Soft magnetic alloy, magnetic core, and method for manufacturing the same

Abstract

The application relates to the technical field of soft magnetic materials, in particular to a soft magnetic alloy, a magnetic core and a preparation method thereof. The soft magnetic alloy comprises the following elements in atomic percentage: Si 15%-17%, B 4%-6%, Cu 0.3%-0.5%, Nb 4%-6%, and the balance is Fe and inevitable impurities. A certain amount of Si, B, Cu and Nb elements are introduced into the alloy system, the formation of an amorphous matrix is promoted by Si and B, in the annealing heat treatment process, the synergistic precipitation and pinning effect of Cu and Nb are matched, a nanocrystalline structure with small size, high number density and uniformity is obtained, the soft magnetic performance of the alloy is significantly improved, the relative initial permeability of the magnetic core prepared by using the soft magnetic alloy can reach more than 215,000, the relative maximum permeability can reach more than 1,160,000, and the strict requirements of high-precision current transformers on the performance of the magnetic core can be met.

Description

Technical Field

[0001] This invention relates to the field of soft magnetic materials technology, and in particular to a soft magnetic alloy, a magnetic core, and a method for preparing the same. Background Technology

[0002] Soft magnetic alloys are key fundamental materials in fields such as power, electronics, and precision instruments. Their core function is to efficiently guide and concentrate magnetic field lines under the influence of an applied magnetic field. The relative initial permeability (μi) characterizes the ease with which a material can be magnetized in a weak magnetic field, directly affecting the sensitivity and signal-to-noise ratio of devices such as sensors, transformers, and high-frequency weak signal processing equipment. Meanwhile, the relative maximum permeability (μm) reflects the maximum magnetization capability of a material under a moderate magnetic field, which is crucial for the energy efficiency, temperature rise, and miniaturization of power devices such as transformers and inductors.

[0003] Iron-based nanocrystalline alloys have become one of the mainstream materials for manufacturing medium- and high-performance current transformer cores due to their combination of high saturation magnetic induction, high permeability, low coercivity, and excellent high-frequency, low-loss characteristics. Through reasonable composition design, the relative initial permeability of existing iron-based nanocrystalline alloys can reach approximately 150,000, and the relative maximum permeability can reach approximately 800,000, which basically meets the requirements of current transformers of conventional accuracy levels.

[0004] However, with the development of smart grids, new energy power generation, and high-precision metering, more stringent requirements are being placed on the measurement accuracy, linearity, temperature stability, and low-current characteristics of current transformers, and the corresponding accuracy levels are moving towards higher levels. Under this trend, the "surplus" of magnetic properties of existing iron-based nanocrystalline alloys is gradually becoming insufficient.

[0005] In view of this, the present invention is hereby proposed. Summary of the Invention

[0006] The purpose of this invention is to provide a soft magnetic alloy, a magnetic core, and a method for preparing the same. The magnetic core prepared using the soft magnetic alloy of this invention has a uniform and fine nanocrystalline structure, a relative initial permeability of over 215,000, and a relative maximum permeability of over 1,160,000, which can meet the high precision requirements of current transformers.

[0007] To achieve the above-mentioned objectives of the present invention, a first aspect of the present invention provides a soft magnetic alloy comprising the following elements in atomic percentage: Si 15%–17%, B 4%–6%, Cu 0.3%–0.5%, Nb 4%–6%, with the balance being Fe and unavoidable impurities.

[0008] In a specific embodiment of the present invention, the ratio of the atomic percentage of Si to the atomic percentage of B is 2.65 to 4, preferably 3 to 3.4.

[0009] In a specific embodiment of the present invention, the ratio of the atomic percentage of Cu to the atomic percentage of Nb is 0.06 to 0.1, preferably 0.07 to 0.09.

[0010] In a specific embodiment of the present invention, the sum of the atomic percentage of Si and the atomic percentage of B is 20% to 22%, preferably 20.5% to 21.5%.

[0011] In a specific embodiment of the present invention, the sum of the atomic percentage of Cu and the atomic percentage of Nb is 4.4% to 6.4%, preferably 5.3% to 5.5%.

[0012] In a specific embodiment of the present invention, the atomic percentages of Si, B, Cu, and Nb satisfy the following: (Si+B) / (Cu+Nb) is 3.28 to 4.78, preferably 3.7 to 4.1.

[0013] A second aspect of the present invention provides a magnetic core comprising the soft magnetic alloy provided in the first aspect of the present invention.

[0014] In a specific embodiment of the present invention, the average grain size of the nanocrystals in the magnetic core is 10-15 nm.

[0015] In a specific embodiment of the present invention, the number density of nanocrystals in the magnetic core is not less than 1400 per μm. 2 Preferably, it is 1400–1700 particles / μm 2 .

[0016] In a specific embodiment of the present invention, the relative initial permeability of the magnetic core is not less than 190,000; the relative maximum permeability of the magnetic core is not less than 1,040,000.

[0017] In a specific embodiment of the present invention, the coercivity of the magnetic core is not higher than 0.52 A / m, preferably 0.3 to 0.52 A / m.

[0018] A third aspect of the present invention provides a method for preparing the magnetic core of the second aspect of the present invention, comprising the following steps: (a) The raw materials are proportioned according to the atomic percentage of each element in the soft magnetic alloy, and then melted to obtain the master alloy; (b) The master alloy is processed into alloy strip using a single-roll melt spin quenching method; (c) The alloy strip is wound to form an annular magnetic core blank; (d) The annular magnetic core blank is subjected to annealing heat treatment to obtain the magnetic core.

[0019] In a specific embodiment of the present invention, the annealing heat treatment includes: holding at 300-350°C for 85-95 minutes, raising the temperature to 420-460°C and holding for 115-125 minutes, raising the temperature to 550-575°C and holding for 85-95 minutes, and then cooling to room temperature.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The present invention introduces a certain amount of Si, B, Cu and Nb elements into the alloy system. Through the synergistic promotion of Si and B to form an amorphous matrix, and in the annealing heat treatment process, the synergistic precipitation and pinning effect of Cu and Nb are combined to obtain a nanocrystalline structure with small size, high number density and uniformity, which significantly improves the soft magnetic properties of the alloy.

[0021] (2) The magnetic core made of the soft magnetic alloy of the present invention has a relative initial permeability of more than 215,000 and a relative maximum permeability of more than 1,160,000, which can meet the strict requirements of high-precision current transformers for magnetic core performance. Attached Figure Description

[0022] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0023] Figure 1 This is a microstructure diagram of the magnetic core provided in Embodiment 1 of the present invention; Figure 2 This is a microstructure image of the magnetic core provided in Embodiment 1 of the present invention at another magnification. Detailed Implementation

[0024] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0025] The first aspect of the present invention provides a soft magnetic alloy comprising the following elements in atomic percentage: Si 15%–17%, B 4%–6%, Cu 0.3%–0.5%, Nb 4%–6%, with the balance being Fe and unavoidable impurities.

[0026] This invention develops a new alloy by introducing a certain amount of Si, B, Cu, and Nb elements into the alloy system. Through the synergistic promotion of the formation of the amorphous matrix by Si and B, and the synergistic precipitation and pinning effect of Cu and Nb during the annealing heat treatment, a nanocrystalline structure with small size, high number density and uniformity is obtained, which significantly improves the soft magnetic properties of the alloy.

[0027] The introduction of silicon (Si) can significantly improve the magnetic properties of the alloy. Si can be dissolved in α-Fe, which can significantly reduce the magnetocrystalline anisotropy constant and the saturation magnetostriction coefficient, thereby reducing the sensitivity of the magnetic properties to stress. At the same time, Si can increase the resistivity of the alloy and effectively suppress eddy current losses. However, with the increase of Si content, the brittleness of the alloy increases significantly, which not only affects the yield of strip preparation, but also the internal stress introduced will have an adverse effect on the magnetic properties of the magnetic core. Therefore, in the soft magnetic alloy of the present invention, the Si content, by atomic percentage, is 15% to 17%, for example, it can be 15%, 15.2%, 15.5%, 15.8%, 16%, 16.2%, 16.5%, 16.8%, 17%, or any combination thereof.

[0028] Boron (B) is a strong amorphous-forming element. The introduction of B can significantly reduce the critical cooling rate for amorphous formation in alloys, making it easier for the melt to form a fully amorphous structure through rapid quenching. However, excessive B can lead to increased melt viscosity, poorer strip fabrication processability, and increased brittleness, cracks, or uneven thickness, ultimately impairing the magnetic properties of the core. Therefore, in the soft magnetic alloy of this invention, the B content, by atomic percentage, is 4% to 6%, for example, it can be 4%, 4.2%, 4.5%, 4.8%, 5%, 5.2%, 5.5%, 5.8%, 6%, or any combination thereof.

[0029] Introducing an appropriate amount of Cu into the alloy can cause it to segregate in the amorphous matrix during the early stages of annealing, forming clusters of 2–5 nm in size. These clusters can serve as heterogeneous nucleation sites for α-Fe grains, contributing to the formation of high-number-density nanocrystalline grains and reducing the magnetocrystalline anisotropy constant. However, excessive Cu will lead to an increase in cluster size, resulting in an increase in nanocrystalline grain size and a decrease in number density, which is detrimental to the magnetic properties of the core. Therefore, in the soft magnetic alloy of this invention, the Cu content, by atomic percentage, is 0.3%–0.5%, for example, it can be 0.3%, 0.32%, 0.35%, 0.38%, 0.4%, 0.42%, 0.45%, 0.48%, 0.5%, or any combination thereof.

[0030] Introducing an appropriate amount of Nb into the alloy allows it to work synergistically with Cu during annealing. Cu clusters act as heterogeneous nucleation sites for α-Fe grains, promoting grain nucleation. Nb then segregates at grain boundaries, effectively pinning crystals and preventing migration, thus controlling grain size growth and keeping it within a smaller range, further reducing the magnetocrystalline anisotropy constant. Furthermore, Nb can increase the crystallization temperature of the amorphous matrix, broaden the annealing process window, and improve the alloy's thermal stability. However, when the Nb content is too high, the alloy melt viscosity increases, the processability of the strip deteriorates, and defects such as increased brittleness, cracks, or uneven thickness easily occur, impairing the magnetic properties of the core. Therefore, in the soft magnetic alloy of this invention, the Nb content, by atomic percentage, is 4% to 6%, for example, it can be 4%, 4.2%, 4.5%, 4.8%, 5%, 5.2%, 5.5%, 5.8%, 6%, or any combination thereof.

[0031] In a specific embodiment of the present invention, the ratio of the atomic percentage of Si to the atomic percentage of B is 2.65 to 4, for example, it can be a range of 2.65, 2.67, 2.8, 3, 3.1, 3.2, 3.3, 3.4, 3.6, 3.8, 4, or any combination thereof, preferably 3 to 3.4. The synergistic effect of B and Si elements lowers the liquidus temperature, widens the supercooled liquid phase region, and promotes the formation of amorphous phases during rapid quenching. Controlling the ratio of their atomic percentages within the above range is more conducive to providing the basic conditions for the formation of fine and uniform nanocrystals in the subsequent annealing heat treatment process.

[0032] In a specific embodiment of the present invention, the ratio of the atomic percentage of Cu to the atomic percentage of Nb is 0.06 to 0.1, for example, it can be a range of 0.06, 0.07, 0.075, 0.08, 0.085, 0.09, 0.1, or any combination thereof, preferably 0.07 to 0.09. On an amorphous matrix, Cu and Nb elements synergistically regulate the formation of nanocrystals during the annealing heat treatment. Controlling the atomic percentages of Cu and Nb to meet the above conditions is more conducive to the formation of fine and uniform nanocrystal structures.

[0033] In a specific embodiment of the present invention, the sum of the atomic percentage of Si and the atomic percentage of B is 20% to 22%, for example, it can be a range of 20%, 20.5%, 20.8%, 21%, 21.2%, 21.5%, 22% or any two of them, preferably 20.5% to 21.5%.

[0034] In a specific embodiment of the present invention, the sum of the atomic percentage of Cu and the atomic percentage of Nb is 4.4% to 6.4%, for example, it can be a range of 4.4%, 4.8%, 5%, 5.3%, 5.35%, 5.4%, 5.45%, 5.5%, 5.8%, 6%, 6.2%, 6.4% or any two of them, preferably 5.3% to 5.5%.

[0035] In a specific embodiment of the present invention, the atomic percentages of Si, B, Cu, and Nb satisfy the following: (Si+B) / (Cu+Nb) is 3.28 to 4.78, for example, it can be a range of 3.28, 3.4, 3.6, 3.7, 3.75, 3.8, 3.85, 3.89, 3.92, 4, 4.07, 4.1, 4.3, 4.5, 4.78 or any combination thereof, preferably 3.7 to 4.1.

[0036] This invention achieves a superior microstructure by simultaneously controlling the properties of the amorphous matrix and the precipitation behavior of nanocrystals. The sum of the atomic percentages of Si and B elements within a certain range ensures that the alloy has a certain ability to form an amorphous matrix. The sum of the atomic percentages of Cu and Nb elements within a certain range provides good nucleation and growth suppression conditions for the formation of fine-sized, high-number-density nanocrystals during subsequent annealing. The ratio of the sum of the atomic percentages of Si and B (Si+B) to the sum of the atomic percentages of Cu and Nb (Cu+Nb) within the above range is beneficial to the balance between the stability of the amorphous matrix, the size and number density of nanocrystals, and significantly improves the soft magnetic properties of the alloy.

[0037] A second aspect of the present invention provides a magnetic core comprising the soft magnetic alloy provided in the first aspect of the present invention.

[0038] The magnetic core of the present invention has a two-phase structure of amorphous matrix and nanocrystalline structure. In a specific embodiment of the present invention, the average grain size of the nanocrystals in the magnetic core is 10-15 nm, for example, it can be a range of 10 nm, 11 nm, 12 nm, 12.5 nm, 13 nm, 14 nm, 14.5 nm, 15 nm or any combination thereof.

[0039] In a specific embodiment of the present invention, the number density of nanocrystals in the magnetic core is not less than 1400 nanocrystals / μm. 2 For example, it can be 1400 / μm 2 1450 cells / μm 2 1500 / μm 2 1550 cells / μm 2 1600 / μm 2 1650 cells / μm 2 1700 / μm 2Or a range consisting of any two of them, such as 1400–1700 cells / μm 2 .

[0040] In a specific embodiment of the present invention, the relative initial permeability of the magnetic core is not less than 190,000, for example, it can be a range of 190,000, 195,000, 200,000, 205,000, 210,000, 215,000, 220,000 or any two of them; the relative maximum permeability of the magnetic core is not less than 1,040,000, for example, it can be a range of 1,040,000, 1,050,000, 1,080,000, 1,100,000, 1,120,000, 1,150,000, 1,170,000, 1,180,000 or any two of them.

[0041] In a specific embodiment of the present invention, the coercivity of the magnetic core is not higher than 0.52 A / m, preferably 0.3 to 0.52 A / m, and specifically can be a range of 0.3 A / m, 0.32 A / m, 0.35 A / m, 0.4 A / m, 0.45 A / m, 0.5 A / m, 0.52 A / m, or any combination thereof.

[0042] A third aspect of the present invention provides a method for preparing the magnetic core of the second aspect of the present invention, comprising the following steps: (a) The raw materials are proportioned according to the atomic percentage of each element in the soft magnetic alloy, and then melted to obtain the master alloy; (b) The master alloy is made into alloy strip by single-roll melt spin quenching; (c) Winding the alloy strip to form a ring-shaped magnetic core blank; (d) The toroidal core blank is subjected to annealing heat treatment to obtain the core.

[0043] In a specific embodiment of the present invention, in step (a), the raw materials include pure iron (purity not less than 99.95%), pure silicon (purity not less than 99.6%), ferroborone, pure copper (purity not less than 99.99%), and ferroniobium. In ferroborone, the mass percentage of boron (B) includes, but is not limited to, 20%; in ferroniobium, the mass percentage of nitrogen (Nb) includes, but is not limited to, 60%.

[0044] In a specific embodiment of the present invention, step (a) involves smelting pure iron and ferroniobium under vacuum conditions, followed by the addition of pure silicon, ferroboron, and pure copper. The mixture is heated until completely melted, then slag is removed and steel is poured to obtain a master alloy. Further, pure iron and ferroniobium are placed in a crucible, and a vacuum is drawn to below 100 Pa. The mixture is heated at 160–200 kW. After the pure iron and ferroniobium melt, the power is gradually reduced after 3–5 minutes. When the molten steel temperature reaches 1400–1500°C, the power is cut off. Pure silicon, ferroboron, and pure copper are added, and the power is adjusted to 200–240 kW. After all the raw materials have melted, the power is reduced to 35–40 kW and maintained for 25–35 minutes, then the power is cut off. When the molten steel temperature drops to 1200–1300°C, slag is removed and steel is poured. After pouring, the mixture is allowed to cool. The master alloy is removed from the furnace when the induction coil temperature drops below 200°C.

[0045] In a specific embodiment of the present invention, in the single-roll melt quenching method, the master alloy is placed in the crucible of the strip forming machine, melted, poured into an intermediate ladle, and sprayed through a nozzle onto a high-speed rotating cooling copper roller, where it solidifies into a strip and is ejected. The rotational speed of the copper roller is 1400–1600 r / min, the casting temperature is 1300–1400℃, and the gap between the nozzle and the copper roller is 0.5–1 mm. Furthermore, the tolerance between the length of the nozzle slit and the width of the alloy strip is ±0.2 mm, and the width of the nozzle slit is 1–1.5 mm.

[0046] In a specific embodiment of the present invention, the thickness of the alloy strip is 30–34 μm.

[0047] In a specific embodiment of the present invention, the outer diameter of the toroidal magnetic core blank is 18.9±0.2 mm, the inner diameter is 15.6±0.2 mm, and the height is 12±0.2 mm. Further, the weight of the toroidal magnetic core blank is 6.3±0.2 g.

[0048] In a specific embodiment of the present invention, the winding process in step (c) is performed using conventional magnetic core winding equipment. The present invention provides a specific optional winding method, but is not limited thereto: the spool diameter is 15.6±0.2 mm, the winding thickness is 3.3±0.2 mm, and the winding speed is 2000–2500 rpm.

[0049] In a specific embodiment of the present invention, the annealing heat treatment includes: holding at 300-350°C for 85-95 minutes, raising the temperature to 420-460°C and holding for 115-125 minutes, raising the temperature to 550-575°C and holding for 85-95 minutes, and then cooling to room temperature.

[0050] In a specific embodiment of the present invention, the annealing heat treatment is performed in a vacuum furnace. Specifically, the annular magnetic core blank is placed in the vacuum furnace, a vacuum is drawn, and heating is started when the gauge pressure reaches -0.1 MPa.

[0051] In a specific embodiment of the present invention, during the annealing heat treatment, the temperature is raised from room temperature to 300-350°C within 28-32 minutes, for example, to a range of 300°C, 310°C, 320°C, 330°C, 340°C, 350°C, or any combination thereof, and held at that temperature for 85-95 minutes, for example, to a range of 85 minutes, 88 minutes, 90 minutes, 92 minutes, 95 minutes, or any combination thereof; then, the temperature is raised to 420-460°C within 58-62 minutes, for example, to a range of 420°C, 430°C, 440°C, 450°C, 460°C, or any combination thereof. The temperature is maintained within a range of 115–125 min, for example, 115 min, 118 min, 120 min, 122 min, 125 min, or any combination thereof; then the temperature is increased to 550–575℃ within 73–77 min, for example, 550℃, 555℃, 560℃, 565℃, 570℃, 575℃, or any combination thereof, and maintained for 85–95 min, for example, 85 min, 88 min, 90 min, 92 min, 95 min, or any combination thereof; after the maintenance period, the temperature is cooled to room temperature.

[0052] In a specific embodiment of the present invention, cooling to room temperature includes: cooling the annular magnetic core blank to below 200°C in the furnace, and then air-cooling it to room temperature after it is removed from the furnace. During the furnace cooling process, an external fan can be used to blow air onto the outer surface of the furnace body to accelerate the heat dissipation rate of the furnace body.

[0053] Examples 1-13 This embodiment provides a method for preparing a magnetic core, including the following steps: (1) According to the composition of the soft magnetic alloy in Table 1, pure iron (purity of 99.95%), pure silicon (purity of 99.6%), ferroboron (mass percentage of B of 20%), pure copper (purity of 99.99%) and ferroniobium (mass percentage of Nb of 60%) were used as raw materials for batching. Then, pure iron and ferroniobium were placed in a crucible in a vacuum induction furnace. When the vacuum degree reached 100 Pa, the furnace was heated with a power of 180 kW. After the material melted, the power was reduced after 4 min. When the temperature of the molten steel reached 1450 ℃, the power was cut off and the lid was opened to add pure silicon, ferroboron and pure copper. Then the power was adjusted to 220 kW. After all the material melted, the power was reduced to 40 kW and held for 30 min. Then the power was cut off. When the temperature of the molten steel dropped to 1250 ℃, the slag was removed and the steel was poured. After the steel was poured, the furnace was cooled. When the temperature of the induction coil in the furnace dropped to below 200 ℃, the master alloy was taken out of the furnace.

[0054] (2) The master alloy is placed in the crucible of the strip making machine, melted and poured into the intermediate ladle, sprayed through the nozzle onto the high-speed rotating cooling copper roller, and instantly solidified into a thin strip that is thrown out to obtain an alloy strip with a thickness of 32±2μm and a width of 12±0.2mm; wherein, the copper roller speed is 1500r / min, the steel pouring temperature is 1350℃, the gap between the nozzle and the copper roller is 0.5~1mm (e.g. 1mm), the length of the nozzle slit is equal to the width of the sprayed strip (tolerance ±0.2mm), and the nozzle slit width is 1~1.5mm (e.g. 1.5mm).

[0055] (3) Using conventional magnetic core winding equipment, the alloy strip obtained in step (2) is wound into a magnetic core blank with an outer diameter of 18.9 mm, an inner diameter of 15.6 mm, a height of 12 mm, and a weight of 6.48 g. During the winding process, the diameter of the winding shaft is 15.6 mm, the winding thickness is 3.3 mm, and the winding speed is 2250 rpm.

[0056] (4) Place the magnetic core blank obtained in step (3) into a vacuum furnace and start evacuating. When the gauge pressure reaches -0.1MPa, start heating. Within 30 minutes, raise the temperature from room temperature to 325℃ and hold for 90 minutes. Then, within 60 minutes, continue to raise the temperature to 440℃ and hold for 120 minutes. Then, within 75 minutes, continue to raise the temperature to 560℃ and hold for 90 minutes. Then, cool the furnace to 200℃ and remove it from the furnace and air-cool it to room temperature to obtain the magnetic core.

[0057] Table 1. Composition (%, atomic percentage) of soft magnetic alloys in different embodiments

[0058] Example 14 group Example 14 uses the same method for preparing the magnetic core as Example 1, except that the annealing heat treatment in step (4) is different. The specific differences are as follows: Example 14a: The magnetic core blank obtained in step (3) was placed in a vacuum furnace and a vacuum was drawn. When the gauge pressure reached -0.1 MPa, the electric heating was started. The temperature was raised from room temperature to 300°C within 30 min and held for 100 min. Then, the temperature was raised to 420°C within 60 min and held for 130 min. Then, the temperature was raised to 550°C within 75 min and held for 80 min. Then, the temperature was cooled to 200°C in the furnace and then removed from the furnace and air-cooled to room temperature. Example 14b: The magnetic core blank obtained in step (3) was placed in a vacuum furnace and a vacuum was drawn. When the gauge pressure reached -0.1MPa, the electric heating was started. The temperature was raised from room temperature to 350℃ within 30 minutes and held for 80 minutes. Then, the temperature was raised to 460℃ within 60 minutes and held for 110 minutes. Then, the temperature was raised to 575℃ within 75 minutes and held for 100 minutes. Then, the temperature was cooled to 200℃ in the furnace and then removed from the furnace and air-cooled to room temperature. Example 14c: The magnetic core blank obtained in step (3) was placed in a vacuum furnace and vacuuming was started. When the gauge pressure reached -0.1MPa, the electric heating was started. The temperature was raised from room temperature to 420℃ within 30 minutes and held for 80 minutes. Then, the temperature was raised to 480℃ within 60 minutes and held for 110 minutes. Then, the temperature was raised to 575℃ within 75 minutes and held for 100 minutes. Then, the temperature was cooled to 200℃ in the furnace and then removed from the furnace and air-cooled to room temperature.

[0059] Comparative Examples 1-4 The preparation methods of magnetic cores in Comparative Examples 1 to 4 refer to Example 1, the only difference being that the composition of the soft magnetic alloy in step (1) is different.

[0060] The compositions of the soft magnetic alloys in Comparative Examples 1–4 are shown in Table 2.

[0061] Table 2. Composition (%, atomic percentage) of soft magnetic alloys with different comparative proportions

[0062] Experimental Example The microstructure of the magnetic cores obtained by annealing heat treatment in different embodiments and comparative examples of the present invention was observed and statistically analyzed. Figures 1-2 This is a microstructure image of the magnetic core provided in Embodiment 1 of the present invention, by... Figure 1 It can be seen that the microstructure of the magnetic core contains a large number of grains with a size of nanometers; from Figure 2 The interatomic spacing is 0.2034 nm, indicating that the grains are α-Fe grains; the statistical results are shown in Table 3.

[0063] Table 3 Statistical results of microstructure

[0064] The statistical analysis results above show that by introducing a certain amount of Si, B, Cu, and Nb elements into the alloy system, the present invention can obtain a nanocrystalline structure with small size, high number density, and uniformity by synergistically promoting the formation of the amorphous matrix through Si and B, and by combining the synergistic precipitation and pinning effect of Cu and Nb during the annealing heat treatment process.

[0065] The magnetic properties of the magnetic cores prepared in different embodiments and comparative examples were further tested, and the test results are shown in Table 4.

[0066] Table 4. Magnetic property test results of different magnetic cores

[0067] The test results above show that the magnetic core made of the soft magnetic alloy of the present invention can achieve a relative initial permeability of over 215,000 and a relative maximum permeability of over 1,160,000, which can meet the stringent requirements of high-precision current transformers for magnetic core performance.

[0068] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A soft magnetic alloy, characterized in that, Includes the following elements, expressed as an atomic percentage: Si 15%–17%, B 4%–6%, Cu 0.3%–0.5%, Nb 4%–6%, with the balance being Fe and unavoidable impurities.

2. The soft magnetic alloy according to claim 1, characterized in that, It has at least one of the following characteristics: (1) The ratio of the atomic percentage of Si to the atomic percentage of B is 2.65 to 4; (2) The ratio of the atomic percentage of Cu to the atomic percentage of Nb is 0.06 to 0.

1.

3. The soft magnetic alloy according to claim 1, characterized in that, It has at least one of the following characteristics: (1) The ratio of the atomic percentage of Si to the atomic percentage of B is 3 to 3.4; (2) The ratio of the atomic percentage of Cu to the atomic percentage of Nb is 0.07 to 0.

09.

4. The soft magnetic alloy according to claim 1, characterized in that, It has at least one of the following characteristics: (1) The sum of the atomic percentages of Si and B is 20% to 22%; (2) The sum of the atomic percentages of Cu and Nb is 4.4% to 6.4%; (3) The atomic percentages of Si, B, Cu and Nb satisfy the following: (Si+B) / (Cu+Nb) is 3.28 to 4.

78.

5. The soft magnetic alloy according to claim 1, characterized in that, It has at least one of the following characteristics: (1) The sum of the atomic percentages of Si and B is 20.5% to 21.5%; (2) The sum of the atomic percentages of Cu and Nb is 5.3% to 5.5%; (3) The atomic percentages of Si, B, Cu and Nb satisfy the following: (Si+B) / (Cu+Nb) is 3.7 to 4.

1.

6. A magnetic core, characterized in that, Including the soft magnetic alloy described in any one of claims 1 to 5.

7. The magnetic core according to claim 6, characterized in that, It has at least one of the following characteristics: (1) In the magnetic core, the average grain size of the nanocrystals is 10-15 nm; (2) In the magnetic core, the number density of nanocrystals is not less than 1400 per μm. 2 .

8. The magnetic core according to claim 6, characterized in that, The relative initial permeability of the magnetic core is not less than 190,000; the relative maximum permeability of the magnetic core is not less than 1,040,000; and the coercivity of the magnetic core is not higher than 0.52 A / m.

9. The method for preparing the magnetic core according to any one of claims 6 to 8, characterized in that, Includes the following steps: (a) The raw materials are proportioned according to the atomic percentage of each element in the soft magnetic alloy, and then melted to obtain the master alloy; (b) The master alloy is processed into alloy strip using a single-roll melt spin quenching method; (c) The alloy strip is wound to form an annular magnetic core blank; (d) The annular magnetic core blank is subjected to annealing heat treatment to obtain the magnetic core.

10. The preparation method according to claim 9, characterized in that, The annealing heat treatment includes: holding at 300-350℃ for 85-95 minutes, then raising the temperature to 420-460℃ and holding for 115-125 minutes, then raising the temperature to 550-575℃ and holding for 85-95 minutes, and finally cooling to room temperature.

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