A pinless embedded tool used in FSSW and FSW of aluminum alloy

A pinless tool design was proposed to achieve high butt tensile strength in aluminum alloy sheets (∼3 mm thick) in friction stir welding (FSW), where a 7 mm long cylindrical insert rod made of aluminum alloy was tightly embedded into a hollow cylindrical tool. The effects of rod diameter (d) on the welding properties and mechanism of weld formation were investigated. For friction stir spot welding (FSSW), the maximum rate of temperature rise was about 12.8 °C/s, and the failure load was about 2 kN for this pinless tool (d = 10 mm), with these being about 7.4 °C/s and 1.35 kN for the plain one. For FSW, the failure load was about 1.46 kN for this tool, and about 0.72 kN for the plain one. The abutting edges of sheets with a thickness of 3 mm could be welded using this pinless tool.