Manufacturing method of steel high-pressure hydrogen storage cylinder

Abstract

The invention discloses a manufacturing method of a steel high-pressure hydrogen storage cylinder, the gas cylinder is made of 4130X steel, and the 4130X steel comprises the following components in percentage by mass: 0.28%-0.33% of C, 0.40%-0.60% of Mn, 3.20%-3.80% of Ni, 0.15%-0.35% of Si, less than or equal to 0.035% of P, less than or equal to 0.040% of S, 0.80%-1.10% of Cr, 0.15%-0.25% of Mo, 0.01%-0.04% of Ti, 0.02%-0.05% of Nb, 0.08%-0.14% of V, 0.03%-0.06% of Al, 0.10%-0.15% of Cu, 0.001%-0.003% of B and the balance of Fe; the method has the characteristics that the comprehensive mechanical property and the fatigue failure resistance of the cylinder shoulder of the gas cylinder are improved, and the service life of the gas cylinder can be effectively prolonged.

Description

Technical Field

[0001] This invention relates to the field of hydrogen storage container technology, and in particular to a method for manufacturing a steel high-pressure hydrogen storage cylinder. Background Technology

[0002] High-pressure hydrogen storage cylinders are the core equipment of the hydrogen energy storage and transportation system, and their safe service performance is directly related to the development quality of the hydrogen energy industry. 4130X low alloy high-strength steel is widely used in the manufacture of steel high-pressure hydrogen storage cylinders with pressures up to 30MPa due to its excellent hardenability, high tensile strength and good formability.

[0003] However, in actual service, 4130X steel cylinders must withstand the combined effects of high-pressure hydrogen environment and cyclic fatigue loads for extended periods, making them highly susceptible to hydrogen-induced fatigue failure. In particular, the cylinder shoulder, as the structural transition zone between the neck and body, undergoes severe uneven plastic deformation during spinning, which not only alters the microstructure but also generates high residual tensile stress. The coupling effect of residual tensile stress and high-pressure hydrogen makes the cylinder shoulder a high-risk area for hydrogen-induced fatigue failure. Statistics show that approximately 65% ​​of high-pressure hydrogen storage cylinder failures originate from fatigue cracking at the cylinder shoulder. These issues have become a core bottleneck restricting the service life of 4130X steel cylinders.

[0004] Existing technologies have attempted to improve the problem by adding microalloying elements such as Ti, Nb, and V, and by adjusting the spinning process parameters. However, the problem of mismatched deformation capacity in different deformation areas of the bottle shoulder and the generation of additional residual stress still exist, and the hydrogen-induced fatigue failure problem in the bottle shoulder area cannot be fundamentally solved. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies in the hydrogen-induced fatigue failure of gas cylinder shoulders, and to provide a method for manufacturing steel high-pressure hydrogen storage cylinders.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A method for manufacturing a high-pressure hydrogen storage cylinder made of steel, wherein the cylinder is made of 4130X steel, and the mass percentage of each component of the 4130X steel is as follows: C: 0.28%-0.33%, Mn: 0.40%-0.60%, Ni: 3.20%-3.80%, Si: 0.15%-0.35%, P≤0.035%, S≤0.040%, Cr: 0.80%-1.10%, Mo: 0.15%-0.25%, Ti: 0.01%-0.04%, Nb: 0.02%-0.05%, V: 0.08%-0.14%, Al: 0.03%-0.06%, Cu: 0.10%-0.15%, B: 0.001%-0.003%, with the balance being iron (Fe). Make the Ni equivalent in 4130X steel ≥12.5: ; The method for manufacturing the bottle shoulder includes the following steps: Step 1: Weigh the components of 4130X steel according to their mass percentages. Place all elements except Al, Cu, and B into a vacuum induction melting furnace. Control the vacuum induction melting furnace to evacuate and raise the temperature, so that the components melt into molten steel. Add the weighed Al to the molten steel and hold it at the temperature for a period of time to melt Al. Add the weighed Cu to the molten steel and hold it at the temperature for a period of time to melt Cu. Add the weighed B to the molten steel and perform electroslag remelting. Step 2: After casting and forging the molten steel into a round billet, the round billet is pierced and rolled to obtain a tubular billet. The ends of the tubular billet are cold-spun with gradient temperature control at both ends, and the mouth of the billet is cold-spun to obtain the gas cylinder.

[0007] This invention innovatively introduces three elements, Al, Cu, and B, to form a six-element synergistic system with the original Ti, Nb, and V. Through three-step graded melting, the solid solution and distribution of elements are precisely controlled to achieve a quadruple synergistic effect of "grain refinement, precipitation strengthening, grain boundary strengthening, and increase in irreversible hydrogen traps".

[0008] Ni equivalent is a key indicator used to comprehensively characterize the synergistic effect of elements such as carbon (C), manganese (Mn), copper (Cu), silicon (Si), chromium (Cr), molybdenum (Mo), and boron (B) on hardenability in steel. All of these elements can significantly improve the stability of supercooled austenite, shifting the continuous cooling transformation (CCT) curve to the right, thereby reducing the critical cooling rate for obtaining a fully martensitic structure. The Ni equivalent range set by this invention can ensure the hardenability of steel, meet the requirements of uniform lath martensite transformation across the entire cross-section of a 12mm thick gas cylinder wall, and at the same time take into account the matching of strength and toughness.

[0009] This invention employs gradient temperature control on the bottle shoulder, combining the transition characteristics of the bottle shoulder structure with spinning, and dividing the deformation zone according to the three-dimensional criteria of structure-stress-deformation. The conical transition section near the bottle mouth needs to undergo drastic necking; the arc section in the middle of the bottle shoulder has a smooth transition; and the straight section near the bottle body only requires minor adaptation.

[0010] This invention uses vacuum induction melting + electroslag remelting to prepare gas cylinders. During melting, the required mass percentage of elements is added. The resulting steel ingot is then shaped, pierced, hot rolled, cold-spun for the cylinder shoulder, annealed online, and tempered to obtain a gas cylinder with a cylinder shoulder that has high strength, toughness, and high resistance to fatigue failure.

[0011] Preferably, the irreversible hydrogen trap HCF in 4130X steel is ≥1.2. .

[0012] The calculation logic and physical meaning of the hydrogen trap synergistic factor are as follows: The types, binding energies, and densities of hydrogen traps formed by different microalloying elements vary, and the weighting coefficients correspond to the effectiveness priority of the elements in forming hydrogen traps. Among them, Nb-formed NbC nanocarbides have the highest binding energy with hydrogen atoms (approximately 80 kJ / mol-100 kJ / mol), forming a strong irreversible hydrogen trap; Ti-formed TiC / TiN composite inclusions have the next highest binding energy (approximately 70 kJ / mol-90 kJ / mol); V-formed VC carbides have a moderately high binding energy (approximately 60 kJ / mol-80 kJ / mol); Al-formed Al2O3 heterogeneous nucleation cores can indirectly increase grain boundary density (grain boundaries are natural hydrogen traps); Cu-formed Cu-rich nanoprecipitates have a binding energy of approximately 40-60 kJ / mol. When HCF ≥ 1.2, the irreversible hydrogen trap density in the steel can be ensured to be ≥ 5 × 10¹. 5 cm⁻³ can effectively capture diffusible hydrogen atoms in the material, reducing the concentration of diffusible hydrogen to ≤0.3ppm; the above concentration level can significantly inhibit the diffusion and enrichment of hydrogen atoms in the stress concentration area of ​​the bottle shoulder, and avoid the initiation and propagation of hydrogen-induced cracks.

[0013] Preferably, the cold spinning of the bottle shoulder includes the following steps: The tubular blank is horizontally clamped using a chuck. Three induction heating coils are set on the outer side of the right side of the tubular blank, corresponding to the bottle shoulder. The distance between each induction heating coil and the surface of the tubular blank is 15cm-18cm. Each induction heating coil heats the tubular blank, so that the bottle shoulder area reaches the preset temperature. The further away from the right bottle opening, the lower the temperature of the bottle shoulder area. The spinning roller of the spinning machine is inserted into the gap between each induction heating coil and the surface of the tubular blank to spin the bottle shoulder. Release the chuck, reverse the tubular blank to the left and right, and repeat the above steps to spin-form the left side of the tubular blank into a bottle shoulder.

[0014] Preferably, three infrared thermometers are used to detect the temperature of the bottle shoulder area heated by the three induction heating coils. The bottle shoulder areas heated by the three induction heating coils are respectively called the high deformation zone, medium deformation zone, and low deformation zone. The high deformation zone, medium deformation zone, and low deformation zone are progressively farther away from the bottle mouth. The preset temperatures of the high deformation zone, medium deformation zone, and low deformation zone are 350℃-400℃, 280℃-320℃, and 200℃-250℃, respectively.

[0015] A gradient temperature control system is adopted for the bottle shoulder. Combining the transition characteristics of the bottle shoulder structure with spinning, the deformation zone is divided according to the three-dimensional criteria of structure-stress-deformation. The conical transition section near the bottle mouth is the high deformation zone (deformation ≥30%), which requires drastic necking. The arc section in the middle of the bottle shoulder is the medium deformation zone (deformation 15%-30%), with a smooth transition. The straight section near the bottle body is the low deformation zone (deformation ≤15%), which only requires minor adaptation. The temperature is continuously monitored in real time using an infrared thermometer to avoid local overheating or underheating caused by uneven spacing.

[0016] As a preferred option, the cold spinning parameters for the high deformation zone are as follows: temperature 350℃-400℃, temperature fluctuation range ≤±5℃; mandrel speed of spinning machine 80r / min-100r / min, spinning wheel feed 1.2mm / r-1.5mm / r, single pass reduction 3mm-5mm, to achieve rapid necking of the conical section and initial wall thickness reduction; The cold spinning parameters in the deformation zone are as follows: temperature is 280℃-320℃, temperature fluctuation range ≤±5℃; mandrel speed of spinning machine is 100r / min-120r / min, spinning wheel feed is 0.8mm / r-1.2mm / r, single pass reduction is 2mm-3mm, to ensure that the arc section surface is smooth and wrinkle-free, and the stress distribution is uniform; The cold spinning parameters for the low deformation zone are as follows: temperature is 200℃-250℃, temperature fluctuation range is ≤±5℃; the mandrel speed of the spinning machine is 100r / min-120r / min, the spinning wheel feed is 0.8mm / r-1.2mm / r, and the single-pass reduction is 2mm-3mm, achieving a smooth connection between the bottle shoulder and the straight section of the bottle body.

[0017] The temperature range of 350℃-400℃ for the high deformation zone is determined based on the material properties of 4130X steel: the static recrystallization initiation temperature of 4130X steel is approximately 550℃, and 350℃-400℃ is far below the recrystallization temperature threshold. Performing large deformation (≥30%) spinning at this temperature can effectively avoid grain coarsening caused by dynamic recrystallization, ensuring a foundation for finer microstructure during subsequent tempering. Simultaneously, this temperature significantly reduces the deformation resistance of 4130X steel compared to room temperature, resulting in more uniform plastic flow during severe necking and preventing cracking defects caused by localized stress concentration. Furthermore, the 350℃-400℃ temperature environment maintains the solid solution state of microalloying elements such as Ti, Nb, and V, preventing premature carbide precipitation and preserving the driving force for precise precipitation strengthening during the subsequent tempering stage. The temperature range of the low deformation zone is 200℃-250℃. At this temperature, the material has high deformation resistance and can fully exert the cold work hardening effect during spinning with small deformation (≤15%). The strength of this region is improved through dislocation multiplication and grain refinement. At the same time, the low temperature environment can induce slight pre-precipitation of microalloying elements, forming dispersed nanoscale pre-precipitation sites, which provide a nucleation basis for precipitation strengthening in subsequent annealing and tempering processes. The temperature range of the medium deformation zone is 280℃-320℃, which serves as a transition temperature between the high and low deformation zones. This allows for a smooth transition between stress and structure, avoiding additional residual stress caused by sudden temperature changes. Simultaneously, differentiated parameters are matched: feed rate in the high deformation zone is 1.2mm / r-1.5mm / r, and reduction is 3mm-5mm / pass (rapid prototyping); feed rate in the medium / low deformation zone is 0.8mm / r-1.2mm / r, and reduction is 2mm-3mm / pass (precision shape control). Constructing a "deformation-temperature-microalloying" synergistic mechanism: large deformation provides nucleation sites for microalloyed carbides, temperature gradient matches the solid solution-precipitation characteristics of elements, and at the same time optimizes the solid solution of Cu and the segregation state of B grain boundaries; Temperature and stress are monitored and controlled in real time during spinning. After the end is straightened, microalloy pre-precipitation sites are formed, laying the foundation for subsequent performance improvement.

[0018] Preferably, the vacuum degree in the vacuum induction melting furnace in step 1 is below 5.0×10⁻³Pa, and the temperature inside the furnace is monitored by the internal temperature measuring thermocouple of the vacuum induction melting furnace to raise the temperature to 1500℃-1550℃. In step 1, Al is added to the molten steel at a uniform rate through the inert gas-protected feeding device in the furnace top charging hopper, and the temperature is maintained for 20-25 minutes. After adding Al, maintain the vacuum level and heating power unchanged, and keep the temperature for 20-25 minutes to ensure that Al reacts fully with the molten steel.

[0019] Al has a higher deoxidation priority than Ti, Nb, and V, and can preferentially combine with O in molten steel to form fine Al2O3 inclusions. This avoids O from combining with key microalloying elements such as Ti, Nb, and V to form ineffective oxides, thus ensuring the subsequent precipitation efficiency of Ti, Nb, and V carbides. The generated nanoscale Al2O3 inclusions can serve as heterogeneous nucleation cores, working synergistically with subsequent forging processes to refine the as-cast grains, laying a clean microstructure foundation for the synergistic effect of the hexa-element microalloying system.

[0020] Raise the temperature inside the vacuum induction melting furnace to 1600℃, and feed Cu into the middle region of the molten steel at a uniform speed through a sealed feeding pipe protected by inert gas. Hold the temperature for 30-35 minutes, and then start the electromagnetic stirring device inside the vacuum induction melting furnace for stirring. Cu powder is fed into the central region of molten steel at a uniform rate through a sealed feeding pipe protected by inert gas (argon). The feeding rate is controlled at 0.3-0.5 kg / min to prevent Cu powder from floating on the surface of the molten steel and causing oxidation or volatilization. After the Cu powder is added, the current vacuum level, temperature and heating power in the furnace are maintained constant for 30-35 minutes. During this period, the electromagnetic stirring device in the furnace is activated (stirring frequency of 15-20 Hz) to ensure that Cu is uniformly dissolved in the molten steel and to avoid compositional segregation. Cu can form a nano-scale Cu-rich precipitate in the steel, which has both precipitation strengthening and auxiliary hydrogen trapping functions, while improving the steel's resistance to hydrogen-induced cracking. The solid solution and precipitation behavior of Cu can be matched with the carbide precipitation of Ti, Nb and V to avoid mutual interference between different precipitates. At the same time, the addition of Cu can make up for the lack of toughness improvement in traditional microalloyed steel, and achieve synergistic optimization of strength and toughness.

[0021] The molten steel is poured into the electroslag remelting furnace, and the temperature inside the furnace is stabilized at 1500℃-1550℃. When the rising rate of the molten steel in the crystallizer of the electroslag remelting furnace is 1.2mm / min-1.5mm / min, element B is added.

[0022] Boron (B) is added to the slag pool at a uniform rate through an inert gas-protected feeding pipe above the crystallizer, with the feeding rate controlled at 0.05-0.1 kg / min. This ensures that B slowly diffuses into the molten steel through the slag pool, avoiding excessive local concentrations that could lead to component segregation. After the addition of B, the current voltage and current parameters are maintained, and electroslag remelting continues for 40-45 minutes to ensure uniform distribution of B in the molten steel. B can significantly strengthen grain boundaries, inhibit hydrogen-induced grain boundary cracking, and improve the hardenability of steel, ensuring the uniformity of lath martensite structure after quenching and tempering. Because of its small atomic radius (0.082 nm), B can preferentially segregate at grain boundaries during the solidification of molten steel, forming BN compounds or B atom segregation layers, reducing grain boundary energy, hindering the enrichment and diffusion of hydrogen atoms at grain boundaries, and inhibiting grain boundary slip.

[0023] As a preferred method, obtaining a round billet by casting and forging molten steel includes the following specific steps: The molten steel is poured into the mold and cast into a billet; the billet is heated to 1200℃-1250℃ and held for 4h-5h. A multi-pass light-pressure forging process is adopted, with a forging ratio ≥5, to obtain a round billet of ø200-ø220.

[0024] The final melting temperature is controlled at 1620-1650℃, and the temperature is held for 30 minutes to ensure uniform solid solution of the six-element microalloying elements. Then, the mixture is cooled to form a cast billet.

[0025] The billet is heated to 1200-1250℃ and held for 4-5 hours. The billet is then forged using a multi-pass light-pressure forging process with a forging ratio ≥5 to obtain a round billet of ø200-220. Through the synergistic effect of the forging process and Al2O3 heterogeneous nucleation, the grains are initially refined.

[0026] Preferably, the process of piercing and rolling the round billet to obtain the tubular billet includes the following specific steps: The round billet is placed in a gas-fired heating furnace, and the furnace temperature is raised to 1180℃-1220℃ and held for ≥40 minutes. At 1180℃-1220℃, the billet is pierced using a two-roll skew rolling mill. The piercing mill rolls are angled at 12°-15° and aligned with the center of the billet. The mandrel extension of the two-roll skew rolling mill is 80mm-100mm, the piercing speed is 1.5m / s-2.0m / s, and the piercing end temperature is stabilized at 1050℃-1100℃. This yields a billet with an outer diameter of ø220mm-ø280mm and an inner diameter of ø14mm. A billet with a diameter of 0-200 mm and a wall thickness of 40-50 mm is rolled on a three-roll continuous tube mill for thinning. The rolling passes are set to 3-5 times, with the thinning rate of the first pass controlled at 25%-30%, the thinning rate of the second to fifth passes at 35%-40%, and the total thinning rate at 60%-70%. A tubular billet with an outer diameter of ø280-ø320 mm, a wall thickness of 12-15 mm, and an inner diameter of ø256-ø290 mm is obtained. The initial rolling temperature is 1050℃-1100℃, and the final rolling temperature is 850℃-900℃.

[0027] The initial rolling temperature is connected to the piercing end temperature, which is 1050-1100℃. The final rolling temperature is precisely controlled at 850-900℃ to ensure that the rolled billet obtains a uniform austenitic structure. At the same time, it creates thermodynamic conditions for the subsequent formation of Cu, Ti, Nb and other element precipitates, resulting in tubular billets.

[0028] Preferably, step 2 is followed by the following steps: annealing: Local annealing is performed using a bottle shoulder local induction annealing machine. The gas cylinder is placed horizontally in the V-shaped hydraulic positioning fixture of the annealing machine. The CNC displacement platform is activated to move the arc-shaped fitting induction heating coil to the bottle shoulder area, so that the arc-shaped fitting induction heating coil covers the bottle shoulder. The distance between the inner side of the arc-shaped fitting induction heating coil and the outer surface of the bottle shoulder is kept constant at 8mm-10mm. 50mm thick aluminum silicate insulation cotton is wrapped around the non-heated areas of the bottle body and bottle mouth. About three thermocouples are attached to the outer wall of the bottle shoulder to detect the temperature of each area of ​​the bottle shoulder. When the temperature of the bottle shoulder reaches 550℃-580℃, it is kept at this temperature for 30min-40min and then naturally air-cooled to room temperature.

[0029] This invention wraps the non-heated areas of the bottle body and mouth with 50mm thick aluminum silicate insulation cotton to reduce heat conduction from the bottle shoulder area to non-target areas. A thermocouple (temperature measurement accuracy ±1℃) is attached to the outer wall of each of the three deformation zones (high, medium, and low) on the bottle shoulder. The thermocouple signals are connected to the temperature control system to achieve real-time temperature monitoring and closed-loop control throughout the annealing process. The induction heating power is 25 kW-30 kW, and the heating rate is controlled at 8℃ / min-10℃ / min to avoid excessively rapid heating leading to localized overheating or thermal stress concentration on the bottle shoulder. When the thermocouples detect that the temperature in all three deformation zones reaches 550℃-580℃, heating is stopped, followed by a 30-40 minute holding period. After the holding period, the heating power is turned off, and the bottle is allowed to cool naturally to room temperature. This can initially eliminate more than 60% of the residual tensile stress from spinning, while providing energy conditions for the formation of composite precipitates of Al, Cu, Ti, Nb, and V, further optimizing the hydrogen trap distribution.

[0030] Preferably, the annealing process further includes the following steps: Conditioning: The gas cylinder is placed in a gas heating furnace and heated to 880℃-900℃, and held at that temperature for 2-3 hours. A high-pressure water mist quenching process is used to cool the gas cylinder using nozzles, reducing its temperature to room temperature. Within the 600℃-400℃ range, the cooling rate is ≥30℃ / s. The gas cylinder is then placed in a resistance tempering furnace, where it is first heated to 450℃ and held for 1 hour, and then heated to 550℃-600℃ and held for 2.5-3.0 hours.

[0031] Based on the 3.2%-3.8% Ni equivalent range of 4130X steel in this invention, a high-pressure water mist quenching process is used to quench the heated gas cylinder. Thermocouples are used to monitor the cylinder temperature, and the cooling rate is controlled by nozzles. Within the critical phase transformation range of 600℃-400℃, the cooling rate is ≥30℃ / s, ensuring a uniform and fine lath martensite structure across the entire 12mm wall thickness of the cylinder. Immediately after quenching, the cylinder is placed in a staged tempering process: first, the temperature is raised to 450℃ and held for 1 minute. h, then heat to 550℃-600℃ and hold for 2.5h-3.0h, then air cool to room temperature; during the segmented tempering process, the precipitation sequence of multi-element microalloying elements is precisely controlled: Cu-rich nanophase is preferentially precipitated at 450℃, Ti-Nb-V composite nanocarbide is precipitated in large quantities at 550℃-600℃, and at the same time, Al2O3 inclusions and B grain boundary segregation layers work together to finally form a multi-element strengthening and hydrogen trapping system of "composite carbide + Cu-rich phase + Al2O3 + B grain boundary strengthening".

[0032] Therefore, the present invention has the following beneficial effects: A six-element synergistic microalloying system, "Ti-Nb-V-Al-Cu-B", was proposed, which breaks through the limitations of traditional ternary microalloying. The addition of Al, Cu and B elements forms functional complementarity with the original elements: Al realizes deoxidation purification and heterogeneous nucleation, Cu realizes precipitation strengthening and resistance to hydrogen-induced cracking, and B realizes grain boundary strengthening and hardenability improvement. A three-step graded smelting and addition process was set up, and the timing of addition was precisely controlled according to the physicochemical properties of each element: Al was deoxidized and purified in the early stage of smelting, Cu was ensured solid solubility in the middle stage of smelting, and B was prevented from volatilizing in the electroslag remelting stage. This solved the technical problem of mutual interference and loss of effective content when adding multiple elements, and ensured that the synergistic effect of the six-element system was fully exerted. By using an original Ni equivalent formula to control the Ni equivalent, the Ni equivalent can be controlled above 12.5 at room temperature, which can ensure that the hardenability of the steel meets the requirements of uniform lath martensite transformation of the entire cross section of the 12mm thick gas cylinder wall, while also taking into account the matching of strength and toughness. A hydrogen trapping synergy factor (HCF) formula was proposed to accurately quantify the synergistic construction efficiency of the pentagonal microalloying system for irreversible hydrogen traps. By controlling HCF ≥ 1.2, the irreversible hydrogen trap density in the steel can be ensured to be ≥ 5 × 10¹. 5 cm⁻³, with a diffusible hydrogen concentration ≤0.3ppm, fundamentally suppresses hydrogen-induced fatigue failure and provides a quantitative basis for the precise control of the material's resistance to hydrogen embrittlement; The entire process of "six-element micro-alloying - gradient cold spinning - segmented tempering" is synergistic: the cold work hardening effect of cold spinning enhances the driving force of element precipitation, and segmented tempering precisely controls the timing of multi-element precipitates, ultimately forming a composite system of "multi-element precipitation strengthening + grain boundary strengthening + hydrogen trap enhancement". Compared with existing technologies, the yield strength is increased by ≥3% and the elongation is increased by ≥10% (30MPa H2 environment). By adjusting the chemical composition and improving the manufacturing process, the comprehensive mechanical properties and fatigue failure resistance of the steel in the shoulder area of ​​the gas cylinder have been significantly improved, effectively extending the service life of the gas cylinder. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the deformation zone division of the gas cylinder shoulder area according to the present invention; Figure 2 This is a metallographic image of Embodiment 1 of the present invention; Figure 3 This is a comparison diagram of stress-strain curves of Embodiment 1 and the comparative example of the present invention in air and 30 MPa H2 environments, respectively; Figure 4 A comparison of ΔK-da / dN curves of Embodiment 1 and the comparative example of the present invention under air and 30 MPa H2 environments, respectively. Detailed Implementation

[0034] The present invention will now be further described with reference to the accompanying drawings and specific embodiments.

[0035] Example 1 A method for manufacturing a high-pressure hydrogen storage cylinder made of steel, wherein the cylinder is made of 4130X steel, and the mass percentage of each component of 4130X steel is as follows: C: 0.300%, Mn: 0.500%, Ni: 3.500%, Si: 0.200%, P: 0.010%, S: 0.020%, Cr: 1.000%, Mo: 0.200%, Nb: 0.050%, Ti: 0.040%, V: 0.140%, Al: 0.060%, Cu: 0.150%, B: 0.002%, with the balance being Fe; calculated... =13.95, HCF=1.33; satisfies Requirements: ≥12.5, HCF≥1.2; High-pressure hydrogen storage cylinders are manufactured using 4130X steel with the above-mentioned composition. The cylinder diameter is 300mm and the wall thickness is 12mm.

[0036] Step 1-1: First, perform the vacuum induction melting process: Load the proportioned 4130X steel base material (all components except Al, Cu, and B) into the vacuum induction melting furnace, close the furnace body and cover, start the vacuum pump group to evacuate the furnace, and reduce the vacuum degree inside the furnace to below 5.0×10⁻³Pa; connect the medium frequency induction heating power supply, set the heating power to 220kW, and heat the furnace material at a heating rate of 10℃ / min, monitor the furnace temperature in real time, and stop heating and hold the temperature when the furnace temperature reaches 1500℃; Al blocks with a purity ≥ 99.99% (0.045% by mass) are added to the molten steel at a uniform rate through an inert gas (argon) protected feeding device in the furnace top charging hopper. The feeding rate is controlled at 0.6 kg / min to avoid high-temperature volatilization of Al. After Al is added, the vacuum level and heating power are kept constant, and the temperature is maintained for 25 minutes to ensure that Al reacts fully with the molten steel. Steps 1-2: Maintain a vacuum level of no less than 5.0 × 10⁻³ Pa in the vacuum induction melting furnace, adjust the medium-frequency induction heating power to 240 kW, and continue heating the molten steel at a heating rate of 6℃ / min, monitoring the temperature in real time using in-furnace thermocouples; when the molten steel is completely melted and the temperature stabilizes at 1600℃, feed electrolytic Cu powder (0.120% by mass) with a purity ≥ 99.99% into the middle region of the molten steel at a uniform speed through a sealed feeding pipe protected by inert gas (argon), controlling the feeding rate at 0.5 kg / min to prevent Cu powder from floating on the surface of the molten steel and causing oxidation or volatilization; after the Cu powder is added, maintain the current vacuum level, temperature, and heating power in the furnace unchanged, and continue to hold the temperature for 30 minutes, during which time start the in-furnace electromagnetic stirring device (stirring frequency of 15 Hz) to ensure that Cu element is uniformly dissolved in the molten steel and avoid compositional segregation; Steps 1-3, the electroslag remelting stage, are carried out in an electroslag remelting furnace, with the addition of element B (0.002% by mass), and the slag layer thickness controlled at 100 mm. After closing the furnace lid, argon gas is introduced as a protective atmosphere to maintain the gas pressure inside the furnace at 0.06 MPa, preventing air from mixing in and causing oxidation of the molten steel. Connect the DC power supply to the electroslag remelting furnace, set the arc ignition voltage to 60V and the working current to 3000A, and start the electroslag remelting process. Monitor the molten pool temperature in real time, and when the temperature is stabilized at 1500℃±5℃ and the rising rate of the molten steel in the crystallizer is maintained at 1.5mm / min, start adding element B. Select ferroborone alloy (15% B mass fraction, alloy purity ≥99.5%) as the B source, and add it to the slag pool at a uniform rate through the inert gas-protected feeding pipe above the crystallizer according to the target addition amount. Control the feeding rate at 0.1kg / min to ensure that element B slowly diffuses into the molten steel through the slag pool, avoiding excessive local concentration that may cause component segregation. After the addition of element B is completed, maintain the current voltage and current parameters unchanged and continue electroslag remelting for 45 minutes to ensure that element B is evenly distributed in the molten steel. Step 2-1: After completing the three-step element addition, precisely control the final melting temperature to 1650℃ and hold for 30 minutes to ensure uniform solid solution of the hexa-element microalloying elements. Then cool to form a billet. Heat the billet to 1200℃ and hold for 5 hours. Use a multi-pass light-pressure forging process with a forging ratio of 5 to obtain a round billet with a diameter of ø220. Through the synergistic effect of the forging process and Al2O3 heterogeneous nucleation, the grains are initially refined. Step 2-2: Place the round billet into a gas heating furnace, set the heating rate to 12 °C / min. After heating up to the target furnace temperature of 1200 °C, keep the heating power constant and the soaking time is 40 min. Monitor the temperature in real time through a thermocouple to ensure that the temperature uniformity error in the radial and axial directions of the billet is ≤ ±5 °C. Perform piercing on the soaked round billet on a two-high skew rolling piercing mill. The initial piercing temperature is the same as the soaking temperature of the gas heating furnace, which is 1200 °C. Set the roll inclination angle of the piercing mill to 15° and align it with the center of the round billet. The nose extension is 100 mm, and the piercing rate is 2.0 m / s. The piercing end temperature is stabilized at 1100 °C to avoid excessive solid solution of Cu element or volatilization of B element caused by local overheating. After piercing, a billet with an outer diameter of ø280 mm, an inner diameter of ø200 mm, and a wall thickness of 40 mm is obtained. Subsequently, perform elongation and thinning on the pierced round billet on a three-high continuous rolling mill, adopting a "progressive thinning" design. The number of rolling passes is set to 5 times, among which the reduction rate in the first pass is controlled at 30%, and the reduction rate in the 2nd - 5th passes is reduced to 40%. The total reduction rate is 70%. After continuous rolling, a tubular billet with an outer diameter of ø300 mm, a wall thickness of 12 mm, and an inner diameter of ø276 mm is obtained. The initial continuous rolling temperature is connected with the piercing end temperature, which is 1100 °C. Precisely control the final rolling temperature to 900 °C to ensure that the rolled billet obtains a uniform austenite structure, and at the same time create thermodynamic conditions for the formation of precipitation phases of Cu and elements such as Ti and Nb, and obtain a tubular billet. Step 2-3: Perform cold spinning on the shoulder of the tubular billet: Use a chuck to horizontally clamp the tubular billet to ensure that there is no eccentric shaking of the billet during the spinning process. Before spinning, start the zone induction heating device supporting the spinning machine. This device includes 3 groups of independently temperature-controlled induction coils, corresponding to the high deformation zone, medium deformation zone, and low deformation zone of the shoulder as shown respectively Figure 2 The coil-to-billet surface spacing is constantly 15 cm. Use an infrared thermometer to continuously monitor the temperature in real time to avoid local overburning or insufficient heating caused by uneven spacing. Combine the transition characteristics of the shoulder structure and the spinning simulation results to divide the deformation zone according to the three-dimensional criterion of "structure - stress - deformation": High deformation zone: The conical transition section near the bottle mouth needs to complete severe necking forming. Heat through the first group of induction coils, set the heating power to 80 kW, precisely control the temperature to 400 °C, and the temperature fluctuation range is ≤ ±5 °C. Set the core mold rotation speed to 100 r / min, the swivel feed to 1.5 mm / r, and the single-pass reduction to 5 mm. Adopt a rapid forming mode with a large single-pass deformation to achieve rapid necking of the conical section and preliminary thinning of the wall thickness. In the middle deformation zone: the arc section in the middle of the bottle shoulder has a smooth transition in shape; it is heated by the second set of induction coils, with the heating power set at 60kW and the temperature controlled at 320℃; the core mold speed is increased to 120r / min, the rotary wheel feed is 1.2mm / r, and the single-pass pressing amount is 3mm. A smooth transition mode is adopted to ensure that the arc section surface is smooth and wrinkle-free, and the stress distribution is uniform. Low deformation zone: Heated by the third set of induction coils, with a heating power of 40kW and a temperature control of 250℃; the core mold speed is maintained at 120r / min, the rotary wheel feed is 1.2mm / r, and the single-pass pressing amount is 3mm. A precise shape control mode is adopted to achieve a smooth connection between the bottle shoulder and the straight section of the bottle body, while giving full play to the cold work hardening effect to improve the strength of this area. After the bottle shoulder is cold-spinned, the residual heat from the bottle shoulder spinning (bottle mouth temperature 260℃) is used to perform cold spinning on the bottle mouth. The mandrel speed is 80r / min, the rotary wheel feed is 0.8mm / r, and the mouth is gradually closed in 4 passes with a single pass pressing amount of 2mm. The bottle mouth has an outer diameter of ø80mm, an inner diameter of ø68mm, and a wall thickness of 12mm. It is smoothly and gradually connected to the 12mm wall thickness of the bottle shoulder. The curvature of the transition zone is R60mm, thus obtaining the gas cylinder. Release the chuck, reverse the tubular blank to the left and right, and repeat the above steps to spin-form the left side of the tubular blank into a bottle shoulder.

[0037] Step 3: Immediately transfer the gas cylinder to the cylinder shoulder local induction annealing machine for local annealing. Place the gas cylinder horizontally within the V-shaped hydraulic positioning fixture of the annealing machine. Start the CNC displacement platform to precisely move the arc-shaped fitting induction heating coil to the cylinder shoulder area, ensuring that the arc-shaped fitting induction heating coil covers the high, medium, and low deformation zones of the cylinder shoulder. The distance between the inner side of the arc-shaped fitting induction heating coil and the outer surface of the cylinder shoulder is 10mm. Wrap 50mm thick aluminum silicate insulation cotton around the non-heated areas of the cylinder body and mouth to reduce heat conduction from the cylinder shoulder area to non-target areas. Attach one thermocouple (temperature measurement accuracy ±1℃) to the outer wall of each of the high, medium, and low deformation zones of the cylinder shoulder. Connect the thermocouple signals to the temperature control system to achieve real-time temperature monitoring and closed-loop control throughout the annealing process. Set the induction heating power to 30kW and the heating rate to 10℃ / min to avoid overheating or thermal stress concentration in the bottle shoulder due to excessively rapid heating. When the thermocouple detects that the temperature of all three deformation zones has reached 580℃, stop heating and then keep it at that temperature for 40 minutes. After the holding period, turn off the heating power and allow it to cool naturally to room temperature. Step 4: Place the gas cylinder in a gas heating furnace and heat it to 900℃. Hold it at this temperature for 2 hours to ensure austenite homogenization. At this point, Cu is fully dissolved and B is evenly distributed at the grain boundaries. Use a high-pressure water mist quenching machine to quench the heated gas cylinder. Use thermocouples to monitor the cylinder temperature and control the cooling rate through nozzles. The cooling rate is 35℃ / s in the critical range of 600℃-400℃ to obtain a uniform and fine lath martensite structure. Immediately after quenching, place the gas cylinder in a resistance tempering furnace and use a segmented tempering process: first heat to 450℃ and hold for 1 hour, then heat to 600℃ and hold for 3.0 hours, and then air cool to room temperature.

[0038] Example 2 The mass percentages of the components in the 4130X steel in Example 2 are as follows: C: 0.330%, Mn: 0.60%, Ni: 3.800%, Si: 0.300%, P: 0.015%, S: 0.010%, Cr: 1.10%, Mo: 0.250%, Nb: 0.045%, Ti: 0.035%, V: 0.130%, Al: 0.050%, Cu: 0.140%, B: 0.003%, with the balance being Fe; calculated... =15.5, HCF=1.20; satisfies The requirements are ≥12.5 and HCF≥1.2; other contents in Example 2 are the same as in Example 1.

[0039] Example 3 The mass percentages of the components in the 4130X steel in Example 3 are as follows: C: 0.320%, Mn: 0.450%, Ni: 3.600%, Si: 0.250%, P: 0.010%, S: 0.010%, Cr: 0.900%, Mo: 0.150%, Nb: 0.048%, Ti: 0.038%, V: 0.120%, Al: 0.055%, Cu: 0.135%, B: 0.002%, with the balance being Fe; calculated... =14.6, HCF=1.20; satisfies The requirements are ≥12.5 and HCF≥1.2; other contents in Example 3 are the same as in Example 1.

[0040] Example 4 The mass percentages of the components in the 4130X steel in Example 4 are as follows: C: 0.280%, Mn: 0.400%, Ni: 3.200%, Si: 0.150%, P: 0.010%, S: 0.020%, Cr: 0.800%, Mo: 0.180%, Nb: 0.046%, Ti: 0.036%, V: 0.138%, Al: 0.058%, Cu: 0.138%, B: 0.001%, with the balance being Fe; calculated... =12.8, HCF=1.26; satisfies The requirements are ≥12.5 and HCF≥1.2; other contents in Example 4 are the same as in Example 1.

[0041] I. Tissue observation and performance testing of the gas cylinder samples prepared in Example 1: 1. Remove a sample from the shoulder of the gas cylinder, mechanically grind the sample with #400-#2000 silicon carbide sandpaper, then polish the sample with 1μm diamond suspension; etch the sample in 4% nitric acid ethanol solution for 15s, rinse the sample with anhydrous ethanol and dry it with a hair dryer, and observe the metallographic structure of the sample using an optical microscope, such as... Figure 2 As shown, the grain size of the sample has decreased, remaining at around 10 μm. 2. Slow strain rate tensile tests (SSRT) were conducted on Example 1 and the comparative example on an Instron 8801 servo hydraulic universal testing machine. The stress-strain curves of the 4130X steel gas cylinder shoulder samples were obtained in laboratory air and 30 MPa H2 environment, as shown in the figure. Figure 3 The performance test results are shown in Table 1 and Table 2; The comparative sample was taken from the shoulder of a 4130X steel high-pressure hydrogen storage cylinder manufactured by a gas cylinder manufacturer. The mass percentages of the components in the comparative sample were: Nb: 0.020%, Ti: 0.012%, V: 0.055%, with no Ni, Al, Cu, or B added. The types and mass percentages of the remaining elements were the same as in Example 1.

[0042] The comparative proportion was calculated. =10.8, less than 12.5, does not meet the requirements of this invention. The requirement of ≥12.5 is not met; the calculated HCF of the comparative example is 0.4, which is less than 1.2, and does not meet the requirement of HCF≥1.2 of this invention.

[0043] Table 1. Performance test results of Example 1 and Comparative Example in air environment As can be seen from the results in Table 1, the yield strength and tensile strength of the 4130X steel in Example 1 are higher than those of the control group, and the elongation is also slightly increased.

[0044] Table 2. Performance test results of Example 1 and Comparative Example under 30MPa H2 environment. As can be seen from the results in Table 2, the elongation of the 4130X steel in Example 1 was significantly greater than that in the comparative example in a hydrogen environment, indicating that the 4130X steel in Example 1 had better resistance to hydrogen embrittlement than the comparative example.

[0045] from Figure 3 It can be seen that in a laboratory air environment, the strength of Example 1 is higher than that of the comparative example, and its elongation is also slightly greater. However, in a 30MPa H2 environment, the strength of Example 1 and the comparative example remains basically unchanged, but their elongation is significantly reduced, and the elongation of Example 1 is significantly higher than that of the comparative example. This indicates that the present invention not only improves the strength of 4130X steel, but also significantly improves the resistance of 4130X steel to hydrogen embrittlement under high-pressure hydrogen environment.

[0046] 3. Fatigue crack propagation tests (FCG) were conducted on the samples from the shoulder area of ​​4130X steel gas cylinders in Example 1 and the comparative example on an Instron 8801 servo hydraulic universal testing machine. The ΔK-da / dN curves of the samples were obtained in laboratory air and 30 MPa H2 environment. Figure 4 The performance test results are shown in Table 3.

[0047] Table 3. Fatigue crack propagation rate and acceleration factor of Example 1 and the comparative example at ΔK40 in air and 30MPa H2 environment. As can be seen from the results in Table 3, the crack propagation rate of Example 1 in the air environment is slightly lower than that of the comparative example, but the crack propagation rate of Example 1 in the H2 environment is significantly lower than that of the comparative example, and the acceleration factor of Example 1 is significantly lower than that of the comparative example, indicating that the fatigue failure resistance of the gas cylinder shoulder of the present invention is better than that of the comparative example.

[0048] from Figure 4 It can be seen that in a laboratory air environment, the crack propagation rates of both Example 1 and the comparative example are relatively low, with Example 1 exhibiting a slightly slower crack propagation rate than the comparative example. However, in a 30MPa H2 environment, the crack propagation rates of both Example 1 and the comparative example are significantly increased, with Example 1 showing a significantly faster crack propagation rate than the comparative example. This indicates that the present invention significantly improves the resistance of 4130X steel to hydrogen-induced fatigue failure.

[0049] In summary, the strength and plasticity of Example 1 are superior to those of the comparative example in air, while the plasticity of Example 1 is significantly superior to that of the comparative example in H2 environment; furthermore, the fatigue crack propagation resistance of Example 1 in high-pressure hydrogen environment is significantly superior to that of the comparative example; indicating that the present invention significantly improves the comprehensive mechanical properties and fatigue failure resistance of the gas cylinder shoulder, and can effectively extend the service life of the gas cylinder.

[0050] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for manufacturing a high-pressure hydrogen storage cylinder made of steel, wherein the cylinder is made of 4130X steel, characterized in that, The 4130X steel has the following composition by mass percentage: C: 0.28%-0.33%, Mn: 0.40%-0.60%, Ni: 3.20%-3.80%, Si: 0.15%-0.35%, P≤0.035%, S≤0.040%, Cr: 0.80%-1.10%, Mo: 0.15%-0.25%, Ti: 0.01%-0.04%, Nb: 0.02%-0.05%, V: 0.08%-0.14%, Al: 0.03%-0.06%, Cu: 0.10%-0.15%, B: 0.001%-0.003%, with the balance being iron (Fe). Make the Ni equivalent in 4130X steel ≥12.5: ； The method for manufacturing the bottle shoulder includes the following steps: Step 1: Weigh the components of 4130X steel according to their mass percentages. Place all elements except Al, Cu, and B into a vacuum induction melting furnace. Control the vacuum induction melting furnace to evacuate and raise the temperature, so that the components melt into molten steel. Add the weighed Al to the molten steel and hold it at the temperature for a period of time to melt Al. Add the weighed Cu to the molten steel and hold it at the temperature for a period of time to melt Cu. Add the weighed B to the molten steel and perform electroslag remelting. Step 2: After casting and forging the molten steel into a round billet, the round billet is pierced and rolled to obtain a tubular billet. The ends of the tubular billet are cold-spun with gradient temperature control at both ends, and the mouth of the billet is cold-spun to obtain the gas cylinder.

2. The method for manufacturing a steel high-pressure hydrogen storage cylinder according to claim 1, characterized in that, To ensure that the irreversible hydrogen trap HCF in 4130X steel is ≥1.2, 。 3. The method for manufacturing a steel high-pressure hydrogen storage cylinder according to claim 1, characterized in that, The cold spinning of the bottle shoulder includes the following steps: The tubular blank is horizontally clamped using a chuck. Three induction heating coils are set on the outer side of the right side of the tubular blank, corresponding to the bottle shoulder. The distance between each induction heating coil and the surface of the tubular blank is 15cm-18cm. Each induction heating coil heats the tubular blank, so that the bottle shoulder area reaches the preset temperature. The further away from the right bottle opening, the lower the temperature of the bottle shoulder area. The spinning roller of the spinning machine is inserted into the gap between each induction heating coil and the surface of the tubular blank to spin the bottle shoulder. Release the chuck, reverse the tubular blank to the left and right, and repeat the above steps to spin-form the left side of the tubular blank into a bottle shoulder.

4. The method for manufacturing a steel high-pressure hydrogen storage cylinder according to claim 3, characterized in that, Three infrared thermometers were used to detect the temperature of the bottle shoulder area heated by the three induction heating coils. The bottle shoulder areas heated by the three induction heating coils were respectively called the high deformation zone, medium deformation zone, and low deformation zone. The high deformation zone, medium deformation zone, and low deformation zone are successively farther away from the bottle mouth. The preset temperatures of the high deformation zone, medium deformation zone, and low deformation zone are 350℃-400℃, 280℃-320℃, and 200℃-250℃, respectively.

5. The method for manufacturing a steel high-pressure hydrogen storage cylinder according to claim 4, characterized in that, The cold spinning parameters for the high deformation zone are as follows: temperature is 350℃-400℃, temperature fluctuation range is ≤±5℃; the mandrel speed of the spinning machine is 80r / min-100r / min, the feed of the spinning wheel is 1.2mm / r-1.5mm / r, and the single-pass reduction is 3mm-5mm, so as to achieve rapid necking of the conical section and initial wall thickness reduction; The cold spinning parameters in the deformation zone are as follows: temperature is 280℃-320℃, temperature fluctuation range ≤±5℃; mandrel speed of spinning machine is 100r / min-120r / min, spinning wheel feed is 0.8mm / r-1.2mm / r, single pass reduction is 2mm-3mm, to ensure that the arc section surface is smooth and wrinkle-free, and the stress distribution is uniform; The cold spinning parameters for the low deformation zone are as follows: temperature is 200℃-250℃, temperature fluctuation range is ≤±5℃; the mandrel speed of the spinning machine is 100r / min-120r / min, the spinning wheel feed is 0.8mm / r-1.2mm / r, and the single-pass reduction is 2mm-3mm, achieving a smooth connection between the bottle shoulder and the straight section of the bottle body.

6. The method for manufacturing a steel high-pressure hydrogen storage cylinder according to claim 1, characterized in that, In step 1, the vacuum degree inside the vacuum induction melting furnace is below 5.0×10⁻³Pa. The temperature inside the furnace is monitored by the internal temperature measuring thermocouple of the vacuum induction melting furnace, and the temperature is raised to 1500℃-1550℃. In step 1, Al is added to the molten steel at a uniform rate through the inert gas-protected feeding device in the furnace top charging hopper, and the temperature is maintained for 20-25 minutes. Raise the temperature inside the vacuum induction melting furnace to 1600℃, and feed Cu into the middle region of the molten steel at a uniform speed through a sealed feeding pipe protected by inert gas. Hold the temperature for 30-35 minutes, and then start the electromagnetic stirring device inside the vacuum induction melting furnace for stirring. The molten steel is poured into the electroslag remelting furnace, and the temperature inside the furnace is stabilized at 1500℃-1550℃. When the rising rate of the molten steel in the crystallizer of the electroslag remelting furnace is 1.2mm / min-1.5mm / min, element B is added.

7. The method for manufacturing a steel high-pressure hydrogen storage cylinder according to any one of claims 1, 2, 3, 4, 5, or 6, characterized in that, The process of obtaining a round billet by casting and forging molten steel includes the following specific steps: The molten steel is poured into the mold and cast into a billet; the billet is heated to 1200℃-1250℃ and held for 4h-5h. A multi-pass light-pressure forging process is adopted, with a forging ratio ≥5, to obtain a round billet of ø200-ø220.

8. The method for manufacturing a steel high-pressure hydrogen storage cylinder according to claim 1, characterized in that, The process of piercing and rolling the round billet to obtain the tubular billet includes the following specific steps: The round billet is placed in a gas-fired heating furnace, and the furnace temperature is raised to 1180℃-1220℃ and held for ≥40 minutes. At 1180℃-1220℃, the billet is pierced using a two-roll skew rolling mill. The piercing mill rolls are angled at 12°-15° and aligned with the center of the billet. The mandrel extension of the two-roll skew rolling mill is 80mm-100mm, the piercing speed is 1.5m / s-2.0m / s, and the piercing end temperature is stabilized at 1050℃-1100℃. This yields a billet with an outer diameter of ø220mm-ø280mm and an inner diameter of ø14mm. A billet with a diameter of 0-200 mm and a wall thickness of 40-50 mm is rolled on a three-roll continuous tube mill for thinning. The rolling passes are set to 3-5 times, with the thinning rate of the first pass controlled at 25%-30%, the thinning rate of the second to fifth passes at 35%-40%, and the total thinning rate at 60%-70%. A tubular billet with an outer diameter of ø280-ø320 mm, a wall thickness of 12-15 mm, and an inner diameter of ø256-ø290 mm is obtained. The initial rolling temperature is 1050℃-1100℃, and the final rolling temperature is 850℃-900℃.

9. The method for manufacturing a steel high-pressure hydrogen storage cylinder according to claim 1, characterized in that, Step 2 is followed by the following steps: annealing: Local annealing is performed using a bottle shoulder local induction annealing machine. The gas cylinder is placed horizontally in the V-shaped hydraulic positioning fixture of the annealing machine. The CNC displacement platform is activated to move the arc-shaped fitting induction heating coil to the bottle shoulder area, so that the arc-shaped fitting induction heating coil covers the bottle shoulder. The distance between the inner side of the arc-shaped fitting induction heating coil and the outer surface of the bottle shoulder is 8mm-10mm. 50mm thick aluminum silicate insulation cotton is wrapped around the non-heated areas of the bottle body and bottle mouth. About three thermocouples are attached to the outer wall of the bottle shoulder to detect the temperature of each area of ​​the bottle shoulder. When the temperature of the bottle shoulder reaches 550℃-580℃, it is kept at this temperature for 30min-40min and then naturally air-cooled to room temperature.

10. The method for manufacturing a steel high-pressure hydrogen storage cylinder according to claim 9, characterized in that, Following the annealing process, the following steps are also included: Conditioning: The gas cylinder is placed in a gas heating furnace and heated to 880℃-900℃, and held at that temperature for 2-3 hours. A high-pressure water mist quenching process is used to cool the gas cylinder using nozzles, reducing its temperature to room temperature. Within the 600℃-400℃ range, the cooling rate is ≥30℃ / s. The gas cylinder is then placed in a resistance tempering furnace, where it is first heated to 450℃ and held for 1 hour, and then heated to 550℃-600℃ and held for 2.5-3.0 hours.

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