A series of model steels containing copper levels up to 0.48wt%, nickel up to 0.22wt% and silicon levels of 0.52wt% were oxidised in air at 1050 and 1150??C, and in a CO2-N2 mixture at 1250??C for times of up to 3 hours. The scaling kinetics were measured and the behaviour of copper-rich phase formation at the scale/metal interface was investigated. When oxidised at 1050/1150??C, significant quantities of copper-rich phase were observed for most model steels. The relatively high oxidation rate under these conditions led to the rapid development of a copper-rich layer with little copper diffusing into the metal. However, when oxidised at 1250??C, the copper-rich phase did not form for a significant amount of time; and for some model steels, not at all. This was attributed to the considerably lower oxidation rate and the fact that more copper was found to have diffused into the metal. Alloying additions of nickel and silicon were found to be beneficial in reducing the amount of copper-rich phase measured at the scale/metal interface under the conditions investigated at 1150??C and 1250??C. This occurred because nickel and silicon addition promoted the occlusion of copper-rich phase into the scale. Copper enrichment during oxidation was modelled using a numerical description of the diffusion processes involved. Predictions of the time for commencement of copper-rich phase formation at 1250??C were in close agreement with observation. Agreement between predicted and observed copper-rich layer thickness was less successful under conditions where occlusion was significant, and the measured thickness varied non-uniformly with time. The cracking susceptibility of the model steels was examined using a hot compression test. Oxidation was performed in air at 1050, 1150 and 1250??C and most specimens were compressed at 1050??C. The amount of cracking was found to increase with the amount of copper-rich phase precipitated at the scale/metal interface during oxidation. In general, nickel addition reduced the amount of cracking at all temperatures; and under some conditions prevented cracking altogether. Silicon reduced or completely suppressed cracking when the subscale formed was liquid. The beneficial effects of nickel and silicon addition were attributed to their effect of promoting copper occlusion.

Thesis (Ph.D.)--University of Wollongong, 2005. / Typescript. Includes bibliographical references: leaf 252-266.

Thesis (M.Sc.(Applied Science-Metallurgy))--University of Pretoria, 2008. / Abstract in English. Includes bibliographical references (leaves 136-145).

Thesis (M.S.)--West Virginia University, 1998. / Title from document title page. Document formatted into pages; contains xv, 98 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 84).

Thèse (M.Sc.A.)-- Université du Québec à Chicoutimi, 2002. / Document électronique également accessible en format PDF. CaQCU

Este trabalho refere-se à otimização energética na produção de fio-máquina, onde os aços estudados foram os de baixo carbono. O trabalho foi desenvolvido com o apoio de uma empresa parceira que cedeu as instalações e acesso às informações necessários ao desenvolvimento da dissertação. O objetivo geral do trabalho foi reduzir o consumo de energia de reaquecimento de tarugos para laminação de vergalhões e fio-máquina em rolos. Os objetivos específicos foram: descrever os preceitos teóricos a respeito do processo de reaquecimento; realizar um levantamento do estado da arte em relação à influência das variáveis de enfornamento nas propriedades do material e em relação ao consumo de energia em fornos de reaquecimento; melhorar o conhecimento existe na empresa parceira do estudo a respeito do processo de enfornamento e otimizar o processo de enfornamento na empresa. Para desenvolvimento da trabalho foi necessário o acompanhamento das energias envolvidas: energia de deformação e energia de reaquecimento. Quanto maior a temperatura de laminação, menor será a energia necessária para deformar o material, porém, maior será a energia de reaquecimento, ocorrendo maior consumo de combustível. Para analisar o consumo das energias, foi feito o acompanhamento da corrente elétrica das principais gaiolas para duas bitolas, depois, foi alterada a temperatura e medida novamente a corrente elétrica e o consumo do gás natural. Esta sequência de testes e medições visou identificar oportunidades para redução da temperatura de laminação e a influência na corrente elétrica das gaiolas do laminador. Uma das premissas, da realização deste trabalho, é que sejam alcançados os objetivos estabelecidos com a manutenção da qualidade do material e de suas propriedades mecânicas. Após a realização dos testes, constatou-se que é possível laminar com temperatura 20°C abaixo dos valores praticados atualmente, porém, a grande limitação é a última gaiola do trem médio de laminação, que trabalha, nestas condições, com a corrente elétrica no limite de desarme, sendo muito grande o risco de parada eminente do laminador. Recomenda-se implantar um investimento para aumentar a potência do acionamento desta gaiola. Com a redução em 20°C nas temperaturas de ajuste do forno economiza-se, nas condições do estudo, 0,36 Nm³/t. / This master dissertation refers to energy optimization in the production of wire rod from low-carbon steels. The work was supported by a partner company that gave access to the facilities and information necessary for the development of the dissertation. The general objective of this work was to reduce the energy consumption of billet reheating for rolling rebar and wire rod in coils. The specific objectives were: to describe the theoretical precepts about the reheating process; to describe the state of the art regarding the influence of variables in reheating process and its relation to energy consumption; improve knowledge exist in the partner company about the process and optimize the reheating process of the company. For development work was necessary monitoring of the energies involved, deformation energy and reheating energy. If the temperature of the process is higher, the energy required to deform the material is lower, however, the energy of rewarming is higher, causing higher fuel consumption. To analyze the deformation energy, the electrical current was monitored at two main cages for two different products, then the temperature was changed and the electric current was measured again as well as the consumption of natural gas. This sequence of tests and measurements aimed at to identify opportunities to reduce the process temperature and the influence of electrical current in rolling cages. One of the assumptions of the present study is to achieve the goals maintaining the quality of the material and its mechanical properties. After the tests, we found that it is possible laminar temperature 20°C below than the values currently practiced, however, the major limitation is the M4 cage that works, on these conditions, with the electrical current in the trip limit, being very great risk of imminent stop of the rolling mill. It is recommended to increase the power of the drive cage. With the reduction at 20°C in temperature adjustment of the oven, it saves 0.36 Nm³/t.

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Made available in DSpace on 2014-12-17T14:58:06Z (GMT). No. of bitstreams: 1 RodrigoMS_DISSERT.pdf: 4460162 bytes, checksum: 823c9d3e0475b4431fb15b4de861b51b (MD5) Previous issue date: 2011-03-30 / In the State of Rio Grande do Norte potteries are distributed in several counties in the four meso, which are: West Potiguar, Center Potiguar, Agreste Potiguar and East Portiguar. The ceramics, mostly, are responsible for products used in construction as bricks, tiles and white brick and wood used as fuel. This paper had a primary focus in the region of Serid?. The furnaces in this region, used to manufacture bricks are configured Caieira and Valt, in most of them using principles rustic, usually operated in an empirical way, using principles of control rather primitive, predominantly visual control. The focus of this study was to analyze the differences in the thermophysical, mechanical and geometric characteristics of bricks produced by Caieira and vault furnaces, using the NBR 15720 and the evaluation of energy efficiency in both furnaces. Thermophysical characteristics were analyzed through tests to determine the water absorption obtained from the difference between dry mass and wet mass of the sample and analysis of the thermal gradient, the mechanical characteristics from determination of the compressive strength of ceramic brick popularly known as bricks and also analyzed the geometrical characteristics of the bricks in order to verify the homogeneity of manufacturing. The tests showed that the energy difference of the two furnaces is not considered responsible for a significant difference in the properties of the products / No estado do Rio Grande do Norte as olarias s?o distribu?das em diversos munic?pios, nas quatro mesorregi?es, que s?o: Oeste Potiguar, Centro Potiguar, Agreste Potiguar e Leste Potiguar. As cer?micas, em sua maioria, s?o respons?veis por produtos utilizados na constru??o civil como tijolos furados, tijolos brancos e telhas e utilizam como combust?vel a lenha. Este trabalho teve um enfoque principal na ind?stria cer?mica na regi?o do Serid?. Os fornos nessa regi?o, utilizados para a fabrica??o de tijolos furados possuem a configura??o caieira e ab?bada, geralmente operados de forma emp?rica, utilizando princ?pios de controle bastante primitivos, sendo predominante o controle visual. O objetivo deste trabalho foi analisar as diferen?as nas caracter?sticas termof?sicas, mec?nicas e geom?tricas dos tijolos produzidos pelos fornos caieira e ab?bada, utilizando a NBR 15720, que trata de blocos de alvenaria e a avalia??o do rendimento energ?tico de ambos os fornos. Foram analisadas as caracter?sticas termof?sicas por meio dos ensaios de determina??o da absor??o de ?gua obtido a partir da diferen?a entre a massa seca e a massa ?mida das amostras e da an?lise do gradiente t?rmico; as caracter?sticas mec?nicas a partir da determina??o da resist?ncia ? compress?o dos blocos cer?micos popularmente conhecidos como tijolos e tamb?m foram analisadas as caracter?sticas geom?tricas dos tijolos com o objetivo de verificar a homogeneidade da fabrica??o. Os ensaios realizados mostraram que a diferen?a energ?tica dos dois tipos de fornos analisados n?o ? respons?vel por uma diferen?a significativa nas propriedades dos produtos produzidos