High-grade ferro-niobium alloy and method for producing same

Abstract

This application belongs to the field of metallurgical technology, specifically relating to a high-grade niobium-iron alloy and its preparation method. The preparation method includes: obtaining a low-grade niobium-iron alloy; melting the low-grade niobium-iron alloy to obtain a melt; subjecting the melt to pulsed current treatment until complete solidification to obtain an alloy block; dividing the alloy block into region one and region two according to the current density of the pulsed current treatment; obtaining an iron block in region one; and the current density in region one being greater than or equal to 5.0 × 10⁻⁶. 8 A / m 2 In region two, a high-grade niobium-iron alloy is obtained, and the current density in region two is less than 5.0 × 10⁻⁶. 8 A / m 2 This application purifies the low-grade niobium-iron alloy molten system under the synergistic effect of an inert atmosphere and pulsed current, which is beneficial for removing inclusions and impurity elements in the melt and enriching niobium in the iron matrix, thereby obtaining a high-grade niobium-iron alloy with a niobium mass fraction of 60-70 wt%.

Description

Technical Field

[0001] This application relates to the field of metallurgical technology, specifically to a high-grade niobium-iron alloy and its preparation method. Background Technology

[0002] Ferroniobium alloys are primarily used as microalloying additives in the smelting of high-temperature alloys, stainless steels, and high-strength low-alloy steels. By introducing niobium into molten steel, grain refinement and precipitation strengthening can be achieved to a certain extent, thereby improving the strength, toughness, and creep properties of the steel, and also having a beneficial effect on corrosion resistance. Therefore, the compositional stability and smelting yield of ferroniobium alloys have a significant impact on the performance of steel products.

[0003] Currently, the industrial production of niobium-iron alloys still faces problems such as low yield, large fluctuations in alloy composition, and complex processes, resulting in high production costs and insufficient product quality consistency, making it difficult to meet the needs of large-scale and continuous production.

[0004] In existing technologies, the main methods for preparing ferroniobium alloys include the aluminothermic reduction of niobium oxide and the electrothermal smelting of niobium concentrate. The aluminothermic reduction of niobium oxide has a relatively simplified process flow, but in practical applications, it suffers from the difficulty in precisely controlling the amount of aluminum involved in the reaction, easily leading to high residual aluminum content or an imbalance in the aluminum-iron ratio, thus affecting the compositional stability and metallurgical quality of the ferroniobium alloy. While the electrothermal smelting of niobium concentrate can yield ferroniobium alloys with high niobium content, this method typically suffers from long smelting cycles, insufficient continuous operation capability, and high energy consumption and equipment load, making it difficult to balance production efficiency and cost control.

[0005] Several technical solutions have been proposed to address the problems related to ferroniobium alloys and their smelting. For example, existing technologies disclose a method for producing ferroniobium alloys that uses the aluminothermic process combined with refining to reduce energy consumption and simplify the process. However, the proportion of raw materials in the aluminothermic reduction stage of this method has not yet been precisely controlled, and the yield and quality stability of the ferroniobium alloy still have room for improvement. Existing technologies also propose a method for producing ferroniobium using smelting furnace ash as a reducing agent. This method reduces production costs by recycling the furnace ash, but due to the limited effective content of aluminum and niobium in the reducing agent during the smelting process, its reduction efficiency and the yield of ferroniobium alloys remain insufficient.

[0006] In summary, existing niobium-iron alloy smelting technologies still have room for improvement in terms of reducing efficiency, stabilizing alloy composition, increasing smelting yield, and simplifying process flow. It is necessary to further propose a niobium-iron alloy preparation technology that is easier to control in terms of process parameters, has higher smelting efficiency, and is conducive to reducing production costs. Summary of the Invention

[0007] To address the aforementioned technical problems, this application provides a method for preparing a high-grade niobium-iron alloy, comprising: obtaining a low-grade niobium-iron alloy; melting the low-grade niobium-iron alloy to obtain a melt; subjecting the melt to pulsed current treatment until complete solidification to obtain an alloy block; dividing the alloy block into region one and region two according to the current density of the pulsed current treatment; obtaining an iron block in region one; and wherein the current density in region one is greater than or equal to 5.0 × 10⁻⁶. 8 A / m 2 In region two, a high-grade niobium-iron alloy is obtained, and the current density in region two is less than 5.0 × 10⁻⁶. 8 A / m 2 .

[0008] In a preferred embodiment of the preparation method of a high-grade niobium-iron alloy described in this application, the smelting atmosphere is argon, and the purity of the argon is not less than 99.99%.

[0009] As a preferred embodiment of the preparation method of the high-grade niobium-iron alloy described in this application, the heating temperature of the smelting is 1550-1650℃, the heating rate of the smelting is 4-6℃ / min, and the holding time of the smelting is 10-30min.

[0010] As a preferred embodiment of the preparation method of the high-grade niobium-iron alloy described in this application, the composition of the low-grade niobium-iron alloy, by mass percentage, is: Nb: 15%-25%, Al: 3%-5%, Si: 3%-5%, C: 0.1%-0.3%, S: 0.1%-0.3%, P: 0.3%-0.5%, Ta: 0.1%-0.3%, with the remainder being Fe and unavoidable impurities.

[0011] As a preferred embodiment of the preparation method of high-grade niobium-iron alloy described in this application, the pulse current treatment adopts a constant voltage energizing method, the voltage of the pulse current treatment is 5-8V, the current of the pulse current treatment is 115-125A, the time of the pulse current treatment is 20-40min, the duty cycle of the pulse current treatment is 10%-30%, and the pulse frequency of the pulse current treatment is 800-1200Hz.

[0012] As a preferred embodiment of the preparation method of high-grade niobium-iron alloy described in this application, the electrode material used in the pulse current treatment is a high-melting-point conductive material, which includes at least one of carbon, graphite, tungsten, or molybdenum; a non-uniform current field is formed inside the melt, and the current density of the pulse current treatment gradually decreases from near the electrode to far away from the electrode, exhibiting a continuous gradient distribution.

[0013] As a preferred embodiment of the preparation method of the high-grade niobium-iron alloy described in this application, under the action of the pulsed current treatment, the non-metallic inclusions in the melt migrate, aggregate, and float, thereby achieving purification and impurity removal.

[0014] As a preferred embodiment of the method for preparing a high-grade niobium-iron alloy as described in this application, under the action of the pulsed current treatment, niobium in the melt migrates and accumulates, thereby achieving the preparation of a high-grade niobium-iron alloy.

[0015] This application also provides a high-grade niobium-iron alloy, which is prepared by the above-described method for preparing high-grade niobium-iron alloy.

[0016] As a preferred embodiment of the high-grade niobium-iron alloy described in this application, the composition of the high-grade niobium-iron alloy, by mass percentage, is: Nb: 60%-70%, Al≤0.1%, Si≤0.1%, C≤0.01%, S≤0.01%, P≤0.05%, Ta≤0.01%, with the remainder being Fe and unavoidable impurities.

[0017] The beneficial effects of this application are as follows:

[0018] This application proposes a method for preparing high-grade niobium-iron alloy, aiming to address the problems of difficulty in improving purity, limited composition control, and lengthy processes in the existing upgrading process of low-grade niobium-iron alloys. This application provides a method for purifying, regionally enriching, and directionally separating low-grade niobium-iron alloy melts using pulsed current. This method, through melting, pulsed current treatment, and subsequent partitioning, achieves the migration and removal of inclusions in the melt and the formation of high-niobium regions, thereby improving the utilization value of low-grade niobium-iron alloys.

[0019] This study found that when a low-grade niobium-iron alloy molten system is treated under the synergistic effect of an inert atmosphere and pulsed current, a non-uniform current field is formed inside the melt, with differences in current density in different regions. Sampling and composition analysis of different regions of the solidified alloy block revealed significant differences in Nb and Fe content across different current density regions, with higher Nb content in low current density regions and higher Fe content in high current density regions. Under the non-uniform current field and the transient electromagnetic effects it induces, inclusions and different components in the melt exhibit different migration behaviors. Non-metallic inclusions migrate, aggregate, and float, while niobium-containing components accumulate in low current density regions, thus forming niobium-rich and niobium-poor regions after solidification. Based on these regional compositional differences, the alloy block can be divided into sections according to the current density corresponding to each region to obtain high-grade niobium-iron alloy and iron blocks, respectively. Specifically, the current density of the region corresponding to the iron block is greater than or equal to 5.0 × 10⁻⁶. 8 A / m 2The current density in the region corresponding to the high-grade niobium-iron alloy was less than 5.0 × 10⁻⁶. 8 A / m 2 Using the above technical solution, a low-grade niobium-iron alloy molten system is purified under the synergistic effect of an inert atmosphere and pulsed current. A continuous current density gradient distribution is formed within the melt, from high to low current density regions. The low current density regions have higher niobium and lower iron content, while the high current density regions have lower niobium and higher iron content. It should be noted that the current density distribution is a continuous gradient, while the Nb and Fe content distributions are regional variations related to the current density distribution formed under this non-uniform current field, exhibiting significant differences in niobium-rich and iron-rich areas between different regions. Under the action of the non-uniform current field and the transient electromagnetic force it induces, inclusions and different components in the melt exhibit different migration behaviors, which is beneficial for removing inclusions and impurity elements from the melt. Niobium-containing components accumulate in the low current density regions, achieving niobium enrichment in the iron matrix, thereby obtaining a high-grade niobium-iron alloy with a niobium mass fraction of 60-70 wt%.

[0020] Existing technologies suffer from problems such as difficulty in controlling aluminum content, low yield, unstable quality, and high cost during the production of ferroniobium alloys. Therefore, this application provides a method for purifying ferroniobium alloys in an atmosphere furnace using a pulsed power supply. Compared with existing technologies, this application provides a method for purifying ferroniobium alloys in an atmosphere furnace using a pulsed power supply, which has the following advantages:

[0021] 1. By using a pulsed power supply to purify and remove impurities from Nb in an inert gas, the content of oxide inclusions can be effectively controlled, the ferro-niobium alloy melt can be improved, and the quality stability and product performance of ferro-niobium alloy can be significantly improved.

[0022] 2. The process parameters and flow of this application have been optimized and designed. While taking into account the stability of product quality, it is conducive to improving the recovery rate of niobium and the acquisition rate of high-grade niobium-iron alloy, thereby effectively improving production efficiency and overcoming the shortcomings of traditional methods such as long cycle and low efficiency of continuous operation.

[0023] 3. By adopting pulse power supply technology, the efficient purification and refining of niobium-iron alloys is achieved, which greatly improves production efficiency and overcomes the shortcomings of traditional methods such as long cycle time and low efficiency of continuous operation.

[0024] 4. The method described in this application reduces the production cost of ferroniobium alloys, improves the economic benefits of the products, and has a significant cost advantage;

[0025] 5. The process flow of this application is simplified, easy to operate, and easy to scale up for production, meeting the modern industry's demand for high-quality and high-efficiency niobium-iron alloys. Detailed Implementation

[0026] The technical solutions in the embodiments will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0027] This application provides a method for preparing a high-grade niobium-iron alloy, comprising:

[0028] To obtain a low-grade niobium-iron alloy, the low-grade niobium-iron alloy is placed in a crucible, and the crucible is placed in the furnace chamber of a vacuum atmosphere furnace. The composition of the low-grade niobium-iron alloy, by mass percentage, is: Nb: 15%-25%, Al: 3%-5%, Si: 3%-5%, C: 0.1%-0.3%, S: 0.1%-0.3%, P: 0.3%-0.5%, Ta: 0.1%-0.3%, with the remainder being Fe and unavoidable impurities.

[0029] Specifically, the crucible is an alumina crucible with an alumina mass fraction of not less than 95%. Its inner wall has a dense sintered structure, and the inner wall of the crucible is provided with an anti-corrosion lining or isolation coating, preferably not less than 99.99%. The crucible is pre-baked before loading, with a pre-baking temperature of 200-800℃ and a time of 0.5-4h, to remove adsorbed water and volatile impurities from the crucible, thereby reducing secondary contamination of the melt during the smelting process.

[0030] The furnace was evacuated to reduce the furnace pressure to 1×10⁻⁶. -1 Pa-1×10 1 After vacuuming, inert gas is introduced for replacement protection; the process of vacuuming and introducing inert gas for replacement is repeated multiple times to reduce the residual oxygen content and water vapor content in the furnace until the oxygen content in the furnace is less than the set threshold.

[0031] Specifically, the inert gas is argon, specifically industrial high-purity or ultra-high-purity argon with a purity of not less than 99.99%. After vacuuming, the argon is introduced into the furnace via dynamic displacement at a pressure of 0.02-0.10 MPa and a flow rate of 0.5-10 L / min. After displacement, the furnace is maintained under positive pressure to keep the oxygen content below a predetermined threshold, thereby inhibiting melt oxidation and the generation of gas inclusions. The vacuuming and inert gas introduction process is repeated 3-4 times.

[0032] The first vacuum pump reduced the furnace pressure to 1×10⁻⁶. -1 Pa-1-10 1The pressure is maintained at 1 Pa for 10-30 minutes; subsequent vacuuming reduces the furnace pressure to 1 × 10⁻⁶ Pa. -1 Pa-1-10 1 Pa, and maintain the pressure for 3-15 minutes; after each vacuuming, inert gas is introduced into the furnace to raise the furnace pressure to 0.02-0.10 MPa and maintain it for 3-15 minutes, then the furnace pressure is released to atmospheric pressure or slightly higher than atmospheric pressure before the next vacuuming is performed, so as to realize the cyclic replacement of "gas filling - holding - releasing - re-vacuuming"; during the repeated replacement process, the furnace atmosphere is monitored by an oxygen content detector and / or a dew point meter, and when the residual oxygen content in the furnace is lower than the predetermined threshold.

[0033] Low-grade niobium-iron alloy is heated and melted under an inert gas protective atmosphere, and held at a set melting temperature range to obtain a melt with uniform composition.

[0034] Specifically, the melting and heating temperature is 1550-1650℃, and resistance heating is used to heat and melt the raw materials in the crucible. The heating rate is 4-6℃ / min. After reaching the melting and heating temperature, a holding treatment is performed for 10-30 minutes to ensure that the raw materials are fully melted and form a melt with uniform composition. During the holding process, the melt is homogenized. At the same time, the furnace is kept in an inert gas protective atmosphere during the melting and holding process, preferably maintaining a positive pressure of 0.5-5 kPa. After the melt is formed, a settling and clarification treatment is performed for 2-20 minutes.

[0035] The melt is subjected to pulsed current treatment until complete solidification to obtain an alloy block. Specifically, the pulsed current treatment involves inserting or contacting a high-melting-point conductive electrode into the melt while it is in a molten state, and applying a pulsed current to the melt using a pulsed power supply. This creates a periodic alternating electric field and a transient electromagnetic force field within the melt. Under the action of the pulsed current, charged particles and non-metallic inclusions with electrical differences in the melt undergo electromigration driven by the electric field. Simultaneously, due to the non-uniform current density distribution within the melt, an additional driving force is generated under the influence of the current density gradient. The electrode material used in the pulsed current treatment is a high-melting-point conductive material, including at least one of carbon, graphite, tungsten, or molybdenum. A non-uniform current field is formed within the melt, and the current density during the pulsed current treatment gradually decreases from near the electrode to far away from the electrode, exhibiting a continuous gradient distribution.

[0036] Under the influence of electromigration, non-metallic inclusions in the melt undergo directional migration, aggregation, and growth along the current density gradient, gradually accumulating and floating upwards towards the upper part of the molten pool or the interface region. This improves inclusion removal efficiency, reduces the content of oxygen, sulfur, and other impurities in the melt, and achieves purification and impurity removal. Under pulsed current treatment, niobium in the melt migrates and accumulates, achieving the preparation of high-grade niobium-iron alloys. Specifically, the current density in the region corresponding to the iron block is greater than or equal to 5.0 × 10⁻⁶. 8 A / m 2 The current density in the region corresponding to the high-grade niobium-iron alloy was less than 5.0 × 10⁻⁶. 8 A / m 2 .

[0037] The alloy block was divided into two regions, Region 1 and Region 2, based on the current density of the pulsed current treatment. Region 1 yielded the iron block, and the current density in Region 1 was greater than or equal to 5.0 × 10⁻⁶. 8 A / m 2 In region two, a high-grade niobium-iron alloy was obtained, and the current density in region two was less than 5.0 × 10⁻⁶. 8 A / m 2 The composition of the high-grade niobium-iron alloy, by mass percentage, is as follows: Nb: 60%-70%, Al≤0.1%, Si≤0.1%, C≤0.01%, S≤0.01%, P≤0.05%, Ta≤0.01%, with the remainder being Fe and unavoidable impurities.

[0038] Specifically, a pulsed current is applied to the melt using a pulsed power supply to generate an electric field and electromagnetic stirring effect in the melt. The electrodes of the pulsed power supply are made of a high-melting-point conductive material, including at least one of carbon, graphite, niobium, tungsten, or molybdenum. The electrodes are rod-shaped, and the electrode surface is provided with an anti-corrosion dense layer or an anti-adhesion coating. The electrodes pass through the furnace cover and are in communication with the melt through an insulating sealing assembly. The electrodes are inserted into the melt or make conductive contact with the upper part of the melt, and the depth of the electrodes inserted into the melt is 10%-80% of the height of the melt.

[0039] Specifically, the pulse power supply adopts a constant voltage supply method, with a voltage of 5-8V, and the voltage is maintained within a predetermined stable range through sampling feedback control; the pulse current processing current is 115-125A; the duty cycle is 10%-30%, the pulse frequency is 800-1200Hz, and the duration is 20-40 minutes; the voltage is any two or any range between 5V, 6V, 7V, and 8V; the current is 115A, 116A, 117A, 118A, 119A, 120A, and 121A. The range between any two of 122A, 123A, 124A, and 125A; the range between any two of duty cycles of 10%, 15%, 20%, 25%, and 30%; the range between any two of pulse frequencies of 800Hz, 900Hz, 1000Hz, 1100Hz, and 1200Hz; and the range between any two of time periods of 20min, 25min, 30min, 35min, and 40min.

[0040] Specifically, during the pulse energizing process, the temperature of the melt is monitored, and the temperature of the melt is kept within a predetermined range by adjusting the pulse energizing parameters; at the same time, the current, voltage or electrode-melt circuit impedance during the pulse energizing process is monitored, and when the monitored parameters reach a preset threshold, the pulse power supply performs protection control, which includes at least one of current limiting, voltage reduction, pausing pulse output or power off.

[0041] Example 1

[0042] To obtain a low-grade ferroniobium alloy, the low-grade ferroniobium alloy is placed in a crucible, and the crucible is placed in the furnace chamber of a vacuum atmosphere furnace. The composition of the low-grade ferroniobium alloy, by mass percentage, is: Nb: 20%, Al: 4%, Si: 4%, C: 0.2%, S: 0.2%, P: 0.4%, Ta: 0.2%, with the remainder being Fe and unavoidable impurities.

[0043] The furnace was evacuated to reduce the furnace pressure to 1×10⁻⁶. -1 Pa-1×10 1 After Pa, an inert gas is introduced for displacement protection; the inert gas is argon, which is industrial high-purity argon with a purity of not less than 99.99%.

[0044] Low-grade niobium-iron alloy is heated and melted under an inert gas protective atmosphere, and held at a set melting temperature range to obtain a melt with uniform composition.

[0045] The melting and heating temperature is 1600℃. Resistance heating is used to heat and melt the raw materials in the crucible. The heating rate is 5℃ / min. After reaching the melting and heating temperature, the materials are held for 20 minutes to ensure that the raw materials are fully melted and form a melt with uniform composition.

[0046] The melt was subjected to pulsed current treatment until complete solidification to obtain an alloy block. The electrode material used for the pulsed current treatment was a high-melting-point conductive material, specifically graphite. A non-uniform current field was formed inside the melt, and the current density of the pulsed current treatment gradually decreased from near the electrode to far away from the electrode, exhibiting a continuous gradient distribution. Under the action of the pulsed current treatment, non-metallic inclusions in the melt migrated, aggregated, and floated to the surface; niobium in the melt migrated and became enriched. Specifically, the current density in the region corresponding to the obtained iron block was greater than or equal to 5.0 × 10⁻⁶. 8 A / m 2 The current density in the region corresponding to the high-grade niobium-iron alloy was less than 5.0 × 10⁻⁶. 8 A / m 2 The pulse current processing method is as follows: when the melt is in a molten state, a high melting point conductive electrode is inserted into the melt, and a pulse current is applied to the melt through a pulse power supply; the pulse power supply adopts a constant voltage energizing method, the voltage of the pulse current processing is 6V, the current is 120A, the time is 30min, the duty cycle is 20%, and the pulse frequency is 1000Hz.

[0047] The alloy block was divided into two regions, Region 1 and Region 2, based on the current density of the pulsed current treatment. Region 1 yielded the iron block, and the current density in Region 1 was greater than or equal to 5.0 × 10⁻⁶. 8 A / m 2 In region two, a high-grade niobium-iron alloy was obtained, and the current density in region two was less than 5.0 × 10⁻⁶. 8 A / m 2 ;

[0048] The high-grade niobium-iron alloy prepared in Example 1 was tested, and the results showed that, by mass percentage, the composition of the high-grade niobium-iron alloy was: Nb: 66%, Al: 0.08%, Si: 0.07%, C: 0.008%, S: 0.006%, P: 0.03%, Ta: 0.007%, with the remainder being Fe and unavoidable impurities.

[0049] Example 2

[0050] The difference between this embodiment and Embodiment 1 is that the voltage for pulse current processing is 5V, the current is 125A, the time is 20min, the duty cycle is 10%, and the pulse frequency is 1200Hz. The other steps are the same as in Embodiment 1.

[0051] The high-grade niobium-iron alloy prepared in Example 2 was tested, and the results showed that, by mass percentage, the composition of the high-grade niobium-iron alloy was: Nb: 64%, Al: 0.07%, Si: 0.09%, C: 0.009%, S: 0.007%, P: 0.02%, Ta: 0.006%, with the remainder being Fe and unavoidable impurities.

[0052] Example 3

[0053] The difference between this embodiment and Embodiment 1 is that the voltage of the pulse current processing is 8V, the current is 115A, the time is 40min, the duty cycle is 30%, and the pulse frequency is 800Hz. The other steps are the same as in Embodiment 1.

[0054] The high-grade niobium-iron alloy prepared in Example 3 was tested, and the results showed that, by mass percentage, the composition of the high-grade niobium-iron alloy was: Nb: 65%, Al: 0.06%, Si: 0.08%, C: 0.007%, S: 0.007%, P: 0.04%, Ta: 0.009%, with the remainder being Fe and unavoidable impurities.

[0055] Comparative Example 1

[0056] The difference between this comparative example and Example 1 is that the pulse current processing current is 100A, while the other steps are the same as in Example 1.

[0057] The high-grade niobium-iron alloy prepared in Comparative Example 1 was tested, and the results showed that, by mass percentage, the composition of the high-grade niobium-iron alloy was: Nb: 41%, Al: 0.12%, Si: 0.13%, C: 0.016%, S: 0.014%, P: 0.08%, Ta: 0.013%, with the remainder being Fe and unavoidable impurities.

[0058] Comparative Example 2

[0059] The difference between this comparative example and Example 1 is that the pulse current processing current is 150A, while the other steps are the same as in Example 1.

[0060] The high-grade niobium-iron alloy prepared in Comparative Example 2 was tested, and the results showed that, by mass percentage, the composition of the high-grade niobium-iron alloy was: Nb: 48%, Al: 0.11%, Si: 0.14%, C: 0.012%, S: 0.015%, P: 0.07%, Ta: 0.014%, with the remainder being Fe and unavoidable impurities.

[0061] Comparative Example 3

[0062] The difference between this comparative example and Example 1 is that the voltage for pulse current processing is 3V, while the other steps are the same as in Example 1.

[0063] The high-grade niobium-iron alloy prepared in Comparative Example 3 was tested, and the results showed that, by mass percentage, the composition of the high-grade niobium-iron alloy was: Nb: 42%, Al: 0.16%, Si: 0.13%, C: 0.015%, S: 0.016%, P: 0.09%, Ta: 0.015%, with the remainder being Fe and unavoidable impurities.

[0064] Comparative Example 4

[0065] The difference between this comparative example and Example 1 is that the voltage for pulse current processing is 10V, while the other steps are the same as in Example 1.

[0066] The high-grade niobium-iron alloy prepared in Comparative Example 4 was tested, and the results showed that, by mass percentage, the composition of the high-grade niobium-iron alloy was: Nb: 47%, Al: 0.15%, Si: 0.11%, C: 0.019%, S: 0.014%, P: 0.08%, Ta: 0.016%, with the remainder being Fe and unavoidable impurities.

[0067] Comparative Example 5

[0068] The difference between this comparative example and Example 1 is that the pulse frequency of the pulse current processing is 500Hz, while the other steps are the same as in Example 1.

[0069] The high-grade niobium-iron alloy prepared in Comparative Example 5 was tested, and the results showed that, by mass percentage, the composition of the high-grade niobium-iron alloy was: Nb: 43%, Al: 0.15%, Si: 0.17%, C: 0.013%, S: 0.012%, P: 0.06%, Ta: 0.013%, with the remainder being Fe and unavoidable impurities.

[0070] Comparative Example 6

[0071] The difference between this comparative example and Example 1 is that the pulse frequency of the pulse current processing is 1500Hz, while the other steps are the same as in Example 1.

[0072] The high-grade niobium-iron alloy prepared in Comparative Example 6 was tested, and the results showed that, by mass percentage, the composition of the high-grade niobium-iron alloy was: Nb: 46%, Al: 0.14%, Si: 0.13%, C: 0.015%, S: 0.013%, P: 0.08%, Ta: 0.014%, with the remainder being Fe and unavoidable impurities.

[0073] As can be seen from the above embodiments and comparative examples: Example 1 combined with Comparative Example 1 shows that when the pulse current treatment current is too low, the driving force is relatively insufficient, resulting in poor niobium enrichment effect; Example 1 combined with Comparative Example 2 shows that when the pulse current treatment current is too high, the electromagnetic stirring and convection in the melt are enhanced, weakening the stability of the local enrichment region, causing some disturbance to the already formed component separation, and reducing the niobium enrichment effect; Example 1 combined with Comparative Example 3 shows that when the voltage of the pulse current treatment is too low, the actual electric field strength established in the melt is insufficient, the current density gradient is weakened, and the resulting electromigration and transient electromagnetic effects are weak, which is not conducive to the migration, aggregation and floating separation of inclusions, nor is it conducive to the directional migration and enrichment of niobium-containing components to the low current density region, thus the Nb content in the obtained high-grade niobium-iron alloy is significantly reduced; Example 1 combined with Comparative Example 4 shows that when the voltage of the pulse current treatment is too high, the local... Excessive electric field can easily cause local overheating and enhance disturbance and backmixing within the melt, disrupting the stable separation of the already formed niobium-rich and niobium-poor regions, thereby reducing the niobium enrichment effect and worsening the impurity removal effect. Example 1, combined with Comparative Example 5, shows that when the pulse frequency is too low, the number of pulses per unit time decreases, and the driving effect of the periodic electric field and electromagnetic force on the components and inclusions in the melt is insufficient, resulting in insufficient migration, aggregation, and flotation of inclusions. The enrichment degree of niobium-containing components in specific regions is low, thus reducing the Nb content in the final product. Example 1, combined with Comparative Example 6, shows that when the pulse frequency is too high, the effective action time of a single pulse is too short, and the niobium-containing components and inclusions in the melt have not had time to complete sufficient migration and separation. Furthermore, excessively frequent pulse switching weakens the directional enrichment effect, resulting in insufficient formation of niobium-rich regions, ultimately leading to a lower Nb content in the obtained product than in Example 1. In summary, voltage and pulse frequency significantly affect the formation of non-uniform current field and current density gradient distribution inside the melt, and further affect the removal effect of inclusions and the directional migration and regional enrichment of niobium-containing components. Only when the voltage, frequency and current parameters are within the range described in this application can a better purification and impurity removal effect and a higher niobium enrichment effect be obtained.

[0074] The above description is only a preferred embodiment of this application and does not limit the patent scope of this application. All equivalent structural transformations made using the content of this application's specification under the inventive concept of this application, or direct / indirect applications in other related technical fields, are included within the patent protection scope of this application.

Claims

1. A method for producing high-grade ferro-niobium, characterized by, include: A low-grade niobium-iron alloy is obtained, and the alloy is melted to obtain a melt. The melt is then subjected to pulsed current treatment until it completely solidifies to obtain an alloy block. The alloy block is divided into two regions, Region 1 and Region 2, according to the current density of the pulsed current treatment. Iron blocks are obtained from Region 1, where the current density is greater than or equal to 5.0 × 10⁻⁶. 8 A / m 2 In region two, a high-grade niobium-iron alloy is obtained, and the current density in region two is less than 5.0 × 10⁻⁶. 8 A / m 2 ; The composition of the low-grade niobium-iron alloy, by mass percentage, is as follows: Nb: 15%-25%, Al: 3%-5%, Si: 3%-5%, C: 0.1%-0.3%, S: 0.1%-0.3%, P: 0.3%-0.5%, Ta: 0.1%-0.3%, with the remainder being Fe and unavoidable impurities; The pulse current processing adopts a constant voltage energizing method. The voltage of the pulse current processing is 5-8V, the current of the pulse current processing is 115-125A, the time of the pulse current processing is 20-40min, the duty cycle of the pulse current processing is 10%-30%, and the pulse frequency of the pulse current processing is 800-1200Hz.

2. The method of claim 1, wherein the high-grade ferro-niobium alloy is prepared by the steps of: The smelting atmosphere is argon, and the purity of the argon is not less than 99.99%. ​ 3. The method for preparing a high-grade niobium-iron alloy according to claim 1, characterized in that, The heating temperature for melting is 1550-1650℃, the heating rate for melting is 4-6℃ / min, and the holding time for melting is 10-30min.

4. The method for preparing a high-grade niobium-iron alloy according to claim 1, characterized in that, The electrode material used in the pulse current treatment is a high melting point conductive material, which includes at least one of carbon, graphite, tungsten, or molybdenum; a non-uniform current field is formed inside the melt, and the current density of the pulse current treatment gradually decreases from near the electrode to far away from the electrode, exhibiting a continuous gradient distribution.

5. The method for preparing a high-grade niobium-iron alloy according to claim 1, characterized in that, Under the action of the pulsed current treatment, the non-metallic inclusions in the melt migrate, aggregate, and float, thereby achieving purification and impurity removal.

6. The method for preparing a high-grade niobium-iron alloy according to claim 1, characterized in that, Under the action of the pulsed current treatment, niobium in the melt migrates and accumulates, thereby realizing the preparation of high-grade niobium-iron alloy.

7. A high-grade niobium-iron alloy, characterized in that, It is prepared by the preparation method of a high-grade niobium-iron alloy according to any one of claims 1-6.

8. A high-grade niobium-iron alloy according to claim 7, characterized in that, The high-grade niobium-iron alloy has the following composition by mass percentage: Nb: 60%-70%, Al≤0.1%, Si≤0.1%, C≤0.01%, S≤0.01%, P≤0.05%, Ta≤0.01%, with the remainder being Fe and unavoidable impurities.