Hook evolution and inclusion entrapment during initial solidification process of continuous casting slab

Abstract

A two-dimensional numerical model was established to describe the mechanism of hook formation and evolution during the initial solidification process of continuous casting slab. Melting, coarsening, growing, and burying stages were observed to follow hook formation at the meniscus. The coordinates at which the hook was finally buried into the shell were determined for different casting speeds and pouring temperatures. The final hook depth was predicted to be approximately 1.8-2.9 mm, which was confirmed by metallographic experiments. A physical model was established based on the calculated shell shape, and the process by which the inclusions were entrapped by the hook structure was investigated. The results indicated that the floating inclusions were most likely entrapped under the nascent hook, and the inclusions gathering near the meniscus were easily captured by the upper part of the nascent hook when overflow of the molten steel occurred. The hooklike structure increased the area of the shell inner face, which resulted in swirling flow of the molten steel near the shell and increased the probability of the inclusions being captured.