Kenneth S. Coley

Simultaneous reduction and carburization of ilmenite

Western Australian ilmenite was reduced using “Collie” coal at temperatures in the range 1587 to 1790 K to form carbon-saturated iron and titanium oxycarbide. The oxycarbide phase formed from Ti3O5 at temperatures below 1686 K and from Ti2O3 at temperatures above 1686 K. At 1686 K, both mechanisms occurred. The reaction rate was controlled by oxidation of carbon by carbon dioxide generated by reduction of the oxide phase. The final product at temperatures up to 1686 K was a fine dispersion of titanium oxycarbide in iron. At 1790 K, the reducing oxide tended to remain intact and formed a coarser distribution. In general, manganese impurities from the ilmenite were confined to the iron phase in the product, although some of the coarser oxycarbide particles formed at 1790 K contained trapped manganese at the internal pores.

RESIDENCE TIME OF METAL DROPLETS IN SLAG-METAL-GAS EMULSIONS THROUGH TOP GAS BLOWING

Abstract A mathematical model for evaluating the residence time of metal droplets in slag-metal-gas emulsions through top gas blowing is proposed. The model is based on the equation of accelerated moving bodies in a moving fluid. The parameters used in the model are based on the available data from both room and high temperature experiments. Using the proposed model provides a formal way to extend the experimental results of the residence time of the droplets for an evaluation of the conditions in an industrial furnace. This connects theoretical understanding, experimental results and plant data in to a coherent and quantitative model of the process. On propose un modèle mathématique pour évaluer le temps de séjour de gouttelettes de métal dans des émulsions de scorie–métal–gaz par soufflage de gaz vers le haut. Le modèle est basé sur l’équation des corps accélérés en mouvement dans un fluide en mouvement. Les paramètres utilisés dans le modèle sont basés sur les données disponibles provenant tant d’expériences à la température de la pièce qu’à hautes températures. Utilisant le modèle proposé fournit une manière formelle d’étendre les résultats expérimentaux du temps de séjour des gouttelettes à une évaluation des conditions dans un four industriel. Ceci rattache la compréhension théorique, les résultats expérimentaux et les données de l’usine en un modèle cohérent et quantitatif du procédé.

Analysis of interfacial area changes during spontaneous emulsification of metal droplets in slag

In some metal/slag reactions involving spontaneous emulsification, there is a significant increase of interfacial area, which in turn affects the global rate. In previous work by the authors, the reaction between Fe-Al alloy droplets and CaO-SiO2-Al2O3 slag was investigated. Re-evaluation of the data has shown that at an initial reaction rate above 9 × 10−7 mol min−1 mm−2, the maximum change in interfacial area increases linearly with the initial rate and with the change of free energy due to chemical reaction. There were found to be two sources of interfacial area increase: (a) flattening of the original droplet, which was independent of initial rate; and (b) separation of smaller droplets, which was dependent on the initial rate.

Hot-corrosion of silicon carbide in combustion gases at temperatures above the dew point of salts

Abstract To evaluate the performance of SiC to operating environments expected in future ceramic gas turbines, SiC samples were exposed in a low velocity burner rig at temperatures above the dew point of sodium sulphate (Na 2 SO 4 ). Under these conditions, the corrosion behaviour should be independent of the sulphur content of the fuel, if Na 2 SO 4(g) is not involved in the corrosion process. At 1000°C, SiC degradation was dependent on the sulphur levels in the fuel and the rates were controlled by the properties of the glassy corrosion products. Although there was an effect of P SO 3 on a Na 2 O at 1300°C, the formation of an inner crystalline silica layer protected the material in both combustion gases so that the effect of p SO 3 on corrosion was concealed. These results indicate that Na 2 SO 4(g) is involved in the corrosion process at temperatures above the dew point, contrary to what might be predicted from thermodynamic considerations. The role of sodium on enhancing the rate of corrosion is discussed.

On the stability of amorphous silica coatings for high-temperature service☆

Abstract Amorphous silica coatings significantly improve the resistance of Incoloy 800H to attack in aggressive atmospheres at temperatures up to 1000 °C. Eventually, however, failure occurs due to crystallisation of the silica and solid-solid interactions between the coating and substrate. Crystalline silica nucleated beneath a layer of alloy, which had been depleted in chromium on forming a pre-coating oxide layer. Due to the difference in chemical stability of amorphous and crystalline silica, silicon and oxygen diffused through the depleted alloy layer resulting in migration of this alloy layer towards the coating surface. Diffusion calculations suggest migration rates that are reasonably consistent with those observed experimentally.

Agglomeration of Non-metallic Inclusions at Steel/Ar Interface: In-Situ Observation Experiments and Model Validation

Better understanding of agglomeration behavior of nonmetallic inclusions in the steelmaking process is important to control the cleanliness of the steel. In this work, a revision on the Paunov simplified model has been made according to the original Kralchevsky–Paunov model. Thus, this model has been applied to quantitatively calculate the attractive capillary force on inclusions agglomerating at the liquid steel/gas interface. Moreover, the agglomeration behavior of Al2O3 inclusions at a low carbon steel/Ar interface has been observed in situ by high-temperature confocal laser scanning microscopy (CLSM). The velocity and acceleration of inclusions and attractive forces between Al2O3 inclusions of various sizes were calculated based on the CLSM video. The results calculated using the revised model offered a reasonable fit with the present experimental data for different inclusion sizes. Moreover, a quantitative comparison was made between calculations using the equivalent radius of a circle and those using the effective radius. It was found that the calculated capillary force using equivalent radius offered a better fit with the present experimental data because of the inclusion characteristics. Comparing these results with other studies in the literature allowed the authors to conclude that when applied in capillary force calculations, the equivalent radius is more suitable for inclusions with large size and irregular shape, and the effective radius is more appropriate for inclusions with small size or a large shape factor. Using this model, the effect of inclusion size on attractive capillary force has been investigated, demonstrating that larger inclusions are more strongly attracted.

Progress in Slag Foaming in Metallurgical Processes

Professor Fruehan has been a pioneer in the fundamental understanding of slag foaming in ironmaking and steelmaking processes. Although considerable progress has been made in our understanding of the phenomena, there are still unanswered questions regarding the mechanisms in industrial processes and how to control them. At McMaster University, we have been working on conditions that are relevant to foaming in electric arc furnaces (EAFs) where these phenomena are central to modern EAF practices. This work will be reviewed and put in the context of what is known from a fundamental standpoint.

The Dynamic Interfacial Oxygen Potential Between Iron-Carbon Droplets and Oxidizing Slag

The dynamic nature of the interfacial oxygen potential during dephosphorization was investigated based on the concept that

KINETICS OF COAL INJECTION INTO IRON OXIDE CONTAINING SLAGS

P_{{{\text{O}}_{2} }}