1. 4/17/2020 Dr.Abhishek Sharma
By
Dr. Abhishek Sharma
Metal Joining
(FRICTION STIR WELDING)
KME-403
Unit - IV
GL BAJAJ INSTITUTE OF TECHONOLOGY & MANAGEMENT
1
2. Solid State Welding - Friction Welding (FRW)
•FRW process in which coalescence is achieved by frictional heat
combined with pressure
•When properly carried out, no melting occurs at faying surfaces
•No filler metal, flux, or shielding gases normally used
•Process yields a narrow HAZ
•Can be used to join dissimilar metals
•Commonly used for aluminum and its alloys.
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4. WORKING PRINCIPLE OF FSW
➢FSW a cylindrical, shouldered tool with a profiled probe/pin is rotated and slowly
plunged into the joint line between two pieces butted together.
➢The parts have to be suitably clamped rigidly on a backing bar to prevent the abutting
joint faces from being forced apart.
➢The length of the pin is slightly less than the required weld depth. The
plunging is stopped when the tool shoulder touches the surface of the job.
➢Frictional heat is generated between the wear resistant welding tool and the material
of the work pieces.
➢The plasticized material is transferred the front edge of the tool to back edge of the
tool probe and it’s forged by the intimate contact of the tool shoulder and pin profile.
➢As the tool is moved along the seam the desired joint is created.
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5. STEPS OF FSW PROCESS
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6. MICROSTRUCTURE ANALYSIS OF FSW
The macro and microstructural investigation reveal that the friction stir
weldment is composed of four different regions namely
1. Weld Nugget (WN) or stirred zone,
2. Thermo-Mechanically Affected Zone (TMAZ),
3. Heat Affected Zone (HAZ) and
4. Unaffected material.
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7. Unaffected material or parent metal
▪ This is material remote from the weld, which has not been deformed.
▪ it may have experienced a thermal cycle from the weld .but it is not affected by the
heat in terms of microstructure or mechanical properties.
Heat affected zone (HAZ)
▪ In this region the material has experienced a thermal cycle which has modified the
microstructure and/or the mechanical properties.
▪ However, there is no plastic deformation occurring in this area.
MICROSTRUCTURE ANALYSIS OF FSW
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8. PIN DESIGN
Tool pin the most important part of FSW arrangement. It mainly perform the stirring
function and also frictional heating. Some of popular pin profile is described below:
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TOOL USED:
Wear resistance, Chemical stability, Should withstand high temperature.
Commonly used tool materials: High speed steel, EN Steel, PCBN
10. ADVANTAGES:
• Good mechanical properties .
• Improved safety due to the absence of toxic fumes or the spatter of
molten material.
• No consumables and no filler or gas shield is required for aluminum.
• Easily automated on simple milling machines — lower setup costs and
less training.
• Can operate in all positions (horizontal, vertical, etc)
• Generally good weld appearance and minimal thickness under/over-
matching, thus reducing the need for expensive machining after welding.
• Low environmental impact.
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11. DISADVANTAGES:
Exit hole left when tool is withdrawn.
Large down forces required with heavy-duty clamping necessary to hold
the plates together.
Less flexible than manual and arc processes (difficulties with thickness
variations and non-linear welds).
Initial cost of the machine is very high compared to fusion welding.
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CHALLENGES OF FSW
Main applications of FSW remain limited to Aluminium and its alloys.
It also faces challenges from welding of dissimilar metals.
Recently researches have been made on steel and dissimilar metals by
changing the process parameters. The results are satisfactory.
APPLICATION
Shipbuilding and Offshore, Aerospace, Automotive Railways, Fabrication, Robotics
Personal Computers
