molybdenum bar of the history of tungsten

Development of tungsten industry from the outset with the light bulb industry closely linked. In 1878, Edison (T.A.Edison) invented the carbon filament light bulbs.

But this bulb there is a serious drawback, mainly life is too molybdenum bar short. Nearly 20 years later (1897), osmium carbon filament yarn and tantalum wire was replaced, but the Os, Ta melting

Points lower, and thus low operating temperature and light effects.

1879 Edison carbon filament probation and hundreds of hours of use. Although the "carbon" has a high melting point (3550 ℃), but it has a low "sublimation"

Temperature. Sublimation at low temperatures directly from solid to gaseous state, making it easy to consume, life is short. And must be completely isolated from the air (will burn in air)

. A melting point of almost all the current (3410 ℃) tungsten wire, the advantage of lower melting point which is lower than the "sublimation" rate. Can be heated to a higher "carbon

Silk "higher temperatures. Tungsten same will burn in air,molybdenum crucible  requiring bulbs evacuated.

To prevent sublimation of the filament within the lamp contains an inert gas such as argon gas is mainly (argon) and does not contain oxygen. So that part of the gas by collision

Of tungsten atoms can return to the filament. Although the inert gas increases the service life of the filament, but also paid a price. Since the original vacuum bulb

The increased presence of an inert gas heat conduction and convection, the energy away, so reducing the equilibrium temperature. Sublimation gas tungsten inert gas formed in the weak

The particles can also be formed on the surface convection within the lamp black spots.

In 1903, according to Jay zafirlukast (A.Just) and Hannah door (F.Hannaman) patents, Hungary for the first time to create a tungsten filament. It is the freedom of hydrogen containing carbon filament

Tungsten oxyhalide steam heated to a high temperature by the current, the carbon is completely replaced by tungsten. Incandescent filaments thus obtained contain more or less of carbon, not brittle

Very serious, and when using the lamp filament continuously densified filament thus vary the electrical parameters.

In 1904, Jay Sterling and Hannah door recognize the impact of carbon on the brittle carbon compounds mixed binder and tungsten, and then extruded into filaments, and then in hydrogen

Reduction by heating the metal. Tungsten prepared in this way is very brittle, but because it is a much better light efficiency, or to replace the carbon filament, osmium and tantalum wire filament lamp used for the production

Bubble.

Preparation of these methods are not fine tungsten wire. To solve this problem, in 1907, a low nickel content of tungsten alloy available, it is through machining methods

Prepared, but it is seriously hampered the application of brittleness. Until 1909, Coolidge (w.D.Coolidge) General Electric Company by powder metallurgy

Legal tungsten billet was then produced by machining ductile tungsten filament at room temperature, thereby laying the foundation for tungsten processing industry, but also laid the powder metallurgy

Foundation.

However, this "ductility" tungsten filament light bulb lit after showed significant brittleness. In 1913, Ping Qi (Pintsch) invented the thorium tungsten wire (ThO2 content of 1% to

2%), so that the incandescent lamp is greatly reduced brittleness. Initially, the filament sag (see anti-sag tungsten performance) is not a problem, because the filament

Straight wire, but after 1913, Langmuir (Langmuir) will be replaced by straight wire spiral wire, so that when the lamp, high operating temperature and weight to make the role of

Filament sag, so pure tungsten and tungsten thorium are difficult to meet the requirements.

In order to solve the short life tungsten sagging and other issues, in 1917, Perth (A.Pacz) invented the high temperature "deformation" of the tungsten filament. At first, he was in the preparation of pure tungsten

When using a refractory crucible roasting WO3, WO3 restore accidentally discovered this tungsten spiral made of tungsten powder resulting abnormal mysteriously re-crystallized by no sagging. Follow

Later, after 218 repeated experiments, he finally found that the addition of potassium and sodium silicate in tungstate (WO3 · H2O), after reduction, pressing, sintering, machining

And other prepared tungsten wire, after a fairly coarse recrystallized grain structure, neither soft and anti-sagging, this is the first non-sag tungsten wire. Perth found no fewer than laid

Vertical tungsten production base, now called the United States still does not sag tungsten as "218 tungsten wire", to commemorate this major discovery Perth.

However, the first production of non-sag tungsten brittle than thorium tungsten severe that some tungsten bulb factory insist on using thorium as a filament. But with no sag tungsten production

Process of continuous development and improvement, people gradually realize that tungsten oxide is added in the same K, Si, Al compounds that can make a good tungsten filament molybdenum plates at high temperatures

Anti-sag performance, while having been satisfied after recrystallization temperature ductility. This is now commonly known as "AKS tungsten wire," or "does not sag tungsten wire" or

"Doped tungsten wire," Mir doped chan Carolina (T.Millner) in 1931, this improvement will not sag effect is called "GK effect."