Orientador: Gilberto de Magalhães Bento Golçaves / Banca: Carlos Elias da Silva Junior / Banca: Geraldo Luiz Palma / Resumo: Este trabalho avaliou as ocorrências mecânicas, macro e microestrutural em metal de solda de juntas de aço estrutural temperado e revenido, soldadas pelo processo a arco elétrico com proteção gasosa (GMAW) de 80%Ar-20%CO2, em modo convencional e pulsado, utilizando eletrodo de alma metálica ("metal cored"), designação AWS E70C-6M. As soldas foram realizadas em dois passes, um por lado de juntas preparadas com chanfro duplo "V"60º. Para uma mesma energia teórica de soldagem, comparativamente verificou-se aumentos nas eficiências de deposição e térmica do processo para a soldagem com arco pulsado, além de uma maior influência na diluição do metal de base e nas características geométricas dos cordões. Entretanto, foi constatada maior resistência mecânica para os metais de solda obtidos em modo convencional, atribuído à ocorrência de um refinamento microestrutural mais intenso nesta condição de soldagem. A expectativa desta contribuição é de que disponibilize maiores informações em metalurgia da soldagem para atender principalmente o segmento de fabricação de equipamentos e sistemas mecânicos aplicados a serviços abrasivos / Abstract: This study evaluated the mechanical, macro and microestrurtural events on metal weld joints of quenched and tempered structural steel, welded by eletric arc process with protective gas (GMAW) of 80% Ar-20% CO2 in conventional and pulsed mode using metal cored electrode, designation AWS E70C-6M. The welds were made in two passes, one on each side of joints prepared with 60º double "V" bevel. For a given theoretical energy welding, comaratively there was increases in the efficiencies of deposition and thermal for pulsed arc welding process, and a greater influence on the dilution of the base metal and the geometrical characteristics of the cords. However, was observed a higher mechanical strength for a weld metals obtained in conventional manner, attributed to the occurrence of an intense microstructural refinement in this welding condition. The expectation of this contribution is to make evailable more information on welding metallurgy to meet especially the segment of manufacturing equipment and mechanical systems applied to abrasive services / Mestre

Made available in DSpace on 2014-06-11T19:28:20Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-01-17Bitstream added on 2014-06-13T19:57:37Z : No. of bitstreams: 1 sarni_mij_me_bauru.pdf: 941928 bytes, checksum: 4ead015efe149db89a0c631bd5132b8b (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Este trabalho avaliou as ocorrências mecânicas, macro e microestrutural em metal de solda de juntas de aço estrutural temperado e revenido, soldadas pelo processo a arco elétrico com proteção gasosa (GMAW) de 80%Ar-20%CO2, em modo convencional e pulsado, utilizando eletrodo de alma metálica (metal cored), designação AWS E70C-6M. As soldas foram realizadas em dois passes, um por lado de juntas preparadas com chanfro duplo V60º. Para uma mesma energia teórica de soldagem, comparativamente verificou-se aumentos nas eficiências de deposição e térmica do processo para a soldagem com arco pulsado, além de uma maior influência na diluição do metal de base e nas características geométricas dos cordões. Entretanto, foi constatada maior resistência mecânica para os metais de solda obtidos em modo convencional, atribuído à ocorrência de um refinamento microestrutural mais intenso nesta condição de soldagem. A expectativa desta contribuição é de que disponibilize maiores informações em metalurgia da soldagem para atender principalmente o segmento de fabricação de equipamentos e sistemas mecânicos aplicados a serviços abrasivos / This study evaluated the mechanical, macro and microestrurtural events on metal weld joints of quenched and tempered structural steel, welded by eletric arc process with protective gas (GMAW) of 80% Ar-20% CO2 in conventional and pulsed mode using metal cored electrode, designation AWS E70C-6M. The welds were made in two passes, one on each side of joints prepared with 60º double V bevel. For a given theoretical energy welding, comaratively there was increases in the efficiencies of deposition and thermal for pulsed arc welding process, and a greater influence on the dilution of the base metal and the geometrical characteristics of the cords. However, was observed a higher mechanical strength for a weld metals obtained in conventional manner, attributed to the occurrence of an intense microstructural refinement in this welding condition. The expectation of this contribution is to make evailable more information on welding metallurgy to meet especially the segment of manufacturing equipment and mechanical systems applied to abrasive services

Dans le domaine des dépôts réalisés par projection thermique, les dernières recherches ont permis de développer des dépôts nanostructures par projection de suspensions (SPS) ou de solutions de précurseurs (SPPS). L’injection de liquide est une technique prometteuse qui a le potentiel pour devenir industriellement viable. Cependant, un meilleur contrôle des interactionsplasma/matériaux est nécessaire. En effet, les torches à courant continu mono-cathodes génèrent un plasma fortement fluctuant qui modifie les transferts thermiques et dynamiques vers les gouttelettes injectées, entraînant un traitement non-homogène de ces dernières. Cela influence directement les microstructures des dépôts obtenus et leurs propriétés. Des travaux antérieurs ont montrés les origines de ces instabilités. Une alternative à l’atténuation de ces instabilités est proposée : le renforcement et la modulation. L’ajustement des paramètres opératoires a permis d’obtenir un plasma pulsé laminaire avec modulation de ces propriétés. Une torche à courant continu modulé de faible puissance est utilisée avec de l'azote pur comme gaz plasmagène. Ce dispositif est synchronisé avec un système d'injection jet d’encre Drop-On-Demand pour reproduire les mêmes conditions d'interactions plasma / matériau pour chaque gouttelette injectée. Des solutions et des suspensions sont injectées pour réaliser des dépôts homogènes avec une microstructure contrôlée. Les objectifs de ces travaux sont d'abord de caractériser et de comprendre les transferts thermiques et dynamiques plasma / gouttelettes. Deuxièmement, de mettre en évidence l'influence de la synchronisation et des paramètres opératoires sur les dépôts obtenus. / In the field of thermal spray coating processes, research has led to the development of nanostructured coatings by suspension plasma spraying (SPS) and precursor solution plasma spraying (SPPS). Liquid injection are promising techniques with the potential to become industrially viable. However, a better control of plasma/material interactions is necessary. Mono-electrode DC torches indeed generate strongly fluctuating plasma that modifies the thermal and dynamic transfers to the injected droplet, resulting in an inhomogeneous treatment of the latter. This directly influences the texture and microstructure of deposits and subsequently their properties. Previous works have shown the origins of these instabilities. As an alternative to instabilities attenuations, a new approach is proposed: the reinforcement and modulation of the instabilities. The adjustment of process parameters has allowed obtaining a pulsed laminar plasma with a modulation of its properties. A low powered home-made modulated DC torch is used and operates with pure nitrogen as plasma forming gas. This device is synchronized with a Drop-On-Demand injection system to reproduce the same conditions of plasma/material interactions for each injected droplet. Solutions and suspensions are injected to make homogeneous coatings with controlled microstructure. The objectives of this work are firstly to characterize and understand plasma / droplet heat and dynamics transfers. Secondly, to highlight the influence of the synchronization and operating parameterson the coatings obtained.

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