Friction stir welding - the method
Friction stir welding (FSW) is a welding process without any added filler material. It uses frictional heating to soften the pieces of material being joined in such a way that they merge without melting into a liquid state. Two workpieces are butted together and then a hard, rotating tool with a special tip profile – with a pin and a shoulder – is pressed into the joint and travels along its length. The heat produced under the shoulder of the tool plasticizes the material without reaching the melting point. The material flows around the rotating pin and becomes consolidated into a homogeneous mass, forming a strong joint on cooling.