The process developed by Laser Zentrum Hannover and its partner scientists in the Joining and Cutting of Metals group of the MESCHLAS project eliminates intermetallic phases in large scale metal foam sandwiches. The process uses a transportable axis system and a mobile diode laser, provided by Scientific and Efficient Technologies and LASER on demand. It was tested on a gear unit foundation at Blohm + Voss Naval.
Intermetallic phases are prevented by first removing the aluminum foam that adheres to the top sheets of the panel, which are made of steel. The components are then positioned exactly, so there's no gap. Using conventional spot welding, panels are fixed, and the butt welds and fillet welds are laser welded, using a diode laser with a wavelength between 900nm and 1,030nm and an output of 5kW. The team's tests show that continuous weld seams are possible and a gap as small as 0.6mm can be bridged. Speeds of 0.2 m/min to 1.5 m/min could be achieved depending on material thicknesses, which were up to 5mm.
The group's partners include the Fraunhofer Institute for Machine Tools and Forming Technology (IWU), Blohm + Voss Naval, and Precitec Optronik. The larger MESCHLAS project's goal is to achieve lightweight construction using sandwich technology, including materials and processes. Its financial support comes from the Federal Ministry of Economics and Technology.