High-grade hydrogen transmission pipeline steel and preparation method thereof

Abstract

The invention belongs to the technical field of ferrous metallurgy, and relates to high-grade hydrogen transmission pipeline steel and a preparation method thereof.The high-grade hydrogen transmission pipeline steel is prepared from, by mass, 0.02%-0.04% of C, 0.20%-0.30% of Si, 1.20%-1.30% of Mn, smaller than or equal to 0.010% of P, smaller than or equal to 0.0010% of S, 0.015%-0.055% of Alt, smaller than or equal to 0.0020% of N, smaller than or equal to 0.0010% of O, smaller than or equal to 0.0001% of H, 0.90%-1.00% of Cr, 0.40%-0.50% of Mo, 0.020%-0.030% of Ti, 0.05%-0.07% of Nb, 0.40%-0.50% of Ni and the balance iron and inevitable impurities; various performance indexes, especially hydrogen induced crack resistance indexes, of the composite material are outstanding, CSR is equal to 0, CLR is equal to 0, CTR is equal to 0, slow tensile IRA and IEL are smaller than or equal to 20% in a solution A, KIH of a stepped compact tensile sample is larger than or equal to 100 MPa.m < 1 / 2 > in a 6.3 MPa pure hydrogen environment, and the fatigue life is larger than or equal to 500,000 times; according to the method, the technical problems in the research and development process of the steel material for the hydrogen conveying pipeline are solved, the technical scheme is relatively simple and easy to implement, the obtained product is high in performance stability and controllable in cost, and popularization and application in long-distance, large-scale and safe conveying pipeline construction of high-pressure hydrogen are facilitated.

Description

Technical Field

[0001] The invention belongs to the technical field of iron and steel metallurgy and relates to a high-grade hydrogen pipeline steel and a preparation method thereof. Background Art

[0002] The use of hydrogen energy is a national strategy for green development. The use of clean energy such as wind, solar, and tidal energy for power generation is uncontrolled, which will result in a large amount of abandoned electricity. Using the hydrogen production process to produce hydrogen from abandoned electricity, and then storing and transporting it to users for use, is a green energy development path. With the development of clean energy, the demand for hydrogen is gradually increasing, and traditional vehicle transportation methods cannot meet user needs. The use of pipeline hydrogen transportation has the characteristics of large transportation volume, low energy consumption, and low cost. It is an economical way to achieve large-scale long-distance transportation of hydrogen. Among them, natural gas hydrogen blending technology, as an effective way to save energy and reduce carbon emissions, has been widely favored by the industry in recent years.

[0003] Compared with traditional energy sources such as natural gas and oil, hydrogen has the characteristics of fast combustion speed, low ignition energy, high flame temperature, large explosion limit and light weight, which makes the risk of hydrogen pipelines much higher than that of natural gas pipelines. In addition, in terms of material loss, hydrogen causes material cracks, which will reduce the toughness and ductility of steel. Under certain high temperature conditions, H will combine with C in the matrix to form CH4 gas, causing hydrogen fracture or hydrogen embrittlement inside the steel and decarburization on the steel surface. In particular, H is enriched in defects inside the steel, causing pipeline steel failure (hydrogen sulfide stress corrosion cracking SSCC and hydrogen-induced cracking HIC). At present, domestic hydrogen pipelines are mainly short-distance, low-risk pure hydrogen pipelines or natural gas hydrogen-blended pipelines, and the materials used are mainly low-grade seamless or low-grade normalized pipeline L245 welded pipes with a yield strength of 245MPa.

[0004] Pure hydrogen or hydrogen gas is mixed into natural gas in a certain volume ratio to form a mixed gas that can improve the combustion performance of terminal equipment, effectively increase the combustion value, and reduce nitrogen oxide pollution and carbon dioxide emissions. In terms of long-distance, large-scale transportation of hydrogen-blended natural gas, pipeline transportation is more economical, safer and greener than traditional tank transportation.

[0005] However, hydrogen molecules have a strong permeability to metals, which can easily lead to hydrogen embrittlement or hydrogen damage in pipelines. There are three major technical difficulties in the development of hydrogen pipelines: First, H combines with C in the matrix to form CH4 gas under high temperature, causing decarburization of the steel surface and microcracks inside, so a low-carbon component design should be adopted; second, because hydrogen atoms can easily gather and generate cracks at the interface between the two phases, the purity of the molten steel should be as high as possible; third, high plasticity and high toughness materials should be obtained by improving the original design to avoid hydrogen embrittlement.

[0006] The existing technology cannot solve the above technical problems well. For example: Invention CN115584441A discloses a hot-rolled coil with a yield strength of 245MPa for hydrogen pipelines and a production method thereof. However, the strength level of the steel obtained by the invention is low and does not have the performance in the hydrogen transmission environment. Invention CN113862549B discloses a production method for L360QS hydrogen pipeline steel. The invention does not mention the hydrogen embrittlement sensitivity and fracture toughness tests, and the inspection items under hydrogen environment conditions are insufficient. Invention CN116656927A discloses a production method for TMCP hydrogen-doped hydrogen pipeline steel. In the invention, there is no mention of experimental data in 10MPa pure hydrogen environment and 4.0MPa pure hydrogen environment.

[0007] Therefore, a process technology and method for high-grade hydrogen pipeline steel are needed to solve the above technical problems. Summary of the invention

[0008] The technical solution adopted by the present invention to solve the technical problem is: a high-grade hydrogen pipeline steel, the chemical composition of the high-grade hydrogen pipeline steel and its mass percentage are: C0.02-0.04%, Si0.20-0.30%, Mn1.20-1.30%, P≤0.010%, S≤0.0010%, Alt0.015-0.055%, N≤0.0020%, O≤0.0010%, H≤0.0001%, Cr0.90-1.00%, Mo0.40-0.50%, Ti0.020-0.030%, Nb0.05-0.07%, Ni0.40-0.50%, and the balance is iron and unavoidable impurities.

[0009] Preferably, the chemical composition of the high-grade hydrogen pipeline steel meets the following conditions: (Mg+Pr) / S=3.0-5.0.

[0010] Preferably, the hydrogen-induced cracking resistance index of the high-grade hydrogen pipeline steel is CSR=0, CLR=0, CTR=0 in solution A, no cracks in SSC test, slow tensile IRA, IEL≤20%, and in a 6.3MPa pure hydrogen environment, the step-type compact tensile specimen KIH≥100MPa.m 1 / 2 , fatigue life ≥ 500,000 times.

[0011] Preferably, the yield strength Rt0.5 of the high-grade hydrogen pipeline steel is 580-700 MPa, the tensile strength is 680-780 MPa, and the elongation after fracture A 50 35~45%, -30℃ impact energy KV2≥350J, SA(-30℃)100%, HV10≤260, Rt0.5 / Rm≤0.90, DWTT(-30℃)≥98%.

[0012] The present invention also discloses a method for preparing high-grade hydrogen pipeline steel, which is used to prepare the above-mentioned high-grade hydrogen pipeline steel. The method comprises:

[0013] Top and bottom combined blowing converter smelting, refining outside the furnace, large slab continuous casting, slab reheating, rough rolling, finishing rolling, controlled cooling, coiling, slow cooling; in the controlled cooling step, the cooling rate is 40-50°C / S; in the coiling step, the coiling temperature is determined according to the cooling control factor Q and the cooling rate in the cooling step, Q=coiling temperature / cooling rate, 8.0≤Q≤11, to ensure the fracture toughness index and organizational uniformity, the laminar cooling water temperature is ≤20°C.

[0014] Preferably, in the slab reheating step, the heating temperature is 1100-1300° C., and the heating time is 1 h-3 h;

[0015] In the rough rolling step, the starting temperature of the rough rolling is 1100-1200°C. To avoid rolling in the two-phase zone, the rough rolling is performed by floating temperature waiting. When the outlet temperature reaches 910-990°C, it enters the finishing rolling unit.

[0016] In the finishing rolling step, the multi-stand hot rolling mill is used for rolling, and the final rolling temperature is 800-850°C;

[0017] During laminar cooling, the steel plate is immediately water-cooled after finishing rolling, and the front-stage rapid cooling process is adopted. The forced cooling system is opened from the first group, and new water is added to make the laminar cooling water temperature quickly ≤20℃, and the cooling rate is 40~50℃ / S;

[0018] In the coiling step, it is determined according to the cooling control factor Q and the cooling rate in the cooling step, Q = coiling temperature / cooling rate, 8≤Q≤11;

[0019] In the slow cooling step, after the steel coil leaves the laminar cooling unit, it enters the slow cooling pit for natural cooling for 60 to 84 hours.

[0020] Preferably, in the finish rolling step, a 7-stand hot rolling mill is used for rolling.

[0021] The beneficial effects of the present invention are:

[0022] 1. The hydrogen pipeline steel prepared by the present invention has outstanding performance indicators, especially the hydrogen-induced crack resistance indicator, which meets the requirements of CSR=0, CLR=0, CTR=0 in solution A, slow tensile IRA, IEL≤20%, and step-type compact tensile specimen KIH≥100MPa.m in a 6.3MPa pure hydrogen environment. 1 / 2 , fatigue life ≥ 500,000 times.

[0023] 2. The solution of the present invention is relatively simple and easy to implement. The obtained product has high performance stability and controllable cost, and has high market competitiveness.

[0024] 3. The present invention has effectively solved the above three major technical problems faced in the research and development of hydrogen pipeline steel materials, developed a high-grade hydrogen pipeline steel, accelerated the upgrading of products, and is conducive to the promotion and use in the construction of hydrogen pipeline networks. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a metallographic structure diagram of hydrogen pipeline steel of Example 1 of a high-grade hydrogen pipeline steel and a preparation method thereof of the present invention;

[0026] Figure 2 This is the metallographic structure diagram of the pipeline steel of Comparative Example 1 of the present invention;

[0027] Figure 3 This is a fracture morphology diagram of a slow tensile notch specimen of Example 1 of the present invention;

[0028] Figure 4 This is a fracture morphology diagram of a slow tensile notch specimen of Comparative Example 1 of the present invention;

[0029] Figure 5 is a load-crack opening displacement curve diagram of Example 1 of the present invention;

[0030] Figure 6 It is a comparative load-crack opening displacement curve diagram of the present invention. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the relevant technologies in the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] refer to Figures 1 to 6 In this embodiment, the chemical composition (mass percentage) of the high-grade hydrogen pipeline steel is: C0.02-0.04%, Si0.20-0.30%, Mn1.20-1.30%, P≤0.010%, S≤0.0010%, Alt0.015-0.055%, N≤0.0020%, O≤0.0010%, H≤0.0001%; ​​in addition, the above components also contain Cr0.90-1.00%, Mo0.40-0.50%, Ti0.020-0.030%, Nb0.05-0.07%, Ni0.40-0.50%, (Mg+Pr) / S is controlled at 3.0-5.0, and the balance is iron and unavoidable impurities.

[0033] The high-grade hydrogen pipeline steel provided in this embodiment has a yield strength Rt0.5 of 580-700 MPa, a tensile strength of 680-780 MPa, and an elongation after fracture A 50 35~45%, -30℃ impact energy KV2≥350J, SA(-30℃)100%, HV10≤260, Rt0.5 / Rm≤0.90, DWTT(-30℃≥98%. In addition, the hydrogen-induced crack resistance index requires CSR=0, CLR=0, CTR=0 in solution A, no cracks in SSC test, slow tensile IRA, IEL≤20%, in 6.3MPa pure hydrogen environment, step-type compact tensile specimen KIH≥100MPa.m 1 / 2 , fatigue life ≥ 500,000 times.

[0034] The specific principle of adding each chemical element in this embodiment is:

[0035] Carbon (C): The main element that affects the toughness, hardness, strength and welding performance of pipeline steel. It acts on pipeline steel through solid solution strengthening and precipitation strengthening. As the C content increases, the toughness, ductility and welding performance of the steel decrease. It intensifies the central segregation of the steel and reduces the resistance to HIC and SSCC. For hydrogen pipeline steel, as the strength grade increases, the C content in the steel tends to decrease. Therefore, the C content in this technical solution is 0.02-0.04%.

[0036] Manganese (Mn): In hydrogen pipeline steel, it has the following main functions: (1) Increase the solubility product of (Nb, Ti) (C, N) in austenite, inhibit their precipitation in austenite, reduce the nano-precipitation size of carbides, nitrides and carbonitrides, and promote precipitation strengthening effect; (2) Manganese in steel can easily cause segregation, forming banded pearlite in the center of the plate thickness, making the banded structure ≥ level 2, and some even reaching level 3, deteriorating the acid corrosion resistance HIC and SSCC performance of the steel, and The Mn in the steel reacts with S to form strip-shaped MnS inclusions. Central segregation and strip-shaped MnS inclusions easily cause HIC and SSCC failure. Compared with pipeline steels of the same grade, the Mn content of the steel is controlled; (3) Solid solution strengthening is the main method in steel, which has a certain beneficial effect on toughness; (4) Mn expands the γ phase region, increases the γ→α phase transformation temperature, promotes the nucleation of acicular ferrite, reduces the pearlite content, and refines the ferrite grain size; therefore, in this embodiment, it is limited to 1.20-1.30%.

[0037] Silicon (Si): A strong deoxidizing element in steel, it plays a role in solid solution strengthening and reduces the solubility of C in austenite. Si can strongly inhibit the precipitation of carbides along the grains during bainite transformation, which is beneficial to improving the grain boundary bonding strength and increasing toughness. However, if the silicon content is too high, it is easy to cause the plasticity, toughness and weldability of the steel to decrease. In addition, it also produces red iron oxide defects, which is not conducive to the removal of iron oxide scale on the steel plate. Therefore, in this embodiment, Si is controlled at 0.20-0.30%.

[0038] Phosphorus (P) and sulfur (S): S combines with Mn to form MnS inclusions, which can also reduce the low-temperature impact toughness of pipeline steel. It is the main element that affects the HIC and SSCC performance of pipeline steel. P is easy to form segregation in steel, deteriorate weldability, reduce the low-temperature impact toughness of steel, and increase the tough-brittle transition temperature. Therefore, the P and S contents should be reduced as much as possible to reduce the center segregation of the material to ensure that CSR=0, CLR=0, and CTR=0 of hydrogen pipeline steel under solution A. In this embodiment, P≤0.010% and S≤0.0010% are set in the composition, and Ca and Mg inclusion modification treatment technology is used to make the inclusions in the steel fully spheroidized, small and uniform, and reduce the adverse effects caused by them.

[0039] Aluminum (Al): A strong deoxidizing element in steel, which significantly reduces the oxygen content of steel and generates Al2O 3， At the same time, the aluminum in the steel combines with nitrogen to generate AlN, which refines the grains and improves strength and toughness. However, too high an aluminum content leads to a significant increase in Al2O3 inclusions, which destroys the cleanliness of the molten steel and causes nozzle nodules. The Alt of this technical solution is limited to 0.015-0.055%.

[0040] Magnesium (Mg) and praseodymium (Pr): In this technical solution, the morphology and size of sulfide and oxide inclusions are controlled through composite treatment of Mg and Pr, the low-temperature toughness is improved, the anisotropy of the steel plate is effectively improved, and the tensile properties KIH of the step-type compact specimen in a 6.3MPa pure hydrogen environment are improved. To ensure the best effect, this embodiment limits (Mg+Ca) / S to 3.0-5.0.

[0041] Titanium (Ti): It can increase the recrystallization temperature and austenite transformation temperature of steel, control the grain size during continuous casting and heating, and form TiN particles with nitrogen. It is a strong carbonitride forming element, Ti / N≥3.42. During the heating process, it inhibits the growth of austenite grains, plays a role in grain refinement and precipitation strengthening, and improves the low-temperature toughness of steel; in addition, Ti and Nb composite strengthening prolongs the precipitation incubation period of NbC, so that the carbide of Nb-Ti composite steel begins to precipitate later, making the precipitate more dispersed and fine. It improves the thermal stability of (NbTi)(CN), improves the toughness of the steel plate, improves the welding performance of the steel plate, and has a good inhibitory effect on the growth of austenite grains during heating and the coarsening of grains in the welding heat affected zone. In this embodiment, the amount of titanium added is 0.020-0.030%.

[0042] Niobium (Nb): inhibits excessive growth of austenite grains, delays the transformation of γ→α structure, is conducive to the formation of acicular ferrite, refines ferrite grains, improves the toughness of steel, and obtains fine structure. During hot rolling, niobium carbonitride delays recrystallization and grain growth, and by pinning dislocations, more dislocation density is retained in the matrix, thereby improving the strength and toughness of steel. To achieve the precipitation strengthening effect of replacing V and reduce the cost of steel, the amount of niobium added in this embodiment is 0.05-0.07%.

[0043] Oxygen (O), nitrogen (N), hydrogen (H): The high gas content in the steel reduces the fatigue life of the hydrogen pipeline steel. Nitrogen forms high-melting-point TiN particles, which can inhibit excessive grain growth during heating and improve the strength and toughness of the steel. When the N content is too high, the high concentration of free N atoms causes failure, pins dislocations, increases yield strength, and reduces toughness. For the oxygen content in the steel, deoxidation treatment is required at the end of smelting to reduce oxide inclusions and bubbles, improve the internal quality of the steel, and at the same time help improve the dynamic tear resistance and low-temperature impact toughness of the hydrogen pipeline steel. H can easily cause defects such as hydrogen embrittlement and white spots in steel. For hydrogen pipeline steel, the lower the H content in the material, the better. Therefore, in this technical solution, the O content is limited to ≤0.0010%, the N content is limited to ≤0.0020%, and the H content is limited to ≤0.0001%.

[0044] Chromium (Cr): It is a carbide-forming element, mainly used for precipitation strengthening, to improve the hardness of steel plates, replace V alloys, and improve the corrosion resistance and hydrogen-induced cracking resistance of steel. However, excessive chromium reduces the elongation of steel plates, leads to the formation of low-melting-point Cr-Mn composite oxides, forms surface cracks during hot working, and has an adverse effect on welding performance. In this technical solution, Cr is limited to 0.90-1.00%.

[0045] Molybdenum (Mo): It can improve the hardenability of steel, promote phase transformation, and is conducive to the formation of acicular ferrite. It strengthens the matrix and prevents softening of the heat-affected zone after welding. While improving the strength, it can also improve the sensitivity to hydrogen-induced cracking. Control Mo0.40~0.50%.

[0046] Nickel (Ni): Nickel is a non-carbide forming element, generally dissolved in the steel matrix solid solution, which reduces the phase transition temperature, refines the grains, improves the strength and toughness, and can also improve hot brittleness. Ni can improve the HIC resistance of steel. This is because it can form a dense oxide film in an environment with a high acid concentration, which reduces the entry of hydrogen atoms into the steel matrix, slows down H2S corrosion, and improves HIC resistance. The preferred Ni content in this embodiment is 0.40-0.50wt%.

[0047] This embodiment also provides a method for preparing hydrogen pipeline steel, including top and bottom combined blowing converter smelting, refining outside the furnace, large slab continuous casting, slab reheating, rough rolling, finishing rolling, controlled cooling, coiling, and slow cooling; wherein in the controlled cooling step, the cooling rate is 40-50°C / S; in the coiling step, the coiling temperature is determined according to the cooling control factor Q and the cooling rate in the cooling step, Q=coiling temperature / cooling rate, 8.0≤Q≤11, to ensure the fracture toughness index and the uniformity of the structure, the laminar cooling water temperature is ≤20°C. Wherein:

[0048] (1) In the slab reheating step, the heating temperature is 1200-1240° C. and the heating time is 1.5 h-2 h;

[0049] (2) Rough rolling: The starting temperature of rough rolling is 1150-1180°C. To avoid two-phase rolling, the rough rolling is carried out by moving the temperature. When the outlet temperature reaches 950°C, it enters the finishing rolling unit.

[0050] (3) Finish rolling: 7-stand hot rolling mill, final rolling temperature 805-835°C;

[0051] (4) Laminar cooling: After finishing rolling, the steel plate is immediately water-cooled, and the front-stage rapid cooling process is adopted. The forced cooling system is opened from the first group. The method of adding new water can be adopted to make the laminar cooling water temperature quickly ≤20℃, and the cooling rate is 40~50℃ / S;

[0052] (5) Coiling: determined by the cooling control factor Q and cooling rate in the cooling step, Q = coiling temperature / cooling rate, 8≤Q≤11;

[0053] (6) Slow cooling: After the steel coil leaves the laminar cooling unit, it enters the slow cooling pit for natural cooling for 72 hours.

[0054] Example

[0055] Examples 1 to 5

[0056] The chemical element ratios of the steel strips in Examples 1 to 5 and Comparative Examples 1 to 2 of the hydrogen pipeline steel described in the following steps are shown in Table 1, and the detailed process parameters in Examples 1 to 5 and Comparative Examples 1 to 2 are shown in Table 2. Figure 1 The structural structure of the steel plate matrix in Example 1 is acicular ferrite. Figure 2 The microstructure of the matrix of Comparative Example 1 is polygonal ferrite + bainite. Figure 3 It means that the slow tensile notch specimen of Example 1 has no cracks. Figure 4 This indicates that the slow tensile notch specimen of Comparative Example 1 has crack defects. Figure 5 represents the load-crack opening displacement curve of Example 1, Figure 5 It represents the load-crack opening displacement curve of comparative example 1.

[0057] (1) 180 tons of top and bottom blown converter smelting raw materials;

[0058] (2) Continuous casting: To ensure the edge quality, a chamfered crystallizer is used;

[0059] (3) reheating the slab at a temperature of 1200 to 1240° C. for a heating time of 90 to 120 minutes, and a slab thickness of 210 to 250 mm;

[0060] (4) Rough rolling: The starting temperature of rough rolling is 1150-1180℃. To avoid two-phase rolling, rough rolling is performed by floating temperature waiting. When the outlet temperature is ≤950℃, it enters the finishing rolling unit.

[0061] (5) Finishing rolling: rolling by 7-stand hot rolling mill, final rolling temperature 805-835°C;

[0062] (6) Laminar cooling: After the steel plate is finished rolling, it is immediately water-cooled, and the front-stage rapid cooling process is adopted. The forced cooling system is opened from the first group. The method of adding new water can be adopted to control the laminar cooling water temperature to be ≤20℃ quickly, and the cooling rate is 40~50℃ / S;

[0063] (7) Coiling: The coiling temperature is determined according to the cooling control factor Q and the cooling rate in the controlled cooling step, Q = coiling temperature / cooling rate, 8.0≤Q≤11;

[0064] (8) Slow cooling: After the steel coil leaves the laminar cooling unit, it enters the slow cooling pit for natural cooling for 72 hours.

[0065] Table 1 (wt%)

[0066]

[0067] Table 2

[0068]

[0069] Table 3

[0070]

[0071] Table 4

[0072]

[0073] The mechanical properties and hydrogen compatibility tests of the steel plates involved in the above-mentioned Examples 1 to 5 and Comparative Examples 1 to 2 were conducted with reference to the standards of GB / T 14164, GB / T 8650A and GB / T 34542.2, as shown in Tables 3 and 4. The test results show that the hydrogen pipeline steel plate obtained by the technical solution of this embodiment not only has good strength and toughness, low-temperature drop hammer tearing performance, and a low yield ratio of ≤0.90, but also has excellent hydrogen compatibility performance, fatigue performance, etc., which meets the urgent needs of long-distance, large-scale and safe transportation of high-pressure hydrogen.

[0074] In summary, the hydrogen pipeline steel prepared by the present invention has outstanding performance indicators, especially the hydrogen-induced crack resistance indicator, which meets the requirements of CSR=0, CLR=0, CTR=0 in solution A, slow tensile IRA, IEL≤20%, and step-type compact tensile specimen KIH≥100MPa in a 6.3MPa pure hydrogen environment. a .m 1 / 2 , fatigue life ≥ 500,000 times. Therefore, the present invention solves the above three major technical problems faced in the research and development of hydrogen pipeline steel materials, develops a high-grade hydrogen pipeline steel, accelerates the upgrading of products, and is conducive to the promotion and use in the construction of hydrogen pipeline networks.

[0075] It should be emphasized that the above are only preferred embodiments of the present invention and do not impose any form of limitation on the present invention. Any simple modification of the above embodiments based on the technical essence of the present invention also falls within the protection scope of the present invention. Other equivalent changes and modifications still fall within the scope of the technical solution of the present invention.

Claims

1. A high-grade hydrogen pipeline steel, characterized in that: The chemical composition and mass percentage of the high-grade hydrogen pipeline steel are: C0.02-0.04%, Si0.20-0.30%, Mn1.20-1.30%, P≤0.010%, S≤0.0010%, Alt0.015-0.055%, N≤0.0020%, O≤0.0010%, H≤0.0001%, Cr0.90-1.00%, Mo0.40-0.50%, Ti0.020-0.030%, Nb0.05-0.07%, Ni0.40-0.50%, and the balance is iron and unavoidable impurities.

2. The high-grade hydrogen pipeline steel according to claim 1, characterized in that: The chemical composition of the high-grade hydrogen pipeline steel meets the following conditions: (Mg+Pr) / S=3.0-5.

0.

3. The high-grade hydrogen pipeline steel according to claim 1, characterized in that: The high-grade hydrogen pipeline steel has hydrogen-induced crack resistance indicators of CSR=0, CLR=0, CTR=0 in solution A, no cracks in SSC test, slow tensile IRA, IEL≤20%, and in a 6.3MPa pure hydrogen environment, KIH≥100MPa.m for the step-type compact tensile specimen 1 / 2 , fatigue life ≥ 500,000 times.

4. The high-grade hydrogen pipeline steel according to claim 1, characterized in that: The high-grade hydrogen pipeline steel has a yield strength Rt0.5 of 580-700 MPa, a tensile strength of 680-780 MPa, and an elongation after fracture A 50 35~45%, -30℃ impact energy KV2≥350J, SA(-30℃)100%, HV10≤260, Rt0.5 / Rm≤0.90, DWTT(-30℃)≥98%.

5. A method for preparing high-grade hydrogen pipeline steel, characterized in that: The preparation method is used to prepare the high-grade hydrogen pipeline steel according to any one of claims 1 to 4, and the preparation method comprises: Top and bottom combined blowing converter smelting, refining outside the furnace, large slab continuous casting, slab reheating, rough rolling, finishing rolling, controlled cooling, coiling, slow cooling; in the controlled cooling step, the cooling rate is 40-50°C / S; in the coiling step, the coiling temperature is determined according to the cooling control factor Q and the cooling rate in the cooling step, Q=coiling temperature / cooling rate, 8.0≤Q≤11, and the laminar cooling water temperature is ≤20°C.

6. The method for preparing a high-grade hydrogen pipeline steel according to claim 5, characterized in that: In the slab reheating step, the heating temperature is 1100-1300° C. and the heating time is 1h-3h; In the rough rolling step, the starting temperature of the rough rolling is 1100-1200°C, the rough rolling is performed by moving to wait for the temperature, and when the outlet temperature reaches 910-990°C, it enters the finishing rolling unit; In the finishing rolling step, a multi-stand hot rolling mill is used for rolling, and the final rolling temperature is 800-850° C. During the laminar cooling, the steel plate is immediately water-cooled after finishing rolling, and the front-stage rapid cooling process is adopted. The forced cooling system is opened from the first group, and new water is added to make the laminar cooling water temperature quickly ≤20°C, and the cooling rate is 40-50°C / S; In the coiling step, the cooling control factor Q and the cooling rate in the cooling step are determined, Q = coiling temperature / cooling rate, 8≤Q≤11; In the slow cooling step, after the steel coil leaves the laminar cooling unit, it enters the slow cooling pit for natural cooling for 60 to 84 hours.

7. The method for preparing a high-grade hydrogen pipeline steel according to claim 6, characterized in that: In the finishing rolling step, a 7-stand hot rolling mill is used for rolling.

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