The coupling mechanisms in the CO2 laser welding of copper

The CO2 laser is a potentially powerful tool for welding, allowing high integrity joints to be produced with minimal thermal damage and high joint completion rates. Its use in the joining of reflective, high conductivity materials, such as copper is, however, limited. The current work examined the high power CO2 laser welding of oxygen free high conductivity copper and in particular the coupling mechanisms which appear to control the consistency of the process. The role of the plasma control jet was found to have a fundamental influence on the coupling behaviour. Due to the practical problems of direct observation of the jet gas flow during welding, the process was modelled using a flow simulation package. The results of the simulation enabled a satisfactory theory for the coupling mechanism to be developed. Plasma plume formation and maintenance during the welding process appeared to be responsible for coupling and to occur by a non-conventional mechanism. The theory explains the anomalies in previous work and indicates how the process consistency may be improved.