Characteristics of plasma plume and effect mechanism of lateral restraint during high power CO2 laser welding process

A novel lateral restraint method was proposed to suppress plasma plume of high power CO2 laser welding using a pair of copper blocks with cooling water. The plasma plume was observed with a high-speed camera, and its core zone and periphery zone were investigated based on the specific processing algorithm. With the specially designed shifting unit, the spectrum of plasma plume was scanned both in 1-D and 2-D mode. Based on the selected spectral lines, electron temperature and electron number density of plasma plume were calculated. The characteristics of plasma plume, as well as the restraint mechanism, were discussed both in 1-D and 2-D mode. Results showed that the cooling effect, blowing effect and the static pressure were enhanced by the lateral restraint, and the restraint effect of the near-wall low-temperature area limited the expansion of plasma plume greatly.