Process for the production of niobium ingots based on secondary material from electron beam melted superconducting niobium ingots

Abstract

This invention relates to the field of superconducting materials technology, specifically to a method for preparing niobium ingots from secondary materials generated during electron beam melting of superconducting niobium ingots. The method includes: collecting the secondary materials and subjecting them to hydrogenation treatment to obtain hydrogenated materials; dehydrogenating the powdered hydrogenated materials within a second preset temperature range to obtain dehydrogenated powdered secondary materials; uniformly mixing the powdered secondary materials with high-purity niobium powder of 4N grade or higher at a predetermined ratio within a preset mixing time to obtain a preform; pressing the preform into preforms using a hydraulic press to obtain preforms; sintering the preforms in a high-temperature reduction furnace to obtain pre-sintered strips; melting the pre-sintered strips to obtain secondary material niobium plates; and further melting the secondary material niobium plates to obtain high-purity niobium ingots with a purity ≥99.99%. This invention reduces niobium ingot resource waste, ensures resource recycling, and effectively improves the comprehensive utilization rate of niobium ingot resources.

Description

Technical Field

[0001] This invention relates to the field of superconducting materials technology, and specifically to a method for preparing niobium ingots from secondary materials generated by electron beam melting of superconducting niobium ingots. Background Technology

[0002] In the wave of rapid global technological development, superconducting materials, with their unique physical properties such as zero resistance and perfect diamagnetism, have become core foundational materials in fields such as medical magnetic resonance imaging, particle accelerators, and high-sensitivity magnetic detection. As a key foundational material in the field of superconductivity, the demand for superconducting niobium ingots is rising sharply with the widespread application of superconducting technology. Currently, electron beam melting furnaces, with their precise high-temperature, high-vacuum melting environment, have become the mainstream production equipment for preparing superconducting niobium ingots. This process can effectively remove impurities from niobium raw materials, improving the purity and performance of niobium ingots. However, during the electron beam melting process of superconducting niobium ingots, niobium reacts with trace amounts of oxygen and nitrogen remaining in the melting equipment, generating large amounts of volatile substances such as niobium oxides and niobium nitrides, while also producing slag containing niobium. With the continued expansion of the market demand for superconducting niobium ingots, the annual output of secondary materials such as niobium oxides and niobium nitrides has exceeded 50 tons, with niobium content generally exceeding 50%, and some even reaching 70%, representing enormous resource value. Currently, there is a lack of effective methods for recovering niobium ingots from secondary materials generated during electron beam melting of superconducting niobium ingots. This not only wastes niobium ingot resources, but also causes some environmental pollution from the discarded secondary materials. Summary of the Invention

[0003] To address the environmental pollution and resource waste caused by secondary materials generated during electron beam melting of superconducting niobium ingots, this invention aims to provide a method for preparing niobium ingots based on secondary materials generated during electron beam melting of superconducting niobium ingots. The specific technical solution adopted is as follows: In a first aspect, embodiments of the present invention disclose a method for preparing niobium ingots from secondary materials generated during electron beam melting of superconducting niobium ingots. The method includes: collecting secondary materials generated during the electron beam melting process of superconducting niobium ingots; hydrogenating the secondary materials within a preset hydrogen pressure range and a first preset temperature range to obtain hydrogenated materials; pulverizing and sieving the hydrogenated materials to obtain powdered hydrogenated materials; and dehydrogenating the powdered hydrogenated materials within a second preset temperature range. The dehydrogenated powdered secondary material is obtained; the powdered secondary material is mixed evenly with high-purity niobium powder of grade 4N or above in a predetermined ratio at a predetermined mixing time to obtain a preform; the preform is pressed into shape by a hydraulic press to obtain a preform bar; the preform bar is sintered in a high-temperature reduction furnace to obtain a pre-sintered bar; the pre-sintered bar is smelted in a pool melting electron beam furnace to obtain a secondary material niobium plate; the secondary material niobium plate is smelted again in a drip melting electron beam furnace to obtain a high-purity niobium ingot with a purity ≥99.99%.

[0004] Optionally, the preset hydrogen pressure range is 0.2 to 0.6 Pa, and the first preset temperature range is 200 to 1600 °C.

[0005] Optionally, the particle size of the powdered hydrogenated material is ≤1mm.

[0006] Optionally, the second preset temperature range is 400 to 1800°C.

[0007] Optionally, the predetermined ratio between the powdered secondary material and the high-purity niobium powder with a purity of 4N or higher is (0.2 to 2.7) kg: (1.3 to 6.8) kg, and the mixing time is 12 to 26 hours.

[0008] Optionally, the length, width and height of the precast strip are (220 to 600) * (30 to 70) * (30 to 70) mm.

[0009] Optionally, the melting power of the pool-melting electron beam furnace for melting the pre-bonded bars is 200 to 450 KW; the length, width and height of the secondary material niobium plate are (700 to 1600) * (150 to 220) * (30 to 50) mm.

[0010] Optionally, the melting power of the drip-melting electron beam furnace for secondary melting of niobium plates is 500 to 1600 KW.

[0011] Optional, the purity of high-purity niobium ingots is ≥99.99%.

[0012] Optionally, the collection of secondary materials generated during the electron beam melting of superconducting niobium ingots includes: collecting volatile substances adhering to the inner surface of the furnace and around the crucible during the melting of superconducting niobium ingots in a horizontal electron beam melting furnace to obtain secondary materials, including niobium oxides and niobium nitrides.

[0013] The technical solution disclosed in this invention provides a method for fully recovering and utilizing niobium from secondary materials generated during electron beam melting of superconducting niobium ingots. This is achieved through a systematic hydrogenation, dehydrogenation, mixing, pressing, sintering, and multi-stage melting process, reducing niobium ingot waste, ensuring resource recycling, effectively improving the comprehensive utilization rate of niobium ingot resources, and preventing environmental pollution. Specifically, under preset hydrogen pressure and a first preset temperature, hydrogenation allows secondary materials, such as niobium oxides, to undergo a reduction reaction with hydrogen to generate water vapor. Niobium nitrides break nitrogen-niobium bonds through a hydrothermal effect, achieving efficient removal of oxygen and nitrogen impurities and laying the foundation for subsequent niobium ingot purification. After crushing, grinding, and dehydrogenation, the hydrogenated material forms porous nano-sized niobium powder. When mixed with 4N-grade high-purity niobium powder (purity ≥99.99%) in a predetermined ratio, interfacial diffusion between micron-nano particles is achieved, resulting in a smaller error in the uniformity of the pre-formed material composition and ensuring the stability of the final purified niobium ingot. The pool-melting electron beam furnace first melts and casts the pre-formed strips into dense niobium plates, removing residual carbon, iron, and other metallic impurities. The droplet-melting electron beam furnace further refines the grains through droplet-by-drop melting. Multi-stage melting improves the efficiency of nitride removal, thereby further increasing the purity of the niobium ingots in the secondary material. Furthermore, embodiments of the present invention can flexibly adjust process parameters such as hydrogen pressure, temperature, and mixing ratio within a preset range according to the composition and impurity content of the secondary material, adapting to the processing needs of different batches of secondary material and ensuring the stability, flexibility, and reliability of the recycling process. Detailed Implementation

[0014] To further illustrate the technical means and effects adopted by the present invention to achieve its intended purpose, the following, in conjunction with preferred embodiments, details the specific implementation, structure, features, and effects of a method for preparing niobium ingots based on secondary materials generated from electron beam melting of superconducting niobium ingots according to the present invention. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0015] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0016] Traditional methods often utilize an exothermic reaction between aluminum powder and niobium oxide or niobium nitride to reduce niobium metal. However, this method has the following drawbacks: Low resource utilization efficiency: During the aluminothermic reaction, the high temperature (1500-2000℃) causes niobium to easily combine with residual nitrogen to form stable nitrides. Furthermore, the Al2O3 slag generated by the reaction (accounting for 40%-60% of the reaction products) tightly wraps the unreacted niobium particles, resulting in a niobium recovery rate of only 40%-50%. The niobium content in the slag is still as high as 20%-30%, leading to secondary resource waste. Severe environmental pollution: The reaction process generates a large amount of aluminum and niobium-containing dust, and the free aluminum powder in the dust is prone to explosion when it comes into contact with air.

[0017] To address the aforementioned issues, this invention employs pretreatment processes such as hydrogenation, grinding and sieving, dehydrogenation, mixing, and graded melting to render the secondary material into a powder state. This powder is then mixed with high-purity niobium powder to form a final product, preventing secondary pollution to the environment. Subsequent processes, including sintering and electron beam melting, maximize the efficient removal of impurities from the secondary material. Furthermore, the amount of secondary material generated during remelting is minimal, resulting in a high recovery rate.

[0018] The following describes in detail the specific scheme of the method for preparing niobium ingots based on secondary materials generated from electron beam melting of superconducting niobium ingots provided by the present invention.

[0019] This invention discloses a method for preparing niobium ingots from secondary materials generated during electron beam melting of superconducting niobium ingots, comprising the following steps: a) Collect secondary materials generated during the electron beam melting of superconducting niobium ingots, and hydrogenate the secondary materials within a preset hydrogen pressure range and a first preset temperature range to obtain hydrogenated materials.

[0020] b) The hydrogenated material is crushed and sieved to obtain powdered hydrogenated material, and the powdered hydrogenated material is dehydrogenated within a second preset temperature range to obtain dehydrogenated powdered secondary material.

[0021] c) After mixing the powdered secondary material with high-purity niobium powder of grade 4N or above in a predetermined ratio and at a predetermined mixing time, a preform is obtained. The preform is then pressed into shape by a hydraulic press to obtain a preform bar. The preform bar is then sintered in a high-temperature reduction furnace to obtain a pre-sintered bar.

[0022] d) The pre-formed strips are smelted using a pool-melting electron beam furnace to obtain secondary material niobium plates. The secondary material niobium plates are then smelted again using a drip-melting electron beam furnace to obtain high-purity niobium ingots, wherein the purity of the high-purity niobium ingots is ≥99.99%.

[0023] Specifically, during the electron beam melting process of superconducting niobium ingots, niobium reacts with trace amounts of residual oxygen and nitrogen in the melting equipment, generating a large amount of volatile substances such as niobium oxides and niobium nitrides. These volatile substances easily adhere to the inner surface of the furnace and around the crucible during the melting of superconducting niobium ingots in a horizontal electron beam furnace. Therefore, this embodiment of the invention collects the volatile substances adhering to the inner surface of the furnace and around the crucible during the melting of superconducting niobium ingots in a horizontal electron beam furnace, obtaining secondary materials, including niobium oxides and niobium nitrides.

[0024] Furthermore, in order to efficiently remove oxygen and nitrogen impurities from secondary materials such as niobium oxide and niobium nitride, this embodiment of the invention involves hydrogenating the secondary materials within a preset hydrogen pressure range and a first preset temperature range. Niobium oxide undergoes a reduction reaction with hydrogen to generate water vapor, while niobium nitride breaks nitrogen-niobium bonds through a hydrothermal effect, achieving efficient removal of oxygen and nitrogen impurities and obtaining hydrogenated materials. This lays the foundation for the subsequent high-purity purification of niobium ingots. The first preset temperature range and the preset hydrogen pressure range can be adjusted according to the oxygen and nitrogen impurity content in the secondary materials, thereby adapting to the processing requirements of different batches of secondary materials and ensuring the stability, flexibility, and reliability of the recovery process. Specifically, the preset hydrogen pressure range is 0.2 to 0.6 Pa, and the first preset temperature range is 200 to 1600 °C.

[0025] Furthermore, after obtaining the hydrogenated material with oxygen and nitrogen impurities removed, the lumpy hydrogenated material is transformed into a powdered hydrogenated material with uniform particle size distribution through airflow milling and vibrating sieving (controlling the screen aperture ≤1mm), significantly increasing the surface area. The high specific surface area increases the hydrogen desorption rate during subsequent dehydrogenation and expands the contact area between powder particles, creating conditions for interfacial diffusion when mixed with high-purity niobium powder, ensuring minimal deviation in the elemental distribution of the preform. In an optional embodiment of this invention, the particle size of the powdered hydrogenated material is ≤1mm.

[0026] Furthermore, under the second preset temperature and vacuum conditions, the powdered hydrogenated material undergoes a dehydrogenation reaction, with a hydrogen desorption rate exceeding 99.5%, preventing residual hydrogen from forming porosity defects during subsequent melting. More importantly, during the dehydrogenation process, trace amounts of oxygen and nitrogen impurities remaining in the powdered hydrogenated material are further reduced, combining with active niobium atoms on the material surface. These combine to form gaseous H2O and NH3 through lattice diffusion, further removing oxygen and nitrogen impurities and providing a high-purity substrate for subsequent mixing. The dehydrogenated niobium powder, due to the removal of hydrogen atoms, forms nanoscale pores, creating a sponge-like porous structure with improved surface adsorption performance. When mixed with 4N-grade high-purity niobium powder, micron-sized high-purity particles can be embedded in the nanopores, forming a stable interface through mechanical interlocking and atomic diffusion. This enhances the interparticle bonding force during the pressing process and increases the pre-formed density after sintering, providing high-quality raw materials for subsequent electron beam melting. In one optional embodiment of this invention, the second preset temperature range is 400 to 1800°C.

[0027] Furthermore, by mixing the dehydrogenated powdered secondary material with high-purity niobium powder (≥99.99%) of grade 4N or higher in a predetermined ratio, the final composition of the niobium ingot can be flexibly adjusted. By supplementing with high-purity niobium powder, residual impurities (such as iron and silicon) in the dehydrogenated powdered secondary material can be diluted to below the target concentration, reducing the amount of impurities in the finished niobium ingot and improving the purity of the final niobium ingot. In a three-dimensional mixer, the powdered secondary material and high-purity niobium powder of grade 4N or higher can embed micron-sized particles into nanopores, achieving a nested distribution of nano- to micron-sized particles to obtain a preform. When the preform is pressed by a hydraulic press, the powder flowability increases by 50%, improving the uniformity of powder mixing and resulting in more stable preforms, avoiding the sintering cracking problems caused by uneven mixing of traditional block materials. In addition, under the high pressure of the hydraulic press, air between powder particles is effectively expelled, and the particles interlock to form a mechanically interlocking structure. The preforms, after pressing, have high density and compressive strength, possessing excellent self-support, facilitating subsequent sintering and handling. Custom molds allow for the pressing of preforms into preforms of various specifications, adapting to the melting requirements of different electron beam furnaces, offering high flexibility. In the high-temperature reduction furnace, the surface atoms of the particles within the preforms gain sufficient energy, undergoing diffusion and migration, gradually transforming point contacts between particles into surface contacts, forming a continuous metal matrix. After sintering, the density of the preforms is further improved compared to the original preforms, with reduced porosity, effectively improving the material's electrical conductivity and mechanical strength. Furthermore, sintering the preforms in a high-temperature reduction furnace enables directional grain growth and refinement. The fine and uniform grain structure significantly enhances the toughness and fatigue resistance of niobium ingots, avoiding brittle fracture problems caused by coarse grains. In addition, the uniform microstructure formed during sintering helps with uniform heat conduction during subsequent electron beam melting, reducing localized overheating and component segregation, and improving melting efficiency and yield. In one optional embodiment of the present invention, the predetermined ratio between the powdered secondary material and high-purity niobium powder with a purity of 4N or higher is (0.2 to 2.7) kg : (1.3 to 6.8) kg, and the mixing time is 12 to 26 hours. The specifications of the length, width, and height of the preform are (220 to 600) * (30 to 70) * (30 to 70) mm. That is, the length of the preform is between 220 and 600 mm, the width is between 30 and 70 mm, and the height is between 30 and 70 mm.

[0028] Furthermore, the pool-melting electron beam furnace forms a large-area molten pool through electron beam scanning, enabling rapid fusion of pre-formed strips under high vacuum and high temperature. The stirring effect of the electron beam promotes uniform diffusion of the melt composition, eliminating local density differences that may exist during pre-formed strip pressing and sintering, laying the foundation for subsequent deep purification. Under continuous stirring in the molten pool, low-boiling-point impurities rapidly detach from the melt surface. After pool melting, the total amount of metallic impurities is significantly reduced, effectively reducing the impurity load during the dripping melting stage. During pool melting, liquid niobium rapidly fills the mold under the action of gravity and surface tension, forming a dense secondary material niobium plate after cooling. This eliminates residual micropores inside the pre-formed strip, providing the dripping electron beam furnace with a smooth surface and dense structure, avoiding melting interruptions caused by billet defects. The dripping electron beam furnace uses a high-energy-density electron beam for single-point focusing, causing the secondary material niobium plate to melt drop by drop. Under these conditions, high-melting-point impurities (such as nitrides and oxides) are repelled to the surface during the rapid solidification of niobium droplets due to their difference in melting point from niobium, and are removed as the molten material falls off. This significantly reduces the impurity content and improves the purity of niobium ingots. During droplet melting, the droplets rapidly solidify to form a fine equiaxed crystal structure. Compared to the coarse columnar crystals produced by traditional melting, the grain boundary area is increased, significantly improving the strength, toughness, and superconducting properties of niobium ingots. Through progressive purification via two-stage melting, the yield of high-purity niobium ingots is greatly improved. In one optional embodiment of this invention, the melting power of the pool-melting electron beam furnace for melting the pre-bonded strips is 200 to 450 kW; the length, width, and height of the secondary material niobium plate are (700 to 1600) * (150 to 220) * (30 to 50) mm. The length of the secondary niobium plate is between 700 and 1600 mm, the width is between 150 and 220 mm, and the height is between 30 and 50 mm. The melting power of the drip-melting electron beam furnace for secondary melting of the secondary niobium plate is 500 to 1600 KW. The purity of the high-purity niobium ingot is ≥99.99%.

[0029] The technical solution disclosed in this invention provides a method for fully recovering and utilizing niobium from secondary materials generated during electron beam melting of superconducting niobium ingots. This is achieved through a systematic hydrogenation, dehydrogenation, mixing, pressing, sintering, and multi-stage melting process. This reduces niobium ingot waste, ensures resource recycling, effectively improves the comprehensive utilization rate of niobium ingot resources, alleviates the shortage of niobium resources, and avoids environmental pollution. Specifically, under preset hydrogen pressure and a first preset temperature, hydrogenation allows secondary materials, such as niobium oxides, to undergo a reduction reaction with hydrogen to generate water vapor. Niobium nitrides break nitrogen-niobium bonds through a hydrothermal effect, achieving efficient removal of oxygen and nitrogen impurities and laying the foundation for subsequent niobium ingot purification. After crushing, grinding, and dehydrogenation, the hydrogenated material forms porous nano-sized niobium powder. When mixed with 4N-grade high-purity niobium powder (purity ≥99.99%) in a predetermined ratio, interfacial diffusion between micron-nano particles is achieved, resulting in a smaller error in the uniformity of the pre-formed material composition and ensuring the stability of the final purified niobium ingot. The pool-melting electron beam furnace first melts and casts the pre-formed strips into dense niobium plates, removing residual carbon, iron, and other metallic impurities. The droplet-melting electron beam furnace further refines the grains through droplet-by-drop melting. Multi-stage melting improves the efficiency of nitride removal, thereby further increasing the purity of the niobium ingots in the secondary material. Furthermore, embodiments of the present invention can flexibly adjust process parameters such as hydrogen pressure, temperature, and mixing ratio within a preset range according to the composition and impurity content of the secondary material, adapting to the processing needs of different batches of secondary material and ensuring the stability, flexibility, and reliability of the recycling process.

[0030] To further understand the present invention, the method for recovering niobium ingots from secondary materials generated by electron beam melting of superconducting niobium ingots provided by the present invention will be described in detail below with reference to embodiments. The scope of protection of the present invention is not limited by the following embodiments. Example 1

[0031] 1) Volatile substances adhering to the inner surface of the furnace and around the crucible during the melting of superconducting niobium ingots in a horizontal electron beam melting furnace are collected. These secondary materials include niobium oxides and niobium nitrides. The collected volatile substances are placed in a hydrogen atmosphere as secondary materials, with the hydrogen pressure controlled at 0.4 Pa and the temperature at 800 °C, and hydrogenated for 8 hours. The hydrogenated materials are then cooled to room temperature to obtain hydrogenated materials.

[0032] 2) The hydrogenated material obtained in step 1) is crushed, and then ground and sieved to obtain powdered hydrogenated material with a particle size of 0.5 mm.

[0033] 3) Place the powdered hydrogenated material obtained in step 2) in a vacuum furnace and dehydrogenate it at a temperature of 600℃ for 4 hours to obtain the dehydrogenated powdered secondary material.

[0034] 4) Mix the dehydrogenated powdered secondary material obtained in step 3) with high-purity niobium powder with a purity of 4N5 at a ratio of 1kg:3kg, and mix for 18 hours to obtain the preform.

[0035] 5) Press the preform material obtained in step 4) into shape using a hydraulic press to obtain a preform strip with a specification of 400*50*50mm.

[0036] 6) The preform obtained in step 5) is sintered in a high-temperature reduction furnace at 1200°C for 6 hours to obtain the pre-sintered strip.

[0037] 7) Using the pre-bonded strips obtained in step 6) as raw materials, melt them in a pool melting electron beam furnace with a melting power of 300KW to obtain secondary material niobium plates with specifications of 1000*180*40mm.

[0038] 8) The secondary material niobium plate obtained in step 7) is subjected to secondary smelting in a drip-melting electron beam furnace with a smelting power of 800KW to obtain high-purity niobium ingots with a purity of 99.995%.

[0039] The niobium ingots obtained in the embodiments of the present invention were tested and found to have a purity of up to 99.995%, which meets the requirements for superconducting materials. Example 2

[0040] 1) Volatile substances adhering to the inner surface of the furnace and around the crucible during the melting of superconducting niobium ingots in a horizontal electron beam melting furnace are collected. These secondary materials include niobium oxides and niobium nitrides. The collected volatile substances are placed in a hydrogen atmosphere as secondary materials, with the hydrogen pressure controlled at 0.5 Pa and the temperature at 1000 °C, and hydrogenated for 10 hours. The hydrogenated materials are then cooled to room temperature to obtain hydrogenated materials.

[0041] 2) The hydrogenated material obtained in step 1) is crushed, and then ground and sieved to obtain powdered hydrogenated material with a particle size of 0.8 mm.

[0042] 3) Place the powdered hydrogenated material obtained in step 2) in a vacuum furnace and dehydrogenate it at a temperature of 1200℃ for 6 hours to obtain the dehydrogenated powdered secondary material.

[0043] 4) Mix the dehydrogenated powdered secondary material obtained in step 3) with high-purity niobium powder with a purity of 4N8 at a ratio of 1.5kg:5kg, and mix for 20 hours to obtain the pre-formed material.

[0044] 5) Press the preform material obtained in step 4) into shape using a hydraulic press to obtain a preform strip with a specification of 500*60*60mm.

[0045] 6) The preform obtained in step 5) is sintered in a high-temperature reduction furnace at 1400°C for 8 hours to obtain the pre-sintered strip.

[0046] 7) Using the pre-bonded strips obtained in step 6) as raw materials, the strips are smelted in a pool-melting electron beam furnace with a smelting power of 400KW to obtain secondary material niobium plates with specifications of 1200*200*45mm.

[0047] 8) Using the niobium plate obtained in step 7) as raw material, a secondary smelting process is carried out using a drip-melting electron beam furnace with a smelting power of 1000KW to obtain high-purity niobium ingots with a purity of 99.997%.

[0048] The niobium ingots obtained in the embodiments of the present invention were tested and found to have a purity of up to 99.997%, which meets the requirements for superconducting materials. Example 3

[0049] 1) Volatile substances adhering to the inner surface of the furnace and around the crucible during the melting of superconducting niobium ingots in a horizontal electron beam melting furnace are collected. These secondary materials include niobium oxides and niobium nitrides. The collected volatile substances are placed in a hydrogen atmosphere as secondary materials, with the hydrogen pressure controlled at 0.6 Pa and the temperature at 600 °C, and hydrogenated for 6 hours. The hydrogenated materials are then cooled to room temperature to obtain hydrogenated materials.

[0050] 2) The hydrogenated material obtained in step 1) is crushed, and then ground and sieved to obtain powdered hydrogenated material with a particle size of 1 mm.

[0051] 3) Place the powdered hydrogenated material obtained in step 2) in a vacuum furnace and dehydrogenate it at 800°C for 5 hours to obtain the dehydrogenated powdered secondary material.

[0052] 4) Mix the dehydrogenated powdered secondary material obtained in step 3) with high-purity niobium powder with a purity of 4N6 at a ratio of 2kg:4kg, and mix for 24 hours to obtain the preform.

[0053] 5) Press the preform material obtained in step 4) into shape using a hydraulic press to obtain a preform strip with a specification of 300*40*40mm.

[0054] 6) The preform obtained in step 5) is sintered in a high-temperature reduction furnace at 1300°C for 7 hours to obtain the pre-sintered strip.

[0055] 7) Using the pre-bonded strips obtained in step 6) as raw materials, the strips are smelted in a pool-melting electron beam furnace with a smelting power of 350KW to obtain secondary material niobium plates with specifications of 900*170*35mm.

[0056] 8) Using the niobium plate obtained in step 7) as raw material, a secondary smelting process is carried out using a drip-melting electron beam furnace with a smelting power of 700KW to obtain high-purity niobium ingots with a purity of 99.992%.

[0057] The niobium ingots obtained in the embodiments of the present invention were tested and found to have a purity of up to 99.992%, which meets the requirements for superconducting materials.

[0058] Through the various embodiments of the present invention, the physical morphology of secondary materials is reconstructed through a hydrogenation-crushing-dehydrogenation process. Combined with high-purity niobium powder ratio control and two-stage electron beam melting, the recovery rate of niobium in volatiles is increased to an ultra-high purity of 99.99%, achieving efficient recovery and avoiding resource waste. The hydrogenation stage employs precise hydrogen control at low pressure (0.2 to 0.6 Pa), and the dehydrogenation process achieves full hydrogen recovery through high-temperature pyrolysis. Compared to acid leaching, this eliminates the emission of fluorine / chlorine-containing waste liquid, making it more environmentally friendly. The combined pool melting and drip melting electron beam melting achieves a vacuum level of 10⁻³ Pa, avoiding air pollution. Thus, the technical solution provided by the embodiments of the present invention, through a physical reconstruction-ultra-vacuum melting technical route, combines economic efficiency and environmental friendliness.

[0059] It should be noted that the order of the above embodiments of the present invention is merely for descriptive purposes and does not represent the superiority or inferiority of the embodiments. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0060] The various embodiments in this specification are described in a progressive manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

Claims

1. A method for preparing niobium ingots from secondary materials generated during electron beam melting of superconducting niobium ingots, characterized in that, The method for preparing niobium ingots based on secondary materials generated from electron beam melting of superconducting niobium ingots includes: Secondary materials generated during the electron beam melting of superconducting niobium ingots are collected, and hydrogenated within a preset hydrogen pressure range and a first preset temperature range to obtain hydrogenated materials. The hydrogenated material is pulverized and then sieved to obtain powdered hydrogenated material. The powdered hydrogenated material is then dehydrogenated within a second preset temperature range to obtain dehydrogenated powdered secondary material. After the powdered secondary material is mixed evenly with high-purity niobium powder of grade 4N or above in a predetermined ratio and at a predetermined mixing time, a preform is obtained. The preform is then pressed into shape by a hydraulic press to obtain a preform bar. The preform bar is then sintered in a high-temperature reduction furnace to obtain a pre-sintered bar. The pre-formed strips are smelted using a pool-melting electron beam furnace to obtain secondary material niobium plates. The secondary material niobium plates are then smelted again using a drip-melting electron beam furnace to obtain high-purity niobium ingots with a purity ≥ 99.99%.

2. The method for preparing niobium ingots based on secondary materials generated from electron beam melting of superconducting niobium ingots according to claim 1, characterized in that, The preset hydrogen pressure range is 0.2 to 0.6 Pa, and the first preset temperature range is 200 to 1600 °C.

3. The method for preparing niobium ingots based on secondary materials generated from electron beam melting of superconducting niobium ingots according to claim 1, characterized in that, The particle size of the powdered hydrogenated material is ≤1mm.

4. The method for preparing niobium ingots based on secondary materials generated from electron beam melting of superconducting niobium ingots according to claim 1, characterized in that, The second preset temperature range is 400 to 1800°C.

5. The method for preparing niobium ingots based on secondary materials generated from electron beam melting of superconducting niobium ingots according to claim 1, characterized in that, The predetermined ratio between the powdered secondary material and high-purity niobium powder with a purity of 4N or higher is (0.2 to 2.7) kg : (1.3 to 6.8) kg, and the mixing time is 12 to 26 hours.

6. The method for preparing niobium ingots based on secondary materials generated from electron beam melting of superconducting niobium ingots according to claim 1, characterized in that, The length, width and height of the precast strip are (220 to 600) * (30 to 70) * (30 to 70) mm.

7. The method for preparing niobium ingots based on secondary materials generated from electron beam melting of superconducting niobium ingots according to claim 1, characterized in that, The melting power of the pool-melting electron beam furnace for melting the pre-formed bars is 200 to 450 kW.

8. The method for preparing niobium ingots based on secondary materials generated from electron beam melting of superconducting niobium ingots according to claim 1, characterized in that, The melting power of the drip-melting electron beam furnace for the secondary melting of the niobium plate is 500 to 1600 KW.

9. The method for preparing niobium ingots based on secondary materials generated from electron beam melting of superconducting niobium ingots according to claim 1, characterized in that, The length, width, and height of the secondary material niobium plate are (700 to 1600) * (150 to 220) * (30 to 50) mm.

10. The method for preparing niobium ingots based on secondary materials generated from electron beam melting of superconducting niobium ingots according to claim 1, characterized in that, The secondary materials generated during the electron beam melting process of superconducting niobium ingots include: Volatile substances adhering to the inner surface of the furnace and around the crucible during the melting of superconducting niobium ingots in a horizontal electron beam melting furnace are collected to obtain the secondary material, which includes niobium oxide and niobium nitride.