Tungsten Copper Powder CIP Process

Except HIP (Hot Isostatic Pressing), there is a kind of CIP (Cold Isostatic Pressing) correspondly. It generally to press the sealed materials in plastic mold from each direction at room temperature simultaneously, which used more for powdered metal or non-metallic materials, molding, providing a pre-sintered compacts for following sintering. Tungsten copper alloy is composed of two mutually soluble Cu and W, which has a great difference in physical and chemical properties, called pseudo alloy. So it is difficult to manufactured by conventional method, must be fabricated by powder metallurgy (PM). 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 uneven distribution; by comparison, CIP has more uniform molding pressure, which can ensure the compacts have uniform density and net shape, low consumption of mold and high molding efficiency under low molding pressure.

In addition, it is important that the controlling of pressing rate in CIP process, and can directly affect the density of the density of compact. It not only has an effect on state friction and work hardening of powder particles, but also has an effect on gas escaping. If the compression speed is too fast, not easy to escape the gas, the gas left in the blanks in the relatively more in the subsequent sintering process are correspondingly difficult to eliminate left voids or pores. What’s more, pressing too fast will make the inside of the powder aggregate greater stress, resulting in relief after the compacts elastic aftereffect. Therefore, reduce the speed of pressing pressure and extend the dwell time appropriately can delivery the pressure completely and have sufficient time for air escaping, which is also beneficial for density distribution and avoiding the elastic after-effect.

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