Steel for high-strength high-toughness high-hic-resistance thick-walled seamless steel pipe for lng terminal, seamless steel pipe and method for producing the same

Abstract

This invention provides steel for thick-walled seamless steel pipes used in LNG receiving stations with high strength, toughness, and resistance to hydrogen-induced cracking, seamless steel pipes, and their production methods. The composition is C 0.05%–0.10%, Si 0.20%–0.40%, Mn 1.70%–2.00%, Cr 0.30%–0.60%, Mo 0.10%–0.30%, Ni 0.40%–0.60%, Cu 0.030%–0.050%, Ti 0.015%–0.035%, Al 0.015%–0.025%, P≤0.015%, S≤0.010%, N 0.0060%–0.0090%, B 0.0020%–0.0040%, TO≤0.0040%, with the remainder being Fe and other unavoidable impurities. Compared with existing technologies, the seamless steel pipe of the present invention has excellent strength, toughness and resistance to hydrogen-induced cracking.

Description

Technical Field

[0001] This invention belongs to the field of alloys and relates to the field of seamless steel pipe manufacturing, specifically to steel for thick-walled seamless steel pipes used in LNG receiving stations with high strength, toughness and high resistance to hydrogen-induced cracking, seamless steel pipes and their production methods. Background Technology

[0002] Liquefied natural gas (LNG) is widely recognized as the cleanest fossil fuel on Earth. It is colorless, odorless, non-toxic, and non-corrosive, making it a primary energy source. During LNG pipeline transportation, LNG terminals are needed at intervals to facilitate operations such as transport, maintenance, and pressurization. Currently, LNG receiving terminals are relatively large, and their scale will further expand as LNG demand increases.

[0003] The higher the strength of steel, the easier it is for hydrogen atoms to accumulate at grain boundaries and other microstructures, making high-strength steel more susceptible to hydrogen embrittlement and hydrogen-induced cracking. Seamless steel pipes used in LNG terminals have increased strength, and the LNG transport environment contains a certain amount of hydrogen, making them even more prone to hydrogen-induced cracking. Therefore, the demand for high-strength, thick-walled seamless steel pipes resistant to hydrogen-induced cracking in LNG receiving terminals is increasingly strong.

[0004] Patent CN 112981248A, published on June 18, 2021, refers to a continuously cast round billet for manufacturing X80 seamless steel pipes and its production method. The composition includes: C: 0.07–0.09%, Si: 0.21–0.29%, Mn: 1.0–1.1%, P≤0.008%, S≤0.003%, Cr: 0.28–0.32%, V: 0.32–0.48%, Nb: 0.025–0.035%, Mo: 0.38–0.42%, Al… The composition of the raw material billet is as follows: 0.025–0.035% Fe, 0.010–0.020% Ti, 0.93–0.97% Ni, 0.09–0.11% Cu, O ≤30ppm, N ≤80ppm, with the balance being Fe and unavoidable impurities. The surface of the continuously cast large round billet is free from visible cracks, scabs, sand holes, pores, pinholes, and other defects. The product quality meets the requirements for pipe manufacturing, and the resulting steel pipe will not exhibit weak weld impact resistance in low-temperature environments. This patent describes the production process of the raw material billet used for X80 seamless steel pipes. However, it does not mention key indicators such as the diameter, wall thickness, and performance of the final product, thus failing to meet the requirements for seamless steel pipes used in LNG receiving stations.

[0005] Patent CN 110404972A, published on November 5, 2019, discloses a method for producing seamless steel pipes with a diameter of 1422mm. This patent details the production process: X80 steel solid round billets are heated, then pierced, rolled, temperature-controlled rolled, sizing, quenched, tempered, cooled, straightened, and cut to a fixed length to obtain seamless steel pipes with a diameter of 1422mm. The product has good quality and relatively low production costs, meeting the high quality requirements, cost sensitivity, and high output requirements of natural gas pipeline construction. Furthermore, it eliminates the need for heating wires wrapped around the pipe during use, significantly reducing operating costs. However, the steel pipe has low impact resistance, making it unsuitable for use in LNG environments.

[0006] Therefore, it is urgent to track the characteristics of seamless steel pipes used in LNG receiving terminals, develop a high-strength, high-toughness, large-diameter and thick-walled seamless steel pipe resistant to hydrogen-induced cracking, and design a targeted heat treatment process for the steel pipe. Summary of the Invention

[0007] The purpose of this invention is to provide steel for thick-walled seamless steel pipes used in LNG receiving terminals with high strength, toughness, and resistance to hydrogen-induced cracking. Through composition design and matching, steel with excellent strength, toughness, and resistance to hydrogen-induced cracking is obtained, which can be used to produce thick-walled seamless steel pipes for LNG receiving terminals with high strength, toughness, and resistance to hydrogen-induced cracking.

[0008] Another objective of this invention is to provide seamless steel pipes and their production methods. Seamless steel pipes with a wall thickness of 40–60 mm are manufactured using the aforementioned high-strength, high-toughness, and high-hydrogen-cracking-resistant thick-walled seamless steel pipes for LNG receiving stations. After heat treatment, the product exhibits a tensile strength ≥680 MPa, a yield strength ≥615 MPa, and a KV2 ≥240 J at -50℃ at half the wall thickness. It also possesses good cross-sectional uniformity, a cross-sectional hardness difference ≤20 HBW, and excellent resistance to hydrogen-induced cracking.

[0009] The specific technical solution of this invention is as follows:

[0010] The steel used for thick-walled seamless steel pipes for high-strength, high-toughness, and high-resistance to hydrogen-induced cracking LNG receiving terminals comprises the following components by weight percentage:

[0011] C 0.05%–0.10%, Si 0.20%–0.40%, Mn 1.70%–2.00%, Cr 0.30%–0.60%, Mo 0.10%–0.30%, Ni 0.40%–0.60%, Cu 0.030%–0.050%, Ti 0.015%–0.035%, Al 0.015%–0.025%, P≤0.015%, S≤0.010%, N 0.0060%–0.0090%, B 0.0020%–0.0040%, TO≤0.0040%, with the remainder being Fe and other unavoidable impurities.

[0012] The steel used for the high-strength, high-toughness, and high-resistance to hydrogen-induced cracking LNG receiving terminals meets the following requirements in terms of composition:

[0013] 30.0≤A≤50.0;

[0014] A=(4.5×%C)×(1+3.4×%Mn)×(1+0.7×%Si)×(1.2+2.6×%Cu)×(1+2.7

[0015] ×%Ni)×(1+3.1×%Cr)×(1+2.3×%Mo)×(1+1.8×%Ti+4.6×%N+4.2×%B);

[0016] Y≥2.5%; Y=2.5×%Cr+3.8×%Mo+16.5×%Ni+2.5×%Cu-1×%C-4×%Mn-15×%B.

[0017] The seamless steel pipe provided by this invention is produced using the steel used for the high-strength, high-toughness, and high-resistance to hydrogen-induced cracking LNG receiving station thick-walled seamless steel pipe.

[0018] The wall thickness of the seamless steel pipe is ≥40mm; preferably, the wall thickness is 40mm~60mm.

[0019] The seamless steel pipe has 100% tempered sorbite on its inner wall, half wall thickness, and outer wall; the grain size is 20-27 μm, and the difference in grain size between the inner wall, half wall thickness, and outer wall is ≤1 μm.

[0020] The seamless steel pipe has a tensile strength ≥680MPa, yield strength ≥615MPa at 1 / 2 wall thickness, KV2 ≥240J at -50℃, A ≥22%, and Z ≥50%; and has good cross-sectional uniformity with a cross-sectional hardness difference ≤20HBW, preferably ≤16HBW; it is tested for hydrogen-induced cracking according to GB / T 8650, and meets the requirements of CSR ≤1.5% and CLR ≤12% in solution A, which meets the high-pressure transportation requirements of LNG receiving stations.

[0021] This invention provides a method for producing steel for thick-walled seamless steel pipes used in LNG receiving stations with high strength, toughness, and high crack tip opening displacement, including a hot forming process and a heat treatment process.

[0022] The thermoforming process includes billet heating temperature, tube insertion deformation, tube insertion rate, single tube expansion deformation, and tube expansion rate.

[0023] The billet heating temperature is 1000℃~1100℃, the tube deformation is 10%~25%, and the tube threading speed is 0.20~0.40s. -1 The deformation amount per expansion cycle is 10%–20%, and the expansion rate is 0.10–0.20 s. -1 .

[0024] The heat treatment process includes quenching and tempering.

[0025] The quenching process involves an initial furnace temperature of ≤400℃ and a heating temperature of T. 淬火加热 840~960℃; heat preservation time t 淬火保温 The steel pipe wall thickness S and heating temperature T 淬火加热 The decision is 160 + (S / 2) - (T) 淬火加热 / 9)≤t 淬火保温 ≤170+(S / 2)-(T 淬火 Heating / 9), water cooling; where the steel pipe wall thickness S is in mm, and the heating temperature T 淬火加热 The unit is ℃, and the holding time is t. 淬火保温 The unit is min. When calculating the above formula, simply substitute the data before the unit into the formula.

[0026] The tempering: tempering temperature T 回火加热 580~700℃, holding time t 回火保温 The steel pipe wall thickness S and tempering temperature T 回火加热 The decision is 410 + (S / 2) - (T) 回火加热 / 2)≤t 回火保温 ≤420+(S / 2)-(T 回火加热 / 2), water cooling, where the steel pipe wall thickness S is in mm, and the heating temperature T 回火加热 The unit is ℃, and the holding time is t. 回火保温 The unit is min. When calculating the above formula, simply substitute the data before the unit into the formula.

[0027] The design concept of this invention is as follows:

[0028] Carbon (C): Carbon is the cheapest strengthening element in steel. Each 0.01% increase in dissolved C can increase strength by approximately 45 MPa. C forms precipitates with alloying elements in steel, resulting in precipitation strengthening. C significantly improves hardenability, enabling thick-walled steel pipes to acquire a martensitic structure in the center. However, as its content increases, plasticity and toughness decrease; therefore, the C content is controlled between 0.05% and 0.10%.

[0029] Si: Si is an effective solid solution strengthening element in steel, increasing its strength and hardness. Si also acts as a deoxidizer during steelmaking. However, Si tends to segregate at austenite grain boundaries, reducing grain boundary bonding and causing brittleness. Furthermore, Si easily causes elemental segregation in steel. Therefore, the Si content is controlled between 0.20% and 0.40%.

[0030] Mn: Mn can play a solid solution strengthening role, but its solid solution strengthening ability is weaker than that of Si. Mn is an austenite stabilizing element that can significantly improve the hardenability of steel and reduce decarburization. Mn combined with S can prevent hot brittleness caused by S. However, excessive Mn will reduce the plasticity of steel. Therefore, the Mn content should be controlled between 1.70% and 2.00%.

[0031] Cr: Cr is a carbide-forming element. Cr can improve the hardenability and strength of steel, but it easily causes temper brittleness. Cr can improve the oxidation resistance and corrosion resistance of steel, but excessive Cr content will increase crack susceptibility. The Cr content should be controlled between 0.30% and 0.60%.

[0032] Mo: Mo primarily improves the hardenability of steel. Mo dissolved in the matrix helps maintain high stability of the steel's microstructure during tempering and effectively reduces the segregation of impurity elements such as P, S, and As at grain boundaries, thereby improving the steel's toughness and reducing temper brittleness. Mo reduces the stability of M7C3; when the Mo content is high, acicular Mo2C will form, leading to a reduction in the Mo content in the matrix. Mo can improve the strength of steel through the combined effects of solid solution strengthening and precipitation strengthening, and it can also alter the steel's toughness by changing the precipitation of carbides. Therefore, the Mo content should be controlled between 0.10% and 0.30%.

[0033] Ni: Ni can form an infinitely miscible solid solution with Fe. It is an austenite stabilizing element, expanding the phase region, increasing the stability of supercooled austenite, shifting the C-curve to the right, and improving the hardenability of steel. Ni can refine the width of martensite laths, increasing strength. Ni significantly lowers the ductile-brittle transition temperature of steel and improves low-temperature toughness. Ni is a precious metal element; excessive addition leads to excessively high costs. The Ni content should be controlled between 0.40% and 0.60%.

[0034] Ti: Ti plays a wide role in steel. It can act as a deoxidizer, and it can form carbonitrides with C and N to precipitate in the steel, thus providing precipitation strengthening. It can also pin grain boundaries to inhibit grain growth. The Ti content should be controlled between 0.015% and 0.035%.

[0035] Cu: Cu expands the austenite phase region. Elemental Cu can act as a second phase, significantly improving strength and enhancing the tempering stability and strength of the microstructure. However, excessive Cu content will lead to Cu brittleness. Therefore, the Cu content should be controlled between 0.030% and 0.050%.

[0036] Al: Al is the main deoxidizer in steelmaking. Al combines with N to form finely dispersed AlN, which maintains a coherent relationship with the matrix. This strengthens and refines the microstructure, increases resistance to fatigue crack initiation and propagation, and thus improves the endurance strength of steel. The Al content is controlled between 0.015% and 0.025%.

[0037] TO and N: TO forms oxide inclusions in steel, so TO should be controlled at ≤0.0040%; N can form fine precipitates with nitride-forming elements in steel to refine the microstructure, and can also precipitate Fe4N, which has a slow diffusion rate, leading to aging of the steel and reduced processing performance. Therefore, N should be controlled at ≤0.0090% (0.0060%).

[0038] B: Adding B can improve hardenability and increase strength. Furthermore, B acts as a grain boundary remover, eliminating harmful elements such as P and S at grain boundaries, thereby increasing the bonding strength between grain boundaries and promoting improved toughness. Control B content to 0.0020%–0.0040%, P ≤ 0.015%, and S ≤ 0.010%.

[0039] Thick-walled seamless steel pipes are superior to those with a wall thickness exceeding 40mm, as they require high toughness and resistance to hydrogen-induced cracking when serving in LNG environments. The strength of the steel can be improved by adding beneficial alloying elements, the toughness can be improved by using effective element ratios, and the resistance to hydrogen-induced cracking can be improved by forming an effective solid hydrogen precipitation phase. This study of the alloy system shows that, under this composition, Mn is the most effective alloying element in improving hardenability and strength, hence the coefficient is 3.4. Mo also contributes significantly to hardenability and strength by improving tempering stability and interacting with Mn, with a coefficient of 2.3. Cr is a major substitutional solid solution element and carbide-forming element, contributing 3.1 to strength. Ni and Cu do not form carbides in steel, but improve hardenability and strength by altering the crystal morphology through solid solution strengthening, with coefficients of 2.7 and 2.6, respectively. C is a non-metallic element and the most important interstitial solid solution strengthening element in steel, affecting both strength and toughness, hence the coefficient is 4.5. Si is a non-metallic element and also a major solid solution strengthening element in steel, contributing 0.7 to the steel's performance. Ti, N, and B are microalloying elements that improve steel strength through interaction and the formation of a second phase. In addition, N and B can improve steel strength by altering the crystal lattice of C, hence the coefficients are 1.8, 4.6, and 4.2, respectively. Since the strength, plasticity, and toughness of steel are inversely proportional, and high strength leads to a decrease in plasticity and toughness, the strength cannot be increased indiscriminately to ensure the overall performance of steel. Let the strengthening factor in steel be represented by A, then 30.0 ≤ A ≤ 50.0;

[0040] A=(4.5×%C)×(1+3.4×%Mn)×(1+0.7×%Si)×(1.2+2.6×%Cu)(1+2.7×%Ni)×(1+3.1×%Cr)×(1+2.3×%Mo)×(1+1.8×%Ti+4.6×%N+4.2×%B).

[0041] Seamless steel pipes used in LNG receiving terminals require good resistance to hydrogen-induced cracking during service, necessitating strict control over the proportions of C, Mn, B, Cr, Mo, Ni, and Cu. While C, Mn, and B significantly improve steel strength, their tendency to deviate can lead to microstructure inhomogeneity, increasing entropy and causing localized weakening of the matrix, thus exacerbating hydrogen-induced cracking. Cr and Mo can form a second phase with C and N in the steel, acting as a fixed source of hydrogen, thus providing resistance to hydrogen-induced cracking. Ni increases the stacking fault energy, dislocation density, and dislocation slip rate, further enhancing resistance to hydrogen-induced cracking. Cu exhibits good nanoscale bonding with steel, forming a semi-coherent relationship that effectively immobilizes hydrogen, hindering hydrogen-induced cracking. Let Y represent the hydrogen-induced cracking resistance factor in steel, then Y ≥ 2.5%; Y = 2.5 × %Cr + 3.8 × %Mo + 16.5 × %Ni + 2.5 × %Cu - 1 × %C - 4 × %Mn - 15 × %B.

[0042] Compared with the prior art, the present invention obtains seamless steel pipes with a wall thickness of 40-60mm through composition design, production method, and heat treatment design. The tensile strength at 1 / 2 wall thickness of the product is ≥680MPa, yield strength is ≥615MPa, and KV2 at -50℃ is ≥240J. It also has good cross-sectional uniformity and cross-sectional hardness difference ≤20HBW. At the same time, it has good resistance to hydrogen-induced cracking. Attached Figure Description

[0043] Figure 1 Examples 2 show the crack propagation on the inner wall, half radius, and outer wall of the seamless steel pipe.

[0044] Figure 2 The crack propagation is shown on the inner wall, half radius, and outer wall of the seamless steel pipe in Comparative Example 2. Detailed Implementation

[0045] The present application will be further illustrated below with reference to several specific embodiments and comparative examples.

[0046] Examples 1-3

[0047] The steel for thick-walled seamless steel pipes used in high-strength, high-toughness, and high-resistance to hydrogen-induced cracking LNG receiving terminals comprises the following mass percentage composition as shown in Table 1. The balance not shown in Table 1 is Fe and other unavoidable impurities.

[0048] Comparative Examples 1-3

[0049] A type of steel for seamless steel pipes comprises the following composition by weight percentage as shown in Table 1, where the balance not shown in Table 1 is Fe and other unavoidable impurities.

[0050] Table 1 Chemical composition (wt%) of embodiments and comparative examples of the present invention

[0051] steel grades C Si Mn Cr Ni Mo Cu Al Example 1 0.07 0.31 1.91 0.46 0.56 0.29 0.031 0.018 Example 2 0.07 0.30 1.86 0.54 0.46 0.30 0.040 0.021 Example 3 0.09 0.27 1.81 0.55 0.56 0.13 0.047 0.022 Comparative Example 1 0.06 0.34 1.92 0.51 0.46 0.28 0.041 0.024 Comparative Example 2 0.08 0.38 1.91 0.51 0.41 0.19 0.048 0.017 Comparative Example 3 0.05 0.33 1.78 0.59 0.57 0.20 0.034 0.022 steel grades P S N TO Ti B A value Y value Example 1 0.010 0.007 0.0067 0.0026 0.018 0.0028 40.18 3.82 Example 2 0.013 0.009 0.0082 0.0030 0.016 0.0020 39.64 2.64 Example 3 0.010 0.009 0.0075 0.0019 0.028 0.0039 44.28 3.84 Comparative Example 1 0.015 0.002 0.0082 0.0022 0.022 0.0022 33.98 2.26 Comparative Example 2 0.007 0.006 0.0080 0.0036 0.032 0.0022 39.02 1.13 Comparative Example 3 0.008 0.003 0.0074 0.0022 0.026 0.0020 28.75 4.53

[0052] The seamless steel pipes described in the embodiments and comparative examples are produced through the following process, including hot forming and heat treatment, as detailed below:

[0053] Smelting in an electric arc furnace or converter → refining in an LF furnace → RH or VD vacuum degassing → continuous casting of round billets (≥φ700mm) → slow cooling of round billets, billet blanking → heating of round billets → piercing → sizing → tension reduction → heat treatment → flaw detection → grinding → packaging and warehousing.

[0054] Specifically:

[0055] Electric furnace smelting: oxygen is determined before tapping, and steel is left in place during tapping to avoid slag discharge;

[0056] LF furnace: C, Si, Mn, Cr, Ni, Mo, Ti, Cu and other elements are adjusted to the target values;

[0057] Vacuum degassing: Pure degassing time ≥ 15 minutes, ensuring that the [H] content after vacuum treatment is ≤ 1.5 ppm, avoiding white spots in the steel and causing hydrogen embrittlement;

[0058] Continuous casting: The target temperature of molten steel in the ladle is controlled at 10-40℃ above the liquidus temperature, and round billets with a diameter of ≥700mm are continuously cast.

[0059] Seamless steel pipe manufacturing route: round billet (700mm diameter) blanking → round billet heating → piercing → sizing → tension reduction → heat treatment → flaw detection → grinding → packaging and warehousing.

[0060] Controlling the thermoforming process: billet heating temperature 1000℃~1100℃, tube deformation 10%~25%, tube threading speed 0.20~0.40s. -1 The deformation amount per expansion cycle is 10%–20%, and the expansion rate is 0.10–0.20 s. -1 .

[0061] Seamless steel pipe heat treatment: Bogie furnace heating → heat preservation → quenching → tempering → heat preservation → air cooling.

[0062] The quenching process involves an initial furnace temperature of ≤400℃ and a heating temperature of T. 淬火加热 840~960℃; heat preservation time t 淬火保温 The steel pipe wall thickness S and heating temperature T 淬火加热 The decision is 160 + (S / 2) - (T) 淬火加热 / 9)≤t 淬火保温 ≤170+(S / 2)-(T 淬火Heating / 9), water cooling; where the steel pipe wall thickness S is in mm, and the heating temperature T 淬火加热 The unit is ℃, and the holding time is t. 淬火保温 The unit is min. When calculating the above formula, simply substitute the data before the unit into the formula.

[0063] The tempering: tempering temperature T 回火加热 580~700℃, holding time t 回火保温 The steel pipe wall thickness S and tempering temperature T 回火加热 The decision is 410 + (S / 2) - (T) 回火加热 / 2)≤t 回火保温 ≤420+(S / 2)-(T 回火加热 / 2), water cooling, where the steel pipe wall thickness S is in mm, and the heating temperature T 回火加热 The unit is ℃, and the holding time is t. 回火保温 The unit is min. When calculating the above formula, simply substitute the data before the unit into the formula.

[0064] The performance testing methods are as follows:

[0065] Organization: Samples were taken from the seamless steel pipe body at the outer wall, half thickness (56 mm), and inner wall for metallographic, grain size, and hardness difference analysis.

[0066] Performance: Samples were taken from the seamless steel tube body, and tensile, impact, and hydrogen-induced cracking specimens were collected at 1 / 2 thickness (thickness of 56 mm). Performance tests were conducted according to GB / T228, GB / T229, and GB / T 8650. The heat treatment process is shown in Table 2, and the mechanical properties are shown in Table 3.

[0067] Table 2 lists the process details of the embodiments and comparative examples of the present invention.

[0068]

[0069] Table 3. Performance testing results of embodiments and comparative examples of the present invention.

[0070]

[0071]

[0072] Cross-sectional hardness fluctuation is determined by measuring Brinell hardness at three locations along the wall thickness of the steel pipe: the outer side, half the wall thickness, and the inner side. The difference in hardness is calculated, and the maximum value is taken.

[0073] The chemical composition and production methods of the steels in Examples 1-3 were appropriately controlled, ensuring that the chemical composition was 30.0 ≤ A ≤ 50.0 and 2.5% ≤ Y, resulting in steels with good strength, plasticity, toughness, and resistance to hydrogen-induced cracking. Comparative Example 1 had an unsuitable chemical composition, with a Y value less than 2.5, leading to poor resistance to hydrogen-induced cracking even under the heat treatment conditions of this invention. Comparative Example 2 also had an unsuitable chemical composition, with a Y value less than 2.5, and the heat treatment process did not meet the requirements of this invention, resulting in material with excessively low strength, insufficient plasticity and toughness, and insufficient resistance to hydrogen-induced cracking. Comparative Example 3 had improperly controlled chemical composition, with a small A value, and improper hot forming and heat treatment processes, resulting in insufficient strength, toughness, and resistance to hydrogen-induced cracking.

Claims

1. A steel for thick-walled seamless steel pipes used in high-strength, high-toughness, and high-resistance to hydrogen-induced cracking LNG receiving terminals, characterized in that... The steel used for thick-walled seamless steel pipes for high-strength, high-toughness, and high-resistance to hydrogen-induced cracking LNG receiving terminals comprises the following components by mass percentage: C 0.05%–0.10%, Si 0.20%–0.40%, Mn 1.70%–2.00%, Cr 0.30%–0.60%, Mo 0.10%–0.30%, Ni 0.40%–0.60%, Cu 0.030%–0.050%, Ti 0.015%–0.035%, Al 0.015%–0.025%, P ≤0.015%, S≤0.010%, N 0.0060%–0.0090%, B 0.0020%–0.0040%, TO≤0.0040%, with the remainder being Fe and other unavoidable impurities. The steel used for the high-strength, high-toughness, and high-resistance to hydrogen-induced cracking LNG receiving terminals meets the following requirements in terms of composition: 30.0≤A≤50.0； A=(4.5×%C)×(1+3.4×%Mn)×(1+0.7×%Si)×(1.2+2.6×%Cu) ×(1+2.7×%Ni)×(1+3.1×%Cr)×(1+2.3×%Mo)×(1+1.8×%Ti+4.6×%N+4.2×%B); The steel used for the high-strength, high-toughness, and high-resistance to hydrogen-induced cracking LNG receiving station thick-walled seamless steel pipes shall meet the following requirements: Y≥2.5%; Y=2.5×%Cr+3.8×%Mo+16.5×%Ni+2.5×%Cu-1×%C-4×%Mn-15×%B.

2. A seamless steel pipe, characterized in that, It is produced using the high-strength, high-toughness, and high-resistance to hydrogen-induced cracking LNG receiving station thick-walled seamless steel pipe as described in claim 1.

3. The seamless steel pipe according to claim 2, characterized in that, The seamless steel pipe has 100% tempered sorbite on its inner wall, half wall thickness, and outer wall; the grain size is 20-27 μm, and the difference in grain size between the inner wall, half wall thickness, and outer wall is ≤1 μm.

4. The seamless steel pipe according to claim 2 or 3, characterized in that, The seamless steel pipe has a tensile strength ≥680MPa, a yield strength ≥615MPa at 1 / 2 wall thickness, a KV2 ≥240J at -50℃, an A ≥22%, and a Z ≥50%. The cross-sectional hardness difference is ≤20HBW; GB / T 8650 shall be used for hydrogen-induced cracking testing, and the CSR and CLR shall be ≤1.5% and ≤12% in solution A.

5. A method for producing a seamless steel pipe according to any one of claims 2-4, characterized in that, The production method includes thermoforming and heat treatment processes.

6. The production method according to claim 5, characterized in that, The hot forming process includes: tube blank heating temperature 1000-1100℃, pipe deformation 10-25%, pipe speed 0.20-0.40s -1 , pipe expansion single deformation 10-20%, pipe expansion speed 0.10-0.20s -1 .

7. The production method according to claim 5, characterized in that, The heat treatment process includes: quenching and tempering; The quenching process involves an initial furnace temperature of ≤400℃ and a heating temperature of T. 淬火加热 840~960℃; heat preservation time t 淬火保温 The steel pipe wall thickness S and heating temperature T 淬火加热 Decision: 160 + (S / 2) - (T) 淬火加热 / 9)≤t 淬火保温 ≤170+(S / 2)-(T 淬火 Heating / 9), water cooling; where the steel pipe wall thickness S is in mm, and the heating temperature T 淬火加热 The unit is ℃, and the holding time is t. 淬火保温 The unit is min.

8. The production method according to claim 7, characterized in that, The tempering: tempering temperature T 回火加热 580~700℃, holding time t 回火保温 The steel pipe wall thickness S and tempering temperature T 回火加热 The decision is 410 + (S / 2) - (T) 回火加热 / 2) ≤t 回火保温 ≤420+(S / 2)-(T 回火加热 / 2), water cooling, where the steel pipe wall thickness S is in mm, and the heating temperature T 回火加热 The unit is ℃, and the holding time is t. 回火保温 The unit is min.

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