Double-laser all-position welding method for oil and gas pipeline

Abstract

The invention relates to the technical field of laser welding, and provides an oil and gas pipeline double-laser all-position welding method which adopts external welding equipment to weld butt joint circular seams of a first pipe fitting and a second pipe fitting. The welding equipment comprises a supporting frame, a rotating disc rotationally installed on the supporting frame, a first laser welding assembly and a second laser welding assembly, wherein the first laser welding assembly and the second laser welding assembly are driven by the rotating disc and symmetrically arranged. The double-laser all-position welding method for the oil and gas pipeline comprises the following steps that S1, pipe ends are prepared and assembled; s2, equipment positioning and centering; s3, aligning a laser welding head; s4, synchronous rotary welding is carried out; and S5, welding is completed. According to the double-laser all-position welding method for the oil and gas pipeline, through system cooperation of double-laser collaborative operation, automatic centering, precise alignment and process control, high-quality, high-efficiency and high-environment-adaptability oil and gas pipe fitting welding is achieved, and the problems that in conventional welding, the dilution rate is large, and welding deformation occurs are solved.

Description

Technical Field

[0001] This application relates to the field of laser welding technology, and more specifically, to a dual-laser all-position welding method for oil and gas pipelines. Background Technology

[0002] Currently, the on-site circumferential welding of existing metallurgical composite pipes for oil and gas transportation mostly adopts the traditional TIG welding process at the pipe ends. Although this process is technically mature, it has many inherent defects when dealing with composite pipes composed of carbon steel base pipes and corrosion-resistant alloy lining pipes. Due to the significant differences in chemical composition, thermophysical properties, and coefficient of expansion between the two materials, the heat input during TIG welding is large and concentrated, leading to excessive dilution of corrosion-resistant alloying elements, severely weakening the corrosion resistance of the weld zone, and making it difficult to ensure pipeline safety when transporting high-sulfur media. At the same time, the large heat input also causes severe welding deformation at the pipe ends, requiring extremely stringent assembly precision, often necessitating on-site manual trimming, resulting in low construction efficiency and high costs. In addition, in the harsh environment of pipeline laying in the field, natural wind can easily interfere with the stability of the TIG arc, directly affecting the welding quality. Therefore, there is an urgent need for a new pipeline welding method that can reduce heat input and dilution rate, suppress welding deformation, improve assembly efficiency and precision, and adapt to harsh field construction environments. Summary of the Invention

[0003] This application aims to at least address the problems in the related technology where the conventional welding method for composite pipe fittings is TIG welding at the pipe ends. Since the composite pipe is made of two materials with significant differences in chemical composition, structure and expansion coefficient, the welding process suffers from high dilution rate, low welding efficiency, large deformation of the pipe ends after welding, and high cost.

[0004] To solve the above-mentioned technical problems, this application is implemented as follows: This application provides a dual-laser all-position welding method for oil and gas pipelines. An external welding device is used to weld the butt joint circumferential seam of a first and second pipe fitting. The welding device includes a support frame, a rotating disk rotatably mounted on the support frame, and a first laser welding assembly and a second laser welding assembly symmetrically arranged and driven by the rotating disk. The dual-laser all-position welding method for oil and gas pipelines includes the following steps: S1, Pipe end preparation and assembly: The butt joint surfaces of the first and second pipe fittings are respectively processed into mutually matching outwardly protruding bevels and inwardly concave bevels, so that the two pipes can automatically align and form a butt joint circumferential seam with bevel angles during assembly; S2, Equipment positioning and alignment: The support frame is fitted onto the butt joint of the first and second pipe fittings, and multiple sets of circumferentially distributed circumferential positioning components are used to automatically align and center the axis of the support frame with the axes of the first and second pipe fittings, so that the rotation axis of the rotating disk... S3. Alignment of laser welding heads: Adjust the first and second laser welding components mounted on the rotating disk so that the light output directions of the first laser welding head of the first laser welding component and the second laser welding head of the second laser welding component are the same as the direction of the inclined surface of the butt joint, and the first and second laser welding heads are symmetrically arranged 180 degrees apart in the circumferential direction; S4. Synchronous rotation welding: Start the circumferential rotation power component to drive the rotating disk to rotate around the axis of the first and second pipe components, and simultaneously start the first and second laser welding components so that the laser beams emitted by the first and second laser welding heads act on the butt joint at the same time; S5. Welding completed: After the rotating disk rotates 180 degrees, turn off the first and second laser welding components to complete the welding of the entire circumferential joint.

[0005] This application provides a dual-laser all-position welding method for oil and gas pipelines. Through the coordinated operation of dual lasers, automatic alignment, precise alignment, and process control, it achieves high-quality, high-efficiency, and highly environmentally adaptable welding of oil and gas pipeline components. In the high-efficiency precision welding scenario, the welding equipment is driven by a circumferentially rotating power component to rotate a rotating disk, causing the first and second laser welding heads, arranged 180 degrees symmetrically, to rotate synchronously around the axes of the first and second pipe components. Both laser beams act simultaneously on the butt joint circumferential seam, and a single laser head only needs to rotate half a revolution to complete the full circumference welding, significantly improving efficiency compared to single-laser head welding and effectively avoiding cable entanglement. In the automatic alignment and stable support scenario, the support frame uses multiple sets of circumferentially distributed positioning components to drive rollers to press against the pipe wall, automatically completing the precise alignment and fixation of the welding equipment axis with the axes of the first and second pipe components, providing a stable reference for subsequent welding. Simultaneously, the butt joints of the first and second pipe components adopt an outwardly protruding and inwardly concave bevel design, allowing for automatic alignment during assembly, greatly improving assembly accuracy and efficiency. In the context of weld formation and quality control, the first and second laser welding heads are installed using angled mounting supports with a specific tilt angle to ensure that the output direction of the laser beam is always consistent with the bevel direction of the butt joint. That is, the output angle of the first and second laser welding heads is always the same as the bevel angle of the butt joint. This can minimize the reflection loss of laser energy and enable heat to be conducted uniformly and synchronously along the bevel depth direction. This approach ensures complete penetration at the weld root, preventing defects such as incomplete fusion or insufficient penetration caused by uneven energy distribution due to beam tilt. Furthermore, precisely controlled heat input effectively suppresses alloy element burn-off or weld depression caused by overheating, reducing overall thermal stress and deformation of the butt joint. This installation method also effectively prevents slag from falling back and damaging the laser head. Additionally, by independently controlling the dual-sided laser power, the thermophysical performance differences between the base tube and the inner liner tube can be precisely compensated. By controlling the laser spot to form a confocal or overlapping molten pool at the weld root, complete fusion and overall forming quality at the weld root are ensured, fundamentally solving the problems of high dilution rate and welding deformation. In field-adaptive scenarios, laser welding offers high energy density, low heat input, and strong resistance to wind interference. Combined with automated alignment and welding processes, it improves the reliability, quality consistency, and overall efficiency of on-site field construction.

[0006] Additional aspects and advantages of this application will become apparent in the following description or may be learned by practice of this application. Attached Figure Description

[0007] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1This is a flowchart of a dual-laser all-position welding method for oil and gas pipelines according to an embodiment of this application; Figure 2 This is a schematic diagram of the welding equipment in one embodiment of this application; Figure 3 for Figure 2 One of the partial structural schematic diagrams of the welding equipment in the illustrated embodiment; Figure 4 for Figure 2 A second partial structural schematic diagram of the welding equipment in the illustrated embodiment; Figure 5 for Figure 2 An enlarged structural diagram of part A in the welding equipment of the embodiment shown; Figure 6 This is a schematic diagram of the welding of a first pipe fitting and a second pipe fitting according to an embodiment of this application.

[0008] in, Figures 2 to 6 The correspondence between the reference numerals and component names in the attached drawings is as follows: 200 Welding equipment, 210 First laser welding assembly, 212 First laser welding head, 214 First angle mounting support, 220 Second laser welding assembly, 222 Second laser welding head, 224 Second angle mounting support, 230 Rotary disk, 240 Circumferential rotation power assembly, 250 Support frame, 252 Upper disk, 254 Lower disk, 256 Intermediate connecting rod, 260 Circumferential positioning assembly, 262 Cylinder, 264 Linear guide rail, 266 Roller, 270 Vision sensor, 280 Butt joint circumferential seam, 302 First pipe fitting, 304 Second pipe fitting, 306 Outer protruding bevel, 308 Inner concave bevel. Detailed Implementation

[0009] To better understand the above-mentioned objectives, features, and advantages of this application, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0010] Many specific details are set forth in the following description in order to provide a full understanding of this application. However, this application may also be implemented in other ways different from those described herein. Therefore, the scope of protection of this application is not limited to the specific embodiments disclosed below.

[0011] The following reference Figures 1 to 6 This application describes a dual-laser all-position welding method for oil and gas pipelines provided according to some embodiments.

[0012] like Figures 1 to 6As shown, one embodiment of this application provides a dual-laser all-position welding method for oil and gas pipelines. An external welding device is used to weld the butt joint circumferential seam of a first pipe fitting and a second pipe fitting. The welding device includes a support frame, a rotating disk rotatably mounted on the support frame, and a first laser welding assembly and a second laser welding assembly symmetrically arranged and driven by the rotating disk. The dual-laser all-position welding method for oil and gas pipelines includes the following steps: S1, pipe end preparation and assembly: The butt joint surfaces of the first and second pipe fittings are respectively processed into mutually matching outwardly protruding bevels and inwardly concave bevels, so that the two pipes can automatically align and form a butt joint circumferential seam with bevel angles during assembly; S2, equipment positioning and alignment: The support frame is fitted onto the butt joint of the first and second pipe fittings, and multiple sets of circumferentially distributed circumferential positioning assemblies are used to automatically align and center the axis of the support frame with the axis of the first and second pipe fittings, so that the rotating disk... S3. Alignment of laser welding heads: Adjust the first and second laser welding components mounted on the rotating disk so that the light output directions of the first laser welding head of the first laser welding component and the second laser welding head of the second laser welding component are the same as the direction of the inclined surface of the butt joint, and the first and second laser welding heads are symmetrically arranged 180 degrees apart in the circumferential direction; S4. Synchronous rotation welding: Start the circumferential rotation power component to drive the rotating disk to rotate around the axis of the first and second pipes, and simultaneously start the first and second laser welding components so that the laser beams emitted by the first and second laser welding heads act on the butt joint at the same time; S5. Welding completed: After the rotating disk rotates 180 degrees, turn off the first and second laser welding components to complete the welding of the entire circumferential joint.

[0013] Specifically, such as Figure 2As shown, the welding equipment 200 provided in this application is an external welding equipment. The welding equipment 200 includes a first laser welding component 210, a second laser welding component 220, a rotary disk 230, a circumferential rotation power component 240, a support frame 250, and a circumferential positioning component 260. The first laser welding assembly 210 includes a first laser welding head 212 and a first angle mounting bracket 214; the second laser welding assembly 220 includes a second laser welding head 222 and a second angle mounting bracket 224; a rotating disk 230 is used to mount the first laser welding assembly 210 and the second laser welding assembly 220; a circumferential rotation power assembly 240 is used to drive the rotating disk 230 to rotate, thereby driving the first laser welding assembly 210 and the second laser welding assembly 220 to rotate around the axis of the first pipe fitting 302 and the second pipe fitting 304; the support frame 250 is a squirrel cage structure, and the squirrel cage support frame 250 is connected in the middle by a circular intermediate connecting rod 256, which is the load-bearing component of the whole equipment; the circumferential positioning assembly 260 includes a cylinder 262, a linear guide rail 264 and rollers 266, which are distributed in two rows circumferentially, with three sets in each row, for fixing the equipment and the first pipe fitting 302 and the second pipe fitting 304, and automatically aligning the axis of the first pipe fitting 302 and the second pipe fitting 304.

[0014] like Figure 3 and Figure 4 As shown, the first laser welding assembly 210 includes a first laser welding head 212 and a first angle mounting bracket 214. The first laser welding head 212 is the laser welding execution component, used to generate laser melting to weld the pipe fitting material. The first angle mounting bracket 214 is used to mount the first laser welding head 212. The first angle mounting bracket 214 has a certain tilt angle, which is the same as the tilt angle of the end face weld of the first pipe fitting 302 and the second pipe fitting 304, to ensure that the laser emitted from the laser welding head is aligned with the weld. That is, the tilt angle of the butt joint is the same as the angle of the butt joint end face of the first pipe fitting 302 and the second pipe fitting 304. One end protrudes outward and the other end is concave inward, which facilitates automatic alignment during assembly to form a butt joint 280. In addition, the second laser welding assembly 220 has the same mechanism and principle as the first laser welding assembly 210, and the second laser welding assembly 220 and the first laser welding assembly 210 are distributed at 180 degrees on the circumferential rotating disk.

[0015] like Figure 4 and Figure 5As shown, the rotary disk 230 is used to mount the first laser welding assembly 210 and the second laser welding assembly 220. The rotary disk 230 can rotate around the axis of the first pipe 302 and the second pipe 304, thereby driving the first laser welding assembly 210 and the second laser welding assembly 220 to rotate around the axis of the first pipe 302 and the second pipe 304, thus realizing circumferential welding of the first pipe 302 and the second pipe 304. In addition, the circumferential rotation power assembly 240 is mounted on the support frame 250 and is used to drive the rotary disk 230 to rotate. The circumferential rotation power assembly 240 specifically includes a servo motor, a reducer, a gear rack, etc., which will not be described in detail here. In addition, the support frame 250 has a squirrel cage structure, including an upper disk 252, a lower disk 254 and an intermediate connecting rod 256, which is the load-bearing component of the entire welding equipment. The squirrel cage structure facilitates the installation of the circumferential rotation power assembly 240 and the circumferential positioning assembly 260, and the hollow structure facilitates fixation to the first pipe 302 and the second pipe 304. In addition, the circumferential positioning component 260 includes a cylinder 262, a linear guide rail 264 and rollers 266, which are distributed in two rows with three sets in each row. They are used to fix the equipment and the first pipe 302 and the second pipe 304, and at the same time ensure that the equipment automatically aligns the axis of the first pipe 302 and the second pipe 304 with the center line.

[0016] like Figure 6 As shown, the mating end face of the first pipe fitting 302 is processed with an external chamfered bevel structure to form an externally protruding bevel 306, and the mating end face of the second pipe fitting 304 is processed with an internal chamfered bevel structure to form an internally concave bevel 308. After the two pipe fittings are assembled, the externally and internally chamfered bevel structures interlock to form a butt joint circumferential seam 280 with a beveled angle. The first laser welding head 212 and the second laser welding head 222 are adjusted so that their beam emission direction is consistent with the tilt direction of the externally protruding bevel 306 and the internally concave bevel 308. This design improves alignment accuracy and construction efficiency. Furthermore, by ensuring the consistent orientation of the laser beam and the bevels, optimal energy injection is achieved at the mating end faces of the assembled pipes, effectively ensuring full fusion and excellent forming at the weld root, while suppressing welding deformation caused by uneven heat input.

[0017] The dual-laser all-position welding method for oil and gas pipelines provided in this application achieves high-quality, high-efficiency, and highly environmentally adaptable oil and gas pipeline welding through the systematic coordination of dual lasers, automatic alignment, precise alignment, and process control. In the high-efficiency precision welding scenario, the welding equipment is driven by a circumferentially rotating power component that rotates a rotating disk, causing the first and second laser welding heads, arranged 180 degrees symmetrically, to rotate synchronously around the axes of the first and second pipe fittings. Both laser beams act simultaneously on the butt joint circumferential seam, and a single laser head only needs to rotate half a revolution to complete the full circumference welding, significantly improving efficiency compared to single-laser head welding and effectively avoiding cable entanglement. In the automatic alignment and stable support scenario, the support frame uses multiple sets of circumferentially distributed positioning components to drive rollers to press against the pipe wall, automatically completing the precise alignment and fixation of the welding equipment axis with the axes of the first and second pipe fittings, providing a stable reference for subsequent welding. Simultaneously, the butt joints of the first and second pipe fittings adopt an outwardly protruding and inwardly concave bevel design, allowing for automatic alignment during assembly, greatly improving assembly accuracy and efficiency. In the context of weld formation and quality control, the first and second laser welding heads are installed using angled mounting supports with a specific tilt angle to ensure that the output direction of the laser beam is always consistent with the bevel direction of the butt joint. That is, the output angle of the first and second laser welding heads is always the same as the bevel angle of the butt joint. This can minimize the reflection loss of laser energy and enable heat to be conducted uniformly and synchronously along the bevel depth direction. This approach ensures complete penetration at the weld root, preventing defects such as incomplete fusion or insufficient penetration caused by uneven energy distribution due to beam tilt. Furthermore, precisely controlled heat input effectively suppresses alloy element burn-off or weld depression caused by overheating, reducing overall thermal stress and deformation of the butt joint. This installation method also effectively prevents slag from falling back and damaging the laser head. Additionally, by independently controlling the dual-sided laser power, the thermophysical performance differences between the base tube and the inner liner tube can be precisely compensated. By controlling the laser spot to form a confocal or overlapping molten pool at the weld root, complete fusion and overall forming quality at the weld root are ensured, fundamentally solving the problems of high dilution rate and welding deformation. In field-adaptive scenarios, laser welding offers high energy density, low heat input, and strong resistance to wind interference. Combined with automated alignment and welding processes, it significantly improves the reliability, quality consistency, and overall efficiency of on-site construction.

[0018] Specifically, as oil and gas extraction gradually shifts towards acidic gas fields with high sulfur content, these high-sulfur oil and gas gases corrode oil and gas pipelines like sulfuric acid. Conventional anti-corrosion technologies and pipe materials are insufficient to ensure the safe transportation of oil and gas. Metallurgical composite pipes, combining the mechanical properties of the base pipe (carbon steel) and the corrosion resistance of the inner lining pipe (corrosion-resistant alloy steel), are widely used in the petrochemical industry. However, due to the long length of oil and gas pipelines, segmented welding is required. Currently, welding of oil and gas pipelines is carried out on-site, with the commonly used welding method being TIG welding (Tungsten Inert Gas Welding). Because the composite pipe consists of two materials with significant differences in chemical composition, structure, and coefficient of expansion, welding suffers from high dilution rates, low welding efficiency, large deformation of the pipe ends after welding, and high costs. Furthermore, on-site manual trimming is required, the inner lining is typically thin, and strict requirements are placed on pipe end assembly, leading to the base material melting into the weld and reducing the structure's corrosion resistance.

[0019] To address the shortcomings of existing technologies, this application provides a dual-laser all-position welding method for oil and gas pipelines.

[0020] like Figure 1 As shown, this application proposes a dual-laser all-position welding method for oil and gas pipelines, and the specific steps are as follows: S1. Pipe end preparation and assembly: The mating end faces of the first pipe fitting and the second pipe fitting are respectively processed into mutually matching external protruding bevels and internal concave bevels, so that the two pipes can automatically center and form a mating ring seam with bevel angle when assembled. S2. Equipment positioning and alignment: The support frame is fitted onto the joint of the first and second pipe fittings, and multiple sets of circumferentially distributed circumferential positioning components are used to automatically align and center the axis of the support frame with the axis of the first and second pipe fittings, so that the rotation axis of the rotating disk coincides with the axis of the first and second pipe fittings, and the fixing is completed. S3. Laser welding head alignment: Adjust the first laser welding assembly and the second laser welding assembly mounted on the rotating disk so that the light output direction of the first laser welding head of the first laser welding assembly and the second laser welding head of the second laser welding assembly are the same as the direction of the inclined surface of the butt joint, and the first laser welding head and the second laser welding head are symmetrically arranged 180 degrees apart in the circumferential direction. S4. Synchronous Rotation Welding: Start the circumferential rotation power component to drive the rotating disk to rotate around the axis of the first pipe and the second pipe. At the same time, start the first laser welding component and the second laser welding component simultaneously, so that the laser beams emitted by the first laser welding head and the second laser welding head act on the butt joint circumferential seam at the same time. S5. Welding complete: After the rotating disk rotates 180 degrees, the first laser welding component and the second laser welding component are turned off to complete the welding of the entire circumferential seam.

[0021] Specifically, such as Figure 1 As shown, in step 1, the design of the concave and convex bevels forms a self-positioning tenon and mortise structure. When the first and second pipe fittings are joined, the fit of the bevels naturally guides the pipe opening to the center position, achieving preliminary radial alignment. This reduces the difficulty of high-precision assembly of large pipes and lays the foundation for obtaining high-quality circumferential welds. In step 2, the hollow structure of the squirrel-cage support frame facilitates the overall "fitting" of the equipment into the pipe body. The working principle of the circumferential positioning component is that multiple cylinders drive rollers to synchronously feed radially along a linear guide until all rollers are in contact with the pipe wall. Since the rollers are evenly distributed in the circumferential direction, the constraint force they exert on the pipe wall will automatically "pull" the axis of the support frame to coincide with the pipe axis, completing precise automatic alignment and clamping, ensuring the reference accuracy of the subsequent welding rotation movement. In step 3, the tilt angle of the angle mounting support is preset according to the angle of the pipe end bevel. Installing the laser welding head through this support ensures that the axis of the laser beam is always consistent with or coincides with the bevel of the weld. This incident light maximizes the utilization efficiency of laser energy, ensuring uniform penetration on both sides of the weld. Simultaneously, the tilted light output direction effectively avoids spatter during welding, protecting the laser head. The 180-degree symmetrical arrangement of the two laser heads results in a more even distribution of welding heat input circumferentially, helping to reduce welding stress and deformation. In step 4, the circumferential rotational power assembly provides smooth and precise rotational drive. The two laser welding heads emit light while rotating around the pipe axis, each responsible for a 180-degree weld area. This dual-station design theoretically doubles welding efficiency, and since each laser head only needs to rotate half a revolution, it completely avoids the problem of cable entanglement during continuous rotation, making it particularly suitable for continuous construction of long pipelines in the field. In step 5, after the rotating disk has rotated 180 degrees, the two laser heads have completed a full circumference of the weld. At this point, the lasers are turned off, and the welding process ends. This method achieves a single-pass welding of the entire circumference, with a one-time weld formation, good joint consistency, and stable and reliable quality.

[0022] Thus, the dual-laser all-position welding method for oil and gas pipelines provided in this application, by employing external welding equipment and sequentially executing the steps of pipe end bevel assembly, automatic equipment centering, laser head tilting alignment, and synchronous dual-laser rotation welding, completes a complete oil and gas pipeline welding process, namely, a composite pipe welding process. This method utilizes the symmetrical arrangement and semi-circular rotation of the dual laser heads to double welding efficiency and avoid cable entanglement; the cooperation of the cage frame and circumferential positioning components enables rapid and precise self-centering of the equipment; and the use of angled mounting supports ensures the effective angle between the laser beam and the weld seam, as well as slag protection for the laser head. Through synergistic effects, it ultimately achieves the technical effects of reducing the welding dilution rate and deformation of assembled pipe fittings, improving assembly accuracy and welding efficiency, and enhancing adaptability to field construction.

[0023] Compared with existing technologies, the advantages of the dual-laser all-position welding method for oil and gas pipelines provided in this application are as follows: First, laser welding replaces TIG welding, reducing welding deformation and dilution rate in assembled pipe fittings (i.e., composite pipes) and improving welding quality. Second, laser welding replaces TIG welding; due to the high energy density of the laser, the influence of wind on the welding arc is eliminated when welding oil and gas pipeline fittings in the field, improving welding quality. Third, the two ends of the welded pipe fittings are respectively spliced ​​with concave and convex joints, facilitating automatic alignment and centering, improving assembly efficiency, and reducing costs. Fourth, using dual-laser welding, each laser head only needs to rotate 180°, improving welding efficiency and avoiding equipment cable entanglement. Fifth, the dual lasers are installed at an angle, preventing weld slag from falling onto the laser head and extending the laser head's service life.

[0024] In some embodiments, optionally, such as Figure 1 and Figure 5 As shown, the circumferential positioning assembly includes a cylinder, a linear guide rail, and rollers; in step S2, the specific steps for automatic alignment and centering are as follows: the cylinder drives the rollers to extend along the linear guide rail until all rollers are in contact with the outer walls of the first and second pipe fittings. Under the action of the circumferentially distributed rollers, the axis of the support frame is automatically aligned with the axis of the first and second pipe fittings.

[0025] Specifically, the cylinder acts as the power source, providing precise linear thrust, while the linear guide provides rigid guidance for the radial movement of the rollers, ensuring their precise and synchronized trajectory. The rollers, as the final actuators, contact the pipe wall. The automatic alignment and centering principle is as follows: multiple rollers are evenly distributed circumferentially. When they are driven by the cylinder to extend radially synchronously and ultimately press against the outer walls of the first and second pipe fittings, the axis of the support frame is automatically constrained and corrected to coincide with the pipe axis, based on the system's adaptive principle, thus achieving high-precision automatic alignment and clamping. This design improves the efficiency and accuracy of on-site installation, reduces reliance on operator skills, and provides a stable and reliable benchmark for subsequent laser welding processes, fundamentally guaranteeing the weld formation quality.

[0026] In some embodiments, the first laser welding head and the second laser welding head are optionally mounted on a first angle mounting bracket and a second angle mounting bracket with tilt angles, respectively, and the tilt angles of the first angle mounting bracket and the second angle mounting bracket are the same as the bevel angle of the butt joint.

[0027] Specifically, the specific tilt angle design of the first and second angle mounting supports is a key element in achieving precise alignment of the laser beam with the butt joint seam. The technical principle is as follows: by pre-setting the tilt angle of the mounting supports to match the angle of the weld bevel formed at the pipe end, the output axis of the laser welding head fixed on it can naturally align with or coincide with the weld bevel. This ensures that the laser energy is concentrated at the weld root, achieving synchronous and uniform melting and full bonding of the base materials on both sides, resulting in a high-quality weld with consistent penetration and good shape. Simultaneously, this tilted mounting method allows the laser head to be offset from directly above the weld, effectively preventing metal spatter and weld slag generated during welding from contaminating or damaging the laser lens due to gravity. This achieves stable and continuous laser beam alignment without the need for a complex real-time tracking system, improving the reliability of the welding process and the consistency of weld quality, and extending the service life of the laser welding head.

[0028] In some embodiments, optionally, such as Figure 1 As shown, in step S4, before starting the first laser welding assembly and the second laser welding assembly, a protective gas is introduced into the butt joint area.

[0029] Specifically, introducing a protective gas into the butt joint area before laser welding begins establishes and maintains a localized inert gas environment, effectively isolating the molten metal from reactive components such as oxygen and nitrogen in the air. This prevents oxidation and nitriding reactions of the weld metal in both liquid and high-temperature solid states, avoiding welding defects such as oxide inclusions and porosity, and ensuring the stability of the chemical composition of the corrosion-resistant alloying elements, thus maintaining the required corrosion resistance of the weld area. This improves the metallurgical quality and density of the weld, ensuring the corrosion resistance of the welded joint, especially the inner corrosion-resistant alloy lining, and enabling the overall performance of the assembled pipe fittings to meet stringent environmental requirements.

[0030] In some embodiments, optionally, such as Figure 1 As shown, in step S4, the laser focus positions of the first laser welding head and the second laser welding head are set to the distance from the surface of the first pipe to the center of the wall thickness of the second pipe.

[0031] Specifically, the laser focal points of the first and second laser welding heads are precisely set from the surface of the first pipe fitting to its wall thickness center, and from the surface of the second pipe fitting to its wall thickness center. This is a key process control for achieving balanced fusion of dissimilar materials. Since laser energy is most concentrated at the focal point, positioning the focal point from the surface of the pipe fitting to its wall thickness center allows the laser energy to act simultaneously and evenly on both the carbon steel base pipe and the corrosion-resistant alloy liner pipe. This promotes the synchronous melting of two materials with significantly different thermophysical properties, such as melting point and thermal conductivity, forming a stable common molten pool at the weld root. This effectively avoids defects such as incomplete fusion on one side or overheating and collapse on the other side due to uneven energy distribution, ensuring the symmetry and integrity of the weld fusion pattern throughout its thickness direction, thereby improving the root fusion quality of the composite pipe butt joint circumferential seam.

[0032] In some embodiments, optionally, such as Figure 1 As shown, in step S4, the first laser welding head and the second laser welding head are controlled to perform rotary welding at a linear speed of 0.5m / min to 5m / min.

[0033] Specifically, controlling the rotational welding speed of the first and second laser welding heads within the range of 0.5 m / min to 5 m / min is a key process parameter for achieving the optimal balance between high-quality welding and high-efficiency production, as the welding speed directly determines the duration of laser energy action per unit weld length. When the speed is below 0.5 m / min, excessively long thermal action time leads to excessive heat input, easily causing problems such as burn-through of the composite tube, weld depression, or coarse grains, while also severely limiting welding efficiency. Conversely, when the speed exceeds 5 m / min, excessively short thermal action time may result in insufficient melting of the base material, producing defects such as incomplete fusion, insufficient penetration, or discontinuous weld formation. By limiting the speed within this optimized range, it is possible to maximize welding efficiency while ensuring sufficient penetration and good weld formation, and effectively control welding heat input, thereby suppressing welding deformation of the composite tube caused by differences in the thermophysical properties of dissimilar materials.

[0034] In some embodiments, optionally, such as Figure 1 As shown, in step S4, the laser power of the first laser welding head and the second laser welding head are independently controlled to compensate for the difference in thermophysical properties between the base tube and the inner liner tube of the first and second pipe fittings.

[0035] Specifically, the independent control of laser power for the first and second laser welding heads is a setting specifically designed for the welding characteristics of dissimilar materials in composite pipes. Taking metallurgical composite pipes as an example, the base pipe (e.g., carbon steel) and the lining pipe (e.g., corrosion-resistant alloy) differ in key thermophysical properties such as laser absorptivity, thermal conductivity, and melting point. If symmetrical equal-power welding is used, the material on the side with lower heat input demand will overheat, while the other side may not melt sufficiently. By independently controlling the power on both sides, higher laser power can be allocated to the side with lower absorptivity or higher heat capacity, while appropriate power can be allocated to the other side. This precisely compensates for this inherent difference, allowing both materials to reach their melting temperature simultaneously, forming a uniform and stable common molten pool at the root. This setup achieves a perfect metallurgical bond at the interface of dissimilar materials, fundamentally eliminating defects such as incomplete fusion, undercut, or elemental loss caused by heat input mismatch, and improving the weld formation quality, mechanical properties, and long-term reliability in corrosive environments.

[0036] In some embodiments, optionally, such as Figure 1 As shown, in step S4, the first laser welding head and the second laser welding head are controlled to emit lasers to form a confocal or overlapping molten pool in the root region of the butt joint.

[0037] Specifically, controlling the laser beams emitted from the first and second laser welding heads to form a confocal or overlapping molten pool in the root region of the butt joint is the core technology for achieving high-quality full penetration welding. By precisely adjusting the relative position and optical path of the two laser heads, two high-energy-density laser beams act together on the deepest root region of the weld. When the two beams are confocal, their energy is superimposed at the focal point, increasing the energy density in that region, which is sufficient to overcome the surface tension of the molten pool and the back pressure of metal vapor, ensuring complete penetration at the root. When the two beams overlap at a certain angle, a wider and more uniform thermal field with a larger energy distribution is created at the root, which is conducive to forming a wide and stable common molten pool. This promotes full fusion and metallurgical bonding of the base materials on both sides at the root, avoiding root fusion defects caused by insufficient energy or misalignment, thereby ensuring the long-term safe use performance of the entire composite pipe welded joint in harsh corrosive environments.

[0038] In some embodiments, optionally, such as Figure 6 As shown, in step S1, the mating end face of the first pipe fitting is processed into an external chamfered bevel structure to form an externally protruding bevel, and the mating end face of the second pipe fitting is processed into an internal chamfered bevel structure to form an internally concave bevel. After the two pipe fittings are assembled, the external chamfered bevel structure and the internal chamfered bevel structure are interlocked to form a mating ring seam with a bevel angle. In step S3, the first laser welding head and the second laser welding head are adjusted so that their light emission direction is consistent with the tilt direction of the externally protruding bevel and the internally concave bevel.

[0039] Specifically, by combining a specific inner and outer chamfering interlocking structure with laser beam directional control, efficient and high-precision assembly and welding are achieved. The technical principle lies in the fact that the outer and inner chamfers form a "mortise and tenon" positioning structure, automatically guiding the pipe openings to precise axial and radial alignment positions during the docking of two pipe fittings. Simultaneously, setting the laser welding head's output direction to align with the inclination direction of the inner and outer bevels means the laser beam will be incident parallel to the bevel. This incident method ensures uniform laser energy distribution along the entire length of the bevel, simultaneously heating and melting the entire mating surface of the inner and outer chamfers, ensuring eutectic fusion of the two base materials at the maximum contact surface, thus forming a high-quality weld with uniform penetration and a complete joint surface. The technical effects are: firstly, the mechanical self-positioning structure significantly reduces the difficulty and time of pipe assembly, improving alignment accuracy and construction efficiency; secondly, the consistent orientation of the laser beam and the bevel achieves optimal energy injection into the pipe docking end faces, effectively ensuring full fusion and excellent weld formation at the weld root, while suppressing welding deformation caused by uneven heat input.

[0040] In some embodiments, the first and second pipe fittings may be specifically metallurgical composite pipes, wherein the base pipe of the metallurgical composite pipe is carbon steel and the inner lining pipe is corrosion-resistant alloy steel.

[0041] Specifically, the first and second pipe fittings to be welded are defined as metallurgical composite pipes composed of a carbon steel base pipe and a corrosion-resistant alloy steel liner. The core challenge in welding such composite pipes is ensuring both structural strength, primarily borne by the carbon steel base pipe, and maintaining the corrosion resistance of the inner wall, guaranteed by the corrosion-resistant alloy liner. The welding method of this application employs a dual-laser welding process with precise and controllable heat input, combined with independent power control and precise focus adjustment. This minimizes thermal damage to the corrosion-resistant alloy layer and the melting of carbon steel elements, thus reducing the dilution rate. This ensures that the chemical composition and metallographic structure of the weld area are essentially consistent with the base material of the liner, maintaining its inherent excellent corrosion resistance. This solves the technical problem of traditional welding methods being unable to simultaneously achieve both mechanical and corrosion resistance when connecting such composite pipes. It provides a safe, reliable, and efficient field connection solution for oil and gas pipelines in harsh corrosive environments such as those with high sulfur content, significantly extending the pipeline's service life.

[0042] In some embodiments, optionally, such as Figure 1 and Figure 3 As shown, in step S4, a vision sensor is used to monitor the state of the weld pool in real time, and the laser power or welding speed of the first laser welding head and the second laser welding head are dynamically adjusted according to the monitoring results.

[0043] Specifically, a vision sensor is used to monitor and control the welding process in real time, achieving intelligent and adaptive precision welding. The vision sensor can capture the geometry, surface morphology, and thermal radiation characteristics of the molten pool in real time. This image data is transmitted to the control system in real time, processed and analyzed by a preset algorithm model, thereby indirectly determining the weld penetration, forming quality, and potential defect trends. Based on this analysis, the control system dynamically and adaptively adjusts the laser power or welding speed of the first and second laser welding heads. For example, when the molten pool size is detected to be too small or the brightness insufficient, the system will slightly increase the laser power to ensure complete penetration; when the molten pool is detected to be unstable or may collapse, the system will fine-tune the welding speed to optimize heat input. This improves the consistency and stability of the welding process, actively compensating for welding quality fluctuations caused by factors such as workpiece assembly gap fluctuations, pipe end ellipticity deviations, or environmental interference. While significantly reducing reliance on operator experience, it effectively eliminates defects such as incomplete fusion and burn-through, ensuring high quality and high reliability for each circumferential weld.

[0044] In the description of this application, the term "multiple" refers to two or more. Unless otherwise expressly defined, the terms "upper," "lower," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. The terms "connection," "installation," "fixing," etc., should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection or an indirect connection through an intermediate medium. For those skilled in the art, the specific meaning of the above terms in this application can be understood according to the specific circumstances.

[0045] In the description of this specification, the terms "one embodiment," "some embodiments," "specific embodiment," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of this application. 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.

[0046] The above are merely preferred embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for dual-laser all-position welding of oil and gas pipelines, characterized in that, An external welding device is used to weld the butt joint circumferential seam of the first and second pipe fittings. The welding device includes a support frame, a rotating disk rotatably mounted on the support frame, and a first laser welding assembly and a second laser welding assembly symmetrically arranged and driven by the rotating disk. The dual-laser all-position welding method for oil and gas pipelines includes the following steps: S1. Pipe end preparation and assembly: The mating end faces of the first pipe and the second pipe are respectively processed into mutually matching external protruding bevels and internal concave bevels, so that the two pipes can automatically center and form a mating ring seam with bevel angle when assembled. S2. Equipment positioning and alignment: The support frame is fitted onto the joint between the first pipe and the second pipe, and multiple sets of circumferentially distributed circumferential positioning components are used to automatically align and center the axis of the support frame with the axis of the first pipe and the second pipe, so that the rotation axis of the rotating disk coincides with the axis of the first pipe and the second pipe, and the fixing is completed. S3. Laser welding head alignment: Adjust the first laser welding assembly and the second laser welding assembly mounted on the rotating disk so that the light emission direction of the first laser welding head of the first laser welding assembly and the second laser welding head of the second laser welding assembly are the same as the direction of the inclined surface of the butt joint, and the first laser welding head and the second laser welding head are symmetrically arranged 180 degrees apart in the circumferential direction. S4. Synchronous Rotation Welding: Start the circumferential rotation power assembly to drive the rotary disk to rotate around the axis of the first pipe and the second pipe, and simultaneously start the first laser welding assembly and the second laser welding assembly, so that the laser beams emitted by the first laser welding head and the second laser welding head act on the butt joint circumferential seam at the same time. S5. Welding complete: After the rotating disk rotates 180 degrees, the first laser welding component and the second laser welding component are turned off, completing the welding of the entire circumferential seam.

2. The dual-laser all-position welding method for oil and gas pipelines according to claim 1, characterized in that, The circumferential positioning assembly includes a cylinder, a linear guide rail, and rollers; In step S2, the specific steps of automatic alignment and centering are as follows: the cylinder drives the rollers to extend along the linear guide rail until all rollers are in contact with the outer walls of the first pipe and the second pipe. Under the action of circumferential distribution, the axis of the support frame is automatically aligned with the axis of the first pipe and the second pipe.

3. The dual-laser all-position welding method for oil and gas pipelines according to claim 1, characterized in that, The first laser welding head and the second laser welding head are respectively mounted on a first angle mounting bracket and a second angle mounting bracket with tilt angles, and the tilt angles of the first angle mounting bracket and the second angle mounting bracket are the same as the slope angle of the butt joint.

4. The dual-laser all-position welding method for oil and gas pipelines according to claim 1, characterized in that, In step S4, before starting the first laser welding assembly and the second laser welding assembly, a protective gas is introduced into the mating circumferential seam area.

5. The dual-laser all-position welding method for oil and gas pipelines according to claim 1, characterized in that, In step S4, the laser focus positions of the first laser welding head and the second laser welding head are set to the distance from the surface of the first pipe to the center of the wall thickness of the second pipe.

6. The dual-laser all-position welding method for oil and gas pipelines according to claim 1, characterized in that, In step S4, the first laser welding head and the second laser welding head are controlled to perform rotary welding at a linear speed of 0.5m / min to 5m / min.

7. The dual-laser all-position welding method for oil and gas pipelines according to claim 1, characterized in that, In step S4, the laser power of the first laser welding head and the second laser welding head are independently controlled to compensate for the differences in thermophysical properties between the base tube and the inner liner tube of the first and second pipe fittings.

8. The dual-laser all-position welding method for oil and gas pipelines according to claim 1, characterized in that, In step S4, the first laser welding head and the second laser welding head are controlled to emit lasers to form a confocal or overlapping molten pool in the root region of the butt joint.

9. The dual-laser all-position welding method for oil and gas pipelines according to claim 1, characterized in that, In step S1, the mating end face of the first pipe fitting is processed into an external chamfered bevel structure to form the externally protruding inclined surface, and the mating end face of the second pipe fitting is processed into an internal chamfered bevel structure to form the internally concave inclined surface. After the two pipe fittings are assembled, the outer chamfered bevel structure and the inner chamfered bevel structure fit together to form the butt joint with a beveled angle. In step S3, the first laser welding head and the second laser welding head are adjusted so that their light emission direction is consistent with the tilt direction of the outward protruding slope and the inward concave slope.

10. The dual-laser all-position welding method for oil and gas pipelines according to claim 8, characterized in that, In step S4, a visual sensor is used to monitor the state of the weld pool in real time, and the laser power or welding speed of the first laser welding head and the second laser welding head are dynamically adjusted according to the monitoring results.

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