High-permeability iron-silicon soft magnetic powder core and preparation method thereof

Abstract

The invention belongs to the technical field of soft magnetic materials, and particularly relates to a high-permeability iron-silicon soft magnetic powder core and a preparation method thereof. The iron-silicon soft magnetic powder core is composed of iron-silicon magnetic powder and two silicon oxide insulation coating layers on the surface of the magnetic powder. The preparation method comprises the following steps: primary insulation coating: uniformly mixing gas-atomized iron-silicon magnetic powder according to a particle size ratio requirement, adding kaolin, potassium silicate and water, heating and frying; 2) secondary insulation coating: repeating the step 1) once; performing compression molding: adding a release agent and a strength enhancer silicon resin, and performing compression molding; and magnetic core heat treatment, wherein the pressed and formed magnetic core is put into protective gas to be subjected to sintering heat treatment, and then the surface of the magnetic core is spin-coated with epoxy resin powder. The iron-silicon soft magnetic powder core is high in magnetic conductivity, low in magnetic core loss, good in direct current bias performance, high in quality factor, simple in insulation process and high in production efficiency, and iron-silicon products with high magnetic conductivity can be produced on a large scale.

Description

Technical Field

[0001] The present invention belongs to the technical field of soft magnetic materials, and particularly relates to a high-permeability iron-silicon soft magnetic powder core and a preparation method thereof. Background Art

[0002] Iron-silicon soft magnetic powder core materials have excellent DC bias characteristics, a saturation magnetic flux density of up to 16,000 Gauss, good temperature stability, and high energy storage. Iron-silicon soft magnetic powder cores are particularly suitable for fields such as home appliances, UPS power supplies, photovoltaic inverters, new energy vehicles (OBC), wind power, and hydropower generation. In recent years, the country's advocacy of carbon peak and carbon neutrality has led to the rapid rise of the new energy industry, which has strongly promoted the rapid development of soft magnetic materials.

[0003] At present, the highest magnetic permeability of iron-silicon magnetic powder can only reach 125 μ. Currently, the only high-permeability metal soft magnetic powder cores (≥160 μ) that can be made are iron-silicon-aluminum, iron-nickel, and iron-nickel-molybdenum materials. However, the prices of iron-nickel-molybdenum and iron-nickel are expensive, the market demand is small, and the DC Bias of iron-silicon-aluminum is much lower than that of iron-silicon. Therefore, high-permeability iron-silicon soft magnetic powder cores have great market prospects.

[0004] The invention patent with the patent number CN104575911A discloses a preparation method of a high-permeability iron-nickel-molybdenum magnetic powder core; water-atomized iron-nickel-molybdenum powder is selected; film-forming treatment; insulation treatment; adding a high-temperature resistant binder to prepare an iron-nickel-molybdenum magnetic powder core with a magnetic permeability reaching 190. Since iron-nickel-molybdenum is expensive, about 7 times that of iron-silicon, it has no price advantage.

[0005] The invention patent with the patent number CN103500643A discloses a manufacturing method of an iron-silicon-boron 90 μ soft magnetic powder core. This process is to crush amorphous ribbons to obtain amorphous powder, and then add iron-silicon powder or nickel powder to the amorphous powder. The insulation coating uses phosphoric acid passivation, and then add low-melting glass powder and epoxy resin. Although the insulation process is simple and the production efficiency is high, the cost of adding nickel powder and amorphous ribbons is still much higher than that of iron-silicon.

[0006] Therefore, how to develop a high-permeability iron-silicon soft magnetic powder core is a technical problem that those skilled in the art need to overcome. Summary of the Invention

[0007] In view of this, the present invention is to overcome the above-mentioned deficiencies existing in the prior art, a high-permeability iron-silicon soft magnetic powder core and a preparation method thereof. The iron-silicon soft magnetic powder core prepared by this method has high inductance, low loss, and good DC bias performance.

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

[0009] A high-permeability iron-silicon soft magnetic powder core is composed of iron-silicon magnetic powder and two layers of silicon oxide insulation coating layers on the surface of the magnetic powder.

[0010] Preferably, the particle size ratio of the iron-silicon magnetic powder is as follows: -120 to +200 mesh accounts for 18.1 to 26.4%, -200 to +325 mesh accounts for 23 to 34.3%, -325 to +400 mesh accounts for 9.7 to 13.1%, and below -400 mesh accounts for 26.4 - 37.5%.

[0011] Preferably, the iron-silicon soft magnetic core uses gas-atomized iron-silicon magnetic powder, and the silicon content in the iron-silicon magnetic powder is 5.5 to 6.5%, and the balance is iron. More preferably, the silicon content in the iron-silicon magnetic powder is 5.5 to 6.5%.

[0012] Preferably, water, kaolin, and potassium silicate are used to form a silicon oxide insulating coating layer on the surface of the iron-silicon magnetic powder.

[0013] Preferably, the iron-silicon soft magnetic powder core is prepared from iron-silicon magnetic powder according to the particle size ratio, and through primary insulation coating, secondary insulation coating, pressing molding, magnetic core heat treatment, and surface painting. The pressing molding pressure is 18 - 22 t / cm 2 .

[0014] A preparation method of a high magnetic permeability iron-silicon soft magnetic powder core, the method specifically includes the following steps:

[0015] 1) Primary insulation coating: Mix the gas-atomized iron-silicon magnetic powder evenly according to the particle size ratio requirements, add kaolin, potassium silicate, and water, and heat and stir dry;

[0016] 2) Secondary insulation coating: Repeat step 1) for the iron-silicon magnetic powder after primary insulation coating;

[0017] 3) Pressing molding: Add a release agent and a strength enhancer silicone resin to the powder after insulation coating in step 2), and carry out pressing molding;

[0018] 4) Magnetic core heat treatment: Put the magnetic core obtained by pressing molding in step 3) into a protective gas for sintering heat treatment, and then spin-coat the surface of the magnetic core with epoxy resin powder to prepare the iron-silicon soft magnetic powder core.

[0019] Preferably, in step 1) and step 2), the dosage of kaolin is 0.2 - 0.5% of the weight of the iron-silicon magnetic powder, the dosage of potassium silicate is 0.2 - 0.5% of the weight of the iron-silicon magnetic powder, and the dosage of water is 8% of the weight of the iron-silicon magnetic powder;

[0020] The heating temperature for each insulation coating is 120°C.

[0021] Preferably, in step 3), the mold release agent is microcrystalline wax or zinc stearate, the strength enhancer is methyl silicone resin, and the dosage of the mold release agent is 0.2-0.4% of the weight of the iron-silicon magnetic powder; the dosage of the strength enhancer is 0.1-0.2% of the weight of the iron-silicon magnetic powder.

[0022] Preferably, in step 4), the heat treatment temperature is 700°C - 800°C, and the heat preservation time is 30 - 120 min; the protective gas is at least one of nitrogen and hydrogen.

[0023] It can be seen from the above technical solutions that, compared with the prior art, the present invention has the following excellent effects:

[0024] (1) The present invention uses water, kaolin, and potassium silicate to form a silicon oxide insulating coating layer on the surface of the iron-silicon magnetic powder, which has advantages such as high thermal stability and electrical insulation, so that the finally prepared iron-silicon soft magnetic powder core has low core loss and high DC superposition.

[0025] (2) The present invention adopts a particle size ratio, where -120 to +200 mesh accounts for 18.1 - 26.4%, -200 to +325 mesh accounts for 23 - 34.3%, -325 to +400 mesh accounts for 9.7 - 13.1%, and below -400 mesh accounts for 26.4 - 37.5%. The advantage of the combination of thick and thin particles can improve the magnetic permeability μ value of the magnetic core and effectively reduce the core loss at the same time.

[0026] (3) In the present invention, the insulation process is simple, the production efficiency is high, large-scale production can be carried out, the preparation process is energy-saving and environmentally friendly, and the prepared products have excellent performance; moreover, the magnetic core has high magnetic permeability and DC bias performance, low power loss, etc., and the product performance is at the leading level in the industry. Description of the Drawings

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained according to the provided drawings without creative efforts.

[0028] Figure 1 It is a characteristic table of commercially available 125u iron-silicon soft magnetic powder cores, where (a) is the DC Bias characteristic curve and (b) is the Coreloss characteristic curve.

[0029] Figure 2 It is a characteristic table of the 147u iron-silicon soft magnetic powder cores prepared in the embodiments of the present invention, where (a) is the DC Bias characteristic curve and (b) is the Core loss characteristic curve. Detailed Embodiments

[0030] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0031] Example 1

[0032] 1) Take gas atomized iron-silicon magnetic powder, where the silicon content is 6.0%, and the particle size ratio of the iron-silicon magnetic powder is,

[0033] -120 to +200 mesh accounts for 22.4%, -200 to +325 mesh accounts for 32.8%, -325 + 400 mesh accounts for 11.3%, and below -400 mesh accounts for 33.5%. Mix the powder evenly according to the above ratio;

[0034] 2) Primary insulation coating: Pour the mixed iron-silicon magnetic powder into an insulation device, and then pour in the mixed insulation liquid of kaolin, potassium silicate, and water. After stirring the iron-silicon magnetic powder and the insulation liquid for 30 minutes, heat and stir-fry until dry. The dosage of kaolin is 0.2% of the weight of the iron-silicon magnetic powder, the dosage of water is 8% of the weight of the iron-silicon magnetic powder, the dosage of potassium silicate is 0.2% of the weight of the iron-silicon magnetic powder, and the heating temperature is controlled at 120°C;

[0035] 3) Secondary insulation coating: Pour the iron-silicon magnetic powder after primary insulation cooling into the insulation device again. Repeat the addition amount of the primary insulation chemical materials, where the dosage of kaolin is 0.2% of the weight of the iron-silicon magnetic powder, the dosage of water is 8% of the weight of the iron-silicon magnetic powder, the dosage of potassium silicate is 0.2% of the weight of the iron-silicon magnetic powder, and the heating temperature is controlled at 120°C;

[0036] 4) Compression molding: Add 0.3% of zinc stearate by weight of the iron-silicon magnetic powder as a demolding agent before compression molding, add 0.15% of methyl silicone resin, mix the powder evenly and then press it into a magnetic ring with dimensions of 26.9mm * 14.8mm * 11.1mm. The molding pressure is 20 tons per square centimeter; Put the molded magnetic core into a heat treatment furnace, introduce nitrogen and keep it at 760°C for 50 minutes, and then cool it naturally, where the nitrogen flow rate is set to 8m 3 / h;

[0037] 5) Chamfer and deburr the magnetic core after infiltration, and at the same time, spin-coat the surface of the magnetic ring with epoxy resin powder, and obtain an iron-silicon soft magnetic powder core after curing. The magnetic properties of the obtained iron-silicon soft magnetic powder core are shown in Table 1.

[0038] Example 2

[0039] 1) Take gas atomized iron-silicon magnetic powder, where the silicon content is 6.0%. The particle size ratio of the iron-silicon magnetic powder is as follows: -120 to +200 mesh accounts for 22.4%, -200 to +325 mesh accounts for 32.8%, -325 + 400 mesh accounts for 11.3%, and below -400 mesh accounts for 33.5%. Mix the powder evenly according to the above ratio;

[0040] 2) Insulating coating: Pour the mixed iron-silicon magnetic powder into an insulating device, and then pour in the mixed insulating liquid of kaolin, potassium silicate, and water. After stirring the iron-silicon magnetic powder and the insulating liquid for 30 minutes, heat and stir-fry until dry. The dosage of kaolin is 0.4% of the weight of the iron-silicon magnetic powder, the dosage of water is 8% of the weight of the iron-silicon magnetic powder, the dosage of potassium silicate is 0.4% of the weight of the iron-silicon magnetic powder, and the heating temperature is controlled at 120 °C;

[0041] 3) Compression molding: Add 0.3% of zinc stearate by weight of the iron-silicon magnetic powder as a mold release agent before compression molding, add 0.15% of methyl silicone resin, and after mixing the powder evenly, press it into a magnetic ring with dimensions of 26.9 mm * 14.8 mm * 11.1 mm. The molding pressure is 20 tons per square centimeter; Put the molded magnetic core into a heat treatment furnace, introduce nitrogen, keep it at 760 °C for 50 min, and then cool it naturally, where the nitrogen flow rate is set at 8 m 3 / h;

[0042] 4) Chamfer and deburr the magnetic core after infiltration, and at the same time, spin-coat the surface of the magnetic ring with epoxy resin powder. After curing, an iron-silicon soft magnetic powder core is obtained. The magnetic properties of the obtained iron-silicon soft magnetic powder core are shown in Table 1.

[0043] Example 3

[0044] 1) Take gas atomized iron-silicon magnetic powder, where the silicon content is 6.0%. The particle size ratio of the iron-silicon magnetic powder is as follows: -120 to +200 mesh accounts for 22.4%, -200 to +325 mesh accounts for 32.8%, -325 + 400 mesh accounts for 11.3%, and below -400 mesh accounts for 33.5%. Mix the powder evenly according to the above ratio;

[0045] 2) Insulating coating: Pour the mixed iron-silicon magnetic powder into an insulating device, and then pour in the mixed insulating liquid of kaolin, potassium silicate, and water. After stirring the iron-silicon magnetic powder and the insulating liquid for 30 minutes, heat and stir-fry until dry. The dosage of kaolin is 0.5% of the weight of the iron-silicon magnetic powder, the dosage of water is 8% of the weight of the iron-silicon magnetic powder, the dosage of potassium silicate is 0.5% of the weight of the iron-silicon magnetic powder, and the heating temperature is controlled at 120 °C;

[0046] 3) Compression molding: Before compression molding, 0.3% of zinc stearate by weight of the iron-silicon magnetic powder is added as a mold release agent, and 0.15% of methyl silicone resin is added. After the powder is mixed evenly, it is compressed into a magnetic ring with dimensions of 26.9mm * 14.8mm * 11.1mm. The molding pressure is 20 tons per square centimeter; the molded magnetic core is placed in a heat treatment furnace, nitrogen is introduced, and it is kept at 760 °C for 50 min, and then cooled naturally, where the nitrogen flow rate is set at 8m 3 / h;

[0047] 4) After the magnetic core is infiltrated, chamfering and deburring are carried out. At the same time, the surface of the magnetic ring is spin-coated with epoxy resin powder, and after curing, an iron-silicon soft magnetic powder core is obtained. The magnetic properties of the obtained iron-silicon soft magnetic powder core are shown in Table 1.

[0048] Example 4

[0049] 1) Take gas atomized iron-silicon magnetic powder, where the silicon content is 5% - 6.5%, and the particle size ratio of the iron-silicon magnetic powder is that -120 to +200 mesh accounts for 22.4%, -200 to +325 mesh accounts for 32.8%, -325 + 400 mesh accounts for 11.3%, and below -400 mesh accounts for 33.5%. The powder is mixed evenly according to the above ratio;

[0050] 2) Primary insulation coating: Pour the mixed iron-silicon magnetic powder into an insulation device, and then pour in a mixed insulation liquid of kaolin, potassium silicate, and water. After the iron-silicon magnetic powder and the insulation liquid are stirred for 30 minutes, it is heated and stir-fried until dry. The dosage of kaolin is 0.25% of the weight of the iron-silicon magnetic powder, the dosage of water is 8% of the weight of the iron-silicon magnetic powder, the dosage of potassium silicate is 0.25% of the weight of the iron-silicon magnetic powder, and the heating temperature is controlled at 120 °C;

[0051] 3) Secondary insulation coating: Pour the iron-silicon magnetic powder after primary insulation cooling into the insulation device again. Repeat the addition amount of the primary insulation chemical materials, where the dosage of kaolin is 0.25% of the weight of the iron-silicon magnetic powder, the dosage of water is 8% of the weight of the iron-silicon magnetic powder, the dosage of potassium silicate is 0.25% of the weight of the iron-silicon magnetic powder, and the heating temperature is controlled at 120 °C;

[0052] 4) Compression molding: Before compression molding, 0.3% of zinc stearate by weight of the iron-silicon magnetic powder is added as a mold release agent, and 0.15% of methyl silicone resin is added. After the powder is mixed evenly, it is compressed into a magnetic ring with dimensions of 26.9mm * 14.8mm * 11.1mm. The molding pressure is 20 tons per square centimeter; the molded magnetic core is placed in a heat treatment furnace, nitrogen is introduced, and it is kept at 760 °C for 50 min, and then cooled naturally, where the nitrogen flow rate is set at 8m 3 / h;

[0053] 5) After the magnetic core is infiltrated, chamfering and deburring are carried out. At the same time, the surface of the magnetic ring is spin-coated with epoxy resin powder, and after curing, an iron-silicon soft magnetic powder core is obtained. The magnetic properties of the obtained iron-silicon soft magnetic powder core are shown in Table 1.

[0054] Example 5

[0055] 1) Take gas-atomized iron-silicon magnetic powder, where the silicon content is 6.0%. The particle size ratio of the iron-silicon magnetic powder is that -120 to +200 mesh accounts for 22.4%, -200 to +325 mesh accounts for 32.8%, -325 + 400 mesh accounts for 11.3%, and below -400 mesh accounts for 33.5%. Mix the powders evenly according to the above ratios;

[0056] 2) Primary insulation coating: Pour the mixed iron-silicon magnetic powder into the insulation equipment, and then pour in the mixed insulation liquid of kaolin, potassium silicate, and water. After the iron-silicon magnetic powder and the insulation liquid are stirred for 30 minutes, heat and stir-fry until dry. The dosage of kaolin is 0.2% of the weight of the iron-silicon magnetic powder, the dosage of water is 8% of the weight of the iron-silicon magnetic powder, the dosage of potassium silicate is 0.2% of the weight of the iron-silicon magnetic powder, and the heating temperature is controlled at 120°C;

[0057] 3) Secondary insulation coating: Pour the iron-silicon magnetic powder with primary insulation coating into the insulation equipment. Take 0.3% of methyl silicone resin by the weight of the iron-silicon magnetic powder and 7% of methylal liquid by the weight of the iron-silicon magnetic powder. Pour the methyl silicone resin into the methylal, stir the methylal liquid until the methyl silicone resin is completely dissolved, and then pour it into the powder. Do not turn on the heating function until the powder is completely dry; set aside

[0058] 4) Compression molding: Before compression molding, add 0.3% of zinc stearate by the weight of the iron-silicon magnetic powder as a demolding agent. After the demolding agent and the powder are mixed evenly, compress them into a magnetic ring with dimensions of 26.9mm * 14.8mm * 11.1mm. The molding pressure is 20 tons per square centimeter; put the molded magnetic core into a heat treatment furnace, introduce nitrogen, keep it at 760°C for 50 minutes, and then cool it naturally, where the nitrogen flow rate is set to 8m 3 / h;

[0059] 5) After the magnetic core is infiltrated, chamfering and deburring are carried out. At the same time, the surface of the magnetic ring is spin-coated with epoxy resin powder, and after curing, an iron-silicon soft magnetic powder core is obtained. The magnetic properties of the obtained iron-silicon soft magnetic powder core are shown in Table 1.

[0060] Table 1 Magnetic properties of the iron-silicon soft magnetic powder cores obtained in Examples 1 to 5

[0061]

[0062]

[0063] As can be seen from Table 1, for the FeSi soft magnetic powder cores prepared by this method, the DC bias performance is over 20% under the condition of 100 Oe; the power loss is about 600 mW / cm 3 at 50 KHz and 100 mT, and the performance is at the leading level in the industry.

[0064] Example 6

[0065] 1) Take gas atomized FeSi magnetic powder, where the silicon content is 5% - 6.5%. The particle size ratio of the FeSi magnetic powder is that -120 to +200 mesh accounts for 22.4%, -200 to +325 mesh accounts for 32.8%, -325 + 400 mesh accounts for 11.3%, and below -400 mesh accounts for 33.5%. Mix the powders evenly according to the above ratios;

[0066] 2) Primary insulation coating: Pour the mixed FeSi magnetic powder into the insulation equipment, and then pour in the mixed insulation liquid of kaolin, potassium silicate, and water. After stirring the FeSi magnetic powder and the insulation liquid for 30 minutes, heat and stir-fry until dry. The dosage of kaolin is 0.2% of the weight of the FeSi magnetic powder, the dosage of water is 8% of the weight of the FeSi magnetic powder, the dosage of potassium silicate is 0.2% of the weight of the FeSi magnetic powder, and the heating temperature is controlled at 120 °C;

[0067] 3) Secondary insulation coating: Pour the FeSi magnetic powder after primary insulation cooling into the insulation equipment again. Repeat the addition amount of the primary insulation chemical materials, where the dosage of kaolin is 0.2% of the weight of the FeSi magnetic powder, the dosage of water is 8% of the weight of the FeSi magnetic powder, the dosage of potassium silicate is 0.2% of the weight of the FeSi magnetic powder, and the heating temperature is controlled at 120 °C;

[0068] 4) Compression molding: Add 0.3% of zinc stearate based on the weight of the FeSi magnetic powder as a release agent before compression molding, add 0.15% of methyl silicone resin, and after mixing the powders evenly, press them into a magnetic ring with dimensions of 26.9 mm * 14.8 mm * 11.1 mm. The molding pressure is applied at 18, 19, 20, 21, 22 tons / cm²; Put the molded magnetic core into the heat treatment furnace, introduce nitrogen, keep it at 760 °C for 50 min, and then cool it naturally, where the nitrogen flow rate is set at 8 m 3 / h;

[0069] 5) After the magnetic core is infiltrated, chamfer and deburr it. At the same time, spin-coat the surface of the magnetic ring with epoxy resin powder, and after curing, obtain the FeSi soft magnetic powder core. The magnetic properties of the obtained FeSi soft magnetic powder core are shown in Table 2. It can be seen from the test performance that the greater the pressure, the lower the loss of the magnetic core and the better the DC superposition.

[0070] Table 2 Magnetic properties of FeSi soft magnetic powder cores obtained by pressing at different pressures

[0071]

[0072] As can be seen from Table 2, under the same insulation coating process and heat treatment temperature under the same conditions, when the pressure is greater, the magnetic permeability μ value of the magnetic core is higher, and at the same time, the DC superposition and loss are also better; and within the pressure range that the mold can withstand, the greater the pressure, the better the magnetic core performance.

[0073] Example 7

[0074] 1) Take gas-atomized iron-silicon magnetic powder, where the silicon content is 5% - 6.5%, and the particle size ratio of the iron-silicon magnetic powder is that -120 to +200 mesh accounts for 22.4%, -200 to +325 mesh accounts for 32.8%, -325 + 400 mesh accounts for 11.3%, and below -400 mesh accounts for 33.5%. Mix the powders evenly according to the above ratios;

[0075] 2) Primary insulation coating: Pour the mixed iron-silicon magnetic powder into the insulation equipment, and then pour in the mixed insulation liquid of kaolin, potassium silicate, and water. After stirring the iron-silicon magnetic powder and the insulation liquid for 30 minutes, heat and stir-fry until dry. The dosage of kaolin is 0.25% of the weight of the iron-silicon magnetic powder, the dosage of water is 8% of the weight of the iron-silicon magnetic powder, the dosage of potassium silicate is 0.25% of the weight of the iron-silicon magnetic powder, and the heating temperature is controlled at 120°C;

[0076] 3) Secondary insulation coating: Pour the iron-silicon magnetic powder after primary insulation cooling back into the insulation equipment. Repeat the addition amount of the primary insulation chemical materials, where the dosage of kaolin is 0.25% of the weight of the iron-silicon magnetic powder, the dosage of water is 8% of the weight of the iron-silicon magnetic powder, the dosage of potassium silicate is 0.25% of the weight of the iron-silicon magnetic powder, and the heating temperature is controlled at 120°C; Set aside

[0077] 4) Compression molding: Add 0.3% of zinc stearate by weight of the iron-silicon magnetic powder as a mold release agent before compression molding, add 0.15% of methyl silicone resin, mix the powders evenly and then press them into a magnetic ring with dimensions of 26.9mm * 14.8mm * 11.1mm. The molding pressure is 21 tons per square centimeter; Put the molded magnetic core into a heat treatment furnace, introduce nitrogen, and the annealing temperatures are 700°C, 730°C, 750°C, 780°C, and 800°C respectively, hold for 50 minutes, and then cool naturally, where the nitrogen flow rate is set to 8m 3 / h;

[0078] 5) Chamfer and deburr the magnetic core after infiltration, and at the same time, spin-coat the surface of the magnetic ring with epoxy resin powder, and a kind of iron-silicon soft magnetic powder core is obtained after curing. The magnetic properties of the obtained iron-silicon soft magnetic powder core are shown in Table 3.

[0079] Table 3 Magnetic properties of iron-silicon soft magnetic powder cores obtained at different annealing temperatures

[0080]

[0081] As can be seen from Table 3, for the same insulation coating process and the same pressure, the magnetic permeability of the magnetic core is higher when the heat treatment temperature is higher, and lower when the heat treatment temperature is lower. At the same time, the DC superposition becomes better, but the loss also begins to deteriorate. The loss and DC superposition performance are the best when the heat treatment temperature is between 730°C and 780°C.

[0082] Example 8

[0083] 1) Take gas-atomized iron-silicon magnetic powder, where the silicon content is 6.0%. The particle size ratio of the iron-silicon magnetic powder is set in 4 groups with different particle size distributions according to Table 4. After mixing evenly, label the particle size distributions A#, B#, C#, and D#;

[0084] 2) Primary insulation coating: Pour the mixed iron-silicon magnetic powder into the insulation equipment respectively, set four groups of different particle size ratios A#, B#, C#, and D#, and then pour in the mixed insulation liquid of kaolin, potassium silicate, and water. After the iron-silicon magnetic powder and the insulation liquid are stirred for 30 minutes, heat and stir-fry until dry. The dosage of kaolin is 0.25% of the weight of the iron-silicon magnetic powder, the dosage of water is 8% of the weight of the iron-silicon magnetic powder, the dosage of potassium silicate is 0.25% of the weight of the iron-silicon magnetic powder, and the heating temperature is controlled at 120°C;

[0085] 3) Secondary insulation coating: Pour the iron-silicon magnetic powder after primary insulation cooling into the insulation equipment again. Repeat the addition amount of the primary insulation chemical materials, where the dosage of kaolin is 0.25% of the weight of the iron-silicon magnetic powder, the dosage of water is 8% of the weight of the iron-silicon magnetic powder, the dosage of potassium silicate is 0.25% of the weight of the iron-silicon magnetic powder, and the heating temperature is controlled at 120°C;

[0086] 4) Compression molding: Add 0.3% of zinc stearate based on the weight of the iron-silicon magnetic powder as a mold release agent before compression molding, add 0.15% of methyl silicone resin, mix the powder evenly and then press it into a magnetic ring with dimensions of 26.9mm * 14.8mm * 11.1mm. The molding pressure is 21 tons per square centimeter; Put the molded magnetic core into the heat treatment furnace, introduce nitrogen, keep it at 800°C for 50 minutes, and then cool it naturally, where the nitrogen flow rate is set to 8m 3 / h;

[0087] 5) After the magnetic core is infiltrated, chamfer and deburr it. At the same time, spin-coat the surface of the magnetic ring with epoxy resin powder, and after curing, obtain an iron-silicon soft magnetic powder core. The relationship between the particle size ratio and the magnetic permeability μ of the powder is shown in Tables 4, 5, and 6 below.

[0088] Table 4 Different particle size ratios

[0089] Project 120 - 200 mesh 200 - 325 mesh 325 - 400 mesh <400 mesh A# Gas atomization - 120 mesh ferrosilicon 22.40％ 32.80％ 11.30％ 33.50％ B# Gas atomization - 120 mesh ferrosilicon 15.30％ 40.50％ 8.90％ 35.30％ C# Gas atomization - 120 mesh ferrosilicon 16.8％ 33.8％ 10.50％ 38.90％ D# Gas atomization - 120 mesh ferrosilicon 17.90％ 39.50％ 9.80％ 32.80％

[0090] Table 5 Magnetic properties of iron-silicon soft magnetic powder cores obtained by pressing different particle size ratios

[0091]

[0092] Table 6 Test data of weight and density of iron-silicon soft magnetic powder cores obtained by pressing with different particle size ratios

[0093]

[0094] From the test data of different particle size ratios in Table 4, it can be seen that the sum of A# particle sizes -325 to -400 mesh accounts for 44.8%, the sum of B# particle sizes -325 to -400 mesh accounts for 44.2%, the sum of C# particle sizes -325 to -400 mesh accounts for 49.4%, and the sum of D# particle sizes -325 to -400 mesh accounts for 42.8%. The proportion of C# particle size is the largest at 49.8% > A# particle size 44.8% > B# particle size 44.2% > D# particle size 44.2%.

[0095] From the test data of magnetic permeability in Table 5, it can be seen that A# particle size 145.2μ > C# particle size 141.3μ > B# particle size > D# particle size 130.1.

[0096] From the test data of weight and density in Table 6, it can be seen that the weight of the A# particle size magnetic core is the heaviest at 28.74 g, and the density is 7.297 g / cm 3 > The weight of the C# particle size magnetic core is 28.72 g, and the density is 7.279 g / cm 3 > The weight of the B# particle size magnetic core is 28.64 g, and the density is 7.242 g / cm 3 > The weight of the D# particle size magnetic core is 28.51 g, and the density is 7.216 g / cm 3 .

[0097] From these test data, it can be seen that the heavier the weight of the magnetic core, the higher the density. At the same time, the higher the strength of the magnetic core, the higher the corresponding magnetic permeability. The loose packing density and pressing characteristics between the coarse and fine powder particles will all affect the magnetic permeability. Therefore, to improve the magnetic permeability, the problem of the bonding degree between the powder particles must be solved. When the density and strength are the highest with a proper combination of coarse and fine particles, the magnetic permeability of the magnetic core is higher.

[0098] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A high magnetic permeability iron silicon soft magnetic powder core, characterized in that: It consists of iron silicon magnetic powder and two layers of silicon oxide insulating coating on the surface of the magnetic powder.

2. The high magnetic permeability iron silicon soft magnetic powder core according to claim 1, characterized in that: The particle size ratio of the iron silicon magnetic powder is: -120 to +200 mesh accounts for 18.1 to 26.4%, -200 to +325 mesh accounts for 23 to 34.3%, -325 to +400 mesh accounts for 9.7 to 13.1%, and below -400 mesh accounts for 26.4 to 37.5%.

3. A high magnetic permeability iron silicon soft magnetic powder core according to claim 1 or 2, characterized in that: The iron silicon soft magnetic core adopts gas atomized iron silicon magnetic powder, and the silicon content in the iron silicon magnetic powder is 5.5-6.5%, and the balance is iron.

4. A high magnetic permeability iron silicon soft magnetic powder core according to claim 1 or 2, characterized in that: Water, kaolin and potassium silicate are used to form a silicon oxide insulating coating layer on the surface of iron silicon magnetic powder.

5. A high magnetic permeability iron silicon soft magnetic powder core according to claim 1 or 2, characterized in that: The iron silicon soft magnetic powder core is made of iron silicon magnetic powder according to the particle size ratio, and is subjected to primary insulation coating, secondary insulation coating, pressing, core heat treatment and surface coating. The pressing pressure is 18-22t / cm 2 .

6. A method for preparing a high magnetic permeability iron silicon soft magnetic powder core according to any one of claims 1 to 5, characterized in that: The method specifically comprises the following steps: 1) Primary insulation coating: Mix the atomized iron silicon magnetic powder evenly according to the particle size ratio requirements, add kaolin, potassium silicate and water, and heat and fry until dry; 2) Secondary insulation coating: Repeat step 1) for the iron silicon magnetic powder after the primary insulation coating; 3) Compression molding: adding a release agent and a strength enhancer, silicone resin, to the powder after the insulation coating in step 2) and performing compression molding; 4) Magnetic core heat treatment: The magnetic core pressed and formed in step 3) is placed in a protective gas for sintering heat treatment, and then the surface of the magnetic core is spin-coated with epoxy resin powder to prepare the iron silicon soft magnetic powder core.

7. The method for preparing a high magnetic permeability iron silicon soft magnetic powder core according to claim 6, characterized in that: In step 1) and step 2), the amount of kaolin used is 0.2-0.5% of the weight of the ferrosilicon magnetic powder, the amount of potassium silicate used is 0.2-0.5% of the weight of the ferrosilicon magnetic powder, and the amount of water used is 8% of the weight of the ferrosilicon magnetic powder; The insulation coating heating temperature is 120°C each time.

8. The method for preparing a high magnetic permeability iron silicon soft magnetic powder core according to claim 6, characterized in that: In step 3), the release agent is microcrystalline wax or zinc stearate, the strength enhancer is methyl silicone resin, and the amount of the release agent is 0.2-0.4% by weight of the iron silicon magnetic powder; the amount of the strength enhancer is 0.1-0.2% by weight of the iron silicon magnetic powder.

9. The method for preparing a high magnetic permeability iron silicon soft magnetic powder core according to claim 6, characterized in that: In step 4), the heat treatment temperature is 700° C. to 800° C., and the holding time is 30 to 120 minutes; the protective gas is at least one of nitrogen and hydrogen.

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