Sheet gap control by laser preheating before laser welding on lap joint of galvannealed steel sheets and its effect on weldability

Abstract

Recently, remote laser welding has come to be used in the automobile manufacture. However, it is well known that welding defects are created depending on the gap amount during laser lap welding of galvannealed/galvanized steel sheets. Pits and blowholes occurr due to vaporization of galvannealed/galvanized coating in the case of a zero or small sheet gap, while burn-through of the upper sheet of the lap joint occurrs in the case of the large gap. In this paper, the sheet gap control process by laser preheating was investigated to avoid defect creations for both cases of the small and large gap during laser welding on the lap joint of galvannealed steel sheets. As a result, it was found that this process could control the gap between steel sheets and improve laser lap weldability of galvannealed steel sheets in both cases of the small and large gap.