The wire drawing blank can be produced by rotary forging or rolling. The billet produced by the rolling method has a large deformation and a more uniform structure, which is conducive to subsequent processing. The tungsten wire is drawn from the tungsten wire blank using the "warm wire drawing" method. First, it is pulled to a diameter of 1.3 mm on a chain stretching machine, and then the diameter is 0.2, 0.06, and less than 0.06 mm by rough drawing, middle drawing and fine drawing respectively. As the diameter decreases, the heating temperature should be reduced and the drawing speed should be increased. The deformation of the pass is generally between 10 and 20%.
The wire drawing adopts gas-air mixing heating, and the temperature is 900～400℃. The thick wire uses a cemented carbide die, and the thin wire uses a diamond die. The mold material, hole shape, and grinding technology have a great influence on the quality of the wire. The quality, particle size, proportion, and coating method of the graphite lubricant also affect the quality of the wire.
The non-uniformity of the wire diameter is one of the most important reasons for wire breakage during use. A deviation of 0.2 to 0.4 microns will greatly reduce the life of the tungsten wire in the vacuum tube. The diameter of the filament can be measured by the gravimetric method or the vacuum standard current method. In the wire drawing process, as the diameter decreases, the deformation resistance increases (for example, the breaking strength of a tungsten wire with a diameter of 0.1 to 0.3 mm can be as high as 350kg·N/mm2), and its plasticity also decreases accordingly. In order to improve the reprocessing performance, it is generally necessary to perform stress relief intermediate annealing. In addition, electrolytic corrosion can be used to process the wire into a thin wire with a diameter of less than 0.01 mm.