Effect of rare earth yttrium on hot ductility of 20CrMnTi steel with 0.05% Tin

The effect of Y on the hot ductility of 20CrMnTi steel with 0.05% Sn was investigated. The results show that there is a trough in the hot ductility-temperature curve. With the increase in the Y content, the trough shifts to a lower temperature and becomes shallow, and the hot brittle range becomes narrow. The effect of Y, which was no more than 0.05%, on the austenite grain size of the steels examined was negligibly small in the present research. In addition, Y greatly enhancing the hot ductility of 20CrMnTi steel with 0.05% Sn was due mainly to its suppressing the Sn segregation, retarding the austenite/ferrite transformation and accelerating the onset of dynamic recrystallization (DRX). Moreover, Y segregating to the grain boundaries could strengthen the grain boundaries, occupy vacancy sites induced by deformation, and prevent the formation and propagation of micro-cracks at the grain boundaries. Y could also decrease the segregation of the impurity S at the grain boundaries to some extent, which is good for the improvement of the hot ductility. In the present case, adding 0.05%Y can obtain the best effect in improving the hot ductility of 20CrMnTi steel with 0.05% Sn.