Researchers at the Fraunhofer Institut für Lasertechnik (ILT; Aachen, Germany) have, in what they believe is a first, succeeded in deep-penetration welding a 2-mm stainless-steel sheet. Until now, laser-diode welding has been restricted to ordinary welding by melting, which leads only to superficial, pot-shaped seams with an aspect ratio (depth/width) of typically 0.5. Conversely, deep-penetration welding, as achieved by CO2 and Nd:YAG lasers, is very useful for generating deeply welded connections with improved mechanical solidity and, in comparison to welding by mere melting, a reduced heat-affected zone.
Welding depths up to 6 mm were reported in more recent samples, achieved by applying a 2.5-kW, broadband 900-nm laser diode (Rofin Sinar; Hamburg, Germany). Thus, the ILT team expects rapid development in laser-diode deep welding. Improvements should come in the form of better beam shape and controlled processes, including control of the gas supply.