Laser Welding of Zinc Coated Steel Without a Pre-set gap

The major problem during laser welding of zinc coated sheet steel in an overlap configuration is the zinc vapour produced at the interface between two sheets. The vapour tends to evacuate through the keyhole and melt pool, particularly when no gap is present between the overlapped sheets. This causes process instabilities and results in the formation of pores and severe undercut. The aim of this work is to build an understanding of the material behaviour, particularly the zinc behaviour when welding zinc coated steels in overlap configuration without a pre-set gap. The interaction between zinc vapour and welded materials was investigated mainly by experimental approaches. Questions concerning when and how stable welds can be obtained are answered by introducing a mechanism describing the dynamic balance between the zinc vapour, the keyhole and the weld pool.Materials Science & EngineeringMechanical, Maritime and Materials Engineerin