Effect of natural and artificial ageing on steel mechanical properties and fracture toughness

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 non-equilibrium 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 ageing processes in steels of different chemical compositions due to bulk diffusion and carbon dislocation core diffusion (dislocation pipe diffusion). The effect of strain ageing on mechanical properties and the CTOD parameter value has been examined.

1. Skakov, Yu.A., Starenie metallicheskikh splavov [Aging of metal alloys], Moscow: Metallurgiya, 1971, pp. 118–132.

2. Bernshteyn, M.L., Kurdyumov, G.V., Meskin, V.S., Popov, A.A., et al., Metallovedenie i termicheskaya obrabotka stali i chuguna. T. 2: Stroenie stali i chuguna [Metallurgy and heat treatment of steel and cast iron. V. 2: The structure of steel and cast iron]: a reference book in 3 vols., Moscow: Intermet Inzhiniring, 2005.

3. Skakov, Yu.A., Protsessy stareniya v splavakh [Aging processes in alloys], Moscow: Mashinostroenie, 1972.

4. Khotinov, V.A., Polukhina, O.N. Selivanova, O.V. Farber, V.M., Vliyanie deformatsionnogo stareniya na mekhanicheskie svoystva pri rastyazhenii v metalle trub klassa prochnosti Kh80 [Effect of strain aging on tensile mechanical properties in metal of pipes of strength class Kh80], Materialovedenie, 2019, No 1, pp. 9–14.

5. Kanfor, S.S., Korpusnaya stal [Case steel], Leningrad: publishing house of the shipbuilding industry, 1960.

6. State Standard GOST 52927-2015: Rolled products of normal, increased and high-strength steel for shipbuilding. Specifications, Moscow: Standartinform, 2015.

7. Korotovskaya, S.V., Kruglova, A.A., Orlov, V.V., Khlusova, E.I., Sravnitelnoe issledovanie fazovykh prevrashcheniy, struktury i svoystv margantsevonikelevoy stali posle zakalki s otpuskom i termomekhanicheskoy obrabotki [Comparative study of phase transformations, structure and properties of manganese-nickel steel after quenching with tempering and thermomechanical treatment], Problemy chernoy metallurgii i materialovedeniya, 2010, No 4, pp. 60–67.

8. Vasiliev, A.A., Golikov P.A., Modeli dlya rascheta koeffitsienta diffuzii ugleroda v stalyakh i primery ikh prakticheskogo ispolzovaniya [Models for calculating the diffusion coefficient of carbon in steels and examples of their practical use], St Petersburg: Politekh-press, 2019.

9. Tapasa, K., Osetsky, Yu.N., Bacon, D.J., Computer simulation of interaction of an edge dislocation with б-carbon interstitial in б-iron and effects on glide, Acta Materialia, 2007, No 55, pp. 93–104.

10. Vasilev, А.А., Lee, H-C., Kuzmin, N.L., Nature of strain aging stages in bake hardening steel for automotive application, Materials Science and Engineering A, 2008, No 485, pp. 282–289.