Micro–macro creep damage simulation for welded joints

Abstract

AbstractAssessment of Type IV creep damage in pipe welds is important for residual life prediction of fossil power plants. Actual creep damage is firstly microscopic, such as the initiation and coalescence of small defects, and lastly macroscopic, such as the propagation of crack-like defects. In this paper, an outline of the micro – macro combined creep damage simulation on the basis of the grain-boundary-fracture-resistance model is shown, and is applied to the creep damage simulation of both low-alloy steel welds and high-chromium steel welds. Firstly modelling of the simulation for low-alloy steel welds such as 2.25Cr –1Mo steel (ASME P-22) is discussed, and application examples are shown such as creep rupture specimens in the laboratory and welds in actual power piping. Secondly a trial is carried out to reproduce the number density of small defects in the heat-affected zone of welded joints of modified 9Cr –1Mo steel (ASME P-91). The possibility of predicting the microscopic damage is demonstrated.Keywords: high Cr steelscreepcreep damageType IVwelded joints