Numerical investigation on the influence of the electro-resistance welding pipe manufacturing process on the local variation of the yield strength of the pipe material

Abstract

In the present research work, a finite element model of the electro-resistance welding pipe forming process chain is developed using the ABAQUS/Explicit software. The forming process, which is composed of 22 tandem roll stations, has been fully modeled in the developed finite element simulation. In order to account for the Bauschinger effect on the pipe material properties as a consequence of the loading and the unloading during the process, a non-linear kinematic hardening model has been utilized in all the proposed finite element simulation models. The constants for the non-linear kinematic hardening model were estimated by means of cyclic experiments on the K55 steel pipe material. In order to properly simulate the electric arc welding (electro-resistance welding) operation, the ABAQUS welding interface has been utilized to account for the joining between the two edges of the formed pipe as well as to assess the influence of the welding-induced temperature field on the residual stresses on the pipe material. The sizing operation, which is the final station of the electro-resistance welding process, has been also accounted in the developed finite element method model and is composed of six tandem rolls. To export and import the results between two different modules, a mapping strategy has been utilized and allowed exporting the element results, in terms of stress, strain, and temperature, and importing them into the following simulation module. Finally, in order to estimate the influence of each process station on the yield strength of the material, a finite element simple tension test simulation has been implemented in ABAQUS/Static, mapping the results of each station on the tensile specimen. This mapping operation allowed to estimate the yield stress of the material after each of the three process stations, a consequence of the residual stresses present in the material, and has been carried out on eight circumferential locations around the pipe, evenly spaced with a 22.5° angle. The model has been validated by comparing the geometrical results, in terms of average pipe diameter and thickness, obtained from the finite element model with those of the relevant industrial production, showing deviations equal to 1.25% and 1.35% (forming) and 1.29% and 1.43% (sizing), respectively, proving the reliability of the proposed process chain analysis simulation. The results will show how the process-induced residual stresses arising on the pipe material make the material yield strength to vary from station to station as well as having different values along the circumferential direction of the pipe.