Sabine DENIS Institut Jean Lamour, UMR 7198 CNRS ... Heat Treatment Processes! Institut Jean Lamour,

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Transcript of Sabine DENIS Institut Jean Lamour, UMR 7198 CNRS ... Heat Treatment Processes! Institut Jean Lamour,

Heat Treatment Processes

Institut Jean Lamour, UMR 7198 CNRS - Universit de Lorraine

Parc de Saurupt, 54011 Nancy Cedex France

Sabine DENIS

ANF Mtallurgie fondamentale 22-25 oct 2012, Aussois

SOLIDIFICATION

FORMING

HEAT TREATMENT

WELDING CUTTING ...

LIQUID METAL PROCESSING

Microstructures Mechanical properties

Problem of heat treatment of metallic alloys

Etude Sogerail, Irsid, LSG2M, Cemef

Study Sogerail, Irsid, LSG2M, Cemef

Heat treatment of metallic alloys

Control of microstructures

desired mechanical properties

Control of thermal gradients

avoid/limit deformations

avoid/limit residual stresses (quenching)

or obtain desired residual stress distributions

(surface heat treatments, thermochemical treatments)

Better optimization = modelling and numerical simulation

Development of internal stresses during cooling

qualitative approach (Rose et Bhler 1968)

Origin of internal stresses :

Heterogeneous deformations

- thermal

- phase transformations

Origin of residual stresses and deformations :

Heterogeneous deformations - plastic

- phase transformations

Example of experimental residual stress profiles Water quenching of a 60NiCrMo11 steel cylinder (diameter 40mm, length 120mm)

Sachs method X ray diffraction

1 r/R

RX

Sachs

PhD Josserand 1980

Fluid thermal metallurgical mechanical couplings in heat treatment

FLUID FLOW material

Process heating, cooling

1972prediction of thermal stresses (Al alloys, Ti alloys) 1980 main advances including phase transformations in steels 2000 precipitation Al alloys - consideration of fluid flow (gaz quenching)

DEFORMATION X

Fluid thermal metallurgical mechanical couplings in heat treatment

FLUID FLOW material

Process : heating, cooling

Overview of necessary experimental knowledge, present models,

some open questions and example of results in steels

DEFORMATION

Modelling of phase transformation kinetics

(for the purpose of predicting internal stresses and deformations)

Global models (JMAK): (1980 -1995)

- Modelling anisothermal kinetics from CCT diagrams

- Modelling kinetics from IT diagrams (additivity principle)

PHASE RC : prediction of kinetics during heating and cooling in steels from isothermal kinetics (additivity principle) HEATING IT diagram austenitization kinetics carbon content of austenite and grain size

yk = ymaxk (1 - exp (- bk tnk))

COOLING : IT diagram

austenite proeutectod constituent pearlite, bainite . incubation period : Scheils method S =finc ti /i

i = f(T, grain size, comp., stress) . progress n, b = f (T, grain size, comp., stress)

austnite martensite : ym = y [1 exp (- (Ms T))]

Ms = f (grain size, comp., stress) Hardness: HV = i,k dykHVk HVk= f(Tformation, comp.)

PhD Fernandes, Farias, Mey

Example : Gaz quenching of carburized cylinders

Cylinders diameter 16mm length 48mm

steel 27MnCr5

Austenitization 930C 40min

Gaz quenching (nitrogen 4 bars)

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8distance sous la surface (mm)

taux

de

carb

one

(%)

0

200

400

600

800

1000

0 100 200 300 400 500 600 700

surfacecentre

tem

pra

ture

(C

)

temps (s)

Temperature evolutions (median plane)

Radial carbon profile

Dissertation C. Aubry 1998

0

20

40

60

80

100

3 102

4 102

5 102

6 102

7 102

8 102

9 102

0 0,2 0,4 0,6 0,8 1

austniteferritebainitemartensitetaux norm d'autorevenu

duret

frac

tion

volu

miq

ue (%

)

duret (HV

)

distance sous la surface (mm)

0 100 200 300 400 500

austniteferritebainitemartensitetaux norm d'autorevenu

0

20

40

60

80

100

temps (s)

frac

tion

volu

miq

ue (

%)

0

20

40

60

80

100

0 100 200 300 400 500 600

austnitemartensitetaux norm d'autorevenu

frac

tion

volu

miq

ue (

%)

temps (s)

Final microstructure and

hardness distributions

Kinetics of transformation

surface

centre

14

0 1 2 3 4 5 60

0.2

0.4

0.6

0.8

1

Austnite.Perlite.Ferrite.Martensite.

Temps (s).

Frac

tion

volu

miq

ue.

80

200

400

600

800

1000

1200

0 1 2 3 4 5 6 7

0.0.5651.0651.542

Tem

pra

ture

(C

).

Temps (s).

Profondeur (mm):

Traitement Pt=960W. V=4.5mm/s.

FRAC

TION

VOL

UMIQ

UEPROFONDEUR (mm).

0

0.2

0.4

0.6

0.8

1

0 0.5 1 1.5

1

Austnite rsiduelle.

Martensite homogne.

Mart. riche en carbone. Mart. pauvre en

carbone.

Ferrite.

Perlite.

2345

Pt=960W. V=4.5mm/s

Dissertation Boufoussi 1993

Ex. Prediction of microstructures during laser hardening of steels Plate moving under laser beam steel C42 Source laser Pt.

Zone affecteDplacement de la pice. V.

Gaz de protection

OptiqueDistributionnergtique

15

Dure

t.

Profondeur (mm).

0

200

400

600

800

1000

0 0.5 1 1.5

Calcul.Exp. Hv 0.3

0

200

400

600

800

1000

0 1 2 3 4 5

CalculExp. Hv 0.3.

Dure

t.

Largeur (mm).

Hardness and microstructure distributions comparison calculation-experiment

width HAZ : exp. 8,4mm calculation 8,5mm

depth HAZ: exp. 0,85mm calculation 1,06mm

Modelling of phase transformation kinetics

(for the purpose of predicting internal stresses and deformations)

Global models (JMAK): most commonly used for steels

- Modelling anisothermal kinetics from CCT diagrams

- Modelling kinetics from IT diagrams (additivity principle)

can predict volume fractions of the phases for complex situations

limitations : no morphological parameters of the microstructures

difficult to take into account prior plastic deformation effects

Nucleation, growth, coarsening models

- precipitation in Al alloys D. Godard 1999

- tempering of martensite in steels Y. Wang 2006

volume fractions of the precipitates, size distributions matrix chemical composition

Multicomponent alloys - concommittant precipitations - thermodynamic equilibrium : . solubility product (stochiometric compositions) or coupling with THERMOCALC - nucleation rate homogeneous/heterogeneous nucleation, take account of elastic strain energy - growth (dissolution) coarsening rates diffusion controlled local equilibrium at interfaces Gibbs Thomson effect and effect of elastic strain energy

Results volume fractions of the precipitates size distributions matrix chemical composition

Modelling of phase transformation kinetics : nucleation, growth, coarsening

during the treatments isothermal and anisothermal

0

0,2

0,4

0,6

0,8

1

0 100 200 300 400 500 600 700

carbure !, cal.cmentite cal.

carbure !, exp.cmentite, exp.

Temprature (C)

0

0,05

0,1

0,15

0

100

200

300

400

500

600

0 20 40 60 80 100

Carbure !Cmentite

Temprature

Temps (s)

0

0,005

0,01

0,015

0,02

0,025

0,03

0,035

0,04

1 10 100 1000 104 105

C, Cal.Cr, Cal.Mn,Cal.Cr, Exp.Mn,Exp.

Composition (atomique)

Temps (s)

0

2 10-9

4 10-9

6 10-9

8 10-9

1 10-8

0

100

200

300

400

500

600

0 20 40 60 80 100

Rayon critique, Cal.Rayon moyen Cal.

Temprature

Temps (s) 0

2 10-8

4 10-8

6 10-8

8 10-8

1 10-7

1 10 100 1000 104 105

Rayon critique, Cal.Rayon moyen, Cal.Rayon Exp.

Temps (s)

Cementite

carbides (Fe2,4C) coherent, homogeneous nucleation, cementite (Fe,M)3C) incoherent, heterogeneous nucleation (disloc.)

PhD Y. Wang 2006

Modelling of precipitation during tempering of martensite in steels

steel 80MnCr5 heating : 10C/s holding at 500C

100nm

100nm 600C 2h

Fluid thermal metallurgical mechanical couplings in heat treatment

FLUID FLOW material

DEFORMATION

Temprature

Temprature de transformatio