Non-sag Tungsten Wire Production Process

Non-sag tungsten wire is added strengthening elements (such as, potassium, silicon) to increase its resistance to high temperature creep properties.
Non-sag tungsten wire production process includes several major processes: doping, reduction, profiling, sintering, annealing, and stretching.
Use ammonium paratungstate (APT) as raw material. Generally the process is: sintering APT into tungsten trioxide at a temperature of 500 ℃ around in the air, or make a slight reduction to blue tungsten oxide in hydrogen at 450 ℃ around. The production of incandescent wire of tungsten wire needs to dope a small amount of potassium oxide, silica and alumina into tungsten trioxide or blue tungsten oxide, and the total amount of the three is less than 1%, the tungsten doping process, which is invented by Baez in 1922. After reduction process, the doped tungsten oxide will reduce to tungsten powder with hydrogen. Reduction process is generally carried out in two steps: the first step is reduced to tungsten oxide at about 630 ℃, the second step is in the reduction of a metal tungsten powder at about 820 ℃. The purpose is to make a two-step reduction of potassium incorporated into fully play the role and control of particle size. Such doped tungsten powder and then get compressed into an elongated square bars in a special mold. The square bars in hydrogen powered, with self-resistance heating (at temperature of about 3000 ℃) method sintered, tungsten sintered density can reach more than 85% of the theoretical value. Using the method of swaging, this tungsten can be processed into tungsten rod,whose diameter is about 3mm. Then further procession is drawing with a mold into a variety of different thickness of the tungsten wire.

 

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