Over the last 10 years, friction stir welding has been considered one of the most important innovations in the field of welding. It is a solid-state joining procedure that is versatile, environmentally friendly and effective in terms of energy consumption. So, what is friction stir welding? Friction stir welding is a contact welding procedure that uses the heat generated by friction to fuse two different materials together. This joining method does not use any consumables in the process.
In stir friction welding, the welding machine rotates to create friction. The heat generated by the friction is then used to make the weld. Friction stir welding requires specially developed equipment. The equipment rotates at high speed over the joints that you weld together. As the equipment rotates at high speed over the metal, heat is generated. You can use friction stir welding in welding two types of joints: butt joints, and lap joints. The welding tool used in this welding process consists of two parts. It has a cylindrical part called the shoulder, which acts on the weld. In addition, there is a pin that extends from the shoulder.
First, the pin is introduced into the seam to hold the shoulder in place. The shoulder is then rotated on top of the workpiece. It gives it enough time to generate the optimum temperature and allow it to be engulfed by the material. Once this is achieved, the device moves across the weld, creating an uninterrupted weld. Here, the softened particles are "stirred" by the pins to melt them together. This is where the procedure derives its name from "friction stir welding". Due to the increased contact temperature, three types of reflow are generated in the material. The three types of reflow are the thermochemically affected zone, the weld nucleus and the heat affected zone. The nucleus is a pool of molten metal that has cooled and solidified into a circular joint. The thermomechanically influenced zone is the zone of exclusion created in friction welded joints. It is the transition zone located between the stir zone and the heat-affected zone. The area where the base material is not melted is called the heat affected zone. However, the properties and microstructure are influenced by the heat-intensive cutting operation.
The stir friction welding process is mainly used in industry to join all grades of aluminium alloys, whether cast, rolled or extruded. Depending on the alloy grade and capacity of the stir friction welding machine, stir friction welding has been proven to weld aluminium alloy butt joints with thicknesses between 0.3 mm and 75 mm in one pass.
Other materials that have been combined with Friction Stir Welding include magnesium, titanium, copper, nickel and steel alloys, while plastic and metal matrix composites (MMC) have also been explored. Friction stir welding has also been shown to join different combinations of these materials, including aluminium and steel. Friction stir welding has been used in a variety of FSW products in industries ranging from aerospace to shipbuilding and railways to electronics, such as the EV battery tray FSW.