Austenite to ferrite transformation after hot deformation of low carbon steel

The aim of this work is to get the ferrite nucleation criteria from the recrystallized austenite grain after hot deformation in non isothermal condition. A series of rolling experiments have been performed with industrial C-Mn steel in two different temperatures of 1060 and 960 °C with sequence cooling cycle. The microstructure changes that taking place during hot rolling and after cooling has been examined by metallographic evaluation which allows the identification of ferrite transformation after austenite recrystallization. The recrystallization control was carried out using interrupted cooling method to obtain transformation from actual austenite grain. Using an approach of grain boundary interfacial area (S _v) calculation, which attempts to account the number of sites for potential nucleation of ferrite in thermomechanically processed austenite, an essential correlation of the correspond measured grains was developed. The influence of delay interval time after recrystallization to transformation is observed and the implication obtained is discussed. From those results, a hypothetical interaction between parameter and nucleation is described. It is concluded that, strain and holding time has a major role on the recrystallization process of austenite and bring an effect to ferrite grain refinement. The calculated S _v has indicated the potential sites of nucleation that are proliferated with increasing strain.