A laser-arc double-sided composite multi-layer welding method for thick plate T-joint

Abstract

This invention belongs to the field of laser arc welding technology, and particularly relates to a laser-arc double-sided composite multi-layer welding method for thick plate T-joints. The steps are as follows: workpiece preparation, including surface treatment of the workpiece; workpiece fixing, including beveling the bottom end of the stiffener plate in the workpiece, fixing the stiffener plate and base plate, and leaving a gap between the stiffener plate and base plate; pre-welding preparation, including installing welding torches and lasers on both sides of the stiffener plate and fixing them with auxiliary devices, connecting the welding torch power supply to the workpiece and welding torch, and connecting the laser power supply to the laser; welding operation, starting the laser and welding torch to begin welding, first performing the root pass welding, and after the root pass welding is completed, performing multi-layer filler welding. Utilizing these structures, the efficiency of root pass welding and multi-layer welding of thick plate T-joints is improved, the stability of the laser and arc welding process is enhanced, welding defects such as incomplete penetration / fusion and porosity are avoided, and the weld microstructure and mechanical properties are improved.

Description

Technical Field

[0001] This invention belongs to the field of laser arc welding technology, and particularly relates to a laser-arc double-sided composite multilayer welding method for thick plate T-joints. Background Technology

[0002] With the continuous development of human science and technology, the quality requirements for thick plate structures in specialized manufacturing fields such as aerospace, pressure vessels, and drilling equipment are becoming increasingly stringent, leading to a growing demand and a continuous increase in the types of materials required. Currently, thick plates are widely used in large equipment such as ships and heavy machinery in industrial production. However, welding problems in the production of thick-walled components are becoming increasingly prominent. Therefore, achieving efficient and reliable connections between thick plates has become one of the key technologies for manufacturing large integral components. Currently, the main welding methods for thick plates include traditional arc welding, electron beam welding, and narrow-gap welding. Traditional arc welding typically requires large-angle, large-area U-shaped or Y-shaped bevels when welding thick plates, achieving welding through multiple layers and passes. Due to the large bevel area, welding efficiency is low.

[0003] Laser welding technology boasts advantages such as high efficiency, high precision, and high automation. Furthermore, with the emergence and rapid development of industrial-grade lasers, laser welding is playing an increasingly important role in several key fields, including automotive, energy, and aerospace. For thick and very thick plates, the filling area of ​​the bevel should be minimized, necessitating a large blunt edge and narrow bevel design. However, when welding large blunt edge bevels with existing high-power lasers, a liquid column easily forms at the molten pool front, generating significant spatter, which severely impacts the weld formation in laser root pass and multi-layer welding.

[0004] Chinese patent "Method for Double-Sided Laser-Arc Composite Welding of Thick Plate T-Joints" (Authorization Announcement No.: CN102126088B), authorized on May 8, 2013, discloses a technical solution that involves mirror-setting two welding torches and two laser beams on both sides of the upright plate of a thick plate T-joint for simultaneous laser-arc composite welding. The distance D between the incident point of the laser beam on the welding area and the end of the welding wire of the welding torch is 2mm to 6mm. Because the distance between the incident point of the laser beam on the welding area and the end of the welding wire of the welding torch is relatively large in this patent, it seriously affects the melting and filling efficiency of the welding wire, and thus affects the welding formation efficiency. Summary of the Invention

[0005] The purpose of this invention is to provide a laser-arc double-sided composite multilayer welding method for thick plate T-joints to solve the above-mentioned problems, improve the efficiency of root pass welding and multilayer welding of thick plate T-joints, improve the stability of laser and CMT / MIG welding processes, avoid welding defects such as incomplete penetration / incomplete fusion and porosity, and improve the weld microstructure and mechanical properties.

[0006] To achieve the above objectives, the present invention provides the following solution:

[0007] A laser-arc double-sided composite multilayer welding method for thick plate T-joints, the steps of which are as follows:

[0008] Workpiece processing involves surface treatment of the welded workpiece to remove impurities from its surface.

[0009] The workpiece is fixed by beveling the bottom end of the stiffening plate in the welded workpiece, arranging the stiffening plate and the base plate in the shape of a T-joint and fixing them with a welding fixture, leaving a gap between the stiffening plate and the base plate.

[0010] Before welding, a welding gun and a laser are installed on both sides of the stiffener and below the base plate, and fixed with auxiliary devices. The power supply of the welding gun is connected to the workpiece and the welding gun, and the power supply of the laser is connected to the laser.

[0011] In the welding operation, the laser and the welding gun are started to begin welding. First, a root pass is performed, and after the root pass is completed, a multi-layer fill pass is performed.

[0012] Preferably, during the root pass welding, a first CMT / MIG welding torch, a first laser beam, a second laser beam, and a shielding gas nozzle are symmetrically arranged sequentially on both sides of the stiffener along the welding direction. A first ultrasonic amplitude transformer is connected to the bottom end of the substrate, with the top of the first ultrasonic amplitude transformer located directly below the first CMT / MIG welding torch. The first ultrasonic amplitude transformer and the first CMT / MIG welding torch are coplanar. A TIG lower welding torch is provided on the bottom surface of the substrate, and the welding point of the TIG lower welding torch is located between the first laser beam and the second laser beam. The first CMT / MIG welding torch and the substrate are electrically connected to a TIG welding torch power supply, and the TIG lower welding torch and the substrate are electrically connected to a TIG power supply.

[0013] Preferably, during multi-layer filler welding, a TIG welding gun, welding wire, a fourth laser beam, a third laser beam, and a second CMT / MIG welding gun are symmetrically arranged sequentially on both sides of the stiffener along the welding direction. A second ultrasonic amplitude transformer is fixedly connected to one side of each of the two TIG welding guns. A TIG lower welding gun is provided on the bottom surface of the substrate. The welding point of the TIG lower welding gun is located between the fourth laser beam and the third laser beam. The welding wire is electrically connected to a hot wire power supply. The first CMT / MIG welding gun and the substrate are electrically connected to a TIG welding gun power supply. The TIG lower welding gun and the substrate are electrically connected to a TIG power supply. The second CMT / MIG welding gun and the substrate are electrically connected to a CMT / MIG welding gun power supply.

[0014] Preferably, the gap height reserved between the stiffening plate and the base plate is 0.01 to 1 mm, the bottom end of the stiffening plate is provided with a bevel, the bevel is a V-shaped bevel, the bevel angle of the bottom end of the stiffening plate is 1° to 40°, and the bottom width of the stiffening plate is greater than 6 mm.

[0015] Preferably, the heat source distance between the two first CMT / MIG welding guns is 0mm; the spot distance between the two first laser beams is 0mm; and the spot distance between the two second laser beams is 0mm.

[0016] Preferably, the filament spacing between the first CMT / MIG welding torch and the first laser beam is 0-1mm, the spot distance between the first laser beam and the second laser beam is 0.3mm-16mm, the first laser beam forms a heat-conducting weld pool, the power of the first laser beam is 60-3000W, and the second laser beam forms a keyhole type weld pool, the power of the second laser beam is 800-10000W.

[0017] Preferably, the ultrasonic vibration frequency of the first ultrasonic amplitude transformer is 10-80 kHz, and the ultrasonic amplitude is 1-70 μm; the wire feed speed of the first CMT / MIG welding torch is 1-10 m / min, and the current is 10-270 A; the shielding gas flow rate of the shielding gas nozzle is 1-60 L / min, and the current of the TIG welding torch is 5-180 A.

[0018] Preferably, the heat source distance between the two second CMT / MIG welding torches on both sides is 0mm; the spot distance between the two third laser beams is 0mm; the spot distance between the two fourth laser beams is 0mm; and the heat source distance between the TIG welding torch and the fourth laser beam is 0-20mm.

[0019] Preferably, the distance between the second CMT / MIG welding torch and the filament of the third laser beam is 0-1mm, the distance between the third laser beam and the fourth laser beam is 0.3mm-16mm, the third laser beam forms a heat-conducting weld pool, the power of the third laser beam is 60-3000W, and the fourth laser beam forms a keyhole weld pool, the power of the fourth laser beam is 800-10000W.

[0020] Preferably, the ultrasonic vibration frequency of the second ultrasonic amplitude transformer is 10-80 kHz, and the ultrasonic amplitude is 1-70 μm; the wire feeding speed of the second CMT / MIG welding torch is 1-10 m / min, the wire feeding speed of the welding wire is 1-10 m / min, the current of the second CMT / MIG welding torch is 10-270 A, and the current of the hot wire power supply is 10 A-300 A.

[0021] Compared with the prior art, the present invention has the following advantages and technical effects:

[0022] 1. During the root pass welding, the ultrasonic cavitation effect, combined with the preheating and melting effect of the low-energy laser beam, allows the liquid droplets to stably enter the gap between the stiffener and the substrate, improving the ductility and fluidity of the liquid droplets, reducing the generation of bubbles, improving the utilization rate of laser energy, and improving the efficiency of root pass welding and the quality of the weld.

[0023] 2. In multi-layer filler welding, the heating arc is in front, which can preheat and bond the base material. At the same time, the energy of ultrasonic vibration is transmitted to the welding site through the TIG welding torch. This can effectively remove the metal oxide film and adsorbed impurities on the surface of each weld layer. This effectively solves the problem of low welding efficiency caused by the need to clean and grind the weld bead and the surrounding area to be welded after each layer of filler welding in existing thick plate multi-layer welding methods. It also allows the welding wire to achieve higher melting and filling efficiency by utilizing the structure in multi-layer filler welding.

[0024] 3. In multi-layer filler welding, along the welding direction, the low-energy TIG welding torch is in front, the fourth laser beam is behind, and the third laser beam acts behind the fourth laser beam. This not only improves the utilization rate of laser energy and welding efficiency, but also helps to melt the solid metal in front of the third laser beam to reduce rigidity, and at the same time changes the shape of the molten pool to suppress the liquid column and welding spatter in the molten pool.

[0025] 4. During the root pass and multi-layer filler passes, the welding wire moves back and forth. The low-energy laser beam and the welding wire are close together, which can play a combined role in attracting and compressing the arc, improving the stability of the arc and the stability of the droplet transfer. Moreover, the welding wire is far away from the high-energy laser beam, so it will not impact the keyhole formed by the high-energy laser beam in the molten pool, improving the stability of the keyhole in the molten pool and reducing the porosity of the weld. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly described below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a schematic diagram illustrating the working principle of the root pass welding of this invention;

[0028] Figure 2 This is a schematic diagram illustrating the working principle of multilayer filler welding in this invention;

[0029] Figure 3 Cross-sectional view of the composite structure of the stiffener and substrate of the present invention;

[0030] Figure 4This is a cross-sectional view of a weld in the prior art under the same process parameters as the root pass welding of this invention;

[0031] Figure 5 A cross-sectional view of the weld seam for the invention of the root pass weld;

[0032] Figure 6 This is a cross-sectional view of a weld in the prior art under the same process parameters as the multilayer filler welding of the present invention;

[0033] Figure 7 This is a cross-sectional view of the weld seam in the multi-layer filler weld of the present invention.

[0034] Reference numerals: 1. First CMT / MIG welding torch; 2. First laser beam; 3. Second laser beam; 4. Keyhole; 5. Molten pool; 6. Rib; 7. Substrate; 8. First ultrasonic amplitude transformer; 9. Shielding gas nozzle; 10. TIG welding torch; 11. Second CMT / MIG welding torch; 12. Third laser beam; 13. Fourth laser beam; 14. Second ultrasonic amplitude transformer; 16. CMT / MIG welding torch power supply; 17. TIG welding torch power supply; 18. TIG lower welding torch; 19. Hot wire power supply; 20. Welding wire; 21. TIG power supply. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0037] Reference Figure 1-7 As shown, a laser-arc double-sided composite multilayer welding method for thick plate T-joints is described, and the steps of the method are as follows:

[0038] Workpiece processing involves surface treatment of the welded workpieces to remove impurities from their surface.

[0039] The workpiece is fixed by beveling the bottom end of the stiffening plate 6 in the welding workpiece, arranging the stiffening plate 6 and the base plate 7 in the shape of a T-joint and fixing them with a welding fixture, leaving a gap between the stiffening plate 6 and the base plate 7.

[0040] Before welding, install welding guns and lasers on both sides of stiffener 6 and below base plate 7, and fix them with auxiliary devices. Connect the power supply of welding gun to the workpiece and welding gun, and connect the power supply of laser to laser.

[0041] For welding operations, start the laser and welding gun to begin welding, first perform the root pass welding, and after the root pass welding is completed, perform multi-layer filler welding.

[0042] During the root pass, the positive terminal of the CMT / MIG welding torch power supply 16 is connected to the first CMT / MIG welding torch 1, and the negative terminal of the CMT / MIG welding torch power supply 16 is connected to the base material. This connection method can improve the droplet transfer efficiency.

[0043] During multi-layer filler welding, the negative terminal of the TIG welding torch power supply 17 is connected to the TIG welding torch 10, and the positive terminal of the TIG welding torch power supply 17 is connected to the base material. This connection method can increase the heat input to the base material and improve the melting efficiency. The positive terminal of the hot wire power supply 19 is connected to the welding wire 20, and the negative terminal of the hot wire power supply 19 is connected to the TIG welding torch 10. This can generate a molten wire arc between the TIG welding torch 10 and the welding wire 20, which not only improves the melting efficiency of the welding wire 20 but also has a smaller thermal impact on the base material.

[0044] To further optimize the design, during the root pass welding, a first CMT / MIG welding torch 1, a first laser beam 2, a second laser beam 3, and a shielding gas nozzle 9 are symmetrically arranged on both sides of the stiffener 6 along the welding direction. A first ultrasonic amplitude transformer 8 is connected to the bottom of the substrate 7. The top of the first ultrasonic amplitude transformer 8 is located directly below the first CMT / MIG welding torch 1. The first ultrasonic amplitude transformer 8 and the first CMT / MIG welding torch 1 are coplanar. A TIG lower welding torch 18 is provided on the bottom surface of the substrate 7. The welding point of the TIG lower welding torch 18 is located between the first laser beam 2 and the second laser beam 3. The first CMT / MIG welding torch 1 and the substrate 7 are electrically connected to a TIG welding torch power supply 17. The TIG lower welding torch 18 and the substrate 7 are electrically connected to a TIG power supply 21.

[0045] refer to Figure 1 As shown, during the root pass welding, the first CMT / MIG welding torch 1 is positioned at the forefront of the forward movement. At this time, the first CMT / MIG welding torch 1 performs welding. The first ultrasonic amplitude transformer 8, located directly below the first CMT / MIG welding torch 1, works in conjunction with the first CMT / MIG welding torch 1 to form ultrasonic cavitation. This refers to the phenomenon where, when the ultrasonic energy is sufficiently high, tiny bubbles (cavitation nuclei) existing in the liquid vibrate, grow, and continuously accumulate acoustic energy under the action of the ultrasonic field. When the energy reaches a certain threshold, the cavitation bubbles rapidly collapse and close. Ultrasonic cavitation can remove bubbles from the liquid droplets at the welding point of the first CMT / MIG welding torch 1, improving the root pass welding efficiency and weld quality. The first laser beam 2, located behind the first CMT / MIG welding torch 1, emits a lower-energy laser to accelerate the extension of the liquid droplets, allowing them to quickly enter the gap reserved between the stiffener 6 and the substrate 7. The second laser beam 3, located behind the first laser beam 2, emits a higher-energy laser, forming a keyhole-shaped molten pool 5 at the weld. Figure 1-2As shown in the keyhole 4, since the welding wire on the first CMT / MIG welding gun 1 is far away from the high-energy second laser beam 3, it will not impact the welding site in the molten pool 5, thus improving the stability of the keyhole type molten pool 5.

[0046] Reference Figure 4 As shown, the weld cross-section obtained by using the existing technology for root pass welding has defects such as incomplete penetration and porosity. This is because when the welding wire of conventional laser filler welding melts, the laser energy required is relatively small when applied to the base material, resulting in incomplete penetration. Furthermore, since the welding wire needs to melt and is close to the high-energy laser beam, it is easy to impact the welding site in the molten pool 5, generating welding bubbles. In addition, the oxide film on the surface of the metal material enters the molten pool 5 and generates metallurgical bubbles, further reducing the quality of the weld.

[0047] The present invention refers to Figure 5 As shown, the root pass welding method of this invention utilizes ultrasonic cavitation and the preheating and melting effect of a low-energy laser beam during the root pass welding operation to rapidly drip liquid droplets into the pre-reserved gap between the stiffener 6 and the substrate 7. This improves the ductility of the liquid droplets, reduces bubble generation, and thus improves laser utilization, welding efficiency, and weld quality. The protective gas nozzle 9 at the rear sprays protective gas forward to protect the welding site.

[0048] In a further optimized design, during multi-layer filler welding, TIG welding torches 10, welding wires 20, a fourth laser beam 13, a third laser beam 12, and a second CMT / MIG welding torch 11 are symmetrically arranged on both sides of the stiffener 6 along the welding direction. A second ultrasonic amplitude transformer 14 is fixedly connected to one side of each of the two TIG welding torches 10. A TIG lower welding torch 18 is provided on the bottom surface of the substrate 7. The welding point of the TIG lower welding torch 18 is located between the fourth laser beam 13 and the third laser beam 12. The welding wire 20 is electrically connected to a hot wire power supply 19. The first CMT / MIG welding torch 1 and the substrate 7 are electrically connected to a TIG welding torch power supply 17. The TIG lower welding torch 18 and the substrate 7 are electrically connected to a TIG power supply 21. The second CMT / MIG welding torch 11 and the substrate 7 are electrically connected to a CMT / MIG welding torch power supply 16.

[0049] Reference Figure 6As shown, in existing multi-layer filler welding operations, porosity is prone to occur in the weld layer of the weld cross-section, and the weld formation of each layer is uneven, reducing the weld quality. This is due to the defects of laser-CMT / MIG hybrid welding. Since the CMT / MIG transition mode differs from ordinary MIG / MAG, it is a short-circuit transition. When the laser filament spacing is too close, it easily interferes with the laser effect, impacting the welding site and causing defects such as porosity. Conversely, when the laser filament spacing is increased, a composite effect cannot be formed, affecting the stability of the arc and the stability of the droplet transfer, thus affecting the weld formation quality. Moreover, the oxide film on the surface of the metal material can easily enter the molten pool 5, forming metallurgical bubbles.

[0050] And reference Figure 2 , 7 As shown, the multi-layer filler welding scheme of this invention is less prone to obvious welding defects between multiple weld layers in the weld cross-section. This is because during multi-layer filler welding, when the welding wire moves forward or backward, the low-energy third laser beam 12 and the welding wire have a close filament spacing, which can play a combined role in attracting and compressing the arc, improving the stability of the arc and the stability of the droplet transfer. Moreover, the welding wire is far from the high-energy fourth laser beam 13, so it will not impact the welding site formed by the high-energy fourth laser beam 13, improving the stability of the welding site and reducing the porosity of the weld. The third laser beam 12 is set at the front of the second CMT / MIG welding torch 11 to reduce the rigidity of the solid metal at the front end of the second CMT / MIG welding torch 11, and at the same time change the shape of the molten pool 5 to suppress the liquid column of the molten pool 5 and welding spatter in high-power laser deep penetration welding.

[0051] Further optimization of the scheme: the gap height reserved between stiffener 6 and base plate 7 is 0.01 to 1 mm; a bevel is set at the bottom end of stiffener 6; the bevel is a V-shaped bevel; the bevel angle at the bottom end of stiffener 6 is 1° to 40°; and the bottom width of stiffener 6 is greater than 6 mm.

[0052] The scheme was further optimized so that the heat source spacing of the first CMT / MIG welding gun 1 on both sides is 0mm; the spot spacing of the two first laser beams 2 is 0mm; and the spot spacing of the two second laser beams 3 is 0mm.

[0053] Further optimization of the scheme: the filament spacing between the first CMT / MIG welding torch 1 and the first laser beam 2 is 0-1mm; the spot distance between the first laser beam 2 and the second laser beam 3 is 0.3mm-16mm; the first laser beam 2 forms a heat-conducting weld pool with a power of 60-3000W; and the second laser beam 3 forms a keyhole weld pool with a power of 800-10000W.

[0054] Further optimization of the scheme: the ultrasonic vibration frequency of the first ultrasonic amplitude transformer 8 is 10-80KHz, and the ultrasonic amplitude is 1-70um; the wire feeding speed of the first CMT / MIG welding torch 1 is 1-10m / min, and the current is 10-270A; the shielding gas flow rate of the shielding gas nozzle 9 is 1-60L / min, and the current of the TIG welding torch 18 is 5-180A.

[0055] Further optimization of the scheme: the heat source spacing of the second CMT / MIG welding torches 11 on both sides is 0mm; the spot spacing of the two third laser beams 12 is 0mm; the spot spacing of the two fourth laser beams 13 is 0mm; and the heat source spacing between the TIG welding torch 10 and the fourth laser beam 13 is 0-20mm.

[0056] Further optimization of the scheme: the filament spacing between the second CMT / MIG welding torch 11 and the third laser beam 12 is 0-1mm; the distance between the third laser beam 12 and the fourth laser beam 13 is 0.3mm-16mm; the third laser beam 12 forms a heat-conducting weld pool with a power of 60-3000W; and the fourth laser beam 13 forms a keyhole weld pool with a power of 800-10000W.

[0057] Further optimization of the scheme: the ultrasonic vibration frequency of the second ultrasonic amplitude transformer 14 is 10-80KHz, and the ultrasonic amplitude is 1-70um; the wire feeding speed of the second CMT / MIG welding torch 11 is 1-10m / min, the wire feeding speed of the welding wire 20 is 1-10m / min, the current of the second CMT / MIG welding torch 11 is 10-270A, and the current of the hot wire power supply 19 is 10A-300A.

[0058] During the root pass and multi-layer fill pass welding, the moving speed of the auxiliary device (i.e., the welding speed) is 0.1m to 5m / min. The second CMT / MIG welding torch 11 can spray shielding gas.

[0059] When the welding speed is below 0.1 mm / min, the heat input to the base material is too high, which affects the weld structure and mechanical properties of the base material and reduces the welding production efficiency. When the welding speed is too high (greater than 5 mm / min), the stability of the welding process decreases, which affects the wetting and spreading effect of the molten droplets after the first CMT / MIG welding torch 1 welding wire melts during the root pass. In multi-layer filler welding, it affects the weld formation and makes it easy to have welding defects such as undercut.

[0060] The auxiliary device is preferably a welding workbench or a welding robot arm and a welding fixture. When a welding workbench is used, the welding workbench moves the T-joint by programming a corresponding welding program. When a welding robot arm and a welding fixture are used, the welding fixture holds the first CMT / MIG welding torch 1, the TIG lower welding torch 18, the first ultrasonic amplitude transformer 8 or the second ultrasonic amplitude transformer 14, and the shielding gas nozzle for the root pass welding. When multi-layer filler welding is performed, the welding fixture holds the TIG welding torch 10, the second CMT / MIG welding torch 11, the first ultrasonic amplitude transformer 8 or the second ultrasonic amplitude transformer 14, and the TIG lower welding torch 18. The welding robot arm is connected to this welding fixture, and the welding robot arm moves the welding fixture by programming a corresponding welding program.

[0061] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0062] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A laser-arc double-sided composite multilayer welding method for T-joints of thick plates, characterized in that, The steps of the method are as follows: Workpiece processing involves surface treatment of the welded workpiece to remove impurities from its surface. The workpiece is fixed by beveling the bottom end of the stiffening plate (6) in the welded workpiece, placing the stiffening plate (6) and the base plate (7) in the shape of a T-joint and fixing them with a welding fixture, leaving a gap between the stiffening plate (6) and the base plate (7). Before welding, a welding gun and a laser are installed on both sides of the stiffener (6) and below the base plate (7), and fixed by an auxiliary device. The power supply of the welding gun is connected to the workpiece and the welding gun, and the power supply of the laser is connected to the laser. In the welding operation, the laser and the welding gun are started to begin welding. First, the root pass is welded, and after the root pass is finished, multiple fill passes are welded. During the root pass welding, a first CMT / MIG welding gun (1), a first laser beam (2), a second laser beam (3), and a protective gas nozzle (9) are symmetrically arranged on both sides of the stiffener (6) along the welding direction. The bottom end of the substrate (7) is connected to a first ultrasonic amplitude transformer (8). The top end of the first ultrasonic amplitude transformer (8) is located directly below the first CMT / MIG welding gun (1). The first ultrasonic amplitude transformer (8) and the first CMT / MIG welding gun (1) are coplanar. The bottom surface of the substrate (7) is provided with a TIG lower welding gun (18). The welding point of the TIG lower welding gun (18) is located between the first laser beam (2) and the second laser beam (3). The first CMT / MIG welding gun (1) and the substrate (7) are electrically connected to a TIG welding gun power supply (17). The TIG lower welding gun (18) and the substrate (7) are electrically connected to a TIG power supply (21). During multi-layer filler welding, TIG welding guns (10), welding wires (20), a fourth laser beam (13), a third laser beam (12), and a second CMT / MIG welding gun (11) are symmetrically arranged on both sides of the stiffener (6) along the welding direction. A second ultrasonic amplitude transformer (14) is fixedly connected to one side of each of the two TIG welding guns (10). A TIG lower welding gun (18) is provided on the bottom surface of the substrate (7). The welding point of the TIG lower welding gun (18) is located between the fourth laser beam (13) and the third laser beam (12). The welding wire (20) is electrically connected to a hot wire power supply (19). The first CMT / MIG welding gun (1) and the substrate (7) are electrically connected to a TIG welding gun power supply (17). The TIG lower welding gun (18) and the substrate (7) are electrically connected to a TIG power supply (21). The second CMT / MIG welding gun (11) and the substrate (7) are electrically connected to a CMT / MIG welding gun power supply (16).

2. The laser-arc double-sided composite multilayer welding method for thick plate T-joints according to claim 1, characterized in that, The gap height reserved between the stiffening plate (6) and the base plate (7) is 0.01~1mm. The bottom end of the stiffening plate (6) is provided with a bevel. The bevel is a V-shaped bevel. The bevel angle of the bottom end of the stiffening plate (6) is 1º~40º. The bottom width of the stiffening plate (6) is greater than 6mm.

3. The laser-arc double-sided composite multilayer welding method for thick plate T-joints according to claim 1, characterized in that, The heat source spacing between the first CMT / MIG welding guns (1) on both sides is 0mm; the spot spacing between the two first laser beams (2) is 0mm; and the spot spacing between the two second laser beams (3) is 0mm.

4. The laser-arc double-sided composite multilayer welding method for thick plate T-joints according to claim 1, characterized in that, The filament spacing between the first CMT / MIG welding torch (1) and the first laser beam (2) is 0~1mm, the spot distance between the first laser beam (2) and the second laser beam (3) is 0.3mm~16mm, the first laser beam (2) forms a heat-conducting weld pool, the power of the first laser beam (2) is 60~3000W, the second laser beam (3) forms a keyhole weld pool, and the power of the second laser beam (3) is 800~10000W.

5. The laser-arc double-sided composite multilayer welding method for thick plate T-joints according to claim 1, characterized in that, The first ultrasonic amplitude transformer (8) has an ultrasonic vibration frequency of 10~80KHz and an ultrasonic amplitude of 1~70um; the first CMT / MIG welding torch (1) has a wire feeding speed of 1~10m / min and a current of 10~270A; the shielding gas flow rate of the shielding gas nozzle (9) is 1~60L / min and the current of the TIG welding torch (18) is 5~180A.

6. The laser-arc double-sided composite multilayer welding method for thick plate T-joints according to claim 1, characterized in that, The heat source spacing between the second CMT / MIG welding torches (11) on both sides is 0 mm; the spot spacing between the two third laser beams (12) is 0 mm; the spot spacing between the two fourth laser beams (13) is 0 mm; the heat source spacing between the TIG welding torch (10) and the fourth laser beam (13) is 0~20 mm.

7. The laser-arc double-sided composite multilayer welding method for thick plate T-joints according to claim 1, characterized in that, The distance between the second CMT / MIG welding torch (11) and the filament of the third laser beam (12) is 0~1mm, the distance between the third laser beam (12) and the fourth laser beam (13) is 0.3mm~16mm, the third laser beam (12) forms a heat-conducting weld pool, the power of the third laser beam (12) is 60~3000W, the fourth laser beam (13) forms a keyhole weld pool, the power of the fourth laser beam (13) is 800~10000W.

8. The laser-arc double-sided composite multilayer welding method for thick plate T-joints according to claim 1, characterized in that, The second ultrasonic amplitude transformer (14) has an ultrasonic vibration frequency of 10~80KHz and an ultrasonic amplitude of 1~70um; the second CMT / MIG welding torch (11) has a wire feeding speed of 1~10m / min, the welding wire (20) has a wire feeding speed of 1~10m / min, the second CMT / MIG welding torch (11) has a current of 10~270A, and the hot wire power supply (19) has a current of 10A-300A.

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