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No processo Eletrodo Tubular (Flux Cored Arc Welding – FCAW), a transferência do metal de adição (transferência metálica) para o material de base, de forma a obter o cordão de solda, determina a qualidade da solda e, portanto, estudos sobre este fenômeno são demandados. Assim, neste trabalho, a transferência metálica durante o processo FCAW é investigada filmando-se esse fenômeno com o auxílio de visualização por infravermelho próximo. Durante a revisão da literatura, não se encontrou outros trabalhos que utilizassem tal metodologia. Deve-se ressaltar que a radiação emitida pelo arco, fumos e partículas (respingos) durante o processo dificulta a visualização do processo. O monitoramento da transferência metálica do processo FCAW foi realizado dentro do envelope de trabalho de tensão e velocidade de alimentação do eletrodo E71T-1 (1,2 mm de diâmetro) e Ar+25%CO2, como gás de proteção. Foi utilizado um sistema de visualização por infravermelho próximo desenvolvido localmente a uma taxa de 300 quadros por segundo, de forma a contribuir para o entendimento do processo e avaliação das características da transferência metálica, diferentemente de outros processos, os quais utilizaram a técnica de perfilografia (shadowgrafia). Foi possível observar a formação e transferência da gota durante o processo e identificar os diferentes modos de transferência ao se variar os parâmetros de tensão e velocidade de alimentação nos mapas de transferência. Os resultados finais do trabalho são os mapas de transferência, os quais estabelecem condições adequadas e fundam as bases para o desenvolvimento de estratégias de controle do arco para o processo FCAW. In the Flux Cored Arc Welding (FCAW) process, the transfer of filler metal (metal transfer modes) to the base material to accomplish the weld bead determines the weld quality and therefore studies of such phenomena is demanded. Thus, in this work, the metal transfer through the FCAW process is investigated by filming the phenomena with the assist of near infrared visualization. During the literature survey, it was found that this technic has not been used so far for analyzing the FCAW process. It must be pointed out that the radiation emitted from the weld arc, fumes and particles (spattering) in this process represent a barrier for these studies based in the process visualization. The monitoring of metal transfer for FCAW process was carried out within the operational envelope of voltage and wire feed speed with the electrode E71T-1 (1.2 mm diameter) and Ar+25%CO2 as a shielding gas. A local developed near infrared filming with frame rate of 300 Hz was employed for metal transfer visualization in order to contribute to a better understanding of this process and evaluating characteristics of metal transfer, unlike previous studies, which used shadowgraph technique. It can clearly be seen how the droplet is created and transferred in this process and also identify the different modes of metal transfer by changing the parameters of voltage and wire feed speed in metal transfer maps. The final result of this study is the metal transfer mode maps, which establish suitable conditions and provide the basis for developing arc control strategies for the FCAW process. Dissertação (Mestrado)

Os métodos clássicos de inspeção utilizados para detectar e encontrar perturbações nos processos de soldagem são baseados comumente na medição direta de seus parâmetros como da tensão do arco, corrente de soldagem, velocidade de alimentação, etc. Usando esses métodos de inspeção implica inserção dos sensores em todo o processo de soldagem e sua presença poderia alterar o comportamento, por exemplo, da transferência metálica e, consequentemente, uma qualidade irregular da junta soldada, bem como provocaria o aumento do custo de produção. Para reduzir essas implicações é necessário usar um método de inspeção não intrusiva. Neste artigo mostrar-se métodos não intrusivos para a inspeção de qualidade de solda. Estes métodos baseiam-se na fusão de sensores, a extração da informação global vinda dos dados fornecidos por cada sensor, como por exemplo, a detecção de emissão de radiação de luz pela espectroscopia, o sensoreamento acústico do arco eléctrico ou as emissões de infravermelho, correlacionando o insumo de calor do processo. Finalmente, a fusão de dados será aplicada a um controlo estatístico para detectar e encontrar perturbações no processo de soldagem. Os resultados mostram que a fusão de sensores pode ser utilizada como uma ferramenta para medir indiretamente a qualidade nos processos de soldagem, especificamente no processo GMAW. The classical inspection methods used for detecting and finding disturbances in welding process are based on direct measurement of its parameters as arc voltage, welding current, wire feed speed, etc. Using these inspection methods implies sensors insertion around the welding process and its presence could alter the metallic transference behavior and consequently an uneven quality as well as it can increase the production cost. For reducing these implications is necessary using a non intrusive inspection method. In this paper we will show nonintrusive methods to the weld quality inspection. These methods are based on sensor fusion, the extraction of global information coming from the interrelation data given by each sensor that, for example, sensing the spectroscopy radiation emission, the acoustic sensing of the electrical arc, the infrared emissions indicating the heat content of the weld. Finally, the fusion data will be applied to a statistical control for detecting and finding welding disturbances. The results will show that sensor fusion could be used as a tool to measure indirectly the weld quality in the GMAW process.

The present study shows the relationship between welding quality and optical-acoustic emissions from electric arcs, during welding runs, in the GMAW-S process. Bead on plate welding tests was carried out with pre-set parameters chosen from manufacturing standards. During the welding runs interferences were induced on the welding path using paint, grease or gas faults. In each welding run arc voltage, welding current, infrared and acoustic emission values were acquired and parameters such as arc power, acoustic peaks rate and infrared radiation rate computed. Data fusion algorithms were developed by assessing known welding quality parameters from arc emissions. These algorithms have showed better responses when they are based on more than just one sensor. Finally, it was concluded that there is a close relation between arc emissions and quality in welding and it can be measured from arc emissions sensing and data fusion algorithms.

Most of the inspection methods used for detection and localization of welding disturbances are based on the evaluation of some direct measurements of welding parameters. This direct measurement requires an insertion of sensors during the welding process which could somehow alter the behavior of the metallic transference. An inspection method that evaluates the GMA welding process evolution using a non-intrusive process sensing would allow not only the identification of disturbances during welding runs and thus reduce inspection time, but would also reduce the interference on the process caused by the direct sensing. In this paper a non-intrusive method for weld disturbance detection and localization for weld quality evaluation is demonstrated. The system is based on the acoustic sensing of the welding electrical arc. During repetitive tests in welds without disturbances, the stability acoustic parameters were calculated and used as comparison references for the detection and location of disturbances during the weld runs.

Garantizar la calidad en soldadura no es una tarea trivial. Para ello diversas inspecciones de control de calidad son realizadas, en detrimento, los costos y tiempos de producción se elevan. Existen diversos sistemas automatizados de soldadura, éstos son auxiliados por sistemas de control basados en el monitoreo de parámetros de soldadura. Sin embargo son reducidos los sistemas automatizados de monitoreo de calidad que en su mayoría son diseñados para el proceso TIG. Durante la soldadura, el arco eléctrico produce emisiones acústicas y electromagnéticas que se manifiestan como sonido y luminosidad. El objetivo del presente trabajo es mostrar que estas emisiones del arco pueden ser utilizados para el monitoreo de la calidad de la soldadura para el proceso MAG-S. Se realizaron múltiples experimentos de soldadura en posición plana donde se indujeron perturbaciones consistentes presencia de grasa y ausencia de gas de protección. En cada experimento se adquirió simultáneamente señales de tensión y corriente así como señales de emisiones del arco eléctrico. A partir de las emisiones acústicas y electromagnéticas en la banda de ultravioleta, se midió la frecuencia de cortocircuitos. A partir de la emisión electromagnética en la banda infrarroja se midió la estabilidad del proceso de soldadura. Los resultados muestran que las emisiones del arco pueden ser utilizadas para el monitoreo y detección de perturbaciones en soldadura y con el entendimiento de las variaciones de cada emisión podría identificarse determinados tipos de perturbaciones. Ensuring quality in welding is not a trivial task. For this purpose several quality control checks are performed, at the expense, costs and production times are increased. There are several automated welding systems and they are assisted by control systems based on monitoring of welding parameters. However, automated quality monitoring systems are limited and they are mostly designed for the TIG welding processes. During welding, the arc produces acoustic and electromagnetic emissions that occur as sound and light. The aim of this paper is to show that the emissions of the welding arc can be used to monitoring the quality of welding in MAG-S process. Multiple welding experiments were performed in flat position; in each experiment were induced perturbations by grease on plate and shielding gas absence. Current and voltage signals and arc emission signals were acquired simultaneously. The short circuit frequency was measured from acoustic and electromagnetic emission in the ultraviolet band. The welding stability was measured from infrared emission. The results show that the emissions of welding arc can be used for monitoring and detecting of disturbances in welding and with the understanding of the variations of each disturbance could be possible to identify certain types of disturbances.

Improved product quality and production methods, and decreased production costs are important objectives of industries. Welding processes are part of this goal. There are many studies about monitoring and controlling welding process. This work presents a non-intrusive on-line monitoriment system and some algorithms capable of detecting GTAW weld defects. Some experiments were made to simulate weld defects by disturbing the electric arc. The data comes from a spectrometer which captures perturbations on the electric arc by the radiation emission of chosen lines. Algorithms based on change detection methods are used to indicate the presence and localization of those defects.