Steel for seamless steel tube, bimetal metallurgical composite oil casing and preparation method of bimetal metallurgical composite oil casing

Abstract

The invention discloses steel for a seamless steel tube, a bimetal metallurgical composite oil sleeve and a preparation method of the bimetal metallurgical composite oil sleeve, and relates to the technical field of manufacturing of oil sleeves for oil and gas development. The steel for the seamless steel pipe comprises the following chemical components in percentage by mass: 0.2%-0.3% of C, 0.6%-0.75% of Si, 1.05%-1.15% of Mn, 0.75%-0.84% of Cr, 0.3%-0.38% of Mo, 0.15%-0.23% of Ni, 0.07%-0.12% of Nb, 0.015%-0.03% of Al, 0.015%-0.03% of Ca, the balance of Fe and inevitable impurities, and the content of harmful elements P, S, N, O and H is controlled in a lower range. The steel for the seamless steel pipe has high strength and high toughness and can reach the 80-140 ksi steel grade level, and the 0 DEG C transverse Charpy V-shaped notch impact toughness is larger than or equal to 120 J.

Description

Technical Field

[0001] The present invention relates to the technical field of oil casing manufacturing for oil and gas development, and in particular to a seamless steel pipe steel, a bimetallic metallurgical composite oil casing and a preparation method thereof. Background Art

[0002] Bimetallic metallurgical composite pipe is a pipe made by combining two dissimilar metals through metallurgical bonding technology. It has both inner layer corrosion resistance and outer layer mechanical strength. It is currently gradually being used as oil casing (oil pipe and casing) in oil and natural gas extraction.

[0003] During oil and gas extraction, tubing and casing, as the sole pathways for oil and gas extraction and key components for wellbore support, face extremely complex and harsh operating conditions. The high temperatures and high pressures found deep within the formation place extremely high demands on the mechanical properties of bimetallic composite tubing and casing. Therefore, there is an urgent need to develop high-strength, high-toughness steels suitable for these harsh operating conditions. Summary of the Invention

[0004] Based on the above-mentioned deficiencies in the prior art, the purpose of the present invention is to provide a steel for seamless steel pipes, a bimetallic metallurgical composite oil casing and a preparation method thereof, aiming to provide a high-strength and high-toughness steel for the preparation of bimetallic metallurgical composite oil casing suitable for harsh working conditions.

[0005] The technical solutions of the present invention are as follows: A first aspect of the present invention provides a steel for a seamless steel pipe, wherein the steel for a seamless steel pipe comprises the following chemical components in percentage by mass: C 0.2%~0.3%, Si 0.6%~0.75%, Mn 1.05%~1.15%, P≤0.015%, S≤0.005%, Cr0.75%~0.84%, Mo 0.3%~0.38%, Ni 0.15%~0.23%, Nb 0.07%~0.12%, Al 0.015%~0.03%, Ca 0.015%~0.03%, N≤0.008%, O+H+N≤0.01%, the balance is Fe and unavoidable impurities.

[0006] Optionally, the steel for seamless steel pipe includes the following chemical components in percentage by mass: C 0.2%~0.23%, Si 0.6%~0.65%, Mn 1.05%~1.08%, P 0.011%~0.015%, S0.003%~0.005%, Cr 0.75%~0.78%, Mo 0.3%~0.34%, Ni 0.15%~0.18%, Nb 0.07%~0.08%, Al 0.015%~0.02%, Ca 0.015%~0.018%, N 0.006%~0.008%, 0.008%≤O+H+N≤0.01%, the balance is Fe and unavoidable impurities.

[0007] Optionally, the steel for seamless steel pipe includes the following chemical components in percentage by mass: C 0.24%~0.3%, Si 0.66%~0.75%, Mn 1.09%~1.15%, P 0.01%~0.012%, S0.002%~0.003%, Cr 0.79%~0.84%, Mo 0.33%~0.38%, Ni 0.19%~0.23%, Nb 0.09%~0.12%, Al 0.022%~0.03%, Ca 0.02%~0.03%, N 0.005%~0.006%, 0.007%≤O+H+N≤0.008%, the balance is Fe and unavoidable impurities.

[0008] A second aspect of the present invention provides a bimetallic metallurgical composite oil casing, wherein the bimetallic metallurgical composite oil casing comprises an inner liner pipe and an outer base pipe sleeved outside the inner liner pipe, wherein the inner liner pipe and the outer base pipe are metallurgically bonded; The outer base pipe is made of the seamless steel pipe steel described above in the present invention; The inner lining pipe comprises the following chemical components in percentage by mass: C 0.15%~0.22%, Si≤1%, Mn 0.25%~1%, P≤0.02%, S≤0.01%, Ni 0.5%~1.5%, Cr12%~14%, Mo 0.2%~0.6%, Cu≤0.25%, the balance is Fe and unavoidable impurities.

[0009] A third aspect of the present invention provides a bimetallic metallurgical composite oil casing, wherein the bimetallic metallurgical composite oil casing comprises an inner liner pipe and an outer base pipe sleeved outside the inner liner pipe, wherein the inner liner pipe and the outer base pipe are metallurgically bonded; The outer base pipe is made of the seamless steel pipe steel described above in the present invention; The inner lining pipe comprises the following chemical components in percentage by mass: C≤0.03%, Si≤0.5%, Mn≤0.5%, P≤0.02%, S≤0.005%, Ni 4%~6%, Cr 13%~15%, Mo 1.5%~2.5%, Cu 0.3%~1%, N 0.05%~0.15%, Ti 0.01%~0.5%, V≤0.5%, the balance is Fe and unavoidable impurities.

[0010] A fourth aspect of the present invention provides a method for preparing the bimetallic metallurgical composite oil casing as described above, comprising the following steps: S1. After smelting, continuous casting, die forging, hot rolling and heat treatment according to the chemical composition and mass percentage of the liner pipe, the liner bar is obtained; S2. According to the chemical composition and mass percentage of the steel used for the seamless steel pipe, steelmaking, continuous casting, perforation and hot rolling are carried out to obtain the seamless steel pipe; S3, after heating the seamless steel pipe to 130-180° C., placing the lining bar inside the seamless steel pipe for heat assembly so that the lining bar and the seamless steel pipe form an interference fit, then sealing and welding the joint surfaces of the lining bar and the seamless steel pipe at both ends and evacuating the pipe to form a mechanical composite pipe blank; S4. The mechanical composite tube blank is subjected to die forging, piercing, hot continuous rolling, cold rolling, heat treatment and thread processing to obtain the bimetallic metallurgical composite oil casing.

[0011] Optionally, in step S4, the step of die forging the mechanical composite tube blank specifically includes: The mechanical composite tube blank is heated to 1150-1250° C., kept warm for 2-3 hours, and then die forged with an initial forging temperature of 1130-1160° C., a final forging temperature of 900-950° C., a forging ratio of ≥3, and air-cooled after die forging to obtain a first metallurgical composite tube blank.

[0012] Optionally, in step S4, the steps of piercing and hot rolling specifically include: The first metallurgical composite tube billet is heated to 1130-1180° C., kept warm for 2-3 hours, and hot pierced; then hot continuous rolling is performed with an initial rolling temperature of 1130° C. and a final rolling temperature of 900-950° C., followed by water cooling to 650° C. and air cooling to obtain a second metallurgical composite tube billet.

[0013] Optionally, in step S4, the cold rolling step specifically includes: Cold rolling the second metallurgical composite tube blank to obtain a third metallurgical composite tube blank; During the cold rolling process, the deformation of a single pass is not greater than 30%. When the total deformation is 30% to 50%, an annealing treatment is performed. The annealing treatment step is to keep the temperature at 900 to 950° C. for 1.5 to 2 hours and then air cool.

[0014] Optionally, in step S4, the heat treatment step specifically includes: The third metallurgical composite tube billet is heated to 900-950° C., kept at this temperature for 1.5-2 hours, and then water-cooled. Subsequently, the tube billet is tempered at 570-690° C. for 2-3 hours, and then water-cooled. Beneficial effects: The steel for seamless steel pipe provided by the present invention has high strength and high toughness, the minimum room temperature yield strength can reach 80-140ksi steel grade level, the tensile strength is greater than or equal to 689-1034MPa, the elongation is greater than or equal to 25%, and the 0℃ transverse Charpy V-notch impact toughness is greater than or equal to 120J. It can be used to prepare bimetallic metallurgical composite oil casing suitable for harsh working conditions. DETAILED DESCRIPTION

[0015] The present invention provides a seamless steel pipe steel, a bimetallic metallurgical composite oil casing, and a method for manufacturing the same. To clarify the objectives, technical solutions, and effects of the present invention, the present invention is described in further detail below. It should be understood that the specific embodiments described herein are intended only to illustrate the present invention and are not intended to limit the present invention.

[0016] Unless otherwise defined, all technical terms and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0017] An embodiment of the present invention provides a steel for a seamless steel pipe, wherein the steel for a seamless steel pipe comprises the following chemical components in percentage by mass: C (carbon) 0.2%~0.3%, Si (silicon) 0.6%~0.75%, Mn (manganese) 1.05%~1.15%, P (phosphorus) ≤0.015%, S (sulfur) ≤0.005%, Cr (chromium) 0.75%~0.84%, Mo (molybdenum) 0.3%~0.38%, Ni (nickel) 0.15%~0.23%, Nb (niobium) 0.07%~0.12%, Al (aluminum) 0.015%~0.03%, Ca (calcium) 0.015%~0.03%, N (nitrogen) ≤0.008%, O+H+N≤0.01% (O is oxygen, H is hydrogen, N is nitrogen), the balance is Fe (iron) and unavoidable impurities.

[0018] The steel for seamless steel pipes provided in the embodiments of the present invention has high strength and high toughness. The minimum room temperature yield strength can reach 80 to 140 ksi steel grade levels (specifically, 80 ksi, 95 ksi, 110 ksi, 125 ksi, and 140 ksi steel grade levels, respectively). The tensile strength is greater than or equal to 689 to 1034 MPa, the elongation is greater than or equal to 25%, and the 0°C transverse Charpy V-notch impact toughness is greater than or equal to 120 J. The steel can be used to prepare bimetallic metallurgical composite oil casing suitable for harsh working conditions.

[0019] The steel used for the seamless steel pipe in this embodiment is medium-low carbon low alloy steel, specifically a pure steel with medium-low carbon, added with Mn, Cr, Mo, and Si, with small amounts of Ni and Nb added for microalloying, and Si-Al deoxidation. The chemical composition and mass percentage ranges are as follows: C: It is a strengthening element in steel. Too low a content is not conducive to improving the hardenability of steel and is not conducive to improving the strength of steel. Too high a content is not conducive to the plasticity, toughness and corrosion resistance of steel. Taking all factors into consideration, its mass percentage should be controlled within the range of 0.2% to 0.3%.

[0020] Si: Mainly used to improve strength, oxidation resistance and thermal fatigue resistance. Taking all factors into consideration, its mass percentage should be controlled within the range of 0.6% to 0.75%.

[0021] Mn: It is dissolved in steel to improve the hardenability and strength of the steel. Taking all factors into consideration, its mass percentage should be controlled within the range of 1.05% to 1.15%.

[0022] Cr: Mainly used to improve the hardenability and tempering stability of steel, thereby improving the strength and corrosion resistance of steel. However, too high a content will increase the cost. Taking all factors into consideration, its mass percentage should be controlled within the range of 0.75% to 0.84%.

[0023] Mo: Mainly used to improve the hardenability and tempering stability of steel, thereby improving the strength and comprehensive mechanical properties of steel. However, too high a content will increase the cost. Taking all factors into consideration, its mass percentage should be controlled within the range of 0.3% to 0.38%.

[0024] Ni: Improves low-temperature toughness and hot working properties. Taking all factors into consideration, its mass percentage should be controlled within the range of 0.15% to 0.23%.

[0025] Nb: When added to steel, it forms NbC and NbN with C and N in the steel, which inhibits austenite grain growth and refines grains, thereby improving strength and toughness. However, excessive Nb content will form excessive carbonitrides, increasing the brittleness of the steel and leading to increased costs. Taking all factors into consideration, its mass percentage should be controlled within the range of 0.07% to 0.12%.

[0026] Al: An important deoxidizer, it forms oxides with oxygen to deoxidize, and nitrides with nitrogen to eliminate some of the negative effects of nitrogen. It also refines grains and improves strength and toughness. Taking all factors into consideration, its mass percentage should be controlled within the range of 0.015% to 0.03%.

[0027] Ca: It can improve the properties and morphology of inclusions, thereby increasing the plasticity, toughness, and corrosion resistance of steel, and can ensure the deformation control effect of inclusions. Taking all factors into consideration, its mass percentage should be controlled within the range of 0.015% to 0.03%.

[0028] P: is a harmful element that mainly affects the plasticity, toughness and corrosion resistance of steel. Taking all factors into consideration, its mass percentage should be controlled within the range of ≤0.015%.

[0029] S: This is a harmful element that primarily affects the plasticity, toughness, and corrosion resistance of steel. Taking all factors into consideration, its mass percentage should be controlled within the range of ≤0.005%.

[0030] O, H, and N: These are harmful elements that primarily affect the plasticity, toughness, and corrosion resistance of steel. Taking all factors into consideration, the mass percentage of N should be controlled within the range of ≤0.008% (i.e., less than or equal to 0.008%); the sum of the mass percentages of O, H, and N should be controlled within the range of ≤0.01% (i.e., less than or equal to 0.01%).

[0031] In some embodiments, the steel for seamless steel pipe comprises the following chemical components in percentage by weight: C 0.2%~0.23%, Si 0.6%~0.65%, Mn 1.05%~1.08%, P 0.011%~0.015%, S0.003%~0.005%, Cr 0.75%~0.78%, Mo 0.3%~0.34%, Ni 0.15%~0.18%, Nb 0.07%~0.08%, Al 0.015%~0.02%, Ca 0.015%~0.018%, N 0.006%~0.008%, 0.008%≤O+H+N≤0.01%, the balance is Fe and unavoidable impurities.

[0032] In this embodiment, the steel used for the seamless steel pipe has high strength and high toughness, and the minimum room temperature yield strength reaches a steel grade level of 80 to 95 ksi.

[0033] In some embodiments, the steel for seamless steel pipe comprises the following chemical compositions in percentage by weight: C 0.2%~0.21%, Si 0.6%~0.63%, Mn 1.05%~1.07%, P 0.013%~0.015%, S0.003%~0.005%, Cr 0.75%~0.77%, Mo 0.3%~0.32%, Ni 0.15%~0.16%, Nb 0.07%, Al0.015%~0.018%, Ca 0.015%~0.017%, N 0.007%~0.008%, 0.009%≤O+H+N≤0.01%, the balance is Fe and unavoidable impurities.

[0034] In this embodiment, the steel used for the seamless steel pipe has high strength and high toughness, and the minimum room temperature yield strength reaches 80ksi steel grade level.

[0035] In some embodiments, the steel for seamless steel pipe comprises the following chemical compositions in percentage by weight: C 0.22%~0.23%, Si 0.64%~0.65%, Mn 1.06%~1.08%, P 0.011%~0.012%, S0.003%~0.004%, Cr 0.76%~0.78%, Mo 0.31%~0.34%, Ni 0.17%~0.18%, Nb 0.08%, Al0.019%~0.02%, Ca 0.016%~0.018%, N 0.006%~0.007%, 0.008%≤O+H+N≤0.009%, the balance is Fe and unavoidable impurities.

[0036] In this embodiment, the steel used for the seamless steel pipe has high strength and high toughness, and the minimum room temperature yield strength reaches 95ksi steel grade level.

[0037] In some embodiments, the steel for seamless steel pipe comprises the following chemical compositions in percentage by weight: C 0.24%~0.3%, Si 0.66%~0.75%, Mn 1.09%~1.15%, P 0.01%~0.012%, S0.002%~0.003%, Cr 0.79%~0.84%, Mo 0.33%~0.38%, Ni 0.19%~0.23%, Nb 0.09%~0.12%, Al 0.022%~0.03%, Ca 0.02%~0.03%, N 0.005%~0.006%, 0.007%≤O+H+N≤0.008%, the balance is Fe and unavoidable impurities.

[0038] In this embodiment, the steel used for the seamless steel pipe has high strength and high toughness, and the minimum room temperature yield strength reaches a steel grade level of 110 to 140 ksi.

[0039] In some embodiments, the steel for seamless steel pipe comprises the following chemical compositions in percentage by weight: C 0.24%~0.25%, Si 0.66%~0.67%, Mn 1.09%~1.1%, P 0.01%~0.012%, S0.002%~0.003%, Cr 0.79%~0.8%, Mo 0.33%~0.35%, Ni 0.19%~0.2%, Nb 0.09%, Al0.022%~0.023%, Ca 0.02%~0.022%, N 0.005%~0.006%, 0.007%≤O+H+N≤0.008%, the balance is Fe and unavoidable impurities.

[0040] In this embodiment, the steel used for the seamless steel pipe has high strength and high toughness, and the minimum room temperature yield strength reaches a steel grade level of 110ksi.

[0041] In some embodiments, the steel for seamless steel pipe comprises the following chemical compositions in percentage by weight: C 0.26%~0.27%, Si 0.69%~0.71%, Mn 1.11%~1.12%, P 0.01%~0.011%, S0.002%~0.003%, Cr 0.81%~0.82%, Mo 0.34%~0.36%, Ni 0.21%~0.22%, Nb 0.1%~0.11%, Al 0.025%~0.026%, Ca 0.025%~0.026%, N 0.005%~0.006%, 0.007%≤O+H+N≤0.008%, the balance is Fe and unavoidable impurities.

[0042] In this embodiment, the steel used for the seamless steel pipe has high strength and high toughness, and the minimum room temperature yield strength reaches the 125ksi steel grade level.

[0043] In some embodiments, the steel for seamless steel pipe comprises the following chemical compositions in percentage by weight: C 0.28%~0.3%, Si 0.73%~0.75%, Mn 1.13%~1.15%, P 0.011%~0.012%, S0.002%~0.003%, Cr 0.83%~0.84%, Mo 0.37%~0.38%, Ni 0.21%~0.23%, Nb 0.11%~0.12%, Al 0.027%~0.03%, Ca 0.028%~0.03%, N 0.005%~0.006%, 0.007%≤O+H+N≤0.008%, the balance is Fe and unavoidable impurities.

[0044] In this embodiment, the steel used for the seamless steel pipe has high strength and high toughness, and the minimum room temperature yield strength reaches a steel grade level of 140ksi.

[0045] At present, the chemical composition of the outer base pipe metal and the inner liner corrosion-resistant alloy of the bimetallic metallurgical composite oil casing is very different, which will lead to abnormal growth of the diffusion layer or mismatch of thermal expansion coefficient, and ultimately lead to problems such as low interface bonding strength between the outer base pipe and the inner liner, easy collapse and bulging of the inner liner. In addition, due to the large difference in chemical composition between the outer base pipe metal and the inner liner corrosion-resistant alloy, it will lead to phase change temperature window conflict and cooling rate mismatch, so heat treatment is difficult, and the heat treatment process has a great influence on its mechanical properties and corrosion resistance. Therefore, the chemical composition design and reasonable coordination of the outer base pipe and the inner liner are particularly important. In addition, various corrosive media contained in oil and gas, such as H2S (hydrogen sulfide), CO2 (carbon dioxide) and highly mineralized formation water (containing Cl - , i.e., chloride ions), can easily lead to pipe corrosion, seriously affecting the service life and safety of bimetallic metallurgical composite oil casing. Based on this, an embodiment of the present invention further provides a bimetallic metallurgical composite oil casing, wherein the bimetallic metallurgical composite oil casing comprises an inner liner and an outer base pipe sleeved outside the inner liner, the inner liner and the outer base pipe being metallurgically bonded; The outer base pipe is made of the seamless steel pipe steel described above in the embodiment of the present invention; The inner lining pipe comprises the following chemical components in percentage by mass: C (carbon) 0.15%~0.22%, Si (silicon) ≤1%, Mn (manganese) 0.25%~1%, P (phosphorus) ≤0.02%, S (sulfur) ≤0.01%, Ni (nickel) 0.5%~1.5%, Cr (chromium) 12%~14%, Mo (molybdenum) 0.2%~0.6%, Cu (copper) ≤0.25%, the balance is Fe (iron) and unavoidable impurities.

[0046] In this embodiment, the inner liner is made of 13Cr martensitic stainless steel, which has excellent resistance to corrosion from various corrosive media. C ensures hardenability, but carbide precipitation must be controlled; Cr forms a passivation film, enhancing corrosion resistance; Ni improves toughness and reduces brittleness; Mo inhibits pitting and crevice corrosion; and controlled S and P impurity levels reduce grain boundary segregation and prevent a decrease in corrosion resistance. Furthermore, in this embodiment, the outer base tube (medium-low carbon low-alloy steel) and inner liner (13Cr martensitic stainless steel) with specific chemical compositions form an effective metallurgical bond, achieving an interfacial bond strength of 400 MPa or greater. This addresses the problems of low interfacial bond strength between the outer base tube and inner liner, and the susceptibility of the inner liner to collapse and bulging, common in existing bimetallic metallurgical composite oil casing. Furthermore, the outer base tube with this specific chemical composition exhibits high strength and toughness, while the inner liner with this specific chemical composition exhibits excellent corrosion resistance. As a result, the bimetallic metallurgical composite oil casing and tubing, constructed from an outer base pipe and inner liner with this specific chemical composition, exhibits high strength, high toughness, and excellent corrosion resistance (resistance to CO2 corrosion, pitting corrosion, and H2S stress corrosion). The bimetallic metallurgical composite oil casing and tubing achieves minimum room-temperature yield strengths of 80 ksi, 95 ksi, 110 ksi, 125 ksi, and 140 ksi steel grades, respectively. The pipes also boast yield strengths of 634 to 1091 MPa, tensile strengths of 746 to 1186 MPa, transverse Charpy V-notch impact toughness at 0°C of 123 to 163 J, and elongation of 25 to 35%. In an environment with CO2 partial pressure ≤ 3MPa and temperature ≤ 120℃, the corrosion rate is ≤ 0.3mm / a (millimeter per year); the critical pitting temperature is ≥ 50℃; in an environment with H2S partial pressure ≤ 0.001MPa, it passes the NACE TM0177 A method (i.e., Laboratory test method A for resistance of metals to sulfide stress cracking and stress corrosion cracking in hydrogen sulfide environments) test, using solution A.

[0047] In some embodiments, the inner liner (13Cr martensitic stainless steel) comprises the following chemical components in percentage by weight: C 0.15%~0.22%, Si 0.35%~0.73%, Mn 0.25%~1%, P 0.015%~0.018%, S 0.008%~0.01%, Ni 0.5%~1.5%, Cr 12%~14%, Mo 0.2%~0.6%, Cu 0.11%~0.15%, the balance is Fe and unavoidable impurities.

[0048] An embodiment of the present invention further provides a bimetallic metallurgical composite oil casing, wherein the bimetallic metallurgical composite oil casing comprises an inner liner pipe and an outer base pipe sleeved outside the inner liner pipe, wherein the inner liner pipe is metallurgically bonded to the outer base pipe; The outer base pipe is made of the seamless steel pipe steel described above in the embodiment of the present invention; The inner lining pipe comprises the following chemical components in percentage by mass: C (carbon) ≤0.03%, Si (silicon) ≤0.5%, Mn (manganese) ≤0.5%, P (phosphorus) ≤0.02%, S (sulfur) ≤0.005%, Ni (nickel) 4%~6%, Cr (chromium) 13%~15%, Mo (molybdenum) 1.5%~2.5%, Cu (copper) 0.3%~1%, N (nitrogen) 0.05%~0.15%, Ti (titanium) 0.01%~0.5%, V (vanadium) ≤0.5%, the balance is Fe (iron) and unavoidable impurities.

[0049] In this embodiment, the material of the liner is super 13Cr martensitic stainless steel, which has good resistance to corrosion by various corrosive media. C is used to reduce carbide precipitation. Low C design can reduce carbide precipitation, reduce brittleness, and avoid grain boundary corrosion. Ni is used to improve toughness and resistance to H2S stress corrosion cracking (SSC). Mo is used to inhibit pitting and crevice corrosion. High Ni and Mo can improve resistance to H2S stress corrosion cracking and pitting corrosion. Cr is used to enhance the stability of the passivation film. Cu is used to improve CO2 corrosion resistance. N is used for solid solution strengthening and grain refinement. N and Cu are added in combination to enhance the repair ability of the passivation film. It is suitable for high Cl - environment. In addition, in this embodiment, an outer base pipe (medium-low carbon low alloy steel) and an inner liner pipe (super 13Cr martensitic stainless steel) with a specific chemical composition are used. The two can form an effective metallurgical bond, and the interface bonding strength reaches 400 MPa or above. This solves the problems of low interface bonding strength between the outer base pipe and the inner liner pipe of existing bimetallic metallurgical composite oil casing and the inner liner pipe, and the inner liner pipe is prone to collapse and bulging. At the same time, the outer base pipe with this specific chemical composition has high strength and high toughness, and the inner liner pipe with this specific chemical composition has good corrosion resistance. Therefore, the bimetallic metallurgical composite oil casing and the outer base pipe and the inner liner pipe with this specific chemical composition have high strength, high toughness and good corrosion resistance (resistance to CO2 corrosion, pitting corrosion and H2S stress corrosion). The bimetallic metallurgical composite oil casing and tubing can achieve strengths reaching 80ksi, 95ksi, 110ksi, 125ksi, and 140ksi steel grades, respectively. Yield strengths range from 634 to 1091 MPa, tensile strengths from 746 to 1186 MPa, transverse Charpy V-notch impact toughness at 0°C from 123 to 163 J, and elongation from 25% to 35%. In environments with a CO2 partial pressure of ≤5 MPa and a temperature of ≤150°C, the corrosion rate is ≤0.1 mm / a, the critical pitting temperature is ≥80°C, and the pipe passes NACE TM0177 Method A testing (using Solution A) in environments with a H2S partial pressure of ≤0.01 MPa and a pH of ≥3.5.

[0050] In some embodiments, the inner liner (super 13Cr martensitic stainless steel) comprises the following chemical components in percentage by weight: C 0.015%~0.021%, Si 0.21%~0.37%, Mn 0.3%~0.49%, P 0.013%~0.019%, S0.003%~0.005%, Ni 4%~6%, Cr 13%~15%, Mo 1.5%~2.5%, Cu 0.3%~1%, N 0.05%~0.15%, Ti 0.01%~0.5%, V 0.01%~0.5%, the balance is Fe and unavoidable impurities.

[0051] The present invention also provides a method for preparing the bimetallic metallurgical composite oil casing as described above, comprising the following steps: S1. After smelting, continuous casting, die forging, hot rolling and heat treatment according to the chemical composition and mass percentage of the liner pipe, the liner bar is obtained; S2. According to the chemical composition and mass percentage of the steel used for the seamless steel pipe, steelmaking, continuous casting, perforation and hot rolling are carried out to obtain the seamless steel pipe; S3, after heating the seamless steel pipe to 130-180° C., placing the lining bar inside the seamless steel pipe for heat assembly so that the lining bar and the seamless steel pipe form an interference fit, then sealing and welding the joint surfaces of the lining bar and the seamless steel pipe at both ends and evacuating the pipe to form a mechanical composite pipe blank; S4. The mechanical composite tube blank is subjected to die forging, piercing, hot continuous rolling, cold rolling, heat treatment and thread processing to obtain the bimetallic metallurgical composite oil casing.

[0052] In addition to the chemical composition of the outer base pipe and the inner liner, the preparation process of the bimetallic metallurgical composite oil casing also affects the interface bonding strength between the outer base pipe and the inner liner. The preparation process provided in this embodiment combined with the chemical composition of the outer base pipe and the inner liner can form an effective metallurgical bond between the outer base pipe and the inner liner, and the interface bonding strength reaches 400 MPa or above. The bimetallic metallurgical composite oil casing prepared by the preparation method provided in this embodiment has both corrosion resistance and high strength and high toughness, which can meet the demand for bimetallic metallurgical composite oil casing in corrosive oil and gas efficient development.

[0053] In step S1, in some embodiments, the steps of die forging, hot rolling and heat treatment specifically include: The bars obtained after continuous casting are heated to 1100-1200°C (e.g., 1100°C, 1120°C, 1150°C, 1180°C, or 1200°C) for die forging, and then hot rolled at a temperature of 1100-900°C (i.e., the initial rolling temperature is 1100°C and the final rolling temperature is 900°C). The bar obtained after hot continuous rolling is heated to 950-1050°C (for example, 950°C, 960°C, 980°C, 1000°C, 1010°C, 1020°C, 1030°C or 1050°C), kept at this temperature for 1-2 hours (for example, 1 hour, 1.5 hours or 2 hours), water quenched, and tempered at 620-680°C (for example, 620°C, 630°C, 650°C, 660°C or 680°C) for 2-3 hours (for example, 2, 2.5 or 3 hours).

[0054] In step S2, in some embodiments, the steps of piercing and hot rolling specifically include: The continuous casting billet bar obtained after continuous casting is heated to 1170-1200°C (for example, 1170°C, 1180°C, 1190°C or 1200°C), kept warm for 1.5-2h (for example, 1.5h, 1.8h or 2h), hot pierced, and then hot rolled at a temperature of 1150-900°C (that is, the initial rolling temperature is 1150°C and the final rolling temperature is 900°C), and air cooled after hot rolling.

[0055] In step S3, in some embodiments, the interference is 0.3-0.5 mm, for example, 0.3 mm, 0.4 mm, or 0.5 mm.

[0056] In step S4, in some embodiments, the step of die forging the mechanical composite tube blank specifically includes: The mechanical composite tube blank is heated to 1150-1250° C. (for example, 1150° C., 1160° C., 1170° C., 1180° C., 1190° C., 1200° C., 1210° C., 1220° C., 1230° C., 1240° C., or 1250° C.), and kept at this temperature for 2-3 hours (for example, 2 hours, 2.5 hours, or 3 hours) to allow the metals of the seamless steel pipe and the lining bar to fully diffuse. The tube is then die-forged with an initial forging temperature of 1130-1160° C. (for example, 1130° C., 1140° C., 1150° C., or 1160° C.), a final forging temperature of 900-950° C. (for example, 900° C., 910° C., 920° C., 930° C., 940° C., or 950° C.), a forging ratio of ≥3 (for example, 3, 4, or 5), and air-cooled after die-forging to obtain a first metallurgical composite tube blank.

[0057] In this embodiment, the metals of the seamless steel pipe and the liner bar can be metallurgically bonded, that is, the outer base pipe and the inner liner pipe can be metallurgically bonded.

[0058] In some embodiments, the steps of piercing and hot rolling specifically include: The first metallurgical composite tube billet is heated to 1130-1180° C. (for example, 1130° C., 1140° C., 1150° C., 1160° C., 1170° C., or 1180° C.), kept warm for 2-3 hours (for example, 2 hours, 2.5 hours, or 3 hours), and hot pierced; then hot continuous rolling is performed with an initial rolling temperature of 1130° C. and a final rolling temperature of 900-950° C. (for example, 900° C., 910° C., 920° C., 930° C., 940° C., or 950° C.), followed by water cooling to 650° C. and then air cooling to obtain a second metallurgical composite tube billet.

[0059] In some embodiments, the cold rolling step specifically includes: Cold rolling the second metallurgical composite tube blank to obtain a third metallurgical composite tube blank; During the cold rolling process, the deformation of a single pass is not greater than 30%. When the total deformation is 30% to 50%, an annealing treatment is performed. The annealing treatment comprises the steps of keeping the temperature at 900 to 950°C (for example, 900°C, 910°C, 920°C, 930°C, 940°C or 950°C) for 1.5 to 2 hours (for example, 1.5 hours, 1.8 hours or 2 hours) and then air cooling.

[0060] In some embodiments, the heat treatment step specifically includes: The third metallurgical composite tube is heated to 900-950° C. (for example, 900° C., 910° C., 920° C., 930° C., 940° C., or 950° C.), kept warm for 1.5-2 hours (for example, 1.5 hours, 1.8 hours, or 2 hours), and then water-cooled. Subsequently, the tube is tempered at 570-690° C. (for example, 570° C., 600° C., 610° C., 630° C., 650° C., 670° C., or 690° C.) for 2-3 hours (for example, 2 hours, 2.5 hours, or 3 hours), and then water-cooled.

[0061] In some embodiments, the thread processing step specifically includes: API (American Petroleum Institute) standard thread processing or special thread processing.

[0062] The present invention will be further described below by means of specific examples.

[0063] In the following examples, the chemical composition and mass percentage of the outer base pipe of the bimetallic metallurgical composite oil casing are shown in Table 1, and the chemical composition and mass percentage of the inner liner pipe are shown in Table 2.

[0064] Table 1. Chemical composition and mass percentage of the outer and inner substrate tubes in various embodiments

[0065] Table 2 Chemical composition of the inner liner tube in each embodiment and the mass percentage of the chemical composition

[0066] In Table 1, the "80," "95," "110," "125," and "140" in parentheses indicate corresponding steel grades of 80 ksi, 95 ksi, 110 ksi, 125 ksi, and 140 ksi, respectively. In Table 2, the "13Cr" in parentheses indicates 13Cr martensitic stainless steel, and the "Super 13Cr" in parentheses indicates super 13Cr martensitic stainless steel. In Table 2, "-" indicates the absence of the corresponding chemical component. For example, the bimetallic metallurgical composite oil casing liner in Example 1 does not contain nitrogen, titanium, or vanadium.

[0067] In Tables 1 and 2, the balance of the chemical compositions of the embodiments is Fe and inevitable impurities (taking Embodiment 1 in Table 1 as an example, the sum of the mass percentages of C, Si, Mn, P, S, Cr, Mo, Ni, Nb, Ca, Al, N, H, O, Fe and inevitable impurities is 100%, and the same applies to the other embodiments).

[0068] Example 1 This embodiment provides a method for preparing a bimetallic metallurgical composite oil casing, comprising the following steps: (1) Preparation of seamless steel pipes: Steelmaking and continuous casting were carried out according to the chemical composition and mass percentage of the outer base pipe in Example 1 in Table 1 to obtain a continuous casting billet bar; the continuous casting billet bar was heated to 1200°C, kept warm for 2 hours, and hot-pierced, and then hot-rolled at a temperature of 1150-900°C (i.e., the initial rolling temperature was 1150°C and the final rolling temperature was 900°C). After hot-rolling, the steel pipe was air-cooled to obtain a seamless steel pipe having a metallographic structure of ferrite + pearlite + bainite.

[0069] (2) Preparation of lining rods: According to the chemical composition of the lining pipe and the mass percentage of the chemical composition in Example 1 in Table 2, smelting and continuous casting are carried out to obtain rods; the rods are heated to 1200°C for die forging, and then hot rolled at a temperature of 1100-900°C (i.e., the initial rolling temperature is 1100°C and the final rolling temperature is 900°C). The rods obtained after hot rolling are heated to 1000°C, kept warm for 1.5 hours, water quenched, and tempered at 650°C for 2 hours to obtain lining rods whose metallographic structure is tempered martensite.

[0070] (3) Preparation of mechanical composite tube blanks: cleaning the inner surface of the seamless steel tube prepared above, and cleaning the outer surface of the lining rod prepared above; The cleaned seamless steel pipe is heated to 150°C, and the cleaned lining rod is placed inside the seamless steel pipe for hot assembly so that the two achieve an interference fit with an interference fit of 0.4mm. The joint surfaces of the seamless steel pipe and the lining rod are then sealed and vacuumed to form a mechanical composite tube blank.

[0071] (4) Die forging: The mechanical composite tube blank prepared above is heated to 1200°C and kept warm for 3 hours to allow the metal of the seamless steel pipe and the lining bar to fully diffuse. Then, die forging is performed with an initial forging temperature of 1150°C, a final forging temperature of 930°C, and a forging ratio of 5 to achieve metallurgical bonding between the seamless steel pipe and the lining bar. After die forging, the tube blank is air-cooled to form the first metallurgical composite tube blank.

[0072] (5) Piercing and hot rolling: The first metallurgical composite tube blank prepared above was heated to 1180°C, kept at this temperature for 3 h, and then hot-pierced; then hot-rolled with an initial rolling temperature of 1130°C and a final rolling temperature of 930°C, followed by water cooling to 650°C and air cooling to obtain a second metallurgical composite tube blank.

[0073] (6) Cold rolling: Before cold rolling, the oxide scale on the outer surface of the second metallurgical composite tube is cleaned, and then cold rolled to the required size to obtain the third metallurgical composite tube. Cold rolling is performed three times in total, with a single-pass deformation of 15%. After the second cold rolling, it is heated to 930℃ and kept at this temperature for 2 hours, then air-cooled, and then cold rolled for the third time.

[0074] (7) Tempering heat treatment and thread processing: The third metallurgical composite tube blank prepared above was heated to 930°C, kept at this temperature for 1.5 hours, and then water-cooled. It was then tempered at 690°C for 2 hours and then water-cooled. After thread processing at both ends of the tube, a bimetallic metallurgical composite oil casing was obtained, which included an outer base tube with an outer diameter of 177.8 mm and a wall thickness of 10.05 mm (whose metallographic structure was tempered bainite) and an inner liner tube with a wall thickness of 2.0 mm (whose metallographic structure was tempered martensite) located inside the outer base tube.

[0075] Example 2 This embodiment provides a method for preparing a bimetallic metallurgical composite oil casing, which differs from Example 1 only in that: In step (1), steelmaking is performed according to the chemical composition of the outer base tube and the mass percentage of the chemical composition in Example 2 in Table 1.

[0076] In step (2), smelting is performed according to the chemical composition and mass percentage of the liner pipe in Example 2 in Table 2.

[0077] Example 3 This embodiment provides a method for preparing a bimetallic metallurgical composite oil casing, which differs from Example 1 only in that: In step (1), steelmaking is performed according to the chemical composition of the outer base tube and the mass percentage of the chemical composition in Example 3 in Table 1.

[0078] In step (2), smelting is performed according to the chemical composition and mass percentage of the liner pipe in Example 3 in Table 2.

[0079] In step (7), the temperature is kept at 650°C for 2 hours for tempering.

[0080] Example 4 This embodiment provides a method for preparing a bimetallic metallurgical composite oil casing, which differs from Example 1 only in that: In step (1), steelmaking is performed according to the chemical composition of the outer base tube and the mass percentage of the chemical composition in Example 4 in Table 1.

[0081] In step (2), smelting is performed according to the chemical composition and mass percentage of the liner pipe in Example 4 in Table 2.

[0082] In step (7), the temperature is kept at 650°C for 2 hours for tempering.

[0083] Example 5 This embodiment provides a method for preparing a bimetallic metallurgical composite oil casing, which differs from Example 1 only in that: In step (1), steelmaking is performed according to the chemical composition of the outer base tube and the mass percentage of the chemical composition in Example 5 in Table 1.

[0084] In step (2), smelting is performed according to the chemical composition and mass percentage of the liner pipe in Example 5 in Table 2.

[0085] In step (7), the temperature is kept at 630°C for 2 hours for tempering.

[0086] Example 6 This embodiment provides a method for preparing a bimetallic metallurgical composite oil casing, which differs from Example 1 only in that: In step (1), steelmaking is performed according to the chemical composition of the outer base tube and the mass percentage of the chemical composition in Example 6 in Table 1.

[0087] In step (2), smelting is performed according to the chemical composition and mass percentage of the liner pipe in Example 6 in Table 2.

[0088] In step (7), the temperature is kept at 630°C for 2 hours for tempering.

[0089] Example 7 This embodiment provides a method for preparing a bimetallic metallurgical composite oil casing, which differs from Example 1 only in that: In step (1), steelmaking is performed according to the chemical composition of the outer base tube and the mass percentage of the chemical composition in Example 7 in Table 1.

[0090] In step (2), smelting is performed according to the chemical composition and mass percentage of the liner pipe in Example 7 in Table 2.

[0091] In step (7), the steel is tempered at 600°C for 2 hours.

[0092] Example 8 This embodiment provides a method for preparing a bimetallic metallurgical composite oil casing, which differs from Example 1 only in that: In step (1), steelmaking is performed according to the chemical composition of the outer base tube and the mass percentage of the chemical composition in Example 8 in Table 1.

[0093] In step (2), smelting is performed according to the chemical composition and mass percentage of the liner pipe in Example 8 in Table 2.

[0094] In step (7), the steel is tempered at 600°C for 2 hours.

[0095] Example 9 This embodiment provides a method for preparing a bimetallic metallurgical composite oil casing, which differs from Example 1 only in that: In step (1), steelmaking is performed according to the chemical composition of the outer base tube and the mass percentage of the chemical composition in Example 9 in Table 1.

[0096] In step (2), smelting is performed according to the chemical composition and mass percentage of the liner pipe in Example 9 in Table 2.

[0097] In step (7), the tempering is carried out at 570°C for 2 hours.

[0098] Example 10 This embodiment provides a method for preparing a bimetallic metallurgical composite oil casing, which differs from Example 1 only in that: In step (1), steelmaking is performed according to the chemical composition of the outer base tube and the mass percentage of the chemical composition in Example 10 in Table 1.

[0099] In step (2), smelting is performed according to the chemical composition and mass percentage of the inner liner pipe in Example 10 in Table 2.

[0100] In step (7), the tempering is carried out at 570°C for 2 hours.

[0101] The mechanical properties of the bimetallic metallurgical composite oil casing in each embodiment were tested, specifically the yield strength and tensile strength R m , elongation A , 0℃ transverse Charpy V-notch impact toughness A kv The interface bonding strength test between the inner liner pipe and the outer base pipe was carried out. The results are shown in Table 3.

[0102] Table 3. Mechanical properties test results of bimetallic metallurgical composite oil casing in various embodiments

[0103] Note: Different steel grades of bimetallic metallurgical composite oil casing use different total deformation ratios when testing yield strength. For 80ksi and 95ksi steel grades, the yield strength ratio is used. R t0.5 (i.e. the tensile stress corresponding to the total tensile deformation of 0.5%), the yield strength of the 110ksi steel grade test R t0.6 (i.e. the tensile stress corresponding to the total tensile deformation of 0.6%), the yield strength of the 125ksi steel grade test R t0.65 (i.e. the tensile stress corresponding to the total tensile deformation of 0.65%), the yield strength of the 140ksi steel grade test R t0.7 (i.e. the tensile stress corresponding to the total tensile deformation of 0.7%).

[0104] The inner liner of the bimetallic metallurgical composite oil casing in each embodiment was tested for corrosion resistance, specifically CO2 corrosion resistance, pitting corrosion resistance and H2S stress corrosion resistance. The results are shown in Table 4.

[0105] Table 4. Corrosion resistance test results of bimetallic metallurgical composite oil casing liner in various embodiments

[0106] In Table 4, the pitting corrosion resistance test was carried out according to ASTM G48, which is a standard test method for pitting and crevice corrosion resistance of stainless steel and related alloys using ferric chloride solution.

[0107] From the above test results, it can be seen that the yield strength of the 80ksi steel grade bimetallic metallurgical composite oil casing provided by the present invention is R t0.5The yield strength of the 95ksi steel grade bimetallic metallurgical composite oil casing is 634-637MPa, the tensile strength is 746-749MPa, the elongation is 35%, the 0℃ transverse Charpy V-notch impact toughness is 161-163J, the interface bonding strength between the outer base pipe and the inner liner is 411-415MPa, and it has good corrosion resistance. R t0.5 The yield strength of the 110ksi steel grade bimetallic metallurgical composite oil casing is 735-738MPa, the tensile strength is 845-848MPa, the elongation is 32%, the 0℃ transverse Charpy V-notch impact toughness is 151-153J, the interface bonding strength between the outer base pipe and the inner liner is 441-443MPa, and it has good corrosion resistance. R t0.6 The yield strength of the 125ksi steel grade bimetallic metallurgical composite oil casing is 881-883MPa, the tensile strength is 990-992MPa, the elongation is 30%, the 0℃ transverse Charpy V-notch impact toughness is 142-144J, the interface bonding strength between the outer base pipe and the inner liner is 485-489MPa, and it has good corrosion resistance. R t0.65 The tensile strength is 978-980MPa, the tensile strength is 1075-1077MPa, the elongation is 28%, the 0℃ transverse Charpy V-notch impact toughness is 133-136J, the interface bonding strength between the outer base pipe and the inner liner is 518-522MPa, and it has good corrosion resistance; the yield strength of 140ksi steel grade bimetallic metallurgical composite oil casing is R t0.7 The tensile strength is 1089-1091 MPa, the tensile strength is 1184-1186 MPa, the elongation is 25%, the 0℃ transverse Charpy V-notch impact toughness is 123-125J, the interface bonding strength between the outer base pipe and the inner liner pipe is 555-559 MPa, and it has good corrosion resistance.

[0108] It should be understood that the application of the present invention is not limited to the above examples. For those skilled in the art, improvements or changes can be made based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A steel for seamless steel pipe, characterized in that: The steel for seamless steel pipe includes the following chemical components in percentage by mass: C 0.2%~0.3%, Si 0.6%~0.75%, Mn 1.05%~1.15%, P≤0.015%, S≤0.005%, Cr 0.75%~0.84%, Mo 0.3%~0.38%, Ni 0.15%~0.23%, Nb 0.07%~0.12%, Al 0.015%~0.03%, Ca0.015%~0.03%, N≤0.008%, O+H+N≤0.01%, the balance is Fe and unavoidable impurities.

2. The steel for seamless steel pipe according to claim 1, characterized in that: The steel for seamless steel pipe includes the following chemical components in percentage by mass: C 0.2%~0.23%, Si 0.6%~0.65%, Mn 1.05%~1.08%, P 0.011%~0.015%, S 0.003%~0.005%, Cr 0.75%~0.78%, Mo 0.3%~0.34%, Ni 0.15%~0.18%, Nb 0.07%~0.08%, Al0.015%~0.02%, Ca 0.015%~0.018%, N 0.006%~0.008%, 0.008%≤O+H+N≤0.01%, the balance is Fe and unavoidable impurities.

3. The steel for seamless steel pipe according to claim 1, characterized in that: The steel for seamless steel pipe includes the following chemical components in percentage by mass: C 0.24%~0.3%, Si 0.66%~0.75%, Mn 1.09%~1.15%, P 0.01%~0.012%, S 0.002%~0.003%, Cr 0.79%~0.84%, Mo 0.33%~0.38%, Ni 0.19%~0.23%, Nb 0.09%~0.12%, Al0.022%~0.03%, Ca 0.02%~0.03%, N 0.005%~0.006%, 0.007%≤O+H+N≤0.008%, the balance is Fe and unavoidable impurities.

4. A bimetallic metallurgical composite 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, wherein the inner liner pipe is metallurgically bonded to the outer base pipe; The outer base pipe is made of the steel for seamless steel pipe according to any one of claims 1 to 3; The inner lining pipe comprises the following chemical components in percentage by mass: C 0.15%~0.22%, Si≤1%, Mn 0.25%~1%, P≤0.02%, S≤0.01%, Ni 0.5%~1.5%, Cr 12%~14%, Mo 0.2%~0.6%, Cu≤0.25%, the balance is Fe and unavoidable impurities.

5. A bimetallic metallurgical composite 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, wherein the inner liner pipe is metallurgically bonded to the outer base pipe; The outer base pipe is made of the steel for seamless steel pipe according to any one of claims 1 to 3; The inner lining pipe comprises the following chemical components in percentage by mass: C≤0.03%, Si≤0.5%, Mn≤0.5%, P≤0.02%, S≤0.005%, Ni 4%~6%, Cr 13%~15%, Mo1.5%~2.5%, Cu 0.3%~1%, N 0.05%~0.15%, Ti 0.01%~0.5%, V≤0.5%, the balance is Fe and unavoidable impurities.

6. A method for preparing a bimetallic metallurgical composite oil casing according to claim 4 or 5, characterized in that: The steps include: S1. After smelting, continuous casting, die forging, hot rolling and heat treatment according to the chemical composition and mass percentage of the liner pipe, the liner bar is obtained; S2. According to the chemical composition and mass percentage of the steel used for the seamless steel pipe, steelmaking, continuous casting, perforation and hot rolling are carried out to obtain the seamless steel pipe; S3, after heating the seamless steel pipe to 130-180° C., placing the lining bar inside the seamless steel pipe for heat assembly so that the lining bar and the seamless steel pipe form an interference fit, then sealing and welding the joint surfaces of the lining bar and the seamless steel pipe at both ends and evacuating the pipe to form a mechanical composite pipe blank; S4. The mechanical composite tube blank is subjected to die forging, piercing, hot continuous rolling, cold rolling, heat treatment and thread processing to obtain the bimetallic metallurgical composite oil casing.

7. The preparation method according to claim 6, characterized in that In step S4, the step of die forging the mechanical composite tube blank specifically includes: The mechanical composite tube blank is heated to 1150-1250° C., kept warm for 2-3 hours, and then die forged with an initial forging temperature of 1130-1160° C., a final forging temperature of 900-950° C., a forging ratio of ≥3, and air-cooled after die forging to obtain a first metallurgical composite tube blank.

8. The preparation method according to claim 7, characterized in that In step S4, the steps of piercing and hot rolling specifically include: The first metallurgical composite tube billet is heated to 1130-1180° C., kept warm for 2-3 hours, and hot pierced; then hot continuous rolling is performed with an initial rolling temperature of 1130° C. and a final rolling temperature of 900-950° C., followed by water cooling to 650° C. and air cooling to obtain a second metallurgical composite tube billet.

9. The preparation method according to claim 8, characterized in that In step S4, the cold rolling step specifically includes: Cold rolling the second metallurgical composite tube blank to obtain a third metallurgical composite tube blank; During the cold rolling process, the deformation of a single pass is not greater than 30%. When the total deformation is 30% to 50%, an annealing treatment is performed. The annealing treatment step is to keep the temperature at 900 to 950° C. for 1.5 to 2 hours and then air cool.

10. The preparation method according to claim 9, characterized in that In step S4, the heat treatment step specifically includes: The third metallurgical composite tube billet is heated to 900-950° C., kept at this temperature for 1.5-2 hours, and then water-cooled. Subsequently, the tube billet is tempered at 570-690° C. for 2-3 hours, and then water-cooled.

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