During the current research and development activities at Tata Steel Teesside Technology Centre, UK, the inclined plane test (IPT) is adopted as a quick method to measure the viscosity/ fluidity of mould powders being used currently for continuous casting of different steel qualities and section sizes. The usefulness of the IPT method was also validated by comparing the viscosities that were measured by a high temperature viscometer. It has been established that the IPT measured viscosity values are comparable with the mould powder supplier's data. The IPT ribbon lengths of different powders have been correlated with the viscosities using an Arrhenius type relationship. The ribbon lengths of the solidified fluxes were found to have a good correlation with the molar ratios of the corresponding powders. Hence, the relationship was further tuned to develop a viscosity prediction model using the chemical compositions of the mould fluxes (i.e. the model can be used for a quick assessment of mould flux viscosity based on its chemical composition).

Various physiochemical properties of mould powders, such as viscosity and break point, are found to be related to chemical composition through molar ratios, such as number of non-bridging oxygen per tetrahedrally coordinated atom and oxygen to silicon. A number of relationships have been developed between physical properties and molar ratios, and a mathematical model has been developed using the relationships to develop a quick method for analysing the suitability of the mould powder for continuous casting. The method can predict viscosity within a range of temperatures, break temperature, and the effect of inclusion pick-up on the mould powder viscosity. A Microsoft Office Excel interface has been developed to display the results, including the viscosity versus temperature curve and the effect of alumina pick-up. The model output results have been validated using a high temperature viscometer.

Maintenance of adequate permeability in the lower zone of a blast furnace is crucial for stable and efficient furnace operation. Permeability in the lower zone is influenced by the changing levels of hot metal and slag in addition to other operational factors. Thus, accumulation of liquids in the hearth and inadequate drainage will lead to deterioration in permeability, thereby limiting wind acceptance and furnace productivity. Therefore, the knowledge of the liquid level in the hearth and factors influencing drainage would be helpful for ensuring high permeability. Effort has been made in the present study to analyse the effect on liquid level of casting parameters such as casting rate (CR), production rate, gun up to knock out time (GKT), slag delay, cast duration (CD) and number of casts (NC). The relationships between casting parameters, liquid level and permeability resistance in the lower zone have been derived mathematically based on material balance. From known casting parameters, the liquid levels have been estimated. The prediction of liquid levels by the model was in good agreement with the furnace data on permeability resistance. In order to maintain high permeability in the lower zone, the optimum values of GKT, NC and CR for different production rates have been suggested to the plant. List of symbolsA Area of hearth, m 2 CD Cast duration, min CP Casting to production ratio CR Casting rate, t min 21 GKT Gun up to knock out time, min H 1 Height of metal and slag when tap hole is closed, m H 2 Height of metal and slag during iron only flow, m H 3 Height of hot metal and slag during iron and slag casting, m H i Height of metal when tap hole is closed, m H s Height of slag when tap hole is closed, m K_Low Permeability resistance in the lower part of the furnace NC Number of casts P Hot metal production, thm day 21 P m Production rate of metal, t min 21 P s Production rate of slag, t min 21 Q m Casting rate of metal, t min 21 Q s Casting rate of slag, t min 21 S Slag rate, kg thm 21 t m Duration of iron only flow, mint ms Duration of combined iron and slag flow, min V s Ascending velocity of slag level, m h 21 r m Density of liquid metal, t m 23 r s Density of slag, t m 23 e Porosity of dead man (0.33) ß

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