Pilot plant study of clogging rates in low carbon and stainless steel grades

Abstract

In the present paper, the clogging tendency of aluminium or silicon killed low carbon and stainless steel grades has been investigated using pilot scale equipment. Steel was melted and deoxidised in a 600 Hz induction furnace, then teemed through a temperature controlled nozzle into a mould situated on a scale measuring the teemed mass. The steel and nozzle temperatures could be adjusted within ±1°C. It was found that the clogging rate, when teeming through a hot nozzle, increased with an increasing amount of alumina phase present in the steel melt. This, in combination with composition analysis and a detailed crystallographic investigation using electron backscatter diffraction, suggested that the clogging was created by deoxidation products from the steel melt. Furthermore, it was found that the freezing effect onto the nozzle wall when teeming non‐clogging steel through a cold nozzle was of the same order of magnitude as the clogging rate of the aluminium killed steels teemed through a hot nozzle. Successful trials were also performed where the nozzle accretion during teeming was eliminated by the addition of negative oxygen interacting elements such as aluminium or silicon to the melt. A theoretical assessment based on a mass balance and thermodynamic equilibrium predicted that the removal efficiency increased with a decreased total oxygen content of the steel melt.