Numerical simulation of residual stress in post internal-welding process of bimetal composite pipe and optimization of welding sequence

Abstract

With the increasing demand for energy, energy extraction is developing towards a more complex corrosive environment containing a large amount of CO2, H2S and Cl−. Bimetal composite pipes because of both good corrosion resistance and strength are getting more and more research and application. In this paper, L415/316L bimetal mechanical lined pipes were welded by two processes (single-side welding process and post internal-welding process) the residual stress of which was studied by combining numerical simulation and experiment. Then the welding sequences of the post internal-welding process were compared and analyzed. The results show that there is already a certain amount of residual stress in the pipe after overlay welding. The residual stress of single-side welding process and post internal-welding process is too large and distributes in the danger zone, which is easy to lead to failure. By adjusting sequence of the post internal-welding, it can effectively change the level of the residual stress and reduce the stress of the overlay layer, the internal-welding layer and the backing welding layer, which is beneficial to improve the safety of the bimetal mechanical lined pipe.