Comparison of Prediction Models for Mechanical Properties of Thermally Aged Cast Austenitic Stainless Steels

Abstract

The cast austenitic stainless steel (CASS) is used for the primary loop pipes of some PWR plants. It is known that these stainless steels are susceptible to thermal aging during plant operation. This material degradation decreases the fracture toughness (J-R curve) and increases the tensile strength, which affects the possibility of the fracture of the pipes. The JPOG prediction models for aged CASS materials were developed based on the CASS material test data for PWR plants in Japan, which was presented in ASME PVP2005-71528. The JPOG prediction models consist of the model to predict the true stress-true strain curve and the model to predict the J-resistance parameters, such as the Js at ductile crack initiation (JIc) and at Δa = 6 mm (J6) in terms of the ferrite contents and aging time. In the US and France, similar degradation models were developed using their own databases or internationally combined one. In this work, three prediction models for thermal aging of CASS were compared and benchmark analyses were performed under Japanese PWR plants operating condition.