Download FRICTION STIR WELDING

FRICTION STIR WELDING
Introduction
 Welding using friction as the major resource
 No filler material involved
 Welds created by,
a) Frictional heating
b) Mechanical deformation
History
 Invented by TWI in 1991 in England
 28 organizations worldwide use FSW
Friction Welding
 Heat from mechanical energy conversion
Linear friction welding
Rotary friction welding
Friction Stir Welding
Sufficient downward force to maintain
pressure and to create friction heat
Shoulder which creates friction
heat
and welding pressure
Probe which Stir the material
Rotating probe
provides friction
heat and pressure
which joins the
material
Sufficient
downward force
to maintain
pressure and to
create friction
heat
Microstructure Analysis
A. Unaffected material
B. Heat affected zone (HAZ)
C. Thermo-mechanically affected zone (TMAZ)
D. Weld nugget (Part of thermo-mechanically affected zone)
Microstructure analysis
Optical micrographs of regions (a), (b) and (c) of the stir nugget.
Joint Geometries
It can be used in all positions,
Horizontal
Vertical
Overhead
Orbital
Material Suitability
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Copper and its alloys
Lead
Titanium and its alloys
Magnesium alloys
Zinc
Plastics
Mild steel
Stainless steel
Nickel alloys
Welding Steel using FSW
Tools Parameters
Common Tools
Self Reacting Pin Tool
Adjustable Pin Tool
Fixed Pin Tool
Retractable Pin Tool
Some of the FSW Machines
ESAB SuperStir TM machine FW28
ESAB Machine
Advantages
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Diverse materials: Welds a wide range of alloys, including
previously un-weldable (and possibly composite materials)
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Durable joints: Provides twice the fatigue resistance of fusion welds.
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Versatile welds: Welds in all positions and creates straight or
complex-shape welds
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Retained material properties: Minimizes material distortion
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Safe operation: Does not create hazards such as welding fumes,
radiation, high voltage, liquid metals, or arcing
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No keyholes: Pin is retracted automatically at end of weld
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Tapered-thickness weld joints: Pin maintains full penetration
Comparison with other joining processes
FSW vs Fusion Welding
» Improved Mechanical
Properties
» Reduced Distortion
» Reduced Defect Rate
» Parent Metal Chemistry
» Simplifies Dissimilar Alloy
Welding
» Fewer Process Variables
» Eliminates Consumables
» Reduces Health Hazard
FSW vsRivetting
» Reduced Part Count
» Reduced Production
Time
» Reduced Defect Rates
» Increase in Load
Carrying Capability»
Improved Fracture
Performance
» Eliminates Consumables
» Less Operator
Dependent
Disadvantages
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Work pieces must be rigidly clamped
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Backing bar required (except where self-reacting tool or directly
opposed tools are used)
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Keyhole at the end of each weld
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Cannot make joints which required metal deposition (e.g. fillet
welds)
Barriers for FSW
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Special clamping system necessary
Only for simple joint geometries (e.g. butt joint)
License required from TWI
Few applications in the construction industry
Corrosion protection is needed
Future Developments
 Laser-assisted friction stir welding
 Possible use of induction coil and other mechanism
Conclusion
 An alternative to fusion welding
 Advanced technologies are in the offing
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