Composite iron-nickel magnetic powder core and preparation method and application thereof

Abstract

The invention provides a composite iron-nickel magnetic powder core and a preparation method and application thereof, and the preparation method comprises the following steps: (1) carrying out heat treatment on iron-nickel alloy magnetic powder, mixing the iron-nickel alloy magnetic powder with silicon resin and a surfactant, carrying out ball milling treatment, carrying out magnetic separation, and carrying out heat treatment to obtain silicon dioxide coated iron-nickel alloy composite magnetic powder; (2) passivating the composite magnetic powder, mixing the obtained magnetic powder with a coupling agent, and carrying out ball milling treatment; and (3) mixing the material obtained in the step (2) with silicon resin, carrying out ball milling treatment to obtain completely coated iron-nickel alloy composite magnetic powder, and pressing to obtain the composite iron-nickel magnetic powder core. Good interface bonding is formed between the magnetic crystal grains and the non-magnetic crystal grains through ball milling, and the formed coating layer is stable and uniform in structure, so that the magnetic powder core with good electromagnetic performance is prepared. The method has the advantages of being uniform in microstructure, high in controllability and the like, and the high-quality magnetic powder core can be prepared.

Description

Technical Field

[0001] The invention belongs to the technical field of magnetic materials and relates to a composite iron-nickel magnetic powder core and a preparation method and application thereof. Background Art

[0002] Iron-nickel magnetic powder core is a metal powder magnetic core made of alloy powder of Fe and Ni. This magnetic powder core has stable working performance under high power, high DC bias or high frequency AC, and has been widely used in switching regulation inductors, online noise filters, flyback transformers, power factor correction and pulse transformers.

[0003] At present, the main method for preparing metal magnetic powder cores is to mix metal magnetic powder and insulating material evenly, then cover the surface of the magnetic powder with a uniform and dense insulating material, and then perform compression molding and necessary heat treatment to obtain the final product. However, the power loss of the magnetic powder core is closely related to the type of insulating material used, the amount added, and the coating method. With the trend of high-frequency electronic equipment, the demand for metal magnetic powder cores with excellent properties such as high magnetic permeability and low loss has become a trend that must be pursued.

[0004] CN114156034A discloses a low-loss iron-nickel magnetic powder core composite coating method with a silicon dioxide surface coating structure, wherein the silicon dioxide powder is coated on the powder surface in a mechanical energy manner by stirring.

[0005] CN114156034A discloses a low-loss iron-nickel magnetic powder core composite coating method, which comprises the following steps: surface-treating iron and nickel respectively and then coating them with silicon dioxide, then mixing the two in proportion, coating them with epoxy-modified silicone resin solution, adding a lubricant, pressing and molding, and heat treating to obtain a low-loss iron-nickel magnetic powder core.

[0006] The above scheme coats silicon dioxide by stirring, and the coating layer formed by the obtained magnetic powder core may not be tight enough, resulting in high loss of the final magnetic powder core. At the same time, it takes several hours of stirring, which is also time-consuming in production. Summary of the invention

[0007] The purpose of the present invention is to provide a composite iron-nickel magnetic powder core and its preparation method and application. The present invention forms a good interface bonding between magnetic grains and non-magnetic grains through ball milling, and the formed coating layer structure is stable and uniform, thereby obtaining a magnetic powder core with good electromagnetic properties. The method has the advantages of uniform microstructure and strong controllability, and can prepare high-quality magnetic powder cores.

[0008] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

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

[0010] (1) subjecting the iron-nickel alloy magnetic powder to a one-step heat treatment, mixing it with a first silicone resin and a surfactant, subjecting it to a one-step ball milling treatment, and subjecting it to a two-step heat treatment after magnetic separation to obtain a silicon dioxide-coated iron-nickel alloy composite magnetic powder;

[0011] (2) after passivation treatment of the silicon dioxide coated iron-nickel alloy composite magnetic powder, the obtained magnetic powder is mixed with a coupling agent and subjected to a two-step ball milling treatment;

[0012] (3) The material obtained in step (2) is mixed with the second silicone resin and subjected to three-step ball milling treatment to obtain a completely coated iron-nickel alloy composite magnetic powder, which is then pressed to obtain the composite iron-nickel magnetic powder core.

[0013] The method of the present invention uses high temperature and high mechanical energy generated by high-energy ball milling to promote the decomposition of silicone resin to produce silicon dioxide and form a silicon dioxide coating layer on the surface of the powder. The coating layer is uniform, has good insulation, good thermal stability and high strength. Subsequently, it is passivated with phosphoric acid, surface treated with a coupling agent and coated with silicone resin. The iron-nickel magnetic powder core finally obtained has the characteristics of low magnetic loss and high magnetic permeability.

[0014] Preferably, the iron-nickel alloy magnetic powder in step (1) comprises iron-nickel alloy atomized magnetic powder.

[0015] Preferably, the mesh size of the iron-nickel alloy magnetic powder is 200-500 meshes, for example, 200 meshes, 250 meshes, 300 meshes, 400 meshes or 500 meshes.

[0016] Preferably, the one-step heat treatment includes a first-stage heat treatment and a second-stage heat treatment.

[0017] Preferably, the temperature of the first stage heat treatment is 600-800°C, for example, 600°C, 650°C, 700°C, 750°C or 800°C.

[0018] Preferably, the heating rate of the first stage heat treatment is 8-12°C / min, for example, 8°C / min, 9°C / min, 10°C / min, 11°C / min or 12°C / min.

[0019] Preferably, the heat treatment period is 20 to 40 minutes, for example, 20 minutes, 25 minutes, 30 minutes, 35 minutes or 40 minutes.

[0020] Preferably, the temperature of the second stage heat treatment is 300-500°C, for example, 300°C, 350°C, 400°C, 450°C or 500°C.

[0021] Preferably, the cooling rate of the second stage heat treatment is 12 to 18°C / min, for example, 12°C / min, 13°C / min, 14°C / min, 15°C / min or 18°C / min.

[0022] Preferably, the second stage heat treatment lasts for 20 to 40 minutes, for example, 20 minutes, 25 minutes, 30 minutes, 35 minutes or 40 minutes.

[0023] Preferably, after the one-step heat treatment, the product is sieved through a 200-500 mesh (eg, 200 mesh, 250 mesh, 300 mesh, 400 mesh or 500 mesh, etc.) sieve.

[0024] Preferably, in step (1), the first silicone resin comprises methyl MQ silicone resin.

[0025] Preferably, the mass ratio of the iron-nickel alloy magnetic powder to the first silicone resin is (15-25):1, for example: 15:1, 18:1, 20:1, 22:1 or 25:1, etc.

[0026] Preferably, the surfactant comprises oleic acid.

[0027] Preferably, the mass ratio of the total mass of the iron-nickel alloy magnetic powder and the first silicone resin to the surfactant is (30-50):1:1, for example: 30:1, 35:1, 40:1, 45:1 or 50:1.

[0028] Preferably, the temperature of the one-step ball milling treatment is 300-400°C, for example, 300°C, 320°C, 350°C, 380°C or 400°C.

[0029] Preferably, the speed of the one-step ball milling treatment is 700-900 rpm, for example, 700 rpm, 750 rpm, 800 rpm, 850 rpm or 900 rpm.

[0030] Preferably, during the one-step ball milling process, the ball mill runs for 7.5 to 8.5 minutes and stops for 1.5 to 2.5 minutes.

[0031] Preferably, the one-step ball milling treatment lasts for 2 to 3 hours, for example, 2 hours, 2.2 hours, 2.5 hours, 2.8 hours or 3 hours.

[0032] The present invention utilizes the high temperature generated by high-energy ball milling to reach the decomposition temperature of silicone resin. The silicone resin is heated to decompose on the surface of the iron-nickel alloy to generate silicon dioxide. The generated silicon dioxide continuously adheres to the surface of the iron-nickel alloy. Under the continuous high-energy impact of the ball, a silicon dioxide coating layer with gaps, uniformity, good insulation and high strength is finally formed on the surface of the iron-nickel alloy powder.

[0033] Preferably, the two-step heat treatment in step (1) includes three-stage heat treatment and four-stage heat treatment.

[0034] Preferably, the temperature of the three-stage heat treatment is 500-700°C, for example, 500°C, 550°C, 600°C, 650°C or 700°C.

[0035] Preferably, the heating rate of the three-stage heat treatment is 10-20°C / min, for example: 10°C / min, 12°C / min, 15°C / min, 18°C / min or 20°C / min.

[0036] Preferably, the time for the three-stage heat treatment is 15 to 25 minutes, for example: 15 minutes, 18 minutes, 20 minutes, 23 minutes or 25 minutes.

[0037] Preferably, the temperature of the four-stage heat treatment is 650-750°C, for example, 650°C, 680°C, 700°C, 720°C or 750°C.

[0038] Preferably, the heating rate of the four-stage heat treatment is 20-40°C / min, for example, 20°C / min, 25°C / min, 30°C / min, 35°C / min or 40°C / min.

[0039] Preferably, the time for the four-stage heat treatment is 30 to 60 minutes, for example: 30 minutes, 35 minutes, 40 minutes, 50 minutes or 60 minutes.

[0040] Preferably, the passivation treatment in step (2) comprises: mixing the silicon dioxide-coated iron-nickel alloy composite magnetic powder with phosphoric acid and a solvent, and then grinding the mixture.

[0041] Preferably, the mass ratio of the silica-coated iron-nickel alloy composite magnetic powder to phosphoric acid is (250-1000):1, for example: 250:1, 300:1, 400:1, 500:1 or 1000:1, etc., preferably (400-600):1.

[0042] In the method of the present invention, although there is a silicon dioxide coating layer, phosphoric acid can still penetrate into the internal iron-nickel alloy and generate phosphate in the pores to achieve the purpose of passivation.

[0043] Preferably, the solvent comprises acetone.

[0044] Preferably, the grinding speed is 50-100 rpm, for example, 50 rpm, 60 rpm, 70 rpm, 80 rpm or 100 rpm.

[0045] Preferably, the grinding treatment time is 5 to 10 minutes, for example: 5 minutes, 6 minutes, 7 minutes, 8 minutes or 10 minutes.

[0046] Preferably, after the grinding treatment, the product is sieved through a 100-300 mesh (for example, 100 mesh, 150 mesh, 200 mesh, 250 mesh or 300 mesh, etc.) sieve.

[0047] Preferably, the coupling agent in step (2) includes KH-570 and / or γ-methoxypropyltrimethoxysilane.

[0048] Preferably, the mass ratio of the magnetic powder to the coupling agent is (150-250):1, for example: 150:1, 180:1, 200:1, 220:1 or 250:1, etc.

[0049] Preferably, the solvent of the two-step ball milling treatment comprises alcohol.

[0050] Preferably, the speed of the two-step ball milling treatment is 50-100 rpm, for example, 50 rpm, 60 rpm, 70 rpm, 80 rpm or 100 rpm.

[0051] Preferably, the two-step ball milling treatment lasts for 5 to 10 minutes, for example, 5 minutes, 6 minutes, 7 minutes, 8 minutes or 10 minutes.

[0052] Preferably, after the two-step ball milling treatment, the product is sieved through a 100-300 mesh (for example, 100 mesh, 150 mesh, 200 mesh, 250 mesh or 300 mesh, etc.) sieve.

[0053] Preferably, in step (3), the second silicone resin comprises silicone glue.

[0054] Preferably, the mass ratio of the material to the second silicone resin is (80-120):1, for example: 80:1, 90:1, 100:1, 110:1 or 120:1, etc.

[0055] Preferably, the solvent of the three-step ball milling process comprises acetone.

[0056] Preferably, the speed of the three-step ball milling treatment is 80-120 rpm, for example, 80 rpm, 90 rpm, 100 rpm, 110 rpm or 120 rpm.

[0057] Preferably, the three-step ball milling treatment takes 3 to 8 minutes, for example, 3 minutes, 4 minutes, 5 minutes, 6 minutes or 8 minutes.

[0058] Preferably, the pressing in step (3) comprises: mixing the iron-nickel alloy composite magnetic powder with stearic acid, pressing and then calcining to obtain the composite iron-nickel magnetic powder core.

[0059] During the pressing process of the present invention, the magnetic ring is calcined. After this calcination, the outermost silicone resin is decomposed again to form silicon dioxide, which is densely distributed in the gaps between the molded magnetic ring powders and is tightly connected to the previous silicon dioxide coating layer; at the same time, this annealing step also removes the internal stress generated during the pressing process.

[0060] Preferably, the mass of the stearic acid is 0.1-0.3% of the mass of the iron-nickel alloy composite magnetic powder, for example, 0.1%, 0.15%, 0.2%, 0.25% or 0.3%.

[0061] Preferably, the pressing pressure is 1200-2000 MPa, for example, 1200 MPa, 1400 MPa, 1500 MPa, 1800 MPa or 2000 MPa.

[0062] Preferably, the calcining atmosphere includes nitrogen.

[0063] Preferably, the roasting includes one-stage roasting and two-stage roasting.

[0064] Preferably, the temperature of the first stage roasting is 350-400°C, for example, 350°C, 360°C, 370°C, 380°C or 400°C.

[0065] Preferably, the heating rate of the first stage roasting is 15-25°C / min, for example, 15°C / min, 18°C / min, 20°C / min, 22°C / min or 25°C / min.

[0066] Preferably, the calcination period is 20 to 40 minutes, for example, 20 minutes, 25 minutes, 30 minutes, 35 minutes or 40 minutes.

[0067] Preferably, the temperature of the second-stage calcination is 700-800°C, for example, 700°C, 720°C, 750°C, 780°C or 800°C.

[0068] Preferably, the heating rate of the second-stage calcination is 15-25°C / min, for example, 15°C / min, 18°C / min, 20°C / min, 22°C / min or 25°C / min.

[0069] Preferably, the second-stage roasting time is 20 to 40 minutes, for example, 20 minutes, 25 minutes, 30 minutes, 35 minutes or 40 minutes.

[0070] In a second aspect, the present invention provides a composite iron-nickel magnetic powder core, which is prepared by the method described in the first aspect.

[0071] In a third aspect, the present invention provides an application of the composite iron-nickel magnetic powder core as described in the second aspect, wherein the composite iron-nickel magnetic powder core is used for a switching regulation inductor, an online noise filter, a flyback transformer, a power factor correction or a pulse transformer.

[0072] Compared with the prior art, the present invention has the following beneficial effects:

[0073] (1) In the method of the present invention, because silicon dioxide is close to iron-nickel alloy magnetic powder in chemical composition and crystal structure, the two have a high degree of matching, which can reduce the formation of defects such as dislocations and grain boundaries between the coating layer and the base material, improve the bonding strength and bonding effect of the interface, reduce the main hysteresis loss at low frequency, and increase the insulation of the powder, reducing the main eddy current loss at high frequency. The subsequent passivation coating process once again increases the insulation between the powders, and the composite magnetic powder finally obtained has excellent magnetic properties such as high magnetic permeability and low frequency and high frequency low loss.

[0074] (2) The preparation process of the present invention is simple, the production efficiency is high, and it can be mass-produced industrially. The loss magnetic permeability and other properties of the composite powder can also be controlled by changing the ball milling and subsequent coating process, thereby meeting the market demand for different application scenarios. The outer coating layer of the composite iron-nickel magnetic powder core is composed of multiple layers of silicon dioxide, and the obtained composite powder has a light density and strong corrosion resistance.

[0075] (3) The magnetic permeability of the composite iron-nickel magnetic powder core prepared by the method of the present invention can reach more than 145, and the magnetic loss can reach 134mW / cm at 50kHz and 100mT 3 Below, 1MHz, 50mT magnetic loss can reach 1776mW / cm 3 the following. DETAILED DESCRIPTION

[0076] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0077] Example 1

[0078] This embodiment provides a composite iron-nickel magnetic powder core, and the preparation method of the composite iron-nickel magnetic powder core is as follows:

[0079] (1) 500-mesh iron-nickel alloy gas atomized magnetic powder was heat-treated in an electric furnace: in a nitrogen atmosphere, the temperature was first raised to 700°C at 10°C / min and kept at this temperature for 30 minutes, then cooled to 400°C at 15°C / min and kept at this temperature for 30 minutes, and then cooled to room temperature with the furnace. The iron-nickel alloy powder obtained after heat treatment was sieved with a 500-mesh sieve, and the fine powder obtained by sieving the 500-mesh sieve was mixed with SM-901 (methyl MQ silicone resin) at a mass ratio of 20:1, and a surfactant (oleic acid) was added to assist ball milling. The ball milling process used a tungsten carbide ball mill and balls. Before ball milling, the ball mill was evacuated, the ball-to-material ratio was 20:1, the rotation speed was 750rpm, and the unidirectional operation mode was adopted. The temperature of the ball mill was monitored by a thermocouple and controlled at 360°C. The ball mill was operated for 8 minutes and stopped for 2 minutes, and the total operation time was 2 hours. The ratio of powder to oleic acid was 40:1. The excess silicon dioxide and silicon dioxide-coated iron-nickel alloy composite magnetic powder were separated by magnetic separation to obtain a powder with a particle size of 15 μm. In a nitrogen atmosphere, the temperature was first increased to 600°C at 10°C / min and kept for 20 min, then increased to 700°C at 20°C / min and kept for 30 min, and then cooled in the furnace to obtain silicon dioxide-coated iron-nickel alloy composite magnetic powder.

[0080] (2) The composite magnetic powder and phosphoric acid are placed in a polytetrafluoroethylene ball mill at a mass ratio of 500:1, and the ball milling is performed using a planetary ball mill. Acetone is used as the ball milling solvent, and the amount of acetone is just enough to immerse the ball material. Zirconia balls are used as the balls. The ball-to-material ratio is 10:1. The rotation speed is 100 rpm. The ball milling time is 5 min. After drying, the mixture is sieved through 200 mesh. The obtained magnetic powder and KH-570 are placed in a polytetrafluoroethylene ball mill at a mass ratio of 150:1. The mixture is milled using a planetary ball mill. Alcohol is used as the ball milling solvent. Zirconia balls are used as the balls. The ball-to-material ratio is 10:1. The rotation speed is 100 rpm. The ball milling time is 5 min. After drying, the mixture is sieved through 200 mesh.

[0081] (3) The obtained magnetic powder and Dow Corning 3145 (a silicone rubber) were placed in a polytetrafluoroethylene ball mill at a mass ratio of 100:1, and ball milled using a planetary ball mill. Acetone was used as the ball milling solvent, zirconium oxide balls were used as the ball milling balls, the ball-to-material ratio was 10:1, the rotation speed was 100 rpm, and the ball milling time was 5 min. After drying, the powder was granulated through 80 mesh to obtain a completely coated iron-nickel alloy composite magnetic powder. The magnetic powder was mixed with aluminum stearate in an amount of 0.3%, and pressed into a magnetic ring using a servo press at 1500 MPa. The mold size was 12.7 mm*7 mm (inner and outer diameters of the ring).

[0082] The pressed ring is placed in an electric furnace for heat treatment: in a nitrogen atmosphere, the temperature is first raised to 370°C at 20°C / min and kept at that temperature for 30 minutes, then raised to 740°C at 20°C / min and kept at that temperature for 30 minutes, and then cooled to room temperature in the furnace to obtain the composite iron-nickel magnetic powder core.

[0083] Example 2

[0084] This embodiment provides a composite iron-nickel magnetic powder core, and the preparation method of the composite iron-nickel magnetic powder core is as follows:

[0085] (1) 200-mesh iron-nickel alloy gas atomized magnetic powder was selected for heat treatment in an electric furnace: in a nitrogen atmosphere, the temperature was first raised to 600°C at 10°C / min and kept for 40 minutes, then cooled to 300°C at 15°C / min and kept for 40 minutes, and then cooled to room temperature with the furnace. The iron-nickel alloy powder obtained after heat treatment was sieved with a 200-mesh sieve, and the fine powder obtained by sieving the 200-mesh sieve was mixed with SM-901 (methyl MQ silicone resin) at a mass ratio of 15:1, and a surfactant (oleic acid) was added to assist ball milling. The ball milling process uses a tungsten carbide ball mill and balls. Before ball milling, the ball mill is evacuated, the ball-to-material ratio is 20:1, the rotation speed is 700 rpm, and the unidirectional operation mode is adopted. The temperature of the ball mill is monitored by a thermocouple and controlled at 350°C. The ball mill runs for 8 minutes and stops for 2 minutes, running for a total of 2 hours. The ratio of powder to oleic acid is 50:1. The excess silicon dioxide and silicon dioxide-coated iron-nickel alloy composite magnetic powder were separated by magnetic separation to obtain a powder with a particle size of 15 μm. In a nitrogen atmosphere, the temperature was first increased to 500°C at 10°C / min and kept for 25 min, then increased to 650°C at 20°C / min and kept for 60 min, and then cooled in the furnace to obtain silicon dioxide-coated iron-nickel alloy composite magnetic powder.

[0086] (2) The composite magnetic powder and phosphoric acid are placed in a polytetrafluoroethylene ball mill at a mass ratio of 250:1, and the ball milling is performed using a planetary ball mill. Acetone is used as the ball milling solvent, and the amount of acetone is just enough to immerse the ball material. Zirconia balls are used as the balls. The ball-to-material ratio is 10:1. The rotation speed is 50 rpm. The ball milling time is 10 min. After drying, the mixture is sieved through a 100-mesh sieve. The obtained magnetic powder and KH-570 are placed in a polytetrafluoroethylene ball mill at a mass ratio of 150:1. The mixture is ball milled using a planetary ball mill. Alcohol is used as the ball milling solvent. Zirconia balls are used as the balls. The ball-to-material ratio is 10:1. The rotation speed is 100 rpm. The ball milling time is 5 min. After drying, the mixture is sieved through a 100-mesh sieve.

[0087] (3) The obtained magnetic powder and Dow Corning 3145 (a silicone rubber) were placed in a polytetrafluoroethylene ball mill at a mass ratio of 100:1, and ball milled using a planetary ball mill. Acetone was used as the ball milling solvent, zirconium oxide balls were used as the ball milling balls, the ball-to-material ratio was 10:1, the rotation speed was 100 rpm, and the ball milling time was 5 min. After drying, the powder was granulated through 80 mesh to obtain a completely coated iron-nickel alloy composite magnetic powder. The magnetic powder was mixed with aluminum stearate in an amount of 0.3%, and pressed into a magnetic ring using a servo press at 1500 MPa. The mold size was 12.7 mm*7 mm (inner and outer diameters of the ring).

[0088] The pressed ring is placed in an electric furnace for heat treatment: in a nitrogen atmosphere, the temperature is first raised to 370°C at 20°C / min and kept at that temperature for 30 minutes, then raised to 740°C at 20°C / min and kept at that temperature for 30 minutes, and then cooled to room temperature in the furnace to obtain the composite iron-nickel magnetic powder core.

[0089] Example 3

[0090] (1) 500-mesh iron-nickel alloy gas atomized magnetic powder was selected for heat treatment in an electric furnace: in a nitrogen atmosphere, the temperature was first raised to 800°C at 10°C / min and kept at this temperature for 20 minutes, then cooled to 500°C at 15°C / min and kept at this temperature for 20 minutes, and then cooled to room temperature with the furnace. The iron-nickel alloy powder obtained after heat treatment was sieved with a 500-mesh sieve, and the fine powder obtained by sieving the 500-mesh sieve was mixed with SM-901 (methyl MQ silicone resin) at a mass ratio of 25:1, and a surfactant (oleic acid) was added to assist ball milling. The ball milling process used a tungsten carbide ball mill and balls. Before ball milling, the ball mill was evacuated, the ball-to-material ratio was 20:1, the rotation speed was 900 rpm, and the unidirectional operation mode was adopted. The temperature of the ball mill was monitored by a thermocouple and controlled at 400°C. The ball mill was operated for 8 minutes, stopped for 2 minutes, and operated for a total of 2 hours. The ratio of powder to oleic acid was 30:1. The excess silicon dioxide and silicon dioxide-coated iron-nickel alloy composite magnetic powder were separated by magnetic separation to obtain a powder with a particle size of 15 μm. In a nitrogen atmosphere, the temperature was first increased to 700°C at 10°C / min and kept for 20 min, then increased to 750°C at 20°C / min and kept for 30 min, and then cooled in the furnace to obtain silicon dioxide-coated iron-nickel alloy composite magnetic powder.

[0091] (2) The composite magnetic powder and phosphoric acid are placed in a polytetrafluoroethylene ball mill at a mass ratio of 1000:1, and the mixture is milled in a planetary ball mill. Acetone is used as the milling solvent, the amount of acetone is just enough to immerse the ball material, zirconia balls are used as the balls, the ball-to-material ratio is 10:1, the rotation speed is 100 rpm, the milling time is 5 min, and after drying, the mixture is sieved through 200 mesh. The obtained magnetic powder and γ-methoxypropyltrimethoxysilane are placed in a polytetrafluoroethylene ball mill at a mass ratio of 150:1, and the mixture is milled in a planetary ball mill. Alcohol is used as the milling solvent, zirconia balls are used as the balls, the ball-to-material ratio is 10:1, the rotation speed is 100 rpm, the milling time is 5 min, and after drying, the mixture is sieved through 200 mesh.

[0092] (3) The obtained magnetic powder and Dow Corning 3145 (a silicone rubber) were placed in a polytetrafluoroethylene ball mill at a mass ratio of 120:1, and milled using a planetary ball mill. Acetone was used as the milling solvent, zirconium oxide balls were used as the balls, the ball-to-material ratio was 10:1, the rotation speed was 100 rpm, and the milling time was 5 min. After drying, the powder was granulated with 80 mesh to obtain a completely coated iron-nickel alloy composite magnetic powder. The magnetic powder was mixed with aluminum stearate in an amount of 0.3%, and pressed into a magnetic ring using a servo press at 2000 MPa. The mold size was 12.7 mm*7 mm (inner and outer diameters of the ring).

[0093] The pressed ring is placed in an electric furnace for heat treatment: in a nitrogen atmosphere, the temperature is first raised to 400°C at 20°C / min and kept at that temperature for 20 minutes, then raised to 800°C at 20°C / min and kept at that temperature for 20 minutes, and then cooled to room temperature in the furnace to obtain the composite iron-nickel magnetic powder core.

[0094] Example 4

[0095] The only difference between this embodiment and embodiment 1 is that the mass ratio of the silicon dioxide-coated iron-nickel alloy composite magnetic powder to phosphoric acid is 1000:1, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0096] Example 5

[0097] The only difference between this embodiment and embodiment 1 is that the mass ratio of the silicon dioxide-coated iron-nickel alloy composite magnetic powder to phosphoric acid is 250:1, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0098] Example 6

[0099] The only difference between this embodiment and embodiment 1 is that the mass ratio of the magnetic powder and the silicone glue in step (2) is 75:1, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0100] Example 7

[0101] The only difference between this embodiment and embodiment 1 is that the mass ratio of the magnetic powder and the silicone glue in step (2) is 150:1, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0102] Comparative Example 1

[0103] The only difference between this comparative example and Example 1 is that in step (1), the iron-nickel alloy atomized magnetic powder is not subjected to heat treatment, and the other conditions and parameters are exactly the same as those in Example 1.

[0104] Comparative Example 2

[0105] The only difference between this comparative example and Example 1 is that the ball milling process is not performed in step (1), and the other conditions and parameters are exactly the same as those in Example 1.

[0106] Comparative Example 3

[0107] The only difference between this comparative example and Example 1 is that the ball milling speed in step (1) is 500 rpm, the ball mill runs for 5 min and stops for 1 min, the ball milling temperature is 290° C., and the other conditions and parameters are exactly the same as those in Example 1.

[0108] Comparative Example 4

[0109] The only difference between this comparative example and Example 1 is that no heat treatment is performed after the magnetic separation in step (1), and the other conditions and parameters are exactly the same as those in Example 1.

[0110] Comparative Example 5

[0111] The only difference between this comparative example and Example 1 is that phosphoric acid and coupling agent are not added in step (2), and other conditions and parameters are exactly the same as those in Example 1.

[0112] Performance Test:

[0113] According to the standard SJ20966 2006, the performance of the composite iron-nickel magnetic powder core prepared in the embodiment and the comparative example was tested using an IWATSUB H analyzer (SY 8219). The test results are shown in Table 1:

[0114] Table 1

[0115]

[0116]

[0117] As can be seen from Table 1, from Examples 1-3, the magnetic permeability of the composite iron-nickel magnetic powder core prepared by the method of the present invention can reach more than 145, and the magnetic loss can reach 134mW / cm at 50kHz and 100mT. 3 Below, 1MHz, 50mT magnetic loss can reach 1776mW / cm 3 the following.

[0118] By comparing Example 1 with Examples 4-5, it can be seen that in the preparation process of the composite iron-nickel magnetic powder core of the present invention, the addition amount of phosphoric acid will affect its performance. The mass ratio of the silicon dioxide-coated iron-nickel alloy composite magnetic powder to phosphoric acid is controlled at 400-600:1, and the performance of the composite iron-nickel magnetic powder core is better. If the addition amount of phosphoric acid is too high, the phosphate generated by the reaction of the powder surface with phosphoric acid increases, and the adhesion between the phosphate and the silicone glue is better than the adhesion between the alloy and the silicone glue. Therefore, within a certain range, the increase in phosphate can make the coating layer tighter, thereby reducing the high-frequency loss of the obtained magnetic powder core, but with the increase in the amount of phosphate, the amount of corroded alloy also increases, and the magnetic permeability of the magnetic powder core finally obtained will decrease; if the addition amount of phosphoric acid is too low, the high-frequency loss of the magnetic powder core finally obtained will increase, but the magnetic permeability will increase.

[0119] By comparing Example 1 with Examples 6-7, it can be seen that during the preparation process of the composite iron-nickel magnetic powder core of the present invention, the amount of silicone glue added will affect its performance. When the mass ratio of the magnetic powder and the silicone glue in step (2) is controlled at 80-120:1, the performance of the composite iron-nickel magnetic powder core obtained is better. If the amount of silicone glue added is too high, the magnetic permeability of the magnetic powder core will decrease. This is because the more non-magnetic material is added to the magnetic powder core, the lower the magnetic permeability of the obtained magnetic powder core will be. At the same time, the silicone glue plays a coating role. Within a certain range, an increase in the amount of silicone glue added will reduce the high-frequency loss of the obtained magnetic powder core; if the amount of silicone glue added is too low, the magnetic permeability of the obtained magnetic powder core will increase, but the high-frequency loss will also increase.

[0120] By comparing Example 1 with Comparative Example 1, it can be seen that in the method of the present invention, if the iron-nickel alloy atomized magnetic powder is not heat treated, the magnetic permeability and loss performance will deteriorate, which is related to the fact that the internal stress inside the original powder has not been eliminated.

[0121] By comparing Example 1 and Comparative Example 2, it can be seen that in the method of the present invention, high-energy ball milling is not performed to coat the silica, and the magnetic permeability of the powder is slightly reduced, but the low-frequency and high-frequency losses are greatly deteriorated. The reason is that the defects between the coating layer and the iron-nickel powder increase and the insulation of the coating layer decreases, resulting in a significant increase in low-frequency hysteresis loss and high-frequency eddy current loss.

[0122] By comparing Example 1 and Comparative Example 3, it can be seen that in the method of the present invention, reducing the rotation speed causes the temperature during the ball milling process to fail to reach the decomposition temperature of the silicone resin, resulting in the high-energy ball milling process not coating the powder with silica, resulting in the deterioration of the final magnetic permeability and loss.

[0123] From the comparison between Example 1 and Comparative Example 4, it can be seen that in the method of the present invention, if the heat treatment after high-energy ball milling is not performed to remove stress, the magnetic permeability will be greatly reduced, and the loss will also increase accordingly.

[0124] From the comparison between Example 1 and Comparative Example 5, it can be seen that in the method of the present invention, without the passivation and coupling agent surface treatment process, the magnetic permeability of the obtained magnetic powder core is slightly increased, but the low-frequency and high-frequency losses are greatly deteriorated.

[0125] The applicant declares that the above is only a specific implementation mode 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 thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing a composite iron-nickel magnetic powder core, It is characterized in that The preparation method comprises the following steps: (1) subjecting the iron-nickel alloy magnetic powder to a one-step heat treatment, mixing it with a first silicone resin and a surfactant, subjecting it to a one-step ball milling treatment, and subjecting it to a two-step heat treatment after magnetic separation to obtain a silicon dioxide-coated iron-nickel alloy composite magnetic powder; (2) after passivation treatment of the silicon dioxide coated iron-nickel alloy composite magnetic powder, the obtained magnetic powder is mixed with a coupling agent and subjected to a two-step ball milling treatment; (3) The material obtained in step (2) is mixed with the second silicone resin and subjected to three-step ball milling treatment to obtain a completely coated iron-nickel alloy composite magnetic powder, which is then pressed to obtain the composite iron-nickel magnetic powder core.

2. The preparation method according to claim 1, It is characterized in that The iron-nickel alloy magnetic powder in step (1) comprises an iron-nickel alloy atomized magnetic powder; Preferably, the mesh size of the iron-nickel alloy magnetic powder is 200-500 mesh; Preferably, the one-step heat treatment includes a first-stage heat treatment and a second-stage heat treatment; Preferably, the temperature of the first stage heat treatment is 600-800°C; Preferably, the heating rate of the first stage heat treatment is 8-12°C / min; Preferably, the heat treatment period is 20 to 40 minutes; Preferably, the temperature of the second stage heat treatment is 300-500°C; Preferably, the cooling rate of the second stage heat treatment is 12-18°C / min; Preferably, the second stage heat treatment lasts for 20 to 40 minutes; Preferably, after the one-step heat treatment, the product is sieved through a 200-500 mesh sieve.

3. The preparation method according to claim 1 or 2, It is characterized in that Step (1) the first silicone resin comprises methyl MQ silicone resin; Preferably, the mass ratio of the iron-nickel alloy magnetic powder to the first silicone resin is (15-25):1; Preferably, the surfactant comprises oleic acid; Preferably, the mass ratio of the total mass of the iron-nickel alloy magnetic powder and the first silicone resin to the surfactant is (30-50):1; Preferably, the temperature of the one-step ball milling treatment is 300-400°C; Preferably, the speed of the one-step ball milling treatment is 700-900 rpm; Preferably, during the one-step ball milling process, the ball mill runs for 7.5 to 8.5 minutes and stops for 1.5 to 2.5 minutes; Preferably, the one-step ball milling treatment lasts for 2 to 3 hours.

4. The preparation method according to any one of claims 1 to 3, It is characterized in that The two-step heat treatment in step (1) includes a three-stage heat treatment and a four-stage heat treatment; Preferably, the temperature of the three-stage heat treatment is 500-700°C; Preferably, the heating rate of the three-stage heat treatment is 10-20°C / min; Preferably, the three-stage heat treatment lasts for 15 to 25 minutes; Preferably, the temperature of the four-stage heat treatment is 650-750°C; Preferably, the heating rate of the four-stage heat treatment is 20-40°C / min; Preferably, the four-stage heat treatment lasts for 30 to 60 minutes.

5. The preparation method according to any one of claims 1 to 4, It is characterized in that The passivation treatment in step (2) comprises: mixing the silicon dioxide-coated iron-nickel alloy composite magnetic powder with phosphoric acid and a solvent, and then grinding the mixture; Preferably, the mass ratio of the silicon dioxide-coated iron-nickel alloy composite magnetic powder to phosphoric acid is (250-1000):1, preferably (400-600):1; Preferably, the solvent comprises acetone; Preferably, the grinding speed is 50-100 rpm; Preferably, the grinding process lasts for 5 to 10 minutes; Preferably, the powder is sieved through a 100-300 mesh sieve after the grinding process.

6. The preparation method according to any one of claims 1 to 5, It is characterized in that The coupling agent in step (2) includes KH-570 and / or γ-methoxypropyltrimethoxysilane; Preferably, the mass ratio of the magnetic powder to the coupling agent is (150-250):1; Preferably, the solvent of the two-step ball milling treatment comprises alcohol; Preferably, the speed of the two-step ball milling treatment is 50-100 rpm; Preferably, the two-step ball milling treatment lasts for 5 to 10 minutes; Preferably, the product is sieved through a 100-300 mesh sieve after the two-step ball milling treatment.

7. The preparation method according to any one of claims 1 to 6, It is characterized in that Step (3) the second silicone resin comprises silicone glue; Preferably, the mass ratio of the material to the second silicone resin is (80-120):1; Preferably, the solvent of the three-step ball milling process comprises acetone; Preferably, the speed of the three-step ball milling process is 80-120 rpm; Preferably, the three-step ball milling process takes 3 to 8 minutes.

8. The preparation method according to any one of claims 1 to 7, It is characterized in that The pressing in step (3) comprises: mixing the iron-nickel alloy composite magnetic powder with stearic acid, pressing and then calcining to obtain the composite iron-nickel magnetic powder core; Preferably, the mass of the stearic acid is 0.1-0.3% of the mass of the iron-nickel alloy composite magnetic powder; Preferably, the pressing pressure is 1200-2000 MPa; Preferably, the calcining atmosphere comprises nitrogen; Preferably, the roasting includes one-stage roasting and two-stage roasting; Preferably, the temperature of the first stage roasting is 350-400°C; Preferably, the heating rate of the first stage roasting is 15-25°C / min; Preferably, the roasting time is 20 to 40 minutes; Preferably, the temperature of the second stage roasting is 700-800°C; Preferably, the heating rate of the second stage roasting is 15-25°C / min; Preferably, the second-stage roasting time is 20 to 40 minutes.

9. A composite iron-nickel magnetic powder core, It is characterized in that The composite iron-nickel magnetic powder core is prepared by the method according to any one of claims 1 to 8.

10. An application of the composite iron-nickel magnetic powder core as claimed in claim 9, It is characterized in that The composite iron-nickel magnetic powder core is used for switch regulation inductors, online noise filters, flyback transformers, power factor correction or pulse transformers.

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