Friction Stir Welding (FSW)

During the last ten years Sapa has invested a lot in Friction Stir Welding (FSW) – a friction welding technique developed and patented by the Welding Institute in Great Britain. In 1996, as the first company in the world, Sapa started production on industrial scale using FSW as a jointing method. Today we are a world leader in the area of industrial use of FSW and we can offer our customers panels that are up to 14.5 metres long and 3 metres wide.

FSW is a method that makes it possible to weld components with high requirements as regards compression strength and tightness. The method allows the production of wide panels, such as, for example, roofs or walls for trains that are difficult or impossible to extrude. The jointing of elements takes place in solid state. A rotating tool creates pressure and friction heat on the weld interfaces which makes the metal mix together and for a joint of the best quality. The temperature of the material next to the joint reaches 500°C as a maximum for some fractions of a second and then the material cools down quickly. The low temperature makes that the melting pint is not exceeded, which happens in conventional friction welding.

The FSW method has proved to give joints with high strength values without inclusions or impurities. Tensile tests have shown that the welds are almost entirely stress-free. Det Norske Veritas, that has checked the joints in, among other things, bending tests and x-ray examination, has approved the process for demanding solutions in railway and marine applications.

FSW greatly improves the working environment. The welding light, smoke and formation of ozone are eliminated completely. Steel brushing, grinding and intermediate bead cleaning are not necessary either.

Some advantages of Friction Stir Welding:

A simple process that gives completely void-free, tight joints with high strength. Minimal influence of heat on the material. Only small heat stress in the material and flat surfaces.  Good mechanical properties. The production process involves few, easily controlled variables which allows tight tolerance values. Ensures good working environment.

Joining of aluminium by FSW is obtained by plunging a quickly rotating tool into the weld interface and moving the tool along the joint. The rotating tool produces high friction heat and causes a severe plastic deformation of aluminium. The strong mechanical influence under high pressure from the tool pushes the weld interfaces together and a homogenous structure is formed. 

More Information about FSW

• General information about FSW (Pdf file, 761 KB)
• Depth information about FSW (Pdf file, 234 KB)