Method and device for laser welding at least two metal components made of different materials

Abstract

The invention relates to a method for laser welding at least two metal components (10), the components (10) being formed from different materials, and the method having the features of claim 1, and to a device for laser welding having the features of the additional independent claim.

Description

[0001] Title: Method and device for laser welding at least two metallic components made of different materials

[0002] Description

[0003] The invention relates to a method for laser welding at least two metallic components having the features of claim 1 and to a device for laser welding having the features of the independent claim.

[0004] For laser welding of at least two metallic

[0005] Single-mode lasers are usually used for components made from different materials, particularly to create a thin weld seam. The disadvantage is that at higher welding speeds, unwanted humps and / or spatter can occur. Furthermore, with a lap joint arrangement of the components to be welded, for example, the penetration depths of the laser beam can be irregular and, in extreme cases, the components can be severed. Undesirable intermetallic phases are generated, which can weaken the weld seam and increase the electrical resistance.

[0006] It is therefore an object of the present invention to provide a method and a device for laser welding at least two metallic components, wherein the components are made of different materials, wherein the above disadvantages are eliminated.

[0007] The above object is achieved by a method for laser welding at least two metallic components, wherein the components are made of different materials, with the features of claim 1. The method comprises the steps:

[0008] Providing the components. At least one of the components may be a section of battery foil, a busbar, a cover, and / or a (battery) cell connector.

[0009] Generating a first laser beam.

[0010] Generating a second laser beam .

[0011] Focusing the first and the second laser beam onto the components in such a way that the two laser beams generate a laser spot on a surface of at least one of the components. The laser spot comprises a, in particular circular, core region and a, in particular annular, edge region. An average laser power density in the core region is higher than an average laser power density in the edge region. The core region is generated by means of the first laser beam. The edge region is generated by means of the second laser beam. The first laser beam has a beam parameter product in a range from 0.36 mm*mrad to 0.8 mm*mrad (millimeters * milliradians), in particular of a maximum of 0.6 mm*mrad.

[0012] The core region of the laser spot can have a diameter in a range of 30 pm (micrometers) to 500 pm, in particular 30 pm to 80 pm. The edge region of the laser spot can have an outer diameter that is 2 to 6 times larger than the diameter of the core region of the laser spot.

[0013] This allows the welding speed to be increased, whereby humps, irregular penetration depths and / or intermetallic phases can be avoided or at least reduced. Due to the required beam parameter product, the core area can be implemented in a single-mode manner. Thin weld seams can be produced. Due to the increased welding speed, the

[0014] (welding) process time minimized.

[0015] The first and second laser beams can be superimposed. The first laser beam and the second laser beam can each have a circular cross-section. Alternatively, the second laser beam can have an annular, in particular a circular ring-shaped, cross-section. In any case, the second laser beam has a larger outer diameter in the plane of the component surface than the first laser beam. Due to the laser spot resulting on the component surface with a core region and an edge region, the so-called "keyhole" can be stabilized during welding, which in particular leads to a reduction in spatter and stabilizes the welding process.

[0016] Preferably, the first laser beam can have a better beam quality than the second laser beam. Accordingly, the second laser beam can have a poorer beam quality than the first laser beam. The second laser beam can, in particular, have a beam parameter product in a range from 1 mm*mrad to 16 mm*mrad, in particular a maximum of 4 mm*mrad.

[0017] This allows the laser spot, especially the edge area, to be optimally generated.

[0018] According to a further development of the method, the components can be arranged in a lap joint.

[0019] The two components can be metallic components of a battery, in particular a lithium-ion battery. The claimed method can reduce the electrical resistance and thus increase the service life of the battery. At least one of the components can have a thickness in a range from 3 pm (micrometers) to 50 pm, in particular in a range from 6 pm to 20 pm. It is also conceivable that at least one of the components can have a thickness of 0.1 mm (millimeters) to 3 mm, in particular in a range from 0.2 mm to 1 mm.

[0020] According to a further development of the method, at least one of the components can comprise, in particular consist of, copper, aluminum, iron, and / or steel. At least one of the components can be made of sheet metal.

[0021] Using this process, different metallic components can be optimally welded together.

[0022] According to a further development of the method, the first and / or the second laser beam can each be generated by means of at least one CW (Continuous Wave) laser.

[0023] The CW laser can be designed as an infrared laser and have a wavelength in a range from 800 nm (nanometers) to 1200 nm, in particular from 1030 nm or 1070 nm.

[0024] The CW laser can be designed as a laser with a wavelength in the visible range. The CW laser can be designed as a VIS (visible) laser. The wavelength of the VIS laser can be in a range from 400 nm to 450 nm (blue) or 515 nm (green).

[0025] The CW laser can have a power in a range from 100 W to 6000 W (watts), in particular in a range from 500 W to 2000 W. The CW laser can be designed as a single-mode laser or a multi-mode laser.

[0026] This allows the first and / or second laser beam to be generated using simple means.

[0027] According to a development of the method, at the start of a welding process, the average laser power density in the core region and the average laser power density in the edge region can each be increased in a ramp-like manner (in particular by correspondingly adjusting the laser power of the first or second laser beam). The average laser power density in the edge region can be increased at least partially before the average laser power density in the core region is increased. In other words, the average laser power density in the edge region can be increased first. The average laser power density in the core region is increased while the average laser power density in the edge region is being increased or afterwards.

[0028] This allows for better control of penetration depth and therefore more uniform penetration. Furthermore, spatter can be reduced. The welding process as a whole can thus be further optimized.

[0029] According to a further development of the method, at the end of a welding process, the average laser power density in the core region and the average laser power density in the edge region can each be ramped down (in particular by appropriately adjusting the laser power of the first or second laser beam). The average laser power density in the edge region can be ramped down at least partially after the average laser power density in the core region has been ramped down. In other words, the average laser power density in the core region can be ramped down first.

[0030] While the average laser power density in the core area is being reduced, or subsequently, the average laser power density in the peripheral area is reduced. This allows for better control of the penetration depth and therefore more uniform implementation. Furthermore, spatter can be reduced. The overall welding process can thus be further optimized.

[0031] According to a further development of the method, during a welding process the laser spot can be moved on the surface at a speed in a range of 50 mm / s (millimeters per second) to 2000 mm / s, in particular in a range of 100 mm / s to 400 mm / s.

[0032] This allows the welding process to be accelerated and thus the welding time to be reduced.

[0033] According to a further development of the method, the laser spot can be moved across the surface during a welding process in several parallel paths or in a hatched pattern. A beam splitter can be used to create parallel paths.

[0034] This allows the connection area between the two components to be enlarged, thus improving the weld joint. The welding process as a whole can be further optimized.

[0035] The laser spot on the surface can be moved using scanner optics. The scanner optics can have an image ratio in a range from 1:1 to 5:1, preferably from 2:1 to 3:1. The scanner optics can comprise at least one ultralight mirror. This allows the laser spot to be moved quickly and precisely across the workpiece using simple means.

[0036] According to a further development of the method, the laser spot can be oscillated on the surface with an amplitude during a welding process. The amplitude can be greater than 0.3 mm (millimeters).

[0037] This allows the molten area to be enlarged. The welding process can thus be further stabilized and optimized.

[0038] According to a further development of the method, during a welding process, the average laser power density in the core region and / or the average laser power density in the edge region can each be varied at a frequency, in particular pulsed or modulated. The frequency can be in a range from 100 Hz (Hertz) to 50 kHz (Kilohertz).

[0039] This allows the penetration depth to be implemented more evenly. Furthermore, spatter can be reduced. The welding process as a whole can thus be further optimized.

[0040] According to a further development of the method, a position of the laser spot and / or the components can be determined during a welding process. This can be done using an optical sensor. The optical sensor can be designed as a camera.

[0041] Alternatively or additionally, a measurement of the penetration depth can be provided. This can be performed using optical coherence tomography (OCT). Furthermore, the temperature of the surface and / or at the weld point (in the area of ​​the laser spot) can be measured. This can be achieved using a pyrometer.

[0042] This allows tolerances to be controlled and reduced, making the welding process more stable.

[0043] It may be provided to divide a weld into segments, each segment being at least 5% of the length of the entire weld.

[0044] According to a development of the method, the laser spot can be generated by means of a fiber with a, in particular circular, core region and a, in particular annular, edge region. The first laser beam can be coupled into the core region of the fiber. The second laser beam can be coupled into the edge region of the fiber. The core region of the laser spot can be generated by means of the first laser beam guided in the core region of the fiber. The edge region of the laser spot can be generated by means of the second laser beam guided in the edge region of the fiber. The first laser beam and the second laser beam can be fed from different laser beam modules.

[0045] The fiber can have an intermediate layer (cladding) between the core region and the edge region. The intermediate layer can have a maximum thickness of 20 pm, in particular a maximum thickness of 15 pm, and furthermore, a lower refractive index than the core region and the ring region of the fiber. This allows the core region and the edge region of the laser spot to be implemented using simple means.

[0046] The above object is achieved by a device for laser welding at least two metallic components, wherein the components are made of different materials, having the features of the independent claim. The device is configured to carry out the method according to the above embodiments.

[0047] With regard to the advantages that can be achieved, reference is made to the relevant explanations of the method. The measures described in connection with the method and / or those explained below can be used to further refine the device.

[0048] Further features, details and advantages of the invention will become apparent from the wording of the claims and from the following description of embodiments with reference to the drawings. They show schematically:

[0049] Fig. 1 is a perspective view of two components to be welded with a laser spot; and

[0050] Fig. 2 is a diagram of an average laser power density of a core region and an average laser power density of an edge region of the laser spot according to Figure 1.

[0051] In the following, a method for

[0052] Laser welding of at least two metallic components 10 is explained, wherein the components 10 are made of different materials.

[0053] Figure 1 shows a perspective view of two components 10 to be welded with a laser spot 12. In this example, two components 10 are arranged in a lap joint (i.e., overlapping one another). At least one of the components 10 can comprise, in particular consist of, copper, aluminum, iron, and / or steel.

[0054] The procedure includes the following steps:

[0055] Providing the components 10 .

[0056] Generating a first laser beam.

[0057] Generating a second laser beam .

[0058] The first and the second laser beam are focused on the components 10 in such a way that the two laser beams generate the laser spot 12 on a surface 14 of at least one of the components 10.

[0059] In the present case, the laser spot 12 is generated on the upper component 10 in Figure 1. In the present case, the surface 14 is an upper side of the upper component 10 in Figure 1, i.e., a side of the upper component 10 facing away from the lower component 10.

[0060] The laser spot 12 has a core region 16, in this case circular. The laser spot 12 has an edge region 18, in this case circular. An average laser power density 20 (cf. Figure 2) in the core region 16 is higher than an average laser power density 22 (cf. Figure 2) in the edge region 18. The core region 16 is generated by means of the first laser beam. The edge region 18 is generated by means of the second laser beam. The first laser beam has a beam parameter product in a range from 0.36 mm*mrad to 0.8 mm*mrad, in particular of a maximum of 0.6 mm*mrad.

[0061] The second laser beam can have a beam parameter product in a range of 1 mm*mrad to 16 mm*mrad, in particular of a maximum of 4 mm*mrad.

[0062] The first and / or the second laser beam can each be generated by means of at least one CW laser (not shown).

[0063] The laser spot 12 can be generated using a fiber with a core region and an edge region. The first laser beam can be coupled into the core region of the fiber, and the second laser beam can be coupled into the edge region of the fiber.

[0064] During a welding process, the laser spot 12 can be moved on the surface 14 at a speed in a range from 50 mm / s to 2000 mm / s, in particular in a range from 100 mm / s to 400 mm / s.

[0065] In the present case, the laser spot 12 is moved on the surface 14 in several parallel paths 24. The paths 24 are merely indicated in Figure 1 by dashed lines. It is also conceivable for the laser spot 12 to be moved in a hatched pattern. During the welding process, the laser spot 12 can be oscillated on the surface 14 with an amplitude. The amplitude can be greater than 0.3 mm.

[0066] Alternatively or additionally, during the welding process, the average laser power density 20 of the core region 16 and / or the average laser power density 22 of the edge region 18 can each be varied at a frequency, in particular pulsed or modulated. The frequency can be in a range from 100 Hz to 50 kHz.

[0067] Furthermore, the position of the laser spot 12 and / or the components 10 can be determined during the welding process. This can be achieved using an optical sensor.

[0068] Figure 2 shows a diagram of the average laser power density 20 in the core region 16 and the average laser power density 22 in the edge region 18 of the laser spot 12 according to Figure 1. For better differentiation, the average laser power density 20 in the core region 16 is shown in dashed lines.

[0069] The mean laser power density 26 is plotted over time 28. In other words, the temporal profiles of the mean laser power density 20 in the core region 16 and the mean laser power density 22 in the edge region 18 are shown.

[0070] At the start of the welding process, the average laser power density 20 in the core region 16 and the average laser power density 22 in the edge region 18 are each ramped up in a ramp-like manner. The average laser power density 22 in the edge region 18 is ramped up at least partially (in time) before the average laser power density 20 in the core region 16 is ramped up.

[0071] In the present case, the ramp-up of the average laser power density 22 in the edge region 18 is started at a first time t1. At a second time t2, which follows the first time t1, the ramp-up of the average laser power density 20 in the core region 16 is started. At a third time t3, which follows the second time t2, the ramp-up of the average laser power density 22 in the edge region 18 is ended. At a fourth time t4, which follows the third time t3, the ramp-up of the average laser power density 20 in the core region 16 is ended.

[0072] It is also conceivable that the ramp-up of the average laser power density 20 in the core region 16 is only started when the ramp-up of the average laser power density 22 in the edge region 18 is finished (i.e. t2 follows chronologically after t3).

[0073] When the average laser power densities 20, 22 are increased, it can be clearly seen in Figure 2 that the average laser power density 20 in the core region 16 of the laser spot 12 is higher than the average laser power density 22 in the edge region 18 of the laser spot 12.

[0074] At the end of the welding process, the average laser power density 20 in the core area 16 and the average laser power density 22 in the edge area 18 are each ramped down. In this case, the average laser power density 22 in the edge area 18 is at least partially (temporally) after a

[0075] Shutdown of the average laser power density 20 in the core area 16 shut down.

[0076] In the present case, the reduction of the average laser power density 20 in the core region 16 is started at a fifth time t5. At a sixth time t6, which follows the fifth time t5, the reduction of the average laser power density 22 in the edge region 18 is started. At a seventh time t7, which follows the sixth time t6, the reduction of the average laser power density 20 in the core region 16 is ended. At an eighth time t8, which follows the seventh time t8, the reduction of the average laser power density 22 in the edge region 18 is ended.

[0077] It is also conceivable that the shutdown of the average laser power density 22 in the edge region 18 is only started when the shutdown of the average laser power density 20 in the core region 16 is completed (i.e. t 6 follows chronologically after t 7 ).

Claims

Patent claims 1. A method for laser welding at least two metallic components (10), wherein the components (10) are made of different materials, comprising the steps: Providing the components (10); generating a first laser beam; generating a second laser beam; focusing the first and second laser beams onto the components (10) such that the two laser beams generate a laser spot (12) on a surface (14) of at least one of the components (10), wherein the laser spot (12) comprises a, in particular circular, core region (16) and a, in particular annular, edge region (18), wherein an average laser power density (20) in the core region (16) is higher than an average laser power density (22) in the edge region (18), wherein the core region (16) is generated by means of the first laser beam and the edge region (18) is generated by means of the second laser beam, wherein the first laser beam has a beam parameter product in a range from 0.36 mm*mrad to 0.8 mm*mrad, in particular of a maximum of 0.6 mm*mrad.

2. Method according to claim 1, characterized in that the second laser beam has a beam parameter product in a range from 1 mm*mrad to 16 mm*mrad, in particular of a maximum of 4 mm*mrad.

3. Method according to claim 1 or 2, characterized in that the components (10) are arranged in a lap joint.

4. Method according to one of the preceding claims, characterized in that at least one of the components (10) comprises, in particular consists of, copper, aluminum, iron and / or steel.

5. Method according to one of the preceding claims, characterized in that the first and / or the second laser beam are each generated by means of at least one CW laser.

6. Method according to one of the preceding claims, characterized in that at the start of a welding process the average laser power density (20) in the core region (16) and the average laser power density (22) in the edge region (18) are each ramped up in a ramp-like manner, wherein the average laser power density (22) in the edge region (18) is ramped up at least partially in time before the average laser power density (20) in the core region (16) is ramped up.

7. Method according to one of the preceding claims, characterized in that at the end of a welding process, the average laser power density (20) in the core region (16) and the average laser power density (22) in the edge region (18) are each ramped down, wherein the average laser power density (22) in the edge region (18) is at least partially temporally after a ramping down of the average laser power density (20) in the core area (16) is reduced.

8. Method according to one of the preceding claims, characterized in that during a welding process the laser spot (12) is moved on the surface (14) at a speed in a range of 50 mm / s to 2000 mm / s, in particular in a range of 100 mm / s to 400 mm / s.

9. Method according to one of the preceding claims, characterized in that during a welding process the laser spot (12) is moved on the surface (14) in several mutually parallel paths (24) or in a hatched pattern.

10. Method according to one of the preceding claims, characterized in that during a welding process the laser spot (12) is oscillated on the surface (14) with an amplitude, in particular wherein the amplitude is greater than 0.3 mm.

11. Method according to one of the preceding claims, characterized in that during a welding process the average laser power density (20) in the core region (16) and / or the average laser power density (22) in the edge region (18) is / are each varied with a frequency, in particular pulsed or modulated, in particular wherein the frequency is in a range from 100 Hz to 50 kHz.

12. Method according to one of the preceding claims, characterized in that during a welding process a position of the laser spot (12) and / or the components (10), in particular by means of an optical sensor.

13. Method according to one of the preceding claims, characterized in that the laser spot (12) is generated by means of a fiber with a, in particular circular, core region and a, in particular annular, edge region, wherein the first laser beam is coupled into the core region of the fiber and the second laser beam is coupled into the edge region of the fiber, wherein the first laser beam and the second laser beam are preferably fed from different laser beam modules.

14. Device for laser welding at least two metallic components (10), wherein the components (10) are made of different materials, characterized in that the device is designed to carry out the method according to one of the preceding claims.

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