Achieving Low-Porosity Laser Welds in Aerospace Aluminium Alloy

Aluminium is currently the preferred material and riveting the preferred joining method for the manufacture of thin-gauge airframe structures. Although the potential of laser welding as a low-distortion alternative for such applications is recognised, questions are still being raised about the weld quality, and in particular the porosity levels, that can be achieved in aluminium. This paper focuses on the cleaning of parent material and filler material prior to welding, the use of a twin-spot energy profile in the laser beam focus and the use of a low-moisture shielding gas and shielding gas delivery, and their individual and combined influence on the presence of weld metal porosity for Nd:YAG laser welds in 3.2mm thickness 2024 aluminium alloy. The paper describes how, through careful selection of processing conditions and aforementioned factors, fully penetrating, square-edge butt welds were achievable with levels of weld metal porosity lower than those specified in the stringent weld quality class of standards relevant to the aerospace industry, including the European BS EN ISO 13919-2:2001 and the American AWS D17.1.