Submitted by Izabel Franco (izabel-franco@ufscar.br) on 2016-09-13T19:55:14Z No. of bitstreams: 1 DissALBS.pdf: 7658447 bytes, checksum: 19eb5b4bde9f17023deef594771a766e (MD5) / Approved for entry into archive by Marina Freitas (marinapf@ufscar.br) on 2016-09-15T13:40:30Z (GMT) No. of bitstreams: 1 DissALBS.pdf: 7658447 bytes, checksum: 19eb5b4bde9f17023deef594771a766e (MD5) / Approved for entry into archive by Marina Freitas (marinapf@ufscar.br) on 2016-09-15T13:40:35Z (GMT) No. of bitstreams: 1 DissALBS.pdf: 7658447 bytes, checksum: 19eb5b4bde9f17023deef594771a766e (MD5) / Made available in DSpace on 2016-09-15T13:40:43Z (GMT). No. of bitstreams: 1 DissALBS.pdf: 7658447 bytes, checksum: 19eb5b4bde9f17023deef594771a766e (MD5) Previous issue date: 2015-02-26 / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Improving the steel processing is a major focus of the metallurgical industry because the need of materials and products with lower weight and more strength, in addition to increasingly stringent specifications imposed by buyers. The knowledge and kinetic control of the phenomena that occur during hot processing such as recrystallization, precipitation and grain growth are mandatory for the grain size refinement, which is a parameter that determines the properties of semi-finished products. In hot strip rolling the material is subjected to deformation schedules consisting of five to seven passes, with rolling mill arranged one in front of the other, performing a continuous operation. Over the years, several paths have been followed to investigate the industrial processing. One can cite as examples the use of pilot plants, physical simulations, and numerical simulations. The objective of this study was, therefore, to model the process of the hot strip rolling, enabling the analysis of how the process parameters such as temperature, strain, strain rate and austenitic grain size evolve during rolling of the C-Mn steels, using the commercial software DEFORM™ 3D developed for forming processes analysis. Seven rolling passes of an industrial process described were simulated. The results shown a good agreement of the load and temperature levels attained during simulation with the literature values, indicating that the model used to represent the industrial rolling process is suitable. The numerical reconstruction of processing shows clearly the presence of the strain, temperature and strain rate gradients during hot strip rolling mill, generating microstructural gradients. The evolution of rolling process minimizes the gradients, but some ones still remain at the end of rolling process. Thus, this study shows the effectiveness of the model to predict the evolution of the microstructure in a hot rolling process. / Aperfeiçoar o processamento dos aços é um dos principais focos da indústria metalúrgica devido à necessidade de materiais mais resistentes e produtos com menor peso, além das especificações cada vez mais rigorosas impostas pelos compradores. O conhecimento e controle da cinética dos fenômenos que ocorrem durante o processamento mecânico a quente como a recristalização, a precipitação e o crescimento de grão são mandatórios para o refinamento do tamanho dos grãos, o qual é um parâmetro que determina as propriedades dos produtos semiacabados. No processo de laminação de tiras a quente o material é submetido a sequências de deformação constituídas de cinco a sete passes, realizando uma operação contínua. Vários caminhos têm sido seguidos para investigar o processamento industrial, podem-se citar como exemplos a utilização de plantas pilotos, a simulação física e a simulação numérica. O objetivo deste trabalho foi, portanto, modelar o processo de laminação de tiras a quente, possibilitando analisar como os parâmetros do processo tais como temperatura, deformação, taxa de deformação e tamanho de grão austenítico evoluem durante a laminação de aços C-Mn, utilizando o software DEFORM™ 3D, desenvolvido para análises de processos de conformação. Foram simulados sete passes de laminação de um processo industrial descrito na literatura. Os resultados mostraram uma boa concordância entre os valores de carga e temperatura simulados com os valores medidos na planta industrial, indicando que o modelo utilizado para representar o processo é adequado. A reconstrução numérica do processamento mostra claramente a presença de gradientes de deformação, de temperatura e de taxa de deformação durante a laminação de tiras a quente, gerando gradientes microestruturais. A evolução da laminação minimiza os gradientes, todavia alguns ainda permanecem no final da laminação. Esse estudo mostrou a eficácia do modelo em predizer a evolução microestrutural do aço em um processo de laminação a quente.

Объектом исследования является технология изготовления детали типа стакан из сплава АМг2М. Цель работы – анализ технологических процессов, применяемых при изготовлении детали типа стакан из сплава АМг2М. В процессе работы проведено экспериментальное исследование глубокой вытяжки детали типа стакан из сплава АМг2М, а также конечно-разностное моделирование процесса в 3D постановке. В результате исследования получены данные о распределении напряжений и деформаций детали типа стакан. Сделаны выводы о факторах, при которых возникает проблема образования гофр. / The object of research is the technology of manufacturing a detail of the type of a glass made of AMg2M alloy. The purpose of this work is to analyze the technological processes used in the manufacture of a component of the AMG2M alloy glass type. In the course of the work, an experimental study was carried out of the deep drawing of a detail of the type of a glass made of AMg2M alloy, as well as finite-difference modeling of the process in a 3D setting. As a result of the study, data were obtained on the distribution of stresses and deformations of a glass-like part. Conclusions are drawn about the factors that cause the problem of corrugation.

Объектом исследования является технология изготовления детали типа стакан из сплава АМг2М. Цель работы – анализ технологических процессов, применяемых при изготовлении детали типа стакан из сплава АМг2М. В процессе работы проведено экспериментальное исследование глубокой вытяжки детали типа стакан из сплава АМг2М, а также конечно-разностное моделирование процесса в 3D постановке. В результате исследования получены данные о распределении напряжений и деформаций детали типа стакан. Сделаны выводы о факторах, при которых возникает проблема образования гофр. / The object of research is the technology of manufacturing a detail of the type of a glass made of AMg2M alloy. The purpose of this work is to analyze the technological processes used in the manufacture of a component of the AMG2M alloy glass type. In the course of the work, an experimental study was carried out of the deep drawing of a detail of the type of a glass made of AMg2M alloy, as well as finite-difference modeling of the process in a 3D setting. As a result of the study, data were obtained on the distribution of stresses and deformations of a glass-like part. Conclusions are drawn about the factors that cause the problem of corrugation.

Constitutive behavior models for steels are typically semi-empirical, however recently neural network is also being used. Existing neural network models are highly complex with a large network structure i.e. the number of neurons and layers. Furthermore, the network structure is different for different grades of steel. In the present study a simple neural network structure, 3:4:1, is developed which models flow behavior better than other models available in literature. Using this neural network structure constitutive behavior of 8 steels: 4 carbon steels, V and V-Ti microalloyed steels, an austenitic stainless steel and a high speed steel could be modeled with reasonable accuracy. The stress-strain behavior for the vanadium microalloyed steel was obtained from hot compression tests carried out at 850-1150 C and 0.1-60 s-1. It is found that a better estimate of the constants in the semi-empirical model developed for this steel could be obtained by simultaneous nonlinear regression. A model that can predict the effect of chemical composition on the constitutive behavior would be industrially useful for e.g., in optimizing rolling schedules for new grades of steel. In the present study, a neural network model, 5:6:1, is developed which predicts the flow behavior for a range of carbon steels. It is found that the effect of manganese is best accounted for by taking Ceq=C+Mn/6 as one of the inputs of the network. Predictions from this model show that the effect of carbon on flow stress is nonlinear. The hot strip mill at Jindal Vijaynagar Steel Ltd., Toranagallu, Karnataka, India, was simulated for calculating the rolling loads, finish rolling temperature (FRT) and microstructure evolution. DEFORM-2d a commercial finite element package was used to simulate deformation and heat transfer in the rolling mill. The simulation was carried out for 18 strips of 2-4 mm thickness with compositions in the range and 0.025-0.139 %C. The rolling loads and FRT could be calculated within 15 % and 15 C respectively. Analysis based on the variation in the roll diameter, roll gap and the effect of roll flattening and temperature of the roll showed that an error of 6 % is inherent in the prediction of loads. Simulation results indicated that strain induced transformation to ferrite occurred in the finishing mill. The microstructure after rolling was validated against experimental data for ferrite microstructure and mechanical properties. The mechanical properties of steels with predominantly ferrite microstructures depend on the prior austenite grain size, strain retained before transformation and cooling rate on the run-out table. A parametric study based on experimental data available in literature showed that a variation in cooling rate by a factor of two on the run-out table gives rise to only a 20 MPa variation in the mechanical properties.

No description available.