Exploratory Investigations of Low Charpy-V Upper Shelf Energy Steels with Irradiation.

摘要

Steel plates and weld deposits exhibiting relatively low Charpy-V C sub v upper-shelf energy levels in the preirradiation condition are present in certain older reactor pressure vessels. Because the postirradiation notch ductility behavior of such materials is not well understood, a series of investigations has been undertaken for representative compositions. Forgings typical of older steel production are also being studied to develop specific trend information. This report describes exploratory investigations with a low upper-shelf A302-B plate, a companion weld heat-affected zone (HAZ), a low upper-shelf A533-B weld and an A508-2 forging which exhibited a high C sub v energy correlation (>135 J, 100 ft lb) at the drop-weight nil-ductility transition (NDT) temperature. Standard C sub v and fatigue-precracked C sub v specimens were employed for notch ductility and dynamic fracture toughness K sub j determinations, respectively. The studies indicated: (1) approximately equal radiation effects to longitudinal and transverse test orientations for the plate, (2) a significantly lower C sub v upper-shelf level for the HAZ compared to the parent plate, (3) greater radiation sensitivity by the HAZ compared to the parent plate as evidenced by transition-temperature elevation, (4) a postirradiation upper-shelf energy for the weld below the code index value of 68 J (50 ft.lb) minimum, and (5) a trend in fracture toughness versus C sub v upper-shelf energy suggestive of a correspondence in these properties.