A thermo-gravimetric technique was used to determine the hydrogen solubilities of some Al 2 O 3 -CaOMgO-SiO 2 quaternary slags. The focus of the work was to determine the water capacities in slags having lower SiO 2 concentrations, which were relevant to industrial practices. The majority of the experiments were carried out in the temperature interval 1747 to 1827 K with water pressure of 157 mbar. The reliability of the experiments was confirmed using a quenching technique. The temperature was found to have a negligible effect on the water solubilities. The composition of the slag did not seem to significantly affect the water capacity. However, as the slag composition approached CaO saturation, a considerable increase of the solubility was noticed.

Ladle treatment plays increasingly important role in making clean steels nowadays. In many industrial practices, synthetic ladle slags are based on the Al 2 O 3 -CaO-MgOSiO 2 quaternary system. Usually, the compositions of the slags are targeted on the single liquid region of the phase diagram. On the other hand, the phase diagram information of the Al 2 O 3 -CaO-MgO-SiO 2 quaternary involves considerable uncertainties. The available sections of the phase diagrams in this system in Slag Atlas 1) are after Osborn et al., 2,3) Gutt and Russel 4) as well as Cavalier and SandreoDendon.5) Unfortunately, many liquidus temperatures are given as dotted lines. Disagreements between the phase diagram and the reality have been found by both the present research laboratory and the steel industry.6) Since ladle refining is very often operated at temperatures between 1 823 K and 1 923 K, the present communication aims at a study of a number of slag compositions to examine whether these slags are single liquids or multiphase mixtures at 1 858 K.While the differential thermal analysis (DTA) is well established to determine the temperature of phase transformation, the measurements of the liquidus temperatures of slags using this technique are difficult because of the invariable supercooling of the slags. The exothermic peak associated with the solid separation at the liquidus temperature occurs at much lower temperatures. During the heating mode, the compositional inhomogenities would result in considerable uncertainties. Hence, a quenching technique was employed in the present studyThe Al 2 O 3 , CaO, MgO and SiO 2 oxide powders were calicined at 1 073 K for 24 h before being thoroughly mixed in an agate mortar. The oxide mixtures were pressed into small pellets of about 1.3 g and sealed in a glass bottle. The bottle was kept in a desiccator before the experiment.A horizontal furnace was employed for most of the experiments. The experimental setup is schematically shown in Fig. 1. The furnace had KANTHAL SUPER 1800 (molybdenum silicide) heating elements with a maximum working temperature of 1 973 K. The furnace having an even temperature zone of 40 mm was controlled with an accuracy of Ϯ3 K by a programmable EORUTHERM 2408 P4 regulator using a Pt-30%Rh/Pt-6%Rh thermocouple. The alumina reaction tube had the dimensions of 60 mm o.d. and 50 mm i.d. Platinum crucibles were used to hold the samples. The crucibles were carefully shaped to avoid creeping-out of the slag during the experiments. An alumina holder was used to support two crucibles along with the samples. In a typical run, the samples on the alumina holder were carefully introduced into the reaction chamber and placed in the even temperature zone. Argon gas was passed through the reaction tube at low flow rate. A constant argon flow was maintained through out the experiment. The samples were heated up to 1 858 K and kept there for more than 5 h. After equilibration of the samples, the sample holder was rapidly pulled out of the furnace. After a quick visual examination, ...

The focus of the present work was to develop a water capacity model for the quaternary slag system AI 203-CaO-MgO-Si02. In the model, a silicate melt was considered to consist of two ion groupings, viz. cation grouping and oxygen ion. The water capacity of a melt is supposed to depend on the interactions between the cations in the presence of oxygen ions. These interactions were determined on the basis of the experimentally measured water solubility data. Only binary interactions were employed in the model. For the system CaO-Si0 2, disagreement in the literature data was found. Since the interaction between Ca 2 + and Si 4 + would play an important role, experiments were carried out to determine the water capacities of some CaO-Si0 2 slags. For this purpose a thermogravimetric method was employed. Iso-lines of water capacities at constant MgO contents were predicted by the model and compared with the experimental data from literature. The model calculations agreed well with the experimental results.