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Comportement de l'arc électrique et fusion de l'électrode consommable dans un four de refusion VAR

Abstract : The present study is aimed to improve our knowledge of the electric arc in the Vacuum Arc Remelting VAR process, as weil as characterize the cathode melting stage. The first step consisted in investigating, thanks to an experimental modulus, the behaviour of the electric arc during the remelting of zirconium alloys, for various operating conditions. High speed video camera observations have put in evidence the influence of the cathode tip shape and the effect of applying an external magnetic field on the movement of the clusters of cathode spots. Besides, infrared thermography measurements show qualitatively that the electrode height thermally affected by the arc is very sm ail and depends on the melt rate. The goal of the second part of this work is the development of a numerical model to simulate the motion of clusters of spots at the tip of the cathode. Coupling this approach with the simulation of the behaviour of a plasma jet emitted by a single cluster, previously established in LSG2M, enables calculating the power distribution at the VAR ingot top as a function of process parameters (current, electrode geometry and external magnetic field). ln a third step, a thermal model of the consumable electrode during melting has been written, assuming a 2D axisymmetrical geometry. Using the operating parameters as model inputs, it predicts in particular the melting rate value and evolution of the cathode tip shape. The model was validated through simulating the three successive remeltings of a zirconium alloy, following an industrial processing route.
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Hafid El Mir. Comportement de l'arc électrique et fusion de l'électrode consommable dans un four de refusion VAR. Autre. Institut National Polytechnique de Lorraine, 2005. Français. ⟨NNT : 2005INPL040N⟩. ⟨tel-01749981⟩



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