WELDING DEVICE WITH NOZZLE DEVICE FOR COOLING A WORKPIECE DURING THE WELDING PROCESS

Description

[0001] The invention relates to a welding device, in particular for an arc welding process, e.g. in the form of WAAM (Wire Arc Additive Manufacturing). A welding device of this type is described in GB2532024.

[0002] When using arc welding technology for joining, weld overlay, and additive manufacturing (also known as wire arc additive manufacturing), heat is introduced into the component or structure by melting or partially melting the base and filler material. This heat input accumulates, especially when multiple layers of filler material are applied.

[0003] In WAAM (Wire Arc Additive Manufacturing), established MSG processes are used to apply a metallic material layer by layer, creating a 3D structure or corresponding workpiece. A problem arises from the fact that the workpiece heats up during the welding process, leading to changes in electrical and thermal conditions, alterations in the layer structure, deformation, and the appearance of discoloration.

[0004] Furthermore, the mechanical and technological properties of the materials undergo an uncontrolled change, as each additional layer thermally affects the previous layers.

[0005] Currently, attempts are being made to address the problems described above by incorporating pauses for the workpiece to cool down. The high melting rate of MIG / MAG processes is somewhat diminished by the necessity of these cooling pauses.

[0006] In principle, it is possible to cool WAAM structures with gas flows, thus improving metallurgical properties and reducing or eliminating the need for cooling breaks. However, such solutions only work for very simple structures, such as the construction of a tube (circular path), and even then only if the structure being built rotates around its own axis and the welding torch does not move. The cooling nozzles can always be positioned at a constant distance from the welding torch. The cooling position does not need to be changed.

[0007] As soon as the pipe no longer rotates around its own axis (rotary table), the torch moves, or more complex geometries are welded, the position to be cooled changes constantly.

[0008] Based on this, the present invention aims to provide a welding device that is improved with regard to the aforementioned problem.

[0009] This problem is solved by a welding device having the features of claim 1. Advantageous embodiments of the invention are specified in the corresponding dependent claims and are described below.

[0010] The invention thus advantageously allows the workpiece to be cooled near the energy input in order to counteract overheating, even if the direction of movement and / or orientation of the welding torch changes during welding, since several cooling nozzles are available which can be supplied with a cooling medium.

[0011] According to the invention, the cooling nozzles of the nozzle device are arranged next to each other in a circumferential direction of the welding torch, preferably equidistantly, so that the cooling nozzle array runs ring-shaped around the welding torch.

[0012] This is particularly advantageous in applications where good accessibility is essential. The ring-shaped arrangement allows the cooling nozzles to be positioned around the welding torch in a very small installation space.

[0013] Furthermore, according to the invention, the cooling nozzle array comprises several rows of cooling nozzles, wherein the cooling nozzle array has at least one radial row, preferably several radial rows, of cooling nozzles extending towards the center point, and wherein at least two nozzles are arranged on each row, the nozzles being arranged at different radial distances from the center point. In particular, the cooling nozzle array represents a two-dimensional field or array of cooling nozzles, wherein the individual rows can be linear or curved, especially annular. Particularly in the case where several rows of cooling nozzles are used or present, individual cooling nozzles can also be directed inwards towards the still-hot weld seam or structure.

[0014] Furthermore, according to one embodiment of the invention, it is provided that several cooling nozzles (in particular a selected row, several selected rows or all rows) of the cooling nozzle array can be supplied with an adjustable volume flow of a specific cooling medium.

[0015] According to a further embodiment of the invention, it is provided that at least one cooling nozzle of the nozzle device can be supplied with a first cooling medium and at least one further cooling nozzle of the nozzle device can be supplied with a second cooling medium, wherein the second cooling medium differs in its composition from the first cooling medium.

[0016] The cooling medium for the individual cooling nozzles can therefore be changed, or different cooling nozzles can be supplied with different cooling media. For example, it is possible to supply cooling nozzles located close to the arc with a cooling medium, particularly a gas, especially an inert gas, while cooling nozzles located further away from the arc can be supplied with an active gas, a gas with increased active components, or even a liquid such as water. This significantly increases the cooling effect without affecting the arc, for example, through the water.

[0017] According to the invention, the cooling nozzle array is rotatable about a rotational axis, so that, in particular, the cooling nozzles are movable around the welding torch, thus preferably directing a coolant flow emitted by one or more cooling nozzles onto a still-hot surface of the at least one workpiece, even if the welding torch has already changed its orientation and / or direction of movement during welding. In this case, one axis of rotation of this rotation can coincide with a longitudinal axis of the welding torch, but can also have an inclination relative to this longitudinal axis (e.g., if the cooling nozzle array is tiltable about a further tilting axis, see below).

[0018] Furthermore, according to one embodiment of the invention, the welding device for rotating the cooling nozzle array around the axis of rotation comprises at least one electric motor or a pneumatic drive (or similar motion units).

[0019] According to a further embodiment of the invention, the welding device is designed to set a rotation angle of the cooling nozzle array with respect to the axis of rotation based on a temperature signal and / or based on an automatic calculation based on a known or planned movement sequence of the welding torch during the welding process.

[0020] Furthermore, according to one embodiment of the invention, the cooling nozzle array is provided to be tiltable about a tilting axis, in particular about a horizontal tilting axis. This makes it easier to always direct the flow of the cooling medium to the optimal cooling position (generally in the direction of movement of the welding torch behind the welding process or behind the current weld pool, so that the cooling or cooling position follows the welding torch).

[0021] Furthermore, according to one embodiment of the invention, the welding device has temperature sensors (particularly advantageously optical sensors) configured to detect a temperature distribution of the workpiece produced by means of the welding device.

[0022] According to a further embodiment of the invention, the welding device is designed to control or adjust the volume flow of a cooling medium discharged through the respective cooling nozzle based on the detected temperature distribution or temperature information, so that, in particular, the temperature distribution can be approximated to a desired temperature distribution. Furthermore, a cooling point on the surface of the at least one workpiece can be controlled in this way based on the temperature information.

[0023] The nozzle assembly can include valves, for example, located upstream of the cooling nozzles, to control the flow rates. These valves can be pneumatically or electrically actuated. They can be, for example, proportional valves. Alternatively, sliding orifices can be used.

[0024] Furthermore, the known path contours can be used to calculate (e.g., through simulation) where heat will accumulate on the workpiece. Accordingly, these areas can be cooled more intensively than areas where no heat buildup is predicted.

[0025] Preferably, the cooling strategy is determined based on a delay calculation. The respective flow rate or volumetric flow of a cooling medium through the respective cooling nozzle is preferably variably adjustable, e.g., by using proportional valves.

[0026] To intensify cooling, the welding device or the nozzle device is designed to open several cooling nozzles simultaneously or to discharge a cooling medium simultaneously via several cooling nozzles.

[0027] The individual cooling nozzles can, for example, be mounted on the nozzle assembly via a thread, making them easily replaceable.

[0028] Furthermore, the individual cooling nozzles can exhibit different flow characteristics and can thus be adapted to the respective application. In particular, the respective cooling nozzle can, for example, generate a rotationally symmetrical flow field or a non-rotationally symmetrical flow field. For this purpose, the corresponding cooling nozzle can, for example, be designed as a slot nozzle.

[0029] Furthermore, according to one embodiment of the invention, the welding device is designed to supply a cooling nozzle located closer to the arc than another cooling nozzle with a lower volume flow of cooling medium than the other cooling nozzle, in order to reduce the risk of interaction between the cooling medium and a process gas (e.g., shielding gas) used in the welding process. The process gas may be, for example, a shielding gas and / or a focusing gas emitted by the welding torch to protect the weld area from oxidation or to control the arc.

[0030] Furthermore, according to one embodiment of the invention, the welding device is designed to discharge one or more of the following media as a cooling medium via at least one cooling nozzle: argon, helium, nitrogen, hydrogen, air, carbon dioxide, or a mixture of a selection of the aforementioned gases. The welding device can have a container for each cooling medium used, which is fluidically connected to, or can be connected to, the nozzle device (e.g., via the valves mentioned above).

[0031] Another aspect of the present invention relates to a method for welding at least one workpiece, wherein the workpiece is built up layer by layer using a welding device according to the invention and is cooled by means of the nozzle device.

[0032] The present invention can be used particularly effectively in additive manufacturing (e.g. WAAM), since this involves a strong introduction of heat into the workpiece.

[0033] However, the solution according to the invention can also be used for conventional welding processes or overlay welding.

[0034] The principle according to the invention is particularly advantageous in applications where the welding direction changes frequently or constantly, or in applications where increased distortion occurs. The invention can be used in processes that supply the filler material via wire as well as via powder. The invention is fundamentally suitable for all welding processes (especially MIG / MAG, TIG, plasma welding, laser welding, and special processes such as hybrid welding, tandem welding, etc.).

[0035] The invention advantageously allows the preservation of the mechanical and technological properties of the materials. At the same time, it achieves an increase in production speeds, as no cooling phases are necessary between the individual layers (often more than 50%).

[0036] Furthermore, the invention enables a reduction of thermal distortion to a minimum. The layer structure becomes predictable, and lower unevenness of the 3D structure to be produced can be achieved (so-called near-net shape is improved). The invention also enables a reduction in discoloration.

[0037] In the following, embodiments, further features and advantages of the present invention will be explained with reference to the figures. The figures show: Fig. 1 a schematic top view of an embodiment of a welding device according to the invention during a welding process, wherein the welding torch undergoes a change of direction of 90°, Fig. 2 a schematic top view of an embodiment of a welding device according to the invention during a welding process, wherein the welding torch undergoes a change of direction of 180°, Fig. 3 a schematic side view of an embodiment of a welding device according to the invention with a cooling nozzle array that is rotatably mounted on the welding torch, Fig. 4 a further schematic side view of the in the Figure 3 The welding device shown, and Fig. 5 a schematic side view of a welding device not according to the invention.

[0038] The Figure 1 and 2show a schematic top view of an embodiment of a welding device 1 according to the invention during a welding process, wherein the welding torch 2 changes direction by 90° (cf. Fig. 1 ) or 180°C (see Fig. 2 ).

[0039] The welding device 1 according to Figure 1 and 2 The device has a welding torch 2 for carrying out the welding process, which is designed to generate an electric arc so that, for example, a welding filler or a surface of a workpiece to be manufactured can be melted in order to build up the workpiece layer by layer, for example, within the framework of a WAAM process.

[0040] In order to be able to cool the workpiece in a targeted manner during the welding process, the welding device 1 has a nozzle device 20 arranged on the welding torch 2, which has a cooling nozzle array 21, which has at least a row 22 of cooling nozzles 23, wherein the respective cooling nozzle 23 can be supplied with an adjustable volume flow of a cooling medium 4 to cool the workpiece.

[0041] The cooling nozzle array 21 is according to Figure 1 and 2 rotatable about a rotational axis R, so that in particular the cooling nozzles 23 can be moved around the welding torch 2. In the Figure 1 and 2 The axis of rotation is perpendicular to the plane of the leaf.

[0042] Thus, for example, when the welding torch changes direction by 90°, as described in the Figure 1As shown, by rotating the cooling nozzle array around the axis of rotation R, the cooling position 230, i.e., the surface area 230 of the workpiece which is supplied with a cooling medium 4, can be adapted to the change of direction, ideally such that the cooling position in the direction of movement B of the welding torch 2 lies behind the instantaneous weld pool which is generated by the arc of the welding torch. Figure 2 shows the adjustment of the cooling position 230 when the direction of the welding torch 2 changes by 180°.

[0043] The in the Figure 1 and 2 The welding device shown (1) can be used, for example, according to… Figure 3The cooling nozzle array 21 shall have at least one row 22 of cooling nozzles 23, the cooling nozzles 23 being at different distances from the arc 3 of the welding torch. The cooling nozzle array 21 is pivotable about a rotational axis R, the rotational angle W being adjustable by means of a suitable actuator that causes the rotation of the cooling nozzle array 21. Additionally, the cooling nozzle array can be tilted or pivoted about a tilting axis y, here, for example, a horizontal tilting axis y. A specific cooling medium 4 can be discharged through the individual cooling nozzles 23 with a variable volume flow rate. Different cooling media 4, 40 can also be discharged via the cooling nozzles 23. Furthermore, the rotational angle W of the cooling nozzle array 21 with respect to the rotational axis R and / or a tilting angle W' with respect to the tilting axis y can be set based on a temperature signal, which can be provided, for example, by a temperature sensor 24.Furthermore, the temperature signal can be used to adjust the volume flows of the cooling media 4, 40.

[0044] The cooling medium(s) can be one of the following: argon, helium, nitrogen, hydrogen, air, carbon dioxide, or a mixture of a selection of the aforementioned gases.

[0045] As further in the Figure 4 As shown, the cooling nozzle array 21 of the welding device 1 has according to Figure 3 several rows 22 on cooling nozzles 23, whereby, for example, it is possible to direct the coolant flows 4 of the cooling nozzles of the outermost rows 22 inwards in order to concentrate the cooling power on the path traveled by the welding torch 2.

[0046] Figure 5 shows a further embodiment of a non-inventive welding device 1, wherein here, in contrast to the Figures 3 and 4the cooling nozzles 23 are arranged in a ring shape around the welding torch 2 in a circumferential direction U of the welding torch 2, preferably equidistant from each other, so that the cooling nozzle array 21 runs in a ring shape around the welding torch 2.

Claims

1. Welding device (1) for welding at least one workpiece, comprising: - a welding torch (2), which is designed to create an electric arc (3) for welding the at least one workpiece, - a nozzle apparatus (20) arranged on the welding torch (2), which apparatus comprises a cooling nozzle array (21), the cooling nozzle array (21) having at least one radial row of cooling nozzles and at least two cooling nozzles being arranged on the row, it being possible to supply the relevant cooling nozzle (23) with an adjustable volume flow of a cooling medium (4) for cooling the workpiece, characterized in that the cooling nozzle array (21) is rotatable about a rotational axis (R) such that the cooling nozzles (23) are movable around the welding torch (2), in that the cooling nozzle array (21) comprising a plurality of rows (22) of cooling nozzles (23) and cooling nozzles (23) of the nozzle apparatus (20) being arranged next to one another in a circumferential direction (U) of the welding torch (2), preferably equidistantly, such that the cooling nozzle array (21) extends in a ring shape around the welding torch (2).

2. Welding device according to any of the preceding claims, characterized in that a plurality of cooling nozzles (23) of the cooling nozzle array (21) can be supplied with an adjustable volume flow of a particular cooling medium (4).

3. Welding device according to any of the preceding claims, characterized in that at least one cooling nozzle (23) can be supplied with a first cooling medium (4) and at least one further cooling nozzle can be supplied with a second cooling medium (40), the second cooling medium (40) differing from the first cooling medium (4) in its composition.

4. Welding device according to any of the preceding claims, characterized in that the welding device (1) is designed to adjust a rotation angle (W) of the cooling nozzle array (21) with respect to the rotational axis (R) on the basis of a temperature signal and / or on the basis of an automatic calculation based on a known movement sequence of the welding torch (2) during the welding process.

5. Welding device according to any of the preceding claims, characterized in that the cooling nozzle array (21) can be tilted about a tilting axis (y), in particular a horizontal tilting axis.

6. Welding device according to any of the preceding claims, characterized in that the welding device (1) comprises at least one temperature sensor (24) which is configured to detect a temperature distribution of a workpiece produced by means of the welding device (1).

7. Welding device according to claim 6, characterized in that the welding device (1) is designed to control, on the basis of the detected temperature distribution, a volume flow of a cooling medium (4, 40) discharged through the relevant cooling nozzle (23).

8. Welding device according to any of the preceding claims, characterized in that the relevant cooling nozzle (23) is fixed to the nozzle apparatus (20) via a thread.

9. Welding device according to any of the preceding claims, characterized in that the welding device (1) is designed to supply a cooling nozzle (23) of the cooling nozzle array (21) that is closer to the electric arc (3) than a further cooling nozzle (23) with a lower volume flow of a cooling medium (4) than the further cooling nozzle (23) in order to reduce the risk of interaction of the cooling medium (4) with a process gas of the welding process.

10. Welding device according to any of the preceding claims, characterized in that the welding device (1) is designed to discharge one of the following media as a cooling medium (4, 40) via at least one cooling nozzle (23): argon, helium, nitrogen, hydrogen, air, carbon dioxide, or a mixture of a selection of the aforementioned gases.

11. Method for welding at least one workpiece, wherein the workpiece is constructed in layers by means of a welding device (1) according to any of the preceding claims and is cooled by means of the nozzle apparatus (20).