Optimizing process conditions in friction stir-diffusion lap welding of aluminum alloy with cold rolled steel

This paper deals with the development of friction stir diffusion bonding between 2 mm thick 5052 Aluminum alloy and Cold rolled Steel for cladding application. The investigation focuses on the effect of process conditions on tensile-shear strength of produced lap joint by considering four independent welding parameters: Tool rotational speed, welding speed, tool axial force and tool offset in the consecutive pass. A short tool-pin was utilized to avoid tool penetration into the steel substrate and mechanical mixing between clad material and the substrate. In order to optimize the process parameters for maximum joint strength and minimize the number of tests, Taguchi orthogonal array L9 with four factors and three levels was used. Results revealed that tool rotational speed had the greatest influence on produced weld strength. On the other hand, the tool pin length or penetration depth was found to have more effect on weld strength than the axial force. Moreover, clamps' rigidity had a great impact on joint strength. For the selected material and tool, the optimum welding conditions were found to be 1000 rpm rotational speed, 12 kN plunging force, 100 mm/min welding speed and 12 mm tool offset.