Small and medium caliber hot bending elbow pipe for hydrogen delivery and manufacturing method thereof

Abstract

The application discloses a small and medium caliber hot bending elbow pipe for hydrogen delivery and a manufacturing method thereof, and specifically comprises the following steps: step 1, selecting a hot-rolled coil plate, and carrying out uncoiling and flattening on the selected hot-rolled coil plate; step 2, carrying out edge milling on the flattened coil plate and then carrying out roll forming to obtain a coiled pipe; step 3, welding the coiled pipe according to welding process requirements, and processing the coiled pipe after welding; step 4, hot bending the coiled pipe processed in step 3 to form an elbow pipe, and carrying out heat treatment on the elbow pipe; and step 5, carrying out inspection on the elbow pipe after heat treatment. The application solves the problems of large wall thickness fluctuation and poor hydrogen embrittlement resistance of the existing small and medium caliber hot bending elbow pipe.

Description

Technical Field

[0001] This invention belongs to the field of hot bending technology, specifically relating to small and medium diameter hot bending pipes for hydrogen transportation. This invention also relates to a method for manufacturing the aforementioned small and medium diameter hot bending pipes. Background Technology

[0002] Hydrogen energy is a secondary clean energy source and a zero-carbon energy source, possessing four major characteristics: cleanliness, high efficiency, safety, and sustainability. Although there are various methods of hydrogen transportation, pipeline transport remains the most widespread and convenient, offering significant advantages in transportation efficiency and cost. Due to the unique physical and chemical properties of hydrogen, compared to natural gas, as the transportation pressure increases, the composition and strength of the pipe material, metallurgical defects, and pipe manufacturing processes have a significant impact on hydrogen damage to the pipe material. The relative reduction of area under slow tension can decrease by more than 60% for pipes of the same steel grade but with different microstructures, posing a severe challenge to the integrity and service safety of pipelines. Developing hydrogen transport pipes with excellent resistance to hydrogen embrittlement is key to achieving large-scale, long-distance hydrogen transportation.

[0003] Hot bending refers to a pipe bending process that involves heating a metal pipe to a certain temperature using heat treatment, and then applying external force to bend it into a desired angle or curve. Currently, small- and medium-diameter hot bending pipes for hydrogen transportation mainly use seamless pipes, with steel grades of X52 and below. Although seamless pipes are widely used for hydrogen pipeline transportation, their inherent technological characteristics present several challenges. First, seamless pipes are formed by heating and piercing steel billets, resulting in significant wall thickness fluctuations. Second, the carbon equivalent of the billet is relatively high, making the billet surface prone to defects such as rolling cracks during piercing. Furthermore, weld cracks are easily observed during on-site circumferential welding, making it difficult to guarantee the quality of the welded joints. Additionally, since carbon is a primary solid solution strengthening element, higher carbon content increases the hydrogen embrittlement sensitivity of the pipeline steel, which is detrimental to hydrogen transportation. The key technology for using hot bending pipes for hydrogen transportation lies in ensuring that the hot bending pipes possess good resistance to hydrogen embrittlement and excellent low-temperature toughness while maintaining a low carbon equivalent.

[0004] In view of the above, it is necessary to improve the manufacturing process of hot-bent pipes for hydrogen transportation, and solve the problems of high carbon equivalent, large wall thickness fluctuation, poor resistance to hydrogen embrittlement, and easy cracking of the welded joint of the circumferential weld of the original small and medium diameter seamless hot-bent pipes, so as to reduce the tendency of hydrogen embrittlement and hydrogen-induced cracking, and meet the requirements of safe long-distance transportation of medium and high pressure hydrogen. Summary of the Invention

[0005] The purpose of this invention is to provide a method for manufacturing small- and medium-diameter hot-bent pipes for hydrogen transportation, which solves the problems of large wall thickness fluctuations and poor resistance to hydrogen embrittlement in existing small- and medium-diameter hot-bent pipes.

[0006] Another object of the present invention is to provide a small-to-medium diameter hot-bent pipe for hydrogen transportation.

[0007] The first technical solution adopted in this invention is a method for manufacturing small-to-medium diameter hot-bent pipes for hydrogen transportation, specifically including the following steps: Step 1: Select hot-rolled coils and uncoil and level them. Step 2: After milling the edges of the leveled coil, roll forming is performed to obtain the coiled tube; Step 3: Weld the rolled pipe according to the welding process requirements, and process the welded rolled pipe. Step 4: The rolled tube processed in step 3 is hot-bent into a bent tube, and the bent tube is then heat-treated. Step 5: Inspect the heat-treated bent pipe.

[0008] The first technical solution of the present invention is further characterized in that, In step 1, the hot-rolled coil is composed of the following raw material components by weight percentage: C: 0.03~0.06%, Si: 0.05~0.45%, Mn: 0.7~1.3%, S≤0.002%, P≤0.008%, Ni: 0.01~0.3%, Cr: 0.01~0.3%, Cu: 0.01~0.35%, Nb: 0.01~0.10%, V: 0.001~0.05%, Ti≤0.04%, Mo≤0.15%, Al≤0.04%, B≤0.0005%, with the balance being Fe. The total content of all the above components is 100%. Furthermore, CEPcm ≤ 0.15; the metallographic structure contains A, B, C, D, and DS type non-metallic inclusions of grade 1.0, banded structures of grade 1.5, and grain size of grade 9.

[0009] In step 2, the edge milling is performed using a sliding plate milling machine with a pressure roller device to process the edge of the plate into an X-shaped bevel, with a single bevel angle ≤ 60°.

[0010] Step 3 welding is divided into pre-welding and precision welding; Pre-welding is performed using high-frequency resistance welding, with a welding frequency of 200kHz~500kHz, a welding speed of 10m / min~15m / min, and an extrusion amount of 2mm~10mm. The process involves external welding followed by internal welding. Specifically, the external welding is performed using a dual-wire submerged arc welding system. The first wire uses DC reverse polarity with a welding current of 650A~1100A and a welding voltage of 31V~36V; the second wire uses AC polarity with a welding current of 580A~800A and a welding voltage of 34V~38V; the welding speed is 1.2m / min~1.5m / min. The internal welding process is as follows: welding is performed using a double-wire submerged arc automatic welding system. The first wire uses DC reverse polarity, with a welding current of 550A~800A and a welding voltage of 31V~35V; the second wire uses AC polarity, with a welding current of 400A~600A and a welding voltage of 33V~38V; the welding speed is 1.2m / min~1.5m / min.

[0011] The inner welding wire is Atlantic CHF-SH welding wire, the outer welding wire is CHW-SG welding wire, and the flux is CHW102SH sintered flux.

[0012] In step 3, the welded coiled pipe is processed to expand the diameter of the entire pipe body. The expansion of the entire pipe body adopts the expansion module and segment expansion method. The expansion length of each segment is 2~3m, and the length of each step forward is 0.8m~1.0m. The pipe body expansion rate is 0.7%~0.9%. After the expansion is completed, the pipe body is subjected to continuous X-ray inspection, hydrostatic test, ultrasonic flaw detection of weld and base material, pipe end chamfering, pipe end radiography, and process pipe butt welding.

[0013] In step 4, the hot bending process specifically adopts an online quenching process, using a medium-frequency induction heating coil for heating. The medium-frequency frequency is 300HZ~380HZ, the voltage is 485V~600V, the power is 260KW~600KW, and the bending tube advance rate is 24mm / min~40mm / min. The gap between the induction heating coil and the quenching water ring is 18mm~20mm, and the gap between the two rings on the inner arc side is 20mm~22mm.

[0014] In step 4, the heat treatment involved placing the bent tube into a heat treatment furnace for tempering. The heat treatment temperature was 520℃~540℃, and the holding time was 40min~60min.

[0015] The second technical solution adopted in this invention is a small-diameter hot-bent tube for hydrogen transportation, which is manufactured by the above-mentioned manufacturing method of the small-diameter hot-bent tube for hydrogen transportation.

[0016] The beneficial effects of this invention are: (1) The manufacturing method of the small-diameter hot-bent pipe for hydrogen transportation of the present invention leverages the advantages of high-frequency resistance welding for efficient pre-welding and straight-seam submerged arc welding, and adopts a heat treatment process of quenching and tempering, which significantly improves forming efficiency and weld quality. It can effectively solve the problems of high carbon equivalent, large wall thickness fluctuation, poor resistance to hydrogen embrittlement, and easy cracking of circumferential weld joints in existing small-diameter seamless hot-bent pipes. The hot-bent pipes manufactured have the characteristics of low raw material cost, high production efficiency, stable and reliable weld performance, excellent resistance to hydrogen embrittlement, and easy cracking of circumferential weld joints.

[0017] Furthermore, the hot-bent pipe body and weld seam of the manufactured hot-bent pipe body and weld seam under slow strain rate tensile stress in a smooth sample at 7.2MPa hydrogen environment showed a reduction in area of ​​less than 5% and a fracture toughness KIC ≥ 180MPa·m1 / 2, indicating that the hot-bent pipe has excellent resistance to hydrogen-induced cracking and meets the transportation requirements of medium and high pressure pure hydrogen pipelines at 7.2MPa.

[0018] (2) The welding process of the manufacturing method of the small-diameter hot-bent pipe for hydrogen transportation of the present invention adopts the submerged arc welding process of first welding the outside and then welding the inside. This allows for a relatively larger adjustment range of the internal welding process parameters, which is conducive to improving the pass rate of submerged arc welds and improving the quality of welds.

[0019] (3) In the manufacturing method of the small-diameter hot-bent pipe for hydrogen transportation of the present invention, when the full pipe body is expanded, the main pipe of the hot-bent pipe adopts a segmented full pipe body expansion process, which can effectively solve the problem of large ellipticity and residual stress of the pipe body after high frequency pre-welding. The outer diameter deviation of the straight pipe section of the bend is measured by the circumference method: -1mm to 2mm. Within 100mm from the pipe end of the straight pipe section of the bend, the out-of-roundness is ≤0.6%D, and the out-of-roundness of the bend section is ≤2.5%D. The verticality of the pipe end of the bend is ≤2.5mm, which can meet the requirements of on-site circumferential welding of the pipeline. Attached Figure Description

[0020] Figure 1 This is a schematic flowchart illustrating the manufacturing method of the small-diameter hot-bent pipe for hydrogen transportation according to the present invention. Detailed Implementation

[0021] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0022] Example 1 The present invention relates to a method for manufacturing small-to-medium diameter hot-bent pipes for hydrogen transportation, such as... Figure 1 As shown, the specific steps include: Step 1: Select hot-rolled coils and uncoil and level them. Specifically, uncoiling involves starting the uncoiler, which rotates the drum and unfolds the steel coil. During uncoiling, it's crucial to control the uncoiling speed to avoid loosening or damage to the coil due to excessive speed or slowness. The unfolded coil is then leveled using a leveling machine. A leveling machine typically consists of multiple leveling rollers. By adjusting the pressure and gap between these rollers, the steel coil receives uniform pressure as it passes through the leveling machine, achieving the desired leveling effect.

[0023] Step 2: After milling the edges of the leveled coil, roll forming is performed to obtain the coiled tube; Furthermore, the edge milling process employs a sliding plate milling machine with a pressure roller device to process the edge bevel into an X-shaped bevel.

[0024] Step 3: Weld the rolled pipe according to the welding process requirements, and process the welded rolled pipe. Furthermore, welding is divided into pre-welding and precision welding. Then, the welded rolled pipe is processed to expand the diameter of the entire pipe body. After the diameter expansion is completed, the pipe body is subjected to continuous X-ray inspection, hydrostatic test, ultrasonic flaw detection of weld and base material, pipe end chamfering, pipe end radiography, and process pipe butt welding.

[0025] Specifically, X-ray continuous inspection and observation of images are used to determine whether there are defects inside the workpiece; The hydrostatic test is used to determine whether the workpiece has any abnormalities such as leakage or deformation, and whether the workpiece can return to its original shape and size after the pressure is released. Ultrasonic testing of welds and base metal is used to determine the size, location, and nature of defects. By measuring parameters such as the height and location of the defect wave, and considering factors such as the thickness of the workpiece, the equivalent magnitude of the defect is determined. The weld or base metal is then judged to be acceptable according to the standard's specified acceptance level.

[0026] The pipe end is inspected by radiography to check for defects such as internal porosity, slag inclusions, and incomplete penetration after beveling.

[0027] Step 4: The rolled tube processed in step 3 is hot-bent into a bent tube, and the bent tube is then heat-treated. Step 5: Inspect the heat-treated bent pipe.

[0028] Example 2 The present invention relates to a method for manufacturing a small-to-medium diameter hot-bent pipe for hydrogen transportation, which specifically includes the following steps: Step 1: Select hot-rolled coils and uncoil and level them. In step 1, the hot-rolled coil is composed of the following raw material components by weight percentage: C: 0.03~0.06%, Si: 0.05~0.45%, Mn: 0.7~1.3%, S≤0.002%, P≤0.008%, Ni: 0.01~0.3%, Cr: 0.01~0.3%, Cu: 0.01~0.35%, Nb: 0.01~0.10%, V: 0.001~0.05%, Ti≤0.04%, Mo≤0.15%, Al≤0.04%, B≤0.0005%, with the balance being Fe. The total content of all the above components is 100%.

[0029] Furthermore, CEPcm ≤ 0.15; the metallographic structure contains A, B, C, D, and DS type non-metallic inclusions of grade 1.0, banded structures of grade 1.5, and grain size of grade 9.

[0030] Step 2: After milling the edges of the leveled coil, roll forming is performed to obtain the coiled tube; Furthermore, the edge milling process uses a sliding plate milling machine with a pressure roller device to process the edge bevel into an X-shaped bevel, with a single bevel angle ≤60°.

[0031] Step 3: Weld the rolled pipe according to the welding process requirements, and process the welded rolled pipe. Furthermore, welding is divided into pre-welding and precision welding. Then, the welded rolled pipe is processed to expand the diameter of the entire pipe body. After the diameter expansion is completed, the pipe body is subjected to continuous X-ray inspection, hydrostatic test, ultrasonic flaw detection of weld and base material, pipe end chamfering, pipe end radiography, and process pipe butt welding.

[0032] Specifically, the pre-welding adopts high-frequency resistance welding for pre-welding, with a welding frequency of 200kHz~500kHz, a welding speed of 10m / min~15m / min, and an extrusion amount of 2mm~10mm; the fine welding is to weld the outside first and then the inside.

[0033] Step 4: The rolled tube processed in step 3 is hot-bent into a bent tube, and the bent tube is then heat-treated. Furthermore, in step 4, the heat treatment involved placing the bent tube into a heat treatment furnace for tempering heat treatment at a temperature of 520℃~540℃ and a holding time of 40min~60min.

[0034] Step 5: Inspect the heat-treated bent pipe.

[0035] Example 3 Step 1: Select hot-rolled coils and uncoil and level them. Step 2: After milling the edges of the leveled coil, roll forming is performed to obtain the coiled tube; Step 3: Weld the rolled pipe according to the welding process requirements, and process the welded rolled pipe. Furthermore, welding is divided into pre-welding and precision welding. Then, the welded rolled pipe is processed to expand the diameter of the entire pipe body. After the diameter expansion is completed, the pipe body is subjected to continuous X-ray inspection, hydrostatic test, ultrasonic flaw detection of weld and base material, pipe end chamfering, pipe end radiography, and process pipe butt welding.

[0036] Specifically, the pre-welding adopts high-frequency resistance welding for pre-welding, with a welding frequency of 200kHz~500kHz, a welding speed of 10m / min~15m / min, and an extrusion amount of 2mm~10mm; the fine welding is to weld the outside first and then the inside.

[0037] Specifically, the expansion of the entire pipe body adopts the expansion module and segmented expansion method. The expansion length of each segment is 2m to 3m, and the length of each step forward is 0.8m to 1.0m. The expansion rate of the pipe body is 0.7% to 0.9%.

[0038] Step 4: The rolled tube processed in step 3 is hot-bent into a bent tube, and the bent tube is then heat-treated. Furthermore, in step 4, the hot bending process specifically adopts an online quenching process, using a medium-frequency induction heating coil for heating. The medium-frequency frequency is 300HZ~380HZ, the voltage is 485V~600V, the power is 260KW~600KW, and the bending tube advance rate is 24mm / min~40mm / min. Adjust the gap between the induction heating coil and the quenching water ring near the weld seam to 18mm~20mm according to the specifications of the bent pipe, and the gap between the two coils on the inner arc side to 20mm~22mm.

[0039] Furthermore, in step 4, the heat treatment involved placing the bent tube into a heat treatment furnace for tempering heat treatment at a temperature of 520℃~540℃ and a holding time of 40min~60min.

[0040] Step 5: Inspect the heat-treated bent pipe.

[0041] Example 4 The present invention relates to a method for manufacturing a small-to-medium diameter hot-bent pipe for hydrogen transportation, which specifically includes the following steps: Step 1: Select hot-rolled coils and uncoil and level them. In step 1, the hot-rolled coil is composed of the following raw material components by weight percentage: C: 0.03~0.06%, Si: 0.05~0.45%, Mn: 0.7~1.3%, S≤0.002%, P≤0.008%, Ni: 0.01~0.3%, Cr: 0.01~0.3%, Cu: 0.01~0.35%, Nb: 0.01~0.10%, V: 0.001~0.05%, Ti≤0.04%, Mo≤0.15%, Al≤0.04%, B≤0.0005%, with the balance being Fe. The total content of all the above components is 100%.

[0042] Furthermore, CEPcm ≤ 0.15; the metallographic structure contains A, B, C, D, and DS type non-metallic inclusions of grade 1.0, banded structures of grade 1.5, and grain size of grade 9.

[0043] Step 2: After milling the edges of the leveled coil, roll forming is performed to obtain the coiled tube; Furthermore, the edge milling uses a sliding plate milling machine pressure roller device to process the edge bevel into an X-shaped bevel. Different milling machine lower cutter holder shim specifications are selected to control the blunt edge height after edge milling, and different cutter holder specifications are selected to control the upper and lower bevel angles after edge milling. The maximum processing angle is 60° on one side, and the maximum processing wall thickness is 20mm.

[0044] Step 3: Weld the rolled pipe according to the welding process requirements, and process the welded rolled pipe. Furthermore, welding is divided into pre-welding and precision welding. Then, the welded rolled pipe is processed to expand the diameter of the entire pipe body. Expanding the diameter of the entire pipe body can effectively solve the problems of excessive ellipticity and residual stress of the pipe body after high-frequency pre-welding. After the diameter expansion is completed, the pipe body is subjected to continuous X-ray inspection, hydrostatic test, ultrasonic flaw detection of weld and base material, pipe end chamfering, pipe end radiography, and process pipe butt welding.

[0045] Specifically, the pre-welding adopts high-frequency resistance welding for pre-welding, with a welding frequency of 200kHz~500kHz, a welding speed of 10m / min~15m / min, and an extrusion amount of 2mm~10mm.

[0046] The process involves external welding followed by internal welding. Specifically, the external welding is performed using a dual-wire submerged arc welding system. The first wire uses DC reverse polarity with a welding current of 650A~1100A and a welding voltage of 31V~36V; the second wire uses AC polarity with a welding current of 580A~800A and a welding voltage of 34V~38V; the welding speed is 1.2m / min~1.5m / min. The internal welding process is as follows: welding is performed using a double-wire submerged arc automatic welding system. The first wire uses DC reverse polarity, with a welding current of 550A~800A and a welding voltage of 31V~35V; the second wire uses AC polarity, with a welding current of 400A~600A and a welding voltage of 33V~38V; the welding speed is 1.2m / min~1.5m / min.

[0047] Furthermore, the inner welding wire is Atlantic CHF-SH welding wire, the outer welding wire is CHW-SG welding wire, and the flux is CHW102SH sintered flux.

[0048] Step 4: The rolled tube processed in step 3 is hot-bent into a bent tube, and the bent tube is then heat-treated. Furthermore, in step 4, the hot bending process specifically adopts an online quenching process, using a medium-frequency induction heating coil for heating. The medium-frequency frequency is 300HZ~380HZ, the voltage is 485V~600V, the power is 260KW~600KW, and the bending tube advance rate is 24mm / min~40mm / min. The gap between the induction heating coil and the quenching water ring is 18mm~20mm, and the gap between the two rings on the inner arc side is 20mm~22mm.

[0049] Furthermore, in step 4, the heat treatment involved placing the bent tube into a heat treatment furnace for tempering heat treatment at a temperature of 520℃~540℃ and a holding time of 40min~60min.

[0050] Step 5: Inspect the heat-treated bent pipe.

[0051] On the other hand, the present invention also provides a small-to-medium diameter hot-bent tube for hydrogen transportation, which is manufactured by the above-described method for manufacturing a small-to-medium diameter hot-bent tube for hydrogen transportation.

[0052] Example 5 The manufacturing method of the small-diameter hot-bent pipe for hydrogen transportation in this embodiment, taking the manufacturing of a hot-bent pipe with specifications of IB360Φ273.1×8.8mm as an example, specifically includes the following steps: Step 1: Select a hot-rolled coil of L360M with a wall thickness of 8.8mm. Its chemical composition is shown in Table 1 below. Uncoil and level the selected hot-rolled coil. Table 1 Chemical composition (wt%) of hot-rolled coil in Example 1

[0053] Step 2: After milling the edges of the leveled coil, roll forming is performed to obtain the coiled tube; Specifically, a sliding plate milling machine with pressure rollers is used to process the edge of the 8.8mm rolled plate into an X-shaped bevel. The bevel angle is 45° on the upper bevel and 37.5° on the lower bevel, with a blunt edge of 3mm.

[0054] Step 3: Weld the rolled pipe according to the welding process requirements, and process the welded rolled pipe. Specifically, high-frequency resistance welding is first used for high-frequency pre-welding at a frequency of 200kHz, a welding speed of 15m / min, and an extrusion amount of 2mm. Then, an outside-to-inside welding process is adopted. The external welding process is as follows: welding is performed using a double-wire submerged arc automatic welding system. The first wire uses DC reverse polarity, and the welding process parameters are: current I = 650A, voltage U = 33V; the second wire uses AC, current I = 580A, voltage U = 34V; welding speed V = 1.4m / min. The internal welding process is as follows: Dual-wire submerged arc welding is used. The first wire uses DC reverse polarity, with welding parameters of current I = 550A and voltage U = 33V; the second wire uses AC, with current I = 420A and voltage U = 34V; the welding speed is V = 1.4m / min. The internal welding wire is Atlantic CHF-SH, the external welding wire is CHW-SG, and the flux is CHW102SH sintered flux.

[0055] The welded rolled pipe is then processed to expand the diameter of the entire pipe body; the expanded pipe body is then subjected to continuous X-ray inspection, hydrostatic pressure test, ultrasonic flaw detection of weld and base material, pipe end chamfering, pipe end radiography, and process pipe butt welding.

[0056] Step 4: The rolled tube processed in step 3 is hot-bent into a bent tube, and the bent tube is then heat-treated. Specifically, an online quenching process is adopted, using a medium-frequency induction heating coil for heating. The medium-frequency frequency is 300HZ, the voltage is 485V, the power is 260KW, and the pipe bending speed is 30mm / min. The gap between the induction heating coil and the quenching water ring near the weld is adjusted according to the pipe bending specifications and controlled at 20mm. The gap between the two rings on the inner arc side is controlled at 22mm.

[0057] Finally, the bent pipe was placed in a heat treatment furnace for tempering heat treatment at a temperature of 520℃ for 50 minutes.

[0058] Step 5: Inspect the heat-treated bent pipe.

[0059] According to DEC-OGP-S-PL-001-2022-2 "Technical Specification for Induction Heating Bends for Oil and Gas Pipeline Engineering", the hot-bent pipe prepared in this embodiment was subjected to physical and chemical property tests. The mechanical properties all meet the standard requirements. The test results are as follows: Pipe body yield strength R... t0.5 395MPa~442MPa; Pipe body tensile strength R m :528MPa~563MPa; pipe body yield ratio R t0.5 / R m 0.83~0.88; Elongation of pipe body A: 40~45%; Tensile strength of weld Rm: 550MPa~578MPa; Transverse impact energy of pipe body at -10℃: 330J~365J; Impact energy of weld at -10℃: 163J~245J; Impact energy of heat-affected zone at -10℃: 308J~367J; Hardness of welded joint: 173HV 10 ~192HV 10 .

[0060] According to DEC-OGP-S-PL-001-2022-2 "Technical Specification for Induction Heating Bends for Oil and Gas Pipeline Engineering", the geometric dimensions of the hot-bent bends were inspected, and the results all met the standard requirements. The inspection results are as follows: the outer diameter deviation of the straight section of the bend measured by the circumference method is -1mm to 1mm; the out-of-roundness of the straight section of the bend within 100mm from the pipe end is 1mm, and the out-of-roundness of the bent section is 4mm; the verticality of the pipe end of the bend is 1.5mm, which can meet the requirements of on-site circumferential welding of the pipeline.

[0061] The hydrogen embrittlement resistance of the hot-bent pipe prepared in this embodiment was tested. According to GB / T34542.2 "Test Method for Hydrogen Compatibility of Metallic Materials for Hydrogen Storage and Transportation Systems", the hydrogen compatibility of the hot-bent pipe was evaluated under a 7.2 MPa hydrogen environment. The slow strain rate tensile reduction of area loss rates of the pipe body and weld smooth specimens were 4.3% and 4.6%, respectively, and the fracture toughness K... IC 189 MPa·m 1 / 2 and 193 MPa·m 1 / 2 This indicates that hot-bent pipes have excellent resistance to hydrogen-induced cracking and can meet the transportation requirements of 7.2MPa medium-high pressure pure hydrogen pipelines.

[0062] Example 6 The manufacturing method of the small-to-medium diameter hot-bent pipe for hydrogen transportation in this embodiment, taking the manufacturing of a hot-bent pipe with specifications of Φ610×17.8mm as an example, specifically includes the following steps: Step 1: Select a hot-rolled coil of L360M with a wall thickness of 17.8mm. Its chemical composition is shown in Table 2 below. Uncoil and level the selected hot-rolled coil. Table 2 Chemical composition (wt%) of hot-rolled coil in Example 2

[0063] Step 2: After milling the edges of the leveled coil, roll forming is performed to obtain the coiled tube; Specifically, a sliding plate milling machine with pressure rollers is used to process the edge of the 17.8mm rolled plate into an X-shaped bevel. The bevel angle is 50° on the upper bevel and 37.5° on the lower bevel, with an 8mm blunt edge.

[0064] Step 3: Weld the rolled pipe according to the welding process requirements, and process the welded rolled pipe. Specifically, high-frequency resistance welding is first used for high-frequency pre-welding at a frequency of 500kHz, a welding speed of 12m / min, and an extrusion amount of 8mm. Then, an outside-to-inside welding process is adopted. The external welding process is as follows: welding is performed using a double-wire submerged arc automatic welding system. The first wire uses DC reverse polarity, and the welding process parameters are: current I = 1050A, voltage U = 34V; the second wire uses AC, current I = 750A, voltage U = 36V; welding speed V = 1.25m / min. The internal welding process is as follows: Dual-wire submerged arc welding is used. The first wire uses DC reverse polarity, with welding parameters of current I = 750A and voltage U = 34V; the second wire uses AC, with current I = 600A and voltage U = 35V; the welding speed is V = 1.25m / min. The internal welding wire is Atlantic CHF-SH, the external welding wire is CHW-SG, and the flux is CHW102SH sintered flux.

[0065] The welded rolled pipe is then processed to expand the diameter of the entire pipe body; the expanded pipe body is then subjected to continuous X-ray inspection, hydrostatic pressure test, ultrasonic flaw detection of weld and base material, pipe end chamfering, pipe end radiography, and process pipe butt welding.

[0066] Step 4: The rolled tube processed in step 3 is hot-bent into a bent tube, and the bent tube is then heat-treated. Specifically, an online quenching process is adopted, using a medium-frequency induction heating coil for heating. The medium-frequency frequency is 380HZ, the voltage is 600V, the power is 560KW, and the pipe bending speed is 30mm / min. The gap between the induction heating coil and the quenching water ring near the weld is adjusted according to the pipe bending specifications and controlled at 20mm. The gap between the two rings on the inner arc side is also controlled at 20mm.

[0067] Finally, the bent pipe was placed in a heat treatment furnace for tempering heat treatment at a temperature of 540℃ for 60 minutes.

[0068] Step 5: Inspect the heat-treated bent pipe.

[0069] According to DEC-OGP-S-PL-001-2022-2 "Technical Specification for Induction Heating Bends for Oil and Gas Pipeline Engineering", the physicochemical properties of the hot-bent pipe were tested. The mechanical properties all met the standard requirements. The test results are as follows: Pipe body yield strength R... t0.5 380MPa~440MPa; Pipe body tensile strength R m :540MPa~578MPa; pipe body yield ratio R t0.5 / R m 0.83~0.88; Elongation of pipe body A: 42%~45%; Tensile strength of weld Rm: 560MPa~582MPa; Transverse impact energy of pipe body at -10℃: 333J~355J; Impact energy of weld at -10℃: 158J~238J; Impact energy of heat-affected zone at -10℃: 298J~353J; Hardness of welded joint: 176HV10 ~193HV 10 .

[0070] According to DEC-OGP-S-PL-001-2022-2 "Technical Specification for Induction Heating Bends for Oil and Gas Pipeline Engineering", the geometric dimensions of the hot-bent bends were inspected, and the results all met the standard requirements. The inspection results are as follows: the outer diameter deviation of the straight section of the bend measured by the circumference method is 0mm~1mm; the out-of-roundness of the straight section of the bend within 100mm from the pipe end is 1.5mm, and the out-of-roundness of the bent section is 3.8mm; the verticality of the pipe end of the bend is 1.5mm, which can meet the requirements of on-site circumferential welding of the pipeline.

[0071] The hydrogen embrittlement resistance of the hot-bent pipe prepared in this embodiment was tested. According to GB / T34542.2 "Test Method for Hydrogen Compatibility of Metallic Materials for Hydrogen Storage and Transportation Systems", the hydrogen compatibility of the hot-bent pipe was evaluated under a 7.2 MPa hydrogen environment. The slow strain rate tensile reduction of area loss rates of the pipe body and weld smooth specimens were 4.4% and 4.7%, respectively, and the fracture toughness K... IC 196 MPa·m 1 / 2 and 212 MPa·m 1 / 2 This indicates that hot-bent pipes have excellent resistance to hydrogen-induced cracking and can meet the transportation requirements of 7.2MPa medium-high pressure pure hydrogen pipelines.

[0072] Finally, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0073] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0074] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for manufacturing small-to-medium diameter hot-bent pipes for hydrogen transportation, characterized in that, Specifically, the following steps are included: Step 1: Select hot-rolled coils and uncoil and level them. Step 2: After milling the edges of the leveled coil, roll forming is performed to obtain the coiled tube; Step 3: Weld the rolled pipe according to the welding process requirements, and process the welded rolled pipe. Step 4: The rolled tube processed in step 3 is hot-bent into a bent tube, and the bent tube is then heat-treated. Step 5: Inspect the heat-treated bent pipe.

2. The method for manufacturing a small-to-medium diameter hot-bent pipe for hydrogen transportation according to claim 1, characterized in that, In step 1, the hot-rolled coil is composed of the following raw material components by mass percentage: C: 0.03~0.06%, Si: 0.05~0.45%, Mn: 0.7~1.3%, S≤0.002%, P≤0.008%, Ni: 0.01~0.3%, Cr: 0.01~0.3%, Cu: 0.01~0.35%, Nb: 0.01~0.10%, V: 0.001~0.05%, Ti≤0.04%, Mo≤0.15%, Al≤0.04%, B≤0.0005%, with the balance being Fe. The total content of all the above components is 100%. Furthermore, CEPcm ≤ 0.15; the metallographic structure contains A, B, C, D, and DS type non-metallic inclusions of grade 1.0, banded structures of grade 1.5, and grain size of grade 9.

3. The method for manufacturing a small-to-medium diameter hot-bent pipe for hydrogen transportation according to claim 1, characterized in that, In step 2, the edge milling is performed using a sliding plate milling machine with a pressure roller device to process the edge of the plate into an X-shaped bevel, with a single bevel angle ≤ 60°.

4. The method for manufacturing a small-to-medium diameter hot-bent pipe for hydrogen transportation according to claim 1, characterized in that, In step 3, welding is divided into pre-welding and precision welding. The pre-welding is performed using high-frequency resistance welding, with a welding frequency of 200kHz~500kHz, a welding speed of 10m / min~15m / min, and an extrusion amount of 2mm~10mm. The process involves external welding followed by internal welding. Specifically, the external welding is performed using a dual-wire submerged arc welding system. The first wire uses DC reverse polarity with a welding current of 650A~1100A and a welding voltage of 31V~36V; the second wire uses AC polarity with a welding current of 580A~800A and a welding voltage of 34V~38V; the welding speed is 1.2m / min~1.5m / min. The internal welding process is as follows: welding is performed using a double-wire submerged arc automatic welding system. The first wire uses DC reverse polarity, with a welding current of 550A~800A and a welding voltage of 31V~35V; the second wire uses AC polarity, with a welding current of 400A~600A and a welding voltage of 33V~38V; the welding speed is 1.2m / min~1.5m / min.

5. The method for manufacturing a small-to-medium diameter hot-bent pipe for hydrogen transportation according to claim 4, characterized in that, The inner welding wire is Atlantic CHF-SH welding wire, the outer welding wire is CHW-SG welding wire, and the flux is CHW102SH sintered flux.

6. The method for manufacturing a small-to-medium diameter hot-bent pipe for hydrogen transportation according to claim 1, characterized in that, In step 3, the welded coiled pipe is processed to expand the diameter of the entire pipe body. The expansion of the entire pipe body adopts the expansion module and the segmented expansion method. The expansion length of each segment is 2~3m, and the length of each step forward is 0.8m~1.0m. The pipe body expansion rate is 0.7%~0.9%. After the expansion is completed, the pipe body is subjected to continuous X-ray inspection, hydrostatic test, ultrasonic flaw detection of weld and base material, pipe end chamfering, pipe end radiography, and process pipe butt welding.

7. The method for manufacturing a small-to-medium diameter hot-bent pipe for hydrogen transportation according to claim 1, characterized in that, In step 4, the hot bending process specifically adopts an online quenching process, using a medium-frequency induction heating coil for heating. The medium-frequency frequency is 300HZ~380HZ, the voltage is 485V~600V, the power is 260KW~600KW, and the bending tube advance rate is 24mm / min~40mm / min. The gap between the induction heating coil and the quenching water ring is 18mm~20mm, and the gap between the two rings on the inner arc side is 20mm~22mm.

8. The method for manufacturing a small-to-medium diameter hot-bent pipe for hydrogen transportation according to claim 1, characterized in that, In step 4, the heat treatment involves placing the bent tube into a heat treatment furnace for tempering heat treatment at a temperature of 520℃~540℃ and a holding time of 40min~60min.

9. A small-to-medium diameter hot-bent pipe for hydrogen transportation, characterized in that, The small-diameter hot-bent tube for hydrogen transportation is manufactured by the manufacturing method of the small-diameter hot-bent tube for hydrogen transportation as described in any one of claims 1 to 8.

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