Metal Sintering Process ...Powder Metal Forming
The fabrication of metal shapes from small particles of metal by sintering is an old
technology of over 1000 years.   The sintering of metal and ceramics on a large
scale is however a much more recent development. Sintering is mainly used for cermets i.e components made for a combination
of metal and ceramics
Sintering has a number of advantages.
The sintering process results in brittle components which often require further heat treatment before use. The tooling costs are relatively high and so large batch quantities are required for economic production runs compared to other processes.Production of Powders
The powder production methods are by either chemical or mechanical processes.
Three main methods are using for production of the sintered shapes from the powders
When highly porous components are required, they can be produced by loose sintering.
The powder is poured or vibrated into a mould, which is heated to the sintering temperature.
The sintered parts shrink on cooling and shapes are only processed which can be removed
from the mould on completion of the process.
The powder is formed into the required shape by mechanical or hydraulic pressure. The pressures
are fairly low from about 80 N. mm-2 for soft copper based alloys to 80N.mm-2 for steels.
The pressures used are sufficient to produce cold welding of the powder granules. The process
imparts sufficient strength to hold the powder together allowing the parts to be handled for the
This process involve heating the powder to a temperature above the recrystallisation temperature of the metal during the pressing process. The resulting components have a high density and accurate dimensions. The process is best completed in a reducing atmosphere or a vacuum to eliminate the risk of oxidisation of the metal. If the temperature needed is below 1000 o C then metal dies can be used otherwise graphite or ceramic materials should be used. The hot pressing process is normally carried out a pressures below 30 N mm-2Sintering Systems
Prior to sintering the components they are heated to a temperature sufficient to evaporate
any volatile components.
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