In the FOLAMI project, the Laser Zentrum Hannover e.V. (LZH), together with eight partners from industry and research, wants to develop a novel method for the laser beam welding of mixed joints of steel and aluminum. In this way, they want to reduce manufacturing and production costs in shipbuilding.
To join large ship components cost-effectively and efficiently, shipyards such as Meyer Werft, which is involved in the project, use laser beam welding processes for joints of the same material. For deformable, thick-walled mixed joints of steel and aluminum, explosion welding is currently used. However, this process is complex, time-consuming, and cost-intensive, restricts the design freedom, and the resulting joint has only low strength. This mixed joint is necessary, for example, for adapters that connect aluminum ship superstructures to steel hulls.
To produce joints that meet the requirements of shipbuilders, the project consortium plans to develop a new welding method. This is intended to create a high-strength, lap-welded joint with an undercut. To achieve this, the partners plan to use two intersecting laser beams. They also expect the approach to increase the formability of the component.
In the sub-project "Laser beam welding of form-fit steel-aluminum mixed joints through weld penetration depth control" of the LZH, the scientists want to develop the form-fit and material-fit welding process of mixed joints and also apply the analysis of spectral process emissions. In that way, the weld penetration depth, and thus also the microstructure and the proportion of intermetallic phases shall be regulated. Thus, plate thickness jumps, material batch changes, or surface differences shall be compensated.
Based on the results of the LZH, B.I.G., Coherent and Precitec Optronik GmbH intend to jointly develop an innovative laser processing head for welding depth-controlled laser beam welding. For the new welding method, they will both analyze the spectral process emissions and further develop the welding depth control based on short-coherence interferometry. In addition, the LZH, in cooperation with the semi-finished product manufacturers LASER on demand and Hilbig, will accompany the welding tests in an environment similar to the shipyard. During the project, the laser-welded semi-finished products will be evaluated by Lürssen Werft and Meyer Werft, among others, so that the process can be quickly implemented on an industrial scale. Parallel to the process development, Fraunhofer LBF will evaluate the fatigue strength of the joints through experimental investigations and, on this basis, derive a simulation model for estimating the (cyclic) seam properties.
In addition to the Laser Zentrum Hannover e.V., B.I.G. Technology Services GmbH, Coherent (Deutschland) GmbH, Fraunhofer-Institut für Betriebsfestigkeit und Systemzuverlässigkeit LBF, Hilbig GmbH, LASER on demand GmbH , Fr. Lürssen Werft GmbH & Co. KG, MEYER WERFT GmbH & Co. KG and Precitec Optronik GmbH are involved in the project „FOLAMI - Form-fit laser beam welding of the mixed joint of steel and aluminum for serviceable semi-finished products in shipbuilding". It is funded by the German Federal Ministry for Economic Affairs and Energy (BMWi) as part of the "Maritime Research Program" under the technical supervision of Forschungszentrum Jülich GmbH (PtJ) (grant number: 03SX547B).