Numerical simulation of welding residual stress of Incoloy 825/L360QS bimetallic clad pipes

Nearly half of China’s proven natural gas fields are high-sulfur gas fields, which faces severe corrosion challenges. Bimetal clad pipes are widely used in the natural gas transportation industry due to their excellent corrosion resistance, mechanical properties and cost-effectiveness. However, stress corrosion cracking is a common occurrence for bimetallic clad pipes in high-sulfur gas field environments. Therefore, studying welding properties of base material and welds of bimetallic clad pipes is crucial for safety. A thermomechanical-coupled finite element model of bimetallic clad pipes was established with SYSWELD software. Residual stresses of welded joints were measured by hole-drilling strain gauge method, the calculated results matched well with the experimental measurements, which validated adequacy of the computational approach, and distribution rule of residual stresses in multi-layer and multi-pass welds of bimetallic clad pipes was revealed. The results showed that the base layer experienced compressive stresses on the central cross-section, which decreased gradually with distance from the fusion line. On the weld side, axial and circumferential stresses exhibited a cap-shaped distribution with tensile stresses. The peak stress in the liner layer was higher than that in the base layer, while the radial stress was smaller. The stress near the fusion line was higher, and different stress mechanisms existed between the base layer and the liner layer. High-stress areas concentrated near the fusion line and transition zone were susceptible to cracking.