Solidification features of the thin steel sheets in keyhole welding

Stability of the weld pool during laser keyhole welding depends on a number of interrelated physical phenomena. Understanding these phenomena is essential for good control of the welding process. A considerable body of theoretical work has been published concerning identification of the keyhole and weld pool dynamics in penetration laser welding of thin steel sheets. The present paper describes a method for obtaining information about weld bead formation. This technique provides data about the three dimensional shape of the weld pool and has been used to reconstruct the weld pool in 0.75 and 1.2 mm sheet steel. The method has been used to identify different keyhole penetration modes and reveal differences in weld pool solidification for specified thicknesses. Solidification rates in different regions of the weld pool have also been calculated and presented. This study provides a methodology that can be used to support modelling of weld pool formation during laser keyhole welding.