The warm rolling of steels is becoming an increasingly common practice in industry. Nevertheless, the poor formability of warm rolled low carbon (LC) steels is problematic, as this property is important in deep drawing applications, which require uniform deformation. Compression tests were conducted to study the effect of chromium content on rate sensitivity (m), using two experimental LC-chromium alloys and an extralow carbon (ELC) steel. Samples were tested at various temperatures and strain rates, and the flow stress was measured for each condition. A second dynamic strain aging (DSA) peak was present in both LC-Cr alloyed steels, indicating that chromium raised the DSA temperature range into that for warm rolling. At these temperatures, the chromium addition reduced m as compared to the ELC steel, increasing the shear band content of the warm rolled microstructures. This increased shear band content modified the type and distribution of the recrystallization nuclei. Thus, it is expected that LC-Cr steels will have better formability after warm rolling than unmodified LC steels.

The permanent mold casting process is a relatively popular and effective casting technology that can produce near-net-shape aluminum components with integrity, particularly for the automotive and aerospace industries. It is well recognized by the casting industry that it is essential to control the cooling of permanent mold castings in order to improve the quality of the castings, so there is a considerable incentive to develop a more effective method of mold cooling to control the temperature distribution of the mold and the casting. The current technologies for controlled cooling are air or water cooling passages and chill inserts. Each of these cooling methods presents certain disadvantages, and none offer optimum cooling control. Based on these considerations, a novel, effective and controllable water-based heat pipe has been successfully developed to be used as a new method of permanent mold cooling where high heat fluxes are normally encountered. Heat pipes featuring this design have been incorporated in an experimental permanent mold made of HI3 tool steel that contains three symmetric steps. Computer modeling for the permanent mold casting process has been accomplished to predict the effect and potential of heat pipe cooling for permanent mold casting. Castings of A3 56 alloy have been produced by this permanent mold. The effects of heat pipe cooling on permanent mold castings have been evaluated by analyzing the temperature distribution of the mold and the casting, as well as by measuring the dendrite arm spacing and shrinkage distribution of the castings. The effect of heat pipe cooling on the mold solidification time of castings of A356 alloy with different coating types was also studied. Industrial trials have been carried out to evaluate this new cooling technology on an industrial scale casting machine. Because the space around the mold installed on a low pressure die casting machine is very limited, it is often very difficult to install the heat pipe in the specific desired location in the mold. A new version flexible heat pipe cooling system has been developed for the industrial casting process. Preliminary and industrial tests of the heat pipe cooling system have been performed. The effects of heat pipe cooling, as well as the effects of using traditional water and air cooling on the low pressure die casting were studied. Data on the cooling rates obtained by heat pipes, as well as some microstructures and measurements of the dendrite arm spacing are presented in this thesis. Modeling and experimental results have shown that the water based heat pipe can provide high cooling rates in casting processes. The dendrite arm spacing (DAS) of A356 alloy is refined considerably by the heat pipes, and changes in the shrinkage pattern are provided by the dramatic changes in the heat flow patterns.

The effect of pulp potential on the recovery of copper, lead, zinc and iron from the ore of Kidd Creek Mines (Timmins, Ontario) was examined. Air and nitrogen as flotation gases were compared for their effect on the metallurgical response (recovery and the separation efficiency of Cu/Zn and Cu/Fe). / The extraction of metal cations from the mineral surface in-situ by EDTA at varying pulp potentials and with various reagent schemes was performed, and the differences in extraction from concentrates and tailings was examined. The effect of aeration on the extraction of cations Cu, Pb, Zn and Fe was analysed as well as its effect on dissolved oxygen (Dynamic Dissolved Oxygen). Plant surveys of pulp potential, pH and extraction by EDTA are compared to laboratory values. / The optimum pulp potential for the recovery of copper with no collector addition was -50 mV (vs Ag/AgCl). Collector increased the range of pulp potential where maximum copper recovery could be achieved. The maximum separation efficiency between copper/zinc and copper/iron was approximately -230mV and -50mV, respectively. / Copper was not extracted by EDTA, possibly due to its incorporation in the lattice of pyrite and sphalerite. The extraction of iron, zinc, and lead from the feed decreased with increased aeration, and was not strongly affected by the addition of SO2, lime or collector. / The factors Em and Es (mg metal per gram of solid and mg of metal per gram of metal, respectively) were developed to analyse the data obtained. The differences in the extraction of iron between tails and concentrates was strongly related to the separation efficiency. / Extractions at specific pulp potentials were found to be similar between the plant and laboratory.

Thickening is the separation of suspended solid particles from a liquid by gravity settling. As a feed stream enters the thickener, the solids settle to the bottom. Clarified liquid overflows the top and the settled solids (underflow) is removed. Thickeners are widely used in the minerals and metal processing industry. / To assist in the monitoring and control of thickeners a conductivity probe has been developed. Test work was carried out on a concentrate thickener at the Copper Cliff, Ontario Division of Inco Limited in Sudbury. / The conductivity probe is a multicell arrangement. It exploits the difference in conductivity between liquid, slurry and settled solids. A conductivity profile is collected which locates the interfaces (liquid/slurry, slurry/settled solids) by detecting the change in conductivity, The conductivity profile can be readily converted to a solids concentration profile using a model due to Maxwell. From the solids profile, a solids inventory are obtained along with an estimation of underflow density. The main tasks in this thesis were to (a) develop a method of on-line calibration and (b) develop a level estimation procedure. The former was achieved by designing a portable probe and lowering it in to predetermined positions corresponding to rings on the probe. The time between re-calibration was also established (ca. 10 days). In the case of the level a previous method using a 0--1 scale has been converted to a true bed height using the bed height estimated by the operators using a weighted rope.

The mineral processing group of McGill University developed a novel gas holdup probe that consists of two conductivity flow cells: an open cell used to estimate dispersion (slurry + air) conductivity and a syphon cell used to estimate slurry conductivity. These two values are entered into Maxwell's model to calculate gas holdup. / In this work some design criteria for conductivity flow cells and the syphon cell are given. Effect of geometrical cell constant and electrode width on cell behaviour are analyzed. New dimensions for open and syphon cells are proposed. Conditions to prevent bubbles from being entrained into the syphon cell are established. / The new design of the gas holdup probe was tested successfully over a prolonged period at the INCO Matte Separation Plant (Copper Cliff, Ontario). Tests carried out in waste paper de-inking at BOWATER (Gatineau, Quebec) showed the gas holdup values given by the probe agreed with the values obtained from pressure. The noise associated with the gas holdup signal obtained by the probe could be used to diagnose sparger operation. / Gas holdup showed some degree of correlation with flotation efficiency of waste paper de-inking and flotation rate constant. Chemistry and rheology of the feed are other factors to be considered. Estimation of bubble surface area flux should consider rheology properties (liquid viscosity and density).

In the electrolytic production of zinc, cobalt is removed from zinc electrolyte by cementation with zinc dust Prior to electrowinning. Although the thermodynamics for this reaction are favourable, kinetic barriers to cobalt reduction render the method impractical unless activators such as antimony or arsenic in conjunction with copper are used. There is a large body of work studying the effect of these additives, yet the mechanism by which they act is still poorly understood. Moreover, regardless of the beneficial effect of the activators, from time to time the process fails to meet the target level of 0.1 mg/L cobalt in the purified electrolyte, with negative consequences in the electrowinning operation. Even when the target conditions are met, zinc dust consumption is excessively high: satisfactory operation requires up to 300 times the stoichiometric amount of zinc dust. / In the present work the role of the antimony/copper activators was investigated in a batch cementation process using synthetic electrolyte. The objectives were to study the fundamentals of cobalt cementation in zinc sulfate electrolyte with conventional additives, to clarify the action of additives and their role in cementation, and to identify and test novel additives. (Abstract shortened by UMI.)

A 7.6 cm laboratory Knelson Concentrator (LKC) was used to evaluate the performance of the gold gravity circuits at Lucien Beliveau (Val d'Or, Quebec) and Dome Mines (South Porcupine, Ontario). / A detailed sampling program was conducted on the grinding and gravity circuits. To evaluate the size-by-size unit performance of Knelson Concentrators of 76 and 51 cm, an HG-7 Mineral Deposit spiral and four Denver Duplex mineral jigs (0.6 m x 0.9 m), total and gravity recoverable (determined by the LKC) gold content were measured in their feed, concentrate and tails. Sample dilution with silica was used as a tool to enhance Knelson recovery in samples with a high sulphide content. / At the Lucien Beliveau mill, gold was recovered consistently in all size fractions greater than 38 $ mu$m, averaging 45% in the 76 cm plant Knelson Concentrator. Unit jig recovery for the Dome mill was only 25% (of the total mill feed). (Abstract shortened by UMI.)

Iron content in aluminum-silicon casting alloys, which contribute to the formation of Al$ sb5$FeSi intermetallic, can be very detrimental to the physical properties of the final cast part. / Thermal analysis could provide a cost effective and reliable method to quantify the iron content of the alloy melt before the casting process is performed. The formation of the Al$ sb5$FeSi intermetallic can be resolvable on the cooling curves for aluminum-silicon alloys if the iron content is equal to or greater than 0.6%wt when the cooling rate is 0.10$ sp circ$C/sec. As the iron content gradually increases, the formation temperature of Al$ sb5$FeSi increases and this results in an increase in the duration of the Al$ sb5$FeSi thermal anomaly. A time based parameter associated with the Al$ sb5$FeSi thermal anomaly is also used to quantify the Fe content. Time parameters can be very accurate if the melt volume and heat extraction for the solidifying thermal analysis sample are strictly controlled. / Results of Fe quantification via apparent time parameter of the Al$ sb5$FeSi crystallization for 356,319 and 413 alloys using thermal analysis has been completed for this thesis. (Abstract shortened by UMI.)

The Liquid Metal Cleanliness Analyzer (LiMCA) is used by the primary aluminum industry to evaluate melt cleanliness, on-line. The size and number of inclusions are counted via the electric sensing zone (ESZ) or Coulter Counter principle applied to molten metal. Thus far, it has been impossible to discriminate these inclusions one from the other using this technique. / Particle discrimination can be accomplished by analyzing the in-coming signals. The McGill LiMCA unit has been upgraded with Digital Signal Processing (DSP) technology. Therefore, ESZ voltage signals generated by the LiMCA probe are digitized and then treated using DSP. The start slope, end slope, maximum voltage height, time to reach the maximum voltage, total signal duration time, start time and end time of each pulse are calculated via. DSP technology for each voltage pulse. These seven parameters can be used to discriminate and characterize one signal from the next. / Once the LiMCA signals have been digitized and reduced they are analyzed to verify if certain signals have distinguishable characteristics. / Particles discrimination was carried out in water modelling tests. (Abstract shortened by UMI.)

Distinct yield drops and serrations were observed on the stress-strain curves of a 304 type stainless steel when tested at high temperatures (850--1200ºC). A proposed explanation for the behavior is static strain aging (SSA) and dynamic strain aging (DSA), respectively, caused by the presence of substitutional elements. / Much of the previous work on this topic has been focused on the effects of interstitials, namely carbon and nitrogen, at lower temperatures (100--300ºC, depending on the strain rate). However, for substitutional elements to have the same effect, the temperature range must be significantly higher. To further investigate the likelihood that SSA and DSA are caused by substitutional elements, the domain (i.e. temperature and strain rate range) within which yield drops and serrated yielding are observed was studied. / The results of this investigation showed that the appearance of SSA is dependent upon the pass strain, interpass time and strain rate, whereas the presence of DSA serrations was strongly dependent upon strain rate. The disappearance of yield drops involves interpass times in excess of one second. This is hypothesized to result from the disappearance of the deformation vacancies and of the associated non-equilibrium segregation. The impurity element phosphorus was isolated as the most probable cause of the observed phenomenon. This is a result of its high diffusivity, combined with its high binding energy.