Sintering Furnaces

Vacuum Furnace Challenges

There is a fundamental problem which makes design and manufacture of a furnace designed to operate under vacuum substantially more difficult compared to a furnace designed to operate at atmospheric pressure in air or other gas atmospheres. This problem is the crushing force created by atmospheric air molecules acting on the vacuum containment vessel from which more than 99% of the air molecules have been removed. This force on even a moderately sized vacuum chamber is typically more than a ton, and for larger chambers will be many tons. If the vacuum vessel is not strong enough to support a car, or perhaps many cars, without distortion, it will fail.

This problem applies to all vacuum vessels. Since the strength of most structural materials declines rapidly with increasing temperature, this problem is more severe with vacuum furnaces, since at least some of the heat generated by the furnace will eventually reach the vacuum vessel, the amount of this heating determined largely by the effectiveness of intervening thermal insulation packs, if any.

What About Vacuum Ovens?

The term vacuum furnaces is generally applied to heating equipment with a maximum use temperature above 600° C. For applications below 600° C, vacuum ovens are readily available. Vacuum ovens use the external heating method described above, but because of the lower temperature requirements, they can be manufactured to substantially larger sizes. Standard laboratory equipment supply houses stock vacuum ovens limited to elastomer seal temperature, with a maximum oven use temperature of 200-300° C. Vacuum furnace manufacturers can provide externally heated moderate size vacuum ovens for use to 600° C by adding water cooled sealing flanges to the vacuum vessel.

The following sections describe two approaches to the vacuum furnace challenge.

Vacuum Furnace Solution #1

Vacuum Furnace Solution #2