Method for welding at least two components and laser welding device

Abstract

The invention relates to a method for welding at least two components, said welding being carried out along a welding path extending over a component surface of at least one of the components, in which method the welding is carried out, at least three laser beams, in particular five to thirty laser beams, are directed consecutively consecutively onto the welding line at the same time and are moved at the same feed speed across the component surface in a welding direction extending along the welding line, whereby the welding line is passed by all laser beams one after the other at least in a length region, during the movement of the laser beams in the welding direction, laser power is continuously introduced into at least one of the components by means of each of the laser beams. The invention further relates to laser welding equipment.

Description

Technical Field

[0001] The present application relates to a method for welding at least two components, wherein the welding is performed along a welding path extending on a component surface of at least one of the components, and also to a laser welding device for welding two components. Background Art

[0002] When welding components using a laser beam, so-called humping can occur. Humping refers to the upward movement of a molten bead as the melt solidifies. This rise in melt velocity occurs particularly at high welding speeds and is due to periodic contractions and accumulations of the melt at the trailing edge. The more dynamic the molten pool produced during melting, the greater the risk of humping. The risk of humping is particularly high in continuous welding methods with high welding speeds. Summary of the Invention

[0003] The object of the present application is to enable welding of at least two components at high welding speeds with a particularly low risk of humping.

[0004] According to the present application, this object is achieved by the subject matter of the independent claims. Other possible embodiments of the present application are given in the dependent claims, the description, and the drawings. The features, advantages, and possible embodiments described within the scope of the description for one of the subject matter of an independent claim should at least be considered by analogy as the features, advantages, and possible embodiments of the corresponding subject matter of the other independent claims, as well as any possible combination of the subject matter of the independent claims (if necessary in combination with one or more dependent claims).

[0005] The present application relates to a method for welding at least two components, wherein the welding is performed along a weld path extending across the component surface of at least one of the components. Welding is a group of joining methods used to permanently join two or more components. Laser welding is primarily used for welding components that require high welding speeds, a narrow and thin weld seam shape, and minimal thermal deformation. Laser welding is generally performed without the addition of additional material. In laser welding, laser radiation is focused by at least one optical device. In this method, at least three laser beams, in particular five to thirty laser beams, are directed simultaneously, one after the other, onto the weld path. This means that at least three laser beams simultaneously impinge on the weld path and, thus, on at least one component surface of the at least one component. The laser beams impinge on the weld path at different points along the weld path. Furthermore, in this method, the laser beams are moved across the component surfaces at the same feed rate in the welding direction extending along the weld path. Consequently, the weld path is traversed by all laser beams one after the other, at least over a length region. The arrangement is such that, during the movement of the laser beams in the welding direction, laser power is continuously introduced into at least one of the components by each of the laser beams. This ensures that, during the movement of the laser beams in the welding direction, laser power is continuously introduced into the at least one component by all of the laser beams. In particular, the arrangement is such that the laser beams move at the same feed rate, in particular in the same welding direction, thereby ensuring that the relative positions of the points of intersection of the laser beams along the welding path remain unchanged during the welding of the components. The laser welding device providing the laser beams can be operated in continuous operation. This means that the laser beams are generated uninterruptedly, i.e., continuously, and directed onto the welding path. This continuous operation is also referred to as continuous wave operation (CW operation). Since the at least three laser beams are directed onto the welding path one after the other in the welding direction, the melt generated by the welding process solidifies particularly slowly at the trailing edge of the processing zone (due to the elongated molten pool). This effectively prevents the aforementioned hump phenomenon even at high welding speeds.

[0006] In a possible embodiment of the present application, the laser beams are arranged one after the other in a (straight) line. This allows for particularly fast welding of straight, and therefore linear, sections of the welding path. The linear arrangement of the laser beams allows for particularly reliable lengthening of the molten pool, particularly from the first laser beam in the line to the last laser beam in the line in the welding direction. Consequently, the melt solidifies particularly slowly at the trailing edge, making it possible to particularly effectively avoid humping at high welding speeds.

[0007] In another possible embodiment of the present application, the corresponding parameters of at least one of the laser beams are set so as to produce vaporization capillaries. Such vaporization capillaries can also be referred to as keyholes. It is possible to set the parameters of the laser beams so that one of the preceding laser beams along the welding path in the welding direction does not produce vaporization capillaries (e.g., due to heat conduction welding), while at least one of the following laser beams along the welding path in the welding direction produces vaporization capillaries, thereby achieving deep penetration welding. This makes it possible to particularly effectively avoid the hump phenomenon.

[0008] In this context, it can be provided that corresponding parameters are set for all laser beams so that each laser beam generates a vaporization capillary. This means that, for example, based on the laser power selected for each of the laser beams and / or based on the selected distances between the individual images of the laser beams incident on the welding path, each laser beam generates a vaporization capillary in at least one of the components. The more laser beams that each generate a vaporization capillary, the more the hump phenomenon can be avoided.

[0009] In another possible embodiment of the present application, the distance between the center points of the images of two laser beams arranged one behind the other along the welding path is greater than at least 20% of the width of the weld seam produced by the welding process, extending perpendicularly to the welding direction and on the component surface. In particular, the distance between the center points of the images of two laser beams arranged one behind the other along the welding path is greater than at least 25% of the width of the weld seam produced by the welding process. The greater the distance between the center points of the images of two laser beams arranged directly one behind the other along the welding path, the more reliably a separate vaporization capillary is generated for each of the laser beams. The distance between laser beams directly adjacent to one another in the welding direction or along the welding path is at most sufficient to ensure that a coherent molten pool is generated by all laser beams simultaneously directed onto the welding path. This makes it possible to particularly reliably avoid the hump phenomenon at very high welding speeds.

[0010] In another possible embodiment of the present application, the distance between the center points of two images of laser beams arranged one behind the other along the welding path is greater than the diameter of the corresponding images. This stabilizes the at least one generated vaporization capillary and, in turn, the energy input of each laser beam into the at least one component. Furthermore, this allows for a precise weld penetration depth to be achieved over the entire weld path, thereby achieving a particularly high degree of gas-tightness in the weld seam produced during welding. Furthermore, if the distance between the center points of directly adjacent laser beam images along the welding path is greater than the diameter of the corresponding images, it is possible to generate a particularly long weld pool using these laser beams, thereby enabling particularly high welding speeds when welding the components due to the reduced risk of humping.

[0011] In another possible embodiment of the present application, the laser power difference between the laser beams is provided to be at most 80%, in particular at most 20%. In particular, the laser beams directed simultaneously onto the welding path have the same laser power. This allows the melt to solidify particularly slowly at the trailing edge of the processing zone due to the elongated molten pool, thereby particularly effectively preventing the hump phenomenon and allowing the components to be welded together at particularly high welding speeds.

[0012] In another possible embodiment of the present application, at least one of the laser beams comprises a core beam and a cladding beam annularly surrounding the core beam, wherein in particular, the laser power of the core beam comprises at least 80% of the total laser power of the respective laser beam. This means that at most 20% of the total laser power of the respective laser beam is provided by the cladding beam of the respective laser beam. It can be provided that all laser beams each comprise a core beam and a cladding beam annularly surrounding the core beam. In particular, the image of the cladding beam on the component surface of the at least one component circumferentially surrounds, in particular annularly surrounds, the image of the core beam on the at least one component surface.

[0013] In this connection, it can be provided in particular that the laser power of the core beam and / or the laser power of the cladding beam is periodically varied, wherein laser power is continuously introduced into at least one of the components via these laser beams during welding. In other words, the laser power of the core beam and / or the laser power of the cladding beam can be pulsed or modulated. If it is provided that both the laser power of the core beam and the laser power of the cladding beam are periodically varied, this variation of the respective laser power is adapted so that at each moment, laser power is introduced into at least one of the components via either at least the core beam or at least the cladding beam. For example, the core beam and the cladding beam can be pulsed with peak values ​​that are offset in time and thus pulsed in a temporally offset manner. By periodically varying the laser power of the core beam and / or the laser power of the cladding beam, the weld pool can be particularly effectively stabilized.

[0014] The present application also relates to a laser welding apparatus for welding at least two components, the welding being performed along a welding path extending along a component surface of at least one of the components. The laser welding apparatus is configured to simultaneously direct at least three laser beams, in particular five to thirty laser beams, one after the other, onto the welding path and to move them across the component surface at the same feed rate in a welding direction extending along the welding path. As a result, the welding path is traversed successively by all laser beams, at least over a length region. During the movement of the laser beams in the welding direction, laser power is continuously introduced into at least one of the components by each of the laser beams. In particular, the laser welding apparatus is configured to arrange the laser beams so that they generate a common, coherent molten pool. In particular, the laser welding apparatus is configured to perform the method already described in conjunction with the method for welding at least two components according to the present application.

[0015] Other features of the present application can be derived from the following description of the drawings and from the drawings. The features and feature combinations mentioned above in the specification and the features and feature combinations described below and / or shown individually in the drawings can be used not only in the respectively indicated combination but also in other combinations or alone without departing from the scope of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The figure shows:

[0017] Figure 1 is a schematic top view of a component surface of a component, onto which a plurality of laser beams are directed. DETAILED DESCRIPTION

[0018] Attached Figure 1In particular, the two components 12 to be welded to each other are arranged along the surface 10 of the component 12. Figure 1 Components 12 are stacked on top of each other in a stacking direction extending in the plane of the drawing. Components 12 are, in particular, corresponding battery components, in particular battery components for a vehicle battery of a motor vehicle. For example, at least one of the battery components may be a cell contact system. Components 12 stacked on top of each other in the stacking direction and to be welded together may be made of the same material or of different materials. Alternatively, at least one of components 12 may be a component of a bipolar plate or a bipolar plate, in particular for a fuel cell or electrolyzer.

[0019] In particular, two components 12 can be welded to one another using a laser welding system. The laser welding system is configured to provide a plurality of laser beams 14. To weld the components 12, at least three laser beams 14 (in the present case, more than three laser beams 14) are simultaneously directed onto a welding path 16 in succession. It is provided that laser power is simultaneously introduced into at least one of the components 12 by all of the laser beams 14 simultaneously directed onto the welding path 16. It is also provided that, during the welding of the components 12, laser power is continuously introduced into at least one of the components 12 by means of at least one of these laser beams 14, in particular by means of all of the laser beams 14. In particular, the laser beams 14 can be operated within the scope of continuous operation, which can also be referred to as so-called continuous wave operation.

[0020] By directing the laser beams 14 onto the welding path 16, a molten pool is generated, which forms a weld seam 18 upon solidification of the molten material. The components 12 are held together by the weld seam 18. In the present embodiment, all laser beams 14 are arranged one behind the other in a straight line along the welding path 16. To weld the components 12 together, all laser beams 14 are moved along the welding path 16 at the same feed rate in the welding direction 20. Consequently, the welding path 16 is irradiated by all laser beams 14 at least at most points along the welding path 16. The arrangement of the laser beams 14 one behind the other in the longitudinal direction of the welding path 16 results in only a single, elongated molten pool being generated by all laser beams 14. Consequently, the melt solidifies particularly slowly at the trailing edge of the processing zone. This reliably prevents the so-called hump phenomenon, even at high welding speeds.

[0021] exist Figure 1 In the example, the corresponding image 22 of each laser beam 14 caused by the laser beam 14 on the component surface 10 of the component 12 can be particularly well recognized. In this case, the distance 24 between two images 22 that are directly adjacent to each other in the welding direction 20 extends from the center point of one of the images 22 being viewed to the center point of the other image 22 being viewed. Figure 1, which can be particularly well identified. It is currently provided that the distance 24 between the center points of directly adjacent images 22 in the welding direction 20 is greater than the diameter 26 of the corresponding image 22. It is currently provided that all images 22 have at least substantially the same diameter 26. Furthermore, it is currently provided that all images 22 have at least substantially the same distance 24 from the corresponding lower image 22. It is also currently provided that the distance 24 between the center points of directly adjacent images 22 in the welding direction 20 is greater than at least 20%, in particular at least 25%, of the width 28 of the weld seam 18 produced by welding, the width 28 extending perpendicularly to the welding direction 20 on the component surface 10. It is provided that the parameters of the laser beams 14 are adjusted so that at least two of the laser beams 14 each produce a vaporization capillary. In particular, it is provided that the parameters of the laser beams 14 are adjusted so that all laser beams 14 each produce a vaporization capillary. In the present case, it is also provided that the laser power differs by at most 80%, in particular by at most 20%, between the individual laser beams 14. In particular, it is provided that all laser beams 14 have the same power as one another.

[0022] In the present case, it is provided that the beam diameters of all laser beams 14 are identical in a common plane perpendicular to the beam direction. This means that all images 22 have at least substantially the same diameter 26. This allows for particularly thin weld seams 18 to be produced, and requires a particularly low heat input for the welded component 12. Alternatively, it is possible for the largest individual beam diameter of the laser beams 14 to be at most ten times greater than the smallest individual beam diameter of the laser beams 14.

[0023] It is possible that at least one of the laser beams 14, and in particular all of the laser beams 14, each comprises a core beam and a cladding beam annularly surrounding the core beam. To generate each laser beam 14 having a core beam and a cladding beam, two sub-laser beams with the same optical axis and different beam diameters can be superimposed on each laser beam 14. By providing each laser beam 14 with a core beam and a cladding beam, the generated evaporation capillaries can be particularly well stabilized. In particular, it is provided that the power share in the core beam accounts for at least 80% of the total power of the corresponding laser beam 14. These laser beams 14, comprising the corresponding core beam and cladding beam, can be provided by means of corresponding optical cables using two-in-one technology (i.e., having a ring fiber and a core fiber), wherein the two-in-one main beam can be split into a plurality of individual beams.

[0024] In particular, a continuous wave laser beam source, optionally with modulated or pulsed laser power, is provided as a laser welding device, wherein the modulation amplitude is at most 10% of the maximum power. The method is particularly useful for bipolar plates for fuel cells or electrolytic cells, as it allows for producing tight welds with particularly low heat input and achieving particularly high productivity. Alternatively, the method can also be used to weld two battery components, particularly cell contacts made of at least two different materials, as it allows for welds with particularly low intermetallic phases and produces particularly strong welds with particularly low heat input. Furthermore, the method can alternatively be used to weld foil stacks comprising at least one aluminum foil. The method enables the production of thin welds 18 with short interaction times, thereby significantly reducing the risk of crack formation. Consequently, the method enables welding at particularly high welding speeds with a particularly low heat input. Furthermore, the precise welding process achieves particularly good gas-tightness. In hybrid connections, the formation of intermetallic phases can be particularly effectively limited. Furthermore, the method also reduces the formation of cracks, in particular in the case of foils comprising aluminum that overlap one another.

[0025] Therefore, the method can be used for laser welding pure iron-based, aluminum-based or copper-based thin metal foils, or for hybrid connections. In particular, it is provided that the sheet thickness of at least one joining part and therefore at least one component in the component 12 is in the range of 7 microns to 1000 microns, especially in the range of 7 microns to 20 microns for electrode foils, and especially in the range of 75 microns to 500 microns for conductors. As the laser beam source for generating the laser beam 14, a single-mode laser with a power of 100 watts to 3000 watts per beam source or a multi-mode laser with a power of 1000 watts to 24,000 watts per beam source can be used. In particular, the total power of all laser beams 14 on the component 12 is 1000 watts to 6000 watts. The laser power of each laser beam 14 is in the range of 10 watts to 8000 watts, especially in the range of 50 watts to 700 watts. The laser welding apparatus may include at least one optical element for splitting the at least one laser input beam into a plurality of individual beams, for example, a multifocal lens or an optical wedge, in particular a diffractive or refractive optical element. The laser beams 14 may be provided by one laser beam source and one optical device, or by at least two laser beam sources and one optical device, or by one laser beam source and at least two optical devices, or by at least two laser beam sources and at least two optical devices. The beam parameter product of the laser beam 14 may be in the range of 0.38 mm*mrad to 16 mm*mrad, in the range of 0.4 mm*mrad to 0.6 mm*mrad for a single-mode laser, or in the range of 2 mm*mrad to 4 mm*mrad for a multimode laser. The diameter 26 of each image 22 may be in the range of 10 to 300 micrometers, in the range of 30 to 50 micrometers for a single-mode laser, and in the range of 50 to 170 micrometers for a multimode laser. In particular, all images 22 of the laser beam 14 have a diameter 26 in the range from 0.1 to ten times the diameter of the frontmost laser beam 14 with respect to the welding direction 20 , in particular the same diameter 26 as the frontmost laser beam 14 .

[0026] Currently, the laser beams 14 are arranged in a linear fashion, in particular without lateral offset. If at least one of the laser beams 14 is arranged with a lateral offset, the lateral offset is less than or equal to the maximum beam diameter of all images 22 of the laser beam 14. The laser welding system may use an infrared laser with a wavelength in the range of 800 to 1200 nanometers, in particular a wavelength of 1030 or 1070 nanometers. Alternatively or additionally, the laser welding system may include a VIS (visible light) laser with a wavelength in the range of 400 to 450 nanometers for blue light and / or a wavelength in the range of 515 nanometers for green light.

[0027] Currently, the feed speed is in the range of 100 mm / s to 10,000 mm / s, in particular in the range of 300 mm / s to 4,000 mm / s. The laser welding system can, in particular, have PFO33-2 scanner optics as scanner optics, which have an imaging ratio of 1:1 to 5:1, in particular 1.5:1 to 2:1. Alternatively or additionally, the laser welding system can have BEO flying optics with an imaging ratio of 1:1 to 5:1, in particular 1.5:1 to 2:1.

[0028] In general, this application demonstrates how to achieve multi-point "inline" laser welding.

[0029] Reference Signs List

[0030] 10 Component surface

[0031] 12 components

[0032] 14 laser beams

[0033] 16 welding routes

[0034] 18 welds

[0035] 20 welding direction

[0036] 22 Imaging

[0037] 24 distance

[0038] 26 diameter

[0039] 28 width

Claims

1. A method for welding at least two components (12), wherein the welding is performed along a welding path (16) extending on a component surface (10) of at least one of the components (12), wherein at least three laser beams (14), in particular five to thirty laser beams (14), are simultaneously directed one after the other onto the welding path (16) and are moved at the same feed speed in a welding direction (20) extending along the welding path (16) over the component surface (10), so that the welding path (16) is traveled successively by all laser beams (14) at least in a length region, wherein: During the movement of the laser beams (14) in the welding direction (20), laser power is continuously introduced into at least one of the components (12) by means of each of the laser beams (14).

2. The method according to claim 1, It is characterized by: The laser beams (14) are arranged one after another in a straight line.

3. The method according to claim 1 or 2, It is characterized by: For at least one of the laser beams (14), corresponding parameters are adjusted so that vaporization capillaries are generated.

4. The method according to claim 3, It is characterized by: For all laser beams (14), the corresponding parameters are adjusted so that each laser beam (14) generates an evaporation capillary.

5. The method according to any one of the preceding claims, It is characterized by: The distance between the center points of the images (22) of two laser beams (14) arranged one behind the other along the welding path (16) is greater than at least 20% of the width (28) of the weld seam (18) produced by the welding, which extends perpendicularly to the welding direction (20) and on the component surface (10).

6. The method according to any one of the preceding claims, It is characterized by: The distance between the center points of the images (22) of two laser beams (14) arranged one behind the other along the welding path (16) is greater than the diameter of the corresponding images (22).

7. The method according to any one of the preceding claims, It is characterized by: The laser power difference between the laser beams (14) is at most 80%, in particular at most 20%.

8. The method according to any one of the preceding claims, It is characterized by: At least one of the laser beams (14) comprises a core beam and a cladding beam annularly surrounding the core beam, wherein it is particularly provided that the core beam has at least 80% of the total laser power of the laser beam (14).

9. The method according to claim 8, It is characterized by: The laser power of the core beam and / or the laser power of the cladding beam is varied periodically, wherein during welding, the laser power is continuously introduced into at least one of the components (12) by means of the laser beam (14).

10. A laser welding device for welding at least two components (12), the welding being performed along a welding path (16) extending on a component surface (10) of at least one of the components (12), the laser welding device being adapted to direct at least three laser beams (14), in particular five to thirty laser beams (14), simultaneously and one after the other onto the welding path (16) and to move them at the same feed speed in a welding direction (20) extending along the welding path (16) over the component surface (10), so that the welding path (16) is traveled successively by all laser beams (14) at least in a length region, wherein: During the movement of the laser beams (14) in the welding direction (20), laser power is continuously introduced into at least one of the components (12) by means of each of the laser beams (14).

Images