Texture evolution in warm rolled low-carbon steels

The effect of warm and cold rolling parameters on the development of annealing textures and their effects on the final formability were studied in two LC steels containing 0.8%Cr. Warm rolling temperatures between 640 and 750°C were employed, together with reductions of 65% to 80%. The effects of an additional cold rolling reduction of 40%, different initial hot band grain sizes (HBGSs) and a decrease in the heating rate during annealing were also studied. The ND fibre, <111>//ND, of the recrystallization texture was strengthened as the warm rolling temperature was decreased. A noticeable improvement in both the continuity and intensity of the ND fibre was obtained when samples were submitted to an additional 40% cold rolling reduction. The ND fibre was even more continuous and intense when a low heating rate was utilized, yielding r-values of 1.2 and 1.3 for the warm rolled and warm plus cold rolled samples, respectively. On the other hand, the volume fraction of grains containing shear bands is slightly lower for the finer HBGS. However, this does not reduce the amount of in-grain nucleation of gamma grains, suggesting that shear bands are not the only factor that has to be considered in the improvement of warm rolling textures. Although the normal anisotropy is not affected by the HBGS, much lower Deltar values were associated with the finer grained steel.;The texture changes taking place during recrystallization were examined using electron back-scattered diffraction. The recrystallization textures resemble the deformation textures but with a more extensive alpha fibre that includes the {113}<471> orientation; the gamma fibre extends to the {554}<225>. These two orientations are related to the {112}<110> deformed grains by near 26° rotations about selected <110> axes. Nevertheless, both orientations appear in the early stages of recrystallization, an observation that does not support the oriented growth theory. The {111} < hkl> orientations are the first to recrystallize while the alpha fibre is present until the end of recrystallization. It is finally consumed by all types of grains as well as by subgrain coalescence. The relatively constant volume fractions of the main orientations and the similarities in the growth rates for the {111} < hkl> and random orientations suggest that recrystallization is controlled by the oriented nucleation concept.