* cea, den, dm2s, semt, lta, 91191 gif sur yvette, france. ** cea, drt, liten, dtbh, lcta, 38054...

* CEA, DEN, DM2S, SEMT, LTA, 91191 Gif sur Yvette, France. ** CEA, DRT, LITEN, DTBH, LCTA, 38054 Grenoble, France.*** LMT-Cachan, ENS de Cachan/CNRS/UPMC (University Paris 6), 94235 Cachan, France.

Prediction of (residual stresses and) microstructural state after multi-pass GTA-Welding

of X10CrMoVNb9-1 martensitic steel

Farah Hanna*,***, Guilhem Roux**Olivier Asserin*, René Billardon***

Club Cast3M 2010

-Thick forged components assembled by multipass GTAWelding

- Martensitic steel X10CrMoVNb9-1a possible candidate forVery High Temperature Reactors

- Numerical simulation of welding process

Industrial background and motivations

Numerical simulation of multi-pass GTAWelding

Initial state after welding(microstructure, residual stresses,…)

MUSICA test case2

Pseudo-binary equilibrium diagram

Fe-Cr à 0.1% wt C [Easterling, 1992]

During heating (1st pass)Base material (tempered martensite) → Austenite → δ Ferrite → Liquid

During coolingLiquid → δ Ferrite → Austenite → Quenched martensite

During subsequent heating (2nd and following passes) Quenched martensite → Tempered martensite → Austenite → …

Continuous Cooling diagram

"T91" [Duthilleul, 2003]

X10CrMoVNb9-1 steel - Phase changes

[Roux 2007]

[Roux 2006]

[Hanna 2009]

[Hanna 2010]3

Martensite tempering

Tempered @ 500°C for 6 min.

Tempered @ 500°C for 1h

Tempered @ 750°C for 5h30

Martensite tempering → Carbides precipitation

Heat treatments

4

Measurement of carbides precipitation

S

specimenS

ref

V (chemical composition)

T

Indirect measurement of carbides precipitation

through the percentage of free carbon in the matrix

by Thermo-Electric Power measurements (Seebeck effect)

Cold junctionHot junctionSpecimen

5

Precipitation evolution Tempering evolutionTEPQ = 10.78

TEPAR = 11.49

TEPQ = 10.78

TEPAR = 11.49

QT

AR Q

TEP TEPx

TEP TEP

Definition of the “tempering factor”

Measurement of carbides precipitation

TEP measurements after different tempering heat treatments (TT , tT )

6

Fick law

Conservation law

Isothermal case

Temperature dependence of the diffusion coefficient and generalisation

Proposed evolution law for tempering factor xT

1D CJ D grad C J D

x

��

1DC C Jdiv J

t t x

��

x Dt

1

10 0

1exp exp

nnH H

x D t x D xR T n R T

10

1exp 1n

T T T TTh

Hx D x x H T T

n R T

Modelling of martensite tempering

r+h

7

10

1exp 1 ( )n

T T T TTh

Hx D x x H T T

n R T

130 2.410

278.2KJ/mol

3.61

D

H

n

Identification of tempering model

•coherent with Cr bulk diffusion and carbides growth-coalescence•not applicable to tempering at T < 475°C (with long holding times)

(secondary ageing, embrittlement) 8

Hardness vs. tempering factor

0

0

1exp

185 513 0.374

TTM Q Q AR

AR Q

xHV HV HV HV

x

HV HV x

9

Modelling the thermo-metallurgical-mechanical behaviour

Thermal

Metallurgical Mechanical

Standard anisothermal mechanical behaviour for each phase

Multiphasic behavior

MODELMODEL

(Phase changes enthalpies)

Phase changes

UMAT formalism integration

explicit integration

Lois Castem

CHAB_NOR_R

CHAB_NOR_X

CHAB_SINH_R

CHAB_SINH_X

10

Modelling the multiphasic behaviour

Two scale mixing mechanical law:

•Reuss approach

•Voigt approach[Goth 2002]

11 1)2()2(

1)1()1(

CxCx

)1(11 )2(1111 11

11

)1(11

)2(11 )2()2()1()1( CxCx

11

•Hill & Berveiller-Zaoui type approach [Cailletaud, 87] [Pilvin, 90]

Intergranular accommodation variables

[Robert 2007] for welding

11

1212

Modelling the multiphasic behaviour

•Hill & Berveiller-Zaoui type approach [Cailletaud, 87] [Pilvin, 90]

Intergranular accommodation variables

[Robert 2007] for welding

TRIP (Transformation Induced Plasticity):

[Hamata 1992]

[Coret 2001]

[Roux 2007]

12

Mechanical behaviour of each phase

Anisotropic elastoviscoplastic mechanical behaviour

Norton Law

Isotropic hardening

Linear and non-linear Kinematic hardening

avec

avec

Tempering martensite (reception state)

essais de viscosité en phase martensitique revenue

-800

-600

-400

-200

0

200

400

600

800

-0.05 -0.04 -0.03 -0.02 -0.01 0 0.01 0.02 0.03 0.04 0.05

dL/Lo

F/S

o (

MP

a)

T=20°C

T=400°C

T=500°C

T=700°C

T=900°C

T=1000°C

essais de viscosité en phase martensitique revenue

0

100

200

300

400

500

600

700

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08

dL/Lo

F/S

o (

MP

a)

T=20°C

T=400°C

T=500°C

T=700°C

T=900°C

T=1000°C

13

Quenched martensiteessais de viscosité en phase martensitique trempée

0

200

400

600

800

1000

1200

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08

dL/Lo

F/S

o (

MP

a)

T=20°C

T=200°C

T=300°C

T=400°C

essais de viscosité en phase martensitique trempée

-1500

-1000

-500

0

500

1000

1500

-0.05 -0.04 -0.03 -0.02 -0.01 0 0.01 0.02 0.03 0.04 0.05

dL/Lo

F/S

o (

MP

a)

T=20°C

T=200°C

T=300°C

T=400°C

Tempering occurs for T> 400°C Austenite

essais de viscosité en phase austénitique

0

50

100

150

200

250

300

350

400

450

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08

dL/Lo

F/S

(M

Pa

)

T=200°C

T=300°C

T=400°C

T=500°C

T=600°C

T=700°C

T=800°C

T=900°C

T=1000°C

essais de viscosité en phase austénitique

0

5

10

15

20

25

30

35

40

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08

dL/Lo

F/S

o (

MP

a)

T=1000°C

T=1100°C

T=1200°C

T=1300°C

T=1500°C

No kinematic hardening

Mechanical behaviour of each phase

14

Mixing tempered and quenched martensites

Experimental procedure

Model for quenched+

tempered martensite

experiments at xt=0.6 (500°C)

+

•Tempering has a softening effect on elasticity and isotropic hardening

•No dependance of temperature on mixing evolution

•Linear dependance of mechanical parameters with tempering state ([Inoue 85] approach)

linear evolution for simulations

essai à 300°C

0

200

400

600

800

1000

1200

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08

dL/Lo

co

ntr

ain

te (

MP

a)

martensite

martensite revenue

50%-50%

MT=20%-MB=80%

MT=80%-MB=20%

15

essai à 300°C

0

200

400

600

800

1000

1200

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08

dL/Lo

co

ntr

ain

te (

MP

a)

martensite

austénite

50%-50%

MT=20%-AU=80%

MT=80%-AU=20%

βeta model:

essai à 300°C

0

200

400

600

800

1000

1200

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08

dL/Lo

co

ntr

ain

te (

MP

a)

martensite

austénite

50%-50%

MT=20%-AU=80%

MT=80%-AU=20%

Reuss approach:

essai à 300°C

0

200

400

600

800

1000

1200

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08

dL/Lo

co

ntr

ain

te (

MP

a)

martensite

austénite

50%-50%

MT=20%-AU=80%

MT=80%-AU=20%

Voigt approach:

Mixing austenite and quenched martensite

16

17

Simulation of dilatometry tests

Free dilatometry curve:

TRIP experiments:

-0.01

-0.005

0

0.005

0.01

0.015

0 200 400 600 800 1000 1200

0MPa

100MPa

50MPa

25MPa

-25MPa

-50MPa

100MPa

17

1818

Simulation of Satoh experiment

T

-500

-400

-300

-200

-100

0

100

200

300

400

500

600

0 200 400 600 800 1000 1200 1400

temperature (°C)

co

ntr

ain

te (

MP

a)

modele serie

modele en B

modele parallele

experimental cycle n°1

Overestimation of TRIP effect

Coupling between hardening of mother and daughter phases and

TRIP

[Petit-Grotabussiat 2000] for 16MND5 alloy

Very low influence of homogenization rule

No plasticity of quenched martensite phase

18

1919

Simulation of Disk Spot experiment

Test at DEN/DM2S/SEMT/LTA

8mmR=50mm

thermocouplescapteurs de déplacement

torche TIG

Inverse analysis identification of heat source intensity and spatial

distribution [Roux 2006]

Experimental set-up : [Cavallo 1998] [Cano 1999]

19


δ -ferrite

Prediction of final metallurgical state:

Residual stresses on upper surface (X ray diffraction measurements):

-350

-250

-150

-50

50

150

250

350

450

5 10 15 20 25 30 35 40 45 50

Distance from disk center (mm)

Rad

ial r

esid

ual s

tres

ses

(MP

a)

experimental RX residual stresses

simulated residual stresses for Betamodel

simulated residual stresses for Reussapproach

simulated residual stresses for Voigtapproach

-250

-150

-50

50

150

250

350

450

5 10 15 20 25 30 35 40 45 50


Tan

gen

tial

res

idu

al s

tres

ses

(MP

a) Experimental residual stresses for

Beta modelsimulated residual stresses for Betamodelsimulated residual stresses for Reussapproachsimulated residual stresses forVoigtapproach

Radial shift (bad HAZ prediction?) 20


Residual stresses on upper surface (X ray diffraction measurements):

-300

-200

-100

0

100

200

300

400

500

0 5 10 15 20 25 30 35 40 45 50


Rad

ial

resi

du

al s

tres

ses

(MP

a)

Experimental residual stesses

simulated residual stresses forBeta modelsimulated residual stresses forReuss approachsimulated residual stresses forVoigt approach

-300

-200

-100

0

100

200

300

400

500

0 5 10 15 20 25 30 35 40 45 50


Tan

gen

tial

res

idu

al s

tres

ses

(MP

a) Experimental residual stresses

simulated residual stresses forBeta modelsimulated residual stresses forReuss approachsimulated residual stresses forVoigt model

Again overestimation of TRIP effect

Similar stress distribution with Beta model and Voigt Approach

21


Residual stresses on half thickness (Neutron diffraction measurements):

-200

-100

0

100

200

300

400

500

600

5 10 15 20 25 30 35 40 45 50


Rad

ial

resi

du

al s

tres

ses

(MP

a)

Experimental residual stresses

simulated residual stresses forBeta model

simulated residual stresses forReuss approach

simulated residual stresses forVoigt approach

-300

-200

-100

0

100

200

300

400

500

600

700

800

5 10 15 20 25 30 35 40 45 50

Distance from disk center (mm)T

ange

nti

al r

esid

ual

str

esse

s (M

Pa)





-200

-100

0

100

200

300

400

5 10 15 20 25 30 35 40 45 50


Nor

mal

res

idu

al s

tres

ses

(MP

a)





22

2323

Multipass MUSICA experiment

Experimental set-up at DEN/DM2S/SEMT/LTA

TC1

TC2

TC3

Temperature measurements

TIG multipass welding

Inverse identification of heat source for each pass [Hanna 2006]

23

-2.5

-2

-1.5

-1

-0.5

0

0.5

1

0 1000 2000 3000 4000 5000 6000 7000 8000 9000

time (s)

vert

ical

dis

pla

cem

ent

(mm

)

w ith tempering

w ithout tempering


Prediction of final metallurgical state:

With temperingWithout tempering

Strong tempering effect of previous passes

Vertical distorsion

Quenched martensite

24


Residual stresses:

Sxx

Syy

Szz

With tempering Without tempering

25

•Differential model has been developed to model phase change

During cooling : - martensite transformation

During heating : - austenitization of quenched and tempered martensites

- tempering of martensite

•This thermometallurgical model allows for the prediction of hardness profiles through welds by simple post-processing of heat transfer analyses

•This thermometallurgical model has been coupled to elasto-viscoplastic constitutive equations identified for each metallurgical phase

•A simple homogenization approach has been used associated to martensitic transformation

•This model could be applied for bainitic transformation (case of the 16MnD5 steel)

•This thermometallurgical mechanical model has been implemented in Cast3M and validated in terms of residual stresses prediction for welding experiments

26

Conclusion & perspectives

Not presented here

26

* cea, den, dm2s, semt, lta, 91191 gif sur yvette, france. ** cea, drt, liten, dtbh, lcta, 38054...

Documents

mechanical law

steel phase changes

evolution law

r chab

x chab

tep ar

welding microstructure

multipass gtawelding