Metal inert gas arc welding process and arrangement for carrying out the process

Abstract

A metal inert gas arc welding process in which a multi-wire welding torch (40) is mechanized along a path to execute a predetermined weld seam on a workpiece (32, 100a, 100b, 101a, 101b), and in which a first arc (51) is generated between a first consumable wire electrode (50) and the workpiece, and a second arc (61) is generated between a second consumable wire electrode (60) and the workpiece to transfer wire electrode material into a weld pool, wherein the first wire electrode (50) is supplied by a first power source (4) and the second wire electrode (60) by a second power source (6), and at least a third wire (70) is fed directly into the weld pool, wherein the first and second wire electrodes (50, 60) and the third wire (70) are guided in the multi-wire welding torch (40) such that the wires exiting the multi-wire welding torch (40) (50, 60,70) essentially lie in a common plane (GE) and that in the common plane the first wire electrode (50) and the second wire electrode (60) form an angle of equal magnitude with opposite signs to the third wire (70), characterized in that, during the execution of the metal inert gas arc welding process, starting from a predetermined direction of movement of the multi-wire welding torch (40) to the path line, the multi-wire welding torch (40) is moved backwards on the path line without rotation of the multi-wire welding torch (40) to perform a reversal of movement, and with the beginning of the backward movement of the multi-wire welding torch (40), the third wire (70) is initially not fed into the weld pool, and thereafter, in a transition phase, a current source (5) of the third wire (70) is supplied starting from a predetermined initial operating value of at least one process parameter current,Voltage and feed rate are controlled to a predetermined steady-state operating value of at least one process parameter.

Description

[0001] The invention relates to a metal inert gas arc welding process in which a multi-wire welding torch is mechanized along a path to execute a predetermined weld seam on a workpiece, and in which a first arc is generated between a first consumable wire electrode and the workpiece, and a second arc is generated between a second consumable wire electrode and the workpiece to deposit wire electrode material into a molten pool, wherein the first wire electrode is supplied by a first power source and the second wire electrode by a second power source, and at least a third wire is fed directly into the molten pool.

[0002] Such a metal inert gas arc welding process is well known in the field. Starting with a two-arc arc welding process, in which a first arc is generated between a first consumable wire electrode and the workpiece, and a second arc is generated between a second consumable wire electrode and the workpiece to transfer wire electrode material into a weld pool, a welding process is disclosed, for example, in patent application CN 105817750 A, in which a third welding wire is fed into the welding process. The addition of this wire enables improved material feed, so that, with high electrical deposition power, increased welding speeds and / or increased volume filling can be achieved, making the generic process suitable for both thin and thick sheet metal workpieces.

[0003] According to this welding process, the three welding wires form a triangle, with the first and second wire electrodes, each forming a separate arc, positioned at right angles to the welding direction and all welding wires at an angle to the vertical. However, it has been found that the deposition rates achievable with this welding process are not yet sufficient in certain applications to achieve the desired welding speeds or volume fillings.

[0004] German patent application JP 2016-49,537 A relates to a multi-electrode gas metal arc welding process in which welding is performed using a gas metal arc welding wire for a preceding electrode and a subsequent electrode, wherein a flux-cored wire is introduced into the molten metal between the preceding and subsequent electrodes, and a current flow is provided through the flux-cored wire into the molten metal. The preceding electrode, the subsequent electrode, and the flux-cored wire can be located in a common plane in the described welding process. Patent US 9,085,041 B2 relates to a system and a method, for example, a metal inert gas arc welding process, for initiating and using a combined wire feed and power source system.In one embodiment, a first welding torch is connected to a power supply and guides a first electrode to the weld pool via an arc welding process. Behind the guide arc is a hot wire heated by resistance heating; behind this hot wire, a further arc welding process takes place using a second power supply, a second torch, and a second arc welding wire. German patent application JP 2002-219 571 A relates to a control method for three-electrode arc welding for performing welding operations by generating three arcs from a welding torch between three electrically insulated welding wires and a workpiece to be welded.Patent KR 10 2 362 487 B1 relates to a welding system with a first, preceding welding torch, a second welding torch following the first, and a control unit for controlling the welding parameters of the first and second welding torches. In one embodiment, a filler wire feed unit is also provided, which is arranged between the first and second welding torches such that the filler wire, melted by the heat of at least one of the welding torches, is supplied. German patent application DE 10 2016 209 124 A1 relates to a method for welding seams using a multi-electrode arrangement. In one embodiment, this arrangement can have three welding heads, of which a first welding head and a third welding head are arranged symmetrically with respect to a second welding head.All wire electrodes of the multi-electrode arrangement simultaneously generate an arc during the welding process, with all wire electrodes simultaneously creating a common weld pool.

[0005] The present invention is based on the objective of modifying the known metal inert gas arc welding process in such a way that higher volume deposition rates can be provided in order to reduce welding times.

[0006] The above problem is already solved process-wise by a metal inert gas arc welding process with the features of claim 1. In the metal inert gas arc welding process according to the invention, a multi-wire welding torch is guided mechanistically along a path to execute a predetermined weld seam on a workpiece, wherein a first arc is generated between a first consumable wire electrode and the workpiece, and a second arc is generated between a second consumable wire electrode and the workpiece to transfer wire electrode material into a molten pool, and wherein the first wire electrode is supplied by a first power source and the second wire electrode by a second power source, and at least a third wire is guided to the molten pool, which, after solidification, forms a respective section of the weld seam.In the metal inert gas arc welding process according to the invention, the first and second wire electrodes and the third wire are guided in the multi-wire welding torch in such a way that the wires exiting the torch lie essentially in a common plane and that in the common plane the first wire electrode and the second wire electrode take the same angle with opposite signs to the third wire.

[0007] The welding process according to the invention is based on the idea of ​​guiding the first and second wire electrodes, as well as the at least one third wire, geometrically relative to each other in the multi-wire welding torch such that the at least three wires are geometrically arranged after exiting the welding torch in such a way that improved utilization of the energy introduced into the weld pool by the arcs of the two wire electrodes can be provided for melting the at least one third wire introduced into the weld pool. For this purpose, the at least three wires are guided in the multi-wire welding torch with electrical insulation from each other such that, after exiting the multi-wire welding torch, they lie essentially in a common plane with respect to their wire axes.The term "wires lying substantially in a common plane" means that the two wire electrodes define a common plane, with the third wire arranged between the wire electrodes and lying within a circle whose area is perpendicular to said plane and whose center is located in the plane, wherein the radius of the circle is 5 mm, preferably 3 mm, and particularly preferably identical to the radius of the third wire. This applies in particular to a stickout length of 10 mm for the third wire, where the stickout length is defined as the distance from the point where the third wire exits its associated guide sleeve (current nozzle), i.e., from the torch.

[0008] With the described geometric arrangement of the two wire electrodes and the third wire relative to each other after exiting the multi-wire welding torch, improved volume filling or increased welding speed can be provided by optimally introducing energy into the welding process with regard to the third wire.

[0009] For clarification, it should be noted that the geometric arrangement of the first and second wire electrodes and the third wire according to the invention, within essentially a plane after the wires exit the multi-wire welding torch, corresponds to a wire arrangement in which the wires are arranged on a straight line oriented perpendicular to the third wire, wherein the two wire electrodes form an angle to the third wire that is equal in magnitude but has different signs.

[0010] Additional advantageous features and further developments of the invention are specified in the following general description, the figures, the figure description and the dependent claims.

[0011] It has been found that, to cover the greatest possible number of welding applications, an angle of 7.0° to 11.5° is set between the third wire and the first and second wire electrodes, preferably an angle between 8.5° to 10°, and particularly preferably an angle between 9.2° to 9.6°. This allows the multi-wire welding torch to be designed with respect to the internal guides of the three wires such that, after exiting the torch, the wires are set at the specified angles to each other, for example, that the angle of the first wire electrode to the third wire is 9.4° and the angle of the second wire electrode to the third wire is -9.4°, wherein preferably the wires intersect in a common plane or a straight line that lies in this plane and is perpendicular to the third wire.

[0012] Advantageously, the mechanized guidance of the torch along a path to execute the predetermined weld seam on a workpiece can be carried out by means of a machine system, for example, a robot, a chassis, or a gantry. Using a robot to guide the multi-wire welding torch offers the advantage of great flexibility in defining the path, whereas for the continuous execution of a recurring weld seam using the metal inert gas arc welding process according to the invention, a machine system with reduced mobility, tailored to the specific welding task, can also be used.

[0013] In one embodiment, the multi-wire welding torch can be guided such that the substantially common plane of the three wires runs tangentially to the weld seam, particularly for forming narrow weld seams. To bridge or cover wider gaps with the metal inert gas arc welding process according to the invention, it is advantageous to guide the welding torch to the weld seam such that the common plane runs at an angle ≠ 0 to the tangent to the weld seam, particularly at an angle in the range of ± 45°, preferably at an angle in the range of ± 20°, and most preferably within a magnitude angle range of 5° to 12.5°. According to the invention, the respective arc process parameters or the feed rate of the third wire into the weld pool can be adapted to this orientation of the welding torch and thus to the desired width of the weld seam.Such a variation is particularly feasible when using a robot arm to guide the multi-wire welding torch.

[0014] As explained, the first and second wire electrodes, as well as the third wire, can be guided in the welding torch in such a way that the wires exiting the torch intersect along an imaginary extension. This allows the respective arc focal points to be directed precisely onto the third wire, ensuring optimal melting of the third wire in the weld pool by the energy transferred to the weld pool via the two wire electrodes and their arcs. The energy transferred to the third wire can be precisely adjusted, for example, by varying the distance of the multi-wire welding torch from the weld pool, i.e., by varying the height of the torch.

[0015] In order to synchronize the processes taking place in the metal inert gas arc welding process according to the invention, it can be advantageously provided that the welding process according to the invention is controlled by a central control system, in particular a robot control system for moving the multi-wire welding torch, wherein the central control system, in addition to moving the multi-wire welding torch, controls the power source of the first power source for carrying out an arc welding process and the power source of the second power source for carrying out a second arc welding process that is coordinated with the first arc welding process, in particular synchronized in time.

[0016] Depending on the specific application, the type of both arc welding processes may be the same, for example, a pulsed arc welding process, a spray arc welding process, a short-arc welding process, or a transition arc welding process, optionally with different welding parameters, whereby the respective process cycles of the two arc welding processes may be phase-shifted relative to each other. However, according to the invention, the type of the two arc welding processes may also be different; for example, the first arc welding process may be a pulsed arc welding process and the second arc welding process a short-arc welding process.

[0017] Preferably, communication between the central control unit, the first power source, and the second power source can be carried out via a bus system, for example a CAN bus system, wherein the information for controlling the welding processes can preferably be transmitted from the central control unit to a power source connected to the control bus system as a master power source, which takes over the operation of its own power source for carrying out one of the two welding processes and transmits control information to the second power source connected to the control bus as a slave power source, which is then implemented or executed by the second power source to provide the second welding process.

[0018] Preferably, the control information from the central control, in particular the robot control, to the power sources includes a process type, for example one of the welding process types specified above, and the process parameters necessary for its execution, with the respective power source then controlling the specified welding process with the specified process parameters.

[0019] To avoid delays in the timing of the two arc welding processes, it is preferably possible to provide that an exchange of synchronization information for the synchronization of the first arc welding process and the second arc welding process takes place directly between the two power sources, i.e. not via the central control.

[0020] In an exemplary embodiment of the method according to the invention, it can be provided that the first arc welding process and the second arc welding process are each a pulsed arc welding process, process parameters such as welding voltage amplitudes and welding current amplitudes are identical in magnitude, but with respect to a process cycle, each comprising at least one basic current phase and one pulsed current phase, are controlled with a phase shift relative to each other, in particular by 180°. For example, it can be provided that the wire feed of the lead wire electrode (guide wire) in the welding process, which provides the first arc, is controlled with a lower wire feed speed than the wire feed speed of the follower wire electrode (follower wire) in the welding method according to the invention, which provides the second arc.As shown, it is also possible to control the respective arc welding process parameters such as welding voltage, welding current and / or wire feed differently for both arc processes in order to adapt these parameters to the respective welding task or its framework conditions such as workpiece material, material of the wire electrodes or the third wire, workpiece thickness, joint width, etc.

[0021] According to the invention, a further current source provides for a resistance current flow through the third wire, in particular up to the weld pool, whereby additional energy can be introduced into the third wire, for example to increase the deposition rate and / or to increase the welding speed. However, according to the invention, the electrical parameters of the third current source are controlled or set in such a way that no arc can be established between the third wire and the weld pool, but instead a current flows through the solid wire up to the weld pool; thus, a galvanic current path exists through the third wire in all intended operating phases.

[0022] It may be advantageous to provide that a wire feed device for the first wire electrode is controlled by the first power source and a wire feed device for the second wire electrode is controlled by the second power source, since the respective setting of the wire feed is essentially determined by the respective welding process, which, as described, is carried out or controlled by a power source assigned to this welding process.

[0023] In the welding process according to the invention, electrical power is supplied by a third power source for resistance heating of the third wire, wherein the wire feed device for the third wire can be controlled by the third power source, i.e., the power source of the third wire. It can also be provided that this third power source receives its process parameters, i.e., for example, the current / voltage values ​​to be set, as well as information for controlling the wire feed device for the third wire, from the master power source, which in turn can receive the necessary process information from the central control unit.

[0024] The described geometric arrangement of the two wire electrodes, each generating a welding arc, and the third wire significantly simplifies operating situations in which the multi-wire welding torch is guided several times along a path to produce a predetermined weld seam, e.g., a combination weld, to perform a specific welding task. It can be advantageously provided that, when carrying out the welding process according to the invention, starting from a predetermined direction of movement of the multi-wire welding torch, the multi-wire welding torch is moved backward along the path without rotating the multi-wire welding torch, in particular without rotating the multi-wire welding torch by an angle of 180°, to reverse its movement.Such a simple reversal of movement of the multi-wire welding torch facilitates the control of the mechanized guidance system, particularly the control of a welding robot, since the robot does not need to be controlled to execute a rotation of the robot axis supporting the multi-wire welding torch. Instead, in the welding process according to the invention, the welding torch can be controlled for backward movement along the path, while, to maintain the welding arc processes of the guide electrode and the follower electrode, it can be provided that, immediately before or during the reversal of movement of the multi-wire welding torch, the two power sources, each assigned to a specific arc welding process, are switched between the two by the central control system with regard to the execution of the respective welding process and its parameterization.For example, if the first wire electrode is controlled by the first power source to execute a first arc welding process with associated parameters and the second power source to execute the second arc welding process with associated parameters during a forward movement along the path, the second power source to execute the first arc welding process with the associated parameters and the first power source to execute the second arc welding process with the associated parameters are controlled by the central control unit with or after the reversal of movement of the multi-wire welding torch.

[0025] In both embodiments where the third wire is fed into the weld pool as a cold wire in the metal inert gas arc welding process according to the invention, and in embodiments where the third wire is energized by means of a third power source, it can be advantageous to initially refrain from feeding the third wire into the welding process and instead activate the two arc-related power sources to carry out the respective welding process. Depending on the embodiment, such a delay in feeding the third wire can be in the millisecond to second range.Advantageously, after such a delay phase, in a subsequent transition phase, the power source for the third wire can, starting from a predetermined initial operating value, control at least one process parameter from the group of process parameters current, voltage, and feed rate to a predetermined steady-state operating value, for example, via a ramp. Specifically, during the delay phase for starting the welding process, the feed to the third wire can be omitted, while the power source controls a heating current through the third wire in this phase to preheat it.After the delay phase, the third wire can be fed into the system at a predetermined feed rate, for example, zero, during the transition phase. A ramp control system can then maintain a predetermined steady-state feed rate. This steady-state rate could, for example, be the amplitude of a modulation.

[0026] Similar to the initiation of the metal inert gas arc welding process according to the invention, a change in the feed rate of the third wire into the weld pool can be provided to prepare for or initiate a reverse control of the multi-wire welding torch. For example, during a forward movement of the multi-wire welding torch towards a reversal point, the feed rate of the third wire can be reduced, in particular by means of a ramp control, especially such that at the time the reversal point on the trajectory is reached, the feed rate of the third wire is zero or even negative.Following a reversal of direction in the guidance of the multi-wire welding torch, the third power source can, in a transition phase, control at least one process parameter from the group of process parameters current, voltage, and feed rate to a predetermined steady-state operating value during this transition phase. This control can be implemented such that, before reaching the reversal point for the reverse movement of the multi-wire welding torch, at least one process parameter, in particular the current and feed rate of the third power source, is ramped down. After reaching the reversal point, these process parameters are then returned to steady-state operating values ​​in a second transition phase. These steady-state operating values ​​could, for example, be the amplitudes of a respective welding process parameter.

[0027] It has been found that, when carrying out the metal inert gas arc welding process according to the invention, the two welding arcs should have a minimum distance of 5 mm between their arc bases and the weld pool in order to avoid fluctuations in the welding process. Therefore, according to the invention, it can be provided that the multi-wire welding torch is guided to the weld pool during operation in such a way that the distance between an arc base of the first wire electrode and an arc base of the second wire electrode is greater than 5 mm.

[0028] Furthermore, the inventors have discovered that a particularly high reproducibility of the welding result can be achieved when carrying out the metal inert gas arc welding process according to the invention if the multi-wire welding torch is guided to the weld pool in such a way that the distance of an arc base point of the first and / or the second wire electrode to an entry point of the third wire into the weld pool is < 10 mm, in particular < 7.5 mm.

[0029] It can be particularly advantageous to provide that the distance between the two arc base points of the wire electrodes and the entry point of the third wire is identical and < 7.5 mm.

[0030] In order to compensate for deviations in the movement of the multi-wire welding torch and / or deviations in the geometry of the workpiece from target values ​​during the execution of the welding process according to the invention, it can be advantageously provided that the multi-wire welding torch is moved along the path line with a superimposed pendulum movement perpendicular to the path line and, depending on at least one time-varying state variable such as welding current and / or welding voltage, seam tracking signals are generated for at least one of the two welding arcs during the movement of the multi-wire welding torch, from which lateral correction signals and / or vertical correction signals are generated to track the position of the multi-wire welding torch, with which the movement of the welding torch is adjusted to produce the weld seam.It can be advantageous to use the state variables of the welding arc of the so-called guide wire to determine these seam tracking signals. This guide wire is characterized by the fact that it is the wire electrode whose welding arc precedes the welding arc of the other wire electrode in the direction of movement of the multi-wire welding torch. Accordingly, the following wire electrode is referred to as the follower wire.

[0031] Particularly in embodiments where the common plane of the two wire electrodes and the third wire described above is tilted relative to the tangent of the weld seam, for example by 45°, both arcs are not centered on the weld seam. Therefore, in embodiments where said common plane is not tangent to the weld seam, it may be advantageous to use the seam tracking signals for adjusting the position of the multi-wire welding torch by deriving time-varying state variables of both welding arcs in order to generate lateral correction signals.

[0032] As explained above, the metal inert gas arc welding process according to the invention can advantageously be carried out in such a way that predetermined thresholds regarding the distance between the two arc bases in the weld pool, or between the arc bases of the first and second wire electrodes and the entry point of the third wire into the weld pool, are maintained. For this purpose, it can be provided that state variables of at least one of the arcs, for example, current or voltage of the at least one arc, are used to generate height signals in order to optionally vary the height of the multi-wire welding torch and thereby adjust the specified distances between the two arc bases, or between the arc base and the entry point of the third wire, in particular such that these values ​​lie within the thresholds described above of > 5 mm and < 7.5 mm, respectively.

[0033] It has been found that, for the formation of a homogeneous weld seam, the third wire can advantageously be fed to the weld pool at varying speeds, in particular with a sinusoidal modulation of the speed. These modulations can be in the range of a few hertz, especially in the range of approximately 5 Hz. It can be provided that the amplitude of the modulation of the feed speed is smaller than a base feed speed, so that the third wire is fed continuously during the execution of the metal inert gas arc welding process according to the invention, with the exception of the start-up and reversal situations of the process described above.

[0034] However, according to the invention, it is also possible for the third wire to be fed in reverse, i.e., there are feeding situations in which the third wire is fed in and, furthermore, at least one time phase in which the third wire is withdrawn from the melt bath. This embodiment can be particularly advantageous when using a cold third wire, which in this embodiment is not heated by the described third power source.

[0035] To prevent oxidation of the materials used to produce the specified weld seam, it can be advantageous to supply the first and second wire electrodes, as well as at least one third wire, to the welding process under a common shielding gas atmosphere. Such a common shielding gas atmosphere can be provided by a suitable design of the multi-wire welding torch in the form of a common gas nozzle for the wires.

[0036] It has been found that the metal inert gas arc welding process according to the invention is particularly suitable for producing a weld seam in the form of a mixed alloy that is particularly resistant, for example, to weathering. For this purpose, it can be advantageously provided that the two wire electrodes, i.e., the electrodes for providing the two welding arcs, have an identical alloy, and the third wire has a different alloy, in particular a higher alloy. In another embodiment, it can also be provided that the three wires each comprise or have different alloys.

[0037] The metal inert gas arc welding process according to the invention can be adjusted, in particular, to set or change the penetration into the workpiece with respect to the respective guide wire as neutral, trailing, or thrusting. For this purpose, it can be provided that the third wire is guided neutrally to the weld seam, i.e., neither thrusting nor trailing, or that the welding torch is tilted to a plane that runs perpendicular to the weld path, wherein the tilt angle can preferably be set between 3° and 20°, in particular between 5° and 10°.

[0038] The above problem is further solved by a mechanized welding arrangement, in particular a robot welding arrangement, which is designed and set up to carry out a metal inert gas arc welding process according to the invention as explained above.

[0039] The system according to the invention comprises at least one multi-wire welding torch and a guiding device such as a robot, a chassis, or a gantry, which is configured and designed to guide the multi-wire welding torch along a path to execute a predetermined weld seam on a workpiece. The multi-wire welding torch is configured and designed to receive a first wire electrode, a second wire electrode, and at least a third wire, to guide them internally, and to design the outlet side such that the wires exiting the multi-wire welding torch lie essentially in the common plane described above, wherein in the common plane the first wire electrode and the second wire electrode form an angle with essentially the same magnitude but opposite signs with respect to the third wire.Furthermore, the welding arrangement according to the invention comprises a first power source for supplying the first wire electrode and at least a second power source for supplying the second wire electrode for generating a first and second arc between the two melting wire electrodes and the workpiece.

[0040] The invention is explained below by describing an embodiment of the metal inert gas arc welding process according to the invention, as well as an arrangement for carrying out the process and some related modifications, with reference to the accompanying drawings, wherein Fig. 1 in a schematic representation the structure of a robot welding arrangement designed according to the invention for carrying out the metal inert gas arc welding process according to the invention with a cold third wire supplied to the welding process, Fig. 2 a further embodiment of a robot welding arrangement according to the invention in a schematic representation for carrying out a metal inert gas arc welding process according to the invention with a hot third wire supplied to the welding process, Fig. 3 the multi-wire welding torch of the robot welding arrangement according to the invention in a side view with installed gas nozzle to provide a common shielding gas atmosphere for the wires guided in the torch, Fig. 4 Another side view of the multi-wire welding torch without gas nozzle and with the arc shown, Fig. 5 the multi-wire welding torch used in the inventive system with a representation of possible stickout lengths and the associated wire base distances with the gas nozzle removed, Fig. 6 in a perspective view the multi-wire welding torch of the Fig. 3, Fig. 4 to Fig. 5, arranged to execute a fillet weld on a workpiece, Fig. 7 in a perspective view the arrangement of the multi-wire welding torch relative to a workpiece for producing a Y-seam with a pulling arrangement of the leading wire electrode, Fig. 8 an arrangement of the multi-wire welding torch for producing a Y-seam according to the illustration of the Fig. 7, however with multi-wire welding torches rotated by 45° to the seam tangent, Fig. 9. Another arrangement of the multi-wire welding torch for producing a Y-seam according to the illustration of the Fig. 7, however inclined by a predetermined tilt angle relative to a plane perpendicular to the weld, and Fig. 10 shows the time course of the wire speed of the third wire during the execution of the metal inert gas arc welding process according to the invention in three embodiments.

[0041] An exemplary robot welding arrangement 1 for carrying out the metal inert gas arc welding process according to the invention is shown in Fig. Figure 1 shows a perspective view. This includes a welding robot 2 to whose hand axis a multi-wire welding torch 40 is attached by means of a coupling 15. The welding robot 2 guides the torch along a predefined path to produce a desired weld seam, in this case a Y-seam, on the workpiece 32. The movement of the welding robot 2 is controlled via the control and supply line 31 by the robot controller located in a mains-powered robot control cabinet 3, which, in the described embodiment, functions as the central controller for the entire robot welding arrangement 1. Depending on the embodiment, the necessary path for executing a predefined weld seam can be learned by manually guiding the multi-wire welding torch 40 and entered into the robot controller. However, it is also possible for such a path to be stored directly electronically in the central controller or robot controller.

[0042] The multi-wire welding torch 40 is designed and configured to supply two consumable wire electrodes in a protective gas atmosphere to the metal inert gas arc welding process according to the invention, wherein a first arc is generated between the first consumable wire electrode and the workpiece 32, and a second arc is generated between the second consumable wire electrode and the workpiece to transfer wire electrode material into the weld pool. Both wire electrodes are electrically insulated from each other both in their feed and in the multi-wire welding torch 40. For this purpose, the robot welding arrangement 1 has a welding power source 4 for the electrical supply of the first wire electrode.A first wire feeder 7 is provided for supplying this first wire. This feeder takes the wire from a first wire storage container 12 via the supply line 19 and feeds it to the multi-wire welding torch 40 via the first torch hose assembly 16. A first shielding gas reservoir 10 is also connected to the welding power source 4. Accordingly, the connecting hose assembly 22 for the first wire between the welding power source 4 and the wire feeder 7 includes a control line for controlling the wire feeder 7 and the electrical connection between the welding power source 4 and the wire feeder 7, in which the first wire is connected. The torch hose assembly 16 for the first wire thus includes a shielding gas supply and the connected first wire for providing the first wire electrode in the multi-wire welding torch 40.To close the supply circuit, a welding line is provided from the first welding power source 4 to the workpiece 32.

[0043] The central control unit in the robot control cabinet 3 is connected to the first welding power source 4 via the control line 25 and, depending on the embodiment, can, for example, control the welding power source 4 to execute a predefined welding process type, such as pulsed current welding with associated process parameters. Such a process parameter can, in particular, also include the control of the wire feed device 7 assigned to the first wire.

[0044] For supplying the second wire electrode and operating the second arc in the inventive gas-shielded arc welding process, essentially the same measures and components are provided as for supplying the first wire electrode and operating the first arc in the inventive robot welding arrangement 1. The second wire for providing the second wire electrode is taken from a wire storage 14 by a wire feed device 9 via the supply line 21, whereby contact of the wire to an associated second welding power source 6 is made via the second connecting hose assembly 24 in the second wire feed device 9.A shielding gas reservoir 11 can also be provided for the second wire, which is connected to the second welding power source 6. From there, the shielding gas is fed via the second connecting hose assembly 24 to the wire feed device 9 and from there, together with the second wire connected in the wire feed device 9, into the torch hose assembly 18 and to the torch head 40. The closing of the second welding circuit for generating the second arc in a second welding arc process is achieved here by the welding line 30, which establishes an electrical contact between the workpiece 32 and the welding power source 6.The second welding power source 6 is also controlled by the central robot control via the control line 27, for example in such a way that this central control controls the second welding power source 6 to carry out a specified welding process type with specified process parameters, whereby the second welding power source 6 then also controls the specified welding process with the specified process parameters.

[0045] In one embodiment, it may also be provided that only a single shielding gas reservoir is included, which feeds a common shielding gas nozzle on the multi-wire welding torch.

[0046] Depending on the embodiment, the welding process type performed by the first welding power source 4 and the welding process type performed by the second welding power source 6 can be identical, for example, a pulse welding process, optionally with different process parameters. Furthermore, the respective pulse phases can be controlled synchronously or, for example, alternately according to a phase shift of 50%. In the described embodiment, synchronization of both power sources 4 and 6 can be achieved via a direct synchronization line 33 between the two power sources 4 and 6.

[0047] To provide higher deposition rates or shorter welding times when carrying out the metal inert gas arc welding process, the robot welding arrangement is configured according to... Fig. 1. The feeding of a third wire into the multi-wire welding torch 40. In the Fig. In the embodiment of the robot welding arrangement 1 shown in Figure 1, the third wire is fed to the welding torch or the welding process cold, i.e., not heated, by taking the third wire from the third wire storage 13 through the wire feed device 8 via the supply line 20 and feeding it to the welding torch 40 via the third torch hose assembly 17. In this embodiment, the third wire is not electrically connected; therefore, the third wire can be supplied to the torch head 40 without potential, with the wires guided in the torch head 40 being insulated from each other. In this embodiment, the control of the third wire feed device 8 can be provided via one of the two power sources 4, 6, here power source 4; the corresponding control line is marked with reference numeral 23a.

[0048] In principle, it can be provided that the central control in the robot control cabinet 3 controls the execution of the metal inert gas arc welding process according to the invention depending on the guidance of the multi-wire welding torch 40 along the path, in which the two power sources 4, 6 control the execution of predetermined welding process types with predetermined welding parameters, i.e. predetermined parameter settings such as welding voltage, welding current, wire feed, wherein, for example, in the present example, the power source 4 can also receive instructions from the central control for the operation of the third wire feed device 8 for driving the third wire.

[0049] An increase in the deposition rate or welding speed and / or simpler control during the execution of the method according to the invention is based in particular on the fact that the wires in the multi-wire welding torch 40 are guided, or that the torch is designed, in such a way that the wires leave the multi-wire welding torch 40 in a predetermined manner and can be fed to the welding process in a specific geometric arrangement. Before discussing this in detail, the construction of a second robot welding arrangement according to the invention will first be described with reference to Fig. 2 explained.

[0050] The robot welding arrangement 1' of the Fig. 2 differs from the robot welding arrangement 1 of the Fig. 1 solely by the fact that the third wire, which is introduced into the welding process according to the invention by being supplied as a solid wire to the melt pool produced by the two arcs of the first and second wire electrode via the multi-wire welding torch 40, is not supplied cold, but in a heated state.

[0051] For this purpose, the robot welding arrangement 1' has a further power source 5 for providing a heating current through the third wire, over which no arc can be formed to the weld pool. Instead, in this variant of the inventive method, the third wire is fed directly to the weld pool via the multi-wire welding torch 40 by means of the wire drive 8; the current path is a pure wire path without the formation of an arc. It can be seen that by providing preheating of the third wire by means of a current flow through the third wire, an even greater melting capacity can be provided by the robot welding system or, in the implementation of the inventive metal inert gas arc welding process, by means of a current flow through the third wire.Depending on the embodiment, the current carried through the third wire and supplied by the power source 5 can be a direct current or an alternating current, depending on the wire material used, for example with an amplitude of 150 to 250 amperes, in particular about 200 amperes.

[0052] The third wire can be connected in the wire feed device 8 of the third wire, as with the first and second wire electrodes. In this respect, the connecting hose assembly 23 between the power source 5 and the wire feed device 8 has, in addition to a control line for controlling the wire feed device 8 by the power source 5, a corresponding electrical line to supply the third wire with the described heating current. The circuit for the heating current of the third wire is closed via the power line 29 provided between the power source 5 and the workpiece 32. The control of the third power source 5, and thus also of the wire feed device 8 of the third wire, is carried out either indirectly or, as in the embodiment of the Fig. As specified in Figure 2, the power supply is directly connected to the central robot controller via the control line 26, which is located between the robot control cabinet 3 and the third power source 5. It can be provided, in particular, that the central controller, the two power sources 4, 6 of the two wire electrodes, and the power source 5 of the third wire are connected to a common bus system, especially a CAN bus, via which the central controller (here, the robot controller) controls the two or three power sources 4, 5, 6, depending on the controlled movement of the welding robot 2, to carry out a respective welding process with a corresponding arc. Depending on the respective welding process, the respective power source 4, 6 then controls the respective wire feed device 8, 7.

[0053] It can also be provided that the central control unit is connected via a bus to only one of the two power sources 4, 6, each of which performs an arc welding process, and then transmits the process and control parameters for all power sources to this selected power source. The selected power source then transmits control information to the other power sources via a control bus or control lines. In this embodiment, the power source connected to the central control unit can be configured as the master power source. In all variants, a synchronization line 33 can be provided between the two power sources 4, 6, each performing an arc welding process, to ensure delay-free coordination of the two welding arc processes during the execution of the metal inert gas arc welding process according to the invention.

[0054] Fig. Figure 3 shows a top view of the multi-wire welding torch 40, in which the first, second, and third wires are guided such that, after exiting the multi-wire welding torch 40, they are oriented relative to each other in a predetermined manner. This orientation or arrangement relates, firstly, to the fact that the two wires or wire electrodes 50 and 60, which perform an arc welding process, each form an angle α with the third wire 70, which is equal in magnitude but opposite in sign. Furthermore, all three wires 50, 60, and 70 lie essentially in a common plane GE. Ideally, the axes of the wires 50, 60, and 70 can therefore lie in this common plane GE.With the specified geometric orientation of the wires to each other, such that the wires 50, 60, 70 intersect at point S in an imaginary extension, the energy introduced into the third wire 70 by the welding processes of the outer wires 50, 60 can be varied in the shielding gas arc welding process according to the invention by varying a so-called stickout length, in particular with regard to the middle wire 70, which will be discussed in more detail below.

[0055] Fig. 4 shows a representation similar to the Fig. 3 with the difference that the torch with the gas nozzle 41 removed is shown during a welding process in which an arc 51, 61 burns between the two wire electrodes 50, 60 and the workpiece 32 or the melt pool, each having an arc base 52, 62 to the workpiece 32 or the melt pool.

[0056] To increase the melting rate, the third wire 70, which in the embodiment according to the invention is located between the two wire electrodes 50, 60 with respect to the tilt angle α, is inserted into the molten pool generated by the two arcs 51, 61. Depending on the embodiment, this third wire 70, which is supplied to the two arc welding processes, can be introduced either as an unheated wire or as a heated wire, as explained above. The three wires 50, 60, 70 are identifiable in the multi-wire welding torch 40 as being insulated or arranged relative to each other, in the described embodiment by a contact tip 42, 43 and 44 assigned to the respective wire 50, 60, 70, the latter tip 44 serving solely as an insulating tube in the case of an embodiment with a cold wire. Fig. 4 are also characteristic quantities of the welding process according to the invention in the form of the so-called stickout length S0, which with reference to the third wire 70 denotes the distance of the exit end of the third wire 70 from the tube 44 to the weld pool or the workpiece 32 and specifies the distance d between the two arc base points 52, 62 of the two arcs 51, 61.

[0057] Fig. 5 corresponds to the representation of the Fig. 3, whereby the gas nozzle 41 is again removed, thus allowing a view of the contact tips 42, 43, 44. For a suitable tilt angle of α ≈ ± 9.4° of the wire electrodes 50, 60 to the third wire 70, the resulting distances d1 of the base points of the wires 50, 70 are given for a stickout length range S0 to 25 mm. It has been found that, to provide a stable welding process for a variety of applications, the distance of the arc base point 52 of the first wire electrode 50 to the arc base point 62 of the second wire electrode 60 should be ≥ 5 mm. Similarly, the multi-wire welding torch 40 can be guided to the weld pool in such a way that the distance between an arc base point 52, 62 of the first or second wire electrode 50, 60 and an entry point of the third wire 70 into the weld pool is < 10 mm, in particular < 7.5 mm. According to Fig. These geometries can be easily adjusted by setting a respective stickout length S0 when guiding the multi-wire welding torch 40. This allows the penetration depth to be adjusted for different material thicknesses and material types of the respective workpiece. Due to the almost central arrangement of the third wire 70, this wire melts firstly by immersion of the third wire 70 in the weld pool and secondly by the action of the two arc welding processes of the two wire electrodes 50, 60.

[0058] The two arc welding processes carried out by the power sources 4 and 6 can be identical welding processes with respect to type and process parameters. It is also possible for the two arc welding processes to be of the same type but with different parameters, particularly phase-shifted relative to each other. Furthermore, it is also within the scope of the invention if the two power sources 4 and 6 carry out completely different types of arc welding processes, for example, a short-arc welding process and a pulsed arc welding process. Both direct current and alternating current arc welding processes can be used to carry out the method according to the invention.

[0059] In the shielded gas arc welding process according to the invention, the diameter of the wires 50, 60, 70 can be identical and, for example, be between 1.2 mm and 1.6 mm. However, it is also possible for the wire diameters to be different, for example, the wire diameter of wires 50, 60 being 1.6 mm and the wire diameter of the additional wire 70, which can be fed as a cold or hot wire, having a smaller diameter, for example 1.2 mm.

[0060] In an embodiment not shown, it may also be possible to add a further cold or hot wire to the welding process according to the invention or to carry out a combination of the welding process according to the invention with a laser beam welding process for further energy input.

[0061] The welding process according to the invention can in principle be used to execute all known welds, for example to produce a fillet weld, a V-weld, an HV weld, a Y-weld, a HY-weld or an I-weld.

[0062] Fig. Figure 6 shows a section of the multi-wire welding torch 40 of the robot welding system designed according to the invention, oriented for producing a fillet weld along a weld line 80 for joining the workpieces 101a, 101b. To optimize the weld, seam tracking with automatic tracking of the multi-wire welding torch 40 can be provided in the welding process according to the invention by moving this torch along the path line with a superimposed oscillating motion perpendicular to the path line, see the motion curve P in the copied motion diagram. For seam tracking, seam tracking signals can be generated depending on at least one time-varying state variable such as welding current or welding voltage during the movement of the multi-wire welding torch 40.From these seam tracking signals, lateral correction signals can be generated, which can be used to adjust the movement of the cutting torch to create the weld seam. In the in . Fig. In the welding situation described in section 6, when the welding torch moves to the right, it is advantageous to use the welding arc 51 of the guiding wire 50 or a time-varying state variable of the welding arc 51 to determine the specified seam tracking signals. In cases where the welding arc is a pulsed arc, the current profile of the arc can be advantageously used to generate seam tracking signals.

[0063] Based on the presentation of Fig. It is understandable that when the direction of the torch is reversed, for example to produce sequentially successive weld seams, no additional movement of the multi-wire welding torch 40, in particular no rotation of the welding torch about its axis, is necessary, but instead the welding torch can simply be set into a backward movement. Since, with the backward movement of the welding torch, the guide wire becomes the follower wire and the previously following wire becomes the guide wire, the central control, here the robot control, controls the two power sources 4, 6 in such a way that the other arc welding process is carried out.Depending on the embodiment, it may be provided that, in particular, the feed rate of the third wire 70 is reduced before reaching the reversal point, especially in a ramp-like manner, possibly to zero, and increases again after or with the initiation of the reversal of movement of the multi-wire welding torch 40, especially up to a predetermined stationary value.

[0064] Fig. Figure 7 shows the multi-wire welding torch 40 for producing a Y-shaped weld with a marked weld line 80 for joining the workpieces 101a, 101b which are adjacent to each other in one plane. As explained, during operation the energy introduced into the third wire 70 by the two arcs 51, 61 or the weld pool can be adjusted, in particular by setting a predetermined stickout length S0. For this purpose, the inventive gas-shielded arc welding process can be provided that, during the movement of the multi-wire welding torch 40, height signals are generated by one or both of the welding arcs 51, 62 as a function of a time-varying state variable such as welding current or welding voltage. From these height correction signals, height correction signals are generated to maintain the position of the multi-wire welding torch 40.These height correction signals can then be used to guide the multi-wire welding torch 40, for example to set a threshold value with respect to the distance between the arc bases 52, 62 of the wire electrodes 50, 60 or with respect to the distance d1 of the entry point of the third wire 70 into the weld pool to each of the arc bases 52, 62 of the wire electrodes 50, 60 forming the arc.

[0065] The inventive method or robotic welding system can also be used to produce wide weld seams with high volume deposition. For this purpose, the multi-wire welding torch 40 can be rotated about an axis that runs coaxially or at least parallel to the third wire 70, see [reference]. Fig. 8. In this embodiment, the multi-wire welding torch 40 is guided in such a way that the common plane GE, see Fig. 3, runs within a range of ± 45° to a tangent to the weld seam or weld line. Since in the representation of the Fig. Since the seam line 80 is straight, the tangent to the weld seam, or the seam line, is coincident with it. In this welding torch arrangement, a sequential weld sequence can also be created by a simple backward or back-and-forth movement of the torch, without having to rotate the torch during the reversal movement. Only the exchange of welding processes in the respective power sources needs to be carried out, as the former follower wire becomes the guide wire and vice versa.

[0066] In the embodiments described so far, in the metal inert gas arc welding processes according to the invention, the third wire 70 had a neutral welding position, so that when the torch movement is reversed, the leading wire has an essentially identical welding position to the previously leading wire. However, the method according to the invention is not limited to such a configuration. For example, it is also possible to tilt the welding head, starting from a neutral welding position of the third wire 70, relative to a plane that is perpendicular to the weld line or the weld seam (see figure). Fig. 9. In certain embodiments, it may preferably be provided that the multi-wire welding head 50 is tilted so that the leading wire has a neutral or slightly penetrating position.

[0067] Preferably, the wire speeds of the first wire (50) and the second wire (60) can be the same, particularly in cases where both arc welding processes are identical, e.g., pulsed arc welding processes. Depending on the application, the wire speed V can be... DR The third wire 70 must be adapted to it. The time course for three different welding processes is shown in Fig. Figure 10. In many cases, the wire feed rate of the third wire V can be adjusted. DR The wire speed should be set to a constant value; however, delaying the introduction of the third wire (70) into the welding process may be useful for starting or reversing the movement. The middle graph shows the wire speed V. DRThe third wire 70 has a base speed onto which an alternating quantity with a predetermined amplitude, lower than the base speed, is modulated, for example, at a frequency of 5 Hz, which can lead to a flaky weld. Such modulation onto a base wire speed of the third wire 70 can occur both when it is a hot wire and when it is fed unheated, i.e., a cold wire.

[0068] The lower graph of the Fig.Figure 10 shows the time course of the wire speed of the third wire 70 with reversal; that is, in this embodiment, the third wire 70 is transported in phases towards the multi-wire welding torch 40 and withdrawn in other phases. Such operation of the third wire feed device can be particularly advantageous when the two arc welding processes operate with significantly different energy inputs to the local area of ​​the third wire 70. Such reversal of the wire speed of the third wire 70 is preferably suitable when it is fed as a cold wire. Although reversal is also possible in principle in cases where the third wire is a hot wire, additional measures may then be necessary to prevent the formation of a third welding arc by the third wire 70.

[0069] As those skilled in the art will recognize, in most welding situations the described metal inert gas arc welding process can be carried out with a cold wire as the third wire as well as with a hot wire as the third wire. Furthermore, it should be noted that the described multi-wire welding torch, designed for use with a cold wire as the third wire, can also be used for the inventive gas inert arc welding process with a hot wire as the third wire without any special modifications. Reference symbol list 1, 1' Robot welding setup / welding setup 2 welding robots 3 robot control cabinet 4. First power source / welding power source 5. Third wire power source / hot wire power source 6 second power source / welding power source 7 Wire feed device 8 Wire feed device 9 Wire feed device 10 gas storage tanks 11 gas storage facilities 12 wire storage devices 13 wire storage devices 14 wire storage devices 15 Clutch 16 Burner hose package 17 Burner hose package 18 Burner hose package 19 Supply line 20 Supply line 21 Supply line 22 Connecting hose 23 Connecting hose 23a Control line 23b Wire feed device for the third wire 24 Connection hose package 25 Control line 26 Control line 27 Control line 28 welding lines 29 Power line 30 welding leads 31 Robot control line 32 workpieces 33 Synchronization line 40 multi-wire welding torches 41 Gas nozzle 42 Power nozzle first wire 43 Power nozzle second wire 44 Contact nozzle / tube third wire 50 first wire electrode / wire 51 arcs 52 Arc base 60 second wire electrode / wire 61 arcs 62 Arc base 70 third wire electrode / wire 72 Wire base 80 Seam line 100a workpiece 100b workpiece 101a Workpiece 101b Workpiece P pendulum curve d Distance between arc bases 52, 62 d1 Distance between the wires at the base GE common plane of wires α Tilt angle S virtual intersection S0 Stickout Length R Welding direction

Claims

A metal inert gas arc welding process in which a multi-wire welding torch (40) is mechanized along a path to execute a predetermined weld seam on a workpiece (32, 100a, 100b, 101a, 101b), and in which a first arc (51) is generated between a first consumable wire electrode (50) and the workpiece, and a second arc (61) is generated between a second consumable wire electrode (60) and the workpiece to transfer wire electrode material into a weld pool, wherein the first wire electrode (50) is supplied by a first power source (4) and the second wire electrode (60) by a second power source (6), and at least a third wire (70) is fed directly into the weld pool, wherein the first and second wire electrodes (50, 60) and the third wire (70) are guided in the multi-wire welding torch (40) such that the wires exiting the multi-wire welding torch (40) (50, 60,70) essentially lie in a common plane (GE) and that in the common plane the first wire electrode (50) and the second wire electrode (60) form an angle of equal magnitude with opposite signs to the third wire (70), characterized in that, during the execution of the metal inert gas arc welding process, starting from a predetermined direction of movement of the multi-wire welding torch (40) to the path line, the multi-wire welding torch (40) is moved backwards on the path line without rotation of the multi-wire welding torch (40) to perform a reversal of movement, and with the beginning of the backward movement of the multi-wire welding torch (40), the third wire (70) is initially not fed into the weld pool, and thereafter, in a transition phase, a current source (5) of the third wire (70) is supplied starting from a predetermined initial operating value of at least one process parameter current,Voltage and feed rate are controlled to a predetermined steady-state operating value of at least one process parameter. Metal inert gas arc welding process according to claim 1, characterized in that the multi-wire welding torch (40) is guided such that the common plane (GE) runs at an angle within a range of ± 45° to a tangent to the weld seam. Metal inert gas arc welding process according to claim 1 or 2, characterized in that the first wire electrode (50), second wire electrode (60) and third wire (70) are guided in the multi-wire welding torch (40) such that the wires (50, 60, 70) exiting the multi-wire welding torch (40) intersect in an imaginary extension. A metal inert gas arc welding process according to claim 1, 2 or 3, characterized in that the metal inert gas arc welding process is controlled by a central control unit for the movement of the multi-wire welding torch (40), wherein the central control unit controls the power source (4) of the first wire electrode (50) for carrying out a first arc welding process and the power source (6) of the second wire electrode (60) for carrying out a second arc welding process synchronized in time to the first arc welding process, wherein welding process parameters such as welding voltage, welding current, and / or wire feed of the two arc welding processes may be different. Metal inert gas arc welding process according to claim 4, characterized in that the central control controls the third power source (5) to provide a resistance current flow through the third wire (70) that is matched to the arc welding processes. A metal inert gas arc welding process according to one of claims 1 to 5, characterized in that, with or after the reversal of movement of the multi-wire welding torch (40), the second power source (6) for carrying out the first arc welding process and the first power source (4) for carrying out the second arc welding process are controlled by the central control unit, if immediately before the reversal of movement of the multi-wire welding torch (40), the first power source (4) for carrying out the first arc welding process and the second power source (6) for carrying out the second arc welding process were controlled by the central control unit. Metal inert gas arc welding process according to one of claims 1 to 6, characterized in that, to start the welding process, the third wire (70) is initially not fed into the weld pool, and then, in a transition phase, the power source (5) of the third wire (70) is controlled from a predetermined starting operating value of at least one process parameter from the group of process parameters current, voltage and feed rate to a predetermined steady-state operating value. Metal inert gas arc welding process according to one of claims 1 to 7, characterized in that a wire feed device (7) for the first wire electrode (50) is controlled by the first power source (4), a wire feed device (8) for the second wire electrode (60) is controlled by the second power source (6) and a wire feed device (9) for the third wire (70) is controlled by the third power source (5). Metal inert gas arc welding process according to one of claims 1 to 8, characterized in that the multi-wire welding torch (40) is guided to the weld pool in such a way that a distance (d) of an arc base point (52) of the first wire electrode (50) to an arc base point (62) of the second wire electrode (60) is greater than 5 mm. Metal inert gas arc welding process according to one of claims 1 to 9, characterized in that the multi-wire welding torch (40) is guided to the weld pool in such a way that a distance (d) of an arc base point (52) of the first and / or second wire electrode (50, 60) to an entry point of the third wire (70) into the weld pool is less than 10 mm. A metal inert gas arc welding process according to one of claims 1 to 10, characterized in that the multi-wire welding torch (40) is moved along the path with a superimposed pendulum motion perpendicular to the path and, depending on at least one time-varying state variable such as welding current or welding voltage, seam tracking signals are generated for at least one of the two welding arcs during the movement of the multi-wire welding torch (40), from which lateral correction signals are generated to track the position of the multi-wire welding torch (40) with respect to the predetermined weld seam, with which the movement of the multi-wire welding torch (40) is adjusted to produce the weld seam. A metal inert gas arc welding process according to one of claims 1 to 11, characterized in that during the movement of the multi-wire welding torch (40) in the execution of the metal inert gas arc welding process, height signals are generated depending on at least one time-varying state variable such as welding current or welding voltage of at least one of the two welding arcs, from which height correction signals are generated for the height tracking of the position of the multi-wire welding torch (40), with which the guidance of the multi-wire welding torch (40) is adapted to produce the weld seam. Metal inert gas arc welding process according to claim 12, characterized in that the guidance of the multi-wire welding torch (40) for the production of the weld seam is adjusted with the generated height correction signals to comply with predetermined threshold values ​​with regard to the distance of the arc base points (52, 62) of the wire electrodes (50, 60, 70) to each other and / or with regard to the distance of the entry point of the third wire (70) into the weld pool to one of the respective arc base points (52, 62) of the wire electrodes 50, 60, 70). Metal inert gas arc welding process according to one of claims 1 to 13, characterized in that the third wire (70) is fed to the weld pool at varying speed. Metal inert gas arc welding process according to one of claims 1 to 14, characterized in that the third wire (70) is fed in a reversing manner. Metal inert gas arc welding process according to claim 15, characterized in that the reversing feed of the third wire (70) is carried out depending on or synchronized in time with at least one welding parameter of the first and / or the second wire electrode (50, 60). Metal inert gas arc welding process according to one of claims 1 to 16, characterized in that the first and second wire electrodes (50, 60) and the at least one third wire (70) are supplied to the welding process under a common shielding gas atmosphere. Metal inert gas arc welding process according to one of claims 1 to 17, characterized in that the two wire electrodes (50, 60) have an identical alloy and the third wire (70) has an alloy different from this identical alloy. Metal inert gas arc welding process according to one of claims 1 to 18, characterized in that the third wire (70) is guided neutrally, or the multi-wire welding torch (40) is tilted to a plane perpendicular to the welding path, wherein the tilt angle is between 5° and 20°. Welding arrangement (1, 1') designed and configured for carrying out a metal inert gas arc welding process according to one of claims 1 to 19 .

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