Common production methods and characteristics of spherical tungsten powder

Common production methods and characteristics of spherical tungsten powder

Sep 03, 2023

As an important intermediate product of transition metal tungsten, tungsten powder is often used to produce tungsten products such as tungsten oxide, tungstate, tungsten carbide, tungsten rod and tungsten rod due to its strong reducibility. However, due to the different particle shapes of W powder, the physical and chemical properties and specific uses of tungsten products are also different. According to the different particle shapes, tungsten powder can be divided into spherical tungsten powder and irregular tungsten powder.
Spherical tungsten powder is often used as a high-tech material in fields such as thermal spraying, porous materials, filter materials, rocket sweating materials, and powder metallurgy industry due to its good flowability and high compaction density. What are the production methods for tungsten powder? What are their characteristics?
(1) Arc spray gun method: Using a regular DC arc welding machine as the power source, the S (3) P-3 arc spray gun is used to transmit and control the intersection of two consumable electrode tungsten wires to start arc melting, and compressed air is used to atomize to form the required product. This method has simple equipment, but unstable product quality and poor consistency, which is not conducive to industrial production.
(2) Plasma method: Tungsten powder is added to a plasma jet to melt the surface of tungsten powder particles into droplets, which contract due to surface tension to form a sphere, and then rapidly cool to obtain the product. This method has the advantages of highly concentrated plasma energy, convenient and flexible use, high heat utilization rate, low cost, high product purity and sphericity.
(3) Vapor deposition method: In 1963, researchers invented a process for obtaining large particle size (40-650) spherical tungsten powder from WF6 using vapor deposition method, but it has not yet achieved large-scale production.
(4) Tungsten powder re oxidation reduction method: Tungsten powder undergoes local oxidation at a certain temperature, oxidation time, and air atmosphere, forming a special tungsten oxide with complex composition, fine particle size, and large specific surface area; The reduction reaction will be beneficial for removing the edges and corners of the original tungsten powder. This method can still use traditional equipment, with low production costs and narrow product granularity range.
(5) Ammonium paratungstate cyclic oxidation-reduction method: Using ultrapure ammonium paratungstate as raw material, purple tungsten is obtained by calcination in an argon atmosphere. The purple tungsten is reduced in hydrogen gas with a purity of 99.99% and a dew point below -40. Then, it is oxidized in air to WO3, which is reduced in hydrogen gas to obtain the desired product. This method can produce submicron spherical tungsten powder, but the process route is long and the parameters are difficult to control, making it unsuitable for industrial production.
(6) Ammonium tungstate super stirring drying reduction method: The saturated ammonium tungstate solution is ultrasonically stirred and mixed with a dispersant. During stirring, concentrated sulfuric acid is added to produce a precipitate, which is filtered out, dried and crushed, and then reduced in a hydrogen reduction furnace to obtain the product. This method has a long process route, difficult to control process parameters, and significant waste liquid pollution.
Spherical tungsten powder is the main raw material for tungsten alloys, tungsten materials, and hard alloys; Spherical tungsten powder can be mixed with other metal powders to make tungsten alloys; Spherical tungsten powder can be processed to obtain tungsten materials such as tungsten rods, tungsten wires, and tungsten rods; Spherical tungsten powder can be made into tungsten carbide powder through carbon treatment, and tungsten carbide powder can be made into hard alloy cutting tools such as milling cutters, drill bits, molds, etc.

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