O método de nitretação em descarga elétrica um processo termo-físico-químico que permite a introdução de nitrogênio atômico e a deposição de nitretos de elementos liga em substratos ferrosos e aços, conferindo-lhes melhores propriedades mecânicas e tribológicas. O processo desenvolve-se em um meto plasmático gerado e mantido por pressão. / The method of nitriding in electrical dischargeis a thermal-physical-chcmical process which ai lows the introduction of atomic nitrogen and the deposition of the nitrides of binding elements in ferrous substrata and steel materiais, this providing them with better mechanical and tribologic properties. The process takes place in a plasmatic environment, orlginated and kept by means of an eletrical discharge in gases at low pressure.

Neste trabalho estudou-se o comportamento do aço ABNT 1006, em soluções de água do mar sintética diluída em presença e ausência de bactérias Pseudomonas aeruginosa, bem como de seus produtos metabólicos. Também investigou-se o comportamento de um inibidor de corrosão hexametafosfato de sódio, nestes meios. Utilizou-se os seguintes métodos: técnicas de microbiologia, medições da variação do potencial de corrosão com o tempo, ensaios gravimétricos e determinação de curvas de polarização potenciostática. O hexametafosfato de sódio comportou-se como inibidor catódico, e observou-se a formação de um filme na superficie do aço. Em sistemas com bactérias ocorreu a formação de um biofilme na superfície metálica, induzindo a corrosão do tipo pite. A presença de bactérias também alterou a atuação do filme do inibidor. / This paper evaluated the behavior of ABNT 1006 steel in contact with solutions of diluted artificial sea water containing bacteria Pseudomonas aeruginosa and their metabolic products. The behavior of ABNT 1006 steel in such conditions was then compared to that observed in solutions with no bacteria culture. The study also investigated the effectiveness of sodium hexametaphosphate as a corrosion inhibitor in those media. The following methods were employed: microbiological techniques, measurement of potential/time curves, weight loss measurements and of potentiostatic polarization curves. The analyses showed that sodium hexametaphosphate behaved as a cathodic inhibitor forming a film on the steel surface. It was also observed the formation of a biofilm on the metal surface, which induced its pitting in media containing bacteria. The presence of bacteria also influenced the action o f the inhibitor.

A specially designed, highly restrained speciamen test (60º groove angle) was successfully used to study root run weld metal solidification cracking origins and tendencies. Thirty six submerged arc welds were made on two High Yield Strangth Quenched and Tempered base steels (HY100 and Q2N0, with two low alloy wires (LINDE 95 and OERLIKON S3 NiMo 1), two basic fluxes (OP41TT and OP121TT), and six welding parameters combination at three energy inputs, viz: 1.9, 2.8 and 4.1 KJ/mm. The weld metal solidification cracking phenomenon showed up to be extremely complex and basically dependent on chemical composition, solidification (primary) structures, microsegregation, flux type, dendrites size and orientation, and base metals stress state. The most resistant welds to this defect were those made using Q2N base steel, OP121TT flux and OERLIKON S3 NiMo 1 wire. A combination of the following properties are thought to have induced this result: high carbide-to-ferrite elements forming in the base metal; flux promoting weld centerline equiaxed structure and less microsegregation; wire chemical composition, with high Mn/Si ratio, inducing also less microsegragation at the weld centerline; lower carbon and nickel combined contetens in presence of also lower phosphorus and sulphur contents. The Q2N greater ability to relieve the strain around the weld pool at high temperature is another possibility, albeit not practically demonstrated. The welding paramenters main influence on solidification cracking tendency was found to be through change in centreline solidification macrostructure and dendrite size, but the stress fields within and around the weld pool are also thought to play a significant role. The dendrite size holds a strong relationship with weld bead geometric factors, such as weld bead height-to-width ration and, principally, external area-to-perimeter ratio. The dendrite size measured on the weld bead longitudinal section must be corrected, for it depends on the angle between the dendrite growth direction and the weld bead symmetry line in a transverse section. Thus, the actual dendrite size rate of change with welding parameters is not that observed through metallographic analysis. Four types of centreline solidification macrosturctures were identified and associated with solidification cracking tendency, viz: stray, competitive columnar, centreline and equiaxed. The former three macrostructures were found to be dependent on welding paramenters, whilst the latter was promoted by the OP121TT flux. Experiments have shown that this flux releases more than twice the amount of gas(es) released by the OP41TT flux. The time available for reactions between the weld pool liquid metal and the surrounding atmosphere was evaluated through an (approximate) weld pool retention time, given as the weld ripple lag-to-welding speed amount of fused slag and deoxidants recovery. The root run welds have shown a secondary microstructure principally composed of ferrite with aligned M-A-C, acicular ferrite and martensite. No differences were detected between weld metals deposited by both wires of fluxes, being noticed the change in microstructure size only. A good correlation was found between transformation temperature and cooling time. Evidence was found of ‘cold’ or high temperature ( not solidification) cracking propagation from existing solidification cracking, and carbides segregation along the solidification cracking path. Change in the groove angle to 0º and 120º modified the general weld bead geometry and reduced the solidification cracking tendency. Cold wire addition reduced the centreline solidification cracking tendency, with no action on transverse cracks. A device was designed to make exploratory welds with wire oscillation keeping the welding head still. Low oscillation frequencies ( below 10 Hz) in the welging direction have shown to be very effective to overcome both, transverse and centreline solidification cracks. Stress relieving the base metals considerably reduced the solidification cracking tendency. The all-weld metal mechanical properties were assessed through the use of a specimen desing which allowed the obtention of practically nil diluted wels, made with 1.9 and 4.1 KJ/mm energy inputs and the two wires and fluxes combinations. The results have shown that even at the highest energy input it is possible to obtain weld metals with relatively high yield strength and toughness, using any one of the available flux/wire combinations. The results have shown that even at the highest energy input it is possible to obtain weld metals with relatively high yield strength and toughness, using any one of the available fluz/wire combinations. The results yielded not less than 600 N/mm² Yield Strength and average Charpy V-notch energy absorbed of 80 J at -40º, with transition temperature to quasicleavage fracture mode occurring below -40ºC and at or above – 80ºC. The basic techniques utilized included metallographic analysis using light microscope, transmission Electron Microscope and Scanning Electron Microscope; weld metals ‘in situ’ thermal analysis; all-weld metal mechanical tests; hardeness.

Este trabalho contém uma investigação teórico experimental do comportamento à flexão de telhas metálicas autoportantes formadas à frio. São apresentados de forma sucinta o processo de fabricação, o estado da arte, bem como as propriedades mecânicas do aço. A parte experimental do trabalho utilizou 4 espécimes ensaiados, onde cada espécime era constituído por 5 telhas autoportantes, sendo realizado um total de 16 ensaios de flexão, onde as variáveis foram o elemento de ligação das telhas denominado capa, seu sistema de fixação e o número de parafusos utilizados na referida ligação. As conclusões contidas nesta investigação estão fundamentadas na comparação entre os valores experimentais dos deslocamentos verticais e da resistência última dos espécimes ensaiados e as recomendações da “Load and Resistance Factor Design Specification for Cold-Formed Steel Structural Members”, complementadas por uma análise linear elástica com base no método de elementos finitos. / An experimental and theoretical investigation of the flexural behaviour of cold-formed steel roofs is presented in this thesis. In a brief way, the manufactoring process, the state-of-the-art and the steel mechanical properties are presented. The experimental work was carried out on 4 test specimen, having each test specimen 5 corrugated steel sheets. A total amount of 16 flexural tests was performed and the variables considered were: the influence of the top roof, the number of connecting using bolts between each neighbour panel sheet and the process of roof fixing. The flexural behaviour was analysed using the vertical displacements and the ultimate flexural strenght. Conclusions are based on the comparision between the experimental work and theorical analysis into the light of the code “Load and Resistance Factor Design Specification for Cold-Formed Steel Structural Members”, and also elastic linear analysis using the finite element method.

O método de nitretação em descarga elétrica um processo termo-físico-químico que permite a introdução de nitrogênio atômico e a deposição de nitretos de elementos liga em substratos ferrosos e aços, conferindo-lhes melhores propriedades mecânicas e tribológicas. O processo desenvolve-se em um meto plasmático gerado e mantido por pressão. / The method of nitriding in electrical dischargeis a thermal-physical-chcmical process which ai lows the introduction of atomic nitrogen and the deposition of the nitrides of binding elements in ferrous substrata and steel materiais, this providing them with better mechanical and tribologic properties. The process takes place in a plasmatic environment, orlginated and kept by means of an eletrical discharge in gases at low pressure.

Neste trabalho estudou-se o comportamento do aço ABNT 1006, em soluções de água do mar sintética diluída em presença e ausência de bactérias Pseudomonas aeruginosa, bem como de seus produtos metabólicos. Também investigou-se o comportamento de um inibidor de corrosão hexametafosfato de sódio, nestes meios. Utilizou-se os seguintes métodos: técnicas de microbiologia, medições da variação do potencial de corrosão com o tempo, ensaios gravimétricos e determinação de curvas de polarização potenciostática. O hexametafosfato de sódio comportou-se como inibidor catódico, e observou-se a formação de um filme na superficie do aço. Em sistemas com bactérias ocorreu a formação de um biofilme na superfície metálica, induzindo a corrosão do tipo pite. A presença de bactérias também alterou a atuação do filme do inibidor. / This paper evaluated the behavior of ABNT 1006 steel in contact with solutions of diluted artificial sea water containing bacteria Pseudomonas aeruginosa and their metabolic products. The behavior of ABNT 1006 steel in such conditions was then compared to that observed in solutions with no bacteria culture. The study also investigated the effectiveness of sodium hexametaphosphate as a corrosion inhibitor in those media. The following methods were employed: microbiological techniques, measurement of potential/time curves, weight loss measurements and of potentiostatic polarization curves. The analyses showed that sodium hexametaphosphate behaved as a cathodic inhibitor forming a film on the steel surface. It was also observed the formation of a biofilm on the metal surface, which induced its pitting in media containing bacteria. The presence of bacteria also influenced the action o f the inhibitor.

Este trabalho contém uma investigação teórico experimental do comportamento à flexão de telhas metálicas autoportantes formadas à frio. São apresentados de forma sucinta o processo de fabricação, o estado da arte, bem como as propriedades mecânicas do aço. A parte experimental do trabalho utilizou 4 espécimes ensaiados, onde cada espécime era constituído por 5 telhas autoportantes, sendo realizado um total de 16 ensaios de flexão, onde as variáveis foram o elemento de ligação das telhas denominado capa, seu sistema de fixação e o número de parafusos utilizados na referida ligação. As conclusões contidas nesta investigação estão fundamentadas na comparação entre os valores experimentais dos deslocamentos verticais e da resistência última dos espécimes ensaiados e as recomendações da “Load and Resistance Factor Design Specification for Cold-Formed Steel Structural Members”, complementadas por uma análise linear elástica com base no método de elementos finitos. / An experimental and theoretical investigation of the flexural behaviour of cold-formed steel roofs is presented in this thesis. In a brief way, the manufactoring process, the state-of-the-art and the steel mechanical properties are presented. The experimental work was carried out on 4 test specimen, having each test specimen 5 corrugated steel sheets. A total amount of 16 flexural tests was performed and the variables considered were: the influence of the top roof, the number of connecting using bolts between each neighbour panel sheet and the process of roof fixing. The flexural behaviour was analysed using the vertical displacements and the ultimate flexural strenght. Conclusions are based on the comparision between the experimental work and theorical analysis into the light of the code “Load and Resistance Factor Design Specification for Cold-Formed Steel Structural Members”, and also elastic linear analysis using the finite element method.

O método de nitretação em descarga elétrica um processo termo-físico-químico que permite a introdução de nitrogênio atômico e a deposição de nitretos de elementos liga em substratos ferrosos e aços, conferindo-lhes melhores propriedades mecânicas e tribológicas. O processo desenvolve-se em um meto plasmático gerado e mantido por pressão. / The method of nitriding in electrical dischargeis a thermal-physical-chcmical process which ai lows the introduction of atomic nitrogen and the deposition of the nitrides of binding elements in ferrous substrata and steel materiais, this providing them with better mechanical and tribologic properties. The process takes place in a plasmatic environment, orlginated and kept by means of an eletrical discharge in gases at low pressure.

Neste trabalho estudou-se o comportamento do aço ABNT 1006, em soluções de água do mar sintética diluída em presença e ausência de bactérias Pseudomonas aeruginosa, bem como de seus produtos metabólicos. Também investigou-se o comportamento de um inibidor de corrosão hexametafosfato de sódio, nestes meios. Utilizou-se os seguintes métodos: técnicas de microbiologia, medições da variação do potencial de corrosão com o tempo, ensaios gravimétricos e determinação de curvas de polarização potenciostática. O hexametafosfato de sódio comportou-se como inibidor catódico, e observou-se a formação de um filme na superficie do aço. Em sistemas com bactérias ocorreu a formação de um biofilme na superfície metálica, induzindo a corrosão do tipo pite. A presença de bactérias também alterou a atuação do filme do inibidor. / This paper evaluated the behavior of ABNT 1006 steel in contact with solutions of diluted artificial sea water containing bacteria Pseudomonas aeruginosa and their metabolic products. The behavior of ABNT 1006 steel in such conditions was then compared to that observed in solutions with no bacteria culture. The study also investigated the effectiveness of sodium hexametaphosphate as a corrosion inhibitor in those media. The following methods were employed: microbiological techniques, measurement of potential/time curves, weight loss measurements and of potentiostatic polarization curves. The analyses showed that sodium hexametaphosphate behaved as a cathodic inhibitor forming a film on the steel surface. It was also observed the formation of a biofilm on the metal surface, which induced its pitting in media containing bacteria. The presence of bacteria also influenced the action o f the inhibitor.

O Biodiesel é obtido a partir de óleos vegetais, gorduras animais, óleo de fritura, e matérias graxas de alta acidez. A introdução do Biodiesel na matriz energética brasileira contribui para a preservação ambiental e diminui a dependência dos derivados do petróleo. O monitoramento de parâmetros indicativos da qualidade do produto em todos os elos da cadeia, do produtor até a bomba de abastecimento nos postos revendedores, bem como sua utilização em veículos automotivos, tem por meta preservar a confiança do consumidor, visando os mercados nacional e internacional. O objetivo geral deste trabalho é investigar a estabilidade do Biodiesel de soja (B100) e suas blendas com óleo Diesel (B20 e B5), com e sem adição de antioxidante, e sua compatibilidade com aço inoxidável e aço carbono, ao longo de seis meses de imersão. As placas metálicas permaneceram imersas em amostras do combustível nesse período, retirando-se periodicamente alíquotas para análise. Os resultados por Rancimat indicam que o B100 contendo antioxidante pode ser armazenado e transportado em aço carbono até o limite de 45 dias enquanto para o B20 esse prazo é de 180 dias, com ou sem adição de antioxidante. A avaliação dos dados por análise multivariada confirma estes resultados. / Biodiesel is produced from vegetable oils, animal fat, frying oil, grease and even materials of high acidity. Introduction of Biodiesel into the Brazilian energetic matrix contributes to environmental preservation and reduces dependence on petroleum. The aim of this study is to investigate the chemical stability of soybean Biodiesel (B100) and its blends with Diesel (B20 and B5), with and without addition of antioxidant, besides its compatibility with stainless and carbon steel, over a six months immersion period. The metallic plates remain immersed for one hundred and eighty days on fuel samples from which aliquots are periodically removed for analysis. The monitoring parameters indicative of the product quality in all chain links, from the producer to the supply pump at gas stations, as well as its use in vehicles, has the goal of preserving consumer confidence, targeting the domestic and international markets. Results by Rancimat essays indicate that, when added with an antioxidant B100 can be stored and transported in carbon steel up to a limit of 45 days while for B20 this period is 180 days, with or without addition of antioxidant. Multivariate data analyses, including infrared spectra confirms these results.