United States Nuclear Regulatory Commission - Protecting People and the Environment

Effects of Thermal Aging on Fracture Toughness and Charpy-Impact Strength of Stainless Steel Pipe Welds (NUREG/CR-6428, ANL-95/47)

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Publication Information

Manuscript Completed: November 1995
Date Published:
May 1996

Prepared by:
D.J. Gavenda, W.F. Michaud, T.M. Galvin, W.F. Burke, and O.K. Chopra

Energy Technology Division
Argonne National Laboratory
9700 South Cass Avenue
Argonne, Illinois 60439

M.E. Mayfield, NRC Project Manager

Prepared for:
Division of Engineering
Office of Nuclear Regulatory Research
U.S. Nuclear Regulatory Commission
Washington, DC 20555-0001

NRC FIN A-2212

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Abstract

The degradation of fracture toughness, tensile, and Charpy-impact properties of Type 308 stainless steel (SS) pipe welds due to thermal aging has been characterized at room temperature and 290°C. Thermal aging of SS welds results in moderate decreases in Charpy-impact strength and fracture toughness. For the various welds in this study, upper-shelf energy decreased by 50–80 J/cm2. The decrease in fracture toughness J-R curve or JIC is relatively small. Thermal aging had little or no effect on the tensile strength of the welds. Fracture properties of SS welds are controlled by the distribution and morphology of second-phase particles. Failure occurs by the formation and growth of microvoids near hard inclusions; such processes are relatively insensitive to thermal aging. The ferrite phase has little or no effect on the fracture properties of the welds. Differences in fracture resistance of the welds arise from differences in the density and size of inclusions. Mechanical-property data from the present study are consistent with results from other investigations. The existing data have been used to establish minimum expected fracture properties for SS welds.

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