Friction Stir Welding
page Introduction Process principles Weldable alloys Process characteristics Welding parameters Tools Design principles Tools for steels Retractable pin tool Bobbin tool Process speed Aluminium Application areas Aerospace Space industry Civil aviation Aerospace R&D Shipbuilding Application advances Parts and components Automotive industry Automotive applications Tailor welded blanks (TWB´s) Superplastic forming Extruders and extrusions – with special focus on rolling-stock panels Steel and other high-temperature materials Application examples Case study: Swedish Nuclear 28 30 32 32 4 6 6 7 7 7 8 8 8 10 10 13 15 15 15 16 16 18 18 19 21 22 27 27 Conclusions 46 Economics Example of cost analysis Compared to arc welding 41 42 44 Quality and enviromental aspects Environmental aspects of Friction Stir Welding Less weld-seam preparation Fewer resources Noise, an underestimated health threat Energy saving FSW process Less post-treatment and impact on the environment Friction Stir Welded components offer through-life environmental gains Quality 40 40 39 39 39 39 39 39 39 Equipment Full-scale automation for high-volume applications Modular flexibility for “standard” applications Robotised for more complex applications 37 37 37 page 37
Case study: Marine Aluminium a.s, Norway 35
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Introduction to the FSW Technical Handbook
Friction Stir Welding (FSW) was invented by Wayne Thomas at TWI (The Welding Institute), and the first patent applications were filed in the UK in December 1991. Initially, the process was regarded as a “laboratory” curiosity, but it soon became clear that FSW offers numerous benefits in the fabrication of aluminium products. Friction Stir Welding is a solid-state process, which means that the objects are joined without reaching melting point. This opens up whole new areas in welding technology. Using FSW, rapid and high quality welds of 2xxx and 7xxx series alloys, traditionally considered unweldable, are now possible. To assure high repeatability and quality when using In FSW, a cylindrical shouldered tool with a profiled pin is rotated and plunged into the joint area between two pieces of sheet or plate material. The parts have to be securely clamped to prevent the joint faces from being forced apart. Frictional heat between the wear resistant welding tool and the workpieces causes the latter to soften without reaching melting point, allowing the tool to traverse along the weld line. The plasticised material, FSW, the equipment must possess certain features. Most simple welds can be performed with a conventional CNC machine, but as material thickness increases and “arc-time” is extended, purpose-built FSW equipment becomes essential. Friction Stir Welding can be used to join aluminium sheets and plates without filler wire or shielding gas. Material thicknesses ranging from 0.5 to 65 mm can be welded from one side at full penetration, without porosity or internal voids. In terms of materials, the focus has traditionally been on non-ferrous alloys, but recent advances have challenged this assumption, enabling FSW to be applied to a broad range of materials. transferred to the trailing edge of the tool pin, is forged...