We began development of swirling-flow submerged entry nozzles in 1997 as a fundamental and effective measure for controlling the flow pattern in continuous casting molds. As a first step, we developed a swirling-flow submerged entry nozzle for round billet casting at the Wakayama works. We then began developing swirling-flow submerged entry nozzles for slab casting. The main purpose of the present work was to demonstrate that the formation of swirling flow in submerged entry nozzle improves productivity and the quality of products in continuous casting. We examined swirling-flow submerged entry nozzles with a swirl blade in these main bodies because such an arrangement is the easiest way to apply swirling flow to submerged entry nozzles in continuous casters without investment by facilities. We had only to change the submerged entry nozzle in the experiment. Swirling-flow submerged entry nozzles for slab casting were developed and their operation examined at the Wakayama and Kashima works. It was found that the proposed submerged entry nozzles increased the casting speed and improved the surface quality of slabs and steel sheets.

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Fluorine-free mould flux has been required to reduce corrosion of continuous casters. In this paper, Na2Ca2Si3O9 has been applied to an alternative crystalline phase of Ca4Si2O7F2 (cuspidine) that crystallized in commercial flux films. Effects of basicity described as T.CaO/SiO2 and additions of Li2O, Na2O, MgO and/or MnO into Na2Ca2Si3O9 composition mould flux on viscosity and solidification temperature were studied and the solidified specimens were examined by X-ray diffraction to identified crystalline phases.The viscosity of the mould flux is reduced with increaing of the basicity or the basic components contents. The solidification temperature decreased slightly as the basicity increased from 0.47 to 0.60, whereas it increased steeply with increasing of the basicity from 0.60 to 0.70. The solidification temperature also steeply increased when large amounts of these basic components were added. With increasing of the basic components amounts, the first peak intensity of the target phase, Na2Ca2Si3O9, decreased while that of Na2Ca2Si2O7, which had higher melting point than the target phase, increased. It is indicated that the solidification temperature is related to Na2Ca2Si2O7 crystallization.Carbon steel was cast with one of the developed fluorin-free mould fluxes and slab without any surface cracking was obtained.

The effects of interfacial properties such as interfacial tension and wettability on the adhesion, agglomeration, and coalescence of inclusions on the immersion nozzle in a continuous casting process have not yet been evaluated quantitatively. In the present work, we focused on the neck growth of alumina balls at sintering because the adhesion, agglomeration, and coalescence of inclusions are regarded as being the consequence of sintering of oxides. We compared the neck growth of alumina balls at sintering in molten iron with that under an Ar gas atmosphere in order to clarify the effects of interfacial properties between alumina balls and molten iron on the sintering of alumina balls in molten iron. We found that neck growth in molten iron proceeds much faster than that under an Ar gas atmosphere. In addition, an equation for the neck growth of alumina balls in molten iron was formulated by evaluating the interfacial properties, i.e., the interfacial tension and wettability, between alumina balls and molten iron. The calculated results derived by considering the capillary phenomena of molten iron at the gap between alumina balls as the effect of wettability were in reasonable agreement with the experimental results in molten iron. These findings show that the non-wetting by molten iron of alumina balls promotes neck growth of alumina balls at sintering in molten iron.