Optimal design of round-oval-round roll pass for the steel bar rolling process

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AbstractThis study aims to determine the optimal values of the round-oval-round roll pass design parameters. This was applied on two consecutive passes: round-oval and oval-round. That produces a circular cross section from an input of a larger circular cross section through an intermediate oval pass. The design variables were the oval groove radius and depth. The optimization objectives were to minimize the rolling torque and to maximize the area reduction ratio. A nonlinear, double-stage, three-dimensional finite element model (FEM) is used to calculate the rolling torque and the output shape dimensions. The two-staged FEM yielded realistic and highly accurate results as it imitates the real rolling process, using the actual oval results of the first step directly as input to the second step. The results of the FEM were verified experimentally. A polynomial surrogate meta-model, representing the rolling process, was developed based on the FEM utilizing multivariate regression. Optimal design solutions and design curves were developed. The established optimization procedures achieved a reduction in rolling torque of more than 6% or an increase in the area reduction ratio of up to 11%. The optimal solutions were confirmed using FE and experiment.