The role of inclusions and austenite grain size on intragranular nucleation of ferrite in medium carbon microalloyed steels

Abstract

The beneficial aspects of intragranular ferrite formation on mechanical properties of welds have been reported in the literature for decades. In recent years, this concept has been successfully extended to medium carbon forging steel to refine the microstructure and optimise ductility and toughness. The aim of this work is to demonstrate that intragranular formation of ferrite could be enhanced by increasing the austenite grain size and/or optimising the nature of the inclusions. In this sense, the isothermal decomposition of austenite in allotriomorphic and idiomorphic ferrite for two medium carbon steels microalloyed with vanadium and titanium have been studied. The experimental results reported in this work allows to conclude that austenite grain size and the nucleation potency of inclusions are two parameters that should be considered linked to promote the full decomposition of austenite into intragranularly nucleated ferrite.