Friction stir welding
In 1996, as the first company in the world, we started production on an industrial scale using friction stir welding (FSW) as a joining method. Today, we can offer customers aluminium panels that are up to 18 meters long and 3.5 meters wide.
Some advantages of friction stir welding:
- A process that results in completely pore-free, tight joints with high strength
- Minimum heat influence on the material, with small heat stress only in the material and flat surfaces
- Good mechanical properties, with few, easily controlled variables, allowing tight tolerances
FSW is a method that makes it possible to weld components with high compression strength and tightness requirements. The method allows the production of wide panels, such as roofs or walls of trains, which are difficult or impossible to extrude.
The joining of elements takes place in solid state. A rotating tool creates pressure and friction heat on the joined surfaces so that the metal is mixed together and forms a top quality joint. The temperature of the material next to the joint reaches a maximum of 500 °C during some fractions of a second and then falls quickly. The low temperature ensures that the melting point is not exceeded, which is the case in conventional friction welding. FSW significantly improves the working environment, because welding light, smoke and ozone formation are eliminated. Steel brushing, grinding and intermediate bead cleaning are not required.
The FSW method provides high-strength joints without inclusions of impurities. Tensile tests show that the welded joints are almost completely free from stress. Det Norske Veritas has conducted bending and X-ray tests of the joints and approved the process for complex solutions in railway and marine applications.
Joining aluminium by FSW
The joining of aluminium by FSW is based on a quickly rotating tool that is inserted into the joint and moved along it. The rotating tool generates high friction heat and causes a heavy plastic deformation of aluminium. The strong mechanical influence under high pressure from the tool presses together the weld surfaces forming a homogenous structure.