9. Low-pressure atmospheres

9.1 Principle and implementation of low-pressure processes

The absence of atmosphere provides an inert environment in a treatment furnace, preventing any chemical action on the metal surface.

There are two categories of vacuum furnaces: hot-wall furnaces, whose operating temperature is limited to 700 ˚C, and cold-wall furnaces, whose temperature can reach 2,000 ˚C. Vacuum, used in industrial furnaces, corresponds to residual pressures of 10 ⁵ to 10 ^-3 Pa. There are several classes of vacuum:

• rough vacuum ............................................................ 10 ⁵ at 133...