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Tungsten, Tungsten Alloy and Molybdenum Products

Powder Metallurgey

What is Powder Metallurgy?

Powder metallurgy is a process which involves converting poder into a solid objext.powder technology is a highly developed method of manufacturing reliable ferrous and non ferrous parts.ferrous metallurgy involves the process based on iron,steel and iron alloy , while non-ferrousmetallurgy involves the process base on tungsten , tungsten alloy and other metals.powder metallurgy is continually and rapidly evolving technology embracing most metallic and alloy materials, and a wide variety of shapes.

Modern powder metallurgy is a conbination of art and science.crushing,grinding,and using chemical reactions are common ways to produce powderatomization is a technique in which the material is melted into a molten liquid and forced through a small nozzle or tube at high velocity.it makes the liquid to separate into individual droplets as it exits the nozzle or tube.the droplets are collected and allowed to harden , resulting in fine, well-proportioned powder.once the powder is produced, it is converting to components by compaction in rigid dies using various kinds of compacting process.typically the powder is placed in the flexible mold, while a machine delivers pressurized liquid or gas to the pressure mold.the pressure ranges from 15000 psi to 40000 psi.the method doesn’t require lubricants when powder is compacted.afterwrds, the object is strengthened by sintering.sintering for metallurgical bonding at a certain controled of time and temperature under protective atmosphere in sintering furnaces.imparting special properties with post sintering operations.this kind of pressing-sintering process is widely called powder metallurgy (PM).detailed see the flow chart belows.

Powder metallurgy technology is the main production process of refractory metal especially tungsten and its alloy. Powder metallurgy allows us to produce materials with melting points of well over 2000℃.The tungsten powder is mixed with the possible alloy elements and then filled into molds. The mixture is then compressed at pressures of up to 2 000 barye. The resulting conpacted workpiece (also known as a "green compact") is then sintered in special furnaces at temperatures of over 2000℃。During this process, the part acquires its density and its microstructure forms. The very special properties of tungsten materials - such as their excellent thermal stability, their hardness or their flow characteristics - are due to the use of the appropriate forming methods, for example forging, rolling or drawing. Only when all these steps finish perfectly we can achieve exacting quality demands and manufacture products of outstanding purity and quality.

Why use Powder Metallurgy?

Powder metallurgy technology is the main production process of refractory metal especially tungsten and its alloy. Powder metallurgy allows us to produce materials with melting points of well over 2000℃.The tungsten powder is mixed with the possible alloy elements and then filled into molds. The mixture is then compressed at pressures of up to 2 000 barye. The resulting conpacted workpiece (also known as a "green compact") is then sintered in special furnaces at temperatures of over 2000℃。During this process, the part acquires its density and its microstructure forms. The very special properties of tungsten materials - such as their excellent thermal stability, their hardness or their flow characteristics - are due to the use of the appropriate forming methods, for example forging, rolling or drawing. Only when all these steps finish perfectly we can achieve exacting quality demands and manufacture products of outstanding purity and quality.

Metal Injection Molding (MIM)

Metal injection molding, abbreviated as MIM, is a high-tech near net shaping process to mass-produce small metal parts with complex shape,high precision and good performance.it is a metalworking process by which finely-powdered metal is mixed with a certain amount of binder materials to comprise a feedstock capable of being handled by plastic processing equipment through a process known as injection mold forming.MIM is widely catering to variety of industries such as automotive,commercial,aerospace,cellular telephones,dental instruments,electronic heat sinks ,hermetic packages,industrial tools,fluid spray systems,hard disk drives,pharmaceutical devices,surgical instruments and sporting equipment.-greater freedom in shape design-more homogeneous micro-structure,higher density-achieve net shape features such as internal and external threads,profiled holes and finely detailed surface textures,knurling,engraving and markings.-consistent quality and high production efficiency,raw materials can be reused in mass production,costs can be largely reduced.

Near Net Shape(NNS)

Near net shape abbreviated as NNS, is an industrial manufacturing technique. The name implies that the initial production of the item is very close to the final (net) shape, reducing the need for surface finishing. Reducing traditional finishing such as machining or grinding eliminates more than two-thirds of the production costs in some industries.The process for producing near net shape metal parts is improved by sintering a compact in a reducing atmosphere where the compact contains a metal and chemically-bound oxygen in the form of a metal oxide,for example, and the chemically-bound oxygen is in an amount sufficient to improve the sintering of the compact. Improved sintering is facilitated when the metal oxide forms a metal/metal oxide eutectic during reduction of the chemically-bound oxygen in a reducing atmosphere during the sintering process. The compact can contain a metal oxide and a solution compound to produce an alloy part, provided the chemically-bound oxygen is present in an amount sufficient to improve sintering. In a preferred embodiment, the compact also contains a reinforcement compound and is sintered to make a metal matrix composite. The resultant density of the near-net shape metal parts made by the improved sintering process is preferably about 97% or more of the theoretical density.By utilizing this near-net shape approach,economization is realized by the elimination of excess material and the time and energy necessary to remove unwanted stock from mill shapes.pressed parts are then subjected to high temperature sintering in hydrogen.as the parts are slowly heated, the hydrogen reduces metal oxides present and provides a clean,active surface on each of the very small metal particles.Let’s tunneling to tungsten heavy alloy products by near-net shapes approach.the most frequently encountered shapes formed by near-net shapes are those of cylindrical rods.After sintering, the final microstructure consists of coarsened-large spherical BCC(body-centered cubic) tungsten grains dispersed in FCC(face-centered cubic) solidified matrix. The final tungsten grain size is typically about 20–60 μm in diameter. The properties of LPS(liquid-phase sintering) materials in general are degraded by prolonged final stage of sintering time. Hence, short sintering times are preferred in practice. However, the liquid-phase sintered tungsten heavy alloys are susceptible to distortion and slumming due to the large difference between tungsten and liquid matrix. Thus, understanding and controlling the microstructure evaluation in terms of composition, densification, processing like heating rate, solubility properties, and the structural rigidity are of great importance to materials engineers and scientists in the processing of tungsten heavy alloysWEISON have been manufacturing near-net shape parts made from tungsten powder and tungsten alloy materials for many years. .Hot Isostatic Pressing’s Near-Net Shape.HIP near-net shape is a new application of HIP technology.making use of the technology could one-time forming metal parts which are of complex structure and density up to 100%.Compared with traditional processing methods that are difficult to shape up for high-melting and complex structure of metallic materials.however HIP’s NNS have unique advantage to accomplish.