A high silicon steel flaky magnetic powder core and a method for manufacturing the same

Abstract

The application discloses a high-silicon steel flaky powder magnetic powder core and a preparation method thereof, relates to the technical field of magnetic powder cores, and comprises the following steps: taking pure iron and high-purity silicon as raw materials for smelting, and then preparing high-silicon steel thin strips through single-roller rapid quenching; the content of silicon in the high-silicon steel thin strips is 4.5%-7.0%, and the balance is Fe; rough crushing and air flow fine crushing are sequentially performed to obtain high-silicon steel flaky powder, and annealing treatment is performed under a first protective atmosphere; surface coating is performed on the annealed high-silicon steel flaky powder through an insulation modifier to obtain coated magnetic powder; the coated magnetic powder is subjected to hot pressing to obtain a magnetic core blank; stress relief annealing is performed on the magnetic core blank, and furnace cooling is performed to obtain the high-silicon steel flaky powder magnetic powder core. Brittleness and order phase precipitation are inhibited through rapid quenching, high thickness-diameter ratio flaky powder is obtained in combination with air flow crushing, the composite insulation layer has the characteristics of high pressure resistance and high temperature resistance, the density of the magnetic core is improved through hot pressing, and the obtained magnetic powder core has high magnetic permeability, low high-frequency loss and high resistivity.

Description

Technical Field

[0001] This invention relates to the field of magnetic powder core preparation technology, specifically to a high-silicon steel sheet-like magnetic powder core and its preparation method. Background Technology

[0002] As power electronic devices evolve towards higher frequencies, smaller sizes, and higher power densities, the requirements for soft magnetic materials in high-frequency inductors, transformers, and magnetic devices for new energy vehicles are constantly increasing. Traditional laminated silicon steel, under medium-to-high frequency conditions, is prone to significant eddy current losses due to the continuous interlayer conductive paths, thus limiting its application in high-frequency fields. In contrast, powder core materials, with their higher resistivity, flexible forming methods, and suitability for fabricating complex magnetic circuit structures, have attracted widespread attention in high-frequency soft magnetic devices.

[0003] High-silicon steel possesses high resistivity, low magnetostriction coefficient, and good soft magnetic properties, making it a potential material for fabricating high-frequency, low-loss powder magnetic cores. Current methods for preparing high-silicon steel powder magnetic cores typically involve atomization followed by ball milling to create flake-like particles, aiming to improve the high-frequency performance of the core. While this method can yield powders with a certain flake morphology, it suffers from several drawbacks: First, the atomized powder is usually near-spherical, making it difficult to control the aspect ratio and morphological uniformity of the flake particles during subsequent ball milling. Second, mechanical ball milling easily introduces significant plastic deformation and surface defects, leading to powder work hardening and increased surface activity, which in turn affects soft magnetic properties and subsequent insulation coating. Third, the aforementioned process is lengthy and requires substantial equipment investment, hindering cost reduction.

[0004] Furthermore, existing powder cores are typically cold-pressed and coated with a single insulating system such as phosphate or resin. This process presents several problems in practical applications: First, cold pressing limits particle rearrangement and plastic coordination, restricting the increase in core pressing density and consequently affecting permeability. Second, the single insulating layer is prone to cracking, peeling, or local discontinuity during high-voltage pressing, leading to increased local conductive contact between particles and thus increasing eddy current losses in the core. Especially when simultaneously increasing pressing density and maintaining insulation integrity are required, existing processes often struggle to balance both permeability and high-frequency loss performance. Summary of the Invention In view of the shortcomings of the prior art, the purpose of this invention is to provide a high-silicon steel sheet magnetic powder core and its preparation method, aiming to solve at least one of the problems in the above-mentioned background art.

[0005] One aspect of the present invention is to provide a method for preparing a high-silicon steel sheet-like magnetic powder core, the method comprising: High-silicon steel strips are prepared by smelting pure iron and high-purity silicon as raw materials and then by single-roll rapid quenching. The thickness of the high-silicon steel strips is 30μm-40μm, and the silicon content in the high-silicon steel strips is 4.5%-7.0%, with the balance being Fe. The high-silicon steel strip is subjected to jaw crushing and airflow crushing in sequence to obtain high-silicon steel flake powder. The particle size of the high-silicon steel flake powder is 50μm-200μm and the thickness is 5μm-20μm. The high-silicon steel flake powder is annealed at a first preset temperature under a first protective atmosphere and then cooled in the furnace. Surface coating of annealed high-silicon steel flake powder with an insulating modifier is used to obtain coated magnetic powder. The coated magnetic powder is hot-pressed at a second preset temperature and preset pressure to obtain a magnetic core blank. The magnetic core blank is subjected to stress-relief annealing at a third preset temperature under a second protective atmosphere and then cooled in the furnace to obtain a high-silicon steel sheet-shaped magnetic powder core.

[0006] According to one aspect of the above technical solution, the first preset temperature is 800℃-900℃, and the annealing time is 2h-3h.

[0007] According to one aspect of the above technical solution, the amount of the insulating modifier added is 1.5%-3% of the mass of the high silicon steel flake powder, and the coating thickness of the coated magnetic powder is 0.5μm-2μm.

[0008] According to one aspect of the above technical solution, the insulating modifier comprises a nano-SiO2 dispersion and a phosphate coupling agent, wherein the mass ratio of the nano-SiO2 dispersion to the phosphate coupling agent is (3-5):1, the particle size of the nano-SiO2 is not greater than 50nm, the content of nano-SiO2 in the nano-SiO2 dispersion is 20wt%-40wt%, and the pH is 3.8-4.2. The phosphate coupling agent comprises KH570 and a phosphate ester auxiliary agent, and the mass ratio of KH570 to the phosphate ester auxiliary agent is (2-4):1.

[0009] According to one aspect of the above technical solution, the surface coating method includes: Mix at 300 rpm - 500 rpm for 30 min - 60 min; Dry at 80℃-90℃ for 2-3 hours; Curing temperature: 120℃-150℃ for 1-2 hours.

[0010] According to one aspect of the above technical solution, the particle size of the jaw crusher is 1mm-5mm; The particle size of the high-silicon steel flake powder is controlled by adjusting the speed of the classifying wheel to 2000 r / min-3000 r / min and the pulverizing air pressure to 0.35 MPa-0.5 MPa. The thickness-to-diameter ratio of the high-silicon steel flake powder is 1:(5-15).

[0011] According to one aspect of the above technical solution, the second preset temperature is 110℃-130℃, the preset pressure is 500MPa-700MPa, and the pressing time is 15s-60s.

[0012] Another aspect of the present invention is to provide a high-silicon steel sheet-like powder magnetic core, wherein the high-silicon steel sheet-like powder magnetic core is prepared by the above-described method for preparing high-silicon steel sheet-like powder magnetic core.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. A technical route combining thin strip continuous casting with rapid quenching and two-stage mechanical crushing is adopted. Single-roll rapid quenching suppresses the precipitation of brittle phases in high-silicon steel, giving the thin strip good toughness. High aspect ratio sheet powder can be directly obtained through jaw crushing and air jet crushing. Compared with the traditional ball milling process, this method fundamentally avoids work hardening, lattice distortion, and microcracks introduced by severe plastic deformation, significantly reduces the coercivity of the powder, lays the material foundation for obtaining low-loss magnetic cores, simplifies the process, and greatly reduces production costs.

[0014] 2. A hot-pressing process is used instead of traditional cold pressing. Preheating the mold imparts appropriate thermoplasticity to the high-silicon steel sheet powder. Under high pressure, the powder particles not only rearrange but also undergo micro-plastic deformation to fill pores, increasing the core density. This invention effectively eliminates internal porosity, significantly shortens non-magnetic gaps in the magnetic circuit, and improves the effective permeability of the core.

[0015] 3. An inorganic-organic composite insulation system consisting of nano-SiO2 dispersion and phosphate coupling agent was constructed. Nano-SiO2 forms a high-temperature resistant, high-hardness inorganic framework on the particle surface, while the phosphate coupling agent acts as a molecular bridge, chemically bonding the inorganic layer to the metal matrix, thus resolving the contradiction that single-layer insulation is brittle due to its inorganic nature and soft due to its organic nature. Combined with the high densification effect of hot pressing, this composite insulation layer is less prone to cracking, peeling, or penetration under high pressure, improving core resistivity and reducing high-frequency total iron loss. Detailed Implementation

[0016] To make the objects, features, and advantages of the invention more apparent and understandable, the invention may be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of the invention will be thorough and complete. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0017] This invention provides a method for preparing high-silicon steel sheet-like magnetic powder cores, the method comprising: steps S1-S6. Step S1: Using pure iron and high-purity silicon as raw materials, smelting is carried out, and then high-silicon steel strip is prepared by single-roll rapid quenching. The thickness of the high-silicon steel strip is 30μm-40μm, and the silicon content in the high-silicon steel strip is 4.5%-7.0%, with the balance being Fe. The smelting vacuum degree is 1×10 -3 Pa-6×10 -4 Pa, with a melting temperature of 1580℃-1650℃ and a holding time of 8min-15min, adopts a single-roller rapid quenching process. The extremely high cooling rate inhibits the precipitation of brittle ordered phases (such as B2 and DO3 phases) in high silicon steel, while retaining the toughness of the high-temperature disordered phase. This allows the originally extremely brittle high silicon steel to be made into flake powder through subsequent mechanical crushing rather than violent ball milling, fundamentally avoiding the work hardening of the powder.

[0018] Step S2: The high silicon steel strip is subjected to jaw crushing and airflow crushing in sequence to obtain high silicon steel flake powder. The particle size of the high silicon steel flake powder is 50μm-200μm and the thickness is 5μm-20μm. The particle size of the jaw crusher is 1mm-5mm; The airflow fine crushing process controls the particle size of the high-silicon steel flake powder by adjusting the speed of the classifying wheel to 2000-3000 r / min and the crushing air pressure to 0.35 MPa-0.5 MPa. The thickness-to-diameter ratio of the high-silicon steel flake powder is 1:(5-15). This thickness-to-diameter ratio of the flake powder, obtained through controlled strip crushing, is a necessary prerequisite for achieving high-density molding through hot pressing.

[0019] The combination of jaw crusher and air jet milling replaces the traditional atomization and ball milling process. Jaw crusher initially reduces the size, while air jet milling uses high-speed airflow to detach the thin strip along grain boundaries or defects, rather than plastically deforming it, thus obtaining flake-shaped powder with a high aspect ratio and relatively smooth edges. This morphology is beneficial for forming a dense packing during pressing and for extending the vortex path.

[0020] Step S3: The high silicon steel flake powder is annealed at a first preset temperature under a first protective atmosphere and then cooled in the furnace. The first protective atmosphere is a nitrogen atmosphere. The first preset temperature is 800℃-900℃, and the annealing time is 2h-3h. This eliminates internal stress and lattice distortion introduced by breakage, repairs lattice defects caused during breakage, reduces the coercivity of the powder, and increases the initial magnetic permeability. Simultaneously, an appropriate annealing temperature allows for slight oxidation of the powder surface, forming a thin natural oxide film that aids in insulation.

[0021] Step S4: The annealed high-silicon steel sheet powder is coated with an insulating modifier to obtain coated magnetic powder. The amount of the insulating modifier added is 1.5%-3% of the mass of the high silicon steel flake powder, and the coating thickness of the magnetic powder is 0.5μm-2μm.

[0022] The insulating modifier comprises a nano-SiO2 dispersion and a phosphate coupling agent. The nano-SiO2 dispersion forms a high-temperature resistant, high-hardness inorganic framework on the powder surface, providing primary insulation properties and resisting high pressure during hot pressing. One end of the phosphate coupling agent molecule hydrolyzes and binds to SiO2, while the other end's organic functional groups react with the metal surface, acting as a "molecular bridge," greatly enhancing the adhesion between the insulating layer and the metal substrate and preventing coating peeling under high pressure. This solves the problems of brittleness in single phosphate layers and poor temperature resistance in single resin layers.

[0023] The mass ratio of nano-SiO2 dispersion to phosphate coupling agent is (3-5):1, the particle size of nano-SiO2 is not greater than 50nm, the content of nano-SiO2 in nano-SiO2 dispersion is 20wt%-40wt%, the pH is 3.8-4.2, and the phosphate coupling agent includes KH570 and phosphate ester auxiliary agent, with a mass ratio of KH570 to phosphate ester auxiliary agent of (2-4):1.

[0024] The surface coating method includes: Mix at 300 rpm - 500 rpm for 30 min - 60 min; Dry at 80℃-90℃ for 2-3 hours; Curing temperature: 120℃-150℃ for 1-2 hours.

[0025] Step S5: The coated magnetic powder is hot-pressed at a second preset temperature and preset pressure to obtain a magnetic core blank; The second preset temperature is 110℃-130℃, the preset pressure is 500MPa-700MPa, and the pressing time is 15s-60s. Hot pressing is the core difference between this method and traditional cold pressing. Preheating (at the second preset temperature) gives the powder particles a certain degree of plasticity. Under high pressure, not only can particle rearrangement occur, but micro-plastic deformation can also occur, filling the pores, thereby increasing the core density and directly improving the magnetic permeability.

[0026] Furthermore, hot pressing will force the powder to adopt a high-adhesion insulation structure to prevent insulation failure under high pressure; the insulation layer also buffers stress during hot pressing, protecting the sheet-like high-silicon steel from being crushed and preserving the advantages of the sheet structure.

[0027] Step S6: The magnetic core blank is subjected to stress-relief annealing at a third preset temperature under a second protective atmosphere and then cooled in the furnace to obtain a high-silicon steel sheet-shaped magnetic powder core.

[0028] The second protective atmosphere is a vacuum atmosphere or a nitrogen atmosphere, the third preset temperature is 600℃-800℃, the stress annealing holding time is 30min-120min, and the heating rate is 3℃ / min-10℃ / min. This eliminates residual stress generated during hot pressing, further stabilizes the magnetic domain structure, releases energy stored due to plastic deformation, and thus further reduces hysteresis loss and coercivity.

[0029] Furthermore, during the stress annealing process, the organic insulation is pyrolyzed and transformed into carbonaceous auxiliary insulation, while the inner layer of SiO2 inorganic insulation remains stable and serves as the main insulation layer. This not only achieves stress release and loss reduction in the powder, but also ensures that the particle insulation does not fail throughout the process.

[0030] The present invention is further illustrated below with specific embodiments: Example 1 Embodiment 1 of the present invention provides a method for preparing high-silicon steel sheet-like magnetic powder cores, wherein the recycling method includes: steps S1-S6. Step S1: Take 6.5% high-purity Si and 93.5% pure Fe by mass percentage, vacuum melt them, and then perform single-roll rapid quenching. The melting vacuum degree is 0.2 × 10⁻⁶. -3 Pa, with a melting temperature of 1620℃ and a holding time of 10 min, a high silicon steel strip with a thickness of 35μm and a width of 80mm was obtained. Step S2: The high silicon steel strip is crushed to 2mm-4mm by a jaw crusher, and then further crushed by an air jet crusher (grading wheel at 2500r / min). The crushing air pressure is adjusted to 0.4MPa to obtain high silicon steel flake powder with a particle size of 80μm-150μm and a thickness of about 10μm. Step S3: Anneal the high silicon steel sheet powder at 850°C for 2.5 hours under a nitrogen atmosphere, then cool it. The cooling rate from 850°C to 670°C is 8°C / min, the cooling rate from 670°C to 400°C is 3°C / min, and the cooling rate from 400°C to room temperature is 5°C / min. Step S4: Take 1000g of annealed high-silicon steel sheet powder and add it to a high-speed mixer. Preheat to 70℃, spray in 2wt% (relative to the mass of high-silicon steel sheet powder) of nano-SiO2 dispersion (particle size 20nm, 30wt%) and 0.5wt% of phosphate ester additive, mix at 400r / min for 45min, dry at 80℃ for 3h, and cure at 140℃ for 1.5h. The mass ratio of KH570 to phosphate ester additive is 3:1.

[0031] Step S5: Place the preform into a hot press mold, preheat the hot press mold to 120°C, apply a pressure of 600MPa, hold the pressure for 30s, and obtain the magnetic core blank. Step S6: The magnetic core blank is subjected to stress-relief annealing at 700°C for 2 hours under nitrogen atmosphere at a heating rate of 5°C / min. After cooling, the cooling rate is 5°C / min from 700°C to 670°C, 3°C / min from 670°C to 400°C, and 5°C / min from 400°C to room temperature to obtain a ring-shaped high-silicon steel sheet magnetic powder core with an outer diameter of 33 mm, an inner diameter of 19.7 mm, and a height of 10.67 mm.

[0032] Example 2 The difference between Embodiment 2 and Embodiment 1 of the present invention is as follows: Step S5: Preheat the hot pressing mold to 120°C, apply a pressure of 500MPa, hold the pressure for 15s, and obtain the magnetic core blank. Other steps and conditions remain unchanged.

[0033] Example 3 The difference between Embodiment 3 and Embodiment 1 of the present invention is as follows: Step S4: Take 1000g of annealed high silicon steel sheet powder and add it to a high-speed mixer. Preheat the mixer to 70°C and spray in 1wt% nano-SiO2 dispersion and 0.25wt% KH570 insulation modifier. Other steps and conditions remain unchanged.

[0034] Example 4 The difference between Embodiment 4 and Embodiment 1 of the present invention is as follows: In step S2, the high-silicon steel strip is crushed to 2mm-4mm by a jaw crusher, and then further crushed by an air jet crusher (grading wheel at 3000r / min) to obtain high-silicon steel flake powder with a particle size of 50μm-100μm, a thickness of about 10μm, and a thickness-to-diameter ratio of about 1:5. Other steps and conditions remain unchanged.

[0035] Example 5 The difference between Embodiment 5 and Embodiment 1 of the present invention is as follows:

[0036] Step S3: Anneal the high silicon steel sheet powder at 800°C for 2.5 hours under a nitrogen atmosphere, while keeping other steps and conditions unchanged.

[0037] Example 6 The difference between Embodiment 6 and Embodiment 1 of the present invention is as follows: Step S6: The magnetic core blank is subjected to stress-relief annealing at 600°C for 2 hours under a nitrogen atmosphere with a heating rate of 5°C / min. Other steps and conditions remain unchanged.

[0038] Example 7 The difference between Embodiment 7 and Embodiment 1 of the present invention is as follows: Step S1: Take 6.0% high-purity Si and 94.0% pure Fe by mass percentage, while keeping other steps and conditions unchanged.

[0039] Comparative Example 1 The difference between Comparative Example 1 and Example 1 of the present invention is as follows: In step S6, hot pressing is changed to cold pressing, and 600MPa pressure is applied at room temperature for molding, while other steps and conditions remain unchanged.

[0040] Comparative Example 2 The difference between Comparative Example 2 and Example 1 of the present invention is as follows: In step S2, the powder is atomized into spherical powder and then ball-milled for 10 hours to produce high-silicon steel flake powder. Other steps and conditions remain unchanged. Specifically, high-purity nitrogen gas was used as the atomizing medium, the atomization pressure was 3.2 MPa, the nozzle orifice diameter was 3.0 mm, and near-spherical high-silicon steel powder with a particle size of 25 μm-35 μm was collected. The spherical powder had no flaky structure. High-silicon steel flaky powder was prepared by planetary high-energy ball milling for 10 h.

[0041] Comparative Example 3 The difference between Comparative Example 3 and Example 1 of the present invention is as follows: In step S4, only 2wt% epoxy resin is used for coating, while other steps and conditions remain unchanged.

[0042] Comparative Example 4 The difference between Comparative Example 4 and Example 1 of this invention is as follows: In step S4, the coating method is changed to phosphoric acid passivation. 100g of annealed high silicon steel sheet powder is immersed in 85% ethanolic phosphoric acid solution and stirred for 30min. The high silicon steel sheet powder accounts for 1wt% of the mass of the ethanolic phosphoric acid solution. After filtration, it is dried at 120℃ for 1h. Other steps and conditions remain unchanged.

[0043] Comparative Example 5 The difference between Comparative Example 5 and Example 1 of this invention is that: In step S1, the silicon content is 4.2%, and the other steps and conditions remain unchanged.

[0044] Comparative Example 6 The difference between Comparative Example 6 and Example 1 of the present invention is as follows: In step S1, the silicon content is 7.2%, and the other steps and conditions remain unchanged.

[0045] Comparative Example 7 The difference between Comparative Example 7 and Example 1 of this invention is that: Step S3 is omitted, while other steps and conditions remain unchanged.

[0046] Comparative Example 8 The difference between Comparative Example 8 and Example 1 of the present invention is as follows: In step S3, the first preset temperature is 750℃, and other steps and conditions remain unchanged.

[0047] Comparative Example 9 The difference between Comparative Example 9 and Example 1 of this invention is as follows: In step S3, the first preset temperature is 950℃, and the other steps and conditions remain unchanged.

[0048] Comparative Example 10 The difference between Comparative Example 10 and Example 1 of the present invention is that: In step S6, the third preset temperature is 400℃, while other steps and conditions remain unchanged.

[0049] Comparative Example 11 The difference between Comparative Example 11 and Example 1 of the present invention is that: In step S4, only 2wt% (relative to the mass of high silicon steel sheet powder) of nano-SiO2 dispersion is sprayed in, without adding phosphate coupling agent, and other steps and conditions remain unchanged.

[0050] Comparative Example 12 The difference between Comparative Example 12 and Example 1 of the present invention is that: In step S4, only 0.5 wt% of phosphate ester coupling agent is sprayed in, without adding nano-SiO2 sol, while other steps and conditions remain unchanged.

[0051] Comparative Example 13 The difference between Comparative Example 13 and Example 1 of the present invention is as follows: Step S4: Spray in 1 wt% nano-SiO2 dispersion and 0.5 wt% phosphate ester coupling agent, while keeping other steps and conditions unchanged.

[0052] Comparative Example 14 The difference between Comparative Example 14 and Example 1 of the present invention is as follows: Step S4: Spray in 2wt% nano-SiO2 dispersion and 0.1wt% phosphate ester coupling agent, while keeping other steps and conditions unchanged.

[0053] Comparative Example 15 The difference between Comparative Example 15 and Example 1 of the present invention is that: Step S2 involves only jaw crushing, without fine crushing by air jet crusher, while other steps and conditions remain unchanged.

[0054] Comparative Example 16 The difference between Comparative Example 16 and Example 1 of the present invention is as follows: Step S2: Crushing by jaw crusher is cancelled, and only fine crushing by air jet crusher is performed. Other steps and conditions remain unchanged.

[0055] Please refer to Table 1 below, which shows the parameters corresponding to the above embodiments and comparative examples of the present invention. Specifically, the effective permeability (100kHz) was measured by winding a high-silicon steel sheet magnetic powder core with 25 turns of coil and measuring it with an LCR meter; the total power consumption (100kHz / 100mT) was measured by winding an excitation coil with 35 turns and an induction coil with 15 turns on a high-silicon steel sheet magnetic powder core, measuring the unit volume loss by measuring the active power input to the magnetic ring using the Bm test setting of the Yanqi SY8219 device; the resistivity was calculated by passing current through a regular block sample using the four-probe method and measuring the voltage; the coercivity was measured by applying Hs=8000A / m to the magnetic ring (turns ratio 100:3) using a Lianzhong DC hysteresis loop meter to obtain the static hysteresis loop; and the DC bias permeability retention rate was measured (@100Oe) by first measuring the initial inductance at 100kHz, then measuring the inductance after superimposing a 100Oe DC bias, and finally calculating the result.

[0056] Table 1:

[0057] As shown in Table 1, the degree of flake-like structure (aspect ratio) of the powder is a core factor affecting the performance of magnetic powder cores. Simply coarsely crushing without airflow fine crushing, or only finely crushing without initial coarse crushing, cannot yield the desired flake-like structure. High aspect ratio flake-like powder can effectively reduce the demagnetizing field and eddy current losses, thereby achieving higher permeability and lower power consumption.

[0058] Furthermore, the method of insulating coating of the powder is crucial. Composite coating, which combines nano-silica sol with phosphate ester coupling agent, is significantly more effective than single coating (such as using only epoxy resin, only phosphate ester, or only phosphoric acid passivation). Composite coating can better improve resistivity and suppress eddy current losses, and there is an optimal range for the ratio of coating agents. Deviating from this range will lead to a decrease in resistivity or an increase in power consumption.

[0059] Secondly, heat treatment processes (including annealing and stress-relief annealing) are indispensable. Omitting annealing will significantly reduce magnetic permeability and drastically increase power consumption and coercivity, indicating that annealing plays a decisive role in eliminating internal stress and restoring magnetic properties. There is an optimal range for annealing temperature; too low a temperature will not be effective, while too high a temperature may cause grain coarsening, thus degrading magnetic properties. Combined with staged slow cooling, it is particularly beneficial for reducing internal stress. Similarly, the stress-relief annealing temperature also needs to be moderate; too low a temperature will result in incomplete stress elimination, while too high or too low a temperature is detrimental to performance balance. At the same time, the forming method has a significant impact: hot pressing is significantly better than cold pressing, and appropriately increasing the hot pressing pressure helps to improve the density and magnetic properties of the billet.

[0060] Finally, silicon content has a significant impact on the intrinsic properties of materials. A silicon content deviating from 6.5% will lead to a performance imbalance: if the content is too low, the resistivity decreases and the eddy current loss increases dramatically; if the content is too high, the magnetic permeability decreases. Therefore, a silicon content of 6.5% is the optimal composition for achieving a balance between high resistivity and good magnetic permeability.

[0061] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0062] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this patent should be determined by the appended claims.

Claims

1. A method for preparing a high-silicon steel sheet-like magnetic powder core, characterized in that, The method includes: High-silicon steel strips are prepared by smelting pure iron and high-purity silicon as raw materials and then by single-roll rapid quenching. The thickness of the high-silicon steel strips is 30μm-40μm, and the silicon content in the high-silicon steel strips is 4.5%-7.0%, with the balance being Fe. The high-silicon steel strip is subjected to jaw crushing and airflow crushing in sequence to obtain high-silicon steel flake powder. The particle size of the high-silicon steel flake powder is 50μm-200μm and the thickness is 5μm-20μm. The high-silicon steel flake powder is annealed at a first preset temperature under a first protective atmosphere and then cooled in the furnace. Surface coating of annealed high-silicon steel flake powder with an insulating modifier is used to obtain coated magnetic powder. The coated magnetic powder is hot-pressed at a second preset temperature and preset pressure to obtain a magnetic core blank. The magnetic core blank is subjected to stress-relief annealing at a third preset temperature under a second protective atmosphere and then cooled in the furnace to obtain a high-silicon steel sheet-shaped magnetic powder core.

2. The method for preparing high-silicon steel sheet-like magnetic powder cores according to claim 1, characterized in that, The first preset temperature is 800℃-900℃, and the annealing time is 2h-3h.

3. The method for preparing high-silicon steel sheet-like magnetic powder core according to claim 1, characterized in that, The amount of the insulating modifier added is 1.5%-3% of the mass of the high silicon steel flake powder, and the coating thickness of the magnetic powder is 0.5μm-2μm.

4. The method for preparing high-silicon steel sheet-like magnetic powder core according to claim 3, characterized in that, The insulating modifier comprises a nano-SiO2 dispersion and a phosphate coupling agent, wherein the mass ratio of the nano-SiO2 dispersion to the phosphate coupling agent is (3-5):1, the particle size of the nano-SiO2 is not greater than 50nm, the content of nano-SiO2 in the nano-SiO2 dispersion is 20wt%-40wt%, and the pH is 3.8-4.

2. The phosphate coupling agent comprises KH570 and a phosphate ester auxiliary agent, wherein the mass ratio of KH570 to the phosphate ester auxiliary agent is (2-4):

1.

5. The method for preparing high-silicon steel sheet-like magnetic powder core according to claim 4, characterized in that, The surface coating method includes: Mix at 300 rpm - 500 rpm for 30 min - 60 min; Dry at 80℃-90℃ for 2-3 hours; Curing temperature: 120℃-150℃ for 1-2 hours.

6. The method for preparing high-silicon steel sheet-like magnetic powder core according to claim 1, characterized in that, The particle size of the jaw crusher is 1mm-5mm; The particle size of the high-silicon steel flake powder is controlled by adjusting the speed of the classifying wheel to 2000 r / min-3000 r / min and the pulverizing air pressure to 0.35 MPa-0.5 MPa. The thickness-to-diameter ratio of the high-silicon steel flake powder is 1:(5-15).

7. The method for preparing high-silicon steel sheet-like magnetic powder core according to claim 1, characterized in that, The second preset temperature is 110℃-130℃, the preset pressure is 500MPa-700MPa, and the pressing time is 15s-60s.

8. The method for preparing high-silicon steel sheet-like magnetic powder core according to claim 1, characterized in that, The first protective atmosphere is a nitrogen atmosphere, and the second protective atmosphere is a vacuum atmosphere or a nitrogen atmosphere.

9. The method for preparing high-silicon steel sheet-like magnetic powder core according to claim 1, characterized in that, The third preset temperature is 600℃-800℃, the stress annealing holding time is 30min-120min, and the heating rate is 3℃ / min-10℃ / min.

10. A high-silicon steel sheet-like magnetic powder core, characterized in that, The high-silicon steel sheet magnetic powder core is prepared by the method described in any one of claims 1-9.

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