A method of welding a supercritical CO2 transport pipeline pipe

Abstract

The embodiment of the application provides a welding method of supercritical CO2 conveying pipeline pipe, and particularly relates to the long pipeline welding technical field, and the welding method comprises the following steps: assembling and pairing the machined groove, then performing preheating treatment, performing root welding in a manual upward welding mode, and forming a root welding layer; when the temperature of the root welding layer is in a designed temperature range, performing hot welding above the root welding layer in a manual upward welding mode, and forming a hot welding layer; when the temperature of the hot welding layer is in the designed temperature range, performing multi-layer and multi-pass filling welding above the hot welding layer in an automatic upward welding mode, and forming a filling layer; when the temperature of the filling layer is in the designed temperature range, performing surface welding above the last layer of filling in an automatic upward welding mode, and forming a surface layer, so that the welding between two steel pipes is completed. Through the welding method, the requirement of supercritical CO2 conveying on the low-temperature impact toughness of the girth welding joint is met.

Description

Technical Field

[0001] This application relates to the field of welding technology for long-distance pipelines, specifically to a welding method for critical CO2 transport pipeline materials. Background Technology

[0002] CO2 transportation is a crucial link in the CCUS (Capture, Storage, and Utilization) industry chain, connecting CO2 capture and storage. Currently, the most economical method of CO2 transportation is supercritical CO2 pipeline transportation. However, supercritical CO2 is prone to rapid phase transitions and abrupt changes in physical properties, resulting in a large temperature drop during depressurization and release, which can easily lead to low-temperature brittle fracture. Therefore, high requirements are placed on the low-temperature impact toughness of the pipe ring weld joints.

[0003] Existing welding processes are mainly designed for the transportation of substances such as natural gas and oil. However, the mechanical properties of ring welded joints produced using these processes do not meet the requirements for mechanical properties of ring welded joints during supercritical CO2 transportation. Summary of the Invention

[0004] This application provides a welding method for supercritical CO2 transport pipeline materials. This method solves the problem in the prior art that the circumferential weld joint of the supercritical CO2 transport pipeline material is prone to brittle fracture at low temperatures due to the low low-temperature impact toughness of the circumferential weld joint.

[0005] This application provides a welding method for supercritical CO2 transport pipeline materials, the method comprising:

[0006] Two sections of steel pipe to be welded are beveled, and the bevel is V-shaped, with a face angle of 25-35° and a blunt edge height of 1-2mm. The blunt edge is a vertical edge with a height at the bottom of the bevel.

[0007] The two steel pipe sections that have undergone beveling are beveled and assembled, with a pipe end assembly gap of 2.5-4mm, which is the distance between the two blunt edges.

[0008] The assembled bevel is preheated and heat-insulated. Based on a first gas shielded welding machine with a welding current of 95-130A, an arc voltage of 9.5-12V, and a shielding gas flow rate of 12-17L / min, and solid welding wire, the bevel is root-welded manually in an upward welding manner to form a root weld layer.

[0009] When the temperature of the root weld layer is within the preset temperature range, the welding current of the first gas shielded welding machine is adjusted to 130-160A, and based on the first gas shielded welding machine and the solid welding wire, the upper part of the root weld layer is hot-welded by the manual upward welding method to form a hot-welded layer.

[0010] When the temperature of the hot-welded layer is within the preset temperature range, a second gas shielded welding machine with a welding current of 180-240A, an arc voltage of 22-24V, a shielding gas flow rate of 22-27L / min, and a wire feeding speed of 6.2-7.0m / min and a flux-cored welding wire are used to perform multi-layer, multi-pass filler welding on the top of the hot-welded layer in an automatic upward welding manner to form a filler layer;

[0011] When the temperature of the filler layer is within the preset temperature range, the welding current of the second gas shielded welding machine is adjusted to 160-220A, the arc voltage is adjusted to 21-23V, and the wire feed speed is adjusted to 6.0-6.2m / min. Based on the second gas shielded welding machine and the flux-cored welding wire, the filler layer is covered by the automatic upward welding method to form a cover layer, thus completing the welding between the two sections of the steel pipe.

[0012] Optionally, the face angle of the bevel is 25°, 27°, 30° or 35°;

[0013] The blunt edge height is 1mm, 1.2mm, 1.4mm, 1.6mm, 1.8mm or 2mm.

[0014] Optionally, the gap between the nozzle assembly is 2.5mm, 2.7mm, 3.0mm, 3.2mm, 3.4mm, 3.6mm, 3.8mm or 4mm.

[0015] Optionally, the assembled bevel is preheated, including:

[0016] The preheating temperature ranges from 80 to 100°C.

[0017] Optionally, the preheating temperature is 80°C, 90°C, or 100°C.

[0018] Optionally, the preset temperature range is 60-100℃.

[0019] Optionally, the preset temperature is 60℃, 70℃, 80℃, 90℃ or 100℃.

[0020] Optionally, the solid welding wire has the following mass percentage composition: C 0.06%~0.15%, Mn 1.40%~1.85%, Si 0.80%~1.15%, P≤0.025%, S≤0.025%, Ni≤0.15%, Cr≤0.15%, Mo≤0.15%, V≤0.03%, Cu≤0.50%, with the balance being Fe;

[0021] The diameter of the solid welding wire ranges from 1.6 to 3.2 mm.

[0022] Optionally, the diameter of the solid welding wire is 1.6mm, 2.0mm, 2.5mm or 3.2mm.

[0023] Optionally, the flux-cored welding wire has the following mass percentage composition: C≤0.12%, Mn≤1.75%, Si≤0.80%, P≤0.03%, S≤0.03%, Ni 0.80~1.20%, Mo≤0.35%, Al≤1.8%, with the balance being Fe;

[0024] The diameter of the flux-cored welding wire is in the range of 1.2-1.6 mm.

[0025] Optionally, the diameter of the flux-cored welding wire is 1.2 mm or 1.6 mm.

[0026] Optionally, before performing root welding on the bevel using a manual upward welding method and before performing hot welding on the top of the root weld layer using the same manual upward welding method, the method further includes:

[0027] Connect the first gas shielded welding machine to the DC power supply via reverse connection, and connect the first gas shielded welding machine to the Ar gas cylinder.

[0028] Optionally, before performing multi-layer, multi-pass filler welding on top of the heat-welded layer using an automatic upward welding method and before performing capping welding on top of the filler layer using the same automatic upward welding method, the method further includes:

[0029] The second gas shielded welding machine is connected via DC power reverse connection, and the second gas shielded welding machine is connected to an Ar+CO2 gas cylinder, wherein the CO2 content in the Ar+CO2 gas cylinder is greater than 15% and less than or equal to 25%.

[0030] Beneficial effects:

[0031] This application provides a welding method for supercritical CO2 transport pipeline materials. The method includes: beveling two sections of steel pipe to be welded, wherein the bevel is V-shaped, the face angle of the bevel is 25-35°, and the blunt edge height is 1-2mm, wherein the blunt edge is a vertical edge with a height at the bottom of the bevel; and assembling the two sections of steel pipe after beveling, wherein the pipe end assembly gap is 2.5-4mm, wherein the pipe end assembly gap is the distance between the two blunt edges.

[0032] The assembled bevel is preheated and heat-insulated. Based on a first gas shielded welding machine with a welding current of 95-130A, an arc voltage of 9.5-12V, and a shielding gas flow rate of 12-17L / min, and solid welding wire, the bevel is root-welded manually in an upward welding manner to form a root weld layer.

[0033] When the temperature of the root weld layer is within the preset temperature range, the welding current of the first gas shielded welding machine is adjusted to 130-160A, and based on the first gas shielded welding machine and the solid welding wire, the upper part of the root weld layer is hot-welded by the manual upward welding method to form a hot-welded layer.

[0034] When the temperature of the hot-welded layer is within the preset temperature range, a second gas shielded welding machine with a welding current of 180-240A, an arc voltage of 22-24V, a shielding gas flow rate of 22-27L / min, and a wire feeding speed of 6.2-7.0m / min and a flux-cored welding wire are used to perform multi-layer, multi-pass filler welding on the top of the hot-welded layer in an automatic upward welding manner to form a filler layer;

[0035] When the temperature of the filler layer is within the preset temperature range, the welding current of the second gas shielded welding machine is adjusted to 160-220A, the arc voltage is adjusted to 21-23V, and the wire feed speed is adjusted to 6.0-6.2m / min. Based on the second gas shielded welding machine and the flux-cored welding wire, the filler layer is covered by the automatic upward welding method to form a cover layer, thus completing the welding between the two sections of the steel pipe.

[0036] The welding method provided in this application can meet the requirements of low-temperature impact toughness of the ring weld joint for supercritical CO2 transportation, avoid the danger and damage caused by the failure of the ring weld joint due to the large temperature drop during the release and depressurization of supercritical CO2. At the same time, this welding method can reduce the interference of human factors on welding quality, reduce personnel costs, improve welding efficiency, improve the stability of the ring weld joint quality, and ensure welding quality. Attached Figure Description

[0037] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1 This is a flowchart illustrating a welding method for a supercritical CO2 transport pipeline according to an embodiment of this application.

[0039] Figure 2 This is a beveling diagram of a welding method for a supercritical CO2 transport pipeline provided in an embodiment of this application;

[0040] Figure 3 This is a schematic diagram of the weld layer of a welding method for a supercritical CO2 transport pipeline provided in an embodiment of this application.

[0041] Reference numerals: 1-root weld layer, 2-thermal weld layer, 3-filler layer, 4-capping layer. Detailed Implementation

[0042] 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, 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.

[0043] Currently, the welding of existing supercritical CO2 transmission pipeline projects in China mainly adopts the welding process commonly used in natural gas pipelines. However, pipelines welded using this process are prone to brittle fracture of the circumferential weld joints due to low-temperature impact when transporting supercritical CO2. Based on international research on supercritical CO2 pipeline transportation projects, it has been found that small-diameter steel pipes are often used for supercritical CO2 transportation. However, the application of combined automatic welding processes for small-diameter steel pipes is currently limited. Therefore, this application proposes a welding method for small-diameter steel pipes. This method can address the impact of supercritical CO2 transportation on the mechanical properties of circumferential weld joints, while simultaneously improving welding efficiency and ensuring the stability of weld quality.

[0044] like Figure 1 and Figure 2 As shown, Figure 1 This embodiment provides a flowchart of a welding method for supercritical CO2 transport pipeline materials. Figure 2 This diagram illustrates the beveling process for a welding method used in this embodiment of a supercritical CO2 transport pipeline. The method includes the following steps:

[0045] S11: The two sections of steel pipe to be welded are beveled, and the bevel is V-shaped, with a face angle of 25-35° and a blunt edge height of 1-2mm. The blunt edge is a vertical edge with a height at the bottom of the bevel.

[0046] Supercritical CO2 refers to CO2 produced under conditions exceeding the critical pressure and temperature. The transportation of supercritical CO2 typically utilizes small-diameter steel. Therefore, in this embodiment, a small-diameter steel pipe of type X65 was selected as the pipe to be welded. The X65 pipeline steel pipe must meet the following mass percentage requirements: C≤0.12%, Si≤0.45%, Mn≤1.60%, P≤0.025%, S≤0.015%, Nb+Ti+V≤0.15%, Cu≤0.50%, Ni≤0.50%, Cr≤0.50%, Mo≤0.50%, with the balance being Fe. Furthermore, the X65 pipeline steel pipe must have a carbon equivalent (Ceq)≤0.43% and a cold crack sensitivity (CEpcm)≤0.25%.

[0047] Specifically, according to process requirements, the two sections of X65 steel pipe to be welded are processed with a V-shaped bevel. The purpose is to obtain a weld that penetrates the entire thickness of the steel pipe, and the V-shaped bevel is convenient to process and weld. The groove formed into a specific geometric shape at the part to be welded is called a bevel. The angle between the end face of the bevel and the bevel face is called the bevel face angle. The vertical edge with height at the bottom of the bevel is called the blunt edge. In this embodiment, the bevel face angle ranges from 25-35°, and the blunt edge height is 1-2mm, the purpose of which is to prevent the root of the bevel from being burned through.

[0048] S12: The two steel pipe sections that have completed the beveling process are beveled and assembled, and the gap between the pipe ends is 2.5-4mm. The gap between the pipe ends is the distance between the two blunt edges.

[0049] In this embodiment, two steel pipes that have already undergone beveling are beveled and then assembled. The distance between the blunt edges of the two steel pipes is the assembly gap. The assembly gap for X65 steel pipes ranges from 2.5 to 4 mm. If the assembly gap is too small, the root of the bevel will be difficult to penetrate, requiring the use of a smaller welding wire, which will slow down the welding process. If the assembly gap is too large, more filler metal is needed, which will increase welding costs and easily lead to welding deformation. An assembly gap of 2.5-4 mm will neither slow down the welding process nor cause welding deformation.

[0050] One embodiment of this application also provides a schematic diagram of the weld layer of a welding method for supercritical CO2 transport pipeline materials, as shown in the figure. Figure 3 As shown, it involves root weld layer 1, hot weld layer 2, filler layer 3, and cover layer 4.

[0051] S13: The assembled bevel is preheated and heat-insulated. Based on a first gas shielded welding machine with a welding current of 95-130A, an arc voltage of 9.5-12V, and a shielding gas flow rate of 12-17L / min, and solid welding wire, the bevel is root-welded manually in an upward welding manner to form root weld layer 1.

[0052] In this embodiment, a flame heating method is used to heat the assembled bevel and surrounding area to a predetermined temperature. After reaching this temperature, the bevel is kept warm, primarily to reduce the weld cooling rate and welding stress. The welding current of the first gas-shielded welding machine is set within the range of 95-130A, the arc voltage within the range of 9.5-12V, and the shielding gas flow rate within the range of 12-17L / min. Using the first gas-shielded welding machine and solid welding wire, root welding is performed on the bevel manually from top to bottom, ultimately forming root weld layer 1.

[0053] The manual upward welding method refers to the operator holding a welding torch connected to the first gas-shielded welding machine and welding from bottom to top. By using the first gas-shielded welding machine and solid welding wire, a dual effect of gas protection and self-protection through flux residue is achieved, preventing oxidation and corrosion of the weld layer during and after welding, thus improving the low-temperature impact toughness of the weld layer and weld seam. The root weld layer 1 provides support for subsequent weld layers and protects the back side of the subsequent weld seam from gas erosion and damage.

[0054] S14: When the temperature of the root weld layer 1 is within the preset temperature range, the welding current of the first gas shielded welding machine is adjusted to 130-160A, and based on the first gas shielded welding machine and the solid welding wire, the upper part of the root weld layer 1 is hot-welded by the manual upward welding method to form the hot-welded layer 2.

[0055] In this embodiment, the temperature of the newly welded root weld layer 1 is relatively high, requiring cooling. Once the temperature of the root weld layer 1 has decreased to a preset range, the welding current of the first gas-shielded welding machine is adjusted to the range of 130-160A, while the arc voltage and shielding gas flow rate remain unchanged. Based on the root weld layer 1, the same first gas-shielded welding machine and solid welding wire are used for manual upward welding to form a hot-welded layer 2. The hot-welded layer 2 ensures complete fusion between the root weld layer 1 and the steel pipe, and the hot welding removes the slag.

[0056] S15: When the temperature of the hot-welded layer 2 is within the preset temperature range, based on a second gas shielded welding machine with a welding current of 180-240A, an arc voltage of 22-24V, a shielding gas flow rate of 22-27L / min, and a wire feeding speed of 6.2-7.0m / min and a flux-cored welding wire, multi-layer, multi-pass filler welding is performed on the top of the hot-welded layer 2 in an automatic upward welding manner to form a filler layer 3.

[0057] In this embodiment, a welding carriage is fixed to the steel pipe using a track matching the pipe diameter, and a flux-cored welding wire is installed in the contact nozzle of the second gas-shielded welding machine. Once the temperature of the hot-welded layer 2 has decreased to a preset temperature range, the welding current of the second gas-shielded welding machine is set to 180-240A, the arc voltage to 22-24V, the shielding gas flow rate to 22-27L / min, and the wire feed speed to 6.2-7.0m / min. Based on the hot-welded layer 2, multiple layers and multiple passes of filler welding are performed automatically upwards using the second gas-shielded welding machine and the flux-cored welding wire to form the filler layer 3.

[0058] During each filler weld, the filler layer 3 needs to be welded at its upper end when the temperature of the previous filler layer 3 is within the range of 60℃ to 100℃ to form a new filler layer 3, until the filler weld reaches the upper part of the bevel. The automatic upward welding method refers to the operator using a handheld control panel to control the welding carriage connected to the second gas-shielded welding machine, driving the welding torch to weld from bottom to top. By utilizing the second gas-shielded welding machine and flux-cored wire, a dual effect of gas protection and self-protection through flux residue can be achieved, preventing oxidation and corrosion of the weld layer during and after welding, and improving the low-temperature impact toughness of the weld layer and weld seam.

[0059] S16: When the temperature of the filler layer 3 is within the preset temperature range, adjust the welding current of the second gas shielded welding machine to 160-220A, the arc voltage to 21-23V, and the wire feeding speed to 6.0-6.2m / min. Based on the second gas shielded welding machine and the flux-cored welding wire, perform a cover welding on the top of the filler layer 3 in the automatic upward welding manner to form a cover layer 4, thus completing the welding between the two sections of the steel pipe.

[0060] In this embodiment, when the temperature of the filler layer 3 reaches the preset temperature range, the welding current of the second gas-shielded welding machine is adjusted to the range of 160-220A, the arc voltage to the range of 21-23V, and the wire feed speed to the range of 6.0-6.2m / min. Based on the filler layer 3, a cover weld is performed using the second gas-shielded welding machine and flux-cored wire in an automatic upward welding manner to form a cover layer 4. During each cover weld, a new cover weld is performed on top of the bottom cover layer 4 when its temperature is within the range of 60℃ to 100℃, until the welding between the two X65 pipeline steel pipe sections is completed.

[0061] In another embodiment of this application, the face angle of the bevel is 25°, 27°, 30° or 35°; the blunt edge height is 1mm, 1.2mm, 1.4mm, 1.6mm, 1.8mm or 2mm.

[0062] In this embodiment, the bevel angle can be selected as 25°, 27°, 30°, or 35°. These bevel angles can provide suitable penetration depth and aesthetics while reducing the amount of filler metal. The blunt edge height can be 1mm, 1.2mm, 1.4mm, 1.6mm, 1.8mm, or 2mm. These blunt edge heights can reduce welding deformation without affecting welding quality and aesthetics.

[0063] The gap between the pipe fittings is 2.5mm, 2.7mm, 3.0mm, 3.2mm, 3.4mm, 3.6mm, 3.8mm or 4mm.

[0064] Specifically, within the range of 2.5-4mm, the gap between the pipe ends can be 2.5mm, 2.7mm, 3.0mm, 3.2mm, 3.4mm, 3.6mm, 3.8mm, or 4mm. These pipe end gap values ​​facilitate root welding, hot welding, filler welding, and capping welding using the welding method provided in this application, to complete the welding of two sections of small-diameter X65 pipeline steel pipes.

[0065] The assembled bevel is preheated, including a preheating temperature range of 80-100℃.

[0066] The preheating temperature is 80℃, 90℃ or 100℃.

[0067] Specifically, the assembled bevels need to undergo preheating treatment, with a temperature range of 80-100℃. Within this range, the preheating temperature can be 80℃, 90℃, or 100℃. This preheating temperature setting reduces the susceptibility to cold cracking at the X65 pipeline steel bevel and allows moisture to evaporate from the bevel, facilitating better adhesion between the weld wire molten material and the bevel during root welding.

[0068] The preset temperature range is 60-100℃.

[0069] The preset temperature is 60℃, 70℃, 80℃, 90℃ or 100℃.

[0070] Specifically, subsequent hot welding, filler welding, and capping welding can only be performed when the temperature of the root weld layer 1, hot weld layer 2, and filler layer 3 reaches 60-100℃. Within this preset temperature range, the required temperatures for the root weld layer 1, hot weld layer 2, and filler layer 3 can be 60℃, 70℃, 80℃, 90℃, or 100℃. Setting this predetermined temperature range facilitates mutual melting between the root weld layer 1 and hot weld layer 2, between the hot weld layer 2 and filler layer 3, and between the filler layer 3 and capping layer 4, thereby improving the interlayer bonding strength, enhancing weld stability, ensuring weld quality, and improving weld impact toughness.

[0071] The solid welding wire has the following mass percentage composition: C 0.06%~0.15%, Mn 1.40%~1.85%, Si 0.80%~1.15%, P≤0.025%, S≤0.025%, Ni≤0.15%, Cr≤0.15%, Mo≤0.15%, V≤0.03%, Cu≤0.50%, with the balance being Fe;

[0072] The diameter of the solid welding wire ranges from 1.6 to 3.2 mm.

[0073] The diameter of the solid welding wire is 1.6mm, 2.0mm, 2.5mm or 3.2mm.

[0074] Specifically, when the mass percentage composition of the solid welding wire is: C 0.06%–0.15%, Mn 1.40%–1.85%, Si 0.80%–1.15%, P≤0.025%, S≤0.025%, Ni≤0.15%, Cr≤0.15%, Mo≤0.15%, V≤0.03%, Cu≤0.50%, with the balance being Fe, the strength of the solid welding wire matches the steel grade. Combined with the process parameters in the welding method of this application, this results in a uniform, non-dispersed, and stable root weld layer 1. Furthermore, solid welding wires with this percentage composition are easier to obtain. In this embodiment, the diameter of the solid welding wire ranges from 1.6 to 3.2 mm. Within this range, the diameter can be 1.6 mm, 2.0 mm, 2.5 mm, or 3.2 mm. Using solid welding wires within this range improves the forming effect of the steel pipe ring weld joint.

[0075] The flux-cored welding wire has the following mass percentage composition: C≤0.12%, Mn≤1.75%, Si≤0.80%, P≤0.03%, S≤0.03%, Ni 0.80~1.20%, Mo≤0.35%, Al≤1.8%, with the balance being Fe;

[0076] The diameter of the flux-cored welding wire is in the range of 1.2-1.6 mm.

[0077] The diameter of the flux-cored welding wire is 1.2 mm or 1.6 mm.

[0078] Specifically, when the mass percentage composition of the flux-cored welding wire is: C≤0.12%, Mn≤1.75%, Si≤0.80%, P≤0.03%, S≤0.03%, Ni 0.80~1.20%, Mo≤0.35%, Al≤1.8%, with the balance being Fe, the strength of the flux-cored welding wire matches the steel grade. Combined with the process parameters in the welding method of this application, the flux residue flotation efficiency is high, resulting in excellent dehydrogenation, improved low-temperature impact toughness, and oxidation prevention. In this embodiment, the diameter of the flux-cored welding wire ranges from 1.2 to 1.6 mm, and within this range, the diameter can be either 1.2 mm or 1.6 mm.

[0079] Before performing root welding on the bevel using manual upward welding and before performing hot welding on the top of the root weld layer 1 using the same manual upward welding method, the method further includes:

[0080] Connect the first gas shielded welding machine to the DC power supply via reverse connection, and connect the first gas shielded welding machine to the Ar gas cylinder.

[0081] Specifically, connect the DC power supply to the first gas shielded welding machine using a reverse connection method. Then, connect the gas output pipe of the first gas shielded welding machine to the Ar gas cylinder. Open the valve of the Ar gas cylinder to allow Ar to flow to the first gas shielded welding machine. Connecting the first gas shielded welding machine to the Ar gas cylinder is to prevent nitrogen from mixing into the welding area and to protect the welding area from oxygen, thus avoiding oxidation reactions in the welding area and reducing welding quality.

[0082] Before performing multi-layer, multi-pass filler welding on top of the hot-welded layer 2 using an automatic upward welding method and before performing capping welding on top of the filler layer 3 using the same automatic upward welding method, the method further includes:

[0083] The second gas shielded welding machine is connected via DC power reverse connection, and the second gas shielded welding machine is connected to an Ar+CO2 gas cylinder, wherein the CO2 content in the Ar+CO2 gas cylinder is greater than 15% and less than or equal to 25%.

[0084] Specifically, the DC power supply is connected to the second gas shielded welding machine using a reverse connection method. Then, the gas output pipe of the second gas shielded welding machine is connected to the Ar+CO2 gas cylinder. The valve of the Ar+CO2 gas cylinder is opened, allowing Ar+CO2 to flow to the first gas shielded welding machine. The CO2 content in the Ar+CO2 gas cylinder is greater than 15% and less than or equal to 25%. Excluding CO2, the remaining gas in the Ar+CO2 gas cylinder is Ar.

[0085] To better illustrate this application, the following specific examples are provided:

[0086] This embodiment provides an automatic welding method for X65 pipeline steel pipe assembly. Specifically, X65 pipeline steel pipe with specifications of 323.9×10mm is selected, which comprises the following components by mass percentage:

[0087] Composition: C 0.05%, Si 0.18%, Mn 1.14%, P 0.009%, S 0.002%, Cu 0.09%, Ni 0.14%, Cr 0.12%, Mo 0.0075%, Ti 0.008%, V 0.04%, Al 0.03%, Als 0.02%, Nb 0.04%, B 0.0001%, Ca 0.0005%, balance Fe; carbon equivalent (Ceq) 0.29%, Pcm 0.13%.

[0088] First, the joint of the two sections of X65 pipeline steel pipe to be welded is processed into a bevel with a face angle of 30°, and a blunt edge with a height of 1.5mm is set at the bottom of the bevel, with a spacing of 4mm between the blunt edges.

[0089] Then, the bevel was preheated to 80℃ using a flame heating method. The first gas-shielded welding machine was connected to the power supply using a DC power reverse polarity method, and its parameters for root welding were set as follows: welding current 110A, arc voltage 10.5V, and gas flow rate 14L / min. Solid welding wire of GB / T 39280-2020 ER50-6 was selected, and root welding was performed manually to form root weld layer 1.

[0090] When the temperature of the root weld layer 1 is within the range of 60℃ to 100℃, solid welding wire of model GB / T 39280-2020ER50-6 is used. The welding current is adjusted to 140A, the arc voltage to 10.5V, and the gas flow rate to 14L / min. The root weld layer 1 is then hot-welded manually from the top to the bottom using an upward welding method to form the hot-welded layer 2.

[0091] The welding carriage is fixed to the steel pipe using a track matching the pipe diameter. A GB / T10045-2018T55 4T1-1 M21 A-N2 H5 type flux-cored welding wire is installed in the contact nozzle of the second gas-shielded welding machine. The welding current during filler welding is controlled at 180–240A, the arc voltage at 22V, the gas flow rate at 25L / min, and the wire feed speed at 6.2m / min. When the temperature of the heat-welded layer 2 is within the range of 60℃–100℃, multiple layers of filler welding are performed on the upper part of the heat-welded layer 2 using an automatic upward welding method to form a filler layer 3. Furthermore, during each filler welding layer, when the temperature of the previous filler layer 3 is within the range of 60℃–100℃, filler welding is performed on its upper part to form a new filler layer 3, until the filler welding reaches the upper part of the bevel.

[0092] Install the GB / T10045-2018 T55 4T1-1 M21 A-N2 H5 type flux-cored welding wire into the contact nozzle of the second gas-shielded welding machine, and control the welding current to be 160-220A, the arc voltage to be 22V, the gas flow rate to be 25L / min, and the wire feed speed to be 6.0m / min during the capping welding. When the temperature of the upper part of the last filler layer 3 is within the range of 60℃~100℃, perform multi-layer, multi-pass capping welding on the upper end of the filler layer 3 using an automatic upward welding method to form the capping layer 4. Furthermore, when performing each capping welding layer, when the temperature of the bottom capping layer 4 is within the range of 60℃~100℃, perform a new capping welding on its upper end until the welding between the two X65 pipeline steel pipe sections is completed.

[0093] The solid welding wire of model ER70S-6 contains the following components by weight percentage:

[0094] C 0.066%, Mn 1.46%, Si 0.84%, S 0.093%, P 0.0014%, Cr 0.040%, Ni 0.028%, Cu 0.073%, Mo 0.0042%, V 0.0018%, balance Fe.

[0095] The flux-cored welding wire of model T55 4T1-1 M21 A-N2 H5 contains the following components by weight percentage:

[0096] C 0.08%, Mn 1.45%, P 0.008%, S 0.011%, Si 0.31%, Cu 0.07%, Cr 0.03%, V 0.003%, Ni 0.9%, Mo 0.005%, balance Fe.

[0097] Another embodiment of this application provides an automatic welding method for X65 pipeline steel pipe assembly. Specifically, an X65 pipeline steel pipe with a specification of 219.1×10mm is selected, which comprises the following components by mass percentage:

[0098] Composition: C 0.05%, Si 0.2%, Mn 1.18%, P 0.008%, S 0.002%, Cu 0.09%, Ni 0.14%, Cr 0.16%, Mo 0.008%, Ti 0.011%, V 0.037%, Al 0.046%, Als 0.040%, Nb 0.051%, B 0.0003%, Ca 0.0005%, balance Fe; carbon equivalent (Ceq) 0.3%, Pcm 0.14%.

[0099] First, the joint of the two sections of X65 pipeline steel pipe to be welded is processed into a bevel with a face angle of 30°, and a blunt edge with a height of 1.0mm is set at the bottom of the bevel, with a spacing of 3mm between the blunt edges.

[0100] Then, the bevel was preheated to 80℃ using a flame heating method. The first gas-shielded welding machine was connected to the power supply using a DC power reverse polarity method, and its parameters for root welding were set as follows: welding current 120A, arc voltage 10V, and gas flow rate 14L / min. Solid welding wire of model GB / T 39280-2020ER50-6 was selected, and root welding was performed manually to form root weld layer 1.

[0101] When the temperature of the root weld layer 1 is within the range of 60℃ to 100℃, solid welding wire of model GB / T39280-2020ER50-6 is used. The welding current is adjusted to 150A, the arc voltage to 10V, and the gas flow rate to 14L / min. The root weld layer 1 is then hot-welded by manual upward welding to form the hot-welded layer 2.

[0102] The welding carriage is fixed to the steel pipe using a track matching the pipe diameter. A GB / T10045-2018T55 4T1-1 M21 A-N2 H5 type flux-cored welding wire is installed in the contact nozzle of the second gas-shielded welding machine. The welding current during filler welding is controlled at 180–240A, the arc voltage at 23V, the gas flow rate at 26L / min, and the wire feed speed at 6.2m / min. When the temperature of the heat-welded layer 2 is within the range of 60℃–100℃, multiple layers of filler welding are performed on the upper part of the heat-welded layer 2 using an automatic upward welding method to form a filler layer 3. Furthermore, during each filler welding layer, when the temperature of the previous filler layer 3 is within the range of 60℃–100℃, filler welding is performed on its upper part to form a new filler layer 3, until the filler welding reaches the upper part of the bevel.

[0103] The GB / T10045-2018 T55 4T1-1 M21 A-N2 H5 type flux-cored welding wire is installed in the contact nozzle of the second gas-shielded welding machine. During cap welding, the welding current is controlled at 160-220A, the arc voltage at 23V, the gas flow rate at 26L / min, and the wire feed speed at 6.0m / min. When the temperature of the upper part of the final filler layer 3 is within the range of 60℃ to 100℃, multiple layers of cap welding are performed on the upper part of the filler layer 3 using an automatic upward welding method to form the cap layer 4. Furthermore, during each cap welding layer, when the temperature of the bottom cap layer 4 is within the range of 60℃ to 100℃, a new cap welding is performed on its upper part until the welding between the two X65 pipeline steel pipe sections is completed.

[0104] The solid welding wire of model ER70S-6 contains the following components by weight percentage:

[0105] C 0.084%, Mn 1.47%, Si 0.83%, S 0.012%, P 0.0082%, Cr 0.020%, Ni 0.0096%, Cu 0.038%, Mo 0.0041%, V 0.0019%, balance Fe.

[0106] The flux-cored welding wire of model T55 4T1-1 M21 A-N2 H5 contains the following components by weight percentage:

[0107] C 0.05%, Mn 1.42%, P 0.010%, S 0.008%, Si 0.26%, Cu 0.06%, Cr 0.03%, V 0.002%, Ni 0.86%, Mo 0.014%, balance Fe.

[0108] This application also provides the following examples to further illustrate the beneficial effects of this application:

[0109] The impact toughness of the circumferential welded joints obtained by the welding method provided in this application for X65 pipeline steel pipes with specifications of 323.9×10mm and 219.1×10mm was evaluated under low-temperature conditions. The low-temperature impact temperatures were set at -30℃ and -45℃, and the method provided in the standard GB / T 31032 "Welding and Acceptance of Steel Pipelines" was used to repeatedly conduct three tests on the weld layer provided in the above embodiment and the weld layer obtained by ordinary welding methods to obtain the single value and average value of the impact energy at the weld center and the weld fusion line. The test results obtained by welding the 323.9×10mm X65 pipeline steel pipe using the welding method provided in this application, the 219.1×10mm X65 pipeline steel pipe using the welding method provided in this application, and the X65 pipeline steel pipe using ordinary welding are numbered sequentially as No. 1, No. 2, and No. 3. Specific parameters are shown in Table 1.

[0110] Table 1

[0111]

[0112]

[0113] As shown in Table 1, the circumferential weld joint of X65 pipeline steel pipe with specifications of 323.9×10mm obtained by the welding method provided by the present invention has good impact toughness under low temperature conditions. As shown in Experiment 1, at -30℃, the single impact energy value of the weld center is above 90J, with an average value of 110.52J, and the single impact energy value of the fusion line is above 70J, with an average value of 145.41J; at -45℃, the single impact energy value of the weld center is above 75J, with an average value of 89.05J, and the single impact energy value of the fusion line is above 160J, with an average value of 182.57J.

[0114] The circumferential weld joint obtained by the welding method provided by the present invention for X65 pipeline steel pipe with specifications of 219.1×10mm exhibits good impact toughness under low-temperature conditions. As shown in Experiment 2, at -30℃, the single impact energy value at the weld center is above 90J, with an average value of 107.35J, and the single impact energy value at the fusion line is above 140J, with an average value of 174.63J. At -45℃, the single impact energy value at the weld center is above 70J, with an average value of 85.65J, and the single impact energy value at the fusion line is above 90J, with an average value of 141.02J.

[0115] The test results obtained by the ordinary welding method showed that, under the condition of -30℃, the single impact energy of the weld center was above 12J, with an average of 27.43J, and the single impact energy of the fusion line was above 179J, with an average of 194.42J; while under the condition of -45℃, the single impact energy of the weld center was above 11J, with an average of 14.12J, and the single impact energy of the fusion line was above 31J, with an average of 98.63J.

[0116] It is evident that the circumferential weld joint obtained by welding X65 pipeline steel pipe using the method provided in this application exhibits good low-temperature impact toughness, which meets the requirements for pipeline transportation of supercritical CO2.

[0117] Although preferred embodiments of the present application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the embodiments of the present application.

[0118] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0119] Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or terminal device 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 terminal device. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or terminal device that includes that element. The character " / " generally indicates an "or" relationship between the preceding and following objects.

[0120] The above provides a detailed description of a welding method for a critical CO2 transport pipeline provided in this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A welding method for supercritical CO2 transport pipeline materials, characterized in that, The method includes: Two sections of steel pipe to be welded are beveled, with the bevel being V-shaped, the face angle of the bevel being 25-35°, and the blunt edge height being 1-2mm. The blunt edge is a vertical edge with a height at the bottom of the bevel. X65 small-diameter steel pipes are selected as the steel pipes to be welded, and the mass percentage of the X65 pipeline steel pipes meets the following requirements: C≤0.12%, Si≤0.45%, Mn≤1.60%, P≤0.025%, S≤0.015%, Nb+Ti+V≤0.15%, Cu≤0.50%, Ni≤0.50%, Cr≤0.50%, Mo≤0.50%, with the balance being Fe. The carbon equivalent of the X65 pipeline steel pipe is ≤0.43%, and the cold crack sensitivity is ≤0.25%. The two steel pipe sections that have undergone beveling are beveled and assembled, with a pipe end assembly gap of 2.5-4mm, which is the distance between the two blunt edges. The assembled bevel is preheated and heat-insulated. Based on a first gas shielded welding machine with a welding current of 95-130A, an arc voltage of 9.5-12V, and a shielding gas flow rate of 12-17L / min, and solid welding wire, the bevel is root-welded manually in an upward welding manner to form a root weld layer. When the temperature of the root weld layer is within the preset temperature range, the welding current of the first gas shielded welding machine is adjusted to 130-160A, and based on the first gas shielded welding machine and the solid welding wire, the upper part of the root weld layer is hot-welded by the manual upward welding method to form a hot-welded layer. The solid welding wire has the following mass percentage composition: C 0.06%~0.15%, Mn 1.40%~1.85%, Si 0.80%~1.15%, P≤0.025%, S≤0.025%, Ni≤0.15%, Cr≤0.15%, Mo≤0.15%, V≤0.03%, Cu≤0.50%, with the balance being Fe; and the diameter of the solid welding wire ranges from 1.6 to 3.2 mm. When the temperature of the hot-welded layer is within the preset temperature range, a second gas shielded welding machine with a welding current of 180-240A, an arc voltage of 22-24V, a shielding gas flow rate of 22-27L / min, and a wire feed speed of 6.2-7.0m / min and a flux-cored wire are used to perform multi-layer, multi-pass filler welding on the top of the hot-welded layer in an automatic upward welding manner to form a filler layer. The preset temperature range is 60-100℃. When the temperature of the filler layer is within the preset temperature range, the welding current of the second gas shielded welding machine is adjusted to 160-220A, the arc voltage is adjusted to 21-23V, and the wire feeding speed is adjusted to 6.0-6.2m / min. Based on the second gas shielded welding machine and the flux-cored welding wire, the filler layer is covered by automatic upward welding to form a cover layer, thus completing the welding between the two sections of the steel pipe. The flux-cored wire has the following mass percentage composition: C≤0.12%, Mn≤1.75%, Si≤0.80%, P≤0.03%, S≤0.03%, Ni 0.80~1.20%, Mo≤0.35%, Al≤1.8%, with the balance being Fe; and the diameter of the flux-cored wire is in the range of 1.2-1.6mm.

2. The welding method according to claim 1, characterized in that, The face angle of the bevel is: 25°, 27°, 30° or 35°; The blunt edge height is 1mm, 1.2mm, 1.4mm, 1.6mm, 1.8mm or 2mm.

3. The welding method according to claim 1, characterized in that, The gap between the pipe fittings is 2.5mm, 2.7mm, 3.0mm, 3.2mm, 3.4mm, 3.6mm, 3.8mm or 4mm.

4. The welding method according to claim 1, characterized in that, The assembled bevel is preheated, including: The preheating temperature range is 80-100℃.

5. The welding method according to claim 4, characterized in that, The preheating temperature is 80℃, 90℃ or 100℃.

6. The welding method according to claim 1, characterized in that, The preset temperature is 60℃, 70℃, 80℃, 90℃ or 100℃.

7. The welding method according to claim 1, characterized in that, The diameter of the solid welding wire is 1.6mm, 2.0mm, 2.5mm or 3.2mm.

8. The welding method according to claim 1, characterized in that, The diameter of the flux-cored welding wire is 1.2 mm or 1.6 mm.

9. The welding method according to claim 1, characterized in that, The method further includes, before performing root welding on the bevel using a manual upward welding method and before performing hot welding on the top of the root weld layer using the same manual upward welding method: Connect the first gas shielded welding machine to the DC power supply via reverse connection, and connect the first gas shielded welding machine to the Ar gas cylinder.

10. The welding method according to claim 1, characterized in that, Before performing multi-layer, multi-pass filler welding on top of the hot-welded layer using an automatic upward welding method and before performing capping welding on top of the filler layer using the same automatic upward welding method, the method further includes: The second gas shielded welding machine is connected via DC power reverse connection, and the second gas shielded welding machine is connected to an Ar+CO2 gas cylinder, wherein the CO2 content in the Ar+CO2 gas cylinder is greater than 15% and less than or equal to 25%.

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