Thorium Tungsten Electrode of The Origin And Development

Stainless steel electrode melting point of pure tungsten (3650K), the electron emission capability, high modulus , low vapor pressure , the first to be used as an electron -emitting material , but the pure tungsten emission efficiency is low , and in the formation of a high temperature recrystallization equiaxed grain structure will become brittle and easy to break. To overcome these shortcomings , countries Materials workers dedicated to research and development of new electrode materials , tungsten -based doping several high melting point, low power electronic escape rare earth metal oxides, can improve the recrystallization temperature , and can activate the electron emission . However, in the rare earth tungsten electrodes on the basis of research , despite some achievements , but the current global market, replace the use of tungsten electrodes still a long way .

1913 Pinch (Pintsch) found that tungsten - thorium dioxide electrode material in pure tungsten with 2% ( mass fraction ) of about thorium dioxide , which escapes power reduction is reduced to nearly half of 2.63eV ( pure tungsten is 4.55eV), greatly improving the emission efficiency of up to 50mA / W ~ 70mA / W ( pure tungsten electrodes by carbonization only 25mA / W ~ 40mA / W). Moreover tungsten - arc thorium dioxide and stability performance greatly improved than that of pure tungsten . But thorium is a natural radioactive elements, its long half-life of α -ray 1.4 × 1014 years, the production and use of radioactive pollution on the environment and human health hazard ; growing environmental awareness restricts its development, but tungsten - thorium dioxide electrode arc stability and durability can not meet the growing demand for welding technology , so countries have been conducting research materials and workers to develop new generation of thorium tungsten electrode material .


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