Ijmet 10 01_147

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International Journal of Mechanical Engineering and Technology (IJMET)
Volume 10, Issue 01, January 2019, pp. 1452-1462, Article ID: IJMET_10_01_147
Available online at http://www.iaeme.com/ijmet/issues.asp?JType=IJMET&VType=10&IType=1
ISSN Print: 0976-6340 and ISSN Online: 0976-6359
© IAEME Publication Scopus Indexed
INVESTIGATION ON MECHANICAL
PROPERTIES OF GAS METAL ARC WELDED
STAINLESS STEEL SPECIMENS USING AND
TAGUCHI METHOD
M. Vinosh
Assistant Professor, Department of Mechanical Engineering, Sri Krishna College of
Engineering and Technology, Coimbatore, Tamilnadu, 641008, India
S. Vignesh M. Vignesh Moorthy S. P. Vinith and V. M. Pream prakas
UG Scholar, Department of Mechanical Engineering, Sri Krishna College of Engineering and
Technology, Coimbatore, Tamilnadu, 641008, India
ABSTRACT
Gas metal arc welding (GMAW) process is most widely used in industries for
fabrication works, due to higher productivity. The weld quality depends on the process
parameters of GMAW. This research investigates the influence of process parameters
affecting the mechanical properties of weldment. Thus, identification of the GMWA
process parameters that significantly affect the quality of GMWA processed parts is
more important in terms of productivity. Then process environment has been assumed
consisting of four variables like welding current, welding voltage, shielding gas, gas
flow rate and wire feed rate. Taguchi optimization technique has been applied to
determine the optimal limits, which can maximize the GMWA quality in certain
environment. Signal to noise ratio (S/N ratio) were calculated for each data and used
to obtain the optimum level of every input parameter. The study also shows that the
use of the Taguchi Method has productively enhanced on the existing process
parameters.
Keywords: GMAW, Process Parameters, Taguchi, Optimization, Mechanical
properties.
Cite this Article: M. Vinosh, S. Vignesh M. Vignesh Moorthy S. P. Vinith and V. M.
Pream prakas , Investigation on Mechanical Properties of Gas Metal Arc Welded
Stainless Steel Specimens using and Taguchi Method, International Journal of
Mechanical Engineering and Technology, 10(1), 2019, pp. 1452-1462.
http://www.iaeme.com/IJMET/issues.asp?JType=IJMET&VType=10&IType=1

M. Vinosh, S. Vignesh M. Vignesh Moorthy S. P. Vinith and V. M. Pream prakas
1. INTRODUCTION
The gas metal arc welding (GMAW) process has been of great importance for welding
construction all over the world. In this process an electric arc forms between a consumable
wire electrode and the work piece, which heats the work piece causing them to melt and join.
Along with the wire electrode, a shielding gas feeds through the welding gun, which shields
the process from air contaminants. The process can be semi-automated or fully automated.
The most important gases (active and inactive) which have been used to protect the weld pool
are Argon (Ar), Helium (He), Carbon dioxide (CO2), Oxygen (O2) or mixture of these gases.
A common problem faced by the manufacturer is the control of the process input parameters,
to obtain a good welded joint with the required bead geometry and weld quality with minimal
detrimental residual stresses and distortion. The input parameters play a very significant role
in determining the quality of a welded joint. Amit RatanBiswas at al. [1] examined the
dissimilar metal weld of stainless steel AISI 304 and medium carbon steel 45C8 using
GMAW by varying properties like welding current, voltage, speed and gas flow rate with
ANOVA and mechanical properties like Yield strength, ultimate tensile strength, weld zone
hardness, weld bead thickness and reinforcement of the welded joint have been reported.
Nabendu Ghosh et al. [2] used a L9 orthogonal array of Taguchi method with three levels of
the input welding parameters: welding current, gas flow rate and nozzle to plate distance and
the quality of the weld has been evaluated in terms of yield strength, ultimate tensile strength
and percentage of elongation of the welded specimens. N R Anand et al. [3] P.Sathiya et al.
[4] and Izzatul Aini Ibrahim et al. [5] investigated the effect of shielding gas on mechanical
properties of weldment for austenitic stainless steel material. Pawan kumar et al. [6] used
Taguchi method to design the following process parameters, welding current, welding voltage
and gas flow rate to optimize the mechanical properties of the welded specimen of austenitic
stainless steel AISI 304 and low carbon steel. From the literature it was clear that welding
current significantly affects the mechanical properties of weldment. L.Suresh et al. [7]
discussed about the mechanical properties of austenitic stainless steel (AISI 304 & AISI 316)
for the process of tungsten inert gas (TIG) and metal inert gas (MIG) welding, Taguchi
method was used to design the orthogonal array and both processes were compared and found
that TIG welded specimen has higher tensile strength as compared to MIG welded specimen.
Chandersh. N. Patel et al. [8] had investigated the relationship between input parameters such
as welding current, wire diameter and wire feed rate to the output parameter of hardness by
using Taguchi method. S.R. Meshram, N.S. Pohokar [9] examined the effect of GMAW
process parameters on stainless steel plate of AISI 410 grade of 12 mm thickness. Grey-based
Taguchi method and analysis of variance (ANOVA) was used to find the significant process
parameters. It was found that the welding speed is the most influencing factor and Gas flow
rate is least influencing factor on output parameters. Sharadchandra.V.Kantute, Prof.
R.S.Sakarkar [10] discussed about the tensile strength of welded joints of carbon steel pipes.
The variation of welding parameters like welding current, gas flow rate and root gap were
observed on tensile strength. Taguchi and ANOVA were used to find the significant
parameter. Arun Nanda et al. [11] used Taguchi method to design the process parameters to
optimize mechanical properties of weldment specimen for austenitic stainless steel (AISI
304). S. R. Patil and C. A. Waghmare [12] studied the weld characteristics of the materials
and optimized the weld parameters to attain the maximum tensile strength of welded joints for
AISI 1030 Mild steel.
2. METHODOLOGY
 Selection of base material and filler material.
 Identify the important process parameters in GMAW.

Investigation on Mechanical Properties of Gas Metal Arc Welded Stainless Steel
Specimens using and Taguchi Method
 Selection of orthogonal array based on parameters and levels.
 To conduct the experiment as per the selected orthogonal array.
 To conduct the mechanical testing of the welded specimen.
 Find the optimum process parameters.
 To conduct the confirmation test.
 To identify the significant factors.
2.1. SELECTION OF BASE MATERIAL AND FILLER WIRE
Austenite stainless steel 316 sheet of 4 mm thickness is used as a base material. It has yield
strength of 290 MPa and ultimate tensile strength of 580 MPa. The filler wire ER 308 of
diameter 0.8 mm is used for welding. The chemical composition of base material and filler
wire are shown in Table 1.
Table 1 Chemical composition of base material
Grade Comp. C Mn Si Cr Ni Mo P S Ni
316
Min 16.00 10.00 2.00
Max 0.08 2.00 0.075 18.00 14.00 3.00 0.045 0.030 0.10
2.2. Identify the process parameters
From the literature review and the previous work done by the researchers, concluded that the
below mentioned parameters are the most important process parameters, which have the
greater influence than the other process parameters, over the mechanical properties of the
weldment. The most important process parameters considered are,
 Welding Current (Amps)
 Welding Voltage (Volts)
 Gas Flow Rate (LPM)
 Shielding Gas
 Wire Feed Rate (m/min)
2.3. Selection of orthogonal array
Taguchi technique is used to plan the experiments. The Taguchi method has become an
influential tool to improve the outputs during research and development, so that better quality
products can be produced quickly at minimum cost. Dr. Taguchi of Nippon telephone and
telegraph company, has established a method based on orthogonal array experiments. Taguchi
orthogonal arrays are highly fractional orthogonal designs, which can be used to estimate the
main effects using least number of experimental runs. The working range of the process
parameters under this study are shown in Table 2. Number of process parameter is five and
the level of each parameter is three. To select an orthogonal array for an experiment, first the
total degrees of freedom is needed. The degree of freedom for the experiment is 10, based on
that the matrix of orthogonal array is selected. In this study L27 is selected as an orthogonal
array matrix as shown in the Table 3.

Table 2 Process parameters and their levels
S.No Process Parameters Units Level 1 Level 2 Level 3
1 Welding Current Amps 100 120 140
2 Welding Voltage Volts 19 22 25
3 Gas flow rate LPM 15 12 10
4 Shielding Gas - Pure CO2 Ar + 8% CO2 Ar +18% CO2
5 Wire feed rate m/min 2 2.5 3
Table 3 Experimental layout of orthogonal array (L27)
Orthogonal
Array
Welding
Current
(A)
Welding
Voltage (V)
Shielding Gas
Gas Flow Rate
(LPM)
Wire Feed
rate (m/min)
1 100 19 Pure CO2 10 2
2 100 22 Pure CO2 10 2.5
3 100 25 Pure CO2 10 3
4 100 19 Ar + 8% CO2 12 2
5 100 22 Ar + 8% CO2 12 2.5
6 100 25 Ar + 8% CO2 12 3
7 100 19 Ar + 18% CO2 15 2
8 100 22 Ar + 18% CO2 15 2.5
9 100 25 Ar + 18% CO2 15 3
10 120 19 Pure CO2 15 2
11 120 22 Pure CO2 15 2.5
12 120 25 Pure CO2 15 3
13 120 19 Ar + 8% CO2 10 2
14 120 22 Ar + 8% CO2 10 2.5
15 120 25 Ar + 8% CO2 10 3
16 120 19 Ar + 18% CO2 12 2
17 120 22 Ar + 18% CO2 12 2.5
18 120 25 Ar + 18% CO2 12 3
19 140 19 Pure CO2 12 2
20 140 22 Pure CO2 12 2.5
21 140 25 Pure CO2 12 3

22 140 19 Ar + 8% CO2 15 2
23 140 22 Ar + 8% CO2 15 2.5
24 140 25 Ar + 8% CO2 15 3
25 140 19 Ar + 18% CO2 10 2
26 140 22 Ar + 18% CO2 10 2.5
27 140 25 Ar + 18% CO2 10 3
2.4. Conduct the experiments based on orthogonal array
In this study, an automated metal active gas welding machine with the polarity of direct
current electrode positive (DCEP) is employed for conducting the welding experiments. The
specimens were prepared in a dimension of 100 x 100 x 4 mm and the butt joints were made
using the experimental layout as shown in Table 3. Prior to welding, the specimens were
dipped in a NaOH solution then they were wire brushed and degreased using acetone. The
welded joints were completed in a single pass, since 4 mm plate is used in this study.
2.5. Mechanical properties
The aim of the tensile test is to evaluate the yield strength, ultimate strength and plasticity of
the welded joints. The test is done using a computer assisted universal testing machine. 27
tensile test specimens were prepared according to ASTME E8 standard as shown in the Figure
1. For all the specimen’s failure occurred in the base metal region. The ultimate strength of
the welded joint was more than the base metal strength.
Figure 1 Dimension of the tensile specimen in mm
The Hardness test of the weld specimen was carried out using a brinell hardness testing
machine. In the specimen 5 locations were marked at an interval of 1 cm from the welded
region on both sides to conduct the hardness test of the specimen. The mean values of five
different measurements were taken as the exact value for the hardness of the specimen. It was
found that the weld metal shows the highest hardness value, whereas the heat affected zone
shows the intermediate hardness value and the base metal shows lowest hardness value. In
order to evaluate the impact toughness values of welded joint, a series of charpy V-notch test
were carried out for specimens welded with different process parameters. The dimension of
the work piece is shown in the Figure 2.
Figure 2 Dimension of the impact specimen in mm.

Notches were prepared in the base metal and weld zone. The impact toughness of an un-
welded base metal was found to be 60 Joules, which is comparatively lower than the other
weld metal impact strengths. Mechanical properties of weldment as shown in Table 4.
Table 4 Mechanical properties of austenitic stainless steel 316 weldments
Orthogonal
Array
Tensile
strength in
MPa
Hardness
in BHN
Toughness (J)
1 588 218 59
2 594 226 64
3 583 235 61
4 580 240 69
5 585 244 70
6 578 249 67
7 586 236 62
8 591 238 67
9 582 242 64
10 589 248 68
11 593 254 74
12 584 258 71
13 591 242 66
14 598 247 72
15 595 253 69
16 596 234 63
17 602 240 68
18 592 244 66
19 600 248 68
20 608 251 76
21 594 257 73
22 608 242 67
23 615 246 70
24 604 250 69
25 590 254 74
26 598 257 78
27 586 264 76

Figure 3 Orthogonal Array Vs Tensile Strength in MPa
Figure 4 Orthogonal Array Vs Hardness in BHN
0
50
100
150
200
250
300
350
400
450
500
550
600
650
700
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29
TensileStrengthinMpa
Orthogonal Array
0
50
100
150
200
250
300
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29
HardnessinBHN
Orthogonal Array

Figure 5 Orthogonal Array Vs Toughness in Joules
3. FINDING THE OPTIMUM PROCESS PARAMETERS FOR
MAXIMIZING THE MECHANICAL PROPERTIES OF THE
WELDMENT
Taguchi signal to noise ratio (S/N) serve as an objective function for optimization, which
helps in data analysis and prediction of optimum result. The term signal represents the mean
value for the output and the term noise represents the deviations of the output characteristics.
Therefore the S/N ratio is used to measure the quality characteristics deviating from the
desired value. Normally the S/N ratios is given by the below formula,
N = -10 log (M.S.D)
In this study, a higher mechanical property of weldment leads to a stronger weld. So
larger-the-better quality characteristics was taken and it is expressed by,
S/N = -10 log10 (mean sum of square of reciprocal of measured data)
The results of mechanical properties of the weldment and S/N ratio are shown in the Table
5. The response Table 6 shows the average of each response characteristics, for each level of
each factor.
Table 5 S/N ratio of weldment
S.No S/N ratios S.No S/N ratios S.No S/N ratios
1 39.8407 10 41.05306 19 41.055
2 40.51337 11 41.74014 20 41.94481
3 40.15031 12 41.42007 21 41.64041
4 41.14688 13 40.80039 22 40.92325
5 41.27261 14 41.50604 23 41.2833
6 40.93506 15 41.18259 24 41.17701
7 40.28396 16 40.4091 25 41.73952
8 40.91008 17 41.03504 26 42.16329
9 40.55241 18 40.80541 27 41.97476
0
10
20
30
40
50
60
70
80
90
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29
ToughnessinJoules
Orthogonal Array

Table 6 Response table for mechanical properties
Level WC WV SH GFR WFR
1 40.62 40.81 41.04 41.10 40.81
2 41.11 41.37 41.14 41.04 41.37
3 41.54 41.09 41.10 41.14 41.09
Delta .92 .57 .10 .10 .57
Rank 1 2.5 4 5 2.5
Figure 6 Graph for S/N ratio of different parameters
For the study purpose we have chosen larger is better for S/N ratio, Figure 6 shows the
plot for mechanical properties against the S/N ratio. The welding current gradually goes on
increasing till 41.54 and hence 140 A was chosen as an optimum point, the welding voltage
attained the maximum peak of 41.37 and suddenly it started decreasing, hence 22 V was taken
as a optimum value. Next coming to the shielding gas the S/N ratio increased to a value of
41.14 and later it started to decrease, for this Ar + 8% CO2 was taken as an optimum value.
The gas flow rate was gradually increasing from the beginning and attained a maximum value
of 41.14, subsequently 15 LPM was chosen as an optimum point, the wire feed rate shows the
sudden increase to a peak value of 41.37 and it suddenly dropped, from this 2.5 m/min was
chosen as an optimum wire feed rate. The parameters and the optimum values are given in the
Table 7
Table 7 The optimum value for input parameter
Parameters Level Value S/N ratio
Welding current Level 3 140A 41.54
Welding voltage Level 2 22 V 41.37
Shielding gas Level 2 Ar+8%CO2 41.14
Gas flow rate Level 3 15 LPM 41.14
Wire feed rate Level 2 2.5 m/min 41.37

The ANOVA was carried out at 95% confidence level. The purpose of ANOVA is to
investigate which welding process parameters significantly affect the mechanical properties of
the weldment
Table 8 Result of analysis of variance for mechanical properties (ANOVA)
Source DF Seq SS Adj MS F ratio % of contribution
Welding current 2 3.82643 1.913295 1.809 48.82
Welding voltage 2 1.45460 0.72730 0.688 22.37
Shielding Gas 2 0.04246 0.02123 0.020 6.50
Gas flow rate 2 0.04554 0.02277 0.022 7.15
Wire feed rate 2 1.13423 0.56712 0.536 17.43
Error 16 2.11497 1.05748
Total 26 8.61866
ANOVA Table 8 concluded that the welding current significantly affects the mechanical
properties of weldment followed by the voltage with contribution of 22.37%, wire feed rate
with contribution of 17.43%, shielding gas with contribution of 6.50% and the least
contribution was from the gas flow rate with 7.15%.
4. CONCLUSION
The influence of GMAW parameters such as welding current, welding voltage, shielding gas,
gas flow rate and wire feed rate on mechanical properties such as tensile, hardness and
toughness of stainless steel 316 weldments have been studied and the following conclusions
were obtained.
By use of taguchi method the optimal parameter combination is find out and its parameter
values are 140 Amps welding current, 24 V welding voltage, shielding gas mixture of
Ar+8%CO2, 15 LPM of gas flow rate and 2.5 m/min wire feed rate for GMA welding.
From the ANOVA it is concluded that the welding current is most significant parameter
for affecting the mechanical properties of the weldment.
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