For isostatic pressing

Many pressure vessels used for isostatic pressing must be classified as thick walled . The literature on this subject is considerable but, unfortunately, in many countries rules for minimum requirements of design, fabrication, operation, inspection, and certification of such vessels is lacking. Design and fabrication are very much in the domain of specialists who rely to a great extent on past experience. 

When we require complex shapes, we go for isostatic pressing. In this operation, pressure is applied from all sides uniformly with the help of a fluid. Thus, the problem of density variation, which could be there in dry pressing, can be avoided. The mold here should be flexible. When the pressing is carried out at room temperature, it is called cold isostatic pressing (CIP), and when carried out at high temperatures, it is called hot isostatic pressing (HIP). 

For isostatic pressing, the powdered material is contained in a rubber envelope and the pressnre is apphed isostaticaUy by a flnid (i.e., it has the same magnitude in aU directions). More complicated shapes are possible than with nniaxial pressing however, the isostatic technique is more time consuming and expensive. 

P/MForging. Even after conventional repressing of a P/M component, it is stiU difficult to increase density above 95%. However, hiU density in a P/M part improves its properties. Hot isostatic pressing in autoclaves works weU, especiaUy for titanium and superaUoy components, but the capital equipment is expensive and production rates are slow. 

Alumina—graphite refractories, almost all continuous casting ware, have come into much greater use as continuous casting has spread in steelmaking. These refractories are used in shrouds that conduct the molten metal from the ladle to the tundish, in the subentry tubes that take the metal from the tundish to the mold, in isostatically pressed stopper rods, and in shroud tubes for slab and bloom casters. The alumina—graphite compositions are used in these products because of the thermal-shock resistance and corrosion resistance they impart to the product. 

Steel alloyed with 1% A1 is more resistant to oxidation at high temperatures. The macro- and microscopic homogeneity of the distribution of all elements is better for powder metallurgical, hot isostatically pressed steels. Combining these advantages should result in better performance of high-speed steels. 

Production of submicron powder for hot pressing or hot isostatic pressing of high-precision tooling (see Ch. 19). 

The EBRD process has been demonstrated applicable to the atomization of a variety of reactive and refractory metals and alloys in addition to Ti alloys. The process is being further developed to utilize highly contaminated raw materials and to produce high quality powders for hot isostatic pressing application without additional treatment. 

The die-and-punch method of compact imparts an anisotropic pressure to the compact. It is possible to apply pressure equally in all directions using a process called isostatic pressing, in which the powder is compacted with a fluid, such as hydraulic fluid, water, or an inert gas. Isostatic pressing is carried out using formed, flexible molds, called cans, that contain the powder and allow the pressure from the fluid to be transferred to the powder. The flexible molds are then stripped off the compact after densification. Isostatic pressing eliminates the die-wall friction inherent in die compaction and allows for consolidation of large components. However, isostatic pressing... 

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