A 90mpa seamless steel pipe for hydrogen storage and a manufacturing method and use thereof

Abstract

The present application relates to a kind of 90MPa seamless steel pipe for hydrogen storage and its preparation method and use, include by mass percentage: C 0.32-0.35%, Si 0.2-0.25%, Mn 0.8-0.9%, Cr 1-1.1%, Mo 0.45-0.5%, Ni 0.2-0.3%, S≤0.003%, P≤0.01%, N≤0.007%, H≤0.0002%, O≤0.0025%, Ti≤0.015%, Cu≤0.2%, the balance is Fe.By the component of steel pipe is designed, can obtain the seamless steel pipe for high pressure hydrogen storage bottle type container with high strength, high toughness, high hardenability, with higher comprehensive mechanical property and lower hydrogen embrittlement sensitivity, can significantly reduce the design wall thickness of high pressure hydrogen storage bottle type container and high pressure hydrogen embrittlement sensitivity, meet the design requirement of 90MPa hydrogen storage container not to explode first leak.

Description

Technical Field

[0001] This invention relates to the field of ferrous metal smelting and metal forming and processing, specifically to a 90MPa seamless steel pipe for hydrogen storage, its preparation method and application. Background Technology

[0002] Currently, most existing hydrogen refueling stations use bottle-type containers made of seamless steel pipes for high-pressure hydrogen storage, with a storage pressure of 45 MPa and the material being AISI 4130X. To increase the driving range of hydrogen fuel cell vehicles, the storage pressure of the onboard hydrogen storage system needs to be increased from the current 35 MPa to 70 MPa. Therefore, to shorten the refueling time for hydrogen fuel cell vehicles and meet the future demand for rapid refueling of 70 MPa onboard cylinders, the high-pressure hydrogen storage containers in hydrogen refueling stations need to reach a storage pressure of over 90 MPa.

[0003] For example, existing technology (Zhai Jianming, Xu Tong, Wang Hongxia, et al. Experimental study on hydrogen embrittlement sensitivity of steel 4130X for hydrogen storage cylinders [J]. China Special Equipment Safety, 2017, 33(12):7.) discloses the study on the performance of hydrogen storage containers made of 4130X material.

[0004] However, due to the limited tensile strength of 4130X material, the design wall thickness of the bottle-type container increases significantly with increasing operating pressure, leading to incomplete hardening during heat treatment. Furthermore, with increasing operating pressure, the hydrogen embrittlement problem of 4130X material in high-pressure hydrogen environments becomes increasingly prominent. Moreover, as hydrogen pressure increases and the container wall thickness increases, the fracture toughness of 4130X decreases. The critical crack depth reached for steady-state crack propagation on the inner surface of the container is less than the container wall thickness, failing to meet the design conditions for leakage-before-explosion (LBB), severely impacting the service life of high-pressure hydrogen storage containers.

[0005] Although carbon fiber wound containers with aluminum alloy and stainless steel inner liner can solve the problem of hydrogen embrittlement under high-pressure hydrogen environment, the reliance on imported carbon fiber materials, their high cost, and long delivery cycle restrict the widespread application of carbon fiber wound containers.

[0006] Therefore, there is an urgent need to develop a low-cost seamless steel pipe material with high strength, high toughness, high hardenability, and low hydrogen embrittlement sensitivity in high-pressure hydrogen environments, which can ensure the realization of LBB design for high-pressure hydrogen storage containers. Summary of the Invention

[0007] In view of the problems existing in the prior art, the purpose of the present invention is to provide a seamless steel pipe for hydrogen storage with a pressure of 90MPa, its preparation method and application, to achieve the preparation of a low-cost seamless steel pipe material with high strength, high toughness, high hardenability, and low hydrogen embrittlement sensitivity in high-pressure hydrogen environment, which can ensure the realization of LBB design of high-pressure hydrogen storage container.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] In a first aspect, the present invention provides a 90MPa seamless steel pipe for hydrogen storage, wherein the 90MPa seamless steel pipe for hydrogen storage comprises, by weight percentage:

[0010] C 0.32-0.35%, Si 0.2-0.25%, Mn 0.8-0.9%, Cr 1-1.1%, Mo 0.45-0.5%, Ni 0.2-0.3%, S≤0.003%, P≤0.01%, N≤0.007%, H≤0.0002%, O≤0.0025%, Ti≤0.015%, Cu≤0.2%, balance Fe.

[0011] The steel provided by this invention, through the design of the steel pipe composition, can produce a seamless steel pipe with high strength, high toughness, and high hardenability for high-pressure hydrogen storage cylinder containers. It has high comprehensive mechanical properties and low hydrogen embrittlement sensitivity, which can significantly reduce the design wall thickness and high-pressure hydrogen embrittlement sensitivity of high-pressure hydrogen storage cylinder containers, and meet the design requirements of 90MPa hydrogen storage containers to prevent leakage before explosion.

[0012] As a preferred embodiment of the present invention, the 90MPa seamless steel pipe for hydrogen storage comprises, by weight percentage:

[0013] C 0.33-0.35%, Si 0.24-0.25%, Mn 0.85-0.9%, Cr 1.05-1.1%, Mo 0.48-0.5%, Ni 0.28-0.3%, S≤0.003%, P≤0.01%, N≤0.007%, H≤0.0002%, O≤0.0025%, Ti≤0.015%, Cu≤0.2%, balance Fe.

[0014] In a second aspect, the present invention provides a method for preparing a 90MPa seamless steel pipe for hydrogen storage as described in the first aspect, the method comprising:

[0015] After preparing the raw materials according to the formula, the process involves electric arc furnace steelmaking, ladle refining, vacuum degassing, and electrode ingot casting to obtain electrode ingots.

[0016] The obtained electrode ingot was electroslag remelted under a protective atmosphere, and then subjected to a first heat preservation, forging, cooling, annealing, second heat preservation, and piercing hot rolling to obtain a 90MPa seamless steel pipe for hydrogen storage.

[0017] As a preferred technical solution of the present invention, aluminum material is added during the electric furnace steelmaking process to control the P content in the molten steel to be ≤0.01% and the C content to be 0.05-0.15% by mass percentage.

[0018] Preferably, the tapping temperature of the electric arc furnace steelmaking is 1635-1665℃.

[0019] As a preferred technical solution of the present invention, the ladle refining process uses CaO-Al2O3-SiO2-MgO refining slag for treatment.

[0020] Preferably, the ladle refining process uses bottom-blown argon gas throughout.

[0021] Preferably, the flow rate of the argon gas is 100-150 NL / min.

[0022] Preferably, the molten iron obtained from ladle refining has a content of P ≤ 0.01% and S ≤ 0.008% by mass percentage.

[0023] As a preferred embodiment of the present invention, the vacuum degassing is performed under a protective atmosphere.

[0024] Preferably, the temperature of the molten steel during vacuum degassing is 1660-1680℃.

[0025] Preferably, the absolute vacuum degree during the vacuum degassing is <67 Pa.

[0026] Preferably, the flow rate of the protective atmosphere in the vacuum degassing is 80-100 NL / min.

[0027] Preferably, the absolute vacuum degree is maintained for more than 20 minutes during the vacuum degassing process. After the vacuum is broken, the flow rate of the protective atmosphere is reduced to 40-60 NL / min, and soft blowing and stirring are performed.

[0028] Preferably, the time for soft blowing and stirring is ≥15 min.

[0029] As a preferred embodiment of the present invention, the electrode ingot is cast under a protective atmosphere.

[0030] Preferably, the electroslag remelting is performed using a GaF2-GaO-Al2O3-MgO quaternary slag system under a protective atmosphere.

[0031] Preferably, the ingot obtained by electroslag remelting contains S ≤ 0.003% and O ≤ 15 × 10⁻⁶ by mass percentage. -6N≤40×10 -6 .

[0032] As a preferred technical solution of the present invention, the first insulation includes a first stage insulation and a second stage insulation.

[0033] Preferably, the heating rate of the first stage of heat preservation is 80-90℃ / h.

[0034] Preferably, the insulation temperature of the first stage of insulation is 750-800℃.

[0035] Preferably, the heat preservation time in the first stage is 1-1.4 hours.

[0036] Preferably, the heating rate of the second stage of heat preservation is 90-100℃ / h.

[0037] Preferably, the insulation temperature of the second stage is 1150-1180℃.

[0038] Preferably, the heat preservation time in the second stage is 1.5-2 hours.

[0039] Preferably, the total forging ratio of the forging blank is >3.

[0040] Preferably, the final forging temperature of the forging billet is ≥850℃.

[0041] Preferably, the forging process is performed at least once.

[0042] Preferably, the cooling includes slow cooling inside the furnace and air cooling after exiting the furnace.

[0043] Preferably, the slow cooling time inside the furnace is ≥24 hours.

[0044] Preferably, the final temperature of the slow cooling in the furnace is 50-80°C.

[0045] Preferably, the annealing is performed by holding at a temperature of 600-650℃ for 8-9 hours, then slowly cooling to 200-250℃ at a cooling rate of 60-70℃ / h, and then air-cooling after removal from the furnace.

[0046] As a preferred technical solution of the present invention, the second insulation includes sequential insulation of a first temperature zone, insulation of a second temperature zone, insulation of a third temperature zone, and insulation of a fourth temperature zone.

[0047] Preferably, the insulation temperature of the first temperature zone is 550-600℃.

[0048] Specifically, the insulation time for the first temperature zone is 1.5-2 hours.

[0049] Specifically, the insulation temperature of the second temperature zone is 850-900℃.

[0050] Specifically, the insulation time for the second temperature zone is 1.5-2 hours.

[0051] Specifically, the insulation temperature of the third temperature zone is 1050-1100℃.

[0052] Specifically, the insulation time for the third temperature zone is 1.5-2 hours.

[0053] Specifically, the insulation temperature of the fourth temperature zone is 1250-1290℃.

[0054] Specifically, the insulation time for the fourth temperature zone is 1.5-2 hours.

[0055] Specifically, the sum of the heating time and the heat preservation time in the second heat preservation process is ≥24h.

[0056] Preferably, the temperature of the billet fed into the piercing hot rolling process is 1260-1280℃.

[0057] Thirdly, the present invention provides the use of the 90MPa seamless steel pipe for hydrogen storage as described in the first aspect, the use of which includes the preparation of hydrogen storage containers using the aforementioned 90MPa seamless steel pipe for hydrogen storage.

[0058] Compared with existing technical solutions, the present invention has the following beneficial effects:

[0059] (1) The seamless steel pipe provided by the present invention improves the hardenability of the material by specifically designing the contents of C, Mn, Cr, Mo and Ni, and by utilizing the synergistic effect between elements, so as to ensure that the hydrogen storage container with a pressure of 90MPa can be hardened through the entire wall thickness when quenched on one side. At the same time, by controlling the contents of C, Mn and Cr, the strength of the material is improved by utilizing the synergistic effect between elements. By increasing the Mo content, the impact toughness and fracture toughness of the steel can be improved. By increasing the tempering resistance of the steel, a higher tempering temperature is adopted, which is beneficial to reduce the internal stress, dislocation density and distortion during quenching, thereby reducing the hydrogen embrittlement sensitivity. By adding Ni, the grains can be refined, and the plasticity and toughness of the material can be improved.

[0060] (2) In the steelmaking and pipe-making process of the seamless steel pipe preparation process provided by the present invention, the combination of electroslag remelting and forging billet-making processes is adopted to improve the purity of steel, eliminate segregation, refine grains, and improve toughness and resistance to hydrogen embrittlement; at the same time, non-metallic inclusions are reduced through steelmaking process and the inner surface roughness is reduced during pipe-making process, thereby improving the material's resistance to high-pressure hydrogen embrittlement.

[0061] 5) The seamless steel pipe obtained by this invention has high hardenability, ensuring complete hardening during the heat treatment of high-pressure thick-walled containers, and has good strength, toughness and plasticity matching, high fracture toughness and low hydrogen embrittlement sensitivity. It can reduce the design wall thickness of high-pressure hydrogen storage containers and realize the LBB design of 90MPa hydrogen storage containers, which is conducive to the development of high-pressure hydrogen storage containers towards high pressure and high capacity. Attached Figure Description

[0062] Figure 1 These are metallographic photographs of the steel pipe obtained in Example 1;

[0063] Figure 2 This is a metallographic photograph of the steel pipe obtained in Example 2.

[0064] The present invention will now be described in further detail. However, the examples described below are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims. Detailed Implementation

[0065] To better illustrate the present invention and facilitate understanding of its technical solutions, typical but non-limiting embodiments of the present invention are as follows:

[0066] This embodiment provides a 90MPa seamless steel pipe for hydrogen storage, wherein the 90MPa seamless steel pipe for hydrogen storage comprises, by weight percentage:

[0067] C 0.32-0.35%, Si 0.2-0.25%, Mn 0.8-0.9%, Cr 1-1.1%, Mo 0.45-0.5%, Ni 0.2-0.3%, S≤0.003%, P≤0.01%, N≤0.007%, H≤0.0002%, O≤0.0025%, Ti≤0.015%, Cu≤0.2%, balance Fe.

[0068] Specifically, the 90MPa seamless steel pipe for hydrogen storage comprises, by mass percentage: C 0.33-0.35%, Si 0.24-0.25%, Mn 0.85-0.9%, Cr 1.05-1.1%, Mo 0.48-0.5%, Ni 0.28-0.3%, S≤0.003%, P≤0.01%, N≤0.007%, H≤0.0002%, O≤0.0025%, Ti≤0.015%, Cu≤0.2%, with the balance being Fe.

[0069] In this invention, the carbon (C) content in the 90MPa seamless steel pipe for hydrogen storage is 0.32-0.35% by mass. For example, it can be 0.32%, 0.325%, 0.33%, 0.335%, 0.34%, 0.345%, or 0.35%, but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable. Increasing the C content can improve the tensile strength, yield strength, and hardenability of chromium-molybdenum steel. Although the plasticity and toughness of the material decrease accordingly, the toughness, plasticity, and resistance to hydrogen embrittlement can be improved by adding an appropriate amount of Ni and increasing the Mo content. To achieve a reasonable balance between strength and toughness, the C content is determined to be in the range of 0.32-0.35%.

[0070] In this invention, the Si content in the 90MPa seamless steel pipe for hydrogen storage is 0.2-0.25% by mass, for example, it can be 0.2%, 0.21%, 0.22%, 0.23%, 0.24%, or 0.25%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable. Si can dissolve in ferrite and austenite to improve the hardness and strength of steel. However, Si dissolved in steel is detrimental to the toughness of steel and promotes the segregation of impurity elements P and S at grain boundaries, thus worsening the steel's resistance to delayed fracture. Therefore, its content is controlled at 0.20-0.25%.

[0071] In this invention, the Mn content in the 90MPa seamless steel pipe for hydrogen storage is 0.8-0.9% by mass, for example, it can be 0.8%, 0.81%, 0.82%, 0.83%, 0.84%, 0.85%, 0.86%, 0.87%, 0.88%, 0.89%, or 0.9%, etc., but is not limited to the listed values; other unlisted values ​​within this range are also acceptable. Mn can significantly improve the hardenability and strength of steel; however, Mn and S in steel usually exist in the form of MnS inclusions, which reduces the transverse impact toughness of the steel and increases its hydrogen embrittlement sensitivity. Therefore, the Mn content can be increased to 0.80-0.90%, and the S content can be controlled below 0.003% to avoid the formation of MnS inclusions.

[0072] In this invention, the Cr content in the 90MPa seamless steel pipe for hydrogen storage is 1-1.1% by mass, for example, it can be 1.01%, 1.02%, 1.03%, 1.04%, 1.05%, 1.06%, 1.07%, 1.08%, 1.09%, or 1.1%, but is not limited to the listed values; other unlisted values ​​within this range are also acceptable. Cr content can improve the hardenability and strength of steel. However, when the Cr content exceeds 1.20%, it will deteriorate the toughness and cold workability of the steel. Therefore, the range of Cr content is determined to be 1.0-1.10%.

[0073] In this invention, the Mo content in the 90MPa seamless steel pipe for hydrogen storage is 0.45-0.5% by mass, for example, it can be 0.45%, 0.455%, 0.46%, 0.465%, 0.47%, 0.475%, 0.48%, 0.485%, 0.49%, 0.495%, or 0.5%, etc., but is not limited to the listed values; other unlisted values ​​within this range are also acceptable. Mo can significantly improve the hardenability and tempering resistance of steel. Furthermore, Mo can segregate at the original austenite grain boundaries, reducing the segregation of S and P impurities at the grain boundaries, improving the grain boundary bonding strength, and enhancing the toughness of the material. However, when the Mo content exceeds 0.6%, over-aging occurs; therefore, the Mo content range is determined to be 0.45-0.50%.

[0074] Furthermore, Mo can improve the tempering resistance of steel. Increased tempering resistance allows for the use of higher tempering temperatures. To achieve the same strength, higher tempering temperatures can reduce quenching internal stress, dislocation density, and distortion, which is beneficial for reducing high-pressure hydrogen embrittlement susceptibility. Although the Mn content is appropriately increased to improve hardenability, strict control of the S content can effectively reduce MnS inclusions and avoid affecting the high-pressure hydrogen embrittlement resistance.

[0075] In this invention, the Ni content in the 90MPa seamless steel pipe for hydrogen storage is 0.2-0.3% by mass, for example, it can be 0.2%, 0.21%, 0.22%, 0.23%, 0.24%, 0.25%, 0.26%, 0.27%, 0.28%, 0.29%, or 0.3%, but is not limited to the listed values; other unlisted values ​​within this range are also acceptable. Ni can improve the hardenability, toughness, and plasticity of steel; however, it will reduce the strength of the steel, and Ni is expensive. Therefore, the Ni content is controlled at 0.20-0.30%.

[0076] Furthermore, hydrogen exhibits varying diffusivity and solubility in different microstructures. Consequently, different microstructures also exhibit varying susceptibility to hydrogen embrittlement. Tempered sorbite obtained after high-temperature tempering demonstrates superior resistance to high-pressure hydrogen embrittlement compared to martensite. Additionally, finer grains after heat treatment result in larger grain boundary surface areas, leading to a more pronounced barrier effect against hydrogen-carrying Cottrell gas clusters and dislocations, and a greater role in hindering microcrack propagation. Simultaneously, grain boundaries can trap more hydrogen, helping to reduce the local hydrogen content at defect sites. Fine-grained grain boundaries are more compact, enhancing grain boundary bonding and increasing the critical hydrogen content required for crack propagation. Increasing the internal surface area of ​​grain boundaries per unit volume reduces the segregation concentration of S and P impurities at grain boundaries, shifting the fracture mechanism from intergranular fracture to transgranular fracture, thereby increasing the fracture stress and high-pressure hydrogen embrittlement susceptibility of the steel. In addition to optimizing the heat treatment process, adding an appropriate amount of Ni to the steel, obtaining high-purity billets through ladle refining and electroslag remelting during steelmaking, and upsetting and drawing the billets all contribute to obtaining fine grains.

[0077] In this invention, the sulfur content in the 90MPa seamless steel pipe for hydrogen storage is ≤0.003% by mass, for example, it can be 0.003%, 0.002% or 0.001%, etc., but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0078] In this invention, the phosphorus content in the 90MPa seamless steel pipe for hydrogen storage is ≤0.01% by mass. For example, it can be 0.01%, 0.009%, 0.008%, 0.007%, 0.006%, 0.005%, 0.004%, 0.003%, 0.002%, or 0.001%, etc., but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0079] In this invention, the N content in the 90MPa seamless steel pipe for hydrogen storage is ≤0.007% by mass, for example, it can be 0.007%, 0.006%, 0.005%, 0.004%, 0.003%, 0.002%, or 0.001%, etc., but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0080] In this invention, the H content in the 90MPa seamless steel pipe for hydrogen storage is ≤0.0002% by mass, for example, it can be 0.0002%, 0.00018%, 0.00016%, 0.00014%, 0.00012%, 0.0001%, etc., but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0081] In this invention, the oxygen content in the 90MPa seamless steel pipe for hydrogen storage is ≤0.0025% by mass, for example, it can be 0.0025%, 0.002%, 0.0015%, 0.001%, 0.0005%, or 0.0001%, etc., but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0082] In this invention, N, H, O, S, and P are typically harmful impurity elements in steel. Therefore, the content of N should be controlled below 70 ppm, the content of O should be controlled below 25 ppm, the content of H should be controlled below 2 ppm, the content of S should be controlled below 0.003%, and the content of P should be controlled below 0.010%.

[0083] In this invention, the Ti content in the 90MPa seamless steel pipe for hydrogen storage is ≤0.015% by mass. For example, it can be 0.015%, 0.014%, 0.013%, 0.012%, 0.011%, 0.01%, or 0.001%, etc., but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0084] In this invention, the Cu content in the 90MPa seamless steel pipe for hydrogen storage is ≤0.2% by mass. For example, it can be 0.2%, 0.18%, 0.16%, 0.14%, 0.12%, 0.1%, or 0.01%, etc., but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0085] The seamless steel pipe provided by this invention can achieve a tensile strength of 850-950 MPa through conventional quenching and tempering heat treatment by appropriately adjusting the C, Cr and Mo contents, while maintaining high toughness and plasticity, as well as good resistance to high-pressure hydrogen embrittlement.

[0086] Furthermore, alloying elements Cr, Mo, and Ti can form more stable carbides in steel than Fe3C. The fine spherical carbides that are uniformly dispersed in the lattice increase the area of ​​the interface with the matrix, becoming irreversible traps for capturing hydrogen, which can slow down the diffusion of hydrogen in steel and help reduce the hydrogen embrittlement sensitivity of steel. The segregation or inclusion of elements such as Si, Mn, S, and P at the grain boundaries increases the hydrogen embrittlement sensitivity of steel.

[0087] Furthermore, the present invention provides a method for preparing the aforementioned 90MPa seamless steel pipe for hydrogen storage, the method comprising:

[0088] After preparing the raw materials according to the aforementioned formula, the process involves electric arc furnace steelmaking, ladle refining, vacuum degassing, and electrode ingot casting in one step to obtain electrode ingots.

[0089] The obtained electrode ingot was electroslag remelted under a protective atmosphere, and then subjected to a first heat preservation, forging, cooling, annealing, second heat preservation, and piercing hot rolling to obtain a 90MPa seamless steel pipe for hydrogen storage.

[0090] Specifically, aluminum is added during the electric arc furnace steelmaking process to control the P content in the molten steel to be ≤0.01% and the C content to be 0.05-0.15% by mass.

[0091] Specifically, the amount of aluminum added is 1.5-5 kg / t, for example, it can be 1.5 kg / t, 2 kg / t, 2.5 kg / t, 3 kg / t, 3.5 kg / t, 4 kg / t, 4.5 kg / t or 5 kg / t, but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0092] Specifically, the tapping temperature of the electric arc furnace steelmaking is 1635-1665℃, for example, it can be 1635℃, 1640℃, 1645℃, 1650℃, 1655℃, 1660℃ or 1665℃, etc., but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0093] During the electric arc furnace steelmaking process, intermediate alloys such as ferrosilicon intermediate alloy, ferromanganese intermediate alloy, ferrochrome intermediate alloy, ferromolybdenum intermediate alloy, and nickel powder are added according to the formula.

[0094] Specifically, the ladle refining process uses CaO-Al2O3-SiO2-MgO refining slag for treatment.

[0095] In this invention, the CaO-Al2O3-SiO2-MgO refining slag comprises, by mass percentage:

[0096] CaO 45-55%, Al2O3 25-28%, SiO2 10-15%, MgO 8-10%.

[0097] The bottom-blown argon gas used in the ladle refining process.

[0098] The flow rate of the argon gas is 100-150 NL / min, for example, it can be 100 NL / min, 110 NL / min, 120 NL / min, 122 NL / min, 124 NL / min, 126 NL / min, 128 NL / min, 130 NL / min, 140 NL / min or 150 NL / min, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0099] In the ladle refining process, carbon powder and aluminum powder are added for deoxidation.

[0100] The amount of toner added is 1.8-2.5 kg / t, for example, it can be 1.8 kg / t, 1.9 kg / t, 2 kg / t, 2.1 kg / t, 2.2 kg / t, 2.3 kg / t, 2.4 kg / t, 2.5 kg / t, 2.6 kg / t, 2.7 kg / t or 2.8 kg / t, but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0101] The amount of aluminum powder added is 0.5-0.6 kg / t, for example, it can be 0.5 kg / t, 0.52 kg / t, 0.54 kg / t, 0.56 kg / t, 0.58 kg / t or 0.6 kg / t, but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0102] The molten iron obtained from ladle refining contains P ≤ 0.01% and S ≤ 0.008% by mass percentage.

[0103] Wherein, the P content in the molten iron obtained by ladle refining is ≤0.01% by mass, for example, it can be 0.01%, 0.008%, 0.006%, 0.004%, 0.002% or 0.001, etc., but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0104] Wherein, the S content in the molten iron obtained from ladle refining is ≤0.008% by mass percentage, for example, it can be 0.008%, 0.006%, 0.004%, 0.002% or 0.001%, etc., but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0105] Specifically, the vacuum degassing is carried out under a protective atmosphere.

[0106] Specifically, the temperature of the molten steel during vacuum degassing is 1660-1680℃, for example, it can be 1660℃, 1665℃, 1670℃, 1675℃ or 1680℃, but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0107] Specifically, the absolute vacuum degree in the vacuum degassing is <67Pa, for example, it can be 65Pa, 60Pa, 55Pa, 50Pa, 45Pa, 40Pa, 30Pa, 20Pa or 10Pa, etc., but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0108] Specifically, the flow rate of the protective atmosphere in the vacuum degassing is 80-100 NL / min, and the holding time is ≥20 min. For example, it can be 80 NL / min, 85 NL / min, 90 NL / min, 95 NL / min or 100 NL / min, etc., and the holding time can be 20 min, 30 min, 40 min, 50 min or 60 min, etc., but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0109] Specifically, during the vacuum degassing process, the absolute vacuum is maintained for more than 20 minutes. After the vacuum is broken, the flow rate of the protective atmosphere is reduced to 40-60 NL / min, and soft blowing and stirring are performed.

[0110] The time for soft blowing and stirring is ≥15 min, for example, it can be 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, 50 min, 60 min, 70 min or 80 min, etc., but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0111] Specifically, the electrode ingot is cast under a protective atmosphere.

[0112] In this invention, the protective atmosphere includes helium, neon, or argon, which are commonly used protective atmospheres in the art.

[0113] Specifically, the electroslag remelting is carried out under a protective atmosphere using a GaF2-GaO-Al2O3-MgO quaternary slag system.

[0114] The GaF2-GaO-Al2O3-MgO quaternary slag system comprises, by mass percentage:

[0115] GaF2 50-60%, CaO 20-25%, Al2O3 15-20%, MgO 3-5%.

[0116] Specifically, the ingot obtained by electroslag remelting contains S ≤ 0.003% and O ≤ 15 × 10⁻⁶ by mass percentage. -6 N≤40×10 -6 .

[0117] Wherein, the S content in the ingot obtained by electroslag remelting is ≤0.003% by mass percentage, for example, it can be 0.003%, 0.002% or 0.001%, etc., but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0118] Wherein, the O content in the ingot obtained by electroslag remelting is ≤15×10 by mass percentage. -6 For example, it could be 15×10-6 14×10 -6 12×10 -6 10×10 -6 8×10 -6 6×10 -6 4×10 -6 2×10 -6 Or 1×10 -6 The values ​​may include, but are not limited to, the listed values; other unlisted values ​​within this range also meet the requirements.

[0119] Wherein, the N content in the ingot obtained by electroslag remelting is ≤40×10 by mass percentage. -6 For example, it could be 40×10 -6 35×10 -6 30×10 -6 25×10 -6 20×10 -6 15×10 -6 10×10 -6 5×10 -6 Or 1×10 -6 The values ​​may include, but are not limited to, the listed values; other unlisted values ​​within this range also meet the requirements.

[0120] Specifically, the first insulation includes a first-stage insulation and a second-stage insulation.

[0121] The heating rate of the first stage of heat preservation is 80-90℃ / h, for example, it can be 80℃ / h, 82℃ / h, 84℃ / h, 86℃ / h, 88℃ / h or 90℃ / h, etc., but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0122] The insulation temperature of the first stage is 750-800℃, such as 750℃, 760℃, 770℃, 780℃, 790℃ or 800℃, but not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0123] The insulation time for the first stage is 1-1.4 hours, such as 1 hour, 1.1 hours, 1.2 hours, 1.3 hours or 1.4 hours, but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0124] The heating rate of the second stage of heat preservation is 90-100℃ / h, for example, it can be 90℃ / h, 92℃ / h, 94℃ / h, 96℃ / h, 98℃ / h or 100℃ / h, etc., but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0125] The insulation temperature for the second stage is 1150-1180℃, such as 1150℃, 1155℃, 1160℃, 1165℃, 1170℃, 1175℃ or 1180℃, but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0126] The insulation time for the second stage is 1.5-2 hours, such as 1.5 hours, 1.6 hours, 1.7 hours, 1.8 hours, 1.9 hours or 2 hours, but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0127] Specifically, the total forging ratio of the forging billet is >3, for example, it can be 3.5, 4, 4.5 or 5, but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0128] Specifically, the forging process shall be performed at least once, for example, once, twice, three times or four times, but not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0129] Specifically, the final forging temperature of the forging billet is ≥850℃, for example, it can be 850℃, 900℃, 950℃ or 1000℃, etc., but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0130] Specifically, the cooling includes slow cooling inside the furnace and air cooling after exiting the furnace.

[0131] Specifically, the slow cooling time inside the furnace is ≥24h, for example, it can be 24h, 26h, 28h, 30h, 35h or 40h, etc., but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0132] Specifically, the final temperature of the slow cooling inside the furnace is 50-80℃, for example, it can be 50℃, 60℃, 70℃ or 80℃, but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0133] Specifically, the annealing process involves holding the furnace at 600-650℃ for 8-9 hours, then slowly cooling it to 200-250℃ at a rate of 60-70℃ / h, and finally air-cooling it after removal from the furnace.

[0134] In this invention, the holding temperature for annealing is 600-650℃, for example, it can be 600℃, 610℃, 620℃, 630℃, 640℃ or 650℃, etc., but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0135] In this invention, the annealing holding time is 8-9 hours, for example, it can be 8 hours, 8.2 hours, 8.4 hours, 8.6 hours, 8.8 hours or 9 hours, but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0136] In this invention, after annealing and holding, the temperature is slowly cooled to 200-250℃ at a rate of 60-70℃ / h. For example, the rate can be 60℃ / h, 62℃ / h, 64℃ / h, 66℃ / h, 68℃ / h, or 70℃ / h, etc. The slow cooling temperature is 200-250℃, for example, 200℃, 210℃, 220℃, 230℃, 240℃, or 250℃, etc., but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0137] Specifically, the second insulation includes sequential insulation of a first temperature zone, insulation of a second temperature zone, insulation of a third temperature zone, and insulation of a fourth temperature zone.

[0138] Specifically, the insulation temperature of the first temperature zone is 550-600℃, for example, it can be 550℃, 560℃, 570℃, 580℃, 590℃ or 600℃, etc., but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0139] Specifically, the insulation time for the first temperature zone is 1.5-2 hours, for example, it can be 1.5 hours, 1.6 hours, 1.7 hours, 1.8 hours, 1.9 hours or 2 hours, but it is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0140] Specifically, the insulation temperature of the second temperature zone is 850-900℃, for example, it can be 850℃, 860℃, 870℃, 880℃, 890℃ or 900℃, etc., but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0141] Specifically, the insulation time for the second temperature zone is 1.5-2 hours, for example, it can be 1.5 hours, 1.6 hours, 1.7 hours, 1.8 hours, 1.9 hours or 2 hours, but it is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0142] Specifically, the insulation temperature of the third temperature zone is 1050-1100℃, for example, it can be 1050℃, 1060℃, 1070℃, 1080℃, 1090℃ or 1100℃, etc. Other unlisted values ​​within this range also meet the requirements.

[0143] Specifically, the insulation time of the third temperature zone is 1.5-2 hours, for example, it can be 1.5 hours, 1.6 hours, 1.7 hours, 1.8 hours, 1.9 hours or 2 hours, but it is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0144] Specifically, the insulation temperature of the fourth temperature zone is 1250-1290℃, for example, it can be 1250℃, 1260℃, 1270℃, 1280℃ or 1290℃, etc., but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0145] Specifically, the insulation time of the fourth temperature zone is 1.5-2 hours, for example, it can be 1.5 hours, 1.6 hours, 1.7 hours, 1.8 hours, 1.9 hours or 2 hours, but it is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0146] Specifically, the sum of the heating time and the heat preservation time in the second heat preservation is ≥24h, for example, it can be 24h, 26h, 28h, 30h, 32h, 34h or 36h, etc., but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0147] The furnace temperature of the forged billet after the second heat treatment shall not be lower than 1250℃. That is, if the heating temperature of the last stage of the second heat treatment is lower than 1250℃, the furnace temperature needs to be raised to above 1250℃ before it is taken out of the furnace.

[0148] Specifically, the temperature of the billet fed into the piercing hot rolling process is 1260-1280℃.

[0149] In this invention, the heated forging billet is pierced by a tapered roller piercing mill to reduce its diameter, then rolled into a tube by a three-roll ASSEL tube rolling mill, and then sized to an outer diameter of 485mm by a five-stand three-roll micro-tension sizing mill. The residual temperature of the steel pipe at 200℃~300℃ is used for heat straightening to ensure that the bending degree of the steel pipe does not exceed 1.5mm / m.

[0150] The pipes obtained after piercing and hot rolling can undergo further surface treatment to achieve good surface properties, such as shot blasting, grinding, and polishing. For example, rough grinding is performed in 3-5 passes using a 60-80 mesh grinding wheel with a grinding depth of 60-100 μm per pass; fine grinding is performed in 3-5 passes using a 120-140 mesh grinding wheel with a grinding depth of 40-60 μm per pass; and polishing is performed in 2-3 passes using a 160-200 mesh flap wheel, resulting in an inner surface roughness ≤ Ra 6.3 μm.

[0151] Furthermore, the present invention provides the use of the aforementioned 90MPa seamless steel pipe for hydrogen storage, the use of which includes the preparation of hydrogen storage containers using the aforementioned 90MPa seamless steel pipe for hydrogen storage.

[0152] Furthermore, to illustrate the superior performance of the seamless steel pipe for hydrogen storage at 90 MPa provided by the present invention, actual embodiments are described below:

[0153] Example 1

[0154] This embodiment provides a seamless steel pipe for hydrogen storage with a pressure of 90MPa and a specification of Φ485×60.7mm. The chemical composition is detailed in Table 1.

[0155] The preparation process is as follows:

[0156] (1) Steelmaking is carried out using an electric furnace (EF). Steel core aluminum (addition amount is 3kg / t) is added to the molten steel for deoxidation. The P is controlled at 0.010% and C at 0.01% by mass percentage. The tapping temperature is controlled at 1650℃. According to the sampling analysis results, appropriate amounts of ferrosilicon, ferromanganese, ferrochrome, ferromolybdenum and nickel powder are pre-adjusted to adjust the alloy composition during the tapping process.

[0157] (2) The molten steel is transferred to the LF for ladle refining. The refining process uses CaO-Al2O3-SiO2-MgO refining slag (CaO 50%, Al2O3 23%, SiO2 12%, MgO 9%) for desulfurization and removal of non-metallic inclusions. Argon is blown into the furnace bottom throughout the process (argon flow rate is 125NL / min). Carbon powder is added in batches (addition amount is 2.1kg / t) for carbonization and deoxidation. Aluminum powder is added in small batches (addition amount is 0.55kg / t) for full deoxidation. The contents of C, Si, Mn, Cr, Mo and Ni are finely adjusted to the range of the composition by adding carbon and alloying components, and P is 0.010% and S is 0.008%.

[0158] (3) After slag removal, the LF ladle is transferred to the VD station for vacuum degassing. Argon gas is turned on and the argon gas flow rate is adjusted to 50 NL / min. The molten steel temperature is controlled at 1670℃. The vacuum pump is started to draw a vacuum to a degree of 65 Pa. The argon gas flow rate is increased to 90 NL / min and maintained for 25 minutes. After the vacuum is broken, a sample is taken, and H ≤ 2 × 10⁻⁶. -6 O≤25×10 -6 N≤70×10 -6 After breaking the air, maintain a soft blowing and stirring time of 25 minutes to ensure uniform steel composition and temperature, and then cast the electrode ingot under an argon protective atmosphere.

[0159] (4) The electrode ingot is peeled off and the ends are completely removed. Then, electroslag remelting is carried out using a GaF2-GaO-Al2O3-MgO quaternary slag system (GaF2 55%, CaO 22%, Al2O3 17%, MgO 4%) under an inert gas protective atmosphere (argon). This prevents hydrogen gain during the electroslag remelting process and effectively deoxidizes, desulfurizes, removes nitrogen, and eliminates non-metallic inclusions, ensuring that S≤0.003% and O≤15×10⁻⁶. -6 N≤40×10 -6 After electroslag remelting, Φ500mm electroslag ingots are cast.

[0160] (5) The electroslag ingot is heated in two stages. The first stage heating rate is 85℃ / h, and the temperature is held for 1.0h when it reaches 780℃. The second stage heating rate is 95℃ / h, and the temperature is held for 1.5h when it reaches 1170℃.

[0161] (6) The heated electroslag ingot is transferred to a high-speed forging machine for one upsetting and drawing to ensure that the total forging ratio is 3.5 and the final forging temperature is 900℃;

[0162] (7) The forged billet with a diameter of Φ500mm is slowly cooled in the furnace for 24 hours to 65℃, and then annealed. The annealing process involves holding the billet at 625℃ for 8.5 hours and then slowly cooling it to 225℃ at a rate of 65℃ / h. The billet is then removed from the furnace and air-cooled.

[0163] (8) The forging billet is rough machined on the surface, and each piece is subjected to 100% magnetic particle testing on the outer surface in accordance with the provisions of NB / T47013.4. The qualified level is Grade I.

[0164] (9) The forging billet is subjected to a second heat preservation in the annular heating furnace, which is to heat in four heating temperature zones in sequence. The heat preservation temperatures of the four heating temperature zones are 570℃, 870℃, 1070℃ and 1270℃, respectively. After heating to the set temperature in each temperature zone, it is held for 1.9h. The total heating and heat preservation time in the four temperature zones is 35h.

[0165] (10) The heated forging billet (temperature is 1270℃) is pierced by a tapered roller piercing mill to reduce its diameter, and then rolled into a three-roll ASSEL rolling mill. Then, it is sized to an outer diameter of 485mm by a five-stand three-roll micro-tension sizing mill. The steel pipe is then warm straightened using the residual temperature of 250℃ to ensure that the bending degree of the steel pipe is 1mm / m.

[0166] (11) The inner and outer surfaces of the steel pipe are shot blasted. The inner wall of the steel pipe is ground and polished in three stages. The rough grinding is done in 4 passes, with a grinding wheel of 70 mesh and a grinding amount of 80μm per pass. The fine grinding is done in 4 passes, with a grinding wheel of 130 mesh and a grinding amount of 50μm per pass. The polishing is done in 2 passes, with a blade wheel of 180 mesh, so that the roughness Ra of the inner surface is 6.3μm.

[0167] Example 2

[0168] This embodiment provides a seamless steel pipe for hydrogen storage with a pressure of 90MPa and a specification of Φ485×60.7mm. The chemical composition is detailed in Table 1.

[0169] The preparation process is as follows:

[0170] (1) Steelmaking is carried out using an electric furnace (EF). Steel core aluminum (addition amount is 1.5kg / t) is added to the molten steel for deoxidation. The P is controlled at 0.08% and C at 0.05% by mass percentage. The tapping temperature is controlled at 1635℃. According to the sampling analysis results, appropriate amounts of ferrosilicon, ferromanganese, ferrochrome, ferromolybdenum and nickel powder are pre-adjusted to adjust the alloy composition during the tapping process.

[0171] (2) The molten steel is transferred to the LF for ladle refining. The refining process uses CaO-Al2O3-SiO2-MgO refining slag (CaO 45%, Al2O3 28%, SiO2 10%, MgO 8%) for desulfurization and removal of non-metallic inclusions. Argon is blown into the furnace bottom throughout the process (argon flow rate is 150NL / min). Carbon powder is added in batches (addition amount is 2.5kg / t) for carbonization and deoxidation. Aluminum powder is added in small batches (addition amount is 0.6kg / t) for full deoxidation. The contents of C, Si, Mn, Cr, Mo and Ni are finely adjusted to the range of the composition by adding carbon and alloying components, and P is 0.0050% and S is 0.002%.

[0172] (3) After slag removal, the LF ladle is transferred to the VD station for vacuum degassing. Argon gas is turned on and the argon gas flow rate is adjusted to 60 NL / min. The molten steel temperature is controlled at 1680℃. The vacuum pump is started to draw a vacuum to a degree of 20 Pa. The argon gas flow rate is increased to 100 NL / min and maintained for 40 minutes. After rupturing the vacuum, a sample is taken, and H ≤ 2 × 10⁻⁶. -6 O≤25×10 -6 N≤70×10 -6 After breaking the air, maintain a soft blowing and stirring time of 40 minutes to ensure uniform steel composition and temperature, and then cast the electrode ingot under an argon protective atmosphere.

[0173] (4) The electrode ingot is peeled off and the ends are completely removed. Then, electroslag remelting is carried out using a GaF2-GaO-Al2O3-MgO quaternary slag system (GaF2 60%, CaO 20%, Al2O3 15%, MgO 4%) under an inert gas protective atmosphere (argon). This prevents hydrogen gain during the electroslag remelting process and effectively deoxidizes, desulfurizes, removes nitrogen, and eliminates non-metallic inclusions, ensuring that S≤0.003% and O≤15×10⁻⁶. -6 N≤40×10 -6 After electroslag remelting, Φ500mm electroslag ingots are cast.

[0174] (5) The electroslag ingot is heated in two stages. The first stage heating rate is 90℃ / h, and the temperature is held for 1.0h when it reaches 750℃. The second stage heating rate is 90℃ / h, and the temperature is held for 1.5h when it reaches 1180℃.

[0175] (6) The heated electroslag ingot is transferred to a high-speed forging machine for two upsetting and drawing processes to ensure a total forging ratio of 5; the final forging temperature is 950℃.

[0176] (7) The forged billet with a final forging of Φ500mm is slowly cooled in the furnace for 40 hours to 80℃, and then annealed. The annealing process involves holding the billet at 600℃ for 8 hours and then slowly cooling it to 250℃ at a cooling rate of 70℃ / h. The billet is then removed from the furnace and air-cooled.

[0177] (8) The forging billet is rough machined on the surface, and each piece is subjected to 100% magnetic particle testing on the outer surface in accordance with the provisions of NB / T47013.4. The qualified level is Grade I.

[0178] (9) The forging billet is heated in the ring heating furnace for the second heat preservation. It is heated in four heating temperature zones in sequence. The temperature ranges of the four heating temperature zones are 550℃, 850℃, 1050℃ and 1260℃ respectively. After heating to the set temperature in each temperature zone, it is held for 1.8h. The total heating and holding time in the four temperature zones is 33h.

[0179] (10) The heated forging billet (temperature is 1260℃) is pierced by a tapered roller piercing machine to reduce the diameter, and then rolled into a three-roll ASSEL rolling mill. Then, it is sized to an outer diameter of 485mm by a five-stand three-roll micro-tension sizing machine. The steel pipe is then warm straightened using the residual temperature of 300℃ to ensure that the bending degree of the steel pipe is 1mm / m.

[0180] (11) The inner and outer surfaces of the steel pipe are shot blasted. The inner wall of the steel pipe is ground and polished in three stages. The rough grinding is done in 3 passes, with a grinding wheel of 60 mesh and a grinding amount of 100μm per pass. The fine grinding is done in 3 passes, with a grinding wheel of 120 mesh and a grinding amount of 40μm per pass. The polishing is done in 2 passes, with a blade wheel of 200 mesh, so that the roughness Ra of the inner surface is 4.3μm.

[0181] Example 3

[0182] This embodiment provides a seamless steel pipe for hydrogen storage with a pressure of 90MPa and a specification of Φ485×60.7mm. The chemical composition is detailed in Table 1.

[0183] The preparation process is as follows:

[0184] (1) Steelmaking is carried out using an electric furnace (EF). Steel core aluminum (addition amount is 5kg / t) is added to the molten steel for deoxidation. The P is controlled at 0.09% and C at 0.15% by mass percentage. The tapping temperature is controlled at 1665℃. According to the sampling analysis results, appropriate amounts of ferrosilicon, ferromanganese, ferrochrome, ferromolybdenum and nickel powder are pre-adjusted to adjust the alloy composition during the tapping process.

[0185] (2) The molten steel is transferred to the LF for ladle refining. The refining process uses CaO-Al2O3-SiO2-MgO refining slag (CaO 55%, Al2O3 25%, SiO2 15%, MgO 10%) for desulfurization and removal of non-metallic inclusions. Argon is blown into the furnace bottom throughout the process (argon flow rate is 100NL / min). Carbon powder is added in batches (addition amount is 1.8kg / t) for carbonization and deoxidation, and aluminum powder is added in small batches (addition amount is 0.5kg / t) for full deoxidation. The contents of C, Si, Mn, Cr, Mo and Ni are finely adjusted to the range of the composition by adding carbon and alloying components, and P is 0.0010% and S is 0.005%.

[0186] (3) After slag removal, the LF ladle is transferred to the VD station for vacuum degassing. Argon gas is turned on and the argon gas flow rate is adjusted to 40 NL / min. The molten steel temperature is controlled at 1660℃. The vacuum pump is started to draw a vacuum to a degree of 40 Pa. The argon gas flow rate is increased to 80 NL / min and maintained for 30 minutes. After breaking the vacuum, a sample is taken, and H ≤ 2 × 10⁻⁶. -6 O≤25×10 -6 N≤70×10 -6 After breaking the air, maintain a soft blowing and stirring time of 30 minutes to ensure uniform steel composition and temperature, and then cast the electrode ingot under an argon protective atmosphere.

[0187] (4) The electrode ingot is peeled off and the ends are completely removed. Then, electroslag remelting is carried out using a GaF2-GaO-Al2O3-MgO quaternary slag system (GaF2 50%, CaO 25%, Al2O3 20%, MgO 3%) under an inert gas protective atmosphere (argon). This prevents hydrogen gain during the electroslag remelting process and effectively deoxidizes, desulfurizes, removes nitrogen, and eliminates non-metallic inclusions, ensuring that S≤0.003% and O≤15×10⁻⁶. -6 N≤40×10 -6 After electroslag remelting, Φ500mm electroslag ingots are cast.

[0188] (5) The electroslag ingot is heated in two stages. The first stage heating rate is 80℃ / h, and the temperature is held for 1.0h when it reaches 800℃. The second stage heating rate is 100℃ / h, and the temperature is held for 1.5h when it reaches 1150℃.

[0189] (6) The heated electroslag ingot is transferred to a high-speed forging machine for upsetting and drawing three times to ensure a total forging ratio of 4; the final forging temperature is 850℃.

[0190] (7) The forged billet with a final forging of Φ500mm is slowly cooled in the furnace for 36 hours to 50℃, and then annealed. The annealing process involves holding the billet at 650℃ for 9 hours and then slowly cooling it to 200℃ at a cooling rate of 60℃ / h. The billet is then removed from the furnace and air-cooled.

[0191] (8) The forging billet is rough machined on the surface, and each piece is subjected to 100% magnetic particle testing on the outer surface in accordance with the provisions of NB / T47013.4. The qualified level is Grade I.

[0192] (9) The forging billet is heated in the ring heating furnace for the second heat preservation. It is heated in four heating temperature zones in sequence. The temperature ranges of the four heating temperature zones are 600℃, 900℃, 1100℃ and 1280℃ respectively. After heating to the set temperature in each temperature zone, it is held for 2 hours. The total heating and holding time in the four temperature zones is 36 hours.

[0193] (10) The heated forging billet (temperature is 1280℃) is pierced by a tapered roller piercing mill to reduce its diameter, and then rolled into a tube by a three-roll ASSEL rolling mill. Then, it is sized to an outer diameter of 485mm by a five-stand three-roll micro-tension sizing mill. The steel pipe is then warm straightened using the residual temperature of 200℃ to ensure that the bending degree of the steel pipe is 1.2mm / m.

[0194] (11) The inner and outer surfaces of the steel pipe are shot blasted. The inner wall of the steel pipe is ground and polished in three stages. The rough grinding is done in 5 passes, with a grinding wheel of 80 mesh and a grinding amount of 60μm per pass. The fine grinding is done in 5 passes, with a grinding wheel of 140 mesh and a grinding amount of 60μm per pass. The polishing is done in 3 passes, with a blade wheel of 200 mesh, so that the roughness Ra of the inner surface is 2.2μm.

[0195] Comparative Example 1

[0196] This embodiment provides a steel pipe with a diameter of 485×66.8mm made of 4130X steel. The chemical composition of the steel pipe is detailed in Table 1.

[0197] The preparation process is as follows: after preparing the raw materials according to the formula, the billet is obtained by electric furnace steelmaking, ladle refining and vacuum degassing in sequence, and then by second heating and piercing hot rolling to obtain steel pipe;

[0198] The process involves electric arc furnace (EF) steelmaking followed by ladle refining and vacuum degassing to produce 4130X steel. The mass fractions of harmful elements are controlled as follows: As ≤ 0.010%, Sn ≤ 0.010%, Sb ≤ 0.010%, Pb ≤ 0.010%, Bi ≤ 0.010%, and their sum: Σ(As + Sn + Sb + Pb + Bi) ≤ 0.025%, H ≤ 2 × 10⁻⁶. -6 O≤25×10 -6 N≤70×10 -6 ;

[0199] After vacuum degassing, the ladle is transferred to the continuous casting station, and the continuous casting speed is controlled at 0.30 m / min. The crystallizer and the solidification end are electromagnetically stirred to improve the density of the continuous casting billet and reduce center segregation, center porosity and shrinkage cavities. The resulting round billet with a diameter of Φ450 mm is put into the heat preservation pit for slow cooling, and the cooling time is 170 h.

[0200] After the billet is heated (to 1270°C), it is pierced and then hot rolled using the ASSEL mill to produce seamless steel pipes.

[0201] The inner and outer surfaces of the seamless steel pipe are shot blasted, the inner wall is ground and polished to make the roughness of the inner surface < Ra6.3μm;

[0202] The steel pipe is subjected to 100% ultrasonic testing, eddy current testing, and automatic thickness measurement using a fully automatic ultrasonic and eddy current combined automatic testing equipment. The acceptance level for ultrasonic testing is Class I as specified in NB / T 47013.3-2015, and the acceptance level for eddy current testing is Class B as specified in GB / T 7735-2004. The wall thickness of the steel pipe is not allowed to be less than the minimum design wall thickness.

[0203] Comparative Example 2

[0204] The only difference from Example 1 is that the Si content in the steel pipe is 0.35% by mass.

[0205] Comparative Example 3

[0206] The only difference from Example 1 is that the Si content in the steel pipe is 0.15% by mass.

[0207] Comparative Example 4

[0208] The only difference from Example 1 is that the Mn content in the steel pipe is 0.6% by mass.

[0209] Comparative Example 5

[0210] The only difference from Example 1 is that the Cr content in the steel pipe is 0.8% by mass.

[0211] Comparative Example 6

[0212] The only difference from Example 1 is that the Mo content in the steel pipe is 0.2% by mass.

[0213] Comparative Example 7

[0214] The only difference from Example 1 is that the steel pipe does not contain Ni and is replaced by an equal amount of Fe.

[0215] Comparative Example 8

[0216] The only difference from Example 1 is that the electrode ingot is not subjected to electroslag remelting.

[0217] Comparative Example 9

[0218] The only difference from Example 1 is that forging is not performed, and the corresponding first heat preservation and cooling are omitted, that is, the electroslag ingot is directly subjected to the second heat preservation.

[0219] Comparative Example 10

[0220] The only difference from Example 1 is that the first stage of insulation in the first insulation is not performed.

[0221] Comparative Example 11

[0222] The only difference from Example 1 is that the second stage of insulation in the first insulation is not performed.

[0223] Comparative Example 12

[0224] The only difference from Example 1 is that the first temperature zone insulation in the second insulation is not performed.

[0225] Comparative Example 13

[0226] The only difference from Example 1 is that the second temperature zone insulation in the second insulation is not performed.

[0227] Comparative Example 14

[0228] The only difference from Example 1 is that the third temperature zone insulation in the second insulation is not performed.

[0229] Comparative Example 15

[0230] The only difference from Example 1 is that the fourth temperature zone insulation in the second insulation is not performed.

[0231] Table 1

[0232]

[0233] The performance of the steel pipes obtained in the examples and comparative examples was compared and analyzed, as follows:

[0234] 1. Hardenability test

[0235] Sample blocks were cut from steel pipes and processed into 200 mm long samples according to GB / T 225-2006. The hardenability was tested. The samples were heated at 890℃ for 50 min, and then the ends of the samples were quenched. The hardness value (HRC) at different distances from the quenched end face was tested. Since the preparation process has little effect on hardenability, only the samples of Examples 1-3 and Comparative Examples 1-7 were tested for hardenability. The results are detailed in Table 2.

[0236] Table 2

[0237]

[0238] Based on a comparison of previous heat treatment data for 4130X steel, when the hardness after quenching is lower than HRC43, the quenched microstructure is not entirely martensite. After tempering, the fully tempered sorbite microstructure required by GB / T33145-2023 cannot be obtained, resulting in tensile strength lower than the design requirement of 760 MPa and yield strength lower than the design requirement of 515 MPa. Therefore, when hardenability is defined by the hardness value HRC43, the hardenability depth measured for the steel pipe in Comparative Example 1 is approximately 50 mm. For the steel pipes in Examples 1-3, the measured hardenability depth is approximately 160 mm. This indicates that the seamless steel pipe provided by this invention significantly improves the hardenability of the steel through chemical composition optimization.

[0239] 2. Metallographic examination

[0240] A 2000mm long sample tube was cut from a steel pipe, and after sealing both ends, it underwent quenching and tempering heat treatment. For Comparative Example 1, the steel pipe was quenched at 880℃ for 90 minutes; the quenching solution was an 8% polymer aqueous solution; the tempering temperature was 590℃ for 150 minutes, and it was air-cooled after removal from the furnace. For Example 1, the steel pipe was quenched at 890℃ for 90 minutes; the quenching solution was an 8% polymer aqueous solution; the tempering temperature was 620℃ for 150 minutes, and it was air-cooled after removal from the furnace. Samples were then cut from the heat-treated sample tubes and metallographically examined according to GB / T 6394-2017. The obtained metallographic photographs are shown below. Figure 1 and Figure 2 As shown in the figure, the metallographic structure of the steel pipe in Comparative Example 1 and the steel pipe in Example 1 is tempered sorbite. The grain size of the steel pipe in Comparative Example 1 is grade 8, and the grain size of the steel pipe in Example 1 is grade 10.

[0241] The non-metallic inclusion ratings and grain size ratings of the steel pipes in the examples and comparative examples are shown in Table 3. It can be seen that the purity of the steel pipes in Examples 1-3 is significantly better than that of the steel pipes prepared in the comparative examples.

[0242] Table 3

[0243]

[0244]

[0245] 3. Mechanical performance testing

[0246] Samples were taken from heat-treated steel pipes and subjected to tensile and impact tests according to GB / T 228.1-2021 and GB / T 229-2020, respectively. The test results are shown in Tables 4 and 5.

[0247] Table 4

[0248]

[0249]

[0250] Table 5

[0251]

[0252] Under the premise of meeting the requirements of T / CATSI 05003-2020 (yield ratio less than 0.86 and elongation after fracture greater than 20%), the tensile strength and yield strength of the steel pipes in Examples 1-3 are more than 10% higher than those in Comparative Examples 1-15, and the impact toughness is significantly improved. Therefore, when the material meets the requirements of high-pressure hydrogen compatibility, a higher allowable stress can be used to reduce the design wall thickness of the hydrogen storage container, which is conducive to the development of hydrogen storage containers towards high pressure and large capacity.

[0253] In summary, the seamless steel pipe provided by this invention has a tensile strength ≥889MPa, a yield strength ≥730MPa, a yield ratio ≤0.837, an elongation after fracture ≥20.6%, and an impact absorption energy ≥164J / cm². 2 .

[0254] 4. Slow strain rate tensile test

[0255] Slow strain rate tensile tests were conducted according to GB / T 34542.2-2018 and GB / T 15970.7-2017. For mechanical property testing, six specimens were cut from the steel pipes of Comparative Example 1 and Example 1 after heat treatment and were machined into smooth round bar tensile specimens. Three specimens from the steel pipe of Comparative Example 1 (specimen numbers A-1-1, A-1-2, A-1-3) and three specimens from the steel pipe of Example 1 (specimen numbers B-1-1, B-1-2, B-1-3) were subjected to slow strain rate tensile tests in air at 90 MPa. Additionally, three specimens from steel pipe A (specimen numbers A-2-1, A-2-2, A-2-3) and three specimens from steel pipe B (specimen numbers B-2-1, B-2-2, B-2-3) were subjected to slow strain rate tensile tests in hydrogen gas at 90 MPa. The strain rate for all specimens was 1.5 × 10⁻⁶.-5 The average values ​​of the test results for the three samples are listed in Table 6 for comparison.

[0256] Table 6

[0257]

[0258] The comparison shows that the test results in hydrogen environment and air environment have little effect on the tensile strength and yield strength of steel pipe A under high pressure of 90MPa, but have a greater effect on elongation after fracture and reduction of face. The elongation after fracture in hydrogen environment is about 11.4% lower than that in air environment, which no longer meets the requirements of T / CATSI 05003-2020.

[0259] For the steel pipe obtained in Example 1, the high-pressure hydrogen environment has little effect on its tensile strength and yield strength, but a more significant effect on its elongation after fracture and reduction of face. However, the elongation after fracture in the hydrogen environment is less than 10% lower than that in the air environment, and still meets the requirements of T / CATSI 05003-2020.

[0260] 5. Hydrogen embrittlement sensitivity test

[0261] Hydrogen embrittlement sensitivity tests were conducted according to GB / T 34542.3-2018. For the steel pipes that underwent quenching and tempering heat treatment in the mechanical property tests, their mechanical properties are shown in Table 4. Six samples were cut from the steel pipes and processed into circular discs with a diameter of 58 mm and a thickness of 0.75 mm according to the requirements of GB / T 34542.3-2018. Three A samples (corresponding to Example 1) and three B samples (corresponding to Example 1) were tested using helium and hydrogen gas, respectively. Both helium and hydrogen gas were pressurized at constant pressurization rates of 0.1 MPa / min, 0.5 MPa / min, and 1.0 MPa / min until the discs burst. The burst pressure P corresponding to different pressurization rates in a helium environment was measured. He And the burst pressure P corresponding to different pressurization rates in a hydrogen environment. H2 Then calculate the hydrogen embrittlement sensitivity coefficients corresponding to different boost rates: i = P He / P H2 The experimental results are shown in Table 7:

[0262] Table 7

[0263]

[0264] It can be seen that the maximum hydrogen embrittlement sensitivity coefficient of the steel pipe obtained in Comparative Example 1 is 1.23, and the maximum hydrogen embrittlement sensitivity coefficient of the steel pipe obtained in Example 1 is 1.17, both of which meet the requirement of GB / T 34542.3-2018 that the hydrogen embrittlement sensitivity coefficient is less than 2. Even though the tensile strength and yield strength of the steel pipe obtained in Example 1 are higher than those of the steel pipe obtained in Comparative Example 1, its hydrogen embrittlement sensitivity is still slightly lower than that of the steel pipe obtained in Comparative Example 1, making it more suitable for high-pressure hydrogen-contaminated applications.

[0265] 6. Fracture toughness test and Leak-before-Bubble (LBB) determination

[0266] For a hydrogen storage container with a design pressure of 90 MPa and an outer diameter D0 of 485 mm, the design wall thickness t when using the steel pipe obtained in Comparative Example 1 is 66.8 mm. For the steel pipe obtained in Example 1, the guaranteed tensile strength and yield strength can be increased to 850 MPa and 580 MPa respectively, and the design wall thickness t of the hydrogen storage container can be reduced to 60.7 mm. This not only saves material costs and easily meets the hardenability requirements, but also facilitates the implementation of a pre-explosion leak (LBB) design for the hydrogen storage container. To ensure the container achieves the "pre-explosion leak" design requirement, the critical crack size must be greater than the container's wall thickness. This ensures that even if the crack propagates along the wall thickness and penetrates the entire wall thickness, the container will leak first, rather than experiencing a sudden explosion failure. This allows for timely leak detection and avoids sudden explosions, which is particularly important for the safe use of high-pressure hydrogen storage containers. To achieve the LBB design of the container, the fracture toughness K of the container material needs to be considered. IC Tests were performed, and then the maximum stress intensity factor K was calculated when the crack depth a extended to 0.8t, according to Appendix D of ASME VIII-3-2021 and Appendix F of GB / T 34019-2017. I The LBB determination shall be made in accordance with the judgment criteria given in GB / T34019-2017.

[0267] Samples were taken from the inner surface of the steel pipes obtained in Comparative Examples 1 (A-1, A-2, A-3) and Examples 1 (B-1, B-2, B-3), respectively. Three compact tensile specimens were machined from each specimen according to the requirements of T / CATSI 05003-2020 and GB / T 21143-2014. The plane strain fracture toughness K in 90 MPa hydrogen gas was measured. IC The results are shown in Table 8.

[0268] Table 8

[0269]

[0270] Furthermore, the most common crack on the inner surface of the container cylinder is a semi-elliptical axial-radial crack with a depth / length ratio (a / l) of 1 / 3. The maximum stress intensity factor K caused by an internal pressure of 90 MPa when the crack depth a extends to 0.8 t is calculated according to Appendix D of ASME VIII-3-2021 and Appendix F of GB / T 34019-2017. I The LBB (Leaf Bullet) determination criteria given in GB / T 34019-2017 are as follows:

[0271] a) When the crack propagates to 0.8t, K I <K IC ;

[0272] b): 0.2t < (K) IC / R p0.2 ) 2 .

[0273] When the design pressure is 90 MPa and the outer diameter D0 is 485 mm, the maximum stress intensity factor K of the materials obtained in Comparative Example 1 and Example 1 caused by internal pressure is... I The calculation results and LBB determination results are shown in Table 9.

[0274] Table 9

[0275] <![CDATA[K I / MPa·m 1 / 2 ]]> <![CDATA[K IC / MPa·m 1 / 2 ]]> 0.2t / mm <![CDATA[(K IC / R p0.2 ) 2 / mm]]> LBB judgment Comparative Example 1 94.5 74.5 13.36 12.55 Not satisfied Example 1 91.6 96.0 12.14 16.56 satisfy

[0276] It can be seen that the fracture toughness of the steel pipe obtained in Example 1 in a 90MPa hydrogen environment is 28.8% higher than that of the traditional 4130X (Comparative Example 1). 4130X does not meet the requirements of the 90MPa hydrogen storage container LBB design, while the seamless steel pipe provided by the present invention can meet the requirements of the 90MPa hydrogen storage container LBB design.

[0277] The present invention is described in detail through the above embodiments, but the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for the components used in the present invention, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

[0278] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0279] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0280] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A seamless steel pipe for hydrogen storage with a pressure of 90 MPa, characterized in that, The 90MPa seamless steel pipe for hydrogen storage comprises, by mass percentage: C 0.32-0.35%, Si 0.2-0.25%, Mn 0.8-0.9%, Cr 1-1.1%, Mo 0.45-0.5%, Ni 0.2-0.3%, S≤0.003%, P≤0.01%, N≤0.007%, H≤0.0002%, O≤0.0025%, Ti≤0.015%, Cu≤0.2%, balance Fe; The 90MPa seamless steel pipe for hydrogen storage is prepared using the following method: After preparing the raw materials according to the formula, the process involves electric arc furnace steelmaking, ladle refining, vacuum degassing, and electrode ingot casting to obtain electrode ingots. The obtained electrode ingot was electroslag remelted under a protective atmosphere, and then subjected to a first heat preservation, forging, cooling, annealing, second heat preservation, and piercing hot rolling to obtain a 90MPa seamless steel pipe for hydrogen storage.

2. The seamless steel pipe for hydrogen storage at 90MPa as described in claim 1, characterized in that, The 90MPa seamless steel pipe for hydrogen storage comprises, by mass percentage: C 0.33-0.35%, Si 0.24-0.25%, Mn 0.85-0.9%, Cr 1.05-1.1%, Mo 0.48-0.5%, Ni 0.28-0.3%, S≤0.003%, P≤0.01%, N≤0.007%, H≤0.0002%, O≤0.0025%, Ti≤0.015%, Cu≤0.2%, balance Fe.

3. A method for preparing a seamless steel pipe for hydrogen storage at 90 MPa as described in claim 1 or 2, characterized in that, The preparation method includes: After preparing the raw materials according to the formula, the process involves electric arc furnace steelmaking, ladle refining, vacuum degassing, and electrode ingot casting to obtain electrode ingots. The obtained electrode ingot was electroslag remelted under a protective atmosphere, and then subjected to a first heat preservation, forging, cooling, annealing, second heat preservation, and piercing hot rolling to obtain a 90MPa seamless steel pipe for hydrogen storage.

4. The preparation method according to claim 3, characterized in that, In the electric arc furnace steelmaking process, aluminum is added for treatment, and the P content in the molten steel is controlled to be ≤0.01% by mass, and C is 0.05-0.15%.

5. The preparation method according to claim 3, characterized in that, The tapping temperature of the electric arc furnace steelmaking process is 1635-1665℃.

6. The preparation method according to claim 3, characterized in that, The ladle refining process uses CaO-Al2O3-SiO2-MgO refining slag for treatment.

7. The preparation method according to claim 3, characterized in that, The entire process of ladle refining uses bottom-blown argon gas.

8. The preparation method according to claim 7, characterized in that, The flow rate of the argon gas is 100-150 NL / min.

9. The preparation method according to claim 3, characterized in that, The molten iron obtained from ladle refining has a mass percentage content of P ≤ 0.01% and S ≤ 0.008%.

10. The preparation method according to claim 3, characterized in that, The vacuum degassing is performed under a protective atmosphere.

11. The preparation method according to claim 3, characterized in that, The temperature of the molten steel during the vacuum degassing process is 1660-1680℃.

12. The preparation method according to claim 3, characterized in that, The absolute vacuum degree during vacuum degassing is <67 Pa.

13. The preparation method according to claim 10, characterized in that, The flow rate of the protective atmosphere during vacuum degassing is 80-100 NL / min.

14. The preparation method according to claim 3, characterized in that, During the vacuum degassing process, the absolute vacuum level is maintained for more than 20 minutes. After the vacuum is broken, the flow rate of the protective atmosphere is reduced to 40-60 NL / min, and soft blowing and stirring are performed.

15. The preparation method according to claim 14, characterized in that, The time for soft blowing and stirring is ≥15 min.

16. The preparation method according to claim 3, characterized in that, The electrode ingot casting is carried out under a protective atmosphere.

17. The preparation method according to claim 3, characterized in that, The electroslag remelting is carried out under a protective atmosphere using a GaF2-GaO-Al2O3-MgO quaternary slag system.

18. The preparation method according to claim 3, characterized in that, The ingots obtained by electroslag remelting contain S ≤ 0.003% and O ≤ 15 × 10⁻⁶ by mass percentage. -6 N≤40×10 -6 .

19. The preparation method according to claim 3, characterized in that, The first insulation includes a first-stage insulation and a second-stage insulation.

20. The preparation method according to claim 19, characterized in that, The heating rate during the first stage of heat preservation is 80-90℃ / h.

21. The preparation method according to claim 19, characterized in that, The insulation temperature for the first stage of insulation is 750-800℃.

22. The preparation method according to claim 19, characterized in that, The insulation time for the first stage is 1-1.4 hours.

23. The preparation method according to claim 19, characterized in that, The heating rate for the second stage of heat preservation is 90-100℃ / h.

24. The preparation method according to claim 19, characterized in that, The insulation temperature for the second stage is 1150-1180℃.

25. The preparation method according to claim 19, characterized in that, The heat preservation time for the second stage is 1.5-2 hours.

26. The preparation method according to claim 3, characterized in that, The total forging ratio of the forging blank is >3.

27. The preparation method according to claim 3, characterized in that, The final forging temperature of the forging billet is ≥850℃.

28. The preparation method according to claim 3, characterized in that, The forging process is performed at least once.

29. The preparation method according to claim 3, characterized in that, The cooling process includes slow cooling inside the furnace and air cooling after exiting the furnace.

30. The preparation method according to claim 3, characterized in that, The slow cooling time inside the furnace is ≥24 hours.

31. The preparation method according to claim 3, characterized in that, The final temperature of the slow cooling inside the furnace is 50-80℃.

32. The preparation method according to claim 3, characterized in that, The annealing process involves holding the furnace at 600-650℃ for 8-9 hours, then slowly cooling it to 200-250℃ at a rate of 60-70℃ / h, and finally air-cooling it after removal from the furnace.

33. The preparation method according to claim 3, characterized in that, The second insulation includes sequential insulation of the first temperature zone, the second temperature zone, the third temperature zone, and the fourth temperature zone.

34. The preparation method according to claim 33, characterized in that, The insulation temperature for the first temperature zone is 550-600℃.

35. The preparation method according to claim 33, characterized in that, The insulation time for the first temperature zone is 1.5-2 hours.

36. The preparation method according to claim 33, characterized in that, The insulation temperature for the second temperature zone is 850-900℃.

37. The preparation method according to claim 33, characterized in that, The insulation time for the second temperature zone is 1.5-2 hours.

38. The preparation method according to claim 33, characterized in that, The insulation temperature of the third temperature zone is 1050-1100℃.

39. The preparation method according to claim 33, characterized in that, The insulation time for the third temperature zone is 1.5-2 hours.

40. The preparation method according to claim 33, characterized in that, The insulation temperature of the fourth temperature zone is 1250-1290℃.

41. The preparation method according to claim 33, characterized in that, The insulation time for the fourth temperature zone is 1.5-2 hours.

42. The preparation method according to claim 33, characterized in that, The sum of the heating time and the heat preservation time in the second heat preservation process is ≥24h.

43. The preparation method according to claim 3, characterized in that, The temperature of the billet fed into the pierced hot rolling process is 1260-1280℃.

44. The use of a seamless steel pipe for hydrogen storage at 90 MPa as described in claim 1 or 2, characterized in that, The applications include the fabrication of hydrogen storage containers using the aforementioned 90MPa seamless steel pipes for hydrogen storage.

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