1. Raw material preparation: from tungsten ore to tungsten powder

Tungsten ore mining and beneficiation
Tungsten ore is mainly scheelite and wolframite, which are obtained through open-pit or underground mining.

Beneficiation: impurities are removed by gravity separation, flotation and other methods to obtain high-grade tungsten concentrate

Purification of tungsten concentrate
Alkali decomposition: scheelite generates soluble sodium tungstate; scheelite is sintered at high temperature to convert into sodium tungstate.

Acid neutralization: ammonium metatungstate precipitate is generated, filtered and dried.

Reduction to tungsten powder
In a tubular reduction furnace, hydrogen is used for reduction in two steps.

2. Pressing and sintering: making tungsten billets

Powder pressing
Tungsten powder is mixed with a small amount of forming agent, loaded into a steel mold, and molded into a tungsten billet with a diameter of 3~20mm by molding (pressure 50~200MPa).
Purpose: to give the billet initial strength for subsequent processing.

Sintering densification
Pre-sintering: In a hydrogen atmosphere, heat at 1000~1300℃ to remove the forming agent and form a preliminary metallurgical bond.

High-temperature sintering: In a vertical melting furnace, a large current is passed to make the billet Solid phase sintering at 1500~3000℃, atomic diffusion fills the pores, and the density can reach 85%~95% of the theoretical density.
Key: Sintering temperature and time determine the grain size and density of tungsten bars, affecting subsequent processing performance.

3. Plastic processing: from billet to filament

Tungsten's high melting point makes it impossible to form by melt casting, and it needs to be gradually refined by cold processing + annealing:

Rotary forging
The sintered tungsten bars have high hardness and low plasticity. First, a rotary forging machine is used for multiple forgings at room temperature (300~800℃) to reduce the diameter from 10~20mm to 2~5mm, while crushing coarse grains and improving plasticity.

Wire drawing (multi-pass drawing)
Lubricant: Graphite or molybdenum disulfide is commonly used to reduce friction and cool the mold.
Wire drawing die: Made of cemented carbide or diamond, the aperture is gradually reduced.
Intermediate annealing: After each drawing pass, Annealing in a hydrogen atmosphere at 600~1000℃ eliminates work hardening and restores plasticity.
Final size: can be made into fine tungsten wire with a diameter of 0.01~1mm, used in light bulbs, electronic devices, etc.

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