DESIGN AND DEVELOPMENT OF BOBBIN FSW TOOLS FOR JOINING OF METALS

Abstract

The bobbin friction stir welding tool is a double sided friction stir welding tool. It has many advantages over conventional single sided friction stir welding tool are rectangular processed zone, zero net axial force on work piece and the problems like root defect and lack of penetration is also eliminated. Friction stir welding (FSW) is a technique used initially for welding of aluminium alloys as it is a solid state process so no melting takes place thus there is no defects of liquid state welding can be seen that are arise in the process of solidification. There is also no need of filler material in FSW so the problems regarding compositional variables are also absent and a sound joint can be produced without any metallurgical discontinuity. The bobbin friction stir welding (BFSW) procedure has further points of interest over ordinary friction stir welding in the decrease of welding powers, quicker welding, and reduce fixturing. The primary motivation behind this examination was to know the appropriate design and process variables that affect weld quality. Report starts with the definition of friction stir welding, the explanation of the process and parameters that are used in friction stir welding and the different conventional tool design and then some brief on the design of bobbin friction stir welding tool. It was purely an experimental work in which many designs at different parameters were tested until a joint was made then research was continued to optimize the parameters to get a sound weld. Design of tool pin is very important in case of friction stir welding. After selection of diameter of pin, we have to maintain a proper ratio between pin diameter and shoulder diameter to impart appropriate amount of heat during joining. A proper design is achieved by different trials at different parameters. Microstructure, metallographic and mechanical properties of the samples was studied to find out the effect of parameters used. Optimum parameters were found to be 386 rpm, 26 mm/min and zero-degree tilt angle in friction stir welding machine. Maximum strength of 164.539 MPa was obtained at this set of parameters.