Technology of powder metallurgy parts near net shape powder metallurgy workers has long been one focus of the study subjects. Over the past decade, the study of new technology, new technology after another. These new technologies, the emergence of new technology to solve the short-flow low-cost powder metallurgy materials forming problems, greatly contributed to the rapid development of powder metallurgy parts. Currently, powder metallurgy parts manufacturing technology development is to increase density, reduce costs and complexity of high-precision near net shape parts mouth.
In 2000, Germany’s Fraunhofer Institute has developed one of these are known as the flow temperature and pressure of the short process of low-cost near-net shape technology. The temperature and pressure process technology-based and combines the advantages of metal injection molding technology. By improving the mobility of mixed powders, filling ability and formability, can 😯 ~ 130 , in the traditional press on the precision forming of parts with complex geometries, such as the vertical direction with a groove with the suppression of the hole and threaded hole and other parts. 2 without the need for subsequent machining. Flow temperature and pressure forming technology not only to overcome the traditional powder metallurgy forming a complex geometry in the gaps, but also avoid the high cost of metal injection molding technology is a great potential of new technology, has a very broad application prospects.
Flow temperature and pressure forming a new type of powder metallurgy parts, as near net shape technology, its main features can be summarized as follows: 1) forming parts with complex geometry flow using temperature and pressure can be directly formed with grooves perpendicular to the direction of repression, holes and screw holes and other parts, while the use of the shape of the cold manufacture of such parts is very difficult or even impossible, manganese powder the general need to complete the subsequent machining, CNC press to realize that the use of complex and precise movements , can only produce a relatively simple type of parts. Fraunhofer researchers used a special mold, the T-hole, hole, L-shaped cavity mold hole has been studied and successfully prepared a T-shaped parts. The results show that the well-mixed powder flow is sufficient to avoid cracks in the corner. Fraunhofer researchers have also used the shape with a slight taper to successfully direct the punch forming a deep blind hole parts, blind holes and wall thickness of the high rate of up to 3 to 7, the changes in wall thickness in the range of 1 ~ 3mm . Flow temperature and pressure can also be precision ground forming threaded holes. With the external thread of the bolt with a core mold after compaction, it will tighten the bolt out from the semi-finished products, and then sintering can be obtained thread. According to shrinkage by selecting the appropriate core diameter of the bolt thread can be suppressed without the required 2 machining.
2) The compacts of high density, density, temperature and pressure than the uniform flow of powder loading density as high, so after the semi-finished products by the temperature and pressure can reach very high density values. In addition to density, the powder flowability as well, forming parts and more uniform density. Or use a simple model red (no auxiliary floating red multi-axis model) can be multi-step forming of powder metallurgy parts.
3) the adaptability of materials Fraunhofer researchers conducted a variety of metal powder flow of warm compaction studies, have made a more significant results, including low alloy steel powder (Distolay AE), stainless steel 316L powder, silicon powder pure Ti powder and WC-Co hard metal powder. Flow temperature and pressure process in principle applicable to all the powder system, the only requirement is that the powder sintering must be good enough to eventually reach the required density and performance.
4) to simplify the process, reducing costs forming parts using conventional powder metallurgy method to suppress in the direction perpendicular to the grooves, cross holes and other shape, need to design very complex molds or 2 times after sintering machining to complete. Although injection molding technology in the shape of forming part of the complex and almost without any restrictions. However, due to large number of added binder, nickel powder in the heating process in part because of the influence of gravity to deform. Therefore, it often requires an additional more complicated and more expensive binder removal process, making the injection molding of high cost than conventional powder metallurgy technology, so the injection molding of parts may not be able to meet its design features to replace the conventional powder metallurgy parts to the application of injection molding technology has been somewhat restricted.
The flow temperature and pressure forming technology, either directly without the need for complex geometries 2 subsequent machining; the other hand, the flow temperature and pressure forming process, the use of a special binder and lubricant content is moderate, the configuration of the hybrid powder has a high viscosity and critical shear strength, the heating process does not occur in the deformation, which can be directly removed during sintering binder. Thus, the traditional powder forming process and injection molding process compared to current techniques for temperature and pressure forming of complex geometry parts, the only simplifies the production process, but also significantly reduces manufacturing costs.
