Orientador: Anselmo Eduardo Diniz / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-19T18:33:44Z (GMT). No. of bitstreams: 1 Aguiar_MarceloMendesde_M.pdf: 3795090 bytes, checksum: a76ee2a93e8e7595881459d7a6d71b50 (MD5) Previous issue date: 2012 / Resumo: Normalmente, a utilização de aços ferramenta endurecidos, juntamente com as formas complexas típicas das peças utilizadas na área de moldes e matrizes, oferecem dificuldade na usinagem por fresamento, principalmente nas operações de acabamento que exijam o uso de ferramentas longas. A técnica de fresamento HSM (High Speed Machining - usinagem em altas velocidades, ou ainda High Speed Milling - fresamento em altas velocidades) tem se tornado uma alternativa para realizar este tipo de usinagem, reduzindo, ou às vezes até eliminando operações de eletro-erosão e polimento. Tipicamente, as fresas de pastilhas de metal duro intercambiáveis tem sido usadas em operações de desbaste e semi-acabamento, enquanto nas operações de acabamento ou em usinagem de geometrias que exijam ferramentas com pequenos diâmetros ainda predomina o uso de fresas inteiriças. O objetivo principal deste estudo é avaliar a influência de cinco variáveis de processo de fresamento com alta velocidade de corte, sobre o acabamento da superfície usinada. A influência do desgaste das ferramentas sobre o acabamento superficial, ao longo de 400 minutos de usinagem, também foi avaliado, além de uma comparação entre ferramentas inteiriças de metal duro e ferramentas de pastilha intercambiável montada em corpo de metal duro, a fim de avaliar a viabilidade técnica do uso deste segundo tipo de ferramenta, em substituição às tradicionais fresas inteiriças utilizadas em operações de acabamento. Na maioria dos experimentos realizados, pequenos valores de rugosidade foram mantidos, demonstrando que operações de acabamento em aço ABNT H13 IM com dureza de 50 HRC é possível com vida longa de ferramenta, mesmo utilizando-se valor de 500 m/min para velocidade de corte. Além disto, a análise da influência das variáveis de processo utilizadas neste trabalho mostrou que é possível, sob algumas condições, utilizar tanto ferramentas inteiriças, quanto de pastilha intercambiável montada em corpo de metal duro em operações de acabamento / Abstract: Typically, the use of hardened tool steels, along with complex shapes typical of the parts used in the field of molds and dies, offer difficulty in machining by milling, mainly in finishing operations that demand the use of long tool. The HSM (High Speed Machining or High Speed Milling) has become a possible alternative for making this type of machining, reducing, or sometimes eliminating electric discharge machining and polishing operations. Usually, indexable carbide insert mills has been used for roughing and semi-finishing, while in finishing operations or when the machining geometries that require tools with small diameters the integral tools are used yet. The main objective of this study is to evaluate the influence of five process variables, with high cutting speed, on the finish of the machined surface. The influence of tool wear on surface finish through 400 minutes of milling was also evaluated, as well as a comparison between integral carbide mills and indexable insert mounted at cemented carbide toolholder endmills, in order to evaluate the technical feasibility of using this second type of tool, replacing the traditional integral carbide endmills used in finishing operations. In most experiments, small roughness values were maintained, showing that finishing operations on AISI H13 IM with a hardness of 50 HRC is possible with long tool life, even using the cutting speed of 500 m/min. Furthermore, the analysis of the influence of process variables used in this study showed that is possible, under some conditions, the use either integral carbide tools, or indexable insert mounted at cemented carbide toolholder endmills on finishing operations / Mestrado / Materiais e Processos de Fabricação / Mestre em Engenharia Mecânica

Zinc phosphate conversion coating has been applied to improve the corrosion resistance and paint adhesion. However, zinc phosphate crystals dissolve in a highly alkaline environment, which reduces the corrosion resistance of base metal. To improve the phosphate stability in a highly alkaline environment, a post-rinse treatment has been applied to phosphate coating by rinsing with an aqueous solution which contains certain anions or cations. Chromatepost-rinse treatment is the most widely used method and has shown a great improvement in corrosion resistance. But, due to the environmental problems caused by chromate ions, non-chromate post-rinse treatment should be developed, which has equal or better corrosion resistance than does chromate post-rinse treatment. In this research, inorganic silicate with addition of Ca²⁺, Ba²⁺, Ni²⁺, Mg²⁺, has been extensively evaluated together with silane solution, γ -aminopropyltriethoxysilane ( γ -A.P.S., NH₂(CH₂)₃Si(OC₂H₅)₃), which was applied after the post-rinse treatment. The evaluation was carried out by the highly advanced surface analysis techniques such as SEM/EDX, AES, SIMS, and XRD and polarization measurements. / Master of Science

Orientador: Rodnei Bertazzoli / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-08-13T22:40:42Z (GMT). No. of bitstreams: 1 Machado_CarlosHenriquedeCampos_M.pdf: 20350934 bytes, checksum: 9d0ed15edcf31e375ad6d36587a7ca3f (MD5) Previous issue date: 2009 / Resumo: o processo de deposição das ligas de zinco vem encontrando aplicações cada vez maiores na indústria de galvanoplastia, especificamente na produção de auto peças destinadas às empresas montadoras de veículos. Neste trabalho, o processo de deposição da liga Zn-Co foi estudado através da técnica de voltametria cíclica para kientificar as regiões de potenciais para a deposição dos constituintes da liga. A seguir, foram simuladas variações composicionais e operacionais do eletrólito para deposição da liga Zn-Co, normalmente observadas em linhas de produção. Adicionalmente, além das variações do eletrólito, foram estudadas amostras de peças (ferro fundido nodular como substrato) obtidas em condições adversas de processamento. O objeti,vo foi estudar a influência desses parâmetros na composição final do depósito, e na resistência à corrosão através de ensaios acelerados em câmara de névoa salina. O processo para deposição da líga Zn-Co apresentou boa estabilidade e', baixa sensibilidade às variações de concentração que podem ocorrer no cotidiano de uma linha de produção. Os ensaios em célula de Hull mostraram que variações deliberadas de 2 g.L-1 a 8 g.L-1 de Co (II) no banho produzem depósitos com 0,6 % a 1,6 % de Co na liga. Na faixa recomendada de trabalho de 4 g.L-1 a 6 g.L-1. obtém-se 0,9 % a 1,2 %. Os ensaios acelerados de corrosão em câmara de névoa salina mostraram que, mesmo nas condições mais improváveis de funcionamento, onde o teor de cobalto pode cair para 0,6 %, a camada resiste a mais de 500 horas de ensaio. Tempo de ensaio de 720 horas foi obtido quando [Zn(II)]=46 g.L-1 e [Co(II)]=4,6 g.L-1. ou seja, [Zn(II)]/[Co(II)]=10 / Abstract: Zinc alloy coatings have found large application in the metal finishing índustry, particularly for coatíng automotive parts. In thís work, the deposítíon of Zn-Co process was characterízed by cyclic voltammetry in order to identify the rangCe of deposition potential of the alloy and its constituents. Then, variations of deposition parameters and bath composition were símulated in order to study their influence on the coating properties. In addition, beside plating variation, samples produced under qnideal process condítion were studied. The plating bath presented good stability and low sensibility to variations usually observed in the industrial production. Hull-cell, experiments shown that, despite the deliberated changes in bath composítion, ,cobalt concentration in the alloy is always wíthín the range of 0,6 % to 1,6 %. Recommended values are from 0,9 % to 1,2 %. Salt spray tests shown that the Zn-Co coating lasted 500 h of test and, in the optimum deposition conditions, 720 h was obtained / Mestrado / Materiais e Processos de Fabricação / Mestre em Engenharia Mecânica

Environmental legislation is becoming more stringent as people are realising the need for conservation and a reduction of environmental degradation in order to facilitate sustainable development. To ease legislative pressures, companies need to work together in symbiotic networks, whereby co-operation between companies results in far more innovative practices than if the companies acted individually. Success in an industrial network is largely dependent on cleaner production, where industries seek to redirect from waste treatment to waste minimisation. Cleaner production has already received international recognition and waste minimisation initiatives have been used as a tool of cleaner production. Two polluting industrial sectors within South Africa, the textile and metal finishing sectors, were chosen to investigate waste minimisation concepts. One company from each sector was used as a case study. The dissertation followed company network identification, potential to participate within an industrial symbiotic network, and waste minimisation opportunities. Suppliers and buyers, up and down the product line were identified. Relationships with these partners should be advanced such that environmental concerns are at the forefront of any decision-making. In light of developing industrial networks and maintaining symbiotic relationships, the company's potential was investigated by interviewing employees of various ranks. Both companies were partially suited to participate within an industrial symbiotic network and company-specific barriers were identified, such as ineffective internal communication. The waste minimisation investigation followed a four-phase approach of planning and organisation; pre-assessment; assessment; and feasibility study. In both the companies investigated, water savings were identified as the waste minimisation focus area with potential for improvement. In total, potential water savings of over R80 000 per annum were identified. In the textile company, the weaving department and bleach house were further investigated. Cloth weaving errors were attributed to machine stops, as each stop has the potential to result in a cloth fault. In the bleach house the potential existed to reduce the number of rinse tanks. Although a modem and automated process, the plating plant in the metal finishing company was identified as having potential waste minimisation opportunities. Of particular interest was the reduction of solution carry over from the plating tanks into subsequent tanks. Extended drip times were investigated. Additional waste minimisation opportunities included repairing pipe leaks, replacing the degreasing solvent, trichloroethylene, with a less harmful cleaning agent and establishing a symbiotic relationship with the oil supplier, Castrol. Over and above the main waste minimisation opportunities highlighted, other recommendations and potential savings were identified. Each case study emphasises that simple waste minimisation initiatives, without expending capital, reduce demands on natural resource, such as water, and benefit the company financially. Successful waste minimisation leads to further cleaner production initiatives, which may then initiate better network interactions with the further potential of promoting sustainable development. / Thesis (M.Sc.Eng.)-University of Natal, Durban, 2002.