Influence of Strain Hardening and Annealing Effect on the Prediction of Welding Residual Stresses in a Thick-Wall 316 Stainless Steel Butt-Welded Pipe Joint
LI Suo, CHEN Weiqi, HU Long, DENG Dean()
College of Materials Science and Engineering, Chongqing University, Chongqing 400045, China
Cite this article:
LI Suo, CHEN Weiqi, HU Long, DENG Dean. Influence of Strain Hardening and Annealing Effect on the Prediction of Welding Residual Stresses in a Thick-Wall 316 Stainless Steel Butt-Welded Pipe Joint. Acta Metall Sin, 2021, 57(12): 1653-1666.
Stress corrosion cracking (SCC) is a major problem in the welded components of austenitic stainless steel in nuclear power plants. High tensile residual stress is an important factor resulting in the SCC of materials. Austenitic stainless steel has a strong tendency for work hardening owing to its fcc crystal structure and low stacking-fault energy. High plastic strain can accumulate during a multipass welding process. On the other hand, accumulated strain hardening can be reduced or even eliminated during the welding thermal cycles owing to dynamic recovery, recrystallization, and grain growth below the melting point, which is called the annealing effect. Influence of strain hardening and annealing effect needs to be investigated to predict the welding-induced residual stresses accurately in austenitic stainless steel joints. In this study, a new time-temperature-dependent annealing model was proposed based on the Johnson-Mehl-Avrami equation. Numerical Satoh tests were performed to clarify the influence of strain-hardening models (i.e., the isotropic strain-hardening model and Chaboche mixed isotropic-kinematic strain-hardening model) and annealing models (i.e., the single-stage annealing model and new time-temperature-dependent annealing model) on the formation of residual stresses and the accumulated plastic strain during multiple thermal cycles. Thermoelastic-plastic finite element (FE) analyses were carried out to predict the welding residual stresses and accumulated plastic strain in a thick-wall 316 stainless steel butt-welded pipe joint with 85 welding passes. The residual stresses of the welded joint were measured by the sectioning method, inherent strain method, and deep-hole drilling method. The simulations of welding residual stresses were compared with the measurements. Annealing effect significantly influences the formation of accumulated plastic strain and welding residual stresses, neglecting which will result in a significant overestimation of FE results. The proposed annealing model showed an excellent match to the experimental data. With the consideration of the annealing effect, the isotropic strain-hardening model overestimated the welding residual stresses slightly, while the FE results of welding residual stresses using the Chaboche mixed strain-hardening model showed better agreement with the measurements. The single-stage annealing model revealed a recommended annealing temperature of 900-1000°C for austenitic stainless steel such as 316 stainless steel.
Fig.1 Schematic of the multipass butt-welded pipe joint and the locations of thermocouple (TC1, TC2, and TC3) (unit: mm)
Fig.2 Schematic of welding start/end location and welding direction of the welded joint
Fig.3 Schematic of the locations for residual stress measurements in the welded joint
Fig.4 Schematics of the initial and subsequent yield surfaces in the isotropic strain hardening model (a) and the Chaboche mixed isotropic-kinematic strain-hardening model (b) (σ1, σ2, and σ3 are principal stresses; α—back stress)
T / oC
Isotropic hardening model
Chaboche mixed isotropic-kinematic hardening model
σ0 / MPa
K / MPa
m
Qinf / MPa
β
C1 / MPa
C2 / MPa
γ1
γ2
20
125.6
519.2
0.24
153.4
6.9
156435
6134
1410.85
47.19
275
97.6
475.5
0.28
154.7
6.9
100631
5568
1410.85
47.19
550
90.9
444.9
0.32
150.6
6.9
64341
6227
1410.85
47.19
750
71.4
259.4
0.26
57.9
6.9
56232
4108
1410.85
47.19
900
66.2
47.0
0.06
0
6.9
0.05
292
1410.85
47.19
1000
31.8
0
0
0
6.9
0
0
1410.85
47.19
1100
19.7
0
0
0
6.9
0
0
1410.85
47.19
1400
2.1
0
0
0
6.9
0
0
1410.85
47.19
Table 1 Parameters in the isotropic strain-hardening model and the Chaboche mixed isotropic-kinematic strain-hardening model for 316LN stainless steel[9]
Fig.5 Comparisons of the predicted cyclic stress-strain curves with the experimental data[23] for 316LN stainless steel at room temperature
T / oC
fA
b
n
600
0.10
0.05
0.59
680
0.20
0.19
0.50
750
0.30
0.54
0.34
825
0.40
0.79
0.26
900
0.84
0.32
0.33
1000
1.00
0.68
0.37
Table 2 Material parameters in the new time-temperature-dependent annealing model for 304L stainless steel
Fig.6 Flowchart of the UHARD subroutine of the new time-temperature-dependent annealing model (t—time, ΔH—increment of the von Mises equivalent plastic strain, —accumulated plastic strain, H'—accumlated hardening term, f—annealing factor, TA—annealing temperature, σs—yield stress, the prefix Δ represents the increment of variables at the current time step, the subscripts t and t + Δt represent variables at the previous and current time steps, respectively)
Fig.7 Comparisons of the annealing factors of the new annealing model (lines) with experimental data (symbols)[4] at different annealing time and temperatures for 304L stainless steel
Fig.8 Finite element (FE) mesh and the number of welding passes of the 316 stainless steel butt-welded pipe joint (Numbers show the welding passes)
Case
Strain hardening model
Annealing model
A
Isotropic
Neglected
B
Isotropic
Single-stage model with TA = 1000℃
C
Isotropic
New time-temperature-dependent model
D
Chaboche mixed isotropic-kinematic
Neglected
E
Chaboche mixed isotropic-kinematic
Single-stage model with TA = 1000℃
Table 3 Simulation cases of the Satoh test and the welded joint
Fig.9 Comparisons of the simulated results and the measurements[28] of axial stresses in the Satoh test
Fig.10 Evolutions of the simulated accumulated plastic strain during the first (a) and second (b) thermal cycles in the numerical Satoh test
Fig.11 Comparisons of simulated results and measurements[16] of welding thermal cycles for the final welding pass of the 316 stainless steel butt-welded pipe joint
Fig.12 Distributions of hoop residual stresses in the 316 stainless steel butt-welded pipe joint
Fig.13 Distributions of axial residual stresses in the 316 stainless steel butt-welded pipe joint
Fig.14 Comparisons of simulated results and measurements[16] of hoop (a) and axial (b) residual stresses at the outside surface of the 316 stainless steel butt-welded pipe joint (Insets show the locations of the outside surface; SM—sectioning method)
Fig.15 Comparisons of simulated results and measurements[16] of hoop (a) and axial (b) residual stresses at the inside surface of the 316 stainless steel butt-welded pipe joint (Insets show the locations of the inside surface)
Fig.16 Comparisons of simulated results and measurements[16,17] of hoop (a) and axial (b) residual stresses along the weld centerline (WCL) of the 316 stainless steel butt-welded pipe joint (Insets show the locations of the WCL; IS—inherent strain method, DHD—deep-hole drilling)
Fig.17 Comparisons of simulated results of the accumulated plastic strain along the WCL of the 316 stainless steel butt-welded pipe joint (Inset shows the location of the WCL)
Fig.18 Evolutions of the simulated accumulated plastic strain and the hoop stress at point P during the final welding thermal cycle (Insets show the locations of point P)
Case
Hoop residual stress / MPa
Axial residual stress / MPa
FE-SM
FE-IS
FE-DHD
FE-SM
FE-IS
FE-DHD
A
79
28
58
94
-23
-85
B
19
-6
26
43
-18
-83
C
13
-11
18
39
-15
-83
D
30
-35
-22
37
-6
-84
E
-15
-72
-56
4
-3
-83
Table 4 Average differences between FE results and measurements[16,17] of welding residual stresses in the 316 stainless steel butt-welded pipe joint
1
Ming H L, Zhang Z M, Wang J Q, et al. Microstructure and local properties of a domestic safe-end dissimilar metal weld joint by using hot-wire GTAW [J]. Acta Metall. Sin., 2017, 53: 57
Kansai Electric Power Company. Results of the investigation on the welded joint in the pressurizer spray line piping of the unit 3 of the Oi nuclear power plant (Data set) [R]. Tokyo: Nuclear Regulation Authority, 2020
Mankins W L. Recovery, recrystallization, and grain-growth structures [A]. ASM Handbook, Vol.9: Metallography and Microstructures [M]. Ohio: ASM International, 2004: 207
4
Qiao D X. Strain hardening recovery and its influence on welding residual stresses in reactor safe-end in power plants [D]. Beijing: Tsinghua University, 2013
乔东虓. 核电安全端焊接中应变硬化回复及其对残余应力的影响 [D]. 北京: 清华大学, 2013
5
Deng D A, Kiyoshima S. Influence of annealing temperature on calculation accuracy of welding residual stress in a SUS304 stainless steel joint [J]. Acta Metall. Sin., 2014, 50: 626
邓德安, Kiyoshima S. 退火温度对SUS304不锈钢焊接残余应力计算精度的影响 [J]. 金属学报, 2014, 50: 626
6
Zang W L, Gunnars J, Dong P S, et al. Improvement and validation of weld residual stress modelling procedure [R]. Stockholm: Swedish Radiation Safety Authority, 2009
7
Xu J J, Gilles P, Duan Y G, et al. Temperature and residual stress simulations of the NeT single-bead-on-plate specimen using SYSWELD [J]. Int. J. Press. Vessels Pip., 2012, 99-100: 51
8
Xu J J. Effect of material hardening model on welding residual stresses of 316L stainless steel [J]. Trans. China Weld. Inst., 2014, 35(3): 97
Muránsky O, Hamelin C J, Smith M C, et al. The effect of plasticity theory on predicted residual stress fields in numerical weld analyses [J]. Comput. Mater. Sci., 2012, 54: 125
10
Muránsky O, Hamelin C J, Patel V I, et al. The influence of constitutive material models on accumulated plastic strain in finite element weld analyses [J]. Int. J. Solids Struct., 2015, 69-70: 518
11
Deng D A, Zhang C H, Pu X W, et al. Influence of material model on prediction accuracy of welding residual stress in an austenitic stainless steel multi-pass butt-welded joint [J]. J. Mater. Eng. Perform., 2017, 26: 1494
12
Wang Q, Liu X S, Wang P, et al. Numerical simulation of residual stress in 10Ni5CrMoV steel weldments [J]. J. Mater. Process. Technol., 2017, 240: 77
13
Geng L Y, Tu S D, Gong J M, et al. Simulation of residual stress in butt girth welding of ultra-thick 13MnNiMoR steel cylinder by different material hardening models [J]. Mater. Mech. Eng., 2019, 43(3): 60
Yu X H, Qiao D X, Feng Z L, et al. High temperature dynamics strain hardening behavior in stainless steels and nickel alloys [A]. Proceedings of the ASME 2014 Pressure Vessels and Piping Conference [C]. Anaheim, CA, USA: ASME, 2014: V06BT06A072
15
Yu X H, Crooker P, Wang Y L, et al. High-temperature deformation constitutive law for dissimilar weld residual stress modeling: Effect of thermal load on strain hardening [A]. Proceedings of the ASME 2015 Pressure Vessels and Piping Conference [C]. Boston, MA, USA: ASME, 2015: V06BT06A073
16
Japan Nuclear Energy Safety Organization. Annual report on the integrity assessment of flawed components with structural discontinuity [R]. Tokyo: Japan Nuclear Energy Safety Organization, 2005
Hojo K, Ogawa K, Ogawa N, et al. Sensitivity analysis of residual stress simulation of dissimilar metal joint of safe end nozzle and key issues for standard procedure to maintenance rules [A]. Proceedings of the ASME 2010 Pressure Vessels and Piping Division/K-PVP Conference [C]. Bellevue, WA, USA: ASME, 2010: 929
18
Ruud C O. Residual stress measurements [A]. ASM Handbook, Vol.8: Mechanical Testing and Evaluation [M]. Ohio: ASM International, 2000: 886
19
Ma N S, Nakacho K, Ohta T, et al. Inherent strain method for residual stress measurement and welding distortion prediction [A]. Proceedings of the ASME 2016 35th International Conference on Ocean, Offshore and Arctic Engineering [C]. Busan, South Korea: ASME, 2016: V009T13A001
20
Ogawa K, Chidwick L O, Kingston E J, et al. Measurement of residual stresses in the dissimilar metal weld joint of a safe-end nozzle component [A]. Proceedings of the ASME 2009 Pressure Vessels and Piping Conference [C]. Prague, Czech Republic: ASME, 2009: 529
21
Dai P Y, Hu X, Lu S J, et al. Influence of size factor on calculation accuracy of welding residual stress of stainless steel pipe by 2D axisymmetric model [J]. Acta Metall. Sin., 2019, 55: 1058
Lu S J, Wang H, Dai P Y, et al. Effect of creep on prediction accuracy and calculating efficiency of residual stress in post weld heat treatment [J]. Acta Metall. Sin., 2019, 55: 1581
Depradeux L, Coquard R. Influence of viscoplasticity, hardening, and annealing effects during the welding of a three-pass slot weld (NET-TG4 round robin) [J]. Int. J. Press. Vessels Pip., 2018, 164: 39
24
Ludwik P. Elements der Technologischen Mechanik [M]. Berlin, Heidelberg: Springer-Verlag, 1909: 32
25
Chaboche J L. A review of some plasticity and viscoplasticity constitutive theories [J]. Int. J. Plast., 2008, 24: 1642
26
Leblond J B, Mottet G, Devaux J, et al. Mathematical models of anisothermal phase transformations in steels, and predicted plastic behaviour [J]. Mater. Sci. Technol., 1985, 1: 815
27
Satoh K. Transient thermal stresses of weld heat-affected zone by both-ends-fixed bar analogy [J]. Trans. Jpn. Weld. Soc., 1972, 3: 125
28
Depradeux L. Simulation numérique du soudage-acier 316L-validation sur cas tests de complexité croissante [D]. Lyon, France: INSA de Lyon, 2004
29
Deng D A, Zhang Y B, Li S, et al. Influence of solid-state phase transformation on residual stress in P92 steel welded joint [J]. Acta Metall. Sin., 2016, 52: 394
Deng D A, Ren S D, Li S, et al. Influence of multi-thermal cycle and constraint condition on residual stress in P92 steel weldment [J]. Acta Metall. Sin., 2017, 53: 1532
