friction stir welding full report

[seminar class]

Presented by:
Clinton M Mathews
N Subbaiyan
Vivek Varughese Thomas
T Suresh

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FRICTION STIR WELDING
INTRODUCTION
• Welding is the joining of two similar or dissimilar metals.
• Friction is the resistive force that occurs when two surfaces travel along each other when forced together.
• It causes physical deformation and heat buildup.
FUSION WELDING
• Fusion welding is a group of processes that bond metals together by heating a portion of each piece above the melting point and causing them to flow together.
• Usually uses a filler material to insure the joint is filled
• All fusion welding processes have three requirements.
 Heat
 Shielding
 Filler material
Friction stir welding process
• Friction stir welding is a new solid state joining process.
• Here a cylindrical shouldered tool along with a profiled probe is rotated and fed at a constant traverse rate in to the joint.
• Frictional heat generated between the wear resistant welding tool and the work piece along with mechanical mixing heat causes the stirred material to soften without reaching the melting point and allows the traversing of the tool along the weld line.
• The plasticised material is transferred from the leading edge of the tool to its trailing edge and is forged by the intimate contact of the tool shoulder and the pin profile thus leaving a solid bond between two phases
Working
• Microstructure classification of friction stir welding
Micro structural Zones
 Unaffected material or parent metal: This is material remote from the weld, which has not been deformed, and which although it may have experienced a thermal cycle from the weld is not affected by the heat in terms of microstructure or mechanical properties.
 Heat affected zone (HAZ): This region lies closer to the weld centre there is no plastic deformation occurring in this area.
 Thermo-mechanically affected zone (TMAZ): In this region, the material has been plastically deformed by the friction stir welding tool, and the heat from the process will also have exerted some influence on the material
 Weld Nugget : The stir zone (also nugget,) is a region of heavily deformed material that roughly corresponds to the location of the pin during welding. 4] A unique feature of the stir zone is the common occurrence of several concentric rings which has been referred to as an ‘onion-ring’ structure.
Process advantages
• Low distortion, even in long welds.
• Excellent mechanical properties as proven by fatigue, tensile and bend tests.
• No arc, fume, spatter and porosity
• low shrinkage.
• Can operate in all positions.
• Non consumable tool.
• No filler wire, gas shielding.
• Can weld aluminium and copper of >50mm thickness on one pass
Limitations of Friction stir welding
• Work pieces must be rigidly clamped
• Backing bar required (except for self reacting and directly opposed tools)
• Key holes at the end of each weld
• Cannot make joints that require metal deposition
• Less flexible than manual and arc processes
Applications of friction stir welding
1. Ship building and marine industries
– Panels for decks, bulk heads and floors
– Hulls and superstructures
– Helicopter landing platforms
– Mast and booms (sailing boat)
– Applications of friction stir welding
2. Aerospace industry
– cryogenic fuel tank for space vehicles
– Aviation fuel tanks
– Military and scientific rockets
– Various primary and secondary structural component
3. Railway and Land transport.
– high speed trains
– railway tankers and goods wagon
– wheel rims
– motor cycle and bicycle frames