Keyhole bottom separation in two beam Nd–YAG laser welding

Abstract

A pair of Nd–YAG laser beams transmitted through optical fibres from two oscillators have been condensed separately and combined at a single point on the workpiece in order to enhance welding ability. Bead on plate tests were carried out with symmetric arrangements of condensing optics in two different welding directions. Transition from penetration with one keyhole bottom to penetration with two bottoms occurred as the laser power increased when the angles of incidence of the laser beams were 30 or 45°. No transition occurred at 15°. Melting efficiency increased dramatically at the transition power, the transition conditions being determined by laser power and heat input.