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The zinc-coated steel sheets are the indispensablebasic metal materials for car body.However.the zinc coatings with 10W boiling point andvapor expand effect which have anegative influence in weld pooI during laser lapwelding.are the roadblock hold backingthe application ofadvanced laser welding technologyespecially in automotive industry.
In this paper based on admitting a prerequisite thatthe Zn needs time to complete phasechanges(solid-liquid-gaseous state)as welI as thetransfers of heat and mass，theexpelling behavior ofthe Zn and the criticaIlaserwelding conditions are analyzedqualitatively by observing the expelling statusofzinc vapor and correspondingmorphologies of weld seam.The experimental resultsindicate that,the all of Znexpelling phenomena belong to intermittent expellingmode and quasi.continuousexpelling mode.The available laser weldingconditions lcad to the laminar flow statedominanted in welding pool and the quasi.continuousexpelling mode.In this case.theMarangini effect has a critical function to transferthe Zn arrive the interface betweenmelt and atmosphere with a best velocity and shortesttrip then expel out from weldingpool before the Zn formed a breakage blast in weldingp001.The related experiments andanalyses are presented in this paper.