Steelmaking. Improvement of CC Tundish Recycle Operation in Hot Condition.

In recent years, the diversification in steel grades and smaller lot in weight is strongly desired among customers. Those results in the decrease of sequential casting ratio, and the refractory cost of tundish raises. To solve this problem, tundish recycle operation in hot condition was developed in Chita Plant, Daido Steel Co. Moreover several improvements are applied to TDR operation to extend TD life. They are summarized as follows: (1) The immersion nozzle quick exchange operation and the slide valve quick exchange operation have been developed in order to avoid the problem of refractory life such as immersion nozzle and slide valve. (2) The improvement of stopper tip refractory makes it possible to decrease the failure in not only stopping molten steel at the end of cast but also the break of stopper tip at the beginning of cast. As the result, we succeeded in the extension of the TDR operation and the TD refractory cost is decreased to 40% of that without TDR operation.