阅读说明：本技术 一种软磁复合粉末、软磁粉芯及其制备方法 (Soft magnetic composite powder, soft magnetic powder core and preparation method thereof ) 是由 董亚强 龚梦吉 黎嘉威 贺爱娜 于 2021-06-30 设计创作，主要内容包括：本发明提供一种软磁复合粉末、软磁粉芯及其制备方法,该软磁复合粉末包括软磁粉末、氧化镁和有机粘结剂,所述氧化镁包覆所述软磁粉末形成绝缘包覆层,所述有机粘结剂包覆所述绝缘包覆层形成有机包覆层。发明的软磁复合粉末具有多层包覆结构,氧化镁形成无机绝缘包覆层,其具有耐高温、热导率高、高电阻率的性能,能够改善软磁粉芯散热性能,在氧化镁外部再包覆有机粘结剂形成有机包覆层,能够降低损耗,提高抗氧化、耐腐蚀性能,由此该软磁复合粉末具有很好的直流偏置性能,能满足更大电流应用环境,且具有很好的散热性,对软磁粉芯元件发热问题有很好的改善效果。(The invention provides soft magnetic composite powder, a soft magnetic powder core and a preparation method thereof. The soft magnetic composite powder has a multilayer coating structure, the magnesium oxide forms an inorganic insulating coating layer, the soft magnetic composite powder has the performances of high temperature resistance, high thermal conductivity and high resistivity, the heat dissipation performance of a soft magnetic powder core can be improved, and the organic binding agent is coated outside the magnesium oxide to form an organic coating layer, so that the loss can be reduced, the oxidation resistance and the corrosion resistance can be improved, the soft magnetic composite powder has good direct current bias performance, can meet the application environment of larger current, has good heat dissipation performance, and has a good improvement effect on the heating problem of a soft magnetic powder core element.)

1. The soft magnetic composite powder is characterized by comprising soft magnetic powder, magnesium oxide and an organic binder, wherein the magnesium oxide coats the soft magnetic powder to form an insulating coating layer, and the organic binder coats the insulating coating layer to form an organic coating layer.

2. Soft magnetic composite powder according to claim 1, characterised in that the mass of the magnesium oxide is 0.01-10% of the mass of the soft magnetic powder.

3. Soft magnetic composite powder according to claim 1, characterised in that the soft magnetic powder is selected from one or several of the group consisting of ferro silicon chromium powder, carbonyl iron powder, ferro silicon aluminium powder, amorphous powder, nanocrystalline powder, ferro nickel molybdenum powder.

4. Soft magnetic composite powder according to claim 1, characterized in that the particle size of the soft magnetic powder is in the range of-100 mesh to +1000 mesh.

5. Soft magnetic composite powder according to claim 1, characterized in that the organic binder is selected from one or several of epoxy resins, silicone resins, polyvinyl alcohols, phenolic resins.

6. A method for preparing a soft magnetic composite powder according to claim 1, comprising the steps of:

s1, dissolving magnesium acetate in absolute ethyl alcohol in the container A, adding the soft magnetic powder, and stirring to uniformly disperse the soft magnetic powder in the solution;

s2, dissolving oxalic acid in absolute ethyl alcohol to prepare an oxalic acid-ethanol solution, dripping the oxalic acid-ethanol solution into a continuously stirred container A, performing suction filtration after full reaction, and drying to obtain soft magnetic powder coated with a magnesium oxide precursor;

s3, carrying out vacuum annealing on the soft magnetic powder coated with the magnesium oxide precursor at high temperature to obtain the soft magnetic powder coated with magnesium oxide;

and S4, coating the magnesium oxide coated soft magnetic powder by using an organic binder to obtain the soft magnetic composite powder.

7. The method for preparing a soft magnetic composite powder according to claim 6, wherein in the step S1, the mass of magnesium acetate is 1-20% of the mass of absolute ethyl alcohol, and in the step 2, the molar ratio of oxalic acid to magnesium acetate is greater than or equal to 1.

8. The method for preparing a soft magnetic composite powder according to claim 6, wherein the vacuum annealing temperature in the step 3 is 450 to 750 ℃.

9. A soft magnetic powder core obtained by press-molding the soft magnetic composite powder according to claim 1 after adding a lubricant thereto and annealing the molded product.

10. The soft magnetic powder core according to claim 9, wherein said soft magnetic composite powder comprises soft magnetic powder, and said lubricant is present in an amount of 0.5% to 5% by mass of said soft magnetic powder.

Technical Field

The invention relates to the technical field of soft magnetic materials, in particular to soft magnetic composite powder, a soft magnetic powder core and a preparation method thereof.

Background

In the era of rapid development of electronic information technology, soft magnetic materials become one of indispensable materials in electronic devices due to unique electromagnetic conversion characteristics, and molded inductors serve as important application fields of the soft magnetic materials, better meet the development trend of miniaturization trend of the electronic devices, and are widely applied to electronic devices such as circuit boards, notebook computers, DC-DC converters and the like at present. The induced electromotive force generation circuit has the functions of filtering, oscillating, delaying, trapping and the like in the circuit, has the functions of direct current passing and alternating current blocking, is mainly applied to BUCK and BOOST circuits, generates the change of induced electromotive force at two ends of an inductor through the change of the magnetic flux of the inductor, and generates voltage boosting or voltage reduction by matching the induced electromotive force with other voltages in the circuit. With the emergence of the rapid charging technology, a power supply tends to develop at high frequency, low voltage and large current, and the die pressing inductance requires that soft magnetic powder has higher saturation magnetic induction Bs and more excellent direct current bias performance so as to meet the application environment of large current; meanwhile, the soft magnetic powder core inductor is required to have higher resistivity and faster heat dissipation capability so as to adapt to megahertz (MHz) high-frequency working conditions and relieve the phenomenon of serious heating of an inductor element.

The soft magnetic powder disclosed in the prior art cannot meet the requirements of die-pressing inductance, such as:

chinese patent publication No. CN104028751B discloses a high-insulation coating treatment method for a metal soft magnetic composite material. The method adopts ethylene glycol magnesium as a magnesium source, and prepares the magnesium oxide layer by a sol-gel method, but the process is complex and harsh, and is not beneficial to batch production, and the prepared soft magnetic composite material has poor heat dissipation performance and large loss.

Chinese patent publication No. CN10324740B discloses a method for preparing a metal soft magnetic composite material, which uses nano oxide dispersion liquid to perform insulation coating on metal magnetic powder. The method has the problems of poor dispersion stability and poor adhesion of nano particles to magnetic powder, and the prepared soft magnetic powder has poor insulation, improved direct current bias performance and increased loss.

Disclosure of Invention

Aiming at the defects of the prior art, the invention mainly aims to provide the soft magnetic composite powder for the die pressing inductor with high direct current bias and quick heat dissipation, the soft magnetic powder core and the preparation method thereof.

In order to solve the above problems, a first aspect of the present invention provides a soft magnetic composite powder comprising a soft magnetic powder, magnesium oxide and an organic binder, wherein the magnesium oxide covers the soft magnetic powder to form an insulating covering layer, and the organic binder covers the insulating covering layer to form an organic covering layer.

Compared with the prior art, the soft magnetic composite powder has a multilayer coating structure, the magnesium oxide forms an inorganic insulating coating layer, the soft magnetic composite powder has the performances of high temperature resistance, high heat conductivity and high resistivity, the heat dissipation performance of a soft magnetic powder core can be improved, the organic binding agent is coated outside the magnesium oxide to form an organic coating layer, the loss can be reduced, and the oxidation resistance and the corrosion resistance can be improved.

Optionally, the mass of the magnesium oxide is 0.01% to 10% of the mass of the soft magnetic powder. The mass ratio of the magnesium oxide is controlled, different coating effects can be achieved, and the soft magnetic composite powder can obtain the required performance within the range.

Optionally, the soft magnetic powder has a particle size ranging from-100 mesh to +1000 mesh. The particle size affects the properties of the soft magnetic composite powder, and is limited in order to obtain a soft magnetic powder core having low loss, high dc bias properties, high magnetic permeability, and the like.

Optionally, the soft magnetic powder is selected from one or more of iron silicon chromium powder, carbonyl iron powder, iron silicon aluminum powder, amorphous powder, nanocrystalline powder, iron nickel powder and iron nickel molybdenum powder. The materials have better direct current bias performance, and one or more of the materials can be selected.

Optionally, the organic binder is selected from one or more of epoxy resin, silicone resin, polyvinyl alcohol and phenolic resin. The loss can be reduced by the coating insulating layer formed by the organic binder, and the material has good binding and coating performances and high resistivity, and one or more of the materials can be selected.

The second aspect of the present invention provides a method for producing a soft magnetic composite powder, for producing the above soft magnetic composite powder, comprising the steps of:

s1, dissolving magnesium acetate in absolute ethyl alcohol in the container A, adding the soft magnetic powder, and stirring to uniformly disperse the soft magnetic powder in the solution;

s2, dissolving oxalic acid in absolute ethyl alcohol to prepare an oxalic acid-ethanol solution, dripping the oxalic acid-ethanol solution into a continuously stirred container A, performing suction filtration after full reaction, and drying to obtain soft magnetic powder coated with a magnesium oxide precursor;

s3, carrying out vacuum annealing on the soft magnetic powder coated with the magnesium oxide precursor at high temperature to obtain the soft magnetic powder coated with magnesium oxide;

and S4, coating the magnesium oxide coated soft magnetic powder by using an organic binder to obtain the soft magnetic composite powder.

Compared with the prior art, the process steps are simple, particularly, the magnesium oxide coating process selects magnesium acetate and oxalic acid as coating layer preparation raw materials, the magnesium oxide precursor is coated on the surface of the soft magnetic powder through the combined action of a sol-gel method and a precipitation method, and then the precursor is converted into magnesium oxide through heat treatment.

Optionally, in the step S1, the mass of the magnesium acetate is 1% to 20% of the mass of the anhydrous ethanol, and in the step S2, the molar ratio of the oxalic acid to the magnesium acetate is greater than or equal to 1. The content of the magnesium source is controlled by controlling the addition amount of the magnesium acetate, the magnesium acetate can be ensured to be dissolved in the absolute ethyl alcohol, the smooth reaction is ensured, and the magnesium acetate in the absolute ethyl alcohol can be ensured to react completely by using the amount of the oxalic acid.

Optionally, in the step 3, the vacuum annealing temperature is 450-750 ℃. And controlling the vacuum annealing temperature to completely convert the magnesium oxide precursor into magnesium oxide, wherein the vacuum annealing temperature can influence the performance of the soft magnetic composite powder, and the soft magnetic composite powder with the required performance can be obtained by controlling the temperature.

In a third aspect, the present invention provides a soft magnetic powder core obtained by adding a lubricant to the soft magnetic composite powder, press-molding the mixture, and annealing the molded product.

Compared with the prior art, the soft magnetic powder core is mainly prepared from the soft magnetic composite powder, so that the soft magnetic powder core has higher direct current bias performance, can meet the requirement of a larger current application environment, has more excellent oxidation resistance and corrosion resistance, better heat dissipation and lower loss, and can be applied to molded inductors.

Optionally, the soft magnetic composite powder comprises soft magnetic powder, and the lubricant is 0.5-5% by mass of the soft magnetic powder. And a small amount of lubricant is added, so that the soft magnetic powder core is convenient to demould after being pressed and formed.

Drawings

FIG. 1 is a topographical view of a soft magnetic composite powder prepared in example 1 of the present invention;

FIG. 2 is a comparison graph of DC bias performance of a soft magnetic powder core with a double-layer cladding structure of magnesium oxide and epoxy resin combined and a soft magnetic powder core with a single-layer cladding structure of epoxy resin prepared in example 1 of the present invention;

FIG. 3 is a graph showing the comparison of the loss of the soft magnetic powder core with a single-layer coating structure of epoxy resin and a double-layer coating structure of magnesium oxide and epoxy resin prepared in example 1;

FIG. 4 is a graph comparing the oxidation and corrosion resistance of a soft magnetic powder core with a double-layer cladding structure and an epoxy resin single-layer cladding structure, which is prepared in example 1 of the present invention, and magnesium oxide and epoxy resin;

fig. 5 is a comparison graph of the heat dissipation performance of the soft magnetic powder core with the double-layer cladding structure and the soft magnetic powder core with the single-layer cladding structure of the epoxy resin, which are prepared in example 1 of the present invention, and the magnesium oxide and the epoxy resin are combined together.

Detailed Description

In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below. It should be noted that the following examples are only used to illustrate the implementation method and typical parameters of the present invention, and are not used to limit the scope of the parameters of the present invention, so that reasonable variations can be made and still fall within the protection scope of the claims of the present invention.

It is noted that the endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and that such ranges or values are understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.

The embodiment of the invention discloses soft magnetic composite powder which comprises soft magnetic powder, magnesium oxide and an organic binder, wherein the magnesium oxide coats the soft magnetic powder to form an insulating coating layer, and the organic binder coats the insulating coating layer to form an organic coating layer.

In the embodiment of the invention, the soft magnetic powder is selected from one or more of iron silicon chromium powder, carbonyl iron powder, iron silicon aluminum powder, amorphous powder, nanocrystalline powder, iron nickel powder and iron nickel molybdenum powder, and the materials have better direct current bias performance. The particle size of the soft magnetic powder affects the performance, and is limited to be-100 meshes to +1000 meshes in order to obtain a soft magnetic powder core with low loss, high direct current bias performance, high magnetic permeability and the like.

In the embodiment of the invention, the magnesium oxide forms the inorganic insulating coating, has the performances of high temperature resistance, high thermal conductivity and high resistivity, can improve the heat dissipation performance of the soft magnetic powder core, and increases the air gap in the soft magnetic powder core by the magnesium oxide insulating material, thereby enhancing the direct current bias performance. The content of magnesium oxide can produce different coating effects, and the mass of magnesium oxide is controlled to be 0.01-10%, preferably 1-8% of the mass of the soft magnetic powder, so that the soft magnetic composite powder can obtain the required performance.

In the embodiment of the invention, the magnesium oxide is coated with the organic binder to form the organic coating layer, so that the loss can be reduced, and the oxidation resistance and the corrosion resistance can be improved. The organic binder is selected from one or more of epoxy resin, organic silicon resin, polyvinyl alcohol and phenolic resin, and the material has good binding and coating properties and high resistivity.

The soft magnetic composite powder in the embodiment of the invention has a multilayer coating structure, can reduce loss, improve oxidation resistance and corrosion resistance, has good direct current bias performance, can meet a larger current application environment, also has good heat dissipation performance, and has a good improvement effect on the heating problem of a soft magnetic powder core element.

Another embodiment of the present invention discloses a method for preparing the above soft magnetic composite powder, comprising the steps of:

s1, dissolving magnesium acetate in absolute ethanol in the container a, adding the soft magnetic powder, and stirring to uniformly disperse the soft magnetic powder in the solution.

S2, dissolving oxalic acid in absolute ethyl alcohol to prepare an oxalic acid-ethanol solution, dripping the oxalic acid-ethanol solution into a container A which is continuously stirred, performing suction filtration after full reaction, and drying to obtain the soft magnetic powder coated with the magnesium oxide precursor.

And S3, carrying out vacuum annealing on the soft magnetic powder coated with the magnesium oxide precursor at high temperature to obtain the soft magnetic powder coated with the magnesium oxide.

And S4, coating the magnesium oxide coated soft magnetic powder by using an organic binder to obtain the soft magnetic composite powder.

The production method has simple process steps, particularly the magnesium oxide coating process selects magnesium acetate and oxalic acid as coating layer preparation raw materials, the magnesium oxide precursor is coated on the surface of the soft magnetic powder through the combined action of a sol-gel method and a precipitation method, and then the precursor is converted into magnesium oxide through heat treatment, so the coating effect is good, the reaction is safe and rapid, and the method is suitable for industrial production.

According to a preferred embodiment of the present invention, in step S1, the mass of magnesium acetate is 1% to 20% of the mass of absolute ethyl alcohol, so as to ensure that magnesium acetate can be dissolved in absolute ethyl alcohol, thereby enabling the reaction to occur and controlling the content of the magnesium source, so that the soft magnetic composite powder can obtain the desired properties.

According to a preferred embodiment of the invention, in step 2, the molar ratio of oxalic acid to magnesium acetate is greater than or equal to 1, and the quantity of oxalic acid is such as to ensure the completion of the reaction of the magnesium acetate in the absolute ethanol.

According to a preferred embodiment of the present invention, in step 3, the vacuum annealing temperature is 450 to 750 ℃, the vacuum annealing temperature is controlled to completely convert the magnesium oxide precursor into magnesium oxide, and the vacuum annealing temperature affects the performance of the soft magnetic composite powder, for example, the magnetic permeability is excellent at 500 ℃, the loss is low at 700 ℃, the dc bias performance is good, and the soft magnetic composite powder with the required performance can be obtained by controlling the temperature.

The invention also discloses a soft magnetic powder core, which comprises the soft magnetic composite powder and the lubricant in the embodiment, wherein the mass of the lubricant is 0.5-5% of the mass of the soft magnetic powder, the soft magnetic composite powder is pressed and formed after the lubricant is added, the lubricant is added for facilitating demoulding, the soft magnetic powder core is prepared after the powder core which is pressed and formed is annealed, the pressing and forming pressure is 400-800 MPa, and the annealing temperature is 200-400 ℃.

Compared with the prior art, the soft magnetic powder core has higher direct current bias performance, can meet the requirement of a larger current application environment, has more excellent oxidation resistance and corrosion resistance, better heat dissipation and lower loss, can be applied to a molded inductor, and has good application and popularization prospects.

The present invention will be described in detail below by way of specific examples. The shape, direct current bias performance, loss and oxidation corrosion resistance of the prepared soft magnetic powder core are tested according to the conventional testing method of the magnetic powder core, and the heat dissipation performance of the soft magnetic powder core is shown by testing the change of the temperature of the magnetic powder core along with time in the using process.

Example 1

In the embodiment, the raw material is iron-silicon-chromium soft magnetic powder with better magnetic permeability and saturation magnetic induction intensity, and the particle size of the powder D50 is 15 μm; the magnesium oxide accounts for 3% of the mass of the soft magnetic powder. The preparation method comprises the following steps:

s1, dissolving magnesium acetate in absolute ethyl alcohol, stirring and dissolving until the solution is clear and transparent, adding the iron-silicon-chromium soft magnetic powder, and continuing stirring to uniformly disperse the powder in the solution, wherein the process is completed in the container A. The mass of magnesium acetate was 15.96% of the mass of the soft magnetic powder.

S2, preparing an oxalic acid-ethanol solution, wherein the mass of oxalic acid is 9.38% of that of the soft magnetic powder, and the oxalic acid-ethanol solution is dissolved in absolute ethyl alcohol; dripping oxalic acid-ethanol solution into a container A which is continuously stirred to generate reaction, growing white granular substances on the surface of iron-silicon-chromium powder, and then continuously stirring the solution in the container A for 10 min; and carrying out suction filtration and drying on the substances in the container A to obtain the soft magnetic powder coated with the magnesium oxide precursor.

S3, annealing the soft magnetic powder coated with the magnesium oxide precursor in vacuum at 700 ℃ for 1h to obtain MgO-coated iron-silicon-chromium powder.

S4, dissolving epoxy resin in an acetone solution, adding MgO to coat the iron-silicon-chromium powder, and coating in the solution, wherein the mass of the epoxy resin is 1% of that of the iron-silicon-chromium powder, so as to obtain the soft magnetic composite powder, and the morphological structure of the soft magnetic composite powder is shown in figure 1.

S5, uniformly mixing the soft magnetic composite powder with zinc stearate with the mass of 0.5 percent of that of the iron-silicon-chromium powder, pressing and molding under 600MPa, and carrying out heat treatment at 200 ℃ to obtain a test sample of the soft magnetic powder core.

Through tests, the direct current bias performance of the soft magnetic powder core test sample prepared by the embodiment is 97% under an external field of 100 Oe; under the conditions of 100kHz and 100mT, the unit power loss P_cv＝2600mW/cm³. During the sample loss test, the maximum temperature was 21 ℃ and the temperature was raised by 2.5 ℃.

As shown in fig. 2 to 4, compared with the comparative sample of comparative example 1, the test sample of example 1 has better dc bias performance, less loss, lower temperature and temperature rise, better heat dissipation performance, lower corrosion degree under the same salt spray corrosion condition, and better corrosion resistance.

Example 2

In the embodiment, the raw material is iron-silicon soft magnetic powder with better magnetic permeability and lower loss, and the particle size D50 is 48 μm; the magnesium oxide accounts for 2% of the mass of the soft magnetic powder. The preparation method comprises the following steps:

s1, dissolving magnesium acetate in absolute ethyl alcohol, stirring and dissolving until the solution is clear and transparent, adding the iron-silicon soft magnetic powder, and continuing stirring to uniformly disperse the powder in the solution, wherein the process is completed in the container A. The mass of magnesium acetate was 10.64% of the mass of the soft magnetic powder.

S2, preparing an oxalic acid-ethanol solution, wherein the mass of oxalic acid is 6.25% of the mass of the soft magnetic powder, and the oxalic acid solution is dissolved in absolute ethyl alcohol; dripping oxalic acid-ethanol solution into a container A which is continuously stirred to generate reaction, growing white granular substances on the surface of the iron-silicon powder, and then continuously stirring the solution in the container A for 10 min; and carrying out suction filtration and drying on the substances in the container A to obtain the soft magnetic powder coated with the magnesium oxide precursor.

S3, annealing the soft magnetic powder coated with the magnesium oxide precursor in vacuum for 1h at 700 ℃ to obtain MgO-coated iron-silicon powder.

And S4, dissolving epoxy resin in an acetone solution, adding MgO coated iron-silicon powder, and coating in the solution, wherein the mass of the epoxy resin is 1% of that of the iron-silicon powder, so as to prepare the soft magnetic composite powder.

S5, uniformly mixing the soft magnetic composite powder with zinc stearate with the mass of 0.5 percent of that of the iron-silicon-chromium powder, pressing and molding under 800MPa, and carrying out heat treatment at 200 ℃ to obtain a soft magnetic powder core test sample.

Through tests, the direct current bias performance of the soft magnetic powder core test sample prepared by the embodiment is 71% under an external field of 100 Oe; under the conditions of 100kHz and 100mT, the unit power loss P_cv＝1300mW/cm³. Compared with the comparative sample of comparative example 2, the corrosion condition of the test sample is obviously improved under the same salt spray corrosion condition. During the sample loss test, the test sample had a lower temperature and a smaller temperature rise, with a maximum temperature of 20.5 ℃ and a temperature rise of only 2 ℃.

Example 3

In the embodiment, the raw material is FeSiBCCr amorphous soft magnetic powder with better loss, and the particle size D50 of the powder is 20 mu m; the mass of the magnesium oxide accounts for 1 percent of the mass of the magnetic powder. The preparation method comprises the following steps:

s1, dissolving magnesium acetate in absolute ethyl alcohol, stirring and dissolving until the solution is clear and transparent, adding FeSiBCCr amorphous soft magnetic powder, and continuing stirring to uniformly disperse the powder in the solution, wherein the process is completed in a container A. The mass of magnesium acetate was 5.32% of the mass of the soft magnetic powder.

S2, preparing an oxalic acid-ethanol solution, wherein the mass of oxalic acid is 3.13% of that of the magnetic powder, and the oxalic acid solution is dissolved in absolute ethyl alcohol; dripping oxalic acid-ethanol solution into a container A which is continuously stirred to generate reaction, growing white granular substances on the surface of FeSiBCCr amorphous soft magnetic powder, and then continuously stirring the solution in the container A for 10 min; and carrying out suction filtration and drying on the substances in the container A to obtain the soft magnetic powder coated with the magnesium oxide precursor.

S3, annealing the soft magnetic powder coated with the magnesium oxide precursor in vacuum for 1h at 500 ℃ to obtain MgO-coated FeSiBCCr amorphous soft magnetic powder.

S4, dissolving epoxy resin in acetone solution, adding MgO coated FeSiBCCr amorphous soft magnetic powder, and coating in the solution, wherein the mass of the epoxy resin is 1% of the mass of the soft magnetic powder, thus preparing the soft magnetic composite powder.

S5, uniformly mixing the soft magnetic composite powder with zinc stearate with the mass of 0.5 percent of that of the iron-silicon-chromium powder, pressing and molding under 600MPa, and carrying out heat treatment at 200 ℃ to obtain a test sample of the soft magnetic powder core.

Through tests, the direct current bias performance of the soft magnetic powder core test sample prepared by the embodiment is 68% under an external field of 100 Oe; under the condition of 100kHz and 50mT, the unit power loss P_cv481.8mW/cm 3. Compared with the comparative sample of comparative example 3, the corrosion condition of the test sample is obviously improved under the same salt spray corrosion condition. Meanwhile, in the sample loss test process, the test sample has lower temperature and smaller temperature rise, the maximum temperature is 20 ℃, and the temperature rise is only 1.5 ℃.

Example 4

In the present example, carbonyl iron powder was selected as the raw material, and the particle size D50 of the powder was 100 μm; the mass of the magnesium oxide accounts for 5 percent of the mass of the magnetic powder. The preparation method comprises the following steps:

s1, dissolving magnesium acetate in absolute ethyl alcohol, wherein the mass of the magnesium acetate is 20% of that of the absolute ethyl alcohol, stirring and dissolving until the solution is clear and transparent, adding carbonyl iron powder, and continuously stirring to uniformly disperse the powder in the solution, wherein the process is completed in a container A.

S2, preparing an oxalic acid-ethanol solution, dripping the oxalic acid-ethanol solution into a container A which is continuously stirred to generate reaction, growing white granular substances on the surface of carbonyl iron powder, and continuously stirring the solution in the container A for 10 min; and carrying out suction filtration and drying on the substances in the container A to obtain the soft magnetic powder coated with the magnesium oxide precursor.

S3, carrying out vacuum annealing on the soft magnetic powder coated with the magnesium oxide precursor for 1.5h at 500 ℃ to obtain MgO-coated carbonyl iron powder.

S4, dissolving organic silicon resin in acetone solution, adding MgO coated carbonyl iron powder, and coating in the solution, wherein the mass of the organic silicon resin is 1% of that of the soft magnetic powder, thus preparing the soft magnetic composite powder.

S5, uniformly mixing the soft magnetic composite powder with zinc stearate accounting for 1 percent of the mass of the iron-silicon-chromium powder, pressing and molding under 500MPa, and carrying out heat treatment at 300 ℃ to obtain the soft magnetic powder core.

Example 5

In the embodiment, the raw material is iron-silicon-aluminum powder, and the particle size D50 of the powder is 150 μm; the mass of the magnesium oxide accounts for 10 percent of the mass of the magnetic powder. The preparation method comprises the following steps:

s1, dissolving magnesium acetate in absolute ethyl alcohol, wherein the mass of the magnesium acetate is 10% of that of the absolute ethyl alcohol, stirring and dissolving until the solution is clear and transparent, adding the ferrosilicon aluminum powder, and continuing stirring to uniformly disperse the powder in the solution, wherein the process is completed in the container A.

S2, preparing an oxalic acid-ethanol solution, dripping the oxalic acid-ethanol solution into a container A which is continuously stirred to generate reaction, growing white granular substances on the surface of the sendust powder, and continuously stirring the solution in the container A for 10 min; and carrying out suction filtration and drying on the substances in the container A to obtain the soft magnetic powder coated with the magnesium oxide precursor.

And S3, carrying out vacuum annealing on the soft magnetic powder coated with the magnesium oxide precursor for 0.5h at 750 ℃ to obtain MgO-coated iron-silicon-aluminum powder.

And S4, dissolving polyvinyl alcohol in an acetone solution, adding MgO-coated iron-silicon-aluminum powder, and coating in the solution, wherein the mass of the polyvinyl alcohol is 2% of that of the soft magnetic powder, so as to prepare the soft magnetic composite powder.

S5, uniformly mixing the soft magnetic composite powder with zinc stearate accounting for 5 percent of the mass of the iron-silicon-chromium powder, pressing and molding under 400MPa, and carrying out heat treatment at 400 ℃ to obtain the soft magnetic powder core.

Example 6

In this example, nanocrystalline powder was used as the raw material, and the particle size D50 of the powder was 13 μm; the mass of the magnesium oxide accounts for 0.1 percent of the mass of the magnetic powder. The preparation method comprises the following steps:

s1, dissolving magnesium acetate in absolute ethyl alcohol, wherein the mass of the magnesium acetate is 1% of that of the absolute ethyl alcohol, stirring and dissolving until the solution is clear and transparent, adding nanocrystalline powder, and continuing stirring to uniformly disperse the powder in the solution, wherein the process is completed in a container A.

S2, preparing an oxalic acid-ethanol solution, dripping the oxalic acid-ethanol solution into a container A which is continuously stirred to generate reaction, growing a white granular substance on the surface of the nanocrystalline powder, and continuously stirring the solution in the container A for 10 min; and carrying out suction filtration and drying on the substances in the container A to obtain the soft magnetic powder coated with the magnesium oxide precursor.

S3, annealing the soft magnetic powder coated with the magnesium oxide precursor in vacuum for 2h at 450 ℃ to obtain MgO-coated nanocrystalline powder.

S4, dissolving phenolic resin in acetone solution, adding MgO coated nanocrystalline powder, and coating in the solution, wherein the mass of the epoxy resin is 3% of that of the soft magnetic powder, so as to obtain the soft magnetic composite powder.

S5, uniformly mixing the soft magnetic composite powder with zinc stearate accounting for 2 percent of the mass of the iron-silicon-chromium powder, pressing and molding under 700MPa, and carrying out heat treatment at 350 ℃ to obtain the soft magnetic powder core.

Example 7

In the embodiment, iron-nickel powder is selected as the raw material, and the particle size of the iron-nickel powder D50 is 25 μm; the mass of the magnesium oxide accounts for 6 percent of the mass of the magnetic powder. The preparation method comprises the following steps:

s1, dissolving magnesium acetate in absolute ethyl alcohol, wherein the mass of the magnesium acetate is 15% of that of the absolute ethyl alcohol, stirring and dissolving until the solution is clear and transparent, adding iron-nickel powder, and continuing stirring to uniformly disperse the powder in the solution, wherein the process is completed in a container A.

S2, preparing an oxalic acid-ethanol solution, dripping the oxalic acid-ethanol solution into a container A which is continuously stirred to generate reaction, growing white granular substances on the surface of the iron-nickel powder, and then continuously stirring the solution in the container A for 10 min; and carrying out suction filtration and drying on the substances in the container A to obtain the soft magnetic powder coated with the magnesium oxide precursor.

S3, annealing the soft magnetic powder coated with the magnesium oxide precursor in vacuum at 600 ℃ for 1h to obtain MgO-coated iron-nickel powder.

S4, dissolving epoxy resin in acetone solution, adding MgO coated iron nickel powder, and coating in the solution, wherein the mass of the epoxy resin is 5% of that of the soft magnetic powder, thus obtaining the soft magnetic composite powder.

S5, uniformly mixing the soft magnetic composite powder with zinc stearate accounting for 4% of the mass of the iron-silicon-chromium powder, pressing and molding under 750MPa, and carrying out heat treatment at 250 ℃ to obtain the soft magnetic powder core.

Example 8

In the embodiment, iron-nickel-molybdenum powder is selected as a raw material, and the particle size of the powder D50 is 85 μm; the mass of the magnesium oxide accounts for 4 percent of the mass of the magnetic powder. The preparation method comprises the following steps:

s1, dissolving magnesium acetate in absolute ethyl alcohol, wherein the mass of the magnesium acetate is 16% of that of the absolute ethyl alcohol, stirring and dissolving until the solution is clear and transparent, adding iron-nickel-molybdenum powder, and continuously stirring to uniformly disperse the powder in the solution, wherein the process is completed in a container A.

S2, preparing an oxalic acid-ethanol solution, dripping the oxalic acid-ethanol solution into the container A which is continuously stirred to generate reaction, growing white granular substances on the surface of the iron-nickel-molybdenum powder, and continuously stirring the solution in the container A for 10 min; and carrying out suction filtration and drying on the substances in the container A to obtain the soft magnetic powder coated with the magnesium oxide precursor.

S3, annealing the soft magnetic powder coated with the magnesium oxide precursor in vacuum for 1h at 500 ℃ to obtain MgO-coated iron-nickel-molybdenum powder.

S4, dissolving epoxy resin in acetone solution, adding MgO coated iron nickel molybdenum powder, and coating in the solution, wherein the mass of the epoxy resin is 1.5% of that of the soft magnetic powder, thus obtaining the soft magnetic composite powder.

S5, uniformly mixing the soft magnetic composite powder with zinc stearate accounting for 1.5 percent of the mass of the iron-silicon-chromium powder, pressing and molding under 800MPa, and carrying out heat treatment at 400 ℃ to obtain the soft magnetic powder core.

Example 9

In the embodiment, the raw material is mixed powder of iron-silicon-chromium powder and iron-silicon powder, and the particle size of the powder D50 is 75 μm; the mass of the magnesium oxide accounts for 8 percent of the mass of the magnetic powder. The preparation method comprises the following steps:

s1, dissolving magnesium acetate in absolute ethyl alcohol, wherein the mass of the magnesium acetate is 8% of that of the absolute ethyl alcohol, stirring and dissolving until the solution is clear and transparent, adding soft magnetic powder, and continuing stirring to uniformly disperse the powder in the solution, wherein the process is completed in a container A.

S2, preparing an oxalic acid-ethanol solution, dripping the oxalic acid-ethanol solution into a container A which is continuously stirred to generate reaction, growing white granular substances on the surface of the soft magnetic powder, and then continuously stirring the solution in the container A for 10 min; and carrying out suction filtration and drying on the substances in the container A to obtain the soft magnetic powder coated with the magnesium oxide precursor.

S3, carrying out vacuum annealing on the soft magnetic powder coated with the magnesium oxide precursor for 1h at 600 ℃ to obtain MgO-coated soft magnetic powder.

S4, dissolving epoxy resin in acetone solution, adding MgO coated soft magnetic powder, and coating in the solution, wherein the mass of the epoxy resin is 2% of the mass of the soft magnetic powder, thus obtaining the soft magnetic composite powder.

S5, uniformly mixing the soft magnetic composite powder with zinc stearate accounting for 2.5 percent of the mass of the iron-silicon-chromium powder, pressing and molding under 500MPa, and carrying out heat treatment at 250 ℃ to obtain the soft magnetic powder core.

Example 10

In the embodiment, the raw material is mixed powder of iron-nickel powder and iron-nickel-molybdenum powder, and the particle size of the powder D50 is 90 μm; the mass of the magnesium oxide accounts for 0.01 percent of the mass of the magnetic powder. The preparation method comprises the following steps:

s1, dissolving magnesium acetate in absolute ethyl alcohol, wherein the mass of the magnesium acetate is 1% of that of the absolute ethyl alcohol, stirring and dissolving until the solution is clear and transparent, adding soft magnetic powder, and continuing stirring to uniformly disperse the powder in the solution, wherein the process is completed in a container A.

S2, preparing an oxalic acid-ethanol solution, dripping the oxalic acid-ethanol solution into a container A which is continuously stirred to generate reaction, growing white granular substances on the surface of the soft magnetic powder, and then continuously stirring the solution in the container A for 10 min; and carrying out suction filtration and drying on the substances in the container A to obtain the soft magnetic powder coated with the magnesium oxide precursor.

And S3, carrying out vacuum annealing on the soft magnetic powder coated with the magnesium oxide precursor for 1h at 750 ℃ to obtain MgO-coated soft magnetic powder.

S4, dissolving epoxy resin in acetone solution, adding MgO to coat the soft magnetic powder, and coating in the solution, wherein the mass of the epoxy resin is 0.5% of that of the soft magnetic powder, thus obtaining the soft magnetic composite powder.

S5, uniformly mixing the soft magnetic composite powder with zinc stearate accounting for 3 percent of the mass of the iron-silicon-chromium powder, pressing and molding under 600MPa, and carrying out heat treatment at 200 ℃ to obtain the soft magnetic powder core.

Comparative example 1

In this comparative example, the same iron-silicon-chromium soft magnetic powder as in example 1 was selected as the raw material. Only the epoxy resin insulation coating was performed, and the epoxy resin content was the sum of the MgO and the epoxy resin content in example 1. After the coating, the powder was uniformly mixed with zinc stearate of 0.5 wt.% of the mass of the magnetic powder, and the mixture was molded under 600MPa and heat-treated at 200 ℃ to obtain a comparative sample.

The DC bias performance of the comparative sample is 78% under an external field of 100 Oe; at 100kHz/100mT, P_cv＝4100mW/cm³. Compared with the test sample of the example 1, under the same salt spray corrosion condition, the comparative sample is more severely corroded and has poorer corrosion resistance; during the sample loss test, the comparative sample has higher temperature and larger temperature rise, the maximum temperature is 26.8 ℃, and the temperature rise is 8.3 ℃.

Comparative example 2

In this comparative example, the same iron-silicon soft magnetic powder as in example 2 was selected as the raw material. Only the epoxy resin insulation coating is performed, and the epoxy resin content is the sum of the MgO content and the epoxy resin content in example 2. After the coating, the powder was uniformly mixed with zinc stearate of 0.5 wt.% of the mass of the magnetic powder, press-molded at 800MPa, and heat-treated at 200 ℃ to obtain a comparative sample.

Compared with the test sample of the example 2, under the same salt spray corrosion condition, the comparative sample is more severely corroded and has poorer corrosion resistance; the comparative samples had higher temperatures and greater temperature rises during the sample loss test.

Comparative example 3

In this comparative example, the same FeSiBCCr amorphous soft magnetic powder as in example 3 was selected as the raw material. Only the epoxy resin insulation coating is performed, and the epoxy resin content is the sum of the MgO content and the epoxy resin content in example 3. After the coating, the powder was uniformly mixed with zinc stearate of 0.5 wt.% of the mass of the magnetic powder, and the mixture was molded under 600MPa and heat-treated at 200 ℃ to obtain a comparative sample.

Compared with the test sample of example 3, the comparative sample is more corroded and has poorer corrosion resistance under the same salt spray corrosion condition; the comparative samples had higher temperatures and greater temperature rises during the sample loss test.

Although the present invention is disclosed above, the present invention is not limited thereto. Various changes and modifications may be effected therein by one skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.