And just to add on Lawrence's statement regarding "Powder Metallurgy..."
Here's an explanation in more detail to help one understand one of the many different processes used in powder metallurgy...
While tungsten has the highest melting point of any metal, its powdery oxide form becomes volatile at 580 degrees Celsius. This allows mills to alloy it with the oxides of thorium, molybdenum or rhenium as well as the newer oxides such as cerium & lanthanum and other oxides for different uses besides the manufacturing of non-consumable electrodes through a process known as
"sintering and pressing, otherwise known sometimes as densification."
First, the oxide powders are mixed together in a rectangular crucible and placed inside a sealed chamber filled only with hydrogen gas. Next, a hydraulic press compacts the powder while the crucible heats the mixture to 1800 degrees Celsius. After a few hours, the powder transforms into a solid metal block called an "ingot." In many cases, the crucible (and hence the ingot) will be shaped like the electrode, resulting in a finished product. Otherwise, the ingot is removed to another part of the factory where it is ground into its final shape with the help of a powerful laser or tungsten-carbide grinder.
Respectfully,
Henry