Media supply during laser welding

Abstract

The invention relates to a laser welding apparatus (10) for welding two joining partners (50) along a welding joint, the laser welding apparatus (10) comprising: an optical monitoring device (12), which can be aligned with an observation region (X) around the welding joint in order to detect a progress of the welding joint; a laser welding head (14) that is designed to direct a laser processing beam (B) onto at least one of the joining partners (50), by means of a welding optics on the basis of the detected progress of the welding joint along the welding joint; and a supply device (20), which is designed to provide a welding additive and / or a process gas, and which is arranged on the laser welding head (14) such that the welding additive and / or the process gas can be supplied to a welding process from a supply direction following the laser beam (B). The invention further relates to a supply device (20) for use in the laser welding apparatus (10), and a method for welding two joining partners (50).

Description

[0001] Media supply during laser welding

[0002] Field of the invention

[0003] The present invention relates to the field of laser welding. In particular, the invention relates to the supply of welding filler material and / or process gas in a laser welding process, as well as to a laser welding device and a supply device for laser welding.

[0004] State of the art

[0005] Laser welding processes in which metallic workpieces are melted and welded together along a weld joint by a laser beam are known from the prior art. In laser welding with filler metal, the filler metal and the process gas for shielding the molten pool or the solidifying weld seam are generally supplied through separate nozzles mounted opposite one another on a welding head. The filler metal is preferably introduced in the form of a metal wire in a dragging motion - i.e. from the front in the feed direction - into the interaction zone between the laser beam and the workpiece. The process gas - preferably an inert shielding gas such as nitrogen or argon - is preferably directed in a dragging motion - i.e. from behind - onto the molten pool or, using a linear nozzle, onto the solidifying weld seam.

[0006] When welding filler material and process gas are supplied simultaneously, the accessibility of the component is significantly restricted due to the opposing arrangement of the respective nozzles and the welding process zone is not or only with difficulty visible to sensors, in particular for detecting the position of the joint (or the weld groove) in the run-up to the melting zone.

[0007] CN 2905302Y describes a combination nozzle for the piercing supply of welding consumables and process gas. The disadvantage of this nozzle is its rigid design. Regardless of the welding task, the complete nozzle is required for each media supply – even if, for example, only a supply of process gas is needed to shield the molten pool, but no welding consumables or a linear process gas supply to shield the solidifying weld seam. For many welding tasks, this combination nozzle therefore has an unnecessarily negative impact on the dynamics and contour freedom of the welding process.

[0008] One object of the present invention is to improve the precision of laser welding and thus the quality of welded joints, regardless of the welding task. At the same time, the dynamics and / or accessibility of laser beam welding with media supply are to be improved depending on the welding task.

[0009] The invention

[0010] The problem underlying the invention is solved by the subject matter of the independent claims. Further possible embodiments of the invention are specified in the subclaims, the description, and the drawings. Features, advantages, and possible embodiments presented in the description for one of the subject matter of the independent claims are to be regarded at least analogously as features, advantages, and possible embodiments of the respective subject matter of the other independent claims, as well as any possible combination of the subject matter of the independent claims, optionally in conjunction with one or more of the subclaims.

[0011] According to a first aspect, a laser welding device is provided for welding two joining partners along a weld joint. The joining partners can preferably be metallic joining partners. The laser welding device comprises an optical monitoring unit that can be aligned with an observation area around the weld joint in order to detect a course of the weld joint. The phrase "around the weld joint" in this context is to be understood to mean that the weld joint runs at least partially through the observation area and is captured by the field of view of the monitoring unit. By knowing the exact course of the weld joint, the welding process can be carried out with particular precision.

[0012] The laser welding device further comprises a laser welding head configured to direct a laser processing beam onto at least one of the joining partners by means of welding optics based on the detected course of the weld seam along the weld seam. The laser beam is preferably directed onto both joining partners to be welded. Through the interaction with the laser beam, the joining partners are locally melted and solidify after the laser beam passes over them, forming a common weld seam. Typically, a weld path can be preprogrammed for a particular welding task. However, the actual course of the weld seam may deviate from the preprogrammed course in practice.If the actual course of the weld joint deviates from the pre-programmed course, the feed direction can be corrected by detecting the weld joint (using the monitoring unit) immediately before the laser beam. This can increase welding precision and thus the quality of the welding result. To detect the actual course of the weld joint, the monitoring unit can preferably be arranged on the laser welding head and carried along with it. It is also possible for the monitoring unit to be at least partially integrated into the laser welding head, with a monitoring laser beam from the monitoring unit being directed onto the welding zone coaxially with the processing laser beam. The diameter of the monitoring laser beam is generally larger than the diameter of the processing laser beam.In this way, the weld seam can be detected in advance of the laser beam, even when aligned coaxially with the processing laser beam. The monitoring device can additionally or alternatively comprise a camera that can be aligned to the welding zone at an angle or coaxially with the processing laser beam. The monitoring device can, for example, be based on an OCT system (OCT = Optical Coherence Topography). Suitable process monitoring technologies are advertised by the applicant, for example, under the names "SeamLine" or "OCT Night Position Control and Monitoring."

[0013] The laser welding device also comprises a feed device configured to provide a welding filler material and / or a process gas (or shielding gas) and arranged on the laser welding head such that the welding filler material and / or the process gas can be fed to a welding process from a feed direction following the laser beam. In other words, the welding filler material and / or the process gas can be fed to the welding process in a piercing manner.

[0014] The welding consumable is added to the welding process in an interaction zone between the laser beam and at least one joining partner. The interaction of the laser beam with the joining partners creates a molten pool in the interaction zone, which can also be referred to as the processing area. The welding consumable is added to the molten pool and, together with the joining partners, forms the resulting weld seam during the welding process.

[0015] The welding consumable can be fed into the welding process by means of the feed device, preferably in the form of a wire or powder. Powdered welding consumables are typically fed into the welding process under pressure together with an inert gas.

[0016] The process gas can be supplied to the welding process via the supply device coaxial with the filler metal and / or via an elongated section following the laser beam during the welding process. When powdered filler metal is supplied, a separate process gas supply may be unnecessary to shield the molten pool, as the carrier gas of the powder stream essentially replaces the effect of the process gas. The elongated section of the linear process gas supply is designed to shield the melt solidifying behind the molten pool, which forms the weld seam, from the environment—particularly to prevent oxidation due to reactions with atmospheric oxygen.

[0017] Preferably, the observation area of ​​the monitoring unit is offset in a first direction relative to the laser beam in a surface plane of the joining partners. Furthermore, the feed device can be arranged on a side of the laser welding head facing away from the first direction. Alternatively, a monitoring beam (for example a monitoring laser beam) can also be arranged concentrically to the processing laser beam, wherein the observation area can be larger than a projection of the laser beam on the surface plane of the joining partners. The monitoring beam can, for example, also be moved back and forth across the workpiece (i.e., across the joining partners) in a pendulum motion transverse to the feed direction, advancing in advance of the laser processing beam. It is important that the monitoring unit detects the weld joint in the immediate advance of the laser beam in order to specify a precise feed direction for the processing laser beam.By arranging the feeding device downstream of the processing laser beam, the monitoring device can ensure free visibility in the feed direction of the processing laser beam.

[0018] The feed device and / or the monitoring device can also be mounted on the laser welding head so that they can rotate via a common or separate rotation module. This allows a monitoring laser beam and / or the feed device that is not guided concentrically to the processing laser beam to be aligned independently of the orientation of the laser welding head, and in particular, to follow the welding contour.

[0019] According to a second aspect, a feed device for selectively feeding a welding filler material and / or a process gas to a welding process is provided. The feed device is suitable for use in a laser welding device according to one of the variants described above. The feed device comprises a fastening element designed to fasten the feed device to the laser welding head of a laser welding device. The fastening element can comprise a rotary module that can be controlled by a machine control system or separately, with which the fastening element can be rotated about a longitudinal axis of the laser welding head. The longitudinal axis of the laser welding head can run essentially centrally through a focusing optics of the laser welding head.

[0020] The feed device further comprises an elongated carrier element which is mounted in the fastening element and in the interior of which a media channel is formed which extends along a longitudinal axis of the carrier element. The carrier element can preferably be designed as a hollow cylinder. The carrier element can be tiltably mounted in the fastening element. For this purpose, the fastening element can in particular have a spherical or hemispherical protuberance at at least one position of its outer circumference, which can be mounted in a recess of the fastening element which is complementary in shape to the protuberance. It can preferably be provided that a longitudinal axis of the carrier element can be arranged at an acute angle to an exit direction of the processing laser beam. For the controlled tilting of the carrier element, the fastening element can, for example, be a screw (e.g.a worm screw) and a spring element that fix the support element in the fastening element from two sides.

[0021] By changing the screw's rotational position, the support element can be pressed against the spring element. This allows the alignment angle or tilt position of the support element in the fastening element to be changed.

[0022] The feed device further comprises an elongated base element that can be received in the media channel of the support element and in whose interior a feed channel for the welding filler material is formed. The feed channel is designed for guiding and feeding a welding filler material to a molten pool during a laser welding process. The base element can preferably be hollow-cylindrical. In particular, the feed channel can be designed for feeding a wire-shaped welding filler material. Alternatively, the feed channel can also be designed for feeding a powder-shaped welding filler material.

[0023] In particular, the base element can be mounted in the media channel of the support element, forming an annular gap. The gap can serve, in particular, as a through-flow conduit for a process gas for coaxial process gas supply.

[0024] The feed device can further comprise a first gas feed element in the form of a hollow cylindrical sleeve that can be slipped over the base element and fastened to the outer circumference of the base element and / or the carrier element. The fastening is preferably reversible. Depending on the welding task for which the feed device is to be used, the first feed element can be selectively attached to the feed device. For welding tasks in which no coaxial process gas supply is required to cover the molten pool, the first gas feed element can be omitted, which can have a positive effect on the weight and dimensions of the feed device and thus directly on the dynamics and / or accessibility of the laser welding device. For example, the base element or the carrier element can have an external thread and the first gas feed element can have an internal thread designed to engage with the corresponding external thread.Alternatively, for example, a plug-in closure may be provided for releasably fastening the first gas supply element to the base element and / or the carrier element.

[0025] The supply device can further comprise a second gas supply element. The second gas supply element can be fastened to the base element and / or the support element. An elongated outlet opening is formed on the underside of the second gas supply element. The term "underside" refers to a directional indication during operation of the second gas supply element, e.g., during a welding process. The second gas supply element further has at least two gas channels that open into the outlet opening at an acute angle. The outlet opening can preferably be delimited laterally by a housing. The housing can be detachably fastened to a base body of the second gas supply element. The at least two oblique gas channels, as well as other possible connecting channels for the process gas supply, can be milled or drilled into the base body. The base body can preferably be made of aluminum or an aluminum alloy.The side enclosure of the outlet opening can preferably be made of copper or another material with good thermal conduction properties. In a side view, the second gas supply element can have approximately the shape of a parallelogram or a rhombus. This shape has proven advantageous for a piercing media supply to the welding process.

[0026] The second gas supply element can have a recess for receiving the first gas supply element. In this case, the first gas supply element can be reversibly fastened in the second gas supply element. In this way, the second gas supply element can be fastened to the base element and / or the support element by means of the first gas supply element. The integration of the first gas supply element into the second gas supply element further allows the simultaneous supply of gas to the molten pool and to the solidifying weld seam in the immediate downstream of the molten pool.

[0027] Preferably, a first gas channel can be formed for the first gas supply element, which extends from a first gas connection across the gap between the carrier element and the base element and opens into an annular outlet opening formed by an annular gap between the first gas supply element and the base element. The gap between the carrier element and the base element can comprise both annular and one or more channel-shaped sections. To form the annular outlet opening, the base element has a conically tapered outer circumference at its outlet-side end. The first gas supply element has a conically tapered inner diameter at its outlet-side end. In the assembled state, the end of the base element projects beyond the end of the first gas supply element, wherein the respective conical regions at least partially overlap in the axial direction.In this way, an annular gap is formed which directs a process gas along the outer circumference of the base element onto the molten pool during a welding process.

[0028] The second gas supply element can have a separate, second gas connection. In other words, the gas connection of the second gas supply element is independent of the gas connection of the first gas supply element. This allows the coaxial and linear gas supply to be controlled independently of each other, increasing welding flexibility and potentially reducing process gas consumption.

[0029] The base element and / or the first gas supply element and / or at least one housing of the second gas supply element surrounding the elongated outlet opening (on the underside or in the lower region of the second gas supply element) can be made of copper or a copper alloy. Alternatively, the elements in question can also be made of another material with particularly good thermal conduction properties. During the welding process, the elements in question are located particularly close to the interaction zone between the laser beam and the workpiece and are thus exposed to high temperatures. Due to the good thermal conduction properties of copper, the heat is dissipated into the nearest components of the supply unit, which can be made of aluminum, for example, and which can preferably be actively cooled (e.g. by arranging cooling channels in the corresponding areas and connecting them to a cooling system).Due to the modular design of the feed unit, the elements subject to particularly high heat stress can be replaced separately, which increases the overall economic efficiency of the feed element.

[0030] According to a third aspect, a method for welding two joining partners along a weld joint is provided, which can be carried out using a laser welding device according to one of the variants described above. The method comprises detecting a profile of the weld joint using the optical monitoring device. The profile of the weld joint is recorded in advance of the processing laser beam. The method further comprises melting the joining partners using the processing laser beam in a predeterminable feed direction along the weld joint. The profile of the weld joint detected by the monitoring device can be compared with a weld contour predetermined in advance by a welding program. In the event of deviations between the detected profile and the predetermined weld contour, the feed direction of the processing laser beam can be adjusted accordingly.

[0031] The method comprises selectively feeding a welding consumable and / or a process gas to the welding process from a direction opposite to the feed direction. In other words, the welding consumable and / or the process gas is fed into the welding process in a piercing manner. The media supply is carried out in an arbitrarily selectable exclusive or combined selection of the following:

[0032] • The welding filler material is fed into a molten pool created by the laser beam;

[0033] • The process gas is directed (in a directed beam) onto the molten pool to shield the molten pool;

[0034] • The process gas is directed onto an elongated area following the molten pool to shield the solidifying weld seam.

[0035] This selective media supply allows the welding process to be individually and efficiently adapted to a welding task.

[0036] Preferably, a monitoring laser beam of the optical monitoring device can be directed at least partially coaxially to the processing laser beam onto the surface of the joining partners by means of the welding optics, wherein in the surface plane of the joining partners, a diameter of the monitoring laser beam is larger than a diameter of the processing laser beam. In this way, it can be ensured that the weld joint is detected by the monitoring laser beam in the advance to the molten pool. Alternatively or additionally, a monitoring laser beam can be directed onto the surface plane of the joining partners in the feed direction, ahead of the processing laser beam. In this way, the monitoring laser beam can be guided completely independently of the processing laser beam and directed onto the surface of the joining partners to detect the weld joint.

[0037] Examples of implementation

[0038] The following description of preferred embodiments, in conjunction with the drawings, serves to explain the invention in more detail.

[0039] They show:

[0040] Fig. 1 Schematic of a laser welding device according to the invention;

[0041] Fig. 2 A block diagram to explain a method for welding two joining partners by means of a laser welding device according to the invention;

[0042] Figs. 3a-b A feeding device according to the invention according to a first variant;

[0043] Figs. 4a-b A feeding device according to the invention according to a second variant; and

[0044] Figs. 5a-b A feeding device according to the invention according to a third variant.

[0045] A laser welding device 10 according to the invention for welding two joining partners 50 along a weld joint is described in more detail below with reference to Figure 1. The laser welding device 10 comprises an optical monitoring unit 12, which can be aligned with an observation area X around the weld joint in order to detect a profile of the weld joint. In Figure 1, the weld joint runs along the image plane. The laser welding device further comprises a laser welding head 14, which is designed to direct a laser processing beam B onto at least one of the joining partners 50 by means of welding optics based on the detected profile of the weld joint along the weld joint. Since Figure 1 shows a side view of the laser welding device 10 along a welding direction or feed direction D, only one of the joining partners 50 is visible. It should also be noted that the monitoring unit 12 can be used for various types of joints.A typical application is the welding of two plate-shaped, metallic (e.g., steel, aluminum, or copper) joining partners in a butt joint, lap joint, or T-joint. The laser welding device 10 further comprises a feed device 20, which is designed to provide a welding filler material and / or a process gas (not shown in the figures) and is arranged on the laser welding head 14 such that the welding filler material and / or the process gas can be fed to a welding process from a feed direction following the laser beam B.

[0046] The welding filler material can be supplied to the welding process by means of the supply device 20 in the form of a wire or in powder form. Furthermore, the process gas can be supplied to the welding process by means of the supply device 20 coaxially to the welding filler material and / or via an elongated region following the laser beam B during the welding process.

[0047] The observation area X, onto which an observation laser beam 122 of the monitoring device 12 is directed, is, as shown in Figure 1, offset in a surface plane of the joining partners 50 in a first direction (which in the case of Figure 1 corresponds to the feed direction D) relative to the laser beam B. The feed device 20, on the other hand, is arranged on the laser welding head 14 in a trailing manner with respect to the laser welding process shown, i.e., trailing the feed of the laser welding head 14.

[0048] In connection with Figure 2, a method for welding two joining partners 50 using the laser welding device 10 is described below. The method comprises, in a first step 102, detecting a profile of the weld joint using the optical monitoring device 12. For this purpose, the monitoring laser beam 122 is directed in the feed direction D, leading to the processing laser beam B, onto the surface plane of the joining partners 50.

[0049] In a second step 104, the method comprises melting the joining partners 50 by means of the processing laser beam B in the feed direction D along the weld joint. In a third step 106, the method comprises selectively feeding a welding filler material and / or a process gas to the welding process from a direction opposite to the feed direction D. Depending on the welding task, a welding filler material can be fed to a molten pool 52 generated by the laser beam B, and / or the process gas can be directed onto the molten pool 52 to shield the molten pool 52, and / or the process gas can be directed onto an elongated region following the molten pool 52 to shield the solidifying weld seam 54.

[0050] In conjunction with Figures 3a to 5b, various variants of a feed device 20 according to the invention for selectively feeding a welding filler material and / or a process gas to a welding process are described below. Each of the feed devices 20 comprises a fastening element 22 designed to fasten the feed device 20 to the laser welding head 14 of a laser welding device 10. Furthermore, each feed device 20 comprises an elongate support element 24, which is mounted in the fastening element 22 and in whose interior a media channel is formed, which extends along a longitudinal axis of the support element 24. Furthermore, each feed device 20 comprises an elongate base element 26, which can be received in the media channel of the support element 24 and in whose interior a feed channel 262 for the welding filler material is formed.A feed for the welding filler material into the feed channel 262 is indicated in Figure 1 by the reference symbol "W" and a corresponding arrow. The feed device 20 according to Figures 3a and 3b is configured in the form shown for the sole supply of welding filler material, i.e., without additional process gas supply.

[0051] The supply device 20 can - as shown in the variant according to Figures 4a and 4b - additionally have a first gas supply element 28 which has the shape of a hollow cylindrical sleeve which can be slipped over the base element 26 and fastened to the outer circumference of the base element 26 and / or the carrier element 24.

[0052] Alternatively or additionally, a supply device 20 according to the invention can have a second gas supply element 29. This variant is illustrated in Figures 5a and 5b. The second gas supply element 29 can be fastened to the base element 26 and / or the support element 24. Furthermore, an elongated outlet opening 292 for a process gas is formed on the underside of the second gas supply element 29, which can be directed via at least two gas channels 294 at an acute angle via the outlet opening 292 onto a weld seam 54.

[0053] Between the base element 26 and the support element 24, a first gas channel 25 for the first gas supply element 28 is formed. This first gas channel extends from a first gas connection G1 across a gap between the support element and the base element and opens into an annular outlet opening formed by an annular gap between the first gas supply element 28 and the base element 26. The second gas supply element 29 has a separate, second gas connection G2.

[0054] The base element 26 and / or the first gas supply element 28 and / or at least one housing 296 of the second gas supply element 29 surrounding the elongated outlet opening 292 may be made of copper or a copper alloy.

Claims

Patent claims 1. Laser welding device (10) for welding two joining partners (50) along a welding joint, the laser welding device (10) comprising: An optical monitoring unit (12) which can be aligned to an observation area (X) around the weld joint in order to detect a course of the weld joint; A laser welding head (14) which is designed to direct a laser processing beam (B) by means of a welding optics on the basis of the detected course of the weld joint along the weld joint onto at least one of the joining partners (50); and A feed device (20) which is designed to provide a welding filler material and / or a process gas and which is arranged on the laser welding head (14) in such a way that the welding filler material and / or the process gas can be fed to a welding process from a feed direction following the laser beam (B).

2. Laser welding device (10) according to claim 1, wherein the welding filler material can be fed to the welding process by means of the feed device (20) in the form of a wire or in powder form.

3. Laser welding device (10) according to claim 1 or 2, wherein the process gas can be supplied to the welding process by means of the supply device (20) coaxially to the welding filler material and / or via an elongated region following the laser beam (B) in the welding process.

4. Laser welding device (10) according to one of the preceding claims, wherein the observation area in a surface plane of the joining partners (50) is offset in a first direction relative to the laser beam (B); and wherein the feed device (20) is arranged on a side of the laser welding head (14) facing away from the first direction.

5. Feeding device (20) for selectively feeding a welding filler material and / or a process gas to a welding process and for use in a laser welding device (10) according to one of claims 1 to 4; the feeding device (20) comprising: A fastening element (22) which is designed to fasten the feeding device (20) to the laser welding head (14) of a laser welding device (10); An elongated support element (24) which is mounted in the fastening element (22) and in the interior of which a media channel is formed which extends along a longitudinal axis of the support element (24); and An elongated base element (26) which can be received in the media channel of the carrier element (24) and in the interior of which a feed channel (262) for the welding filler material is formed.

6. Feeding device (20) according to claim 5, further comprising: A first gas supply element (28) which has the shape of a hollow cylindrical sleeve which can be slipped over the base element (26) and fastened to the outer circumference of the base element (26) and / or the support element (24).

7. Feeding device (20) according to claim 5 or 6, further comprising: A second gas supply element (29) which can be fastened to the base element (26) and / or the support element (24), on the underside of which an elongated outlet opening (292) is formed, and which has at least two gas channels (294) which open at an acute angle into the outlet opening (292).

8. Feeding device (20) according to claim 7, Wherein the second gas supply element (29) has a recess for receiving the first gas supply element (28) and wherein the second gas supply element (29) can be fastened to the base element (26) and / or the carrier element (24) by means of the first gas supply element (28).

9. Feeding device (20) according to one of claims 6 to 8, Wherein a first gas channel (25) is formed for the first gas supply element (28), which extends from a first gas connection (Gl) across a gap between the carrier element (24) and the base element (26) and which opens into an annular outlet opening formed by an annular gap between the first gas supply element (28) and the base element (26).

10. Feed device (20) according to one of claims 7 to 9, wherein the second gas feed element (29) comprises a separate, second Gas connection (G2).

11. Feed device (20) according to one of claims 5 to 10, wherein the base element (26) and / or the first gas feed element (28) and / or at least one housing (296) of the second gas feed element (29) surrounding the elongated outlet opening are made of copper or a copper alloy.

12. A method for welding two joining partners (50) along a welding joint by means of a laser welding device (10) according to one of claims 1 to 4, the method comprising the steps: Detecting (102) a course of the weld joint by means of the optical monitoring device (12); Melting (104) the joining partners by means of the processing laser beam (B) in a predeterminable feed direction (D) along the weld joint; Selectively feeding (106) a welding filler material and / or a process gas to the welding process from a direction opposite to the feed direction (D); Whereby the welding filler material is a Laser processing beam (B) generates melt pool (52); and / or Wherein the process gas is directed onto the melt pool (52) to shield the melt pool (52); and / or The process gas is directed onto an elongated region following the molten bath (52) to shield the solidifying weld seam (54).

13. The method according to claim 12, wherein a monitoring laser beam of the optical monitoring device (12) is directed at least partially by means of the welding optics coaxially to the processing laser beam (B) onto the surface of the joining partners (50), wherein in the surface plane of the joining partners (50) a diameter of the monitoring laser beam is greater than a diameter of the processing laser beam (B).

14. The method according to claim 12, wherein a monitoring laser beam (122) is directed onto the surface plane of the joining partners (50) in advance of the processing laser beam (B) in the feed direction.

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