Analysis of Hook Formation Mechanism in Ultra Low Carbon Steel using CON1D Heat Flow - Solidification Model

Abstract

Subsurface hook formation at the meniscus during the continuous casting of steel slabs is an important cause of surface defects, owing to their easy entrapment of mold flux and inclusion-laden gas bubbles. This work investigates the fundamentals of meniscus solidification and how hooks form by a combination of advanced computational models and plant measurements. From experimental results, the pitch deviation of oscillation mark depends on mold level fluctuation so the pitch deviation shows the stability of production conditions. The predicted shell thickness at upper end of the oscillation mark is related to the measured thickness of hook. During hook formation, the initial solidifying shell is partly melted by the molten steel. The extent of melting correlates with the location of the liquidus line near the meniscus for a given set of casting conditions. Thus, shallower hooks also correlate with a thinner initial solidifying shell. Deviations between these predicted hook characteristics and measurements correlate with level fluctuations, as indicated by variations in oscillation mark pitch. This work shows that hook shape is greatly affected by heat flux at the meniscus region.