Numerical simulation and lifetime study of the high-temperature creep behavior of P91 pipeline with a soft zone

Abstract

In this paper, the local low hardness P91 pipe fittings of a power plant are taken as the research object, and the distribution of the soft area of the pipe fittings is determined by on-site “gridded” hardness testing, and the three-dimensional finite element model of the normal and soft areas of the pipe fittings is constructed. FEA technology was used to numerically simulate the high-temperature creep behaviour of pipe fittings based on the Norton model. Through numerical simulation, it is found that due to the creep relaxation effect of the material, the creep stress of the pipe fitting is redistributed during the creep process at high temperatures and the position of the peak stress shifts from the pipe ID to the OD. The soft zone will have an impact on the creep stress redistribution inside the pipe fitting, the peak stress of the pipe fitting is not in the soft zone, and the stress level in the soft zone is always lower than the normal zone. After numerical simulation, the stress value of the soft zone in the creep steady state is obtained, which can provide data support for safety assessment and life assessment.