Modelling and Optimizing GTAW of SS303 Weld Parameters using
Factorial Design approach
P. Kulantai Samy
1D. Balaji
2E. Sathish Kumar
3S. Alexander
41
PG Student
2,3,4Assistant Professor
1,3,4
SRRCET, Karaikudi, TN, India
2P. R. Engineering College, Thanjavur, Tamil Nadu, Indi
Abstract— Gas Tungsten Arc Welding (GTAW) is a
commonly used welding process that produces an arc between a non-consumable electrode and the work to be welded. This experimental study aims at optimizing various Gas Tungsten Arc welding parameters including welding voltage (V), welding current (I), gas flow rate (GFR), nozzle to plate distance (NPD) and Torch angle (Ө) by developing a mathematical model for sound weld deposit volume of a SS303 specimen. Factorial design approach has been useful for discovery the relationship between various process parameters, weld deposit volume and the hardness of the welded area. The study revealed that the welding voltage, current and gas flow rate varies directly with weld deposit volume and inverse relationship is found between torch angle and NPD with weld deposit Area.
Key words: Gas Tungsten Arc Welding, Factorial Design Approach, Weld Deposit Area
I. INTRODUCTION
The selection of improper GTAW process parameters increases the power consumption, man power and cost of the product. So that optimization of GTAW process parameters is must, to produce effective products.
This experimental aims at optimizing various gas metal arc welding parameters such as welding voltage(V), current(I), speed(S), nozzle to plate distance(NPD), gas flow rate(G), torch angle(θ). Factorial design approach is used to found input and output parameters relationship and also develop a mathematical model for various output parameters with respect to the input parameters.
II. EQUIPMENTS USED IN GTAW
A. Welding Torch
The size of the welding torch nozzle be contingent on the amount of shielded area desired. The size of the gas nozzle will be subject to diameter of the electrode, the joint configuration, and the accessibility to the joint by the welder
Fig. 1: GTAW torch, disassembled
B. Power Supply
Maintaining a suitably steady arc distance is difficult if a constant voltage power source is used instead, since it can cause dramatic heat variations and make welding more difficult. Direct current with a negatively charged electrode is frequently employed when welding steels, nickel, titanium, and other metals.
Fig. 2: GTAW power supply
C. Electrode
The electrode used in GTAW is made of tungsten or a tungsten alloy, the diameter of the electrode can vary between 0.5 and 6.4 mm (0.02 and 0.25 in), and their length can range from 75 to 610 mm (3.0 to 24 in).
D. Shielding Gas
Argon is the most commonly used shielding gas for GTAW, since it helps prevent defects due to a varying arc length. Another common shielding gas, helium, copper and aluminum.
III. MATERIAL SELECTION
Grade 303 signifies the optimum in machinability amongst the austenitic stainless steels. It is mainly used when production includes extensive machining in automatic screw machines. Machinability Rating is approximately 78%.
Grade 303Se (UNS S30323) has a selenium rather than sulphur addition, improving the hot and cold forming characteristics over those of 303 and providing a smoother machined surface finish.
A. Chemical Composition
The alloy’s chemical composition, given in Table 1, is designed to provide exceptional resistance to many corrosive environment Grade C M n S i P S C r N i Se 30 3 min. - - - - 0.1 5 1 7 8 - Max . 0.1 5 2 1 0. 2 - 1 9 1 0 30 3 Se min. - - - - 0.0 6 1 7 8 0.1 5 Max . 0.1 5 2 1 0. 2 - 1 9 1 0 min Table 1: Composition Ranges for 303 Grade Stainless Steel
IV. EXPERIMENTAL DETAILS
A. Base Material
SS303 is used as the base material for all the investigation.
B. Filler Metal
Solid wire of 1.6 mm diameter TIG-521 (ER-NiCr-3) as per the AWS/SFA - 5.14 standards is used as the filler metal.
C. Power Source
MOSFET Inverter DC TIG200ET welding machine has been used for the welding trials. It is a multi-operator power source suitable for Tig welds various metals.
D. Hardness Test
The hardness test of the material and the weldment is measured by using Rockwell Hardness Testing Machine under the following conditions.
Load – 150 Kgf Scale – C
Indenter – Diamond Dial – Black
E. Experimental Procedure
The test specimen having 6 mm thickness is used as the welding trails. The dimension of the workpiece is shown in the figure 3.
MOSFET Inverter DC TIG200ET welding machine has been used for the welding trials.
Solid wire of 1.6 mm diameter TIG-521 (ER-NiCr-3) as per the AWS/SFA - 5.14 standards is used as the filler metal.
Based on the preliminary test trails upper and lower values are fixed
Weld beads are deposited using the welding conditions stipulated by the design matrix
The welding gun is allowed to cool in room temperature and the spatter is cleaned from the nozzle after each run. After finishing the welding trails to calculate the weld deposit Area (WDA) for all the welded pieces and are tabulated.
The hardness of the weldment is measured by using the Rockwell Hardness Test
The results of the experiments are analyzed on the basis of relationship between the input variables and output responses of the welding trails.
F. Workpiece Dimensions
The test specimen having 4 mm thickness is used as the welding trails. The dimension of the work piece is shown in the following figure.
Fig. 3: Work piece dimensions All dimensions are in mm
G. Tensile Test Specimen
Fig. 4: Flat test tensile specimen (ASTM E8) All dimensions are in mm
Dimensions In mm (take)
Gage length Lo 50.8
Width B 12.95
Thickness T 6
Fillet radius(min.) R 6.35
Overall length (min.) L 203.2
Length of reduced section (min.) Lc 57.15 Length of grip section (min.) Lg 50.8 Width of grip section (approx.) Bg 19.05
Table 2: Dimensions of Tensile Specimen
Parameters Range
Polarity DCSP
Voltage 14-18 V
Current 90-130 A
Torch angle 60-75 Deg
Filler metal travel 15-30 Deg
NPD 1.7-2 mm
Type of gas 100% Ar
Tungsten Electrode EW-Th2 (2% Thoriated) Gas flow rate 6.6-23.4 Lt/min
Table 3: Welding Parameters V. EXPERIMENTAL DESIGN
A. Factorial Design Approach and Terminology
Factorial experiments authorities to evaluate the combined effect of two or more testing variables when evaluated simultaneously. Information gotten from factorial experiments is more complete than those found from a series of single factor experiments, in the sense that factorial experiments permit the evaluation of interaction effects. An interaction effect is an effect attributable to the combination of variables above and beyond that which can be predicted from the variables considered separately.
The dimensions of a factorial experiment are indicated by the number of levels of each factor. For p*q factorial experiment, PQ dissimilar treatment combinations are possible. As number of factor rises, or as the number of levels within a factor rises, the number of treatment combinations in a factorial experiment upsurges quite rapidly.
The P potential levels may be grouped in to P levels (p<q) by either combining adjoining levels or deliberately selecting what are considered to be representative levels.
When p = P then the factor is called the fixed factor. When the selection of the p levels from the potential P levels is determined by some systematic, non-random procedure, then also the factor is considered a fixed factor. In this later case, the selection procedure, reduce the potential P levels top effective levels .Under this type of selection procedure, the
effective, potential number of levels of factor in the population may be designated as P effective and P effective = p.
In contrast to this systematic selection procedure, if the p levels of factor A included in the experiment represents a random sample from the potential p levels, then the factor is considered to be random factor. In term of sampling fraction, the definition of fixed and random factors may be brief as mentioned in Table 4. Cases for the sampling fraction take up a value between 0 and 1 do occur in practice. Though, cases for sampling fraction is either 1 or very close to 0 encountered more frequently. Main effects are defined in terms of parameters.
Sampling fraction Factor p/P or p/Peffective =1 A is a fixed factor
p/P = 0 A is a random factor
Table 4: Relationship between Sampling Fraction and Fixed Random Factors
The main effect for the level is the difference between the mean of all potential observations on the dependent variable at the level and grand mean of all potential observations.
VI. METHODOLOGY
While keeping the wire diameter constant, which is 1.6 mm in this case. So the five variables were used as treatment variables for the model.
A. Treatment Variables
Voltage (V) Current (I)
Nozzle To Plate Distance (NPD) Gas flow rate (G)
Torch angle (θ)
The numbers of levels for to be included in the experiment were chosen for each factor as per the design, These numbers of levels were two for each so as per the definition it is a 2n (2*2*2*2*2) factorial experiment. Where n is number of factors. If full factorial approach had been practiced, the number treatment combination would have been 32. But without affecting the accuracy of the model and the objective of the test we went for half factorial approach according to which the number of treatment combinations becomes 2n-1 (25-1 = 24 = 16). The levels for each factor were the highest value and the lowest value of the factors in between and at which the outcome was acceptable. These values were outcomes of trials runs. Highest value has been represented by ‘+’ and the lowest value has been represented by ‘-’ as mentioned in Table 5. As per the design matrix the final runs were conducted and the response i.e. the weld deposit Volume was measured and noted down against each combination.
The calculation was done as per the following model.
B. Design Matrix
According to half factorial approach the Number of treatment combinations = 2n-1 (25-1 =16)
Where,
Highest value = ‘+’ Lowest value = ‘-’ Number of factors = ‘n
X1, X2, X3, X4, and X5 are the various input parameters
X1 = Voltage (V) X2 = Current (I)
X3 = Nozzle to plate distance (NPD) X4 = Gas flow rate (GFR)
X5 = Torch angle (θ) S. No Voltage (V) Current (I) NPD Gas flow rate (G) Torch angle (θ) X1 X2 X3 X4 X5 1 + + + + + 2 - + + + - 3 + - + + - 4 - - + + + 5 + + - + - 6 - + - + + 7 + - - + + 8 - - - + - 9 + + + - - 10 - + + - + 11 + - + - + 12 - - + - - 13 + + - - + 14 - + - - - 15 + - - - - 16 - - - - +
Table 5: Model Showing the Treatment Variables
C. Mathematical Model Developed
Assuming the values of responses as y1, y2, y3, y4, y5, y6, y7, y8,…….y15, y16 against the treatment Combinations 1, 2, 3, 4, 5, 6, 7, 8,……15, 16 respectively (as per the S. No. in the matrix design)
Relation between main effects interactions effects and the response has been shown in the following equation:
Y = b0 + b1X1 + b2X2 + b3X3 + b4X4 + b5X5 + b12(X1X2) + b13(X1X3) + b14(X1X4) + b15(X1X5) +b23(X2X3) + b24(X2X4) + b34(X3X4) + b35(X3X5) +
b45(X4X5) Here,
Y is the optimized weld deposit area
yi (i = 1 to 16) is the response of the ith treatment combination
b0 is the mean of all the responses (j =1 to 5) is the coefficient of jth main factor (j = 1 for voltage, 2 for current, 3 for NPD, 4 for Gas flow rate, 5 for Torch angle)
bjk ( j, k=1 to 5) is the coefficient for interaction factor.
Values of all these coefficients were calculated as followings: b0 = ∑ yi / 16 = [(y1+y2+y3+y4+y5+y6+y7+y8+y9+y10 +y11+y12+y13+y14+y15+y16)] / 16 b1=[(y1-y2+y3-y4+y5-y6+y7-y8+y9-y10+y11-y12+y 13-y14+y15-y16)] / 16 b2=[(y1+y2-y3-y4+y5+y6-y7-y8+y9+y10-y11-y12+y 13+y14-y15-y16)] / 16 b3=[(y1+y2+y3+y4-y5-y6-y7-y8+y9+y10+y11+y12-y13-y14-y15-y16)] / 16 b4=[(y1+y2+y3+y4+y5+y6+y7+y8-y9-y10-y11-y12-y13-y14-y15-y16)] / 16 b5=[(y1-y2-y3+y4-y5+y6+y7-y8-y9+y10+y11-y12+y 13-y14-y15-y16)] / 16 b12=[(y1-y2-y3+y4+y5-y6-y7+y8+y9-y10-y11+y12 +y13-y14-y15+y16)] / 16
b13=[(y1-y2+y3-y4-y5+y6-y7+y8+y9-y10+y11-y12-y13+y14-y15+y16)] / 16 b23=[(y1+y2-y3-y4-y5-y6+y7+y8+y9+y10-y11-y12-y13-y14+y15+y16)] / 16 b24=[(y1+y2-y3-y4+y5+y6-y7-y8-y9-y10+y11+y12-y13-y14+y15+y16)] / 16 b25=[(y1-y2+y3-y4-y5+y6-y7+y8-y9+y10-y11+y12 +y13-y14+y15+y15)] / 16 b34=[(y1+y2+y3+y4-y5-y6-y7-y8-y9-y10-y11-y12+ y13+y14+y15+y16)] / 16 b35=[(y1-y2-y3+y4+y5-y6-y7+y8-y9+y10+y11+y12-y13+y14+y15+y16)] / 16 b45=[(y1-y2-y3+y4-y5+y6+y7-y8+y9-y10-y11+y12-y13+y14+y15+y16)] / 16
VII. EXPERIMENTAL RESULTS
By means of the half factorial approach subsequent are the optimized values of treatment variables gotten as mentioned in the table 6.
Fig. 5: Welded SS 303 specimen S n X1 X2 X3 X4 X5 Yi Yj (volt s) (Amp s) (m m) (lt/h r) (De g) (mm 2) (Scal e: C) 1 18 130 2 1400 75 32 92 2 14 130 2 1400 60 21 109 3 18 90 2 1400 60 26 104 4 14 90 2 1400 75 22 108 5 18 130 1.7 1400 60 22 107 6 14 130 1.7 1400 75 28 108 7 18 90 1.7 1400 75 23 106 8 14 90 1.7 1400 60 26 108 9 18 130 2 400 60 29 105 10 14 130 2 400 75 35 117 11 18 90 2 400 75 26 105 12 14 90 2 400 60 19 85 13 18 130 1.7 400 75 30 95 14 14 130 1.7 400 60 27 99 15 18 90 1.7 400 60 20 96 16 14 90 1.7 400 75 28 105 Table 6: Optimized Gas Tungsten Arc Welding Parameters
Now as per the equations mentioned earlier the values of different effects for the Weld deposite volume (WDV) can be calculated as below:
Fig. 6: Experimental Value Vs Model Value
A. ANOVA for selected factorial model
p-value
Sum of Source Mean Squares df F Square Value Prob > F
Model 26463.25 10 2646.32 6.68 5 significant 0.024 A-Voltage 1944.81 1 1944.81 4.91 0.0776 B-Current 1949.22 1 1949.22 4.92 0.0773 C-NPD 0.022 1 0.022 5.68E-05 0.9943 D-GFD 331.24 1 331.24 0.84 0.4025 E-Torch Angles 3504.64 1 3504.64 8.85 0.031 AD 1246.09 1 1246.09 3.15 0.1363 BC 1528.81 1 1528.81 3.86 0.1067 BD 9148.92 1 9148.92 23.09 0.0049 CE 678.6 1 678.6 1.71 0.2476 DE 6130.89 1 6130.89 15.47 0.011 Residual 1981.03 5 396.21 Cor Total 28444.28 15
Table 7: Analysis of variance Table [Partial Sum Of Squares - Type 3 The Model F-value of 6.68 implies the model is
significant. There is only a 2.45% chance that a "Model F-Value" this large could occur due to noise.
Values of "Prob > F" below 0.0500 designate model terms are significant. In this case E, BD, DE are significant model terms. If there are many unimportant model terms, model reduction may develop your model.
Std. Dev. 19.9 R-Squared 0.9304
Mean 250.5 Adj R-Squared 0.7911
C.V. % 7.95 Pred R-Squared 0.2868 PRESS 20285.75 Adeq Precision 7.825
Table 8: STD. DEV.
The "Pred R-Squared" of 0.2868 is not as close to the "Adj R-Squared" of 0.7911 as one might normally expect. This may specify a possible problem with your model and/or data. Things to study are model reduction, outliers, response transformation, etc.
"Adeq Precision" measures the signal to noise ratio. A ratio greater than 4 is desirable. Your ratio of 7.825 designates a satisfactory signal. This model can be used to route the design space.
Coefficient Factor Standard Estimate 95% CI df 95% CI Error
Low High VIF Intercept 250.5 1 4.98 237.7 263.3
A-Voltage -11 1 4.98 -23.82 1.77 1 B-Current 11.04 1 4.98 -1.75 23.83 1 C-NPD -0.04 1 4.98 -12.83 12.75 1 D-GFD 4.55 1 4.98 -8.24 17.34 1 E-Torch Angles 14.8 1 4.98 2.01 27.59 1 AD -8.83 1 4.98 -21.62 3.97 1 BC 9.77 1 4.98 -3.02 22.57 1 BD 23.91 1 4.98 11.12 36.7 1 CE 6.51 1 4.98 -6.28 19.3 1 DE -19.6 1 4.98 -32.37 -6.78 1
Table 9: Individual and Interaction Parameter Effect
1) Final Equation in Terms of Coded Factors
WDA=250.50-11.02A+11.04B-0.037C+4.55D+14.80E-8.83AD+9.77BC +23.91BD+6.51CE-19.57DE
2) Final Equation in Terms of Actual Factors
WDA=+1315.56333+2.43000Voltage-7.62817Current-
749.41667NPD+0.23961GFD-4.03811TorchAngles-8.82500E-003VoltageGFD+3.25833CurrentNPD+ 2.39125E003CurrentGFD+5.78889NPDTorch Angles
-5.22000E-003 GFD Torch Angles
Fig. 7: current, voltage Vs Weld deposite volume
Fig. 8: current, voltage Vs Weld deposite volume
Fig. 9: Gfr, voltage Vs Weld deposite volume
Fig. 10: npd, A-voltage Vs Weld deposite volume
Fig. 11: npd, B-voltage Vs Weld deposite volume
Fig. 12: Torch angle, B-voltage Vs Weld deposite volume
Fig. 13: Torch angle, npd Vs Weld deposite volume wda =+33.54587-5.72265* voltage+1.17235* current-0.039556 * gfr-16.86208* npd-0.060206*
ta+4.26875E-003* voltage * current+1.77950E-ta+4.26875E-003* voltage * gfr+1.93708* voltage * npd+9.39750E-005 * current *
gfr-0.47912 * current * npd-8.07167E-003* current * ta+0.66878* npd * ta
Fig. 14: Number of iterations Vs Hardness Response2 HRC
Source Sum of Squares df Mean Square F Value p-value Prob > F Model 895.75 12 74.65 9.66 0.0436 A-Voltage 52.56 1 52.56 6.8 0.0798 B-Current 14.06 1 14.06 1.82 0.2702 D-GFD 76.56 1 76.56 9.91 0.0514 E-Torch Angles 33.06 1 33.06 4.28 0.1305 AB 95.06 1 95.06 12.3 0.0393 AE 162.56 1 162.56 21 0.0195 BC 45.56 1 45.56 5.89 0.0935 BD 76.56 1 76.56 9.91 0.0514 BE 95.06 1 95.06 12.3 0.0393 CD 68.06 1 68.06 8.81 0.0592 CE 14.06 1 14.06 1.82 0.2702 DE 162.56 1 162.56 21 0.0195 Residual 23.19 3 7.73 Cor Total 918.94 15
Table 10: Analysis of Variance Table [Partial Sum of Squares - Type 3 The Model F-value of 9.66 implies the model is
significant. There is only a 4.36% chance that a "Model F-Value" this large could occur due to noise. Values of "Prob > F" below 0.0500 designate model terms are significant.
In this case AB, AE, BE, DE are significant model terms. Values more than 0.1000 specify the model terms are not important.
If there are many irrelevant model terms, model reduction may develop your model.
Std. Dev. 2.78 R-Squared 0.9748
Mean 103.06 Adj R-Squared 0.8738 C.V. % 2.7 Pred R-Squared 0.2823
PRESS 659.56 Adeq Precision 12.769 Table 11: STD. DEV.
The "Pred R-Squared" of 0.2823 is not as close to the "Adj R-Squared" of 0.8738 as one might normally expect. This may indicate a possible problem with your model and/or data. Things to study are model reduction, response transformation.
"Adeq Precision" measures the signal to noise ratio. A ratio greater than 4 is desirable. Your ratio of 12.769 indicates an adequate signal. This model can be used to navigate the design space.
Coefficient Standard 95% CI 95% CI
Factor Estimate df Error Low High VIF
Intercept 103.06 1 0.7 100.9 105.27 A-Voltage -1.81 1 0.7 -4.02 0.4 1 B-Current 0.94 1 0.7 -1.27 3.15 1 D-GFD 2.19 1 0.7 -0.02 4.4 1 E-Torch Angles 1.44 1 0.7 -0.77 3.65 1 AB -2.44 1 0.7 -4.65 -0.23 1 AE -3.19 1 0.7 -5.4 -0.98 1 BC 1.69 1 0.7 -0.52 3.9 1 BD -2.19 1 0.7 -4.4 0.024 1 BE -2.44 1 0.7 -4.65 -0.23 1 CD -2.06 1 0.7 -4.27 0.15 1 CE 0.94 1 0.7 -1.27 3.15 1 DE -3.19 1 0.7 -5.4 -0.98 1
Table 12: Individual and Interaction of Parametre Effect
1) Predicted mathematical model for Y HRC
YHRC = 103.06 + (-1.81) X1 + 0.937X2 + 0.062X3 + 2.1875X4 + 1.437X5 + (-4.312) (X1X2) + (0.187) (X1X3) + 1.18) (X1X4) + 3.18) (X1X5) + (1.69) (X2X3) + (-2.187) (X2X4) + (-2.437) (X2X5) + (-2.062) (X3X4) + (24.687) (X3X5) + (9.937) (X4X5) Constraints Name Goal Lo wer Upp er Low er Upp er Impo rtanc e Lim it Lim it Wei ght Wei ght A:Volt age is in range 14 18 1 1 3 B:Curr ent is in range 90 130 1 1 3 C:NP D is in range 1.7 2 1 1 3 D:GF D is in range 400 140 0 1 1 3 E:Torc h Angles is in range 60 75 1 1 3 WDA maxim ize 166. 8 331. 7 1 1 2 HRC is in range 85 117 1 1 3
Number Voltage Current NPD GFD Torch Angles WDA HRC Desirability 1 14 130 2 1400 75 321 108 0.94 2 14.1 130 2 1400 75 320 108 0.93 3 14 130 2 1400 71.2 320 108 0.93 4 14.2 130 2 1384 75 318 107 0.92 5 14 130 2 1400 64.3 318 108 0.92 6 14 130 2 1383 64.1 317 108 0.91 7 14 130 2 1400 68.1 317 108 0.91 8 14 130 2 1400 60.7 317 108 0.91 9 14 130 2 1400 64.1 317 108 0.91 10 14 130 1.9 1400 60.3 316 109 0.91 11 14 128 2 1330 75 315 108 0.9 12 14 130 1.9 1399 61.4 313 109 0.89 13 14 130 1.8 1400 60.5 313 110 0.89 14 14 130 1.8 1400 60.4 312 110 0.88 15 14 130 1.7 1398 60 312 110 0.88 16 14 130 1.7 1400 60.1 311 110 0.88 17 14 130 2 1193 74.9 311 110 0.87 18 14.3 130 1.8 1400 60 310 110 0.87 19 14.1 130 1.7 1400 60.4 310 110 0.87 20 14 130 1.9 1400 67.3 310 108 0.87 21 14 130 1.7 1400 60.9 310 110 0.87 22 14 130 1.7 1400 62.4 308 110 0.86 23 14.7 130 1.9 1400 60.6 308 108 0.86 24 14 130 1.9 1400 74.9 306 107 0.84 25 14 126 1.9 1400 71.7 305 108 0.84 26 15.6 130 2 1400 60 302 107 0.82 27 14 90 1.7 400 75 299 106 0.8 28 14.4 90 1.7 417 75 297 106 0.79 29 14.1 90.2 1.7 400 74.6 297 106 0.79 30 16.2 90 1.7 400 75 296 103 0.78 31 14.2 90.8 1.8 400 75 295 107 0.78 32 17.9 90 1.7 400 75 294 101 0.77 33 14.1 90 1.9 400 74.8 294 107 0.77 34 14 119 2 1177 74.9 294 109 0.77 35 17.9 90.5 1.7 400 75 294 101 0.77 36 16.9 130 2 1383 72.9 292 99 0.76 37 14 93 2 405 75 292 109 0.76 38 14 98.9 2 400 75 291 111 0.75 39 14 128 2 481 75 289 117 0.74 40 17 130 2 1400 62.2 288 105 0.74 41 14 127 2 696 73.3 288 114 0.74 42 14 101 1.8 400 75 288 108 0.73 43 18 130 2 752 75 281 100 0.69 44 14.1 115 1.8 400 75 274 109 0.65
Table 14: Optimized Solutions 44 Solutions found
Number of Starting Points: 46
S. No Voltage Current NPD GFD Torch Angles 1 14 90 2 400 60 2 14 90 1.7 400 75 3 18 130 2 1400 75 4 14 130 1.7 400 60 5 18 90 1.7 1400 75 6 18 130 2 400 60 7 18 90 2 1400 60 8 18 90 1.7 400 60 9 18 90 2 400 75 10 14 90 1.7 1400 60 11 14 90 2 1400 75 12 14 130 1.7 1400 75 13 18 130 1.7 400 75 14 18 130 1.7 1400 60 15 14 130 2 400 75 16 14 130 2 1400 60 17 14.62 119.16 1.77 424.45 64.18 18 14.69 99.22 1.72 785 60.35 19 16.5 109.75 1.78 1089.02 65.22 20 17.5 117.75 1.85 1000.8 61.01 21 15.71 127.18 1.77 595.73 64.51 22 15.52 92.72 1.83 715.85 61.75 23 14.3 105.21 1.82 415.42 68.07 24 14.88 107.59 1.85 1101.68 60.54
25 17.64 98.47 1.99 1164.41 69.87 26 14.65 115.23 1.84 729.33 63.74 27 14.61 121.1 1.71 687.11 67.51 28 17.3 121.95 2 1032.09 61.78 29 16.57 118.39 1.98 1057.31 74.36 30 14.14 96.81 1.71 1026.03 60.44 31 14.58 96.71 1.81 1205.24 74.56 32 14.06 93.69 1.85 1027.07 67.47 33 14.82 94.2 1.89 718.08 71.71 34 17 113.82 1.91 692.28 63.44 35 14.22 116.09 1.85 658.04 64.17 36 15.49 121.72 1.75 495.75 64.01 37 16.54 120.62 1.77 723.39 64.35 38 16.33 118.9 1.97 716.34 60.54 39 15.47 100.85 2 1338.46 66.23 40 15.93 116.68 1.82 400.78 65.54 41 16.53 97.37 1.78 681.22 74.76 42 17.47 100.76 1.94 1303.22 69.07 43 15.73 125.4 1.77 1121.58 60.14 44 15.55 101.92 1.76 993.79 66.43 45 14.5 104.51 1.99 644.46 69.49 46 14.93 123.61 1.99 788.2 67.13
Table 15: Optimized Solutions
Fig. 15: GFD, Voltage Vs HRC Where,
YWDV = Optimized Weld deposite volume YHRC = Optimized Hardness
VIII. CONCLUSION
Results indicate that processes variables influence the weld deposit volume to a significant extent. Various welding variables which influence weld deposit volume were identified and their quantitative influence on the same was investigated. Penetration and total area are increased when the welding current is increased but reinforcement marginally increases and then decreases. The welds made using electrode negative polarity (DCEN), a small diameter electrode, low voltage and low welding speed produce small bead area. A factorial technique can be employed easily for developing mathematical models for various output parameters with respect to input parameters. The mathematical model was analyzed and individual and interaction effects were studied. Various welding variables which influence hardness were identified. The mathematical model which was developed by the design of expert software which was subjected to numerical optimization the optimum parameters were found.
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