Powder metallurgy is a branch of metallurgy, which include: ① Preparation of metal powders; ② metal powder or metal powder and non-metallic powder mixtures, and the forming and sintering of metal and metal - non-metallic materials and products . Manufacture and use of metal powder, experienced a very long time. Early mechanical crushing method with the gold, silver, copper and bronze powder, pottery and other utensils used for more decorative coatings. Half of the 18th century and l19 half of the century, Russia, Britain, Spain and other countries once the scale of the system to take a sponge factory platinum particles, after pressing, forging and pressing, sintering process manufacturing coins and valuable artifacts. 1909 U.S. Kuli Ji invented a method of manufacturing powder metallurgy tungsten filament light bulb, laid the foundation of modern powder metallurgy. After 20 years, powder metallurgy method of manufacturing the tungsten, molybdenum products, hard alloy, bronze oil-bearing, porous filters, set of brushes, etc., and gradually formed a set of powder metallurgy technology. 30 years of iron and carbon vortex grinding iron powder came after the use of powder metallurgy iron-based mechanical parts get developed rapidly. After World War II, the rapid development of powder metallurgy technology, new production processes and technical equipment, new materials and products continue to emerge, opening up some areas of special materials to manufacture to become an important component of modern industrial part.
In the production of powder metallurgy materials, iron-based materials in production on the majority, followed by copper-based materials, carbide, and refractory metals. The past 20 years, the high-performance alloy steel, aluminum and titanium-based powder metallurgy material development very seriously. The basic process includes powder extraction, forming and sintering. Powder Preparation methods can be summarized as mechanical and physical-chemical methods into two categories. Specific methods include mechanical crushing method, reduction, atomization, electrolysis, manganese powder vapor deposition, liquid deposition, reduction - of the legal and so on. One widely used method is the reduction, spray method and electrolytic method (see iron). Commonly used in compression molding technology has become increasingly mechanized automation; hot forming (including hot pressing, hot isostatic pressing, hot extrusion, hot forging, spark sintering, etc.) is to suppress the sintering process and the merger, the density of the material and performance were significantly increased (see powder forming). Sintered powder particles at high temperature the migration of substances between the complex process, which resulted in metal particles with the body to strengthen and further sintering densification. Sintered into solid and liquid phase sintering sintering (see powder metallurgy sintering). After sintering or hot forming materials and products as required blanks can be a variety of cold deformation processing, thermoplastic processing, machining and heat treatment.
Powder before forming often require pretreatment, pretreatment including grading, removal of impurities, annealing, ingredients (adding his kind of metal powder or non-metallic powder and additives), mixing and so on. Raw material powder metallurgy materials performance impact on the performance of very large, so from the quality and economic considerations, should attach importance to the choice of raw material powder and powder pretreatment.
Technical and economic characteristics ① production casting methods can not or difficult to produce a special performance and high-performance materials. For example, porous materials is the use of conscious control and porous properties of powder metallurgy products; false alloys, metallic and non-metallic composite materials, refractory metals and metal compounds, composites, powder and fiber composite materials is the use of powder metallurgy and flexible batching process ( See porous materials, friction materials, friction materials, electrical materials, powder metallurgy magnetic materials, powder metallurgy powder dispersion strengthened alloys of refractory metal materials, cemented carbide, cermet); powder metallurgy alloy and powder metallurgy superalloy is atomized powder without the use of macro-segregation and the cast and the second phase fine uniform grain characteristics. ② metal loss is small. The raw material powder can be made directly to the final finished or near finished shape and size of products, boron powder which require little or no machining; process is short, less investment in equipment. It is suitable for mass production of low to medium load to withstand the mechanical parts.
With the development of powder metallurgy technology, to clarify the process of powder pressing and sintering process, the basic laws of nature and theoretical research progress. Powder metallurgy is to explore the theory of repression to suppress the process of particle movement and deformation of the law, describe the density of compacts and the suppression of the relationship between pressure. Theory of sintered powder metallurgy sintering process of mass transfer and pore variation mechanism, described in the sintered density and sintering parameters relationship. In addition, the powder metallurgy technology, metal powder supplier driven by a series of test technologies associated with it, mainly powder physical and chemical properties of the determination of pore size, quantity and form of measurement, the porous body (including the near-dense The sintered body) physical and mechanical properties of the measurement and so on. 70 years, powder metallurgy has been basically formed a well-established theory, but also technology, testing methods, and many special field of science and technology equipment. Source:http://www.mhcmp.com