Multiple welding method

Abstract

In order to propose a multiple welding method with at least two electrodes (3A, 3B) for melting, which enables a stable welding process on the electrodes (3A, 3B) and a lower heat input into the base material (6) compared to a multiple pulse welding method, it is provided according to the invention that a welding process with a short-circuit welding phase (SPAl, SPBl) and a hot welding phase (SPA2, SPB2) is carried out on each of the at least two electrodes (3A, 3B), the hot welding phase having a higher heat input into the base material (6) than the short-circuit welding phase (SPAl, SPBl), wherein the short-circuit welding phase (SPAl, SPBl) and the hot welding phase (SPA2, SPB2) are periodically alternated, and the short-circuit welding phases (SPAl, SPBl) of the welding processes of the at least two electrodes (3A, 3B) are synchronized in time according to at least one defined first synchronization event (SEAl, SEBl) of each short-circuit welding phase (SPAl, SPBl).

Description

TECHNICAL FIELD

[0001] The invention relates to a method for carrying out a multiple welding process with at least two electrodes which melt, wherein after igniting the arc on each electrode a welding process is carried out between the electrode and the base material, and the welding processes of the at least two electrodes are synchronized in time. The invention furthermore relates to a device for carrying out a multiple welding process. BACKGROUND

[0002] Metal gas shielded welding processes (MSG) have been known in the prior art for many years. Metal gas shielded welding processes comprise, for example, metal inert gas processes (MIG) or also metal active gas processes (MAG), in which a melting electrode composed of a metal electrode material is surrounded by a so-called shielding gas. Metal gas shielded welding processes are generally used to apply a weld seam (build-up welding) on a base material or to join two base materials (lap welding). In both cases, an arc is ignited between the electrode and the base material by means of an electric welding voltage or an electric welding current generated thereby, which melts the electrode and the region of the base material around the electrode, thereby forming a material-locking connection. The electrode material is generally the same or similar to the base material. The electrode is fed to the welding point at a specific feed speed, wherein the feed speed can be fixedly predetermined, for example by hand in manual welding or by setting on the welding device, or the feed speed can also be dependent on other parameters, for example on the welding speed with which the electrode is moved relative to the base material, or on the current, etc.

[0003] In order to improve the welding performance, multiple welding methods are also known in which at least two electrodes are simultaneously welded, wherein a separate welding process is carried out for each electrode. Multiple welding methods include, for example, the so-called double impulse welding method, in which two impulse welding processes are simultaneously carried out. Here, at least two electrodes in the form of welding wires are melted into a common weld pool or are each melted into a separate weld pool. For this purpose, a separate welding device, i.e. a power source, a welding torch, a control unit and, if necessary, a wire feed unit, is usually used for each impulse welding process. The impulse welding process is implemented using each welding device in such a way that the respective control unit controls or regulates the welding parameters, i.e. in particular the welding current, the welding voltage, the wire feed and, if necessary, the amount of shielding gas, accordingly. In order to prevent possible negative mutual influences of the simultaneously carried out impulse welding processes, which can reduce the welding quality, it is also known that the two impulse welding processes can be synchronized in time. Here, for example, a pulse frequency is predetermined on one welding device, the other welding device follows the pulse frequency accordingly. As a result, the two welding processes are synchronized with one another and carry out welding at the same pulse frequency, so that a stable droplet detachment occurs on both electrodes. Double welding methods with synchronized welding processes are disclosed, for example, in documents DE 112 014 001 441 T5 and US 8,946,596 B2.

[0004] In single welding methods in which welding is carried out using only one melting electrode, the so-called CMT-Mix welding process has also been known for some time, as disclosed, for example, in document EP 1 677 940 B1. Here, a short circuit welding phase with a relatively low heat input into the base material, in which a counter movement of the welding wire is implemented, is alternated with an impulse welding phase with a higher heat input relative to the short circuit welding phase. The advantage of this method over conventional methods, such as pure impulse welding, is that only very low heat input into the base material is achieved by means of the regulated current supply and the auxiliary effect of the welding wire movement at the material transition. As a result, the CMT-Mix method can also be used for metal hybrid connections, for example for the connection of steel and aluminum. However, a multiple welding method in which the CMT-Mix welding process can be carried out on two electrodes has not been known to date, since an unstable welding process can occur here. SUMMARY

[0005] It is therefore an object of the present application to propose a multiple welding method which enables a stable welding process on the electrodes and a lower heat input into the base material compared to multiple impulse welding methods.

[0006] According to the application, the task is solved in that a welding process with a short-circuit welding phase and a hot welding phase is carried out on at least two electrodes, respectively, the hot welding phase having a higher heat input into the base material than the short-circuit welding phase, wherein the short-circuit welding phases and the hot welding phases are periodically alternated, and at least the short-circuit welding phases of the welding processes of the at least two electrodes are synchronized in time according to at least one defined first synchronization event per short-circuit welding phase. Thereby, the short-circuit welding phases carried out on the electrodes of the multiple welding method have a defined temporal relationship to each other, whereby a negative influence of the welding processes on each other can be avoided.

[0007] Preferably, the short-circuit welding phases are synchronized in time here in such a way that a first phase shift is defined between the first synchronization events, wherein, for example, the time of the short-circuit formation in the short-circuit welding phase or the time of the increased wire feed speed carried out for the short-circuit formation can be used as the first synchronization event. Thereby, a fixed temporal relationship between the short-circuit welding phases can be set in a simple way, wherein, for example, the phase shift can be determined in the form of a phase angle or a phase time.

[0008] At least one short-circuit cycle is preferably carried out in the short-circuit welding phase, in which the respective electrode is moved in the direction of the base material until a short circuit is formed, and after the short circuit is formed, it is moved in the opposite direction away from the base material, wherein one to ten short-circuit cycles are preferably carried out in the short-circuit welding phase. The droplet detachment from the electrode can be improved by the opposite wire feed. The heat input into the base material can be varied by defining the number of short-circuit cycles.

[0009] Preferably, a spray arc welding phase with a constant welding current is used as the hot welding phase, or a pulse welding phase is carried out with a plurality of pulse cycles successive at a pulse frequency, in which a base current phase with a base current and a pulse current phase with a pulse current higher than the base current are alternated, respectively. When using a pulse welding phase, a known CMT-Mix welding process can thus be advantageously carried out on the electrodes of the multiple welding method.

[0010] It is advantageous if the pulse welding phases of the welding processes of the at least two electrodes are synchronized in time according to at least one defined second synchronization event per pulse welding phase. Thereby, the pulse welding phases also have a defined temporal relationship to each other, and a CMT-Mix welding process can be carried out on the two (or more) electrodes of the multiple welding method, respectively, without the two (or more) welding processes negatively influencing each other.

[0011] Preferably, the pulsed welding phases are synchronized in time in such a way that a second phase shift is specified between second synchronization events, wherein, preferably, characteristic instants in the pulsed welding phase are used as second synchronization events, such as, for example, the instant of a change in the welding parameter or the instant of a droplet detachment from the electrode. Thereby, a defined time relationship can be defined in a simple manner.

[0012] The task is furthermore solved by the apparatus mentioned at the outset in that the control unit is designed to carry out a welding process having a short-circuit welding phase and a hot welding phase, the hot welding phase having a higher heat input into the base material than the short-circuit welding phase, the short-circuit welding phase and the hot welding phase being periodically alternated; and the control unit of at least the first welding device is designed to send at least one synchronization information about a defined first synchronization event of a short-circuit welding phase of a welding process carried out using the first welding device to the control unit of at least one second welding device via a communication link; wherein the control unit of the at least one second welding device is designed to synchronize a welding process carried out using the second welding device in time with the welding process of the first welding device in accordance with a defined first synchronization event of a short-circuit welding phase of a welding process carried out using the second welding device by means of the synchronization information obtained.

[0013] Advantageous design options of the apparatus are proposed in the present application. BRIEF DESCRIPTION OF DRAWINGS

[0014] The application is explained in detail below with reference to the attached drawings, which show by way of example, schematically and non-restrictively, advantageous design options of the application. In the drawings: Figures 1 to 5 The application is explained in detail below with reference to the attached drawings, which show by way of example, schematically and non-restrictively, advantageous design options of the application. In the drawings:

[0015] Figure 1 The structure of an apparatus for carrying out a multiple welding method is shown;

[0016] Figure 2 A time curve of welding parameters of a multiple welding method according to a first advantageous implementation form of the application is shown;

[0017] Figure 3 A time curve of welding parameters of a multiple welding method according to a second advantageous implementation form of the application is shown;

[0018] Figure 4 A time curve of welding parameters of a multiple welding method according to a third advantageous implementation form of the application is shown;

[0019] Figure 5 A time curve of welding parameters of a multiple welding method according to a fourth advantageous implementation form of the application is shown. DETAILED DESCRIPTION

[0020] InFigure 1 A device 1 for carrying out a multiple welding method (e.g. MIG / MAG welding) with at least two electrodes 3A, 3B which are melted is shown schematically in Fig. 1. Here, the device 1 has two mutually independent welding apparatuses A, B with which a defined welding process can be carried out on a common workpiece 6 composed of a metal base material 6. It is of course also possible to provide more than two welding apparatuses A, B, but it is sufficient for understanding the present application to provide two welding apparatuses A, B. The welding apparatuses A, B also do not have to be implemented as separate units, but it is also conceivable that the two (or more) welding apparatuses A, B are provided, for example, in a common housing. This, however, does not change the fact that each welding apparatus A, B itself constitutes its own welding circuit for carrying out the respective welding process.

[0021] As is known, the welding apparatuses A, B can each have a welding power source 2A, 2B, a wire feed unit 14A, 14B and a welding torch 4A, 4B (MIG / MAG welding apparatus). The welding power sources 2A, 2B provide the required welding voltage UA, UB, which is applied to the wire as the electrode 3A, 3B which is melted, respectively. The wire is fed to the respective welding torch 4A, 4B with a specific feed speed vA, vB predetermined by the respective welding process by means of the wire feed unit 14A, 14B. The feeding can be implemented, for example, within the supply pipe 5A, 5B or also externally thereto. The wire feed unit 14A, 14B can be integrated in the welding apparatus A, B, respectively, but can also be a separate unit, as is shown in Fig. 2. Figure 1

[0022] ​Additionally, suitable drive units 18A, 18B can also be provided in the welding torches 4A, 4B for generating the feed speed vA, vB, which can likewise be controlled by the respective control unit 9A, 9B. Generally, the drive units 17A, 17B; 18A, 18B can for example be embodied as driven roller pairs between which the welding wire is conveyed. If the welding device A, B has only drive units 17A, 17B outside the welding torch, this is also referred to as a so-called "push system". In this system, the welding wire is essentially pushed in the direction of the welding torch 4A, 4B. If additionally the indicated drive units 18A, 18B in the welding torch 4A, 4B are also provided, this is also referred to as a so-called "push-pull system". In this system, the welding wire can not only be pushed in the direction of the welding torch 4A, 4B by the drive units 17A, 17B, but can also be pulled in the direction of the welding torch 4A, 4B by the drive units 18A, 18B.

[0023] The "push-pull system" is in particular used in welding processes in which the feed speed vA, vB and, if necessary, also the feed direction can be changed relatively quickly, for example in CMT welding processes. If necessary, a suitable welding wire buffer can also be provided in the "push-pull system", for example in the form of a known welding wire storage unit. The welding wire buffer can be arranged between the (push) drive unit 17A, 17B located outside the welding torch 4A, 4B and the (pull) drive unit 18A, 18B provided in the welding torch 4A, 4B.

[0024] To carry out the welding process, an arc is ignited between the electrode 3A, 3B or the welding wire, respectively, and the base material 6 (= workpiece), as symbolically indicated here by the lightning symbol. By means of the arc, the material of the base material 6 is locally melted on the one hand and a so-called molten pool 15 is generated. On the other hand, the welding wire is fed to the molten pool 15 with the aid of a specific feed speed vA, vB and melted by the arc in order to apply the material of the electrode 3A, 3B being melted to the workpiece 6. In the case of a movement of the welding torch 4A, 4B relative to the workpiece 6, a weld seam (in the Figure 1 direction of the normal on the drawing plane) can thus be produced.

[0025] In the respective supply pipes 5A, 5B, further lines (for example control lines or coolant lines, not shown) can also be provided between the welding device A, B and the respective welding torch 4A, 4B, if necessary. It is also possible to use a shielding gas in order to shield the molten bath 15 from ambient gases, in particular oxygen contained therein, in order to avoid oxidation. Here, inert gases (for example argon), reactive gases (for example CO2) or mixtures thereof are generally used, which can likewise be fed to the welding torch 4A, 4B by means of suitable shielding gas lines 12A, 12B via the supply pipes 5A, 5B. The shielding gas is generally stored in a separate (pressure) container 7A, 7B, which can be fed to the welding device A, B (or directly to the welding torch 4A, 4B) by means of suitable lines. In the case of the use of the same shielding gas, it is also possible to provide one common container for both (all) welding devices A, B. The supply pipes 5A, 5B can be coupled to the welding torch 4A, 4B and to the welding device A, B, for example by means of suitable couplings.

[0026] In order to respectively form a welding circuit of the welding device A, B, the welding power source 2A, 2B can be connected to the base material 6 by means of a ground line 8A, 8B, respectively. One pole (generally the negative pole) of the welding power source 2A, 2B is connected to the ground line 8A, 8B. The other pole (generally the positive pole) of the welding power source 2A, 2B is connected to the welding torch 4A, 4B by means of a suitable current line 13A, 13B (or vice versa). Thus, for each welding process a welding circuit is formed by means of the arc and the base material 6.

[0027] In the welding device A, B, a control unit 9A, 9B can also be provided, respectively, which controls and monitors the respective welding process (including the respective wire feed). For this purpose, in the control unit 9A, 9B the welding parameters required for the welding process (for example the feed speed vA, vB, the welding current IA, IB, the welding voltage UA, UB, the pulse frequency fA, fB, etc.) are predetermined or adjustable. In order to control the respective welding process, the control unit 9A, 9B is connected to the welding power source 2A, 2B and to the wire feed unit 14A, 14B (for example in particular the drive unit 17A, 17B). In order to input or display certain welding parameters or welding states, a user interface 10A, 10B connected to the control unit 9A, 9B can also be provided.

[0028] Furthermore, the welding devices A, B can also be provided with suitable (not shown) interfaces via which the welding devices A, B can be connected to a higher-ranking control unit via which the entire multiple welding method can be controlled. For example, a (not shown) central control unit can be provided which is connected to both welding devices A, B (or to a plurality of welding devices) and via which the welding processes of the welding devices A, B can be controlled. The welding devices A, B are of course fully known and therefore are not discussed in more detail at this point.

[0029] The two welding torches 4A, 4B can also be arranged locally relative to one another such that the electrodes or welding wires 3A, 3B work in two separate molten baths instead of in one common molten bath 15 on the workpiece 6, as is shown in Figure 1 The arrangement relative to one another can be fixed, for example in the arrangement in which the two welding torches 4A, 4B are arranged in a (not shown) welding robot which guides the two welding torches 4A, 4B. The arrangement can also be variable, for example in the arrangement in which one welding torch 4A, 4B is guided by one welding robot each. Instead of a welding robot, another suitable guiding device can of course also be provided, for example a gantry crane of the type which is preferably capable of movement in a plurality of (preferably three) axes. It is, however, also possible to provide one common welding torch for both electrodes 3A, 3B, as is indicated by the dashed line in Figure 1 It is not important here whether with the welding torches 4A, 4B a lap welding or a build-up welding or some other welding method is implemented. It is of course also possible in principle to carry out the multiple welding method manually, for example in the manner that one or more welding torches 4A, 4B are guided by hand.

[0030] The control units 9A, 9B of the welding devices A, B can be connected by means of a communication link 11 via which synchronization information Y can be transmitted and / or received by means of which the two welding processes can be synchronized in time. Preferably, the welding devices A, B are constructed such that the synchronization information Y can be exchanged between the control units 9A, 9B, as is indicated by the double arrow in Figure 1 Thereby, the two welding devices A, B can be used not only as "leading devices" but also as "following devices". The "leading device" welding device A or B can transmit the synchronization information Y and the "following device" welding device A or B can use the synchronization information Y in order to synchronize the welding process carried out with the "following device" welding device A or B in time to the welding process of the "leading device" welding device A or B. The communication link 11 can be, for example, a wired or wireless connection between the control units 9A, 9B or between the user interfaces 10A, 10B, for example a fully known data bus.

[0031] In the simplest case, the synchronization information Y can be a single synchronization pulse, which is transmitted by the transmitting welding device A or B to at least one other (receiving) welding device A or B, respectively, over the communication link 11. Here, the synchronization pulse can be transmitted between the two welding devices A, B as a current or voltage pulse over a wired communication link 11, for example. It is also possible, however, for the communication link 11 to be implemented as a data bus over which bus messages are transmitted. In this case, the synchronization pulse can be transmitted as a bus message, which can be implemented not only wired (cable, glass fiber, etc.) but also wirelessly (Wifi, Bluetooth, etc.). In the receiving welding device A or B, the respectively implemented welding process can be synchronized with the welding process of the transmitting welding device A or B by means of the received synchronization pulse.

[0032] According to the invention, the control units 9A, 9B are configured to implement a welding process with a short-circuit welding phase SPA1, SPB1 and a hot welding phase SPA2, SPB2, respectively, the hot welding phase having a higher heat input into the base material 6 than the short-circuit welding phase, the short-circuit welding phase and the hot welding phase being periodically alternated (see Fig. 2). Figures 2-5 It is furthermore provided that the control unit 9A of at least the first welding device A is configured to transmit synchronization information Y about a defined first synchronization event SEA1 of the short-circuit welding phase SPA1 of the welding process implemented with the first welding device A over the communication link 11 to the control unit 9B of the at least one second welding device B. The control unit 9B of the at least one second welding device B is configured to synchronize the welding process implemented with the second welding device B in time with the welding process of the first welding device A in accordance with a defined first synchronization event SEB1 of the short-circuit welding phase SPB1 of the welding process implemented with the second welding device B by means of the obtained synchronization information Y. The first welding device A thus serves as a "lead device" welding device, while the second welding device B serves as a "follow-up device" welding device. Figures 2-5 Figures 2-5

[0033] ​​For example, the characteristic moment in the short-circuit welding phase SPA1, SPB1 in the respectively executed welding process can be used as the first synchronization event SEA1, SEB1, which is known or can be detected as simply as possible. For example, a rapid change in a welding parameter, such as the welding current I, the welding voltage U or the feed speed v, for example a rising or falling edge in a time curve, can be used as the first synchronization event SEA1, SEB1. Here, the synchronization information Y can comprise, for example, a first phase shift φ1 between the first synchronization event SEA1 in the welding process of the first welding device A and the first synchronization event SEB1 in the welding process of the second welding device B. Here, for example, an angle of 0-360° with respect to a periodically repeated welding cycle or also time can be used as the phase shift φ, as will be explained later on according to Figures 2-5 This will be explained in more detail.

[0034] It is known that the short-circuit welding phase SPA1, SPB1 is characterized by the short-circuit formation when the respective electrode 3A, 3B contacts the base material 6. Thus, the characteristic moment of the short-circuit formation for the short-circuit welding phase SPA1, SPB1 can advantageously be specified as the first synchronization event SEA1, SEB1 of the short-circuit welding phase SPA1, SPB1. The moment of the short-circuit formation can be determined, for example, from the curve of the welding current I or the welding voltage U, as will be explained later on according to Figures 2-5 This will be explained in more detail. However, instead of the actual moment of the short-circuit formation, for example, also a known moment of increasing the feed speed v can be used as the first synchronization event SEA1, SEB1, which is intentionally executed in order to substantially force the short-circuit formation. Alternatively, also a known moment of decreasing the welding current IA, IB can be used as the first synchronization event SEA1, SEB1, which is intentionally executed in order to substantially force the short-circuit formation. By intentionally decreasing the welding current IA, IB, the arc energy of the arc can be reduced, so that a short-circuit is formed. The increase of the feed speed v and the decrease of the welding current IA, IB can be realized, for example, temporally staggered, wherein the moment of increasing the feed speed v or the moment of decreasing the welding current IA, IB can be used as the first synchronization event SEA1, SEB1. However, the increase of the feed speed v and the decrease of the welding current IA, IB can also be realized simultaneously, so that the common moment can be used as the first synchronization event SEA1, SEB1.

[0035] To improve droplet detachment during the short-circuit welding stages SPA1 and SPB1, it is advantageous to implement at least one short-circuit cycle ZKA and ZKB during these stages. During this cycle, electrodes 3A and 3B are moved toward the base material 6 until a short circuit is formed, and then moved away from the base material 6 in the opposite direction after the short circuit is formed. This movement can be achieved in a known manner by having corresponding control units 9A and 9B drive the corresponding wire feed units 14A and 14B. The duration of the short-circuit welding stages SPA1 and SPB1 (which have a lower heat input to the base material 6 compared to the hot welding stages) can be flexibly defined, for example, by predetermining a specific number of short-circuit cycles ZKA and ZKB, such as two to ten short-circuit cycles ZKA and ZKB for each stage. Preferably, the opposite wire feed is implemented during each short-circuit cycle ZKA and ZKB, i.e., moving toward the base material 6 until a short circuit is formed, and then moving away from the base material 6 after the short circuit is formed. Of course, the opposite direction of the wire feed, i.e., the reverse direction of the feed speeds vA and vB, is merely optional. For example, the short-circuit welding stages SPA1 and SPB1 can also be implemented with only a variable feed speed v without changing the direction of wire movement.

[0036] For example, known pulse welding stages can be used ( Figures 2-5 The short-circuit welding stages SPA1 and SPB2 are used as the hot welding stages. Thus, the CMT-Mix welding process described at the beginning can be performed in parallel using two welding devices A and B, in which the short-circuit welding stages SPA1 and SPB1 and the pulse welding stages SPA2 and SPB2 alternate periodically. Here, in the pulse welding stages, multiple pulse cycles ZPA and ZPB are typically performed successively at specific pulse frequencies fA and fB, in which a base current stage with base currents IGA and IGB alternates with a pulse current stage IPA and IPB with pulse currents higher than the base currents IGA and IGB. However, for example, a known (not shown) spray arc welding stage can also be used as the hot welding stages SPA2 and SPB2, which has substantially constant welding currents IA and IB.

[0037] Preferably, the same welding process is carried out on both electrodes 3A, 3B in parallel, in such a way that the control units 9A, 9B of both welding devices A, B set the same predetermined or predeterminable welding parameters ((U, I, v), f, etc.). If, for example, the pulsed welding phases are carried out as hot welding phases SPA2, SPB2 using both welding devices A, B, it is advantageous to use the same pulse frequency fA, fB in both pulsed welding phases. However, the pulse frequency fA, fB in the pulsed welding phase of one welding device A, B can also be an integer multiple of the pulse frequency fA, fB of the pulsed welding phase of the other welding device A, B, respectively.

[0038] If the pulsed welding phases (CMT-Mix welding process) are each specified as hot welding phases SPA2, SPB2, it is advantageous to synchronize the welding processes carried out using the at least two welding devices A, B on the at least two electrodes 3A, 3B in time in accordance with at least one defined second synchronization event SEA2, SEB2 of each pulsed welding phase. It is thereby possible to synchronize at least two parallelly carried out (CMT-Mix) welding processes in time in such a way that not only the two short-circuit welding phases but also the two pulsed welding phases are in a defined temporal relationship to one another, for example in accordance with Figures 2-5 This will be explained in detail further below.

[0039] The pulsed welding phases SPA2, SPB2 can be synchronized in time, for example, like the short-circuit welding phases, in such a way that a second phase shift φ2 is specified between the defined second synchronization events SEA2, SEB2, for example in the form of a phase angle or a time. It is also possible to use characteristic moments in the pulsed welding phases SPA2, SPB2, for example the moments of droplet detachment of the respective electrode 3A, 3B or the moments of rapid change of a welding parameter (for example rising or falling edges in the time curve of, for example, the welding current I, the welding voltage U or the feed speed v) as second synchronization events SEA2, SEB2.

[0040] By the synchronization in time of the two (preferably CMT-Mix) welding processes according to the application, it is now possible to carry out the (at least) two welding processes stably and with as little mutual influence as possible, since the two welding processes are run in a defined temporal relationship to one another. The respective moments of short-circuit formation (or the moments at which the increased feed speed for triggering the short circuit is specified or the moments at which the reduced welding current for triggering the short circuit is specified) and / or the moments of droplet detachment can be detected, for example, by the respective control unit 9A, 9B or can also be known, for example, if a pre-set welding process with known welding parameters (known time curves of the welding current I, the welding voltage U, the feed speed v, etc.) is used.

[0041] The control unit 9A of the first welding device A can for example implement a first welding process in that it sets specific welding parameters, such as a specific welding current IA, a welding voltage UA and a specific feed speed VA, by means of the control unit 9A (for example a predetermined CMT-Mix welding process with a short circuit welding phase SPA1 and a pulsed welding phase as hot welding phase SPA2). Similarly, the control unit 9B of the second welding device B can implement a second welding process in that it sets specific welding parameters, such as for example a specific welding current IB, a welding voltage UB and a specific feed speed VB, by means of the control unit 9B (for example again a CMT-Mix welding process with a short circuit welding phase and a pulsed welding phase as hot welding phase SPB2).

[0042] Here, the control unit 9A of the first welding device A ("pilot device") can send synchronization information Y about at least one first synchronization event SEA1 of the short circuit welding phase SPA1 of the first welding process (for example the time of short circuit formation) and (optionally) about at least one second synchronization event SEA2 of the pulsed welding phase SPA2 of the first welding process (for example the time of droplet detachment of the electrode 3A) to the control unit 9B of the second welding device B by means of the communication link 11, for example as synchronization pulses or as bus messages. The control unit 9B of the second welding device B ("follower device") can use the obtained synchronization information Y to synchronize the implemented second (CMT-Mix) welding process in time with the first (CMT-Mix) welding process of the first welding device A. In particular, the control unit 9B of the second welding device B can synchronize the short circuit welding phase SPB1 in time with the short circuit welding phase SPA1 of the first welding device A according to the first synchronization event SEB1 (for example the time of short circuit formation) by means of the synchronization information Y. Additionally, the control unit 9B of the second welding device B can synchronize the pulsed welding phase SPB2 in time with the pulsed welding phase SPA2 of the first welding device A according to the second synchronization event SEB2 (for example the time of droplet detachment from the electrode 3B) by means of the synchronization information Y, if necessary.

[0043] The synchronization information Y can for example contain a specific first phase shift φ1 by which the short circuit welding phases SPA1, SPB1 are implemented offset in time from each other. The first phase shift φ1 is predetermined, but can also be settable (for example by means of the user interfaces 10A and / or 10B). Similarly, the synchronization information Y can contain a specific second phase shift φ2 by which the pulsed welding phases SPA2, SPB2 are implemented offset in time from each other. It can for example be considered to implement the short circuit welding phases SPA1, SPB1 synchronously, i.e. with a first phase shift φ1 = 0, and also the pulsed welding phases SPA2, SPB2 synchronously, i.e. with a second phase shift φ2 = 0, as in the example of a CMT-Mix welding process with a short circuit welding phase and a pulsed welding phase as hot welding phase, as shown in Fig. 2.Figure 3 As shown in the diagram. However, different synchronization times can certainly be chosen, such as φ1=0, φ2≠0 ( Figure 2 ); φ1≠0, φ2=0( Figure 5 ); φ1=φ2≠0 ( Figure 4 ), where φ1 < φ2, φ1 > φ2, or φ1 = φ2.

[0044] According to the following text Figures 2 to 5 Advantageous designs for synchronization according to the invention are described. Here, for welding processes performed in parallel on (here, two) electrodes 3A and 3B, curves of welding currents IA and IB, welding voltages UA and UB, and feed rates vA and vB with respect to time t are shown overlapping, respectively. Here, solid lines relate to a first welding process performed on electrode 3A using a first welding device A, for example, in a multi-welding method, while dashed lines relate to a second welding process performed on electrode 3B using a second welding device B, for example. Here, two CMT-Mix welding processes are exemplarily shown as first and second welding processes, in which short-circuit welding stages SPA1 and SPB1 and pulse welding stages, i.e., hot welding stages SPA2 and SPB2, are periodically alternated, respectively. In single-electrode welding methods using one electrode, the CMT-Mix welding process is known in principle, and therefore only aspects essential to the invention are discussed in more detail here. As mentioned, a jet arc welding stage with substantially constant welding currents IA and IB can also be used as a hot welding stage instead of a pulse welding stage. In this case, synchronization of SPA1 and SPB1 during the short-circuit welding stage is sufficient.

[0045] As is well known, multiple pulse cycles ZPA and ZPB with predetermined or adjustable pulse frequencies fPA and fPB can be executed successively during the pulse welding stages SPA2 and SPB2. Here, the pulse frequencies fPA and fPB correspond to the reciprocals of the period durations TZPA and TZPB of the pulse cycles ZPA and ZPB, as shown in... Figure 2The examples are exemplarily shown according to one pulse cycle ZPA and ZPB of the second (pulse) welding stages SPA2 and SPB2, respectively. In each pulse cycle ZPA and ZPB, a base current phase with base currents IGA and IGB typically alternates with a pulse current phase with pulse currents IPA and IPB that are higher than the base currents IGA and IGB. Such current pulses are generated through each pulse cycle ZPA and ZPB to achieve the purposeful detachment of the molten droplet from the corresponding electrodes 3A and 3B. The timing of the droplet detachment can, for example, be used for the pulse welding stages SPA2 and SPB2 as a characteristic second synchronization event SEA2 and SEB2 in the sense of the invention, so that the two pulse welding stages SPA2 and SPB2 are synchronized in time, as will be explained in more detail below.

[0046] Here, the pulse frequencies fPA and fPB, the base currents IGA and IGB, and the pulse currents IPA and IPB can be selected in equal or different amounts. The time curves of the welding voltages UA and UB shown in the middle figure qualitatively correspond to the curves of the welding currents IA and IB, and therefore will not be discussed in more detail here. Generally, the voltage U during the welding process is generated from the voltage drop on the arc and the voltage drop at the free end of the welding wire. The feed rates vA and vB of electrodes 3A and 3B are essentially constant during the pulse welding stages SPA2 and SPB2, as can be seen in the figure below, and vary when transitioning from or to the corresponding short-circuit welding stages SPA1 and SPB1. However, it is also possible to consider non-constant feed rates vA and vB during the pulse welding stages SPA2 and SPB2. The duration of the entire pulse welding phase SPA2 and SPB2 (which is generated from the number of pulse cycles ZPA and ZPB and their cycle durations TZPA and TZPB) can be adjusted, for example, by a predetermined time or by a predetermined number of pulse cycles ZPA and ZPB and their cycle durations TZPA and TZPB.

[0047] exist Figures 2 to 5 In the example shown, the welding current IB, welding voltage UB, and feed rate vB of the second electrode 3B are numerically slightly lower than those of the first electrode 3B. This is because the first electrode 3A is defined as the guide electrode, while the second electrode 3B is defined as the follower electrode. The guide electrode leads the follower electrode along the welding direction (= the direction in which the welding torches 4A and 4B move to generate the weld). This means that the follower electrode works into the molten pool already generated by the guide electrode, thus requiring slightly lower welding energy. Of course, this is merely an example, and the same welding parameters can be used in both welding processes.

[0048] It is known that at least one short-circuit cycle ZKA, ZKB is implemented in the short-circuit welding phase SPA1, SPB1, in which the respective electrode 3A, 3B is moved in the direction of the base material until a short circuit is formed, and preferably also in the opposite direction away from the base material 6 after the short circuit has been formed, as can be seen in the following figures according to the feed speed vA, vB. The moment of short-circuit formation can be identified by an increase in the welding current IA, IB or, in particular, by a simultaneous drop in the welding voltage UA, UB. In the sense of the present application, the moment of short-circuit formation can advantageously be used as a characteristic first synchronization event SEA1, SEB1 of the short-circuit welding phase SPA1, SPB1, so that the two short-circuit welding phases SPA1, SPB1 can be synchronized with one another in time, as will be elucidated further below. Alternatively, however, instead of the actual moment of short-circuit formation as the characteristic first synchronization event SEA1, SEB1 of the short-circuit welding phase SPA1, SPB1, for example, the moment of a brief increase in the feed speed vA, vB, which is implemented intentionally shortly before the actual moment of short-circuit formation in order to trigger the short-circuit formation, can also be used (as is exemplarily shown in the middle). Figure 5

[0049] In the example shown, only one unique short-circuit cycle ZKA, ZKB is shown for each short-circuit welding phase SPA1, SPB1, respectively, but of course a plurality of short-circuit cycles ZKA, ZKB can also be implemented. For example, two to ten short-circuit cycles ZKA, ZKB can be implemented per short-circuit welding phase SPA1, SPB1. By specifying the number of short-circuit cycles ZKA, ZKB, the duration of the short-circuit welding phase SPA1, SPB1 can be defined, and thus the time in which less heat input into the base material 6 should be achieved (relative to the hot welding phase SPA2, SPB2 or the pulsed welding phase) is limited. The welding current IA, IB can also be varied in the short-circuit cycles ZKA, ZKB, in particular a specific profile of the welding current IA, IB can be adjusted by the respective control unit 9A, 9B. For example, in addition to the opposite wire feed speed vA, vB, during the short-circuit cycles ZKA, ZKB, the welding current IA, IB can be increased from a base current (which can be identical to or different from the base current IGA, IGB of the pulsed welding phase SPA2, SPB2) to a boost current which is higher relative to the base current (and lower relative to the pulse current IPA, IPB of the pulsed welding phase SPA2, SPB2) and again decreased to the base current in order to support the droplet detachment.

[0050] In accordance with the present application, the short-circuit welding phase SPA1, SPB1 is followed by a hot welding phase SPA2, SPB2, in which the welding current IA, IB is increased to a value which is higher than the boost current of the short-circuit welding phase SPA1, SPB1, and the welding voltage UA, UB is increased to a value which is higher than the welding voltage of the short-circuit welding phase SPA1, SPB1. In the hot welding phase SPA2, SPB2, the welding current IA, IB and the welding voltage UA, UB are thus increased to values which are higher than the values of the short-circuit welding phase SPA1, SPB1, so that a higher heat input into the base material 6 is achieved in the hot welding phase SPA2, SPB2 than in the short-circuit welding phase SPA1, SPB1. Figure 2 ​In the example shown, the short-circuit welding phases SPA1, SPB1 are synchronized in time with a first phase shift φ1 = 0, i.e. the short-circuit periods ZKA, ZKB of the two parallelly conducted welding processes on the electrodes 3A, 3B are conducted simultaneously. The synchronization is achieved, as described above, on the basis of at least one first synchronization event SEA1, SEB1 of each short-circuit welding phase SPA1, SPB1, respectively, wherein the moment of short-circuit formation in the short-circuit periods ZKA, ZKB is specified as the first synchronization event SEA1, SEB1. In the example shown, the pulsed welding phases SPA2, SPB2 are synchronized in time with a second phase shift φ2 = 180°, i.e. the pulse periods ZPA, ZPB are conducted offset in time from one another, as can be seen from the welding currents IA, IB and from the welding voltages UA, UB. The synchronization of the pulsed welding phases SPA2, SPB2 is again achieved on the basis of at least one second synchronization event SEA2, SEB2 of each pulsed welding phase SPA2, SPB2, respectively, wherein the moment of droplet detachment, i.e. the increase from the base current IGA, IGB to the pulse current IPA, IPB, is specified as the second synchronization event SEA2, SEB2. The pulse frequencies fA, fB are preferably of the same size, as can be seen in Figure 2 However, the pulse frequencies can also be of different sizes, wherein a respectively higher pulse frequency fA, fB is preferably an integer multiple of a respectively lower pulse frequency fA, fB.

[0051] In the example according to Figure 3 the short-circuit welding phases SPA1, SPB1 are synchronized in time with a phase shift φ1 = 0 and likewise the pulsed welding phases SPA2, SPB2 are synchronized in time with a phase shift φ2 = 0°, i.e. not only the short-circuit periods ZKA, ZKB but also the pulse periods ZPA, ZPB are conducted synchronously, as can be seen from the welding currents IA, IB and from the welding voltages UA, UB. Similarly, the synchronization is again achieved on the basis of the moment of short-circuit formation as the first synchronization event SEA1, SEB1 of the short-circuit welding phases SPA1, SPB1 and on the basis of the droplet detachment as the second synchronization event SEA2, SEB2 of the pulsed welding phases SPA2, SPB2.

[0052] In the example according to Figure 4In the example, the short-circuit welding stages SPA1 and SPB1 are synchronized in time with a phase shift of φ1 = 180°, and the pulse welding stages SPA2 and SPB2 are also synchronized in time with a phase shift of φ2 = 180°. This means that not only the short-circuit periods ZKA and ZKB, but also the pulse periods ZPA and ZPB are implemented in time-staggered manner, as can be seen from the welding currents IA and IB, the welding voltages UA and UB, and for the short-circuit welding stages SPA1 and SPB1, also from the feed rates vA and vB. Synchronization is achieved by using the moment of short-circuit formation as the first synchronization event SEA1 and SEB1 for the short-circuit welding stages SPA1 and SPB1, and by using the moment of droplet detachment as the second synchronization event SEA2 and SEB2 for the pulse welding stages SPA2 and SPB2. Of course, other characteristic moments can also be specified as the first synchronization event SEA1 and SEB1 and the second synchronization event SEA2 and SEB2.

[0053] Finally, in accordance with Figure 5 In the example, the short-circuit welding stages SPA1 and SPB1 are synchronized in time with a phase shift of φ1 = 180°, and the pulse welding stages SPA2 and SPB2 are synchronized in time with a phase shift of φ2 = 0°. This means that the short-circuit periods ZKA and ZKB are implemented out of time, while the pulse periods ZPA and ZPB are implemented synchronously, as can be seen from the welding currents IA and IB, the welding voltages UA and UB, and for the short-circuit welding stages SPA1 and SPB1, also from the feed rates vA and vB. Furthermore, synchronization is achieved by using the moment of short-circuit formation as the first synchronization event SEA1 and SEB1 for the short-circuit welding stages SPA1 and SPB1, and by using the droplet shedding as the second synchronization event SEA2 and SEB2 for the pulse welding stages SPA2 and SPB2.

[0054] For the sake of completeness, in Figure 5 In the lower part of the diagram, the previously mentioned brief increases in feed rates vA and vB as alternative synchronization events SEA1' and SEB1' (dotted lines) for the short-circuit welding stages SPA1 and SPB1 are also shown. Here, the feed rates vA and vB are intentionally and briefly increased at defined times to trigger short-circuit formation. Figure 5 The increase in wire feed rate is depicted in a jump-like manner. Of course, the increase in wire feed rate can also be achieved continuously. Here, since the welding process is known and the welding parameters are known, the timing is also known.

[0055] By the synchronization in time according to the application, the welding processes of the parallel implementation of the multiple welding method can be coordinated in the desired manner with one another, so that the two (or more) welding processes negatively influence one another as little as possible. Finally, it should be mentioned that the described embodiments are of course merely exemplary and not restrictive of the application, and the specific implementation is left to the discretion of the person skilled in the art.

Claims

1. Method for carrying out a multiple welding process on a base material (6) with at least two electrodes (3A, 3B) which are melted, wherein A welding process is performed between the electrodes (3A, 3B) and the base material (6) after the arc is ignited on each electrode (3A, 3B), and the welding process of the at least two electrodes (3A, 3B) is synchronized in time. The welding process is characterized by performing a welding process with a short-circuit welding stage (SPA1, SPB1) and a hot welding stage (SPA2, SPB2) on the at least two electrodes (3A, 3B), respectively, wherein the hot welding stage has a higher heat input to the base material (6) relative to the short-circuit welding stage (SPA1, SPB1); the short-circuit welding stage (SPA1, SPB1) and the hot welding stage (SPA2, SPB2) alternate periodically; and the welding process of the at least two electrodes (3A, 3B) is synchronized in time according to at least one defined first synchronization event (SEA1, SEB1) of each short-circuit welding stage (SPA1, SPB1).

2. The method of claim 1, wherein, The short-circuit welding stages (SPA1, SPB1) are synchronized in time by defining a first phase shift (φ1) between the first synchronization events (SEA1, SEB1).

3. The method according to claim 1 or 2, characterized in that, The moment when a short circuit is formed during the short-circuit welding stages (SPA1, SPB1), or the moment when the feed rate is increased (vA, vB) for the purpose of short circuit formation, or the moment when the welding current is reduced (IA, IB) for the purpose of short circuit formation, is used as the first synchronization event (SEA1, SEB1).

4. The method according to claim 1 or 2, characterized in that, At least one short-circuit cycle (ZKA, ZKB) is performed during the short-circuit welding stages (SPA1, SPB1), during which the corresponding electrodes (3A, 3B) are moved toward the base material (6) until a short circuit is formed, and after the short circuit is formed, they are moved away from the base material (6) in the opposite direction.

5. The method according to claim 1 or 2, characterized in that, The pulse welding stage or the spray arc welding stage is used as the hot welding stage (SPA2, SPB2). In the pulse welding stage, multiple pulse cycles (ZPA, ZPB) are implemented in succession with pulse frequencies (fA, fB). In the pulse cycle, a base current stage with a base current (IGA, IGB) and a pulse current stage with a higher pulse current (IPA, IPB) than the base current (IGA, IGB) are alternated respectively. In the spray arc welding stage, a constant welding current is used.

6. The method of claim 5, wherein, The pulse welding phase (SPA1, SPB1) synchronizes the welding process of the at least two electrodes (3A, 3B) in time according to at least one defined second synchronization event (SEA2, SEB2) of each pulse welding phase (SPA2, SPB2).

7. The method of claim 6, wherein, In the time-synchronized pulse welding phase (SPA2, SPB2), a second phase shift (φ2) is defined between the second synchronization events (SEA2, SEB2).

8. The method according to claim 6 or 7, characterized in that, The characteristic moments in the pulse welding stages (SPA2, SPB2) are used as the second synchronization events (SEA2, SEB2).

9. The method of claim 4, wherein, Two to ten short-circuit cycles (ZKA, ZKB) are performed during the short-circuit welding stage.

10. The method of claim 8, wherein, The characteristic moments used as the second synchronization events (SEA2, SEB2) in the pulse welding phase (SPA2, SPB2) are the moments when the welding parameters (U, I, v) change or when the molten droplets fall off the electrodes (3A, 3B).

11. Apparatus (1) for carrying out a multiple welding method, wherein The apparatus includes at least two welding devices (A, B), which are used to perform a welding process on the base material (6) using electrodes (3A, 3B) for melting. Each welding device (A, B) has a control unit (9A, 9B) for controlling the corresponding welding process. The control units (9A, 9B) of the at least two welding devices (A, B) are connected via a communication link (11) to synchronize the welding processes in time. The control units (9A, 9B) are configured to perform welding processes having a short-circuit welding stage (SPA1, SPB1) and a hot welding stage (SPA2, SPB2), respectively. The hot welding stage has a higher heat input to the base material (6) than the short-circuit welding stage. The welding stages alternate periodically; and at least the control unit (9A) of the first welding device (A) is configured to send at least one synchronization information (Y) of a first synchronization event (SEA1) defined for the short-circuit welding stage (SPA1) of the welding process implemented by the first welding device (A) to the control unit (9B) of at least one second welding device (B) via a communication link (11); the control unit (9B) of the at least one second welding device (B) is configured to, by means of the obtained synchronization information (Y), synchronize the welding process implemented by the second welding device (B) with the welding process of the first welding device (A) in time according to the first synchronization event (SEB1) defined for the short-circuit welding stage (SPB1) of the welding process implemented by the second welding device (B).

12. The apparatus of claim 11, wherein, The synchronization information (Y) includes at least one first phase shift (φ1) between the first synchronization events (SEA1, SEB1).

13. The apparatus of claim 11 or 12, wherein, The moment when a short circuit forms during the short-circuit welding stages (SPA1, SPB1), or the moment when the feed rate is increased (vA, vB) for the purpose of short circuit formation, or the moment when the welding current is reduced (IA, IB) for the purpose of short circuit formation, is defined as the first synchronous event (SEA1, SEB1).

14. The apparatus of claim 13, wherein, Each welding device (A, B) has a wire feed unit (14A, 14B) which can be driven by the control unit (9A, 9B), wherein the control unit (9A, 9B) is configured to perform at least one short-circuit cycle (ZKA, ZKB) in the short-circuit welding stage (SPA1, SPB1), in which the wire feed unit (14A, 14B) moves the electrode (3A, 3B) toward the base material (6) until a short circuit is formed, and moves away from the base material (6) in the opposite direction after the short circuit is formed.

15. The apparatus of claim 13, wherein, The control units (9A, 9B) are configured to implement a pulse welding stage (SPA2, SPB2) having multiple pulse cycles (ZPA, ZPB) with successive pulse frequencies (fA, fB) as the hot welding stage, in which a base current stage with a base current (IGA, IGB) and a pulse current stage with a higher pulse current (IPA, IPB) than the base current (IGA, IGB) alternate respectively; or the control units (9A, 9B) are configured to implement a spray arc welding stage with a constant welding current as the hot welding stage (SPA2, SPB2).

16. The apparatus of claim 12 or 14, wherein, The control unit (9A) of at least the first welding device (A) is configured to send synchronization information (Y) of a second synchronization event (SEA2) defined for the pulse welding phase (SPA2) of the welding process implemented by the first welding device (A) to the control unit (9B) of the at least one second welding device (B) via a communication link (11); wherein the control unit (9B) of the at least one second welding device (B) is configured to, by means of the obtained synchronization information (Y), synchronize the welding process implemented by the second welding device (B) with the welding process of the first welding device (A) in time according to the second synchronization event (SEB2) defined for the pulse welding phase (SPB2) of the welding process implemented by the second welding device (B).

17. The apparatus according to claim 16, characterized in that, The synchronization information (Y) includes at least one second phase shift (φ2) between the second synchronization events (SEA2, SEB2).

18. The apparatus according to claim 14, characterized in that, Two to ten short-circuit cycles (ZKA, ZKB) can be implemented during the short-circuit welding stage (SPA1, SPB1).

19. The apparatus according to claim 17, characterized in that, The synchronization information (Y) includes at least one second phase shift (φ2) between the second synchronization events (SEA2, SEB2), wherein a characteristic moment in the pulse welding phase (SPA2, SPB2) is defined as the second synchronization event (SEA2, SEB2).

20. The apparatus according to claim 19, characterized in that, In the pulse welding phases (SPA2, SPB2), the characteristic moments defined as the second synchronization events (SEA2, SEB2) are the moments when the molten droplets fall off the electrodes (3A, 3B) or when the welding parameters (U, I, v) change.

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