Effect of Anode Heat Transfer on Melted Penetration in Welding Process by Free-burning Argon Arc.

Tanaka, Manabu; Terasaki, Hidenori; Ushio, Masao

doi:10.2355/isijinternational.42.1005

Cited by 14 publications

(5 citation statements)

References 16 publications

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“…In the present work, the temperature gradient in the plasma decreases with increasing the flow rate of the gas injected through the hollow cathode whereas it decreases with decreasing the flow rate of the gas injected through the hollow cathode in the simulation by Tashiro et al [18]. The trend and order of magnitude of the heat flux to the crucible anode are comparable to those reported for the heat flux to the anode in transferred arcs [18,32]. The differences found between the present and previous results [18] are due to the difference in the simulation conditions stated above.…”

Section: Effect Of Gas Flow Rate On the Arc Characteristics And Arc H...supporting

confidence: 80%

Modeling of a transferred arc inside a crucible with gas injection through a hollow cathode

Laly¹,

Ramachandran²

2018

J. Phys. D: Appl. Phys.

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A transferred arc system consisting of a crucible type anode and hollow cathode with gas injection is being considered for melting and evaporation of materials to improve the heat transfer efficiency. Knowledge of arc behavior inside the crucible and the effect of gas injection through the cathode on the characteristics of the arc are required to optimize the process parameters for better process efficiency. The available literature on this is very limited. A 2D steady-state axi-symmetrical mathematical model of a DC transferred arc is developed and the plasma arc created between a hollow cathode with gas injection and a crucible anode is simulated. The effects of cathode geometry and gas flow through the cathode on the arc characteristics are studied for different electrode gaps and arc currents. The effect of gas flow through the cathode on the arc voltage is clarified for various electrode gaps and arc currents. The gas flow through the cathode is strong enough to push the arc root attachment from the center of the anode and the plasma covers the entire surface of the crucible bottom at higher gas flow rates. Irrespective of the gas flow rate, arc current, and arc length, the higher arc heating efficiency is achieved when the arc root attachment starts to move away from the center of the anode/arc voltage is minimal. The characteristics of the arc inside the crucible and open arc are compared for different flow rates of the gas injected through the cathode. The present model is validated by comparing the predicted results with previously published results.

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Section: Effect Of Gas Flow Rate On the Arc Characteristics And Arc H...supporting

confidence: 80%

Modeling of a transferred arc inside a crucible with gas injection through a hollow cathode

Laly¹,

Ramachandran²

2018

J. Phys. D: Appl. Phys.

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“…Results of heat flux density as a function of radius have to be obtained by Abel inversion, so that it is particularly difficult to obtain the heat flux density at the centre of the arc, as this estimate needs to be obtained by obtaining differences between measurements of the integrated heat energy received from all other arc radii contributing to the total heat transfer to the electrode segment. The experimental procedure is also described in the more recent paper of Tanaka et al (2002).…”

Section: Comparison Of Predictions Of Heat and Current Density With E...mentioning

confidence: 99%

‘LTE-diffusion approximation’ for arc calculations

Lowke

Tanaka

2006

J. Phys. D: Appl. Phys.

164

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This paper proposes the use of the ‘LTE-diffusion approximation’ for predicting the properties of electric arcs. Under this approximation, local thermodynamic equilibrium (LTE) is assumed, with a particular mesh size near the electrodes chosen to be equal to the ‘diffusion length’, based on De/W, where De is the electron diffusion coefficient and W is the electron drift velocity. This approximation overcomes the problem that the equilibrium electrical conductivity in the arc near the electrodes is almost zero, which makes accurate calculations using LTE impossible in the limit of small mesh size, as then voltages would tend towards infinity. Use of the LTE-diffusion approximation for a 200 A arc with a thermionic cathode gives predictions of total arc voltage, electrode temperatures, arc temperatures and radial profiles of heat flux density and current density at the anode that are in approximate agreement with more accurate calculations which include an account of the diffusion of electric charges to the electrodes, and also with experimental results. Calculations, which include diffusion of charges, agree with experimental results of current and heat flux density as a function of radius if the Milne boundary condition is used at the anode surface rather than imposing zero charge density at the anode.

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“…The exper imental difficulties of using arc plasmas in the near-electrode region is obvious, due to the sharp change in plasma state over a very small distance [1][2][3][4][5][6]. Successful near-anode region modeling and experiments have been carried out by Tanaka, Ushio and coworkers [7][8][9][10][11], and Dinulescu [12]. On the other hand it has been found [13] that the near-cathode region involves highly non-linear multi-field coupling, which makes the complete simulation of arc-cathode interactions quite a time-consuming job.…”

Section: Introductionmentioning

confidence: 99%

Thermal and electrical influences from bulk plasma in cathode heating modeling

Tang

Wang

Zhang

et al. 2016

Plasma Sources Sci. Technol.

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In this paper, a numerical calculation is performed for the purpose of estimating the thermal and electrical influences from bulk plasma in cathode heating modeling, in other words researching the necessity of a coupling bulk plasma in near-cathode layer modeling. The proposed model applied in the present work is an improved one from previous work.In this model, the near-cathode region is divided into two parts: the sheath and the ionization layer. The Schottky effect at the cathode surface is considered based on the analytic solution of a 1D sheath model. It is noted that the arc column is calculated simultaneously in the near-cathode region and the cathode bulk. An application is presented for an atmospheric free burning argon arc with arc currents of 50 A-600 A.The modeling results show three interesting points: (1) at the cathode surface, energy transport due to heat conduction of heavy particles and electrons is comparable to total heating flux, no matter whether the arc discharge is performed in a high (400 A) or low current (50 A) situation; (2) the electrical influence from bulk plasma on the cathode heating modeling becomes obvious in a high current situation (>400 A) for the spot mode; (3) the near-cathode layer voltage drop (U tot ) is larger in the diffuse mode than in the spot mode for the same current, which is just the opposite to that for decoupled modeling.

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Effect of Anode Heat Transfer on Melted Penetration in Welding Process by Free-burning Argon Arc.

Abstract: Fig. 4. Cross-sectional area of weld penetration for the arc length of 2.5 mm, 5 mm and 10 mm under the same conditions with Fig. 2.

Cited by 14 publications

References 16 publications

Modeling of a transferred arc inside a crucible with gas injection through a hollow cathode

Modeling of a transferred arc inside a crucible with gas injection through a hollow cathode

‘LTE-diffusion approximation’ for arc calculations

Thermal and electrical influences from bulk plasma in cathode heating modeling

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