Austenitic stainless steel plate for sodium-cooled fast reactor fuel cladding, manufacturing method and welding method thereof

Abstract

The invention provides an austenitic stainless steel plate for a sodium-cooled fast reactor fuel cladding and a manufacturing and welding method of the austenitic stainless steel plate. The austenitic stainless steel plate comprises, by weight, 0.07%-0.08% of C, 0.20%-0.30% of Si, 5.0%-6.0% of Mn, smaller than or equal to 0.015% of P, smaller than or equal to 0.002% of S, 12.5%-13.5% of Cr, 12.5%-13.5% of Ni, 2.0%-3.0% of Mo, 0.15%-0.25% of N, 0.15%-0.25% of V, 0.10%-0.15% of Nb, 0.0015%-0.0025% of B and the balance Fe and inevitable impurities. The production method of the steel plate comprises smelting, heating, rolling and heat treatment.

Description

Technical Field

[0001] This invention belongs to the field of metallic materials, and specifically relates to an austenitic stainless steel plate for cladding of sodium-cooled fast reactor fuel, its manufacturing process, and its welding method. Background Technology

[0002] Sodium-cooled fast reactors (SNFRs) offer significantly higher fuel utilization compared to traditional Generation 3 reactors: SNFRs are currently the only reactor type capable of relatively easy fuel breeding, converting depleted uranium and spent fuel into new nuclear fuel, greatly improving fuel utilization. They also boast high thermal efficiency: using liquid metallic sodium as a coolant, SNFRs achieve core outlet temperatures of 500-600°C at near-atmospheric pressure, enhancing thermal efficiency. Furthermore, they offer high safety: SNFRs incorporate multiple safety measures in their design, such as an intermediate loop to prevent sodium-water reactions from affecting core safety, and a pooled structure utilizing the heat capacity and natural circulation of the sodium pool to enhance core safety. The performance requirements for stainless steel used in SNFR fuel cladding are primarily focused on high radiation resistance and creep resistance, excellent mechanical properties at both room and high temperatures, and uniform microstructure, especially resistance to intergranular corrosion at medium carbon content. These requirements ensure long-term stable operation of the stainless steel in high-temperature, high-radiation environments, thereby guaranteeing the safe and efficient operation of the SNFR.

[0003] This invention utilizes a chemical composition design approach of medium-carbon + manganese-nitrogen-vanadium alloying, combined with pulsed magnetostrictive oscillation (PMO) technology, to effectively control the average size and number density of vanadium nitride (VN) particles in steel, for the production of austenitic stainless steel medium-thick plates for sodium-cooled fast reactor fuel cladding. Simultaneously, multi-pass rolling in the crystallization zone, followed by water cooling and solution heat treatment, further optimizes the average size and number density of oxide particles in the steel under medium-carbon conditions, improving the steel plate's resistance to intergranular corrosion and its overall mechanical properties. Excellent welding technology and process parameters ensure good weldability of the material. Currently, there are few related patents in China; those mainly related to this invention include the following: CN201610498260.5 A method for reducing chain carbides in high-performance heat-resistant stainless steel materials, compared with the chemical composition of the invention: C: 0.08%~0.15%, Si: ≤0.1%, Mn: 0.35%~0.65%, P: ≤0.015%, S: ≤0.010%, Cr: 10%~12%, Mo: 0.1%~0.4%, V: 0.15%~0.25%, Ni: 0.3%~0.7%, Co: 2.5%~3.5%, W: 2.4%~3.0%, Nb: 0.05~0.12%, N: 0.01%~0.035%. B: 0.01%~0.025%, Al≤0.015%, 1.5 kg / ton of rare earth element Zr is added during the first smelting, and electrode rods are cast. The electrode rods are then subjected to electroslag remelting to obtain electroslag steel ingots. The electroslag ingots are placed in a heating furnace, heated to 1150~1170℃, held for a certain time, and then forged to form billets. The billets are then placed in a heating furnace, heated to 1150~1170℃, held for a certain time, and then forged into finished products. The heat-resistant stainless steel produced by this invention has a uniform microstructure, thus significantly improving the high-temperature creep performance and fatigue life of the alloy material. The comparative patent uses a secondary electroslag remelting and forging method to produce steel plates, which has higher production costs, higher energy consumption, more pollution, and poorer uniformity in plate shape and performance of the products.

[0004] CN201080058577.8 describes a method for manufacturing high-carbon martensitic stainless steel containing 0.40-0.80% carbon and 11-16% chromium as the main components. In this method, molten stainless steel is supplied from a tundish through a nozzle to the steel pool in a thin-strip continuous casting apparatus to cast stainless steel sheets. Immediately after casting, hot-rolled annealed strip is produced using online rolls at a reduction rate of 5-40%, aiming to reduce the primary carbides in the microstructure of the hot-rolled annealed strip to below 10 μm. This prior art differs fundamentally from the present invention in terms of chemical composition, stainless steel type, and steel plate thickness. Furthermore, the comparative invention exhibits lower carbide control, failing to reach the advanced level of 10-100 nm. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide an austenitic stainless steel plate for cladding of sodium-cooled fast reactor fuel, its manufacturing process, and its welding method.

[0006] This invention utilizes a chemical composition design approach of medium-carbon + manganese-nitrogen alloying, combined with pulsed magnetostrictive oscillation (PMO) technology, to effectively control the average size and number density of vanadium nitride (VN) particles in steel, enabling the production of medium-thick austenitic stainless steel plates for sodium-cooled fast reactor fuel cladding. Simultaneously, multi-pass rolling in the crystallization zone, followed by post-rolling water cooling and solution heat treatment, further optimizes the average size and number density of oxide particles in the steel under medium-carbon conditions, improving the steel plate's resistance to intergranular corrosion and its overall mechanical properties. Excellent welding techniques and process parameters ensure the material's superior weldability.

[0007] The objective of this invention is achieved as follows: One of the technical solutions of this invention is to provide an austenitic stainless steel plate for cladding fuel in a sodium-cooled fast reactor. The composition of the steel plate by weight percentage is as follows: C: 0.07%~0.08%, Si: 0.20%~0.30%, Mn: 5.0%~6.0%, P≤0.015%, S≤0.002%, Cr: 12.5%~13.5%, Ni: 12.5%~13.5%, Mo: 2.0%~3.0%, N: 0.15%~0.25%, V: 0.15%~0.25%, Nb: 0.10%~0.15%, B: 0.0015%~0.0025%, with the remainder being Fe and unavoidable impurities.

[0008] The reasons for using the above-mentioned components are as follows: C: Carbon is a strong austenite-forming and stabilizing element. Carbon readily precipitates as carbides with other alloying elements. Therefore, increasing the carbon content improves the strength of stainless steel but decreases its impact toughness and raises its ductile-brittle transition temperature. Furthermore, the presence of supersaturated carbon will precipitate as carbides, leading to chromium depletion in adjacent regions and making austenitic stainless steel highly susceptible to intergranular corrosion. This invention addresses this problem using grain boundary engineering. To ensure the strength of the steel plate, this invention requires that the C content in the steel be controlled within the range of 0.07%-0.08%.

[0009] Si: Adding an appropriate amount of silicon to stainless steel can improve its oxidation and sulfidation resistance, and impart excellent corrosion resistance to strong oxidizing media such as concentrated nitric acid and concentrated sulfuric acid. This is related to the formation of a silicon-rich oxide protective film on the surface of stainless steel. However, a negative effect is that when the silicon content is less than 1% and within the normal range for stainless steel, a higher silicon content will reduce the corrosion resistance of chromium-nickel austenitic stainless steel and significantly increase its susceptibility to solid solution intergranular corrosion. Therefore, the Si content in this invention is controlled at 0.20%-0.30%.

[0010] Mn: Manganese possesses excellent austenitic stabilizing properties. Its effects are particularly pronounced when the manganese content in austenitic stainless steel reaches 5.0% or higher: it significantly improves the steel's strength at both room and high temperatures, making it more durable and possessing a good strength-toughness balance; it also improves the steel's hot plasticity, giving it better ductility and malleability during processing. Furthermore, manganese is an effective deoxidizer and desulfurizer. Due to its strong affinity for sulfur, it can form manganese sulfide in steel, effectively eliminating the harmful effects of residual sulfur and further improving the quality and performance of the steel. Therefore, the Mn content in steel should be controlled between 5.0% and 6.0%.

[0011] P: Phosphorus is a harmful element in steel, increasing its cold brittleness, worsening its weldability, reducing its plasticity, and impairing its cold bending performance. Furthermore, P is particularly sensitive to radiation embrittlement. Therefore, the lower the P content in steel, the better; this invention requires it to be no more than 0.015%.

[0012] Sulfur (S) is generally considered a harmful element. It readily forms brittle sulfides with alloying elements in steel, causing hot brittleness and reducing ductility and toughness. S also tends to accelerate radiation embrittlement. Therefore, this invention requires that the S content in steel be limited to below 0.002%.

[0013] Chromium (Cr): Chromium is one of the most important elements in stainless steel, particularly in austenitic stainless steel. The interaction between chromium and nickel forms a stable austenitic structure. In pure austenitic stainless steel, the chromium content has no significant effect on mechanical properties. However, when ferrite or σ phases are present in the steel, increasing the chromium content leads to increased strength but decreased ductility and toughness. As the Cr content increases from 24% to 26%, the austenite phase content gradually decreases, while the ferrite phase content increases; yield strength and tensile strength both continuously increase, elongation initially decreases and then increases, and reduction of area continuously decreases. Impact absorption energy initially decreases and then increases, while resistance to electrochemical corrosion and stress corrosion is enhanced. Therefore, this invention requires a Cr content of 12.5%-13.5% in the steel.

[0014] Ni: Nickel can improve the strength, toughness, and corrosion resistance of ferritic stainless steel. For austenitic stainless steel, within the nickel content range where martensitic transformation may occur, the strength of the steel decreases while its plasticity increases with increasing nickel content. When a stable austenitic structure is present, the addition of nickel can further improve its plasticity and toughness, and austenitic stainless steel has better rust resistance and corrosion resistance; however, increasing the nickel content leads to an increase in the intergranular corrosion susceptibility of austenitic stainless steel. Therefore, this invention requires the Ni content in the steel to be controlled at 12.5%-13.5%.

[0015] Mo: Molybdenum is an important alloying element widely used in stainless steel. Studies have confirmed that in marine atmospheres, chromium alone, even with a chromium content as high as nearly 24%, is insufficient to completely prevent the corrosion of stainless steel; molybdenum must be added. However, the beneficial effect of molybdenum on the corrosion resistance of stainless steel depends on the presence of sufficient chromium in the steel. Moreover, as the chromium content in the steel increases, the beneficial effects of molybdenum also increase significantly. For austenitic stainless steel, molybdenum has a significant solid solution strengthening effect. Molybdenum can also improve the corrosion resistance of stainless steel, but excessively high molybdenum content is detrimental to the stress corrosion resistance of austenitic stainless steel. An appropriate amount of molybdenum is beneficial for improving the resistance of stainless steel to stress corrosion cracking; therefore, this invention requires the Mo content in the steel to be controlled at 2.0%-3.0%.

[0016] Nitrogen (N): In austenitic stainless steel, nitrogen can partially replace nickel to conserve nickel. It also plays a role in solid solution strengthening, significantly improving the room temperature and high temperature strength of austenitic stainless steel. Nitrogen can also improve the corrosion resistance of austenitic stainless steel. When nitrogen combines with appropriate amounts of chromium and molybdenum, it can significantly improve the resistance to pitting and crevice corrosion in austenitic stainless steel, and this resistance increases with increasing nitrogen content. Therefore, this invention requires the nitrogen content in the steel to be controlled at 0.15%-0.25%.

[0017] Vanadium (V) is an excellent deoxidizer for steel, refining the grain structure of austenitic stainless steel and thus improving its strength and toughness to a certain extent. Secondly, the carbides formed by vanadium and carbon can enhance the corrosion resistance of austenitic stainless steel under high temperature and pressure, strengthening its corrosion resistance. Furthermore, vanadium can inhibit the growth of austenitic grains, producing a grain-refining strengthening effect, which helps improve the hardness and wear resistance of the steel. Therefore, this invention requires the V content in the steel to be controlled at 0.15%-0.25%.

[0018] Niobium (Nb) is one of the important alloying elements in Cr-Ni austenitic stainless steels, second only to molybdenum in usage, and its role is multifaceted, especially important in heat-resistant stainless steels used in high-temperature applications. It can partially replace expensive molybdenum. Under high-temperature conditions, dispersed second-phase particles Fe2Nb precipitate in the material, inhibiting grain growth, improving high-temperature strength, and preventing material softening caused by high temperatures. At the same time, Nb can also reduce or avoid the precipitation of harmful Cr23C6 type carbides, reducing the microhardness of the material and effectively improving low-temperature toughness. Therefore, this invention requires the Nb content in the steel to be controlled at 0.10%-0.15%.

[0019] B: Boron has the effect of purifying grain boundaries. It can inhibit the segregation of harmful impurity elements such as sulfur and phosphorus at grain boundaries, thereby improving the hot plasticity of steel and ensuring the long-term stable operation of stainless steel in high temperature and high radiation environment, thus ensuring the safe and efficient operation of sodium-cooled fast reactor. Therefore, this invention requires the B content in steel to be controlled at 0.0015%-0.0025%.

[0020] The second technical solution of the present invention is to provide a method for manufacturing austenitic stainless steel plates for cladding fuel in sodium-cooled fast reactors, which mainly includes smelting, heating, rolling and heat treatment. (1) Smelting: The EAF electric furnace uses industrial pure iron with strict control over the content of impurity elements; the AOD converter strictly controls the chromium and nickel content, and the S content is controlled at 25-30ppm after tapping; the slag is skimmed off immediately after tapping from the converter, skimming it to 10-15cm, and high-calcium wire is fed for LF ladle refining, with strict control over the content of harmful elements such as P and S; the VOD vacuum treatment process takes 15-20 minutes, with argon protection throughout.

[0021] The SCC continuous casting billet casting process is as follows: After vacuum treatment, molten steel is poured through a 200mm cross-section thick slab continuous casting machine under argon protection throughout the process. Pulse magnetostrictive oscillation (PMO) solidification homogenization technology is adopted in the crystallizer. The superheat range of the tundish is 20-32℃. The steel is pulled at a constant temperature and speed with a water temperature of 17-21℃, a specific water volume of 0.8-1.0L·kg-1, a crystallizer water volume of 155-165t·h-1, a peak current of 300-350 KA and a treatment frequency of 40-45 KHz. After the continuous casting billet comes off the line, it is immediately cooled individually for 24-30 hours to ensure that excess H elements are fully discharged and to prevent the billet from cracking.

[0022] (2) Heating: The steel billet is heated in a continuous furnace at a temperature of 1220-1240℃. The heating time of the steel billet is controlled at 7-9 min / mm.

[0023] (3) Full recrystallization rolling and cooling: After the heated steel billet exits the furnace, it is descaled in a descaling box, followed by descaling once before the second pass and again before the penultimate pass. Rolling is performed in a fully recrystallized zone, with an initial rolling temperature of 1120~1150℃ and a final rolling temperature of 1000~1030℃. The reduction rate per pass is 19%~32%. The entire rolling process is completed in the fully recrystallized zone, promoting dynamic recrystallization of austenite and thus refining the grains. After rolling, it enters the ACC laminar flow zone for water cooling, further inhibiting austenite grain growth and ensuring uniform microstructure. The initial cooling temperature is 960-990℃, the water inlet flow rate is 500-520 m³ / h, the water outlet flow rate is 1240-1260 m³ / h, the roll speed is 1.0-1.2 m / s, and the inflection temperature is 450-480℃.

[0024] (4) Solution heat treatment After rolling, the material enters a continuous solution heat treatment furnace for solution heat treatment. The holding temperature is 1080±10℃, the net holding time is 2.5±0.5min / mm, and the material is water-cooled.

[0025] The third technical solution of the present invention is to provide a welding method for austenitic stainless steel plates used for fuel cladding in sodium-cooled fast reactors.

[0026] Using TIG welding, 1-1.5% Zr is added as filler metal during the welding process. A large number of fine ZrC, ZrO2 and other spherical reinforcing particles are dispersed on the joint. The welding current is 20-30 A and the arc ultrasonic frequency is reduced by 25-30 kHz. The weld has small pore size and few pores. The tensile strength of the joint can reach 87%-90% of the base metal. The precipitation, growth and agglomeration of nano oxides such as ZrC and ZrO2 improve the weld strength while refining the grains. The synergistic effect of fine grain toughening and dispersion toughening improves the comprehensive mechanical properties of the weld.

[0027] This invention provides an austenitic stainless steel plate for cladding of sodium-cooled fast reactor fuel, its manufacturing process, and its welding method. The produced steel plate has a thickness of 15-25 mm. Compared with the prior art, the advantages are as follows: 1. PMO technology utilizes pulsed current generated by secondary cooling pulse magnetostrictive oscillation to promote nucleation through an "electro-induced supercooling" effect, effectively increasing the equiaxed crystal ratio at the center of the billet, eliminating shrinkage cavities, and suppressing element enrichment at the solidification center. The internal quality of continuously cast billets treated with PMO is significantly improved. The average equiaxed crystal ratio at the center of the billet is 12-14%, and the average size and number density of vanadium nitride (VN) particles in the billet reach 2.2-3.2 nm and (0.6-1.0) × 10²⁴ nm, respectively. -3 .

[0028] 2. The entire rolling process is completed in the fully recrystallized zone, which promotes the dynamic recrystallization of austenite and thus refines the grains. After rolling, the austenite grains are cooled in the ACC laminar flow zone to further suppress the growth of austenite grains and ensure the uniformity of the microstructure.

[0029] 3. The solution heat treatment temperature is higher than the austenitizing temperature. After water cooling following solution heat treatment, the average size and number density of vanadium nitride (VN) particles in the steel are refined to 1.2-2.2 nm and precipitated to 1.0-1.8 × 10²⁴ nm, respectively. -3The grain size grade is 3-4. The final finished steel plate exhibits the following transverse tensile properties at room temperature: yield strength 300-350 MPa, tensile strength 600-650 MPa, elongation after fracture 40%-45%, elongation after fracture at 650℃ 22-25%, room temperature impact energy approximately 270-300 J, creep life exceeding 8000-9000 hours at 650℃ / 120MPa, and no irradiation swelling under heavy ion irradiation at 450℃ / 200dpa. After sensitization treatment, the intergranular corrosion resistance of the delivered steel plate is tested using Method E in GB / T 4334-2020 "Corrosion of Metals and Alloys - Test Method for Intergranular Corrosion of Stainless Steel," and no cracks are observed after bending.

[0030] 4. TIG welding is convenient and economical. At room temperature, the welded joint has the following transverse properties: yield strength 300-350 MPa, tensile strength 530-580 MPa, elongation after fracture 40-45%, elongation after fracture at 650℃ 22-25%, room temperature impact energy approximately 240-270 J, creep life exceeding 8000-9000 hours at 650℃ / 120MPa, and no radiation swelling under heavy ion irradiation at 450℃ / 200dpa. Attached Figure Description

[0031] Figure 1 Example 1: Metallographic photograph of a stainless steel plate in its delivery condition. Figure 2 Example 1: Microstructure of TIG weld seam in stainless steel plate with 1% Zr filler metal Figure 3 Example 1: Images of intergranular corrosion in stainless steel plates Detailed Implementation

[0032] The present invention will be further illustrated below through examples.

[0033] According to the component ratio of the technical solution, the present invention performs smelting, heating, rolling and heat treatment.

[0034] heating: The steel billet is heated in a continuous furnace at a heating and soaking temperature of 1220-1240℃. The heating time for the steel billet is controlled at 7-9 min / mm. Rolling: Rolling is performed in the fully recrystallized zone, with an initial rolling temperature of 1120~1150℃ and a final rolling temperature of 1000~1030℃. The reduction rate per pass is 19%~32%. The entire rolling process is completed in the fully recrystallized zone, which promotes the dynamic recrystallization of austenite and thus refines the grains. After rolling, the material enters the ACC laminar flow zone for water cooling, which further inhibits the growth of austenite grains and ensures the uniformity of the microstructure. The initial cooling temperature is 960-990℃, the water intake is 500-520 m3 / h, the water output is 1240-1260 m3 / h, the roll speed is 1.0-1.2 m / s, and the inflection temperature is 450-480℃. Heat treatment: After rolling, the product enters a continuous solution heat treatment furnace for solution heat treatment. The process is as follows: holding temperature: 1080±10℃, net holding time: 2.5±0.5min / mm, water cooling.

[0035] Furthermore, the smelting and casting process is as follows: The EAF electric furnace uses industrial pure iron with strict control over the content of impurity elements; the AOD converter strictly controls the chromium and nickel content, and the S content is controlled at 25-30ppm after tapping; the slag is skimmed off immediately after tapping from the converter, skimming it to 10-15cm, and high-calcium wire is fed for LF ladle refining, with strict control over the content of harmful elements such as P and S; the VOD vacuum treatment process takes 15-20 minutes, with argon protection throughout. The SCC continuous casting billet casting process is as follows: After vacuum treatment, molten steel is poured through a 200mm cross-section thick slab continuous casting machine under argon protection throughout the process. Pulse magnetostrictive oscillation (PMO) solidification homogenization technology is adopted in the crystallizer. The superheat range of the tundish is 20-32℃. Steel is pulled at constant temperature and speed with a water temperature of 17-21℃, a specific water volume of 0.8-1.0L·kg-1, a crystallizer water volume of 155-165t·h-1, a peak current of 300-350 KA and a treatment frequency of 40-45 KHz. After the continuous casting billet comes off the line, it is immediately cooled individually for 24-30 hours.

[0036] A welding method for austenitic stainless steel plates used for fuel cladding in sodium-cooled fast reactors is characterized by the use of TIG welding, the addition of 1-1.5% Zr as filler metal during the welding process, the dispersion of a large number of fine ZrC, ZrO2 and other spherical reinforcing particles on the joint, the welding current of 20-30 A, the ultrasonic frequency of the arc reduced by 25-30 kHz, and the tensile strength of the joint reaching 87-90% of that of the base material.

[0037] Furthermore, the welded joint performance is as follows: at room temperature, the transverse yield strength is 400-450 MPa, the tensile strength is 590-640 MPa, the elongation after fracture is 40-45%, and the room temperature impact energy is approximately 270-300 J; at 650℃, the yield strength is 300-350 MPa, the tensile strength is 490-540 MPa, the elongation after fracture is 22-25%, and the 550℃ impact energy is approximately 170-200 J; the creep life at 650℃ / 130MPa exceeds 11000-12000 hours; and there is no irradiation swelling under heavy ion irradiation at 500℃ / 290dpa.

[0038] The composition of the steel plate in this embodiment of the invention is shown in Table 1. The main smelting process parameters of the steel billet in this embodiment of the invention are shown in Table 2. The main rolling process parameters of the steel plate in this embodiment of the invention are shown in Table 3. The main parameters of solution heat treatment and welding in this invention are shown in Table 4. The microstructure of the steel in this embodiment of the invention is shown in Table 5. The mechanical properties of the steel base material in this embodiment of the invention are shown in Table 6. The welding mechanical properties of the steel in this embodiment of the invention are shown in Table 7.

[0039] Table 1. Composition (wt%) of steel billets in embodiments of the present invention

[0040] Table 2. Main process parameters for steel billet smelting in the embodiments of the present invention

[0041] Table 3 Main process parameters for steel rolling in the embodiments of the present invention

[0042] Table 4 Main parameters of solution heat treatment and welding in this invention

[0043] Table 5. Steel microstructure of embodiments of the present invention

[0044] Table 6 Mechanical properties of steel base material in embodiments of the present invention

[0045] Note: The resistance to intergranular corrosion is tested using Method E in GB / T 4334-2020 "Corrosion of metals and alloys - Test method for intergranular corrosion of stainless steel".

[0046] Table 7 Welding mechanical properties of steel in embodiments of the present invention

[0047] To illustrate the present invention, the present invention has been appropriately and sufficiently described above through embodiments. The above embodiments are only for illustrating the present invention and are not intended to limit the present invention. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Any modifications, equivalent substitutions, improvements, etc., should be included within the protection scope of the present invention. The patent protection scope of the present invention should be defined by the claims.

Claims

1. An austenitic stainless steel plate for cladding fuel in a sodium-cooled fast reactor, characterized in that, By weight percentage, it includes the following components: C: 0.07%~0.08%, Si: 0.20%~0.30%, Mn: 5.0%~6.0%, P≤0.015%, S≤0.002%, Cr: 12.5%~13.5%, Ni: 12.5%~13.5%, Mo: 2.0%~3.0%, N: 0.15%~0.25%, V: 0.15%~0.25%, Nb: 0.10%~0.15%, B: 0.0015%~0.0025%, with the remainder being Fe and unavoidable impurities.

2. The austenitic stainless steel plate for cladding fuel in a sodium-cooled fast reactor according to claim 1, characterized in that, The steel plate exhibits the following transverse tensile properties at room temperature: yield strength 300-350 MPa, tensile strength 600-650 MPa, elongation after fracture 40%-45%, elongation after fracture at 650℃ 22%-25%, room temperature impact energy 270-300 J, creep life exceeding 8000 hours at 650℃ / 120MPa, and no irradiation swelling under heavy ion irradiation at 450℃ / 200dpa.

3. The austenitic stainless steel plate for cladding fuel in a sodium-cooled fast reactor according to claim 1, characterized in that, The intergranular corrosion resistance of the steel plate was tested using Method E in GB / T 4334-2020 "Corrosion of metals and alloys - Test method for intergranular corrosion of stainless steel", and no cracks were found after bending.

4. The austenitic stainless steel plate for cladding fuel in a sodium-cooled fast reactor according to claim 1, characterized in that, The average size and number density of vanadium nitride particles in the steel plate were refined to 1.2-2.2 nm and precipitated to 1.0-1.8 × 10²⁴ nm, respectively. -3 Grain size grade 3-4.

5. A method for manufacturing an austenitic stainless steel plate for cladding of sodium-cooled fast reactor fuel according to any one of claims 1 to 4, comprising smelting, heating, rolling, and heat treatment, characterized in that, heating: The steel billet is heated in a continuous furnace at a heating and soaking temperature of 1220-1240℃, while the heating time of the steel billet is controlled at 7-9 min / mm. Full recrystallization rolling and cooling: Rolling is performed in the fully recrystallized zone, with an initial rolling temperature of 1120~1150℃ and a final rolling temperature of 1000~1030℃. The reduction rate per pass is 19%~32%, and the entire rolling process is completed in the fully recrystallized zone. After rolling, laminar cooling is performed with an initial cooling temperature of 960-990℃ and a water flow rate of 500-520m³. 3 / h, water flow rate 1240-1260m³ 3 / h, roller speed 1.0-1.2m / s, incandescent temperature 450-480℃; Solution heat treatment: After rolling, the product enters a continuous solution heat treatment furnace for solution heat treatment. The process is as follows: holding temperature: 1080±10℃, net holding time: 2.5±0.5min / mm, water cooling.

6. A method for manufacturing an austenitic stainless steel plate for cladding fuel in a sodium-cooled fast reactor according to claim 5, characterized in that, The smelting and casting processes are as follows: After tapping, the sulfur content is controlled at 25-30 ppm; after tapping from the converter, slag is skimmed down to 10-15 cm, and high-calcium wire is fed for LF ladle refining to control the content of harmful elements such as P and S; the VOD vacuum treatment process takes 15-20 minutes and is protected by argon gas throughout. The continuous casting process for the slab is as follows: After vacuum treatment, molten steel is poured through a 200mm thick slab continuous casting machine under argon protection throughout the process. Pulse magnetostrictive oscillation solidification and homogenization technology is employed in the crystallizer. The superheat range of the tundish is 20-32℃, and the steel is drawn at a constant temperature and speed. The water temperature is 17-21℃, and the specific water volume is 0.8-1.0 L·kg. -1 The crystallizer water volume is 155-165 t·h -1 The peak current of the PMO treatment is 300-350 kA and the treatment frequency is 40-45 kHz. After the continuous casting billet comes off the line, it is immediately cooled individually for 24-30 hours.

7. A welding method for an austenitic stainless steel plate for a sodium-cooled fast reactor fuel cladding according to any one of claims 1 to 4, characterized in that, Using TIG welding, 1%-1.5% Zr is added as filler metal during the welding process. Spherical reinforcing particles of ZrC and ZrO2 are dispersed on the joint. The welding current is 20-30 A and the arc ultrasonic frequency is reduced by 25-30 kHz. The tensile strength of the joint can reach 87%-90% of the base material.

8. A welding method for austenitic stainless steel plate for cladding fuel in a sodium-cooled fast reactor according to claim 7, characterized in that, The welded joint performance is as follows: at room temperature, the transverse yield strength is 400-450 MPa, the tensile strength is 590-640 MPa, the elongation after fracture is 40-45%, and the impact energy at room temperature is 270-300 J; at 650℃, the yield strength is 300-350 MPa, the tensile strength is 490-540 MPa, the elongation after fracture is 22-25%, and the impact energy at 550℃ is 170-200 J; the creep life at 650℃ / 130 MPa exceeds 11,000 hours, and there is no irradiation swelling under heavy ion irradiation at 500℃ / 290 dpa.

Images