Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2016-06-10T00:17:19Z No. of bitstreams: 1 RicardoPiresDeSouza_TESE.pdf: 6120519 bytes, checksum: 9fff267c4280206b4148045fe28e44aa (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2016-06-10T23:50:18Z (GMT) No. of bitstreams: 1 RicardoPiresDeSouza_TESE.pdf: 6120519 bytes, checksum: 9fff267c4280206b4148045fe28e44aa (MD5) / Made available in DSpace on 2016-06-10T23:50:18Z (GMT). No. of bitstreams: 1 RicardoPiresDeSouza_TESE.pdf: 6120519 bytes, checksum: 9fff267c4280206b4148045fe28e44aa (MD5) Previous issue date: 2015-12-03 / Defeitos superficiais em pe?as de a?os oneram os custos das industrias de fundi??o devido a necessidade de retrabalhos. Os moldes de areia s?o os mais utilizados em industrias de fundi??o e um dos grandes respons?veis por proporcionar os defeitos superficiais. Este estudo tem como objetivo otimizar os n?veis das vari?veis do processo de moldagem visando minimizar a ocorr?ncia de defeitos superficiais nas pe?as de a?o fundidas em moldes de areia de s?lica ligados quimicamente por processo de cura a frio. Na metodologia utilizou-se o planejamento de experimentos com parcelas subdivididas, sendo considerados no estudo os fatores de porcentagem de resina na formula??o do molde, adi??o de ?xido de ferro, tipo de tinta, m?todo da aplica??o de tinta, quantidade de camadas de tinta, utiliza??o de ar quente nos moldes e tempo de espera do molde antes do vazamento. Foram analisados como vari?veis respostas os defeitos de eros?o, inclus?o de areia, penetra??o, porosidade e acabamento superficial. Foram realizados ensaios de resist?ncia ? tra??o para avaliar a influ?ncia dos fatores nos par?metros mec?nicos e para os par?metros microestruturais foram realizadas as an?lises de difra??o de raios X, microscopia eletr?nica de varredura (MEV) e an?lises t?rmicas (TG/DSC/dilatometria). Os resultados elucidam que para o defeito de eros?o, o ?nico fator significativo, com n?vel de confian?a de 95%, foi o tipo de tinta, sendo que a tinta ? base de alumina obteve resultados superiores. Para o defeito de inclus?o de areia, houve tr?s fatores significativos, sendo os melhores resultados alcan?ados com a tinta ? base de alumina aplicados com spray e a utiliza??o de ar quente no molde antes do vazamento do metal. Para o defeito de penetra??o, houve quatro fatores significativos, sendo os melhores resultados alcan?ados com 0,8% de resina e adi??o de ?xido de ferro na formula??o do molde, com a tinta sendo aplicada com pincel e tempo de espera de 24 horas antes do vazamento. Para o defeito de porosidade, com n?vel de confian?a de 95%, n?o houve fatores significativos. Para o defeito de acabamento superficial, os melhores resultados foram alcan?ados com 0,8% da resina na formula??o do molde e aplica??o da tinta com pincel. Visando obter os n?veis dos fatores que otimizem todos os defeitos simultaneamente, efetuou-se uma m?dia ponderada dos resultados de cada tipo de defeito, concluindo-se que os melhores n?veis dos fatores foram: 0,8% de resina e adi??o de ?xido de ferro na formula??o da molde, aplica??o de duas camadas de tinta aplicadas com pincel ou spray, com a utiliza??o de ar quente no molde antes do vazamento e 24 horas de espera do molde pronto antes do vazamento. Esses n?veis dos fatores otimizados foram utilizadas em um experimento de confirma??o que ratificaram os resultados obtidos, auxiliando para a redu??o dos retrabalhos e consequentemente na redu??o dos custos das pe?as de a?o fundidas. / Surface defects on steel parts borne costs of smelting industries due to the need of rework. Sand molds are frequently used in foundry industries and largely responsible for providing surface defects. This study aims to optimize the levels of the molding process variables to minimize the occurrence of surface defects in steel castings in silica sand molds chemically linked by cold cure process. The methodology used the experimental design with split plot, being considered in the study the resin percentage factors in the mold formulation, addition of iron oxide, type of paint, the paint application method, amount of ink layers, use of hot air along the lines and waiting time of the mold before casting. They were analyzed as response variables erosion defects, sand inclusion, penetration, porosity and surface finish. Tensile strength tests were performed to evaluate the influence of factors on mechanical parameters and the microstructural parameters were carried out the analysis of X-ray diffraction, scanning electron microscopy (SEM) and thermal analysis (TG / DSC / dilatometry). The results elucidate that for the faulty erosion, the only significant factor with a 95% confidence level was the type of ink and the ink alumina-based superior results obtained. For the sand inclusion of defect, there were three significant factors, with best results obtained with alumina-based paint and spray applied using hot air in the mold before casting the metal. For the defect penetration, there were four significant factors, the best results being achieved with 0.8% of resin and addition of iron oxide in the molding formulation, the paint being applied by brush and standby time of 24 hours before leak. For the defect porosity with a 95% confidence level, no significant factors. For the defect surface finish, the best results were achieved with the 0.8% formulation of the resin in the mold and application of the paint brush. To obtain the levels of the factors that optimize all defects simultaneously, we performed a weighted average of the results of each type of fault, concluding that the best levels of the factors were: 0.8% resin and addition of iron oxide in the formulation of the template, application of two coats of paint applied with a brush or spray, using hot air in the mold before casting and 24 hours of waiting ready the mold before casting. These levels of the optimized factors were used in an experiment to confirm that ratified the results, helping to reduce rework and consequently reducing costs of cast steel parts.

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2017-11-01T21:11:49Z No. of bitstreams: 1 JulianoAugustoMedeirosDeMenezesEOliveira_DISSERT.pdf: 8358330 bytes, checksum: a0ec67f844a5bacdf6c24e821ebe74d1 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2017-11-07T19:34:30Z (GMT) No. of bitstreams: 1 JulianoAugustoMedeirosDeMenezesEOliveira_DISSERT.pdf: 8358330 bytes, checksum: a0ec67f844a5bacdf6c24e821ebe74d1 (MD5) / Made available in DSpace on 2017-11-07T19:34:31Z (GMT). No. of bitstreams: 1 JulianoAugustoMedeirosDeMenezesEOliveira_DISSERT.pdf: 8358330 bytes, checksum: a0ec67f844a5bacdf6c24e821ebe74d1 (MD5) Previous issue date: 2017-08-25 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES) / As ligas de alum?nio na composi??o eut?tica apresentam como caracter?stica baixa temperatura de fus?o e uma microestrutura complexa formada por constituintes eut?ticos. Elas podem ser aplicadas na ind?stria de fundi??o, por apresentarem adicionalmente alta fluidez e baixa tend?ncia ? forma??o de porosidade e de trincamento a quente. Foram produzidas por fundi??o em areia as ligas eut?ticas do sistema Al-Cu (bin?ria), Al-Cu-Si e Al-Cu-Mg (tern?rias) e Al- Cu-Si-Mg (quatern?ria). As ligas foram analisadas microestruturalmente no estado bruto de fus?o e no estado ap?s tratamento t?rmico de homogeneiza??o ? 495 ?C por at? 24 horas, via Fluoresc?ncia de Raios-X (FRX), Difra??o de Raios-X (DRX) e Microscopia Eletr?nica de Varredura (MEV) com sistema de Energia Dispersiva de Varredura (EDS). Os resultados mostraram a forma??o das principais fases constituintes no estado de equil?brio termodin?mico, a forma??o significativa de constituintes eut?ticos e a forma??o em pequena quantidade de intermet?licos Al5FeSi (plaquetas) e AlFeSiMgCu (escrita chinesa), comumente encontradas devido ? presen?a intr?nseca do ferro como impureza em ligas de alum?nio. / The aluminum alloys in the eutectic composition have a characteristic low melting temperature and a complex microstructure formed by eutectic constituents. They can be applied in the foundry industry, as they additionally present high fluidity and low tendency to the formation of porosity and hot cracking. The Al-Cu (binary), Al-Cu-Si and Al-Cu-Mg (ternary) and Al- Cu-Si-Mg (quaternary) systems were produced by sand casting. The alloys were analyzed microstructurally in the as-cast condition and after homogenizing heat treatment at 495 ? C for until 24 hours, via x-rays fluorescence (FRX), x-rays diffraction (XRD) and scanning electron microscopy (SEM) with dispersive scanning energy system (EDS). The results showed the formation of the main constituent phases in the thermodynamic equilibrium state, the significant formation of eutectic constituents and the formation of a small amount of intermetallic Al5FeSi (platelets) and AlFeSiMgCu (chinese writing), commonly found due to the intrinsic presence of iron as an impurity In aluminum alloys.

Submitted by Caroline Xavier (caroline.xavier@pucrs.br) on 2017-06-26T14:53:16Z No. of bitstreams: 1 TES_DIMAS_JOAO_RODRIGUES_NETO_PARCIAL.pdf: 405454 bytes, checksum: d48967a61777e3e773d5a2112997ee13 (MD5) / Made available in DSpace on 2017-06-26T14:53:16Z (GMT). No. of bitstreams: 1 TES_DIMAS_JOAO_RODRIGUES_NETO_PARCIAL.pdf: 405454 bytes, checksum: d48967a61777e3e773d5a2112997ee13 (MD5) Previous issue date: 2017-01-19 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES / For a satisfactory clinical performance, pre-fabricated Co-Cr cylinders must have metallurgical compatibility to Co-Cr based cast alloys. A uniform interface with adequate union and resistance, with absence of interfacial reaction and porosities must be obtained. The present in vitro study aimed to evaluate the metallurgical compatibility at the interface between pre-fabricated Co-Cr cylinders and alloys for Co-Cr compound casting applying different casting techniques. In manuscript 2 the metallurgical compatibility and the interface between implant and alloy cylinders were evaluated for Co-Cr casting with different melting temperatures. Methodology: Three pre-fabricated Co-Cr prosthetic implant cylinders (Neodent, Pi-Br?nemark, Dentium) were subjected to casting with Co-Cr alloy using different casting techniques (Flame Torch, Induction / Centrifugation, Induction / Vacuum). Optical microscopy and Scanning Electron Microscopy (SEM) were used to characterize the obtained microstructures. The elementary composition of the cylinders and diffusion characteristics in the interfacial region between molten alloy and cylinder were determined by dispersive energy spectroscopy (EDS). Vickers microhardness was measured at interface, cylinder and cast alloy. The ANOVA and Tukey test were used to evaluate microhardness values. In the manuscript 2 cylinders based on Co-Cr were overfused with alloys with different melting temperatures and all microstructural analysis and microhardness tests were performed. Results: In the manuscript 1 a union between pre-fabricated cylinders and Co-Cr based alloys was observed microstructurally. An ideal interface was obtained with absence of interfacial reaction or significant porosities with the casting with the induction techniques (centrifugation and vacuum), but excess of porosities and failures were observed with the Torch casting technique. In manuscript 2 a microstructural bond was observed between the alloys and the cylinder, evidencing that both high melt alloy and low melt alloy presented compatibility with the Co-Cr cylinder. Microhardness values, both in manuscript 1 and in manuscript 2 also proved to form a satisfactory interface. Conclusions: It was concluded from manuscript 1 and 2 that both high and low melt temperature Co-Cr have metallurgical compatibility to pre-fabricated Co-Cr cylinders, showing an ideal interface. However, the technique of casting applied is relevant, and the torch technique has been shown to be less indicated due to the lack of standardization of the obtained results. / Para um bom desempenho clinico, cilindros de pilares pr? fabricados de Co-Cr devem apresentar compatibilidade metal?rgica a ligas de sobrefundi??o a base de Co-Cr. Uma interface uniforme com adequada uni?o e resist?ncia, com aus?ncia de rea??o interfacial e porosidades devem ser obtidas. O presente estudo, in vitro, objetivou atrav?s do manuscrito 1 avaliar a compatibilidade metal?rgica na interface entre cilindros pr? fabricados de Co-Cr e ligas para sobrefundi??o de Co-Cr com diferentes t?cnicas de fundi??o. No manuscrito 2, foi avaliado a compatibilidade metal?rgica e a interface entre cilindro de implante e ligas para sobrefundi??o de Co-Cr com diferentes temperaturas de fus?o. Metodologia: Tr?s cilindros pr?-fabricados para pr?tese sobre implantes em Co-Cr (Neodent, Pi-Br?nemark, Dentium) foram sorefundidos com liga de Co-Cr com diferentes t?cnicas de fundi??o (Ma?arico, Indu??o/centrifuga??o, Indu??o/v?cuo). Microscopia ?ptica e Microscopia eletr?nica de varredura (MEV) foram usadas para caracteriza??o das microestruturas. A composi??o elemental dos cilindros e caracter?sticas de difus?o na regi?o interfacial entre liga fundida e cilindro foram determinadas atrav?s de espectroscopia por energia dispersiva (EDS). Microdureza de Vickers foi aplicada na interface, cilindro e liga fundida. Foi aplicado o teste de ANOVA e Tukey para avalia??o dos valores microdureza. No manuscrito 2, cilindros a base de Co-Cr foram sobrefundidos com ligas com diferentes temperaturas de fus?o e foi realizada toda analise microestrutural e testes de microdureza. Resultados: No manuscrito 1 observou-se microestruturalmente uma uni?o entre cilindros pr? fabricados e ligas a base de Co-Cr. Foi obtida uma interface ideal com aus?ncia de rea??o interfacial ou porosidades significantes com a fundi??o com as t?cnicas por indu??o (centrifuga??o e v?cuo), por?m excesso de porosidades e falhas foram observados com a t?cnica de fundi??o ? ma?arico. No manuscrito 2 observou-se uma uni?o microestrutural entre as ligas e o cilindro avaliado, evidenciando que tanto liga de alta fus?o, quanto de baixa fus?o apresentam compatibilidade ao cilindro de Co-Cr. Valores de microdureza, tanto no manuscrito 1 como no manuscrito 2 tamb?m comprovaram a forma??o de uma interface satisfat?ria. Conclus?es: Concluiu-se atrav?s do manuscrito 1 e 2 que ligas de alta e baixa temperatura de fus?o a base de Co-Cr apresentam compatibilidade metalurgica a cilindros pr? fabricados de Co-Cr apresentando uma interface ideal. Por?m, a t?cnica de fundi??o aplicada ? relevante, sendo que a t?cnica ? ma?arico se mostra a menos indicada devido a falta de padroniza??o dos resultados obtidos.