<p>A new metallurgical reactor called the LB furnace is being developed at McMaster University for potential applications in ironmaking, cokemaking and waste oxide recycling.</p> <p>A bench-scale LB furnace has been built in our laboratory and a series of experiments on ironmaking was carried out with the use of this furnace. The mass balance and thermal efficiency were analyzed for the overall process.</p> <p>A two-dimensional mathematical model for the turbulent, reacting flows in a confined system has been developed to determine the rates of fluid flow, combustion and heat transfer in the reduction/combustion chamber of this furnace. Measurements of velocity and tracer concentration distributions in two room temperature physical models of the chamber were conducted and were used to assess, the validity of the mathematical model.</p> <p>The following-conclusions can be drawn: (1) The LB furnace has the potential to efficiently produce sponge iron or liquid hot metal of desired composition.</p> <p>(2) The mathematical modelling has been shown to be effective in the study of transport phenomena of the turbulent, reacting flows in this metallurgical reactor and has contributed to a better design of the process.</p> / Doctor of Philosophy (PhD)

<p>The effect of hydrogen has been studied on a grade X65 high strength low alloy (HSLA) pipeline steel using a four point bend test. Hydrogen was introduced into single V-notched test samples by a standard BP method. Slow bend tests were conducted on both the base metal and on the heat affected zone (HAZ) of a commercially welded plate. It was found that hydrogen reduced the plastic strain required for crack initiation and increased the rate of crack propagation in three orientations of the base metal and in one orientation of the HAZ. Tests using a higher strain rate, showed that hydrogen still promoted crack initiation but did not affect the rate of crack propagation. Metallographic examination indicated that the orientations of inclusions played an important role in determining the path of crack propagation and delamination.</p> / Master of Engineering (ME)

<p>The thermodynamics of Fe-Nb-C, Fe-Ti-C, Fe-Nb-N austenites and that of binary carbides and nitrides of Ti and Nb essential in the understanding of the precipitation behaviour in microalloyed steels has been investigated in this study. A dynamic gas equilibration technique has been used in the experimental investigation of the thermodynamics of ternary austenites and binary carbides of Ti and Nb. The results obtained in this study have been analyzed using the modified Wagner formalism for dilute ternary austenites and the sublattice - subregular model suggested by Hillert and Staffansson for the interstitial carbides and nitrides. The solubilities of NbC, TiC and NbN in austenite have been determined from the isoactivity measurements done in this study. The solubility minimum and the variation of solubility limits of carbides of Ti and Nb and the increase in carbon content at constant carbon activity have been quantitatively related to the ternary interaction parameter. The C-Nb, C-Ti and N-Nb interaction parameters have been determined. The dissolution free energies of Nb and Ti in fee Fe have been obtained from the analysis of the solubilities of NbC, NbN and TiC in their respective austenites.</p> <p>Expressions describing the variation of the partial molar free energies of the components in the binary carbides and nitrides of transition metals have been obtained via statistical mechanical considerations. The pair interaction free energies involved in the statistical mechanical description of interstitial solutions have been related to the interaction parameters in the sublattice model. The carbon activity measurements in the NbCy and TiCy phases and the nitrogen activity measurements in the NbNy phase obtained in this study together with the data available in the literature have been analyzed to obtain the interaction parameters in the sublattice model. The limitations in applying the classical Wagner-Schottky model to highly nonstoichiometric compounds have been discussed. The necessary modifications to this classical model have been made by referring to the expressions obtained via the statistical mechanical approach.</p> <p>The microalloyed ternary austenite - nonstoichiometric carbide equilibrium has been evaluated for the Fe-Nb-C and Fe-Ti-C systems. The effects due to solute interactions and the nonstoichiometry of the precipitate have been clarified. The solubility of TiN in Fe-Ti-N austenite has been calculated using the dissolution free energy of Ti evaluated in this study. Rational correlations between the ternary interaction parameters and the free energies of formation of carbides and nitrides have been established. Using this correlation an approximate value of the nitrogen-titanium interaction parameter has been evaluated.</p> / Doctor of Philosophy (PhD)

<p>The elastic interaction of the new phase coherent particles with tetragonal distortion is considered. The analysis shows that the elastic energy may be minimized by the formation of regular tridimensional arrays.</p> <p>Studies of the variations of the interaction energy of the Tyapkin array with respect to displacements and volume perturbation of the particles (in the finite approximation) lead to the conclusion that the periodic distribution is stable.</p> / Master of Engineering (ME)

<p>An experimental investigation has been conducted to study the factors influencing the formation and behaviour of the primary slag phase formed in commercial iron ore pellets when reduced under conditions simulating those encountered in the iron blast furnace. Weight loss during reduction, metallographic and electron microprobe analysis techniques have been employed. Possible implications for blast furnace operation are discussed.</p> / Master of Science (MS)

<p>PubIished standard free energy changes and activity data for iron and its binary and ternary alloys have been used to evaluate the general linear series (Wagner) expansion of the activity coefficient and these were employed in turn for the accurate thermodynamic determinations of the liquids line and the field in steels with additions of Mn, Si, Ni, Cr, Mo, Cu, V, Nb and Co. Computer programs based on several derived analytic formulae were used to predict multicomponent constant composition and isothermal phase diagrams for total alloy additions up to 5 wt%.</p> / Master of Engineering (ME)

<p>The rate of corrosion of silica and alumino-silicate refractories in Armco iron and iron-carbon melts was measured. An interpretation of the rate data required an experimental investigation of the kinetics of the reactions between iron oxide and silica, and carbon and silica.</p> <p>A standard "immersion" technique was used under both static and dynamic conditions. The corrosion of the refractories in Armco iron melts was initially controlled by a chemical reaction process but changed rapidly to a steady-state, diffusion-controlled process. A liquid silicate product layer built up at the interface during the induction period. The steady-state rate of corrosion was independent of the oxygen content of the melt and was also found to be a linear function of the peripheral velocity of the refractory specimen. The rate of corrosion for the various refractories was measured and found to be controlled by diffusion of iron and oxygen in the silicate layer.</p> <p>The rate of corrosion of these refractories in carbon-saturated iron melts was also studied. The rate was found to be independent of the silicon concentration and the carbon concentration in the melt (in the range 2.3%C to saturation). The rate was independent of the rate of rotation of the refractory specimen. The results were interpreted in terms of chemical reaction control at the refractory/metal interface, with the dissociation of silica proposed as the controlling reaction. The rate was found to be strongly temperature dependent indicating reaction control.</p> <p>This experimental investigation has provided new insights into the mechanism of corrosion of silica and alumino-silicate refractories in iron melts.</p> / Doctor of Philosophy (PhD)

<p>The nature of reactions between sodium sulphide slag and carbon-saturated-iron and -copper alloys were studied to obtain a more clear understanding of slag/metal reactions as well as to enhance the knowledge with respect to decopperization and desulphurization reactions. A model has been developed for the kinetics of reactions, taking into consideration the chemical reactions at the gas/slag and metal/slag boundaries as well as diffusion of sodium vapour in the gas phase. The rate constants have been determined by comparing the experimental results with the proposed model of the system using a CDC 6400 computer. Some understanding of the thermodynamics of sulphide solutions, never studied before, was accomplished through calculations. Suggestions were made for the most efficient use of sulphide slags for removing copper and sulphur from carbon-saturated iron melts. It is hoped that this work will open a new area of research on the fundamentals of slag/metal reactions involving sulphides. Such investigations may be helpful in understanding the slag/metal systems involving oxides.</p> / Doctor of Philosophy (PhD)

<p>Experimental investigations of the attack of carbon-free and carbon-bearing magnesite refractories by synthetic steelmaking slags at 1600°C and relevant theoretical analysis are documented in this thesis.</p> <p>The attack of carbon-free magnesite brick by steelmaking slags was studied by immersing cylindrical specimens in molten slag contained in a noble metal crucible. The major variable of study was the composition of the slag, i.e., the alumina and magnesia contents and the lime-silica ratio.</p> <p>The reacted samples are examined macroscopically in terms of elongation, slag climb and penetration. Microscopic examination by petrographic techniques and microprobe analysis further illustrate the macroscopic observations associated with the chemical reactions taking place between the refractories and the penetrating slag.</p> <p>The role of carbon in extending the lining life of BOF carbon-bearing refractories is the main objective of this research. Test crucibles were reacted with slags. The reacted samples were microscopically studied. The formation and destruction of a dense MgO layer in reacted specimens was studied. Theoretical analysis of the formation of the dense MgO layer was undertaken based on the assumption, that the formation of MgO is the resul t of a gaseous reac.tion between magnesium vapor and carbon dibxide.</p> <p>This work has been carried out under conditions relevant to refractory problems involved in a few major steelmaking vessels. The results obtained here have shed light on the kinetics and mechanism of the attack of magnesite refractories by steelmaking slags.</p> / Doctor of Philosophy (PhD)

<p>An ironmaking process has been proposed in which composite iron ore-coal pellets are smelted to produce liquid iron. Studies have determined the manner in which individual composite pellets react, their compositional limitations and the chemical compositions of the resultant slag and iron.</p> <p>Laboratory reduction experiments were performed on various composite pellets bonded with bentonite, cement or calcium carbonate. Ore-coal pellets bonded with bentonite reacted to form a fayalite-type slag high in iron oxide content and an iron melt low in carbon (2%) but high in sulphur (0.3%) contents. Ore-coal pellets which were made self-fluxing by being bonded with cement or calcium carbonate produced a basic slag low in iron oxide content and an iron melt containing over 3% carbon and below 0.05% sulphur. The off-gas from reaction of ore-coal pellets was profound to be mostly carbon monoxide and hydrogen which in combustion with oxygen is to supply the heat required by the process.</p> <p>A computer model of the process was constructed using heat and mass balance equations which illustrated the effects of changes in process variables on input material requirements. Indications from a process analysis are considered to be positive for an ironmaking process based on composite pellet smelting. However, the ultimate success of the process will depend on whether sufficient heat can be retained within the reaction vessel where it is needed. To this end, hot-model "pilot plant" experimental trials are recommended.</p> / Doctor of Philosophy (PhD)