Nanocrystalline magnetic core with high permeability across full frequency range, and preparation method therefor and use thereof

Abstract

The present invention belongs to the field of magnetic materials. Particularly disclosed are a nanocrystalline magnetic core with high permeability across the full frequency range, and a preparation method therefor and use thereof. In the present invention, nanocrystallization of an amorphous alloy is induced by means of a force-magnetic composite heat treatment technology, effectively solving the problems of non-uniform nucleation and excessive growth of nanocrystals in conventional heat treatment. As a result, the permeability of the magnetic core is significantly improved across the full frequency range of 1-100 kHz, particularly achieving an effective permeability of up to 45,000 or above at a high frequency of 100 kHz.

Description

A nanocrystalline magnetic core with high permeability across the entire frequency band, its preparation method and application Technical Field

[0001] This invention belongs to the field of magnetic materials, specifically relating to a nanocrystalline magnetic core with high permeability across the entire frequency band, its preparation method, and its applications. Background Technology

[0002] Benefiting from the accelerated application of third-generation wide-bandgap semiconductor power devices, the development of matching high-frequency, high-efficiency inductors and high-power-density transformers towards miniaturization, integration, and low energy consumption has become an inevitable trend. Iron-based amorphous / nanocrystalline soft magnetic alloys, as a new generation of "dual-green" energy-saving materials, are considered ideal materials for fabricating high-frequency, high-efficiency inductors and high-power-density transformers due to their excellent comprehensive soft magnetic properties, such as high saturation magnetic induction, low coercivity, high permeability, and low loss.

[0003] Iron-based amorphous / nanocrystalline soft magnetic alloys are typically produced by rapidly cooling a master alloy with high-speed copper rollers to create amorphous strips, which are then wound into amorphous magnetic cores. Amorphous magnetic cores generally require appropriate heat treatment processes to finely control the alloy's microstructure. Specifically, the precipitation of a single magnetic α-Fe phase on the amorphous matrix transforms into a dual-phase structure of amorphous and nanocrystalline components, forming a nanocrystalline magnetic core. This unique dual-phase nanostructure is the main reason why nanocrystalline magnetic cores exhibit excellent overall soft magnetic properties. Therefore, the heat treatment process plays a decisive role in obtaining high-performance nanocrystalline magnetic cores. Conventional heat treatment methods for amorphous magnetic cores include annealing in an atmosphere furnace.

[0004] Due to the slow heating / cooling rates in industrial furnaces, amorphous magnetic cores, under high-temperature heat treatment, suffer from two main problems: incomplete grain precipitation if the heating time is too short, and uneven grain precipitation and excessive growth if the heating time is too long. Both of these situations deteriorate the performance of the obtained nanocrystalline magnetic cores, especially significantly reducing their permeability. Essentially, the superior soft permeability of nanocrystalline magnetic cores stems primarily from two factors: first, optimized heat treatment processes, controlling nanocrystal precipitation and growth by adjusting appropriate heat treatment temperatures and holding times, resulting in fine and uniform nanocrystals on an amorphous matrix, forming a dual-phase composite structure of amorphous and nanocrystalline; second, the use of magnetic fields to induce grain orientation growth, causing nanocrystals to align along the direction of the applied magnetic field, thereby inducing magnetic anisotropy and controlling the shape of the hysteresis loop. However, on the one hand, the crystallization process of amorphous alloys is highly sensitive to heat treatment temperature and time. In existing heat treatment techniques, the precipitation and growth of nanocrystals depend solely on the duration of temperature exposure, making it difficult to effectively control the size and distribution of nanocrystals, thus limiting the improvement in permeability. On the other hand, limited by magnetic field strength, magnetic field annealing makes it difficult to completely orient the nanocrystals. Furthermore, due to the unidirectional nature of the magnetic field applied to the core, permeability optimization can only be achieved within specific frequency ranges of the nanocrystalline core; that is, increasing low-frequency permeability (below 50kHz) and decreasing high-frequency permeability (above 50kHz), or increasing high-frequency permeability (above 50kHz) and decreasing low-frequency permeability (below 50kHz). Therefore, both conventional heat treatment and magnetic field application have significant limitations in improving the permeability of nanocrystalline cores, especially at high frequencies where the increase is limited. There is an urgent need to develop a new amorphous core fabrication technology to improve the permeability of nanocrystalline cores. Summary of the Invention

[0005] In view of the problem of low permeability of nanocrystalline magnetic cores in the prior art, the present invention will provide a nanocrystalline magnetic core with high permeability across the entire frequency band, its preparation method and application.

[0006] To achieve the above objectives, the following technical solutions are specifically included:

[0007] A method for preparing a nanocrystalline magnetic core includes the following steps:

[0008] (1) The amorphous magnetic core is subjected to a first heat treatment and a second heat treatment in sequence. After cooling and depressurization, a pre-burnt magnetic core is obtained. The temperature of the first heat treatment is 490-520℃, and the temperature of the second heat treatment is 550-600℃. The pressure of the first heat treatment and the second heat treatment is greater than atmospheric pressure.

[0009] (2) The pre-burnt magnetic core is subjected to magnetic field heat treatment and then cooled to obtain the nanocrystalline magnetic core.

[0010] In the method of this invention, the nanocrystallization of amorphous alloys is induced by force-magnetic composite heat treatment technology, which effectively solves the problems of uneven nucleation and excessive growth of nanocrystals in conventional heat treatment, comprehensively improves the overall electromagnetic performance of nanocrystalline magnetic cores, and obtains nanocrystalline magnetic core materials with high permeability across the entire frequency band. In particular, the permeability in the high-frequency band can reach more than 45,000, effectively solving the defect of low permeability in high-frequency magnetic cores.

[0011] In the method of the present invention, in step (1), the main purpose of the first heat treatment and the second heat treatment is to crystallize the amorphous magnetic core, which aims to promote the precipitation of a large number of fine α-Fe nanocrystals on the amorphous substrate; in step (2), while the grains in the magnetic core are precipitating and growing, the grains are induced to grow in orientation along the direction of the magnetic field by the action of the magnetic field, and appropriate magnetic anisotropy is introduced under the action of the external magnetic field; therefore, by controlling the precipitation, size and growth orientation of nanocrystals by the method of the present invention, the comprehensive soft magnetic properties of the obtained nanocrystalline magnetic core are improved.

[0012] Preferably, in step (1), the pressure of the first heat treatment is 20-60 MPa, the time of the first heat treatment is 20-120 min, and the heating rate of the first heat treatment is 1-30 °C / min.

[0013] Preferably, the pressure of the second heat treatment is 30-120 MPa, the time of the second heat treatment is 30-90 min, the heating rate of the second heat treatment is 1-5 °C / min, and the cooling rate is 5-600 °C / min.

[0014] Preferably, in step (1), the pressurization method of the first heat treatment and the second heat treatment is selected from at least one of pressurization by inert gas pressure and pressurization by die extrusion; the amorphous magnetic core in step (1) is made of amorphous strip wound together, and the magnetic field direction of the magnetic field heat treatment in step (2) is parallel to the width direction of the amorphous magnetic core.

[0015] Preferably, in step (1), the amorphous magnetic core comprises the following elements in atomic percentage: Fe 60-80%, Si 10-20%, B 0-10%, Cu 0-3%, Nb 0-5%, Ni 0-15%, Co 0-10%, and V 0-10%.

[0016] More preferably, the amorphous magnetic core is Fe. 73.5 Si 15.5 B7Cu1Nb3, Fe 73.5 Si 15.5 B7Cu1V1Nb2、Fe 73.5 Si 13.5 B9Cu1Nb3, Fe63.5 Ni 10 Si 15.5 B7Cu1Nb3, Fe 63.5 Co5Ni5Si 15.5 B7Cu1Nb3, Fe 68.5 Co5Si 15.5 At least one of B7Cu1Nb3.

[0017] Preferably, in step (1), the cooling and depressurization method is to first cool the system naturally to below 200°C, and then release the system pressure to atmospheric pressure.

[0018] Preferably, in step (2), the temperature of the magnetic field heat treatment is 460-530℃, the time of the magnetic field heat treatment is 1-180min, and the magnetic field strength of the magnetic field heat treatment is 800-3000Gs.

[0019] Preferably, in step (2), the rate of heating to the magnetic field heat treatment temperature is 1-20℃ / min.

[0020] Preferably, in step (2), the cooling method is natural cooling.

[0021] Preferably, the permeability of the nanocrystalline magnetic core is greater than or equal to 45,000.

[0022] More preferably, the permeability of the nanocrystalline magnetic core is 80,000-120,000 at a frequency of 1 kHz, 70,000-110,000 at a frequency of 10 kHz, and 45,000-60,000 at a frequency of 100 kHz.

[0023] This invention also provides an application of the nanocrystalline magnetic core described above in the preparation of new energy vehicles, photovoltaic energy storage devices, electronic camera devices, and 5G communication devices. The nanocrystalline magnetic core of this invention has high magnetic permeability and is more suitable for application in the preparation of the above-mentioned devices.

[0024] Compared with existing technologies, the present invention has the following advantages: The present invention induces nanocrystallization of amorphous alloys through force-magnetic composite heat treatment technology, which effectively solves the problems of uneven nucleation and excessive growth of nanocrystals in conventional heat treatment, resulting in a significant improvement in the permeability of the magnetic core across the entire frequency band of 1-100kHz, especially at the high frequency of 100kHz with an effective permeability of over 45,000, meeting the application requirements of high-performance nanocrystalline magnetic cores in industrial fields such as new energy vehicles, photovoltaic energy storage, consumer electronics, and 5G communications. At the same time, this heat treatment method is universally applicable to nanocrystalline magnetic powder cores and strips. Attached Figure Description

[0025] Figure 1 shows the X-ray diffraction (XRD) pattern of the self-made amorphous ribbon.

[0026] Figure 2 is a comparison diagram of the microstructure between Example 1 (left) and Comparative Example 3 (right).

[0027] Figure 3 is a physical image of the magnetic core prepared in Example 1.

[0028] Figure 4 shows the relationship between the effective permeability and frequency of the iron-based nanocrystalline soft magnetic alloy cores in Examples 1-12.

[0029] Figure 5 shows the relationship between the effective permeability and frequency of the iron-based nanocrystalline soft magnetic alloy cores in Comparative Examples 1–4. Detailed Implementation

[0030] To better illustrate the purpose, technical solution, and advantages of this invention, specific embodiments will be used to further explain the invention below. Unless otherwise specified, the test methods used in the embodiments and / or comparative examples are conventional methods; the materials and reagents used, unless otherwise specified, are commercially available.

[0031] Amorphous ribbons can be made in-house or purchased commercially. The Fe used below 73.5 Si 15.5 B7Cu1Nb3 is an amorphous ribbon made by conventional processes, and its XRD is shown in Figure 1. The self-made method may include the following process: (1) component ratio; (2) master alloy melting; (3) strip spinning and strip winding to obtain the corresponding amorphous ribbon.

[0032] Example 1

[0033] (1) The alloy Fe, in atomic percentage terms 73.5 Si 15.5 B7Cu1Nb3 amorphous ribbon is wound into an amorphous magnetic core, and then the amorphous magnetic core is placed in a gas furnace. The furnace is evacuated and filled with inert argon gas to create a certain pressure in the system. The system is heated to the first heat treatment temperature of 500°C at a heating rate of 10°C / min, and at the same time, argon gas is continuously added to pressurize the system to the first heat treatment pressure of 30MPa. The system is then held at this temperature and pressure for 90 minutes.

[0034] (2) Continue heating and pressurizing at a heating rate of 3℃ / min to the second heat treatment temperature of 580℃, and at the same time continue to pressurize with argon gas to the second heat treatment pressure of 60MPa, and hold at this temperature and pressure for 60min; then cool down to below 200℃ and start to release the pressure to the chamber pressure, and set the cooling rate to natural cooling with the furnace to obtain the pre-burnt magnetic core;

[0035] (2) Magnetic field heat treatment: The pre-burnt magnetic core is placed in the magnetic field heat treatment furnace and heated to 500°C at a heating rate of 10°C / min. At this time, a magnetic field parallel to the width direction of the amorphous ribbon is applied with a magnetic field strength of 1500Gs. The magnetic field heat treatment is carried out at this temperature and magnetic field for 60 minutes. The furnace is then cooled to room temperature to obtain a nanocrystalline magnetic core.

[0036] Examples 2-12 and Comparative Examples 1-4

[0037] The only difference between Examples 2-12, Comparative Examples 1-4 and Example 1 is that in steps (1)-(3), the heating rate or temperature or pressure of the first heat treatment, the heating rate or temperature or pressure of the second heat treatment, the temperature or magnetic field strength and time of the magnetic field heat treatment are as detailed in Table 1.

[0038] Table 1

[0039] The nanocrystalline magnetic cores prepared above were subjected to performance tests: the inductance L of the core was measured using a Keysight Agilent 4294A precision impedance analyzer under an applied magnetic field of 1 A / m and a frequency range of 1 kHz to 100 kHz; the effective permeability μ was measured. e The value is obtained through the inductance L conversion formula: μ e = (L×L) e ) / (N 2 ×A e ),

[0040] Where L is the core inductance, μ e L is the effective permeability of the magnetic core. e A is the magnetic circuit length of the magnetic core. e Where is the effective cross-sectional area of ​​the magnetic core, and N is the number of coil turns (test condition is 1 turn). The test results are shown in Table 2.

[0041] Conventional heat treatment processes, such as the preparation method in Comparative Example 3, are used as the basis for comparison. The rate of change X of the magnetic permeability of the magnetic core prepared in other embodiments of the present invention and Comparative Example 3 using conventional heat treatment processes is calculated: X f =(μ n -μ 对比例3 ) / μ 对比例3 *100%, where μ n The effective permeability (μ) of a magnetic core fabricated in a specific embodiment or comparative example at frequency f. 对比例3 The effective permeability of the magnetic core obtained in Comparative Example 3 at frequency f is shown in Table 2.

[0042] Table 2

[0043] As can be seen from the TEM image and grain distribution diagram in Comparative Example 3, the sample suffers from uneven heating during conventional heat treatment, leading to uneven nucleation of nanocrystals, incomplete grain precipitation, and excessive growth. Therefore, this invention first performs a first heat treatment to ensure uniform heating of the amorphous magnetic core, providing a foundation for the second heat treatment. Then, the temperature is increased and / or the pressure is further increased. By using a slow heating rate and selecting an appropriate holding time, sufficient time is ensured for grain precipitation at a higher temperature. Under the influence of air pressure, the grains grow slowly and uniformly, avoiding uneven heating due to overheating, incomplete grain precipitation due to insufficient holding time, or excessive grain growth due to excessive holding time. Finally, magnetic field heat treatment is combined to cause all nanocrystals to rotate. The combined force field heat treatment and magnetic field heat treatment ensure complete grain precipitation and uniform size in the nanocrystalline magnetic core, as shown in Figure 2, achieving the goal of improving the permeability of the nanocrystalline magnetic core across the entire frequency band.

[0044] In Examples 1-12 above, the effective permeability of the nanocrystalline magnetic core is 80,000-120,000 at a frequency of 1 kHz; 70,000-110,000 at 10 kHz; and 45,000-60,000 at 100 kHz. Compared with Comparative Examples 1-4, the improvement in permeability of Examples 1-12 is significantly higher under the 1-100 kHz range, especially at the 100 kHz high-frequency condition, where the effective permeability reaches over 45,000.

[0045] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a nanocrystalline magnetic core, characterized in that, Includes the following steps: (1) The amorphous magnetic core is subjected to a first heat treatment and a second heat treatment in sequence. After cooling and depressurization, a pre-burnt magnetic core is obtained. The temperature of the first heat treatment is 490-520℃, and the temperature of the second heat treatment is 550-600℃. The pressure of the first heat treatment and the second heat treatment is greater than atmospheric pressure. (2) The pre-burnt magnetic core is subjected to magnetic field heat treatment and then cooled to obtain the nanocrystalline magnetic core.

2. The method for preparing a nanocrystalline magnetic core as described in claim 1, characterized in that, In step (1), the pressure of the first heat treatment is 20-60 MPa, the time of the first heat treatment is 20-120 min, and the heating rate of the first heat treatment is 1-30 °C / min.

3. The method for preparing a nanocrystalline magnetic core as described in claim 1, characterized in that, In step (1), the pressure of the second heat treatment is 30-120 MPa, the time of the second heat treatment is 30-90 min, the heating rate of the second heat treatment is 1-5℃ / min, and the cooling rate is 5-600℃ / min.

4. The method for preparing a nanocrystalline magnetic core as described in claim 1, characterized in that, In step (1), the pressurization method of the first heat treatment and the second heat treatment is selected from at least one of pressurization by inert gas pressure and pressurization by die extrusion; the amorphous magnetic core in step (1) is made of amorphous strip wound together, and the magnetic field direction of the magnetic field heat treatment in step (2) is parallel to the width direction of the amorphous magnetic core.

5. The method for preparing a nanocrystalline magnetic core as described in claim 1, characterized in that, In step (1), the amorphous magnetic core comprises the following elements in atomic percentage: Fe 60-80%, Si 10-20%, B 0-10%, Cu 0-3%, Nb 0-5%, Ni 0-15%, Co 0-10%, and V 0-10%.

6. The method for preparing a nanocrystalline magnetic core as described in claim 1, characterized in that, In step (2), the temperature of the magnetic field heat treatment is 460-530℃, the time of the magnetic field heat treatment is 10-90min, and the magnetic field strength of the magnetic field heat treatment is 800-3000Gs.

7. The method for preparing a nanocrystalline magnetic core as described in claim 1, characterized in that, In step (1), the cooling and depressurization method is to first cool the system naturally to below 200°C, and then release the system pressure to atmospheric pressure; in step (2), the cooling method is natural cooling.

8. A nanocrystalline magnetic core prepared by the method of any one of claims 1-7.

9. The nanocrystalline magnetic core as described in claim 8, characterized in that, At a frequency of 1 kHz, the permeability of the nanocrystalline magnetic core is 80,000-120,000; at 10 kHz, the permeability of the nanocrystalline magnetic core is 70,000-110,000; and at 100 kHz, the permeability of the nanocrystalline magnetic core is 45,000-60,000.

10. The application of the nanocrystalline magnetic core according to claim 8 or 9 in the preparation of new energy vehicles, photovoltaic energy storage equipment, electronic camera equipment, and 5G communication equipment.

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