Laser hybrid welding method for butt joint of plates with different thicknesses

Abstract

The invention discloses a laser hybrid welding method for butt joint of plates with different thicknesses, which comprises the following steps of: preheating base metals and / or reducing the gap between the base metals by moving along the length direction of the gap between the base metals under the guidance of a TIG (Tungsten Inert Gas) welding gun, and welding the base metals of which the gap is reduced by moving a laser welding head along the length direction of the gap, meanwhile, the MAG welding gun moves in the length direction of the gap to weld the base metal subjected to laser welding, the gradient of the connecting position of the plates with the different thicknesses is reduced, in the moving process of the laser welding head, two servo motors in the laser welding head drive two reflectors to swing to change the propagation path of laser, and the laser welding is completed. And the laser swings on the two sides of the gap between the to-be-welded base metal in a reciprocating mode, the power of the laser is changed according to the plate thickness of the base metal, and the swing amplitude of the laser is determined according to the width of the gap. The gradient power mode enables the weld penetration depth to be more uniform, heat input to be smaller, laser power to be changed, and the problems of incomplete fusion, incomplete penetration or burn-through in the prior art are solved.

Description

Technical Field

[0001] The invention relates to a laser composite welding method for butting plates of unequal thickness and belongs to the technical field of welding. Background Art

[0002] With the continuous advancement of industrialization, the construction machinery and other equipment industries have entered a new stage, and cranes are one of their important equipment branches. At this stage, higher requirements are put forward for its lifting capacity, flexibility, working space and other performances. As a key component of the crane, the telescopic arm plays a decisive role in the quality of its entire machine. The quality of the two long longitudinal welds of the upper and lower covers of the telescopic arm is crucial and determines the overall quality of the telescopic arm. Its commonly used material is high-strength steel plate, such as Q550-Q1200, etc., with a thickness of 4-12mm.

[0003] The traditional welding method is metal active gas welding (MAG), which has a large heat input, and the workpiece needs to be turned over, which is inefficient. If you want to weld through, you need to make a groove, the welding process is not stable, and the filling material increases. Laser hybrid welding combines the advantages of laser and arc welding, with low heat input, high weld quality, improved bridging ability, easy single-sided welding and double-sided forming, high welding efficiency, saving welding materials and shielding gas, etc. In actual working conditions, the upper plate is generally a thinner grooved steel plate, which is obtained by bending 90°, and the lower plate is a thicker open U-shaped steel plate. The boom often uses a combination of plates of unequal thickness to reduce its own weight while meeting the strength requirements, such as Figure 1 As shown, the plate thickness difference is generally 0-3mm, and the material is high-strength steel for engineering structures.

[0004] In the laser hybrid welding under the existing technology, the laser power is constant, and the gap adaptability is improved to a certain extent compared with conventional laser welding, but the gap compatibility is still poor. Laser oscillation is mostly used in laser self-melting and laser wire filling welding processes. In the field of laser composite, laser oscillation is rarely used. A small number of people use laser oscillation for laser composite, and only use constant laser power, and it is applied to welding of equal thickness plates. For laser hybrid welding of unequal thickness plates, the use of constant laser power may result in incomplete fusion (such as Figure 6 (as shown) Welding defects such as overheating of thin plates, especially when the plate thickness difference is large. Summary of the invention

[0005] The purpose of the present invention is to provide a method for butting plates of unequal thickness by laser composite welding, so as to solve the technical defect in the prior art that incomplete fusion may occur and the welding quality may be affected by using laser composite welding for plates of unequal thickness.

[0006] In order to solve the above problems, the technical solution adopted by the present invention is: a method for butt-jointing laser composite welding of plates of unequal thickness, which adopts a TIG welding gun as a guide, moves along the length direction of the gap between the parent materials to be welded to preheat the parent materials and / or reduce the gap between the parent materials, and the laser welding head moves along the length direction of the gap to weld the parent materials with the reduced gap, and at the same time, the MAG welding gun moves along the length direction of the gap to weld the parent materials after laser welding, thereby reducing the slope of the connection between the plates of unequal thickness. During the movement of the laser welding head, two servo motors therein respectively drive two reflectors to swing to change the propagation path of the laser, so that the laser swings back and forth on both sides of the gap between the parent materials to be welded, and the laser power is changed according to the thickness of the parent material, and the laser swing amplitude is determined according to the width of the gap.

[0007] As a further improvement of the present invention, the laser in the laser welding head oscillates as the laser welding head moves, and the waveform of the laser oscillation is linear, sinusoidal, "8", "∞", C or circular.

[0008] As a further improvement of the present invention, for welding materials that are prone to pores, the laser oscillation waveform adopts an "8" shape, an "∞" shape, or a circle. For welding materials that are not prone to pores, the laser oscillation waveform adopts a straight line, a sine shape, or a C shape.

[0009] As a further improvement of the present invention, the TIG welding gun, laser welding head and MAG welding gun are all installed on the robot's manipulator, and the TIG welding gun and MAG welding gun are respectively located on the front and rear sides of the laser welding head. When in use, the robot's manipulator drives the TIG welding gun, laser welding head and MAG welding gun to move.

[0010] As a further improvement of the present invention, it also includes a teach pendant, which is connected to the robot control cabinet, the TIG welding gun and the MAG welding gun are connected to the TIG power supply and the MAG power supply respectively, the TIG power supply and the MAG power supply are connected to the robot control cabinet, the robot control cabinet is connected to the PLC controller, the current of the TIG welding gun and the current and voltage parameters of the MAG welding gun are set by the teach pendant and transmitted to the TIG power supply and the MAG power supply through the robot control cabinet, the laser is connected to the robot control cabinet and the laser host computer, the laser host computer is used to set the power, laser gradient frequency and power gradient waveform of the laser emitted by the laser when in use and transmit them to the laser, the two servo motors in the laser welding head are connected to the laser control board, the laser control board is connected to the laser head host computer and the robot control cabinet, the laser head host computer is used to set the swing frequency, swing amplitude and waveform of the laser in the laser welding head when in use and transmit them to the laser control board, and the laser control board controls the rotation of the servo motor output shaft.

[0011] As a further improvement of the present invention, the laser is connected to the robot control cabinet via a PLC controller.

[0012] As a further improvement of the present invention, the laser oscillation frequency of the laser welding head is 0-150 Hz, and the swing amplitude is 0-5 mm.

[0013] As a further improvement of the present invention, the power of the laser on the side with a larger thickness of the mother material is greater than the power of the laser on the side with a smaller thickness of the mother material. If the gap width between the mother materials is small, the swing amplitude of the laser is small, and if the gap width between the mother materials is large, the swing amplitude of the laser is large.

[0014] As a further improvement of the present invention, the TIG welding gun melts part of the parent material during guiding, so that the parent materials on both sides of the gap form a partial overlap.

[0015] In summary, the beneficial effects of the present invention are:

[0016] 1. Compared with pure laser welding, the laser hybrid welding process can improve the process bridging ability, increase the adaptability to the gap, reduce the accuracy requirements of incoming materials and parent material assembly accuracy, and is more suitable for general industrial manufacturing conditions.

[0017] 2. Compared with gas shielded welding, the laser hybrid welding process does not require beveling, which greatly reduces the amount of welding wire filling. Therefore, it can greatly reduce welding deformation and save a lot of consumables such as welding wire and shielding gas.

[0018] 3. TIG welding guidance can first melt a small amount of base material on both sides to reduce the gap between the two plates, or even melt the base material on both sides to form a partial overlap, which can reduce the possibility of defects such as welding penetration and lack of fusion due to excessive gap during laser composite welding on the rear side, and indirectly improve the welding quality and stability. TIG guidance also has the function of preheating the base material. The higher the temperature of carbon steel base material, the higher the absorption efficiency of laser. Therefore, preheating the base material can reduce the laser power of welding, thereby improving the stability of the welding process and indirectly reducing welding energy consumption.

[0019] 4. The laser oscillation in the laser welding head further improves the bridging ability, increases the adaptability to the gap, reduces the accuracy requirements of the incoming materials and the assembly accuracy requirements of the parent material, and at the same time stirs the molten pool, reduces defects such as pores and unfused, increases the width of the laser weld, and reduces the difficulty of manual teaching.

[0020] 5. When the laser swings left and right, the power can be set to change gradually, and the left and right peak and base power can be set separately, and the frequency and swing amplitude can also be set separately, so that the penetration depth is more uniform and the strength is higher, avoiding defects such as unfused roots of thick plates and undercuts. When no gradual change is required, the laser power is set unchanged and the welding is restored to constant laser power. Compared with the constant laser power swing mode, the gradual power mode makes the weld penetration more uniform and the heat input is smaller. When the constant laser power swings, in order to ensure the penetration of thin plates, the laser power setting will be too small, but for the thick plate side, the laser power will be obviously too low, resulting in too low heat input, and may cause unfused and incomplete penetration. In order to ensure that the thick plate side can be penetrated, the laser power setting will be too large, but for the thin plate side, the laser power will be obviously too high, resulting in too large heat input. In severe cases, burn-through may even occur. The laser power changes in this application do not have the above problems.

[0021] 6. The present invention has a variety of laser oscillation waveforms to choose from, such as straight line, sinusoidal waveform, "8" shape, "∞" shape, C shape, circle, etc. According to actual needs, the laser composite welding process under TIG guidance can select a suitable process waveform, which has a wide range of applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a cross-sectional view of the boom.

[0023] Figure 2 It is a front view of the distribution of the TIG welding gun, the laser welding head and the MAG welding gun in the present invention.

[0024] Figure 3 It is a left view showing the distribution of the TIG welding gun, the laser welding head and the MAG welding gun in the present invention.

[0025] Figure 4 It is the control circuit diagram in the present invention.

[0026] Figure 5 It is a schematic cross-sectional view of a high-quality weld welded by the present invention.

[0027] Figure 6 It is a schematic cross-sectional view of an unfused weld in laser MAG hybrid welding of the prior art.

[0028] Figure 7 It is a schematic diagram of the main parameters of the laser in the present invention.

[0029] Figure 8 This is a weld diagram of Example 1 of the present invention.

[0030] Fig. 9 This is a weld diagram of Example 2 of the present invention.

[0031] Fig.10 It is the weld diagram of Example 3 of the present invention. DETAILED DESCRIPTION

[0032] The specific implementation modes of the invention are further described below in conjunction with the accompanying drawings.

[0033] The laser composite welding method for butting plates of unequal thickness of the present invention adopts a TIG welding gun as a guide, and moves along the length direction of the gap between the parent materials to be welded to preheat the parent materials and / or reduce the gap between the parent materials. When the TIG welding gun moves, a small amount of parent materials on both sides of the gap can be melted, thereby reducing the gap between the two parent materials, and even the parent materials on both sides are melted to form a local overlap. At the same time, the laser welding head moves along the length direction of the gap to weld the parent materials with the reduced gap. Since the gap between the parent materials is first reduced by the TIG welding gun, or the parent materials are partially overlapped, the possibility of defects such as welding penetration or lack of fusion caused by excessive gap during laser composite welding can be reduced, and the quality and stability of welding can be improved. The TIG welding gun guides the function of preheating the parent material. Because the higher the temperature of the carbon steel parent material, the higher the absorption efficiency of the laser. Therefore, preheating the parent material can reduce the laser power of welding, thereby improving the stability of the welding process and indirectly reducing the welding energy consumption. The present invention also simultaneously moves the MAG welding gun along the length direction of the gap to weld the laser-welded parent material, thereby reducing the slope of the connection between plates of unequal thickness.

[0034] During the movement of the laser welding head, two servo motors located in the laser welding head respectively drive two reflectors to swing and change the propagation path of the laser, so that the laser swings back and forth on both sides of the gap between the parent materials to be welded. The laser swing in the present invention further improves the bridging ability, increases the adaptability to the gap between the parent materials, reduces the accuracy of the incoming materials and the accuracy requirements of the parent material assembly, and at the same time stirs the molten pool, reduces defects such as pores and unfused, increases the width of the laser weld, and reduces the difficulty of manual teaching. The present invention changes the power of the laser according to the thickness of the parent material, and determines the swing amplitude of the laser according to the width of the gap. When welding plates of unequal thickness, the power of the laser on the side with a larger thickness of the parent material is greater than the power of the laser on the side with a smaller thickness of the parent material. If the width of the gap between the parent materials is small, the swing amplitude of the laser is small, and if the gap between the parent materials is large, the swing amplitude of the laser is large.

[0035] The oscillation of the laser in the laser welding head of the present invention moves with the movement of the laser welding head, and the waveform of the laser oscillation is linear, sinusoidal, "8"-shaped, "∞"-shaped, C-shaped, or circular. For metal materials such as aluminum alloys and high-alloy materials, during the welding process, since the surface of the welding wire and the base material contains a small amount of water vapor and oil, it is easy to decompose into gases such as hydrogen, oxygen, and carbon monoxide under high temperature conditions, resulting in easy occurrence of pores during welding. Therefore, for the welding of such materials that are prone to pores during welding, the oscillation waveform of the laser adopts an "8" shape, "∞" shape, or a circle. For metal materials such as carbon steel, which have a large gas solubility and show a low tendency to generate bubbles during welding, it is not easy to have pores during welding. For the welding of such materials, the oscillation waveform of the laser adopts a linear, sinusoidal, or C-shaped waveform.

[0036] In the present invention, the TIG welding gun, the laser welding head and the MAG welding gun are all installed on the manipulator of the robot, and the TIG welding gun and the MAG welding gun are respectively located at the front and rear sides of the laser welding head, wherein the laser welding head is in a vertical state, and the bottom ends of the TIG welding gun and the MAG welding gun are inclined toward the direction of the laser welding head, such as Figure 2 and Figure 3 As shown, in the use state, the robot's manipulator moves to drive the TIG welding gun, laser welding head and MAG welding gun to move synchronously along the length direction of the gap between the base materials. The TIG welding gun and the MAG welding gun are connected to the TIG power supply and the MAG power supply respectively. The TIG power supply and the MAG power supply are connected to the robot control cabinet. The robot control cabinet is connected to the PLC controller and the teach pendant. The current of the TIG welding gun and the current and voltage parameters of the MAG welding gun are set by the teach pendant and transmitted to the TIG power supply and the MAG power supply through the robot control cabinet. The laser is connected to the PLC controller and the laser host computer. The laser host computer is used to set the power, laser gradient frequency and power gradient waveform of the laser emitted by the laser in the use state and transmit them to the laser. The two servo motors in the laser welding head are connected to the laser control board. The laser control board is connected to the laser head host computer and the robot control cabinet. The laser head host computer is used to set the swing frequency, swing amplitude and waveform of the laser in the laser welding head in the use state and transmit them to the laser control board. Figure 4 As shown, the laser control board controls the rotation of the output shaft of the servo motor. The two reflectors in the present invention are respectively fixed on the output shafts of the two servo motors, and the output shafts of the servo motors rotate to drive the two reflectors to swing.

[0037] The laser head control route in the present invention is as follows: the laser swing waveform, swing amplitude and frequency are set on the laser head host computer, and the swing program is transmitted to the laser head control board, thereby controlling the swing of the two servo motors inside the laser head. The reflector on the motor shaft will swing accordingly, thereby changing the propagation path of the laser and realizing the laser swing function.

[0038] The gradual laser control route of the present invention is: set the laser left and right peak power, laser base power, power gradual frequency, and waveform on the laser host computer (wherein the power gradual frequency and waveform must correspond to the laser swing frequency and waveform), such as Figure 7 As shown, the program is transmitted to the laser. At this time, if the laser receives the light output signal, it will emit a laser beam with gradually changing power according to the power, waveform and frequency set by the program, which will be transmitted to the laser head through the optical fiber and finally act on the workpiece.

[0039] The signal control routes of the three aspects of MAG and TIG arc opening and closing, laser opening and closing, laser head internal laser swing opening and closing, and robot action opening and closing in the present invention are as follows: the robot teaching pendant connected to the robot control cabinet sets MAG welding and TIG welding parameters (including arc welding arc starting and arc ending signals), laser light output and light off signals, laser head internal swing opening and closing signals, and robot path planning, etc. Among them, MAG welding and TIG welding parameters (including arc welding arc starting and arc ending signals) are transmitted to the MAG power supply and TIG power supply through the robot control cabinet, and then arc welding is started and welded according to the set parameters through the MAG and TIG welding guns, and finally the arc is closed. The laser light output and light off signals are transmitted to the PLC through the robot control cabinet, and the PLC controls the laser light output and light off. The laser head internal swing opening and closing signals are transmitted to the laser head control board through the robot control cabinet, and the laser head control board controls the start and end of the laser swing. The robot path controls the rotation of each servo motor of the robot through the robot control cabinet to realize the movement of the end of the robot. The robot itself is a prior art and is not an improvement of the present invention.

[0040] The laser oscillation frequency of the laser welding head in the present invention is 0-150 Hz, and the swing amplitude is 0-5 mm.

[0041] Before welding, the present invention sets a suitable TIG welding current according to the thickness and gap of the left and right plates, determines the relative posture of the MAG welding gun and the laser head, sets a suitable filament spacing and laser defocus, then sets the left and right peak power of the laser and the laser base power, then sets the laser swing frequency, swing amplitude and waveform, then selects the power gradient frequency and waveform, and the power gradient frequency and waveform must correspond to the laser swing frequency and waveform, and finally determines the current and voltage of MAG welding. The laser base power in the present invention refers to the power of the laser passing through the gap between the parent materials.

[0042] According to the weld condition after welding, the present invention appropriately adjusts the peak power and swing amplitude on the thick plate side when there is unfused or undercut on the thick plate side of the weld back. If the weld width on the back of the weld is narrow, the swing amplitude can be appropriately adjusted, and the left and right peak powers of the laser and the base power of the laser can be appropriately increased. At the same time, the welds under different waveform conditions can be tested, and the most suitable waveform can be selected to obtain the best weld quality. Figure 5 shown.

[0043] Example 1

[0044] The welding material in this embodiment is high-strength steel LG700 for engineering machinery. The thicknesses of the two plates are 6 mm and 4 mm respectively. They are butt-jointed with a gap of 0 mm. The shielding gas is 82% Ar+18% CO2 with a gas flow rate of 20 L / min. The welding wire is ER100S with a diameter of 1.2 mm.

[0045] The welding parameters are as follows: welding speed is 1.5m / min, TIG welding current is 110A, the distance between the vertical projection point of the TIG tungsten needle tip on the upper surface of the test plate and the center point of the laser beam spot on the test plate is 10mm; the laser power base power is 6.0kW, the laser left peak power is 6.5kW, the laser right peak power is 5.5kW, the power gradient frequency is 100Hz, a sinusoidal gradient waveform is selected, the defocus amount is -2mm, the filament spacing is 3mm, the swing amplitude is 0.4mm, the swing frequency is 100Hz, and a sinusoidal swing waveform is selected; the MAG welding current is 260A, the welding voltage is 26V, and the wire extension length is 17mm.

[0046] The weld penetration is smooth and uniform, achieving the preset welding effect, such as Figure 8 shown.

[0047] Example 2

[0048] The welding material in this embodiment is high-strength steel LG700 for engineering machinery. The thickness of the two plates are 6mm and 5mm respectively. They are butt-jointed with a gap of 0.3mm. The shielding gas is 82% Ar+18% CO2 with a gas flow rate of 20L / min. The welding wire is ER100S with a diameter of 1.2mm.

[0049] The welding parameters are as follows: welding speed is 1.5m / min, TIG welding current is 130A, the distance between the vertical projection point of the TIG tungsten needle tip on the surface of the test plate and the center point of the laser beam spot on the test plate is 10mm; the laser power base power is 6.0kW, the laser left peak power is 6.5kW, the laser right peak power is 5.0kW, the power gradient frequency is 80Hz, a sinusoidal gradient waveform is selected, the defocus amount is -2mm, the filament spacing is 3mm, the swing amplitude is 0.7mm, the swing frequency is 80Hz, and a sinusoidal swing waveform is selected; the MAG welding current is 270A, the welding voltage is 27V, and the wire extension length is 17mm.

[0050] The weld penetration is smooth and uniform, achieving the preset welding effect, such as Fig. 9 shown.

[0051] Example 3

[0052] The welding material in this embodiment is high-strength steel LG700 for engineering machinery. The thicknesses of the two plates are 8mm and 6mm respectively. They are butt-jointed with a gap of 0.6mm. The shielding gas is 82% Ar+18% CO2 with a gas flow rate of 20L / min. The welding wire is ER100S with a diameter of 1.2mm.

[0053] The welding parameters are: welding speed is 1.4m / min, TIG welding current is 130A, the distance between the vertical projection point of the TIG tungsten needle tip on the upper surface of the test plate and the center point of the laser beam spot on the test plate is 10mm; the laser power base power is 6.8kW, the laser left peak power is 7.2kW, the laser right peak power is 6.0kW, the power gradient frequency is 60Hz, a sinusoidal oscillating waveform is selected, the defocus amount is -3mm, the filament spacing is 3.5mm, the swing amplitude is 1.0mm, the swing frequency is 60Hz, and a sinusoidal oscillating waveform is selected; MAG welding current is 300A, welding voltage is 29V, and the wire dry extension length is 17mm.

[0054] The weld penetration is smooth and uniform, achieving the preset welding effect, such as Fig.10 shown.

[0055] The parts not specifically described in the above description are all prior art, or can be implemented by prior art. Moreover, the specific implementation cases described in the present invention are only preferred implementation cases of the present invention, and are not used to limit the scope of implementation of the present invention. That is, all equivalent changes and modifications made according to the content of the patent scope of the present invention should be regarded as the technical scope of the present invention.

Claims

1. A method for butt-jointing plates of unequal thickness by laser composite welding, characterized in that: Guided by a TIG welding gun, the head moves along the length direction of the gap between the base materials to be welded to preheat the base materials and / or reduce the gap between the base materials. The laser welding head moves along the length direction of the gap to weld the base materials with reduced gaps. Meanwhile, the MAG welding gun moves along the length direction of the gap to weld the base materials after laser welding, thereby reducing the slope of the joints of plates of unequal thickness. During the movement of the laser welding head, the two servo motors inside the head respectively drive the two reflectors to swing to change the propagation path of the laser, so that the laser swings back and forth on both sides of the gap between the base materials to be welded, and the laser power is changed according to the thickness of the base materials, and the laser swing amplitude is determined according to the width of the gap.

2. The method for butting plates of unequal thickness according to claim 1 is characterized in that: The oscillation of the laser in the laser welding head moves with the laser welding head, and the waveform of the laser oscillation is linear, sinusoidal, "8", "∞", C or circular.

3. The method for butting plates of unequal thickness according to claim 2 is characterized in that: For welding materials that are prone to pores, the laser oscillation waveform uses an "8" shape, an "∞" shape, or a circle. For welding materials that are not prone to pores, the laser oscillation waveform uses a straight line, a sine wave, or a C shape.

4. The method for butting plates of unequal thicknesses according to claim 1 is characterized in that: The TIG welding gun, laser welding head and MAG welding gun are all installed on the robot's manipulator, and the TIG welding gun and MAG welding gun are located on the front and back sides of the laser welding head respectively. When in use, the robot's manipulator drives the TIG welding gun, laser welding head and MAG welding gun to move.

5. The method for butting plates of unequal thickness according to claim 4 is characterized in that: It also includes a teaching pendant, which is connected to the robot control cabinet. The TIG welding gun and the MAG welding gun are connected to the TIG power supply and the MAG power supply respectively. The TIG power supply and the MAG power supply are connected to the robot control cabinet, and the robot control cabinet is connected to the PLC controller. The current of the TIG welding gun and the current and voltage parameters of the MAG welding gun are set by the teaching pendant and are transmitted to the TIG power supply and the MAG power supply through the robot control cabinet. The laser is connected to the robot control cabinet and the laser host computer. The laser host computer is used to set the power, laser gradient frequency and power gradient waveform of the laser emitted by the laser when in use and transmit them to the laser. The two servo motors in the laser welding head are connected to the laser control board. The laser control board is connected to the laser head host computer and the robot control cabinet. The laser head host computer is used to set the swing frequency, swing amplitude and waveform of the laser in the laser welding head when in use and transmit them to the laser control board. The laser control board controls the rotation of the servo motor output shaft.

6. The method for butting plates of unequal thickness according to claim 5 is characterized in that: The laser is connected to the robot control cabinet through a PLC controller.

7. The method for butting plates of unequal thicknesses according to claim 1 is characterized in that: The laser oscillation frequency of the laser welding head is 0-150Hz, and the swing amplitude is 0-5mm.

8. The method for butting plates of unequal thicknesses according to claim 1 is characterized in that: On the side where the base material thickness is larger, the laser power is greater than that on the side where the base material thickness is smaller. If the gap width between the base materials is small, the laser swing is small, and if the gap width between the base materials is large, the laser swing is large.

9. The method for butting plates of unequal thicknesses according to claim 1 is characterized in that: The TIG welding torch melts part of the base material during the guiding process, so that the base materials on both sides of the gap form a partial overlap.

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