A soft magnetic powder core with excellent low-frequency magnetic properties and its preparation method

Abstract

This invention proposes a metal soft magnetic powder core with excellent low-frequency magnetic properties and its preparation method, belonging to the field of magnetic materials. Using at least nano-boron powder and iron-silicon soft magnetic alloy powder as raw materials, high-temperature diffusion and high-temperature nitriding treatments are employed. Part of the nano-boron powder forms a high-resistivity iron-silicon-boron permeation layer on the surface of the iron-silicon soft magnetic alloy powder, while some nano-boron powder forms a boron nitride insulating layer with both high resistivity and high thermal stability between the iron-silicon soft magnetic alloy powders, effectively controlling eddy currents. Hot pressing further increases the density of the metal soft magnetic powder core, reduces the demagnetizing field, thereby improving permeability and reducing hysteresis loss. Thus, excellent low-frequency magnetic properties of high density, high permeability, and low loss are simultaneously obtained in the metal soft magnetic powder core.

Description

Technical Field

[0001] This invention relates to the field of magnetic materials, specifically to a soft magnetic powder core with excellent low-frequency magnetic properties and its preparation method. Background Technology

[0002] Soft magnetic materials, as an important component of magnetic materials, possess magnetic properties such as high saturation magnetic induction, high permeability, high stability, low coercivity, low magnetostriction coefficient, and low loss, and are widely used in various power electronic equipment. Currently, the soft magnetic materials used at low frequencies are mainly silicon steel, amorphous materials, and pure iron. Compared to silicon steel, amorphous materials, and pure iron, metal soft magnetic powder cores have lower eddy current losses due to the presence of high-resistivity non-magnetic phases such as insulating coatings and air gaps between metal particles. This gives metal soft magnetic powder cores a significant performance advantage in the high-frequency range where eddy currents account for a large proportion. However, these non-magnetic phases also increase the demagnetizing field inside the powder core, leading to a decrease in permeability and an increase in hysteresis loss. Furthermore, hysteresis loss is the dominant loss in metal soft magnetic powder cores at low frequencies, making it difficult to apply metal soft magnetic powder core materials in power equipment and motors with low operating frequencies.

[0003] To address the issues of low permeability and high low-frequency loss in soft magnetic powder cores, it is necessary to effectively increase the powder core density by reducing the air gap and lowering the insulation content while ensuring low eddy current loss, thereby weakening the demagnetizing field inside the powder core. However, traditional cold pressing and warm pressing processes for soft magnetic powder cores cannot significantly increase the powder core density, thus failing to effectively improve the low-frequency magnetic properties of soft magnetic powder cores. Summary of the Invention

[0004] This invention proposes a metal soft magnetic powder core with excellent low-frequency magnetic properties and its preparation method, which can simultaneously obtain high-density, high-permeability and low-loss metal soft magnetic powder cores, effectively improving the low-frequency magnetic properties of metal soft magnetic powder cores.

[0005] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution.

[0006] This invention proposes a metal soft magnetic powder core with excellent low-frequency magnetic properties, comprising at least iron-silicon soft magnetic alloy powder and boron nitride; wherein the surface of the iron-silicon soft magnetic alloy powder contains an iron-silicon-boron infiltration layer, and the boron nitride exists between the iron-silicon soft magnetic alloy powder particles.

[0007] The density of the metal soft magnetic powder core is 7.25–7.51 g / cm³. 3 .

[0008] The maximum permeability of the metal soft magnetic powder core is 254 to 1150.

[0009] The loss of the metal soft magnetic powder core at 1kHz / 500mT is 20.5~27W / kg.

[0010] This invention also provides a method for preparing the above-described metal soft magnetic powder core with excellent low-frequency magnetic properties, comprising at least the following steps:

[0011] 1-5% by mass of nano boron powder and 95-99% by mass of iron-silicon soft magnetic alloy powder are mixed evenly to obtain the magnetic powder to be formed.

[0012] Under a first preset pressure, the magnetic powder to be formed is pre-pressed to obtain a pre-pressed green blank;

[0013] The pre-pressed green blank is heat-treated in an inert atmosphere at a first preset temperature for 30-60 minutes, and then heat-treated in a nitrogen atmosphere at a second preset temperature for 1-2 hours to obtain a pre-fired green blank.

[0014] Under a second preset pressure, the pre-fired blank is kept at a third preset temperature for 1 to 5 minutes in a nitrogen atmosphere and then hot-pressed to obtain a soft magnetic metal powder core.

[0015] The nano-boron powder has a particle size of less than 100 nm; the iron-silicon soft magnetic alloy powder has a silicon content of 5.2-5.8% and a particle size of -80 mesh.

[0016] In the preparation method of the present invention,

[0017] The first preset pressure is 50-100 MPa;

[0018] The second preset pressure is 200-400 MPa;

[0019] The first preset temperature is 650–950°C;

[0020] The second preset temperature is 1000~1200℃;

[0021] The third preset temperature is 700-1100℃.

[0022] The above preparation method can yield a metal soft magnetic powder core with excellent low-frequency magnetic properties.

[0023] In summary, this invention proposes a metal soft magnetic powder core with excellent low-frequency magnetic properties and its preparation method. An iron-silicon-boron permeation layer is formed on the surface of the iron-silicon soft magnetic alloy powder, increasing the surface resistivity of the magnetic powder and helping to reduce eddy currents on the powder surface and between the powder particles. A boron nitride insulating layer with both high resistivity and high thermal stability is generated between the iron-silicon soft magnetic alloy powder particles, effectively isolating the eddy current path between them and maintaining low eddy current losses in the metal soft magnetic powder core. Hot pressing reduces the air gap ratio inside the metal soft magnetic powder core, significantly increasing its density and effectively weakening the demagnetizing field inside the core, which helps to improve the permeability and reduce hysteresis losses. Thus, high density, high permeability, and low loss are simultaneously achieved within the metal soft magnetic powder core, effectively improving its low-frequency magnetic properties. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a flowchart illustrating the preparation process of the metal soft magnetic powder core of the present invention.

[0026] Figure 2 The images show scanning electron microscope (SEM) and X-ray energy dispersive spectroscopy (EDS) images of the metal soft magnetic powder core obtained in Example 2. Detailed Implementation

[0027] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0028] It should be understood that the present invention can be implemented in various forms and should not be construed as being limited to the embodiments set forth herein. Rather, providing these embodiments will make the disclosure thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Unless otherwise specified, “%” and “parts” as shown in the following embodiments refer to “% by mass” and “parts by mass”, respectively.

[0029] The technical solution of the present invention will be further described in detail below with reference to several embodiments and accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] This invention provides a metal soft magnetic powder core with excellent low-frequency magnetic properties, comprising at least iron-silicon soft magnetic alloy powder and boron nitride. The iron-silicon soft magnetic alloy powder surface contains an iron-silicon-boron infiltration layer, and the boron nitride is present between the iron-silicon soft magnetic alloy powder particles. The iron-silicon-boron infiltration layer increases the resistivity of the iron-silicon soft magnetic alloy powder surface, weakens eddy currents on the powder surface, and works with boron nitride to achieve insulation between the iron-silicon soft magnetic alloy powder particles, thereby helping to weaken eddy currents between the iron-silicon soft magnetic alloy powder particles and effectively controlling eddy current losses. Simultaneously, the metal soft magnetic powder core provided by this invention significantly increases the powder core density through hot pressing, thereby reducing the demagnetizing field within the powder core and achieving an increase in permeability and a decrease in hysteresis loss. The combined effect of the iron-silicon-boron infiltration layer, boron nitride, and high density simultaneously achieves effective improvement in permeability and low-frequency losses in the metal soft magnetic powder core provided by this invention.

[0031] In one embodiment of the present invention, the density of the metal soft magnetic powder core is, for example, 7.25–7.51 g / cm³. 3 The maximum permeability is, for example, 254–1150, and the loss of the metal soft magnetic powder core at 1 kHz / 500 mT is, for example, 20.5–27 W / kg. Thus, this invention achieves high density, high permeability, and low loss properties in the metal soft magnetic powder core.

[0032] Please see Figure 1 As shown, the present invention provides a method for preparing a metal soft magnetic powder core with excellent low-frequency magnetic properties, including but not limited to steps S10-S40.

[0033] Step S10: Mix 1-5% by mass of nano-boron powder with 95-99% by mass of iron-silicon soft magnetic alloy powder to obtain the magnetic powder to be formed.

[0034] Step S20: Under the first preset pressure, the magnetic powder to be formed is pre-pressed to obtain a pre-pressed green blank.

[0035] Step S30: Heat-treat the pre-pressed green billet in an inert atmosphere at a first preset temperature for 30-60 minutes, and then heat-treat it in a nitrogen atmosphere at a second preset temperature for 1-2 hours to obtain a pre-fired billet.

[0036] Step S40: Under the second preset pressure, the pre-fired blank is kept at a third preset temperature for 1-5 minutes in a nitrogen atmosphere to perform hot pressing sintering and obtain a metal soft magnetic powder core.

[0037] Please see Figure 1 As shown, in one embodiment of the present invention, in steps S10-S20, the particle size of the nano-boron powder is, for example, less than 100 nm, the silicon content in the iron-silicon soft magnetic alloy powder is, for example, 5.2-5.8%, and the remaining component is, for example, iron. The particle size of the iron-silicon soft magnetic alloy powder is, for example, -80 mesh. The first preset pressure for pressing the magnetic powder to be formed is, for example, 50-100 MPa. The present invention ensures the uniform distribution of nano-boron powder in the pre-pressed green blank by uniformly mixing the nano-boron powder and the iron-silicon soft magnetic alloy powder before pressing, thus ensuring the performance stability of the metal soft magnetic powder core and simultaneously increasing the density of the metal soft magnetic powder core.

[0038] Please see Figure 1 As shown, in one embodiment of the present invention, in step S30, the first preset temperature is, for example, 650–950°C. During the heat treatment at the first preset temperature, the pre-pressed green blank is treated in an inert atmosphere, for example, under an inert gas such as argon or helium. Under the inert atmosphere, boron in the nano-boron powder diffuses into the adjacent iron-silicon soft magnetic alloy powder, forming an iron-silicon-boron infiltration layer on the surface of the iron-silicon soft magnetic alloy powder. The iron-silicon-boron infiltration layer can increase the resistivity of the iron-silicon soft magnetic alloy powder surface, which helps to reduce eddy currents on the magnetic powder surface and between the magnetic powder particles.

[0039] Please see Figure 1 As shown, in one embodiment of the present invention, in step S30, the second preset temperature is, for example, 1000–1200°C. During the heat treatment at the second preset temperature, the pre-pressed green compact is treated in nitrogen. Under a nitrogen atmosphere, the boron nanoparticles that have not diffused into the adjacent iron-silicon soft magnetic alloy powder react with nitrogen to form boron nitride between the iron-silicon soft magnetic alloy powders. Boron nitride has high resistivity and excellent thermal stability, which is beneficial for maintaining the insulation between the iron-silicon soft magnetic alloy powders, thereby achieving effective control of eddy current losses. The present invention performs two high-temperature treatments on the pre-pressed green compact under different atmospheres to form an iron-silicon boron penetration layer with excellent soft magnetic properties on the surface of the iron-silicon soft magnetic alloy powder, thereby increasing the resistivity of the iron-silicon soft magnetic alloy powder surface. A high-resistivity and high-thermal-stability boron nitride insulating layer is formed between the iron-silicon soft magnetic alloy powders to maintain the insulation between the iron-silicon soft magnetic alloy powders. Finally, a high resistivity is achieved in the metal soft magnetic powder core, which helps to suppress eddy current losses within the powder core. In this embodiment, the volume resistivity of the metal soft magnetic powder core is, for example, 245–846 μΩ·m.

[0040] Please see Figure 1As shown, in one embodiment of the present invention, in step S40, the second preset pressure is, for example, 200-400 MPa, and the third preset temperature is, for example, 700-1100°C. That is, the pre-sintered blank obtained in step S30 is hot-pressed and sintered, and the hot-pressing and sintering is carried out in a nitrogen atmosphere, which can avoid the decomposition of boron nitride. Compared with cold pressing or warm pressing processes, hot-pressing and sintering significantly reduces the air gap ratio inside the metal soft magnetic powder core and increases the density of the metal soft magnetic powder core, thereby effectively weakening the demagnetizing field inside the metal soft magnetic powder core, helping to improve the permeability of the metal soft magnetic powder core and reduce the hysteresis loss of the metal soft magnetic powder core.

[0041] The combined effect of the three beneficial factors—iron-silicon-boron permeation layer, boron nitride, and high density—achieves effective improvement in both magnetic permeability and low-frequency loss in the metal soft magnetic powder core provided by this invention.

[0042] To further understand the present invention, specific embodiments will be cited to explain the invention in more detail. These embodiments should not be construed as limiting. Appropriate modifications can be made within the scope of the present invention, and all such modifications fall within the technical scope of the present invention.

[0043] Example 1

[0044] Step S10: Mix 1% by mass of boron nanoparticles with a particle size of less than 100 nm with 99% of -80 mesh iron-silicon soft magnetic alloy powder to obtain the magnetic powder to be formed.

[0045] Step S20: Pre-press the magnetic powder to be formed under a pressure of 50 MPa to obtain a pre-pressed green blank.

[0046] Step S30: First, heat-treat the pre-pressed green billet in an argon atmosphere at 650°C for 30 minutes to allow boron to diffuse into the surface of the iron-silicon soft magnetic alloy powder and form an iron-silicon-boron infiltration layer. Then, heat-treat it in a nitrogen atmosphere at 1000°C for 1 hour to convert the boron that has not diffused between the iron-silicon soft magnetic alloy powders into boron nitride, thereby obtaining the pre-sintered billet.

[0047] Step S40: The pre-burned blank is held at 200 MPa and in a nitrogen atmosphere at 700°C for 1 minute for hot pressing sintering to obtain a metal soft magnetic powder core with a high resistivity and excellent soft magnetic properties on the surface of the iron-silicon soft magnetic alloy powder, and a boron nitride insulating layer with high resistivity and high thermal stability between the iron-silicon soft magnetic alloy powder particles.

[0048] The density of the soft magnetic powder core prepared by hot pressing is 7.51 g / cm³. 3 It has a maximum permeability of 1150 and a loss of 27W / kg at 1kHz / 500mT, exhibiting excellent low-frequency magnetic properties.

[0049] Example 2

[0050] Step S10: Mix 3% by mass of boron nanoparticles with a particle size of less than 100 nm with 97% of -80 mesh iron-silicon soft magnetic alloy powder to obtain the magnetic powder to be formed.

[0051] Step S20: The magnetic powder to be formed is pre-pressed under a pressure of 75 MPa to obtain a pre-pressed green blank.

[0052] Step S30: First, heat-treat the pre-pressed green billet in an argon atmosphere at 800℃ for 45 minutes to allow boron to diffuse into the surface of the iron-silicon soft magnetic alloy powder and form an iron-silicon-boron infiltration layer. Then, heat-treat it in a nitrogen atmosphere at 1100℃ for 1.5 hours to convert the boron that has not diffused between the iron-silicon soft magnetic alloy powders into boron nitride, thereby obtaining the pre-sintered billet.

[0053] Step S40: The pre-burned billet is held at 300 MPa and in a nitrogen atmosphere at 900°C for 3 minutes for hot pressing sintering to obtain a metal soft magnetic powder core with a high resistivity and excellent soft magnetic properties on the surface of the iron-silicon soft magnetic alloy powder, and a boron nitride insulating layer with high resistivity and high thermal stability between the iron-silicon soft magnetic alloy powder particles.

[0054] The density of the soft magnetic powder core prepared by hot pressing is 7.4 g / cm³. 3 It has a maximum permeability of 550 and a loss of 20.5 W / kg at 1 kHz / 500 mT, exhibiting excellent low-frequency magnetic properties.

[0055] Example 3

[0056] Step S10: Mix 5% by mass of boron nanoparticles with a particle size of less than 100 nm with 95% by mass of -80 mesh iron-silicon soft magnetic alloy powder to obtain the magnetic powder to be formed.

[0057] Step S20: Pre-press the magnetic powder to be formed under a pressure of 100MPa to obtain a pre-pressed green blank.

[0058] Step S30: First, heat-treat the pre-pressed green billet in an argon atmosphere at 950°C for 60 minutes to allow boron to diffuse into the surface of the iron-silicon soft magnetic alloy powder and form an iron-silicon-boron infiltration layer. Then, heat-treat it in a nitrogen atmosphere at 1200°C for 2 hours to convert the boron that has not diffused between the iron-silicon soft magnetic alloy powders into boron nitride, thereby obtaining the pre-sintered billet.

[0059] Step S40: The pre-sintered blank is held at 400 MPa and 1100 °C in a nitrogen atmosphere for 5 minutes for hot pressing sintering to obtain a metal soft magnetic powder core with a high resistivity and excellent soft magnetic properties on the surface of the iron-silicon soft magnetic alloy powder, and a boron nitride insulating layer with high resistivity and high thermal stability between the iron-silicon soft magnetic alloy powder particles, thereby obtaining excellent magnetic properties at low frequencies.

[0060] The density of the soft magnetic powder core prepared by hot pressing is 7.25 g / cm³. 3 It has a maximum permeability of 254 and a loss of 25.3 W / kg at 1 kHz / 500 mT, exhibiting excellent low-frequency magnetic properties.

[0061] Comparative Example 1

[0062] Step S10: Mix 5% by mass of boron nanoparticles with a particle size of less than 100 nm with 95% by mass of -80 mesh iron-silicon soft magnetic alloy powder to obtain the magnetic powder to be formed.

[0063] Step S20: The magnetic powder to be formed is pre-pressed under a pressure of 75 MPa to obtain a pre-pressed green blank.

[0064] Step S30: The pre-fired blank is held at a pressure of 300 MPa in a nitrogen atmosphere at 900°C for 3 minutes and then hot-pressed. During the hot-pressing process, some nano-boron powder reacts with iron-silicon soft magnetic alloy powder. There are metal soft magnetic powder cores with a boron nitride insulating layer with high resistivity and high thermal stability between the iron-silicon soft magnetic alloy powders.

[0065] The density of the soft magnetic powder core prepared by hot pressing is 7.35 g / cm³. 3 The maximum permeability is 700, and the loss at 1kHz / 500mT is 41W / kg.

[0066] Comparative Example 2

[0067] Step S10: Mix 5% by mass of boron nanoparticles with a particle size of less than 100 nm with 95% by mass of -80 mesh iron-silicon soft magnetic alloy powder to obtain the magnetic powder to be formed.

[0068] Step S20: The magnetic powder to be formed is pre-pressed under a pressure of 75 MPa to obtain a pre-pressed green blank.

[0069] Step S30: First, heat-treat the green billet in an argon atmosphere at 800℃ for 45 minutes to allow boron to diffuse into the surface of the iron-silicon soft magnetic alloy powder and form an iron-silicon-boron infiltration layer. Then, heat-treat it in a nitrogen atmosphere at 1100℃ for 1.5 hours to convert the boron that has not diffused between the iron-silicon soft magnetic alloy powders into boron nitride, thereby obtaining a pre-sintered billet.

[0070] Step S40: Hold the pre-fired billet at a pressure of 300 MPa for 3 minutes and perform cold pressing to obtain a metal soft magnetic powder core with an iron-silicon soft magnetic alloy powder particle having an iron-silicon boron infiltration layer with high resistivity and excellent soft magnetic properties on the surface and a boron nitride insulating layer with high resistivity and high thermal stability between the iron-silicon soft magnetic alloy powder particles.

[0071] The density of the soft magnetic powder core prepared by cold pressing is 6.5 g / cm³.3 The maximum permeability is 81, and the loss at 1kHz / 500mT is 45W / kg.

[0072] Comparative Example 3

[0073] Taking the iron-silicon soft magnetic powder cores currently sold on the market, which are prepared using oxide or inorganic acid salt insulation processes and cold or warm pressing processes, as an example, the density of the iron-silicon soft magnetic powder core is less than 7.0 g / cm³. 3 The maximum permeability is less than 90, and the loss at 1kHz / 500mT is higher than 30W / kg.

[0074] Please see Figure 2 As shown, the metal soft magnetic powder core obtained in Example 2 was subjected to scanning electron microscopy and X-ray energy dispersive spectroscopy (EDS) tests. The figures show that after boron diffusion, boron nitriding, and hot pressing, the iron-silicon soft magnetic alloy powder and the boron nanoparticles are tightly bonded. A clear and uniformly distributed nitrogen signal exists between the iron-silicon soft magnetic alloy powder and the boron nanoparticles, indicating successful nitriding of the boron nanoparticles. Boron shows enrichment signals on the surface and in the interstices of the iron-silicon alloy powder; however, it should be noted that because boron is a lightweight element, the boron signal obtained by EDS analysis is not as pronounced as the nitrogen signal.

[0075] Combining Examples 1-3 and Comparative Example 1, the metal soft magnetic powder core obtained through boron diffusion, boron nitriding, and hot pressing exhibits reduced loss compared to a metal soft magnetic powder core formed solely by hot pressing. This indicates that forming an iron-silicon-boron infiltration layer on the surface of the iron-silicon soft magnetic alloy powder, and a boron nitride insulating layer between the iron-silicon soft magnetic alloy powders, can simultaneously and effectively improve both permeability and low-frequency loss within the metal soft magnetic powder core. Combining Examples 1-3 and Comparative Example 2, the metal soft magnetic powder core obtained through boron diffusion, boron nitriding, and hot pressing exhibits increased density and maximum permeability compared to a metal soft magnetic powder core formed by boron diffusion, boron nitriding, and cold pressing. Simultaneously, low-frequency loss is reduced. This indicates that the hot pressing process increases the density of the metal soft magnetic powder core, effectively weakens the demagnetizing field within the metal soft magnetic powder core, and helps to improve the permeability and reduce the loss of the metal soft magnetic powder core. In conjunction with Examples 1-3 and Comparative Example 3, compared to commercially available iron-silicon soft magnetic powder cores, this invention employs boron diffusion, boron nitriding, and hot pressing processes that differ from existing technologies, significantly improving the density and permeability of the metal soft magnetic powder core while reducing low-frequency losses. The metal soft magnetic powder core prepared by this invention simultaneously achieves high density, high permeability, and low loss, thus enhancing the low-frequency magnetic performance of the metal soft magnetic powder core.

[0076] In summary, this invention proposes a metal soft magnetic powder core with excellent low-frequency magnetic properties and its preparation method. Through high-temperature diffusion treatment, an iron-silicon-boron permeation layer is formed on the surface of the iron-silicon soft magnetic alloy powder, thereby increasing the surface resistivity and reducing eddy currents. Through high-temperature nitriding, a boron nitride insulating layer with both high resistivity and high thermal stability is generated between the iron-silicon soft magnetic alloy powder particles, further reducing eddy currents between the powder particles. Through hot-pressing sintering, the density of the metal soft magnetic powder core is significantly increased, reducing the demagnetizing field. Thus, high density, high permeability, and low loss are simultaneously achieved within the metal soft magnetic powder core, effectively improving its low-frequency magnetic properties.

[0077] The above description is merely a preferred embodiment of this application and an explanation of the technical principles used. Those skilled in the art should understand that the scope of the invention involved in this application is not limited to the technical solutions formed by a specific combination of the above-mentioned technical features, but should also cover other technical solutions formed by any combination of the above-mentioned technical features or their equivalent features without departing from the inventive concept. For example, technical solutions formed by replacing the above-mentioned features with technical features with similar functions disclosed in this application (but not limited to) each other.

[0078] Apart from the technical features described in the specification, the other technical features are known to those skilled in the art. To highlight the innovative features of this invention, the other technical features will not be described in detail here.

Claims

1. A method for preparing a metal soft magnetic powder core with excellent low-frequency magnetic properties, characterized in that, At least the following steps are included: 1-5% by mass of nano boron powder and 95-99% by mass of iron-silicon soft magnetic alloy powder are mixed evenly to obtain the magnetic powder to be formed. Under a first preset pressure, the magnetic powder to be formed is pre-pressed to obtain a pre-pressed green blank; The pre-pressed green blank is heat-treated in an inert atmosphere at a first preset temperature for 30-60 minutes, and then heat-treated in a nitrogen atmosphere at a second preset temperature for 1-2 hours to obtain a pre-fired blank; the first preset pressure is 50-100 MPa; the first preset temperature is 650-950℃; and the second preset temperature is 1000-1200℃. Under a second preset pressure, the pre-fired blank is held at a third preset temperature in a nitrogen atmosphere for 1-5 minutes for hot pressing sintering to obtain a metal soft magnetic powder core; the second preset pressure is 200-400 MPa, and the third preset temperature is 700-1100℃. The metal soft magnetic powder core includes at least iron-silicon soft magnetic alloy powder and boron nitride, wherein the surface of the iron-silicon soft magnetic alloy powder contains an iron-silicon-boron infiltration layer, and the boron nitride exists between the iron-silicon soft magnetic alloy powders; The density of the metal soft magnetic powder core is 7.25~7.51 g / cm³. 3 The loss of the metal soft magnetic powder core at 1kHz / 500mT is 20.5~27W / kg, and the maximum permeability of the metal soft magnetic powder core is 254~1150.

2. The method for preparing a metal soft magnetic powder core with excellent low-frequency magnetic properties according to claim 1, characterized in that, The particle size of the boron nanoparticles is less than 100 nm.

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