Melt flow and microstructural characteristics in beam oscillation superimposed laser welding of 304 stainless steel

•Beam oscillation technology was applied to butt welded 304 stainless steel.•The effects of beam oscillation on weld morphology and weld defects were investigated.•The beam oscillation can increase the solidification rate, reduce the size of molten pool and refine grain size.•The content of ferrite was reduced and more skeletal ferrite was observed in the fusion zone and mechanical properties were increased.