An anti-rust soft magnetic composite material, its preparation method and application

Abstract

The present invention belongs to the technical field of soft magnetic materials, and particularly relates to an anti-rust soft magnetic composite material, a preparation method thereof and an application. The preparation method of the anti-rust soft magnetic composite material comprises the following steps: S1, performing a first coating on iron-based powder with a coating liquid, adding a silicone resin and a solvent for curing, crushing to obtain coated iron-based powder, then forming and annealing; S2, performing a second coating on the annealed product with the coating liquid, and drying and baking to obtain the anti-rust soft magnetic composite material; wherein, the coating liquid comprises a nano-oxide and a silane coupling agent; the obtained anti-rust soft magnetic composite material can take into account both anti-rust performance and magnetic performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of soft magnetic materials, and particularly relates to an anti-rust soft magnetic composite material, a preparation method thereof and an application thereof. Background Art

[0002] Common iron-based alloy soft magnetic composite materials include iron-silicon soft magnetic composite materials, iron-silicon-aluminum soft magnetic composite materials, iron-nickel soft magnetic composite materials and pure iron soft magnetic composite materials, which are widely used in power electronic devices such as active filters, inverters, and uninterruptible power supplies. At present, most soft magnetic composite materials are prepared by powder metallurgy processes such as insulation coating, pressing forming and annealing heat treatment, and have the advantages of easy processing and excellent magnetic properties. However, since most soft magnetic composite materials mainly consist of iron, they are prone to rust in humid air or when stored for a long time, and their anti-rust ability is poor. To prevent the rust of iron-based alloy soft magnetic composite materials, in actual production, the method of painting or soaking in anti-rust oil is often used to isolate the magnetic core from the air to prevent rust. However, painting is easy to pollute the environment, and the outer skin of the paint layer is likely to fall off after long-term use; while soaking the magnetic core in anti-rust oil, since it is difficult to completely discharge the air in the tiny air gaps inside the magnetic core, it is difficult for the anti-rust oil to completely enter the air gaps inside the magnetic core, and it is difficult to achieve the purpose of comprehensive anti-rust and long-term anti-rust. In addition, some researchers have used silane coupling agents to carry out anti-rust treatment on soft magnetic composite materials, but this method requires pickling or alkali washing of the magnetic core during the anti-rust process, generally using strong acids and strong alkalis, and both strong acids and strong alkalis will cause passivation of the surface of the magnetic powder, resulting in the deterioration of the magnetic properties of the soft magnetic composite material. Therefore, it is of great significance to develop a process method that does not affect the magnetic properties of the magnetic core and can achieve long-term and comprehensive anti-rust for optimizing the comprehensive physical properties of iron-based alloy soft magnetic composite materials. Summary of the Invention

[0003] Therefore, the technical problem to be solved by the present invention is to overcome the defect that the anti-rust effect of the anti-rust method of soaking in anti-rust oil is poor, the anti-rust method of painting has high cost, large pollution, increases the size of the product and is easy to fall off, and the treatment with silane coupling agent cannot balance the anti-rust performance and magnetic properties, and provide an anti-rust soft magnetic composite material, a preparation method thereof and an application thereof.

[0004] To this end, the present invention provides the following technical solutions:

[0005] The first aspect of the present invention provides a preparation method of an anti-rust soft magnetic composite material, wherein the preparation method includes the following steps:

[0006] S1, performing a first coating on the iron-based powder with a coating liquid, adding a silicone resin and a solvent for curing, crushing to obtain coated iron-based powder, and then performing molding and annealing;

[0007] S2. The annealed product is second-coated with a coating liquid, and after drying and baking, a rust-proof soft magnetic composite material is obtained.

[0008] Among them, the coating liquid includes nano-oxides and a silane coupling agent.

[0009] According to the present invention, the specific preparation method of the coating liquid includes the following steps: nano-oxides, a first solvent, a wetting agent, a dispersant, and a stabilizer are first mixed to obtain a modified nano-oxide rust-proof liquid; a silane coupling agent, a second solvent, a weak acid reagent, and a diluent are second mixed to obtain a mixed liquid, and the modified nano-oxide rust-proof liquid is added to the mixed liquid for third mixing to obtain the coating liquid.

[0010] According to the present invention, before the first coating, there is also a step of pre-coating and pre-annealing the iron-based powder with the coating liquid to obtain pre-coated iron-based powder.

[0011] In the present invention, the coating liquid used for the first coating of the pre-coated iron-based powder is not the coating liquid used in the pre-coating process, but a fresh coating liquid.

[0012] According to the present invention, the nano-oxides include gaseous nano-silica and / or gaseous nano-aluminum oxide.

[0013] According to the present invention, based on the mass of the first solvent, the mass of the nano-oxides is 5-7 wt%, the mass of the wetting agent is 0.2-0.5 wt%, the mass of the dispersant is 0.2-0.8 wt%, and the mass of the stabilizer is 0.4-1 wt%.

[0014] According to the present invention, the nano-oxides are a mixture with different particle sizes, and the average particle size of the nano-oxides is 20-100 nm.

[0015] According to the present invention, the first solvent includes an alcohol solvent.

[0016] In the present invention, the alcohol solvent includes at least one of ethanol and propanol.

[0017] According to the present invention, the wetting agent includes a non-ionic organic wetting agent. Further, the wetting agent includes at least one of alkyl alcohol polyoxyethylene ether (such as Triton X-100) and alkylphenol polyoxyethylene ether (such as OP-10, YHC0019S).

[0018] According to the present invention, the dispersant includes a non-ionic organic dispersant. Further, the dispersant includes at least one of polyvinylpyrrolidone (PVP) and polyvinyl alcohol (PVA).

[0019] According to the present invention, the stabilizer includes at least one of silane compounds; further, the silane compound includes γ-aminopropyltriethoxysilane.

[0020] According to the present invention, the mass ratio of the silane coupling agent, the second solvent, the weak acid reagent and the diluent is 1:(90 - 140):(0.05 - 0.8):(10 - 20), and may be optionally 1:(100 - 120):(0.1 - 0.3):(10 - 15).

[0021] According to the present invention, the silane coupling agent includes at least one of amino silane coupling agents and acrylic silane coupling agents.

[0022] In the present invention, the amino silane coupling agent may specifically be KH550 or KH570.

[0023] According to the present invention, the second solvent includes alcohol solvents.

[0024] In the present invention, the alcohol solvents include at least one of ethanol and propanol.

[0025] According to the present invention, the weak acid reagent includes inorganic acids, and may be optionally phosphoric acid.

[0026] According to the present invention, the diluent includes water.

[0027] According to the present invention, the temperature of the first mixing is 20 - 30°C and the time is 10 - 15 min.

[0028] According to the present invention, the temperature of the second mixing is 30 - 40°C and the time is 30 - 40 min.

[0029] According to the present invention, the temperature of the third mixing is 70 - 90°C and the time is 30 - 40 min.

[0030] According to the present invention, in the pre - coating, the mass ratio of the iron - based powder to the silane coupling agent in the coating liquid is 100:0.3 - 0.8.

[0031] According to the present invention, the iron - based powder includes iron powder and / or magnetic iron - based alloy powder; further, the magnetic iron - based alloy powder includes at least one of iron powder, iron - silicon - aluminum alloy, iron - nickel alloy, and iron - silicon alloy.

[0032] According to the present invention, the particle sizes of the iron - based powder are different, and the average particle size of the iron - based powder is 10 - 60 μm.

[0033] According to the present invention, the temperature of the pre - coating is 50 - 80°C and the time is 50 - 100 min; optionally, the temperature of the pre - coating is 60 - 70°C and the time is 60 - 90 min.

[0034] According to the present invention, the temperature of the pre-annealing is 750 - 850 °C, and the time is 60 - 90 min.

[0035] In the present invention, the product obtained by pre-annealing and then naturally cooling is also crushed and screened, and the specific average particle size is selected according to actual needs.

[0036] According to the present invention, in the first coating, the mass ratio of the iron-based powder to the silane coupling agent in the coating liquid is 100:0.3 - 0.8.

[0037] According to the present invention, the temperature of the first coating is 50 - 80 °C, and the time is 50 - 100 min; optionally, the temperature of the first coating is 60 - 70 °C, and the time is 60 - 90 min.

[0038] According to the present invention, the silicone resin includes organosilicone resin; optionally, the organosilicone resin includes at least one of methyl silicone resin, ethyl silicone resin, and polydimethylsiloxane.

[0039] According to the present invention, the solvent includes ketone solvents and / or ester solvents, optionally, the solvent includes at least one of acetone and ethyl acetate.

[0040] According to the present invention, based on the mass of the iron-based powder, the mass of the silicone resin is 0.8 - 1.2 wt%, and the mass of the solvent is 2 - 3 wt%.

[0041] According to the present invention, the temperature of the curing is 60 - 80 °C, and the time is 30 - 60 min.

[0042] In the present invention, curing can increase the overall bonding strength of the system, enhance the formability, and facilitate subsequent operations. The coated iron-based powder obtained after curing and cooling is sieved, and the specific average particle size is selected according to actual needs.

[0043] According to the present invention, the temperature of the molding is 20 - 30 °C, the pressure is 800 - 2000 MPa, and the time is 10 - 20 s.

[0044] According to the present invention, a release agent is also added during the molding.

[0045] According to the present invention, based on the mass of the iron-based powder, the mass of the release agent is 0.3 - 0.4 wt%.

[0046] According to the present invention, the release agent is a stearate, including zinc stearate and / or aluminum stearate.

[0047] According to the present invention, the temperature of the annealing is 650 - 750 °C, and the time is 60 - 90 min.

[0048] In the present invention, the annealing can remove the internal stress generated during the molding pressing process. The gas atmosphere for annealing is a protective gas. Typically and non - restrictively, the gas atmosphere is nitrogen.

[0049] According to the present invention, in the second coating, the mass ratio of the annealed product to the silane coupling agent in the coating liquid is 100:0.3 - 0.8.

[0050] According to the present invention, the temperature of the second coating is 70 - 90 °C and the time is 60 - 90 min.

[0051] According to the present invention, the temperature of the drying is 60 - 80 °C and the time is 60 - 120 min.

[0052] According to the present invention, the temperature of the baking is 180 - 240 °C and the time is 60 - 90 min.

[0053] The second aspect of the present invention protects an anti - rust soft magnetic composite material prepared by the foregoing preparation method.

[0054] The third aspect of the present invention protects the application of the foregoing anti - rust soft magnetic composite material in an inductor, a transformer, a filter, a motor or a sensor.

[0055] The technical solution of the present invention has the following advantages:

[0056] 1. For the preparation method of an anti - rust soft magnetic composite material of the present invention, the preparation method includes the following steps: S1, performing the first coating on the iron - based powder with a coating liquid, adding a silicone resin and a solvent for curing, crushing to obtain a coated iron - based powder, and then performing molding and annealing; S2, performing the second coating on the annealed product with a coating liquid, and obtaining the anti - rust soft magnetic composite material after drying and baking; wherein, the coating liquid includes nano - oxides and a silane coupling agent; the present invention does not adopt the method of dipping in anti - rust oil nor the method of spraying paint, avoiding the disadvantages brought by these two methods; through the synergistic effect of multiple - step coatings of the first coating and the second coating, even if wear or breakage occurs during the use of the soft magnetic composite material, due to the existence of the coating layer on the outer surface of the iron - based powder, the overall anti - rust performance is still maintained well, ensuring that the soft magnetic composite material can be used for a long time; the first coating specifically uses a silane coupling agent to modify the surface of the iron - based powder to generate Si - O bonds, and the free end of O in the Si - O bond is connected to the elements in the nano - oxides with excellent hydrophobic and insulating properties to form a bond, forming a coating layer, enabling the anti - rust soft magnetic composite material to balance the anti - rust performance and magnetic properties; in addition, performing the second coating effectively repairs the coating layer damaged due to molding pressing of the intermediate product, prevents high loss, and enhances the anti - rust effect.

[0057] 2. In the present invention, for the preparation method of the specific coating liquid, first, nano-oxides, a first solvent, a wetting agent, a dispersant, and a stabilizer are subjected to a first mixing to obtain a modified nano-oxide rust preventive liquid. Among them, the wetting agent, the dispersant, and the stabilizer act synergistically to make the rust preventive liquid uniform and stable. The silane coupling agent, a second solvent, a weak acid reagent, and a diluent are subjected to a second mixing to obtain a mixed liquid, and the modified nano-oxide rust preventive liquid is added to the mixed liquid for a third mixing to obtain the coating liquid. The weak acid in the coating liquid is used to catalyze the hydrolysis of the silane coupling agent. Since there are multiple components in the coating liquid and the weak acid has a low acidity and will not react with the metal to cause passivation of the metal surface, it can avoid the deterioration of magnetic properties caused by strong acid pickling. The step-by-step addition makes the mixing more sufficient, and the finally formed coating liquid is a relatively stable colloid with nano-oxides uniformly distributed therein, which helps the hydrolysis products of the silane coupling agent and the nano-oxides to uniformly coat the surface of the iron-based powder during coating, ensuring the uniformity and stability of the coating layer.

[0058] In the present invention, first, a pre-coating and pre-annealing process are carried out, and then the first coating is carried out, which can make the coating more uniform. The pre-coating and the first coating act synergistically to form a firm coating layer on the surface of the iron-based powder, enhancing the strength of the overall coating layer and effectively avoiding the situation where the coating layer peels off due to the application of high pressure during the subsequent forming process.

[0059] 3. In the present invention, the specific types and dosages of the nano-oxides, the first solvent, and the additives can further improve the uniformity and stability of the dispersion of the nano-oxides in the rust preventive liquid, making the formed coating layer more uniform and stable.

[0060] 4. In the present invention, the specific types and dosages of the silane coupling agent, the second solvent, the acid agent, and the diluent can further increase the amount of silanol generated by the hydrolysis of the silane coupling agent, making the surface modification of the iron-based powder more sufficient and ensuring the uniformity and adhesion of the subsequent film formation.

[0061] 5. By further defining the pre-coating conditions in the present invention, the uniformity and film-forming force of the coating layer on the surface of the iron-based powder can be further improved, the insulation between the powders can be ensured, the resistivity of the prepared soft magnetic composite material can be increased, and the finally prepared soft magnetic composite material has lower losses.

[0062] 6. By further defining the pre-annealing conditions in the present invention, the bonding force of the Si-O bonds formed after sintering on the surface of the iron-based powder and coming from the elements in the nano-oxides can be further improved, ensuring the strength and insulation of the coating layer.

[0063] 7. By further defining the coating conditions in the present invention, the uniformity and film-forming force of the coating layer on the surface of the iron-based powder can be further improved, the insulation between the powders can be further improved, and thus the loss characteristics of the prepared soft magnetic composite material can be further reduced.

[0064] 8. The present invention further defines the second coating conditions, which can further improve the uniformity and film-forming strength of the coating layer of the soft magnetic composite material, increase the overall insulation, surface hydrophobicity, and air isolation ability of the soft magnetic composite material, thereby further reducing the loss and improving the rust prevention performance of the soft magnetic composite material. Description of the Drawings

[0065] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0066] Figure 1 It is the SEM image of the uncoated iron-based powder in Example 1;

[0067] Figure 2 It is the SEM image of the coated iron-based powder in Example 1;

[0068] Figure 3 It is the picture of the rust-proof soft magnetic composite material provided in Example 1 after 960 h of double 85 tests;

[0069] Figure 4 It is the picture of the rust-proof soft magnetic composite material provided in Comparative Example 1 after 24 h of double 85 tests;

[0070] Figure 5 It is the picture of the rust-proof soft magnetic composite material provided in Example 2 after 960 h of double 85 tests;

[0071] Figure 6 It is the picture of the rust-proof soft magnetic composite material provided in Comparative Example 2 after 12 h of double 85 tests. Detailed Embodiments

[0072] The following embodiments are provided to better further understand the present invention. It is not limited to the best embodiment, and does not limit the content and protection scope of the present invention. Any product that is the same as or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior art features falls within the protection scope of the present invention.

[0073] For those embodiments where specific experimental steps or conditions are not specified, the operations or conditions of the conventional experimental steps described in the literature in this field can be followed. For the reagents or instruments whose manufacturers are not specified, they are all conventional reagent products that can be obtained through commercial purchase.

[0074] Fumed nano-silica: from Hubei Huifu Materials Co., Ltd., grade HB-139;

[0075] Fumed nano-aluminum oxide: from Hubei Huifu Materials Co., Ltd., grade ALUNA-100;

[0076] Ferrosilicon-aluminum alloy powder: from Henan Zhongzuan New Materials Co., Ltd., with a composition including 85 wt% iron, 9 wt% silicon, and 6 wt% aluminum;

[0077] Ferrosilicon alloy powder: from Henan Zhongzuan New Materials Co., Ltd., with a composition including 95.5 wt% iron and 4.5 wt% silicon;

[0078] Wetting agent YHC3031S: from Foshan Youhua New Materials Technology Co., Ltd.;

[0079] Dispersant YHC0019S: from Foshan Youhua New Materials Technology Co., Ltd.;

[0080] Stabilizer YHC0090S: from Foshan Youhua New Materials Technology Co., Ltd.;

[0081] The concentration of phosphoric acid is 85 wt%;

[0082] The water is deionized water;

[0083] Polydimethylsiloxane (from Shanghai Dingfen Chemical Technology Co., Ltd., with a weight-average molecular weight of 9000 - 14000 g / mol);

[0084] Forming is carried out using a servo press.

[0085] Example 1

[0086] This example provides a method for preparing an anti-rust soft magnetic composite material. The specific method is as follows:

[0087] S1, Mix 5 g of fumed nano-silica with an average particle size of 60 nm, 100 g of ethanol, 0.2 g of wetting agent YHC3031S, 0.2 g of dispersant YHC0019S, and 0.5 g of stabilizer YHC0090S at 25 °C and let it stand for 10 min to obtain a modified fumed nano-silica anti-rust liquid; Mix 4 g of silane coupling agent KH550, 400 g of ethanol, 1 g of phosphoric acid, and 50 g of deionized water at 25 °C and let it stand for 30 min to obtain a mixed solution. Add all the modified fumed nano-silica anti-rust liquid to the mixed solution and heat it in a water bath at 80 °C for 30 min for the third mixing to obtain a coating liquid;

[0088] S2. Use the coating liquid in S1 to pre - coat 1 kg of iron - silicon - aluminum alloy powder with an average particle size of 35 μm. Among them, the mass ratio of the iron - silicon - aluminum alloy powder to the silane coupling agent KH550 in the coating liquid is 100:0.4. The temperature of the pre - coating is 60 °C and the time is 60 min. And perform pre - annealing. The temperature of the pre - annealing is 780 °C and the time is 60 min. Cool naturally, and obtain pre - coated iron - silicon - aluminum alloy powder after sieving;

[0089] S3. Use the coating liquid in S1 to perform the first coating on the pre - coated iron - silicon - aluminum alloy powder. Among them, the mass ratio of the iron - silicon - aluminum alloy powder to the silane coupling agent KH550 in the coating liquid is 100:0.4. The temperature of the first coating is 60 °C and the time is 60 min. Add 8 g of polydimethylsiloxane and 20 g of acetone for curing, bake at 60 °C for 60 min, cool naturally, and obtain coated iron - silicon - aluminum alloy powder after crushing and sieving. The picture of the iron - silicon - aluminum alloy powder without coating is as shown in Figure 1 shown, and the picture of the coated iron - silicon - aluminum alloy powder is as shown in Figure 2 shown. It can be seen from Figure 2 that the surface of the iron - silicon - aluminum powder is evenly coated and the coating effect is good. Add 4 g of zinc stearate and mix, then perform molding. The temperature of molding is 25 °C, the pressure is 1800 MPa, and the pressure is maintained for 10 s. Anneal in a nitrogen environment. The temperature of annealing is 700 °C and the time is 60 min;

[0090] S4. Use the coating liquid in S1 to perform the second coating on the annealed product. Among them, the mass ratio of the annealed product to the silane coupling agent KH550 in the coating liquid is 100:0.5. The temperature of the second coating is 80 °C and the time is 60 min. Dry in an oven at 60 °C for 120 min, and then bake at 220 °C for 60 min to obtain a rust - proof soft magnetic composite material. The situation of performing the double 85 test for 960 h in Example 1 is as shown in Figure 3 shown. It can be seen from Figure 3 that there are no rust spots on the surface of the rust - proof soft magnetic composite material (ring material) and it is smooth.

[0091] Example 2

[0092] This example provides a preparation method of a rust - proof soft magnetic composite material. The specific method is as follows:

[0093] S1. Mix 5 g of fumed nano - silica with an average particle size of 75 nm, 100 g of ethanol, 0.2 g of wetting agent YHC3031S, 0.2 g of dispersant YHC0019S, and 0.5 g of stabilizer YHC0090S at 25 °C and let it stand for 10 min to obtain a modified fumed nano - silica rust inhibitor solution. Mix 6 g of silane coupling agent KH550, 700 g of ethanol, 2 g of phosphoric acid, and 80 g of deionized water at 25 °C and let it stand for 30 min to obtain a mixed solution. Add all the modified fumed nano - silica rust inhibitor solution to the mixed solution and heat it in a water bath at 80 °C for 30 min for the third mixing to obtain a coating solution.

[0094] S2. Pre - coat 1 kg of iron - silicon alloy powder with an average particle size of 30 μm using the coating solution in S1. The mass ratio of the iron - silicon alloy powder to the silane coupling agent KH550 in the coating solution is 100:0.4. The pre - coating temperature is 60 °C and the time is 60 min. And perform pre - annealing. The pre - annealing temperature is 760 °C and the time is 60 min. Let it cool naturally. After sieving, obtain pre - coated iron - silicon alloy powder.

[0095] S3. First coat the pre - coated iron - silicon alloy powder using the coating solution in S1. The mass ratio of the iron - silicon alloy powder to the silane coupling agent KH550 in the coating solution is 100:0.5. The first coating temperature is 60 °C and the time is 60 min. Add 12 g of polydimethylsiloxane and 30 g of acetone for curing, bake at 60 °C for 60 min, let it cool naturally, crush and sieve to obtain coated iron - silicon alloy powder. Add 4 g of zinc stearate and mix, and perform molding. The molding temperature is 25 °C, the pressure is 1000 MPa, and keep the pressure for 10 s. Anneal in a nitrogen environment. The annealing temperature is 750 °C and the time is 60 min.

[0096] S4. Second coat the annealed product using the coating solution in S1. The mass ratio of the annealed product to the silane coupling agent KH550 in the coating solution is 100:0.5. The second coating temperature is 80 °C and the time is 60 min. Dry it in an oven at 60 °C for 120 min, and then bake at 240 °C for 60 min to obtain a rust - proof soft magnetic composite material. The situation of the double 85 - test for 960 h in Example 2 is as Figure 5 shown. Example 2 and Example 1 are pressed using different molds, so the configurations of the rust - proof soft magnetic composite materials are different. It can be seen from Figure 5 that the upper surface of the rust - proof soft magnetic composite material is smooth and has no rust spots.

[0097] Example 3

[0098] This example provides a preparation method of a rust - proof soft magnetic composite material. The specific method is as follows:

[0099] In the same manner as in Example 1, except that "5 g of fumed nano-silica with an average particle size of 60 nm, 100 g of ethanol, 0.2 g of wetting agent YHC3031S, 0.2 g of dispersant YHC0019S, and 0.5 g of stabilizer YHC0090S" is changed to "5 g of fumed nano-silica with an average particle size of 60 nm, 100 g of ethanol, 0.4 g of wetting agent Triton X-100, 0.3 g of dispersant polyvinylpyrrolidone, and 0.4 g of stabilizer γ-aminopropyltriethoxysilane".

[0100] Example 4

[0101] This example provides a method for preparing an anti-rust soft magnetic composite material. The specific method is as follows:

[0102] In the same manner as in Example 1, except that "6 g of silane coupling agent KH550, 700 g of ethanol, 2 g of phosphoric acid, and 80 g of deionized water" is changed to "5 g of silane coupling agent KH570, 700 g of ethanol, 4 g of phosphoric acid, and 80 g of deionized water".

[0103] Example 5

[0104] This example provides a method for preparing an anti-rust soft magnetic composite material. The specific method is as follows:

[0105] In the same manner as in Example 1, except that "the temperature of pre-coating is 60 °C and the time is 60 min" is changed to "the temperature of pre-coating is 80 °C and the time is 90 min".

[0106] Example 6

[0107] This example provides a method for preparing an anti-rust soft magnetic composite material. The specific method is as follows:

[0108] In the same manner as in Example 1, except that "the temperature of pre-annealing is 780 °C and the time is 60 min" is changed to "the temperature of pre-annealing is 850 °C and the time is 90 min".

[0109] Example 7

[0110] This example provides a method for preparing an anti-rust soft magnetic composite material. The specific method is as follows:

[0111] In the same manner as in Example 1, except that "the temperature of the first coating is 60 °C and the time is 60 min" is changed to "the temperature of the first coating is 80 °C and the time is 90 min".

[0112] Example 8

[0113] This example provides a method for preparing an anti-rust soft magnetic composite material. The specific method is as follows:

[0114] In the same manner as in Example 1, except that "the temperature of the second coating is 80 °C and the time is 60 min" is changed to "the temperature of the second coating is 90 °C and the time is 90 min".

[0115] Example 9

[0116] This example provides a method for preparing an anti-rust soft magnetic composite material. The specific method is as follows:

[0117] In the same manner as in Example 1, except that "60 nm gas-phase nano-silica with an average particle size" is changed to "60 nm gas-phase nano-aluminum oxide with an average particle size".

[0118] Example 10

[0119] This example provides a method for preparing an anti-rust soft magnetic composite material. The specific method is as follows:

[0120] In the same manner as in Example 1, except that "iron-silicon-aluminum alloy powder with an average particle size of 35 μm" is changed to "iron powder with an average particle size of 35 μm".

[0121] Example 11

[0122] This example provides a method for preparing an anti-rust soft magnetic composite material. The specific method is as follows:

[0123] S1. Mix 5 g of gas-phase nano-silica with an average particle size of 60 nm, 100 g of ethanol, 0.2 g of wetting agent YHC3031S, 0.2 g of dispersant YHC0019S, and 0.5 g of stabilizer YHC0090S at 25 °C and let it stand for 10 min to obtain a modified gas-phase nano-silica anti-rust liquid; mix 4 g of silane coupling agent KH550, 400 g of ethanol, 1 g of phosphoric acid, and 50 g of deionized water at 25 °C and let it stand for 30 min to obtain a mixed solution. Add all the modified gas-phase nano-silica anti-rust liquid to the mixed solution and heat it in a water bath at 80 °C for 30 min for the third mixing to obtain a coating liquid;

[0124] S2. Perform the first coating on the iron-silicon-aluminum alloy powder with the coating liquid in S1. Among them, the mass ratio of the iron-silicon-aluminum alloy powder to the silane coupling agent KH550 in the coating liquid is 100:0.4. The temperature of the first coating is 60 °C, the time is 60 min. Add 8 g of polydimethylsiloxane and 20 g of acetone for curing, bake at 60 °C for 60 min, cool naturally, crush and screen to obtain coated iron-silicon-aluminum alloy powder, add 4 g of zinc stearate and mix, perform molding, the molding temperature is 25 °C, the pressure is 1800 MPa, keep the pressure for 10 s, and anneal in a nitrogen environment, the annealing temperature is 700 °C, and the time is 60 min;

[0125] S3. Use the coating liquid in S1 to perform a second coating on the annealed product. Among them, the mass ratio of the annealed product to the silane coupling agent KH550 in the coating liquid is 100:0.5. The temperature of the second coating is 80 °C, the time is 60 min, dry in an oven at 60 °C for 120 min, and then bake at 220 °C for 60 min to obtain the rust-proof soft magnetic composite material.

[0126] Comparative Example 1

[0127] This comparative example provides a method for preparing a soft magnetic composite material. The specific method is as follows:

[0128] Mix and cure 1 kg of iron-silicon-aluminum alloy powder with an average particle size of 35 μm, 8 g of polydimethylsiloxane, and 20 g of acetone. Bake at 60 °C for 60 min, cool naturally, crush and screen to obtain the coated iron-silicon-aluminum alloy powder, add 4 g of zinc stearate and mix, then perform molding. The molding temperature is 25 °C, the pressure is 1800 MPa, and the pressure is maintained for 10 s. Anneal in a nitrogen environment. The annealing temperature is 700 °C and the time is 60 min. The situation of performing the double 85 test for 24 h in Comparative Example 1 is as Figure 4 shown. It can be seen from Figure 4 that there are rust spots on the rust-proof soft magnetic composite material.

[0129] Comparative Example 2

[0130] This comparative example provides a method for preparing a soft magnetic composite material. The specific method is as follows:

[0131] Cure 1 kg of iron-silicon alloy powder with an average particle size of 35 μm, 12 g of polydimethylsiloxane, and 30 g of acetone. Bake at 60 °C for 60 min, cool naturally, crush and screen to obtain the coated iron-silicon alloy powder, add 4 g of zinc stearate and mix, then perform molding. The molding temperature is 25 °C, the pressure is 1000 MPa, and the pressure is maintained for 10 s. Anneal in a nitrogen environment. The annealing temperature is 750 °C and the time is 1 h. The situation of performing the double 85 test for 12 h in Comparative Example 2 is as Figure 6 shown. It can be seen from Figure 6 that there are a large number of rust spots on the rust-proof soft magnetic composite material.

[0132] Comparative Example 3

[0133] This comparative example provides a method for preparing a rust-proof soft magnetic composite material. The specific method is as follows:

[0134] In the same way as in Example 1, the difference is that "gas-phase nano-silica with an average particle size of 60 nm" is changed to "ordinary silica with an average particle size of 15 μm".

[0135] Comparative Example 4

[0136] This comparative example provides a method for preparing an anti-rust soft magnetic composite material. The specific method is as follows:

[0137] S1, Mix 5 g of gas-phase nano-silica dioxide with an average particle size of 60 nm, 100 g of ethanol, 0.2 g of wetting agent YHC3031S, 0.2 g of dispersant YHC0019S, and 0.5 g of stabilizer YHC0090S at 25 °C and let it stand for 10 min to obtain a modified gas-phase nano-silica dioxide anti-rust solution; Mix 4 g of silane coupling agent KH550, 400 g of ethanol, 1 g of phosphoric acid, and 50 g of deionized water at 25 °C and let it stand for 30 min to obtain a mixed solution. Add all the modified gas-phase nano-silica dioxide anti-rust solution to the mixed solution and heat it in a water bath at 80 °C for 30 min for the third mixing to obtain a coating solution;

[0138] S2, Pre-coat 1 kg of iron-silicon-aluminum alloy powder with an average particle size of 35 μm using the coating solution in S1. Among them, the mass ratio of the iron-silicon-aluminum alloy powder to the silane coupling agent KH550 in the coating solution is 100:0.4. The pre-coating temperature is 60 °C and the time is 60 min; And perform pre-annealing. The pre-annealing temperature is 780 °C and the time is 60 min. Cool naturally, and after crushing and sieving, obtain pre-coated iron-silicon-aluminum alloy powder;

[0139] S3, Coat the pre-coated iron-silicon-aluminum alloy powder with the coating solution in S1. Among them, the mass ratio of the iron-silicon-aluminum alloy powder to the silane coupling agent KH550 in the coating solution is 100:0.4. The coating temperature is 60 °C and the time is 60 min. Add 8 g of polydimethylsiloxane and 20 g of acetone for curing, bake at 60 °C for 60 min, cool naturally, and after crushing and sieving, obtain coated iron-silicon-aluminum alloy powder. Add 4 g of zinc stearate and mix, and perform molding. The molding temperature is 25 °C, the pressure is 1800 MPa, and the pressure is maintained for 10 s. Anneal in a nitrogen environment. The annealing temperature is 700 °C and the time is 60 min to obtain an anti-rust soft magnetic composite material.

[0140] Test example

[0141] In accordance with the standard SJ20966-2006, use an IWATSUB-H analyzer (SY-8219) to detect the performance of the prepared soft magnetic composite material. The external magnetic field frequency is 50 kHz and the magnetic field strength is 100 mT;

[0142] Perform a double 85 (85 °C, relative humidity of 85% RH) experiment on the prepared soft magnetic composite material. Observe it every 12 h, and the test duration is 960 h. Record the time when rust spots appear if rust spots appear within 960 h; If no rust spots appear after the test time reaches 960 h, record the result as "none" after observation to evaluate the anti-rust performance;

[0143] The specific results are shown in Table 1.

[0144] Table 1 Loss and rust spots of the tested soft magnetic composite materials

[0145]

[0146] In Example 1, the raw material is iron-silicon-aluminum alloy powder; in Example 2, the raw material is iron-silicon alloy powder; in Example 10, the raw material is iron powder. The raw materials in the examples are different iron-based powders. The loss of the existing iron-silicon-aluminum soft magnetic composite material is about 140 mW / cm 3 or so, the loss of the iron-silicon soft magnetic composite material is about 400 mW / cm 3 or so, and the loss of the pure iron soft magnetic composite material is about 500 W / cm 3 or so. The soft magnetic composite material prepared by the present invention has lower loss and better magnetic properties compared with the existing soft magnetic composite materials. Moreover, the soft magnetic composite material prepared by the present invention will not have rust spots or will take a longer time to appear rust spots, and can take into account the anti-rust performance and magnetic properties.

[0147] Obviously, the above embodiments are only examples given for clear illustration and are not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to enumerate all the implementation manners here. And the obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A method for preparing an anti-rust soft magnetic composite material, characterized in that, The preparation method comprises the following steps: S1. The iron-based powder is subjected to a first coating with a coating liquid, silicon resin and a solvent are added for curing, and then crushed to obtain a coated iron-based powder, which is then formed and annealed. Before the first coating, there are also steps of pre-coating the iron-based powder with a coating liquid and pre-annealing to obtain a pre-coated iron-based powder. S2. The annealed product is subjected to a second coating with a coating liquid, and after drying and baking, a rust-proof soft magnetic composite material is obtained. Among them, the coating liquid includes nano-oxides and a silane coupling agent. The preparation method of the coating liquid comprises the following steps: the nano-oxides, a first solvent, a wetting agent, a dispersing agent and a stabilizer are subjected to a first mixing to obtain a modified nano-oxide rust-proof liquid; the silane coupling agent, a second solvent, a weak acid reagent and a diluent are subjected to a second mixing to obtain a mixed liquid, and the modified nano-oxide rust-proof liquid is added to the mixed liquid for a third mixing to obtain the coating liquid.

2. The preparation method according to claim 1, characterized in that, The nano-oxides include fumed nano-silica and / or fumed nano-aluminum oxide.

3. The preparation method according to claim 1, characterized in that, Based on the mass of the first solvent, the mass of the nano-oxides is 5-7 wt%, the mass of the wetting agent is 0.2-0.5 wt%, the mass of the dispersing agent is 0.2-0.8 wt%, and the mass of the stabilizer is 0.4-1 wt%.

4. The preparation method according to claim 1, characterized in that, The average particle size of the nano-oxides is 20-100 nm.

5. The preparation method according to claim 1, characterized in that, The first solvent includes an alcohol solvent.

6. The preparation method according to claim 1, wherein The wetting agent includes a non-ionic organic wetting agent.

7. The preparation method according to claim 1, characterized in that, The dispersing agent includes a non-ionic organic dispersing agent.

8. The preparation method according to claim 1, characterized in that, The stabilizer includes at least one of silane compounds.

9. The preparation method according to claim 1, characterized in that, The mass ratio of the silane coupling agent, the second solvent, the weak acid reagent and the diluent is 1:(90-140):(0.05-0.8):(10-20).

10. The preparation method according to claim 1, wherein, The silane coupling agent includes at least one of an amino silane coupling agent and an acrylic silane coupling agent.

11. The preparation method according to claim 1, characterized in that, The second solvent includes an alcohol solvent.

12. The preparation method according to claim 1, characterized in that, The weak acid reagent includes an inorganic acid.

13. The preparation method according to claim 1, characterized in that, The diluent includes water.

14. The preparation method according to claim 1, characterized in that, The temperature of the first mixing is 20-30 °C, and the time is 10-15 min; and / or, the temperature of the second mixing is 30-40 °C, and the time is 30-40 min; and / or, the temperature of the third mixing is 70-90 °C, and the time is 30-40 min.

15. The preparation method according to claim 6, characterized in that, The wetting agent includes at least one of alkyl alcohol polyoxyethylene ether and alkyl phenol polyoxyethylene ether.

16. The preparation method according to claim 7, wherein The dispersing agent includes at least one of polyvinylpyrrolidone and polyvinyl alcohol.

17. The preparation method according to claim 8, characterized in that, The silane compound includes γ-aminopropyltriethoxysilane.

18. The preparation method according to claim 9, wherein The mass ratio of the silane coupling agent, the second solvent, the weak acid reagent and the diluent is 1:(100-120):(0.1-0.3):(10-15).

19. The preparation method according to claim 12, characterized in that, The weak acid reagent includes phosphoric acid.

20. The preparation method according to claim 1, characterized in that, In the pre-coating, the mass ratio of the iron-based powder to the silane coupling agent in the coating liquid is 100:0.3-0.

8.

21. The preparation method according to claim 1, characterized in that, The iron-based powder includes iron powder and / or magnetic iron-based alloy powder.

22. The preparation method according to claim 1, characterized in that, The average particle size of the iron-based powder is 10-60 μm.

23. The preparation method according to claim 1, characterized in that, The temperature of the pre-coating is 50-80 °C, and the time is 50-100 min.

24. The preparation method according to claim 1, characterized in that, The temperature of the pre-annealing is 750 - 850 °C, and the time is 60 - 90 min.

25. The preparation method according to claim 1, characterized in that, In the first coating, the mass ratio of the iron-based powder to the silane coupling agent in the coating liquid is 100:0.3 - 0.

8.

26. The preparation method according to claim 1, characterized in that, The temperature of the first coating is 50 - 80 °C, and the time is 50 - 100 min.

27. The preparation method according to claim 1, characterized in that, The silicone resin includes organosilicone resin.

28. The preparation method according to claim 1, characterized in that, In the curing step, the solvent includes ketone solvents and / or ester solvents.

29. The preparation method according to claim 1, characterized in that, In the curing step, based on the mass of the iron-based powder, the mass of the silicone resin is 0.8 - 1.2 wt%, and the mass of the solvent is 2 - 3 wt%.

30. The preparation method according to claim 1, characterized in that, The temperature of the curing is 60 - 80 °C, and the time is 30 - 60 min.

31. The preparation method according to claim 1, characterized in that, The temperature of the molding is 20 - 30 °C, the pressure is 800 - 2000 MPa, and the time is 10 - 20 s.

32. The preparation method according to claim 1, wherein A mold release agent is also added in the molding.

33. The preparation method according to claim 1, wherein, The temperature of the annealing is 650 - 750 °C, and the time is 60 - 90 min.

34. The preparation method according to claim 21, characterized in that, The magnetic iron-based alloy powder includes at least one of iron-silicon-aluminum alloy, iron-nickel alloy, and iron-silicon alloy.

35. The preparation method according to claim 23, wherein, The temperature of the pre-coating is 60 - 70 °C, and the time is 60 - 90 min.

36. The preparation method according to claim 26, characterized in that, The temperature of the first coating is 60 - 70 °C, and the time is 60 - 90 min.

37. The preparation method according to claim 27, characterized in that, The organosilicone resin includes at least one of methyl silicone resin, ethyl silicone resin, and polydimethylsiloxane.

38. The preparation method according to claim 28, wherein, In the curing step, the ketone solvent includes acetone; and / or, the ester solvent includes ethyl acetate.

39. The preparation method according to claim 32, characterized in that, In the curing step, based on the mass of the iron-based powder, the mass of the mold release agent is 0.3 - 0.4 wt%; and / or, the mold release agent includes stearate.

40. The preparation method according to any one of claims 1 to 39, characterized in that, In the second coating, the mass ratio of the product after annealing to the silane coupling agent in the coating liquid is 100:0.3 - 0.8; and / or, the temperature of the second coating is 70 - 90 °C, and the time is 60 - 90 min; and / or, the temperature of the drying is 60 - 80 °C, and the time is 60 - 120 min; and / or, the temperature of the baking is 180 - 240 °C, and the time is 60 - 90 min.

41. An anti-rust soft magnetic composite material prepared by the preparation method according to any one of claims 1 - 40.

42. Application of the anti-rust soft magnetic composite material according to claim 41 in an inductor, transformer, filter, motor, or sensor.

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