Este é um artigo publicado em acesso aberto (Open Access) sob a licença Creative Commons Attribution Non-Commercial, que permite uso, distribuição e reprodução em qualq'uer meio, sem restrições desde que sem fins comerciais e que o trabalho original seja corretamente citado. br (AS)Resumo: A principal motivação deste trabalho foi a procura da resposta para o dilema entre que as maiores taxas de produção de eletrodos revestidos com pó de ferro se devem às suas capacidade de trabalhar com maior corrente ou à uma maior eficiência de fusão metálica do ferro adicionado na forma de pó. Um estudo neste sentido foi feito utilizando-se três eletrodos comerciais, cuja principal distinção referia-se ao teor de pó de ferro no revestimento. Os eletrodos foram caracterizados em relação às suas dimensões, densidade e composição (via MEV-EDS) do revestimento. Utilizando-se dois níveis de corrente, foram avaliadas as taxas de fusão e deposição e a geometria do cordão na confecção de filetes na posição plana (junta em ângulo). Pelos resultados, verificou-se que, independentemente da intensidade da corrente, as taxas de fusão e deposição são maiores no sentido crescente da maior concentração de pó de ferro no revestimento. Ficou demonstrado que o mecanismo gerador de maiores taxas de deposição e fusão se deve à menor energia requerida para fundir o ferro do revestimento em forma de pó que o contido na alma metálica. A maior capacidade nominal de condução corrente proporcionada pelo eletrodo com pó de ferro é uma razão secundária.Palavras-chave: Eletrodo revestido; Pó de ferro; Taxa de fusão. The Role of Iron Powder on the Deposition Mechanism in Coated ElectrodeAbstract: The main motivation for this work was a search for an answer to the dilemma of which higher deposition rates of metal powder based coating electrodes are due to either their capacity of working at higher currents or a higher fusion efficiency of the metal powder. This study was developed using three commercial coated electrodes, which main distinction was the iron powder content in their coatings. The electrodes were characterized in relation to their dimensions, coating densities and compositions (via MEV-EDS). Using two current levels, fusion and deposition rates and bead geometry from fillet carried out in flat position (T-joint) were assessed. From the results, fusion and deposition are greater when the iron concentration in the coating are higher, regardless the current level. It was demonstrated that the mechanism for reaching higher deposition rates is related to a lower required energy to melt the iron in powder than in solid state. A higher nominal carrying current capacity acquired by the electrode with iron powder is a secondary reason. Key-words:Shielded Metal Arc Welding; Coated electrode; Iron poder; Deposition rate. IntroduçãoSegundo Liu [1], na metade do século 20 a indústria de bens de capital percebeu o impacto revolucionário da introdução do processo de soldagem, mais especificamente a soldagem com eletrodo revestido. Rapidamente, as indústrias...

The insertion of electric cars in the autonomous world market is growing. The higher acquisition cost and lower autonomy of electric traction, in relation to internal combustion traction, are still the main factors that restrict the sale of this type of vehicle. Even so, in the long term, the lack of an infrastructure that supports the transition to the electric vehicle matrix, can result in a bottleneck in the change of energy source. Therefore, the main objective of this article is to present, through a literature review, the main challenges related to the implementation of electric vehicles in Brazil. The general challenges described include the study of the storage capacity of more efficient batteries and the comparative analysis between electric, hybrid and conventional cars. Meanwhile, the challenges in Brazil were portrayed from the analysis of the grid and electricity distribution matrix and through statistical data of Brazilian lithium reserves. Thus, it appears that solid-state, lithium-sulfur and lithium-air batteries have theoretical storage capacities superior to the current generation of lithium-ion batteries used in automobiles. It was also possible to verify that it is necessary to increase the supply of electric energy in Brazil, in order to meet the future demand for vehicles powered by the electric grid. In addition, a variety of information relevant to technological development research related to this topic was obtained.

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Welding is one of the most employed process for joining steel pipes. Although, manual welding is still the most used one, mechanized version and even automatized one have increased its demand. Thus, this work deals with girth welding of API 5L X65 pipes with 8" of nominal diameter and 8.0 mm thickness, beveled with V-30º narrow gap. Torch is moved by a bug carrier (mechanized welding) and further the parameters are controlled as a function of angular position (automatized welding). Welding parameters are presented for filling the joint with two-passes (root and filling/capping passes). Parameters for the root pass were extracted from previous author´s work with weldments carried out in plates, but validated in this work for pipe welding. GMAW processes were assessed with short-circuit metal transfer in both conventional and derivative modes using different technologies (RMD, STT and CMT). After the parameter determination, mechanical testing was performed for welding qualification (uniaxial tension, face and root bending, nick break, Charpy V-notch impact, microhardness and macrograph). The initially obtained results for RMD and CMT were acceptable for all testing and, in a second moment, also for the STT. However, weld beads carried out by using the conventional process failed and revealed the existence of lack of fusion, which required further parametrization. Thus, a Parameter-Variation System for Girth Welding (SVP) was designed and built to allow varying the welding parameters as a function of angular position by using an inclinometer. The parameters were set for each of the three angular positions (flat, vertical downhill and overhead). By using such equipment and approach, the conventional process with parameter variation allowed reducing the welding time for joint accomplishment of the order of 38% for the root pass and 30% for the filling/capping pass.