Les fours de frittage pour le métallurgie des poudres et des céramiques techniques.
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Sintering furnaces are used in powder metallurgy as well as in the ceramic industry. In both cases powder grains are grown together by diffusion of material at the contact points, so that a bulk body is formed. The mergence of the crystallites happens at a temperature below the melting point of the selected materials in a sintering furnace.
Powder metallury is a technology for manufacturing bulky shaped metall parts with special material properties, which cannot be assigned by using a conventional casting processes. This method is quite often much more cost effective compared to machining the parts from bulk material. The metal powder is filled in a form and grouted. During sintering, the single grains are merged and a hard, more or less porous body with well defined dimensions is formed. Sintering is done in a sintering furnace or kiln or oven.
Koyo mesh belt sintering furnace for powder metallurgy
Quite often protective gas has to be used in order to avoid oxidation and corrosion of the metal. This is particularily important because of the large surface area of grouted metal powder, which is very sensitive to oxidation. Depending on the material, forming gas, endo gas or exo gas can be used. All gases can be generated in a gas generator, located directly beside the furnace. Alternatively, sintering under vacuum conditions can be done in a vacuum furnace, kiln, oven. These furnaces, kilns, ovens work discontinously usually.
Koyo vacuum sintering furnace (2300°C)
The first step in the manufacturing ot technical ceramic is the formation of a green body. In most cases
artificial raw material is used. The green body contains beside the ceramic powder normally also moisture and organic binders.
This green body has to be dried. Then all organic materials, which are volatile, and can be evaporated or burned have to be removed
from the ceramic green body. The last step is the firing or sintering process. In this step the ceramic body gets its mechanical strength.
For all process steps, ceramic ofens and kilns can be used.
The goal of the ceramic technology is to produce bodies with high mechanical strength. The ceramic bonding and therefore also the body strength can be reached only by firing at high temperature in a sintering oven or bottom-up kiln or vertical furnace.
Koyo sintering furnace for sintering technical ceramic
Sintering of ceramic parts can also be done in a continuous furnace. Ceramic conveyor chains, walking beam system or pusher type furnaces can be used, which can stand the necessary high temperature conditions.
Koyo continuous sintering furnace 1800°C
The firing conditions enable the sintering process and the formation of the real ceramics. The transactions during firing results in hardening and solidification of the products. Porosity is reduced and the body shrinks. Firing time and atmosphere influence these properties of the engineering ceramics. The form of the body also influences the selection of the recipe: Thin and dense parts can be fired faster than large and thick ones.
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