Four Factors that influence the preparation of tungsten powder by tungstic acid


Reduction temperature, temperature rise rate, hydrogen flow and humidity, raw material load and reduction time will all influence the preparation of tungsten powders by tungstic acid.

Influence of reduction temperature and temperature rise rate

In the process of obtaining tungstic acid, the raw material that used in the preparation of tungsten metal powders, the migration rate of gas phase will directly influence the reaction speed and the appearance of end products as the hydrogen reduction of tungstic acid is a kind of gas-solid multiphase reaction. When the reduction temperature becomes high, the reaction speed becomes fast and the gas phase migration becomes fierce, the powders will be sintered and recrystallized, which can promote the powder agglomeration and coarsening of tungsten powder particles. On the contrary, the ultrafine tungsten carbide powder can be made when gas migration is smooth and steady and the vapor that is generated in the reaction is easy to spread and overflow. Besides, under different temperature, tungsten powders that have different particle size can be produced so as to meet the requirements of industry.

tungsten powder and tungstic acid

Influence of hydrogen flow and humidity

When the hydrogen flow is higher, the reaction will be carried out more smoothly as the moisture will be removed rapidly and the reduction will be carried out more thoroughly, which will be beneficial for nucleation, thus the powders that have excellent particles can be generated. Vapor can be regarded as the basic condition of reduction reaction gas phase migration, besides, the hydrogen humidity will also have important effect on the reduction reaction.

Influence of raw material load

Raw material load will also influence the particle size of reduced tungsten powders. The material layer will become thicker when the raw material load becomes bigger. The material thickness is the key to determine whether the powder can be reduced thoroughly or not. When the material layer is too thick, the powders in the bottom layer cannot be reduced thoroughly, which can influence the quality of tungsten powder after reduction process. Therefore, the raw material load should be controlled strictly at the time of loading.

Influence of reduction time

The reduction time can mainly influence the particle size of tungsten powder and oxygen content. Powders cannot be reduced thoroughly when the reduction time is too short; while the grain will be easy to largen when the oxygen content is too high and the reduction time is too long, which can also waste energy at the same time. As a result, the reduction time should be controlled strictly.