Zirconium alloy ingot, high-quality zr-sn-nb alloy strip for nuclear power, and preparation method for high-quality zr-sn-nb alloy strip and use thereof

Abstract

The present application relates to the technical field of material preparation, and discloses a zirconium alloy ingot, a high-quality Zr-Sn-Nb alloy strip for nuclear power, and a preparation method for the high-quality Zr-Sn-Nb alloy strip and a use thereof. The present application employs a process of direct hot rolling and coiling of a large zirconium alloy slab, and technical parameters for hot continuous rolling of the large slab, i.e., slab thickness, hot rolling temperature, rolling speed, and deformation per pass are mainly controlled, thereby ensuring critical properties such as corrosion resistance of the zirconium alloy. This process increases the deformation amount, weakens a basal texture, enhances a transverse texture, and improves the microstructure and properties of a finished strip.

Description

A zirconium alloy ingot, a high-quality Zr-Sn-Nb alloy strip for nuclear power, its preparation method and application Technical Field

[0001] This application relates to the field of materials preparation technology, and in particular to a zirconium alloy ingot, a high-quality Zr-Sn-Nb alloy strip for nuclear power, its preparation method and application. Background Technology

[0002] Zirconium possesses excellent nuclear properties and is a key material for manufacturing pressurized water reactor (PWR) fuel assemblies, widely used in cladding tubes, pressure tubes, grids, and other nuclear fuel elements. As nuclear reactors continue to evolve towards higher burnup, higher thermal efficiency, and higher safety and reliability, more stringent requirements are being placed on zirconium alloy materials. To meet the needs of third-generation nuclear power development, two new zirconium alloys, SZA-4 (nominal composition Zr-0.8Sn-0.25Nb-0.35Fe-0.1Cr-0.05Ge) and SZA-6 (nominal composition Zr-0.5Sn-0.5Nb-0.3Fe-0.015Si), have been developed. These alloys exhibit superior corrosion resistance and creep resistance, meeting the requirements for use in third-generation PWR fuel assemblies.

[0003] Zirconium alloy strip is an essential material for manufacturing nuclear fuel assembly grids. Its stamping performance, corrosion resistance, creep performance, and fatigue performance play a decisive role in the dimensional stability and service reliability of nuclear fuel assemblies. Due to the close-packed hexagonal α-phase crystal structure of zirconium alloy, the number of slip systems activated during plastic deformation is limited, resulting in poor deformation capacity at low temperatures. Therefore, the existing processing technology for nuclear-grade zirconium alloy strip involves: first, cutting the billet into suitable sizes, homogenizing it, and then hot-rolling small slabs (600mm-1200mm in length) into single sheets. To prevent cracking, the deformation per pass is generally controlled between 15% and 25%. After intermediate annealing and cold working to a certain thickness, multiple sheets are welded into a coil, which is then cold-rolled and heat-treated to produce the finished strip. Because the deformation per pass in single-sheet rolling is small, multiple rolling passes are required to obtain the final dimensions. Furthermore, to maintain the appropriate rolling temperature, multiple heating cycles are necessary between passes, resulting in very low production efficiency for zirconium alloy strip. Furthermore, the microstructure and properties of the weld area differ from those of the base material. Due to the influence of the weld, there are problems with poor dimensional uniformity and strip shape consistency during the cold rolling process of the strip coil, and there is also a risk of strip breakage. The effective length between welds in the prepared strip is 15-30 meters, the continuity of the strip "progressive die" punching is poor, and the strip punching utilization rate is less than 70%. Summary of the Invention

[0004] This application aims to at least partially address one of the technical problems in the related art.

[0005] Therefore, embodiments of this application propose a zirconium alloy ingot, a high-quality Zr-Sn-Nb alloy strip for nuclear power, its preparation method, and its application.

[0006] In a first aspect, this application proposes a zirconium alloy ingot, wherein, by mass content, the zirconium alloy ingot contains 0.5% to 1.0% Sn, 0.2% to 1.1% Nb, 0.08% to 0.14% O, 0.2% to 0.5% Fe, and 0.01% to 0.02% Si.

[0007] Secondly, this application proposes a method for preparing high-quality Zr-Sn-Nb alloy strip for nuclear power, utilizing the zirconium alloy ingot proposed in the first aspect of this application, including the following steps:

[0008] (a) The zirconium alloy ingot is forged into a slab by free forging;

[0009] (b) The slab is directly subjected to β-phase quenching and the surface oxide scale is removed, and then hot-rolled once to a continuous length of more than 40m to obtain a hot-rolled slab.

[0010] (c) The hot-rolled slab is bent into a coil and homogenized until the grain size of the coil is above grade 8.0 and the transverse texture factor is above 0.35;

[0011] (d) The strip obtained in step (c) is mechanically and chemically polished to make its surface roughness less than 1.6 μm, and then bent into a roll at room temperature;

[0012] (e) The strip obtained in (d) is uncoiled and cold-rolled to obtain a seamless strip, which is then degreased and annealed to obtain the finished strip.

[0013] Further, in step (a), the free forging adopts a two-fire forging process, with a forging temperature of 850-1100℃ and a holding time of 60-240min.

[0014] Further, in step (a), the thickness of the slab is 80-150 mm and the length is 2000-6000 mm.

[0015] Furthermore, in step (b), the β-phase quenching temperature is 50–120°C higher than the β-phase transformation temperature of the zirconium alloy.

[0016] Further, in step (b), a hot rolling mill is used for hot rolling at a temperature of 550–700°C and a deformation of 75%–95%, and the slab is hot rolled in 8–15 passes to a thickness of 3–7 mm.

[0017] Furthermore, in step (c), the homogenization treatment is performed by holding at 580–650°C for 2–6 hours, and the homogenization temperature is lower than the hot rolling temperature.

[0018] Further, in step (e), the cold rolling deformation during the cold rolling process is 60% to 95%, the rolling speed is 30 to 120 m / min, and the deformation per pass is 5% to 20%.

[0019] Furthermore, in step (e), the grain size of the finished strip is above grade 10.0, and the transverse texture factor is above 0.30.

[0020] Thirdly, this application discloses high-quality Zr-Sn-Nb alloy strips for nuclear power prepared by the method described in the second aspect above.

[0021] Fourthly, this application proposes the application of high-quality Zr-Sn-Nb alloy strips prepared by the method proposed in the second aspect above, or high-quality Zr-Sn-Nb alloy strips proposed in the third aspect above, in nuclear fuel assemblies.

[0022] Compared to existing technologies, the beneficial effects of this application are as follows:

[0023] The Zr-Sn-Nb alloy strip preparation in this application adopts a direct hot rolling and coiling process for large slabs, which eliminates the single-slab hot rolling, surface treatment, single-slab cold rolling and welding coiling processes in the existing process. The production efficiency can be increased by about 30%, while reducing weld waste and increasing the effective utilization rate of strip by 10%.

[0024] This application adopts a direct hot rolling process for zirconium alloy slabs into coils, which mainly controls the technical parameters of hot continuous rolling of slabs, namely slab thickness, hot rolling temperature, rolling speed and deformation per pass, to ensure key properties such as corrosion resistance of zirconium alloys. This process increases the deformation, weakens the base texture, improves the transverse texture, and improves the microstructure and properties of the finished strip.

[0025] This application eliminates the adverse effects of the weld area on the cold rolling deformation of the strip by adopting seamless rolling, eliminates the risk of strip breakage, and improves the rolling stability of zirconium alloy strip and the accuracy of strip shape and dimensional control.

[0026] The zirconium alloy ingot used in this application has a Sn content of 0.5%–1.0%, a Nb content of 0.2%–1.1%, an O content of 0.08%–0.14%, a Fe content of 0.2%–0.5%, and a Si content of 0.01%–0.02%, which gives the alloy excellent corrosion resistance, effectively inhibits the harmful effects of elements such as N, C, Al, and Ti, while ensuring good comprehensive mechanical properties. The finished product has excellent stamping performance and meets the application requirements of structural materials under in-pile irradiation conditions. Attached Figure Description

[0027] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:

[0028] Figure 1 is a flowchart of the preparation method of the high-quality Zr-Sn-Nb alloy strip for nuclear power in this application;

[0029] Figure 2 is a metallographic diagram of the hot-rolled annealed strip coil of Embodiment 1 of this application;

[0030] Figure 3 is a metallographic diagram of the finished strip material of Embodiment 1 of this application;

[0031] Figure 4 is a pole diagram of the texture of the hot-rolled annealed strip coil in Embodiment 1 of this application;

[0032] Figure 5 is a pole figure of the finished strip texture of Embodiment 1 of this application;

[0033] Figure 6 is a pole figure of the finished strip texture of Comparative Example 1 of this application. Detailed Implementation

[0034] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application.

[0035] As shown in Figure 1, the method for preparing the high-quality Zr-Sn-Nb alloy strip for nuclear power according to this application includes the following steps:

[0036] (a) A zirconium alloy ingot is forged into a slab by free forging, wherein, by mass content, the zirconium alloy ingot contains 0.5% to 1.0% Sn, 0.2% to 1.1% Nb, 0.08% to 0.14% O, 0.2% to 0.5% Fe, and 0.01% to 0.02% Si;

[0037] (b) The slab is directly subjected to β-phase quenching and the surface oxide scale is removed, and then hot-rolled once to a continuous length of more than 40m to obtain a hot-rolled slab.

[0038] (c) The hot-rolled slab is bent into a coil and homogenized until the grain size of the coil is above grade 8.0 and the transverse texture factor is above 0.35;

[0039] (d) The strip obtained in step (c) is mechanically and chemically polished to make its surface roughness less than 1.6 μm, and then bent into a roll at room temperature;

[0040] (e) The strip obtained in (d) is uncoiled and cold-rolled to obtain a seamless strip, which is then degreased and annealed to obtain the finished strip.

[0041] In step (a), a two-fire forging process is used to process the zirconium alloy ingot into a slab through free forging, so as to improve the microstructure of the zirconium alloy and enhance its processing performance.

[0042] The forging temperature is 850–1100℃, and the holding time is 60–240 min. The forging temperature can be any value within the range of 850℃, 900℃, 950℃, 1000℃, 1050℃, 1100℃, or any combination of two values. A suitable forging temperature results in good deformation plasticity and high-quality forgings. Excessive forging temperature leads to severe gas pollution, decreased alloy plasticity, and deterioration of the microstructure, resulting in poor forging quality. Insufficient forging temperature leads to high deformation resistance, making deformation difficult and increasing the likelihood of cracks. After forging, the slab thickness is 80–150 mm and the length is 2000–6000 mm.

[0043] The zirconium alloy ingots required for forging contain 0.5%–1.0% Sn, 0.2%–1.1% Nb, 0.08%–0.14% O, 0.2%–0.5% Fe, and 0.01%–0.02% Si, giving the alloy excellent corrosion resistance, effectively inhibiting the harmful effects of elements such as N, C, Al, and Ti, while ensuring good comprehensive mechanical properties. The finished product has excellent stamping performance, meeting the application requirements of structural materials under in-pile irradiation conditions.

[0044] When the Sn content exceeds the range, whether the Sn content is too low or too high, it will affect the corrosion resistance of the alloy. In addition, a low Sn content will also reduce the strength of the material.

[0045] When the Nb content exceeds the range, a low Nb content will affect the corrosion resistance of the alloy, while Nb has a significant strengthening effect. A high Nb content will increase the deformation resistance, thereby increasing the hot working temperature.

[0046] When the oxygen content exceeds the range, a low oxygen content reduces the mechanical strength, while a high oxygen content worsens the material's processing performance, making it prone to defects such as edge cracks during plastic deformation. It also affects the stamping and forming performance of the finished strip.

[0047] When the Fe content exceeds the range, a low Fe content will reduce mechanical strength, while a high Fe content will significantly reduce plasticity and worsen processing performance.

[0048] When the Si content exceeds the range, a low Si content reduces mechanical strength, while a high Si content has a certain impact on impact toughness.

[0049] In step (b), the forged slab is directly subjected to β-phase quenching without being shortened to homogenize it. The β-phase quenching temperature is 50–120°C higher than the (α+β) / β-phase transformation temperature of the zirconium alloy, ensuring that all second-phase particles completely dissolve and resulting in a quenched microstructure with uniform composition and structure. Specifically, the slab is held at the β-phase quenching temperature in an atmospheric environment for 90–240 minutes, followed by water quenching.

[0050] The process of removing surface oxide scale is as follows: the slab obtained by β-phase quenching is heated to 550-700℃, pressure is applied to flatten the slab shape, and the oxide scale on the surface of the slab is removed by machining to obtain a clean surface and the dimensions required for the next process. Among them, the machining removal of oxide scale on the surface of the slab can be carried out by planing.

[0051] The hot rolling process is as follows: hot rolling is carried out using a hot continuous rolling mill at a temperature of 550–700℃ and a deformation of 75%–95%. The slab is hot rolled in 8–15 passes to a thickness of 3–7 mm and a continuous length of over 40 m to obtain a hot-rolled slab. The hot continuous rolling mill has multiple continuously arranged stands, allowing the slab to be rolled continuously in multiple passes.

[0052] In step (c), the hot-rolled slab is coiled at a temperature of 100–400°C to ensure a good coil shape for easy transfer and subsequent processing. The homogenization process involves holding the coil at 580–650°C for 2–6 hours, with the homogenization temperature lower than the aforementioned hot-rolling temperature, resulting in a uniform microstructure and a dispersed precipitate phase. Homogenization is continued until the coil grain size is above 8.0 and the transverse texture factor is above 0.35. The homogenization process is then followed by atmospheric annealing to allow recrystallization of the material, restoring the plasticity required for subsequent processing.

[0053] In some embodiments, the annealing process is performed using a resistance furnace.

[0054] In step (d), the mechanical polishing and chemical polishing processes are as follows: After the zirconium alloy strip obtained in step (c) is leveled, the surface of the strip is first treated with sandblasting or shot blasting, then mechanically polished to remove surface oxide scale, cracks, and other defects that affect subsequent processing. Next, continuous immersion chemical polishing is performed in a mixture of HNO3, HF, and deionized water to make the corrosion more uniform. After mechanical and chemical polishing, the surface roughness Ra of the strip is made not to exceed 1.6 μm, and it is then coiled at room temperature.

[0055] In step (e), the cold rolling process involves uncoiling and cold rolling the zirconium alloy obtained in step (d). The cold rolling deformation is 60%–95%, the rolling speed is 30–120 m / min, and the deformation per pass is 5%–20%, resulting in a seamless strip with the required dimensions and surface finish for each pass. It is understood that if the strip thickness remains unchanged before and after cold rolling, annealing at 540–650℃ is performed as needed to restore its workability. Degreasing involves soaking and rinsing the strip in an alkaline solution; annealing is performed at 560–650℃. The final strip has a grain size of ≥10.0 and a transverse texture factor of ≥0.30.

[0056] The high-quality Zr-Sn-Nb alloy strip for nuclear power prepared in this application can be used in the preparation of nuclear fuel assemblies.

[0057] The present application will now be described in detail with reference to the embodiments.

[0058] Example 1

[0059] S1: The ingot is forged into a slab using a two-fire forging process to improve the microstructure and processing performance. The forging temperature is 1050℃ and the holding time is 180min. The forged slab has a thickness of 120mm and a length of 4000mm. The zirconium alloy ingot contains, by mass, 0.5% Sn, 0.5% Nb, 0.13% O, 0.3% Fe, and 0.015% Si.

[0060] S2: The slab obtained in S1 is not cut short, and it is directly subjected to β-phase quenching to homogenize it. The homogenization treatment temperature is 1050℃, and it is held at the temperature for 180 minutes in an atmospheric environment, and then water quenched.

[0061] S3: Heat the slab after S2 treatment to 600℃, apply pressure to flatten the shape, and remove the oxide scale from the surface of the slab by machining. The thickness of the slab after treatment is 110mm.

[0062] S4: The slab obtained in S3 is hot rolled using a hot continuous rolling mill at a temperature of 598℃ and a deformation of 95%. It is then hot rolled in 12 passes to a thickness of 5mm and a continuous length of approximately 60m.

[0063] S5: The hot-rolled sheet obtained in S4 is rolled into a coil at 300℃, and the coil has a good tower shape.

[0064] S6: The zirconium alloy strip obtained in S5 is homogenized at a temperature of 600℃ for 3 hours. The resulting strip has a fine and uniform microstructure with a grain size of 11.0 and a transverse texture factor of 0.385.

[0065] S7: After the strip obtained in S6 is leveled, it is first surface treated by shot peening and mechanical polishing to remove oxide scale, cracks and other defects on the surface of the strip that affect subsequent processing. Then, it is continuously immersed in chemical polishing. The surface roughness Ra of the strip after surface treatment should be 1.2μm. It is then rolled into a coil at room temperature.

[0066] S8: The zirconium alloy strip coil treated by S7 is uncoiled and cold rolled with a cold rolling deformation of 80% and a rolling speed of 60m / min. It is then annealed at 580℃ once in the middle to restore plasticity and obtain the weldless strip with the required dimensions and surface of the finished product.

[0067] S9: The strip obtained in S8 is continuously degreased and annealed at 580℃ to obtain the required microstructure and properties of the finished strip. The finished strip has a fine and uniform microstructure, a grain size of 12.0 grade, and a transverse texture factor of 0.311.

[0068] Example 2

[0069] S1: The ingot is forged into a slab using a two-fire forging process to improve the microstructure and processing performance. The forging temperature is 1070℃ and the holding time is 180min. The forged slab is 110mm thick and 6000mm long. The content of Sn is 0.8%, Nb is 0.25%, O is 0.11%, Fe is 0.25%, and Si is 0.02% by mass.

[0070] S2: The slab obtained in S1 is not cut short, and it is directly subjected to β-phase quenching to homogenize it. The homogenization temperature is 1070℃, and it is held at the temperature for 120 minutes in an atmospheric environment, and then water quenched.

[0071] S3: Heat the slab after S2 treatment to 590℃, apply pressure to flatten the shape, and remove the oxide scale from the surface of the slab by machining. The thickness of the slab after treatment is 100mm.

[0072] S4: The slab obtained in S3 is hot rolled using a hot continuous rolling mill at a temperature of 590℃ and a deformation of 96%. It is then hot rolled in 14 passes to a thickness of 4mm and a continuous length of approximately 150m.

[0073] S5: The hot-rolled sheet obtained in S4 is rolled into a coil at 200℃, and the coil has a good tower shape.

[0074] S6: The zirconium alloy strip obtained in S5 is homogenized at a temperature of 590℃ for 4 hours. The resulting strip has a fine and uniform microstructure with a grain size of 10.5 and a transverse texture factor of 0.366.

[0075] S7: After the strip obtained in S6 is leveled, it is first surface treated by shot peening and mechanical polishing to remove oxide scale, cracks and other defects on the surface of the strip that affect subsequent processing. Then, it is continuously immersed in chemical polishing. The surface roughness Ra of the strip after surface treatment should be 1.2μm. It is then rolled into a coil at room temperature.

[0076] S8: The zirconium alloy strip coil treated by S7 is uncoiled and cold rolled with a cold rolling deformation of 85% and a rolling speed of 55m / min. It is then annealed at 590℃ once in the middle to restore plasticity and obtain a weldless strip with the required dimensions and surface for the finished product.

[0077] S9: The strip obtained in S8 is continuously degreased and annealed at 590℃ to obtain the required microstructure and properties of the finished strip. The finished strip has a fine and uniform microstructure, a grain size of 11.5, and a transverse texture factor of 0.315.

[0078] Example 3

[0079] S1: The ingot is forged into a slab using a two-fire forging process to improve the microstructure and processing performance. The forging temperature is 1030℃ and the holding time is 120min. The forged slab has a thickness of 90mm and a length of 3000mm. The zirconium alloy ingot contains, by mass, 0.7% Sn, 1.0% Nb, 0.12% O, 0.5% Fe, and 0.01% Si.

[0080] S2: The slab obtained in S1 is not cut short, and it is directly subjected to β-phase quenching to homogenize it. The homogenization temperature is 1030℃, and it is held at the temperature for 90 minutes in an atmospheric environment, and then water quenched.

[0081] S3: Heat the slab after S2 treatment to 580℃, apply pressure to flatten the shape, and remove the oxide scale from the slab surface by machining. The thickness of the slab after treatment is 80mm.

[0082] S4: The slab obtained in S3 is hot rolled using a hot continuous rolling mill at a temperature of 580℃ and a deformation of 96%. It is then hot rolled in 14 passes to a thickness of 3mm and a continuous length of approximately 80m.

[0083] S5: The hot-rolled sheet obtained in S4 is rolled into a coil at 350°C, and the coil has a good tower shape.

[0084] S6: The zirconium alloy strip obtained in S5 is homogenized at a temperature of 580℃ for 3 hours. The resulting strip has a fine and uniform microstructure with a grain size of 11.0 and a transverse texture factor of 0.356.

[0085] S7: After the strip obtained in S6 is leveled, it is first surface treated by shot peening and mechanical polishing to remove oxide scale, cracks and other defects on the surface of the strip that affect subsequent processing. Then, it is continuously immersed in chemical polishing. The surface roughness Ra of the strip after surface treatment should be 1.2μm. It is then rolled into a coil at room temperature.

[0086] S8: The zirconium alloy strip coil treated by S7 is uncoiled and cold rolled with a cold rolling deformation of 85% and a rolling speed of 80m / min. It is then annealed at 580℃ once in the middle to restore plasticity and obtain the weldless strip with the required dimensions and surface of the finished product after one pass of deformation.

[0087] S9: The strip obtained in S8 is continuously degreased and annealed at 580℃ to obtain the required microstructure and properties of the finished strip. The finished strip has a fine and uniform microstructure, a grain size of 11.5, and a transverse texture factor of 0.314.

[0088] Comparative Example 1

[0089] S1: The ingot is forged into a slab using a two-fire forging process to improve the microstructure and processing performance. The forging temperature is 1050℃ and the holding time is 180min. The forged slab has a thickness of 110mm and a length of 3000mm. The zirconium alloy ingot contains, by mass, 0.7% Sn, 1.0% Nb, 0.11% O, 0.3% Fe, and 0.015% Si.

[0090] S2: The slab obtained in S1 is cut into sections of 1000mm length using a saw, and then subjected to β-phase quenching to homogenize them. The homogenization treatment temperature is 1050℃, and the sections are held at this temperature for 90 minutes under atmospheric conditions before being water quenched.

[0091] S3: The oxide scale on the surface of the slab after S2 treatment is removed by mechanical processing. The thickness of the slab after treatment is 100mm.

[0092] S4: The slab obtained in S3 is hot-rolled in two passes using a four-roll reversible hot rolling mill. The first pass has a heating temperature of 580℃ and a hot rolling deformation of 80%, and is rolled to a thickness of 20mm in 10 passes. After surface treatment such as sandblasting and mechanical polishing, each slab is cut into 1000mm lengths using a shear. The resulting 1000mm length slabs are then heated for the second pass. The second pass has a heating temperature of 580℃ and a hot rolling deformation of 80%, and is rolled to a thickness of 3.5mm in 10 passes.

[0093] S5: The hot-rolled sheet obtained in S4 is homogenized at a temperature of 580℃ for 1.5 hours. Surface treatments such as sandblasting, mechanical polishing, and pickling are used to remove oxide scale, cracks, and other defects that affect subsequent processing. Each sheet is cut into 1000mm lengths using a shearing machine.

[0094] S6: The zirconium alloy sheet obtained from S5 is subjected to intermediate cold rolling using a four-roll reversible cold rolling mill with a cold rolling deformation of 66%. After degreasing, finishing and trimming, the sheets are butt-welded into coils using argon arc welding. The coils are then annealed in a vacuum annealing furnace to restore plasticity. The annealing temperature is 580℃ and the holding time is 2h.

[0095] S7: The zirconium alloy strip coil with weld seam after S6 treatment is uncoiled and cold rolled with a cold rolling deformation of 80% and a rolling speed of 30m / min. It is then annealed at 580℃ once in the middle to restore plasticity and obtain the strip with the required size and surface of the finished product for the deformation of the pass. The weld seam area and the range of 100mm on both sides are unacceptable areas. The effective length of the strip between weld seams shall not exceed 30m.

[0096] S9: The strip obtained in S8 is continuously degreased and annealed at 580℃ to obtain the required microstructure and properties of the finished strip. The finished strip has a fine and uniform microstructure, a grain size of 11.5, and a transverse texture factor of 0.238.

[0097] Comparative Example 2

[0098] The difference from Example 1 is that the zirconium alloy ingot contains 0.25% Sn, 0.5% Nb, 0.11% O, 0.3% Fe, and 0.015% Si.

[0099] Comparative Example 3

[0100] The difference from Example 1 is that the zirconium alloy ingot contains 0.5% Sn, 0.1% Nb, 0.11% O, 0.3% Fe, and 0.015% Si.

[0101] Comparative Example 4

[0102] The difference from Example 1 is that the zirconium alloy ingot contains 0.5% Sn, 0.5% Nb, 0.15% O, 0.3% Fe, and 0.015% Si.

[0103] Comparative Example 5

[0104] The difference from Example 1 is that the zirconium alloy ingot contains 0.5% Sn, 0.5% Nb, 0.11% O, 0.6% Fe, and 0.015% Si.

[0105] Comparative Example 6

[0106] The difference from Example 1 is that the zirconium alloy ingot contains 0.5% Sn, 0.5% Nb, 0.11% O, 0.3% Fe, and 0.03% Si.

[0107] Experimental Example 1

[0108] The strips prepared in Examples 1-3 and Comparative Example 1 were subjected to mechanical property tests at room temperature and 315°C, respectively, according to ASTM E8 / E8M and ASTM E21. The test results are shown in Table 1 below. Wherein, UST is tensile strength, YS is yield strength, and E is elongation after fracture.

[0109] Table 1:

[0110] Table 1 shows that the tensile strength and elongation of Examples 1-3 are basically consistent, and the yield strength ratio is significantly lower than that of the comparative example. This indicates that the examples improved the material's microstructure and reduced the yield strength ratio through optimized hot working process, thus improving the material's stamping performance while ensuring its strength. Comparative Example 2 has relatively low tensile strength due to its low Sn content; Comparative Example 3 has significantly lower tensile strength due to its low Nb content, which weakens the strengthening effect; Comparative Example 4 has significantly higher strength due to its high O content, but its processing performance deteriorates, making it unsuitable for stamping finished strips; Comparative Example 5 has significantly lower elongation and reduced processing plasticity due to its high Fe content, making it prone to edge cracking defects during processing; Comparative Example 6 has relatively higher strength due to its high Si content, but its elongation decreases and its plasticity deteriorates.

[0111] Experimental Example 2

[0112] The corrosion performance of the strips prepared in Examples 1-3 and Comparative Example 1 was tested. The test procedure was as follows: three samples were randomly selected from the strips and placed in high-temperature steam at 400±3℃ and 10.3±0.7MPa for 72-80 hours. The weight gain due to corrosion was measured and the appearance after corrosion was observed. The test results are shown in Table 2.

[0113] Table 2:

[0114] Table 2 shows that the corrosion weight gain and post-corrosion appearance of Examples 1-3 and Comparative Examples 4-6 are basically consistent, indicating that the corrosion performance of the finished strips prepared by both methods is comparable and meets the technical requirements for Zr-Sn-Nb strips used in nuclear power. This is mainly because both processes can strictly control the hot working and heat treatment processes after quenching, and the second phase of the finished products is finely dispersed, fully leveraging the advantages of the good corrosion resistance of the Zr-Sn-Nb alloy. Comparative Example 2, due to its lower Sn content, and Comparative Example 3, due to its lower Nb content, both exhibit inferior corrosion resistance compared to the other examples.

[0115] Experimental Example 3

[0116] The grain size of the strips prepared in Examples 1-3 and Comparative Example 1 was tested according to ASTM E112-13. The test results are shown in Table 3.

[0117] Table 3:

[0118] As shown in Table 3, since the total processing deformation is basically the same between the examples and the comparative examples, the transverse and longitudinal grain sizes of the finished strips are comparable, indicating that the finished strips prepared by both examples are in a fine and uniform recrystallized state, and the grain size can meet the technical requirements of Zr-Sn-Nb strips for nuclear power.

[0119] Test Example 4

[0120] The texture factor of the tapes prepared in Examples 1-3 and Comparative Example 1 was tested using the EBSD (backscattered electron diffraction) method. The test results are shown in Table 4.

[0121] Table 4:

[0122] As shown in Table 4, compared with Comparative Examples 1 to 6, Examples 1 to 3 show a decrease in the normal texture factor and an increase in the transverse texture factor. This indicates that the examples, through optimization of the hot working process, increased the rolling deformation, weakened the base texture, improved the transverse texture, improved the microstructure and properties of the finished strip, and improved the stamping formability of the finished strip.

[0123] Experimental Example 5

[0124] Metallographic examination and texture testing were performed on the hot-rolled annealed strip and finished strip prepared in Example 1, and the test results are shown in Figures 2 to 5. Texture testing was performed on the finished strip prepared in Comparative Example 1, and the test results are shown in Figure 6.

[0125] As shown in Figures 2 and 3, the hot-rolled strip is annealed at a temperature of 580–650℃ for 2–6 hours to homogenize it until the grain size of the strip is above grade 8.0. After the hot-rolled annealed strip undergoes 60%–95% cold rolling deformation, the grain structure is further refined, and after the finished product annealing, a fine and uniform recrystallized structure is finally obtained.

[0126] As shown in Figures 4 and 5, the amount of rolling deformation was increased by optimizing the hot working process. After annealing, the hot-rolled strip coil exhibited a typical bimodal texture, which provided a good microstructure basis for cold deformation. During the cold deformation process, the zirconium alloy was restricted by its close-packed hexagonal crystal structure, resulting in an increase in basal texture and a decrease in transverse texture.

[0127] As shown in Figures 5 and 6, the embodiment optimizes the hot working process, increases the rolling deformation, which helps to weaken the base texture, improve the transverse texture, improve the microstructure and properties of the finished strip, and improve the stamping formability of the strip.

[0128] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms may refer to different embodiments or examples. Furthermore, the specific features, structures, materials, or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0129] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0130] Although embodiments of this application have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the claims and their equivalents.

Claims

1. A zirconium alloy ingot, wherein, by mass content, the zirconium alloy ingot contains 0.5% to 1.0% Sn, 0.2% to 1.1% Nb, 0.08% to 0.14% O, 0.2% to 0.5% Fe, and 0.01% to 0.02% Si.

2. A method for preparing high-quality Zr-Sn-Nb alloy strip for nuclear power, utilizing the zirconium alloy ingot described in claim 1, comprising the following steps: (a) The zirconium alloy ingot is forged into a slab by free forging; (b) The slab is directly subjected to β-phase quenching and the surface oxide scale is removed, and then hot-rolled once to a continuous length of more than 40m to obtain a hot-rolled slab. (c) The hot-rolled slab is bent into a coil and homogenized until the grain size of the coil is above grade 8.0 and the transverse texture factor is above 0.35; (d) The strip obtained in step (c) is mechanically and chemically polished to make its surface roughness less than 1.6 μm, and then bent into a roll at room temperature; (e) The strip obtained in (d) is uncoiled and cold-rolled to obtain a seamless strip, which is then degreased and annealed to obtain the finished strip.

3. The method as described in claim 2, wherein, In step (a), the free forging adopts a two-fire forging process, with a forging temperature of 850-1100℃ and a holding time of 60-240min.

4. The method of claim 2, wherein, In step (a), the thickness of the slab is 80-150 mm and the length is 2000-6000 mm.

5. The method of claim 2, wherein, In step (b), the β-phase quenching temperature is 50–120°C higher than the β-phase transformation temperature of the zirconium alloy.

6. The method of claim 2, wherein, In step (b), hot rolling is carried out using a hot continuous rolling mill at a temperature of 550–700°C and a deformation of 75%–95%. The slab is hot rolled in 8–15 passes to a thickness of 3–7 mm.

7. The method of claim 2, wherein, In step (c), the homogenization treatment is performed by holding the temperature at 580–650°C for 2–6 hours, and the temperature of the homogenization treatment is lower than the hot rolling temperature.

8. The method of claim 2, wherein, In step (e), the cold rolling deformation during the cold rolling process is 60% to 95%, the rolling speed is 30 to 120 m / min, and the deformation per pass is 5% to 20%.

9. The method of claim 2, wherein, In step (e), the finished strip has a grain size of 10.0 or higher and a transverse texture factor of 0.30 or higher.

10. A high-quality Zr-Sn-Nb alloy strip for nuclear power, prepared by the method described in any one of claims 2 to 9.

11. The application of the high-quality Zr-Sn-Nb alloy strip prepared by the method according to any one of claims 2 to 9 or the high-quality Zr-Sn-Nb alloy strip for nuclear power according to claim 10 in nuclear fuel assemblies.

Images