Present era focuses to quality and cost competitiveness to each and every steel makers. The reason why the ingot-casting route has been replaced by continuous casting. High and higher is the sequence length, less and lesser is the cost. Any premature failure to tundish refractories terminates the casting and degrades steel quality. It is observed that steel makers face the problem of alumina build up on the bore wall of sub-merged nozzle. To achieve longer sequence length SEN/SES plays a vital role on tundish life. Clogging of nozzle due to alumina buildup brings a serious problem in casting often observed particularly in low carbon aluminium killed steel. Clogging takes place due to incomplete elimination of solid inclusions suspended in liquid steel. Alumina particles along with other non-metallic inclusions slowly & continuously started building up to inner wall initially. Once a thin coat gets adhere to the inner surface it accelerates the growth even against the ferro-static force of the steel. As a result the effective diameter of the bore reduces unevenly from inlet to exit end. It is more pronounced in two or four port nozzle design. This brings a disturbance of steel flow & causes unstable operation. Alumina particles of few micron size which have not been absorbed by ladle/tundish/mould slag hardly effects the steel quality but larger agglomerates adhere to nozzle peels off from the nozzle bore causes problem by bringing many defects in cast products. In this paper, the problem of alumina adhesion on the inner wall of sub-entry nozzle has been taken up for study with respect to defects noticed in cast products. Based on the investigation made on clogging material, a probable mechanism for its occurrence has been cited. A special type of carbon free anti-clogging composite mix is developed & its application method to the inner wall of the nozzle has been shown. The special characteristics of this material is to form a dense texture with very fine pore size distribution when it gets heat treated in reducing atmosphere. Fine dense texture of this material gives advantage to prevent the deposition of alumina and keeps the bore clean throughout the casting process. In addition to material development vis-à-vis a new approach is suggested on nozzle bore & port design. Developed anti-clogging material applied to the nozzle along with the new bore & port design initially tried in laboratory pilot furnace & subsequently tried successfully an integrated steel unit. Arecommended preheating schedule being followed throughout the trial to prevent choking of nozzle due to metal chilling. Trial details have been highlighted with conclusive findings, which provide a great benefit to steel makers.
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