Initial Assessments of Notch Ductility Behavior of A533 Pressure Vessel Steel with Neutron Irradiation

Abstract

Exploratory assessments were made of the Charpy-V notch ductility characteristics of heavy section A533-B and A533-C steel plate and submerged arc weldments following neutron irradiation at 550 F. The experimental evaluations were performed largely with commercial production materials and included comparisons of materials in both Class 1 and Class 2 strength ranges. Postirradiation notch ductility properties of one 53/4-in. A533-B Class 1 electroslag weldment were also developed. Assessments made of relative irradiation performance were assisted by a compilation of recent information on the response of the ASTM reference A302-B steel plate. Major research findings include the observation of significant variability in radiation embrittlement sensitivity of A533-B and A533-C steel, wherein the sensitivity level of plate and weld metal in some cases exceeded that of the ASTM reference plate. High radiation embrittlement sensitivity was noted for both submerged arc weld deposits examined; however, the data suggested that the performance of the weld heat-affected zone paralleled that of the parent plate. High embrittlement sensitivity was also noted for the electroslag weld deposit in contrast to markedly low sensitivity of the weldment parent plate. The notch ductility behavior of A533 plate and weld metal under 550 F irradiation was not found influenced measurably by either the strength class (Class 1 or 2) or by the particular grade of steel (Grade B or C). Similarly, there were no marked variations in irradiation response through the thickness of plate or weld metals, or between RW (longitudinal) versus WR (transverse) orientations in cross-rolled plate. In accordance with observations on special laboratory heats of A302-B steel, the study demonstrates that the radiation embrittlement resistance of commercially produced A533 steel plate and weld deposits can be predicted in part from their individual chemical compositions. High copper and phosphorus contents generally signify high sensitivity to 550 F radiation-induced changes in notch ductility characteristics.