Method for joining at least two components

Abstract

A method for joining at least two components (B1, B2) by producing an overlap joint using laser welding, characterized in that: - the first component (B1) is arranged on the second component (B2), wherein the first component (B1) has at least one circular and / or conical material recess (1) as an inlet for a laser beam (2) of a laser welding device (3), - the laser welding device (3) is positioned in alignment above the material recess (1), and - the production of the overlap joint is carried out by at least one spot welding of the laser beam (2) in the at least one material recess (1) of the first component (B1), characterized in that a larger amount of energy, which is greater than that which is present in the center of the material recess, is introduced homogeneously in thicker edge regions of the conical material recess (1).

Description

The invention relates to a method for connecting at least two components according to the features of the preamble of claim 1.As described in DE 11 2015 006 504 T5, a method for laser welding a workpiece stack containing at least two overlapping workpieces made of steel is known from the prior art. A laser beam is directed onto an upper surface of the workpiece stack-up to form a keyhole surrounded by a molten steel pool. The laser beam is conveyed along a predefined welding pattern that includes non-linear inner welding paths and an enclosing outer perimeter welding path that surrounds the non-linear inner welding paths. As the laser beam travels along the nonlinear inner welding paths, the keyhole penetrates the workpiece stack entirely from the top surface to the bottom surface.DE 10 2017 117 992 A1 discloses a method for laser welding a workpiece stack-up which contains overlapping workpieces made of metal. The method includes directing a laser beam onto an upper surface of the workpiece stack-up to create a molten metal pool and optionally a keyhole, and rotating the laser beam to move a focal point of the laser beam along a helical path having a central helical axis oriented transverse to the upper and lower surfaces of the workpiece stack-up.DE 10 2021 131 399 A1 describes a pressing device for a laser welding device. The pressing device comprises an arm element with opposing mounting and pressing ends. A pressing pad at the pressing end has an opening through which a laser beam can irradiate a workpiece assembly pressed by the pressing device. The mounting end has a fixing structure for detachably fixing the pressing device to the laser welding device. The arm member is shaped so that the aperture is positioned at a known fixed distance from a laser source of the laser welding apparatus. The pressing pad has a pressing surface on a side facing the workpiece to apply a joining force to the workpiece assembly at a welding location. At least one of the size, shape and smoothness of the pressing surface enables sliding contact movement of the pressing surface along a surface of the workpiece assembly during application of the pressing force.The translation of European patent specification DE 693 15 409 T2 discloses an arrangement for providing improved efficiency in laser bonding. In particular, a part 12 in the assembly is formed to include means for concentrating a beam of radiation at a predetermined mounting location (or multiple locations). The concentrating means may be in the form of an aperture, such as a conical or parabolic aperture, which concentrates the radiation on the area being worked significantly. Alternatively, when the piece portion is transparent to the wavelength of radiation, the concentrating means may be in the form of a lens or grating formed on the surface of the piece portion.German patent DE 10 2015 121 064 B3 discloses a method for joining joining partners of the same kind of composition, comprising: - arranging a first joining partner in mechanical contact with a second joining partner; - applying a first laser beam through a recess in the first joining partner to a first surface region of the second joining partner; - laser-induced generation of a melt between the first surface region and a second surface region of the second joining partner lying opposite the first surface region, wherein the first surface region is melted to the melt at least in sections; - moving the melt at least into a section of the recess and holding the melt at least partially within the recess; - solidifying the melt, whereby the two joining partners are anchored to one another via the melt solidified in the recess.German patent DE 196 22449 C1 discloses the following: In the method for granulating a surface of a workpiece, according to the invention, a recess is produced in the workpiece which passes through the workpiece and onto which a body is placed on one side of the workpiece. With a laser beam entering the recess on the other side of the workpiece, the body is then welded to the workpiece in the recess.Austrian utility model specification AT 008 826 U1 discloses a method for connecting at least two metallic components lying one above the other via at least one welded connection by means of laser welding, wherein the laser beam is guided in the region of the welded connection point in such a way that a welding path wound several times around one another is obtained.The object of the invention is to specify a method for connecting at least two components which is improved compared with the prior art.The object is achieved according to the invention by a method for connecting at least two components having the features of claim 1.Advantageous embodiments of the invention are the subject matter of the dependent claims.In a method for connecting at least two components by producing an overlap connection by means of laser welding, also referred to as laser beam welding, according to the invention the first component is arranged on the second component, wherein the first component has at least one circular and / or conical material recess as inlet for a laser beam of a laser welding device. Circular or round refers to the cross section of the material recess, wherein the latter then has a constant diameter over its length. The material recess designated as round or circular is thus in particular hollow-cylindrical.The material recess runs with its axial direction starting from an upper side of the first component in the direction of an underside of the first component. The conical material recess narrows downward, i.e. in the direction of the second component arranged below the first component. The material recess can also be designed, for example, in the axial direction in sections to be conical and / or round in sections, in particular can have a plurality of different conical sections or can have alternately conical and round sections.The laser welding device is positioned aligned over the material recess. The overlapping connection is produced by at least one punctiform welding of the laser beam into the at least one material recess of the upper first component, i.e. via a punctiform joining geometry by, in particular pulsed, laser welding into the material recess of the upper first component. The laser welding is thus carried out in an exactly positioned manner in the material recess.According to the invention, a larger amount of energy is introduced in each case homogeneously distributed manner in thicker edge regions of the conical material recess, as a result of which the connection is welded in well and uniformly.The solution according to the invention solves in particular the problem that previously the joining of components, in particular with different material thicknesses, with an overlap joint by means of laser welding can be carried out only with difficulty. In particular in the case of an upper first component which is thicker than the lower second component, there has hitherto been the risk of undesired welding through the lower second component. In addition, temperature-sensitive components can be damaged by high energy inputs on account of a required high power input.The solution according to the invention, in particular the at least one material recess in the upper first component, avoids these problems and risks.The method according to the invention enables reliable welding of component connections made of materials of different thicknesses and temperature-sensitive components.The material recess is introduced into this first component, for example, directly in the production process, for example, in a punching process, for producing the first component, i.e., in particular, by the same processing method that is used for producing the first component, for example, in the same method step that is used for producing the first component. This introduction of the material recess is thus cost-neutral. Alternatively, the material recess can also be introduced in another manner.The method according to the invention is suitable in particular for joining mixed connections, for example for joining a component made of aluminum to a component made of copper, since a proportion of melt of the upper first component and a mixing ratio can be set by the material cutout.If the material recess is formed continuously, i.e. penetrating the first component, a gap can be identified by means of a height measurement on the lower second component, if this is present. Such a gap has a negative effect on the welding result. Knowing the presence of the gap, measures can be taken to eliminate this gap and / or adjust the welding parameter.The method according to the invention is suitable in particular for connecting electrical components, in particular for a cell connector as the upper first component. Such a cell connector connects in particular poles of battery cells of a battery, for example of a vehicle battery, in particular of a drive battery.Due to the material recess according to the invention, thicker components can also be welded reliably.The process according to the invention achieves a particularly high strength of the connections.For the method according to the invention, a plurality of material recesses and a corresponding number of point welds can be applied to a component, i.e. to the first component, as required, in order to weld the latter to the second component.By means of the method according to the invention, it is also possible to weld more than two components to one another, i.e. a plurality of component layers, corresponding for example to three or more components arranged one above the other, for example a 3-sheet metal connection. The first component is the upper component and is formed in the described manner, i.e. it has the at least one material recess.Exemplary embodiments of the invention are explained in more detail below with reference to drawings.The following are shown: FIG. 1 schematically shows an exemplary sequence of a method for connecting at least two components by producing an overlap connection by means of laser welding, and FIG. 2 schematically shows various exemplary embodiments of a first component of the overlap connection.Corresponding parts are provided with the same reference numerals in all figures. FIG. 1 shows, by way of example, a sequence of a method for connecting at least two components B 1, B 2 by producing an overlap connection by means of laser welding. An alignment of the two components B 1, B 2 is made clear by means of a three-dimensional coordinate system. In the example shown, the two components B 1, B 2 are configured to be flat, i.e. they each have a longitudinal extent parallel to an x-axis X and a transverse extent parallel to a y-axis Y. The first component B 1 has a thickness t 1 parallel to a z-axis Z. The second component B 2 has a thickness t 2 parallel to the z-axis Z.The first component B 1 has at least one circular or, as shown in the example according to FIG. 1, conical material recess 1 as inlet for a laser beam 2 of a laser welding device 3. In the example shown, the first component B 1 has two such material recesses 1. The respective material recess 1 runs, as shown in a left-hand detail section in FIG. 1, with its axial direction starting from an upper side of the first component B 1 in the direction of an underside of the first component B 1, i.e. the axial direction runs parallel to the z-axis Z. The respective material recess 1, which is designed conically in the example shown, narrows downward.A material thickness of the upper first component B 1 is locally thinned out by the respective material recess 1, as shown in FIG. 1, or the material recess 1 penetrates the first component B 1, i.e. it is continuous, as shown in several of the embodiments of the first component B 1 shown by way of example in FIG. 2. FIG. 2 illustrates, by way of example, different embodiments of the first component B 1. In this case, different shapes of the material recesses 1, which are closed continuously or at the bottom, and different base body shapes of the first component B 1 are illustrated.As already described, the respective material recess 1 in FIG. 1 is designed to be conical and not continuous, but rather as a blind hole. For example, the respective material recess 1 has a largest diameter d at the upper side of the first component B 1 of 7.5 mm or less than 7.5 mm.In FIG. 2, five different embodiments of planar first components B 1 are shown by way of example on the left-hand side, i.e. they have a planar basic body shape. On the right side, two embodiments of shaped, in particular specifically shaped, first components B 1 are shown by way of example, in order to enable tolerance compensation, for example.The embodiments in FIG. 2 have, by way of example, differently configured material recesses 1. On the left side, the first component B 1 arranged at the very top has circular material recesses 1, which have a constant diameter, i.e. are not designed conically. These material recesses 1 are formed so as to completely penetrate the first component B 1. They are thus each designed as a hollow cylinder open on both end sides, i.e. as a through opening.The embodiment of the first component B 1 illustrated below has conical material recesses 1 having a constant cone shape, i.e. having a constant angle of inclination with respect to the axis of the material recess 1.The embodiment of the first component B 1 illustrated below has conical material recesses 1 having a constant cone shape, i.e. having a constant angle of inclination with respect to the axis of the material recess 1. these material recesses 1 end at the underside of the first component B 1, i.e. the underside is still closed, for example, so that these material recesses 1 do not completely penetrate the first component B 1 and are thus each formed as a blind hole, or a hole can already be formed, for example, by a lower tip of the respective material recess 1, in the underside of the first component B 1, so that these material recesses 1 then completely penetrate the first component B 1.The next-to-last illustrated embodiment of the first component B 1 on the left-hand side of FIG. 2 has material recesses 1 with a conical upper portion and a circular, in particular hollow cylindrical, lower portion, which thus has a constant diameter. In this case, this diameter of the circular lower section is smaller than a smallest diameter of the conical upper section, so that a shoulder is formed between the two sections. These material recesses 1 are formed so as to completely penetrate the first component B 1.The last illustrated embodiment of the first component B 1 on the left-hand side of FIG. 2 has circular material recesses 1 which have a constant diameter, i.e. are not formed conically. These material recesses 1 do not penetrate the first component B 1. They are thus designed as a hollow cylinder with a closed lower end face and an open upper end face. This respective material recess 1 thus forms a blind hole.The upper embodiment of the first component B 1 on the right side of FIG. 2 has conical material recesses 1 with a constant cone shape, i.e. with a constant angle of inclination to the axis of the material recess 1. They are each formed in a wave trough of the wave-shaped basic body shape of the first component B 1.The lower embodiment of the first component B 1 on the right-hand side of FIG. 2 has conical material recesses 1 with a constant cone shape, i.e. with a constant angle of inclination to the axis of the material recess 1. These base sections are designed, for example, as inverted truncated cones or truncated pyramids, i.e. standing upside down. The material recesses 1 of this embodiment of the first component B 1 are thus each formed as a blind hole.In the method for connecting the two components B 1, B 2, which method is schematically illustrated in FIG. 1, the first component B 1 is arranged on the second component B 2, as illustrated on the left in FIG. 1. The laser welding device 3 is positioned aligned over the respective material recess 1, as shown on the right in FIG. 1. The overlapping connection is produced by at least one punctiform welding of the laser beam 2 into the at least one material recess 1 of the upper first component B 1, i.e. via a punctiform joining geometry by, in particular pulsed, laser welding into the respective material recess 1 of the upper first component B 1. The laser welding is thus carried out in an exactly positioned manner in the respective material recess 1.The welding is effected, for example, by means of a single pulse in combination with a changed, in particular variable, intensity profile. The welding is thus achieved by means of a single pulse of the laser beam 2 with a changed, in particular variable, intensity profile which can be controlled or adjusted via the cross section. The laser beam 2 thus has a higher intensity 1 in the edge regions of the respective material recess 1, so that a larger amount of energy is introduced all around in the thicker edge regions of the conical material recess 1 and the connection is thus welded in well and uniformly. Due to the higher intensity I in the edge regions of the respective material recess 1, the greater material thickness present there is melted and mixed reliably. The intensity profile of the laser beam 2 is or is advantageously adapted to the variable material thickness. The laser beam 2 is not moved here, but rather stands for the length of the pulse rigidly at the point, namely above the position of the material recess 1.In FIG. 1, the higher intensity I of the laser beam 2 is schematically shown in the edge regions of the respective material recess 1, in that the laser beam 2 is shown in the edge regions of the material recess 1 in which it has the higher intensity I with solid lines and in the center of the material recess 1 with dashed lines for the lower intensity I. An intensity diagram schematically illustrates a profile of the intensity I in the x direction, i.e. in the direction parallel to the x axis X, across the diameter of the material recess 1. It is also clear from this that the intensity I of the laser beam 2 is higher in the edge regions of the material recess 1 and lower in the center of the material recess 1.The intensity I of the laser beam 2 is the quotient of the power P and the beam area A of the laser beam 2:In a right detail section in FIG. 1, the welded connection is shown in the region of one of the material recesses 1. Material of the first component B 1 from edge regions of the material recess 1 and below the material recess 1 and material of the second component B 2 have been melted and mixed. This melt is resolidified, whereby the two components B 1, B 2 are welded to one another.

Claims

Method for connecting at least two components (B1, B2) by producing an overlap connection by means of laser welding, characterized in that - the first component (B1) is arranged on the second component (B2), wherein the first component (B1) has at least one circular and / or conical material recess (1) as inlet for a laser beam (2) of a laser welding device (3), - the laser welding device (3) is positioned in alignment over the material recess (1), and - the production of the overlap connection is carried out by at least one punctiform welding-in of the laser beam (2) in the at least one material recess (1) of the first component (B1), characterized in that a larger amount of energy, which is greater than that present in the center of the material recess, is introduced in each case homogeneously distributed manner in thicker edge regions of the conical material recess (1).

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