Hot deformation and recrystallisation of low Mn steels with different Ti/N ratio

Abstract

The effects of small titanium and nitrogen additions on the mechanical properties and microstructural characteristics of four different low carbon, low manganese steels have been studied using a Gleeble thermomechanical simulator and TEM investigations. The Ti/N ratio in these steels as well as the size and distribution of TiN particles play a major role in determining the mechanical properties, the resulting austenite grain size as well as the size of inclusion precipitates. The best mechanical properties were obtained in the steel with a Ti/N ratio lower than the stoichiometric value. This steel also had the smallest austenite grain size after reheating as well as the highest rate of dynamic recrystallisation during hot deformation. The nature and rate of recrystallisation seem to be determined by an intricate interplay between the size and distribution of titanium nitrides and the prevailing austenite grain size.

Keywords:

• Low Mn steel
• Hot deformation
• Recrystallisation
• Ti/N ratio

This work was conducted as part of an Australian Research Council (ARC) – Linkage grant no. LP0669602 with BlueScope Steel as industrial partner. The authors gratefully acknowledge the financially support of the ARC and BlueScope Steel. The authors also wish to thank The University of Wollongong for the provision of laboratory facilities and the encouragement to conduct this investigation.