The influence of various factors on the geometric profile of laser lap welded T-joints

Abstract

The effect of processing parameters, assembly parameters, and plate thickness on the weld bead geometry was examined, and the microstructure and microhardness of the typical joints were investigated in this paper. There are two kinds of welds, these are the Y-type and V-type welds in different heat input. Heat input has a small effect on bead width at the interface when the thickness of face plate is more than 3 mm. The variation of bead geometry is little when gap and offset size is small, while porosity or depression forms with increasing gap and offset. Plate thickness exerts a remarkable effect on the bead width at interface, and a big bead width at interface can be achieved by adopting thin face plate. The centricity of the laser beam is a big problem in laser lap welding T-joints with thin core plate, while bead width at interface is small in laser lap welding T-joints with thick face plate. Microstructure of heat-affected zone and fusion zone is composed of lath martensite and bainitic ferrite. Microhardness of fusion zone is lowest due to the coarse lath martensite. The desired bead geometry of laser lap welded T-joints can be produced by adopting low welding speed, thin face plate, and small gap.