Modified Prediction Model of Tensile Properties for Thermally Aged Cast Austenitic Stainless Steel of Static Cast

Abstract It is known that the tensile properties of cast austenitic stainless steel (CASS) increase, and the fracture toughness decreases due to thermal aging. The JSME on Fitness for Service (FFS) provides evaluation procedures for the fracture behavior of thermally aged CASS pipe using a fracture toughness prediction model (H3T model) and a tensile property prediction model (true stress strain (TSS) model) for an arbitral thermal aging condition. These models were developed by using database from CASS produced by centrifugal cast and static cast. On the other hand, some recent reports indicate that cast process (centrifugal or static) may affect fracture toughness of CF8M after thermal aging. In this paper, the data of tensile properties and fracture toughness were investigated for static cast materials, and the prediction accuracy of the original H3T and TSS models was evaluated. As a result, it was found that the H3T model is applicable to CASS produced by static cast and the TSS model has less accuracy for this material. The revised TSS model for CASS by static cast was developed and confirmed that the revised TSS model had sufficient prediction accuracy with independent of specific chemical components and ferrite content.