Ijetr021140

International Journal of Engineering and Technical Research (IJETR)
ISSN: 2321-0869, Volume-2, Issue-1, January 2014
88 www.erpublication.org

Abstract— The Welding process can be defined as a method
to join material usually metals and thermoplastics, by causing
coalescence. This is often done by melting the work pieces and
adding a filler material to form a pool of molten material
(the weld pool) that cools to become a strong joint,
with pressure sometimes used in conjunction with heat, or by
itself, to produce the weld. Thus Cost reduction and
productivity improvement in welding operation can therefore
generate considerable impacts on competitiveness of various
manufacturing industries. The other factors which plays a
major role in determination of weld quality is welding time,
depth of penetration, heat, surrounding conditions. The other
methods used to perform the deep penetration processes are
energy beam methods such as laser beam welding and electron
beam welding. The primary disadvantages are their very high
equipment costs (though these are decreasing) and a
susceptibility to thermal cracking. Also these energy beam
methods are very expensive and thus does not suits for many
applications. This paper presents an inexpensive welding
process with much smaller weld joint and good depth of
penetration. This work thus focuses on improving weld
penetration without substantial cost increase. Instead of using
another welding process, arc welding process will be performed
in a novel method. These processes use a welding power
supply to create and maintain an electric arc between an
electrode and the base material to melt metals at the welding
point. They use either direct or alternating current, and
consumable or non-consumable electrodes. The welding region
is sometimes protected by some type of inert or semi-inert gas,
known as a shielding gas, and filler material is sometimes used
as well. Common types of arc welding process are submerged
metal arc welding, gas metal arc welding, flux core arc welding,
tungsten gas welding and submerged arc welding.
Index Terms—two way arc welding, modern technologies,
penetration, welding
I. INTRODUCTION
It is known that arc welding can achieve deeper penetration
than other arc welding because of its more concentrated arc
and plasma jet. However, the majority of the welding current
in arc welding earths through the top surface of the base
metal. This earthling of current leads to low weld penetration,
thus only the plasma jet which has been ionized and heated by
the arc, rather than the arc itself, can directly penetrate into
the keyhole. If the arc can directly penetrate into the keyhole,
the penetration will be significantly increased. Hence, this
paper proposes increasing the penetration by placing a
second electrode on the opposite side of the work piece. The
Manuscript received January 19, 2014.
Sambhav Jain, Mechanical Engineering, Jamia Millia Islamia, New
Delhi, India, +9654337070.
Nisarg Shah, Mechanical Engineering, Babaria Institute of technology,
Gujarat, India, +9409213539
two torches are directly connected to the two terminals of the
power supply. Thus this completes arc and the hence the
current flows. The resultant welding current loop becomes
power supply-torch-work-torch-power supply instead of the
conventional power supply-torch-work-power-supply loop.
As a result, the welding current, thus the arc, is guided into
the joint. Another method to improve penetration in arc
welding is to improve the energy density of the arc because
energy density is
the primary
factor
responsible for
the penetration
difference
between
laser/electron
beam welding
and arc welding.
Hence, this
study explores another method to improve arc concentration
and arc energy density to improve penetration with arc
welding.
II. WORKING PRINCIPLE
The basic working principle of the process is to place the
second torch in opposite direction to the first torch referred as
primary torch, welding current flows through the keyhole,
instead of earthing through the work surface, in the proposed
process. Thus, the plasma arc is guided into the joint and it
becomes more concentrated. Hence, the penetration
capability is increased to a great extent. It is apparent that the
welding current must flow through the work during DSAW.
Thus, the process proposed above, of arc welding in
improving penetration provides a better weld joint.
In case of plasma arc welding the gas gets ionized after
passage of electric current through it and it becomes a
conductor of electricity. In ionized state atoms break into
electrons (-) and ions (+) and the system contains a mixture
of ions, electrons and highly exited atoms. The degree of
ionization may be between 1% and greater than 100%.
Thus the whole process is divided in two stages viz.
electropositive and electronegative periods. The major
difference that is the arc is more concentrated in
electronegative period and the penetration is primarily due to
electronegative period.
TWO WAY ARC WELDING FOR DEEPER AND
NARROWER PENETRATION
Sambhav Jain, Nisarg Shah

TWO WAY ARC WELDING FOR DEEPER AND NARROWER PENETRATION
It is known that the PAW torch has a constricting orifice such
that electrons emitted from the tungsten electrode flow
through the ionized plasma gas and form a highly constricted
plasma jet. This plasma jet melts the workpiece and can
displace the molten metal to form a keyhole or deep narrow
cavity. Therefore, the PAW/GTAW torch combination may
generate the keyhole double-sided arcing phenomenon.
The concentration of the plasma arc can be explained by the
welding current direction and its induced magnetic field. In
The proposed process, the welding current flows
approximately normally through the work. Welding current
in such a direction generates a magnetic field. Under the
effect of this magnetic field, the current lines are driven
towards the axis. The welding current is concentrated both in
the arcs and in the work. Because of the spatial correlation
between the welding current and the arc distribution, the arcs
are therefore converged.
A. ANALYSIS OF HEAT AFFECTED ZONE (HAZ)
The heat affected zone is the factor that determines the
properties of the weld. For any application the depth of the
weld pool is pre determined thus ratio of the depth and the
width of the pool play a major role in the determination of
HAZ. Thus it is clearly stated that the increase in the
penetration can only be achieved by increasing the width of
the weld pool. Thus width of the pool becomes the primary
factor in determination of the heat affected zone. It is noted
that with the increase in the current supply, the depth and
width of the pool increases simultaneously and thus the ratio
remain unchanged, thus for increasing the depth of
penetration, heating is to done from both the sides which
primarily increases the depth due to increased depth to width
ratio.
B. DEFECTS IN WELDING
The major welding defects are the undercuts, porosity,
distortion, incomplete penetration and lamellar tearing, gas
inclusion.
This method solves most of the problems associated with the
plasma arc welding. In case of convectional plasma arc
welding the plasma pressure, gravity results in separation of
liquid pool from the welding torch solid material, however
the undercut may develop when the force between the solid
material and melted material is not sufficient due to which the
cross-sectional thickness of the base metal reduces. This
defect is however solved in this process because of the
simultaneous welding at the bottom of the work piece due to
which the gravity serves as the retaining force.
Distortion in welding process occurs due to shrinkage of the
heated metal. Since the two way arc welding heats the metal
from both the sides, thus thermal distortion is reduced.
III. EXPERIMENTAL SET-UP
For setting up the experiment, we analyzed the material
TC4 titanium alloy with following chemical composition:
AL V Fe C N O H Ti
6.0 4.1 0.05 0.01 .027 0.12 .006 Bal.
The basic dimension selected for the experiment is
120mm*60mm*4.35mm. The work piece was firstly
grounded with stainless steel brush and sandpaper to remove
the oxide film, and then cleaned with acetone to remove the
organism such as oily soil. It is also seen that at high
temperature, the welding of tungsten is very difficult due to
its high chemical reactivity. Large amount of oxygen,
nitrogen and hydrogen is used during the welding. The
welding speed was approximately 200 mm/min. The
diameter of the nozzle and the electrode was 12 and 3
respectively.
The welding joints were then carefully observed with
optical microscope. Tensile tests were carried out on
INSTRON series IX auto material test machine at a cross
head speed of 1mm/min.
IV. INFERENCE FROM EXPERIMENT
A. Physical Appearance of the Weld
The surface of the weld joint was smooth and fine, when the
current of the two torches was 80 A. The weld zones and the
heat affected zone are well protected with no defects of
deformation. Gas cavities and cracks were also reduced.
B. Macrostructure and Microstructure of welds
The experiments concluded that the two way arc welding was
much superior to the convectional arc welding; since the
amount of penetration was much more noticed in case of two
way arc welding. The figure clearly depicts the arc weld joint
in the case of two way arc welding. This not only increases
the penetration but reduces heat input and saves energy.
In the case of microstructure of the base metal, the structure

International Journal of Engineering and Technical Research (IJETR)
ISSN: 2321-0869, Volume-2, Issue-1, January 2014
Of heat affected zone was changed and the grains are fine for
growing into equiaxed grains during the thermal cycles
involving rapid heating and cooling.
C. Tensile Strength
The tensile strength tests were conducted on the work piece.
Dimples and polygons contours were observed in fracture
photos taken by SEM. Along with this uneven distribution of
dimples were observed with clear overlaying of tear ridges.
Cavities under dimples were also observed. The large size
dimples were seen surrounded by some exiguous one. The
coarse columned grains in the fusion zone were rapidly
formed and thus leading in harmful elements concentrating of
grain boundaries. This results in reduction of binding force of
grain boundary and resisting force of fracture of titanium
alloy. Thus it shows that the fracture mode of the titanium
alloy weld joint is of mixed ductile and brittle characteristics
because of dimple and contour faces of grains. But the
dimples are the main appearances, thus the fracture is of
ductile mode.
V. ARC CONCENTRATION
The arc behaviors for regular Plasma arc welding and TWO
WAY ARC WELDING before and after the keyhole is
established are very different. First, in comparison with
regular plasma arc, the plasma arc in TWO WAY ARC
WELDING becomes much more concentrated despite the use
of similar welding parameters.
Second, after the weld joint is established, the plasma arc in
two way arc welding is further concentrated while the regular
plasma arc remains unchanged. During Two way arc
welding, current has to flow from one torch to another
through the work piece. If the current flows through the work
piece instead of the joint, the electrons must exit from the
work piece through the cathode on the GTAW side surface of
the work piece to the GTAW electrode. Because of the large
current needed for welding, the electrons tend to emit from
the work piece from an area rather than a small spot. Hence,
the work piece cathode is typically much less focused than
the anode. As a result, the GTAW arc in DSAW is much
broader than the plasma arc.
The trajectory of the electrons (current) in the plasma arc
column is not affected by the work piece. However, for
regular Plasma arc welding, the electrons have a nearly
90-deg transition in direction when they enter the work piece.
To realize such a large transition in travel direction, the
electrons must change their direction prior to ―landing‖ on
the work piece. The arc column in regular plasma arc
welding, thus, must be subject to a divergence. Hence, the
plasma arc in two way arc welding is much more
concentrated than the regular plasma arc. The establishment
of the keyhole further enhances the concentration of the
plasma arc in two way arc welding. After the keyhole is
established, the current may take the keyhole as the path. In
this case, the current flows through the keyhole without being
affected by the work piece cathode, the diameter of which is
much larger than that of the keyhole. The plasma arc can thus
be further concentrated. Hence, the density of the plasma arc
is at least doubled after the keyhole is established. The
GTAW arc is still broad after the keyhole is established. This
indicates that; although the electrons can flow through the
keyhole to minimize the voltage, part of them actually flows
through the work piece, causing a cathode on the work piece.
Therefore, during keyhole two way arcs welding, only part of
the current goes through the keyhole. The rest of the current
flows through the work piece
VI. CHARACTERISTICS OF WELD JOINT
The cross sections of double-sided arc welds are
approximately symmetrical and hourglass shaped. Although
detailed studies are needed to determine the effectiveness of
this shape in thermal distortion and residual stress reduction,
it is certain the thermal distortion and residual stress must be
reduced.
A. GRAIN STRUCTURE
Generally, the solidification structure is controlled by the
solidification parameters— the solidification growth rate R
and the thermal gradient in the liquid GL. The ratio of the two
parameters GL/R normally changes from a maximum value
at the fusion boundary to a minimum along the center of the
weld. These changing solidification conditions result in a
weld solidification structure changing from planar at the weld
boundary to columnar dendrite and then to equiaxed dendrite
grain along the weld center. For TWO WAY ARC
WELDING process, it was found the fraction and width of
the fine equiaxed grain region gradually increases in the weld
metal zone along with an increase in the depth of penetration.
It is known that when the penetration increases, the amount of
molten metal increases. Such an increase in the amount of
molten material helps heat the work piece before cooling;
hence, the thermal gradient during cooling is reduced. This
tends to allow an increase in the amount of fine equiaxed
grains produced.
VII. CONCLUSION
Double-sided arcing phenomenon and technique have been
used to develop the keyhole TWO WAY ARC WELDING
process. Observation and analysis show the
through-thickness direction of the current and the
establishment of the keyhole both plays significant roles in
enhancing arc concentration. Experimental data and analysis
suggest at least part of the current flows through the keyhole
if the keyhole provides a minimum voltage path. The
presence of the current in the keyhole generates an energy
compensation not found in other arc welding processes. The
keyhole TWO WAY ARC WELDING process has proven
capable of achieving deep, narrow joint penetration on
square-groove, thick stainless steel plates up to 1⁄2-in. in a

TWO WAY ARC WELDING FOR DEEPER AND NARROWER PENETRATION
single pass. Keyhole TWO WAY ARC WELDING reduces
heat input into the work piece by at least 70% in comparison
with regular keyhole PAW, which achieves the deepest and
narrowest penetration at the least heat input of all existing arc
welding processes. In other words, keyhole TWO WAY
ARC WELDING requires only 30% of the heat input needed
by keyhole PAW. Welds produced by keyhole TWO WAY
ARC WELDING are less than 1 mm wider than those
produced by the laser process. To penetrate the same
thickness of stainless steel plates up to 1⁄2in. thick, the heat
input into the work piece by the keyhole TWO WAY ARC
WELDING process is approximate five times as much as that
input by a high-power (approximately 10-kW)laser. Welds
produced by keyhole TWO WAY ARC WELDING are
approximately symmetrical and hour glass shaped. Keyhole
TWO WAY ARC WELDING tends to increase the amount
of the desirable equiaxed grains in the solidified welds.
Detailed studies are needed to fully disclose the metallurgical
implications and mechanical properties for keyhole TWO
WAY ARC WELDING of different materials, including the
impact of heat input reduction and symmetrical shape on
thermal distortion and residual stress, and to quantitatively
analyze the phenomena during double sided arcing and the
keyhole two way arc welding process.
Through the experimental set up it can be concluded that the
titanium alloy can be successfully welded by two way arc
welding at appropriate welding parameters. The welded joint
has good surface appearance without obvious deformation
and defects of cracks and gas acavities.
The two way arc welding process is superior over the regular
single side arc welding on the aspect of low heat ninput,
decreasing the width and deformation of welds and refining
grains. The joints can reach 96.14% tensile strength and
70.85% elongation of the base metal.
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Press
Sambhav Jain is pursuing bachelor of technology in
mechanical engineering fro m Jamia Millia Islamia, New
Delhi. He has keen interest in manufacturing engineering
processes.
Nisarg Shah is a student of mechanical engineering from babaria
institute of technology, Gujarat. He has interests in manufacturing
engineering.

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