friction stir welding. introduction welding using friction as the major resource no filler...
TRANSCRIPT
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 weldingRotary friction welding
Friction Stir Welding
Shoulder which creates friction heatand welding pressure
Probe which Stir the material
Sufficient downward force to maintain pressure and to create friction heat
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
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
Fixed Pin ToolSelf Reacting Pin Tool
Adjustable Pin Tool Retractable Pin Tool
Some of the FSW Machines
ESAB SuperStir TM machine FW28
ESAB Machine
Advantages Diverse materials: Welds a wide range of alloys, including
previously un-weldable (and possibly composite materials)
Durable joints: Provides twice the fatigue resistance of fusion welds.
Versatile welds: Welds in all positions and creates straight or complex-shape welds
Retained material properties: Minimizes material distortion
Safe operation: Does not create hazards such as welding fumes, radiation, high voltage, liquid metals, or arcing
No keyholes: Pin is retracted automatically at end of weld
Tapered-thickness weld joints: Pin maintains full penetration
Comparison with other joining processes
FSW vs Fusion Welding FSW vsRivetting » Improved Mechanical
Properties » Reduced Distortion » Reduced Defect Rate » Parent Metal Chemistry » Simplifies Dissimilar Alloy Welding » Fewer Process Variables » Eliminates Consumables » Reduces Health Hazard
» Reduced Part Count » Reduced Production Time» Reduced Defect Rates » Increase in Load Carrying Capability» Improved Fracture Performance » Eliminates Consumables » Less Operator Dependent
Disadvantages
Work pieces 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)
Barriers for FSW
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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