Tungsten Copper Powder CIP Process

Compared with HIP (Hot Isostatic Pressing) process, CIP (Cold Isostatic Pressing) is a kind of molding process that commonly all directions sealed in plastic mold material simultaneously even pressure at room temperature, and more for powdered metal or non-metallic materials, molding, which provides a pre-sintered compacts for sintering. Tungsten copper is a kind of psudoalloy consists of W and Cu mutually soluble and has a great difference in physical and chemical properties. So it is difficult to prepare by conventional methods, which must be prepared by PM (Powder Metallurgy) process. According to different pressure transmission fluid, including cold isostatic wet bag method and the dry bag method isostatic pressing and soft mode.

Since the conventional molding method between the powder and the powder, powder and punch and die wall there is a certain friction, so that during the pressing force distribution and transmission of certain changes occur, and also resulted in various parts of the compact density and intensity distribution uneven; by comparison, CIP has more uniform forming pressure, which can ensure under lower pressures have pressed leather uniform density and integrity of shape and small loss of mold, high molding efficiency.

In addition, it should be noticed that pressing speed controlling is also a significant factor of the blank density during CIP process. It not only affects the state of friction and work hardening powder particles, but also affects the case of gas escaping. If the compression speed is too fast, the gas can not escape easily, which left in the blanks in the relatively more in the subsequent sintering process are correspondingly difficult to eliminate left voids or pores. Furthermore, pressing too fast will make the inside of the powder aggregate greater stress, resulting in relief the compacts elastic aftereffect. Therefore, in the process of compacting, reduce the speed and extend the dwell time appropriately can ensure that pressure transmission fully, air between powders have sufficient time to escape and be beneficial for density distribution.