The latest evolutions in the tundish design is the introduction of H – shaped tundish. The H-shaped design essentially consists of linked troughs, which allow the bridging of a ladle exchange period without the fall in tundish weight as experienced in conventional tundishes. In normal operation, a single set of hydraulics is used to manipulate the ladle gates from the tundish platform, such that the teeming rate drops to zero during the ladle change. Once the new heat has been “hooked up” and the ladle has been opened, the teeming rate is increased beyond the steady-state rate in order to refill the tundish back to its normal operating level as quickly as possible. Once this level is reached, the teeming rate is throttled back to match the casting rate in the mold.
In an H-shaped tundish, separate hydraulics allow two ladles to be poured into the tundish simultaneously, and the teeming rates of the old and new heat are matched to equal the output rate of the caster strand, such that the tundish level will remain constant. Published results on interstitial free and drawn-and-ironed grades cast on such a tundish suggest that the quality of the ladle exchange portion is comparable to that cast under steady-state conditions in the middle of a ladle.
Another advantage of the H-shaped tundish is the elimination of thermal events associated with heat losses through the tundish walls, as can be induced by large tundish level fluctuations.
