Tungsten Wire for Halogen Lamp Filaments

Tungsten halogen lamps are highly efficient light sources that utilize tungsten as the filament. The reason for choosing tungsten as the filament is closely related to its unique physical and chemical properties.

I. Characteristics of Tungsten wire

Tungsten has a high melting point, reaching 3410°C, making it one of the highest melting points found in nature. This allows the tungsten wire to remain stable in the high-temperature operating environment of tungsten halogen lamps (approximately 2500-3000°C), resisting melting or deformation. Furthermore, tungsten has excellent thermal and electrical conductivity, effectively converting electrical energy into heat and light. Its high strength and creep resistance ensure that the filament is less susceptible to sagging or breakage under long-term high-temperature operation. Tungsten's relatively low evaporation rate at high temperatures extends the life of the filament.

II. Working Principle of a Tungsten Halogen Lamp

A tungsten halogen lamp uses a small amount of halogen gas (such as iodine or bromine) to fill the bulb, creating a "halogen-tungsten cycle." At high temperatures, tungsten atoms evaporate from the tungsten wire surface and combine with the halogen to form a tungsten halide compound. This compound decomposes in a cooler area (such as the bulb wall), releasing tungsten atoms that are deposited back onto the filament, slowing filament wear and extending the life of the bulb. The high melting point and low evaporation rate of the tungsten wire are key to achieving this cycle, ensuring the filament can emit stable light even at high temperatures.

III. Tungsten wire Manufacturing Process

The preparation of tungsten wire requires a complex process. First, high-purity tungsten powder is extracted from tungsten ore. Tungsten rods are formed through pressing and sintering, and then fine tungsten wires are drawn. The tungsten wires undergo annealing to increase ductility and strength, and are finally wound into a spiral or double-helix structure suitable for tungsten halogen lamps. Impurity levels must be strictly controlled during the manufacturing process to ensure stable filament performance.

IV. Advantages of Tungsten wire in Tungsten Halogen Lamps

The high luminous efficiency of tungsten wires has led to their widespread use in lighting and projection equipment. Compared with traditional incandescent lamps, tungsten halogen lamps have a longer lifespan, higher luminous efficiency, and light color that is closer to natural light and has good color rendering due to the high temperature resistance of the tungsten wire and the halogen cycle mechanism.

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