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Verfahren zum Fuegen von mindestens zwei Bauteilen mittels Laserstrahlung

Method for joining two components of homogeneous and inhomogeneous metallic materials by laser radiation, comprises forming a welding seam along a main path and/or a welding spot at a fixed main position in the area of a joining edge
 
: Schulz, W.; Olowinsky, A.; Gedicke, J.

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Frontpage ()

DE 102007038502 A: 20070814
DE 102007038502 A: 20070814
B23K0026
Deutsch
Patent, Elektronische Publikation
Fraunhofer ILT ()

Abstract
(A1) Verfahren zum Fuegen von mindestens zwei Bauteilen aus metallischen Werkstoffen mittels Laserstrahlung durch Ausbilden einer Schweissnaht, das dadurch gekennzeichnet ist, dass zusaetzlich zu der Bewegung entlang einer Hauptbahn beim Nahtschweissen bzw. zusaetzlich zu einer festen Hauptposition beim Punktschweissen und einer Hauptrichtung der Laserstrahlachse relativ zur Oberflaechenormale des Werkstuecks als Parameter die Leistung, die Richtung des Laserstrahls relativ zur Hauptrichtung und die Position an der Oberflaeche des Werkstoffs relativ zu den Positionen entlang der Hauptbahn bzw. zur Hauptposition so eingestellt werden, dass die Schweisskapillare unabhaengig von der Hauptbahn mit veraenderlicher Tiefe relativ zur Materialdicke mit veraenderlicher Richtung relativ zur Hauptrichtung und mit veraenderlicher Position entlang einer Nebenbahn so gefuehrt wird, dass eine geometrische Form des Schmelzbades und eine geometrische Form des resultierenden Nahtquerschnitts erreicht wird und dass als weiterer Parameter der Radius des Laserstrahls relativ zu gewuenschten Breite der Schweissnaht bzw. des Schweisspunktes so eingestellt wird, dass das Verhaeltnis V der Durchmesser von Schweissnaht d?Naht? und Schweisskapillare d?Kapillare? bzw. der Durchmesser von Schweisspunkt und Schweisskapillare eine Mindestgroesse ueberschreitet. Es wird auch eine Vorrichtung angegeben.

 

WO 2009021716 A1 UPAB: 20090311 NOVELTY - The method for joining two components of homogeneous and inhomogeneous metallic materials (100, 101) by laser radiation, comprises forming a welding seam (106) along a main path and/or a welding spot at a fixed main position in the area of a joining edge, in which the laser radiation is partially absorbed in an interaction zone and forms a molten bath, covering a part of the joining edge by the molten bath to form a carrying cross-section after hardening a melt, and focusing the laser radiation along the joining edge on a small beam width with a main direction of the laser beam axis. DETAILED DESCRIPTION - The method for joining two components of homogeneous and inhomogeneous metallic materials (100, 101) by laser radiation, comprises forming a welding seam (106) along a main path and/or a welding spot at a fixed main position in the area of a joining edge, in which the laser radiation is partially absorbed in an interaction zone and forms a molten bath, covering a part of the joining edge by the molten bath to form a carrying cross-section after hardening a melt, and focusing the laser radiation along the joining edge on a small beam width with a main direction of the laser beam axis relative to normal to a surface of the material. The beam size resulting from the focusing and/or the smallest diameter of the laser beam of the focused laser radiation is held in the area of the interaction zone forming itself by the laser radiation and material along the joining edge of the materials. The diameter of the laser beam and the welding cavity (105) are slightly adjusted as required carrying cross-section of the welding seam during welding. In addition to the movement along the main path or position during seam/spot welding and the main direction of the laser beam axis in relation to the normal to the surface of the workpiece, the power and direction of the laser beam in relation to the main direction and the position on the surface of the material relative to the positions along the main path or to the main position are set as parameters, so that the welding cavity is guided independently of the main path with varying depth relative to the material thickness, with varying direction relative to the main direction and with varying position along a secondary path, so that a geometric form of the molten bath and the resultant seam cross section are achieved, which determine the local component dimensions along the main path and the resulting internal stresses in the component along the main path in dependence of the joint type. The radius of the laser beam relative to the desired width of the welding is set as a further parameter, so that the ratio (V) of the diameters of the welding seam and cavity or the diameters of the welding spot and the cavity exceeds a minimum value. The smallest cross section of double cone lies nearer to the workpiece surface and opening angle with the power of the laser beam is adjusted. The cross section of the welding seam reaches the carrying cross section along the main path. The length of the welding cavity remains small along the secondary path in comparison to width of the molten bath. The depth of the cavity is changed by controlling the power and/or the path speed and takes different large values by periodically controlling the power. The secondary path is passed through in the form of a curve with double dots. A system from several materials is processed with three layers and the weld connects only the upper two layers. A T-joint having a flange and a bar, the power and the opening angle of the laser beam are adjusted during the welding. The smallest cross-section of the double cone is adjusted on the surface of the flange. The laser beam is guided on the spiral-shaped path with variable radius at the joining edge, which is maximally seized by the full opening angle. A pre-determined value is reached for an angle distortion during welding, in which the opening angle and the depth of the closest cross section are adjusted. The depth is measured from the upper edge of the workpiece. For the angle distortion, the value is reached zero degree, in which the depth of the closest cross section is equally adjusted to the half material thickness and the opening angle is largely adjusted, up to which the actual angle distortion of the material- and laser parameter falls below a predetermined value based on unavoidable fluctuations of the internal stresses in the material. The width of the welding seam and/or the diameters of the welding spot are adjusted to the direction of the laser beam by a tumbling motion around a point in dependence of the distance to the material surface. The temperature in the molten bath is homogeneously kept nearer to the melting temperature with a given distribution and is adjusted to larger values only in a small environment of the welding cavity. The temperature is adjusted in the fixed part of the welding seam behind the molten bath with the given distribution. The laser beam heats the retral part of the molten bath. The effect of the adjustment of the parameters is controlled. The thermal emission of the hot surface of the molten bath and reflections of an additional illuminating source are obtained with a camera. The expansion of the intensive luminescent area of the camera shooting and the intensity of the measuring signal are used to control the actual resulting geometrical form of the molten bath and the additional efficiency of the control. The thermal emission of the hot surface of the molten bath is obtained with a photodiode. The length of the expansion of the intensive luminescent area and the intensity is qualitatively detected by a spatially averaged signal of the photodiode. The secondary path is passed through several times and the movement of the laser beam is superimposed by optical elements, so that the welding seam and/or spot are produced with variable welding seam width over the welding seam depth. A periodically passed secondary path is provided with a semi-major axis towards the main movement and with a semi-minor axis vertical to the main movement. A galvanometer scanner with diffractive optical element is used as optical element. The laser beam axis is bent opposite to the component surface. A rotational movement of the laser beam is carried out around the laser beam axis by optical components. A rotating prism with a torus mirror is used as optical component. USE - Method for joining two components of homogeneous and inhomogeneous metallic materials by laser radiation. ADVANTAGE - The method is capable of economically, accurately and reliably joining the two components with high quality and high strength and stability in less time-consuming manner.

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