Tungsten, or wolfram, is a chemical element with the symbol W and
atomic number 74. The name tungsten comes from the former Swedish name for the
tungstate mineral scheelite, tung sten or “heavy stone”, most
important properties for tungsten is high melting point and high density.
Meanwhile, the hardness is high and it’s quite fragile compare to other
refractory metals. All the properties make tungsten metal hard to be machined,
here we will introduce the machining process for tungsten rod, wire, and
bar.
After sintering, the tungsten blank will be
forged, to make a higher density and better mechanical properties.
Process for tungsten
rod from blank: Spin forging and drawing
several times a suitable ingot, repeated annealing is necessary during the
several times of drawing, it might be broken when drawing if not annealed. Mold
is engaged in the process in order to draw to desired diameter. Remove the
oxide surface, graphite is used as lubricant, this step will also remove it
from the surface of rod. Regular surface treatment is grinding or finish
turning, to make sure the tolerance and surface roughness in good range.
Process for tungsten
wire: Drawing from tungsten rods, many times with
annealing each time.
There are many surface treatments methods for
thin tungsten wire, please click here for more information.
Process for tungsten
rectangular bar or square bar: 1. Forging the blank to
suitable size, drawing a bit to closed size, also annealing and mold are
engaged. 2.Remove the oxide and grinding the surface. The grinding surface is
more difficult since it is need to be done face by face, normally the end face
is turning instead grinding, it the side face is too small, it will also be
turning only. The other way to produce tungsten bar is cut form tungsten plate,
next article we will talk about process for rolling tungsten products. The
method depends on the specific dimensions of tungsten bar. If it is thin and
narrow, it will be from tungsten
plate.
If the tungsten complex parts are made from bar,
and rod and other machining processes such as: laser cut, water jet cut,
drilling, turning, wire cutting, etc. will be chosen according to drawing and
process technology.
As tungsten is fragile, the process &
machine selection is very important. It might be crack in the process
seriously, or not able to reach the tolerance. The raw material and annealing
process counts a lot too.