A bimetallic metallurgically clad pipe billet for oil and gas service and a method of making the same

Abstract

This invention discloses a bimetallic metallurgical composite pipe blank for oil and gas transportation and its preparation method, relating to the technical field of bimetallic metallurgical composite pipe blank preparation. The preparation method includes the following steps: using a low-carbon low-alloy steel outer base pipe with a specific chemical composition and a stainless steel / corrosion-resistant alloy inner liner pipe, after roughening treatment, chemical nickel plating on the inner surface of the outer base pipe, assembly, and hot isostatic pressing treatment with specific process parameters, a metallurgical bonding interface is formed between the low-carbon low-alloy steel outer base pipe and the stainless steel / corrosion-resistant alloy inner liner pipe, which is composed of atomic interdiffusion of the outer base pipe, the nickel layer, and the inner liner pipe. This interface has a high bonding strength of not less than 300 MPa, and is uniform, dense, and defect-free, without continuous oxide films and brittle intermetallic compound layers.

Description

Technical Field

[0001] This invention relates to the field of bimetallic metallurgical composite pipe blank preparation technology, and in particular to a bimetallic metallurgical composite pipe blank for oil and gas transportation and its preparation method. Background Technology

[0002] In oil and gas field extraction and transportation, especially in deep-sea environments with high hydrogen sulfide (H2S), high carbon dioxide (CO2), and high chloride ion content, pipelines simultaneously face the challenges of high pressure, high stress, and extreme media corrosion. Pipelines made of a single material struggle to simultaneously achieve high strength, high toughness, excellent corrosion resistance, and low cost. For example, internal corrosion is a significant problem with carbon steel or low-alloy steel pipes, while using stainless steel or nickel-based alloy pipes entirely is extremely expensive. Therefore, bimetallic composite pipes, constructed with high-strength, low-carbon, low-alloy steel as the load-bearing base and a thin-walled corrosion-resistant alloy as the inner cladding, have become the most economical and reliable solution. However, they still face the following challenges: From a manufacturing perspective, the preparation of such bimetallic composite pipes typically requires first obtaining a composite pipe blank, which is then processed into a final product with the required dimensions and performance (i.e., bimetallic composite pipe) through processes such as hot extrusion, hot rolling and / or cold rolling, and heat treatment. The interfacial bonding quality of the composite pipe blank is crucial in determining the performance of the finished pipe. Existing methods for preparing composite pipe blanks, such as hot rolling composite, explosive composite, or direct hot pressing composite, have significant limitations. For example, hot rolling composite requires large deformation at high temperatures, and the interface is prone to oxidation, forming brittle phases; explosive composite results in a wavy interface, leading to work hardening and residual stress, and is difficult to form large-diameter pipe blanks; direct hot pressing composite suffers from the formation of a continuous oxide film between the aluminum, silicon, and chromium elements in low-carbon, low-alloy steel and the interface during heating, severely hindering atomic diffusion, and the migration of carbon elements easily forms a brittle carbide layer, resulting in a bonding strength typically less than 200 MPa, making interlayer delamination prone to occur during subsequent processing or service.

[0003] Furthermore, from a materials perspective, existing outer base tubes and inner lining tubes differ significantly in physical properties (such as coefficient of thermal expansion and phase transformation behavior) and metallurgical characteristics (diffusion of alloying elements and carbon migration), making it highly susceptible to forming brittle carbides (such as Cr) at the interface. 23 C6), nitrides (such as Cr2N), and intermetallic compounds (such as σ phase). These brittle phases severely impair the bonding strength and toughness of the interface, leading to interface failure of the composite tube blank during subsequent processing or service.

[0004] Therefore, developing a method for preparing a metallurgically bonded bimetallic composite tube blank that can achieve stable interface and high strength (≥300MPa) for oil and gas transportation is crucial for promoting the application of high-performance bimetallic metallurgical composite tubes.

[0005] Therefore, existing technologies still need to be improved and developed. Summary of the Invention

[0006] Based on the shortcomings of the prior art, the purpose of this invention is to provide a bimetallic metallurgical composite pipe blank for oil and gas transportation and its preparation method. The aim is to provide a pipe blank preparation method that can achieve a stable and high-strength (≥300MPa) metallurgical bond at the interface, and to solve the problem of low interface bonding strength caused by the huge differences in physical properties and metallurgical characteristics between the existing outer base pipe and inner liner pipe.

[0007] The technical solution of the present invention is as follows: In a first aspect, the present invention provides a method for preparing a bimetallic metallurgical composite pipe blank for oil and gas transportation, comprising the following steps: S1. Provide an outer base tube and an inner liner tube, and roughen the inner surface of the outer base tube and the outer surface of the inner liner tube so that the roughness of the inner surface of the outer base tube and the outer surface of the inner liner tube is 4.0 μm to 8.0 μm; The outer base tube comprises the following chemical components in weight percentage: The composition comprises: C 0.02%–0.22%, Si 0.10%–0.50%, P ≤0.015%, S ≤0.005%, Al 0.010%–0.050%, N ≤0.010%, O ≤0.002%, H ≤0.0002%; and includes one or more of the following chemical components in mass percentage: Mn 1.00%–1.80%, Cr 0.15%–0.35%, Mo 0.15%–0.35%, Ni 0.15%–0.35%, Cu 0.15%–0.25%, B 0.0005%–0.001%, V 0.01%–0.12%, Nb 0.01%–0.12%, Ti 0.010%–0.050%, RE 0.0010%–0.020%, Ca 0.010%~0.035%; the balance is Fe and unavoidable impurities, and V+Nb+Ti≤0.15%; The inner lining tube is made of 316L austenitic stainless steel, 2205 duplex stainless steel, Incoloy 825 corrosion-resistant alloy or Inconel 625 corrosion-resistant alloy. S2. Perform chemical nickel plating on the inner surface of the roughened outer base tube to form a nickel layer with a thickness of 0.01 mm to 0.05 mm, thus obtaining an outer base tube with a nickel layer on the inner surface. S3. Place the roughened inner liner into the outer base tube with a nickel layer on the inner surface, then seal the two ends of the inner liner and the outer base tube and vacuum them to form an assembly. S4. The assembly is placed under an inert atmosphere, at a temperature of 1050℃~1250℃ and an isostatic pressure of 100 MPa~200 MPa, and kept at the temperature and pressure for 2~6 hours. Then, it is cooled during the pressure holding or depressurization process to obtain the bimetallic metallurgical composite pipe blank for oil and gas transportation.

[0008] Optionally, the outer diameter of the outer base tube is 50 mm to 510 mm, and the wall thickness of the outer base tube is 10 mm to 60 mm; the wall thickness of the inner liner tube is 3 mm to 10 mm.

[0009] Optionally, in step S1, the roughening treatment specifically includes: sandblasting with white corundum alumina sand with a particle size of 60-120 mesh at a sandblasting pressure of 0.3 MPa-0.6 MPa; and / or, Step S1 also includes the steps of alkali washing, acid washing, water washing and drying of the roughened outer base tube and inner liner tube.

[0010] Optionally, the alkaline washing step specifically includes: The roughened outer base tube and inner liner tube are placed in an alkaline degreasing solution at 60℃~70℃ and ultrasonically cleaned for 20~30 minutes to obtain an alkaline-washed outer base tube and an alkaline-washed inner liner tube. The pickling steps specifically include: After alkali washing, the outer base tube is placed in a solution containing 5wt%–10wt% HCl and 0.3wt%–0.8wt% hexamethylenetetramine and soaked at 40℃–50℃ for 5–15 minutes. After alkali washing, the inner liner is placed in a solution containing 10wt%–20wt% HNO3 and 2wt%–5wt% HF and soaked at 50℃–60℃ for 3–10 minutes.

[0011] Optionally, the plating solution used in the electroless nickel plating is prepared by the following method: The plating solution is prepared by mixing 20-35 g / L nickel sulfate, 25-35 g / L sodium hypophosphite, 10-20 g / L sodium citrate, 5-15 ml / L lactic acid, 10-20 g / L sodium acetate, 1-5 mg / L stabilizer, and water. Then, ammonia is added to adjust the pH of the system to 4.5-5.5.

[0012] Optionally, the temperature of the plating solution used in the electroless nickel plating is 85°C to 92°C; the stabilizer includes at least one of thiourea and iodate.

[0013] Optionally, in step S3, after the roughened inner tube is cooled to below -50°C, it is coaxially placed in an outer base tube with a nickel layer on its inner surface at a temperature of room temperature to 80°C, such that the radial gap between the two is 0.15 mm to 1.0 mm on one side.

[0014] Optionally, step S4 specifically includes: The assembly was placed in a hot isostatic pressing apparatus and evacuated to a vacuum level of ≤1×10⁻⁶. -2 After Pa, inert gas is introduced, and then the temperature and pressure are simultaneously increased to 1050℃~1250℃ and 100 MPa~200 MPa at a heating rate of no more than 150℃ / h and a pressure increase rate of no more than 30 MPa / h, and held at the temperature and pressure for 2~6 hours. Then, during the pressure holding or depressurization process at a rate ≤15 MPa / h, the tube blank is water-cooled to 400℃~600℃, then depressurized and air-cooled to room temperature to obtain the bimetallic metallurgical composite tube blank for oil and gas transportation.

[0015] Optionally, when the inner liner is made of 316L austenitic stainless steel or 2205 duplex stainless steel, the temperature is raised to 1100℃~1180℃; when the inner liner is made of Incoloy 825 corrosion-resistant alloy or Inconel 625 corrosion-resistant alloy, the temperature is raised to 1150℃~1250℃.

[0016] In a second aspect, the present invention provides a bimetallic composite pipe blank for oil and gas transportation, wherein the bimetallic composite pipe blank for oil and gas transportation includes an outer base pipe and an inner liner pipe coaxially arranged from the outside to the inside, and the outer base pipe and the inner liner pipe are metallurgically bonded by a nickel layer between them. The outer base tube comprises the following chemical components in weight percentage: The composition comprises: C 0.02%–0.22%, Si 0.10%–0.50%, P ≤0.015%, S ≤0.005%, Al 0.010%–0.050%, N ≤0.010%, O ≤0.002%, H ≤0.0002%; and includes one or more of the following chemical components in mass percentage: Mn 1.00%–1.80%, Cr 0.15%–0.35%, Mo 0.15%–0.35%, Ni 0.15%–0.35%, Cu 0.15%–0.25%, B 0.0005%–0.001%, V 0.01%–0.12%, Nb 0.01%–0.12%, Ti 0.010%–0.05%, RE 0.0010%–0.020%, Ca 0.010%~0.035%, V +Nb+Ti≤0.15%; The inner lining tube is made of 316L austenitic stainless steel, 2205 duplex stainless steel, Incoloy 825 corrosion-resistant alloy, or Inconel 625 corrosion-resistant alloy.

[0017] Beneficial Effects: In this invention, the chemical composition of the outer base tube is first designed and matched with a corresponding inner liner tube. The outer base tube is made of low-carbon, low-alloy steel, with steel grades meeting API 5L standards of L245, L360, L415, L450, or L485. The inner liner tube is made of stainless steel or a corrosion-resistant alloy. Then, the outer base tube and inner liner tube are roughened to achieve a surface roughness Ra value of 4.0 μm to 8.0 μm, increasing the actual surface area and mechanical interlocking effect. This ensures the adhesion of subsequent plating layers and provides sufficient mechanical interlocking and diffusion channels for diffusion bonding. Finally, a uniform, dense, and well-bonded nickel layer with a thickness of 0.01 mm to 0.05 mm is deposited on the inner surface of the roughened outer base tube using electroless nickel plating. Next, the roughened inner liner is placed on top of an outer base tube with a nickel layer on its inner surface for assembly. Then, hot isostatic pressing (HIP) is performed using the specific process parameters mentioned above. Under high temperature and pressure, a transition zone is formed where atoms at the interface of the outer base tube with a specific chemical composition, the nickel layer, and the inner liner tube of a specific material interdiffusion and metallurgical bonding occur. This transition zone has a uniform and dense structure, is defect-free, and lacks continuous oxide films and brittle intermetallic compound layers. Simultaneously, the nickel layer between the outer base tube and the inner liner effectively isolates carbon diffusion from the outer base tube to the inner liner tube, preventing Cr... 23 The precipitation of carbides such as C6 is prevented, while the interface enrichment and oxidation of elements such as Al and Si on the outer base tube side are prevented, resulting in a pure diffusion-bonded interface, i.e., a transition zone, dominated by solid solutions. Finally, a bimetallic composite tube blank with an interfacial shear strength of not less than 300 MPa between the outer base tube and the inner liner tube is prepared, ensuring that the bimetallic composite tube blank can withstand subsequent large deformation processing such as hot piercing and hot rolling, and its integrity during service. This invention can achieve reliable composite bonding of outer base tubes with strengths from L245 to L485 steel grades with 316L, 2205, 825, and 625 corrosion-resistant materials, as well as reliable composite bonding of large-diameter outer base tubes with inner liner tubes.

[0018] This invention uses an outer base tube with a specific chemical composition to match an inner liner tube of a specific material, and combines it with a nickel layer. Through the above-mentioned preparation method, a bimetallic metallurgical composite tube blank with an interfacial strength of not less than 300 MPa is prepared. This effectively solves the problem of low interfacial bonding strength caused by the huge differences in physical properties and metallurgical characteristics between the outer base tube and the inner liner tube in the prior art. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the preparation process of bimetallic composite pipe blanks for oil and gas transportation in an embodiment of the present invention. Detailed Implementation

[0020] This invention provides a bimetallic metallurgical composite pipe blank for oil and gas transportation and its preparation method. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0022] If the embodiments of the present invention involve descriptions such as "first" or "second", such descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated.

[0023] This invention provides a method for preparing a bimetallic metallurgical composite pipe blank for oil and gas transportation, wherein, as shown in the embodiments of the present invention... Figure 1 As shown, it includes the following steps: S1. Provide an outer base tube and an inner liner tube, and roughen the inner surface of the outer base tube and the outer surface of the inner liner tube so that the roughness of the inner surface of the outer base tube and the outer surface of the inner liner tube is 4.0 μm to 8.0 μm; The outer base tube comprises the following chemical components in weight percentage: The composition comprises: C (carbon) 0.02%–0.22%, Si (silicon) 0.10%–0.50%, P (phosphorus) ≤0.015%, S (sulfur) ≤0.005%, Al (aluminum) 0.010%–0.050%, N (nitrogen) ≤0.010%, O (oxygen) ≤0.002%, H (hydrogen) ≤0.0002%; and includes one or more of the following chemical components in mass percentage: Mn (manganese) 1.00%–1.80%, Cr (chromium) 0.15%–0.35%, Mo (molybdenum) 0.15%–0.00%. 0.35%, Ni (nickel) 0.15%–0.35%, Cu (copper) 0.15%–0.25%, B (boron) 0.0005%–0.001%, V (vanadium) 0.01%–0.12%, Nb (niobium) 0.01%–0.12%, Ti (titanium) 0.010%–0.050%, RE (rare earth elements) 0.0010%–0.020%, Ca (calcium) 0.010%–0.035%; the balance is Fe (iron) and unavoidable impurities, and V+Nb+Ti≤0.15%; The inner lining tube is made of 316L austenitic stainless steel, 2205 duplex stainless steel, Incoloy 825 corrosion-resistant alloy or Inconel 625 corrosion-resistant alloy. S2. Perform chemical nickel plating on the inner surface of the roughened outer base tube to form a nickel layer with a thickness of 0.01 mm to 0.05 mm, thus obtaining an outer base tube with a nickel layer on the inner surface. S3. Place the roughened inner liner into the outer base tube with a nickel layer on the inner surface, then seal the two ends of the inner liner and the outer base tube and evacuate the vacuum to form an assembly (with a tube-in-tube structure, and sealing is performed to prevent gas from entering the interface in subsequent processes). S4. The assembly is placed under an inert atmosphere, at a temperature of 1050℃~1250℃ and an isostatic pressure of 100 MPa~200 MPa, and kept at the temperature and pressure for 2~6 hours. Then, it is cooled during the pressure holding or depressurization process to obtain the bimetallic metallurgical composite pipe blank for oil and gas transportation.

[0024] In this invention, firstly, the chemical composition of the outer base tube is designed and matched with a corresponding inner liner tube. The outer base tube is made of low-carbon, low-alloy steel, with steel grades meeting API 5L standards of L245, L360, L415, L450, or L485. The inner liner tube is made of stainless steel or a corrosion-resistant alloy. Then, both the outer base tube and the inner liner tube are roughened to achieve a surface roughness Ra value of 4.0 μm to 8.0 μm, increasing the actual surface area. This ensures the adhesion of subsequent plating layers and provides sufficient mechanical engagement and diffusion channels for diffusion bonding. Finally, a uniform, dense, and well-bonded nickel layer with a thickness of 0.01 mm to 0.05 mm is deposited on the inner surface of the roughened outer base tube using a chemical nickel plating method. Next, the roughened inner liner is placed on top of an outer base tube with a nickel layer on its inner surface for assembly. Then, hot isostatic pressing (HIP) is performed using the specific process parameters mentioned above. Under high temperature and pressure, interdiffusion and metallurgical bonding of atoms at the interfaces of the outer base tube with a specific chemical composition, the nickel layer, and the inner liner tube made of a specific material are achieved, forming a transition zone (i.e., a metallurgical interface). This transition zone has a uniform and dense structure, is defect-free, and lacks continuous oxide films and brittle intermetallic compound layers. Simultaneously, the nickel layer between the outer base tube and the inner liner effectively isolates carbon diffusion from the outer base tube to the inner liner, preventing Cr... 23The precipitation of carbides such as C6 is prevented, while the interface enrichment and oxidation of elements such as Al and Si on the outer base tube side are prevented, resulting in a pure diffusion-bonded interface, i.e., a transition zone, dominated by solid solutions. Finally, a bimetallic composite tube blank with an interfacial shear strength of not less than 300 MPa between the outer base tube and the inner liner tube is prepared, ensuring that the bimetallic composite tube blank can withstand subsequent large deformation processing such as hot piercing and hot rolling, and its integrity during service. This invention can achieve reliable composite bonding of outer base tubes with strengths from L245 to L485 steel grades with 316L, 2205, 825, and 625 corrosion-resistant materials, as well as reliable composite bonding of large-diameter outer base tubes with inner liner tubes.

[0025] Generally, the outer base tube and the inner liner tube differ greatly in physical properties (coefficient of thermal expansion, phase transformation behavior) and metallurgical characteristics (diffusion of alloying elements, carbon migration), making it extremely easy to form brittle carbides (such as Cr) at the interface. 23 C6), nitrides (such as Cr2N), and intermetallic compounds (such as σ phase). These brittle phases severely impair the interfacial bonding strength and toughness, leading to interfacial failure of the composite tube blank during subsequent processing or service. This invention, by matching an outer base tube with a specific chemical composition to an inner liner tube of a specific material, and simultaneously incorporating a nickel layer, utilizes the aforementioned specific preparation method to achieve the preparation of a bimetallic metallurgical composite tube blank with an interfacial strength of not less than 300 MPa. This effectively solves the problem of low interfacial bonding strength caused by the significant differences in physical and metallurgical properties between the outer base tube and the inner liner tube in existing technologies.

[0026] In step S1, the outer base tube is made of low-carbon, low-alloy steel, with a steel grade of L245, L360, L415, L450, or L485 according to the API 5L standard. The roles of different chemical components in the outer base tube are as follows: Carbon (C) is the most important strengthening element in steel. Increasing the C content can significantly improve the hardenability of steel and thus increase its strength. However, excessive C content will impair the ductility and toughness of the steel. Taking all factors into consideration, the C content should be controlled within the range of 0.02% to 0.22%.

[0027] Si is commonly found in steel as a precipitated element and deoxidizer. Appropriate amounts of Si can improve the hardenability of steel, thereby increasing its strength, corrosion resistance, and tempering stability. However, excessive Si content can increase the tendency for segregation in steel, promote the formation of banded structures, and thus impair the steel's ductility and toughness. Considering all factors, the Si content should ideally be controlled within the range of 0.10% to 0.50%.

[0028] Al reacts with oxygen to form fine, uniformly distributed oxides, which can refine grains and improve strength and toughness. It is also an important deoxidizer. The Al content should be controlled within the range of 0.010% to 0.050%.

[0029] Mn is mainly used to improve the hardenability of steel, thereby increasing its strength. It can partially replace the more expensive chromium (Cr). However, Mn has a strong tendency to segregate, and excessive content can lead to uneven microstructure and properties. Considering all factors, the Mn content should be controlled within the range of 1.00% to 1.80%.

[0030] Cr is mainly used to improve the hardenability and tempering stability of steel, thereby increasing its strength; however, excessive Cr content will increase costs. Considering all factors, the Cr content should ideally be controlled within the range of 0.15% to 0.35%.

[0031] Mo is mainly used to improve the hardenability of steel, thereby increasing its strength and tempering stability; however, excessive content is not economically viable. Mo also helps to reduce phosphorus segregation. Considering all factors, the Mo content should be controlled within the range of 0.15% to 0.35%.

[0032] Ni is mainly used to improve the hardenability of steel, thereby increasing its strength and low-temperature toughness. It can also reduce the hot cracking tendency of Cu-containing steel, but excessive content will increase costs. Taking all factors into consideration, the Ni content should be controlled within the range of 0.15% to 0.35%.

[0033] Cu can improve corrosion resistance in non-oxidizing media and reduce susceptibility to pitting corrosion; it can also improve the fluidity of steel, thereby improving casting process performance. However, excessive content can lead to Cu embrittlement. Taking all factors into consideration, the Cu content should be controlled between 0.15% and 0.25%.

[0034] Adding boron (B) to steel can significantly improve its hardenability and thus its strength, but excessive amounts can cause boron embrittlement. Considering all factors, the B content should ideally be controlled within the range of 0.0005% to 0.001%.

[0035] When v is added to steel, it forms VC and VN with the carbon and nitrogen in the steel. This helps to inhibit austenite grain growth and refine the grains, thereby improving strength and toughness. However, excessive v content will form too many v carbonitride compounds, increasing the brittleness of the steel and leading to higher costs. Considering all factors, the v content should ideally be controlled within the range of 0.01% to 0.12%.

[0036] When nitrogen (Nb) is added to steel, it forms NbC and NbN compounds, which inhibit austenite grain growth and refine the grain structure, thereby improving strength and toughness. However, excessive Nb content can lead to the formation of too many carbon and nitrogen compounds, increasing the brittleness of the steel and raising costs. Considering all factors, the Nb content should ideally be controlled within the range of 0.01% to 0.12%.

[0037] Adding titanium (Ti) to steel has deoxidizing and nitrogen-fixing effects. It combines with carbon (C) and nitrogen (N) in the steel to form TiC and TiN, which inhibit austenite grain growth and refine the grain structure, thereby improving strength and toughness. However, excessive Ti content can lead to the formation of too many Ti carbon and nitrogen compounds, increasing the brittleness of the steel and raising costs. Considering all factors, the Ti content should ideally be controlled within the range of 0.010% to 0.050%.

[0038] RE has multiple functions, including purifying molten steel, refining grains, modifying inclusions, and alloying. Taking all factors into consideration, the content of RE should be controlled within the range of 0.0010% to 0.020%.

[0039] Ca can improve the properties and morphology of inclusions, thereby enhancing the toughness and corrosion resistance of steel. Considering all factors, the Ca content should ideally be controlled within the range of 0.010% to 0.035%.

[0040] P is a harmful impurity element that mainly affects the ductility and toughness of steel. The P content should be controlled within the range of 0% to 0.015%.

[0041] Sulfur (S) is a harmful impurity element that mainly affects the ductility and toughness of steel. The S content should be controlled within the range of 0% to 0.005%.

[0042] N, H, and O are harmful gaseous elements that mainly affect the ductility and toughness of steel. Their contents should be controlled within the range of N ≤ 0.010%, O ≤ 0.002%, and H ≤ 0.0002%.

[0043] The aforementioned alloying elements and their content ranges are not only related to obtaining bimetallic composite pipe blanks with excellent bonding strength, but also to the final bimetallic composite pipe products that possess strength, plasticity, toughness, and corrosion resistance. These alloying elements and their constituent systems must also be adaptable to subsequent processing techniques such as hot piercing, hot continuous rolling, cold rolling, and heat treatment to ensure the production of bimetallic composite pipe products for oil and gas transportation with excellent overall performance.

[0044] In some embodiments, the outer diameter (i.e., outer diameter) of the outer base tube is 50 mm to 510 mm (e.g., it can be 50 mm, 100 mm, 150 mm, 200 mm, 250 mm, 300 mm, 350 mm, 400 mm, 450 mm, 500 mm, or 510 mm, etc.), and the wall thickness of the outer base tube is 10 mm to 60 mm (e.g., it can be 10 mm, 20 mm, 30 mm, 40 mm, 50 mm, or 60 mm, etc.); the wall thickness of the inner liner tube is 3 mm to 10 mm (e.g., it can be 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, or 10 mm, etc.).

[0045] In this invention, the isotropic pressure provided by hot isostatic pressing ensures the uniformity and consistency of the interface between the outer base pipe and the inner liner pipe, especially for the pipe diameter and wall thickness.

[0046] In some embodiments, the roughening process specifically includes: sandblasting with white corundum abrasive with a particle size of 60-120 mesh (e.g., 60, 70, 80, 90, 100, 110, or 120 mesh, etc.), and a sandblasting pressure of 0.3 MPa-0.6 MPa (e.g., 0.3 MPa, 0.4 MPa, 0.6 MPa, or 0.6 MPa, etc.).

[0047] In some embodiments, step S1 further includes the steps of alkali washing, acid washing, water washing and drying of the roughened outer base tube and inner liner tube.

[0048] By performing the above-mentioned treatment on the outer base tube and the inner liner tube in this invention, a specific surface morphology and extremely high cleanliness can be obtained.

[0049] In some embodiments, the alkaline washing step (specifically, ultrasonic alkaline washing, the purpose of which is to thoroughly remove grease) specifically includes: The roughened outer base tube and inner liner tube are placed in an alkaline degreasing solution at 60℃~70℃ (e.g., 60℃, 62℃, 65℃, 68℃ or 70℃, etc.) and ultrasonically cleaned for 20~30 minutes (e.g., 20 minutes, 22 minutes, 25 minutes, 28 minutes or 30 minutes, etc.) to obtain the alkaline-washed outer base tube and alkaline-washed inner liner tube.

[0050] The alkaline degreasing solution comprises the following components in varying amounts: NaOH 30 g / L~50 g / L, Na2CO3 20 g / L~30 g / L, Na3PO4 10 g / L~20 g / L, surfactant 2 g / L~5 g / L, and water.

[0051] The surfactant includes at least one of potassium phenol ethoxyphosphate (PPE1040K), alkyl glycoside (APG), and alkylphenol polyoxyethylene ether. The alkyl glycoside includes n-hexyl glucoside (APG06), and the alkylphenol polyoxyethylene ether includes at least one of polyoxyethylene-8-octylphenyl ether (X-100).

[0052] Specifically, the surfactant is a compound of APG06, PPE1040K and X-100 in a mass ratio of 2:2:1.

[0053] In some embodiments, the pickling (i.e., pickling activation, the purpose of which is to remove the passivation film and obtain an activated surface) step specifically includes: After alkaline washing, the outer base tube is placed in a solution containing 5wt%–10wt% HCl and 0.3wt%–0.8wt% hexamethylenetetramine (as a corrosion inhibitor) and immersed at 40℃–50℃ for 5–15 minutes (e.g., 5 minutes, 6 minutes, 7 minutes, 8 minutes, 10 minutes, 12 minutes, or 15 minutes, etc.). After alkali washing, place the inner liner in a solution containing 10wt%–20wt% (mass percentage) HNO3 and 2wt%–5wt% (mass percentage) HF, and immerse it at 50℃–60℃ (e.g., 50℃, 52℃, 55℃, 58℃, or 60℃, etc.) for 3–10 minutes (e.g., 3 minutes, 4 minutes, 5 minutes, 6 minutes, 7 minutes, 8 minutes, 9 minutes, or 10 minutes, etc.).

[0054] In some embodiments, the washing and drying steps specifically include: Rinse with deionized water at least three times, then dehydrate with anhydrous ethanol and dry thoroughly in a drying oven at 90°C–110°C. The treated surface should meet the cleanliness standard of a continuous water film.

[0055] The above steps of alkaline washing, acid washing, water washing and drying can effectively remove the passivation film and obtain an activated surface.

[0056] In step S2, in some embodiments, the plating solution used for electroless nickel plating is prepared by the following method: The plating solution is prepared by mixing 20-35 g / L nickel sulfate, 25-35 g / L sodium hypophosphite, 10-20 g / L sodium citrate, 5-15 ml / L lactic acid, 10-20 g / L sodium acetate, 1-5 mg / L stabilizer, and water. Then, ammonia is added to adjust the pH of the system to 4.5-5.5.

[0057] The specific concentrations of nickel sulfate can be 20 g / L, 22 g / L, 25 g / L, 28 g / L, 30 g / L, 32 g / L, or 35 g / L, etc.; the specific concentrations of sodium hypophosphite can be 25 g / L, 26 g / L, 27 g / L, 28 g / L, 29 g / L, 30 g / L, 32 g / L, or 35 g / L, etc.; the specific concentrations of sodium citrate can be 10 g / L, 12 g / L, 15 g / L, 18 g / L, or 20 g / L; the specific concentrations of lactic acid can be 5 mL / L, 6 mL / L, 8 mL / L, 10 mL / L, 11 mL / L, 12 mL / L, 13 mL / L, or 15 mL / L, etc.; the specific concentrations of sodium acetate can be 10 g / L, 12 g / L, 15 g / L, 18 g / L, or 20 g / L; and the specific concentrations of stabilizers can be 1 mg / L, 2 mg / L, etc. mg / L, 3 mg / L, 4 mg / L or 5 mg / L, etc.

[0058] In some embodiments, the temperature of the electroless nickel plating solution is 85°C to 92°C (e.g., 85°C, 86°C, 87°C, 88°C, 89°C, 90°C, 91°C, or 92°C, etc.); the stabilizer includes at least one of thiourea and iodate.

[0059] To ensure a uniform coating, the plating solution must circulate within the inner cavity of the outer base tube. Furthermore, the specific electroless nickel plating time can be adjusted based on the nickel layer thickness and deposition rate (10 μm / h to 25 μm / h). For example, if the nickel layer thickness is 0.02 mm and the deposition rate is 10 μm / h, the electroless nickel plating time would be 2 hours.

[0060] In step S3, in some embodiments, after the roughened inner liner is cooled to below -50°C, it is coaxially placed inside an outer base tube with a nickel layer on its inner surface, which has a temperature of room temperature to 80°C. The radial gap between the two (i.e., the distance between the outer surface of the inner liner and the inner surface of the outer base tube with the plating, which is half the difference between the inner diameter of the outer base tube with the nickel plating and the outer diameter of the inner liner) is 0.15 mm to 1.0 mm, for example, it can be 0.15 mm, 0.2 mm, 0.25 mm, 0.3 mm, 0.35 mm, 0.4 mm, 0.45 mm, 0.5 mm, 0.55 mm, 0.6 mm, 0.65 mm, 0.7 mm, 0.75 mm, 0.8 mm, 0.85 mm, 0.9 mm, 0.95 mm, or 1.0 mm. In this embodiment, a temperature difference method is used to assist assembly to prevent damage to the nickel layer. The inner liner is cooled to a low temperature (e.g., below -50°C) to shrink, while the outer base tube is kept at room temperature or slightly heated (≤80°C), and then quickly aligned and assembled. Furthermore, the aforementioned gap ensures smooth assembly and provides space for the plastic deformation of the outer base tube during subsequent hot isostatic pressing.

[0061] In some implementations, step S4 specifically includes: The assembly was placed in a hot isostatic pressing apparatus and evacuated to a vacuum level of ≤1×10⁻⁶. -2 After Pa, an inert gas (such as high-purity argon, which serves as the pressure medium and protective gas) is introduced. Then, the temperature and pressure are simultaneously increased to 1050℃~1250℃ (e.g., 1050℃, 1060℃, 1070℃, 1080℃, 1090℃, 1100℃, 1120℃, 1150℃, 1180℃, 1200℃, 1210℃, 1220℃, 1230℃, 1240℃ or 1250℃, etc.) and 100 MPa~200 MPa (e.g., 100 MPa, 120 MPa, 150 MPa, 180 MPa or 200 MPa, etc.) at a heating rate not exceeding 150℃ / h and a pressure increase rate not exceeding 30MPa / h, and held at these temperatures and pressures for 2~6 hours (e.g., 2 hours, 3 hours, 4 hours, 5 hours or 6 hours, etc.). Stop heating, and then water cool to 400℃~600℃ (e.g., water cooling to 600℃, 500℃, 400℃, etc., depending on the characteristics of the inner liner material) during the pressure holding or depressurization process at a rate ≤15 MPa / h (e.g., 15 MPa / h, 14 MPa / h, 13 MPa / h, 12 MPa / h, 11 MPa / h, 10 MPa / h, 9 MPa / h, 8 MPa / h, 7 MPa / h, or 6 MPa / h, etc.) while maintaining pressure or at a rate ≤15 MPa / h (e.g., 15 MPa / h, 14 MPa / h, 13 MPa / h, 12 MPa / h, 11 MPa / h, 10 MPa / h, 9 MPa / h, 8 MPa / h, 7 MPa / h, or 6 MPa / h, etc.) while depressurizing. Then depressurize and air cool to room temperature to obtain the bimetallic metallurgical composite pipe blank for oil and gas transportation.

[0062] In this embodiment, during hot isostatic pressing, the aforementioned temperature causes significant atomic interdiffusion between the nickel layer and the metals on both sides, forming a solid solution bond; the aforementioned pressure ensures tight microscopic contact at the interface, eliminates porosity, and promotes plastic flow of the metal at the interface. In this invention, the bimetallic composite tube blank prepared by the above method achieves complete metallurgical bonding between the low-carbon, low-alloy steel outer base tube and the inner liner tube through a transition zone formed by the diffusion of the original nickel layer. This transition zone has a dense structure, without continuous oxide films or brittle intermetallic compound layers. According to ASTM A265 standard, the interfacial shear strength is not less than 300 MPa in compression-shear tests.

[0063] In this embodiment, the cooling system used helps prevent sensitization of the corrosion-resistant material of the inner lining tube and alleviates thermal stress.

[0064] In some embodiments, when the inner liner is made of 316L austenitic stainless steel or 2205 duplex stainless steel, the temperature is raised to 1100℃~1180℃ (e.g., 1100℃, 1120℃, 1130℃, 1140℃, 1150℃, or 1180℃, etc.); when the inner liner is made of Incoloy 825 corrosion-resistant alloy or Inconel 625 corrosion-resistant alloy, the temperature is raised to 1150℃~1250℃ (e.g., 1150℃, 1180℃, 1200℃, 1210℃, 1220℃, 1230℃, 1240℃, or 1250℃, etc.).

[0065] This invention also provides a bimetallic composite pipe blank for oil and gas transportation, wherein the bimetallic composite pipe blank for oil and gas transportation includes an outer base pipe and an inner liner pipe coaxially arranged from the outside to the inside, and the outer base pipe and the inner liner pipe are metallurgically bonded by a nickel layer between them. The outer base tube comprises the following chemical components in weight percentage: The composition comprises: C 0.02%–0.22%, Si 0.10%–0.50%, P ≤0.015%, S ≤0.005%, Al 0.010%–0.050%, N ≤0.010%, O ≤0.002%, H ≤0.0002%; and includes one or more of the following chemical components in mass percentage: Mn 1.00%–1.80%, Cr 0.15%–0.35%, Mo 0.15%–0.35%, Ni 0.15%–0.35%, Cu 0.15%–0.25%, B 0.0005%–0.001%, V 0.01%–0.12%, Nb 0.01%–0.12%, Ti 0.010%–0.05%, RE 0.0010%–0.020%, Ca 0.010%~0.035%, V +Nb+Ti≤0.15%; The inner lining tube is made of 316L austenitic stainless steel, 2205 duplex stainless steel, Incoloy 825 corrosion-resistant alloy, or Inconel 625 corrosion-resistant alloy.

[0066] In the following examples, the alkaline degreasing solution used includes the following components in varying amounts: The mixture contains 40 g / L NaOH, 25 g / L Na2CO3, 15 g / L Na3PO4, 2 g / L surfactant, and water; wherein the surfactant is a compound of APG06, PPE1040K, and X-100 in a mass ratio of 2:2:1.

[0067] The preparation method of the plating solution includes the following steps: Mix 30 g / L nickel sulfate (NiSO4·6H2O), 30 g / L sodium hypophosphite (NaH2PO2·H2O), 15 g / L sodium citrate, 10 mL / L lactic acid, 150 g / L sodium acetate, and 2 mg / L thiourea with water, and then add ammonia to adjust the pH of the system to 5.0.

[0068] The chemical composition and mass percentage of the outer base tube and inner liner tube used in the following embodiments are shown in Table 1.

[0069] Table 1. Chemical composition and mass percentage of the outer base tube and inner liner tube used in Examples 1-5

[0070] In Table 1, the chemical composition of the different outer base tubes contains Fe as the remainder and unavoidable impurities; the chemical composition of the inner liner tubes in Examples 1-3 and Example 5 contains Fe as the remainder and unavoidable impurities; the chemical composition of the inner liner tube in Example 4 contains Ni as the remainder and unavoidable impurities.

[0071] "-" indicates that the element is not present. For example, in Example 1, the outer base tube does not contain Cr, Ni, Mo, Cu, B, Nb, Ti, RE, and Ca.

[0072] Example 1 This embodiment provides a method for preparing a bimetallic metallurgical composite tube blank (L245 / 316L composite tube blank), including the following steps: (1) Provide an outer base tube and an inner liner: The chemical compositions of the two are the same as those of the outer base tube and the inner liner in Example 1 shown in Table 1. The outer base tube is made of API 5L L245 steel grade and has a size of φ114.3 mm × 12 mm (i.e., an outer diameter of 114.3 mm and a wall thickness of 12 mm; when similar descriptions appear again below, their meanings refer to the explanation here). The inner liner is made of 316L austenitic stainless steel and has a size of φ89 mm × 4 mm.

[0073] The preparation method of the outer base tube includes the following steps: According to the chemical composition and mass percentage of the outer base tube in Example 1 of Table 1, steelmaking and continuous casting are carried out to obtain continuously cast billets; the continuously cast billets are heated to 1200℃, held for 2 hours, hot piercing is performed, and then hot continuous rolling is carried out in the temperature range of 1180~950℃ (initial rolling temperature is 1180℃, final rolling temperature is 950℃), followed by air cooling to obtain the outer base tube.

[0074] The preparation method of the inner liner includes the following steps: According to the chemical composition and mass percentage of the inner liner in Example 1 of Table 1, steelmaking and continuous casting were carried out to obtain continuously cast billets. The continuously cast billets were heated to 1180°C, held for 3 hours, and hot pierced. Then, hot continuous rolling was carried out in the temperature range of 1150-1080°C (initial rolling temperature is 1150°C, final rolling temperature is 1080°C). After rolling, water was sprayed for cooling to obtain the inner liner.

[0075] (2) Surface pretreatment: The original surface defect layer of the outer base tube and inner liner tube was removed by precision machining. Then, it was sandblasted with white corundum sand with a particle size of 100 mesh at a sandblasting pressure of 0.4 MPa to make the surface roughness Ra of the inner surface of the outer base tube and the outer surface of the inner liner tube 6.0 μm. Then, it was ultrasonically cleaned in an alkaline degreasing solution at 70℃ for 30 minutes, followed by acid pickling (for the outer base tube, the pickling solution was an aqueous solution containing 8wt% HCl and 0.5wt% hexamethylenetetramine, the pickling temperature was 45℃, the time was 10 min, and the surface was uniformly grayish-white; for the inner liner tube, the pickling solution was an aqueous solution containing 15wt% HNO3 and 4wt% HF, the pickling temperature was 55℃, and the time was 5 min). After acid pickling, it was immediately rinsed three times with running deionized water, then dehydrated with anhydrous ethanol, and placed in a drying oven at 110℃ for thorough drying. The treated surface achieved the cleanliness standard of "continuous water film".

[0076] (3) Electroless nickel plating: After preheating the surface-treated outer base tube, it is immersed in a plating solution maintained at 90°C. To ensure uniform plating, the plating solution needs to circulate within the inner cavity of the outer base tube. The nickel plating time is 1.5 hours, resulting in a plating layer with a thickness of 0.025 mm. Then, it is rinsed with hot water and dried to obtain an outer base tube with a nickel layer on the inner surface.

[0077] (4) Assembly: Cool the inner tube after surface pretreatment to -60°C and coaxially insert it into the outer base tube with nickel layer on the inner surface at room temperature. The gap between the two is 0.64 mm. After vacuuming, weld and seal the two ends to form an assembly of tube-in-tube structure.

[0078] (5) Hot isostatic pressing diffusion bonding: The assembly is placed in a hot isostatic press and evacuated to a vacuum of 1×10⁻⁶. -2 After Pa, high-purity argon gas (≥99.999%) is introduced, and the temperature and pressure are simultaneously increased at a rate of 100℃ / h and 20 MPa / h to 1130℃ and 150 MPa. The temperature and pressure are maintained for 3 hours. After the end, under the condition of maintaining full pressure, the gas is water-cooled to 400℃ and then depressurized, and then air-cooled to room temperature.

[0079] The bimetallic composite tube blank prepared above was tested, and the results showed that ultrasonic testing indicated 100% bonding at the interface. According to ASTM A265 standard, the interfacial shear strength was 328 MPa.

[0080] Example 2 This embodiment provides a method for preparing a bimetallic metallurgical composite tube blank (L360 / 2205 composite tube blank), including the following steps: (1) Provide an outer base tube and an inner liner tube: The chemical compositions of the two are the chemical compositions of the outer base tube and the inner liner tube in Example 2 shown in Table 1, respectively. The outer base tube is made of API 5L L360 steel grade and has a size of φ219.1 mm × 18 mm. The inner liner tube is made of 2205 duplex stainless steel and has a size of φ182 mm × 8 mm.

[0081] The preparation method of the outer base tube includes the following steps: According to the chemical composition and mass percentage of the outer base tube in Example 2 of Table 1, steelmaking and continuous casting are carried out to obtain continuously cast billets. The continuously cast billets are heated to 1230°C, held for 2 hours, and hot pierced. Then, they are hot rolled at a temperature of 1200-950°C (initial rolling temperature is 1200°C, final rolling temperature is 950°C). After rolling, they are air-cooled to obtain the outer base tube.

[0082] The preparation method of the inner liner includes the following steps: According to the chemical composition and mass percentage of the inner liner in Example 2 of Table 1, steelmaking and continuous casting were carried out to obtain continuously cast billets. The continuously cast billets were heated to 1240°C, held for 3 hours, and hot pierced. Then, hot continuous rolling was carried out in the temperature range of 1200-1150°C (initial rolling temperature of 1200°C and final rolling temperature of 1150°C). After rolling, water was sprayed for cooling to obtain the inner liner.

[0083] (2) Surface pretreatment: The original surface defect layer of the outer base tube and inner liner tube was removed by precision machining. Then, it was sandblasted with white corundum sand with a particle size of 100 mesh at a sandblasting pressure of 0.4 MPa to achieve a surface roughness Ra of 7.0 μm on the inner surface of the outer base tube and the outer surface of the inner liner tube. Then, it was ultrasonically cleaned in an alkaline degreasing solution at 70℃ for 30 minutes, followed by acid pickling (for the outer base tube, the pickling solution was an aqueous solution containing 8wt% HCl and 0.5wt% hexamethylenetetramine, the pickling temperature was 45℃, and the time was 10 min, resulting in a uniform grayish-white surface; for the inner liner tube, the pickling solution was an aqueous solution containing 15wt% HNO3 and 4wt% HF, the pickling temperature was 55℃, and the time was 5 min). After acid pickling, it was immediately rinsed three times with running deionized water, then dehydrated with anhydrous ethanol, and thoroughly dried in a drying oven at 110℃. The treated surface achieved the cleanliness standard of "continuous water film".

[0084] (3) Electroless nickel plating: After preheating the surface-treated outer base tube, it is immersed in a plating solution maintained at 90°C. To ensure uniform plating, the plating solution needs to circulate within the inner cavity of the outer base tube. The nickel plating time is 2 hours, resulting in a plating layer with a thickness of 0.035 mm. Then, it is rinsed with hot water and dried to obtain an outer base tube with a nickel layer on the inner surface.

[0085] (4) Assembly: Cool the inner tube after surface pretreatment to -60°C and coaxially insert it into the outer base tube with nickel layer on the inner surface at room temperature. The gap between the two is 0.53 mm. After vacuuming, the two ends are welded and sealed to form an assembly of tube-in-tube structure.

[0086] (5) Hot isostatic pressing diffusion bonding: The assembly is placed in a hot isostatic press and evacuated to a vacuum of 1×10⁻⁶. -2 After Pa, high-purity argon gas (≥99.999%) is introduced, and the temperature and pressure are simultaneously increased at a rate of 100℃ / h and 20 MPa / h to 1120℃ and 160 MPa. The temperature and pressure are maintained for 3.5 hours. After the end, under the condition of maintaining full pressure, the gas is water-cooled to 600℃ and then depressurized, and then air-cooled to room temperature.

[0087] The bimetallic composite tube blank prepared above was tested, and the results showed that ultrasonic testing indicated 100% bonding at the interface. According to ASTM A265 standard, the interfacial shear strength was 335 MPa.

[0088] Example 3 This embodiment provides a method for preparing a bimetallic metallurgical composite tube blank (L415 / 825 composite tube blank), including the following steps: (1) Provide an outer base tube and an inner liner: The chemical compositions of the two are the chemical compositions of the outer base tube and the inner liner in Example 3 shown in Table 1, respectively. The outer base tube is made of API 5L L415 steel grade and has a size of φ50 mm × 10 mm. The inner liner is made of Incoloy 825 corrosion-resistant alloy and has a size of φ28 mm × 3 mm.

[0089] The preparation method of the outer base tube includes the following steps: According to the chemical composition and mass percentage of the outer base tube in Example 3 of Table 1, steelmaking and continuous casting are carried out to obtain continuously cast billets. The continuously cast billets are heated to 1250°C, held for 2 hours, and hot piercing is performed. Then, hot continuous rolling is carried out in the temperature range of 1200°C to 950°C (initial rolling temperature is 1200°C, and final rolling temperature is 950°C). After rolling, water is sprayed for cooling to obtain the outer base tube.

[0090] The preparation method of the inner liner includes the following steps: According to the chemical composition and mass percentage of the inner liner in Example 3 of Table 1, steelmaking and continuous casting were carried out to obtain continuously cast billets. The continuously cast billets were heated to 1250°C and held for 3 hours for hot piercing. Then, hot continuous rolling was carried out in the temperature range of 1200-1150°C (initial rolling temperature is 1200°C, final rolling temperature is 1150°C). After rolling, water was sprayed for cooling to obtain the inner liner.

[0091] (2) Surface pretreatment: The original surface defect layer of the outer base tube and inner liner tube is removed by precision machining. Then, it is sandblasted with white corundum sand with a particle size of 100 mesh at a sandblasting pressure of 0.4 MPa to make the surface roughness Ra of the inner surface of the outer base tube and the outer surface of the inner liner tube 4.5 μm. Then, it is ultrasonically cleaned in an alkaline degreasing solution at 70℃ for 30 minutes, followed by acid pickling (for the outer base tube, the pickling solution is an aqueous solution containing 8wt% HCl and 0.5wt% hexamethylenetetramine, the pickling temperature is 45℃, the time is 10 min, and the surface is uniformly grayish-white; for the inner liner tube, the pickling solution is an aqueous solution containing 15wt% HNO3 and 4wt% HF, the pickling temperature is 55℃, and the time is 5 min). After acid pickling, it is immediately rinsed three times with running deionized water, then dehydrated with anhydrous ethanol, and placed in a drying oven at 110℃ for thorough drying. The treated surface should meet the cleanliness standard of "continuous water film".

[0092] (3) Electroless nickel plating: After preheating the surface-treated outer base tube, immerse it in a plating solution maintained at 90°C. To ensure uniform plating, the plating solution needs to circulate within the outer base tube. The nickel plating time is 1 hour, resulting in a plating layer with a thickness of 0.015 mm. After plating, rinse with hot water and dry.

[0093] (4) Assembly: Cool the inner tube to -60°C and coaxially insert it into the outer base tube with a nickel layer on the inner surface at room temperature. The gap between the two is 0.99 mm. After vacuuming, weld the two ends to seal, forming an assembly of tube-in-tube structure.

[0094] (5) Hot isostatic pressing diffusion bonding: The assembly is placed in a hot isostatic press and evacuated to a vacuum of 1×10⁻⁶. -2 After Pa, high-purity argon gas (≥99.999%) is introduced, and the temperature and pressure are simultaneously increased at a rate of 100℃ / h and 20 MPa / h to 1180℃ and 140 MPa. The temperature and pressure are maintained for 2.5 hours. After the end, under the condition of maintaining full pressure, the gas is water-cooled to 550℃ and then depressurized, and then air-cooled to room temperature.

[0095] The bimetallic composite tube blank prepared above was tested, and the results showed that ultrasonic testing indicated 100% bonding at the interface. According to ASTM A265 standard, the interfacial shear strength was 345 MPa.

[0096] Example 4 This embodiment provides a method for preparing a bimetallic metallurgical composite tube blank (L450 / 625 composite tube blank), including the following steps: (1) Provide an outer base tube and an inner liner: The chemical compositions of the two are the same as those of the outer base tube and the inner liner in Example 4 shown in Table 1. The outer base tube is made of API 5L L450 steel grade and has a size of φ406.4 mm × 25 mm. The inner liner is made of Inconel 625 corrosion-resistant alloy and has a size of φ355 mm × 6 mm.

[0097] The preparation method of the outer base tube includes the following steps: According to the chemical composition and mass percentage of the outer base tube in Example 4 of Table 1, steelmaking and continuous casting were carried out to obtain continuously cast billets. The continuously cast billets were heated to 1260°C and held for 2 hours for hot piercing. Then, rough rolling was carried out in the temperature range of 1200-950°C (initial rolling temperature of 1200°C and final rolling temperature of 950°C), and finish rolling was carried out in the temperature range of 900-750°C (initial rolling temperature of 900°C and final rolling temperature of 750°C). After rolling, the billets were cooled by water spraying to 500°C and then air-cooled to obtain the outer base tube.

[0098] The preparation method of the inner liner includes the following steps: According to the chemical composition and mass percentage of the inner lining tube in Example 4 of Table 1, steelmaking and continuous casting are carried out to obtain continuously cast billets; the continuously cast billets are heated to 1200°C, held for 3 hours, hot piercing is performed, and then hot extrusion is performed in the temperature range of 1200-1100°C, followed by water cooling to obtain the inner lining tube.

[0099] (2) Surface pretreatment: The original surface defect layer of the outer base tube and inner liner tube was removed by precision machining, and then sandblasted with 100-mesh white corundum sand at a pressure of 0.4 MPa to achieve a surface roughness Ra of 8.0 μm for the inner surface of the outer base tube and the outer surface of the inner liner tube. Then, ultrasonic cleaning was performed in an alkaline degreasing solution at 70℃ for 30 minutes, followed by acid pickling (for the outer base tube, the pickling solution was an aqueous solution containing 8wt% HCl and 0.5wt% hexamethylenetetramine, the pickling temperature was 45℃, and the time was 10 min, resulting in a uniform grayish-white surface; for the inner liner tube, the pickling solution was an aqueous solution containing 15wt% HNO3 and 4wt% HF, the pickling temperature was 55℃, and the time was 5 min). Immediately after acid pickling, the tube was rinsed three times with running deionized water, then dehydrated with anhydrous ethanol, and thoroughly dried in a drying oven at 110℃. The treated surface achieved a "continuous water film" cleanliness standard.

[0100] (3) Electroless nickel plating: After preheating the surface-treated outer base tube, it is immersed in a plating solution maintained at 90°C. To ensure uniform plating, the plating solution needs to circulate within the outer base tube. The nickel plating time is 3.5 hours, resulting in a plating layer with a thickness of 0.05 mm. Then, it is rinsed with hot water and dried.

[0101] (4) Assembly: Cool the inner tube to -60°C and coaxially insert it into the outer base tube with a nickel layer on the inner surface at room temperature. The gap between the two is 0.66 mm. After vacuuming, weld the two ends to seal, forming an assembly of tube-in-tube structure.

[0102] (5) Hot isostatic pressing diffusion bonding: The assembly is placed in a hot isostatic press and evacuated to a vacuum of 1×10⁻⁶. -2 After Pa, high-purity argon gas (≥99.999%) is introduced, and the temperature and pressure are simultaneously increased at a rate of 100℃ / h and 20 MPa / h to 1200℃ and 180 MPa. The temperature and pressure are maintained for 4.5 hours. After the end, under the condition of maintaining full pressure, the gas is water-cooled to 600℃ and then depressurized, and then air-cooled to room temperature.

[0103] The bimetallic composite tube blank prepared above was tested, and the results showed that ultrasonic testing indicated 100% bonding at the interface. According to ASTM A265 standard, the interfacial shear strength was 312 MPa.

[0104] Example 5 This embodiment provides a method for preparing a bimetallic metallurgical composite tube blank (L485 / 316L composite tube blank), including the following steps: (1) Provide an outer base tube and an inner liner tube: The chemical composition of the two is the same as that of the outer base tube and the inner liner tube in Example 5 shown in Table 1. The outer base tube is made of API 5L L485 steel grade and has a size of φ508 mm × 30 mm. The inner liner tube is made of 316L austenitic stainless steel and has a size of φ446 mm × 10 mm.

[0105] The preparation method of the outer base tube includes the following steps: According to the chemical composition and mass percentage of the outer base tube in Example 5 of Table 1, steelmaking and continuous casting were carried out to obtain continuously cast billets. The continuously cast billets were heated to 1260°C and held for 2 hours for hot piercing. Then, rough rolling was carried out in the temperature range of 1200-950°C (initial rolling temperature of 1200°C and final rolling temperature of 950°C), and finish rolling was carried out in the temperature range of 900-750°C (initial rolling temperature of 900°C and final rolling temperature of 750°C). After rolling, the billets were cooled by water spraying to 500°C and then air-cooled to obtain the outer base tube.

[0106] The preparation method of the inner liner includes the following steps: According to the chemical composition and mass percentage of the inner liner in Example 5 of Table 1, steelmaking and continuous casting were carried out to obtain continuously cast billets. The continuously cast billets were heated to 1200°C, held for 3 hours, and hot pierced. Then, hot continuous rolling was carried out in the temperature range of 1150-1080°C (initial rolling temperature is 1150°C, final rolling temperature is 1080°C). After rolling, water was sprayed for cooling to obtain the inner liner.

[0107] (2) Surface pretreatment: The original surface defect layer of the outer base tube and inner liner tube was removed by precision machining, and then sandblasted with 100-mesh white corundum sand at a pressure of 0.4 MPa to achieve a surface roughness Ra of 7.5 μm. Then, the surface was ultrasonically cleaned in an alkaline degreasing solution at 70℃ for 30 minutes, followed by acid pickling (for the outer base tube, the pickling solution was an aqueous solution containing 8wt% HCl and 0.5wt% hexamethylenetetramine, the pickling temperature was 45℃, and the time was 10 min, resulting in a uniform grayish-white surface; for the inner liner tube, the pickling solution was an aqueous solution containing 15wt% HNO3 and 4wt% HF, the pickling temperature was 55℃, and the time was 5 min). Immediately after acid pickling, the surface was rinsed three times with running deionized water, then dehydrated with anhydrous ethanol, and thoroughly dried in a drying oven at 110℃. The treated surface achieved a "continuous water film" cleanliness standard.

[0108] (3) Electroless nickel plating: After preheating the surface-treated outer base tube, it is immersed in a plating solution maintained at 90°C. To ensure uniform plating, the plating solution needs to circulate within the outer base tube. The nickel plating time is 4 hours, resulting in a plating layer with a thickness of 0.048 mm. Then, it is rinsed with hot water and dried.

[0109] (4) Assembly: Cool the inner tube to -60°C and coaxially insert it into the outer base tube with a nickel layer on the inner surface at room temperature. The gap between the two is 0.96 mm. After vacuuming, weld the two ends to seal, forming an assembly of tube-in-tube structure.

[0110] (5) Hot isostatic pressing diffusion bonding: The assembly is placed in a hot isostatic press and evacuated to a vacuum of 1×10⁻⁶. -2 After Pa, high-purity argon gas (≥99.999%) is introduced, and the temperature and pressure are simultaneously increased at a rate of 100℃ / h and 20 MPa / h to 1150℃ and 170 MPa. The temperature and pressure are maintained for 5 hours. After the end, under the condition of maintaining full pressure, the gas is water-cooled to 400℃ and then depressurized, and then air-cooled to room temperature.

[0111] The bimetallic composite tube blank prepared above was tested, and the results showed that ultrasonic testing indicated 100% bonding at the interface. According to ASTM A265 standard, the interfacial shear strength was 321 MPa.

[0112] Comparative Example 1 This comparative example provides a method for preparing a bimetallic metallurgical composite tube blank, which differs from Example 1 only in that: Step (3) electroless nickel plating is omitted; step (4) after assembly is not vacuumed or sealed at both ends; in step (5), no protective atmosphere is used; the hot isostatic pressing temperature is 1000℃; the pressure is 50MPa; and the heat and pressure are maintained for 1 hour. Other process parameters are exactly the same as in Example 1. After obtaining the bimetallic metallurgical composite tube blank, a compression-shear test was performed according to ASTM A265 standard. Its interfacial shear strength was only 175 MPa, and ultrasonic testing revealed local unbonded signals at the interface.

[0113] Comparative Example 2 This comparative example provides a method for preparing a bimetallic metallurgical composite tube blank, which differs from Example 3 only in that: Step (3) electroless nickel plating is omitted. After assembly in step (4), vacuuming and end sealing are not performed. In step (5), no protective atmosphere is used, the hot isostatic pressing temperature is 1300℃, the pressure is 250 MPa, and the heat and pressure are maintained for 7 hours. Other process parameters are exactly the same as in Example 3.

[0114] After the bimetallic composite tube blank was prepared, it was subjected to compression and shear test according to ASTM A265 standard. Its interfacial shear strength was only 195 MPa, and ultrasonic testing revealed local unbonded signals at the interface.

[0115] Comparative Example 3 This comparative example provides a method for preparing a bimetallic metallurgical composite tube blank, which differs from Example 4 only in that: Step (3) electroless nickel plating is omitted. After assembly in step (4), vacuuming and end sealing are not performed. In step (5), no protective atmosphere is used, the hot isostatic pressing temperature is 950℃, the pressure is 80 MPa, and the heat and pressure are maintained for 0.5 hours. Other process parameters are exactly the same as in Example 4.

[0116] After the bimetallic composite tube blank was prepared, it was subjected to compression and shear test according to ASTM A265 standard. Its interfacial shear strength was only 185 MPa, and ultrasonic testing revealed local unbonded signals at the interface.

[0117] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A method for preparing a bimetallic metallurgical composite pipe blank for oil and gas transportation, characterized in that, Includes the following steps: S1. Provide an outer base tube and an inner liner tube, and roughen the inner surface of the outer base tube and the outer surface of the inner liner tube so that the roughness of the inner surface of the outer base tube and the outer surface of the inner liner tube is 4.0 μm to 8.0 μm; The outer base tube comprises the following chemical components in weight percentage: The composition comprises: C 0.02%–0.22%, Si 0.10%–0.50%, P ≤0.015%, S ≤0.005%, Al 0.010%–0.050%, N ≤0.010%, O ≤0.002%, H ≤0.0002%; and includes one or more of the following chemical components in mass percentage: Mn 1.00%–1.80%, Cr 0.15%–0.35%, Mo 0.15%–0.35%, Ni 0.15%–0.35%, Cu 0.15%–0.25%, B 0.0005%–0.001%, V 0.01%–0.12%, Nb 0.01%–0.12%, Ti 0.010%–0.050%, RE 0.0010%–0.020%, Ca 0.010%~0.035%; the balance is Fe and unavoidable impurities, and V+Nb+Ti≤0.15%; The inner lining tube is made of 316L austenitic stainless steel, 2205 duplex stainless steel, Incoloy 825 corrosion-resistant alloy or Inconel 625 corrosion-resistant alloy. S2. Electroless nickel plating is performed on the inner surface of the roughened outer base tube to form a nickel layer with a thickness of 0.01 mm to 0.05 mm, resulting in an outer base tube with a nickel layer on the inner surface. S3. Place the roughened inner liner into the outer base tube with a nickel layer on the inner surface, then seal the two ends of the inner liner and the outer base tube and vacuum them to form an assembly. S4. The assembly is placed under an inert atmosphere, at a temperature of 1050℃~1250℃ and an isostatic pressure of 100 MPa~200 MPa, and kept at the temperature and pressure for 2~6 hours. Then, it is cooled during the pressure holding or depressurization process to obtain the bimetallic metallurgical composite pipe blank for oil and gas transportation.

2. The preparation method according to claim 1, characterized in that, The outer diameter of the outer base tube is 50 mm to 510 mm, and the wall thickness of the outer base tube is 10 mm to 60 mm; the wall thickness of the inner liner tube is 3 mm to 10 mm.

3. The preparation method according to claim 1, characterized in that, In step S1, the roughening treatment specifically includes: sandblasting with white corundum alumina sand with a particle size of 60-120 mesh at a sandblasting pressure of 0.3 MPa-0.6 MPa; and / or, Step S1 also includes the steps of alkali washing, acid washing, water washing and drying of the roughened outer base tube and inner liner tube.

4. The preparation method according to claim 3, characterized in that, The alkaline washing step specifically includes: The roughened outer base tube and inner liner tube are placed in an alkaline degreasing solution at 60℃~70℃ and ultrasonically cleaned for 20~30 minutes to obtain an alkaline-washed outer base tube and an alkaline-washed inner liner tube. The pickling steps specifically include: After alkali washing, the outer base tube is placed in a solution containing 5wt%–10wt% HCl and 0.3wt%–0.8wt% hexamethylenetetramine and soaked at 40℃–50℃ for 5–15 minutes. After alkali washing, the inner liner is placed in a solution containing 10wt%–20wt% HNO3 and 2wt%–5wt% HF and soaked at 50℃–60℃ for 3–10 minutes.

5. The preparation method according to claim 1, characterized in that, The electroless nickel plating solution is prepared by the following method: The plating solution is prepared by mixing 20-35 g / L nickel sulfate, 25-35 g / L sodium hypophosphite, 10-20 g / L sodium citrate, 5-15 ml / L lactic acid, 10-20 g / L sodium acetate, 1-5 mg / L stabilizer, and water. Then, ammonia is added to adjust the pH of the system to 4.5-5.

5.

6. The preparation method according to claim 5, characterized in that, The temperature of the plating solution used in the electroless nickel plating is 85℃~92℃; the stabilizer includes at least one of thiourea and iodate.

7. The preparation method according to claim 1, characterized in that, In step S3, after the roughened inner tube is cooled to below -50°C, it is coaxially placed in an outer base tube with a nickel layer on its inner surface at a temperature of room temperature to 80°C, such that the radial gap between the two is 0.15 mm to 1.0 mm on one side.

8. The preparation method according to claim 1, characterized in that, Step S4 specifically includes: The assembly was placed in a hot isostatic pressing apparatus and evacuated to a vacuum level of ≤1×10⁻⁶. -2 After Pa, inert gas is introduced, and then the temperature and pressure are simultaneously increased to 1050℃~1250℃ and 100 MPa~200 MPa at a heating rate of no more than 150℃ / h and a pressure increase rate of no more than 30 MPa / h, and held at the temperature and pressure for 2~6 hours. Then, during the pressure holding or depressurization process at a rate ≤15 MPa / h, the tube blank is water-cooled to 400℃~600℃, and then depressurized and air-cooled to room temperature to obtain the bimetallic metallurgical composite tube blank.

9. The preparation method according to claim 8, characterized in that, When the inner liner is made of 316L austenitic stainless steel or 2205 duplex stainless steel, the temperature is raised to 1100℃~1180℃; when the inner liner is made of Incoloy 825 corrosion-resistant alloy or Inconel 625 corrosion-resistant alloy, the temperature is raised to 1150℃~1250℃.

10. A bimetallic composite pipe blank for oil and gas transportation, characterized in that, The bimetallic composite pipe blank for oil and gas transportation includes an outer base pipe and an inner liner pipe arranged coaxially from the outside to the inside, and the outer base pipe and the inner liner pipe are metallurgically bonded by a nickel layer between them. The outer base tube comprises the following chemical components in weight percentage: The composition comprises: C 0.02%–0.22%, Si 0.10%–0.50%, P ≤0.015%, S ≤0.005%, Al 0.010%–0.050%, N ≤0.010%, O ≤0.002%, H ≤0.0002%; and includes one or more of the following chemical components in mass percentage: Mn 1.00%–1.80%, Cr 0.15%–0.35%, Mo 0.15%–0.35%, Ni 0.15%–0.35%, Cu 0.15%–0.25%, B 0.0005%–0.001%, V 0.01%–0.12%, Nb 0.01%–0.12%, Ti 0.010%–0.05%, RE 0.0010%–0.020%, Ca 0.010%~0.035%, V +Nb+Ti≤0.15%; The inner lining tube is made of 316L austenitic stainless steel, 2205 duplex stainless steel, Incoloy 825 corrosion-resistant alloy, or Inconel 625 corrosion-resistant alloy.

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