WELDING EQUIPMENT AND WELDING PROCEDURES

Description

[0001] The invention relates to a welding device and a method for FSW welding of workpieces with different friction melting temperatures with the features in the independent material and method claims.

[0002] Such a friction stir welding device and a friction stir welding method are known from WO 2017 / 167964 A1. The friction stir welding device is used for friction stir welding or friction stir welding of workpieces with different friction melting temperatures and comprises a friction stir welding tool with a rotating, driven friction stir welding element in the form of a friction stir welding pin. Furthermore, a detection device is provided that detects frictional contact between the friction stir welding element and the higher-melting workpiece at the friction welding point during the welding process. The detection device comprises a vibration sensor that detects vibrations occurring during such frictional contact and measures their frequency and / or amplitude.

[0003] Based on the measurement results, the strength of the contact and / or the level of the contact force of the FSW welding pin on the higher melting workpiece can be regulated.

[0004] US 2018 / 221986 A1 (basis for the preamble of claims 1 and 8) describes a friction welding device with a temperature sensor in the projection of the welding tool.

[0005] During welding, the control unit controls the rotation and movement speed of the tool to keep the temperature within a specified range and thus ensure welding quality.

[0006] DE 101 39 687 C1 describes a friction stir tool for friction welding, which can be controlled with sufficient measuring accuracy according to the temperature in the welding zone, wherein the temperature values in the welding zone are recorded with a temperature sensor, the measuring point of which is arranged in the pin of the friction stir tool.

[0007] KR 102 265 585 B1 describes a friction welding tool with adjustable probe length and shoulder groove depth. A carrier made of a material with low thermal conductivity is coupled in such a way that heat conduction between the probe and the shaft is inhibited. This enables more precise control of the welding process and improves the quality of the welds.

[0008] It is an object of the present invention to provide an FSW welding device and an FSW welding method with an improved detection technique for detecting frictional contact of the FSW welding element with the higher melting workpiece.

[0009] The invention solves this problem with an FSW welding device and an FSW welding method and the features in the independent device and method claims.

[0010] The invention relates to the so-called FSW welding, which in German is also called Rührreibschweissen and in English as Friction-Stir-Welding (abbreviated FSW).

[0011] Contacted workpiece areas, particularly workpiece edges, of preferably two, three, or more workpieces to be welded are plasticized by the moving FSW welding element and the frictional movement, as well as the frictional heat generated at the FSW friction point, and then bond to form an FSW weld seam. The FSW friction point is the point between the workpieces to be welded where the moving, rotating FSW welding element is located during its feed movement along a predetermined friction FSW welding path, causing the plasticization of the workpieces by displacing the workpiece material. Behind the advanced FSW welding element, the plasticized workpiece materials flow together again to form the FSW weld seam.

[0012] The invention further relates to the FSW welding of workpieces with significantly different melting and plasticizing temperatures. These can be, for example, workpieces made of steel and a light metal, in particular an aluminum alloy. The difference in melting temperatures is, for example, 200°C or more, preferably 500°C or more. In a FSW pairing of steel and an aluminum alloy, the difference is approximately 900°C.

[0013] FSW welding and the plasticizing of the workpiece materials take place at plasticizing temperatures below the melting temperature. The plasticizing temperature is the determining factor.

[0014] The melting and plasticizing temperature ratios are similar for the workpieces. The workpiece material with the higher melting temperature also has a higher plasticizing temperature than the workpiece material with the lower melting temperature and lower plasticizing temperature. For simplicity, the melting temperature will be used to characterize the workpieces below. The workpiece or workpiece material with the higher melting and plasticizing temperature will be referred to as the higher-melting workpiece or workpiece material, and the workpiece or workpiece material with the lower melting and plasticizing temperature will be referred to as the lower-melting workpiece or workpiece material.

[0015] FSW welding can be performed with different workpiece arrangements at the FSW friction point, e.g., with butt joints or lap joints. FSW welding of fillet welds is also possible. The workpieces to be welded can have a plate-like shape, for example, or they can have other shapes. The FSW welding path is directed along the joint area or contact area between the workpieces to be welded.

[0016] When welding butt joints or lap joints with FSW, the FSW welding element is aligned essentially perpendicular to the main plane of the workpieces, which lie side by side in a butt joint and on top of each other in a lap joint. The FSW welding element can be aligned exactly perpendicular to the said main plane. It can also have a slight feed angle of, for example, up to 3° against the direction of the FSW welding path.

[0017] When welding fillet welds using FSW, the FSW welding element is directed at an angle into the joint area or into the fillet formed between the workpieces aligned at a fillet angle of, for example, 90°. The FSW welding element can be directed, for example, along the bisector of the fillet angle between the workpieces. The FSW welding element can be oriented perpendicular to the joint area or the FSW weld path, or it can have the aforementioned feed inclination.

[0018] The goal is to plasticize both workpieces at the FSW friction point to achieve good weld quality. To achieve this, the FSW welding element should also make sufficient frictional contact with the higher-melting workpiece and plasticize it at the FSW friction point.

[0019] In FSW welding, the FSW welding element is preferably first brought into contact with the lower-melting workpiece and then moved to the higher-melting workpiece, bringing it into frictional contact. This has advantages for the precise detection of frictional contact with the higher-melting workpiece.

[0020] The penetration depth of the FSW welding element on workpieces or workpiece materials with different melting points can vary. Preferably, the penetration depth on the higher-melting workpiece or workpiece material is smaller, in particular several times smaller, than the penetration depth on the lower-melting workpiece or workpiece material.

[0021] The claimed detection technology, using a thermoelectric measuring device, detects the frictional contact of the FSW welding element with the higher-melting workpiece by thermoelectrically recording the friction temperature on the two or more workpieces to be welded. A change in the friction temperature can be detected. When the FSW welding element is moved at the beginning of the welding process, it can be thermally detected whether the desired frictional contact is established or exists. As the welding process progresses, it can be thermally detected whether the frictional contact is maintained in the desired form or is lost. The greater the difference between the melting temperatures and the plasticizing temperatures of the workpieces, the better the detection accuracy.

[0022] If said frictional contact exists with the workpiece that has a higher melting point than the other workpiece, the temperature at the FSW friction point rises or reaches a high temperature level. If said frictional contact with the higher-melting workpiece does not exist or is lost and the FSW welding element is only in frictional contact with the lower-melting workpiece, the temperature at the FSW friction point or process point drops. These temperature changes can signal the existence and, if applicable, the strength of frictional contact between the FSW welding element and the higher-melting workpiece. The temperature changes can be used to control the FSW welding process, particularly in FSW track welding.

[0023] Frictional contact between the FSW welding element and the higher-melting workpiece can also be detected in other ways. This can be done, for example, by recording and monitoring the feed force and / or by a vibration sensor and / or a temperature sensor.

[0024] The claimed thermoelectric detection technology has the advantage of being less susceptible to interference and offering better detection accuracy for friction contact changes compared to the prior art. The claimed detection technology is also less sensitive to environmental influences, such as climate fluctuations, disruptive vibrations from neighboring machines, or the like.

[0025] The thermoelectric measuring device can advantageously utilize the Seebeck effect and be designed as a so-called Seebeck measuring device. It can have an electrical measuring circuit with an electrical measuring element for measuring the electrical energy induced in the measuring circuit by the Seebeck effect.

[0026] The Seebeck effect allows for particularly good, sensitive, and responsive detection of temperature changes associated with changes in frictional contact. For this purpose, it is advantageous to work with shallow penetration depths of the FSW welding element on the higher-melting workpiece. These can be approximately 0.2 to 0.5 mm, preferably 0.2 to 0.3 mm.

[0027] In the aforementioned Seebeck effect, an electrical voltage is generated in a circuit consisting of two different electrical conductors when there is a temperature difference between the contact points of the conductors. This voltage is attributed to thermal diffusion currents in a material. At the hot end of an electrical conductor, there are more electrons with high energy, which move by diffusion to the cold end of the electrical conductor. The electrons with less energy, which are also present, move in the opposite direction. This represents heat conduction by electrons. Any imbalance in the currents is compensated by an electric field. The resulting voltage is the Seebeck voltage. This can be measured by the electrical measuring element and, if necessary, evaluated and reported to an electrical control system.

[0028] The claimed welding device can comprise an automatic handling device with a control system. The handling device can hold and guide the FSW welding tool during the welding process, thereby generating a relative movement between the workpieces to be welded and the FSW welding tool along a predetermined FSW welding path, with frictional contact of the FSW welding element with the workpieces of different melting points. This automatic path welding can be performed with different joint shapes, in particular with lap joints or butt joints.

[0029] In lap joint welding, the moving, rotating FSW welding element is first advanced to the lower-melting workpiece and penetrates it until frictional contact with the higher-melting workpiece is established. In butt joint welding, the moving, rotating FSW welding element is first advanced to the lower-melting workpiece, e.g., with a lateral offset from the joint area or the FSW welding path, and then, by a lateral movement, is brought closer to the higher-melting workpiece and brought into frictional contact. In both cases, the resulting frictional contact is detected thermoelectrically.

[0030] The thermoelectric measuring device can be connected to the control system of the automatic handling device. This enables, for example, monitored and, if necessary, controlled path tracking during frictional welding. If the thermoelectric measuring device detects a lack or loss of said frictional contact with the higher-melting workpiece, the handling device can move the frictional welding tool toward or away from the frictional welding path. In butt-joint welding, this can be a lateral advance or return movement to the frictional welding path located between the contacting workpiece edges. In lap-joint welding, the handling device can press the frictional welding tool through the lower-melting workpiece onto the frictional welding path formed between the superimposed contact surfaces of the workpieces by means of a preferably rotationally fixed tool shoulder.By pressing further, any thickness deviations of the lower melting workpiece can also be compensated.

[0031] Thermoelectric detection of frictional contact with the higher-melting workpiece enables process monitoring and quality assurance during the FSW welding process. The temperature and frictional contact data can be stored and evaluated. This can be done with reference to time and / or FSW weld path, FSW path position, or FSW weld seam position. For acceptable FSW welding quality, frictional contact must be detected and recorded over a minimum distance or a minimum length of the FSW weld seam, e.g., 90% of the total length. Otherwise, a warning is issued.

[0032] On the other hand, thermoelectric detection of a lack of or loss of frictional contact between the FSW welding element and the higher-melting workpiece can generate a warning signal. A lack of or loss of frictional contact can, for example, indicate possible wear, particularly shortening, of the FSW welding element.

[0033] Such wear can be remedied by changing the FSW welding tool or by readjusting the preferably pin-shaped FSW welding element in the adjustable FSW welding tool. The automatic handling device can press the FSW welding tool against the impacted workpieces with a predetermined feed force. In particular, a tool shoulder that is wider than the preferably protruding, pin-shaped FSW welding element can be pressed into place.

[0034] The electrical measuring circuit of the thermoelectric measuring device, in particular a Seebeck measuring device, can comprise electrically and possibly thermally conductive lines, each of which is connected to the electrical measuring element at one of its ends. At the other end, said lines can be connected or can be connected to areas on the welding tool and, if applicable, a workpiece that are subject to different temperatures during the welding process.

[0035] The said end of one line is connected, for example, to the FSW welding element. Due to the heat conduction of the preferably metallic SW welding element, this line end is at a higher temperature than the line end of the other line, which is connected, for example, to a different and lower temperature-controlled point on the FSW welding tool. This point is arranged, for example, on a preferably rotationally fixed and electrically conductive tool shoulder. The line end of the other line can alternatively or additionally be connected to a workpiece, in particular to the workpiece with the higher melting point. Different temperatures therefore exist at these two line ends, which can be detected by the electrical measuring element in the measuring circuit using the Seebeck effect. The workpieces can be electrically conductive.

[0036] The controller may have a control module, which may be integrated into the controller, for example, as a software module and / or as a hardware module, or may be assigned to the controller. The control module is connected to the detection device, in particular the thermoelectric measuring device. A signaling connection may exist, in particular, with the electrical measuring element. Communication and data exchange may be wired or, preferably, wireless, e.g., via radio, WLAN, or the like.

[0037] The control module can issue a warning if a thermoelectrically detected failure or loss of frictional contact between the FSW welding element and the higher-melting workpiece is detected. Alternatively or additionally, the control module can trigger and, if necessary, regulate a follow-up relative movement of the automatic handling device to establish frictional contact.

[0038] The claimed handling device for holding and guiding the FSW welding tool can be designed in various ways. The handling device can also carry the detection device along with the FSW welding tool.

[0039] A preferred embodiment is a multi-axis, programmable industrial robot, particularly an articulated-arm robot or a knuckle-arm robot. The handling device, particularly said industrial robot, guides and moves the FSW welding tool and the accompanying detection device along the FSW welding path relative to the workpieces to be welded. Preferably, the FSW welding tool and the accompanying detection device are moved relative to stationary and clamped workpieces. The kinematics can also be different, particularly reversed. Two such industrial robots can also be used for the relative movement, one of which moves the FSW welding tool and the detection device, and the other moves the workpieces to be welded. The automatic handling device can otherwise be designed in a different way, e.g., as a CNC-controlled FSW welding machine.Partial manual operation is also possible.

[0040] The FSW welding tool and its FSW welding element are also designed differently. The FSW welding element is pin-shaped. It is driven in rotation around its longitudinal axis. The FSW welding tool also includes the aforementioned tool shoulder. This is arranged in a rotationally fixed manner. The FSW welding element protrudes axially beyond the tool shoulder with a pin length determined by the process and workpiece. An adjusting device enables adjustment and possible axial readjustment of this pin length due to wear.

[0041] In an advantageous embodiment, the FSW welding pin can comprise a preferably cylindrical shaft and a pin head with a prismatic peripheral edge. The peripheral edge can, for example, have three straight edge flanks offset by 120°. An FSW welding pin can also have a shape that promotes melt flow, e.g., with one or more peripheral threaded sections, guide grooves, or the like.

[0042] Further advantageous embodiments of the invention are specified in the subclaims.

[0043] The invention is illustrated schematically and by way of example in the drawings. In detail: Figure 1: an FSW welding device with an automatic handling device, an FSW welding tool and a detection device as well as two differently melting and to be welded workpieces, Figure 2: a schematic representation of the FSW welding tool and the detection device during butt friction welding of two differently melting workpieces, Figure 3: a plan view of the arrangement of Figure 2 , Figure 4: a schematic representation of an FSW welding tool and the detection device for a lap joint welding of differently melting workpieces with frictional contact to the higher melting workpiece, Figure 5: the arrangement of Figure 4 with a worn FSW welding element without frictional contact to the higher melting workpiece, Figure 6: a plan view of the arrangements of Figures 4 and 5 and Figures 7 to 11: Variants of a pin-like FSW welding element in different views.

[0044] The invention relates to a FSW welding device (1) and a FSW welding method. These are intended and designed for FSW welding of workpieces (2, 3) with substantially different melting temperatures.

[0045] In the exemplary embodiments shown, the workpieces (2, 3) are plate-like, in particular designed as sheets. The workpieces (2, 3) are preferably made of a metallic material. In the exemplary embodiments shown, one workpiece (2) has the lower melting temperature and plasticizing temperature, wherein the workpiece material is formed, for example, as a light metal, in particular an aluminum alloy, or in another suitable manner. The workpiece material of the other workpiece (3) with the higher melting temperature and plasticizing temperature is formed, for example, from steel or cast iron or another preferably ferrite-based metal or in another suitable manner. The workpieces (2, 3) are thermally and optionally electrically conductive.

[0046] The FSW welding device (1) comprises an FSW welding tool (5) with a driven and moving, rotating, FSW welding element (6). The FSW welding element (6) has a pin- or rod-like shape and is designed as an FSW welding pin that rotates about its longitudinal axis and has, for example, a cylindrical or conical shape. The preferably metallic FSW welding pin is thermally conductive. The FSW welding tool (5) also has a tool shoulder (7) that is wider than the pin-like FSW welding element (6) and is arranged at its upper end. The FSW welding element (6) can be connected to the tool shoulder (7) rigidly or in an axially movable and rotatable manner.

[0047] In the embodiment shown, the cylindrical tool shoulder (7), for example, is arranged in a rotationally fixed manner on the FSW welding tool (5). The FSW welding element (6), which is driven in rotation by a drive (not shown), penetrates the tool shoulder (7) and projects axially beyond it by a free pin length, the size of which depends on the workpiece thickness and the process requirements for a correct FSW weld seam (23). The FSW welding element (6) is arranged axially movable on the FSW welding tool (5) and is connected to an adjusting device (11) which sets the said free pin length and adjusts it as required, e.g. in the event of head-side wear or shortening.

[0048] For FSW welding, the workpieces (2, 3) to be welded are brought into contact with their edges and plasticized or melted by the rotating FSW welding element (6) and bond together to form a Figure 3 and6 shown FSW weld seam (23). The FSW welding element (6) engages and frictionally contacts both workpieces at an FSW friction point (12). The engagement depth with the workpieces (2, 3) varies, with a significantly greater engagement depth on the lower-melting workpiece (2) than on the higher-melting workpiece (3). The engagement depth on the higher-melting workpiece (3) can be very shallow, for example, 0.3 mm.

[0049] The type of intervention on the workpieces (2,3) depends on the type of welding joint. Figures 1 to 3A butt joint is shown, where the two workpieces (2, 3) butt together at their facing edges. The FSW welding element (6) is inserted at this joint and FSW friction point (12) and engages both workpieces (2, 3) in frictional engagement along its free pin length and its outer surface. The insertion depth of the FSW welding element (6) depends on the workpiece thickness and is selected to ensure complete welding of both workpieces (2, 3) in the gap at their contact point.

[0050] Figures 4 to 6 illustrate a variation of a lap joint, in which the workpieces (2, 3) overlap one another. The FSW welding element (6) penetrates the lower-melting workpiece (2) and then engages and frictionally contacts the higher-melting workpiece (3) at the FSW friction point (12) with its front end at the free pin length. This front end can be designed as a conical tip.

[0051] In the FSW welding process, the FSW welding element (6), for example, is first advanced to the lower-melting workpiece (2) and brought into engagement. Subsequently, a corresponding movement establishes frictional contact and engagement with the higher-melting workpiece (3). In both cases, the tool shoulder (7) is pressed against the workpieces (2, 3) with a force (F) acting in the z-direction or axial direction of the FSW welding element (6).

[0052] In butt welding, the FSW welding element (6) is pressed circumferentially against the end face of the higher-melting workpiece (3) to be welded with a force acting transversely and in the y-direction. In lap welding, the FSW welding element (6) is pressed end-on into the higher-melting workpiece (3). In the FSW welding process, the moving, particularly rotating FSW welding element (6) is moved along a predetermined FSW welding path (4). The FSW friction point (12) moves along the FSW welding path (4).

[0053] The FSW welding tool (5) can have one or more sensors that record forces and / or moments acting on the FSW welding element (6). This allows the feed force to be measured in the z- and / or y-direction.

[0054] The FSW welding device (1) further comprises a detection device (17) designed to detect frictional contact between the FSW welding element (6) and the higher-melting workpiece (3) at the FSW friction point (12) during the FSW welding process. The detection device (17) has a thermoelectric measuring device (18) that detects frictional contact between the FSW welding element (6) and the higher-melting workpiece (3) by detecting the friction temperature and a change in the friction temperature at the workpieces (2, 3).

[0055] The thermoelectric measuring device (18) is designed as a Seebeck measuring device and has an electrical measuring circuit (19) with electrical lines (21, 22) and an electrical measuring element (20). It is Figure 2 , 4 and 5 shown schematically.

[0056] The electrical lines (21, 22) are each connected to the electrical measuring element (20) at one end. The other end is connected to points on the FSW welding tool (5) with different temperature levels. The temperature differences result, on the one hand, from the high temperature generated when the FSW welding element (6) comes into frictional contact with the workpiece (3) which has a higher melting point, and, on the other hand, from the lower normal temperature in the workpiece area. The other end of the line (22) is connected to the FSW welding element (6) and absorbs the high temperature generated during said frictional contact. The other end of the second line (21) is connected to the tool shoulder (7) and absorbs the lower temperature at the connection point.Said end of the line (21) can alternatively also be connected to a workpiece (2, 3), in particular to the higher-melting workpiece (3). Figure 5 illustrates this line connection.

[0057] The FSW welding device also comprises a preferably automatic handling device (13) with a controller (14). The handling device (13) holds and guides the FSW welding tool (5) during the welding process and generates a relative movement between the workpieces (2, 3) to be welded and the FSW welding tool (5) along a predetermined FSW welding path (4) with frictional contact of the FSW welding element (6) with the differently melting workpieces (2, 3). The workpieces (2, 3) are preferably arranged stationary and clamped in their mutual FSW welding positions.

[0058] In the embodiment shown, the handling device (13) is designed as a multi-axis movably driven and programmed industrial robot (14), e.g. as a six-axis articulated arm robot, on whose multi-axis robot hand the FSW welding tool (5) and the carried detection device (17), which comprises a thermoelectric measuring device (18), are mounted.

[0059] The thermoelectric measuring device (18), in particular the electrical measuring element (20), is connected to the control (15) of the automatic handling device (13). The control (15) has, according to Figure 1a control module (16) connected to the detection device (17), in particular the thermoelectric measuring device (18). The thermoelectric measuring device (18) and / or the control module (16) detect, via temperature measurement, whether or not the desired frictional contact of the FSW welding element (6) with the higher-melting workpiece (3) exists during the FSW friction welding process.

[0060] The controller (15) contains control programs, in particular a path control, for tracking the FSW welding path (4). If frictional contact with the higher-melting workpiece (3) is not yet established or has been lost, the controller (15) can track the FSW welding tool (5) and its FSW welding element (6) and, for example, return them to the FSW welding path and into frictional contact with the higher-melting workpiece (3) as part of a process control.

[0061] Figures 2 and 3illustrate this process during butt welding. When the FSW welding element (6) and the FSW friction point (12) are located at the desired position between the workpieces (2, 3) and are guided along the FSW welding path (4), the FSW weld seam (23) is created, formed from the mutually bonded workpiece materials. Figure 3The middle section shows a lateral deviation of the FSW welding element (6) from the specified FSW welding path (4) and a concomitant loss of frictional contact. This manifests itself in a detectable reduction in the plasticizing temperature acting on the FSW welding element (6) in the lower-melting workpiece (2). This is detected by the thermoelectric measuring device (18) and reported to the control module (16), which simultaneously records the current robot position. The control module (16) then initiates a return movement, symbolized by an arrow, to the FSW welding path (4) and into the desired frictional contact of the FSW welding element (6) with the higher-melting workpiece (3). This is detected by the temperature increase resulting from frictional contact. The pre-programmed FSW welding path (4) can then be further tracked.

[0062] In the case of lap joint welding according to Figures 4 to 6The FSW welding element (6) is advanced through the lower-melting workpiece (2), which is positioned on top, toward the higher-melting workpiece (3). As soon as the desired frictional contact with the higher-melting workpiece (3) occurs at the frontal FSW friction point (12), this is detected by the thermoelectric measuring device (18) through the corresponding temperature increase. The FSW welding element (6) can then be moved with its FSW friction point (12) along the specified FSW welding path (4).

[0063] If, for example, according to Figure 5If the desired frictional contact between the FSW welding element (6) and the higher-melting workpiece (3) is not established at the specified infeed and the expected temperature rise does not occur, this can have various causes. One cause can be thickness tolerances of the lower-melting workpiece (2). These can be equalized by appropriately increased repositioning and an increase in the contact pressure (F). Another cause can be possible frontal wear of the FSW welding element (6) and a shortening of the intended free pin length. The FSW welding element (6) can then be replaced or readjusted manually or using the adjusting device (11). The tip of the FSW welding element (6) defines the tool center point (TCP) of a robot-guided tool. When the FSW welding element (6) is replaced or readjusted, the TCP is adjusted accordingly in the control system (15).

[0064] If, during lap joint welding along the FSW welding path (4), the aforementioned frictional contact with the higher-melting workpiece (3) is lost, e.g. due to tolerances of the lower-melting workpiece (2) or due to wear of the FSW welding element (6), a warning can be issued by the control module (16). On the other hand, the FSW holding element (6) can be adjusted in the z-direction by the handling device (13) and pressed down more forcefully until the aforementioned frictional contact is re-established or, if it is not achieved within a predetermined period of time, the FSW welding element (6) is axially adjusted. In these cases, a warning signal can also be issued and / or the welding process can be stopped.

[0065] The detection device (17) can have additional components for detecting the desired frictional contact between the FSW welding element (6) and the higher-melting workpiece (3). The latter generally also has greater hardness and strength. Such a component can be formed, for example, by the aforementioned force and / or moment sensor. When the rotating FSW welding element (6) impacts the higher-melting workpiece (3), the reaction force increases and can be detected by a sensor.

[0066] Another component of the detection device (17) can be a vibration sensor. This can detect modified and, in particular, amplified vibrations that occur during said frictional contact with the higher-melting and harder workpiece (3). The generation of vibrations can be promoted and amplified, e.g., by appropriately shaping the higher-melting workpiece (3) at the intended friction point (12) and the predetermined welding path (4). Another possibility is a vibration-optimized design of the welding element (6).

[0067] Figures 7 to 11illustrate various embodiments of pin-like and rotatingly driven FSW welding elements (6) or welding pins. These have a shaft (8) with a pin head (9) at the front end. The pin head (9) is the area that comes into engagement and frictional contact with the workpieces (2, 3) to be welded and plasticizes, in particular melts, the adjacent workpiece areas through friction. The pin head (9) can be cylindrical or conical. It can have a shape on the outer circumference that promotes the flow of plasticized mass, which is formed, for example, by one or more circumferential threaded sections, guide grooves or the like. The shaft (8) has, for example, a partially cylindrical shape and can have one or more circumferential flattened areas for positive force transmission by the rotary drive. Figures 7 and 9also illustrate the possibility of forming a tool shoulder (7) on the circumference of the FSW welding element (6) and moving it during the drive movement.

[0068] Figures 8, 10 and 11 illustrate a pin shape that is favorable for lap joint welding and a frontal friction point (12) or a frontal friction contact with the higher-melting workpiece (3). The pin head (9) can have a prismatic peripheral edge (10). This can, for example, comprise three straight edge flanks offset by 120°. A conical shape of the pin head (9) with an increasing diameter toward the shank (8) is also advantageous.

[0069] Modifications to the embodiments shown and described are possible in various ways and within the scope of the claims. In particular, the features of the various embodiments can be combined with one another and interchanged as needed. For example, in FSW butt welding and / or FSW fillet welding, the FSW welding element (6) can be positioned directly into the joint and contact area between the workpieces to be welded and simultaneously brought into frictional contact with the workpieces. LIST OF REFERENCE SYMBOLS

[0070] 1Welding device, FSW welding device 2Workpiece with lower melting point 3Workpiece with higher melting point 4FSW welding path 5FSW welding tool 6FSW welding element, FSW welding pin 7Tool shoulder 8Shaft 9Pin head 10Head circumference 11Adjusting device 12FSW friction point 13Handling device 14Industrial robot, articulated-arm robot 15Control system 16Control module 17Detection device 18Thermoelectric measuring device 19Electrical measuring circuit 20Electrical measuring element 21Electrical line 22Electrical line 23FSW weld seam

Claims

1. Welding device for the friction stir welding, FSW, of workpieces (2, 3) with different friction melting temperatures, the FSW device (1) comprising an FSW tool (5), which has a driven rotary FSW element (6), and a detection device (17) which is designed to detect a frictional contact between the FSW element (6) and the higher-melting workpiece (3) at the friction weld point (12) during the FSW process, - wherein the detection device (17) comprises a thermoelectric measuring device (18) that detects a frictional contact between the FSW element (6) and the higher-melting workpiece (3) by recording a change in the frictional temperature on the workpieces (2, 3), - wherein the welding device (1) is designed to plasticize the two workpieces (2, 3) at the FSW friction point (12) and also, by way of the FSW element (6), come into sufficient frictional contact with the higher-melting workpiece (3) and plasticize the higher-melting workpiece at the FSW friction point (12), characterized in that the FSW tool comprises the rotationally driven, pin-like FSW element (6), a tool shoulder (7) which surrounds the protruding FSW element (6) and is non-rotatably arranged on the FSW tool (5), and an adjustment device (11) for the axially protruding length of the FSW element (6).

2. Welding device according to Claim 1, characterized in that the FSW device (1) comprises an automatic handling device (13) having a controller (14), which during the welding process holds and guides the FSW tool (5) and generates a relative movement between the workpieces (2, 3) to be welded and the FSW tool (5) along a predefined welding path (4) with frictional contact between the FSW element (6) and the differently frictionally melting workpieces (2, 3).

3. Welding device according to Claim 2, characterized in that the thermoelectric measuring device (18) is connected to the controller (15) of the automatic handling device (13).

4. Welding device according to according to Claim 1, 2 or 3, characterized in that the thermoelectric measuring device (18) is in the form of a Seebeck measuring device and has an electrical measuring circuit (19) with an electric measuring element (20).

5. Welding device according to Claim 4, characterized in that the electrical measuring circuit (19) comprises electrically and thermally conductive lines (21, 22) each connected at one line end to the electric measuring element (20) and each being connected or connectable at the other line end to regions on the welding tool (5) and, if appropriate, on a workpiece (2, 3) that are temperature-controlled differently during the welding process.

6. Welding device according to one of Claims 2 to 5, characterized in that the controller (15) has a monitoring module (16) which is connected to the detection device (17) and, during the welding process and if it is thermoelectrically detected that the frictional contact between the FSW element (6) and the higher-melting workpiece (3) does not exist or has been lost, issues a warning and / or triggers and, if appropriate, regulates a readjusting relative movement of the handling device (13) for establishing the friction welding contact.

7. Welding device according to one of Claims 2 to 6, characterized in that the handling device (13) is in the form of a multiaxially movably driven and programmable industrial robot (14), which guides and moves the FSW tool (5) and the accompanying detection device (17) along the welding path (4) relative to the workpieces (2, 3) to be welded.

8. Method for the friction stir welding of workpieces (2, 3) with different friction melting temperatures by means of an FSW device (1), the FSW device (1) comprising an FSW tool (5), which has a driven rotary FSW element (6), and a detection device (17) which detects a frictional contact between the FSW element (6) and the higher-melting workpiece (3) at the friction weld point (12) during the welding process, wherein the detection device (17) comprises a thermoelectric measuring device (18) that detects a frictional contact between the FSW element (6) and the higher-melting workpiece (3) by measuring a change in the frictional temperature on the workpieces (2, 3), wherein the two workpieces (2, 3) are plasticized at the FSW friction point (12) and in that, by way of the FSW element (6), the higher-melting workpiece (3) is also sufficiently frictionally contacted and plasticized at the FSW friction point (12), characterized in that the FSW tool (5) comprises the rotationally driven, pin-like FSW element (6), a tool shoulder (7) which surrounds the protruding FSW element (6) and is non-rotatably arranged on the FSW tool (5), and an adjustment device (11) for the axially protruding length of the FSW element (6).

9. Welding method according to Claim 8, characterized in that the FSW device (1) comprises an automatic handling device (13) having a controller (14), which during the welding process holds and guides the FSW tool (5) and generates a relative movement between the workpieces (2, 3) to be welded and the FSW tool (5) along a predefined welding path (4) with frictional contact between the FSW element (6) and the differently frictionally melting workpieces (2, 3).

10. Welding method according to Claim 8 or 9, characterized in that the thermoelectric measuring device (18) measures the frictional temperature, in particular a change in the frictional temperature, by means of the Seebeck effect during the welding process.

11. Welding method according to Claim 8, 9 or 10, characterized in that, during the welding process, the thermoelectric measuring device (18) thermoelectrically detects the presence or absence of the frictional contact between the FSW element (6) and the higher-melting workpiece (3) and notifies a monitoring module (16) in the controller (14) of the automatic handling device (13) .

12. Welding method according to Claim 11, characterized in that, when a lap weld is being produced between the workpieces (2, 3), the FSW device (1) measures a wear on the FSW element (6) by thermoelectrically detecting an absence of frictional contact with the higher-melting workpiece (3) and issues a warning or readjusts the FSW element (6) to establish the friction welding contact.

13. Welding method according to Claim 11, characterized in that, when a butt joint is being welded between the workpieces (2, 3), the FSW device (1), in particular the handling device (13), measures a deviation of the FSW element (6) from the predefined welding path (4) by thermoelectrically detecting an absence of friction welding contact on the higher-melting workpiece (3) and regulates a readjustment of the FSW element (6) to the predefined welding path (4).