In 1907, a tungsten alloy with low nickel content came out. It was prepared by mechanical processing, but its severe brittleness prevented its application. Until 1909, W·D·Coolidge of General Electric Company of the United States produced tungsten billets through powder metallurgy, and then used mechanical processing to produce tungsten wires that are ductile at room temperature, thus establishing the tungsten wire processing industry. The foundation also laid the foundation of powder metallurgy.
However, this "ductile" tungsten alloy exhibits obvious brittleness after the bulb is ignited. In 1913, Pintsch invented the thorium tungsten wire (ThO2 content of 1% to 2%), which greatly reduced the brittleness of the incandescent filament. At first, the sagging of the filament was not a problem, because the filament was straight at this time, but after 1913, Langmuir changed the straight filament to the spiral filament. This way, when the bulb is used, the working temperature and dead weight are high. The effect of sag makes the filament droop, so pure tungsten and thorium tungsten are difficult to meet the requirements of use.
In order to solve the problems of tungsten wire sagging and short life span, in 1917, A. Pacz invented a tungsten alloy that was "undeformable" at high temperatures. At first, he used a refractory crucible to bake WO3 when preparing pure tungsten. He accidentally discovered that the tungsten wire spiral made from tungsten powder obtained by reduction of this WO3 was unusually mysterious and no longer sag after being recrystallized. Subsequently, after 218 repeated experiments, he finally found that the tungsten wire made by adding potassium and sodium silicate to tungstic acid (WO3·H2O) after reduction, pressing, sintering, and processing, recrystallized to form equivalent The coarse grain structure is neither soft nor sag resistant. This is the earliest tungsten wire that does not sag. Perth’s discovery laid the foundation for the production of non-sagging tungsten wires until the United States still called non-sagging tungsten wires "218 tungsten wires" to commemorate this major discovery of Perth.