7. Hydrogen-based atmospheres

7.1 Hydrogen properties applied to heat treatment

From a chemical point of view, during annealing operations, hydrogen ensures the reducing character of the atmosphere, to prevent the formation of oxides on the steel surface, to obtain good surface cleanliness (elimination of oil residues) and a bright metallic surface appearance.

From a physical point of view, hydrogen's high thermal conductivity coefficient promotes heat exchange between the gas and the surface, and improves heat transfer between the load and the furnace wall [22] . In addition, thanks to hydrogen's low viscosity, the use of a highly hydrogenated atmosphere considerably increases gas circulation (by increasing turbine rotation...