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org (ISSN-2349-5162)

TIG WELDING AND EFFECT OF VARIOUS

PARAMETERS ON TIG WELDING: A REVIEW
1
Vikarm, 2Yajvinder, 3Ghanshyam Das
DEPARTMENT OF MECHANICAL ENGINEERING,
GURU JAMBHESHWAR UNIVERSITY OF SCIENCE AND TECHNOLOGY, HISAR
_________________________________________________________________________________________________
Abstract: This paper represents a review on TIG welding and effect of various process parameters on TIG welding process. GTAW
plays an important role in those industries where it is important to control the metallurgical properties and weld bead shape. TIG
welding process compared to other arc welding process, low heat affected zone, no slag, in a single pass its productivity is relatively
low and high heat concentration. Knowledge of process variables is important and necessary to produce weld of satisfactory quality.
The parameters such as welding speed, current, voltage, gas flow rate etc. affects the weld strength in the form of weld bead geometry
and mechanical strength. Various techniques are proposed in literature to achieve the better optimization of these parameters.

Keywords: TIG welding, process parameters, welding current, speed, voltage

________________________________________________________________________________________________________

• Introduction
TIG welding is a type of welding process and these types of welding is widely used in modern industries for joining the
similar or dissimilar materials. TIG welding is also called gas tungsten arc welding (GTAW). The main advantages of TIG
welding process it require low heat affected zone, absence of slag, joining of similar and dissimilar metals at very high
quality weld. The quality and accuracy of joints mainly depends upon welding speed, shielding gas, power supply, gas flow
rate, voltage. TIG welding techniques is relatively a high strength welding techniques as compared to others. TIG welding
process has been a most popular choice of welding process when a considerable precision welding operation and a high
level of weld quality is required. In the TIG welding process the main problem is limited thickness of material which can
be welded in single pass, weak tolerance to some material composition and the low productivity. In TIG welding uses a
separate filler metal and a non-consumable electrode with an inert shielding gas (Ar, He). It is a manual welding process in
which welder uses both hands to weld, one hand is used to adding the filler rod to the weld joint and other hands for
holding the TIG torch that is produce the arc.

Fig.1 TIG welding process

The setup of TIG welding is consists of a cylinder of argon gas, welding torch, cable for current supply, a suitable power
sources, tubing for gas supply and water tubing for cooling the torch. The shape of welding torch having a cap type at one
end to protect the rather long tungsten electrode against emergency or accident breakage, In TIG welding tungsten is used

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because it is very hard, brittle and radioactive material. This is used limited as compared to others metals. TIG welding
requires three main things the first one is heat which is produced by electricity passing through the tungsten electrode by
creating an arc to the weld. The second things is shielding gas comes from a cylinder of gas flow to the weld area to protect
from air and the last things is filler rod or metal that is added by hand into the arc and melted. A small section of stainless
steel, mild steels and non-ferrous metals such as magnesium, aluminium, and copper alloys are mainly welded by TIG
welding. The process gives the operator greater control and safety over the weld as compared to metal inert gas welding,
allowing for stronger and higher quality welds. However, GTAW being significantly slower than most other welding
techniques is comparatively more complex, hazardous and difficult to master.
• problem statement and formulation
• Gurram et al., [2013] studied the effect of copper and aluminium addition on mechanical properties and corrosion
behavior of AISI 430 ferritic stainless steel gas tungsten arc welds. Authors welded stainless steel plates by TIG
welding process. The plates of 5 mm thickness are used for preparing the welded butt joint. Authors evaluated the
mechanical and corrosion behaviour of TIG welded joints. They conclude that the ferritic stainless steel joints
fabricated by the addition of 2 gm Al in post-weld annealed condition resulted in better tensile properties compared
to all other joints, They also concluded that there is a marginal improvement in the ductility of ferritic stainless
steel weldments by the addition of 2 gm Cu in post-weld annealed condition compared to all other joints and base
metal.

• Abdalla et al., [2015] studied the analysis of the mechanical behaviour of AISI 4130 steel after TIG and laser
welding process. Authors welded stainless steel AISI 4130 plate by TIG and laser welding process. The plates of 1
mm thickness are used for preparing the welded butt joint for each test. Authors evaluated the mechanical
behaviour of TIG and laser welded joints on such parameters power 750W (LASER), 148W (TIG), speed
60mm/sec (LASER), 1.65mm/sec (TIG), voltage 7.4V (TIG), current 20A (TIG). They concluded that laser
welding process easily automated and produces phase transformation area about ten times smaller than TIG
welding process. The hardness in the fusion zone is quite high for both processes, but it was reduced to about 200
HV for the laser welded steel and about 100 HV in TIG process after tempering. The tempering applied after
welding process improved the ductility of the steel, transforming the martensite and enhance the compatibility
between the phases.

Fig.2 LASER and TIG welding microstructure view

• Baddu and Raole, [2014] studied the mechanical properties and microstructural investigations of TIG welded 40
mm and 60 mm thick SS316l samples for fusion reactor vacuum vessel applications. They welded stainless steel
316l plates by TIG welding process for fusion reactor vacuum application. The plates of 40 mm and 60 mm
thickness are used for preparing the double V groove welded joint. Authors evaluated the mechanical and
microstructure behaviour of TIG welded joints. They concluded that the samples have exhibited the higher tensile
strength in both the 40 mm and 60 mm thick plates compared with base metal. Impact fracture energy of the WZ
was less as compared to BM and HAZ.

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• Zou et al., [2015] studied the mechanical properties of advanced active-TIG welded duplex stainless steel and
ferrite steel. They welded duplex stainless steel and ferrite steel plates by TIG welding process. The plate of 1 mm
thickness and 0.2 mm notch is used for preparing the welded joint. They used welding speed, current, arc length,
electrode diameter, shielding gas as input parameters. Authors evaluated the mechanical properties of TIG welded
joints. They concluded that the weld oxygen content played a significant role in affecting the weld shape of both
steels, which could be controlled by adjusting the oxygen content and the shielding gas of the AA-TIG welding
process. They also concluded that with the increase in the weld oxygen content, the weld shape became narrow and
deep for both steels. The Vickers hardness of the weld metals of both steels was not affected by the oxygen content
in the shielding gas.

Fig.3 Active-TIG welding process

• Lei et al., [2011] studied the microstructure and mechanical properties in TIG welding of CLAM steel. Authors
welded CLAM steel plates by TIG welding process. The plate of 0.5 mm thickness is used for preparing the
welded joint. Authors evaluated the mechanical and microstructure behaviour of TIG welded joints. They used a1,
a2 original CLAM composite filler as filler material. They concluded that the tensile strength was reduced when
the PWHT temperature rise, tensile strength of WM is higher than that of HAZ and BM. The microstructure of the
weld metal for every specimen was found to be tempered martensite with a little of delta ferrite. Hardening at WM
and softening in HAZ is detected in the TIG weld joint. Microhardness in WM decreased when the temperature of
PWHT increased. The ultimate tensile stress of weld metal is higher than that of HAZ and BM. Absorbed energy
increased with PWHT temperature rising, until PWHT was done at 760◦C/30min, the specimen ductile fractured in
local area

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Fig.4 Micro hardness distributions on TIG weld joints (a) cross-section of TIG weld joint (b) using the original
CLAM composition filler metal (c) using the modified composition.

• Sathiya et al., [2015] studied the comparative study on transverse shrinkage, mechanical and metallurgical
properties of AA2219 aluminium weld joints prepared by gas tungsten arc and gas metal arc welding processes.
They welded AA2219 alloy by TIG and MIG welding process. The plate of 25 mm thickness is used for preparing
the welded butt joint. Authors evaluated transverse shrinkage, mechanical and metallurgical properties of TIG and
MIG welded joint. They used welding current 185A (MIG) and 195A (TIG), voltage 28V (MIG) and 10.5V (TIG),
groove design V shaped, speed 25 cm/min. (MIG) and 10 cm/min. (MIG), polarity and gas flow rate as input
parameters. They concluded that the transverse shrinkage generated in GTAW weld joint is comparatively lower
that in GMAW weld joint. The tensile strength of GTAW weld joint is higher than that of the GMAW weld joint.
The hardness values of TIG and MIG welds are lesser than heat affected zone and base metal.

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Fig.5 Hardness distribution across the transverse section of weld joints

• Ahmadi and Ebrahimi, [2015] studied the welding of 316L austenitic stainless steel with activated tungsten inert
gas process. Authors welded stainless steel 316L plates by activated TIG welding process. The plate of 9 mm
thickness is used for preparing the welded joint. Authors evaluated the mechanical and morphology properties of
TIG welded joints. They used a flux from 0.1 to 8 mg/cm2 were carried out to study the effects of coating density
of flux on the weld penetration. The process parameters are electrode diameters3.2 mm, current 150A, and arc
length 3 mm, gas flow rate 12L/MIN. They concluded that the weld penetration is increased while the weld metal
width decreased; among the fluxes SiO2 flux had a significant effect on enhancing the weld penetration in A-TIG.
A-TIG welding can increase ultimate tensile strength of weldment because of increasing the retained delta ferrite
content of stainless steel welds.

• Kah and Martikainen, [2013] studied the influence of shielding gases in the welding of metals. They welded
stainless steel plates by TIG and laser welding process. The plate of 5 mm thickness is used for preparing the
welded joint. Authors evaluated the mechanical properties and microstructure of TIG welded joints. They used
helium, argon, hydrogen as shielding gas. They concluded that for carbon steel, increasing the oxidation potential
of the shielding gas decreases the toughness and tensile strength of the weld deposit. For ferritic stainless steel,
increasing the amount of carbon dioxide in shielding gases can increase the martensite content at the grain
boundary.

• Liu et al., [2015] studied the activated flux inert gas welding of 8 mm-thick AISI 304 austenitic stainless steel.
They welded stainless steel AISI 304 plates by activated TIG welding process. The plate of 8 mm thickness is used
for preparing the welded joint. Authors evaluated the mechanical properties of TIG welded joints. They used
welding current 150A, voltage 25V, speed 60-75mm/min, gas flow rate 10-15 l/min. as input parameters and
ER304 as filler material. Authors concluded that activated flux powder in TIG welding can increase the content of
delta-ferrite in weld metal, but does not significantly change the microstructure and chemical components of A-
TIG weld compared with those of C-TIG weld. The tensile strength and elongation of A-TIG weld joints are
superior to those of C-TIG welding and no crack or defect with single length more than 3 mm is detected on the
surface of bended welds after bending test.

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Fig.6 Activated flux inert TIG welding

• Atapour et al., [2014] studied the microstructure and corrosion behaviour of multipass gas tungsten arc welding
304L stainless steel. Authors welded stainless steel 304L plates by TIG welding process. The plate of 6 mm
thickness is used for preparing the welded joint. Authors evaluated the mechanical and corrosion properties of TIG
welded joints. They used ER 308 filler rod as filler material. They concluded that all the weld were essentially
austenitic with the presence of a small amount of ferrite. The hardness values from the weld zone towards the base
metal increased in all weldments while the maximum values obtained for three passes welded specimen due to the
increase in the ferrite content and grain. The corrosion resistance also increased.

Fig.7 microhardness profile showing the hardness values at different zone

• Molak et al., [2009] studied the Measurement of mechanical properties in a 316L stainless steel welded joint.
Authors welded stainless steel 316L plates by TIG welding process. The plate of 8 mm thickness is used for
preparing the welded joint. The authors evaluated the mechanical properties and microstructure or image
correlation study of TIG welded joints. They concluded that Optical strain measurements based on Digital Image
Correlation can be very helpful for strain measurements during the static tensile test of a micro sample. The
differences in mechanical properties of the material examined with the use of micro samples and standard samples
are significant. Especially for the case of yield strength and elongation to failure values.

Fig.8 stress- strain diagram for different weld zone

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• Kumar et al., [2015] studied the experimental process of TIG welding of a stainless steel plate. They welded
stainless steel 304 plates by TIG welding process. The plate of 6 mm thickness is used for preparing the welded
joint. Authors evaluated the metal deposition rate of TIG welded joints by using orthogonal array (L9). They used
DOE (design of experiment) approach to find out the final results. They used current, gas flow rate, root face, and
welding time as input parameters. Authors concluded that the current and root face affect the metal deposition rate
very significantly. They found that optimal input parameter current, gas flow rate, root face and welding time are
90A, 2.0 ltr/min, 20mm and 95 second.

• Ghosh et al., [2016] studied the parametric optimization of MIG welding on 316L austenitic stainless steel by grey-
based taguchi method. Authors welded stainless steel 316L by MIG welding process. The plate of 3 mm thickness
is used for preparing the welded butt joint. Authors evaluated the mechanical properties of MIG welded joint. They
used welding current, gas flow rate and nozzle length as input parameters. They concluded that the x ray test result
shows that lack of penetration and visual inspection indicate the undercut, spatter and blow holes in some sample.
The optimum parameters founded by taguchi method are current 10A, gas flow rate 20l/min and nozzle distance 15
mm and current is more significant as compared to gas flow rate and nozzle distance.

Fig.9 Response graph for mean desirability

• Gulenc et al., [2005] studied the experimental study of hydrogen in argon as a shielding gas in MIG welding of
austenite stainless steel. Authors welded stainless steel 304L by MIG welding process. The plate of 10 mm
thickness is used for preparing the welded joint. Authors evaluated the mechanical and microstructure properties of
MIG welded joint. They used welding current and shielding gas as input parameters. They concluded that the
sample welded at 240A current and with 1.5% H2-Ar shielding media had shown good tensile property. When the
amount of hydrogen in Ar is increase, then toughness of welding joint is increased. The hardness value is higher at
base metal as compared to heat affected and weld zone.
• PROCESS PARAMETERS
In TIG and MIG welding process variables play an important role in the quality, bead geometry and weld penetration.
Knowledge of process variables is important and necessary to produce weld of satisfactory quality. The process
variables are changing from one range to other to produce desired results and that are not completely independent.
The following parameters affect the quality of the weld:
• Welding current
When the current is high, TIG welding leads to splatter and work piece gets damaged. When the current is low,
TIG welding leads to sticking of the filler wire. Fixed current mode is used to the voltage to maintain a constant
arc current. Larger heat affected zone (HAZ) can be found for lower welding current.
• Welding voltage
Welding voltage may be fixed or adjusted. It depends upon the TIG welding equipment. A high initial voltage
allows for easy arc initiation. Too high voltage, can lead to a large variable in welding quality.
• Welding speed
When the welding speed is increased, heat input per unit length of weld decreases and penetration of weld
decreases. Welding speed controls the bead size and penetration of weld. It does not depend on current.
Excessive high welding speed causes the uneven bead shapes, increase the tendency to porosity.

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• Gas flow rate

Gas flow rate is important factor which is affected the results and output. Flow rate range generally is 6-7
litre/min. In TIG uses a lot of shielding gas so it pays to set up the gas flow accuracy for obtains proper results.
• Welding current
When the current is high, TIG welding leads to splatter and work piece gets damaged. When the current is low,
TIG welding leads to sticking of the filler wire. Fixed current mode is used to the voltage to maintain a constant
arc current. Larger heat affected zone (HAZ) can be found for lower welding current.

• ADVANTAGES AND DISADVANTAGES

Advantages of TIG welding:

• Electrode is non-consumable used in process and thin section is easily welded.
• Welds can be made with or without filler metal.
• Better control on welding variable and no slag and splatter problem.
• In TIG welding low distortion of work piece because of the small heat effected zone.
• The TIG process has many applications and uses because it can be used to make high quality welds in almost any
metals and alloys.
• It can be done by both automatic and manual techniques and can be applied in all positions.
• TIG may be used on a wide range of metal thickness.

Disadvantages of TIG welding:

• The UV rays is brighter as compared to others welding process.
• It is a slower process than consumable electrode arc welding process.
• Overall expensive is more. Welding supplies is expensive as compared to others because the arc travel speed and
metal deposition rate is slow and tungsten electrode is also expensive
• The contamination comes during the transfer of molten tungsten from the weld. Exposure of the hot filler rod to air
using wrong welding techniques causes weld metal contamination.

• CONCLUSION
Various parameters like welding current, speed, voltage, gas flow rate, electrode diameter etc. are important to achieve the
better quality. Microstructure properties will be studied at different zone of welding and founded that how the temperature
distribution affected the base metal, heat affected zone and weld zone. The joints fabricated by TIG process exhibited
higher tensile strength as compared to GMAW joints. The superior tensile properties of TIG joints are due to the formation
of uniformly distributed and very fine strengthening precipitates in the weld region. TIG welding parameters affects the
weld strength in the form of weld bead geometry and mechanical strength. TIG welding specimen can bear higher
elongation and yield strength.

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