.

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

[0019] As a preference, in step (4), the annealing temperature is 700-750℃, the heating rate is 8-10℃ / min, the holding time is 1h, and the annealing atmosphere is nitrogen.

[0020] An MHz-level low-loss iron-silicon-aluminum magnetic powder core prepared by the infiltration diffusion method as described above.

[0021] The present application has the following beneficial effects: 1. The present application uses the principle of metal diffusion solid solution, uses low-melting-point tin-based metal materials to wet and diffusion anneal the soft magnetic alloy powder, and obtains the iron-silicon-aluminum magnetic powder core material which can be applied to high frequency or even MHz frequency working conditions, breaks through the material limit, fills the gap of the iron-silicon-aluminum magnetic powder core material which is almost not used in the working frequency in China, and the material loss of the present application is extremely low and the magnetic permeability is stable under the working conditions, which is far superior to ordinary soft magnetic composite materials; 2. In the diffusion annealing process, tin atoms are solid-soluted from the outside to the inside of the alloy powder, and a concentration gradient distribution is formed. This unique microstructure greatly improves the microstress distribution of the alloy powder, reduces the concentrated stress, and is beneficial to improve the magnetic permeability and reduce the magnetic hysteresis loss. More importantly, since the metal element tin is enriched on the surface layer of the iron-silicon-aluminum grain to generate paramagnetic FeSn2 intermetallic compound in situ, and the iron-silicon-aluminum matrix itself is ferromagnetic, the newly constructed heterogeneous magnetic structure on the original iron-silicon-aluminum matrix breaks the strong demagnetizing field distribution, making it more difficult for domain wall resonance to occur and reducing the residual loss caused by domain wall resonance at high frequency. 3. The present application uses metal molten liquid in the powder treatment stage instead of organic or inorganic compound solution, avoiding the discharge of harmful substances such as waste gas, and being green and environmentally friendly. The tin-based metal material is easy to recycle and can be reused, and the production cost is lower. Compared with the existing solution treatment method, the process flow is reduced, the process flow is shortened, and the production is more efficient. 4. The iron-silicon-aluminum soft magnetic composite material of the present application increases the use frequency to the high frequency MHz range and has extremely low loss, while also having high effective magnetic permeability and performance stability. Under the condition of 1MHz / 50mT, the iron-silicon-aluminum magnetic powder core material prepared by the present application has a loss as low as 606.4kW / m 3 , and the effective magnetic permeability is higher than 60; under the condition of 50kHz to 1MHz, the magnetic permeability change rate is less than 0.1%, the magnetic permeability stability is high, and the material performance of the present application is far superior to the existing material performance, which can be well applied to the MHz high frequency field and solve the problem that the soft magnetic composite material cannot be used efficiently and stably at high frequency. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is a structural schematic diagram of the powder in the infiltration diffusion process;

[0023] Figure 2 is a micro-morphology diagram of the iron-silicon-aluminum magnetic powder core material powder prepared in Example 3 and a corresponding Sn element distribution diagram. DETAILED DESCRIPTION

[0024] For the purpose of making the technical scheme, advantages of the present application clearer, the technical scheme of the present application will be described clearly and completely in conjunction with the specific embodiments. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. In the present application, unless specified, all the parts and percentages are by weight, and all the devices and materials can be purchased from the market or commonly used in the industry.

[0025] The endpoints of the ranges and any values disclosed in the present application are not limited to the precise values recited. The endpoints of the ranges and values are approximations that are understood to encompass values approximating these.

[0026] Disclosed in the present application is a preparation method of MHz-level low-loss FeSiAl magnetic powder core, comprising the following steps:

[0027] (1) Powder infiltration: completely immerse the FeSiAl alloy powder in molten Sn-based metal material, and take out after sufficient wetting; (2) diffusion annealing: perform diffusion annealing on the wetted FeSiAl powder in an annealing atmosphere;

[0028] (3) Press forming: add a binder, stir uniformly, heat and dry, then add a release agent, stir uniformly, and press into a green body;

[0029] (4) Heat treatment: perform annealing on the green body in step (3) in a protective atmosphere, and cool to obtain the MHz-level low-loss FeSiAl magnetic powder core.

[0030] In the present application, in step (1), the melting point of the Sn-based metal material is not higher than 300℃. Specifically, the Sn-based metal material is tin or a Sn-based alloy, and the Sn-based alloy comprises tin and at least one metal selected from iron and copper. The combination can be selected according to actual needs, and specifically can be pure tin, or a low-melting-point Sn-Fe alloy, a Sn-Cu alloy, or a Sn-Fe-Cu alloy.

[0031] In the present scheme, in step (1), the holding temperature of the molten tin-based metal material is not less than 300 DEG C, so that the tin-based metal material is completely melted. Further, the holding temperature of the molten tin-based metal material is 300 DEG C to 400 DEG C, and is specifically selected from 300 DEG C, 320 DEG C, 340 DEG C, 360 DEG C, 380 DEG C, 400 DEG C, etc. A holding temperature that is too high will cause energy waste. The infiltration time is not less than 0.5 h, and further, the infiltration time is 0.5 h to 2 h, and is specifically selected from 0.5 h, 1 h, 1.5 h, 2 h, etc. The original powder is fully infiltrated by the tin-based molten liquid, and the wetting property is not increased by prolonging the infiltration time. Other values within the range can also be used, which are not limited herein.

[0032] In step (1), the composition of the iron-silicon-aluminum alloy powder is as follows, in terms of mass percentage: Fe: 84.5% to 84.9%, Si: 9.6%, and the balance being Al. The iron-silicon-aluminum alloy powder is a metal-atomized synthesized iron-silicon-aluminum alloy powder, which can be prepared by the following steps: according to the designed alloy composition ratio, the corresponding weights of iron blocks, silicon ingots and aluminum blocks are weighed and placed in a vacuum medium frequency furnace for melting. The molten steel is poured into an atomization device, and at the same time, the molten steel is impacted by high-pressure nitrogen gas for rapid cooling to obtain an iron-silicon-aluminum alloy powder. The obtained iron-silicon-aluminum alloy powder is subjected to particle size screening. The iron-silicon-aluminum alloy powder with a mesh number of 200 to 1000 is selected in the present scheme.

[0033] In some embodiments, the diffusion annealing temperature in step (2) is 850 DEG C to 1000 DEG C, and can be specifically selected from 850 DEG C, 900 DEG C, 950 DEG C, 1000 DEG C, etc. The heating rate is 10 DEG C / min to 12 DEG C / min, and can be specifically selected from 10 DEG C / min, 11 DEG C / min, 12 DEG C / min, etc. The holding time is 1 h to 2 h, and can be specifically selected from 1 h, 1.5 h, 2 h, etc. Other values within the range can also be used, which can be specifically selected according to actual needs, and are not limited herein.

[0034] In some embodiments, in step (3), the binder is a methyl acetate solution of silicone resin or an acetone solution of silicone resin. The binder can also be other binders commonly used in the art. In the present application, the binder used is composed of 0.5 wt% silicone resin and 5 wt% methyl acetate / acetone. In step (3), the drying temperature is 130-180℃, which can be selected from 130℃, 140℃, 150℃, 160℃, 170℃, 180℃, etc.; the drying time is 10 min. The release agent is selected from one or more of zinc stearate, calcium stearate, barium stearate and paraffin, and the amount of release agent added is 0.3-0.4 wt%, which can be selected from 0.3 wt%, 0.32 wt%, 0.34 wt%, 0.36 wt%, 0.38 wt%, 0.4 wt%, etc., or other values within the range, which can be selected according to actual needs, and is not limited herein. The amount added here is based on the weight of the iron-silicon-aluminum alloy powder.

[0035] In some embodiments, in step (3), the green body of ring type is pressed, and the unit forming pressure is 18-20 t / cm 3 , which can be selected from 18 t / cm 3 , 19 t / cm 3 , 20 t / cm 3 , etc., or other values within the range, which can be selected according to actual needs, and is not limited herein.

[0036] In some embodiments, in step (4), the annealing temperature is 700-750℃, which can be selected from 700℃, 710℃, 720℃, 730℃, 740℃, 750℃, etc., or other values within the range, which can be selected according to actual needs, and is not limited herein; the heating rate is 8-10℃ / min, which can be selected from 8℃ / min, 8.5℃ / min, 9℃ / min, 9.5℃ / min, 10℃ / min, etc., or other values within the range, which can be selected according to actual needs, and is not limited herein; the holding time is 1 hour, the annealing atmosphere is nitrogen, and rapid cooling is performed after holding is completed, to obtain the MHz-level low-loss iron-silicon-aluminum magnetic powder core.

[0037] Generally, the MHz-level low-loss iron-silicon-aluminum magnetic powder core prepared needs to be placed in an impregnation solution, soaked for a certain period of time, cleaned, placed in an oven for baking, and then placed in a coating machine for spraying to obtain a finished magnetic powder core. The impregnation solution can be a commonly used impregnation solution of 0.5% mixed epoxy resin and methyl acetate, or other commonly used impregnation solutions in the art.

[0038] The present application also discloses a MHz-level low-loss iron-silicon-aluminum magnetic powder core prepared by the method described above.

[0039] The following is further illustrated in conjunction with the examples. The following abbreviated "mass ratio" is based on the iron-silicon-aluminum alloy powder.

[0040] Example 1:

[0041] A preparation method of an MHz-level low-loss iron-silicon-aluminum magnetic powder core, comprising the following steps:

[0042] (1) Powder infiltration: completely immerse the iron-silicon-aluminum alloy powder in molten tin-based metal material, and take it out after sufficient infiltration. The holding temperature of the molten tin-based metal material is 360°C, and the infiltration time is 0.5h. The melting point of tin is about 232°C.

[0043] (2) Diffusion annealing: the infiltrated iron-silicon-aluminum powder is subjected to diffusion annealing in hydrogen. The diffusion annealing temperature is 920°C, the heating rate is 10°C / min, and the holding time is 1.5h.

[0044] (3) Press forming: add a binder composed of 0.5wt% organic silicon resin and 5wt% acetone, stir uniformly and heat to dry, keep the temperature at 130°C for 10min, and then place it to cool; then add a release agent, which is 0.4wt% zinc stearate, and stir uniformly. Under the unit forming pressure of 18-20t / cm 3 , a ring-shaped green body is pressed;

[0045] (4) Heat treatment: the green body in step (3) is annealed in a nitrogen atmosphere furnace at 730°C for 1 hour, and then cooled, immersed, baked and sprayed to form a magnetic powder core sample.

[0046] In this embodiment, the iron-silicon-aluminum alloy powder is an 800-mesh metal-atomized synthesized iron-silicon-aluminum powder. In the iron-silicon-aluminum alloy powder, the content of each component is as follows in mass percentage: Fe 84.6%, Si 9.6%, and the rest is Al.

[0047] Example 2:

[0048] The difference between this embodiment and Example 1 is that in step (2), the holding time of diffusion annealing is 1h, and other conditions remain the same as in Example 1.

[0049] Example 3:

[0050] The difference between this embodiment and Example 1 is that in step (2), the holding time of diffusion annealing is 2h, and other conditions remain the same as in Example 1.

[0051] Example 4:

[0052] The difference between the embodiment and the embodiment 1 is that, in the step (2), the holding temperature of the diffusion annealing is 900℃, and the other conditions are consistent with the embodiment 1.

[0053] Embodiment 5:

[0054] The difference between the embodiment and the embodiment 1 is that, in the step (2), the holding temperature of the diffusion annealing is 940℃, and the other conditions are consistent with the embodiment 1.

[0055] Embodiment 6:

[0056] The difference between the embodiment and the embodiment 5 is that, in the step (2), the holding time of the diffusion annealing is 2h, and the other conditions are consistent with the embodiment 1.

[0057] Embodiment 7:

[0058] The difference between the embodiment and the embodiment 1 is that, in the step (1), the content of each component of the iron-silicon-aluminum alloy powder is, in mass percentage, Fe 84.5%, Si 9.6%, and the rest is Al. The other conditions are consistent with the embodiment 1.

[0059] Embodiment 8:

[0060] The difference between the embodiment and the embodiment 1 is that, in the step (1), the content of each component of the iron-silicon-aluminum alloy powder is, in mass percentage, Fe 84.9%, Si 9.6%, and the rest is Al. The other conditions are consistent with the embodiment 1.

[0061] Embodiment 9:

[0062] The difference between the embodiment and the embodiment 1 is that, in the step (1), the infiltrating liquid is a tin-iron-copper molten alloy liquid, Sn 96%, Fe 2.5%, and Cu 1.5%, and the melting point is lower than 300℃.

[0063] Comparative example 1:

[0064] (1) Powder preparation: according to the alloy powder component ratio of Fe: 84.6%, Si: 9.6%, Sn: 1%, and the rest is Al, the corresponding weights of iron block, silicon ingot, aluminum block and tin block are weighed and put into a vacuum medium frequency furnace for melting. The molten steel is poured into an atomization device, and high-pressure nitrogen gas is used to impact the steel liquid for rapid cooling to obtain an iron-silicon-aluminum-tin alloy powder. The obtained iron-silicon-aluminum-tin alloy powder is subjected to particle size screening, and the iron-silicon-aluminum-tin alloy powder with a mesh number of 800 is selected.

[0065] (2) Stress annealing: the iron-silicon-aluminum-tin alloy powder in the step (1) is placed in a nitrogen atmosphere furnace at 800℃ for stress annealing, and the holding time is 1h.

[0066] Other conditions are consistent with step (3) (4) in example 1.

[0067] Comparative example 2:

[0068] The difference between the present comparative example and example 1 is that the step (1) powder infiltration operation is not performed, and other conditions are consistent with example 1.

[0069] Comparative example 3:

[0070] The difference between the present comparative example and example 1 is that in step (2), the holding time of diffusion annealing is 0.5h, and other conditions are consistent with example 1.

[0071] Comparative example 4:

[0072] The difference between the present comparative example and example 1 is that in step (2), the holding temperature of diffusion annealing is 800℃, and other conditions are consistent with example 1.

[0073] The performance of the magnetic powder core samples prepared in examples 1-9 and comparative examples 1-4 is tested. Among them, the soft magnetic alloy powder obtained after infiltration and diffusion annealing in example 1 is observed by SEM to observe the micro-morphology and element distribution, and it can be seen that Sn is uniformly distributed, and the results are shown in Figure 1 The inductance value of the Fe-Si-Al magnetic powder core sample is tested by LCR table, and the permeability is converted by formula. The power loss of the Fe-Si-Al magnetic powder core is tested by Rockake SY-8218 type AC B-H analyzer under the condition of 1MHz / 50mT. The test results are shown in Table 1:

[0074] Table 1: Performance test results of magnetic powder core samples prepared in examples 1-6 and comparative examples 1-4

[0075] Group P cv (kW / m 3 )(1MHz / 50mT)]]> Magnetic permeability Magnetic permeability change rate (%) (50 kHz - 1 MHz) Example 1 660.5 62.7 ＜0.1% Example 2 770.7 61.6 ＜0.1% Example 3 606.4 61.5 ＜0.1% Example 4 798.9 62.8 ＜0.1% Example 5 673.6 61.1 ＜0.1% Example 6 664.4 60.6 ＜0.1% Example 7 866.7 59.9 ＜0.1% Example 8 808.6 65.9 ＜0.1% Example 9 820.8 62.0 ＜0.1% Comparative Example 1 4101.1 57 2.3% Comparative Example 2 3903.1 60.4 3% Comparative Example 3 1527.3 57.1 1.7% Comparative Example 4 1865.1 58.2 1.9%

[0076] Result analysis: from the above table 1, under the MHz frequency band, the magnetic core loss P cv of the magnetic powder core prepared in examples 1-9 is lower than 870 kW / m 3 , which is much lower than the magnetic core loss of the magnetic powder core prepared in comparative example 1 without infiltration after diffusion annealing. This is because after the tin is infiltrated into the molten metal liquid in the present application, the tin element is dissolved from the outside to the inside of the alloy powder during the diffusion annealing process, as shown in Figure 1 . In this way, on the one hand, a concentration gradient distribution is formed, and this unique microstructure greatly improves the microstress distribution of the alloy powder, reduces the concentrated stress, and is beneficial to improve the magnetic permeability and reduce the hysteresis loss. On the other hand, as shown in Figure 2As shown, the Sn element is uniformly distributed on the powder surface of the FeSiAl magnetic powder core. Due to the tin element enrichment on the surface layer, a paramagnetic FeSn2 iron-tin intermetallic compound will be generated in situ during the annealing heat treatment, and the base itself is ferromagnetic. The formation of the heterogeneous magnetic structure breaks the strong demagnetization field distribution of the original base, making it more difficult for the domain wall resonance to occur, improving the high-frequency stability of the material, and reducing the residual loss generated by the domain wall resonance at high frequency. The synergistic effect of the two mechanisms enables the present application to break through the performance limit of existing materials, not only having extremely low loss and relatively high permeability under high-frequency megahertz working conditions, but also having relatively stable high-frequency performance. The magnetic powder core prepared in Comparative Example 1 has a significantly larger loss and a decreased permeability under the condition of 1 MHz / 50 mT, because in Comparative Example 1, the annealing is directly performed without the effect of tin atom diffusion and solid solution, and the effect of stress improvement is limited. Moreover, no new magnetic phase structure is constructed, and the influence on the magnetic domain motion is minimal.

[0077] As can be seen from Table 1, the adjustment of the diffusion annealing temperature and holding time will have a significant impact on the performance. If the diffusion temperature is too low or the reaction time is too short, the diffusion reaction will not be sufficient, and the tin atoms cannot effectively solid solution into the FeSiAl base and react. If the temperature is too high or the holding time is too long, the gradient distribution of tin atoms will change to uniform distribution, deviating from the original structure design, and the performance will be poor.

[0078] In summary, the magnetic powder core prepared under the preparation conditions of Example 3 has the best performance. Under the condition of 1 MHz / 50 mT, the loss is as low as 606.4 kW / m 3 , and the effective permeability is higher than 60. The permeability change rate in the megahertz frequency range is less than 0.1%, and the performance is excellent and stable.

[0079] Although the embodiments of the present application have been shown and described above, it should be understood that the above embodiments are exemplary and should not be construed as limiting the present application. Those skilled in the art can make changes, modifications, replacements, variations, deletions of part of the features, additions of features or recombination of features within the scope of the present application without departing from the principles and purposes of the present application. Any simple modification, equivalent change and modification made according to the innovative principles of the present application to the above embodiments shall still fall within the scope of the present application.

Claims

1. A method for preparing a MHz-level low-loss FeSiAl magnetic powder core by infiltration diffusion, characterized in that, The method comprises the following steps: (1) powder infiltration: completely immerse the iron-silicon-aluminum alloy powder in a molten tin-based metal material, and take it out after sufficient wetting; (2) diffusion annealing: perform diffusion annealing on the wetted iron-silicon-aluminum powder in a hydrogen atmosphere, wherein tin atoms are solid-solved from the outside to the inside of the iron-silicon-aluminum alloy powder to form a concentration gradient distribution, and FeSn2 intermetallic compound is generated in situ with Fe; (3) compression molding: add a binder, stir uniformly, heat and dry, then add a release agent, stir uniformly, and then press into a green part; (4) heat treatment: perform annealing on the green part in step (3) in a protective atmosphere, and cool to obtain an MHz-level low-loss iron-silicon-aluminum magnetic powder core; In step (1), the composition of the iron-silicon-aluminum alloy powder, in terms of mass percentage, comprises: Fe: 84.5-84.9%, Si: 9.6%, and the rest is Al.

2. The method according to claim 1, wherein the method is characterized by, In step (1), the melting point of the tin-based metal material is not higher than 300°C.

3. The method according to claim 1, wherein the method is characterized by, The tin-based metal material is tin or a tin-based alloy, and the tin-based alloy comprises tin and at least one metal selected from iron and copper.

4. The method according to claim 1, wherein the method is characterized by, In step (1), the holding temperature of the molten tin-based metal material is not less than 300°C, and the infiltration time is not less than 0.5h.

5. The method according to claim 1, wherein the method is characterized by: In step (2), the diffusion annealing temperature is 850-1000°C, the heating rate is 10-12°C / min, and the holding time is 1-2h.

6. The method according to claim 1, wherein the method is characterized by: In step (3), the binder is a methyl acetate solution of silicone resin or an acetone solution of silicone resin, the drying temperature is 130-180°C, the drying time is 10min, the release agent is selected from one or more of zinc stearate, calcium stearate, barium stearate, and paraffin wax, and the addition amount of the release agent is 0.3-0.4wt%.

7. The method according to claim 1, wherein the method is characterized by, In step (3), the green compact is pressed into a ring shape, with a unit forming pressure of 18-20 t / cm 3 .

8. The method according to claim 1, wherein the method is characterized by: In step (4), the annealing temperature is 700-750°C, the heating rate is 8-10°C / min, the holding time is 1h, and the annealing atmosphere is nitrogen.

9. An MHz-level low-loss iron-silicon-aluminum magnetic powder core prepared by the infiltration diffusion method according to any one of claims 1-8.

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