Fluid flow and filtration phenomena associated with filtration of liquid aluminum using reticulated ceramic filters were systematically investigated. It was found that fluid flow through this type of filter could be described by Darcy's Law up to a Reynolds number of 8, and the permeability of this type of filter ranged from about $9 times10 sp{-3}$ to $4 times10 sp{-2} rm mm sp2$. / Parameters affecting filtration processes during the initial period were identified, some of which could be quantified numerically using a 2-D computational domain. According to these numerical analyses, the clean filter coefficient for this type of filter was linearly dependent on the dimensionless Stokes velocity of the suspended particles, had a $-$0.96 power dependence on the Peclet number, a $-$6.93 power dependence on the effective porosity of the filter, and exhibited only a weak dependence on the Reynolds number, in the Darcy velocity regime. / The dynamic behaviour of this type of filter was analyzed theoretically and simulated numerically using newly proposed correlations relating the filter coefficient and the pressure drop to the amount of particles captured within the filter (the specific deposit), and a model describing the morphology of captured particles. The simulated results showed that the filtration efficiency and the pressure drop increased with inlet particle concentration and filtration time; these increases were however, insignificant when the inlet particle concentration was less than 1 ppm for filtration periods of two hours, however, when the inlet concentration (initial and continued) reached 10 ppm, the change became appreciable. / Experimental data, obtained from liquid aluminum filtration tests conducted by the author in both laboratory and industrial settings, compared favourably with the numerical results.

Oxidation experiments were carried out on six different aluminum alloy compositions in order to determine the effects that silicon, strontium, and magnesium have on the oxidation behavior at temperatures between 700 and 800°C. This was determined through weight gain studies using a thermogravimetric balance, microscopic examination of sample surfaces and cross-sections, and chemical analysis of the phases formed during oxidation. / The addition of 12% silicon to aluminum promoted the formation of alpha-alumina nodules on the sample surface at 800°C by reducing the viscosity of the molten metal to allow for better feeding of fresh metal through cracks in the top oxide. Strontium was found to prevent the formation of oxide nodules in an Al-12%Si alloy through the formation of a strontium containing oxide. Similarly, in a commercial 356 alloy, strontium greatly reduced the extent of oxidation by preventing the preferential oxidation of magnesium. It is believed that the mechanism responsible for this is also through the formation of a strontium containing oxide. / Oxidation experiments conducted on an Al-3%Mg alloy revealed that magnesium preferentially oxidizes to form two oxides, firstly MgO, and secondly MgAl 2O4, which forms only from the reaction of MgO and aluminum. Weight gains for this alloy were greatly affected by the oxidizing temperature. Higher temperatures shortened the incubation time to breakaway oxidation and decreased the time required to oxidize all the magnesium from the alloy.

Along with the essential importance of the metallurgical sector, one must recognise that it is also one of the largest sources of environmental pollution. In particular, the problem of electric arc furnace (EAF) dusts is of a growing concern due to the increase in popularity of EAF steelmaking. This dust is classified as a hazardous product due to the elevated content of toxic metals (e.g., Cr). / Studies on the properties of EAF dusts are sparse. Experiments were performed in order to determine the chemical and physical characteristics of the dust. It was determined that EAF dust is constituted of randomly distributed agglomerations of homogeneously nucleated particles and entrained particles. The main elements present within the particular dust were iron and chromium, the latter due to the fact that the dust used was formed within a stainless steel mini-mill. The main phases present within the dust were Fe2O3/Fe 3O4 and Cr2O3. / Thermal remediation experiments were then carried out in a computer controlled thermogravimetric system. The parameters studied during the tests included temperature, residence time and heating rate. In addition, the behaviour of the EAF dust during remediation was studied; in terms of weight and volume loss, gas evolution, particle morphology and resulting leachability of the treated product. Furthermore, it was observed that at temperatures greater than 1200°C metal leachability decreased significantly due to a decrease in toxic metal concentration within the treated product and the formation of a resistant, dense, plate-like morphology. At 1600°C, no toxic metals leached out of the remediated EAF dust and volume reduction was significant, resulting in a product that would be safe and more economical to landfill.

The CANMET-McGill Mathematical Model has been expanded and improved to provide a more comprehensive predictive tool for simulation of temperature evolution in the hot rolling of steel. The model uses a Windows(TM)-based, user-friendly, graphical interface and the explicit finite-difference method in two dimensions to simulate the rolling of flat product. / Data input options were expanded to allow an initial temperature gradient in the steel to be rolled, the inclusion of a runout table in the calculations, specific chemical compositions and a choice of emissivity values. / A novel, chemistry-dependent thermal conductivity term was developed to account for the variation in heat conduction through the thickness of the steel and to ensure that the temperature of the entire cross-section is accurately predicted. In addition, the model now calculates a heat of transformation for phase changes from austenite to ferrite, pearlite and bainite. / An automated self-calibration module was included to facilitate the calibration of the model's predictions to empirically obtained temperature setpoints. / The model's temperature predictions were validated against both industrial and laboratory data with excellent results.

The effect of Si on the kinetics of Nb(C,N) precipitation was investigated by using fractional softening measurements. Compression specimens, with diameters of 7.6 mm and lengths of 11.4 mm, were prepared from four Nb microalloyed steels containing a range of Si concentrations from 0.01 wt% to 0.41 wt%. The stress relaxation method was used in the beginning of this work, but the majority of the experimental results were derived from double-hit compression tests, with a strain of 0.3 applied to represent each pass at a strain rate of 0.1/sec. A solution heat treatment was applied immediately prior to each test. / It was found that the rate of Nb(C,N) precipitation in hot deformed austenite increases with Si concentration. This phenomenon is attributed to the increases in both the Nb diffusivity and the activities of C and N that result from Si addition. Based on the Dutta and Sellars model, an expression for the effect of strain rate on the precipitation start time has been proposed. The present experimental results can then be extrapolated to mill conditions.

The aim of this work was to develop a viable solvent-extraction based system for the separation of rhodium (Rh) from aqueous chloride solutions. Ultimately, two different systems were developed. Kelex 100, a commercially available derivative of 8-hydroxyquinoline, was used as the extractant reagent in both of these systems. One of the systems involved the supported liquid membrane (SLM) extraction of Rh. In this system a very thin microporous "Gore-Tex" polymer sheet, impregnated with an organic solution of Kelex 100, served as the SLM. The other system involved the conversion of the chlorocomplexes of Rh to bromocomplexes prior to their solvent extraction with Kelex 100. / The results of the lab-scale experiments using a SLM of Kelex 100 having a surface area of 44 cm2 are reported. The optimum conditions for Rh permeation were found as a feed solution of 2.5 M HCl and a strip solution of 0.1 M HCl. The SLM was quite stable at the optimum conditions with no sign of organic loss or membrane deterioration after 72 hours of operation. It was determined that the HCl activity gradient across the membrane acts as the driving force that "pumps" the non-aquated Rh chlorocomplexes against their concentration gradient. The mechanism of Rh permeation was the ion-pair formation between the protonated Kelex 100 and RhCl6 3- complexes. The rate of Rh permeation was in the order of 10-6 mol.m-2.s-1. The mechanism of HCl and H2O permeation, which were co-extracted along with Rh chlorocomplexes, were found to be the hydration of protons at the low feed acid region and the formation of microemulsions at the high feed acid region. The permeated acid and water were separated from the SLM receiving phase by contacting the latter phase with an organic solution of trioctylamine (TOA). The chlorocomplexes of Rh(III) and acid are readily extracted to the TOA organic phase and subsequently subjected to differential stripping with a concentrated solution of Cl- and a mild NaOH solution, respectively. By interfacing the TOA solvent extraction with the SLM of Kelex 100 highly concentrated solutions of Rh (at least 10 times the initial concentration) and raffinates essentially free of rhodium were produced. / The UV-Visible investigations revealed that the bromocomplexes of Rh undergo aquation to a much lesser extent than that of the chlorocomplexes. The chlorocomplexes of Rh were converted to bromocomplexes by precipitating first the Na(NH4)2Rh(NO2)6 salt and subsequently dissolving that in an HBr solution. The newly formed bromocomplexes of Rh(III) responded very favorably to extraction with Kelex 100. Relatively high distribution coefficients, about 20, and very steep extraction isotherms were generated. The freshly loaded Kelex 100 organic was efficiently stripped upon contact with a strip solution of 6--8 M HCl and a contact time of 10--12 hours. The developed system shows high promise from a practical implementation point of view.

The kinetics of calcium and sodium removal at 730$ sp circ$C by chlorination from commercial purity (99.7% Al) and aluminum-1wt% magnesium alloys has been investigated. The contribution of chlorine containing gas bubbles, of intermediate reaction products generated by the chlorination process, as well as evaporation through the melt surface, to the removal of calcium and/or sodium has been documented quantitatively. Experimental parameters investigated were chlorine concentration in the gas bubbles and gas flow rate. The measurement of frequency of bubble formation at the tip of the gas bubbling nozzle enabled the surface areas of the bubbles to be estimated which in turn enabled melt phase mass transfer coefficients for the bubbles to be calculated. / It was demonstrated that the removal of calcium and sodium followed first order reaction kinetics with respect to calcium and sodium concentrations. The removal of the above mentioned elements was represented well by a kinetic model in which mass transfer of sodium and calcium in melt phase was rate limiting. / In the case of the magnesium containing alloys, the MgCl$ sb2$ salt phase that was generated during chlorination was found to have a profound effect on the removal of calcium and sodium. The contribution of the salt phase to the removal of these elements was calculated to reach as high as 60%. In commercial purity aluminum, however, while the major contribution to the removal of calcium was from the chlorine containing gas bubbles, the major contribution to the removal of sodium was calculated to be evaporation of sodium through the melt surface.

Flotation of sphalerite with xanthate in the presence of iron ions has been studied as a function of pH. Sphalerite floated readily at pH 8-11 in the presence of ferrous ions, but not in the presence of ferric ions. The Fe$ sp{2+}$ ion concentration, pH and oxygen concentration were shown to be factors in controlling flotation. Electrokinetic measurements indicated that the surface charge increased in the presence of Fe$ sp{2+}$ ions and oxygen, and decreased upon adding xanthate and in the presence of Fe$ sp{2+}$ ions with the absence of oxygen. / As a prelude to surface analysis to try to identify the species responsible for the sphalerite flotation, bulk precipitates formed from iron salt and xanthate solutions under various conditions were obtained and analysed. Analysis techniques included ultraviolet spectroscopy, infrared spectroscopy, x-ray diffraction and Mossbauer spectroscopy. / It was tentatively concluded that the bulk precipitates contained three ferric components: two hydroxy xanthates, Fe(OH)$ sb2$X and Fe(OH)X$ sb2$ and an iron oxide, FeO$ sb{ rm x}.$ / Iron xanthate precipitates prepared over the pH range 6-12 showed a flotation response and electrokinetic behaviour similar to those of Fe$ sp{2+}$/xanthate-treated sphalerite. / An ex situ X-ray photoelectron spectroscopic (XPS), ex situ infrared (DRIFTS) and in situ infrared (ATR) investigation of the interaction of sphalerite with ferrous, ferric and xanthate ions at pH 10 was undertaken. The formation of the hydrophobic surface species was found to involve initial adsorption of Fe$ sp{2+},$ followed by oxidation to Fe$ sp{3+}$ and subsequent reaction with xanthate. There was no significant incorporation of Fe$ sp{3+}.$ / A three-step reaction mechanism is proposed to account for Fe$ sp{2+}$ ion activation of sphalerite: (i) adsorption of Fe(OH)$ sp+,$ (ii) oxidation to Fe(OH)$ sp{2+}$ on the surface, (iii) reaction with xanthate to form Fe(OH)$ sb2$X or Fe(OH)X$ sb2.$

Zinc-based electrogalvanized coatings have attracted increasing interest from the automobile industry and steelmakers because of their excellent corrosion resistance and good mechanical properties. The coating properties are closely related to the microstructure of deposit. Among them, texture is a key factor which influences the coating properties. This study demonstrates the microstructure and corrosion behaviors of the electrodeposited zinc, zinc-iron, and zinc-nickel coatings on steel sheet deposited at different current density, pH and coating thicknesses. The evolution of the coating microstructure--texture, surface morphology, interplanar spacings, microstress, alloy content, and phase composition--is investigated in various deposition conditions. This work also demonstrates the influence of the coating microstructure upon corrosion behavior. In addition, the early stage of deposition behavior is observed in order to demonstrate the growth mechanism of deposits. / The surface morphology and texture of coatings are investigated using AFM (Atomic Force Microscope), SEM and x-ray diffractometers. Corrosion behaviors are analyzed by the Tafel extrapolation method from the potentiodynamic polarization curves as well as by the electrochemical noise tests. / It is found that the zinc based coatings show a significant variation in texture with the change of deposition parameters. The present work suggests that the transformation of texture is closely related to the evolution of coating morphology and the change of alloy content in the deposit as well as phase composition. This work also demonstrates that there is a correlation between morphology and the texture of coatings. The morphology of hexagonal platelets represents the basal $ {0001 }$ fiber texture. The morphology of hexagonal ridges represents the pyramidal non-fiber texture and the morphology of triangular-based pyramids represents the pyramidal $ {$101X$ }$ fiber texture. From the corrosion test, it is found that the texture of coatings strongly influences corrosion resistance. The coatings with strong $ {0001 }$ texture have better corrosion resistance than the coatings with weak $ {0001 }$ texture or a $ {$101X$ }$ fiber texture component. The influence of alloy content and phase composition upon corrosion behavior is also discussed. Consequently, it is proposed how to optimize the deposition process to obtain the desirable texture, morphology and alloy content of the deposit for better corrosion resistance.

The aim of this work is to offer a quantitative assessment as to what extent the texture and the microstructure influence the cold headability of steel wires. / For this, a set of cold drawn low carbon steel wires/AISI 1030 were prepared. The samples were drawn, without heat treatment, in between passes of up to 78% reduction in area (RA) in 5 passes. The deformed samples were then heat treated according to various schedules. / Texture development was studied at a given thickness, by measuring the (110), (200) and (211) pole figures by X-ray diffraction; furthermore, the results were represented and using the Orientation Distribution Function (ODF). A strong $ langle$110$ rangle$ texture was found. / Using special dies, compression tests were made in order to obtain information on such mechanical properties as the yield strength and the homogeneous strain energy. / Multiple regression analysis was made in order to correlate the aspect ratio, the grain size, the Taylor factor and the maximum ODF intensity against the yield strength and the homogeneous strain energy.