Design, Fabrication and Testing of Friction Stir Welded Joints

摘要

Friction-stir welding (FSW) is a solid-state joining process that uses a third body tool to join two faying surfaces. Frictional heat between the welding tool and the work pieces causes the latter to soften without reaching the melting point, allowing the tool to traverse along the weld line. It then mechanically intermixes the two pieces of metal at the place of joint; the softened metal can be joined using mechanical pressure (which is applied by the tool), much like joining clay or dough. In this project, CNC Milling Machine is used to weld the parts together. The parts being welded are made up of dissimilar materials like Aluminum and Copper. The rotational speed is varied from 900 rpm to 1500 rpm while the welding speed is kept constant at 25 mm/min. The other parameter involved is the axial load, which reaches 200 bars. The dimensions of the parts are (100mmx50mmx3mm) which are welded to form a butt joint. The effect of different tool pin profiles on the quality of the welded joint is also studied for welding. Different tool pin profiles considered are threaded, taper, circular/round and square. The tools are designed using Pro/E and are manufactured on a Lathe machine. After the parts are welded, various practical tests are performed on the welded parts that include the tensile strength, microstructure study and the Vickers’s hardness test. The experimental results proved that the highest tensile strength of the welded joint i.e., 81.073 N/mm2 was achieved with the threaded tool profile at speed 900 rpm with feed 25 mm/min and the highest hardness value of 267HV was achieved with the round tool profile at 1500 rpm and feed of 25 mm/min.