Effect of prior machining deformation on the development of tensile residual stresses in weld-fabricated nuclear components |
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Authors: | PS Prevey PW Mason DJ Hornbach JP Molkenthin |
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Affiliation: | (1) Lambda Research, 45227 Cincinnati, OH, USA;(2) ABB-Combustion En- gineering, 06095 Windsor, CT, USA |
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Abstract: | Austenitic alloy weldments in nuclear systems may be subject to stress- corrosion cracking (SCC) failure if the sum of residual
and applied stresses exceeds a critical threshold. Residual stresses developed by prior machining and welding may either accelerate
or retard SCC, depending on their magnitude and sign. A combined x- ray diffraction and mechanical procedure was used to determine
the axial and hoop residual stress and yield strength distributions into the inside- diameter surface of a simulated Alloy
600 penetration J- welded into a reactor pressure vessel. The degree of cold working and the resulting yield strength increase
caused by prior machining and weld shrinkage were calculated from the line- broadening distributions. Tensile residual stresses
on the order of +700 MPa were observed in both the axial and the hoop directions at the inside- diameter surface in a narrow
region adjacent to the weld heat- affected zone. Stresses exceeding the bulk yield strength were found to develop due to the
combined effects of cold working of the surface layers during initial machining and subsequent weld shrinkage. The residual
stress and cold work distributions produced by prior machining were found to influence strongly the final residual stress
state developed after welding. |
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Keywords: | Alloy 600 machining residual stress stress-corrosion cracking welding |
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