Basic models, animations and unsolved problems in · PDF fileBasic models, animations and unsolved problems in welding ... • A basic heat conduction model ... Phase Transformations

1Phase Transformations & Complex Properties Research Group, Cambridge University, 19 August 2011

Basic models, animations and unsolvedproblems in welding

T. DebRoy

• A basic heat conduction model – benefits and limitations• Applications of heat transfer and fluid flow models

Unusual weld pool shapesWeld surface profiles Effect of surface active elementsWelding two plates with different sulfur contentsUphill, downhill, tilted, L and V configurationsWeld metal composition changeWhy Sievert’s Law cannot be directly applied in welding

• Tailoring weld geometry

Thanks to: A. Kumar, W. Zhang, B. Ribic, C.H. Kim, W. Pitscheneder, G. G. Roy, A. Arora, S. Mishra, T. J. Lienert, P. A. A. Khan, X. He, T. A. Palmer, A. De


• Heat transfer and melting

• Evaporation of elements & dissolution of gases

• Solidification &structural changes

• Flow of liquid metal

Basic models in welding

Models the essential physical processes

“Essential” => of interest to many for meaningfulunderstanding of the process and the weld metal

• Properties


Rosenthal model for heat conduction in welding - a most widely used basic model

Rosenthal model for heat conduction in welding

Analytical solution to calculate temperature fields, cooling rates and weld geometry

Widely used - simple, phenomenological and insightful

But ignores convection which is the main mechanism of heat transfer in many cases

“For an engineer in search of a theory, the simpler the better”(paraphrased)

Professor D. Brian Spaldingpicture from http://www.cham.co.uk/about.php


Four main difficulties of heat conduction models

"Everything should be made as simple as possible, but not simpler."

— Albert Einstein

From: http://rescomp.stanford.edu/~cheshire/EinsteinQuotes.html


Y, mm

Z,m

m

-4 -2 0 2 401234

1000K

1745K

304 stainless Laser-arc hybrid

21Cr-6Ni-9Mn steelElectron beamFriction stir welding

Aluminum alloy AA2524

Laser beam welding

NaNO3

Steel

Al-5182

Problem 1: diversity of weld shapes cannot be predicted from heat conduction equation

All these shapes have been explained considering convective heat transfer

6

Problem 2: weld orientation effect cannot be explained

This effect has been explained considering convective heat transfer

7

Problem 3: The effects of minor alloying elements cannot be explained ignoring convection

The effects of oxygen and sulfur has been explained considering convective heat transfer

1900 W

(d)(c)

1900 W

(d)(d)(c)(c)

5200 W

(a) (b)20 ppm sulfur 150 ppm sulfur

5200 W

(a) (b)(b)20 ppm sulfur 150 ppm sulfur

* Minor changes in composition => major changes in geometry* Does not always happen!

8

“…the heat conduction equation has been found to be inadequate in representing experimental cooling curves” SVENSSON, GRETOFT and BHADESHIA, An analysis of cooling curves from the fusion zone of steel weld deposits, Scand. J. Metallurgy, vol. 15, pp. 97-103, 1986.

Problem 4: Heat conduction equations overpredict cooling rates

Convective heat transfer calculations do not have any such problems.

They recommended use ofempirical correlations

The heat conduction equations predict high temperature gradients and cooling rates because mixing of hot and cold liquids is ignored.


Heat and fluid flow models and their diverse applications


GTA weld pool with deformed free surface


Heat and fluid flow models - diverse applications

The Main EngineTransient, three dimensional, heat, mass and

momentum transfer numerical model

Transient temperature and velocity fields, mixing of consumables, heating and

cooling rates, weld geometry

Solidification parameters, solidification growth rates, temperature gradients etc.

Output

Phase transformation in the fusion and heat affected zone Grain growth in the heat affected zone

Inclusion type, size and distributionPore structure, gas dissolution etc

Applications

Welding ProcessesGas tungsten arc (GTA), Gas metal arc (GMA), Laser (conduction &keyhole), Electron beam, GTA-Laser hybrid, Friction stir welding

Deformed free surface, loss of alloying elements, composition change etc.


Many more applications

1. Fusion zone (FZ) and heat affect zone (HAZ) geometries2. Grain size and topological features in the HAZ3. Evolution of inclusion composition and size distribution4. Evolution of microstructure in both FZ and HAZ5. Control of cooling rates6. Composition change owing to selective vaporization of

alloying elements7. Control of hydrogen and nitrogen in steel weldments8. Joining of dissimilar materials including steels of different

surface active elements such as sulfur and oxygen9. Prevention of macro-porosity in laser welding10. Enhancing fatigue property through improved surface

finishing

13

1. Understanding unusual weld pool shapes


Arora, Roy, and DebRoy, Scripta Materialia, 2009

Wavy weld pool boundary

Hemispherical boundaryArc welding of Al 5182 Zhao, DebRoy, Met. Trans B, 2001

Concave at the center Laser melting of NaNO3Limmaneevichitr, Kou, Welding Journal, 2000

Convex at the center Arc welding of steelElmer, Palmer, Zhang, DebRoy, STWJ, 2008



Wavy weld pool boundary

High Marangoni number, Ma, leads to formation of wavy weld pool boundary

=Ma =Ma =Ma

forceViscousforcetensionSurface

αμγΔ

=)dT/d(TL

Ma =

= L Characteristic lengthΔT Temperature differencedγ/dT First derivative of surface

tension wrt temperatureα Thermal diffusivityμ Viscosity


Origin of wavy weld pool boundary

==

0.014Pr15400Ma

==

8.2Pr77600Ma

==

0.012Pr298000Ma

Marangoni (Ma) and Prandtl (Pr) numbers can be used to predict the shape of the wavy weld pool boundary

==

1.3Pr37400Ma

forceViscousforcetensionSurface

Ma =

ratediffusionThermalratediffusionViscous

Pr =

Marangoni number (Ma)

Pra

ndtl

num

ber(

Pr)

100 102 104 106 108 101010-3

10-2

10-1

100

101


17

2. Surface profiles


Why study surface profile?

Improper parameters ⇒ poor mechanical properties ⇒ defects ⇒ failure

θ hθ - weld toe angleh - weld reinforcement height

Stre

ss ra

nge

Cycles to crack initiation

increasing θ

Stre

ss ra

nge

Cycles to crack initiation

increasing h


Development of bead profile in GMA welds


Calculated and experimental GMA bead shape

Experimental data from Kim and Na, Welding J., 1995 (5) 141s

Fusion boundary

3 mm

(C)

260 A25 mm

Fusion boundary

3 mm

(C)

260 A25 mm

21

Effect of welding parameters on the solidified surface profile

49o

2.842.7913.20Exp.

47o

3.952.8212.60Exp.

53o

5.053.1211.32Exp. Calc.Calc.Calc.

Test case C(260 A, 25 mm)

Test case B(280 A, 20 mm)

Test case A(300 A, 15 mm)

49o50o59oToe angle - θ

2.904.005.00Penetration (mm) – P2.802.803.02Bead Height (mm) – h13.2412.8211.20Bead width (mm) - W

Wh

P

θ

22

3. Effect of surface active elements


dxdT

dTd

dxd

⋅σ

=σ

=τ

Negative orpositive

Negative

Convection in Fe and Fe-S Melts

⎟⎠⎞

⎜⎝⎛

∂∂

∂γ∂

+∂∂

∂γ∂

=∂∂

μxC

CxT

Tf

zu

L


High power welding - sulfur affects penetration

20 ppm sulfur 150 ppm sulfur

Minor changes in composition major changes in geometry

5200 WPe >> 80

20.0 cm/s

2236

K

2000

K

1620

K

2108

K

1900

K

20.0 cm/s16

20K


2.0 cm/s

1620

K

1700

K

1727

K

20 ppm sulfur 150 ppm sulfur

Minor change in composition Insignificant change in geometry

Low power welding - sulfur doesnot influence penetration

1900 WPe << 1

1720

K

1700

K

1620

K0.5 cm/s


Variable penetration - summary

Experiments

Modeling

• reveal what happens: sometimes thedepth changes with % S

Modeling is a path to understand the science of welding

• surface active elements improve penetration only when convectionis important ( high Pe )

• but do not reveal why

27

4. Welding two plates with different sulfur contents

28

Identifying factors affecting weld pool geometry

Distribution of sulfur on the top surface

304L 303

I = 150 A, V = 10.5 V, Welding speed = 1.7 mm/s

S = 0.003 wt% S = 0.293 wt%

I = 101 A, V = 9.6 V, Welding speed = 1.7 mm/s

S = 0.024 wt%304RL

S = 0.003 wt%304L

304L

304RL

The arc shifts towards the low sulfur side

High SLow S

S gradient

29

Sulfur distribution in the weld

60 62.5 65 67.5 70 72.5 75 77.5 80Y-axis (mm)

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

Sulfu

r (w

t%)

Calculated ResultsExperimental Results

Case 2

Weld pool edges:Left edge at 66.6 mmRight edge at 74.2 mmPlates join at 72.7 mm

0.03 0.08 0.13 0.18 0.23 0.28Sulfur (wt%)

0

0.2

0.4

0.6

0.8

1

1.2Z-

axis

(mm

)

Experimental ResultsCalculated Results

Case 2

Welding conditions: 150 A, 10.8 V, welding speed is 1.7 mm/sNo significant sulfur concentration gradient=> Not much influence on weld bead shift

High SLow S

S gradient

EPMA results

30

Reason for arc shift

+ ++ e-

e-

e-

Electrode

Arc + +e-

e-

Electrode

Arc

M+M+

Low S High S

• Sulfur covers more surface on high sulfur side => less metal sites on the surface.

• Sulfur has strong interaction with low ionization potential metals like Mn. Higher the sulfur the more it prevents ionization.

31

Incorporating arc shift

Maximum penetration occurs approximately below the arc

location

Amount of arc shift is approximated by length AB

Empirical relation for amountof arc shift

0 0.5 1 1.5 2 2.5 30

0.5

1

1.5

2

2.5

3

Cen

ter L

ine

Shift

(CLS

), m

m Experimental dataLinear fit

( ) ( )0.420.24RL J/mm -wt%,

UVICC

42.024.019.0 ⎟

⎠⎞

⎜⎝⎛ ×

×−×

32

Temperature and velocity fields & Sulfur distribution

Welding conditions: 150 A, 10.8 V, welding speed is 1.7 mm/s

No significant sulfur gradient except very close to the edges

Fair agreement between the calculated and experimental

weld pool geometry

33

5. Uphill, downhill, tilt, L and V configurations

34

14001000

800 600

600

800

1000

1400

1785

100 cm/s5 mm

600

60010001400

1745

800

1000

1400

100 cm/s

5 mm

Welding direction

y

xz

X = 0mm

X = 5mm

Arc position at x = 0

Welding torch

X = 0 mm

X = 0 mm

1745

1785

1400

1000 60

0

600800 10001400

100 cm/s

5 mm

X = 5 mm

600800100014001745

178514

00

1000

800

600

X

100 cm/s5 mm

X = 5 mm

Welding ConditionsI = 362 AV = 33 V

Uw = 4.2 mm/sCTWD = 22.2 mmwf = 211.7 mm/s

Temperatures: in KelvinWeld pool boundary: 1745 K

uLPe 120= =α

u: Liquid velocityL: Weld pool widthα: Thermal diffusivity

Effect of tilt angle

35

Effect of lift angle

1

2

3

Z(cm

)

23

45

6

X (cm)

0

1Y(cm

)

1000140017

85

1000

1745

1400

1745

800

800

YX

Z

50 cm/s

Electrode

1

2

3

Z(cm

)

23

45

6

X (cm)

0

1Y(cm

)

800

10001400

1785

10001400

1745

1745

800

YX

Z

50 cm/s

Electrode

T1900178517451100800600500

25 cm/s

T1900178517451100800600500

25 cm/s

36

I = 362 AV = 33 VU = 4.2 mm/swf = 211.7 mm/s

I = 250 AV = 29 VU = 7.0 mm/swf = 150.0 mm/s

I = 362 AV = 33 VU = 6.4 mm/swf = 211.7 mm/s

I = 322.6 AV = 32 VU = 5.3 mm/swf = 190.5 mm/s

Weld bead geometry

I = 362 A, V = 33 VU = 4.2 mm/swf = 211.7 mm/s

Weld bead is depressed in thecenter during downhill weldingHump formation duringuphill weldingMore penetration duringuphill welding

Y (cm)-0.5 0 0.5 1

V-shape, 10 Uphill

V shape, Horizontal

oV-shape, 10 Downhillo


6. Composition change

38

Pronounced weld metal composition change

Temperature field and weld pool size are important factors

39

Composition change is more pronounced at low powers – why?

40

High Power Welding

Laser Beam

Base Metal

Weld Pool

Why is the composition change more pronounced at low powers?

• Pool size increases strongly with increase in power – alloyingelement loss is spread over a larger volume

• Most of the evaporation takes place under the beam

Low Power Welding

Laser Beam

Base Metal

Weld Pool

41

Temperature from Vapor Composition

Vaporization rate of AVaporization rate of B=

pA

pB√ (MB/MA)

JA

JB= = f (T)

Laser beam

Molten pool

Vapor flux

Base metal

DepositQuartz tube

42


1600 2000 2400 2800 3200 3600Temperature (K)

0

5

10

15

20

25

30

J Fe/

J Mn

10.8

3125 K

Vaporization rate of AVaporization rate of B=

pApB

√(MB/MA)JA

JB=

43


2485243523080.313

3060309027610.210530 W,4.0 ms pulse

2865300528790.325

3110312532700.2601067 W,

3.0 ms pulse

Temperature from JCr/ JMn

(K)

Temperaturefrom JFe/ JMn

(K)

Peak temperature from numerical

heat transfer (K)

Spot radius (mm)Power and pulse

44

Model Validation

-0.5

-0.5

0

0

0.5

0.5

1.1 1.11.2 1.21.3 1.31.4 1.41.5 1.5

x (mm)

z(m

m)

500 mm/s1697 K

-0.5

-0.5

0

0

0.5

0.5

1.1 1.11.2 1.21.3 1.31.4 1.41.5 1.5

x (mm)

z(m

m)

500 mm/s

1697 K

Laser power: 1967 W and pulse duration: 3 ms.

Experimental and Calculated Weld Pool Cross Sections

(a) beam radius: 0.43 mm

(b) beam radius: 0.57 mm

45

Main Metallic Species in the Vapor

Power Density (W/mm2)

Wei

ghtP

erce

ntof

Cri

nV

apor

(%)

2000 3000 4000 50000

10

20

30

40

50

Calculated valueExperimental value

Iron and chromium were the dominant species in the vapor

Power Density (W/mm2)

Wei

ghtP

erce

ntof

Fein

Vap

or(%

)

2000 3000 4000 500020

30

40

50

60

70

80

Calculated valueExperimental value

46

1000 2000 3000 4000 5000 6000 7000Power Density (W/mm2)

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

Com

posi

tion

Cha

nge

(%) Fe

MnCrNi

Weld Metal Composition Change

Initial concentrations:Mn: 1 wt% , Cr: 18.1 wt%,

Ni: 8.6 wt%, Fe: 72.3 wt% %100

mV

m)i(%V)i n

1ii

io

(% ×Δ−ρ

Δ−ρ=

∑=

V: volume of weld pool ρ: density of liquid metal Δmi: weight loss of element i n: number of vapor species

Final weight percent of element i:

Assumption: uniform weld pool composition resulting from strong recirculating flow

47

Fe Mn Cr Ni-0.6

-0.4

-0.2

0

0.2

0.4

0.6w

t. %

y

yExperimental valueCalculated value

Laser power: 1067 W, pulse duration: 3.0 ms, and beam radius: 0.225 mm.

Change of Composition of Weld Pool

48Laser power: 1067 W, pulse duration: 3.0 ms, and beam radius: 0.325 mm

Composition Change of Weld Pool Microprobe trace

0

0.5

1

1.5

2

2.5

0 400 800 1200 1600Distance (µm)

Con

cent

rati o

n of

Mn

(wt.

%)

Con

cent

ratio

n of

Cr

(wt.

%)

14

16

18

20

22

24

0 400 800 1200 1600Distance (µm)

49

Recoil and Surface Tension ForcesLaser power: 1067 W, pulse duration: 3.0 ms, and beam diameter: 0.405 mm.

∫ Δπ= Br

0r dr)r(Pr2FRecoil force:

σπ= 0s r2FSurface tension force:

x (mm)

Tem

pera

ture

(K)

0 0.1 0.2 0.3 0.41500

2000

2500

3000

3500

0.1 ms0.4 ms

1 ms3 ms

mushy zone

Recoil force > Surface tension force => Expulsion of metal drops

50t > 2.6 ms, Recoil force > Surface tension force => Expulsion of metal drops

0 0.5 1 1.5 2 2.5 3Time (ms)

0

200

400

600

Forc

e (g

m-c

m/s

ec 2

)

Recoil force

Surface tension

Recoil and Surface Tension Forces

51Progressive deformation of the free surface

Free Surface Deformation

x (mm)

z(m

m)

-0.4 -0.2 0 0.2 0.41.1

1.2

1.3

1.4

1.5

600 mm/s

1697 K

x (mm)

z(m

m)

-0.4 -0.2 0 0.2 0.41.1

1.2

1.3

1.4

1.5

600 mm/s1697 K

x (mm)

z(m

m)

-0.4 -0.2 0 0.2 0.41.1

1.2

1.3

1.4

1.5

600 mm/s

1697 K

x (mm)

z(m

m)

-0.4 -0.2 0 0.2 0.41.1

1.2

1.3

1.4

1.5

1697 K600 mm/s

1 ms 2 ms

3 ms 4 ms

52

3 4 5 6 7 8 9 10 11 12Power density (kW/mm 2)

0

0.1

0.2

0.3

0.4

0.5l/d

No expulsionExpulsion

l

d

Free Surface Deformation

53

Critical Laser Power Density

3.0 ms pulse 4.0 ms pulse

Critical laser power density:

8.0 kW/mm2

Critical laser power density:

7.0 kW/mm2

0 0.5 1 1.5 2Laser Power (kW)

0

0.2

0.4

0.6

0.8

1

Spot

Dia

met

er (m

m)

Heavy expulsionIntermittent expulsionVaporNo vapor

4.0

7.010.0

0 0.5 1 1.5 2 2.5Laser Power (kW)

0

0.2

0.4

0.6

0.8

1

Spot

Dia

met

er (m

m)


8.0

6.0

10.0

4.0

54

Effects of Welding Variables

1 3 5 7 9Pulse Duration (ms)

0

4

8

12

16

20Po

wer

Den

sity

(kW

/mm

2)



7. Dissolution of gases

5656

Nitrogen Dissolution In The Weld Pool

Nitrogen concentration in the weld metal is much higher than that predicted by Sieverts’ law

But why?

5757

Nitrogen dissolution from a plasma environment

SYSTEM GAS/METAL PLASMA/METAL

SPECIES N2/Fe

LAW SIEVERTS’ LAW ??

/FeNN,,N,N,N *2

*22

+

SYSTEM

GAS/METAL

PLASMA/METAL Source of N Gas

Thermal Dissociation

Thermal Dissociation Electron Impact Electromagnetic Effects

Partial Pressure

12 N 2 (g) → N (g )

PN = K eqTs PN 2

1 / 2

PN > K eqTs PN 2

1 / 2

PN = K eqTd PN 2

1 / 2

Ts = Sample Temperature Td = Temperature at which N2(g) dissociates

5858

Nitrogen - Iron System

DIATOMIC NITROGEN MONATOMIC NITROGEN

5959

Physical modeling with isothermal metal drops

Pump andPressure Control

Pressure Gauge

Gas Mixture

SampleSample Holder

PlasmaPower Source,RF Generator

Fibre Optic Cable

Computer System

EmissionSpectrograph

CCD Detector

CCD Detector ControllerDetector Interface

WaterNitrogen

PrismOpticalPyrometer

6060

Enhanced dissolution of nitrogenin isothermal metal drops

• Nitrogen solubilities up to 30 times larger than Sieverts’ Law predictions.• Small changes in sample temperature cause large variations in N.

6161

Emission spectroscopy of glow discharges

He-1%N2

• Experimental verification for the presence of species in the plasma phase.

6262

Nitrogen dissolution in the weld pool

Much higher than Sieverts’ law values of nitrogen concentration can be predicted by a two temperature model

But how?

6363

• Dissociation temperatures are 100-215 K above the sample temperatureBut welds are not isothermal!

N(wt.%) = PN 2 exp − 1R

ΔG Td°

Td+

ΔG Ts°

Ts

⎛

⎝ ⎜ ⎜

⎞

⎠ ⎟ ⎟

⎛

⎝ ⎜ ⎜

⎞

⎠ ⎟ ⎟

Two temperature model – useful and simple back of the envelop estimation of concentration

6464

Inside Arc Column Outside Arc Column[ ] )ppm(N)g(N → [ ] )ppm(N)g(N22

1 →

[ ] ⎟⎟⎠

⎞⎜⎜⎝

⎛−=

°ΔRT

GN

)g(NexpPN [ ] ( )⎟⎟⎠

⎞⎜⎜⎝

⎛−=

°ΔRT

G2/1N

)g(2N2 expPN

z

y

x

0dydc =

[N] = 20 ppm

[N] = 20 ppm

Nitrogen concentrations at the weld pool surface

6565

Species concentrations in the plasma

Species concentrations in Ar-5%N2 plasma

Important species: Ar, N2 and N

s

6666

Calculation of nitrogen concentration in the weld pool

Main tasks:

Compute temperature and velocity fields in the weld pool

Compute species concentrations in the plasma above the weld pool

Compute nitrogen concentrations on the weld pool surface

Compute nitrogen concentrations in the entire specimen

6767

Comparison between modeling andexperimental results

TRAVEL SPEED: 0.847 cm/sec

Modeled results with nitrogen supersaturations between 50 and 75% higher than Sieverts’ Lawcalculations for P(N2) =1 atm correspond well with experimental results.

68

Many other applicationshttp://www.matse.psu.edu/modeling



Tailoring weld geometry – has been done

Tailoring structure and properties?

71

Designer welds via multiple paths

Requirements: Geometry, cooling rate, or microstructure

Variable set 1

Variable set 2

Variable set 3

Variable set 4

Variable set 5

Variable set 6

Variable set 7

Variable set 8

Target weld geometry, cooling rate or other attributes

72

Tailoring weld geometry

Desired weld pool geometry

Genetic algorithm

Genetic Algorithm

Calculated weld pool geometry

⎟⎟⎠

⎞⎜⎜⎝

⎛

rrr UU,

VV,

IIofSets

2

e

c2

e

c

1ww

1pp

O2(f) ⎟⎟⎠

⎞⎜⎜⎝

⎛−+⎟

⎟⎠

⎞⎜⎜⎝

⎛−=

73

Tailoring weld attributes

Target: Form a weld of the following dimensions:

Penetration : 1.23 mm Width : 4.47 mm

This weld was actually fabricated by GTA welding

7 mm/sWelding Speed

11.2 VVoltage140 ACurrent

1.23 mm

4.47 mm

Bag, De and DebRoy, Materials and Manufacturing Processes., 2009

74

Objective function

( )2

obs

obsc2

obs

obsc

ppp

www

fO ⎟⎟⎠

⎞⎜⎜⎝

⎛ −+⎟

⎟⎠

⎞⎜⎜⎝

⎛ −=

W – weld pool width

P – weld pool penetration

Superscript c – computed values

Superscript obs – experimentally observed values

{ } { }***321}{ vVI

vv

VV

IIffff

mxmnmn

=⎭⎬⎫

⎩⎨⎧

=≡

f – welding variable set

I – Current

V - Voltage

v– welding speed

Subscript mn– minimum allowed value

Subscript mx – maximum allowed value


75

Objective function with I*, V* and v*

O(f) for the initial population O(f) after ten generations

Eight alternate welding conditions achieved after

fifteen generations


76

Multiple combinations of welding parameters result in roughly the same target geometry

Target geometry: penetration = 1.23 mm, width = 4.47 mmI = 140 A, V = 11.2 V, Welding speed = 7 mm/s

4.551.248.610.5166.5(8)4.451.234.812.5106(7)4.631.28912.6149(6)4.531.238.214.4117(5)4.341.189.610.3163(4)

1.251.24

1.24

Penetration(mm)

4.605.110.6135(3)4.577.111.5140(2)

4.544.39.8134(1)

Width(mm)

U(mm/s)

V(Volt)

I(amp)

Individual solutions


77

Geometries of fabricated welds

4.54 mm

1.24 mm

(1)

134 A, 9.8 V, 4.3 mm/s

4.60 mm

1.25 mm

(3)

135 A, 10.6 V, 5.1 mm/s

4.57 mm

1.24 mm

(2)

140 A, 11.5 V, 7.1 mm/s

4.34 mm

1.18 mm

(4)

163 A, 10.3 V, 9.6 mm/s


78

Geometries of fabricated welds

4.53 mm

1.23 mm

(5)

117 A, 14.4 V, 8.2 mm/s

4.63 mm

1.28 mm

(6)

149 A, 12.6 V, 9 mm/s

4.45 mm

1.23 mm

(7)

106 A, 12.5 V, 4.8 mm/s

4.55 mm

1.24 mm

(8)

166.5 A, 10.5 V, 8.6 mm/s


79

Multiple sets of welding variables can produce a target geometry

Arc welding of SS304 to produce 4.47 mm wide and 1.23 mm deep pool

1.251.244.654.558.610.5166.5

1.211.234.264.454.812.5106.1

1.301.284.904.639.012.6149.0

1.191.234.234.538.214.4117.0

1.221.184.604.349.610.3163.0

1.271.254.784.605.110.6134.8

1.211.244.894.577.111.5140.3

1.201.244.814.544.39.8134.0

measuredcomputedmeasuredcomputed

Penetration (mm)Width (mm)Velocity (mm/s)

Voltage(V)Current (A)

Obtained by GA Obtained by experiments

80

Thank you very much

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