Product Code: ICA13_1506

Multi-Pass-Narrow-Gap-Laser Beam-Welding of Hot Crack Sensitive Thick Aluminum Plates
Authors:
Renald Schedewy, Fraunhofer Institute for Material and Beam Technology; Dresden Germany
Berndt Brenner, Fraunhofer Institute for Material and Beam Technology; Dresden
Dirk Dittrich, Fraunhofer Institute for Material and Beam Technology; Dresden Germany
Eckhard Beyer, Fraunhofer Institute for Material and Beam Technology, University of Technology Dresden; Dresden Germany
Presented at ICALEO 2013

Heat treatable aluminum alloys are one of the most important materials for light weight constructions of the modern economy. They combine very high specific strength and excellent corrosion resistance. Furthermore they are perfectly suitable for forging, extrusion and rolling. That provides a wide range of application fields of high loaded light weight constructions. However, a large variety of semi-finished products have to be welded in the final construction. Here an important current process limit for laser beam welding is the thickness of the aluminum sheets. And even though the limits currently have been extended with the availability of multikilowatt lasers, some of the limiting issues are still present because of physical reasons of aluminum like the high heat conductivity, the large heat capacity and the high thermal expansion coefficient. Especially for deep penetration welding the insufficient dilution of filler wire into the root of the weld seam is rising with the material thickness. This point causes an increasing risk of hot cracks and weld seam under matching.

This paper presents a welding technique for welding sheet metal of substantially wall thicknesses which can overcome the mentioned problems. It uses beam sources with multimode or single mode beam quality which can perfectly inserted into a weld groove with a high aspect ratio of an average gap size of 2-3 mm. In that way a multiple layer welding for sheet thicknesses up to 50 mm can be realized by using economically low laser power. An improved melting of the wire and a good gap bridging capability could be achieved by a beam scanning technique. This provides high process reliability and ensures the homogeneous mixture of the alloying elements with the base material to obtain multi layer weld seams with high strength and without welding defects.