Orbital welding method and device for producing a chain of joining points by means of different welding cycles

Abstract

The invention relates to an orbital welding method in which two joining partners (152, 154), which are tubular at least in a joining region (150), are arranged relative to one another, in particular in a lap joint, and in which a chain (211) of joining points (210) running in the circumferential direction of the joining partners (152, 154) is produced in the joining region (150), which chain integrally connects the joining partners (152, 154), wherein, in order to produce the chain (211) of joining points (210), an arc burns between a welding electrode (126) and at least one of the joining partners (152, 154), wherein the arc is operated with a characteristic curve which has a sequence of welding cycles each with at least a high-current phase and a low-current phase, and wherein the sequence of welding cycles comprises welding cycles which differ in at least one welding parameter, and / or the characteristic curve has, before or after the sequence of welding cycles, one or more cycles which differ from the welding cycles in at least one welding parameter. The invention further relates to an orbital welding device (100, 101) and a system (700) having such an orbital welding device (100, 101).

Description

[0001] Orbital welding process and device for generating a chain of joining points using different welding cycles

[0002] The present invention relates to an orbital welding process in which two joining partners which are tubular in at least one joining area are arranged relative to each other, in particular in an overlap joint, and in which a chain of joining points extending circumferentially to the joining partners is generated in the joining area, which connects the joining partners in a material-bonded manner.The present invention further relates to an orbital welding device, preferably for use in the aforementioned orbital welding process, comprising a welding head having a receptacle for positioning a joining area of ​​two joining partners that are at least tubular in the joining area, in particular a fitting and a pipe end, a welding power source and a welding electrode connected thereto, an electrode recirculation mechanism and an electrode drive for driving the electrode recirculation mechanism, wherein the electrode recirculation mechanism is configured to move the welding electrode circumferentially around the receptacle, and a control device configured to control the orbital welding device in such a way that, by means of the welding electrode, a chain of joining points extending circumferentially around the joining partners is generated on two joining partners arranged in the receptacle, which connects the joining partners in a material-bonded manner.The present invention further relates to a system.

[0003] In the prior art, arc-based orbital welding processes, in particular tungsten inert gas (TIG) welding, are used, for example, for the metallurgical joining of pipes. In this process, the pipe ends to be joined are typically butt-jointed and welded together by guiding the welding tool circumferentially (orbitally) around the joint. The welding torch can be guided manually or automatically. On the outside of the pipes, discoloration can be largely suppressed by the shielding gas used in TIG welding; however, residual heat in the workpiece can still cause oxidation after the welding process. To protect the inner surface of the pipes from oxidation, additional measures are required, such as purging the pipes with forming gas.

[0004] Orbital welding of copper pipes has proven particularly challenging in this respect. Due to copper's high thermal conductivity, the heat introduced into the material from the outside during the welding process is quickly dissipated, requiring higher energy levels to reach the necessary temperatures at the weld point. This results in increased energy consumption, making the use of battery-powered welding equipment difficult. Furthermore, copper's high thermal conductivity leads to significant heating of the pipe's inner surface, making it particularly susceptible to discoloration and oxidation.

[0005] Furthermore, the use of battery-powered welding equipment, especially handheld devices, is made more difficult by the fact that the welding power sources commonly used in the prior art require rather expensive and / or large electronic components, for example rather expensive and large coupling transformers, which are poorly suited for a handheld device.

[0006] Against this background, the present invention is based on the objective of providing a welding power source, a method for operating it, an orbital welding device with such a welding power source, a system with such an orbital welding device and an orbital welding method, with which at least some of the aforementioned problems can be reduced or avoided.The aforementioned problem is solved according to the invention by an orbital welding process in which two joining partners, at least in one joining area tubular, are arranged relative to each other, in particular in a lap joint, in which a chain of joining points extending in the circumferential direction of the joining partners is generated in the joining area, which connects the joining partners in a material-bonded manner, wherein an arc burns between a welding electrode and at least one of the joining partners to generate the chain of joining points, wherein the arc is operated with a current characteristic curve which has a sequence of welding cycles with at least one high-current phase and one low-current phase, and wherein the sequence of welding cycles includes welding cycles which differ in at least one welding parameter, and / or the current characteristic curve has one or more cycles before or after the sequence of welding cycles which differ from the welding cycles in at least one welding parameter.

[0007] During the process, the welding electrode is guided around the joining partners, particularly in the circumferential direction.

[0008] The orbital welding process described above, or one of the embodiments described below, can be carried out in particular using the orbital welding device described below, or an embodiment thereof.

[0009] The aforementioned problem is further solved according to the invention by an orbital welding device with a welding head having a receptacle for positioning a joining area of ​​two joining partners that are at least tubular in the joining area, in particular a fitting and a pipe end, with a welding power source and a welding electrode connected thereto, with an electrode circulation mechanism and an electrode drive for driving the electrode circulation mechanism, wherein the electrode circulation mechanism is configured to move the welding electrode circumferentially around the receptacle, and with a control device configured to control the orbital welding device in such a way that, by means of the welding electrode, a chain of joining points extending circumferentially around the joining partners is generated on two joining partners arranged in the receptacle, which connects the joining partners in a material-bonded manner, wherein the control device is configured toto control the orbital welding device for generating the chain of joining points in such a way that an arc burns between the welding electrode and at least one of the joining partners, wherein the arc is operated with a current characteristic curve that has a sequence of welding cycles with at least one high-current phase and one low-current phase, and wherein the sequence of welding cycles includes welding cycles that differ in at least one welding parameter, and / or the current characteristic curve has one or more cycles before or after the sequence of welding cycles that differ from the welding cycles in at least one welding parameter.

[0010] The orbital welding process described above can be carried out in particular using the orbital welding device described above or an embodiment thereof.

[0011] By means of the orbital welding process and the orbital welding device described above, two joining partners, in particular a fitting and a pipe end, can be joined together by orbital welding in a materially bonded manner, preferably in a fluid-tight manner.

[0012] It is conceivable that, in addition to the two joining partners, one or more further joining partners are provided, which are materially bonded to one or both of the two joining partners during the orbital welding process. The arc burning between the welding electrode and at least one of the joining partners, i.e., the current flowing through the burning arc (welding current), is operated according to a current characteristic curve. The current intensity of the current flowing through the burning arc, i.e., the welding current intensity, is also referred to here as welding current intensity.

[0013] The current characteristic curve is predefined, for example, stored in the memory of a control unit of the orbital welding device. To operate the arc according to the current characteristic curve, a current control system is preferably provided, which regulates the welding current through the arc according to the current characteristic curve, for example, via the welding voltage or the output voltage of an internal voltage source as the control variable. In this way, the current's temporal profile, as defined by the current characteristic curve, can be applied to the welding current.

[0014] The current characteristic curve exhibits a sequence of welding cycles, each with at least one high-current phase and one low-current phase. The current characteristic curve thus comprises several successive welding cycles, with each individual welding cycle containing at least one high-current phase and one low-current phase. The welding cycles can, in particular, consist of a high-current phase and a low-current phase. The rising current edge during the transition from the low-current phase to the high-current phase and the falling current edge during the transition from the high-current phase to the low-current phase are, in this context, included in the high-current phase.

[0015] The sequence of welding cycles preferably comprises several identical welding cycles. The welding parameters of the welding cycles can vary across the sequence. For example, it is conceivable that the welding current and / or duration of the welding cycles are reduced over the course of the sequence, for instance to compensate for the heating of the components due to the welding process.

[0016] The sequence of welding cycles includes, in particular, welding cycles that differ in at least one welding parameter. It has been found that in an orbital welding process, it is advantageous to vary the welding parameters of the individual welding cycles during the sequence, especially to compensate for changing boundary conditions during orbital welding. For example, it has been observed that the joining partners heat up continuously during the sequence of welding cycles because some of the welding energy introduced to create the individual joint points is dissipated into the material, increasing the temperature in the area of ​​subsequent joint points. By adjusting the welding parameters during the sequence of welding cycles, such changes in boundary conditions can be compensated for.In this way, the welding quality of the chain of joining points can be improved, in particular a consistent quality of the chain of joining points in the circumferential direction can be achieved.

[0017] In addition to or as an alternative to welding cycles that differ in at least one welding parameter, the current characteristic curve exhibits one or more cycles before or after the sequence of welding cycles that differ from the welding cycles of the sequence in at least one welding parameter. The current characteristic curve thus has several successive sections, one of which is formed by the sequence of welding cycles. It has been found that this method also improves the weld quality of the chain of joints.

[0018] The current characteristic curve can, for example, include a warm-up cycle, particularly with a warm-up phase and preferably a relaxation phase, and / or a sequence of start-up welding cycles before the sequence of welding cycles, wherein the start-up welding cycles preferably also each have a high-current phase and a low-current phase. The one or more cycles before the sequence of welding cycles can therefore, in particular, be a warm-up cycle and / or a sequence of start-up welding cycles. Furthermore, the current characteristic curve after the sequence of welding cycles can, for example, include a sequence of end-up welding cycles, wherein the end-up welding cycles preferably also each have a high-current phase and a low-current phase. The one or more cycles after the sequence of welding cycles can therefore, in particular, be a sequence of end-up welding cycles.

[0019] The warm-up cycle, the sequence of start welding cycles, or the sequence of end welding cycles differ, where applicable, from the welding cycles of the sequence of welding cycles, particularly in at least one welding parameter.

[0020] During successive welding cycles, individual weld points (joining points) are created locally in succession, forming a chain of joining points. During the high-current phases, welding energy is introduced locally into the joining partners at a high energy density, causing the material of the joining partners to melt and forming a molten pool (also called a weld pool) for the respective joining point to be created. The low-current phases provided between the high-current phases, during which welding energy is introduced into the joining partners at a lower energy density, allow the molten pool of a joining point created during a high-current phase to solidify at least partially before the next joining point is created, thus preventing a continuously moving, extensive molten pool along the joining zone.The weld pool generated for the next joining point does not merge with the weld pool of the preceding joining point, as the latter has already solidified completely or at least to such an extent that the liquid weld pools do not touch. The chain of joining points is thus achieved through the sequential solidification of the joining points. In contrast, arc welding processes, particularly TIG welding processes, are typically operated with a continuously advanced weld pool, which forms at the start of the welding process and then follows the torch movement. As the torch moves along the joining zone, the current energy input continuously melts new material volume, while material volume solidifies continuously as it leaves the current joining zone.The relatively large melt pool volume in such a process requires a fairly high energy input and also complicates the process control in orbital welding, since the large melt pool volume means that the direction of gravity acting on the melt pool relative to the welding direction and the joining partner has a significant influence on the process and therefore requires complex parameterization of the welding process depending on the welding position.

[0021] In the sequential solidification process described here, the melt pool volume is small, thus requiring less energy. Furthermore, a large, moving melt pool is avoided, so that the behavior of the melt pool is relatively independent of the welding position, which significantly simplifies process control in orbital welding.

[0022] It has been found that the amount of energy required for sequential solidification, in particular the welding energy per welding cycle, can be reduced to such an extent that the heating of the joining partners, especially on the inside, is limited to such an extent that oxidation and discoloration can be reduced or completely prevented even without forming gas flow.

[0023] Preferably, the sequence of welding cycles comprises welding cycles with different welding energies. The welding cycles can therefore differ from one another, particularly in the welding parameter of welding energy. Specifically, the welding energy of the welding cycles can decrease over the course of the sequence. In this way, for example, continuous heating of the joining partners during the sequence of welding cycles can be compensated for in order to achieve a consistent weld quality across the chain of joints.

[0024] In this context, welding energy is understood as the time integral of the welding power, where the welding power corresponds to the product of welding current and welding voltage. The welding energy Esz of a welding cycle can therefore be calculated using the following formula: where tszo is the start time of the welding cycle, tszi is the end time of the welding cycle, Uout(t) is the welding voltage and Iioad(t) is the welding current.

[0025] The welding energies of the individual welding cycles are preferably in the range of 30–240 J, more preferably 35–220 J, and particularly 40–195 J. Preferably, the durations of the high-current phases, the welding currents during the high-current phases, the durations of the low-current phases, and the welding currents during the low-current phases are selected such that the welding energies of the individual welding cycles are in the range of 30–240 J, preferably 35–220 J, and particularly 40–195 J. The welding voltage, particularly during the high-current phase, is preferably determined by current control according to the current characteristic curve with which the arc is operated.

[0026] It has been found that the optimal selection of welding parameters, particularly welding energies, depends on the wall thickness of the joining partners, especially in the joining area. Therefore, preferably at least one welding parameter of the orbital welding process, in particular at least one welding parameter of the current characteristic, is adjusted depending on the wall thickness of one or both joining partners.Accordingly, the control unit of the orbital welding device is preferably configured to obtain wall thickness information about the wall thickness of one or both joining partners, in particular via user input at a user interface, and to set at least one welding parameter for generating the chain of joining points, in particular at least one welding parameter of the current characteristic, depending on the wall thickness information obtained, in particular one or more of the following welding parameters: welding energy, durations and / or welding currents of the high-current phases of the welding cycles, durations and / or welding currents of the low-current phases of the welding cycles. Additionally or alternatively, one or more of the following welding parameters may also be set depending on the wall thickness or...The following parameters can be set based on the received wall thickness information: duration and / or welding current of the warm-up phase, duration and / or welding current of the relaxation phase, durations and / or welding currents of the high-current phase of the start welding cycles, durations and / or welding currents of the low-current phase of the start welding cycles, durations and / or welding currents of the high-current phase of the end welding cycles, durations and / or welding currents of the low-current phase of the end welding cycles.

[0027] The wall thicknesses of the joining partners are preferably the same in the joining area or preferably differ from each other by a maximum of 25%. If joining partners with very different wall thicknesses are used in the joining area, the welding parameters can be selected, in particular, depending on the wall thickness of one of the joining partners, for example, depending on the larger or smaller wall thickness. It is also conceivable that the welding parameters are selected depending on an average value of the wall thickness of both joining partners.

[0028] It was found in particular that the ranges of preferred welding energies for sequential solidification depend on the wall thickness of the joining partners. Therefore, the welding energy is preferably set depending on the wall thickness.In particular, the welding energy per welding cycle is preferably in the range of 30–90 J, more preferably 35–70 J, more preferably 40–60 J if the wall thickness of one or both joining partners is in the range of 0.5–1.1 mm, for example 1 mm, and / or in the range of 30–100 J, more preferably 35–80 J, more preferably 43–63 J if the wall thickness of one or both joining partners is in the range of 1.1–1.3 mm, for example 1.2 mm, and / or in the range of 60–180 J, more preferably 70–150 J, more preferably 80–130 J if the wall thickness of one or both joining partners is in the range of 1.3–1.7 mm, for example 1.5 mm, and / or in the range of 110–240 J, more preferably 120– 220 J, especially 135 - 195 J if the wall thickness of one or both joining partners is in the range of 1.7 - 2.5 mm, for example 2 mm.

[0029] In a corresponding embodiment of the orbital welding device, the control unit is configured to obtain wall thickness information about the wall thickness of one or both joining partners and to adjust the welding energies of the individual welding cycles depending on the wall thickness information obtained, preferably such that the welding energy per welding cycle is in the range of 30–90 J, more preferably 35–70 J, particularly 40–60 J, when the wall thickness of one or both joining partners is in the range of 0.5–1.1 mm, for example 1 mm, and / or in the range of 30–100 J, more preferably 35–80 J, particularly 43–63 J, when the wall thickness of one or both joining partners is in the range of 1.1–1.3 mm, for example 1.2 mm, and / or in the range of 60–180 J, more preferably 70–150 J, particularly 80– 130 J, is the case when the wall thickness of one or both joining partners is in the range of 1.3 - 1.7 mm, for example at 1.5 mm,and / or in the range of 110–240 J, more preferably 120–220 J, particularly 135–195 J, if the wall thickness of one or both joining partners is in the range of 1.7–2.5 mm, for example, 2 mm. The control unit can obtain the wall thickness information, for example, from a memory of the orbital welding device, in particular by reading it out, or by user input via a user interface of the orbital welding device. The wall thickness information can directly contain the wall thickness (e.g., in mm). However, the wall thickness information can also contain information that corresponds to a specific wall thickness, for example, a type designation of a joining partner used, which implies a specific wall thickness.

[0030] In the orbital welding device, the welding head is mounted to position a joining area between two components that are at least tubular in shape. Each component has a joining area where they are to be welded together. In the case of a push-on fitting, the joining area of ​​the fitting can, for example, include an area at the fitting opening, and the joining area of ​​a pipe end to be welded to it can include the area of ​​the pipe end that is located at the fitting opening when the fitting is pushed on. In the case of a push-in fitting, the joining area of ​​the fitting can, for example, include an area at a stop edge for a pipe end, and the joining area of ​​a pipe end to be welded to it can include the area of ​​the pipe opening that abuts the stop edge when the fitting is inserted.The joining area of ​​the fitting and the joining area of ​​the pipe end, more generally the respective joining areas of the two joining partners, together form the joining area of ​​the two joining partners.

[0031] The orbital welding apparatus comprises a welding power source and a welding electrode connected to it. The welding power source is specifically designed to provide the welding current for the welding process. Furthermore, the welding power source can be specifically designed to provide a high-voltage pulse for the contactless ignition of an arc between the welding electrode and one of the components being joined. The welding electrode is specifically a non-consumable electrode, particularly a tungsten electrode with or without filler materials. The orbital welding apparatus is specifically designed to perform a TIG welding process.

[0032] Using the electrode recirculation mechanism, the welding electrode can be automatically and controllably moved circumferentially around the joining area of ​​the components arranged in the fixture during the orbital welding process, in order to weld them together, particularly by means of a chain of joining points. The electrode drive can be, for example, a motor.

[0033] The control unit can, in particular, comprise at least one processor and at least one memory containing instructions, the execution of which on the at least one processor causes the operation of the orbital welding device. In particular, the control unit can be configured to control the welding power source and / or the electrode drive. Specifically, the control unit can control the welding power source and / or the electrode drive according to predefined values ​​for welding parameters, in particular for the durations of the high-current phases and for the welding current intensities of the high-current phases, so that the arc is operated according to the current characteristic curve.

[0034] The aforementioned problem is further solved according to the invention by a system comprising the orbital welding device described above or an embodiment thereof and a fitting.

[0035] The fitting is specifically designed to be used together with the orbital welding device to create a metallurgical bond between the fitting and a joining partner, particularly a pipe end, by means of orbital welding. For this purpose, the fitting is preferably adapted to the geometry of the orbital welding device. In particular, the fitting and the welding head of the orbital welding device can have corresponding contours to position the fitting in a predetermined position within the welding head.

[0036] The fitting can, in particular, have an outer contour and the welding head a fitting fixing contour corresponding to the outer contour in order to hold the fitting in a predetermined fitting position. The outer contour can, in particular, be an axial contour to hold the fitting in a predetermined axial fitting position.

[0037] The following describes various further embodiments of the orbital welding process, the orbital welding device, and the system, with each embodiment applying independently to the orbital welding process, the orbital welding device, and the system. Furthermore, the individual embodiments can be combined with one another as desired.

[0038] To achieve a high energy density for melting the materials of the joining partners, particularly with given welding energies, and to reduce the dissipation of the welding energy introduced locally into the joining partners or the weld pool into the surrounding material, the high-current phase of the welding cycles is preferably very short. In one embodiment, the duration of the high-current phase of the welding cycles is therefore in the range of 8–65 ms, preferably 10–55 ms, and particularly 12–40 ms. The durations of the rising and falling current edges at the beginning and end of the high-current phase are included in the total duration of the high-current phase.

[0039] To achieve a high temporal energy density for the weld pool during the high-current phase of the welding cycles, the welding current during this phase is preferably quite high. In one embodiment, the welding current during the high-current phase of the welding cycles therefore reaches at least 170 A, preferably at least 250 A. More preferably, the welding current during the high-current phase of the welding cycles is at least temporarily in the range of 170–450 A, more preferably 220–400 A, and particularly 250–350 A. In particular, the current characteristic can be predefined accordingly. By combining a short high-current phase with a high welding current, in combination with small electrode spacing, a high spatial and temporal energy density is achieved at the position of the joint to be created, without excessively heating the surrounding material of the joining partners, especially on their inner surfaces.

[0040] In one embodiment, the duration of the low-current phase of the welding cycles is at least 6 ms, preferably at least 9 ms, and particularly at least 11 ms. This minimum duration ensures sufficient solidification of the weld pool. More preferably, the duration of the low-current phase of the welding cycles is in the range of 6–60 ms, preferably 9–48 ms, and particularly 11–28 ms. This maximum duration allows for the simultaneous achievement of high welding speeds.

[0041] In one embodiment, the welding current during the low-current phase of the welding cycles is 130 A or less, preferably 100 A or less. This ensures that the welding energy supplied during the low-current phase is insufficient to initiate further melting at the joining partners or to keep the weld pool molten, allowing the weld pool to solidify at least partially during this phase. The drastic reduction in welding current from the high-current to the low-current phase thus results in the formation of a chain of joining points through sequential solidification. The current flowing during the low-current phase serves to maintain the arc system functionally for the next high-current phase, eliminating the need for re-ignition.For this purpose, the welding current during the low-current phase is preferably in the range of 3–130 A, more preferably 10–100 A, and particularly 13–80 A. The specified minimum current ensures that the arc can be reliably maintained during the low-current phase.

[0042] It has been found that the preferred ranges for the duration and welding current of the high-current and low-current phases for sequential solidification depend on the wall thickness of the joining partners. Therefore, the duration of the high-current phase, the welding current of the high-current phase, the duration of the low-current phase, and / or the welding current of the low-current phase are preferably set depending on the wall thickness. In particular, the control unit of the orbital welding device can be configured to set the welding current of the high-current phase, the duration of the low-current phase, and / or the welding current of the low-current phase depending on wall thickness information received about one or both joining partners.

[0043] In one embodiment, the duration of the high-current phase of a welding cycle is preferably in the range of 8–50 ms, more preferably 10–30 ms, particularly 12–20 ms if the wall thickness of one or both joining partners is in the range of 0.5–1.1 mm, for example 1 mm, and / or in the range of 10–50 ms, more preferably 14–35 ms, particularly 16–22 ms if the wall thickness of one or both joining partners is in the range of 1.1–1.3 mm, for example 1.2 mm, and / or in the range of 10–55 ms, more preferably 13–35 ms, particularly 20–30 ms if the wall thickness of one or both joining partners is in the range of 1.3–1.7 mm, for example 1.5 mm, and / or in the range of 15–65 ms. ms, more preferably 20 - 55 ms, particularly 30 - 40 ms, if the wall thickness of one or both joining partners is in the range of 1.7 - 2.5 mm, for example 2 mm.

[0044] In one embodiment, the welding current of the high-current phase of a welding cycle is preferably at least temporarily in the range of 170–400 A, more preferably 220–350 A, and in particular 250–320 A.

[0045] A, if the wall thickness of one or both joining partners is in the range of 0.5 - 1.1 mm, for example 1 mm, and / or in the range of 170 - 400 A, more preferably 240 - 360 A, in particular 270 - 330 A, if the wall thickness of one or both joining partners is in the range of 1.1 - 1.3 mm, for example 1.2 mm, and / or in the range of 180 - 400 A, more preferably 250 - 360 A, in particular 280 - 330 A, if the wall thickness of one or both joining partners is in the range of 1.3 - 1.7 mm, for example 1.5 mm, and / or in the range of 210 - 450 A, more preferably 250 - 400 A, in particular 290 - 350 A, if the wall thickness of one or both joining partners is in the range of 1.7 - 2.5 mm, for example at 2 mm.

[0046] In one embodiment, the duration of the low-current phase of a welding cycle is preferably in the range of 6–30 ms, more preferably 9–20 ms, and in particular 11–15 ms if the wall thickness of one or both joining partners is in the range of 0.5–1.1 mm, for example 1 mm, and / or in the range of 6–30 ms, more preferably 10–22 ms, and in particular 12–16 ms if the wall thickness of one or both joining partners is in the range of 1.1–1.3 mm, for example 1.2 mm, and / or in the range of 10–40 ms, more preferably 10–30 ms, and in particular 13–20 ms if the wall thickness of one or both joining partners is in the range of 1.3–1.7 mm, for example 1.5 mm, and / or in the range of 10–60 ms. preferably 13 - 48 ms, particularly 16 - 28 ms, if the wall thickness of one or both joining partners is in the range of 1.7 - 2.5 mm, for example 2 mm.

[0047] In one embodiment, the welding current of the low-current phase of a welding cycle is preferably in the range of 3–70 A, more preferably 10–30 A, particularly 13–15 A if the wall thickness of one or both joining partners is in the range of 0.5–1.1 mm, for example 1 mm, and / or in the range of 3–70 A, more preferably 10–35 A, particularly 13–18 A if the wall thickness of one or both joining partners is in the range of 1.1–1.3 mm, for example 1.2 mm, and / or in the range of 3–100 A, more preferably 10–90 A, particularly 20–70 A if the wall thickness of one or both joining partners is in the range of 1.3–1.7 mm, for example 1.5 mm, and / or in the range of 3–130 A, more preferably 10– 100 A, especially 20 - 80 A, if the wall thickness of one or both joining partners is in the range of 1.7 - 2.5 mm, for example 2 mm.

[0048] In one embodiment, the welding current intensities and / or the duration of the high-current phases of the welding cycles preferably decrease over the course of the sequence of welding cycles. For example, the welding current of the high-current phases can decrease by an average of 0.1 to 0.5 A per welding cycle. In this way, the heating of the joining partners during the sequence of welding cycles can be compensated for in order to achieve a consistent quality of the weld seam formed by the chain of joining points in the circumferential direction. Furthermore, energy consumption can be reduced in this way, which is particularly advantageous for a handheld device.

[0049] In one embodiment, the current characteristic curve includes a warm-up cycle prior to the sequence of welding cycles. This allows the joining partners to be preheated, resulting in a more reliable and reproducible formation of the weld pool for the first joining point. The warm-up cycle comprises, in particular, at least one warm-up phase and optionally a relaxation phase following the warm-up phase. During the warm-up phase, and especially during the entire warm-up cycle, the welding electrode is preferably not moved.

[0050] The warm-up phase preferably has a lower welding current than the high-current phases of the welding cycles. This prevents the joining partners from melting during the warm-up phase. The welding current during the warm-up phase is preferably in the range of 100–250 A, more preferably 120–220 A. If the wall thickness of one or both joining partners is in the range of 0.5–1.1 mm, for example 1 mm, the welding current during the warm-up phase is further preferably in the range of 100–230 A, more preferably 120–200 A.

[0051] The specified welding current strengths for the warm-up phase ensure sufficient preheating of the joining partners, while simultaneously keeping the volume of molten material in the subsequently formed weld pool for the first joining point low.

[0052] The warm-up phase preferably has a longer duration than the high-current phase of the welding cycles. This allows sufficient energy to be introduced into the joining partners for adequate preheating. The duration of the warm-up phase is preferably in the range of 100–1700 ms, particularly 150–1500 ms. Preferably, the duration of the warm-up phase is in the range of 100–1000 ms, particularly 150–800 ms, if the wall thickness of one or both joining partners is in the range of 0.5–1.3 mm, for example 1 mm or 1.2 mm, and / or in the range of 150–1100 ms, particularly 300–900 ms, if the wall thickness of one or both joining partners is in the range of 1.3–1.7 mm, for example 1.5 mm, and / or in the range of 300–1700 ms, particularly 600–1500 ms, if the wall thickness of one or both joining partners is in the range of 1.7–2.5 mm, for example 2 mm.

[0053] The welding current can decrease during the warm-up phase, for example at a rate below 5 A / ms, and especially below 1 A / ms. This allows for more uniform heating of the components being joined as their temperature increases.

[0054] The heating phase can optionally be followed by a relaxation phase with a lower welding current. During the relaxation phase, the energy or heat introduced during the heating phase can distribute itself among the joining partners, resulting in more uniform preheating. In this way, the joining partners can be preheated not only locally, but also globally, due to their thermal conductivity.

[0055] At the end of the warm-up phase, the welding current is preferably reduced to the relaxation phase current using a current ramp in the range of 10–100 A / ms. This prevents the welding electrode from sticking if a weld pool forms during the warm-up phase.

[0056] In one embodiment, the current characteristic curve includes a series of start-up welding cycles prior to the sequence of welding cycles, preferably between a warm-up cycle and the sequence of welding cycles. The start-up welding cycles preferably each have at least one high-current phase and one low-current phase. The welding electrode is preferably moved circumferentially during the sequence of start-up welding cycles. It has been found that the formation of the first weld point does not always reliably occur during the first high-current phase, but may only occur during the second, third, etc., high-current phase. However, after the formation of the first weld point, further weld points are reliably generated in the subsequent high-current phases.By performing a series of start welding cycles before the start of the sequence of welding cycles, it can be ensured that the formation of the first joining point has taken place before the start of the sequence of welding cycles, so that joining points are reliably generated from the beginning of the sequence of welding cycles.

[0057] To create a circumferentially closed chain of weld points, the weld points produced during the initial welding cycles are preferably welded over during the subsequent sequence of welding cycles, particularly at the end of the sequence. Specifically, the welding electrode is preferably moved through an angle of at least 360° during the sequence of welding cycles and the optional sequence of final welding cycles. More preferably, the welding electrode can be moved through an angle of at least 360° during the sequence of welding cycles. Together with the movement of the welding electrode during the sequence of initial welding cycles, the welding electrode is thus moved through an angle of more than 360°. In this way, a closed chain of weld points is achieved, regardless of which of the initial welding cycles the first weld point is produced in.

[0058] To accelerate the formation of the first weld point, the welding energies of one or more start welding cycles are preferably higher than the welding energies of the welding cycles. In particular, the welding current in the high-current phase of one or more of the start welding cycles can be higher than the welding currents of the high-current phases of the welding cycles. Additionally or alternatively, the duration of the high-current phase of one or more of the start welding cycles can be longer than the durations of the high-current phases of the welding cycles.

[0059] The welding current and / or the duration of the high-current phases of the initial welding cycles can decrease over the course of the sequence of initial welding cycles, specifically approaching the welding current and / or duration of the high-current phase of the first welding cycle in the sequence. This allows for a smoother transition from the initial welding cycles to the subsequent welding cycles, resulting in a cleaner chain of weld points. Furthermore, this reduces the risk of the welding electrode sticking to the weld pool. In addition, this method saves energy, which is particularly advantageous for handheld welding machines.

[0060] In one embodiment, the welding current intensities of the high-current phases of the initial welding cycles can decrease to a level below that of the high-current phases of the first welding cycles as the sequence of initial welding cycles progresses. This further reduces the risk of the welding electrode adhering to the weld pool. Preferably, however, the welding energy of the initial welding cycles remains higher than that of the subsequent welding cycles. This can be achieved, particularly in initial welding cycles with lower welding current intensities of the high-current phases compared to the first welding cycles, by extending the duration of the high-current phases in these initial welding cycles.

[0061] During one or more of the initial welding cycles, preferably the first few, the welding current is preferably reduced at the end of the high-current phase to the welding current of the low-current phase using a current ramp in the range of 10–100 A / ms. At the initial joining point, the dynamics in the weld pool are increased due to the initial merging of the individual weld pools at the two joining partners. By reducing the welding current more gently from the high-current phase to the low-current phase, this dynamic can be reduced, thus preventing the electrode from sticking to the weld pool.

[0062] Electrode sticking can be further prevented by ensuring that the welding current during the low-current phase is higher in one or more, particularly the first, start-up welding cycles than the welding current during the low-current phase of the welding cycles. Preferably, the welding currents during the low-current phases of one or more, particularly the first, start-up welding cycles are in the range of 10–60 A if the wall thickness of one or both joining partners is in the range of 0.5–1.1 mm, for example, 1 mm, and / or in the range of 10–100 A if the wall thickness of one or both joining partners is in the range of 1.1–2.5 mm, for example, 1.2 mm, 1.5 mm, or 2 mm.

[0063] In one embodiment, the current characteristic curve, following a sequence of welding cycles, includes a sequence of end welding cycles. The end welding cycles preferably each have at least one high-current phase and one low-current phase. During the sequence of start welding cycles, the welding electrode is preferably moved circumferentially.

[0064] For a tight weld, the last one or more weld points in the chain of weld points overlap with the first weld points created, especially those created during the optional sequence of start welding cycles. Because the first weld points are overlapped, this area has a reduced electrode gap and an increased risk of the welding electrode sticking to the weld pool.

[0065] To reduce this risk, the high-current phases of one or more end welding cycles preferably have lower welding currents than the high-current phases of the welding cycles. Furthermore, the welding currents and / or the durations of the high-current phases of the end welding cycles preferably decrease over the course of the sequence of start welding cycles, particularly more so than the optional decrease in the welding currents and / or durations of the high-current phases of the welding cycles over the course of the sequence of welding cycles.

[0066] During one or more final welding cycles, preferably the last one, the welding current is reduced at the end of the high-current phase, preferably with a current ramp in the range of 10–100 A / ms. This allows the final weld point, which is not overlapped by a subsequent weld point, to be formed more uniformly, thus improving the appearance of the weld.

[0067] In one embodiment, the distance between the tip of the welding electrode and at least one of the joining partners is a maximum of 1.5 mm, preferably a maximum of 1.2 mm. Preferably, the distance between the welding electrode and a first joining partner, in particular a pipe end, is in the range of 0.3–1.5 mm, preferably 0.4–1.4 mm, particularly 0.5–1.3 mm, and / or the distance between the welding electrode and a second joining partner, in particular a fitting, is in the range of 0.15–1.2 mm, preferably 0.25–1.1 mm, particularly 0.35–1.0 mm. In this way, a very short arc length and thus a high spatial energy density for local heating of the joining partners or the weld pool are achieved, enabling the creation of a chain of clean joints with sequential solidification of the joints using the specified welding energies.The short arc length achieved in this way also promotes the high dynamics of the welding current, with short high-current phases at very high welding current and low-current phases at very low welding current. In this way, significantly higher energy densities can be achieved locally and temporally for a given welding energy than would be the case with the considerably longer distances between the welding electrode and the joining partner in conventional TIG arc welding processes. It was found that the ranges of favorable distances between the tip of the welding electrode and the joining partners depend on the wall thickness of the joining partners. Accordingly, the distance of the welding electrode to a first of the joining partners, in particular the pipe end, is preferably in the range of 0.3–1.3 mm, more preferably 0.4–1.1 mm, and particularly 0.5–0.85 mm, when the wall thickness of one or both joining partners is in the range of 0.5–1.3 mm.

[0068] 1.3 mm, for example at 1 mm or 1.2 mm, and / or in the range of 0.45 - 1.4 mm, more preferably 0.5 - 1.3 mm, in particular 0.6 -

[0069] 1.2 mm if the wall thickness of one or both joining partners is in the range of 1.3 - 1.7 mm, for example 1.5 mm, and / or in the range of 0.55 - 1.5 mm, more preferably 0.6 - 1.4 mm, in particular 0.7 -

[0070] 1.3 mm if the wall thickness of one or both joining partners is in the range of 1.7 - 2.5 mm, for example 2 mm.

[0071] Additionally or alternatively, the distance between the welding electrode and a second joining partner, in particular a fitting, is preferably in the range of 0.15 - 1.2 mm, more preferably 0.25 - 0.9 mm, particularly 0.35 - 0.65 mm, if the wall thickness of one or both joining partners is in the range of 0.5 -

[0072] 1.3 mm, for example 1 mm or 1.2 mm, and / or in the range of 0.2 - 1.2 mm, more preferably 0.25 - 1.0 mm, in particular 0.4 - 0.9 mm, if the wall thickness of one or both joining partners is in the range of 1.3 - 1.7 mm, for example 1.5 mm, and / or in the range of 0.2 - 1.2 mm, more preferably 0.25 - 1.1 mm, in particular 0.4 - 1.0 mm, if the wall thickness of one or both joining partners is in the range of 1.7 - 2.5 mm, for example 2 mm.

[0073] In the system, the corresponding contours of the fitting and the welding head of the orbital welding device, preferably the outer contour of the fitting, in particular the axial contour, and the corresponding fitting fixing contour of the welding head, are preferably adapted to each other in such a way that, when the fitting is arranged in the predetermined position, a welding edge of the fitting provided for generating the chain of joining points and / or a pipe end inserted into or pushed onto the fitting assumes the distances to the tip of the welding electrode described above.

[0074] In one embodiment, the fitting position is such that the joining area of ​​the fitting, for example an edge of the fitting where the fitting is to be welded to the pipe end, is arranged in the area of ​​the welding electrode, in particular with a predetermined distance between the tip of the welding electrode and the edge of the fitting, in particular with a distance from one of the previously mentioned preferred distance ranges of the welding electrode to the fitting.

[0075] In this way, precise alignment of the welding electrode to the joining partners, especially to the fitting and pipe end, is possible, particularly with a small distance between the tip of the welding electrode and the joining partners, so that the welding energy can be introduced into the joining partners or the weld pool with high spatial energy density during the high current phase.

[0076] In one embodiment, particularly when the fitting is a push-on fitting, the fitting position is such that the tip of the welding electrode has a radial distance to the outer surface of the pipe end in the range of 0.3–1.5 mm, preferably 0.4–1.4 mm, more preferably 0.5–1.3 mm, particularly 0.60–0.80 mm, and / or an axial distance to the welding edge or stop edge in the range of 0.15–1.2 mm, preferably 0.25–1.1 mm, more preferably 0.35–1.0 mm, particularly 0.40–0.70 mm. In this embodiment, the welding electrode is preferably oriented obliquely inwards with respect to the longitudinal direction.

[0077] In one embodiment, particularly when the fitting is a push-fit fitting, the fitting position is such that the tip of the welding electrode has a radial distance from the outer surface of the pipe end and / or the outer surface of the fitting in the range of 0.3–1.5 mm, preferably 0.4–1.4 mm, and more specifically 0.40–0.80 mm. In this embodiment, the welding electrode is preferably oriented radially inwards towards the receiving surface with respect to the longitudinal direction.

[0078] In one embodiment, the duration of the individual welding cycles is in the range of 14–125 ms, preferably 19–103 ms, and particularly 23–68 ms. Good welding speeds can thus be achieved.

[0079] In one embodiment, the average welding voltage during the high-current phase and / or during the low-current phase of the welding cycles is in the range of 6–16 V, preferably 8–14 V, and particularly 9–12 V. This range for the average welding voltage has proven suitable for achieving advantageous welding energies in conjunction with the preferred ranges for the welding current and the duration of the high-current phase. This is particularly true when the wall thickness of one or both joining partners is in the range of 0.5–1.3 mm, for example, 1 mm or 1.2 mm.

[0080] In one embodiment, the welding electrode is driven circumferentially around the joining partners during the sequence of welding cycles and, if present, preferably also during the sequence of start welding cycles and / or, if present, preferably during the sequence of end welding cycles, particularly during the low-current phases. In particular, the control device can be configured to control the electrode drive such that the welding electrode is driven circumferentially around the joining partners during the sequence of welding cycles and, if present, preferably also during the sequence of start welding cycles and / or, if present, preferably during the sequence of end welding cycles, particularly during the low-current phases. In this way, the chain of joining points is generated circumferentially around the joining partners.

[0081] During the low-current phase, the arc burns with only a low welding current while the weld pool solidifies, so that moving the welding electrode during the low-current phase has little effect on the welding result. In one embodiment, the welding electrode is stationary during the high-current phase or moves at a lower speed than during the low-current phase. This allows for cleaner weld joints. In another embodiment, the welding electrode moves at a constant speed during both the high-current and low-current phases. This allows for simpler process control.

[0082] In one embodiment, the welding electrode is moved circumferentially around the joining partners at an average welding speed in the range of 0.8–2.6 m / min, preferably 1.1–2.2 m / min, and particularly 1.3–1.9 m / min. In particular, the control device can be configured to control the electrode drive such that the welding electrode is moved circumferentially around the joining partners at an average welding speed in the range of 0.8–2.6 m / min, preferably 1.1–2.2 m / min, and particularly 1.3–1.9 m / min. It has been found that good welding results can be achieved at these welding speeds with relatively short welding times for the entire welding process. This is especially true when the wall thickness of one or both joining partners is in the range of 0.5–1.1 mm, for example, 1 mm.

[0083] In one embodiment, the joining points are placed next to each other with an overlap, the overlap of two adjacent joining points preferably being in the range of 35–90%, more preferably 40–85%, and particularly 60–80%. In this way, a fluid-tight chain of joining points can be formed. In particular, the welding speed is preferably selected such that a corresponding overlap is achieved. The percentage overlap, as used here, refers to the overlap in terms of the area of ​​the joining points. If a joining point overlaps 70% of an adjacent joining point, it covers 70% of the latter's area. It has been found that the joining points are generally approximately circular. The welding parameters—welding speed, overlap of the joining points, and duration of a welding cycle—are specifically adapted to one another.

[0084] In particular, these welding parameters and other welding parameters such as welding current during the high-current phase and duration of the low- or high-current phase are selected such that the molten weld pools of two adjacent joining points do not touch. For example, with a greater overlap of the joining points, a longer welding cycle duration with a longer low-current phase is preferably selected so that the weld pool of the preceding joining point solidifies sufficiently before the weld pool for the adjacent joining point is generated during the low-current phase, thus preventing the molten weld pools of the two joining points from touching.

[0085] In one embodiment, the heat input during the sequence of welding cycles is in the range of 40–114 J / mm, more preferably 51–80 J / mm, particularly 59–70 J / mm, if the wall thickness of one or both joining partners is in the range of 0.5–1.1 mm, for example 1 mm, and / or in the range of 40–120 J / mm, more preferably 55–90 J / mm, particularly 63–83 J / mm, if the wall thickness of one or both joining partners is in the range of 1.1–1.3 mm, for example 1.2 mm, and / or in the range of 60–170 J / mm, more preferably 70–130 J / mm, particularly 80–110 J / mm, if the wall thickness of one or both joining partners is in the range of 1.3–1.7 mm, for example 1.5 mm. and / or in the range of 90 - 200 J / mm, more preferably 100 - 190 J / mm, in particular 115 - 170 J / mm, if the wall thickness of one or both joining partners is in the range of 1.7 - 2.5 mm, for example 2 mm.

[0086] In particular, the welding energies, durations, and speed of the welding cycles can be adjusted so that the heat input remains within the aforementioned ranges. With these heat inputs, a robust welding process with sequential solidification can be achieved, especially without overheating the inner surfaces of the joining partners.

[0087] The term "line energy" refers to the cumulative welding energy relative to the length of the chain of joining points in the circumferential direction of the joining partners.

[0088] For example, if the cumulative welding energies of the welding cycles to produce a chain of joining points with a length of 10 mm are 1500 J, then the line energy is 1500 J / 10 mm = 150 J / mm.

[0089] In one embodiment, at least one of the joining partners, in particular both joining partners, is made of copper or a copper alloy. In particular, the fitting or the pipe end can be made of copper or a copper alloy. In particular, the orbital welding device or an embodiment thereof can be used for orbital welding of joining partners made of copper or a copper alloy.

[0090] It was found that the described method, particularly with the previously described welding parameters, is especially suitable for performing orbital welding on copper fittings and copper pipes. In particular, it was found that the orbital welding process can be carried out on copper fittings and copper pipes without oxidation or discoloration on the inside of the fitting or pipe end, even without purging with forming gas.

[0091] In one embodiment, the orbital welding device comprises a handheld unit that includes the welding head and preferably a handle connected to the welding head. Preferably, the welding power source and the control unit can also be housed in the handheld unit. Furthermore, the handheld unit can have a battery or accumulator, a receptacle or connection for one, particularly for a replaceable accumulator. For example, a connection for plugging in a replaceable accumulator can be provided. This enables flexible and easy operation of the orbital welding device even under confined working conditions.

[0092] Preferably, the orbital welding device is designed entirely as a handheld unit, in particular with an integrated or attachable battery, especially a replaceable battery. This allows for particularly flexible and easy use of the orbital welding device.

[0093] It is also conceivable that the orbital welding device, in addition to the handheld unit, includes at least one case or backpack, connected to the handheld unit, for example, via a hose package, in which components of the orbital welding device, such as the welding power source and / or a battery or accumulator, or a holder for one, are located. In this way, the handheld unit can be designed to be more compact and lighter, thus simplifying its operation. At the same time, the orbital welding device remains portable.

[0094] In one embodiment, the welding power source has a coil comprising a first coil terminal, a second coil terminal, and an intermediate tap, wherein a first winding of the coil is electrically connected between the first coil terminal and the intermediate tap, and a second winding of the coil is electrically connected between the intermediate tap and the second coil terminal. It has been found that the use of such a coil with an intermediate tap for a welding power source makes it possible to provide the ignition voltages necessary for an orbital welding process, particularly for contactless ignition, and regulated welding currents, and allows the welding power source to be manufactured more compactly and / or cost-effectively than conventional welding power sources, for example, welding power sources with a coupling transformer.Preferably, the welding power source has a voltage supply with two terminals, in particular a first and a second terminal, and an electronically controlled intermediate tap switch. The welding power source is further preferably wired such that the first winding of the coil can be switched between the terminals of the voltage supply via the intermediate tap and the intermediate tap switch, and that the first and second windings of the coil can be switched between the terminals of the voltage supply via the second coil terminal and the outputs of the welding power source. A welding power source wired in this way enables the reliable generation of the necessary ignition voltages for igniting an arc for orbital welding.Furthermore, a welding power source connected in this way also enables a reliable welding process after the ignition of the welding arc, in that the welding current can build up directly after ignition in the arc through the same coil.

[0095] The terminals of the power supply are, in particular, points in the circuit diagram of the welding power source to which another part of the electrical circuit of the welding power source, for example, the coil, is connected. These terminals may be mechanical connection elements, such as sockets. However, it is also conceivable that the terminals of the power supply are simply a connection point between a component of the power supply and an electrical conductor for connecting another part of the electrical circuit of the welding power source, or simply any point on a conductor running from a component of the power supply to another part of the electrical circuit.

[0096] In a further embodiment, one or more welding parameters for generating the chain of joining points are set depending on the temperature of one or both joining partners. In particular, the orbital welding device, especially in the welding head, can have one or more temperature sensors with which measured values ​​for the temperature of one or both joining partners can be measured, and the control device can be configured to set the one or more welding parameters, especially the current characteristic, depending on the measured temperature values. Preferably, one or more welding parameters of a heating cycle are set depending on the temperature or depending on the measured temperature values ​​of one or both joining partners, in particular one or more of the following welding parameters: duration and / or welding current of the heating phase, duration and / or welding current of the relaxation phase.For example, the duration of the warm-up phase and / or the welding current of the warm-up phase can be reduced if the temperatures of one or both joining partners are above 25 °C before or at the beginning of the warm-up phase, or increased if the temperatures of one or both joining partners are below 15 °C.

[0097] Furthermore, one or more welding parameters of the start welding cycles and / or welding cycles, in particular one or more of the following welding parameters: durations and / or welding currents of the high current phase of the start welding cycles, durations and / or welding currents of the low current phase of the start welding cycles, durations and / or welding currents of the high current phase of the welding cycles, durations and / or welding currents of the low current phase of the welding cycles, depending on the temperature or depending on the measured temperature values ​​of one or both joining partners, can be set.

[0098] It is even conceivable that one or more welding parameters of the final welding cycles, in particular one or more of the following welding parameters: durations and / or welding currents of the high-current phase of the final welding cycles, durations and / or welding currents of the low-current phase of the final welding cycles, are set depending on the temperature or depending on the measured temperature values ​​of one or both joining partners. Further features and advantages of the orbital welding process, the orbital welding device, and the system will become apparent from the following description of exemplary embodiments, with reference to the accompanying drawing.

[0099] The drawing shows

[0100] Fig. 1 shows a first embodiment of the orbital welding device,

[0101] Fig. 2a-d shows the welding head of the orbital welding device from Fig. 1,

[0102] Fig. 3 shows a schematic block representation of the functional components of the orbital welding device from Fig. 1.

[0103] Fig. 4 shows a schematic block representation of the welding power source of the orbital welding device from Fig. 1.

[0104] Fig. 5a-b shows a schematic representation of the creation of a joining point in the orbital welding process.

[0105] Fig. 6a-c shows an embodiment of the orbital welding process on a fitting and a pipe end,

[0106] Fig. 7 shows another embodiment of the orbital welding device,

[0107] Fig. 8 shows a more detailed schematic block representation of the welding power source from Fig. 1.

[0108] Fig. 9 shows a detailed view of the welding head of the orbital welding device from Fig. 1 or 7 with the fitting arranged in the holder; Fig. 10 shows time diagrams of different voltage and current intensities during the ignition process of an embodiment of the orbital welding process.

[0109] Fig. 11a-b shows a schematic block diagram and a diagram illustrating welding current control in an embodiment of the orbital welding process.

[0110] Fig. 12 shows a diagram with an example of a welding current characteristic for an embodiment of the orbital welding process, as well as associated diagrams for the weld pool volume and the joining point formation and

[0111] Fig. 13 shows a diagram with another example of a welding current characteristic for a further embodiment of the orbital welding process.

[0112] Fig. 1 shows a schematic representation of an embodiment of the orbital welding device.

[0113] The orbital welding device 100 is designed as a mobile welding device in the form of a handheld unit 102. In the present embodiment, the handheld unit 102 comprises all components of the orbital welding device 100, making the orbital welding device 100 very flexible to handle, even under difficult installation conditions.

[0114] The handheld device 102 comprises a welding head 104, which has a receptacle 106 in which a joining area of ​​two joining partners, for example a pipe end and a fitting, can be arranged. The handheld device 102 further comprises a handle 108 with a shaft 110 on which the welding head 104 is arranged, and a grip 112 for holding and operating the handheld device 102. The grip 112 has a connection 114 at its end opposite the shaft 110 for an interchangeable accumulator unit 116. The shaft 110 further has a connection 115 for an interchangeable shielding gas magazine 120.

[0115] The handle 108 houses various components for operating the orbital welding device 100, namely, in particular, an adjustment mechanism 122 for adjusting the welding head 104 between an open and a closed position, an electrode drive 124 for driving a welding electrode 126 in the welding head 104, a welding power source 128 for providing the ignition voltage and welding current for the orbital welding process, a control unit 130 for controlling the orbital welding device 100, a valve 132 for controlling the shielding gas supply, and a user interface 134 comprising display and operating elements 136 for configuring the orbital welding device 100, as well as a torch trigger 138 for starting an orbital welding process. Furthermore, the accumulator unit 116 includes an accumulator 140, for example, a lithium-ion accumulator, and the shielding gas magazine 120 includes a shielding gas container 142.

[0116] Figures 2a-d show the welding head 104 of the orbital welding device 100 in a schematic, perspective view, in the open position (Fig. 2a), in the open position after arranging a joining area 150 of two joining partners, namely a fitting 152 and a pipe end 154, in the receptacle 106 (Fig. 2b), as well as in the closed position before (Fig. 2c) and during the execution of an orbital welding process (Fig. 2d).

[0117] The welding head 104 has a fixed part 160, which circumferentially surrounds the receptacle 106, and a movable part 162. In the open position, the movable part 162 is at least partially retracted into the fixed part 160, exposing an insertion opening 164 in the circumferential direction. In the closed position, the movable part 162 closes the insertion opening 164, so that the receptacle 106 is essentially completely closed in the circumferential direction. In the axial direction, the receptacle 106 extends between a first opening 166 and a second opening 168.

[0118] To adjust the welding head 104 between the open and closed positions, an adjustment mechanism 170 is provided on the welding head 104. Furthermore, an electrode circulation mechanism 172 is provided on the welding head 104, with which the welding electrode 126 can be moved circumferentially around the receptacle 106 in the closed position of the welding head 104 for carrying out an orbital welding process.

[0119] Fig. 3 shows a schematic block diagram of the functional components of the orbital welding device 100 from Fig. 1. The accumulator 140 supplies all electrical components of the orbital welding device 100 with electrical energy. In particular, the accumulator 140 supplies the welding power source 128, the control unit 130 and the electrode drive 124.

[0120] The welding power source 128 provides the ignition voltage for arc ignition and the welding current for the orbital welding process. For this purpose, the welding power source 128 has two outputs 174, 176, one of which is electrically conductively connected to the welding electrode 126 during an orbital welding process, and the other is electrically conductively connected to one or more contacting elements 178 for contacting a joining partner arranged in the receptacle 106.

[0121] The electrode drive 124 preferably has an electric motor and is connected, for example via an axis 180, to the electrode recirculation mechanism 172 in order to transmit the movement, for example a rotary movement, from the electric motor to the electrode recirculation mechanism 172, so that the electrode recirculation mechanism 172 moves the welding electrode around the receptacle 106.

[0122] The control device 130 is designed to control the orbital welding device 100 and for this purpose may in particular have at least one microprocessor 182 and a memory 184 with instructions, the execution of which on the at least one microprocessor 182 effects the control of the orbital welding device 100.

[0123] Furthermore, the control unit 130 is connected to the user interface 134 to output user output, for example via a screen included by the display and control elements 136, and to receive user input, for example via buttons or touchscreen included by the display and control elements 136 or from the burner button 138.

[0124] The control unit 130 is specifically designed to control an orbital welding process. For this purpose, the control unit 130 is connected to the electrode drive 124, the valve 132 for controlling the shielding gas flow to the welding head 104, and the welding power source 128.

[0125] In the present embodiment, the adjustment mechanism 122 is mechanically designed, allowing a user to manually actuate the adjustment mechanism 170 to move the welding head 104 between the closed and open positions. Alternatively, or additionally, the adjustment mechanism 122 could be motorized, for example, by having an electric motor controllable via the control unit 130, so that the welding head 104 can be automatically adjusted between the closed and open positions. The shielding gas reservoir 142, which contains a shielding gas, in particular an inert gas, and is preferably replaceable, is connected to the welding head 104 via the valve 132. The welding head 104 preferably has a shielding gas guide to deliver the shielding gas to the area of ​​the welding electrode 126 for the orbital welding process.

[0126] Fig. 4 shows a schematic block diagram of the functional components and connections of the welding power source 128. The welding power source 128 has two inputs 186, 188 for connecting the two poles of the accumulator 140 and two outputs 174, 176 for providing the ignition voltage and the welding current and for electrically conductive connection with the contacting element 178 and the welding electrode 126.

[0127] The welding power source 128 has an electronic circuit 190 which is supplied by the voltage, in particular DC voltage, applied to the inputs 186, 188 and can provide an ignition voltage for igniting an arc and a welding current for supplying an arc welding process via the outputs 174, 176. The electronic circuit 190 can, for example, comprise one or more electronic switches, in particular a half-bridge circuit, and preferably at least one coil.

[0128] The electronic circuit 190 can further include its own control device, for example a microprocessor, which controls the operation of the welding power source 128, in particular by controlling one or more switches of the electronic circuit 190.

[0129] The electronic circuit 190 is functionally configured to provide a high-voltage pulse at outputs 174 and 176 for igniting the welding arc. This is illustrated in Fig. 4 by the functional module HV ignition 194. Furthermore, the electronic circuit 190 is configured to provide welding current control, allowing the current intensity of a welding current flowing through outputs 174 and 176, i.e., the welding current intensity, to be regulated, particularly according to a predefined current characteristic. This is illustrated in Fig. 4 by the functional module welding current control 192.

[0130] Accordingly, the control unit of the welding power source 128 can be configured, in particular, to generate a high-voltage pulse to ignite a welding arc and subsequently to provide a welding current for an orbital welding process, and in particular to regulate the welding current. The control unit of the welding power source 128 is preferably configured to regulate the welding current according to a predetermined or predefinable welding current characteristic curve when the arc is burning.

[0131] The welding power source 128 can be connected to, or is connected to, the control unit 130 and can thus be controlled by the control unit 130. In particular, the control unit 130 can control the control unit of the welding power source 128 in order to initiate and / or configure the control of the operation of the welding power source 128 by the control unit of the welding power source 128.

[0132] Instead of two separate control units, it is also conceivable that the control unit 130 and the control unit of the welding power source 128 are designed as a common control unit, for example as a microprocessor.

[0133] The following explains the execution of an orbital welding process with the orbital welding device 100, namely the execution of an orbital welding process on a pipe end 154 and a fitting 152.

[0134] Figures 5a and 5b each show a schematic cross-sectional view of the joining area 150 of fitting 152 and pipe end 154 arranged in the welding head 104, with the figures showing only the upper half. Some of the components of the welding head 104 are shown with dashed lines.

[0135] The fitting 152 is pushed onto the pipe end 154, as shown in Fig. 5a. For this purpose, the inner cross-section of the fitting 152 is preferably adapted to the outer cross-section of the pipe end 154 in such a way that only a small gap remains between the outer wall of the pipe end 154 and the inner wall of the fitting 152.

[0136] The overlap joint formed in this way between pipe end 154 and fitting 152 forms the joining area 150, in which fitting 152 and pipe end 154 are to be welded together.

[0137] To perform the orbital welding process, the welding head 104 is first moved to the open position via the adjustment mechanism 122, so that the movable part 162 of the welding head 104 exposes the insertion opening 164 (Fig. 2a). The hand-held device 102 with the welding head 104 can then be placed laterally with the insertion opening 164 onto the joining area 150 of the pipe end 154 and the fitting 152 pushed onto it, so that the joining area 150 is arranged in the receptacle 106 (Fig. 2b), while the remaining part of the fitting 152 and the remaining part of the pipe end 154 extend out of the receptacle 106 through the openings 166, 168.

[0138] The welding head 104 is then moved into the closed position via the adjustment actuator 122 (Fig. 2c). In the closed position, the joining area 150 of the pipe end 154 and the fitting 152 is preferably fixed in the receptacle 106 by the stationary part 160 and the movable part 162 of the welding head 104 by means of a positive and / or non-positive locking mechanism, particularly in the axial direction and more preferably also in the azimuthal direction. Furthermore, this fixing preferably also aligns the pipe end 154 and the fitting 152, and most preferably centers the pipe end 154 in the fitting 152. In Fig. 5a, the contours 200, 202 fixing the fitting 152 and the pipe end 154 are shown schematically with dashed lines. The fixing is achieved in particular by the joining area 150 being arranged in the area of ​​the welding electrode 126.The welding electrode 126 is directed obliquely inwards, in particular at an angle to the radial direction in the range of 5–45°, for example 45°, and can be directed obliquely in the circumferential direction, i.e., in the welding direction, for example at an angle in the range of 0–15° to the radial direction. In the arrangement shown in Fig. 5a, the tip of the welding electrode 126 points towards the overlap joint. The contours 200, 202 can, in particular, at least partially form one or more contacting elements 178 for electrically connecting the fitting 152 and the pipe end 154 to an output of the welding power source 128.

[0139] The contours 200 are specifically adapted to the outer contour of the fitting. The contours 200, 202 that fix the fitting 152 and the pipe end 154 can be designed, in particular, to clamp the fitting 152 and the pipe end 154, especially to hold them in a force-fit position. Such fixation of the fitting 152 and / or the pipe end 154 ensures reliable electrical contact between the fitting 152 and the pipe end 154.

[0140] The orbital welding device 100 with the welding head 104 and the fitting 152 form a system 700.

[0141] In the closed position of the welding head 104, the joining area 150 is preferably completely enclosed in the circumferential direction, so that the shielding gas supplied during the orbital welding process is retained in the joining area 150 and the surroundings, in particular the user, are protected from welding fumes and UV light generated during the orbital welding process. After adjusting the welding head 104 to the closed position, the user can trigger the start of the orbital welding process, for example by pressing the torch trigger 138. The control unit 130 controls the electrode drive 124 and the welding power source 128 such that the welding electrode 126 creates a chain 211 of weld points 210 in the circumferential direction, which materially join the fitting 152 and the pipe end 154.

[0142] Figures 5a-b schematically illustrate the creation of a joint 210. To create a first joint 210, the welding power source 128 initially generates a high-voltage pulse, which causes a contactless ignition of an arc between the welding electrode 126 and the fitting 152 or pipe end 154. Subsequently, the welding power source 128 regulates the welding current according to a welding current characteristic curve, which includes, in particular, a sequence of high-current and low-current phases. During the high-current phases, the heat input caused by the arc leads to the formation of a molten pool (also referred to as a weld pool) at the overlap joint of fitting 152 and pipe end 154, which at least partially solidifies during the low-current phase and forms a joint 210.To ensure that the next weld point is offset circumferentially from the previous weld point, the control unit 130 activates the electrode drive 124, causing it to move the welding electrode 126 circumferentially. During the next high-current phase, the welding power source 128 melts a new weld pool for the adjacent weld point, which preferably overlaps with the first weld point. A new ignition is not required for the second and subsequent weld points, as the arc preferably burns continuously until the last weld point.

[0143] In this way, the chain 211 of joining points 210 is gradually created, by which fitting 152 and pipe end 154 are preferably fluid-tightly connected to each other at the overlap joint. Figures 6a-b show the creation of the joining points 210 in schematic sectional views corresponding to the section plane labeled "Via" in Figure 5a, where Figure 6a shows a point in time during the ongoing orbital welding process and Figure 6b shows a point in time after completion of the orbital welding process. Figure 6c shows a perspective view of the finished joint (weld) of fitting 152 and pipe end 154.

[0144] After the weld has been completed, the welding power source 128 reduces the welding current to zero, extinguishing the arc. By actuating the adjustment mechanism 122, the user can then return the welding head 104 to the open position and remove the welding head 104 laterally from the now materially bonded fitting 152 and pipe end 154.

[0145] Fig. 7 shows another embodiment of the orbital welding device. The orbital welding device 101 has a similar structure and function to the orbital welding device 100. Functionally corresponding components are therefore provided with the same reference numerals, even if they may be arranged or designed differently in some respects, and reference is made to the description of Figs. 1-6c above.

[0146] The orbital welding device 101 differs from the orbital welding device 100 in that some components, namely the shielding gas cylinder 142 and the accumulator 140 in Fig. 7, are designed separately from the handheld device and connected to it by corresponding gas and electrical lines. This allows the handheld device to be designed more compactly and lighter.

[0147] Furthermore, larger inert gas cylinders 142 and accumulators 140 can be used in this way. The inert gas cylinder 142 and the accumulator 140 can, for example, be arranged in a separate case or backpack.

[0148] Instead of a battery, a mains connection can also be provided to supply power to the handheld device 102 of the welding power source 128. This allows for longer operation, albeit with less flexibility in handling. Fig. 8 shows a more detailed schematic block diagram of the welding power source 128.

[0149] As already explained with reference to Fig. 4, the welding power source 128 has a first and second input 186, 188 for connecting a DC voltage source, such as the accumulator 140, as well as a first and second output 174, 176 for supplying an arc welding process. Furthermore, the welding power source 128 includes the electronic circuit 190, which is supplied via the inputs 186, 188 and can provide an ignition voltage for igniting an arc and a welding current for supplying an arc welding process via the outputs 174, 176.

[0150] The welding power source 128 has its own control unit 198, which is connected to the control unit 130. As previously explained, the control unit 130 and the control unit 198 of the welding power source 128 can also be configured as a single, combined control unit.

[0151] The welding power source 128, or rather the electronic circuit 190 of the welding power source 128, now comprises a coil 604, which has a first coil terminal 606, an intermediate tap 608, and a second coil terminal 610. A first winding section 612 of the coil 604 is connected between the first coil terminal 606 and the intermediate tap 608, and a second winding section 614 of the coil 604 is connected between the intermediate tap 608 and the second coil terminal 610. The first and second winding sections 612, 614 are arranged axially offset side by side on a coil core 616, for example, a ferrite core, which has a gap 618 located within the second winding section 614 and is closed by means of two legs 620, 622 outside the first and second winding sections 612, 614.

[0152] The first winding section 612 has a number of turns Ni and an inductance Li. The second winding section 614 has a number of turns N2 and an inductance L2. In the present embodiment, for example, Ni = 3 and N2 = 10, resulting, for example, in an inductance ratio L2 / L1 > 3.

[0153] The welding power source 128 further comprises a power supply 624, which has a first and second terminal 626, 628 as outputs and is configured to modify the voltage applied to the first and second inputs 186, 188 and provide it via the terminals 626, 628. For this purpose, the power supply 624 comprises an electronic switching unit 196, preferably with a half-bridge circuit 197, the output of which is connected to the first terminal 626 and which, during operation, preferably provides a pulsed voltage at the terminals 626, 628, in particular a voltage that switches back and forth between 0 V or a voltage range around 0 V, for example 0–1 V, and a voltage value Uack or a voltage range around Uack. When switching to a voltage value of 0 V orIn a voltage range around 0 V, the electronic switching unit 196 is preferably connected such that the two terminals 626, 628 are electrically connected, for example via a low resistance such as the through-resistance of the switch S2.

[0154] Uakk preferably corresponds to the voltage applied to inputs 186 and 188 or to the battery voltage. Uakk can also correspond to the voltage of an optional DC-DC converter, in particular a boost converter, powered via inputs 186 and 188 or the battery. Due to finite internal resistances (e.g., the contact resistance of switch S2), the voltage available in the various switching states can be current-dependent. Accordingly, the electronic switching unit 196 switches back and forth between two voltage ranges.

[0155] For operation, the accumulator can, for example, be connected with its positive terminal to input 186 and with its negative terminal to input 188. The potential at input 188 can be considered, for example, as the reference potential OV (virtual ground). The potential Uakk is then present at input 186.

[0156] The half-bridge circuit 197 comprises two electronic switches Si and S2, which are implemented as FETs. The power supply 624 can apply the potential from input 186 to the first terminal 626 of the power supply 624 by closing switch Si and opening switch S2, and the potential from input 188 by closing switch S2 and opening switch Si, so that the voltage between the first and second terminals 626, 628 of the power supply 624 can be switched back and forth between 0 V and Uakk.

[0157] Furthermore, the welding power source 128 includes an electronically controllable intermediate tap switch 644, which can include, for example, a FET 646, in particular a SiC-FET, and a gate-side driver circuit 648, with which the gate-source voltage of the FET 646 can be switched back and forth between a voltage UGS_O opening the FET 646 and a voltage UGS_I closing the FET 646.

[0158] The control unit 198 of the welding power source 128 is designed to control the welding power source 128, in particular to control the electronic switching unit 196, for example to switch the electronic switching elements Si and S2 of the half-bridge circuit 197 and to control the intermediate tap switch 644 and is connected to these for this purpose.

[0159] The first terminal 626 of the power supply 624 is electrically connected to the first coil terminal 606 of the coil 604. Furthermore, the intermediate tap 608 of the coil 604 is electrically connected to the second terminal 628 of the power supply via the intermediate tap switch 644. In this way, the welding power source 128 is connected such that the first winding 612 of the coil 604 is connected between terminals 626 and 628 of the power supply 624 via the intermediate tap 608 and the intermediate tap switch 644. The second coil terminal 610 of the coil is further electrically connected to the first output 174 of the welding power source 128, and the second output 176 of the welding power source 128 is electrically connected to the second terminal 628 of the power supply 624.In this way, the welding power source 128 is connected in such a way that the first and second winding part 612, 614 of the coil 604 are connected via the second coil connection 610 and the outputs 174, 176 of the welding power source 128 between the connections 626, 628 of the voltage supply 624.

[0160] Between the intermediate tap 608 of the coil 604 and the intermediate tap switch 644, one or more diodes 652, in particular SiC or Schottky diodes, one of which is shown in Fig. 8, are connected. The one or more diodes 652 have, in particular, a reverse recovery time of preferably less than 50 ns.

[0161] A capacitor 654 is preferably connected between the first and second outputs 174, 176 of the welding power source 128, for example in the form of one or more capacitors, one of which is shown by way of example in Fig. 8.

[0162] Furthermore, a welding current measuring sensor 656 is provided, with which measured values ​​for the welding current flowing via outputs 174 and 176 can be measured. The welding current measuring sensor 656 can be, for example, a Hall sensor or a current-sensing resistor. The control unit 198 is connected to the welding current measuring sensor 656 for determining measured values ​​for the welding current. In this way, the control unit 198 can, in particular, regulate the welding current as a function of the measured values ​​for the welding current with the welding current measuring sensor 656. The welding electrode 126 or the electrode holder therefor and the one or more contacting elements 178 for contacting a joining partner arranged in the receptacle 106 of the orbital welding device 100 are each connected to an output 174, 176 of the welding power source 128, for example, in Fig. 8 the welding electrode 126 or the electrode holder therefor.The electrode holder is connected to the second output 176 and the one or more contacting elements 178 to the first output 174. Between the welding electrode 126 and the joining partner, which is contacted during operation by the one or more contacting elements 178, lies a distance 668, over which an arc is to be ignited during operation and burn for a welding process.

[0163] Figure 9 shows a sectional view of the welding head 104 of the orbital welding device 100 from Fig. 1 or the orbital welding device 101 from Fig. 7, with the joining area of ​​the pipe end 154 arranged in the receptacle 106 and the fitting 152 pushed onto it. The welding head 104 is shown schematically in Fig. 9 with dashed lines. The orbital welding device 100 and the fitting 152 form a system 700.

[0164] Fitting 152 has a fitting body 706 which has a tubular joining area 708 with a fitting opening 710 for inserting the pipe end 154. In the present embodiment, fitting 152 is designed as a double fitting, also referred to as a socket; however, this is only an example.

[0165] The fitting body 706 has an outer contour 714 that extends on the outside of the fitting 152 from the fitting opening 710. A first contour element 720, in the form of a radially outwardly projecting bead, and a second contour element 722, in the form of a radially inwardly recessed groove, are arranged on the outer contour 714 of the fitting body 706. The first contour element 720 forms an axial contour for the positive locking of the fitting body 706 in the longitudinal direction. The second contour element 722 forms an azimuthal contour for the positive locking of the fitting body 706 in the circumferential direction. At the fitting opening 710, the fitting body 706 forms a weld edge 732 with a shoulder 734, which has a reduced wall thickness compared to the wall thickness of the adjacent area of ​​the fitting body 706. Paragraph 734 is formed by a step 735 on the outer contour 714.

[0166] The area of ​​the pipe end 154 at the fitting opening 710 represents the joining area 705 of the pipe end 154. The joining area 708 of the fitting 152 and the joining area 705 of the pipe end 154 together form the joining area 707 (corresponding to joining area 150 from Fig. 5a) of the two joining partners, fitting 152 and pipe end 154.

[0167] The welding head 104 has a fitting fixing contour 750 corresponding to the outer contour 714 of the fitting 152. The fitting fixing contour 750 is formed by the fixed part 160 of the welding head 104 and partly also by the movable part 162 of the welding head 104, in particular by provided locking ring segments 402, 403, which, in the closed position of the welding head 104, at least partially close the insertion opening 164 and fix the fitting 152 to the part of the fitting fixing contour 750 formed by the fixed part 160.

[0168] The fitting fixing contour 750 comprises on the fixed part 160 of the welding head 104 a groove-shaped axial fixing contour 752 corresponding to the axial contour 724 for receiving the first bead-shaped contour element 720 and a bead-shaped azimuthal fixing contour 754 corresponding to the azimuthal contour 726 for engaging in the groove-shaped second contour element 722.

[0169] Furthermore, the fitting fixing contour 750 on the movable part 162 of the welding head for receiving 106 includes fitting contact surfaces 758 on the closure ring segments 402 and 403. The closure ring segments 402, 403 thus represent movable fixing elements that form part of the fitting fixing contour 750.

[0170] The welding head 104 also has a pipe fixing contour 760, which is also formed by the fixed part 160 of the welding head 104 and partly also by the movable part 162 of the welding head 104, in particular by further provided closure ring segments 404, 405.

[0171] To carry out a welding process in the joining area 707 of fitting 152 and pipe end 154, the pipe end 154 with the attached fitting 152 is arranged in the open position of the welding head 104 through the insertion opening in the receptacle 106, such that the axial contour 724 is arranged substantially in the area of ​​the axial fixing contour 752 and the azimuthal contour 726 is substantially aligned with the azimuthal fixing contour 754. The welding head 104 is then moved from the open position to the closed position, so that the locking ring segments 402 - 405 clamp the fitting 152 and the pipe end 154, so that the axial contour 724 is in contact with the axial fixing contour 752 and the azimuthal fixing contour 754 is in contact with the azimuthal contour 726 in such a way that the fitting 152 is held in the axial and azimuthal fitting position specified by axial fixing contour 752 and azimuthal fixing contour 754.

[0172] The fitting fixing contour 750 of the welding head 104 is therefore designed to come into contact with the axial contour 724 and the azimuthal contour 726 of the fitting 152 in the closed position of the welding head 104 and with the joining area 708 of the fitting 152 arranged in a predetermined fitting position in the receptacle 106, such that the joining area 708 of the fitting 152 is positively locked in the predetermined fitting position. In particular, the axial contour 724 with respect to the welding edge 732 and the fitting fixing contour 750 with respect to the welding electrode 126 are adapted such that the tip of the welding electrode 126 has a predetermined distance to the pipe end 154 or to the welding edge 732 of the fitting 152 in every rotational position of the electrode recirculation mechanism 172 or welding electrode 126.

[0173] Preferably, the specified fitting position is such that the welding electrode 126 maintains a radial distance Sr to the outer surface of the pipe end 154 in the range of 0.30 - 1.50 mm, preferably 0.4 - 1.4 mm, in particular 0.5 - 1.3 mm, and an axial distance Sa to the welding edge 732 in the range of 0.15 - 1.2 mm, preferably 0.25 - 1.1 mm, in particular 0.35 - 1.0 mm.

[0174] The operation of the welding power source 128 and the orbital welding device 100 with this welding power source 128 is described below with reference to Figs. 10, 11a-b, and 12. Fig. 10 first illustrates a high-voltage (HV) ignition for igniting the welding arc. Figs. 11a-b and 12 then illustrate an example of a welding current control for carrying out the orbital welding process after ignition of the welding arc.

[0175] Figure 10 shows three diagrams over a common time axis. The diagrams are labelled (a), (b) and (c) respectively on the right-hand side; hereafter, the individual diagrams will be referred to accordingly as Fig. 10(a), Fig. 10(b) and Fig. 10(c). Fig. 10(a) shows the gate-source voltage Ucs(t) produced by the gate-side driver circuit 648 to control the FET 646, Fig. 10(b) shows the current IzA(t) flowing through the first winding section 612 and the intermediate tap switch 644, and Fig. 10(c) shows the voltage Uout(t) between the first and second outputs 174, 176 of the welding power source 128.

[0176] In an orbital welding process using the orbital welding device 100 (or 101), a joining area of ​​two joining partners, namely in particular a fitting and a pipe, is first arranged in the area of ​​the welding electrode 662, and one or both of the joining partners are contacted with the contacting means 664. Subsequently, the control unit 130, for example upon receiving a corresponding user input via the user interface 134, starts a welding process and controls the control unit 198 of the welding power source 128 for this purpose.

[0177] The control unit 198 controls the welding power source 128 such that an ignition process is carried out. During the ignition process, the control unit 198, by appropriately controlling the driver circuit 648, causes the intermediate tap switch 644 to close at time to. Furthermore, the control unit 198, by controlling the switching unit 196, causes the potential Uakk to be applied to the first coil terminal 606 from time ti. Preferably, ti > to. As a result, from time ti, a coil ignition voltage approximately equal to the battery voltage is present between the first coil terminal 606 and the intermediate tap 608. This causes a current to flow through the first winding 612 of the coil 604, the intermediate tap 608, and the intermediate tap switch 644 with increasing current IzA(t), as shown in Fig. 10(b).

[0178] After a time interval At has elapsed since the start of current flow through the first winding section 612, or upon reaching a predetermined current intensity IzA(t), i.e., at time t2 in Fig. 10, the control device 198 causes the intermediate tap switch 644 to open, thus interrupting the current flow through the intermediate tap 608. The current intensity IzA(t) flowing through the intermediate tap 608 and the intermediate tap switch 644 then drops abruptly. This change in current causes a significant voltage increase at the intermediate tap 608 due to the inductance of the first winding section 612 of the coil 604. This voltage increase, amplified by the ratio L2 / L1 of the inductances, leads to an even greater voltage increase at the second coil terminal 610, resulting in voltage spikes sufficient to ignite an arc across the path 668, as shown in Fig. 10(c).

[0179] The inductance of coil 604 and the capacitance 654, together with any existing resistances such as line resistances, form a damped resonant circuit, wherein the capacitance 654 is preferably selected such that the frequency of the resonant circuit is in the range of 1–2 MHz. This results in a decaying high-frequency high-voltage pulse across the path 668 at time t2, which ignites the arc.

[0180] In this way, the coil 604 and the intermediate tap switch 644, together with the control described above by the control device 198, ensure that the electronic circuit 190 functionally provides an HV ignition 194.

[0181] Figures 11a-b illustrate the welding current control of the welding power source 128 for carrying out a welding process after arc ignition. Figure 11a shows a schematic representation of the components of the welding power source 128 involved in the welding current control. Figure 11b shows a diagram illustrating the control of the electronic switching unit 196 by the control device 198.

[0182] After the welding arc is ignited, the intermediate tap switch 644 remains open. Therefore, no current flows through the intermediate tap switch 644 during welding current regulation, so that current flows through both windings 612, 614 of the coil 604 and the coil 604 behaves like a normal two-pole coil.

[0183] The control unit 198 controls the switching unit 196 for welding current control based on the measured values ​​for the welding current hoad obtained from the welding current sensor 656. Fig. 11a shows an example of the logic implemented in the control unit 198 for carrying out the welding current control. In this example, the welding current sensor 656 provides a measured voltage Ucurrent, proportional to the welding current hoad, as the measured value for the welding current. In the control unit 198, this measured voltage Ucurrent is compared by means of a comparator 670, 671, with an upper threshold voltage Uhigh and a lower threshold voltage Uiow, respectively, which correspond to an upper and lower threshold welding current. The threshold voltages Uhigh and Uiow are selected such that they lie above and below a voltage Uset, respectively, which corresponds to the current target welding current according to the current characteristic curve.

[0184] Fig. 11b shows a possible course of the measured voltage Ucurrent over time during welding current control.

[0185] If the measured voltage Ucurrent exceeds the upper threshold voltage Uhigh, the comparator 670 outputs a voltage signal Ucompi.out to a switching logic 672 implemented in the control unit 198. This voltage signal Ucompi.out causes the switching logic 672 to open the switching element Si and close the switching element S2. As a result, the first coil terminal 606 is pulled to the potential of the second terminal 628, or the second output 176. Thus, the coil 604, with its two coil terminals 606 and 610, is effectively directly connected to the outputs 174 and 176, and the welding process is powered by the energy stored in the coil 604. The energy stored in the coil 604, and consequently the welding current flowing through the coil 604 and the outputs 174 and 176, decreases, which also reduces the measured voltage Ucurrent.

[0186] If the measured voltage Ucurrent falls below the lower threshold voltage Ui OWj, the comparator 671 outputs a voltage signal Ucom. P 2_out is sent to the switching logic 672, which causes it to open the switching element S2 and close the switching element Si. This results in the first coil terminal 606 being pulled to the potential of the first input 186, so that the coil 604 and the accumulator 140 connected to inputs 186 and 188 are effectively connected in series between outputs 174 and 176. The energy stored in the accumulator 140 then powers the welding process and increases the welding current, which in turn increases the energy stored in the coil 604. The increasing welding current also causes the measuring voltage Ucurrent to rise again.

[0187] The opening of switch Si or S2 is indicated as "0" and the closing as "1" in Fig. 11b in the row corresponding to the respective switch. The control logic described with reference to Fig. 11a-b thus allows for simple and robust welding current control. It has been found that this welding current control enables reliable regulation of the welding current even with fluctuating loads between outputs 174 and 176, for example, with varying arc lengths.

[0188] The comparators 670, 671 and the switching logic 672 are shown as separate functional units in Fig. 11a. Alternatively, these functional units can also be integrated into a single circuit. It is also conceivable to implement the comparators 670, 671 and / or the switching logic 672 at least partially using analog electronic components. For example, the comparators 670, 671 can be implemented using operational amplifiers.

[0189] Instead of a welding current control according to Figs. 11a-c, another type of welding current control is also conceivable.

[0190] Figure 12 shows three diagrams of a welding process following the ignition process over a common time axis. The diagrams are labeled (a), (b), and (c) on the right-hand side; hereafter, the individual diagrams will be referred to accordingly as Fig. 12(a), Fig. 12(b), and Fig. 12(c). Fig. 12(a) shows a first example of a welding current characteristic Iset,i(t) according to an embodiment of the orbital welding process. Fig. 12(b) shows the corresponding volume Vs of the weld pool of the respective current weld point (joining point), and Fig. 12(c) shows an idealized representation of the chain of joining points successively generated in the circumferential direction u. The black-filled circles schematically illustrate liquid areas of the joining points, i.e., the respective weld pools of the joining points, and the hatched areas illustrate solidified areas of the joining points.

[0191] The current characteristic Iset,i(t) shown in Fig. 12(a) serves to control the welding process after the arc ignition at time t2, as previously described with reference to Fig. 10. In particular, after arc ignition, the control unit 198 initiates a welding process in which the arc is operated with the current characteristic shown in Fig. 12(a). For welding current control according to this welding current characteristic, the control unit 198 is specifically configured to adjust the values ​​of Uset, Uiow, and Uhigh for the welding current control described with reference to Fig. 11a-b in such a time-dependent manner that the welding current is controlled to the current target welding current Iset,i(t) according to the current characteristic, so that a corresponding welding current is established. In this way, the current characteristic Iset,i(t) shown in Fig. 12(a) is imposed on the welding current by the welding current control described in Fig. 11a-b.Alternatively, the current characteristic Iset,i(t) shown in Fig. 12(a) can also be imposed on the welding current by another type of welding current control.

[0192] The current characteristic curve comprises a warm-up cycle (#0) with a warm-up phase (At°hot) and a relaxation phase (At°coid), as well as a sequence of welding cycles (#1, #2, #3 ...) each with a high-current phase (Athot) and a low-current phase (Atcoid). The current characteristic curve Iset.i thus has two distinct, sequential sections, the first being the warm-up cycle and the second being the sequence of welding cycles.

[0193] During the warm-up phase, the welding current is regulated to a warm-up phase welding current (I°hot) to preheat the joining partners 152, 154 with the burning arc. The warm-up phase welding current (I°hot) is selected to prevent the formation of a weld pool. During the relaxation phase, the welding current is reduced to a low welding current (Icoid).

[0194] During the high-current phase of the welding cycles, the welding current is regulated to a high-current phase welding current level (Ihot) to generate the weld pool required for each joint. During the low-current phase, the welding current is reduced to the low-current welding current level (Icoid), allowing the previously generated weld pool to solidify at least partially, while the arc remains continuously lit and does not need to be re-ignited for the next welding cycle.

[0195] The welding parameters of the current characteristic curve can be set as follows, for example:

[0196] I°hot = 100 - 250 A, for example 150 A, At°hot = 100 - 1700 ms, for example 200 ms, Ihot = 170 - 450 A, for example 300 A,

[0197] Athot = 8 - 65 ms, for example 15 ms,

[0198] Icoid = 3 - 130 A, for example 20 A,

[0199] Atcoid = 6 - 60 ms, for example 15 ms.

[0200] The welding voltage Uout is set by the current control and averages, for example, 9–12 V. With Ihot = 300 A and Athot = 15 ms, this results, for example, in a welding energy Esz per welding cycle in the range of 30–240 J, preferably 35–220 J, and particularly 40–195 J. The aforementioned welding parameters can be adjusted depending on the wall thickness of one or both joining partners. The duration of the relaxation phase At°coid can be selected, for example, from the range of 6–60 ms, such as 15 ms.

[0201] The current characteristic curve, with its warm-up cycle (first section), thus includes a cycle preceding the sequence of welding cycles (second section), which differs from the welding cycles of the sequence in several welding parameters. In particular, the warm-up phase of the warm-up cycle has a different duration and welding current than the corresponding high-current phases of the welding cycles. The welding energies Esz(a) of the individual welding cycles, where a is the respective cycle number (e.g., 1 for cycle #1, 2 for cycle #2, etc.), can be calculated using the following formula: where tszo(a) is the start time and tszi(a) is the end time of the respective welding cycle #a, and further, Uout(t) is the welding voltage and hoad(t) is the welding current. For example, the start time for welding cycle #1, tszo(i), is the time shown in Fig. 12 at the transition from the warm-up cycle #0 to the welding cycle #1, and the end time for welding cycle #1, tszi(i), is the time shown in Fig. 12 at the transition from welding cycle #1 to welding cycle #2. In particular, the end time for a welding cycle #a, tszi(a), and the start time for the subsequent welding cycle #a+l, tszo(a+i), coincide, i.e., tszifa) = tsZ0(a+l).

[0202] The following describes the welding process, in particular the successive generation of the chain of weld points (joining points) during the sequence of welding cycles:

[0203] During the preheating cycle (#0) the welding electrode is stationary and the joining partners are preheated.

[0204] During the high-current phase of the first welding cycle (#1), the arc in this example creates the initial melt pool for the first joining point. As shown in Fig. 12(b), the melt pool volume of the first joining point increases during the high-current phase (At°hot), meaning the arc gradually melts more material from the joining partners. The increasing melt pool is illustrated in Fig. 12(c) by the expanding, black-filled circle. The high-current phase is therefore the melting phase of the welding cycle.

[0205] In the subsequent low-current phase of the first welding cycle, the welding current is so low that the first weld point solidifies at least partially or completely through heat dissipation into the surrounding material before the next weld point is created in the subsequent high-current phase. Accordingly, the weld pool volume decreases in the low-current phase, as shown in Fig. 12(b). The weld pool solidifies from the edge, as illustrated in Fig. 12(c) by the increasing light hatching from the edge. The low-current phase therefore includes a solidification phase.

[0206] After the first weld point is created, for example during the low-current phase of the first welding cycle, the electrode drive is activated, causing the welding electrode to move circumferentially around the joining partners. The second weld point is therefore created, as illustrated in Fig. 12(c), offset circumferentially from the first weld point and overlapping it. Alternatively, the welding electrode can also be moved continuously during the sequence of welding cycles, for example starting with the high-current phase of the first welding cycle (#1).

[0207] During the high-current phase (athot) of the second welding cycle (#2), the weld pool volume increases again and solidifies during the subsequent low-current phase (atcoid). The subsequent weld points are created successively and overlapping with the preceding weld point in a corresponding manner, whereby a weld point created in a high-current phase solidifies at least partially in the subsequent low-current phase before a new weld point is created.

[0208] This sequential solidification of the individual joining points during the welding process keeps the weld pool volume V relatively small. In particular, this prevents the formation of a continuous weld pool.

[0209] The very short duration of the high-current phase, with its high welding current and correspondingly high welding power, also means that only a small amount of heat can dissipate into the surrounding material. This allows the energy to be introduced very locally with high spatial energy density. As a result, the low welding energy of, for example, 30–240 J per welding cycle is sufficient to create the joint. In this way, excessive heating of the joining partners on the inside, and thus oxidation there, can be avoided even without purging with forming gas.

[0210] A small weld pool volume also has the advantage that it is held in place more effectively by surface tension and adhesion (between the weld pool and the solid base material), whereas a larger weld pool can flow downwards or away from the position of the joint point due to gravity. Therefore, the process allows for the production of a uniform weld seam in the form of a chain of joint points, relatively independent of the welding position.

[0211] The welding electrode is moved in such a way that adjacent weld points overlap by approximately 60–80%. This produces a reliable, tight weld. With a welding energy per high-current phase, for example, in the range of 40–60 J, and especially with a wall thickness of 1 mm between the joining partners, the weld points have a diameter in the range of 2.0–4.0 mm, particularly 2.1–3.6 mm, and more specifically 2.3–3.3 mm. For example, the weld points can have a diameter of approximately 2.5 mm and an area of ​​approximately 4.9 mm². 2To achieve an overlap of adjacent weld points in the range of 60–80%, the welding electrode in this example can be positioned so that the centers of two adjacent weld points are approximately 0.7 mm apart. With a cycle frequency in the range of 90–130 Hz (i.e., 90–130 welding cycles per second), average welding speeds in the range of 1.2–1.4 m / min can be achieved in this way.

[0212] The welding process described above can produce a weld seam from a circumferentially extending chain of welding points (joining points).

[0213] Fig. 13 shows a diagram with another example of a current characteristic curve Iset,2(t) for a further embodiment of the orbital welding process. As previously described for the current characteristic curve from Fig. 12(a), the current characteristic curve Iset,2(t) from Fig. 13 is superimposed on the welding current after arc ignition at time t2 by the welding current control described in Fig. 11a-b. In particular, the values ​​of Uset, Uiow, and Uhigh for the welding current control described with reference to Fig. 11a-b are set as a function of time such that the welding current is controlled to the current target welding current Iset,2(t) according to the current characteristic curve. Alternatively, the current characteristic curve Iset,2(t) shown in Fig. 13 can also be superimposed on the welding current by a different type of welding current control.

[0214] The welding current characteristic Iset,2(t) comprises four temporally successive sections, namely a warm-up cycle (section 1), a sequence of start welding cycles (section 2), a sequence of welding cycles (section 3) and a sequence of end welding cycles (section 4).

[0215] The welding parameters of the welding current characteristic Iset,2(t) are preferably set depending on the wall thickness of one or both joining partners. For example, the control unit 130 can receive wall thickness information via user input at the user interface 134 and then set the welding parameters depending on the wall thickness information and thus depending on the wall thickness.

[0216] The heating cycle (#0) comprises a heating phase At°hot and a relaxation phase At°coid. During the heating phase At°hot, the welding current is preferably in the range of 100–250 A and preferably decreases slightly over the duration of the heating phase, for example at a rate of less than 1 A / ms. The duration of the heating phase is preferably selected from a range dependent on the wall thickness of one or both joining partners according to the following table:

[0217] At the end of the warm-up phase, the current is reduced to the welding current of the relaxation phase, preferably at a rate of 10–100 A / ms. The welding current during the relaxation phase is preferably below 80 A.

[0218] The warm-up cycle is followed by a series of start welding cycles. Each start welding cycle (#1, #2, ... #nl) has a high-current phase (At). s hot(a) and a low-current phase At scoid(a), where a is the respective cycle number (e.g., 1 for cycle #1, 2 for cycle #2, etc.). The welding current of the high-current phase I s hot(a) is preferably increased during the first start welding cycle (a=l) and is decreased from start welding cycle to start welding cycle, for example linearly according to the following formula:

[0219] I S hot(a) — I hot_ max — (a - l) - A, where A is the decrease in current per welding start cycle and I s hot_max is preferably selected from a range dependent on the wall thickness of one or both joining partners according to the following table:

[0220] If, for example, the joining partners each have a wall thickness of 1 mm in the joining area, then I s hot_max preferably chosen from the range 285 - 400 A, for example a value of I s hot_ max — 310 A.

[0221] At the end of each high-current phase, the current is ramped down to the welding current of the respective low-current phase in the range of 10–100 A / ms. For example, the welding current of the low-current phase can be in the range of 50–100 A during the first few welding cycles and then reduced to below 40 A in subsequent welding cycles.

[0222] During the sequence of start welding cycles, the initial weld pool and the first joining point are formed. The number of start welding cycles is preferably in the range of 4–15, for example 10 (i.e., n = 11).

[0223] The sequence of start welding cycles is followed by a sequence of welding cycles. Each welding cycle (#n, #n+l, ... #ml) has a high-current phase Athot(a) and a low-current phase Atcoid(a), where a is the respective cycle number (e.g., n for cycle #n, n+1 for cycle #n+l, etc.). The welding current of the high-current phases Ihot(a) and their duration preferably depend on the wall thickness of one or both joining partners and fall within a range shown in the following table:

[0224] Preferably, the welding current of the high-current phases decreases slightly from welding cycle to welding cycle at the beginning of the sequence of welding cycles, for example for the first 20 welding cycles (i.e. up to #n+19), for example according to the following

[0225] Formula:

[0226] Ihot(a) = I s hot(n - 1) - (a - n - 1)*B, where I shot(a) as defined above, and B is the decrease in current per welding cycle. B can, for example, be in the range of 0.2–0.5 A, perhaps at 0.3 A. Preferably, the welding current of the high-current phases Ihot(a) remains constant thereafter (e.g., from #n+19). At the end of the high-current phase, the current can be reduced to the welding current of the respective low-current phase using a ramp of several hundred A / ms. The welding current of the low-current phases Icoid(a) of the welding cycles and their durations preferably depend on the wall thickness of one or both joining partners within a range according to the following table:

[0227] With the decreasing welding current of the high-current phases as a consequence of the welding cycles, the sequence of welding cycles therefore includes welding cycles that differ in at least one welding parameter, namely the welding current.

[0228] The sequence of welding cycles is followed by a sequence of final welding cycles. The final welding cycles (#m, #m+l, ...) each have a high-current phase At. E hot(a) and a low-current phase At E coid(a), where a is the respective cycle number (e.g., m for cycle #m, m+1 for cycle #m+l, etc.). The welding current of the high-current phases I E hot(a) of the final welding cycles takes, starting from the welding current I E The hot (ml) of the high-current phase of the last welding cycle decreases further from one final welding cycle to the next. Furthermore, the welding current intensity of the low-current phase I can also be affected. E coid(a) compared to the low current phases in the sequence of welding cycles can be further reduced.

[0229] During the final welding cycle, the welding current is preferably reduced with a ramp of 10 - 100 A / ms, preferably to below 60 A, before the arc is extinguished.

[0230] The number of welding cycles plus final welding cycles is selected such that the welding electrode is moved at least 360° during the sequence of welding cycles and the sequence of final welding cycles, for example preferably 70 - 170, more preferably 90 - 150, in particular 100 - 135, for a fitting with a nominal diameter of 28 mm.

[0231] Using the previously described current characteristic Iset,2(t), the joining partners are preheated during the warm-up cycle to facilitate the creation of the joining points. During the sequence of start welding cycles, the creation of an initial weld pool and the first joining point is ensured. In the subsequent welding cycles and the final welding cycles, the actual chain of joining points is created, with the joining points created during the start welding cycles being welded over at the end. The parameterization of the final welding cycles prevents the welding electrode from sticking during this over-welding process and produces a uniform final joining point.

[0232] With the warm-up cycle (section 1) and the sequence of start welding cycles (section 2), the current characteristic Iset,2(t) therefore exhibits several cycles before the sequence of welding cycles (section 3) that differ from the welding parameters of the sequence of welding cycles in several welding parameters. Furthermore, with the sequence of end welding cycles (section 4), the current characteristic Iset,2(t) therefore exhibits several cycles after the sequence of welding cycles (section 3) that differ from the welding parameters of the sequence of welding cycles in several welding parameters. The welding parameters of the current characteristic Iset,i(t) and Iset,2(t) can be adjusted depending on the temperature of one or both joining partners. For this purpose, a temperature sensor 680 (see Fig. 9) is preferably provided in the welding head 104, which is arranged in such a way that it can, for example, detect the temperature of the fitting 152 when it is arranged in the specified fitting position.The control unit 198 is designed to receive measured values ​​from the temperature sensor 680 and to adjust the welding parameters of the current characteristic curve used based on these measured values. In this way, consistent weld quality can be achieved even with different ambient or joining partner temperatures.

[0233] Reference symbol list:

[0234] 100, 101 Orbital welding device

[0235] 102 Handheld device

[0236] 104 Welding head

[0237] 106 recording

[0238] 108 Handle part

[0239] 110 shaft

[0240] 112 Handle

[0241] 114 Connection for a battery unit

[0242] 115 Connection for a shielding gas magazine

[0243] 116 Accumulator unit

[0244] 120 shielding gas magazine

[0245] 122 Adjustment actuation

[0246] 124 Electrode drive

[0247] 126 Welding electrode

[0248] 128 Welding power source

[0249] 130 Control unit

[0250] 132 Valve

[0251] 134 User interface 136 Display and control elements

[0252] 138 burner buttons

[0253] 140 accumulator

[0254] 142 protective gas cylinders

[0255] 150, 707 Joining area of ​​fitting and pipe end

[0256] 152 Fitting

[0257] 154 Pipe end

[0258] 160 fixed part

[0259] 162 moving part

[0260] 164 Insertion opening

[0261] 166 first opening

[0262] 168 second opening

[0263] 170 Adjustment mechanism

[0264] 172 Electrode circulation mechanism

[0265] 174, 176 outputs of the welding power source

[0266] 178 contact elements

[0267] 180 axis

[0268] 182 microprocessor

[0269] 184 storage spaces

[0270] 186, 188 entrances

[0271] 190 electronic circuit

[0272] 192 Welding current control

[0273] 194 HV ignition

[0274] 196 electronic switching unit

[0275] 198 Control unit

[0276] 200, 202 contours

[0277] 210 Joining point

[0278] 211 chain of joining points, 403, 404, 405 locking ring segments

[0279] 604 coil

[0280] 606 first coil connection 608 intermediate tap

[0281] 610 second coil connection

[0282] 612 first winding part of the coil

[0283] 614 second winding part of the coil

[0284] 616 coil core

[0285] 618 gap

[0286] 620 thighs

[0287] 624 Power supply, 628 Power supply connections

[0288] 644 Intermediate tap switch

[0289] 646 Field-effect transistor

[0290] 648 driver circuit

[0291] 652 diodes

[0292] 654 capacity

[0293] 656 Welding current measuring sensor

[0294] 662 Welding electrode

[0295] 664 Contacting means

[0296] 668 tracks, 671 comparators

[0297] 672 Switching logic

[0298] 680 temperature sensor

[0299] 700 System

[0300] 705 Joining area of ​​the pipe end

[0301] 706 Fitting bodies

[0302] 708 Fitting joint area

[0303] 710 Fitting opening

[0304] 714 Outer contour of the fitting, 722 Contour element

[0305] 724 Axial contour

[0306] 726 Azimuthal contour

[0307] 732 Weld edge 734 Heel

[0308] 735 level

[0309] 750 Fitting fixing contour

[0310] 752 Axial fixation contour

[0311] 754 Azimuthal fixation contour

[0312] 758 fitting system surfaces

[0313] 760 Pipe fixing contour

Claims

P a t e n t a n s p r ü c h e 1. An orbital welding process in which two tubular joining partners (152, 154) are arranged relative to each other, particularly in a lap joint, and in which a chain (211) of joining points (210) extending circumferentially to the joining partners (152, 154) is generated in the joining area (150, 707), which connects the joining partners (152, 154) by a material bond, characterized in that an arc burns between a welding electrode (126) and at least one of the joining partners (152, 154) to generate the chain (211) of joining points (210), wherein the arc is operated with a current characteristic curve that has a sequence of welding cycles with at least one high-current phase and one low-current phase, and wherein the sequence of welding cycles includes welding cycles which differ in at least one welding parameter, and / or the current characteristic curve shows one or more cycles before or after the sequence of welding cycles,which differ in at least one welding parameter from the welding cycles of the sequence of welding cycles.

2. Orbital welding device (100, 101), with a welding head (104) which has a receptacle (106) for positioning a joining area (150, 707) of two joining partners which are at least tubular in the joining area, in particular a fitting (152) and a pipe end (154), with a welding power source (128) and a welding electrode (126) connected thereto, with an electrode circulation mechanism (172) and an electrode drive (124) for driving the electrode circulation mechanism (172), wherein the electrode circulation mechanism (172) is configured to move the welding electrode (126) circumferentially around the receptacle (106), and with a control device (130, 198) configured to control the orbital welding device (100, 101) such that, by means of the welding electrode (126), a chain (211) of joining points (210) extending circumferentially around the joining partners (152, 154) is generated on two joining partners (152, 154) arranged in the receptacle (106), which connects the joining partners (152, 154) in a material-bonded manner, characterized in that the control device (130, 198) is configured to control the orbital welding device (100, 101) to generate the chain (211) of joining points (210) in such a way that an arc burns between the welding electrode (126) and at least one of the joining partners (152, 154),wherein the arc is operated with a current characteristic curve which has a sequence of welding cycles, each with at least one high-current phase and one low-current phase, and wherein the sequence of welding cycles includes welding cycles which differ in at least one welding parameter, and / or the current characteristic curve has one or more cycles before or after the sequence of welding cycles which differ from the welding cycles in at least one welding parameter.

3. Orbital welding method according to claim 1 or orbital welding device according to claim 2, characterized in that the sequence of welding cycles comprises welding cycles with different welding energy (Esz), preferably the welding energy (Esz) of the welding cycles decreases in the course of the sequence of welding cycles.

4. Orbital welding method according to claim 1 or 3 or orbital welding device according to claim 2 or 3, characterized in that the current characteristic curve includes a warm-up cycle with at least one warm-up phase prior to the sequence of welding cycles, which preferably has a lower welding current than the high-current phases of the welding cycles and / or a longer duration than the high-current phases of the welding cycles, and optionally with a relaxation phase which has a lower welding current than the warm-up phase.

5. Orbital welding method according to one of claims 1, 3 or 4 or orbital welding device according to one of claims 2 to 4, characterized in that the current characteristic before the sequence of welding cycles, preferably between a warm-up cycle and the sequence of welding cycles, has a sequence of start welding cycles with at least one high current phase and one low current phase, wherein the high current phases of one or more start welding cycles preferably reach a higher welding current and / or have a longer duration than the high current phases of the welding cycles.

6. Orbital welding method according to one of claims 1 or 3 to 5 or orbital welding device according to one of claims 2 to 5, characterized in that the current characteristic curve after the sequence of welding cycles has a sequence of final welding cycles with at least one high current phase and one low current phase, wherein the high current phases of one or more final welding cycles preferably have lower welding current strengths than the high current phases of the welding cycles.

7. Orbital welding method according to one of claims 1 or 3 to 6 or orbital welding device according to one of claims 2 to 6, characterized in that, during the sequence of start welding cycles, the welding current intensities and / or durations of the high-current phases decrease during the sequence of start welding cycles, and / or that, during the sequence of welding cycles, the welding current intensities and / or durations of the high-current phases decrease during the sequence of welding cycles, and / or that, during the sequence of end welding cycles, the welding current intensities and / or durations of the high-current phases decrease during the sequence of end welding cycles.

8. Orbital welding method according to one of claims 1 or 3 to 7 or orbital welding device according to one of claims 2 to 7, characterized in that during the warm-up phase the welding current is reduced at the end of the warm-up phase by a current ramp in the range of 10 - 100 A / ms to the welding current of the relaxation phase and / or that during one or more start welding cycles and / or during one or more end welding cycles the welding current is reduced at the end of the high current phase by a current ramp in the range of 10 - 100 A / ms to the welding current of the low current phase.

9. Orbital welding method according to one of claims 1 or 3 to 8 or orbital welding device according to one of claims 2 to 8, characterized in that at least one welding parameter for generating the chain (211) of joining points (210) is set depending on the wall thickness and / or depending on the temperature of one or both joining partners, in particular at least one welding parameter of the sequence of welding cycles or at least one welding parameter of a cycle before or after the sequence of welding cycles.

10. Orbital welding process according to claim 9 or Orbital welding device according to claim 9, characterized in that one or more of the following welding parameters are set depending on the wall thickness and / or temperature of one or both joining partners: welding energies, durations and / or welding currents of the high-current phases of the welding cycles, durations and / or welding currents of the low-current phases of the welding cycles, duration and / or welding current of the warm-up phase of the warm-up cycle, if present, duration and / or welding current of the relaxation phase of the warm-up cycle, if present, durations and / or welding currents of the high-current phases of the sequence of start welding cycles, if present, durations and / or welding currents of the low-current phases of the sequence of start welding cycles, if present, durations and / or welding currents of the high-current phases of the sequence of end welding cycles, if present, durations and / or welding currents of the low-current phases of the sequence of end welding cycles, if present.

11. Orbital welding process according to one of claims 1 or 3 to 10. Orbital welding device according to one of claims 2 to 10, characterized in that the welding current (Ihot) during the high current phase of the welding cycles reaches at least 170 A, preferably at least 250 A, more preferably during the high current phase of the welding cycles is at least temporarily in the range of 170 - 450 A, more preferably 220 - 400 A, in particular 250 - 350 A.

12. Orbital welding process according to one of claims 1 or 3 to 11 or orbital welding device according to one of claims 2 to 11, characterized in that the duration (athot) of the high current phase of the welding cycles is in the range of 8 - 65 ms, preferably 10 - 55 ms, in particular 12 - 40 ms.

13. Orbital welding method according to one of claims 1 or 3 to 12 or orbital welding device according to one of claims 2 to 12, characterized in that the distance of the tip of the welding electrode (126) to at least one of the joining partners (152, 154) is a maximum of 1.5 mm, preferably a maximum of 1.2 mm.

14. Orbital welding process according to one of claims 1 or 3 to 13 or orbital welding device according to one of claims 2 to 13, characterized in that the welding current (icoid) during the low current phase of the welding cycles is 130 A or less, preferably 100 A or less, preferably in the range 3 - 130 A, more preferably 10 - 100 A, in particular 13 - 80 A.

15. Orbital welding process according to one of claims 1 or 3 to 14 or orbital welding device according to one of claims 2 to 14, characterized in that the duration (Atcoid) of the low current phase of the welding cycles is in the range of 6 - 60 ms, preferably 9 - 48 ms, in particular 11 - 28 ms.

16. Orbital welding process according to one of claims 1 or 3 to 15 or orbital welding device according to one of claims 2 to 15, characterized in that the mean welding voltage (U) during the high current phase and / or during the low current phase of the welding cycles is in the range of 6 - 16 V, preferably 8 - 14 V, in particular 9 - 12 V.

17. Orbital welding process according to one of claims 1 or 3 to 16 or orbital welding apparatus according to one of claims 2 to 16, characterized in that the welding electrode (126) is in the sequence of welding cycles and preferably also in the sequence of start welding cycles, if present, and / or in the sequence of end welding cycles, if present, in circumferential direction of the joining partners (152, 154) is carried out, especially during the low current phases.

18. Orbital welding process according to one of claims 1 or 3 to 17 or orbital welding device according to one of claims 2 to 17, characterized in that the welding electrode (126) is moved in the circumferential direction of the joining partners (152, 154) at an average welding speed in the range of 0.8 - 2.6 m / min., preferably 1.1 - 2.2 m / min., in particular 1.3 - 1.9 m / min.

19. Orbital welding method according to one of claims 1 or 3 to 18 or orbital welding device according to one of claims 2 to 18, characterized in that the joining points (210) are placed next to each other overlapping, wherein the overlap of two adjacent joining points (210) is preferably in the range of 35 - 90%, more preferably 40 - 85%, in particular 60 - 80%.

20. Orbital welding method according to one of claims 1 or 3 to 19 or orbital welding device according to one of claims 2 to 19, characterized in that the orbital welding device (100, 101) comprises a hand-held device (102) comprising the welding head (104).

21. Orbital welding method according to one of claims 1 or 3 to 20 or orbital welding device according to one of claims 2 to 20, characterized in that the welding power source (128) has a coil (604) having a first coil connection (606), a second coil connection (610) and an intermediate tap (608), wherein a first winding part (612) of the coil (604) is electrically connected between the first coil connection (606) and the intermediate tap (608) and a second winding part (614) of the coil (604) is electrically connected between the intermediate tap (608) and the second coil connection (610).

22. Orbital welding method according to one of claims 1 or 3 to 21 or orbital welding device according to one of claims 2 to 21, characterized in that one or more welding parameters for generating the chain (211) of joining points (210) is set depending on the temperature of one or both joining partners (152, 154).

23. System (700) comprising an orbital welding device (100, 101) according to one of claims 2 to 22 and a fitting (152).

24. System according to claim 23, characterized in that the fitting (152) has an outer contour (714) and the welding head (104) has a fitting corresponding to the outer contour (714). has a fixing contour (750) to hold the fitting (152) in a predetermined fitting position.

Images