Construction methods and systems for connecting heating pipelines

Abstract

This invention relates to the field of pipe welding, and particularly to a method and system for the construction of thermal pipe butt joints. The method includes the following steps: pre-setting a stepped bevel at the pipe joint to be butt joint, featuring a smooth transition between a large-angle transition section and a narrow-gap welding section, with micro-grooves on the surface; fixing the pipe joint using a pipe butt joint device; dynamically calibrating the support force using a pressure sensor and control terminal to ensure the pipe joint alignment deviation is within a standard range; and performing welding using DC positive polarity TIG welding, pulsed TIG welding, or hot-wire TIG welding. The system includes a pipe butt joint device and a welding device. This solution optimizes arc energy distribution through a double-step bevel, enhances fusion through micro-grooves, improves butt joint accuracy through dynamic calibration, controls thermal deformation, and optimizes weld quality through CNC welding. It can reduce defect rates, decrease filler metal usage, increase deposition efficiency, improve first-pass yield, shorten the cycle time, and reduce costs.

Description

Technical Field

[0001] This invention relates to the field of pipe welding, and in particular to a method and system for connecting thermal pipelines. Background Technology

[0002] In the field of thermal pipeline construction, narrow-gap bevel welding technology is widely used due to its advantages such as reducing the amount of filler metal and improving welding efficiency. However, existing narrow-gap bevel forms (such as narrow-gap "U" bevels and ultra-narrow-gap single Y bevels) have revealed a series of technical bottlenecks in actual construction: First, the narrow bevel space makes it difficult for the arc energy to be evenly applied to both sides and the root of the bevel, resulting in insufficient interlayer fusion during multi-layer filler welding, which easily leads to defects such as incomplete fusion and slag inclusions; Second, the alignment accuracy requirements are extremely high, and pipeline deformation caused by welding heat input can damage the alignment accuracy. After deformation, narrow-gap bevels are prone to welding torch jamming, affecting welding continuity; Third, improper control of thermal deformation can lead to excessive misalignment, making it difficult to accurately control the reinforcement height during cap welding, and the bevel shape may change during welding, thus affecting the stress distribution of the weld and reducing the service life of the pipeline. These problems not only increase construction costs and subsequent maintenance risks, but also make it difficult to meet the stringent requirements for welding quality and safety of high-pressure and high-temperature thermal pipelines. Therefore, there is an urgent need to develop a new construction method that can solve the problem of narrow gap groove fusion, improve the accuracy control of the joint, and optimize the geometry of the weld. Summary of the Invention

[0003] To address the problems mentioned in the background section, this invention provides a method for constructing a thermal pipeline connection, and also provides a system for constructing a thermal pipeline connection.

[0004] The thermal pipeline connection construction method provided by this invention adopts the following technical solution:

[0005] A stepped bevel is pre-set at the pipe opening to be connected. The stepped bevel consists of a large-angle transition section from top to bottom and a narrow-gap welding section. The two sections are smoothly connected. Then, tiny grooves are pre-set at equal intervals on the bevel surface.

[0006] Align the ends of the two pipes to be connected and fix them with a pipe alignment tool. Monitor the contact pressure between the pipe alignment tool and the two pipes, and adjust the support force according to the pressure to ensure that the deviation of the pipe ends of the two pipes is within the standard range.

[0007] Weld the ends of the two pipes.

[0008] Furthermore, the bevel angle α of the large-angle transition section is 15 ~ 20°, and the width L1 is 8 ~ 10 mm; the bevel angle b of the narrow-gap welding section is 5 ~ 7°, and the width L2 is 5 ~ 7 mm; the transition fillet radius between the large-angle transition section and the narrow-gap welding section is 1 ~ 1.5 mm.

[0009] Furthermore, the depth of the micro-grooves on the bevel surface is 0.2 ~ 0.3 mm, and the spacing between the grooves is 3 ~ 5 mm.

[0010] Furthermore, at the support point where the pipe fitting device contacts the pipe, multiple pressure sensors are evenly arranged around the pipe opening, with several pressure sensors distributed at each support point.

[0011] Next, the pipe ends of the two pipes are welded. First, an internal root weld is performed using DC positive polarity TIG welding. After the internal root weld is completed, a root pass weld is performed on the narrow gap weld section using pulsed TIG welding. After the root pass weld is completed, a filler weld is performed using hot wire TIG welding. The filler weld is performed layer by layer from the bottom of the narrow gap upwards. Each layer of weld is welded in three passes, with adjacent layers welded in opposite directions and staggered. Then, a cover pass weld is performed.

[0012] The heating pipeline connection construction system includes:

[0013] A pipe alignment device includes a pipe alignment tool and a support adjuster installed inside the pipe alignment tool. The pipe alignment tool is used to fix the pipe ends to be connected, and the support adjuster is used to adjust the support force on the pipe ends.

[0014] The welding equipment uses a track-mounted all-position automatic welding machine equipped with a DC positive TIG welding torch for internal root welding, a narrow gap pulse TIG welding machine for root welding of narrow gap welding sections, and a hot wire TIG welding torch for full bevel filling welding and cover welding.

[0015] Furthermore, the pipe alignment device includes a pipe alignment tool, which includes a plurality of protrusions arranged in a ring. Each of the protrusions has a support block and a support adjuster installed inside both ends. The support block includes a retaining block that can be slidably embedded in the protrusion. A pressure sensor is installed at the outer end of the retaining block, and the support adjuster is connected to the inner end of the retaining block.

[0016] Furthermore, the support adjuster includes a threaded rod connected to the abutment block. The upper end of the threaded rod is fitted with a matching threaded sleeve. The outer wall of the threaded sleeve is fitted with a bearing. The outer wall of the bearing is fixed inside the protrusion. An adjusting rod is fixedly connected to the top of the threaded sleeve. The adjusting rod extends through the protrusion to the outer end of the protrusion. An adjusting block is fixedly connected to the top of the adjusting rod located at the outer end of the protrusion. A rotating connecting groove is provided on the adjusting block.

[0017] The beneficial effects of this invention are as follows: The double-step bevel structure optimizes the arc energy distribution, and the micro-grooves enhance mechanical and metallurgical fusion, increasing the sidewall fusion depth and fusion area, and reducing defects such as interlayer incomplete fusion and porosity. The pressure sensor and control terminal dynamically calibrate the support force, improving nozzle alignment accuracy. Combined with a low-heat-input welding process, this reduces welding thermal deformation and avoids welding torch jamming. The CNC welding process precisely controls the weld reinforcement and transition fillet radius, and the multi-layer weld bead staggered superposition optimizes stress distribution, reducing the risk of stress concentration and improving weld surface formation quality and fatigue resistance. The narrow gap structure reduces the amount of filler metal, and hot-wire TIG welding improves deposition efficiency. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the stepped bevel structure of the pipe opening during the construction of the thermal pipeline connection in this application.

[0019] Figure 2 This is a schematic diagram of the radial cross-section of the pipe alignment device during the construction of the thermal pipeline connection in this application;

[0020] Figure 3 yes Figure 2 A magnified view of a portion of the image.

[0021] In the diagram, 100 is the pipe alignment tool, 200 is the support block, 300 is the support adjuster, and 101 is the protrusion.

[0022] 201. Clamping block, 202. Pressure sensor, 301. Threaded rod, 302. Threaded sleeve, 303. Adjusting block, 304. Adjusting rod, 305. Bearing. Detailed Implementation

[0023] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0024] This invention discloses a method for connecting thermal pipelines, including the following steps:

[0025] S1. Create a stepped bevel at the pipe opening to be connected, such as... Figure 1As shown, the stepped bevel consists of a large-angle transition section from top to bottom and a narrow-gap welding section. The two sections transition smoothly, and then tiny grooves are evenly spaced on the bevel surface. Specifically, when creating the stepped bevel at the pipe ends to be joined, a CNC beveling machine is used for precise cutting. The geometric parameters of the large-angle transition section and the narrow-gap welding section are set by programming: first, the upper large-angle transition section is milled or turned with a bevel angle of 15~20° and a width of 8~10mm; then, the lower narrow-gap welding section is machined with a bevel angle of 5~7° and a width of 5~7mm. The joint between the two sections is milled with a circular arc cutter with a radius of 1~1.5mm to form a smooth transition. The tiny grooves are created using a micro-milling cutter or laser processing module of the same machine, evenly spaced on the bevel surface with a spacing of 3~5mm and a depth of 0.2~0.3mm. The shape of the grooves can be rectangular or arc-shaped depending on the equipment capabilities (the specific shape is not limited in practice).

[0026] The bevel angle a of the large-angle transition section is 15 ~ 20°, and the width L1 is 8 ~ 10 mm. The bevel angle b of the narrow-gap welding section is 5 ~ 7°, and the width L2 is 5 ~ 7 mm. The transition fillet radius between the large-angle transition section and the narrow-gap welding section is 1 ~ 1.5 mm.

[0027] The bevel angle α of the large-angle transition section is designed to be 15~20° and the width L1 is 8~10mm. This is mainly based on the balance between the accessibility of the welding torch and the heating efficiency of the arc. The bevel angle of 15~20° can avoid the welding torch jamming problem caused by the narrow entry of the traditional narrow gap bevel, and can also ensure that the arc energy is evenly applied to the sidewall of the bevel. At this angle, the welding torch nozzle and the sidewall of the bevel can maintain a safe distance of 3~5mm, and the arc can cover the sidewall to a depth of 2~3mm, which increases the fusion depth of the sidewall. The width of 8~10mm provides sufficient room for the welding torch to move. Especially in all-position welding (such as overhead welding), the welding torch can achieve ±15° tilt adjustment, which solves the problem that the arc cannot effectively heat the sidewall due to the narrow bevel. At this width, the amount of filler metal is reduced compared with the traditional U-shaped bevel, while ensuring the fluidity of the molten pool and reducing the risk of slag inclusions between layers.

[0028] A narrow-gap welding section with a bevel angle b of 5-7° and a width L2 of 5-7mm represents the optimal solution between minimizing filler metal and ensuring arc stability. The 5-7° micro-angle avoids the "magnetic blow" phenomenon that easily occurs with perfectly parallel bevels, while simultaneously reducing the filler metal amount per layer compared to traditional U-grooves. Combined with hot-wire TIG welding, this significantly improves welding efficiency. At this width, the arc energy density is concentrated, and the heat input can be controlled at 100-150J / mm, effectively reducing welding thermal deformation. Furthermore, the "constrained arc" effect created by the narrow gap, combined with the oscillating molten pool effect of pulsed TIG welding, reduces the porosity of the weld compared to traditional processes.

[0029] The depths of the large-angle transition section and the narrow-gap welding section are dynamically adjusted according to the pipe wall thickness during implementation. Typically, the depth of the large-angle transition section is 1 / 3 to 1 / 2 of the pipe wall thickness, and the depth of the narrow-gap welding section is the remaining wall thickness. For example, for a 12mm thick pipe, the depth of the large-angle transition section is set to 5-6mm, and the depth of the narrow-gap welding section is 6-7mm. This design ensures sufficient penetration of the root weld to the root (the root weld depth needs to reach 3-4mm) and provides a stable structure for the narrow-gap welding section.

[0030] The micro-grooves on the bevel surface are designed with a depth of 0.2~0.3mm and a spacing of 3~5mm. The core principle is to create a dual interface of mechanical fusion and metallurgical bonding by increasing the micro-roughness of the bevel surface. The 0.2~0.3mm depth allows the grooves to be fully filled by molten metal during welding, forming a "mortise and tenon" mechanical fit, while avoiding excessive reduction in the effective thickness of the bevel due to excessive depth. The 3~5mm spacing is based on an optimized balance between fusion area and processing efficiency. Orthogonal experiments have verified that this spacing increases the fusion area by 18%~22% compared to a planar bevel, and the metal matrix between adjacent grooves can effectively conduct welding thermal stress, reducing the risk of interlayer cracks. In multi-layer welding, the rate of interlayer non-fusion defects is reduced by 35% compared to traditional processes.

[0031] The shape of the groove can be rectangular, arc-shaped, or V-shaped, depending on the characteristics of the processing equipment (the specific shape is not limited in practice). Rectangular grooves are suitable for CNC milling, with advantages such as low tool cost and high processing speed, making them suitable for batch construction of carbon steel pipes; arc-shaped grooves are achieved through laser processing, and their smooth transition can reduce stress concentration and improve the fatigue resistance of the weld, making them suitable for high-strength materials such as alloy steel; V-shaped grooves use inclined surfaces to guide the flow of the molten pool, promoting the wetting of molten metal to the bottom of the groove and enhancing the root fusion effect, making them particularly suitable for overhead welding operations in all-position welding.

[0032] S2. Align the ends of the two pipes to be connected and fix them with a pipe alignment tool. Specifically, first, pre-treat the ends of the pipes to be connected by using an electric wire brush to remove rust, oil, and oxides within a 20mm range inside and outside the pipe ends. Align the ends of the two pipes and use a laser alignment instrument to monitor the gap between the pipe ends. Adjust the pipe ends axially at intervals of 1~1.5m using an adjustable jack to ensure that the misalignment of the pipe ends is ≤1.0mm and the bevel gap is controlled at 2~3mm (measured with a feeler gauge). Fix the axial position of the pipes with temporary support fixtures.

[0033] The pressure sensors monitor the contact pressure between the pipe alignment tool and the two pipes. Specifically, multiple pressure sensors are evenly arranged around the pipe opening at the support points where the pipe alignment tool contacts the pipes. Several pressure sensors are distributed at each support point. The pressure sensors are connected to the control terminal. The control terminal has a built-in pressure matrix corresponding to each support point under standard pipe alignment conditions with different parameters. The control terminal continuously and cyclically collects pressure data, compares the real-time pressure data Pi of each support point with the corresponding pressure element in the pressure matrix, marks support points where the pressure difference exceeds the threshold range, calculates the adjustment range of the support point, and issues an adjustment command for the support point.

[0034] In practice, the control terminal continuously collects real-time pressure data Pi from the pressure sensor 20 times per second. After collection, it quickly retrieves the corresponding standard pressure matrix Pstd from the built-in database based on the pipe diameter, wall thickness, and material parameters of the pipe to be connected. The real-time pressure data Pi is compared with each element in the standard pressure matrix Pstd to obtain the pressure deviation value ΔPi, where ΔPi = Pi - Pstd(i), Pi is the real-time pressure value at point i, and Pstd(i) is the standard pressure value at point i. A pressure deviation threshold ΔP_threshold, set according to the actual pipe conditions, is compared with the pressure deviation value ΔPi. For example, for pipes with larger diameters and harder materials, the pressure deviation threshold is set to ±0.5N. When the pressure deviation value ΔPi at one or more support points exceeds the threshold ΔP_threshold, the control terminal activates the PID control algorithm. Using the pressure deviation value ΔPi, the rate of change of deviation, and the integral value of the deviation as inputs, and based on pre-set proportional coefficients, integral coefficients, and derivative coefficients, the accurate support force adjustment ΔFi for each support point is calculated. For example, when the pressure deviation is small but persistent, the algorithm will output appropriate adjustment instructions to gradually correct the pressure.

[0035] The control terminal converts the calculated support force adjustment ΔFi into intuitive calibration commands. The interface clearly marks the support points requiring adjustment with prominent colors, displaying each support point's number, the specific value of the required support force, and the adjustment direction (green arrows indicate increasing support force, red arrows indicate decreasing support force). After the operator completes the adjustment, the control terminal immediately begins the next round of pressure data acquisition and analysis. If the pressure deviation still exceeds the threshold, a calibration command is generated again, continuously cycling this process until the difference between the pressure value at each support point and the corresponding element in the standard pressure matrix meets the accuracy requirements. Throughout the welding process, the control terminal continuously monitors pressure data and dynamically optimizes the support force calibration strategy based on changes in welding current and voltage, ensuring precise nozzle alignment.

[0036] The control terminal has a built-in database that uses a large amount of historical construction data and simulation experiments to construct a pressure matrix for pipelines under standard alignment conditions with different parameters. Specifically, in the laboratory, for thermal pipelines of different diameters (such as DN200~DN1200), wall thicknesses (4mm~16mm), and materials (carbon steel, alloy steel, etc.), test pieces are processed according to the stepped bevel standard, and high-precision pressure sensors are used to collect pressure data at each support point of the pipeline alignment tool under standard alignment conditions.

[0037] Before each experiment, the pipe is fixed on a high-precision adjustable fixture. A laser tracker is used to adjust the pipe opening to an absolutely aligned state (deviation controlled within ±0.01mm). After stabilizing for 10 minutes, the pressure data at each support point is recorded. For each pipe specification, the experiment is repeated more than 20 times, and the average value is taken as the standard pressure value. Simultaneously, the pressure distribution of the pipe under different operating conditions (different installation angles, ambient temperatures, etc.) in the standard aligned state is simulated to correct and supplement the experimental data.

[0038] These data were categorized and organized according to pipe specifications (diameter, wall thickness, material), the number of alignment tool support points, and layout parameters to construct a multi-dimensional pressure matrix model. Each pressure matrix was named with a specific identifier (e.g., "DN500~8mm~CS" represents a carbon steel pipe with a diameter of 500mm and a wall thickness of 8mm), and the elements in the matrix corresponded to the pressure values ​​of different support points under standard alignment conditions.

[0039] S3. Weld the ends of the two pipes, starting with internal root welding. Internal root welding uses DC positive polarity TIG welding with a welding current of 80-100A, an arc length of 2-3mm, and a welding speed of 8-10cm / min. In DC positive polarity TIG welding (tungsten inert gas welding), the workpiece is connected to the positive terminal of the power supply, and the tungsten electrode is connected to the negative terminal. This concentrates the arc energy, resulting in a higher molten pool temperature and greater penetration, suitable for the penetration requirements of the root weld. For stepped bevels, where the bottom width of the narrow gap welding section is only 5-7mm, DC positive polarity can precisely heat the root of the bevel by concentrating the arc energy, avoiding excessive melting or incomplete fusion of the sidewalls due to arc diffusion. Simultaneously, the "cathode cleaning" effect of the arc (when the workpiece is the positive terminal) effectively removes the oxide film on the bevel surface (such as the Fe3O4 layer that may exist in the pipe base material), improving fusion quality. Furthermore, the non-consumable tungsten electrode avoids filler metal contamination, ensuring the purity of the root weld and meeting the stringent requirements for weld tightness in thermal pipelines. A welding current of 80-100A can form a stable arc. Combined with an arc length of 2-3mm, this produces a 3-4mm penetration depth at the root of the bevel, precisely covering the thickness of the stepped bevel root. The current density is controlled at 180-230A / mm² (1.2mm tungsten electrode diameter), forming a molten pool with a diameter of approximately 5-6mm. This matches the 5-7mm width at the bottom of the narrow gap section, preventing molten metal from overflowing to the bevel sidewall and forming weld beads, which would affect subsequent root pass welding. An arc length of 2-3mm (energy density approximately 200-250W / mm²) reduces arc dispersion, concentrating heat at the root. This is especially effective in vertical and overhead welding positions, resisting the downward force of the molten pool and maintaining a uniform weld bead height on the back (0.5-1.5mm). The argon shielding gas diameter is maintained at 8-10mm to ensure an oxygen content of <50ppm in the arc zone, preventing weld oxidation and porosity. Welding speed of 8-10 cm / min ensures the heat input is controlled at 96-120 J / mm, lower than the 150 J / mm of traditional processes, reducing the width of the heat-affected zone and minimizing circumferential shrinkage deformation of the pipe. Uniform speed movement ensures weld width fluctuation ≤ ±0.3 mm, forming a root weld bead 6-8 mm wide and 1.0-1.8 mm high, providing a flat fusion base for the root pass in narrow gaps and preventing welding torch jamming due to uneven root surfaces. Internal root welding utilizes a track-type all-position automatic welding machine, with a laser tracker calibrating the distance between the welding torch and the root of the bevel in real time. The welding torch operates along a circular track at a constant linear speed.

[0040] After the inner root weld is completed, a root pass is performed on the narrow gap weld section. Pulsed TIG welding is used for the root pass, with the welding torch inserted deep into the narrow gap weld section below the bevel. The pulse frequency is 50-100Hz, the peak current is 120-150A, and the base current is 30-50A. Pulsed TIG welding generates a periodic arc impact force through pulsed current, effectively solving the problems of insufficient molten pool fluidity and incomplete interlayer fusion within the narrow gap bevel. In the narrow gap weld section, traditional continuous current welding is prone to thermal deformation due to excessively high arc energy concentration. However, the intermittent energy input of pulsed current reduces the average heat input, and combined with the "constrained arc" effect of the narrow gap, reduces circumferential shrinkage deformation of the pipe. Regarding parameter settings, a pulse frequency of 50-100Hz allows the arc to oscillate at high frequency, promoting gas escape through the oscillating molten pool and reducing the porosity inside the weld compared to traditional processes. The peak current of 120~150A provides instantaneous high energy within the pulse cycle, which can form a penetration depth of 2.5~3.5mm on the sidewall of the bevel, ensuring full fusion between the sidewall and the root weld in the narrow gap section; the base current of 30~50A keeps the arc from going out, while reducing the average current density (about 80~100A / mm²), avoiding excessive melting of the bevel edge due to continuous high heat input.

[0041] When the welding torch penetrates into the narrow gap welding section, maintain a 2-3 mm gap between the torch nozzle and the bevel sidewall to ensure effective argon protection (flow rate 10-12 L / min, oxygen content <50 ppm). The periodic energy variation of the pulsed arc allows the molten pool to fully melt during the peak current phase and briefly cool and solidify during the base current phase, forming a dynamic balance of "molten pool oscillation-solidification." Especially in vertical and overhead welding positions, this helps resist the downward force of gravity on the molten pool, maintaining uniform weld bead thickness (2-3 mm between layers). This provides a flat base surface for subsequent filler welding and prevents the hot wire TIG welding torch from getting stuck due to unevenness in the root pass.

[0042] During filler welding, hot-wire TIG welding is used to address the dimensional differences between the upper large-angle transition section and the lower narrow-gap welding section. The hot wire temperature is controlled at 300~400℃, and the welding current is 180~220A. Filling is carried out layer by layer from the bottom of the narrow gap. Each layer of weld is welded in three passes, with adjacent layers welded in opposite directions and staggered by 1 / 3 of the width. By preheating the welding wire to 300~400℃, the welding wire reaches a semi-molten state before entering the molten pool. Combined with the arc energy generated by the 180~220A welding current, the heat input is controlled at 150~200J / mm while ensuring the penetration depth (2.5~3.5mm), which is about 30% lower than that of traditional TIG welding. This effectively suppresses the circumferential shrinkage deformation of the pipeline caused by continuous filling. For the dimensional difference between the upper large-angle transition section (8~10mm wide) and the lower narrow-gap welding section (5~7mm wide) of the stepped groove, the high deposition rate (3~4kg / h) of hot-wire TIG welding can significantly improve the filling efficiency, especially in the large-angle section where the welding torch can be swung to cover a wide area, while the narrow-gap section utilizes the arc confinement effect to ensure sidewall fusion. In terms of parameter settings, the hot wire temperature and welding current work synergistically: the low-temperature section (300℃) is suitable for the low heat input requirements of the narrow-gap section, the high-temperature section (400℃) is used for rapid filling in the large-angle section, and the current is adjusted by adjusting the arc energy density (approximately 250~300W / mm²) to ensure the fluidity of the molten pool and avoid poor fusion or slag inclusions in the narrow gap.

[0043] After the root pass is completed, the starting point for filling is the junction of the top of the narrow gap welding section and the large angle transition section. The first pass of the first layer starts from the center of the bottom of the groove (the surface of the inner root weld), and the welding torch swings back and forth along the centerline with an amplitude of 5-8mm to form a center weld bead with a width of about 5-6mm, covering 80% of the bottom 5-7mm width of the narrow gap section. The first pass of the second layer starts from the left wall of the groove, offset towards the center by 1 / 3 width (about 2-2.5mm), and overlaps with the previous layer by 1 / 3 to form the left fusion band. The third pass starts from the right wall, similarly covering the right area, ensuring that each layer of three welds completely covers the groove cross-section and the fusion width with both side walls is ≥2mm. The welding direction of adjacent layers is reversed by switching the welding torch swing trajectory (e.g., the first layer swings from left to right, and the next layer from right to left). At the same time, the starting position of each layer is offset by 1 / 3 of the groove width (about 3-4mm) in the circumferential direction, forming a spiral upward lap weld structure. In this way, each weld layer forms a stress dispersion angle of 30~45° relative to the previous layer. Combined with the interpass temperature control of hot-wire TIG welding (≤200℃), the welding stress can be evenly distributed along the circumference of the pipe wall, avoiding concentrated cracking. The thickness of each filler layer is monitored in real time by a laser rangefinder and controlled within 2~2.5mm, ensuring that the flatness error of the filler surface is ≤±0.2mm, providing a precise base surface for the capping weld.

[0044] During the cap weld, adjust the welding torch angle and move it along the edge of the bevel at the large angle transition section to control the weld reinforcement and ensure a smooth transition between the cap layer and the large angle transition section at the upper part of the bevel. By controlling the welding torch trajectory and energy input, a smooth transition between the cap weld and the large angle transition section is achieved, while keeping the reinforcement within the range of 0.8~1.2mm to avoid stress concentration caused by geometric deviations. In terms of parameter settings, the hot wire temperature is adjusted to 250~300℃ (lower than the 300~400℃ for filler welding), and the welding current is reduced to 150~180A. By reducing the deposition rate, the amount of weld metal filler is reduced. Combined with the welding torch angle adjustment (40~45° angle with the bevel edge), the molten pool covers only a 2~3mm area at the bevel edge, forming a thin cap layer. The welding speed is increased to 10~12cm / min, and the heat input is controlled at 120~150J / mm to ensure rapid cooling and shaping of the weld surface, avoiding overheating that could lead to reinforcement bulging or undercut. In operation, the welding torch uses a laser rangefinder (accuracy ±0.1mm) at the end of a flexible support to monitor the distance to the bevel edge in real time. A servo motor drives the welding torch to make uniform circular motion along the bevel edge of the large-angle transition section, with the trajectory deviation controlled within ±0.2mm. Each capping weld is performed in two passes: the first pass moves along the left edge of the bevel, with the welding torch tilted 10-15° towards the center, covering the left wall and the bevel edge, forming a weld bead 4-5mm wide; the second pass moves along the right edge, tilting in the opposite direction at the same angle, covering the right wall and the bevel edge. The two weld bead overlaps by 1-2mm at the center to ensure a smooth surface. During welding, the argon gas flow rate is increased to 12-15L / min, and a double-layer gas shield is used for protection (inner layer diameter 8mm, outer layer diameter 15mm) to prevent weld oxidation and porosity. By presetting the bevel angle parameters through the CNC system, the welding torch automatically adapts to the 15~20° bevel slope, ensuring that the angle between the weld bead and the bevel is always maintained at 20~25°, forming a smooth transition radius of R1.5~2.0mm. After three-dimensional laser scanning detection, the surface roughness Ra of the capping layer is ≤6.3μm, and the uniformity error of the excess height is ≤±0.15mm, which meets the requirements of surface forming and stress distribution of thermal pipelines.

[0045] The present invention also provides a thermal pipeline connection construction system, comprising:

[0046] A pipe alignment device includes a pipe alignment tool and a support adjuster installed inside the pipe alignment tool. The pipe alignment tool is used to fix the pipe ends to be connected, and the support adjuster is used to adjust the support force on the pipe ends.

[0047] Specifically, such as Figures 2-3As shown, the pipe alignment device of this application includes a pipe alignment tool 100. The pipe alignment tool 100 includes a plurality of protrusions 101 arranged in a ring. Each of the two ends of the protrusion 101 is equipped with a support block 200 and a support adjuster 300. The support block 200 includes a retaining block 201 that can be slidably embedded in the protrusion 101. A pressure sensor 202 is installed at the outer end of the retaining block 201, and the support adjuster 300 is connected to the inner end of the retaining block 201. The support adjuster 300 includes a threaded rod 301 connected to the abutment block 201. The upper end of the threaded rod 301 is fitted with a matching threaded sleeve 302. The outer wall of the threaded sleeve 302 is fitted with a bearing 305. The outer wall of the bearing 305 is fixed inside the protrusion 101. An adjusting rod 304 is fixedly connected to the top of the threaded sleeve 302. The adjusting rod 304 extends through the protrusion 101 to the outer end of the protrusion 101. An adjusting block 303 is fixedly connected to the top of the adjusting rod 304 located at the outer end of the protrusion 101. A rotating connecting groove is formed on the adjusting block 303.

[0048] The adjusting rod 304 can be rotated using a power tool or manually by rotating the connecting groove, thereby driving the threaded sleeve 302 to rotate. The rotation of the threaded sleeve 302 causes the threaded rod 301 to extend or retract, allowing the clamping block 201 to partially extend out of the lower end of the protrusion 101, adjusting the support force at the corresponding point. The clamping block 201 can slide within the protrusion 101, and corresponding limiting strips and limiting grooves can be provided on the side wall where the clamping block 201 contacts the protrusion 101. This invention does not impose any limitations on this.

[0049] Specifically, the pipe fitting 100 adopts a ring-shaped steel structure with 6-8 protrusions 101 evenly distributed around the pipe opening (the specific number is adjusted according to the pipe diameter, such as 6 for DN500 and 8 for DN1200). Each protrusion is arranged radially, and its inner arc surface matches the curvature of the outer wall of the pipe. Rectangular grooves are opened inside both ends of the protrusions 101 to embed the support blocks 200. The groove depth is 20-25mm, and the width is adapted to the clamping block 201 (gap ≤ ±0.2mm), ensuring that the clamping block 201 can slide along the axial direction of the groove. A longitudinal limiting strip is set on the side wall of the groove, and a limiting groove is opened at the corresponding position of the clamping block 201 to form a sliding guide structure to avoid displacement.

[0050] The clamping block 201 is made of hard alloy, with the outer end machined into an arc surface (the radius is consistent with the outer wall of the pipe), and a miniature pressure sensor 202 (accuracy ±0.1N) is embedded in it. The surface of the sensor is flush with the arc surface of the clamping block to ensure accurate pressure measurement when in contact with the pipe.

[0051] A cylindrical cavity with a diameter of 15mm and a depth of 18mm is machined inside bump 101 (located slightly to the outer end of the middle of the bump) to serve as a circuit integration cavity. A sensor mounting groove with a diameter of 5mm and a depth of 2mm is formed on the outer arc surface of the clamping block 201. After the miniature piezoresistive pressure sensor is interference-fitted, it is sealed with high-temperature epoxy resin. The bottom surface of the sensor is connected to the metal substrate of the clamping block through thermally conductive silicone grease to ensure pressure transmission efficiency. The sensor signal line is introduced into the bump circuit cavity through an axial through-hole inside the clamping block, and the orifice is sealed with a silicone sealing ring.

[0052] Within the circuit cavity of bump 101, a multi-layer circuit board integrates a wireless module (such as Nordic RF52840, supporting Bluetooth 5.2 and 2.4GHz RF), a miniature lithium battery (3.7V / 150mAh, Φ10mm×5mm), and a signal conditioning circuit. Sensor leads connect to the PCB board via spring-loaded connectors. The signal conditioning circuit includes an amplification and filtering module and an analog-to-digital converter, converting the pressure signal into a digital value before transmitting it to the wireless module. A 0.1mm thick copper foil shielding layer is laid on the back of the PCB board, connecting to the bump's metal housing via a grounding post, forming complete electromagnetic shielding. The battery uses a drawer-type mounting structure, with a push-pull battery cover on the outside of the cavity for quick replacement. The wireless module transmits signals via an inverted-F antenna (IFA) on the PCB board. At the antenna location on bump 101, ABS engineering plastic replaces the metal material, forming a 20mm diameter circular non-metallic signal window to ensure RF signal penetration.

[0053] The inner end of the clamping block is connected to the threaded rod 301 via a threaded hole. The threaded rod has a diameter of 8~12mm (selected according to pipe diameter), a pitch of 1.5~2mm, and a rust-proof surface treatment. The threaded sleeve 302 of the support adjuster 300 has a fit accuracy of 6H / 6g with the threaded rod 301. The outer wall of the threaded sleeve is fitted with a deep groove ball bearing 305 (model 6203~2RS) via an interference fit. The outer ring of the bearing is fixed in the bearing seat on the inner wall of the protrusion 101 to ensure no radial wobble when the threaded sleeve rotates. The adjusting rod 304 passes through the through hole at the outer end of the protrusion (clearance ≤0.3mm). The adjusting block 303 at the top is designed as a regular hexagon (distance between opposite sides 14~19mm), compatible with electric torque wrenches or manual wrenches. The surface of the adjusting block has anti-slip textures, and the rotation angle accuracy can reach ±1°.

[0054] The pressure monitoring and control unit includes pressure sensors and a control terminal. The pressure sensors are distributed at the support parts where the pipe alignment tool contacts the pipe. The pressure sensors are connected to the control terminal. The control terminal has a built-in standard pressure matrix for pipes with different parameters. The control terminal collects pressure data in real time, compares it with the standard pressure matrix, and calculates the support force adjustment amount through a PID control algorithm. It generates a calibration command containing the support point number, adjustment value and direction. The support force is calibrated through the support adjuster to keep the pipe alignment deviation within the standard range.

[0055] For example, the pipe alignment tool has 6-8 protrusions 101 evenly distributed around its circumference (8 for DN800). Each protrusion has 2 sensors embedded in its two ends, resulting in 12-16 pressure monitoring points covering a 360° circumference of the pipe, with a spacing of ≤150mm. The wireless module within the circuit cavity of each protrusion acts as a slave node, communicating with the control terminal master node in a star topology. The communication distance is ≤10m, using 2.4GHz frequency hopping technology with a data refresh rate of 100Hz. The control terminal uses an industrial tablet PC with built-in dual Bluetooth 5.2 modules, a processor, and memory. The control terminal displays the pressure values, deviation values, and adjustment status of each sensor in real time.

[0056] For example, the screen displays the pressure value of each bump sensor in real time (accuracy 0.1N, display resolution 0.01N), standard pressure matrix value and real-time deviation value (ΔP). Values ​​exceeding the standard (|ΔP|> threshold) are marked with flashing red, and adjustment instructions (such as "bump 2 - left: +0.6N") are displayed dynamically.

[0057] In practice, the terminal can also be connected to an electric adjustment tool (such as a Makita DTP180Z electric torque wrench) via an RS-485 bus to receive adjustment feedback signals (thread rod rotation angle, support force change value) and form a closed-loop control.

[0058] The welding equipment includes an all-position automatic rail welding machine with a DC positive TIG welding torch for internal root welding, a narrow gap pulse TIG welding machine for root pass welding in narrow gap welding sections, a hot wire TIG welding torch for full bevel fill welding, and a CNC welding torch for cover welding.

[0059] For example, the internal root welding uses an Austrian Fronius TPS / i 400 rail-mounted all-position automatic welding machine, paired with a custom DC positive polarity TIG welding torch (1.2mm tungsten electrode diameter, 8mm nozzle diameter). The rail employs a magnetic adsorption structure, allowing for 360° welding around the pipe. The welding torch is equipped with a laser tracker to monitor the distance between the torch and the root of the bevel in real time, automatically adjusting the torch position via a closed-loop servo system. Welding parameters are preset via a built-in controller: welding current 80~100A, arc length 2~3mm, welding speed 8~10cm / min (stepper motor driven), and argon gas flow rate 8~10L / min.

[0060] The narrow-gap root pass welding equipment uses the Japanese OTC FD-B4 narrow-gap pulse TIG welding machine. The welding torch adopts a gooseneck structure (bending radius 15mm, nozzle diameter 5mm), which can penetrate into a narrow gap area of ​​5~7mm below the bevel. The pulse parameters are adjustable in the following ranges: frequency 50~100Hz, peak current 120~150A (accuracy ±2A), base current 30~50A. It is equipped with a dual gas supply system: inner layer argon gas flow rate 10~12L / min (to protect the arc), outer layer argon gas flow rate 5~8L / min (to suppress spatter), and an oxygen content monitor displays the oxygen content in the arc zone in real time. The welding torch oscillation mechanism supports ±15° tilt adjustment, with an amplitude of 2~3mm, ensuring a sidewall fusion depth of 2.5~3.5mm.

[0061] The filler welding equipment uses the American Miller Auto-Continuum hot-wire TIG welding system. The hot wire temperature is controlled by an independent temperature control module, and the hot wire feed speed is 5~8m / min (servo motor driven). The welding torch integrates a three-channel wire feeding mechanism, which can realize the sequential filling of three weld passes per layer (the first pass is the center weld pass, and the second and third passes are the left and right side weld passes). The welding current is 180~220A, the arc voltage is 10~12V, the welding torch oscillation frequency is 15~20 times / min, the oscillation amplitude is 5~8mm, and the switching of the direction of adjacent weld passes is automatically completed by PLC, with a staggered distance of 1 / 3 of the weld pass width.

[0062] The cover weld equipment uses a German KUKA KR C4 CNC welding torch, equipped with a laser rangefinder and a five-axis linkage mechanism, enabling trajectory fitting along the bevel edge of a large-angle transition section. The welding torch angle is automatically adjustable from 20° to 45° (angle with the bevel edge), with a welding current of 150-180A, a hot wire temperature of 250-300℃, and a welding speed of 10-12cm / min. A double-layer gas shield is used (inner layer diameter 8mm, flow rate 12-15L / min; outer layer diameter 15mm, flow rate 20-25L / min), with an airflow stabilizing device at the end of the gas shield to ensure effective protection. The cover weld bead is preset to two passes by the CNC system, with an overlap of 1-2mm, a height control accuracy of ±0.15mm, and a surface roughness Ra≤6.3μm.

[0063] Example 1: Construction of DN500×8mm carbon steel thermal pipeline connection

[0064] Including the following steps:

[0065] The beveling process uses a Swiss GF Machining Solutions CNC grinding machine to process a double-step bevel. The upper section has a large angle transition section with an angle of 18° and a width of 8.5mm, while the lower section has a narrow gap section with an angle of 6° and a width of 6mm. The transition fillet radius is 1.2mm.

[0066] The micro-grooves are laser-processed to a depth of 0.28 mm and a spacing of 3.5 mm, distributed in an arc shape. After processing, a 3D scanner showed that the bevel angle deviation was ±0.03 mm and the groove depth deviation was ±0.01 mm.

[0067] For pipe end pretreatment and alignment, a 25mm area inside and outside the pipe end is first cleaned with an electric wire brush, and the dimensions are checked with a bevel gauge to ensure they meet design requirements. A laser alignment instrument is used to initially adjust the pipe end misalignment to 0.8mm and the bevel gap to 2.5mm. The pipe alignment device uses a 6-protrusion structure (DN500 compatible), with two high-precision pressure sensors (accuracy ±0.03N) embedded in the end blocks of each protrusion. The control terminal retrieves the standard pressure matrix "DN500~8mm~CS". The pressure at each support point is monitored in real time, and the threaded rod is dynamically adjusted using an external electric torque wrench to control the pressure deviation within ±0.15N. Ultimately, the pipe end misalignment is 0.3mm, and the gap uniformity is ±0.05mm. The deviation is close to the instrument's measurement limit and can be ignored.

[0068] During the welding process, the inner root weld was performed using a Fronius TPS / i 400 rail welder, DC positive polarity TIG welding, with a current of 90A, an arc length of 2.2mm, a speed of 9cm / min, an argon flow rate of 9L / min, a back weld reinforcement of 1.0mm, a penetration depth of 3.8mm, and a weld width of 7.0mm. The root pass was welded using an OTC narrow-gap pulsed TIG welder, with a pulse frequency of 80Hz, a peak current of 130A, a base current of 40A, the welding torch extending deep into the narrow gap, an argon flow rate of 11L / min, an interpass thickness of 2.1mm, and a sidewall penetration depth of 3.0mm. The filler weld was performed using a Miller hot-wire TIG welder, with a hot-wire temperature of 350℃, a current of 200A, and three passes per layer, with adjacent layers in opposite directions and staggered by 2.8mm, a fill speed of 7cm / min, an interpass temperature of 180℃, and a total fill thickness of 5.5mm.

[0069] The cover weld was performed using a KUKA CNC welding torch with a current of 160A, a hot wire temperature of 280℃, a speed of 11cm / min, a weld reinforcement height of 1.0mm, a weld bead and bevel transition radius of R1.6mm, and a surface roughness of Ra=4.8μm.

[0070] Experimental Example 1:

[0071] The misalignment and gap uniformity at eight equally divided points on the circumference of the nozzle were measured using a laser tracker (Leica AT960). The peak pressure deviation at each support point was monitored and recorded in real time using a pressure sensor.

[0072] The measured misalignment at eight points around the pipe end was 0.28mm, 0.31mm, 0.29mm, 0.30mm, 0.27mm, 0.32mm, 0.29mm, and 0.30mm, with an average of 0.295mm. The difference between the maximum and minimum values ​​was 0.05mm, all less than 0.5mm (the industry standard allowable value is 1.0mm). For bevel gap uniformity, the measured gap at eight points was 2.45~2.55mm, with a deviation of ±0.05mm, far less than the industry standard requirement of ±0.3mm. In the pressure deviation peak test, the pressure deviation at each support point was controlled within ±0.2N throughout the welding process, with a maximum adjustment of 0.8N.

[0073] Other performance indicator test data are shown in Table 1 below:

[0074] Testing items Measured value Standard requirements X-ray detection level Level I Level I Tensile strength 425MPa ≥410MPa Side bending test (180°) No cracks qualified Impact energy (weld) 128J ≥105J Water pressure test (1.5 times the pressure) No leakage, pressure drop 0.01 MPa No leakage, ≤0.05MPa

[0075] Table 1 Performance Test Data of Example 1

[0076] This application achieves dynamic calibration of the pressure sensor and control terminal, controlling the pipe alignment deviation to approximately 0.3mm, which is only one-third of the industry standard and close to the instrument measurement error range, thus being negligible. This embodiment verifies the significant effect of the double-step beveling and intelligent alignment system in controlling thermal deformation and improving alignment accuracy. All indicators are superior to traditional processes, meeting the construction requirements of high-pressure thermal pipelines.

[0077] Example 2: Construction of DN800×12mm alloy steel thermal pipeline connection

[0078] The double-step bevel has an upper large-angle transition section with an angle of 16° and a width of 9mm, and a lower narrow-gap section with an angle of 5° and a width of 5.5mm. The transition fillet radius is 1.3mm. The large-angle section has a depth of 6mm (half the wall thickness), and the narrow-gap section also has a depth of 6mm. V-shaped micro-grooves, 0.25mm deep and spaced 3mm apart, are machined on the bevel surface, forming a sloping guide structure through laser processing to enhance the fluidity of the molten pool. Post-processing inspection: bevel angle deviation ±0.04mm, groove depth deviation ±0.01mm, surface roughness Ra=3.2μm.

[0079] The pipe alignment control uses an 8-protrusion pipe alignment device, with each abutment block embedding 2 pressure sensors (accuracy ±0.02N). The control terminal retrieves the "DN800~12mm~AS" pressure matrix and dynamically adjusts the support force to ensure that the misalignment is ≤0.4mm and the bevel gap is 2.8±0.04mm.

[0080] During welding, the inner root weld is performed using DC positive polarity TIG welding with a current of 95A, an arc length of 2.5mm, a speed of 8cm / min, and a root penetration depth of 4.2mm to ensure complete penetration at the bottom of the narrow gap. The root pass is performed using pulsed TIG welding with a pulse frequency of 90Hz, a peak current of 145A, a base current of 40A, a welding torch oscillation amplitude of 3mm (±1.5°), an argon flow rate of 12L / min, and a sidewall penetration depth of 3.5mm. The molten pool oscillation frequency is synchronized with the pulse to promote gas escape and sidewall fusion. The filler weld is performed using hot-wire TIG welding with a hot wire temperature of 380℃ and a current of 210A. Each layer is welded in three passes (center pass + left and right offset passes), with adjacent layers in opposite directions and staggered by 2.5mm. The welding torch oscillation frequency is 18 times / min, and the arc energy density is 280W / mm², ensuring a sidewall fusion width ≥2.5mm in the narrow gap section and a fusion depth ≥3mm in the large angle section. The cover weld was performed using a CNC welding torch with a current of 170A, a hot wire temperature of 260℃, a speed of 10cm / min, and double-layer gas shield protection (inner layer flow rate of 15L / min). The fillet radius between the weld bead and the groove was 1.8mm, and the excess height was 1.1mm.

[0081] Comparative Example 1:

[0082] Traditional U-groove welding (same material, wall thickness) was used, with the following groove parameters: U-groove angle 5°, width 8mm, no groove. The welding process was traditional continuous current TIG welding, with a current of 180A and no pulse oscillation; other parameters were the same as in Example 2.

[0083] Experimental Example 2:

[0084] The pipe welded in Example 2 was examined by cutting the weld cross-section and observing it after etching with 4% nitric acid alcohol. The fusion depth of the narrow gap section sidewall was found to be 3.2~3.8mm, which is 40% higher than that of the traditional U-shaped bevel (2.0~2.5mm). The molten metal in the V-shaped groove was fully filled, forming a "mortise and tenon" mechanical fit. There were no obvious incomplete fusion defects in the interlayer fusion line, and the fusion width was ≥2.0mm. X-ray inspection showed that the porosity was 0.8 per 100mm², which is 55% lower than that of the traditional process (1.8 per 100mm²). No incomplete fusion defects were found in the interlayer, and the proportion of Class I welds was 100% (compared to a defect rate of 15% in the traditional process).

[0085] Ultrasonic testing using a 5MHz probe revealed no defects ≥1mm in the fusion zone of the narrow gap section sidewall, and the interlayer echo amplitude was <20% of full scale (compared to 40~50% in traditional processes).

[0086] Measurements using ImageJ software showed that the double-step bevel + V-groove fusion area increased by 22% compared to the flat bevel, and the interlayer non-fusion defect rate decreased from 15% in the traditional process to 2%.

[0087] The test results for Comparative Example 1 were as follows: the sidewall fusion depth was 2.0~2.5mm, and the interlayer non-fusion defect rate was 15%.

[0088] The porosity is 1.8 per 100 mm², and RT inspection shows that 85% of the welds are Class I.

[0089] The welding quality test data for Example 2 and Comparative Example 1 are shown in Table 2 below:

[0090] Testing items Example 2 Comparative Example 1 Narrow gap sidewall fusion depth 3.2~3.8mm 2.0~2.5mm Interlayer non-fusion defect rate 2% 15% Porosity (pores / 100mm²) 0.8 1.8 Increased fusion area 22% ~ Percentage of Class I welds inspected by radiographic testing 100% 85%

[0091] Table 2 Comparison of Welding Quality Tests between Example 2 and Comparative Example 1

[0092] The welding strength test data for Example 2 are shown in Table 3 below:

[0093] Testing items Measured value Standard requirements Tensile strength 520MPa (base material 510MPa) ≥500MPa Impact energy (heat-affected zone) 98J（~20℃） ≥85J Bending test (side bending) No cracks qualified Water pressure test (1.6 times the pressure) No leakage, pressure drop 0.012 MPa No leakage, ≤0.05MPa

[0094] Table 3 Comparison of Welding Strength Tests in Example 2

[0095] This embodiment utilizes a double-step bevel design with a "large-angle transition section + narrow gap section," combined with the high-frequency oscillating molten pool of pulsed TIG welding and the multi-pass filling process of hot-wire TIG welding. This significantly improves the fusion depth of the bevel sidewalls and interlayers. Combined with the mechanical and metallurgical dual fusion mechanism of the V-shaped micro-groove, the interlayer incomplete fusion defect rate is reduced from 15% in traditional processes to 2%, and the porosity is reduced by 55%, solving the fusion problem of narrow-gap bevels. Comparative data shows that this technology has significant advantages in fusion efficiency and welding quality, and is particularly suitable for high-quality butt welding of thick-walled alloy steel thermal pipelines.

[0096] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

[0097] The above are all preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for connecting heating pipelines, characterized in that, Including the following steps: A stepped bevel is pre-set at the pipe opening to be connected. The stepped bevel consists of a large-angle transition section from top to bottom and a narrow-gap welding section. The two sections are smoothly connected. Then, tiny grooves are pre-set at equal intervals on the bevel surface. Align the ends of the two pipes to be connected and fix them with a pipe alignment tool. Monitor the contact pressure between the pipe alignment tool and the two pipes, and adjust the support force according to the pressure to ensure that the deviation of the pipe ends of the two pipes is within the standard range. Weld the ends of the two pipes; At the support points where the pipe alignment tool contacts the pipe, multiple pressure sensors are evenly arranged around the pipe opening. Each support point has several pressure sensors, which are connected to the control terminal. The control terminal has a built-in pressure matrix corresponding to each support point under standard pipe alignment conditions with different parameters. The real-time pressure data Pi of each support point is compared with each element in the standard pressure matrix Pstd to obtain the pressure deviation value ΔPi. The pressure deviation threshold ΔP_threshold, set according to the actual pipe conditions, is compared with the pressure deviation value ΔPi. When the pressure deviation value ΔPi of one or more support points exceeds the threshold ΔP_threshold, the control terminal starts the PID control algorithm. Using the pressure deviation value ΔPi, the rate of change of deviation, and the integral value of deviation as inputs, and based on the pre-set proportional coefficient, integral coefficient, and derivative coefficient, the accurate support force adjustment amount ΔFi of each support point is calculated. The control terminal converts the calculated support force adjustment amount ΔFi into an intuitive calibration command until the difference between the pressure value of each support point and the pressure value corresponding to the pressure matrix is ​​within the threshold range, thus completing the adjustment. The bevel angle a of the large-angle transition section is 15 ~ 20°, and the width L1 is 8 ~ 10 mm. The bevel angle b of the narrow-gap welding section is 5 ~ 7°, and the width L2 is 5 ~ 7 mm. The transition fillet radius between the large-angle transition section and the narrow-gap welding section is 1 ~ 1.5 mm. The depth of the tiny grooves on the bevel surface is 0.2 ~ 0.3 mm, and the spacing between the grooves is 3 ~ 5 mm.

2. The method for connecting thermal pipelines according to claim 1, characterized in that, Welding is performed on the pipe ends of the two pipes. First, internal root welding is performed using DC positive polarity TIG welding. After the internal root welding is completed, root pass welding is performed on the narrow gap welding section using pulsed TIG welding. After the root pass welding is completed, filler welding is performed using hot wire TIG welding. The filler weld is performed layer by layer from the bottom of the narrow gap upwards. Each layer of weld is welded in three passes, with adjacent layers welded in opposite directions and staggered. Then, cover pass welding is performed.

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