Operating Principle

 Distortion Comparison

Comparison of Microstructure

          Friction stir welding, a process invented at TWI, UK.  Friction stir welding uses a rotating cylindrical shouldered tool with a pin that is slowly plunged into the work pieces to be joined (the figure alongside shows a butt weld). Frictional heat is generated between the welding tool and the work piece. The tool is wear resistant and is of a much harder material than the work piece. This heat causes the work piece material to soften without reaching the melting point. The rotation of the tool heats up and plasticizes the materials it is in contact with, and as the tool moves along the joint line the material from the front of the tool is swept around this plasticized region from to the back, thus forming a welded joint. 

Friction Stir Welding is a solid state energy efficient joining technique with several advantages.

Process Advantages:

1. Solid State Welding Process

   • No melting of base metal

   • No loss of alloying element

   • No fumes or spatter

2. Can easily weld

   • 3D seam

   • Butt, Lap, T-Joint etc.

3. Simple Process

   • No shielding gas

   • No consumables (filler wire)

   • No surface treatment

Unique features of FSW:

• Very low distortion

• No porosity or solidification cracking

• Weld region has a fine grain structure than the base metal

• Excellent Mechanical properties (strength, elongation, etc.)

Linear FSW

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