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With the demand for longer casting sequences and cleaner hydrogen free steels, new spray on working linings are being developed for tundishes which offer rapid automated application, improved metallurgical benefits and longer life.
During the past six years, the method of installing refractory working linings in continuous casting tundishes has seen a dramatic change from the preformed board system to a monolithic sprayed lining.
Since the early 1970s, there has been a spectacular growth in continuous casting on a worldwide basis. The level of growth is shown in Fig 1 and amounts to some 422Mt worldwide and 15Mt within the UK during 1989.
REFRACTORY LININGS - PAST AND PRESENT
In tandem with the rapid growth in continuous casting there has been a progressive development in tundish design, both from a size and geometry point of view, and in the refractories used as lining materials.
At concept, the tundish was a simple refractory lined box designed for the discharge of steel through one or more nozzles into the moulds of the continuous caster. Workers in the field of continuous casting soon realised that the capacity and geometry of the tundish could influence the stability and rate of flow of metal into the mould, and significantly contribute to cleaner steel practice. The continuing trend therefore is towards deeper and larger capacity tundishes designed to give maximum steel residence time, to give slag and inclusions the opportunity to float out before being carried into the caster mould.
Unlike the small early tundishes of some 5-10 tonne capacity, present day tundishes, particularly for slab or bloom casting, can hold steel weights in the range of 65 tonnes.
Early tundishes were lined with refractories freely available at the time within the steelworks - these being generally firebrick. It is not difficult to realise the damage and high repair cost attributable to the deskulHng operation when very often the whole lining would be lost, resulting in a reline for every use of the tundish.
A change of brick quality to alumina and then basic did little to reduce the damage and it was not until parting compounds were applied directly to the brickwork that the deskulling operation became easier, leading to less damage of what was now becoming a more...