| Tensile testing was carried out on five microalloyed steels in order to investigate the hot ductility behaviour between 800 and 1300;Above 1400;In the temperature range 800-1300;For the C-Mn-Al steel, the ductility is the lowest following the direct heat treatment because of the presence of a greater volume percent of AlN precipitates at the grain boundaries compared to the Nb-Ti-Al steels. In contrast, after annealing and sensitizing, the C-Mn-Al grade displays the highest ductility because of the sluggish rate of precipitation of AlN in austenite.;Above 1400;Finally, Ti additions to Nb containing steels improve the ductility because some of the Nb is combined with TiN particles both as complex TiNb(C,N) and by precipitating as NbC on existing particles. The addition of V to the Nb-Ti-Al steels (which contains also Ni and Cr) increases the ductility because of the retardation of Nb(C,N) precipitation. However, after the sensitizing treatment, at low test temperatures, the V containing grade displays the lowest ductility because of the coarser grains. (Abstract shortened by UMI.)... |
