What is the Basic Principle of Tungsten Smelting?

Tungsten exists mainly as tungsten ore-disulfide, and the most important ores of WS2 are tungstates, such as scheelite (calcium tungstate, CaWO4), rhodochrosite (lead tungstate, PbWO4) and a mixture of wolframite (ferrous tungstate, FeWO4) and manganese tungstate (MnWO4) or both. The tungsten ore is concentrated by magnetic and mechanical processes, and then the concentrate is fused with alkali. The crude melt is leached with water to obtain a sodium tungstate solution, from which aqueous tungsten trioxide is precipitated after acidification, and the oxide is then dried and reduced to metal with hydrogen.