High-temperature nitric acid corrosion resistant zirconium alloy and preparation method and application thereof

Abstract

The invention belongs to the technical field of zirconium-based alloy material preparation, and particularly discloses a high-temperature nitric acid corrosion resistant zirconium alloy and a preparation method and application thereof.The zirconium alloy is composed of, by mass, 0.2%-3.0% of Nb, 1.0%-3.0% of Hf, 0.2%-3.0% of Ti, impurity control elements and the balance Zr, the preparation method sequentially comprises the following steps: proportioning and smelting (vacuum consumable arc smelting is more than or equal to 3 times), forging (the cogging temperature is 1050 + / -20 DEG C, and the finish forging temperature is more than or equal to 800 DEG C), two-heating-number hot rolling (650 + / -20 DEG C, and the single-pass deformation is 10%-15%), surface treatment and vacuum annealing, and structure homogenization and stress relief are realized through process parameter control. The problems of stress corrosion cracking, high cost, difficulty in component control and the like of the existing zirconium alloy in a high-temperature nitric acid environment are solved, and the zirconium alloy provided by the invention has excellent high-temperature corrosion resistance and is particularly suitable for spent fuel post-treatment key equipment so as to improve the closed cycle safety of nuclear fuel.

Description

Technical Field

[0001] The present invention belongs to the technical field of zirconium-based alloy material preparation, and in particular relates to a zirconium alloy resistant to high-temperature nitric acid corrosion, a preparation method and an application thereof. Background Art

[0002] As a clean, efficient, and low-emission green energy source, nuclear power plays a key role in the global energy transition, and its share in national energy structures continues to rise. In recent years, with the recovery of nuclear power industries around the world, both demand for nuclear fuel and the generation of spent fuel have surged. Therefore, to ensure the sustainable development of nuclear power, the nuclear power industry is pursuing a closed, recyclable nuclear fuel cycle.

[0003] The generation of spent fuel (used, irradiated nuclear fuel) is essential during nuclear power plant operations, and its effective management and safe handling are becoming increasingly crucial. Reprocessing technology is a key component in ensuring the recovery of reusable U and Pu elements and reducing the amount of radioactive waste in spent fuel. Key spent fuel reprocessing equipment is exposed to high-temperature, highly oxidizing and radioactive nitric acid environments for extended periods, placing stringent demands on the materials used for their corrosion resistance and radiation resistance. Zirconium alloys, due to their excellent corrosion resistance, mechanical strength, and ability to rapidly form a protective oxide film in corrosive environments, are ideal materials for key spent fuel reprocessing equipment.

[0004] France currently leads the world in spent fuel reprocessing. While its widely used Zr-702 zirconium alloy exhibits excellent uniform corrosion resistance, it carries the risk of stress corrosion cracking in boiling nitric acid environments. Furthermore, highly oxidizing radionuclides such as uranium and plutonium in the spent fuel solution can further accelerate corrosion. To address this issue, Japanese researchers have attempted to improve the performance of Zr-702 alloy by adding elements such as Ta, W, Fe, and Cr. While Ta and W can mitigate stress corrosion, their melting points exceed 3000°C, exceeding 1000°C above the melting point of Zr, making uniform distribution difficult during alloying and limiting large-scale application. Fe and Cr are prone to segregation, and the high volatility of Cr complicates composition control. Furthermore, excessively large second-phase particles can induce pitting corrosion, exacerbating material failure. Therefore, developing a low-cost, high-performance zirconium alloy suitable for extreme nitric acid environments has become a pressing technical challenge in nuclear power reprocessing.

[0005] In view of this, this invention is proposed. Summary of the Invention

[0006] The present application aims to overcome the above-mentioned shortcomings of the prior art, and provides a high-temperature nitric acid corrosion-resistant zirconium alloy as well as a preparation method and application thereof, which are mainly used to solve the problems of stress corrosion cracking, uneven element distribution, high cost, and difficult composition control of the existing zirconium alloy in a high-temperature nitric acid environment, and achieve a balance between high corrosion resistance, good processing performance, and economy of the zirconium alloy for a spent fuel reprocessing key equipment under extreme conditions.

[0007] The present application aims to overcome the above-mentioned shortcomings of the prior art, and provides a high-temperature nitric acid corrosion-resistant zirconium alloy as well as a preparation method and application thereof, which are mainly used to solve the problems of stress corrosion cracking, uneven element distribution, high cost, and difficult composition control of the existing zirconium alloy in a high-temperature nitric acid environment, and achieve a balance between high corrosion resistance, good processing performance, and economy of the zirconium alloy for a spent fuel reprocessing key equipment under extreme conditions. In a first aspect, the present application provides a high-temperature nitric acid corrosion-resistant zirconium alloy, which is composed of the following components in terms of mass percentage: Nb: 0.2% to 3.0%, Hf: 1.0% to 3.0%, Ti: 0.2% to 3.0%, Fe: ≤0.15%, Cr: ≤0.1%, O: ≤0.1%, C: ≤0.01%, H: ≤0.01%, N: ≤0.01%, and the balance being Zr and unavoidable impurity elements.

[0008] Preferably, the zirconium alloy is composed of the following components in terms of mass percentage: Nb: 0.5% to 1.5%, Hf: 2.0% to 2.5%, Ti: 0.5% to 1.0%, Fe: ≤0.05%, Cr: ≤0.01%, O: ≤0.05%, C: ≤0.001%, H: ≤0.001%, N: ≤0.001%, and the balance being Zr and unavoidable impurity elements.

[0009] Among them, the Hf element is introduced from the industrial-grade sponge zirconium raw material without zirconium hafnium separation, the Nb element and the Ti element are alloying elements, the Fe and Cr are alloy control elements (control the number and size of the second phase particles), and the O, N, H, and C elements are impurity control elements. The uniform corrosion rate of the zirconium alloy in a nitric acid solution with a temperature of 90℃ and a concentration of 6mol / L is less than 0.008mm / a (measured by a 240-hour corrosion experiment according to the ASTM G31 standard).

[0010] It should be noted that the present application realizes a performance breakthrough of the zirconium alloy by precisely controlling the composition and content of each alloying element, especially by selecting Nb, Hf, and Ti elements as alloying elements to improve the high-temperature nitric acid corrosion resistance of the material, and the specific action mechanism is as follows: First, efficient use of the Hf element: the present application uses industrial-grade sponge zirconium as a base material, which contains about 2% (mass percentage) of Hf elements, avoids additional adding procedures, and reduces production costs. In addition, Hf can significantly improve the self-corrosion potential of the zirconium alloy in a high-temperature nitric acid environment, effectively inhibits stress corrosion cracking, and at the same time, its high thermal neutron absorption cross section endows the material with excellent radiation resistance, providing reliable and safe protection for spent fuel reprocessing equipment.

[0011] Second, the synergistic strengthening effect of Nb: As a key alloying element, Nb is easily passivated, reacting with oxygen to form a stable oxide that effectively blocks the intrusion of corrosive media. The addition of Nb not only enhances the alloy's strength and creep resistance but also significantly improves its stress corrosion resistance. Furthermore, compared to Ta, Nb is abundant in the Earth's crust and has a lower melting point, significantly reducing the difficulty of alloy smelting and manufacturing costs. The third is the composite protection provided by the Ti element: Ti exerts a fine-grain strengthening effect, optimizing the alloy microstructure. Simultaneously, Ti generates TiO2 in the passivation film, forming a composite oxide film with zirconium, significantly enhancing the stability of the passivation film and thus effectively improving the material's resistance to stress corrosion cracking.

[0012] Fourth, the control of impurities and trace elements: The present invention strictly limits the content of Fe and Cr, reduces the generation of second-phase particles, and avoids the degradation of the corrosion resistance of the alloy due to corrosion and shedding of the second phase; at the same time, it strictly controls impurity elements such as O, N, H, and C to minimize their negative impact on the mechanical properties and corrosion resistance of the alloy, ensuring the comprehensive performance of the material is stable and reliable.

[0013] In a second aspect, the present invention further provides a method for preparing the above-mentioned zirconium alloy resistant to high temperature nitric acid corrosion, which specifically comprises the following steps: Step 1: Ingredients and smelting The ingredients are blended according to the target weight percentage of the zirconium alloy. The raw materials for the Zr and Hf elements—Hf-containing industrial-grade zirconium sponge—are combined with Zr-Nb master alloy chips, the raw material for the Nb element, and industrial-grade titanium sponge, the raw material for the Ti element. Specifically, the Zr-Nb master alloy chips and industrial-grade titanium sponge are evenly layered between two layers of zirconium sponge and pressed into a consumable electrode block. This is then melted using a vacuum consumable arc melting method for at least three passes to produce a zirconium alloy ingot with the target composition. Step 2: Forging, heat treatment and surface treatment The zirconium alloy ingot obtained in step 1 is forged, and the blank forging temperature is set to 1050±20°C, and the final forging temperature is controlled to be not lower than 800°C. If it is lower than 800°C, it is allowed to be returned to the furnace for heating, and the heating temperature is consistent with the forging temperature, and the single reduction is maintained at 30% to 50%; after forging, the blank is placed in a heat treatment furnace at 1050±20°C and kept warm for 30min to 40min, and then water-cooled quenching treatment is performed to obtain a zirconium alloy forging; then the zirconium alloy forging is milled to remove surface oxide scale and defects (cracks, folds, forging scratches generated during the forging process, and oxide inclusions generated during the heat treatment process, etc.) to obtain a zirconium alloy forging with a metallic color. Step 3: Hot rolling The zirconium alloy forging obtained in step 2 is hot rolled in two passes. First, the forging is heated at 650±20℃ for 30min~40min, then hot rolled to 1 / 2 of the target deformation. Then, it is returned to the furnace and heated to 650±20℃ and kept at this temperature for 20min~30min, and then rolled to the target thickness to obtain the zirconium alloy rolled piece. The deformation of each pass is controlled at 10%~15%.

[0014] Step 4: Surface treatment and vacuum annealing The zirconium alloy rolled piece obtained in step 3 is subjected to surface treatment. During the surface treatment, the oxide scale on the surface of the zirconium alloy rolled piece is preliminarily removed by sandblasting, and then the zirconium alloy rolled piece is polished by a grinder and polisher to remove surface impurities and micro-defects, thereby obtaining a zirconium alloy rolled piece with a metallic luster; the zirconium alloy rolled piece with a metallic luster is then placed in a vacuum annealing furnace, heated to 500° C. to 550° C., and kept warm for 2 h to 3 h under a vacuum degree not higher than 0.05 Pa, thereby finally obtaining a zirconium alloy resistant to high-temperature nitric acid corrosion.

[0015] The zirconium alloy forgings obtained in step 2 and the zirconium alloy rolled products obtained in step 3 are plates or bars.

[0016] It should be noted that the optimization of ingredients and smelting in step 1 of the present invention is based on the following considerations: Since the melting point of Nb (2468°C) is higher than that of Zr (1852°C), the use of Zr-Nb master alloy chips as an additive raw material can reduce the melting temperature difference and prevent element segregation. Furthermore, since the melting point of Ti (1668°C) is slightly lower than that of Zr, small particles of industrial-grade sponge titanium are used to facilitate rapid melting. The two (Zr-Nb master alloy chips and industrial-grade sponge titanium) are laid flat between layers of zirconium sponge and pressed into a consumable electrode block to ensure uniform element distribution. Furthermore, the vacuum consumable arc melting method employed in the present invention effectively isolates the ingot from air, preventing the introduction of gaseous impurities. The melting process, which involves at least three refining steps, removes gaseous impurities from the ingot through repeated purification and promotes the full and uniform diffusion of alloying elements throughout the ingot, ensuring consistent composition.

[0017] The second step of the present invention adopts a high-temperature forging process, selects the blank forging temperature to be 1050±20℃, and controls the final forging temperature to be not less than 800℃, which can effectively reduce the forging deformation resistance caused by the coarse and uneven cast structure in the ingot, and inhibits the cracking of the blank during the forging process. At the same time, the single forging reduction is controlled to be 30% to 50%. Since the deformation resistance of forging is too high, it is not conducive to the penetration of forging deformation into the interior of the blank, which makes the cast structure inside the blank unevenly broken. Excessive deformation force can easily lead to the occurrence of cracks, deteriorate the plasticity of the material, and be detrimental to subsequent processing. Therefore, by controlling the single deformation amount, the internal structure of the blank can be fully broken, the structure can be refined and uniform, and the diffusion of defects such as cracks and pores into the interior of the blank can be reduced, thereby ensuring the plasticity of the material. In addition, after forging to the target size, the blank is subjected to appropriate quenching heat treatment to inhibit the slow phase transformation of β-Zr to α-Zr, thereby forming fine-grained martensite (fine needle-shaped α ， Martensite) structure, improves the strength of the material, increases the mechanical properties of the material, and can make the internal stress evenly distributed to avoid cracks and other defects.

[0018] Step three of the present invention uses a two-pass hot rolling process to fully fragment the material's grain structure, reducing the size and amount of second-phase particles, thereby improving the material's overall mechanical and corrosion resistance. Simultaneously, by controlling the reheating temperature and time, as well as the deformation per pass, residual stresses can be reduced, cracks and other defects can be avoided, and material processing performance can be guaranteed.

[0019] In step 4 of the present invention, by controlling the annealing temperature, time and vacuum conditions, processing residual stress is effectively eliminated and the mechanical properties of the material are improved. At the same time, the high vacuum environment prevents oxidation of the material, controls the increase in the content of impurity elements such as O, N, H, and C, and reduces the damage to the corrosion and mechanical properties.

[0020] In the present invention, step 2 and step 4 respectively perform different surface treatments on the zirconium alloy material, thereby effectively removing oxide scale and micro defects on the surface of the zirconium alloy material, preventing the oxide scale and micro defects from extending into the interior of the zirconium alloy rolled piece during subsequent processing, reducing material failure behaviors caused by such treatments, and ensuring that the material has good mechanical properties and corrosion properties.

[0021] Thirdly, the high-temperature nitric acid corrosion-resistant zirconium alloy described in the present invention, or the high-temperature nitric acid corrosion-resistant zirconium alloy produced by the aforementioned preparation method, is suitable for use in spent fuel reprocessing equipment, including fuel dissolution tanks and separation and purification components. Its low corrosion rate (<0.008 mm / a) and radiation stability in highly oxidizing (6 mol / L HNO3), high-temperature (≤100°C) and high-radiation environments significantly improve the safety and service life of reprocessing systems, promoting the engineering application of closed nuclear fuel cycle technology.

[0022] Compared with the prior art, the present invention has the following beneficial effects: The present invention precisely controls the composition and content of alloying elements, uses an industrial-grade sponge zirconium substrate to retain its inherent Hf element to reduce costs, utilizes the easy passivation properties of the Nb element (Nb is added in the form of Zr-Nb alloy chips, effectively avoiding the problem of uneven element distribution caused by differences in melting points of alloying elements), improves stress corrosion resistance and reduces smelting difficulty, and utilizes Ti (Ti additions exceeding 3% can severely strengthen the alloy, resulting in poor processing performance. Therefore, Ti in the present invention is preferably selected between 0.5% and 1.0%, with Nb as the main alloying element. The performance focuses on low cost, good processing performance, and good corrosion resistance, targeting the field of nuclear spent fuel reprocessing) to achieve grain refinement and a composite oxide film to enhance the stability of the passivation film. Meanwhile, impurity elements such as Fe, Cr, O, N, H, and C are strictly controlled. These solutions address the problems of stress corrosion cracking, uneven element distribution, high cost, and difficult composition control in existing zirconium alloys in high-temperature nitric acid environments. At the same time, the preparation process sequentially passes through steps such as multiple vacuum consumable arc melting, high-temperature forging, two-pass hot rolling, surface treatment and vacuum annealing. In addition, the heating temperature, time and deformation amount and other related parameters of the material are strictly controlled during the preparation process to eliminate the residual stress during processing and ensure that the grain structure of the material is fine and evenly distributed, effectively controlling the amount and size of the second phase precipitation, so that the finally prepared alloy material has a uniform corrosion rate of less than 0.008mm / a in 90℃, 6mol / L nitric acid solution. It has high corrosion resistance, good processing performance and economy, and is suitable for key equipment of spent fuel reprocessing, significantly improving system safety and service life, and promoting the engineering application of nuclear fuel closed cycle technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings are incorporated in and constitute a part of this specification and, together with the description, serve to explain the principles of the invention.

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0025] Figure 1 This is a flow chart of the method for preparing a high-temperature nitric acid corrosion-resistant zirconium alloy according to the present invention; Figure 2 This is a physical picture of the uniform corrosion device for the zirconium alloy prepared in Examples 1 to 5 of the present invention in a nitric acid environment with a temperature of 90° C. and a concentration of 6 mol / L; Figure 3The corrosion rate-time curve of the zirconium alloy prepared in Examples 1 to 5 of the present invention in a nitric acid environment with a temperature of 90° C. and a concentration of 6 mol / L is shown; Figure 4 This is a macroscopic photograph of the surface of the zirconium alloy prepared in Example 1 of the present invention after being uniformly corroded in a nitric acid environment at a temperature of 90° C. and a concentration of 6 mol / L for 240 hours; Figure 5 This is a SEM photograph of the corrosion morphology of the zirconium alloy prepared in Example 1 of the present invention after uniform corrosion in a nitric acid environment with a temperature of 90° C. and a concentration of 6 mol / L for 240 hours. DETAILED DESCRIPTION

[0026] Exemplary embodiments will be described in detail herein, with examples illustrated in the accompanying drawings. In the following description, when referring to the drawings, identical numerals in different figures represent identical or similar elements, unless otherwise indicated. The embodiments described in the following exemplary embodiments are not intended to represent all possible embodiments consistent with the present invention. Instead, they are merely examples consistent with certain aspects of the present invention as detailed in the appended claims.

[0027] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the present invention is described in further detail below with reference to the accompanying drawings and embodiments.

[0028] Example 1 This embodiment aims to prepare a zirconium alloy plate resistant to high-temperature nitric acid corrosion. The zirconium alloy plate is composed of the following components, calculated by mass percentage: Nb: 0.5%, Hf: 2.2%, Ti: 0.5%, Fe ≤ 0.05%, Cr ≤ 0.01%, with the balance being Zr and unavoidable impurity elements. The impurity contents are controlled to be O ≤ 0.05%, C ≤ 0.001%, H ≤ 0.001%, and N ≤ 0.001%.

[0029] like Figure 1 As shown, the preparation process of the high-temperature nitric acid corrosion-resistant zirconium alloy plate of this embodiment is as follows: 1) Batching and Melting: According to the designed composition of the high-temperature nitric acid corrosion-resistant zirconium alloy plate, the corresponding weight of Zr-Nb master alloy chips and industrial-grade titanium sponge are weighed and evenly spread between two layers of zirconium sponge (industrial-grade zirconium sponge containing Hf without zirconium and hafnium separation) and pressed into a consumable electrode. This is then subjected to three vacuum consumable melting cycles to obtain a zirconium alloy ingot with the target composition. 2) Forging, heat treatment, and surface treatment: The zirconium alloy ingot obtained in step 1) is heated to 1030° C. and forged at a single forging reduction of 40% and a final forging temperature of 800° C. After forging to a target thickness, the ingot is recharged into a furnace, heated to 1030° C. and held at that temperature for 30 minutes, then removed from the furnace and subjected to water-cooled quenching treatment; the surface of the quenched ingot is milled to remove oxide scale and defects on the surface of the ingot, giving it a metallic color, thereby obtaining a zirconium alloy forging; 3) Two-pass hot rolling: The zirconium alloy forging obtained in step 2) is first heated to 630°C and held for 30 minutes, and then hot rolled in one pass, with the deformation of each pass controlled at 10%, and hot rolled to 1 / 2 of the target deformation; the hot-rolled plate is then returned to the furnace, heated to 630°C and held for 20 minutes, and then hot rolled in a second pass, with the deformation of each pass controlled at 10%, and rolled to the target thickness, to obtain the zirconium alloy rolled plate; 4) Surface treatment and vacuum annealing: The zirconium alloy rolled piece obtained in step 3) is sandblasted to remove surface oxide scale, and then polished with a grinder to obtain a zirconium alloy rolled piece with a metallic luster. The zirconium alloy rolled piece is then placed in a vacuum annealing furnace, heated to 500°C, and maintained at a vacuum of no more than 0.05 Pa for 3 hours to eliminate processing stress and prevent oxidation, thereby obtaining a high-temperature nitric acid corrosion-resistant zirconium alloy plate.

[0030] Performance testing a) Composition Testing: The measured composition (by mass percentage) of the high-temperature nitric acid corrosion-resistant zirconium alloy plate prepared in this example is: Nb: 0.502%, Hf: 2.165%, Ti: 0.497%, Fe: 0.0482%, Cr: 0.0045%, O: 0.0352%, C: 0.0010%, H: 0.0006%, and N: 0.0002%. All of these compositions meet design requirements and exhibit good compositional uniformity.

[0031] b) Corrosion resistance test: Figure 2 As shown in the figure, the high temperature nitric acid corrosion resistant zirconium alloy plate prepared in this embodiment was subjected to uniform corrosion performance test in a nitric acid solution with a temperature of 90°C and a concentration of 6 mol / L. Figure 3 The test results show that the uniform corrosion rate of the zirconium alloy plate in a nitric acid solution with a temperature of 90°C and a concentration of 6 mol / L is less than 0.006 mm / a, indicating that the alloy has excellent corrosion resistance in a high-temperature, highly oxidizing environment. In addition, the macroscopic photograph of the sample surface after 240 hours of corrosion under the same conditions ( Figure 4 ) shows no obvious corrosion damage; SEM morphology ( Figure 5 ) showed that the passivation film was intact and dense, with no signs of pitting or intergranular corrosion, further verifying the corrosion resistance and stability of the zirconium alloy.

[0032] Example 2 This embodiment aims to prepare a zirconium alloy plate resistant to high-temperature nitric acid corrosion. The zirconium alloy plate is composed of the following components, calculated by mass percentage: Nb: 0.5%, Hf: 2.2%, Ti: 1.0%, Fe ≤ 0.05%, Cr ≤ 0.01%, with the remainder being Zr and unavoidable impurity elements. The impurity contents are controlled to be O ≤ 0.05%, C ≤ 0.001%, H ≤ 0.001%, and N ≤ 0.001%.

[0033] like Figure 1 As shown, the preparation process of the high-temperature nitric acid corrosion-resistant zirconium alloy plate of this embodiment is as follows: 1) Batching and Melting: According to the designed composition of the high-temperature nitric acid corrosion-resistant zirconium alloy plate, the corresponding weight of Zr-Nb master alloy chips and industrial-grade titanium sponge are weighed and evenly spread between two layers of zirconium sponge (industrial-grade zirconium sponge containing Hf without zirconium and hafnium separation) and pressed into a consumable electrode. This is then subjected to three vacuum consumable melting cycles to obtain a zirconium alloy ingot with the target composition. 2) Forging, heat treatment, and surface treatment: The zirconium alloy ingot obtained in step 1) is heated to 1030° C. and forged at a single forging reduction of 30% and a final forging temperature of 800° C. After forging to a target thickness, the ingot is recharged into a furnace, heated to 1030° C. and held at that temperature for 40 minutes, then removed from the furnace and subjected to water-cooled quenching treatment; the surface of the quenched ingot is milled to remove oxide scale and defects on the surface of the ingot, giving it a metallic color, thereby obtaining a zirconium alloy forging; 3) Two-pass hot rolling: The zirconium alloy forging obtained in step 2) is first heated to 650°C and held for 30 minutes, and then hot rolled in one pass, with the deformation of each pass controlled at 10%, until the hot rolling reaches 1 / 2 of the target deformation. The hot-rolled plate is then returned to the furnace, heated to 650°C and held for 20 minutes, and then hot rolled in a second pass, with the deformation of each pass controlled at 15%, until the target thickness is reached, thereby obtaining the zirconium alloy rolled plate. 4) Surface treatment and vacuum annealing: The zirconium alloy rolled piece obtained in step 3) is sandblasted to remove surface oxide scale, and then polished with a grinder to obtain a zirconium alloy rolled piece with a metallic luster. The zirconium alloy rolled piece is then placed in a vacuum annealing furnace, heated to 500° C., and maintained at a vacuum degree of no more than 0.05 Pa for 3 hours to eliminate processing stress and avoid oxidation, thereby obtaining a high-temperature nitric acid corrosion-resistant zirconium alloy plate.

[0034] Performance testing a) Composition Testing: The measured composition (by mass percentage) of the high-temperature nitric acid corrosion-resistant zirconium alloy plate prepared in this example is: Nb: 0.505%, Hf: 2.135%, Ti: 0.997%, Fe: 0.0493%, Cr: 0.0032%, O: 0.0332%, C: 0.0008%, H: 0.0006%, and N: 0.0002%. All of these compositions meet design requirements and exhibit good compositional uniformity.

[0035] b) Corrosion resistance test: Figure 2 As shown in the figure, the high temperature nitric acid corrosion resistant zirconium alloy plate prepared in this embodiment was subjected to uniform corrosion performance test in a nitric acid solution with a temperature of 90°C and a concentration of 6 mol / L. Figure 3 The test results show that the uniform corrosion rate of the zirconium alloy plate in a nitric acid solution with a temperature of 90°C and a concentration of 6 mol / L is less than 0.007 mm / a, indicating that the alloy has excellent corrosion resistance in a high-temperature, highly oxidizing environment.

[0036] Example 3 This embodiment aims to prepare a zirconium alloy plate resistant to high-temperature nitric acid corrosion. The zirconium alloy plate is composed of the following components, calculated by mass percentage: Nb: 1.5%, Hf: 2.2%, Ti: 0.5%, Fe ≤ 0.05%, Cr ≤ 0.01%, with the remainder being Zr and unavoidable impurity elements. The impurity contents are controlled to be O ≤ 0.05%, C ≤ 0.001%, H ≤ 0.001%, and N ≤ 0.001%.

[0037] like Figure 1 As shown, the preparation process of the high-temperature nitric acid corrosion-resistant zirconium alloy plate of this embodiment is as follows: 1) Batching and Melting: According to the designed composition of the high-temperature nitric acid corrosion-resistant zirconium alloy plate, the corresponding weight of Zr-Nb master alloy chips and industrial-grade titanium sponge are weighed and evenly spread between two layers of zirconium sponge (industrial-grade zirconium sponge containing Hf without zirconium and hafnium separation) and pressed into a consumable electrode. Then, through four vacuum consumable melting processes, a zirconium alloy ingot with the target composition is obtained. 2) Forging, heat treatment, and surface treatment: The zirconium alloy ingot obtained in step 1) is heated to 1050° C. and forged at a single forging reduction of 40% and a final forging temperature of 820° C. After forging to a target thickness, the ingot is recharged into a furnace, heated to 1050° C. and held there for 35 minutes, then removed from the furnace and subjected to water-cooled quenching treatment. The surface of the quenched ingot is milled to remove oxide scale and defects on the surface of the ingot, giving it a metallic color, thereby obtaining a zirconium alloy forging; 3) Two-pass hot rolling: The zirconium alloy forging obtained in step 2) is first heated to 650°C and held for 35 minutes, and then subjected to a first-pass hot rolling process, with the deformation amount per pass controlled at 15%, and hot-rolled to 1 / 2 of the target deformation amount; the hot-rolled plate is then returned to the furnace, heated to 650°C and held for 25 minutes, and then subjected to a second-pass hot rolling process, with the deformation amount per pass controlled at 10%, and rolled to the target thickness, to obtain a zirconium alloy rolled plate; 4) Surface treatment and vacuum annealing: The zirconium alloy rolled piece obtained in step 3) is sandblasted to remove surface oxide scale, and then polished with a grinder to obtain a zirconium alloy rolled piece with a metallic luster. The zirconium alloy rolled piece is then placed in a vacuum annealing furnace, heated to 530° C., and maintained at a vacuum degree of no more than 0.05 Pa for 2.5 hours to eliminate processing stress and prevent oxidation, thereby obtaining a high-temperature nitric acid corrosion-resistant zirconium alloy plate.

[0038] Performance testing a) Composition Testing: The measured composition (by mass percentage) of the high-temperature nitric acid corrosion-resistant zirconium alloy plate prepared in this example is: Nb: 1.505%, Hf: 2.115%, Ti: 0.501%, Fe: 0.0472%, Cr: 0.0037%, O: 0.0348%, C: 0.0008%, H: 0.0006%, and N: 0.0004%. All of these compositions meet design requirements and exhibit good compositional uniformity.

[0039] b) Corrosion resistance test: Figure 2 As shown in the figure, the high temperature nitric acid corrosion resistant zirconium alloy plate prepared in this embodiment was subjected to uniform corrosion performance test in a nitric acid solution with a temperature of 90°C and a concentration of 6 mol / L. Figure 3 The test results show that the uniform corrosion rate of the zirconium alloy plate in a nitric acid solution with a temperature of 90°C and a concentration of 6 mol / L is less than 0.005 mm / a, indicating that the alloy has excellent corrosion resistance in a high-temperature, highly oxidizing environment.

[0040] Example 4 This embodiment aims to prepare a zirconium alloy plate resistant to high-temperature nitric acid corrosion. The zirconium alloy plate is composed of the following components, calculated by mass percentage: Nb: 1.5%, Hf: 2.2%, Ti: 1.0%, Fe ≤ 0.05%, Cr ≤ 0.01%, with the remainder being Zr and unavoidable impurity elements. The impurity contents are controlled to be O ≤ 0.05%, C ≤ 0.001%, H ≤ 0.001%, and N ≤ 0.001%.

[0041] like Figure 1 As shown, the preparation process of the high-temperature nitric acid corrosion-resistant zirconium alloy plate of this embodiment is as follows: 1) batching and smelting: according to the component design of the high-temperature nitric acid corrosion-resistant zirconium alloy plate, the corresponding weight of Zr-Nb intermediate alloy scrap and industrial-grade sponge titanium is weighed and evenly laid in the middle of two layers of sponge zirconium (Hf-containing industrial-grade sponge zirconium without hafnium-zirconium separation) and pressed into a consumable electrode; then through 5 times of vacuum consumable smelting, a zirconium alloy ingot with a target component is obtained; 2) forging, heat treatment and surface treatment: the zirconium alloy ingot obtained in step 1) is heated to 1070℃ and open-die forged, the single reduction of the forging is 50%, and the final forging temperature is 850℃, after forging to the target thickness; the blank is reloaded into the furnace, heated to 1070℃ and kept for 40 min, then taken out for water quenching treatment; the surface of the quenched blank is milled to remove the scale and defects on the surface of the blank and make it metallic, obtaining a zirconium alloy forge piece; 3) two-fire hot rolling: the zirconium alloy forge piece obtained in step 2) is first heated to 670℃ and kept for 40 min, then one-fire hot rolling is performed with a single pass deformation of 10%, and the hot rolling is stopped when the deformation reaches 1 / 2 of the target deformation; then the hot-rolled plate is reheated to 670℃ and kept for 30 min, and two-fire hot rolling is performed with a single pass deformation of 15%, and the hot rolling is stopped when the thickness reaches the target thickness, obtaining a zirconium alloy rolled piece in the form of a plate; 4) surface treatment and vacuum annealing: the zirconium alloy rolled piece obtained in step 3) is sandblasted to remove the surface scale, then the surface is polished by a polishing machine to obtain a zirconium alloy rolled piece with a metallic luster; then the zirconium alloy rolled piece is loaded into a vacuum annealing furnace, heated to 550℃, and kept for 3h under a vacuum degree of not more than 0.05Pa to eliminate processing stress and avoid oxidation, finally obtaining a high-temperature nitric acid corrosion-resistant zirconium alloy plate.

[0042] Performance testing a) component test: the actual component (mass percentage) of the high-temperature nitric acid corrosion-resistant zirconium alloy plate prepared in this embodiment is: Nb: 1.497%, Hf: 2.219%, Ti: 1.023%, Fe: 0.0492%, Cr: 0.0032%, O: 0.0355%, C: 0.0010%, H: 0.0005%, N: 0.0002%. The above components all meet the design requirements and have good component uniformity.

[0043] b) corrosion resistance test: as shown in Figure 2 , the high-temperature nitric acid corrosion-resistant zirconium alloy plate prepared in this embodiment is tested for uniform corrosion resistance in a nitric acid solution with a temperature of 90℃ and a concentration of 6mol / L. Figure 3 The test results show that the uniform corrosion rate of the zirconium alloy plate in the nitric acid solution with a temperature of 90℃ and a concentration of 6mol / L is less than 0.007mm / a, indicating that the alloy has excellent corrosion resistance in a high-temperature strong oxidizing environment.

[0044] Example 5 This embodiment aims to prepare a zirconium alloy plate resistant to high-temperature nitric acid corrosion. The zirconium alloy plate is composed of the following components, calculated by mass percentage: Nb: 1.0%, Hf: 2.2%, Ti: 0.75%, Fe ≤ 0.05%, Cr ≤ 0.01%, with the remainder being Zr and unavoidable impurity elements. The impurity contents are controlled to be O ≤ 0.05%, C ≤ 0.001%, H ≤ 0.001%, and N ≤ 0.001%.

[0045] like Figure 1 As shown, the preparation process of the high-temperature nitric acid corrosion-resistant zirconium alloy plate of this embodiment is as follows: 1) Batching and Melting: According to the designed composition of the high-temperature nitric acid corrosion-resistant zirconium alloy plate, the corresponding weight of Zr-Nb master alloy chips and industrial-grade titanium sponge are weighed and evenly spread between two layers of zirconium sponge (industrial-grade zirconium sponge containing Hf without zirconium and hafnium separation) and pressed into a consumable electrode. This is then subjected to three vacuum consumable melting cycles to obtain a zirconium alloy ingot with the target composition. 2) Forging, heat treatment, and surface treatment: The zirconium alloy ingot obtained in step 1) is heated to 1070° C. and forged at a single forging reduction of 40% and a final forging temperature of 850° C. After forging to a target thickness, the ingot is recharged into a furnace, heated to 1070° C. and held at that temperature for 40 minutes, then removed from the furnace and subjected to water-cooled quenching treatment; the surface of the quenched ingot is milled to remove oxide scale and defects on the surface of the ingot, giving it a metallic color, thereby obtaining a zirconium alloy forging; 3) Two-pass hot rolling: The zirconium alloy forging obtained in step 2) is first heated to 650°C and held for 35 minutes, and then hot rolled in one pass, with the deformation of each pass controlled at 15%, until the hot rolling reaches 1 / 2 of the target deformation. The hot-rolled plate is then returned to the furnace, heated to 650°C and held for 25 minutes, and then hot rolled in a second pass, with the deformation of each pass controlled at 10%, until the target thickness is reached, thereby obtaining the zirconium alloy rolled plate. 4) Surface treatment and vacuum annealing: The zirconium alloy rolled piece obtained in step 3) is sandblasted to remove surface oxide scale, and then polished with a grinder to obtain a zirconium alloy rolled piece with a metallic luster. The zirconium alloy rolled piece is then placed in a vacuum annealing furnace, heated to 550° C., and maintained at a vacuum degree of no more than 0.05 Pa for 2.5 hours to eliminate processing stress and prevent oxidation, thereby obtaining a high-temperature nitric acid corrosion-resistant zirconium alloy plate.

[0046] Performance testing a) Composition Testing: The measured composition (by mass percentage) of the high-temperature nitric acid corrosion-resistant zirconium alloy plate prepared in this example is: Nb: 1.013%, Hf: 2.221%, Ti: 0.753%, Fe: 0.0472%, Cr: 0.0039%, O: 0.0347%, C: 0.0009%, H: 0.0006%, and N: 0.0002%. All of these compositions meet design requirements and exhibit good compositional uniformity.

[0047] b) Corrosion resistance test: Figure 2 As shown in the figure, the high temperature nitric acid corrosion resistant zirconium alloy plate prepared in this embodiment was subjected to uniform corrosion performance test in a nitric acid solution with a temperature of 90°C and a concentration of 6 mol / L. Figure 3 The test results show that the uniform corrosion rate of the zirconium alloy plate in a nitric acid solution with a temperature of 90°C and a concentration of 6 mol / L is less than 0.005 mm / a, indicating that the alloy has excellent corrosion resistance in a high-temperature, highly oxidizing environment.

[0048] In summary, Examples 1 to 5 of the present invention, by precisely controlling the ratios of alloying elements such as Nb, Hf, and Ti, combined with optimized vacuum melting, forging and hot rolling, vacuum annealing, and surface treatment processes, produce zirconium alloy plates having uniform corrosion rates of less than 0.008 mm / a in a 6 mol / L nitric acid solution at 90°C, far below the industry standard. Furthermore, the plates exhibit good compositional uniformity and are free of the risk of stress corrosion cracking. These zirconium alloy plates successfully achieve technological breakthroughs in high-temperature nitric acid corrosion resistance, low cost, and ease of processing, providing a reliable, high-performance material solution for key equipment in spent fuel reprocessing.

[0049] The foregoing description is intended only to provide specific embodiments of the present invention, which will enable those skilled in the art to understand and implement the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention.

[0050] It should be understood that the present invention is not limited to the above description and that various modifications and changes may be made without departing from the scope thereof. The scope of the present invention is limited only by the appended claims.

Claims

1. A zirconium alloy resistant to high temperature nitric acid corrosion, characterized in that: The zirconium alloy is composed of the following components by mass percentage: Nb: 0.2% to 3.0%, Hf: 1.0% to 3.0%, Ti: 0.2% to 3.0%, Fe≤0.15%, Cr≤0.1%, and the balance is Zr and unavoidable impurity elements, and the impurities are controlled to have O≤0.1%, C≤0.01%, H≤0.01%, and N≤0.01%.

2. The high temperature nitric acid corrosion resistant zirconium alloy according to claim 1, characterized in that: The zirconium alloy is composed of the following components in terms of mass percentage: Nb: 0.5% to 1.5%, Hf: 2.0% to 2.5%, Ti: 0.5% to 1.0%, Fe≤0.05%, Cr≤0.01%, and the remainder is Zr and unavoidable impurity elements, and the impurities are controlled to have O≤0.05%, C≤0.001%, H≤0.001%, and N≤0.001%.

3. The high temperature nitric acid corrosion resistant zirconium alloy according to claim 2, characterized in that: The zirconium alloy has a uniform corrosion rate of less than 0.008 mm / a in a nitric acid solution with a temperature of 90° C. and a concentration of 6 mol / L.

4. A method for preparing a high-temperature nitric acid corrosion-resistant zirconium alloy according to any one of claims 1 to 3, characterized in that: The following steps are involved: Step 1: Mixing the ingredients according to the target composition percentage of the zirconium alloy and then smelting to obtain a zirconium alloy ingot with the target composition; Step 2: Forging the zirconium alloy ingot obtained in step 1, and sequentially performing heat treatment and surface treatment on the forged blank to obtain a zirconium alloy forging; Step 3: hot rolling the zirconium alloy forging obtained in step 2 to obtain a zirconium alloy rolled piece; Step 4: The zirconium alloy rolled piece obtained in step 3 is subjected to surface treatment and then vacuum annealing treatment to obtain a zirconium alloy resistant to high temperature nitric acid corrosion.

5. The method for preparing a high-temperature nitric acid corrosion-resistant zirconium alloy according to claim 4, characterized in that: In step 1, when preparing the ingredients, the Zr element and the Hf element are industrial-grade sponge zirconium containing Hf, the Nb element is Zr-Nb master alloy chips, and the Ti element is industrial-grade sponge titanium.

6. The method for preparing a high-temperature nitric acid corrosion-resistant zirconium alloy according to claim 4, characterized in that: In step 1, the smelting is performed by vacuum consumable arc melting, and the number of smelting times is greater than or equal to 3 times.

7. The method for preparing a high-temperature nitric acid corrosion-resistant zirconium alloy according to claim 4, characterized in that: In step 2, the forging parameters are set as follows: the blank forging temperature is 1050±20°C, the final forging temperature is greater than or equal to 800°C, and the single forging reduction is 30% to 50%; The heat treatment process is as follows: firstly, the forged billet is placed in a heat treatment furnace at 1050±20°C and kept at this temperature for 30min to 40min, and then the billet is subjected to water cooling quenching treatment; The surface treatment process is: performing milling on the surface of the blank after water-cooling quenching treatment to remove oxide scale and defects on the surface of the blank, so that the surface of the blank presents a metallic color.

8. The method for preparing a high-temperature nitric acid corrosion-resistant zirconium alloy according to claim 4, characterized in that: In step 3, the hot rolling is performed in two steps: first, the zirconium alloy forging is heated at 650±20°C for 30 to 40 minutes, and then rolled to 1 / 2 of the target deformation; then, the zirconium alloy forging is returned to the furnace and heated at 650±20°C for 20 to 30 minutes, and then rolled to the target thickness, thereby obtaining the zirconium alloy rolled piece; Among them, the deformation of each single pass during hot rolling is 10% to 15%.

9. The method for preparing a high-temperature nitric acid corrosion-resistant zirconium alloy according to claim 4, characterized in that: In step 4, the surface treatment process is as follows: first, the zirconium alloy rolled piece is sandblasted to remove the oxide scale on the surface, and then the surface is polished by a grinding and polishing machine to obtain a zirconium alloy rolled piece with a metallic luster; The vacuum annealing process is as follows: placing the zirconium alloy rolled piece showing metallic luster into a vacuum annealing furnace, heating it to 500° C. to 550° C., and maintaining the vacuum degree at less than or equal to 0.05 Pa for 2 h to 3 h.

10. Use of the high-temperature nitric acid corrosion-resistant zirconium alloy according to any one of claims 1 to 3, or the high-temperature nitric acid corrosion-resistant zirconium alloy prepared by the preparation method according to any one of claims 4 to 9 in spent fuel reprocessing equipment.

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