A high-efficiency welding method for close-packed tubes

Abstract

This invention proposes a high-efficiency welding method for closely spaced pipes, belonging to the field of welding technology. It solves the problems in the industry where manual shielded metal arc welding (SMAW) is mainly used for fillet welds of closely spaced pipe joints. This method results in high labor intensity for welding operators, low production efficiency, and weld quality that is greatly affected by the operator, making it difficult to guarantee weld quality. This invention uses solid carbon dioxide gas shielded welding wire; employs a deep-penetration, low-spatter pulsed power supply; and determines the welding sequence as a left-hand welding method. Using solid welding wire for gas shielded welding of pipe joints improves production efficiency and reduces production costs. Compared with the commonly used SMAW method, solid welding wire reduces fume generation, purifies the operating environment, and improves the company's environmental protection level.

Description

Technical Field

[0001] This invention belongs to the field of welding technology, and in particular relates to a high-efficiency welding method for closely spaced pipes. Background Technology

[0002] The header is an important component of power plant boilers. The header body is equipped with a large number of densely packed pipe joints. These joints are characterized by a wide variety of specifications, complex structures, small bevel spacing, and limited welding space. In the industry, fillet welds for these densely packed pipe joints are mainly done manually using shielded metal arc welding (SMAW). This method results in high labor intensity for welding operators, low production efficiency, and welding quality that is significantly affected by the operator, making it difficult to guarantee weld quality. Summary of the Invention

[0003] In view of this, in order to solve the technical problems mentioned in the background art, the present invention proposes a high-efficiency welding method for closely spaced pipes. This method is a novel process that is adapted to the special gas shielded welding process of closely spaced pipe joints, uses a deep penetration and low spatter pulse power supply, and is applicable to the entire operation process as the curvature and angle of the bevel change.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: a high-efficiency welding method for closely packed pipes, comprising the following steps: Step 1: Pre-welding preparation: Select solid carbon dioxide gas shielded welding wire; use a deep penetration, low spatter pulse power supply; determine the welding sequence as left-hand welding method; Step 2: Arc Initiation Stage: Insert the welding torch through the gap between two adjacent pipes, and align the welding wire between the 2 and 3 points of the target pipe joint to initiate the arc; set the angle between the welding torch and the axis of the pipe joint and the axis of the main pipe to be 45°, and the angle between the welding torch and the welding direction to be 75°-80°. Step 3: Welding the upper half of the circle: Between 3 o'clock and 6 o'clock: The angle between the welding torch and the weld bead gradually increases from 75° to 90°, increasing by 5° for each clock position, and welding is performed by pulling the torch. Between 6 o'clock and 9 o'clock: The angle between the welding torch and the weld bead gradually increases from 90° to 105°, increasing by 5° for each clock position, and welding is performed by pushing the torch. Step 4: Welding in the second half of the cycle: Move to the opposite side of the workpiece and start the arc from the 9 o'clock position; Between 9:00 and 12:00: the angle between the welding torch and the weld gradually increases from 75° to 90°; Between 12 o'clock and 3 o'clock: the angle between the welding torch and the weld gradually increases from 90° to 105°; Step 5: Arc termination protection: When terminating the arc, the damping current is activated, and the delayed gas supply is maintained after the arc is extinguished, using CO2 to continuously protect and cool the molten pool.

[0005] Preferably, in step 4, the welding torch needs to be swung at the joint to ensure that the molten pool completely covers the previous arc crater.

[0006] Preferably, in step 5, the attenuation current is 100A and the voltage is 18V.

[0007] Compared with the prior art, the beneficial effects of the high-efficiency welding method for closely packed tubes described in this invention are: 1. In the prior art, after the welding of shielded metal arc welding is completed, the flux coating needs to be cleaned. However, the present invention uses solid carbon dioxide gas shielded welding wire and carbon dioxide gas as the protective medium, which eliminates the generation of flux coating, reduces the cleaning process, and improves work efficiency. 2. This invention overcomes the problem of low weld performance in gas-shielded welding of flux-cored wire, improves the weld performance of the product, and makes it easier to ensure long-term operation of the product; 3. This invention uses a pulse power supply, which significantly improves the metal cladding efficiency and overcomes the shortcomings of commonly used shielded metal arc welding methods, such as low efficiency and reliance on the operator's skill level. 4. The MAG welding of the header pipe joint of the present invention is more suitable for welding with small angle and narrow groove, avoiding the defects such as slag inclusion, lack of fusion and incomplete root penetration that are easily generated in the weld by other operation methods. 5. This invention uses solid welding wire melting and gas shielded welding to achieve continuous multi-layer and multi-pass welding, which makes it easier to automate welding; 6. This invention uses a deep penetration and low spatter pulse power supply, and is applicable to a new process method that varies with the curvature and angle of the bevel throughout the entire operation, filling the gap in the domestic high-efficiency welding of header close-packed pipe joints; 7. The present invention uses solid welding wire gas shielded welding to weld pipe joints, which can improve production efficiency and reduce production costs. Compared with the commonly used welding shielded metal arc welding method, the use of solid welding wire arc welding reduces the amount of smoke and dust generated, purifies the operating environment, and improves the company's environmental protection level. 8. The widespread application of the solid welding wire gas shielded welding pipe joint of this invention not only greatly improves the welding efficiency of products and reduces the work of cleaning up spatter after welding, but also represents a bold innovation in the traditional manufacturing process of headers. At the same time, it improves the production and manufacturing level of our company's header pipe joints and provides valuable experience and technical support for the comprehensive realization of the goal of intelligent manufacturing. Attached Figure Description

[0008] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a schematic diagram of the welded finished product of the present invention. Figure 1 ; Figure 2 This is a schematic diagram of the welded finished product of the present invention. Figure 2 ; Figure 3 This is a schematic diagram of the overall welded finished product. Detailed Implementation

[0009] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention. Furthermore, it should be noted that, for ease of description, only the parts relevant to the invention are shown in the drawings, and not all of them. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein is for the purpose of describing specific embodiments only and is not intended to limit the invention.

[0010] See Figure 1 This embodiment describes a high-efficiency welding method for closely spaced pipes, and the specific operation steps are as follows: Step 1: Arc Initiation. Pass the welding torch between the two closely spaced pipes, aligning the welding wire between the 2 o'clock and 3 o'clock positions on the left pipe joint. Initiate the arc welding at this point, maintaining a 45° angle between the welding torch and both the pipe joint and the main pipe. This facilitates observation of the arc initiation point and also benefits welding on the other side. When starting welding, maintain a 75-80° angle between the welding torch and the welding direction (weld bead). After arc initiation, observe whether the weld is well fused. Once both sides of the bevel are well fused, begin moving the welding torch to start welding.

[0011] Step 2: Welding the upper half of the circumference. The welding direction is left-hand welding, meaning welding from right to left. Specifically, start the arc between the 2 o'clock and 3 o'clock positions, weld towards the 6 o'clock position, and finally towards the 9 o'clock position. During the welding process, maintain a 45° angle between the welding torch and both the small and large pipe joints.

[0012] During the welding process from the 3 o'clock position to the 6 o'clock position, the angle between the welding torch and the weld bead should gradually increase from 75°, reaching 90° at the 6 o'clock position. At this point, note that as the welding position moves from 3 o'clock to 6 o'clock, the welding torch angle should gradually change from 75° to 90°, changing by 5° each hour, slowly and gradually, avoiding excessive speed. This is similar to pull-and-pull welding. Observe both sides of the bevel during welding to ensure good fusion, without any incomplete fusion or slag inclusions. Ensure the weld bead is uniform, smooth, and flat.

[0013] During the welding process from the 6 o'clock position to the 9 o'clock position, the angle between the welding torch and the weld bead should gradually increase from 90°, reaching 105° at the 9 o'clock position. Note that as the welding position moves from 6 o'clock to 9 o'clock, the welding torch angle should gradually change from 90° to 105°, changing by 5° each hour, slowly and gradually, avoiding rapid changes. This is similar to push-pull welding. When welding at the 9 o'clock position, the welding torch and weld bead should be at a 105° angle to avoid a perpendicular weld bead. Since there is a small pipe joint to the left of the 9 o'clock position, a 90° angle between the welding torch and the weld bead can easily obstruct the weld seam and affect visibility. A 105° angle avoids this, facilitates weld observation, and prevents weld misalignment and defects.

[0014] The third step is welding in the second half of the cycle. After completing the welding from 3 to 9 o'clock, move to the opposite side of the main pipe header and weld from 9 o'clock to 12 o'clock to 3 o'clock. The arc starts at the 9 o'clock position and ends at the arc crater. The angle between the welding torch and the weld bead should gradually increase from 75°, reaching 90° at the 12 o'clock position. Note that as the welding position moves from 9 o'clock to 12 o'clock, the welding torch angle should gradually change from 75° to 90°, changing by 5° for each clock position. After starting the arc, the welding torch can be swung left and right slightly to quickly fill the entire arc crater, ensuring good fusion on both sides of the bevel before moving the welding torch to continue welding. During the welding process from 12 o'clock to 3 o'clock, the angle between the welding torch and the weld bead should gradually increase from 90°, reaching 105° at the 3 o'clock position. At this point, pay attention to moving the welding rod from 12 o'clock to 3 o'clock, and gradually changing the welding torch angle from 90° to 105°, with a 5° change at each clock position. When joining at the 3 o'clock position, ensure that the molten pool completely covers the arc starting point at the 3 o'clock position. To ensure good fusion, slightly raise the arc by 1mm after joining to increase the voltage. At the same time, slightly oscillate the welding torch to ensure that the molten pool completely fuses the joint, avoiding the formation of slag inclusions.

[0015] Step 4: When ending the arc, use a decaying current (preferably 100A and 18V) and end the arc on the bevel. Avoid sudden arc stopping or ending the arc in the middle of the weld. After the arc is extinguished, do not remove the welding torch immediately. Use delayed shielding gas (i.e., continue supplying gas after the arc is extinguished, do not stop supplying carbon dioxide gas, and delay the gas supply time) to protect and cool the weld. This can effectively prevent the formation of arc crater cracks, arc crater defects, and shrinkage cavities.

[0016] This invention selects appropriate spot welding positions for spot welding and arc initiation welding, maintains the "left welding method" welding state throughout the welding process, adjusts the arc angle to adapt to the entire bevel position of the pipe joint, and implements anti-arc crater arc termination and other operational procedures. Through a series of operational technical measures, the welding quality is guaranteed.

[0017] Example 1: Welding of the close-packed pipe joints in the header of a power plant boiler. Equipment selection: Deep penetration, low spatter pulsed MAG welding machine, CO2 shielding gas, and solid wire.

[0018] Detailed operating procedures: Step 1: Initiating the arc: as shown Figure 1 As shown, the welding torch passes through the gap between two closely spaced pipes. The tip of the welding wire is positioned between points 2 and 3 on the left side of the pipe joint. The welding torch posture is adjusted as follows: 45° angle with the smaller pipe, 45° angle with the larger pipe, and 75°-80° angle with the direction of weld travel. After igniting the arc, confirm that the fusion on both sides is good before moving the torch.

[0019] Step 2: Welding from 3 o'clock to 6 o'clock: Weld counterclockwise. As the position moves down, the angle between the welding torch and the weld increases linearly. At the 6 o'clock position, the angle becomes 90° (similar to vertical welding upwards). This process requires ensuring that the angle changes by approximately 5° at each clock position.

[0020] Step 3: Welding from 6 o'clock to 9 o'clock: Continue welding counterclockwise. Increase the angle to 105°. Since the 9 o'clock position is close to the adjacent pipe, maintaining a 105° angle can effectively avoid interference, ensure a clear line of sight, and prevent weld misalignment.

[0021] Step 4: Joint Treatment: After completing the upper half of the welding, move to the opposite side. Initiate an arc at the 9 o'clock position and oscillate the welding torch to fill the crater. Complete the welding from the 9 o'clock position to the 3 o'clock position using the same angle variation rule.

[0022] Step 5: Finishing: When approaching the starting point at 3 o'clock, activate the current attenuation function (100A / 18V) and end the arc within the bevel. Keep the welding torch in place until the delayed gas supply ends to prevent crater cracks.

[0023] Results verification: Non-destructive testing (UT / RT) showed that the welds were free of incomplete fusion, slag inclusions and cracks, with a first-pass yield of over 98%, and welding efficiency was improved by 150% compared to the original process.

[0024] The embodiments of the present invention disclosed above are merely illustrative of the invention. These embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention.

Claims

1. A high-efficiency welding method for closely packed pipes, characterized in that: Includes the following steps: Step 1: Pre-welding preparation: Select solid carbon dioxide gas shielded welding wire; use a deep penetration, low spatter pulse power supply; The welding sequence is determined to be left-hand welding. Step 2: Arc Initiation Stage: Insert the welding torch through the gap between two adjacent pipes, and align the welding wire between the 2 and 3 points of the target pipe joint to initiate the arc; set the angle between the welding torch and the axis of the pipe joint and the axis of the main pipe to be 45°, and the angle between the welding torch and the welding direction to be 75°-80°. Step 3: Welding the upper half of the circle: Between 3 o'clock and 6 o'clock: The angle between the welding torch and the weld bead gradually increases from 75° to 90°, increasing by 5° for each clock position, and welding is performed by pulling the torch. Between 6 o'clock and 9 o'clock: The angle between the welding torch and the weld bead gradually increases from 90° to 105°, increasing by 5° for each clock position, and welding is performed by pushing the torch. Step 4: Welding in the second half of the cycle: Move to the opposite side of the workpiece and start the arc from the 9 o'clock position; Between 9:00 and 12:00: the angle between the welding torch and the weld gradually increases from 75° to 90°; Between 12 o'clock and 3 o'clock: the angle between the welding torch and the weld gradually increases from 90° to 105°; Step 5: Arc termination protection: When terminating the arc, the damping current is activated, and the delayed gas supply is maintained after the arc is extinguished, using CO2 to continuously protect and cool the molten pool.

2. The high-efficiency welding method for closely packed pipes according to claim 1, characterized in that: In step 4, the welding torch needs to be swung at the joint to ensure that the molten pool completely covers the previous arc crater.

3. The high-efficiency welding method for closely packed pipes according to claim 1, characterized in that: In step 5, the attenuation current is 100A and the voltage is 18V.

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