A single-pass forming welding method

Abstract

The present application belongs to the technical field of welding, and particularly relates to a single-pass forming welding method. The method comprises (1) processing V-shaped grooves on the test plates to be welded; (2) assembling the test plates to be welded; (3) when filling a welding pass by adopting double-wire gas-electric vertical welding, the front wire is swung left and right, and the rear wire is swung front and back; wherein the gap d1 between the arc starting end and the root is 9-12.5 mm, the gap d2 between the arc ending end and the root is 1.125d1+0.1t*tanα; α is the single-sided groove angle, and t is the thickness of the test plate to be welded. The welding method can realize single-pass forming welding of 60-85 mm thick steel plates on one side, and shorten the welding cycle of the thick steel plate; the method can make the molten metal of the welding pool have good fluidity and spreadability from the root of the weld to the surface of the weld, and the weld and the base material can be well fused, so that single-sided welding and double-sided one-time forming are realized, and welding defects such as weld edge biting, slag inclusion, incomplete fusion, incomplete penetration and uneven forming are effectively avoided.

Description

Technical Field

[0001] This invention belongs to the field of welding technology, specifically relating to a single-pass forming welding method. Background Technology

[0002] Currently, with the rapid development of structural components towards larger sizes, heavier loads, and longer spans, the demand for extra-thick, high-strength structural steel plates is increasing. This increase in the use of thick plates inevitably places higher demands on welding efficiency. Gas-electric vertical welding (EGW) combines gas-shielded arc welding and flux-cored wire arc welding. It utilizes a sliding block to block the molten weld metal, achieving vertical welding. An external gas mixture can be added for auxiliary protection. EGW is a high-efficiency welding method with high heat input, offering good weld quality, fast deposition rate, and low overall cost. It is widely used in the construction of large steel structures in shipbuilding, petrochemical, and other related industries.

[0003] Single-wire gas-electric vertical welding technology not only boasts excellent weld quality and mechanical properties but also high welding efficiency, enabling one-time forming welding of steel plates with thicknesses ranging from 9 to 40 mm. However, for steel plates with thicknesses of 60 to 85 mm, single-wire gas-electric vertical welding struggles to achieve one-time forming. To overcome this limitation, double-wire gas-electric vertical welding was developed, enabling single-sided welding of steel plates with thicknesses of 35 to 85 mm with double-sided forming in a single pass, making it a highly efficient welding technology. Due to the slow welding speed of gas-electric vertical welding, the softening of the metal around the weld is relatively uniform along the weld direction, and the expansion of the heated metal is relatively uniform in all aspects. However, the metal behind the welding heat source has already solidified and begun to contract, causing the unwelded portions of the weld joint to converge, resulting in a narrowing gap at the root of the weld plate. If the welding process method is not properly selected or the welding process parameters are not properly controlled, welding defects such as undercut, slag inclusions, incomplete fusion, incomplete penetration, uneven forming, and inconsistent weld width are easily produced, making it impossible to obtain a well-formed weld. Existing technologies typically employ a welding mode where the back welding wire does not oscillate and the front welding wire oscillates when welding thick steel plates. However, the welds obtained by this welding method are prone to the aforementioned welding defects, such as weld shrinkage leading to a smaller weld gap, slag inclusions, lack of fusion, and inconsistent weld width. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the defects in the prior art when welding thick steel plates, such as reduced weld gap, slag inclusion, lack of fusion, and inconsistent weld width, thereby providing a single-pass forming welding method.

[0005] To this end, the present invention provides the following technical solution.

[0006] This invention provides a single-pass welding method, comprising the following steps:

[0007] (1) Perform V-groove machining on the test plate to be welded;

[0008] (2) Assemble the test plate to be welded; wherein, the root gap d1 at the arc starting end is 9-12.5mm, and the root gap d2 at the arc ending end is 1.125d1+0.1t×tanα;

[0009] (3) When using double-wire gas electric vertical welding to fill the weld bead, the front wire swings back and forth and left and right, and the rear wire swings back and forth.

[0010] Where α is the bevel angle on one side and t is the thickness of the test plate to be welded.

[0011] When the front yarn swings back and forth and left and right, the swing amplitude of the left and right swing is 25-35mm, and the swing amplitude of the back and forth swing is 10-25mm.

[0012] When the front yarn swings back and forth and left and right, the dwell time for the left and right swing is 1-2 seconds, and the dwell time for the back and forth swing is 0-1 second.

[0013] When the back yarn swings back and forth, the swing amplitude is 5-15mm.

[0014] Step (3) includes first performing a gas shielded welding for the bottom sealing at the arc starting end of the test plate to be welded, and then using a double-wire gas electric vertical welding to fill the weld bead.

[0015] Furthermore, in the welding method, the front wire is connected to DC reverse polarity, and the rear wire is connected to DC forward polarity;

[0016] Preferably, the welding current is 380-420A and the voltage is 44-45V.

[0017] In the welding method, the wire extension is 35-45mm;

[0018] Preferably, the distance between the rear wire and the root of the weld is 15-20mm;

[0019] Preferably, the distance between the front filament and the back filament is 25-35 mm.

[0020] In the welding method, the single-sided bevel angle α is 10°±1.

[0021] In the welding method described, the welding speed is 3-5 cm / min.

[0022] In the welding method, the thickness t of the test plate to be welded is 60-85mm.

[0023] The technical solution of this invention has the following advantages:

[0024] 1. The single-pass forming welding method provided by the present invention includes (1) performing V-groove processing on the test plate to be welded; (2) assembling the test plate to be welded; (3) when using double-wire gas electric vertical welding to fill the weld bead, the front wire swings back and forth and left and right, and the rear wire swings back and forth; wherein, the root gap d1 at the arc starting end is 9-12.5mm, and the root gap d2 at the arc ending end is 1.125d1+0.1t×tanα; α is the single-sided groove angle, and t is the thickness of the test plate to be welded. This welding method enables single-sided, single-pass forming welding of 60-85mm thick steel plates, shortening the welding cycle of extra-thick steel plates. It boasts advantages such as high welding efficiency and simple, controllable operation. This method ensures that the molten metal in the weld pool has good fluidity and spreadability from the weld root to the weld surface, allowing for good fusion between the weld and the base material. It achieves single-sided welding with double-sided forming in one pass, effectively avoiding welding defects such as undercut, slag inclusion, lack of fusion, incomplete penetration, and uneven forming, thus improving welding quality and efficiency. Furthermore, this method effectively solves the problem of gradually decreasing transverse shrinkage of the bevel gap along the weld length, resulting in a uniformly formed weld and reducing welding internal stress.

[0025] This method employs a welding mode where the front wire swings back and forth and left and right, and the rear wire swings back and forth. It controls the root gap at the arc initiation end and the root gap at the arc termination end, enabling single-pass forming welding of 60-85mm thick steel plates. This shortens the welding cycle of extra-thick steel plates and has advantages such as high welding efficiency and simple and controllable operation. This method allows the molten metal in the weld pool to have good fluidity and spreadability from the weld root to the weld surface, ensuring good fusion between the weld and the base material. It achieves single-sided welding with double-sided forming in one pass, effectively avoiding welding defects such as weld undercut, slag inclusion, lack of fusion, incomplete penetration, and uneven forming, thus improving welding quality and efficiency.

[0026] This method uses a single-sided beveling technique, which simplifies the beveling process and improves processing efficiency compared to the double-sided beveling process.

[0027] Compared with welding processes such as SAW, GMAW, FCAW, GMAW+EGW, and FCAW+EGW, the present invention adopts a dual-wire gas-electric vertical welding process for the test plate to be welded, which can realize single-pass forming welding of steel with high heat input for 60-85mm thickness, significantly improving welding efficiency and shortening the production cycle.

[0028] Based on the characteristics related to the transverse shrinkage deformation of the weld, the bevel form of the butt weld, the butt gap, the thickness of the steel plate, and the cross-sectional area of ​​the weld, the root gap d1 at the arc-starting end is set to 9-12.5mm, and the root gap d2 at the arc-ending end is calculated and set according to the formula 1.125d1+0.1t×tanα. This effectively solves the problem of the gradually decreasing transverse shrinkage gap of the bevel gap along the weld length, so that the present invention can obtain a uniformly formed weld and reduce welding internal stress. At the same time, the present invention strictly controls the bevel gap, which can avoid the transverse shrinkage deformation of the steel plate caused by the welding thermal cycle during the welding process, resulting in a gradual decrease in the bevel gap from the arc-starting end to the arc-ending end, and the inability to guarantee the uniformity of the weld width along the weld length.

[0029] 2. The single-pass forming welding method provided by the present invention, by controlling the distance between the rear wire and the weld root, the distance between the front wire and the rear wire, the back-and-forth swing amplitude of the rear wire, the back-and-forth and left-and-right swing amplitude of the front wire, and the dwell time, can make the molten metal in the weld pool have good fluidity and spreading from the weld root to the weld surface, and the weld and the base material can be well fused, effectively avoiding welding defects such as undercut, slag inclusion, lack of fusion, and incomplete penetration, thereby improving the welding quality.

[0030] Applying a gas-shielded weld (GSW) layer to the arc-starting end of the test plate before welding ensures a gapless connection between the water-cooled copper slider and the test plate, preventing molten metal leakage or burn-through during the welding process. Applying an arc-starting flux over the GSW layer aids in the initial arc combustion of the twin-wire gas-shielded vertical welding, ensuring stable arc combustion and preventing arc deviation. This method effectively solves the problems of arc-starting difficulty, molten metal leakage, and burn-through that occur at the beginning of twin-wire gas-shielded vertical welding. Attached Figure Description

[0031] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0032] Figure 1 This is a cross-sectional view of the assembled test plate in an embodiment of the present invention;

[0033] Figure 2 This is a schematic diagram of the V-shaped bevel of the test plate to be welded in an embodiment of the present invention;

[0034] Figure 3 This is a schematic diagram illustrating the positional relationship between the front filament, the back filament, and the root in an embodiment of the present invention, as well as the swing direction and amplitude of the front and back filaments. Detailed Implementation

[0035] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0036] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0037] The single-pass forming welding method provided in the following embodiments, and the cross-sectional view of the structure of the assembled test plate to be welded are shown in the figure. Figure 1 As shown, the welding method specifically includes:

[0038] (1) Perform V-groove machining on the two test plates to be welded, with a single-sided bevel angle α of 10°±1. Grind away rust, oil, scale, and other contaminants within a 40-50mm range on both sides of the bevel to expose the metallic luster. The thickness of the test plates to be welded is 60-85mm. The V-groove is as follows: Figure 2 As shown.

[0039] (2) Assemble the two test plates to be welded using the Karma assembly method. The root gap d1 at the arc-starting end is 9-12.5mm, and the root gap d2 at the arc-ending end is 1.125d1 + 0.1t × tanα. Install a copper gasket on the back of the bevel, ensuring the center of the gasket is aligned with the center of the bevel. Secure it with an iron wedge and connect the water cooling system. Figure 1 As shown.

[0040] (3) ① Adjust the welding torch and slider: The copper slider and welding torch should always be in the center position. The copper slider is connected to the water cooling system and the gas supply system, such as Figure 1 As shown, the welding torch position is as follows Figure 1 As shown, during the welding process, the front torch oscillates back and forth and left and right, causing the front wire to oscillate back and forth and left and right; the rear torch oscillates back and forth, causing the rear wire to oscillate back and forth; the oscillation direction and amplitude are as follows. Figure 3 As shown;

[0041] ② Adjustment parameters: The front wire uses DC reverse polarity, the rear wire uses DC positive polarity, the wire extension is 35-45mm, the distance between the rear wire and the weld root is 15-20mm, and the distance between the front and rear wires is 25-35mm; Figure 3 As shown;

[0042] The amplitude of the front yarn's back-and-forth oscillation is 10-25mm, with a dwell time of 0-1s; the amplitude of its left-and-right oscillation is 25-35mm, with a dwell time of 1-2s; the direction and amplitude of the front yarn's oscillation are as follows: Figure 3As shown;

[0043] The back yarn oscillates back and forth with an amplitude of 5-15mm; the direction and amplitude of the back yarn oscillation are as follows: Figure 3 As shown;

[0044] The welding current is 380-420A, the voltage is 44-45V, and the welding speed is 3-5cm / mm;

[0045] ③ At the arc-starting end of the test plate to be welded, a layer of sealing weld is performed using gas shielded welding. The flux coating is knocked off, and then a layer of arc-starting agent is laid on top. Then, double-wire gas-electric vertical welding is used to fill the weld bead until the weld is full.

[0046] Example 1

[0047] This embodiment provides a single-pass forming welding method. The cross-sectional view of the assembled test plate is shown below. Figure 1 As shown, it includes the following steps:

[0048] (1) Perform V-groove machining on the two test plates to be welded, with a single-sided bevel angle α of 10°±1. Grind away rust, oil, scale, and other contaminants within a 40-50mm range on both sides of the bevel to expose the metallic luster. The thickness of the test plates to be welded is 60mm. A schematic diagram of the V-groove machining is shown below. Figure 2 .

[0049] (2) Assemble the two test plates to be welded using clamping. The root gap d1 at the arc-starting end is 10±0.5mm, and the root gap d2 at the arc-ending end is 1.125d1+0.1t×tanα. Install a copper gasket on the back of the bevel, ensuring the center of the gasket is aligned with the center of the bevel. Finally, secure it with an iron wedge and connect it to the water cooling system. Figure 1 As shown.

[0050] (3) The copper slider and welding torch are always in the center position. The copper slider is connected to the water cooling system and the gas supply system, such as Figure 1 As shown, the welding torch position is as follows Figure 1 As shown, during the welding process, the front torch oscillates back and forth and left and right, causing the front wire to oscillate back and forth and left and right; the rear torch oscillates back and forth, causing the rear wire to oscillate back and forth. The oscillation direction and amplitude are as follows: Figure 3 As shown;

[0051] Adjust the welding wire, with the front wire using DC reverse polarity and the rear wire using DC positive polarity. The wire extension is 40mm, the distance between the rear wire and the weld root is 15mm, and the distance between the front and rear wires is 25mm.

[0052] Adjust the welding parameters as follows: welding current 380A, welding voltage 44V, back wire swing amplitude 5mm, front wire swing amplitude 15mm, dwell time 0.5S, left and right swing amplitude 25mm, dwell time 1S, welding speed 5cm / min.

[0053] At the arc-starting end of the test plate to be welded, a layer of sealing weld is performed using gas shielded welding. The flux coating is knocked off, and a layer of welding wire scraps (arc-starting agent) is laid on top. Then, the weld bead is filled using double-wire gas-electric vertical welding until the weld is full.

[0054] Example 2

[0055] This embodiment provides a single-pass forming welding method, including the following steps:

[0056] (1) Perform V-groove processing on the two test plates to be welded, with a single-sided groove angle α of 10°±1. Grind and remove rust, oil, oxide scale and other contaminants within a 40-50mm range on both sides of the groove to expose the metallic luster. The thickness of the test plates to be welded is 70mm.

[0057] (2) Assemble the two test plates to be welded by clamping them together. The root gap d1 at the arc starting end is 11mm±0.5mm, and the root gap d2 at the arc ending end is 1.125d1+0.1t×tanα. Install a copper pad on the back of the bevel so that the center of the pad is aligned with the center of the bevel. Finally, fix it with an iron wedge.

[0058] (3) Adjust the welding wire. The front wire is connected to DC reverse polarity, and the rear wire is connected to DC positive polarity. The wire extension is 40mm. The distance between the rear wire and the root of the weld is 15mm. The distance between the front wire and the rear wire is 30mm. Adjust the welding parameters. The welding current is 400A, the welding voltage is 44V, the swing amplitude of the rear wire back and forth is 10mm, the swing amplitude of the front wire back and forth is 20mm, the dwell time is 1S, the swing amplitude of the left and right swing is 30mm, the dwell time is 1S, and the welding speed is 4cm / min.

[0059] At the arc-starting end of the test plate to be welded, a layer of sealing weld is performed using gas shielded welding. The flux coating is knocked off, and a layer of arc-starting flux (welding wire scrap) is laid on top. Then, the weld bead is filled using double-wire gas-electric vertical welding until the weld is full.

[0060] Example 3

[0061] This embodiment provides a single-pass forming welding method, including the following steps:

[0062] (1) Perform V-groove processing on the two test plates to be welded, with a single-sided groove angle α of 10°±1. Grind and remove rust, oil, oxide scale and other contaminants within a 40-50mm range on both sides of the groove to expose the metallic luster. The thickness of the test plates to be welded is 80mm.

[0063] (2) Assemble the two test plates to be welded by clamping them together. The root gap d1 at the arc starting end is 12mm±0.5mm, and the root gap d2 at the arc ending end is 1.125d1+0.1t×tanα. Install a copper pad on the back of the bevel so that the center of the pad is aligned with the center of the bevel. Finally, fix it with an iron wedge.

[0064] (3) Adjust the welding wire. The front wire is connected to DC reverse polarity, and the rear wire is connected to DC positive polarity. The wire extension is 40mm. The distance between the rear wire and the root of the weld is 20mm. The distance between the front wire and the rear wire is 35mm. Adjust the welding parameters. The welding current is 400A, the welding voltage is 45V, the swing amplitude of the rear wire back and forth is 15mm, the swing amplitude of the front wire back and forth is 20mm, the dwell time is 1S, the swing amplitude of the left and right swing is 35mm, the dwell time is 2S, and the welding speed is 3cm / min.

[0065] At the arc-starting end of the test plate to be welded, a layer of sealing weld is performed using gas shielded welding. The flux coating is knocked off, and a layer of arc-starting flux (welding wire scrap) is laid on top. Then, the weld bead is filled using double-wire gas-electric vertical welding until the weld is full.

[0066] Comparative Example 1

[0067] This comparative example provides a single-pass forming welding method. The difference from Example 1 is that the rear wire remains stationary while the front wire swings back and forth without swinging left and right. Everything else is the same as Example 1.

[0068] Comparative Example 2

[0069] This comparative example provides a single-pass forming welding method. The difference from Example 1 is that the root gap at the arc starting end is the same as the root gap at the arc ending end, d1=d2=10±0.5mm. All other aspects are the same as in Example 1.

[0070] Test case

[0071] This experimental example provides the performance test results of the test plates after welding in each embodiment and comparative example. The weld quality was observed after welding, and the results are shown in Table 1.

[0072] Table 1. Weld inspection results for each embodiment and comparative example.

[0073]

[0074] As can be seen from Table 1, the welding method provided by the present invention can enable the weld to fuse well with the base material, avoiding problems such as undercut, slag inclusion, lack of fusion, and incomplete penetration, thereby improving the welding quality.

[0075] Comparative Example 1 illustrates that changing the oscillation direction of the front and rear wires can cause problems such as incomplete fusion and incomplete penetration in the weld. Comparative Example 2 illustrates that when the root gap at the arc initiation end and the root gap at the arc termination end are the same, problems such as shrinkage and deformation of the weld gap will occur. This invention, by controlling the oscillation of the front and rear wires, and the root gaps at the arc initiation end and the arc termination end, can ensure good fusion between the weld and the base material, achieving single-sided welding with double-sided one-time forming. This effectively avoids welding defects such as weld undercut, slag inclusion, incomplete fusion, incomplete penetration, and uneven forming, improving welding quality and efficiency. It can also solve the problem of gradually decreasing transverse shrinkage of the bevel gap along the weld length, obtaining a uniformly formed weld and reducing welding internal stress.

[0076] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A welding method for single-pass forming, characterized in that, Includes the following steps: (1) Perform V-groove machining on the test plate to be welded; (2) Assemble the test plate to be welded; wherein, the root gap d1 at the arc starting end is 9-12.5mm, and the root gap d2 at the arc ending end is 1.125d1+0.1t×tanα; (3) When using double-wire gas electric vertical welding to fill the weld bead, the front wire swings back and forth and left and right, and the rear wire swings back and forth. Where α is the bevel angle on one side and t is the thickness of the test plate to be welded; When the back yarn swings back and forth, the swing amplitude is 5-15mm.

2. The welding method according to claim 1, characterized in that, When the front yarn swings back and forth and left and right, the swing amplitude of the left and right swing is 25-35mm, and the swing amplitude of the back and forth swing is 10-25mm.

3. The welding method according to claim 1 or 2, characterized in that, When the front yarn swings back and forth and left and right, the dwell time for the left and right swing is 1-2 seconds, and the dwell time for the back and forth swing is 0-1 second.

4. The welding method according to claim 3, characterized in that, Step (3) includes first performing a gas shielded welding for the bottom sealing at the arc starting end of the test plate to be welded, and then using a double-wire gas electric vertical welding to fill the weld bead.

5. The welding method according to claim 4, characterized in that, The front wire uses DC reverse connection, and the rear wire uses DC positive connection.

6. The welding method according to claim 5, characterized in that, The welding current is 380-420A and the voltage is 44-45V.

7. The welding method according to claim 6, characterized in that, The dry extension of the welding wire is 35-45mm.

8. The welding method according to claim 7, characterized in that, The distance between the back wire and the root of the weld is 15-20mm.

9. The welding method according to claim 8, characterized in that, The distance between the front and back yarns is 25-35mm.

10. The welding method according to claim 9, characterized in that, The single-sided bevel angle α is 10°±1.

11. The welding method according to claim 10, characterized in that, The welding speed is 3-5 cm / min.

12. The welding method according to claim 11, characterized in that, The thickness t of the test plate to be welded is 60-85mm.

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