Thermophysical properties of thoriated tungsten above 3600 K by a pulse-heating method

Abstract

Thoriated tungsten (tungsten, 98% thorium oxide, 2%) is a widely used electrode material for inert-gas arc-welding. A subsecond pulse-heating technique was applied to rod specimens; radiance temperature was measured by highspeed pyrometry. Literature values of the temperature dependence of the normal spectral emissivity of tungsten were used to obtain true temperatures, with the melting point of thoriated tungsten as a calibration point. Experimental results obtained in the temperature range from 3600 K to the melting point (3693 K) are presented and discussed, along with data obtained during the initial part of the free cooling period. The electrical resistivity results show a regular behavior up to the melting point, indicating that thoria remains an insulator up to 3680 K. During heating, a heat capacity anomaly is found near 3666 K, interpreted as the melting point of thoria. During cooling, two anomalies are found, the first one with a peak near 3660 K and a second one (possibly a Frenkel disorder) with a peak near 3148 K.

Materiais para eletrodos que emitem termionicamente em soldagem a arco

“…Esses resultados estão também coerentes com resultados experimentais reportados na literatura, por exemplo, por Tanaka [14] e Ushio [15]. Na prática, a redução de calor gerado nos acoplamentos, que faz com que o eletrodo dopado opere em temperatura inferior a do eletrodo de W puro, se reflete na queda de tensão de trabalho.…”

Preparation of thorium dioxide nanofibers by electrospinning

“…Thoria-based fuels will be used in Advanced Heavy Water Reactors [6], and it is also used as a blanket material in Fast Breeder Reactors [7]. Thoria is also employed in special optical glasses, in refractory ceramic materials [8], in welding rods for tungsten workup [9], and potentially as composite heterogeneous catalysts [10e12].…”

Physical changes in tungsten and thoriated tungsten electrodes after subsecond heating

“…The samples were resistively heated to the tungsten melting point very quickly (times in the order of 1 s), but heating was stopped before fusion was complete and the samples remained intact. Technical details of the equipment used have been given elsewhere [9][10][11] and the results of the thermophysical measurements in tungsten [ 12,13] and thoriated tungsten [ 14,15] are given in complementary publications. The physical changes caused by the rapid heating were examined using electron microscopy and X-ray microanalysis.…”