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- Resumen es exacto "Nowadays, about 97% of the world’s steel is produced through the continuous casting process. Among the different types of existing casters, curved machines have advantages in terms of productivity and ease of evacuation. In return, the bar must undergo a straightening process. In this Thesis, a methodology is developed in order to determine cracking risk in the straightening of round bars, a field in which there is little background. The developed methodology consists of a thermal simulation of the casting strand, followed by a mechanical model that calculates stresses and strains at each point of the bar. These results feed failure criteria in order to calculate internal and surface cracking risks. Laboratory tests are carried out in order to adjust the surface cracking criterion, which show a broader and deeper ductility trough for Nb-alloyed steels. In addition, a formulation for continuous straightening is developed, based on minimizing the curvature variation of the bar, suitable to be applied in new designs or modifications of existing casters. Continuous straightening configurations show a smoother transition than discrete radii layouts, measured in terms of strain rate. Finally, the results of the described methodology are compared against defect rates actually surveyed in industrial plants, in order to assess the predictability of the model. In every case, the occurrence and location of the cracks agree with the results of the simulations. The methodology developed in this Thesis has been used to evaluate scenarios of productivity increase, quality improvement in the final product, reduction of production costs and determination of operating windows in different steel mills."
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