TIG WELDING

WOLLEGA UNIVERSTY

COLLEGE OF ENGINEERING TECHNOLOGY

DEPARTEMENT OF MECHANICAL ENGINEERING

PROJECT OF MANUFACTURING ENGINEERING II

ID NO
GROUP MEMEBERS
0299/15
1, BIRBIRSA BETIE……………………………
0189/15
2,BELACHEW ABDETA
0080/15
3,ALEMU TEMANA
0499/15
4,GELAYE ASEFA
1092/15
5,WACTOLE BEYANA 0935/15
6,ROBE TESFAYE

SUB MITED TO DR.HARISH

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Acknowledgment
First of all great thanks WOLLEGA UNIVERSTY Department of mechanical Engineering next to
my God helps to do this project. secondly my instructor DR HARISH. he advice for finish these
project and give more knowledge on MANUFACTURING ENGINEERING course which contain
more knowledge .also I have more Thanks all my friend for giving additional information for us.
And for surprise me when I am tired and all my Dormitory students for contributing any
materials for this project.

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ABSTRACT
To improve welding quality of Aluminum (Al) plate an automated TIG welding system has been
developed, by which welding speed can be control during welding process. Welding of Al plate
has been performed in two phases. During 1st phase of welding, single side welding performed
over Al plate and during 2nd phase both side welding performed for Al plate by changing
different welding parameters. Effect of welding speed and welding current on the tensile strength
of the weld joint has been investigated for both type of weld joint. Optical microscopic analysis
has been done on the weld zone to evaluate the effect of welding parameters on welding quality.
Micro-hardness value of the welded zone has been measured at the cross section to understand
the change in mechanical property of the welded zone.KAPLAN TURBINE UESD I

Keywords: Automated TIG Welding System, Micro hardness Test, Tensile Test

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CHAPTER ONE

1. INTRODUCTION
Welding is a permanent joining process used to join different materials like metals, alloys
or plastics, together at their contacting surfaces by application of heat and or pressure. During
welding, the work-pieces to be joined are melted at the interface and after solidification a
permanent joint can be achieved. Sometimes a filler material is added to form a weld pool of
molten material which after solidification gives a strong bond between the materials. Weld
ability of a material depends on different factors like the metallurgical changes that occur during
welding, changes in hardness in weld zone due to rapid solidification, extent of oxidation due to
reaction of materials with atmospheric oxygen and tendency of crack formation in the joint
position.

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Weldability; it is defined as the capability of being welded into in separable joints having
properties such as weld strength proper microstructure etc. Weldablitiy of a metal is decided by
the weld quality and the ease with which it can be obtained.

Weldability depends on the following major factors;

 Melting point
 Thermal conductivity
 Thermal expansion
 Surface condition
 Microstructure after welding

By proper shielding atmosphere, proper fluxing material, proper filler metal, proper welding
procedure and in some case by proper heat treatment of the metal before and after deposition
we can correct the metallurgical, chemical ,physical and thermal characteristics of a metal if
these are considered undesirable and un favorable with respect to weld ability.

General Welding Safety Rules

1. Arc rays from the welding process produce intense visible and invisible (ultraviolet and
nfrared) rays that can burn eyes and skin. Sparks fly off from the weld.
2. Wear a welding helmet fitted with a proper shade of filter to protect your face and eyes when
welding or watching (see ANSI Z49.1 and Z87.1 listed in Safety Standards).
3. Use protective screens or barriers to protect others from flash, glare, and sparks; warn others
not to watch the arc.
4. Wear body protection made from durable, flame−resistant material (leather, heavy cotton,
wool). Body protection includes oil-free clothing such as leather gloves, heavy shirt, cuff less
trousers, high shoes, and a cap.
5. Before welding, adjust the auto-darkening lens sensitivity setting to meet the application.
6. Stop welding immediately if the auto-darkening lens does not darken when the arc is struck.
See the Owner’s Manual for more information.
7. Arc rays from the welding process produce intense visible and invisible (ultraviolet and
infrared) rays that can burn eyes and skin. Sparks fly off from the weld.
8. Use impact resistant safety spectacles or goggles and ear protection at all times when

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using welding helmet.

9. Inspect the auto-lens frequently. Immediately replace any scratched, cracked, or pitted
cover lenses or auto-lenses.
10. NOISE can damage hearing. Noise from some processes or equipment can damage Hearing.
Wear approved ear protection if noise level is high.
11. READ INSTRUCTIONS. Read and follow all labels and the Owner’s Manual carefully
before installing, operating, or servicing unit. Read the safety information at the beginning of
the manual and in each section. Use only genuine replacement parts from the
Manufacturer. Perform maintenance and service according to the Owner’s Manuals,
industry standards, and national, state, and local codes.
12. FUMES AND GASES can be hazardous. Welding produces fumes and gases.
Breathing these fumes and gases can be hazardous to your health.
13. Keep your head out of the fumes. Do not breathe the fumes.
14. If inside, ventilate the area and/or use local forced ventilation at the arc to remove welding
fumes and gases. The recommended way to determine adequate ventilation is to sample for the
composition and quantity of fumes and gases to which personnel are exposed.
15. If ventilation is poor, wear an approved air-supplied respirator.
16. Read and understand the Safety Data Sheets (SDSs) and the manufacturer’s instructions for
adhesives, coatings, cleaners, consumables, coolants, degreasers, fluxes, and metals.
17. Work in a confined space only if it is well ventilated, or while wearing an air-supplied
respirator.
18. Always have a trained watchperson nearby. Welding fumes and gases can displace air and
lower the oxygen level causing injury or death. Be sure the breathing air is safe.
19. Do not weld in locations near degreasing, cleaning, or spraying operations. The heat and rays
of the arc can react with vapors to form highly toxic and irritating gases.
20. Do not weld on coated metals, such as galvanized, lead, or cadmium plated steel, unless the
coating is removed from the weld area, the area is well ventilated, and while wearing an air
supplied respirator. The coatings and any metals containing these elements can give off toxic
fumes if welded.

1.1 Different type of welding processes

Based on the heat source used welding processes can be categorized as follows:

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1.1.1 Arc Welding:

In arc welding process an electric power supply is used to produce an arc between electrode and
the work-piece material to joint, so that work-piece metals melt at the interface and welding
could be done. Power supply for arc welding process could be AC or DC type. The electrode
used for arc welding could be consumable or non-consumable. For non-consumable electrode an
external filler material could be used.
1.1.2 Gas Welding:
In gas welding process a focused high temperature flame produced by
Combustion of gas or gas mixture is used to melt the work pieces to be joined. An external filler
material is used for proper welding. Most common type gas welding process is Oxyacetylene gas
welding where acetylene and oxygen react and producing some heat.
1.1.3 Resistance Welding
In resistance welding heat is generated due to passing of high amount current (1000–100,000 A)
through the resistance caused by the contact between two metal surfaces. Most common types
resistance welding is Spot-welding, where a pointed electrode is used. Continuous type spot
resistance welding can be used for seam-welding
where a wheel-shaped electrode is used.
1.1.4 High Energy Beam Welding:
In this type of welding a focused energy beam with high
Intensity such as Laser beam or electron beam is used to melt the work pieces and join them
Together. These types of welding mainly used for precision welding or welding of advanced
material or sometimes welding of dissimilar materials, which is not possible by conventional
welding process.
1.1.5 Solid-State Welding:
Solid-state welding processes do not involve melting of the work piece materials to be joined.
Common types of solid-state welding are ultrasonic welding,
explosion welding, electromagnetic pulse welding, friction welding, friction-stir-welding etc.

Arc Welding
Among all these types of welding processes arc welding is widely used for different types of
materials. Common types of arc welding process are:

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a) Shielded Metal Arc Welding (SMAW) or Manual Metal Arc Welding: This is most
common type arc welding process, where a flux coated consumable electrode is used. As the
electrode melts, the flux disintegrates and produces shielding gas that protect the weld area from
atmospheric oxygen and other gases and produces slag which covers the molten filler metal as it
transfer from the electrode to the weld pool. The slag floats to the surface of weld pool and
protects the weld from atmosphere as it solidifies.
b) Gas Metal Arc Welding (GMAW) or Metal inert or active gas welding
(MIG/MAG): In this type of welding process a continuous and consumable wire electrode is
used. A shielding gas generally argon or sometimes mixture of argon and carbon dioxide are
blown through a welding gun to the weld zone.
c) Gas Tungsten Arc Welding (GTAW) or Tungsten Inert Gas (TIG): GTAW or TIG
welding process is an arc welding process uses a non-consumable tungsten electrode to produce
the weld. The weld area is protected from atmosphere with a shielding gas generally Argon or
Helium or sometimes mixture of Argon and Helium. A filler metal may also feed manually for
proper welding. GTAW most commonly called TIG welding process was developed during
Second World War. With the development of TIG welding process, welding of difficult to weld
materials e.g. Aluminum and Magnesium become possible. The use of TIG today has spread to a
variety of metals like stainless steel, mild steel and high tensile steels, Al alloy, Titanium alloy.
Like other welding system, TIG welding power sources have also improved from basic
transformer types to the highly electronic controlled power source today.

1.2 Basic mechanism of TIG welding:

TIG welding is an arc welding process that uses a non-consumable tungsten electrode to produce
the weld. The weld area is protected from atmosphere by an inert shielding gas (argon or
helium), and a filler metal is normally used. The power is supplied from the power source
(rectifier), through a hand-piece or welding torch and is delivered to a tungsten electrode which
is fitted into the hand piece. An electric arc is then created between the tungsten electrode and
the work piece using a constant-current welding power supply that produces energy and
conducted across the arc through a column of highly ionized gas and metal vapours [1]. The
tungsten electrode and the welding zone are protected from the surrounding air by inert gas. The
electric arc can produce temperatures of up to 20,000oC and this heat can be focused to melt and

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join two different part of material. The weld pool can be used to join the base metal with or
without filler material. Schematic diagram of TIG welding a
nd mechanism of TIG welding are shown in fig. 1 & fig. 2 respectively.

Fig 1: Schematic Diagram of TIG Welding System. [Ref: 1]

Fig. 2: Principle of TIG Welding. [Ref: 1]

Tungsten electrodes are commonly available from 0.5 mm to 6.4 mm diameter and 150 - 200
mm length. The current carrying capacity of each size of electrode depends on whether it is
connected to negative or positive terminal of DC power source. The power source required to

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maintain the TIG arc has a drooping or constant current characteristic which provides an
essentially constant current output when the arc length is varied over several millimetres. Hence,
the natural variations in the arc length which occur in manual welding have little effect on
welding current. The capacity to limit the current to the set value is equally crucial when the
electrode is short circuited to the work piece, otherwise excessively high current will flow,
damaging the electrode. Open circuit voltage of power source ranges from 60 to 80 V.

1.3 Types of welding current used in TIG welding

a. DCSP (Direct Current Straight Polarity): In this type of TIG welding direct current is used.
Tungsten electrode is connected to the negative terminal of power supply. This type of
connection is the most common and widely used DC welding process. With the tungsten being
connected to the negative terminal it will only receive 30% of the welding energy (heat). The
resulting weld shows good penetration and a narrow profile.
b. DCRP (Direct Current Reverse Polarity): In this type of TIG welding setting tungsten
electrode is connected to the positive terminal of power supply. This type of connection is used
very rarely because most heat is on the tungsten, thus the tungsten can easily overheat and burn
away. DCRP produces a shallow, wide profile and is mainly used on very light material at low
Amp.
c. AC (Alternating Current): It is the preferred welding current for most white metals, e.g.
aluminum and magnesium. The heat input to the tungsten is averaged out as the AC wave passes
from one side of the wave to the other. On the half cycle, where the tungsten electrode is
positive, electrons will flow from base material to the tungsten. This will result in the lifting of
any oxide skin on the base material. This side of the wave form is called the cleaning half. As the
wave moves to the point where the tungsten electrode becomes negative the electrons will flow
from the welding tungsten electrode to the base material. This side of the cycle is called the
penetration half of the AC wave forms.
d. Alternating Current with Square Wave: With the advent of modern electricity AC welding
machines can now be produced with a wave form called Square Wave. The square wave has
better control and each side of the wave can give a more cleaning half of the welding cycle and
more penetration [2].

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1.4 Advantages of TIG welding

TIG welding process has specific advantages over other arc welding process as follows

I. Narrow concentrated arc

II. Able to weld ferrous and non-ferrous metals
III. Does not use flux or leave any slag (shielding gas is used to protect the weld-pool and
tungsten electrode)
IV. No spatter and fumes during TIG welding

1.5 Applications of TIG Welding

The TIG welding process is best suited for metal plate of thickness around 5- 6 mm. Thicker
material plate can also be welded by TIG using multi passes which results in high heat inputs,
and leading to distortion and reduction in mechanical properties of the base metal. In TIG
welding high quality welds can be achieved due to high degree of control in heat input and filler
additions separately. TIG welding can be performed in all positions and the process is useful for
tube and pipe joint. The TIG welding is a highly controllable and clean process needs very little
finishing or sometimes no finishing. This welding process can be used for both manual and
automatic operations. The TIG welding process is extensively used in the so-called high-tech
industry applications such as;
I. Nuclear industry
II. Aircraft
III. Food processing industry
IV. Maintenance and repair work
V. Precision manufacturing industry
VI. Automobile industry

1.6 Process parameters of TIG welding

The parameters that affect the quality and outcome of the TIG welding process are
given below;
a) Welding Current
Higher current in TIG welding can lead to splatter and work piece become damage. Again lower
current setting in TIG welding lead to sticking of the filler wire. Sometimes larger heat affected
area can be found for lower welding current, as high temperatures need to applied for longer
periods of time to deposit the same amount of filling materials. Fixed current mode will vary the
voltage in order to maintain a constant arc current.

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b) Welding Voltage
Welding Voltage can be fixed or adjustable depending on the TIG welding equipment. A high
initial voltage allows for easy arc initiation and a greater range of working tip distance. Too high
voltage, can lead to large variable in welding quality.
c) Inert Gases:
The choice of shielding gas is depends on the working metals and effects on the welding cost,
weld temperature, arc stability, weld speed, splatter, electrode life etc. it also affects the finished
weld penetration depth and surface profile, porosity, corrosion resistance, strength, hardness and
brittleness of the weld material. Argon or Helium may be used successfully for TIG welding
applications. For welding of extremely thin material pure argon is used. Argon generally
provides an arc which operates more smoothly and quietly. Penetration of arc is less when Argon
is used than the arc obtained by the use of Helium. For these reasons argon is preferred for most
of the applications, except where higher heat and penetration is required for welding metals of
high heat conductivity in larger thicknesses. Aluminum and copper are metals of high heat
conductivity and are examples of the type of material for which helium is advantageous in
welding relatively thick sections. Pure argon can be used for welding of structural steels, low
alloyed steels, stainless steels, aluminum, copper, titanium and magnesium. Argon hydrogen
mixture is used for welding of some grades of stainless steels and nickel alloys. Pure helium may
be used for aluminum and copper. Helium argon mixtures may be used for low alloy steels,
aluminum and copper.
d) Welding speed:
Welding speed is an important parameter for TIG welding. If the welding speed is
Increased, power or heat input per unit length of weld is decreases, therefore less weld
Reinforcement results and penetration of welding decreases. Welding speed or travel speed is
Primarily control the bead size and penetration of weld. It is interdependent with current.
Excessive high welding speed decreases wetting action, increases tendency of undercut,
Porosity and uneven bead shapes while slower welding speed reduces the tendency to
Porosity.

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1.7 Properties and advantages of Al:

Aluminum is a very light weight metal (specific weight of 2.7 g/cm3). Use of Aluminum in
automobile and aerospace reduces dead-weight and energy consumption. Strength of Aluminum
can be improved as per the required properties for various Applications by modifying the
composition of its alloys. Aluminum is a highly corrosion resistant material. Different types of
surface treatment can further improve its corrosion resistance property. Aluminum is an excellent
heat and electricity conductor and in relation to its weight is almost twice as good a conductor as
copper. This has made aluminum the most commonly used material in major power transmission
lines. Aluminum is ductile and has a low melting point. In a molten condition it can be rocessed
in a number of ways. Its ductility allows products of aluminum to be basically formed close to
the end of the product’s design [3].

1.8 Welding of Aluminum and Aluminum alloy

Aluminum can be joined in many ways such as bolting, riveting (temporary joint) and welding
(permanent methods). Aluminum and its alloys are welded in industry by a variety of methods.
Thermal conductivity of Aluminum is quite high; therefore heat is easily conducted away from
the welding area. It is essential that the heat source is powerful enough to rapidly reach
aluminum’s melting point of 565 /650ºC. Coefficient of thermal expansion of Aluminum is also
high compared to steel, so it is prone to distortion and stress inducement if the proper welding
procedure is not followed. Aluminum is a reactive metal that quickly forms an oxide layer on the
surface and strength of the weld area become weak. Therefore welding of Aluminum by
conventional arc welding process is become difficult. By understanding the welding
characteristics and utilizing proper procedures Aluminum and its alloys could be easily weld.
The most common commercial aluminum and aluminum alloy welding methods use an electric
arc with either a continuously fed wire electrode [with DC current, with and without pulsed
current] or a permanent tungsten electrode plus filler wire with AC current. To ensure an
acceptable weld quality, there are two basic factors to consider - breaking loose and removing
the oxide film, and preventing the formation of new oxide during the weld process. It is essential
that proper preparations and precautions always be taken before welding commences. The
surfaces to be joined and the area around the weld zone [~50 mm] must be degreased using as
solvent [acetone or toluene] and a clean cloth. The area must be clean and completely dry as
grease and moisture can form gases and cause pores in the welded joint [4]

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CHAPTER TWO

LITERATURE REVIEW
2.1 TIG Welding :
Sanjeev kumar et. al [5] attempted to explore the possibility for welding of higher thickness
plates by TIG welding. Aluminum Plates (3-5mm thickness) were welded by Pulsed Tungsten
Inert Gas Welding process with welding current in the range 48-112 A and gas flow rate 7 -15
l/min. Shear strength of weld metal (73MPa) was found less than parent metal (85 MPa). From
the analysis of photomicrograph of welded specimen it has been found that, weld deposits are
form co-axial dendrite micro-structure towards the fusion line and tensile fracture occur near to
fusion line of weld deposit. Indira Rani et. al [6] investigated the mechanical properties of the
weldments of AA6351 during the GTAW /TIG welding with non-pulsed and pulsed current at
different frequencies. Welding was performed with current 70-74 A, arc travel speed 700-760
mm/min, and pulse frequency 3 and 7 Hz. From the experimental results it was concluded that
the tensile strength and YS of the weldments is closer to base metal. Failure location of
weldments occurred at HAZ and from this we said that weldments have better weld joint
strength. Ahmed Khalid Hussain et. al [7] investigated the effect of welding speed on tensile
strength of the welded joint by TIG welding process of AA6351 Aluminium alloy of 4 mm
thickness. The strength of the welded joint was tested by a universal tensile testing machine.
Welding was done on specimens of single v butt joint with welding speed of 1800 -7200
mm/min. From the experimental results it was revealed that strength of the weld zone is less than
base metal and tensile strength increases with reduction of welding speed. Tseng et. al [8]
investigated the effect of activated TIG process on weld morphology, angular distortion, delta
ferrite content and hardness of 316 L stainless steel by using different flux like TiO2, MnO2,
MoO3, SiO2 and Al2O3. To join 6 mm thick plate author uses welding current 200 Amp,
welding speed 150 mm/min and gas flow rate 10 l/min. From the experimental results it was
found that the use of SiO2 flux improve the joint penetration, but Al2O3 flux deteriorate the
weld depth and bead width compared with conventional TIG process. Narang et. al [9]
performed TIG welding of structural steel plates of different thickness with welding current in
the range of 55 -95 A, and welding speed of 15-45 mm/sec. To predict the weldment
macrostructure zones, weld bead reinforcement, penetration and shape profile characteristics

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along with the shape of the heat affected zone (HAZ), fuzzy logic based simulation of TIG
welding process has been done.Karunakaran et. al [10] performed TIG welding of AISI 304L
stainless steel and compare the weld bead profiles for constant current and pulsed current setting.
Effect of welding current on tensile strength, hardness profiles, microstructure and residual stress
distribution of welding zone of steel samples were reported. For the experimentation welding
current of 100- 180 A, welding speed 118.44 mm/min, pulse frequency 6 Hz have been
considered. Lower magnitude of residual stress was found in pulsed current compared to
constant current welding. Tensile and hardness properties of the joints enhanced due to formation
of finer grains and breaking of dendrites for the use of pulsed current. Raveendra et. al [11]
done experiment to see the effect of pulsed current on the characteristics of weldments by
GTAW. To weld 3 mm thick 304 stainless steel welding current 80-83 A and arc travel speed
700-1230 mm/min. More hardness found in the HAZ zone of all the weldments may be due to
grain refinement. Higher tensile strength found in the non-pulsed current weldments. It was
observed that UTS and YS value of non-pulsed current were more than the parent metal and
pulsed current weldments. Sakthivel et.al [12] studied creep rupture behaviour of 3 mm thick
316L austenitic stainless steel weld joints fabricated by single pass activated TIG and multi-pass
conventional TIG welding processes. Welding was done by using current in the range of 160-280
A, and welding speed of 80-120 mm/min. Experimental result shows that weld joints possessed
lower creep rupture life than the base metal. It was also found that, single pass activated TIG
welding process increases the creep rupture life of the steel weld joint over the multi-pass TIG
weld joints. Tetsumi Yuri et. al [13] investigated high cycle and low cycle fatigue properties of
SUS304L, SUS316L steel and the effects of welding structure by TIG welding process. Welding
was done with U-shaped groove and the weld was done by multi-passes with voltage of 8-10 V,
a current of 120-210 A, and welding speed of 800 mm/min. From the experimental results it was
revealed that in high-cycle fatigue tests, the ratio of fatigue strength to tensile strength of the
weld metals is lower than that of base metal. However, in low-cycle fatigue tests, the fatigue
lives of the weld metals were slightly shorter than that of base metals. Norman et. al [14]
investigated the microstructures of autogenous TIG welded Al-Mg-Cu- Mn alloy for a wide
range of welding conditions. Welding was done with current in the range100-190 A and welding
speed 420-1500 mm/min. The fine microstructure was observed at
the centre of the weld which was form due to higher cooling rate at the weld centre compared

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to the fusion boundary. It was observed that as the welding speed increases, the cooling rate
at the centre of the weld also increases, producing smaller size dendrite structure. Song et. al
[15] successfully joined dissimilar metals of 5A06 Al alloy and AISI 321 stainlesssteel of
thickness 3 mm by TIG welding-brazing with different filler materials. TIG welding–brazing
was carried out by AC-TIG welding source with welding current 135 A, arc length3.0–4.0mm,
welding speed 120 mm/min and argon gas flow rate 8–10 lit/min. It was found hat addition of Si
preventing the build-up of the IMC layer, minimising its thickness. The author also investigated
(Song et. al 2009) spreading behaviour of filler metal on the groove surface and microstructure
characteristics for butt joint. For the experimentation welding current in the range of 90-170 A
and welding speed in the range of 100-220 mm/min, were used for 2 mm thick plate. Wang et.
al [16] studied the influences of process parameters of TIG arc welding on the microstructure,
tensile property and fracture of welded joints of Ni-base super-alloy. For welding plate width of
1.2-1.5 mm, welding current in the range of 55-90 A, with variable welding speed in the range
2100-2900 mm/min was used. From experimental result it was observed that, the heat input
increases with increase of welding current and decrease of welding speed. Kumar and
Sundarrajan [17] performed pulsed TIG welding of 2.14 mm AA5456 Al alloy using welding
current (40-90) A, welding speed (210-230) mm/min. Taguchi method was employed to optimize
the pulsed TIG welding process parameters for increasing the mechanical properties and a
Regression models were developed. Microstructures of all the welds were studied and correlated
with the mechanical properties. 10-15% improvement in mechanical properties was observed
after planishing due to or redistribution of internal stresses in the weld. Preston et.al [18]
developed a finite element model to predict the evolution of residual stress and distortion
dependence on the yield stress-temp for 3.2 mm 2024 Al alloy by TIG welding. Akbar Mousavi
et.al [19] analysed the effect of geometry configurations on the residual stress distributions in
TIG weld from predicted data and compared it with data obtained by XRay diffraction method.
Attempts were made to analyse the residual stresses produced in the TIG welding process using
2D and 3D finite element analysis. For welding of 10 mm thick 304 grade stainless steel welding
current in the range 80-225 A, voltage 15 V, and welding velocity in the range of 90-192
mm/min were employed. Ahmet durgutlu et.al [20] investigated the effect of hydrogen in argon
as shielding gas for TIG welding of 316L austenitic stainless steel. They used current 115 A,
welding speed 100 mm/min and gas flow rate 10 l/min for welding of 4 mm thick plate. For all

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shielding media, hardness of weld metal is lower than that of HAZ and base metal. Penetration
depth, weld bead width and mean grain size in the weld metal increases with increasing
hydrogen content. The highest tensile strength was obtained for the sample welded under
shielding gas of 1.5%H2–Ar. Wang Rui et. al [21] investigated the effect of process parameters
i.e. plate thickness, welding heat input on distortion of Al alloy 5A12 during TIG welding. For
welding they used current (60-100) A, welding speed (800-1400) mm/min and thickness of w/p
(2.5-6) mm. The results show that the plate thickness and welding heat input have great effect on
the dynamic process and residual distortion of out-of-plane. Dongjie Li et.al [22] proposed a
double-shielded TIG method to improve weld penetration and compared with the traditional TIG
welding method under different welding parameters i.e welding speed, arc length and current.
They used gas flow rate 10 l/min, welding speed (90-300) mm/min, current (100-200) A and
thickness of w/p 10 mm. The results show that the changes in the welding parameters directly
impact the oxygen concentration in the weld pool and the temperature distribution on the pool
surface. Lu et. al [23] proposed a double-shielded TIG welding process for the welding of 9 mm
thick Cr13Ni5Mo stainless steel by using pure He as inner shielding layer and mixture of He and
CO2 gas as the outer shielding layer. Welding current and welding speed considered for the
experimentation in the range of 120-140 A and 90-300 mm/min respectively. The double–
shielded TIG welding process display efficiency 2-4 times greater than that of traditional TIG
welding. A change in the direction of the surface tension affects the fusion zone profile which
results a larger weld depth. This process allows a high welding efficiency comparing with
traditional TIG welding. Urena et. al [24] investigated the influence of the interfacial reaction
between the Al alloy (2014) matrix and SiC particle reinforcement on the fracture behaviour in
TIG welded Al matrix composites. TIG welding was carried out on 4 mm thick AA2014/SiC/Xp
sheets using current setting in the range of 37-155 A and voltage of 14-16.7 V. From
experimental results it was found that, the failure occurred in the weld metal with a tensile
strength lower than 50% of the parent material. Fracture of the welded joint was controlled by
interface deboning through the interface reaction Layer. Probability of interfacial failure
increases in the weld zone due to formation of Aluminum-carbide which lowers the
matrix/reinforcement interface strength. Sivaprasad et.al [25] performed TIG welding of 2.5
mm thick Nickel based 718 alloy using welding current in the range of 44-115 A, voltage 13-15
V and welding speed 67 mm/min. the influence of magnetic arc oscillation on the fatigue

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behaviour of the TIG weldments in two different post-weld heat treatment conditions were
studied. Wang Xi-he et. al [26] performed TIG welding of Si Cp /6061 Al composites without
and with Al-Si filler using He-Ar mixed as shielding gas. For the welding authors uses gas flow
rate 6.9 l/min, welding speed 1800 mm/min, current-60 A. The results show that addition of
50 vol.% helium in shielding gas improves the arc stability, and quality of welding improves
when the Al–Si filler is added. The microstructure of the welded joint shows non-uniformity
with SiC particles distributing in the weld Centre. Qinglei et. al [27] analyzed microstructure,
element distribution, phase constituents and micro hardness for welding joint of Mo-Cu
composite and 18-8 stainless steel plates of thickness 2.5 mm carried out by TIG welding process
with Cr-Ni fillet wires. Welding has done with speed (49.8-64.2)mm/min, gas flow rate-8 l/min,
arc voltage-(28-32) V and welding current -90 A. Formation of γ-Fe(Ni) phases and
Fe0.54Mo0.73 compound must contributed to the high micro hardness. The results indicate that
austenite and ferrite phases were obtained in the weld metal. The micro hardness near the fusion
zone at Mo–Cu composite side increased from weld metal to fusion zone, and the peak value
appeared near the boundary between fusion zone and Mo–Cu composite. Lothongkum et. al
[28] investigated the TIG welding of 3 mm thick AISI 316L stainless steel plate at different
welding position. Pure argon gas and mixture of argon with nitrogen (1-4 vol.%) were used as
shielding gas with a flow rate of 8 l/min during top and back sides of welds. Effects of welding
speeds and nitrogen contents in argon shielding gas on pulse currents were study to achieve an
acceptable weld bead profile with complete penetration. It was found that increasing nitrogen
contents in argon gas decreases the pulse currents and increasing welding speed will increase the
pulse current.

2.2 Problem identification and objective of the work

From the literature review, it is found that welding of Aluminum is a big challenge by
conventional arc welding process. Again repeatability of welding depends on its control on
welding speed and other processing parameters. In this work to perform welding of 3 mm
Aluminum plate, an automated TIG welding setup was made. Welding of the Aluminum plate
was done by changing the welding current and welding speed to get a high strength joint. To get
better strength welding of the Aluminum plate also done from both side. Effect of welding speed
and applied current on the tensile strength of weld joint, micro hardness of the weld pool and
macrostructure of the joint was analyzed.

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CHAPTER THREE

Experimental Work and Methodology

3.1 Development of an automated TIG welding system

For proper welding and control on welding parameters mainly on welding speed an automated
welding setup has been developed in-house. The automated welding setup with its main
components is shown in fig. 3.

Fig. 3 – Experimental set-up for TIG welding

The welding setup consists mainly following parts

a) Speed control unit (movable tractor) – Here, speed control unit is a movable tractor which run
with a predefined speed required for welding. TIG welding torch is fixed with it using a clamp in
a particular angle so that during welding a stable and continuous arc form. Welding speed can be
change using a regulator. Distance between the torch tip and work piece and angle of torch tip
can also be control using the adjustable knob.
b) Rail track –Movable tractor is run in a particular speed over this rail track in a straight line.

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c) TIG Welding torch- Torch is fixed with the movable tractor unit. A tungsten electrode is fixed
in the torch and Ar gas is flow through this.
d) TIG welding machine– This is the main part of TIG welding setup by which controlled
amount of current and voltage is supplied during welding. A Rectifier (made by FRONIUS) with
current range 10-180 A and voltage up to 230 V, depending on the current setting has been used.
e) Gas cylinder- For TIG welding Ar gas is supplied to the welding torch with a particular flow
rate so that an inert atmosphere formed and stable arc created for welding. Gas flow is control by
regulator and valve.
f) Work holding table- a surface plate (made of grey cast iron) is used for holding the work piece
so that during welding gap between the tungsten electrode and work piece is maintained. Proper
clamping has been used to hold the work piece.
g) The torch was maintained at an angle approximate 90° to the work piece.

3.2 Calibration of speed

Before start the experiment speed of the movable tractor was calibrated to get a required welding
speed and found different speed value which is shown in table 1.
Table 1: Speed value on speed controlled tractor

Number on equipment Speed value(mm/s)

Number on equipment Speed value(mm/s)
1 2.5
1.5 3
2 3.5
2.5 4
3 4.5
3.5 5
4 5.5
4.5 6

3.3 Experimental planning and procedure:

For the present work, experimentation was done in two phase. In first phase, butt welding of Al
plate (3 mm thickness) done at one side with different current setting and welding speed. In
second phase, butt welding of Al plate done both side by varying welding speed and current
setting.
3.3.1 Experimental procedure:

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Commercial Aluminum plate of thickness 3 mm was selected as work piece material for the
present experiment. Al plate was cut with dimension of 120 mm x 50 mm with the help of band-
saw and grinding done at the edge to smooth the surface to be joined. After that surfaces are
polished with emery paper to remove any kind of external material. After sample preparation,
Aluminium plates are fixed in the working table with flexible clamp side by side and welding
done so that a butt join can be formed. TIG welding with Alternate Current (AC) was used in
experiments as it concentrates the heat in the welding area. Zirconiated tungsten electrodes of
diameter 3.4 mm was taken as electrode for this experiment. The end of the electrode was
prepared by reducing the tip diameter to 2/3 of the original diameter by grinding and then
striking an arc on a scrap material piece. This creates a ball on the end of the electrode. Generally
an electrode that is too small for the welding current will form an excessively large ball, whereas
too large an electrode will not form a satisfactory ball at all. For the first phase of experiment
welding parameters selected are shown in table 2. Before performing the actual experiment a
number of trial experiments have been performed to get the appropriate parameter range where
welding could be possible and no observable defects like undercutting and porosity occurred.

Table 2: Welding parameters for 1st phase of experiments

Parameters Range
Welding current (100-140) A
Voltage 50 v
Speed (3.5-4) mm/s
Distance of tip from weld centre 3 mm
Gas flow rate (8-10) l/min.
Current type AC
Dimension 120mm*50mm*3mm
Table 2: Welding parameters for 1st phase of experiments

After performing the welding, welded specimens were cut with dimension of 100 mm
x 25 mm for tensile test, which were further cut in to I shape. Tensile test was performed with
universal tensile testing machine (Instron-600) with maximum load capacity of 600 kN.
Further, a 10 mm x5 mm x3 mm specimen were cut at the cross section for microstructural study
and micro-hardness measurement from each sample. Before microhardness measurement cross
section of the welded specimen mounted and polished with 220, 600 and 1200 grit size polishing
paper sequentially. Micro-hardness was measured with Vickers micro-hardness tester (LECO

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micro hardness tester LM 248 AT). Optical image of the cross section of the welded zone was
taken with an optical microscope

CHAPTER 4

RESULT AND DISCUSSION

Welding width for all the samples were measured and calculated average welding width as
shown in table 4. Average value of welding width then plotted against the applied welding
current for different welding speed as shown in Fig. 5. From the plot it is clearly seen that
welding width increases almost linearly with increase of welding current. Fig.4 shows the
welded butt joint specimen, where welding performed with different welding speed and current
setting as described in table 3.

4.1 Optical Microscopy Images Of The Weld Zone At The Cross Section

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Fig. 7: Optical microscopy photograph at the cross section of the welding done with different
current setting and welding speed

Fig. 7 shows the optical image of the welded zone at the cross section for the specimen prepared
with different welding speed and current setting. From the images no specific change could be
observed for the weld specimen. However, cross section of the weld zone shows a clear effect of
the welding parameters like applied current and welding speed. Fig. 7 shows the optical
photograph at the cross section of the welding performed with different current setting and
welding speed. From the figure it can be seen that welding is not performed full depth of the
work piece. Depending on the welding speed and current setting this welding penetration is
changed. It can be say from the observation of the figure that as welding current increases
welding depth also increases for fixed value of welding speed. Again for a particular value of
welding current welding depth found decreases as the welding speed increases.
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4.2 Micro-hardness test

Micro-hardness value of the welded zone was measured for all the welded specimens at the cross
section to understand the change in mechanical property of the welded zone. Fig. 8 and 9 shows
the micro-hardness value at the welded zone taken from the Centre of the welding zone towards
the base material for different samples performed with different welding speed and welding
current. From the graph it is found that for almost all the sample micro hardness value increases
in the welding zone than the base material and these values are in the range of 40 to 80 HV in the
welded zone. After a certain distance these value reduces to the hardness of the base material for
the sample processed with welding speed 3.5 mm/s and different current setting as shown in Fig.
8. However for the welding done with welding speed 4 mm/s and different current setting micro-
hardness value reaches to the micro-hardness value of base material after 5 to 6 mm.

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CHAPTER 5
CONCLUSION
From the experiment of TIG welding of Aluminum plate following conclusion can be made
With the automated welding system uniform welding of Aluminum plate can be possible.
Welding strength or tensile strength of the weld joint depends on the welding parameters
like welding speed and welding current.
With the increase in current, tensile strength of the weld joint increases.
Hardness value of the weld zone change with the distance from weld center due to change of
microstructure.
At lower welding speeds strength is more due to more intensity of current.
For both side welding tensile strength is found almost equivalent to the strength of base
material.
For both sided welding performed with high current (180 A), welding speed have no specific
effect on tensile strength of the weld joint.

Future scope
In present work welding is performed without any filler material. Filler Rod/wire feeding system
can be included in the system so that by using filler rod/wire thicker plate can be welded.
Welding setup can also be use for welding of some other materials.

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REFERENCES
[1] en.wikipedia.org/wiki/GTAW
[2] www.weldwell.co.nz/site/weldwell
[3] http://www.azom.com/article.aspx?ArticleID=1446
[4] www.micomm.co.za/portfolio/alfa
[5] Kumar, S.(2010) Experimental investigation on pulsed TIG welding of aluminum

plate. Advanced Engineering Technology.1(2), 200-211

[6] Indira Rani, M., & Marpu, R. N.(2012). Effect of Pulsed Current Tig Welding
Parameters on Mechanical Properties of J-Joint Strength of Aa6351. The
International Journal of Engineering And Science (IJES),1(1), 1-5.
[7] Hussain, A. K., Lateef, A., Javed, M., & Pramesh, T. (2010). Influence of Welding
Speed on Tensile Strength of Welded Joint in TIG Welding Process. International
Journal of Applied Engineering Research, Dindigul, 1(3), 518-527.
[8] Tseng, K. H., & Hsu, C. Y. (2011). Performance of activated TIG process in austenitic
stainless steel welds. Journal of Materials Processing Technology, 211(3), 503-512.
[9] Narang, H. K., Singh, U. P., Mahapatra, M. M., & Jha, P. K. (2011). Prediction of the weld
pool geometry of TIG arc welding by using fuzzy logic controller. International Journal of
Engineering, Science and Technology, 3(9), 77-85.
[10] Karunakaran, N. (2012). Effect of Pulsed Current on Temperature Distribution, Weld Bead
Profiles and Characteristics of GTA Welded Stainless Steel Joints. International Journal of
Engineering and Technology, 2(12).
.

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