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A otimização de processos e a redução de custos são os dois principais fatores que sustentam a competitividade das indústrias atualmente. Diante deste cenário, buscou-se otimizar o processo de fabricação de barras trefiladas de aço mola SAE 9254, através da eliminação do recozimento anterior ao processo de trefilação, por intermédio de um resfriamento controlado no cooling conveyor, na laminação.. Para isso, a taxa de resfriamento do fio-máquina após a laminação foi variada a fim de garantir a homogeneização da dureza ao longo das espiras, característica essa essencial para o processamento na trefila. Além da redução de custos com o recozimento, se o objetivo fosse alcançado, poder-se-ia otimizar o processo de reaquecimento deste aço na laminação. Como resultado, seria possível melhorar a qualidade superficial do fio-máquina e, por conseqüência, aumentar o rendimento metálico do produto, sem que a descarbonetação máxima e média fossem prejudicadas. Os experimentos foram desenvolvidos com base no resfriamento do fio-máquina no cooling conveyor. Durante o processamento na laminação, foi realizada uma amostragem especial a fim de mapear a variação das propriedades ao longo das espiras. Os resultados apontaram que é possível a otimização do processo de fabricação do aço mola SAE 9254, principalmente para a condição de resfriamento na laminação quando utilizado um escalonamento na velocidade de transporte do fio-máquina no cooling conveyor. Este incremento nas velocidades de deslocamento do material, feita através do escalonamento da velocidade, propicia uma alteração nos “pontos quentes” das espiras, gerando uma uniformidade maior em seu resfriamento, garantindo assim, uma homogeneidade nas propriedades mecânicas. / The process optimization and cost reduction are the two main factors that gives sustainability for today industries competitiveness. For this reason, it was attempted to optimize the manufacturing process of cold draw bars of SAE 9254 spring steel by eliminating pre-annealing of wire drawing, through a controlled cooling on the cooling conveyor, in the rolling mill process. For this, the cooling rate of wire rod after rolling process was varied to ensure the homogeneity of hardness along the coil, the essential feature for wire drawing process. In addition to reducing costs annealing, if the purpose was reached, the reheating process would be optimized in the rolling mill. As a result, it would be possible to improve the surface quality of wire rod and, consequently, increase the metallic yield of the product, without the decarburization maximum and average were damaged. The experiments were developed based on wire rod cooling thermograph in the cooling conveyor. During rolling mill processing, special sampling was performed to map the variation of properties along the coils. The results showed that it is possible to optimize the manufacturing process of the SAE 9254 spring steel, mainly for the cooling condition in the rolling process when scaling speeds in wire rod transportation was used on the cooling conveyor. This speed increase of the material transportation, through the scaling speed, provides a change in "hot spots" of the coils, generating a greater uniformity in their cooling, thus ensuring uniformity in mechanical properties.

Hot rolling process is heat input process. The heat energy in hot rolled steel coils can be utilized. At SSAB Strip Product Borlänge when the hot rolled steel coils came out of the hot rolling mill they are at the temperature range of 500°C to 800°C. Heat energy contained by the one hot rolled steel coil is about 1981Kwh whereas the total heat energy for the year 2008 is 230 GWh/year.The potential of heat is too much but the heat dissipation rate is too slow. Different factors on which heat dissipation rate depends are discussed.Three suggestions are proposed to collect the waste heat from hot rolled steel coils.The 2nd proposal in which water basin is suggested would help not only to collect the waste heat but to decrease in the cooling time.

A otimização de processos e a redução de custos são os dois principais fatores que sustentam a competitividade das indústrias atualmente. Diante deste cenário, buscou-se otimizar o processo de fabricação de barras trefiladas de aço mola SAE 9254, através da eliminação do recozimento anterior ao processo de trefilação, por intermédio de um resfriamento controlado no cooling conveyor, na laminação.. Para isso, a taxa de resfriamento do fio-máquina após a laminação foi variada a fim de garantir a homogeneização da dureza ao longo das espiras, característica essa essencial para o processamento na trefila. Além da redução de custos com o recozimento, se o objetivo fosse alcançado, poder-se-ia otimizar o processo de reaquecimento deste aço na laminação. Como resultado, seria possível melhorar a qualidade superficial do fio-máquina e, por conseqüência, aumentar o rendimento metálico do produto, sem que a descarbonetação máxima e média fossem prejudicadas. Os experimentos foram desenvolvidos com base no resfriamento do fio-máquina no cooling conveyor. Durante o processamento na laminação, foi realizada uma amostragem especial a fim de mapear a variação das propriedades ao longo das espiras. Os resultados apontaram que é possível a otimização do processo de fabricação do aço mola SAE 9254, principalmente para a condição de resfriamento na laminação quando utilizado um escalonamento na velocidade de transporte do fio-máquina no cooling conveyor. Este incremento nas velocidades de deslocamento do material, feita através do escalonamento da velocidade, propicia uma alteração nos “pontos quentes” das espiras, gerando uma uniformidade maior em seu resfriamento, garantindo assim, uma homogeneidade nas propriedades mecânicas. / The process optimization and cost reduction are the two main factors that gives sustainability for today industries competitiveness. For this reason, it was attempted to optimize the manufacturing process of cold draw bars of SAE 9254 spring steel by eliminating pre-annealing of wire drawing, through a controlled cooling on the cooling conveyor, in the rolling mill process. For this, the cooling rate of wire rod after rolling process was varied to ensure the homogeneity of hardness along the coil, the essential feature for wire drawing process. In addition to reducing costs annealing, if the purpose was reached, the reheating process would be optimized in the rolling mill. As a result, it would be possible to improve the surface quality of wire rod and, consequently, increase the metallic yield of the product, without the decarburization maximum and average were damaged. The experiments were developed based on wire rod cooling thermograph in the cooling conveyor. During rolling mill processing, special sampling was performed to map the variation of properties along the coils. The results showed that it is possible to optimize the manufacturing process of the SAE 9254 spring steel, mainly for the cooling condition in the rolling process when scaling speeds in wire rod transportation was used on the cooling conveyor. This speed increase of the material transportation, through the scaling speed, provides a change in "hot spots" of the coils, generating a greater uniformity in their cooling, thus ensuring uniformity in mechanical properties.

A otimização de processos e a redução de custos são os dois principais fatores que sustentam a competitividade das indústrias atualmente. Diante deste cenário, buscou-se otimizar o processo de fabricação de barras trefiladas de aço mola SAE 9254, através da eliminação do recozimento anterior ao processo de trefilação, por intermédio de um resfriamento controlado no cooling conveyor, na laminação.. Para isso, a taxa de resfriamento do fio-máquina após a laminação foi variada a fim de garantir a homogeneização da dureza ao longo das espiras, característica essa essencial para o processamento na trefila. Além da redução de custos com o recozimento, se o objetivo fosse alcançado, poder-se-ia otimizar o processo de reaquecimento deste aço na laminação. Como resultado, seria possível melhorar a qualidade superficial do fio-máquina e, por conseqüência, aumentar o rendimento metálico do produto, sem que a descarbonetação máxima e média fossem prejudicadas. Os experimentos foram desenvolvidos com base no resfriamento do fio-máquina no cooling conveyor. Durante o processamento na laminação, foi realizada uma amostragem especial a fim de mapear a variação das propriedades ao longo das espiras. Os resultados apontaram que é possível a otimização do processo de fabricação do aço mola SAE 9254, principalmente para a condição de resfriamento na laminação quando utilizado um escalonamento na velocidade de transporte do fio-máquina no cooling conveyor. Este incremento nas velocidades de deslocamento do material, feita através do escalonamento da velocidade, propicia uma alteração nos “pontos quentes” das espiras, gerando uma uniformidade maior em seu resfriamento, garantindo assim, uma homogeneidade nas propriedades mecânicas. / The process optimization and cost reduction are the two main factors that gives sustainability for today industries competitiveness. For this reason, it was attempted to optimize the manufacturing process of cold draw bars of SAE 9254 spring steel by eliminating pre-annealing of wire drawing, through a controlled cooling on the cooling conveyor, in the rolling mill process. For this, the cooling rate of wire rod after rolling process was varied to ensure the homogeneity of hardness along the coil, the essential feature for wire drawing process. In addition to reducing costs annealing, if the purpose was reached, the reheating process would be optimized in the rolling mill. As a result, it would be possible to improve the surface quality of wire rod and, consequently, increase the metallic yield of the product, without the decarburization maximum and average were damaged. The experiments were developed based on wire rod cooling thermograph in the cooling conveyor. During rolling mill processing, special sampling was performed to map the variation of properties along the coils. The results showed that it is possible to optimize the manufacturing process of the SAE 9254 spring steel, mainly for the cooling condition in the rolling process when scaling speeds in wire rod transportation was used on the cooling conveyor. This speed increase of the material transportation, through the scaling speed, provides a change in "hot spots" of the coils, generating a greater uniformity in their cooling, thus ensuring uniformity in mechanical properties.

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No description available.

L'objectif initial de la thèse était de proposer une nouvelle modélisation simplifiée du laminage permettant un calcul rapide, si possible en temps réel, afin que le modèle soit éventuellement intégré à un outil de pilotage des machines de production. Ce modèle ne doit pas négliger les déformations élastiques afin de pouvoir être éventuellement appliqué à l'étude de phénomènes associés à la variation de largeur de la bande ou à des phénomènes de planéité. Il doit par ailleurs être assez ouvert pour que l'on puisse y intégrer éventuellement une description de la microstructure du matériau polycristallin et prendre en compte la déformation des cylindres de laminage. Pour atteindre cet objectif, nous avons proposé de tenter de construire un modèle simplifié semi-analytique du laminage. Dans ce type de modèle, le gradient de la transformation globale peut alors être décomposé multiplicativement en un produit d'une première transformation locale « plastique » , qui transforme le voisinage local initial de dans la configuration relâchée, par une seconde transformation locale « élastique » qui transforme la configuration relâchée dans la configuration actuelle . Cette décomposition est à la base de l'analyse thermodynamique de l'évolution mécanique lorsque le matériau subit de grandes transformations élastoplastiques, laquelle analyse fournit les concepts d'efforts intérieurs et de variables d'état nécessaires à l'écriture de ce comportement. Nous avons montré deux approches permettant le calcul analytique de ces champs lorsque l'histoire de est connue au voisinage d'une particule .Nous avons ensuite proposé l'étude d'une classe particulière d'évolutions élastoplastiques que nous avons appelées « simples radiales » et nous avons montré que les évolutions obéissaient à un principe de minimum énergétique. Nous avons enfin conjecturé que ce principe pouvait être étendu en régime permanant pour permettre de construire une modélisation simplifiée des processus de laminage / The initial aim of the thesis was to propose a new simplified model for rolling allowing a rapid calculation, if possible, in real time, so that the model would eventually integrate into a management tool production machines. This model should not neglect the elastic deformations in order to be applied to the study of phenomena associated with the change in bandwidth or flatness phenomena. It must also be open enough that we can integrate the description of microstructure of polycrystalline material and possibly take into account the deformation of rolling rolls. To achieve this goal, we proposed to build a simplified semi-analytical model of rolling. In this type of model, the gradient of global transformation can be multiplicatively decomposed of the first local transformation "plastic" which transforms the initial local neighborhood of in the relaxed configuration, and the second local transformation "elastic" which transforms the relaxed configuration in the current configuration. This decomposition is the basis of thermodynamic analysis of the mechanical evolution when the material undergoes large elastoplastic transformations, which provides the concepts of internal forces and necessary variable state to write this behavior. We showed two approaches to the analytical calculation of the mechanical fields when the history of was known in the neighborhood of particle .We then proposed to study a particular class of elastoplastic evolution that we called "simple radial" and we showed that the evolutions followed the principle of minimum energy. Finally, we conjectured that this principle can be extended in steady state, which allowed to build a simplified model of the rolling process

Ce travail de doctorat porte sur l'utilisation des mathématiques analytiques dans le cadre de méthodes inverses appliquées à l'industrie. Ces travaux tiennent au développement de capteurs inverses en temps réel adaptés au laminage industriel. Le producteur d'acier ArcelorMittal dirige un projet européen, qui vise à montrer la faisabilité de capteurs mesurant les champs (température, contraintes) dans le contact entre le produit et l'outil sans altérer les conditions de ce contact. Les travaux de thèse présentés dans ce mémoire ont été réalisés au sein du laboratoire Navier et financé par l'école des Ponts ParisTech. Cependant un contrat sur trois ans signé avec ArcelorMittal a permis à l'auteur d'être partie prenante de ce projet européen, et ainsi de voir ses recherches concrétisées par une demande industrielle réelle. L'enjeu de cette thèse est double, académique et industriel. Académique en ce sens que les travaux cherchent à recenser et utiliser efficacement les méthodes de résolution analytiques existantes, pour des problèmes inverses en thermoélasticité, dans le cadre d'une métrologie en temps réel. En effet, les solutions analytiques sont souvent exploitées comme des cas purement théoriques, trouvant à bien des égards un certain succès dans la culture de l'ingénieur (comme c'est le cas par exemple du calcul en élasticité linéaire des facteurs d'intensité de contraintes), mais qui par bien des aspects sont reléguées à des cas d'écoles anciens servant au mieux à valider des codes de calculs numériques sur des exemples particulièrement simples. Ces solutions et méthodes de résolution analytiques ne font d'ailleurs guère plus l'objet de recherches en mathématiques pures. Cependant les problématiques propres, liées au caractère inverse des problèmes à traiter, pénalisent les méthodes de résolution numériques, en ce sens que les problèmes inverses sont mal posés, et qu'une stabilisation des algorithmes numériques est nécessaire mais souvent délicate si l'on considère les conditions extrêmes (champs très singuliers) appliquées aux outils industriels de laminage. Par ailleurs la métrologie en temps réel exclut l'utilisation de codes numériques trop coûteux en temps de calcul (méthodes itératives etc...). Ces deux aspects contribuent à renouveler assez largement l'intérêt pour les solutions analytiques. Il convient alors d'en regrouper (dans la mesure du possible) les méthodes les plus efficaces (en termes de précision et de temps de calcul notamment) et les plus adaptées pour la métrologie. Nous verrons notamment différents développements en séries élémentaires permettant non seulement de donner à une suite de points mesurés une forme analytique, mais également de simplifier les équations aux dérivées partielles à résoudre. D'autre part l'enjeu de cette thèse est également industriel, car ces travaux s'inscrivent dans une démarche de développement de capteurs adaptés à la mise en forme de l'acier par laminage. Ainsi l'étude de la robustesse au bruit de mesure, les contraintes technologiques liées à l'insertion des capteurs, les limitations en terme de fréquence d'acquisition et les problématiques de calibrage sont au coeur des développements. Ainsi, l'ensemble des travaux présentés, peut constituer une sorte de réhabilitation des méthodes analytiques, dont la supériorité sur les méthodes numériques (en termes de temps de calcul et parfois aussi de précision) est mise en lumière, dans le contexte précis de la métrologie en temps réel sur des géométries simples. Trois méthodes inverses en deux dimensions, adaptées au laminage industriel, ont été menées à bien (élastique isotherme, thermique et couplage thermoélastique), ainsi qu'une série d'applications expérimentales réalisées sur le laminoir de laboratoire d'ArcelorMittal. Par ailleurs, des extensions en trois dimensions des méthodes inverses élastiques et thermiques sont également détaillées / This thesis is about the use of analytical mathematics within the framework of inverse methods applied to industry. These works are devoted to the development of sensors using real-time inverse methods adapted for rolling process. Steel producer ArcelorMittal leads a European project that aims to demonstrate the feasibility of sensors measuring fields (temperature, stress) in the contact between the product and the tool without altering physical conditions of this contact. The thesis has been funded by l'école des Ponts ParisTech. However, a three-year contract signed with ArcelorMittal has enabled the author to be part of the European project, and thus his research has been motivated by a real industrial demand. The aim of this thesis is twofold, academic and industrial; academic in the sense that these works seek to identify and use efficiently existing analytical methods for inverse problems occurring in thermo-elasticity in the context of real-time metrology. Indeed, analytical solutions are often exploited as purely theoretical cases, finding in many ways some success in engineering (for example in linear elasticity with stress intensity factors), but are most of the time relegated to the validation of numerical codes under simple assumptions. As a matter of fact, there is no research any more in pure mathematics concerning these solutions and analytical methods. However, the specific complications related to the inverse nature of problems under consideration, penalize numerical algorithms because inverse problems are ill-posed and stabilization is needed. But it remains often difficult if we consider the extreme loads (very sharp gradients) applied to industrial tools during rolling. Moreover, the real-time metrology excludes the use of numerical codes too costly in terms of computation time (iterative methods etc...). Both aspects contribute to renew widely interest for analytical solutions. It is then necessary to collect most effective and efficient (in terms of computation time and precision) methods and emphasis the most suitable for metrology. We will see various series expansions, not only to give a sequence of measured points an analytical form, but also to simplify the partial differential equations to solve. On the other hand, the goal of this thesis is also industrial, as these works are part of a process of development of sensors adapted for steel rolling industry. Thus, the robustness to measurement noise, technological constraints related to the local measurement systems (such as limitations in terms of frequency of acquisition) and calibration issues are central in the developments. Thus, the whole work can be a kind of rehabilitation of analytical methods. Their superiority over numerical methods (in terms of computation time and sometime accuracy) is highlighted, in the specific context of metrology in real-time on simple geometries. Three inverse methods in two-dimensions suitable for rolling process were developed successfully (isothermal elastic, thermal and thermoelastic coupling) and a series of experimental tests were made on the laboratory mill of ArcelorMittal. In addition, three-dimensional extensions of elastic and thermal inverse methods are also detailed