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 setup was constructed to study the nucleation and growth of non‐metallic inclusions in liquid steel. The setup allows easy control of the atmosphere in the reaction chamber as well as fast and smooth movement of the sample. A liquid steel sample can be moved smoothly from the reaction chamber to the quenching zone of room temperature in 2 s. The rapid freezing of the sample enables the study of the formation, growth and distribution of the inclusions. A preliminary study on the homogeneous nucleation of alumina was carried out. Experimental evidence of homogeneous nucleation in the region of aluminium supersaturation was found in the sample quenched 5 s after aluminium addition. Fast agglomeration was also observed. In all the samples quenched 15 s or longer after the aluminium addition, agglomerated alumina clusters were found.

In order to gain an insight into the mixing behaviour of slag and metal under different stirring conditions, samples of slag/metal interface were collected from an industrial 65 ton ladle furnace using a new sampling technique. Different stirring conditions and sampling positions in the ladle were chosen. Complementary cold model experiments were also performed. The experimental results strongly suggested that the shear force between the two liquids played an important role in slag-metal mixing. Evidence for the existence of slag droplets each surrounded by a very thin metal film was found in the samples taken under both gas stirred and induction stirred conditions. This observation strongly suggested that slag-metal system behaved similarly as oil-water system, wherein, the shear force owing to the bulk flow led to a packed 'sphere bed' of oil droplets each coated by a thin water film above the water bath. On the basis of the experimental results, preliminary mathematical models were developed to describe the rate of mass exchange at the slag/metal interface.

The present study was carried out to investigate the impact of slag-refractory lining reactions on the formation of inclusions during ladle treatment of steel. The experiments were conducted on an industrial scale in the ladle at Uddeholm Tooling AB in Hagfors, Sweden. The inclusion chemistry and population during ladle treatment were studied along with the composition of the ladle glaze, taken from the ladle lining. The inclusions in the steel were classified into four groups according to the Swedish standard SS 111116. SEM/EDS analyses were carried out to identify the phases present in both the inclusions and the ladle glaze. The number of inclusions in the steel before deoxidation was found to increase with the ladle age, i.e. the number of times the ladle had been in use. A similar increase was also found after vacuum degassing and before casting. A great portion of inclusions before casting was found to be supplied by ladle glaze. This observation was further confirmed and explained by thermodynamic analysis. The present results show that ladle glaze is a major source of inclusions in the ladle at Uddeholm Tooling.