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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
141

Influence of weldiing modes to strength and residual of low carbon steel joints / Suvirinimo režimų įtaka mažaanglio plieno jungčių stiprumui ir liekamiesiems įtempimams

Johns Eyioma, Izuwah 17 June 2014 (has links)
In this study, microstructural, micro hardness evaluation and residual stress distribution, of low carbon steel after single pass gas metal arc welding technique (GMAW) were investigated. The goal of this investigation were to reveal the microstructures, micro hardness, residual stress distribution and tensile strength of welded joints by using welding current as varying parameter. In order to realize this objective, welded plate of low carbon steel with thickness of 2.5mm and 250mm long by 200mm wide were welded together with different welding current of 70A, 100A through MIG process. Four different parts of samples were tried. The first part of samples was annealed in a furnace to a temperature of 750 and allowed to cool in air before welding. While the second was not heated, third and fourth trials were heated to a temperature of 200˚C and 580˚C respectively after the welding and allowed cooling in air. Nikon optic microscope and CSM micro hardness testing instrument were used to determine the microstructure of the weld bead and HAZ of the samples, and hardness tests were carried out at different zones of welded joint. Micro hardness behavior was observed by using CSM instrument using 20N load for indentation, which reveals the correlation between hardness, elasticity and plasticity on the heat affected zone (HAZ) and weld bead of the welded plates. The samples were subjected to tensile strength and the distribution of residual stress of the weld. Tensile strength test... [to full text] / Šiame darbe aprašomi mikrostruktūros, mikrokietumo nustatymo bei liekamųjų įtempimų pasiskirstymo tyrimai mažo anglingumo plienuose po lankinio suvirinimo. Tyrimo tiksla - nustatyti suvirintos jungties mikrostuktūros ir mikrokietųmo priklausomybę nuo suvirinimo srovės, kaip kintamo dydžio. Remiantis užduotimi buvo suvirintos 2.5 mm storio, 250 mm ilgio ir 200 mm pločio mažaanglio plieno plokštės, naudojant skirting dydžio (70A ir 100A) suvirininant apsauginių dujų aplinkoje (MIG) srovę. Buvo paruoštos keturios partijos bandinių. Pirmoji partija, proies suvirinant, buvo atkaitinta 750°C temperatųroje, ir ataušintas ore. Tuo tarpu antroji partija nebuvo apdorojama, o trečioji ir ketvirtoji atleista 200 C° ir 580°C temperatūroje ir atvėsinta ore. Suvirinimo vonelės ir erminio poveikio zonos mikrostruktūrai tirti bei mikrokietumui nustatyti buvo naudotas Nicon optinis mikroskopas bei CSM mikrokietumo bandymų įrenginys. Matuojant CSM įrenginiu, 20N įspaudimo apkrova, buvo pastebėtas įdomus kietuvo būvis, kuris atskleidė ryšį tarp kietumo, elastingumo ir plastiškumo esantį suvirintų plokštelių terminio poveikio zonoje bei suvirinimo vonelėje. Buvo matuojamas suvirintų bandinių stiprumas tempiant ir liekamųjų įtempimų pasiskirstymas. Tempimo stiprumo bandymų duomenys parodė ducharakteringus suirimo atvejus – plastiio-elastinio bei trapaus tipo. Liekamųjų įtempimų bandymų rezultati neparodė rėikšmingos liekamųjų įtempimų įtakos pasirinktomis sąlygomis suvirintuose bandiniuose.
142

Factors affecting stress assisted corrosion cracking of carbon steel under industrial boiler conditions

Yang, Dong 09 June 2008 (has links)
Failure of carbon steel boiler tubes from waterside has been reported in the utility boilers and industrial boilers for a long time. In industrial boilers, most waterside tube cracks are found near heavy attachment welds on the outer surface and are typically blunt, with multiple bulbous features indicating a discontinuous growth. These types of tube failures are typically referred to as stress assisted corrosion (SAC). For recovery boilers in the pulp and paper industry, these failures are particularly important as any water leak inside the furnace can potentially lead to smelt-water explosion. Previous research shows that metal properties, environmental variables, and stress conditions are the major factors influencing SAC crack initiation and propagation in carbon steel boiler tubes. A significant volume of work has also been published to show that the use of carbon steel in high temperature water applications strongly depends upon the formation and stability of a protective magnetite oxide film on the waterside of boiler tubes. This present study is aimed at evaluating above stated variables individually and interactively to identify SAC crack initiation and crack propagation behavior in carbon steel boiler tubes. Other goal of this research is to understand the mechanism of bulbous SAC crack formation under industrial boiler operating conditions, thus to figure out a practical way to predict and prevent SAC type failures in the industrial boilers.
143

Avaliação do copolímero de acrilonitrila e 2-vinil-2-oxazolina na eficiência de inibição de corrosão química em meio salino / Evaluation of the efficiency of acrylonitrile and 2-vinyl-2-oxazoline copolymer as chemical corrosion inhibitors in saline medium

Sergio Sampaio Mardirossian 29 February 2012 (has links)
Processos corrosivos geram perdas incalculáveis para a sociedade. Existe, portanto, uma incessante busca por métodos cada vez mais econômicos, eficientes e que não gerem impacto ao meio-ambiente. Polímeros heterocíclicos são macromoléculas de elevada performance que vêm sendo estudados como inibidores de corrosão por atenderem as premissas citadas acima. Neste trabalho realizou-se a modificação química da poliacrilonitrila com a incorporação de grupos 2-vinil-2-oxazolina no teor teórico de 20%. O copolímero obtido e a poliacrilonitrila não modificada foram caracterizados por espectroscopia na região do infravermelho e avaliados como inibidores de corrosão para alumínio e aço carbono em meio salino em temperatura de 60C. As concentrações utilizadas foram de 20, 50, 100 e 200 ppm e os períodos de checagem: 1, 2, 3 e 4 semanas. Os polímeros estudados apresentaram atividade inibitória de corrosão apenas para o aço carbono. Para o alumínio, o ensaio em branco apresentou a menor taxa de corrosão dentre todos os ensaios realizados / Corrosive processes, still generate unmeasurable losses to society. There is therefore a constant search for methods that are more economical, efficient and that does not generate impact to the environment. High performance heterocyclic polymers are macromolecules which have been studied as corrosion inhibitors for meeting the premises mentioned above. In this work, a chemical modification of polyacrylonitrile with the incorporation of 2-vinyl-2-oxazoline groups at the theoretical rate of 20% is proposed. The obtained copolymer and not modified polyacrylonitrile were characterized qualitatively by infrared spectroscopy and evaluated as corrosion inhibitors for aluminum and carbon steel in saline medium at 60 C. The concentrations used were 20, 50, 100 and 200ppm and checking timeline of: 1, 2, 3 and 4 weeks. The results indicate that the studied polymers showed corrosion inhibiting activity only for carbon steel. For aluminum, blank test showed the lowest rate of corrosion of all tests performed
144

Improved decision support within biocorrosion management for Oil and Gas water injection systems / Amélioration de l’aide à la décision dans la gestion de la biocorrosion des systèmes d’injection d’eau de l’industrie du gaz et du pétrole

Stipaničev, Marko 27 August 2013 (has links)
L’objectif de ce projet, réalisé dans le cadre du réseau BIOCOR, est de fournir aux opérateurs intervenant dans les systèmes d’injection d’eau, un support amélioré d’aide à la décision. L’implication de composants biologiques dans la corrosion de l’acier au carbone ainsi que les synergies potentielles avec d’autres éléments (contrainte mécanique, propriétés intrinsèques du matériau…) ont été étudiées. Les travaux ont montré que la production du sulfure (une réelle menace pour l’acier) par voie biologique avait différentes origines dans l’eau de mer, les différents taux de production pouvant déterminer diverses cinétiques et morphologies de la corrosion. Les paramètres clé sont la disponibilité des accepteurs d’électrons et la température du milieu environnant. Les bactéries sulfato-réductrices (BSR) sont responsables d’attaques plus sévères que les bactéries sulfidogéniques ou du genre Clostridium, deux groupes identifiés dans le système étudié. L’activité microbienne affecte également les processus de minéralisation qui ont lieu naturellement à la surface de l’acier doux, conduisant à des architectures composées de minéraux à base de fer II et III, comme le sulfure de fer, la magnétite, les oxy-hydroxydes de fer, la chukanovite et la rouille verte (sulfatée ou carbonatée) ainsi que des dépôts calcaires. Les couches internes de ces structures peuvent constituer un habitat favorable, dans lequel les BSR peuvent se développer en utilisant le sulfate de la rouille verte sulfatée comme accepteur terminal d’électrons pour leur respiration dissimilatrice. Ce processus conduit à la dégradation continue de l’acier. Enfin, l’influence de la microstructure du matériau et l’impact du stress mécanique sur la biocorrosion ont été identifiés : les joints de grains et les inclusions jouent un rôle important dans les premières étapes de la corrosion, qui s’estompe avec le temps d’immersion. Un taux élevé de bactéries couplé à une contrainte mécanique conduit à une augmentation de la détérioration sans toutefois révéler des mécanismes nouveaux par rapport à l’absence de contrainte. De plus, l’activité sulfidogénique des bactéries ne semble pas conduire aux mécanismes de rupture par fissuration (Stress Corrosion Cracking). En conclusion, les résultats de ce travail indiquent les situations qui pourraient (ou non) conduire à s’écarter de la ‘fenêtre de sécurité’ pour un système donné. / The objective of this work, achieved in the framework of the BIOCOR European Network, has been to provide the operators of Sea-Water Injection System (SWIS) with improved decision support. The implication of biological component on carbon steel corrosion was explored as well as the possible synergy with other elements (mechanical stress, material properties…). This work showed that biogenic sulphide production, a corrosion threat for steel, can have different origins in seawater. The production rate can determine kinetics and morphology of corrosion attack, which might be governed by the type of microorganisms present. The key parameters are the availability of electron acceptors and the surrounding environment temperature. Sulfate-Reducing Bacteria (SRB) exhibit more vigorous attack compared to sulfidogenic bacteria or genera Clostridium, both found in the studied SWIS. Microbial activity also affects the mineralization process naturally occurring on carbon steel surface leading to architectures composed of mixed iron (II) and (III) minerals such as iron sulfides, magnetite, iron oxyhydroxides, chukanovite and green rust (sulfated or carbonated) as well as calcareous deposits. Inner layers of these structures could possibly provide an anaerobic habitat for SRBs, where they can flourish by using sulfate from GR(SO42-) as a terminal electron acceptor for their dissimilatory respiration. This enables continuous degradation of steel. Finally, significance of material microstructure and impact of mechanical stress on corrosion processes was also recognized. Grain boundaries and inclusions are playing a role during the initial stage of corrosion attack. This impact can diminish during the immersion time. An elevated bacterial activity coupled with mechanical stress leads to an increase of material deterioration. However, the mechanisms are not different from those usually observed for unstressed steel. Moreover, sulfidogenic microbial activity does not seem to lead to a failure mechanism related to Stress Corrosion Cracking (SCC). In conclusion, the outcomes indicate the possible situations, which may (or may not) lead to breach the safe operating window for a given SWIS.
145

Avaliação do copolímero de acrilonitrila e 2-vinil-2-oxazolina na eficiência de inibição de corrosão química em meio salino / Evaluation of the efficiency of acrylonitrile and 2-vinyl-2-oxazoline copolymer as chemical corrosion inhibitors in saline medium

Sergio Sampaio Mardirossian 29 February 2012 (has links)
Processos corrosivos geram perdas incalculáveis para a sociedade. Existe, portanto, uma incessante busca por métodos cada vez mais econômicos, eficientes e que não gerem impacto ao meio-ambiente. Polímeros heterocíclicos são macromoléculas de elevada performance que vêm sendo estudados como inibidores de corrosão por atenderem as premissas citadas acima. Neste trabalho realizou-se a modificação química da poliacrilonitrila com a incorporação de grupos 2-vinil-2-oxazolina no teor teórico de 20%. O copolímero obtido e a poliacrilonitrila não modificada foram caracterizados por espectroscopia na região do infravermelho e avaliados como inibidores de corrosão para alumínio e aço carbono em meio salino em temperatura de 60C. As concentrações utilizadas foram de 20, 50, 100 e 200 ppm e os períodos de checagem: 1, 2, 3 e 4 semanas. Os polímeros estudados apresentaram atividade inibitória de corrosão apenas para o aço carbono. Para o alumínio, o ensaio em branco apresentou a menor taxa de corrosão dentre todos os ensaios realizados / Corrosive processes, still generate unmeasurable losses to society. There is therefore a constant search for methods that are more economical, efficient and that does not generate impact to the environment. High performance heterocyclic polymers are macromolecules which have been studied as corrosion inhibitors for meeting the premises mentioned above. In this work, a chemical modification of polyacrylonitrile with the incorporation of 2-vinyl-2-oxazoline groups at the theoretical rate of 20% is proposed. The obtained copolymer and not modified polyacrylonitrile were characterized qualitatively by infrared spectroscopy and evaluated as corrosion inhibitors for aluminum and carbon steel in saline medium at 60 C. The concentrations used were 20, 50, 100 and 200ppm and checking timeline of: 1, 2, 3 and 4 weeks. The results indicate that the studied polymers showed corrosion inhibiting activity only for carbon steel. For aluminum, blank test showed the lowest rate of corrosion of all tests performed
146

Estudo comparativo entre arames na soldagem de mancais de ferro fundido em compressores herméticos para refrigeração / Comparative study between alloys applied in cast iron main bearings weld in hermetic compressors to refrigeration

Diego Rodrigo da Silva 14 August 2014 (has links)
Nos dias atuais, com o mercado altamente seletivo, com vários fabricantes e fornecedores de diversos tipos de produtos e serviços, a qualidade se tornou uma necessidade premente, na qual uma empresa que forneça bens e/ou serviços com baixa qualidade corre sérios riscos de ser descartada pelos mercados consumidores. Assim, a importância da qualidade é que se converteu em um requisito básico para uma empresa competir e se manter no mercado. As empresas veem a qualidade como uma ferramenta para a redução de custos e para a melhoria de sua imagem junto ao mercado consumidor. Neste contexto, de melhora da imagem junto ao mercado consumidor e de redução de custos, o presente trabalho foi realizado em uma importante e tradicional multinacional de grande porte que produz compressores herméticos para refrigeração, com o intuito de estudar a soldagem do mancal de ferro fundido à carcaça de aço de baixo carbono em compressores rotativos (rolete excêntrico), utilizados em aparelhos de ar condicionado. A solda realizada de maneira falha pode permitir a perda do entreferro do motor, resultando em um ruído característico, chamado stall. Este trabalho avaliou diferentes tipos de arames, buscando garantir um processo com qualidade e baixo custo. Testes foram realizados utilizando como peças teste carcaças e mancais dos compressores. Verificou-se que o arame sólido ANSI/AWS A5.18 ER70S-6, atualmente utilizado, não é o mais indicado para a respectiva soldagem, em virtude da microestrutura e da resistência da soldagem obtida. A solução técnica apropriada é a utilização do arame ERNiFeMn-CI que elimina a fragilização das zonas parcialmente fundidas e diluídas próximos ao metal de solda, enquanto o arame metal cored E70C-6M representa um compromisso entre as propriedades da junta soldada e custo do processo. / Nowadays, with the highly selective market, with several manufacturers and suppliers of various types of products and services, quality has become a pressing need, in which a company that provides services with a low quality at serious risk of being discarded by the consumer markets. Thus, the importance of quality is that it has become a basic requirement for a company to compete and stay in the market. Companies see the Quality as a tool to reduce costs and to improve its image with the consumer market. In this context, the improvement of the image with the consumer market and costs reduction, this study was conducted in a major traditional large multinational that produces hermetic compressors to refrigeration, in order to study the welding of cast iron bearings with low carbon steel houses in rotary compressors (eccentric roller) used in air conditioners. The welding performed in a failure may allow loss of the air gap of the motor, resulting in a characteristic noise, called stall. This study evaluated different types of alloys, aiming to ensure process quality and low cost. Trials were done using low carbon steel houses and cast iron bearings of the compressors. After innumerous tests, it was found that the ANSI/AWS A5.18 ER70S-6 solid wire, currently used, is not the most suitable for their welding, in view of microstructure and resistance of the weld obtained. The appropriate technical solution is to use the wire ERNiFeMn-CI eliminating the weakening of partially melted and diluted zones near the weld metal, while metal cored wire E70C-6M represents a compromise between the properties of welded joint and the cost of the process.
147

Oxidação do aço carbono 1008 em meio aquoso aerado de ácido sulfúrico: estudo do sinergismo álcool-benzotriazol como inibidores / Effect of benzotriazole (BTAH) as inhibiting of corrosion for the 1008 carbon steel using as solvent water and mixtures water-alcohol

Gisele Cristiane Becher Ribas 31 January 2006 (has links)
Foi realizado o estudo do sinergismo álcool - benzotriazol como inibidores de oxidação para o aço carbono 1008 em meio de H2SO4 0,5 mol/L-1. Foram utilizados os álcoois metanol, etanol e propanol em frações molares iguais a 0,008. Utilizaram-se como técnicas para o estudo eletroquímico das interfaces: medidas de potencial de circuito aberto em função do tempo, ensaios gravimétricos, curvas de polarização potenciostática anódica e catódica e espectroscopia de impedância eletroquímica. A caracterização da superfície e a análise dos produtos de corrosão foi feita por microscopia óptica; microscopia eletrônica de varredura e espectrometria por dispersão de energia. Os resultados mostraram que a corrosão é generalizada para o aço carbono 1008 em todos meios estudados. O efeito sinérgico álcool BTAH, foi verificado em todos os meios contendo álcool - BTAH 1,0.10-3 mol/L-1. O benzotriazol se comporta como um inibidor catódico e anódico sobre o aço carbono em todos os meios estudados. Estudos de polarização mostraram que na região de Tafel da reação H+/H2 o filme inibidor em meio de BTAH e da mistura etanol - BTAH obedece à isoterma de adsorção de Langmuir. Ensaios por microscopia eletrônica de varredura seguidas de EDS mostraram que as inclusões após ataque em meio de H2SO4 0,5 mol/L-1 + BTAH 1.0.10-2 mol/L-1 + etanol são totalmente dissolvidas, justificando a eficiência máxima inferior a 100%. / The synergic effect of mixtures of alcohol - benzotriazole as corrosion inhibitors for the 1008 carbon steel in 0.5 mol.L-1 H2SO4 medium was studied. Methanol, ethanol and propanol were used in molar fractions equal to 0.008. The techniques used for the electrochemical study of the interfaces were: open circuit potential measurements, weight loss experiments, anodic and cathodic potentiostatic polarization curves and electrochemical impedance spectroscopy; the surface characterization and the corrosion product analysis were performed by optical microscopy, scanning electron microscopy - SEM and energy dispersive spectroscopy - EDS. The results showed the occurrence of generalized corrosion on 1008 carbon steel surfaces in all the studied media. The synergic effect of alcohol / BTAH was observed in all the media containing 1.0.10-3 mol.L-1 BTAH. Benzotriazol acts as a cathodic and anodic inhibitor on 1008 carbon steel in all the studied media. Polarization studies showed that the inhibitor film follows the Langmuir isotherm in the presence of BTAH and ethanol-BTAH, in the Tafel region correspondent to the H+/H2 reaction. Scanning electron microscopy and energy dispersive measurements revealed total dissolution of the inclusions after surface attack in 0.5 mol.L-1 H2SO4 + 1.0.10-2 mol.L-1 BTAH + ethanol medium, justifying the maximum efficiency lower than 100 %.
148

Caracterização de juntas soldadas de Aços Carbono e Aços Inoxidáveis utilizando arame AWS E309L T1-1 / Characterization of welded joints of Carbon Steels and Stainless Steels using Shield Bright AWS E309L T1-1

Cunha, Henrique Miguel [UNESP] 04 August 2016 (has links)
Submitted by Henrique Miguel Cunha null (henriquemcunha@msn.com) on 2016-09-09T01:02:59Z No. of bitstreams: 1 Henrique Miguel Cunha.pdf: 6274612 bytes, checksum: d69abd398495bac1a4aaaefbeae180ca (MD5) / Approved for entry into archive by Juliano Benedito Ferreira (julianoferreira@reitoria.unesp.br) on 2016-09-12T21:34:26Z (GMT) No. of bitstreams: 1 cunha_hm_me_ilha.pdf: 6274612 bytes, checksum: d69abd398495bac1a4aaaefbeae180ca (MD5) / Made available in DSpace on 2016-09-12T21:34:26Z (GMT). No. of bitstreams: 1 cunha_hm_me_ilha.pdf: 6274612 bytes, checksum: d69abd398495bac1a4aaaefbeae180ca (MD5) Previous issue date: 2016-08-04 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A aplicação do Arame Tubular E309L, nos processos de fabricação, apresenta grandes vantagens entre os consumíveis. Além de proporcionar propriedades mecânicas favoráveis à união por soldagem, esse consumível pode ser utilizado em aços carbono, aços inoxidáveis e dissimilares. Por essas razões, constantemente encontramos esse arame especificado nos procedimentos de soldagem nos setores fabris. Esse arame é também o mais utilizado na fabricação das novas turbinas de usinas hidrelétricas, como é o caso das turbinas Francis que estão sendo instaladas na Usina de Belo Monte localizado no rio Xingu em Altamira/PA. Este trabalho visou caracterizar o aço inoxidável Martensítico ASTM A743 CA6NM utilizado nas pás das turbinas hidráulicas, o aço inoxidável austenítico SA 316 e aço carbono A-36, ambos utilizados em equipamentos fabris em geral. Dessa forma, analisou-se o comportamento desses diferentes metais de base quando submetidos ao processo de união por soldagem utilizando o Arame Tubular E309L e proteção gasosa com a mistura C-25 (25% CO2 + 75% Argônio). Utilizou-se chapas dissimilares (Aço Carbono e Aço Inoxidável Austenítico) com 10 mm de espessura e chapas de aços inoxidáveis martensíticos com espessura de 6 mm, chanfros em “V”, ângulo de bisel de 30o, nariz e abertura de raiz de 3,0 mm. Foram estudados tanto o metal de solda quanto a zona termicamente afetada através de análises metalográficas, ensaios de tração, ensaios de impacto charpy e ensaios de dureza Vickers, nos quais foram possíveis verificar que a utilização do arame E309L T1-1 nas condições citadas foram satisfatórias, apresentando cordão de solda e ZTA com elevada resistência à tração, presença de microconstituintes como Bainita e ferrita delta, promovendo a ocorrência de elevada tenacidade nessas regiões. / Application of Shield Bright E309L in manufacturing processes, has high advantages among consumables. Besides providing mechanical properties favorable to joining by welding, the consumable can be used in carbon steels, stainless steels and dissimilar steels. For these reasons, constantly we find the E309L specified in the welding procedures used in industry today. This Shield Bright is also the most used in the manufacture of new turbines of hydroelectric power plants, as is the case of Francis turbine being installed in the Belo Monte Dam on the Xingu River located in Altamira / PA - Brazil. This study aimed to characterize the martensitic stainless steel ASTM A743 CA6NM used in the blades of hydraulic turbines, the austenitic stainless steel SA 316 and carbon steel A-36, both used in industrial equipment in general. Thus, we analyzed the behavior of these different base metals when subjected to the joining process by welding using the Shield Bright E309L and using a shielding gas of C-25 mixture (25% CO2 + 75% Argon). It was used dissimilar plates (carbon steel and austenitic stainless steel) with 10 mm steel thickness and martensitic stainless plates with a thickness of 6 mm, bevel groove “V” with angle of 30°, root face and root gap of 3,0 mm. We analyzed all regions of the metal plate through metallographic analysis, tensile tests, Charpy impact tests and Vickers hardness tests, in which they were possible to verify that the use of the Shield Bright E309L were satisfactory in the regions, featuring high tensile strength, presence of microconstituents (bainite and ferrite delta), providing high tenacity in these regions.
149

Caracterização magnética de aço com a superfície endurecida

Silva, Gustavo Rodrigues da 03 December 2010 (has links)
Neste trabalho foram investigadas as propriedades magnéticas (curva de histerese e ruído Barkhausen) de alguns aços (ABNT 1045, 1050 e 1548) cujas superfícies foram endurecidas por indução. O objetivo era de desenvolver um ensaio não-destrutivo para determinar a espessura da camada endurecida, assim evitando a necessidade de realizar medidas (destrutivas) de microdureza. Medidas da susceptibilidade magnética mostraram um pico (ferrita) em torno de 800 A/m e outro (martensita) em torno de 3500 A/m. Assim procuramos correlacionar a amplitude do pico de ferrita com a espessura da camada dura na superfície. Para esta finalidade foram desenvolvidos sensores para medir ruído Barkhausen e um filtro para o processamento do sinal. Foi possível correlacionar medidas de microdureza com algumas características observadas nas medições magnéticas, como, por exemplo, a amplitude do sinal de ruído Barkhausen e o campo magnético do pico do sinal Barkhausen. Deste modo, encontrou-se uma relação entre a amplitude do ruído Barkhausen e a espessura da camada superficial. Seria desejável complementar essas medidas com outras e sugestões para uma continuação do trabalho são detalhadas. / Submitted by Marcelo Teixeira (mvteixeira@ucs.br) on 2014-06-03T20:29:34Z No. of bitstreams: 1 Dissertacao Gustavo Rodrigues da Silva.pdf: 8142476 bytes, checksum: 29c4748e15d0fbcc852d788b9f1fa011 (MD5) / Made available in DSpace on 2014-06-03T20:29:34Z (GMT). No. of bitstreams: 1 Dissertacao Gustavo Rodrigues da Silva.pdf: 8142476 bytes, checksum: 29c4748e15d0fbcc852d788b9f1fa011 (MD5) / This work investigates the magnetic properties (hysteresis loop and Barkhausen noise) in some steels (ABNT 1045, 1050 and 1548) whose surfaces had been hardened by induction. The goal was to develop a non-destructive test procedure to determine the thickness of the hardened layer, thus avoiding the need to perform (destructive) measurements of the microhardness. Measurements of the magnetic susceptibility showed a peak (ferrite) around 800 A / m and other (martensite) at around 3500 A / m. Therefore, a correlation was sought between the peak amplitude of ferrite with the thickness of hard layer on the surface. For this purpose sensors were developed to measure Barkhausen noise as well as a filter for signal processing. It was possible to correlate measurements of microhardness with some features observed in magnetic measurements, for example, the amplitude of the Barkhausen noise and magnetic field of peak Barkhausen signal. Thus, a relationship was found between the amplitude of the Barkhausen noise and the thickness of the surface layer. It would be desirable to supplement these with other measurements and suggestions for further work are detailed.
150

Caracterização de juntas soldadas de Aços Carbono e Aços Inoxidáveis utilizando arame AWS E309L T1-1 /

Cunha, Henrique Miguel. January 2016 (has links)
Orientador: Vicente Afonso Ventrella / Resumo: A aplicação do Arame Tubular E309L, nos processos de fabricação, apresenta grandes vantagens entre os consumíveis. Além de proporcionar propriedades mecânicas favoráveis à união por soldagem, esse consumível pode ser utilizado em aços carbono, aços inoxidáveis e dissimilares. Por essas razões, constantemente encontramos esse arame especificado nos procedimentos de soldagem nos setores fabris. Esse arame é também o mais utilizado na fabricação das novas turbinas de usinas hidrelétricas, como é o caso das turbinas Francis que estão sendo instaladas na Usina de Belo Monte localizado no rio Xingu em Altamira/PA. Este trabalho visou caracterizar o aço inoxidável Martensítico ASTM A743 CA6NM utilizado nas pás das turbinas hidráulicas, o aço inoxidável austenítico SA 316 e aço carbono A-36, ambos utilizados em equipamentos fabris em geral. Dessa forma, analisou-se o comportamento desses diferentes metais de base quando submetidos ao processo de união por soldagem utilizando o Arame Tubular E309L e proteção gasosa com a mistura C-25 (25% CO2 + 75% Argônio). Utilizou-se chapas dissimilares (Aço Carbono e Aço Inoxidável Austenítico) com 10 mm de espessura e chapas de aços inoxidáveis martensíticos com espessura de 6 mm, chanfros em “V”, ângulo de bisel de 30o, nariz e abertura de raiz de 3,0 mm. Foram estudados tanto o metal de solda quanto a zona termicamente afetada através de análises metalográficas, ensaios de tração, ensaios de impacto charpy e ensaios de dureza Vickers, nos quais... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Application of Shield Bright E309L in manufacturing processes, has high advantages among consumables. Besides providing mechanical properties favorable to joining by welding, the consumable can be used in carbon steels, stainless steels and dissimilar steels. For these reasons, constantly we find the E309L specified in the welding procedures used in industry today. This Shield Bright is also the most used in the manufacture of new turbines of hydroelectric power plants, as is the case of Francis turbine being installed in the Belo Monte Dam on the Xingu River located in Altamira / PA - Brazil. This study aimed to characterize the martensitic stainless steel ASTM A743 CA6NM used in the blades of hydraulic turbines, the austenitic stainless steel SA 316 and carbon steel A-36, both used in industrial equipment in general. Thus, we analyzed the behavior of these different base metals when subjected to the joining process by welding using the Shield Bright E309L and using a shielding gas of C-25 mixture (25% CO2 + 75% Argon). It was used dissimilar plates (carbon steel and austenitic stainless steel) with 10 mm steel thickness and martensitic stainless plates with a thickness of 6 mm, bevel groove “V” with angle of 30°, root face and root gap of 3,0 mm. We analyzed all regions of the metal plate through metallographic analysis, tensile tests, Charpy impact tests and Vickers hardness tests, in which they were possible to verify that the use of the Shield Bright E309L were satisfact... (Complete abstract click electronic access below) / Mestre

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