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Úloha síranu železnatého jako regulátoru tuhnutí a redukčního činidla portlandského slínku / The Role of Ferrous Sulphate as a Setting Regulator and a Portland Clinker Reduction AgentMončeková, Miroslava January 2016 (has links)
In 2003, the European Community Obligation (directive 2003/5C/EC) regulates a maximal value of soluble hexavalent chromium to 0.0002 % (per weight of dry cement). This limitation leads to modifications of the regular Portland cement by using of suitable reduction agents. Therefore, the possibilities of chromium reduction become a very actual topic. The primary goal of this work is a basic research of the ferrous sulphate influence on hexavalent chromium reduction and also its influence on Portland clinker hydration process. The reduction ability was determined by UV/VIS method. The mechanism and ferrous sulphate influence on Portland clinker hydration process was observed by isothermal calorimetry and mechanical strength tests. XRD method, SEM-EDS analysis and Raman microscopy were used for identification of formed hydration products. Study of hydration mechanism occurring in this system was focused on the divergence observations from the regular Portland cement hydration. Pore solution analysis provided significant information about chromium behavior during the hydration process (substitution and releasing). Chromium incorporation into structure of hydration products during the reduction process was also studied in the pure tricalciumaluminate system with targeted Cr6+ content. This work suggests the possible substitution of the trivalent and hexavalent chromium into structure of monosulphate (AFm) phase.
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Проектное управление модернизацией производственной системы на металлургических предприятиях в концепции бережливого производства : магистерская диссертация / Project management of the modernization of the production system at metallurgical enterprises in the concept of lean manufacturingЗырянов, К. Ю., Zyryanov, K. Y. January 2020 (has links)
The developed methodology for the modernization of the enterprise’s production system, based on a step-by-step method of managing production processes (6 sigma), the concept of lean manufacturing and statistical data analysis, can be used in projects to modernize the production systems of metallurgical enterprises, increasing their efficiency and competitiveness by: rational use of resources; increase labor productivity; staff involvement. The developed project for the modernization of the enterprise’s production system can be “replicated” at metallurgical enterprises, allowing them to reduce losses, rationally use resources and increase labor productivity. The concept of a project to modernize the enterprise’s production systems using lean manufacturing technologies and project management has found its practical application at the non-ferrous metallurgy enterprise KUZOTsM OJSC. / Разработанная методика модернизации производственной системы предприятия, основанная на пошаговом методе управления процессами производства (6 сигм), концепции бережливого производства и статистическом анализе данных, может быть использована в проектах по модернизации производственных систем металлургических предприятий, повышая эффективность их деятельности и конкурентоспособности за счет: рационального использования ресурсов; повышения производительности труда; вовлеченности персонала. Разработанный проект модернизации производственной системы предприятия может «тиражироваться» на металлургических предприятиях, позволяя сокращать потери, рационально использовать ресурсы и повышать производительность труда. Концепция проекта модернизации производственных систем предприятия с использованием технологий бережливого производства и проектного управления нашло свое практическое применение на предприятии цветной металлургии ОАО «КУЗОЦМ».
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Совершенствование управления технологическими инновациями на предприятиях по глубокой переработке цветных металлов : магистерская диссертация / Improving the management of technological innovation in enterprises for the processing of non-ferrous metalsПолуяхтов, С. Б., Poluyakhtov, S. B. January 2020 (has links)
The process of creating technological innovations in enterprises for the processing of non-ferrous metals is characterized by high complexity and complexity, which stems from the large number of functional units involved, as well as the need to balance the interests of individual functional units with client requirements and achieve an acceptable level of economic efficiency for the enterprise. Therefore, the development of a set of issues dedicated to the management of technological innovation is an important and urgent task. The main idea of the study is that the existing system of organizing business processes for the creation and management of technological innovations in enterprises for the processing of non-ferrous metals in the current economic situation does not allow effective management of the business process. The paper presents a process approach to management, the main feature of which is that when optimizing the process, you must be able to stop on time. The novelty of the thesis lies in the development of an algorithm for managing technological innovation in enterprises for the deep processing of non-ferrous metals. A feature of the algorithm is the choice of the direction of innovation, taking into account the capabilities of the enterprise, the analysis of customer requests, the determination of the required parameters for implementation, the selection of the owner of the process and the determination of key performance indicators, which makes it possible to reasonably make managerial decisions and effectively use all types of enterprise resources. / Процесс создания технологических инноваций на предприятиях по глубокой переработке цветных металлов характеризуется высокой сложностью и комплексностью, которая проистекает из большого количества задействованных функциональных подразделений, а также необходимостью балансирования интересов отдельных функциональных подразделений с требованиями клиента и достижением приемлемого уровня экономической эффективности для предприятия. Поэтому разработка комплекса вопросов, посвящённых управлению технологическими инновациями, представляет собой важную и актуальную задачу. Основная идея исследования заключается в том, что существующая система организации бизнес-процессов создания и управления технологическими инновациями на предприятиях по глубокой переработке цветных металлов в сложившейся экономической ситуации не позволяет эффективно управлять бизнес-процессом. В работе представлен процессный подход к управлению, основной особенностью которого является то, что при оптимизации процесса необходимо уметь вовремя остановиться. Новизна диссертации заключается в разработке алгоритма управления технологическими инновациями на предприятиях по глубокой переработке цветных металлов. Особенностью алгоритма является выбор направления инноваций с учётом возможностей предприятия, анализ запросов заказчиков, определение требуемых параметров для внедрения, выбор владельца процесса и определение ключевых показателей эффективности, что позволяет обоснованно принимать управленческие решения и эффективно использовать все виды ресурсов предприятия.
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Развитие росийско-китайской торговли черными металлами : магистерская диссертация / Development of the Russian-Chinese trade in ferrous metalsДун, Ч., Dong, Z. January 2021 (has links)
ВКР (магистерская диссертация) состоит из введения, трех глав, заключения, библиографического списка, включающего 62 наименования, 2 приложения. Работа включает 31 таблицу и 9 рисунков. Общий объем ВКР (магистерской диссертации) – 138 страниц. Цель магистерской диссертации – развитие теоретико-методических основ и направлений российско-китайской торговли черными металлами. Научная новизна исследования состоит в комплексном современном исследовании российско-китайского внешнеторгового сотрудничества и определении потенциальных направлений их дальнейшего развития. В качестве авторских разработок можно вынести следующие: оценено современное состояние и динамика развития российско-китайских внешнеторговых отношений; определены резервы и направления развития российско-китайского партнерства во внешней торговле. Практическая значимость работы выражается в возможности использования основных положений и результатов в разработке стратегии развития внешнеэкономической деятельности между Россией и Китаем. / The master's thesis consists of an introduction, three chapters, a bibliographic list, including 62 titles, 2 appendices. The work includes 31 tables and 9 figures. The total volume of the dissertation is 138 pages. The purpose of the dissertation is to develop the theoretical and methodological foundations of the Russian-Chinese trade in ferrous metals. Scientific novelty of research in a comprehensive study of Russian-Chinese foreign trade cooperation and their perspective further development. As author's developments, the following can be taken out: assessed the current state and dynamics of the development of Russian-Chinese foreign trade relations; reserves and directions of development of the Russian-Chinese partnership in foreign trade.
The practical significance of the work is expressed in the possibility of using the main provisions and results in the development of a strategy for the development of foreign economic activity between Russia and China.
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Развитие росийско-китайской торговли цветными металлами : магистерская диссертация / Development of the Russian-Chinese trade in non-ferrous metalsЛай, Х., Lai, H. January 2021 (has links)
ВКР (магистерская диссертация) состоит из введения, трех глав, заключения, библиографического списка, включающего 62 наименования. Работа включает 10 таблиц и 13 рисунков. Общий объем ВКР (магистерской диссертации) – 85 страниц. Ключевые слова: торговля цветными металлами, международные отношения, развитие торговли. Цель магистерской диссертации – исследование, оценка и анализ состояния российско-китайской торговли цветными металлами, выявление проблем и перспектив развития. исследование современного состояния российско-китайской торговли цветными металлами и разработать методические рекомендации к ее развитию Научные и практические результаты - оценено современное состояние и динамика развития российско-китайских внешнеторговых отношений - выявлены специфические особенности внешнеторговых отношений - предложены потенциальные направления дальнейшего развития российско-китайской торговли цветными металлами. Предложенные в работе меры по решению существующих в российско-китайской торговле цветными металлами проблем позволят перейти на новый этап развития. Дальнейшее развитие двусторонних отношений между Китаем и Россией имеют широкие перспективы долгосрочного и тесного взаимовыгодного сотрудничества. / The WRC (master's thesis) consists of an introduction, three chapters, a conclusion, a bibliographic list, including 62 titles. The work includes 10 tables and 13 figures. The total volume of the FQP (master's thesis) is 85 pages. Key words: non-ferrous metals trade, international relations, trade development. The purpose of the master's thesis is to research, assess and analyze the state of the Russian-Chinese trade in non-ferrous metals, to identify problems and development prospects. study of the current state of the Russian-Chinese trade in non-ferrous metals and develop guidelines for its development. Scientific and practical results: assessed the current state and dynamics of the development of Russian-Chinese foreign trade relations; revealed the specific features of foreign trade relations; potential directions of further development of the Russian-Chinese trade in non-ferrous metals have been proposed. The measures proposed in the work to solve the problems existing in the Russian-Chinese trade in non-ferrous metals will make it possible to move to a new stage of development. Further development of bilateral relations between China and Russia has broad prospects for long-term and close mutually beneficial cooperation.
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Investigation Of Chemical Processes For The Production Of Commercially Viable High Volume Value-Added Products From Bauxite ResidueGostu, Sumedh 12 January 2018 (has links)
Bayer processing of bauxite employed for production of alumina yield a residue red-mud. The worldwide annual-rate of red-mud generation is approximately 120 million tons, and most of this is stockpiled. Red mud is rich in elements like aluminum, titanium and rare earths, in addition to the major iron-bearing constituents. The objective of this research is to explore such a strategy to extract Iron as fine particulate magnetite. Pyrometallurgical reduction experiments using carbon mixtures and a novel hydrometallurgical route are experimented. Reduction experiments performed with petroleum coke as a reductant resulted in incomplete reduction. The ‘optimal conditionsÂ’ for gaseous state reduction are determined to be: a processing temperature of 540oC ± 10oC, partial pressures CO (g) and CO2 (g) each of 0.070atm (bar) ± 0.001atm.(bar)/ inert diluent-gas: N2 (g), for a conversion-time of 30min. A mathematical-model was developed on the basis of unidirectional-diffusion of CO2 (g) within the CO2 (g)–CO (g)–N2 (g) gas-phase of the porous product-layer. Magnetic separation applied to the optimally reduced sample in: obtaining a magnetic portion with high iron and non-magnetic portion containing nonferrous (Al, Ti) is not successful. This finding was subsequently attributed to the nanometer length-scales crystallites of the predominant iron-containing phase, hydrated ferric-oxide(s) as determined by STEM micrographs. In addition, the presence of substitution for Fe3+ by Al3+ and Ti3+/4+ are determined with the help of MÖssbauer spectrograms. A hydrometallurgical route involving selective leaching and precipitation of iron in red-mud is tried. Red-mud is leached in oxalic acid at: 95˚C, 15 % Pulp density, 2.5 h leaching time, 1.5 pH. Kinetic studies yielded the leaching mechanism to be predominantly fluid film control. Ferric oxalate in the leach liquor is reduced to insoluble ferrous oxalate selectively using Iron powder. The ferrous oxalate formed is ~98 % pure. The precipitated ferrous oxalate is magnetically separated and reduced in Nitrogen atmosphere to form fine particulate magnetite. Additionally an economic feasibility study was conducted for the hydro and pyro alternatives to produce magnetite using Monte Carlo Simulations by imparting uncertainties in various input cost components. A traditional process was also compared to the proposed approaches for Total Capital Investment (TCI), Total Product Cost (TPC), Net Present Value (NPV) and sensitivity analysis. ~52 % reduction in Total product cost, 46 % reduction in Total Capital Investment was achieved for the hydrometallurgical process when compared to the traditional approach.
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Potencial evocado auditivo de tronco encefálico e análise proteômica em ratos expostos a chumbo e suplementados com ferro / Brainstem auditory-evoked potential and proteomic analysis in rats exposed to lead and supplemented with ironZucki, Fernanda 21 June 2013 (has links)
A falta de consenso na literatura acerca dos efeitos tóxicos do chumbo no sistema auditivo é notória, tanto em estudos clínicos quanto experimentais. Em adição, tem sido relatado que o ferro apresenta um efeito protetor na toxicidade cerebral causada pelo chumbo. Assim, estudos clínicos e bioquímicos têm sido realizados no intuito de compreender a relação entre o chumbo e o sistema auditivo, bem como identificar possíveis substâncias protetoras para a toxicidade deste metal. Neste sentido, no presente estudo verificou-se o processo maturacional do nervo auditivo e tronco encefálico, associado à análise proteômica da porção auditiva do tronco encefálico de ratos expostos a acetato de chumbo e suplementados com sulfato ferroso. O experimento foi realizado por seis semanas com 30 ratos (Rattus norvergicus, variedade Wistar) machos, recém-desmamados, divididos em seis grupos de cinco animais cada, sendo um controle, que recebeu água deionizada; dois grupos experimentais que receberam 100 mg/L de Pb(CH3COO)2 na água de beber, sendo administrado simultaneamente para um deles 20 mg/kg de FeSO4 a cada dois dias; dois grupos que receberam a dose de 400 mg/L de Pb (CH3COO)2 na água de beber, onde para um deles foi administrado simultaneamente 20 mg/kg de FeSO4 a cada dois dias e um grupo experimental que recebeu água deionizada e uma solução de 20 mg/kg de FeSO4 a cada dois dias. O processo maturacional do sistema auditivo foi verificado por meio da análise do Potencial Evocado Auditivo de Tronco Encefálico (PEATE) em dois momentos distintos, antes e depois da exposição ao chumbo. Os animais foram então sacrificados, coletado sangue e removido o tronco encefálico. A concentração de chumbo no sangue e tronco encefálico, apresentou um efeito dose-resposta, confirmado pela alta correlação entre a concentração nos dois compartimentos (r2=0,905, p<0,0001), tendo o sulfato ferroso reduzido a concentração de chumbo no sangue e no tecido, embora a diferença só tenha sido significativa para o sangue grupo que recebeu 100 mg/L de Pb(CH3COO)2). Com relação ao PEATE observou-se diferença estatisticamente significativa para o interpico I-II (p=0,049) nos grupos experimentais 100 mg/L Pb(CH3COO)2 e 400 mg/L Pb(CH3COO)2 e interpico I-IV, quando comparados os grupos 100 mg/L Pb(CH3COO)2 e 100 mg/L Pb(CH3COO)2 + FeSO4 (p=0,033). A análise proteômica apontou uma diminuição considerável no número de spots proteicos detectados em todos os grupos experimentais em relação ao controle, bem como uma redução na expressão do padrão proteico. Assim, o presente estudo reforça a hipótese do papel deletério do chumbo nas dosagens de 100 e 400 mg/L de Pb (CH3COO)2 na maturação do nervo auditivo e região do núcleo coclear, com possível efeito protetor do ferro. A análise proteômica do tronco encefálico de ratos demonstrou que o acetato de chumbo altera a expressão proteica desta estrutura, contudo o efeito protetor do sulfato ferroso não foi confirmado nas proteínas identificadas. / There is a lack of consensus in the literature about the toxic effects of lead in the auditory system, both in clinical and experimental studies. In addition to that, it has been reported that iron has a protective effect on brain toxicity caused by lead. Therefore, clinical and biochemical studies have been carried out to understand the relationship between Pb and the auditory function, as well as if the ferreous sulfate as an otoprotectant. In this study the maturational process of the auditory nerve and brainstem and the proteomic profile of the auditory portion of the brainstem of rats exposed to lead and supplemented with iron were evaluated. The experiment was carried out for six weeks with 30 wealing rats (Rattus norvegicus, Wistar), divided into six groups of five animals each: a control group that received deionized water; two experimental groups receiving 100 mg/L Pb(CH3COO)2 in drinking water, being given 20 mg/kg FeSO4 simultaneously to one of them every two days; two groups received 400 mg/LPb(CH3COO)2 in drinking water, where to one of them was given 20 mg/kg FeSO4 simultaneously every two days; and an experimental group that received deionized water and a solution of 20 mg/kg FeSO4 every two days. The maturational process of the auditory system was verified by analyzing the Brainstem Auditory-Evoked Potential (BAEP) at two different times, before and after lead exposure. The animals were sacrificed, their blood collected and brainstem removed. The concentration of lead in blood and brain stem showed a dose-response, confirmed by correlation between the concentration in the two compartments (rr2 = 0.905, p <0.0001). Ferreous sulfate reduced the levels of lead in blood and tissue, although the difference was only significant for blood (group receiving 100 mg/L Pb(CH3COO)2). Concerning to BEAP we observed a statistically significant difference for the interpeak I-II (p = 0.049) in the experimental groups 100 and 400 mg/L Pb(CH3COO)2 and for the interpeak I-IV, when groups 100 and 100 mg/L Pb(CH3COO)2 + FeSO4 were compared (p = 0.033). The proteomic analysis showed a considerable decrease in the number of protein spots detected in all experimental groups compared to control, as well as a reduction in the expression pattern of the proteins. Thus, the present study reinforces the hypothesis of deleterious role of Pb in dosages of 100 and 400 mg/L Pb(CH3COO)2 in the maturation of the auditory nerve and cochlear nucleus region, with a possible protective effect of ferreous sulfate. The proteomic analysis of the brainstem of rats showed that lead acetate alters protein expression of this structure. However, the protective effect of ferreous sulfate was not confirmed for the identified proteins.
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Esudo do aço inoxidável especial UNS S31254 visando seu emprego em técnicas eletroanalíticas / Study of special stainless steel UNS S31254 aiming its use in electroanalytical techniquesTerra, Lúcia Helena 19 August 2004 (has links)
O aço especial UNS S31254 (aço 254), um aço inoxidável austenítico contendo 20,1% de cromo, 18,4% de níquel e 6,42% de molibdênio foi estudado com o objetivo de ser aplicado em técnicas eletroanalíticas, tais como a potenciometria, a condutimetria e como eletrodo indicador em medidas de pH. Os estudos eletroanalíticos foram precedidos de curvas de polarização potenciostáticas e potenciodinâmicas e de ensaios não eletroquímicos (FTICR, MEV e XPS), em que se caracterizou a presença do filme passivante. Grande parte dos estudos incluíram, para efeito de comparação, os aços UNS S 31603 (aço 316 L) e UNS S31678 (aço F 138), o primeiro de largo emprego comercial e o último, aplicável em implantes ortopédicos. Os estudos, realizados a 25° C, se iniciaram com a caracterização eletroquímica dos referidos materiais imersos em meios aquosos de ácidos clorídrico, acético, nítrico, sulfúrico e galacturônico, e dos sais cloreto de sódio, sulfato de sódio e nitrato de sódio, variando-se a concentração do eletrólito. O aço 254 se mostrou passivado, na grande maioria dos meios estudados, em toda a faixa de potenciais que se estende do potencial de corrosão (Ecorr, potencial de circuito aberto estacionário) até o potencial de transpassivação (onde ocorre o rompimento do filme e, na maioria dos meios, a oxidação generalizada da superfície e a reação H2O/O2). Em meio de ácido acético a faixa de potencial em que o referido aço se mantém passivado é a mais ampla, indicando que o rompimento do filme passivo exige maior energia, em virtude do maior teor de molibdênio superficial detectado por MEV. A corrosão por pite foi observada em meios de HCI e de NaCI a potenciais mais positivos do que o de transpassivação. A caracterização da superfície por MEV mostrou que as inclusões presentes no aço são constituídas basicamente de óxidos de alumínio e de cálcio. A análise por XPS da superfície do aço 254 apenas polido e exposto ao ar revelou a presença de Mo (VI) na superfície; em meio de NaCI 0,15 mol L-1 há o enriquecimento gradual de Mo (VI) quando se varia o potencial desde o Ecorr, passando por um potencial passivo e se estendendo a um potencial 50 mV acima do potencial de transpassivação. O aço 254 pode ser empregado em substituição à platina em todas as determinações eletroanalíticas realizadas neste trabalho, envolvendo titulações potenciométricas, medidas condutimétricas e determinação de pH. Em medidas de pH em sistemas com força iônica mais baixa, entretanto, é necessário um controle mais adequado do tratamento superficial, além dos realizados neste trabalho, para que a resposta do petencial seja mais rápida. Estes estudos podem contribuir para baixar o custo de análises industriais e de experimentos que venham a ser realizados em laboratórios diáticos. / Special UNS S31254 stainless steel (254 SS), an austenitic stainless steel with 20.1% Cr, 18.4% Ni and 6.42% Mo has been studied in order to be applied in electroanalytical techniques as potentiometry, conductimetry and as a sensor in pH measurements. The electroanalytical studies were preceded of potentiostatic and potentiodynamic polarization curves. The surface characterization was made using FTCIR, SEM and XPS as techniques. The studies have included, for comparison, UNS S 31603 (316 L SS) and UNS S31678 (F 138 SS); the former is commercially employed in a large extension and the latter is applicable in orthopedic implants. The experiments were made at 25° C, beginning with the electrochemical characterization of the ferrous materiais in different aqueous media: chloridric, acetic, sulfuric, nitric and D-galacturonic acids and saline solutions of sodium chloride, sodium sulfate and sodium nitrate, changing the electrolyte concentration. SS 254 is passivated in most of the studied media, on the entire potential range analyzed (from corrosion potential to transpassivation potential). In acetic media it was observed the largest potential range where 254 SS is passivated, indicating that a higher energy is necessary to disrupt the passivant film, due to a higher Mo concentration at the surface, detected using SEM. Pitting corrosion was observed in HCl and NaCl media at potential more positive than Etr. SEM surface characterizations have shown aluminium oxide and calcium oxide inclusions. XPS analyses have indicated the presence of Mo (VI) on the polished surface and that there is a gradual Mo (VI) increasing, in solution, when the potential changes from Ecorr to E > Etr. 254 SS can be used in potentiometric and conductimetric titrations and as a sensor electrode for pH measurements. However, in biological applications a more adequate surface treatment is needed in order to obtain rapid responses. Overall the results suggest that 254 can be used as substitute of platinum in different electroanalytical techniques. This finding contributes to lower the cost of experiments to be performed in didactic laboratories and/or industrial analyses.
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Estudo da microestrutura, da textura cristalográfica e da recristalização em chapas obtidas por lingotamento contínuo e semicontínuo da liga de alumínio AA4006. / A study of the microstructure, crystallographic texture, and recrystallization in AA4006 alloy strips produced by twin roll caster and direct chill processes.Souza, Fabrício Mendes 29 February 2012 (has links)
A liga de alumínio designada AA4006 é muito utilizada na indústria. É uma liga do sistema Al-Fe-Si, com teores (% em massa) de Si na faixa de 0,8 a 1,2% e Fe entre 0,5 e 0,8%. Apesar de ser bastante utilizada, ela foi pouco estudada. Neste trabalho foi realizado um estudo comparativo da microestrutura e da textura cristalográfica entre chapas da liga AA4006 produzidas por dois processos industriais de lingotamento: contínuo (Twin roll caster TRC) e semicontínuo (Direct chill DC). Para a caracterização microestrutural, foram utilizadas as técnicas de microscopia óptica com luz polarizada, microscopia eletrônica de varredura com microanálise química, medidas de condutividade elétrica e ensaios de dureza Brinell. A textura cristalográfica foi determinada por difração de raios X. Foram detectadas e discutidas diferenças significativas nas morfologias e distribuições de grãos e de partículas de fases intermetálicas. O estudo da textura cristalográfica foi realizado ao longo da espessura das tiras e os resultados mostraram variações significativas da textura entre as chapas ao longo da espessura. A chapa produzida por lingotamento contínuo apresentou uma típica textura de cisalhamento nas proximidades de sua superfície, enquanto nas regiões mais internas a fibra foi observada. O estudo da recristalização de chapas metálicas laminadas a frio é muito útil para a obtenção da temperatura de amolecimento do material submetido a um tratamento térmico. Tratamentos térmicos isócronos no intervalo de uma hora foram feitos em amostras das duas chapas e a chapa produzida pelo processo TRC apresentou a temperatura para 50% de recristalização em torno de 290 ºC e a amostra da chapa produzida pelo processo DC em torno de 270 ºC. A textura cristalográfica pode mudar com a recristalização e com a laminação do metal. Utilizando estas etapas de processamento do material, a orientação dos grãos de uma tira metálica pode ser otimizada, a fim de, por exemplo, melhorar a estampabilidade de chapas na obtenção de um dado produto com valor agregado. Neste trabalho as curvas de amolecimento para duas chapas produzidas por lingotamento contínuo e lingotamento semicontínuo da liga de alumínio AA4006 também foram determinadas e comparadas. Embora as diferenças detectadas entre as curvas de amolecimento tenham sido pequenas, foi possível verificar que a recristalização da chapa produzida por twin roll caster TRC ocorre em temperaturas mais elevadas do que na chapa produzida pelo processo direct chill DC. Resultados da textura cristalográfica em amostras destas chapas (laminadas e recozidas) foram obtidos utilizando difração de raios X e difração de elétrons retroespalhados EBSD. Estes resultados indicaram a presença da textura de cisalhamento na superfície e a fibra no centro da amostra laminada a frio (70% de redução) da chapa obtida por lingotamento contínuo. Na amostra da chapa obtida por lingotamento semicontínuo, a componente cubo e a fibra foram vistas na superfície e no centro. Uma textura fraca com grãos orientados ao acaso foi vista nas duas amostras (TRC e DC) recristalizadas das duas chapas, possivelmente, devido à nucleação estimulada por partículas. A fibra desapareceu nas amostras (TRC e DC) recristalizadas. / AA4006 Aluminum alloy is extensively used in industry. It belongs to the Al-Fe-Si system, with Si between 0,8 and 1,2 % mass, and Fe between 0,5 and 0,8 % mass. This alloy is less studied despite its extensive use. A comparative microstructural study has been performed in as-received AA4006 alloy strip produced by two industrial casting processes: twin roll caster (TRC) and direct chill (DC). Polarized optical microscopy, scanning electron microscopy with microanalysis, electrical conductivity measurements and Brinnel hardness tests have been used for microstructural characterization. Significant differences in the grain and intermetallic particle sizes, morphologies and distributions were detected and are discussed. Thermal treatments effects on the silicon content in solid solution were also studied. Crystallographic textures have been also determined. Textures across thickness of both sheets have been analyzed and compared. Results showed significant texture changes across thickness of the specimens. Texture analysis was carried out using X-ray diffraction technique. Twin roll caster (TRC) sheet presented the typical shear texture near the surface, while, in internal regions, the -fibre was observed. A recrystallization study of cold rolled metallic sheets is very important to obtain softening temperature for the material during annealing. After cold rolling with 70% of reduction in thickness, followed by isochronous heat treatments, the samples of the two sheets produced by TRC and DC presented a 50% recrystallization temperature around 290 ºC and 270 ºC, respectively. Crystallographic texture can change during the metal rolling and recrystallization. These processing steps can optimize the grain orientation distribution in a metal strip to improve, for instance, the stamping process, in order to obtain an aggregated value product. Softening curves were also compared and determined for the two sheets (rolled and annealed) of the AA4006 aluminum alloy produced by twin roll caster TRC and direct chill DC processes. It was detected that the recrystallization of the strip produced by TRC process occurs at a higher temperature than that for the DC process, despite the little differences in their softening curves. Crystallographic texture results, for the sheet samples, were obtained by using X-ray diffraction and electron back scatter diffraction EBSD techniques. These results indicated the shear texture presence on the surface and fiber at the center of the cold rolled (70% area reduction) sample for the sheet produced by TRC process. In the sheet sample produced by the DC process, under the same conditions, the cube component and fiber texture (at the surface and at the center) were observed. A texture with random oriented grains was detected in two deformed and recrystallized samples of the two sheets (TRC and DC). It is suggested that this texture occurs due to the particle stimulated nucleation. There was fiber absence in the recrystallized samples (TRC and DC).
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Studie av en medeltida husgrund : en analys av bronsfynd från husgrund 6, Västergarn, Gotland / An analysis of bronze from a medieval building-foundationOlsson, Tobias January 2012 (has links)
This essay is an analysis of the objects made of bronze found in an excavation Västergarn parish, Gotland, in 2010, conducted by the University of Gotland. The studied material presented in this essay comes from contexts inside, as well as nearby the foundation of a medieval building which purpose is still not certain. The first purpose of this study is to present the bronze-objects found inside and nearby the foundation of house 6, and to see if there are any datable objects. There is also a discussion whether there has been any bronze-crafting in the area. The second purpose is to make a contextual analysis to see if there are any differences between the material found outside and inside of the building, and what conclusions can be made regarding the function and use of the building. A spatial analysis has also been made to distinguish any patterns of the distribution of material inside and around the house.The result of this essay is partly a presentation of the material, but also that there has occurred some bronze-crafting in the form of cutting metal sheets inside or near the foundation treated in this essay. There is no evidence for casting bronze near the house foundation.The frequency of finds from outside the foundation compared to the frequency of finds within the foundation is nearly quadruple, which is to be expected since there probably has been a wooden floor inside the house to prevent all but the tiniest objects from falling through. Objects that landed on the floor were cleaned out, just to land near the entrance of the building. The finds from within the building much resembles the finds from outside the building, and the distribution-patterns of the trench indicates that the entrance to the building probably was located near the north-west corner or near the south-east corner.Hopefully, this study contributes another piece to the great puzzle that is Västergarn.
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