Effect of tempering process on the mechanical properties and corrosion resistance of E690 marine steel

Abstract

Abstract This study investigated the effect of the tempering process on the microstructure, mechanical properties, and corrosion resistance of E690 marine steel, aiming to replicate actual production conditions and reduce costs. Various techniques, including metallurgical microscopy, scanning electron microscopy, transmission electron microscopy, electron backscatter diffraction, impact experiments, tensile tests, and electrochemical corrosion tests, were employed to evaluate the material’s properties and performance. The results indicated that as the tempering temperature increased, the tempering degree in the tempered martensite structure improved, martensite strips coarsened, the size of precipitated carbides increased, and the proportion of large-angle grain boundaries decreased. Consequently, the tensile and yield strengths initially increased and then decreased, while the impact toughness and elongation gradually improved. At a tempering temperature of 600 °C, the steel exhibited the best overall mechanical properties, with a tensile strength of 729 MPa, a yield strength of 649 MPa, and an elongation of 18%. Furthermore, at a tempering temperature of 550 °C, the test steel showed optimal corrosion resistance, with a corrosion rate of 0.03233 mm/y and an open-circuit potential of -0.36 V.