Horizontal position welding method and device for double-laser-assisted MIG electric arc

Abstract

According to the double-laser-assisted MIG arc horizontal position welding method and device, through asymmetric narrow gap groove design (a3gt, a1gt and a2), the angle of an upper side groove is slightly larger than that of a lower side groove, the laser irradiation effect of an upper side wall can be improved, it is guaranteed that the upper side groove can be fully covered with laser and an arc, and the tendency of incomplete fusion defects is reduced; and meanwhile, the lasers are arranged in an asymmetric form, auxiliary lasers are obliquely emitted to the upper side wall of the groove from bottom to top to form an auxiliary laser molten pool, the height (d4) of the molten pool is widened, the problem that the molten pool on the upper side wall is prone to incomplete fusion under the action of gravity during horizontal welding of traditional laser-arc hybrid welding can be effectively solved, and the welding quality is improved.

Description

Technical Field

[0001] This invention relates to the field of welding technology, and more specifically, to a method and apparatus for horizontal welding using a dual-laser assisted MIG arc. Background Technology

[0002] In the welding process of titanium alloy pipes, narrow-gap welding technology has the advantages of high welding efficiency, low heat input, small welding deformation, and excellent weld quality, making it particularly suitable for fields with extremely high welding quality requirements, such as aerospace, shipbuilding, and chemical industries. For pipe structure welding operations, horizontal welding is favored due to its unique process characteristics. By rationally arranging multiple welding machines to operate simultaneously, welding efficiency can be increased several times over.

[0003] During horizontal welding, the weld pool naturally flows downwards due to gravity, making the upper bevel position prone to incomplete fusion defects. This defect manifests as the weld metal failing to fully fuse with the base metal, forming tiny gaps or slag inclusions. According to actual production statistics, without special measures, the incidence of incomplete fusion defects at the upper bevel position during horizontal welding is as high as 15%–20%, severely affecting the mechanical properties of the welded joint. Traditional welding process optimization methods, such as increasing welding heat input and adjusting welding angles, can improve the incomplete fusion problem to some extent, but often lead to other undesirable results, such as an expanded heat-affected zone and increased welding deformation. Especially in the welding of titanium alloys, which are extremely sensitive to heat input, excessive heat input can significantly reduce the mechanical properties of the joint. Patent 202411554539.1 innovatively combines an asymmetric inclined bevel with asymmetric arc oscillation and asymmetric vibration wire feeding technology, effectively reducing the impact of gravity on the weld pool. However, the welding speed is slow, with wire feeding speed typically at 1-2 m / min, and each filler layer thickness is approximately 2 mm, making defect control relatively easy. In contrast, MIG welding has a faster wire feeding speed, typically 8-10 m / min, with each filler layer thickness approximately 5-8 mm, and a weld pool volume approximately five times that of TIG. Stabilizing the weld pool is difficult during horizontal welding. Furthermore, in traditional laser-MIG horizontal welding, the presence of the laser further exacerbates the downward flow of the weld pool, leading to incomplete fusion on the upper side of the horizontal weld bevel and excessive fusion on the lower side. Additionally, the large size of the welding torch tip in narrow-gap MIG welding prevents the up-down and left-right oscillations seen in TIG welding, which can easily cause short circuits with the sidewalls during oscillation. Therefore, controlling the weld pool stability is extremely difficult, and there are currently no research reports on laser-MIG horizontal welding in the industry.

[0004] Therefore, there is an urgent need for a welding method that can effectively solve the lack of fusion defects in the MIG horizontal welding process while ensuring welding quality. Summary of the Invention

[0005] The purpose of this invention is to provide a horizontal welding method and apparatus using dual laser-assisted MIG arc welding. By using an asymmetric narrow gap bevel design (a3>a1>a2) and an asymmetric dual laser-assisted welding method, the problem of incomplete fusion of the sidewall at the upper bevel position during horizontal welding is solved, thereby achieving efficient and high-quality titanium alloy pipe welding.

[0006] To achieve the above objectives, the present invention provides a horizontal welding method using a dual-laser assisted MIG arc, comprising the following steps:

[0007] Step S1: Fix the pipe: Place the titanium alloy pipe opening vertically and fix it by horizontal welding;

[0008] Step S2 Bevel Design: Asymmetrical narrow gap bevels are machined on the titanium alloy pipe. The angle between the upper sidewall of the bevel and the horizontal plane is a1, and the angle between the lower sidewall and the horizontal plane is a2. The edge of the lower sidewall is chamfered, and the angle between the plane where the chamfer is located and the horizontal plane is a3, where a3>a1>a2.

[0009] Step S3 Laser preheating: Start the main laser (3-2) and the auxiliary laser (3-3). The laser emitted by the auxiliary laser (3-3) is obliquely shot from bottom to top along the first optical path (3-2c) to the upper side wall of the bevel to form an auxiliary laser molten pool (3-3a). The laser emitted by the main laser (3-2) is shot into the root of the bevel along the horizontal direction (3-1c) to form a main laser molten pool (3-2a), for preheating and fusion.

[0010] Step S4 Arc Welding: Start the MIG arc welding torch (3-1) and make the MIG arc welding torch (3-1) burn stably under the guidance of the laser. The MIG arc welding torch (3-1) and the main laser (3-2) are injected into the root of the bevel in the same horizontal direction (3-1c) to form an arc molten pool (3-1a). The arc molten pool (3-1a) forms a eutectic pool with the main laser molten pool (3-2a) and the auxiliary laser molten pool (3-3a).

[0011] Step S5 Parameter Adjustment: Monitor the molten pool morphology and temperature distribution in real time. When the molten pool width fluctuation is ≤1mm, it is considered stable. If it is unstable, dynamically adjust the power of the main laser and the auxiliary laser, the MIG arc parameters, the welding speed and the turntable speed.

[0012] Furthermore, the values ​​of a1, a2, and a3 are 8°~12°, 5°~8°, and 12°~24°, respectively.

[0013] During horizontal welding, the molten pool metal flows downwards naturally due to gravity, resulting in insufficient heating of the upper sidewall of the bevel and causing incomplete fusion defects, which affects the quality of the weldment. This invention addresses this issue with a special bevel design, setting a1>a2 to increase the laser irradiation effect on the upper sidewall; and a3>a2 to prevent the lower side of the bevel from blocking the first optical path formed by the secondary laser, thereby expanding the molten pool area on the upper side of the bevel and reducing the tendency for incomplete fusion defects caused by gravity.

[0014] In this invention, the values ​​of a1-a2 are preferably greater than 0 and less than 5°; this setting can effectively prevent the secondary laser from deviating and reduce the occurrence of incomplete fusion defects on the lower sidewall of the bevel.

[0015] Furthermore, the diameter of the titanium alloy pipe is 3~8m, the weld length is 10~30m, and the wall thickness is not less than 20mm; the root gap width of the asymmetric narrow gap bevel is 8~12mm, and the top gap width is 14~20mm.

[0016] Traditional flat welding methods for large-diameter pipes typically require large equipment to be placed horizontally and fixed to the pipes, resulting in a large footprint and inconvenience due to the inability to weld in situ. This invention employs horizontal welding to weld titanium alloy pipes with diameters of 3-8m, making it convenient to use when the pipes are difficult to move or rotate.

[0017] The root of the bevel is preferably designed as an arc to reduce stress concentration and improve welding quality.

[0018] Furthermore, in step S3, the depth of the eutectic pool reaches 1-3 mm. This setting ensures full fusion of the bevel sidewalls and root, avoiding incomplete fusion defects.

[0019] This invention first uses laser for preheating. The main laser is injected horizontally into the root of the bevel to induce stable combustion of the MIG arc. The auxiliary laser is injected obliquely upwards to the upper sidewall of the bevel, directly preheating and melting the metal of the upper sidewall, compensating for the downward flow of the molten pool caused by gravity, so that the depth of the molten pool reaches 1~3mm, and the sidewall and root of the bevel are fully fused.

[0020] Furthermore, in step S4, the wire feed speed of the MIG arc welding gun (3-1) is 5~10m / min, the power of the main laser (3-2) is 3~10kW, and the power of the auxiliary laser (3-3) is 1~6kW.

[0021] The primary and secondary lasers preferably have a scanning swing function.

[0022] In this invention, the main and auxiliary lasers are turned on first, and MIG arc welding is turned on after 2 to 3 seconds; the main and auxiliary lasers preferably oscillate periodically.

[0023] Furthermore, each time the position of the secondary laser (3-3) moves, the first optical path (3-2c) moves accordingly, which is recorded as one welding operation. The thickness of the weld layer formed by each welding operation is 6~10mm.

[0024] The present invention also provides a horizontal welding device for dual laser-assisted MIG arc welding, which is applied to the horizontal welding method of dual laser-assisted MIG arc welding described in the above technical solution. The device includes a rotating fixing unit (4) for placing a titanium alloy pipe (1) to be welded. The device also includes a dual laser-assisted MIG arc welding unit (3) and a position adjustment unit (2). One end of the position adjustment unit (2) is connected to the dual laser-assisted MIG arc welding unit (3).

[0025] The dual-laser assisted MIG arc welding unit (3) includes a MIG arc welding torch (3-1), a main laser (3-2), a secondary laser (3-3), and a rotating mechanical unit (3-4); the laser emitted by the main laser (3-2) and the MIG arc welding torch (3-1) are concentrically arranged; the secondary laser (3-3) is arranged on the rotating mechanical unit (3-4) for adjusting the incident angle of the secondary laser (3-2).

[0026] Furthermore, the dual laser-assisted MIG arc welding device (3) also includes a protective cover (3-5), which is disposed on the side of the MIG arc welding gun (3-1) near the titanium alloy pipe (1).

[0027] This invention uses a protective cover to control the interpass temperature of welding to below 150°C and maintains the temperature of the MIG arc welding torch at ≤80°C.

[0028] In this invention, the protective cover is preferably a water-cooled copper protective cover to ensure the stable operation of the laser head and MIG welding torch in a high-temperature environment.

[0029] Furthermore, one end of the rotating mechanical unit (3-4), the main laser (3-2), and the MIG arc welding gun (3-1) is connected to a fixing device (5), and one end of the fixing device (5) is connected to a position adjustment unit (2) for adjusting the position of the laser and the MIG arc welding gun.

[0030] Furthermore, the dual laser-assisted MIG arc welding unit (3) has multiple units that are equally spaced along the rotating fixing unit (4).

[0031] This invention employs multiple sets of dual-laser assisted MIG arc welding units symmetrically distributed around the pipe to achieve symmetrical parallel transverse welding. Compared with the traditional flat welding method, which can only be performed by one welding machine located directly above the pipe weld, this invention further improves efficiency.

[0032] In this invention, a robotic arm and a motion truss are preferably used to fix and connect the dual laser-assisted MIG arc welding unit for spatial position adjustment of the welding device.

[0033] This invention employs an asymmetrical narrow-gap bevel design (a3>a1>a2), where the upper bevel angle is slightly larger than the lower bevel angle. This increases the laser irradiation effect on the upper sidewall, ensuring that the laser and arc fully cover the upper bevel and reducing the tendency for incomplete fusion defects. Simultaneously, the laser is arranged asymmetrically, with the main laser and arc welding torch concentrically connected. The main laser molten pool is located in front of the arc welding molten pool, forming a traditional laser-arc hybrid welding structure with the arc welding torch. This creates a eutectic pool on the weld bead, effectively suppressing spatter and increasing penetration. The secondary laser, following the first beam, diagonally crosses upwards above the bevel sidewall, assisting in widening the upper sidewall molten pool. This effectively suppresses incomplete fusion defects that easily occur in the upper sidewall molten pool under gravity during traditional laser-arc hybrid horizontal welding, thus improving welding quality.

[0034] Compared with existing technologies, the method for dual-laser assisted MIG arc welding of titanium alloy pipes described in this invention has the following advantages:

[0035] (1) The present invention uses horizontal welding for welding. Compared with traditional flat welding, multiple parallel welding mechanical motion mechanisms can be used, which has good welding adaptability, effectively improves the welding efficiency of titanium alloy pipe circumferential welds, and shortens the manufacturing cycle.

[0036] (2) The present invention uses dual laser-assisted MIG arc to overcome the problem that the welding torch contact tip is large in the existing MIG narrow gap welding, and cannot be swung up, down and left and right like TIG welding. When swung, it is easy to short-circuit with the side wall discharge. The laser significantly enhances the stability of the MIG arc, gives full play to the advantages of MIG filling efficiency, and effectively improves welding efficiency and welding quality.

[0037] (3) Innovative bevel design, combined with asymmetric dual-laser assisted MIG arc, effectively solves the sidewall non-fusion defect and releases the quality risk of titanium alloy pipe circumferential weld. Attached Figure Description

[0038] Figure 1 A schematic diagram of a titanium alloy pipe and a multi-parallel welding mechanical motion mechanism;

[0039] Figure 2 Schematic diagram of a dual-laser assisted MIG arc welding device;

[0040] Figure 3 This is a schematic diagram of the bevel shape and laser optical path;

[0041] Figure 4 This is a schematic diagram showing the dimensional relationship of the molten pool;

[0042] Figure 5 This is a schematic diagram of the melt layer.

[0043] Explanation of reference numerals in the attached figures:

[0044] 1. Titanium alloy pipe; 1-1. Asymmetric narrow gap bevel; 2. Position adjustment unit; 3. Dual laser assisted MIG arc welding unit; 4. Rotation and fixing unit; 3-1. MIG arc welding torch; 3-1a. Arc molten pool; 3-2. Main laser; 3-2a. Main laser molten pool; 3-1c. Horizontal direction; 3-2c. First optical path; 3-3. Secondary laser; 3-3a. Secondary laser molten pool; 3-4. Rotational mechanical unit; 3-5. Protective cover; 5. Fixing device. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the described embodiments are only some, not all, of the embodiments of this invention. The specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0046] It should be noted that all directional and positional terms used in this invention, such as "up," "down," "left," "right," "front," "back," "vertical," "horizontal," "inner," "outer," "top," "lower," "tail end," "head end," and "center," are only used to explain the relative positional relationships and connection situations between components in a specific state. They are merely for the convenience of describing the invention and do not require the invention to be constructed and operated in a specific orientation; therefore, they should not be construed as limitations on the invention. Furthermore, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Additionally, the meaning of "and / or" throughout the text includes three parallel solutions. Taking "A and / or B" as an example, it includes solution A, solution B, or a solution where both A and B are satisfied simultaneously.

[0047] In this invention, unless otherwise explicitly specified and limited, the terms "connection," "fixed," etc., should be interpreted broadly. For example, "fixed" can mean a fixed connection, a detachable connection, or an integral part; it can mean a mechanical connection or an electrical connection; it can mean a direct connection or an indirect connection through an intermediate medium; it can mean the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0048] Example 1:

[0049] Implementation of titanium alloy pipe welding process

[0050] Four high-precision welding robots are symmetrically installed around the pipe to achieve precise adjustment of the spatial position of the welding torch.

[0051] Pipe parameters: Diameter: 4m, Wall thickness: 50mm, Material: TA2 titanium alloy, Bevel design: Root gap width: 10mm, Top gap width: 20mm, Bevel bottom radius: R=3mm.

[0052] Beveling design: a1 is 10°, a2 is 6°, and a3 is 18°.

[0053] Laser-MIG hybrid welding torch settings: Main laser power: 6kW, secondary laser power: 3kW; MIG arc parameters: wire feed speed: 8m / min. The welding machine adjusts the arc current and voltage according to the TA2 titanium alloy material and 50mm wall thickness to ensure arc stability and sufficient penetration. Ensure a single-layer filler weld thickness of 5-8mm.

[0054] Welding process:

[0055] Step 1: Initial Positioning

[0056] Fix the titanium alloy pipe on a high-precision turntable and adjust the pipe position so that the center of the bevel is aligned with the welding torch.

[0057] The welding path and parameters are set by the control system, including laser power (6kW for the main laser and 3kW for the auxiliary laser), MIG arc parameters (wire feed speed 8m / min), and the rotation speed of the turntable is adjusted to control the welding speed.

[0058] Step 2: Dual-laser cross-scanning

[0059] The dual-laser system is activated, with the main laser spot positioned in front of the weld pool and the secondary laser spot incident from bottom to top onto the upper sidewall of the bevel.

[0060] The main laser preheats and fuses the root of the bevel, while the secondary laser covers a 2mm area on the upper sidewall of the bevel to ensure that the sidewall and root of the bevel are fully preheated.

[0061] Step 3: MIG Arc Start

[0062] After the laser-molten pool is formed, the MIG arc is initiated. The arc burns stably under the induction of the laser-molten pool, forming a eutectic pool with the laser-molten pool.

[0063] Step 4: Welding Process Control

[0064] A real-time CCD image monitoring system monitors the molten pool morphology and temperature distribution, and determines the weld to be stable when the molten pool width fluctuation is ≤1mm. The control system dynamically adjusts the laser power, arc parameters, and welding speed to ensure welding quality.

[0065] Welding results:

[0066] All layers are welded sequentially, with a single layer filler thickness of 5-6 mm. Weld quality: free from defects such as incomplete fusion and cracks; stable molten pool morphology; and significantly improved welding efficiency.

[0067] After welding, ultrasonic testing and X-ray inspection were used to check the weld quality. The weld was free of defects such as lack of fusion and cracks. The ultrasonic testing results showed that there were no defects inside the weld, and the X-ray inspection results showed that the weld density was uniform and met the Class I requirements in NB / T47013.2 standard.

[0068] Mechanical property testing

[0069] Tensile tests were conducted on the welded joint, and the test results showed that the tensile strength of the welded joint reached more than 95% of that of the base material.

[0070] Example 2

[0071] Implementation of titanium alloy pipe welding process

[0072] Four high-precision welding robots are symmetrically installed around the pipe to achieve precise adjustment of the spatial position of the welding torch.

[0073] Pipe parameters: Diameter: 4m, Wall thickness: 50mm, Material: TA2 titanium alloy, Bevel design: Root gap width: 10mm, Top gap width: 20mm, Bevel bottom radius: R=3mm.

[0074] Beveling design: a1 is 12°, a2 is 8°, and a3 is 20°.

[0075] Laser-MIG hybrid welding torch settings: Main laser power: 6kW, secondary laser power: 3kW; MIG arc parameters: wire feed speed: 9m / min. The welding machine adjusts the arc current and voltage according to the TA2 titanium alloy material and 50mm wall thickness to ensure arc stability and sufficient penetration. Ensure a single-layer filler weld thickness of 6-9mm.

[0076] Welding process:

[0077] Step 1: Initial Positioning

[0078] Fix the titanium alloy pipe on a high-precision turntable and adjust the pipe position so that the center of the bevel is aligned with the welding torch.

[0079] The welding path and parameters are set through the control system, including laser power (6kW for the main laser and 3kW for the auxiliary laser), MIG arc parameters (wire feed speed 9m / min), and the turntable speed is adjusted to control the welding speed.

[0080] Step 2: Dual-laser cross-scanning

[0081] The dual-laser system is activated, with the main laser spot positioned in front of the weld pool and the secondary laser spot incident from bottom to top onto the upper sidewall of the bevel.

[0082] The main laser preheats and fuses the root of the bevel, while the secondary laser covers a 2mm area on the upper sidewall of the bevel to ensure that the sidewall and root of the bevel are fully preheated.

[0083] Step 3: MIG Arc Start

[0084] After the laser-molten pool is formed, the MIG arc is initiated. The arc burns stably under the induction of the laser-molten pool, forming a eutectic pool with the laser-molten pool.

[0085] Step 4: Welding Process Control

[0086] A real-time CCD image monitoring system monitors the molten pool morphology and temperature distribution, and determines the weld to be stable when the molten pool width fluctuation is ≤1mm. The control system dynamically adjusts the laser power, arc parameters, and welding speed to ensure welding quality.

[0087] Welding results:

[0088] All layers are welded sequentially, with a single layer filler thickness of 6-9 mm. Weld quality: free from defects such as incomplete fusion and cracks; stable molten pool morphology; and significantly improved welding efficiency.

[0089] After welding, ultrasonic testing and X-ray inspection were used to check the weld quality. The weld was free of defects such as lack of fusion and cracks. The ultrasonic testing results showed that there were no defects inside the weld, and the X-ray inspection results showed that the weld density was uniform and met the Class I requirements in NB / T47013.2 standard.

[0090] Mechanical property testing

[0091] Tensile tests were conducted on the welded joint, and the test results showed that the tensile strength of the welded joint reached more than 95% of that of the base material.

[0092] Example 3

[0093] Implementation of titanium alloy pipe welding process

[0094] Four high-precision welding robots are symmetrically installed around the pipe to achieve precise adjustment of the spatial position of the welding torch.

[0095] Pipe parameters: Diameter: 4m, Wall thickness: 50mm, Material: TA2 titanium alloy, Bevel design: Root gap width: 10mm, Top gap width: 20mm, Bevel bottom radius: R=3mm.

[0096] Beveling design: a1 is 9°, a2 is 5°, and a3 is 15°.

[0097] Laser-MIG hybrid welding torch settings: Main laser power: 6kW, secondary laser power: 3kW; MIG arc parameters: wire feed speed: 6m / min. The welding machine adjusts the arc current and voltage according to the TA2 titanium alloy material and 50mm wall thickness to ensure arc stability and sufficient penetration. Ensure a single-layer filler weld thickness of 4-6mm.

[0098] Welding process:

[0099] Step 1: Initial Positioning

[0100] Fix the titanium alloy pipe on a high-precision turntable and adjust the pipe position so that the center of the bevel is aligned with the welding torch.

[0101] The welding path and parameters are set by the control system, including laser power (6kW for the main laser and 3kW for the auxiliary laser), MIG arc parameters (wire feed speed 6m / min), and the turntable speed is adjusted to control the welding speed.

[0102] Step 2: Dual-laser cross-scanning

[0103] The dual-laser system is activated, with the main laser spot positioned in front of the weld pool and the secondary laser spot incident from bottom to top onto the upper sidewall of the bevel.

[0104] The main laser preheats and fuses the root of the bevel, while the secondary laser covers a 2mm area on the upper sidewall of the bevel to ensure that the sidewall and root of the bevel are fully preheated.

[0105] Step 3: MIG Arc Start

[0106] After the laser-molten pool is formed, the MIG arc is initiated. The arc burns stably under the induction of the laser-molten pool, forming a eutectic pool with the laser-molten pool.

[0107] Step 4: Welding Process Control

[0108] A real-time CCD image monitoring system monitors the molten pool morphology and temperature distribution, and determines the weld to be stable when the molten pool width fluctuation is ≤1mm. The control system dynamically adjusts the laser power, arc parameters, and welding speed to ensure welding quality.

[0109] Welding results:

[0110] All layers are welded sequentially, with a single layer filler thickness of 4-6 mm. Weld quality: free from defects such as incomplete fusion and cracks; stable molten pool morphology; and significantly improved welding efficiency.

[0111] After welding, ultrasonic testing and X-ray inspection were used to check the weld quality. The weld was free of defects such as lack of fusion and cracks. The ultrasonic testing results showed that there were no defects inside the weld, and the X-ray inspection results showed that the weld density was uniform and met the Class I requirements in NB / T47013.2 standard.

[0112] Mechanical property testing

[0113] Tensile tests were conducted on the welded joint, and the test results showed that the tensile strength of the welded joint reached more than 95% of that of the base material.

[0114] Comparative Example 1

[0115] The titanium alloy pipe was welded using the process method of Example 1, with the only difference being: in step two, dual laser cross scanning was performed, with symmetrical, periodically oscillating lasers set up, and the main laser spot and the secondary laser spot located on both sides of the weld pool, symmetrically distributed.

[0116] Welding results:

[0117] The spatter was obvious, the weld formation was poor, and the appearance did not meet the requirements of non-destructive testing. Ultrasonic testing results showed that there were no fusion, cracks and a large number of pore defects inside the weld.

[0118] Mechanical property testing

[0119] Tensile tests were conducted on the welded joint, and the results showed that the tensile strength of the welded joint did not reach 80% of that of the base material.

[0120] Comparative Example 2

[0121] Titanium alloy pipes were welded using the process method of Example 1, with the only difference being the bevel design: a1 is 10°, a2 is 10°, and a3 is 18°.

[0122] Welding results:

[0123] The molten pool flows downward under the influence of gravity, resulting in poor weld formation. Ultrasonic testing revealed localized incomplete fusion defects on the upper sidewall.

[0124] Mechanical property testing

[0125] Tensile tests were conducted on the welded joints, and the results showed that the tensile strength of the welded joints was not all higher than 90% of that of the base material, and some individual samples were lower than 80% of that of the base material.

[0126] Comparative Example 3

[0127] Titanium alloy pipes were welded using the process method of Example 1, with the only difference being the bevel design: a1 is 10°, a2 is 6°, and a3 is 6°.

[0128] Welding results:

[0129] The secondary laser directly penetrates the lower side of the bevel, but is blocked and cannot penetrate to the bottom, resulting in more spatter and poor weld formation. Ultrasonic testing results show that there are many non-fusion defects on the upper sidewall and a large number of pore defects inside the weld.

[0130] Mechanical property testing

[0131] Tensile tests were conducted on the welded joint, and the results showed that the tensile strength of the welded joint did not reach 80% of that of the base material.

[0132] Comparative Example 4

[0133] Titanium alloy pipes were welded using the process method of Example 1, with the only difference being the bevel design: a1 is 12°, a2 is 5°, and a3 is 20°.

[0134] Welding results:

[0135] The difference between the upper and lower bevel angles is greater than 7° (the values ​​of a1-a2), which causes the bottom position of the secondary laser incident to shift. Ultrasonic testing results show that there are some unfused defects on the upper sidewall.

[0136] Mechanical property testing

[0137] Tensile tests were conducted on the welded joints, and the test results showed that the tensile strength of the welded joints was not all higher than 90% of that of the base material, and the tensile strength of some individual samples was lower than 80% of that of the base material.

[0138] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A method of twin laser assisted MIG arc horizontal welding characterized by, The method comprises the following steps: Step S1: fixing the pipe: placing the titanium alloy pipe in a vertical direction and fixing it by horizontal welding; Step S2: designing a groove: processing an asymmetric narrow-gap groove on the titanium alloy pipe, the included angle between the upper side wall of the groove and the horizontal plane is a1, the included angle between the lower side wall and the horizontal plane is a2, the edge of the lower side wall is provided with a chamfer, and the included angle between the plane where the chamfer is located and the horizontal plane is a3, wherein a3>a1>a2; Step S3: laser preheating: starting the main laser (3-2) and the auxiliary laser (3-3), the laser emitted by the auxiliary laser (3-3) is obliquely incident on the upper side wall of the groove from bottom to top along the first light path (3-2c) to form an auxiliary laser molten pool (3-3a), and the laser emitted by the main laser (3-2) is incident on the root of the groove along the horizontal direction (3-1c) to form a main laser molten pool (3-2a) for preheating and fusion; Step S4: arc welding: starting the MIG arc welding gun (3-1), and making the MIG arc welding gun (3-1) stably burn under the induction of the laser, the MIG arc welding gun (3-1) and the main laser (3-2) are incident on the root of the groove along the same horizontal direction (3-1c) to form an arc molten pool (3-1a), and the arc molten pool (3-1a) forms a common molten pool with the main laser molten pool (3-2a) and the auxiliary laser molten pool (3-3a); Step S5: parameter control: real-time monitoring of the molten pool shape and temperature distribution, when the molten pool width fluctuation is ≤1mm, it is determined to be stable, if not, the power of the main laser and the auxiliary laser, the MIG arc parameters, the welding speed and the rotation speed of the rotary table are dynamically adjusted.

2. The method of claim 1, wherein, The values of a1, a2 and a3 are respectively 8°-12°, 5°-8° and 12°-24°.

3. The method according to claim 1 or 2, characterized in that, The diameter of the titanium alloy pipe is 3-8m, the weld length is 10-30m, and the wall thickness is not less than 20mm; the root gap width of the asymmetric narrow-gap groove is 8-12mm, and the top gap width is 14-20mm.

4. The method according to claim 1 or 2, characterized in that, In step S3, the depth of the common molten pool reaches 1-3mm.

5. The method of claim 1, wherein, In step S4, the wire feeding speed of the MIG arc welding gun (3-1) is 5-10m / min, the power of the main laser (3-2) is 3-10kW, and the power of the auxiliary laser (3-3) is 1-6kW.

6. The method of claim 1, wherein, The position of the auxiliary laser (3-3) moves once, and the first light path (3-2c) moves accordingly, which is recorded as one welding, and the thickness of the welding layer formed by each welding is 6-10mm.

7. A twin laser assisted MIG arc horizontal welding apparatus characterized by, The method is applied to the horizontal welding method of the double-laser assisted MIG arc in any one of claims 1-7, which comprises a rotating fixing unit (4) for placing the titanium alloy pipe (1) to be welded, and the device further comprises a double-laser assisted MIG arc welding unit (3) and a position adjusting unit (2), one end of the position adjusting unit (2) is connected with the double-laser assisted MIG arc welding unit (3). The double laser assisted MIG arc welding unit (3) comprises a MIG arc welding gun (3-1), a main laser (3-2), a secondary laser (3-3) and a rotating mechanical unit (3-4); the laser emitted by the main laser (3-2) and the MIG arc welding gun (3-1) are concentrically arranged; the secondary laser (3-3) is arranged on the rotating mechanical unit (3-4) and used for adjusting the incident angle of the secondary laser (3-2).

8. The apparatus of claim 7, wherein, The double laser assisted MIG arc welding device (3) further comprises a protective cover (3-5) arranged on the side of the MIG arc welding gun (3-1) close to the titanium alloy pipeline (1).

9. The apparatus of claim 7, wherein, The rotating mechanical unit (3-4), the main laser (3-2) and the MIG arc welding gun (3-1) are connected with a fixing device (5) at one end, and the fixing device (5) is connected with a position adjusting unit (2) at one end, which is used for adjusting the positions of the laser and the MIG arc welding gun.

10. The apparatus of claim 7, wherein, The double laser assisted MIG arc welding unit (3) is multiple and distributed at equal intervals along the rotating fixing unit (4).

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