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Conventional Process For Tungsten Wire Production

2024-01-05 18:00:06

Most tungsten wire production USES ammonium paratungstate (APT) as raw material. The general process is to roast ammonium paratungstate in air at about 500℃

tungsten wire manufacture

Tungsten trioxide, or slightly reduced to blue tungsten oxide in hydrogen gas at about 450 ° c. To make an incandescent filament, tungsten needs to be mixed with a small amount of potassium oxide, silicon oxide and alumina in either tungsten trioxide or blue tungsten oxide, all of which add up to less than 1%. This is the tungsten doping process that bartz invented in 1922. The doped tungsten oxide is reduced to metallic tungsten powder by hydrogen gas. The reduction process is generally carried out in two steps: the first step is to reduce to tungsten dioxide (brown tungsten oxide) at about 630℃, and the second step is to reduce to metallic tungsten powder at about 820℃. The purpose of the two-step reduction is to make full use of the added potassium and control the powder size. The obtained doped tungsten powder is then pressed into a special mould to make a thin square strip. After the square bar is electrified in hydrogen gas and sintered by self-resistance heating (the temperature reaches about 3000℃), the density of the sintered tungsten bar can reach more than 85% of the theoretical value. This tungsten bar can be processed into a tungsten rod with a diameter of about 3mm by rotary forging, and then it can be further processed into tungsten wires of various thicknesses by die drawing. For example, the diameter of tungsten filament used in 220V and 15W incandescent lamps is about 15µ. M, and the 10000W bromotungsten lamp used tungsten filament diameter of about 1.25mm. The diameter of the thinner tungsten filament such as 220V and 10W incandescent lamp tungsten filament is about 12µ. M should be made by electrolytic corrosion.


When the diameter of tungsten filament reaches the micron scale, it is difficult to accurately measure its diameter with conventional calipers. Therefore, internationally, the diameter of tungsten filament below 0.2mm is usually expressed by the weight of its cutting length of 200mm filament segment. For example, the diameter of the tungsten filament of 15W incandescent lamp can be expressed by 0.679mg/200mm.


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