2020 年 61 巻 2 号 p. 276-281
Friction stir welding is a relatively new welding process that provides advantages over conventional fusion welding processes including the possibility of joining non-fusion-weldable alloys, reducing distortion, and improving their mechanical properties. In the present study, the effects of the tool pin surface geometry on heat transfer and material flow during friction stir welding were investigated. Tapered cylindrical tool pins made of H13 hot work tool steel with and without grooves were used in experiments to join AA6061 aluminum alloy plates at a tool rotation speed of 1800 rpm and transverse speed of 50 mm/min. The changes in workpiece temperature during the process were recorded using K-type thermocouples embedded at four locations. From the experiments, it was found that welds made with the grooved tool pin exhibited better mechanical properties such as tensile strength and microhardness owing to enhanced material flow. It was also observed that the grooved tool pin generated less heat; this could be the reason for the superior properties of the welds it produced during joining processes. From the experiments, it was found that welds s formed by the tool pin with grooves showed better mechanical properties than those formed without grooves, owing to the enhanced material flow. Moreover, the welding strength was improved by using the tool pin with grooves. It was also observed that the tool pin without grooves generated more heat than that with grooves, which could be the reason for the inferior properties of the welds produced using the grooved pin.
