Influence of process parameters on depth of

IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308
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Volume: 02 Issue: 10 | Oct-2013, Available @ http://www.ijret.org 220
INFLUENCE OF PROCESS PARAMETERS ON DEPTH OF
PENETRATION OF WELDED JOINT IN MIG WELDING PROCESS
Biswajit Das1
, B. Debbarma2
, R. N. Rai3
, S. C. Saha4
1
Research Scholar, 2
Assistant Professor, 3
Associate Professor, 4
Professor, National Institute of Technology, Agartala,
India, erbiswajit1984@gmail.com, bishopdabork@yahoo.co.in, nareshay@yahoo.co.in,
subashchandrsaha@yahoo.co.in
Abstract
The effect of various welding process parameters on the weldability of Mild Steel specimens of grade EN-3A having dimensions
150mm× 100mm× 6 mm, welded by metal inert gas welding were investigated. The welding current, arc voltage, welding speed, are
chosen as welding parameters. The depth of penetrations were measured for each specimen after the welding operation is done on
closed butt joint and the effects of welding speed, current, voltage parameters on depth of penetration were investigated.
Index Terms: Mild Steel (EN-3A), metal inert gas welding, welding current, arc voltage and welding speed.
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1. INTRODUCTION
Metal inert gas/ metal active gas (MIG/MAG) welding is an
arc welding process, the melting takes place by Joule effect
and a continuous electric arc, where the additional metal is
supplied by a roll of wire [1]. The weld is made by falling
successive drops on the weld puddle. Argon gas (MIG
welding) or active gas, CO2 (MAG welding) are used as
plasma for providing protective atmosphere for the weld
metal, so that contamination between oxygen and nitrogen is
avoided. Electric energy is supplied from the welding
generator for melting between wire and workpiece to weld.
According to two different control modes (1) the arc mode,
where voltage supplied from the generator is controlled to
reach a point chosen by the welder. (2) the short-circuit mode,
where current flows at pre-defined law, in gas metal arc
welding the molten metal drop detachment form an electrode
have complex interactions between different physical
phenomena. Some of the researchers have studied the
electromagnetic effects [2-5], and some studied the thermal
effects [6] and the fluid dynamics [7]. It is an arc welding
process where heat is generated for arc between the workpiece
and a consumable electrode. A bare solid wire called electrode
is continuously fed to the weld zone, it becomes filler metal as
it is consumed. Gas metal-arc welding overcomes the
restrictions of using electrode of limited length and overcomes
the inability to weld in various positions, which is a limitation
of submerged-arc welding [8]. In gas metal arc welding, the
variations of power supplies, shielding gases and electrodes
have significant effects, resulting in different process
variations [9]. All important metals used in different
commercial applications such as aluminium, copper, stainless
steel and carbon steel can be joined by this MIG welding
process by choosing appropriate electrode, shielding gas and
different welding conditions [10]. It has been very important
to know the performance of a welding process over a wide
range of input process parameters. MIG welding is such a
welding process which is extensively used in the industries for
its high precision and accuracy capability. But performance of
the welding depends largely upon the parameters like voltage,
current and also on type of work-piece materials, electrode
material combinations. A large amount of research works have
been noticed to find out the most suitable combination of input
process parameters for a desired output. Ghosal et al.
established an ANN model to predict and optimize penetration
depth of CO2 laser MIG hybrid welding for 5005 Al-Mg
alloy. The input parameters are power, focal distance, torch
angle, distance between laser and welding torch [11].
Ganjigatti et al. also investigated the input-output relationships
of MIG welding by regression analysis. Input parameters are
welding speed, voltage, gas flow rate, nozzle to plate distance,
torch angle and the responses are bead height, bead width, and
bead penetration [12]. Junsheng et al. investigated the effect of
welding heat input on the weld pool behavior in MIG welding
for low carbon steel [13]. Now a days most of the welding is
done by different arc welding processes; therefore it is
essential to investigate the effects of welding parameters on
the weldability of the materials during the arc welding. Mild
steel is the most common form of steel provides material
properties that are acceptable for many applications. In our
present study workpiece of mild steel material of grade EN-3A
has been used.

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2. EXPERIMENTAL DETAILS
2.1 Selection of Welding Parameters
Depth of penetration of a butt welded joint depends on a
number of influencing factors like welding parameters,
properties of workpieces, electrode used, welding
phenomenon etc. Studies reveal that, the Welding speed,
Voltage, Current are the three welding parameters which
influence in determining the depth of penetration of a butt
welded joint and thus these three parameters are considered as
design factor in the present study.
2.2 Selection of Response Variables
A literature review has been carried out which shows whether
experimental or analytical, most of the studies concentrates on
finding the depth of penetration of welded joint of different
material for different input parameters.
2.3 Work Piece Material Used
The present study is carried out with low carbon steel of grade
EN-3A. The chemical composition of base metal EN-3A and
wire En-3A are shown in Table 1 and Table 2 respectively.
2.4 Specimen Preparation
In the present work, two mild steel specimens, with
dimensions of 150 mm x 100 mm x 6 mm of each was used as
the workpiece. These specimens were prepared with a V-
shaped groove, where the groove angle, the root face, and the
root gap were 30°, 3 mm and 0.75 mm respectively. Thereafter
24 pairs of such specimen with constant groove angle, and
root face were prepared, and faces were cleaned by a surface
grinder. To make a butt joint, two plates were tacked at the
two ends along the width, with a constant root gap of 0.75
mm. Once the welding is over all the plates were cut by using
a power hacksaw, to a required shape for measuring depth of
penetration. The welding torch was mounted on a fixed arm of
a portable gas cutting machine, which can move at different
known speed. Copper coated mild steel wire of 1.2 mm
diameter was used in the experiment as the electrode. The wire
was fed through the welding gun by a roller drive system. The
shielding gas used was CO2, supplied in a regulated manner at
a constant flow rate and at a constant pressure.
2.5 Design of Experiment
In the present study welding speed (m/min), voltage (v) and
current (A) are selected as design factors while other
parameters have been assumed to be constant over the
experimental domain Taguchi’s L25 orthogonal design have
been implemented here with five levels to carry out the
experiments as it allows only 25 numbers of experiments
which reflects the whole process quite satisfactorily while
being economic and as well as time saving. The levels are
chosen on the basis of the recommendations made by the
machine manufacture i.e. Technocrates Plasma Systems Pvt.
Ltd. The recommended welding conditions while MIG
welding are given in the Table 3.
Table -1: Chemical composition of the base metal, EN-3A
Element
Weight
%
Element
Weight
%
C 0.15 S 0.021
Mn 0.78 P 0.029
0.23 Si
Table -2: Chemical composition of the wire, EN-3A
Element
Weight
%
Element
Weight
%
C 0.16 S 0.020
Mn 0.76 P 0.026
0.22 Si
Table -3: Recommended welding conditions
Parameter Unit Minimum
Value
Maximum
Value
Current Ampere 0 400
Voltage Volt 0 54
Welding speed m/min 0.11 1.10
The five levels chosen within the recommended welding
parameters by trial and error method are given in the Table 4.
Table -4: Selected levels for welding parameters
Parameter
Unit
Level1
Level2
Level3
Level4
Level5
Current Ampere 140 150 160 170 180
Voltage Volt 24 25 26 27 28
Welding
speed
m/min 0.165 0.179 0.193 0.206 0.220
Taguchi’s L25 orthogonal design for the above mentioned
three welding parameters along with 5 levels are given in the
Table 5.

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Table -5: Design of experiment using Taguchi’s L25
orthogonal design
Experiment
No.
Current (A) Voltage(V) Welding
speed
(m/min)
1 140 24 0.165
2 140 25 0.179
3 140 26 0.193
4 140 27 0.206
5 140 28 0.220
6 150 24 0.179
7 150 25 0.193
8 150 26 0.206
9 150 27 0.220
10 150 28 0.165
11 160 24 0.193
12 160 25 0.206
13 160 26 0.220
14 160 27 0.165
15 160 28 0.179
16 170 24 0.206
17 170 25 0.220
18 170 26 0.165
19 170 27 0.179
20 170 28 0.193
21 180 24 0.220
22 180 25 0.165
23 180 26 0.179
24 180 27 0.193
25 180 28 0.206
2.6 Experimental Setup
A CPT400, CO2 MIG/MAG WELDING MACHINE
THYRISTORISED OR STEP CONTROL, manufactured by
Technocrats Plasma Systems Pvt. Ltd. is used for MIG
welding test. This machine is shown in Fig -1.
Fig -1: CO2 MIG/MAG Welding Machine Thyristorised or
Step Control
The important specifications of the MIG welding machine
have been shown below:
Maximum welding current : 400 A
Open circuit voltage (V) DC : 54V
Approx weight (kgs.) : 200
Cooling : Forced air
Wire dia (mm) mild steel : 1.2
For mounting the welding torch, for maintaining known
welding speed, a portable gas cutting machine has been used
during the experiment, shown in Fig -2
Fig -2: View of gas cutting machine used during experiment
for controlling different welding speed
The important specification of the portable gas cutting
machine has been shown below:
Make : ESAB India Ltd.
Volts : 220V-250V
AC/DC AMPS : 0.35
3. RESULTS & DISCUSSIONS
Initially, specimens were prepared and the experiments were
conducted as per the design of experiment and the welding
was carried out.
Table -6: Experimental Results
SNo.
Experiment
No.
Current
(A)
Voltage
(v)
Welding
Speed
(m/min)
Penetration
(mm)
1 1 140 24 0.165 5.3
2 2 140 25 0.179 5.1
3 3 140 26 0.193 4.9

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4 4 140 27 0.206 4.7
5 5 140 28 0.220 4.6
6 6 150 24 0.179 5.2
7 7 150 25 0.193 5.0
8 8 150 26 0.206 4.9
9 9 150 27 0.220 4.8
10 10 150 28 0.165 6.7
11 11 160 24 0.193 5.2
12 12 160 25 0.206 5.0
13 13 160 26 0.220 4.9
14 14 160 27 0.165 6.9
15 15 160 28 0.179 6.5
16 16 170 24 0.206 5.1
17 17 170 25 0.220 5.0
18 18 170 26 0.165 6.9
19 19 170 27 0.179 6.7
20 20 170 28 0.193 6.5
21 21 180 24 0.220 5.1
22 22 180 25 0.165 6.9
23 23 180 26 0.179 6.8
24 24 180 27 0.193 6.5
25 25 180 28 0.206 6.4
To visualize the influence of the designed process parameters
over Depth of Penetration and also to find their nature of
variation with respect to the designed parameters, three
dimensional surface plots have been developed using
MINITAB 14 software and shown in Fig 3, 4, 5. The surface
plots physically represent the variation of the depth of
penetration with the welding process parameters. In each of
the plots, two welding parameters are varied simultaneously
along X and Y axis while the depth of penetration is recorded
along Z axis. It is seen from these plots that there is significant
amount of curvature indicating non-linearity in the variation.
Fig -3: Surface plot of depth of penetration with respect to
Voltage and Current
Voltage and Welding Speed
Current and Welding Speed
It is evident from the Fig. 3 and Fig. 4 that higher voltage (>
26.5 V) causes abrupt rise in penetration depth value whereas
Fig. 3 and Fig. 5 depicts that very high current (> 150 A) also
causes the same. And also it could be found from Fig. 4 and
Fig. 5 that very high welding speed (> 0.16 m/min) causes
decrease in penetration depth. These may be due to the reason
that, at the higher welding speed, it gets less time to penetrate

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the weld puddle. And as the current and voltage increases it
creates more heat, so more metal is melted and thus it creates
more depth of penetration.
CONCLUSIONS
An experimental study has been done for finding the depth of
penetration of welded joint in MIG welding process for
welding a mild steel specimen of grade EN-3A. The
conclusion may be drawn, from Fig 3, 4, 5 that higher voltage
(> 26.5 V) causes abrupt rise in penetration depth value,
whereas Fig. 3 and Fig. 5 depicts that very high current (> 150
A) also causes the same. And also it could be found from Fig.
4 and Fig. 5 that very high welding speed (> 0.16 m/min)
cause’s decrease in penetration depth.
ACKNOWLEDGEMENTS
The authors would like to acknowledge HOD Mechanical
Engineering Department, the entire supporting staffs of the
Department of National Institute of Technical Teacher’s
Training & Research, Kolkata, for their valuable suggestions
and help during the entire experimental work.
REFERENCES
[1] S. Adolfsson, A.Bahrami, G. Bolmsj, I. Claesson, On-line
quality monitoring in short-circuit gas metal arc welding,
Weld, Res. Suppl. 78 (2) (1999) 59-73.
[2] Y. S. Kim, Metal Transfer in Gas Metal Arc Welding,
PhD. Thesis, Massachusetts Institute of Technology, June
1989.
[3] L. Jones, T. Eagar, J. Lang, A dynamic model of drops
detaching from a gas metal arc welding electrode, Appl. Phys.
31 (1998) 107–123.
[4] L. Jones, T. Eagar, J. Lang, Magnetic forces acting on
molten drops in gas metal arc welding, Appl. Phys. 31 (1998)
93–106.
[5] J.C. Amson, Lorentz force in the molten tip of an arc
electrode, Brit. J. Appl. Phys. 16 (1965) 1169–1179.
[6] Y.-S. Kim, D. McElliot, T. Eagar, Analyses of electrode
heat transfer in gas metal arc welding, Weld. Res. Suppl.
(1991) 20–31.
[7] S. Choi, C. Yoo, Y.-S. Kim, Dynamic simulation of metal
transfer in GMAW. Part I: Globular and spray transfer modes,
Weld. Res. Suppl. (1998) 38–44.
[8] Syamal Mukherjee, “ Metal Fabrication Technology”, PHI
Learning Private Ltd.
[9] Welding Handbook. Fundamentals of welding, vol. 1, 7th
ed. Miami, Florida: American Welding Society; 1981, P.7-9.
[10] Welding Handbook. Welding processes-arc and gas
welding and cutting, brazing and soldering, vol. 2, 7th ed.
Miami, Florida: American Welding Society; 1978. p. 114–6.
[11] Sujit Ghosal, Sudipto Chaki, ‘Estmation and optimization
of depth of penetration in hybrid CO2 laser-MIG welding
using ANN-optimization hybrid model’, International Journal
of Advance Manufacturing Technology, Vol.47, PP.1149-
1157,2010.
[12] J.P.Ganjigatti, D.K.Pratihar, A.RoyChoudhury,
‘Modeling of the MIG welding process using statistical
approaches’, International Journal of Advance Manufacturing
Technology, Vol.35, PP.1166-1190,2008.
[13] SUN Junsheng, WU Chuansong, ‘The effect of welding
heat input on the weldpool behavior in MIG welding’, Science
in China (Series E), Vol.45,PP.291-299.
BIOGRAPHIES
Biswajit Das is a PhD student at National
Institute of Technology, Agartala. He holds an
M.Tech degree in Manufacturing Technology.
His research areas are metallic alloys, composite
materials, manufacturing technology. He is also
having teaching and industrial experience for a
long period of time in MNC’s in India and at NIT Agartala.
Bishop Debbarma, is working as Assistant
Professor in NIT Agartala. He has published
many papers in many Journals.
Dr. R. N. Rai is working as Associate Professor
in NIT Agartala. He is having around 12 years of
teaching and research experience. He has
published more than 20 papers in both National
and International Journals. He is guiding many
PhD and M.Tech students. He is an active member of many
professional bodies in India.
Dr. S. C. Saha is working as Professor in NIT
Agartala. He is having around 31 years of
teaching and research experience. He had also
acted as Principal of Tripura Engineering College,
Director I/C of NIT Agartala. He has published
around 30 papers in both National and International Journals.
He is also writer of 2 books. He has guided many PhD and
M.Tech students. He is an active member of many
professional bodies in India.

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