Thesis (M.S.)--Ohio University, August, 1998. / Title from PDF t.p.

Thesis (M.S.)--West Virginia University, 2002. / Title from document title page. Document formatted into pages; contains ix, 145 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 63-65).

Thesis (M.S.)--West Virginia University, 2000. / Title from document title page. Document formatted into pages; contains vii, 38 p. : ill. Includes abstract. Includes bibliographical references (p. 29-30).

Thesis (M.S.)--University of Wisconsin--Madison, 1968. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

O desgaste em revestimentos refratários é um dos problemas críticos encontrados em ambientes siderúrgicos, que limita a produtividade do processo devido a necessidade de paradas para manutenção nos equipamentos industriais, em favor da substituição do revestimento refratário em regiões desgastadas. Para identificar e caracterizar os mecanismos de desgaste gerados pela ação do banho metal/escória na microestrutura de materiais refratários utilizados como revestimento de panelas de aço de aciaria elétrica, o objetivo deste trabalho foi dividido em três etapas. A primeira etapa é denominada de estudo \"Post-Mortem\", que consiste na amostragem dos tijolos refratários da panela de aço, ao qual foram preparados para análises físico-químicas e microestruturais para a identificação dos mecanismos de desgastes atuantes. A segunda etapa consistiu na preparação dos tijolos novos (mesma composição química dos tijolos post mortem) de maneira a avaliar seu comportamento em relação ao ataque por escória e/ou metal em ensaios termoquímicos e analisar os resultados obtidos com os tijolos \"Post - Mortem\". A terceira etapa foi baseada nos resultados obtidos das investigações das etapas anteriores, ao qual, foram propostos novos tijolos comerciais com diferentes formulações, em parceria com uma indústria brasileira de materiais refratários (Togni refratários), que atenda melhor as exigências das aciarias elétricas. Os resultados que foram apresentados por esta tese, comprovaram que os revestimentos próximos ao ideal, seria os refratários com matriz de cromo (amostra AC_1) e matriz de carbono (amostra AC_2). / Wear on linning refractory is the critical problems found in steelmaking environments, which limits process productivity due to the need for maintenance shutdowns in industrial equipments, in favor of replacing the refractory lining on wear regions. The objective of this work was to identify and characterize the wear mechanisms generated by the action of the metal/slag bath in the microstructure of refractory materials used as coating of steel pans of electric steelmaking, in order to prolong the campaign time of steel pans. This work was divided into three steps. The first step is called a \"Post-Mortem\" study, which consists of the sampling of the refractory bricks of the steel ladle, to which they were prepared for physicochemical and microstructural analyzes to identify the mechanisms of active wear. The second step consisted in the preparation of the new bricks in order to evaluate their behavior in relation to the slag attack in thermochemical tests and to analyze the results obtained with the \"Post - Mortem\" bricks. Based on the results of these initial investigations, new commercial bricks with different formulations were proposed, in partnership with a Brazilian refractory materials industry (Togni refractory), which better meets the requirements of electric steel mills. The results presented by this thesis are innovative and have characteristics in terms of technological contribution in the steel and refractory industries.

Measurements of oxygen activities in a matte at high-temperature could be useful to determine and control the repartition of different elements, such as iron, copper, and nickel between the oxidised phase, (the slag) and the sulphide phase, (the matte). Electrochemical measurement of oxygen partial pressure in equilibrium with the melt can be performed by using solid electrolytes such as the zirconia solid electrolyte. The oxygen measurements in Cu-Ni-Fe-S matte were studied experimentally by measuring the partial pressure of oxygen through the EMF, using a silica-saturated slag and either a CO-CO2-SO2 gas mixture or Ar gas, at 1250oC. The calculated equilibrium oxygen partial pressure varied from 1.53x10-8 to 2.64x10-7atm. Oxygen measurements were conducted by using fully stabilized zirconia as solid electrolyte. Two different solid reference electrodes were used: Cr/Cr2O3 and Fe/FeO. EMF measurements obtained with Cr/Cr2O3 solid reference electrode were less stable and accurate compared to those with Fe/FeO solid reference electrode. Therefore, EMF measurements on oxygen concentration point out that the Fe/FeO is more suitable solid reference electrode for this application than Cr/Cr2O3. Analyses were obtained using the SEM, (scanning electron microscope) and the electron probe microanalyser. The measured oxygen concentration was found to be sensitive to the iron content in the matte. / Dissertation (MEng (Metallurgy))--University of Pretoria, 2007. / Materials Science and Metallurgical Engineering / unrestricted

In the iron ore pelletizing, the sintering of the pellets takes place in a rotary kiln which is lined with refractory bricks. During the process, deposited materials such as iron ore slag, additives, binders and fly ash stick on the surface of the lining, and with time, by infiltration and diffusion, a corroded layer is formed. Some of the reactions occurred in that layer are promoted by the presence of alkalis. Refractory/deposited materials reactions and infiltration of deposited materials were studied at laboratory scale. In this study, techniques such as differential scanning calorimetry (DSC), x-ray diffractometry (XRD) and scanning electron microscopy (SEM) were used. Reaction temperatures, phase transformations and infiltration depth of deposited materials were determinated. Additions of alkalis into the materials involved were used to enhance the reactions between them. Using powder mixtures the results of DSC show that in addition of K2CO3 the reaction temperature range is 850-950°C showing formation of new phases around 850°C with kalsilite and around 950°C with leucite; in addition of the mixture Na2CO3 and K2CO3, there is a broader temperature interval of 600-925°C with formation of kalsilite at lower temperatures and nepheline at higher temperatures. In the characterization of the infiltration of deposited materials into the brick it was observed that nepheline was formed mainly in the corroded brick layer but K feldespathoids (leucite, kalsilite, kaliophilite) were formed beneath the corroded brick layer. / <p>Validerat; 20110705 (anonymous)</p>

This project was the first step in developing a control system for the open slag bath furnace at Highveld Steel, in order to maximize production levels and product quality. In this dissertation, available knowledge from literature and practical experience is included. This is then processed to propose a realistic control system with the current resources available at Highveld Steel. Through research and practical experience it is shown that these furnaces are extremely sensitive to raw material quality and consistency of decision making. This is a result of the open bath configuration that necessitates the careful control of the excess energy, and the raw material composition supplied to the furnace. Through this project it was shown that both the productivity and the product quality (vanadium recovery) can be increased by simply controlling the feed-topower ratio and correct use of correction material. This has the effect of stabilizing the process energy balance which results in smaller slag temperature variations and therefore also less product quality variability. Through controlling the feed-power-ratio, energy consumption was also shown to be reduced, since excess power is minimized without negatively impacting on productivity. In this project a proposal is made to control the flow of material between the two stages in the process, which is based on either being kiln or furnace constrained. A better tapping scheduling is also proposed, based on both material accumulations inside the furnace and the charging condition of the furnace. This results in having sufficient pressure to tap iron and slag at good rates and should also yield consistent tapping weights and add to general process stability. However, engineering availability strongly impacts on both process control and furnace productivity. Consistent availability of the furnace and its supporting systems is hence essential for optimal operation. / Dissertation (MEng)--University of Pretoria, 2009. / Materials Science and Metallurgical Engineering / unrestricted

Titania slag is a feedstock to the pigment industry, which in turn provides titania pigment to producers of everyday products like paper, cosmetics and toothpaste. Titania slag is the primary product of the pyrometallurgical process of ilmenite smelting – the other products being iron and CO gas. Titania slag is typically tapped from the furnace into blocks of approximately 20 tons. After cooling these blocks are crushed and milled to size fractions suitable for the processes of the pigment producers. These processes are broadly grouped into two types of technology: the chloride route (during which titania slag is reacted with chlorine and subsequently re oxidised thereby removing the impurities) and the sulphate route (in this process the titania slag is purified after dissolving the slag in sulphuric acid). Due to the nature of these two processes, several specifications are imposed on the quality of the titania slags. The fluidised-bed technology used in the chloride process limits the size distribution of the slag to between 106 µm and 850 µm. Ilmenite smelting industries consequently crush and mill the titania slag to below 850 µm. The fraction below 106 µm is then sold to the sulphate market. Since the coarser chloride grade product is the more valuable product, slag producers continuously strive to improve the ratio between the coarser and finer fractions. This study reports on parameters which influence the particle size distribution of titania slags and therefore the split between the coarser (more valuable) and finer (less valuable) products. Pilot-scale slag ingots were used to identify chemical and process variables which influence the yield of coarser material. The microstructure of as-cast and milled slag was examined, and indicated a role of silicate phases in the crushing behaviour. Industrial-scale slag ingots were used to test whether the roles of tapping rate and water cooling (as identified from the pilot-scale ingots) also applied under industrial conditions. A numerical method was applied to estimate the thermal conductivity of the solidified slag (from measurements on pilot-scale ingots), and to predict the cooling and solidification behaviour of industrial-scale ingots. The study concludes that the chemical composition and cooling conditions of the slag block play central roles in the final particle size distribution of the slag. / Thesis (PhD (Metallurgical Engineering))--University of Pretoria, 2009. / Materials Science and Metallurgical Engineering / unrestricted

<p> The partitioning of niobium to slag and gaseous niobium oxide vapourizing from metal/slag may cause niobium losses and erratic recovery rates in steelmaking practices. Knowledge of the volatility and activities of niobium oxides in slag melts are of great value for both theoretical evaluation and practical applications in niobium microalloyed steels. Because of the multi-valence state of niobium ions in slags, the behaviour of niobium in metallurgical slags is complicated. So far, little systematic attempts have been made and activity data of niobium oxides in slags are extremely scarce. The aim of this study is to determine precise data on the vapour pressures of niobium oxides, and consequently, to obtain information on thermodynamic quantities of niobium oxides in slag melts.</p> <p> The thermodynamic properties of niobium oxide in CaO-SiO2-NbOx and CaOSiO2-Al2O3-NbOx slag melts were determined by employing the transpiration method from 1800-1873K under a controlled atmosphere. To confirm the validity of the transpiration method for the measurement of thermodynamic properties, the binary alloy system silver-gold was chosen for a comparison with the same property which has been measured by other recognized procedures. The agreement with literature results confirmed that the measurement yields reliable results for thermodynamic activity data by the transpiration method.</p> <p> The vapourization of liquid Nb2O5 was studied as a function of partial pressure of oxygen in the system and this confirms that atmosphere control is the essential condition for the vapourization study. The gaseous niobium oxide species was verified to be NbO2; hence, Nb2O5 vapourizes by the reaction Nb2O5(1) = 2NbO2(g)+1/2O2(g). Heat of vapourization was estimated by applying the second law method and comparison with the literature showed a fairly good agreement.</p> <p> The thermodynamic properties of niobium oxide in the slag system of CaO-SiO2-NbOx and CaO-SiO2-Al2O3-NbOx were measured by varying the experimental conditions of slag basicities, slag compositions, temperature and oxygen partial pressures. From the basicity dependency of the activity coefficient for each oxide in this study, it is proposed that niobium oxide behaves as an amphoteric oxide and niobium pentoxide as an acidic oxide. On the other hand, it was observed in the redox equilibrium experiment that NbO2.5 becomes predominant as the slag basicity increases. However, insufficient interaction parameters as well as parameter conversions prevent the application of the regular solution model. The co-relationship between the ionic diameter and ionic energy was discovered and shows good agreement with calcium oxide and silicon oxide. With the interaction parameter and converting parameter attained, the regular solution model shows good agreement for the activity coefficients between measurement and calculation.</p> / Thesis / Doctor of Philosophy (PhD)