O presente trabalho investiga a soldabilidade dos aços ARBL (Alta Resistência e Baixa Liga) API 5L X80) e a tenacidade da ZAC (Zona Afetada pelo Calor), assim como a sua correlação com o ensaio CTOD (Crack Tip Opening Displacement) nos processos de soldagem Eletrodo Revestido estudado por Silva [2009] e GMAW-STT® (Gas Metal Arc Welding Surface Tension Transfer®) no passe de raiz com FCAW (Flux Core Arc Welding) para os passes de enchimento e acabamento. Foram utilizados corpos de provas SENB em chapa com espessura de 19 mm e chanfro em ½ V, onde ficaria mais fácil a localização do entalhe na região de grãos grosseiros na zona afetada pelo calor (parte reta do chanfro). Ensaio de tração e impacto Charpy entalhe com 1/2 V foram utilizados para determinar as propriedades mecânicas e de impacto do material testado. Foram comparados os processos SMAW (Eletrodo Revestido), muito utilizado para a soldagem de gasodutos e oleodutos, com os processos GMAW-STT® e FCAW, que têm maior produtividade do que o SMAW. A soldabilidade dos aços ARBL está associada às regiões da ZAC (Zona Afetada pelo Calor) que, por sua vez, encontra-se correlacionado com o processo de soldagem, composição química e com os parâmetros de soldagem utilizados durante o processo de solda, sendo que a qualificação dos procedimentos geralmente não exige o ensaio de tenacidade, como o CTOD. / This work studies HSLA steels (High Strength Low Alloy) API 5L X80 weldability, HAZ (Heat Affected Zone) fracture behavior and their relationship with the CTOD test (Crack Tip Opening Displacement) on the welding processes SMAW (Shielded Metal Arc Welding) studied by Silva [2009] and GMAW-STT® (Gas Metal Arc Welding Surface Tension Transfer®) in the root pass with FCAW (Flux Core Arc Welding) others welding passes. There were used 19 mm width SENB plate samples with a half V groove, where would be easier to locate the crack in the HAZ coarse grain region. Conventional tensile and Charpy V-Notch were performed to determinate mechanical and impact properties of the tested materials. SMAW process, widely used for gas and oil pipelines welding, was compared with GMAW and FCAW processes which have a better productivity than the first one. The HSLA steels weldability is related with HAZ region which also depends on welding process, its parameters and material chemical composition. Normally is not necessary to perform toughness test as CTOD test to evaluate the procedures.

Precipitation strengthened nickel-base superalloys, such as IN 738, are very difficult to weld by fusion welding techniques due to their high susceptibility to heat-affected zone (HAZ) intergranular liquation cracking. An improvement in weldability could be realized by the deployment of innovative welding processes and/or the modification of the materials’ microstructural characteristics. Laser-arc hybrid welding is a relatively new welding process that appears to possess great potentials for joining the difficult-to-weld nickel-base superalloys. The research described in this Ph.D. dissertation was initiated to perform a systematic and comprehensive study of the cracking susceptibility of nickel-base IN 738 superalloy welds made by laser-arc hybrid welding process, and how to minimize it by using a combination of pre-weld microstructural modification and the application of various welding filler alloys. Laser-arc hybrid welding produced a desirable weld geometry in IN 738 Superalloy. Cracking did not occur exclusively in the fusion zone. Analysis of the fusion zone material using EPMA, SEM, TEM and EBSD revealed elemental partitioning pattern, the presence of secondary solidification reaction constituents and the grain structure of the fusion zone. Non-equilibrium liquation of various second phases that were present in the alloy prior to welding contributed to intergranular liquation in the HAZ that consequently resulted in extensive HAZ intergranular cracking. A very significant reduction in HAZ intergranular liquation cracking was achieved by the use of an industrially deployable and effective pre-weld thermal processing procedure developed during this research work. This novel procedure, designated as FUMT, was developed on the basis of the control of both boride formation and intergranular boron segregation in the pre-weld material. Propensity for HAZ intergranular liquation cracking in the weldments was also observed to vary depending on the Al+Ti+Nb+Ta concentration of the weld metal produced by different filler alloys, which can be attributed to variation in the extent of precipitation hardening in the weld metals. The newly developed FUMT treatment procedure, coupled with the selection of an appropriate type of filler alloy, is effective in reducing HAZ intergranular cracking both during laser-arc hybrid welding and during post-weld heat treatment (PWHT) of the laser-arc hybrid welded IN 738 superalloy.

Precipitation strengthened nickel-base superalloys, such as IN 738, are very difficult to weld by fusion welding techniques due to their high susceptibility to heat-affected zone (HAZ) intergranular liquation cracking. An improvement in weldability could be realized by the deployment of innovative welding processes and/or the modification of the materials’ microstructural characteristics. Laser-arc hybrid welding is a relatively new welding process that appears to possess great potentials for joining the difficult-to-weld nickel-base superalloys. The research described in this Ph.D. dissertation was initiated to perform a systematic and comprehensive study of the cracking susceptibility of nickel-base IN 738 superalloy welds made by laser-arc hybrid welding process, and how to minimize it by using a combination of pre-weld microstructural modification and the application of various welding filler alloys. Laser-arc hybrid welding produced a desirable weld geometry in IN 738 Superalloy. Cracking did not occur exclusively in the fusion zone. Analysis of the fusion zone material using EPMA, SEM, TEM and EBSD revealed elemental partitioning pattern, the presence of secondary solidification reaction constituents and the grain structure of the fusion zone. Non-equilibrium liquation of various second phases that were present in the alloy prior to welding contributed to intergranular liquation in the HAZ that consequently resulted in extensive HAZ intergranular cracking. A very significant reduction in HAZ intergranular liquation cracking was achieved by the use of an industrially deployable and effective pre-weld thermal processing procedure developed during this research work. This novel procedure, designated as FUMT, was developed on the basis of the control of both boride formation and intergranular boron segregation in the pre-weld material. Propensity for HAZ intergranular liquation cracking in the weldments was also observed to vary depending on the Al+Ti+Nb+Ta concentration of the weld metal produced by different filler alloys, which can be attributed to variation in the extent of precipitation hardening in the weld metals. The newly developed FUMT treatment procedure, coupled with the selection of an appropriate type of filler alloy, is effective in reducing HAZ intergranular cracking both during laser-arc hybrid welding and during post-weld heat treatment (PWHT) of the laser-arc hybrid welded IN 738 superalloy.

Made available in DSpace on 2014-10-09T12:28:54Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:57:01Z (GMT). No. of bitstreams: 0 / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

O presente trabalho investiga a soldabilidade dos aços ARBL (Alta Resistência e Baixa Liga) API 5L X80) e a tenacidade da ZAC (Zona Afetada pelo Calor), assim como a sua correlação com o ensaio CTOD (Crack Tip Opening Displacement) nos processos de soldagem Eletrodo Revestido estudado por Silva [2009] e GMAW-STT® (Gas Metal Arc Welding Surface Tension Transfer®) no passe de raiz com FCAW (Flux Core Arc Welding) para os passes de enchimento e acabamento. Foram utilizados corpos de provas SENB em chapa com espessura de 19 mm e chanfro em ½ V, onde ficaria mais fácil a localização do entalhe na região de grãos grosseiros na zona afetada pelo calor (parte reta do chanfro). Ensaio de tração e impacto Charpy entalhe com 1/2 V foram utilizados para determinar as propriedades mecânicas e de impacto do material testado. Foram comparados os processos SMAW (Eletrodo Revestido), muito utilizado para a soldagem de gasodutos e oleodutos, com os processos GMAW-STT® e FCAW, que têm maior produtividade do que o SMAW. A soldabilidade dos aços ARBL está associada às regiões da ZAC (Zona Afetada pelo Calor) que, por sua vez, encontra-se correlacionado com o processo de soldagem, composição química e com os parâmetros de soldagem utilizados durante o processo de solda, sendo que a qualificação dos procedimentos geralmente não exige o ensaio de tenacidade, como o CTOD. / This work studies HSLA steels (High Strength Low Alloy) API 5L X80 weldability, HAZ (Heat Affected Zone) fracture behavior and their relationship with the CTOD test (Crack Tip Opening Displacement) on the welding processes SMAW (Shielded Metal Arc Welding) studied by Silva [2009] and GMAW-STT® (Gas Metal Arc Welding Surface Tension Transfer®) in the root pass with FCAW (Flux Core Arc Welding) others welding passes. There were used 19 mm width SENB plate samples with a half V groove, where would be easier to locate the crack in the HAZ coarse grain region. Conventional tensile and Charpy V-Notch were performed to determinate mechanical and impact properties of the tested materials. SMAW process, widely used for gas and oil pipelines welding, was compared with GMAW and FCAW processes which have a better productivity than the first one. The HSLA steels weldability is related with HAZ region which also depends on welding process, its parameters and material chemical composition. Normally is not necessary to perform toughness test as CTOD test to evaluate the procedures.

Made available in DSpace on 2014-10-09T12:28:54Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:57:01Z (GMT). No. of bitstreams: 0 / Um dos mais críticos problemas encontrados na união de materiais distintos é a formação de tensões residuais, que ocorre principalmente pelo fato desses materiais possuírem coeficientes de expansão térmica e condutividades térmicas diferentes. Neste trabalho foi estudada a técnica de soldagem laser entre o aço carbono AISI 1010 e o aço inoxidável AISI 304. Os materiais foram unidos por solda autógena de topo com um laser de Nd:YAG contínuo. O principal objetivo do estudo foi a identificação da influência dos parâmetros de soldagem, pela análise das tensões residuais na zona termicamente afetada (ZTA). Foi executado um planejamento fatorial de três fatores a dois níveis com uma réplica, em que foram variadas a potência, a velocidade de soldagem e a posição focal do feixe laser. Na superfície da amostra foram realizadas medidas de tensão residual pela técnica de difração de raios X, para estudar sua variação em função dos parâmetros investigados. O método do furo cego foi também utilizado para avaliar a tensão residual ao longo da profundidade das amostras até a profundidade de 1 mm. Além das medidas de tensão residual, os cordões de solda foram avaliados por microscopia óptica e eletrônica de varredura (MEV), que tiveram como objetivos determinar a geometria do cordão e mudanças na microestrutura, também foram feitas medidas de microdureza Vickers para se avaliar a extensão da ZTA. Para se avaliar as propriedades mecânicas da união foram realizados ensaios de tração e fadiga. O software MINITAB 15 foi utilizado para a análise das tensões residuais nas diferentes profundidades da ZTA obtidas pelo método do furo cego. Foi utilizada também a regressão estatística baseada nas diferentes influências da entrada e combinação dos fatores na tensão residual geradas nessa união. Os resultados indicam que o desenvolvimento de modelos pode prever as respostas satisfatoriamente e fornecer aos usuários um guia para definir os melhores parâmetros de união. / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Le perçage est un procédé de fabrication répandu dans le milieu industriel. Le secteur aéronautique a recours à ce procédé pour usiner de nombreuses pièces. Les chambres de combustions en sont un exemple. Exposées à des cycles thermiques sévères, elles sont percées d’une multitude de trous de refroidissement. Chez Safran Helicopter Engines, motoriste spécialisé dans la conception de turbines à gaz pour hélicoptères, ce perçage est réalisé à l’aide d’un procédé d’usinage unique : le perçage par percussion laser à la volée. Ce procédé phare leur permet de réaliser des milliers de trous inclinés dans des tôles en matériaux réfractaires. Safran Helicopter Engines cherche à maintenir son avance dans la production de turbines en s’appuyant sur les innovations constantes du procédé de perçage. Ce travail de thèse s’est articule autour du développement d’un nouveau procédé de perçage laser. De manière à définir un procédé fiable et efficace, plusieurs stratégies de perçage sont étudiées via les possibilités offertes par un laser à fibre milliseconde de haute puissance. Les résultats obtenus laissent entrevoir des perspectives intéressantes en termes d’augmentation de cadence de production à qualité d’usinage équivalente. L’amélioration des performances a été démontrée expérimentalement sur un banc d’essais représentatif des machines de production. Des trous de 400 μm de diamètre incliné à 60o ont pu être réalisés avec un cycle de perçage raccourci au minimum d’un facteur 2. Cette thèse présente également des éléments de compréhension des phénomènes de formation d’un trou. Pour cela, une modélisation des processus thermo hydrodynamiques impliqués dans le procédé de perçage laser a été développée. Ce modèle basé sur une approche par éléments finis repose sur l’étude thermique au cours de l’interaction entre le faisceau laser et la matière. Une partie du modèle inclut les phénomènes de propagation du faisceau dans la cavité en cours de formation afin de traduire de manière plus réaliste le dépôt d’énergie. / Drilling is a well-known manufacturing process. The aeronautic industry uses this process to machine a lot of elements. Among them, we can mention turbine blades, fuel injectors, combustion chambers. The latter are exposed to serious thermal stresses. To limit their impacts, combustion chambers are drilled with multiples cooling holes. At Safran Helicopter Engines, engines manufacturer specialized in engines design for helicopters, drilling is performed with a unique machining process : on the fly laser percussion drilling. This flagship process allows drilling thousands of tilted holes on refractory materials. Safran Helicopter Engines seeks to preserve its leading position in turbo engines manufacturing by looking for steady innovative drilling process. This thesis is structured around the development of a new laser drilling process. To define a reliable and efficient process, several drilling strategies were studied through the possibilities offered by a high-power millisecond fiber laser. The presented results allow catching a glimpse of the possibilities of production improvement. The performance enhancement was established through experimentation with a test bench. Holes of 400 μm diameter with an angle of 60o were drilled with a reduced processing time thanks to this new drilling process. In this thesis, we also propose a theoretical approach describing the hole formation. A mathematical model, accounting for all the physical process taking place during the drilling process is introduced. This model is based on finite elements method and considers the laser beam propagation within the drilled holes by solving Maxwell equations

VACULA Jakub: Optimization of plasma cutting parameters Diploma thesis of the attendance engineer´s study – Mechanical Engineering, specialization Machinery Technology. Academic year 2008/2009. Faculty of Mechanical Engineering of University of Technology in Brno, Institute of the Manufacturing Technology. The Diploma thesis is concerned with the thermal division of a material, concretely by the plasma cutting. It monitors the operational parameters influence of this process to the result quality of cut and the purpose is to optimize these parameters from the qualitative standpoint. The experiment was executed at the plasma cutting equipment Fine Focus 800 of the company KJELLBERG with the utilization of the material S 690 QL. On the base of the literary study of the thermal division of the materials problems it was also described the comparison of the plasma cutting with the method of the division of materials by the oxygen, both from the point of view of the quality, and from the economical point of view.

No description available.

[pt] Foram utilizados dois sistemas de aço API 5L X80, Nb-Cr e Nb-Cr-Mo, para obter as diferentes regiões da ZTA pertencentes a uma soldagem multipasse. Estas regiões são denominadas de: região de grãos grosseiros inalterados (RGGI), região de grãos refinados reaquecidos supercriticamente (RGRRS), região de grãos grosseiros reaquecidos intercriticamente (RGGRI), região de grãos grosseiros reaquecidos subcriticamente (RGGRS). Estas regiões foram obtidas para dois aportes de calor (1,2 e 2,5 kJ/mm) e a RGGRI por ser considerada a região onde poderiam ser formadas zonas frágeis localizadas (ZFL) foram utilizados também aportes de calor de 3,0 e 4,0 kJ/mm. Cada uma das regiões obtidas pela simulação física foi submetida a ensaios mecânicos de impacto Charpy e dureza, assim como a análises metalográficos por microscopia ótica (MO) e microscopia eletrônica de varredura (MEV). Foi possível observar que as microestruturas pertencentes a uma ZTA simulada obtidas com o equipamento (GleebleR3800) se mostram compatíveis com aquelas pertencentes a uma soldagem real. Este resultado comprova que as velocidades de resfriamento obtidas pela simulação foram similares àquelas da soldagem real. A adição de Mo ao sistema Nb-Cr-Mo não promoveu mudanças significativas tanto a nível microestrutural, observado por MO e MEV, como em termos de propriedades mecânicas. / [en] Two API 5L steels grade X80 of the systems Nb-Cr and Nb-Cr-Mo, were submitted to physical simulation in order to obtain different regions of the HAZ similar to those of a multipass welding, the coarse grained heat affected zone (CGHAZ), supercritically coarse grained heat affected zone (SCCGHAZ), intercritically coarse grained heat affected zone (ICCGHAZ), subcritically coarse grained heat affected zone (SCGHAZ). The welding simulation was carried out on a Gleeble R 3800 considering two thermal cycles and different heat inputs 1.2, 2.5, 3.0 and 4,0 kJ/mm, typical of a girth weld. All HAZ zones were simulated only for 1.2 and 2.5kJ/mm. Since the ICCGHAZ is the probable weak link where a local brittle zone (LBZ) can occur, this region was simulated for all heat inputs studied. All simulated regions were subjected to traditional mechanical tests such as impact Charpy-V at -40 and -60C and microhardness Hv1kg. Metallographic analysis by optical microscopy (OM) and scanning electron microscopy (SEM) and fractography were also performed. The microstructures obtained for the different regions of the HAZ, by simulation were close to those of a real welding, however, the cooling rates obtained by simulation were slower than that obtained in a real welding. The mechanical properties and microstructure of the different regions of the HAZ for the systems NbCr and NbCrMo indicate that the microstructural and mechanical behavior of the intercritical region (ICCGHAZ) was considered to be similar to a local brittle zone (LBZ) for all conditions studied.