Method for improving hydrogen embrittlement resistance of high-manganese austenitic steel weld joint

Abstract

The invention discloses a method for improving hydrogen embrittlement resistance of a high-manganese austenitic steel weld joint. High-manganese austenitic steel serves as a base material; a single V shape is adopted, and the groove angle is 60 degrees; carrying out submerged arc welding; the welding seam is cleaned; carrying out 3-4 times of single-cycle treatment on the welding seam; and setting the number of single cycles according to the step (5). According to the method, through the combined effect of cold deformation and heat treatment, the steel weld joint structure performance of the high-manganese austenitic steel is improved, the stress and crystal defect distribution of a weld joint area are changed, the weld joint structure is subjected to static recrystallization, and original thick columnar crystals are converted into fine isometric crystals; therefore, the hydrogen embrittlement sensitivity of the welding seam is reduced to be not higher than 22.0% from not lower than 34.6% before treatment, and the hydrogen embrittlement sensitivity of a parent body is reduced to be not higher than 21.5%.

Description

Technical Field

[0001] This invention relates to the field of welding of metallic materials, and specifically to a method for improving the hydrogen embrittlement resistance of high-manganese austenitic steel welds through cold deformation and heat treatment. Background Technology

[0002] 316L austenitic stainless steel is widely used in liquid hydrogen storage and transportation equipment due to its excellent toughness and resistance to hydrogen embrittlement. However, its metastable austenite to martensite transformation at low temperatures significantly reduces its resistance to hydrogen embrittlement. Furthermore, its low yield strength makes it difficult to meet the load-bearing requirements of large-scale liquid hydrogen storage and transportation equipment, and its high nickel content also leads to high costs. In contrast, high-manganese austenitic steel, with higher yield strength and lower cost, is becoming an ideal alternative material for manufacturing liquid hydrogen storage tanks. Welding is an essential step in the construction of liquid hydrogen storage and transportation facilities. During welding, high heat input, low cooling rate, and the directional solidification behavior of the weld pool collectively promote the formation of coarse columnar crystal structures in the weld. The grain boundaries of these columnar crystals provide rapid diffusion channels for hydrogen atoms, making the diffusion coefficient of hydrogen atoms at the grain boundaries 1 to 2 orders of magnitude higher than that within the grains. Combined with the continuous distribution of grain boundaries, hydrogen atoms can rapidly migrate and accumulate along the grain boundaries. Meanwhile, solute element segregation is more likely to occur at columnar grain boundaries. The local enrichment of elements such as Mn and C alters the chemical environment of the grain boundaries, allowing them to capture more hydrogen atoms through physical or chemical adsorption. This synergistic effect leads to local hydrogen concentrations far exceeding the material's hydrogen embrittlement critical value, significantly exacerbating the risk of hydrogen embrittlement. Furthermore, defects such as pores and microcracks often preferentially form at columnar grain boundaries. These defects act as hydrogen traps, causing hydrogen atoms to accumulate within them, resulting in extremely high local hydrogen concentrations and further increasing the material's hydrogen embrittlement susceptibility. Simultaneously, hydrogen atoms diffusing into the grain interior tend to exist as interstitial atoms, pinning mobile dislocations by forming hydrogen-Cottrell gas clusters and hindering their slip movement. This process significantly reduces the material's ability to achieve plastic deformation through dislocation slip, collectively promoting hydrogen embrittlement failure. This series of processes synergistically leads to brittle fracture of the material, resulting in high hydrogen embrittlement susceptibility in the weld. Previous studies have also shown that the resistance to hydrogen embrittlement of welds in high-manganese austenitic steel is significantly lower than that of the base metal. This performance difference poses a serious threat to the mechanical properties and long-term service life of welded structures made of high-manganese austenitic steel.

[0003] Currently, the main technical methods for improving the hydrogen embrittlement resistance of weld metals focus on optimizing alloy composition, adjusting welding processes, and surface protection technologies. Regarding alloy composition optimization, the addition of microalloying elements or rare earth elements is often used to form fine, dispersed hydrogen traps, aiming to increase the density of intragranular hydrogen traps, reduce hydrogen diffusion capacity, and potentially refine grain size. However, this may introduce brittle phases or worsen weldability and significantly increase costs. In terms of welding process adjustment, techniques such as reducing heat input, rapid welding, and narrow weld bead techniques can effectively control the welding thermal cycle, shorten the high-temperature dwell time, reduce the hydrogen content absorbed by the weld, and refine grain size to improve toughness. However, these measures may increase the risk of incomplete fusion and place higher demands on welding speed and precision control. Regarding surface protection, techniques such as electroplating Ni-P alloys and Cr coatings can act as physical barriers to effectively prevent the penetration of environmental hydrogen into the substrate. However, coatings are prone to failure due to wear or scratches, and microcracks may form at the coating-weld interface, becoming potential hydrogen traps and leading to localized hydrogen enrichment. While the methods described above can reduce the hydrogen embrittlement sensitivity of welds to some extent, they typically suffer from limitations such as limited improvement, complex processes, and high costs. More importantly, these measures cannot fundamentally bridge the significant gap in hydrogen embrittlement resistance between the weld zone and the base metal caused by the inherent differences in solidification structure.

[0004] Chinese Patent Publication No. CN114107630 A discloses a heat treatment method for improving the hydrogen embrittlement resistance of martensitic stainless steel, stainless steel and its application. This document describes a heat treatment process for precipitation-hardening martensitic stainless steel, involving solution treatment at a temperature 50-100°C above the austenitizing temperature of the martensitic stainless steel to introduce a certain amount of austenite into the matrix, followed by aging treatment at 480°C~510°C for at least 4 hours. This process generates austenite in the martensitic stainless steel, which captures hydrogen, reducing the content of diffusible hydrogen and refining the matrix structure. In the examples of the treated martensitic stainless steel, the tensile strength before hydrogen charging was 1405 MPa, the elongation was 12.5%, and the elongation after hydrogen charging was 4.7%, with a hydrogen embrittlement sensitivity of only 13.6%, achieving a balance between high strength and toughness and resistance to hydrogen embrittlement. However, this process is mainly applicable to martensitic stainless steel and relies on the formation of austenite during heat treatment to capture hydrogen, so its applicability to steels that are not suitable for generating austenite through heat treatment is limited. Chinese Patent Publication No. CN117448804 A discloses a method for improving the hydrogen embrittlement resistance of high-strength steel and a high-strength steel material. This document describes a method of forming a hydrogen embrittlement resistant cladding layer on the surface of high-strength steel (such as Q125 or SCM435 high-strength steel) by laser melting of high-entropy alloy powder (e.g., FeCoCrNiMn powder) using a laser device. The laser power is ≤800W, the powder feed rate is ≤1.3r / min, and the laser scanning rate is 6mm / s-10mm / s. In the high-strength steel examples, after immersing the SCM435 high-strength steel with the hydrogen embrittlement resistant cladding layer in a hydrogen-rich solution for 1 hour, the strength was almost unaffected, and the plasticity decreased by only 14.3%, indicating a significant improvement in hydrogen embrittlement resistance. However, this process requires laser equipment for cladding treatment. For high-strength steel components with complex shapes, the uniformity of the cladding layer may be difficult to guarantee, and the thickness of the cladding layer needs to be controlled between 0.1mm and 1.5mm; excessive thickness may affect the overall mechanical properties.

[0005] Therefore, there is an urgent need to develop a new, simple, and efficient process to effectively improve the coarse columnar grain structure of the weld, thereby fundamentally enhancing its resistance to hydrogen embrittlement to meet increasingly stringent service environment requirements. This technology not only effectively improves the weld's resistance to hydrogen embrittlement but also simultaneously improves its toughness and plasticity, while reducing costs and simplifying the production process. It is of great value in promoting the safe and reliable application of high-manganese austenitic steel welded structures in hydrogen-related environments. Summary of the Invention

[0006] This invention overcomes the shortcomings of existing technologies by proposing a method that improves the microstructure and properties of high-manganese austenitic steel welds through a combination of cold deformation and heat treatment. This method alters the stress and crystal defect distribution in the weld region, causing static recrystallization and transforming the original coarse columnar grains into fine equiaxed grains. This significantly improves the weld region's resistance to hydrogen embrittlement. The original coarse columnar grains with an average grain size of approximately 85μm-125μm are transformed into fine equiaxed grains with an average grain size of approximately 8μm-18μm, significantly increasing grain boundaries in the weld microstructure, hindering hydrogen accumulation, and simultaneously achieving a uniform microstructure and improving segregation. It also reduces the total elongation loss rate of the weld from no less than 34.6% before treatment to no more than 22.0%, and the total elongation loss rate of the parent material to no more than 21.5%. This method significantly reduces the weld's hydrogen embrittlement sensitivity and has broad application value in improving the hydrogen embrittlement resistance of high-manganese austenitic steel welds.

[0007] Technical measures to achieve the above objectives A method for improving the hydrogen embrittlement resistance of high-manganese austenitic steel welds, comprising the following steps: 1) The base material for welding is high-manganese austenitic TWIP steel with a thickness of 15-25mm, and multi-pass submerged arc welding is used; 2) Bevel type and angle: Single V-shape, bevel angle: 60° ° horn; 3) Perform submerged arc welding, with the welding voltage controlled at 25-32V, the welding current controlled at 400-600A, the welding speed at 42-50cm / min, and the heat input controlled at 15-20kJ / cm; 4) Clean the weld seam, steps: A. Grinding and polishing the weld seam; B. Soak the sample in a solution of 10% nitric acid and 5% hydrofluoric acid for at least 5 minutes. C. Rinse with anhydrous ethanol; D. Allow the weld to dry naturally until the weld surface is free of stains; 5) Perform 3 to 4 single-cycle treatments on the weld, wherein the single-cycle treatment includes the following steps: A. Perform cold deformation and rolling 4-5 times, controlling the cumulative reduction rate at 20-25%; B. Perform recrystallization annealing under nitrogen protection, with the annealing temperature controlled at 900-1100℃ and held at this temperature for 30-60 minutes; C. Cool the temperature to no more than 300°C at a cooling rate of not less than 10°C / s. 6) Continue with step 5) until the set number of cycles is reached; it should be noted that the temperature of the last single-cycle recrystallization annealing is controlled at 750-850℃, and held at this temperature for 5-10 minutes.

[0008] The key difference is that the cooling method described in step 5) C is water cooling or air cooling.

[0009] The specific composition and weight percentage of the submerged arc weld metal are as follows: 20.0-25% Mn, 0.1-0.5% C, 0.1-0.5% Si, 2-4% Cr, 0.50-1.0% Cu, with the remainder being Fe and unavoidable impurities.

[0010] The flux comprises the following components and weight percentages: 1.0–1.8% CaO, 16–20% SiO2, 28–32% CaF2, 12–16% Al2O3, 2–4% Fe2O3, 28–34% MgO, with the remainder being Fe and unavoidable impurities. The flux is then heated in a muffle furnace at 250–300°C and pre-dried for 2.5–3.5 hours.

[0011] The components and their weight percentages of the welding wire are: 20-32% Mn, 0.4-1.5% C, 0.05-0.15% Si, 3-6% Cr, 0.5-1.0% Cu, with the remainder being Fe; the diameter of the welding wire is 2.8-3.4 mm.

[0012] The high-manganese austenitic steel has the following elemental chemical composition and weight percentage: 0.5-1.4% C, 22-30% Mn, 3-10% Cr, 0.7-1.2% Ni, 0.5-1.0% Cu, with the remainder being Fe and unavoidable impurities.

[0013] The role and mechanism of the main processes in this invention The reason this invention employs submerged arc welding, with welding voltage controlled at 25–32V, welding current controlled at 400–600A, welding speed at 42–50cm / min, and heat input controlled at 15–20kJ / cm, is that: high-manganese austenitic steel, due to its high manganese content, is prone to problems such as alloy element loss, coarse grains in the heat-affected zone, hot cracking, and unstable weld performance during welding. Submerged arc welding flux forms slag and protective gas, which can isolate air, reduce the loss of manganese and other alloying elements, and reduce defects such as porosity and inclusions; stable medium heat input can suppress coarse grains in the heat-affected zone and retain the material's toughness; high current combined with medium speed achieves a large molten pool, reducing the number of welding passes and thermal cycles, and lowering the risk of hot cracking. The reason why this invention uses a mixed solution of 10% nitric acid and 5% hydrofluoric acid for soaking, and controls the soaking time to be no less than 5 minutes, is that hydrofluoric acid can efficiently dissolve the surface oxide scale, and nitric acid can assist in purification and inhibit excessive corrosion of the substrate through passivation, thereby obtaining a clean and uniform surface. The reason why the weld is subjected to 3 to 4 single-cycle treatments in this invention is to eliminate residual stress and avoid early cracking caused by stress superposition during subsequent service. At the same time, recrystallization annealing transforms columnar crystals into equiaxed crystals, eliminates structural differences, and reduces compositional segregation to synergistically improve resistance to hydrogen embrittlement. The reason why this invention involves rolling 4 to 5 passes in cold deformation and controlling the cumulative reduction rate at 20 to 25% is that in multi-pass rolling, the dislocation density increases sharply with the reduction rate, thereby lowering the recrystallization temperature of the material for easier control. This also results in finer grains after recrystallization annealing. The reason why the recrystallization annealing temperature under nitrogen protection is controlled at 900-1100℃ and held at this temperature for 30-60 minutes in this invention is that after cold deformation treatment, when the material is heated above the recrystallization temperature, the coarse columnar grain boundaries, dendrite arm interstices, and lattice distortion concentration regions (such as dislocation accumulation sites) have high energy and become nucleation sites for new equiaxed crystals. These newly formed equiaxed crystals continue to grow by consuming the surrounding distorted columnar crystal regions until the original columnar crystals are completely replaced by fine equiaxed crystals, thereby fundamentally improving the resistance of the weld area to hydrogen embrittlement. Using nitrogen as a protective gas can isolate oxygen and inhibit oxidation and decarburization. Nitrogen can regulate the recrystallization process, inhibit columnar crystal growth, refine recrystallized grains, promote the formation of equiaxed crystals, increase the grain boundary area by 3-5 times, and significantly increase hydrogen trapping sites.

[0014] The reason this invention employs a cooling rate of not less than 10°C / s to a temperature not exceeding 300°C is that rapid cooling accelerates the transformation of austenite to ferrite or martensite in the weld, which helps refine the weld's microstructure. Simultaneously, a high cooling rate effectively suppresses carbide precipitation, reducing segregation in the weld and thus improving its uniformity and toughness. Furthermore, controlling the cooling temperature to not exceed 300°C prevents cracking in the weld due to excessive thermal stress during cooling. This temperature range also considers the weld's coefficient of thermal expansion and phase transformation behavior, ensuring that the weld maintains good stability and mechanical properties after cooling. The reason why the final single-cycle recrystallization annealing temperature is controlled at 750–850℃ and held at this temperature for 5–10 minutes is that within this temperature range, the weld microstructure can fully recrystallize, allowing for uniform grain growth, while avoiding abnormal grain growth caused by excessively high temperatures. Controlling the holding time ensures the full progress of the recrystallization process and the effective release of internal stress in the weld. Furthermore, the 750–850℃ temperature range also takes into account the phase transformation point of the weld material, enabling the weld to maintain good stability and processing performance after annealing. The reason why the chemical composition and weight percentage of the submerged arc weld metal are controlled as follows in this invention is: 20.0-25% Mn, 0.1-0.5% C, 0.1-0.5% Si, 2-4% Cr, 0.50-1.0% Cu, with the remainder being Fe and unavoidable impurities. This is because the content range of Mn can effectively improve the strength and toughness of the weld, and at the same time improve the resistance to hot cracking to a certain extent; the appropriate addition of C can enhance the hardness and wear resistance of the weld, but too high a content may lead to increased brittleness, so it is controlled within the range of 0.1-0.5% to achieve the best balance; Si helps to improve the fluidity and deoxidation capacity of the weld, and promotes the compactness of the weld; the addition of Cr can significantly improve the corrosion resistance and heat resistance of the weld; Cu enhances the strength and toughness of the weld to a certain extent, and also helps to improve its corrosion resistance.

[0015] The reason why the composition and weight percentage of the flux in this invention are controlled as follows: 1.0-1.8% CaO, 16-20% SiO2, 28-32% CaF2, 12-16% Al2O3, 2-4% Fe2O3, 28-34% MgO, with the remainder being Fe and unavoidable impurities; and the flux is heated in a muffle furnace at 250-300°C and then pre-dried for 2.5-3.5 hours, is that this composition design and pretreatment process can significantly improve the overall performance of the weld, especially its resistance to hydrogen embrittlement. CaO and SiO2, as basic components, help form a stable slag, protecting the weld from air contamination. The addition of CaF2 lowers the melting point of the slag, promotes its fluidity and coverage, and ensures uniform protection of the weld. Al2O3 enhances the viscosity and stability of the slag, preventing premature slag detachment. MgO, on the other hand, has excellent desulfurization and dephosphorization capabilities, which can effectively remove harmful impurities in the weld and improve the toughness and crack resistance of the weld.

[0016] Therefore, by precisely controlling the composition of the flux and the pretreatment process, this invention can significantly improve the overall performance of the weld, especially its resistance to hydrogen embrittlement, meeting the needs of various complex application scenarios. For example, in the process of oil and gas extraction and transportation, equipment often needs to operate in high-pressure, hydrogen-rich environments. The flux and pretreatment process of this invention can ensure that the weld still has excellent resistance to hydrogen embrittlement under such extreme conditions, effectively preventing weld failure due to hydrogen-induced cracking, thereby ensuring the safe operation of equipment and reducing safety accidents and economic losses caused by weld problems. At the same time, in the aerospace field, the performance requirements for welds are extremely stringent, especially in terms of resistance to hydrogen embrittlement. The flux and process provided by this invention can meet these high-performance requirements, ensuring the safe operation of aerospace equipment in harsh environments and contributing to the country's aerospace industry. In addition, this invention also shows broad application prospects in the fields of marine engineering and chemical equipment, providing strong technical support for improving the safety and reliability of equipment in these fields. Compared with the prior art, this invention improves the microstructure and properties of high-manganese austenitic steel welds through the combined action of cold deformation and heat treatment, and changes the stress and crystal defect distribution in the weld area, causing static recrystallization of the weld microstructure, transforming the original coarse columnar crystals into fine equiaxed crystals. As a result, the hydrogen embrittlement sensitivity of the weld is reduced from no less than 34.6% before treatment to no more than 22.0%, and the hydrogen embrittlement sensitivity of the matrix is ​​reduced to no more than 21.5%. Detailed Implementation

[0017] Example 1 A method for improving the hydrogen embrittlement resistance of high-manganese austenitic steel welds, comprising the following steps: 1) The base material for welding is high-manganese austenitic TWIP steel with a thickness of 20mm, and the welding method is 3-pass submerged arc welding; The elemental chemical composition and weight percentage of the high-manganese austenitic steel are: 0.54% C, 26.3% Mn, 5.2% Cr, 0.82% Ni, 0.71% Cu, with the remainder being Fe and unavoidable impurities; 2) Bevel type and angle: Single V-shape, bevel angle: 60° ° ; 3) Perform submerged arc welding, with the welding voltage controlled at 30V, the welding current controlled at 500A, the welding speed at 50cm / min, and the heat input controlled at 20kJ / cm; The flux composition and weight percentage content are as follows: 1.2% CaO, 17.3% SiO2, 29.5% CaF2, 13% Al2O3, 2.4% Fe2O3, 29.4% MgO, with the remainder being Fe and unavoidable impurities; the flux was pre-dried for 3.2 hours after being heated at 276°C in a muffle furnace. The components and weight percentages of the welding wire are as follows: 22% Mn, 0.43% C, 0.06% Si, 3.6% Cr, 0.85% Cu, with the remainder being Fe; the diameter of the welding wire is 2.8 mm. Upon testing, the chemical composition and weight percentage of the submerged arc weld metal were found to be: 24% Mn, 0.45% C, 0.15% Si, 2.3% Cr, 0.5% Cu, with the remainder being Fe and unavoidable impurities. 4) Clean the weld seam, steps: A. Grind and polish the weld, and use a grinding wheel to remove weld slag and surface oxide scale; B. Soak the sample in a solution of 10% nitric acid and 5% hydrofluoric acid for 8 minutes. C. Rinse with anhydrous ethanol; D. Allow to air dry naturally, and ensure the weld surface is free of stains after drying; 5) Perform four single-cycle treatments on the weld, the single-cycle treatment including the following steps: A. Perform cold deformation and rolling in 4 passes, controlling the cumulative reduction rate at 22.5%; B. Recrystallization annealing is carried out under nitrogen protection at a temperature of 905℃ and held at this temperature for 55 minutes. C. Cool the temperature to 297°C at a cooling rate of 11°C / s. 6) Follow step 5) above until the set number of single cycles is reached; it should be noted that the recrystallization annealing temperature for the fourth single cycle is 820℃, and the temperature is held for 5 minutes.

[0018] Testing revealed that in this embodiment, the total elongation loss rate of the weld was reduced from 36.0% before treatment to 12.3%, and the total elongation loss rate of the matrix was reduced to 10.2%. The grain size of the weld before treatment was approximately 87μm-91μm, and the grain size after treatment was approximately 10μm-12μm.

[0019] Example 2 A method for improving the hydrogen embrittlement resistance of high-manganese austenitic steel welds, comprising the following steps: 2) The base material for welding is high-manganese austenitic TWIP steel with a thickness of 25mm, and the welding method is 4-pass submerged arc welding; The elemental chemical composition and weight percentage of the high-manganese austenitic steel are: 0.62% C, 25.10% Mn, 4.7% Cr, 0.80% Ni, 0.50% Cu, with the remainder being Fe and unavoidable impurities; 2) Bevel type and angle: Single V-shape, bevel angle: 60° ° ; 3) Perform submerged arc welding, with the welding voltage controlled at 25V, the welding current controlled at 530A, the welding speed at 46cm / min, and the heat input controlled at 17kJ / cm. The flux composition and weight percentage content are as follows: 1.1% CaO, 16.7% SiO2, 28.7% CaF2, 12.4% Al2O3, 2.6% Fe2O3, 28.4% MgO, with the remainder being Fe and unavoidable impurities; the flux was pre-dried for 2.8 hours after being heated at 259°C in a muffle furnace. The components and weight percentages of the welding wire are as follows: 21% Mn, 0.54% C, 0.08% Si, 4.2% Cr, 0.54% Cu, with the remainder being Fe; the diameter of the welding wire is 3.0 mm. Upon testing, the chemical composition and weight percentage of the submerged arc weld metal were found to be: 22.4% Mn, 0.24% C, 0.3% Si, 3.7% Cr, 0.55% Cu, with the remainder being Fe and unavoidable impurities. 4) Clean the weld seam, steps: A. Grind and polish the weld, and use a grinding wheel to remove weld slag and surface oxide scale; B. Soak the sample in a solution of 10% nitric acid and 5% hydrofluoric acid for 7 minutes. C. Rinse with anhydrous ethanol; D. Allow to air dry naturally, and ensure the weld surface is free of stains after drying; 5) Perform four single-cycle treatments on the weld, the single-cycle treatment including the following steps: A. Perform cold deformation and rolling in 5 passes, controlling the cumulative reduction rate at 23.5%; B. Recrystallization annealing is carried out under nitrogen protection at a temperature of 900℃ and held at this temperature for 60 minutes. C. Cool the temperature to 263°C at a cooling rate of 12°C / s; 6) Follow step 5) above until the set number of cycles of 4 is reached; it should be noted that the recrystallization annealing temperature of the 4th single cycle is 795℃, and the temperature is held for 7 minutes.

[0020] Testing revealed that in this embodiment, the total elongation loss rate of the weld was reduced from 40.5% before treatment to 11.1%, and the total elongation loss rate of the matrix was reduced to 13.4%. The grain size of the weld before treatment was approximately 89μm-96μm, and the grain size after treatment was approximately 12μm-15μm.

[0021] Example 3 A method for improving the hydrogen embrittlement resistance of high-manganese austenitic steel welds, comprising the following steps: 3) The base material for welding is high-manganese austenitic TWIP steel with a thickness of 18mm, and a 4-pass submerged arc welding method is used; The elemental chemical composition and weight percentage of the high-manganese austenitic steel are: 0.76% C, 23.4% Mn, 5.4% Cr, 0.9% Ni, 0.54% Cu, with the remainder being Fe and unavoidable impurities; 2) Bevel type and angle: Single V-shape, bevel angle: 60° ° ; 3) Perform submerged arc welding, controlling the welding voltage at 26V, the welding current at 450A, the welding speed at 45cm / min, and the heat input at 18kJ / cm; The flux composition and weight percentage content are as follows: 1.3% CaO, 17.3% SiO2, 29.5% CaF2, 13.8% Al2O3, 3.2% Fe2O3, 28.7% MgO, with the remainder being Fe and unavoidable impurities; the flux was pre-dried for 3.0 hours after being heated at 264°C in a muffle furnace. The components and weight percentages of the welding wire are as follows: 23% Mn, 0.75% C, 0.07% Si, 3.2% Cr, 0.51% Cu, with the remainder being Fe; the diameter of the welding wire is 3.2 mm. Upon testing, the chemical composition and weight percentage of the submerged arc weld metal were found to be: 22.8% Mn, 0.15% C, 0.5% Si, 2.6% Cr, 0.66% Cu, with the remainder being Fe and unavoidable impurities. 4) Clean the weld seam, steps: A. Grind and polish the weld, and use a grinding wheel to remove weld slag and surface oxide scale; B. Soak the sample in a solution of 10% nitric acid and 5% hydrofluoric acid for 6 minutes. C. Rinse with anhydrous ethanol; D. Allow to air dry naturally, and ensure the weld surface is free of stains after drying; 5) Perform four single-cycle treatments on the weld, the single-cycle treatment including the following steps: A. Perform cold deformation and rolling in 5 passes, controlling the cumulative reduction rate at 24.2%; B. Recrystallization annealing is carried out under nitrogen protection at a temperature of 950℃ and held at this temperature for 50 minutes. C. Cool the temperature to 271°C at a cooling rate of 15°C / s. 6) Follow step 5) above until the set number of cycles of 4 is reached; it should be noted that the recrystallization annealing temperature of the 4th single cycle is 810℃, and the temperature is held for 6 minutes.

[0022] Testing revealed that in this embodiment, the total elongation loss rate of the weld was reduced from 34.6% before treatment to 13.7%, and the total elongation loss rate of the matrix was reduced to 12.3%. The grain size of the weld before treatment was approximately 93μm-97μm, and the grain size after treatment was approximately 6μm-10μm.

[0023] Example 4 A method for improving the hydrogen embrittlement resistance of high-manganese austenitic steel welds, comprising the following steps: 4) The base material for welding is high-manganese austenitic TWIP steel with a thickness of 22mm, and the welding method is 4-pass submerged arc welding; The elemental chemical composition and weight percentage of the high-manganese austenitic steel are: 1.3% C, 25.7% Mn, 7.1% Cr, 0.78% Ni, 0.59% Cu, with the remainder being Fe and unavoidable impurities; 2) Bevel type and angle: Single V-shape, bevel angle: 60° ° ; 3) Perform submerged arc welding, with the welding voltage controlled at 27V, the welding current controlled at 430A, the welding speed at 43cm / min, and the heat input controlled at 16kJ / cm. The flux composition and weight percentage content are as follows: 1.4% CaO, 18.5% SiO2, 31.2% CaF2, 14.7% Al2O3, 3.9% Fe2O3, 29.7% MgO, with the remainder being Fe and unavoidable impurities; the flux was pre-dried for 2.6 hours after being heated at 277°C in a muffle furnace. The components and weight percentages of the welding wire are as follows: 28% Mn, 0.67% C, 0.09% Si, 5.2% Cr, 0.81% Cu, with the remainder being Fe; the diameter of the welding wire is 3.3 mm. Upon testing, the chemical composition and weight percentage of the submerged arc weld metal were found to be: 23.7% Mn, 0.17% C, 0.2% Si, 2.7% Cr, 0.73% Cu, with the remainder being Fe and unavoidable impurities. 4) Clean the weld seam, steps: A. Grind and polish the weld, and use a grinding wheel to remove weld slag and surface oxide scale; B. Soak the sample in a solution of 10% nitric acid and 5% hydrofluoric acid for 6.5 minutes. C. Rinse with anhydrous ethanol; D. Allow to air dry naturally, and ensure the weld surface is free of stains after drying; 5) Perform three single-cycle treatments on the weld, the single-cycle treatment including the following steps: A. Perform cold deformation and rolling in 5 passes, controlling the cumulative reduction rate at 24.7%; B. Recrystallization annealing is carried out under nitrogen protection at a temperature of 976℃ and held at this temperature for 40 minutes. C. Cool the temperature to 278°C at a cooling rate of 16°C / s. 6) Follow step 5) above until the set number of cycles of 3 is reached; it should be noted that the recrystallization annealing temperature of the third single cycle is 760℃, and the temperature is held at this temperature for 9.5 minutes.

[0024] Testing revealed that in this embodiment, the total elongation loss rate of the weld was reduced from 39.4% before treatment to 18.6%, and the total elongation loss rate of the matrix was reduced to 21.3%. The grain size of the weld before treatment was approximately 113μm-118μm, and the grain size after treatment was approximately 13μm-17μm.

[0025] Example 5 A method for improving the hydrogen embrittlement resistance of high-manganese austenitic steel welds, comprising the following steps: 5) The base material for welding is high-manganese austenitic TWIP steel with a thickness of 24mm, and a 3-pass submerged arc welding method is used; The elemental chemical composition and weight percentage of the high-manganese austenitic steel are: 0.9% C, 27.9% Mn, 8.3% Cr, 0.93% Ni, 0.9% Cu, with the remainder being Fe and unavoidable impurities; 2) Bevel type and angle: Single V-shape, bevel angle: 60° ° ; 3) Perform submerged arc welding, with the welding voltage controlled at 28V, the welding current controlled at 420A, the welding speed at 44cm / min, and the heat input controlled at 19kJ / cm. The flux composition and weight percentage content are as follows: 1.6% CaO, 19.2% SiO2, 29.4% CaF2, 15.1% Al2O3, 2.7% Fe2O3, 33.5% MgO, with the remainder being Fe and unavoidable impurities; the flux was pre-dried for 3 hours after being heated at 292°C in a muffle furnace. The components and weight percentages of the welding wire are as follows: 31% Mn, 1.3% C, 0.13% Si, 4.6% Cr, 0.83% Cu, with the remainder being Fe; the diameter of the welding wire is 3.1 mm. Upon testing, the chemical composition and weight percentage of the submerged arc weld metal were found to be: 24.8% Mn, 0.27% C, 0.37% Si, 3.3% Cr, 0.64% Cu, with the remainder being Fe and unavoidable impurities. 4) Clean the weld seam, steps: A. Grind and polish the weld, and use a grinding wheel to remove weld slag and surface oxide scale; B. Soak the sample in a solution of 10% nitric acid and 5% hydrofluoric acid for 7 minutes. C. Rinse with anhydrous ethanol; D. Allow to air dry naturally, and ensure the weld surface is free of stains after drying; 5) Perform three single-cycle treatments on the weld, the single-cycle treatment including the following steps: A. Perform cold deformation and rolling in 4 passes, controlling the cumulative reduction rate at 24.2%; B. Recrystallization annealing is carried out under nitrogen protection at a temperature of 993℃ and held at this temperature for 45 minutes. C. Cool the temperature to 296°C at a cooling rate of 18°C / s. 6) Follow step 5) above until the set number of cycles of 3 is reached; it should be noted that the recrystallization annealing temperature of the third single cycle is 785℃, and the temperature is held at this temperature for 8.5 minutes.

[0026] Testing revealed that in this embodiment, the total elongation loss rate of the weld was reduced from 45.6% before treatment to 20.8%, and the total elongation loss rate of the matrix was reduced to 15.7%. The grain size of the weld before treatment was approximately 123μm-126μm, and the grain size after treatment was approximately 8μm-14μm.

[0027] This specific embodiment is merely a best example and is not intended to limit the implementation of the technical solution of the present invention.

Claims

1. A method for improving the hydrogen embrittlement resistance of welds in high-manganese austenitic steel, comprising the following steps: 1) The base material for welding is high-manganese austenitic TWIP steel with a thickness of 15-25mm, and multi-pass submerged arc welding is used; 2) Bevel type and angle: Single V-shape, bevel angle: 60° ° ; 3) Perform submerged arc welding, with welding voltage controlled at 25-32V, welding current controlled at 400-600A, welding speed at 42-50cm / min, and heat input controlled at 15-20kJ / cm; use SAW flux and WW welding wire; 4) Clean the weld seam. The cleaning steps are as follows: A. Perform routine grinding and polishing on the weld; B. Soak the sample in a solution of 10% nitric acid and 5% hydrofluoric acid for at least 5 minutes. C. Rinse with anhydrous ethanol; D. Allow the weld to dry naturally until the surface is free of stains. 5) Perform 3 to 4 single-cycle treatments on the weld, wherein the single-cycle treatment includes the following steps: A. Perform cold deformation and rolling 4-5 times, controlling the cumulative reduction rate at 20-25%; B. Recrystallization annealing is carried out under nitrogen protection, with the annealing temperature controlled at 900-1100℃ and held at this temperature for 30-60 minutes. C. Cool the temperature to no more than 300°C at a cooling rate of not less than 10°C / s. 6) Continue with step 5) until the set number of cycles is reached; it should be noted that the temperature of the last single-cycle recrystallization annealing is controlled at 750-850℃, and held at this temperature for 5-10 minutes.

2. The method for improving the hydrogen embrittlement resistance of high-manganese austenitic steel welds as described in claim 1, characterized in that: The cooling method described in step 5) C is water cooling or air cooling.

3. The method for improving the hydrogen embrittlement resistance of high-manganese austenitic steel welds as described in claim 1, characterized in that: The chemical composition and weight percentage of the submerged arc weld metal are as follows: 20.0-25% Mn, 0.1-0.5% C, 0.1-0.5% Si, 2-4% Cr, 0.50-1.0% Cu, with the remainder being Fe and unavoidable impurities.

4. The method for improving the hydrogen embrittlement resistance of high-manganese austenitic steel welds as described in claim 1, characterized in that: The composition and weight percentage of the flux are as follows: 1.0–1.8% CaO, 16–20% SiO2, 28–32% CaF2, 12–16% Al2O3, 2–4% Fe2O3, 28–34% MgO, with the remainder being Fe and unavoidable impurities; The flux is then heated in a muffle furnace at 250–300°C and pre-dried for 2.5–3.5 hours.

5. The method for improving the hydrogen embrittlement resistance of high-manganese austenitic steel welds as described in claim 1, characterized in that: The components and weight percentages of the welding wire are as follows: 20-32% Mn, 0.4-1.5% C, 0.05-0.15% Si, 3-6% Cr, 0.5-1.0% Cu, with the remainder being Fe and unavoidable impurities; the diameter of the welding wire is 2.8-3.4 mm.

6. The method for improving the hydrogen embrittlement resistance of high-manganese austenitic steel welds as described in claim 1, characterized in that: The elemental chemical composition and weight percentage of the high-manganese austenitic steel are as follows: 0.5-1.4% C, 22-30% Mn, 3-10% Cr, 0.7-1.2% Ni, 0.5-1.0% Cu, with the remainder being Fe and unavoidable impurities.