manufacturing process of tungsten carbide powder

Tungsten carbide powder is based on W powder obtained by carburizing.Characteristics of tungsten carbide powder (especially its size) is mainly dependant on particle size of tungsten powder and the carbonization temperature and time. Chemical control is also important, the carbon content must remain constant (weight ratio close to 6.13% of the theoretical ratio in order to pass the follow-up process). To control the powder size, you can add a small amount of vanadium and / or chromium in carburizing process before. Downstream in different technological conditions and the final processing uses the different needs of the tungsten carbide particle size, specific carbon content, combination of vanadium content and chromium content, by changing these combinations,which can produce different kinds of tungsten carbide powder.

The tungsten carbide powder and metal bonded together by mixing ground to produce a brand of hard alloy powder, can be used in various different combinations.The cobalt content of the most commonly used 3% - 25% (weight ratio), and the need to enhance the corrosion resistance of the tool case, you need to add nickel and chromium. In addition, you can also add other components of the alloy, the further improvement of the metal bond. For example, adding ruthenium in WC-Co hard alloy, can significantly improve the toughness without decreasing its hardness.Increasing the binder content but also can improve the toughness of cemented carbide, but will reduce the hardness.

Reduce the WC particle size can improve the hardness of the material, but in the sintering process, the granularity of tungsten carbide must remain unchanged. The sintering, binding and growth process of tungsten carbide particles by dissolution precipitation. In the actual sintering process, in order to form a fully dense material, metal bond to become liquid (called the liquid phase sintering). By adding other transition metal carbides, including vanadium carbide (VC) (Cr3C2), chromium carbide, titanium carbide, tantalum carbide (TiC) (TaC) and niobium carbide (NbC), long can control the speed of tungsten carbide particles. These metal carbide is usually in tungsten carbide powder and metal bonded together with mixed grinding, although vanadium carbide and chromium carbide can be formed in the carburizing of tungsten carbide powder.

Use of waste hard alloy material recycling can produce grade tungsten carbide powder. The recovery and reuse of waste hard alloy existing in cemented carbide industry for a long history, is an important part of the whole industry chain of economic, it helps to reduce the cost of materials, saving natural resources and avoid the harmless disposal of waste materials. General waste hard alloy by APT (ammonium paratungstate) process, zinc recovery process or by crushing and used again. The "regeneration" of tungsten carbide powder is usually more compact, predictable, because of its surface area than directly through the tungsten carbide powder made of tungsten. 

The smaller the carburizing process

The process parameters of tungsten carbide powder and mixed metal bonded grinding processing conditions is essential.Two kinds of grinding technology is the most commonly used milling and milling superfine. These two processes can make powder grinding evenly mixed, and can reduce the particle size. After pressing the workpiece to have enough strength to keep the workpiece the shape, and make the operator or the mechanical hand can pick up the workpiece, usually need to add an organic binder in milling. The chemical bond can affect the density and strength of pressed workpiece. In order to facilitate the operation, it is better to add a binder of high strength, but it will lead to suppress low density, and may cause lumps, defects in the final product.

Finish milling,usually by spray drying of powder, produced by the organic binder in the free flow of condensed clumps together. Through adjusting the organic binder composition, can be customized according to the needs of the mass flow and charge density. By screening out the coarser or finer particles, the particle size distribution can be further customized. And to ensure that it has good fluidity in a mold cavity.