Creep crack growth behavior of steam pipe steels: Effects of inclusion content and primary creep

Abstract

For remaining life prediction analyses of steam pipes, creep fracture behavior was evaluated on ex-service 2-1/4Cr-lMo steel weldments. Composite specimens consisting of base, fusion line and weld metals were used to develop creep deformation and creep crack growth rate properties in the fusion line area. Steel weldments exhibited comparable creep deformation rates in the fusion line area regardless of inclusion content. In the fusion line area, the steel weldment with a lower inclusion content demonstrated slower creep crack propagation rates. The developed life prediction methodology for steam pipes was extended to evaluate the influence of primary creep. The inclusion of primary creep in the life prediction assessment using the developed creep properties was found to decrease the creep crack growth life. Thus, the life prediction methodology without considering primary creep can result in a nonconservative estimate of remaining lives of steam pipes.