Product Code: ICAL05_307

Hybrid Bifocal Laser Welding of Aluminium
Authors:
Andreas Trautmann, Iwb Technical University of Munich; Garching Germany
Michael Zaeh, IWB, Technical University of Munich; Garching Germany
Presented at ICALEO 2005

This paper renders the welding of extruded aluminium by a hybrid bifocal laser system. The aluminium alloy considered is EN AW-6060 (AlMgSi0,5) temper T66 without and with filler wire Al4047 A (SG-AlSi12). The hybrid laser system consists of a combination of an Nd:YAG laser with a high power diode laser (HPDL), both of 3 kW maximum output power. The beam parameter product (BPP) of the employed Nd:YAG laser of 25 mm*mrad translates with an optical system of focal length f = 150 mm into a circular focus of diameter 0.45 mm whereas the BBP of the HPDL of 85 x 200 mm*mrad can achieve a rectangular focus of 0.9 x 3.7 mm. This paper presents research into the fundamentals governing the melt pool dynamics of the resulting superposition of keyhole by conduction mode welding and assays the ramifications in aluminium welding by avail of exemplary butt joints in 2 mm thick plate specimens. The phenomena considered are the dissolution of the surface oxygen layer, the influence of different inert and active shielding gas mixtures. By comparing the results attainable by bifocal laser hybrid welding to the constituent laser processes synergetic effects of the laser hybrid can be demonstrated. These are namely the doubling of the welding speed from 2.0 m min-1 to 3.75 m min-1, the reduction of the roughness of the weld surface from 60 ?m to about 10 ?m and the increase in energy transfer efficiency. The experimental investigations verifying these synergies are outlined and discussed.