Axial Contraction during Torsion Simulation of Steel Rolling at High Temperatures

The deformation textures determined in previous experiments on the free-end torsion testing of pure copper (99.95%) bars are reviewed. At room temperature and 125°C, lengthening is observed up to shear strains of 11 or 12. By contrast, at 200 and 300°C, shortening takes place after initial shear strains of about 10 and 5, respectively. Simulations are carried out using polycrystal plasticity methods with the aim of reproducing the experimental textures. It is shown that the lengthening generally observed at ambient temperatures is entirely attributable to the characteristics of dislocation glide in fcc metals. By contrast, the “shortening” that takes place at elevated temperatures cannot be reproduced in this way and requires introduction of the concepts of the nucleation and growth of new grains. Comparison of the experimental results and the predictions of the simulations leads to the conclusion that the very large axial contractions frequently reported during the torsion simulation of steel rolling schedules are due to dynamic recrystallization.