Abstract
Decarburisation of the submerged entry nozzles (SEN) during the preheating process was investigated based on plant trials and thermodynamic modelling at three different steel plants. During the trials the preheating processes were mapped, the temperature profiles were registered and post-mortem studies of the SENs with scanning electron microscopy were performed. Typically, the glass/silicon powder will form a dense and protective layer inside the SEN when heated over 1100°C. However, this study found that the temperature distribution inside the SEN did not always reach this critical temperature. Thus, decarburisation of the SEN was found at all steel plants. The overall results illustrate that the control of the preheating process needs to be improved at all steel plants. It is suggested that future research should be focused on the development of new coating materials to prevent decarburisation of the refractory base material, which would decrease the chances of clogging during casting.
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