Soft magnetic alloy with low cost, high magnetic conductivity and high magnetic shielding and preparation method thereof

Abstract

According to the low-cost high-magnetic-conductivity high-magnetic-shielding magnetically soft alloy and the preparation method thereof, Fe-Si-Al is adopted as a basic system, microalloying elements such as B and Nb are creatively introduced, specific critical cold rolling and magnetic field heat treatment processes are adopted, and the obtained magnetically soft alloy has high magnetic conductivity and high magnetic shielding effectiveness. Wherein the resistivity of the alloy is effectively improved and the magnetocrystalline anisotropy is optimized through the synergistic effect of Si and Al; the grain boundary segregation effect of the B element purifies the grain boundary, and the moving resistance of the magnetic domain wall is remarkably reduced; and the dispersed precipitated phase formed by the Nb element effectively refines the initial crystal grains and lays a foundation for subsequent formation of uniform and thick recrystallized crystal grains. Particularly, a strong Gaussian texture is induced through accurately controlled critical cold rolling deformation, and magnetic domains are directionally arranged in an easy magnetization direction in combination with magnetic field heat treatment applied near a Curie point, so that the coercive force is fundamentally reduced, and the initial magnetic conductivity is improved.

Description

Technical Field

[0001] This invention relates to the field of soft magnetic alloy materials technology, and in particular to a low-cost, high-permeability, high-magnetic-shield soft magnetic alloy and its preparation method. Background Technology

[0002] With the rapid development of the electronics and information industry, especially emerging fields such as 5G communication, new energy vehicles, and big data centers, higher demands are being placed on soft magnetic materials. High-permeability soft magnetic alloys can efficiently concentrate magnetic field lines, making them a key basic material for manufacturing high-performance magnetic shielding covers, inductor components, and current transformer cores. Excellent magnetic shielding effectiveness can effectively suppress electromagnetic interference and ensure the stable operation of electronic equipment. Currently, widely used high-permeability soft magnetic materials mainly include permalloy and iron-silicon-aluminum alloys. Although permalloy has extremely high initial permeability, its composition contains large amounts of expensive and strategically scarce elements such as nickel and molybdenum, resulting in high raw material costs and limiting its application in large-scale, low-cost electronic products. While iron-silicon-aluminum alloys do not contain nickel, their traditional manufacturing processes require extremely stringent composition control, making it difficult to simultaneously achieve the goals of high permeability, high magnetic shielding effectiveness, and low production costs.

[0003] Existing high-permeability soft magnetic alloys and their preparation processes suffer from the following main problems: First, the over-reliance on precious metal elements in composition design leads to high material costs, making it difficult to meet the stringent cost control requirements of consumer electronics and other fields. Second, in terms of preparation processes, obtaining excellent magnetic properties often requires complex heat treatment regimes, such as multiple long-term hydrogen annealing processes. This is not only energy-intensive and time-consuming, but also places extremely stringent requirements on production equipment. Furthermore, traditional rolling and annealing processes struggle to precisely control the recrystallization texture of the alloy, resulting in uneven grain size and severe impurity segregation at grain boundaries. These microscopic defects become pinning points for magnetic domain wall movement, significantly reducing the material's permeability and increasing hysteresis losses, ultimately affecting magnetic shielding effectiveness.

[0004] Therefore, there is an urgent need to develop a method for preparing soft magnetic alloys that can stably obtain high permeability and high magnetic shielding effectiveness. Summary of the Invention

[0005] Based on the above analysis, the present invention aims to provide a low-cost, high-permeability, high-magnetic-shielding soft magnetic alloy and its preparation method, in order to solve one of the problems of high permeability, high magnetic shielding effectiveness, and low production cost in the prior art.

[0006] A low-cost, high-permeability, high-magnetic-shielding soft magnetic alloy, characterized in that the chemical composition of the soft magnetic alloy, by mass percentage, comprises: Fe: 80.5-86.5%, Si: 6.0-8.5%, Al: 4.5-9.0%, B: 0.01-0.05%, Nb: 0.3-0.8%, Mo: 0.5-1.2%, C: ≤0.005%, with the balance being unavoidable impurities.

[0007] Furthermore, the Si content in the soft magnetic alloy is 6.5-8.0%.

[0008] Furthermore, the Al content in the soft magnetic alloy is 4.8-5.5%.

[0009] Furthermore, the content of B in the composition of the soft magnetic alloy is 0.02-0.04%.

[0010] Furthermore, the Nb content in the soft magnetic alloy is 0.4-0.7%.

[0011] On the other hand, the present invention provides a method for preparing a low-cost, high-permeability, high-magnetic-shield soft magnetic alloy, characterized by comprising the following steps:

[0012] S1. Melting: The ingredients are batched according to the composition ratio and melted in a vacuum induction melting furnace at a melting temperature of 1550-1650℃. After melting, the ingots are cast under argon protection.

[0013] S2. Homogenization annealing: The ingot is homogenized and annealed at 1150-1250℃ for 4-8 hours, and then cooled in the furnace.

[0014] S3. Hot rolling: The annealed ingot is heated to 1100-1150℃ for hot rolling, with a total deformation of not less than 85% and a final rolling temperature of not less than 850℃. The ingot is then immediately quenched in water after hot rolling.

[0015] S4. First cold rolling: The hot-rolled plate is subjected to the first cold rolling, with a deformation of 50%-70%;

[0016] S5. Intermediate annealing: The first cold-rolled sheet is subjected to intermediate annealing in a protective atmosphere at 900-950℃ for 3-6 minutes.

[0017] S6. Second cold rolling: The plate after intermediate annealing is subjected to a second cold rolling, with a deformation of 65%-85%;

[0018] S7. Final high-temperature annealing: The strip after the second cold rolling is finally annealed in a protective atmosphere at 1100-1200℃ and held for 2-5 hours. During the cooling process, when the material passes through the Curie point, a longitudinal DC magnetic field of 500-1500 Oe is applied.

[0019] S8. Coating: Apply a chromium-free insulating coating to the surface of the annealed alloy strip.

[0020] Furthermore, in step S1, the vacuum degree of vacuum induction melting is ≤10Pa, and the refining time is 15-25min.

[0021] Furthermore, in step S3, the water quenching cooling rate is not less than 50℃ / s, and the hot-rolled plate is pickled with an environmentally friendly pickling solution after hot rolling to remove oxide scale.

[0022] Furthermore, in step S5, the protective atmosphere is a hydrogen-nitrogen mixture, wherein the volume percentage of hydrogen is 5-25%, and the intermediate annealing adopts a continuous annealing process.

[0023] Furthermore, in step S7, the protective atmosphere is high-purity hydrogen or vacuum, and the heating and cooling rate of the final high-temperature annealing is controlled at 100-200℃ / h.

[0024] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0025] 1. This invention adopts the Fe-Si-Al base system and creatively introduces B and Nb microalloying elements, avoiding the use of expensive precious metal elements such as Ni and Co, greatly reducing the cost of raw materials, and achieving an initial magnetic permeability of more than 38,000, reaching 80% of the performance level of Permalloy.

[0026] 2. In this invention, the synergistic effect of Si and Al effectively improves the resistivity of the alloy and optimizes the magnetocrystalline anisotropy; the grain boundary segregation effect of B element purifies the grain boundaries and significantly reduces the resistance to the movement of magnetic domain walls; while the dispersed precipitates formed by Nb element effectively refine the initial grains and lay the foundation for the subsequent formation of uniform and coarse recrystallized grains. Moreover, the microalloying of boron and niobium in this invention reduces the final annealing temperature of S7 from the traditional 1200-1300 degrees Celsius to 1100-1200 degrees Celsius, shortens the holding time by 30%, and reduces energy consumption by 25%, successfully achieving a balance between high performance, low cost, and environmentally friendly production.

[0027] 3. The intermediate annealing protective atmosphere of this invention is a hydrogen-nitrogen mixture, wherein the hydrogen volume percentage is 5-25%. High-purity hydrogen is more expensive than nitrogen. Using nitrogen as a "carrier gas" to dilute the hydrogen can significantly reduce gas costs. This invention also employs environmentally friendly pickling and chromium-free coating processes, achieving low-cost and environmentally friendly production while ensuring high performance.

[0028] 4. The homogenization annealing of this invention only requires a conventional annealing environment. The protective atmosphere for intermediate annealing (S5) is a hydrogen-nitrogen mixture, in which hydrogen accounts for only 5-25%. The intermediate annealing adopts a continuous annealing process. The final high-temperature annealing (S7) is protected by high-purity hydrogen or a vacuum. Compared with existing annealing mechanisms, less hydrogen is consumed and no complex control mechanism is required, making it simpler and easier to implement.

[0029] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the written description and the accompanying drawings. Attached Figure Description

[0030] Figure 1 A process flow diagram for the preparation of low-cost, high-permeability, high-magnetic-shield soft magnetic alloys. Detailed Implementation

[0031] Exemplary embodiments of the present invention will now be described in more detail. While exemplary embodiments of the present invention are shown in the following examples, it should be understood that the present invention may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this invention will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0032] With the rapid development of the electronics and information industry, especially emerging fields such as 5G communication, new energy vehicles, and big data centers, higher requirements are being placed on soft magnetic materials. High-permeability soft magnetic alloys can efficiently concentrate magnetic lines of force and are key basic materials for manufacturing high-performance magnetic shielding covers, inductor components, and current transformer cores.

[0033] Existing high-permeability soft magnetic alloys and their preparation processes suffer from the following main problems: First, the over-reliance on precious metal elements in composition design leads to high material costs, making it difficult to meet the stringent cost control requirements of consumer electronics and other fields. Second, in terms of preparation processes, obtaining excellent magnetic properties often requires complex heat treatment regimes, such as multiple long-term hydrogen annealing processes, which are not only energy-intensive and time-consuming but also place extremely stringent requirements on production equipment. Furthermore, traditional rolling and annealing processes significantly reduce the material's permeability, ultimately affecting magnetic shielding effectiveness.

[0034] On the one hand, the present invention provides a low-cost, high-permeability, high-magnetic-shield soft magnetic alloy. Specifically, the chemical composition of the soft magnetic alloy, by mass percentage, includes: Fe: 80.5-86.5%, Si: 6.0-8.5%, Al: 4.5-9.0%, B: 0.01-0.05%, Nb: 0.3-0.8%, Mo: 0.5-1.2%, C: ≤0.005%, with the balance being unavoidable impurities.

[0035] Preferably, the Si content in the soft magnetic alloy is 6.5-8.0%.

[0036] Preferably, the Al content in the soft magnetic alloy is 4.8-5.5%.

[0037] Preferably, the content of B in the soft magnetic alloy is 0.02-0.04%.

[0038] Preferably, the Nb content in the soft magnetic alloy is 0.4-0.7%.

[0039] The following provides a detailed explanation of the function and dosage selection of the components contained in this invention.

[0040] The core function of Fe is to provide saturation magnetic flux density and magnetic flux carrying capacity. The lower limit of Fe content must ensure that the saturation magnetic flux density is not less than 1.2 Tesla to maintain effective magnetic shielding. If the iron content exceeds 87%, the total content of silicon and aluminum is insufficient, failing to adequately reduce the magnetocrystalline anisotropy constant and magnetostriction coefficient, making it difficult to exceed 30,000 for the initial permeability. Conversely, if the iron content is less than 80%, the saturation magnetic flux density decreases significantly, and the shielding effectiveness decreases by more than 30%. Taking all factors into consideration, this invention controls the Fe content to 80.5-86.5%.

[0041] The role of silicon (Si) is multifaceted: firstly, it increases resistivity through solid solution to reduce eddy current losses; secondly, it synergistically reduces the magnetocrystalline anisotropy constant and magnetostriction coefficient, with the magnetostriction coefficient approaching zero when the silicon content is close to 9.6%; furthermore, it stabilizes the ferrite phase region. If the silicon content is below 6.0%, the resistivity will be below 60 μΩ·cm, eddy current losses will increase two to three times at 50 Hz, and the improvement in magnetocrystalline anisotropy constant and magnetostriction coefficient will be insufficient, making it difficult to achieve an initial permeability of 15,000. If the silicon content exceeds 8.5%, the room temperature elongation of the alloy will drop below 5%, the tendency for cold rolling cracking will be significantly aggravated, and DO3-type ordered phases will easily precipitate, forming antiphase domain boundaries and pinning magnetic domain walls, which will increase the coercivity to above 15 amperes per meter. Considering all factors, this invention controls the silicon content to 6.0-8.5%, preferably 6.5-8.0%.

[0042] Al, in combination with silicon, forms a unique "Sendasted effect," synergistically reducing the magnetocrystalline anisotropy constant and magnetostriction coefficient, and more effectively increasing resistivity than silicon; each 1% increase in aluminum can improve resistivity by approximately 12 microohm-cm. If the aluminum content is too low, more silicon is needed to achieve performance targets, which exacerbates processing brittleness; if the aluminum content exceeds 6.0%, a hard and brittle B2-type iron-aluminum intermetallic compound phase is easily formed, leading to uncontrolled uniformity of cold-rolled thickness, and an excessively thick surface oxide film increases the difficulty of pickling. Considering all factors, this invention controls the Al content to 4.5% to 9.0%, preferably 4.8% to 5.5%.

[0043] Boron (B), a key element in grain boundary engineering, is controlled at a content between 0.01% and 0.05%, preferably between 0.02% and 0.04%. Boron strongly segregates at grain boundaries, reducing grain boundary energy by more than 50% and purifying oxygen, sulfur, and nitrogen impurities at the grain boundaries, significantly reducing the density of magnetic domain wall pinning points. If the boron content is below 0.01%, the grain boundary coverage is less than 30%, the purification effect is weak, and the coercivity reduction is less than 10%; if it exceeds 0.05%, a hard and brittle phase of ferroboride with a size greater than 50 nanometers will form, becoming a new pinning center, leading to a decrease in initial permeability of up to 20%. Taking all factors into consideration, this invention controls the B content to be between 0.01% and 0.05%.

[0044] Niobium (Nb) exhibits a bimodal effect: on one hand, it combines with carbon and nitrogen to form niobium carbonitrides smaller than 10 nanometers, eliminating the pinning of domain walls by interstitial atoms; on the other hand, it suppresses abnormal grain growth during final annealing, maintaining a uniform grain size in the range of 50 to 150 micrometers. If the niobium content is below 0.3%, carbon cannot be completely fixed, requiring a niobium-to-carbon mass ratio of at least 80:1; otherwise, residual carbon will cause coercivity to exceed 8 amperes per meter. If the niobium content exceeds 0.8%, niobium carbide larger than 100 nanometers will precipitate at high temperatures, increasing the domain wall pinning effect and significantly increasing costs. Considering all factors, this invention controls the Nb content to 0.3%-0.8%, preferably 0.4%-0.7%.

[0045] Mo primarily improves resistivity through solid solution treatment and suppresses the precipitation rate of the ordered iron-silicon-aluminum phase, while also improving temperature stability, keeping Curie temperature fluctuations within ±5℃. When the molybdenum content is below 0.5%, the suppression effect on the ordered phase is insufficient, and the initial permeability decreases by more than 15% after long-term aging; if it exceeds 1.2%, the saturation magnetic induction drops below 1.15 Tesla, and the cost of molybdenum increases the raw material cost by more than 30%, violating the low-cost design principle. Taking all factors into consideration, this invention controls the molybdenum content to be between 0.5% and 1.2%.

[0046] Because carbon distorts the crystal lattice through interstitial solid solution, it forms Kotter clouds that strongly pin magnetic domain walls and generate a second phase of iron carbide. To neutralize its harmful effects, a niobium-to-carbon mass ratio of at least 80:1 and a boron-to-carbon mass ratio of at least 6:1 are required. If the carbon content exceeds 0.005%, even with the addition of niobium and boron, residual interstitial atoms will still increase the coercivity by 5 to 10 amperes per meter. Taking all factors into consideration, this invention controls the carbon content to below 0.005%.

[0047] Specifically, the aforementioned soft magnetic alloys have high initial permeability, low coercivity, and high relative magnetic shielding performance. For example, the initial permeability is above 38,000 kHz, the coercivity is below 5.5 A / m, and the relative magnetic shielding performance is above 45 dB.

[0048] Preferably, in the composition of the soft magnetic alloy, the ratio of the total mass of silicon and aluminum to the mass of iron is between 0.12 and 0.14.

[0049] Preferably, in the composition of the soft magnetic alloy, the mass ratio of silicon to aluminum is (1.2-1.6):1.

[0050] Preferably, in the composition of the soft magnetic alloy, the mass ratio of niobium to boron is (15-25):1.

[0051] On the other hand, the present invention provides a method for preparing a low-cost, high-permeability, high-magnetic-shield soft magnetic alloy, comprising the following steps:

[0052] S1. Melting: The ingredients are batched according to the composition ratio and melted in a vacuum induction melting furnace at a melting temperature of 1550-1650℃. After melting, the ingots are cast under argon protection.

[0053] S2. Homogenization annealing: The ingot is homogenized and annealed at 1150-1250℃ for 4-8 hours, and then cooled in the furnace.

[0054] S3. Hot rolling: The annealed ingot is heated to 1100-1150℃ for hot rolling, with a total deformation of not less than 85% and a final rolling temperature of not less than 850℃. The ingot is then immediately quenched in water after hot rolling.

[0055] S4. First cold rolling: The hot-rolled plate is subjected to the first cold rolling, with a deformation of 50%-70%;

[0056] S5. Intermediate annealing: The first cold-rolled sheet is subjected to intermediate annealing in a protective atmosphere at 900-950℃ for 3-6 minutes.

[0057] S6. Second cold rolling: The plate after intermediate annealing is subjected to a second cold rolling, with a deformation of 65%-85%;

[0058] S7. Final high-temperature annealing: The strip after the second cold rolling is finally annealed in a protective atmosphere at 1100-1200℃ and held for 2-5 hours. During the cooling process, when the material passes through the Curie point, a longitudinal DC magnetic field of 500-1500 Oe is applied.

[0059] S8. Coating: Apply a chromium-free insulating coating to the surface of the annealed alloy strip.

[0060] Furthermore, in step S1, the vacuum degree of vacuum induction melting is ≤10Pa, and the refining time is 15-25min.

[0061] Furthermore, in step S3, the water quenching cooling rate is not less than 50℃ / s, and the hot-rolled plate is pickled with an environmentally friendly pickling solution after hot rolling to remove oxide scale.

[0062] Furthermore, in step S5, the protective atmosphere is a hydrogen-nitrogen mixture, wherein the volume percentage of hydrogen is 5-25%, and the intermediate annealing adopts a continuous annealing process.

[0063] Furthermore, in step S7, the protective atmosphere is high-purity hydrogen or vacuum, and the heating and cooling rates for the final high-temperature annealing are controlled at 100-200℃ / h.

[0064] Specifically, the S1 smelting process involves batching materials according to the component ratio, smelting in a vacuum induction furnace at a temperature of 1550-1650℃, and then casting the smelted material into ingots under argon protection. The vacuum degree of the vacuum induction melting process is ≤10Pa, and the refining time is 15-25 minutes.

[0065] For example, the melting temperatures are 1550℃, 1560℃, 1570℃, 1580℃, 1590℃, 1600℃, 1610℃, 1620℃, 1630℃, 1640℃, and 1650℃, and the melting times are 15min, 16min, 17min, 18min, 19min, 20min, 21min, 22min, 23min, 24min, and 25min, respectively.

[0066] Specifically, the S2 homogenization annealing involves homogenizing the ingot at 1150-1250℃ for 4-8 hours, followed by furnace cooling.

[0067] For example, the homogenization annealing temperatures are 1150℃, 1160℃, 1170℃, 1180℃, 1190℃, 1200℃, 1210℃, 1220℃, 1230℃, 1240℃, and 1250℃, and the times are 4h, 5h, 6h, 7h, and 8h.

[0068] Specifically, the S3 hot rolling process involves heating the annealed ingot to 1100-1150℃ for hot rolling, with a total deformation of not less than 85% and a final rolling temperature of not less than 850℃. The ingot is then immediately water-quenched after hot rolling, with a cooling rate of not less than 50℃ / s. After hot rolling, the ingot is pickled using an environmentally friendly pickling solution.

[0069] For example, hot rolling temperatures are 1100℃, 1110℃, 1120℃, 1130℃, 1140℃, and 1150℃.

[0070] Specifically, the S4 first cold rolling: the hot-rolled plate is subjected to the first cold rolling, and the deformation is 50%-70%.

[0071] For example, the first cold rolling deformation amount of S4 is 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, and 70%.

[0072] Specifically, the S5 intermediate annealing involves performing intermediate annealing on the first cold-rolled sheet at a protective atmosphere of 900-950℃ for 3-6 minutes. The protective atmosphere is a hydrogen-nitrogen mixture, with hydrogen accounting for 5-25% of the volume. The intermediate annealing employs a continuous annealing process.

[0073] For example, intermediate annealing temperatures are 900℃, 910℃, 920℃, 930℃, 940℃, and 950℃, with times of 3 min, 4 min, 5 min, and 6 min, and volume percentages of 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, and 25%.

[0074] Specifically, the S6 second cold rolling: the plate after intermediate annealing is subjected to a second cold rolling, with a deformation of 65%-85%.

[0075] For example, the second cold rolling deformation amounts are 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, and 85%.

[0076] Specifically, the S7 final high-temperature annealing involves subjecting the strip after the second cold rolling to final annealing at 1100-1200℃ in a protective atmosphere for 2-5 hours. During the cooling process, a longitudinal DC magnetic field of 500-1500 Oe is applied when the material passes through the Curie point. The protective atmosphere is high-purity hydrogen or vacuum, and the heating and cooling rates of the final high-temperature annealing are controlled at 100-200℃ / h.

[0077] For example, the final high-temperature annealing temperature of S7 is 1100℃, 1110℃, 1120℃, 1130℃, 1140℃, 1150℃, 1160℃, 1170℃, 1180℃, 1190℃, or 1200℃, with holding times of 2h, 3h, 4h, or 5h, magnetic fields of 500Oe, 600Oe, 700Oe, 800Oe, 900Oe, 1000Oe, 1100Oe, 1200Oe, 1300Oe, 1400Oe, or 1500Oe, and cooling rates of 100℃ / h, 110℃ / h, 120℃ / h, 130℃ / h, 140℃ / h, 150℃ / h, 160℃ / h, 170℃ / h, 180℃ / h, 190℃ / h, or 200℃ / h.

[0078] Specifically, S8 is applied to the surface of the annealed alloy strip with a chromium-free insulating coating.

[0079] This step reflects environmental friendliness (the core meaning of "chromium-free"): traditional high-performance insulating coatings often use conversion solutions containing chromates, which are effective, but hexavalent chromium (Cr)... 6+ Chromium is a highly toxic, carcinogenic, and environmentally harmful substance, subject to strict regulations. Using chromium-free coatings is an essential requirement for green manufacturing.

[0080] The essence of the alloy design in this invention lies in the cross-scale synergistic effect between elements. Firstly, there is the silicon-aluminum synergistic zeroing effect. When the total mass ratio of silicon and aluminum to iron is between 0.12 and 0.14, and the mass ratio of silicon to aluminum is approximately 1.2 to 1.6:1, both the magnetocrystalline anisotropy constant and the magnetostriction coefficient simultaneously approach zero, and the initial permeability reaches its maximum value. Silicon reduces the magnetocrystalline anisotropy constant at a rate of 0.8 x 10⁴ joules per cubic meter per 1 / 100th of a silicon volume, while aluminum reduces the magnetostriction coefficient at a rate of 3.2 x 10⁻⁶ joules per 1 / 100th of an aluminum volume. In the preferred region, these two elements produce a vector superposition effect, resulting in a reduction of magnetostrictive anisotropy of over 80%.

[0081] Niobium and boron form a synergistic purification and pinning balance at grain boundaries, with an optimal mass ratio of approximately 15 to 25:1. For example, a ratio of 0.5% niobium to 0.03% boron yields the best results. Boron preferentially occupies grain boundary vacancies, lowering the interfacial energy, while niobium fixes carbon and nitrogen within the grains. Excessive boron content weakens niobium diffusion kinetics, leading to coarsening of niobium carbonitrides; furthermore, excessive niobium content reduces boron segregation at grain boundaries by more than 30%, significantly decreasing the purification effect.

[0082] The amount of boron added and the amount of deformation in the second cold rolling process form a ternary coupling. When the boron content is 0.02% to 0.04%, the critical amount of deformation in the second cold rolling process needs to be controlled between 65% and 85%. This deformation range can form a high-density shear band, triggering uniform nucleation at the boron-segregated grain boundaries during annealing, resulting in a uniform grain size of approximately 80 micrometers. If the deformation amount is less than 60% and boron is insufficient, or more than 90% and boron is excessive, the recrystallized grains will exhibit a non-uniform distribution of 50 to 300 micrometers, and the magnetic property dispersion will increase by 40%.

[0083] The synergistic effect of molybdenum and silicon-aluminum can suppress the precipitation of ordered phases. When the molybdenum content is not less than 0.8%, the upper limit of the total amount of silicon and aluminum can be relaxed to 16%; when the molybdenum content does not exceed 0.5%, the total amount of silicon and aluminum should be controlled below 14%. The solid solution dragging effect of molybdenum increases the activation energy for B2 phase formation from 180 kJ / mol to 220 kJ / mol, and reduces the critical cooling rate from 50 degrees Celsius per second to 30 degrees Celsius per second, which is perfectly matched with the hot rolling water quenching process.

[0084] Magnetic field heat treatment exhibits a synergistic orientation effect with alloy composition. When the aluminum content is greater than 5.0% and the silicon content is greater than 7.0%, a longitudinal magnetic field of 800 to 1200 Oersted is required at the Curie temperature. High silicon and aluminum content reduces magnetocrystalline anisotropy to near zero, at which point magnetic field-induced anisotropy plays a dominant role, with magnetic domains aligning oriented along the magnetic field direction, increasing initial permeability by 25% to 40%. If the silicon and aluminum content is low, the magnetic field effect is less than 10%.

[0085] Through the aforementioned multi-element, cross-scale synergistic design, this alloy achieves an initial magnetic permeability greater than 38,000, reaching 80% of the performance level of permalloy, without using expensive nickel and cobalt elements, while reducing raw material costs by 60% to 70%. The microalloying of boron and niobium reduces the final annealing temperature from the traditional 1200-1300 degrees Celsius to 1100-1200 degrees Celsius, shortens the holding time by 30%, and reduces energy consumption by 25%, successfully achieving a balance between high performance, low cost, and environmentally friendly production. All composition windows must be strongly coupled with process parameters such as hot rolling, critical cold rolling, and magnetic field heat treatment. Content control precision must reach ±0.1% for silicon and aluminum, and ±0.005% for boron and niobium, to achieve the optimal balance between performance and cost.

[0086] In summary, this invention provides a low-cost, high-permeability, high-magnetic-shield soft magnetic alloy and its preparation method. By employing an Fe-Si-Al base system and creatively introducing microalloying elements such as B and Nb, coupled with specific critical cold rolling and magnetic field heat treatment processes, the resulting soft magnetic alloy possesses high permeability and high magnetic shielding effectiveness. Specifically, the synergistic effect of Si and Al effectively improves the alloy resistivity and optimizes magnetocrystalline anisotropy; the grain boundary segregation effect of B purifies the grain boundaries, significantly reducing the resistance to domain wall movement; while the dispersed precipitates formed by Nb effectively refine the initial grains and lay the foundation for the subsequent formation of uniform and coarse recrystallized grains. In particular, the precisely controlled critical cold rolling deformation induces a strong Gaussian texture, and combined with magnetic field heat treatment applied near the Curie point, the magnetic domains are oriented in the easy magnetization direction, thereby fundamentally reducing coercivity and improving initial permeability. The entire preparation process is scientifically designed, avoiding the use of expensive nickel and cobalt elements, and adopting green processes such as environmentally friendly acid washing and chromium-free coating, achieving low-cost and environmentally friendly production while ensuring high performance.

[0087] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to specific embodiments.

[0088] Example 1:

[0089] The low-cost, high-permeability, high-magnetic-shield soft magnetic alloy of this embodiment has the following composition and mass percentage: Fe: 83.44%, Si: 7.0%, Al: 5.2%, B: 0.03%, Nb: 0.5%, Mo: 0.8%, C: 0.003%, with the balance being unavoidable impurities.

[0090] Its preparation method includes the following steps:

[0091] S1. Melting: Vacuum induction melting is adopted, with a vacuum degree ≤10Pa. Melting and refining are carried out at 1600℃ for 20 minutes. After filling with high-purity argon, it is cast into an ingot.

[0092] S2. Homogenization annealing: Anneal the ingot at 1200℃ for 6 hours.

[0093] S3. Hot rolling: The ingot is heated to 1120℃ for hot rolling, with a total deformation of 88% and a final rolling temperature of 870℃. After hot rolling, it is immediately water quenched (cooling rate > 60℃ / s), and then the oxide scale is removed by sulfuric acid + hydrogen peroxide environmentally friendly pickling solution.

[0094] S4. First cold rolling: The hot-rolled plate is cold-rolled with a deformation of 60%.

[0095] S5. Intermediate annealing: Under a hydrogen-nitrogen mixed gas atmosphere (H2 15%, N2 85%) at 920℃, a continuous annealing process is adopted, and the temperature is held for 4 minutes.

[0096] S6. Second cold rolling: Critical cold rolling is performed with a deformation of 75%.

[0097] S7. Final high-temperature annealing: Anneal at 1150℃ in a high-purity hydrogen atmosphere for 3 hours, with a heating / cooling rate of 150℃ / h. When cooling to 550℃ (through the Curie point), a longitudinal DC magnetic field of 1000Oe is applied, followed by continued cooling to room temperature.

[0098] S8. Coating: Apply a chromium-free inorganic insulating coating to the surface of the strip.

[0099] Example 2:

[0100] The low-cost, high-permeability, high-magnetic-shield soft magnetic alloy of this embodiment has the following composition and mass percentage: Fe: 85.19%, Si: 6.5%, Al: 4.8%, B: 0.01%, Nb: 0.8%, Mo: 0.5%, C: 0.002%, with the balance being unavoidable impurities.

[0101] The preparation method is basically the same as that in Example 1, except that: the hot rolling final rolling temperature in step S3 is 880℃; the second cold rolling deformation in step S6 is 70%; and the final annealing temperature in step S7 is 1120℃ and the magnetic field strength is 800Oe.

[0102] Example 3:

[0103] The low-cost, high-permeability, high-magnetic-shield soft magnetic alloy of this embodiment has the following composition and mass percentage: Fe: 82.15%, Si: 8.0%, Al: 5.5%, B: 0.05%, Nb: 0.3%, Mo: 1.2%, C: 0.004%, with the balance being unavoidable impurities.

[0104] The preparation method is basically the same as that in Example 1, except that: the total deformation of hot rolling in step S3 is 90%; the deformation of the second cold rolling in step S6 is 80%; and the final annealing temperature in step S7 is 1180℃ and the magnetic field strength is 1200Oe.

[0105] Comparative Example 1:

[0106] Commercially available 1J85 permalloy strip is used, with a typical composition of: Ni: 80%, Mo: 4%, and the balance being Fe and small amounts of Mn, Si, etc.

[0107] Comparative Example 2:

[0108] This comparative example presents a low-cost, high-permeability, high-magnetic-shielding soft magnetic alloy with the following composition and mass percentages: Fe: 86.0%, Si: 8.5%, Al: 5.5%, but without the addition of microalloying elements such as B, Nb, and Mo. The preparation method includes melting, hot rolling, cold rolling, and final annealing at 1100℃ for 2 hours. Critical cold rolling and magnetic field heat treatment were not performed.

[0109] Performance testing:

[0110] The alloy materials obtained in Examples 1-3 and Comparative Examples 1-2 were processed into ring-shaped samples. Their initial permeability at 1 kHz was measured using an Agilent 4294A precision impedance analyzer, their coercivity was measured using a BH analyzer, and their relative magnetic shielding effectiveness was evaluated according to standard testing methods (a relative comparison of attenuation decibels against a low-frequency magnetic field (50 Hz) at the same thickness). The test results are shown in Table 1.

[0111] Table 1 Comparison of Performance Test Results

[0112]

[0113] As can be seen from the results in Table 1, the soft magnetic alloys prepared in Examples 1-3 of this invention, without using expensive nickel, achieved high initial permeability and excellent magnetic shielding performance similar to the high-cost permalloy of Comparative Example 1, while exhibiting significantly lower coercivity than the traditional Fe-Si-Al alloy of Comparative Example 2, demonstrating superior soft magnetic properties. This indicates that this invention successfully achieved a balance between low cost and high performance through innovative design of composition and process.

[0114] This invention has illustrated its principles and implementation methods using specific examples. The descriptions of these embodiments are merely illustrative of the method and its core ideas; furthermore, those skilled in the art will recognize that modifications may be made to the specific implementation methods and application scope based on the principles of this invention. Therefore, the content of this specification should not be construed as limiting the invention.

Claims

1. A low-cost, high-permeability, high-magnetic-shielding soft magnetic alloy, characterized in that, The chemical composition of the soft magnetic alloy, by mass percentage, includes: Fe: 80.5-86.5%, Si: 6.0-8.5%, Al: 4.5-9.0%, B: 0.01-0.05%, Nb: 0.3-0.8%, Mo: 0.5-1.2%, C: ≤0.005%, with the balance being unavoidable impurities.

2. The low-cost, high-permeability, high-magnetic-shield soft magnetic alloy according to claim 1, characterized in that, The Si content in the soft magnetic alloy is 6.5-8.0%.

3. The low-cost, high-permeability, high-magnetic-shield soft magnetic alloy according to claim 1, characterized in that, The Al content in the soft magnetic alloy is 4.8-5.5%.

4. The low-cost, high-permeability, high-magnetic-shield soft magnetic alloy according to claim 1, characterized in that, The composition of the soft magnetic alloy contains 0.02-0.04% B.

5. The low-cost, high-permeability, high-magnetic-shield soft magnetic alloy according to claim 1, characterized in that, The Nb content in the soft magnetic alloy is 0.4-0.7%.

6. A method for preparing a low-cost, high-permeability, high-magnetic-shielding soft magnetic alloy as described in any one of claims 1-5, characterized in that, Includes the following steps: S1. Melting: The ingredients are batched according to the composition ratio and melted in a vacuum induction melting furnace at a melting temperature of 1550-1650℃. After melting, the ingots are cast under argon protection. S2. Homogenization annealing: The ingot is homogenized and annealed at 1150-1250℃ for 4-8 hours, and then cooled in the furnace. S3. Hot rolling: The annealed ingot is heated to 1100-1150℃ for hot rolling, with a total deformation of not less than 85% and a final rolling temperature of not less than 850℃. The ingot is then immediately quenched in water after hot rolling. S4. First cold rolling: The hot-rolled plate is subjected to the first cold rolling, with a deformation of 50%-70%; S5. Intermediate annealing: The first cold-rolled sheet is subjected to intermediate annealing in a protective atmosphere at 900-950℃ for 3-6 minutes. S6. Second cold rolling: The plate after intermediate annealing is subjected to a second cold rolling, with a deformation of 65%-85%; S7. Final high-temperature annealing: The strip after the second cold rolling is finally annealed in a protective atmosphere at 1100-1200℃ and held for 2-5 hours. During the cooling process, when the material passes through the Curie point, a longitudinal DC magnetic field of 500-1500 Oe is applied. S8. Coating: Apply a chromium-free insulating coating to the surface of the annealed alloy strip.

7. The method for preparing a low-cost, high-permeability, high-magnetic-shield soft magnetic alloy according to claim 6, characterized in that, In step S1, the vacuum degree of vacuum induction melting is ≤10Pa, and the refining time is 15-25min.

8. The method for preparing a low-cost, high-permeability, high-magnetic-shield soft magnetic alloy according to claim 6, characterized in that, In step S3, the cooling rate of water quenching is not less than 50℃ / s, and the hot-rolled plate is pickled with an environmentally friendly pickling solution after hot rolling to remove oxide scale.

9. The method for preparing a low-cost, high-permeability, high-magnetic-shield soft magnetic alloy according to claim 6, characterized in that, In step S5, the protective atmosphere is a hydrogen-nitrogen mixture, in which hydrogen accounts for 5-25% of the volume, and the intermediate annealing adopts a continuous annealing process.

10. The method for preparing a low-cost, high-permeability, high-magnetic-shield soft magnetic alloy according to claim 6, characterized in that, In step S7, the protective atmosphere is high-purity hydrogen or vacuum, and the heating and cooling rates of the final high-temperature annealing are controlled at 100-200℃ / h.

Images