Experimental determinations of the viscosities of some Al 2 O 3 -CaO-"FeO" ternary slags were carried out in the temperature range from 1550 to 1764 K using the rotation cylinder method. The measurements were conducted in the composition range from 36 to 48 mass pct Al 2 O 3 , 28 to 42 mass pct CaO, and 10 to 33 mass pct FeO. The viscosity was found to show a decreasing trend with the increase of FeO content. Based on the experimental data, the liquidus temperatures of the slags were evaluated using the second derivatives of the activation energies for viscous flow with respect to temperature. The evaluated liquidus temperatures were compared with the results of differential thermal analysis (DTA) on the same slag samples.
This study focused on slag‐foaming phenomena, the main emphasis being on slags used in the electric arc furnace (EAF) practice in the manufacture of stainless steel. Plant trials were carried out at Sandvik Steel for slags of high and low chromium content. The viscosity of the slags was predicted using a mathematical model for multi‐component slags developed at KTH, Stockholm. Next, the foaming characteristics were predicted using different relationships suggested in the literature. The predicted foaming behavior was then compared to estimations of foaming determined visually and acoustically by operators. Sound measurements were also carried out during the trials. In comparing foaming characteristics determined from sound measurements with the operator estimations, a relationship was found to exist between the two.
In a preliminary study 1) to determine the viscosities of some slags in the Al 2 O 3 -CaO-FeO system, the experimental results indicate the possibility of the existence of a ternary compound in this ternary. The present communication intends to report further experimental evidences regarding the existence of such a ternary compound using differential thermal analysis (DTA), scanning electron microscope examination (SEM) and X-ray diffraction technique.The phase diagram of the Al 2 O 3 -CaO-FeO (saturated with iron) ternary system recommended by Slag Atlas 2) is due to Wrampelmeyer et al. 3) This diagram is reproduced in Fig. 1 along with the phase diagrams of the three binary systems.2) The phase relationships proposed by Wrampelmeyer et al.3) do not seem to suggest the existence of any ternary compound in the temperature range close to 1 823 K. It was on the basis of this phase diagram, viscosity measurements in the present laboratory were planned.Attempts were made to carry out viscosity measurements in the composition range covering most of the liquid region. The eleven slag compositions studied are marked in Fig. 1. The compositions in mass percent are presented in Table 1.The viscosity measurements were carried out on a Brookfield digital viscometer (model RVDV-III) using rotating cylinder method. The oxygen partial pressures in the reaction chambers were followed by oxygen sensors during the whole course of the sample-preparation and viscosity measurement. An oxygen partial pressure of about 10 Ϫ10 atm was observed in both cases. The samples were prepared by mixing precalcined Al 2 O 3 and CaO with FeO synthesized 1) in appropriate proportions in a ball mill for 1 h. The samples were directly used in the case of DTA measurements. Reproducible results from DTA measurements could not be obtained in the case of the samples S6-S11, due probably to incomplete slag formation. For viscosity measurements, 200 g of the powder mixture was premelted in pure iron crucibles at a maximum temperature of 1 753 K. The premelting was carried out in purified argon atmosphere as described in the earlier work.1) The samples were furnace cooled after premelting and the estimated rate of cooling could approximately correspond to about 7 K down to 1 473 K.In the case of samples S6-S11, the samples were not fully molten when the above procedure was adopted. In order to reach higher temperatures, the above operations were carried out in molybdenum crucibles. In these cases, a number of experiments failed as the Mo crucibles became brittle during the pre-melting stage and ran out of the crucibles. In a few cases, the FeO in the slag was reduced and the slag composition was found to be altered. In view of these difficulties and uncertaninties, viscosity measurements as well as SEM analyses of these slag samples had to be abandoned.Detailed description of the experimental setup and procedure for the viscosity measurements has been given in an earlier publication.4) The use of iron crucible and spindle restricted the maximum temperat...
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