Experimental filling friction friction stir welding of exit hole and numerical simulation-A Modified technique to apply practically for pipe AA5456

Filling Friction Stir Welding (FFSW) is a solid state joining process which uses a rotating tool consisting of a shoulder and a semi-consumable pin. One of its applications is preventing from forming an exit hole at the end of the Friction Stir Welded samples. It is important to choose the appropriate tool design and welding parameters in order to fill exit hole for a given situation. A tree dimensional (3D) model is developed using finite element (FE) commercial code DEFORM 3D/Implicit. In the present study, 7.5mm thick AA5456 rolled plates and pipes were successfully welded by FFSW without Exit-Hole using a semi-consumable similar pin (5456) and semi-consumable dissimilar pins (7075 & 2024) on lap joint specimens. The influences of the pin material, pin geometry, rotation speed (rpm) and plunge velocity (Z axis speed) on the mechanical properties of the joints were investigated. Microstructure of the joints, especially at the interface, was examined by SEM and optical microscopy. The optimized process parameter for AA5456 was obtained by tool rotation speed of 800 rpm, plunge velocity of 50 mm/min, similar cone angle pin of 8o. The hardness profile of the welds exhibited a W-shaped appearance in processes and the minimum hardness was measured in the HAZ. Radiographic, Pneumatic and Hydraulic tests was done in order to verify the ability of being used in the industrial applications. Results showed that the strength of filled Exit hole is 7% higher than the strength of the joint with the non-filled exit hole.

Keywords:

Filling Friction stir welding , consumable pin , exit hole , Lap joint , AA5456