Fundamental Experimental and Modelling Analysis of the Keyhole Front in Laser Welding

摘要

During deep penetration laser welding, a vapour capillary, called the keyhole, governs the distribution of the laser beam energy into deeper regions of the workpiece. Ultra-high speed imaging enabled to observe a wavy surface topology and its downward flow at the keyhole front. Trends were obtained from imaging and from a simplified mathematical model. The calculations have shown that the experimentally observed wavy patterns streaming down the keyhole basically cause averaging of the absorption instead of Fresnel's angle-dependency for a smooth surface, leading to opposite trends for 1 μm- compared to 10 μm-lasers. The combination of experimental and modelling analysis turned out to be advantageous for improved understanding of the laser keyhole welding phenomena.