Various electric vehicle concepts have established themselves in the automotive industry with the aim of meeting legal requirements regarding the fleet emission standards, reducing the CO2 emission and the fuel consumption of passenger cars. In addition to the conventional electric vehicles, there are numerous hybrid approaches in which the vehicle is driven by a combustion engine and an electric motor, such as Plug-in-Hybird or Range Extender. What all concepts have in common is the powertrain possessing at least one electric motor, which requires different welding tasks to be performed during its manufacturing. One of these welding tasks is the joining of adjacent hairpin wires made of copper, used in the stators, realizing an edge joint. Welding such joints presents various challenges on the material and process side, which can be solved by means of electron beam welding. There are two copper materials being relevant for the applications appearing in electric traction systems: Cu-OFE and Cu-ETP. The Cu-OFE alloy is well suited for welding due to its low oxygen content. As opposed to, applying Cu-ETP entails challenges when welding due to the residual oxygen content, making this alloy poorly suitable for welding. Due to the further challenges in the welding of copper, electron beam welding (EBW) can be regarded as the predestined welding process. On the one hand, electron beam welding has a very high power density, helping overcome the barriers caused by the high thermal conductivity of the copper. Furthermore, no reflection of the incident beam takes place. On the other hand, the process offers the possibility of being able to influence the degassing conditions in a targeted manner through the relative movement between the beam and workpiece. The aim of the planned research work is to investigate and extend the knowledge about the relationships between material, welding process parameters, variants and the welding result, with particular regard to the joint cross-section, porosity, spatter formation and contact resistance, fundamentally on individual hairpin pairs.
