Analytical modelling for thermal field simulation in laser beam welding (Modellazione analitica per la simulazione dei campi termici nella saldatura al fascio laser)

In the present work an analytical method is proposed in order to evaluate the thermal fields generated during a laser beam travel on thick plate, with the aim of developing a less complex approach from the point of view of calculation if compared to the various numerical models developed in recent years. The "keyhole" full penetration welding mode, characteristic of the high power laser, was simulated, considering the phenomenological laws of conduction, by means of a line thermal source along the whole thickness and two point sources located respectively on the surface and at the position of the beam focus inside the joint. This model was fitted on the basis of the fusion zone profile, which was experimentally detected. Welding was carried out by means of a CO2 laser beam single pass on two squared edged AISI 304L plates, which were butt-positioned. Then the model was applied to evaluate the thermal fields, the fusion zone composition and the solidification mode.