Composite soft magnetic powder core and preparation method and application thereof

Abstract

The application provides a composite soft magnetic powder core and a preparation method and application thereof, and the preparation method comprises the following steps: mixing silicon tetrachloride, an organic alcohol solvent and an alloy powder to obtain a mixture; mixing a transition metal salt solution, a precipitant and the mixture, and drying to obtain a pretreated alloy powder; mixing a binder, a release agent and the pretreated alloy powder, and pressing, and then performing heat treatment to obtain the composite soft magnetic powder core. The application can passivate the alloy powder, improve the air gap of the powder, reduce the eddy current loss, generate a silicon dioxide layer after heat treatment, and further improve the performance by chemical reaction on the surface of the alloy powder; in addition, the co-precipitation method can further improve the compactness of the alloy powder surface coating without reducing the passivation effect, effectively generate a high permeability ferrite, improve the high-frequency permeability of the composite soft magnetic powder core, and ensure the loss characteristics.

Description

Technical Field

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

[0002] Currently, magnetic materials are widely used in television, communication systems, electrical systems, and audio equipment. Their main applications are energy conversion, current parameter transformation, and providing a constant magnetic field. Metallic magnetic powder cores, with operating frequencies and power ratings between metals and ferrites, fill this gap. They are primarily used as main transformers in switching power supplies and high-frequency chokes, and can also be used in high-power circuits and video dimming equipment, serving as current blockers, transformers, and matching agents. Soft magnetic metallic materials such as permalloy, iron-silicon, and iron-silicon-aluminum possess high μ and high Bs properties, low resistivity, and excellent constant permeability. Their fabrication process is simple, requiring no high-temperature sintering, and their dimensions are easily controlled. However, because eddy current losses increase dramatically with frequency, they cannot meet the requirements of high-frequency applications.

[0003] Metal magnetic powder cores are generally formed by uniformly mixing and pressing magnetic powder with an insulating medium. The powder particles are very small, and because they are separated by a non-magnetic insulating medium, their resistivity is much higher than that of metals or alloys, resulting in significantly lower eddy current losses. Furthermore, magnetic powder cores can store a considerable amount of energy through internal air gaps during magnetization. Therefore, the performance of magnetic powder cores depends on the magnetic permeability, particle size, and morphology of the powder, as well as the powder filling ratio, the content of the insulating medium, the molding pressure, and the heat treatment process. Existing technologies have made significant progress in modifying amorphous nanocrystalline, ultracrystalline, and composite magnetic powders; however, further improvements are still needed in the resistivity and eddy current loss performance of magnetic powder cores.

[0004] CN 103440950A discloses an in-situ preparation method for magnetic powder cores. The method uses sol-gel to prepare uniform nano-ferrite particles on the surface of soft magnetic alloy powder in situ. The novel ferrite composite magnetic powder core is prepared by pressing and heat treatment. Ferrite is used as an insulating coating agent for soft magnetic alloy powder, which overcomes the disadvantage of reduced matrix magnetic properties when using traditional non-magnetic materials as coating agents and obtains higher magnetic permeability and saturation magnetization. However, the sol-gel method is prone to agglomeration, resulting in uneven powder coating.

[0005] The existing methods for preparing ferrite-coated magnetic powder cores mainly employ chemical co-precipitation to coat the ferrite shell, followed by pre-firing, pressing, and annealing. Although this method avoids flattening and phosphating the iron-silicon-aluminum powder, reducing experimental contamination, improving the permeability and quality factor of the composite magnetic core, and broadening the application frequency range of the magnetic powder core, the co-precipitation method has a low heat treatment temperature, which cannot effectively form a ferrite layer with high permeability. Furthermore, the addition of strong alkali during co-precipitation can cause some materials, such as Al, to segregate, which is not conducive to maintaining the high permeability performance of the material.

[0006] Based on the above research, there is a need to provide a method for preparing composite soft magnetic powder cores that can generate a coating layer through in-situ chemical reaction, so that the composite soft magnetic powder core has low eddy current loss while maintaining high magnetic permeability. Summary of the Invention

[0007] The purpose of this invention is to provide a composite soft magnetic powder core, its preparation method, and its application. The preparation method can coat a layer of silicon dioxide on the surface of alloy powder through a chemical reaction. While carrying out the chemical reaction, it can react with the alloy powder to change the air gap of the powder. Then, a ferrite layer is coated by an improved co-precipitation method, which ensures that the composite soft magnetic powder core has good magnetic permeability performance and low loss characteristics.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] In a first aspect, the present invention provides a method for preparing a composite soft magnetic powder core, the method comprising the following steps:

[0010] (1) Mix silicon tetrachloride, organic alcohol solvent and alloy powder to obtain a mixture;

[0011] (2) After mixing and drying the transition metal salt solution, precipitant and the mixture described in step (1), a pretreated alloy powder is obtained;

[0012] (3) After mixing and pressing the binder, release agent and the pretreated alloy powder described in step (2), heat treatment is performed to obtain the composite soft magnetic powder core.

[0013] In the preparation method of the composite soft magnetic powder core provided by this invention, silicon tetrachloride and organic alcohol solvent are used to chemically react on the surface of alloy powder to generate hydrochloric acid and silicate ester compounds. The generated hydrochloric acid can passivate the surface alloy of the alloy powder and react with the alloy to increase the air gap of the alloy powder, thereby improving the resistivity of the composite soft magnetic powder core and reducing losses. Compared with the use of conventional passivating agents such as phosphoric acid for passivation, the silicate ester compounds generated by silicon tetrachloride and organic alcohol solvent can generate a silicon dioxide coating layer during subsequent heat treatment, further improving performance. In addition, in order to simultaneously improve the high-frequency permeability of the composite soft magnetic powder core, a precipitation method is used to coat transition metal ferrite. On the basis of silicon dioxide coating, a ferrite layer can be coated again, which further improves the density of the coating on the surface of the alloy powder and improves the high-frequency permeability of the composite soft magnetic powder core, while maintaining loss characteristics.

[0014] The alloy powder used in this invention has not undergone passivation treatment.

[0015] Preferably, the organic alcohol solvent in step (1) includes any one or a combination of at least two of methanol, ethanol, propanol or isopropanol, with typical but not limited combinations including a combination of methanol and ethanol, or a combination of propanol and isopropanol.

[0016] The organic alcohol solvent used in this invention is preferably the aforementioned lower fatty alcohol, which ensures the smooth reaction between silicon tetrachloride and the organic alcohol solvent.

[0017] Preferably, the content of silicon tetrachloride in step (1) is 0.1-1.5 wt% of the mass of the alloy powder in step (1), for example, it can be 0.1 wt%, 0.3 wt%, 0.5 wt%, 0.7 wt%, 0.9 wt%, 1.1 wt%, 1.3 wt% or 1.5 wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0018] The addition of silicon tetrachloride described in this invention, when within a reasonable range, can further improve the passivation effect. If the addition of silicon tetrachloride is too low, the passivation effect will be poor, and the beneficial effects of increasing the air gap ratio and reducing losses will not be achieved. If the addition of silicon tetrachloride is too high, the air gap ratio will be too high, resulting in increased losses.

[0019] Preferably, the content of the organic alcohol solvent in step (1) is 80-150 wt% of the mass of the alloy powder in step (1), for example, it can be 80 wt%, 90 wt%, 100 wt%, 110 wt%, 120 wt%, 130 wt%, 140 wt% or 150 wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0020] Preferably, the alloy powder in step (1) comprises FeSiAl.

[0021] Preferably, in the FeSiAl, the Fe content is 88-91 wt%, for example, 88 wt%, 89 wt%, 90 wt%, or 91 wt%; the Si content is 5.5-6.5 wt%, for example, 5.5 wt%, 5.7 wt%, 5.9 wt%, 6.1 wt%, 6.3 wt%, or 6.5 wt%; and the Al content is 3-4.5 wt%, for example, 3 wt%, 3.3 wt%, 3.5 wt%, 3.7 wt%, 3.9 wt%, 4.1 wt%, 4.3 wt%, or 4.5 wt%, but is not limited to the listed values; other unlisted values ​​within the range are also applicable.

[0022] Preferably, the mixing of silicon tetrachloride, organic alcohol solvent and alloy powder in step (1) includes: first mixing silicon tetrachloride and alloy powder to obtain mixed powder, then adding the mixed powder to organic alcohol solvent and stirring under vacuum for 20-40 min, for example, 20 min, 25 min, 30 min, 35 min or 40 min, but not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0023] Preferably, the transition metal salt solution in step (2) includes any one or a combination of at least two of zinc salt, manganese salt, calcium salt, aluminum salt or iron salt. Typical but not limited combinations include combinations of zinc salt and manganese salt, or combinations of aluminum salt and iron salt, and preferably a combination of zinc salt, manganese salt and calcium salt.

[0024] When the transition metal salts used in this invention are zinc salts, manganese salts, and calcium salts, a ZnMnCa ferrite coating layer can be formed on the surface of the alloy powder. The ferrite generated by the selection of specific transition metals can improve the permeability of the magnetic powder core at high frequencies, so that the magnetic powder core has both low eddy current loss and high high-frequency permeability. At the same time, compared with ZnMn ferrite, the ZnMnCa ferrite of this invention can reduce the sintering temperature after Ca doping and form a high-resistivity layer at the grain boundary, thereby increasing the grain boundary resistivity and reducing material loss, which can further improve the high-frequency permeability.

[0025] Preferably, the calcium salt comprises an organic calcium salt.

[0026] The calcium salt described in this invention is an organic calcium salt. Since most inorganic calcium salts are not easily soluble in water and cannot co-precipitate with other metal salts, and compared with inorganic calcium salts such as calcium chloride, which contains chlorine, introducing impurities and not meeting environmental standards, organic calcium salts are preferred.

[0027] Preferably, the organic calcium salt comprises any one or a combination of at least two of calcium gluconate, calcium lactate, calcium threonate, or calcium citrate. Typical but non-limiting combinations include a combination of calcium gluconate and calcium lactate, or a combination of calcium threonate and calcium gluconate.

[0028] Preferably, the amount of zinc salt added is 0.01-0.1 wt% of the mass of the alloy powder in step (1), for example, it can be 0.01 wt%, 0.03 wt%, 0.05 wt%, 0.07 wt%, 0.09 wt% or 0.1 wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0029] Preferably, the amount of manganese salt added is 0.01-0.2 wt% of the mass of the alloy powder in step (1), for example, it can be 0.01 wt%, 0.03 wt%, 0.05 wt%, 0.07 wt%, 0.09 wt%, 0.1 wt%, 0.13 wt%, 0.15 wt%, 0.17 wt%, or 0.2 wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0030] Preferably, the amount of calcium salt added is 10-30 wt% of the total amount of zinc salt and manganese salt added, for example, it can be 10 wt%, 12.5 wt%, 15 wt%, 17.5 wt%, 20 wt%, 22.5 wt%, 25 wt%, 27.5 wt%, or 30 wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0031] The amount of calcium salt added in this invention should be within a reasonable range. If the amount of calcium salt added is too high, an amorphous glass phase will be formed at the grain boundary, making it difficult to increase μ and instead making it easy to decrease.

[0032] Preferably, the amount of precipitant added in step (2) is such that the pH of the system after mixing in step (2) is greater than 7.5. For example, it can be 7.6, 7.9, 8.1, 8.3, 8.5, 8.7, 8.9, 9.1, 9.3, 9.5, 9.7, 9.9 or 10, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable. Preferably, 7.5 < pH < 9.

[0033] In order to complement the hydrochloric acid generated by the reaction of silicon tetrachloride and organic alcohol solvent in step (1) for passivation of alloy powder, this invention ensures that the pH during co-precipitation is not too high, thus avoiding the impact on the passivation effect. This allows the chemical reaction in step (1) and the co-precipitation reaction in step (2) to complement each other and improve the overall performance of the composite soft magnetic powder core.

[0034] Preferably, the mixing time in step (2) is 5-20 min, for example, it can be 5 min, 10 min, 15 min or 20 min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0035] Preferably, the precipitant in step (2) includes any one or a combination of at least two of carbonates, bicarbonates or ammonia, for example, a combination of carbonates and ammonia, or a combination of bicarbonates and ammonia, preferably a combination of bicarbonates and ammonia.

[0036] This invention uses a combination of bicarbonate and ammonia as a precipitant, instead of directly using strong alkaline hydroxides such as sodium hydroxide as a precipitant. This achieves the co-precipitation effect and ensures that different transition metals are evenly distributed on the surface of the alloy powder, without damaging the passivation layer obtained after the chemical reaction in step (1). Directly using hydroxides for co-precipitation will damage the passivation layer and reduce the combined effect of steps (1) and (2).

[0037] Preferably, the bicarbonate includes ammonium bicarbonate, and the carbonate includes ammonium carbonate.

[0038] Preferably, the mixing of the transition metal salt solution, the precipitant and the mixture described in step (1) in step (2) includes: first adding the transition metal salt solution to the mixture described in step (1), stirring for 5-10 minutes, for example, 5 minutes, 10 minutes or 15 minutes, and then adding the precipitant.

[0039] Preferably, the heat treatment in step (3) is carried out in an oxygen-containing protective gas.

[0040] The heat treatment described in this invention is carried out in an oxygen-containing protective gas. On the one hand, this can convert the silicate ester compound obtained in step (1) into silicon dioxide. On the other hand, in order to match the high temperature of the heat treatment in this invention, it is carried out in a protective gas.

[0041] Preferably, the oxygen-containing protective gas contains 1-3 wt% oxygen, for example, 1 wt%, 1.25 wt%, 1.5 wt%, 1.75 wt%, 2 wt%, 2.25 wt%, 2.5 wt%, 2.75 wt%, or 3 wt%, but is not limited to the listed values; other unlisted values ​​within the range are also applicable.

[0042] Preferably, the protective gas includes nitrogen and / or an inert gas.

[0043] Preferably, the inert gas includes any one or a combination of at least two of argon, helium, krypton, radon, or neon.

[0044] Preferably, the heat treatment temperature in step (3) is T, where 750℃ < T ≤ 850℃. For example, it can be 760℃, 770℃, 790℃, 800℃, 810℃, 820℃, 830℃, 840℃ or 850℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0045] The heat treatment described in this invention is carried out at a relatively high temperature. At a lower temperature, effective ferrite cannot be generated, while at a higher temperature, it will damage the magnetic powder core and increase energy consumption.

[0046] Preferably, the heat treatment time in step (3) is 15-30 min, for example, it can be 15 min, 20 min, 25 min or 30 min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0047] Preferably, after the heat treatment in step (3) is completed, the temperature is lowered to 600-750℃, for example, it can be 600℃, 620℃, 640℃, 660℃, 680℃, 700℃, 720℃, 740℃ or 750℃, and kept at that temperature in an inert atmosphere for 1-4 hours, for example, it can be 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours or 4 hours, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0048] Preferably, the pressing temperature in step (3) is 135-150°C, for example, it can be 135°C, 140°C, 145°C or 150°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0049] Preferably, the pressure of the hot pressing in step (3) is 13-15 T / cm. 2 For example, it could be 13.5T / cm 2 14T / cm 2 14.5T / cm 2 Or 15T / cm 2 The time is 120-150 seconds, for example, it can be 120 seconds, 130 seconds, 140 seconds or 150 seconds, but it is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0050] Preferably, the amount of binder added in step (3) is 2-8 wt% of the mass of the pretreated alloy powder in step (2), for example, it can be 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt% or 8 wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0051] Preferably, the adhesive in step (3) comprises polyethylene and / or polypropylene.

[0052] Preferably, the amount of release agent added in step (3) is 0.1-1 wt% of the mass of the pretreated alloy powder in step (2), for example, it can be 0.1 wt%, 0.3 wt%, 0.5 wt%, 0.7 wt%, 0.9 wt% or 1 wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0053] Preferably, the release agent in step (3) comprises barium stearate and / or calcium stearate.

[0054] As a preferred embodiment of the preparation method of the present invention, the preparation method includes the following steps:

[0055] (1) Mix silicon tetrachloride, organic alcohol solvent and alloy powder to obtain a mixture;

[0056] The content of silicon tetrachloride is 0.1-1.5 wt% of the mass of the alloy powder in step (1), and the content of the organic alcohol solvent is 80-150 wt% of the mass of the alloy powder in step (1).

[0057] (2) The transition metal salt solution, precipitant and the mixture described in step (1) are mixed, and the amount of precipitant added is such that the pH of the mixed system is 7.5 < pH < 9. After drying, the pretreated alloy powder is obtained.

[0058] The precipitant comprises a combination of bicarbonate and ammonia.

[0059] The transition metal salt solution includes zinc salt, manganese salt and organic calcium salt. The amount of zinc salt added is 0.01-0.1 wt% of the mass of the alloy powder in step (1), the amount of manganese salt added is 0.01-0.2 wt% of the mass of the alloy powder in step (1), and the amount of organic calcium salt added is 0-30 wt% of the total amount of zinc salt and manganese salt, but excluding 0 wt%.

[0060] (3) The binder, release agent and the pretreated alloy powder described in step (2) are mixed and pressed into shape at 135-150℃. Then, under a protective atmosphere with an oxygen content of 1-3wt%, the mixture is heat-treated at a temperature of 750℃ < T ≤ 850℃ for 15-30 minutes. The mixture is then cooled to 600-750℃ and kept at that temperature in an inert atmosphere for 1-4 hours to obtain the composite soft magnetic powder core.

[0061] Secondly, the present invention provides a composite soft magnetic powder core, which is obtained by the preparation method described in the first aspect.

[0062] The composite soft magnetic powder core of the present invention is coated with silicon dioxide and ferrite, preferably with a silicon dioxide layer and a ferrite layer sequentially coated on the surface.

[0063] Preferably, the ferrite layer comprises a ZnMnCa ferrite layer.

[0064] Thirdly, the present invention provides an application of the composite soft magnetic powder core as described in the second aspect, the application including a filter inductor for a power supply system.

[0065] Compared with the prior art, the present invention has the following beneficial effects:

[0066] This invention, through a chemical reaction on the surface of alloy powder, not only passivates the alloy powder, improves the air gap of the powder, and reduces eddy current loss, but also generates a silicon dioxide layer after heat treatment to protect the alloy magnetic powder, further improving the performance of the composite soft magnetic powder core; at the same time, combined with the improved co-precipitation method, using bicarbonate or carbonate as a precipitant, ferrite is prepared at a higher temperature, which can further improve the density of the alloy powder surface coating without reducing the aforementioned passivation effect, effectively generating high-permeability ZnMnCa ferrite, improving the high-frequency permeability of the composite soft magnetic powder core, while ensuring loss characteristics. Therefore, through the chemical reaction in step (1), the improved co-precipitation method in step (2), and the specific heat treatment process in step (3), this invention enables the composite soft magnetic powder core to have both low eddy current loss and excellent high-frequency permeability performance. Detailed Implementation

[0067] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0068] Example 1

[0069] This embodiment provides a method for preparing a composite soft magnetic powder core, the method comprising the following steps:

[0070] (1) Mix silicon tetrachloride and 100g of FeSiAl alloy powder to obtain a mixed powder, then add the mixed powder to ethanol and stir under vacuum for 20min to obtain a mixture;

[0071] The content of silicon tetrachloride is 1.2 wt% of the mass of the alloy powder in step (1), and the content of ethanol is 100 wt% of the mass of the alloy powder in step (1).

[0072] (2) Add the transition metal salt solution to the mixture described in step (1), stir for 10 min, then add NH4HCO3 and NH4OH until the pH of the system is 8, and then dry to obtain the pretreated alloy powder;

[0073] The transition metal salt solution includes zinc sulfate, manganese sulfate and calcium gluconate. The amount of zinc sulfate added is 0.035 wt% of the mass of the alloy powder in step (1), the amount of manganese sulfate added is 0.06 wt% of the mass of the alloy powder in step (1), and the amount of calcium gluconate added is 15.8 wt% of the total amount of zinc sulfate and manganese sulfate added.

[0074] (3) Mix polyethylene, calcium stearate, and the pretreated alloy powder described in step (2) at 150°C and 14.5 T / cm. 2 After being pressed for 150 seconds under pressure, the composite soft magnetic powder core is heat-treated at 800°C for 20 minutes in a nitrogen atmosphere with an oxygen content of 1 wt%. Then, it is cooled to 600°C and kept at 2 hours in pure nitrogen to obtain the composite soft magnetic powder core.

[0075] The amount of polyethylene added is 5 wt% of the mass of the pretreated alloy powder in step (2), and the amount of calcium stearate added is 0.5 wt% of the mass of the pretreated alloy powder in step (2).

[0076] Example 2

[0077] This embodiment provides a method for preparing a composite soft magnetic powder core, the method comprising the following steps:

[0078] (1) Mix silicon tetrachloride and 100g of FeSiAl alloy powder to obtain a mixed powder, then add the mixed powder to methanol and stir under vacuum for 30min to obtain a mixture;

[0079] The content of silicon tetrachloride is 1 wt% of the mass of the alloy powder in step (1), and the content of methanol is 100 wt% of the mass of the alloy powder in step (1).

[0080] (2) Add the transition metal salt solution to the mixture described in step (1), stir for 10 min, then add NH4HCO3 and NH4OH until the pH of the system is 8.5, and then dry to obtain the pretreated alloy powder;

[0081] The transition metal salt solution includes zinc sulfate, manganese sulfate and calcium gluconate. The amount of zinc sulfate added is 0.03 wt% of the mass of the alloy powder in step (1), the amount of manganese sulfate added is 0.05 wt% of the mass of the alloy powder in step (1), and the amount of calcium gluconate added is 12.5 wt% of the total amount of zinc sulfate and manganese sulfate added.

[0082] (3) Mix polyethylene, calcium stearate and the pretreated alloy powder described in step (2), and heat at 135°C and 14 T / cm 2 After being pressed for 120 seconds under pressure, the composite soft magnetic powder core is heat-treated at 850°C for 15 minutes in a nitrogen atmosphere with an oxygen content of 1 wt%, then cooled to 650°C and kept at that temperature in pure nitrogen for 1.5 hours to obtain the composite soft magnetic powder core.

[0083] The amount of polyethylene added is 4 wt% of the mass of the pretreated alloy powder in step (2), and the amount of calcium stearate added is 0.4 wt% of the mass of the pretreated alloy powder in step (2).

[0084] Example 3

[0085] This embodiment provides a method for preparing a composite soft magnetic powder core, the method comprising the following steps:

[0086] (1) Mix silicon tetrachloride and 100g of FeSiAl alloy powder to obtain a mixed powder, then add the mixed powder to ethanol and stir under vacuum for 30min to obtain a mixture;

[0087] The content of silicon tetrachloride is 1.4 wt% of the mass of the alloy powder in step (1), and the content of ethanol is 100 wt% of the mass of the alloy powder in step (1).

[0088] (2) Add the transition metal salt solution to the mixture described in step (1), stir for 10 min, then add NH4HCO3 and NH4OH until the pH of the system is 7.8, and then dry to obtain the pretreated alloy powder;

[0089] The transition metal salt solution includes zinc sulfate, manganese sulfate and calcium gluconate. The amount of zinc sulfate added is 0.1 wt% of the mass of the alloy powder in step (1), the amount of manganese sulfate added is 0.12 wt% of the mass of the alloy powder in step (1), and the amount of calcium gluconate added is 22.7 wt% of the total amount of zinc sulfate and manganese sulfate added.

[0090] (3) Mix polyethylene, calcium stearate and the pretreated alloy powder described in step (2), and heat at 150°C with a temperature of 14 T / cm. 2After being pressed for 120 seconds under pressure, the composite soft magnetic powder core is heat-treated at 800°C for 20 minutes in a nitrogen atmosphere with an oxygen content of 2wt%, then cooled to 700°C and kept at 2 hours in pure nitrogen to obtain the composite soft magnetic powder core.

[0091] The amount of polyethylene added is 5 wt% of the mass of the pretreated alloy powder in step (2), and the amount of calcium stearate added is 0.5 wt% of the mass of the pretreated alloy powder in step (2).

[0092] Example 4

[0093] This embodiment provides a method for preparing a composite soft magnetic powder core, the method comprising the following steps:

[0094] (1) Mix silicon tetrachloride and 100g of FeSiAl alloy powder to obtain a mixed powder, then add the mixed powder to propanol and stir under vacuum for 20min to obtain a mixture;

[0095] The content of silicon tetrachloride is 0.8 wt% of the mass of the alloy powder in step (1), and the content of propanol is 80 wt% of the mass of the alloy powder in step (1).

[0096] (2) Add the transition metal salt solution to the mixture described in step (1), stir for 5 minutes, then add ammonium carbonate and NH4OH until the pH of the system is 8, and then dry to obtain the pretreated alloy powder;

[0097] The transition metal salt solution includes zinc chloride, manganese chloride and calcium lactate. The amount of zinc chloride added is 0.02 wt% of the mass of the alloy powder in step (1), the amount of manganese chloride added is 0.05 wt% of the mass of the alloy powder in step (1), and the amount of calcium lactate added is 14.3 wt% of the total amount of zinc chloride and manganese chloride added.

[0098] (3) Mix polypropylene, barium stearate and the pretreated alloy powder described in step (2), and heat at 150°C with a temperature of 15 T / cm. 2 After being pressed for 120 seconds under pressure, the composite soft magnetic powder core was heat-treated at 760°C for 30 minutes in an argon atmosphere with an oxygen content of 3wt%. Then, it was cooled to 700°C and kept at 4 hours in pure argon to obtain the composite soft magnetic powder core.

[0099] The amount of polypropylene added is 2 wt% of the mass of the pretreated alloy powder in step (2), and the amount of barium stearate added is 0.1 wt% of the mass of the pretreated alloy powder in step (2).

[0100] Example 5

[0101] This embodiment provides a method for preparing a composite soft magnetic powder core, the method comprising the following steps:

[0102] (1) Mix silicon tetrachloride and 100g of FeSiAl alloy powder to obtain a mixed powder, then add the mixed powder to ethanol and stir under vacuum for 40min to obtain a mixture;

[0103] The content of silicon tetrachloride is 0.1 wt% of the mass of the alloy powder in step (1), and the content of ethanol agent is 150 wt% of the mass of the alloy powder in step (1).

[0104] (2) Add the transition metal salt solution to the mixture described in step (1), stir for 10 min, then add NH4HCO3 and NH4OH until the pH of the system is 8.5, and then dry to obtain the pretreated alloy powder;

[0105] The transition metal salt solution includes zinc sulfate, manganese sulfate and calcium gluconate. The amount of zinc sulfate added is 0.04 wt% of the mass of the alloy powder in step (1), the amount of manganese sulfate added is 0.07 wt% of the mass of the alloy powder in step (1), and the amount of calcium gluconate added is 18.2 wt% of the total amount of zinc sulfate and manganese sulfate added.

[0106] (3) Mix polypropylene, barium stearate and the pretreated alloy powder described in step (2), and heat at 150°C with a temperature of 13 T / cm. 2 After being pressed for 120 seconds under pressure, the composite soft magnetic powder core is heat-treated at 800°C for 15 minutes in a nitrogen atmosphere with an oxygen content of 1 wt%. Then, it is cooled to 700°C and kept at 1 hour in pure nitrogen to obtain the composite soft magnetic powder core.

[0107] The amount of polypropylene added is 3 wt% of the mass of the pretreated alloy powder in step (2), and the amount of barium stearate added is 0.3 wt% of the mass of the pretreated alloy powder in step (2).

[0108] Example 6

[0109] This embodiment provides a method for preparing a composite soft magnetic powder core. The preparation method is the same as in Example 1, except that the content of silicon tetrachloride in step (1) is 0.08 wt% of the mass of the alloy powder in step (1).

[0110] Example 7

[0111] This embodiment provides a method for preparing a composite soft magnetic powder core. The preparation method is the same as in Example 1, except that the content of silicon tetrachloride in step (1) is 1.6 wt% of the mass of the alloy powder in step (1).

[0112] Example 8

[0113] This embodiment provides a method for preparing a composite soft magnetic powder core. Except for the pH of the system in step (2) being 7.5, the preparation method is the same as in Example 1.

[0114] Example 9

[0115] This embodiment provides a method for preparing a composite soft magnetic powder core. Except for the pH of the system in step (2) being 9, the preparation method is the same as that in Example 1.

[0116] Example 10

[0117] This embodiment provides a method for preparing a composite soft magnetic powder core. Except for the pH of the system in step (2) being 10.5, the preparation method is the same as in Example 1.

[0118] Example 11

[0119] This embodiment provides a method for preparing a composite soft magnetic powder core. Except for step (2), in which sodium hydroxide is directly added to make the pH of the system 8, the preparation method is the same as in Example 1.

[0120] Example 12

[0121] This embodiment provides a method for preparing a composite soft magnetic powder core. The preparation method is the same as that in Example 1, except that calcium gluconate is not added in step (2).

[0122] Example 13

[0123] This embodiment provides a method for preparing a composite soft magnetic powder core. The preparation method is the same as in Example 1, except that in step (2), calcium gluconate is replaced with calcium chloride in an equal amount.

[0124] Example 14

[0125] This embodiment provides a method for preparing a composite soft magnetic powder core. Except for the heat treatment in step (3) which is carried out under pure nitrogen gas without oxygen, the preparation method is the same as in Example 1.

[0126] Comparative Example 1

[0127] This comparative example provides a method for preparing a composite soft magnetic powder core. The preparation method is the same as that in Example 1 except that step (2) is not performed.

[0128] Comparative Example 2

[0129] This comparative example provides a method for preparing a composite soft magnetic powder core. The preparation method is the same as in Example 1, except that the silicon tetrachloride in step (1) is replaced with an equal amount of phosphoric acid.

[0130] The composite soft magnetic powder cores provided in the above embodiments and comparative examples were tested for permeability and loss under test conditions of 100 kHz and 100 mT. The test results are shown in Table 1.

[0131] Table 1

[0132]

[0133]

[0134] As can be seen from the table above:

[0135] (1) As can be seen from Examples 1-14 and Comparative Examples 1-2, the preparation method of the present invention can coat a specific substance through the cooperation of steps (1), (2) and (3) to obtain a composite soft magnetic powder core with excellent performance. Furthermore, step (1) of the present invention can not only replace the conventional passivation process, but also generate a silicon dioxide layer, which further improves the performance of the magnetic powder core.

[0136] (2) As can be seen from Examples 1 and 6-14: the silicon tetrachloride added in step (1) of the present invention should be within a reasonable range to ensure the passivation effect, etc.; the pH of the system during co-precipitation in step (2) should be slightly alkaline and not too high, and strong alkaline substances such as sodium hydroxide should not be used directly as precipitants, so that steps (1) and (2) can be matched to ensure the passivation effect and co-precipitation effect at the same time. Meanwhile, organic calcium salts need to be added in step (2); the heat treatment process in step (3) is carried out at a high temperature and oxygen-containing gas needs to be introduced to form a silicon dioxide coating layer. Therefore, the present invention obtains a composite soft magnetic powder core with excellent performance through the mutual cooperation between the steps.

[0137] In summary, this invention provides a composite soft magnetic powder core, its preparation method, and its application. The preparation method can passivate and coat the surface of the alloy powder with silicon dioxide through a chemical reaction, thereby improving the air gap of the powder. Then, a ferrite layer is coated by an improved co-precipitation method. Therefore, the composite soft magnetic powder core of this invention has good magnetic permeability performance and low loss characteristics.

[0138] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for producing a composite soft magnetic powder core, characterized by, The preparation method includes the following steps: (1) Mix silicon tetrachloride, organic alcohol solvent and alloy powder to obtain a mixture; (2) After mixing and drying the transition metal salt solution, precipitant and the mixture described in step (1), a pretreated alloy powder is obtained; (3) After mixing and pressing the binder, release agent and the pretreated alloy powder in step (2), heat treatment is performed to obtain the composite soft magnetic powder core.

2. The production method according to claim 1, characterized by, The organic alcohol solvent in step (1) includes any one or a combination of at least two of methanol, ethanol, propanol or isopropanol.

3. The production method according to claim 1, characterized by, The content of silicon tetrachloride in step (1) is 0.1-1.5 wt% of the mass of the alloy powder in step (1).

4. The method of claim 1, wherein, The content of the organic alcohol solvent in step (1) is 80-150 wt% of the mass of the alloy powder in step (1).

5. The preparation method according to claim 1, characterized in that, The alloy powder in step (1) includes FeSiAl.

6. The method of claim 1, wherein, The transition metal salt solution in step (2) includes any one or a combination of at least two of zinc salts, manganese salts, or iron salts.

7. The preparation method according to claim 1, characterized in that, The transition metal salt solution in step (2) is a combination of zinc salt and manganese salt.

8. The preparation method according to claim 6, characterized in that, The amount of zinc salt added is 0.01-0.1 wt% of the mass of the alloy powder in step (1).

9. The preparation method according to claim 6, characterized in that, The amount of manganese salt added is 0.01-0.2 wt% of the mass of the alloy powder in step (1).

10. The method of claim 1, wherein, The amount of precipitant added in step (2) is such that the pH of the system after mixing in step (2) is greater than 7.

5.

11. The method of claim 1, wherein, The amount of precipitant added in step (2) is such that the pH of the system after mixing in step (2) is 7.5 < pH < 9.

12. The method of claim 1, wherein, The precipitant in step (2) includes any one or a combination of at least two of carbonates, bicarbonates, or ammonia.

13. The method of claim 12, wherein, The precipitant in step (2) is a combination of bicarbonate and ammonia.

14. The method of claim 12, wherein, The bicarbonate includes ammonium bicarbonate, and the carbonate includes ammonium carbonate.

15. The method of claim 1, wherein, The heat treatment in step (3) is carried out in an oxygen-containing protective gas.

16. The method of claim 15, wherein, The oxygen-containing protective gas contains 1-3 wt% oxygen.

17. The preparation method according to claim 15, characterized in that, The protective gas includes nitrogen and / or an inert gas.

18. The method of claim 1, wherein, The heat treatment temperature in step (3) is T, where 750℃ < T ≤ 850℃.

19. The method of claim 1, wherein, The heat treatment time in step (3) is 15-30 min.

20. The method of claim 1, wherein, After the heat treatment in step (3) is completed, the temperature is lowered to 600-750℃ and kept at that temperature in an inert atmosphere for 1-4 hours.

21. The method of claim 1, wherein, The pressing temperature in step (3) is 135-150℃.

22. The method of claim 1, wherein, The amount of binder added in step (3) is 2-8 wt% of the mass of the pretreated alloy powder in step (2).

23. The method of claim 1, wherein, The adhesive in step (3) includes polyethylene and / or polypropylene.

24. The method of claim 1, wherein, The amount of release agent added in step (3) is 0.1-1 wt% of the mass of the pretreated alloy powder in step (2).

25. The method of claim 1, wherein, The release agent in step (3) includes barium stearate and / or calcium stearate.

26. The method of claim 1, wherein, The preparation method includes the following steps: (1) Mix silicon tetrachloride, organic alcohol solvent and alloy powder to obtain a mixture; The content of silicon tetrachloride is 0.1-1.5 wt% of the alloy powder in step (1), and the content of organic alcohol solvent is 80-150 wt% of the alloy powder in step (1). (2) The transition metal salt solution, precipitant and the mixture described in step (1) are mixed, and the amount of precipitant added is such that the pH of the mixed system is 7.5 < pH < 9. After drying, the pretreated alloy powder is obtained. The precipitant comprises a combination of bicarbonate and ammonia. The transition metal salt solution includes zinc salt and manganese salt. The amount of zinc salt added is 0.01-0.1 wt% of the mass of the alloy powder in step (1), and the amount of manganese salt added is 0.01-0.2 wt% of the mass of the alloy powder in step (1). (3) Mix the binder, release agent and the pretreated alloy powder described in step (2), press it into shape at 135-150℃, heat treat it at 750℃<T≤850℃ for 15-30min in a protective atmosphere with an oxygen content of 1-3wt%, then cool it down to 600-750℃ and keep it in an inert atmosphere for 1-4h to obtain the composite soft magnetic powder core.

27. A composite soft magnetic powder core, characterized by The composite soft magnetic powder core is obtained by the preparation method described in any one of claims 1-26.

28. Use of the composite soft magnetic powder core according to claim 27, characterized in that The applications include filtering inductors for power supply systems.

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