Nonaging Steel

steel with a low carbon content (up to 0.10–0.15 percent), whose mechanical properties change little with the passage of time after cold working.

The tendency toward strain aging, which after prolonged storage of cold-rolled sheet steel leads, upon subsequent cold forging, to the appearance of slip bands on its surface, is eliminated or weakened in nonaging steels. The main reason for the phenomenon is the pinning of dislocations by atoms of carbon and particularly nitrogen. Therefore, to reduce the tendency of steel toward strain aging, the nitrogen content of the solid solution must be reduced. This is achieved by binding the nitrogen to nitride-forming elements. Nonaging steel is produced with aluminum additives (killed steel) or vanadium additives (rimmed steel). Nonaging steel is used mainly in automotive industry for making cold-forged parts.