Friction stir welding

1. FRICTION STIR WELDING
R Gopikrishnan
S7 Mechanical
Roll No: 40

2. Introduction
 Welding using friction as the major resource
 No filler material involved
 Welds created by,
a) Frictional heating
b) Mechanical deformation

3. History
 Invented by TWI in 1991 in England
 28 organizations worldwide use FSW

4. Friction Welding
 Heat from mechanical energy conversion
Linear friction welding
Rotary friction welding

5. Friction Stir Welding
Shoulder which creates friction
heat
and 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

6. 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)

7. Microstructure analysis
Optical micrographs of regions (a), (b) and (c) of the stir nugget.

8. Joint Geometries
It can be used in all positions,
Horizontal
Vertical
Overhead
Orbital

9. Material Suitability
 Copper and its alloys
 Lead
 Titanium and its alloys
 Magnesium alloys
 Zinc
 Plastics
 Mild steel
 Stainless steel
 Nickel alloys

10. Welding Steel using FSW

11. Tools Parameters

12. Common Tools
Fixed Pin Tool
Self Reacting Pin Tool
Adjustable Pin Tool Retractable Pin Tool

13. Some of the FSW Machines
ESAB SuperStir TM machine FW28 ESAB Machine

14. 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

15. 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

16. 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)

17. 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

18. Future Developments
 Laser-assisted friction stir welding
 Possible use of induction coil and other mechanism

19. Conclusion
 An alternative to fusion welding
 Advanced technologies are in the offing

20. THANK YOU