Effect of magnetic stirring on grain structure refinement Part 2 – Nickel alloy weld overlays

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 qualquer meio, sem restrições desde que sem fins comerciais e que o trabalho original seja corretamente citado. Resumo: Na busca por melhorias de processos e técnicas de soldagem mecanizada/ automatizada, a combinação de modos operacionais, em adição à possibilidade de combinar níveis de corrente de soldagem, tem ganhado espaço. Por meio dessas combinações é possível variar a energia do arco, o que, aliado a movimentos impostos ao próprio arco, pode possibilitar distribuir a energia de forma otimizada para controlar a formação da solda. Uma forma de impor movimento ao arco é por oscilação magnética. Assim, este trabalho explora a sincronização da oscilação magnética com a soldagem TIG. Para tal, foi desenvolvido um sistema para controle simultâneo da oscilação magnética e da fonte de soldagem. Em seguida, foi feita uma caracterização da deflexão (em função da tensão do eletroímã, da corrente de soldagem e do comprimento do arco) baseada em filmagens de alta velocidade e proposto um modelo simples para a deflexão. A oscilação magnética com sincronização foi comparada à sem sincronização, tendo como base de análise o efeito sobre a largura dos cordões de solda. No caso da oscilação sincronizada, foi variado o nível de energia do arco de acordo com sua posição na peça, sendo possível aumentar a largura do cordão no lado da oscilação com maior energia do arco.Palavras-chave: Oscilação magnética; Sincronização; TIG. GTA Welding with Synchronized Magnetic OscillationAbstract: In the search for improvements in processes and mechanized/automated welding techniques, the combination of operational modes, in addition to the possibility of combining welding current levels, has gained attention. Through these combinations it is possible to vary the arc energy, which, along with movements applied to the arc itself, might allow distribute the energy in an optimized way to control the weld formation. One way to apply movement to the arc is by means of magnetic oscillation. Thus, this work exploits the synchronization between magnetic oscillation and the TIG welding process. For that, a system to control the magnetic oscillation and a welding power source simultaneously was devised. In the following, an arc deflection characterization was carried out (varying electromagnet voltage, welding current and arc length) based on high-speed filming and a simplified model for arc deflection proposed. The magnetic oscillation with synchronization was compared to the conventional one (with no synchronization), taking the effect on the weld bead width the basis for analyses. The synchronized oscillation technique successfully allowed vary the arc energy according to its position on the work piece, being possible to increase the weld width on the side of the oscillation with higher arc energy.Key-words: Magnetic oscillation; Synchronization; TIG. IntroduçãoA busca por melhorias de ...

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“…[9][10][11][12][13][14]. Entretanto, a oscilação magnética sincronizada com o processo de soldagem TIG não parace ter sido ainda explorada.…”

Section: Soldagem Tig Com Oscilação Magnética Sincronizadaunclassified

Soldagem TIG com Oscilação Magnética Sincronizada

2016

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“…Electromagnetic stirring (EMS) is an application of electromagnetic force, when performing arc welding, to refine the microstructure of the weld and thus to enhance its weldability [14][15][16]. For aluminum alloys, it could refine the grains and change the grain orientation [17][18][19].…”

Section: Introductionmentioning

confidence: 99%

“…Recently, it was revealed that EMS could restrain the transformation of ferritic phases in the heat-affected zone (HAZ) and prompt the dense and intersectional dendrites to form in the CF8A weldments [8]. For nickel-based alloys, it can also reduce the grain size of alloy 718 and 52M welds to increase the fatigue life and improve the signal/noise ratio of non-destructive ultrasonic examination, respectively [15,17,21,22]. The primary mechanism for grain refinement by EMS could result from dendrite detachment.…”

Section: Introductionmentioning

confidence: 99%

The Impact of EMS on the Temperature Fluctuations, Appearance, and Microstructure of GTA Stainless Steel Welds

Jeng

Lee

et al. 2020

Metals

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The purpose of this study was to evaluate the temperature fluctuation induced by electromagnetic stirring (EMS) and to investigate the influence of temperature fluctuation on the appearance and microstructure of the stainless steel welds. CF8A and 308L were used for the base metal and weld metal, respectively. Bead-on-plate welding (BOP) was conducted with a linear welding machine of gas tungsten arc welding (GTAW) with EMS. The experimental results show that EMS could prompt temperature alteration rates (TARs) to fluctuate between positive and negative, and enlarge the max/min ratios. Smaller ripples and surface roughness would be induced on the welds, while the dilution and the depth-to-width ratios both decreased. As a result, the ferritic and austenitic grains become more isotropic and their grain sizes become smaller.

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“…Low-frequency electromagnetic stirring can efficiently refine the grains of nickel-based alloys. At the stirring frequency 7 Hz, the nickel-based alloy weldments show the lowest fraction of columnar dendrites [4,5].…”

mentioning

confidence: 99%

“…Electromagnetic stirring (EMS) is often adopted in the processes of gas tungsten arc welding (GTAW) and plasma arc welding (PAW) to refine grains and to modify the characteristics of the grain boundary to improve weldability [4][5][6][7][8][9][10][11][12][13][14]. It is mainly contributed to the Lorentz force resulting from the interaction between the welding current and the imposed magnetic field.…”

mentioning

confidence: 99%

Effects of Electromagnetic Stirring on the Cast Austenitic Stainless Steel Weldments by Gas Tungsten Arc Welding

Jeng

Lee

et al. 2018

Metals

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Cast austenitic stainless steel (CASS) often contains high contents of silicon, phosphorus, and sulfur to prompt low melting phases to form in the welds. As a result, welding defects can be induced to degrade the welds. This study's purpose was to investigate the effects of electromagnetic stirring (EMS) on the CASS weldments. The results showed that the ferrites in the heat affected zone (HAZ) had tortuous grain boundaries, while those that were close to the fusion lines had transformed austenites. EMS could reduce the influence of the welding heat to make the grain boundaries less tortuous and the transformed austenites smaller. Although their temperature profiles were almost the same, the gas-tungsten-arc-welding (GTAW) weld had smaller grains with massive ferrite colonies and more precipitates, while the GTAW+EMS weld had denser ferrite colonies with multi-orientations, but fewer precipitates. The hardness of the base metals and HAZs were typically higher than that of the welds. For both of the welds, the root was the region with the highest hardness. The hardness decreased from the root to the cap regions along the thickness direction. The GTAW weld had a higher hardness than the GTAW+EMS weld. At room temperature, the GTAW+EMS weld had a higher notched tensile strength and elongation than the GTAW weld. This could be attributed to the observation that the GTAW+EMS weld had dense and intersecting dendrites and that more austenites were deformed during tensile testing.

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Effect of magnetic stirring on grain structure refinement Part 2 – Nickel alloy weld overlays

Cited by 36 publications

References 19 publications

Soldagem TIG com Oscilação Magnética Sincronizada

Soldagem TIG com Oscilação Magnética Sincronizada

The Impact of EMS on the Temperature Fluctuations, Appearance, and Microstructure of GTA Stainless Steel Welds

Effects of Electromagnetic Stirring on the Cast Austenitic Stainless Steel Weldments by Gas Tungsten Arc Welding

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