Research on strip deformation in the cage roll-forming process of ERW round pipes

Abstract

Cage roll forming is an advanced roll-forming technique to manufacture electric resistance welded (ERW) round pipes. In the cage roll-forming process, many small rolls are arranged along the outer surface of the deformable strip to bend the strip edge in a more smooth way. Furthermore, these small rolls can be used for forming pipes of different sizes. Therefore, cage roll forming can reduce roll change time and improve forming quality, as compared with the conventional step roll forming. However, very few studies can be found about cage roll forming, due to its complexity, and the industrial practice depends greatly on experience rather than science-based design today. In this work, the whole cage roll-forming process is simulated with the explicit elastic–plastic finite element method, and the strip deformation during the cage roll-forming process has been investigated in detail. Through the simulation, the “non-bending area” phenomenon is found, and the ranges of the non-bending area at different forming stands are obtained. In addition, the longitudinal strain at the inside edge and center are predicted, and by comparison, it can be known that the deformation of the strip edge is usually larger and edge buckling is most likely to occur at the entry sides of No.1–No.3 fin-pass stands. Finally, the circumferential length, opening distance and the profiles of the deformed strip are measured on the cage roll-forming mill. There is a good agreement between the experimental and simulated results.