Doped Tungsten Wire Low Temperature Ductility Influence Factors

Doped tungsten low temperature ductility is the main influence factor of tungsten wire spooling property, and spooling property will largely affect use efficiency of the bulbs, so understanding the influence factors of low temperature ductility of doped tungsten wire, thereby to expand the applications of tungsten wire.                              

Theoretically, since the doped tungsten wire grains are longitudinally fibrous structure, and the fracture behavior is intragranular fracture, so it has good ductility. Beside, its plastic-brittle transition temperatures well below than room temperature can well meet the filament winding shaping requirement. However, due to the doped tungsten wire has complex production technology, and in the production process is prone to error, resulting in deterioration of low temperature ductility, affecting spooling property of tungsten wire. Here's a brief analysis of influence factors of the low temperature ductility of doped tungsten wire:

1. The purity of the raw materials
Experimental results show that high-purity tungsten powder having excellent ductility at room temperature, namely, tungsten itself is not brittle. Therefore, low temperature ductility of tungsten will mainly influenced by impurities. Nickel and iron impurity elemental content is too high will increase tungsten wire’s low temperature ductility, resulting in a certain degree difficulty of post-processing.

2. Additives
In order to make tungsten wire has good high temperature sag resistance, tungsten wire will dop some additional agents including Al, Si, and K and so on. But these elements will have no beneficial impact on low temperature ductility performance of the tungsten wire, so during the doping process should better control the amount of additional agents.

3. The surface condition of doped tungsten wire
During the processes, tungsten wire may appear more surface defects, which can mainly be attributed to surface mechanical damage and surface contamination. These defects will increase tungsten wire’s low temperature ductility. In order to eliminate surface defects caused by the machining usually uses electrolytic cleaning method to clean tungsten wire, so that it can improve the surface condition of tungsten wire, increase smoothness. Thereby reducing the tungsten wire’s stress concentration in the process of winding reduces low temperature ductility of tungsten wire.

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