Non-sag Tungsten Wire Diameter Consistency

Non-sag tungsten wire with poor diameter consistency will lead to poor photoelectric parameter of incandescent bulbs, and some will affect the life of the lamp. Non-sag tungsten wire can used for the production of incandescent lamps filament and tungsten halogen lamps filament, and gas discharge lamp filament electrodes, a small number of non-sag tungsten wire is applied to high-temperature furnace for heating materials, tube heater and the composite material stiffener. Use as a gas discharge lamp cathode, in order to reduce the electron work function, should add 0.5 to 3% of thorium, called thorium tungsten wire, to non-sag tungsten wire or tungsten rods. Because Thorium is a radioactive element, and can pollute the environment, cerium rather than thorium is used for making tungsten cerium wire or tungsten cerium rod. But the evaporation rate of cerium is high, tungsten cerium wire or tungsten cerium rod can only be applied in small-power discharge lamp. Tungsten becomes very brittle by high temperature recrystallization, and it can easily break in case of a shock or vibration. In some of the requirements of high reliability electric lighting products, in order to prevent wire breakage, we often add 3 to 5% of rhenium, called tungsten-rhenium wire, to non-sag tungsten wire, which can make the extension of tungsten brittle transition temperature drops to room temperature or below. This is a very strange effect of rhenium, has not yet been able to find a substitute element to produce the same effect. At room temperature, tungsten has good acid and alkali capacity, but in the humid air it is easily oxidized, so fine tungsten wire can not be stored for too long in a humid environment. Besides, tungsten begin to react with carbon at 1200 ℃ and down, so we should pay attention to this issue when we are burning hydrogen treatment of filament, or graphite lubricant will react with tungsten and the wire would become brittle fracture.

 

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