Tungsten Content /%≥
The sum of impurity elements /%≤
The content of each element /%≤
In addition to a small amount of tungsten filament used as the heating material of high temperature furnace, the heat of electron tube and the reinforcement of composite materials, most of the tungsten filament is used to make various incandescent lamps and halogen tungsten lamps and electrodes of gas discharge lamps. For THE TUNGSTEN WIRE OR TUNGSTEN ROD USED AS THE cathode of a gas discharge lamp, 0.5~3% THORIUM should be added, which is called tungsten and thORIUM wire, in order to reduce the electron escape work. Because thorium is a radioactive element and pollutes the environment, it is useful to make tungsten cerium wire or tungsten cerium rod instead of thorium. However, cerium has a high evaporation rate, so the tungsten cerium wire or rod can only be used for low-power gas discharge lamps.
The production of tungsten wire mostly uses ammonium paratungstate (APT) as raw material. The general process is to roast ammonium paratungstate into tungsten trioxide in air at about 500℃, or slightly reduce it into blue tungsten oxide in hydrogen at about 450℃. The tungsten filament for an incandescent light bulb requires tungsten trioxide or blue tungsten oxide mixed with small amounts of potassium oxide, silicon oxide, and alumina, which together amount to no more than 1%.
High temperature performance. Incandescent lamp with tungsten wire working temperature between 2300 ~ 2800 ℃, and often general lamp power, the greater the filament, the higher the working temperature and thus, the work of the filament temperature than recrystallization temperature of tungsten filament, at this point, the filament in under the action of its weight, wire section between two hook will produce sagging phenomenon, serious when, filament downwards to the bulb glass shell of a collision.
Room temperature performance. The room temperature performance of tungsten wire is shown in the winding performance. Tungsten wire due to its long processing flow, if the process management is not good, it is easy to make tungsten wire produce many small cracks or local brittle, so that it is easy to break when winding the wire. The fracture fracture caused by the crack is hair-like, while the fracture caused by the brittleness of the wire is crystal flaring.
Consistency of wire diameter. The uniformity of tungsten filament diameter is an important reason for the photoelectric parameters of incandescent bulbs, and some of them will affect the service life of the bulbs.