Retracted: In Situ Observation of Phase Transformations of Pearlite Heat‐Resistant Steel during Solidification

Abstract

The phase transformation of pearlite heat‐resistant steel during solidification is observed using high‐temperature confocal scanning laser microscopy. The precipitation of the δ‐ferrite (δ) phase proceeds in a cellular manner at cooling rates of 5 and 15 °C min−1, whereas precipitation occurs in a dendritic manner at a cooling rate of 100 °C min−1. Furthermore, a change in the solidification path is observed at high cooling rates. When the experimental steel is cooled at a low cooling rate of 5 °C min−1, the sequence of continuous solidification is L → L + δ → L + δ + γ → δ + γ, which is consistent with that of equilibrium. However, when the cooling rate increases to 15 and 100 °C min−1, the sequence of continuous solidification is L → L + δ → L + δ + γ → L + γ→γ. Furthermore, at various cooling rates, the interface of the peritectic transformation of δ → γ presents three different modes: planar and cellular modes controlled by solute diffusion and massive transformation controlled by the processes that occur at the transformation interfaces. The different δ → γ transformation modes and the associated different degrees of volume shrinkage are hypothesized to lead to uneven strand shell growth during continuous casting.