FRICTION STIR WELDING

mammettiredMechanics

Nov 18, 2013 (4 years and 1 month ago)

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A
N

I
NTRODUCTION

TO

FRICTION STIR WELDING

K.K.
Ramachandran

Dept. of Mechanical Engineering

Govt. Engineering College
Thrissur

INTRODUCTION


Friction Stir Welding (FSW) was invented
by Wayne Thomas at TWI (The Welding
Institute), England in the year 1991


Friction Stir Welding is a solid
-
state
process, that the objects are joined below
the melting point with the help of
pressure


Frictional heating by the rotation of a tool


Mechanical deformation


extrusion and forging


The heat generated in the joint area is typically
about 80
-
90% of the melting temperature.



In FSW, a cylindrical shouldered tool with
a profiled pin is rotated and plunged into
the joint area between the two pieces of
material to be joined.


Suitable for joining of Al and alloys, Mg
and alloys, Cu and alloys, Ti and alloys,
steel, … and joining of dissimilar metals
and alloys


S
CHEMATICS

OF

FSW


W
HY

FSW


Normally metals and alloys are joined by fusion welding
process


All fusion welding processes (particularly for materials
having low
weldability

such as copper are characterized by
welding defects.


Some Al, Cu and Mg alloy series are not at all fusion
weldable


Welding of different materials and much different in
thickness are impossible/very difficult


The main defects noticed are; porosity, hot cracking, HIC,
NIC, residual stresses, distortion, grain growth, HAZ,
composition changes at the weld nugget and HAZ, ….


Other problems, such as environmental pollution due to
welding fumes and slag, very high energy consumption, pre
and post weld treatments, high initial investment, …

K
EY

FEATURES

OF

FSW


Solid state process


Low thermal distortion


Good dimensional stability


No loss in alloying elements


Excellent metallurgical properties


Fine micro structure


No cracking, porosity and other welding defects


Environmental friendly hence called green welding
technology


No shielding gas


No use of chemical for cleaning


No slag and fumes


Highly energy efficient

FSW P
ROCESS

PARAMETERS


Tool geometry


Tool rotational and traverse speed


Tool tilt angle


Pin plunge depth


Pre
-
heating/cooling


Required for HMP materials


High thermal conductivity materials


Required for LMP materials
pre
-
cooling


High crystal growth and dissolution of precipitate even at
low temperatures

Pre
-
heating


Temperature distribution


Heat is generated due to friction and plastic
deformation


Microstructure


Mechanical properties


Hardness


HAZ


TMAZ


Residual stress


depends on temperature
distribution

FSW
TOOLS


For low melting point metals and alloys the tool
material normally used is high carbon steel


For steel, titanium and its alloys
the difficulty is
mainly associated with finding a tool material
that can withstand the high temperatures


W and its alloys particularly with Rhenium


Mo


W alloys


PCB


One of the most promising tool materials so far is the
so called PCBN

FSW T
OOL

& G
EOMETRIES



More tool shoulder geometries, viewed
from underneath the shoulder


Worl
TM

and MX
Triflute
TM

tools developed by
TheWelding

Institute (TWI), UK


Flared
-
Triflute
TM

tools developed
by
TheWelding

Institute (TWI), UK


Other Tools Types


Retractable pin tool


The Retractable Pin Tool (RPT) or Adjustable Probe Tool is a
machine feature in which the pin of the FSW tool may be
moved independently of the tool’s shoulder


Useful for material thickness variations and to close the exit
hole of the weld


Bobbin tool


The bobbin tool employs a technique that enables double
-
sided welding


The tool is having two shoulders


Two types


fixed bobbin tool and self
-
retracting bobbin tool


Circumferential welding machine, featuring
Bobbin Tool

J
OINT

CONFIGURATIONS

FOR

FSW

(
a) square butt, (b) edge butt, (c) T butt joint, (d) lap joint,
(e)
multiple lap
joint, (f) T lap joint, and (g) fillet joint

M
ETAL

FLOW

AND

PROCESSING

ZONES


(a) Metal flow patterns and (b) metallurgical
processing zones developed during FSW

M
ICROSTRUCTURE


A typical macrograph showing various
microstructural

zones in FSP 7075Al
-
T651 (standard
threaded pin, 400
rpm and
51 mm/min)

G
RAIN

SIZE

DISTRIBUTION

IN 7050A
L

WELD

NUGGET


APPLICATIONS


AEROSPACE (1997 onwards)


high
-
strength
aluminum

alloys such as 2XXX
and 7XXX series are widely used for aerospace
structures such as fuselage, fins, wings, etc.


such high
-
strength
aluminum

alloys are difficult
to join by conventional fusion welding due to the
occurrence of hot cracking during welding.



Therefore, conventionally, joining in aerospace
structures is mostly by riveting


Eclipse Aviation
-

Eclipse 500 aircraft


Boeing


Aircraft, Delta rocket tanks, ….


ARMOR manufacturing


Ship building


Automotive industry


Different material


Different thickness


Body friction stir spot welding


Oil and Natural Gas


Locomotive


Everywhere

FRICTION STIR PROCESSING


Friction stir processing was developed based on
the basic concept of FSW in 2005 by
Mishra

(?)


In this the tool is traversed over the surface of
the metal/alloy (3


5 mm plunge depth)


The objectives include;


Microstructural

modification in metallic materials


Imparting
superplasticity

at the surface


Producing composite surface layer


homogenization of
nanophase

aluminum

alloys and
metal matrix composites


Microstructural

refinement


A friction stir processed piston

Robotic controlled FSP

Q
UERIES

PLEASE

Thank you