Physical simulation of liquid steel motion in a thin-slab continuous caster mold

Abstract

Industrial experience of steel casting at the thin-slab continuous caster (CC) revealed processes, having negative effect on the quality of internal structure and surface of CC thin slab. The main problems are as follows: flat streams of liquid steel, flowing through submerged snorkel into restricted dead volume, form circulating flows of extremely high velocity in both liquid core and on the slab surface. This circumstance makes specific requirements to the design and parameters of the submerged snorkel to supply the metal into the thin-slab CC mold. Despite the more than 25 years’ experience of the snorkel form and geometric parameters development, there is no single opinion on its optimal design. Results of physical simulation of the liquid motion processes in a thinslab Caster mold presented (for slab maximum width 1800 mm, thickness – 90 mm) of JSC “Vyksa Steel-works” casting and rolling complex. Description of the physical model facility quoted, as well as description of the experiment methodology and its results. The speed was measured and structure of liquid steel flows revealed in depth and sub-surface layers, as well as in slag-forming mixture at the mold surface. The comparison of two principally different variants of liquid steel feeding into the mold made. The two variants were as follows: by a flat down-directed stream with a narrow central divider (direct-flow submerged snorkel) and by four streams , two of them directed down under an angle relating the vertical axe, and the other (about 20% of total liquid consumption) – directed upward to the bath mirror (the snorkel of “hammer” type). It was determined, that steel casting with technological speed through the direct-flow snorkel was most effective into the slab of 1400 mm width and less, since in this case the sub-surface flows speed did not resulted in the intensive waves formation, constant whirls formation and slag particles dragging into deep layers of the slab. For steel casting into slab of width more than 1400 mm, it is reasonable to use a snorkel of the “hammer” type, which enables to create a favorable stable structure of circulation and decrease the tendency of slag particles dragging in the deep layers of the slab.