Numerical investigation of energy input characteristics for high-power fiber laser welding at different positions

Abstract

Partial penetration welding with a fiber laser at a 9-kW laser power was carried out on 20-mm-thick plates at different positions and analyzed by both experimental and numerical methods. Experiments were carried out for four different angular positions at 1.5 m/min welding speed. All four cases showed a tail-like structure of molten pool on the top surface. The in-depth mechanisms of the energy input characteristics in fiber laser position welding for eight different positions were studied by numerical simulation using the volume-of-fluid (VOF) method. Experimental and numerical results were compared for four cases and showed fair agreement. Observation of flow pattern and bead shape revealed that gravity had little influence on bead shape and flow structure, but changed the pore structure considerably. Flow structure showed a periodic behavior which probably nullified the effect of gravity in position welding. Most of the laser rays reached the bottom of the keyhole without interruption and then multiple reflections started within the keyhole. The first five reflections inside the keyhole delivered around 70 % of the total energy.