Numerical Simulation of Uncoiling and Roller Leveling Processes from Steel Coils

Uncoiling and roller leveling play an important role in pipe forming because it is prerequisite to make products with good quality. Uncoiling and roller leveling are used to reduce undesired characteristics such as imperfections in sheet flatness and residual stress. Considering residual stress in steel coil which has been ignored to date, a simplified coiling process is combined with uncoiling and leveling processes to investigate their effects on residual stress and curvature. The objective of this thesis research focuses particularly on studying the influence of coil diameter, uncoiling direction and leveling settings on residual stress and residual strip curvature after leveling. The numerical analysis is based on finite element method (FEM). 2-D finite element models are built using ABAQUS to numerically simulate coiling, uncoiling and roller leveling processes. By varying coil diameters, the uncoiling direction (CW uncoiling and CCW uncoiling), intermeshes of top rollers in the FEA model, the respective effect of the each factor on residual stress and residual strip curvature are investigated. The simulation results indicate that leveling process decreases the magnitude of maximum tensile and compressive stresses considerably. The neutral axis is not at the middle line in the thickness direction, but shifted towards the top surface for CW uncoiling and towards the bottom surface for CCW uncoiling. There is a high correlation between coil diameter and residual stress as well as between coil diameter and residual curvature. Compared with CW uncoiling, CCW uncoiling is able to reduce maximum residual tensile and compressive stresses, but also produce a higher residual curvature. Within the intermesh range experimented in this thesis, the intermesh of the first top roller has an impact on the magnitude of both maximum tensile stress and compressive stress, but the intermesh of the last top roller does not