Abstract

The hot rolling of bars issued from continuous casting is a manufacturing process aiming to achieve the desired product cross-section, the refinement of material structure and the annihilation of internal defects such as shrinkage porosity. The mastering of the void closure phenomenon during rolling is crucial to guarantee the internal soundness of finished products. The pore closure process is strongly influenced by the defects dimensions and orientation related to the applied loadings which tends to limit the application of classical models to estimate void closure during complex forming route. In this study, a methodology is developed to predict the evolution of a single pore undergoing a complex loading route thanks to finite element computations, design of experiments, and surrogate modeling techniques. The mechanical loading during the first stand of an industrial rolling route is firstly characterized by measurements performed at the center of the product using numerical modeling. The loadings are secondly applied as boundary conditions of a simulation performed on a Representative Volume Element (RVE) containing an ellipsoid defect. This scale transition is carried out to reduce the computational time needed to evaluate the void evolution using an explicit representation of the cavity. A design of experiments (DoE) is then generated by means of the pSeven® software and consists in defining several combinations of the values of the geometrical parameters of the void (main axes dimensions and three rotation angles) integrated in the RVE. For each morphology, the automatic post-processing of the numerical results allows computing the void evolution as the ratio between the final pore volume and its initial volume. Eventually, the dataset is used to build a surrogate model. Knowing the initial geometry of the void, this model provides an almost immediate estimation of the final volume of a pore undergoing a loading route representative of hot rolling.