Preparation method of a high-strength and high-current-carrying superconducting alloy

Abstract

The present invention discloses a preparation method of a high-strength and high-current-carrying superconducting alloy. The method includes: First, mixing zirconium, hafnium, niobium, titanium and tantalum metal particles and then pressing them into alloy sheets; Second, heating the alloy sheets for vacuum degassing; Third, subjecting the alloy sheets to arc melting to obtain melting blocks; Fourth, turning over the melting blocks and repeating arc melting to obtain superconducting alloys. By designing the composition of each alloy, combining the pressing and arc melting processes and the heating vacuum degassing step, the present invention avoids the oxidation of metal raw materials by residual air, thereby ensuring the high strength and high current-carrying performance of the superconducting alloy, as well as excellent current shunting and current-carrying performance, improving the stability of the magnet coil, reducing the magnet volume, and significantly reducing the material and operation costs. It is applicable to large magnets such as fusion and NMR.

Description

Technical Field

[0001] The present invention belongs to the technical field of superconducting alloy preparation, and particularly relates to a preparation method of a high-strength and high-current-carrying superconducting alloy. Background Art

[0002] Due to the zero-resistance property of superconducting materials, they are widely used in ultra-strong magnetic field fields such as power transmission cables, magnetic confinement fusion devices, large hadron accelerators, and ultra-high-field NMR.

[0003] In superconducting magnets, the wire is subjected to very strong stress, and the magnitude of the stress is directly related to the magnetic field strength of the magnet and the diameter of the magnet. For magnetic confinement fusion, it has an ultra-high magnetic field strength and a large diameter. The highest field strength of the currently under-construction International Thermonuclear Experimental Reactor (ITER) is 14.3 T, and the diameter reaches 8 meters. The magnetic field strength of the China Fusion Engineering Test Reactor (CFETR) designed and completed in China is even as high as 16 T, and the diameter of the magnet reaches more than 10 meters. In the future, the magnetic field strength and magnet diameter of fusion commercial reactors will further increase.

[0004] Under such high magnetic field strength and such high magnet diameter, the superconducting wire for preparing the magnet is subjected to great stress. To prevent damage to the superconducting wire, the superconducting wire is prepared into an armored conductor (CICC conductor) and then made into a magnet. That is, the superconducting wire is stranded into a cable and then inserted into a thick-walled high-strength 316 stainless steel tube. After being compacted, the high-strength stainless steel provides mechanical support for the superconducting wire, and a high-strength CICC conductor is made. Then, the CICC conductor is wound into the final fusion magnet.

[0005] However, the non-superconducting stainless steel tube in the CICC conductor accounts for nearly 40% of the entire conductor area, resulting in a significant decrease in the current-carrying performance of the CICC conductor. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a preparation method of a high-strength and high-current-carrying superconducting alloy in view of the above-mentioned deficiencies of the prior art. By designing the alloy composition, combining the tablet pressing and arc melting processes, and adding a heating vacuum degassing link before melting to avoid oxidation of the metal raw materials by residual air, the superconducting alloy has high strength, high current-carrying performance, and excellent current-carrying and current-sharing performance, greatly improving the stability of the magnet coil, and solving the problem of the large proportion of non-superconducting materials in the armored conductor and the significant decrease in current-carrying performance.

[0007] To solve the above technical problem, the technical solution adopted by the present invention is: a preparation method of a high-strength and high-current-carrying superconducting alloy, characterized in that the method includes the following steps:

[0008] Step 1: Mixing and tableting metal raw materials: Mix high-purity zirconium, hafnium, niobium, titanium and tantalum metal particles and tablet them to obtain alloy sheets;

[0009] Step 2: Vacuum degassing: Place the alloy sheet obtained in step 1 into a vacuum furnace, evacuate the vacuum, heat it up and keep it warm for vacuum degassing, and take it out after cooling down;

[0010] Step 3, melting: placing the alloy sheet taken out after cooling in step 2 into an arc melting furnace for arc melting to obtain a molten block;

[0011] Step 4: Repeated smelting: The smelted block obtained in step 3 is turned over while continuing to maintain the vacuum condition, and then arc smelting is repeated to obtain a superconducting alloy; the strength of the superconducting alloy is greater than 1 GPa, and the critical current density is greater than 1×10 4 A / cm 2 .

[0012] The above-mentioned method for preparing a high-strength, high-current-carrying superconducting alloy is characterized in that the mass ratio of the high-purity zirconium, hafnium, niobium, titanium, and tantalum metal particles in step 1 is 1:0.5 to 1:1:1:1. Generally, high purity refers to a mass purity of 99.9% or higher.

[0013] The above-mentioned method for preparing a high-strength and high-current-carrying superconducting alloy is characterized in that in step 2, the vacuum is pumped to 10 -4 Pa, then heat to 400℃~500℃ and keep warm for 1h~2h, and keep 10 -4 The present invention controls the vacuum degree, heating temperature and holding time of vacuum degassing to fully remove the gas adsorbed on the surface of the metal raw material in the alloy sheet.

[0014] The above-mentioned method for preparing a high-strength and high-current superconducting alloy is characterized in that the vacuum degree of the arc melting in step 3 is 1×10 -3 Pa below, current density 1.4A / mm 2 ~1.6A / mm 2 .

[0015] The above-mentioned method for preparing a high-strength and high-current-carrying superconducting alloy is characterized in that the vacuum degree of the repeated arc melting in step 4 is 1×10 -3 Pa below, current density 0.4A / mm 2 ~1.0A / mm 2 .

[0016] During the initial arc melting of the present invention, a relatively large current is applied to the alloy sheet with low density after pressing to fully melt the alloy sheet for melting, and then during repeated arc melting, for the dense melting block obtained after the initial arc melting, a relatively small current can be used to achieve melting and sufficient melting.

[0017] The above-mentioned method for preparing a high-strength and high-current-carrying superconducting alloy is characterized in that the number of times of repeated arc melting in step four is 6 to 7 times. By controlling the number of times of repeated arc melting, the present invention enables the melting block to achieve a completely uniform melting effect.

[0018] The present invention has the following advantages compared with the prior art:

[0019] 1. The present invention sequentially mixes raw materials, presses tablets, evacuates air under vacuum, conducts arc melting and repeated arc melting to prepare a high-strength and high-current-carrying superconducting alloy. By designing the composition of each alloy and combining the tablet pressing and arc melting processes, the high strength and high-current-carrying performance of the superconducting alloy are ensured.

[0020] 2. The yield strength of the superconducting alloy prepared by the present invention can reach more than twice that of 316L stainless steel used for the superconducting conductor armor of a fusion reactor. That is, using a pipe wall with 1 / 2 wall thickness of 316L stainless steel armor, the support strength of a conventional armor can be achieved. The reduction of this 1 / 2 wall thickness reduces the cross-sectional area of the superconducting conductor by 1 / 4, increases the current-carrying performance of the superconducting conductor by 1.25 times, increases the magnetic field strength of the magnet prepared by it by 1.4 times, and reduces the volume of the magnet by nearly 40%. Therefore, on the premise of unchanged magnet aperture, the magnetic field strength is greatly increased, the volume is greatly reduced, the comprehensive performance of large magnets such as fusion reactors is greatly improved, the operation cost is reduced, and the commercialization process of fusion reactors is accelerated.

[0021] 3. The superconducting alloy prepared by the present invention has excellent current-carrying performance. Its current-carrying performance is about 30 times that of Cu and 1000 times that of the current-carrying performance of 316L of a conventional fusion conductor armor. Therefore, this superconducting alloy has extremely excellent current shunting performance, thus greatly improving the stability of the magnet coil, which is beneficial to the normal and stable operation of large commercial magnets such as fusion and NMR that operate stably for a long time.

[0022] 4. After mixing and pressing the metal raw materials into tablets, the present invention conducts heating and vacuum degassing, which avoids the oxidation of the alloy by the interstitial air in the metal raw materials, reduces the oxygen content, and thus avoids the reduction of the mechanical properties and current-carrying performance of the superconducting alloy caused by excessive oxygen content.

[0023] 5. The preparation process of the present invention is simple, the process is reasonable, and the obtained high-strength and high-current-carrying superconducting alloy plays an important role in improving the performance of large coils such as fusion power generation and large NMR, and reducing costs.

[0024] The technical solution of the present invention is further described in detail below through examples. DETAILED DESCRIPTION

[0025] Example 1

[0026] This embodiment includes the following steps:

[0027] Step 1: Mixing and tableting metal raw materials: Mixing zirconium, hafnium, niobium, titanium and tantalum metal particles with a mass purity of more than 99.9% in a mass ratio of 1:1:1:1:1 and tableting to obtain alloy sheets;

[0028] Step 2: Vacuum degassing: Place the alloy sheet obtained in step 1 into a vacuum furnace and evacuate to 1×10 -4 Pa, then heated to 400℃ and kept warm for 2h for vacuum degassing, then taken out after cooling, and the whole heating, keeping and cooling process was kept at 1×10 -4 Vacuum degree below Pa;

[0029] Step 3, melting: the alloy sheet taken out after cooling in step 2 is placed in an arc melting furnace for arc melting to obtain a molten block; the vacuum degree of the arc melting is 1×10 -3 Pa below, current density 1.4A / mm 2 ;

[0030] Step 4: Repeated melting: Turn the smelted block obtained in step 3 over while continuing to maintain the vacuum condition, and then repeat the arc melting for 7 times to obtain a superconducting alloy; the vacuum degree of the repeated arc melting is 1×10 -3 Pa below, current density 0.4A / mm 2 .

[0031] After testing, the yield strength of the superconducting alloy prepared in this embodiment reaches 1.186GPa, which is more than 10 times the yield strength of 316L stainless steel. The strong magnetic field superconducting conductor armor prepared using this superconducting alloy can reduce the wall thickness by more than 70%, reducing the cross-sectional area of the superconducting conductor by 1 / 3 and improving the current carrying performance of the superconducting conductor by 1.4 times. The magnetic field strength of the magnet prepared by this alloy is increased by 1.6 times, and the volume of the magnet is reduced by nearly 50%. The critical current density of this superconducting alloy reaches 1.67×10 4 A / mm 2 Its current-carrying performance is 27 times that of copper and over 1,000 times that of 316L stainless steel. This means that even thinner armor can be made using this superconducting alloy, while still maintaining comprehensive current-diversion performance over 300 times that of conventional 316L. Therefore, using the superconducting alloy of this embodiment as a sheathing material for superconducting wire not only improves magnetic field performance and reduces material costs, but also provides greater stability.

[0032] Example 2

[0033] This embodiment includes the following steps:

[0034] Step 1, mixing and pressing metal raw materials: zirconium, hafnium, niobium, titanium and tantalum metal particles with a mass purity of more than 99.9% are mixed according to a mass ratio of 1:0.5:1:1:1 and then pressed to obtain alloy sheets;

[0035] Step 2, vacuum degassing: the alloy sheets obtained in Step 1 are put into a vacuum furnace, evacuated to below 1×10 -4 Pa, then heated to 500 °C and kept warm for 1 h for vacuum degassing, taken out after cooling, and the vacuum degree below 1×10 -4 Pa is maintained throughout the heating, insulation and cooling processes;

[0036] Step 3, melting: the alloy sheets taken out after cooling in Step 2 are put into an arc melting furnace for arc melting to obtain melting blocks; the vacuum degree of the arc melting is below 1×10 -3 Pa, and the current density is 1.6 A / mm 2 ;

[0037] Step 4, repeated melting: the melting blocks obtained in Step 3 are turned over under the condition of maintaining vacuum, and then arc melting is repeated 7 times to obtain a superconducting alloy; the vacuum degree of the repeated arc melting is below 1×10 -3 Pa, and the current density is 1.0 A / mm 2 .

[0038] After testing, the yield strength of the superconducting alloy prepared in this embodiment reaches 1.03 GPa, which is more than 10 times the yield strength of 316L stainless steel. The strong magnetic field superconducting conductor armor prepared with this superconducting alloy can reduce the wall thickness by more than 70%, reducing the cross-sectional area of the superconducting conductor by 1 / 3, increasing the current-carrying performance of the superconducting conductor by 1.4 times, increasing the magnetic field strength of the magnet prepared by it by 1.6 times, and reducing the volume of the magnet by nearly 50%; the critical current density of this superconducting alloy reaches 1.5×10 4 A / mm 2 , and its current-carrying performance is 25 times that of copper and more than 900 times that of 316L stainless steel. That is, a thinner armor can be prepared with this superconducting alloy, and the comprehensive current-sharing performance is still more than 290 times that of conventional 316L. Therefore, using the superconducting alloy of this embodiment as the sheath material of superconducting wire not only improves the magnetic field performance, reduces the material cost, but also has better stability.

[0039] Example 3

[0040] This embodiment includes the following steps:

[0041] Step 1. Mixing and tabletting of metal raw materials: Zirconium, hafnium, niobium, titanium and tantalum metal particles with a mass purity of more than 99.9% are mixed according to a mass ratio of 1:0.8:1:1:1 and then tabletted to obtain alloy tablets.

[0042] Step 2. Vacuum degassing: The alloy tablets obtained in Step 1 are placed in a vacuum furnace, and the vacuum is pumped to below 1×10 -4 Pa, then heated to 500 °C and held for 1 h for vacuum degassing. After cooling, they are taken out, and the vacuum degree below 1×10 -4 Pa is maintained throughout the heating, holding and cooling processes.

[0043] Step 3. Melting: The alloy tablets taken out after cooling in Step 2 are placed in an arc melting furnace for arc melting to obtain melting blocks; the vacuum degree of the arc melting is below 1×10 -3 Pa, and the current density is 1.5 A / mm 2 ;

[0044] Step 4. Repeated melting: The melting blocks obtained in Step 3 are turned over while maintaining the vacuum condition, and then arc melting is repeated 7 times to obtain a superconducting alloy; the vacuum degree of the repeated arc melting is below 1×10 -3 Pa, and the current density is 0.6 A / mm 2 .

[0045] After testing, the yield strength of the superconducting alloy prepared in this embodiment reaches 1.13 GPa, which is more than 10 times the yield strength of 316L stainless steel. The superconducting conductor armor prepared with this superconducting alloy can reduce the wall thickness by more than 70%, reduce the cross-sectional area of the superconducting conductor by 1 / 3, increase the current-carrying performance of the superconducting conductor by 1.45 times, increase the magnetic field strength of the magnet prepared with it by 1.65 times, and reduce the volume of the magnet by nearly 50%; the critical current density of this superconducting alloy reaches 1.8×10 4 A / mm 2 , and its current-carrying performance is 32 times that of copper and more than 1100 times that of 316L stainless steel. That is, a thinner armor can be prepared with this superconducting alloy, and the comprehensive current-sharing performance is still more than 330 times that of conventional 316L. Therefore, using the superconducting alloy of this embodiment as the cladding material of superconducting wire not only improves the magnetic field performance, reduces the material cost, but also has better stability.

[0046] The above is only a preferred embodiment of the present invention and does not impose any limitation on the present invention. Any simple modification, change and equivalent change made to the above embodiments according to the technical essence of the invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing a high-strength and high-current-carrying superconducting alloy, characterized in that: The method comprises the following steps: Step 1: Mixing and tableting metal raw materials: High-purity zirconium, hafnium, niobium, titanium, and tantalum metal particles are mixed and tableted to obtain alloy sheets; the mass ratio of the high-purity zirconium, hafnium, niobium, titanium, and tantalum metal particles is 1:0.5 to 1:1:1:1; Step 2: Vacuum degassing: Place the alloy sheet obtained in step 1 into a vacuum furnace and evacuate to 10 -4 Pa, then heat it up and keep it warm for vacuum degassing, then take it out after cooling down, and keep it warm for 10 -4 Vacuum degree below Pa; Step 3: Melting: The alloy sheet taken out after cooling in step 2 is placed in an arc melting furnace for arc melting to obtain a molten block; the vacuum degree of the arc melting is 1×10 -3 Below Pa; Step 4: Repeat the smelting: Turn the smelted block obtained in step 3 over while continuing to maintain the vacuum condition, and then repeat the arc smelting to obtain a superconducting alloy; the superconducting alloy has a strength greater than 1 GPa and a critical current density greater than 1×10 4 A / cm 2 .

2. The method for preparing a high-strength and high-current-carrying superconducting alloy according to claim 1, characterized in that: In step 2, the temperature is raised to 400°C~500°C and then kept at this temperature for 1h~2h.

3. The method for preparing a high-strength and high-current-carrying superconducting alloy according to claim 1, characterized in that: The current density of the arc melting in step 3 is 1.4A / mm 2 ~1.6A / mm 2 .

4. The method for preparing a high-strength and high-current-carrying superconducting alloy according to claim 1, characterized in that: The vacuum degree of repeated arc melting in step 4 is 1×10 -3 Pa below, current density 0.4A / mm 2 ~1.0A / mm 2 .

5. The method for preparing a high-strength and high-current-carrying superconducting alloy according to claim 1, characterized in that: The arc melting in step 4 is repeated 6 to 7 times.