A high-grade hydrogen transmission pipeline steel and its preparation method

Abstract

The present invention belongs to the technical field of iron and steel metallurgy, and relates to a high-grade hydrogen transmission pipeline steel and a preparation method thereof. The chemical composition of the high-grade hydrogen transmission pipeline steel and its mass percentage content are as follows: C 0.02 - 0.04%, Si 0.20 - 0.30%, Mn 1.20 - 1.30%, P ≤ 0.010%, S ≤ 0.0010%, Alt 0.015 - 0.055%, N ≤ 0.0020%, O ≤ 0.0010%, H ≤ 0.0001%, Cr 0.90 - 1.00%, Mo 0.40 - 0.50%, Ti 0.020 - 0.030%, Nb 0.05 - 0.07%, Ni 0.40 - 0.50%, and the balance is iron and unavoidable impurities; each performance index of the present invention is outstanding, especially the hydrogen-induced cracking resistance index, meeting CSR = 0, CLR = 0, CTR = 0 under solution A, slow tensile IRA, IEL ≤ 20%, in a 6.3 MPa pure hydrogen environment, the KIH of the stepped compact tension specimen ≥ 100 MPa·m<supgt;1 / 2< / supgt;, and the fatigue life ≥ 500,000 times; the present invention solves the technical problems faced in the research and development of materials for hydrogen transmission pipeline steel, the technical solution is relatively simple and easy to implement, the performance stability of the obtained product is high and the cost is controllable, which is conducive to popularization and use in the construction of high-pressure hydrogen long-distance, large-scale and safe transmission pipelines.

Description

Technical Field

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

[0002] The power generation using clean energy such as wind energy, solar energy, and tidal energy is uncontrollable and will generate a large amount of curtailed electricity. Applying the curtailed electricity to the hydrogen production process to produce hydrogen, and then storing, 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 the traditional vehicle transportation method cannot meet the user's needs. Using pipeline hydrogen transportation has the characteristics of large transportation volume, low energy consumption, and low cost, and is an economical way to achieve large-scale long-distance hydrogen transportation. Among them, the natural gas blending hydrogen technology, as an effective way to save energy and reduce carbon, has been widely favored by the industry in recent years.

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

[0004] Mixing pure hydrogen or hydrogen into natural gas in a certain volume ratio can improve the combustion performance of terminal equipment, effectively increase the calorific value, and reduce nitrogen oxide pollution and carbon dioxide emissions. In terms of long-distance, large-scale hydrogen-blended natural gas transportation, compared with traditional canned transportation, pipeline transportation is more economical, safe, and green.

[0005] However, hydrogen molecules have extremely strong permeability to metals, which easily causes hydrogen embrittlement or hydrogen damage to pipelines. During the research and development process of hydrogen transmission pipelines, there are mainly three major technical problems: First, at high temperature, H combines with C in the matrix to form CH4 gas, causing decarburization on the steel surface and microcracks inside, and low-carbon composition design should be adopted; Second, since hydrogen atoms are extremely easy to accumulate at the two-phase interface and generate cracks, the higher the purity of molten steel, the better; Third, obtaining high-plasticity and high-toughness materials through improving the original design to avoid the occurrence of hydrogen embrittlement.

[0006] The prior art cannot solve the above technical problems well. For example, Invention CN115584441A discloses a hot-rolled coil for hydrogen transmission pipelines with a yield strength of 245 MPa and its production method. However, the strength level of the steel obtained by this invention is relatively low and does not possess hydrogen transmission environment performance. Invention CN113862549B discloses a production method of L360QS hydrogen transmission pipeline steel. This invention does not mention hydrogen embrittlement sensitivity and fracture toughness tests, and the inspection items under hydrogen environment conditions are insufficient. Invention CN116656927A discloses a production method of TMCP hydrogen-doped hydrogen transmission pipeline steel. In this invention, the experimental data under 10 MPa pure hydrogen environment and 4.0 MPa pure hydrogen environment are not mentioned.

[0007] Therefore, a process technology and method for high-grade hydrogen transmission 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 problems is: a high-grade hydrogen transmission pipeline steel, and the chemical composition and its mass percentage content of the high-grade hydrogen transmission pipeline steel are: C 0.02 - 0.04%, Si 0.20 - 0.30%, Mn 1.20 - 1.30%, P ≤ 0.010%, S ≤ 0.0010%, Alt 0.015 - 0.055%, N ≤ 0.0020%, O ≤ 0.0010%, H ≤ 0.0001%, Cr 0.90 - 1.00%, Mo 0.40 - 0.50%, Ti 0.020 - 0.030%, Nb 0.05 - 0.07%, Ni 0.40 - 0.50%, and the balance is iron and unavoidable impurities.

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

[0010] Preferably, the hydrogen-induced cracking resistance index of the high-grade hydrogen transmission pipeline steel is CSR = 0, CLR = 0, CTR = 0 under Solution A, there is no crack in the SSC test, both slow tensile IRA and IEL are ≤ 20%, and under 6.3 MPa pure hydrogen environment, the KIH of the stepped compact tension specimen is ≥ 100 MPa·m 1 / 2 , and the fatigue life is ≥ 500,000 times.

[0011] Preferably, the yield strength R t0.5 of the high-grade hydrogen transmission pipeline steel is 580 - 700 MPa, the tensile strength R m is 680 - 780 MPa, the elongation after fracture A 50 is 35 - 45%, the impact energy KV2 at -30°C ≥ 350 J, SA100% at -30°C, HV10 ≤ 260, R t0.5 / R m≤0.90, DWTT ≥ 98% at -30°C.

[0012] The present invention also discloses a preparation method of a high-grade hydrogen transmission pipeline steel, which is used to prepare the above-mentioned high-grade hydrogen transmission pipeline steel. The preparation method includes:

[0013] Top and bottom combined blowing converter smelting, secondary refining, heavy slab continuous casting, slab reheating, rough rolling, finish rolling, laminar cooling, coiling, slow cooling; in the laminar 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 laminar cooling step, Q = coiling temperature / cooling rate, 8.0 ≤ Q ≤ 11. To ensure the fracture toughness index and tissue uniformity, the water temperature of the laminar cooling water ≤ 20°C.

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

[0015] In the rough rolling step, the rough rolling starting temperature is 1100 - 1200°C. To avoid rolling in the two-phase region, the rough rolling is carried out with floating waiting for temperature, and when the outlet temperature reaches 910 - 990°C, it enters the finish rolling mill;

[0016] In the finish rolling step, it is rolled by a multi-stand hot continuous rolling mill, and the finishing rolling temperature is 800 - 850°C;

[0017] During laminar cooling, after the steel plate exits the finish rolling, it is immediately water-cooled. The front-section rapid cooling process is adopted. Starting from the first group, the forced cooling system is turned on, and by adding new water, the water temperature of the laminar cooling water is quickly ≤ 20°C, and the cooling rate is 40 - 50°C / 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 exits the laminar cooling unit, it enters the slow cooling pit for natural cooling for 60 - 84h.

[0020] Preferably, in the finish rolling step, it is rolled by a 7-stand hot continuous rolling mill.

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

[0022] 1. The performance indexes of the hydrogen transmission pipeline steel prepared by the present invention are outstanding, especially the hydrogen-induced cracking resistance index, meeting CSR = 0, CLR = 0, CTR = 0 under solution A, slow tensile IRA, IEL ≤ 20%, and in a 6.3 MPa pure hydrogen environment, the KIH of the stepped compact tension specimen ≥ 100 MPa·m 1 / 2 , and the 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 preferably solves the above three major technical problems faced in the research and development of materials for hydrogen transmission pipeline steel, develops a high-grade hydrogen transmission pipeline steel, accelerates the upgrading of products, and is conducive to popularization and use in the construction of hydrogen pipeline networks. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0027] Figure 3 is the fracture morphology diagram of the slow tensile notched specimen in Example 1 of the present invention;

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

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

[0030] Figure 6 is the load-crack opening displacement curve diagram of the comparative example of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] Next, the related technologies in the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0032] Refer to Figures 1 to 6 , in this embodiment, the chemical composition (mass percentage) of the high-grade hydrogen transmission pipeline steel is: C 0.02-0.04%, Si 0.20-0.30%, Mn 1.20-1.30%, P≤0.010%, S≤0.0010%, Alt 0.015-0.055%, N≤0.0020%, O≤0.0010%, H≤0.0001%; in addition, Cr 0.90-1.00%, Mo 0.40-0.50%, Ti 0.020-0.030%, Nb 0.05-0.07%, Ni 0.40-0.50%, and (Mg + Pr) / S are controlled at 3.0-5.0, and the balance is iron and inevitable impurities.

[0033] The high-grade hydrogen transmission pipeline steel provided by this embodiment: the yield strength Rt0.5 is 580-700 MPa, the tensile strength is 680-780 MPa, and the elongation after fracture A 50 is 35-45%, the impact energy KV2 at -30°C ≥ 350 J, SA(-30°C) 100%, HV10 ≤ 260, Rt0.5 / Rm ≤ 0.90, DWTT(-30°C) ≥ 98%. In addition, for the hydrogen-induced cracking resistance index, it is required that CSR = 0, CLR = 0, CTR = 0 in solution A, there is no crack in the SSC test, the slow tensile IRA and IEL ≤ 20%, and in a pure hydrogen environment of 6.3 MPa, the KIH of the stepped compact tension specimen ≥ 100 MPa·m 1 / 2 , and the fatigue life ≥ 500,000 cycles.

[0034] The specific principles for adding each chemical element in this embodiment are as follows:

[0035] Carbon (C): The main element affecting the toughness, hardness, strength and welding performance of pipeline steel, which 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 exacerbates the center segregation of the steel and reduces the resistance to HIC and SSCC. For hydrogen transmission pipeline steel, as the strength grade increases, the C content in the steel shows a downward trend. Therefore, the C content in this technical solution is 0.02-0.04%.

[0036] Manganese (Mn): In hydrogen transmission pipeline steel, it mainly has the following functions: (1) increasing the solubility product of (Nb, Ti)(C, N) in austenite, inhibiting its precipitation in austenite, reducing the nano-precipitation size of carbides, nitrides and carbonitrides, which is beneficial to the precipitation strengthening effect; (2) manganese in the steel is very likely to cause segregation, generating banded pearlite in the center of the plate thickness, making the banded structure ≥ grade 2, and some even reaching grade 3, deteriorating the anti-acid corrosion HIC and SSCC performance. Moreover, Mn in the steel reacts with S to form strip-shaped MnS inclusions. Center segregation and strip-shaped MnS inclusions are likely to cause HIC and SSCC failures. Compared with pipeline steel of the same grade, the Mn content of the steel is controlled; (3) mainly strengthening by solid solution in the 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, it is limited to 1.20-1.30% in this embodiment.

[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 phase transformation temperature of steel, control the grain size during continuous casting and heating processes, form TiN particles with nitrogen, and is a strong carbide and nitride forming element with 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. Additionally, the combined strengthening of Ti and Nb prolongs the precipitation incubation period of NbC, making the carbide precipitation time of Nb-Ti composite steel relatively late, and the precipitates are more dispersed and finer. It improves the thermal stability of (NbTi)(CN), enhances the toughness of the steel plate, improves the welding performance of the steel plate, and effectively inhibits the growth of austenite grains during the heating process and the coarsening of grains in the welding heat-affected zone. In this embodiment, the addition amount of titanium is 0.020 - 0.030%.

[0042] Niobium (Nb): It inhibits the excessive growth of austenite grains, delays the γ→α phase transformation, is beneficial to the formation of acicular ferrite, refines the ferrite grains, improves the toughness of steel, and obtains a fine microstructure. During hot rolling, niobium carbonitride delays recrystallization and grain growth. By pinning dislocations, more dislocation density is retained in the matrix, improving the strength and toughness of the steel. It achieves the precipitation strengthening effect to replace V, reducing the cost of the steel. In this embodiment, the addition amount of niobium is 0.05 - 0.07%.

[0043] Oxygen (O), Nitrogen (N), Hydrogen (H): High gas content in steel reduces the fatigue life of hydrogen transmission pipeline steel. Nitrogen forms high-melting-point TiN particles, which can inhibit the excessive growth of grains during the heating process and improve the strength and toughness of the steel. When the N content is too high, a high concentration of free N atoms causes failure, pins dislocations, increases the yield strength, and reduces the toughness. Regarding the oxygen content in steel, deoxidation treatment is required at the end of smelting to reduce oxide inclusions and bubbles, improve the internal quality of the steel, and is also beneficial to improving the anti-dynamic tearing performance and low-temperature impact toughness of hydrogen transmission pipeline steel. H easily causes defects such as hydrogen embrittlement and white spots in steel. For hydrogen transmission 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 strengthening by precipitation, increasing the hardness of the steel plate, replacing V alloy, and improving the corrosion resistance and hydrogen-induced cracking resistance of the steel. However, excessive chromium reduces the elongation after fracture of the steel plate, leading to the formation of low-melting-point Cr-Mn composite oxides and surface cracks during hot working, which has an adverse effect on the 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, be beneficial to the formation of acicular ferrite, strengthen the matrix, prevent softening in the heat-affected zone after welding. While increasing the strength, it can also improve the sensitivity to hydrogen-induced cracking. Control the Mo content to be 0.40 - 0.50%.

[0046] Nickel (Ni): Nickel belongs to non-carbide forming elements, generally dissolves in the steel matrix solid solution, reduces the phase transformation temperature, refines the grain size, improves 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 relatively high acid concentration, reducing the entry of hydrogen atoms into the steel matrix, slowing down H2S corrosion, and improving the HIC resistance. In this embodiment, the Ni content is preferably 0.40 - 0.50 wt%.

[0047] This embodiment also provides a preparation method for hydrogen transmission pipeline steel, including top-bottom combined blowing converter smelting, secondary refining, slab continuous casting, slab reheating, rough rolling, finish rolling, controlled cooling, coiling, and slow cooling; among them, 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 tissue uniformity, the laminar cooling water temperature ≤ 20 °C. Among them:

[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 rough rolling starting temperature is 1150 - 1180 °C. To avoid rolling in the two-phase region, rough rolling performs floating waiting for temperature. When the outlet temperature reaches 950 °C, it enters the finish rolling mill;

[0050] (3) Finish rolling: Rolling with a 7-stand hot continuous rolling mill, the final rolling temperature is 805 - 835 °C;

[0051] (4) Laminar cooling: After the steel plate exits the finish rolling, it is immediately water-cooled. Adopt the front-section rapid cooling process. Starting from the first group, open the forced cooling system. The way of adding new water can be used to quickly make the laminar cooling water temperature ≤ 20 °C, and the cooling rate is 40 - 50 °C / S;

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

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

[0054] Examples

[0055] Examples 1 - 5

[0056] For Examples 1 to 5 of the hydrogen pipeline steel and Comparative Examples 1 to 2, the chemical element ratios of the steel strips are shown in Table 1, and the detailed process parameters of Examples 1 to 5 and Comparative Examples 1 to 2 are shown in Table 2. Figure 1 It indicates that the microstructure of the steel plate matrix in Example 1 is acicular ferrite. Figure 2 It indicates that the microstructure of the matrix in Comparative Example 1 is polygonal ferrite + bainite. Figure 3 It indicates that there is no crack in the slow tensile notched specimen of Example 1. Figure 4 It indicates that there are crack defects in the slow tensile notched specimen of Comparative Example 1. Figure 5 It indicates the load-crack opening displacement curve of Example 1. Figure 5 It indicates the load-crack opening displacement curve of Comparative Example 1.

[0057] (1) Smelting raw materials in a 180-ton top and bottom combined blown converter.

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

[0059] (3) Reheating the slab, with the heating temperature being 1200 - 1240 °C, the heating time being 90 min - 120 min, and the slab thickness being 210 - 250 mm.

[0060] (4) Rough rolling: The rough rolling starting temperature is 1150 - 1180 °C. To avoid two-phase zone rolling, floating waiting for temperature is carried out during rough rolling, and it enters the finishing mill when the outlet temperature ≤ 950 °C.

[0061] (5) Finishing rolling: Rolling with a 7-stand hot continuous rolling mill, and the final rolling temperature is 805 - 835 °C.

[0062] (6) Laminar cooling: After the steel plate exits the finishing mill, it is immediately water-cooled. The front-section rapid cooling process is adopted. Starting from the first group, the forced cooling system is turned on. The way of increasing new water can be used to control the laminar cooling water temperature to be rapidly ≤ 20 °C, and the cooling rate is 40 - 50 °C / 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, and 8.0 ≤ Q ≤ 11.

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

[0065] Table 1 (wt%)

[0066]

[0067] Table 2

[0068]

[0069] Table 3

[0070]

[0071] Table 4

[0072]

[0073] Refer to the standards of GB / T 14164, GB / T 8650A and GB / T 34542.2 to conduct mechanical property and hydrogen compatibility tests on the steel plates involved in the aforementioned Examples 1 to 5 and Comparative Examples 1 to 2. As shown in Table 3 and Table 4, the test results show that: the hydrogen transmission pipeline steel plate obtained by the technical solution of this embodiment not only has good strength and toughness, low-temperature drop-weight tear performance, and a low yield ratio ≤ 0.90, but also has excellent hydrogen compatibility performance, fatigue performance, etc., meeting the urgent needs of long-distance, large-scale, and safe transmission of high-pressure hydrogen.

[0074] In summary, the performance indicators of the hydrogen transmission pipeline steel prepared by the present invention are outstanding, especially the hydrogen-induced cracking resistance index, meeting CSR = 0, CLR = 0, CTR = 0 under Solution A, slow tensile IRA, IEL ≤ 20%, and in a 6.3 MPa pure hydrogen environment, the KIH of the stepped compact tension specimen ≥ 100 MPa·m 1 / 2 , and the fatigue life ≥ 500,000 times. Therefore, the present invention preferably solves the above three major technical problems faced in the research and development of hydrogen transmission pipeline steel materials, develops a high-grade hydrogen transmission pipeline steel, accelerates the upgrading of products, and is conducive to popularization and use in the construction of hydrogen pipe networks.

[0075] It should be emphasized that: the above are only the preferred embodiments of the present invention, and do not impose any form of limitation on the present invention. Any simple modification made to the above embodiments based on the technical essence of the present invention also belongs to 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 transmission pipeline steel, characterized in that, The chemical composition and its mass percentage of the high-grade hydrogen transmission pipeline steel are as follows: C 0.02 - 0.04%, Si 0.20 - 0.30%, Mn 1.20 - 1.30%, P ≤ 0.010%, S ≤ 0.0010%, Alt 0.015 - 0.055%, N ≤ 0.0020%, O ≤ 0.0010%, H ≤ 0.0001%, Cr 0.90 - 1.00%, Mo 0.40 - 0.50%, Ti 0.020 - 0.030%, Nb 0.05 - 0.07%, Ni 0.40 - 0.50%, (Mg + Pr) / S = 3.0 - 5.0, and the balance is iron and inevitable impurities; The hydrogen-induced cracking resistance indexes of the high-grade hydrogen transmission pipeline steel are CSR = 0, CLR = 0, CTR = 0 in Solution A, no cracks in the SSC test, both slow tensile IRA and IEL ≤ 20%, and in a 6.3 MPa pure hydrogen environment, the KIH of the stepped compact tension specimen ≥ 100 MPa·m 1 / 2 , and the fatigue life ≥ 500,000 cycles.

2. The high-grade hydrogen transmission pipeline steel according to claim 1, wherein, The yield strength R of the high-grade hydrogen transmission pipeline steel t0.5 is 580 - 700 MPa, the tensile strength R m is 680 - 780 MPa, the elongation after fracture A 50 is 35 - 45%, the impact energy KV2 at -30°C ≥ 350 J, SA100% at -30°C, HV10 ≤ 260, R t0.5 / R m ≤ 0.90, DWTT ≥ 98% at -30°C.

3. A preparation method of a high-grade hydrogen transmission pipeline steel, characterized in that, The preparation method is used to prepare the high-grade hydrogen transmission pipeline steel described in any one of claims 1 to 2, and the preparation method includes the following steps: Top and bottom combined blowing converter smelting, secondary refining, heavy slab continuous casting, slab reheating, rough rolling, finish rolling, laminar flow cooling, coiling, slow cooling; in the laminar flow 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 laminar flow cooling step, Q = coiling temperature / cooling rate, 8.0 ≤ Q ≤ 11, and the water temperature of the laminar flow cooling water ≤ 20 °C.

4. The preparation method of a high-grade hydrogen transmission pipeline steel according to claim 3, characterized in that: In the slab reheating step, the heating temperature is 1100 - 1300 °C, and the heating time is 1 h - 3 h; In the rough rolling step, the rough rolling starting temperature is 1100 - 1200 °C, and the rough rolling is carried out with floating waiting for temperature. When the outlet temperature reaches 910 - 990 °C, it enters the finish rolling mill; In the finish rolling step, it is rolled by a multi-stand hot continuous rolling mill, and the final rolling temperature is 800 - 850 °C; During the laminar flow cooling, after the steel plate exits the finish rolling, it is immediately water-cooled. The front-section rapid cooling process is adopted. Starting from the first group, the forced cooling system is opened, and the way of adding fresh water is used to quickly make the water temperature of the laminar flow cooling water ≤ 20 °C, and the cooling rate is 40 - 50 °C / s; In the slow cooling step, after the steel coil exits the laminar flow cooling unit, it enters the slow cooling pit for natural cooling for 60 - 84 h.

5. The preparation method of a high-grade hydrogen transmission pipeline steel according to claim 4, characterized in that, In the finish rolling step, it is rolled by a 7-stand hot continuous rolling mill.

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