Seamless steel tube for low temperature and processing technology thereof

Abstract

The invention discloses a low-temperature seamless steel tube and a processing technology thereof, and relates to the technical field of seamless steel tubes, the processing technology comprises the following steps: sequentially carrying out converter smelting, secondary refining, vacuum degassing and continuous casting on raw materials according to a formula to obtain a tube blank; the pipe blank is sequentially subjected to heating, perforating, continuous rolling, pipe removing, tension reducing and heat treatment, and an original pipe is obtained; the original pipe is sequentially subjected to surface pretreatment, electroplating and chemical vapor deposition, and a first steel pipe is obtained; and the first steel pipe is sequentially immersed in the 3-aminopropyltriethoxysilane solution and the cerium dibutyl phosphate suspension and dried, and the seamless steel pipe used at the low temperature is obtained.

Description

Technical Field

[0001] This invention relates to the field of seamless steel pipe technology, specifically a seamless steel pipe for low-temperature applications and its processing technology. Background Technology

[0002] In the field of seamless steel pipe technology, seamless steel pipes used in low-temperature environments face numerous challenges. With the continuous development of industry, such as in cryogenic liquid storage and transportation, and cryogenic chemical industry, the performance requirements for seamless steel pipes used in cryogenic environments are becoming increasingly stringent.

[0003] Traditional seamless steel pipes exhibit a significant decrease in toughness at low temperatures, making them prone to brittle fracture, which seriously affects the safe operation of related equipment. In terms of chemical composition, conventional seamless steel pipe design fails to adequately consider performance optimization under low-temperature conditions. For example, certain alloying elements negatively impact the toughness of the steel pipe at low temperatures, resulting in poor performance under pressure and impact.

[0004] In terms of processing technology, existing processes are insufficient to create an ideal protective structure on the surface of steel pipes. Ordinary surface treatments cannot effectively improve the corrosion resistance of steel pipes, making them highly susceptible to corrosion damage in low-temperature and corrosive environments, shortening their service life, and increasing maintenance costs and safety risks. Therefore, developing a seamless steel pipe with excellent low-temperature performance and corrosion resistance, along with its processing technology, is urgently needed. Summary of the Invention

[0005] The purpose of this invention is to provide a seamless steel pipe for low-temperature applications and its processing technology, so as to solve the problems raised in the prior art.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A processing technology for seamless steel pipes for low temperature applications includes the following steps: S1: The raw materials are sequentially smelted in a converter, refined in a secondary refining process, degassed in a vacuum, and continuously cast according to the formula to obtain a pipe billet;

[0008] S2: The tube blank is sequentially heated, pierced, continuously rolled, removed, tension reduced in diameter, and heat treated to obtain the original tube;

[0009] S3: The original pipe is subjected to surface pretreatment, electroplating, and chemical vapor deposition in sequence to obtain the first steel pipe;

[0010] S4: The first steel pipe is sequentially immersed in 3-aminopropyltriethoxysilane solution and dibutyl phosphate cerium suspension, and then dried to obtain a seamless steel pipe for low temperature use.

[0011] Furthermore, the chemical composition of the tube blank, by mass percentage, is C: 0.15-0.16%, Si: 0.36-0.40%, Mn: 1.43-1.50%, Als (acid-soluble aluminum): 0.15-0.32%, Ti: 0.15-0.21%, Nb: 0.42-0.51%, N: 0.0028-0.0032%, and the balance being Fe and unavoidable impurities.

[0012] Furthermore, the heat treatment temperature is 890-910℃, and the time is 40-60min.

[0013] Furthermore, the specific steps of the surface pretreatment include: grinding the surface of the original tube sequentially with 180, 320, 800, 1200, and 2500 grit sandpaper, polishing with 3-4μm diamond polishing fluid, ultrasonically cleaning with acetone for 5-10 minutes, and drying with compressed air.

[0014] Furthermore, the specific electroplating steps include: using nickel sulfamate solution and copper sulfate solution to electroplat a copper layer on the surface of the original tube in sequence, and then electroplating a nickel layer on the copper layer.

[0015] Furthermore, the nickel sulfamate solution contains a main salt concentration of 200-450 g / L, a boric acid concentration of 30-50 g / L, a temperature of 55-60℃, and a pH of 3.9-4.1; the copper sulfate solution contains a main salt concentration of 50-100 g / L, a sulfuric acid concentration of 50-100 g / L, a temperature of 20-25℃, and a pH of 3.9-4.1; the electroplating parameters include: a current of 8-10 A, a copper layer thickness of 13-15 μm, and a nickel layer thickness of 12-14 μm.

[0016] Furthermore, the specific steps of the chemical vapor deposition include: placing the original tube in a tube furnace with a vacuum of 5 mtorr, introducing a mixed gas of argon and hydrogen at a pressure of 1.8-2.2 torr and a flow rate of 250-280 sccm, preheating to 1060-1061℃ and maintaining it for 40-45 min, introducing hexane at a flow rate of 1-1.2.2 sccm, maintaining it at 1060-1061℃ for 55-60 min, and cooling to room temperature under the flow of a mixed gas of argon and hydrogen at a pressure of 1.8-2.2 torr and a flow rate of 250-280 sccm.

[0017] Furthermore, in step S4, the method for preparing seamless steel pipes for low temperature includes the following steps: Step (1): 3-aminopropyltriethoxysilane is added to N,N-dimethylaminoformamide and stirred evenly to obtain a 3-aminopropyltriethoxysilane solution.

[0018] Step (2): Add cerium dibutyl phosphate to deionized water, disperse by ultrasonication, add 3-aminopropyltriethoxysilane, stir evenly to obtain cerium dibutyl phosphate suspension;

[0019] Step (3): Immerse the first steel pipe in 3-aminopropyltriethoxysilane solution, heat to 100-105℃ and react for 6-6.5h, add dibutyl phosphate cerium suspension, cool to 50-55℃ and react for 12-24h, wash with a water-ethanol mixture with a volume ratio of 1:1, and dry to obtain a seamless steel pipe for low temperature use.

[0020] Furthermore, the concentration of the 3-aminopropyltriethoxysilane solution is 18.8-20 g / L; in the preparation of the dibutyl phosphate cerium suspension, the mass ratio of 3-aminopropyltriethoxysilane to dibutyl phosphate cerium is 1.88:(2-4);

[0021] Furthermore, the preparation method of cerium dibutyl phosphate includes the following steps: adding dibutyl phosphate and sodium carbonate to deionized water, ultrasonically dispersing, adding cerium trichloride, stirring the reaction, collecting the solid product, washing the product with deionized water, and vacuum drying at 75-80℃ to obtain cerium dibutyl phosphate; in the preparation process of cerium dibutyl phosphate, the amount of cerium trichloride added is 0.033-0.035 mol / L.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] 1. This invention further adjusts the Nb and Ti composition based on the composition of 16Mn seamless steel pipe. TiN particles are difficult to dissolve in austenite at 1250℃, effectively preventing austenite grain growth and suppressing the formation of Widmanstätten structure. The refined grains reduce internal defects, making crack propagation paths more tortuous and consuming more energy, thus improving low-temperature toughness. During high-temperature deformation, the Nb alloy suppresses recrystallization, resulting in austenite grains containing both recrystallized and non-recrystallized parts. The non-recrystallized grains are coarse, forming coarse ferrite grains and acicular structures (Widmanstätten structure) after cooling, reducing toughness. Normalizing eliminates the coarse acicular structure, refines the grains, and the precipitation of Nb(C,N) fixes the C and N elements, reducing the damage to plasticity and toughness caused by interstitial atoms.

[0024] 2. This invention successfully deposits a graphene coating on the modified low-carbon steel surface by electroplating a copper-nickel double layer, thereby improving the corrosion resistance of the low-carbon steel. Graphene itself has excellent structural stability and can maintain its structural integrity at low temperatures (such as liquid nitrogen) without embrittlement or phase transformation, which greatly improves the low-temperature corrosion resistance of seamless steel pipes. At the same time, it does not have a negative impact on the mechanical properties of seamless steel pipes, expands the application range of seamless steel pipes, and extends the low-temperature service life of seamless steel pipes.

[0025] 3. This invention overcomes the challenges of high carbon solubility in low-carbon steel at high temperatures and low catalytic efficiency of iron, making direct CVD growth of graphene on low-carbon steel difficult. Electroplating with copper or nickel can alter the surface chemical properties and structure, inhibiting carbon diffusion. Copper's low carbon solubility prevents carbon diffusion into the steel substrate; nickel acts as a catalyst to promote graphene growth. Furthermore, controlling the electroplating layer thickness optimizes the surface, facilitating graphene deposition. The surface-deposited graphene is further modified with siloxanes, and then the bifunctional inhibitor cerium dibutyl phosphate is loaded onto its surface to further enhance corrosion resistance. Detailed Implementation

[0026] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] Example 1: A processing technology for seamless steel pipes for low temperature applications, comprising the following steps: S1: The raw materials are sequentially smelted in a converter, refined twice, degassed in a vacuum, and continuously cast according to the formula to obtain a pipe billet;

[0028] S2: The tube blank is sequentially heated, pierced, continuously rolled, tube removed, tension reduced in diameter, and heat-treated at 900℃ for 40 minutes to obtain the original tube;

[0029] S3: The surface of the original tube was polished sequentially with 180, 320, 800, 1200, and 2500 grit sandpaper, polished with 3μm diamond polishing fluid, ultrasonically cleaned with acetone for 5 minutes, and dried with compressed air. Copper layers were electroplated sequentially on the pretreated original tube surface using nickel sulfamate solution and copper sulfate solution, followed by nickel plating on the copper layer. The electroplated original tube was placed in a tube furnace with a vacuum of 5 mtorr, and a mixture of argon and hydrogen gas was introduced at a pressure of 1.8 torr and a flow rate of 250 sccm. The tube was preheated to 1060℃ and maintained for 40 minutes. Hexane was introduced at a flow rate of 1 sccm and the tube was maintained at 1060℃ for 55 minutes. The tube was then cooled to room temperature under the flow of a mixture of argon and hydrogen gas at a pressure of 1.8 torr and a flow rate of 250 sccm to obtain the first steel tube.

[0030] The nickel sulfamate solution has a main salt concentration of 200 g / L, a boric acid concentration of 30 g / L, a temperature of 55°C, and a pH of 4; the copper sulfate solution has a main salt concentration of 50 g / L, a sulfuric acid concentration of 50 g / L, a temperature of 20°C, and a pH of 4; the electroplating parameters include: a current of 8 A, a copper layer thickness of 13 μm, and a nickel layer thickness of 12 μm.

[0031] S4: Add 3-aminopropyltriethoxysilane to N,N-dimethylaminocarbamate and stir until homogeneous to obtain a 3-aminopropyltriethoxysilane solution with a concentration of 18.8 g / L.

[0032] S5: Add 2g of cerium dibutyl phosphate to deionized water, disperse by ultrasonication, add 1.88g of 3-aminopropyltriethoxysilane, stir evenly to obtain a cerium dibutyl phosphate suspension;

[0033] S6: Immerse the first steel pipe in 3-aminopropyltriethoxysilane solution, heat to 100°C and react for 6 hours, add dibutyl phosphate cerium suspension, cool to 55°C and react for 12 hours, wash with a water-ethanol mixture solution with a volume ratio of 1:1, and dry to obtain a seamless steel pipe for low temperature use.

[0034] The chemical composition of the tube blank, by mass percentage, is C: 0.15%, Si: 0.36%, Mn: 1.50%, Als: 0.32%, Ti: 0.21%, Nb: 0.42%, N: 0.0032%, with the balance being Fe and unavoidable impurities.

[0035] Example 2: A processing technology for seamless steel pipes for low temperature applications, comprising the following steps: S1: The raw materials are sequentially smelted in a converter, refined twice, degassed in a vacuum, and continuously cast according to the formula to obtain a pipe billet;

[0036] S2: The tube blank is sequentially heated, pierced, continuously rolled, tube removed, tension reduced in diameter, and heat-treated at 900℃ for 40 minutes to obtain the original tube;

[0037] S3: The surface of the original tube was polished sequentially with 180, 320, 800, 1200, and 2500 grit sandpaper, polished with 3μm diamond polishing fluid, ultrasonically cleaned with acetone for 5 minutes, and dried with compressed air. Copper layers were electroplated sequentially on the pretreated original tube surface using nickel sulfamate solution and copper sulfate solution, followed by nickel plating on the copper layer. The electroplated original tube was placed in a tube furnace with a vacuum of 5 mtorr, and a mixture of argon and hydrogen gas was introduced at a pressure of 1.8 torr and a flow rate of 250 sccm. The tube was preheated to 1060℃ and maintained for 40 minutes. Hexane was introduced at a flow rate of 1 sccm and the tube was maintained at 1060℃ for 55 minutes. The tube was then cooled to room temperature under the flow of a mixture of argon and hydrogen gas at a pressure of 1.8 torr and a flow rate of 250 sccm to obtain the first steel tube.

[0038] The nickel sulfamate solution has a main salt concentration of 200 g / L, a boric acid concentration of 30 g / L, a temperature of 55°C, and a pH of 4; the copper sulfate solution has a main salt concentration of 50 g / L, a sulfuric acid concentration of 50 g / L, a temperature of 20°C, and a pH of 4; the electroplating parameters include: a current of 9 A, a copper layer thickness of 14 μm, and a nickel layer thickness of 13 μm.

[0039] S4: Add 3-aminopropyltriethoxysilane to N,N-dimethylaminocarbamate and stir until homogeneous to obtain a 3-aminopropyltriethoxysilane solution with a concentration of 18.8 g / L.

[0040] S5: Add 2g of cerium dibutyl phosphate to deionized water, disperse by ultrasonication, add 1.88g of 3-aminopropyltriethoxysilane, stir evenly to obtain a cerium dibutyl phosphate suspension;

[0041] S6: Immerse the first steel pipe in 3-aminopropyltriethoxysilane solution, heat to 100°C and react for 6 hours, add dibutyl phosphate cerium suspension, cool to 55°C and react for 12 hours, wash with a water-ethanol mixture solution with a volume ratio of 1:1, and dry to obtain a seamless steel pipe for low temperature use.

[0042] The chemical composition of the tube blank, by mass percentage, is C: 0.15%, Si: 0.36%, Mn: 1.50%, Als: 0.32%, Ti: 0.21%, Nb: 0.42%, N: 0.0032%, with the balance being Fe and unavoidable impurities.

[0043] Example 3: A processing technology for seamless steel pipes for low temperature applications, comprising the following steps: S1: The raw materials are sequentially smelted in a converter, refined twice, degassed in a vacuum, and continuously cast according to the formula to obtain a billet;

[0044] S2: The tube blank is sequentially heated, pierced, continuously rolled, tube removed, tension reduced in diameter, and heat-treated at 900℃ for 40 minutes to obtain the original tube;

[0045] S3: The surface of the original tube was polished sequentially with 180, 320, 800, 1200, and 2500 grit sandpaper, polished with 3μm diamond polishing fluid, ultrasonically cleaned with acetone for 5 minutes, and dried with compressed air. Copper layers were electroplated sequentially on the pretreated original tube surface using nickel sulfamate solution and copper sulfate solution, followed by nickel plating on the copper layer. The electroplated original tube was placed in a tube furnace with a vacuum of 5 mtorr, and a mixture of argon and hydrogen gas was introduced at a pressure of 1.8 torr and a flow rate of 250 sccm. The tube was preheated to 1060℃ and maintained for 40 minutes. Hexane was introduced at a flow rate of 1 sccm and the tube was maintained at 1060℃ for 55 minutes. The tube was then cooled to room temperature under the flow of a mixture of argon and hydrogen gas at a pressure of 1.8 torr and a flow rate of 250 sccm to obtain the first steel tube.

[0046] The nickel sulfamate solution has a main salt concentration of 200 g / L, a boric acid concentration of 30 g / L, a temperature of 55°C, and a pH of 4; the copper sulfate solution has a main salt concentration of 50 g / L, a sulfuric acid concentration of 50 g / L, a temperature of 20°C, and a pH of 4; the electroplating parameters include: a current of 10 A, a copper layer thickness of 15 μm, and a nickel layer thickness of 14 μm.

[0047] S4: Add 3-aminopropyltriethoxysilane to N,N-dimethylaminocarbamate and stir until homogeneous to obtain a 3-aminopropyltriethoxysilane solution with a concentration of 18.8 g / L.

[0048] S5: Add 2g of cerium dibutyl phosphate to deionized water, disperse by ultrasonication, add 1.88g of 3-aminopropyltriethoxysilane, stir evenly to obtain a cerium dibutyl phosphate suspension;

[0049] S6: Immerse the first steel pipe in 3-aminopropyltriethoxysilane solution, heat to 100°C and react for 6 hours, add dibutyl phosphate cerium suspension, cool to 55°C and react for 12 hours, wash with a water-ethanol mixture solution with a volume ratio of 1:1, and dry to obtain a seamless steel pipe for low temperature use.

[0050] The chemical composition of the tube blank, by mass percentage, is C: 0.15%, Si: 0.36%, Mn: 1.50%, Als: 0.32%, Ti: 0.21%, Nb: 0.42%, N: 0.0032%, with the balance being Fe and unavoidable impurities.

[0051] Comparative Example 1: A processing technology for seamless steel pipes for low temperature applications, comprising the following steps: S1: The raw materials are sequentially smelted in a converter, refined in a secondary refining process, degassed in a vacuum, and continuously cast according to the formula to obtain a pipe billet;

[0052] S2: The tube blank is sequentially heated, pierced, continuously rolled, tube removed, tension reduced in diameter, and heat-treated at 900℃ for 40 minutes to obtain the original tube;

[0053] S3: The surface of the original tube was polished sequentially with 180, 320, 800, 1200, and 2500 grit sandpaper, polished with 3μm diamond polishing fluid, ultrasonically cleaned with acetone for 5 minutes, and dried with compressed air. Copper layers were electroplated sequentially on the pretreated original tube surface using nickel sulfamate solution and copper sulfate solution, followed by nickel plating on the copper layer. The electroplated original tube was placed in a tube furnace with a vacuum of 5 mtorr, and a mixture of argon and hydrogen gas was introduced at a pressure of 1.8 torr and a flow rate of 250 sccm. The tube was preheated to 1060℃ and maintained for 40 minutes. Hexane was introduced at a flow rate of 1 sccm and the tube was maintained at 1060℃ for 55 minutes. The tube was then cooled to room temperature under the flow of a mixture of argon and hydrogen gas at a pressure of 1.8 torr and a flow rate of 250 sccm to obtain the first steel tube.

[0054] The nickel sulfamate solution has a main salt concentration of 200 g / L, a boric acid concentration of 30 g / L, a temperature of 55°C, and a pH of 4; the electroplating parameters include a current of 8 A and a copper layer thickness of 13 μm.

[0055] S4: Add 3-aminopropyltriethoxysilane to N,N-dimethylaminocarbamate and stir until homogeneous to obtain a 3-aminopropyltriethoxysilane solution with a concentration of 18.8 g / L.

[0056] S5: Add 2g of cerium dibutyl phosphate to deionized water, disperse by ultrasonication, add 1.88g of 3-aminopropyltriethoxysilane, stir evenly to obtain a cerium dibutyl phosphate suspension;

[0057] S6: Immerse the first steel pipe in 3-aminopropyltriethoxysilane solution, heat to 100°C and react for 6 hours, add dibutyl phosphate cerium suspension, cool to 55°C and react for 12 hours, wash with a water-ethanol mixture solution with a volume ratio of 1:1, and dry to obtain a seamless steel pipe for low temperature use.

[0058] The chemical composition of the tube blank, by mass percentage, is C: 0.15%, Si: 0.36%, Mn: 1.50%, Als: 0.32%, Ti: 0.21%, Nb: 0.42%, N: 0.0032%, with the balance being Fe and unavoidable impurities.

[0059] Comparative Example 2: A processing technology for seamless steel pipes for low temperature applications, comprising the following steps: S1: The raw materials are sequentially smelted in a converter, refined twice, degassed in a vacuum, and continuously cast according to the formula to obtain a pipe billet;

[0060] S2: The tube blank is sequentially heated, pierced, continuously rolled, tube removed, tension reduced in diameter, and heat-treated at 900℃ for 40 minutes to obtain the original tube;

[0061] S3: The surface of the original tube was polished sequentially with 180, 320, 800, 1200, and 2500 grit sandpaper, polished with 3μm diamond polishing fluid, ultrasonically cleaned with acetone for 5 minutes, and dried with compressed air. Copper layers were electroplated sequentially on the pretreated original tube surface using nickel sulfamate solution and copper sulfate solution, followed by nickel plating on the copper layer. The electroplated original tube was placed in a tube furnace with a vacuum of 5 mtorr, and a mixture of argon and hydrogen gas was introduced at a pressure of 1.8 torr and a flow rate of 250 sccm. The tube was preheated to 1060℃ and maintained for 40 minutes. Hexane was introduced at a flow rate of 1 sccm and the tube was maintained at 1060℃ for 55 minutes. The tube was then cooled to room temperature under the flow of a mixture of argon and hydrogen gas at a pressure of 1.8 torr and a flow rate of 250 sccm to obtain the first steel tube.

[0062] The copper sulfate solution has a main salt concentration of 50 g / L, a sulfuric acid concentration of 50 g / L, a temperature of 20°C, and a pH of 4; the electroplating parameters include a current of 8 A and a nickel layer thickness of 12 μm.

[0063] S4: Add 3-aminopropyltriethoxysilane to N,N-dimethylaminocarbamate and stir until homogeneous to obtain a 3-aminopropyltriethoxysilane solution with a concentration of 18.8 g / L.

[0064] S5: Add 2g of cerium dibutyl phosphate to deionized water, disperse by ultrasonication, add 1.88g of 3-aminopropyltriethoxysilane, stir evenly to obtain a cerium dibutyl phosphate suspension;

[0065] S6: Immerse the first steel pipe in 3-aminopropyltriethoxysilane solution, heat to 100°C and react for 6 hours, add dibutyl phosphate cerium suspension, cool to 55°C and react for 12 hours, wash with a water-ethanol mixture solution with a volume ratio of 1:1, and dry to obtain a seamless steel pipe for low temperature use.

[0066] The chemical composition of the tube blank, by mass percentage, is C: 0.15%, Si: 0.36%, Mn: 1.50%, Als: 0.32%, Ti: 0.21%, Nb: 0.42%, N: 0.0032%, with the balance being Fe and unavoidable impurities.

[0067] Comparative Example 3: A processing technology for seamless steel pipes for low temperature applications, comprising the following steps: S1: The raw materials are sequentially smelted in a converter, refined twice, degassed in a vacuum, and continuously cast according to the formula to obtain a billet;

[0068] S2: The tube blank is sequentially heated, pierced, continuously rolled, tube removed, tension reduced in diameter, and heat-treated at 900℃ for 40 minutes to obtain the original tube;

[0069] S3: The surface of the original tube was polished sequentially with 180, 320, 800, 1200, and 2500 grit sandpaper, polished with 3μm diamond polishing fluid, ultrasonically cleaned with acetone for 5 minutes, and dried with compressed air. Copper layers were electroplated sequentially on the pretreated original tube surface using nickel sulfamate solution and copper sulfate solution, followed by nickel plating on the copper layer. The electroplated original tube was placed in a tube furnace with a vacuum of 5 mtorr, and a mixture of argon and hydrogen gas was introduced at a pressure of 1.8 torr and a flow rate of 250 sccm. The tube was preheated to 1060℃ and maintained for 40 minutes. Hexane was introduced at a flow rate of 1 sccm and the tube was maintained at 1060℃ for 55 minutes. The tube was then cooled to room temperature under the flow of a mixture of argon and hydrogen gas at a pressure of 1.8 torr and a flow rate of 250 sccm to obtain the first steel tube.

[0070] The nickel sulfamate solution has a main salt concentration of 200 g / L, a boric acid concentration of 30 g / L, a temperature of 55°C, and a pH of 4; the copper sulfate solution has a main salt concentration of 50 g / L, a sulfuric acid concentration of 50 g / L, a temperature of 20°C, and a pH of 4; the electroplating parameters include: a current of 8 A, a copper layer thickness of 4 μm, and a nickel layer thickness of 6 μm.

[0071] S4: Add 3-aminopropyltriethoxysilane to N,N-dimethylaminocarbamate and stir until homogeneous to obtain a 3-aminopropyltriethoxysilane solution with a concentration of 18.8 g / L.

[0072] S5: Add 2g of cerium dibutyl phosphate to deionized water, disperse by ultrasonication, add 1.88g of 3-aminopropyltriethoxysilane, stir evenly to obtain a cerium dibutyl phosphate suspension;

[0073] S6: Immerse the first steel pipe in 3-aminopropyltriethoxysilane solution, heat to 100°C and react for 6 hours, add dibutyl phosphate cerium suspension, cool to 55°C and react for 12 hours, wash with a water-ethanol mixture solution with a volume ratio of 1:1, and dry to obtain a seamless steel pipe for low temperature use.

[0074] The chemical composition of the tube blank, by mass percentage, is C: 0.15%, Si: 0.36%, Mn: 1.50%, Als: 0.32%, Ti: 0.21%, Nb: 0.42%, N: 0.0032%, with the balance being Fe and unavoidable impurities.

[0075] Comparative Example 4: A processing technology for seamless steel pipes for low temperature applications, comprising the following steps: S1: The raw materials are sequentially smelted in a converter, refined twice, degassed in a vacuum, and continuously cast according to the formula to obtain a billet;

[0076] S2: The tube blank is sequentially heated, pierced, continuously rolled, tube removed, tension reduced in diameter, and heat-treated at 900℃ for 40 minutes to obtain the original tube;

[0077] S3: The surface of the original tube was polished sequentially with 180, 320, 800, 1200, and 2500 grit sandpaper, polished with 3μm diamond polishing fluid, ultrasonically cleaned with acetone for 5 minutes, and dried with compressed air. Copper layers were electroplated sequentially on the pretreated original tube surface using nickel sulfamate solution and copper sulfate solution, followed by nickel plating on the copper layer. The electroplated original tube was placed in a tube furnace with a vacuum of 5 mtorr, and a mixture of argon and hydrogen gas was introduced at a pressure of 1.8 torr and a flow rate of 250 sccm. The tube was preheated to 1060℃ and maintained for 40 minutes. Hexane was introduced at a flow rate of 1 sccm and the tube was maintained at 1060℃ for 55 minutes. The tube was then cooled to room temperature under the flow of a mixture of argon and hydrogen gas at a pressure of 1.8 torr and a flow rate of 250 sccm to obtain the first steel tube.

[0078] The nickel sulfamate solution has a main salt concentration of 200 g / L, a boric acid concentration of 30 g / L, a temperature of 55°C, and a pH of 4; the copper sulfate solution has a main salt concentration of 50 g / L, a sulfuric acid concentration of 50 g / L, a temperature of 20°C, and a pH of 4; the electroplating parameters include: a current of 8 A, a copper layer thickness of 37 μm, and a nickel layer thickness of 33 μm.

[0079] S4: Add 3-aminopropyltriethoxysilane to N,N-dimethylaminocarbamate and stir until homogeneous to obtain a 3-aminopropyltriethoxysilane solution with a concentration of 18.8 g / L.

[0080] S5: Add 2g of cerium dibutyl phosphate to deionized water, disperse by ultrasonication, add 1.88g of 3-aminopropyltriethoxysilane, stir evenly to obtain a cerium dibutyl phosphate suspension;

[0081] S6: Immerse the first steel pipe in 3-aminopropyltriethoxysilane solution, heat to 100°C and react for 6 hours, add dibutyl phosphate cerium suspension, cool to 55°C and react for 12 hours, wash with a water-ethanol mixture solution with a volume ratio of 1:1, and dry to obtain a seamless steel pipe for low temperature use.

[0082] The chemical composition of the tube blank, by mass percentage, is C: 0.15%, Si: 0.36%, Mn: 1.50%, Als: 0.32%, Ti: 0.21%, Nb: 0.42%, N: 0.0032%, with the balance being Fe and unavoidable impurities.

[0083] Comparative Example 5: A processing technology for seamless steel pipes for low temperature applications, comprising the following steps: S1: The raw materials are sequentially smelted in a converter, refined twice, degassed in a vacuum, and continuously cast according to the formula to obtain a pipe billet;

[0084] S2: The tube blank is sequentially heated, pierced, continuously rolled, tube removed, tension reduced in diameter, and heat-treated at 900℃ for 40 minutes to obtain the original tube;

[0085] S3: The surface of the original tube was polished sequentially with 180, 320, 800, 1200, and 2500 grit sandpaper, polished with 3μm diamond polishing fluid, ultrasonically cleaned with acetone for 5 minutes, and dried with compressed air. The pretreated original tube was placed in a tube furnace with a vacuum of 5 mtorr, and a mixture of argon and hydrogen was introduced at a pressure of 1.8 torr and a flow rate of 250 sccm. It was preheated to 1060℃ and maintained for 40 minutes. Hexane was introduced at a flow rate of 1 sccm and maintained at 1060℃ for 55 minutes. It was then cooled to room temperature under the flow of a mixture of argon and hydrogen at a pressure of 1.8 torr and a flow rate of 250 sccm to obtain the first steel tube.

[0086] S4: Add 3-aminopropyltriethoxysilane to N,N-dimethylaminocarbamate and stir until homogeneous to obtain a 3-aminopropyltriethoxysilane solution with a concentration of 18.8 g / L.

[0087] S5: Add 2g of cerium dibutyl phosphate to deionized water, disperse by ultrasonication, add 1.88g of 3-aminopropyltriethoxysilane, stir evenly to obtain a cerium dibutyl phosphate suspension;

[0088] S6: Immerse the first steel pipe in 3-aminopropyltriethoxysilane solution, heat to 100°C and react for 6 hours, add dibutyl phosphate cerium suspension, cool to 55°C and react for 12 hours, wash with a water-ethanol mixture solution with a volume ratio of 1:1, and dry to obtain a seamless steel pipe for low temperature use.

[0089] The chemical composition of the tube blank, by mass percentage, is C: 0.15%, Si: 0.36%, Mn: 1.50%, Als: 0.32%, Ti: 0.21%, Nb: 0.42%, N: 0.0032%, with the balance being Fe and unavoidable impurities.

[0090] Comparative Example 6: A processing technology for seamless steel pipes for low temperature applications, comprising the following steps: S1: The raw materials are sequentially smelted in a converter, refined twice, degassed in a vacuum, and continuously cast according to the formula to obtain a pipe billet;

[0091] S2: The tube blank is sequentially heated, pierced, continuously rolled, tube removed, tension reduced in diameter, and heat-treated at 900℃ for 40 minutes to obtain the original tube;

[0092] S3: The surface of the original tube was polished sequentially with 180, 320, 800, 1200, and 2500 grit sandpaper, polished with 3μm diamond polishing fluid, ultrasonically cleaned with acetone for 5 minutes, and dried with compressed air. Copper layers were electroplated sequentially on the pretreated original tube surface using nickel sulfamate solution and copper sulfate solution, followed by nickel plating on the copper layer. The electroplated original tube was placed in a tube furnace with a vacuum of 5 mtorr, and a mixture of argon and hydrogen gas was introduced at a pressure of 1.8 torr and a flow rate of 250 sccm. The tube was preheated to 1060℃ and maintained for 40 minutes. Hexane was introduced at a flow rate of 1 sccm and the tube was maintained at 1060℃ for 55 minutes. The tube was then cooled to room temperature under the flow of a mixture of argon and hydrogen gas at a pressure of 1.8 torr and a flow rate of 250 sccm to obtain the first steel tube.

[0093] The nickel sulfamate solution has a main salt concentration of 200 g / L, a boric acid concentration of 30 g / L, a temperature of 55°C, and a pH of 4; the copper sulfate solution has a main salt concentration of 50 g / L, a sulfuric acid concentration of 50 g / L, a temperature of 20°C, and a pH of 4; the electroplating parameters include: a current of 8 A, a copper layer thickness of 13 μm, and a nickel layer thickness of 12 μm.

[0094] S4: Add 3-aminopropyltriethoxysilane to N,N-dimethylaminocarbamate and stir until homogeneous to obtain a 3-aminopropyltriethoxysilane solution with a concentration of 18.8 g / L.

[0095] S5: Add 2g of cerium dibutyl phosphate to deionized water, disperse by ultrasonication, add 1.88g of 3-aminopropyltriethoxysilane, stir evenly to obtain a cerium dibutyl phosphate suspension;

[0096] S6: Immerse the first steel pipe in 3-aminopropyltriethoxysilane solution, heat to 100°C and react for 6 hours, add dibutyl phosphate cerium suspension, cool to 55°C and react for 12 hours, wash with a water-ethanol mixture solution with a volume ratio of 1:1, and dry to obtain a seamless steel pipe for low temperature use.

[0097] The chemical composition of the tube blank, by mass percentage, is: C: 0.15%, Si: 0.36%, Mn: 1.50%, Als: 0.32%, Ti: 0.21%, V: 0.065%, N: 0.0030%, with the balance being Fe and unavoidable impurities.

[0098] Experiment: Impact toughness test: The seamless steel pipes prepared in the above examples and comparative examples were tested according to the ASTM A370 impact test standard at temperatures of -90℃ and -100℃.

[0099] Corrosion resistance test: The seamless steel pipes prepared in the above examples and comparative examples were completely immersed in 10% H2SO4 solution / 10% NaOH solution at room temperature of 27°C. After 5 days, they were taken out, washed to remove corrosion, dried and weighed again. The corrosion rate was calculated by the weight loss method.

[0100] The experimental results are shown in Table 1 below.

[0101] Table 1 Performance Test Data of Seamless Steel Pipes for Low Temperature Use

[0102]

[0103] Conclusion: The seamless steel pipe for low-temperature applications prepared by this invention has excellent low-temperature mechanical properties and corrosion resistance.

[0104] Comparative Example 1 only had a copper layer electroplated, Comparative Example 2 only had a nickel layer electroplated, and Comparative Example 5 had direct deposition, which is not conducive to the growth of graphene on the surface of low carbon steel, resulting in reduced performance.

[0105] In Comparative Example 3, the electroplated layer was too thin, allowing iron to diffuse through the grain boundaries and penetrate the copper / nickel layer to reach the surface, thus inhibiting graphene formation. Simultaneously, carbon may infiltrate the steel substrate, preventing the formation of uniform graphene and reducing performance.

[0106] In Comparative Example 4, the excessively thick electroplated layer caused thermomechanical stress to induce layer cracking, allowing copper to diffuse to the nickel surface and hindering the growth of multilayer graphene. Furthermore, the excessively thick nickel layer led to excessive carbon dissolution and precipitation upon cooling, forming carbon soot instead of graphene, thus reducing performance.

[0107] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A processing technology for seamless steel pipes used at low temperatures, characterized in that: Includes the following steps: S1: The raw materials are smelted in a converter, refined in a secondary refining process, degassed in a vacuum, and continuously cast according to the formula to obtain a tube billet. S2: The tube blank is sequentially heated, pierced, continuously rolled, removed, tension reduced in diameter, and heat treated to obtain the original tube; S3: The original pipe is subjected to surface pretreatment, electroplating, and chemical vapor deposition in sequence to obtain the first steel pipe; S4: The first steel pipe is sequentially immersed in 3-aminopropyltriethoxysilane solution and dibutyl phosphate cerium suspension, and then dried to obtain a seamless steel pipe for low temperature use.

2. The processing technology for a seamless steel pipe for low-temperature applications according to claim 1, characterized in that: The chemical composition of the tube blank, by mass percentage, is C: 0.15-0.16%, Si: 0.36-0.40%, Mn: 1.43-1.50%, Als: 0.15-0.32%, Ti: 0.15-0.21%, Nb: 0.42-0.51%, N: 0.0028-0.0032%, with the balance being Fe and unavoidable impurities.

3. The processing technology for a seamless steel pipe for low-temperature applications according to claim 1, characterized in that: The heat treatment temperature is 890-910℃, and the time is 40-60min.

4. The processing technology for a seamless steel pipe for low-temperature applications according to claim 1, characterized in that: The specific steps of the surface pretreatment include: grinding the surface of the original tube sequentially with 180, 320, 800, 1200 and 2500 grit sandpaper, polishing with 3-4μm diamond polishing liquid, ultrasonically cleaning with acetone for 5-10 minutes, and drying with compressed air.

5. The processing technology for a seamless steel pipe for low-temperature applications according to claim 1, characterized in that: The specific electroplating steps include: using nickel sulfamate solution and copper sulfate solution to electroplat a copper layer on the surface of the original tube in sequence, and then electroplating a nickel layer on the copper layer.

6. The processing technology for a seamless steel pipe for low-temperature applications according to claim 5, characterized in that: The nickel sulfamate solution has a main salt concentration of 200-450 g / L, a boric acid concentration of 30-50 g / L, a temperature of 55-60℃, and a pH of 3.9-4.1; the copper sulfate solution has a main salt concentration of 50-100 g / L, a sulfuric acid concentration of 50-100 g / L, a temperature of 20-25℃, and a pH of 3.9-4.

1. The electroplating parameters include: current of 8-10A, copper layer thickness of 13-15μm, and nickel layer thickness of 12-14μm.

7. The processing technology for a seamless steel pipe for low-temperature applications according to claim 1, characterized in that: The specific steps of the chemical vapor deposition include: placing the original tube in a tube furnace with a vacuum of 5 mtorr, introducing a mixture of argon and hydrogen gas at a pressure of 1.8-2.2 torr and a flow rate of 250-280 sccm, preheating to 1060-1061℃ and maintaining it for 40-45 min, introducing hexane at a flow rate of 1-1.2.2 sccm, maintaining it at 1060-1061℃ for 55-60 min, and cooling to room temperature under the flow of a mixture of argon and hydrogen gas at a pressure of 1.8-2.2 torr and a flow rate of 250-280 sccm.

8. The processing technology for a seamless steel pipe for low-temperature applications according to claim 1, characterized in that: In step S4, the method for preparing seamless steel pipes for low temperature includes the following steps: Step (1): 3-aminopropyltriethoxysilane is added to N,N-dimethylaminoformamide and stirred evenly to obtain a 3-aminopropyltriethoxysilane solution. Step (2): Add cerium dibutyl phosphate to deionized water, disperse by ultrasonication, add 3-aminopropyltriethoxysilane, stir evenly to obtain cerium dibutyl phosphate suspension; Step (3): Immerse the first steel pipe in 3-aminopropyltriethoxysilane solution, heat to 100-105℃ and react for 6-6.5h, add dibutyl phosphate cerium suspension, cool to 50-55℃ and react for 12-24h, wash with a water-ethanol mixture solution with a volume ratio of 1:1, and dry to obtain a seamless steel pipe for low temperature use.

9. The processing technology for a seamless steel pipe for low-temperature applications according to claim 7, characterized in that: The concentration of the 3-aminopropyltriethoxysilane solution is 18.8-20 g / L; in the preparation of the dibutyl phosphate cerium suspension, the mass ratio of 3-aminopropyltriethoxysilane to dibutyl phosphate cerium is 1.88:(2-4).

10. A seamless steel pipe for cryogenic use prepared by the processing technology of any one of claims 1-9.

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