Viscosity measurements of some mould flux slags

Continuous casting has been the dominating process for steel casting over the past decades. During the process, mould fluxes are added to enable a smooth functioning of the process, enabling better process performance and products with less defects. The viscosity of the mould flux slag is a key parameter determining the optimum casting conditions. Several experimental studies have earlier been carried out in order to determine viscosity data for mould flux slags, both industrial ones as well as synthetic slags with compositions close to industrial mould fluxes. However, the continuous evolving of new steel grades, casting dimensions and product quality in the steel industry also demands better control and development of the mould fluxes. In industrial practice for clean steel production, the Al2O3 pick up has generally been observed to be about 2-4 %. In view of this, the present study was initiated to experimentally investigate the viscosity of mould fluxes used in Swedish steel industry and the effect of dissolution of alumina in the same. The industrial implications of the slag viscosities measured in the present work are discussed. Viscosities of mould fluxes for continuous casting in steel production have been measured by the rotating cylinder method. Seven industrial mould fluxes, with different compositions, used were included in the study. The effect of the Al2O3 content in the mould fluxes was also investigated. Even relatively small additions of Al2O3 show a significant increase in viscosity. The measurements were carried out in the temperature range of 1 373 to 1 673 K.