Composite Rare Earth Tungsten Electrode Production Technology

Adding rare earth into tungsten electrodes can refine tungsten grain and can change the tungsten electrode plastic-brittle transition temperature, to improve the performance of the electrode. But composite rare earth electrode production technology is more complex and production costs are high, and therefore could not be widely used. Improving production technology of composite electrode has important significance for the composite electrode industrial production. Production technology includes the doping process, reduction process and sintering process.

Thorium tungsten electrode generally uses tungsten oxide and thorium oxide as raw material doped directly. Cerium tungsten electrode generally uses tungsten oxide and rare earth nitrate as raw material to doping. For multiple composite rare earth tungsten electrode usually uses APT and rare earth nitrates as raw material doped directly. This doping method not only efficient, and eliminates APT calcining process, shorten the production process. Uniformly doped with these two materials can improve the mechanical property of the composite electrode so that the electrode has a high finished product rate and high electron emission property.

Composite rare earth tungsten electrodes are usually produced by powder metallurgy method. In this production method, the quality of metal powder plays a decisive role on electrode quality. During the reduction process usually uses secondary reduction method. In the first reduction appropriate increase particles size and increase reduction temperature gradients which are conducive to improving the particle size of the metal powder.

Sintering process mainly affects electrode’s density, grain size, rare earth oxides distribution and high temperature evaporation loss amount and so on. During sintering process for composite rare earth tungsten electrode production should control the sintering temperature. Because if the sintering temperature too high the tungsten grain will grow dramatically to reduce the diffusion coefficient of rare earth oxide, to increase electrode’s burning rate. And the sintering temperature too high will make the rare earth oxide forming low-melting substance grew up together, to increased segregation, resulting in rare earth oxide evaporation loss, unevenly distributed.