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Slag Film Formation
Compositions of the traditional high-basicity mold flux (TB, based on current industrial practice) and the ultrahigh-basicity mold flux (HB) used in this work are summarized in Table 1. Fluxes were prepared using analytical reagents (CaF2, CaCO3, SiO2, Na2CO3, Li2CO3, MgO, and Al2O3). To obtain solid slag films, 300 g of slag sample was placed in a graphite crucible with 60 mm inner diameter and melted at 1400 °C in a resistance furnace. The slag film was solidified on a
Table 1 Composition of mold fluxes (wt%)
Fig. 1 The direction and position of surface roughness measurements a and the positions of thickness measurements b of slag films recovered from the wide face of the water-cooled probe
water-cooled copper probe (water flow rate: 1.7L/min) with a smaller size (Width 20 mm x Height 15 mm x Thickness 6.35 mm) and larger width-thick ratio than previously used probes [10, 11]. To reveal the solidification process of films, different probe immersion times (15, 30, 45, and 60 s) were used.
Slag Film Analysis
The surface roughness (of the surface which had been in contact with the probe) was measured with a contact profilometer and the film thickness was measured with a point micrometer, using six measurements of each for every film. The specific positions of the measurements are shown in Fig. 1. The internal structure of the film was inspected by optical and scanning electron microscopy (SEM) after mounting samples in resin, polishing and sputter coating with 2 nm of platinum for SEM. The overall closed porosity of film was measured by the density difference between solid films and films pulverized to an average powder particle size smaller than 45 im. The density of solid and pulverized films was measured by an Ultrapycnometer 1000.
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