Iron-silicon magnetic powder core and preparation method and application thereof

Abstract

The invention provides an iron-silicon magnetic powder core and a preparation method and application thereof, and the preparation method comprises the following steps: (1) pre-treating aerosolized iron-silicon magnetic powder, and grading and proportioning to obtain mixed magnetic powder; (2) mixing the mixed magnetic powder, a passivator and a solvent, drying, and cooling to obtain passivated magnetic powder; (3) the passivated magnetic powder is subjected to insulation treatment and then pressed, and the iron-silicon magnetic powder core is obtained after annealing heat treatment.The method can improve the density and effective magnetic conductivity of the iron-silicon magnetic powder core, so that the iron-silicon magnetic powder core has more excellent magnetic performance, loss is greatly reduced, efficiency is greatly improved, and energy waste is reduced.

Description

Technical Field

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

[0002] With the development of technology, various soft magnetic powder cores are widely used in fields such as new energy, electrical, communication, and automotive industries, and various soft magnetic powder cores are required to develop in the directions of miniaturization, intelligence, high integration, and low loss. At present, there are mainly various soft magnetic powder cores such as iron powder cores and metal magnetic powder cores on the market. Among them, the iron powder core has a high saturation magnetic induction intensity, but a low resistivity, and is usually used in the low-frequency band, with large eddy current losses at high frequencies; although the loss of the metal magnetic powder core is greatly reduced compared with the iron powder core, its DC superposition characteristics and high-frequency loss still limit its large-scale application. At present, the mainly applied metal magnetic powder core is the iron-silicon magnetic powder core. Although the iron-silicon magnetic powder core has a low cost and high DC superposition performance, its loss is high and the heat generation is serious, which is not conducive to the energy-saving and high-efficiency of the device.

[0003] CN113035541A discloses a method for coating iron-silicon powder with modified silica sol. The main method adopted is to mix 80% of silica sol, 10% of sodium silicate solution and 10% of water evenly to prepare a modified silica sol coating solution, place the iron-silicon powder in the modified silica sol coating solution for 1 to 3 minutes and then dry it to prepare the iron-silicon powder coated with modified silica sol. Subsequently, the modified silica sol-coated iron-silicon powder, kaolin, FK glue, phenolic resin and zinc stearate are mixed and stirred evenly to obtain a mixture, and finally a magnetic powder core is obtained by pressing.

[0004] CN102294475A discloses an iron-silicon material and a preparation method of a μ60 iron-silicon magnetic powder core. The method for preparing the magnetic powder core adopted therein includes steps such as particle size classification (mainly the particle size ratio of 200-mesh, 100-mesh, and 60-mesh magnetic powders), passivation, insulation coating, molding by pressing, and heat treatment, and then a magnetic powder core is obtained.

[0005] Although the iron-silicon magnetic powder cores prepared by the above-mentioned schemes have a low cost and high DC superposition performance, their loss is high and the heat generation is serious, which is not conducive to the energy-saving and high-efficiency of the device. Summary of the Invention

[0006] The purpose of the present invention is to provide an iron-silicon magnetic powder core, a preparation method thereof, and an application thereof. The method of the present invention can improve the density and effective magnetic permeability of the iron-silicon magnetic powder core, so that the iron-silicon magnetic powder core has more excellent magnetic properties, the loss is greatly reduced, the efficiency is greatly improved, and the energy waste is reduced.

[0007] To achieve the purpose of this invention, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides a method for preparing an iron-silicon magnetic powder core, and the preparation method includes the following steps:

[0009] (1) Pretreat and then classify and proportion the gas-atomized iron-silicon magnetic powder to obtain a mixed magnetic powder;

[0010] (2) Mix the mixed magnetic powder, a passivator and a solvent, dry and then cool to obtain a passivated magnetic powder;

[0011] (3) Perform insulation treatment on the passivated magnetic powder and then press it, and obtain the iron-silicon magnetic powder core after annealing heat treatment.

[0012] Through pretreatment, the present invention can improve the internal microstructure of the magnetic powder, reduce the surface hardness of the magnetic powder, which is more conducive to the improvement of density in the subsequent pressing process, and further improve the magnetic properties of the magnetic core. By adopting a unique secondary passivation process (mixing and drying the passivator is the first passivation, and cooling is the second passivation), the insulation between magnetic powders is improved, and the loss characteristics of the magnetic core are further improved.

[0013] Preferably, the pretreatment in step (1) includes heat-treating the gas-atomized iron-silicon magnetic powder and then cooling it to room temperature.

[0014] Preferably, the temperature of the heat treatment is 650-800 °C, for example: 650 °C, 680 °C, 700 °C, 750 °C or 800 °C, etc.

[0015] Preferably, the time of the heat treatment is 2-3 h, for example: 2 h, 2.2 h, 2.5 h, 2.8 h or 3 h, etc.

[0016] Preferably, the cooling rate < 30 °C / h.

[0017] Preferably, the atmosphere of the pretreatment includes any one or a combination of at least two of vacuum, hydrogen, nitrogen or argon.

[0018] Preferably, the classification and proportioning in step (1) includes passing the pretreated iron-silicon magnetic powder through 600-mesh, 500-mesh, 350-mesh and 200-mesh sieves respectively, and then mixing and proportioning according to the ratio of 600-mesh:500-mesh:350-mesh:200-mesh = (5-7):(4-2):0.5:0.5 (for example: 5:4:0.5:0.5, 6:4:0.5:0.5, 6:3:0.5:0.5, 7:2:0.5:0.5 or 5:2:0.5:0.5, etc.).

[0019] The classification and proportioning of the present invention can greatly reduce the eddy current loss of the magnetic core at high frequencies. At the same time, through reasonable particle size matching and pretreatment of the magnetic powder, the stress in the atomized magnetic powder is eliminated, the plastic deformation ability of the magnetic powder is improved, the hardness of the magnetic powder is reduced, the density of the magnetic core is increased, and thus the comprehensive magnetic properties of the magnetic core are improved.

[0020] Preferably, the passivator described in step (2) includes phosphoric acid and / or aluminum dihydrogen phosphate.

[0021] Preferably, the mass ratio of the passivator to the mixed magnetic powder is (0.1 - 1):100, such as: 0.1:100, 0.2:100, 0.5:100, 0.8:100 or 1:100, etc.

[0022] Preferably, the solvent includes any one or a combination of at least two of deionized water, acetone or absolute ethanol.

[0023] Preferably, the drying method described in step (2) includes any one or a combination of at least two of natural drying, heating drying or vacuum drying.

[0024] Preferably, the cooling method includes cooling the mixed material in liquid nitrogen.

[0025] Preferably, the cooling time > 20 min.

[0026] Preferably, the insulation treatment described in step (3) includes mixing the passivated magnetic powder and the modified insulation adhesive solution, and then drying and sieving.

[0027] Preferably, the modified insulation adhesive solution includes a mixed solution of silica sol, silane coupling agent and polyurethane.

[0028] The present invention adopts a modified insulation adhesive solution, which can make the insulating silicon particles more easily adsorbed on the surface of the magnetic powder to achieve a better insulation effect, thereby reducing the loss of the magnetic powder core.

[0029] Preferably, the mass ratio of the modified insulation adhesive solution to the passivated magnetic powder is (1 - 2):100, such as: 1:100, 1.2:100, 1.5:100, 1.8:100 or 2:100, etc.

[0030] Preferably, the mesh number of the sieve for sieving is 80 - 140 meshes, such as: 80 meshes, 90 meshes, 100 meshes, 120 meshes or 140 meshes, etc.

[0031] Preferably, the pressing described in step (3) includes mixing the material after insulation treatment with a mold release agent and then pressing.

[0032] Preferably, the mold release agent includes zinc stearate.

[0033] Preferably, the mass ratio of the mold release agent to the material is (0.2 - 0.6):100, such as: 0.2:100, 0.3:100, 0.4:100, 0.5:100 or 0.6:100, etc.

[0034] Preferably, the pressure for pressing is 1500 - 2000 MPa, for example: 1500 MPa, 1600 MPa, 1700 MPa, 1800 MPa, 2000 MPa, etc.

[0035] Preferably, the atmosphere for the annealing heat treatment in step (3) includes nitrogen and / or inert gas.

[0036] Preferably, the temperature for the annealing heat treatment is 680 - 720 °C, for example: 680 °C, 690 °C, 700 °C, 710 °C, 720 °C, etc.

[0037] Preferably, the time for the annealing heat treatment is 1 - 2 h, for example: 1 h, 1.2 h, 1.5 h, 1.8 h, 2 h, etc.

[0038] In a second aspect, the present invention provides an iron - silicon magnetic powder core, which is prepared by the method as described in the first aspect.

[0039] In a third aspect, the present invention provides an inductive component, which includes the iron - silicon magnetic powder core as described in the second aspect.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] (1) Through pretreatment, the present invention can improve the microstructure inside the magnetic powder, reduce the surface hardness of the magnetic powder, which is more conducive to the improvement of density in the subsequent molding process, and then improve the magnetic properties of the magnetic core. By adopting a unique secondary passivation process (mixing and drying the passivating agent is the first passivation, and cooling is the second passivation), the insulation between magnetic powders is improved, and the loss characteristics of the magnetic core are further improved.

[0042] (2) The method of the present invention can improve the density and effective magnetic permeability of the iron - silicon magnetic powder core, making the iron - silicon magnetic powder core have more excellent magnetic properties, greatly reducing the loss, greatly improving the efficiency, and reducing energy waste.

[0043] (3) After being prepared by the method of the present invention, the iron - silicon magnetic powder core can increase the density of the magnetic powder core, thereby increasing its effective magnetic permeability and reducing the loss. The effective magnetic permeability of the prepared magnetic powder core can reach above 82, and Pcv can reach 405 mW / cm 3 Hereinafter, the compacted density can reach above 6.67 g / cm 3 . Specific Embodiments

[0044] The technical solutions of the present invention will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.

[0045] Example 1

[0046] This embodiment provides an iron silicon magnetic powder core, and the preparation method of the iron silicon magnetic powder core is as follows:

[0047] (1) Atomized iron silicon magnetic powder is selected, and the magnetic powder is placed in a heat treatment furnace, the furnace temperature is raised to 740°C, kept at this temperature for 2 hours, and then slowly cooled to room temperature and taken out of the furnace, the cooling rate is 25°C / h, the atmosphere in the furnace is vacuum, and the heat-treated magnetic powder is graded and stored according to 600 mesh, 500 mesh, 350 mesh, and 200 mesh, and the powder is mixed according to the mass ratio of 600 mesh: 500 mesh: 350 mesh: 200 mesh = 7:2:0.5:0.5, and the magnetic powder is evenly mixed to obtain mixed magnetic powder;

[0048] (2) fully mixing the mixed magnetic powder with phosphoric acid and acetone, and drying to obtain passivated magnetic powder, wherein the amount of phosphoric acid used is 0.2% of the alloy magnetic powder, and the magnetic powder can be completely immersed in the solvent, heating and drying at 80° C. while stirring, and cooling in liquid nitrogen for no less than 20 minutes to obtain passivated magnetic powder;

[0049] (3) 65% of silica sol, 1% of silane coupling agent and 34% of polyurethane are mixed to obtain a modified insulating adhesive solution, the passivated magnetic powder is mixed with the modified insulating adhesive solution and a solvent, and then dried, and the completely dried magnetic powder is crushed and sieved to obtain the insulating magnetic powder for standby use, wherein the amount of the insulating adhesive solution is 1.5% of the mass of the iron silicon magnetic powder; the solvent is acetone, which can completely soak the magnetic powder in the solvent; the drying is carried out by natural drying, the mesh size of the sieve is 140 mesh, the magnetic powder is mixed at a mass ratio of 0.4:100, pressed at 1900 MPa, and annealed at 700°C for 1 hour to obtain the iron silicon magnetic powder core.

[0050] Example 2

[0051] This embodiment provides an iron silicon magnetic powder core, and the preparation method of the iron silicon magnetic powder core is as follows:

[0052] (1) Atomized iron silicon magnetic powder is selected, and the magnetic powder is placed in a heat treatment furnace, the furnace temperature is raised to 720°C, kept at this temperature for 2 hours, and then slowly cooled to room temperature and taken out of the furnace, the cooling rate is 28°C / h, the atmosphere in the furnace is vacuum, and the heat-treated magnetic powder is graded and stored according to 600 mesh, 500 mesh, 350 mesh, and 200 mesh, and the powder is mixed according to the mass ratio of 600 mesh: 500 mesh: 350 mesh: 200 mesh = 7:2:0.5:0.5, and the magnetic powder is evenly mixed to obtain mixed magnetic powder;

[0053] (2) fully mixing the mixed magnetic powder with aluminum dihydrogen phosphate and acetone, and drying to obtain passivated magnetic powder, wherein the amount of aluminum dihydrogen phosphate used is 1% of the alloy magnetic powder, and the magnetic powder can be completely immersed in the solvent, heating and drying at 80° C. while stirring, and cooling in liquid nitrogen for no less than 20 minutes to obtain passivated magnetic powder;

[0054] (3) 65% of silica sol, 1% of silane coupling agent and 34% of polyurethane are mixed to obtain a modified insulating adhesive solution, the passivated magnetic powder is mixed with the modified insulating adhesive solution and a solvent, and then dried, and the completely dried magnetic powder is crushed and sieved to obtain the insulating treated magnetic powder for standby use, wherein the amount of the insulating adhesive solution is 1% of the mass of the iron silicon magnetic powder; the solvent is acetone, which can completely soak the magnetic powder in the solvent; the drying is carried out by natural drying, the mesh size of the sieve is 140 mesh, the magnetic powder is mixed at a mass ratio of 0.2:100, pressed at 1500MPa, and annealed at 680°C for 2h to obtain the iron silicon magnetic powder core.

[0055] Example 3

[0056] This embodiment provides an iron silicon magnetic powder core, and the preparation method of the iron silicon magnetic powder core is as follows:

[0057] (1) Atomized iron silicon magnetic powder is selected, and the magnetic powder is placed in a heat treatment furnace, the furnace temperature is raised to 800°C, kept at this temperature for 2 hours, and then slowly cooled to room temperature and taken out of the furnace, the cooling rate is 25°C / h, the atmosphere in the furnace is vacuum, and the heat-treated magnetic powder is graded and stored according to 600 mesh, 500 mesh, 350 mesh, and 200 mesh, and the powder is mixed according to the mass ratio of 600 mesh: 500 mesh: 350 mesh: 200 mesh = 6:3:0.5:0.5, and the magnetic powder is evenly mixed to obtain mixed magnetic powder;

[0058] (2) fully mixing the mixed magnetic powder with phosphoric acid and acetone, and drying to obtain passivated magnetic powder, wherein the amount of phosphoric acid used is 0.1% of the alloy magnetic powder, and the magnetic powder can be completely immersed in the solvent, heating and drying at 80° C. while stirring, and cooling in liquid nitrogen for no less than 20 minutes to obtain passivated magnetic powder;

[0059] (3) 65% of silica sol, 1% of silane coupling agent and 34% of polyurethane are mixed to obtain a modified insulating adhesive solution, the passivated magnetic powder is mixed with the modified insulating adhesive solution and a solvent, and then dried, and the completely dried magnetic powder is crushed and sieved to obtain the insulating magnetic powder for standby use, wherein the amount of the insulating adhesive solution is 2% of the mass of the iron silicon magnetic powder; the solvent is acetone, which can completely soak the magnetic powder in the solvent; the drying is carried out by natural drying, the mesh size of the sieve is 80 mesh, the magnetic powder is mixed at a mass ratio of 0.6:100, pressed at 2000 MPa, and annealed at 720°C for 1 hour to obtain the iron silicon magnetic powder core.

[0060] Example 4

[0061] The difference between this embodiment and Embodiment 1 is only that the proportion of 600-mesh magnetic powder after sieving is 60%, and the proportion of 500-mesh magnetic powder is 30%. Other conditions and parameters are exactly the same as those in Embodiment 1.

[0062] Embodiment 5

[0063] The difference between this embodiment and Embodiment 1 is only that the proportion of 600-mesh magnetic powder after sieving is 50%, and the proportion of 500-mesh magnetic powder is 40%. Other conditions and parameters are exactly the same as those in Embodiment 1.

[0064] Embodiment 6

[0065] The difference between this embodiment and Embodiment 2 is only that the temperature of the pretreatment is 600 °C. Other conditions and parameters are exactly the same as those in Embodiment 1.

[0066] Embodiment 7

[0067] The difference between this embodiment and Embodiment 2 is only that the temperature of the pretreatment is 820 °C. Other conditions and parameters are exactly the same as those in Embodiment 1.

[0068] Embodiment 8

[0069] The difference between this embodiment and Embodiment 2 is only that the cooling rate after the pretreatment is 40 °C / min. Other conditions and parameters are exactly the same as those in Embodiment 1.

[0070] Embodiment 9

[0071] The difference between this embodiment and Embodiment 2 is only that no liquid nitrogen cooling is carried out. Other conditions and parameters are exactly the same as those in Embodiment 1.

[0072] Embodiment 10

[0073] The difference between this embodiment and Embodiment 2 is only that the liquid nitrogen cooling time is 15 min. Other conditions and parameters are exactly the same as those in Embodiment 1.

[0074] Comparative Example 1

[0075] The difference between this comparative example and Embodiment 1 is only that conventional 600-mesh iron-silicon magnetic powder with a particle size < 76 μm is selected for the test, and no particle size screening and grading are carried out. Other conditions and parameters are exactly the same as those in Embodiment 1.

[0076] Comparative Example 2

[0077] The difference between this comparative example and Embodiment 2 is only that no pretreatment is carried out. Other conditions and parameters are exactly the same as those in Embodiment 1.

[0078] Performance test:

[0079] The density ρ of the magnetic core was measured using the drainage method. Subsequently, the magnetic core was wound, and the inductance L was measured using an LCR meter. The effective magnetic permeability μ of the toroidal magnetic core was calculated. The test frequency was 100 kHz. The AC loss of the magnetic core was measured using a Japanese Iwasaki SY-8218 soft magnetic B-H analyzer. The test conditions were: 50 kHz, 100 mT, and the temperature was 25 °C. The test results are shown in Table 1:

[0080] Table 1

[0081] μ <![CDATA[Pcv (mW / cm 3 )]]> <![CDATA[ρ (g / cm 3 )]]> Example 1 88 390 6.70 Example 2 82 380 6.75 Example 3 82 405 6.67 Example 4 70 420 6.60 Example 5 68 440 6.55 Example 6 75 420 6.55 Example 7 68 440 6.48 Example 8 70 410 6.60 Example 9 73 425 6.56 Example 10 60 455 6.45 Comparative Example 1 75 460 6.45 Comparative Example 2 60 450 6.45

[0082] As can be seen from Table 1, from Examples 1-3, it can be obtained that the effective magnetic permeability of the magnetic powder core prepared by the method of the present invention can reach more than 82, and Pcv can reach 405 mW / cm 3 Below, the compaction density can reach more than 6.67 g / cm 3 .

[0083] By comparing Example 1 with Examples 4-5, it can be obtained that although using 600-mesh magnetic powder can obtain higher μ, Bs, and ρ, the deterioration of the loss characteristics is very obvious. If the particle size grading is not reasonable, it will lead to a decrease in the density of the magnetic core, which is not conducive to the optimization of the comprehensive magnetic properties.

[0084] By comparing Example 1 with Examples 6-8, it can be obtained that the pretreatment temperature and cooling rate will affect the effect of the prepared magnetic powder core. Since the temperature is too low, the purpose of improving the microstructure cannot be achieved, while too high a temperature will lead to the generation of new phases, and too fast a cooling rate will cause stress to reappear inside the magnetic powder, which is not conducive to the improvement of the plastic deformation ability of the magnetic powder.

[0085] By comparing Example 1 with Examples 9-10, it can be obtained that not undergoing liquid nitrogen cooling treatment, or too short a time will result in a large increase in loss.

[0086] By comparing Example 1 with Comparative Example 1, it can be obtained that the grading ratio of the present invention can greatly reduce the eddy current loss of the magnetic core at high frequencies. At the same time, through reasonable particle size matching and pretreatment of the magnetic powder, the stress in the atomized magnetic powder is eliminated, the plastic deformation ability of the magnetic powder is improved, the hardness of the magnetic powder is reduced, the density of the magnetic core is increased, and thus the comprehensive magnetic properties of the magnetic core are improved.

[0087] By comparing Example 1 with Comparative Example 2, it can be obtained that the present invention can improve the microstructure inside the magnetic powder through pretreatment, reduce the surface hardness of the magnetic powder, and is more conducive to the increase of density during the subsequent molding process, thereby improving the magnetic properties of the magnetic core.

[0088] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A preparation method of an iron-silicon magnetic powder core, characterized in that, the preparation method comprises the following steps: (1) Pretreat and classify and proportion the gas-atomized iron-silicon magnetic powder to obtain a mixed magnetic powder; (2) Mix the mixed magnetic powder, a passivator and a solvent, dry and then cool to obtain a passivated magnetic powder; (3) Perform insulation treatment on the passivated magnetic powder and then press it, and obtain the iron-silicon magnetic powder core after annealing heat treatment.

2. The preparation method according to claim 1, characterized in that, the pretreatment in step (1) includes heat-treating the gas-atomized iron-silicon magnetic powder and then cooling it to room temperature; Preferably, the temperature of the heat treatment is 650-800 °C; Preferably, the time of the heat treatment is 2-3 h; Preferably, the cooling rate < 30 °C / h; Preferably, the atmosphere of the pretreatment includes any one or a combination of at least two of vacuum, hydrogen, nitrogen or argon.

3. The preparation method according to claim 1 or 2, characterized in that, the classification and proportioning in step (1) includes passing the pretreated iron-silicon magnetic powder through 600-mesh, 500-mesh, 350-mesh and 200-mesh sieves respectively, and then mixing and proportioning according to the ratio of 600-mesh:500-mesh:350-mesh:200-mesh = (5-7):(4-2):0.5:0.

5.

4. The preparation method according to any one of claims 1-3, characterized in that, the passivator in step (2) includes phosphoric acid and / or aluminum dihydrogen phosphate; Preferably, the mass ratio of the passivator to the mixed magnetic powder is (0.1-1):100; Preferably, the solvent includes any one or a combination of at least two of deionized water, acetone or absolute ethanol.

5. The preparation method according to any one of claims 1-4, characterized in that, the drying method in step (2) includes any one or a combination of at least two of natural drying, heating drying or vacuum drying; Preferably, the cooling method includes cooling the mixed material in liquid nitrogen; Preferably, the cooling time > 20 min.

6. The preparation method according to any one of claims 1-5, characterized in that, the insulation treatment in step (3) includes mixing the passivated magnetic powder and a modified insulation adhesive solution, and then drying and sieving; Preferably, the modified insulation adhesive solution includes a mixed solution of silica sol, silane coupling agent and polyurethane; Preferably, the mass ratio of the modified insulation adhesive solution to the passivated magnetic powder is (1-2):100; Preferably, the mesh number of the sieve for sieving is 80-140 meshes.

7. The preparation method according to any one of claims 1-6, characterized in that, the pressing in step (3) includes mixing the material after insulation treatment with a mold release agent and then pressing; Preferably, the mold release agent includes zinc stearate; Preferably, the mass ratio of the mold release agent to the material is (0.2-0.6):100; Preferably, the pressing pressure is 1500-2000 MPa.

8. The preparation method according to any one of claims 1-7, characterized in that, the atmosphere of the annealing heat treatment in step (3) includes nitrogen and / or inert gas; Preferably, the temperature of the annealing heat treatment is 680-720 °C; Preferably, the time of the annealing heat treatment is 1 to 2 h.

9. An iron-silicon magnetic powder core, characterized in that the iron-silicon magnetic powder core is prepared by the method according to any one of claims 1-8.

10. An inductive component, characterized in that the inductive component comprises the iron-silicon magnetic powder core according to claim 9.