Aging and its effects
Steel aging

This diffusion of interstitials in ferritic steels only occurs after a deviation from equilibrium resulting either from rapid cooling after a thermal cycle in the ferrite: ageing after quenching, or after plastic deformation: ageing after strain-hardening.

Under these conditions, the return to a certain equilibrium is reflected in the evolution of properties as a function of time.

This aging, when it occurs for certain steel grades or after certain thermal cycles, causes only limited changes in properties (slight hardening, reduction in ductility, rise in impact transition temperature) and ancillary consequences such as the return of the bearing to yield strength and vermiculation