Steel for corrosion-resistant steel pipe in acid environment, bimetallic metallurgical composite oil sleeve and preparation method thereof

Abstract

The application discloses a steel pipe for resisting acid environment corrosion, a bimetal metallurgical composite oil casing and a preparation method thereof, and relates to the technical field of oil casing manufacturing for oil and gas development. The steel pipe for resisting acid environment corrosion comprises the following chemical components in percentage by mass: C 0.2-0.3%, Si 0.17-0.37%, Mn 0.3-0.6%, Cr 1.1-1.25%, Mo 0.18-0.3%, Ni≤0.25%, Cu≤0.25%, Nb 0.07-0.12%, V≤0.05%, Al 0.02-0.035%, Ca 0.012-0.025%, and the contents of harmful elements P, S, N, O and H are controlled in a lower range, and the balance is Fe and inevitable impurities. The steel pipe for resisting acid environment corrosion has high strength, high toughness and good hydrogen sulfide stress corrosion resistance.

Description

Technical Field

[0001] This invention relates to the field of oil casing manufacturing technology for oil and gas development, and particularly to steel for acid-resistant corrosion-resistant steel pipes, bimetallic metallurgical composite oil casings and their preparation methods. Background Technology

[0002] Bimetallic composite pipe is a type of pipe made by combining two dissimilar metals through metallurgical bonding technology. It combines the corrosion resistance of the inner layer with the mechanical strength of the outer layer and is gradually being used in oil and gas extraction as oil casing (pipeline and casing).

[0003] In oil and gas extraction, tubing and casing, as the sole channels for oil and gas production and key components supporting the wellbore, face extremely complex and harsh operating conditions. The high-temperature and high-pressure environment deep underground places extremely high demands on the mechanical properties of bimetallic composite tubing and casing. Simultaneously, because some oil and gas extraction environments are corrosive, even higher requirements are placed on the corrosion resistance of bimetallic composite tubing and casing. Therefore, there is an urgent need to develop high-strength, high-toughness steels resistant to acidic environments for the fabrication of bimetallic composite tubing and casing suitable for harsh operating conditions. Summary of the Invention

[0004] Based on the shortcomings of the prior art, the purpose of this invention is to provide steel for acid-resistant corrosion-resistant steel pipes, bimetallic metallurgical composite oil casing and their preparation methods, aiming to provide a high-strength, high-toughness steel with acid-resistant corrosion resistance for the preparation of bimetallic metallurgical composite oil casing suitable for harsh working conditions.

[0005] The technical solution of the present invention is as follows:

[0006] In a first aspect, the present invention provides a steel for use in acid-resistant corrosion-resistant steel pipes, wherein the steel comprises the following chemical composition in weight percentages:

[0007] C 0.2%~0.3%, Si 0.17%~0.37%, Mn 0.3%~0.6%, P≤0.012%, S≤0.003%, Cr1.1%~1.25%, Mo 0.18%~0.3%, Ni≤0.25%, Cu≤0.25%, Nb 0.07%~0.12%, V≤0.05%, Al0.02%~0.035%, Ca 0.012%~0.025%, N≤0.005%, O+H+N≤0.007%, balance Fe and unavoidable impurities.

[0008] Optionally, the steel for the acid-resistant corrosion-resistant steel pipe comprises the following chemical composition by weight percentage:

[0009] C 0.2%~0.25%, Si 0.25%~0.37%, Mn 0.42%~0.6%, P 0.01%~0.012%, S 0.002%~0.003%, Cr 1.1%~1.19%, Mo 0.18%~0.23%, Nb 0.07%~0.09%, Al 0.02%~0.027%, Ca 0.012%~0.017%, N 0.0044%~0.005%, O+H+N≤0.007%, balance Fe and unavoidable impurities.

[0010] Optionally, the steel for the acid-resistant corrosion-resistant steel pipe comprises the following chemical composition by weight percentage:

[0011] C 0.24%~0.3%, Si 0.17%~0.27%, Mn 0.3%~0.53%, P 0.01%~0.011%, S 0.002%~0.003%, Cr 1.15%~1.25%, Mo 0.24%~0.3%, Ni≤0.25%, Cu≤0.25%, Nb 0.1%~0.12%, V≤0.05%, Al 0.025%~0.035%, Ca 0.017%~0.025%, N 0.0039%~0.0043%, O+H+N≤0.0059%, balance Fe and unavoidable impurities.

[0012] In a second aspect, the present invention provides a bimetallic metallurgical composite oil casing, wherein the bimetallic metallurgical composite oil casing includes an inner liner and an outer base tube sleeved outside the inner liner, wherein the inner liner and the outer base tube are metallurgically bonded.

[0013] The outer base tube is made of the acid-resistant corrosion-resistant steel pipe steel described above in this invention;

[0014] The inner liner is either a first inner liner or a second inner liner, and the first inner liner comprises the following chemical components in weight percentage:

[0015] C≤0.05%, Si≤0.5%, Mn≤1%, P≤0.03%, S≤0.03%, Ni 38%~46%, Cr 19.5%~23.5%, Mo 2.5%~3.5%, Cu 1.5%~3%, Ti 0.6%~1.2%, Al≤0.2%, with the balance being Fe and unavoidable impurities;

[0016] The second inner liner tube comprises the following chemical components in weight percentage:

[0017] C≤0.1%, Si≤0.5%, Mn≤0.5%, P≤0.015%, S≤0.015%, Fe≤5%, Cr 20%~23%, Mo 8%~10%, Nb 3.15%~4.15%, Ti≤0.4%, Al≤0.4%, with the balance being Ni and unavoidable impurities.

[0018] A third aspect of the present invention provides a method for preparing the bimetallic metallurgical composite oil casing as described above, comprising the following steps:

[0019] S1. Based on the chemical composition and mass percentage of the inner lining tube, the inner lining bar is obtained by smelting, continuous casting, homogenization annealing, die forging and hot continuous rolling.

[0020] S2. Seamless steel pipes are obtained by steelmaking, continuous casting, piercing and hot rolling based on the chemical composition and mass percentage of the chemical composition of the steel used for acid-resistant corrosion-resistant steel pipes.

[0021] S3. After heating the seamless steel pipe to 150-200°C, the inner lining rod is placed inside the seamless steel pipe for hot assembly, so that the inner lining rod and the seamless steel pipe form an interference fit. Then, the mating surfaces of the inner lining rod and the seamless steel pipe at both ends are sealed and vacuumed to form a mechanical composite tube blank.

[0022] S4. After the mechanical composite tube blank is subjected to die forging, piercing and hot continuous rolling, cold rolling, heat treatment and threading, the bimetallic metallurgical composite oil casing is obtained.

[0023] Optionally, step S4, specifically the step of forging the mechanical composite tube blank, includes:

[0024] The mechanical composite tube blank is heated to 1150-1200℃ and held for 2-3 hours, and then forged in a die. The initial forging temperature is 1130-1160℃ and the final forging temperature is 900-950℃. The forging ratio is ≥3. After die forging, the tube blank is air-cooled to obtain the first metallurgical composite tube blank.

[0025] Optionally, in step S4, the piercing and hot rolling steps specifically include:

[0026] The first metallurgical composite tube blank is heated to 1100-1180℃ and held for 2-3 hours for hot piercing; then it is hot continuous rolling with an initial rolling temperature of 1100℃ and a final rolling temperature of 900-950℃, followed by water cooling to 450℃ and air cooling to obtain the second metallurgical composite tube blank.

[0027] Optionally, in step S4, the cold rolling step specifically includes:

[0028] After cold rolling the second metallurgical composite tube blank, a third metallurgical composite tube blank is obtained.

[0029] During the cold rolling process, when the deformation amount in a single pass is no more than 30% and the total deformation amount is 30% to 50%, an annealing treatment is performed. The annealing treatment involves holding the temperature at 950 to 1050°C for 1.5 to 2 hours and then air cooling.

[0030] Optionally, when the inner liner is a first inner liner, the heat treatment step in step S4 specifically includes:

[0031] The third metallurgical composite tube blank is heated to 920-1150°C, held for 1-2 hours and then water-cooled. Then it is heated to 650-750°C, held for 2-4 hours, spray-cooled to 450°C and then air-cooled. Next, it is heated to 900-950°C, held for 1.5-2 hours and then water-cooled. Finally, it is heated to 580-700°C, held for 2-3 hours and then water-cooled.

[0032] Optionally, when the inner lining tube is a second inner lining tube, the heat treatment step in step S4 specifically includes: heating the third metallurgical composite tube blank to 920-1150°C, holding it at that temperature for 1-2 hours, and then water cooling it; then heating it to 600-900°C, holding it at that temperature for 2-4 hours, spray cooling it to 450°C, and then air cooling it; then heating it to 900-950°C, holding it at that temperature for 1.5-2 hours, and then water cooling it; finally heating it to 580-700°C, holding it at that temperature for 2-3 hours, and then water cooling it.

[0033] Beneficial effects: The acid-resistant steel pipe provided by this invention has high strength, high toughness and good resistance to hydrogen sulfide (H2S) stress corrosion. The minimum room temperature yield strength can reach the level of 80-140 ksi steel grade, the tensile strength is greater than or equal to 689-1034 MPa, the transverse Charpy V-notch impact toughness at -20℃ is greater than or equal to 100 J, and the elongation is greater than or equal to 22%. It can be used to prepare bimetallic metallurgical composite oil casing suitable for harsh working conditions. Detailed Implementation

[0034] This invention provides steel for acid-resistant corrosion-resistant steel pipes, bimetallic metallurgical composite oil casing, and their preparation methods. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention.

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0036] If the embodiments of the present invention involve descriptions such as "first" or "second", such descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated.

[0037] This invention provides a steel for acid-resistant corrosion-resistant steel pipes, wherein the acid-resistant corrosion-resistant steel for steel pipes comprises the following chemical composition by weight percentage:

[0038] C (carbon) 0.2%–0.3%, Si (silicon) 0.17%–0.37%, Mn (manganese) 0.3%–0.6%, P ≤0.012%, S ≤0.003%, Cr (chromium) 1.1%–1.25%, Mo (molybdenum) 0.18%–0.3%, Ni (nickel) ≤0.25%, Cu (copper) ≤0.25%, Nb (niobium) 0.07%–0.12%, V (vanadium) ≤0.05%, Al (aluminum) 0.02%–0.035%, Ca (calcium) 0.012%–0.025%, N (nitrogen) ≤0.005%, O+H+N ≤0.007% (O for oxygen, H for hydrogen), with the balance being Fe (iron) and unavoidable impurities.

[0039] The steel for acid-resistant corrosion-resistant steel pipes provided by this invention has high strength, high toughness, and good resistance to H2S stress corrosion. The minimum room temperature yield strength can reach the steel grade level of 80-140 ksi (specifically, it can reach the steel grade levels of 80 ksi, 90 ksi, 95 ksi, 110 ksi, 125 ksi and 140 ksi respectively), the tensile strength is greater than or equal to 689-1034 MPa, the transverse Charpy V-notch impact toughness at -20℃ is greater than or equal to 100 J, and the elongation is greater than or equal to 22%. It can be used to prepare bimetallic metallurgical composite oil casing suitable for harsh working conditions.

[0040] The acid-resistant corrosion-resistant steel pipe in this embodiment is a low-carbon, low-alloy steel, specifically a medium-low carbon steel with added Cr and Mo, and possibly small amounts of Cu, Ni, and Nb for microalloying, or a small amount of V and Si-Al deoxidized pure steel. The role and mass percentage range of its chemical composition are as follows:

[0041] C is a strengthening element in steel. Too low a content is detrimental to improving the hardenability and strength of the steel; too high a content is detrimental to the ductility, toughness, and corrosion resistance of the steel. Considering all factors, its mass percentage should be controlled within the range of 0.2% to 0.3%.

[0042] Si is a common element in steel. Taking all factors into consideration, its mass percentage should be controlled within the range of 0.17% to 0.37%.

[0043] Mn is a common element in steel, but it has a high tendency to segregate, and high content will reduce the corrosion resistance of steel. Taking all factors into consideration, its mass percentage should be controlled within the range of 0.3% to 0.6%.

[0044] Mo (Mo) is mainly used to improve the hardenability and tempering stability of steel, thereby increasing its strength and overall mechanical properties. However, excessively high content will increase costs. To control segregation, the Mo / P ratio should be ≥15 (i.e., the ratio of the mass percentage of Mo to the mass percentage of P is greater than or equal to 15). Considering all factors, its mass percentage should be controlled within the range of 0.18% to 0.3%.

[0045] Cr: Primarily used to improve the hardenability and tempering stability of steel, thereby enhancing its strength and corrosion resistance. However, excessively high content can increase costs. Considering all factors, its mass percentage should be controlled within the range of 1.1% to 1.25%.

[0046] Cu: Primarily used to improve the corrosion resistance of steel, while also enhancing its hardenability and strength. However, excessive content can cause Cu embrittlement. Considering all factors, its mass percentage should be controlled within the range of ≤0.25% (i.e., less than or equal to 0.25%).

[0047] Ni: It improves low-temperature toughness and hot working properties. Taking all factors into consideration, its mass percentage should be controlled within the range of ≤0.25% (i.e., less than or equal to 0.25%).

[0048] Nb: When added to steel, it forms NbC and NbN with the existing C and N, which can inhibit austenite grain growth and refine the grains, thereby improving strength and toughness. However, excessive content will form too many carbonitriding compounds, increasing the brittleness of the steel and leading to increased costs. Considering all factors, its mass percentage should be controlled within the range of 0.07% to 0.12%.

[0049] V: When added to steel, it forms VC and VN with C and N in the steel. It can inhibit the growth of austenite grains and refine the grains, thereby improving strength and toughness. However, if the content is too high, it will form too many carbon and nitride compounds, which will increase the brittleness of the steel and lead to increased costs. Taking all factors into consideration, its mass percentage should be controlled within the range of ≤0.05% (i.e., less than or equal to 0.05%).

[0050] Al is an important deoxidizer. It forms oxides with oxygen to remove oxygen and forms nitrides with nitrogen to eliminate some of the adverse effects of nitrogen. It also refines grain size and improves strength and toughness. Considering all factors, its mass percentage should be controlled within the range of 0.02% to 0.035%, and the Al / N ratio should be controlled to be ≥4 (i.e., the ratio of the mass percentage of Al to the mass percentage of N is greater than or equal to 4).

[0051] Ca can improve the properties and morphology of inclusions, thereby enhancing the ductility, toughness, and corrosion resistance of steel, and ensuring the deformation control effect of inclusions. Taking all factors into consideration, its mass percentage should be controlled within the range of 0.012% to 0.025%, and Ca / S should be controlled to be ≥4 (i.e., the ratio of the mass percentage of Ca to the mass percentage of N is greater than or equal to 4).

[0052] P: is a harmful element that mainly affects the ductility, toughness, and corrosion resistance of steel. Taking all factors into consideration, its mass percentage should be controlled within the range of ≤0.012% (i.e., less than or equal to 0.012%).

[0053] S: This is a harmful element that mainly affects the ductility, toughness, and corrosion resistance of steel. Taking all factors into consideration, its mass percentage should be controlled within the range of ≤0.003% (i.e., less than or equal to 0.003%).

[0054] H and N: These are harmful elements that mainly affect the ductility, toughness, and corrosion resistance of steel. Taking all factors into consideration, the mass percentage of N should be controlled within the range of ≤0.005% (i.e., less than or equal to 0.005%); the total mass percentage of O, H, and N should be controlled within the range of ≤0.007% (i.e., less than or equal to 0.007%).

[0055] In some embodiments, the steel for acid-resistant corrosion-resistant steel pipes comprises the following chemical composition by weight percentage:

[0056] C 0.2%–0.25%, Si 0.25%–0.37%, Mn 0.42%–0.6%, P 0.01%–0.012%, S 0.002%–0.003%, Cr 1.1%–1.19%, Mo 0.18%–0.23%, Nb 0.07%–0.09%, Al 0.02%–0.027%, Ca 0.012%–0.017%, N 0.0044%–0.005%, O+H+N≤0.007% (more specifically, 0.0061%≤O+H+N≤0.007%), balance Fe and unavoidable impurities.

[0057] In this embodiment, the steel used for acid-resistant corrosion-resistant steel pipes has high strength, high toughness, and good resistance to H2S stress corrosion, reaching the 80-95ksi steel grade level.

[0058] In some embodiments, the steel for acid-resistant corrosion-resistant steel pipes comprises the following chemical composition by weight percentage:

[0059] C 0.2%~0.21%, Si 0.32%~0.37%, Mn 0.51%~0.6%, P 0.01%~0.012%, S 0.002%, Cr 1.1%~1.13%, Mo 0.18%~0.19%, Nb 0.07%, Al 0.02%~0.022%, Ca 0.012%~0.014%, N 0.0047%~0.005%, 0.0064%≤O+H+N≤0.007%, balance Fe and unavoidable impurities.

[0060] In this embodiment, the steel used for acid-resistant corrosion-resistant steel pipes has high strength, high toughness, and good resistance to H2S stress corrosion, reaching the 80ksi steel grade level.

[0061] In some embodiments, the steel for acid-resistant corrosion-resistant steel pipes comprises the following chemical composition by weight percentage:

[0062] C 0.23%~0.25%, Si 0.29%~0.3%, Mn 0.43%~0.46%, P 0.01%~0.011%, S 0.002%~0.003%, Cr 1.14%~1.16%, Mo 0.19%~0.2%, Nb 0.08%, Al 0.024%~0.026%, Ca 0.013%~0.016%, N 0.0045%~0.0046%, 0.0062%≤O+H+N≤0.0064%, balance Fe and unavoidable impurities.

[0063] In this embodiment, the steel used for acid-resistant corrosion-resistant steel pipes has high strength, high toughness, and good resistance to H2S stress corrosion, reaching the 90ksi steel grade level.

[0064] In some embodiments, the steel for acid-resistant corrosion-resistant steel pipes comprises the following chemical composition by weight percentage:

[0065] C 0.22%~0.24%, Si 0.25%~0.31%, Mn 0.42%~0.47%, P 0.01%~0.012%, S 0.002%~0.003%, Cr 1.12%~1.19%, Mo 0.21%~0.23%, Nb 0.09%, Al 0.023%~0.027%, Ca 0.015%~0.017%, N 0.0044%~0.0045%, 0.0061%≤O+H+N≤0.0063%, balance Fe and unavoidable impurities.

[0066] In this embodiment, the steel used for acid-resistant corrosion-resistant steel pipes has high strength, high toughness, and good resistance to H2S stress corrosion, reaching the 95ksi steel grade level.

[0067] In some embodiments, the steel for acid-resistant corrosion-resistant steel pipes comprises the following chemical composition by weight percentage:

[0068] C 0.24%–0.3%, Si 0.17%–0.27%, Mn 0.3%–0.53%, P 0.01%–0.011%, S 0.002%–0.003%, Cr 1.15%–1.25%, Mo 0.24%–0.3%, Ni≤0.25%, Cu≤0.25%, Nb 0.1%–0.12%, V≤0.05%, Al 0.025%–0.035%, Ca 0.017%–0.025%, N 0.0039%–0.0043%, O+H+N≤0.0059% (more specifically, 0.0054%≤O+H+N≤0.0059%), with the balance being Fe and unavoidable impurities.

[0069] In this embodiment, the steel used for acid-resistant corrosion-resistant steel pipes has high strength, high toughness, and good resistance to H2S stress corrosion, reaching the 110-140 ksi steel grade level.

[0070] In some embodiments, the steel for acid-resistant corrosion-resistant steel pipes comprises the following chemical composition by weight percentage:

[0071] C 0.24%~0.25%, Si 0.22%~0.26%, Mn 0.49%~0.53%, P 0.01%~0.011%, S 0.002%~0.003%, Cr 1.15%~1.2%, Mo 0.24%~0.26%, Nb 0.1%, Al 0.025%~0.026%, Ca 0.017%~0.019%, N 0.0042%~0.0043%, 0.0057%≤O+H+N≤0.0059%, balance Fe and unavoidable impurities.

[0072] In this embodiment, the steel used for acid-resistant corrosion-resistant steel pipes has high strength, high toughness, and good resistance to H2S stress corrosion, reaching the 110ksi steel grade level.

[0073] In some embodiments, the steel for acid-resistant corrosion-resistant steel pipes comprises the following chemical composition by weight percentage:

[0074] C 0.26%~0.27%, Si 0.2%~0.27%, Mn 0.36%~0.45%, P 0.01%~0.011%, S 0.002%~0.003%, Cr 1.17%~1.18%, Mo 0.25%~0.27%, Ni 0.2%~0.21%, Cu 0.18%~0.19%, Nb 0.1%~0.11%, V 0.04%~0.05%, Al 0.028%~0.029%, Ca 0.018%~0.019%, N 0.004%~0.0041%, 0.0054%≤O+H+N≤0.0057%, balance Fe and unavoidable impurities.

[0075] In this embodiment, the steel used for acid-resistant corrosion-resistant steel pipes has high strength, high toughness, and good resistance to H2S stress corrosion, reaching the 125ksi steel grade level.

[0076] In some embodiments, the steel for acid-resistant corrosion-resistant steel pipes comprises the following chemical composition by weight percentage:

[0077] C 0.28%~0.3%, Si 0.17%~0.23%, Mn 0.3%~0.48%, P 0.01%~0.011%, S 0.002%~0.003%, Cr 1.21%~1.25%, Mo 0.28%~0.3%, Ni 0.23%~0.25%, Cu 0.22%~0.25%, Nb 0.12%, V 0.03%, Al 0.032%~0.035%, Ca 0.021%~0.025%, N 0.0039%~0.004%, 0.0054%≤O+H+N≤0.0055%, balance Fe and unavoidable impurities.

[0078] In this embodiment, the steel used for acid-resistant corrosion-resistant steel pipes has high strength, high toughness, and good resistance to H2S stress corrosion, reaching the 140ksi steel grade level.

[0079] Currently, the chemical composition of the outer base tube metal and the corrosion-resistant alloy of the inner liner tube in bimetallic composite oil casing differs significantly. This difference can lead to abnormal diffusion layer growth or mismatch in thermal expansion coefficients, ultimately resulting in low interfacial bonding strength between the outer base tube and the inner liner tube, and problems such as easy collapse and bulging of the inner liner tube. Furthermore, the significant difference in chemical composition between the outer base tube metal and the corrosion-resistant alloy of the inner liner tube can cause conflicts in phase transformation temperature windows and mismatch in cooling rates, making heat treatment difficult. The heat treatment process significantly impacts the mechanical properties and corrosion resistance. Therefore, the design and proper matching of the chemical composition of the outer base tube and the inner liner tube are crucial. Additionally, oil and gas contain various corrosive media, such as H2S, CO2 (carbon dioxide), and highly salinized formation water (containing Cl-). - Chloride ions (chloride ions) readily cause corrosion of pipes, severely affecting the service life and safety of bimetallic composite oil casings. Therefore, this invention also provides a bimetallic composite oil casing, wherein the bimetallic composite oil casing includes an inner liner and an outer base pipe sleeved outside the inner liner, the inner liner and the outer base pipe being metallurgically bonded.

[0080] The outer base tube is made of the acid-resistant corrosion-resistant steel pipe as described above in the embodiments of the present invention;

[0081] The inner liner is either a first inner liner or a second inner liner, and the first inner liner comprises the following chemical components in weight percentage:

[0082] C (carbon) ≤0.05%, Si (silicon) ≤0.5%, Mn (manganese) ≤1%, P (phosphorus) ≤0.03%, S (sulfur) ≤0.03%, Ni (nickel) 38%~46%, Cr (chromium) 19.5%~23.5%, Mo (molybdenum) 2.5%~3.5%, Cu (copper) 1.5%~3%, Ti (titanium) 0.6%~1.2%, Al (aluminum) ≤0.2%, with the balance being Fe (iron) and unavoidable impurities;

[0083] The second inner liner tube comprises the following chemical components in weight percentage:

[0084] C (carbon) ≤0.1%, Si (silicon) ≤0.5%, Mn (manganese) ≤0.5%, P (phosphorus) ≤0.015%, S (sulfur) ≤0.015%, Fe (iron) ≤5%, Cr (chromium) 20%~23%, Mo (molybdenum) 8%~10%, Nb (niobium) 3.15%~4.15%, Ti (titanium) ≤0.4%, Al (aluminum) ≤0.4%, with the balance being Ni (nickel) and unavoidable impurities.

[0085] In this embodiment, the first inner liner is made of 825 corrosion-resistant alloy, wherein Ni is used to maintain the austenitic matrix and prevent the precipitation of brittle phases. This is particularly useful in environments containing reducing acids and Cl. -It provides intrinsic resistance in H2S environments, and in combination with elements such as Cr, Mo, Cu, and Ti, it strengthens the passivation film and grain boundary stability, providing resistance to oxidation and creep, and adapting to the high-temperature and high-pressure conditions in oil and gas wells. Cr+Mo alloying can form a stable Cr2O3 passivation film, resisting oxidizing acids and Cl. - Corrosion. Cu can enhance resistance to reducing acids (such as sulfuric acid and phosphoric acid) and inhibit pitting corrosion. Ti can be stabilized to prevent chromium carbide precipitation and avoid intergranular corrosion.

[0086] The second inner liner is made of 625 corrosion-resistant alloy. Ni is used to construct a fully austenitic microstructure, ensuring high-temperature stability and machinability. It also works synergistically with Cr, Mo, and Nb to form a multi-layer passivation film, resisting oxidizing and reducing media, and resisting Cl... - To resist H2S corrosion, the oxide film provides protection and precipitation reinforcement, adapting to the high-temperature and high-pressure operating conditions of oil and gas wells. It maximizes the performance potential of elements such as Mo and Nb, achieving a balance between strength and corrosion resistance. Cr can form a dense Cr2O3 oxide film, resisting oxidation and acidic environment corrosion. Mo can enhance resistance to pitting and crevice corrosion, especially in environments containing Cl. - In the environment, Ni and Mo work synergistically to stabilize grain boundaries and inhibit intergranular corrosion caused by sensitization.

[0087] When the bimetallic composite oil casing uses a first inner liner (made of 825 corrosion-resistant alloy), the bimetallic composite oil casing is suitable for medium to high temperatures (≤150℃) and for applications containing H2S (or CO2) and Cl. - This bimetallic composite casing is suitable for acidic oil and gas well environments (such as shale gas well acid fracturing and sulfur-containing oilfields). Its core advantage lies in its comprehensive corrosion resistance to reducing acids and complex media. When the bimetallic composite casing uses a second inner liner (made of 625 corrosion-resistant alloy), it is suitable for harsh corrosive environments, such as high-Cl environments. - High-temperature, high-pressure wells (>150℃) that coexist with H2S (or CO2). Their comprehensive performance balances corrosion resistance, strength, and cost, making them an ideal choice for deep-sea oil and gas, acidic gas fields, and geothermal wells.

[0088] Furthermore, in this embodiment, an outer base tube and an inner liner tube with specific chemical compositions (825 corrosion-resistant alloy or 625 corrosion-resistant alloy) are used. These two components form an effective metallurgical bond, with an interfacial bonding strength reaching 400 MPa or higher. This solves the problems of low interfacial bonding strength between the outer base tube and the inner liner tube, and the easy collapse and bulging of the inner liner tube in existing bimetallic metallurgical composite oil casings. In addition, the outer base tube with this specific chemical composition has high strength and high toughness, while the inner liner tube with this specific chemical composition has good corrosion resistance. Therefore, the bimetallic metallurgical composite oil casing composed of the outer base tube and the inner liner tube with this specific chemical composition has high strength, high toughness, and good corrosion resistance (resistant to CO2 corrosion, resistant to Cl-).- Corrosion and H2S stress corrosion resistance). The minimum room temperature yield strength of the bimetallic metallurgical composite oil casing can reach steel grade levels of 80ksi, 90ksi, 95ksi, 110ksi, 125ksi and 140ksi respectively, with yield strength of 609~1048MPa, tensile strength of 716~1178MPa, transverse Charpy V-notch impact toughness of 101~152J at -20℃, elongation of 22%~30%, Vickers hardness (load of 10kgf) of 223~368, corrosion rate ≤0.1mm / a (millimeters per year), loaded with 75%~95%SMYS (specified minimum yield strength), and passed the NACE TM0177 A method (i.e., laboratory test method A for metal resistance to sulfide stress cracking and stress corrosion cracking in hydrogen sulfide environment) 720 hours H2S stress corrosion test (using solution A during testing), which can meet the requirements of H2S, CO2 and Cl. - The development of corrosive oil and gas efficiency creates demand for bimetallic composite oil casing.

[0089] In some embodiments, the first inner liner tube comprises the following chemical components in weight percentages:

[0090] C 0.02%~0.04%, Si 0.21%~0.42%, Mn 0.32%~0.69%, P 0.015%~0.023%, S 0.013%~0.02%, Ni 38%~46%, Cr 19.5%~23.5%, Mo 2.5%~3.5%, Cu 1.5%~3%, Ti 0.6%~1.2%, Al 0.12%~0.18%, with the balance being Fe and unavoidable impurities.

[0091] In some embodiments, the second inner liner tube comprises the following chemical components in weight percentages:

[0092] C 0.03%~0.08%, Si 0.25%~0.3%, Mn 0.39%~0.45%, P 0.01%~0.015%, S 0.01%~0.015%, Fe 2.5%~3.5%, Cr 20%~23%, Mo 8%~10%, Nb 3.15%~4.15%, Ti 0.25%~0.35%, Al 0.29%~0.36%, with the balance being Ni and unavoidable impurities.

[0093] This invention also provides a method for preparing the bimetallic metallurgical composite oil casing as described above, comprising the following steps:

[0094] S1. Based on the chemical composition and mass percentage of the inner lining tube, the inner lining bar is obtained by smelting, continuous casting, homogenization annealing, die forging and hot continuous rolling.

[0095] S2. Seamless steel pipes are obtained by steelmaking, continuous casting, piercing and hot rolling based on the chemical composition and mass percentage of the chemical composition of the steel used for acid-resistant corrosion-resistant steel pipes.

[0096] S3. After heating the seamless steel pipe to 150-200°C, the inner lining rod is placed inside the seamless steel pipe for hot assembly, so that the inner lining rod and the seamless steel pipe form an interference fit. Then, the mating surfaces of the inner lining rod and the seamless steel pipe at both ends are sealed and vacuumed to form a mechanical composite tube blank.

[0097] S4. After the mechanical composite tube blank is subjected to die forging, piercing and hot continuous rolling, cold rolling, heat treatment and threading, the bimetallic metallurgical composite oil casing is obtained.

[0098] Besides the chemical composition of the outer base tube and the inner liner tube, the manufacturing process of the bimetallic metallurgical composite oil casing also affects the interfacial bonding strength between the outer base tube and the inner liner tube. Using the manufacturing process provided in this embodiment, combined with the chemical composition of the outer base tube and the inner liner tube, an effective metallurgical bond can be formed between the outer base tube and the inner liner tube, achieving an interfacial bonding strength of 400 MPa or higher. Furthermore, the bimetallic metallurgical composite oil casing prepared by the method provided in this embodiment possesses both corrosion resistance and high strength and toughness, meeting the requirements for casings containing H2S, CO2, and Cl. - The development of corrosive oil and gas efficiency creates demand for bimetallic composite oil casing.

[0099] In step S1, in some embodiments, homogenization annealing specifically includes the following steps:

[0100] The bar obtained after continuous casting is heated to 1130-1170℃ (e.g., 1130℃, 1140℃, 1150℃, 1160℃ or 1170℃, etc.), held at that temperature for 2-3 hours (e.g., 2 hours, 2.5 hours or 3 hours, etc.), and then air-cooled.

[0101] In some embodiments, die forging and hot rolling specifically include the following steps:

[0102] The bar obtained after homogenization annealing is heated to 1120-1150℃ for die forging, and then hot rolling is carried out at a temperature of 1150-950℃ (i.e., the initial rolling temperature is 1150℃ and the final rolling temperature is 950℃). After hot rolling, it is air-cooled.

[0103] In step S2, in some embodiments, piercing and hot rolling specifically include the following steps:

[0104] The continuously cast billet obtained after continuous casting is heated to 1180-1230℃ (e.g., 1180℃, 1200℃, 1210℃, 1220℃ or 1230℃, etc.), held at that temperature for 1.5-2 hours (e.g., 1.5 hours, 1.8 hours or 2 hours, etc.), hot piercing is performed, and then hot continuous rolling is carried out at a temperature of 1150-930℃ (i.e., the initial rolling temperature is 1150℃ and the final rolling temperature is 930℃), followed by controlled cooling.

[0105] In step S3, in some embodiments, the interference is 0.3 to 0.5 mm, for example, it can be 0.3 mm, 0.4 mm or 0.5 mm.

[0106] In step S4, in some embodiments, the step of forging the mechanical composite tube blank specifically includes:

[0107] The mechanical composite tube blank is heated to 1150-1200℃ (e.g., 1150℃, 1160℃, 1170℃, 1180℃, 1190℃, or 1200℃) and held for 2-3 hours (e.g., 2 hours, 2.5 hours, or 3 hours) to allow sufficient metal diffusion between the seamless steel pipe and the inner lining bar. Then, it is die-forged with an initial forging temperature of 1130-1160℃ (e.g., 1130℃, 1140℃, 1150℃, or 1160℃) and a final forging temperature of 900-950℃ (e.g., 900℃, 910℃, 920℃, 930℃, 940℃, or 950℃) and a forging ratio ≥3 (e.g., 3, 4, or 5). After die forging, it is air-cooled to obtain the first metallurgical composite tube blank.

[0108] In this embodiment, the metal of the seamless steel pipe and the inner lining rod can be metallurgically bonded, thus achieving a final metallurgical bond between the outer base pipe and the inner lining pipe.

[0109] In some implementations, the piercing and hot rolling steps specifically include:

[0110] The first metallurgical composite tube blank is heated to 1100-1180℃ (e.g., 1100℃, 1110℃, 1120℃, 1130℃, 1140℃ or 1150℃, etc.) and held at that temperature for 2-3 hours (e.g., 2 hours, 2.5 hours or 3 hours, etc.) for hot piercing; then it is hot continuously rolled with an initial rolling temperature of 1100℃ and a final rolling temperature of 900-950℃ (e.g., 900℃, 910℃, 920℃, 930℃, 940℃ or 950℃, etc.), followed by water cooling to 450℃ and then air cooling to obtain the second metallurgical composite tube blank;

[0111] In some implementations, the cold rolling step specifically includes:

[0112] After cold rolling the second metallurgical composite tube blank, a third metallurgical composite tube blank is obtained.

[0113] During the cold rolling process, when the deformation in a single pass is no more than 30% and the total deformation is 30% to 50%, an annealing treatment is performed. The annealing treatment involves holding the temperature at 950 to 1050°C (e.g., 950°C, 960°C, 970°C, 980°C, 990°C, 1000°C, 1010°C, 1020°C, 1030°C, 1040°C, or 1050°C, etc.) for 1.5 to 2 hours (e.g., 1.5 hours, 1.8 hours, or 2 hours, etc.) followed by air cooling.

[0114] In some embodiments, when the inner liner is a first inner liner, the heat treatment step specifically includes:

[0115] The third metallurgical composite tube blank is heated to 920–1150℃ (e.g., 920℃, 940℃, 960℃, 980℃, 1000℃, 1020℃, 1040℃, 1080℃, 1100℃, 1120℃, or 1150℃, etc.), held at this temperature for 1–2 hours (e.g., 1 hour, 1.5 hours, or 2 hours, etc.), then water-cooled. It is then heated to 650–750℃ (e.g., 650℃, 660℃, 670℃, 680℃, 690℃, 700℃, 710℃, 720℃, 730℃, 740℃, or 750℃, etc.), held at this temperature for 2–4 hours (e.g., 2 hours, etc.). After spray cooling to 450℃ (e.g., 3h or 4h), the temperature is air-cooled, then heated to 900-950℃ (e.g., 900℃, 910℃, 920℃, 930℃, 940℃ or 950℃), held for 1.5-2h (e.g., 1.5h, 1.8h or 2h), and then water-cooled. Finally, the temperature is heated to 580-700℃ (e.g., 580℃, 590℃, 600℃, 610℃, 620℃, 630℃, 640℃, 650℃, 660℃, 670℃, 680℃ or 700℃), held for 2-3h (e.g., 2h, 2.5h or 3h), and then water-cooled.

[0116] In some embodiments, when the inner lining tube is a second inner lining tube, the heat treatment step specifically includes: heating the third metallurgical composite tube blank to 920-1150℃ (e.g., 920℃, 940℃, 960℃, 980℃, 1000℃, 1020℃, 1040℃, 1080℃, 1100℃, 1120℃, or 1150℃, etc.), holding it at that temperature for 1-2 hours (e.g., 1 hour, 1.5 hours, or 2 hours, etc.), then water cooling, and then heating it to 600-900℃ (e.g., 600℃, 700℃, 800℃, or 900℃, etc.), holding it at that temperature for 2-4 hours. (For example, it can be 2h, 3h or 4h, etc.) After spray cooling to 450℃, air cooling is performed, followed by heating to 900-950℃ (for example, it can be 900℃, 910℃, 920℃, 930℃, 940℃ or 950℃, etc.), holding for 1.5-2h (for example, it can be 1.5h, 1.8h or 2h, etc.) and then water cooling, and finally heating to 580-700℃ (for example, it can be 580℃, 600℃, 610℃, 630℃, 650℃, 670℃, 680℃ or 700℃, etc.), holding for 2-3h (for example, it can be 2h, 2.5h or 3h, etc.) and then water cooling.

[0117] In some implementations, the thread machining steps specifically include:

[0118] Perform API (American Petroleum Institute) standard thread machining or special thread machining.

[0119] The present invention will be further described below through specific embodiments.

[0120] In the following embodiments, the chemical composition and mass percentage of the outer base tube of the bimetallic composite oil casing are shown in Table 1, and the chemical composition and mass percentage of the inner liner tube are shown in Tables 2 and 3.

[0121] Table 1. Chemical composition and mass percentage of the outer base tube in each embodiment.

[0122]

[0123] Table 2. Chemical composition and mass percentage of the inner liner in each embodiment.

[0124]

[0125] Table 3. Chemical composition and mass percentage of the inner liner in each embodiment.

[0126]

[0127] In Table 1, "-" indicates that the corresponding chemical components are not present. For example, the outer base tube of the bimetallic metallurgical composite oil casing in Example 1 does not contain Cu, Ni, and V.

[0128] In Table 1, 80, 90, 95, 110, 125 and 140 in parentheses represent the corresponding steel grades of 80ksi, 90ksi, 95ksi, 110ksi, 125ksi and 140ksi, respectively; S in parentheses indicates sulfur resistance and SS indicates super sulfur resistance, with different test loading stress levels (see Table 5).

[0129] In Table 2, 825 in parentheses represents 825 corrosion-resistant alloy. In Table 3, 625 in parentheses represents 625 corrosion-resistant alloy.

[0130] In Tables 1 and 2, the chemical composition of each embodiment includes Fe and unavoidable impurities as the balance. In Table 3, the chemical composition of each embodiment includes Ni and unavoidable impurities as the balance. Taking Example 1 in Table 1 as an example, the sum of the mass percentages of C, Si, Mn, P, S, Cr, Mo, Nb, Ca, Al, N, H, O, Fe, and unavoidable impurities is 100%, and so on for the other cases.

[0131] Example 1

[0132] This embodiment provides a method for preparing a bimetallic metallurgical composite oil casing, comprising the following steps:

[0133] (1) Preparation of seamless steel pipe: According to the chemical composition and mass percentage of the outer base pipe in Example 1 of Table 1, steelmaking and continuous casting are carried out to obtain continuous casting billet bar; the continuous casting billet bar is heated to 1180℃, held for 2h, hot piercing is carried out, and then hot continuous rolling is carried out at a temperature of 1150~930℃ (i.e., the initial rolling temperature is 1150℃ and the final rolling temperature is 930℃). After rolling, controlled cooling is carried out to obtain seamless steel pipe, whose metallographic structure is pearlite + ferrite + bainite.

[0134] (2) Preparation of inner lining bar: According to the chemical composition and mass percentage of the inner lining tube in Example 1 of Table 2, the bar was smelted and continuously cast to obtain the bar; the bar was heated to 1150℃, held for 2 hours, and then air-cooled, i.e., homogenized annealing; the bar obtained after homogenized annealing was heated to 1130℃ for die forging, and then hot rolling was carried out at a temperature of 1150~950℃ (i.e., the initial rolling temperature is 1150℃ and the final rolling temperature is 950℃). After hot rolling, the bar was air-cooled to obtain the inner lining bar, whose metallographic structure is austenite + carbide.

[0135] (3) Preparation of mechanical composite tube blank: The inner surface of the seamless steel tube prepared above is cleaned, and the outer surface of the inner lining bar prepared above is cleaned.

[0136] The seamless steel pipe after heat treatment is heated to 180°C. The inner lining bar after heat treatment is placed inside the seamless steel pipe for hot assembly and the two are made to achieve an interference fit with an interference amount of 0.4mm. Then, the joint surfaces of the inner lining bar and the seamless steel pipe at both ends are sealed and vacuumed to form a mechanical composite tube blank.

[0137] (4) Die forging: The mechanical composite tube blank prepared above is heated to 1180℃ and held for 3h to allow the metal of the seamless steel pipe and the inner lining bar to diffuse fully. Then die forging is carried out with an initial forging temperature of 1150℃, a final forging temperature of 900℃, and a forging ratio of 5 to achieve metallurgical bonding between the seamless steel pipe and the inner lining bar. After die forging, it is air-cooled to form the first metallurgical composite tube blank.

[0138] (5) Piercing and hot rolling: The first metallurgical composite tube blank prepared above is heated to 1180°C and held for 3 hours for hot piercing; then hot rolling is carried out with an initial rolling temperature of 1100°C and a final rolling temperature of 900°C. After water cooling to 450°C, it is air cooled to obtain the second metallurgical composite tube blank.

[0139] (6) Cold rolling: Before cold rolling, the oxide scale on the outer surface of the second metallurgical composite tube blank is cleaned, and then cold rolled to the required size to obtain the third metallurgical composite tube blank. A total of three cold rollings are performed, with a single-pass deformation of 15%. After the second cold rolling, the tube blank is heated to 980℃ and held for 2 hours before air cooling, and then cold rolling is performed for the third time.

[0140] (7) Solution treatment: The third metallurgical composite tube blank prepared above is heated to 1000℃, kept at the temperature for 1.5h, and then cooled with water to obtain the fourth metallurgical composite tube blank.

[0141] (8) Stabilization treatment: The fourth metallurgical composite tube blank is heated to 700°C by medium frequency induction heating, kept at the temperature for 3 hours, spray cooled to 450°C, and then air cooled to obtain the fifth metallurgical composite tube blank.

[0142] (9) Heat treatment and threading: The fifth metallurgical composite tube blank is heated to 910°C, kept at 1.5h and then water-cooled, then kept at 700°C for 2h and water-cooled. After threading at both ends of the tube, a bimetallic metallurgical composite oil casing is obtained, which includes an outer base tube with an outer diameter of 139.7mm and a wall thickness of 9.17mm and an inner liner tube with a wall thickness of 2.5mm located inside the outer base tube.

[0143] Example 2

[0144] This embodiment provides a method for preparing a bimetallic metallurgical composite oil casing, which differs from Embodiment 1 only in that:

[0145] In step (1), steelmaking is carried out according to the chemical composition and mass percentage of the outer base tube in Example 2 of Table 1.

[0146] In step (2), the smelting is carried out according to the chemical composition and mass percentage of the inner lining tube in Example 2 of Table 3.

[0147] In step (4), the final forging temperature is 950℃.

[0148] In step (5), the final rolling temperature is 950℃.

[0149] In step (6), the temperature is heated to 1000℃ and held for 2 hours before being air-cooled.

[0150] Step (8) is aging treatment: medium frequency induction heating is used to heat the fourth metallurgical composite tube blank to 750°C, keep it at that temperature for 3 hours, spray it to 450°C, and then air cool it.

[0151] Example 3

[0152] This embodiment provides a method for preparing a bimetallic metallurgical composite oil casing, which differs from Embodiment 1 only in that:

[0153] In step (1), steelmaking is carried out according to the chemical composition and mass percentage of the outer base tube in Example 3 of Table 1.

[0154] In step (2), the smelting is carried out according to the chemical composition and mass percentage of the inner lining tube in Example 3 of Table 2.

[0155] In step (9), the temperature is then maintained at 680℃ for 2 hours and then cooled with water.

[0156] Example 4

[0157] This embodiment provides a method for preparing a bimetallic metallurgical composite oil casing, which differs from Embodiment 2 only in that:

[0158] In step (1), steelmaking is carried out according to the chemical composition and mass percentage of the outer base tube in Example 4 of Table 1.

[0159] In step (2), the smelting is carried out according to the chemical composition and mass percentage of the inner lining tube in Example 4 of Table 3.

[0160] In step (9), the temperature is then maintained at 680℃ for 2 hours and then cooled with water.

[0161] Example 5

[0162] This embodiment provides a method for preparing a bimetallic metallurgical composite oil casing, which differs from Embodiment 1 only in that:

[0163] In step (1), steelmaking is carried out according to the chemical composition and mass percentage of the outer base tube in Example 5 of Table 1.

[0164] In step (2), the smelting is carried out according to the chemical composition and mass percentage of the inner lining tube in Example 5 of Table 2.

[0165] In step (9), the temperature is then maintained at 660℃ for 2 hours and then cooled with water.

[0166] Example 6

[0167] This embodiment provides a method for preparing a bimetallic metallurgical composite oil casing, which differs from Embodiment 2 only in that:

[0168] In step (1), steelmaking is carried out according to the chemical composition and mass percentage of the outer base tube in Example 6 of Table 1.

[0169] In step (2), the smelting is carried out according to the chemical composition and mass percentage of the inner lining tube in Example 6 of Table 3.

[0170] In step (9), the temperature is then maintained at 660℃ for 2 hours and then cooled with water.

[0171] Example 7

[0172] This embodiment provides a method for preparing a bimetallic metallurgical composite oil casing, which differs from Embodiment 1 only in that:

[0173] In step (1), steelmaking is carried out according to the chemical composition and mass percentage of the outer base tube in Example 7 of Table 1.

[0174] In step (2), the smelting is carried out according to the chemical composition and mass percentage of the inner lining tube in Example 7 of Table 2.

[0175] In step (9), the temperature is then maintained at 640℃ for 2 hours and then cooled with water.

[0176] Example 8

[0177] This embodiment provides a method for preparing a bimetallic metallurgical composite oil casing, which differs from Embodiment 2 only in that:

[0178] In step (1), steelmaking is carried out according to the chemical composition and mass percentage of the outer base tube in Example 8 of Table 1.

[0179] In step (2), the smelting is carried out according to the chemical composition and mass percentage of the inner lining tube in Example 8 of Table 3.

[0180] In step (9), the temperature is then maintained at 640℃ for 2 hours and then cooled with water.

[0181] Example 9

[0182] This embodiment provides a method for preparing a bimetallic metallurgical composite oil casing, which differs from Embodiment 1 only in that:

[0183] In step (1), steelmaking is carried out according to the chemical composition and mass percentage of the outer base tube in Example 9 of Table 1.

[0184] In step (2), the smelting is carried out according to the chemical composition and mass percentage of the inner lining tube in Example 9 of Table 2.

[0185] In step (9), the temperature is then maintained at 610℃ for 2 hours and then cooled with water.

[0186] Example 10

[0187] This embodiment provides a method for preparing a bimetallic metallurgical composite oil casing, which differs from Embodiment 2 only in that:

[0188] In step (1), steelmaking is carried out according to the chemical composition and mass percentage of the outer base tube in Example 10 of Table 1.

[0189] In step (2), the smelting is carried out according to the chemical composition and mass percentage of the inner lining tube in Example 10 of Table 3.

[0190] In step (9), the temperature is then maintained at 610℃ for 2 hours and then cooled with water.

[0191] Example 11

[0192] This embodiment provides a method for preparing a bimetallic metallurgical composite oil casing, which differs from Embodiment 1 only in that:

[0193] In step (1), steelmaking is carried out according to the chemical composition and mass percentage of the outer base tube in Example 11 of Table 1.

[0194] In step (2), the smelting is carried out according to the chemical composition and mass percentage of the inner lining tube in Example 11 of Table 2.

[0195] In step (9), the temperature is then maintained at 580℃ for 2 hours and then cooled with water.

[0196] Example 12

[0197] This embodiment provides a method for preparing a bimetallic metallurgical composite oil casing, which differs from Embodiment 2 only in that:

[0198] In step (1), steelmaking is carried out according to the chemical composition and mass percentage of the outer base tube in Example 12 of Table 1.

[0199] In step (2), the smelting is carried out according to the chemical composition and mass percentage of the inner lining tube in Example 12 of Table 3.

[0200] In step (9), the temperature is then maintained at 580℃ for 2 hours and then cooled with water.

[0201] Mechanical properties tests were performed on the bimetallic composite oil casing in each embodiment, specifically yield strength and tensile strength. R m Elongation A HV10 (Vickers hardness, load 10 kgf), transverse Charpy V-notch impact toughness at -20℃ A kv The interfacial bonding strength between the inner liner and the outer base tube was tested, and the results are shown in Table 4.

[0202] Table 4. Test results of mechanical properties of bimetallic metallurgical composite oil casing in each embodiment.

[0203]

[0204] Note: The total deformation ratio used for yield strength testing of bimetallic composite oil casing varies depending on the steel grade. Specifically, the yield strength is measured for 80ksi, 90ksi, and 95ksi steel grades. R t0.5 (That is, the tensile stress corresponding to a total tensile deformation of 0.5%), the test result for 110ksi steel grade is the yield strength. R t0.6 (That is, the tensile stress corresponding to a total tensile deformation of 0.6%), the test result for 125ksi steel grade is the yield strength. R t0.65 (That is, the tensile stress corresponding to a total tensile deformation of 0.65%), the test result for 140ksi steel grade is the yield strength. R t0.7 (That is, the tensile stress corresponding to a total tensile deformation of 0.7%).

[0205] The corrosion resistance of the bimetallic composite oil casing in each embodiment was tested, specifically the H2S stress corrosion resistance of the outer base pipe and the corrosion rate of the inner liner pipe. The results are shown in Table 5.

[0206] The test conditions for the corrosion rate test of the inner lining pipe are as follows:

[0207] For the 825 corrosion-resistant alloy: H2S partial pressure is 0.1 MPa (approximately 1000 ppm), pH is 3.5, CO2 partial pressure is 5 MPa, Cl... - The concentration was 50,000 ppm (5%), and the temperature was 150°C.

[0208] For the 625 corrosion-resistant alloy: H2S partial pressure is 0.2 MPa (approximately 2000 ppm), pH is 3.5, CO2 partial pressure is 10 MPa, Cl... - The concentration was 100,000 ppm (10%), and the temperature was 200℃.

[0209] Table 5. Corrosion resistance test results of bimetallic metallurgical composite oil casing in each embodiment.

[0210]

[0211] The test results above show that the yield strength of the 80ksi grade bimetallic composite oil casing provided by this invention is [data missing]. R t0.5 The tensile strength is 609–612 MPa, the elongation is 716–720 MPa, the elongation is 30%, the HV10 is 223–225, the transverse Charpy V-notch impact toughness at -20℃ is 151–152 J, the interfacial bond strength between the outer base tube and the inner liner is 461–465 MPa, and it has good corrosion resistance; the yield strength of the 90ksi grade bimetallic metallurgical composite oil casing is... R t0.5 The tensile strength is 678–681 MPa, the elongation is 788–792 MPa, the elongation is 29%, the HV10 is 246–247, the transverse Charpy V-notch impact toughness at -20℃ is 137–139 J, the interfacial bond strength between the outer base tube and the inner liner is 473–476 MPa, and it has good corrosion resistance; the yield strength of the 95ksi grade bimetallic metallurgical composite oil casing is... R t0.5 The tensile strength is 731–735 MPa, the elongation is 850–855 MPa, the elongation is 28%, the HV10 is 265–267, the transverse Charpy V-notch impact toughness at -20℃ is 131–133 J, the interfacial bond strength between the outer base tube and the inner liner is 511–515 MPa, and it has good corrosion resistance; the yield strength of the 110ksi grade bimetallic metallurgical composite oil casing is... R t0.6 The strength is 811–814 MPa, the tensile strength is 932–936 MPa, the elongation is 26%, the HV10 is 291–292, the transverse Charpy V-notch impact toughness at -20℃ is 126–128 J, the interfacial bond strength between the outer base tube and the inner liner is 559–563 MPa, and it has good corrosion resistance; the yield strength of the 125ksi grade bimetallic metallurgical composite oil casing is... R t0.65The tensile strength is 936–939 MPa, the elongation is 1064–1067 MPa, the elongation is 24%, the HV10 is 332–333, the transverse Charpy V-notch impact toughness at -20℃ is 113–116 J, the interfacial bond strength between the outer base tube and the inner liner is 638–642 MPa, and it has good corrosion resistance; the yield strength of the 140ksi grade bimetallic metallurgical composite oil casing is... R t0.7 The strength is 1045-1048 MPa, the tensile strength is 1174-1178 MPa, the elongation is 22%, the HV10 is 366-368, the transverse Charpy V-notch impact toughness at -20℃ is 101-103 J, the interface bonding strength between the outer base tube and the inner liner tube is 698-701 MPa, and it has good corrosion resistance.

[0212] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A bimetallic metallurgically combined oil casing characterized in that, The bimetallic metallurgical composite oil casing comprises an inner liner pipe and an outer base pipe sleeved outside the inner liner pipe, and the inner liner pipe is metallurgically combined with the outer base pipe; The outer base pipe is made of an acid-resistant environment corrosion steel pipe steel; The acid-resistant environment corrosion steel pipe steel comprises the following mass percentage chemical components: C 0.2%~0.3%, Si 0.17%~0.37%, Mn 0.3%~0.6%, P≤0.012%, S≤0.003%, Cr 1.1%~1.25%, Mo 0.18%~0.3%, Ni≤0.25%, Cu≤0.25%, Nb 0.07%~0.12%, V≤0.05%, Al 0.02%~0.035%, Ca 0.012%~0.025%, N≤0.005%, O+H+N≤0.007%, the balance being Fe and inevitable impurities; The inner liner pipe is a first inner liner pipe or a second inner liner pipe, and the first inner liner pipe comprises the following mass percentage chemical components: C≤0.05%, Si≤0.5%, Mn≤1%, P≤0.03%, S≤0.03%, Ni 38%~46%, Cr 19.5%~23.5%, Mo 2.5%~3.5%, Cu 1.5%~3%, Ti 0.6%~1.2%, Al≤0.2%, the balance being Fe and inevitable impurities; The second inner liner pipe comprises the following mass percentage chemical components: C≤0.1%, Si≤0.5%, Mn≤0.5%, P≤0.015%, S≤0.015%, Fe≤5%, Cr 20%~23%, Mo 8%~10%, Nb 3.15%~4.15%, Ti≤0.4%, Al≤0.4%, the balance being Ni and inevitable impurities; The preparation method of the bimetallic metallurgical composite oil casing comprises the following steps: S1, according to the chemical components and mass percentage of the chemical components of the inner liner pipe, smelting, continuous casting, homogenizing annealing, die forging and hot continuous rolling are carried out to obtain an inner liner bar; S2, according to the chemical components and mass percentage of the chemical components of the acid-resistant environment corrosion steel pipe steel, steelmaking, continuous casting, piercing and hot continuous rolling are carried out to obtain a seamless steel pipe; S3, after the seamless steel pipe is heated to 150~200℃, the inner liner bar is arranged inside the seamless steel pipe for hot assembly, so that the inner liner bar and the seamless steel pipe form an interference fit, then the end joint surfaces of the inner liner bar and the seamless steel pipe are sealed and vacuumized to form a mechanical composite pipe blank; S4, after the mechanical composite pipe blank is subjected to die forging, piercing, hot continuous rolling, cold rolling, heat treatment and thread processing, the bimetallic metallurgical composite oil casing is obtained; In step S4, the step of die forging the mechanical composite pipe blank specifically comprises: The mechanical composite pipe blank is heated to 1150-1200 DEG C, and kept for 2-3 hours, and then is die forged, the initial forging temperature is 1130-1160 DEG C, the final forging temperature is 900-950 DEG C, the forging ratio is greater than or equal to 3, and the mechanical composite pipe blank is air cooled after die forging to obtain a first metallurgical composite pipe blank.

2. The bimetallic metallurgically combined oil sleeve of claim 1 wherein, The acid-resistant steel pipe steel comprises the following chemical components in mass percentage: C 0.2%~0.25%, Si 0.25%~0.37%, Mn 0.42%~0.6%, P 0.01%~0.012%, S 0.002%~0.003%, Cr 1.1%~1.19%, Mo 0.18%~0.23%, Nb 0.07%~0.09%, Al 0.02%~0.027%, Ca 0.012%~0.017%, N 0.0044%~0.005, O+H+N≤0.007%, the balance being Fe and inevitable impurities.

3. The bimetallic metallurgically combined oil sleeve of Claim 1 wherein, The acid-resistant steel pipe steel comprises the following chemical components in mass percentage: C 0.24%~0.3%, Si 0.17%~0.27%, Mn 0.3%~0.53%, P 0.01%~0.011%, S 0.002%~0.003%, Cr 1.15%~1.25%, Mo 0.24%~0.3%, Ni≤0.25%, Cu≤0.25%, Nb 0.1%~0.12%, V≤0.05%, Al 0.025%~0.035%, Ca 0.017%~0.025%, N 0.0039%~0.0043%, O+H+N≤0.0059%, the balance being Fe and inevitable impurities.

4. A method of producing a bimetallic metallurgically combined oil casing according to any one of claims 1 to 3, characterized in that, The method comprises the following steps: S1, melting, continuous casting, homogenizing annealing, die forging and hot continuous rolling are performed according to the chemical composition and mass percentage of the chemical composition of the inner lining pipe to obtain an inner lining bar; S2, steelmaking, continuous casting, piercing and hot continuous rolling are performed according to the chemical composition and mass percentage of the chemical composition of the acid-resistant steel pipe steel to obtain a seamless steel pipe; S3, the inner lining bar is arranged inside the seamless steel pipe after the seamless steel pipe is heated to 150-200 DEG C to perform hot assembly, so that the inner lining bar and the seamless steel pipe form an interference fit, then the joint surfaces of the inner lining bar and the seamless steel pipe are sealed and vacuumized to form a mechanical composite pipe blank; S4, the mechanical composite pipe blank is subjected to die forging, piercing and hot continuous rolling, cold rolling, heat treatment and thread processing to obtain the double-metal metallurgical composite oil sleeve pipe. In step S4, the step of die forging the mechanical composite pipe blank specifically comprises: The mechanical composite pipe blank is heated to 1150-1200 DEG C, and kept for 2-3 hours, and then is die forged, the initial forging temperature is 1130-1160 DEG C, the final forging temperature is 900-950 DEG C, the forging ratio is greater than or equal to 3, and the mechanical composite pipe blank is air cooled after die forging to obtain a first metallurgical composite pipe blank.

5. The preparation method according to claim 4, characterized in that, In step S4, the step of piercing and hot continuous rolling specifically comprises: The first metallurgical composite pipe blank is heated to 1100-1180 DEG C, and held for 2-3 hours, and then hot piercing is performed; then hot continuous rolling is performed, the initial rolling temperature is 1100 DEG C, and the final rolling temperature is 900-950 DEG C, then water cooling is performed to 450 DEG C, and then air cooling is performed, and the second metallurgical composite pipe blank is obtained.

6. The production method according to claim 5, wherein In step S4, the cold rolling specifically includes the following steps: After the second metallurgical composite pipe blank is cold rolled, the third metallurgical composite pipe blank is obtained. In the process of cold rolling, when the single pass deformation is not more than 30%, and the total deformation is 30%-50%, annealing treatment is performed, and the annealing treatment specifically includes the following steps: holding at a temperature of 950-1050 DEG C for 1.5-2 hours, and then air cooling.

7. The preparation method according to claim 6, characterized in that, When the inner lining pipe is the first inner lining pipe, in step S4, the heat treatment specifically includes the following steps: The third metallurgical composite pipe blank is heated to 920-1150 DEG C, held for 1-2 hours, and then water cooled, then heated to 650-750 DEG C, held for 2-4 hours, spray cooled to 450 DEG C, and then air cooled, then heated to 900-950 DEG C, held for 1.5-2 hours, and then water cooled, and finally heated to 580-700 DEG C, held for 2-3 hours, and then water cooled.

8. The preparation method according to claim 6, characterized in that, When the inner lining pipe is the second inner lining pipe, in step S4, the heat treatment specifically includes the following steps: The third metallurgical composite pipe blank is heated to 920-1150 DEG C, held for 1-2 hours, and then water cooled, then heated to 600-900 DEG C, held for 2-4 hours, spray cooled to 450 DEG C, and then air cooled, then heated to 900-950 DEG C, held for 1.5-2 hours, and then water cooled, and finally heated to 580-700 DEG C, held for 2-3 hours, and then water cooled.

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