Laser dissimilar welding of copper and steel thin sheets for battery production

Laser processing of metallic thin sheets has gained undoubted industrial interest in the last decade especially due to its implications in the e-mobility field. In particular, dissimilar welding of thin sheets made of different materials, such as aluminum, copper, and steel is nowadays recognized as an effective solution for many joining applications in battery and related component production. According to these considerations, the present paper is aimed at evaluating the possibility to perform a sound joining of thin copper sheets on thin steel ones in a lap-welding configuration. This application is of particular interest especially when cylindrical cells have to be electrically connected to any of the elements constituting the battery, such as printed circuit boards, busbars, etc. By means of a continuous wave fiber laser and a galvo scanner, an experimental campaign was carried out in order to define a process window for characterizing the above-mentioned welding application. The results were characterized by means of metallographic analyses, microhardness measurements, electrical conductivity tests, and scanning electron microscopy-energy dispersive system analyses. Particular attention was placed on the role of process parameters in controlling the penetration depth on the lower steel layer, since it constitutes the external housing of the single cell and a drop through can seriously damage the cell itself.