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. 