High stacking fault energy hydrogen embrittlement resistant austenitic stainless steel and vacuum preparation method thereof

Abstract

This invention provides a high-fault energy, hydrogen-embrittlement-resistant austenitic stainless steel and its vacuum preparation method. The invention employs a medium-manganese composition design, reducing Ni content while obtaining a high-fault energy austenitic matrix, effectively suppressing deformation-induced martensitic transformation. Simultaneously, by adding Nb, V, and Cu microalloying elements, combined with vacuum melting and temperature-controlled forging processes, high-density, dispersed nanoscale niobium-vanadium composite carbonitride precipitates and copper-rich phases are induced in the austenitic matrix. These precipitates are coherent or semi-coherent with the matrix, forming numerous irreversible hydrogen traps that uniformly pin hydrogen atoms, significantly reducing the hydrogen diffusion coefficient and hydrogen flux. This fundamentally suppresses hydrogen enrichment at sensitive sites such as grain boundaries, achieving a balance between high-fault energy and high resistance to hydrogen embrittlement.

Description

Technical Field

[0001] This invention relates to the field of austenitic stainless steel technology, specifically to a high-fault-resistant hydrogen-embrittled austenitic stainless steel and its vacuum preparation method. Background Technology

[0002] Austenitic stainless steel, due to its excellent corrosion resistance, good low-temperature toughness, and high work hardening ability, is widely used in critical structural components in hydrogen-environmentally exposed environments such as hydrogen energy storage and transportation, petrochemicals, and nuclear energy. However, long-term service experience has shown that austenitic stainless steel is prone to hydrogen embrittlement in high-pressure hydrogen or hydrogen-containing media, manifested as a significant decrease in plasticity and accelerated crack initiation and propagation rates, seriously threatening the safety and service life of equipment. With the rapid development of the hydrogen energy industry, the requirements for the hydrogen embrittlement resistance of hydrogen-environmentally exposed materials are increasing. How to effectively suppress hydrogen embrittlement while maintaining the excellent comprehensive properties of austenitic stainless steel has become a key technical problem that urgently needs to be solved in the field of materials science.

[0003] Hydrogen embrittlement is essentially the phenomenon where hydrogen atoms enter the metal matrix, triggering loss of plasticity and brittle fracture under stress. For austenitic stainless steel, the susceptibility to hydrogen embrittlement is closely related to its microstructure, mainly including the following aspects: (1) Stability of austenite and deformation-induced martensitic transformation During deformation, metastable austenitic stainless steel may undergo deformation-induced martensitic transformation due to the presence of austenite. The martensitic phase has a body-centered cubic or body-centered tetragonal structure, exhibiting low hydrogen solubility and high diffusion coefficient, making it highly susceptible to becoming a hydrogen accumulation channel and crack initiation site. Numerous studies have shown that higher austenite stability reduces the likelihood of deformation-induced martensitic transformation and minimizes plasticity loss under hydrogen-containing conditions. Therefore, improving austenite stability is one of the core principles of traditional hydrogen embrittlement resistance design.

[0004] (2) Stacking fault energy and hydrogen diffusion behavior Stacking fault energy (SFE) is a key parameter determining the deformation mechanism of austenitic stainless steel. Low SFE materials are prone to forming deformation twins and ε-martensite, while high SFE materials are dominated by dislocation plane slip. Recent studies have found an intrinsic link between SFE and hydrogen diffusion behavior: as SFE increases, dislocation arrangement tends to become planar, the diffusion rate of hydrogen atoms along dislocation channels accelerates, and the susceptibility to hydrogen-induced cracking increases. In other words, simply improving austenite stability (usually accompanied by increased SFE) may introduce new risks of hydrogen embrittlement.

[0005] (3) Hydrogen trap effect Various crystal defects in materials (such as dislocations, grain boundaries, vacancies, and precipitates) can serve as hydrogen trapping sites. Reversible hydrogen traps (such as dislocations) have weaker interactions with hydrogen, allowing hydrogen atoms to easily detach and diffuse into sensitive regions under stress. Irreversible hydrogen traps (such as nanoscale precipitates and oxide inclusion interfaces), on the other hand, can firmly pin hydrogen atoms, effectively suppressing long-range hydrogen diffusion and local enrichment. Therefore, introducing high-density, high-stability irreversible hydrogen traps is an effective way to improve resistance to hydrogen embrittlement.

[0006] Existing technologies mainly focus on three dimensions: component regulation, purity control, and tissue optimization; however, each has its own insurmountable limitations. (I) Hydrogen embrittlement prevention technology based on composition regulation Stabilizing austenitic microstructure and suppressing deformation-induced martensitic transformation by increasing Ni content (such as 316L, 310S, etc.) is currently the most commonly used technical solution. Ni is a strong austenite stabilizing element; every 1% increase in Ni significantly improves austenite stability. However, Ni is a strategic precious metal with highly volatile prices. High Ni content leads to high material costs, limiting its application in large-scale scenarios such as hydrogen energy storage and transportation. Furthermore, increased Ni content increases SFE (surface efflux), promoting hydrogen diffusion and accumulation, creating a contradictory situation of "suppressing martensitic transformation" versus "exacerbating hydrogen diffusion." Studies have shown that when SFE exceeds approximately 20 mJ / m², the situation becomes more complex. 2 Subsequently, the hydrogen embrittlement sensitivity actually increased with increasing SFE.

[0007] To reduce costs, some studies have attempted to partially replace Ni with Mn. Mn is also an austenite stabilizing element and can effectively improve SFE (sulfurization efficiency). However, existing manganese-for-nickel technology still has shortcomings: the addition of Mn increases the difficulty of controlling impurity elements such as P and S during the smelting process, and easily forms harmful inclusions such as MnS, which become sources of hydrogen accumulation; existing manganese-for-nickel steels often only focus on austenite stability and do not systematically consider the introduction of hydrogen traps, resulting in the failure to effectively solve the problem of aggravated hydrogen diffusion caused by high-level fault energies.

[0008] In recent years, a few studies have attempted to create carbonitride precipitates in steel as hydrogen traps by adding microalloying elements such as Nb, V, and Ti. This technology has been applied in low-alloy high-strength steels, but its application in austenitic stainless steel faces the following problems: the austenitic matrix has a strong solid solution capacity for alloying elements, and if the microalloying elements are not properly combined with hot working, they are prone to forming coarse primary precipitates, which not only fail to effectively pinn hydrogen but also impair the material's ductility and toughness; existing technologies mostly employ conventional hot working processes, failing to fully utilize the deformation-induced precipitation effect, resulting in uneven precipitate distribution and insufficient density, making it difficult to form an effective hydrogen trap network.

[0009] (II) Hydrogen embrittlement prevention technology based on purity control Vacuum induction melting (VIM) or vacuum arc remelting (VAR) can effectively reduce the gas content ([H], [O], [N]) and harmful impurities (P, S) in steel, thereby reducing the source of hydrogen. This technology has been applied in the production of high-quality stainless steel, but it still has shortcomings: relying solely on vacuum melting to reduce the total hydrogen content has a narrow process window, requires extremely high vacuum levels and long refining times, resulting in high costs, low efficiency, and difficulty in reducing the hydrogen content to the ideal level; even at extremely low levels, residual hydrogen may still cause hydrogen-induced cracking if it accumulates at sensitive locations such as grain boundaries, and current technologies lack effective means to control hydrogen distribution.

[0010] (III) Hydrogen embrittlement resistance technology based on tissue optimization Reversible hydrogen traps are introduced at dislocations, twin boundaries, and stacking faults through deformation processes such as cold rolling and warm rolling. This method is simple, but it has significant drawbacks: the dislocations and twins introduced by deformation are metastable structures, which are prone to recovery and recrystallization during high temperatures or long-term service, leading to a decrease in hydrogen trap density and a reduction in resistance to hydrogen embrittlement; large deformation amounts easily induce martensitic phase transformation, especially in metastable austenitic stainless steel, where deformation-induced martensite becomes a sensitive source of hydrogen embrittlement.

[0011] Aging treatment can induce the precipitation of alloying elements to form hydrogen traps, such as nitrides and carbides. However, existing technologies mostly employ a single heat treatment method, resulting in limited density and uniformity of precipitated phases, making it difficult to form a high-density irreversible hydrogen trap network.

[0012] In summary, existing technologies for hydrogen-resistant austenitic stainless steel share the following common technical problems: (1) The contradiction between high-level fault energy and resistance to hydrogen embrittlement has not been effectively reconciled: existing technologies either choose low SFE materials (which pose a risk of martensitic phase transformation) or high SFE materials (which pose a risk of increased hydrogen diffusion), and lack a system solution that takes both into account; cost and performance are difficult to balance: high Ni route has reliable performance but high cost, Mn-to-Ni route has reduced cost but insufficient resistance to hydrogen embrittlement, and existing technologies have not yet found a balance between low cost and high performance.

[0013] (2) Insufficient stability and density of hydrogen traps: Hydrogen traps introduced by traditional deformation are mostly reversible traps with poor stability, while the density of precipitated phase traps introduced by heat treatment is limited, making it difficult to effectively suppress hydrogen diffusion.

[0014] (3) Poor process synergy: Existing technologies mostly start from a single dimension (composition, smelting, thermal processing) and lack a systematic synergistic design of "composition-process-structure", making it difficult to achieve the unity of purity, structure stability and hydrogen trap control. Summary of the Invention

[0015] The purpose of this invention is to overcome the shortcomings and deficiencies of the existing technology and to provide a high-level fault-resistant hydrogen-resistant austenitic stainless steel and its vacuum preparation method.

[0016] The technical solution adopted by this invention is as follows: The first aspect of this invention provides a high-fault-resistant hydrogen-resistant austenitic stainless steel, which includes an austenitic matrix and a niobium-vanadium composite carbonitride precipitate phase and a copper-rich phase dispersed on the austenitic matrix, and its chemical composition by mass percentage is as follows: C: 0.02~0.08%, Mn: 4.0~8.0%, Cr: 17.0~21.0%, Ni: 7.0~11.0%, Mo: 0.5–2.0%, Cu: 1.0–3.0%, V: 0.05~0.25%, Nb: 0.03–0.20%, Si ≤ 0.5%, P ≤ 0.015%, S ≤ 0.005%, O ≤ 0.003%, The balance consists of Fe and unavoidable impurities.

[0017] A second aspect of the present invention provides a vacuum preparation method for high fault energy hydrogen-resistant austenitic stainless steel, comprising the following steps: S1. Vacuum induction melting: Iron-based raw materials, nickel source, chromium source, manganese source, molybdenum source and copper source are placed in the molten pool of a vacuum induction melting furnace, and the vacuum degree is controlled to be ≤0.1 Pa. After melting and refining, deoxidation is carried out, and then vanadium source, niobium source and carbon source are added for alloying. The steel ingot is then cast. S2. High-temperature homogenization treatment: Hold the steel ingot at 1150-1250℃ for 8-24 hours; S3. Temperature-controlled forging: Multiple forging passes are performed within a temperature range of 950-1150℃, with a cumulative deformation of ≥50% and a deformation of 10-20% per pass; S4. Solution treatment: Keep at 1000-1100℃ for 0.5-2 h and then cool. S5. Aging treatment: Keep at 500-700℃ for 2-8 hours and then cool.

[0018] Preferably, step S1 specifically includes the following steps: S1-1, Charging: Place the iron-based raw materials, nickel source, chromium source, manganese source, molybdenum source, and copper source into the molten pool of the vacuum induction melting furnace; S1-2, Melting: Close the furnace door, start the vacuum system, control the vacuum degree ≤0.1 Pa, turn on the power to heat, and gradually increase the power to 400-600 kW, and melt for 30-60 minutes; S1-3, Refining: Adjust the power to 250-450 kW, maintain the molten pool temperature at 1520-1550℃, control the vacuum degree at 0.03-0.08 Pa, and refine for 30-50 minutes; S1-4 Deoxidation and Alloying: Maintain a vacuum degree ≤0.1 Pa, stabilize the molten pool temperature at 1520~1540℃, add deoxidizer for deoxidation, stir for 1-5 minutes, add vanadium source and niobium source to the molten pool, and add carbon source at the same time. Set the power to 300-500 kW, set the molten pool temperature to 1550-1560℃, stir for 3-5 minutes, stop stirring, and let stand for 3-7 minutes; S1-5. Casting: Adjust the temperature of the molten pool to 1540-1550℃ and cast it into steel ingots under argon protection. The casting speed is 10-20 kg / s. After casting, the steel ingots are left to stand in the mold for 20-40 minutes, and then demolded and cooled.

[0019] Preferably, in steps S1-4, the vanadium source and niobium source are added after being preheated to 200-300°C.

[0020] Preferably, in steps S1-4, the deoxidizer is crystalline silicon or aluminum particles.

[0021] Preferably, in step S1, the iron-based raw material is pure iron, the nickel source is electrolytic nickel, the chromium source is ferrochrome or metallic chromium, the manganese source is electrolytic manganese, the molybdenum source is ferromolybdenum, and the copper source is electrolytic copper.

[0022] Preferably, in step S1, the vanadium source is ferrovanadium and the niobium source is ferroniobium.

[0023] Preferably, in step S1, the carbon source is graphite.

[0024] The beneficial effects of this invention are as follows: 1. This invention employs a medium manganese composition design (Mn 4.0–8.0%), achieving a high-level fault-energy austenitic matrix (SFE ≥ 28 mJ / m²) while reducing Ni content. 2 This effectively suppresses deformation-induced martensitic phase transformation. Simultaneously, by adding Nb, V, and Cu microalloying elements and combining vacuum melting and temperature-controlled forging processes, high-density, dispersed nanoscale niobium-vanadium composite carbonitride precipitates and copper-rich phases are induced in the austenitic matrix. These precipitates are coherent or semi-coherent with the matrix, forming numerous irreversible hydrogen traps that uniformly pin hydrogen atoms, significantly reducing the hydrogen diffusion coefficient (by approximately 68%) and hydrogen flux (by approximately 77%). This fundamentally suppresses hydrogen enrichment at sensitive locations such as grain boundaries, achieving a balance between high-level fault energy and high resistance to hydrogen embrittlement.

[0025] 2. This invention partially replaces expensive Ni with inexpensive Mn, reducing the alloy cost by approximately 15-20% compared to traditional 316L stainless steel. Simultaneously, through the fine-grain strengthening and precipitation strengthening effects generated by the nano-precipitates, the material's yield strength (≥315 MPa) and tensile strength (≥615 MPa) are superior to traditional high-nickel austenitic stainless steel, while maintaining an elongation at fracture of over 50%, achieving a synergistic improvement in low cost, high strength, and high plasticity.

[0026] 3. The nano-precipitated phase introduced in this invention is a thermodynamically stable irreversible hydrogen trap, which is not easily recovered or coarsened under high temperature (≤700℃) and long-term service conditions, overcoming the defects of traditional deformation-introduced metastable traps such as dislocations that are prone to recovery and failure. The hydrogen embrittlement sensitivity index (HEI) is as low as about 8%, far lower than the 42.5% of traditional 316L and the 38.2% of the scheme that only improves austenite stability, indicating that the material of this invention has excellent long-term service reliability in hydrogen-exposed environments.

[0027] 4. This invention achieves synergistic control of purity, microstructure uniformity, and hydrogen trap regulation through a combination of processes including vacuum melting, high-temperature homogenization, and temperature-controlled forging. Temperature-controlled forging (950–1150°C) fully utilizes the precipitation temperature window for Nb and V carbonitrides, and the multi-pass, small-deformation design effectively avoids localized overheating and microstructure inhomogeneity. The process window is wider than traditional precision temperature control processes, making it suitable for industrial-scale production. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in further detail below.

[0029] The raw materials used in the following embodiments and comparative examples are as follows: Iron-based raw materials: High-purity industrial pure iron (P ≤ 0.005%, S ≤ 0.003%), as the main source of iron; Nickel source: Electrolytic nickel (Ni ≥ 99.9%); Chromium source: low-sulfur, low-carbon ferrochrome (Cr ≥ 60%, C ≤ 0.10%, S ≤ 0.01%) or metallic chromium; Manganese source: Low-sulfur electrolytic manganese (Mn ≥ 99.7%, S ≤ 0.01%); Molybdenum source: Ferromolybdenum (Mo ≥ 60%); Copper source: Electrolytic copper (Cu ≥ 99.9%); Vanadium source: Ferrovanadium (V ≥ 50%); Niobium source: ferroniobium (Nb ≥ 65%); Carbon source: high-purity graphite (C ≥ 99.9%); Silicon source: crystalline silicon (Si ≥ 98%); Among them, impurities such as phosphorus, sulfur, oxygen, and nitrogen are controlled within the design range by selecting high-purity raw materials and vacuum refining process, and no additional elements are added.

[0030] Example 1 This embodiment provides a high-fault-resistant, hydrogen-embrittlement-resistant austenitic stainless steel and its vacuum preparation method. Its chemical composition, by mass percentage, is as follows: C: 0.052%; Mn: 5.18%; Cr: 18.63%; Ni: 8.47%; Mo: 1.21%; Cu: 1.98%; V: 0.12%; Nb: 0.09%; Si: 0.24%; P: 0.008%; S: 0.003%; [O]: 0.0022%; [N]: 0.008%; The balance consists of Fe and unavoidable impurities.

[0031] Its vacuum preparation method includes the following steps: S1, Vacuum Induction Melting S1-1 Charging: Calculate and weigh each raw material according to the design composition. Load high-purity industrial pure iron, electrolytic nickel, low-sulfur micro-carbon ferrochrome, low-sulfur electrolytic manganese, ferromolybdenum, and electrolytic copper into the crucible of the vacuum induction melting furnace (VIM). Load high-purity graphite into the graphite hopper for later use. Weigh crystalline silicon, ferrovanadium, and ferroniobium separately and place them in the feeder, and preheat to 200-300℃ for later use.

[0032] S1-2 Melting: Close the furnace door and start the vacuum system. When the vacuum level reaches 0.05 Pa, start powering on the heating. Gradually increase the power to 500 kW to completely melt the furnace charge. The melting time is approximately 45 minutes.

[0033] S1-3 Refining: After melting, adjust the power to 350 kW, maintain the molten pool temperature at 1520–1550℃, and refine for 40 minutes, stirring every 10 minutes during this period. Maintain the vacuum level at 0.03–0.08 Pa during the refining process. This stage involves deep deoxidation through a carbon deoxidation reaction, while simultaneously removing gases such as hydrogen and nitrogen.

[0034] S1-4 Deoxidation and Alloying: After refining, maintain a vacuum of ≤0.1 Pa and stabilize the molten pool temperature at 1520-1540℃. Add crystalline silicon or a small amount of aluminum particles (Al ≤ 0.01%) for final deoxidation and stir for 2 minutes. Add ferrovanadium and ferroniobium preheated to 200-300℃ to the molten pool through a feeder. At the same time, add high-purity graphite from the graphite hopper according to the designed carbon content. After adding, increase the power to 400 kW and raise the molten pool temperature to 1550-1560℃. Stir for 3-5 minutes to ensure that V and Nb are fully dissolved and evenly distributed. Stop stirring and let stand for 5 minutes to allow non-metallic inclusions to float to the surface.

[0035] S1-5 Casting: Adjust the temperature of the molten pool to 1540~1550℃, and cast it into steel ingots under argon protection. The casting speed is 15 kg / s. After casting, the steel ingots are left to stand in the mold for 30 minutes, then demolded and air-cooled to room temperature.

[0036] S2, High-temperature homogenization treatment The steel ingots were loaded into a high-temperature bogie-type resistance furnace and placed flat on the bottom pads to ensure uniform heating. The temperature was increased from room temperature to 600°C at a rate of 1°C / min and held for 1 hour. Then, the temperature was increased to 1200°C at a rate of 2°C / min and held at 1200°C for 12 hours. After the holding period, the temperature was cooled to 800°C in the furnace and then removed from the furnace and air-cooled to room temperature. This process eliminated dendrite segregation and allowed microalloying elements such as Nb and V to fully dissolve into the austenite matrix, providing a compositional basis for the dispersion precipitation of nano-sized carbonitrides during the subsequent temperature-controlled forging process.

[0037] S3, Temperature Controlled Forging After high-temperature homogenization, the steel ingots are cleaned and the risers are removed. Then, they undergo temperature-controlled forging on a high-speed forging mill: the ingots are placed in a bogie hearth preheated to 950℃, and the temperature is increased to 1080℃ at a rate of 2℃ / h, held for 2 hours to ensure uniform temperature throughout the ingot. The initial forging temperature is 1080℃, and the final forging temperature is ≥950℃. A multi-pass, small-deformation forging process is used. After forging, the billet is air-cooled to room temperature. The specific forging passes are arranged as shown in Table 1 below. Table 1 Forging process parameters for Example 1 Cumulative deformation calculation: The initial cross-sectional area is approximately 70650 mm², and the final cross-sectional area is approximately 20600 mm². The cumulative deformation is approximately 70.8% (70650-20600) / 70650.

[0038] Forging ratio: Forging ratio = Initial cross-sectional area / Final cross-sectional area ≈ 3.43:1.

[0039] Within the temperature range of 950–1080℃, Nb and V carbonitrides have the greatest nucleation driving force. Dynamic recrystallization and deformation-induced precipitation work together to form a uniformly dispersed nanoscale precipitate. Multiple small deformations avoid local overheating and uneven structure.

[0040] S4, Solution treatment After the forged billet is cut into appropriate sizes, it is placed in a box-type resistance furnace and heated to 1050℃. The holding time is calculated at 1.5 min / mm, and the actual holding time is 60 minutes. After the holding time is completed, it is taken out and water-quenched to room temperature.

[0041] S5, Timeliness Processing The solution-treated billet is placed in a box-type resistance furnace and heated to 600°C. After holding at that temperature for 4 hours, it is air-cooled to room temperature to promote the dispersion precipitation of the copper-rich phase. At the same time, the size and distribution of the niobium-vanadium composite carbonitride precipitate are controlled to keep it within the optimal hydrogen trap size range (10-50 nm).

[0042] Example 2 This embodiment provides a high-fault-resistant, hydrogen-embrittlement-resistant austenitic stainless steel and its vacuum preparation method. Its chemical composition, by mass percentage, is as follows: C: 0.041%; Mn: 6.02%; Cr: 17.88%; Ni: 7.96%; Mo: 1.52%; Cu: 1.51%; V: 0.08%; Nb: 0.14%; Si: 0.28%; P: 0.009%; S: 0.0035%; [O]: 0.0021%; [N]: 0.009%; The balance consists of Fe and unavoidable impurities.

[0043] The vacuum preparation method in this embodiment is the same as that in Embodiment 1.

[0044] Example 3 This embodiment provides a high-fault-resistant, hydrogen-embrittlement-resistant austenitic stainless steel and its vacuum preparation method. Its chemical composition, by mass percentage, is as follows: C: 0.058%; Mn: 4.48%; Cr: 19.23%; Ni: 9.02%; Mo: 0.98%; Cu: 2.48%; V: 0.18%; Nb: 0.07%; Si: 0.21%; P: 0.007%; S: 0.0025%; [O]: 0.0015%; [N]: 0.010%; The balance consists of Fe and unavoidable impurities.

[0045] The vacuum preparation method in this embodiment is the same as that in Embodiment 1.

[0046] Comparative Example 1 This comparative example uses commercially available 316L austenitic stainless steel, whose chemical composition by mass percentage is: C: 0.021%; Mn: 1.52%; Cr: 16.82%; Ni: 12.48; Mo: 2.13; Si: 0.38; P: 0.011; S: 0.003; [O]: 0.0045; The balance consists of Fe and unavoidable impurities.

[0047] In this comparative example, 316L austenitic stainless steel was subjected to the same solution treatment step as step S4 in Example 1.

[0048] Comparative Example 2 This comparative example provides an austenitic stainless steel and its vacuum preparation method, the chemical composition of which, by mass percentage, is as follows: C: 0.048; Mn: 6.02; Cr: 18.52; Ni: 8.97; Mo: 1.18; Si: 0.26; P: 0.009; S: 0.0038; [O]: 0.0031; The balance consists of Fe and unavoidable impurities.

[0049] The vacuum preparation method of this comparative example is basically the same as that of Example 1, except that step S5 is not performed, electrolytic copper is not added in step S1-1, and ferrovanadium and ferroniobium are not added in step S1-4.

[0050] Comparative Example 3 This comparative example provides an austenitic stainless steel and its vacuum preparation method, the chemical composition of which is the same as that of Example 1.

[0051] The vacuum preparation method of this comparative example is basically the same as that of Example 1, except that step S3 is carried out as follows: the steel ingot is placed in a bogie furnace preheated to 1200°C and freely forged in the temperature range of 900-1200°C, with a cumulative deformation of 70%, without controlling the deformation amount per pass or the heat preservation in the furnace.

[0052] Comparative Example 4 This comparative example provides an austenitic stainless steel and its vacuum preparation method, the chemical composition of which, by mass percentage, is as follows: C: 0.055; Mn: 1.02; Cr: 18.52; Ni: 13.48; Mo: 2.05; Cu: 2.02; V: 0.12; Nb: 0.10; Si: 0.25; P: 0.009; S: 0.003; [O]: 0.0025; The balance consists of Fe and unavoidable impurities.

[0053] The vacuum preparation method in this comparative example is the same as that in Example 1.

[0054] Stacking fault energy calculation The SFE values ​​of the samples prepared in Examples 1-3 and Comparative Examples 1-4 at 25°C were calculated using Thermo-Calc software in conjunction with the TCFE9 database. The calculation results are shown in Table 2 below.

[0055] Table 2. SFE values ​​of samples obtained in Examples 1-3 and Comparative Examples 1-4 The SFE of Examples 1-3 were all between 28.1 and 29.5 mJ / m 2 Within this range, it belongs to typical high-level fault-energy austenite; the SFE of comparative examples 1 and 4 are relatively low, at 19.2 mJ / m², respectively.2 and 16.5 mJ / m 2 .

[0056] Mechanical property testing Tensile tests were conducted at room temperature according to GB / T 228.1-2021 standard. The specimens were round bars with a gauge length of 25 mm and a gauge diameter of 5 mm. The strain rate was 5 × 10⁻⁶. -4 s -1 Three samples were tested under each condition, and the average value was taken. The results are shown in Table 3 below.

[0057] Table 3. Mechanical property test results of samples obtained in Examples 1-3 and Comparative Examples 1-4 The yield strength of Examples 1-3 (318–332 MPa) was significantly higher than that of Comparative Example 1 (285 MPa), with an increase of approximately 12–16%, mainly attributed to the dispersion strengthening and grain refinement of the nano-precipitates. The elongation after fracture of Examples 1-3 was ≥51.8%, indicating good plasticity, which was not significantly reduced by the introduction of the precipitates. Although Comparative Example 2 had mechanical properties close to the Examples, the lack of hydrogen traps resulted in insufficient resistance to hydrogen embrittlement. Comparative Example 4 exhibited high strength, but its low SFE (surface elasticity) increased susceptibility to martensitic transformation, which was detrimental to resistance to hydrogen embrittlement.

[0058] Hydrogen permeation performance test The electrochemical hydrogen permeation method using a dual-electrolysis cell was employed, and the test conditions were as follows: Sample size: Φ20 mm × 0.8 mm thin sheet, double-sided grinding to 2000# sandpaper; Hydrogen charging side: 0.2 mol / L NaOH + 0.5 g / L As₂O₃, current density 10 mA / cm² 2 ; Detection side: 0.2 mol / L NaOH, applied constant potential of 0.3 V vs. Hg / HgO; Test temperature: 25±0.5℃; Hydrogen diffusion coefficient D: calculated using the time lag method; Steady-state hydrogen flux J∞: Records the conversion of steady-state current density.

[0059] The test results are as follows: Table 4. Hydrogen permeation performance test results of samples obtained in Examples 1-3 and Comparative Examples 1-4 The hydrogen diffusion coefficient D of Examples 1-3 was only 1.09–1.36 × 10⁻¹¹ m² / s, a decrease of approximately 61–69% compared to Comparative Example 1, approximately 64–71% compared to Comparative Example 2, and approximately 45–56% compared to Comparative Example 3. The trend of steady-state hydrogen flux J∞ was consistent with that of D, with Examples 1-3 showing a decrease of approximately 75–78% compared to Comparative Example 1. These results indicate that the high-density nano-precipitated phase, acting as an irreversible hydrogen trap, effectively captures diffusible hydrogen and significantly reduces the effective diffusion rate of hydrogen in the crystal lattice.

[0060] Hydrogen embrittlement sensitivity test Slow strain rate tensile (SSRT) testing was used to evaluate hydrogen embrittlement susceptibility. The test conditions were as follows: Sample: cylindrical, gauge length section diameter 3 mm, length 15 mm; Strain rate: 1×10 -5 s -1 ; Test environment: Air + electrochemical hydrogen charging (0.5 mol / L H2SO4 + 0.25 g / L As2O3, current density 5 mA / cm²) 2 ) Hydrogen embrittlement index (HEI): HEI = (ψ air – ψ2) / ψ air × 100%, where ψ is the section reduction rate.

[0061] The test results are as follows: Table 5. Hydrogen embrittlement sensitivity test results of samples prepared in Examples 1-3 and Comparative Examples 1-4 The HEI of Examples 1-3 was only 7.2-8.9%, far lower than that of Comparative Example 1 (41.9%) and Comparative Example 2 (37.8%), and also significantly lower than that of Comparative Example 3 (21.9%) and Comparative Example 4 (23.3%). Although Comparative Example 2 had a high fault energy (comparable to the Examples), it lacked nano-precipitated hydrogen traps, resulting in high hydrogen embrittlement sensitivity, demonstrating the crucial role of hydrogen traps. Although Comparative Example 3 added microalloying elements, the lack of temperature-controlled forging resulted in coarse and unevenly distributed precipitates, significantly reducing hydrogen trapping efficiency and leading to a significantly higher HEI than the Examples. Although Comparative Example 4 had a hydrogen trapping density comparable to the Examples, the lower matrix SFE exacerbated hydrogen embrittlement damage due to hydrogen-induced martensitic transformation, resulting in a high HEI of 23.3%.

[0062] Thermal stability test To verify the stability of the hydrogen trap of the material of the present invention under high temperature service conditions, thermal stability comparison tests were conducted on Example 1 and Comparative Example 3.

[0063] Test method: The sample was exposed to heat at 500℃ for different times (0, 50, 100, 200 hours), and then the hydrogen permeability and HEI were tested.

[0064] The test results are as follows: Table 6. Thermal stability test results of samples prepared in Examples 1-3 and Comparative Examples 1-4 In Example 1, after 200 hours of heat exposure at 500°C, the concentrations D and HEI only increased slightly, indicating that the hydrogen traps in the nano-precipitated phase have good thermal stability. In Comparative Example 3, the D and HEI deteriorated significantly with heat exposure time because the precipitated phase coarsened rapidly and was unevenly distributed, causing some hydrogen traps to become unstable at high temperatures.

[0065] The above description discloses only preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention. Therefore, equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. A high-fault-resistant hydrogen-resistant austenitic stainless steel, characterized in that, It comprises an austenitic matrix and niobium-vanadium composite carbonitride precipitates and copper-rich phases dispersed in the austenitic matrix. Its chemical composition, by mass percentage, is as follows: C：0.02～0.08%， Mn: 4.0~8.0%, Cr：17.0～21.0%， Ni: 7.0~11.0%, Mo: 0.5–2.0%, Cu: 1.0–3.0%, V：0.05～0.25%， Nb: 0.03–0.20%, Si ≤ 0.5%, P ≤ 0.015%， S ≤ 0.005%， O ≤ 0.003%， The balance consists of Fe and unavoidable impurities.

2. The vacuum preparation method of a high-fault-energy hydrogen-resistant austenitic stainless steel according to claim 1, characterized in that, Includes the following steps: S1. Vacuum induction melting: Iron-based raw materials, nickel source, chromium source, manganese source, molybdenum source and copper source are placed in the molten pool of a vacuum induction melting furnace, and the vacuum degree is controlled to be ≤0.1 Pa. After melting and refining, deoxidation is carried out, and then vanadium source, niobium source and carbon source are added for alloying. The steel ingot is then cast. S2. High-temperature homogenization treatment: Hold the steel ingot at 1150-1250℃ for 8-24 hours; S3. Temperature-controlled forging: Multiple forging passes are performed within a temperature range of 950-1150℃, with a cumulative deformation of ≥50% and a deformation of 10-20% per pass; S4. Solution treatment: Keep at 1000-1100℃ for 0.5-2 h and then cool. S5. Aging treatment: Keep at 500-700℃ for 2-8 hours and then cool.

3. The vacuum preparation method of a high-fault-energy hydrogen-resistant austenitic stainless steel according to claim 1, characterized in that, Step S1 specifically includes the following steps: S1-1, Charging: Place the iron-based raw materials, nickel source, chromium source, manganese source, molybdenum source, and copper source into the molten pool of the vacuum induction melting furnace; S1-2, Melting: Close the furnace door, start the vacuum system, control the vacuum degree ≤0.1 Pa, turn on the power to heat, and gradually increase the power to 400-600 kW, and melt for 30-60 minutes; S1-3, Refining: Adjust the power to 250-450 kW, maintain the molten pool temperature at 1520-1550℃, control the vacuum degree at 0.03-0.08 Pa, and refine for 30-50 minutes; S1-4 Deoxidation and Alloying: Maintain a vacuum degree ≤0.1 Pa, stabilize the molten pool temperature at 1520~1540℃, add deoxidizer for deoxidation, stir for 1-5 minutes, add vanadium source and niobium source to the molten pool, and add carbon source at the same time. Set the power to 300-500 kW, set the molten pool temperature to 1550-1560℃, stir for 3-5 minutes, stop stirring, and let stand for 3-7 minutes; S1-5. Casting: Adjust the temperature of the molten pool to 1540-1550℃ and cast it into steel ingots under argon protection. The casting speed is 10-20 kg / s. After casting, the steel ingots are left to stand in the mold for 20-40 minutes, and then demolded and cooled.

4. The vacuum preparation method of a high-fault-energy hydrogen-resistant austenitic stainless steel according to claim 3, characterized in that: In steps S1-4, the vanadium source and niobium source are added after being preheated to 200-300℃.

5. The vacuum preparation method of a high-fault-energy hydrogen-resistant austenitic stainless steel according to claim 3, characterized in that: In steps S1-4, the deoxidizer is crystalline silicon or aluminum granules.

6. The vacuum preparation method of a high-fault-energy hydrogen-resistant austenitic stainless steel according to claim 3, characterized in that: In step S1, the iron-based raw material is pure iron, the nickel source is electrolytic nickel, the chromium source is ferrochrome or metallic chromium, the manganese source is electrolytic manganese, the molybdenum source is ferromolybdenum, and the copper source is electrolytic copper.

7. The vacuum preparation method of a high-fault-energy hydrogen-resistant austenitic stainless steel according to claim 3, characterized in that: In step S1, the vanadium source is ferrovanadium and the niobium source is ferroniobium.

8. The vacuum preparation method of a high-fault-energy hydrogen-resistant austenitic stainless steel according to claim 3, characterized in that: In step S1, the carbon source is graphite.

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