Predictions of Current Attachment at Thermionic Cathode for TIG Arcs

Abstract:

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Study of current attachment at thermionic cathode for TIG arc at atmospheric pressure is attempted from numerical calculations of arc-electrodes unified model. The calculations show that the maximum temperature of arc plasma close to the cathode tip for W-2% ThO2 reaches 19,000 K and it is the highest value in comparison with the other temperatures for W-2% La2O3 and W-2% CeO2, because the current attachment at the cathode tip is constricted by a centralized limitation of liquid area of ThO2 due to its higher melting point. The calculations also show that, in cases of W- 2% La2O3 and W-2% CeO2, the liquid areas of La2O3 and Ce2O3 are widely expanded at the cathode tip due to their lower melting points and then produce uniform current attachments at the cathode. It is concluded that the current attachment at thermionic cathode is strongly dependent on work function, melting point and Richardson constant of emitter materials.

Info:

Periodical:

Materials Science Forum (Volumes 580-582)

Edited by:

Changhee Lee, Jong-Bong Lee, Dong-Hwan Park and Suck-Joo Na

Pages:

319-322

DOI:

10.4028/www.scientific.net/MSF.580-582.319

Citation:

M. Tanaka et al., "Predictions of Current Attachment at Thermionic Cathode for TIG Arcs", Materials Science Forum, Vols. 580-582, pp. 319-322, 2008

Online since:

June 2008

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Price:

$35.00

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