Coated iron powder core and preparation method and application thereof
By coating the surface of the iron powder core with manganese-zinc ferrite and combining it with calcium, vanadium and niobium elements, the contradiction between reducing losses and increasing magnetic permeability in traditional iron powder core materials is resolved, achieving a balance between low losses and high magnetic permeability, which is suitable for switching power supplies and high-frequency communication products.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-29
- Publication Date
- 2026-04-03
AI Technical Summary
Traditional iron powder core materials struggle to achieve both low loss and high permeability. Pursuing high permeability leads to increased eddy current losses, while pursuing low loss results in decreased permeability. It is impossible to find a balance between the two.
The core is made of coated iron powder, the matrix material is ferromagnetic powder, and the coating layer is manganese-zinc ferrite. The manganese-zinc ferrite contains calcium, vanadium and niobium elements. The formation of a high-resistivity grain boundary layer is promoted by a grain boundary modifier, which restricts eddy currents and maintains high magnetic permeability.
It significantly reduces eddy current losses while maintaining or improving magnetic permeability. The process is simple, low-cost, and suitable for industrial production.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of magnetic powder core preparation technology, specifically to a coated iron powder core, its preparation method, and its application. Background Technology
[0002] Soft magnetic powder core materials possess characteristics such as high saturation magnetic flux density, excellent DC superposition performance, and low cost, making them widely used in electronic devices such as switching power supplies, output inductors, online noise filters, PFC inductors, chokes, and UPS power supplies. Traditional iron powder core materials are prepared by coating with organic or inorganic insulating materials, adding binders such as epoxy resin, and then pressing and heat-treating the powder. For traditional iron powder core materials, increasing permeability and reducing losses are contradictory. Pursuing high permeability requires thinning the insulating layer to increase the proportion of metal particles, but this leads to a decrease in interparticle insulation resistance, resulting in increased eddy current losses, thus contradicting the goal of reducing magnetic losses. Conversely, pursuing low losses requires thickening the insulating layer to block eddy current paths, but this reduces the volume proportion of metal particles, leading to a decrease in permeability, again contradicting the goal of increasing permeability.
[0003] Therefore, how to optimize and improve the iron powder core and its preparation method to prepare an iron powder core with both low loss and high magnetic permeability is a technical problem that urgently needs to be solved in this field. Summary of the Invention
[0004] To address the problem that traditional iron powder core materials struggle to achieve both low loss and high magnetic permeability, this invention provides a coated iron powder core.
[0005] On the other hand, the present invention also provides a method for preparing a coated iron powder core.
[0006] In a first aspect, the present invention provides a coated iron powder core, the coated iron powder core comprising a matrix material and a coating layer covering the outer surface of the matrix material.
[0007] In one alternative embodiment, the matrix material comprises ferromagnetic powder, and the coating layer comprises manganese-zinc ferrite.
[0008] In one alternative embodiment, the manganese-zinc ferrite includes calcium, vanadium, and niobium.
[0009] In one optional embodiment, the content of manganese-zinc ferrite is 10%-20% based on the mass of the coated iron powder core.
[0010] In one alternative embodiment, the calcium content is 0.010wt%-0.014wt% based on the mass of the manganese-zinc ferrite.
[0011] In one alternative embodiment, the vanadium content is 0.017wt%-0.022wt% based on the mass of the manganese-zinc ferrite.
[0012] In one alternative embodiment, the niobium content is 0.014wt%-0.021wt% based on the mass of the manganese-zinc ferrite.
[0013] In one alternative embodiment, the coated iron powder core further includes a lubricant.
[0014] In one alternative embodiment, the lubricant comprises zinc stearate.
[0015] In one alternative embodiment, the total iron content in the matrix material is ≥99.1 wt%.
[0016] In one alternative embodiment, the ferromagnetic powder comprises secondary reduced iron powder.
[0017] In a second aspect, the present invention provides a method for preparing a coated iron powder core according to the first aspect, comprising the following steps: (1) Iron source, manganese source and zinc source are mixed and sintered to obtain a mixture; (2) The mixture is annealed after being mixed with calcium source, vanadium source and niobium source to obtain manganese zinc ferrite; (3) Mix the ferromagnetic powder and the manganese zinc ferrite to obtain the final product.
[0018] In one optional embodiment, the mass ratio of the iron source, the manganese source, and the zinc source is 65-75:16-30:5-9.
[0019] In one alternative embodiment, the calcium source comprises 250-350 ppm of the mass of the mixture.
[0020] In one alternative embodiment, the vanadium source accounts for 300-400 ppm of the mass of the mixture.
[0021] In one alternative embodiment, the niobium source accounts for 200-300 ppm of the mass of the mixture.
[0022] In one alternative embodiment, the manganese source comprises Mn3O4.
[0023] In one alternative embodiment, the zinc source comprises ZnO.
[0024] In one alternative embodiment, the iron source comprises Fe2O3.
[0025] In one alternative implementation, the calcium source comprises CaCO3.
[0026] In one alternative embodiment, the vanadium source comprises V2O5.
[0027] In one alternative embodiment, the niobium source comprises Nb2O5.
[0028] In an alternative implementation, step (1) further includes adding a first dispersant.
[0029] In an optional embodiment, step (2) further includes adding at least one of a second dispersant and polyvinyl alcohol.
[0030] In one alternative embodiment, the first dispersant and the second dispersant are each independently selected from at least one of amine compounds and alcohol compounds.
[0031] In an alternative implementation, step (3) further includes the addition of zinc stearate.
[0032] In one optional embodiment, the mass ratio of the sum of the ferromagnetic powder and the manganese-zinc ferrite to the mass of the zinc stearate is (500-1000):1.
[0033] In one optional embodiment, the sintering temperature is 800-900°C and the time is 2-3 hours.
[0034] In one optional implementation, the annealing process includes a first annealing process, a second annealing process, a third annealing process, a fourth annealing process, and a cooling process.
[0035] In one optional embodiment, the first annealing temperature is 90-100°C, and the heating rate is 0.20-0.25°C / min.
[0036] In one optional embodiment, the second annealing temperature is 320-330°C, and the heating rate is 0.02-0.30°C / min.
[0037] In one optional embodiment, the third annealing temperature is 1100-1200℃, and the heating rate is 0.60-1.42℃ / min.
[0038] In one optional embodiment, the fourth annealing temperature is 1300-1400℃, the heating rate is 1.40-1.46℃ / min, the holding time is 300-350min, the annealing atmosphere is an inert gas, and the flow rate of the inert gas is 350-450L / min.
[0039] In one optional embodiment, the cooling rate of the cooling process is 0.30-2.10℃ / min, the cooling atmosphere is an inert gas, and the flow rate of the inert gas is 200-400L / min.
[0040] In an optional embodiment, step (3) further includes a pressing process after the mixing process, wherein the pressing process is performed at a pressure of 540-648 MPa for a time of 2-15 min.
[0041] Thirdly, the present invention provides the application of the coated iron powder core according to the first aspect or the coated iron powder core prepared by the preparation method of the second aspect in the preparation of switching power supplies and high-frequency communication products.
[0042] The technical solution of this invention has the following advantages: 1. The coated iron powder core provided by the present invention comprises: the coated iron powder core includes a matrix material and a coating layer covering the outer surface of the matrix material; the matrix material includes ferromagnetic powder, and the coating layer includes manganese-zinc ferrite; the manganese-zinc ferrite includes calcium, vanadium, and niobium; the content of manganese-zinc ferrite is 10%-20% based on the mass of the coated iron powder core. The present invention uses manganese-zinc ferrite containing calcium, vanadium, and niobium, which together act as a grain boundary modifier, promoting the formation of a high-resistivity grain boundary layer, inhibiting grain growth and pinning magnetic domain wall movement, thereby significantly improving the resistivity of manganese-zinc ferrite. Using manganese-zinc ferrite containing calcium, vanadium, and niobium as a coating layer has several advantages. First, manganese-zinc ferrite itself is a soft magnetic material with high resistivity, far exceeding that of pure iron. The manganese-zinc ferrite coating layer acts as a resistance barrier, confining eddy currents within each particle, significantly reducing the size of the eddy current loop and lowering eddy current losses in the iron powder core. Second, in an iron powder core with manganese-zinc ferrite as the coating layer, the iron powder particles and the manganese-zinc ferrite coating layer can form a parallel magnetic circuit in the magnetic field. The thin manganese-zinc ferrite coating layer has very little resistance to magnetic flux, so the permeability of the iron powder core does not decrease significantly. On the contrary, because the manganese-zinc ferrite coating layer can reduce the adverse effects of non-magnetic impurities and air gaps, it may even slightly improve the permeability.
[0043] 2. The preparation method of the coated iron powder core provided by the present invention is simple in terms of materials, process, efficiency, energy consumption, and cost, and is easy to scale up for industrial production, making it suitable for widespread application in industrial production. Detailed Implementation
[0044] The following embodiments are provided to better understand the present invention, but the following embodiments do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the scope of protection of the present invention.
[0045] Unless otherwise specified, all experimental steps or conditions in the examples were performed according to conventional experimental procedures and conditions in the art. Reagents or instruments whose manufacturers are not specified are all commercially available products.
[0046] To address the problems existing in the aforementioned related technologies, according to a first aspect of the present invention, a coated iron powder core is provided, the coated iron powder core comprising a matrix material and a coating layer covering the outer surface of the matrix material; The matrix material includes ferromagnetic powder, and the coating layer includes manganese-zinc ferrite. The manganese-zinc ferrite includes calcium, vanadium, and niobium. The content of manganese-zinc ferrite is 10%-20% based on the mass of the coated iron powder core.
[0047] In some alternative embodiments, the calcium content is 0.010wt%-0.014wt% based on the mass of the manganese-zinc ferrite.
[0048] In some alternative embodiments, the vanadium content is 0.017wt%-0.022wt% based on the mass of the manganese-zinc ferrite.
[0049] In some alternative embodiments, the niobium content is 0.014wt%-0.021wt% based on the mass of the manganese-zinc ferrite.
[0050] In some alternative embodiments, the coated iron powder core also includes a lubricant.
[0051] In some alternative embodiments, the lubricant comprises zinc stearate.
[0052] In some alternative embodiments, the total iron content in the matrix material is ≥99.1 wt%.
[0053] In some alternative embodiments, the ferromagnetic powder comprises secondary reduced iron powder.
[0054] It should be noted that in this invention, the chemical composition detection of the secondary reduced iron powder follows GB / T6730.5—2022 "Determination of Total Iron Content in Iron Ore - Titration Method after Reduction with Titanium Trichloride", and the iron content reaches 99.1%-99.3%; Secondly, the present invention provides a method for preparing a coated iron powder core, comprising the following steps: (1) Iron source, manganese source and zinc source are mixed and sintered to obtain a mixture; (2) The calcium source, vanadium source and niobium source are then mixed and annealed to obtain manganese zinc ferrite; (2) Mix ferromagnetic powder and manganese zinc ferrite to obtain the product.
[0055] It should be noted that the preparation method of the manganese-zinc ferrite specifically includes the following steps: S1. Weigh out the iron source, manganese source, zinc source and first dispersant according to the mass ratio of 65-75:16-30:5-9, add them to deionized water and grind to obtain the first mixture; The first dispersant is at least one of an ammonia compound and an alcohol compound; in the grinding step, the total mass of the iron source, manganese source, and zinc source, the mass ratio of the grinding balls and deionized water is 1:2-3:0.9-1, the grinding speed is 200-300 rpm, and the grinding time is 90-120 min; the grinding balls are φ6.35mm bearing steel balls; S2. Transfer the first mixture to a 5-6 mesh sieve to separate the steel balls and slurry. Dry the slurry at 90°C for 10-20 hours, then crush and sieve (120 mesh or 160 mesh). Sinter at 800-900°C for 2-3 hours to obtain the second mixture. S3. Add calcium source, vanadium source and niobium source to the second mixture, then add them together with the second dispersant to deionized water, grind, sieve through 5-6 mesh, dry at 85-100℃ for 10-20h to obtain the third mixture; The amounts of calcium source, vanadium source, and niobium source added are 250-350 ppm, 300-400 ppm, and 200-300 ppm, respectively; the second dispersant is at least one of an ammonia compound and an alcohol compound; in the grinding step, the mass ratio of the second mixture and the total mass of calcium source, vanadium source, and niobium source to the mass of grinding balls and deionized water is 1:2-3:0.6-0.65, the grinding speed is 200-300 rpm, the grinding time is 150 min, and the grinding balls are φ6.35mm bearing steel balls; S4. The third mixture is mixed with an 8 wt% polyvinyl alcohol (PVA) solution, dried in a windless environment for 3-5 hours, and sieved (40-60 mesh) to obtain manganese-zinc ferrite raw powder; the PVA content in the manganese-zinc ferrite raw powder is 0.8-0.95%; S5. Anneal the raw manganese-zinc ferrite powder to obtain manganese-zinc ferrite powder; the annealing treatment includes a first annealing treatment, a second annealing treatment, a third annealing treatment, a fourth annealing treatment, and a cooling treatment; the first annealing temperature is 90-100℃, and the heating rate is 0.20-0.25℃ / min; the second annealing temperature is 320-330℃, and the heating rate is 0.02-0.30℃ / min; the third annealing temperature is 1100-120℃. The temperature is 0℃, the heating rate is 0.60-1.42℃ / min; the fourth annealing temperature is 1300-1400℃, the heating rate is 1.40-1.46℃ / min, the holding time is 300-350min, and the flow rate of inert gas is 350-450L / min; the cooling rate of the cooling treatment is 0.30-2.10℃ / min, and the flow rate of inert gas is 200-400L / min, to obtain manganese-zinc ferrite powder.
[0056] In some alternative embodiments, the manganese source includes Mn3O4; In some alternative embodiments, the zinc source includes ZnO; In some alternative embodiments, the iron source includes Fe2O3; In some alternative embodiments, the calcium source includes CaCO3.
[0057] In some alternative embodiments, the vanadium source includes V2O5.
[0058] In some alternative embodiments, the niobium source comprises Nb2O5.
[0059] In some alternative implementations, step (3) may also include the addition of zinc stearate.
[0060] In some alternative embodiments, the mass ratio of the sum of the ferromagnetic powder and the manganese-zinc ferrite to the mass of the zinc stearate is (500-1000):1.
[0061] In this invention, polyvinyl alcohol was purchased from Sinopharm Chemical Reagent Co., Ltd., model Acros-183120010.
[0062] Example 1 This embodiment provides a method for preparing a coated iron powder core, the specific steps of which are as follows: (1) Mix 70wt% Fe2O3, 23wt% Mn3O4 and 7wt% ZnO, and add 1mL of ethylene glycol to deionized water for grinding to obtain the first mixture; in the grinding step, the total mass ratio of Fe2O3, Mn3O4 and ZnO to the mass ratio of grinding balls and deionized water is 1:2:0.9, the grinding speed is 200rpm, and the grinding time is 120min; (2) The first mixture was transferred into a 5-mesh sieve to separate the steel balls and slurry. The slurry was placed in a stainless steel pan and dried in a 90°C oven for 10 hours. It was then crushed and passed through a 120-mesh sieve. Then it was placed in a mullite crucible and sintered at 850°C for 2.5 hours. After cooling, the second mixture was obtained. (3) Add CaCO3, V2O5 and Nb2O5 to the second mixture. The concentrations of CaCO3, V2O5 and Nb2O5 are 250ppm, 300ppm and 200ppm of the second mixture, respectively. Then add 1mL of ethylene glycol to deionized water and grind. In the grinding step, the total mass ratio of the second mixture and the calcium source, vanadium source and niobium source to the grinding balls and deionized water is 1:2:0.6. The grinding speed is 200rpm and the grinding time is 150min. Then transfer it to a 5-mesh sieve to separate the steel balls and slurry. Place the slurry in a stainless steel pan and put it in an oven at 90℃ for 10h to obtain the third mixture. (4) The third mixture was placed in a mortar and crushed with a grinding rod, then mixed with an 8 wt% PVA solution, and air-dried naturally for 4 hours in a windless state. The particles were then uniformly crushed with a mortar rod and passed through a 40-mesh sieve to obtain manganese-zinc ferrite raw powder; wherein the PVA content in the manganese-zinc ferrite raw powder was 0.8 wt%. (5) The raw manganese zinc ferrite powder is annealed as follows: the temperature is increased to 95℃ at 0.20℃ / min, then increased to 325℃ at 0.02℃ / min, then increased to 1125℃ at 0.60℃ / min, then increased to 1330℃ at 1.40℃ / min, and finally held at 1330℃ for 300min. A total nitrogen gas flow rate of 350L / min is introduced, and the temperature is reduced to room temperature at a cooling rate of 0.50℃ / min. A total nitrogen gas flow rate of 400L / min is introduced to obtain manganese zinc ferrite powder. The calcium content is 0.010wt%, the vanadium content is 0.017wt%, and the niobium content is 0.014wt% based on the mass of the manganese zinc ferrite. (6) Mix and grind the secondary reduced iron powder (iron content of 99.2wt%) and manganese zinc ferrite powder at a mass ratio of 90:10. The grinding balls are 304 stainless steel balls with a diameter of 5mm. The ball-to-material ratio is 5:1. The ball milling speed is 150rpm and the ball milling time is 60min. Then mix it with zinc stearate at a mass ratio of 500:1. Then press it at 648MPa for 10min to obtain a ring-shaped coated iron powder core with a diameter of 20×10×5mm. The calcium content is 0.010wt%, the vanadium content is 0.017wt%, and the niobium content is 0.014wt% based on the mass of manganese zinc ferrite.
[0063] Example 2 This embodiment provides a method for preparing a coated iron powder core, the specific steps of which are as follows: (1) 70wt% Fe2O3, 23wt% Mn3O4, 7wt% ZnO and 0.5mL ethylene glycol were added to deionized water and ground to obtain the first mixture; in the grinding step, the total mass ratio of Fe2O3, Mn3O4 and ZnO to the mass ratio of grinding balls and deionized water was 1:2.5:0.9, the grinding speed was 300rpm, and the grinding time was 90min; (2) The first mixture was transferred to a 6-mesh sieve to separate the steel balls and slurry. The slurry was placed in a stainless steel pan and dried in a 90°C oven for 15 hours. It was then crushed and passed through a 160-mesh sieve. The mixture was then placed in a mullite crucible and preheated at 850°C for 2.5 hours. After cooling, the second mixture was obtained. (3) Add CaCO3, V2O5 and Nb2O5 to the second mixture. The concentrations of CaCO3, V2O5 and Nb2O5 are 300ppm, 400ppm and 250ppm of the second mixture, respectively. Then add 1mL of ethylene glycol to deionized water for grinding. In the grinding step, the total mass ratio of the second mixture and the calcium source, vanadium source and niobium source to the grinding balls and deionized water is 1:2:0.65. The grinding speed is 300rpm and the grinding time is 150min. Then transfer it to a 5-mesh sieve to separate the steel balls and slurry. Place the slurry in a stainless steel pan and dry it in an oven at 90℃ for 10h to obtain the third mixture. (4) The third mixture was placed in a mortar and crushed with a grinding rod, then mixed with an 8 wt% PVA solution, and air-dried naturally for 4 hours in a windless state. The particles were then evenly crushed with a mortar rod and finally passed through a 50-mesh sieve to obtain manganese-zinc ferrite raw powder; wherein the PVA content in the manganese-zinc ferrite raw powder was 0.9 wt%. (5) The raw manganese zinc ferrite powder is annealed as follows: the temperature is increased to 95°C at 0.20°C / min, then increased to 325°C at 0.10°C / min, then increased to 1125°C at 1.00°C / min, then increased to 1330°C at 1.42°C / min, and finally held at 1330°C for 330 min. The flow rate of nitrogen gas is 400 L / min, and then the temperature is cooled to room temperature at a cooling rate of 1.00°C / min. The total amount of nitrogen gas introduced is 400 L / min, and the manganese zinc ferrite powder is obtained. (6) The secondary reduced iron powder (iron content of 99.2wt%) and manganese zinc ferrite powder with a mass ratio of 85:15 were mixed and ground. The grinding balls were 304 stainless steel balls with a diameter of 5mm. The ball-to-material ratio was 5:1. The ball milling speed was 150rpm and the ball milling time was 60min. Then, it was mixed with zinc stearate at a mass ratio of 750:1. Then, it was pressed at 648MPa for 10min to obtain a ring-shaped coated iron powder core with a diameter of Φ20×Φ10×5mm. The calcium content was 0.012wt%, the vanadium content was 0.022wt%, and the niobium content was 0.017wt% based on the mass of manganese zinc ferrite.
[0064] Example 3 This embodiment provides a method for preparing a coated iron powder core, the specific steps of which are as follows: 1. Preparation of coating agent: (1) 70wt% Fe2O3, 23wt% Mn3O4, 7wt% ZnO and 0.5mL ethylene glycol were added to deionized water and ground to obtain the first mixture; in the grinding step, the total mass of Fe2O3, Mn3O4 and ZnO and the mass-volume ratio of grinding balls and deionized water were 1:3:1, the grinding speed was 300rpm and the grinding time was 90min; (2) The first mixture was transferred to a 6-mesh sieve to separate the steel balls and slurry. The slurry was placed in a stainless steel pan and dried in a 90°C oven for 20 hours. After drying, it was crushed and passed through a 120-mesh sieve. Then it was placed in a mullite saggar and sintered at 850°C for 2.5 hours. After cooling, the second mixture was obtained. (3) Add CaCO3, V2O5, and Nb2O5 to the second mixture. The concentrations of CaCO3, V2O5, and Nb2O5 are 350 ppm, 300 ppm, and 250 ppm of the second mixture, respectively. Add the mixed powder and 1 mL of ethylene glycol to deionized water for grinding. In the grinding step, the total mass ratio of the second mixture and the calcium source, vanadium source, and niobium source to the grinding balls and deionized water is 1:3:0.6. The grinding speed is 300 rpm and the grinding time is 150 min. Then transfer it to a stainless steel pan and dry it in a 90℃ oven for 20 h to obtain the third mixture. (4) The third mixture was placed in a mortar and crushed with a grinding rod, then mixed with an 8 wt% PVA solution, and air-dried naturally for 4 hours in a windless state. The particles were then uniformly crushed with a mortar rod and passed through a 60-mesh sieve to obtain manganese-zinc ferrite raw powder; wherein the PVA content in the manganese-zinc ferrite raw powder was 0.95 wt%. (5) The raw manganese zinc ferrite powder is annealed as follows: the temperature is increased to 95℃ at 0.25℃ / min, then increased to 325℃ at 0.30℃ / min, then increased to 1125℃ at 1.42℃ / min, then increased to 1330℃ at 1.46℃ / min, and finally held at 1330℃ for 350min. A total of 400L / min of nitrogen is introduced, and the temperature is cooled to room temperature at a cooling rate of 2.10℃ / min. A total of 400L / min of nitrogen is introduced to obtain manganese zinc ferrite powder. (6) The secondary reduced iron (iron content of 99.2wt%) and manganese zinc ferrite powder with a mass ratio of 80:20 were mixed and ground. The grinding balls were 304 stainless steel balls with a diameter of 5mm. The ball-to-material ratio was 5:1. The ball milling speed was 150rpm and the ball milling time was 60min. Then, it was mixed with zinc stearate at a mass ratio of 1000:1 and then pressed under a pressure of 648MPa for 10min to obtain a Φ20×Φ10×5mm coated annular iron powder core. Among them, the calcium content was 0.014wt%, the vanadium content was 0.017wt%, and the niobium content was 0.017wt% based on the mass of manganese zinc ferrite.
[0065] Example 4 This embodiment provides a method for preparing a coated iron powder core, the specific steps of which are as follows: (1) Mix 65wt% Fe2O3, 30wt% Mn3O4 and 5wt% ZnO, and add 1mL of hexadecyltrimethylammonium bromide to deionized water for grinding to obtain the first mixture; in the grinding step, the total mass ratio of Fe2O3, Mn3O4 and ZnO to the mass ratio of grinding balls and deionized water is 1:2:0.9, the grinding speed is 200rpm, and the grinding time is 120min; (2) The first mixture was transferred to a 5-mesh sieve to separate the steel balls and slurry. The slurry was placed in a stainless steel pan and dried in a 90°C oven for 10 hours. After drying, it was crushed and passed through a 120-mesh sieve. Then it was placed in a mullite crucible and pre-fired at 850°C for 2.5 hours. After cooling, the second mixture was obtained. (3) Add CaCO3, V2O5 and Nb2O5 to the second mixture. The concentrations of CaCO3, V2O5 and Nb2O5 are 250ppm, 300ppm and 300ppm of the second mixture, respectively. Then add 1mL of hexadecyltrimethylammonium bromide to deionized water for grinding. In the grinding step, the total mass ratio of the second mixture and the calcium source, vanadium source and niobium source to the grinding balls and deionized water is 1:2:0.6. The grinding speed is 200rpm and the grinding time is 150min. Then transfer the mixture to a 5-mesh sieve to separate the steel balls and slurry. Place the slurry in a stainless steel pan and dry it in a 90℃ oven for 10h to obtain the third mixture. (4) The third mixture was placed in a mortar and crushed with a grinding rod, then mixed with an 8 wt% PVA solution and air-dried naturally for 4 hours without wind. The particles were then evenly crushed with a mortar rod and passed through a 40-mesh sieve to obtain manganese-zinc ferrite raw powder; wherein the PVA content in the manganese-zinc ferrite raw powder was 0.8 wt%. (5) Annealing the raw manganese zinc ferrite powder includes: heating to 100℃ at 0.20℃ / min, then heating to 320℃ at 0.2℃ / min, then heating to 1200℃ at 1.0℃ / min, then heating to 1400℃ at 1.43℃ / min, and finally holding at 1400℃ for 340 min, with a total nitrogen flow rate of 350 L / min, and cooling at a rate of 0.30℃ / min with a total nitrogen flow rate of 200 L / min to obtain manganese zinc ferrite powder; (6) The secondary reduced iron powder (iron content of 99.2wt%) and manganese zinc ferrite powder with a mass ratio of 80:20 were mixed and ground. The grinding balls were 304 stainless steel balls with a diameter of 5mm. The ball-to-material ratio was 5:1. The ball milling speed was 150rpm and the ball milling time was 60min. Then, it was mixed with zinc stearate at a mass ratio of 1000:1. The resulting mixed powder was pressed under a pressure of 540MPa for 15min to obtain a Φ20×Φ10×5mm coated annular iron powder core. Among them, the calcium content was 0.010wt%, the vanadium content was 0.017wt%, and the niobium content was 0.021wt% based on the mass of manganese zinc ferrite.
[0066] Example 5 This embodiment provides a method for preparing a coated iron powder core, the specific steps of which are as follows: (1) Mix 75wt% Fe2O3, 16wt% Mn3O4 and 9wt% ZnO, and add 1mL of hexadecyltrimethylammonium bromide to deionized water and grind to obtain the first mixture; in the grinding step, the total mass ratio of Fe2O3, Mn3O4 and ZnO to the mass ratio of grinding balls and deionized water is 1:2:0.9, the grinding speed is 200rpm, and the grinding time is 120min; (2) The first mixture was transferred to a 5-mesh sieve to separate the steel balls and slurry. The slurry was placed in a stainless steel pan and dried in an oven at 90°C for 10 hours. After drying, it was crushed and passed through a 120-mesh sieve. Then it was placed in a mullite crucible and pre-fired at 850°C for 2.5 hours. After cooling, the second mixture was obtained. (3) Add CaCO3, V2O5 and Nb2O5 to the second mixture. The concentrations of CaCO3, V2O5 and Nb2O5 are 350ppm, 400ppm and 200ppm of the second mixture, respectively. Then add 1mL of hexadecyltrimethylammonium bromide to deionized water for grinding. In the grinding step, the total mass ratio of the second mixture and the calcium source, vanadium source and niobium source to the grinding balls and deionized water is 1:2:0.6. The grinding speed is 200rpm and the grinding time is 150min. Then transfer the steel balls and slurry to a 5-mesh sieve to separate them. Place the slurry in a stainless steel pan and dry it in a 90℃ oven for 10h to obtain the third mixture. (4) The third mixture was placed in a mortar and crushed with a grinding rod, then mixed with an 8 wt% PVA solution, and air-dried naturally for 4 hours in a windless state. The particles were then uniformly crushed with a mortar rod and passed through a 40-mesh sieve to obtain manganese-zinc ferrite raw powder; wherein the PVA content in the manganese-zinc ferrite raw powder was 0.8 wt%. (5) The raw manganese zinc ferrite powder is annealed as follows: the temperature is increased to 100℃ at 0.25℃ / min, then increased to 330℃ at 0.08℃ / min, then increased to 1100℃ at 0.80℃ / min, then increased to 1300℃ at 1.45℃ / min, and finally held at 1300℃ for 320min. A total of 450L / min of nitrogen is introduced, and the temperature is reduced to room temperature at a rate of 0.30℃ / min. A total of 200L / min of nitrogen is introduced to obtain manganese zinc ferrite powder. (6) Mix and grind the secondary reduced iron powder (iron content of 99.2wt%) with manganese zinc ferrite powder at a mass ratio of 80:20. The grinding balls are 304 stainless steel balls with a diameter of 5mm. The ball-to-material ratio is 5:1. The ball milling speed is 150rpm and the ball milling time is 60min. Then mix it with zinc stearate at a mass ratio of 500:1. Then press it under a pressure of 600MPa for 2min to obtain a Φ20×Φ10×5mm coated annular iron powder core. Among them, the calcium content is 0.014wt%, the vanadium content is 0.022wt%, and the niobium content is 0.014wt% based on the mass of manganese zinc ferrite.
[0067] Comparative Example 1 This comparative example provides a method for preparing a coated iron powder core, which is basically the same as the steps in Example 1, except that the mass ratio of secondary reduced iron powder to manganese-zinc ferrite powder is 95:5.
[0068] Comparative Example 2 This comparative example provides a method for preparing an insulating coated iron powder core, which is basically the same as the steps in Example 1, except that the mass ratio of secondary reduced iron powder to manganese-zinc ferrite powder is 60:40.
[0069] Comparative Example 3 This comparative example provides a method for preparing an insulating coated iron powder core, which is basically the same as the steps in Example 1, except that in step (3), CaCO3 is replaced with the same mass of V2O5.
[0070] Comparative Example 4 This comparative example provides a method for preparing an insulating coated iron powder core, which is basically the same as the steps in Example 1, except that V2O5 is replaced with the same mass of CaCO3.
[0071] Comparative Example 5 This comparative example provides a method for preparing an insulating coated iron powder core, which is basically the same as the steps in Example 1, except that Nb2O5 is replaced with the same mass of CaCO3.
[0072] Test Example 1 The coated iron powder cores prepared in Examples 1-5 and Comparative Examples 1-5 were subjected to loss testing. Specifically, the total magnetic loss of the iron powder cores was measured using a BH analyzer (SY-8219, Iwasaki) manufactured in Japan. During the measurement, 20 turns of 0.4 mm enameled wire were uniformly wound around the iron powder core, and the loss of the iron powder core was measured under the conditions of Bm=100mT and f=10-50kHz. The loss results are shown in Table 1.
[0073] Table 1. Magnetic loss (mW / cm) of iron powder cores prepared in the examples and comparative examples. 3 Test results
[0074] As can be seen from Table 1, the iron powder cores prepared in Examples 1-5 of this invention have lower magnetic losses compared with Comparative Examples 1-5; in Comparative Example 1, the mass ratio of secondary reduced iron powder to manganese-zinc ferrite powder is 95:5, and its magnetic loss is 2843 mW / cm. 3 This is because the intrinsic high resistivity of manganese-zinc ferrite helps reduce eddy current losses, but a small amount of manganese-zinc ferrite powder is insufficient to significantly reduce eddy current losses; in Comparative Example 2, the mass ratio of secondary reduced iron powder to manganese-zinc ferrite powder is 60:40, and its magnetic loss is 2632 mW / cm. 3 This is because excessive manganese-zinc ferrite powder makes molding difficult, resulting in poor core density and performance degradation under the same molding conditions. Comparative Examples 3-5, where the coating agent does not simultaneously include calcium, vanadium, and niobium, exhibit higher magnetic losses than Examples 1-5. This is because the combined use of calcium, vanadium, and niobium aims to address the high-frequency, high-power consumption problem from both the "grain boundary" and "grain body" dimensions. Removing any one of these elements disrupts the balance, leading to a severe deterioration in performance, particularly loss characteristics.
[0075] Test Example 2 The effective magnetic permeability of the iron powder cores prepared in Examples 1-5 and Comparative Examples 1-5 was tested; specifically, the inductance value was measured using an LCR meter (IM3570A988-06, HIOKI) manufactured in Japan. L During measurement, 20 turns of 0.4mm enameled wire are wound around the iron powder core. The test voltage is 0.3V, and the frequency test range is 1-200kHz. The effective permeability of the magnetic powder core is calculated with reference to the inductance formula, the specific formula of which is as follows:
[0076] in, m Effective permeability; l The effective magnetic circuit length of the toroidal sample is (m). L This is the inductance value; m 0 represents the permeability of free space; N The number of turns of the copper enameled wire; A The effective cross-sectional area of the annular sample (m²) 2 ).
[0077] The test results of the effective magnetic permeability of the iron powder cores prepared in the examples and comparative examples are shown in Table 2.
[0078] Table 2. Effective magnetic permeability test results of iron powder cores prepared in the examples and comparative examples.
[0079] As can be seen from Table 2, the iron powder cores prepared in Examples 1-5 of the present invention have higher magnetic permeability than those in Comparative Examples 1-4. This is because: (1) manganese zinc ferrite has extremely high intrinsic magnetic permeability; (2) an appropriate amount of manganese zinc ferrite powder can form a complete insulating layer on the surface of the ferromagnetic powder, thereby improving the compactness of the iron powder core; (3) calcium, vanadium and niobium elements are introduced into the manganese zinc ferrite powder at the same time to synergistically optimize the microstructure such as grain boundaries and grains.
[0080] In summary, the coated iron powder core prepared by this invention can improve magnetic permeability while reducing losses, thus solving the problem that conventional iron powder cores cannot maintain high magnetic permeability while reducing losses.
[0081] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.
Claims
1. A coated iron powder core, characterized in that, The coated iron powder core includes a matrix material and a coating layer covering the outer surface of the matrix material; The matrix material includes ferromagnetic powder, and the coating layer includes manganese-zinc ferrite. The manganese-zinc ferrite includes calcium, vanadium, and niobium. The content of manganese-zinc ferrite is 10%-20% based on the mass of the coated iron powder core.
2. The coated iron powder core according to claim 1, characterized in that, The calcium content, based on the mass of the manganese-zinc ferrite, is 0.010 wt% - 0.014 wt%. And / or, based on the mass of the manganese-zinc ferrite, the vanadium content is 0.017wt%-0.022wt%; And / or, based on the mass of the manganese-zinc ferrite, the niobium content is 0.014wt%-0.021wt%.
3. The coated iron powder core according to claim 1, characterized in that, The coated iron powder core also includes a lubricant; Optionally, the lubricant includes zinc stearate.
4. The coated iron powder core according to claim 1, characterized in that, The total iron content in the matrix material is ≥99.1 wt%; And / or, the ferromagnetic powder includes secondary reduced iron powder.
5. A method for preparing a coated iron powder core according to any one of claims 1-4, characterized in that, Includes the following steps: (1) Iron source, manganese source and zinc source are mixed and sintered to obtain a mixture; (2) The mixture is annealed after being mixed with calcium source, vanadium source and niobium source to obtain manganese zinc ferrite; (3) Mix the ferromagnetic powder and the manganese zinc ferrite to obtain the final product.
6. The method for preparing the coating agent according to claim 5, characterized in that, The mass ratio of the iron source, the manganese source, and the zinc source is 65-75:16-30:5-9; And / or, the calcium source accounts for 250-350 ppm of the mass of the mixture; And / or, the vanadium source accounts for 300-400 ppm of the mass of the mixture; And / or, the mass of the niobium source accounts for 200-300 ppm of the mass of the mixture.
7. The method for preparing manganese-zinc ferrite powder according to claim 5 or 6, characterized in that, The manganese source includes Mn3O4; And / or, the zinc source includes ZnO; And / or, the iron source includes Fe2O3; And / or, the calcium source includes CaCO3; And / or, the vanadium source includes V2O5; And / or, the niobium source includes Nb2O5.
8. The method for preparing the coating agent according to claim 5 or 6, characterized in that, Step (1) also includes adding a first dispersant; Step (2) also includes adding at least one of a second dispersant and polyvinyl alcohol; Optionally, the first dispersant and the second dispersant are each independently selected from at least one of ammonia compounds and alcohol compounds; Step (3) also includes the addition of zinc stearate; Optionally, the mass ratio of the sum of the iron powder core and the manganese-zinc ferrite to the mass of the zinc stearate is (500-1000):
1.
9. The method for preparing a coated iron powder core according to claim 5, characterized in that, The sintering temperature is 800-900℃, and the time is 2-3 hours; The annealing process includes a first annealing process, a second annealing process, a third annealing process, a fourth annealing process, and a cooling process; Optionally, the first annealing temperature is 90-100℃, and the heating rate is 0.20-0.25℃ / min; Optionally, the second annealing temperature is 320-330℃, and the heating rate is 0.02-0.30℃ / min; Optionally, the third annealing temperature is 1100-1200℃, and the heating rate is 0.60-1.42℃ / min; Optionally, the fourth annealing temperature is 1300-1400℃, the heating rate is 1.40-1.46℃ / min, the holding time is 300-350min, the annealing atmosphere is an inert gas, and the flow rate of the inert gas is 350-450L / min. Optionally, the cooling rate of the cooling treatment is 0.30-2.10℃ / min, the cooling atmosphere is an inert gas, and the flow rate of the inert gas is 200-400L / min; In step (3), after the mixing process, a pressing process is also included, wherein the pressure of the pressing process is 540-648 MPa and the time is 2-15 min.
10. The application of the coated iron powder core according to any one of claims 1-4 or the coated iron powder core prepared by the preparation method according to any one of claims 5-9 in the preparation of switching power supplies and high-frequency communication products.