Prediction of maximum initial strip width in the cage roll forming process of ERW pipes using edge buckling criterion

Cage roll forming is an advanced process for producing electric resistance welded (ERW) pipes. It is designed to improve the strip deformation and to increase the flexibility of production lines compared with the conventional roll forming of ERW pipes. One of the most important parameters of this process is the initial strip width. Accurate prediction of the initial strip width is vital for producing sound pipes with desired dimensional and geometrical tolerances. In this paper, cage roll forming process is simulated with the explicit elastic–plastic finite element method in the MSC Marc Mentat software. Simulation results show that by increasing the initial strip width, more circumferential length reduction is induced to the deformed strip in the fin-pass stands. This effect increases the difference of longitudinal strains at the edge and center of the deformed strip and consequently leads to a high longitudinal compression at the strip edge. Therefore, edge buckling will be unavoidable if the initial width is selected bigger than a specific limit. In order to predict the maximum initial width in cage forming process, an edge buckling criterion was introduced. The circumferential length and the horizontal distance between two deformed strip edges were obtained from the simulation and were compared with the experimental data from a production line. The comparison showed a good agreement and confirmed the finite element simulations.