Orientador: Amauri Garcia / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-08-04T22:38:42Z (GMT). No. of bitstreams: 1 Santos_NewtonSilva_M.pdf: 11404473 bytes, checksum: e3fa93c65cc03106c6ee4c62e3694589 (MD5) Previous issue date: 2005 / Resumo: O presente trabalho descreve o desenvolvimento de um simulador físico estático do processo de lingotamento contínuo rotativo, como parte de uma metodologia experimental auxiliada por um modelo matemático para a determinação de coeficientes transitórios globais de transferência de calor metal/molde ao longo da solidificação. Através desta metodologia, investigou-se a influência da formação do gap de ar entre as paredes do molde e o metal, na cinética total do processo. O simulador fisico foi construído na mesma escala do processo industrial e constitui-se de um trecho de um equipamento de lingotamento contínuo rotativo Properzi. O simulador é equipado com um sistema de refrigeração à água por bicos pulverizadores, canal de vazamento e termopares acoplados a um sistema de aquisição de dados, onde foram realizados experimentos com ligas utilizadas na indústria de condutores elétricos de alumínio. Para a determinação dos coeficientes transitórios de transferência de calor, após o mapeamento experimental das temperaturas, empregou-se o método de comparação teórico-experimental de perfis térmicos (método IHCP) através de um modelo numérico baseado na técnica de diferenças finitas, aplicada em um volume de controle do sistema experimental. Os resultados obtidos demonstraram consistência da metodologia, permitindo a caracterização destes coeficientes e com isso a possibilidade de se prever a evolução da solidificação em processos industriais / Abstract: The present study describes the development of a static experimental set-up representing the solidification system of a Rotary Continuous Caster, as part of a metholology, which connected to a numerical model permits to determine transient global metal/mold heat transfer coefficients along solidification. By using this methodology the influence of air gap formation between mold walls and metal surface on process kinetics has been investigated . The static simulator has the same escale of an industrial caster and is constituted of a Properzi copper wheel sector, equipped with a spray cooling system, a pouring system and a thermocouple arrangement connected to a data aquisition system. Experiments were performed using aluminum alloys of the electrical conductors industry. The heat transfer coefficients were obtained by using a method base don com pari sons of numerically calculated and experimental thermal profiles (lHCP method). The used numerical model is based on a finite difference technique and applied on a control volume from the experimental system. The results have shown that the used methodology is consistent, permitting the characterization of metal/mold heat transfer coefficients and as a consequence, to predict the solidification evolution in industrial processes / Mestrado / Materiais e Processos de Fabricação / Mestre em Engenharia Mecânica

The aluminium alloys for electrical conductivity applications are generally not grain refinedsince the addition of grain refiners drops the electrical conductivity by introducing impuritiesinto the melt. Non-grain refined aluminium may lead to bar fracture and cracks during themetalworking process. The present study focuses to find an optimum balance between the grain refiner addition andthe electrical conductivity of commercial EC grade 1070 aluminium alloy for electricalapplication. In order to reach this goal, the electrical conductivity and the macrostructure ofcommercial EC grade 1070 aluminium (commercial pure aluminium) have been studiedunder a series of controlled lab scale trails. Specific addition levels of different grain refiners(TiBloy, Al-5Ti-1B, Al-3Ti-0.15C, and Al-3Ti-1B) were added to the metal melt and sampleswere taken at specific time intervals. The collected samples were sectioned, ground andmacro-etched. Thereafter, the macrostructure was analysed by the use of a digital camera andthe electrical conductivity was measured at temperature. The obtained result was expressed asa percentage of the International Annealed Copper Standard (IACS %). The macro-structuralanalysis showed that TiBloy, Al-5Ti-1B, and Al-3Ti-1B, with the maximum addition level of0.1%, cannot grin refine commercial pure aluminium. However, at higher grain refiner levelsthe number of columnar grains increased and their size decreased. The Al-3Ti-0.15C master alloy, with the same addition level as the once chosen for the othergrain refiners (up to 0.1%), showed significantly better grain refining. By the addition of0.1% of this grain refiner the macrostructure became very equiaxed already after 30 minutesof grain refiner addition. The fading of the Al-3Ti-0.15 master alloy was, however, observedfor samples with a long holding time. Nevertheless, by maximum addition level (0.1%) and a90 minutes holding time the macrostructure remained as equiaxed grains. The electrical conductivity results showed that none of the applied grain refiners (TiBloy, Al-5Ti-1B, Al-3Ti-0.15C, and Al-3Ti-1B), with the maximum addition level of 0.1%, decreasedthe electrical conductivity of commercial pure aluminium.