Friction Stir Welding - Process advantages

The process advantages result from the fact that the FSW process (as all friction welding of metals) takes place in the solid phase below the melting point of the materials to be joined. The benefits therefore include the ability to join materials which are difficult to fusion weld, for example 2000 and 7000 aluminium alloys. Friction stir welding can use purpose-designed equipment or modified existing machine tool technology. The process is also suitable for automation and adaptable for robot use. Other advantages are as follows:

Low distortion, even in long welds
Excellent mechanical properties as proven by fatigue, tensile and bend tests
No arc
No fume
No porosity
No spatter
Low shrinkage
Can operate in all positions
Energy efficient

Non-consumable tool
One tool can typically be used for up to 1000m of weld length in 6000 series aluminium alloys
No filler wire
No gas shielding for welding aluminium
No welder certification required
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 >50mm thickness in one pass.

The limitations of the FSW process are being reduced by intensive research and development. However, the main limitations of the FSW process are at present:

Workpieces must be rigidly clamped
Backing bar required (except where self-reacting tool or directly opposed tools are used)
Keyhole at the end of each weld
Cannot make joints which required metal deposition (e.g. fillet welds)

TWI invented the process in 1991 and has obtained patents: see FSW - Intellectual Property Rights.