Butt joint construction method and system for heat distribution pipelines

Abstract

The invention relates to the field of pipeline welding, in particular to a heat distribution pipeline butt joint construction method and system.The method comprises the steps that a stepped groove which is in smooth transition through a large-angle transition section and a narrow-gap welding section and provided with tiny grooves in the surface is preset in a to-be-butt-jointed pipe orifice; the pipe orifice is fixed through the pipeline aligning device, and the pressure sensor and the control terminal are used for dynamically calibrating the supporting force, so that the alignment deviation of the pipe orifice is within a standard range; and direct current positive connection TIG welding, pulse TIG welding, hot wire TIG welding and the like are adopted for welding. The system comprises a pipeline aligning device and a welding device. According to the scheme, arc energy distribution is optimized through the double-step grooves, and fusion is enhanced in combination with the tiny grooves; the alignment precision is improved through dynamic calibration, and thermal deformation is controlled; and the numerical control welding optimizes the weld quality. The defect rate can be reduced, the filling metal amount is reduced, the deposition efficiency is improved, the one-time welding qualification rate is improved, the period is shortened, and the cost is reduced.

Description

Technical Field

[0001] The present invention relates to the field of pipeline welding, and in particular to a construction method and system for butt welding of thermal pipelines. Background Art

[0002] In the field of thermal pipeline construction, the narrow-gap groove welding technology is widely used due to its advantages such as reducing the amount of filler metal and improving welding efficiency. However, the existing narrow-gap groove forms (such as narrow-gap "U" groove and ultra-narrow-gap single Y groove) have exposed a series of technical bottlenecks in actual construction: First, the narrow groove space makes it difficult for the arc energy to act uniformly on both sides and the root of the groove, and the interlayer fusion is insufficient during multi-layer filling welding, easily forming defects such as lack of fusion and slag inclusion; Second, the requirement for butt joint accuracy is extremely high, and the pipeline deformation caused by the welding heat input will damage the butt joint accuracy. After the narrow-gap groove is deformed, the welding torch is prone to jamming, affecting the welding continuity; Third, improper control of thermal deformation will lead to an excessive misalignment amount, and it is difficult to accurately control the reinforcement during the cover pass welding. The groove shape may change during the welding process, thereby affecting the weld stress distribution and reducing the service life of the pipeline. These problems not only increase the construction cost and the risk of later maintenance, but also are difficult to meet the strict requirements of high-pressure and high-temperature thermal pipelines for welding quality and safety. Therefore, there is an urgent need to develop a new construction method that can solve the narrow-gap groove fusion problem, improve the control ability of butt joint accuracy, and optimize the weld geometry. Summary of the Invention

[0003] In order to solve the problems mentioned in the above background art, the present invention provides a construction method for butt welding of thermal pipelines, and at the same time provides a construction system for butt welding of thermal pipelines.

[0004] The construction method for butt welding of thermal pipelines provided by the present invention adopts the following technical solutions: Preset a stepped groove at the pipe orifice to be butted. The stepped groove consists of a large-angle transition section and a narrow-gap welding section from top to bottom, and the two sections are smoothly transitioned and connected. Then, preset micro-grooves at equal intervals on the groove surface; Align the pipe orifices of the two pipes to be butted and fix them with a pipe alignment device. Monitor the contact pressure between the pipe alignment device and the two pipes, and adjust the supporting force according to the pressure to make the deviation of the alignment of the pipe orifices of the two pipes within the standard range; Weld the pipe orifices of the two pipes.

[0005] Further, the groove angle a of the large-angle transition section is 15 - 20°, the width L1 is 8 - 10 mm, the groove angle b of the narrow-gap welding section is 5 - 7°, the width L2 is 5 - 7 mm, and the transition fillet radius between the large-angle transition section and the narrow-gap welding section is 1 - 1.5 mm.

[0006] 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.

[0007] Furthermore, at the support parts where the pipe aligner contacts the pipe, a plurality of pressure sensors are evenly arranged circumferentially along the pipe orifice, and several pressure sensors are distributed at each support point.

[0008] Furthermore, the orifices of the two pipes are welded. First, the root pass welding is carried out. The root pass welding uses DC straight polarity TIG welding. After the root pass welding is completed, the backing welding for the narrow-gap welding section is carried out. The backing welding uses pulsed TIG welding. After the backing welding is completed, the filling welding is carried out. The filling welding uses hot wire TIG welding. Filling starts from the bottom of the narrow gap layer by layer upwards. Each layer of weld seam is welded in three passes. The welding directions of adjacent layers are opposite and the weld beads are staggered. Then the cap pass welding is carried out.

[0009] The thermal pipeline butt joint construction system includes: A pipe aligning device, including a pipe aligner and a support adjuster installed inside the pipe aligner. The pipe aligner is used to fix the butted pipe orifices, and the support adjuster is used to adjust the supporting force on the pipe orifices; A welding device. For the root pass welding, an orbital all-position automatic welding machine is equipped with a DC straight polarity TIG welding torch. For the backing welding of the narrow-gap welding section, a narrow-gap pulsed TIG welding machine is used. For the full-bevel filling welding and cap pass welding, a hot wire TIG welding torch is used.

[0010] Furthermore, the pipe aligning device includes a pipe aligner. The pipe aligner includes a number of convex blocks distributed in a ring. Inside both ends of each convex block, a support block and a support adjuster are installed. The support block includes a pressing block that is slidably embedded in the convex block in a limited manner. A pressure sensor is installed at the outer end of the pressing block, and the inner end of the pressing block is connected to the support adjuster.

[0011] Furthermore, the support adjuster includes a threaded rod connected to the pressing block. A fitting threaded sleeve is sleeved on the upper end of the threaded rod. A bearing is sleeved on the outer wall of the threaded sleeve, and the outer wall of the bearing is fixed inside the convex block. The top of the threaded sleeve is fixedly connected to an adjusting rod. The adjusting rod penetrates through the convex block and extends to the outer end of the convex block. At the top of the adjusting rod located outside the convex block, an adjusting block is fixedly connected. A rotary connection groove is provided on the adjusting block.

[0012] The beneficial effects of the present invention are as follows: The double-step groove structure of this application optimizes the arc energy distribution, enhances mechanical and metallurgical fusion with the help of micro-grooves, improves the sidewall fusion depth and fusion area, and reduces the defect rates such as interlayer lack of fusion and porosity. The pressure sensor and the control terminal dynamically calibrate the supporting force, improve the pipe orifice alignment accuracy, combine with the low heat input welding process, reduce welding thermal deformation, and avoid welding torch jamming. The numerical control welding process accurately controls the weld reinforcement and transition fillet. The multi-layer weld beads are staggered and superimposed to optimize the stress distribution, reduce the risk of stress concentration, and improve the surface forming quality and fatigue resistance of the weld. The narrow gap structure reduces the amount of filler metal, and the hot wire TIG welding improves the deposition efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a schematic diagram of the stepped groove structure of the pipe orifice during the butt welding construction of the thermal pipeline of this application; Figure 2 It is a schematic radial cross-section diagram of the pipe alignment device during the butt welding construction of the thermal pipeline of this application; Figure 3 is Figure 2 The partial enlarged view of.

[0014] In the figure, 100. Pipe aligner, 200. Support block, 300. Support adjuster, 101. Protrusion, 201. Tightening block, 202. Pressure sensor, 301. Threaded rod, 302. Threaded sleeve, 303. Adjusting block, 304. Adjusting rod, 305. Bearing. SPECIFIC EMBODIMENTS

[0015] Next, in combination with the embodiments of the present invention, the technical solutions of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0016] The embodiments of the present invention disclose a method for butt welding construction of thermal pipelines, including the steps: S1. Open a stepped groove at the pipe orifice to be butted, such as Figure 1As shown, the stepped groove includes a large-angle transition section and a narrow-gap welding section from top to bottom. The two sections are smoothly transitioned, and then micro-grooves are evenly opened on the groove surface at equal intervals. Specifically, when opening a stepped groove on the pipe orifice to be butt-jointed, a numerical control groove processing device is used for precise cutting, and the geometric parameters of the large-angle transition section and the narrow-gap welding section are set by programming: first, a large-angle transition section of the upper section is milled or turned with a groove angle of 15 - 20° and a width of 8 - 10 mm, and then a narrow-gap welding section of the lower section is processed with a groove angle of 5 - 7° and a width of 5 - 7 mm. The connection between the two sections is milled with an arc tool with a radius of 1 - 1.5 mm to form a smooth transition. The micro-grooves are realized by a micro-milling cutter or a laser processing module of the same device, and are evenly opened on the groove surface at an interval of 3 - 5 mm and a depth of 0.2 - 0.3 mm. The shape of the groove can be selected as rectangular or arc-shaped according to the device capabilities (the specific shape is not limited in implementation).

[0017] The groove angle a of the large-angle transition section is 15 - 20°, the width L1 is 8 - 10 mm, the groove angle b of the narrow-gap welding section is 5 - 7°, the width L2 is 5 - 7 mm, and the transition fillet radius between the large-angle transition section and the narrow-gap welding section is 1 - 1.5 mm.

[0018] The groove angle a of the large-angle transition section is designed to be 15 - 20° and the width L1 is 8 - 10 mm, mainly based on the balance between the accessibility of the welding torch and the arc heating efficiency. The groove angle of 15 - 20° can not only avoid the problem of welding torch jamming caused by the too narrow entrance of the traditional narrow-gap groove, but also ensure that the arc energy acts uniformly on the groove sidewall. At this angle, a safety distance of 3 - 5 mm can be reserved between the welding torch nozzle and the groove sidewall, and the arc can cover a depth of 2 - 3 mm on the sidewall, improving the fusion depth of the sidewall. The width of 8 - 10 mm provides sufficient space for the movement of the welding torch. Especially in all-position welding (such as the overhead welding position), the welding torch can be adjusted at an inclination angle of ±15°, solving the problem that the arc cannot effectively heat the sidewall due to the too narrow groove. The filling metal amount at this width is reduced compared with the traditional U-groove, while ensuring the fluidity of the molten pool and reducing the risk of interlayer slag inclusion.

[0019] The groove angle b of the narrow-gap welding section is 5-7°, and the width L2 is 5-7 mm, which is the optimal solution obtained between minimizing the filler metal amount and ensuring arc stability. The slightly open angle of 5-7° avoids the "magnetic blow" phenomenon that is prone to occur in completely parallel grooves, and at the same time reduces the filler metal amount of each layer of weld metal compared with the traditional U-groove. Combined with hot wire TIG welding, the welding efficiency can be significantly improved. At this width, the arc energy density is concentrated, and the heat input can be controlled within 100-150 J / mm, effectively reducing the welding thermal deformation. Moreover, the "constrained arc" effect formed by the narrow gap and the oscillating molten pool effect of pulsed TIG welding reduce the porosity in the weld compared with the traditional process.

[0020] 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. Generally, the depth of the large-angle transition section is 1 / 3-1 / 2 of the pipe wall thickness, and the depth of the narrow-gap welding section is the remaining wall thickness part. For example, for a pipe with a wall thickness of 12 mm, the depth of the large-angle transition section is set to 5-6 mm, and the depth of the narrow-gap welding section is 6-7 mm. This design not only ensures full penetration of the root by the root pass (the root pass depth needs to reach 3-4 mm), but also provides a stable structure for the welding of the narrow-gap section.

[0021] The micro-grooves on the groove surface are designed with a depth of 0.2-0.3 mm and a spacing of 3-5 mm. The core is to construct a dual interface of mechanical fusion and metallurgical bonding by increasing the micro-roughness of the groove surface. The depth of 0.2-0.3 mm can not only ensure that the grooves are fully filled with molten metal during welding to form a "mortise and tenon" mechanical interlock, but also avoid excessive weakening of the effective thickness of the groove due to too large a depth. The spacing of 3-5 mm is based on the optimized balance of the fusion area and processing efficiency. Verified by orthogonal experiments, the fusion area is increased by 18%-22% compared with the flat groove at this spacing, and the metal matrix between adjacent grooves can effectively conduct the welding thermal stress, reducing the risk of interlayer cracks. The defect rate of interlayer lack of fusion during multi-layer welding is reduced by 35% compared with the traditional process.

[0022] The groove shape can be selected as rectangular, arc-shaped or V-shaped according to the characteristics of the processing equipment (the specific shape is not limited during implementation). The rectangular groove is suitable for numerical control milling, with the advantages of low tool cost and fast processing speed, and is suitable for batch construction of carbon steel pipes; the arc-shaped groove is realized by laser processing, and its smooth transition can reduce stress concentration and improve the fatigue resistance of the weld, and is suitable for high-strength materials such as alloy steel; the V-shaped groove uses the inclined plane to guide the flow of the molten pool, promotes the infiltration of the molten metal to the bottom of the groove, and enhances the root fusion effect, especially suitable for the overhead welding position operation in all-position welding.

[0023] S2. Align the pipe ends of the two pipes to be butt - jointed and fix them with a pipe alignment device. Specifically, first, pre - process the pipe ends of the pipes to be butt - jointed. Use an electric wire brush to remove rust, oil, and oxides within 20 mm inside and outside the pipe ends. Align the two pipe ends, use a laser alignment instrument to monitor the gap at the edge of the pipe ends, and adjust at intervals of 1 - 1.5 m axially at the pipe ends through adjustable jacks to make the misalignment of the pipe ends ≤ 1.0 mm, and control the groove gap within 2 - 3 mm (measured with a feeler gauge), and fix the axial position of the pipes with a temporary support tooling.

[0024] Monitor the contact pressure between the pipe alignment device and the two pipes through pressure sensors, that is, at the support parts where the pipe alignment device contacts the pipes, arrange multiple pressure sensors evenly along the circumferential direction of the pipe ends. Several pressure sensors are distributed at each support point. The pressure sensors are signal - connected to the control terminal. The control terminal has a pressure matrix corresponding to each support point under the standard alignment state of pipes with different parameters built - in. The control terminal continuously and cyclically collects pressure data, compares the real - time pressure data Pi of each support point with the corresponding pressure elements in the pressure matrix, marks the support points where the pressure difference exceeds the threshold range, calculates the adjustment range of the support points, and issues a support point adjustment instruction.

[0025] In specific implementation, the control terminal continuously collects the real - time pressure data Pi of the pressure sensors at a frequency of 20 times per second. After collection, quickly retrieve the corresponding standard pressure matrix Pstd from the built - in database according to the pipe diameter, wall thickness, and material parameters of the pipes to be butt - jointed. Compare the real - time pressure data Pi 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. Compare the pressure deviation value ΔPi with the pressure deviation threshold ΔP_threshold set according to the actual situation of the pipes. For example, for pipes with a larger diameter and harder material, the pressure deviation threshold is set to ±0.5 N. When it is detected that 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 deviation change rate, and the integral value of the deviation as inputs, calculate the accurate support force adjustment amount ΔFi of each support point according to the pre - set proportional coefficient, integral coefficient, and differential coefficient. For example, when the pressure deviation value is small but persists, the algorithm will output a moderate adjustment instruction to gradually correct the pressure.

[0026] The control terminal converts the calculated support force adjustment amount ΔFi into an intuitive calibration instruction, marks the support points to be adjusted in a prominent color on the operation interface, and simultaneously clearly displays the numbers of each support point, the specific values of the support force to be adjusted, and the adjustment directions (a green arrow indicates an increase in the support force, and a red arrow indicates a decrease in the support force). After the operator completes the adjustment operation, the control terminal immediately starts the next round of pressure data collection and analysis. If there is still a pressure deviation exceeding the threshold, a calibration instruction will be generated again, and this process will be continuously cycled until the difference between the pressure values of each support point and the corresponding elements of the standard pressure matrix meets the accuracy requirements. Throughout the welding process, the control terminal continuously monitors the pressure data, combines the changes in welding current and voltage, and dynamically optimizes the support force calibration strategy to ensure accurate alignment of the pipe ends.

[0027] In the built-in database of the control terminal, a pressure matrix under the standard alignment state of pipes with different parameters is constructed through the accumulation of a large amount of historical construction data and simulation experiments. Specifically, in the laboratory, for thermal pipelines with different pipe diameters (such as DN200~DN1200), wall thicknesses (4mm~16mm), and materials (carbon steel, alloy steel, etc.), specimens are processed according to the stepped groove standard, and high-precision pressure sensors are used to collect the pressure data of each support point of the pipe alignment device under the standard alignment state.

[0028] Before each experiment, first fix the pipe on a high-precision adjustable tooling table, adjust the pipe ends to the absolute alignment state (the deviation is controlled within ±0.01mm) through a laser tracker, and after stabilizing for 10 minutes, record the pressure data of each support point at this time. For each specification of pipe, repeat the experiment more than 20 times, and take the average value as the standard pressure value. At the same time, simulate the pressure distribution of the pipe under the standard alignment state under different working conditions (different installation angles, ambient temperatures, etc.), and correct and supplement the experimental data.

[0029] Sort and organize these data according to the pipe specifications (pipe diameter, wall thickness, material), the number of support points of the alignment device, and the layout parameters to construct a multi-dimensional pressure matrix model. Each pressure matrix is named with a specific identifier (such as "DN500~8mm~CS" representing a carbon steel pipe with a pipe diameter of 500mm and a wall thickness of 8mm), and the elements in the matrix correspond to the pressure values of different support points under the standard alignment state. S3. Weld the pipe orifices of the two pipes. First, perform the root pass welding. The root pass welding uses DCEN TIG welding. The welding current is 80 - 100A, the arc length is 2 - 3mm, and the welding speed is 8 - 10cm / min. In DCEN TIG welding (tungsten inert gas welding), the workpiece is connected to the positive pole of the power supply, and the tungsten electrode is connected to the negative pole. The arc energy is concentrated, the molten pool temperature is relatively high, and the penetration depth is relatively large, which is suitable for the penetration requirements of the root pass. For the stepped groove, the bottom width of the narrow gap welding section is only 5 - 7mm. DCEN can accurately heat the root of the groove by concentrating the arc energy, avoiding excessive melting or lack of fusion on the side walls caused by arc dispersion. At the same time, by using the "cathode cleaning" effect of the arc (when the workpiece is the positive pole), the oxide film on the surface of the groove (such as the Fe3O4 layer that may exist in the pipe base metal) can be effectively removed, improving the fusion quality. In addition, the non - consumable tungsten electrode can avoid contamination of the filler metal, ensuring the purity of the root weld and meeting the strict requirements for the weld tightness of the thermal pipeline. A welding current of 80 - 100A can form a stable arc. With an arc length of 2 - 3mm, a penetration depth of 3 - 4mm is generated at the root of the groove, just covering the thickness of the root of the stepped groove. The current density is controlled at 180 - 230A / mm² (tungsten electrode diameter 1.2mm), forming a molten pool with a diameter of about 5 - 6mm, which matches the 5 - 7mm width of the bottom of the narrow gap section, preventing the molten pool metal from overflowing to the side wall of the groove to form a weld bead, which affects the entry of the subsequent backing welding torch. An arc length of 2 - 3mm is a short - arc mode (energy density is about 200 - 250W / mm²), which can reduce arc divergence and make the heat concentrate on the root. Especially in the vertical welding and overhead welding positions, it can effectively resist the downward drop of the molten pool due to gravity, keeping the height of the back weld bead uniform (reinforcement 0.5 - 1.5mm). The diameter of the argon shielding gas hood is maintained at 8 - 10mm to ensure that the oxygen content in the arc area is <50ppm, avoiding the generation of pores due to weld oxidation. The welding speed of 8 - 10cm / min enables the linear energy to be controlled within 96 - 120J / mm, which is lower than 150J / mm of the traditional process, reducing the width of the heat - affected zone and the circumferential shrinkage deformation of the pipe. Moving at a constant speed ensures that the width fluctuation of the weld bead is ≤±0.3mm, forming a root weld bead with a width of 6 - 8mm and a height of 1.0 - 1.8mm, providing a flat fusion base surface for the backing welding of the narrow gap section and avoiding gun jamming caused by unevenness at the root. The root pass welding uses an orbital all - position automatic welding machine, and the distance between the welding torch and the root of the groove is calibrated in real - time through a laser tracker. The welding torch welds along the circular track at a constant linear speed.

[0030] After the internal root welding is completed, the backing welding is carried out on the narrow-gap welding section. The backing welding uses pulsed TIG welding. The welding torch is inserted into the narrow-gap welding section at the lower part of the groove. The pulse frequency is 50 - 100 Hz, and the pulsed arc impact force with a peak current of 120 - 150 A and a base current of 30 - 50 A is generated. Pulsed TIG welding generates periodic arc impact force through pulsed current, which can effectively solve the problems of insufficient fluidity of the molten pool and insufficient interlayer fusion in the narrow-gap groove. In the narrow-gap welding section, traditional continuous current welding is prone to thermal deformation due to excessive concentration of arc energy, while the intermittent energy input of pulsed current can reduce the average heat input. Combined with the "constrained arc" effect of the narrow gap, it can reduce the circumferential shrinkage deformation of the pipeline. In terms of parameter setting, a pulse frequency of 50 - 100 Hz can make the arc generate high-frequency oscillation, promote the escape of gas through the oscillating molten pool, and reduce the porosity of the weld seam compared with the traditional process. The peak current of 120 - 150 A provides instantaneous strong energy within the pulse period, which can form a penetration depth of 2.5 - 3.5 mm on the side wall of the groove to ensure full fusion of the side wall of the narrow-gap section and the root pass. The base current of 30 - 50 A maintains the arc without extinguishing, while reducing the average current density (about 80 - 100 A / mm²) to avoid excessive melting of the groove edge due to continuous high heat input.

[0031] When the welding torch is inserted into the narrow-gap welding section, the distance between the welding torch nozzle and the side wall of the groove is maintained at 2 - 3 mm to ensure the argon protection effect (flow rate 10 - 12 L / min, oxygen content < 50 ppm). The periodic change of the energy of the pulsed arc can also make the molten pool fully melt during the peak current stage and cool and solidify briefly during the base current stage, forming a dynamic balance of "molten pool oscillation - solidification". Especially in the vertical welding and overhead welding positions, it can resist the gravitational drop of the molten pool and keep the thickness of the weld bead uniform (interlayer thickness 2 - 3 mm), providing a flat base surface for the subsequent filler welding and avoiding jamming of the hot wire TIG welding torch due to unevenness of the backing weld bead.

[0032] During the filling welding, considering the dimensional difference between the large-angle transition section in the upper part and the narrow-gap welding section in the lower part, hot wire TIG welding is adopted. The hot wire temperature is controlled at 300 - 400°C, and the welding current is 180 - 220A. Filling starts from the bottom of the narrow gap layer by layer upwards. Each layer of weld seam is welded in three passes. The welding directions of adjacent layers are opposite and the weld beads are staggered by 1 / 3 of the width. By preheating the welding wire to 300 - 400°C, the welding wire reaches a semi-molten state before entering the molten pool. Combining with the arc energy generated by the 180 - 220A welding current, while ensuring the penetration depth (2.5 - 3.5mm), the heat input is controlled at 150 - 200J / mm, which is about 30% lower than that of traditional TIG welding, effectively suppressing the circumferential shrinkage deformation of the pipeline caused by continuous filling. For the dimensional difference between the large-angle transition section (width 8 - 10mm) in the upper part of the stepped groove and the narrow-gap welding section (width 5 - 7mm) in the lower part, the high deposition rate (3 - 4kg / h) of hot wire TIG welding can significantly improve the filling efficiency. Especially in the large-angle section, the wide area is covered by the swing of the welding torch, while in the narrow-gap section, the sidewall fusion is ensured by the arc confinement effect. In terms of parameter setting, the hot wire temperature and the welding current form a synergy: the low-temperature section (300°C) is adapted to the low heat input requirement of the narrow-gap section, and the high-temperature section (400°C) is used for rapid filling in the large-angle section. The current ensures the fluidity of the molten pool by adjusting the arc energy density (about 250 - 300W / mm²), avoiding poor fusion or slag inclusion in the narrow gap.

[0033] After the root pass welding is completed, taking the junction of the top of the narrow-gap welding section and the large-angle transition section as the filling starting point, the first pass of the first layer of weld bead starts from the center of the groove bottom (the surface of the root pass weld bead). The welding torch reciprocates along the center line with a swing amplitude of 5 - 8mm, forming a center weld bead with a width of about 5 - 6mm, covering 80% of the 5 - 7mm width at the bottom of the narrow-gap section. The first pass of the second layer of weld bead starts from the left sidewall of the groove, deviates 1 / 3 of the width (about 2 - 2.5mm) towards the center, and overlaps 1 / 3 with the previous layer of weld bead, forming a left fusion zone. The third pass starts from the right sidewall and similarly covers the right area, ensuring that the three weld beads in each layer completely cover the cross-section of the groove and the fusion width with both sidewalls is ≥2mm. The welding directions of adjacent layers are reversed by switching the swing trajectory of the welding torch (for example, the first layer swings from left to right, and the second layer swings from right to left). At the same time, the starting positions of each layer are staggered by 1 / 3 of the groove width (about 3 - 4mm) along the circumferential direction, forming a spiral rising overlapping weld structure. In this way, each layer of weld seam forms a stress dispersion angle of 30 - 45° with the previous layer. Combining with the interlayer temperature control (≤200°C) of hot wire TIG welding, the welding stress can be evenly distributed along the circumferential direction of the pipe wall, avoiding concentrated cracking. The filling thickness of each layer is monitored in real time by a laser distance sensor and controlled at 2 - 2.5mm, ensuring that the flatness error of the filling surface is ≤±0.2mm, providing an accurate base surface for the capping weld.

[0034] When cap welding, adjust the welding gun angle to move along the edge of the large-angle transition section groove, control the weld excess height, and ensure a smooth transition between the cap layer and the large-angle transition section of the upper section of the groove. By controlling the welding gun trajectory and energy input, the cap layer weld and the large-angle transition section form a smooth transition, and the excess height is controlled within the range of 0.8~1.2mm to avoid stress concentration caused by geometric size deviation. In terms of parameter setting, the hot wire temperature is adjusted to 250~300℃ (lower than 300~400℃ for filling welding), and the welding current is reduced to 150~180A. By reducing the deposition rate and reducing the amount of weld metal filling, the welding gun angle is adjusted (with an angle of 40~45° with the groove edge) so that the molten pool only covers the 2~3mm area of the groove edge to form a thin layer of cap. The welding speed is increased to 10~12cm / min, and the line energy is controlled at 120~150J / mm to ensure that the weld surface is quickly cooled and formed to avoid overheating and excess height bulge or undercut. During the specific operation, the welding gun monitors the distance from the edge of the groove in real time through the laser distance sensor (accuracy ±0.1mm) at the end of the flexible bracket. The servo motor drives the welding gun to make uniform circular motion along the edge of the large-angle transition section groove, and the trajectory deviation is controlled within ±0.2mm. Each layer of cover welding is divided into two passes: the first pass moves along the left edge of the groove, and the welding gun is tilted 10~15° to the center, covering the left wall and the edge of the groove, forming a weld with a width of 4~5mm; the second pass moves along the right edge, tilted in the opposite direction at the same angle, covering the right wall and the edge of the groove, and the two welds overlap 1~2mm in the center to ensure a smooth surface. During the welding process, the argon gas flow rate is increased to 12~15L / min, and a double-layer gas hood is used for protection (inner layer diameter 8mm, outer layer diameter 15mm) to prevent oxidation of the weld from producing pores. The groove angle parameters are preset through the CNC system, and the welding gun automatically adapts to the 15~20° groove bevel to ensure that the angle between the weld and the groove is always maintained at 20~25°, forming a smooth transition radius of R1.5~2.0mm. After 3D laser scanning detection, the surface roughness of the cover layer Ra≤6.3μm, and the uniformity error of the residual height ≤±0.15mm, which meets the surface forming and stress distribution requirements of the thermal pipeline.

[0035] The present invention also provides a thermal pipeline butt joint construction system, comprising: The pipe joint device comprises a pipe joint device and a support regulator installed in the pipe joint device, wherein the pipe joint device is used to fix the butted pipe openings, and the support regulator is used to adjust the supporting force of the pipe openings; Specifically, Figures 2 - 3As shown in the figure, the pipe alignment device of the present application includes a pipe aligner 100. The pipe aligner 100 includes a number of bumps 101 distributed in a ring. Inside both ends of each bump 101, a support block 200 and a support adjuster 300 are installed. The support block 200 includes a pressing block 201 slidably embedded in the bump 101 with limited movement. A pressure sensor 202 is installed at the outer end of the pressing block 201, and the inner end of the pressing block 201 is connected to the support adjuster 300. The support adjuster 300 includes a threaded rod 301 connected to the pressing block 201. A matching threaded sleeve 302 is sleeved on the upper end of the threaded rod 301. An outer wall of the threaded sleeve 302 is sleeved with a bearing 305, and the outer wall of the bearing 305 is fixed inside the bump 101. The top of the threaded sleeve 302 is fixedly connected to an adjusting rod 304. The adjusting rod 304 penetrates through the bump 101 and extends to the outer end of the bump 101. At the top of the adjusting rod 304 located outside the bump 101, an adjusting block 303 is fixedly connected. A rotary connection groove is provided on the adjusting block 303.

[0036] The adjusting rod 304 can be rotated by using a power tool through the rotary connection groove, or the adjusting rod 304 can be rotated manually, thereby driving the threaded sleeve 302 to rotate. By the rotation of the threaded sleeve 302, the threaded rod 301 expands and contracts, so that the pressing block 201 can partially extend out of the lower end of the bump 101 to adjust the supporting force at the corresponding point. Among them, the pressing block 201 can be limitedly slidable in the bump 101 by providing corresponding limiting strips and limiting grooves on the side wall where the pressing block 201 contacts the bump 101. The present invention does not make a limitation.

[0037] Specifically, the pipe aligner 100 is made of a ring-shaped steel structure, and 6 - 8 bumps 101 are evenly distributed along the circumferential direction of the pipe orifice (the specific number is adjusted according to the pipe diameter. For example, 6 bumps are used for DN500, and 8 bumps are used for DN1200). Each bump is arranged radially, and its inner arc surface matches the curvature of the pipe outer wall. Rectangular sliding grooves are provided inside both ends of the bump 101 for embedding the support block 200. The depth of the sliding groove is 20 - 25mm, and the width is adapted to the pressing block 201 (the gap ≤ ±0.2mm) to ensure that the pressing block 201 can be axially limitedly slidable along the sliding groove. Longitudinal limiting strips are provided on the side wall of the sliding groove, and limiting grooves are provided at the corresponding positions of the pressing block 201 to form a sliding guiding structure to avoid deviation.

[0038] The pressing block 201 is made of cemented carbide, and the outer end is processed into an arc surface (the radius is the same as that of the pipe outer wall), and a micro pressure sensor 202 (accuracy ±0.1N) is embedded. The surface of the sensor is flush with the arc surface of the pressing block to ensure accurate pressure measurement when contacting the pipe.

[0039] A cylindrical cavity with a diameter of 15 mm and a depth of 18 mm is machined inside the bump 101 (located at the outer end of the middle of the bump) as a circuit integration cavity. A sensor mounting groove with a diameter of 5 mm and a depth of 2 mm is opened on the arc surface of the outer end of the clamping block 201. After the micro piezoresistive pressure sensor is inserted through interference fit, 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 thermal conductive silicone grease to ensure the pressure conduction efficiency. The sensor signal line is introduced into the bump circuit cavity through the axial through hole inside the clamping block, and the orifice is sealed with a silicone sealing ring.

[0040] In the circuit cavity of the bump 101, a multi-layer circuit board is used to integrate a wireless module (such as Nordic nRF52840, supporting Bluetooth 5.2 and 2.4GHz radio frequency), a micro lithium battery (3.7V / 150mAh, size Φ10mm×5mm) and a signal conditioning circuit. The sensor lead is connected to the PCB board through a spring pin connector. The signal conditioning circuit includes an amplification and filtering module and an analog-to-digital converter, which converts the pressure signal into a digital quantity and transmits it to the wireless module. A 0.1mm thick copper foil shielding layer is laid on the back of the PCB board, which is connected to the metal shell of the bump through the cavity grounding column to form a complete electromagnetic shielding. The battery adopts a drawer-type installation structure, and a push-pull battery cover is set on the outside of the cavity to support quick replacement. The wireless module transmits signals through the inverted F antenna (IFA) on the PCB board. ABS engineering plastics are used to replace metal materials at the corresponding antenna position of the bump 101 to form a circular non-metallic signal window with a diameter of 20mm to ensure the penetration of RF signals.

[0041] The inner end of the clamping block is connected to the threaded rod 301 through a threaded hole. The diameter of the threaded rod is 8~12mm (selected according to the pipe diameter), the pitch is 1.5~2mm, and the surface is rust-proofed. The threaded sleeve 302 supporting the adjuster 300 and the threaded rod 301 have a matching accuracy of 6H / 6g. The outer wall of the threaded sleeve is installed with a deep groove ball bearing 305 (model 6203~2RS) through 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 that there is no radial shaking when the threaded sleeve rotates. The adjustment rod 304 passes through the through hole at the outer end of the protrusion (clearance ≤0.3mm). The top adjustment block 303 is designed as a regular hexagon (distance from opposite sides is 14~19mm), which is suitable for electric torque wrenches or manual wrenches. The surface of the adjustment block is provided with anti-slip patterns, and the rotation angle accuracy can reach ±1°.

[0042] The pressure monitoring and control unit includes a pressure sensor and a control terminal. The pressure sensors are distributed at the supporting parts where the pipe aligner contacts the pipe. The pressure sensors are signal-connected to the control terminal. The control terminal has a standard pressure matrix for pipes with different parameters built in. The control terminal collects pressure data in real time. After comparing with the standard pressure matrix, it calculates the support force adjustment amount through the PID control algorithm, generates a calibration instruction including the support point number, adjustment value and direction, and calibrates the support force through the support regulator to control the pipe orifice alignment deviation within the standard range. Exemplarily, 6 - 8 bumps 101 are evenly distributed circumferentially on the pipe aligner (for example, 8 bumps are provided for DN800). 2 sensors are embedded at each end of each bump's abutting block, with a total of 12 - 16 pressure monitoring points, covering the 360° range of the pipe circumference, and the spacing ≤ 150mm. The wireless module in the circuit cavity of each bump serves as a slave node and communicates with the master node of the control terminal in a star topology. The communication distance ≤ 10m, and the 2.4GHz frequency band hopping technology is adopted, with a data refresh rate of 100Hz. The control terminal uses an industrial tablet computer with dual Bluetooth 5.2 modules, a processor and a memory built in. The control terminal displays the pressure values, deviation values and adjustment status of each sensor in real time.

[0043] Exemplarily, the screen displays the pressure values (accuracy 0.1N, display resolution 0.01N), standard pressure matrix values and real-time deviation values (ΔP) of the sensors of each bump in real time. The exceeded values (|ΔP| > threshold) are marked with red flashing, and the adjustment instructions (such as "Bump 2 - Left: +0.6N") are dynamically displayed.

[0044] During implementation, the terminal can also be connected to an electric adjustment tool (such as Makita DTP180Z electric torque wrench) through the RS - 485 bus, receive the adjustment feedback signals (the rotation angle of the threaded rod, the change value of the support force), and form a closed-loop control.

[0045] For the welding device, for the internal root welding, an orbital all-position automatic welding machine is equipped with a DC straight polarity TIG welding torch. For the root pass welding in the narrow gap welding section, a narrow gap pulsed TIG welding machine is used. For the full groove filling welding, a hot wire TIG welding torch is used. For the capping welding, a numerically controlled welding torch is used.

[0046] Exemplarily, for the root pass welding, an Austrian Fronius TPS / i 400 orbital all-position automatic welding machine is used, equipped with a customized DC straight polarity TIG welding torch (tungsten electrode diameter 1.2 mm, nozzle diameter 8 mm). The orbital adopts a magnetic adsorption structure and can weld around the pipe 360°. The welding torch is equipped with a laser tracker to monitor the distance between the welding torch and the root of the groove in real time, and the position of the welding torch is automatically adjusted through a closed-loop servo system. The welding parameters are preset through the built-in controller: welding current 80 - 100 A, arc length 2 - 3 mm, welding speed 8 - 10 cm / min (driven by a stepper motor), and argon gas flow rate 8 - 10 L / min.

[0047] For the narrow-gap root pass welding equipment, a Japanese OTC FD-B4 narrow-gap pulsed TIG welding machine is used. The welding torch adopts a gooseneck structure (bending radius 15 mm, nozzle diameter 5 mm) and can reach into the 5 - 7 mm narrow-gap area at the lower part of the groove. The adjustable range of the pulse parameters: frequency 50 - 100 Hz, peak current 120 - 150 A (accuracy ±2 A), base current 30 - 50 A. It is equipped with a dual gas supply system: the inner layer argon gas flow rate is 10 - 12 L / min (to protect the arc), and the outer layer argon gas flow rate is 5 - 8 L / min (to suppress spatter). The oxygen content monitor displays the oxygen content in the arc area in real time. The welding torch oscillation mechanism supports an inclination adjustment of ±15° and an oscillation amplitude of 2 - 3 mm to ensure a sidewall fusion depth of 2.5 - 3.5 mm.

[0048] For the fill pass welding equipment, an American Miller Auto~Continuum hot wire TIG welding system is adopted. The hot wire temperature is controlled by an independent temperature control module, and the hot wire feeding speed is 5 - 8 m / min (driven by a servo motor). The welding torch integrates a three-channel wire feeding mechanism and can achieve sequential filling of three weld beads per layer (the first center weld bead, and the second and third left and right side weld beads). The welding current is 180 - 220 A, the arc voltage is 10 - 12 V, the welding torch oscillation frequency is 15 - 20 times / min, and the oscillation amplitude is 5 - 8 mm. The direction switching of adjacent layer weld beads is automatically completed by a PLC, and the stagger distance is 1 / 3 of the weld bead width.

[0049] The cap pass welding equipment uses a German KUKA KR C4 numerically controlled welding torch, equipped with a laser distance sensor and a five-axis linkage mechanism, and can perform trajectory fitting movement along the edge of the groove at the large-angle transition section. The automatic adjustment range of the welding torch angle is 20~45° (the included angle with the groove edge), the welding current is 150~180A, the hot wire temperature is 250~300°C, and the welding speed is 10~12 cm / min. A double-layer gas shroud is adopted (the inner layer has a diameter of 8 mm and a flow rate of 12~15 L / min; the outer layer has a diameter of 15 mm and a flow rate of 20~25 L / min), and an air flow stabilizing device is provided at the end of the gas shroud to ensure the protection effect. The cap pass weld bead is preset by the numerical control system to be formed in two passes, with an overlap of 1~2 mm, the control accuracy of the reinforcement height is ±0.15 mm, and the surface roughness Ra≤6.3 μm.

[0050] Example 1: Butt welding construction of a DN500×8mm carbon steel thermal pipeline It includes the steps: For groove machining, a Swiss GF Machining Solutions numerically controlled grinding machine is used to machine a double-step groove. The angle of the upper large-angle transition section is 18° and the width is 8.5 mm. The angle of the lower narrow-gap section is 6° and the width is 6 mm. The radius of the transition fillet is 1.2 mm.

[0051] The micro-grooves are processed by laser, with a depth of 0.28 mm and a spacing of 3.5 mm, and are distributed in an arc shape. After machining, the three-dimensional scanner detects that the deviation of the groove angle is ±0.03 mm, and the deviation of the groove depth is ±0.01 mm.

[0052] Pre-treatment and alignment fixation of the pipe orifice. First, use an electric wire brush to clean the inner and outer 25 mm range of the pipe orifice, and check the dimensions with a groove gauge to meet the design requirements. Use a laser alignment instrument to initially adjust the misalignment of the pipe orifice to 0.8 mm, and the groove gap is 2.5 mm. The pipe alignment device adopts a 6-bump structure (matched with DN500), and 2 high-precision pressure sensors (accuracy ±0.03 N) are embedded at both ends of each bump. The control terminal retrieves the "DN500~8mm~CS" standard pressure matrix. Real-time monitor the pressure at each support point, and dynamically adjust the threaded rod through an external electric torque wrench to control the pressure deviation within the range of ±0.15 N. Finally, the misalignment of the pipe orifice is 0.3 mm, and the gap uniformity is ±0.05 mm. The deviation amount is close to the measurement limit of the instrument and can be ignored.

[0053] During the welding process, for the root pass welding, a Fronius TPS / i 400 orbital welding machine is used, with DC straight polarity TIG welding, a current of 90 A, an arc length of 2.2 mm, a speed of 9 cm / min, an argon flow rate of 9 L / min, a reinforcement of the back bead of 1.0 mm, a penetration depth of 3.8 mm, and a bead width of 7.0 mm. For the backing weld, an OTC narrow-gap pulsed TIG welding machine is used, with a pulse frequency of 80 Hz, a peak current of 130 A, a base current of 40 A, the welding torch inserted into the narrow-gap section, an argon flow rate of 11 L / min, an interlayer thickness of 2.1 mm, and a sidewall penetration depth of 3.0 mm. For the filling weld, Miller hot wire TIG welding is used, with a hot wire temperature of 350 °C, a current of 200 A, each layer welded in three passes, the adjacent layers in opposite directions and staggered by 2.8 mm, a filling speed of 7 cm / min, an interlayer temperature of 180 °C, and a total filling thickness of 5.5 mm.

[0054] For the capping weld, a KUKA numerically controlled welding torch is used, with a current of 160 A, a hot wire temperature of 280 °C, a speed of 11 cm / min, a reinforcement of 1.0 mm, a transition fillet radius of R1.6 mm between the weld bead and the groove, and a surface roughness Ra = 4.8 μm.

[0055] Test Example 1: The misalignment and gap uniformity at 8 equally spaced points around the pipe orifice are measured by a laser tracker (Leica AT960). The peak pressure deviation at each support point is monitored and recorded in real time by a pressure sensor.

[0056] The measured misalignment values at 8 points around the pipe orifice are 0.28 mm, 0.31 mm, 0.29 mm, 0.30 mm, 0.27 mm, 0.32 mm, 0.29 mm, and 0.30 mm respectively, with an average value of 0.295 mm, a difference between the maximum and minimum values of 0.05 mm, all < 0.5 mm (the allowable value in the industry standard is 1.0 mm). For the groove gap uniformity, the gap measurement values at 8 points are 2.45 - 2.55 mm, with a deviation of ±0.05 mm, far less than the requirement of ±0.3 mm in the industry standard. For the peak pressure deviation test, the pressure deviation at each support point during the whole welding process is controlled within ±0.2 N, and the maximum adjustment amount is 0.8 N.

[0057] The test data of other performance indicators are as shown in Table 1 below: Inspection Items Measured Value Standard Requirement Radiographic Inspection Grade Grade Ⅰ Grade Ⅰ Tensile Strength 425 MPa ≥410 MPa Side Bend Test (180°) No Crack Qualified Impact Energy (Weld) 128J ≥105J Hydrostatic Test (1.5 times pressure) No Leakage, Pressure Drop 0.01 MPa No Leakage, ≤0.05 MPa Table 1 Performance Test Data Sheet of Example 1 Through the dynamic calibration of the pressure sensor and the control terminal in this application, the alignment deviation of the pipe orifice is controlled within about 0.3 mm, which is only 1 / 3 of the industry standard and close to the instrument measurement error range, and can be regarded as "negligible". This embodiment verifies the remarkable effects of the double-step groove and the intelligent butt joint system in controlling thermal deformation and improving alignment accuracy. All indicators are superior to the traditional process and meet the construction requirements of high-pressure thermal pipelines.

[0058] Example 2: Butt welding construction of a DN800×12 mm alloy steel thermal pipeline For the double-step groove, the angle of the large-angle transition section in the upper part is 16°, the width is 9 mm, the angle of the narrow-gap section in the lower part is 5°, the width is 5.5 mm, the transition fillet radius is 1.3 mm, the depth of the large-angle section is 6 mm (half of the wall thickness), and the depth of the narrow-gap section is 6 mm. The surface of the groove is processed with V-shaped micro-grooves with a depth of 0.25 mm and a spacing of 3 mm, and an inclined surface guiding structure is formed by laser processing to enhance the fluidity of the molten pool. After processing and inspection: the deviation of the groove angle is ±0.04 mm, the deviation of the groove depth is ±0.01 mm, and the surface roughness Ra = 3.2 μm.

[0059] For pipe butt joint control, an 8-bump pipe butt joint device is used, and each pressing block is embedded with 2 pressure sensors (accuracy ±0.02 N). The control terminal retrieves the "DN800~12 mm~AS" pressure matrix and dynamically adjusts the supporting force to make the misalignment ≤0.4 mm, and the groove gap is 2.8 ±0.04 mm.

[0060] During welding, the internal root welding is DC straight polarity TIG welding with a current of 95 A, an arc length of 2.5 mm, a speed of 8 cm / min, and a root penetration depth of 4.2 mm to ensure full penetration at the bottom of the narrow gap. The backing welding is pulsed TIG welding with a pulse frequency of 90 Hz, a peak current of 145 A, a base current of 40 A, a welding torch oscillation amplitude of 3 mm (±1.5°), an argon gas flow rate of 12 L / min, a sidewall penetration depth of 3.5 mm, and the molten pool oscillation frequency synchronized with the pulse to promote gas escape and sidewall fusion. The filling welding is hot wire TIG welding with a hot wire temperature of 380 °C and a current of 210 A. Each layer is welded in three passes (center weld pass + left and right offset weld passes). The directions of adjacent layers are opposite and staggered by 2.5 mm. The welding torch oscillation frequency is 18 times / min, and the arc energy density is 280 W / mm² to ensure that the sidewall fusion width in the narrow-gap section ≥2.5 mm and the fusion depth in the large-angle section ≥3 mm. The cover welding is carried out with a numerically controlled welding torch, a current of 170 A, a hot wire temperature of 260 °C, a speed of 10 cm / min, double-layer gas shroud protection (inner layer flow rate 15 L / min), the weld bead and the groove transition fillet R1.8 mm, and the reinforcement height 1.1 mm.

[0061] Comparative Example 1: Using traditional U-groove welding (same material and wall thickness), the groove parameters are as follows: the U-groove angle is 5°, the width is 8 mm, and there is no groove. The welding process is traditional continuous current TIG welding, the current is 180 A, there is no pulse oscillation, and the others are the same as in Example 2.

[0062] Test Example 2: The pipeline obtained by welding in Example 2 was intercepted at the weld cross-section, observed after being corroded by 4% nitric acid alcohol, and the fusion depth of the side wall in the narrow-gap section was 3.2 - 3.8 mm, which was 40% higher than that of the traditional U-groove (2.0 - 2.5 mm); the molten metal in the V-groove was filled completely, forming a "mortise and tenon" mechanical interlock, and there were no obvious unfused defects in the interlayer fusion line, and the fusion width ≥ 2.0 mm. After radiographic inspection, the following results were obtained: the porosity was 0.8 per 100 mm², which was 55% lower than that of the traditional process (1.8 per 100 mm²); no interlayer unfused defects were found, and the proportion of Class I welds was 100% (the defect rate of the traditional process was 15%).

[0063] Through ultrasonic inspection, using a 5 MHz probe for scanning, no defects ≥ 1 mm were found in the fusion zone of the side wall in the narrow-gap section, and the interlayer echo amplitude < 20% of the full scale (40 - 50% for the traditional process).

[0064] Measured by ImageJ software, the fusion area of the double-step groove + V-groove was 22% higher than that of the flat groove, and the interlayer unfused defect rate decreased from 15% of the traditional process to 2%.

[0065] The test results of Comparative Example 1 were as follows: the fusion depth of the side wall was 2.0 - 2.5 mm, and the interlayer unfused defect rate was 15%; The porosity was 1.8 per 100 mm², and the proportion of Class I welds in RT inspection was 85%.

[0066] The welding quality test data of Example 2 and Comparative Example 1 are shown in Table 2 below: Inspection Items Example 2 Comparative Example 1 Narrow Gap Sidewall Fusion Depth 3.2 - 3.8 mm 2.0 - 2.5 mm Interlayer Lack - of - Fusion Defect Rate 2% 15% Porosity (number / 100 mm²) 0.8 1.8 Increase in Fusion Area 22% ~ Proportion of Grade Ⅰ Welds in Radiographic Inspection 100% 85% Table 2 Comparison Table of Welding Quality Test between Example 2 and Comparative Example 1 The welding strength test data of Example 2 are shown in Table 3 below: Inspection Items Measured Value Standard Requirement Tensile Strength 520 MPa (Base Metal 510 MPa) ≥500 MPa Impact Energy (Heat - Affected Zone) 98J（~20℃） ≥85J Bending Test (Side Bend) No Crack Qualified Hydrostatic Test (1.6 times pressure) No Leakage, Pressure Drop 0.012 MPa No Leakage, ≤0.05 MPa Table 3 Comparison Table of Welding Strength Test of Example 2 In this embodiment, through the structural design of the "large-angle transition section + narrow-gap section" of the double-step groove, combined with the high-frequency oscillating molten pool of pulsed TIG welding and the multi-pass filling process of hot-wire TIG welding, the fusion depth of the groove sidewall and the interlayer is significantly improved. Combining the mechanical and metallurgical double fusion mechanisms of the V-shaped micro-groove, the interlayer unfused defect rate is reduced from 15% of the traditional process to 2%, and the porosity is reduced by 55%, solving the fusion problem of the narrow-gap groove. The comparison data shows that this technology has significant advantages in fusion efficiency and welding quality, and is especially suitable for the high-quality butt joint of thick-walled alloy steel thermal pipelines.

[0067] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used 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 recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

[0068] The above are all the preferred embodiments of the present invention and do not limit the protection scope of the present invention accordingly. Therefore, all equivalent changes made according to the structure, shape, and principle of the present invention shall be covered within the protection scope of the present invention.

Claims

1. A method for butt welding construction of thermal pipelines, characterized in that, Including the steps: Preset a stepped groove at the pipe orifice to be butt-jointed. The stepped groove consists of a large-angle transition section and a narrow-gap welding section from top to bottom. The two sections are smoothly transitioned and connected. Then, preset micro-grooves at equal intervals on the groove surface; Align the pipe orifices of the two pipes to be butt-jointed and fix them with a pipe alignment device. Monitor the contact pressure between the pipe alignment device and the two pipes, and adjust the supporting force according to the pressure to make the deviation of the alignment of the two pipe orifices within the standard range; Weld the pipe orifices of the two pipes.

2. The hot pipeline butt joint construction method according to claim 1, characterized in that The groove angle a of the large-angle transition section is 15 - 20°, and the width L1 is 8 - 10mm. The groove angle b of the narrow-gap welding section is 5 - 7°, and the width L2 is 5 - 7mm. The transition fillet radius between the large-angle transition section and the narrow-gap welding section is 1 - 1.5mm.

3. The construction method for butt joint of thermal pipelines according to claim 1, characterized in that, The depth of the micro-grooves on the groove surface is 0.2 - 0.3mm, and the spacing between the grooves is 3 - 5mm.

4. The method for butt joint construction of a thermal pipeline according to claim 1, characterized in that, At the supporting parts where the pipe alignment device contacts the pipe, a plurality of pressure sensors are evenly arranged circumferentially along the pipe orifice, and several pressure sensors are distributed at each support point.

5. The method for butt welding construction of a thermal pipeline according to claim 1, wherein Weld the pipe orifices of the two pipes. First, perform internal root welding. The internal root welding uses DC straight polarity TIG welding. After the internal root welding is completed, perform backing welding on the narrow-gap welding section. The backing welding uses pulsed TIG welding. After the backing welding is completed, perform filling welding. The filling welding uses hot wire TIG welding. Start filling layer by layer from the bottom of the narrow gap. Each layer of weld is welded in three passes. The welding directions of adjacent layers are opposite and the weld beads are staggered. Then, perform capping welding.

6. A system applied to the hot - line pipeline butt - joint construction method according to any one of claims 1 to 5, characterized in that, Including: A pipe alignment device, including a pipe alignment tool and a support adjuster installed in the pipe alignment tool. The pipe alignment tool is used to fix the butted pipe orifices, and the support adjuster is used to adjust the supporting force on the pipe orifices; A welding device. The internal root welding uses an orbital all-position automatic welding machine equipped with a DC straight polarity TIG welding torch. The backing welding of the narrow-gap welding section uses a narrow-gap pulsed TIG welding machine. The full-groove filling welding and capping welding use hot wire TIG welding torches.

7. The system of the hot pipeline butt joint construction method according to claim 6, characterized in that, The pipe alignment device includes a pipe alignment tool (100). The pipe alignment tool (100) includes a number of convex blocks (101) distributed in a ring. Inside the two ends of each convex block (101), a support block (200) and a support adjuster (300) are installed. The support block (200) includes a tightening block (201) that is slidably embedded in the convex block (101) and can be limited. A pressure sensor (202) is installed at the outer end of the tightening block (201), and the inner end of the tightening block (201) is connected to the support adjuster (300).

8. The system of the hot pipeline butt joint construction method according to claim 7, characterized in that, The support regulator (300) includes a threaded rod (301) connected to the abutting block (201). The upper end of the threaded rod (301) is sleeved with a matching threaded sleeve (302). The outer wall of the threaded sleeve (302) is sleeved with a bearing (305). The outer wall of the bearing (305) is fixed within the convex block (101). The top of the threaded sleeve (302) is fixedly connected to an adjusting rod (304). The adjusting rod (304) passes through the convex block (101) and extends to the outer end of the convex block (101). The top of the adjusting rod (304) located at the outer end of the convex block (101) is fixedly connected to an adjusting block (303). A rotary connection groove is formed in the adjusting block (303).

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