modelling and optimization of advanced submerged arc ... · pdf filemodelling and optimization...

International Journal on Mechanical Engineering and Robotics (IJMER)

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ISSN (Print) : 2321-5747, Volume-2, Issue-2,2014

42

Modelling and optimization of advanced submerged arc welding

process for stainless steel cladding

1Hari Om,

2Sunil Pandey

1Associate Professor, Department of Mechanical Engineering, YMCA University of Science & Technology, Faridabad -

121006 (India), 2Professor, Department of Mechanical Engineering, Indian Institute of Technology, Delhi -110016 (India),

Email: [email protected],

[email protected]

Abstract- Industries involved in surfacing operations use

various fusion welding especially arc welding processes.

These operations demand high deposition rates but at low

penetration values in the base metal. Conventional SAW,

besides its high deposition characteristics, employs high

values of welding current and is not many times favoured

for surfacing due to high degree of dilution of surfacing

alloys with base metal. This limits the use of SAW because

high dilution deteriorates intended benefits of surfacing.

Advanced submerged arc welding (ASAW) process, which

was developed in welding research laboratory at IIT Delhi

in the year 2004, provides a solution for the above. The

present work studies the effect of various parameters of the

process on the weld bead width, reinforcement, penetration

and percentage dilution by developing mathematical

models for each. Optimization of this relatively new

process for getting minimal dilution required for surfacing

has also been done.

Key words: Advanced submerged arc welding, weld

overlay cladding, dilution, RSM, central composite design,

I. INTRODUCTION

In some engineering applications, components and

equipment have to be operated under abnormal

atmospheric conditions such as elevated temperature or

highly corrosive environments. This requires

components to be corrosion and/or heat resistant. Some

applications demand high wear resistance of the

components. The adversity of service conditions limits

the service life of components. The replacement cost of

the components is extremely high[1]. The cladding of

stainless steel onto carbon steel brings a nice solution to

the problem of the elaboration of a material which

combines high level mechanical properties and good

resistance to corrosion[2]. Literature reveals that many

austenitic stainless steel grades are used for cladding

carbon or low-alloy steels [3-8].

Weld cladding processes have gained popularity

recently in various industries like chemical and fertilizer

plants, nuclear and steam power plants, food processing

and petrochemical industries[9]. Almost all the arc

welding processes have been used for cladding. Most

popular of these are shielded metal arc welding

(SMAW), gas tungsten arc welding (GTAW), gas metal

arc welding (GMAW), submerged arc welding (SAW)

and flux cored arc welding (FCAW) [1, 3, 5, 7, 8, 10-

14]. Use of non-conventional processes such as

explosion welding, strip roll welding, laser welding,

electron beam cladding, solar cladding and microwave

assisted brazing have also been reported in literature for

cladding purpose [2, 15-20].

In semi-automatic and automatic welding and surfacing

processes, engineers often face problems of relating the

process parameters to the weld bead geometry and

dilution of base metal and their optimization. With these

optimized parameters one can achieve sound joints at a

relatively low cost. In the present work, mathematical

models for various bead parameters have been

developed and optimization of ASAW process has been

done to obtain minimal dilution during cladding.

II. BACKGROUND

1.1 Advanced Submerged Arc Welding

Advanced Submerged Arc Welding (ASAW) process

was developed in Welding Research Laboratory of

Indian Institute of Technology Delhi (Sunil Pandey,

2004, Patent application number: 2533 / DEL / 2008

Dated: November 07, 2008). Its working differs from

conventional submerged arc welding (SAW) in that the

electrode wire is preheated before it is fed to the molten

pool on the work piece by using an auxiliary power

source[21]. The welding setup has two contact tubes

instead of one used in conventional submerged arc

welding process. The schematic diagram of the ASAW

setup is shown in Figure 1. Two contact tubes are

separated with a dielectric gap between them. The main

power source is used for creating arc between the

electrode and the base metal as in the normal welding

operation and the other is used for preheating of the

electrode wire. Figure 2 illustrates the actual ASAW

setup photograph.

mailto:[email protected]


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43

Figure 1: Schematic diagram for Advance Submerged

Arc Welding (ASAW) setup

In the ASAW process, part of the energy required to

melt the wire is extracted through preheating (I2R

heating or simply resistance heating) by passing current

across certain length of the welding wire through

auxiliary power source and rest of the energy for melting

is provided by main welding current. A significant

decrease in welding current due to preheating of wire is

observed which in turn reduces arc force. This results in

lowering down penetration depth and consequently

reduced weld dilution [22].

Process parameters are important as careful selection of

these is responsible for producing quality weld jointsor

weld overlay cladding. Various parameters associated

with the ASAW are similar to SAW e.g., wire feed rate,

welding voltage, travel speed, electrode stick-out,

electrode polarity and flux composition except preheat

current which is a special feature of this process.

1.2 Bead profile and dilution

Figure 3 shows the details of weld bead geometry. The

bead width ‘W’, height of reinforcement ‘H’ and depth

of penetration ‘P’ primarily dictate the shape of

deposited bead. Height of reinforcement ‘H’ basically

represents the protruded portion of the bead which is

built up as a result of filler meal deposition on the base

metal surface and is measured as the distance of highest

point from the base metal surface. Penetration P is the

depth of the base metal melted down due to arc heat and

is measured downward from base metal surface upto

lowest point where melting has taken place.

Performance of a weld clad or joint depends on the

extent of percentage dilution, which indicates the extent

of mixing of parent metal with the filler one and equals

the amount of base metal melted divided by the sum of

base metal melted (AP) and filler metal added (AR), the

quotient of which is multiplied by100 [23].

% Dilution = [AP / (AR + AP)] × 100 (1)

A successful weld cladding requires careful and

optimizedcontrol of the process parameters to secure

low dilution and a crack-free overlay. This needs a

thorough understanding of the process characteristics

affecting the technological and metallurgical

characteristics of the overlays[24].

Figure 2: Schematic weld bead profile

III. EXPERIMENTATION

1.3 Experimental setup

The experiments were carried out using Advanced

Submerged Arc Welding process. A direct current

constant voltage power source and mechanized

submerged arc welding equipment with a current

capacity of 600 amperes at 60% duty cycle was used for

the experimentation. Welding head was modified by

employing two contact tubes with a dielectric gap in

between. First contact tube was connected to a separate

constant current auxiliary power source which was used

for supplying preheat current through the electrode.

Welding current was supplied through second contact

tube across the welding circuit.

1.4 Material selection and identification of process

parameters limits

A ‘single bead on plate’ technique was used to deposit

stainless steel beads on 300mm x 75mm x 12 mm mild

steel plates. SFA/AWS 5.9 class ER308L stainless steel

single bare wire electrode of 3.15 mm diameter was

used as a clad metal. A compatible agglomerated flux

(AWS SFA A-5.23) was used to shield the weld metal

from atmospheric contamination.

Four major independent parameters i.e. wire feed rate

‘F’, travel speed ‘S’, open circuit voltage ‘Vo’, nozzle to

plate distance ‘N’ as suggested by many researchers for

submerged arc welding were chosen for the present

work. An additional fifth parameter i.e. preheating

current ‘IP’, the characteristic ASAW process parameter,

along with the above four was also selected for the

study.

The working limits of selected parameters were finalized

on the basis of extensive trial runs. Minimum and

maximum levels of each parameter as shown in Table 1,

were decided by inspecting the resulting bead on plate

carefully during trial experiments. Only those parameter

limits were selected, which produced beads free of any

visible welding defect like surface porosity, undercut,

overlap, excessive convexity, cracks and showed smooth

and uniform appearance throughout the length[25].

1.5 Recording of responses

Welding current and welding voltage were recorded

during each experimental run. Plates with deposited

Auxiliary Power Source for Preheating Constant Voltage

Welding Power source

Filler Wire Spool

DielectricGap

Flux Hopper

Flux Covering Arc

Wire Electrode

Wire Feed Rollers

Weld Bead

Workpiece connection

Base Metal/Workpiece

Workpiece Support

Direction of welding

Copper contact tube

Electrode connection

Bead Width (W)

Reinforcement (H)

Penetration (P)

HAZ Width

Area of Reinforcement(AR)

Base Metal

HAZ Area

Area of Penetration (AP)


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44

beads were allowed to cool in still air upto room

temperature. Initial and final bead portions of 50 mm

length werediscarded in order to avoid arc start and stop

defects. Three specimens of about15 mm thickness (one

at centre and two at both the ends) were then

transversely cut using abrasive wheel cutter. The

specimens so obtained were then moulded with Bakelite

and polished thereafter, using fine grade emery papers.

Polished specimens were then chemically etched with

2% Nital solution in order to reveal different zones of

deposited bead[26]. Various bead zones like

reinforcement area, penetration area, were measured

after scanning the specimen and using digital measuring

tools.

1.6 Development of mathematical model

1.6.1 Response surface methodology

Response surface methodology (RSM) is useful for

modelling and analysis of problems with several

variables and where objective is to optimize the multiple

responses. Response function Y can be expressed in

terms of process parameters as Y = f (F, S, Vo , N, IP)

The model includes the main effects and interaction

effects of all the factors. Second order polynomial,

which was adopted for the present study, is represented

by following general expression.

y = β0 + βixi + βii xi2 + βij xixj +i<j

ki=1

ki=1

ϵ(2)

Where β0, βiiand βij are the constants and xi, is the

process variable and ϵ is the error term of the model

[27].

1.6.2 Formation of Design matrix and testing the

adequacy of developed models

The five levels of welding parameters based on half

fraction rotatable central composite design (CCD) for

RSM were selected and coded according to Table 1 and

then design matrix consisting 30 test conditions was

created using Design Expert 8 statistical software. This

design matrix is illustrated by Table 2. Adequacy of the

model was confirmed by using Analysis of Variance

(ANOVA) technique. The results of ANOVA for

responses are shown in Table 3. This table shows details

of sum of squares (SS), degrees of freedom (DF), mean

square (MS), F- Ratio and Probability of larger F- value

or simply P-value [28]. Figure 3 represents the normal

probability plot vs. Studentized residuals plots for all the

observations on bead width, reinforcement, penetration

and % dilution. It is concluded that the assumption of a

normal distribution is reasonable since all the plotted

points fall on a straight line.

Figure 3: Normal probability vs. Studentized residuals

for various responses

1.6.3 Checking the significance of coefficients

The statistical significance of the coefficients was tested

by applying the ‘t’ test. Coefficients having ‘t’ values

less than or equal to the standard tabulated ‘t’ value at

95% confidence level, are considered non-significant

and can be ignored along with the responses with which

they are associated and affecting minutely the accuracy

of the proposed model [29, 30]. Table 4contains F-

values and P-values for individual parameters in the

respective models for bead width, reinforcement,

penetration and percentage dilution. Factors with the P-

values less than 0.05 are significant and are included in

the final model.

Internally Studentized Residuals

No

rma

l %

Pro

ba

bil

ity

Normal Plot of Residuals

-3.00 -2.00 -1.00 0.00 1.00 2.00

1

5

10

20

30

50

70

80

90

95

99

Normal plot of Residuals for bead width (W)

(a)


No

rma

l %

Pro

ba

bil

ity


-2.00 -1.00 0.00 1.00 2.00

1

5

10

20

30

50

70

80

90

95

99

Normal plot of Residuals for reinforcement (H)

(b)


No

rma

l %

Pro

ba

bil

ity


-2.00 -1.00 0.00 1.00 2.00 3.00

1

5

10

20

30

50

70

80

90

95

99

Normal plot of Residuals for penetration(P)

(c)


No

rma

l %

Pro

ba

bil

ity


-2.00 -1.00 0.00 1.00 2.00

1

5

10

20

30

50

70

80

90

95

99

Normal plot of Residuals for dilution(%D)

(d)


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45

1.6.4 Optimization using desirability function

In 1980, Derringer and Suich[31] suggested a method

for optimization of multiple response problems in

industries. According to them, an estimated response yi

is transformed into a scale free individual desirability

function ( di ) that varies between 0 & 1. Optimal

parameter conditions for multiple responses are decided

by finding overall desirability value 𝔻 , which is

represented as geometric mean of individual desirability

function (di) as given in following equation 3.

𝔻 = d1. d2 . d3 ⋯⋯ dp 1 p

(3)

where, pis the number of responses to be considered for

optimization.

IV. RESULTS AND ANALYSIS

1.7 Final mathematical models

Following equations have been finalized keeping

significant parameter coefficients and omitting

insignificant parameter coefficients. Equations 4 to 7

represent regressions in terms of coded factors, while

equations 8 to 11 show correlation in terms of actual

factors[32].

1.7.1 Final Equation in Terms of Coded Factors:

ln W = 2.47 − 0.12 × S + 0.14 × Vo ...(4)

H −1.43 = 0.13 − 0.021 × F + 0.023 × S + 0.019 × Vo ...(5)

P = 3.34 + 0.41 × F − 0.23 × S − 0.25 × IP ...(6)

% D = 38.13 + 2.52 × S + 2.89 × Vo − 1.79 ×IP ...(7)

1.7.2 Final Equation in Terms of Actual Factors:

ln(W) = 1.19726 − 0.080839 × S + 0.047684 ×Vo ...(8)

(H)−1.43 = − 0.039 − 5.146 × 10 − 03 × F + 0.0155 × S + 6.31 × 10 − 03 × Vo ...(9)

P = 1.86 + 0.102 × F − 0.155 × S − 5.992 ×10 − 03 × IP ...(10)

% D = − 2.166 + 1.681 × S + 0.962 × Vo − 0.043 × IP ..(11)

1.8 Effect of process parameters on Bead width

Equation 4 suggests that the bead width ‘W’ depends

directly on travel speed and open circuit voltage. As the

travel speed is increased the bead width decreases

because the melting rate per unit length of weld is

decreased. These variations of bead width with the

parameters are depicted in figure 4a.An increase in open

circuit voltage leads to an increase in bead width which

can easily be explained by corresponding increase in arc

length. There are no interactions found between any of

the process parameters. Figure 5 illustrate the variation

of bead width with open circuit voltage at various levels

of travel speed.

1.9 Effects of process parameters on

Reinforcement Height

Reinforcement height ‘H’ is affected by many

parameters. Direct effect of parameters can be clearly

seen. Equation 5 shows that wire feed rate ‘F’, affect the

value of ‘H’ in a positive manner i.e. increasing wire

feed rate leads to increased ‘H’. Travel speed ‘S’ and

open circuit voltage ‘Vo’ affect reinforcement height in a

negative pattern. Rate of decrease in reinforcement

height with respect to travel speed is slightly more than

that with open circuit voltage as shown in figure 4b.

This can be explained as follows; (a) higher the wire

feed rate more will be the amount of molten filler metal,

so for the same bead width, reinforcement height should

increase to accommodate the increased amount of filler

metal (b) for increased travel speeds, less filler metal per

unit length is available which results in smaller

reinforcement (c) as explained earlier larger open circuit

voltage means long and wider arc that produces

comparatively a flatter bead and hence lower

reinforcement height is obtained. Figure 6 shows the

variation of reinforcement with wire feed rate at various

levels of travel speed and open circuit voltage.

1.10 Effects of process parameters on penetration

Correlation shown by Equation 6 in terms of coded

factors illustrate the main effects of wire feed rate ‘F’,

travel speed S and preheat current ‘IP’ on penetration

‘P’. The value of penetration increases with wire feed

rate and decreases with corresponding increase in travel

speed and preheat current as indicated in figure 4c.

Travel speed and preheat current produce almost same

penetration decrease rate. Since more wire feed rate is

associated with higher current values, resulting arc force

thus obtained is more and has the ability to penetrate

deep into base metal. At low travel speeds, heat input

per unit length of the base metal is less and the result is

lesser penetration. Preheat current in ASAW process is

used for maintaining the melting rate of the wire by a

simultaneous decrease in welding current, so a lesser arc

force is available at the base metal surface which

prohibits penetrating intensity. It is again concluded that

there are no interactions found between any of the

parameters. Figure 7 indicates, more clearly, the

variation of penetration with wire feed rate at various

levels of travel.

1.11 Effects of process parameters on % dilution

Correlation given by Equation 7 illustrate that the

significant parameters that affect the percentage dilution

in ASAW process are travel speed ‘S’, open circuit

voltage ‘Vo’ and preheat current ‘IP’. It is understood

that the increase in travel speed and open circuit voltage

increases %dilution but when preheating current is

enhanced the latter is decreased. This variation is clearly

illustrated in figure 4d.

This shows the importance of preheating welding

electrode wire. Increase in dilution with increasing

travel speed can be explained as, with an increase in the


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46

travel speed, amount of molten metal between the arc

and the fresh base metal is decreased and arc is able to

penetrate deeply into the base metal. With an increase in

open circuit voltage upto certain limit the arc becomes

hotter and gains the ability to penetrate deeper into base

metal which in turn, helps in diluting the deposited

metal more.

Increased preheat current lowers down the welding

current which affect the arc force adversely and hence

the penetration. On the other side, there is a little effect

on the filler metal deposition rate as the melting rate is

made up by heat produced due to preheating current

through the electrode. It results in rapid decrease of

penetration area in comparison to reinforcement area

and therefore, the dilution is decreased. Variation of

percentage dilution with respect to various parameters in

the form of response surface plots is shown in Figures8-

10.

Figure 4: Direct effects of parameters on responses

Figure 5: Variation of bead width with open circuit

voltage at various levels of welding speed

Figure 6: Variation of reinforcement with wire feed rate

at various levels of welding speed and open circuit

voltage

8

10

12

14

16

18

-2 -1 0 1 2

Be

ad

wid

th(W

), m

m

Factors at coded value

S

Vo

(a)

3

4

5

6

-2 -1 0 1 2

Re

info

rce

me

nt(

H),

mm


F

S

Vo

(b)

2.5

3.5

4.5

-2 -1 0 1 2

Pe

ne

tra

tio

n (

P),

mm


FSIp

(c)

30

35

40

45

-2 -1 0 1 2

%D

ilu

tio

n (

%D

)


SVoIp

(d)

5

10

15

20

25

30 33 36 39 42

Be

ad

wid

th(W

), m

m

Open Circuit Voltage, V

S=2.5S=4S=5.5S=7S=8.5

F= 28N= 24IP=84

2.5

5

7.5

10

20 24 28 32 36

Re

info

rcm

en

t(H

), m

m

Wire Feed rate(WF), mm/s

S=2.5S=4S=5.5S=7S=8.5

Vo= 36 VN= 24IP= 84

(a)

2.5

5

7.5

10

20 24 28 32 36

Re

info

rce

me

nt(

H),

mm


Vo=30

Vo=33

Vo=36

Vo=39

Vo=42

S= 5.5 N= 24IP= 84

(b)

2

3

4

5

20 24 28 32 36

Pe

ne

tra

tio

n(P

), m

m


S=2.5S=4S=5.5S=7S=8.5

Vo= 36N= 24IP= 84

(a)


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47

Figure 7: Variation of penetration with wire feed rate at

various levels of welding speed and preheating current

Figure 8: Response surface plot showing the variation

of percentage dilution with open circuit voltage and

travel speed

Figure 9: Response surface plot showing variation of

percentage dilution with preheating current and travel

speed

Figure 10: Response surface plot showing variation of

percentage dilution with preheat current and open circuit

voltage

1.12 Optimization for dilution

Optimization of the responses was done by using

desirability function as described in section 2.4.4. For

minimal dilution condition to be obtained as needed in

cladding, area of penetration to total bead area ratio

should be minimum. In order to satisfy this condition

bead width and reinforcement height must be maximum

and penetration depth should be minimum during

cladding [7]. Numerical optimization was carried out

using Design Expert 8.0 statistical software. Minimal

value of dilution equal to 30.49% was obtained with a

desirability function of 0.701 under following optimized

process parameter condition as shown in Table 5.

Confirmation run at the suggested optimized ASAW

process parameters were carried out and the resulting

bead on plate geometry and dilution values, as shown in

Figure 11, were found within the 95% confidence limit.

Figure 11: Confirmatory Bead obtained at optimized

parameter conditions

Table 1: Parameters and their values at various levels

Process

parameter

Units Notation Type of

parameter

Parameter levels

-2 -1 0 +1 +2

Open

Circuit

Voltage

Volts Vo Numeric 30 33 36 39 42

Wire Feed

Rate

Numeric 20 24 28 32 36

Welding

Speed

Numeric 2.5 4 5.5 7 8.5

Nozzle to

plate

distance

Numeric 18 21 24 27 30

Preheat

current

Numeric 0 42 84 126 168

2

3

4

5

20 24 28 32 36

Pe

ne

tra

tio

n(P

), m

m


Ip=0 A

Ip=42 A

Ip=84 A

Ip=126 A

Ip=168 A

S= 5.5 N= 24Vo= 36

(b)

30

33

36

39

42

2.5

4.0

5.5

7.0

8.5

25

30

35

40

45

50

P

ER

CE

NT

AG

E D

ILU

TIO

N

TRAVEL SPEED, mm/s OPEN CIRCUIT VOLTAGE, Volt

0

42

84

126

168

2.5

4.0

5.5

7.0

8.5

25

30

35

40

45

50

P

ER

CE

NT

AG

E D

ILU

TIO

N

TRAVEL SPEED, mm/s PREHEAT CURRENT, Amp

0

42

84

126

168

30

33

36

39

42

30

35

40

45

50

P

ER

CE

NT

AG

E D

ILU

TIO

N

OPEN CIRCUIT VOLTAGE, Volt PREHEAT CURRENT, Amp


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48

Table 2: Design Matrix for experimental runs

Run

No.

Coded ASAW process variables Actual response values

F S Vo N IP W (mm) H (mm) P (mm) %D

1 -1 -1 -1 -1 1 11.6 4.6 3.1 34.5

2 1 -1 -1 -1 -1 10.7 6.8 3.9 30.4

3 -1 1 -1 -1 -1 10.2 3.7 2.9 39.6

4 1 1 -1 -1 1 9.2 5.1 3.2 33.8

5 -1 -1 1 -1 -1 14.8 4.2 3.5 41.6

6 1 -1 1 -1 1 17.8 4.5 3.5 36.4

7 -1 1 1 -1 1 10.9 3.1 2.2 36.2

8 1 1 1 -1 -1 12.8 3.9 3.5 42.9

9 -1 -1 -1 1 -1 11.8 4.8 3.6 35.6

10 1 -1 -1 1 1 12.2 5.5 3.9 33.9

11 -1 1 -1 1 1 8.5 3.9 2.5 35.3

12 1 1 -1 1 -1 8.7 4.7 3.3 34.3

13 -1 -1 1 1 1 16.4 4.1 2.8 34.6

14 1 -1 1 1 -1 14.0 5.5 4.3 36.1

15 -1 1 1 1 -1 12.8 3.0 3.7 49.3

16 1 1 1 1 1 12.2 3.8 3.6 44.2

17 -2 0 0 0 0 9.8 3.4 2.3 36.7

18 2 0 0 0 0 12.5 5.3 4.7 41.0

19 0 -2 0 0 0 14.9 7.2 3.7 26.9

20 0 2 0 0 0 9.2 3.7 2.8 40.9

21 0 0 -2 0 0 8.8 5.5 2.9 29.8

22 0 0 2 0 0 15.0 3.5 3.2 42.5

23 0 0 0 -2 0 12.1 4.1 3.9 44.1

24 0 0 0 2 0 11.0 4.1 2.9 34.3

25 0 0 0 0 -2 11.5 4.0 3.9 47.0

26 0 0 0 0 2 11.0 3.7 2.7 35.9

27 0 0 0 0 0 12.9 3.9 3.1 39.3

28 0 0 0 0 0 12.9 4.1 3.6 41.5

29 0 0 0 0 0 10.9 4.4 3.6 39.8

30 0 0 0 0 0 13.1 3.7 3.7 45.4

Table 3: ANOVA test for the fitted models

Source SS DF MS F-Value P-value Significance

(a) Bead Width (W)

Model 0.844 2 0.422 69.039 < 0.0001 significant Residual 0.165 27 0.006

Lack of Fit 0.143 24 0.006 0.817 0.6772 not significant Pure Error 0.022 3 0.007

Cor Total 1.009 29

Std. Dev.=0.078, R-Squared= 0.836, Adj R-Squared= 0.824

(b) Reinforcement (H)



Cor Total 0.036 29

Std. Dev. = 0.013, R-Squared = 0.875, Adj R-Squared = 0.861

Table 3 continued….

Source SS DF MS F-Value P-value Significance (c) Penetration (P)



Cor Total 9.334 29


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49


(d) %Dilution (%D)

Model 429.462 3 143.154 10.197 0.0001 significant Residual 365.009 26 14.039

Lack of Fit 342.343 23 14.884 1.970 0.3191 not significant

Pure Error 22.666 3 7.555

Cor Total 794.471 29


Table 2: Testing of significance for each parameter in developed models

Factors DF

Bead width (W) Reinforcement (H) Penetration (P) Dilution (%D)

F- Value P-Value F- Value P-Value F- Value P-Value F- Value P-Value

F 1 1.561 0.2235 56.524 < 0.0001 38.179 < 0.0001 0.105 0.7488

S 1 55.964 < 0.0001 72.211 < 0.0001 12.573 0.0016 10.228 0.0039

Vo 1 77.890 < 0.0001 47.806 < 0.0001 0.611 0.4419 13.405 0.0012

N 1 0.605 0.4441 0.001 0.9738 0.001 0.9700 0.366 0.5510

IP 1 0.007 0.9335 1.233 0.2779 14.662 0.0008 5.158 0.0324

Table 3: Optimized ASAW parameter condition for minimal dilution value

F S VO N IP W H P %D Desirability

29.3 4 33 23 126 11.56 5.82 3.46 30.94 0.701

V. CONCLUSION

Dilution has a great impact on the chemical composition

of the SS clad layer as a result of intens mixing with the

substrate, mild steel in this case. Prediction of %dilution

is important in the sense that several mechanical,

metallurgical, chemical properties are greatly influenced

by the extent of dilution. Least amount of dilution is the

need for a cladding opreation. Advanced submerged arc

welding (ASAW) thus enhances the versatility of

conventioal submerged arc welding to make it more

useful for cladding operation as dilution levels can be

reduced significantly by introducing preheating current

through the electrode wire. Findings of present work

may be concluded as follows;

1. Bead width is influence by travel speed and open

circuit voltage

2. Reinforcement is a function of wire feed rate,

travel speed and open circuit voltage

3. Penetration is greatly affected by wire feed rate and

preheating current.

4. Percentage dilution depends on travel speed, open

circuit voltage and preheating current.

5. Advanced submerged arc welding economically

provides an efficient alternative for quality

surfacing /cladding operations as dilution is

considerably reduced.

6. At very low open circuit voltage and travel speeds

submerged arc welding process cannot be operated

to give quality welds. In this situation, advanced

submerged arc welding (ASAW) provides further

significant reduction in dilution maintaining the

other parameters within their range and still

maintaining the quality of welding/surfacing

operation.

7. An optimized value of dilution equal to 30.94%

was obtained as a result of optimization using

desirability function which was later confirmed by

depositing confirmation run.

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