Low-iron-loss dual-coated soft magnetic composite material and preparation method therefor

Abstract

Provided in the present application are a low-iron-loss dual-coated soft magnetic composite material and a preparation method therefor. Raw materials for preparation comprise an insulated coated magnetic powder, a binder and a mold release agent. The insulated coated magnetic powder comprises a SiO2-coated magnetic powder and a boron oxide insulating coating layer with which the surface of the SiO2-coated magnetic powder is coated; the SiO2-coated magnetic powder comprises a metal magnetic powder and a SiO2 insulating coating layer with which the surface of the metal magnetic powder is coated; and the metal magnetic powder comprises a first metal magnetic powder Fe-Si-Ge-R1 and a second metal magnetic powder Fe-Si-Al-C-R2. The low-iron-loss dual-coated soft magnetic composite material prepared by the present application has low losses at medium- and high-frequencies, and also has high initial permeability, thus making it suitable for electrical equipment such as transformers and reactors.

Description

Low iron loss double-coated soft magnetic composite material and preparation method thereof

[0001] Cross-reference to related applications

[0002] The present application is based on and claims priority to Chinese Patent Application No. 202410967805.7, filed on July 18, 2024, entitled "Low iron loss double-coated soft magnetic composite material and preparation method thereof", the entire contents of which are incorporated herein by reference. TECHNICAL FIELD

[0003] The present application relates to the field of soft magnetic composite materials, in particular to a low iron loss double-coated soft magnetic composite material and a preparation method thereof. BACKGROUND

[0004] Soft magnetic composite material is a new type of composite material formed by pressing insulating medium and magnetic powder together through powder metallurgy, also known as magnetic powder core material, which is widely used in various devices.

[0005] Soft magnetic composite materials mainly include iron-silicon powder cores, iron-silicon-aluminum powder cores, iron powder cores, iron-nickel powder cores, iron-nickel-molybdenum powder cores, and amorphous / nanocrystalline powder cores. For iron-silicon powder cores, the addition of silicon elements not only increases the resistivity of the alloy, but also adjusts the magnetic crystal anisotropy constant K, the magnetostriction coefficient λ, the Curie temperature, the saturation magnetization, and the loss and other parameters. Compared with other soft magnetic composite materials, the saturation magnetic flux density of the iron-silicon powder core is outstanding (1.5-1.6T), but its loss is relatively high, especially compared with iron-nickel and iron-silicon-aluminum powder cores. The iron-silicon-aluminum powder core is nearly 0 in the magnetostriction coefficient, showing the advantage of low noise. Although its saturation magnetic flux density is slightly lower than that of the iron powder core, its iron loss is only 20% of that of the iron powder core, and its maximum permeability is also relatively high. Since it does not contain noble metals, its price is more affordable than that of permalloy powder cores and molybdenum permalloy powder cores, and is only slightly higher than that of iron powder cores, so it has a high cost performance. However, the saturation resistance of the iron-silicon-aluminum powder core is relatively weak. The iron powder core is favored for its low price, stable permeability frequency, and excellent DC superposition characteristics, but it performs poorly in high-frequency loss, and is prone to aging due to the use of organic resin as the insulating medium. The permalloy (iron-nickel) powder core has a high saturation magnetic flux density (1.5T) and is also known as a high-flux powder core, but it is expensive and has a large magnetostriction coefficient. The molybdenum permalloy (iron-nickel-molybdenum) powder core is made by adding Mo to the iron-nickel alloy, and its permeability range is the most extensive among all magnetic powder cores, with the best overall performance, showing good temperature stability, low iron loss, and low noise. However, it is the most expensive, and its saturation magnetic flux density is relatively low. The amorphous / nanocrystalline powder core has attracted attention due to the excellent soft magnetic properties of amorphous / microcrystalline alloys, and its permeability frequency stability is good, maintaining high permeability and quality factor even at high frequencies. However, its low effective permeability due to low forming density and the large magnetostriction of amorphous materials still exist after being made into a soft magnetic composite material, so it still faces the problem of high noise.

[0006] At present, it is difficult for soft magnetic composite materials to simultaneously have high saturation magnetic density and low medium and high frequency loss characteristics. With the development of power electronic devices towards large capacity and high efficiency, it is urgent to further improve the magnetic properties of soft magnetic composite materials.

[0007] SUMMARY

[0008] The purpose of the present application is to provide a low-iron-loss double-coated soft magnetic composite material and a preparation method thereof to overcome the problems existing in the prior art. The low-iron-loss double-coated soft magnetic composite material prepared by the present application has low medium and high frequency loss, and also has high initial permeability, and is suitable for electrical equipment such as transformers and reactors.

[0009] The present application is realized by the following technical scheme:

[0010] The application discloses a low-iron-loss double-coated soft magnetic composite material, and a preparation raw material of the low-iron-loss double-coated soft magnetic composite material comprises insulating coated magnetic powder, a binder and a release agent, and a mass ratio of the insulating coated magnetic powder, the binder and the release agent is (100-200):(1-2):(0.1-0.2).

[0011] The insulating coated magnetic powder comprises SiO2-coated magnetic powder and a boron oxide insulating coating layer coated on the surface of the SiO2-coated magnetic powder, and the SiO2-coated magnetic powder comprises metal magnetic powder and a SiO2 insulating coating layer coated on the surface of the metal magnetic powder.

[0012] The metal magnetic powder comprises first metal magnetic powder and second metal magnetic powder.

[0013] The first metal magnetic powder comprises Fe a Si b Ge c R1 d , wherein R1 is Tb or Nd, a, b, c and d are atomic percentages of corresponding elements, a+b+c+d = 100 at%, 87 at% <= a <= 94 at%, 4 at% <= b <= 9 at%, 1 at% <= c <= 2 at%, and 1 at% <= d <= 2 at%.

[0014] The second metal magnetic powder comprises Fe e Si f Al g C h R2 i , wherein R2 is Tb or Nd, e, f, g, h and i are atomic percentages of corresponding elements, e+f+g+h+i = 100 at%, 80 at% <= e <= 88 at%, 6 at% <= f <= 12 at%, 3 at% <= g <= 8 at%, 1 at% <= h <= 2 at%, and 1 at% <= i <= 2 at%.

[0015] Further, the binder is a resin binder, and the release agent is zinc stearate or calcium stearate.

[0016] Further, the particle size of the first metal magnetic powder comprises two ranges, namely, -80 mesh to +150 mesh and -150 mesh to +350 mesh.

[0017] The particle size of the second metal magnetic powder comprises two ranges, namely, -150 mesh to +350 mesh and -350 mesh to +600 mesh.

[0018] Further, in the metal magnetic powder, the first metal magnetic powder with a particle size range of -80 mesh to +150 mesh accounts for 50wt% to 70wt%, the first metal magnetic powder with a particle size range of -150 mesh to +350 mesh accounts for 10wt% to 30wt%, the second metal magnetic powder with a particle size range of -150 mesh to +350 mesh accounts for 10wt% to 30wt%, and the second metal magnetic powder with a particle size range of -350 mesh to +600 mesh accounts for 5wt% to 10wt%.

[0019] A preparation method of a low-iron-loss double-coated soft magnetic composite material, comprising the following steps:

[0020] A SiO2 insulating coating layer is formed on the surface of the metal magnetic powder by wet coating, and after filtration, cleaning and drying, a magnetic powder coated with SiO2 is obtained;

[0021] A boron oxide insulating coating layer is formed on the surface of the magnetic powder coated with SiO2 by dry coating, and an insulating coated magnetic powder is obtained;

[0022] The insulating coated magnetic powder, a binder and a release agent are mixed and compression molded to obtain a soft magnetic powder core;

[0023] The soft magnetic powder core is subjected to atmosphere magnetic field heat treatment to obtain a low-iron-loss double-coated soft magnetic composite material.

[0024] Further, the wet coating is specifically: the metal magnetic powder is mixed with anhydrous ethanol, an amino silane coupling agent, tetraethyl orthosilicate, an iron hydroxide precipitant and a solvent, stirred at room temperature for 1h, heated and stirred in a 60℃ warm water bath at a rotation speed of 300-600r / min for 4h, and a SiO2 insulating coating layer is obtained on the surface of the metal magnetic powder, which is filtered, cleaned with anhydrous ethanol and dried to obtain a magnetic powder coated with SiO2;

[0025] The dry coating is specifically: the magnetic powder coated with SiO2 is mixed with boron oxide particles and mica, heated and stirred at 160℃ for 2h to form a boron oxide insulating coating layer on the surface of the magnetic powder coated with SiO2, and an insulating coated magnetic powder is obtained.

[0026] Further, the mass ratio of the metal magnetic powder, the amino silane coupling agent, the tetraethyl orthosilicate, the iron hydroxide precipitant and the solvent is 100:(3-10):(20-40):(2-5):(800-1200), the solvent includes anhydrous ethanol and deionized water, and the mass ratio of the anhydrous ethanol and the deionized water is 100:(2-5);

[0027] The mass ratio of the magnetic powder coated with SiO2, the boron oxide particles and the mica is 100:(0.5-1):(0.5-1).

[0028] Further, the pressure in the press forming process is 1300-2300 MPa.

[0029] Further, the atmosphere magnetic field heat treatment is specifically: under the protection of carbon dioxide atmosphere, first heating to 200-300 DEG C at a heating rate of 5 DEG C / min, holding for 30-90 min; continuing to heat to 450-550 DEG C at a heating rate of 5 DEG C / min, holding for 20-30 min; continuing to heat to 700-800 DEG C at a heating rate of 5 DEG C / min, holding for 40-80 min, and cooling with the furnace;

[0030] After heating to 200-300 DEG C, holding for 30-90 min, a magnetic field of 50-100 mA is continuously applied until the end.

[0031] Further, the metal magnetic powder is obtained by vacuum alloy smelting to obtain an alloy ingot, and then mechanically or atomizing to obtain the metal magnetic powder. DETAILED DESCRIPTION

[0032] The application will be described in detail as follows:

[0033] The application provides a low-iron-loss double-coated soft magnetic composite material, and the preparation raw material of the low-iron-loss double-coated soft magnetic composite material comprises insulating coated magnetic powder, a binder and a release agent, and the mass ratio of the insulating coated magnetic powder, the binder and the release agent is (100-200):(1-2):(0.1-0.2); the binder is a resin binder; and the release agent is zinc stearate or calcium stearate.

[0034] The insulating coated magnetic powder comprises SiO2 coated magnetic powder and a boron oxide insulating coating layer coated on the surface of the SiO2 coated magnetic powder, and the SiO2 coated magnetic powder comprises metal magnetic powder and a SiO2 insulating coating layer coated on the surface of the metal magnetic powder.

[0035] The metal magnetic powder comprises first metal magnetic powder and second metal magnetic powder.

[0036] The first metal magnetic powder comprises Fe a Si b Ge c R1 d , wherein R1 is Tb or Nd, a, b, c and d are atomic percentages of corresponding elements, a+b+c+d=100 at%, 87 at%≤a≤94 at%, 4 at%≤b≤9 at%, 1 at%≤c≤2 at%, and 1 at%≤d≤2 at%; and the particle size of the first metal magnetic powder comprises two ranges: -80 mesh to +150 mesh and -150 mesh to +350 mesh.

[0037] The second metal magnetic powder comprises Fe e Si f Al g C h R2 i wherein R2 is Tb or Nd, e, f, g, h, i are atomic percentages of corresponding elements, e+f+g+h+i=100at%, 80at%≤e≤88at%, 6at%≤f≤12at%, 3at%≤g≤8at%, 1at%≤h≤2at%, 1at%≤i≤2at%; the particle size of the second metal magnetic powder comprises two ranges: -150 mesh~+350 mesh and -350 mesh~+600 mesh.

[0038] In the metal magnetic powder, the first metal magnetic powder with a particle size range of -80 mesh~+150 mesh accounts for 50wt%-70wt%, the first metal magnetic powder with a particle size range of -150 mesh~+350 mesh accounts for 10wt%-30wt%, the second metal magnetic powder with a particle size range of -150 mesh~+350 mesh accounts for 10wt%-30wt%, and the second metal magnetic powder with a particle size range of -350 mesh~+600 mesh accounts for 5wt%-10wt%.

[0039] The application also provides a preparation method of the above low-iron-loss double-coated soft magnetic composite material, comprising vacuum alloy smelting→mechanical or atomization powdering→powder screening and particle size grading→magnetic powder surface coating→pressing forming→atmosphere magnetic field heat treatment.

[0040] In the vacuum alloy smelting process, the raw materials of the first metal magnetic powder are first smelted, and then the raw materials of the second metal magnetic powder are smelted after the alloy ingot is formed by cooling, and the powder is prepared after smelting is completed.

[0041] The powdering is performed by mechanical or atomization method, preferably, the gas atomization method is selected.

[0042] In the powder screening and particle size grading process, the particle size of the first metal magnetic powder comprises two kinds: -80 mesh~+150 mesh and -150 mesh~+350 mesh, and the particle size of the second metal magnetic powder comprises two kinds: -150 mesh~+350 mesh and -350 mesh~+600 mesh.

[0043] In the metal magnetic powder, the first particle size (-80 mesh~+150 mesh) of the first metal magnetic powder accounts for 50wt%-70wt%, the second particle size (-150 mesh~+350 mesh) of the first metal magnetic powder accounts for 10wt%-30wt%, the first particle size (-150 mesh~+350 mesh) of the second metal magnetic powder accounts for 10wt%-30wt%, and the second particle size (-350 mesh~+600 mesh) of the second metal magnetic powder accounts for 5wt%-10wt%.

[0044] In the process of coating the surface of the magnetic powder, the first coating layer and the second coating layer are coated on the surface of the metal magnetic powder in sequence. The first coating layer is coated by wet coating. The mixed metal magnetic powder, anhydrous ethanol, amino silane coupling agent, tetraethyl orthosilicate, iron hydroxide precipitant and solvent are mixed, stirred at room temperature for 1 h, stirred at 300-600 r / min in a 60℃ water bath for 4 h, and a SiO2insulating coating layer is preliminarily obtained on the surface of the metal magnetic powder. After filtration, the metal magnetic powder is cleaned with anhydrous ethanol and dried. The second coating layer is coated by dry coating. The magnetic powder coated with SiO2, boron oxide particles and mica are mixed and stirred at 160℃ for 2 h to form a boron oxide insulating coating layer.

[0045] In the wet coating, the mass ratio of the metal magnetic powder, the amino silane coupling agent, the tetraethyl orthosilicate, the iron hydroxide precipitant and the solvent is 100:(3-10):(20-40):(2-5):(800-1200). The solvent includes anhydrous ethanol and deionized water, and the mass ratio of the anhydrous ethanol and the deionized water is 100:(2-5). In the dry coating, the mass ratio of the magnetic powder coated with SiO2, the boron oxide particles and the mica is 100:(0.5-1):(0.5-1).

[0046] In the process of press forming, the insulating coated magnetic powder, the binder and the release agent are press formed under a pressure of 1300Mpa-2300Mpa to obtain a soft magnetic powder core.

[0047] The process of atmosphere magnetic field heat treatment includes: for the soft magnetic powder core, under the protection of carbon dioxide atmosphere, first heating at a rate of 5℃ / min to 200-300℃, keeping for 30-90 min, and then applying a magnetic field of 50-100 mA until the end; continuing to heat at a rate of 5℃ / min to 450-550℃, keeping for 20-30 min; continuing to heat at a rate of 5℃ / min to 700-800℃, keeping for 40-80 min, and cooling with the furnace.

[0048] The embodiments of the present application will be described in detail below with reference to the examples. The examples are preferred embodiments of the present application, and cannot limit the scope of the present application. In the following examples, the methods and experimental apparatuses used are conventional methods and apparatuses unless otherwise specified.

[0049] Example 1

[0050] The present example provides a preparation method of a low-iron-loss double-coated soft magnetic composite material, including the following steps:

[0051] Vacuum alloy smelting: two kinds of metal magnetic powders are prepared, the first kind of metal magnetic powder has the following components in atomic percentage: Fe 91%, Si 6%, Ge 1%, Tb 2%, and the second kind of metal magnetic powder has the following components in atomic percentage: Fe 83%, Si 11%, Al 3%, C 2%, Nd 1%.

[0052] Mechanical or atomization method for powder preparation: the first kind of metal magnetic powder has two particle sizes, -80 mesh to +150 mesh and -150 mesh to +350 mesh, and the second kind of metal magnetic powder has two particle sizes, -150 mesh to +350 mesh and -350 mesh to +600 mesh.

[0053] Powder screening and particle size grading: the first kind of metal magnetic powder has a first particle size accounting for 50 wt%, and a second particle size accounting for 10 wt%, the second kind of metal magnetic powder has a first particle size accounting for 30 wt%, and a second particle size accounting for 10 wt%.

[0054] Magnetic powder surface coating: the first coating layer is coated by wet method, the mixed metal magnetic powder, anhydrous ethanol, amino silane coupling agent, tetraethyl orthosilicate, iron hydroxide precipitant and deionized water are mixed, stirred at room temperature for 1 h, stirred at 300 r / min in a 60°C water bath for 4 h, and a SiO2 insulation coating layer is preliminarily obtained on the surface of the powder particles, filtered, cleaned with anhydrous ethanol and dried. The second coating layer is coated by dry method, the coated SiO2 magnetic powder after drying is mixed with boron oxide particles and mica at 160°C for 2 hours to form a boron oxide insulation coating layer.

[0055] In the wet coating method, the mass ratio of the metal magnetic powder, the amino silane coupling agent, the tetraethyl orthosilicate, the iron hydroxide precipitant and the solvent is 100:5:20:4:1000, and the solvent includes anhydrous ethanol and deionized water, and the mass ratio of the anhydrous ethanol and the deionized water is 100:3; in the dry coating method, the mass ratio of the coated SiO2 magnetic powder, the boron oxide particles and the mica is 100:1:0.5.

[0056] The insulation coated magnetic powder is bonded and demolded, the bonding agent is epoxy resin, the demolding agent is zinc stearate, and the mass ratio of the insulation coated magnetic powder, the bonding agent and the demolding agent is 100:1:0.1.

[0057] Pressing forming: the pressing forming pressure of the soft magnetic powder core is 1800Mpa.

[0058] Atmosphere magnetic field heat treatment: under the protection of carbon dioxide atmosphere, first heat to 250℃ at a rate of 5℃ / min, keep for 60min; apply 70mA magnetic field until the end, continue to heat to 500℃ at a rate of 5℃ / min, keep for 25min; continue to heat to 700℃ at a rate of 5℃ / min, keep for 60min, cool down with the furnace, get low iron loss double coated soft magnetic composite material.

[0059] Example 2

[0060] The embodiment provides a preparation method of low iron loss double coated soft magnetic composite material, comprising the following steps:

[0061] Vacuum alloy smelting: prepare two kinds of metal magnetic powders, the first kind of metal magnetic powder has the following components in atomic percentage: Fe 94%, Si 4%, Ge 1%, Nd 1%, the second kind of metal magnetic powder has the following components in atomic percentage: Fe 80%, Si 12%, Al 4%, C 2%, Tb 2%.

[0062] Mechanical or atomization method powdering: adopt mechanical or gas atomization method, the particle size of the first kind of metal magnetic powder includes two kinds of -80 mesh to +150 mesh and -150 mesh to +350 mesh, the particle size of the second kind of metal magnetic powder includes two kinds of -150 mesh to +350 mesh and -350 mesh to +600 mesh.

[0063] Powder screening and particle size grading: the first kind of particle size of the first kind of metal magnetic powder accounts for 70wt%, the second kind of particle size of the first kind of metal magnetic powder accounts for 10wt%, the first kind of particle size of the second kind of metal magnetic powder accounts for 10wt%, the second kind of particle size of the second kind of metal magnetic powder accounts for 10wt%.

[0064] Magnetic powder surface coating: the first coating layer adopts wet coating, the mixed metal magnetic powder, anhydrous ethanol, amino silane coupling agent, tetraethyl orthosilicate, iron hydroxide precipitant and deionized water are mixed, stirred for 1h at room temperature, stirred for 4h at 60℃ water bath under the rotation speed of 450r / min, the SiO2 insulation coating layer is preliminarily obtained on the surface of the powder particles, filtered, cleaned with anhydrous ethanol and dried. The second coating layer adopts dry coating, the SiO2 coated magnetic powder after drying, boron oxide particles and mica are mixed, stirred for 2h at 160℃ to form a boron oxide insulation coating layer.

[0065] In the wet coating, the mass ratio of the metal magnetic powder, the amino silane coupling agent, the tetraethyl orthosilicate, the iron hydroxide precipitant and the solvent is 100:3:40:5:1200, the solvent includes anhydrous ethanol and deionized water, and the mass ratio is 100:2.5; in the dry coating, the mass ratio of the SiO2 coated magnetic powder, the boron oxide particles and the mica is 100:0.8:0.6.

[0066] The insulating coated magnetic powder is bonded and demolded, the bonding agent is epoxy resin, the demolding agent is zinc stearate, and the mass ratio of the insulating coated magnetic powder, the bonding agent and the demolding agent is 100:2:0.1.

[0067] Press forming: the press forming pressure of the soft magnetic powder core is 1300Mpa.

[0068] Atmosphere magnetic field heat treatment: under the protection of carbon dioxide atmosphere, first heat to 280℃ at a heating rate of 5℃ / min, keep for 90min; apply a magnetic field of 50mA until the end, continue to heat to 450℃ at a heating rate of 5℃ / min, keep for 30min; continue to heat to 750℃ at a heating rate of 5℃ / min, keep for 80min, and cool down with the furnace to obtain the low iron loss double coated soft magnetic composite material.

[0069] Example 3

[0070] The embodiment provides a preparation method of a low iron loss double coated soft magnetic composite material, comprising the following steps:

[0071] Vacuum alloy smelting: prepare two kinds of metal magnetic powders, the first kind of metal magnetic powder has the following components in atomic percentage: Fe 87%, Si 9%, Ge 2%, and Nd 2%, and the second kind of metal magnetic powder has the following components in atomic percentage: Fe 83%, Si 6%, Al 8%, C 1%, and Tb 1%.

[0072] Mechanical or atomization method powdering: the first kind of metal magnetic powder has two particle sizes of -80 mesh to +150 mesh and -150 mesh to +350 mesh, and the second kind of metal magnetic powder has two particle sizes of -150 mesh to +350 mesh and -350 mesh to +600 mesh.

[0073] Powder screening and particle size grading: the first kind of particle size of the first kind of metal magnetic powder accounts for 50wt%, the second kind of particle size of the first kind of metal magnetic powder accounts for 30wt%, the first kind of particle size of the second kind of metal magnetic powder accounts for 15wt%, and the second kind of particle size of the second kind of metal magnetic powder accounts for 5wt%.

[0074] Magnetic powder surface coating: the first coating layer is coated by a wet method, the mixed metal magnetic powder, anhydrous ethanol, amino silane coupling agent, tetraethyl orthosilicate, iron hydroxide precipitant and deionized water are mixed, stirred at room temperature for 1h, stirred at 500r / min in a 60℃ water bath for 4h, and a SiO2 insulating coating layer is preliminarily obtained on the surface of the powder particles, and then the powder is filtered, cleaned with anhydrous ethanol and dried. The second coating layer is coated by a dry method, the coated SiO2 magnetic powder after drying is mixed with boron oxide particles and mica, and stirred at 160℃ for 2h to form a boron oxide insulating coating layer.

[0075] In the wet coating, the mass ratio of the metal magnetic powder, the amino silane coupling agent, the tetraethyl orthosilicate, the iron hydroxide precipitator and the solvent is 100:6:30:3:900, and the solvent includes anhydrous ethanol and deionized water, and the mass ratio of the anhydrous ethanol and the deionized water is 100:3; in the dry coating, the mass ratio of the SiO2-coated magnetic powder, the boron oxide particles and the mica is 100:0.9:0.6.

[0076] The insulation-coated magnetic powder is bonded and demolded, the bonding agent is epoxy resin, the demolding agent is zinc stearate, and the mass ratio of the insulation-coated magnetic powder, the bonding agent and the demolding agent is 200:1:0.2.

[0077] Press forming: the press forming pressure of the soft magnetic powder core is 2000Mpa.

[0078] Atmosphere magnetic field heat treatment: under the protection of a carbon dioxide atmosphere, the temperature is first increased to 300℃ at a rate of 5℃ / min, and the temperature is kept for 30min; a magnetic field of 60mA is applied until the end, and the temperature is continued to increase to 500℃ at a rate of 5℃ / min, and the temperature is kept for 25min; the temperature is continued to increase to 780℃ at a rate of 5℃ / min, and the temperature is kept for 40min, and the furnace is cooled, to obtain the low-iron-loss double-coated soft magnetic composite material.

[0079] Example 4

[0080] The embodiment provides a preparation method of a low-iron-loss double-coated soft magnetic composite material, and the method comprises the following steps:

[0081] Vacuum alloy smelting: two kinds of metal magnetic powders are prepared, and the first kind of metal magnetic powder comprises Fe 93%, Si 4%, Ge 1% and Tb 2% in atomic percentage, and the second kind of metal magnetic powder comprises Fe 88%, Si 6%, Al 4%, C 1% and Nd 1% in atomic percentage.

[0082] Mechanical or atomization method powdering: a mechanical method is adopted, the particle size of the first kind of metal magnetic powder comprises two kinds of -80 mesh to +150 mesh and -150 mesh to +350 mesh, and the particle size of the second kind of metal magnetic powder comprises two kinds of -150 mesh to +350 mesh and -350 mesh to +600 mesh.

[0083] Powder screening and particle size grading: the first kind of particle size of the first kind of metal magnetic powder accounts for 60wt%, the second kind of particle size of the first kind of metal magnetic powder accounts for 20wt%, the first kind of particle size of the second kind of metal magnetic powder accounts for 12wt%, and the second kind of particle size of the second kind of metal magnetic powder accounts for 8wt%.

[0084] Magnetic powder surface coating: the first coating layer is coated by wet method, the mixed metal magnetic powder is mixed with anhydrous ethanol, amino silane coupling agent, tetraethyl orthosilicate, iron hydroxide precipitant and deionized water, stirred at room temperature for 1 h, stirred at 600 r / min in 60℃ water bath for 4 h, and the surface of the powder particles is preliminarily coated with a SiO2 insulation coating, filtered, washed with anhydrous ethanol and dried. The second coating layer is coated by dry method, the coated SiO2 magnetic powder after drying is mixed with boron oxide particles and mica, stirred at 160℃ for 2 hours to form a boron oxide insulation coating layer.

[0085] In the wet coating, the mass ratio of metal magnetic powder, amino silane coupling agent, tetraethyl orthosilicate, iron hydroxide precipitant and solvent is 100:8:35:2:800, and the solvent includes anhydrous ethanol and deionized water, and the mass ratio is 100:5; in the dry coating, the mass ratio of coated SiO2 magnetic powder, boron oxide particles and mica is 100:0.5:1.

[0086] The insulation coated magnetic powder is bonded and demolded, the binder is epoxy resin, the demolding agent is zinc stearate, and the mass ratio of insulation coated magnetic powder, binder and demolding agent is 100:1.5:0.1.

[0087] Press forming: the press forming pressure of the soft magnetic powder core is 2300Mpa.

[0088] Atmosphere magnetic field heat treatment: under the protection of carbon dioxide atmosphere, first heat to 200℃ at a rate of 5℃ / min, and keep for 70min; apply a magnetic field of 100mA until the end, continue to heat to 550℃ at a rate of 5℃ / min, keep for 20min; continue to heat to 800℃ at a rate of 5℃ / min, keep for 75min, and cool down with the furnace. Low iron loss double coated soft magnetic composite material is obtained.

[0089] Comparative example 1

[0090] The soft magnetic composite material of the present comparative example is selected from similar alloy composition as example 1, the first metal magnetic powder has a composition of Fe 92%, Si 7%, Ge 1% by mass percentage, and the second metal magnetic powder has a composition of Fe 83%, Si 10%, Al 5%, C 2% by mass percentage. The difference is that the comparative example does not add rare earth elements. The preparation process of the soft magnetic composite material is the same as example 1.

[0091] Comparative example 2

[0092] The soft magnetic composite material of the present comparative example is selected with similar alloy composition as example 1, the first metal magnetic powder has the composition of Fe 92%, Si 6%, Tb 2% by mass percentage, and the second metal magnetic powder has the composition of Fe 83%, Si 11%, Al 5%, Nd 1% by mass percentage. The difference is that the comparative example does not add Ge element and C element. The preparation process of the soft magnetic composite material is the same as example 1.

[0093] Comparative example 3

[0094] The soft magnetic composite material of the present comparative example is selected with similar alloy composition as example 1, but only one kind of magnetic powder is selected, which has the composition of Fe 91%, Si 6%, Ge 1%, Tb 2%, and the particle size contains two kinds of -80 mesh to +150 mesh and -150 mesh to +350 mesh, with the mass ratio of 70wt% and 30wt% respectively. The rest of the preparation process is the same as example 1.

[0095] Comparative example 4

[0096] The soft magnetic composite material of the present comparative example is selected with similar alloy composition as example 1, but only one kind of magnetic powder is selected, which has the composition of Fe 82%, Si 10%, Al 5%, C 2%, Nd 1%, and the particle size contains two kinds of -80 mesh to +150 mesh and -150 mesh to +350 mesh, with the mass ratio of 70wt% and 30wt% respectively. The rest of the preparation process is the same as example 1.

[0097] Comparative example 5

[0098] The soft magnetic composite material of the present comparative example is selected with the same alloy composition as example 1, but only the first insulating coating layer is used. The rest of the preparation process is the same as example 1.

[0099] Comparative example 6

[0100] The soft magnetic composite material of the present comparative example is selected with the same alloy composition as example 1, but only the second insulating coating layer is used. The rest of the preparation process is the same as example 1.

[0101] Comparative example 7

[0102] The soft magnetic composite material of the present comparative example is selected with the same alloy composition as example 1, but the heat treatment stage uses N2 atmosphere heat treatment. The rest of the preparation process is the same as example 1.

[0103] Comparative example 8

[0104] The soft magnetic composite material of the present comparative example is selected with the same alloy composition as example 1, but the heat treatment stage directly heats up to 750℃ at a heating rate of 5℃ / min. The rest of the preparation process is the same as example 1.

[0105] Comparative Example 9

[0106] The soft magnetic composite material of the present comparative example uses the same alloy composition as Example 1, except that no magnetic field is applied during the heat treatment stage, and the rest of the preparation process is the same as Example 1.

[0107] Table 1 lists the saturation magnetic induction Bs, initial permeability μi, and loss P under the conditions of a frequency of 1 kHz and a magnetic field of 1.2 T for Examples 1-4 and Comparative Examples 1-9.

[0108] Table 1

[0109] As can be seen from Table 1, the soft magnetic properties of the soft magnetic composite materials of Comparative Examples 1 and 2, which do not add rare earth elements or Ge elements and C elements, are not as good as those of Example 1, which adds rare earth elements and Ge elements and C elements, because adding these elements helps to refine the alloy powder and improve the magnetic properties. The soft magnetic properties of the soft magnetic composite materials of Comparative Examples 3 and 4, which only use one kind of magnetic powder, are not as good as those of Example 1, which uses two kinds of magnetic powder, because the advantages of the two kinds of metal magnetic powder can be combined to improve the magnetic properties of the soft magnetic composite material at high, medium and low frequencies. The soft magnetic properties of the soft magnetic composite materials of Comparative Examples 5 and 6, which only use the first insulating coating layer or only use the second insulating coating layer, are not as good as those of Example 1, which uses two kinds of insulating coating layers, because the advantages of the two kinds of metal insulating coating layers can be combined to improve the magnetic properties of the soft magnetic composite material at high, medium and low frequencies. The soft magnetic properties of the soft magnetic composite material of Comparative Example 7, which uses N2 atmosphere heat treatment during the heat treatment stage, are not as good as those of Example 1, which uses CO2 atmosphere, because CO2 atmosphere can better protect and prevent oxidation. The soft magnetic properties of the soft magnetic composite material of Comparative Example 8, which directly heats to 750°C at a heating rate of 5°C / min during the heat treatment stage, are not as good as those of Example 1, which uses three-stage heat treatment, because three-stage heat treatment can more effectively eliminate internal stress and improve the internal structure of the magnet. The soft magnetic properties of the soft magnetic composite material of Comparative Example 9, which does not apply a magnetic field during the heat treatment stage, are not as good as those of Example 1, which applies a magnetic field during the heat treatment stage, because applying a magnetic field can effectively improve the magnetic domain structure inside the composite material to ultimately improve the magnetic properties of the soft magnetic composite material.

[0110] Although the present application has been disclosed with reference to the preferred embodiments, it is not intended to limit the application, and any person skilled in the art can make various modifications and modifications without departing from the spirit and scope of the application, and therefore the protection scope of the application should be defined by the claims. Industrial applicability

[0111] The low-iron-loss double-coated soft magnetic composite material of the application comprises two kinds of metal magnetic powders, the first kind of metal magnetic powder comprises Fe-Si-Ge-R1, and the second kind of metal magnetic powder comprises Fe-Si-Al-C-R2, wherein R1 and R2 are one of rare earth elements Tb and Nd, the first kind of metal magnetic powder is based on Fe-Si magnetic powder and adds Ge and rare earth elements, wherein the addition of Ge elements can reduce the coercive force of the soft magnetic powder core and reduce the hysteresis loss, and the hysteresis loss is more obvious in the case of medium and low frequency, and reducing the hysteresis loss can significantly reduce the medium and low frequency loss, and also helps to refine the alloy powder and further improve the magnetic performance; the second kind of metal magnetic powder is based on Fe-Si-Al magnetic powder and adds C and rare earth elements, wherein the addition of C elements can improve the saturation resistance of the soft magnetic composite material, so that the magnetic powder core can still maintain good magnetic performance under high magnetic field strength, and at the same time, it also helps to refine the alloy powder and has no macrosegregation phenomenon, thereby improving the magnetic performance.

[0112] In addition, the two kinds of metal magnetic powders both add rare earth elements Tb or Nd, the rare earth elements Tb and Nd are more active, compared with other rare earth elements, and are more likely to react with impurity elements such as sulfur and oxygen in the alloy to the surface of the molten liquid in the smelting process, and at the same time, a dense oxide film can be formed on the surface of the alloy, so that the master alloy is more pure.

[0113] Further, by reasonably matching the four particle sizes of the two kinds of metal magnetic powders, the particle spacing between the magnetic powders can be effectively adjusted, so as to reduce the internal gap and reduce the gap degree, thereby improving the magnetic permeability, improving the saturation magnetic induction strength and reducing the loss.

[0114] The preparation method of the application adopts two kinds of metal magnetic powders, the first kind of metal magnetic powder has higher loss than the second kind of metal magnetic powder, but has better saturation resistance than the second kind of metal magnetic powder, and by mixing, the advantages of the two kinds of metal magnetic powders can be combined to improve the magnetic performance of the soft magnetic composite material at high, medium and low frequencies, and the raw materials further comprise a binder and a release agent, and by selecting appropriate binders and release agents and corresponding proportions, different molds can be selected to press the compacts into various shapes according to different equipment or part requirements.

[0115] Further, the rare earth elements Tb and Nd can form regular-shaped and small-sized rare earth composite inclusions with Fe elements in the subsequent annealing process, which is beneficial to reducing the loss of the soft magnetic composite material and improving the magnetic performance, but if the amount of addition is excessive, the saturation magnetic induction will decrease.

[0116] Further, two layers of coating layers are adopted, firstly, wet coating is adopted, and hydrolysis and polycondensation reaction of SiO2 precursor tetraethyl orthosilicate is utilized to form flocculent amorphous SiO2 insulating coating layer on the surface of metal magnetic powder, and the excellent insulating performance of silicon dioxide (SiO2) as the first layer of insulating coating can effectively isolate the magnetic domains inside the soft magnetic powder core, reduce the interaction between the magnetic domains, and help to reduce the magnetic resistance of the soft magnetic powder core, wherein the addition of amino silane coupling agent can promote the continuous and uniform formation of the SiO2 insulating coating layer on the surface of the metal magnetic powder, and the addition of ferric hydroxide precipitator can control the thickness and continuity and uniformity of the SiO2 insulating coating layer, so as to better perform the second layer of insulating coating; the second coating layer adopts dry coating to form boron oxide insulating coating layer, and the lower dielectric constant and higher dielectric strength of boron oxide can reduce the energy loss and electromagnetic interference in the signal transmission process, and can improve the overall reactance linearity of the soft magnetic composite material, and further improve the magnetic performance.

[0117] Further, in the coating process, wet coating is performed first and then dry coating is performed, which can more uniformly and effectively coat the second layer without affecting the effect of the first layer of coating, and the larger size of boron oxide can be coupled with the smaller size of SiO2 to improve the thermal stability and chemical stability of the soft magnetic composite material.

[0118] Further, in the first layer of insulating coating process, after stirring at room temperature for 1 h, stirring is performed at a speed of 300-600 r / min in a 60℃ water bath for 4 h, which can make the hydrolysis and polycondensation reaction of tetraethyl orthosilicate more sufficient, and the SiO2 coating more uniform; in the second layer of insulating coating process, the synergistic effect of mica and boron oxide insulating coating helps to improve the magnetic performance of the soft magnetic powder core, including permeability and magnetic saturation strength, thereby improving the overall performance of the soft magnetic powder core.

[0119] Further, in the pressing process, as the pressing pressure increases, the displacement and sliding (rearrangement or reaccumulation) of the metal magnetic powder particles increases the contact area between the particles, and the density of the compact increases linearly, so that excellent magnetic powder core density and permeability can be obtained, and the overall performance is best when the pressing pressure is 1300 Mpa-2300 Mpa. Further increasing the pressing pressure still has limitations for improving the permeability and density of the soft magnetic powder core, and will bring a series of problems such as difficult demolding, damage to the mold, and introduction of excessive internal stress and even damage to the insulating coating layer.

[0120] Further, in the process of atmosphere magnetic field heat treatment, carbon dioxide is selected as the heat treatment gas, which can play a protective and anti-oxidation role, and a three-stage heating treatment is adopted, the first stage is a stress relief stage, which can eliminate internal defects and release internal stress, the second stage temperature can completely decompose the binder and further relax the pressing stress, so that the two kinds of metal magnetic powders and the two layers of insulation coating are more uniformly distributed, and the third stage makes the two kinds of internal magnetic powder metals undergo solid phase transformation reaction, changes the crystal structure of the magnetic powder particles and the insulation layer, and after the first stage, a magnetic field is applied until the end, which can effectively improve the magnetic domain structure inside the composite material, so as to finally improve the magnetic properties of the soft magnetic composite material.

[0121] The low iron loss double-coated soft magnetic composite material prepared in the application has a loss of P0.5T / 1kHz = 130 W / dm3~155 W / dm3, P1.2T / 50Hz = 20 W / dm3~25 W / dm3, and a saturation magnetic flux density Bs = 1.45T~1.55T. The soft magnetic composite material provided in the application has the advantages of high resistivity, low magnetic loss and low eddy current loss, meets the requirements of medium and high frequency use, and is suitable for use in electrical equipment such as transformers and reactors.

Claims

1. A low iron loss double-coated soft magnetic composite material, raw materials for preparing the low iron loss double-coated soft magnetic composite material comprising insulating coated magnetic powder, binder and release agent, mass ratio of the insulating coated magnetic powder, binder and release agent being (100-200) :(1-2) :(0.1-0.2) ; the insulating coated magnetic powder comprising SiO 2 coated magnetic powder and a boron oxide insulating coating layer coated on the surface of the SiO 2 coated magnetic powder, the SiO 2 coated magnetic powder comprising metal magnetic powder and a SiO 2 insulating coating layer coated on the surface of the metal magnetic powder; the metal magnetic powder comprising first metal magnetic powder and second metal magnetic powder; the binder being a resin binder, and the release agent being zinc stearate or calcium stearate. The first metal magnetic powder includes Fe a Si b Ge c R1 d wherein R1 is Tb or Nd, a, b, c, d are atomic percentages of the corresponding elements, a+b+c+d = 100 at%, 87 at% ≤ a ≤ 94 at%, 4 at% ≤ b ≤ 9 at%, 1 at% ≤ c ≤ 2 at%, 1 at% ≤ d ≤ 2 at%; The second metal magnetic powder includes Fe e Si f Al g C h R2 i wherein R2 is Tb or Nd, e, f, g, h, i are the atomic percentages of the corresponding elements, e+f+g+h+i = 100 at%, 80 at% ≤ e ≤ 88 at%, 6 at% ≤ f ≤ 12 at%, 3 at% ≤ g ≤ 8 at%, 1 at% ≤ h ≤ 2 at%, 1 at% ≤ i ≤ 2 at%.

2. The low-loss dual-clad soft magnetic composite of claim 1, wherein, the first metal magnetic powder having two particle size ranges: -80 mesh to +150 mesh and -150 mesh to +350 mesh; 3. The low-loss dual-clad soft magnetic composite of claim 1, wherein, the second metal magnetic powder having two particle size ranges: -150 mesh to +350 mesh and -350 mesh to +600 mesh. in the metal magnetic powder, the first metal magnetic powder with a particle size range of -80 mesh to +150 mesh accounts for 50wt%-70wt%, the first metal magnetic powder with a particle size range of -150 mesh to +350 mesh accounts for 10wt%-30wt%, the second metal magnetic powder with a particle size range of -150 mesh to +350 mesh accounts for 10wt%-30wt%, and the second metal magnetic powder with a particle size range of -350 mesh to +600 mesh accounts for 5wt%-10wt%.

4. The low-loss double wrapped soft magnetic composite of claim 3, wherein, 5.A method for preparing a low iron loss double-coated soft magnetic composite material, comprising the following steps: forming a SiO 2 insulating coating layer on the surface of the metal magnetic powder by wet coating, and after filtration, cleaning and drying, obtaining SiO 2 coated magnetic powder; forming a boron oxide insulating coating layer on the surface of the SiO 2 coated magnetic powder by dry coating, and obtaining insulating coated magnetic powder; mixing the insulating coated magnetic powder, binder and release agent and compression molding to obtain a soft magnetic powder core; subjecting the soft magnetic powder core to magnetic field heat treatment in an atmosphere to obtain a low iron loss double-coated soft magnetic composite material. the wet coating specifically comprising: mixing the metal magnetic powder, anhydrous ethanol, amino silane coupling agent, tetraethyl orthosilicate, iron hydroxide precipitator and solvent, stirring at room temperature for 1h, heating and stirring in a 60℃ water bath at a speed of 300-600r / min for 4h, obtaining a SiO 2 insulating coating layer on the surface of the metal magnetic powder, cleaning and drying after filtration to obtain SiO 2 coated magnetic powder; 6. The method of manufacturing a low-loss double wrapped soft magnetic composite material according to claim 5, wherein, the dry coating specifically comprising: mixing the SiO 2 coated magnetic powder, boron oxide particles and mica, heating and stirring at 160℃ for 2h to form a boron oxide insulating coating layer on the surface of the SiO 2 coated magnetic powder, and obtaining insulating coated magnetic powder. mass ratio of the metal magnetic powder, amino silane coupling agent, tetraethyl orthosilicate, iron hydroxide precipitator and solvent being 100 :(3-10) :(20-40) :(2-5) :(800-1200), the solvent comprising anhydrous ethanol and deionized water, mass ratio of the anhydrous ethanol and deionized water being 100 :(2-5).

7. The method of manufacturing a low-loss double wrapped soft magnetic composite of claim 6, wherein, ​ The mass ratio of the SiO2-coated magnetic powder, boron oxide particles and mica is 100:(0.5-1):(0.5-1).

8. The method of manufacturing a low-loss double wrapped soft magnetic composite of claim 5, wherein, The pressure in the press forming process is 1300-2300 Mpa.

9. The method of manufacturing a low-loss double wrapped soft magnetic composite of claim 5, wherein, The atmosphere magnetic field heat treatment is specifically: under the protection of carbon dioxide atmosphere, first heating to 200-300 DEG C at a heating rate of 5 DEG C / min, holding for 30-90 min; continuing to heat to 450-550 DEG C at a heating rate of 5 DEG C / min, holding for 20-30 min; continuing to heat to 700-800 DEG C at a heating rate of 5 DEG C / min, holding for 40-80 min, and cooling with the furnace; After heating to 200-300 DEG C, holding for 30-90 min, a magnetic field of 50-100 mA is continuously applied until the end.

10. The method of manufacturing a low-loss double wrapped soft magnetic composite of claim 5, wherein, The metal magnetic powder is obtained by vacuum alloy smelting to obtain an alloy ingot, and then using a mechanical or atomization method to powderize the alloy ingot to obtain the metal magnetic powder.

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