Equipment for continuous heat treatment of tungsten filaments wound on molybdenum cores

摘要

The invention relates to continuous heat treatment of coiled tungsten filaments wound onto molybdenum cores, in the course of which said filament is passed first through a humid hydrogen atmosphere of about 1300° C. then through a dry hydrogen atmosphere of a temperature of about 1700° to about 1850° C. The method complying with the invention is characterized by transfer times of the coiled tungsten filaments to be heat-treated through heating zones lying in the range of about 3 to about 7 seconds, preferably about 5 seconds, but the duration of passing through the 1700° to 1850° C. high- temperature is at most 7 seconds. The invention also covers the equipment suitable for accomplishing the method, consisting of two high-melting metallic heating tubes, an inventing wheel, a spiral winding/unwinding device, and a temperature sensing and controlling unit. The equipment complying with the invention is also characterized by the tungsten spiral filaments passing in axial direction through heating tubes of low thermal inertia and made of some low-melting metal directly heated with electric current supplied by an electric power unit, temperature control of which is accomplished by electronically controlling the passed-through current, based on measuring the resistance of the heating tube.