Method and device for welding metal components

Abstract

The invention relates to a method (10) for welding at least two overlapping metal components (12, 14), in particular electrical conductors, by means of a processing laser beam (20) which forms a keyhole in order to form a weld seam (26) in a feed direction (24) of the processing laser beam (20), and by means of a measuring laser beam (40) for determining the welding quality, wherein the measuring laser beam (40) is directed into a keyhole (32) formed by the processing laser beam (20) and is moved within the keyhole (32), transverse to the feed direction (24), in order to determine a keyhole depth (36) and a keyhole width (34); wherein the processing laser beam (20) has at least two partial beams (28, 30), which are formed next to one another transverse to the feed direction (24), for producing the keyhole (32). The invention also relates to a device for carrying out the method (10).

Description

[0001] 2024P00005WC) September 26, 2025

[0002] Method and apparatus for welding metallic components

[0003] Background of the invention

[0004] The invention relates to a method for welding at least two overlapping metallic components by forming a vapor capillary using a processing laser beam to form a weld seam along a feed direction of the processing laser beam and a measuring laser beam to determine the weld quality.

[0005] Such methods and devices are typically used to ensure the weld quality of a weld seam during its creation. This eliminates the need for subsequent, usually destructive, testing procedures, thereby saving additional process steps and a significant amount of material waste.

[0006] To ensure sufficient weld quality, weld penetration depth and weld width are typically determined. The determination is carried out by measuring the vapor capillary generated by the processing laser beam during weld formation. The resulting bonding area between the components can then be derived from these vapor capillary measurements, thus allowing for a preliminary determination of the fatigue strength of the resulting component.

[0007] Such processes are particularly important in the manufacture of electrical conductors, for example, electrical busbars, since it is often required that the components to be joined must not be welded through. A non-destructive visual inspection of the resulting weld is therefore not possible. (2024P00005WC) September 26, 2025

[0008] DE 10 2022 101 093 Al describes a method for determining at least one geometric result quantity and / or at least one quality characteristic of a weld seam on a workpiece, wherein the weld seam is scanned with a measuring beam during its creation.

[0009] The established methods require the formation and maintenance of the vapor capillary to determine weld quality. However, especially when welding electrical conductors, materials are used that promote vapor capillary instability. If the vapor capillary collapses temporarily or permanently, the weld quality cannot be determined, leading to uncertainties regarding fatigue strength. This, in turn, necessitates the use of destructive testing methods, increasing both the complexity and cost of the process.

[0010] Furthermore, the known methods require highly precise alignment of the measuring laser beam with the vapor capillary, as inaccuracies in determining the vapor capillary depth and width result from the similar diameters of the measuring and processing laser beams. This leads to further uncertainties in determining weld quality. Conversely, increasing the diameter of the processing laser beam increases the instability of the vapor capillary.

[0011] It is an object of the invention to provide a method and a device with which the weld quality can be ensured cost-effectively, continuously and reliably while minimizing rejects.

[0012] This problem is solved according to the invention by a method having the features of claim 1. The problem is further solved by a device having the features of claim 11. The dependent claims describe preferred embodiments of the invention. (2024P00005WC) September 26, 2025

[0013] According to the invention, a method for welding at least two metallic components is provided. Preferably, the metallic components are designed as electrical conductors, which makes the advantages of the method particularly favorable for determining the weld quality.

[0014] The process is designed for welding metallic components in a lap joint. In other words, the metallic components overlap in the area intended for welding. The components are typically joined by creating a vapor capillary using a laser beam. This typically involves locally melting a first metallic component and penetrating into the second. The weld is usually formed to a predetermined penetration depth in the second metallic component, but the second component is typically not fully welded through. During the melting process, the laser beam creates a vapor capillary, which is subsequently filled with molten metal and solidifies to form a weld that bondes the metallic components together.To form the weld seam, the processing laser beam is moved along a predetermined welding path in the feed direction over the metallic components.

[0015] The process also includes the use of a measuring laser beam to determine weld quality. In other words, the measuring laser beam can be used to indirectly determine weld quality. Typically, the measuring laser beam is directed into the vapor capillary formed by the processing laser beam and moved within the vapor capillary perpendicular to the feed direction, thereby determining the penetration depth and vapor capillary width. In other words, the geometric shape of the vapor capillary can be determined along a predetermined measuring path. The weld quality can then be determined from the measured vapor capillary depth and width. (2024P00005WC) September 26, 2025

[0016] Preferably, the measuring path runs within a plane orthogonal or perpendicular to the feed direction. Furthermore, the movement of the measuring laser beam preferably involves a swiveling or tilting motion around the feed direction. This allows the geometric shape of the vapor capillary to be determined with particular accuracy.

[0017] According to the invention, the processing laser beam comprises at least two partial beams arranged side by side transversely to the feed direction. An arrangement of the partial beams side by side preferably includes an overlapping arrangement of the partial beams. The partial beams together form the vapor capillary. This allows the resulting laser beam diameter of the processing laser beam to be increased transversely to the feed direction, or in the direction of travel of the measuring path. The inventors have recognized that increasing the laser beam diameter by means of at least two partial beams ensures the stability of the vapor capillary and simultaneously enables reliable alignment of the measuring laser beam within the vapor capillary. This allows for particularly reliable determination of the vapor capillary depth and width, and thus the weld quality.The proposed method thus enables the reliable and continuous determination of the weld quality along the entire formed weld seam during the creation of the weld seam.

[0018] In a preferred embodiment of the method, at least one of the metallic components comprises aluminum, copper, and / or iron. Preferably, the at least one metallic component has a weight fraction of at least 75% by weight of aluminum, copper, or iron. Particularly preferably, the at least one metallic component consists of aluminum, copper, or iron. The method has proven to be particularly advantageous in combination with the aforementioned materials. (2024P00005WC) September 26, 2025

[0019] A preferred embodiment of the method is one in which the measuring laser beam is designed as an optical coherence tomography (OCT) laser beam. This allows the weld penetration depth and vapor capillary width to be determined with particular accuracy, further improving the determination of weld quality.

[0020] A further preferred embodiment of the method involves determining the vapor capillary width in a contact plane between the metallic components. By determining the vapor capillary width in the contact plane of the metallic components, an effective cross-sectional area of ​​the resulting weld can be determined, which is particularly informative with regard to fatigue strength.

[0021] In a particularly preferred embodiment of the method, the measuring laser beam is oscillated around the feed direction transversely to the weld path or weld seam at a frequency of at least 100 Hz, preferably at least 500 Hz, and particularly preferably at least 1000 Hz. This allows the weld quality to be determined at particularly short intervals, making the method even more reliable. Furthermore, the method can be used at higher feed rates while maintaining high process reliability, thereby further reducing production times and consequently production costs.

[0022] A preferred embodiment of the method involves moving the measuring laser beam within a projection of the processing laser beam diameter onto the metallic components. This effectively limits the measurement to the vapor capillary, enabling a higher measurement frequency and thus greater process reliability.

[0023] A further preferred embodiment of the method is one in which the processing laser beam has at least three, preferably at least four, partial beams that form the vapor capillary. By increasing the number of partial beams (2024P00005WC) September 26, 2025, the laser beam diameter can be further increased. In addition, the stability of the vapor capillary can be increased, thus enabling an even more reliable determination of the weld quality.

[0024] In a preferred embodiment of the method, at least one process parameter is changed depending on the desired weld quality. Preferably, the process parameter is changed during the creation of the weld, thereby maintaining high weld quality and minimizing material scrap.

[0025] A preferred further development of the method involves changing the laser power of the processing laser beam to adjust the vapor capillary depth. In other words, the laser power can be changed if measuring the vapor capillary depth reveals that it deviates from a target value. For example, the laser power can be increased if the vapor capillary depth is less than the vapor capillary depth intended for generating the weld penetration depth.

[0026] A further preferred embodiment of the method involves changing the intensity ratio between the laser beam intensity of a core region (at least one partial beam) and the laser beam intensity of a ring region (at least one partial beam) to adjust the vapor capillary width. In other words, the intensity ratio can be changed if measuring the vapor capillary width reveals that it deviates from a target value. For example, the intensity ratio can be reduced if the vapor capillary width in the contact plane is smaller than the vapor capillary width intended to create a bonding cross-section. This allows for a particularly rapid response to deviations in weld quality.

[0027] The underlying problem is further solved by a device for welding together at least two metallic components. (2024P00005WC) 26 September 2025

[0028] The device is set up and designed to carry out the welding process of metallic components described above and below.

[0029] The device according to the invention has at least the following features: a) a scanner optic with a first mirror that can be pivoted in a controlled manner for moving the measuring laser beam; b) a multi-fiber for emitting an output laser beam; c) a splitting device for dividing the output laser beam into several partial beams, which can be directed onto the metallic components in such a way that a single common vapor capillary is formed during welding.

[0030] The scanner optics enable the controlled, rapid, and cost-effective movement or deflection of the measuring laser beam. The scanner optics are particularly advantageous when the weld path has a curved or angular section. In curved or angular sections, the measuring beam must dynamically follow the change in direction of the processing laser beam to ensure accurate measurement of the vapor capillary.

[0031] The generation of the output laser beam is provided by a multi-fiber, preferably a 2-in-1 fiber, which divides the laser power in the output laser beam and in the partial beams into a core component with higher power density and a ring component with lower power density (referred to as "2-in-1 technique" in the case of the 2-in-1 fiber). The multi-fiber comprises a central core fiber and one or more ring fibers that surround the core fiber in a ring-like fashion. The core component results from the core fiber, and the ring component results from the one or more ring fibers (in the case of multiple ring fibers, the ring component comprises several individual ring components, which together then form the ring component). 2024P00005WO September 26, 2025

[0032] The partial beams are typically generated by beam shaping in the splitting device. This is achieved by guiding the initial laser beam between a collimating optic and a focusing optic over one or more optical elements that protrude into at least part of the beam cross-section of the initial laser beam. Typical optical elements for this purpose are wedge plates; however, other diffractive and refractive optical elements can also be used.

[0033] Preferably, the multi-fiber, in particular the 2-in-1 fiber, has a core diameter of 50 micrometers, particularly of 100 micrometers. Further preferably, the multi-fiber, in particular the 2-in-1 fiber, has a ring diameter of 200 micrometers, particularly of 400 micrometers.

[0034] Preferably, the device includes a scanner optic for guiding the processing laser beam onto the metallic components. This makes the device particularly suitable for forming curved and / or angular weld seams.

[0035] The device preferably further comprises a laser beam source for generating the processing laser beam. Particularly preferably, the laser beam source is designed as a NIR laser and has a total power output of at least 4 kilowatts, and in particular at least 8 kilowatts.

[0036] The power proportions of the core and ring components in a partial beam can be adjusted by the proportion of the output laser beam directed into the core fiber and the one or more ring fibers of the multi-fiber. The average power density in the core component is usually at least twice, and often at least four times, higher than in the ring component. The (outer) boundaries of the core and ring components can be defined as the location where the local power density is less than half the average power density in the core or ring component, or, in the case of multiple ring fibers, at the outermost individual ring component. With approximately uniform power density within the core and ring components, or, in the case of multiple ring fibers, at the outermost individual ring component, this corresponds to an FWHM criterion. The diameters and their ratios of the core fiber and the (outermost) ring fiber at the depicted fiber end determine the diameters and / or...The ratios of the core and ring components in each partial beam are determined by the imaging ratio and thus the absolute size of the laser spots. This can be selected or adjusted via the collimating and focusing optics.

[0037] A preferred embodiment of the device is one in which the device is designed to generate a diameter ratio between the diameter of the core portion and the diameter of the ring portion of the metallic components of at least 1:2 and at most 1:9.

[0038] A further preferred embodiment of the device is one in which the diameter ratio is at least 1 :3, preferably 1 :4, particularly preferably 1 :6.

[0039] Further advantages of the invention will become apparent from the description and the drawing. Likewise, the features mentioned above and those described in more detail below can each be used individually or in any combination according to the invention. The embodiments shown and described are not to be understood as an exhaustive list, but rather serve as examples for illustrating the invention.

[0040] Detailed description of the invention and drawing

[0041] Fig. 1 schematically shows a method for welding at least two overlapping metallic components.

[0042] Fig. 2 schematically shows two metallic components during the creation of a weld seam by a processing laser beam.

[0043] Fig. 3 schematically shows the metallic components from Fig. 2 during the measurement of the vapor capillary width and vapor capillary depth with a measuring laser beam. (2024P00005WC) September 26, 2025

[0044] Fig. 1 schematically shows a method 10, which is explained below with reference to the other figures of the drawing.

[0045] Method 10 is suitable and designed for welding together at least two overlapping metallic components 12, 14 (see Figs. 2, 3). The metallic components 12, 14 can, in particular, be designed as electrical conductors. For example, the components 12, 14 can be used to manufacture an electrical busbar (not shown). As shown, method 10 typically provides for the metallic components 12, 14 to be prepared in a process step 16.

[0046] Welding typically takes place subsequently in a process step 18. The welding can be performed using deep penetration welding. Typically, welding is carried out using a processing laser beam 20 (see Figs. 2, 3), wherein the component 12 facing the processing laser beam 20 is typically fully welded, while the component 14 facing away from the processing laser beam 20 is not fully welded. During welding, the processing laser beam 20 is moved along a predetermined weld path 22 (see Fig. 2) in the feed direction 24 (see Figs. 2, 3), thereby forming a weld seam 26 (see Fig. 2).

[0047] According to the invention, the processing laser beam 20 has at least two partial beams 28, 30 (see Fig. 2) arranged side by side transversely to the feed direction 24, which form a common vapor capillary 32 (see Figs. 2, 3). As shown, the partial beams 28, 30 overlap. By using two or more partial beams 28, 30, the vapor capillary 34 can be maintained with particular stability, thus preventing collapse. This facilitates the particularly reliable and continuous measurement of a vapor capillary width 34 (see Fig. 3) and a vapor capillary depth 36 (see Fig. 3), and thus a particularly safe [2024P00005WC] September 26, 2025

[0048] Determination of weld quality according to process step 38 of process 10.

[0049] The measurement is performed during welding by a measuring laser beam 40 (see Figs. 2, 3) which is directed into the vapor capillary 34 formed by the processing laser beam 20, or by the partial laser beams 28, 30. During welding, the measuring laser beam 40 is moved within the vapor capillary 34 transversely to the feed direction 24, thereby determining the geometric dimensions of the vapor capillary 34 in a cross-section transverse to the feed direction 24.

[0050] Preferably, the measuring laser beam 40 is designed as an optical coherence tomography (OCT) measuring laser beam, which enables particularly fast and accurate scanning of the vapor capillary 34. Scanning with an OCT measuring laser beam typically generates a point cloud of individual measurement points 41 (see Fig. 3), which is evaluated in process step 38 to determine the weld quality.

[0051] Preferably, to determine the weld quality, the vapor capillary width 34 in a contact plane 42 (see Fig. 2) between the metallic components 12, 14 is determined. This allows the effective bonding area formed by the weld seam 26 between the components 12, 14 to be determined, which is particularly informative for fatigue strength.

[0052] According to a preferred embodiment, method 10 can provide in process step 44 that at least one process parameter is changed depending on the desired weld quality. This allows the weld quality of the weld seam 26 yet to be produced to be influenced during welding, thereby increasing fatigue strength and further reducing material scrap. (2024P00005WC) September 26, 2025

[0053] Fig. 2 shows schematically the welding of the metallic components 12, 14 according to process step 18 (see Fig. 1) of process 10 (see Fig. 1), wherein a weld seam 26 to be produced is already partially formed.

[0054] The metallic components 12 and 14 are shown in section and overlap each other in the contact area intended for welding. For better illustration, the metallic components 12 and 14 are shown in cross-section.

[0055] The processing laser beam 20 has, as shown, two partial beams 28, 30. Each partial beam 28, 30 has a core region 46, shown with solid lines, and a ring region 48 surrounding the core region, shown with dashed lines. The ring regions 48 of the partial beams 28, 30 form a laser beam diameter 50 of the

[0056] Processing laser beam 20 off.

[0057] The measuring laser beam 40, shown in simplified form in Fig. 2, is directed into the vapor capillary 32 to measure the vapor capillary width 34 and the welding depth 36.

[0058] Fig. 3 shows the metallic components 12, 14 from Fig. 2 in a view opposite to the feed direction 24 to better illustrate the measurement by the measuring laser beam 40.

[0059] The measuring laser beam 40 is moved transversely, and in particular perpendicularly, to the feed direction to determine the geometric extent of the vapor capillary 32. The movement can be translational and / or rotational, preferably scanning an inner contour 52 of the vapor capillary 32. Scanning is typically performed by generating a plurality of measuring points 41, which are then evaluated to derive geometric quantities. For clarity, only two measuring points 41 are provided with a reference numeral. (2024P00005WC) September 26, 2025

[0060] Preferably, the measuring laser beam 40 is held within a projection of the laser beam diameter 50 of the processing laser beam 20 (simplified here) onto the metallic components 12, 14. This allows the measuring range of the measuring laser beam 40 to be limited and the measuring frequency to be increased.

[0061] If the measurement or subsequent evaluation reveals a deviation of the vapor capillary depth 36 from a required welding depth, it may be provided that the laser power of the processing laser beam 20 is changed to adjust the vapor capillary depth 36.

[0062] If the measurement or subsequent evaluation reveals a deviation of the vapor capillary width 36 from a target value, for example due to an insufficient connection cross-section in the contact plane 42, the power output of the core area 46 of at least one partial jet 28, 30 can be increased. This allows the vapor capillary width, and thus the weld quality, to be adjusted during the welding process.

[0063] 2024P00005WC) September 26, 2025

[0064] 10 procedures;

[0065] 12 metallic components;

[0066] 14 metallic components;

[0067] 16th procedural step;

[0068] 18th procedural step;

[0069] 20 processing laser beams;

[0070] 22 Welding membrane;

[0071] 24 Feed direction;

[0072] 26 weld seam;

[0073] 28 partial beams;

[0074] 30 partial beams;

[0075] 32 vapor capillaries;

[0076] 34 Vapor capillary width;

[0077] 36 Vapor capillary depth;

[0078] 38th procedural step;

[0079] 40 measuring laser beam;

[0080] 41 measuring point;

[0081] 42 Contact level;

[0082] 44th procedural step;

[0083] 46 core area;

[0084] 48 ring area;

[0085] 50 laser beam diameter;

[0086] 52 Inner contour.

Claims

2024P00005WC) September 26, 2025 Patent claims 1. Method (10) for welding at least two overlapping metallic components (12, 14), in particular electrical conductors, by forming a vapor capillary using a processing laser beam (20) to form a weld seam (26) along a feed direction (24) of the processing laser beam (20) and a measuring laser beam (40) to determine the weld quality, wherein the measuring laser beam (40) is directed into a vapor capillary (32) formed by the processing laser beam (20) and is moved within the vapor capillary (32) transversely to the feed direction (24) in order to determine a vapor capillary depth (36) and a vapor capillary width (34); characterized in that the processing laser beam (20) has at least two partial beams (28, 30) formed side by side transversely to the feed direction (24) for generating the vapor capillary (32).

2. Method (10) according to claim 1, wherein at least one of the metallic components (12, 14) preferably comprises at least 75 wt% aluminium, copper and / or iron or consists of aluminium, copper or iron.

3. Method (10) according to claim 1 or 2, wherein the measuring laser beam (40) is designed as an OCT measuring laser beam.

4. Method (10) according to one of the preceding claims, wherein the vapor capillary width (34) is determined in a contact plane (42) between the metallic components (12, 14).

5. Method (10) according to one of the preceding claims, wherein the measuring laser beam (40) is directed transversely to the weld path (22) at a frequency of 2024P00005WC) 26 September 2025 at least 100 Hz, preferably at least 500 Hz, particularly preferably at least 1000 Hz, oscillates about the feed direction (24).

6. Method (10) according to one of the preceding claims, wherein the measuring laser beam (40) is moved within a projection of the laser beam diameter (50) of the processing laser beam (20) onto the metallic components (12, 14).

7. Method (10) according to one of the preceding claims, wherein the processing laser beam (20) has at least three, preferably at least four, partial beams (28, 30) which form the vapor capillary (32).

8. Method (10) according to one of the preceding claims, wherein at least one process parameter is changed depending on the desired weld quality.

9. Method (10) according to claim 8, wherein a laser power of the processing laser beam (20) is changed to adjust the vapor capillary depth (36).

10. Method (10) according to claim 8 or 9, wherein the intensity ratio between a laser beam intensity of a core region (46) of at least one partial beam (28, 30) and a laser beam intensity of a ring region (48) of at least one partial beam (28, 30) is changed to adjust the vapor capillary width (34).

11. Device for welding at least two metallic components using a method (10) according to any one of claims 1 to 10, wherein the device has the following features: a) a 2-in-l fiber for emitting an output laser beam; b) a scanner optic with a first mirror that can be pivoted in a controlled manner for moving the measuring laser beam (40); 2024P00005WC) 26 September 2025 c) a splitting device for dividing the output laser beam into several partial beams (28, 30) which can be directed onto the metallic components (12, 14) in such a way that a single common vapor capillary (32) is formed during welding.

12. Device according to claim 11, designed to generate a diameter ratio between a diameter of a core portion to a diameter of a ring portion on the metallic components of at least 1 :2 and at most 1 :

9.

13. Device according to claim 12, wherein the diameter ratio is at least 1 :3, preferably 1 :4, particularly preferably 1 :

6. 17

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