The Study on Effects of Thermal Aging of Dissimilar Weld Zone in a Primary Reactor Cooling System

Abstract:

In a primary reactor cooling system(RCS), a dissimilar weld zone exists between austenitic-ferritic duplex cast stainless steel(CF8M) in a pipe and low-alloy steel(SA508 cl.3) in a nozzle. Thermal aging is observed in CF8M as the RCS is exposed for a long period of time to a reactor operating temperature between 290 and 330°C, while no effect is observed in SA508 cl.3. An investigation of the effect of thermal aging on the various mechanical properties of the dissimilar weld zone is required. The purpose of the present investigation is to find the effect of thermal aging on the dissimilar weld zone. The specimens are prepared by an artificially accelerated aging technique maintained for 100, 300, 900, 1800 and 3600 hrs at 430°C, respectively. The various mechanical tests for the dissimilar weld zone are performed for virgin and aged specimens.

• Periodical: Key Engineering Materials (Volumes 261-263)
• Pages: 1689-0
• DOI: https://doi.org/10.4028/www.scientific.net/KEM.261-263.1689
• Online since: April 2004
• Authors: Jae Do Kwon, Seung Wan Woo, Y.H. Choi
• Keywords: Dissimilar Weld, Duplex Stainless Steel, Heat Affected Zone (HAZ), Low Alloy Steel, Mechanical Property, Thermal Aging

References

[4] The welding process is as follows: Filler metal of ER309L is bonded to SA508 cl.3, using the gas-tungsten arc welding(GTAW) process, as buttering. Then, the buttered SA508 cl.3 and CF8M are boned with a filler metal of ER308L, using the shielded metal arc welding(SMAW) process. The welding conditions for dissimilar materials are shown in Table 1. Post-welding heat treatment(PWHT) is maintained for 6.5 hrs at 614 � in order to remove any residual stress. Radiographic examinations are performed on the defects of the welded materials. The chemical compositions of CF8M, SA508 cl.3, ER308L and ER309L are shown in Table 2. The specimens are prepared using an artificially accelerated aging method in the laboratory, in order to investigate the degradation effects of CF8M on the strength of the material

DOI: 10.5772/28994

[5] The artificially accelerated aging method has an advantage in that the material can be degraded in a short period of time. The aging temperature is 430 � . The thermal embrittlement varies linearly between the aging temperatures of 300 and 400 �