Sintered mechanical parts
Sintering
Sintering is the production phase during which the component acquires the mechanical characteristics required by its intended use. Briefly, this process consists of raising the temperature of the component to a level just below its melting point such that the various elements combine to form a single alloy.
More precisely, this environment encourages the spread of atoms between several grains of the compound thus creating a continuous crystalline structure.
This condition, with the increase in grain size and even distribution of porosity, is consequencial upon the increased temperature.
The other contributing factor is atmosphere which affects the catalytic disassociation of ammonia, or catalytic combustion in oxygen free light hydrocarbon (methane ethane propane).
In the first case, the atmosphere is composed of 75% hydrogen (reducing element) and 25% nitrogen (inert).
This is recommended in particular for the sintering of stainless steel due to the excellent reducing ability of hydrogen and the cleanliness of the process.
In the second case, the composition is carbon monoxide (derived element), water (emitted as condensation), carbon dioxide (low level by-product) and nitrogen (as air).
This type of atmosphere (called endogas) has an inferior reducing ability compared with the previous one and to sinter carbon steels it has to be "diluted” with nitrogen in order to balance its increased carburizing power with the carbon in the material.
The main advantage of endogas is the low operating costs. Other atmospheres used are variations between the two described compositions.
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