Seminar On Friction Stir Welding report Pdf Download
Introduction To Friction Stir Welding
Principle Of Operation
- In friction stir welding (FSW) a cylindrical, shouldered tool with a profiled probe is rotated and slowly plunged into the joint line between two pieces butted together.
- The parts have to be clamped onto a backing bar in a manner that prevents the abutting joint faces from being forced apart.
- Frictional heat is generated between the wear resistant welding tool and the material of the work pieces.
- This heat causes the material to soften without reaching the melting point and allows traversing of the tool along the weld line.
- The maximum temperature reached is of the order of 0.8 of the melting temperature of the material.
- It leaves a solid phase bond between the two pieces.
- The process can be regarded as a solid phase keyhole welding technique since a hole to accommodate the probe is generated, then filled during the welding sequence.
Important welding parameters
- In general, it can be said that increasing the rotation speed or decreasing the traverse speed will result in a hotter weld.
- In order to produce a successful weld it is necessary that the material surrounding the tool is hot enough to enable the extensive plastic flow required and minimize the forces acting on the tool.
- Plunging the shoulder below the plate surface increases the pressure below the tool and helps ensure adequate forging of the material.
- Tilting the tool by 2–4 degrees, such that the rear of the tool is lower than the front, has been found to assist this forging process.
- The plunge depth needs to be correctly set, both to ensure the necessary downward pressure is achieved and to ensure that the tool fully penetrates the weld.
- Low distortion and shrinkage, even in long welds
- Excellent mechanical properties in fatigue and tensile tests
- No arc or fumes
- No porosity
- Can operate in all positions (horizontal, vertical, etc.), as there is no weld pool.
- Energy efficient
- One tool can typically be used for up to 1000m of weld length in 6XXX series aluminium alloys
- No filler wire required
- No gas shielding is also required for welding
- Exit hole left when tool is withdrawn.
- Less flexible than manual and arc processes
- Work pieces must be rigidly clamped
- Often slower traverse rate than some fusion welding techniques.
- Cannot make joints which required metal deposition (e.g. fillet welds)
Application Of Friction Stir Welding:
- Shipbuilding and Marine Construction
- Aerospace Industry
- Wings, fuselages
- Cryogenic fuel tanks for space vehicles
- Aviation fuel tanks
- External throw away tanks for military aircraft
- Military and scientific rockets
- Wheel rims
- Truck bodies & tail lifts for lorries
- Mobile cranes
- Fuel tankers
- Rolling stock of railways and underground carriages
- Railway tankers and goods wagons
- Container bodies.
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