A semi-annular iron-based nanocrystalline magnetic core with high permeability and low loss and its preparation method

Abstract

The application provides a high-permeability and low-loss semi-ring type iron-based nanocrystalline magnetic core and a preparation method thereof, and belongs to the technical field of preparation of iron-based nanocrystalline soft magnetic alloy magnetic rings. The preparation method comprises the following steps: winding an iron-based nanocrystalline strip into a to-be-processed magnetic core with a set filling factor; performing composite magnetic field heat treatment, which comprises a first stage heat treatment of applying a transverse magnetic field and a second stage heat treatment without a magnetic field; pre-baking the magnetic core after the heat treatment, and performing immersion treatment so that an immersion liquid penetrates into the magnetic core; then, completely fixing the inner diameter and the outer diameter of the magnetic core by using a mold, performing 360° rotary baking, and realizing solidification of the immersion liquid; and cutting the magnetic core, polishing the cut end face by using sandpaper, and grinding the cut end face by using iron-based nanocrystalline metal powder, so as to obtain the semi-ring type iron-based nanocrystalline magnetic core with high permeability and low loss. The semi-ring type iron-based nanocrystalline magnetic core with high permeability and low loss is prepared by using an innovative amorphous alloy composition and an alloy preparation method, and has excellent performances such as high permeability and low magnetic loss, and has a great application prospect.

Description

Technical Field

[0001] This invention belongs to the technical field of iron-based nanocrystalline soft magnetic alloy magnetic ring material preparation, and specifically relates to a semi-ring-shaped iron-based nanocrystalline magnetic core with high magnetic permeability and low loss and its preparation method. Background Technology

[0002] Amorphous and nanocrystalline soft magnetic alloys possess high permeability, low coercivity, and excellent high-frequency soft magnetic properties, earning them the title of 21st-century green electronic materials. In recent years, they have received widespread attention and research from academia and industry. With the rapid development of computer network technology, 5G communication, electric vehicles, photovoltaic new energy, and multimedia technology, electronic devices are required to be miniaturized, energy-efficient, and operate at high frequencies. This places newer and higher demands on soft magnetic materials, requiring them to possess higher saturation magnetic induction, higher permeability, lower losses, and good high-frequency performance.

[0003] In recent years, with the continuous development and upgrading of electrical equipment, the requirements for the performance of electrical materials have become increasingly stringent. Transformers, as one of the most important pieces of equipment in the power industry, directly affect the stable operation of the power grid and the efficient utilization of electrical energy. The cutting of the transformer's core component, the iron core, is one of the key factors affecting its performance. Currently, the most common material for cutting the iron core is silicon steel sheet, but its magnetic permeability is low, and its hysteresis loss and eddy current loss are relatively high, seriously affecting the transformer's energy efficiency and stability. Simultaneously, with the development of third-generation semiconductor technology, power electronics technology is moving towards high frequency and high power. For example, the operating current of modules such as on-board chargers for new energy vehicles, DC-DC converters, and motor controllers is increasing, thus copper busbars are increasingly used in current loops in circuits. Ordinary closed-loop common-mode inductors can no longer meet this demand. Currently, the half-cut design solves this problem, facilitating installation, preserving high magnetic permeability and low loss, and allowing for high current carrying capacity.

[0004] To improve the magnetic permeability and reduce magnetic loss of diced iron cores, researchers are now incorporating nanocrystalline materials into the fabrication process. Nanocrystalline materials possess characteristics such as small particle size, uniform grain size, and dense grain boundaries, which can effectively improve the magnetic properties of the material.

[0005] Currently, iron-based nanocrystalline magnetic rings on the market are cut in half to form cut magnetic cores. However, after cutting, the magnetic cores will spread out and there will be gaps on the cut surfaces, making it difficult to retain high permeability and low loss. This results in defects such as low permeability and high loss in the cut magnetic cores.

[0006] Therefore, there is an urgent need for an iron-based nanocrystalline magnetic core that retains high permeability and low loss even after being halved, and its preparation method. Summary of the Invention

[0007] Therefore, the present invention aims to provide a semi-toroidal iron-based nanocrystalline magnetic core with high permeability and low loss and its preparation method, in order to solve at least one technical problem in the background art.

[0008] This invention is implemented as follows:

[0009] A method for preparing a high-permeability, low-loss semi-toroidal iron-based nanocrystalline magnetic core, characterized in that the preparation method includes the following steps:

[0010] Iron-based nanocrystalline ribbons are wound into magnetic cores with a set fill factor.

[0011] Composite magnetic field heat treatment includes a first-stage heat treatment with an applied transverse magnetic field and a second-stage heat treatment without a magnetic field.

[0012] The heat-treated magnetic core is pre-baked and impregnated to allow the impregnating liquid to penetrate the core; then, a mold is used to completely fix the inner and outer diameters of the magnetic core, and it is rotated 360° to bake, thus solidifying the impregnating liquid.

[0013] The magnetic core is cut, and the cut end face is polished with sandpaper and ground with iron-based nanocrystalline metal powder to obtain a semi-ring-shaped iron-based nanocrystalline magnetic core with high magnetic permeability and low loss.

[0014] Preferably, the first stage of heat treatment in the composite magnetic field heat treatment, which involves applying a transverse magnetic field, specifically includes:

[0015] The magnetic core is placed in a heat treatment furnace that has been heated to the initial temperature, a transverse magnetic field is applied, and the temperature is raised to the first temperature at a rate of 1 to 3 °C / min and then held for 30 to 90 min.

[0016] After heating to the second temperature at a rate of 0.5–5 °C / min, hold the temperature for 30–90 min.

[0017] The first temperature is set to 410–430°C, and the second temperature is set to 470–490°C.

[0018] Preferably, the magnetic induction intensity of the transverse magnetic field is 1000 Gs.

[0019] Preferably, the second stage of heat treatment without a magnetic field in the composite magnetic field heat treatment specifically includes:

[0020] After the first stage of heat treatment is completed, the transverse magnetic field is turned off, and the temperature is reduced to the third temperature at a cooling rate of 1 to 10°C, and held for 10 to 50 minutes.

[0021] Increase the temperature to the fourth temperature at a rate of 1–10°C and hold for 30–90 minutes.

[0022] Increase the temperature to the fifth temperature at a rate of 0.5–3°C and hold for 30–120 minutes.

[0023] Finally, air-cool to the sixth temperature before removing from the oven;

[0024] The third temperature is set to 370–390°C; the fourth temperature is set to 470–490°C; the fifth temperature is set to 540–560°C; and the sixth temperature is set to 200–350°C.

[0025] Preferably, the fill factor of the magnetic core to be processed is set to 0.78 to 0.85.

[0026] Preferably, the impregnation treatment specifically includes:

[0027] The pre-baked magnetic core undergoes vacuum impregnation treatment, allowing the impregnation liquid to penetrate into the voids of the magnetic core.

[0028] The magnetic core is placed in an environment free of impregnation liquid and subjected to vacuum dry evacuation;

[0029] Clean the surface of the magnetic core of any remaining impregnation solution.

[0030] Preferably, the impregnating liquid is an insulating varnish.

[0031] Preferably, the cutting end face is polished with sandpaper and ground with iron-based nanocrystalline metal powder, specifically including:

[0032] Use at least two different grit sandpapers to polish the end face of the cut magnetic core in sequence;

[0033] Iron-based nanocrystalline metal powder with D50 = 45~55μm was used as the grinding and polishing powder to grind and polish the end face;

[0034] Preferably, the sandpaper has a grit of 1200 to 2000, and sanding is performed sequentially from coarse to fine sandpaper; the sanding time for each grit is set to 20 ± 5 minutes.

[0035] The above method produces a semi-ring-shaped iron-based nanocrystalline magnetic core with high permeability and low magnetic loss, which can retain both high permeability and low magnetic loss.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] 1. This invention addresses the problems existing in the prior art by proposing a method for preparing a high-permeability, low-loss, half-cut nanocrystalline magnetic ring through innovative amorphous alloy composition and alloy preparation methods. Experimental tests show that the nanocrystalline cut iron core has excellent properties of high permeability and low magnetic loss, and has great application prospects.

[0038] 2. The present invention adopts a composite magnetic field heat treatment process that first heats up, then cools down, and then heats up again, while simultaneously applying a transverse magnetic field at the front end and closing the magnetic field at the rear end. This process maintains constant magnetic permeability and low loss after heat treatment.

[0039] 3. This invention combines vacuum impregnation with vacuum dry drying and 360° rotation baking to ensure uniform adhesive between the strip layers inside the magnetic ring, avoiding delamination which leads to poor curing effect and defects such as low magnetic permeability and high loss.

[0040] 4. The present invention uses iron-based nanocrystalline metal powder to grind the end face, and its grinding and polishing effect is better than that of sandpaper and polishing in the prior art. After grinding, the nanocrystalline powder makes the end face of the magnetic core flatter and coats the end with a layer of magnetic powder, resulting in higher magnetic permeability. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of the temperature program for the composite magnetic field heat treatment in this invention;

[0042] Figure 2 This is a schematic diagram of the mold used for fixing the magnetic core in this invention;

[0043] Figure 3 This is a schematic diagram of the structure in which the magnetic core is fixed in the mold in this invention;

[0044] Figure 4 The end face views of the iron-based nanocrystalline magnetic cores after cutting in Comparative Example 3(A) and Example 1(B);

[0045] Figure 5 This is a schematic diagram of the temperature program for heat treatment in Comparative Example 1.

[0046] Illustration: 1-Mold body, 2-Outer fixing ring, 3-Inner fixing ring, 4-Rotating rod, 5-Magnetic core. Detailed Implementation

[0047] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0048] The high-permeability, low-loss semi-toroidal iron-based nanocrystalline magnetic core of this invention comprises the following steps:

[0049] S1, magnetic ring system

[0050] Using Fe 73.5-a Nb3Cu1(SiB )22.5 M a(at%) iron-based nanocrystalline ribbon (where M is a rare earth element, 0≤a≤2) is wound into a magnetic core using an automatic winding machine. The appropriate tension of the ribbon is adjusted during the winding of the magnetic core. In this invention, the ribbon should not be pulled too loosely when winding the magnetic core, and the filling coefficient N can be controlled at 0.78-0.85.

[0051] S2, Composite magnetic field heat treatment of magnetic core

[0052] Since cutting magnetic cores requires both curing and dicing, and it is necessary to maintain high permeability and low loss after cutting, the heat treatment process of the magnetic cores requires relatively strict requirements. To ensure that the magnetic cores maintain constant permeability and low loss after heat treatment, this invention employs the following... Figure 1 The composite magnetic field heat treatment process shown includes the following specific treatment:

[0053] (1) The first stage of heat treatment was carried out under the action of a transverse magnetic field of 1000 Gs.

[0054] First, place the magnetic core into a heat treatment furnace that has been heated to the initial temperature, and raise the temperature to 410-430℃ at a heating rate of 1-3℃ / min, and hold it at that temperature for 30-90 minutes.

[0055] After the heat preservation is completed, the temperature is increased to 470~490℃ at a rate of 0.5-5℃ / min and maintained for 30-90 minutes;

[0056] (2) Second stage heat treatment without magnetic field

[0057] After the first stage of heat treatment is completed, the transverse magnetic field is turned off, and the temperature is reduced to 370-390℃ at a cooling rate of 1-10℃, and held for 10-50 minutes.

[0058] Heat to 470–490°C at a rate of 1–10°C and hold for 30–90 minutes;

[0059] Heat to 540–560℃ at a rate of 0.5–3℃ and hold for 30–120 minutes;

[0060] Finally, air-cool to 200-350℃ before removing from the oven.

[0061] S3, Core impregnation and curing

[0062] Currently, the main reason why the permeability of iron-based nanocrystalline magnetic rings that are cut in half is not high is related to the curing of the impregnation resin. Since the impregnation is done with insulating varnish followed by high-temperature baking, the varnish, being liquid, inevitably flows during baking, causing delamination of the impregnated core. This results in poor curing, leading to the core spreading out after cutting, gaps on the cut surface, low permeability, and high losses. This invention improves the curing process after impregnation, thus completely eliminating the above problems. Specifically, the following treatment is performed:

[0063] (1) Pre-baking

[0064] After heat treatment, the magnetic core is placed in an oven for pre-baking, usually set to 80℃ for 1 hour, but can be adjusted according to actual needs.

[0065] (2)Vacuum impregnation

[0066] The pre-baked magnetic core is immersed in insulating varnish for impregnation, with a vacuum maintained throughout the process. The vacuum impregnation time is approximately 15 minutes to ensure complete immersion. The core is then removed and placed back into the vacuum impregnation machine's rack for another 15 minutes to remove excess adhesive from the core and ensure uniform adhesive distribution between the strip layers inside the magnetic ring. Finally, the impregnated core is removed, and excess insulating varnish on the end faces is wiped clean with blotting paper.

[0067] (3) 360° rotating baking

[0068] Place the magnetic core into a custom-made container, such as... Figure 2 The mold shown can completely fix the inner and outer diameters of the magnetic core, ensuring that the magnetic core is 100% fixed and will not be deformed. After the magnetic core is fixed in the mold, it is placed in an oven and a fixed motor drives the mold to rotate 360° for baking. This ensures that the insulating varnish inside the magnetic core is uniform from beginning to end and will not flow from one end to the other, thus preventing the phenomenon mentioned above.

[0069] like Figure 2 and Figure 3As shown, the mold includes two sets of symmetrical mold bodies 1. Each set of mold bodies 1 includes two sets of concentric fixed ring cylinders, namely an outer fixed ring cylinder 2 for fixing the outer diameter of the magnetic core and an inner fixed ring cylinder 3 for fixing the inner diameter of the magnetic core. One end of the inner fixed ring cylinder 3 and the outer fixed ring cylinder 2 are connected to form an integral structure. At least two sets of symmetrical rotating rods 4 are provided on the outer wall of each set of mold bodies 1. In specific implementation, the magnetic core 5 is first fitted onto the lower mold body 1, wherein the magnetic core 5 is embedded in the cavity between the inner fixed ring cylinder 3 and the outer fixed ring cylinder 2. Then, the upper mold body 1 and the lower mold body 1 are merged into one, and the upper and lower sets of mold bodies 1 cover the magnetic core. At the same time, the rotating rods 4 outside the upper and lower mold bodies 1 can be merged into a rotating shaft. The rotating shaft is connected to the steering transmission mechanism of the fixed motor. After the motor is started, the mold can be rotated 360° by rotating the rotating shaft.

[0070] S4, Core Cutting

[0071] (1) Cut in half

[0072] The cured magnetic core is placed in a grinding wheel cutting machine with a mesh size of about 600 and a thickness of about 0.5-1.0mm. It is fixed and positioned with a clamp to ensure that the center of the magnetic core and the grinding wheel are on the same straight line, so that the magnetic core can be cut in half 100%.

[0073] (2) Grinding and polishing

[0074] Currently, the traditional grinding and polishing methods in the industry involve using sandpaper of varying coarseness to fineness for grinding, followed by polishing with a polishing cloth. While this method can achieve a mirror finish, it still cannot ensure that the cross-sections of the cut magnetic core fit together perfectly.

[0075] Therefore, this invention first uses at least two different grits of sandpaper, from coarse to fine, to polish the end face of the cut magnetic core, with each grit lasting 20±5 minutes. Then, iron-based nanocrystalline metal powder with D50 = 45~55μm is used as the grinding and polishing powder to polish the end face. Because the nanocrystalline powder has a very fine particle size, it is better than all sandpaper and polishing paste on the market. At the same time, since the nanocrystalline powder is basically the same as the matrix composition of the magnetic core we cut, and the nanocrystalline powder has a magnetic permeability of 50-125H / m, the grinding can make the end face of the magnetic core flatter and coated with a layer of magnetic powder, resulting in higher magnetic permeability after being cut in half. The grinding time and the particle size of the polishing powder can be within the above range. For example, the grinding time can be 15min, 18min, 20min, 22min or 25min, and the polishing powder D50 can be 45μm, 47μm or 50μm, 52μm or 55μm, but it is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0076] Example 1

[0077] A magnetic ring with OD*ID*HT = 90*50*30mm was fabricated using the above process as a high-permeability, low-loss semi-ring-shaped iron-based nanocrystalline magnetic core. The specific steps include the following:

[0078] S1, magnetic ring system

[0079] Iron-based nanocrystalline ribbon with a thickness of 20-23 μm was used, and the ribbon was wound into a magnetic core using an automatic winding machine. The filling factor N was controlled to be 0.78.

[0080] S2, Heat treatment process

[0081] The temperature inside the heat treatment furnace is heated to 300℃. The magnetic core is placed in the heat treatment furnace, and a transverse magnetic field of 1000Gs is applied. The temperature is increased to 420℃ at a rate of 1℃ / min and held for 30 minutes. After holding, the temperature is increased to 480℃ at a rate of 2℃ / min and held for 60 minutes while keeping the transverse magnetic field constant. After holding, the transverse magnetic field is turned off, and the temperature is decreased to 380℃ at a rate of 5℃ and held for 30 minutes. Then, the temperature is increased to 480℃ at a rate of 5℃ / min and held for 60 minutes. Then, the temperature is increased to 550℃ at a rate of 1℃ / min and held for 90 minutes. Finally, the temperature is air-cooled to 350℃ before being removed from the furnace.

[0082] After heat treatment, the measured inductance values ​​of the magnetic core are AL = 300 μH @ 10 kHz; AL = 84 μH @ 100 kHz; according to the permeability calculation formula μe = Ae * Le * 1000 / N 2 *0.4π*Ae, where Le is the magnetic circuit length of the magnetic ring, Ae is the magnetic cross-sectional area of ​​the magnetic ring, and N is the fill factor, set to 0.78. We can calculate: μe=100000@10KHz; μe=30000@100KHz; loss Ps=12W / Kg@20KHz / 0.5T.

[0083] S3, Using the above-mentioned rotary baking curing process

[0084] After heat treatment, the magnetic core is baked in an oven at 80℃ for 1 hour. The pre-baked magnetic core is then impregnated with insulating varnish under vacuum for approximately 15 minutes. The core is then removed and placed back into the vacuum impregnation machine for another 15 minutes. After impregnation, the core is removed and excess insulating varnish is wiped clean from the end faces with absorbent paper. The core is then placed in a custom-made... Figure 2 After being fixed in the mold shown, it is placed in the oven and baked by rotating the mold 360° with a fixed motor to complete the curing.

[0085] After curing in this step, the measured inductance values ​​of the magnetic core are AL = 220 μH @ 10 kHz; AL = 70 μH @ 100 kHz; according to μe = Ae * Le * 1000 / N 2 *0.4π*Ae can be used to calculate: μe=80000@10KHz; μe=25500@100KHz; Ps=13W / Kg@20KHz / 0.5T.

[0086] S4, Core Cutting

[0087] The cured magnetic core is placed in an abrasive wheel cutting machine and cut in half. Then, the end face of the cut magnetic core is polished in sequence with sandpaper of 1200 grit, 1500 grit and 2000 grit, from coarse to fine, for 20±5 minutes each. Then, the end face is polished with D50=50μm iron-based nanocrystalline metal powder as a grinding and polishing powder to obtain a semi-ring iron-based nanocrystalline magnetic core.

[0088] Following this step, the measured inductance values ​​of the semi-toroidal iron-based nanocrystalline magnetic core are AL = 120 μH @ 10 kHz; AL = 40 μH @ 100 kHz; based on μe = Ae * Le * 1000 / N2 * 0.4π * Ae, we can calculate: μe = 42000 @ 10 kHz; μe = 15000 @ 100 kHz; Ps = 13.5 W / Kg @ 20 kHz / 0.5 T.

[0089] Example 2

[0090] In this embodiment, a semi-annular iron-based nanocrystalline magnetic core with OD*ID*HT = 90*50*30mm was fabricated. The difference between this embodiment and Embodiment 1 is that the filling coefficient N after the strip is wound into the magnetic core is controlled to be 0.80 and the process parameters of step S2 are changed. All other parameters, conditions and steps are the same as in Embodiment 1.

[0091] In this embodiment 2, the S2 heat treatment process specifically includes:

[0092] The temperature inside the heat treatment furnace is heated to 300℃. The magnetic core is placed in the heat treatment furnace, and a transverse magnetic field of 1000Gs is applied. The temperature is increased to 410℃ at a rate of 3℃ / min and held for 90 minutes. After holding, the temperature is increased to 470℃ at a rate of 5℃ / min and held for 90 minutes while keeping the transverse magnetic field constant. After holding, the transverse magnetic field is turned off, and the temperature is decreased to 370℃ at a rate of 10℃ and held for 50 minutes. Then, the temperature is increased to 470℃ at a rate of 10℃ / min and held for 90 minutes. Then, the temperature is increased to 540℃ at a rate of 3℃ / min and held for 120 minutes. Finally, the temperature is air-cooled to 200℃ before being removed from the furnace.

[0093] After heat treatment in step S2, the measured inductance values ​​of the magnetic core are AL = 275 μH @ 10 kHz; AL = 82 μH @ 100 kHz; according to the permeability calculation formula μe = Ae * Le * 1000 / N 2 *0.4π*Ae, where Le is the magnetic circuit length of the magnetic ring, Ae is the magnetic cross-sectional area of ​​the magnetic ring, and N is the filling coefficient. It can be calculated that: μe=100000@10KHz; μe=30000@100KHz; loss Ps=11.5W / Kg@20KHz / 0.5T.

[0094] After curing in step S3, the measured inductance values ​​of the magnetic core are AL = 230 μH @ 10 kHz; AL = 68.5 μH @ 100 kHz; according to μe = Ae * Le * 1000 / N 2 *0.4π*Ae can be used to calculate: μe=83000@10KHz; μe=25000@100KHz; Ps=12W / Kg@20KHz / 0.5T.

[0095] After step S4, the measured inductance values ​​of the semi-toroidal iron-based nanocrystalline magnetic core are AL = 125 μH @ 10 kHz; AL = 41.2 μH @ 100 kHz; according to μe = Ae * Le * 1000 / N2 * 0.4π * Ae, we can calculate: μe = 45000 @ 10 kHz; μe = 15100 @ 100 kHz; Ps = 13 W / Kg @ 20 kHz / 0.5 T.

[0096] Example 3

[0097] In this embodiment, a semi-annular iron-based nanocrystalline magnetic core with OD*ID*HT = 90*50*30mm was fabricated. The difference between this embodiment and Embodiment 1 is that the filling coefficient N after the strip is wound into the magnetic core is controlled to be 0.85 and the process parameters of step S2 are changed. All other parameters, conditions and steps are the same as in Embodiment 1.

[0098] In this embodiment 3, S2, the heat treatment process specifically includes:

[0099] The temperature inside the heat treatment furnace is heated to 300℃. The magnetic core is placed in the heat treatment furnace, and a transverse magnetic field of 1000Gs is applied. The temperature is increased to 430℃ at a rate of 2℃ / min and held for 50 minutes. After holding, the temperature is increased to 490℃ at a rate of 0.5℃ / min and held for 30 minutes while keeping the transverse magnetic field constant. After holding, the transverse magnetic field is turned off, and the temperature is decreased to 390℃ at a rate of 1℃ and held for 10 minutes. Then, the temperature is increased to 490℃ at a rate of 1℃ / min and held for 30 minutes. Then, the temperature is increased to 540℃ at a rate of 0.5℃ / min and held for 30 minutes. Finally, the core is air-cooled to 300℃ and removed from the furnace.

[0100] After heat treatment in step S2, the measured inductance values ​​of the magnetic core are AL = 280 μH @ 10 kHz; AL = 88 μH @ 100 kHz; according to the permeability calculation formula μe = Ae * Le * 1000 / N 2 *0.4π*Ae, where Le is the magnetic circuit length of the magnetic ring, Ae is the magnetic cross-sectional area of ​​the magnetic ring, and N is the filling coefficient. It can be calculated that: μe=102000@10KHz; μe=32000@100KHz; loss Ps=10.8W / Kg@20KHz / 0.5T.

[0101] After curing in step S3, the measured inductance values ​​of the magnetic core are AL = 230 μH @ 10 kHz; AL = 72 μH @ 100 kHz; according to μe = Ae * Le * 1000 / N2 * 0.4π * Ae, we can calculate: μe = 83800 @ 10 kHz; μe = 26200 @ 100 kHz; Ps = 11.8 W / Kg @ 20 kHz / 0.5 T.

[0102] After step S4, the measured inductance values ​​of the semi-toroidal iron-based nanocrystalline magnetic core are AL = 128 μH @ 10 kHz; AL = 41.5 μH @ 100 kHz; according to μe = Ae * Le * 1000 / N 2 From *0.4π*Ae, we can calculate: μe=46670@10KHz; μe=15500@100KHz; Ps=12.5W / Kg@20KHz / 0.5T.

[0103] Comparative Example 1

[0104] This comparative example fabricated a semi-ring-shaped iron-based nanocrystalline magnetic core with OD*ID*HT = 90*50*30mm. The difference between this example and Example 1 is step S2, while the other parameters, conditions, and steps are the same as in Example 1.

[0105] The S2 heat treatment process in Comparative Example 1 specifically includes:

[0106] Its temperature control program is as follows Figure 5 As shown, the temperature inside the heat treatment furnace is heated to 300℃, the magnetic core is placed in the heat treatment furnace, and a transverse magnetic field of 1000Gs is applied. The temperature is raised to 420℃ at a rate of 1℃ / min and held for 30min. After the holding period, the temperature is raised to 480℃ at a rate of 2℃ / min and held for 60min. Then the temperature is raised to 550℃ at a rate of 1℃ / min and held for 90min. Finally, the temperature is air-cooled to 350℃ and removed from the furnace.

[0107] After heat treatment in step S2, the measured inductance values ​​of the magnetic core are AL = 260 μH @ 10 kHz; AL = 60 μH @ 100 kHz. According to the permeability calculation formula μe = Ae * Le * 1000 / N2 * 0.4π * Ae, where Le is the magnetic circuit length of the magnetic ring, Ae is the magnetic cross-sectional area of ​​the magnetic ring, and N is the fill factor, set to 0.78, we can calculate: μe = 95000 @ 10 kHz; μe = 22000 @ 100 kHz; loss Ps = 20 W / Kg @ 20 kHz / 0.5 T.

[0108] After curing in step S3, the measured inductance values ​​of the magnetic core are AL = 150 μH @ 10 kHz; AL = 50 μH @ 100 kHz; according to μe = Ae * Le * 1000 / N2 * 0.4π * Ae, we can calculate: μe = 54000 @ 10 kHz; μe = 18200 @ 100 kHz; Ps = 22 W / Kg @ 20 kHz / 0.5 T.

[0109] After step S4, the measured inductance values ​​of the semi-toroidal iron-based nanocrystalline magnetic core are AL = 80 μH @ 10 kHz; AL = 30 μH @ 100 kHz; according to μe = Ae * Le * 1000 / N 2 From *0.4π*Ae, we can calculate: μe=30000@10KHz; μe=10000@100KHz; loss Ps=23.5W / Kg@20KHz / 0.5T.

[0110] Comparative Example 2

[0111] This comparative example fabricated a semi-ring-shaped iron-based nanocrystalline magnetic core with OD*ID*HT = 90*50*30mm. The difference between this example and Example 1 is step S3, while the other parameters, conditions, and steps are the same as in Example 1.

[0112] The specific steps of S3 and core impregnation curing in Comparative Example 1 include: first, vacuum impregnating the core for 15 minutes, then dry-vacuuming for 15 minutes, and then laying it flat and baking until the core is completely cured.

[0113] After heat treatment in step S2, the measured inductance values ​​of the magnetic core are AL = 300 μH @ 10 kHz; AL = 84 μH @ 100 kHz. According to the permeability calculation formula μe = Ae * Le * 1000 / N2 * 0.4π * Ae, where Le is the magnetic circuit length of the magnetic ring, Ae is the magnetic cross-sectional area of ​​the magnetic ring, and N is the fill factor, set to 0.78, we can calculate: μe = 100000 @ 10 kHz; μe = 30000 @ 100 kHz; loss Ps = 12 W / Kg @ 20 kHz / 0.5 T.

[0114] After curing in step S3, the measured inductance values ​​of the magnetic core are AL = 150 μH @ 10 kHz; AL = 50 μH @ 100 kHz; according to μe = Ae * Le * 1000 / N2 * 0.4π * Ae, we can calculate: μe = 54000 @ 10 kHz; μe = 18200 @ 100 kHz; Ps = 15 W / Kg @ 20 kHz / 0.5 T.

[0115] After step S4, the measured inductance values ​​of the semi-toroidal iron-based nanocrystalline magnetic core are AL = 80 μH @ 10 kHz; AL = 30 μH @ 100 kHz; according to μe = Ae * Le * 1000 / N2 * 0.4π * Ae, we can calculate: μe = 30000 @ 10 kHz; μe = 10000 @ 100 kHz; loss Ps = 18 W / Kg @ 20 kHz / 0.5 T.

[0116] Comparative Example 3

[0117] This comparative example fabricated a semi-ring-shaped iron-based nanocrystalline magnetic core with OD*ID*HT = 90*50*30mm. The difference between this example and Example 1 is the polishing process in step S4. All other parameters, conditions, and steps are the same as in Example 1.

[0118] The polishing process in S4 of Comparative Example 1 specifically includes: polishing with traditional 1200-grit, 1500-grit, and 2000-grit sandpaper, followed by polishing with a polishing cloth.

[0119] After heat treatment in step S2, the measured inductance values ​​of the magnetic core are AL = 300 μH @ 10 kHz; AL = 84 μH @ 100 kHz. According to the permeability calculation formula μe = Ae * Le * 1000 / N2 * 0.4π * Ae, where Le is the magnetic circuit length of the magnetic ring, Ae is the magnetic cross-sectional area of ​​the magnetic ring, and N is the fill factor, set to 0.78, we can calculate: μe = 100000 @ 10 kHz; μe = 30000 @ 100 kHz; loss Ps = 12 W / Kg @ 20 kHz / 0.5 T.

[0120] After curing in step S3, the measured inductance values ​​of the magnetic core are AL = 220μH@10KHz; AL = 70μH@100KHz; according to μe = Ae*Le*1000 / N2*0.4π*Ae, we can calculate: μe = 80000@10KHz; μe = 25500@100KHz; Ps = 13W / Kg@20KHz / 0.5T.

[0121] After step S4, the measured inductance values ​​of the semi-toroidal iron-based nanocrystalline magnetic core are AL = 80 μH @ 10 kHz; AL = 30 μH @ 100 kHz; according to μe = Ae * Le * 1000 / N2 * 0.4π * Ae, we can calculate: μe = 30000 @ 10 kHz; μe = 10000 @ 100 kHz; loss Ps = 18 W / Kg @ 20 kHz / 0.5 T.

[0122] Comparative Example 4

[0123] This comparative example fabricated a semi-ring-shaped iron-based nanocrystalline magnetic core with OD*ID*HT = 90*50*30mm. Step S1 was the same as in Example 1, step S2 was the same as in Comparative Example 1, step S3 was the same as in Comparative Example 2, and step S4 was the same as in Comparative Example 3.

[0124] After heat treatment in step S2, the measured inductance values ​​of the magnetic core are AL = 260 μH @ 10 kHz; AL = 60 μH @ 100 kHz; according to the permeability calculation formula μe = Ae * Le * 1000 / N 2 *0.4π*Ae, where Le is the magnetic circuit length of the magnetic ring, Ae is the magnetic cross-sectional area of ​​the magnetic ring, and N is the filling factor, set to 0.78. We can calculate: μe=95000@10KHz; μe=22000@100KHz; loss Ps=20W / Kg@20KHz / 0.5T.

[0125] After curing in step S3, the measured inductance values ​​of the magnetic core are AL = 130 μH @ 10 kHz; AL = 30 μH @ 100 kHz; according to μe = Ae * Le * 1000 / N 2 *0.4π*Ae can be used to calculate: μe=47000@10KHz; μe=13200@100KHz; loss Ps=23.W / Kg@20KHz / 0.5T.

[0126] After step S4, the measured inductance values ​​of the semi-toroidal iron-based nanocrystalline magnetic core are AL = 40μH@10KHz; AL = 15μH@100KHz; according to μe = Ae*Le*1000 / N2*0.4π*Ae, we can calculate: μe = 14500@10KHz; μe = 5000@100KHz; loss Ps = 26.5W / Kg@20KHz / 0.5T.

[0127] The performance of the semi-annular iron-based nanocrystalline magnetic cores finally prepared in Examples 1 to 3 and Comparative Examples 1 to 4 was compared, and the results are shown in Table 1 below.

[0128] Table 1 shows the magnetic core performance of each embodiment and comparative example.

[0129]

[0130] As shown in Table 1, the composite magnetic field heat treatment process, 360° rotating baking and curing of insulating varnish, and iron-based nanocrystalline metal powder grinding and polishing process of the embodiments of the present invention can produce magnetic cores with higher permeability and lower loss rate. A comparison of the embodiments and comparative examples shows that the heat treatment process, impregnation baking, and cutting and polishing processes of the embodiments of the present invention significantly improve the permeability compared to traditional methods; at the same time, the high stacking factor results in a slightly higher low-frequency permeability and slightly lower loss in the produced magnetic core.

[0131] The end face images of the iron-based nanocrystalline magnetic cores after cutting in Comparative Example 3 and Example 1 are shown below. Figure 4 As shown in the figure, the left figure A is the end face after traditional grinding, and the right figure B is the end face after grinding using the sandpaper + iron-based nanocrystalline metal powder process of the present invention. The comparison shows that the grinding process of the present invention can make the end face of the magnetic core flatter.

[0132] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for preparing a semi-ring type iron-based nanocrystalline magnetic core with high magnetic permeability and low loss, characterized in that, The preparation method comprises the following steps: winding the iron-based nanocrystalline strip into a magnetic core with a set filling factor; composite magnetic field heat treatment, including a first stage heat treatment of applying a transverse magnetic field and a second stage heat treatment without a magnetic field; pre-baking the heat-treated magnetic core, impregnating the magnetic core with an impregnating solution, completely fixing the inner diameter and the outer diameter of the magnetic core by using a mold, and performing 360° rotary baking to realize solidification of the impregnating solution; cutting the magnetic core, polishing and grinding the cut end face with iron-based nanocrystalline metal powder to obtain a semi-ring type iron-based nanocrystalline magnetic core with high magnetic permeability and low loss; the first stage heat treatment of applying a transverse magnetic field in the composite magnetic field heat treatment specifically comprises: placing the magnetic core into a heat treatment furnace that has been raised to an initial temperature, applying a 1000Gs transverse magnetic field, and raising the temperature to a first temperature at a heating rate of 1-3 ℃ / min and then maintaining the temperature for 30-90 min; raising the temperature to a second temperature at a heating rate of 0.5-5 ℃ / min and then maintaining the temperature for 30-90 min; wherein the first temperature is set to 410-430 ℃, and the second temperature is set to 470-490 ℃; the second stage heat treatment without a magnetic field in the composite magnetic field heat treatment specifically comprises: after the first stage heat treatment, turning off the transverse magnetic field, lowering the temperature to a third temperature at a cooling rate of 1-10 ℃ / min, maintaining the temperature for 10-50 min; raising the temperature to a fourth temperature at a heating rate of 1-10 ℃, maintaining the temperature for 30-90 min; raising the temperature to a fifth temperature at a heating rate of 0.5-3 ℃, maintaining the temperature for 30-120 min; finally, air cooling to a sixth temperature and discharging the furnace; wherein the third temperature is set to 370-390 ℃, the fourth temperature is set to 470-490 ℃, the fifth temperature is set to 540-560 ℃, and the sixth temperature is set to 200-350 ℃.

2. The preparation method of the semi-ring type iron-based nanocrystalline magnetic core with high magnetic permeability and low loss according to claim 1, characterized in that, The filling factor of the magnetic core to be treated is set to 0.78-0.

85.

3. The preparation method of the semi-ring type iron-based nanocrystalline magnetic core with high magnetic permeability and low loss according to claim 1, characterized in that, The impregnation treatment specifically comprises: performing vacuum impregnation treatment on the pre-baked magnetic core to make the impregnating solution penetrate into the gaps of the magnetic core; placing the magnetic core in an environment without the impregnating solution and performing vacuum dry pumping; cleaning the residual impregnating solution on the surface of the magnetic core.

4. The preparation method of the semi-ring type iron-based nanocrystalline magnetic core with high magnetic permeability and low loss according to claim 3, characterized in that, The impregnating solution is an insulating paint.

5. The preparation method of the semi-ring type iron-based nanocrystalline magnetic core with high magnetic permeability and low loss according to claim 1, characterized in that, The polishing and grinding of the cut end face specifically comprises: polishing the end face of the cut magnetic core with at least two types of sandpaper in sequence; using D50=45-55 μm iron-based nanocrystalline metal powder as polishing powder to polish the end face.

6. The preparation method of the semi-ring type iron-based nanocrystalline magnetic core with high magnetic permeability and low loss according to claim 5, characterized in that, The mesh number of the sandpaper is 1200-2000 mesh, and the polishing is performed with sandpaper from coarse to fine; the polishing time of each mesh number is set to 20±5 min.

7. A semi-loop type iron-based nanocrystalline magnetic core with high permeability and low loss, characterized in that, obtained by the preparation method of any one of claims 1-6.

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