Selection of refractories for elements of tundish at steel continuous casting

Abstract

Selection of design and material for the nuzzle of tundish to a great extent effects stability of steel continuous casting process at billet CCM in long series and quality of the CC billet. Results of study on selection refractory concrete for such important elements of tundish, as nuzzle and funnel for the nuzzle, which ensure “open” commencing of casting, presented. Physical and chemical requirements to refractory concrete for nuzzle presented, related to composition, porosity, compression ultimate strength and heat resistance. As the materials for nuzzle, three kinds of refractory mixtures based on electrocorundum with various relation of filler fraction composition were studied. Two samples of 70×70×70 mm were made of those mixtures by vibro-pressing method; both two were dried at 110 °С within 24 hours and next sintered at 1300 °С within 5 hours. As a result of ultimate strength and open porosity, shrinkage, thermal resistance, change of residual dimensions measuring, some mixtures were excluded from the further experiments. Rejection was made for mixtures, sample of which did not meet requirements on strength and number of thermal cycles. Experiments were also carried out with samples of 50×50×50 mm, made of composition, which showed best results of properties and made ofrefractories СМКРБТ and КС-95. Best results on all the properties were shown by the proposed concrete refractory: thermal resistance – by 24 and 43% higher comparing with СМКРБТ and КС-95 correspondently, ultimate strength after sintering – by 27.4 and 42.4% higher, porosity – by 24 and 40% lower. As the materials for start funnel, four mixtures were considered with various fraction compositions. The samples were tested at 1500 °С within 2 hours and then cooled in the furnace down to 150 °С. As a result of the experiment a mixture was determined, the samples of the concrete had lower shrinkage (0.3%) and higher strength (39.3 MPa). It was the only sample, which remained completely not fused. It was shown that selected fillers of the refractory concrete for the elements of tundish by their fraction composition and binding content meet the requirements for refractories for funnel and nuzzle of CCM tundish.