Du Sichen

Chemical characteristics of inclusions formed at various stages during the ladle treatment of steel

Abstract Industrial data were analysed to shed some light on the formation and growth of non-metallic inclusions during the ladle treatment of a particular grade of tool steel, Orvar Supreme (Fe-0·39C-1·0Si-0·4Mn- 5·2Cr-1·0Mo-0·9V). Seven types of inclusions were detected in samples taken along the processing evolution of the steel. The types of inclusions present were found to vary with the various stages of that evolution. While additions of aluminium to the steel bath were found to affect the composition of the inclusions, only a small number of pure alumina inclusions, agglomerated as clusters, were observed during the initial stages of deoxidation. Ladle glaze was found to be the major source of the inclusions. Most of those left in the steel before tapping were found to be of very small size and to contain high concentrations of Al2O3 and CaO and relatively minor ones of MgO and FeO.

Investigation of the kinetics of reduction of iron titanate (FeTiO3) by hydrogen

In the present study, the reduction kinetics of synthetic ilmenite by H 2 has been carried out using thermogravimetric technique. This has been complemented by X-ray diffraction and scanning electron microscopic (SEM) analyses. The morphology of the reduced product shows that iron metal is distributed around the titanium oxide particles, which has important implications for the separation of iron and titanium dioxide in the recovery of the same from ilmenite. The reduction proceeds very fast in the initial period and a high degree of reduction is obtained in the case of all reductions. A decrease in the reaction rate is observed at later stages of the reduction due to the slow diffusion process. An activation energy for the reduction of FeTiO 3 to iron and titanium dioxide was estimate to be of 108 kJ.mole -1 .

Sulphide Capacities of CaO-Al2O3 Slags in the Temperature Range 1773-1848 K.

The sulphide capacities of CaO-Al 2 O 3 binary slags of nine different compositions were experimentally determined at 1773 and 1848 K using the gas-slag equilibration method. From the results obtained, the sulphide capacities and the molar sulphide capacities have been calculated. The results are compared with data reported in the literature. Comparisons of the experimental C s values with values calculated on the basis of optical basicity concept are presented. The experimental molar sulphide capacities are correlated with Darkens excess stabilities for the system CaO-Al 2 O 3 . A theoretical model for prediction of the sulphide capacity developed in the Department of Theoretical Metallurgy has been used to describe the variation of C s as a function of temperature and composition, in the case of CaO-Al 2 O 3 slags.

Static and dynamic thermophysical property measurements at high temperatures

In view of the importance of generating reliable and self consistent thermophysical data, efforts have been made in the Division of Metallurgy, Royal Institute of Technology, Stockholm to measure the viscosities and thermal diffusivities of multicomponent slags as well as surface- and interfacial tensions. The measurements were also carried out in the dynamic mode to monitor high temperature reactions and understand the underlying mechanisms. In the latter case, the rate of dissolution of alumina in a slag as well as the rate of oxidation of Fe 2+ in a fayalite slag were followed by measuring the viscosities along the reaction coordinate. The reaction rate between liquid iron with different oxygen levels and alumina/silica substrates was studied by the sessile-drop method. The paper illustrates the usefulness of this approach in understanding high temperature phenomena.

An evaluation of the stabilities of the ternary compounds at low oxygen potentials in the ternary system Fe-Na-O

A clarification of the thermodynamic relationships in the ternary system Fe-Na-O at low oxygen potentials is presented. The Gibbs energy of the compound FeNa 4 0 3 was evaluated from the enthalpy data and the phase diagram information available in literature by using the thermodynamic calculation program in the Thermo-Calc Databank System. The phase diagram of the Fe-Na-O ternary system was calculated at 853 K. An oxygen-sodium potential phase diagram of this system computed at the same temperature is also presented. while the compound FeNa 2 0 2 has so far not been structurally identified. A study of the thermodynamics of the above compounds were done earlier /4/ in this laboratory, and from the results a phase stability diagram was drawn corresponding to 873 K, see Fig. 2. The following basic thermodynamic inconsistencies appear in this diagram: 1. The function of the partial pressures for the fourphase equilibrium, gas, Fe2Na204(s), FeNa403(s) and FeNa202(s) given in Table 6 in Dai et al. /4/, viz.

Abating environmentally harmful waste gases

A gas-purification method, based on the condensation of nitrogen, sulfur, and carbon-containing environmentally hazardous gases produced from industrial processes, is proposed in this article. The method, which utilizes the cooling capacity of waste nitrogen in the oxygen plant to condense the hazardous gases, is capable of removing hazardous impurities up to 99.98%. Theoretical calculations underlying the condensation process are presented employing gases produced in a blast furnace and coke oven in an integrated steel plant. The cooling power required for the condensation process is calculated using the waste nitrogen generated from an oxygen plant that generates captive oxygen for the steel plant. Design modifications that need to be made to the oxygen plant in order to utilize the cooling power of the waste nitrogen gas are also presented. As a case study, the advantages of the method are illustrated with purification of coke-oven gas. The economic impact and the investment aspects are also discussed.