In friction stir spot welding, individual spot welds are created by pressing a rotating tool with high force onto the top surface of two sheets that overlap each other in the lap joint. The frictional heat and high pressure develop yielding in the workpiece material, so that the tip of the pin plunges into the joint area between the two sheets and stirs-up the oxides. The pin of the tool is plunged into the sheets until the shoulder is in contact with the surface of the top sheet. The shoulder applies a high forging pressure which bonds the components metallurgically without melting. After a short dwell time, the tool is pulled out of the workpieces again so that a spot weld can be made about every 5 seconds. In this paper the tensile tests are studied, and the results obtained show that the rotational speed of the tool and the distance between two spot welds influences the friction stir spot welding process.
Keywords: friction stir spot welding (FSSW), rotational tool speed, spacing of spot welds, overlap length