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.

TAKAMICHI IIDA, RODERICK GUTHRIE, MIHAIELA ISAC, and NAGENDRA TRIPATHI Recently, the authors presented two models for accurate predictions of the viscosity for pure liquid metals. In this article, the authors checked the models against the viscosities of various liquid high-melting-point metals. These two models give very good agreement with experiment. Using these two models, the viscosities of liquid transition and Group IIA metals were predicted for dysprosium, erbium, molybdenum, neodymium, platinum, scandium, vanadium, yttrium, barium, and strontium. Finally, recommended data were collected for the experimental viscosities of pure liquid metals.

By combining the modified Stokes-Einstein formula with the authors' model for the melting-point viscosity, the authors present a model for accurate predictions of self-diffusivity of liquid metallic elements. The model is expressed in terms of well-known physical quantities and has been applied to various liquid metallic elements for which experimental data are available. The results of calculations show that agreement with experimental data is excellent; the uncertainties in the calculations of the self-diffusivities in various liquid metallic elements are equal to the uncertainties associated with experimental measurements. Also, the authors propose an expression for the temperature dependence of self-diffusivity in liquid metallic elements in terms of melting-point temperature. Using the model, self-diffusivity data are predicted for liquid iron, cobalt, nickel, titanium, aluminum, magnesium, silicon, and so forth.

A chemical characterisation of the non-metallic inclusions in the aluminium killed tool steels during the casting process has been performed. The steel samples taken during the mould fillings, after casting and from the final products have been studied. The chemical compositions of the different phases in the inclusions have been analysed using SEM/EDX. Three types of inclusions, namely, type 6 (spinel surrounded by the calcium-aluminate oxide solution), type 7 (calcium-aluminate oxide solution) and type 9 (alumina based inclusions) have been found in the steel samples during the mould filling. Type 9 inclusions originate from the erosion of the nozzles and the closing gates during the mould fillings. The steel samples after casting contain four types of inclusions namely, types 6, 7, 9, 10 (alumina-silicate oxide solution) and 11 (spinel phase with calcium sulphide). The types of inclusions vary with the position in the ingot. In the steel samples from the final products three types of inclusions were detected, namely types 6, 7 and 11. The investigation have revealed that the increase in the sulphur activity of the steel melt during the casting is the cause of the formation of oxide sulphide and calcium sulphide phases in the inclusions detected after casting and in the final products.

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.