Finite Element Analysis of High Temperature Piping Creep for Considering the Effect of Inner Pressure and Welding Residual Stress

According to Norton creep constitutive equation and different creep parameters of welding material, heat-affected zone material and parent material, welding residual stress, post weld heat treatment(PWHT) residual stress and creep under inner pressure and PWHT residual stress of the welded joint of P91 steel high temperature piping were analyzed by ABAQUS finite element code. The distribution of welding residual stress and PWHT residual stress was obtained. Creep strain distribution after 100,000 hours and dangerous position of the welded joint were predicted. The results show the higher welding residual stress is in the welded joint for the piping wall thickness and constraints. And the welding residual stress can be reduced effectively by the method of PWHT. But, because of the existence of PWHT residual stress, the creep strain is also influenced by the PWHT residual stress. The stress can not be neglected in the strength design of high temperature piping. And much higher creep strain is in the edge between welding seam and heat-affected zone. The presente work provides a reference for the design and predicting maintenance for high temperature piping.