Fe-Si-Al soft magnetic powder core with magnetic conductivity mu of 60 and preparation method of Fe-Si-Al soft magnetic powder core

Abstract

The invention belongs to the technical field of soft magnetic materials, and particularly relates to an iron-silicon-aluminum soft magnetic powder core with magnetic conductivity mu of 60 and a preparation method of the iron-silicon-aluminum soft magnetic powder core. The preparation method specifically comprises the following steps of iron-silicon-aluminum powder particle size proportioning, insulation coating, compression molding, magnetic core heat treatment, infiltration spraying and contact surface polishing; wherein the particle size of the raw material of the aerosolized Fe-Si-Al powder is-200 meshes, the particle size ratio of the aerosolized Fe-Si-Al powder is as follows:-200-+ 325 meshes account for 32.7%,-325-+ 400 meshes account for 11.5%,-400 meshes account for 55.8%, and the powder is uniformly mixed according to the ratio. The Fe-Si-Al EPC22 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 and high in production efficiency, Fe-Si-Al soft magnetic powder core products can be produced on a large scale, and the Fe-Si-Al EPC22 soft magnetic powder core is suitable for being installed in a PCB circuit to be applied and popularized.

Description

Technical Field

[0001] The present invention belongs to the technical field of soft magnetic materials, and particularly relates to an iron-silicon-aluminum soft magnetic powder core with a magnetic permeability μ of 60 and a preparation method thereof. Background Art

[0002] The iron-silicon-aluminum soft magnetic powder core has the characteristics of small size, extremely low loss and high saturation, and can improve the power conversion efficiency and stability. The iron-silicon-aluminum soft magnetic powder core can be designed according to different structures and shapes, and can also be directly installed in a circuit board, so as to achieve smaller size and higher integration. Therefore, the iron-silicon-aluminum soft magnetic powder core is widely used in small integrated circuits, involving fields such as communication, household appliances, UPS power supplies, switching power supplies and new energy vehicles. Due to the high DC bias performance and extremely low loss of the iron-silicon-aluminum soft magnetic powder core, it has great market prospects.

[0003] At present, most of the existing domestic soft magnetic powder cores are mainly toroidal cores. Usually, it is very difficult to wind wires on small-sized cores. The inner diameter size of 0.1 - 2 mm makes the winding difficulty on the soft magnetic powder core very large, and it is impossible to wind the core with an automatic wire winding machine, and the manufacturing process is complex. The iron-silicon-aluminum soft magnetic powder core is just suitable for customizing PCB circuits. The iron-silicon-aluminum soft magnetic powder core has a small volume, is convenient to install, has a high inductance per unit space, and has balanced magnetic shielding and heat dissipation effects. For example, the invention patents with patent numbers CN110853860A and CN110853858A disclose the manufacturing methods of iron-silicon-aluminum-nickel 60μ and 125μ toroidal soft magnetic powder cores. This process uses epoxy resin, acetone, and water for insulation coating, and a binder is added after the coating is completed. The addition of epoxy resin and binder 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 & cracks and other situations in the core. Since most of the single pressing of the toroidal core requires 18 - 22 T / cm 2 , while the single pressing of the iron-silicon-aluminum soft magnetic powder core is 9 - 12 T / cm 2 , and the pressure is only half of that of the toroidal core. The smaller the pressure, the lower the magnetic permeability μ value of the core. Therefore, it is very difficult to make an air-atomized 60μ iron-silicon-aluminum soft magnetic powder core under low-pressure conditions;

[0004] In addition, the invention patent with patent number CN112435822A discloses a preparation method of an efficient iron-silicon-aluminum soft magnetic powder core. This process uses iron-silicon-aluminum alloy interval powders in different mesh number ranges to be filled in a mold by an in-situ composite method and is pressed into a magnetic powder core; the insulation coating uses alumina powder, sodium silicate solution and low-melting glass powder, and silicon resin is added for multiple insulation coatings. The operation steps are numerous, the pressing process is relatively troublesome, and it is also very difficult to operate the above scheme for small-sized cores.

[0005] Therefore, it is an urgent problem for those skilled in the art to provide a soft magnetic iron-silicon-aluminum powder core with a magnetic permeability μ of 60, smaller size, lower loss, and high DC bias performance, as well as a preparation method therefor. Summary of the Invention

[0006] In order to solve the above technical problems, the present invention provides a soft magnetic iron-silicon-aluminum powder core with a magnetic permeability μ of 60 and a preparation method therefor. The soft magnetic iron-silicon-aluminum powder core prepared by this method has a small size, low loss, and good DC bias performance.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A soft magnetic iron-silicon-aluminum powder core with a magnetic permeability μ of 60 is composed of iron-silicon-aluminum magnetic powder and a coating layer on the surface of the iron-silicon-aluminum magnetic powder, which is successively phosphate and silicon oxide.

[0009] Preferably, the particle size ratio of the iron-silicon-aluminum magnetic powder is 32.7% for -200 to +325 mesh, 11.5% for -325 to +400 mesh, and 55.8% for -400 mesh.

[0010] Preferably, the iron-silicon-aluminum magnetic powder used is gas-atomized iron-silicon-aluminum powder, and in the iron-silicon-aluminum powder, the silicon content is 8.5 - 9.5%, the aluminum content is 5.5 - 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 - 0.8% of the weight of the iron-silicon-aluminum powder, and the dosage of the absolute ethanol is 5 - 7% of the weight of the iron-silicon-aluminum powder.

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

[0014] Among them, the dosage of the epoxy resin is 0.8 - 1.2% of the weight of the iron-silicon-aluminum powder, and the dosage of the absolute ethanol is 6 - 8% of the weight of the iron-silicon-aluminum powder.

[0015] The preparation method of the soft magnetic iron-silicon-aluminum powder core with a magnetic permeability μ of 60 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-aluminum powder, heat and stir-fry until dry to complete the first insulating coating; then, after the iron-silicon-aluminum powder completed with the first insulating coating is cooled, add epoxy resin powder and absolute ethanol and mix until the iron-silicon-aluminum powder is dry to complete the second insulating coating, and set aside;

[0017] (2) Compression molding: Add a release agent and a strength enhancer to the iron-silicon-aluminum 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-aluminum soft magnetic powder core with a magnetic permeability μ of 60.

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

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

[0021] The strength enhancer is methyl silicone resin, and the dosage of the strength enhancer is 0.2-0.3% of the weight of the iron-silicon-aluminum powder;

[0022] The pressure of the compression molding is 9-12 t / cm 2 .

[0023] In the present invention, adding epoxy resin can solve the problem of compression molding of gas-atomized iron-silicon-aluminum, and can also be used as an insulation coating agent. Adding methyl silicone resin in the powder is to solve the strength after powder sintering and prevent the magnetic core from cracking due to poor strength after sintering. Adding two different resins can not only ensure the strength of compression molding, but also ensure the strength after annealing, and the powder is more viscous and convenient for compression molding after adding two resins.

[0024] Preferably, the baking temperature in step (3) is 220 °C and the baking time is 4 h;

[0025] 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 40-100 min.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] (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 good DC bias performance and extremely low power loss, and the product performance is at the leading level in the industry;

[0028] (2) The present invention uses iron-silicon-aluminum powder for particle size matching, in which -200 to +325 mesh accounts for 32.7%, -325 to +400 mesh accounts for 11.5%, and -400 mesh accounts for 55.8%. The powder with the above particle size combination has good pressing characteristics and high magnetic core strength, and can effectively reduce the magnetic core loss;

[0029] (3) The present invention uses phosphoric acid, alcohol, epoxy resin, and methyl silicone resin for insulation coating, so that the surface of the iron-silicon-aluminum metal powder obtains a phosphate salt and silicon oxide coating layer, which has advantages such as high thermal stability and electrical insulation, and can be directly installed in the PCB circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] 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 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 according to the provided drawings.

[0031] Figure 1 It is the characteristic curve diagram of the DC bias of the EPC22 magnetic core in the embodiment of the present invention;

[0032] Figure 2 It is the characteristic curve diagram of the Coreloss of the EPC22 magnetic core in the embodiment of the present invention;

[0033] Figure 3 It is the particle size ratio relationship diagram in the embodiment of the present invention;

[0034] Figure 4 It is the EPC22 magnetic core diagram in the embodiment of the present invention;

[0035] Figure 5 It is the diagram of the EPC22 magnetic core installed in the PCB circuit in the embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0036] 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.

[0037] Embodiment 1

[0038] A preparation method of an iron-silicon-aluminum soft magnetic powder core with a magnetic permeability μ of 60 includes the following specific steps:

[0039] (1) Take gas-atomized iron-silicon-aluminum 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-aluminum powder is 32.7% for -200 to +325 mesh, 11.5% for -325 to +400 mesh, and 55.8% for -400 mesh. Mix the powder evenly according to the above ratio;

[0040] (2) Pour the iron-silicon-aluminum 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 0.6% of the weight of the iron-silicon-aluminum powder, the addition amount of absolute ethanol is 5% of the weight of the iron-silicon-aluminum powder, start the heating function after the powder reacts for half an hour, and control the temperature between 100 and 130 °C; after the powder cools, add 1.0% epoxy resin based on the weight of the iron-silicon-aluminum powder and 6% alcohol based on the weight of the iron-silicon-aluminum powder for dry mixing to complete the secondary insulation coating, and dry mix the powder without heating until the powder is dry;

[0041] (3) Add a mold release agent and methyl silicone resin to the iron-silicon-aluminum powder after completing the secondary insulation coating in step (2), where the addition amount of zinc stearate as the mold release agent is 0.3% of the weight of the iron-silicon-aluminum powder, and the addition amount of methyl silicone resin is 0.3% of the weight of the iron-silicon-aluminum powder. After mixing evenly, press it into an EPC22 magnetic core, and the forming pressure is respectively 9, 10, 11, 12 t / cm 2 , and press with four different pressures;

[0042] (4) Put the formed magnetic core into a baking oven and set the temperature to 220 °C for baking for 4 h to complete the degumming action. After baking, put the EPC22 magnetic core into a heat treatment furnace, introduce nitrogen, keep it at 780 °C for 60 min, and then cool it naturally, where the nitrogen flow rate is set to 8 m 3 / h;

[0043] (5) After the EPC22 magnetic core is annealed, infiltrate, spray, and polish the contact surface. After polishing smoothly, obtain an iron-silicon-aluminum EPC22 soft magnetic powder core with a magnetic permeability μ = 60, such as Figure 4 and 5 are the diagrams of the EPC22 installed in the PCB circuit, and after testing, the magnetic properties of the obtained iron-silicon-aluminum EPC22 soft magnetic powder core are shown in Table 1, and the density of the EPC22 magnetic core is shown in Table 2;

[0044] Table 1 Performance of EPC22 iron-silicon-aluminum soft magnetic powder core under different pressure conditions

[0045]

[0046]

[0047] 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 magnetic core loss will improve; and due to the increase in the magnetic permeability μ, the DC superposition becomes lower.

[0048] Table 2 Density of EPC22 iron-silicon-aluminum soft magnetic powder core under different pressure conditions

[0049]

[0050] As can be seen from Table 2, at the same heat treatment temperature and different unit pressures, the greater the pressure, the higher the core density. Among them, the core density is 5.727 g / cm 2 when the pressure is 12 t / cm 3 is the highest, and the pressure is 9 t / cm 2 which is the smallest, and its density is 5.595 g / cm 3 is the smallest.

[0051] Example 2

[0052] A method for preparing an Fe-Si-Al soft magnetic powder core with a magnetic permeability μ of 60 includes the following specific steps:

[0053] (1) Take gas atomized Fe-Si-Al 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-Al powder is 32.7% for -200 to +325 mesh, 11.5% for -325 to +400 mesh, and 55.8% for -400 mesh. Mix the powder evenly according to the above ratio;

[0054] (2) Pour the Fe-Si-Al 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 0.5%, 0.6%, 0.7%, and 0.8% of the weight of the Fe-Si-Al powder respectively, and the addition amount of absolute ethanol is 5% of the weight of the Fe-Si-Al powder. Start the heating function after the powder reacts for half an hour, and control the temperature between 100 and 130 °C; after the powder cools, add 0.9% epoxy resin of the weight of the Fe-Si-Al powder and 6% absolute ethanol of the weight of the Fe-Si-Al powder for dry mixing to complete the second insulation coating. The powder dry mixing is not heated until the powder is dry;

[0055] (3) Add a release agent and methyl silicone resin to the Fe-Si-Al 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 Fe-Si-Al powder, and the addition amount of methyl silicone resin is 0.3% of the weight of the Fe-Si-Al powder. After mixing evenly, press it into an EPC22 core, and the molding pressure is 12 t / cm 2 ;

[0056] (4) Put the formed 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 EPC22 core into a heat treatment furnace, introduce nitrogen, keep it at 780 °C for 60 min, and then cool it naturally. Among them, the nitrogen flow rate is set to 8 m 3 / h;

[0057] (5) After annealing the EPC22 magnetic core is completed, the contact surface is infiltrated, sprayed, and polished. After polishing smoothly, a Fe-Si-Al EPC22 soft magnetic powder core with a magnetic permeability μ = 60 is obtained. After testing, the magnetic properties of the obtained Fe-Si-Al EPC22 soft magnetic powder core are shown in Table 3;

[0058] Table 3 Performance of Fe-Si-Al EPC22 soft magnetic powder core under different phosphoric acid addition amounts

[0059]

[0060] 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 become higher, and the loss of the magnetic core will become worse.

[0061] Example 3

[0062] A preparation method of a Fe-Si-Al soft magnetic powder core with a magnetic permeability μ of 60 includes the following specific steps:

[0063] (1) Take gas-atomized Fe-Si-Al 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-Al powder is that -200 to +325 mesh accounts for 32.7%, -325 to +400 mesh accounts for 11.5%, and -400 mesh accounts for 55.8%. Mix the powder evenly according to the above ratio;

[0064] (2) Pour the Fe-Si-Al 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 0.7% of the weight of the Fe-Si-Al powder, and the addition amount of absolute ethanol is 6% of the weight of the Fe-Si-Al powder. Start the heating function after the powder reacts for half an hour, and control the temperature between 100 and 130 °C; after the powder cools, add 1.0% epoxy resin of the weight of the Fe-Si-Al powder and 6% absolute ethanol of the weight of the Fe-Si-Al powder for dry mixing to complete the second insulation coating. The powder is dry mixed without heating until the powder is dry;

[0065] (3) Add a release agent and methyl silicone resin to the Fe-Si-Al 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 Fe-Si-Al powder, and the addition amount of methyl silicone resin is 0.3% of the weight of the Fe-Si-Al powder. After mixing evenly, press it into an EPC22 magnetic core, and the molding pressure is 12 t / cm 2 ;

[0066] (4) Place the formed magnetic core into a baking oven and bake it at a set temperature of 220 °C for 4 h to complete the degumming operation. After baking, put the EPC22 magnetic core into a heat treatment furnace, introduce nitrogen, and keep it at 700 °C, 720 °C, 740 °C, 780 °C, and 800 °C for 60 min respectively, and then cool it naturally. The nitrogen flow rate is set to 8 m 3 / h;

[0067] (5) After the EPC22 magnetic core is annealed, infiltrate, spray, and polish the contact surface. After polishing smoothly, an Fe-Si-Al EPC22 soft magnetic powder core with a magnetic permeability μ = 60 is obtained. After testing, the magnetic properties of the obtained Fe-Si-Al EPC22 soft magnetic powder core are shown in Table 4;

[0068] Table 4 Properties of EPC22 Fe-Si-Al Soft Magnetic Powder Core at Different Sintering Temperatures

[0069]

[0070] As can be seen from the table, for the same formula and the same forming pressure, when the heat treatment temperature is 700 °C, the magnetic permeability μ of the magnetic core becomes lower, the superposition becomes better, and the loss becomes worse. The main reason is that the heat treatment temperature of the magnetic core is too low; 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.

[0071] Example 4

[0072] A preparation method of an Fe-Si-Al soft magnetic powder core with a magnetic permeability μ of 60, comprising the following specific steps:

[0073] (1) Take gas-atomized Fe-Si-Al powder, in which the silicon content is 9%, the aluminum content is 6%, and the rest is iron. The particle size ratio of the Fe-Si-Al powder is 32.7% for -200 to +325 mesh, 11.5% for -325 to +400 mesh, and 55.8% for -400 mesh. Mix the powder evenly according to the above ratio;

[0074] (2) Pour the Fe-Si-Al 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 0.5% of the weight of the Fe-Si-Al powder respectively, and the addition amount of absolute ethanol is 5% of the weight of the Fe-Si-Al powder. Start the heating function after the powder reacts for half an hour, and control the temperature between 100 and 130 °C; after the powder cools, add 1.2% epoxy resin of the weight of the Fe-Si-Al powder and 6% absolute ethanol of the weight of the Fe-Si-Al powder for dry mixing to complete the second insulation coating. The powder dry mixing is not heated until the powder is dry;

[0075] (3) After the secondary insulation coating of the iron-silicon-aluminum powder in step (2), a release agent and methyl silicone resin are added. The addition amount of zinc stearate as the release agent is 0.3% of the weight of the iron-silicon-aluminum powder, and the addition amount of methyl silicone resin is 0.3% of the weight of the iron-silicon-aluminum powder. After mixing evenly, it is pressed into an EPC22 magnetic core, and the molding pressure is 11 t / cm 2 ;

[0076] (4) The formed magnetic core is put into a baking furnace and baked at a set temperature of 220 °C for 4 h to complete the degumming operation. After baking, the EPC22 magnetic core is put into a heat treatment furnace, and nitrogen is introduced and kept at 780 °C for 60 min, and then cooled naturally. The nitrogen flow rate is set to 8 m 3 / h;

[0077] (5) After the annealing of the EPC22 magnetic core is completed, the contact surface is infiltrated, sprayed, and polished. After polishing smoothly, an iron-silicon-aluminum EPC22 soft magnetic powder core with a magnetic permeability μ = 60 is obtained. After testing, the magnetic properties of the obtained iron-silicon-aluminum EPC22 soft magnetic powder core are shown in Table 5.

[0078] Example 5

[0079] A preparation method of an iron-silicon-aluminum soft magnetic powder core with a magnetic permeability μ of 60, comprising the following specific steps:

[0080] (1) Take gas-atomized iron-silicon-aluminum 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-aluminum powder is that -200 to +325 mesh accounts for 32.7%, -325 to +400 mesh accounts for 11.5%, and -400 mesh accounts for 55.8%. The powder is mixed evenly according to the above ratio;

[0081] (2) Pour the iron-silicon-aluminum 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 primary insulation coating; among them, the addition amount of phosphoric acid is 0.5% of the weight of the iron-silicon-aluminum powder, and the addition amount of absolute ethanol is 5% of the weight of the iron-silicon-aluminum powder. After the powder reacts for half an hour, start the heating function, and the temperature is controlled between 100 and 130 °C; after the powder cools, add 0.8% epoxy resin of the weight of the iron-silicon-aluminum powder and 6% absolute ethanol of the weight of the iron-silicon-aluminum powder for dry mixing to complete the secondary insulation coating. The powder is dry-mixed without heating until the powder is dry;

[0082] (3) After the secondary insulation coating of the iron-silicon-aluminum powder in step (2), a release agent and methyl silicone resin are added. The addition amount of zinc stearate as the release agent is 0.3% of the weight of the iron-silicon-aluminum powder, and the addition amount of methyl silicone resin is 0.2% of the weight of the iron-silicon-aluminum powder. After mixing evenly, it is pressed into an EPC22 magnetic core, and the molding pressure is 11 t / cm 2 ;

[0083] (4) Place the formed magnetic core into a baking oven and set the temperature to 220 °C for 4 hours to complete the degumming operation. After baking, put the EPC22 magnetic core into a heat treatment furnace, introduce nitrogen, keep it at 780 °C for 60 minutes, and then cool it naturally. The nitrogen flow rate is set to 8 m 3 / h;

[0084] (5) After the EPC22 magnetic core is annealed, infiltrate, spray, and polish the contact surface. After polishing smoothly, a kind of iron-silicon-aluminum EPC22 soft magnetic powder core with a magnetic permeability μ = 60 is obtained. After testing, the magnetic properties of the obtained iron-silicon-aluminum EPC22 soft magnetic powder core are shown in Table 5.

[0085] Table 5 Performance of EPC22 iron-silicon-aluminum soft magnetic powder core under different resin addition amounts

[0086]

[0087] 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 greater the addition amounts of epoxy resin and methyl silicone resin, the lower the inductance of the EPC22 magnetic core.

[0088] Based on the above analysis, it can be known that by using the process of the present invention, an iron-silicon-aluminum EPC22 soft magnetic powder core with a magnetic permeability μ = 60 can be mass-produced, and the DC bias performance is more than 80% under the test condition of 100 Oe; the core loss is 150 mW / cm at 100 KHz and 100 mT 3 , such as Figure 1 and 2 are the characteristic curves of EPC22 DC bias and Coreloss, and are the test data of the product at 12 t / cm in Example 1 2 . It can be seen that the magnetic core performance is at the top level in the industry.

[0089] In addition, the particle size ratio and the test data of magnetic permeability and loss are as shown in Table 6 and Figure 3 as follows. It can be known that under the same insulation formula, the coarser the powder particles, the higher the magnetic permeability μ value, and the worse the loss. Among them, the A# gas atomization - 200 mesh iron-silicon-aluminum has the highest magnetic permeability, μ = 65.5.

[0090] Table 6 Test data of particle size, magnetic permeability, and loss

[0091]

[0092] Each embodiment is described in a progressive manner. The key points of each embodiment are the differences from other embodiments. The same and similar parts among the embodiments can be referred to each other.

[0093] The foregoing description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can 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. A sendust soft magnetic powder core with a magnetic permeability μ of 60, characterized in that: The invention is composed of sendust magnetic powder and a coating layer of phosphate and silicon oxide in sequence on the surface of the sendust magnetic powder.

2. The Sendust soft magnetic powder core with a magnetic permeability μ of 60 according to claim 1, characterized in that: The particle size ratio of the Sendust magnetic powder is: -200 to +325 mesh accounts for 32.7%, -325 to +400 mesh accounts for 11.5%, and -400 mesh accounts for 55.8%.

3. The Sendust soft magnetic powder core with a magnetic permeability μ of 60 according to claim 1, characterized in that: The Sendust magnetic powder is atomized Sendust powder, and the silicon content of the Sendust powder is 8.5-9.5%, the aluminum content is 5.5-6.5%, and the balance is iron.

4. The Sendust soft magnetic powder core with a magnetic permeability μ of 60 according to claim 1, characterized in that: The phosphate is prepared from phosphoric acid and anhydrous ethanol; Wherein, the amount of the phosphoric acid is 0.5-0.8% of the weight of the Sendust powder, and the amount of the alcohol is 5-7% of the weight of the Sendust powder.

5. The Sendust soft magnetic powder core with a magnetic permeability μ of 60 according to claim 1, characterized in that: The silicon oxide is prepared by using epoxy resin and anhydrous ethanol; Wherein, the usage amount of the epoxy resin is 0.8-1.2% of the weight of the Sendust powder, and the usage amount of the anhydrous ethanol is 6-8% of the weight of the Sendust powder.

6. A method for preparing a sendust soft magnetic powder core with a magnetic permeability μ of 60 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 sendust powder, and the mixture is heated and fried to dry to complete the primary insulation coating; then, after the sendust powder that has completed the primary insulation coating is cooled, epoxy resin powder and anhydrous ethanol are added and mixed until the sendust powder is dry, thereby completing the secondary insulation coating and setting aside; (2) Pressing and molding: adding a release agent and a strength enhancer to the sendust powder after the secondary insulation coating in step (1), and performing press molding to obtain a magnetic core for later use; (3) Magnetic core heat treatment: The magnetic core obtained in step (2) is subjected to baking, sintering, infiltration spraying and polishing to obtain a sendust soft magnetic powder core with a magnetic permeability μ of 60.

7. The method for preparing a sendust soft magnetic powder core with a magnetic permeability μ of 60 according to claim 6, characterized in that: The heating temperature in step (1) is 100-130°C.

8. The method for preparing a sendust soft magnetic powder core with a magnetic permeability μ of 60 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 sendust powder; The strength enhancer is methyl silicone resin, and the amount of the strength enhancer is 0.2-0.3% of the weight of the sendust powder; The compression molding pressure is 9-12 t / cm 2 .

9. The method for preparing a sendust soft magnetic powder core with a magnetic permeability μ of 60 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 40-100min.

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