A mathematical model has been developed in order to describe theoretically the behavior of the zinc vapors during the laser spot welding of zinc coated steel in lap configuration. The variables considered are laser pulse duration, weld width, sheet thickness and thickness of the zinc coating. The low evaporation point of zinc compared with the high melting point of steel produces deleterious effects during laser welding. It has been shown that if a proper gap is maintained between the sheets a good quality weld can be obtained. A model has been developed for the case of a single spot weld assuming transient conditions. This enables an accurate determination of the weld parameters for the lap joint.
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