Ammonium paratungstate (APT) is used as raw material in the production of tungsten wire. In general, ammonium paratungstate is calcined into tungsten trioxide in air at 500 ℃ or reduced to blue tungsten oxide in hydrogen at 450 ℃. To make tungsten filament of incandescent lamp, a small amount of potassium oxide, silicon oxide and aluminum oxide should be added into tungsten trioxide or blue tungsten oxide, the total amount of which is less than 1%. This is the tungsten doping process invented by buzz in 1922.
The oxide of doped tungsten is reduced to tungsten powder by hydrogen. The reduction process is generally divided into 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 metal tungsten powder at about 820 ℃. The purpose of two-step reduction is to make the mixed potassium fully play its role and control the particle size of the powder. The doped tungsten powder thus obtained is then pressed into a special mold to form a thin square bar. After the square bar is electrified in hydrogen and sintered by the method of self resistance heating (the temperature is about 3000 ℃), the density of tungsten bar after sintering can reach more than 85% of the theoretical value.
This kind of tungsten bar can be processed into a tungsten rod with a diameter of about 3mm by rotary forging, and then further processed into tungsten wires of various thicknesses by die drawing. For example, tungsten wire for 220V, 15W incandescent lamp
When the diameter of tungsten wire reaches micrometer, it is difficult to measure its diameter accurately with the conventional caliper. Therefore, in the world, the tungsten filament with diameter less than 0.2mm is usually used to express the thickness of the filament by the weight of the 200 mm filament section. For example, the diameter of the above-mentioned 15 W incandescent lamp tungsten filament can be expressed by 0.679 mg / 200 mm.
Characteristics and application:
Wb001: good winding performance, no sagging, suitable for general incandescent lamp, double helix or triple helix fluorescent lamp, holiday lamp, bracket wire, etc.
Wb150: good high temperature resistance, excellent processing performance, suitable for halogen lamp, double helix incandescent lamp, etc.
WB584: high recrystallization temperature, high temperature anti sag performance, suitable for shock resistant filament, high color temperature filament and other special lamps.
