Effect of C and Mn Variations Upon the Solidification Mode and Surface Cracking Susceptibility of Peritectic Steels

Abstract

This work studies the effect of chemical composition, C and Mn contents, and cooling rate on both the solidification mode and the evolution of phases during the solidification of three steels; two of hypo-peritectic and one of hyper-peritectic composition. Furthermore, the cracking susceptibility associated to both the differences in mechanical behavior of d and g phases, and contraction during solidification, was inferred. Slight variation of C or Mn, in the order of 0.04 %, promoted significant changes in the evolution of phases during solidification. It was observed that for the hypo-peritectic steel closer to the peritectic point, the Mn microsegregation observed for high cooling rates promoted at the end of solidification a hyper-peritectic solidification mode. On the other hand, independently of the solidification mode and chemical composition of the studied steels, the differences in the mechanical behavior of d and g phases led to a cracking susceptibility in two solid fraction zones. Furthermore, for the steel exhibiting hypo-peritectic solidification mode the peritectic transformation occurred at higher solid fraction compared with the steels showing hyper-peritectic solidification mode. Therefore, the remaining liquid ability to feed the contraction in the solid-liquid shell associated to the peritectic transformation resulted adversely affected. Hence, the cracking susceptibility observed in the hypo-peritectic steel is not only generated by differences in the mechanical behavior of d and g phases, but also by the liquid inability to compensate the contraction associated to the peritectic transformation.

Effect of Magnesium Treatment on the Hot Ductility of Ti-Bearing Peritectic Steel

“…Peritectic reaction of steel is an important transformation mode of Fe-C alloy with a carbon content ranging from 0.10% to 0.53% in the initial stage of solidification [1][2][3][4]. When the primary high-temperature δ-ferrite reacts with the residual molten steel L to produce the γ-austenite, the difference in crystal structure between the δ phase (BCC structure) and the γ phase (FCC structure) results in a large volume contraction in the process of solidification, which causes uneven cooling of the primary shell in the mold, thus forming shells with different thicknesses and high cracking susceptibility [5][6][7][8][9][10]. This cause is considered as the main reason for the surface cracking of this type of steel.…”

Influence of Alloy Elements on Cracking in the Steel Ingot during Its Solidification

“…Some alloys are susceptible to cracking during solidification, which has attracted the interest of many researchers. One of the most important examples in industrial practice is the production of peritectic steels in continuous casting, in which frequently occurring cracks are called hot tears, including surface longitudinal cracks and internal cracks [1][2][3][4][5][6][7][8]. Surface longitudinal crack formation is caused by the brittleness of the dendritic front, and all cracks observed originate and propagate along the interdendrites in the mushy zone [6,8].…”