Iron-based nanocrystalline core for inductor and preparation method thereof

Abstract

The application discloses an iron-based nanocrystalline iron core for an inductor and a preparation method thereof, and belongs to the technical field of magnetic materials. The iron-based nanocrystalline iron core provided by the application contains the following elements in percentage by mass: Fe: 80-85%, B: 5-9%, Si: 6-10%, Cu: 1-3%, Nb: 2-5%, and Nd: 0.1-0.5%. The preparation method comprises the following steps: smelting raw materials to obtain alloy materials; adding lime, fluorite and silica into the alloy materials to form slag materials, and then blowing; vacuumizing, maintaining negative pressure, and cooling in the furnace to obtain a mother alloy ingot; winding the mother alloy ingot into a strip; annealing treatment; deep cooling treatment, spraying, solidification, and finally obtaining the iron-based nanocrystalline iron core. The iron core prepared by the application effectively improves the magnetic performance and stability, and solves the problems of low high-frequency inductance, small impedance and large temperature rise of the inductor.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of magnetic materials, and particularly relates to an iron-based nanocrystalline iron core for an inductor and a preparation method thereof. BACKGROUND

[0002] With the rapid development of electronic technology, as a key component in a circuit, the performance of an inductor has an important influence on the stability and efficiency of the overall circuit. The main functions of an inductor include energy storage, filtering, oscillation, etc., and the material properties and preparation process of the core, the core component of an inductor, directly determine the performance of the inductor. Traditional inductor core materials mostly use ferrite materials, although ferrite materials have certain inductance performance, but there are some problems in actual application, for example, the saturation magnetic induction intensity of ferrite materials is low, which cannot meet the application requirements of high power and high magnetic field intensity; the temperature stability of ferrite materials is poor, and when the temperature changes, the magnetic properties will fluctuate greatly, affecting the stability and reliability of the inductor.

[0003] In comparison, iron-based nanocrystalline materials are concerned due to their unique microstructure and excellent magnetic properties. Iron-based nanocrystalline materials have high magnetic permeability, which can effectively improve the inductance of the inductor; low magnetic loss, which can improve the efficiency of the inductor; and also have good frequency characteristics and temperature stability, which are very suitable for the core of high-frequency and high-power inductors.

[0004] In recent years, with the development of electronic devices towards miniaturization, high frequency and high efficiency, higher requirements are put forward for inductor core materials. The performance of iron-based nanocrystalline materials is highly dependent on precise alloy composition control and heat treatment process. However, due to equipment limitations, the existing vacuum melting furnace is prone to problems of uneven composition of alloy ingots during the melting process. Moreover, during the melting process, multiple vacuum breaking operations are required, and the metal is prone to react with oxygen in the air, resulting in the formation of inclusions and uneven composition, thereby affecting the stability of the product. Improper heat treatment process will also cause problems such as coarse grains and decreased magnetic properties. These problems make the existing iron-based nanocrystalline inductor have problems such as low inductance, small impedance and large temperature rise at high frequency (>200 kHz) in actual application.

[0005] Therefore, it is urgent to develop an iron-based nanocrystalline iron core for an inductor which can effectively improve the magnetic properties and stability of the core, and solve the problems such as low inductance, small impedance and large temperature rise of inductor devices at high frequency. SUMMARY

[0006] Therefore, the application provides an iron-based nanocrystalline iron core for an inductor and a preparation method thereof, which can effectively improve the magnetic properties and stability of the core, and solve the problems such as low inductance, small impedance and large temperature rise of inductor devices at high frequency.

[0007] In a first aspect, the application provides an iron-based nanocrystalline core for an inductor, comprising the following elements in percentage by mass: Fe: 80-85%, B: 5-9%, Si: 6-10%, Cu: 1-3%, Nb: 2-5%, and Nd: 0.1-0.5%.

[0008] By adopting the above technical solution, the application can effectively improve the magnetic properties and stability of the core by optimizing the alloy composition, and solve the problems of low high-frequency inductance, small impedance, and large temperature rise of the inductor.

[0009] In the application, Fe serves as the main magnetic element to provide high magnetic permeability and low magnetic loss, and increasing the content of Fe can increase the saturation magnetic induction intensity and magnetic permeability of the material. The small atomic radius of the B element can disrupt atomic arrangement and increase the degree of disorder of the system, which is conducive to the formation of an amorphous structure. Within a proper range, the B element helps to improve the amorphous forming ability of the material, but excessive B can increase the precipitation of Fe-B phase, inhibit the movement of magnetic domain walls, and deteriorate the soft magnetic properties. The Si element can increase the disorder of atomic arrangement, inhibit the formation of a crystal structure, and improve the amorphous forming ability. In the process of transformation from the amorphous state to nanocrystalline, Si can improve the stability of the amorphous phase, delay the precipitation of primary phase, and inhibit the excessive growth of grains, which helps to form fine and uniform nanocrystalline grains and improve the soft magnetic properties and thermal stability of the material. Nb has a large atomic size and is almost insoluble in a-Fe. In the annealing process, Nb is enriched in the residual amorphous matrix to inhibit the growth of the crystalline phase and stabilize the residual amorphous matrix, but excessive Nb can reduce the magnetic permeability and coercive force of the material. The Cu element can refine the grain size and promote the uniform distribution of grains. A small amount of Cu can improve the soft magnetic properties and amorphous forming ability of the alloy. The Nd element can improve the saturation magnetic induction intensity and magnetic permeability of the material, and improve the magnetic properties and thermal stability.

[0010] By optimizing the proportions of Fe, B, Si, Nb, Cu, and other elements, the application improves the amorphous forming ability of the material, refines the grains, reduces the magnetic loss at high frequencies, and improves the inductance and impedance of the inductor at high frequencies. By adding Nd, the application improves the thermal stability of the material, reduces the impact of temperature changes on the magnetic properties, reduces the temperature rise of the inductor during operation, and improves the long-term stability and reliability.

[0011] Optionally, the iron-based nanocrystalline core comprises the following elements: Fe: 81.6-83%, B: 6-8%, Si: 7.08-8%, Cu: 2-2.5%, Nb: 3-4%, and Nd: 0.3-0.4%.

[0012] Optionally, the raw materials for preparing Fe, B, Si, Cu, Nb, and Nd in the iron-based nanocrystalline core are iron particles, boron-iron blocks, silicon powder, copper particles, niobium-iron blocks, and neodymium powder.

[0013] In the art, "powder" refers to very small particles, "granule" refers to relatively larger particles compared with "powder", and "block" refers to relatively larger solid substances compared with "granule". In the present application, the particle size of "powder" ranges from ≤200 μm, the particle size of "granule" ranges from >200 μm and ≤3000 μm, and the particle size of "block" ranges from >3000 μm.

[0014] In a second aspect, the present application provides a preparation method of the above-mentioned iron-based nanocrystalline iron core for inductors, comprising the following steps:

[0015] Step S1, sequentially put copper particles, boron-iron blocks, iron particles accounting for 10-30 wt% of the total mass of iron particles, silicon powder, neodymium powder, niobium-iron blocks, and the remaining iron particles into a vacuum induction melting furnace for melting, vacuumize to -100 to -120 kPa, heat under argon atmosphere, and obtain an alloy material after melting;

[0016] Step S2, add lime, fluorite, and silica as slagging materials to the alloy material, melt, and then pass a mixed gas of argon and hydrogen to perform blowing, and the blowing time is 10-15 min;

[0017] Step S3, vacuumize to -500 to -550 kPa, maintain negative pressure for 5-10 min, stop vacuumizing and heating, and cool down with the furnace to obtain a master alloy ingot;

[0018] Step S4, roll the master alloy ingot into a strip, and wind to obtain an iron core;

[0019] Step S5, put the iron core into a vacuum heat treatment furnace, vacuumize to -80 to -100 kPa, pass a protective gas, and perform annealing treatment;

[0020] Step S6, perform cryogenic treatment on the annealed iron core, then uniformly spray an epoxy powder coating on the surface of the iron core, and obtain an iron-based nanocrystalline iron core after solidification.

[0021] By adopting the above technical solution, the preparation method of the present application improves the uniformity, microstructure, and magnetic properties of the material. This method not only solves the problems of low inductance, small impedance, and large temperature rise of inductor devices, but also improves the overall performance and stability of the inductor. The preparation method of the present application adds different raw materials with different melting points in batches to ensure that each element is uniformly melted and to avoid local overheating or composition segregation. If all raw materials are added to the melting furnace at once, high-melting-point elements may not be completely melted, while low-melting-point elements may be overheated and volatilized or oxidized.

[0022] The step S1 of the application can remove the air in the smelting furnace to prevent the alloy from being oxidized. The argon atmosphere can protect the alloy from being oxidized and provide a good smelting environment, reducing the generation of oxides and impurities. The step S2 of adding lime, fluorite and silica slag can absorb impurities and gases in the alloy. The step S3 of maintaining negative pressure for 5-10 min can make the dissolved hydrogen in the alloy precipitate in the form of tiny bubbles, further purifying the alloy melt. The step S4 of forming an insulation layer through coating treatment can reduce the eddy current loss and improve the efficiency of the inductor. The step S5 of annealing treatment can optimize the microstructure of the material and improve the magnetic performance and stability. The step S6 of deep cryogenic treatment can further improve the strength and toughness of the material, thereby improving the magnetic performance and thermal stability. Spraying epoxy powder coating can form a uniform and dense protective layer, improving the insulation performance and corrosion resistance of the material; compared with assembling a protective shell, spraying epoxy powder coating can significantly reduce the volume and mass of the material, reduce the amount of copper wire used, and save space and cost.

[0023] Optionally, in the step S1, the heating power is 100-150 KW, and the heating temperature is 1600-1700℃; the purity of argon is ≥99.99%.

[0024] By adopting the above technical solution, the appropriate heating power and heating temperature of the application help to ensure uniform mixing of alloy components and avoid local overheating or incomplete melting. If the heating power or heating temperature is too low, some high-melting-point elements (such as niobium) may not be completely melted, affecting the uniformity of the alloy components. Incomplete melting may also cause composition segregation, affecting the performance of the alloy. If the heating power or heating temperature is too high, local overheating may occur, resulting in defects such as pores and inclusions, affecting the quality of the alloy. Low-melting-point elements (such as copper and silicon) may volatilize due to overheating, causing the composition to deviate from the expected value.

[0025] The high-purity argon of the application can effectively isolate air and prevent the alloy from being oxidized at high temperatures, ensuring the purity of the alloy.

[0026] Optionally, in the step S4, the thickness of the strip is 16-20μm, and the width is 10-20mm.

[0027] By adopting the above technical solution, the thickness of the strip of the application ensures the balance between magnetic performance and processing performance, reduces eddy current loss, improves magnetic performance at high frequencies, and maintains sufficient mechanical strength. If the strip is too thick, it may increase eddy current loss, leading to a decrease in the efficiency of the inductor, and may also cause a decrease in magnetic permeability, affecting the inductance and performance of the inductor at high frequencies. If the strip is too thin, the mechanical strength is low, and it is easy to break during processing and use, and it is more likely to be damaged during winding and processing, increasing the processing difficulty and waste rate.

[0028] The strip width of the application ensures the uniformity of the magnetic circuit and the convenience of processing, improves the heat dissipation performance of the core, reduces the temperature rise, and improves the stability of the inductor. If the strip is too wide or too narrow, it may cause the magnetic circuit of the core to be uneven, affecting the magnetic performance. And the too narrow strip may cause the heat dissipation performance of the core to decrease, increase the temperature rise, and affect the stability of the inductor.

[0029] Optionally, in the step S5, the protective gas is a mixed gas of nitrogen and hydrogen, the volume percentage of nitrogen is 95-98%, the volume percentage of hydrogen is 2-5%, and the gas flow is 300-500 mL·min -1 .

[0030] By adopting the above technical scheme, in the protective gas of the application, nitrogen mainly provides a protective effect to prevent oxidation of the alloy, ensures stable atmosphere, hydrogen provides a reducing and degassing effect to improve the purity and quality of the alloy. The gas flow of the application can ensure the renewal and uniformity of the atmosphere, prevent pollution, and improve the stability of the annealing process.

[0031] Optionally, in the step S5, the annealing process is divided into five stages:

[0032] In the first stage, the temperature in the furnace is raised to 200-220 DEG C at a heating rate of 20-30 DEG C / min, and the temperature is kept for 30-40 min;

[0033] In the second stage, the temperature in the furnace is raised to 370-400 DEG C at a heating rate of 5-10 DEG C / min, and the temperature is kept for 20-30 min;

[0034] In the third stage, the temperature in the furnace is raised to 500-520 DEG C at a heating rate of 3-5 DEG C / min, and the temperature is kept for 60-90 min;

[0035] In the fourth stage, the temperature in the furnace is raised to 560-570 DEG C at a heating rate of 1 DEG C / min, a transverse magnetic field is added, and the temperature is kept for 60-80 min;

[0036] In the fifth stage, the temperature in the furnace is lowered to 200-220 DEG C at a cooling rate of 30-50 DEG C / min.

[0037] By adopting the above technical scheme, the application gradually optimizes the microstructure and magnetic performance of the material through five-stage annealing process, reduces internal stress and defects, and improves the uniformity and stability of the material. The heating rate, temperature and holding time of each stage can ensure that the material is in the best state in each temperature range. The stage annealing process of the application can more effectively control the microstructure and performance of the material compared with the traditional single-stage annealing process, thereby improving the comprehensive performance of the iron-based nanocrystalline core.

[0038] The application can avoid stress concentration and microstructure defects caused by temperature mutation by gradually increasing the temperature. The magnetic permeability can be improved and the magnetic loss can be reduced by keeping the temperature at a certain temperature. The microstructure can be quickly fixed by rapid cooling at the end, and the internal stress during the cooling process can be reduced.

[0039] The first stage of the annealing process in the application is rapid heating, preheating the material to make the temperature uniform and reduce the temperature gradient. The second stage of slow heating rate can reduce the thermal stress in the material and avoid cracks and deformation caused by temperature mutation. The third stage of slower heating rate can further reduce the thermal stress and ensure that the material is uniformly heated at high temperature; the temperature of this stage is close to or slightly higher than the crystallization temperature of the material, and the nanocrystalline phase begins to appear in the material; the formation of nanocrystals can significantly reduce the coercivity and improve the magnetic permeability, and the magnetic properties are preliminarily optimized. The fourth stage is the most critical stage of crystallization. The low heating rate and long time of keeping warm make the nanocrystalline structure uniform, and the addition of a transverse magnetic field can induce the ordered arrangement of magnetic domain structure, improve the magnetic permeability and reduce the magnetic loss. In the fifth stage, rapid cooling can quickly fix the microstructure of the material at high temperature, reduce the internal stress and microstructure changes during the cooling process.

[0040] Optionally, in the fourth stage, the transverse magnetic field is set to a current of 50-100A.

[0041] By adopting the above technical scheme, the transverse magnetic field generated by the current applied in the fourth stage of annealing treatment in the application has moderate strength, which can effectively induce the ordered arrangement of magnetic domain structure and avoid the negative effects of too strong magnetic field. The appropriate magnetic field strength improves the magnetic permeability and reduces the magnetic loss of the material, thereby improving the performance and stability of the inductor.

[0042] Optionally, in the step S6, the cryogenic treatment is to place the iron core at-180 to-200℃ for 120-150min.

[0043] By adopting the above technical scheme, the cryogenic treatment of the application can further improve the strength and toughness of the material, release the residual stress in the material, reduce the adverse effects of internal stress on the performance of the material, thereby optimizing the magnetic properties, improving the thermal stability of the material, and reducing the effects of temperature changes on the magnetic properties.

[0044] Optionally, the temperature of the cryogenic treatment can be provided by a liquid nitrogen environment.

[0045] Optionally, in the step S6, the epoxy powder coating includes bisphenol A type epoxy resin and a curing agent.

[0046] In summary, the application has the following at least one beneficial technical effect:

[0047] 1. The application can effectively improve the magnetic properties and stability of the core by optimizing the alloy composition, solving the problems of low high-frequency inductance, small impedance, and large temperature rise of inductor devices.

[0048] 2. The application improves the amorphous forming ability of the material, refines the grain, reduces the magnetic loss at high frequency, and improves the inductance and impedance of the inductor at high frequency by optimizing the proportions of elements such as Fe, B, Si, Nb, and Cu. By adding Nd element, the thermal stability of the material is improved, the influence of temperature change on magnetic properties is reduced, the temperature rise of the inductor during operation is reduced, and the long-term stability and reliability are improved.

[0049] 3. The preparation method of the application improves the uniformity, microstructure and magnetic properties of the material, and improves the overall performance and stability of the inductor.

[0050] 4. The preparation method of the application ensures uniform melting of each element by adding raw materials with different melting points in batches, avoiding local overheating or composition segregation. BRIEF DESCRIPTION OF DRAWINGS

[0051] Figure 1 Schematic diagram of the iron-based nanocrystalline core prepared for Example 2. DETAILED DESCRIPTION

[0052] In order to make the purpose, technical scheme and advantages of the application clearer, the application will be further described in detail below with examples. It should be understood that the specific examples described herein are only used to explain the application and not to limit the application.

[0053] The inventors of the application found in the research of preparing inductor cores that the existing technology is prone to have uneven composition of alloy ingot during melting process, and during the melting process, the metal is prone to react with oxygen in the air, resulting in the formation of inclusions and uneven composition, which further affects the stability of the product. Improper heat treatment process also causes problems such as coarse grains and decreased magnetic properties. These problems cause the existing iron-based nanocrystalline inductor devices to have low high-frequency inductance, small impedance, and large temperature rise in actual application.

[0054] In order to solve the above problems, the application provides an iron-based nanocrystalline core for inductor, which comprises the following elements in mass percentage: Fe: 80-85%, B: 5-9%, Si: 6-10%, Cu: 1-3%, Nb: 2-5%, Nd: 0.1-0.5%.

[0055] The preparation method comprises the following steps:

[0056] Step S1, put copper particles, boron-iron blocks, 10-30wt% of iron particles relative to the total mass of iron particles, silicon powder, neodymium powder, niobium-iron blocks, and the remaining iron particles into a vacuum induction melting furnace in sequence for melting, vacuum extraction to-100 to-120kPa, heating under argon atmosphere, and obtaining an alloy material after melting;

[0057] Step S2, add lime, fluorite, and silica to the alloy material as slagging materials, melt, and then pass in a mixed gas of argon and hydrogen for blowing, with a blowing time of 10-15min;

[0058] Step S3, vacuum extraction to-500 to-550kPa, maintaining negative pressure for 5-10min, stopping vacuum extraction and heating, and obtaining a master alloy ingot by furnace cooling;

[0059] Step S4, forming the master alloy ingot into a strip and winding to obtain an iron core;

[0060] Step S5, placing the iron core into a vacuum heat treatment furnace, vacuum extraction to-80 to-100kPa, passing in a protective gas, and performing annealing treatment;

[0061] Step S6, performing cryogenic treatment on the annealed iron core, then uniformly spraying epoxy powder coating on the surface of the iron core, and obtaining an iron-based nanocrystalline iron core after solidification.

[0062] The scheme of the present application will be described below in combination with the following specific embodiments. Unless otherwise specified, the raw materials used in the following embodiments are all from ordinary commercially available products, and the devices or equipment used are all purchased from conventional market sales channels. Specific embodiments

[0064] The preparation method of the epoxy powder coating used in Examples 1-4 is as follows: mixing bisphenol A type epoxy resin and a curing agent, then melting and extruding at 110℃, and crushing to obtain an epoxy powder coating; wherein the mass ratio of bisphenol A type epoxy resin to curing agent is 100:15. The bisphenol A type epoxy resin is bisphenol A type epoxy resin BE-501, and the curing agent is an amino-terminated polyether D-230.

[0065] Example 1

[0066] The present embodiment provides an iron-based nanocrystalline iron core for an inductor, which comprises the following elements in mass percentage: Fe: 80%, B: 9%, Si: 6%, Cu: 2.9%, Nb: 2%, and Nd: 0.1%.

[0067] The preparation method comprises the following steps:

[0068] Step S1, put copper particles, boron-iron blocks, 10wt% of iron particles relative to the total mass of iron particles, silicon powder, neodymium powder, niobium-iron blocks, and the remaining iron particles into a vacuum induction melting furnace in sequence for melting, vacuum extraction to-100kPa, heating in an argon atmosphere, and obtaining an alloy material after melting; wherein the heating power is 100KW, the heating temperature is 1600℃, and the purity of argon is ≥99.99%;

[0069] Step S2, add lime, fluorite, and silica as slagging materials to the alloy material, melt, and then pass in a mixed gas of argon and hydrogen for blowing, and the blowing time is 10min;

[0070] Step S3, vacuum extraction to-500kPa, maintain negative pressure for 5min, stop vacuum extraction and heating, and cool down with the furnace to obtain a master alloy ingot;

[0071] Step S4, the master alloy ingot is made into a strip material with a thickness of 16μm and a width of 10mm, and the strip material is wound to obtain an iron core;

[0072] Step S5, put the iron core into a vacuum heat treatment furnace, vacuum extraction to-80kPa, and pass in a protective gas for annealing treatment; wherein the protective gas is a mixed gas of nitrogen and hydrogen, the volume percentage of nitrogen is 98%, the volume percentage of hydrogen is 2%, and the gas flow is 300mL·min -1 .

[0073] The annealing treatment is divided into five stages:

[0074] In the first stage, the temperature in the furnace is raised to 200℃ at a heating rate of 20℃ / min, and the temperature is maintained for 30min;

[0075] In the second stage, the temperature in the furnace is raised to 370℃ at a heating rate of 5℃ / min, and the temperature is maintained for 20min;

[0076] In the third stage, the temperature in the furnace is raised to 500℃ at a heating rate of 3℃ / min, and the temperature is maintained for 60min;

[0077] In the fourth stage, the temperature in the furnace is raised to 560℃ at a heating rate of 1℃ / min, a transverse magnetic field is added, the current is set to 50A, and the temperature is maintained for 60min;

[0078] In the fifth stage, the temperature in the furnace is lowered to 200℃ at a cooling rate of 30℃ / min.

[0079] Step S6, the annealed iron core is subjected to cryogenic treatment, i.e., the iron core is placed at-180℃ for 120min, then epoxy powder paint is uniformly sprayed on the surface of the iron core, and the iron-based nanocrystalline iron core is obtained after solidification.

[0080] Example 2

[0081] The embodiment provides an iron-based nanocrystalline core for an inductor, which comprises the following elements in percentage by mass: Fe: 81.6%, B: 6%, Si: 7.1%, Cu: 2%, Nb: 3%, and Nd: 0.3%.

[0082] The preparation method comprises the following steps:

[0083] In step S1, copper particles, boron-iron blocks, iron particles with a total mass of 20 wt%, silicon powder, neodymium powder, niobium-iron blocks and the remaining iron particles are sequentially put into a vacuum induction melting furnace for melting, vacuum extraction is performed to-110 kPa, heating is performed in an argon atmosphere, and the alloy material is prepared after melting; wherein the heating power is 100 KW, the heating temperature is 1600 DEG C, and the purity of argon is greater than or equal to 99.99%.

[0084] In step S2, lime, fluorite and silica are added to the alloy material as slagging materials, after melting, argon and hydrogen mixed gas is introduced for blowing, and the blowing time is 12.5 min.

[0085] In step S3, vacuum extraction is performed to-525 kPa, the negative pressure is maintained for 7.5 min, vacuum extraction and heating are stopped, and the furnace is cooled to prepare a master alloy ingot.

[0086] In step S4, the master alloy ingot is prepared into a strip material with a thickness of 16 microns and a width of 10 mm, and the strip material is wound to prepare the core.

[0087] In step S5, the core is put into a vacuum heat treatment furnace, vacuum extraction is performed to-90 kPa, and a protective gas is introduced for annealing treatment; wherein the protective gas is a mixed gas of nitrogen and hydrogen, the volume percentage of nitrogen is 98%, the volume percentage of hydrogen is 2%, and the gas flow is 300 mL·min -1 .

[0088] The annealing treatment is divided into five stages.

[0089] In the first stage, the temperature in the furnace is raised to 200 DEG C at a temperature raising rate of 20 DEG C / min, and the temperature is maintained for 30 min.

[0090] In the second stage, the temperature in the furnace is raised to 370 DEG C at a temperature raising rate of 5 DEG C / min, and the temperature is maintained for 20 min.

[0091] In the third stage, the temperature in the furnace is raised to 500 DEG C at a temperature raising rate of 3 DEG C / min, and the temperature is maintained for 60 min.

[0092] In the fourth stage, the temperature in the furnace is raised to 560 DEG C at a temperature raising rate of 1 DEG C / min, a transverse magnetic field is added, the current is set to 50 A, and the temperature is maintained for 60 min.

[0093] Fifth stage: the furnace temperature is decreased to 200℃ at a cooling rate of 30℃ / min.

[0094] Step S6, the annealed iron core is subjected to cryogenic treatment, that is, the iron core is placed in liquid nitrogen at-196℃ for 120min, then epoxy powder paint is uniformly sprayed on the surface of the iron core, and the iron-based nanocrystalline iron core is prepared after curing.

[0095] Example 3

[0096] The embodiment provides an iron-based nanocrystalline iron core for an inductor, which comprises the following elements in percentage by mass: Fe: 84%, B: 5%, Si: 6%, Cu: 1%, Nb: 3.5%, and Nd: 0.5%.

[0097] The preparation method comprises the following steps:

[0098] Step S1, sequentially put copper particles, boron-iron blocks, iron particles accounting for 30wt% of the total mass of the iron particles, silicon powder, neodymium powder, niobium-iron blocks, and the remaining iron particles into a vacuum induction melting furnace for melting, vacuumize to-120kPa, heat in an argon atmosphere, and prepare an alloy material after melting; wherein the heating power is 100KW, and the heating temperature is 1600℃; the purity of argon is greater than or equal to 99.99%;

[0099] Step S2, add lime, fluorite and silica to the alloy material as slagging materials, melt, and then pass argon and hydrogen mixed gas to perform blowing, and the blowing time is 15min;

[0100] Step S3, vacuumize to-550kPa, maintain negative pressure for 10min, stop vacuumizing and heating, and cool down with the furnace to prepare a master alloy ingot;

[0101] Step S4, the master alloy ingot is made into a strip, the thickness of the strip is 16μm, the width of the strip is 10mm, and the strip is wound to prepare an iron core;

[0102] Step S5, place the iron core into a vacuum heat treatment furnace, vacuumize to-100kPa, and pass a protective gas to perform annealing treatment; wherein the protective gas is a mixed gas of nitrogen and hydrogen, the volume percentage of nitrogen is 98%, the volume percentage of hydrogen is 2%, and the gas flow is 300mL·min -1 .

[0103] The annealing treatment is divided into five stages:

[0104] First stage, the furnace temperature is increased to 200℃ at a heating rate of 20℃ / min, and the temperature is maintained for 30min;

[0105] Second stage: the furnace temperature is increased to 370℃ at a heating rate of 5℃ / min, and the temperature is maintained for 20min;

[0106] The third stage: the temperature in the furnace is raised to 500 DEG C at a temperature raising rate of 3 DEG C / min, and the temperature is kept for 60 min;

[0107] The fourth stage: the temperature in the furnace is raised to 560 DEG C at a temperature raising rate of 1 DEG C / min, a transverse magnetic field is added, the current is set to 50 A, and the temperature is kept for 60 min;

[0108] The fifth stage: the temperature in the furnace is reduced to 200 DEG C at a temperature reducing rate of 30 DEG C / min.

[0109] Step S6: the annealed iron core is subjected to cryogenic treatment, that is, the iron core is kept at -200 DEG C for 120 min, then the surface of the iron core is uniformly sprayed with epoxy powder coating, and the iron-based nanocrystalline iron core is prepared after solidification.

[0110] Example 4

[0111] The embodiment provides an iron-based nanocrystalline iron core for an inductor, which comprises the following elements in percentage by mass: Fe: 80%, B: 5%, Si: 8.9%, Cu: 1%, Nb: 5%, and Nd: 0.1%.

[0112] The preparation method comprises the following steps:

[0113] Step S1: copper particles, boron-iron blocks, iron particles with a total mass of 30 wt%, silicon powder, neodymium powder, niobium-iron blocks, and the remaining iron particles are sequentially put into a vacuum induction melting furnace for melting, vacuum extraction is performed to -120 kPa, heating is performed in an argon atmosphere, and the alloy material is prepared after melting; wherein the heating power is 100 KW, the heating temperature is 1600 DEG C, and the purity of the argon is greater than or equal to 99.99%.

[0114] Step S2: lime, fluorite and silica are added to the alloy material as slagging materials, after melting, argon and hydrogen mixed gas is introduced for blowing, and the blowing time is 15 min;

[0115] Step S3: vacuum extraction is performed to -550 kPa, the negative pressure is kept for 10 min, vacuum extraction and heating are stopped, and the furnace is cooled to prepare a master alloy ingot;

[0116] Step S4: the master alloy ingot is made into a strip, the thickness of the strip is 16 mu m, the width of the strip is 10 mm, and the strip is wound to prepare an iron core;

[0117] Step S5: the iron core is put into a vacuum heat treatment furnace, vacuum extraction is performed to -100 kPa, and a protective gas is introduced for annealing treatment; wherein the protective gas is a mixed gas of nitrogen and hydrogen, the volume percentage of the nitrogen is 98%, the volume percentage of the hydrogen is 2%, and the gas flow is 300 mL / min. -1 .

[0118] The annealing process is divided into five stages:

[0119] In the first stage, the temperature in the furnace is raised to 200 DEG C at a rate of 20 DEG C / min, and held for 30 min;

[0120] In the second stage, the temperature in the furnace is raised to 370 DEG C at a rate of 5 DEG C / min, and held for 20 min;

[0121] In the third stage, the temperature in the furnace is raised to 500 DEG C at a rate of 3 DEG C / min, and held for 60 min;

[0122] In the fourth stage, the temperature in the furnace is raised to 560 DEG C at a rate of 1 DEG C / min, a transverse magnetic field is added, the current is set to 50 A, and the temperature is held for 60 min;

[0123] In the fifth stage, the temperature in the furnace is lowered to 200 DEG C at a rate of 30 DEG C / min.

[0124] In step S6, the annealed iron core is subjected to cryogenic treatment, i.e., the iron core is placed at -180 DEG C for 120 min, then epoxy powder paint is uniformly sprayed on the surface of the iron core, and the iron-based nanocrystalline iron core is obtained after solidification.

[0125] Comparative Example 1

[0126] Comparative Example 1 differs from Example 2 in that Comparative Example 1 does not contain Nd element, and contains the following elements by mass percentage: Fe: 81.6%, B: 6%, Si: 7.1%, Cu: 2%, Nb: 3.3%.

[0127] Comparative Example 2

[0128] Comparative Example 2 differs from Example 2 in that in the preparation method of Comparative Example 2, all raw materials are simultaneously placed in the vacuum induction melting furnace for melting in step S1.

[0129] Comparative Example 3

[0130] Comparative Example 3 differs from Example 2 in that in the preparation method of Comparative Example 3, step S6 does not contain cryogenic treatment, and the epoxy powder paint is directly sprayed after room temperature cooling.

[0131] Comparative Example 4

[0132] Comparative Example 4 is an iron core purchased from the market, and the size of the iron core is: inner diameter 32 mm, outer diameter 40 mm, and height 18 mm; the iron core contains the following elements: Fe: 74%, B: 9%, Si: 13%, Cu: 1%, and Nb: 3%.

[0133] Experimental detection

[0134] Detection method: the iron-based nanocrystalline iron core (inner diameter of 32 mm, outer diameter of 40 mm, height of 18 mm) is wound with 1.9 mm copper wire double line 5 times, three windings are wound on the same core to make common mode inductance, and the inductance and impedance value of the inductor are analyzed by impedance analyzer.

[0135] The iron-based nanocrystalline iron cores prepared in examples 1-4 and comparative examples 1-4 are made into common mode inductance, and the inductance and impedance value are detected under the condition that the frequency is 300-1000 kHz. The detection results are shown in table 1.

[0136] Table 1

[0137]

[0138] From the detection results in table 1, it can be seen that the common mode inductance prepared by the iron-based nanocrystalline iron core prepared in examples 1-4 has high inductance and large impedance, which solves the problem of low inductance and small impedance of inductor at high frequency.

[0139] Comparative example 1 does not contain Nd element, and the common mode inductance prepared by the iron-based nanocrystalline iron core has a significant decrease in inductance and impedance value compared with example 2.

[0140] Comparative example 2 does not add raw materials in order, and comparative example 3 does not contain deep cooling treatment. The common mode inductance prepared by the iron-based nanocrystalline iron core prepared in comparative examples 2 and 3 has a decrease in inductance and impedance value.

[0141] Comparative example 4 is an iron core purchased on the market, and the inductance and impedance value of the common mode inductance prepared by the iron core is significantly lower than that of the common mode inductance prepared by the iron-based nanocrystalline iron core prepared in the application.

[0142] Examples 5-10

[0143] Example 5

[0144] The difference between example 5 and example 2 is that in step S1 of example 5, the heating power is 125 KW and the heating temperature is 1650℃.

[0145] Example 6

[0146] The difference between example 6 and example 2 is that in step S1 of example 6, the heating power is 150 KW and the heating temperature is 1700℃.

[0147] Example 7

[0148] The difference between example 7 and example 5 is that in step S5 of example 7, the gas flow of the protective gas is 400 mL·min -1 .

[0149] Example 8

[0150] The difference between example 8 and example 5 is that in step S5 of example 8, the gas flow of the protective gas is 500 mL·min -1 .

[0151] Example 9

[0152] The difference between example 9 and example 8 is that in step S5 of example 9, the annealing process is divided into five stages:

[0153] First stage, the temperature in the furnace is raised to 210 DEG C at a rate of 25 DEG C / min, and the temperature is kept for 35 min;

[0154] Second stage: the temperature in the furnace is raised to 385 DEG C at a rate of 8 DEG C / min, and the temperature is kept for 25 min;

[0155] Third stage: the temperature in the furnace is raised to 510 DEG C at a rate of 4 DEG C / min, and the temperature is kept for 75 min;

[0156] Fourth stage: the temperature in the furnace is raised to 565 DEG C at a rate of 1 DEG C / min, a transverse magnetic field is added, the current is set to 75 A, and the temperature is kept for 70 min;

[0157] Fifth stage: the temperature in the furnace is lowered to 210 DEG C at a rate of 40 DEG C / min.

[0158] Example 10

[0159] The difference between example 10 and example 8 is that in step S5 of example 10, the annealing process is divided into five stages:

[0160] First stage, the temperature in the furnace is raised to 220 DEG C at a rate of 30 DEG C / min, and the temperature is kept for 40 min;

[0161] Second stage: the temperature in the furnace is raised to 400 DEG C at a rate of 10 DEG C / min, and the temperature is kept for 30 min;

[0162] Third stage: the temperature in the furnace is raised to 520 DEG C at a rate of 5 DEG C / min, and the temperature is kept for 90 min;

[0163] Fourth stage: the temperature in the furnace is raised to 570 DEG C at a rate of 1 DEG C / min, a transverse magnetic field is added, the current is set to 100 A, and the temperature is kept for 80 min;

[0164] Fifth stage: the temperature in the furnace is lowered to 220 DEG C at a rate of 50 DEG C / min.

[0165] The iron-based nanocrystalline iron cores prepared in examples 5-10 are made into common mode inductors, and the inductance and impedance values are detected under the condition that the frequency is 300-1000 kHz, and the detection results are shown in table 2.

[0166] Table 2

[0167]

[0168] From the detection results of Table 2, it can be seen that the difference between Example 5, Example 6 and Example 2 is that the heating power and heating temperature in step S1 are different, wherein the common mode inductance made of the iron-based nanocrystalline iron core prepared in Example 5 has the highest inductance and impedance value.

[0169] The difference between Example 7, Example 8 and Example 5 is that the gas flow of the protective gas in step S5 is different, wherein the common mode inductance made of the iron-based nanocrystalline iron core prepared in Example 8 has the highest impedance value.

[0170] The difference between Example 9, Example 10 and Example 8 is that the parameters of the annealing treatment in step S5 are different, wherein the common mode inductance made of the iron-based nanocrystalline iron core prepared in Example 9 has the highest inductance and impedance value.

[0171] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement and improvement made within the principles of the present application shall be included in the protection scope of the present application.

Claims

1. An iron-based nanocrystalline core for an inductor, characterized by, According to the mass percentage, the alloy comprises the following elements: Fe: 80-85%, B: 5-9%, Si: 6-10%, Cu: 1-3%, Nb: 2-5%, Nd: 0.1-0.5%. The preparation method of the inductor with the iron-based nanocrystalline core comprises the following steps: In step S1, copper particles, boron-iron blocks, iron particles with a mass percentage of 10-30wt% of the total mass of iron particles, silicon powder, neodymium powder, niobium-iron blocks, and the remaining iron particles are sequentially put into a vacuum induction melting furnace for melting, vacuum extraction to-100 to-120kPa, heating in an argon atmosphere, and then alloy material is prepared after melting; In step S2, lime, fluorite, and silica are added to the alloy material as slagging materials, and after melting, argon and hydrogen mixed gas is introduced for blowing, and the blowing time is 10-15min; In step S3, vacuum extraction is performed to-500 to-550kPa, and the negative pressure is maintained for 5-10min, then vacuum extraction and heating are stopped, and the furnace is cooled to prepare a master alloy ingot; In step S4, the master alloy ingot is made into a strip, and the iron core is prepared by winding; In step S5, the iron core is placed in a vacuum heat treatment furnace, vacuum extraction is performed to-80 to-100kPa, and protective gas is introduced for annealing treatment; In step S6, the annealed iron core is subjected to cryogenic treatment, and then epoxy powder paint is uniformly sprayed on the surface of the iron core, and the iron-based nanocrystalline core is prepared after solidification; In step S5, the annealing treatment is divided into five stages: In the first stage, the temperature in the furnace is raised to 200-220℃ at a heating rate of 20-30℃ / min, and the temperature is maintained for 30-40min; In the second stage, the temperature in the furnace is raised to 370-400℃ at a heating rate of 5-10℃ / min, and the temperature is maintained for 20-30min; In the third stage, the temperature in the furnace is raised to 500-520℃ at a heating rate of 3-5℃ / min, and the temperature is maintained for 60-90min; In the fourth stage, the temperature in the furnace is raised to 560-570℃ at a heating rate of 1℃ / min, a transverse magnetic field is added, and the temperature is maintained for 60-80min; In the fifth stage, the temperature in the furnace is lowered to 200-220℃ at a cooling rate of 30-50℃ / min; In step S6, the cryogenic treatment is to place the iron core at-180 to-200℃ for 120-150min.

2. The Fe-based nanocrystalline core for an inductor according to claim 1, characterized by The iron-based nanocrystalline core comprises the following elements: Fe: 81.6-83%, B: 6-8%, Si: 7.08-8%, Cu: 2-2.5%, Nb: 3-4%, and Nd: 0.3-0.4%.

3. The Fe-based nanocrystalline core for an inductor according to claim 1, characterized by In step S1, the heating power is 100-150KW, and the heating temperature is 1600-1700℃; the purity of argon is ≥99.99%.

4. The Fe-based nanocrystalline core for an inductor according to claim 1, characterized by In step S4, the thickness of the strip is 16-20μm, and the width is 10-20mm.

5. The Fe-based nanocrystalline core for an inductor according to claim 1, characterized by In the step S5, the protective gas is a mixture of nitrogen and hydrogen, the volume percentage of nitrogen is 95-98%, the volume percentage of hydrogen is 2-5%, and the gas flow rate is 300-500 mL·min -1 .

6. The Fe-based nanocrystalline core for inductors according to claim 1, characterized by, In the fourth stage, the current of the transverse magnetic field is set to 50-100A.

7. The iron-based nanocrystalline core for inductors according to claim 1, characterized by, In step S6, the epoxy powder paint comprises bisphenol A type epoxy resin and a curing agent.

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