TUNGSTEN METAL POWDER PRODUCTION-PUSH-TYPE FURNACE-2

The furnaces are either gas fired or electrically heated in three or four separate zones. Furnace temperatures range between 600 and 1100℃. For smaller and medium W grain sizes, a temperature profile is preferred in order to decrease the time necessary for the last reduction step from WO₂ to W (slow reduction, rate). For larger grain sizes (>6 µm), isothermal reduction conditions are applied.

The reduction is commonly carried out in one stage. Alternatively, a two-stage reduction sequence can be applied instead. In this case, the first reduction stage takes place at lower temperature (500-700℃; formation of brown oxide, WO2) and the second stage at 600-1100℃ (formation of tungsten metal).