Tool Designing for Friction Stir Welding Variants

The shoulder and probe are the major components of the rotating tool of Friction Stir Welding (FSW) technology. When it comes to producing a high-quality weld connection, tool design is crucial. The key design elements that substantially impact weldment quality and microstructure are pin length, pin diameter, shoulder diameter, shoulder profile, pin profile and surface features. A friction stir welding tool can be a fixed (conventional tool, conventional bobbin tool, conventional friction stir spot welding tool, pinless tool) or adjustable (floating bobbin tool, adjustable gap/double reacting bobbin tool, refill friction stir spot welding tool) type. Pin profiles such as square, hexagonal, cylindrical, threaded, and tapered affect the grain size and structure, hardness, heat generation and appearance of the weldment. Concave, convex, and flat shoulder profiles affect particle distribution and microstructure. The weld joint quality is determined by the combined effect of the pin and shoulder profile. This paper reviews the effect of various pins and shoulder profiles on friction stir welded joints. Empirical relationship between pin diameter, shoulder diameter and sample thickness as well as most commonly used dimensions for tools have been presented in the paper.