The Wear of Tundish Stopper Refractories by Inclusion Slags

Abstract

Liquid inclusions in the steel may play an important role in the wear of the stopper tip refractories in tundish operations. In the present study, the attack and wear of the tundish stopper refractories by inclusion slags in OneSteel Whyalla billet product have been investigated.
Three stopper tip refractories, Al₂O₃-C, ZrO₂-C and MgO-C, have been tested with inclusion slags (SiO₂-Al₂O₃-CaO-MnO-FeO) under argon at 1570-1610°C for 1-4h using an in-situ gravimetric technique. The in-situ gravimetric data, combined with autopsy of the samples after the tests, provide valuable insights into the dynamic processes of the slag-refractory interactions and the mechanisms for refractory wear.
It was found that the performance of the three refractories differed considerably and was determined predominantly by the resistance to the chemical attack by the liquid inclusions and the extent of internal carbon-oxide reactions. The FeO in the inclusion had a detrimental effect on the oxidation of carbon in the refractory, causing vigorous reaction and severe wear. The MnO in the slag also reacted with carbon, but to a much lesser extent, while severe wear only occurred when slag attacked the refractory grains. The weight loss, due to internal carbon-oxide reactions, appeared to be an important issue.
Of the refractories tested, the MgO-C performed the worst, suffering from severe inclusion attack on both the carbon and the periclase grains, and considerable weight loss due to internal carbon reaction. The ZrO₂-C showed a reasonable resistance to the chemical attack from the inclusion, with MnO up to 33 wt%; but showed extensive weight loss due to internal carbon reaction. The Al₂O₃-C was the best performer in terms of resistance to both the inclusion attack and internal carbon reaction. The results were found to be in broad agreement with plant experience and observations.