Description of the Hypo-peritectic Steel Solidification under Continuous Cooling and Crack Susceptibility

This study describes the phase evolution during solidification under continuous cooling conditions of a hypo-peritectic multicomponent steel. Additionally, the mechanical behavior and dimensional variation of the solid–liquid skin were evaluated by using mathematical expressions reported in the literature as a function of the proportion of phases and solute distribution respectively. The crack susceptibility of the solid–liquid skin depended on the proportion of phases and it occurred in two solid fraction regions, independently of the cooling rate. For the region exhibiting the lowest solid fraction values this susceptibility was associated to γ phase, while at the highest solid fraction values it was related to δ phase. At the end of the peritectic transformation the highest contraction observed can be considered as an additional contribution to the crack susceptibility in the solid fraction range of 0.92–0.98. The significant microsegregation of Mn observed for high cooling rates promotes a change in the solidification mode, from a hypo-peritectic mode into a hyper-peritectic mode and the expansion of solid formed from the remaining liquid.