Preparation method of corrosion-resistant low-temperature pressure vessel steel for liquid CO2 storage tank

Abstract

The invention discloses a preparation method of corrosion-resistant low-temperature pressure vessel steel for a liquid CO2 storage tank, and relates to the technical field of metal material and low-temperature pressure vessel manufacturing. The method comprises the following steps: firstly, according to the characteristics of high strength, corrosion resistance and low temperature resistance of the steel part, determining the chemical components of the steel part and the weight percentage of each chemical component by optimizing the component design of a composition material; secondly, determining a process preparation method of the target steel, providing technological processes of a smelting continuous casting process, a cooling process and a heat treatment process through a controlled rolling and controlled cooling process, and determining the temperature, time and steel plate deformation of each stage; and finally, the corrosion-resistant, low-temperature-resistant and high-strength steel for the pressure vessel for the liquid CO2 storage tank is prepared.

Description

Technical Field

[0001] This invention relates to the field of metal materials and cryogenic pressure vessel manufacturing technology, and in particular to a method for preparing corrosion-resistant cryogenic pressure vessel steel for liquid CO2 storage tanks. Background Technology

[0002] Liquid CO2 storage tanks, as cryogenic pressure vessels, are widely used in petrochemical, carbon capture and storage (CCS), and food industries. CO2 requires sufficient pressure to maintain its liquid state. However, under high pressure, CO2 readily reacts with water to form carbonic acid (H2CO3), causing severe corrosion to steel tanks. Furthermore, these tanks must withstand high pressure (typically ≥2MPa), thus requiring materials that possess both high strength (≥800MPa level) and excellent corrosion resistance.

[0003] In existing technologies, liquid CO2 storage tanks mainly use low-alloy high-strength steel (such as Q690 and X80), but their corrosion resistance is insufficient, and they are prone to pitting corrosion and stress corrosion cracking during long-term service. Currently, the commonly used method to improve the performance of such tanks is to add various elements, such as using stainless steel or nickel-based alloys, adding Ni to improve low-temperature performance, and using high compression ratios to obtain special bainitic structures or C-Mn-Cr-Mo-Cu alloy bodies to improve the strength of steel components. However, the research and development and production of steel plates for liquid CO2 storage tanks that combine high strength and high corrosion resistance still face many challenges, mainly: firstly, some methods are costly and difficult to apply on a large scale; secondly, existing steel plates cannot effectively meet the new service environment requirements of ≥780MPa; and finally, corrosion resistance cannot be guaranteed under low-cost conditions. Summary of the Invention

[0004] To address the problems in the prior art, this invention provides a method for preparing corrosion-resistant, low-temperature pressure vessel steel for liquid CO2 storage tanks. First, based on the high strength, corrosion resistance, and low-temperature resistance of the steel, the invention optimizes the material composition design to determine the chemical composition and weight percentage of each chemical component. Second, it clarifies the process for preparing the target steel, providing the process flow for smelting, continuous casting, cooling, and heat treatment through controlled rolling and cooling processes, specifying the temperature, time, and steel plate deformation at each stage. Finally, it produces corrosion-resistant, low-temperature resistant, and high-strength pressure vessel steel for liquid CO2 storage tanks. To achieve the above objectives, the technical solution is as follows:

[0005] This invention provides a method for preparing corrosion-resistant cryogenic pressure vessel steel for liquid CO2 storage tanks, the method comprising:

[0006] S1. Based on the performance requirements of the steel for pressure vessels, the weight percentage of the chemical composition of the steel for pressure vessels is obtained by analyzing the weight percentage of the chemical composition of the steel for pressure vessels.

[0007] S2. Based on the weight percentage of the chemical composition of the raw materials for steel preparation and the steel for the pressure vessel, a slab conforming to the weight percentage of the chemical composition is obtained through a smelting and continuous casting process.

[0008] S3. Based on the slab conforming to the weight percentage of the chemical composition, hot-rolled steel is obtained through a heating rolling process;

[0009] S4. Based on the hot-rolled steel, a cooled steel with a mixed structure of bainite and martensite is obtained through a cooling process;

[0010] S5. Based on the cooling steel with a mixed bainitic and martensitic structure, the toughness of the cooling steel with a mixed bainitic and martensitic structure is adjusted by tempering at 600-650℃ to obtain the steel for pressure vessels.

[0011] Optionally, the chemical composition of the steel for the pressure vessel, by weight percentage, includes: carbon: 0.05–0.10%, silicon: 0.15–0.30%, manganese: 1.20–1.60%, chromium: 0.80–1.20%, molybdenum: 0.20–0.40%, nickel: 0.30–0.60%, copper: 0.20–0.40%, niobium + vanadium + titanium: 0.06–0.12%, phosphorus ≤0.012%, and sulfur ≤0.005%.

[0012] Optionally, in S2, based on the weight percentage of the chemical composition of the raw materials for steel preparation and the steel for the pressure vessel, a slab conforming to the weight percentage of the chemical composition is obtained through a continuous casting process, including:

[0013] S21. Based on the weight percentage of the chemical composition of the raw materials for steel preparation and the steel for the pressure vessel, the first-stage billet is obtained through smelting.

[0014] S22. Based on the weight percentage of the chemical composition of the first-stage slab and the pressure vessel steel, the chemical composition of the first-stage slab is controlled by refining to obtain the second-stage slab.

[0015] S23. Based on the weight percentage of the second-stage slab and the chemical composition, the chemical composition of the second-stage slab is controlled by the RH vacuum circulation degassing refining method to obtain the third-stage slab.

[0016] S24. Based on the weight percentage of the third-stage slab and the chemical composition, the chemical composition of the third-stage slab is controlled by continuous casting to obtain a slab that conforms to the weight percentage of the chemical composition.

[0017] Optionally, S3, based on the slab conforming to the weight percentage of the chemical composition, obtains hot-rolled steel through a heated rolling process, including:

[0018] S31. According to the slab conforming to the weight percentage of the chemical composition, heat it to 1150-1200℃ and hold it for 2-3 hours to obtain heated steel;

[0019] S32. Based on the heated steel, the temperature is controlled to be not lower than 1000℃, the first stage of rolling is carried out and the deformation of the heated steel is controlled to be not less than 60%, so as to obtain rolled steel.

[0020] S33. Based on the rolled steel, the temperature is controlled at 800-880℃, and a second stage of finishing rolling is carried out while controlling the deformation of the rolled steel to be not less than 40%, thus obtaining hot-rolled steel.

[0021] Optionally, S4, based on the hot-rolled steel, obtains a cooled steel with a mixed bainitic and martensitic microstructure through a cooling process, including:

[0022] S41. Based on the hot-rolled steel, the temperature of the hot-rolled steel is cooled to 300-550°C at a rate of 15-30°C / s to obtain the first-stage cooled steel.

[0023] S42. Based on the first-stage cooled steel, air cooling is performed to obtain cooled steel with a mixed structure of bainite and martensite.

[0024] Optionally, the mechanical properties of the steel used in the pressure vessel include: yield strength ≥700MPa, tensile strength ≥800MPa, elongation ≥16%, and impact energy at -40℃ ≥60J.

[0025] Optionally, the corrosion resistance characteristics of the steel used in the pressure vessel include: corrosion rate ≤ 0.1 mm / year.

[0026] Compared with the prior art, the technical solution of the present invention has at least the following beneficial effects:

[0027] The above-mentioned scheme achieves a balance between high strength and high toughness in pressure vessel steel under low-temperature conditions by obtaining a fine-grained bainitic structure through Cr-Mo-Ni-Cu composite alloying and controlled rolling and cooling processes. Secondly, it improves the corrosion resistance of pressure vessel steel by forming a dense passivation film on the surface of the pressure vessel steel through the synergistic effect of Cr and Cu and by inhibiting pitting corrosion in the CO2 environment through Mo. Thirdly, it significantly reduces the cost of manufacturing pressure vessel steel and improves its weldability, thus enhancing its practicality. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a flowchart illustrating an embodiment of the method for preparing corrosion-resistant cryogenic pressure vessel steel for liquid CO2 storage tanks according to the present invention;

[0030] Figure 2 This is a flowchart of the smelting continuous casting process of an embodiment of the method for preparing corrosion-resistant low-temperature pressure vessel steel for liquid CO2 storage tanks according to the present invention.

[0031] Figure 3 This is a flowchart of the heating rolling process of an embodiment of the method for preparing corrosion-resistant cryogenic pressure vessel steel for liquid CO2 storage tanks according to the present invention;

[0032] Figure 4 This is a flowchart of the cooling process of an embodiment of the method for preparing corrosion-resistant cryogenic pressure vessel steel for liquid CO2 storage tanks according to the present invention. Detailed Implementation

[0033] The technical solution of the present invention will now be described with reference to the accompanying drawings.

[0034] In embodiments of the present invention, words such as "exemplarily," "for example," etc., are used to indicate that something is an example, illustration, or description. Any embodiment or design described as "exemplary" in the present invention should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of the word "exemplary" is intended to present the concept in a concrete manner. Furthermore, in embodiments of the present invention, the meaning expressed by "and / or" can be both, or either one.

[0035] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with the accompanying drawings and specific embodiments.

[0036] like Figure 1 The flowchart shown is an embodiment of the method for preparing corrosion-resistant cryogenic pressure vessel steel for liquid CO2 storage tanks according to the present invention. The present invention provides a method for preparing corrosion-resistant cryogenic pressure vessel steel for liquid CO2 storage tanks, the method comprising:

[0037] S1. Based on the performance requirements of the steel for pressure vessels, the weight percentage of the chemical composition of the steel for pressure vessels is obtained by analyzing the weight percentage of the chemical composition of the steel for pressure vessels.

[0038] Specifically, the chemical composition of the steel used in the pressure vessel, by weight percentage, includes: carbon: 0.05–0.10%, silicon: 0.15–0.30%, manganese: 1.20–1.60%, chromium: 0.80–1.20%, molybdenum: 0.20–0.40%, nickel: 0.30–0.60%, copper: 0.20–0.40%, niobium + vanadium + titanium: 0.06–0.12%, phosphorus ≤0.012%, and sulfur ≤0.005%.

[0039] Furthermore, the chemical composition weight percentage of the steel used in pressure vessels is based on the following chemical composition characteristics:

[0040] A low carbon content (0.05–0.10%) and a carbon equivalent controlled to ≤0.42% ensure weldability;

[0041] Manganese can improve hardenability and increase the strength of steel plates through solid solution strengthening. Since other alloying elements are added in small amounts in steel, adding 1.20% to 1.60% manganese ensures sufficient strength in the steel plate. Controlling the silicon content within the range of 0.15% to 0.30% strengthens ferrite and inhibits CO2 corrosion.

[0042] Controlling the chromium content within the range of 0.80–1.20% is crucial for forming a dense Cr2O3 passivation film, which is essential for corrosion resistance.

[0043] Controlling the molybdenum content within the range of 0.20% to 0.40% helps to refine the grains and enhance resistance to pitting corrosion.

[0044] By controlling the nickel content within the range of 0.30% to 0.60%, low-temperature toughness is improved, and chromium corrosion resistance is enhanced.

[0045] Controlling the copper content within the range of 0.20–0.40% promotes the stability of the passivation film;

[0046] Adding niobium, vanadium, and titanium in a combined content range of 0.06% to 0.12% refines the grain size through composite microalloying.

[0047] Strictly control the content of harmful elements in molten steel, keeping phosphorus ≤0.012% and sulfur ≤0.005%, thereby reducing the harm of impurity elements and improving the performance stability of steel plates.

[0048] S2. Based on the weight percentage of the chemical composition of the raw materials for steel preparation and the steel for the pressure vessel, a slab conforming to the weight percentage of the chemical composition is obtained through a smelting and continuous casting process.

[0049] Specifically, such as Figure 2The flowchart shown is a smelting and continuous casting process flowchart of an embodiment of the method for preparing corrosion-resistant cryogenic pressure vessel steel for liquid CO2 storage tanks of the present invention. In S2, based on the weight percentage of the chemical composition of the raw materials for steel preparation and the pressure vessel steel, a slab conforming to the weight percentage of the chemical composition is obtained through the smelting and continuous casting process, including:

[0050] S21. Based on the weight percentage of the chemical composition of the raw materials for steel preparation and the steel for the pressure vessel, the first-stage billet is obtained through smelting.

[0051] S22. Based on the weight percentage of the chemical composition of the first-stage slab and the pressure vessel steel, the chemical composition of the first-stage slab is controlled by refining to obtain the second-stage slab.

[0052] S23. Based on the weight percentage of the second-stage slab and the chemical composition, the chemical composition of the second-stage slab is controlled by the RH vacuum circulation degassing refining method to obtain the third-stage slab.

[0053] S24. Based on the weight percentage of the third-stage slab and the chemical composition, the chemical composition of the third-stage slab is controlled by continuous casting to obtain a slab that conforms to the weight percentage of the chemical composition.

[0054] S3. Based on the slab conforming to the weight percentage of the chemical composition, hot-rolled steel is obtained through a heating rolling process;

[0055] Specifically, such as Figure 3 The flowchart shown is a hot rolling process of an embodiment of the method for preparing corrosion-resistant cryogenic pressure vessel steel for liquid CO2 storage tanks according to the present invention. S3, based on the slab conforming to the chemical composition by weight percentage, obtains hot-rolled steel through a hot rolling process, including:

[0056] S31. According to the slab conforming to the weight percentage of the chemical composition, heat it to 1150-1200℃ and hold it for 2-3 hours to obtain heated steel;

[0057] S32. Based on the heated steel, the temperature is controlled to be not lower than 1000℃, the first stage of rolling is carried out and the deformation of the heated steel is controlled to be not less than 60%, so as to obtain rolled steel.

[0058] S33. Based on the rolled steel, the temperature is controlled at 800-880℃, and a second stage of finishing rolling is carried out while controlling the deformation of the rolled steel to be not less than 40%, thus obtaining hot-rolled steel.

[0059] S4. Based on the hot-rolled steel, a cooled steel with a mixed structure of bainite and martensite is obtained through a cooling process;

[0060] Specifically, such as Figure 4The flowchart shown is a sample of the cooling process in an embodiment of the method for preparing corrosion-resistant cryogenic pressure vessel steel for liquid CO2 storage tanks according to the present invention. S4 describes obtaining, through a cooling process, a cooled steel with a mixed bainitic and martensitic structure based on the hot-rolled steel, comprising:

[0061] S41. Based on the hot-rolled steel, the temperature of the hot-rolled steel is cooled to 300-550°C at a rate of 15-30°C / s to obtain the first-stage cooled steel.

[0062] S42. Based on the first-stage cooled steel, air cooling is performed to obtain cooled steel with a mixed structure of bainite and martensite.

[0063] S5. Based on the cooling steel with a mixed bainitic and martensitic structure, the toughness of the cooling steel with a mixed bainitic and martensitic structure is adjusted by tempering at 600-650℃ to obtain the steel for pressure vessels.

[0064] Specifically, the mechanical properties of the steel used in the pressure vessel include: yield strength ≥700MPa, tensile strength ≥800MPa, elongation ≥16%, and impact energy at -40℃ ≥60J.

[0065] The corrosion resistance characteristics of the steel used in this pressure vessel include: corrosion rate ≤ 0.1 mm / year.

[0066] Six embodiments of the method for preparing corrosion-resistant cryogenic pressure vessel steel for liquid CO2 storage tanks according to the present invention are as follows:

[0067] Example 1:

[0068] According to the chemical composition weight percentage of Example 1 in Table 1, a smelting and continuous casting process was carried out, and a slab with a thickness of 200 mm was obtained by converter smelting, LF refining, RH vacuum degassing and continuous casting.

[0069] Heating and rolling: The slab is heated to 1150℃ and held for 2 hours. The rolling is divided into two stages. The first stage is rolled at 1050℃ with a deformation of 60%. The second stage is rolled at 800℃ with a deformation of 40%.

[0070] Cooling: After rolling, the steel plate is water-cooled to 450°C at a rate of 15-30°C / s, followed by air cooling;

[0071] The low-alloy high-strength steel prepared in this embodiment has a multiphase structure consisting of bainite and a small amount of martensite. Tensile, impact, CTOD (Crack Tip Opening Displacement) and corrosion resistance tests were conducted. The specific test results are shown in Table 2.

[0072] Example 2:

[0073] According to the chemical composition weight percentage of Example 1 in Table 1, a smelting and continuous casting process was carried out, and a slab with a thickness of 200 mm was obtained by converter smelting, LF refining, RH vacuum degassing and continuous casting.

[0074] Heating and rolling: The slab is heated to 1150℃ and held for 2 hours. The rolling is divided into two stages. The first stage is rolled at 1050℃ with a deformation of 60%. The second stage is rolled at 800℃ with a deformation of 40%.

[0075] Cooling: After rolling, the steel plate is water-cooled to 450°C at a rate of 15-30°C / s, followed by air cooling;

[0076] Temper at 600℃.

[0077] The low-alloy high-strength steel prepared in this embodiment has a multiphase structure consisting of bainite and a small amount of martensite. Tensile, impact, CTOD (Crack Tip Opening Displacement) and corrosion resistance tests were conducted. The specific test results are shown in Table 2.

[0078] Example 3:

[0079] According to the chemical composition weight percentage of Example 1 in Table 1, a smelting and continuous casting process was carried out, and a slab with a thickness of 200 mm was obtained by converter smelting, LF refining, RH vacuum degassing and continuous casting.

[0080] Heating and rolling: The slab is heated to 1200℃ and held for 3 hours. The rolling is divided into two stages. The first stage is rolled at 1100℃ with a deformation of 70%. The second stage is rolled at 840℃ with a deformation of 50%.

[0081] Cooling: After rolling, the steel plate is water-cooled to 550°C at a rate of 15-30°C / s, followed by air cooling;

[0082] The low-alloy high-strength steel prepared in this embodiment has a multiphase structure consisting of bainite and a small amount of martensite. Tensile, impact, CTOD (Crack Tip Opening Displacement) and corrosion resistance tests were conducted. The specific test results are shown in Table 2.

[0083] Example 4:

[0084] According to the chemical composition weight percentage of Example 1 in Table 1, a smelting and continuous casting process was carried out, and a slab with a thickness of 200 mm was obtained by converter smelting, LF refining, RH vacuum degassing and continuous casting.

[0085] Heating and rolling: The slab is heated to 1200℃ and held for 3 hours. The rolling is divided into two stages. The first stage is rolled at 1100℃ with a deformation of 70%. The second stage is rolled at 840℃ with a deformation of 50%.

[0086] Cooling: After rolling, the steel plate is water-cooled to 550°C at a rate of 15-30°C / s, followed by air cooling;

[0087] Temper at 620℃.

[0088] The low-alloy high-strength steel prepared in this embodiment has a multiphase structure consisting of bainite and a small amount of martensite. Tensile, impact, CTOD (Crack Tip Opening Displacement) and corrosion resistance tests were conducted. The specific test results are shown in Table 2.

[0089] Example 5:

[0090] According to the chemical composition weight percentage of Example 1 in Table 1, a smelting and continuous casting process was carried out, and a slab with a thickness of 200 mm was obtained by converter smelting, LF refining, RH vacuum degassing and continuous casting.

[0091] Heating and rolling: The slab is heated to 1150℃ and held for 2 hours. The rolling is divided into two stages. The first stage is rolled at 1050℃ with a deformation of 70%. The second stage is rolled at 880℃ with a deformation of 75%.

[0092] Cooling: After rolling, the steel plate is water-cooled to 300°C at a rate of 15-30°C / s, followed by air cooling;

[0093] The low-alloy high-strength steel prepared in this embodiment has a multiphase structure consisting of bainite and a small amount of martensite. Tensile, impact, CTOD (Crack Tip Opening Displacement) and corrosion resistance tests were conducted. The specific test results are shown in Table 2.

[0094] Example 6:

[0095] According to the chemical composition weight percentage of Example 1 in Table 1, a smelting and continuous casting process was carried out, and a slab with a thickness of 200 mm was obtained by converter smelting, LF refining, RH vacuum degassing and continuous casting.

[0096] Heating and rolling: The slab is heated to 1150℃ and held for 2 hours. The rolling is divided into two stages. The first stage is rolled at 1050℃ with a deformation of 70%. The second stage is rolled at 880℃ with a deformation of 40%.

[0097] Cooling: After rolling, the steel plate is water-cooled to 300°C at a rate of 15-30°C / s, followed by air cooling;

[0098] Temper at 650℃.

[0099] The low-alloy high-strength steel prepared in this embodiment has a multiphase structure consisting of bainite and a small amount of martensite. Tensile, impact, CTOD (Crack Tip Opening Displacement) and corrosion resistance tests were conducted. The specific test results are shown in Table 2.

[0100] Table 1. Weight percentage of chemical components in each embodiment

[0101]

[0102] P≤0.012%, S≤0.005%

[0103] Table 2 Results of Mechanical and Corrosion Resistance Tests

[0104]

[0105] This invention provides a method for preparing corrosion-resistant, low-temperature pressure vessel steel for liquid CO2 storage tanks. Firstly, based on the high strength, corrosion resistance, and low-temperature resistance of the steel, the invention optimizes the design of the constituent materials to determine the chemical composition and weight percentage of each chemical component. Secondly, it clarifies the process for preparing the target steel, providing the process flow for smelting, continuous casting, cooling, and heat treatment through controlled rolling and cooling processes, specifying the temperature, time, and steel plate deformation at each stage. Finally, it produces corrosion-resistant, low-temperature resistant, and high-strength pressure vessel steel for liquid CO2 storage tanks.

[0106] It is understood that the present invention has been described through the above embodiments and should not be construed as limiting the implementation and scope of the present invention. Those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of the present invention. Furthermore, under the teachings of the present invention, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the protection scope of the present invention.

Claims

1. A method for preparing corrosion-resistant cryogenic pressure vessel steel for liquid CO2 storage tanks, characterized in that, The method includes: S1. Based on the performance requirements of the steel for pressure vessels, the weight percentage of the chemical composition of the steel for pressure vessels is obtained by analyzing the weight percentage of the chemical composition of the steel for pressure vessels. S2. Based on the weight percentage of the chemical composition of the raw materials for steel preparation and the steel for the pressure vessel, a slab conforming to the weight percentage of the chemical composition is obtained through a smelting and continuous casting process. S3. Based on the slab conforming to the stated chemical composition by weight percentage, hot-rolled steel is obtained through a heating rolling process; S4. Based on the hot-rolled steel, a cooled steel with a mixed structure of bainite and martensite is obtained through a cooling process; S5. Based on the cooled steel with a mixed bainitic and martensitic structure, the toughness of the cooled steel with a mixed bainitic and martensitic structure is adjusted by tempering at 600-650℃ to obtain the steel for pressure vessels.

2. The method for preparing corrosion-resistant cryogenic pressure vessel steel for liquid CO2 storage tanks according to claim 1, characterized in that, The chemical composition of the steel used in the pressure vessel, by weight percentage, includes: carbon: 0.05–0.10%, silicon: 0.15–0.30%, manganese: 1.20–1.60%, chromium: 0.80–1.20%, molybdenum: 0.20–0.40%, nickel: 0.30–0.60%, copper: 0.20–0.40%, niobium + vanadium + titanium: 0.06–0.12%, phosphorus ≤0.012%, and sulfur ≤0.005%.

3. The method for preparing corrosion-resistant cryogenic pressure vessel steel for liquid CO2 storage tanks according to claim 1, characterized in that, In step S2, based on the weight percentage of the chemical composition of the raw materials for steel preparation and the steel for the pressure vessel, a slab conforming to the weight percentage of the chemical composition is obtained through a continuous casting process, including: S21. Based on the weight percentage of the chemical composition of the raw materials for steel preparation and the steel for the pressure vessel, a first-stage billet is obtained through smelting. S22. Based on the weight percentage of the chemical composition of the first-stage slab and the pressure vessel steel, the chemical composition of the first-stage slab is controlled by refining to obtain the second-stage slab. S23. Based on the weight percentage of the second-stage slab and the chemical composition, the chemical composition of the second-stage slab is controlled by the RH vacuum circulation degassing refining method to obtain the third-stage slab. S24. Based on the weight percentage of the third-stage slab and the chemical composition, the chemical composition of the third-stage slab is controlled by continuous casting to obtain a slab that conforms to the weight percentage of the chemical composition.

4. The method for preparing corrosion-resistant cryogenic pressure vessel steel for liquid CO2 storage tanks according to claim 1, characterized in that, S3, based on the slab conforming to the stated chemical composition by weight percentage, obtains hot-rolled steel through a heating rolling process, including: S31. According to the slab conforming to the weight percentage of the chemical composition, heat it to 1150-1200℃ and hold it for 2-3 hours to obtain heated steel; S32. Based on the heated steel, the temperature is controlled to be not lower than 1000℃, and the first stage of rolling is carried out while controlling the deformation of the heated steel to be not less than 60%, to obtain rolled steel. S33. Based on the rolled steel, the temperature is controlled at 800-880℃, and a second stage of finishing rolling is carried out while controlling the deformation of the rolled steel to be not less than 40%, to obtain hot-rolled steel.

5. The method for preparing corrosion-resistant cryogenic pressure vessel steel for liquid CO2 storage tanks according to claim 1, characterized in that, S4, based on the hot-rolled steel, obtains cooled steel with a mixed bainitic and martensitic structure through a cooling process, comprising: S41. Based on the hot-rolled steel, the temperature of the hot-rolled steel is water-cooled to 300-550°C at a rate of 15-30°C / s to obtain the first-stage cooled steel. S42. Based on the first stage of cooling steel, air cooling is performed to obtain a cooling steel with a mixed structure of bainite and martensite.

6. The method for preparing corrosion-resistant cryogenic pressure vessel steel for liquid CO2 storage tanks according to claim 1, characterized in that, The mechanical properties of the steel used in the pressure vessel include: yield strength ≥700MPa, tensile strength ≥800MPa, elongation ≥16%, and impact energy at -40℃ ≥60J.

7. The method for preparing corrosion-resistant cryogenic pressure vessel steel for liquid CO2 storage tanks according to claim 1, characterized in that, The corrosion resistance characteristics of the steel used in the pressure vessel include: corrosion rate ≤ 0.1 mm / year.

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