Investigation of Peritectic Behavior of Steel Using a Thermal Analysis Technique

During solidification, the peritectic reaction can occur in a wide range of materials, including ferrous and non-ferrous alloys. The kinetic and thermodynamic principles that govern the peritectic reaction in regard to solute diffusion and phase transformation are well understood, and the negative impact that the peritectic reaction has on the surface quality of as-cast steel products is well documented. In ferroalloys, the peritectic reaction occurs between the hypoperitectic (0.09 pct C) and hyperperitectic (0.53 pct C) regions of the iron-carbon phase diagram. Beside the carbon content, the magnitude of the peritectic reaction in a given steel is affected by the contents of other solute elements. However, our understanding of the effect of all dissolved elements on the peritectic reaction is still evolving. There are over a dozen equations that have been proposed for predicting the peritectic nature of steels. Some of these equations were developed for application to specific groups of steels, chemistries, and casting conditions. In this paper, the predictive power of four peritectic equations is compared to the results from thermal analysis experiments conducted on steels with varying concentrations of dissolved elements. Based on the thermal analysis results, an equation is proposed for calculating the latent heat of the peritectic reaction for a given solute element.