Toughness enhancement of low carbon steel through bainitic transformation

This study investigates the effect of continuous cooling treatment on the impact toughness and ductile-brittle transition temperature of a low carbon ferrite-pearlite dual-phase steel.Impact testing was performed according to ASTM E23 at temperatures ranging from -60ºC to 90ºC. The results indicate a significant increase in toughness of approximately 64% and areduction in the ductile-brittle transition temperature from 50ºC in the as-received condition to 0ºC after heat treatment. These changes were analyzed through microstructural examination and fractographic analysis. A bainitic transformation was observed,leading to microstructural refinement and an associated toughness improvement. Additionally, a change in fracture surface morphology was noted in the heat-treated steel, as the bainitic transformation resulted in an increased ductile fracture area across the tested temperature range.