Effect of Natural and Artificial Aging on Steel Mechanical Properties and Fracture Toughness

Abstract—The operating conditions of welded structures of shipbuilding steels, including operation at northern latitudes, determine high requirements for their quality. Materials used for such structures should guarantee stable mechanical properties, good processability during hull fabrication, and serviceability at subzero temperatures. Strain aging is due to the thermodynamic nonequilibrium of steel structure in its initial state and gradual transition to the equilibrium state provided the diffusion mobility of interstitial atoms is sufficient. In unfavorable conditions, this can lead to the degradation of properties during processing (cold straightening, bending, welding), operation, or long-term storage. The paper studies the probability of natural and artificial aging processes in steels of different chemical compositions due to bulk diffusion and carbon dislocation core diffusion (dislocation pipe diffusion). The effect of strain aging on mechanical properties and the CTOD parameter value has been examined.