The model of plasma formation in the keyhole in liquid metal as well as above the electron beam welding zone is described. The model is based on solution of two equations for the density of electrons and the mean electron energy. The mass transfer of heavy plasma particles (neutral atoms, excited atoms, and ions) is taken into account in the analysis by the diffusion equation for a multicomponent mixture. The electrostatic field is calculated using the Poisson equation. Thermionic electron emission is calculated for the keyhole wall. The ionization intensity of the vapors due to beam electrons and high-energy secondary and backscattered electrons is calibrated using the plasma parameters when there is no polarized collector electrode above the welding zone. The calculated data are in good agreement with experimental data. Results for the plasma parameters for excitation of a non-independent discharge are given. It is shown that there is a need to take into account the effect of a strong electric field near the keyhole walls on electron emission (the Schottky effect) in the calculation of the current for a non-independent discharge (hot cathode gas discharge). The calculated electron drift velocities are much bigger than the velocity at which current instabilities arise. This confirms the hypothesis for ion-acoustic instabilities, observed experimentally in previous research.
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7 January 2015
Research Article|
January 05 2015
Numerical model of the plasma formation at electron beam welding
D. N. Trushnikov;
D. N. Trushnikov
a)
1The Department for Applied Physics,
Perm National Research Polytechnic University
, Perm 614990, Russian Federation
2The Department for Welding Production and Technology of Constructional Materials,
Perm National Research Polytechnic University
, Perm 614990, Russian Federation
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G. M. Mladenov
G. M. Mladenov
b)
3
Institute of Electronics
, Bulgarian Academy of Sciences, 72 Tzarigradsko Shose, 1784 Sofia, Bulgaria
4
Technology Centre of Electron Beam and Plasma Technologies and Techniques
, 68-70 Vrania, ap.10, Banishora, 1309 Sofia, Bulgaria
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a)
Author to whom correspondence should be addressed. Electronic mail: [email protected]
b)
Electronic mail: [email protected]
J. Appl. Phys. 117, 013301 (2015)
Article history
Received:
October 14 2014
Accepted:
December 17 2014
Citation
D. N. Trushnikov, G. M. Mladenov; Numerical model of the plasma formation at electron beam welding. J. Appl. Phys. 7 January 2015; 117 (1): 013301. https://doi.org/10.1063/1.4905193
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