Abstract in Spanish:

Resumen La soldadura subacuática mojada utilizando el proceso con alambre tubular autoprotegido ha sido foco de estudio en los últimos años debido principalmente a su mayor productividad en comparación con el proceso de soldadura manual con electrodo revestido. En la presente investigación se evalúa el efecto del aumento del aporte térmico sobre las características geométricas y microestructurales de cordones de soldadura desarrollados sobre placas de acero ASTM A36. Para este propósito, fueron realizadas tres soldaduras experimentales con diferentes velocidades de avance resultando en tres niveles diferentes de aportación térmica. Las características geométricas evaluadas fueron la penetración, el refuerzo y el ancho de la zona afectada por el calor (ZAC), además, se llevó a cabo el análisis de la porosidad interna y de la microestructura en la sección transversal de cada cordón. Los principales resultados mostraron que el aumento de aporte térmico incrementa el refuerzo, la penetración y el ancho de la ZAC. Por otra parte, la microestructura de la zona de fusión consistió básicamente de ferrita y bainita, mientras que en la ZAC se detectó presencia de martensita. El análisis general de los resultados indicó que es posible obtener soldaduras clase B según el código de soldadura AWS D3.6.

Abstract in English:

Abstract Underwater wet welding using the flux-cored self-shielded wire (FCAW-S) process has been the focus of study in recent years mainly due to its higher productivity compared to the shielded metal arc welding (SMAW) process. In the present investigation, the effect of an increase in heat input on the geometric and microstructural characteristics of weld beads on the ASTM A36 steel plate is evaluated. For this purpose, three experimental weld beads have been produced at different travel speeds, resulting in three different levels of heat input. The geometric characteristics evaluated were the penetration, reinforcement, and heat-affected zone (HAZ) width. In addition, the analysis of the internal porosity and the microstructure in the cross-section of each weld bead was realized. The main results showed that the increment in heat input increases the HAZ's reinforcement, penetration, and width. On the other hand, the microstructure of the fusion zone consisted of ferrite and bainite, while the presence of martensite was detected in the coarse-grained HAZ. The general analysis of the results indicated that it is possible to obtain class B welds according to underwater welding code AWS D3.6.

Abstract in Portuguese:

Resumo A Manufatura Aditiva (MA) representa uma rota de fabricação que vem se desenvolvendo rapidamente nos últimos anos, implementando uma nova opção aos “Processos de Fabricação”. Os benefícios da MA se alinham às demandas por melhoria da qualidade buscadas pelas indústrias na obtenção ou reparação de produtos. Especialistas preveem que a MA conduzirá grandes mudanças na indústria e na sociedade. A manufatura aditiva metálica pode ser desenvolvida por diferentes processos com uso de diferentes fontes de energia como LASER e arco elétrico. O presente trabalho faz uma revisão, que envolve os principais processos de manufatura aditiva por arco elétrico, apresenta uma análise comparativa com outros processos, e também destaca a aplicação do processo Gas Metal Arc Welding (GMAW). Apresenta-se as possibilidades e resultados de diferentes modos de transferência do metal baseada em GMAW, como por exemplo o GMAW Pulsado e tecnologias de transferência por curto-circuito controlado, que têm como objetivo, aplicar o menor aporte térmico e proporcionar maior estabilidade ao processo. Além disso, apresenta-se exemplos de tecnologias e processos utilizados para melhorar os resultados da manufatura aditiva por arco elétrico baseada em GMAW, tais como forjamento, laminação e sistemas de controle do aporte térmico. Finalmente, apresenta-se possíveis direções de pesquisas futuras.

Abstract in English:

Abstract Additive manufacturing (AM) represents a manufacturing route that has been developing rapidly in recent years, implementing a new option for “Manufacturing Processes”. The benefits of AM align with the demands for quality improvement sought by industries when obtaining or repairing their products. Experts predict that AM will lead to major changes in industry and society. Metallic additive manufacturing can be developed by different processes using different energy sources such as LASER and electric arc. The present work provides a review which involves the main processes of wire arc additive manufacturing presents a comparative analysis with other processes, and also highlights the application of the Gas Metal Arc Welding (GMAW). The possibilities and results of different metal transfer modes applied in GMAW-based additive manufacturing are presented, such as Pulsed GMAW and controlled short circuit transfer technologies, which aim to apply the lowest heat input and provide greater stability to the process. In addition, examples of technologies and processes applied to improve the results of GMAW-based wire arc additive manufacturing are presented, such as forging, rolling and heat input control systems. Finally, possible future research directions are presented.

Abstract in Portuguese:

Resumo Quando uma estrutura soldada sofre impacto estrutural, a ductilidade do material é uma das características preponderantes. Contudo, com o crescente destaque e utilização dos aços de alta resistência e baixa liga (ARBL) nem sempre este fator é considerado na sua utilização. Isto pode resultar em instabilidades globais e/ou localizadas numa estrutura. Desta forma, o objetivo principal deste trabalho foi comparar o comportamento ao impacto estrutural de perfis I soldados, produzidos com ASTM A36, um aço estrutural “comum”, e EN10149-2 S700MC, aço ARBL, soldados em filete por processo de soldagem por arco elétrico com atmosfera de proteção gasosa MAG (GMAW) e utilizando metais de adição, AWS ER70S- 6 e AWS ER110S-G, que depositam metais de solda com grandes diferenças em resistência à tração e ductilidade. No desenvolvimento deste trabalho foram elaborados conjuntos soldados (CS) na forma de perfis I de chapas soldadas e mantendo-se as soldas com acabamento original. Os CS foram feitos em ambos materiais variando o metal de adição e condições de reforços. Entre os principais resultados, destaca-se o comportamento do material de alta resistência (EN10149-2 S700MC) quando submetido a carregamento dinâmico, apresentou fratura na mesa superior, com comprimentos significativamente maiores que os apresentados pelo aço ASTM A36, sob mesmas condições de soldagem e carregamento. Além disso, a presença de reforço vertical na estrutura acaba por transferir o carregamento para a mesa oposta do perfil, porém sem anular a condição de fratura no material de alta resistência.

Abstract in English:

Abstract When a weldment suffers structural impact, the base and filler metals ductility is one of the main features. However, despite the increasing use of high strength low alloy steels (HSLA), this factor is not always considered and it can result in global and/or localized instabilities within a structure. So, the main objective of this work was to compare the behavior to structural impact of welded I-profiles, made with ASTM A36 and EN10149-2 S700MC, a regular and a HSLA structural steel, respectively, using GMAW process and AWS ER70S-6 and AWS ER110S-G as filler metals, which produce weld metals with great differences in tensile strength and ductility. Besides, all weldments were made with both filler metals and the profiles with or without stiffening reinforcements (on the web), keeping the original finishing of the fillet welds. Among the main results, the behavior of the material with high strength (EN10149-2 S700MC) when subjected to dynamic loading, have shown fracture on the upper flange, with crack lengths significantly greater than those presented by ASTM A36 steel, under the same welding and loading conditions. Furthermore, the presence of vertical reinforcement acts as a stiffening of the structure and ends up transferring the load to the opposite flange of the profile, however without nullifying the fracture condition in the high-strength material.

Abstract in English:

Abstract This article describes the effect of CO2 LBW performance parameters for the welded joint of 1.5 mm thin sheet of Nimonic 80A superalloy. Superalloy 80A used in high temperature application as aero-engine components- blade, rings, exhaust gas turbine part, nuclear tube support and automobile valve. The study focused on optimizing the welding process for the welded joints. Here, LP, WS, FD, and shielding GR will be optimised to improve the weld quality of Nimnic 80A material. Two different optimization techniques were used. The first method is SOO, which is based on the S/N ratio. The aim of this method is to find the Single-optimal values of process parameters. The second method employed MOO, combining the Taguchi grey relational analysis (TGRA) with the principal component analysis (PCA) technique. The researchers used these methods in an effort to identify the set of parameters for obtaining improved weld quality. Authors find best setting parameters p3-v3-f3-g1, with the specific parameter values are LP 2400 W, WS 1800 mm/min, FD 18 mm, and GR 10 lpm. The optimized parameters have yield significant improvements in the depth of penetration 6.03%, weld bead 8.74%, Vickers hardness 12.5%, and tensile strength 16.48% by using TGRA coupled with PCA.

Abstract in Portuguese:

Resumo Os aços inoxidáveis desfrutam de um cenário propicio para aplicações em variados campos da engenharia. A escolha adequada dos parâmetros de soldagem destes metais pode resultar numa maior produtividade através do aumento da vida útil dos equipamentos. Assim, o objetivo deste trabalho é avaliar a influência do aporte térmico na microestrutura presente na zona afetada pelo calor (ZAC) das juntas soldadas do aço, através de caracterização metalográfica e ensaios mecânicos. O material analisado são chapas de aço inoxidáveis, soldadas pelo processo GMAW, variando os aportes térmicos. Após essa etapa, as chapas foram cortadas, preparadas, realizadas análises metalográficas, ensaios mecânicos de tração e dobramento. A quantificação de fases presentes na zona afetada pelo calor, das três condições experimentadas, 4,2 kJ/cm, 6,7 kJ/cm 9,1 kJ/cm e metal base, foram realizadas nesse estudo, como também as propriedades mecânicas das juntas soldadas. Verificado que as taxas de resfriamento não foram suficientes para provocar mudanças microestruturais significativas no balanço das fases ferrita e martensita, encontradas na ZAC. Já às propriedades mecânicas prevaleceram estáveis nos ensaios de tração e dobramento, não havendo resultados que poderiam vir a impedir a aplicação do material por estar fora do limite de resistência exigido pelas normas de aplicação.

Abstract in English:

Abstract Stainless steels enjoy a favorable scenario for applications in various fields of engineering. The proper choice of welding parameters for these metals can result in greater productivity through increased equipment life. Thus, the objective of this work is to evaluate the influence of heat input on the microstructure present in the heat-affected zone (HAZ) of welded steel joints, through metallographic characterization and mechanical tests. The analyzed material is stainless steel plates, welded by the GMAW process, varying the thermal inputs. After this step, the plates were cut, prepared, metallographic analyses, mechanical tensile and bending tests performed. The quantification of phases presents in the heat-affected zone, of the three conditions experienced, 4.2 kJ/cm, 6.7 kJ/cm 9.1 kJ/cm and base metal, were carried out in this study, as well as the mechanical properties of the welded joints. It was verified that the cooling rates were not enough to cause significant microstructural changes in the balance of delta ferrite and martensite phases, found in the HAZ. As for the mechanical properties, they were stable in the tensile and bending tests, with no results that could prevent the application of the material because it was outside the resistance limit required by the application standards.

Abstract in Portuguese:

Resumo O ensaio não-destrutivo por partículas magnéticas é uma técnica amplamente utilizada na indústria para identificação de descontinuidades superficiais e subsuperficiais em materiais ferromagnéticos, tanto nas etapas de fabricação (peças semiacabadas) quanto em condições de serviço. As peças precisam ser submetidas a um campo magnético, o qual possibilita a movimentação das partículas magnéticas e o acúmulo em regiões com descontinuidades. Todavia, o magnetismo residual pode ocasionar problemas em etapas de processamento, como a soldagem e usinagem. Nesse sentido, o presente trabalho se propôs a investigar o comportamento de peças que são submetidas a inspeção magnética e as possíveis consequências do magnetismo residual. As peças de diferentes composições químicas foram submetidas ao ensaio e tiveram os valores de intensidade de campo magnético medidos e passaram por etapas de soldagem (GTAW). Foi possível identificar a ocorrência, em baixa intensidade, do fenômeno de sopro magnético durante a soldagem. Por não representar um risco elevado ao resultado da solda, pôde-se concluir que, para esse caso especificamente e sob as condições estabelecidas para os experimentos, a desmagnetização após o ensaio é facultativa. A desmagnetização após os processos de soldagem pode ser explicada pelo aumento da temperatura acima do ponto de Curie.

Abstract in English:

Abstract Non-destructive magnetic particle testing is a technique widely used in industry to identify surface and subsurface discontinuities in ferromagnetic materials, both in the manufacturing stages (semi-finished parts) and in service conditions. The parts need to be subjected to a magnetic field, which allows magnetic particles to move and accumulate in areas with discontinuities. However, residual magnetism can cause problems in processing stages such as welding and machining. With this in mind, this study set out to investigate the behavior of parts subjected to magnetic inspection and the possible consequences of residual magnetism. Parts of different chemical compositions were subjected to the test and had the magnetic field strength values measured and underwent welding steps (GTAW). It was possible to identify the low-intensity occurrence of the phenomenon of magnetic blowing during welding. As it does not represent a high risk to the result of the weld, it can be concluded that, for this specific case and under the conditions established for the experiments, demagnetization after the test is optional. Demagnetization after the welding processes can be explained by the increase in temperature above the Curie point.

Abstract in Portuguese:

Resumo A fabricação de peças pelo processo de Manufatura Aditiva por Deposição a Arco (MADA) tem como característica o uso de fontes de soldagem aplicadas em GMAW, GTAW e PAW. O controle dos parâmetros durante a construção das peças é fundamental para contribuir com a redução do aporte térmico, possibilitando assim a aplicação de uma técnica para controlar o calor imposto sobre a deposição das camadas. O monitoramento do processo consiste em detectar variações no processo durante as deposições das camadas e vários são os recursos utilizados, tais como: emissão acústica, sistemas de visão computacional, sensores para coletar informações quanto à radiação térmica e/ou temperatura da peça, além da captura de informações quanto às variáveis elétricas. O objetivo deste trabalho é apresentar uma metodologia para o controle dos parâmetros durante a deposição das camadas de modo a atuar no equipamento por meio de um algoritmo de controle e um sistema de aquisição de dados, atuando no processo. Um estudo da influência dos parâmetros sobre a geometria e estabilidade de arco é apresentado. Um planejamento experimental baseado na técnica de Projeto Robusto foi aplicado para viabilizar o número de experimentos. Os resultados sugerem o efeito benéfico da duração do ciclo sobre a estabilidade do arco, comportamento da poça de fusão e geometria final.

Abstract in English:

Abstract Manufacturing parts using the Wire Arc Additive Manufacturing (WAAM) process is characterized by the use of welding sources applied in GMAW, GTAW, and PAW. The control of the parameters during manufacturing is fundamental to contribute to the reduction of the heat input, thus making it possible to apply a technique to control the heat imposed on the deposition of the layers. The process monitoring consists in detecting variations in the process during layers’ deposition, using a variety of resources, such as: acoustic emission, computer vision systems, sensors to collect information on thermal radiation and/or temperature of the part, in addition to capturing information on electrical variables. The objective of this work is to present a methodology for controlling the parameters during deposition of the layers in order to command the equipment with a control algorithm and a data acquisition system, acting on the process. A study of the influence of the parameters on arc geometry and stability is presented. An experimental design based on the Robust Design technique was applied to make the number of experiments feasible. The results suggest the beneficial effect of cycle length on arc stability, melt pool behavior and the final geometry.

Abstract in Portuguese:

Resumo A manufatura aditiva é uma tecnologia que permite a fabricação de peças através da adição sucessiva de material em camadas. Essa técnica permite a impressão de polímeros, metais, cerâmicas, biomateriais e materiais compósitos. Os materiais depositados podem ser arame, pó ou líquido. A Manufatura Aditiva por Deposição a Arco (MADA) é uma técnica promissora no processamento de ligas metálicas, onde, o Cold Metal Transfer (CMT) é uma variação do processo MIG/MAG que proporciona menor aporte térmico durante a transferência de material, influenciando na qualidade final da peça. Sendo assim, este trabalho tem como objetivo apresentar uma revisão bibliográfica das estratégias de deposições e comparar os efeitos causados ao se utilizarem diferentes parâmetros, especificamente pela MADA. Com isso, foi possível identificar que o controle do aporte térmico é um fator decisivo para evitar defeitos e melhorar o acabamento superficial das peças. Diferentes estratégias e parâmetros alteram a microestrutura e, como consequência, as propriedades mecânicas da peça.

Abstract in English:

Abstract Additive manufacturing is a technology that enables the production of parts through the successive addition of material in layers. This technique allows for the printing of polymers, metals, ceramics, glass, biomaterials, and composite materials. The deposited materials can be wire, powder, or liquid form. Wire and Arc Additive Manufacturing (WAAM) is a promising technique in the processing of metal alloys, where Cold Metal Transfer (CMT) is a variation of the GMAW process that provides lower heat input during material transfer, having impact on the part quality. Therefore, this study aims to present a literature review of deposition strategies and to compare the effects caused by using different parameters, specifically in WAAM. As a result, it was possible to identify that controlling the heat input is a decisive factor in preventing defects and improving the surface finish of the parts. Different strategies and parameters alter the microstructure and, consequently, the mechanical properties of the part.

Abstract in English:

Abstract This work established a process window aimed at minimizing discontinuities and improving mechanical properties in dissimilar friction stir welded joints between AA6063-T6 and AA5052-H32 alloys. A different set of rotational and traverse speed value combinations were experimentally evaluated using graphical analysis, which was compared to information from the literature. Microstructure characterization of the welded joints was conducted using optical microscopy, X-ray diffraction, and SEM-EDS. Microhardness measurements were performed, and an experimental design statistical analysis was carried out to establish the correlation between the process parameters and tensile properties. The results showed that a speed ratio of 1800/163 (R=ω/v rev/mm) produced discontinuity-free welded joints with higher microhardness and tensile strength values, being 159 MPa for ultimate strength.

Abstract in English:

Abstract In this study, we focused on a lap joint arrangement made with a vertical machining machine to examine the impacts of adding Titanium Carbide nanofibers (TiCnf) to the weld pool of Grade AZ31 magnesium alloy. During the investigation, we followed ASTM guidelines for measuring tensile strength and yield strength, percentage of elongation, and Vickers hardness strength. The information gathered showed that welds with a peak tensile strength of 452 MPa showed a remarkable rise in TiCnf content of around 1.5 wt%. Additionally, it was revealed that adding more nanofibers considerably increased micro hardness. This improvement led to polished and distortion-free grain structures, especially in the Heat-Affected Zone (HAZ) and Thermo-Mechanically Affected Zone (TMT). The mechanical qualities of the welds were ultimately improved as a result.

Abstract in Portuguese:

Resumo O processo de manufatura aditiva a arco arame ou WAAM (Wire Additive Arc Welding) é reconhecido como um processo capaz de confeccionar peças de elevada complexidade geométrica, com propriedades mecânicas comparáveis às do material fundido. Entretanto, existem desafios significativos associados ao WAAM, como microestruturas e propriedades mecânicas indesejáveis, elevadas tensões residuais e distorção geométrica. Este estudo visa contribuir com a seleção de parâmetros de deposição do aço VP50IM utilizando WAAM via TIG (Tungsten Inert Gas) pulsado e caracterização do empilhamento gerado, utilizando a metodologia Central Composto Completo, CCC. Neste estudo variou-se a corrente de pico (Cp) e de base (Cb), velocidade de alimentação de arame durante pico (Vap), base (Vab) e velocidade de soldagem (Vs). O parâmetro ideal apresentado foi Cp=200A, Cb=100A, Vap=2,9cm/min, Vab=1,2cm/min e Vs=20cm/min. Ensaios de tração mostraram uma resistência até 15% maior nas amostras na seção longitudinal ao sentido de soldagem em comparação ao sentido transversal. Ensaios de dureza demonstraram uma dureza até 9% menor no centro do empilhamento em comparação ao topo e base. A análise de fratura dos corpos de prova evidenciou fratura dúctil.

Abstract in English:

Abstract The wire arc additive manufacturing process or WAAM (Wire Additive Arc Welding) is recognized as a process able of making pieces of high geometric complexity, with mechanical properties comparable to those of the cast material. However, there are significant challenges associated with WAAM, such as undesirable microstructures and mechanical properties, high residual stresses and geometric distortion. This study aims to contribute to the selection of deposition parameters for VP50IM steel using WAAM via pulsed TIG (Tungsten Inert Gas) and characterization of the generated stacking, using the Central Composite Complete methodology, CCC. In this study, the peak (Cp) and base (Cb) current, wire feed speed during peak (Vap), base (Vab) and welding speed (Vs) were varied. The ideal parameter presented was Cp=200A, Cb=100A, Vap=2.9cm/min, Vab=1.2cm/min and Vs=20cm/min. Tensile tests showed up to 15% greater resistance in the samples in the longitudinal section in the welding direction compared to the transverse direction. Hardness tests demonstrated up to 9% less hardness at the center of the stack compared to the top and bottom. The fracture analysis of the specimens showed ductile fracture.

Abstract in English:

Abstract In this present examination, AA6092 alloys are friction-stir welded at various welding conditions to develop a welded joint with optimal ultimate tensile strength (UTS) and microhardness. This work deals with replacement of application of AA6061 alloys as bumper and bonnet by means of AA6092 alloys and this alloys tensile strength and microhardness is further increased by performing friction stir welding. This study investigates the performance of the friction stir welded butt joints of AA6092 alloys by varying the FSW process parameters such as tool rotational speed (TRS), welding speed (WS), axial load (AL), tool tilt angle (TTA), tool pin profile (TPP), shoulder diameter (SD), etc. In the current investigation, the empirical relationships are developed between most contributing FSW process parameters (TRS, WS, and AL) and their output responses (UTS and weld nugget microhardness (WNH)). The optimal UTS and WNH is predicted by the desirability approach of response surface methodology (RSM). The conforming values of input FSW process parameters are TRS of 1451.67 rpm, WS of 42.22 mm/min, and AL of 5.29 kN. For the existing examination, calculated UTS and WNH are 465.6 MPa and 151.8 HRB respectively, and the results of validation experiments are also invariable with these values.

Abstract in English:

Abstract Accurate measurement of the residual stress in welded joints is still a major challenge for both welding quality control and non-destructive testing. One of the most recent and innovative magnetic techniques for this purpose, known as Magnetic Barkhausen Noise (MBN), is based on the reorganization of magnetic domains (regions with uniform magnetic orientations) in the presence of a varying magnetic field in the studied ferromagnetic material. A significant difficulty in using this method for the analysis of welded joints lies in evaluating of the contribution that each altered material property induces in the resulting noise signal. Therefore, the objective of this study was to correlate the MBN signal with the typical changes that occur in the weld bead and its specific regions during the welding process applied to ASTM A36 steel. Thus, the root mean square (RMS) value of the signal was correlated with micro- and macrostructural changes in the joint, as well as with hardness and residual stress state, including its tensile and compressive magnitudes, demonstrating to be an effective non-destructive tool for characterizing of welded structures.

Abstract in English:

Abstract In hybrid welding, due to the large number of welding parameters and the coupling between different welding parameters, any change of welding parameters will have a significant impact on the weld section size, so it is always essential to choose reasonable welding parameters to improve the stability of the weld. In this paper, an automatic measurement system for weld section size is designed. The center point of the weld section contour is taken as the origin of the polar coordinate system, and the pixel coordinates of the boundary points on the weld section contour are detected every 15 degrees. Based on 32 groups of laser-arc hybrid welding experiments, the BP (Back Propagation) neural network is used to establish the prediction model between the input parameters (welding current, laser power, welding Angle, welding gap, and weld blunt) and the output weld section size. Aiming to the problem of too many input and output parameters of the BP neural network, a multiple population genetic algorithm (MPGA) is introduced to optimize the internal weights and thresholds of the BP neural network to improve the prediction accuracy. Finally, the difference between the dimensions of the left and right sides of the weld is calculated as the symmetry of the weld profile. The results show that the measurement accuracy of the automatic measurement system can reach 98%, and the prediction accuracy of the section size and symmetry can reach about 90% with the optimized BP neural network. The research method in this paper is of great significance to the study of welding process parameter optimization.

Abstract in English:

Abstract Duplex stainless steels have superior mechanical and corrosion properties with better toughness and ductility compared to austenitic and ferritic stainless steels due to their dual phase microstructure i.e. austenite and ferrite, which is attractive for gas pipelines. In this study, effects of different heat inputs and interpass temperatures were investigated on the mechanical and microstructural properties of UNS-S31803-(2205) duplex stainless steel welds using two different welding methods i.e. Gas Tungsten Arc Welding and Shielded Metal Arc Welding in place of conventionally used Submerged Arc Welding. UNS-S31803-(2205) duplex stainless steel pipe was joined using ER2209 (GTAW) filler wire and ESAB OK67.55 (SMAW) electrode. Pure argon was used as shielding gas and for back-root protection. Microstructural examinations and mechanical tests were carried out in accordance with PTS and ASME standards. Results showed that, two different welding methods generated a weld joint with higher strength and hardness than base metal at certain heat inputs and interpass temperatures. Weld metal properties were within the defined limits of standards and the critically selected interpass temperature and heat input which induced different cooling conditions with multiple passes produced a welded joint without the formation of deleterious sigma phase in weld metal and the heat affected zone.