Sulfide capacities of iron-oxide containing slags in the "FeO"-Al 2 O 3 -SiO 2 , "FeO"-CaO-SiO 2 , "FeO"-MgO-SiO 2 , and "FeO"-MnO-SiO 2 systems were experimentally determined using gas-slag equilibration technique. The experiments were conducted in a temperature range of 1673 to 1923 K. The experimental data were employed to optimize the model parameters of a sulfide capacity model developed earlier in the present laboratory. Based on these parameters, along with those obtained in previous works, an equation was suggested to predict the sulfide capacities of the "FeO"-Al 2 O 3 -CaO-MgO-MnO-SiO 2 slags. The results of model predictions show reasonable agreement with the experimental values of the six-component slags determined as a part of this work.

It was found in the samples taken at and below the slag line that a slag infiltrated layer was covered by an outer layer containing many MgO 'islands' of various sizes. The microstructure of the infiltrating slag was the same as the matrix of the outer layer. The slag was found to decompose into the compound 3CaO.Al 2 O 3 and a liquid phase during the cooling process. The former phase along with tiny MgO particles from the ladle glaze was found to be one of the major sources of inclusions during the degassing and flotation periods of ladle treatment. Thermodynamic analysis indicated that the reaction between the ladle glaze and the slag from the electric arc furnace resulted in the formation of MgO-Al 2 O 3 spinel and an oxide solution, which were also the main inclusions found at the initial stages of ladle treatment. Evidence of this reaction was found in the lining samples taken above the slag line.

These collisions and agglomerations have also been subjected to mathematical modelling. Nevertheless, the Industrial data were analysed to shed some light on development of process models and their optimisation with the formation and growth of non-metallic inclusions regard to inclusion engineering necessitate a deeper underduring the ladle treatment of a particular grade of standing of the behaviours of inclusions during the entire tool steel, Orvar Supreme (Fe-0•39C-1•0Si-0•4Mncourse of the process. Indeed, the results of laboratory studies 5•2Cr-1•0Mo-0•9V). Seven types of inclusions were cannot be incorporated into a process model unless the detected in samples taken along the processing mechanisms of formation, growth, and separation of inclusions evolution of the steel. The types of inclusions in a steelmaking process are well understood. Moreover, present were found to vary with the various stages any meaningful modelling approach should also consider of that evolution. While additions of aluminium to the operation of these mechanisms under realistic industrial the steel bath were found to affect the composition conditions. of the inclusions, only a small number of pureThe present work is a preliminary study within a long alumina inclusions, agglomerated as clusters, were term project to design a comprehensive process model of ladle observed during the initial stages of deoxidation.treatment. It aims to understand the behaviours of inclusions Ladle glaze was found to be the major source of the along the history of the ladle process at Uddeholm Tooling inclusions. Most of those left in the steel before AB in Hagfors, Sweden. Industrial data are analysed from tapping were found to be of very small size and to a thermodynamic point of view. To discuss the results, the contain high concentrations of Al 2 O 3 and CaO and inclusions are classi ed into several types with respect to relatively minor ones of MgO and FeO.I&S/1671 size, chemistry, and morphology.

An experimental study was carried out at Uddeholm Tooling, Hagfors, Sweden to examine the impact of ladle glaze on the formation of non-metallic inclusions during the ladle treatment process. Steel samples were taken at various stages of the process and from ladles of different ages. Inclusion numbers were counted under an optical microscope. It was found that the total number of inclusions increased with the ladle age before deoxidation and at the end of the ladle treatment. The increase was substantial after the ladle had been used more than 18 times. Inclusions having the smallest sizes were found to make a large contribution to this increase. This observation was further confirmed by the difference between total oxygen content and dissolved oxygen content in the steel samples, which also showed an increase with ladle age. Analysis by SEM-EDX revealed two types of inclusions before casting, namely, inclusions consisting only of an oxide solution having a composition very close to 3CaO.Al 2 O 3 , and inclusions consisting of the same oxide solution as well as MgO phase. This finding was in accordance with the reported result that both 3CaO.Al 2 O 3 and MgO were present in the slag infiltrated layer of the ladle glaze. It was concluded that ladle glaze is the foremost source of non-metallic inclusions in tool steel during ladle treatment.

Metallurgy,In the present work, a new modelling approach has been put forward to study slag-metal reactions. Su]phur refining in a gas-stirred ladle has been taken as

process in both the preparation of the samples containing CaO-CaF 2 -SiO 2 and the subsequent viscosity measurements. Firstly, the evaporation of CaF 2 in pure solid or dissolved form would take place according to the follow-

The behaviors of several types of inclusions at a high temperature were examined using a confocal scanning laser microscope (CSLM, 1LM21H/SVF17SP). Although alumina inclusions tended to impact on each other, agglomerate, and grow quickly, no other inclusion type, such as spinel as well as solid and liquid calcium aluminate, was observed to attract each other. The results of confocal microscope study were compared with the industrial investigation. For this purpose, many steel samples were taken at different stages of ladle treatment. The samples were analyzed by scanning and light optical microscopes. Approximately 50,000 inclusions of several types were examined. Only alumina inclusions were attracted to each other and agglomerate. No agglomeration by attractive behavior was observed in the other types of inclusions, including liquid inclusions. Both the industrial data and the in situ observation by CSLM indicate that, although the attraction force and the agglomeration play a significant role in the growth of alumina inclusions, the agglomeration of spinel and calcium aluminate inclusions does not need special consideration in ladle treatment. The agglomeration of liquid calcium aluminate inclusions took place only when they occasionally met as a result of external force, which led to low collision probability. However, the agglomeration of the liquid calcium aluminate inclusions along with alumina particles could be detrimental in the casting process.

Dissolution of different CaO samples into molten synthetic ‘FeO’‐SiO2 and ‘FeO’‐SiO2‐CaO slags was carried out in a closed tube furnace at 1873 K. The slag was kept stagnant. It was found that the dissolution rate was very fast when CaO rod was dipped into ‘FeO’‐SiO2 slag. In the case of ‘FeO’‐SiO2‐CaO slag, the dissolution of CaO rod in the stagnant slag was retarded after the initial period (2 minutes). Only less than 16 percent CaO reacted with the slag, irrespective of the type of lime. Three phase‐regions were identified in the reacted part of the lime rod by SEM‐EDS analysis. The formation of these regions was explained thermodynamically. A dense layer of 2CaO · SiO2 was found to be responsible for the total stop of the dissolution. It could be concluded that constant removal of the 2CaO · SiO2 layer would be of essence to obtain a high dissolution rate of lime. In this connection, it was found necessary to study the dissolution of lime in moving slag to reach a reliable conclusion regarding the relevance of the reactivity obtained by water ATSM test to the real reactivity of lime in high temperature slag.