Resumo Nesse trabalho foi proposto avaliar diferentes composições de fluxos para arco submerso factíveis de utilização em suporte de raiz por fluxo, para soldagem de passes de raiz depositados pelo processo de soldagem MIG/MAG. O objetivo foi identificar o efeito dos fluxos sobre a qualidade geométrica do passe de raiz. Para fins de comparação entre fluxos, foi desenvolvido um método para utilização de fluxo como suporte de raiz. Critérios de não aceitabilidade, baseados na geometria do cordão, foram propostos para a análise do desempenho. Cinco diferentes tipos de fluxos foram avaliados sob uma condição de corrente de soldagem (visando alta produção), faixa de folga de raiz e velocidade de soldagem. Análises estatísticas para diferenciar médias e redução de incerteza foram aplicadas como ferramenta. Os efeitos de cada fluxo sobre a geometria da raiz foram analisados. Como conclusão, verificou-se que as características dos fluxos agem de forma concorrente como suporte de raiz. A basicidade parece ser governante na altura de reforço, enquanto a granulometria parece ser governante sobre a convexidade da raiz. Já a regularidade da raiz depende tanto da granulometria como da basicidade. O efeito do ponto de fusão é incerto, não predominando sobre as demais em nenhum dos três critérios.

Abstract In this study, it was proposed to evaluate different flux compositions for submerged arc welding that are feasible for use as root backing flux in root pass welding performed by the MIG/MAG welding process. The aim was to identify the effect of these fluxes on the geometric quality of the root pass. For comparison purposes, a method was developed to use the flux as root support. Non-acceptance criteria, based on bead geometry, were proposed to analyze performance. Five different types of fluxes were evaluated under a single welding current condition (aiming at high productivity), root gap range, and welding speed. Statistical analyses to differentiate means and reduce uncertainty were applied as tools. The effects of each flux on the root geometry were analyzed. As a conclusion, it was observed that the characteristics of the fluxes act in a competing manner as root support. Basicity appears to be a determining factor in reinforcement height, while grain size seems to govern root convexity. The regularity of the root depends on both grain size and basicity. The effect of melting point remains uncertain, not prevailing over the others in any of the three criteria.

Abstract Resistance spot welding is a widely used welding process for thin plates in industries such as aerospace and automotive. This process involves the combination of heat, force, and electricity, and the development of numerical simulation technology for welding processes has enabled the simulation of complex welding phenomena. Numerical simulation can reduce the need for extensive experimental work and improves welding production efficiency. In this article, the focus is on studying the temperature field and process parameters of resistance spot welding of (0.2+0.2 mm) 304 stainless steel. Initially, a three-dimensional symmetric model was created using Solid Works, and then Abaqus is used to perform a numerical analysis of the thermal-electric three-field coupling. The impact of welding parameters (welding current and welding time) on the temperature field and nugget diameter are analyzed. Next, welding experiments are conducted on the workpiece using different welding times and welding currents. The morphology and diameter changes of the molten material nucleus are observed using a high-magnification digital microscope. The results of the numerical simulation analysis and spot welding experiment analysis for resistance spot welding of 304 stainless steel with an equal thickness of 0.2+0.2 mm show a high level of consistency. Finally, tensile testing is carried out on the solder joints, combining this with the diameter to evaluate their strength and quality for the determination of the optimal welding process parameters.

Abstract This study presents an effective method for laser welding, using welding energy as a reference to increase productivity without compromising quality. The research examines the influence of laser power and welding speed on ASTM A36 steel, testing eight combinations of these variables while keeping welding energy constant. Unlike conventional methods that optimize individual variables, this approach establishes a relationship between welding energy, power density, and interaction time, creating a model for consistent results. Through visual, mechanical, and microstructural analyses, the study identifies different laser welding modes: conduction, penetration, and excessive penetration, contributing to a better understanding of their effects on material behavior. In this context, welding energy alone is not sufficient, as different combinations of power and speed generate distinct results. This occurs due to the relationship between welding efficiency and power density, which directly influences keyhole formation, plasma plume behavior, and weld bead morphology. These variations affect energy distribution and the occurrence of defects, such as underfill and irregularities in the weld profile. The findings provide valuable insights for optimizing laser welding in low-carbon steels, helping to refine process parameters and improve weld quality.

Abstract The identification of relevant information in vibration signals has been a subject of study for decades, leading to significant advancements. This field is increasingly recognized as essential for diagnosis, prognosis, and failure prediction, ensuring safety, estimating quality conditions, and monitoring processes across various domains. Researchers have developed numerous approaches to extract and classify features within vibration signals, aiming to identify patterns and useful process information. Many of these approaches have proven effective with vibration signals from various manufacturing processes, including welding, and mechanical, civil, and electrical engineering systems. However, few studies have focused on vibration signals in the Friction Welding process, specifically Rotary Friction Welding (RFW). During RFW, simultaneous application of rotation and compressive forces joins two surfaces, generating complex vibration waves that carry unique information about deformations between the parts' surfaces. The main challenge in diagnosing vibrations in RFW is that the vibration signal is often contaminated with noise due to uneven heating, causing fluctuations in roughness, friction coefficient, and variable ripples over time. This study aims to develop a hybrid signal analysis methodology to investigate the potential for quality diagnosis using vibration signals from the continuous drive friction welding (CDFW) process. The proposed method combines the Dickey-Fuller test (DF) for stationarity identification, Empirical Mode Decomposition (EMD) for frequency recognition, Principal Component Analysis (PCA) for compression, visualization, and data classification, and Short-Time Fourier Transform (STFT) for graphical frequency representation over time. Analyses confirmed that vibration signals are significantly affected by corresponding changes in process evolution. It was demonstrated that vibration signals can characterize CDFW quality. Experimental results also showed that applying EMD, PCA, and STFT to vibration signals successfully identified relevant characteristics of process evolution in the time-frequency domain.

Abstract In certain sectors, such as shipbuilding and offshore, corrosion causes considerable costs by material loss and rework, making material protection by shop primer necessary to create a protective barrier. FCAW is widely used in these situations but its attributes are compromised when carried out over the protective layer. The comprehension of shop primer influence during welding and its relationship with the obtained results are not completely understood. This work aimed to verify the influence of ethyl zinc silicate shop primer thickness layers applied to steel plates during welding and on the weld metal and slag characteristics produced by class E71T1-C1A2-CS2 wire. The current and voltage monitoring was carried out during welding, the weld bead dimensions and microstructure were evaluated, and the slag generated was analyzed. Primer layer thickness increased weld bead width and penetration. The electrical parameters did not indicate changes in the arc. Dilution changes resulting from increased penetration did not impact the microstructure of the weld metal. Measurements of the bead contact angle and analysis of the slag together with the analysis of electrical signals indicated, by elimination, that the thickness of the shop primer layer was responsible for the change in the fluidity of the liquid metal.

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 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 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.

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 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 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 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.

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 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.

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 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.

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.

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 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 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.

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.