Mechanism for improving low temperature impact toughness and fatigue durability of high-strength low-alloy steels for applications in the Arctic region

The effect of a lattice curvature on impact toughness at low temperatures is studied for the 09Mn2Si and 10Mn2VNbAl high-strength low-alloy (HSLA) steels having different compositions of doping elements. It is shown that the formation of the lattice curvature (several degrees/micrometer), in particular by helical rolling, significantly increases the low-temperature impact toughness of the HSLA steels, regardless of the alloying element compositions. This means that the observed effect could be characteristic of other HSLA steels subjected to complex thermo-mechanical treatment with the formation of the lattice curvature of a certain degree. Authors suggest that the perlite $$\rightarrow $$ bainite phase transformation develops under helical rolling at a temperature of $$\sim $$   $$850\,^\circ \hbox {C}$$ . As a result, bainite is formed in the lattice curvature zones characterized by the presence of interstitial mesoscopic structural states where random rotational deformation modes could develop. This drastically improves the low temperature impact toughness of the HSLA steels and contributes to enhance their fatigue life and wear resistance.