Pressing cold hydrostatic

Because of the low-melting-point tin alloy, the extrusion must be carried out such that the billet is never allowed to heat above about 230°C. At such low temperatures, hydrostatic extrusion has a significant advantage because of its lower extrusion pressures, compared with conventional extrusion. Reduction of the billet cannot be carried out economically with the low reduction ratios associated with cold conventional extrusion. Although hydrostatic extrusion is not commercially practiced on large (20 to 25 cm in diameter) billets in the United States, the adaptation of commercial-sized conventional presses for hydrostatic extrusion of superconducting composites is a practical possibility. 

Cold Isostatic Pressing. In isostatic pressing, the powder is filled into flexible molds made of rubber or elastomers and subjected to hydrostatic pressure. The pressure is commonly in the range of 200 to 400 MPa. As a result of the uniform pressure, a much higher uniformity in density is achieved. Isostatic pressing has gained much... 

There are many variations on using the cold isostatic press (CIP) here we just emphasize some basic themes. Figure 23.3 illustrates the so-called wet-bag CIP process. Powder is weighed into a rubber bag and a metal mandrel is inserted that makes a seal with the mouth of the rubber bag. The sealed bag is placed inside a high-pressure chamber that is filled with a fluid (normally a soluble oil/ water mixture) and is hydrostatically pressed. The pressures used can vary from about 20 MPa up to IGPa depending upon the press and the application. For production units the pressure is usually <400 MPa. Once pressing is complete, the pressure is released slowly, the mold is removed from the pressure chamber, and the pressed component is removed from the mold. 

---