Material of Tungsten Heater

Due to the seventy percent of the tungsten raw material has been almost consumed, people developed a way to purify relatively poor ore. Quality of tungsten filament of tungsten heater can be affected by many factors, therefore, technicians should control and check strictly for the choice of materials and production process. For example, the production of good toughness metal powder which need to use a high purity tungsten.

In order to prevent further growth of the grains, a small amount of volatile alkali silicates, such as thorium oxide, aluminum oxide, non volatile calcium oxide would be added into the tungsten powder. After mixing, tungsten powder is pressed into the shape of the rod, then heating it at a high sintering temperature which should be controlled at 3,000 degrees Celsius. In this step, the sintering time and temperature must be controlled strictly, and it should be operated in a closed environment, so as to ensure that the finished heater performance can be better controlled.

Under the conditions of 1300 ℃, sintering rod would be forged or beat, after passing each smaller chip, the cross-sectional area of sintering rod will be reduced five percent. Thereafter, the tungsten rods would be heated by sintering carbide filament drawing die, then it would be straighten highly polished, so as to obtain the finer heating filament. Although the electrical resistivity of tungsten is not so good as other materials, in the case of 3400 ℃, high melting point of tungsten will make it be the ideal heating material. At room temperature, the change of electrical resistivity of tungsten is small, depending on their previous treatment. Although these changes are small, the tungsten also show the similar resistivity at high temperature, this feature is very important. Due to this characteristic, heater can be mass-produced in according with a uniform voltage and current levels.

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