The numerical modelling of Joule heating effects in thoriated tungsten cathodes of high-current plasma arcs

Casado, E.; Colomer, V.

doi:10.1088/0022-3727/33/11/313

Cited by 18 publications

(13 citation statements)

References 24 publications

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“…Temperature gradients of the order of 10 4 K/µm are reported in this region [22]. The problem is further complicated by the existence of protrusions at the microscopic scale, both originally present and induced by erosion; this in turn depends on tip shape, angle [23] and material [24] and on the presence of contaminants, e.g. oxygen, hydrocarbons and water vapours in the surrounding gas.…”

Section: Tig Arc Structure and Propertiesmentioning

confidence: 99%

A Langmuir multi-probe system for the characterization of atmospheric pressure arc plasmas

Fanara

Richardson

2001

J. Phys. D: Appl. Phys.

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The 'high-pressure' atmospheric (TIG) arc plasma is studied by means of a multi-Langmuir probe system. In order to determine the appropriate regime of operation, definitions of the plasma parameters for the description of the argon arc are considered and evaluations are presented. A description of the probe basic techniques is followed by an in-depth discussion of the different regimes of probe operation. The emphasis is put on atmospheric and flowing (arc) regimes. Probe sheath theories are compared and "Nonidealities" like cooling due to plasma-probe motion and probe emission mechanisms are then described.The extensive literature review reveals that the existing probe theories are inappropriate for a use in the TIG arc, because of 'high' pressure (atmospheric), broad range of ionization across the arc, flowing conditions, and ultimately, to the uncertainty about onset of Local Thermodynamical Equilibrium. The Langmuir probe system is built to operate in floating and biased conditions. The present work represents the first extensive investigation of electrostatic probes in arcs where the experimental difficulties and the primary observed quantities are presented in great detail. Analysis methodologies are introduced and experimental results are presented towards a unified picture of the resulting arc structure by comparison with data from emission spectroscopy. Results from different measurements are presented and comparison is made with data on TIG arcs present in literature. Probe obtained temperatures are lower than the values obtained from emission spectroscopy and this 'cooling' is attributed to electron-ion recombination. However, it is believed that probes can access temperatures regions not attainable by emission spectroscopy. Only axial electric potential and electric field are obtained because of the equipotential-probe requirement. Estimations of the sheath voltage and extension are obtained and a qualitative picture of the ion and electron current densities within the arc is given.on floating and plasma potentials and estimates of the sheath voltage are made, which are then compared with the results of Chapter 4. Chapter 13 deals with further 'electrical' parameters (current densities, electric field and electrical conductivity). In Chapter 14 several experimental results are presented together in order to gain a unified picture of the resulting arc structure and some observations about possible conduction structures within arcs are made. Finally Chapter 15, after a summary of the whole work, reports the conclusions obtained and suggests further investigations.

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Section: Tig Arc Structure and Propertiesmentioning

confidence: 99%

A Langmuir multi-probe system for the characterization of atmospheric pressure arc plasmas

Fanara

Richardson

2001

J. Phys. D: Appl. Phys.

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“…Several studies [1][2][3][4][5] have been conducted by experimental observation and numerical simulation in order to investigate the electrode consumption. Sadek et al 1) observed the electrodes tip microstructure after a TIG welding operation.…”

Section: Introductionmentioning

confidence: 99%

“…Casado et al 3) developed a one dimensional model considering a diffusion of additives on the electrode axis and investigated the effect of Joule heating on the electrode lifetime under high current conditions. Nishiyama et al 4) investigated the effects of the electrode shape and the current value on the electrode lifetime by the computational model considering not only Joule heating but also a heat conduction from the arc plasma.…”

Section: Introductionmentioning

confidence: 99%

The Relation Between Electrode Lifetime and Additive Consumption During TIG Welding

Tanaka

Yamada

Shigeta

et al. 2019

QUARTERLY JOURNAL OF THE JAPAN WELDING SOCIETY

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The temporal evaluation in the distribution of additives inside the electrode was clarified by the cross-section observation of the electrode after the arc discharge and the numerical simulation. The effect of the adsorption energy of additives on the electrode lifetime was also investigated by the numerical simulation. During the arc discharge, additives whose work function is lower than tungsten are gradually consumed from the electrode tip due to evaporation of additives on the electrode surface and diffusion of additives inside of the electrode. When the operating temperature of the electrode exceeds the melting point of tungsten, the electrode reaches the lifetime by melting and deforming. Furthermore, by setting an appropriate adsorption energy, the two dimensional experimental result. In addition, the larger the adsorption energy of additives inside of the electrode is, the longer the electrode lifetime is.

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“…The thermodynamic and transport properties of argon, tungsten and stainless steel are given as a function of temperature. 10,[15][16][17][18][19][20][21] The viscosity in the solid-liquid mushy zone is as a function of liquid fraction. Figures 2(a) and 2(b) show the effect of sulfur content on the temperature fields of arc and molten pool.…”

Section: Governing Equationsmentioning

confidence: 99%

Computational Simulation of Arc Melting Process with Complex Interactions

et al. 2006

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The real-time computational simulation of arc melting process with considering complex interactions and solid-liquid mushy zone in molten anode has been successfully conducted to provide the fundamental data for highly economical performance of arc melting process. The configuration of molten anode predicted by realistic numerical model shows the quantitative agreement with the experimental data. The effects of sulfur content concentration in molten metal, arc current and cathode vertex angle on the welding structure is discussed in detail. Finally, the heat exchange efficiency and molten cross-sectional area are evaluated under different arc currents and cathode vertex angles for optimum welding process with high efficiency.KEY WORDS: arc melting system; complex interactions; mushy zone; real-time computational simulation.(8) Evaporation, deformation and charge on the molten anode surfaces are neglected for simplicity. (9) Evaporation, melting and deformation on the cathode surface are neglected for simplicity. Under these assumptions, the governing equations for arc and electrodes region are presented as follows.Conservation c Ar c Ar The initial conditions of arc melting process are the steady thermofluid fields of arc without melting anode. Table 1 shows the system configuration and operating conditions. The thermofluid field is solved by SemiImplicit-Method for Pressure Linked Equation (SIMPLE) method 14) using Tri Diagonal-Matrix Algorithm (TDMA). The electromagnetic field is solved by SOR method. In this study, 90 grid points are adopted in both axial and radial directions. The thermodynamic and transport properties of argon, tungsten and stainless steel are given as a function of temperature. 10,[15][16][17][18][19][20][21] The viscosity in the solid-liquid mushy zone is as a function of liquid fraction. Numerical Conditions and Procedures 22) Numerical Results and DiscussionFigures 2(a) and 2(b) show the effect of sulfur content on the temperature fields of arc and molten pool. The steady state of molten pool is obtained approximately 20 s after arc generation. It is found that sulfur content does not affect the arc flow so much even near interface, however, the welding structure changes drastically by sulfur content. In the case of low sulfur content in SUS304 as shown in Fig. 2(a), the molten metal spreads outward. On the other hand, in the case of high sulfur content in SUS304, the molten pool penetrates downward in the core region.Figures 3(a) and 3(b) show the four kinds of driving forces which affects surface flow induced on the molten pool corresponding as shown in Figs. 2(a) and 2(b). In the case of low sulfur content in SUS304, shear force resulting from cathode jet is stronger at the inner molten region but surface tension is stronger at the outer molten region. Then, total driving force shows positive at the inner molten region but negative at the outer one, which induce the outward and inward flows correspondingly. On the other hand, in case of high sulfur content in SUS304, surface tension...

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The numerical modelling of Joule heating effects in thoriated tungsten cathodes of high-current plasma arcs

Cited by 18 publications

References 24 publications

A Langmuir multi-probe system for the characterization of atmospheric pressure arc plasmas

A Langmuir multi-probe system for the characterization of atmospheric pressure arc plasmas

The Relation Between Electrode Lifetime and Additive Consumption During TIG Welding

Computational Simulation of Arc Melting Process with Complex Interactions

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