Low-loss and high direct current bias magnetic powder core and method for manufacturing the same

Abstract

The application relates to a low-loss and high-DC-bias magnetic powder core and a preparation method thereof, which comprises the following steps: (1) first mixing magnetic powder, phosphoric acid, organic silicon resin and solvent A, then sequentially performing first heat preservation stirring and first heat treatment, and screening to obtain intermediate powder; (2) second mixing chromic acid, solvent B and the intermediate powder obtained in the step (1), then adding water glass and an adhesive to perform third mixing, and drying to obtain insulating magnetic powder; (3) fourth mixing the insulating magnetic powder obtained in the step (2) and a release agent, then sequentially performing shaping and second heat treatment to obtain the low-loss and high-DC-bias magnetic powder core. The preparation method provided by the application adopts inorganic-organic multilayer coating and multiple coating insulation coating methods to ensure the stability and uniformity of the insulation layer and reduce the adverse influence of the coating layer on the soft magnetic performance. Finally, the magnetic core with high permeability, good DC superposition performance and low loss is prepared.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of magnetic materials, in particular to a low-loss and high DC bias magnetic powder core and a preparation method thereof. BACKGROUND

[0002] At present, due to the rapid development of electronic products, the practicability, safety and reliability of inductance components are also constantly improved, and the demand for small-size high-power inductors is also increasing. Soft magnetic alloy inductors are suitable for the development requirements of the miniaturization of electronic products, and can be widely used in various electronic component fields. At present, inductors are mostly prepared by powder metallurgy process, and metal powder is molded by molding, which is called molded inductance. This is a kind of inductance obtained by surface treatment of metal soft magnetic powder, mixing with binder, and then molding.

[0003] Metal soft magnetic powder core is a new type of soft magnetic functional material which uses alloy powder as raw material, coats a layer of insulating material on the surface of the magnetic powder, and then is pressed and formed and annealed after heat treatment. For magnetic materials, the loss is mainly caused by the contact between the magnetic powders, and the loss caused by the interaction between them, especially the loss between the magnetic powders at high frequency. In order to realize the energy saving and high frequency of magnetic devices, it is particularly important to reduce the loss of magnetic powders and improve the efficiency of magnetic powders. Among them, the insulating coating technology is a key link, which plays a decisive role in improving the overall resistivity, reducing the eddy current loss and improving the comprehensive electric-magnetic performance.

[0004] Insulating coating can be divided into organic coating and inorganic coating. Organic coating resins mainly include thermosetting resins (such as epoxy resin, phenolic resin, silicone resin, etc.) and thermoplastic resins (such as polyethylene, polyamide, ethylene-vinyl acetate polymer, polypropylene, PBT, PPS, nylon, etc.). These organic substances have strong adhesion, can ensure that the magnetic powder core has sufficient strength, but have low heat resistance temperature and are easy to decompose in high-temperature annealing process, so it is difficult to maintain the insulation of the surface film of the magnetic powder in high-temperature heat treatment, thereby deteriorating the magnetic properties of the magnetic powder core. Inorganic coating can be divided into inorganic phosphate coating (zinc phosphate, iron phosphate and manganese phosphate), metal oxide coating (SiO2, MgO), ferrite coating and silicate coating. Inorganic substances have high heat resistance temperature, can meet the requirements of magnetic powder core heat treatment, and have high resistivity and low eddy current loss at high frequency, so they are excellent insulating coating agents. However, these inorganic substances have poor adhesion, and the mechanical properties of the magnetic powder core are difficult to meet the application requirements when there is no other binder.

[0005] As CN114512323A, a kind of MnO-SiO2 Insulated coated metal soft magnetic powder core preparation method, the method includes the following steps: to MnO2 Powder is added with silane coupling agent, to MnO2 Powder is modified, make it rich hydroxyl group;To the obtained modified MnO2 Mixed liquor is added with metal magnetic powder and ethanol, after stirring, dry, obtain MnO2 Insulated coated metal magnetic powder;The obtained MnOO2 Insulated coated metal magnetic powder is sieved, and is sieved and granulated, and is pressed into green body;The obtained green body is annealed by heating, and MnO-SiO2 Insulated coated metal soft magnetic powder core finished product is obtained.MnO2 Coating layer is converted into MnO-SiO2 Coating layer by high temperature annealing, the MnO-SiO2 Insulated coated layer generated by in-situ reaction of Si in metal magnetic powder and MnO2 It is more uniform and dense, and the MnO-SiO2 Coating layer is resistant to high temperature and is not easy to decompose and fall off, effectively solving the problem that the phosphoric acid passivation layer is easy to decompose at high temperature.

[0006] CN112687445A discloses a preparation method of aluminum dihydrogen phosphate-based composite insulated coated metal soft magnetic powder core, belonging to the technical field of soft magnetic material preparation. The method uses organic-inorganic composite insulation coating, adds resin to bond the nano magnesium oxide to the magnetic powder, improves the mechanical properties of the green body of the powder core, and solves the problem of easy peeling of inorganic coating during pressing; the subsequent addition of aluminum dihydrogen phosphate makes up for the defect of the organic resin that is not resistant to high temperature, and aluminum dihydrogen phosphate is also a binder that can be condensed into an inorganic polymer with strong adhesion, which helps to improve the mechanical properties of the powder core. In addition, the presence of uniformly dispersed nano magnesium oxide particles helps to improve the high temperature stability of aluminum dihydrogen phosphate. The reason is that P-OH of aluminum dihydrogen phosphate can react with nano magnesium oxide to form P-O-Mg bond, and a three-dimensional network structure is formed through ionic bond and covalent bond, which has high adhesive cohesion.

[0007] The soft magnetic composite material coated with an organic insulation layer cannot be subjected to high temperature annealing after pressing, and the mechanical properties and related magnetic properties of the material cannot meet the application requirements; and the brittleness of the pure inorganic coating layer limits the preparation of high-density green body. SUMMARY

[0008] In view of the problems in the prior art, the purpose of the present application is to provide a low-loss and high DC bias magnetic powder core and a preparation method thereof, to solve the problem that current powder core materials cannot have both high permeability and low loss.

[0009] To achieve this purpose, the present application adopts the following technical solutions:

[0010] In a first aspect, the present application provides a preparation method of a low-loss and high DC bias magnetic powder core, which comprises the following steps:

[0011] (1) First mixing of magnetic powder, phosphoric acid, silicone resin and solvent A, followed by first heat treatment and first heat treatment, and then screening to obtain intermediate powder;

[0012] (2) Second mixing of chromic acid, solvent B and intermediate powder obtained in step (1), followed by adding water glass and adhesive, and then third mixing, and then drying to obtain insulating magnetic powder;

[0013] (3) Fourth mixing of insulating magnetic powder obtained in step (2) and release agent, followed by molding and second heat treatment to obtain low-loss and high DC bias magnetic powder core.

[0014] The preparation method provided by the application ensures the stability and uniformity of the insulating layer by specific design of the coating process, and reduces the adverse effects of the coating layer on the soft magnetic properties. Meanwhile, the specific sequence of phosphoric acid and chromic acid is used for surface passivation modification coating in the surface passivation modification, which improves the soft magnetic properties of the material, and with the help of specific second heat treatment process, a magnetic core with high permeability, good DC superposition performance and low loss is finally obtained.

[0015] In the application, the processing procedure of step (2) can effectively improve the DC superposition of the magnetic powder core with little effect on the performance of permeability and loss.

[0016] In the application, the processing procedure of step (3) can effectively improve the DC superposition performance and reduce the loss of the magnetic powder core, which is beneficial to the preparation of a magnetic powder core with high permeability, low loss and good DC superposition performance.

[0017] As a preferred technical solution of the application, the particle size of the magnetic powder in step (1) is less than 74 μm.

[0018] In the application, by controlling the specific particle size range, the magnetic powder core with high permeability, low loss and good DC superposition performance can be prepared under other processing conditions. If the powder particles are larger, the performance of the magnetic powder will be significantly reduced.

[0019] In the application, the particle size of the magnetic powder is less than 74 μm, which means that the cluster of particles within the range of less than 74 μm, such as the cluster of particles with uniform particle size, such as magnetic powder with particle size of 34 μm, magnetic powder with particle size of 60 μm, and magnetic powder with particle size of 60 μm; or the cluster of particles within a certain particle size range, such as the cluster of particles within the range of 34-72 μm, such as the cluster of particles within the range of 3-25 μm, such as the cluster of particles within the range of 20-64 μm, such as the cluster of particles within the range of 42-58 μm, etc.

[0020] Preferably, the magnetic powder in step (1) comprises one or a combination of at least two of iron powder, iron-silicon powder, iron-silicon-aluminum powder, iron-nickel powder, or iron-silicon-nickel powder.

[0021] As a preferred technical solution of the present application, the amount of phosphoric acid added in step (1) is 0.1-0.5% of the mass of the magnetic powder, for example, it can be 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, or 0.5%, etc., but not limited to the listed values, other values not listed within this range are also applicable.

[0022] Preferably, the amount of organic silicon resin added in step (1) is 0.1-1% of the mass of the magnetic powder, for example, it can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, or 1%, etc., but not limited to the listed values, other values not listed within this range are also applicable.

[0023] Preferably, the amount of organic solvent added in step (1) is 7-8% of the mass of the magnetic powder, for example, it can be 7%, 7.1%, 7.2%, 7.3%, 7.4%, 7.5%, 7.6%, 7.7%, 7.8%, 7.9%, or 8%, etc., but not limited to the listed values, other values not listed within this range are also applicable.

[0024] Preferably, the organic silicon resin in step (1) comprises methyl silicon resin and / or methyl phenyl silicon resin.

[0025] Preferably, the solvent A in step (1) comprises one or a combination of at least two of methanol, butanol, or acetone.

[0026] As a preferred technical solution of the present application, the temperature of the first heat preservation stirring in step (1) is 120-130°C, for example, it can be 120°C, 121°C, 122°C, 123°C, 124°C, 125°C, 126°C, 127°C, 128°C, 129°C, or 130°C, etc., but not limited to the listed values, other values not listed within this range are also applicable.

[0027] Preferably, the time of the first heat preservation stirring in step (1) is 20-30min, for example, it can be 20min, 21min, 22min, 23min, 24min, 25min, 26min, 27min, 28min, 29min, or 30min, etc., but not limited to the listed values, other values not listed within this range are also applicable.

[0028] Preferably, the stirring speed of the first holding stirring in step (1) is 100-120 r / min, for example, it can be 100 r / min, 101 r / min, 102 r / min, 103 r / min, 104 r / min, 105 r / min, 106 r / min, 107 r / min, 108 r / min, 109 r / min, 110 r / min, 111 r / min, 112 r / min, 113 r / min, 114 r / min, 115 r / min, 116 r / min, 117 r / min, 118 r / min, 119 r / min, or 120 r / min, etc., but not limited to the listed values, other values not listed in the range are also applicable.

[0029] Preferably, the first heat treatment in step (1) is carried out under a protective atmosphere.

[0030] Preferably, the temperature of the first heat treatment in step (1) is 780-820℃, for example, it can be 780℃, 782℃, 784℃, 786℃, 788℃, 790℃, 792℃, 794℃, 796℃, 798℃, 800℃, 802℃, 804℃, 806℃, 808℃, 810℃, 812℃, 814℃, 816℃, 818℃, or 820℃, etc., but not limited to the listed values, other values not listed in the range are also applicable.

[0031] Preferably, the time of the first heat treatment in step (1) is 2-2.2 h, for example, it can be 2 h, 2.01 h, 2.02 h, 2.03 h, 2.04 h, 2.05 h, 2.06 h, 2.07 h, 2.08 h, 2.09 h, 2.1 h, 2.11 h, 2.12 h, 2.13 h, 2.14 h, 2.15 h, 2.16 h, 2.17 h, 2.18 h, 2.19 h, or 2.2 h, etc., but not limited to the listed values, other values not listed in the range are also applicable.

[0032] Preferably, the particle size of the intermediate powder obtained in step (1) is 28-74 μm. For the selection of powder particle size, refer to the particle size of magnetic powder.

[0033] As a preferred technical solution of the present application, the addition amount of chromium acid in step (2) is 0.1-0.5% of the mass of the intermediate powder, for example, it can be 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, or 0.5%, etc., but not limited to the listed values, other values not listed in the range are also applicable.

[0034] Preferably, the solvent B added in step (2) is 3-4% of the mass of the intermediate powder, for example, it can be 3%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9% or 4%, etc., but not limited to the listed values, other values not listed in the range are also applicable.

[0035] Preferably, the solvent B in step (2) includes water; and can also be other solvents with equivalent effects such as ethanol, etc.

[0036] Preferably, the amount of water glass added in step (2) is 0.1-0.5% of the mass of the intermediate powder, for example, it can be 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45% or 0.5%, etc., but not limited to the listed values, other values not listed in the range are also applicable.

[0037] In the present application, the modulus of the water glass is 2-2.5, which is used as a coating agent.

[0038] Preferably, the amount of the binder added in step (2) is 1-2% of the mass of the intermediate powder, for example, it can be 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9% or 2%, etc., but not limited to the listed values, other values not listed in the range are also applicable.

[0039] Preferably, the binder in step (2) includes a silicone solution.

[0040] As a preferred technical solution of the present application, the amount of the release agent added in step (3) is 0.1-0.3% of the mass of the insulating magnetic powder, for example, it can be 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.2%, 0.21%, 0.22%, 0.23%, 0.24%, 0.25%, 0.26%, 0.27%, 0.28%, 0.29% or 0.3%, etc., but not limited to the listed values, other values not listed in the range are also applicable.

[0041] Preferably, the release agent in step (3) includes one or a combination of at least two of zinc stearate, calcium stearate, talc or mica powder.

[0042] As a preferred technical solution of the present application, the forming pressure in step (3) is 1000-2000 MPa, for example, it can be 1000 MPa, 1100 MPa, 1200 MPa, 1300 MPa, 1400 MPa, 1500 MPa, 1600 MPa, 1700 MPa, 1800 MPa, 1900 MPa or 2000 MPa, etc., but not limited to the listed values, other values not listed in this range are also applicable.

[0043] In the present application, the specific forming pressure adopted is beneficial to improve the performance of the magnetic powder core. Too high pressure will lead to decrease of DC superposition performance and increase of loss, and too low pressure will lead to obvious decrease of magnetic permeability.

[0044] As a preferred technical solution of the present application, the second heat treatment in step (3) is carried out in a protective atmosphere or a reducing atmosphere.

[0045] Preferably, the temperature of the second heat treatment in step (3) is 600-800℃, for example, it can be 600℃, 610℃, 620℃, 630℃, 640℃, 650℃, 660℃, 670℃, 680℃, 690℃, 700℃, 710℃, 720℃, 730℃, 740℃, 750℃, 760℃, 770℃, 780℃, 790℃ or 800℃, etc., but not limited to the listed values, other values not listed in this range are also applicable.

[0046] Preferably, the time of the heat treatment in step (3) is 30-90 min, for example, it can be 30 min, 32 min, 34 min, 36 min, 38 min, 40 min, 42 min, 44 min, 46 min, 48 min, 50 min, 52 min, 54 min, 56 min, 58 min, 60 min, 62 min, 64 min, 66 min, 68 min, 70 min, 72 min, 74 min, 76 min, 78 min, 80 min, 82 min, 84 min, 86 min, 88 min or 90 min, etc., but not limited to the listed values, other values not listed in this range are also applicable.

[0047] As a preferred technical solution of the present application, the preparation method comprises the following steps:

[0048] (1) First mixing of the magnetic powder, phosphoric acid, organic silicone resin and solvent A, followed by first heat treatment and first heat treatment, and then screening to obtain an intermediate powder;

[0049] (2) mixing the chromic acid, solvent B and the intermediate powder obtained in step (1), then adding water glass and a binder, and after third mixing, drying to obtain an insulating magnetic powder;

[0050] (3) fourth mixing the insulating magnetic powder obtained in step (2) and a release agent, then sequentially forming and second heat treating to obtain a low-loss and high DC bias magnetic powder core;

[0051] In step (1), the particle size of the magnetic powder is less than 74 μm, the magnetic powder comprises one or a combination of at least two of iron powder, iron-silicon powder, iron-silicon-aluminum powder, iron-nickel powder or iron-silicon-nickel powder; the phosphoric acid is added in an amount of 0.1-0.5% of the mass of the magnetic powder; the organic silicon resin is added in an amount of 0.1-1% of the mass of the magnetic powder; the organic solvent is added in an amount of 7-8% of the mass of the magnetic powder; the organic silicon resin comprises methyl silicon resin and / or methyl phenyl silicon resin; the solvent A comprises one or a combination of at least two of methanol, butanol or acetone; the temperature of the first heat treatment is 120-130°C, the time is 20-30 min, and the stirring speed is 100-120 r / min; the temperature of the first heat treatment is 780-820°C, the time is 2-2.2 h, and the heat treatment is performed in a protective atmosphere; and the particle size of the obtained intermediate powder is 28-74 μm;

[0052] In step (2), the chromic acid is added in an amount of 0.1-0.5% of the mass of the intermediate powder; the solvent B is added in an amount of 3-4% of the mass of the intermediate powder, and the solvent B comprises water; the water glass is added in an amount of 0.1-0.5% of the mass of the intermediate powder; and the binder is added in an amount of 1-2% of the mass of the intermediate powder, and the binder comprises a silicon resin solution;

[0053] In step (3), the release agent is added in an amount of 0.1-0.3% of the mass of the insulating magnetic powder, and the release agent comprises one or a combination of at least two of zinc stearate, calcium stearate, talc powder or mica powder; the forming pressure is 1000-2000 MPa; the second heat treatment is performed in a protective atmosphere or a reducing atmosphere; the temperature of the second heat treatment is 600-800°C, and the time is 30-90 min.

[0054] In a second aspect, the present application provides a low-loss and high DC bias magnetic powder core prepared by the preparation method of the first aspect.

[0055] In the present application, the reagents such as phosphoric acid, chromic acid and silicon resin binder, whose concentrations are not specified, are commercially available analytical reagents.

[0056] In the present application, the protective atmosphere can be one or a combination of at least two of nitrogen and / or inert gas, such as helium, neon or argon.

[0057] In the present application, the reducing atmosphere can be hydrogen and / or carbon monoxide, etc.

[0058] Compared with the prior art, the present application has the following beneficial effects:

[0059] (1) The magnetic powder core provided by the present application has a uniform and stable insulating coating layer with high resistance.

[0060] (2) The process of secondary heat treatment, passivation modification and multi-layer coating makes the prepared magnetic powder core have good magnetic permeability, low loss and high DC superposition, etc. 3 For iron-silicon magnetic powder, the magnetic permeability is ≥75H / m, the DC superposition is ≥63%, and the loss is ≤742Kw / m 3 For iron-silicon-aluminum powder, the magnetic permeability is ≥64H / m, the DC superposition is ≥58%, and the loss is ≤220Kw / m 3 For iron-nickel powder, the magnetic permeability is ≥70H / m, the DC superposition is ≥65%, and the loss is ≤248Kw / m . DETAILED DESCRIPTION

[0061] To better illustrate the present application and facilitate understanding of the technical solutions of the present application, the typical but non-limiting embodiments of the present application are as follows:

[0062] Example 1

[0063] The present embodiment provides a preparation method of a low-loss and high-DC-bias magnetic powder core, which comprises the following steps:

[0064] (1) First mix the magnetic powder, phosphoric acid, silicone resin and solvent A, then sequentially perform first heat preservation stirring and first heat treatment, and screen to obtain intermediate powder;

[0065] (2) Second mix the chromic acid, solvent B and the intermediate powder obtained in step (1), then add water glass and adhesive after third mixing, and dry to obtain insulating magnetic powder;

[0066] (3) Fourth mix the insulating magnetic powder obtained in step (2) and release agent, then sequentially perform molding and second heat treatment to obtain a low-loss and high-DC-bias magnetic powder core;

[0067] The magnetic powder in step (1) is a cluster of particles with a particle size of 20-40 μm, and the magnetic powder is a Fe-Si magnetic powder with a mass percentage of 96.5% of Fe, 3.4% of Si, and the balance of other metals (Al, Ni, Cr, and Mn); the added amount of the phosphoric acid is 0.3% of the mass of the magnetic powder; the added amount of the organic silicon resin is 0.6% of the mass of the magnetic powder; the added amount of the organic solvent is 7% of the mass of the magnetic powder; the organic silicon resin is a methyl phenyl silicon resin; the solvent A is ethanol; the temperature of the first heat preservation and stirring is 126°C, the time is 27 min, and the stirring speed is 114 r / min; the temperature of the first heat treatment is 800°C, the time is 2.1 h, and the heat treatment is performed in a nitrogen atmosphere; and the particle size of the obtained intermediate powder is 42-72 μm.

[0068] The added amount of the chromic acid in step (2) is 0.5% of the mass of the intermediate powder; the added amount of the solvent B is 3% of the mass of the intermediate powder, and the solvent B is water; the added amount of the water glass (with a modulus of 2.2) is 0.5% of the mass of the intermediate powder; and the added amount of the binder is 1% of the mass of the intermediate powder, and the binder is a silicon resin solution.

[0069] The added amount of the release agent in step (3) is 0.2% of the mass of the insulating magnetic powder, and the release agent is talc; the pressure of the molding is 1200 MPa; the temperature of the second heat treatment is 660°C, the time is 90 min, and the heat treatment is performed in a helium atmosphere.

[0070] The performance of the obtained magnetic powder core is shown in Table 1.

[0071] Example 2

[0072] The embodiment provides a preparation method of a low-loss and high-DC-bias magnetic powder core, and the preparation method comprises the following steps:

[0073] (1) first mixing a magnetic powder, phosphoric acid, an organic silicon resin, and a solvent A, and then sequentially performing first heat preservation and stirring and first heat treatment to obtain an intermediate powder through screening;

[0074] (2) second mixing chromic acid, a solvent B, and the intermediate powder obtained in step (1), and then adding a water glass and a binder to obtain an insulating magnetic powder through third mixing and drying;

[0075] (3) fourth mixing the insulating magnetic powder obtained in step (2) and a release agent, and then sequentially performing molding and second heat treatment to obtain a low-loss and high-DC-bias magnetic powder core;

[0076] The particle size of the magnetic powder in step (1) is 40-70 μm, the magnetic powder is Fe-Si magnetic powder, and the Fe-Si magnetic powder contains 96.5% of Fe, 3.4% of Si, and the balance of other metals (Al, Ni, Cr and Mn) by mass percentage; the adding amount of the phosphoric acid is 0.2% of the mass of the magnetic powder; the adding amount of the organic silicon resin is 0.7% of the mass of the magnetic powder; the adding amount of the organic solvent is 8% of the mass of the magnetic powder; the organic silicon resin is methyl silicon resin; the solvent A is acetone; the temperature of the first heat preservation and stirring is 120°C, the time is 30 min, and the stirring speed is 100 r / min; the temperature of the first heat treatment is 780°C, the time is 2 h, and the heat treatment is carried out in neon atmosphere; and the particle size of the obtained intermediate powder is 15-40 μm.

[0077] The adding amount of the chromic acid in step (2) is 0.1% of the mass of the intermediate powder; the adding amount of the solvent B is 4% of the mass of the intermediate powder, and the solvent B is water; the adding amount of the water glass (modulus is 2.2) is 0.2% of the mass of the intermediate powder; and the adding amount of the binder is 2% of the mass of the intermediate powder, and the binder is silicon resin solution.

[0078] The adding amount of the release agent in step (3) is 0.1% of the mass of the insulating magnetic powder, and the release agent is mica powder; the pressure of the molding is 2000 MPa; the second heat treatment is carried out in nitrogen atmosphere; the temperature of the second heat treatment is 800°C, and the time is 30 min.

[0079] The performance of the obtained magnetic powder core is shown in Table 1.

[0080] Example 3

[0081] The embodiment provides a preparation method of a low-loss and high-DC-bias magnetic powder core, and the preparation method comprises the following steps:

[0082] (1) first mixing magnetic powder, phosphoric acid, organic silicon resin and solvent A, then sequentially carrying out first heat preservation and stirring and first heat treatment, and screening to obtain intermediate powder;

[0083] (2) second mixing chromic acid, solvent B and the intermediate powder obtained in step (1), then adding water glass and binder, third mixing, and drying to obtain insulating magnetic powder;

[0084] (3) fourth mixing the insulating magnetic powder obtained in step (2) and release agent, then sequentially carrying out molding and second heat treatment to obtain a low-loss and high-DC-bias magnetic powder core;

[0085] The particle size of the magnetic powder in step (1) is 20-50 μm, and the magnetic powder is FeSiAl powder, specifically, the composition is Fe 91.8%, Si 5.1%, Al 3.0%, and the balance is other metals (Cr, Ni, Mg and Mn); the addition amount of the phosphoric acid is 0.5% of the mass of the magnetic powder; the addition amount of the organic silicon resin is 1% of the mass of the magnetic powder; the addition amount of the organic solvent is 7.5% of the mass of the magnetic powder; the organic silicon resin is methyl phenyl silicon resin; the solvent A is methanol; the temperature of the first heat preservation and stirring is 130°C, the time is 20 min, and the stirring speed is 120 r / min; the temperature of the first heat treatment is 820°C, the time is 2.2 h, and the heat treatment is carried out in a helium atmosphere; and the particle size of the obtained intermediate powder is 22-50 μm;

[0086] The addition amount of the chromic acid in step (2) is 0.3% of the mass of the intermediate powder; the addition amount of the solvent B is 3.7% of the mass of the intermediate powder, and the solvent B is water; the addition amount of the water glass (modulus is 2.2) is 0.3% of the mass of the intermediate powder; and the addition amount of the binder is 1.4% of the mass of the intermediate powder, and the binder is a silicon resin solution.

[0087] The addition amount of the release agent in step (3) is 0.3% of the mass of the insulating magnetic powder, and the release agent is calcium stearate; the pressure of the molding is 1000 MPa; the second heat treatment is carried out in a hydrogen atmosphere; the temperature of the second heat treatment is 750°C, and the time is 50 min.

[0088] The performance of the obtained magnetic powder core is shown in Table 1.

[0089] Example 4

[0090] The embodiment provides a preparation method of a low-loss and high-DC-bias magnetic powder core, and the preparation method comprises the following steps:

[0091] (1) first mixing magnetic powder, phosphoric acid, organic silicon resin and solvent A, and then sequentially carrying out first heat preservation and stirring and first heat treatment to obtain an intermediate powder through screening;

[0092] (2) second mixing chromic acid, solvent B and the intermediate powder obtained in step (1), then adding water glass and a binder to obtain an insulating magnetic powder through third mixing and drying;

[0093] (3) fourth mixing the insulating magnetic powder obtained in step (2) and a release agent, and then sequentially carrying out molding and second heat treatment to obtain a low-loss and high-DC-bias magnetic powder core;

[0094] The particle size of the magnetic powder in step (1) is 30-60 μm, and the magnetic powder is Fe-Ni powder, specifically, Fe 51.1%, Ni 48.8%, and the balance is other elements (Si and Cr); the amount of phosphoric acid added is 0.4% of the mass of the magnetic powder; the amount of organic silicon resin added is 0.1% of the mass of the magnetic powder; the amount of organic solvent added is 7.4% of the mass of the magnetic powder; the organic silicon resin is a mixture of methyl silicon resin and methyl phenyl silicon resin in a mass ratio of 1:1; the solvent A is butanol; the temperature of the first heat treatment is 123°C, the time is 23 min, and the stirring degree is 117 r / min; the temperature of the first heat treatment is 810°C, and the time is 2.13 h; and the particle size of the obtained intermediate powder is 32-63 μm.

[0095] The amount of chromic acid added in step (2) is 0.4% of the mass of the intermediate powder; the amount of solvent B added is 3.2% of the mass of the intermediate powder, and the solvent B is water; the amount of water glass added is 0.1% of the mass of the intermediate powder; and the amount of binder added is 1.7% of the mass of the intermediate powder, and the binder is a silicon resin solution.

[0096] The amount of release agent added in step (3) is 0.15% of the mass of the insulating magnetic powder, and the release agent is a mixture of zinc stearate and talc in a mass ratio of 1:1; the pressure of the molding is 1700 MPa; the second heat treatment is carried out in a hydrogen atmosphere; the temperature of the second heat treatment is 700°C, and the time is 70 min.

[0097] The performance of the obtained magnetic powder core is shown in Table 1.

[0098] Example 5

[0099] The difference between Example 1 and the present example is that the order of steps (1) and (2) is changed, i.e., the magnetic powder is subjected to step (2) and then the obtained material is subjected to step (1). The performance of the obtained magnetic powder core is shown in Table 1.

[0100] Example 6

[0101] The difference between Example 1 and the present example is that the phosphoric acid in step (1) is replaced by an equal amount and concentration of nitric acid. The performance of the obtained magnetic powder core is shown in Table 1.

[0102] Example 7

[0103] The difference between Example 1 and the present example is that the chromic acid in step (2) is replaced by an equal amount and concentration of phosphoric acid. The performance of the obtained magnetic powder core is shown in Table 1.

[0104] Example 8

[0105] The difference from Example 1 is only that the heat treatment of step (1) is set after the drying of step (2). The performance of the obtained magnetic powder core is shown in Table 1.

[0106] Example 9

[0107] The difference from Example 1 is only that the phosphoric acid of step (1) is replaced by an equal amount of chromic acid, and the chromic acid of step (2) is replaced by an equal amount of phosphoric acid. The performance of the obtained magnetic powder core is shown in Table 1.

[0108] Example 10

[0109] The difference from Example 1 is only that the heat treatment of step (1) is not performed. The performance of the obtained magnetic powder core is shown in Table 1.

[0110] Example 11

[0111] The difference from Example 1 is only that the silicone resin of step (1) is replaced by an equal amount and concentration of silane coupling agent KH550. The performance of the obtained magnetic powder core is shown in Table 1.

[0112] Example 12

[0113] The difference from Example 1 is only that the water glass of step (2) is replaced by an equal amount and concentration of silane coupling agent KH550. The performance of the obtained magnetic powder core is shown in Table 1.

[0114] Example 13

[0115] The difference from Example 2 is only that the temperature of the first heat treatment is 800°C, the time is 2.1 h, the addition amount of phosphoric acid is 0.3% of the mass of the magnetic powder, the addition amount of the silicone resin is 0.7% of the mass of the magnetic powder, and the temperature of the second heat treatment is 720°C, and the time is 45 min. The performance of the obtained magnetic powder core is shown in Table 1.

[0116] Example 14

[0117] The difference from Example 2 is only that the temperature of the first heat treatment is 800°C, the time is 2.1 h, the addition amount of phosphoric acid is 0.3% of the mass of the magnetic powder, the addition amount of the silicone resin is 0.7% of the mass of the magnetic powder, and the temperature of the second heat treatment is 720°C, and the time is 45 min. The performance of the obtained magnetic powder core is shown in Table 1.

[0118] Example 15

[0119] The difference from Example 3 is that the addition amount of the silicone resin is 0.6% of the mass of the magnetic powder; the addition amount of the organic solvent is 7.3% of the mass of the magnetic powder; the addition amount of the water glass is 0.3% of the mass of the intermediate powder; the addition amount of the binder is 1.4% of the mass of the intermediate powder, and the binder comprises a silicone resin solution; and the performance of the obtained magnetic powder core is shown in Table 1.

[0120] Example 16

[0121] The difference from Example 3 is that the temperature of the first heat treatment is 801℃, the time is 2h, the addition amount of the release agent is 0.21% of the mass of the insulating magnetic powder, the second heat treatment is carried out in a nitrogen atmosphere; the temperature of the second heat treatment is 781℃, and the time is 43min; and the performance of the obtained magnetic powder core is shown in Table 1.

[0122] Example 17

[0123] The difference from Example 4 is that the addition amount of the phosphoric acid is 0.34% of the mass of the magnetic powder; the addition amount of the silicone resin is 0.85% of the mass of the magnetic powder; the addition amount of the organic solvent is 7.6% of the mass of the magnetic powder; the addition amount of the chromic acid is 0.26% of the mass of the intermediate powder; the addition amount of the solvent B is 3.4% of the mass of the intermediate powder; and the addition amount of the water glass is 0.47% of the mass of the intermediate powder. The performance of the obtained magnetic powder core is shown in Table 1.

[0124] Example 18

[0125] The difference from Example 4 is that the addition amount of the phosphoric acid is 0.34% of the mass of the magnetic powder; the addition amount of the chromic acid is 0.25% of the mass of the intermediate powder; and the forming pressure is 1178MPa. The performance of the obtained magnetic powder core is shown in Table 1.

[0126] In the above examples, other metal elements contained in the magnetic powder are elements inevitably introduced in the raw materials during preparation, and do not affect the performance improvement in the present application.

[0127] Table 1

[0128]

[0129]

[0130] In the above examples, the magnetic permeability of the magnetic powder core and the direct current superposition performance under 100Oe are tested under the test conditions of 100kHz and 1V; and the loss of the magnetic powder core is tested under the test conditions of 50kHz, 100mT and 25℃.

[0131] From the results of the above examples, the preparation method provided by the application ensures the stability and uniformity of the insulation layer and reduces the adverse effect of the coating layer on the soft magnetic performance by specific design of the coating process, inorganic-organic multilayer coating and multiple coating insulation coating method. Meanwhile, the specific sequence of phosphoric acid and chromic acid is used for surface passivation modification coating in the surface passivation modification, which improves the soft magnetic performance of the material, and with the help of specific twice heat treatment process, the magnetic core with high permeability, good DC superposition performance and low loss is finally prepared.

[0132] It is declared that the detailed structural features of the application are illustrated by the above examples, but the application is not limited to the above detailed structural features, that is, it does not mean that the application must rely on the above detailed structural features to be implemented. It should be understood by those skilled in the art that any improvement of the application, equivalent replacement of the components selected by the application and increase of auxiliary components, selection of specific modes, etc. fall within the protection scope and disclosure scope of the application.

[0133] The preferred embodiments of the application are described in detail above, but the application is not limited to the specific details in the above embodiments, and within the technical concept scope of the application, the technical solutions of the application can be subjected to various simple modifications, and these simple modifications all belong to the protection scope of the application.

[0134] In addition, it should be noted that each specific technical feature described in the above specific embodiments can be combined in any appropriate manner without contradiction, and in order to avoid unnecessary repetition, the application will not further describe various possible combination manners.

[0135] In addition, various different embodiments of the application can also be combined in any manner, as long as it does not deviate from the idea of the application, and it should be considered as the disclosed content of the application.

Claims

1. A method for preparing a low-loss and high DC bias magnetic powder core, characterized in that, The preparation method includes the following steps: (1) The magnetic powder, phosphoric acid, organosilicon resin and solvent A are mixed in the first mixture, followed by the first heat preservation and stirring and the first heat treatment, and the intermediate powder is obtained by sieving. (2) Chromic acid, solvent B and the intermediate powder obtained in step (1) are mixed for the second time, then water glass and binder are added and mixed for the third time, and then dried to obtain insulating magnetic powder; (3) The insulating magnetic powder and the release agent obtained in step (2) are mixed for the fourth time, and then subjected to molding and second heat treatment in sequence to obtain a low-loss and high DC bias magnetic powder core. The amount of phosphoric acid added in step (1) is 0.1-0.5% of the mass of the magnetic powder; the amount of chromic acid added in step (2) is 0.1-0.5% of the mass of the intermediate powder.

2. The preparation method according to claim 1, characterized in that, The particle size of the magnetic powder in step (1) is <74μm.

3. The preparation method according to claim 1, characterized in that, The magnetic powder in step (1) includes one or a combination of at least two of the following: iron powder, iron-silicon powder, iron-silicon-aluminum powder, iron-nickel powder, or iron-silicon-nickel powder.

4. The preparation method according to claim 1, characterized in that, The amount of silicone resin added in step (1) is 0.1-1% of the mass of the magnetic powder.

5. The preparation method according to claim 1, characterized in that, In step (1), the amount of solvent A added is 7-8% of the mass of the magnetic powder.

6. The preparation method according to claim 1, characterized in that, The organosilicon resin in step (1) includes methyl silicone resin and / or methylphenyl silicone resin.

7. The preparation method according to claim 1, characterized in that, The solvent A in step (1) includes one or a combination of at least two of methanol, butanol or acetone.

8. The preparation method according to claim 1, characterized in that, Step (1) The temperature of the first heat preservation and stirring is 120-130℃.

9. The preparation method according to claim 1, characterized in that, Step (1) The first heat preservation and stirring time is 20-30 minutes.

10. The preparation method according to claim 1, characterized in that, Step (1) The stirring speed of the first heat preservation stirring is 100-120 r / min.

11. The preparation method according to claim 1, characterized in that, Step (1) The first heat treatment is carried out under a protective atmosphere.

12. The preparation method according to claim 1, characterized in that, Step (1) The temperature of the first heat treatment is 780-820℃.

13. The preparation method according to claim 1, characterized in that, Step (1) The first heat treatment time is 2-2.2h.

14. The preparation method according to claim 1, characterized in that, The particle size of the intermediate powder obtained in step (1) is 28-74 μm.

15. The preparation method according to claim 1, characterized in that, In step (2), the solvent B is added at 3-4% of the mass of the intermediate powder.

16. The preparation method according to claim 1, characterized in that, The solvent B in step (2) includes water.

17. The preparation method according to claim 1, characterized in that, The amount of water glass added in step (2) is 0.1-0.5% of the mass of the intermediate powder.

18. The preparation method according to claim 1, characterized in that, The amount of binder added in step (2) is 1-2% of the mass of the intermediate powder.

19. The preparation method according to claim 1, characterized in that, The adhesive in step (2) includes a silicone resin solution.

20. The preparation method according to claim 1, characterized in that, The amount of the release agent added in step (3) is 0.1-0.3% of the mass of the insulating magnetic powder.

21. The preparation method according to claim 1, characterized in that, The release agent in step (3) includes one or a combination of at least two of zinc stearate, calcium stearate, talc or mica.

22. The preparation method according to claim 1, characterized in that, The molding pressure in step (3) is 1000-2000 MPa.

23. The preparation method according to claim 1, characterized in that, Step (3) The second heat treatment is carried out under a protective atmosphere or a reducing atmosphere.

24. The preparation method according to claim 1, characterized in that, In step (3), the temperature of the second heat treatment is 600-800℃.

25. The preparation method according to claim 1, characterized in that, The heat treatment time in step (3) is 30-90 min.

26. The preparation method according to claim 1, characterized in that, The preparation method includes the following steps: (1) The magnetic powder, phosphoric acid, organosilicon resin and solvent A are mixed in the first mixture, followed by the first heat preservation and stirring and the first heat treatment, and the intermediate powder is obtained by sieving. (2) Chromic acid, solvent B and the intermediate powder obtained in step (1) are mixed for the second time, then water glass and binder are added and mixed for the third time, and then dried to obtain insulating magnetic powder; (3) The insulating magnetic powder and the release agent obtained in step (2) are mixed for the fourth time, and then subjected to molding and second heat treatment in sequence to obtain a low-loss and high DC bias magnetic powder core. The magnetic powder in step (1) has a particle size <74μm, and the magnetic powder includes one or a combination of at least two of the following: iron powder, iron-silicon powder, iron-silicon-aluminum powder, iron-nickel powder, or iron-silicon-nickel powder; the amount of phosphoric acid added is 0.1-0.5% of the mass of the magnetic powder; the amount of organosilicon resin added is 0.1-1% of the mass of the magnetic powder; the amount of organic solvent added is 7-8% of the mass of the magnetic powder; the organosilicon resin includes methyl silicone resin and / or methylphenyl silicone resin; solvent A includes one or a combination of at least two of the following: methanol, butanol, or acetone; the temperature of the first heat treatment is 120-130℃, the time is 20-30min, and the stirring speed is 100-120r / min; the temperature of the first heat treatment is 780-820℃, the time is 2-2.2h, and it is carried out under a protective atmosphere; the particle size of the resulting intermediate powder is 28-74μm. In step (2), the amount of chromic acid added is 0.1-0.5% of the mass of the intermediate powder; the amount of solvent B added is 3-4% of the mass of the intermediate powder, and solvent B includes water; the amount of water glass added is 0.1-0.5% of the mass of the intermediate powder; and the amount of binder added is 1-2% of the mass of the intermediate powder, and the binder is a silicone resin solution. The amount of the release agent added in step (3) is 0.1-0.3% of the mass of the insulating magnetic powder. The release agent includes one or a combination of at least two of zinc stearate, calcium stearate, talc, or mica powder. The molding pressure is 1000-2000 MPa. The second heat treatment is carried out in a protective atmosphere or a reducing atmosphere. The temperature of the second heat treatment is 600-800℃ and the time is 30-90 min.

27. A low-loss and high DC bias magnetic powder core, characterized in that, The low-loss and high DC bias magnetic powder core is prepared by the preparation method according to any one of claims 1-26.

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