Refinement of as-cast austenite grain in carbon steel by addition of titanium

Abstract

Synopsis : Effects of Ti addition on as-cast austenite grain size in S45C carbon steel have been investigated in range of Ti addition between 0 and 0.5mol%. The cooling rate was set to be 0.03°C/s. It is shown that the average austenite grain diameter decreases from 1900 to 250, μm as the Ti addition increases from 0 to 0.5 mol%. The microstructural observation revealed that the motion of austenite grain boundary is inhibited at inter-dendritic position, which is ascribable to pinning effect of Ti(C,N) particle. The CALPHAD analysis showed that this particle crystallizes mainly in L+γ-Fe+Ti(C,N) phase field. As increasing Ti addition, the size of Ti(C1N) particle does not substantially change, however, the number of the Ti(C1N) particles increases, leading to further refinement of the austenite grains.