Iron-silicon soft magnetic powder core with magnetic conductivity mu of 90 and preparation method of iron-silicon soft magnetic powder core

Abstract

The invention belongs to the technical field of soft magnetic materials, and particularly relates to an iron-silicon soft magnetic powder core with magnetic conductivity mu of 90 and a preparation method of the iron-silicon soft magnetic powder core. The preparation method specifically comprises the following steps of iron-silicon powder particle size proportioning, insulation coating, compression molding, magnetic core heat treatment, infiltration spraying and contact surface polishing; wherein in the step of gas atomization, the particle size of the raw material of the iron-silicon powder is-200 meshes, the particle size ratio of the iron-silicon powder is as follows:-200 to + 325 meshes accounts for 28.6%,-325 to + 400 meshes accounts for 12.5%,-400 meshes accounts for 58.9%, and the powder is uniformly mixed according to the ratio. The iron-silicon EQ2619 soft magnetic powder core prepared through the method is low in loss, good in direct current bias performance, high in quality factor, simple in insulation process, high in production efficiency, capable of being used for mass production of EQ2619 iron-silicon products and suitable for application and popularization.

Description

Technical Field

[0001] The present invention belongs to the technical field of soft magnetic materials, and particularly relates to an iron-silicon soft magnetic powder core with a magnetic permeability μ of 90 and a preparation method thereof. Background Art

[0002] Iron-silicon soft magnetic powder cores have the characteristics of low loss and high saturation, which can improve the power conversion efficiency and stability. Iron-silicon soft magnetic powder cores can be designed according to different structures and shapes, and can also be directly installed in circuit boards, thus achieving smaller sizes and higher integration. Therefore, iron-silicon-aluminum soft magnetic powder cores are widely used in fields such as 5G communication base stations, power conversion, signal processing, electromagnetic interference, and pattern recognition, involving fields such as communication, home appliances, UPS power supplies, inverters, and new energy vehicles. Due to the high DC bias performance and high saturation magnetic induction intensity of iron-silicon-aluminum soft magnetic powder cores, there is a large market.

[0003] The appearance of iron-silicon soft magnetic powder cores is increasingly tending to the shape of ferrite. Most of the existing soft magnetic powder cores are in the form of toroidal cores. Usually, the wire winding needs to pass through the inner hole of the core, making the winding of copper wires on the soft magnetic powder core difficult. It is impossible to wind the core with the help of simple mechanical equipment, and the copper wire winding process is complex. While iron-silicon cores are just suitable for customizing coils, with small core volume, convenient winding, high inductance per unit space, and balanced magnetic shielding and heat dissipation effects. For example, the invention patent with the patent number CN102314983A discloses a manufacturing method of an iron-silicon 90u toroidal soft magnetic powder core. This process uses phosphoric acid passivation and then adds phenolic resin, and then presses and forms; the addition of phenolic resin not only cannot well eliminate the internal stress of the core, but also is prone to decomposition and carbonization during the sintering process, resulting in pinholes and cracks in the core; since most of the single pressing of toroidal cores requires 18 - 22T / cm 2 , while the single pressing of iron-silicon cores is 9 - 12T / cm 2 , and the pressure is only half of that of toroidal cores. The smaller the pressure, the lower the magnetic permeability μ value of the core. Therefore, it is very difficult to obtain a high-μ EQ soft magnetic core under low-pressure conditions;

[0004] In addition, the invention patent with the patent number CN106252013A discloses a preparation method of iron-nickel soft magnetic powder cores. This process uses hydrogen to anneal and reduce iron-nickel powder, and uses aluminum dihydrogen phosphate for primary coating and sodium silicate and kaolin for secondary insulation coating. The powder needs to be annealed and then subjected to secondary insulation, with many insulation operation steps and low production efficiency; and although the insulation coating with aluminum dihydrogen phosphate can improve the uniformity of the surface coating of the powder and can reduce the loss of the core to a certain extent, the heat treatment temperature of the core is affected by the temperature resistance of aluminum dihydrogen phosphate and cannot be heat-treated under high-temperature conditions.

[0005] Therefore, it is an urgent problem for those skilled in the art to provide an iron-silicon soft magnetic powder core with high permeability and high DC bias performance and its preparation method. Summary of the Invention

[0006] To solve the above technical problems, the present invention provides an iron-silicon soft magnetic powder core with a permeability μ of 90 and its preparation method. The iron-silicon soft magnetic powder core prepared by this method has low loss and good DC bias performance.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] An iron-silicon soft magnetic powder core with a permeability μ of 90, which is composed of iron-silicon magnetic powder and a coating layer on the surface of the iron-silicon magnetic powder, which are phosphate and silicon oxide in sequence.

[0009] Preferably, the particle size ratio of the iron-silicon magnetic powder is that -200 to +325 mesh accounts for 28.6%, -325 to +400 mesh accounts for 12.5%, and -400 mesh accounts for 58.9%.

[0010] Preferably, the iron-silicon magnetic powder used is gas-atomized iron-silicon powder, and the silicon content in the iron-silicon powder is 5-6.5%, and the balance is iron.

[0011] Preferably, the phosphate is prepared from phosphoric acid and absolute ethanol;

[0012] Among them, the dosage of the phosphoric acid is 0.5-1% of the weight of the iron-silicon powder, and the dosage of the absolute ethanol is 6-8% of the weight of the iron-silicon powder.

[0013] Preferably, the silicon oxide is prepared from epoxy resin, methyl silicone resin, methylal and absolute ethanol;

[0014] Among them, the dosage of the epoxy resin is 0.3-0.6% of the weight of the iron-silicon powder, the dosage of the methyl silicone resin is 0.4-0.6% of the weight of the iron-silicon powder, the dosage of the methylal is 6-8% of the weight of the iron-silicon powder, and the dosage of the absolute ethanol is 6-8% of the weight of the iron-silicon powder.

[0015] The preparation method of an iron-silicon soft magnetic powder core with a permeability μ of 90 as described above specifically includes the following steps:

[0016] (1) Insulating coating: Add phosphoric acid and absolute ethanol to the uniformly mixed gas-atomized iron-silicon powder and heat and stir-fry until dry to complete the first insulating coating; then, after the iron-silicon powder after the first insulating coating is cooled, add epoxy resin powder and absolute ethanol and mix evenly by dry mixing, and then add methyl silicone resin and methylal and stir-fry until the iron-silicon powder is dry to complete the second insulating coating, and set aside;

[0017] (2) Compression molding: Add a mold release agent to the iron-silicon powder after the secondary insulation coating is completed in step (1), and perform compression molding to obtain a magnetic core for standby;

[0018] (3) Heat treatment of the magnetic core: Bake, sinter, infiltrate and spray, and polish the magnetic core obtained in step (2), and then obtain an iron-silicon soft magnetic powder core with a magnetic permeability μ of 90.

[0019] Preferably, the heating temperature in step (1) is 100-130 °C.

[0020] Preferably, the mold release agent in step (2) is zinc stearate or K crystal wax, and the dosage of the mold release agent is 0.2-0.4% of the weight of the iron-silicon powder;

[0021] The pressure of the compression molding is 9-12 t / cm 2 .

[0022] In the present invention, the secondary insulation coating mainly solves the powder pressing characteristics, preventing the powder from being unable to be pressed due to poor strength; adding two different resins can not only ensure the strength of the compression molding, but also ensure the strength after annealing, and the powder after the secondary resin insulation coating is more viscous and convenient for compression molding.

[0023] Preferably, the baking temperature in step (3) is 220 °C and the baking time is 4 h;

[0024] The sintering is carried out in a nitrogen atmosphere, the flow rate of the nitrogen is 6-8 m 3 / h, the sintering temperature is 700-800 °C, and the time is 30-120 min.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] (1) The insulation coating process disclosed in the present invention is simple, low in cost, high in production efficiency, and can be mass-produced; at the same time, it has a high magnetic permeability u value, good DC bias performance, and low power loss, and the product performance is at the leading level in the industry;

[0027] (2) The present invention uses iron-silicon powder for particle size matching, among which -200 to +325 mesh accounts for 28.6%, -325 to +400 mesh accounts for 12.5%, and -400 mesh accounts for 58.9%. The powder pressed according to the above particle size combination has good pressing characteristics, high magnetic core strength, can effectively improve the magnetic permeability, and at the same time reduce the porosity of the magnetic core, and can effectively reduce the magnetic core loss;

[0028] (3) By using phosphoric acid, absolute ethanol, epoxy resin, and methyl silicone resin for insulation coating, a phosphate salt and silicon oxide coating layer is obtained on the surface of the FeSiAl metal powder, which has advantages such as high thermal stability and electrical insulation. Finally, the prepared FeSi soft magnetic powder core has low loss and high DC superposition. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on the provided drawings.

[0030] Figure 1 It is a product diagram of Example 4 of the present invention;

[0031] Figure 2 It is a product diagram of Comparative Example 1 of the present invention;

[0032] Figure 3 It is a product diagram of Comparative Example 2 of the present invention;

[0033] Figure 4 It is a particle size ratio relationship diagram of the embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0034] The following will clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0035] Example 1

[0036] A preparation method of an FeSi soft magnetic powder core with a magnetic permeability μ of 90 includes the following specific steps:

[0037] (1) Take gas-atomized FeSi powder, where the silicon content is 5.5%, and the rest is iron. The particle size ratio of the FeSi powder is 28.6% for -200 to +325 mesh, 12.5% for -325 to +400 mesh, and 58.9% for -400 mesh. Mix the powder evenly according to the above ratio;

[0038] (2) Pour the iron-silicon powder into a rotary heating device, then add a mixed liquid of phosphoric acid and absolute ethanol, and heat and stir-fry until dry to complete one-time insulation coating; among them, the addition amount of phosphoric acid is 0.5% of the weight of the iron-silicon powder, the addition amount of absolute ethanol is 7% of the weight of the iron-silicon powder, start the heating function after the powder reacts for half an hour, and control the temperature at 120 °C; after the powder cools, add 0.4% epoxy resin based on the weight of the iron-silicon powder and 7% alcohol based on the weight of the iron-silicon powder for dry mixing, and then add 0.5% methyl silicone resin and 8% methylal liquid based on the weight of the iron-silicon powder for dry mixing to complete the secondary insulation coating. The powder is dry-mixed without heating until the powder is dry;

[0039] (3) Add a mold release agent to the iron-silicon powder after completing the secondary insulation coating in step (2). Among them, the addition amount of zinc stearate as the mold release agent is 0.3% of the weight of the iron-silicon powder, and the addition amount of methyl silicone resin is 0.3% of the weight of the iron-silicon powder. After mixing evenly, press it into an EQ2619 magnetic core, and the forming pressure is respectively 9, 10, 11, 12 t / cm 2 , and press it with four different pressures;

[0040] (4) Put the formed magnetic core into a baking furnace and set the temperature at 220 °C for baking for 4 h to complete the degumming action. After baking, put the EQ2619 magnetic core into a heat treatment furnace, introduce nitrogen, keep it at 780 °C for 50 min, and then cool it naturally. Among them, the nitrogen flow rate is set at 8 m 3 / h;

[0041] (5) After the EQ2619 magnetic core is annealed, infiltrate, spray, and polish the contact surface. After polishing smoothly, obtain an iron-silicon EQ2619 soft magnetic powder core with a magnetic permeability μ = 90. And after testing, the magnetic properties of the obtained iron-silicon EQ2619 soft magnetic powder core are shown in Table 1, and the density of the EQ2619 magnetic core is shown in Table 2;

[0042] Table 1 Performance of EQ2619 iron-silicon soft magnetic powder core under different pressure conditions

[0043]

[0044]

[0045] As can be seen from the table, for the same formula and the same heat treatment temperature, when the forming pressure is larger, the magnetic permeability μ of the magnetic core will increase, the density of the magnetic core will increase, and the core loss will be better; and due to the increase in the magnetic permeability μ, the DC superposition will become lower.

[0046] Table 2 Density of EQ2619 iron-silicon soft magnetic powder core under different pressure conditions

[0047]

[0048] As can be seen from Table 2, the higher the pressing pressure, the higher the density of the magnetic core. When pressed at 9 T / cm 2 , the density of the magnetic core is 6.839 g / cm 3 , and when pressed at 12 T / cm2, the density of the magnetic core is 7.095 g / cm 3 .

[0049] Example 2

[0050] A method for preparing an Fe-Si soft magnetic powder core with a magnetic permeability μ of 90 includes the following specific steps:

[0051] (1) Take gas-atomized Fe-Si powder, where the silicon content is 9%, the aluminum content is 6%, and the rest is iron. The particle size ratio of the Fe-Si powder is 28.6% for -200 to +325 mesh, 12.5% for -325 to +400 mesh, and 58.9% for -400 mesh. Mix the powder evenly according to the above ratio;

[0052] (2) Pour the Fe-Si powder into a rotary heating device, then add a mixed liquid of phosphoric acid and absolute ethanol, and heat and stir dry to complete the first insulation coating; among them, the addition amounts of phosphoric acid are 0.7%, 0.8%, 0.9%, and 1.0% of the weight of the Fe-Si powder respectively, the addition amount of absolute ethanol is 7% of the weight of the Fe-Si powder, start the heating function after the powder reacts for half an hour, and control the temperature at 120 °C; after the powder cools, add 0.4% epoxy resin of the weight of the Fe-Si powder and 7% alcohol of the weight of the Fe-Si powder for dry mixing, and then add 0.5% methyl silicone resin and 8% methylal liquid of the weight of the Fe-Si powder for dry mixing to complete the second insulation coating. The powder is dry-mixed without heating until the powder is dry;

[0053] (3) Add a mold release agent to the Fe-Si powder after completing the second insulation coating in step (2). The addition amount of zinc stearate as the mold release agent is 0.3% of the weight of the Fe-Si powder. After mixing evenly, press it into an EQ2619 magnetic core, and the forming pressure is 12 t / cm 2 ;

[0054] (4) Put the formed magnetic core into a baking furnace and set the temperature at 220 °C for baking for 4 h to complete the degumming operation. After baking, put the EQ2619 magnetic core into a heat treatment furnace, introduce nitrogen and keep it at 780 °C for 50 min, and then cool it naturally, where the nitrogen flow rate is set at 8 m 3 / h;

[0055] (5) After the EQ2619 magnetic core is annealed, infiltrate, spray, and polish the contact surface. After polishing smoothly, obtain an Fe-Si EQ2619 soft magnetic powder core with a magnetic permeability μ = 90. After testing, the magnetic properties of the obtained Fe-Si EQ2619 soft magnetic powder core are shown in Table 3;

[0056] Table 3 Performance of EQ2619 FeSiAl soft magnetic powder cores with different phosphoric acid addition amounts

[0057]

[0058] As can be seen from the table, under the same molding pressure and the same heat treatment temperature, when the addition amount of phosphoric acid is larger, the magnetic permeability μ value of the magnetic core will be lower. At the same time, the DC superposition performance of the magnetic core will be higher, and the loss of the magnetic core will be worse.

[0059] Example 3

[0060] A preparation method of an FeSi soft magnetic powder core with a magnetic permeability μ of 90 includes the following specific steps:

[0061] (1) Take gas atomized FeSi powder, where the silicon content is 9%, the aluminum content is 6%, and the rest is iron. The particle size ratio of the FeSi powder is 28.6% for -200 to +325 mesh, 12.5% for -325 to +400 mesh, and 58.9% for -400 mesh. Mix the powder evenly according to the above ratio;

[0062] (2) Pour the FeSi powder into a rotary heating device, and then add a mixed liquid of phosphoric acid and absolute ethanol, and heat and stir dry to complete the first insulation coating; among them, the addition amount of phosphoric acid is 0.6% of the weight of the FeSi powder, and the addition amount of absolute ethanol is 7% of the weight of the FeSi powder. Start the heating function after the powder reacts for half an hour, and control the temperature at 120°C; after the powder cools, add 0.4% epoxy resin of the weight of the FeSi powder and 7% alcohol of the weight of the FeSi powder for dry mixing. After completion, add 0.5% methyl silicone resin and 8% methylal liquid of the weight of the FeSi powder for dry mixing to complete the second insulation coating. The powder is dry mixed without heating until the powder is dry;

[0063] (3) Add a release agent to the FeSi powder after completing the second insulation coating in step (2). The addition amount of zinc stearate as the release agent is 0.3% of the weight of the FeSi powder. After mixing evenly, press it into an EQ2619 magnetic core, and the molding pressure is 11t / cm 2 ;

[0064] (4) Put the formed magnetic core into a baking furnace and set the temperature at 220°C for baking for 4h to complete the degumming action. After baking, put the EQ2619 magnetic core into a heat treatment furnace, introduce nitrogen, and perform annealing and heat preservation at 700°C, 720°C, 740°C, 780°C, and 800°C for 50min, and then cool naturally, where the nitrogen flow rate is set to 8m 3 / h;

[0065] (5) After the annealing of the EQ2619 magnetic core is completed, infiltrate, spray, and polish the contact surface. After polishing it flat, a Fe-Si EQ2619 soft magnetic powder core with a magnetic permeability μ = 90 is obtained. After testing, the magnetic properties of the obtained Fe-Si EQ2619 soft magnetic powder core are shown in Table 4;

[0066] Table 4 Performance of EQ2619 Fe-Si Soft Magnetic Powder Core at Different Sintering Temperatures

[0067]

[0068] As can be seen from Table 4, for the same formula and the same molding pressure, when the heat treatment temperature is 700 °C, the magnetic permeability μ of the magnetic core becomes lower, the superposition becomes better, and at the same time the loss becomes worse. The main reason is that the heat treatment temperature of the magnetic core is too low; while when the heat treatment temperature is 800 °C, the magnetic permeability μ of the magnetic core becomes higher, the loss becomes better, and the DC superposition becomes worse. The main reason is that the inductance is high, so the DC superposition will be lower;

[0069] (6) Repeat steps (1)-(3) of Example 3. Put the molded magnetic core into a baking furnace and set the temperature to 220 °C for baking for 4 h to complete the degumming operation. After baking, put the EQ2619 magnetic core into a heat treatment furnace, introduce nitrogen, and carry out annealing and heat preservation at 740 °C for 30 min, 50 min, and 70 min respectively, and then cool naturally, where the nitrogen flow rate is set to 8 m 3 / h;

[0070] After the annealing of the EQ2619 magnetic core is completed, infiltrate, spray, and polish the contact surface. After polishing it flat, a Fe-Si EQ2619 soft magnetic powder core with a magnetic permeability μ = 90 is obtained. After testing, the magnetic properties of the obtained Fe-Si EQ2619 soft magnetic powder core are shown in Table 5;

[0071] Table 5 Performance of EQ2619 Fe-Si Soft Magnetic Powder Core at the Same Sintering Temperature and Different Heat Preservation Times

[0072]

[0073] As can be seen from Table 5, for the same formula, the same molding pressure, the same heat treatment temperature, and different heat preservation times, the magnetic permeability & DC superposition & loss of the EQ2619 magnetic core have little difference.

[0074] Example 4

[0075] A preparation method of a Fe-Si soft magnetic powder core with a magnetic permeability μ of 90, comprising the following specific steps:

[0076] (1) Take gas-atomized iron-silicon powder, where the silicon content is 9%, the aluminum content is 6%, and the rest is iron. The particle size ratio of the iron-silicon powder is that -200 to +325 mesh accounts for 28.6%, -325 to +400 mesh accounts for 12.5%, and -400 mesh accounts for 58.9%. Mix the powder evenly according to the above ratio;

[0077] (2) Pour the iron-silicon powder into a rotary heating device, then add a mixed liquid of phosphoric acid and absolute ethanol, and heat and stir dry to complete the first insulation coating; among them, the addition amount of phosphoric acid is 0.5% of the weight of the iron-silicon powder, and the addition amount of absolute ethanol is 7% of the weight of the iron-silicon powder. Start the heating function after the powder reacts for half an hour, and control the temperature between 120°C; after the powder cools, add 0.6% epoxy resin of the weight of the iron-silicon powder and 7% absolute ethanol of the weight of the iron-silicon powder for dry mixing. After completion, add 0.6% methyl silicone resin and 8% methylal liquid of the weight of the iron-silicon powder for dry mixing to complete the second insulation coating. The powder dry mixing is not heated until the powder is dry;

[0078] (3) Add a release agent to the iron-silicon powder after completing the second insulation coating in step (2). Among them, the addition amount of zinc stearate as the release agent is 0.3% of the weight of the iron-silicon powder. After mixing evenly, press it into an EQ2619 magnetic core, and the forming pressure is 12t / cm 2 ;

[0079] (4) Put the formed magnetic core into a baking furnace and set the temperature at 220°C for baking for 4h to complete the degumming operation. After baking, put the EQ2619 magnetic core into a heat treatment furnace, introduce nitrogen, anneal at 780°C for 50min, and then cool naturally. Among them, the nitrogen flow rate is set at 8m 3 / h;

[0080] (5) After the EQ2619 magnetic core is annealed, infiltrate, spray, and polish the contact surface. After polishing smoothly, obtain an iron-silicon EQ2619 soft magnetic powder core with a magnetic permeability μ = 90. After testing, the magnetic properties of the obtained iron-silicon EQ2619 soft magnetic powder core are shown in Table 6, and the product drawing is shown in Figure 3 .

[0081] Example 5

[0082] A preparation method of an iron-silicon soft magnetic powder core with a magnetic permeability μ of 90, including the following specific steps:

[0083] (1) Take gas-atomized iron-silicon powder, where the silicon content is 9%, the aluminum content is 6%, and the rest is iron. The particle size ratio of the iron-silicon powder is that -200 to +325 mesh accounts for 28.6%, -325 to +400 mesh accounts for 12.5%, and -400 mesh accounts for 58.9%. Mix the powder evenly according to the above ratio;

[0084] (2) Pour the iron-silicon powder into a rotary heating device, then add a mixed liquid of phosphoric acid and absolute ethanol, and heat and stir-fry until dry to complete one-time insulation coating; among them, the addition amount of phosphoric acid is 0.5% of the weight of the iron-silicon powder, the addition amount of absolute ethanol is 7% of the weight of the iron-silicon powder, start the heating function after the powder reacts for half an hour, and control the temperature at 120 °C; after the powder cools, add 0.3% epoxy resin of the weight of the iron-silicon powder and 7% absolute ethanol of the weight of the iron-silicon powder for dry mixing, and then add 0.4% methyl silicone resin of the weight of the iron-silicon powder and 8% methylal liquid for dry mixing to complete the secondary insulation coating. The powder is dry-mixed without heating until the powder is dry;

[0085] (3) Add a mold release agent to the iron-silicon powder after completing the secondary insulation coating in step (2). Among them, the addition amount of zinc stearate as the mold release agent is 0.3% of the weight of the iron-silicon powder. After mixing evenly, press it into an EQ2619 magnetic core, and the forming pressure is 12 t / cm 2 ;

[0086] (4) Put the formed magnetic core into a baking oven and set the temperature at 220 °C for baking for 4 h to complete the degumming action. After baking, put the EQ2619 magnetic core into a heat treatment furnace, introduce nitrogen, carry out annealing at 780 °C for 50 min, and then cool naturally. Among them, the nitrogen flow rate is set at 8 m 3 / h;

[0087] (5) After the EQ2619 magnetic core is annealed, infiltrate, spray, and polish the contact surface. After polishing smoothly, obtain an iron-silicon EQ2619 soft magnetic powder core with a magnetic permeability μ = 90. After testing, the magnetic properties of the obtained iron-silicon EQ2619 soft magnetic powder core are shown in Table 6.

[0088] Table 6 Performance of EQ2619 iron-silicon-aluminum soft magnetic powder core under different resin addition amounts

[0089]

[0090] As can be seen from the table, under the same forming pressure and heat treatment temperature, when the primary insulation formula is the same, the higher the addition amounts of epoxy resin and methyl silicone resin, the lower the inductance of the EQ2619 magnetic core.

[0091] Comparative Example 1

[0092] A preparation method of an iron-silicon soft magnetic powder core with a magnetic permeability μ of 90 includes the following specific steps:

[0093] (1) Take gas-atomized iron-silicon powder, in which the silicon content is 9%, the aluminum content is 6%, and the rest is iron. The particle size ratio of the iron-silicon powder is 28.6% for -200 to +325 mesh, 12.5% for -325 to +400 mesh, and 58.9% for -400 mesh. Mix the powder evenly according to the above ratio;

[0094] (2) Pour the iron-silicon powder into a rotary heating device, then add a mixed liquid of phosphoric acid and absolute ethanol, and heat and stir-fry until dry to complete one insulation coating. Among them, the addition amount of phosphoric acid is 0.5% of the weight of the iron-silicon powder, the addition amount of absolute ethanol is 7% of the weight of the iron-silicon powder. Start the heating function after the powder reacts for half an hour, and control the temperature at 120 °C. After the powder cools, add 0.6% epoxy resin based on the weight of the iron-silicon powder and 7% absolute ethanol based on the weight of the iron-silicon powder for dry mixing. The powder is dry-mixed without heating until it is dry.

[0095] (3) Add a release agent to the iron-silicon powder after one insulation coating in step (2). Among them, the addition amount of zinc stearate as the release agent is 0.3% of the weight of the iron-silicon powder. After mixing evenly, press it into an EQ2619 magnetic core, and the molding pressure is 12 t / cm 2 ;

[0096] (4) Put the formed magnetic core into a baking furnace and set the temperature at 220 °C for baking for 4 h to complete the degumming operation. After baking, put the EQ2619 magnetic core into a heat treatment furnace, introduce nitrogen, anneal at 780 °C for 50 min, and then cool naturally. Among them, the nitrogen flow rate is set at 8 m 3 / h;

[0097] (5) After the EQ2619 magnetic core is annealed, infiltrate, spray, and polish the contact surface. After polishing smoothly, obtain an iron-silicon EQ2619 soft magnetic powder core with a magnetic permeability μ = 90. See the product drawing in Figure 1 .

[0098] Comparative Example 2

[0099] A preparation method of an iron-silicon soft magnetic powder core with a magnetic permeability μ of 90, including the following specific steps:

[0100] (1) Take gas-atomized iron-silicon powder, in which the silicon content is 9%, the aluminum content is 6%, and the rest is iron. The particle size ratio of the iron-silicon powder is 28.6% for -200 to +325 mesh, 12.5% for -325 to +400 mesh, and 58.9% for -400 mesh. Mix the powder evenly according to the above ratio;

[0101] (2) Pour the iron-silicon powder into a rotary heating device, then add a mixed liquid of phosphoric acid and absolute ethanol, and heat and stir-fry until dry to complete one insulation coating. Among them, the addition amount of phosphoric acid is 0.5% of the weight of the iron-silicon powder, the addition amount of absolute ethanol is 7% of the weight of the iron-silicon powder. Start the heating function after the powder reacts for half an hour, and control the temperature at 120 °C. After the powder cools, add 0.6% methyl silicone resin based on the weight of the iron-silicon powder and 8% methylal based on the weight of the iron-silicon powder for dry mixing. The powder is dry-mixed without heating until it is dry.

[0102] (3) Add a mold release agent to the iron-silicon powder after one-time insulation coating in step (2). The addition amount of zinc stearate as the mold release agent is 0.3% of the weight of the iron-silicon powder. After mixing evenly, press it into an EQ2619 magnetic core, and the forming pressure is 12 t / cm 2 ;

[0103] (4) Put the formed magnetic core into a baking furnace and set the temperature to 220 °C for 4 h to complete the degumming operation. After baking, put the EQ2619 magnetic core into a heat treatment furnace, introduce nitrogen, anneal at 780 °C for 50 min, and then cool naturally. The nitrogen flow rate is set to 8 m 3 / h;

[0104] (5) After the EQ2619 magnetic core is annealed, infiltrate, spray, and polish the contact surface. After polishing smoothly, obtain an iron-silicon EQ2619 soft magnetic powder core with a magnetic permeability μ = 90. See the product drawing in Figure 2 ;

[0105] It can be seen from the pressing pictures that for the EQ2619 magnetic core pressed only with the epoxy resin formula, there is no strength after annealing, and the legs are easily broken ( Figure 1 ), for the EQ2619 magnetic core pressed only with the methyl silicone resin formula, there is peeling inside during the pressing process ( Figure 2 ), and the powder adhesion is not good; the combined use of epoxy resin and methyl silicone resin can not only ensure the powder forming problem during pressing, but also ensure the magnetic core strength problem after annealing.

[0106] Based on the above analysis, it can be known that an iron-silicon-aluminum EQ2619 soft magnetic powder core with a magnetic permeability μ = 90 prepared by the process of the present invention can be mass-produced, and the DC bias performance is more than 50% under the test condition of 100 Oe; the core loss is 150 mW / cm at 50 KHz and 100 mT 3 , and the magnetic core performance is at the top level in the industry.

[0107] In addition, the particle size ratio and magnetic permeability test data are as shown in Table 7 below and Figure 4 It can be seen that for the same insulation formula, the coarser the powder particles, the higher the magnetic permeability μ value. Among them, the magnetic permeability μ = 131.5 of the particle size ratio 4# is the highest, and the magnetic permeability is tested with a magnetic ring with dimensions of 26.92 * 14.73 * 11.18.

[0108] Table 7 Particle size and magnetic permeability, loss test data

[0109]

[0110] Each embodiment is described in a progressive manner. Each embodiment focuses on the differences from other embodiments. The same and similar parts among the embodiments can be referred to each other.

[0111] The foregoing description of the disclosed embodiments enables those skilled in the art to practice or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An iron silicon soft magnetic powder core with a magnetic permeability μ of 90, characterized in that: The invention is composed of iron silicon magnetic powder and a coating layer of phosphate and silicon oxide in sequence on the surface of the iron silicon magnetic powder.

2. The iron silicon soft magnetic powder core with a magnetic permeability μ of 90 according to claim 1, characterized in that: The particle size ratio of the iron silicon magnetic powder is -200 to +325 meshes accounting for 28.6%, -325 to +400 meshes accounting for 12.5%, and -400 meshes accounting for 58.9%.

3. The iron silicon soft magnetic powder core with a magnetic permeability μ of 90 according to claim 1, characterized in that: The iron silicon magnetic powder is atomized iron silicon powder, and the silicon content in the iron silicon powder is 5-6.5%, and the balance is iron.

4. The iron silicon soft magnetic powder core with a magnetic permeability μ of 90 according to claim 1, characterized in that: The phosphate is prepared from phosphoric acid and anhydrous ethanol; Wherein, the amount of phosphoric acid used is 0.5-1% of the weight of the iron silicon powder, and the amount of anhydrous ethanol used is 6-8% of the weight of the iron silicon powder.

5. The iron silicon soft magnetic powder core with a magnetic permeability μ of 90 according to claim 1, characterized in that: The silicon oxide is prepared by epoxy resin, methyl silicone resin, methylal and anhydrous ethanol; Among them, the amount of the epoxy resin is 0.3-0.6% of the weight of the iron silicon powder, the amount of the methyl silicone resin is 0.4-0.6% of the weight of the iron silicon powder, the amount of the methyl acetal is 6-8% of the weight of the iron silicon powder, and the amount of the anhydrous ethanol is 6-8% of the weight of the iron silicon powder.

6. A method for preparing an iron silicon soft magnetic powder core with a magnetic permeability μ of 90 according to any one of claims 1 to 5, characterized in that: The specific steps include: (1) Insulation coating: phosphoric acid and anhydrous ethanol are added to the uniformly mixed atomized iron silicon powder, and the mixture is heated and fried to dry to complete the primary insulation coating; then, after the iron silicon powder having completed the primary insulation coating is cooled, epoxy resin powder and anhydrous ethanol are added and dry-mixed evenly, and then methyl silicone resin and methylal are added and dry-fried until the iron silicon powder is dry, thereby completing the secondary insulation coating and setting aside; (2) Pressing and molding: adding a release agent to the iron silicon powder after the secondary insulation coating in step (1), and pressing and molding to obtain a magnetic core for standby use; (3) Magnetic core heat treatment: The magnetic core obtained in step (2) is baked, sintered, wetted and polished to obtain an iron silicon soft magnetic powder core with a magnetic permeability μ of 90.

7. The method for preparing an iron silicon soft magnetic powder core with a magnetic permeability μ of 90 according to claim 6, characterized in that: The heating temperature in step (1) is 100-130°C.

8. The method for preparing an iron silicon soft magnetic powder core with a magnetic permeability μ of 90 according to claim 6, characterized in that: The release agent in step (2) is zinc stearate or K crystal wax, and the amount of the release agent is 0.2-0.4% of the weight of the iron silicon powder; The compression molding pressure is 9-12 t / cm 2 .

9. The method for preparing an iron silicon soft magnetic powder core with a magnetic permeability μ of 90 according to claim 6, characterized in that: The baking temperature in step (3) is 220° C. and the baking time is 4 h; The sintering is carried out in a nitrogen atmosphere, and the flow rate of the nitrogen is 6-8m 3 / h, the sintering temperature is 700-800°C, and the sintering time is 30-120min.

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