Pipeline steel for acid environment, bimetal metallurgy composite pipe and preparation method of bimetal metallurgy composite pipe

Abstract

The invention discloses pipeline steel for an acid environment, a bimetal metallurgy composite pipe and a preparation method of the bimetal metallurgy composite pipe, and relates to the technical field of manufacturing of pipes for oil and gas gathering and transportation. The pipeline steel for the acid environment comprises the following chemical components in percentage by mass: 0.07%-0.11% of C, 0.25%-0.37% of Si, 1.15%-1.35% of Mn, less than or equal to 0.012% of P, less than or equal to 0.003% of S, 0.01%-0.03% of Nb, 0.015%-0.03% of Al, 0.01%-0.025% of Ca, less than or equal to 0.005% of N, less than or equal to 0.002% of O, less than or equal to 0.00015% of H, less than or equal to 0.007% of O + H + N and the balance of Fe and inevitable impurities. The pipeline steel for the acid environment has enough strength, high toughness and good hydrogen sulfide stress corrosion resistance and hydrogen induced cracking resistance, and can meet the requirements of gathering and transportation of corrosive oil and gas.

Description

Technical Field

[0001] The present invention relates to the technical field of manufacturing pipes for oil and gas gathering and transportation, and in particular to a pipeline steel for acidic environments, a bimetallic metallurgical composite pipe and a preparation method thereof. Background Art

[0002] Currently, the proportion of corrosive media in oil and gas resources is increasing. For this type of oil and gas, effective corrosion control measures are required not only for oil well pipes used in exploration and development, but also for pipelines used for oil and gas gathering and transportation. Common pipe material options for corrosive oil and gas gathering and transportation pipelines include carbon steel with corrosion inhibitors, non-metallic pipes, stainless steel, and nickel-based alloys. However, these materials suffer from short lifespans, high brittleness, low reliability of joints, and high prices. Recently developed bimetallic composite pipes overcome these drawbacks and are gaining widespread application. Bimetallic composite pipes consist of an outer base pipe and an inner liner (also known as an inner cladding) positioned within the outer base pipe. Compared to bimetallic mechanical composite pipes, bimetallic metallurgical composite pipes offer a higher interface strength between the outer base pipe and the inner liner, leading to their wider application. However, there are still some problems with bimetallic metallurgical composite pipes. For example, the inner liner thickness of bimetallic metallurgical composite pipes is relatively small (usually 1 to 3 mm). When used as oil and gas gathering and transportation pipelines, it is difficult to completely avoid welding defects in the butt girth weld of the oil and gas gathering and transportation pipelines. Therefore, during long-term use, corrosive oil and gas often come into contact with the low-carbon low-alloy steel metal of the outer base pipe, causing localized corrosion or stress corrosion and hydrogen-induced cracking. Stress corrosion and hydrogen-induced cracking are more harmful and have more serious consequences. Therefore, the hydrogen sulfide stress corrosion and hydrogen-induced cracking of the outer base pipe in an acidic environment must be considered. However, at present, the hydrogen sulfide stress corrosion and hydrogen-induced cracking resistance of the outer base pipe in bimetallic metallurgical composite pipes is still relatively limited.

[0003] Therefore, the existing technology still needs to be improved and developed. Summary of the Invention

[0004] In view of the above-mentioned deficiencies in the prior art, the present invention aims to provide a pipeline steel for acidic environments, a bimetallic metallurgical composite pipe and a preparation method thereof, aiming to solve the problem of insufficient hydrogen sulfide stress corrosion and hydrogen-induced cracking resistance of the outer base pipe in the existing bimetallic metallurgical composite pipe.

[0005] The technical solutions of the present invention are as follows: A first aspect of the present invention provides a pipeline steel for use in sour environments, wherein the pipeline steel for use in sour environments comprises the following chemical components in percentage by mass: C 0.07%~0.11%, Si 0.25%~0.37%, Mn 1.15%~1.35%, P≤0.012%, S≤0.003%, Nb0.01%~0.03%, Al 0.015%~0.03%, Ca 0.01%~0.025%, N≤0.005%, O≤0.002%, H≤0.00015%, the balance is Fe and unavoidable impurities; And O+H+N≤0.007%.

[0006] Optionally, the pipeline steel for sour environment includes the following chemical components in percentage by mass: C 0.07%~0.08%, Si 0.31%~0.37%, Mn 1.15%~1.19%, P 0.01%~0.012%, S 0.002%~0.003%, Nb 0.01%, Al 0.022%~0.03%, Ca 0.01%~0.017%, N 0.0045%~0.005%, O 0.0017%~0.0018%, H 0.00014%~0.00015%, the balance is Fe and unavoidable impurities.

[0007] Optionally, the pipeline steel for sour environment includes the following chemical components in percentage by mass: C 0.09%~0.11%, Si 0.25%~0.29%, Mn 1.26%~1.35%, P 0.01%~0.012%, S 0.002%~0.003%, Nb 0.02%~0.03%, Al 0.015%~0.025%, Ca 0.019%~0.025%, N 0.0044%~0.0047%, O 0.0016%~0.0017%, H 0.00013%~0.00014%, the balance is Fe and unavoidable impurities.

[0008] Optionally, the pipeline steel for sour environment includes the following chemical components in percentage by mass: C 0.1%~0.11%, Si 0.25%~0.29%, Mn 1.31%~1.35%, P 0.01%~0.012%, S 0.002%~0.003%, Nb 0.03%, Al 0.018%~0.025%, Ca 0.019%~0.021%, N 0.0046%~0.0047%, O 0.0016%, H 0.00013%, the balance is Fe and unavoidable impurities.

[0009] A second aspect of the present invention provides a bimetallic metallurgical composite pipe, wherein the bimetallic metallurgical composite pipe 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 inner lining pipe comprises the following chemical components in percentage by mass: C≤0.03%, Si≤0.7%, Mn≤1%, P≤0.02%, S≤0.01%, Ni 5.5%~6.5%, Cr 22%~23%, Mo 3.2%~3.5%, N 0.15%~0.2%, the balance is Fe and unavoidable impurities; The outer base pipe is made of the pipeline steel for acidic environment as described above in the present invention.

[0010] A third aspect of the present invention provides a method for preparing the bimetallic metallurgical composite tube as described above, comprising the following steps: S1. According to the chemical composition and mass percentage of the liner pipe, steelmaking, continuous casting, hot rolling and heat treatment are performed to obtain liner bars; S2. Steelmaking, continuous casting, perforation and hot rolling are performed on the pipeline steel for acidic environment according to its chemical composition and mass percentage, thereby obtaining a seamless steel pipe; S3, after heating the seamless steel pipe to 130-150° 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, and heat treatment to obtain the bimetallic metallurgical composite tube.

[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 1150-1180° C., kept warm for 3-5 hours, and then die forged with a final forging temperature of 950° C. and a forging ratio of ≥5. After die forging, the tube blank is air-cooled 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 1150-1180° C., kept warm for 2-3 hours, and hot pierced; then hot rolled with an initial rolling temperature of 1150° C. and a final rolling temperature of 950° C., followed by water cooling to 600° 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 10%, and the total deformation is not greater than 50%. When the cumulative deformation is greater than or equal to 20%, a normalizing treatment is required. The normalizing treatment step is to keep the temperature at 880-910°C for 1-1.5 hours and then air cool.

[0014] Optionally, in step S4, the heat treatment step specifically includes: heating the third metallurgical composite tube to 1020-1070° C., keeping the temperature for 1-2 hours, and then cooling with water; Then heat to 900-930℃, keep warm for 1-1.5h, spray cool to 600℃, and air cool; Finally, heat to 650-700℃, keep warm for 1.5-2h, and then air cool.

[0015] Beneficial Effects: The pipeline steel for sour environments possesses sufficient strength, high toughness, and excellent resistance to hydrogen sulfide stress corrosion and hydrogen-induced cracking. The steel exhibits a minimum room-temperature yield strength of 245 MPa or greater, a tensile strength of 415 MPa or greater, a transverse Charpy V-notch impact toughness of 160 J or greater at -40°C, and a Vickers hardness (under a load of 10 kgf) of 200 or less. When loaded with 72% SMYS (the specified minimum yield strength), the steel exhibits no cracks or fissures after a 720-hour test in a saturated hydrogen sulfide solution according to NACE™ 0177 A (Laboratory Test Method A for Resistance of Metals to Sulfide Stress Cracking and Stress Corrosion Cracking in Hydrogen Sulfide Environments). Furthermore, in a hydrogen-induced cracking test, the steel exhibits a crack sensitivity rate of ≤2%, a crack length rate of ≤15%, and a crack thickness rate of ≤5%, meeting the requirements of corrosive oil and gas gathering and transportation. DETAILED DESCRIPTION

[0016] The present invention provides a pipeline steel for acidic environments, a bimetallic metallurgical composite pipe, and a method for preparing the same. To clarify the objectives, technical solutions, and advantages 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.

[0017] 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.

[0018] An embodiment of the present invention provides a pipeline steel for sour environments (i.e., low-carbon microalloyed pipeline steel), wherein the pipeline steel for sour environments includes the following chemical components in percentage by mass: C (carbon) 0.07%~0.11%, Si (silicon) 0.25%~0.37%, Mn (manganese) 1.15%~1.35%, P (phosphorus) ≤0.012%, S (sulfur) ≤0.003%, Nb (niobium) 0.01%~0.03%, Al (aluminum) 0.015%~0.03%, Ca (calcium) 0.01%~0.025%, N (nitrogen) ≤0.005%, O (oxygen) ≤0.002%, H (hydrogen) ≤0.00015%, the balance is Fe (iron) and unavoidable impurities; and O+H+N≤0.007%.

[0019] In this embodiment, the pipeline steel for sour environments possesses sufficient strength, high toughness, and excellent corrosion resistance (resistance to hydrogen sulfide stress corrosion and hydrogen-induced cracking). The pipeline steel for sour environments has a minimum room temperature yield strength of 245 MPa or greater, a tensile strength of 415 MPa or greater, a transverse Charpy V-notch impact toughness of 160 J or greater at -40°C, and a Vickers hardness (at a load of 10 kgf) of 200 or less. It exhibits no cracks or fissures after a 720-hour test in a saturated hydrogen sulfide solution using the NACE TM0177 A method with a 72% SMYS content. In a hydrogen-induced cracking test, the steel exhibits a crack sensitivity rate of ≤2%, a crack length rate of ≤15%, and a crack thickness rate of ≤5%, meeting the requirements of corrosive oil and gas gathering and transportation.

[0020] Specifically, the minimum room temperature yield strength of the pipeline steel for sour environments provided in this embodiment can reach the levels of L245S (or BS), L290S, L320S, L360S, and L390S steel grades, respectively. Taking L245S (or BS) as an example, L245S (or BS) is a nomenclature based on ISO (International Organization for Standardization) 3183 or API (American Petroleum Institute) 5L, where L represents pipeline steel, 245 or B (i.e., Grade B) indicates a minimum yield strength of 245 MPa, and S indicates sour service conditions, meaning the material must pass hydrogen sulfide stress corrosion testing. Taking L290S as another example, L represents pipeline steel, 290 indicates a minimum yield strength of 290 MPa, and S indicates sour service conditions, meaning the material must pass hydrogen sulfide stress corrosion testing. The meanings of the remaining symbols are similar.

[0021] Among them, the yield strength of L245S steel grade pipeline steel for acidic environment R t0.5 (i.e. the tensile stress corresponding to the total tensile strain of 0.5%) is 245-345MPa, and the tensile strength is 415-565MPa; the yield strength of L290S steel grade pipeline steel for acidic environment R t0.5 The yield strength of L320S steel grade pipeline steel for acidic environment is 290~390MPa, and the tensile strength is 415~565MPa;R t0.5 The yield strength of L360S steel grade pipeline steel for acidic environment is 320~420MPa, and the tensile strength is 435~585MPa; R t0.5 The yield strength of L390S steel grade pipeline steel for acidic environment is 360~460MPa, and the tensile strength is 460~610MPa. R t0.5 The hardness is 390~490MPa, and the tensile strength is 490~640MPa.

[0022] In this embodiment, pure steel with low carbon content, microalloying with Mn and Nb, Si-Al deoxidation to control nitrogen, and Ca treatment to control the morphology and properties of inclusions is used. The chemical composition design is relatively simple and has good overall performance. The role and mass percentage range of each chemical component 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 0.07% to 0.11%.

[0023] Si: It is a common element in steel. Taking all factors into consideration, its mass percentage should be controlled within the range of 0.25% to 0.37%.

[0024] Mn: Mainly used to improve the hardenability of steel, thereby increasing strength, but too high a content will increase segregation tendency and reduce corrosion resistance. Taking all factors into consideration, its mass percentage should be controlled within the range of 1.15% to 1.35%.

[0025] Nb: When added to steel, it forms NbC and NbN with C and N in the steel, which has the effect of hindering the growth of austenite grains and refining the grains, thereby improving strength and toughness. However, excessive content 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 0.01% to 0.03%.

[0026] Al: It is an important deoxidizer. It forms oxides with oxygen to deoxidize, and forms nitrides with nitrogen to eliminate some of the adverse effects of nitrogen. It also refines grains and improves strength and toughness. To ensure effective deoxidation and nitrogen control, it is recommended to control Al / N ≥ 3 (i.e., the ratio of the mass percentage of Al to the mass percentage of N is greater than or equal to 3). 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 enhancing the plasticity, toughness, and corrosion resistance of steel. To ensure the deformation control effect of inclusions, it is advisable to control Ca / S ≥ 3 (that is, the ratio of the mass percentage of Ca to the mass percentage of S is greater than or equal to 3). Taking all factors into consideration, its mass percentage should be controlled within the range of 0.01% to 0.025%.

[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 ≤0.012%.

[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 ≤0.003%.

[0030] O: It 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 ≤0.002%.

[0031] H: 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 ≤0.00015%.

[0032] Nitrogen: A harmful element, it primarily affects the plasticity, toughness, and corrosion resistance of steel. Taking all factors into consideration, its mass percentage should be controlled within 0.005% or less. Furthermore, O+H+N should be controlled within 0.007% or less (the sum of the mass percentages of O, H, and N should be less than or equal to 0.007%).

[0033] In some embodiments, the pipeline steel for sour environments includes the following chemical components in percentage by weight: C 0.07%~0.08%, Si 0.31%~0.37%, Mn 1.15%~1.19%, P 0.01%~0.012%, S 0.002%~0.003%, Nb 0.01%, Al 0.022%~0.03%, Ca 0.01%~0.017%, N 0.0045%~0.005%, O 0.0017%~0.0018%, H 0.00014%~0.00015%, the balance is Fe and unavoidable impurities.

[0034] In this embodiment, the pipeline steel for acidic environment has sufficient strength, high toughness and good corrosion resistance. Specifically, the pipeline steel for acidic environment can reach the level of L245S and L290S steel grades, and the yield strength is Rt0.5 The steel has a tensile strength of 245-390 MPa, a tensile strength of 415-565 MPa, a transverse Charpy V-notch impact toughness of 160 J or greater at -40°C, and a Vickers hardness (load of 10 kgf) of 200 or less. When loaded with 72% SMYS, no cracks or cracking occurred in a saturated hydrogen sulfide solution tested according to the NACE TM0177 A method for 720 hours. In the hydrogen-induced cracking test, the crack sensitivity rate was 0%, the crack length rate was 0%, and the crack thickness rate was 0%, which can meet the needs of corrosive oil and gas gathering and transportation.

[0035] In some embodiments, the pipeline steel for sour environments includes the following chemical components in percentage by weight: C 0.09%~0.11%, Si 0.25%~0.29%, Mn 1.26%~1.35%, P 0.01%~0.012%, S 0.002%~0.003%, Nb 0.02%~0.03%, Al 0.015%~0.025%, Ca 0.019%~0.025%, N 0.0044%~0.0047%, O 0.0016%~0.0017%, H 0.00013%~0.00014%, the balance is Fe and unavoidable impurities.

[0036] In this embodiment, the pipeline steel for acidic environment has sufficient strength, high toughness and good corrosion resistance. Specifically, the pipeline steel for acidic environment can reach the level of L320S, L360S and L390S steel grades, and the yield strength is R t0.5 The tensile strength is 320-490 MPa, the tensile strength is 435-640 MPa, the transverse Charpy V-notch impact toughness at -40°C is greater than or equal to 160 J, and the Vickers hardness (load is 10 kgf) is less than or equal to 200. When loaded with 72% SMYS, no cracks or cracks were found in the saturated hydrogen sulfide solution tested by the NACE TM0177 A method for 720 hours. In the hydrogen-induced cracking test, the crack sensitivity rate is 0%, the crack length rate is 0%, and the crack thickness rate is 0%, which can meet the needs of corrosive oil and gas gathering and transportation.

[0037] In some embodiments, the pipeline steel for sour environments includes the following chemical components in percentage by weight: C 0.1%~0.11%, Si 0.25%~0.29%, Mn 1.31%~1.35%, P 0.01%~0.012%, S 0.002%~0.003%, Nb 0.03%, Al 0.018%~0.025%, Ca 0.019%~0.021%, N 0.0046%~0.0047%, O 0.0016%, H 0.00013%, the balance is Fe and unavoidable impurities.

[0038] In this embodiment, the pipeline steel for acidic environment has sufficient strength, high toughness and good corrosion resistance. Specifically, the pipeline steel for acidic environment can reach the level of L360S and L390S steel grades, and the yield strength is R t0.5 The steel has a tensile strength of 360-490 MPa, a tensile strength of 460-640 MPa, a transverse Charpy V-notch impact toughness of 160 J or greater at -40°C, and a Vickers hardness (load of 10 kgf) of 200 or less. No cracks or cracking were observed in the NACE TM0177 A method saturated hydrogen sulfide solution test for 720 hours using 72% SMYS. In the hydrogen-induced cracking test, the crack sensitivity rate, crack length rate, and crack thickness rate were 0%, which meets the requirements of corrosive oil and gas gathering and transportation.

[0039] At present, the chemical composition of the outer base tube metal and the inner liner corrosion-resistant alloy of the bimetallic metallurgical composite tube is very different, which will lead to abnormal growth of the diffusion layer or mismatch of thermal expansion coefficient, etc., and ultimately lead to problems such as low interface bonding strength between the outer base tube and the inner liner, easy collapse and bulging of the inner liner. In addition, since the chemical composition of the outer base tube metal and the inner liner corrosion-resistant alloy is very different, it will lead to phase change temperature window conflict and cooling rate mismatch, so the 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 tube and the inner liner are particularly important. Based on this, an embodiment of the present invention also provides a bimetallic metallurgical composite tube, wherein the bimetallic metallurgical composite tube includes an inner liner and an outer base tube sleeved outside the inner liner, and the inner liner is metallurgically bonded to the outer base tube; The inner lining pipe comprises the following chemical components in percentage by mass: C (carbon) ≤ 0.03%, Si (silicon) ≤ 0.7%, Mn (manganese) ≤ 1%, P (phosphorus) ≤ 0.02%, S (sulfur) ≤ 0.01%, Ni (nickel) 5.5% to 6.5%, Cr (chromium) 22% to 23%, Mo (molybdenum) 3.2% to 3.5%, N (nitrogen) 0.15% to 0.2%, the balance being Fe (iron) and unavoidable impurities; The outer base pipe is made of the pipeline steel for acidic environment as described above in the embodiment of the present invention.

[0040] In this embodiment, the material of the inner lining pipe is improved 2205 duplex stainless steel (which can be recorded as 2205M1 duplex stainless steel). The inner lining pipe contains H2S (hydrogen sulfide), CO2 (carbon dioxide) and Cl - (chloride ion) environment has good resistance to pitting corrosion, intergranular corrosion and stress corrosion. In addition, in this embodiment, an outer base pipe (pipeline steel for acidic environment) and an inner liner pipe (2205M1 duplex stainless steel) with a specific chemical composition are used. The two can form an effective metallurgical bond, and the interface bonding strength reaches 210MPa and above, which solves the problems of low interface bonding strength between the outer base pipe and the inner liner pipe in the existing bimetallic metallurgical composite pipe, and easy collapse and bulging of the inner liner pipe. At the same time, the outer base pipe has good resistance to hydrogen sulfide stress corrosion and hydrogen-induced cracking, and the inner liner pipe has good resistance to pitting corrosion, intergranular corrosion and stress corrosion. Therefore, the bimetallic metallurgical composite pipe composed of the outer base pipe and the inner liner pipe with a specific chemical composition has good corrosion resistance. In addition, the bimetallic metallurgical composite pipe has sufficient strength and high toughness, and can specifically reach the steel grade levels of L245S, L290S, L320S, L360S and L390S respectively, and its yield strength R t0.5 The tensile strength is 299-444MPa, the tensile strength is 489-568MPa, the longitudinal Charpy V-notch impact toughness at -40℃ is 224-261J, the transverse Charpy V-notch impact toughness at -40℃ is 168-198J, and the Vickers hardness (load 10kgf) is 152-177. When the CO2 partial pressure is ≤0.25MPa, pH ≥4, H2S partial pressure ≤3kPa, Cl - Under the environment of concentration of 5000ppm and temperature of 60℃, the corrosion rate of the inner lining pipe in the bimetallic metallurgical composite pipe is less than 0.02mm / a (millimeter per year); loaded with 72% SMYS, the bimetallic metallurgical composite pipe did not show any cracks or cracks in the saturated hydrogen sulfide solution tested in NACE TM0177 A method for 720 hours; in the hydrogen-induced cracking test, the crack sensitivity rate of the bimetallic metallurgical composite pipe was 0%, the crack length rate was 0%, and the crack thickness rate was 0%, which can meet the requirements of CO2, H2S and Cl - Requirements for oil and gas gathering and transportation.

[0041] In some embodiments, the liner tube comprises the following chemical components in percentage by weight: C 0.01%~0.03%, Si 0.31%~0.7%, Mn 0.34%~1%, P 0.012%~0.015%, S 0.003%~0.005%, Ni 5.5%~6.5%, Cr 22%~23%, Mo 3.2%~3.5%, N 0.15%~0.2%, the balance is Fe and unavoidable impurities.

[0042] In some embodiments, in the bimetallic metallurgical composite pipe, the diameter and wall thickness of the outer base pipe and the wall thickness of the inner liner pipe can be set according to actual needs. For example, the diameter (outer diameter) of the outer base pipe is 60 to 360 mm (for example, it can be 60 mm, 80 mm, 100 mm, 120 mm, 150 mm, 180 mm, 200 mm, 220 mm, 250 mm, 280 mm, 300 mm, 320 mm, 350 mm or 360 mm, etc.), the wall thickness is 5 to 25 mm (for example, it can be 5 mm, 6 mm, 8 mm, 10 mm, 12 mm, 15 mm, 18 mm, 20 mm or 25 mm, etc.), and the wall thickness of the inner liner pipe is 1.5 to 3 mm (for example, it can be 1.5 mm, 1.8 mm, 2 mm, 2.2 mm, 2.5 mm, 2.8 mm or 3 mm, etc.).

[0043] The present invention also provides a method for preparing the bimetallic metallurgical composite tube as described above, which comprises the following steps: S1. According to the chemical composition and mass percentage of the liner pipe, steelmaking, continuous casting, hot rolling and heat treatment are performed to obtain liner bars; S2. According to the chemical composition and mass percentage of the chemical composition of the pipeline steel for acidic environment, steelmaking, continuous casting, perforation and hot rolling are performed to obtain a seamless steel pipe; S3. After heating the seamless steel pipe to 130-150° C. (e.g., 130° C., 140° C., or 150° C.), the lining bar is placed inside the seamless steel pipe for heat assembly, so that the lining bar and the seamless steel pipe form an interference fit. The lining bar and the seamless steel pipe are then sealed and welded at both ends of the joint surface, and vacuum is applied to form a mechanical composite pipe blank. S4. The mechanical composite tube blank is subjected to die forging, piercing, hot continuous rolling, cold rolling, and heat treatment to obtain the bimetallic metallurgical composite tube.

[0044] In addition to the chemical composition of the outer base pipe and the inner liner, the preparation process of the bimetallic metallurgical composite pipe also affects the interface bonding strength between the outer base pipe and the inner liner. The preparation process provided in this embodiment is combined with the chemical composition of the outer base pipe and the inner liner to form an effective metallurgical bond between the outer base pipe and the inner liner. The interface bonding strength reaches 210 MPa or above. The bimetallic metallurgical composite pipe prepared by the preparation method provided in this embodiment has corrosion resistance, sufficient strength and high toughness, and can meet the requirements of CO2, H2S and Cl - Requirements for oil and gas gathering and transportation.

[0045] In step S1, in some embodiments, hot rolling specifically includes the following steps: The bars obtained after continuous casting are heated to 1150-1200°C (for example, 1150°C, 1160°C, 1170°C, 1180°C, 1190°C or 1200°C), kept warm for 2 hours, and then hot rolled at a temperature of 1150-1000°C (i.e., the initial rolling temperature is 1150°C and the final rolling temperature is 1000°C). After rolling, they are immediately water-cooled at a cooling rate greater than 25°C / s, water-cooled to 400°C, and then air-cooled.

[0046] Heat treatment specifically includes the following steps: The bar obtained after hot continuous rolling is heated to 1040-1080°C (for example, 1040°C, 1050°C, 1060°C, 1070°C or 1080°C), kept at this temperature for 2 hours, and rapidly water-cooled at a cooling rate greater than 30°C / s. The bar is then water-cooled to 100°C and then air-cooled.

[0047] In step S2, in some embodiments, the piercing and hot rolling specifically include the following steps: The continuous casting billet bar obtained after continuous casting is heated to 1180-1230°C (for example, 1180°C, 1190°C, 1200°C, 1210°C, 1220°C or 1230°C), kept warm for 2 hours, hot pierced, and then hot rolled at a temperature of 1150-950°C (i.e., the initial rolling temperature is 1150°C and the final rolling temperature is 950°C).

[0048] 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.

[0049] 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 1150-1180° C. (for example, 1150° C., 1160° C., 1170° C., or 1180° C.), and kept warm for 3-5 hours (for example, 3 hours, 4 hours, or 5 hours) to fully diffuse the metal of the seamless steel pipe and the lining bar. Then, die forging is performed with a final forging temperature of 950° C. and a forging ratio of ≥5 (for example, 5, 6, or 7). After die forging, the tube is air-cooled to obtain a first metallurgical composite tube blank.

[0050] In this embodiment, the metals of the seamless steel pipe and the liner bar can be metallurgically bonded, ensuring that the outer base pipe and the inner liner pipe are finally metallurgically bonded.

[0051] In some embodiments, the steps of piercing and hot rolling specifically include: The first metallurgical composite tube billet is heated to 1150-1180° C. (for example, 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 1150° C. and a final rolling temperature of 950° C., followed by water cooling to 600° C. and then air cooling to obtain a second metallurgical composite tube billet.

[0052] 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 10%, and the total deformation is not greater than 50%; when the cumulative deformation is greater than or equal to 20%, a normalizing treatment is required, and the normalizing treatment step is to keep the temperature at 880-910°C (for example, 880°C, 890°C, 900°C or 910°C) for 1-1.5h (for example, 1h, 1.1h, 1.2h, 1.3h, 1.4h or 1.5h, etc.) and then air cool.

[0053] In some embodiments, the heat treatment (including solution treatment, normalizing heat treatment, and stress relief tempering) step specifically includes: The third metallurgical composite tube is heated to 1020-1070° C. (for example, 1020° C., 1030° C., 1040° C., 1050° C., 1060° C., or 1070° C.), kept at this temperature for 1-2 hours (for example, 1 hour, 1.5 hours, or 2 hours), and then water-cooled (i.e., solution treatment is performed to restore the performance of the 2205M1 duplex stainless steel inner liner and ensure corrosion resistance); Then, heat to 900-930°C (for example, 900°C, 910°C, 920°C or 930°C), keep warm for 1-1.5h (for example, 1h, 1.3h or 1.5h), spray cool to 600°C, and then air cool (i.e., normalizing heat treatment, which can improve the structure and refine the grains, thereby improving the mechanical properties); Finally, heat to 650-700°C (for example, 650°C, 660°C, 670°C, 680°C, 690°C or 700°C), keep warm for 1.5-2h (for example, 1.5h, 1.8h or 2h), and then air cool (i.e., stress relief tempering).

[0054] The present invention will be further described below by means of specific examples.

[0055] In the following embodiments, the chemical composition and mass percentage of the outer base pipe of the bimetallic metallurgical composite pipe are shown in Table 1, and the chemical composition and mass percentage of the inner liner pipe are shown in Table 2.

[0056] Table 1. Chemical composition and mass percentage of the outer and inner substrate tubes in various embodiments

[0057] Table 2 Chemical composition of the inner liner tube in each embodiment and the mass percentage of the chemical composition

[0058] In Tables 1 and 2 above, the chemical composition of each example is composed of Fe and inevitable impurities (taking Example 1 in Table 2 as an example, the sum of the mass percentages of C, Si, Mn, P, S, Cr, Ni, Mo, N, Fe, and inevitable impurities is 100%, and the same applies to the remaining examples). In Table 2, the "2205M1" in parentheses indicates 2205M1 duplex stainless steel.

[0059] Example 1 This embodiment provides a method for preparing a bimetallic metallurgical composite tube, comprising the following steps: (1) Preparation of seamless steel pipe: 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 1180°C, kept warm for 2 hours, hot pierced, and then hot rolled (initial rolling temperature was 1150°C, final rolling temperature was 950°C) to obtain a seamless steel pipe, whose metallographic structure was ferrite + pearlite.

[0060] (2) Preparation of lining rods: Steelmaking and continuous casting were carried out according to the chemical composition of the lining pipe and the mass percentage of the chemical composition in Example 1 in Table 2 to obtain rods; the rods were heated to 1150°C, kept warm for 2 hours, and then hot rolled (the initial rolling temperature was 1150°C and the final rolling temperature was 1000°C). After rolling, they were immediately water-cooled (cooling rate was 28°C / s), water-cooled to 400°C and then air-cooled; then heated to 1050°C, kept warm for 2 hours, quickly water-cooled (cooling rate was 35°C / s), water-cooled to 100°C and then air-cooled to obtain lining rods, whose metallographic structure was ferrite + austenite.

[0061] (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 0.5mm. The joint surfaces of the lining rod and the seamless steel pipe at both ends are then sealed and vacuumed to form a mechanical composite pipe blank.

[0062] (4) Die forging: The mechanical composite tube blank prepared above is heated to 1170°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. The final forging temperature is 950°C and the forging ratio is 5. The seamless steel pipe and the lining bar are metallurgically bonded. After die forging, the tube blank is air-cooled to form the first metallurgical composite tube blank.

[0063] (5) Piercing and hot rolling: The first metallurgical composite tube blank prepared above was heated to 1160°C, kept at this temperature for 2 h, and then hot-pierced; then hot-rolled with an initial rolling temperature of 1150°C and a final rolling temperature of 950°C, followed by water cooling to 600°C and air cooling to obtain a second metallurgical composite tube blank.

[0064] (6) Cold rolling: Before cold rolling, the oxide scale on the outer surface of the second metallurgical composite tube billet is cleaned, and then cold rolled to the required size to obtain the third metallurgical composite tube billet; a total of three cold rollings are performed, and the deformation of a single pass is 10%. After the second cold rolling, it is heated to 880 ° C and kept for 1 hour, then air-cooled, and then cold rolled for the third time.

[0065] (7) Heat treatment (including solution treatment, normalizing heat treatment and stress relief tempering): The third metallurgical composite tube blank prepared above is subjected to solution treatment, specifically, the third metallurgical composite tube blank is heated to 1070°C, kept at this temperature for 1.5 hours, and then water-cooled; The third metallurgical composite tube billet after the solid solution treatment is subjected to normalizing heat treatment, specifically, medium frequency induction heating is used to heat the third metallurgical composite tube billet after the solid solution treatment to 900°C, keep the temperature for 1.5 hours, spray cool to 600°C, and then air cool; The third metallurgical composite tube blank after normalizing heat treatment is subjected to stress relief tempering, specifically, the third metallurgical composite tube blank after normalizing heat treatment is heated to 700°C, kept warm for 1.5 hours, and then air-cooled to obtain a bimetallic metallurgical composite tube, which includes an outer base tube with an outer diameter of 168.3 mm and a wall thickness of 9.5 mm and an inner liner tube with a wall thickness of 1.8 mm located inside the outer base tube.

[0066] Example 2 This embodiment provides a method for preparing a bimetallic metallurgical composite tube, which differs from embodiment 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.

[0067] In step (2), steelmaking is performed according to the chemical composition of the inner liner pipe and the mass percentage of the chemical composition in Example 2 in Table 2.

[0068] Example 3 This embodiment provides a method for preparing a bimetallic metallurgical composite tube, which differs from embodiment 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.

[0069] In step (2), steelmaking is performed according to the chemical composition of the liner pipe and the mass percentage of the chemical composition in Example 3 in Table 2.

[0070] Example 4 This embodiment provides a method for preparing a bimetallic metallurgical composite tube, which differs from embodiment 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.

[0071] In step (2), steelmaking is performed according to the chemical composition of the inner liner pipe and the mass percentage of the chemical composition in Example 4 in Table 2.

[0072] Example 5 This embodiment provides a method for preparing a bimetallic metallurgical composite tube, which differs from embodiment 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.

[0073] In step (2), steelmaking is performed according to the chemical composition of the inner liner pipe and the mass percentage of the chemical composition in Example 5 in Table 2.

[0074] The mechanical properties of the bimetallic metallurgical composite pipes in Examples 1 to 5 were tested, specifically the yield strength R t0.5 ,tensile strength R m , elongation A 、HV10 (Vickers hardness, 10kgf load), -40℃ Charpy V-notch impact toughness A kv The interface bonding strength between the inner liner pipe and the outer base pipe was tested, and the results are shown in Table 3.

[0075] Table 3. Mechanical properties test results of bimetallic metallurgical composite tubes in various embodiments

[0076] The corrosion resistance of the bimetallic metallurgical composite pipes in Examples 1 to 5 was tested, specifically the hydrogen sulfide stress corrosion resistance and hydrogen induced cracking (HIC) resistance of the bimetallic metallurgical composite pipes were tested, and the corrosion rate of the inner liner of the bimetallic metallurgical composite pipe was tested. The test environment conditions for the corrosion rate were: CO2 partial pressure ≤ 0.25 MPa, pH ≥ 4, H2S partial pressure ≤ 3 kPa, Cl -The concentration was 5000 ppm and the temperature was 60° C. The results are shown in Table 4.

[0077] Table 4. Corrosion resistance test results of bimetallic metallurgical composite pipes in various embodiments

[0078] From the above test results, it can be seen that the bimetallic metallurgical composite pipe provided by the present invention has sufficient strength and toughness, as well as good resistance to hydrogen sulfide stress corrosion and hydrogen-induced cracking.

[0079] 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 pipeline steel for acidic environment, characterized in that: The pipeline steel for sour environment includes the following chemical components in percentage by mass: C 0.07%~0.11%, Si 0.25%~0.37%, Mn 1.15%~1.35%, P≤0.012%, S≤0.003%, Nb0.01%~0.03%, Al 0.015%~0.03%, Ca 0.01%~0.025%, N≤0.005%, O≤0.002%, H≤0.00015%, the balance is Fe and unavoidable impurities; And O+H+N≤0.007%.

2. The pipeline steel for acidic environment according to claim 1, characterized in that: The pipeline steel for sour environment includes the following chemical components in percentage by mass: C 0.07%~0.08%, Si 0.31%~0.37%, Mn 1.15%~1.19%, P 0.01%~0.012%, S 0.002%~0.003%, Nb 0.01%, Al 0.022%~0.03%, Ca 0.01%~0.017%, N 0.0045%~0.005%, O 0.0017%~0.0018%, H 0.00014%~0.00015%, the balance is Fe and unavoidable impurities.

3. The pipeline steel for acidic environment according to claim 1, characterized in that: The pipeline steel for sour environment includes the following chemical components in percentage by mass: C 0.09%~0.11%, Si 0.25%~0.29%, Mn 1.26%~1.35%, P 0.01%~0.012%, S 0.002%~0.003%, Nb 0.02%~0.03%, Al 0.015%~0.025%, Ca 0.019%~0.025%, N 0.0044%~0.0047%, O 0.0016%~0.0017%, H 0.00013%~0.00014%, the balance is Fe and unavoidable impurities.

4. The pipeline steel for acidic environment according to claim 1, characterized in that: The pipeline steel for sour environment includes the following chemical components in percentage by mass: C 0.1%~0.11%, Si 0.25%~0.29%, Mn 1.31%~1.35%, P 0.01%~0.012%, S 0.002%~0.003%, Nb 0.03%, Al 0.018%~0.025%, Ca 0.019%~0.021%, N 0.0046%~0.0047%, O 0.0016%, H 0.00013%, the balance is Fe and unavoidable impurities.

5. A bimetallic metallurgical composite pipe, characterized in that: The bimetallic metallurgical composite pipe 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 inner lining pipe comprises the following chemical components in percentage by mass: C≤0.03%, Si≤0.7%, Mn≤1%, P≤0.02%, S≤0.01%, Ni 5.5%~6.5%, Cr 22%~23%, Mo3.2%~3.5%, N 0.15%~0.2%, the balance is Fe and unavoidable impurities; The outer base pipe is made of the pipeline steel for acidic environment according to any one of claims 1 to 4.

6. A method for preparing a bimetallic metallurgical composite pipe according to claim 5, characterized in that: The steps include: S1. According to the chemical composition and mass percentage of the liner pipe, steelmaking, continuous casting, hot rolling and heat treatment are performed to obtain liner bars; S2. Steelmaking, continuous casting, perforation and hot rolling are performed on the pipeline steel for acidic environment according to its chemical composition and mass percentage, thereby obtaining a seamless steel pipe; S3, after heating the seamless steel pipe to 130-150° 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, and heat treatment to obtain the bimetallic metallurgical composite tube.

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 1150-1180° C., kept warm for 3-5 hours, and then die forged with a final forging temperature of 950° C. and a forging ratio of ≥5. After die forging, the tube blank is air-cooled 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 1150-1180° C., kept warm for 2-3 hours, and hot pierced; then hot rolled with an initial rolling temperature of 1150° C. and a final rolling temperature of 950° C., followed by water cooling to 600° 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 10%, and the total deformation is not greater than 50%. When the cumulative deformation is greater than or equal to 20%, a normalizing treatment is required. The normalizing treatment step is to keep the temperature at 880-910°C for 1-1.5 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: heating the third metallurgical composite tube to 1020-1070° C., keeping the temperature for 1-2 hours, and then cooling with water; Then heat to 900-930℃, keep warm for 1-1.5h, spray cool to 600℃, and air cool; Finally, heat to 650-700℃, keep warm for 1.5-2h, and then air cool.

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