Tungstic acid is obtained by wet chemical methods from the flotation concentrate. Starting materials for the production of metallic tungsten powder are:
Ammonium paratungstate
Tungstic acid
Tungsten trioxide and
Tungsten blue oxide
These materials are reduced to tungsten powder in hydrogen at a temperature around 1000℃.
Following screening and homogenizing, the tungsten powder is pressed into rods, plates and shapes of different geometry and dimensions by conventional or isostatic pressing. The pressed compacts are then sintered in high purity hydrogen at temperatures of about 2500℃.
By forging, swaging or rolling at temperatures of 1500-1600℃, the sintered tungsten bars and blocks are heavily worked. With increasing degree of deformation, the working temperatures can be lowered. Forgings, rods, sheets of different thicknesses, ribbons, foils and wires are made in this manner.