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No description available.

Friction is one of the most significant physical phenomena influencing metal forming, yet in comparison with metallurgy, heat transfer and mechanics it remains the least understood. The goal of this project was to develop, on as fundamental a level as possible, a friction model based upon the physics of the process to be applied to the hot rolling of steel. A fundamental friction model was developed based upon the simplified approach to the adhesion theory by Straffelini (Wear, 249, 79-85, 2001), which is an extension of Bowden and Tabor's original adhesion theory. In this work, the simplified approach's dependence on the thermodynamic work of adhesion was exploited to apply it over a wide range of temperatures. The thermodynamic work of adhesion describes the work required to form a new surface and is a function of the surface energy of the contacting materials was estimated using two approaches: Rabinowicz's and the geometric mean rule. Since high temperature surface energy data is not generally available the relative change in Young's modulus with temperature was used to estimate a material's surface energy at a desired temperature. Reciprocating friction experiments, which provided a controlled environment in which to investigate friction, were conducted to verify the application of this theory to high temperature conditions and metal-oxide contacting materials. The fundamental model describing friction was applied to the hot rolling of steel via a friction algorithm using the commercial finite element (FE) code MARC. Simply described the friction algorithm calculated a friction coefficient using material properties, defined by the user, and contact temperatures, taken from the rolling model. This resulted in the friction coefficient predicted throughout the roll bite, compared to an average friction coefficient typically employed in rolling models. The combined friction algorithm-rolling model was validated against laboratory rolling experiments. One of the assumptions of the finite element rolling model is the presence of a thin, continuous and adherent scale layer. To achieve this in the laboratory a two pass rolling schedule was employed; the first pass to remove the furnace scale and the second pass to input the desired deformation. The success of the friction algorithm was determined by comparing the experimental torques and loads to the predictions of the finite element model. The FE model with the friction algorithm predicted the friction coefficient to vary in the roll gap between approximately 0.25 and 0.35 and was able to predict the measured rolling torque with an average error of 15%, which was considered acceptable and the accuracy was increased after the bearing torque was considered. The error in the load predictions compared to the measured loads was 13.5% on average, which was also acceptable.

Copper and tin in very low concentrations (< 1 wt%) cause hot shortness in steel during metal forming. This affects the mechanical properties of the finish product. The present investigation aims to establish the thermodynamic and kinetic conditions for the removal of copper and tin from molten scrap steel.

The atmospherically-induced stress corrosion cracking (AISCC) of austenitic stainless steel type AISI 316L was investigated using a U-bend technique, under conditions relevant for storage of intermediate level radioactive waste drums. The specimens were obtained from an actual '500 litre' drum with a wet-bead blasted surface finish. Using MgCI2 as contaminant salt, it was found that at the characteristic equilibrium relative humidity a threshold deposition for AISCC occurrence is found above chloride-ion contamination levels of 10 and 25 µg cm-2 at 50 and 30 °C, respectively. Higher contamination levels were required to produce cracking at room temperature or with the increase of relative humidity to 60 %. The AISCC severity was related to the spatial characteristics of the electrolyte film. Above 100 µg cm-2, crack depth seems to be controlled by the electrolyte thickness as it determines the diffusion path of oxygen to the cathodic surface. Below 100 µg cm-2, crack depth is affected predominantly by the formation of a discontinuous electrolyte film which results in smaller anodic/cathodic domains. Transition from cracking to pitting corrosion with tunnel appearance was observed as test temperature was decreased from 30 °C to room temperature, except at high chloride deposition levels. The results indicate that AISCC occurrence can be limited by restriction of chloride deposition, control of RH away from the deliquescence point of relevant salts and control of temperature. Using an X-ray diffraction technique, it was found that the drum's surface residual stresses are compressive and would provide a degree of protection against AISCC. However, tensile residual stresses can be found in non-blasted areas and in sections of the drum welds. Exposure of corrosion coupons and U-bend specimens III an underground environment that potentially resembles a geological disposal facility did not cause any significant pitting or AISCC after 1.75 years of exposure. This was correlated to a low chloride deposition and a high average RH that would have maintained the hygroscopic deposits in a dilute condition.

Erosion and corrosion of piping and 'equlpments continues to be a problem for the oil and gas sector. This primarily occurs where water and entrained sand are present in produced water. The pipelines used to transport these products are often subjected to multiphase flow regimes, which can result in severe degradation of the internal surfaces with the presence of solid particles and an oil phase in the flow system, and the erosion-corrosion mechanisms become more complicated when compared with those seen in single-phase systems. Therefore, it is essential to understand the degradation mechanisms involved to enable effective material selection to be achieved. In this project, a study on sand mobility was conducted, which focused on the effect of the corrosion inhibitor and oil phase adsorption on the sand particles and the effect of the mobility of sand particles in a flow system. A flow loop coupled with a high-speed camera was designed to enable the sand transport to be visualised. With such a system, the consequence of the corrosion inhibitor and hydrocarbon phase, ISOPAR M, on the adsorption process of the sand particles, and the effect of adsorption on reducing the kinetic energy of sand particles were studied. Zeta potential, which is a function of the mobility of an electrical charge at the slip plane beyond which the electrical charges form a stable entity with the solid particle, was also introduced in this work to confirm the result of the sand transport and to define the condition at which adsorption is possible. The results of zeta potential were in good agreement with the results of the sand mobility obtained by the designed flow loop and adjusted jet impingement rig. The results showed that the adsorption of corrosion inhibitor on the surface of sand particles is only possible if the corrosion inhibitor acquires an opposite charge to the sand particles dispersed in solution (the attraction force is dominant). In the study, the erosion-corrosion of a carbon steel (API-5L-X65), 13Cr martensitic stainless steel and duplex/superduplex stainless steel (22Cr and 25Cr) were assessed by jet impingement using a combination of electrochemical tests and metal loss analysis. The assessments were conducted under a simulated CO2 erosive-corrosive oil and gas surface pipeline with the presence of hydrocarbon and corrosion inhibitor to understand the material degradation mechanisms under different testing media to enable supportive information to be provided for the mitigation of erosion-corrosion in the oil and gas industry. In-situ electrochemistry, LPR, was conducted in order to assess the contribution of the corrosion process on the total degradation of materials. Despite the significant effect of the solution containing 5 vol% ISOPAR M on the total weight loss (TWL), the addition of 5% ISOPAR M did not show a clear reduction in the corrosion rate (higher slope of I'1E/l'1i plot). It was proved in this project that the presence of 5 vol% ISOPAR M not only has an important role in reducing the impact velocity of sand particles, but using CFD simulation it was also proved that the particles had a lower impact angle, and, hence, reduced the overall damage to the mechanical component (erosion-corrosion). The other interesting feature identified in this study is the interaction between the corrosion inhibitor and oil phase, which resulted in enhancing the stability of the emulsion flow and the change in the wettability of the metal surface. Unlike other testing media, the measured contact angles of water droplets on API-5L-X65 surfaces, pre-exposed to the solution containing 100 ppm of corrosion inhibitor and 5 vol% hydrocarbon, led some sites on the surface to change to an oil wet, hydrophobic surface, thereby increasing the corrosion resistance. A three-level experimental design with full replication was developed for the purpose of developing a statistical model (using the commercial package Minitab™) relating to the total weight loss of API-5L-X65. Such a model will enhance the understanding of the performance of a material in a multiphase flow environment. This methodology allows the interaction between the most significant parameters on erosion corrosion to be studied. Finally, this thesis has added to the understanding of erosion-corrosion in conditions containing a hydrocarbon phase and sand particles.

This thesis reports a developmental programme of work undertaken for a number of installations at the Scunthorpe site of Corus plc (formerly British Steel plc). The central theme concerns the optimisation of the combustion of gas mixes produced by onsite processes through parameter prediction, the constituents of the mixtures included blast furnace gas (BFG), coke oven gas (COG), and basic oxygen steelmaking gas (BOS).The main parameters under investigation were calorific value (CV), air/fuel ratio, and specific gravity. Finally, a secondary investigation was conducted into predicting oxygen content in flue gases with a view to reducing recuperator corrosion. Data from three different systems was considered: a power station, a coke oven gas plant and a section mill. All data sets were subject to aliasing both as a result of the slowness of the mass spectrometer measuring devices with respect to gas content fluctuations, and as a result of the relatively long sampling interval employed by the main archiving system. The sets from the section mill were particularly prone to abrupt and extreme variations. Neural network solutions based on function approximation were proposed and developed. There was a specific requirement that any solution be compatible with unsophisticated low-budget hardware. Hence there were major constraints on network size and complexity. A linear time series based network was found to perform more efficiently in the data supplied rather than the more conventional non-linear counterpart. The proposed networks indicated potential gains in accuracy in excess of 50% over a second-order least squares-based method proposed by the collaborating organisation. At the time of writing it is understood that no other similar systems have been investigated in this manner, let alone resulting in a successful minimalist neural network solution. Hence the contribution to knowledge is that it is possible to accurately predict the above parameters with a minimalist linear network, trained with data subjected to varying degrees of aliasing.

No description available.

M. Tech. (Human Resource Management, Faculty of Management Sciences), Vaal University of Technology. / The main purpose of the study was to examine the level of job satisfaction and intention to quit, by employees in a steel manufacturing company. The research methodology used to conduct the study was a combination of a literature review and an empirical study. Due to the small size of the population, no sampling was done although a census had been drawn. The primary data were collected using a structured questionnaire. The measuring instrument contained 25 items. For the main survey, data from 181 respondents were collected and analysed. Participants in the study involved engineers, operators, technicians, artisans, administrative staff and safety, health and environmental specialists in the steel manufacturing company. Data were analysed with the Statistical Package for Social Sciences (SPSS) version 20.0. The Cronbach’s alpha coefficients of the measuring instrument were computed to establish construct validity. Content validity of the scale was ascertained by pre-testing the questionnaire with employees in the steel manufacturing company. Factor analysis was conducted for variables in Section B of the research instrument. Analysis was done using descriptive statistics on the demographic information of respondents. The results were also interpreted through the factor analysis and correlation analysis. The findings regarding employee’s perceptions or feelings about job satisfaction and employees’ intentions to quit their current organisation revealed that the supervision variable is positively correlated with job variable while it is negatively correlated with intention to quit. In addition, job variable is also negatively correlated with intention to quit. This means that effective supervisors are likely to improve employees’ job satisfaction hence decrease their intentions to quit their current organisation and vise versa. In addition, when employees are satisfied with their job environment, this will decrease their intentions to quit their current organisation and vise versa. Judging from the results from respondents, it is clear that when employees are provided with a job that rewards them for their effort and provides opportunities for advancement, they will be satisfied and therefore more likely to stay in the organisation. Hence, the employees at Babcock Ntuthuko Generations are satisfied and they are not intending to leave the organisation. The research information collected through this study can be used to encourage Babcock Ntuthuko management to continue providing employees with a conducive working enviroment to ensure that current and new employees are retained.

Cette thèse s’inscrit dans le projet ASCoPE qui vise à développer les connaissances scientifiques et technologiques nécessaires à la conception et à la réalisation d’un pilote de production d’acier par réduction électrochimique de particules d’hématite en suspension dans un milieu alcalin à 110°C, en vue de proposer un procédé industriel fiable et écologique, comme alternative au procédé classique reposant sur le charbon. Le mélange considéré contient une suspension d’hématite à 12% en volume dans une solution aqueuse de soude à 50% en masse. Cette thèse a pour objectif l’étude de la sédimentation et de la rhéologie des suspensions d’hématite et le comportement hydrodynamique des particules d’hématite dans une cellule inclinée et de quantifier l’éventuel phénomène d’impact sur la cathode / This thesis aims to develop scientific and technological knowledge needed to design a pilot production of steel by electrochemical reduction of hematite particles suspended in an alkaline medium at 110°C in order to provide a reliable and environmentally friendly industrial process, as an alternative to the conventional process based on coal. The mixture considered contains a suspension of hematite of 12% by volume in an aqueous sodium hydroxide solution of 50% by weight. This thesis seeks to study the sedimentation and rheology of hematite suspensions and the hydrodynamic behavior of hematite particles in inclined cell and to quantify the possible phenomeno impact on the cathode