Tungstate Reduction Method

The preparation of tungsten powder using ammonium paratungstate (APT) is the most commonly used method in industry. APT is first calcined into tungsten oxide (yellow tungsten or blue tungsten) under a weak reducing atmosphere, and then reduced to tungsten powder using hydrogen. Wang Yaxiong et al. studied a new one-step process for preparing tungsten powder using ammonium paratungstate as a raw material. The first stage of this process involves the reduction of APT to prepare a blue tungsten intermediate. A certain amount of APT is weighed and purged with nitrogen for 20 minutes in a hydrogen reduction furnace, while a certain proportion of hydrogen and nitrogen mixture is simultaneously introduced to maintain a weak reducing atmosphere within the furnace. Once the temperature reaches a set value, it is held at this temperature to remove moisture and ammonia. The temperature is then increased at a controlled rate to the predetermined hydrogen reduction temperature.

The second stage of hydrogen reduction, using hydrogen, yields tungsten powder. Compared to the traditional two-step reduction method, the tungsten powder prepared by the one-step reduction method using APT has essentially the same grain size, which is controllable, and the product meets the quality requirements of existing market products. Its technological feature is that it combines the calcination of raw material powder and the hydrogen reduction of tungsten oxide into one process, reducing intermediate steps and improving production efficiency.