Abstract
In the practical blast furnace operation, a tap hole mix injected into the tap hole encounters with pig iron and
slag under an elevated temperature and high blowing pressure which reaches 400kPa utmost. This suggests that
the change given to the tap hole mix could never be a mere thermal or physical one.
In order to investigate the tap hole mix structural change, the microscopic observations were made on the
refractory specimens wrapping a pig iron particle and a slag pellet inside, whole of which were heated up at
1500℃. In addition, the tap hole mixes with slag pellets inside were heated at 1500℃ under the load of 200kPa.
In case the tap hole mix contained the oxides in its matrix, molten slag penetrated into pores by capillary force,
resulting in tap hole mix dissolving into slag phase. In case the tap hole mix matrix consisted of only non-oxides,
on the contrary, the slag components did not penetrate by capillary force. Under the load, the molten slag penetrated into much finer pores, broadening the interface boundary between slag and refractory. Then, tap hole mix solution and the liquid phase formation in microstructure were promoted.
The obtained results suggest the refractory microstructure complexity, which affects the tap hole mix performances.
