In most of the heat treatments applied to steels we need protection or controlled atmosphere for protection against scaling, decarburizing and active atmosphere for carburizing, nitriding. As protective atmosphere, most often are used nitrogen and endogas.
The endogas is a protective atmosphere with the following composition: 20% CO, 40% H2, 40% N2, 0.3-0.5% CO2, rest H2O and other gases. The main applications of this kind of protective gas are as base atmosphere for hardening, carburizing, carbonitriding, normalizing and sometimes as active gas for nitrocarburizing. The most important property of endogas is reductive (anti-scaling) and the protection against decarburizing (CO content gives an equivalent carbon potential of 0.4-0.3%C).
Endogas is very often used in steels heat treatment and it is produced by mixing a certain amount of air and methane (propane) gas into a gas generator at 1000°C through a retort filled with catalyst.
The installation that can produce this kind of atmosphere is the Endogas generator.