Arc Appearance and Cathode Spot Distribution in a Long-Gap High-Current Vacuum Arc Controlled by an External Axial Magnetic Field

Montcel, B. Tezenas du; Chapelle, Pierre; Creusot, Christophe; Jardy, Alain

doi:10.1109/tps.2018.2858284

Cited by 7 publications

(3 citation statements)

References 23 publications

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“…Based on the experimental observations regarding VAs controlled by a strong AMF at large contact gaps reported in [17], the model developed in this paper uses as a first approximation a 2D-cylindrical geometry. As shown in Fig.…”

Section: Magnetohydrodynamic Modelmentioning

confidence: 99%

Numerical Study of the Current Constriction in a Vacuum Arc at Large Contact Gap

Montcel

Chapelle

Creusot

et al. 2019

IEEE Trans. Plasma Sci.

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A classical two temperature magnetohydrodynamic modelling approach is used to study the influence of a large contact gap (up to 40 mm) on the behaviour of a diffuse vacuum arc controlled by a 5 mT/kA uniform external axial magnetic field between two copper electrodes with a 20 mm radius. The current constriction and energy flux density at the anode surface are more particularly analyzed, considering both supersonic and subsonic flow conditions. In the case of a supersonic arc, simulations show that the constriction of the current develops in the whole interelectrode region, but the constriction level at the anode surface does not evolve monotonically with the contact gap. The constriction is partly correlated to the radial compression of the plasma. In the case of a subsonic arc, the current constriction is related to the presence of the anode sheath. It occurs only close to the anode (from a constant distance from the anode of around 15 mm). Whereas the current constriction at the anode surface increases when the gap length goes from 10 mm to 20 mm, it no longer evolves when increasing the gap length from 20 mm to 40 mm. For both flow conditions, the evolution with the gap length of the radial profile of the energy flux density transferred by the plasma to the anode is similar as that followed by the current constriction at the anode.

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Section: Magnetohydrodynamic Modelmentioning

confidence: 99%

Numerical Study of the Current Constriction in a Vacuum Arc at Large Contact Gap

Montcel

Chapelle

Creusot

et al. 2019

IEEE Trans. Plasma Sci.

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“…Research groups conducted several experiments to study the behavior of cathode spots on the melting electrode 6 , 11 and the movement and distribution of the arc 6 , 12 – 14 in the vacuum region of VAR process. Tezenas du Montcel et al 6 pointed out that the distribution of cathode spots on the surface of the electrode and the distribution of the arc in the vacuum region are interdependent. Considering distinct cathode spot distributions, they observed three different arc modes: diffuse, diffuse columnar, and multiple arcs.…”

Section: Introductionmentioning

confidence: 99%

“…Simulation input parameters such as geometrical configuration and operation parameters are based on the settings of the experiment, which we recently performed in collaboration with Breitenfeld Edelstahl AG in Austria using an industrial VAR process. The aforementioned experimental studies 6 , 11 – 14 were performed using titanium-based, zirconium-based, or copper-based alloys. In the present study, the electrode (cathode) and ingot (anode) are made of stainless steel, which to the best of our knowledge, has never been used for the experimental investigation in the VAR process.…”

Section: Introductionmentioning

confidence: 99%

Experimental and numerical investigations of arc plasma expansion in an industrial vacuum arc remelting (VAR) process

Karimi-Sibaki

Peyha

Vakhrushev

et al. 2022

Sci Rep

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In the present study, we investigate arc plasma expansion in an industrial vacuum arc remelting (VAR) process using experimental and numerical tools. Stainless steel is the alloy of interest for the electrode (cathode) and ingot (anode). During the operation of the VAR process, behaviors of cathode spots and plasma arc were captured using the high-speed camera (Phantom v2512). We found that spots prefer to onset and remain within the partially melted surface at the center of the electrode tip. Existing spots outside the melting zone accelerate toward the edge of the electrode to extinguish. We observed a fairly symmetrical and centric plasma column during the operation. For further investigation of the observed arc column in our experiment, we used the two-fluid magnetohydrodynamics (MHD) model of plasma proposed by Braginskii. Thus, we modeled the arc column as a mixture of two continuous interpenetrating compressible fluids involving ions and electrons. Through numerical simulations, we calculated plasma parameters such as number density of ions/electrons, electric current density, flow of ions/electrons, temperature of ions/electrons, and light intensity for the observed arc column in our experiment. The calculated light intensity of plasma was compared with images captured by the camera to verify the model. The distribution of electric current density along the surface of the anode, namely ingot, is a decisive parameter that impacts the quality of the final product (ingot) in VAR process. Herein, we confirm that the traditionally used Gaussian distribution of electric current density along the surface of the ingot is viable.

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A Numerical Study on the Influence of an Axial Magnetic Field (AMF) on Vacuum Arc Remelting (VAR) Process

Karimi-Sibaki

Kharicha

Abdi

et al. 2021

Metall Mater Trans B

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A comprehensive numerical model is proposed to study the influence of an axial magnetic field (AMF) on the solidification behavior of a Titanium-based (Ti–6Al–4V) vacuum arc remelting (VAR) ingot. Both static and time-varying AMF are examined. The proposed 2D axisymmetric swirl model includes calculating electromagnetic and thermal fields in the entire system composed of the electrode, vacuum plasma, ingot, and mold. A combination of vector potential formulation and induction equation is proposed to model the electromagnetic field accurately. Calculations of the flow in the melt pool and solidification of the ingot are also carried out. All governing equations are presented in cylindrical coordinate. The presence of a weak AMF, such as the earth magnetic field, can dramatically influence the flow pattern in the melt pool. The “Electro-vortex flow” is predicted ignoring AMF or in the presence of a time-varying AMF. However, the flow pattern is “Ekman pumping” in the presence of a static AMF. The amount of side-arcing has no influence on the pool depth in the presence of an AMF. Modeling results are validated against experiments.

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Arc Appearance and Cathode Spot Distribution in a Long-Gap High-Current Vacuum Arc Controlled by an External Axial Magnetic Field

Cited by 7 publications

References 23 publications

Numerical Study of the Current Constriction in a Vacuum Arc at Large Contact Gap

Numerical Study of the Current Constriction in a Vacuum Arc at Large Contact Gap

Experimental and numerical investigations of arc plasma expansion in an industrial vacuum arc remelting (VAR) process

A Numerical Study on the Influence of an Axial Magnetic Field (AMF) on Vacuum Arc Remelting (VAR) Process

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