Composite soft magnetic powder core and method for producing the same

Abstract

This invention discloses a composite soft magnetic powder core and its preparation method. FeSiAl magnetic powder is added to a mixture of phosphoric acid and ethanol, stirred, and then dried to obtain insulating FeSiAl powder. Tetraethyl orthosilicate and anhydrous ethanol are added to FeNi magnetic powder, stirred, and then diluted with ammonia solution dropwise while stirring. After drying, insulating FeNi powder is obtained. The insulating FeSiAl and FeNi powders are mixed in a certain proportion to obtain composite metal magnetic powder. The composite metal magnetic powder is sieved and granulated, then a resin binder and zinc stearate are added, pressed into a green body, and annealed at high temperature to obtain the finished FeSiAl / FeNi composite powder core. Through the above methods, this invention provides targeted insulating coating for FeSiAl and FeNi magnetic powders, adjusts the permeability of the two magnetic powders, and achieves adjustment of the DC bias curve of the FeSiAl / FeNi composite powder core. This improves its anti-saturation capability under light load conditions, thereby improving light load efficiency and solving the problem of easy saturation of components in high-power applications.

Description

Technical Field

[0001] This invention relates to the field of magnetic material preparation technology, and in particular to a composite soft magnetic powder core and its preparation method. Background Technology

[0002] As power electronic equipment becomes increasingly more high-frequency, miniaturized, and integrated, soft magnetic metal powder cores, due to their high saturation magnetic induction intensity, good frequency stability, excellent DC bias performance, and low eddy current loss, are widely used as important functional materials in switching power supplies, communication power supplies, electric vehicles, inverters, variable frequency air conditioners, and other fields.

[0003] However, with the increasing frequency and miniaturization of electronic components, improving efficiency and reducing temperature rise have become pressing problems. Especially in high-power applications, ensuring unsaturated magnetic cores and low losses requires powder cores with good DC bias performance and low losses. FeNi magnetic powder cores are the primary choice due to their excellent DC bias performance and low losses, but they are expensive. Compared to FeNi powder cores, FeSiAl powder cores, although having poorer DC bias performance, have lower losses and lower costs, and can be used in conjunction with FeNi powder cores. FeSiAl / FeNi composite powder cores offer both excellent DC bias performance and low losses while solving the problem of high product prices, thus saving costs. The application of products based on soft magnetic powder cores in circuits can be categorized into light-load and heavy-load scenarios. Under light-load conditions, the poorer DC bias performance of FeSiAl magnetic powder compared to FeNi magnetic powder becomes the main factor limiting the DC bias performance of FeSiAl / FeNi composite soft magnetic powder cores. Under heavy-load conditions, the superior DC bias performance of FeNi magnetic powder allows the FeSiAl / FeNi composite powder core to still exhibit high anti-saturation capability. Therefore, while ensuring low loss and anti-saturation performance under heavy-load conditions, addressing the issue of poor DC bias performance of FeSiAl / FeNi composite powder cores under light-load conditions is crucial for fabricating high-performance metal soft magnetic powder cores suitable for high-power applications.

[0004] In view of this, it is necessary to explore a novel FeSiAl / FeNi composite powder core that can still maintain good DC bias performance under light load conditions in order to solve the above problems. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing composite soft magnetic powder cores. By subjecting FeSiAl and FeNi magnetic powders to targeted insulating coating treatments, the permeability of FeSiAl magnetic powder is ≤26, and the permeability of FeNi magnetic powder is 1.5 times or even higher. This results in a FeSiAl / FeNi composite powder core, prepared by mixing the two in a certain proportion, exhibiting high anti-saturation capability under both light and heavy loads. This solves the problems of easy saturation and severe heat generation in electronic components used in high-power applications, as well as the low efficiency under light loads. This aligns with the development trend of high-frequency, miniaturized, and integrated magnetic components.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] A method for preparing a composite soft magnetic powder core, the method comprising the following steps:

[0008] FeSiAl magnetic powder was added to a mixture of phosphoric acid and ethanol, stirred, and then dried to obtain insulating FeSiAl powder.

[0009] Tetraethyl orthosilicate and anhydrous ethanol were added to FeNi magnetic powder, and after stirring, ammonia water dilution was added dropwise while stirring. After the addition was completed, stirring was continued for a period of time. After drying, insulating FeNi powder was obtained.

[0010] Composite metal magnetic powder is prepared by mixing FeSiAl powder with insulating coating and FeNi powder with insulating coating in a certain proportion.

[0011] The composite metal magnetic powder is sieved and granulated, then resin binder and zinc stearate are added, pressed into a green body, and then annealed at high temperature to obtain the FeSiAl / FeNi composite powder core product.

[0012] As a further improvement of the present invention, when adding a mixture of phosphoric acid and ethanol to FeSiAl magnetic powder, the mass ratio of FeSiAl magnetic powder, phosphoric acid and ethanol is controlled to be 100:(1.2~1.5):12.

[0013] As a further improvement of the present invention, when tetraethyl orthosilicate and anhydrous ethanol are added to FeNi magnetic powder, and then diluted with ammonia solution after stirring, the solution is added dropwise.

[0014] The mass ratio of the tetraethyl orthosilicate, anhydrous ethanol, ammonia, and deionized water is controlled to be 5:4:2:2;

[0015] The mass ratio of the FeNi magnetic powder to the coating liquid is controlled to be 100:(19.5~26).

[0016] As a further improvement of the present invention, when insulating coated FeSiAl powder and insulating coated FeNi powder are mixed in a certain proportion,

[0017] The proportion of the insulating FeSiAl powder in the composite metal magnetic powder is controlled to be 65% to 85%.

[0018] As a further improvement of the present invention, the magnetic permeability μ1 of the insulating FeSiAl powder is ≤26;

[0019] The magnetic permeability μ2 of the insulating FeNi powder is ≥1.5μ1.

[0020] As a further improvement of the present invention, when the composite metal magnetic powder is sieved and granulated, then a resin binder and zinc stearate are added, and then pressed into a green body,

[0021] The mass ratio of composite metal magnetic powder to resin binder and zinc stearate is controlled to be 100:0.3:0.4.

[0022] As a further improvement of the present invention, when the composite metal magnetic powder is sieved and granulated, then a resin binder and zinc stearate are added, and then pressed into a green body,

[0023] A 200-mesh sieve was used for sieving and granulation, and a two-way floating pressing method was adopted to control the pressing pressure at 1200-1800 MPa.

[0024] As a further improvement of the present invention, the density of the obtained green body is 5.9–7.1 g / cm³. 3 .

[0025] As a further improvement of the present invention, the high-temperature annealing includes:

[0026] The green blanks were placed in an annealing furnace, and the furnace was heated to 200°C at a heating rate of 5°C / min and held for 1 hour under nitrogen protection.

[0027] Then, the temperature was increased to 500℃ at a rate of 5℃ / min and held for 3 hours.

[0028] Then, the product is cooled to room temperature in the furnace to obtain the finished product.

[0029] The present invention also provides a composite soft magnetic powder core, which is prepared by any of the preparation methods described above.

[0030] The beneficial effects of this invention are:

[0031] The present invention provides a method for preparing composite soft magnetic powder cores. This involves adding FeSiAl magnetic powder to a mixture of phosphoric acid and ethanol, stirring, and then drying to obtain insulating FeSiAl powder. Tetraethyl orthosilicate and anhydrous ethanol are added to FeNi magnetic powder, and the mixture is stirred. Ammonia dilution is then added dropwise while stirring. After the addition is complete, stirring continues for a period of time, followed by drying to obtain insulating FeNi powder. The insulating FeSiAl and FeNi powders are mixed in a certain proportion to obtain composite metal magnetic powder. The composite metal magnetic powder is then sieved and granulated, and a resin binder and zinc stearate are added. The mixture is pressed into a green blank and annealed at high temperature to obtain the finished FeSiAl / FeNi composite powder core. Through this method, the present invention achieves targeted insulating coating of FeSiAl and FeNi magnetic powders, adjusting the permeability of the two magnetic powders, thereby adjusting the DC bias curve of the FeSiAl / FeNi composite powder core, improving its anti-saturation capability under light load conditions, and thus improving light load efficiency and solving the problem of easy saturation of components in high-power applications.

[0032] The method for preparing the composite soft magnetic powder core of this invention involves coating FeSiAl magnetic powder with phosphate through in-situ passivation using phosphoric acid, resulting in a dense and uniform coating layer. For FeNi magnetic powder, which exhibits good corrosion resistance, oxide coating is used. The SiO2 insulating layer prepared by the Stobol method has high resistivity, effectively reducing eddy current losses in the magnetic core. Neither coating method involves an organic insulating layer, effectively avoiding the aging problems associated with organic insulating layers. Furthermore, by adjusting the amounts of phosphoric acid and tetraethyl orthosilicate, the permeability of FeSiAl and FeNi can be adjusted respectively, thereby improving the DC bias performance of the FeSiAl / FeNi composite soft magnetic powder core.

[0033] The composite soft magnetic powder core preparation method of the present invention uses FeSiAl and FeNi magnetic powders with low loss, which can effectively reduce the temperature rise of the composite powder core. Under the same requirements, the product volume can be reduced, saving costs and conforming to the development trend of miniaturization and high frequency of electronic components.

[0034] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures pointed out in the description, claims and drawings. Attached Figure Description

[0035] Figure 1 The DC bias curve of the FeSiAl / FeNi composite soft magnetic powder core prepared in Example 1 is shown.

[0036] Figure 2The DC bias curve of the FeSiAl / FeNi composite soft magnetic powder core prepared in Example 2 is shown.

[0037] Figure 3 The DC bias curve of the FeSiAl / FeNi composite soft magnetic powder core prepared in Comparative Example 1 is shown.

[0038] Figure 4 The DC bias curve of the FeSiAl / FeNi composite soft magnetic powder core prepared in Comparative Example 2 is shown.

[0039] Figure 5 The DC bias curves are shown for the FeSiAl / FeNi composite soft magnetic powder cores prepared in Examples 1 and 2 and Comparative Examples 1 and 2. Detailed Implementation

[0040] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0041] The method for preparing composite soft magnetic powder cores provided by this invention includes the following steps:

[0042] FeSiAl magnetic powder was added to a mixture of phosphoric acid and ethanol, stirred, and then dried to obtain insulating FeSiAl powder.

[0043] Tetraethyl orthosilicate and anhydrous ethanol were added to FeNi magnetic powder, and after stirring, ammonia dilution was added dropwise while stirring. After the addition was completed, stirring was continued for a period of time to allow the reaction of tetraethyl orthosilicate hydrolysis to generate nano-silica powder to proceed fully. After drying, insulating FeNi powder was obtained.

[0044] Composite metal magnetic powder is prepared by mixing FeSiAl powder with insulating coating and FeNi powder with insulating coating in a certain proportion.

[0045] The composite metal magnetic powder is sieved and granulated, then resin binder and zinc stearate are added, pressed into a green body, and then annealed at high temperature to obtain the FeSiAl / FeNi composite powder core product.

[0046] When adding a mixture of phosphoric acid and ethanol to FeSiAl magnetic powder, the mass ratio of FeSiAl magnetic powder, phosphoric acid and ethanol is controlled to be 100:(1.2~1.5):12.

[0047] In the process of adding tetraethyl orthosilicate and anhydrous ethanol to FeNi magnetic powder, and then adding ammonia water dilution after stirring, the mass ratio of tetraethyl orthosilicate, anhydrous ethanol, ammonia water and deionized water is controlled to be 5:4:2:2; and the mass ratio of FeNi magnetic powder to coating solution is controlled to be 100:(19.5~26).

[0048] When insulating FeSiAl powder and insulating FeNi powder are mixed in a certain proportion, the proportion of insulating FeSiAl powder in the composite metal magnetic powder is controlled to be 65% to 85%.

[0049] Among them, the magnetic permeability μ1 of the insulating coated FeSiAl powder is ≤26; the magnetic permeability μ2 of the insulating coated FeNi powder is ≥1.5μ1.

[0050] In the process of sieving and granulating the composite metal magnetic powder, adding resin binder and zinc stearate, and pressing it into a green body, the mass ratio of composite metal magnetic powder to resin binder and zinc stearate should be controlled at 100:0.3:0.4. At the same time, a 200-mesh sieve can be used for sieving and granulation, and bidirectional floating pressing should be adopted to control the pressing pressure at 1200-1800MPa.

[0051] The density of the prepared green body was 5.9–7.1 g / cm³. 3 .

[0052] The high-temperature annealing process includes: placing the green blank in an annealing furnace, heating the furnace to 200°C at a heating rate of 5°C / min and holding it at that temperature for 1 hour under nitrogen protection; then heating the furnace to 500°C at a heating rate of 5°C / min and holding it at that temperature for 3 hours; and then cooling the blank to room temperature in the furnace to obtain the finished product.

[0053] The present invention also provides a composite soft magnetic powder core, which is prepared by any of the above-described preparation methods.

[0054] The method for preparing the composite soft magnetic powder core of the present invention will be specifically described below with reference to Examples 1 and 2 and Comparative Examples 1 and 2:

[0055] Example 1

[0056] This embodiment provides a method for preparing a composite soft magnetic powder core using FeSiAl powder with a magnetic permeability of 15 and FeNi powder with a magnetic permeability of 60, comprising the following steps:

[0057] (1) Insulation coating of FeSiAl magnetic powder: 200g of gas-atomized FeSiAl magnetic powder was added to a mixture of 2.4g of phosphoric acid and 24g of ethanol, mechanically stirred for 30min and then dried to obtain gas-atomized FeSiAl powder with magnetic permeability μ1 = 15 after insulation coating.

[0058] (2) FeNi magnetic powder insulation coating: 16g of anhydrous ethanol and 20g of tetraethyl orthosilicate were added to 200g of FeNi magnetic powder and mechanically stirred to obtain a mixture. Then, 8g of ammonia water and 8g of deionized water were taken to prepare an ammonia water dilution solution and added to the mixture at a dropping rate of 0.5ml / min while stirring. After the addition was completed, stirring was continued for 1h to allow the reaction of tetraethyl orthosilicate hydrolysis to generate nano-silica powder to proceed fully. Then, the mixture was dried to obtain FeNi powder with a magnetic permeability μ2 = 60 after insulation coating.

[0059] (3) The FeSiAl magnetic powder with a magnetic permeability of 15 and the FeNi magnetic powder with a magnetic permeability of 60 obtained in steps (1) and (2) are mixed at a ratio of 7:3 to obtain composite metal magnetic powder.

[0060] (4) The composite magnetic powder obtained in step (3) is sieved through a 200-mesh sieve for granulation. Then, 200g of the granulated powder is mixed with 0.6g of resin binder and 0.8g of zinc stearate. Finally, it is subjected to bidirectional floating pressing under a pressure of 1500MPa using a hydraulic press to produce a powder with a density of 6.13g / cm³. 3 raw blanks;

[0061] (5) Place the green blank obtained in step (4) into an annealing furnace and introduce nitrogen gas to purge the air in the furnace. Under the protection of nitrogen gas, perform annealing treatment by heating from room temperature to 200°C at a heating rate of 5°C / min and holding for 1 hour, then heating to 500°C at a heating rate of 5°C / min and holding for 3 hours, and then cooling the furnace to room temperature to obtain the FeSiAl / FeNi composite core product.

[0062] The main magnetic properties of the FeSiAl / FeNi composite powder core prepared in this embodiment, after winding tests, are as follows:

[0063] (1) Under the condition of 100kHz / 1V, the permeability μ=26.5;

[0064] (2) DC bias performance: at 100kHz and H = 300Oe, %μ = 48.1%; at H = 800Oe, %μ = 11.1%; (e.g. Figure 1 (As shown).

[0065] (3) Loss: At 100kHz / 500Gs, Pcv=274mW / cm 3 .

[0066] Example 2

[0067] This embodiment provides a method for preparing a composite soft magnetic powder core using FeSiAl powder with a magnetic permeability of 10 and FeNi powder with a magnetic permeability of 75, comprising the following steps:

[0068] (1) Insulation coating of FeSiAl magnetic powder: 200g of gas-atomized FeSiAl magnetic powder was added to a mixture of 3.0g of phosphoric acid and 24g of ethanol, mechanically stirred for 30min and then dried to obtain gas-atomized FeSiAl powder with magnetic permeability μ1=10 after insulation coating.

[0069] (2) FeNi magnetic powder insulation coating: 12g of anhydrous ethanol and 15g of tetraethyl orthosilicate were added to 200g of FeNi magnetic powder and mechanically stirred to obtain a mixture. Then, 6g of ammonia water and 6g of deionized water were taken to prepare an ammonia water dilution solution and added to the mixture at a dropping rate of 0.5ml / min while stirring. After the addition was completed, stirring was continued for 1h to allow the reaction of tetraethyl orthosilicate hydrolysis to generate nano-silica powder to proceed fully. Then, the powder was dried to obtain FeNi powder with a magnetic permeability μ2 = 75 after insulation coating.

[0070] (3) The FeSiAl magnetic powder with a magnetic permeability of 10 and the FeNi magnetic powder with a magnetic permeability of 75 obtained in steps (1) and (2) are mixed at a ratio of 7:3 to obtain composite metal magnetic powder.

[0071] (4) The composite magnetic powder obtained in step (3) is sieved through a 200-mesh sieve for granulation. Then, 200g of the granulated powder is mixed with 0.6g of resin binder and 0.8g of zinc stearate. Finally, it is subjected to bidirectional floating pressing under a pressure of 1500MPa using a hydraulic press to produce a powder with a density of 6.13g / cm³. 3 raw blanks;

[0072] (5) Place the green blank obtained in step (4) into an annealing furnace and introduce nitrogen gas to purge the air in the furnace. Under the protection of nitrogen gas, perform annealing treatment by heating from room temperature to 200°C at a heating rate of 5°C / min and holding for 1 hour, then heating to 500°C at a heating rate of 5°C / min and holding for 3 hours, and then cooling the furnace to room temperature to obtain the FeSiAl / FeNi composite core product.

[0073] The main magnetic properties of the FeSiAl / FeNi composite powder core prepared in this embodiment, after winding tests, are as follows:

[0074] (1) Under the condition of 100kHz / 1V, the permeability μ=26.5;

[0075] (2) DC bias performance: at 100kHz and H=300Oe, %μ=53.6%; at H=800Oe, %μ=11.0%; (e.g. Figure 2 (As shown).

[0076] (3) Loss: At 100kHz / 500Gs, Pcv=275mW / cm3 .

[0077] Comparative Example 1

[0078] This comparative example provides a method for preparing composite soft magnetic powder cores using FeSiAl powder and FeNi powder, both with a permeability of 26, including the following steps:

[0079] (1) FeSiAl magnetic powder insulation coating: 200g of gas-atomized FeSiAl magnetic powder was added to a mixture of 1.2g of phosphoric acid and 24g of ethanol, mechanically stirred for 30min and then dried to obtain FeSiAl powder with magnetic permeability μ1 = 26 after insulation coating.

[0080] (2) FeNi magnetic powder insulation coating: 28g of anhydrous ethanol and 35g of tetraethyl orthosilicate were added to 200g of FeNi magnetic powder and mechanically stirred to obtain a mixture. Then, 14g of ammonia water and 14g of deionized water were taken to prepare an ammonia water dilution solution and added to the mixture at a dropping rate of 0.5ml / min while stirring. After the addition was completed, stirring was continued for 1h to allow the reaction of tetraethyl orthosilicate hydrolysis to generate nano-silica powder to proceed fully. Then, the mixture was dried to obtain FeNi powder with a magnetic permeability μ2 = 26 after insulation coating.

[0081] (3) Mix the FeSiAl magnetic powder and FeNi magnetic powder with a permeability of 26 obtained in steps (1) and (2) at a ratio of 7:3 to obtain composite metal magnetic powder;

[0082] (4) The composite magnetic powder obtained in step (3) is sieved through a 200-mesh sieve for granulation. Then, 200g of the granulated powder is mixed with 0.6g of resin binder and 0.8g of zinc stearate. Finally, it is pressed by bidirectional floating under a pressure of 1500MPa using a hydraulic press to produce a powder with a density of 6.2g / cm³. 3 raw blanks;

[0083] (5) Place the green blank obtained in step (4) into an annealing furnace and introduce nitrogen gas to purge the air in the furnace. Under the protection of nitrogen gas, perform annealing treatment by heating from room temperature to 200°C at a heating rate of 5°C / min and holding for 1 hour, then heating to 500°C at a heating rate of 5°C / min and holding for 3 hours, and then cooling the furnace to room temperature to obtain the FeSiAl / FeNi composite core product.

[0084] The main magnetic properties of the FeSiAl / FeNi composite powder core prepared in this comparative example, after winding tests, are as follows:

[0085] (1) Under the condition of 100kHz / 1V, the permeability μ=26.6;

[0086] (2) DC bias performance: at 100kHz and H=300Oe, %μ=43.4%; at H=800Oe, %μ=11.2%; (e.g. Figure 3 (As shown).

[0087] (3) Loss: At 100kHz / 500Gs, Pcv=273mW / cm 3 .

[0088] Comparative Example 2

[0089] This comparative example provides a prior art method for preparing composite soft magnetic powder cores, comprising the following steps:

[0090] (1) Preparation of composite magnetic powder: Gas-atomized FeSiAl magnetic powder and FeNi magnetic powder are mixed together in a ratio of 7:3 and mechanically stirred to obtain composite FeSiAl / FeNi magnetic powder;

[0091] (2) FeSiAl / FeNi magnetic powder insulation coating: 28g of anhydrous ethanol and 35g of tetraethyl orthosilicate were added to 200g of composite magnetic powder and mechanically stirred to obtain a mixture. Then, 14g of ammonia water and 14g of deionized water were taken to prepare an ammonia water dilution solution and added to the mixture at a dropping rate of 0.5ml / min while stirring. After the addition was completed, stirring was continued for 1h to allow the reaction of tetraethyl orthosilicate hydrolysis to generate nano-silica powder to proceed fully. Then, the mixture was dried to obtain composite metal magnetic powder with a permeability μ=26 after insulation coating.

[0092] (3) The composite magnetic powder obtained in step (2) is sieved through a 200-mesh sieve for granulation. Then, 200g of the granulated powder is mixed with 0.6g of resin binder and 0.8g of zinc stearate. Finally, it is subjected to bidirectional floating pressing under a pressure of 1500MPa using a hydraulic press to produce a powder with a density of 6.2g / cm³. 3 raw blanks;

[0093] (4) Place the green blank obtained in step (3) into an annealing furnace and introduce nitrogen gas to purge the air in the furnace. Under the protection of nitrogen gas, perform annealing treatment by heating from room temperature to 200°C at a heating rate of 5°C / min and holding for 1 hour, then heating to 500°C at a heating rate of 5°C / min and holding for 3 hours, and then cooling the furnace to room temperature to obtain the FeSiAl / FeNi composite core product.

[0094] The main magnetic properties of the FeSiAl / FeNi composite powder core prepared in this comparative example, after winding tests, are as follows:

[0095] (1) Under the condition of 100kHz / 1V, the permeability μ=26.6;

[0096] (2) DC bias performance: at 100kHz and H = 300Oe, %μ = 43.3%; at H = 800Oe, %μ = 11.2%; (e.g. Figure 4 (As shown).

[0097] (3) Loss: At 100kHz / 500Gs, Pcv=273mW / cm 3 .

[0098] Figure 5 The figure shows the DC bias curves of the FeSiAl / FeNi composite powder cores prepared in four sets of experiments. By comparing the main magnetic performance data of the FeSiAl / FeNi composite powder cores in Comparative Example 1 and Comparative Example 2, it can be seen that regardless of whether the two magnetic powders are uniformly mixed first and then insulated together, or whether the two magnetic powders are individually insulated and then mixed, the magnetic properties of the resulting composite powder cores are almost identical. However, by comparing the main magnetic performance data of Examples 1 and 2 and Comparative Example 1, it was found that when using FeSiAl powder and FeNi powder with a permeability of 26 to prepare the composite soft magnetic powder core (Comparative Example 1), compared with using FeSiAl powder with a permeability ≤26 and FeNi powder with a permeability ≥39 to prepare the composite soft magnetic powder core (Examples 1 and 2), the DC bias performance of the composite powder core prepared under light load (H=300Oe) is significantly lower, only 43.3%, with basically the same permeability and loss. When the permeability of FeSiAl magnetic powder is ≤26, and the permeability of FeNi magnetic powder is 1.5 times or even higher, the obtained FeSiAl / FeNi composite powder core exhibits a significant improvement in DC bias performance under light load (H=300Oe), even reaching as high as 53.6%. Therefore, this invention provides a method for preparing FeSiAl / FeNi composite powder cores that effectively improves the DC bias performance of FeSiAl / FeNi composite powder cores under light load conditions.

[0099] In summary, the method for preparing composite soft magnetic powder cores provided by this invention involves adding FeSiAl magnetic powder to a mixture of phosphoric acid and ethanol, stirring, and then drying to obtain insulating FeSiAl powder. Tetraethyl orthosilicate and anhydrous ethanol are added to FeNi magnetic powder, and after stirring, ammonia dilution is added dropwise while stirring. After the addition is complete, stirring continues for a period of time, and after drying, insulating FeNi powder is obtained. The insulating FeSiAl powder and insulating FeNi powder are mixed in a certain proportion to obtain composite metal magnetic powder. The composite metal magnetic powder is sieved and granulated, then a resin binder and zinc stearate are added, pressed into a green blank, and annealed at high temperature to obtain the finished FeSiAl / FeNi composite powder core. Through the above methods, this invention, by selectively insulating FeSiAl and FeNi magnetic powders, adjusts the permeability of the two magnetic powders, thereby adjusting the DC bias curve of the FeSiAl / FeNi composite powder core, improving its anti-saturation capability under light load conditions, thus improving light load efficiency and solving the problem of easy saturation of components in high-power applications. The FeSiAl magnetic powder is coated with phosphate in situ by phosphoric acid passivation, resulting in a dense and uniform coating layer. For FeNi magnetic powder, which exhibits better corrosion resistance, oxide coating is used. The SiO2 insulating layer prepared by the Stober method has high resistivity, effectively reducing eddy current losses in the magnetic core. Neither coating method involves an organic insulating layer, effectively avoiding the aging problems associated with organic insulating layers. Furthermore, by adjusting the amounts of phosphoric acid and tetraethyl orthosilicate, the permeability of FeSiAl and FeNi can be adjusted respectively, thereby improving the DC bias performance of the FeSiAl / FeNi composite soft magnetic powder core. In addition, the composite soft magnetic powder core preparation method of this invention uses FeSiAl and FeNi magnetic powders with low losses, effectively reducing the temperature rise of the composite powder core. Under the same requirements, it can reduce product size, save costs, and conform to the development trend of miniaturization and high-frequency operation of electronic components.

[0100] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a composite soft magnetic powder core, the method comprising the following steps: FeSiAl magnetic powder was added to a mixture of phosphoric acid and ethanol, stirred, and then dried to obtain insulating coated FeSiAl powder; the magnetic permeability μ1 of the insulating coated FeSiAl powder was ≤26. Tetraethyl orthosilicate and anhydrous ethanol were added to FeNi magnetic powder, and after stirring, ammonia solution was added dropwise while stirring. After the addition was completed, stirring was continued for a period of time. After drying, insulating FeNi powder was obtained. The mass ratio of tetraethyl orthosilicate, anhydrous ethanol, ammonia and deionized water was controlled to be 5:4:2:

2. The mass ratio of the FeNi magnetic powder to the coating liquid is controlled to be 100:(19.5~26); the magnetic permeability μ2 of the insulating coated FeNi powder is ≥1.5μ1; Composite metal magnetic powder is prepared by mixing FeSiAl powder with insulating coating and FeNi powder with insulating coating in a certain proportion. The composite metal magnetic powder is sieved and granulated, then resin binder and zinc stearate are added, pressed into a green body, and then annealed at high temperature to obtain the FeSiAl / FeNi composite powder core product. The high-temperature annealing includes: placing the green blank in an annealing furnace, heating the furnace to 200°C at a heating rate of 5°C / min and holding it at that temperature for 1 hour under nitrogen protection; The temperature was then increased to 500℃ at a rate of 5℃ / min and held for 3 hours; then cooled to room temperature in the furnace to obtain the finished product.

2. The method for preparing composite soft magnetic powder core according to claim 1, wherein, When adding a mixture of phosphoric acid and ethanol to FeSiAl magnetic powder, the mass ratio of FeSiAl magnetic powder, phosphoric acid and ethanol is controlled to be 100:(1.2~1.5):

12.

3. The method for preparing composite soft magnetic powder core according to claim 1, wherein, When insulating FeSiAl powder and insulating FeNi powder are mixed in a certain proportion, The proportion of the insulating FeSiAl powder in the composite metal magnetic powder is controlled to be 65%~85%.

4. The method for preparing composite soft magnetic powder core according to claim 1, wherein, When the composite metal magnetic powder is sieved and granulated, then resin binder and zinc stearate are added, and then pressed into a green body, The mass ratio of composite metal magnetic powder to resin binder and zinc stearate is controlled to be 100:0.3:0.

4.

5. The method for preparing composite soft magnetic powder core according to claim 4, wherein, When the composite metal magnetic powder is sieved and granulated, then resin binder and zinc stearate are added, and then pressed into a green body, A 200-mesh sieve was used for sieving and granulation, and a two-way floating pressing method was adopted to control the pressing pressure at 1200-1800 MPa.

6. The method for preparing composite soft magnetic powder core according to claim 1, wherein, The density of the obtained green body was 5.9~7.1 g / cm³. 3 .

7. A composite soft magnetic powder core, wherein the composite soft magnetic powder core is prepared by the preparation method according to any one of claims 1-6.

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