Study on stress asymmetry of pipeline welded joint in mountainous areas with large slopes

Residual stress strongly influences the safety of welded joints of pipelines in mountainous areas with large slopes. But there isn't an effective calculation model. This paper bases on the Thermal-Metallurgic-Mechanical (TMM) method and establishes the calculation model to study the thermal, microstructure, and stress on X70 pipeline welded joints in mountainous areas with a slope of 25°. A series of simulation cases are conducted to explore the mechanism of stress distribution based on this model. Both the hole-drilling method and the coercive method are used to ensure the error is within 10 %. Compared with the pipeline without slope, the stress distribution of pipelines with large slopes is asymmetric, which is, the heat source deflection and axial force lead to the stress of the higher side is 75 MPa higher than that of the lower side. Furthermore, through the theory of thermal and stress evolution, this paper reveals that the heat source deflection is the initial force, and the axial force is the driving force of the stress asymmetry distribution.