Collapse and peeling frequently occurred on the surface of alumina-base permanent lining castable of T type bloom tundish in China Steel No. 1 plant, especially in the corner portion near impact pool, therefore, refractory cost increases due to a worse performance, 200 casts on an average, and repairing maintenance for refractory. A study of damage mechanism and improvement for castable was carried out in terms of analysis of crack pattern, monitoring of temperature variation of castable surface during operation, and measurement of thermal shock parameters. The results indicate thermal stress, that was mainly caused by a dramatic dropping in temperature of castable surface after a sudden gas shutting off in the last stage of drying and by pouring water into tundish after casting, induced tortoiseshell cracks and resulted in severe spalling and crack damage. Castable that possesses higher Rst value and stable volume change will promote better service performance than an ordinary one. In addition, crack damage in corner area was improved by installation of castable adding steel fiber to increase the property of thermal shock resistance.
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