Carburizing and other carbon control atmospheres all require a source of CO to facilitate the diffusion of carbon into the surface of the metal. One source is through endothermic atmosphere generation, in which air and natural gas are reacted in an external generator to form a gas composed of 20% CO, 40% H2, and 40% N2, with trace amounts of CO2 and moisture.
Another source of CO is the introduction of a blend of 40% nitrogen and 60% methanol into the furnace, which forms a gas of the same composition produced endothermically. The heat of the furnace dissociates the methanol (CH3OH) into CO and H2, which then blends with the nitrogen. Here's how to calculate the amount of methanol needed. For 1000 scf of atmosphere, as an example, 40% or 400 scf will be nitrogen, according to the ratios above. The remaining 60% or 600 scf will be made up of dissociated methanol. Since one gallon of methanol dissociates into approximately 240 scf of gas, 2.5 gallons of methanol would be needed to dissociate into the required 600 scf of atmosphere.
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