Friction-stir welding is an advanced solid-state joining process (the metal is not melted) which involves the use of 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. It was invented and experimentally proven at The Welding Institute UK in December 1991.

1. FRICTION STIR WELDING
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Prepared by:
Divine Sebastian
Lamar University

2. INTRODUCTION
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 Friction Stir Welding
 Unique Features
 Necessity

3. HISTORY AND DEVELOPMENT
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 Developed and patented by TWI in 1991.
 Development at a great pace thanks to the
advancements in Material Science.
 Extensively used worldwide.
 Active R&D

4. WORKING
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 Workpieces to be joined are rigidly fixed.
 Wear resistant tool of different material rotating
at high speed.
 Material becomes plastic due to friction heat.
 Rotation of tool leads to stirring and subsequent
mixing of material at the joining region below
their melting points.
 Good mechanical properties and low distortion
due to low heat input.

5. 5
 The weld produced are sometimes stronger
than the base material.

6. TOOL GEOMETRY
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Design of tool shoulders:
 Concave Shoulder
 Convex Shoulder
Design of Tool pins:
 Round-bottom cylindrical pin
 Flat-bottom cylindrical pin
 Truncated cone pin
Tool Material Characteristics:
 Wear Resistance
 Fracture toughness
 Machinability
 Coefficient of thermal expansion

7. MATERIALS
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 Materials which can be welded:
 Aluminum and its alloys
 High strength materials like steel
 Copper
 Magnesium and Zinc
 Titanium
 Tool Materials:
 Polycrystalline Cubic Boron Nitride(PCBN)
 High speed steels(When used along with milling machines)
 Hot work tool steels
 Nickel and cobalt base alloys
 Refractory metals(W, Mo)
 Tungsten based alloys

8. ADVANTAGES & DISADVANTAGES
 ADVANTAGES
 No fumes or toxic gas.
 Excellent mechanical
properties.
 Can be used to weld
materials that cannot be
welded by fusion welding..
 Dissimilar materials and
alloys can be welded.
 Excellent weld quality
 Low distortion
 Low shrinkage
 Absence of porosity
 Absence of lack of fusion
 DISADVANTAGES
 Very large forces are required
 Very rigid clamping system.
 High initial investment.
 Exit hole remains after the
tool is removed
 Low traverse rate
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9. APPLICATIONS
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 Aerospace
 Ship Building and offshore applications
 Large aluminum structures
 Railway Carriages
 Nasa’s oreon spacecraft

10. RECENT DEVELOPMENTS & CURRENT STATUS
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 Automation
 Robot Systems
 Introduction of new tool materials
 Ship building(Aluminum extensively used)
 Aerospace applications(fuel tanks)

11. CONCLUSION
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 Significance of FSW process
 Possible improvements
 Establishment in small scale industries

12. REFERENCES
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 Experimental study on the effect of welding speed and tool pin profiles on
AA6082-O aluminum friction stir welded butt joints, ‖ vol. 2, no. 5, pp.
268–275, 2010. (Patil H. S)
 Effect of tool pin profile on mechanical properties of single and double
sided FSW AA19000 (Ram Niwas Bishnoi et. al.)
 Influence of Tool Design On the Mechanical Properties and Microstructure
in Friction Stir Welding of AA6351 Aluminium Alloy (M. Karthikeyan.,
Dr.A.K.Shaik Dawood)
 Effect of tool pin profile on aluminum alloy using FSW for optimum
results by finding optimum parameters (V. Patel Chandresh)
 Friction stir joining of aluminium alloys. Bulletin, November/December
1995, (Dawes C J, Thomas W M)