Title screen

[References: 6 tit.]

Commercial low carbon steel of the X80 strength level was studied after controlled rolling and interrupted accelerated cooling. The steel microstructure and its fracture characteristics were evaluated in the test temperature range from +20 to –70°С. It was shown that the high values of mechanical properties (YS = 550?MPa, UTS = 680?MPa), the impact toughness (KCV = 310–400?J/cm2), and cold resistance (critical ductile-brittle transition temperature below— 70°С) are achieved due to the formation of a fine granular bainite structure (40%) in the ferrite matrix (53%). The fraction of brittle troostite (finely dispersed pearlite) after rolling and accelerated cooling is reduced to 6%. The granular bainite structure exhibited fine-grained regions of residual austenite (1–2%), carbides Fe3C, Fe2C, and Mn7C3, as well as FeAl intermetallic particles.