2003 年 21 巻 2 号 p. 213-218
Welding of aluminum alloys (Al-Mg and Al-Mg-Si series) was performed using 2-kW and 3-kW continuous wave Nd: YAG lasers. Two beams were delivered by optical cables 0.6 mm in diameter and focused on the surface of the specimens as twin spots. Overlap joints of 2-mm-thick sheets were made at various welding parameters, including beam distance, beam arrangement and welding speed. The quality of the bead, including its appearance and macrostructure, and the tensile strength of the joints were investigated. At a shorter beam distance of 0.36 mm, the weld bead surface was humped, making it unacceptable in terms of quality. Sound weld beads were obtained at beam distances of 0.6 mm and 1.0 mm. As the beam distance increased, the penetration depth became shallower. At a beam distance of 1.0 mm, the area of fusion zone was too small to provide sufficient strength. The influence of the beam arrangement on penetration depth became larger with a longer beam distance. With inline beam welding at a longer beam distance, the penetration depth became much shallower than cross beam arrangement. In both beam arrangement, twin spot beam with beam distance of 0.6 mm provides higher and stable strength for lap joint of 2 mm-thick aluminum sheets.