TY - JOUR
T1 - Examining stress relaxation in a dissimilar metal weld subjected to post weld heat treatment
AU - Abburi Venkata, K.
AU - Khayatzadeh, S.
AU - Achouri, A.
AU - Araujo De Oliveira, J.
AU - Forsey, A. N.
AU - Gungor, S.
AU - Bouchard, P. J.
AU - Truman, C. E.
PY - 2018/7
Y1 - 2018/7
N2 - Dissimilar metal welds are often required in nuclear power plants to join components made from austenitic steels to those from ferritic steels, particularly in fast breeder reactor plants, in order to join the intermediate heat exchanger to the steam generator. The process of welding alters the microstructure of the base materials and causes residual stresses to form, both because of the change in the microstructure and the differing thermal histories in various regions. Postweld heat treatment (PWHT) is required to relieve the residual stresses and achieve preferable microstructural gradients across the weld joint. Therefore, in order to arrive at the optimal PWHT process, it is necessary to investigate the effects of heat treatment on the joint integrity, microstructure, and residual stress relaxation in the welds. To investigate the effect of PWHT on the residual stress relaxation and corresponding alteration of microstructure across a welded joint, a dissimilar weld between modified 9Cr-1Mo steel and austenitic stainless steel AISI 316LN was made using autogenous electron beam welding. To achieve this, the welding process was first modeled numerically using finite element analysis, and the residual stress predictions were validated by experimental investigation using neutron diffraction. The validated model was then used to study the residual stress relaxation through the simulation of PWHT. The predicted stress relaxation was compared with contour method measurement of residual stresses in the actual welded plate subjected to PWHT. The results indicate that, although somerelaxation of residual stresses occurred during PWHT, there is still a significant portion of highly localized residual stresses left in the specimen.
AB - Dissimilar metal welds are often required in nuclear power plants to join components made from austenitic steels to those from ferritic steels, particularly in fast breeder reactor plants, in order to join the intermediate heat exchanger to the steam generator. The process of welding alters the microstructure of the base materials and causes residual stresses to form, both because of the change in the microstructure and the differing thermal histories in various regions. Postweld heat treatment (PWHT) is required to relieve the residual stresses and achieve preferable microstructural gradients across the weld joint. Therefore, in order to arrive at the optimal PWHT process, it is necessary to investigate the effects of heat treatment on the joint integrity, microstructure, and residual stress relaxation in the welds. To investigate the effect of PWHT on the residual stress relaxation and corresponding alteration of microstructure across a welded joint, a dissimilar weld between modified 9Cr-1Mo steel and austenitic stainless steel AISI 316LN was made using autogenous electron beam welding. To achieve this, the welding process was first modeled numerically using finite element analysis, and the residual stress predictions were validated by experimental investigation using neutron diffraction. The validated model was then used to study the residual stress relaxation through the simulation of PWHT. The predicted stress relaxation was compared with contour method measurement of residual stresses in the actual welded plate subjected to PWHT. The results indicate that, although somerelaxation of residual stresses occurred during PWHT, there is still a significant portion of highly localized residual stresses left in the specimen.
KW - Contour method
KW - Finite element analysis
KW - Postweld heat treatment
KW - Residual stress
KW - Stress relaxation
UR - http://www.scopus.com/inward/record.url?scp=85050794421&partnerID=8YFLogxK
U2 - 10.1520/MPC20180018
DO - 10.1520/MPC20180018
M3 - Article (Academic Journal)
AN - SCOPUS:85050794421
SN - 2379-1365
VL - 7
JO - Materials Performance and Characterization
JF - Materials Performance and Characterization
IS - 4
M1 - MPC20180018
ER -