A preparation method of an iron-based amorphous nanocrystalline master alloy based on low-grade niobium iron
By using low-grade high-alumina niobium-iron-silicon and rare-earth alloy cerium aluminate modifiers, combined with argon blowing and plasma-modified slag-forming agents in a non-vacuum smelting process, the problems of high cost and inclusion removal were solved, and the low-cost, high-purity preparation of iron-based amorphous nanocrystalline master alloys was achieved, which is suitable for industrial applications.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SHANXI NANENG TECHNOLOGY CO LTD
- Filing Date
- 2026-04-22
- Publication Date
- 2026-07-14
AI Technical Summary
The large-scale application of iron-based amorphous and nanocrystalline soft magnetic materials is limited by high costs, mainly due to the high cost of high-grade low-aluminum ferroniobium, and the difficulty of effectively removing inclusions from high-aluminum ferroniobium by existing smelting processes, which affects the purity of the alloy and the yield of niobium.
By replacing high-grade low-aluminum niobium iron with low-grade high-aluminum niobium iron, and combining non-vacuum smelting argon blowing process and secondary refining slag-forming process, rare earth alloy cerium aluminate is used as a modifier, and plasma-modified slag-forming agent is used to synergistically remove inclusions, thereby achieving deep recovery of niobium and effective removal of impurities.
It significantly reduces the production cost of iron-based amorphous and nanocrystalline master alloys, increases the yield of niobium, reduces the content of impurity aluminum, meets the cleanliness requirements of high-purity soft magnetic alloys, and is suitable for large-scale industrial production.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of amorphous nanocrystalline master alloy smelting technology, specifically to a method for preparing iron-based amorphous nanocrystalline master alloys based on low-grade niobium iron. Background Technology
[0002] Iron-based amorphous and nanocrystalline soft magnetic materials are a class of high-performance soft magnetic materials, with Fe-Cu-Nb-Si-B as the core alloy system. The preparation of this material requires two key processes: first, amorphous ribbons are formed through rapid solidification technology, followed by targeted heat treatment to form a composite microstructure of "amorphous matrix + nanocrystals". The formation of this unique structure benefits from the synergistic effect of the alloy components—copper provides nucleation sites, while elements such as niobium inhibit grain growth, ultimately achieving uniform and refined grains at the nanoscale.
[0003] In terms of performance, this material exhibits four core advantages: First, its extremely high permeability and extremely low coercivity facilitate magnetization and demagnetization processes, significantly reducing energy loss. Second, it demonstrates excellent high-frequency loss performance; thanks to the synergistic effect of its nanostructure, high resistivity, and thin-strip morphology, it effectively suppresses eddy current phenomena, outperforming traditional silicon steel and ferrite materials in the mid-to-high frequency range from kHz to hundreds of kHz. Third, its outstanding saturation magnetic induction intensity surpasses that of ferrite materials, providing crucial support for the miniaturization design of electronic devices. Fourth, it possesses good temperature stability, long-term operational stability, and resistance to DC bias, adapting to complex operating conditions. Based on these performance advantages, this material has been widely applied in the field of mid-to-high frequency small-to-medium power electronic equipment, covering high-frequency transformers, common-mode inductors, and noise filters in switching power supplies; photovoltaic inverters and current transformers in smart meters in the new energy industry; and special applications such as automotive electronics, wireless charging, and magnetic shielding. It has successfully filled the performance gap between silicon steel and ferrite, becoming a core supporting material driving the development of power electronic equipment towards higher frequencies, higher efficiency, and miniaturization.
[0004] Despite their significant performance advantages, the large-scale application of iron-based amorphous and nanocrystalline soft magnetic alloys remains limited by high raw material costs. The core of this problem lies in the extremely thin thickness of their intermediate—the iron-based amorphous and nanocrystalline ribbon—which imposes stringent requirements on the cleanliness of the smelting raw materials. In terms of raw material composition, the main smelting raw materials for commercial iron-based amorphous and nanocrystalline master alloys include industrial pure iron, industrial silicon, high-grade low-aluminum ferroniobium, ferroboron, and electrolytic copper. Among these, high-grade low-aluminum ferroniobium accounts for over 69% of the total cost of the master alloy raw materials, becoming the main bottleneck restricting cost reduction. This application proposes a low-cost, non-vacuum smelting method for iron-based amorphous and nanocrystalline master alloys based on high-aluminum ferroniobium and silicon, aiming to overcome the existing high-cost bottleneck and effectively reduce the production cost of iron-based amorphous and nanocrystalline products by addressing both raw material selection and smelting processes. Summary of the Invention
[0005] (a) Technical problems to be solved To address the shortcomings of existing technologies, this invention provides a method for preparing an iron-based amorphous nanocrystalline master alloy based on low-grade niobium iron.
[0006] (II) Technical Solution To achieve the above objectives, the present invention provides the following technical solution: In a first aspect, a method for preparing an iron-based amorphous nanocrystalline master alloy based on low-grade niobium iron is characterized by comprising the following steps: S1. Prepare raw materials: industrial pure iron, industrial silicon, ferroborone, high-alumina niobium ferrosilicon, electrolytic copper, rare earth alloys, and slag-forming agents. S2. Add industrial pure iron, industrial silicon, and ferroboron into the medium-frequency induction furnace to increase the heating power of the medium-frequency induction furnace and reach the target temperature; S3. Mix high-alumina niobium iron silicon with iron oxide powder to obtain a mixture, add it to the molten steel in the medium frequency induction furnace, and start argon blowing for refining at the same time. S4. Add the remaining industrial silicon from step S1 to the surface of the molten steel in step S3, and after argon refining, remove the refining slag on the surface of the molten steel, add electrolytic copper and rare earth alloy, and then argon refining. S5. Add the slag-forming agent into the medium-frequency induction furnace and start the soft-blowing argon process; S6. Power off and cool down to remove the refining slag from the surface of the molten steel, and then pour the molten steel into the ingot mold.
[0007] Further, in step S1, the raw material mass ratio is 55-65% industrial pure iron, 6-8% industrial silicon, 8.7-9.4% ferroboron, 20-30% high-alumina niobium ferrosilicon, 1.22-1.32% electrolytic copper, 0.05-0.15% rare earth alloy, and 0.4-1.5% slagging agent.
[0008] Furthermore, the composition of the high-aluminum niobium-iron-silicon alloy is as follows: 15-30% niobium by mass, 10-25% silicon by mass, 0.6-1.6% aluminum by mass, 0.05-0.12% total impurity elements by mass, and the balance being iron.
[0009] Furthermore, the composition of the ferroboron is: boron element mass fraction of 17~18%, with the balance being iron.
[0010] Further, in step S2, industrial pure iron, industrial silicon, and ferroboron are added to the medium-frequency induction furnace. Industrial silicon, which accounts for 15-50% of the total mass of industrial silicon in the raw materials, is spread at the bottom of the medium-frequency induction furnace, industrial pure iron is placed in the center of the medium-frequency induction furnace, and ferroboron is poured into the gaps between the industrial pure iron. This increases the heating power of the medium-frequency induction furnace to 400-450 kW, achieving the target temperature of 1550-1580℃.
[0011] Furthermore, in step S3, the mass ratio of high-alumina niobium iron silicon to iron oxide is 100:0.8~1.5, and it is added to the molten steel in the medium-frequency induction furnace in 2~3 batches. The heating power of the medium-frequency induction furnace is 200~300 kW, the argon blowing refining time is 15~25 min, and the pressure range is 0.6~1.5 MPa.
[0012] Furthermore, in step S4, the remaining industrial silicon is added to the molten steel in the medium-frequency induction furnace in 2 to 3 batches. The heating power of the medium-frequency induction furnace is 200 to 250 kW, the argon blowing time is 10 to 20 min, and the pressure range is 0.6 to 1.5 MPa.
[0013] Furthermore, in step S4, after adding electrolytic copper and rare earth alloy, the heating power of the medium-frequency furnace is increased by 250~350kW, so that the molten steel in the furnace rises to 1480~1520℃, and the argon blowing process is maintained for 5~10 minutes; the rare earth alloy is cerium aluminate.
[0014] Furthermore, the preparation method of the slag-forming agent in step S5 includes the following steps: A1. Weigh the raw materials by mass percentage: 50-60% calcium oxide, 15-25% silicon dioxide, 10-20% magnesium oxide, 5-10% sodium carbonate, and 0.5-2% lithium fluoride. Mix and stir at 300-400 r / min for 15-20 min to obtain a premix. A2. Put the premixed material into the reaction chamber of the plasma surface treatment machine, seal the equipment, evacuate to 50~100Pa, introduce argon gas into the reaction chamber, control the argon gas flow rate to 150~200 mL / min, keep the pressure in the reaction chamber stable at 150~200 Pa, start the plasma generator, set the radio frequency power to 300~500 W and the time to 15~30 min, turn off the plasma generator, continue to introduce argon gas to cool to room temperature, crush and pass through a 10~60 mesh sieve to obtain the slagging agent.
[0015] Furthermore, in step S5, the soft argon blowing process takes 20 to 40 minutes, and the argon blowing pressure ranges from 0.1 to 0.4 MPa.
[0016] (iii) Beneficial technical effects This invention utilizes a non-vacuum smelting argon blowing process and a secondary refining slag-forming process to maximize the removal of foreign inclusions introduced by high-alumina niobium-iron-silicon alloys. Thermodynamically, iron oxide powder preferentially oxidizes with impurities of aluminum in the high-alumina niobium-iron-silicon alloy, forming alumina-dealuminizing products, thus reducing aluminum's competition for niobium oxidation at the source. Subsequently added rare-earth alloy cerium aluminate further reacts with residual aluminum and oxygen in the molten steel to generate spherical rare-earth aluminate composite inclusions. These inclusions have high interfacial tension and are prone to aggregation and growth. Kinetically, argon blowing refining (pressure 0.6~1.5 MPa) promotes the initial flotation of dealuminizing products, while soft argon blowing refining (pressure 0.1~0.4 MPa) allows fine inclusions to collide, aggregate, and float into the slag phase. Simultaneously, this invention utilizes the strong reducing properties of silicon, spreading the remaining industrial silicon on the surface of the primary refining slag after dealuminization and heating it to melt. This causes niobium oxide formed by burn-off in the slag to return to the molten steel, achieving deep recovery of the precious metal niobium. Through the above synergistic effect, the aluminum content of the impurity in the master alloy prepared by the present invention can be as low as 19~28 ppm, and the niobium element recovery rate is stable at over 99.39%.
[0017] This invention introduces rare-earth alloy cerium aluminate as a modifier in the smelting of iron-based amorphous and nanocrystalline master alloys for the first time. Rare earth elements possess strong deoxidizing, aluminum-fixing, and inclusion-modifying effects, transforming sharp and irregular alumina inclusions in molten steel into spherical cerium aluminate composite inclusions, improving the morphology and distribution of inclusions, and reducing their detrimental effects on magnetic properties. Simultaneously, this invention designs a novel composite slag-forming agent, comprising calcium oxide, silicon dioxide, magnesium oxide, sodium carbonate, and lithium fluoride, and modifies the slag-forming agent using plasma surface treatment technology. The addition of lithium fluoride significantly reduces the slag-steel interfacial tension, promoting inclusions to cross the interface and enter the slag phase; plasma treatment activates the surface of the slag-forming agent particles, improving their wettability and reactivity with molten steel. The aluminum content in Comparative Example 5 is as high as 85 ppm, the aluminum content in Comparative Example 6 is 52 ppm, while the aluminum content in Examples 1-3 is only 19-28 ppm, indicating a significant synergistic impurity removal effect of rare-earth modification treatment and plasma-modified slag-forming agent.
[0018] This invention uses low-grade, high-aluminum niobium-iron-silicon to replace the traditional high-grade, low-aluminum niobium-iron as the source of niobium. Simultaneously, the silicon and iron resources inherent in the low-grade niobium-iron-silicon can directly participate in the preparation of the master alloy, further reducing the amount of industrial pure iron and industrial silicon required. Furthermore, the method of this invention can achieve the preparation of a high-purity master alloy under non-vacuum conditions, reducing equipment investment and operating costs, shortening the smelting cycle, and making it suitable for large-scale continuous industrial production. Detailed Implementation
[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.
[0020] Unless otherwise specified, all components of the iron-based amorphous nanocrystalline master alloy formulation of this invention are commercially available. All parts used in this invention are parts by weight; Industrial pure iron: iron mass fraction ≥99.5%, carbon ≤0.02%, sulfur ≤0.005%, phosphorus ≤0.01%; Industrial silicon: silicon mass fraction ≥ 98.5%, iron ≤ 1.0%, aluminum ≤ 0.5%; Boron iron: Boron mass fraction 17~18%, balance is iron; Electrolytic copper: copper mass fraction 99.95%; Cerium aluminate: 45% by mass of cerium;
[0021] Example 1 A method for preparing an iron-based amorphous nanocrystalline master alloy based on low-grade niobium iron includes the following steps: S1. Raw material preparation: The raw material mass ratio is 60.63% industrial pure iron, 6.45% industrial silicon, 8.72% ferroboron, 22.34% high-alumina niobium ferrosilicon, 1.26% electrolytic copper, 0.10% rare earth alloy, and 0.50% slag-forming agent. S2. Add industrial pure iron, industrial silicon, and ferroboron into the medium-frequency induction furnace. The industrial silicon, which accounts for 20% of the total mass of the industrial silicon in the raw materials, is spread at the bottom of the medium-frequency induction furnace. The industrial pure iron is placed in the center of the medium-frequency induction furnace, and the ferroboron is poured into the gaps between the industrial pure iron. Increase the heating power of the medium-frequency induction furnace to 400 kW to reach the target temperature of 1550℃. S3. Mix high-alumina niobium iron silicon and iron oxide powder in a mass ratio of 100:1.5 to obtain a mixture. Add the mixture to the molten steel in the medium-frequency induction furnace in two batches. At the same time, start argon blowing for refining. The heating power of the medium-frequency induction furnace is 200 kW, the argon blowing time is 15 min, and the pressure range is 0.8 MPa. S4. Add the remaining industrial silicon from step S1 to the surface of the molten steel in step S3 in two batches. The heating power of the medium frequency induction furnace is 200 kW, the argon blowing time is 10 min, and the pressure range is 0.8 MPa. After argon blowing refining, when the temperature of the molten steel in the furnace drops to 1400℃, remove the refining slag on the surface of the molten steel, add electrolytic copper and rare earth alloy cerium aluminate, and argon blow refining. Increase the heating power of the medium frequency furnace to 250 kW, so that the temperature of the molten steel in the furnace rises to 1480℃, and continue to maintain the argon blowing process for 5 min. S5. Add the slag-forming agent into the medium-frequency induction furnace, reduce the heating power of the medium-frequency furnace to 50 kW, start the soft argon blowing process for 20 min, and the argon blowing pressure range is 0.1 MPa. S6. Power off and cool down to 1250℃ to remove the refining slag from the surface of the molten steel, and then pour the molten steel into the ingot mold.
[0022] The composition of the high-alumina niobium-iron-silicon alloy is as follows: 24.4% niobium by mass, 10% silicon by mass, 0.6% aluminum by mass, 0.05% total impurity elements by mass, and the balance being iron.
[0023] The composition of the ferroboron is: 17.9% boron by mass, with the balance being iron.
[0024] The preparation method of the slag-forming agent in step S5 includes the following steps: A1. Weigh the raw materials by mass percentage: 50% calcium oxide, 25% silicon dioxide, 13% magnesium oxide, 10% sodium carbonate, and 2% lithium fluoride. Mix and stir at 300 r / min for 15 min to obtain a premix. A2. The premixed material is put into the reaction chamber of the plasma surface treatment machine. After sealing the equipment, the vacuum is evacuated to 50 Pa. Argon gas is introduced into the reaction chamber, and the argon gas flow rate is controlled at 150 mL / min. The pressure in the reaction chamber is kept stable at 150 Pa. The plasma generator is started, and the radio frequency power is set to 300 W and the time is 15 min. The plasma generator is turned off, and argon gas is continued to be introduced to cool to room temperature. The mixture is crushed and passed through a 10-mesh sieve to obtain the slagging agent.
[0025] Example 2
[0026] A method for preparing an iron-based amorphous nanocrystalline master alloy based on low-grade niobium iron includes the following steps: S1. Prepare raw materials: The raw material mass ratio is 60.16% industrial pure iron, 6.08% industrial silicon, 8.72% ferroboron, 22.79% high-alumina niobium ferrosilicon, 1.25% electrolytic copper, 0.10% rare earth alloy, and 0.90% slag-forming agent. S2. Add industrial pure iron, industrial silicon, and ferroboron into the medium-frequency induction furnace. The industrial silicon, which accounts for 35% of the total mass of the industrial silicon in the raw materials, is spread at the bottom of the medium-frequency induction furnace. The industrial pure iron is placed in the center of the medium-frequency induction furnace, and the ferroboron is poured into the gaps between the industrial pure iron. Increase the heating power of the medium-frequency induction furnace to 420 kW and reach the target temperature of 1560℃. S3. Mix high-alumina niobium iron silicon and iron oxide powder in a mass ratio of 100:1.2 to obtain a mixture. Add the mixture to the molten steel in the medium-frequency induction furnace in 3 batches. At the same time, start argon blowing for refining. The heating power of the medium-frequency induction furnace is 250 kW, the argon blowing time is 20 min, and the pressure range is 1.0 MPa. S4. Add the remaining industrial silicon from step S1 to the surface of the molten steel in step S3 in three batches. The heating power of the medium frequency induction furnace is 230 kW, the argon blowing time is 15 min, and the pressure range is 1.0 MPa. After argon blowing and refining, when the temperature of the molten steel in the furnace drops to 1410℃, remove the refining slag on the surface of the molten steel, add electrolytic copper and rare earth alloy cerium aluminate, and argon blow and refine. Increase the heating power of the medium frequency furnace by 300 kW to raise the temperature of the molten steel in the furnace to 1500℃, and continue to maintain the argon blowing process for 10 min. S5. Add the slag-forming agent into the medium-frequency induction furnace, reduce the heating power of the medium-frequency furnace to 100 kW, start the soft argon blowing process for 30 min, and the argon blowing pressure range is 0.2 MPa. S6. Power off and cool down to 1260℃ to remove the refining slag from the surface of the molten steel, and then pour the molten steel into the ingot mold.
[0027] The composition of the high-alumina niobium-iron-silicon alloy is as follows: 24.4% niobium by mass, 12% silicon by mass, 1.2% aluminum by mass, 0.09% total impurity elements by mass, and the balance being iron.
[0028] The composition of the ferroboron is: 17.9% boron by mass, with the balance being iron.
[0029] The preparation method of the slag-forming agent in step S5 includes the following steps: A1. Weigh the raw materials by mass percentage: 58% calcium oxide, 22% silicon dioxide, 10% magnesium oxide, 9% sodium carbonate, and 1% lithium fluoride. Mix and stir at 350 r / min for 20 min to obtain a premix. A2. Put the premixed material into the reaction chamber of the plasma surface treatment machine, seal the equipment, evacuate to 80 Pa, introduce argon gas into the reaction chamber, control the argon gas flow rate to 180 mL / min, keep the reaction chamber pressure stable at 180 Pa, start the plasma generator, set the radio frequency power to 400 W and the time to 20 min, turn off the plasma generator, continue to introduce argon gas to cool to room temperature, crush and pass through a 30-mesh sieve to obtain the slagging agent.
[0030] Example 3
[0031] A method for preparing an iron-based amorphous nanocrystalline master alloy based on low-grade niobium iron includes the following steps: S1. Prepare raw materials: The raw material mass ratio is 58.41% industrial pure iron, 6.10% industrial silicon, 9.19% ferroboron, 22.78% high-alumina niobium ferrosilicon, 1.28% electrolytic copper, 0.12% rare earth alloy, and 1.30% slag-forming agent. S2. Add industrial pure iron, industrial silicon, and ferroboron into the medium-frequency induction furnace. The industrial silicon, which accounts for 45% of the total mass of the industrial silicon in the raw materials, is spread at the bottom of the medium-frequency induction furnace. The industrial pure iron is placed in the center of the medium-frequency induction furnace, and the ferroboron is poured into the gaps between the industrial pure iron. The heating power of the medium-frequency induction furnace is increased to 450 kW to reach the target temperature of 1580℃. S3. Mix high-alumina niobium iron silicon and iron oxide powder in a mass ratio of 100:0.8 to obtain a mixture. Add the mixture to the molten steel in the medium-frequency induction furnace in three batches. At the same time, start argon blowing for refining. The heating power of the medium-frequency induction furnace is 300 kW, the argon blowing time is 25 min, and the pressure range is 1.3 MPa. S4. Add the remaining industrial silicon from step S1 to the surface of the molten steel in step S3 in 5 batches. The heating power of the medium frequency induction furnace is 250 kW, the argon blowing time is 20 min, and the pressure range is 1.3 MPa. After argon blowing refining, when the temperature of the molten steel in the furnace drops to 1420℃, remove the refining slag on the surface of the molten steel, add electrolytic copper and rare earth alloy cerium aluminate, and argon blow refining. Increase the heating power of the medium frequency furnace to 350 kW, so that the temperature of the molten steel in the furnace rises to 1520℃, and continue to maintain the argon blowing process for 10 min. S5. Add the slag-forming agent into the medium-frequency induction furnace, reduce the heating power of the medium-frequency furnace to 150 kW, start the soft argon blowing process for 40 min, and the argon blowing pressure range is 0.4 MPa. S6. Power off and cool down to 1280℃ to remove the refining slag from the surface of the molten steel, and then pour the molten steel into the ingot mold.
[0032] The composition of the high-alumina niobium-iron-silicon alloy is as follows: 24.8% niobium by mass, 12% silicon by mass, 1.6% aluminum by mass, 0.12% total impurity elements by mass, and the balance being iron.
[0033] The composition of the ferroboron is: 17.2% boron by mass, with the balance being iron.
[0034] The preparation method of the slag-forming agent in step S5 includes the following steps: A1. Weigh the raw materials by mass percentage: 60% calcium oxide, 23% silicon dioxide, 10% magnesium oxide, 5% sodium carbonate, and 2% lithium fluoride. Mix and stir at 300~400 r / min for 15~20 min to obtain a premix. A2. Put the premixed material into the reaction chamber of the plasma surface treatment machine, seal the equipment, evacuate to 100 Pa, introduce argon gas into the reaction chamber, control the argon gas flow rate to 200 mL / min, keep the pressure in the reaction chamber stable at 200 Pa, start the plasma generator, set the radio frequency power to 500 W and the time to 30 min, turn off the plasma generator, continue to introduce argon gas to cool to room temperature, crush and pass through a 60-mesh sieve to obtain the slagging agent.
[0035] Comparative Example 1: In step S2, the amount of industrial silicon added accounts for 55% of its total mass, and the remaining steps are the same as in Example 1.
[0036] Comparative Example 2: In step S3, the mass ratio of high-alumina niobium iron silicon to iron oxide powder is 100:1.7, and the remaining steps are the same as in Example 1.
[0037] Comparative Example 3: The argon blowing pressure in steps S3 and S4 is 1.8 MPa, and the remaining steps are the same as in Example 1.
[0038] Comparative Example 4: The soft blowing argon process in step S5 takes 10 minutes, and the remaining steps are the same as in Example 1.
[0039] Comparative Example 5: Rare earth alloy cerium aluminate was not added in step S4, and the remaining steps were the same as in Example 1.
[0040] Comparative Example 6: Lithium fluoride was not added in step A1, step A2 was not performed, and the remaining steps were the same as in Example 1.
[0041] Table 1. Test results of mass content of each major element, Nb yield, and Al content of internal impurities in the master alloy.
[0042] As shown in Table 1, the iron-based amorphous nanocrystalline master alloy prepared using the process of this invention exhibits excellent performance in terms of main element composition control, niobium yield, and aluminum impurity removal. The master alloys obtained in Examples 1-3 have stable and controllable compositions, with silicon content controlled at 8.65-8.80%, boron content at 1.56-1.58%, copper content at 1.25-1.28%, and niobium content at 5.45-5.65%, meeting the composition design requirements for Fe-Cu-Nb-Si-B amorphous nanocrystalline soft magnetic alloys. The niobium yield is higher than 99.39%, indicating that the low-grade high-aluminum niobium-iron-silicon alloy, under the synergistic effect of segmented feeding, argon blowing refining, and iron oxide fluxing, dissolves sufficiently and has extremely low oxidation loss. The aluminum impurity content is as low as 19-28 ppm, meeting the cleanliness standard for high-purity soft magnetic alloys, indicating that rare earth modification treatment, plasma-modified slag-forming agents, and soft argon blowing can efficiently remove aluminum impurities introduced by high-aluminum niobium-iron-silicon alloys. As the niobium content in high-alumina niobium-iron-silicon increases, the niobium yield remains stable, and the aluminum impurity is further reduced, indicating that this process has good adaptability to low-grade niobium-iron of different grades.
[0043] In Comparative Example 1, increasing the proportion of pre-processed industrial silicon in the furnace bottom to 55% resulted in a decrease in both silicon and niobium content in the master alloy, with the niobium yield dropping to 97.58% and the aluminum impurity increasing to 58 ppm. Adding excessive silicon increases melt viscosity and inhibits the removal of alumina inclusions, ultimately leading to a decrease in niobium yield and a significant increase in residual aluminum content.
[0044] In Comparative Example 2, increasing the iron oxide ratio to 100:1.7 resulted in excessively strong oxidizing properties in the melt, leading to a significant decrease in niobium yield to 96.57% and an aluminum impurity concentration of 35 ppm.
[0045] In Comparative Example 3, increasing the argon blowing pressure to 1.8 MPa resulted in a niobium yield of only 97.17%, while the aluminum impurity increased sharply to 98 ppm. Excessive argon agitation caused violent turbulence in the molten steel, exacerbating niobium oxidation and significantly compromising the cleanliness of the smelting process.
[0046] In Comparative Example 4, with the soft argon blowing time shortened to 10 min, the niobium recovery rate was 98.18%, while the aluminum impurity increased to 72 ppm. Insufficient soft argon blowing time prevented fine alumina inclusions in the molten steel from fully colliding, aggregating, and floating into the slag phase, resulting in a decrease in the cleanliness of the molten steel. The apparent recovery rate of niobium was also reduced due to inclusion encapsulation.
[0047] Compared with Example 5, which did not contain rare earth cerium aluminate, the niobium yield dropped to 97.98% and the aluminum impurity reached 85 ppm. Rare earth has strong deoxidation, aluminum fixation and inclusion modification effects, and can promote the transformation of aluminum oxide into easily floating composite inclusions; without rare earth treatment, the deoxidation and impurity removal capabilities decreased significantly and the residual aluminum increased significantly.
[0048] Comparative Example 6, using a slag-forming agent without added lithium fluoride and without plasma modification, achieved a niobium yield of 98.59% and an aluminum impurity of 52 ppm. The unmodified slag-forming agent exhibited high interfacial tension with the molten steel, resulting in a high energy barrier for inclusions to cross the interface and enter the slag phase. This led to poorer impurity removal kinetics, resulting in significantly higher residual aluminum than in the example and a reduced niobium yield.
[0049] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.
Claims
1. A method for preparing an iron-based amorphous nanocrystalline master alloy based on low-grade niobium iron, characterized in that, Includes the following steps: S1. Prepare raw materials: industrial pure iron, industrial silicon, ferroborone, high-alumina niobium ferrosilicon, electrolytic copper, rare earth alloys, and slag-forming agents. S2. Add industrial pure iron, industrial silicon, and ferroboron into the medium-frequency induction furnace to increase the heating power of the medium-frequency induction furnace and reach the target temperature; S3. Mix high-alumina niobium iron silicon with iron oxide powder to obtain a mixture, add it to the molten steel in the medium frequency induction furnace, and start argon blowing for refining at the same time. S4. Add the remaining industrial silicon from step S1 to the surface of the molten steel in step S3, and after argon refining, remove the refining slag on the surface of the molten steel, add electrolytic copper and rare earth alloy, and then argon refining. S5. Add the slag-forming agent into the medium-frequency induction furnace and start the soft-blowing argon process; S6. Power off and cool down to remove the refining slag from the surface of the molten steel, and then pour the molten steel into the ingot mold.
2. The method for preparing an iron-based amorphous nanocrystalline master alloy based on low-grade niobium iron according to claim 1, characterized in that, In step S1, the raw material mass ratio is 55-65% industrial pure iron, 6-8% industrial silicon, 8.7-9.4% ferroboron, 20-30% high-alumina niobium ferrosilicon, 1.22-1.32% electrolytic copper, 0.05-0.15% rare earth alloy, and 0.4-1.5% slagging agent.
3. A method for preparing an iron-based amorphous nanocrystalline master alloy based on low-grade niobium iron according to claim 1 or 2, characterized in that, The composition of the high-alumina niobium-iron-silicon alloy is as follows: 15-30% niobium by mass, 10-25% silicon by mass, 0.6-1.6% aluminum by mass, 0.05-0.12% total impurity elements by mass, and the balance being iron.
4. The method for preparing an iron-based amorphous nanocrystalline master alloy based on low-grade niobium iron according to claim 1, characterized in that, In step S2, industrial pure iron, industrial silicon, and ferroboron are added to the medium-frequency induction furnace. Industrial silicon, which accounts for 15-50% of the total mass of industrial silicon in the raw materials, is spread at the bottom of the medium-frequency induction furnace, industrial pure iron is placed in the center of the medium-frequency induction furnace, and ferroboron is poured into the gaps between the industrial pure iron. The heating power of the medium-frequency induction furnace is increased to 400-450 kW to reach the target temperature of 1550-1580℃.
5. The method for preparing an iron-based amorphous nanocrystalline master alloy based on low-grade niobium iron according to claim 1, characterized in that, In step S3, the mass ratio of high-alumina niobium iron silicon to iron oxide is 100:0.8~1.5, and it is added to the molten steel in the medium-frequency induction furnace in 2~3 batches. The heating power of the medium-frequency induction furnace is 200~300 kW, the argon blowing refining time is 15~25 min, and the pressure range is 0.6~1.5 MPa.
6. The method for preparing an iron-based amorphous nanocrystalline master alloy based on low-grade niobium iron according to claim 1, characterized in that, In step S4, the remaining industrial silicon is added to the molten steel in the medium-frequency induction furnace in 2 to 3 batches. The heating power of the medium-frequency induction furnace is 200 to 250 kW, the argon blowing time is 10 to 20 min, and the pressure range is 0.6 to 1.5 MPa.
7. The method for preparing an iron-based amorphous nanocrystalline master alloy based on low-grade niobium iron according to claim 1, characterized in that, In step S4, after adding electrolytic copper and rare earth alloy, the heating power of the medium frequency furnace is increased by 250~350 kW, so that the molten steel in the furnace rises to 1480~1520℃ and the argon blowing process is maintained for 5~10 min; the rare earth alloy is cerium aluminate.
8. The method for preparing an iron-based amorphous nanocrystalline master alloy based on low-grade niobium iron according to claim 1, characterized in that, The preparation method of the slag-forming agent in step S5 includes the following steps: A1. Weigh the raw materials by mass percentage: 50-60% calcium oxide, 15-25% silicon dioxide, 10-20% magnesium oxide, 5-10% sodium carbonate, and 0.5-2% lithium fluoride. Mix and stir at 300-400 r / min for 15-20 min to obtain a premix. A2. Put the premixed material into the reaction chamber of the plasma surface treatment machine, seal the equipment, evacuate to 50~100 Pa, introduce argon gas into the reaction chamber, control the argon gas flow rate to 150~200 mL / min, keep the pressure in the reaction chamber stable at 150~200 Pa, start the plasma generator, set the radio frequency power to 300~500 W and the time to 15~30 min, turn off the plasma generator, continue to introduce argon gas to cool to room temperature, crush and pass through a 10~60 mesh sieve to obtain the slagging agent.
9. The method for preparing an iron-based amorphous nanocrystalline master alloy based on low-grade niobium iron according to claim 1, characterized in that, In step S5, the soft argon blowing process takes 20-40 minutes and the blowing pressure ranges from 0.1 to 0.4 MPa.