The main goal with the master thesis has been to do a status evaluation of the chain machinery with its start chain and wire to secure the production on a short basis due to that a reconstruction is not planned at this time. An evaluation of the condition of the start chain and the rollers in the chain depository has been done. An offer has been requested for a new start chain and the evaluation of the start chains may be a basis for the decision taking. The production has been able to go on, although it has arisen some problems which have been difficult to find the causes for. There is no gathered “picture” of the machinery status and a mapping of each machinery has been compiled of comprehensive logs. Observations and measurements have also been done to prove and elucidate the biggest problems. After the compilation a concentration has been done of the two most frequently problems during the last years, that is to say, 2006 to 2008. The work has finally fallen into suggestions for improvements of routines and suggestions for concepts for construction changes to keep a continuous stable production until a bigger reconstruction will be made. The two problems which have been focused on were the “limit-switches” for the wires and the heat-radiation-shields situated under the tilt bridges. The arrangement for the wire problem shown to be quite simple to implement and its cause was due to that the friction was to big in the shackle, which function is to be pressed down by the wire, and thereby didn’t trigger an alarm on the computer screens. To prevent this, lubrication was done for respective shackle to sustain the production for a short period of time. Although there have been done some concepts to sustain the production for a longer period of time. The problems concerning the heat-radiation-shields under the tilt bridges can be solved mainly by changed maintenance routines, which have been attached in the list which has been formed.

Thesis (M.Sc.)(Metallurgy)--University of Pretoria, 2004. / Includes summary. Includes bibliographical references.

Made available in DSpace on 2014-06-11T19:27:12Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-02-05Bitstream added on 2014-06-13T20:16:12Z : No. of bitstreams: 1 martins_ms_me_guara.pdf: 4378638 bytes, checksum: 5ab218d0c5345113e4a7e43df186b4af (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O presente trabalho tem por objetivo apresentar uma nova proposta de produção do aço para molas de válvulas para motores de combustão interna SAE 9258. Atualmente, este aço é produzido pela rota de lingotamento convencional, e pretende-se adotar o processo de lingotamento contínuo, mantendo-se todas as características mecânicas e metalúrgicas do aço produzido convencionalmente. Cuidados especiais durante o processo de refino secundário (fase líquida) foram levados em consideração para que sejam obtidas inclusões de silicatos deformáveis, essenciais para se conseguir uma vida em fadiga segura para as molas durante a vida útil do motor. Para avaliar essas características do aço foram feitas análises metalográficas da microestrutura em amostras na fase de processamento do aço (fio-máquina) e na fase final do processo (arames), realizados ensaios de tração, ensaios de fadiga axial em corpos-de-prova padronizados (ASTM E 466), ensaios de fadiga por flexão rotativa no arame (Nakamura test), ensaio de fadiga nas molas e análise das superfícies de fratura por fadiga com auxílio de microscopia eletrônica de varredura (MEV), para as duas rotas de produção (lingotamento convencional e contínuo). Os resultados obtidos mostram que não há diferenças com relação a microestrutura, propriedades mecânicas e comportamento em fadiga do aço na fase final de produção (arame) e na forma de produto (molas). Por outro lado, os resultados obtidos para o aço na fase intermediária do processamento (fiomáquina) mostram diferenças com relação à microestrutura, (presença de maior quantidade de carbonetos nas amostras do lingotamento contínuo), e menor redução de área com a consequente redução da resistência à fadiga. / This paper aims to present a new proposal for production of steel for valve springs for internal combustion engines SAE 9258. Currently this steel is produced by ingot casting route, and intended to adopt the continuous casting process, maintaining all the mechanical and metallurgical characteristics of the steel produced conventionally. Special attention during the process of refinement (liquid phase) were taken into account are obtained for silicate inclusions deformable essential to achieving a safe fatigue life for the springs during the life of the engine. To evaluate these features were made of steel metallographic analysis of microstructure in specimens during processing of steel (wire rod) and the final stage (wires) performed tensile tests, axial fatigue tests on specimens standard (ASTM E 466), fatigue tests in rotating bending on the wire (Nakamura test), the fatigue test the springs and examination of the areas of fatigue fracture with the aid of scanning electron microscopy (SEM) for the two production routes (ingot and continuous casting). The results show no differences with respect to microstructure, mechanical properties and fatigue behavior of steel in the final stages of production (wire) and the product form (spring). Moreover, the results obtained for steel in the intermediate stage of processing (wire rod) show differences from the microstructure (the larger amount of carbides in the samples of the continuous casting), lower area reduction with the consequent reduction resistance to fatigue.

Para a garantia do bom desempenho dos fluxantes para lingotamento contínuo de aços no molde, a determinação da sua composição química é importante para garantir as propriedades necessárias para o seu perfeito funcionamento. O carbono é adicionado ao fluxante para controlar a velocidade de fusão do fluxante sobre o aço líquido, já que, se adequada, colabora para a disponibilidade de escória líquida suficiente para alimentar o intervalo existente entre a placa de aço em solidificação e o molde, garantindo a perfeita lubrificação. Neste trabalho é demonstrada a influência do efeito de duas fontes de carbono na velocidade de fusão dos fluxantes, através da utilização de uma nova concepção de forno elétrico no qual são colocados dois cadinhos vazados contendo fluxante in natura. Um dos cadinhos é utilizado para avaliação da amostra de referência. O desenvolvimento das reações de fusão do fluxante com o aumento da temperatura resulta em uma escória que, em função de sua fluidez, gera o escorrimento da massa fundida a uma taxa característica, a qual é registrada em um gráfico de massa x temperatura. Desta forma, é demonstrada a eficiência do uso deste equipamento para avaliação da velocidade de fusão, e da influência da fonte e teor de carbono, possibilitando a avaliação de diferentes alternativas de composições. Os ensaios de microscopia com aquecimento e análises térmicas também foram utilizados. / In order to assure good performance of mould flux for continuous casting of steel, the chemical composition definition is important to guarantee the properties needs to its perfect behavior in the mould. Carbon is added to the mould flux to control the melting rate, since this property is related to the availability of liquid slag to fill in the gap between the solidified steel and the cupper wall that assure a perfect lubrication. This work presents the influence of two carbon sources evaluated by an apparatus designed for testing the melting rate of mould fluxes. It is an electric resistance furnace in which two perforated at the bottom crucibles contain flux sample in natura. One of the crucibles is used for the reference sample. As the temperature increases and the melting of the flux takes place, liquid slag starts dropping from the crucible, which is attached to a load cell. Weight losses and temperature are simultaneously recorded and a plot of mass (grams) versus temperature (degree Celsius) is produced. The effect of carbon content of the flux mixtures on the melting rate has been investigated. The heating microscope and thermal analysis were also evaluated.

[pt] O processo de lingotamento contínua de metais é simulado numericamente. Placas ou tarugos metálicos são produzidos continuamente, mantendo-se o escoamento do material através do molde. A frente de solidificação depende da velocidade de retirada de material e da refrigeração imposta na superfície do lingote. A posição da interface líquido-sólido e o campo de temperaturas na região sólida são determinados, e consideram-se os efeitos da velocidade na curvatura da interface. É analisado um modelo retangular bi-dimensional e a equação da energia é resolvida utilizando-se o método numérica de diferenças finitas das volumes de controle. Os resultados são comparados com soluções analíticas simplificadas onde a termo de transporte não foi considerado e mostram que o calar transportado pelo movimento de lingote tem influência significativa na forma da interface e em sua localização dentro do molde durante o processo. / [en] This work deals with a numerical simulation of the continuous casting process. This process is employed in the fabrication of metallic inguts. The position of the solid-liquid interface is determined together with the temperature field in the solid region. The research is facused on studying the effect of the withdrawal velocity on the interface position, aiming at accidental leakage preventien during the process. In this analysis, the sensible heat is taken into acceunt, in contrast to previous marks reported in the open literature. The present work employed a two-dimensional model. The energy equation was integrated in the rectangular domain by means of the finite-volume method. The liquid regions was at the fusion temperatures, whereas one of the side boundaries was strogly cooled to promote solidification. An algorithm was developed to determine the interface pesition and the domain length. Comparisons of this results obtained with the available solutions obtained excluding sensible heat showed that, depending upon the value of the withdrawal velocity, the sensible heat may or may not be negleted. The simulations was performed with the aid of a microcomputer of the IBM-PC/XT type, employing the Fortran language.

Orientador: Eugênio José Zoqui / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-27T12:27:50Z (GMT). No. of bitstreams: 1 Beil_WendelLeme_M.pdf: 9441091 bytes, checksum: a79e3096e6d5e36f55c442eaac25c9ea (MD5) Previous issue date: 2015 / Resumo: O presente trabalho visa desenvolver um projeto e executar a montagem e teste de um sistema de lingotamento contínuo, aprimorado com o uso da agitação eletromagnética, para a fabricação de lingotes de ligas de Al-Si com estrutura refinada de grãos. Durante seu desenvolvimento, o projeto almejou o estabelecimento de parâmetros construtivos do equipamento, bem como os parâmetros de processamento para obtenção dos lingotes. Os parâmetros estudados foram a altura de metal fundido na cavidade do molde, velocidade de lingotamento, temperatura de vazamento e rugosidade da cavidade do molde. Após serem determinados os parâmetros construtivos e de processamento, procedeu-se a obtenção dos lingotes propriamente ditos, em duas condições de refrigeração: refrigeração primária, somente no molde metálico, e refrigeração primária e secundária (com sistema de refrigeração na saída do lingote). Para cada uma dessas condições foram obtidos lingotes sem a aplicação do campo magnético e, sob a agitação eletromagnética a 1500 W com o campo magnético variando de 12 a 20 Gauss e 3000 W com o campo magnético variando de 22 a 38 Gauss. De posse dos lingotes seguiu-se a caracterização microestrutural por meio de análise metalográfica convencional e análise metalográfica por polarização de imagem, que buscou verificar a eficiência do sistema no refino de grãos. A condição de otimização alcançada sugere a fabricação de ligas de Al-Si nas seguintes condições: a temperatura de vazamento adotada foi de 800 ºC, rugosidade da cavidade do molde de Ra = 0,06 µm, velocidade de lingotamento 3 mm/s e altura de metal fundido na cavidade do molde de 15 a 20 mm, em que alcançou-se o tamanho de grãos com 178 µm e espaçamento interdendrítico de 125 µm, com uma potência de 1500 W e campo magnético de 12 a 20 Gauss / Abstract: This work aims to develop a project and implement the assembly and testing of a continuous casting system , enhanced with the use of electromagnetic stirring to manufacture ingots of Al-Si alloys with refined grain structure. During its development the project aspired to establishing constructive parameters of the equipment, as well as the establishment of the processing parameters for obtain ingots. The parameters studied were: the molten metal height in the mould cavity, the casting speed, the casting temperature, and the roughness of the mould cavity. After setting the construction and processing parameters were obtained obtain the ingots in two cooling conditions: primary cooling (considering only the metal mould), and primary and secondary cooling (with the ingot cooling system in the output). For each of these conditions were obtained ingots without applying the electromagnetic field and with electromagnetic stirring in 1500 W with a variation of electromagnetic field between 12 to 20 Gauss, and 3000 W with a variation eletrocmagnetic field between 22 to 38 Gauss. In possession of ingots followed the microstructural characterization by conventional metallographic analysis and metallographic analysis by polarization imaging, which aims to evaluate the efficiency of the grain refining system. The process optimized condition suggests the manufacturing Al-Si alloy in the following conditions: the pouring temperature was 800 °C, the mould cavity surface roughness Ra = 0.06 µm, casting speed is 3mm/s and molten metal height in the mould cavity of 15 to 20 mm where grain size up to 180 µm and interdendritic spacing of 125 µm, with a power of 1500 W and electromagnetic field of 12 to 20 Gauss / Mestrado / Materiais e Processos de Fabricação / Mestre em Engenharia Mecânica

<p>Cracking in continuous casting has always been one of the main problems of steel mills. Many cracks that occur during solidification are difficult to observe from outside the industrial mold. In order to better understand the formation of this defect, compared with the large-scale simulation used in the entire industrial process, microsimulation is also essential. A comprehensive study of using phase field method to simulate microstructure evolution has been conducted. A variety of two-dimensional models based on phase-filed method has been developed in order to simulate dendrites growth in continuous casting process. The basic concepts of phase-field method are presented. Among those models, Kobayashi model was first introduced to describe the morphology of pure material solidification, in this article, which are pure water and pure iron. In order to get closer to the actual situation of continuous casting, a multi-component model was introduced to solve the problem. To go a step further, by introducing a series of temperature parameters and modifications to a series of terms, the binary alloy directional solidification model was used to simulate the process of dendrite growth in continuous casting. Furthermore, the detailed derivation of the binary alloy solidification model and how to apply the model in open source software will also be introduced in this article. The effects of physical parameters such as anisotropic strength, temperature gradient and cooling rate on the growth and evolution of the dendrite interface were quantitatively analyzed. Finally, potential improvement of this model, optimization to primary cooling section in continuous casting process and various applications of the simulation were discussed.</p>

Fluid flow accompanied by heat transfer, solidification and interrelated chemical reactions play a key role during Continuous Casting (CC) of steel. Generation of defects and production issues are a result of the interaction between mould flux, steel grade and casting conditions. These issues are detrimental to both productivity and quality. Thus, the development of reliable numerical models capable of simulating fluid flow coupled to heat transfer and solidification are in high demand to assure product quality and avoid defects. The present work investigates the influence of steel grade, mould powder and casting conditions on process stability by including heat and mass transfer through liquid steel, slag film layers and solidifying shell. The thesis addresses the application of a numerical model capable of coupling the fluid flow, heat transfer and solidification developed by Swerea MEFOS; based on the commercial CFD code FLUENT v12. The Volume of Fluid (VOF) method, which is an interface tracking technique, is coupled to the flow model for distinction of the interface between steel and slag. The current methodology not only allows the model to describe the behaviour of molten steel during solidification and casting but also makes the assessment of mould powders performance possible.  Direct prediction of lubrication efficiency, which is demonstrated by solid-liquid slag film thickness and powder consumption, is one of the most significant advantages of this model. This prediction is a direct result of the interaction between metal/slag flow, solidification and heat transfer under the influence of mould oscillation and transient conditions.  This study describes the implementation of the model to analyse several steel and mould powder combinations. This led to detection of a combination suffering from quality problems (High Carbon Steel + High Break Temperature Powder) and one, which provides the most stable casting conditions (Low Carbon Steel + Low Break Temperature Powder).  Results indicate the importance of steel pouring temperature, mould powder break temperature and also solidification range on the lubrication efficiency and shell formation. Simulations illustrate that Low Carbon Steel + Low Break Temperature Powder delivers the best lubrication efficiency and thickest formed shell. In contrast, High Carbon Steel + High Break Temperature Powder conveys the minimum lubrication efficiency. Therefore, it was concluded that due to absence of proper powder consumption and solidification rate the latter combination is susceptible to production defects such as stickers and breakouts during the casting sequence.

No description available.

In order to improve the continuous casting process of steel, it’s important to have an understanding of the fuid mechanics of the casting process. As experiments on a real caster are usually impractical, both physical and numerical modeling are important for creating this understanding. This report concerns itself with the creation of a numerical model of a physical model of a slab caster, which uses eutectic bismuth-tin alloy to simulate steel, and is built and operated by Swerim in Luleå, Sweden. The geometry of the model was constructed in Siemens NX, and meshing was done using Ansys Meshing. The CFD model itself was made in Ansys Fluent, and data from previous experiments on the physical model was used to verify it. The numerical model does not model any discrete phases in the liquid metal, including slag, argon fow, solid particles or any form of phase transition or heat transfer. The model uses a pump to continuously recirculate the liquid metal into the tundish, from where it fows down into the mold. Qualitatively, the model shows the expected double-roll fow pattern in the mold, and also pressure gradients in the SEN entry region which are consistent with experimental data. Verifcation was done using experimentally determined pump curves, for which the model shows reasonable behavior for mass fows above roughly 20 kg/s, but deviates somewhat below this value. Verifcation was also done using data for mass fows out of the tundish, which is regulated by the stopper position. Here, a large discrepancy between experimental and simulated data is present. Several explanations for this discrepancy were investigated, including the possibility of improper calibration of the stopper positional tracking and incorrect data for dynamic viscosity of the alloy, but the most likely explanation is that cavitation occurs in the SEN entry region due to a large pressure drop which occurs in this region. Cavitation is not implemented in the model, which leads to incorrect mass fow out of the tundish. If this fow is to be accurately captured, it is likely necessary to implement cavitation modeling in future versions of the numerical model.