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6871 |
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Tuesday, March 09, 2021, Hall 1 2:50 PM Innovations with Electron Beam |
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Effect of beam oscillation parameters on the weld geometry and dilution in electron beam welding of duplex stainless steels with nickel-based filler wire |
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Tamas Toth* / TU Braunschweig / Institute of Joining and Welding, Germany Jonas Hensel / TU Braunschweig, Deutschland K. Dilger/ TU Braunschweig, Deutschland |
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The electron beam welding is gaining an increasing significance in the fabrication of duplex stainless steel structures attributed to economic and quality reasons. The high energy density, combined with a relatively low heat input of this process, which allows the single-pass welding of thick-walled sections, also leads to an unbalanced microstructure after welding due to the rapid cooling of the weld zone. Additionally, the high vacuum required for this technology results in a pronounced nitrogen effusion, further impeding the austenite formation. To overcome these challenges, applying nickel-based filler wire can be considered to be an adequate solution in order to achieve a balanced microstructure without the need of a post-weld heat treatment. Here, realizing a proper dilution of the base material and the filler wire is of crucial importance, which can be influenced with the welding parameters. In the underlying study, the beam oscillation parameters were investigated, with particular focus on the weld geometry as well as on the weld dilution by means of metallographic investigations. It has been revealed, that the shape of the beam oscillation figure exhibits the highest influence on the weld dilution but also on the weld geometry. “Infinity-shaped” beam oscillation figure has been found to be the most expedient in terms of both aspects. It has also been discovered, that increasing beam oscillation frequency led to a better dilution, especially in the upper and middle weld region. Although, it also resulted in a more pronounced “nail head” type of weld geometry combined with a wider heat-affected zone. Furthermore, larger transversal component of the beam oscillation, respecting the welding direction, improved the dilution. Keywords Duplex stainless steels, electron beam welding, weld dilution, beam oscillation, austenite, ferrite, filler wire |