Optimization of Eleven Cross-Roll Straightening Process for 20CrMnTi Bars Based on Combined Hardening Model

Straightness is one of the important indices to measure the quality of bars; multi-roll straightening is an essential process in bar production. Materials undergo multiple cycles of alternating tensile and compressive loading during multi-roll straightening, subject to the influence of the Bauschinger effect. However, most existing studies have failed to adequately account for the Bauschinger effect, leading to insufficient prediction accuracy of the process. This study establishes an eleven-roll straightening finite element model (FEM) for bars based on the nonlinear combined hardening model. The orthogonal experimental design method is employed to optimize the process parameters. Straightening experiments of 20CrMnTi bars using an eleven-roll straightener were conducted. Based on the FEM, the influence patterns of different process parameters on the straightening results were investigated. The results indicate excellent agreement between the eleven-roll straightening finite element simulation results and the experimental results. Using the optimized parameters, both the simulated and experimental straightness after straightening were within 1‰, with a relative error between them below 8%. The findings of this study can improve the prediction accuracy of the eleven-roll bar straightening process and provide reliable theoretical support and technical reference for the optimization of straightening process parameters.