Abstract
Copper is very difficult to be spot welded by conventional fusion welding techniques
due to higher thermal diffusivity. Friction stir spot welding (FSSW) is a novel solid state
welding process which is suitable and competent to spot weld copper. Commercially pure
copper sheets of 3 mm thickness were spot welded by FSSW using industrial friction stir
welding machine. The spot welds were made by varying the tool rotational speed at three
levels. The spot welds were characterized using optical microscopy. The shear fracture load
was evaluated using a computerized tensile testing machine. The results revealed that the tool
rotational speed remarkably influenced the microstructure, shear fracture load and mode of
fracture.