SYLVANIA Tungsten Wire is available in selected combinations of three types and thirteen process variations in diameters from 0.3 to 65 mils (0.008 to 1.65 mm) either on returnable containers or as self-coils, depending on the diameter.  
 
Generally, tungsten wire is made from doped powders, that is, powders in which small quantities of potassium, silicon, and aluminum have been incorporated.  Their purpose is to influence the recrystallized grain structure to reduce the creep rate at the high temperatures of incandescent filaments.  The powders are consolidated under high pressure, sintered at high temperatures and worked by rolling and swaging to heavy rod suitable for drawing.

Tungsten wire drawing is accomplished by coating the wire with a graphite lubricant, heating to a red heat, and then drawing through tungsten carbide or diamond dies.  The process is sometimes referred to as hot cold-working, which means that, while the wire is hot, the temperature is still below the recrystallization range.  Accordingly, as the cross-sectional area is reduced, strength and ductility increase.  The as-drawn wire at finished size subsequently may be cleaned, straightened, or annealed.  Through various drawing methods and annealing steps, SYLVANIA produces different physical characteristics in wire of a given size.  Our control of each manufacturing step from tungsten ore to finished wire assures reliability and reproducibility.

SYLVANIA is a leading manufacturer of tungsten wire used in a broad range of applications in the lamp, electronic-tube, photocopy, computer, vacuum-metallizing, and electric-furnace industries, and in the making of fiber-reinforced materials. 

Wire types can be divided into two groups based on diameter:

Group I – Available in Ultrafine Through Heavy Sizes (<0.020”)

NS / HG 
AKS-doped high-purity nonsag tungsten suitable for coiled filaments and supports in all incandescent, infrared, and high-temperature halogen lamps.  Also used for electronic tube and heater applications as well as electric-furnace elements.  It is available in the broadest range of standard process for the widest variety of applications.

3RW
Wire containing 3.25% rhenium.  This raises the recrystallization temperature, inhibiting recrystallization during use.  Wire remains ductile, making it appropriate for lamps subject to shock or vibration, such as sign lamps.

1TH
Wire containing 1% thoria.  Its principal use is for power-tube filaments and for some types of incandescent lamps for vibration service.

Group II – Available at and above 0.51mm (0.020”)

PW 
Undoped high purity wire for lamp coils in which sag is not important, as in supported coils.  The recrystallization temperature is lower than that of NS, and it is less resistant to sag at high temperatures.

VM
Wire furnished in either stranded or single-wire form for vacuum metallizing.  The wire should also be specified for other applications requiring maximum ductility, but less-critical nonsag characteristics.

2TH
Wire containing 2% thoria for applications requiring high electron emission, such as for arc lamp electrode and power tubes.