Microstructure and mechanical properties of friction-stir welded St52 steel joints

Abstract

The aim of this work is to investigate the mechanical properties and microstructures of friction-stir welded (FSWed) St52 structural steel joints. in this study, St52 steel plates with a thickness of 4 mm were butt-welded by friction-stir welding (FSW) using a tungsten carbide tool having a conical pin. the microstructure of the welded zone consists of equiaxed fine ferrite, grain boundary ferrite, Widmanstatten ferrite, and aggregates of ferrite + cementite. the microhardness measurements showed that the hardness of the welded zone was significantly higher than that of the base metal. the FSWed St52 joint exhibited a significant strength overmatching in the weld region and a strength performance similar to or slightly higher than that of the base plate.