Energy Transfer Modes in Pulsed Laser Seam Welding

A systematic parametric study has been made in pulsed Nd:YAG laser welding to understand the energy transfer modes. Four different energy transfer zones, namely conduction, transition, penetration, and keyhole, have been identified. The traditional classification of energy transfer modes based on the power density value of 10⁶ W/cm² is not strictly applicable as the transfer mode varies with pulse duration. The threshold power density to form keyhole is not constant, but the threshold energy density has been found to be invariant around 2.4 kJ/cm². The pulse duration has been optimized to be of about 8 ms to achieve welds of higher aspect ratio.