Iron-based magnetic core having constant magnetic permeability, preparation method therefor, and use thereof

Abstract

An iron-based magnetic core having a constant magnetic permeability, a preparation method therefor, and a use thereof. The preparation method comprises: sequentially subjecting an iron-based amorphous magnetic core to force field heat treatment and magnetic field heat treatment at specific temperatures.

Description

A Ferro-Based Magnetic Core with Constant Permeability, Its Fabrication Method and Application Technical Field

[0001] This invention belongs to the field of magnetic materials, specifically relating to an iron-based magnetic core with constant magnetic permeability, its preparation method, and its application. Background Technology

[0002] 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. This involves transforming the precipitation of a single magnetic α-Fe phase on the amorphous matrix 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 iron-based magnetic cores. However, current heat treatment processes often produce magnetic cores with high permeability that decreases significantly with increasing frequency, exhibiting unstable permeability. This makes the cores unsuitable for applications requiring stable permeability, particularly limiting the availability of iron-based magnetic cores with effective permeability of 15000-35000 kHz, thus restricting their application.

[0003] Therefore, there is an urgent need to develop a heat treatment process for iron-based magnetic cores to achieve a permeability range of 15,000-35,000 at 1-100 kHz. Summary of the Invention

[0004] In view of the problem in the prior art that it is difficult to obtain iron-based magnetic cores with a permeability in the range of 15000-35000 at 1-100KHz, the present invention will provide an iron-based magnetic core with constant permeability, its preparation method and application.

[0005] To achieve the above objectives, the following technical solutions are specifically included:

[0006] A method for preparing an iron-based magnetic core includes the following steps:

[0007] (1) Heat the iron-based amorphous magnetic core to a preset temperature and simultaneously pressurize it to a preset pressure, then cool it to below 200°C and start releasing the pressure to obtain a pre-burnt magnetic core; the preset temperature is 530-650°C and the preset pressure is greater than atmospheric pressure;

[0008] (2) The pre-burnt magnetic core is subjected to magnetic field heat treatment and cooled to obtain an iron-based magnetic core. The temperature of the magnetic field heat treatment is 435-550℃.

[0009] In the method of the present invention, by subjecting the iron-based amorphous magnetic core to force field heat treatment and magnetic field heat treatment at specific temperatures in sequence, the iron-based magnetic core has the characteristic of having an effective permeability of 15000-35000 at a frequency of 1-100kHz, thus broadening the application scenarios of iron-based magnetic cores.

[0010] Under force field heat treatment, on the one hand, pressure promotes the precipitation of nanocrystals while simultaneously inhibiting their rapid growth. To a certain extent, this controls the grain size, allowing the magnetic core to maintain a relatively low and stable permeability. On the other hand, the presence of the pressure field induces magnetic anisotropy within the magnetic core, increasing domain wall energy. This high domain wall energy prevents domain wall movement, thus, to a certain extent, controlling the domain wall energy to maintain a relatively low and stable permeability. Magnetic field heat treatment, in effect, induces 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. Force field heat treatment and magnetic field heat treatment work in tandem; force field heat treatment controls the grain size and domain wall energy, while magnetic field heat treatment further controls and induces grain orientation growth. This invention, by altering the heat treatment process, controls the grain size, state, magnetic anisotropy, and hysteresis loop shape to obtain a magnetic core with stable permeability in the 1-100 kHz range. Furthermore, the inventors of this invention have discovered through experiments that when the temperatures of force field heat treatment and magnetic field heat treatment are 530-650℃ and 435-550℃ respectively, the magnetic core maintains high stability of permeability at 1-100KHz. Slight deviations from the above two heat treatment temperature ranges may be due to abnormal grain growth, resulting in a significant increase in the rate of change of permeability, making it impossible to achieve the effect of maintaining stable or constant permeability.

[0011] Preferably, in step (1), the preset pressure is 100-200 MPa.

[0012] As the temperature of the force field heat treatment gradually increases, the magnetic anisotropy induced inside the magnetic core can be further enhanced, the domain wall energy can be increased, the magnetic permeability of the magnetic core can be further adjusted, and the stability of the magnetic permeability can be improved. However, if the pressure is too high, the energy consumption will be greater, the requirements for the equipment will be higher, and there may also be certain safety hazards. Therefore, the pressure range mentioned above is selected in this invention, which can better meet the actual working conditions while ensuring the magnetic properties of the magnetic core.

[0013] Preferably, in step (1), the iron-based 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%, Mo 0-10%, and V 0-10%.

[0014] More preferably, the iron-based amorphous magnetic core comprises Fe 73.5 Si 13.5 B9Cu1Nb3, Fe 63.5 Ni 10 Si 15.5 B7Cu1Nb3, Fe 63.5 Co5Ni5Si 15.5 B7Cu1Nb3, Fe 68.5 Co5Si 15.5 At least one of B7Cu1Nb3. The method of the present invention is effective for a variety of iron-based alloys and is adaptable to the heat treatment of different types of amorphous magnetic cores to obtain low-frequency constant permeability magnetic cores.

[0015] Preferably, in step (1), the heating rate of the iron-based amorphous magnetic core to the preset temperature is 5-30℃ / min.

[0016] Preferably, in step (1), the cooling rate is 50-1000℃ / min.

[0017] Further preferably, in step (1), the cooling rate is 100-500℃ / min.

[0018] The method of the present invention can select a heating rate of 5-30℃ / min and a cooling rate of 50-1000℃ / min. Compared with conventional heat treatment processes, the above heating / cooling rate range belongs to the case of rapid heating and rapid cooling, which can shorten the time the magnetic core stays at high temperature, avoid excessive growth of grains in the magnetic core, and make the magnetic permeability of the magnetic core more stable.

[0019] Preferably, the pressurization method includes at least one of inert gas pressurization and die extrusion pressurization.

[0020] Preferably, the inert gas includes at least one of argon and nitrogen.

[0021] Preferably, the magnetic field strength of the magnetic field heat treatment is 800-3000 Gs.

[0022] Preferably, the iron-based amorphous magnetic core in step (1) is formed by winding iron-based amorphous strip, and the magnetic field direction of the magnetic field heat treatment in step (2) is parallel to the width direction of the iron-based amorphous strip.

[0023] Preferably, in step (2), the magnetic field heat treatment time is 20-120 min.

[0024] High temperatures and long durations of magnetic field heat treatment can lead to larger grain sizes in the magnetic core. While this can maintain high permeability stability, it will significantly increase the permeability of the magnetic core. Therefore, when the magnetic field heat treatment time is 20-120 minutes, the permeability and stability of the magnetic core are more in line with the requirements.

[0025] Preferably, in step (2), the cooling is natural cooling. Preferably, the permeability of the iron-based magnetic core is constant at a frequency of 1-100kHz, and the permeability of the iron-based magnetic core is 15000-35000; the iron-based magnetic core contains an amorphous phase and nano-sized grains.

[0026] More preferably, when the permeability of the iron-based magnetic core is constant, the rate of change of the effective permeability of the iron-based magnetic core at a frequency of 1-100kHz is ≤5%.

[0027] The present invention also provides an application of the aforementioned iron-based magnetic core in the fabrication of inductors and high-current power devices.

[0028] Compared with the prior art, the present invention has the following beneficial effects: by subjecting the iron-based amorphous magnetic core to force field heat treatment and magnetic field heat treatment at specific temperatures in sequence, the present invention can obtain an iron-based magnetic core with constant permeability, and the iron-based magnetic core has the characteristic of constant permeability in the range of 15000-35000 at 1-100kHz. Attached Figure Description

[0029] Figure 1 shows the X-ray diffraction (XRD) pattern of the self-made amorphous ribbon.

[0030] Figure 2 is a comparison diagram of the magnetic domain structure between Example 1 (left) and Comparative Example 3 (right).

[0031] Figure 3 is a physical image of the magnetic core prepared in Example 1.

[0032] Figure 4 shows the relationship between the effective permeability and frequency of the iron-based nanocrystalline soft magnetic alloy cores in Examples 1-16.

[0033] Figure 5 shows the relationship between the effective permeability and frequency of the iron-based nanocrystalline soft magnetic alloy cores in Comparative Examples 1–7. Detailed Implementation

[0034] 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.

[0035] The amorphous ribbons used in the following examples and comparative examples can be purchased from the market or obtained by conventional methods. The methods for obtaining the ribbons can include the following processes: (1) component proportioning; (2) master alloy melting; (3) ribbon spinning and ribbon winding to obtain the corresponding amorphous ribbons.

[0036] Example 1

[0037] A method for preparing an iron-based magnetic core includes the following steps:

[0038] (1) The alloy Fe, in atomic percentage terms 73.5 Si 15.5 B7Cu1Nb3 amorphous ribbon (self-made, its XRD results are shown in Figure 1) was wound into an amorphous magnetic core. The amorphous magnetic core was then placed in a furnace, evacuated, and filled with inert argon gas to create a certain pressure in the system. The system was heated to the force field heat treatment temperature of 580℃ at a heating rate of 15℃ / min. At the same time, argon gas was continuously added to pressurize the system to a preset pressure of 150MPa. Subsequently, the system was cooled at a cooling rate of 100℃ / min. After cooling to below 200℃, the pressure was released until room temperature and atmospheric pressure were reached, resulting in a pre-burnt magnetic core.

[0039] (2) The pre-burnt magnetic core is placed in the magnetic field heat treatment furnace and heated to the magnetic field heat treatment temperature of 490°C at a heating rate of 10°C / min. At this time, a magnetic field parallel to the width direction of the magnetic core is applied and held for 60 minutes under the action of a magnetic field strength of 1500Gs. The core is then cooled to room temperature with the furnace to obtain the iron-based magnetic core.

[0040] Examples 2-15 and Comparative Examples 1-7

[0041] The only difference between Examples 2-15 and Comparative Examples 1-7 and Example 1 is that in steps (1)-(2), the heating and cooling rates, force field heat treatment temperature, preset pressure, magnetic field strength, magnetic field heat treatment temperature or holding time are different. See Table 1 for details.

[0042] Example 16

[0043] The difference between this embodiment 1 and the previous embodiment is that the alloy in this embodiment contains Fe by atomic percentage. 63.5 Co5Ni5Si 15.5 B7Cu1Nb3 amorphous ribbon, the amorphous ribbon is obtained in the same way as the amorphous ribbon in Example 1. It can be obtained by commercially available methods or by self-made methods. The self-made method may include the following process: (1) component ratio; (2) master alloy melting; (3) then through strip spinning and strip winding to obtain the corresponding amorphous ribbon.

[0044] Table 1

[0045] The iron-based magnetic cores prepared in the above embodiments and comparative examples were subjected to performance tests: the inductance L of the magnetic core was measured using a Keysight Agilent 4294A precision impedance analyzer with 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 ),

[0046] 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 N is the effective cross-sectional area of ​​the magnetic core, and N is the number of coil turns (test condition: 1 turn).

[0047] μ e Calculation method for rate of change %: μ e Rate of change % = (μ e(1kHz) -μ e(100kHz) ) / μ e(1kHz) ×100%, in this invention μ e A change rate of less than 5% is considered constant permeability.

[0048] Table 2

[0049] Referring to Table 2 and Figures 4-5, and as can be seen from Examples 1-16 and Comparative Examples 1-7, the present invention combines force field and magnetic field heat treatment at specific temperatures, resulting in iron-based magnetic cores containing amorphous phases and nano-sized grains. The resulting iron-based magnetic cores have low, stable or constant effective permeability at 1-100 kHz, with an effective permeability in the range of 15000-35000.

[0050] Under force field heat treatment, on the one hand, pressure promotes the precipitation of nanocrystals while simultaneously inhibiting their rapid growth. To a certain extent, this controls the grain size, allowing the magnetic core to maintain a relatively low and stable permeability. On the other hand, the presence of the pressure field induces magnetic anisotropy within the magnetic core, increasing domain wall energy. This high domain wall energy prevents domain wall movement, thus, to a certain extent, controlling the domain wall energy to maintain a relatively low and stable permeability, as shown in Figure 2. The actual function of magnetic field heat treatment is to induce grain orientation growth, that is, to promote the orientation of nanocrystals along the direction of the applied magnetic field, thereby inducing magnetic anisotropy and controlling the shape of the hysteresis loop. Force field heat treatment and magnetic field heat treatment work in tandem; force field heat treatment controls the grain size and domain wall energy, while magnetic field heat treatment further controls and induces grain orientation growth. This invention, by changing the heat treatment process, controls the grain size, state, magnetic anisotropy, and hysteresis loop shape to obtain a magnetic core with stable permeability in the 1-100 kHz range.

[0051] As can be seen from Examples 1-15 and Comparative Examples 1-7, amorphous magnetic cores need to undergo force field heat treatment and magnetic field heat treatment sequentially. The temperatures of these two heat treatments are key factors affecting the permeability and stability of the magnetic core, indicating that the heat treatment temperature has a significant impact on the grain size, state, and anisotropy within the magnetic core. When the force field heat treatment and magnetic field heat treatment temperatures are 530-650℃ and 435-550℃ respectively, the magnetic core maintains high permeability stability in the 1-100kHz range. Slight deviations from these two temperature ranges may be due to abnormal grain growth, resulting in a significantly increased rate of change in permeability, making it impossible to maintain stable or constant permeability.

[0052] In Examples 2, 1, and 3, the heating rate gradually increases, and the permeability and its rate of change gradually decrease. In Examples 4, 1, and 5, the thermal field temperature gradually increases, and the permeability and its rate of change gradually increase. In Examples 6, 1, and 7, the thermal field pressure gradually increases, and the permeability and its rate of change gradually decrease. In Examples 8, 1, and 9, the cooling rate gradually increases, and the permeability and its rate of change gradually decrease. From Examples 1-9, it can be observed that in force field heat treatment, in addition to the heat treatment temperature, the heating rate, cooling rate, and pressure all have a certain influence on the permeability and its rate of change of the magnetic core. The magnetic cores obtained in Examples 1-9 can maintain a permeability in the range of 15000-35000, and the rate of change of permeability in the 1-100kHz range is less than 5%, with some even maintaining a rate of change of less than 3%. Furthermore, in the force field heat treatment process, the heating process can be achieved simply by setting a corresponding program on the furnace body, while the cooling process requires auxiliary quenching equipment to achieve a cooling rate as high as 500℃ / min.

[0053] In Examples 10, 1, and 11, the magnetic field strength of the magnetic field heat treatment gradually increased, while the change in permeability was minimal, with the change initially increasing and then decreasing. In Examples 12, 1, and 13, the temperature of the magnetic field heat treatment gradually increased, while the permeability gradually decreased, with the change initially increasing and then decreasing. In Examples 14, 1, and 15, the time of the magnetic field heat treatment gradually increased, with the permeability initially decreasing and then increasing, corresponding to the change in permeability initially increasing and then decreasing. From Examples 1, 10-15, it can be observed that the magnetic field strength of the magnetic field heat treatment in the range of 800-3000 Gs has little effect on the magnitude of permeability, but it has a relatively large impact on the rate of change of permeability in the range of 1-100 kHz. Higher temperatures and longer treatment times lead to larger grain sizes in the magnetic core. Although this can maintain high permeability stability, it significantly increases the permeability of the core. Therefore, a magnetic field heat treatment temperature of 530-650℃ and a time of 20-120 min better meets the requirements for the permeability and stability of the magnetic core.

[0054] The amorphous ribbons in Examples 1 and 16 have different compositions. Similar to Example 1, the magnetic core of Example 16 can also maintain a permeability change rate of <5% in the range of 1-100KHz, achieving better permeability stability. This shows that the method of the present invention can be suitable for alloys with different composition types.

[0055] 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 an iron-based magnetic core, characterized in that, Includes the following steps: (1) Heat the iron-based amorphous magnetic core to a preset temperature and simultaneously pressurize it to a preset pressure, then cool it to below 200°C and start releasing the pressure to obtain a pre-burnt magnetic core; the preset temperature is 530-650°C and the preset pressure is greater than atmospheric pressure; (2) The pre-burnt magnetic core is subjected to magnetic field heat treatment and cooled to obtain an iron-based magnetic core. The temperature of the magnetic field heat treatment is 435-550℃.

2. The method for preparing the iron-based magnetic core as described in claim 1, characterized in that, In step (1), the preset pressure is 100-200 MPa.

3. The method for preparing the iron-based magnetic core as described in claim 1, characterized in that, In step (1), the heating rate of the iron-based amorphous magnetic core to the preset temperature is 5-30℃ / min.

4. The method for preparing the iron-based magnetic core as described in claim 1, characterized in that, In step (1), the cooling rate is 50-1000℃ / min; the pressurization method includes at least one of gas pressure pressurization and mold extrusion pressurization.

5. The method for preparing the iron-based magnetic core as described in claim 1, characterized in that, In step (2), the magnetic field strength of the magnetic field heat treatment is 800-3000 Gs, the magnetic field heat treatment time is 20-120 min, and the cooling is natural cooling.

6. The method for preparing the iron-based magnetic core as described in claim 1, characterized in that, The iron-based amorphous magnetic core mentioned in step (1) is formed by winding iron-based amorphous strip, and the magnetic field direction of the magnetic field heat treatment mentioned in step (2) is parallel to the width direction of the iron-based amorphous strip.

7. The method for preparing the iron-based magnetic core as described in claim 1, characterized in that, In step (1), the iron-based 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%, Mo 0-10%, and V 0-10%.

8. An iron-based magnetic core prepared by the method of any one of claims 1-7.

9. The iron-based magnetic core as described in claim 8, characterized in that, The iron-based magnetic core has a constant permeability at frequencies of 1-100kHz, and the permeability of the iron-based magnetic core is 15000-35000; the iron-based magnetic core contains an amorphous phase and nano-sized grains.

10. The application of the iron-based magnetic core according to claim 8 or 9 in the manufacture of inductors and high-current power devices.

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