Effect of Flower Pattern Design on the Springback of High Strength Steel in Cold Roll Forming Process of Pipes

Roll forming is the most commonly used process for producing electric resistance welded pipes. In this process, the geometry of the rolls, which are usually introduced in the form of a flower pattern, should be carefully designed to achieve the desired quality standards. One of the most important parameters which influence the welding quality of high strength steel pipes is the springback of the strip after the forming section. In this paper, four different flower patterns including circular forming, edge forming, double radius forming and reverse forming are designed for the roll forming of a high strength steel pipe. Then, they are evaluated by finite element analysis. In order to compare the springback of the strip in the flower patterns, two geometric criteria are defined based on the change of relative curvature and edge location of the deformed strip. The results show that the circular flower pattern leads to a minimum value for the springback due to more circumferential compression applied to the strip outer layer. The comparison of the numerical and experimental distribution of the relative curvature confirms the validity of the predictions. Finally, the circular flower pattern is recommended for the production of the high strength steel pipes.