High-temperature-stable nitride-strengthened high-barrier-hydrogen- permeation low-activation steel and production method

Abstract

The application discloses a high-thermal-stability nitride reinforced high-hydrogen-permeation-resistance low-activation steel and a production method, and belongs to the technical field of nuclear fusion reactor structure materials. The high-thermal-stability nitride reinforced high-hydrogen-permeation-resistance low-activation steel has the following chemical element mass fractions: C: 0.09-0.12%, Si: 0.2-0.3%, Mn: 0.4-0.6%, Cr: 8.0-8.7%, V: 0.2-0.4%, W: 1.0-1.5%, Ta: 0.1-0.15%, N: 0.02-0.05%, Y: 0.01-0.03%, Ti: less than or equal to 0.005%, and the balance of Fe and inevitable impurities. The production method comprises the following steps: vacuum induction smelting, protective atmosphere electroslag remelting, forging, rolling and heat treatment processes. The application realizes the excellent high-temperature creep strength and hydrogen resistance performance of the low-activation steel, and can meet the harsh service environment requirements of nuclear fusion reactors.

Description

Technical Field

[0001] This invention belongs to the field of nuclear fusion reactor structural materials technology, specifically relating to high thermal stability nitride-reinforced high hydrogen permeability low activation steel and its production method. Background Technology

[0002] As one of the most promising clean energy sources in the global energy transition, nuclear fusion energy has become a research hotspot and strategic competition focus in the international energy field due to its core advantages such as zero greenhouse gas emissions, abundant fuel resources (deuterium can be extracted from seawater), and no long-lived radioactive waste. The European Union's "Fusion 2020 Development Plan" explicitly states that by 2050, it expects to achieve a self-sufficient supply of tritium nuclides needed to sustain thermonuclear reactions in fusion devices and achieve a commercial power generation target of hundreds of megawatts. The realization of this goal will mark the transition of nuclear fusion energy from the experimental stage to practical application, providing crucial support for the upgrading of the global energy structure.

[0003] To achieve the aforementioned power generation capacity of hundreds of megawatts, nuclear fusion devices must efficiently capture and convert the energy released by the fusion reaction. The Test Blanket Module (TBM), as the core functional component of the fusion reactor, undertakes three key tasks: first, capturing the high-energy neutrons and thermal energy produced by the fusion reaction and converting them into usable electrical energy; second, achieving tritium breeding through the nuclear reaction of lithium-based breeding materials with neutrons, ensuring fuel self-sufficiency for the thermonuclear reaction; and third, shielding high-energy radiation to protect the safety of equipment and personnel surrounding the reactor. To ensure energy capture efficiency, the TBM must surround more than 85% of the high-temperature plasma region (area or volume) to maximize the collection of fusion energy. Therefore, the performance stability and operational reliability of the TBM directly determine whether the thermonuclear reaction can continue and whether the power generation efficiency can meet the target; it is the "core skeleton" of the nuclear fusion power generation device.

[0004] The stable operation of a TBM relies on the coordinated support of a large and sophisticated external auxiliary system, including: an initial heat transfer system (which efficiently transfers the thermal energy captured by the TBM to subsequent energy conversion units), an energy generation system (which converts thermal energy into electrical energy through steam circulation or direct energy conversion technology), and a tritium extraction system (which separates and recovers the generated tritium from the breeding material and replenishes it to the plasma reaction chamber for fuel circulation). The compatibility of these auxiliary systems with the TBM further highlights the importance of TBM structural design and material selection.

[0005] Currently, member countries of the International Thermonuclear Experimental Reactor (ITER) project have all chosen stainless steel as the core structural material based on the differences in their own TBM cooling media (such as water or helium). Stainless steel has become the mainstream choice for TBM structural materials at this stage due to its excellent mechanical properties, corrosion resistance, and machinability. However, the operating environment of nuclear fusion reactors is extremely harsh, its core characteristic being strong neutron radiation (irradiation doses can reach 10⁻⁶). 20 ~10 22 n / cm 2 The high temperatures (300–800℃) and medium-high temperatures place extremely high demands on the safety and reliability of structural steel. Based on the different cooling media, structural steel used in nuclear fusion reactors is mainly divided into two categories: Austenitic heat-resistant steel: mainly used in water-cooled cladding modules. Its advantage lies in its good plasticity and toughness at high temperatures. However, under high irradiation dose conditions, the austenitic grain boundaries are prone to vacancy accumulation due to irradiation, resulting in irradiation swelling (volume expansion rate can reach more than 5%), which significantly reduces the dimensional stability and mechanical properties of the components and greatly shortens their service life under high-temperature irradiation environment. It is difficult to meet the requirements of long-term operation of nuclear fusion reactors (design life is usually 30 to 50 years). Ferritic heat-resistant steel: mainly used in helium-cooled cladding modules. Compared with austenitic steel, it has lower irradiation swelling sensitivity, but still faces the key technical bottleneck of hydrogen permeation. Low-activation ferritic / martensitic steel (RAFM steel) has become the most promising candidate material among current fusion reactor structural materials due to its low neutron activation characteristics (low radioactive residue after irradiation, which facilitates later decommissioning), good resistance to irradiation swelling, and moderate high-temperature mechanical properties.

[0006] Despite the significant advantages of RAFM steel, its high hydrogen isotope permeability severely restricts its application: the permeation and diffusion of hydrogen (H), deuterium (D), and tritium (T) in RAFM steel is primarily bulk diffusion, significantly affected by temperature—increasing temperature accelerates the migration rate of hydrogen atoms in the crystal lattice, leading to a substantial increase in steady-state permeation flux (e.g., the permeation flux can increase by 1 to 2 orders of magnitude when the temperature rises from 300℃ to 500℃). Although studies have shown that oxide films formed on the material surface (such as Fe3O4, Cr2O3) or internal defects (such as dislocations and grain boundaries) can reduce permeation flux to some extent by trapping hydrogen atoms, the original oxide films usually have defects such as pores and cracks, resulting in limited trapping effects and difficulty in long-term stability. Hydrogen permeation can trigger a series of serious problems: Tritium loss and fuel self-sustaining failure: Tritium, as a key fuel for nuclear fusion reactions, needs to be continuously generated by breeder materials within the TBM. If hydrogen (tritium) permeates through the RAFM steel into the coolant (such as helium or water) or the reactor vacuum region, it will lead to a large loss of tritium. According to calculations, if the tritium leakage rate exceeds 1%, it will be unable to meet the fuel consumption requirements of the thermonuclear reaction, directly breaking the "tritium self-sustaining cycle" and causing the nuclear fusion device to lose the basis for continuous operation. Material performance degradation and safety risks: Hydrogen atoms penetrating into steel tend to accumulate at grain boundaries, dislocations, defects, and other sites, forming hydrogen molecules (H2) or hydrides (such as FeH2). X This generates internal stress, leading to hydrogen embrittlement (manifested as decreased material plasticity, reduced fracture toughness, and even sudden fracture without significant external force). At the same time, the interaction between hydrogen and alloying elements in steel may exacerbate corrosion, further reducing its mechanical properties and structural integrity. In severe cases, it may cause safety accidents such as TBM leakage, threatening the overall safety of the reactor.

[0007] Therefore, there is an urgent need to develop a new type of low-activation steel that can avoid the thermal instability of carbides and the hazards of coarse TiN inclusions, while also possessing excellent hydrogen barrier properties. To address these issues, existing technological approaches mainly suffer from the following limitations: First, regarding hydrogen permeation prevention, although surface coatings (such as Al2O3) and self-healing oxide layer technologies have been extensively studied, these coatings are prone to peeling and failure under complex thermal cycling and strong neutron irradiation, failing to guarantee service reliability for decades. Therefore, developing 'bulk hydrogen barrier' materials that capture hydrogen through the internal microstructure of the matrix is ​​a better option.

[0008] Secondly, in terms of improving high-temperature mechanical properties, traditional low-activation steels mainly rely on carbides (such as M23C6 or MX-type carbides) for strengthening. However, carbides have poor thermal stability at temperatures exceeding 600°C and are prone to Ostwald ripening (grain coarsening), leading to a sharp decrease in dislocation pinning and material softening. Although oxide dispersion strengthened (ODS) steels have excellent properties, their powder metallurgy preparation process is expensive and difficult to scale up for the production of large components.

[0009] Third, in order to refine the grain size, some existing technologies attempt to add about 0.1% titanium (Ti) to steel. However, in nitrogen-containing systems, titanium readily combines with nitrogen to form coarse, micron-sized TiN square inclusions. These large inclusions not only fail to provide strengthening but also become breeding grounds for crack initiation, severely impairing the impact toughness and processing performance of the steel.

[0010] Therefore, there is an urgent need to develop a new type of low-activation steel that does not contain titanium and can be strengthened by replacing unstable carbides with "high thermal stability nitrides" (such as VN and TaN). This steel should be able to achieve large-scale smelting and preparation while also taking into account excellent high-temperature creep resistance and hydrogen permeation resistance. Summary of the Invention

[0011] This invention provides a high thermal stability nitride-reinforced high hydrogen permeation barrier low activation steel and its production method. By adopting the technical approach of "precisely controlling the N / V / Ta ratio + nano-nitride dispersion strengthening", it overcomes the limitations of poor thermal stability of carbides and coarse TiN inclusions in traditional low activation steel, and obtains a new type of low activation steel with high thermal stability VN and TaN nitrides as the main strengthening phases, while also having excellent hydrogen permeation barrier performance and high temperature creep resistance.

[0012] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a high thermal stability nitride-reinforced high hydrogen permeation barrier low activation steel, wherein the chemical element mass fraction of the low activation steel meets the following requirements: C: 0.09-0.12%, Si: 0.2-0.3%, Mn: 0.4-0.6%, Cr: 8.0-8.7%, V: 0.2-0.4%, W: 1.0-1.5%, Ta: 0.1-0.15%, N: 0.02-0.05%, Y: 0.01-0.03%, Ti≤0.005%, with the balance being Fe and unavoidable impurities.

[0013] The low-activation steel of this invention has an N / V mass fraction ratio of 0.05 to 0.25 and an N / Ti mass fraction ratio of ≥4. The microstructure is tempered martensite, free of TiN inclusions with a size ≥500 nm. The reinforcing phases are nano-sized vanadium-rich nitride (VN) and tantalum-rich nitride (TaN), wherein the average size of VN and TaN particles is controlled within the range of 50 to 200 nm, and the volume fraction of VN and TaN is 2 to 5%.

[0014] The low-activation steel described in this invention possesses excellent hydrogen permeation resistance and high-temperature mechanical properties, with a hydrogen permeation flux of (2.4633~2.5807)×10⁻⁶. −12 mol·H·m -2 ·s -1 At 650℃, the yield strength is 400MPa~450MPa and the elongation is 15%~20%.

[0015] The present invention also provides a method for producing the above-mentioned high thermal stability nitride-reinforced high hydrogen permeation-resistant low activation steel. The final product of the production method is hot-rolled plate, which is prepared by the following steps: vacuum induction melting, protective atmosphere electroslag remelting, forging, rolling, and heat treatment. The heat treatment steps include normalizing and tempering. The normalizing process is held at 1080-1120℃ for 0.5-1 hour and then air-cooled. The tempering process is held at 650-740℃ for 1-2 hours and then air-cooled.

[0016] The vacuum induction melting process described in this invention involves: using a 500kg vacuum induction furnace (VIM), controlling the vacuum level at 0.05–0.15 Pa, and controlling the melting temperature at 1600–1700℃; and at the end of the refining stage, introducing high-purity nitrogen for micro-alloying, with the nitrogen flow rate controlled at 10–30 m³ / h. 3 / h, nitrogen purging time is controlled at 10-20min to ensure that the added elements are fully dissolved; finally, it is cast into a φ200mm consumable electrode.

[0017] The protective atmosphere electroslag remelting process of this invention uses argon as the protective gas, and the argon flow rate is controlled at 5-10 m³ / h. 3 / h; the electroslag remelting voltage is controlled at 35-45V and the current is controlled at 800-1200A to maintain the slag pool temperature at 1900-2000℃; the φ200mm consumable electrode is remelted into a φ300mm electroslag ingot, and the solidification structure is refined by using a forced cooling crystallizer, with the cooling water flow rate controlled at 80-120L / min to further remove harmful impurities such as sulfur and phosphorus.

[0018] The forging process described in this invention involves heating the electroslag ingot to 1100–1150°C and holding it at that temperature for at least 2 hours to ensure the metal is heated thoroughly and uniformly; then, an 800-ton hydraulic press is used for initial forging, with the strain rate controlled at 0.01 s. -1 ~0.1s -1 The forging process is carried out in stages to achieve a total forging ratio of ≥3, and the billet is forged into a 140mm×140mm square billet. During the forging process, the billet temperature is maintained at ≥850℃, and the billet is naturally cooled to room temperature after forging.

[0019] The rolling process described in this invention is as follows: the billet is reheated to 1100℃ and held for 2 hours; a 550 strip mill is used for multi-pass hot rolling, with the reduction in each pass controlled at 15-25%; during the rolling process, the billet temperature needs to be reheated to 950-1000℃ for every 50℃ drop; the total rolling ratio of the multi-pass rolling is ≥2; the final rolling temperature is controlled at 850±20℃; and the hot-rolled plate with a thickness of 18mm is obtained by natural cooling after rolling.

[0020] The beneficial effects of adopting the above technical solution are as follows: 1. This invention eliminates titanium (Ti≤0.005%), completely eliminating the risk of coarse TiN formation and ensuring that nitrogen atoms can fully combine with V and Ta to form fine and dispersed nitrides. 2. This invention introduces nitrogen (0.02~0.05%) to form VN and TaN. Compared with carbides, nitrides have a more negative formation energy and a higher melting point (VN melting point is about 2177℃). At a high temperature of 650℃, the diffusion coefficient is 1-2 orders of magnitude lower than that of carbides, thus possessing extremely high "anti-coarsening ability". 3. This invention adds rare earth Y (0.01-0.03%) to leverage the synergistic effect of N and Y, further optimizing the "size-distribution" characteristics of the second phase, avoiding nitride coarsening or agglomeration, and maximizing the dispersion strengthening effect: while Y forms Y2S3 and YP with impurities such as S and P to purify the molten steel, it can also use Y2O3 as the nucleation core of nitrides, promoting the nucleation of nitrides and refining the particle size of VN and TaN. Attached Figure Description

[0021] Figure 1 This is a scanning electron microscope image of the low-activation steel from Example 1. Detailed Implementation

[0022] The present invention will be further described in detail below with reference to specific embodiments. Example 1

[0023] The production method of high thermal stability nitride-reinforced high hydrogen permeation barrier and low activation steel, the final product being hot-rolled sheet, is prepared through the following processes: vacuum induction melting, protective atmosphere electroslag remelting, forging, rolling, and heat treatment; specific control methods are as follows: 1) Vacuum Induction Melting: High-purity industrial pure iron, metallic chromium, ferrovanadium, pure tantalum, pure yttrium, ferrotungsten, low-carbon ferromanganese, and ferrosilicon are selected as raw materials. Raw materials are rigorously screened to avoid introducing titanium (Ti) impurities, ensuring that the Ti content in the final product is ≤0.005%. A 500kg vacuum induction furnace (VIM) is used, with the vacuum degree controlled at 0.05Pa and the melting temperature controlled at 1640℃. High-purity nitrogen is introduced at the end of the refining process for micro-alloying, with the nitrogen flow rate controlled at 10m³ / min. 3 / h, nitrogen purging time is controlled at 13min to ensure that the added elements are fully dissolved; finally, it is cast into a φ200mm consumable electrode.

[0024] 2) Protective atmosphere electroslag remelting: Argon is used as the protective gas, and the argon flow rate is controlled at 5m³ / h. 3 / h; the electroslag remelting voltage is controlled at 45V and the current is controlled at 800A to maintain the slag pool temperature at 1908℃; the φ200mm consumable electrode is remelted into a φ300mm electroslag ingot, and the solidification structure is refined by using a forced cooling crystallizer, with the cooling water flow rate controlled at 100L / min to further remove harmful impurities such as sulfur and phosphorus.

[0025] 3) Forging process: The electroslag ingot is heated to 1100℃ and held for 3.8 hours to ensure the metal is heated fully and evenly; an 800-ton hydraulic press is used for billet forging, with the strain rate controlled at 0.055s. -1 The forging process is carried out in stages to achieve a total forging ratio of 3, and the billet is forged into a 140mm×140mm square billet. The billet temperature is maintained at 895℃ during the forging process, and it is naturally cooled to room temperature after forging.

[0026] 4) Rolling process: The billet is reheated to 1100℃ and held for 2 hours; a 550 strip mill is used for multi-pass hot rolling, with the reduction in each pass controlled at 15%. During the rolling process, the billet temperature needs to be reheated to 975℃ every time it drops by 50℃; the total rolling ratio of the multi-pass rolling is 2, and the final rolling temperature is controlled at 840℃. After rolling, the billet is naturally cooled to obtain a hot-rolled plate with a thickness of 18mm.

[0027] 5) Heat treatment process: including normalizing and tempering. The normalizing process is to hold at 1080℃ for 0.5 hours and then air cool; the tempering process is to hold at 650℃ for 1 hour and then air cool.

[0028] The chemical composition of the low-activation steel in this embodiment is shown in Table 1, and the performance indicators are shown in Table 2. Example 2

[0029] The production method of high thermal stability nitride-reinforced high hydrogen permeation barrier and low activation steel, the final product being hot-rolled sheet, is prepared through the following processes: vacuum induction melting, protective atmosphere electroslag remelting, forging, rolling, and heat treatment; specific control methods are as follows: 1) Vacuum Induction Melting: High-purity industrial pure iron, metallic chromium, ferrovanadium, pure tantalum, pure yttrium, ferrotungsten, low-carbon ferromanganese, and ferrosilicon are selected as raw materials. Raw materials are rigorously screened to avoid introducing titanium (Ti) impurities, ensuring that the Ti content in the final product is ≤0.005%. A 500kg vacuum induction furnace (VIM) is used, with the vacuum degree controlled at 0.15Pa and the melting temperature controlled at 1673℃. High-purity nitrogen is introduced at the end of the refining process for micro-alloying, with the nitrogen flow rate controlled at 20m³ / h. 3 / h, nitrogen purging time is controlled at 19min to ensure that the added elements are fully dissolved; finally, it is cast into a φ200mm consumable electrode.

[0030] 2) Protective atmosphere electroslag remelting: Argon is used as the protective gas, and the argon flow rate is controlled at 8m³ / min. 3 / h; the electroslag remelting voltage is controlled at 44V and the current is controlled at 1000A to maintain the slag pool temperature at 1995℃; the φ200mm consumable electrode is remelted into a φ300mm electroslag ingot, and the solidification structure is refined by using a forced cooling crystallizer, with the cooling water flow rate controlled at 80L / min to further remove harmful impurities such as sulfur and phosphorus.

[0031] 3) Forging process: The electroslag ingot is heated to 1150℃ and held for 3 hours to ensure the metal is heated fully and evenly; an 800-ton hydraulic press is used for billet forging, with the strain rate controlled at 0.095s. -1 The steel billet is forged in stages to achieve a total forging ratio of 3.3, and forged into a 140mm×140mm square billet. The billet temperature is maintained at 925℃ during the forging process, and it is naturally cooled to room temperature after forging.

[0032] 4) Rolling process: The billet is reheated to 1100℃ and held for 2 hours; a 550 strip mill is used for multi-pass hot rolling, with the reduction in each pass controlled at 25%. During the rolling process, the billet temperature needs to be reheated to 970℃ every time it drops by 50℃; the total rolling ratio of the multi-pass rolling is 2.5, and the final rolling temperature is controlled at 835℃. After rolling, the billet is naturally cooled to obtain a hot-rolled plate with a thickness of 18mm.

[0033] 5) Heat treatment process: including normalizing and tempering. The normalizing process is to hold at 1120℃ for 1 hour and then air cool; the tempering process is to hold at 740℃ for 1.5 hours and then air cool.

[0034] The chemical composition of the low-activation steel in this embodiment is shown in Table 1, and the performance indicators are shown in Table 2. Example 3

[0035] The production method of high thermal stability nitride-reinforced high hydrogen permeation barrier and low activation steel, the final product being hot-rolled sheet, is prepared through the following processes: vacuum induction melting, protective atmosphere electroslag remelting, forging, rolling, and heat treatment; specific control methods are as follows: 1) Vacuum Induction Melting: High-purity industrial pure iron, metallic chromium, ferrovanadium, pure tantalum, pure yttrium, ferrotungsten, low-carbon ferromanganese, and ferrosilicon are selected as raw materials. Raw materials are rigorously screened to avoid introducing titanium (Ti) impurities, ensuring that the Ti content in the final product is ≤0.005%. A 500kg vacuum induction furnace (VIM) is used, with the vacuum level controlled at 0.1Pa and the melting temperature controlled at 1645℃. High-purity nitrogen is introduced at the end of the refining process for micro-alloying, with the nitrogen flow rate controlled at 30m³. 3 / h, nitrogen purging time is controlled at 16min to ensure that the added elements are fully dissolved; finally, it is cast into a φ200mm consumable electrode.

[0036] 2) Protective atmosphere electroslag remelting: Argon is used as the protective gas, and the argon flow rate is controlled at 10 m³ / s. 3 / h; the electroslag remelting voltage is controlled at 43V and the current is controlled at 900A to maintain the slag pool temperature at 1965℃; the φ200mm consumable electrode is remelted into a φ300mm electroslag ingot, and the solidification structure is refined by using a forced cooling crystallizer, with the cooling water flow rate controlled at 120L / min to further remove harmful impurities such as sulfur and phosphorus.

[0037] 3) Forging process: The electroslag ingot is heated to 1146℃ and held for 3.5 hours to ensure the metal is heated fully and evenly; an 800-ton hydraulic press is used for billet forging, with the strain rate controlled at 0.03s. -1 The forging process is carried out in stages to achieve a total forging ratio of 4, and the billet is forged into a 140mm×140mm square billet. The billet temperature is maintained at 945℃ during the forging process, and it is naturally cooled to room temperature after forging.

[0038] 4) Rolling process: The billet is reheated to 1100℃ and held for 2 hours; a 550 strip mill is used for multi-pass hot rolling, with the reduction in each pass controlled at 20%. During the rolling process, the billet temperature needs to be reheated to 968℃ every time it drops by 50℃; the total rolling ratio of the multi-pass rolling is 2.8, and the final rolling temperature is controlled at 865℃. After rolling, the billet is naturally cooled to obtain a hot-rolled plate with a thickness of 18mm.

[0039] 5) Heat treatment process: including normalizing and tempering. The normalizing process is to hold at 1100℃ for 0.7 hours and then air cool; the tempering process is to hold at 700℃ for 2 hours and then air cool.

[0040] The chemical composition of the low-activation steel in this embodiment is shown in Table 1, and the performance indicators are shown in Table 2. Example 4

[0041] The production method of high thermal stability nitride-reinforced high hydrogen permeation barrier and low activation steel, the final product being hot-rolled sheet, is prepared through the following processes: vacuum induction melting, protective atmosphere electroslag remelting, forging, rolling, and heat treatment; specific control methods are as follows: 1) Vacuum Induction Melting: High-purity industrial pure iron, metallic chromium, ferrovanadium, pure tantalum, pure yttrium, ferrotungsten, low-carbon ferromanganese, and ferrosilicon are selected as raw materials. Raw materials are rigorously screened to avoid introducing titanium (Ti) impurities, ensuring that the Ti content in the final product is ≤0.005%. A 500kg vacuum induction furnace (VIM) is used, with the vacuum level controlled at 0.1Pa and the melting temperature controlled at 1615℃. High-purity nitrogen is introduced at the end of the refining process for micro-alloying, with the nitrogen flow rate controlled at 25m³ / h. 3 / h, nitrogen purging time is controlled at 13min to ensure that the added elements are fully dissolved; finally, it is cast into a φ200mm consumable electrode.

[0042] 2) Protective atmosphere electroslag remelting: Argon is used as the protective gas, and the argon flow rate is controlled at 6m³ / min. 3 / h; the electroslag remelting voltage is controlled at 36V and the current is controlled at 850A to maintain the slag pool temperature at 1955℃; the φ200mm consumable electrode is remelted into a φ300mm electroslag ingot, and the solidification structure is refined by using a forced cooling crystallizer, with the cooling water flow rate controlled at 100L / min to further remove harmful impurities such as sulfur and phosphorus.

[0043] 3) Forging process: The electroslag ingot is heated to 1140℃ and held for 2 hours to ensure the metal is heated fully and evenly; an 800-ton hydraulic press is used for billet forging, with the strain rate controlled at 0.06s. -1 The steel billet is forged in stages to achieve a total forging ratio of 4.5, and forged into a 140mm×140mm square billet. The billet temperature is maintained at 950℃ during the forging process, and it is naturally cooled to room temperature after forging.

[0044] 4) Rolling process: The billet is reheated to 1100℃ and held for 2 hours; a 550 strip mill is used for multi-pass hot rolling, with the reduction in each pass controlled at 22%. During the rolling process, the billet temperature needs to be reheated to 985℃ every time it drops by 50℃; the total rolling ratio of the multi-pass rolling is 3, and the final rolling temperature is controlled at 855℃. After rolling, the billet is naturally cooled to obtain a hot-rolled plate with a thickness of 18mm.

[0045] 5) Heat treatment process: including normalizing and tempering. The normalizing process is to hold at 1120℃ for 0.5 hours and then air cool; the tempering process is to hold at 650℃ for 2 hours and then air cool.

[0046] The chemical composition of the low-activation steel in this embodiment is shown in Table 1, and the performance indicators are shown in Table 2. Example 5

[0047] The production method of high thermal stability nitride-reinforced high hydrogen permeation barrier and low activation steel, the final product being hot-rolled sheet, is prepared through the following processes: vacuum induction melting, protective atmosphere electroslag remelting, forging, rolling, and heat treatment; specific control methods are as follows: 1) Vacuum Induction Melting: High-purity industrial pure iron, metallic chromium, ferrovanadium, pure tantalum, pure yttrium, ferrotungsten, low-carbon ferromanganese, and ferrosilicon are selected as raw materials. Raw materials are rigorously screened to avoid introducing titanium (Ti) impurities, ensuring that the Ti content in the final product is ≤0.005%. A 500kg vacuum induction furnace (VIM) is used, with the vacuum level controlled at 0.1Pa and the melting temperature controlled at 1620℃. High-purity nitrogen is introduced at the end of the refining process for micro-alloying, with the nitrogen flow rate controlled at 15m³ / min. 3 / h, nitrogen purging time is controlled at 18min to ensure that the added elements are fully dissolved; finally, it is cast into a φ200mm consumable electrode.

[0048] 2) Protective atmosphere electroslag remelting: Argon is used as the protective gas, and the argon flow rate is controlled at 9m³ / h. 3 / h; the electroslag remelting voltage is controlled at 42V and the current is controlled at 1100A to maintain the slag pool temperature at 1910℃; the φ200mm consumable electrode is remelted into a φ300mm electroslag ingot, and the solidification structure is refined by using a forced cooling crystallizer, with the cooling water flow rate controlled at 110L / min to further remove harmful impurities such as sulfur and phosphorus.

[0049] 3) Forging process: The electroslag ingot is heated to 1105℃ and held for 2.5 hours to ensure the metal is heated fully and evenly; an 800-ton hydraulic press is used for billet forging, with the strain rate controlled at 0.03s. -1 The steel billet is forged in stages to achieve a total forging ratio of 5.2, and forged into a 140mm×140mm square billet. The billet temperature is maintained at 900℃ during the forging process, and it is naturally cooled to room temperature after forging.

[0050] 4) Rolling process: The billet is reheated to 1100℃ and held for 2 hours; a 550 strip mill is used for multi-pass hot rolling, with the reduction in each pass controlled at 18%. During the rolling process, the billet temperature needs to be reheated to 990℃ every time it drops by 50℃; the total rolling ratio of the multi-pass rolling is 3.2, and the final rolling temperature is controlled at 860℃. After rolling, the billet is naturally cooled to obtain a hot-rolled plate with a thickness of 18mm.

[0051] 5) Heat treatment process: including normalizing and tempering. The normalizing process is to hold at 1080℃ for 1 hour and then air cool; the tempering process is to hold at 740℃ for 2 hours and then air cool.

[0052] The chemical composition of the low-activation steel in this embodiment is shown in Table 1, and the performance indicators are shown in Table 2. Example 6

[0053] The production method of high thermal stability nitride-reinforced high hydrogen permeation barrier and low activation steel, the final product being hot-rolled sheet, is prepared through the following processes: vacuum induction melting, protective atmosphere electroslag remelting, forging, rolling, and heat treatment; specific control methods are as follows: 1) Vacuum Induction Melting: High-purity industrial pure iron, metallic chromium, ferrovanadium, pure tantalum, pure yttrium, ferrotungsten, low-carbon ferromanganese, and ferrosilicon are selected as raw materials. Raw materials are rigorously screened to avoid introducing titanium (Ti) impurities, ensuring that the Ti content in the final product is ≤0.005%. A 500kg vacuum induction furnace (VIM) is used, with the vacuum level controlled at 0.1Pa and the melting temperature controlled at 1680℃. High-purity nitrogen is introduced at the end of the refining process for micro-alloying, with the nitrogen flow rate controlled at 25m³ / h. 3 / h, nitrogen purging time is controlled at 15min to ensure that the added elements are fully dissolved; finally, it is cast into a φ200mm consumable electrode.

[0054] 2) Protective atmosphere electroslag remelting: Argon is used as the protective gas, and the argon flow rate is controlled at 7m³ / h. 3 / h; the electroslag remelting voltage is controlled at 40V and the current is controlled at 900A to maintain the slag pool temperature at 1980℃; the φ200mm consumable electrode is remelted into a φ300mm electroslag ingot, and the solidification structure is refined by using a forced cooling crystallizer, with the cooling water flow rate controlled at 105L / min to further remove harmful impurities such as sulfur and phosphorus.

[0055] 3) Forging process: The electroslag ingot is heated to 1130℃ and held for 3 hours to ensure the metal is heated fully and evenly; an 800-ton hydraulic press is used for billet forging, with the strain rate controlled at 0.04s. -1 The steel billet is forged in stages to achieve a total forging ratio of 5.6, and forged into a 140mm×140mm square billet. The billet temperature is maintained at 895℃ during the forging process, and it is naturally cooled to room temperature after forging.

[0056] 4) Rolling process: The billet is reheated to 1100℃ and held for 2 hours; a 550 strip mill is used for multi-pass hot rolling, with the reduction in each pass controlled at 22%. During the rolling process, the billet temperature needs to be reheated to 965℃ every time it drops by 50℃; the total rolling ratio of the multi-pass rolling is 3.6, and the final rolling temperature is controlled at 855℃. After rolling, the billet is naturally cooled to obtain a hot-rolled plate with a thickness of 18mm.

[0057] 5) Heat treatment process: including normalizing and tempering. The normalizing process is to hold at 1090℃ for 0.8 hours and then air cool; the tempering process is to hold at 680℃ for 2 hours and then air cool.

[0058] The chemical composition of the low-activation steel in this embodiment is shown in Table 1, and the performance indicators are shown in Table 2. Example 7

[0059] The production method of high thermal stability nitride-reinforced high hydrogen permeation barrier and low activation steel, the final product being hot-rolled sheet, is prepared through the following processes: vacuum induction melting, protective atmosphere electroslag remelting, forging, rolling, and heat treatment; specific control methods are as follows: 1) Vacuum Induction Melting: High-purity industrial pure iron, metallic chromium, ferrovanadium, pure tantalum, pure yttrium, ferrotungsten, low-carbon ferromanganese, and ferrosilicon are selected as raw materials. Raw materials are rigorously screened to avoid introducing titanium (Ti) impurities, ensuring that the Ti content in the final product is ≤0.005%. A 500kg vacuum induction furnace (VIM) is used, with the vacuum level controlled at 0.1Pa and the melting temperature controlled at 1650℃. High-purity nitrogen is introduced at the end of the refining process for micro-alloying, with the nitrogen flow rate controlled at 28m³ / min. 3 / h, nitrogen purging time is controlled at 12min to ensure that the added elements are fully dissolved; finally, it is cast into a φ200mm consumable electrode.

[0060] 2) Protective atmosphere electroslag remelting: Argon is used as the protective gas, and the argon flow rate is controlled at 6m³ / min. 3 / h; the electroslag remelting voltage is controlled at 38V and the current is controlled at 950A to maintain the slag pool temperature at 1900℃; the φ200mm consumable electrode is remelted into a φ300mm electroslag ingot, and the solidification structure is refined by using a forced cooling crystallizer, with the cooling water flow rate controlled at 108L / min to further remove harmful impurities such as sulfur and phosphorus.

[0061] 3) Forging process: The electroslag ingot is heated to 1150℃ and held for 3.5 hours to ensure the metal is heated fully and evenly; an 800-ton hydraulic press is used for billet forging, with the strain rate controlled at 0.05s. -1 The steel billet is forged in stages to achieve a total forging ratio of 4.8, and forged into a 140mm×140mm square billet. The billet temperature is maintained at 880℃ during the forging process, and it is naturally cooled to room temperature after forging.

[0062] 4) Rolling process: The billet is reheated to 1100℃ and held for 2 hours; a 550 strip mill is used for multi-pass hot rolling, with the reduction in each pass controlled at 24%. During the rolling process, the billet temperature needs to be reheated to 980℃ every time it drops by 50℃; the total rolling ratio of the multi-pass rolling is 4.1, and the final rolling temperature is controlled at 830℃. After rolling, the billet is naturally cooled to obtain a hot-rolled plate with a thickness of 18mm.

[0063] 5) Heat treatment process: including normalizing and tempering. The normalizing process is to hold at 1080℃ for 1 hour and then air cool; the tempering process is to hold at 740℃ for 2 hours and then air cool.

[0064] The chemical composition of the low-activation steel in this embodiment is shown in Table 1, and the performance indicators are shown in Table 2. Example 8

[0065] The production method of high thermal stability nitride-reinforced high hydrogen permeation barrier and low activation steel, the final product being hot-rolled sheet, is prepared through the following processes: vacuum induction melting, protective atmosphere electroslag remelting, forging, rolling, and heat treatment; specific control methods are as follows: 1) Vacuum Induction Melting: High-purity industrial pure iron, metallic chromium, ferrovanadium, pure tantalum, pure yttrium, ferrotungsten, low-carbon ferromanganese, and ferrosilicon are selected as raw materials. Raw materials are rigorously screened to avoid introducing titanium (Ti) impurities, ensuring that the Ti content in the final product is ≤0.005%. A 500kg vacuum induction furnace (VIM) is used, with the vacuum level controlled at 0.1Pa and the melting temperature controlled at 1700℃. High-purity nitrogen is introduced at the end of the refining process for micro-alloying, with the nitrogen flow rate controlled at 12m³ / min. 3 / h, nitrogen purging time is controlled at 20min to ensure that the added elements are fully dissolved; finally, it is cast into a φ200mm consumable electrode.

[0066] 2) Protective atmosphere electroslag remelting: Argon is used as the protective gas, and the argon flow rate is controlled at 5m³ / h. 3 / h; the electroslag remelting voltage is controlled at 35V and the current is controlled at 980A to maintain the slag pool temperature at 2000℃; the φ200mm consumable electrode is remelted into a φ300mm electroslag ingot, and the solidification structure is refined by using a forced cooling crystallizer, with the cooling water flow rate controlled at 88L / min to further remove harmful impurities such as sulfur and phosphorus.

[0067] 3) Forging process: The electroslag ingot is heated to 1100℃ and held for 4 hours to ensure the metal is heated fully and evenly; an 800-ton hydraulic press is used for billet forging, with the strain rate controlled at 0.1s. -1 The steel billet is forged in stages to achieve a total forging ratio of 5.8, and forged into a 140mm×140mm square billet. The billet temperature is maintained at 850℃ during the forging process, and it is naturally cooled to room temperature after forging.

[0068] 4) Rolling process: The billet is reheated to 1100℃ and held for 2 hours; a 550 strip mill is used for multi-pass hot rolling, with the reduction in each pass controlled at 19%. During the rolling process, the billet temperature needs to be reheated to 1000℃ every time it drops by 50℃; the total rolling ratio of the multi-pass rolling is 4, and the final rolling temperature is controlled at 870℃. After rolling, the billet is naturally cooled to obtain a hot-rolled plate with a thickness of 18mm.

[0069] 5) Heat treatment process: including normalizing and tempering. The normalizing process is to hold at 1110℃ for 0.6 hours and then air cool; the tempering process is to hold at 720℃ for 2 hours and then air cool.

[0070] The chemical composition of the low-activation steel in this embodiment is shown in Table 1, and the performance indicators are shown in Table 2. Example 9

[0071] The production method of high thermal stability nitride-reinforced high hydrogen permeation barrier and low activation steel, the final product being hot-rolled sheet, is prepared through the following processes: vacuum induction melting, protective atmosphere electroslag remelting, forging, rolling, and heat treatment; specific control methods are as follows: 1) Vacuum Induction Melting: High-purity industrial pure iron, metallic chromium, ferrovanadium, pure tantalum, pure yttrium, ferrotungsten, low-carbon ferromanganese, and ferrosilicon are selected as raw materials. Raw materials are rigorously screened to avoid introducing titanium (Ti) impurities, ensuring that the Ti content in the final product is ≤0.005%. A 500kg vacuum induction furnace (VIM) is used, with the vacuum level controlled at 0.1Pa and the melting temperature controlled at 1600℃. High-purity nitrogen is introduced at the end of the refining process for micro-alloying, with the nitrogen flow rate controlled at 24m³ / h. 3 / h, nitrogen purging time is controlled at 10min to ensure that the added elements are fully dissolved; finally, it is cast into a φ200mm consumable electrode.

[0072] 2) Protective atmosphere electroslag remelting: Argon is used as the protective gas, and the argon flow rate is controlled at 5.5 m³ / s. 3 / h; the electroslag remelting voltage is controlled at 45V and the current is controlled at 1200A to maintain the slag pool temperature at 1950℃; the φ200mm consumable electrode is remelted into a φ300mm electroslag ingot, and the solidification structure is refined by using a forced cooling crystallizer, with the cooling water flow rate controlled at 112L / min to further remove harmful impurities such as sulfur and phosphorus.

[0073] 3) Forging process: The electroslag ingot is heated to 1120℃ and held for 4 hours to ensure the metal is heated fully and evenly; an 800-ton hydraulic press is used for billet forging, with the strain rate controlled at 0.01s. -1 The steel billet is forged in stages to achieve a total forging ratio of 4.6, and forged into a 140mm×140mm square billet. The billet temperature is maintained at 900℃ during the forging process, and it is naturally cooled to room temperature after forging.

[0074] 4) Rolling process: The billet is reheated to 1100℃ and held for 2 hours; a 550 strip mill is used for multi-pass hot rolling, with the reduction in each pass controlled at 16%. During the rolling process, the billet temperature needs to be reheated to 950℃ every time it drops by 50℃; the total rolling ratio of the multi-pass rolling is 3.4, and the final rolling temperature is controlled at 850℃. After rolling, the billet is naturally cooled to obtain a hot-rolled plate with a thickness of 18mm.

[0075] 5) Heat treatment process: including normalizing and tempering. The normalizing process is to hold at 1105℃ for 0.9 hours and then air cool; the tempering process is to hold at 690℃ for 2 hours and then air cool.

[0076] The chemical composition of the low-activation steel in this embodiment is shown in Table 1, and the performance indicators are shown in Table 2. Table 1 Chemical composition (mass fraction) and performance indicators of each embodiment

[0077] Table 2 Performance Indicators of Low-Activation Steel in Each Example

[0078] The microstructure of Example 1 was tempered martensite with an average grain size of approximately (5–10) μm. The average size of the precipitates at the grain boundaries ranged from (50–120) nm, and the volume fraction of each second phase particle was in the range of (2.2–3.1)%, consisting entirely of VN and TaN nitrides. No TiN inclusions larger than 100 nm were detected. Scanning electron microscope images are shown below. Figure 1 The scanning electron microscopy observations of the microstructures of the other examples (2-9) were similar, all showing tempered martensite structure, with the main reinforcing phases being nanoscale VN and TaN nitrides, and the typical characteristics were consistent with those of Example 1.

[0079] The above embodiments are only used to illustrate and not limit the technical solutions of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the present invention without departing from the spirit and scope of the present invention. Any modifications or partial substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A high thermal stability nitride-reinforced high hydrogen permeation barrier and low activation steel, characterized in that: The chemical element mass fractions of the low-activation steel meet the following requirements: C: 0.09–0.12%, Si: 0.2–0.3%, Mn: 0.4–0.6%, Cr: 8.0–8.7%, V: 0.2–0.4%, W: 1.0–1.5%, Ta: 0.1–0.15%, N: 0.02–0.05%, Y: 0.01–0.03%, Ti ≤ 0.005%, with the balance being Fe and unavoidable impurities.

2. The high thermal stability nitride-reinforced high hydrogen permeation barrier low activation steel according to claim 1, characterized in that: The low-activation steel has an N / V mass fraction ratio of 0.05 to 0.25 and an N / Ti mass fraction ratio of ≥4. The microstructure is tempered martensite, free of TiN inclusions with a size ≥500 nm. The reinforcing phases are nano-sized vanadium-rich nitride (VN) and tantalum-rich nitride (TaN), with the average size of VN and TaN particles controlled in the range of 50 to 200 nm and the volume fraction of VN and TaN being 2 to 5%.

3. The high thermal stability nitride-reinforced high hydrogen permeation barrier low activation steel according to claim 1, characterized in that: The low-activation steel has excellent hydrogen permeation resistance and high-temperature mechanical properties, a hydrogen permeation flux of (2.4633-2.5807)×10 −12 mol·H·m -2 ·s -1 , a yield strength of 400-450 MPa at 650 DEG C, and an elongation of 15-20%.

4. A method for producing high thermal stability nitride-reinforced high hydrogen permeation-resistant low activation steel according to any one of claims 1-3, characterized in that: The final product of the production method is hot-rolled sheet, which is prepared through the following processes: vacuum induction melting, protective atmosphere electroslag remelting, forging, rolling, and heat treatment; the heat treatment process includes normalizing and tempering. The normalizing process is held at 1080-1120℃ for 0.5-1 hour and then air-cooled; the tempering process is held at 650-740℃ for 1-2 hours and then air-cooled.

5. The method for producing high thermal stability nitride-reinforced high hydrogen permeation-resistant low activation steel according to claim 4, characterized in that: The vacuum induction melting process is as follows: the vacuum level is controlled at 0.05–0.15 Pa, and the melting temperature is controlled at 1600–1700 °C; high-purity nitrogen is introduced at the end of the refining stage for micro-alloying, and the nitrogen flow rate is controlled at 10–30 m³ / s. 3 / h, nitrogen filling time controlled at 10-20min; finally cast into a φ200mm consumable electrode.

6. The method for producing high thermal stability nitride-reinforced high hydrogen permeation-resistant low activation steel according to claim 4 or 5, characterized in that: The protective atmosphere electroslag remelting process uses argon as the protective gas, with the argon flow rate controlled at 5-10 m³ / h. 3 / h; the electroslag remelting voltage is controlled at 35-45V, the current is controlled at 800-1200A, and the slag pool temperature is maintained at 1900-2000℃; the φ200mm consumable electrode is remelted into a φ300mm electroslag ingot, and the solidification structure is refined by using a forced cooling crystallizer, with the cooling water flow rate controlled at 80-120L / min.

7. The method for producing high thermal stability nitride-reinforced high hydrogen permeation-resistant low activation steel according to claim 4 or 5, characterized in that: The forging process involves heating the electroslag ingot to 1100–1150°C and holding it at that temperature for at least 2 hours; then using an 800-ton hydraulic press for initial forging, with the strain rate controlled at 0.01 s. -1 ~0.1s -1 The forging process is carried out in stages to achieve a total forging ratio of ≥3, and the billet is forged into a square billet. During the forging process, the billet temperature is maintained at ≥850℃, and the billet is naturally cooled to room temperature after forging.

8. The method for producing high thermal stability nitride-reinforced high hydrogen permeation-resistant low activation steel according to claim 4 or 5, characterized in that: The rolling process is as follows: the reduction amount for each pass is controlled at 15-25%, and the billet temperature needs to be reheated to 950-1000℃ for every 50℃ drop during the rolling process; the total rolling ratio of multiple passes is ≥2, the final rolling temperature is controlled at 850±20℃, and the hot-rolled plate with a thickness of 18mm is obtained by natural cooling after rolling.

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