predicting the microstructure and properties of steel welds

Predicting the Microstructure and

Properties of Steel Welds

MULTIPASS ARC WELD

L.-E. SVENSSON

L.-E. SVENSSON

a

ca

yx

z

100 µm

20 µmBarrite, 1982

120100806040200200

400

600

800

1000

Time / s

120100806040200200

400

600

800

1000

Time / s

Manual Metal Arc Weld

180 Amps

34 Volts

4 mm/s

200 °C interpass

Manual Metal Arc Weld

180 Amps

34 Volts

4 mm/s

200 °C interpass

12

3 45

6

1. Fe-0.4C2. Fe-0.4C-2Si3. Fe-0.4C-1Ni4. Fe-0.4C-1Mn5. Fe-0.4C-1Mn-1Cr6. Fe-0.4C-2Mn

0 1 2 3 4 5 10 10 10 10 10 10

Time / s

800

700

600

500

400

300

200

Tem

pera

ture

/

C

calculations

Barrite, 1982

5 µm

Barrite, 1982

0.110.090.070.050.03

0.2

0.4

0.6

0.8

1.0

Carbon / wt %

Volu

me f

ract

ion Allotriomorphic

Widmanstatten

Acicular

Fe-1Mn-C wt % manual metal arc welds

Bhadeshia & Svensson

Bhadeshia & Svensson

Charpy toughnes

s

Murugananth & Bhadeshia

7Ni 2Mn

7Ni 0.5Mn

7Ni 2Mn

7Ni 0.5Mn

Weld Shape - Stitch Weld at 2.26 kW Laser OutputWith Ar shieldinggasv=45 mm/s; L=5mmv=45 mm/s; L=5mmv=45 mm/s; L=10mmv=40 mm/s; L=15mmv=50 mm/s; L=15mmv=50 mm/s; L=15mmv=40 mm/s; L=20mmv=35 mm/s; L=10mmv=27 mm/s; L=10mmv=35 mm/s; L=5 mmv=27 mm/s; L=5 mmv=50 mm/s; L=20mmWithout shieldinggas2 mm

PARTIALPENETRATIONFULLPENETRATION2.26 kW LASER BEAM

Laser beam

Keyhole

Laser beam

Fusion Zone

m

w

Optically: mainly -ferrite some w-ferrite <5% martensiteTEM: -ferrite much w-ferrite

155, 157 and 170 HVMean Hardness: 161 HV

Grain size100 ±20 m

46% -ferrite21% w-ferrite30% acicular ferrite & bainite 3% martensite

168 HV

Grain size103 m

Measured Calculated

Charpy

fatigue

corrosion

tensile

critical stress intensity

Variables

• C, Mn, Si, Ni, Cr, Mo, V, Co, B, N, O…..

• Thermomechanical processing of steel

• Welding consumable• Welding parameters• Subsequent heat treatment

Empirical Equations

y = a + b (%C) +c (%Mn)

+ d (%Ni) ....

y = a + b (%C) +c (%Mn)

+ d (%Ni) ....

1223

y = a + b (%C) +c (%Mn)

y = a + b (%C) +c (%Mn)

+ d(%C x %Mn)

y = a + b (%C) +c (%Mn)

y = a + b (%C) +c (%Mn)

+ d(%C x %Mn)

y = a + b (%C) +c (%Mn)

y = a + b (%C) +c (%Mn)

+ d(%C x %Mn)

y = sin (%C) + tanh (%Mn)

y = a + b (%C) +c (%Mn)

y = a + b (%C) +c (%Mn)

+ d(%C x %Mn)

y = sin (%C) + tanh (%Mn)

Hyperbolic Tangents

y

f{x }j

1

2(a) (b)

non-linear functions

765432100

1

2

3

4

5

6

7

x

86420-100

0

100

200

300

400

x

86420-100

0

100

200

300

400

x

86420-100

0

100

200

300

400

x

Complexity of model

test error

training error

(a) (b)

(c)(d)

Predict what the next two numbers are likely to be:

2, 4, 6, 8, …….

0.0 0.2 0.4 0.6 0.8 1.00

50

100

150

200

250

300

Nickel / wt.%

10CrMoW

104 h, 550 °C

0.00 0.02 0.04 0.06 0.080

50

100

150

200

250

300

Aluminium / wt.%

10CrMoW

104 h, 600 °C

Brun, Robson, Narayan, MacKay & Bhadeshia

precipitates

solid solution

iron + microstructure550 °C

600 °C

Murugananth & Bhadeshia

Components of Creep Strength, Components of Creep Strength, 2.25Cr1Mo2.25Cr1Mo

0 5000 100000

100

200

300

400

Life / hours

GTA weld at 923 K (data from Nippon Steel)

Cole & Bhadeshia

Cool, 1996

Cool, 1996

As-welded 600 °C

650 °C700 °C

Cool, 1996

Siemens

Mitsui Babcock

Nippon Steel

ABB

Thank you.