Tundish Design & Refractory Lining

Between the ladle and the mould sits a refractory-lined bathtub holding 20–80 tonnes of liquid steel: the tundish. Its original, humble purpose was hydraulic — a buffer that keeps steel flowing to the mould at constant head while 150–300 tonne ladles are swapped above it, making sequence casting (many ladles cast as one continuous strand) possible at all, and a distributor that splits one ladle stream among the two, four, six, or eight strands of billet and bloom machines.

Modern practice loaded a third duty onto the vessel: the tundish is the last chance to clean the steel. Every inclusion that survives the tundish is in the product; every reoxidation event inside it creates inclusions with no downstream remedy except the mould's mercy. From the 1980s onward "tundish metallurgy" became a discipline in its own right — flow engineered for inclusion flotation, linings chosen not to contaminate, streams shrouded against air, slag covers built to absorb what floats out. A well-run tundish removes a substantial fraction of the inclusions that enter it; a badly run one is a generator, undoing the ladle furnace's expensive work in the final ninety seconds before solidification.

Design follows the three duties in tension. Buffer wants volume; distributor wants symmetry; refiner wants long, quiet, surface-directed flow. Every tundish — delta, T, V, or boat-shaped — is a compromise among them, and the furniture inside it exists to bend the compromise toward cleanliness.