A systematic study on three-roll continuous straightening process for LSAW pipes

Abstract

Aiming at the low efficiency and unstable accuracy of the current mold-pressing straightening for LSAW pipes, a three-roll continuous straightening process is proposed in this study, which uses the roller straightening instead of mold bending. According to the novel technology, the calculation model of the theoretical straightening moment is derived based on the springback equation of plane bending with small curvature, and the calculation model of initial curvature is established for the new deflection detection method. Furthermore, the numerical simulation analysis is carried out for the LSAW pipe case, and a straightening experimental platform is built for experiments. The research shows that the accuracy of the theoretical moment equation required for straightening is directly related to the initial curvature, rather than the fitting accuracy of the deflection curve, and the low-order simple-fitting curvature calculation model has the highest reliability. In order to control the section distortion and the straightening blind area, the straightening roller should follow the equal diameter design principle, and the empirical formula of span estimation is given. Under the optimal conditions, the straightness of the corrected tubes can be controlled within 1.5‰ and the ovality of the section can be within 0.5%, which proves the feasibility and reliability of the new process. What’s more, the straightening system built in this work, including process analysis software, is conducive to the automation and popularization of the new process.