Welding Process... Stir Welding.

FSW or Friction Stir Welding is a solid-state joining process (the metal is not melted) that uses a third body tool to join two facing surfaces. Heat is generated between the tool and material which leads to a very soft region near the FSW tool. It then mechanically intermixes the two pieces of metal at the place of the joint, then the softened metal (due to the elevated temperature) can be joined using mechanical pressure (which is applied by the tool), much like joining clay, or dough. It is primarily used on aluminium, and most often on extruded aluminium (non-heat treatable alloys), and on structures which need superior weld strength without a post weld heat treatment.

 Some advantages of FSW are as follows

  • Can weld dissimilar materials
  • Low distortion and shrinkage, even in long welds
  • Excellent mechanical properties in fatigue, tensile and bend tests
  • No arc or fumes
  • No porosity
  • No spatter
  • Can operate in all positions
  • Energy efficient
  • One tool can typically be used for up to 1000m of weld length in 6XXX series aluminium alloys
  • No filler wire required
  • No gas shielding for welding aluminium
  • Some tolerance to imperfect weld preparations - thin oxide layers can be accepted
  • No grinding, brushing or pickling required in mass production
  • Can weld aluminium and copper of >75mm thickness in one pass.
Uses And Applications.
FSW is common used for Shipbuilding and offshore, Aerospace and Automotive.

           The following picture shows a cross section of the affected zone by the welding of aluminum alloy.