title = "Atmosphere Control in Heat Treatment Furnaces"

content = """
The atmosphere inside a heat treatment furnace profoundly affects the chemical condition of the workpiece surfaces during processing. Without atmosphere control, steel heated above approximately 900°F (480°C) in air will oxidize (scale) and lose surface carbon (decarburize)—degrading surface hardness, fatigue strength, and appearance. At Ridgecrest Metalworks, controlled atmospheres are used in carburizing, neutral hardening, annealing, and other operations requiring clean, chemically correct surfaces.

The carbon potential of the furnace atmosphere determines whether the steel surface will gain, lose, or retain carbon during treatment. Carbon potential is the carbon content of steel that would be in equilibrium with the atmosphere at the process temperature. If the atmosphere's carbon potential equals the steel's surface carbon content, no net carbon transfer occurs (neutral atmosphere). If the atmosphere carbon potential exceeds the steel's carbon content, carburizing occurs. If it is lower, decarburization occurs.

Endothermic (endo) gas is the most widely used atmosphere for neutral hardening and as a carrier gas for carburizing. It is generated on-site by passing a mixture of natural gas or propane with air through a catalyst bed at high temperature, producing approximately 40% H2, 40% N2, 20% CO, and traces of CO2 and CH4. This is a reducing atmosphere that prevents oxidation. Carbon potential is controlled by measuring CO2 or H2O (dew point) content with infrared analyzers or oxygen probes and adjusting the enrichment gas (natural gas or propane) flow rate.

Nitrogen-methanol atmosphere is an alternative to endothermic gas: bottled nitrogen is injected with a controlled flow of methanol, which decomposes in the furnace to produce N2, H2, and CO. It provides an on-demand, easily controllable atmosphere without the need for an endothermic generator. It is widely used in batch furnaces.

Exothermic (exo) gas is less expensive (produced by burning a rich gas-air mixture without catalyst) but has higher CO2 and H2O content—it is acceptable for annealing of parts where slight surface condition is acceptable but not for bright hardening.

Pure nitrogen (or nitrogen-hydrogen blends) provides a simple, clean, inert atmosphere for annealing copper, brass, and other non-ferrous metals that require oxidation prevention but not carbon control.
"""

version = "0.0.1"
