A nanocrystalline magnetic core, a nanocrystalline inductor and a preparation method thereof

Abstract

The present invention belongs to the technical field of inductive components. The present invention provides a nanocrystalline magnetic core, a nanocrystalline inductor and a preparation method thereof. The nanocrystalline magnetic core is formed by subjecting an iron-based alloy amorphous straight strip to flash heating magnetoelastic stress treatment, nanocrystallization treatment and magnetic field heat treatment in sequence; the saturation magnetic induction intensity of the nanocrystalline magnetic core is greater than 1.24 T, and the alloy composition of the iron-based alloy amorphous straight strip is Fe-Si-B-Nb-Cu-M f , where M is one or more of Mo, V, Mn, Al, Cr, P, and 0 ≤ f < 3. The nanocrystalline magnetic core has both high saturation magnetic induction intensity and high magnetic permeability, and excellent soft magnetic properties. By using the nanocrystalline magnetic core provided by the present invention, a high magnetic induction nanocrystalline inductor is obtained, which has good frequency impedance characteristics and insertion loss characteristics, and at the same time can improve its anti-saturation ability, which is beneficial to broadening its application range.

Description

Technical Field

[0001] The present invention belongs to the technical field of inductive components, and particularly relates to a nanocrystalline magnetic core, a nanocrystalline inductor and a preparation method thereof. Background Art

[0002] With the rapid development of new energy vehicles and 5G communications, there are always a large number of high-frequency electromagnetic waves in the electronic devices during use. These electromagnetic waves will be emitted outward through external wires, affecting the normal operation of other devices. In order to eliminate the interference signals input on the signal line and various induced interferences, it is necessary to reasonably arrange a filter circuit to filter out common-mode interference. The nanocrystalline inductor is an important part of the filter circuit. The nanocrystalline inductor can not only filter out the common-mode electromagnetic interference on the signal line, but also suppress the electromagnetic interference that does not emit outward by itself.

[0003] This performance of the nanocrystalline inductor is closely related to the magnetic core used inside. The magnetic core generally refers to a sintered magnetic metal oxide material composed of various iron oxide mixtures. Among them, the traditional Mn-Zn ferrite inductor has a low magnetic permeability, saturation magnetic induction intensity, and Curie temperature, which severely limits the application range of the ferrite nanocrystalline inductor. In order to realize the high efficiency and miniaturization of the nanocrystalline inductor, it is necessary to improve the saturation magnetic induction intensity and high-frequency magnetic permeability of its magnetic core. At present, due to its high magnetic induction and high magnetic permeability, iron-based nanocrystals are gradually replacing traditional Mn-Zn ferrites as the iron cores of nanocrystalline inductors. It can improve the efficiency of the nanocrystalline inductor, reduce the volume, reduce the weight, save energy and protect the environment, and is known as a new type of green energy-saving material in the 21st century. At present, it is widely used in the field of power electronics.

[0004] The Chinese patent document with the publication number CN103117153A discloses a nanocrystalline inductor iron core and a preparation method thereof, which are optimized by adjusting the thickness of the iron-based nanocrystalline strip and the process parameters of composite magnetic field heat treatment. More in this patent document is the regulation of nanocrystalline properties, but its magnetic induction intensity is low and the process is relatively complex. Moreover, with the high-frequency development of power supply technology, the requirements for the soft magnetic properties of the nanocrystalline inductor iron core will also be higher and higher. As the frequency increases, the effective magnetic permeability of the existing magnetic core material will rapidly decay, and the inductance will also decrease accordingly. Such changes are not conducive to the design of magnetic devices and the realization of their functions. Summary of the Invention

[0005] Aiming at the above problems, the purpose of the present invention is to provide a nanocrystalline magnetic core, a nanocrystalline inductor and a preparation method thereof. The nanocrystalline magnetic core has both high saturation magnetic induction intensity and high magnetic permeability, and excellent soft magnetic properties. Using the nanocrystalline magnetic core provided by the present invention to obtain a high magnetic induction nanocrystalline inductor, which has good frequency impedance characteristics and insertion loss characteristics, and at the same time can improve its anti-saturation ability, which is beneficial to expanding its application range.

[0006] At present, the magnetic induction intensity of the nanocrystalline iron core of commercially available nanocrystalline inductors is only 1.2T, which greatly limits the miniaturization and anti-saturation ability of nanocrystalline inductors. Therefore, the existing technology needs to be further improved and perfected.

[0007] To achieve the above-mentioned invention purpose, the present invention first provides a nanocrystalline magnetic core with high magnetic induction. The nanocrystalline magnetic core is formed by subjecting an iron-based alloy amorphous straight strip to flash heating magnetoelastic stress treatment, nanocrystallization treatment, and magnetic field heat treatment in sequence; the saturation magnetic induction intensity of the nanocrystalline magnetic core is greater than 1.24T, and the alloy composition of the iron-based alloy amorphous straight strip is Fe-Si-B-Nb-Cu-M f , where M is one or more of Mo, V, Mn, Al, Cr, P, and 0 ≤ f < 3.

[0008] In the present invention, the nanocrystalline magnetic core for preparing a nanocrystalline inductor has an iron-based alloy composition of Fe-Si-B-Nb-Cu-M f , where M is one or more of Mo (molybdenum), V (vanadium), Mn (manganese), Al (aluminum), Cr (chromium), P (phosphorus), and 0 ≤ f < 3; preferably, it is Fe a Si b B c Nb d Cu e M f , and 74 ≤ a ≤ 78, 9 ≤ b ≤ 13, 6 ≤ c ≤ 8, 0.5 ≤ d ≤ 3, 0.5 ≤ e ≤ 1.5, 0 < f ≤ 2.5. This alloy composition has both high saturation magnetic induction intensity and high magnetic permeability, which is beneficial to improving the anti-saturation ability and impedance characteristics of nanocrystalline inductors.

[0009] The nanocrystalline magnetic core of the embodiment of the present invention for a nanocrystalline inductor is formed by subjecting an iron-based alloy amorphous straight strip to flash heating magnetoelastic stress treatment, winding it into an annular magnetic core and then subjecting it to nanocrystallization treatment, and then applying magnetic field heat treatment. Among them, the iron-based alloy amorphous straight strip belongs to the iron-silicon-boron-copper series alloy (Fe-Si-B-Cu series), and the alloy composition is preferably Fe a Si b B c Nb d Cu e M f , and 74 ≤ a ≤ 78, 9 ≤ b ≤ 13, 6 ≤ c ≤ 8, 0.5 ≤ d ≤ 3, 0.5 ≤ e ≤ 1.5, 0 < f ≤ 2.5. It can use commercially available materials, or corresponding raw materials of iron-based alloy components can be prepared into amorphous straight strips of a certain size by the rapid quenching method (for example, the thickness is 18μm and the width can be 10mm). The alloy compositions selected in the embodiments of the present invention include but are not limited to: Fe 76 Si 13B8Nb 1.5 Cu1Mo 0.5 , Fe 74 Si 13 B8Nb2Cu1Mn2, Fe 76 Si 12 B7Nb2Cu1V2, Fe 77 Si 12 B7Nb2Cu1P1, Fe 75 Si 12 B8Nb2Cu1Al2.

[0010] The thermodynamic behavior of the as-prepared (quenched state) of some embodiments of the present invention can be obtained by a differential scanning calorimeter. At the same time, the composite heat treatment in the embodiments of the present invention is divided into three stages. Stage 1: Flash heating magneto-elastic stress treatment; Stage 2: Ordinary heat treatment; Stage 3: Magnetic field heat treatment.

[0011] In the embodiments of the present invention, the flash heating magneto-elastic stress treatment can precipitate clusters, form short-range order similar to α-Fe, reduce the area of the short-range order region similar to FeB, effectively increase the number density of Cu clusters, and finally obtain high-density, fine and uniform nanocrystalline grains. After the nanocrystallization treatment, applying magnetic field heat treatment can induce the competition between uniaxial anisotropy and average random anisotropy, change its magnetization behavior, thereby effectively improving its high-frequency characteristics and the ability of the nanocrystalline inductor to suppress electromagnetic interference.

[0012] Specifically, the flash heating magneto-elastic stress treatment includes: applying a certain tensile force to a straight strip in an atmospheric environment and flash heating it while keeping it warm between two heated iron plates. Preferably, the temperature of the flash heating magneto-elastic stress treatment is between the Cu atom enrichment temperature and the primary crystallization start temperature. Further, the temperature of the flash heating magneto-elastic stress treatment is 390 - 500 °C, the magneto-elastic stress is 1 - 50 MPa, the flash heating rate is 10 - 200 K / s, and the magneto-elastic stress holding time is 2 - 16 s.

[0013] Among them, the temperature (T rc ) of the flash heating magneto-elastic stress treatment is between the Cu atom enrichment temperature and the primary crystallization start temperature, T rc is 390 - 500 °C, preferably 400 - 480 °C; the magneto-elastic stress can be 1 MPa - 50 MPa, preferably 5 - 40 MPa; the flash heating rate is 100 - 200 K / s, and the flash heating magneto-elastic stress holding time can be 2 s - 16 s, such as 4 s, 5 s, 6 s, 8 s, 10 s, etc. At T rcFlash heating at a certain temperature can induce the enrichment of Cu atoms and Fe atoms, providing nucleation sites for the precipitation of nanocrystalline grains in the next step. The competition for growth between these enriched Fe atoms and the newly formed nuclei during the subsequent crystallization can result in uniformly small-sized grains. Meanwhile, the short holding time will not lead to a reduction in available nucleation sites during the subsequent nanocrystallization process due to the coarsening of Cu clusters.

[0014] Subsequently, in the embodiment of the present invention, the straight strip after flash heating and magneto-elastic stress treatment is wound into an annular magnetic core by an automatic winding machine, and then the manufactured annular magnetic core is placed into a heat treatment furnace under an argon protection environment. The magnetic core is heated up with the furnace and held to perform nanocrystallization heat treatment.

[0015] In the embodiment of the present invention, the temperature (T fc ) of the nanocrystallization treatment is 40 °C - 100 °C after the start temperature of the first crystallization, T fc is 540 - 600 °C, and the holding time can be 30 - 75 min, preferably 30 - 60 min. By heat treating at 40 °C - 100 °C after the start temperature of the first crystallization in the embodiment of the present invention, uniformly distributed nanocrystalline grains can be obtained without the precipitation of hard magnetic phases; meanwhile, there are ferromagnetic interactions between these grains, averaging the relatively large magnetocrystalline anisotropy. This exchange coupling effect endows the nanocrystals with a dual-phase coupling structure with excellent soft magnetic properties, enabling the nanocrystalline inductor to have good electromagnetic interference suppression ability.

[0016] After the holding of the nanocrystallization treatment is completed, the magnetic core is cooled with the furnace to room temperature and taken out. Finally, in the embodiment of the present invention, the crystallized annular magnetic core is placed into a magnetic field heat treatment furnace under an argon protection environment. The magnetic core is heated up with the furnace and held. After holding for a certain time, the magnetic core is cooled with the furnace to 250 °C and taken out. Among them, the temperature of the magnetic field heat treatment is near the Curie temperature of the disordered phase. Preferably, the temperature of the magnetic field heat treatment is 360 - 500 °C, the holding time is 30 - 180 min, the direction of the applied magnetic field is perpendicular to the circumferential direction of the sample, and the magnetic field strength is 10 - 64 kA / m.

[0017] The temperature of the magnetic field heat treatment in the embodiment of the present invention is near the Curie temperature (T ac ) of the disordered phase; T ac is preferably 360 - 500 °C, the holding time can be 30 - 180 min, preferably 45 - 160 min. During the magnetic field heat treatment process, the direction of the applied magnetic field is perpendicular to the circumferential direction of the sample (substantially consistent with the easy magnetization direction of the magnetic core); the magnetic field strength can be 10 - 64 kA / m, and the magnetic field is applied at the beginning of the holding, and the magnetic field application stops after the sample is taken out. To avoid the magnetic core material losing its magnetism, the magnetic field heat treatment needs to be carried out at T acNear the temperature, at the same time, magnetic field heat treatment along the easy magnetization direction of the magnetic core can obtain a smooth hysteresis loop, change its magnetization behavior, enable the magnetic core to obtain excellent high-frequency characteristics, and improve the current saturation resistance ability of the nanocrystalline inductor.

[0018] In the embodiment of the present invention, the above-mentioned high magnetic induction nanocrystalline alloy is used, combined with an improved composite heat treatment process. The composite heat treatment is that after the straight strip is subjected to flash heating magnetoelastic stress treatment, it is wound into an annular magnetic core and then subjected to nanocrystallization treatment, and then magnetic field heat treatment is applied; the saturation magnetic induction intensity of the obtained high magnetic induction nanocrystalline magnetic core is greater than 1.24T. By adjusting the composite heat treatment process of the nanocrystalline magnetic core in the embodiment of the present invention, the current saturation resistance ability of the inductor is effectively improved, and it has good frequency impedance characteristics and insertion loss characteristics, which is beneficial to the miniaturization, simplification, etc. of the magnetic device design and the realization of its functions.

[0019] The present invention provides a nanocrystalline inductor, which is composed of the above-mentioned nanocrystalline magnetic core obtained by flash heating magnetoelastic stress and magnetic field composite treatment, a protective box, and two groups of coils wound in the same direction.

[0020] Among them, the alloy composition, flash heating magnetoelastic stress and magnetic field composite heat treatment scheme for the nanocrystalline inductor magnetic core are as described above; it not only has both high saturation magnetic induction intensity and high magnetic permeability, but also has excellent soft magnetic properties and a simple process.

[0021] The protective box described in the embodiment of the present invention is generally a plastic box, preferably made of a high-temperature resistant resin material, and mainly plays a role in protecting the nanocrystalline magnetic core. There are no special restrictions on the structure of the protective box in the embodiment of the present invention, and the conventional ones in the art can be adopted. The wire diameter of the coil can be 0.6 - 1.2 mm, and the coil is only wound in one layer.

[0022] In the preferred embodiment of the present invention, the single-turn inductance of the nanocrystalline inductor is ≥5 μH at 100 kHz, the insertion loss is ≥30 dB, and the single-turn inductance attenuation rate is ≤10% for 0 - 5 A.

[0023] The embodiment of the present invention provides a preparation method of the nanocrystalline inductor as described above, including the following steps:

[0024] S1. The iron-based alloy amorphous straight strip is sequentially subjected to flash heating magnetoelastic stress treatment, nanocrystallization treatment, and magnetic field heat treatment to obtain a high magnetic induction nanocrystalline magnetic core; the alloy composition of the iron-based alloy amorphous straight strip is Fe - Si - B - Nb - Cu - M f , M is one or more of Mo, V, Mn, Al, P, Cr, and 0 ≤ f < 3;

[0025] S2. Place the nanocrystalline magnetic core with high magnetic induction into a protective box for protection. Wind two groups of co-directional common-mode coils around the protected magnetic core with enameled wire to obtain the nanocrystalline inductor.

[0026] The embodiments of the present invention provide the following technical solutions:

[0027] In the embodiments of the present invention, first, a nanocrystalline magnetic core is made by using flash heating magnetoelastic stress and magnetic field composite treatment, etc. Then, the magnetic core after composite heat treatment is placed into a plastic protective box to obtain the high magnetic induction nanocrystalline inductor magnetic core of this embodiment. Finally, wind two groups of co-directional common-mode coils around the protected magnetic core with enameled wire to obtain the nanocrystalline inductor of this embodiment.

[0028] In some embodiments of the present invention, the alloy composition for preparing the nanocrystalline inductor magnetic core is Fe a Si b B c Nb d Cu e M f , where M is one or more of Mo, V, Mn, Al, Cr, P, and 74 ≤ a ≤ 78, 9 ≤ b ≤ 13, 6 ≤ c ≤ 8, 0.5 ≤ d ≤ 3, 0.5 ≤ e ≤ 1.5, 0 ≤ f ≤ 2.5. The raw materials used for preparing this alloy are all commercially available, including industrial pure iron, pure silicon, pure copper, ferroboron (99%), ferroniobium (99%), pure molybdenum, etc.

[0029] The processes such as flash heating magnetoelastic stress and magnetic field composite treatment described in the present invention are as described above, and reference can be made to Figure 1 , Figure 1 which is a schematic diagram of the composite heat treatment process in some embodiments of the present invention. Among them, the flash heating magnetoelastic stress treatment is recorded as stage one, applying a tensile force, and the temperature can be 390 - 500 °C; stage two is to make the material nanocrystalline through ordinary heat treatment, and the temperature can be 540 - 600 °C; stage three is magnetic field heat treatment, applying a magnetic field, and the temperature can be 360 - 500 °C to obtain the nanocrystalline magnetic core.

[0030] Figure 2 is a schematic diagram of the nanocrystalline inductor product in some embodiments of the present invention; where 1 and 2 are coils respectively, 3 is the protective box + magnetic core, 4 is the protective box, and 5 is the magnetic core.

[0031] In the embodiments of the present invention, the high-temperature resistant resin protective box 4 of the nanocrystalline inductor fits with the magnetic core 5 and has the function of protecting the magnetic core. When the protective box and the magnetic core are fitted during use, the leakage magnetic flux generated by the asymmetric distribution of magnetic force lines caused by the movement of the magnetic core can be reduced.

[0032] In an embodiment of the present invention, the nanocrystalline inductor includes two groups of coils 1 and 2 wound in the same direction. The number of turns of each group of coils can be 20 - 40 turns, the wire diameter is 0.6 - 1.2 mm, and each group of coils is wound in only one layer. The purpose of winding the coils in one layer is to avoid generating parasitic capacitance, thereby reducing its impact on the filtering ability of the nanocrystalline inductor in the high-frequency band.

[0033] In the embodiment of the present invention, the single-turn inductance of the nanocrystalline inductor is ≥5 μH at 100 kHz, the insertion loss is ≥30 dB, and the single-turn inductance attenuation rate is ≤10% for 0 - 5 A. The large impedance of the nanocrystalline inductor of the present invention can play a role in attenuating interference when the magnetic field lines are superimposed on each other; the relatively large insertion loss of the nanocrystalline inductor can effectively reduce noise interference; the lower the inductance attenuation rate of the nanocrystalline inductor, the stronger its anti-saturation ability.

[0034] Compared with the existing technology, the beneficial effects of the present invention are as follows: The nanocrystalline inductor core prepared by the present invention has excellent high-frequency performance and other characteristics. Applying it to the nanocrystalline inductor can meet the requirements of its miniaturization, high efficiency, and high frequency, broadening its product market and application prospects in power electronic devices. The flash heating magnetoelastic stress and magnetic field composite heat treatment scheme provided for the nanocrystalline inductor core simplifies the process and provides a new production route for the large-scale production of nanocrystalline inductors. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a schematic diagram of the composite heat treatment process in some embodiments of the present invention;

[0036] Figure 2 It is a schematic diagram of the nanocrystalline inductor product in some embodiments of the present invention; wherein, 1 - coil, 2 - coil, 3 - protective box + magnetic core, 4 - protective box, 5 - magnetic core;

[0037] Figure 3 It is an X-ray diffraction pattern of the as-prepared state (quenched state) and the first-stage treatment state in Example 1;

[0038] Figure 4 It is an X-ray diffraction pattern of Example 1 and Comparative Example 1. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0039] In order to further illustrate the technical solution of the present invention, the preferred implementation schemes of the present invention will be described below in conjunction with embodiments. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the present invention.

[0040] Example 1:

[0041] The alloy composition of this embodiment is Fe 76 Si 13 B8Nb1.5 Cu1Mo 0.5 , and the raw materials used in its preparation are all commercially available, including industrial pure iron, pure silicon, pure copper, pure molybdenum, ferrosilicon (99%) and ferroniobium (99%); an amorphous straight strip with a thickness of 18 μm is obtained by the rapid quenching method. The thermodynamic behavior of the as-prepared state (quenched state) of this example is obtained by a differential scanning calorimeter. At the same time, the composite heat treatment is divided into three stages. Stage 1: Flash heating magnetoelastic stress treatment; Stage 2: Ordinary heat treatment; Stage 3: Magnetic field heat treatment.

[0042] The specific composite heat treatment is as follows: In an atmospheric environment, a 10 mm wide straight strip is applied with a tensile force of 10 MPa and passed between two iron plates heated to 480 °C. The flash heating holding time is 8 s. Subsequently, the straight strip after the flash magnetoelastic stress treatment is wound into an annular magnetic core with an inner diameter of 20 mm, an outer diameter of 23 mm, and a height of 10 mm by an automatic winding machine. The manufactured annular magnetic core is placed in a heat treatment furnace under an argon protection environment, and the magnetic core is heated with the furnace to 550 °C and held for 30 min for nanocrystallization heat treatment. After the holding is completed, the magnetic core is cooled with the furnace to room temperature and taken out. Finally, the crystallized annular magnetic core is placed in a magnetic field heat treatment furnace under an argon protection environment, and the magnetic core is heated with the furnace to 400 °C and held for 60 min. After the holding is completed, the magnetic core is cooled with the furnace to 250 °C and taken out. The direction of the applied magnetic field is perpendicular to the circumferential direction of the sample, so that the easy magnetization direction of the magnetic core is basically the same as the direction of the applied magnetic field. The magnetic field strength is 64 kA / m, the magnetic field is applied at the beginning of the holding, and the applied magnetic field is stopped after the sample is taken out.

[0043] The magnetic core after the composite heat treatment is placed in a plastic protective box to obtain the high magnetic induction nanocrystalline inductor magnetic core of this example. Using an automatic winding machine, two groups of 30-turn co-directional common-mode coils are wound around the protected magnetic core with an enameled wire with a diameter of 0.8 mm to obtain the inductor of this example.

[0044] The insertion loss is obtained by a vector network analyzer (E5072A), and the impedance and inductance are obtained by an impedance analyzer (Agilent4294A) (see Table 1). The saturation magnetic induction intensity of the magnetic core is measured by a vibrating sample magnetometer of model 7410 (see Table 2). The microstructures of the as-prepared state (quenched state), the first-stage treatment state, and the three-stage complete treatment state samples of this example are analyzed by an X-ray diffractometer (D8Advance type XRD), and the results are respectively as Figure 3 , Figure 4 shown.

[0045] Figure 3 are the X-ray diffraction patterns of the as-prepared state (quenched state) and the first-stage treatment state in Example 1; from Figure 3It can be seen that after the flash heating magneto-elastic stress treatment in Stage 1, a crystallization peak appears at 65° for the straight strip, which is caused by the preferred orientation of stress-induced grains, indicating that a small number of grains with smaller sizes are precipitated, and at the same time, its local structure changes to form a short-range ordered structure similar to α-Fe.

[0046] Example 2:

[0047] The alloy composition of this example is Fe 74 Mn2Cu1Si 13 B8Nb2. The raw materials used in its preparation are all commercially available, including industrial pure iron, pure silicon, pure copper, pure manganese, ferroboron (99%) and ferroniobium (99%); an amorphous straight strip with a thickness of 18 μm is prepared by the rapid quenching method. The thermodynamic behavior of the as-prepared state (quenched state) of this example is obtained by a differential scanning calorimeter. At the same time, the composite heat treatment is divided into three stages: Stage 1: Flash heating magneto-elastic stress treatment; Stage 2: Ordinary heat treatment; Stage 3: Magnetic field heat treatment.

[0048] The specific composite heat treatment is as follows: In an atmospheric environment, a 10-mm-wide straight strip is applied with a tensile force of 10 MPa and passed between two iron plates heated to 500 °C, and the flash heating holding time is 8 s. Subsequently, the straight strip after the flash magneto-elastic stress treatment is wound into an annular magnetic core with an inner diameter of 20 mm, an outer diameter of 23 mm, and a height of 10 mm by an automatic winding machine. The manufactured annular magnetic core is placed in a heat treatment furnace under an argon protection environment, and the magnetic core is heated with the furnace to 560 °C and held for 60 min for nanocrystallization heat treatment. After the holding is completed, the magnetic core is cooled with the furnace to room temperature and taken out. Finally, the crystallized annular magnetic core is placed in a magnetic field heat treatment furnace under an argon protection environment, and the magnetic core is heated with the furnace to 400 °C and held for 60 min. After the holding is completed, the magnetic core is cooled with the furnace to 250 °C and taken out. The direction of the applied magnetic field is perpendicular to the circumferential direction of the sample, so that the easy magnetization direction of the magnetic core is basically consistent with the direction of the applied magnetic field. The magnetic field strength is 64 kA / m, and the magnetic field is applied at the beginning of the holding stage, and the magnetic field application is stopped after the sample is taken out.

[0049] The magnetic core after the composite heat treatment is placed in a plastic protective box to obtain the high magnetic induction nanocrystalline inductor magnetic core of this example. The protected magnetic core is wound with an enameled wire with a diameter of 0.8 mm into two groups of 30-turn co-directional common-mode coils by an automatic winding machine to obtain the inductor of this example.

[0050] The insertion loss is obtained by a vector network analyzer (E5072A), the impedance and inductance are obtained by an impedance analyzer (Agilent4294A), and the saturation magnetic induction intensity of the magnetic core is measured using a vibrating sample magnetometer of model 7410 (see Table 2).

[0051] Example 3:

[0052] The alloy composition of this embodiment is Fe 76 V2Cu1Si 12 B7Nb2. The raw materials used in its preparation are all commercially available, including industrial pure iron, pure silicon, pure copper, pure vanadium, ferroboron (99%) and ferroniobium (99%); an amorphous straight strip with a thickness of 18 μm is obtained by the rapid quenching method. The thermodynamic behavior of the as-prepared (quenched) state of this embodiment is obtained by a differential scanning calorimeter. At the same time, the composite heat treatment is divided into three stages. Stage 1: Flash heating magnetoelastic stress treatment; Stage 2: Ordinary heat treatment; Stage 3: Magnetic field heat treatment.

[0053] The specific composite heat treatment is as follows: In an atmospheric environment, a 10-mm-wide straight strip is applied with a tensile force of 20 MPa and passed between two iron plates that have been heated to 460 °C. The flash heating holding time is 6 s. Subsequently, the straight strip after the flash magnetoelastic stress treatment is wound into an annular magnetic core with an inner diameter of 20 mm, an outer diameter of 23 mm, and a height of 10 mm by an automatic winding machine. The manufactured annular magnetic core is placed in a heat treatment furnace under an argon protection environment, and the magnetic core is heated with the furnace to 560 °C and held for 45 min for nanocrystallization heat treatment. After the holding is completed, the magnetic core is cooled with the furnace to room temperature and taken out. Finally, the crystallized annular magnetic core is placed in a magnetic field heat treatment furnace under an argon protection environment, and the magnetic core is heated with the furnace to 420 °C and held for 120 min. After the holding is completed, the magnetic core is cooled with the furnace to 250 °C and taken out. The direction of the applied magnetic field is perpendicular to the circumferential direction of the sample, so that the easy magnetization direction of the magnetic core is basically the same as the direction of the applied magnetic field. The magnetic field strength is 40 kA / m. The magnetic field is applied at the beginning of the holding stage, and the magnetic field application is stopped after the sample is taken out.

[0054] The magnetic core after the composite heat treatment is placed in a plastic protective box to obtain the high magnetic induction nanocrystalline inductor magnetic core of this embodiment. The protected magnetic core is wound with enameled wire with a diameter of 0.8 mm to form two groups of 30-turn co-directional common-mode coils by an automatic winding machine to obtain the inductor of this embodiment.

[0055] The insertion loss is obtained by a vector network analyzer (E5072A), the impedance and inductance are obtained by an impedance analyzer (Agilent4294A), and the saturation magnetic induction intensity of the magnetic core is measured by a vibrating sample magnetometer of model 7410 (see Table 2).

[0056] Example 4:

[0057] The alloy composition of this embodiment is Fe 77 Si 12B7Nb2Cu1P1, and all the raw materials used in its preparation are commercially available, including industrial pure iron, pure silicon, pure copper, ferroboron (99%), ferroniobium (99%) and ferrophosphorus (99%); an amorphous straight strip with a thickness of 18 μm is obtained by the rapid quenching method. The thermodynamic behavior of the as-prepared (quenched) state of this example is obtained by a differential scanning calorimeter. At the same time, the composite heat treatment is divided into three stages. Stage 1: Flash heating and magnetoelastic stress treatment; Stage 2: Ordinary heat treatment; Stage 3: Magnetic field heat treatment.

[0058] The specific composite heat treatment is as follows: In an atmospheric environment, a 10-mm-wide straight strip is applied with a tensile force of 15 MPa and passed between two iron plates heated to 450 °C, and the flash heating holding time is 8 s. Subsequently, the straight strip after the flash magnetoelastic stress treatment is wound into an annular magnetic core with an inner diameter of 20 mm, an outer diameter of 23 mm, and a height of 10 mm by an automatic winding machine. The manufactured annular magnetic core is placed in a heat treatment furnace under an argon protection environment, and the magnetic core is heated with the furnace to 580 °C and held for 30 min for nanocrystallization heat treatment. After the holding is completed, the magnetic core is cooled with the furnace to room temperature and taken out. Finally, the crystallized annular magnetic core is placed in a magnetic field heat treatment furnace under an argon protection environment, and the magnetic core is heated with the furnace to 380 °C and held for 60 min. After the holding is completed, the magnetic core is cooled with the furnace to 250 °C and taken out. The direction of the applied magnetic field is perpendicular to the circumferential direction of the sample, so that the easy magnetization direction of the magnetic core is basically the same as the direction of the applied magnetic field. The magnetic field strength is 60 kA / m, the magnetic field is applied at the beginning of the holding stage, and the magnetic field application is stopped after the sample is taken out.

[0059] The magnetic core after the composite heat treatment is placed in a plastic protective box to obtain the high magnetic induction nanocrystalline inductive magnetic core of this example. The protected magnetic core is wound with two groups of 30-turn co-directional common-mode coils made of enameled wire with a diameter of 0.8 mm by an automatic winding machine to obtain the inductor of this example.

[0060] The insertion loss is obtained by a vector network analyzer (E5072A), the impedance and inductance are obtained by an impedance analyzer (Agilent4294A), and the saturation magnetic induction intensity of the magnetic core is measured by a vibration sample magnetometer of model 7410 (see Table 2).

[0061] Example 5:

[0062] The alloy composition of this example is Fe 75 Si 12B8Nb2Cu1Al2, and all the raw materials used in its preparation are commercially available, including commercially pure iron, pure silicon, pure copper, pure aluminum, ferroboron (99%) and ferroniobium (99%); an amorphous straight strip with a thickness of 18 μm is obtained by the rapid quenching method. The thermodynamic behavior of the as-prepared state (quenched state) of this example is obtained by a differential scanning calorimeter. At the same time, the composite heat treatment is divided into three stages. Stage 1: Flash heating and magnetoelastic stress treatment; Stage 2: Ordinary heat treatment; Stage 3: Magnetic field heat treatment.

[0063] The specific composite heat treatment is as follows: In an atmospheric environment, a 10-mm-wide straight strip is applied with a tensile force of 15 MPa and passed between two iron plates that have been heated to 460 °C. The flash heating and holding time is 8 s. Subsequently, the straight strip after the flash magnetoelastic stress treatment is wound into an annular magnetic core with an inner diameter of 20 mm, an outer diameter of 23 mm, and a height of 10 mm by an automatic winding machine. The manufactured annular magnetic core is placed in a heat treatment furnace under an argon protection environment, and the magnetic core is heated in the furnace to 570 °C and held for 30 min for nanocrystallization heat treatment. After the holding is completed, the magnetic core is cooled in the furnace to room temperature and taken out. Finally, the crystallized annular magnetic core is placed in a magnetic field heat treatment furnace under an argon protection environment, and the magnetic core is heated in the furnace to 420 °C and held for 75 min. After the holding is completed, the magnetic core is cooled in the furnace to 250 °C and taken out. The direction of the applied magnetic field is perpendicular to the circumferential direction of the sample, so that the easy magnetization direction of the magnetic core is basically the same as the direction of the applied magnetic field. The magnetic field strength is 50 kA / m. The magnetic field is applied at the beginning of the holding stage, and the magnetic field application stops after the sample is taken out.

[0064] The magnetic core after the composite heat treatment is placed in a plastic protective box to obtain the high magnetic induction nanocrystalline inductor magnetic core of this example. The protected magnetic core is wound with two groups of 30-turn co-directional common-mode coils made of enameled wire with a diameter of 0.8 mm by an automatic winding machine to obtain the inductor of this example.

[0065] The insertion loss is obtained by a vector network analyzer (E5072A), the impedance and inductance are obtained by an impedance analyzer (Agilent4294A), and the saturation magnetic induction intensity of the magnetic core is measured by a vibrating sample magnetometer of model 7410 (see Table 2).

[0066] Example 6:

[0067] The alloy composition of this example is Fe 75.8 Si 12 B8Nb 2.6 Cu 0.6P1 is prepared from commercially available raw materials, including commercially pure iron, pure silicon, pure copper, ferroboron (99%), ferroniobium (99%) and ferrophosphorus (99%); an amorphous straight strip with a thickness of 18 μm is obtained by the rapid quenching method. The thermodynamic behavior of the as-prepared (quenched) state of this example is obtained by a differential scanning calorimeter. At the same time, the composite heat treatment is divided into three stages: Stage 1: Flash heating and magnetoelastic stress treatment; Stage 2: Ordinary heat treatment; Stage 3: Magnetic field heat treatment.

[0068] The specific composite heat treatment is as follows: In an atmospheric environment, a 10-mm-wide straight strip is applied with a tensile force of 30 MPa and passed between two iron plates heated to 450 °C. The flash heating holding time is 4 s. Subsequently, the straight strip after the flash magnetoelastic stress treatment is wound into an annular magnetic core with an inner diameter of 20 mm, an outer diameter of 23 mm, and a height of 10 mm by an automatic winding machine. The manufactured annular magnetic core is placed in a heat treatment furnace under an argon protection environment. The magnetic core is heated in the furnace to 570 °C and held for 45 min for nanocrystallization heat treatment. After the holding is completed, the magnetic core is cooled in the furnace to room temperature and taken out. Finally, the crystallized annular magnetic core is placed in a magnetic field heat treatment furnace under an argon protection environment. The magnetic core is heated in the furnace to 450 °C and held for 90 min. After the holding is completed, the magnetic core is cooled in the furnace to 250 °C and taken out. The direction of the applied magnetic field is perpendicular to the circumferential direction of the sample, so that the easy magnetization direction of the magnetic core is basically the same as the direction of the applied magnetic field. The magnetic field strength is 50 kA / m. The magnetic field is applied at the beginning of the holding stage, and the magnetic field application is stopped after the sample is taken out.

[0069] The magnetic core after the composite heat treatment is placed in a plastic protective box to obtain the high magnetic induction nanocrystalline inductor magnetic core of this example. The protected magnetic core is wound with two groups of 30-turn co-directional common-mode coils made of enameled wire with a diameter of 0.8 mm by an automatic winding machine to obtain the inductor of this example.

[0070] The insertion loss is obtained by a vector network analyzer (E5072A), the impedance and inductance are obtained by an impedance analyzer (Agilent4294A), and the saturation magnetic induction intensity of the magnetic core is measured by a vibration sample magnetometer of model 7410 (see Table 2).

[0071] Comparative Example 1:

[0072] The alloy composition selected in this comparative example and the alloy composition of Example 1 are both Fe 76 Si 13 B8Nb 1.5 Cu1Mo 0.5, the difference lies in that: the composite heat treatment process only includes stage two and stage three. An amorphous strip with a thickness of 18 μm is obtained by the rapid quenching method. Subsequently, the straight strip is wound into an annular magnetic core with an inner diameter of 20 mm, an outer diameter of 23 mm, and a height of 10 mm through an automatic winding machine. The manufactured annular magnetic core is placed into a heat treatment furnace under an argon protection environment. The magnetic core is heated in the furnace to 550 °C and held for 30 min for nanocrystallization heat treatment. After the heat preservation ends, the magnetic core is cooled in the furnace to room temperature and taken out. Finally, the crystallized annular magnetic core is placed into a magnetic field heat treatment furnace under an argon protection environment. The magnetic core is heated in the furnace to 400 °C and held for 60 min. After the heat preservation ends, the magnetic core is cooled in the furnace to 250 °C and taken out. The direction of the applied magnetic field is perpendicular to the circumferential direction of the sample, so that the easy magnetization direction of the magnetic core is basically consistent with the direction of the applied magnetic field. The magnetic field strength is 64 kA / m. The magnetic field is applied at the beginning of the heat preservation stage, and the magnetic field application stops after the sample is taken out.

[0073] The heat-treated magnetic core is placed into a plastic protective box to obtain the nanocrystalline inductance magnetic core of this comparative example. The protected magnetic core is wound with enameled wire with a diameter of 0.8 mm by an automatic winding machine to form two groups of 30-turn coaxial common-mode coils in the same direction, thus obtaining the nanocrystalline inductor of this embodiment.

[0074] The insertion loss is obtained through a vector network analyzer (E5072A), the impedance and inductance are obtained through an impedance analyzer (Agilent4294A), and the saturation magnetic induction intensity of the magnetic core is measured using a vibration sample magnetometer of model 7410 (see Table 2).

[0075] Comparative Example 2:

[0076] The alloy composition selected in this comparative example is Fe 74 Mn2Cu1Si 13 B8Nb2. An amorphous strip with a thickness of 18 μm is obtained by the rapid quenching method. Subsequently, the straight strip is wound into an annular magnetic core with an inner diameter of 20 mm, an outer diameter of 23 mm, and a height of 10 mm through an automatic winding machine. The manufactured annular magnetic core is placed into a heat treatment furnace under an argon protection environment. The magnetic core is heated in the furnace to 560 °C and held for 60 min for nanocrystallization heat treatment. After the heat preservation ends, the magnetic core is cooled in the furnace to room temperature and taken out. Finally, the crystallized annular magnetic core is placed into a magnetic field heat treatment furnace under an argon protection environment. The magnetic core is heated in the furnace to 400 °C and held for 60 min. After the heat preservation ends, the magnetic core is cooled in the furnace to 250 °C and taken out. The direction of the applied magnetic field is perpendicular to the circumferential direction of the sample, so that the easy magnetization direction of the magnetic core is basically consistent with the direction of the applied magnetic field. The magnetic field strength is 64 kA / m. The magnetic field is applied at the beginning of the heat preservation stage, and the magnetic field application stops after the sample is taken out.

[0077] The heat-treated magnetic core is placed into a plastic protective case to obtain the nanocrystalline inductive magnetic core of this comparative example. The protected magnetic core is wound with two sets of 30-turn co-directional common-mode coils made of enameled wire with a diameter of 0.8 mm using an automatic winding machine to obtain the nanocrystalline inductor of this example.

[0078] The insertion loss is obtained through a vector network analyzer (E5072A), and the impedance and inductance are obtained through an impedance analyzer (Agilent 4294A). The saturation magnetic induction intensity of the magnetic core is measured using a vibration sample magnetometer of model 7410 (see Table 2).

[0079] The differences between Examples 1 and 2 and Comparative Examples 1 and 2 lie in the different composite heat treatment schemes. The impedance, insertion loss, and inductance performance of the nanocrystalline inductors at 100 kHz obtained through different composite heat treatments are shown in Table 1. For the convenience of comparing with the performance of other nanocrystalline inductors, the inductance values of the present invention have all been normalized to represent the inductance per turn L A = L / N 2 . It can be seen from Table 1 that for the nanocrystalline inductor described in the examples of the present invention, the inductance per turn ≥ 5 μH, the insertion loss ≥ 30 dB, and the attenuation rate of the inductance per turn at 0 - 5 A ≤ 10%.

[0080] Table 1: Performance of the inductors of the examples and comparative examples of the present invention

[0081] Impedance (kΩ) Insertion Loss (dB) Inductance (μH) Example 1 4.0 33 5.28 Example 2 4.4 35 5.70 Comparative Example 1 3.0 23 4.21 Comparative Example 2 3.1 24 4.55

[0082] From Figure 4 it can be seen that during the flash heating and magnetoelastic stress treatment in the first stage of Example 1, partial grain preferred orientation was formed and retained, and at the same time, more Si atoms were dissolved in α-Fe during the subsequent crystallization process to form the DO3 structure, enabling the nanocrystalline soft magnetic material to have excellent soft magnetic properties.

[0083] Comparative Example 3:

[0084] The alloy composition selected for this comparative example is Fe 73.5 Si 13.5B9Cu1Nb3, the raw materials used in its preparation are all commercially available, including commercially pure iron, pure silicon, pure copper, ferroboron (99%) and ferroniobium (99%); an amorphous ribbon with a thickness of 18 μm is prepared by the rapid quenching method, and then the ribbon is made into an annular magnetic core with an inner diameter of 20 mm, an outer diameter of 23 mm and a height of 10 mm using an automatic winding machine. The manufactured annular magnetic core is placed into a magnetic field heat treatment furnace under the protective environment of high-purity argon. The annular magnetic core is first kept at a temperature of 450 °C for 60 min, and then continuously heated to 550 °C and kept for 120 min. The magnetic field direction applied in this stage is perpendicular to the circumferential direction of the sample (substantially consistent with the easy magnetization direction of the magnetic core), the magnetic field strength is 64 kA / m, and the applied magnetic field is maintained from the start of heating until the end of the heat treatment process of the annular magnetic core.

[0085] The heat-treated magnetic core is placed into a plastic protective box to obtain the nanocrystalline inductive magnetic core of this comparative example. The protected magnetic core is wound with enameled wire with a diameter of 0.8 mm by an automatic winding machine to form two groups of 30-turn co-directional common-mode coils, thereby obtaining the nanocrystalline inductor of this embodiment.

[0086] The insertion loss is obtained by a vector network analyzer (E5072A), the impedance and inductance are obtained by an impedance analyzer (Agilent4294A), and the saturation magnetic induction intensity of the magnetic core is measured using a vibration sample magnetometer of model 7410 (see Table 2).

[0087] Table 2 shows the variation of the inductance with the applied current at 100 kHz for Examples 1 to 6 and Comparative Examples 1 to 3, and its attenuation ability represents the strength of its anti-saturation ability. B s is the saturation magnetic induction intensity.

[0088] Table 2: Anti-saturation ability of the inductors of Examples 1 to 6 and Comparative Examples 1 to 3 of the present invention

[0089] <![CDATA[B s (T)]]> Single-turn Inductor Attenuation Rate (100 kHz) for 0 - 5A Example 1 1.38 6.2％ Example 2 1.32 8.5％ Example 3 1.36 7.2％ Example 4 1.39 5.7％ Example 5 1.35 7.3％ Example 6 1.34 7.4％ Comparative Example 1 1.38 15.3％ Comparative Example 2 1.32 12.5％ Comparative Example 3 1.24 20.2％

[0090] As can be seen from the comparison, the reason why the embodiments of the present invention have excellent performance is mainly due to the flash magnetoelastic stress treatment and the magnetic field heat treatment. First of all, the flash stress treatment causes clusters to precipitate during the flash stress treatment of the nanocrystalline soft magnetic material, forming a short-range order similar to α-Fe, reducing the area of the short-range order region similar to FeB, and effectively increasing the number density of Cu clusters. At the same time, Fe atoms continuously enrich in the amorphous matrix, and the number of Fe clusters increases continuously, resulting in an increase in the nucleation position density of the α-Fe(Si) phase. Eventually, high-density, fine and uniform nanocrystalline grains can be obtained. Therefore, the present invention can endow the nanocrystalline soft magnetic material with excellent soft magnetic properties, thereby improving the inductance and impedance characteristics of the nanocrystalline inductor. Subsequently, the magnetic field heat treatment can induce the competition between uniaxial anisotropy and average random anisotropy, and a magnetization behavior mainly dominated by rotation, accompanied by domain wall displacement and splitting can be formed. And as the frequency increases, the domain walls are significantly refined, and thus the residual loss can be significantly reduced. Therefore, the present invention can endow it with excellent high-frequency characteristics, thereby improving the current saturation resistance ability of the nanocrystalline inductor.

[0091] In summary, the embodiments of the present invention use a high magnetic induction nanocrystalline alloy and cooperate with an improved composite heat treatment process, so that the obtained high magnetic induction nanocrystalline inductor has good frequency impedance characteristics and insertion loss characteristics, and at the same time improves its saturation resistance ability, can meet the requirements of miniaturization, high efficiency and high frequency, and broadens its application scope.

[0092] The embodiments described above are only used to describe the preferred embodiments of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A nanocrystalline magnetic core, characterized in that, The nanocrystalline magnetic core is formed by subjecting an iron-based alloy amorphous straight strip to flash heating magnetoelastic stress treatment, nanocrystallization treatment, and magnetic field heat treatment in sequence; the temperature of the flash heating magnetoelastic stress treatment is 390 - 500 °C, the magnetoelastic stress is 1 - 50 MPa, the flash heating rate is 10 - 200 K / s, and the magnetoelastic stress holding time is 2 - 16 s; the temperature of the nanocrystallization treatment is 540 - 600 °C, and the holding time is 30 - 75 min; the temperature of the magnetic field heat treatment is 360 - 500 °C, the holding time is 30 - 180 min, the direction of the applied magnetic field is perpendicular to the circumferential direction of the sample, and the magnetic field intensity is 10 - 64 kA / m; The saturation magnetic induction intensity of the nanocrystalline magnetic core is greater than 1.24 T, and the alloy composition of the iron-based amorphous straight strip is Fe a Si b B c Nb d Cu e M f ; and 74 ≤ a ≤ 78, 9 ≤ b ≤ 13, 6 ≤ c ≤ 8, 0.5 ≤ d ≤ 3, 0.5 ≤ e ≤ 1.5, 0 < f ≤ 2.

5.

2. A nanocrystalline inductor is composed of the nanocrystalline magnetic core according to claim 1, a protective box, and two groups of coils wound in the same direction.

3. The nanocrystalline inductor according to claim 2, characterized in that, The protective box is made of a high-temperature resistant resin material, the wire diameter of the coil is 0.6 - 1.2 mm, and the coil is wound only in one layer.

4. The nanocrystalline inductor according to claim 2, wherein The single-turn inductance of the nanocrystalline inductor is ≥5 μH at 100 kHz, the insertion loss is ≥30 dB, and the single-turn inductance attenuation rate is ≤10% for 0 - 5 A.

5. The preparation method of the nanocrystalline inductor according to any one of claims 2 - 4 includes the following steps: S1. Subject an iron-based alloy amorphous straight strip to flash heating magnetoelastic stress treatment, nanocrystallization treatment, and magnetic field heat treatment in sequence to obtain a nanocrystalline magnetic core with high magnetic induction; S2. Place the nanocrystalline magnetic core with high magnetic induction into a protective box for protection, and wind two groups of coaxial common-mode coils around the protected magnetic core with enameled wire to obtain the nanocrystalline inductor.

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