High-permeability iron-nickel EQ 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-nickel EQ soft magnetic powder core and a preparation method thereof. The iron-nickel EQ soft magnetic powder core is composed of iron-nickel magnetic powder and three insulating coating layers, namely phosphate, silicate and silicon oxide and silicate and silicon oxide, which are sequentially arranged on the surface of the magnetic powder. The preparation method comprises the following steps: 1) mixing water-atomized and gas-atomized iron-nickel magnetic powder according to a particle size ratio, adding phosphoric acid and absolute ethyl alcohol, heating and frying to dry to complete primary insulation coating, cooling, adding kaolin and magnesium hydroxide, carrying out dry mixing, adding a sodium silicate solution and water, heating and frying to dry to complete secondary insulation coating; repeating the step of secondary insulation coating to complete third insulation coating; (2) adding a release agent and a magnetic core strength improver, and carrying out compression molding; and (3) the magnetic core is baked and sintered, then the magnetic core is infiltrated, and the EQ contact surface is polished. The iron-nickel EQ soft magnetic powder core is high in magnetic conductivity, low in magnetic core loss, good in direct current bias performance, high in quality factor and capable of being 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 magnetic permeability iron-nickel EQ soft magnetic powder core and a preparation method thereof. Background Art

[0002] The EQ soft magnetic powder core has the characteristics of low loss and high saturation, and can improve the power efficiency and stability. The EQ soft magnetic powder core can be designed according to different structures and shapes, and can also be directly installed in the circuit board, so as to achieve smaller size and higher integration. The EQ soft magnetic powder core is widely used in fields such as 5G communication base stations, power conversion, signal processing, electromagnetic interference, and pattern recognition. It involves fields such as communication, home appliances, UPS power supplies, inverters, and new energy vehicles. Among them, the EQ iron-nickel soft magnetic powder core has the highest DC bias performance, high saturation magnetic induction intensity, and low loss, so it has a large market. However, it is very difficult to produce an iron-nickel EQ soft magnetic powder core with high magnetic permeability.

[0003] The invention patent with the patent number CN102306528A discloses a manufacturing method of an iron-nickel toroidal soft magnetic powder core. This process uses phosphoric acid passivation and then adds phenolic resin, and then presses and forms. The addition of phenolic resin not only cannot well eliminate the internal stress of the magnetic core, but also the resin is prone to decomposition and carbonization during the sintering process, resulting in pinholes and cracks in the magnetic core. Since most of the single pressing of the toroidal magnetic core requires 18-22T / cm 2 , while the single pressing of the EQ magnetic core is 9-12T / cm 2 , and the pressure is only half of that of the toroidal magnetic core. And the smaller the pressure, the lower the magnetic permeability μ value of the magnetic core. Therefore, it is very difficult to make an EQ high-μ magnetic core under low-pressure conditions.

[0004] The invention patent with the patent number CN201610697479.8 discloses a preparation method of an iron-nickel soft magnetic powder core. This process uses hydrogen to anneal and reduce the iron-nickel magnetic powder. The insulation coating uses aluminum dihydrogen phosphate for primary coating, and sodium silicate and kaolin for secondary insulation coating. The powder needs to be annealed and then subjected to secondary insulation. The insulation operation steps are many and the production efficiency is low. In addition, although the insulation coating of aluminum dihydrogen phosphate can improve the uniformity of the surface coating of the powder and can reduce the loss of the magnetic core to a certain extent, the heat treatment temperature of the magnetic core is affected by the temperature resistance of aluminum dihydrogen phosphate and cannot be heat-treated under high-temperature conditions, which has limitations for making high-magnetic-permeability products. And too high temperature will affect the stability of aluminum dihydrogen phosphate, resulting in poor magnetic core characteristics.

[0005] Therefore, how to develop an EQ soft magnetic powder core with high magnetic permeability, and at the same time, an iron-nickel EQ soft magnetic powder core with good DC bias performance is a technical problem that those skilled in the art urgently need to solve. Summary of the Invention

[0006] In view of this, the present invention aims to overcome the above-mentioned deficiencies in the prior art. A high magnetic permeability iron-nickel EQ soft magnetic powder core and its preparation method are provided. The iron-nickel soft magnetic powder core prepared by this method has low loss and good DC bias performance.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] A high magnetic permeability iron-nickel EQ soft magnetic powder core is composed of iron-nickel magnetic powder and three layers of insulating coating layers on the surface of the magnetic powder, which are phosphate, silicate and silicon oxide, silicate and silicon oxide in sequence.

[0009] Preferably, the iron-nickel magnetic powder is a mixture of water-atomized iron-nickel magnetic powder and gas-atomized iron-nickel magnetic powder mixed in a mass ratio of 1:1;

[0010] By mass percentage, the particle size ratio of the water-atomized iron-nickel magnetic powder is -200 to +325 mesh accounting for 25.4% to 33.2%, -325 to +400 mesh accounting for 10.9 to 13%, and -400 mesh accounting for 55.4 to 61.7%;

[0011] By mass percentage, the particle size ratio of the gas-atomized iron-nickel magnetic powder is -200 to +325 mesh accounting for 28.4% to 31.3, -325 to +400 mesh accounting for 8.8 to 11.1%, and -400 mesh accounting for 58.1 to 62.8%.

[0012] Preferably, the nickel content in both the water-atomized iron-nickel magnetic powder and the gas-atomized iron-nickel magnetic powder is 45% to 55%, and the balance is iron.

[0013] Preferably, the phosphate coating layer is coated with phosphoric acid and absolute ethanol, and the silicate and silicon oxide coating layer is coated with sodium silicate, magnesium hydroxide and kaolin.

[0014] Preferably, the pressure for pressing and forming is 9 to 12 t / cm 2 .

[0015] A preparation method of a high magnetic permeability iron-nickel EQ soft magnetic powder core, the method specifically includes the following steps:

[0016] 1) Insulating coating: Mix the water-atomized iron-nickel magnetic powder and the gas-atomized iron-nickel magnetic powder evenly according to the particle size ratio, then add phosphoric acid and absolute ethanol and heat and stir dry to complete the first insulating coating. After cooling, add kaolin and magnesium hydroxide and mix evenly, then add sodium silicate solution and water and heat and stir dry to complete the second insulating coating; repeat the second insulating coating step to complete the third insulating coating;

[0017] 2) Pressing and forming: Add a release agent and a magnetic core strength enhancer to the powder after the insulating coating in step 1), and carry out pressing and forming for standby;

[0018] 3) Core heat treatment: Bake the core formed in step 2) in an oven, and then sinter it in a sintering furnace with a mixed atmosphere of nitrogen and hydrogen. Subsequently, infiltrate and polish the EQ contact surface of the core to obtain the soft magnetic powder core.

[0019] Preferably, the dosage of phosphoric acid in the primary insulation coating is 0.2 - 0.5% of the weight of the iron-nickel magnetic powder, and the dosage of alcohol is 4 - 8% of the weight of the iron-nickel magnetic powder.

[0020] In the secondary insulation coating, the dosage of kaolin is 0.2 - 0.5% of the weight of the iron-nickel magnetic powder, the dosage of magnesium hydroxide is 0.02 - 0.01% of the weight of the iron-nickel magnetic powder, the dosage of sodium silicate is 0.2 - 0.5% of the weight of the iron-nickel magnetic powder, and the dosage of water is 7 - 10% of the weight of the iron-nickel magnetic powder.

[0021] The heating temperature for each insulation coating is 100°C - 130°C.

[0022] Preferably, in step 2), the release agent is zinc stearate or K crystal wax, and the dosage of the release agent is 0.2 - 0.4% of the weight of the iron-nickel magnetic powder; the core strength enhancer is silicone resin, and the dosage of the silicone resin is 0.15 - 0.3% of the weight of the iron-nickel magnetic powder.

[0023] Preferably, in step 3), the baking temperature is 220°C, the baking time is 4 hours, the nitrogen flow rate is 4 - 8 m 3 / h, the hydrogen flow rate is 2 - 2.5 m 3 / h, the sintering temperature is 680°C - 800°C, and the holding time is 30 - 120 min.

[0024] Through the above technical solutions, compared with the prior art, the present invention has the following excellent effects:

[0025] (1) The insulation process disclosed in the present invention is simple, low in cost, and high in production efficiency, and can be mass-produced. At the same time, it has a high magnetic permeability μ value, good DC bias performance, and low power loss, and the product performance is at the leading level in the industry.

[0026] (2) The present invention adopts a combination of water atomized powder + gas atomized powder, with high core strength, which can effectively improve the magnetic permeability and at the same time reduce the porosity of the core, and can effectively reduce the core loss.

[0027] (3) By using phosphoric acid, kaolin, sodium silicate, and magnesium hydroxide for insulation, the present invention enables the surface of the iron-nickel metal powder to obtain a coating layer of silicate and silicon oxide, which has advantages such as high thermal stability and electrical insulation, so that the finally prepared iron-nickel soft magnetic powder core has low loss and high DC superposition. Description of the Drawings

[0028] 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, without creative efforts, other drawings can also be obtained based on the provided drawings.

[0029] Figure 1 It is a relationship diagram of the magnetic permeability of soft magnetic powder cores with different particle size ratios of water atomization + gas atomization powders in Example 4. Specific embodiments

[0030] The following will clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0031] Example 1

[0032] 1) Take gas atomized iron-nickel magnetic powder and water atomized iron-nickel magnetic powder, both with a nickel content of 50%. The particle size ratio of the water atomized iron-nickel magnetic powder is that -200 to +325 mesh accounts for 25.4%, -325 to +400 mesh accounts for 12.9%, and -400 mesh accounts for 61.7%. The particle size ratio of the gas atomized iron-nickel magnetic powder is that -200 to +325 mesh accounts for 28.4%, -325 to +400 mesh accounts for 8.8%, and -400 mesh accounts for 62.8%. Mix the gas atomized iron-nickel magnetic powder and the water atomized iron-nickel magnetic powder evenly according to the mass ratio of 1:1 according to the above proportions.

[0033] 2) Pour the EQ iron-nickel magnetic powder into a rotary heating device, and then add a mixed liquid of anhydrous ethanol + phosphoric acid to complete the first insulation. The addition amount of phosphoric acid is 0.5% of the weight of the iron-nickel magnetic powder, the concentration of phosphoric acid is 100%, the addition amount of anhydrous ethanol is 7% of the powder weight, and the concentration is 100%. After the powder cools, add kaolin and magnesium hydroxide powder and stir evenly, then add a 40% sodium silicate solution and water and heat and stir-fry until dry to complete the second insulation. The addition amount of kaolin is 0.5% of the weight of the iron-nickel magnetic powder, the addition amount of magnesium hydroxide is 0.1% of the weight of the iron-nickel magnetic powder, the addition amount of sodium silicate is 0.5% of the weight of the iron-nickel magnetic powder, and the addition amount of water is 10% of the weight of the iron-nickel magnetic powder. Repeat the second insulation formula for the third insulation, and control the heating temperature at 120°C.

[0034] 3) Before pressing and forming, add 0.3% of zinc stearate by weight of the EQ iron-nickel magnetic powder as a mold release agent, and add 0.15% of HK03 methyl silicone resin by weight of the iron-nickel magnetic powder to improve the core strength. After mixing evenly, press and form the EQ3222 core. The forming pressures are 9, 10, 11, and 12 t / cm 2 , and press with four different pressures;

[0035] 4) Put the formed core into a baking furnace and set the temperature to 220°C for 4 hours to complete the degumming operation. After baking, put the EQ3222 core into a heat treatment furnace. First, introduce nitrogen, and then introduce hydrogen 20 minutes later. Keep it at 780°C for 50 minutes, and then cool it naturally. The nitrogen flow rate is set to 8 m 3 / h, and the hydrogen flow rate is set to 2.5 m 3 / h.

[0036] 5) After the EQ3222 core is annealed, the contact surface needs to be polished. After polishing smoothly, an iron-nickel EQ3222 soft magnetic powder core with a magnetic permeability of 125 μ is obtained. After testing, the density and magnetic properties of the obtained iron-nickel EQ soft magnetic powder core are shown in Table 1-2.

[0037] Table 1 Density of the pressed EQ soft magnetic powder core under different pressure conditions.

[0038]

[0039]

[0040] Table 2 Magnetic properties of the iron-nickel soft magnetic powder core pressed under different pressures

[0041]

[0042] As can be seen from Tables 1 and 2, for the same formula and the same heat treatment temperature, when the forming pressure is greater, the magnetic permeability μ of the core will increase, the core density will increase, and the core loss will be better; and due to the increase in the magnetic permeability μ, the DC superposition will become lower.

[0043] Example 2

[0044] 1) Take gas-atomized iron-nickel magnetic powder and water-atomized iron-nickel magnetic powder, both of which have a nickel content of 50%. The particle size ratio of the water-atomized iron-nickel magnetic powder is 25.4% for -200 to +325 mesh, 12.9% for -325 to +400 mesh, and 61.7% for -400 mesh. The particle size ratio of the gas-atomized iron-nickel magnetic powder is 28.4% for -200 to +325 mesh, 8.8% for -325 to +400 mesh, and 62.8% for -400 mesh. Mix the gas-atomized iron-nickel magnetic powder and the water-atomized iron-nickel magnetic powder evenly according to the mass ratio of 1:1.

[0045] 2) Pour the EQ iron-nickel magnetic powder into a rotary heating device, and then add a mixed liquid of anhydrous ethanol + phosphoric acid (concentration 100%) to complete the first insulation. The addition amount of phosphoric acid is 0.5% of the weight of the iron-nickel magnetic powder, and the addition amount of anhydrous ethanol is 7% of the powder weight. After the powder is cooled, add kaolin and magnesium hydroxide powder and stir evenly, then add a 40% sodium silicate solution and water and heat and stir-fry until dry to complete the second insulation. The dosage of kaolin is 0.2%, 0.3%, 0.4%, 0.5% of the weight of the iron-nickel magnetic powder, the dosage of magnesium hydroxide is 0.02%, 0.04%, 0.07%, 0.10% of the weight of the iron-nickel magnetic powder, the dosage of sodium silicate is 0.2%, 0.3%, 0.4%, 0.5% of the weight of the iron-nickel magnetic powder, and the dosage of water is 10% of the weight of the iron-nickel magnetic powder; repeat the second insulation formula for the third insulation (Table 3), and control the powder heating temperature at 120 °C.

[0046] 3) Before pressing and forming, add 0.3% of zinc stearate based on the weight of the EQ iron-nickel magnetic powder as a mold release agent, and add 0.15% of HK03 methyl silicone resin based on the weight of the iron-nickel magnetic powder to improve the core strength. After mixing evenly, press it into an EQ3222 core, and the forming pressure is 12t / cm 2 Pressure pressing;

[0047] 4) Put the formed core into a baking furnace and set the temperature at 220 °C for baking for 4 hours to complete the degumming operation. After baking, put the EQ3222 core into a heat treatment furnace, first introduce nitrogen, and then introduce hydrogen after 20 minutes. Keep it at 800 °C for 50 minutes, and then cool it naturally. The nitrogen flow rate is set at 8m 3 / h, and the hydrogen flow rate is set at 2.5m 3 / h.

[0048] 5) After the EQ3222 core is annealed, the contact surface needs to be polished. After polishing smoothly, an iron-nickel EQ3222 soft magnetic powder core with a magnetic permeability of 125 μ is obtained. The magnetic properties of the EQ iron-nickel soft magnetic powder core obtained by testing are shown in Table 4.

[0049] Table 3 Formulas of different insulation coating materials

[0050]

[0051] Table 4 Magnetic properties of iron-nickel soft magnetic powder cores pressed with different insulation coating material formulas

[0052]

[0053] As can be seen from Table 4, under the same molding pressure and the same heat treatment temperature, when the usage amounts of kaolin, magnesium hydroxide, and sodium silicate are larger, the magnetic permeability μ of the magnetic core will be lower. At the same time, the DC superposition performance of the magnetic core will be higher, and the loss of the magnetic core will also be better. The main reason is that the amount of insulation becomes larger, and the insulating layer coated between the powder particles is more uniform.

[0054] Example 3

[0055] 1) Take gas-atomized iron-nickel magnetic powder and water-atomized iron-nickel magnetic powder, both of which have a nickel content of 50%. The particle size ratio of the water-atomized iron-nickel magnetic powder is 25.4% for -200 to +325 mesh, 12.9% for -325 to +400 mesh, and 61.7% for -400 mesh. The particle size ratio of the gas-atomized iron-nickel magnetic powder is 28.4% for -200 to +325 mesh, 8.8% for -325 to +400 mesh, and 62.8% for -400 mesh. Mix the gas-atomized iron-nickel magnetic powder and the water-atomized iron-nickel magnetic powder evenly according to the mass ratio of 1:1.

[0056] 2) Pour the EQ iron-nickel magnetic powder into a rotary heating device, and then add a mixed liquid of anhydrous ethanol + phosphoric acid (concentration of 100%) to complete the first insulation. The addition amount of phosphoric acid is 0.3% of the weight of the iron-nickel magnetic powder, and the addition amount of anhydrous ethanol is 7% of the powder weight. After the powder is cooled, add kaolin and magnesium hydroxide powder and stir evenly. Then add a 40% sodium silicate solution and water and heat and stir-fry until dry to complete the second insulation. The addition amount of kaolin is 0.4% of the powder weight, the addition amount of magnesium hydroxide is 0.1% of the powder weight, the addition amount of sodium silicate is 0.4% of the powder weight, and the addition amount of water is 10% of the powder weight. Repeat the second insulation formula for the third insulation. The powder heating temperature is controlled at 120°C.

[0057] 3) Before pressing and molding, add 0.3% of zinc stearate by weight of the EQ iron-nickel magnetic powder as a mold release agent, and add 0.2% of HK03 methyl silicone resin by weight of the iron-nickel magnetic powder to improve the strength of the magnetic core. After mixing evenly, press it into an EQ3222 magnetic core, and the molding pressure is 12 t / cm2.

[0058] 4) Put the molded magnetic core into a baking furnace and set the temperature to 220°C for baking for 4 hours to complete the degumming operation. After baking, put the EQ3222 magnetic core into a heat treatment furnace. First, introduce nitrogen for 20 minutes and then introduce hydrogen. Keep it warm at 680°C, 700°C, 740°C, 780°C, and 800°C for 50 minutes respectively, and then cool it naturally. The nitrogen flow rate is set to 8 m 3 / h, and the hydrogen flow rate is set to 2.5 m 3 / h.

[0059] 5) After the annealing of the EQ3222 magnetic core is completed, the contact surface needs to be polished. After polishing smoothly, a Fe-Ni EQ3222 soft magnetic powder core with a magnetic permeability of 125μ is obtained. The magnetic properties of the obtained EQ Fe-Ni soft magnetic powder core are shown in Table 5.

[0060] Table 5 Magnetic properties of Fe-Ni soft magnetic powder cores pressed at different annealing temperatures

[0061]

[0062] As can be seen from Table 5, for the same formula and the same molding pressure, when the heat treatment temperature is 680°C, the magnetic permeability μ of the magnetic core becomes lower, the superposition becomes better, and at the same time the loss becomes worse. The main reason is that the heat treatment temperature of the magnetic core is too low; while when the heat treatment temperature is 800°C, the magnetic permeability μ of the magnetic core becomes higher and the DC superposition becomes worse. The main reason is that the inductance is high, so the DC superposition will be lower.

[0063] Example 4

[0064] 1) Take gas atomized Fe-Ni magnetic powder and water atomized Fe-Ni magnetic powder, both of which have a nickel content of 50%. The particle size ratios of the water atomized Fe-Ni magnetic powder and the gas atomized Fe-Ni magnetic powder are set in 4 groups according to what is shown in Figure 1 Mix 1# water atomized - 200 mesh powder and A# gas atomized powder evenly by mass ratio of 1:1. Mix 2# water atomized - 200 mesh powder and B# gas atomized powder evenly by mass ratio of 1:1. Mix 3# water atomized - 200 mesh powder and C# gas atomized powder evenly by mass ratio of 1:1. Mix 4# water atomized - 200 mesh powder and D# gas atomized powder evenly by mass ratio of 1:1. 2) Pour the EQ Fe-Ni magnetic powder into a rotary heating device, and then add a mixed liquid of anhydrous ethanol + phosphoric acid (concentration of 100%) to complete the first insulation. The addition amount of phosphoric acid is 0.3% of the weight of the Fe-Ni magnetic powder, and the addition amount of anhydrous ethanol is 7% of the powder weight. After the powder cools, add kaolin and magnesium hydroxide powder and stir evenly, then add a 40% sodium silicate solution and water and heat and stir-fry until dry to complete the second insulation. The addition amount of kaolin is 0.4% of the powder weight, the addition amount of magnesium hydroxide is 0.1% of the powder weight, the addition amount of sodium silicate is 0.4% of the powder weight, and the addition amount of water is 10% of the powder weight. Repeat the second insulation formula for the third insulation. The powder heating temperature is controlled at 120°C;

[0065] 3) Before pressing and forming, add 0.3% of zinc stearate by weight of the EQ Fe-Ni magnetic powder as a mold release agent, and add 0.2% of HK03 methyl silicone resin by weight of the Fe-Ni magnetic powder to improve the strength of the magnetic core. After mixing evenly, press it into an EQ3222 magnetic core, and the molding pressure is 12t / cm2 for pressing.

[0066] 4) Place the formed EQ magnetic core into a baking oven and set the temperature to 220 °C for 4 hours to complete the degumming operation. After baking, put the EQ3222 magnetic core into a heat treatment furnace. First, introduce nitrogen for 20 minutes and then introduce hydrogen. Keep it at 800 °C for 50 minutes, and then cool it naturally. The nitrogen flow rate is set to 8 m 3 / h, and the hydrogen flow rate is set to 2.5 m 3 / h.

[0067] 5) After the EQ3222 magnetic core is annealed, the contact surface needs to be polished. After polishing smoothly, an iron-nickel EQ3222 soft magnetic powder core with a magnetic permeability of 125 μ is obtained. The magnetic properties of the obtained EQ iron-nickel soft magnetic powder core are shown in Table 6.

[0068] Table 6 Test data of magnetic permeability, density and strength of iron-nickel soft magnetic powder cores obtained by pressing different particle size ratios of water atomized + gas atomized iron-nickel magnetic powders.

[0069]

[0070] It can be seen from the above particle size VS magnetic permeability test data that when the proportion of fine powder in the water atomized powder is larger, the strength of the magnetic core is better, and at the same time the magnetic permeability is also higher. Among them, the magnetic permeability of 2# water atomized - 200 mesh iron-nickel + B# gas atomized - 200 mesh iron-nickel is the highest at 133.1 μ, followed by the magnetic permeability of 3# water atomized - 200 mesh iron-nickel + C# gas atomized - 200 mesh iron-nickel at 129.9 μ. When the powder is a combination of thick and thin, the magnetic permeability of the magnetic core is the highest when improving the strength and pressing characteristics of the magnetic core.

[0071] Example 5

[0072] 1) Take gas atomized iron-nickel magnetic powder and water atomized iron-nickel magnetic powder, both of which have a nickel content of 50%. The particle size ratio of the water atomized iron-nickel magnetic powder is 25.4% for -200 to +325 mesh, 12.9% for -325 to +400 mesh, and 61.7% for -400 mesh. The particle size ratio of the gas atomized iron-nickel magnetic powder is 28.4% for -200 to +325 mesh, 8.8% for -325 to +400 mesh, and 62.8% for -400 mesh. Mix the gas atomized iron-nickel magnetic powder and the water atomized iron-nickel magnetic powder evenly according to the mass ratio of 1:1 according to the above ratio.

[0073] 2) Pour the EQ iron-nickel magnetic powder into a rotary heating device, and then add a mixed liquid of anhydrous ethanol + phosphoric acid (concentration of 100%). Complete the first insulation. The addition amount of phosphoric acid is 0.2% of the weight of the iron-nickel magnetic powder, and the addition amount of anhydrous ethanol is 7% of the powder weight. After the powder is cooled, add kaolin and magnesium hydroxide powder and stir evenly, then add a sodium silicate solution with a concentration of 40% and water, and heat and stir-fry until dry to complete the second insulation. The addition amount of kaolin is 0.3% of the powder weight, the addition amount of magnesium hydroxide is 0.08% of the powder weight, the addition amount of sodium silicate is 0.3% of the powder weight, and the addition amount of water is 10% of the powder weight. Repeat the second insulation formula for the third insulation. The powder heating temperature is controlled at 120 °C;

[0074] 3) Before pressing and forming, add 0.3% of zinc stearate based on the weight of the EQ iron-nickel magnetic powder as a release agent, and add 0.2% of HK03 methyl silicone resin based on the weight of the iron-nickel magnetic powder to improve the core strength. After mixing evenly, press and form the EQ3222 core, and the forming pressure is 12t / cm 2 Press.

[0075] 4) Put the formed core into a baking furnace and set the temperature at 220 °C for baking for 4 hours to complete the degumming operation. After baking, put the EQ3222 core into a heat treatment furnace. First, introduce nitrogen for 20 minutes and then introduce hydrogen. Keep it at 780 °C for 50 minutes, and then cool it naturally. The nitrogen flow rate is set at 8m 3 / h, and the hydrogen flow rate is set at 2.5m 3 / h.

[0076] 5) After the EQ3222 core is annealed, the contact surface needs to be polished. After polishing smoothly, an iron-nickel EQ3222 soft magnetic powder core with a magnetic permeability of 125 μ is obtained. The magnetic properties of the obtained EQ iron-nickel soft magnetic powder core are shown in Table 7.

[0077] Comparative Example 1

[0078] 1) Take gas-atomized iron-nickel magnetic powder and water-atomized iron-nickel magnetic powder, both of which have a nickel content of 50%. The particle size ratio of the water-atomized iron-nickel magnetic powder is -200 to +325 mesh accounting for 25.4%, -325 to +400 mesh accounting for 12.9%, and -400 mesh accounting for 61.7%. The particle size ratio of the gas-atomized iron-nickel magnetic powder is -200 to +325 mesh accounting for 28.4%, -325 to +400 mesh accounting for 8.8%, and -400 mesh accounting for 62.8%. Mix the gas-atomized iron-nickel magnetic powder and the water-atomized iron-nickel magnetic powder evenly according to the mass ratio of 1:1 according to the above ratio.

[0079] 2) Pour the EQ iron-nickel magnetic powder into a rotary heating device, and then add a mixed liquid of anhydrous ethanol + phosphoric acid (concentration 100%) to complete the first insulation. The addition amount of phosphoric acid is 0.2% of the weight of the iron-nickel magnetic powder, and the addition amount of anhydrous ethanol is 7% of the powder weight. After the powder is cooled, add kaolin and magnesium hydroxide powder and stir evenly, then add a sodium silicate solution with a concentration of 40% and water, and heat and stir-fry until dry to complete the second insulation. The addition amount of kaolin is 0.6% of the powder weight, the addition amount of magnesium hydroxide is 0.15% of the powder weight, the addition amount of sodium silicate is 0.6% of the powder weight, and the addition amount of water is 10% of the powder weight. The heating temperature of the powder is controlled at 120 °C;

[0080] 3) Before pressing and forming, add 0.3% of zinc stearate based on the weight of the EQ iron-nickel magnetic powder as a mold release agent, and add 0.2% of HK03 methyl silicone resin based on the weight of the iron-nickel magnetic powder to improve the core strength. After mixing evenly, press and form into an EQ3222 magnetic core, and the forming pressure is 12 t / cm 2 Press.

[0081] 4) Put the formed magnetic core into a baking furnace and set the temperature at 220 °C for baking for 4 hours to complete the degumming operation. After baking, put the EQ3222 magnetic core into a heat treatment furnace, first introduce nitrogen for 20 min and then introduce hydrogen, keep it at 780 °C for 50 min, and then cool naturally. The nitrogen flow rate is set at 8 m 3 / h, and the hydrogen flow rate is set at 2.5 m 3 / h.

[0082] 5) After the EQ3222 magnetic core is annealed, the contact surface needs to be polished. After polishing smoothly, an iron-nickel EQ3222 soft magnetic powder core with a magnetic permeability of 125 μ is obtained. The magnetic properties of the EQ iron-nickel soft magnetic powder core obtained by testing are shown in Table 7.

[0083] Table 7 Magnetic properties of iron-nickel soft magnetic powder cores obtained by pressing with different insulation coating times

[0084]

[0085] As can be seen from Table 7, with the same forming pressure and heat treatment temperature, the loss of the powder with three insulation coatings is significantly better than that with two insulation coatings.

[0086] Based on the above analysis, it can be known that the iron-nickel EQ3222 soft magnetic powder core with a magnetic permeability of 125 μ prepared by the process of the present invention can be mass-produced, and the DC bias performance is more than 38% under the test condition of 100 Oe; the core loss is 250 mW / cm at 50 KHz and 100 mT 3 , and the core performance is at the top level in the industry.

[0087] In this specification, the various embodiments are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. For the same or similar parts among the embodiments, reference can be made to each other. For the solutions disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple. For related parts, reference can be made to the description in the method section.

[0088] 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. 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 will be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A high magnetic permeability iron-nickel EQ soft magnetic powder core, characterized in that: The invention is composed of iron-nickel magnetic powder and three insulating coating layers of phosphate, silicate and silicon oxide, silicate and silicon oxide in sequence on the surface of the magnetic powder.

2. The high magnetic permeability iron-nickel EQ soft magnetic powder core according to claim 1, characterized in that: The iron-nickel magnetic powder is a mixture of water-atomized iron-nickel magnetic powder and gas-atomized iron-nickel magnetic powder in a mass ratio of 1:1; In terms of mass percentage, the particle size ratio of the water-atomized iron-nickel magnetic powder is -200 to +325 mesh accounting for 25.4% to 33.2%, -325 to +400 mesh accounting for 10.9 to 13%, and -400 mesh accounting for 55.4 to 61.7%; Calculated by mass percentage, the particle size ratio of the atomized iron-nickel magnetic powder is -200 to +325 meshes accounting for 28.4% to 31.3%, -325 to +400 meshes accounting for 8.8% to 11.1%, and -400 meshes accounting for 58.1% to 62.8%.

3. A high magnetic permeability iron-nickel EQ soft magnetic powder core according to claim 1 or 2, characterized in that: The nickel content in the water-atomized iron-nickel magnetic powder and the gas-atomized iron-nickel magnetic powder is 45% to 55%, and the remainder is iron.

4. A high magnetic permeability iron-nickel EQ soft magnetic powder core according to claim 1 or 2, characterized in that: The phosphate coating layer is coated with phosphoric acid and anhydrous ethanol, and the silicate and silicon oxide coating layers are coated with sodium silicate, magnesium hydroxide and kaolin.

5. A high magnetic permeability iron-nickel EQ soft magnetic powder core according to claim 1 or 2, characterized in that: The iron-nickel EQ soft magnetic powder core is prepared by insulating and coating the iron-nickel magnetic powder, pressing and forming, and heat treating the magnetic core. The pressing pressure is 9 to 12 t / cm 2 .

6. A method for preparing a high magnetic permeability iron-nickel EQ soft magnetic powder core according to any one of claims 1 to 5, characterized in that: The method specifically comprises the following steps: 1) Insulation coating: Mix water-atomized iron-nickel magnetic powder and gas-atomized iron-nickel magnetic powder evenly according to the particle size ratio, then add phosphoric acid and anhydrous ethanol to heat and fry to dry to complete the first insulation coating, add kaolin and magnesium hydroxide after cooling, dry mix evenly, then add sodium silicate solution and water to heat and fry to dry to complete the second insulation coating; repeat the second insulation coating steps to complete the third insulation coating; 2) Pressing and molding: adding a release agent and a magnetic core strength enhancer to the powder after the insulation coating in step 1), pressing and molding, and setting aside; 3) Magnetic core heat treatment: the magnetic core pressed and formed in step 2) is placed in an oven for baking, and then placed in a sintering furnace with a mixed atmosphere of nitrogen and hydrogen for sintering, and then the magnetic core is infiltrated and the EQ contact surface is polished to prepare the soft magnetic powder core.

7. The method for preparing a high magnetic permeability iron-nickel EQ soft magnetic powder core according to claim 6, characterized in that: The amount of phosphoric acid used in the primary insulation coating is 0.2-0.5% of the weight of the iron-nickel magnetic powder, and the amount of anhydrous ethanol used is 4-8% of the weight of the iron-nickel magnetic powder; The amount of kaolin in the secondary insulation coating is 0.2-0.5% of the weight of the iron-nickel magnetic powder, the amount of magnesium hydroxide is 0.02-0.1% of the weight of the iron-nickel magnetic powder, the amount of sodium silicate is 0.2-0.5% of the weight of the iron-nickel magnetic powder, and the amount of water is 7-10% of the weight of the iron-nickel magnetic powder; The insulation coating heating temperature is 100℃~130℃ each time.

8. The method for preparing a high magnetic permeability iron-nickel EQ soft magnetic powder core according to claim 6, characterized in that: In step 2), the release agent is zinc stearate or K crystal wax, and the amount of the release agent is 0.2-0.4% by weight of the iron-nickel magnetic powder; the magnetic core strength enhancer is silicone resin, and the amount of the silicone resin is 0.15-0.3% by weight of the iron-nickel magnetic powder.

9. The method for preparing a high magnetic permeability iron-nickel EQ soft magnetic powder core according to claim 6, characterized in that: In step 3), the baking temperature is 220°C, the baking time is 4 hours, and the nitrogen flow rate is 4-8m 3 / h, hydrogen flow rate is 2~2.5m 3 / h, the sintering temperature is 680℃~800℃, and the holding time is 30~120min.

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