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Comparison of two hot cracking tests JWRI and CRW

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HAL Id: hal-02442274

https://hal-cea.archives-ouvertes.fr/hal-02442274

Submitted on 16 Jan 2020

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Comparison of two hot cracking tests JWRI and CRW Y. Gao, O. Asserin, D. Ayrault, O. Fandeur, M. Ronfard-Haret, D. Solas, P.

Pilvin

To cite this version:

Y. Gao, O. Asserin, D. Ayrault, O. Fandeur, M. Ronfard-Haret, et al.. Comparison of two hot cracking tests JWRI and CRW. FEMS Junior Euromat 2016, Jul 2016, Lausanne, Switzerland. �hal-02442274�

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Numerical Simulation JWRI & CRW

Conclusions and further works

Comparison of two hot cracking tests JWRI and CRW

NUCLEAR ENERGY DIRECTORATE

NUCLEAR ACTIVITIES DIRECTORATE OF SACLAY

SYSTEMS AND STRUCTURES MODELING DEPARTMENT

www.cea.fr

• Compare hot cracking tests for different welding processes, TIG and Laser, using 316L(N) stainless steel alloy

• Develop simulation of type CAFE (Cellular Automaton Finite Element) in order to predict granular structures in welds with the help of metallographic observations + EBSD

• Identify the high temperature behavior law with the help of Gleeble simulator tests

• Develop numerical simulations of hot cracking tests to identify a hot cracking thermomechanical criterion

Context

Contact: yuan.gao@cea.fr

Objectives

Solidification hot cracking

may be encountered when

welding 316L(N) using its

filler metals. This material

is used for the reactor

vessel.

Hot cracking is not allowed in

welds according to the rules of

construction and design of

nuclear components

It requires :

• to prevent this risk

• to ensure that the material

exhibits a satisfactory

weldability

• Propose a hot cracking test which realizes the tradeoff between sensitivity and robustness :

sensitivity to differentiate the nuances of the material and to propose a thermomechanical

hot cracking criterion ;

robustness to avoid the operatives uncertainties and get in repeatability conditions.

• Improve the understanding of hot cracking mechanisms and to identify a

thermomechanical hot cracking criterion by means of the numerical simulation of hot

cracking tests.

• Characterize granular structures around the crack areas to couple multiscale approaches

such as CAFE (Cellular Automata Finite Element) for the prediction of the grain structures

with the thermomechanical behavior of the mushy zone.

JWRI test

Restraint test - CRW

Free restraint test - JWRI

JWRI (Joining and Welding Research Institute) test Maintaining of specimen Trapezoidal specimen Gas backside

protection Welding torch

2D simulated temperature field with the hot crack

JWRI test allows :

• to observe a crack arrest • to analyze hot cracking

mechanisms

• to identify a crack arrest criterion

Comparing the simulation results to the experimental data from the literature [1]

[1] N. CONIGLIO, M. PATRY. Science and Technology of Welding and Joining, vol. 18, No 7, p. 573-580, 2013.

Yuan GAO

a,c

, Olivier ASSERIN

a

, Danièle AYRAULT

a

, Olivier FANDEUR

b

, Marc RONFARD-HARET

a

, Denis SOLAS

d

, Philippe PILVIN

c

a

CEA, DEN, DANS, DM2S, SEMT, LTA, 91191 Gif-sur-Yvette, France

b

CEA, DEN, DANS, DM2S, SEMT, LM2S, 91191 Gif-sur-Yvette, France

c

Université de Bretagne-Sud, LIMATB>IRDL, Rue Saint-Maudé, 56321 Lorient, France

d

Université de Paris-Sud, ICMMO, Rue du Doyen Georges Poitou, 91405 Orsay, France

IV generation nuclear reactor SFR (Sodium Fast Reactor)

2D simulated stress field

ZF

x y

Stress along Y at 8s

JUNIOR EUROMAT July 10-14 2016

Hot cracking in welding

CRW (Controlled Restraint Weldability) test [1]

Advantage of CRW test • both initiation and

arresting crack

Numerical simulation of this test

• Understand local mechanisms of hot

cracking and to identify a hot crack initiation

criterion

The preferential growth direction is the

<100> direction that is aligned with the

temperature gradient

Metallographic observations and experimental results

Structure of the welding seam for elliptical bath

(a): epitaxial grains growing near the fusion line

(b): competitive growth between grains in the melting zone

Micrograph of the epitaxial area Base metal Molten zone Undersides

Sample for the analysis of the cracked part

15mm

Sample for the analysis of the non cracked part

15mm

cracking Welding direction Observation direction

EBSD cartographic for test for (a)

Welding direction

Energy balance: ρ𝐶𝑝 𝜕𝑇

𝜕𝑡 = −𝑑𝑖𝑣 −𝑘𝑔𝑟𝑎𝑑𝑇 + 𝑤

ρ : material density

𝐶𝑝 : specific heat capacity 𝑇 : temperature

𝑘 : thermal conductivity 𝑤 : volumic heat sources Material : aluminum alloy 6061 Welding process : laser

Stress along Y with a restraint of 86 MPa at point P3 over time

-150 -100 -50 0 50 100 150 200 250 0 2 4 6 8 10 0 200 400 600 800 1000 C o nt ra int e Y Y T em pé ra tu re ( °C )

Contrainte YY avec un chargement 86MPa sur la point P3 de l'éprouvette en fonction du temps

'smy86pa3.csv' u 1:2 'T86pa3.csv' u 1:2

ZF

Blue curve : temperature at point P3 over time Violet curve: stress along Y at point P3 over time

St ress alo n g Y (MP a) Temp er at u re (° C)

The equivalent source :

𝑤 𝑚, 𝑡 = 𝐴𝑒𝑥𝑝 −3 𝑥𝑓

2 + 𝑦 𝑓2

𝑟2

𝐴 : power dissipated in the Gaussian 𝑟 : radius of flux distribution

1000.00µm

(a) (b)

Top view : (a) 𝑉𝑠 = 150 𝑚𝑚/𝑚𝑖𝑛; (b) 𝑉𝑠 = 80 𝑚𝑚/𝑚𝑖𝑛

𝜺

𝒃

>

𝜺

𝒂

, observation axial grain

Se ns d e s o ud ag e 𝜺𝒂 𝜺𝒃

Mechanical modeling (elastic -plastic constitutive law + thermal expansion) : Hooke’s law: σ𝑖𝑗 = μ ε𝑖𝑗𝑒 + 𝜐 1 − 2𝜐 𝑡𝑟(ε𝑒)δ𝑖𝑗 𝑎𝑛𝑑 μ = (1+υ)𝐸(𝑇) Strain decomposition : ε𝑖𝑗 = ε𝑖𝑗𝑒 + ε𝑖𝑗𝑝 + ε𝑖𝑗𝑡ℎ Plastic flow : ε𝑖𝑗𝑝 = λ 𝜕𝑓(σ𝜕σ 𝑖𝑗) 𝑖𝑗 Thermal expansion : ε𝑖𝑗𝑡ℎ=α(𝑇 − 𝑇0) δ𝑖𝑗

Evolution of the stress along Y between the liquidus temperature and the solidus temperature at different

points of the specimen

-20 -15 -10 -5 0 5 10 15 20 2 3 4 5 6 7 8 9 C o n tra in te YY en tre la T liq et T so l ( M Pa ) Temps (s)

Contrainte YY entre la Tliq et Tsol avec condition soudage A en 86MPa

'smyy1.csv' u 1:2 'smyy2.csv' u 1:2 'smyy3.csv' u 1:2 'smyy4.csv' u 1:2 'smyy5.csv' u 1:2 'smyy6.csv' u 1:2 'smyy7.csv' u 1:2 'smyy8.csv' u 1:2 'smyy9.csv' u 1:2 'smyy10.csv' u 1:2 'smyy11.csv' u 1:2 'smyy12.csv' u 1:2 'smyy13.csv' u 1:2 'smyy14.csv' u 1:2 'smyy15.csv' u 1:2 'smyy16.csv' u 1:2 'smyy17.csv' u 1:2 'smyy18.csv' u 1:2 P1 P2 P6 P8 P9 P10 P11 P12 P13 P174 P15 P16 P17 P18

Stress along Y with a restraint of 86 MPa between Tliq and Tsol

St ress alo n g Y b et w ee n Tliq an d T sol (MP a) Zone fissurée expérimentale [1] P3 P4 P5 P7

2D simulated temperature field

Temperature at 8s

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