レーザ・アークハイブリッド溶接法による薄鋼板重ね溶接特性

Abstract

In recent years, laser welding has begun to be used for assembly welding of automotive bodies and parts, although it has not yet to be used widely. One restraint is that in laser lap welding, the gap between the lapped sheets must be controlled very tightly. If the gap is wide, burn-through occurs, and, if the gap is excessive, the two sheets cannot be welded together. For this reason, the gap is generally restricted to 0.2 mm or less for laser welding. Laser lap welding of zinc-coated sheets poses additional problems. When lap welding of zinc-coated sheets is performed without any gap, the zinc evaporated between the sheets tends to blow off weld metal, or the zinc vapor tends to remain in the weld metal and form blowholes. Laser-arc hybrid welding was developed to solve these problems. This newly developed welding method maintains the features of laser welding, in that it is highly efficient and does not cause much thermal deformation due to its low heat input. Its proven characteristics are as follows: (1) The gap tolerance in hybrid lap welding is nearly equivalent to the thickness of the sheets to be welded, which is significantly larger than with laser welding. (2) The hybrid lap-welded joint can attain a strength that exceeds that of the base metal, because the bead width is wider than that in laser welding. (3) In hybrid lap welding of zinc-coated steel sheets, the formation of blowholes is restrained significantly compared to laser welding, even when the gap is 0 mm, so that a sound welded joint can be obtained.