Removing approach for flashes of friction stir spot welds

A friction stir spot welding tool with a threaded probe and a flat shoulder was made to join 6061-T6 aluminum sheets under various indentation depths, rotational speeds, indentation rates and dwelling times. Two types of flashes, ring-shape and petal-shape, were found and their forming processes were identified. A concept of combining friction stir spot welding and end milling was proposed to make welds and remove flashes simultaneously. Pictures and micrographs were examined to study the effects of processing parameters on the flash thickness, height, and type, and to obtain the maximum flash thickness/cutter width for tool design. Based on experimental results, a welding tool with two flash-removing cutters was developed to remove flashes during welding. The mechanical properties of friction stir spot welds with and without flashes are further examined to evaluate the performance of the proposed welding tool.