Interaction Steel/Slag/Submerged Entry Nozzle and its Impact on Refractory Wear – Thermochemical Process Simulation

Abstract

This work presents the generation and application of a process model which aims to increase the understanding of submerged entry nozzle (SEN) wear during continuous casting and its dependence on steel and slag compositions. An effective equilibrium reaction zone model was built and applied to calculate the equilibrium compositions of steel and slag at their common interface and in contact with the SEN. The results allow the estimation of the interface tension gradient responsible for Marangoni convection. Further, they include redox reactions at the slag/steel/refractory interface. Calculations were performed for a LC and a TRIP steel grade together with their respective mold fluxes. In both cases, the same SEN was used and the wear was assessed after service. In the case of the TRIP steel, the SEN showed by far lower wear and a less pronounced corrosion groove. The simulation showed that the interface tension difference responsible for Marangoni convection will be rather negligible for the case of TRIP steel, but it amounts to 150 mN/m for LC steel. Moreover, removal of carbon from the SEN zirconia-graphite sleeve will be caused by the reduction of silica in the slag. This is only possible at the three-phase boundary where the activity of the silicon formed is lowered by dissolution in the steel. Also, this effect is by far more distinct for LC steel and is in agreement with the different wear rate and corrosion groove. As a spin-off, the calculated interface tension might be interesting with respect to possible slag intrusion.

Microstructure, properties, and application of low carbon Al2O3‐C refractories used as submerged entry nozzles

“…Annular corrosion grooves can be clearly observed at the slag line for both refractories, indicating strong interaction between the refractory and slag during casting. 13 Kumar et al 34 also found that the corrosion depth of casting mould flux and the dissolution of alumina increased with graphite content in the refractory. However, these two values were only 7.8 and 10.0 mm, respectively, for the low coarse cracks, or bends), confirming the active roles of graphite and SiC whiskers in high-temperature mechanical strength and thermal shock resistance.…”

“…Figure 8 shows the photographs of the longitudinal sections of the two SENs after working for 8 hours. 13 was detected at the interface, indicating that the indirect oxidation of graphite also occurred by reducing Fe 2 O 3 . The maximum depth of the corrosion groove on the left and right side of the traditional Al 2 O 3 -C refractory were 13.6 and 11.0 mm, respectively.…”

“…7 However, the decrease in carbon content usually leads to a dramatic reduction of the resistance to both thermal shock and slag corrosion. 13 This damage tends to be more severe, since the development of continuous casting is moving towards higher casting speeds and lower viscosity fluxes. 10 The in situ formation of nano carbon fibers and/or nano ceramic whiskers was found to have similar advantages as those obtained by the direct incorporation of nanoscale additives.…”

Application of Non-Arrhenius Models to the Viscosity of Mold Flux

“…Viscosity is one of the most important properties of mold flux as it determines the powder consumption and therefore the lubrication of the shell; [1,2] it also affects the formation of the slag rim in the vicinity of the meniscus, [3] the slag entrapment, [4] as well as the erosion of the nozzle. [5] Early models for predicting the viscosity of mold flux were developed by using viscosity measurements that spanned relatively small ranges of temperature and viscosity. The data, derived from these restricted ranges of experimental conditions, were generally linear in reciprocal of temperatures; thus, the early models follow Arrhenius formulation strictly.…”

“…[5] Early models for predicting the viscosity of mold flux were developed by using viscosity measurements that spanned relatively small ranges of temperature and viscosity. The data, derived from these restricted ranges of experimental conditions, were generally linear in reciprocal of temperatures; thus, the early models follow Arrhenius formulation strictly.…”