V.V. Prasitsky – Dr.Sc.(Eng.), Professor, 

Kaluga Branch of the Bauman Moscow State Technical University

E-mail: sintel40@yandex.ru

Kyaw Zay – Post-graduate Student, 

Kaluga Branch of the Bauman Moscow State Technical University E-mail: kyawzay49@gmail.com

For the manufacture of cores of the primary and igniting electrodes used tungsten wire of two types: with additives of aluminum oxide in an amount of 0.03% of the brand BA, and with additives of oxide of thorium in the amount of 1-1,5% BT. Tungsten grade BA is used for the manufacture of cores of electrodes of lamps with a capacity of up to 400 W inclusive. Lamps with a capacity of 7002000 W have electrodes, the cores of which are made of their material BT. The use of thoriated tungsten is explained by the fact that the burners of high-power lamps have long distances between the electrodes and, consequently, a higher ignition voltage, especially at low ambient temperatures. Additive of thorium reduces the work function of tungsten from 4.54 eV to 2.64 to 3.08 eV, thus improve the thermal emission properties of the electrodes and to reduce the ignition voltage. Cores having a diameter greater than 1 mm, it is difficult welded with molybdenum vacuum entry with a thickness of 24-30 micrometers and bad provide a vacuum-tight junction with the quartz when using the stamping method of quartz burners. Therefore, the ends of the segments, which are welded to molybdenum foil and stamped into quartz glass, flatten or sharpened to a maximum thickness of 0.9 mm. The conditioning is made on special presses with heating. After that, the segments are subjected to chemical cleaning and etching according to the previously described modes. During the cutting process, part of the cores may have a length and curvature that do not fit into the permissible boundaries. As the cutting knives wear out, some burrs form at the ends of some cores, which are no longer removed during the tumbling process. To remove cores from the manufacturing process of core emitters with the above disadvantages, a core screening operation is performed on a specialized machine. Cores suitable for use after rejection are supplied to the operation of pressing the electrodes. The article presents methods for manufacturing cores of spiral and sintered electrodes for sodium discharge lamps. It is shown that the proposed methods for the manufacture of cores with a diameter of 1 mm and a diameter of more than 1 mm are rational.

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