1999 Volume 17 Issue 2 Pages 209-215
Two Nd:YAG laser beams were condensed separately and combined at surface of workpiece in order to increase weld penetration depth. Welding characteristics were evaluated by penetration depth and penetration shape in bead-on-plate tests. Transition from penetration with one bottom to penetration with two bottoms occurs as function of welding condition. Penetration with two bottoms might be a sufficient evidence in favor of keyhole bottom separation. A close study of keyhole bottom separation is necessary to understand the increase of weld penetration by multiple laser beams combined. This paper is intended as an investigation on factors of keyhole bottom separation. The authors found that factors of keyhole bottom separation are angle of incidence of laser beams, laser power density, heat input, distance between two laser beams on a surface of workpiece, and welding position. Keyhole bottom separation occurs under conditions determined by high power density of one laser beam and high total heat input, such as 1500 W/mm2 and 104J/cm, respectively, at angle of incidence of 30° in welding using two CW laser beams in combination.
