January 21, 2022

Machining processes of tungsten Ⅱ

Tungsten, or wolfram, is a chemical element with the symbol W and atomic number 74. The most important properties of tungsten are high melting point and high density. Meanwhile, the hardness is high and its ductility is poor to other refractory metals. All the properties make tungsten metal hard to be machined, here we will introduce the machining process for tungsten tube & crucible, Plate, Sheet & Foil. 
As tungsten’s relatively poor machability, 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. 

Tungsten crucible

After sintering, the tungsten blank will be forged, to make a higher density and better mechanical properties. 

Process of tungsten plate: Thicker plate or block is forged from ingot, and ground to tight tolerance. Thinner plate or sheet are made by hot rolling process, annealing if carried between each rolling. Annealing is to make the material stress relieved, or it might be crack in the next rolling process. The selection of roller, annealing time & temper is very important, they affect the internal gain distribution, the mechanical properties of the final plates and sheets.

For the thinner sheets & foil, they are rolled from thick sheets. When down to a certain thickness, let’s say 1mm, the hot rolling process will be changed to cold rolling. It still needs to be annealed even for cold tolling.

Process of tungsten tube: Small tubes (roughly with diameter <100mm) are drilled from rods, larger tubes is made by sintering directly. Will need to make mold first if the tubes are large, you can choose a more economical way to make the tube with a critical outer diameter. Drilling from rods will waste some materials, while sintering needs a tool.

The process of tungsten crucible is similar to tungsten tube, small ones from drilling and larger ones from sintering.

Another way to make tube & crucible is welding, riveting. This is used for parts work short time and has not strictly required for leaking issues, this kind of tubes and crucibles are cheaper.

Edgetech Industries LLC provides high-precision tungsten products.

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