These days, focus of researchers is more on developing high-speed and environment friendly technology in manufacturing techniques and this include friction stir welding. Friction stir welding is a solid state joining process used for applications where the original melt characteristics must remain unchanged as far as possible. It was discovered in December 1991 and experimentally proven by Wayne Thomas and his team at welding institute in UK. A rotating, non consumable welding tool is used in FSW to soften the work material by producing heat due to friction and plastic work, thus permitting the tool to stir the joint surfaces. The weld is formed at temperatures below the melting temperature the workpiece. This technique has been It is the process of joining of metallic components of similar or dis-similar material with the help of a cylindrical rotating tool. After the tool put into the rotation, due to friction between tool and workpiece, heat is generated which softens the material around the tool probe. The localized plastic deformation process occurring in the workpiece due to friction. The plastic deformation occurs at higher temperature, but lower than the melting point temperature of the workpiece. The tool softens both the components around the interface and mixes the softened material from both the components around the interface to provide bonding. On cooling a solid phase bond is created between the Tool Rotation and Traverse Speeds There are two tool speeds to be considered in friction-stir welding; tool rotational speed and tool traverse speed. In general, it is said that by increasing the rotation speed or decreasing the traverse speed will result in a sound weld. In order to make a successful weld it is fundamental that the material incorporating the tool is adequately hot to enable the wide plastic flow required and minimize the forces acting on the tool. If the material is too cool then voids or other flaws may be present in the stir zone.
Tool Tilt and Plunge Depth The plunge depth is defined as the depth of the lowest point of the shoulder below the surface of the welded plate. Plunging the shoulder below the plate surface increases the pressure below the tool. The plunge depth needs to be correctly set, both to ensure the necessary downward pressure is achieved and to ensure that the tool fully penetrates the weld. An excessive plunge depth may result in the pin rubbing on the backing plate surface or a significant under match of the weld thickness compared to the base
