Determination of the critical points in solid-state phase transformation of some hypoeutectoid steels

This study allowed, by dilatometric analyses, both to highlight the solid state transformations that occurred during the continuous heating of two hypoeutectoid steels, as well as to investigate the effect of the heating rate on the critical points at which these transformations occurred. The eutectoid transformation (the pearlite dissolution into austenite) was carried out in a temperatures interval, ranging between pearlite dissolution start temperature (Ac1) and pearlite dissolution finish temperature (denoted Acfp in this article). Increasing the heating rate determined a displacement of the critical points in solid-state phase transformation to higher temperatures; these displacements were more significant for the Acfp point, than for the critical points Ac1 and Ac3