An analysis of the laser-plasma interaction in laser keyhole welding

In penetration welding with a laser, a plasma is formed in the keyhole. In the energy exchange process it is to be expected that a substantial part of the power is absorbed directly at the walls of the keyhole, but another exchange mechanism is the interaction of the laser beam with the plasma. A simple model of this part of the process is described and its properties are investigated. It is found to be consistent, and estimates are obtained for the parameters. The existence of a linking intensity is deduced. This relates the power absorbed by the workpiece per unit thickness of the workpiece to the laser power available at each cross section of the keyhole.