Made available in DSpace on 2014-10-09T12:47:01Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:08:36Z (GMT). No. of bitstreams: 1 08290.pdf: 1216858 bytes, checksum: 06f9803f0f94d1535cd74d6f3549a749 (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Há uma demanda por competitividade entre as indústrias de aços, a fim de alcançar a excelência definida pelo termo clean steel. O processo de desgaseificação a vácuo (VD) ocorre durante o Refino Secundário de aços especiais. Sua principal função é remover gases indesejáveis, especialmente o hidrogênio. Entretanto, durante este processo, o fenômeno de flotação e a absorção de inclusões são reportados. O objetivo do presente trabalho foi estudar a viscosidade de escórias e a capacidade da estação de desgaseificação a vácuo do tipo tanque na limpeza de aços sob uma perspectiva industrial. Para realizar este objetivo, foram coletadas amostras de escória e aço antes e após a etapa de vácuo. Os resultados em limpeza de aço foram relacionados à energia de agitação durante o tratamento a vácuo (associada a um parâmetro cinético - βs) e ao efeito da viscosidade de escórias. É possível observar um decréscimo expressivo na população de inclusões entre as condições antes e após tratamento de desgaseificação a vácuo. A remoção de inclusões durante o vácuo atinge 64, 75 e 78% para as faixas de diâmetro de 2,5-5, 5-15 e ≥ 15 μm, respectivamente. Após o processo de desgaseificação, a composição das inclusões não-metálicas aproxima-se da composição química da escória. O processo de agitação na estação de desgaseificação a vácuo promove uma diminuição significativa na densidade de inclusões na faixa de diâmetro de 2,5-15 μm. Além disso, ao aumentar a intensidade do parâmetro cinético, a composição química de inclusões não-metálicas foi afetada e o teor de enxofre presente no aço líquido foi reduzido. Quanto às viscosidades efetiva das escórias, conclui-se que, para valores mais baixos (0,20 Pa.s) aumenta-se a capacidade da escória na remoção de inclusões, enquanto que valores mais altos (> 0,40 Pa.s) aparentaram ser prejudiciais à limpeza do aço. / There is a demand in competitiveness within the steel industry towards achieving excellence defined by clean steel term. The process of vacuum degassing (VD) occurs during the secondary refining of special steels. Its main function is to remove undesirable gases, primarily hydrogen. However, during this process, flotation phenomenon and inclusions absorption are reported. The aim of the present work was to study the slag viscosity and vacuum degassing (tank type) capacity in steel cleanliness from an industry perspective. To achieve this objective, slag and steel samples were taken before and after vacuum stage. The results in steel cleanliness were related to the stirring energy of the vacuum station (associated to a kinetic parameter – βs) and to the effect of slag viscosity. It is possible to observe an expressive decrease in the population of inclusions between the conditions before and after vacuum degassing treatment. The removal of inclusions during the vacuum stage reaches 64, 75 and 78% in the diameter ranges of 2,5-5, 5-15 and ≥ 15 μm, respectively. After the degassing process, the composition of non-metallic inclusions seemed to approach the slags’ chemical compositions. The stirring process in the vacuum degassing station promotes a significant decrease in the inclusion density with 2,5-15 μm diameter range. Also, by increasing the kinetic parameter intensity, the composition of non-metallic inclusions was affected. The sulfur content present in liquid steel was reduced. Regarding the effective viscosities of slags, it was concluded that lower values (0,20 Pa.s) increased slag capacity in inclusion removal, whereas higher values (> 0,40 Pa.s) was detrimental to steel cleanliness.

Made available in DSpace on 2014-10-09T12:47:01Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:08:36Z (GMT). No. of bitstreams: 1 08290.pdf: 1216858 bytes, checksum: 06f9803f0f94d1535cd74d6f3549a749 (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Magister Scientiae - MSc / This thesis aims to measure the rate of radon loss from water in a systematic way. The dependence on surface area, temperature and concentration will be investigated. The experiments were done at UWC by creating radon using radium sources and then measuring the radon concentrations inside a vacuum chamber to obtain the speed of radon escape from the water. The results are compared to a model [Cal 2002] where the radon concentration in the air and hence the transfer rate is measured using a RAD7 radon detector. Since the equations cannot be solved analytically, a numerical solution is employed. The radon transfer velocity coefficient is found to be (1.9±0.5)×10-6m/s. This value indicates that the escape of radon should not be a problem when a sample is open to the air for a minute or two. / South Africa

This thesis examines the influence of the degassing process on hydrogen contend and on the quality of part casted by high pressure casting technologies. The type of defects occurring in the casting is analyzed based on macrostructure and microstructure observations. For the overall assessment is used the statistical observation of the evolution trend of scrapping during the experiment. The results show that shortening of the degassing time may affect the incidence of porosity defect.

This master’s thesis is focused on optimalization of degassing parameters in the foundry plant and effect of these parameters on mechanical properties of Al-Si alloys. In practical part is used factorial experiment to research effect of degassing parameters on mechanical properties and dichte index. After optimalization the new process is validated by comparing with the previous one. This experiment was taken on AlSi7Mg0,6 alloy in foundry plant MESIT foundry, a.s.

Diploma thesis examines the influence of the preparation and metallurgical treatment on the mechanical properties and structure of aluminium alloys Al-Si. The experimental part was carried out at MSR Engines s.r.o. This part describes the current (sodium modification) and newly proposed (strontium modification) state of preparation and metallurgical processing of melt. There is state the course of experimental melting processes, testing of samples, evaluation of tests and observation of the impact of individual modifiers on the structure.

The work deals with the investigation of the effects of vacuum degassing and decarburization in high alloyed stainless steel. The reason for this is to increase corrosion resistance and mechanical properties. The theoretical part is devoted to the analysis of options to reduce carbon, nitrogen, hydrogen and manganese at atmospheric pressure and in vacuum. In experimental part there is the description of melting, calculation of conditions facilitating reduction of oxide inclusions as a function of the gas pressure in the furnace and the evaluation of the influence of vacuum on the content reduction of carbon, nitrogen and manganese.

The use of aluminum is a key factor in creating an Eco-friendlier automotive industry. The material has good properties and the ability to reuse the material. The requirement on the material in this industry is very high, due to the exposed working environments. The usage of aluminum will reduce the vehicle’s weight, which in turn will reduce emissions.    Aluminum casting is not free from obstacles. The properties can be altered with different casting methods and the design of the casting to a great extent. This master will focus on how the melt quality will have an impact on the material properties and how it is changed during the process. To fully understand what happens to the melt during the casting process, samples are received at different stages for further investigation. Different data is collected to be able to analyze what happens during the process. A quality measurement called the Quality index is used to determine the change in the quality in the different stages. With data from bifilm and density index, conclusions can be made on how and where the impurities are entering the melt and their effect. A conclusion is made that the degassing harms the quality of the melt.

No description available.