Influence of TiN particles distribution on static recrystallisation in structural steels at reheating temperature

Abstract

Results of investigations concerning the influence of Ti and N contents on static recrystallisation kinetics are presented. By means of torsion tests, and applying the back extrapolation method, the statically recrystallised fraction has been determined for four structural steels with different Ti and N contents, at different temperatures, equivalent strain of 0.35 and strain rate of 3.63 s−1. Two reheating temperatures have been used to obtain different austenite grain sizes and different precipitate mean size in steels containing Ti. The results show that a low precipitated volume and a relatively large size of precipitates, at reheating temperature, did not impede grain boundary self‐diffusion during the static recrystallisation, the main mechanism governing static recrystallisation. Nevertheless, the smaller size of the precipitates acted as an obstacle to grain boundary self‐diffusion. These effects were measured by calculation of the activation energy for static recrystallisation. On the other hand, the influence of austenite grain size in steels containing Ti can not be correctly determined, as at each reheating temperature, in addition to a different austenite grain, the distribution of precipitates is also different, affecting the activation energy and making it impossible to clearly appreciate the influence of austenite grain size.