1200MPa-grade low-cost nickel-based alloy for second-generation high-temperature superconducting baseband and preparation method of 1200MPa-grade low-cost nickel-based alloy

Abstract

The invention relates to a 1200MPa-grade low-cost nickel-based alloy for a second-generation high-temperature superconducting baseband and a preparation method of the 1200MPa-grade low-cost nickel-based alloy, and belongs to the technical field of materials. The nickel-based alloy comprises the following chemical components in percentage by weight: 15.0 to 17.0 percent of Cr, 10.0 to 30.0 percent of W, 2.0 to 10.0 percent of Fe, Clt and the balance of Ni. 0.005%, Plt; 0.005%, Slt; 0.002%, Olt; 0.002%, Nlt; 0.002%, and the balance being nickel. The Ni-Cr-W-Fe quaternary alloy component design thought is innovatively put forward, the contents of the W element and the Fe element are optimally designed, the follow-up optimized homogenization treatment, the forging process, the hot rolling process, the solution treatment and the cold machining process are matched, and after the nickel-based alloy is annealed for 5 min at the temperature of 900 DEG C, the nickel-based alloy with the yield strength of 1050 MPa or above and the tensile strength of 300 MPa or above can be obtained. The nickel-based alloy with the tensile strength of 1200 MPa or above and the ductility of 25% or above meets the requirement that the tensile strength of a second-generation high-temperature superconducting high-performance metal-based strip reaches 1200 MPa or above.

Description

Technical Field

[0001] The present invention relates to a 1200 MPa - level low - cost nickel - based alloy for second - generation high - temperature superconducting basebands and a preparation method thereof, belonging to the field of materials technology. Background Art

[0002] Since the discovery of the second - generation superconductor of rare - earth barium copper oxide (REBCO, RE is a rare - earth element), it has attracted extensive international attention. The second - generation high - temperature superconductor has advantages such as a relatively high transition temperature, perfect diamagnetism, high critical current density, and high frozen magnetic field, and has achieved demonstration applications in many fields such as electric power, energy, and magnets. The most critical superconducting layer in REBCO is an oxide material with poor ductility. Since its thickness is generally less than 4 mm, it is also called coated superconductor.

[0003] The realization of the superconducting properties of REBCO requires other multifunctional coatings for protection. Usually, a superconducting layer needs to be epitaxially grown on a flexible metal baseband. The basis of the REBCO superconductor is that the metal baseband, buffer layer, superconducting layer, and protective layer are all built on the metal baseband. Therefore, the comprehensive performance of the metal baseband determines the quality of the REBCO superconducting properties. The ion - beam - assisted biaxial texture deposition technology (IBAD) has no specific requirements for the orientation and properties of the metal baseband and is one of the commonly used methods for commercially preparing REBCO superconducting layers. The optimal preparation process parameters of the IBAD technology are 850 °C - 900 °C. Therefore, it is required that the metal baseband not only has good mechanical properties but also has high tissue stability and excellent oxidation resistance at high temperatures. Currently, the commercially available Hastelloy C276 has excellent comprehensive performance and is the preferred material for superconducting alloy basebands. Although the tensile strength of C276 after cold deformation can be above 1500 MPa, due to the deformation storage energy accumulated by large cold deformation, recrystallization occurs during the preparation process of the superconducting coating, and its tensile strength will be reduced to below 1100 MPa. Moreover, due to its relatively high alloy element content and complex processing technology, its manufacturing cost is relatively high. Therefore, it is urgent to develop an alloy with low cost and mechanical properties equivalent to those of C276.

[0004] In addition, the applicant's three invention patents (application numbers are 202411589006.7, 202411672542.3, and 202411881969.4 respectively) are all targeted improvements based on Hastelloy C276. Although the tensile strength has been improved to a certain extent compared with C276, the alloy component content has increased to a certain extent and the preparation process is more complex, resulting in a significant increase in its manufacturing cost compared with C276. Among them, for the patent with the nitrogen alloy design concept (application number 202411672542.3), the plasticity reaches a maximum of 18.5% after annealing at 900°C for 5 minutes, still showing a certain gap compared with the Ni-Cr-W-Fe quaternary alloy system designed in this invention, which is more than 25%.

[0005] With the development of the second-generation high-temperature and high-field superconductors, higher requirements have been put forward for the operating parameters of key equipment such as high-field superconducting magnets prepared for them. It is required that the metal baseband has higher plasticity indexes while having high strength to meet its needs in aspects such as superconductor winding. In addition, it also needs to maintain the stability of its structure during the high-temperature preparation process of superconductors with a large cold deformation amount, and the tensile strength reaches above 1200 MPa. At present, due to recrystallization, the tensile strength of the commercially available Hastelloy C276 metal baseband is reduced to below 1100 MPa, and its plasticity is low and the cost is high, which cannot meet the development needs of the current second-generation low-cost high-temperature superconducting metal basebands. Therefore, it is urgent to develop a 1200 MPa-grade low-cost nickel-based alloy for the second-generation high-temperature superconductors. Summary of the Invention

[0006] The purpose of this invention is to provide a 1200 MPa-grade low-cost nickel-based alloy for the second-generation high-temperature superconducting baseband and its preparation method. Aiming at the low-cost requirements of the second-generation high-temperature superconducting baseband, the Ni-Cr-W-Fe quaternary composition design concept is innovatively proposed. By optimizing the content of W and Fe elements in the alloy system, using the solid solution strengthening effect and high melting point of W, the strength of the baseband after cold deformation and the stability of the structure are improved, and the recrystallization temperature of the material after cold rolling is increased. Pure purification smelting is adopted to control the O in the alloy to be below 10 ppm to avoid the formation of large-size inclusions. The carbon element content is strictly controlled, and heat treatment processes such as homogenization annealing and solution quenching are adopted to avoid the precipitation of carbides and TCP phases. Finally, through cold deformation, a nickel-based alloy can be obtained with a yield strength reaching above 1400 MPa, a tensile strength reaching above 1500 MPa, and an elongation rate reaching above 3.0%; after annealing at 900°C for 5 minutes, the yield strength reaches above 1050 MPa, the tensile strength reaches above 1200 MPa, the elongation rate reaches above 25.0%, and the strength-plasticity product reaches above 30.0 GPa▪%.

[0007] The technical solution of this invention is: A 1200MPa - grade low - cost nickel - based alloy for second - generation high - temperature superconducting baseband. In terms of weight percentage, its chemical composition is: Cr: 15.0 - 17.0%, W: 15.0 - 35.0%, Fe: 2.0 - 10.0%, C < 0.005%, P < 0.005%, S < 0.002%, O < 0.002%, N < 0.002%, and the balance is nickel.

[0008] For the 1200MPa - grade low - cost nickel - based alloy for second - generation high - temperature superconducting baseband, preferably, W: 20.0 - 30.0%, Fe: 4.5 - 7.5%.

[0009] For the 1200MPa - grade low - cost nickel - based alloy for second - generation high - temperature superconducting baseband, preferably, C < 0.002%, O < 0.001%.

[0010] The preparation method of the 1200MPa - grade low - cost nickel - based alloy for second - generation high - temperature superconducting baseband includes the following steps: (1) Mix each chemical component in proportion, and obtain an ingot through pure - purification smelting and electroslag remelting; (2) Anneal the obtained ingot at a high temperature for homogenization. The temperature of the homogenization annealing treatment is 1220°C - 1250°C, hold for 10h - 20h and then air - cool to room temperature; (3) Forge the ingot after homogenization annealing in the austenite phase region. The forging process is: forging temperature 1220°C - 1240°C, forging ratio above 7.0, and air - cool to room temperature after forging; (4) Hot - roll the forged alloy ingot: the rolling temperature is 1220°C - 1250°C, the reduction per pass of rolling is controlled at 15 - 25%, the total reduction is controlled at 60 - 80%, and water - cool to room temperature after hot - rolling; (5) Perform solution heat treatment after hot - rolling. The solution heat treatment process is: hold at 1200°C - 1230°C for 2 - 4h and then water - quench to room temperature; (6) Perform cold deformation after solution heat treatment. The cold - deformation process is: perform cold deformation at room temperature, and the cold - deformation amount is 55 - 85%.

[0011] For the preparation method of the 1200MPa - grade low - cost nickel - based alloy for second - generation high - temperature superconducting baseband, after cold deformation, the room - temperature performance indexes of the nickel - based alloy are as follows: the yield strength reaches above 1400MPa, the tensile strength reaches above 1500MPa, and the elongation rate reaches above 3.0%.

[0012] For the preparation method of the 1200 MPa grade low-cost nickel-based alloy for the second-generation high-temperature superconducting baseband, preferably, after cold deformation, the room-temperature performance indexes of the nickel-based alloy are as follows: the yield strength is 1400 - 1470 MPa, the tensile strength is 1510 - 1600 MPa, and the elongation is 3.0 - 5.0%.

[0013] For the preparation method of the 1200 MPa grade low-cost nickel-based alloy for the second-generation high-temperature superconducting baseband, after annealing at 900 °C for 5 min, the room-temperature performance indexes of the nickel-based alloy are as follows: the yield strength reaches above 1050 MPa, the tensile strength reaches above 1200 MPa, the elongation reaches above 25.0%, and the product of strength and plasticity reaches above 30.0 GPa·%.

[0014] For the preparation method of the 1200 MPa grade low-cost nickel-based alloy for the second-generation high-temperature superconducting baseband, preferably, after annealing at 900 °C for 5 min, the room-temperature performance indexes of the nickel-based alloy are as follows: the yield strength is 1100 - 1200 MPa, the tensile strength is 1220 - 1300 MPa, the elongation is 25.0 - 28.0%, and the product of strength and plasticity is 32.0 - 35.0 GPa·%.

[0015] The description of the content ranges of the main elements in the present invention is as follows: Cr: Chromium is an important element of the material of the present invention, which determines the corrosion resistance of the material of the present invention. This is because chromium improves the corrosion resistance of the material itself and makes it easy to form a chromium oxide layer on it. However, when the Cr content is less than 15 wt%, the minimum corrosion resistance required for the alloy cannot be obtained. On the other hand, when the Cr content exceeds 17 wt%, chromium-rich intermetallic compounds are likely to precipitate, forming a chromium-depleted zone around the intermetallic compounds, which not only damages the hot working performance and mechanical properties of the material, but also deteriorates the oxidation corrosion resistance of the material. Therefore, in order to ensure that the material of the present invention has excellent corrosion resistance in the corrosive medium, the chromium content in the alloy of the present invention is controlled to be: 15.0 - 17.0 wt%.

[0016] W: The role of tungsten is to play a solution strengthening role in the alloy system. Since the atomic radius of W is larger than that of other elements, the solution strengthening effect is better. Moreover, due to the high melting point of W, appropriately increasing its content will, to a certain extent, increase the recrystallization temperature after cold working of the alloy, which is also one of the most critical design concepts of the present invention. To improve the strength and recrystallization temperature of the materials of the present invention, the higher the W content, the better. However, too high a W content will cause the alloy to form more stable TCP phases such as μ-phase and P-phase, which cannot be completely eliminated even when maintained at a relatively high solution temperature for a long time. To avoid the influence of the precipitation of TCP phases on the mechanical properties of the materials, the content of W needs to be strictly controlled. Moreover, a higher W content also brings certain difficulties to smelting and preparation, and it is necessary to optimize the W content in the quaternary alloy system. Therefore, the optimized content of W in the alloy of the present invention is controlled to be 15.0 - 35.0%, and further optimized to be 20.0 - 30.0%.

[0017] Fe: Adding a certain content of Fe element to the alloy composition system of the materials of the present invention is to balance the requirement of its low cost. In addition, nickel and iron can be infinitely soluble. The addition of Fe replaces the atomic position of Ni, causing lattice distortion and can also play a role in solution strengthening to a certain extent. The addition of too much Fe will form Laves phases with Mo and W in the matrix, thus deteriorating the performance of the materials of the present invention. Therefore, the optimized content of Fe in the alloy of the present invention is controlled to be 2.0 - 10.0%, and further optimized to be 4.5 - 7.5%.

[0018] C: Carbon in the alloy is prone to form carbides with elements such as Cr 23 , 6 C 6 especially during the slow cooling process after solution treatment. Although the precipitation of carbides at the original austenite grain boundary interface can pin dislocations and hinder the movement of the interface, playing a role in precipitation strengthening and effectively improving the strength of the material, the precipitation of these precipitation phases of carbides will affect the superconducting properties of the second-generation superconductors, and it is necessary to strictly control the carbon content in the alloy. Therefore, adopting the design concept of ultra-low carbon composition, the optimized content of C in the alloy of the present invention is controlled as: C < 0.005 wt%, and further optimized to C < 0.002 wt%.

[0019] S, P: In the production of nickel-based alloys, phosphorus and sulfur are usually regarded as harmful impurities because they will significantly reduce the overall performance of the alloy. P will promote the segregation of W and Mo to form Laves phases, thereby increasing the cold brittleness of the alloy, reducing the cohesion of the grain boundaries, thus reducing the ductility and plasticity of the material, and at the same time will also affect the welding performance, resulting in cracks easily occurring in the welded joints. On the other hand, sulfur will increase the tendency of thermal brittleness of the material, especially during the processing, and excessive sulfur will also affect the machining quality of the material, reducing the strength and toughness of the material. Therefore, the content of sulfur and phosphorus in the alloy of the present invention is strictly controlled: S < 0.002 wt%, P < 0.005 wt%.

[0020] O: Oxygen is the main element that produces oxide inclusions in the alloy. In order to reduce the inclusions in the alloy and ensure the purification of the material, it is necessary to minimize the oxygen content. When the oxygen content in the material exceeds a certain limit, especially when the material of the present invention contains a certain amount of Al, it will cause the formation of continuous brittle oxide inclusions in the alloy, resulting in stress concentration during the thin strip processing and leading to the occurrence of strip breakage accidents. Therefore, the oxygen content in the alloy of the present invention is extremely strictly controlled: O < 0.002 wt%, and further optimized to O < 0.001 wt%.

[0021] N: Nitrogen is a strong austenite-forming element, which expands the austenite phase region and shrinks the ferrite phase region, and can inhibit the formation of high-temperature ferrite. Although nitrogen can increase the cold working hardening rate and improve the strength index of the alloy after cold working, due to the addition of a certain amount of B element in the present invention, in order to avoid the formation of BN inclusions, it is necessary to strictly control the N element content in the material of the present invention. Therefore, the nitrogen content in the alloy of the present invention is extremely strictly controlled: N < 0.002 wt%.

[0022] The innovative design concept of the present invention has four points, which are described as follows: 1) Innovative four-element low-cost alloy composition design concept: The main starting point of the present invention is to meet the low-cost requirements of the second-generation high-temperature superconducting baseband, and innovatively propose the Ni-Cr-W-Fe four-element alloy design concept, which meets the low-cost composition design requirements. By adding optimized contents of W and Fe elements, matching the hot working and heat treatment systems, ensuring the complete solid solution of W in the alloy system, and using the high melting point of W to increase the recrystallization temperature after cold deformation of the matrix, the stability of the microstructure of the material of the present invention is guaranteed. The alloy preparation and performance test results prove the correctness of the four-element alloy composition design concept.

[0023] 2) Matching of hot working and heat treatment systems: The Ni-Cr-W-Fe four-element alloy system of the present invention is simple, and the hot working processes such as forging and hot rolling are relatively simplified compared with the invention patents previously applied by the inventor. The back dissolution of μ and P and other TCP phases rich in W in the matrix can be achieved at a lower solution temperature. Without the precipitation of precipitated phases can be achieved under rapid cooling such as water cooling on the premise of ensuring the grain size of the material of the present invention. Therefore, the low cost is further realized in the preparation cost of the material of the present invention.

[0024] 3) Purification smelting technology: The material of the present invention adopts purification smelting technology, strictly controls the contents of elements such as P, S, O, and N that are easy to form inclusions in the alloy, especially controls the oxygen content in the material below 10 ppm, and strictly controls the formation of inclusions in the material of the present invention, laying a good foundation for the preparation of subsequent thin strip superconducting substrates.

[0025] In summary, the present invention innovatively proposes the design concept of the Ni-Cr-W-Fe quaternary alloy composition. By optimizing the contents of the W element and the Fe element, and matching the optimized hot working and heat treatment systems, it is ensured that the W and Fe elements are completely dissolved into the matrix to achieve the effects of solution strengthening and raising the recrystallization temperature, and the strength of the matrix is increased after cold deformation; the C content is controlled to control the precipitation of carbides and ensure complete dissolution into the matrix during homogenization treatment; a purification smelting process is adopted to reduce the oxygen content in the alloy, reduce the inclusion content, and ensure the high purity of the material.

[0026] The advantages and beneficial effects of the present invention are as follows: 1. The quaternary alloy system of the present invention is simple. The Ni matrix ensures the non-magnetic property of the base material, the addition of Fe meets the requirement of low cost, and the Cr content ensures the high-temperature oxidation resistance of the material of the present invention. Finally, with the full play of the solution strengthening of the complete dissolution of W, the simple composition design of the quaternary system and the simplification of the subsequent hot working and heat treatment systems are combined to achieve the low cost of material preparation, laying a solid material foundation for the rapid development of the second-generation high-temperature superconducting industry.

[0027] 2. The present invention adopts a purification smelting technology, which greatly reduces the oxygen content in the material of the present invention. On this basis, the contents of P, S, and N elements in the material are further reduced, ensuring that the inclusion content in the material of the present invention is at an extremely low level, further improving its purity. Superconducting base tapes with a thickness of 20 - 50 μm can be stably prepared, and a nickel-based alloy with high purity and high strength and toughness is obtained.

[0028] 3. The present invention provides a 1200 MPa-level low-cost nickel-based alloy for the second-generation high-temperature superconducting base tape and a key preparation process. By adopting the technical solution provided by the present invention, a nickel-based superalloy with a strength-ductility product reaching more than 30 GPa·% can be stably obtained. The material of the present invention can better support the rapid development of the high-temperature and high-field superconducting industry in China and promote the upgrading of industry products. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Schematic diagram of the scanning microstructure after forging in Example 1.

[0030] Figure 2 Schematic diagram of the scanning microstructure after solution treatment in Example 2.

[0031] Figure 3 Schematic diagram of the scanning microstructure after forging in Comparative Example 1 Figure 4 Schematic diagram of the scanning microstructure after solution treatment in Comparative Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0032] In the specific implementation process, in order to achieve low-cost design, the present invention innovatively proposes a new idea of Ni-Cr-W-Fe quaternary alloy composition design for the requirements of the second-generation high-temperature superconducting baseband. By optimizing the contents of W and Fe elements in the materials of the present invention and matching the subsequent simplified hot working and heat treatment systems, the problem of the stable existence of TCP phases such as W-rich μ phase and P phase caused by the addition of W is solved, and the complete solid solution of W in the materials of the present invention is realized, playing the role of solid solution strengthening and reducing the atomic migration rate of W in the materials of the present invention, and improving the recrystallization temperature of the materials of the present invention after cold deformation. In addition, the addition of a certain content of Fe element realizes the low cost of the composition design of the materials of the present invention. At the same time, by controlling the C content in the materials of the present invention, the precipitation of carbides is controlled; a purification smelting process is adopted to ensure that the oxygen content in the alloy is below 10 ppm, thereby controlling the inclusion content in the alloy at an extremely low level. After cold deformation, the tensile strength of the materials of the present invention reaches above 1500 MPa, and the elongation reaches above 3.0%. After annealing at 900 °C for 5 min, the tensile strength of the materials of the present invention reaches above 1200 MPa, the elongation reaches above 25.0%, and the product of strength and plasticity reaches above 30.0 GPa·%.

[0033] The following examples and drawings will further illustrate the present invention, but do not limit the present invention accordingly. The nickel-based alloys in the examples and the alloys in the comparative examples are processed into standard plate-shaped tensile specimens after smelting and heat treatment for mechanical property testing.

[0034] The preparation process of the low-cost nickel-based alloy for the second-generation high-temperature superconducting baseband of the present invention is: batching → melting → casting and molding → homogenization treatment → forging and hot working → heat treatment → cold working. Examples 1 to 5 are all prepared by the following method, and the specific steps are as follows: (1) Mix each chemical component in proportion, and obtain an ingot through smelting and electroslag remelting; (2) The temperature of the homogenization annealing treatment is 1220 °C to 1250 °C (1220 °C, 1250 °C, 1240 °C, 1230 °C, 1245 °C for Examples 1 to 5 respectively), and after holding for 10 h to 20 h (10 h, 20 h, 15 h, 12 h, 18 h for Examples 1 to 5 respectively), it is air-cooled to room temperature; (3) Forge the ingot after homogenization annealing in the austenite phase region: the forging temperature is 1220 °C to 1240 °C (1220 °C, 1240 °C, 1230 °C, 1225 °C, 1235 °C for Examples 1 to 5 respectively), the forging ratio is greater than 7.0 (7.5, 12.0, 9.0, 10.0, 11.0 for Examples 1 to 5 respectively), and after forging, it is air-cooled to room temperature; (4)The forged alloy ingot is subjected to hot rolling: the rolling temperature is 1200°C to 1230°C (1200°C, 1230°C, 1220°C, 1215°C, 1225°C for Examples 1 to 5 respectively), the reduction per pass of rolling is controlled to be 15% to 25% (15%, 25%, 20%, 22%, 18% for Examples 1 to 5 respectively), the total reduction is controlled to be 60% to 80% (60%, 80%, 70%, 75%, 65% for Examples 1 to 5 respectively), and after hot rolling, it is water-cooled to room temperature; (5)After hot rolling, solution heat treatment is carried out: the solution temperature is 1200°C to 1230°C (1200°C, 1230°C, 1210°C, 1220°C, 1215°C for Examples 1 to 5 respectively), the holding time is 2.0 h to 4.0 h (2.0 h, 4.0 h, 3.0 h, 2.5 h, 3.5 h for Examples 1 to 5 respectively), and after holding, it is water-cooled to room temperature; (6)After solution heat treatment, cold deformation is carried out at room temperature: the cold deformation amount is 55% to 85% (55%, 85%, 70.0%, 65%, 75% for Examples 1 to 5 respectively).

[0035] Next, the present invention will be further elaborated in detail through the accompanying drawings, examples and comparative examples. Example

[0036] In this example, by weight percentage, the chemical composition of the low-cost nickel-based alloy for the second-generation high-temperature superconducting baseband is: Cr: 15.98%, W: 25.02%, Fe: 6.01%, C: 14 ppm, S: 16 ppm, O: 8 ppm, P: 35 ppm, N: 12 ppm, and the balance is nickel. Example

[0037] In this example, by weight percentage, the chemical composition of the low-cost nickel-based alloy for the second-generation high-temperature superconducting baseband is: Cr: 16.96%, W: 29.89%, Fe: 4.52%, C: 16 ppm, S: 17 ppm, O: 7 ppm, P: 40 ppm, N: 15 ppm, and the balance is nickel. Example

[0038] In this example, by weight percentage, the chemical composition of the low-cost nickel-based alloy for the second-generation high-temperature superconducting baseband is: Cr: 15.02%, W: 20.04%, Fe: 7.49%, C: 15 ppm, S: 18 ppm, O: 9 ppm, P: 45 ppm, N: 14 ppm, and the balance is nickel. Example

[0039] In this embodiment, by weight percentage, the chemical composition of the low-cost nickel-based alloy for the second-generation high-temperature superconducting baseband is: Cr: 16.52%, W: 27.49%, Fe: 5.31%, C: 17 ppm, S: 14 ppm, O: 6 ppm, P: 42 ppm, N: 13 ppm, and the balance is nickel. Example

[0040] In this embodiment, by weight percentage, the chemical composition of the low-cost nickel-based alloy for the second-generation high-temperature superconducting baseband is: Cr: 15.47%, W: 22.51%, Fe: 6.74%, C: 19 ppm, S: 15 ppm, O: 5 ppm, P: 30 ppm, N: 16 ppm, and the balance is nickel.

[0041] Comparative Example 1 In this comparative example, by weight percentage, the chemical composition of the nickel-based alloy is: Cr: 15.93%, W: 10.06%, Fe: 1.02%, C: 15 ppm, S: 17 ppm, O: 6 ppm, P: 32 ppm, N: 13 ppm, and the balance is nickel. The chemical composition of the nickel-based alloy in this comparative example is similar to that in Example 1. The main differences are that the contents of W and Fe elements are 10.06% and 1.02% respectively, and other homogenization treatment, forging process, hot rolling process, solution treatment and cold working process are exactly the same as those in Example 1.

[0042] Comparative Example 2 In this comparative example, by weight percentage, the chemical composition of the nickel-based alloy is: Cr: 16.95%, W: 40.03%, Fe: 12.54%, C: 15 ppm, S: 18 ppm, O: 9 ppm, P: 38 ppm, N: 14 ppm, and the balance is nickel. The chemical composition of the nickel-based alloy in this comparative example is similar to that in Example 2. The main differences are that the contents of W and Fe elements are 40.03% and 12.54% respectively, and other homogenization treatment, forging process, hot rolling process, solution treatment and cold working process are exactly the same as those in Example 2.

[0043] Table 1 Mechanical properties of the cold-rolled sheets in the examples and comparative examples Serial number <![CDATA[Yield strength Rp 0.2 , MPa]]> Tensile strength Rm, MPa Elongation A, % Product of strength and plasticity, GPa▪% Example 1 1440 1558 4.5 7.01 Example 2 1468 1598 3.2 5.11 Example 3 1410 1516 5.5 8.34 Example 4 1455 1580 4.0 6.32 Example 5 1426 1540 5.0 7.70 Comparative example 1 1135 1248 9.5 11.86 Comparative example 2 1574 1635 1.5 2.45 As can be seen from Table 1, the present invention adopts an innovative quaternary alloy composition design. By adding W and Fe elements with optimized contents and matching the simplified hot working process and heat treatment system, it is ensured that W is completely dissolved into the matrix. Through a cold rolling reduction of 55% - 85%, a nickel-based alloy with excellent strength-ductility matching can be obtained, with a yield strength above 1410 MPa, a tensile strength above 1516 MPa, and an elongation above 3.2%. In Comparative Example 1, 10.06% and 1.02% of W and Fe elements were added respectively, and neither the W nor the Fe element is within the scope required by the present invention. Compared with Example 1, it is found that the yield strength of the alloy in Comparative Example 1 only reaches 1135 MPa, and the tensile strength reaches 1248 MPa, which is lower than the mechanical property index requirements of the material of the present invention. In Comparative Example 2, the contents of W and Fe elements are relatively high, reaching 40.03% and 12.54% respectively, and neither is within the composition range required by the present invention. Compared with Example 2, it is found that although both the yield strength and the tensile strength are higher than the performance indexes of the material of the present invention, the elongation is only 1.5%, lower than 3.0%, and is not within the plastic index required by the present invention.

[0044] Table 2 Mechanical properties of the cold-rolled sheets of the examples and comparative examples after annealing at 900 °C for 5 min and air cooling Serial number <![CDATA[Yield strength Rp 0.2 , MPa]]> Tensile strength Rm, MPa Elongation A, % Product of strength and plasticity, GPa▪% Example 1 1140 1260 26.4 33.26 Example 2 1196 1288 25.0 32.20 Example 3 1078 1226 27.5 33.72 Example 4 1170 1276 25.3 32.28 Example 5 1105 1250 27.1 33.88 Comparative example 1 895 1086 38.5 41.81 Comparative example 2 1387 1421 2.0 2.84 As can be seen from Table 2, after annealing at 900 °C for 5 min, the yield strength of the material of the present invention is above 1078 MPa, the tensile strength is above 1226 MPa, the elongation is above 25.0%, and the strength-ductility product reaches above 32.20 GPa·%. This is because both the W and Fe elements are completely dissolved into the alloy matrix. Although the material of the present invention does not undergo recrystallization, dynamic recovery occurs, the tensile strength decreases to above 1226 MPa, but the plasticity is significantly improved. In Comparative Example 1, the contents of the added W and Fe elements are relatively low, and the material undergoes complete recrystallization, with its yield strength decreasing to 895 MPa and the tensile strength only being 1086 MPa. Although the strength-ductility product index meets the invention requirements, the yield strength and tensile strength indexes do not meet the requirements of the material of the present invention. In Comparative Example 2, the contents of both the W and Fe elements exceed the range required by the material of the present invention, resulting in a large amount of undissolved TCP phase rich in W in the matrix. Although the yield strength and tensile indexes meet the requirements after annealing, its plasticity is only 2.0%, and the strength-ductility product is only 2.84 GPa·%, not meeting the index requirements of the material of the present invention.

[0045] Such as Figure 1As shown, the scanning microstructure of Example 1 after air cooling following large deformation forging at 1220°C. It can be seen from the figure that after hot working with large deformation in one heat treatment for the material of the present invention, the dendrites of the original as-cast structure are fragmented and homogenized, and during the pre-forging holding stage, the W and Fe elements in the nickel-based alloy matrix are dissolved into the alloy matrix. After forging and cooling, no recrystallization occurs in the material of the present invention.

[0046] As Figure 2 shown, the scanning microstructure of Example 2 after solution treatment at 1230°C for 4 h. It can be seen from the scanning backscattered image that after high-temperature homogenization treatment, one heat treatment of large deformation forging, hot rolling, and solution treatment at 1230°C for 4 h, 29.89 wt% of W and 4.52 wt% of Fe in Example 2 are completely dissolved into the matrix, and there are no precipitation phases rich in W and Fe at the grain boundaries and within the grains.

[0047] As Figure 3 shown, the scanning microstructure of Comparative Example 1 after air cooling following large deformation forging at 1220°C. It can be seen from the figure that since the contents of W and Fe elements in Comparative Example 1 are 10.06 wt% and 1.02 wt% respectively, both lower than the composition range required by the present invention. After one heat treatment of forging, complete recrystallization occurs in the matrix. Although the plasticity and the product of strength and plasticity meet the requirements, its yield strength and tensile strength are significantly lower than the index requirements of the material of the present invention.

[0048] As Figure 4 shown, the SEM microstructure of Comparative Example 2 after solution treatment at 1230°C for 4 h. It can be seen from the scanning backscattered image that since the contents of W and Fe elements in Comparative Example 2 are 40.03 wt% and 12.54 wt% respectively, both higher than the composition range requirements of the present invention. After solution treatment at 1230°C for 4 h, there are still secondary phases rich in W at the grain boundaries and within the grains of the matrix. A large number of large particles of W-rich phases in the alloy matrix result in low plasticity. After holding at 900°C for 5 min, the elongation is only 2.0%.

[0049] The mechanical property test results of the above Examples 1 to 5 show that the original Ni-Cr-W-Fe alloy composition design of the present invention and the simplified hot working preparation and heat treatment system achieve the low-cost preparation of the second-generation high-temperature superconducting baseband. By adopting the technical solution of the embodiment of the present invention, the content of element W is optimized to be between 20% and 30%, and the content of element Fe is optimized to be between 4.5% and 7.5%. Matching the subsequent optimized homogenization treatment, forging process, hot rolling process, solution treatment and cold working process, after cold rolling, the material of the present invention can obtain a yield strength of more than 1410 MPa, a tensile strength of more than 1516 MPa, and an elongation of more than 3.2%; after annealing at 900 °C for 5 minutes, the yield strength of the material of the present invention reaches more than 1078 MPa, the tensile strength reaches more than 1226 MPa, the elongation reaches more than 25.0%, and the product of strength and plasticity reaches more than 32.20 GPa·%, meeting the requirement that the tensile strength of the metal baseband for the second-generation high-temperature superconductors reaches more than 1200 MPa.

[0050] The above embodiments are only used to illustrate the technical concept and characteristics of the present invention, and the purpose is to enable those who are familiar with this technology to understand the content of the present invention and implement it accordingly, and it cannot be used to limit the protection scope of the present invention. All equivalent changes or modifications made according to the spirit and essence of the present invention should be covered within the protection scope of the present invention.

Claims

1. A 1200MPa grade low-cost nickel-based alloy for second-generation high-temperature superconducting base tape, characterized in that: Its chemical composition, in weight percentage, is: Cr: 15.0~17.0%, W: 15.0~35.0%, Fe: 2.0~10.0%, C<0.005%, P<0.005%, S<0.002%, O<0.002%, N<0.002%, and the balance is nickel.

2. The 1200MPa grade low-cost nickel-based alloy for the second generation high-temperature superconducting base tape according to claim 1, characterized in that: Preferably, W: 20.0~30.0%, Fe: 4.5~7.5%.

3. The 1200MPa grade low-cost nickel-based alloy for the second generation high-temperature superconducting base tape according to claim 1, characterized in that: Preferably, C<0.002%, O<0.001%.

4. A method for preparing a 1200MPa grade low-cost nickel-based alloy for a second-generation high-temperature superconducting substrate as claimed in any one of claims 1 to 3, characterized in that: The steps include: (1) Mix the chemical components in proportion, and obtain an ingot through purification smelting and electroslag remelting; (2) subjecting the obtained ingot to homogenization annealing at a high temperature of 1220°C to 1250°C, keeping the temperature for 10h to 20h, and then air cooling to room temperature; (3) Forging the ingot after homogenization annealing in the austenite phase region, the forging process is: forging temperature 1220℃~1240℃, forging ratio above 7.0, and air cooling to room temperature after forging; (4) The forged alloy ingot is hot rolled: the rolling temperature is 1220℃~1250℃, the reduction of each rolling pass is controlled to be 15~25%, the total reduction is controlled to be 60~80%, and the hot rolling is followed by water cooling to room temperature; (5) After hot rolling, solution heat treatment is performed. The solution heat treatment process is: keep at 1200℃~1230℃ for 2~4h and then quench to room temperature; (6) After solution heat treatment, cold deformation is performed. The cold deformation process is: cold deformation at room temperature, and the cold deformation amount is 55~85%.

5. The method for preparing a 1200MPa grade low-cost nickel-based alloy for a second-generation high-temperature superconducting substrate according to claim 4, characterized in that: After cold deformation, the room temperature performance indicators of nickel-based alloys are as follows: yield strength reaches more than 1400MPa, tensile strength reaches more than 1500MPa, and elongation reaches more than 3.0%.

6. The method for preparing a 1200MPa grade low-cost nickel-based alloy for a second-generation high-temperature superconducting substrate according to claim 5, characterized in that: Preferably, after cold deformation, the room temperature performance indicators of the nickel-based alloy are as follows: yield strength is 1400-1470 MPa, tensile strength is 1510-1600 MPa, and elongation is 3.0-5.0%.

7. The method for preparing a 1200MPa grade low-cost nickel-based alloy for a second-generation high-temperature superconducting substrate according to claim 4, characterized in that: After annealing at 900℃ for 5 minutes, the room temperature performance indicators of the nickel-based alloy are as follows: the yield strength reaches above 1050MPa, the tensile strength reaches above 1200MPa, the elongation reaches above 25.0%, and the strength-ductility product reaches above 30.0GPa▪%.

8. The method for preparing a 1200MPa grade low-cost nickel-based alloy for a second-generation high-temperature superconducting substrate according to claim 7, characterized in that: Preferably, after annealing at 900°C for 5 minutes, the room temperature performance indicators of the nickel-based alloy are as follows: yield strength is 1100~1200MPa, tensile strength is 1220~1300MPa, elongation is 25.0~28.0%, and strength-ductility product is 32.0~35.0GPa▪%.

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